Commit | Line | Data |
---|---|---|
420a0d19 CE |
1 | Specification of the Exim Mail Transfer Agent |
2 | ||
3 | Exim Maintainers | |
4 | ||
5 | Copyright (c) 2014 University of Cambridge | |
6 | ||
188b6fee CE |
7 | Revision 4.84.2 02 Mar 2016 EM |
8 | ||
420a0d19 CE |
9 | ------------------------------------------------------------------------------- |
10 | ||
11 | TABLE OF CONTENTS | |
12 | ||
13 | 1. Introduction | |
14 | ||
15 | 1.1. Exim documentation | |
16 | 1.2. FTP and web sites | |
17 | 1.3. Mailing lists | |
18 | 1.4. Exim training | |
19 | 1.5. Bug reports | |
20 | 1.6. Where to find the Exim distribution | |
21 | 1.7. Limitations | |
22 | 1.8. Run time configuration | |
23 | 1.9. Calling interface | |
24 | 1.10. Terminology | |
25 | ||
26 | 2. Incorporated code | |
27 | 3. How Exim receives and delivers mail | |
28 | ||
29 | 3.1. Overall philosophy | |
30 | 3.2. Policy control | |
31 | 3.3. User filters | |
32 | 3.4. Message identification | |
33 | 3.5. Receiving mail | |
34 | 3.6. Handling an incoming message | |
35 | 3.7. Life of a message | |
36 | 3.8. Processing an address for delivery | |
37 | 3.9. Processing an address for verification | |
38 | 3.10. Running an individual router | |
39 | 3.11. Duplicate addresses | |
40 | 3.12. Router preconditions | |
41 | 3.13. Delivery in detail | |
42 | 3.14. Retry mechanism | |
43 | 3.15. Temporary delivery failure | |
44 | 3.16. Permanent delivery failure | |
45 | 3.17. Failures to deliver bounce messages | |
46 | ||
47 | 4. Building and installing Exim | |
48 | ||
49 | 4.1. Unpacking | |
50 | 4.2. Multiple machine architectures and operating systems | |
51 | 4.3. PCRE library | |
52 | 4.4. DBM libraries | |
53 | 4.5. Pre-building configuration | |
54 | 4.6. Support for iconv() | |
55 | 4.7. Including TLS/SSL encryption support | |
56 | 4.8. Use of tcpwrappers | |
57 | 4.9. Including support for IPv6 | |
58 | 4.10. Dynamically loaded lookup module support | |
59 | 4.11. The building process | |
60 | 4.12. Output from "make" | |
61 | 4.13. Overriding build-time options for Exim | |
62 | 4.14. OS-specific header files | |
63 | 4.15. Overriding build-time options for the monitor | |
64 | 4.16. Installing Exim binaries and scripts | |
65 | 4.17. Installing info documentation | |
66 | 4.18. Setting up the spool directory | |
67 | 4.19. Testing | |
68 | 4.20. Replacing another MTA with Exim | |
69 | 4.21. Upgrading Exim | |
70 | 4.22. Stopping the Exim daemon on Solaris | |
71 | ||
72 | 5. The Exim command line | |
73 | ||
74 | 5.1. Setting options by program name | |
75 | 5.2. Trusted and admin users | |
76 | 5.3. Command line options | |
77 | ||
78 | 6. The Exim run time configuration file | |
79 | ||
80 | 6.1. Using a different configuration file | |
81 | 6.2. Configuration file format | |
82 | 6.3. File inclusions in the configuration file | |
83 | 6.4. Macros in the configuration file | |
84 | 6.5. Macro substitution | |
85 | 6.6. Redefining macros | |
86 | 6.7. Overriding macro values | |
87 | 6.8. Example of macro usage | |
88 | 6.9. Conditional skips in the configuration file | |
89 | 6.10. Common option syntax | |
90 | 6.11. Boolean options | |
91 | 6.12. Integer values | |
92 | 6.13. Octal integer values | |
93 | 6.14. Fixed point numbers | |
94 | 6.15. Time intervals | |
95 | 6.16. String values | |
96 | 6.17. Expanded strings | |
97 | 6.18. User and group names | |
98 | 6.19. List construction | |
99 | 6.20. Changing list separators | |
100 | 6.21. Empty items in lists | |
101 | 6.22. Format of driver configurations | |
102 | ||
103 | 7. The default configuration file | |
104 | ||
105 | 7.1. Main configuration settings | |
106 | 7.2. ACL configuration | |
107 | 7.3. Router configuration | |
108 | 7.4. Transport configuration | |
109 | 7.5. Default retry rule | |
110 | 7.6. Rewriting configuration | |
111 | 7.7. Authenticators configuration | |
112 | ||
113 | 8. Regular expressions | |
114 | 9. File and database lookups | |
115 | ||
116 | 9.1. Examples of different lookup syntax | |
117 | 9.2. Lookup types | |
118 | 9.3. Single-key lookup types | |
119 | 9.4. Query-style lookup types | |
120 | 9.5. Temporary errors in lookups | |
121 | 9.6. Default values in single-key lookups | |
122 | 9.7. Partial matching in single-key lookups | |
123 | 9.8. Lookup caching | |
124 | 9.9. Quoting lookup data | |
125 | 9.10. More about dnsdb | |
126 | 9.11. Pseudo dnsdb record types | |
127 | 9.12. Multiple dnsdb lookups | |
128 | 9.13. More about LDAP | |
129 | 9.14. Format of LDAP queries | |
130 | 9.15. LDAP quoting | |
131 | 9.16. LDAP connections | |
132 | 9.17. LDAP authentication and control information | |
133 | 9.18. Format of data returned by LDAP | |
134 | 9.19. More about NIS+ | |
135 | 9.20. SQL lookups | |
136 | 9.21. More about MySQL, PostgreSQL, Oracle, and InterBase | |
137 | 9.22. Specifying the server in the query | |
138 | 9.23. Special MySQL features | |
139 | 9.24. Special PostgreSQL features | |
140 | 9.25. More about SQLite | |
141 | ||
142 | 10. Domain, host, address, and local part lists | |
143 | ||
144 | 10.1. Expansion of lists | |
145 | 10.2. Negated items in lists | |
146 | 10.3. File names in lists | |
147 | 10.4. An lsearch file is not an out-of-line list | |
148 | 10.5. Named lists | |
149 | 10.6. Named lists compared with macros | |
150 | 10.7. Named list caching | |
151 | 10.8. Domain lists | |
152 | 10.9. Host lists | |
153 | 10.10. Special host list patterns | |
154 | 10.11. Host list patterns that match by IP address | |
155 | 10.12. Host list patterns for single-key lookups by host address | |
156 | 10.13. Host list patterns that match by host name | |
157 | 10.14. Behaviour when an IP address or name cannot be found | |
158 | 10.15. Mixing wildcarded host names and addresses in host lists | |
159 | 10.16. Temporary DNS errors when looking up host information | |
160 | 10.17. Host list patterns for single-key lookups by host name | |
161 | 10.18. Host list patterns for query-style lookups | |
162 | 10.19. Address lists | |
163 | 10.20. Case of letters in address lists | |
164 | 10.21. Local part lists | |
165 | ||
166 | 11. String expansions | |
167 | ||
168 | 11.1. Literal text in expanded strings | |
169 | 11.2. Character escape sequences in expanded strings | |
170 | 11.3. Testing string expansions | |
171 | 11.4. Forced expansion failure | |
172 | 11.5. Expansion items | |
173 | 11.6. Expansion operators | |
174 | 11.7. Expansion conditions | |
175 | 11.8. Combining expansion conditions | |
176 | 11.9. Expansion variables | |
177 | ||
178 | 12. Embedded Perl | |
179 | ||
180 | 12.1. Setting up so Perl can be used | |
181 | 12.2. Calling Perl subroutines | |
182 | 12.3. Calling Exim functions from Perl | |
183 | 12.4. Use of standard output and error by Perl | |
184 | ||
185 | 13. Starting the daemon and the use of network interfaces | |
186 | ||
187 | 13.1. Starting a listening daemon | |
188 | 13.2. Special IP listening addresses | |
189 | 13.3. Overriding local_interfaces and daemon_smtp_ports | |
190 | 13.4. Support for the obsolete SSMTP (or SMTPS) protocol | |
191 | 13.5. IPv6 address scopes | |
192 | 13.6. Disabling IPv6 | |
193 | 13.7. Examples of starting a listening daemon | |
194 | 13.8. Recognizing the local host | |
195 | 13.9. Delivering to a remote host | |
196 | ||
197 | 14. Main configuration | |
198 | ||
199 | 14.1. Miscellaneous | |
200 | 14.2. Exim parameters | |
201 | 14.3. Privilege controls | |
202 | 14.4. Logging | |
203 | 14.5. Frozen messages | |
204 | 14.6. Data lookups | |
205 | 14.7. Message ids | |
206 | 14.8. Embedded Perl Startup | |
207 | 14.9. Daemon | |
208 | 14.10. Resource control | |
209 | 14.11. Policy controls | |
210 | 14.12. Callout cache | |
211 | 14.13. TLS | |
212 | 14.14. Local user handling | |
213 | 14.15. All incoming messages (SMTP and non-SMTP) | |
214 | 14.16. Non-SMTP incoming messages | |
215 | 14.17. Incoming SMTP messages | |
216 | 14.18. SMTP extensions | |
217 | 14.19. Processing messages | |
218 | 14.20. System filter | |
219 | 14.21. Routing and delivery | |
220 | 14.22. Bounce and warning messages | |
221 | 14.23. Alphabetical list of main options | |
222 | ||
223 | 15. Generic options for routers | |
224 | 16. The accept router | |
225 | 17. The dnslookup router | |
226 | ||
227 | 17.1. Problems with DNS lookups | |
228 | 17.2. Declining addresses by dnslookup | |
229 | 17.3. Private options for dnslookup | |
230 | 17.4. Effect of qualify_single and search_parents | |
231 | ||
232 | 18. The ipliteral router | |
233 | 19. The iplookup router | |
234 | 20. The manualroute router | |
235 | ||
236 | 20.1. Private options for manualroute | |
237 | 20.2. Routing rules in route_list | |
238 | 20.3. Routing rules in route_data | |
239 | 20.4. Format of the list of hosts | |
240 | 20.5. Format of one host item | |
241 | 20.6. How the list of hosts is used | |
242 | 20.7. How the options are used | |
243 | 20.8. Manualroute examples | |
244 | ||
245 | 21. The queryprogram router | |
246 | 22. The redirect router | |
247 | ||
248 | 22.1. Redirection data | |
249 | 22.2. Forward files and address verification | |
250 | 22.3. Interpreting redirection data | |
251 | 22.4. Items in a non-filter redirection list | |
252 | 22.5. Redirecting to a local mailbox | |
253 | 22.6. Special items in redirection lists | |
254 | 22.7. Duplicate addresses | |
255 | 22.8. Repeated redirection expansion | |
256 | 22.9. Errors in redirection lists | |
257 | 22.10. Private options for the redirect router | |
258 | ||
259 | 23. Environment for running local transports | |
260 | ||
261 | 23.1. Concurrent deliveries | |
262 | 23.2. Uids and gids | |
263 | 23.3. Current and home directories | |
264 | 23.4. Expansion variables derived from the address | |
265 | ||
266 | 24. Generic options for transports | |
267 | 25. Address batching in local transports | |
268 | 26. The appendfile transport | |
269 | ||
270 | 26.1. The file and directory options | |
271 | 26.2. Private options for appendfile | |
272 | 26.3. Operational details for appending | |
273 | 26.4. Operational details for delivery to a new file | |
274 | 26.5. Maildir delivery | |
275 | 26.6. Using tags to record message sizes | |
276 | 26.7. Using a maildirsize file | |
277 | 26.8. Mailstore delivery | |
278 | 26.9. Non-special new file delivery | |
279 | ||
280 | 27. The autoreply transport | |
281 | ||
282 | 27.1. Private options for autoreply | |
283 | ||
284 | 28. The lmtp transport | |
285 | 29. The pipe transport | |
286 | ||
287 | 29.1. Concurrent delivery | |
288 | 29.2. Returned status and data | |
289 | 29.3. How the command is run | |
290 | 29.4. Environment variables | |
291 | 29.5. Private options for pipe | |
292 | 29.6. Using an external local delivery agent | |
293 | ||
294 | 30. The smtp transport | |
295 | ||
296 | 30.1. Multiple messages on a single connection | |
297 | 30.2. Use of the $host and $host_address variables | |
298 | 30.3. Use of $tls_cipher and $tls_peerdn | |
299 | 30.4. Private options for smtp | |
300 | 30.5. How the limits for the number of hosts to try are used | |
301 | ||
302 | 31. Address rewriting | |
303 | ||
304 | 31.1. Explicitly configured address rewriting | |
305 | 31.2. When does rewriting happen? | |
306 | 31.3. Testing the rewriting rules that apply on input | |
307 | 31.4. Rewriting rules | |
308 | 31.5. Rewriting patterns | |
309 | 31.6. Rewriting replacements | |
310 | 31.7. Rewriting flags | |
311 | 31.8. Flags specifying which headers and envelope addresses to rewrite | |
312 | 31.9. The SMTP-time rewriting flag | |
313 | 31.10. Flags controlling the rewriting process | |
314 | 31.11. Rewriting examples | |
315 | ||
316 | 32. Retry configuration | |
317 | ||
318 | 32.1. Changing retry rules | |
319 | 32.2. Format of retry rules | |
320 | 32.3. Choosing which retry rule to use for address errors | |
321 | 32.4. Choosing which retry rule to use for host and message errors | |
322 | 32.5. Retry rules for specific errors | |
323 | 32.6. Retry rules for specified senders | |
324 | 32.7. Retry parameters | |
325 | 32.8. Retry rule examples | |
326 | 32.9. Timeout of retry data | |
327 | 32.10. Long-term failures | |
328 | 32.11. Deliveries that work intermittently | |
329 | ||
330 | 33. SMTP authentication | |
331 | ||
332 | 33.1. Generic options for authenticators | |
333 | 33.2. The AUTH parameter on MAIL commands | |
334 | 33.3. Authentication on an Exim server | |
335 | 33.4. Testing server authentication | |
336 | 33.5. Authentication by an Exim client | |
337 | ||
338 | 34. The plaintext authenticator | |
339 | ||
340 | 34.1. Plaintext options | |
341 | 34.2. Using plaintext in a server | |
342 | 34.3. The PLAIN authentication mechanism | |
343 | 34.4. The LOGIN authentication mechanism | |
344 | 34.5. Support for different kinds of authentication | |
345 | 34.6. Using plaintext in a client | |
346 | ||
347 | 35. The cram_md5 authenticator | |
348 | ||
349 | 35.1. Using cram_md5 as a server | |
350 | 35.2. Using cram_md5 as a client | |
351 | ||
352 | 36. The cyrus_sasl authenticator | |
353 | ||
354 | 36.1. Using cyrus_sasl as a server | |
355 | ||
356 | 37. The dovecot authenticator | |
357 | 38. The gsasl authenticator | |
358 | ||
359 | 38.1. gsasl auth variables | |
360 | ||
361 | 39. The heimdal_gssapi authenticator | |
362 | ||
363 | 39.1. heimdal_gssapi auth variables | |
364 | ||
365 | 40. The spa authenticator | |
366 | ||
367 | 40.1. Using spa as a server | |
368 | 40.2. Using spa as a client | |
369 | ||
370 | 41. Encrypted SMTP connections using TLS/SSL | |
371 | ||
372 | 41.1. Support for the legacy "ssmtp" (aka "smtps") protocol | |
373 | 41.2. OpenSSL vs GnuTLS | |
374 | 41.3. GnuTLS parameter computation | |
375 | 41.4. Requiring specific ciphers in OpenSSL | |
376 | 41.5. Requiring specific ciphers or other parameters in GnuTLS | |
377 | 41.6. Configuring an Exim server to use TLS | |
378 | 41.7. Requesting and verifying client certificates | |
379 | 41.8. Revoked certificates | |
380 | 41.9. Configuring an Exim client to use TLS | |
381 | 41.10. Use of TLS Server Name Indication | |
382 | 41.11. Multiple messages on the same encrypted TCP/IP connection | |
383 | 41.12. Certificates and all that | |
384 | 41.13. Certificate chains | |
385 | 41.14. Self-signed certificates | |
386 | ||
387 | 42. Access control lists | |
388 | ||
389 | 42.1. Testing ACLs | |
390 | 42.2. Specifying when ACLs are used | |
391 | 42.3. The non-SMTP ACLs | |
392 | 42.4. The SMTP connect ACL | |
393 | 42.5. The EHLO/HELO ACL | |
394 | 42.6. The DATA ACLs | |
395 | 42.7. The SMTP DKIM ACL | |
396 | 42.8. The SMTP MIME ACL | |
397 | 42.9. The SMTP PRDR ACL | |
398 | 42.10. The QUIT ACL | |
399 | 42.11. The not-QUIT ACL | |
400 | 42.12. Finding an ACL to use | |
401 | 42.13. ACL return codes | |
402 | 42.14. Unset ACL options | |
403 | 42.15. Data for message ACLs | |
404 | 42.16. Data for non-message ACLs | |
405 | 42.17. Format of an ACL | |
406 | 42.18. ACL verbs | |
407 | 42.19. ACL variables | |
408 | 42.20. Condition and modifier processing | |
409 | 42.21. ACL modifiers | |
410 | 42.22. Use of the control modifier | |
411 | 42.23. Summary of message fixup control | |
412 | 42.24. Adding header lines in ACLs | |
413 | 42.25. Removing header lines in ACLs | |
414 | 42.26. ACL conditions | |
415 | 42.27. Using DNS lists | |
416 | 42.28. Specifying the IP address for a DNS list lookup | |
417 | 42.29. DNS lists keyed on domain names | |
418 | 42.30. Multiple explicit keys for a DNS list | |
419 | 42.31. Data returned by DNS lists | |
420 | 42.32. Variables set from DNS lists | |
421 | 42.33. Additional matching conditions for DNS lists | |
422 | 42.34. Negated DNS matching conditions | |
423 | 42.35. Handling multiple DNS records from a DNS list | |
424 | 42.36. Detailed information from merged DNS lists | |
425 | 42.37. DNS lists and IPv6 | |
426 | 42.38. Rate limiting incoming messages | |
427 | 42.39. Ratelimit options for what is being measured | |
428 | 42.40. Ratelimit update modes | |
429 | 42.41. Ratelimit options for handling fast clients | |
430 | 42.42. Limiting the rate of different events | |
431 | 42.43. Using rate limiting | |
432 | 42.44. Address verification | |
433 | 42.45. Callout verification | |
434 | 42.46. Additional parameters for callouts | |
435 | 42.47. Callout caching | |
436 | 42.48. Sender address verification reporting | |
437 | 42.49. Redirection while verifying | |
438 | 42.50. Client SMTP authorization (CSA) | |
439 | 42.51. Bounce address tag validation | |
440 | 42.52. Using an ACL to control relaying | |
441 | 42.53. Checking a relay configuration | |
442 | ||
443 | 43. Content scanning at ACL time | |
444 | ||
445 | 43.1. Scanning for viruses | |
446 | 43.2. Scanning with SpamAssassin | |
447 | 43.3. Calling SpamAssassin from an Exim ACL | |
448 | 43.4. Scanning MIME parts | |
449 | 43.5. Scanning with regular expressions | |
450 | 43.6. The demime condition | |
451 | ||
452 | 44. Adding a local scan function to Exim | |
453 | ||
454 | 44.1. Building Exim to use a local scan function | |
455 | 44.2. API for local_scan() | |
456 | 44.3. Configuration options for local_scan() | |
457 | 44.4. Available Exim variables | |
458 | 44.5. Structure of header lines | |
459 | 44.6. Structure of recipient items | |
460 | 44.7. Available Exim functions | |
461 | 44.8. More about Exim's memory handling | |
462 | ||
463 | 45. System-wide message filtering | |
464 | ||
465 | 45.1. Specifying a system filter | |
466 | 45.2. Testing a system filter | |
467 | 45.3. Contents of a system filter | |
468 | 45.4. Additional variable for system filters | |
469 | 45.5. Defer, freeze, and fail commands for system filters | |
470 | 45.6. Adding and removing headers in a system filter | |
471 | 45.7. Setting an errors address in a system filter | |
472 | 45.8. Per-address filtering | |
473 | ||
474 | 46. Message processing | |
475 | ||
476 | 46.1. Submission mode for non-local messages | |
477 | 46.2. Line endings | |
478 | 46.3. Unqualified addresses | |
479 | 46.4. The UUCP From line | |
480 | 46.5. Resent- header lines | |
481 | 46.6. The Auto-Submitted: header line | |
482 | 46.7. The Bcc: header line | |
483 | 46.8. The Date: header line | |
484 | 46.9. The Delivery-date: header line | |
485 | 46.10. The Envelope-to: header line | |
486 | 46.11. The From: header line | |
487 | 46.12. The Message-ID: header line | |
488 | 46.13. The Received: header line | |
489 | 46.14. The References: header line | |
490 | 46.15. The Return-path: header line | |
491 | 46.16. The Sender: header line | |
492 | 46.17. Adding and removing header lines in routers and transports | |
493 | 46.18. Constructed addresses | |
494 | 46.19. Case of local parts | |
495 | 46.20. Dots in local parts | |
496 | 46.21. Rewriting addresses | |
497 | ||
498 | 47. SMTP processing | |
499 | ||
500 | 47.1. Outgoing SMTP and LMTP over TCP/IP | |
501 | 47.2. Errors in outgoing SMTP | |
502 | 47.3. Incoming SMTP messages over TCP/IP | |
503 | 47.4. Unrecognized SMTP commands | |
504 | 47.5. Syntax and protocol errors in SMTP commands | |
505 | 47.6. Use of non-mail SMTP commands | |
506 | 47.7. The VRFY and EXPN commands | |
507 | 47.8. The ETRN command | |
508 | 47.9. Incoming local SMTP | |
509 | 47.10. Outgoing batched SMTP | |
510 | 47.11. Incoming batched SMTP | |
511 | ||
512 | 48. Customizing bounce and warning messages | |
513 | ||
514 | 48.1. Customizing bounce messages | |
515 | 48.2. Customizing warning messages | |
516 | ||
517 | 49. Some common configuration settings | |
518 | ||
519 | 49.1. Sending mail to a smart host | |
520 | 49.2. Using Exim to handle mailing lists | |
521 | 49.3. Syntax errors in mailing lists | |
522 | 49.4. Re-expansion of mailing lists | |
523 | 49.5. Closed mailing lists | |
524 | 49.6. Variable Envelope Return Paths (VERP) | |
525 | 49.7. Virtual domains | |
526 | 49.8. Multiple user mailboxes | |
527 | 49.9. Simplified vacation processing | |
528 | 49.10. Taking copies of mail | |
529 | 49.11. Intermittently connected hosts | |
530 | 49.12. Exim on the upstream server host | |
531 | 49.13. Exim on the intermittently connected client host | |
532 | ||
533 | 50. Using Exim as a non-queueing client | |
534 | 51. Log files | |
535 | ||
536 | 51.1. Where the logs are written | |
537 | 51.2. Logging to local files that are periodically "cycled" | |
538 | 51.3. Datestamped log files | |
539 | 51.4. Logging to syslog | |
540 | 51.5. Log line flags | |
541 | 51.6. Logging message reception | |
542 | 51.7. Logging deliveries | |
543 | 51.8. Discarded deliveries | |
544 | 51.9. Deferred deliveries | |
545 | 51.10. Delivery failures | |
546 | 51.11. Fake deliveries | |
547 | 51.12. Completion | |
548 | 51.13. Summary of Fields in Log Lines | |
549 | 51.14. Other log entries | |
550 | 51.15. Reducing or increasing what is logged | |
551 | 51.16. Message log | |
552 | ||
553 | 52. Exim utilities | |
554 | ||
555 | 52.1. Finding out what Exim processes are doing (exiwhat) | |
556 | 52.2. Selective queue listing (exiqgrep) | |
557 | 52.3. Summarizing the queue (exiqsumm) | |
558 | 52.4. Extracting specific information from the log (exigrep) | |
559 | 52.5. Selecting messages by various criteria (exipick) | |
560 | 52.6. Cycling log files (exicyclog) | |
561 | 52.7. Mail statistics (eximstats) | |
562 | 52.8. Checking access policy (exim_checkaccess) | |
563 | 52.9. Making DBM files (exim_dbmbuild) | |
564 | 52.10. Finding individual retry times (exinext) | |
565 | 52.11. Hints database maintenance | |
566 | 52.12. exim_dumpdb | |
567 | 52.13. exim_tidydb | |
568 | 52.14. exim_fixdb | |
569 | 52.15. Mailbox maintenance (exim_lock) | |
570 | ||
571 | 53. The Exim monitor | |
572 | ||
573 | 53.1. Running the monitor | |
574 | 53.2. The stripcharts | |
575 | 53.3. Main action buttons | |
576 | 53.4. The log display | |
577 | 53.5. The queue display | |
578 | 53.6. The queue menu | |
579 | ||
580 | 54. Security considerations | |
581 | ||
582 | 54.1. Building a more "hardened" Exim | |
583 | 54.2. Root privilege | |
584 | 54.3. Running Exim without privilege | |
585 | 54.4. Delivering to local files | |
586 | 54.5. Running local commands | |
587 | 54.6. Trust in configuration data | |
588 | 54.7. IPv4 source routing | |
589 | 54.8. The VRFY, EXPN, and ETRN commands in SMTP | |
590 | 54.9. Privileged users | |
591 | 54.10. Spool files | |
592 | 54.11. Use of argv[0] | |
593 | 54.12. Use of %f formatting | |
594 | 54.13. Embedded Exim path | |
595 | 54.14. Dynamic module directory | |
596 | 54.15. Use of sprintf() | |
597 | 54.16. Use of debug_printf() and log_write() | |
598 | 54.17. Use of strcat() and strcpy() | |
599 | ||
600 | 55. Format of spool files | |
601 | ||
602 | 55.1. Format of the -H file | |
603 | ||
604 | 56. Support for DKIM (DomainKeys Identified Mail) | |
605 | ||
606 | 56.1. Signing outgoing messages | |
607 | 56.2. Verifying DKIM signatures in incoming mail | |
608 | ||
609 | 57. Adding new drivers or lookup types | |
610 | ||
611 | ||
612 | ||
613 | =============================================================================== | |
614 | 1. INTRODUCTION | |
615 | ||
616 | Exim is a mail transfer agent (MTA) for hosts that are running Unix or | |
617 | Unix-like operating systems. It was designed on the assumption that it would be | |
618 | run on hosts that are permanently connected to the Internet. However, it can be | |
619 | used on intermittently connected hosts with suitable configuration adjustments. | |
620 | ||
621 | Configuration files currently exist for the following operating systems: AIX, | |
622 | BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd, GNU/ | |
623 | Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD, | |
624 | OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4, | |
625 | Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware. | |
626 | Some of these operating systems are no longer current and cannot easily be | |
627 | tested, so the configuration files may no longer work in practice. | |
628 | ||
629 | There are also configuration files for compiling Exim in the Cygwin environment | |
630 | that can be installed on systems running Windows. However, this document does | |
631 | not contain any information about running Exim in the Cygwin environment. | |
632 | ||
633 | The terms and conditions for the use and distribution of Exim are contained in | |
634 | the file NOTICE. Exim is distributed under the terms of the GNU General Public | |
635 | Licence, a copy of which may be found in the file LICENCE. | |
636 | ||
637 | The use, supply or promotion of Exim for the purpose of sending bulk, | |
638 | unsolicited electronic mail is incompatible with the basic aims of the program, | |
639 | which revolve around the free provision of a service that enhances the quality | |
640 | of personal communications. The author of Exim regards indiscriminate | |
641 | mass-mailing as an antisocial, irresponsible abuse of the Internet. | |
642 | ||
643 | Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the | |
644 | experience of running and working on the Smail 3 code, I could never have | |
645 | contemplated starting to write a new MTA. Many of the ideas and user interfaces | |
646 | were originally taken from Smail 3, though the actual code of Exim is entirely | |
647 | new, and has developed far beyond the initial concept. | |
648 | ||
649 | Many people, both in Cambridge and around the world, have contributed to the | |
650 | development and the testing of Exim, and to porting it to various operating | |
651 | systems. I am grateful to them all. The distribution now contains a file called | |
652 | ACKNOWLEDGMENTS, in which I have started recording the names of contributors. | |
653 | ||
654 | ||
655 | 1.1 Exim documentation | |
656 | ---------------------- | |
657 | ||
188b6fee | 658 | This edition of the Exim specification applies to version 4.84.2 of Exim. |
420a0d19 CE |
659 | Substantive changes from the 4.83 edition are marked in some renditions of the |
660 | document; this paragraph is so marked if the rendition is capable of showing a | |
661 | change indicator. | |
662 | ||
663 | This document is very much a reference manual; it is not a tutorial. The reader | |
664 | is expected to have some familiarity with the SMTP mail transfer protocol and | |
665 | with general Unix system administration. Although there are some discussions | |
666 | and examples in places, the information is mostly organized in a way that makes | |
667 | it easy to look up, rather than in a natural order for sequential reading. | |
668 | Furthermore, the manual aims to cover every aspect of Exim in detail, including | |
669 | a number of rarely-used, special-purpose features that are unlikely to be of | |
670 | very wide interest. | |
671 | ||
672 | An "easier" discussion of Exim which provides more in-depth explanatory, | |
673 | introductory, and tutorial material can be found in a book entitled The Exim | |
674 | SMTP Mail Server (second edition, 2007), published by UIT Cambridge (http:// | |
675 | www.uit.co.uk/exim-book/). | |
676 | ||
677 | This book also contains a chapter that gives a general introduction to SMTP and | |
678 | Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date | |
679 | with the latest release of Exim. (Note that the earlier book about Exim, | |
680 | published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.) | |
681 | ||
682 | If you are using a Debian distribution of Exim, you will find information about | |
683 | Debian-specific features in the file /usr/share/doc/exim4-base/README.Debian. | |
684 | The command man update-exim.conf is another source of Debian-specific | |
685 | information. | |
686 | ||
687 | As the program develops, there may be features in newer versions that have not | |
688 | yet made it into this document, which is updated only when the most significant | |
689 | digit of the fractional part of the version number changes. Specifications of | |
690 | new features that are not yet in this manual are placed in the file doc/ | |
691 | NewStuff in the Exim distribution. | |
692 | ||
693 | Some features may be classified as "experimental". These may change | |
694 | incompatibly while they are developing, or even be withdrawn. For this reason, | |
695 | they are not documented in this manual. Information about experimental features | |
696 | can be found in the file doc/experimental.txt. | |
697 | ||
698 | All changes to the program (whether new features, bug fixes, or other kinds of | |
699 | change) are noted briefly in the file called doc/ChangeLog. | |
700 | ||
701 | This specification itself is available as an ASCII file in doc/spec.txt so that | |
702 | it can easily be searched with a text editor. Other files in the doc directory | |
703 | are: | |
704 | ||
705 | OptionLists.txt list of all options in alphabetical order | |
706 | dbm.discuss.txt discussion about DBM libraries | |
707 | exim.8 a man page of Exim's command line options | |
708 | experimental.txt documentation of experimental features | |
709 | filter.txt specification of the filter language | |
710 | Exim3.upgrade upgrade notes from release 2 to release 3 | |
711 | Exim4.upgrade upgrade notes from release 3 to release 4 | |
712 | ||
713 | The main specification and the specification of the filtering language are also | |
714 | available in other formats (HTML, PostScript, PDF, and Texinfo). Section 1.6 | |
715 | below tells you how to get hold of these. | |
716 | ||
717 | ||
718 | 1.2 FTP and web sites | |
719 | --------------------- | |
720 | ||
721 | The primary site for Exim source distributions is currently the University of | |
722 | Cambridge's FTP site, whose contents are described in Where to find the Exim | |
723 | distribution below. In addition, there is a web site and an FTP site at | |
724 | exim.org. These are now also hosted at the University of Cambridge. The | |
725 | exim.org site was previously hosted for a number of years by Energis Squared, | |
726 | formerly Planet Online Ltd, whose support I gratefully acknowledge. | |
727 | ||
728 | As well as Exim distribution tar files, the Exim web site contains a number of | |
729 | differently formatted versions of the documentation. A recent addition to the | |
730 | online information is the Exim wiki (http://wiki.exim.org), which contains what | |
731 | used to be a separate FAQ, as well as various other examples, tips, and | |
732 | know-how that have been contributed by Exim users. | |
733 | ||
734 | An Exim Bugzilla exists at http://bugs.exim.org. You can use this to report | |
735 | bugs, and also to add items to the wish list. Please search first to check that | |
736 | you are not duplicating a previous entry. | |
737 | ||
738 | ||
739 | 1.3 Mailing lists | |
740 | ----------------- | |
741 | ||
742 | The following Exim mailing lists exist: | |
743 | ||
744 | exim-announce@exim.org Moderated, low volume announcements list | |
745 | exim-users@exim.org General discussion list | |
746 | exim-dev@exim.org Discussion of bugs, enhancements, etc. | |
747 | exim-cvs@exim.org Automated commit messages from the VCS | |
748 | ||
749 | You can subscribe to these lists, change your existing subscriptions, and view | |
750 | or search the archives via the mailing lists link on the Exim home page. If you | |
751 | are using a Debian distribution of Exim, you may wish to subscribe to the | |
752 | Debian-specific mailing list pkg-exim4-users@lists.alioth.debian.org via this | |
753 | web page: | |
754 | ||
755 | http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users | |
756 | ||
757 | Please ask Debian-specific questions on this list and not on the general Exim | |
758 | lists. | |
759 | ||
760 | ||
761 | 1.4 Exim training | |
762 | ----------------- | |
763 | ||
764 | Training courses in Cambridge (UK) used to be run annually by the author of | |
765 | Exim, before he retired. At the time of writing, there are no plans to run | |
766 | further Exim courses in Cambridge. However, if that changes, relevant | |
767 | information will be posted at http://www-tus.csx.cam.ac.uk/courses/exim/. | |
768 | ||
769 | ||
770 | 1.5 Bug reports | |
771 | --------------- | |
772 | ||
773 | Reports of obvious bugs can be emailed to bugs@exim.org or reported via the | |
774 | Bugzilla (http://bugs.exim.org). However, if you are unsure whether some | |
775 | behaviour is a bug or not, the best thing to do is to post a message to the | |
776 | exim-dev mailing list and have it discussed. | |
777 | ||
778 | ||
779 | 1.6 Where to find the Exim distribution | |
780 | --------------------------------------- | |
781 | ||
782 | The master ftp site for the Exim distribution is | |
783 | ||
784 | ftp://ftp.csx.cam.ac.uk/pub/software/email/exim | |
785 | ||
786 | This is mirrored by | |
787 | ||
788 | ftp://ftp.exim.org/pub/exim | |
789 | ||
790 | The file references that follow are relative to the exim directories at these | |
791 | sites. There are now quite a number of independent mirror sites around the | |
792 | world. Those that I know about are listed in the file called Mirrors. | |
793 | ||
794 | Within the exim directory there are subdirectories called exim3 (for previous | |
795 | Exim 3 distributions), exim4 (for the latest Exim 4 distributions), and Testing | |
796 | for testing versions. In the exim4 subdirectory, the current release can always | |
797 | be found in files called | |
798 | ||
799 | exim-n.nn.tar.gz | |
800 | exim-n.nn.tar.bz2 | |
801 | ||
802 | where n.nn is the highest such version number in the directory. The two files | |
803 | contain identical data; the only difference is the type of compression. The | |
804 | .bz2 file is usually a lot smaller than the .gz file. | |
805 | ||
806 | The distributions will be PGP signed by an individual key of the Release | |
807 | Coordinator. This key will have a uid containing an email address in the | |
808 | exim.org domain and will have signatures from other people, including other | |
809 | Exim maintainers. We expect that the key will be in the "strong set" of PGP | |
810 | keys. There should be a trust path to that key from Nigel Metheringham's PGP | |
811 | key, a version of which can be found in the release directory in the file | |
812 | nigel-pubkey.asc. All keys used will be available in public keyserver pools, | |
813 | such as pool.sks-keyservers.net. | |
814 | ||
815 | At time of last update, releases were being made by Phil Pennock and signed | |
816 | with key 0x403043153903637F, although that key is expected to be replaced in | |
817 | 2013. A trust path from Nigel's key to Phil's can be observed at https:// | |
818 | www.security.spodhuis.org/exim-trustpath. | |
819 | ||
820 | Releases have also been authorized to be performed by Todd Lyons who signs with | |
821 | key 0xC4F4F94804D29EBA. A direct trust path exists between previous RE Phil | |
822 | Pennock and Todd Lyons through a common associate. | |
823 | ||
824 | The signatures for the tar bundles are in: | |
825 | ||
826 | exim-n.nn.tar.gz.asc | |
827 | exim-n.nn.tar.bz2.asc | |
828 | ||
829 | For each released version, the log of changes is made separately available in a | |
830 | separate file in the directory ChangeLogs so that it is possible to find out | |
831 | what has changed without having to download the entire distribution. | |
832 | ||
833 | The main distribution contains ASCII versions of this specification and other | |
834 | documentation; other formats of the documents are available in separate files | |
835 | inside the exim4 directory of the FTP site: | |
836 | ||
837 | exim-html-n.nn.tar.gz | |
838 | exim-pdf-n.nn.tar.gz | |
839 | exim-postscript-n.nn.tar.gz | |
840 | exim-texinfo-n.nn.tar.gz | |
841 | ||
842 | These tar files contain only the doc directory, not the complete distribution, | |
843 | and are also available in .bz2 as well as .gz forms. | |
844 | ||
845 | ||
846 | 1.7 Limitations | |
847 | --------------- | |
848 | ||
849 | * Exim is designed for use as an Internet MTA, and therefore handles | |
850 | addresses in RFC 2822 domain format only. It cannot handle UUCP "bang | |
851 | paths", though simple two-component bang paths can be converted by a | |
852 | straightforward rewriting configuration. This restriction does not prevent | |
853 | Exim from being interfaced to UUCP as a transport mechanism, provided that | |
854 | domain addresses are used. | |
855 | ||
856 | * Exim insists that every address it handles has a domain attached. For | |
857 | incoming local messages, domainless addresses are automatically qualified | |
858 | with a configured domain value. Configuration options specify from which | |
859 | remote systems unqualified addresses are acceptable. These are then | |
860 | qualified on arrival. | |
861 | ||
862 | * The only external transport mechanisms that are currently implemented are | |
863 | SMTP and LMTP over a TCP/IP network (including support for IPv6). However, | |
864 | a pipe transport is available, and there are facilities for writing | |
865 | messages to files and pipes, optionally in batched SMTP format; these | |
866 | facilities can be used to send messages to other transport mechanisms such | |
867 | as UUCP, provided they can handle domain-style addresses. Batched SMTP | |
868 | input is also catered for. | |
869 | ||
870 | * Exim is not designed for storing mail for dial-in hosts. When the volumes | |
871 | of such mail are large, it is better to get the messages "delivered" into | |
872 | files (that is, off Exim's queue) and subsequently passed on to the dial-in | |
873 | hosts by other means. | |
874 | ||
875 | * Although Exim does have basic facilities for scanning incoming messages, | |
876 | these are not comprehensive enough to do full virus or spam scanning. Such | |
877 | operations are best carried out using additional specialized software | |
878 | packages. If you compile Exim with the content-scanning extension, | |
879 | straightforward interfaces to a number of common scanners are provided. | |
880 | ||
881 | ||
882 | 1.8 Run time configuration | |
883 | -------------------------- | |
884 | ||
885 | Exim's run time configuration is held in a single text file that is divided | |
886 | into a number of sections. The entries in this file consist of keywords and | |
887 | values, in the style of Smail 3 configuration files. A default configuration | |
888 | file which is suitable for simple online installations is provided in the | |
889 | distribution, and is described in chapter 7 below. | |
890 | ||
891 | ||
892 | 1.9 Calling interface | |
893 | --------------------- | |
894 | ||
895 | Like many MTAs, Exim has adopted the Sendmail command line interface so that it | |
896 | can be a straight replacement for /usr/lib/sendmail or /usr/sbin/sendmail when | |
897 | sending mail, but you do not need to know anything about Sendmail in order to | |
898 | run Exim. For actions other than sending messages, Sendmail-compatible options | |
899 | also exist, but those that produce output (for example, -bp, which lists the | |
900 | messages on the queue) do so in Exim's own format. There are also some | |
901 | additional options that are compatible with Smail 3, and some further options | |
902 | that are new to Exim. Chapter 5 documents all Exim's command line options. This | |
903 | information is automatically made into the man page that forms part of the Exim | |
904 | distribution. | |
905 | ||
906 | Control of messages on the queue can be done via certain privileged command | |
907 | line options. There is also an optional monitor program called eximon, which | |
908 | displays current information in an X window, and which contains a menu | |
909 | interface to Exim's command line administration options. | |
910 | ||
911 | ||
912 | 1.10 Terminology | |
913 | ---------------- | |
914 | ||
915 | The body of a message is the actual data that the sender wants to transmit. It | |
916 | is the last part of a message, and is separated from the header (see below) by | |
917 | a blank line. | |
918 | ||
919 | When a message cannot be delivered, it is normally returned to the sender in a | |
920 | delivery failure message or a "non-delivery report" (NDR). The term bounce is | |
921 | commonly used for this action, and the error reports are often called bounce | |
922 | messages. This is a convenient shorthand for "delivery failure error report". | |
923 | Such messages have an empty sender address in the message's envelope (see | |
924 | below) to ensure that they cannot themselves give rise to further bounce | |
925 | messages. | |
926 | ||
927 | The term default appears frequently in this manual. It is used to qualify a | |
928 | value which is used in the absence of any setting in the configuration. It may | |
929 | also qualify an action which is taken unless a configuration setting specifies | |
930 | otherwise. | |
931 | ||
932 | The term defer is used when the delivery of a message to a specific destination | |
933 | cannot immediately take place for some reason (a remote host may be down, or a | |
934 | user's local mailbox may be full). Such deliveries are deferred until a later | |
935 | time. | |
936 | ||
937 | The word domain is sometimes used to mean all but the first component of a | |
938 | host's name. It is not used in that sense here, where it normally refers to the | |
939 | part of an email address following the @ sign. | |
940 | ||
941 | A message in transit has an associated envelope, as well as a header and a | |
942 | body. The envelope contains a sender address (to which bounce messages should | |
943 | be delivered), and any number of recipient addresses. References to the sender | |
944 | or the recipients of a message usually mean the addresses in the envelope. An | |
945 | MTA uses these addresses for delivery, and for returning bounce messages, not | |
946 | the addresses that appear in the header lines. | |
947 | ||
948 | The header of a message is the first part of a message's text, consisting of a | |
949 | number of lines, each of which has a name such as From:, To:, Subject:, etc. | |
950 | Long header lines can be split over several text lines by indenting the | |
951 | continuations. The header is separated from the body by a blank line. | |
952 | ||
953 | The term local part, which is taken from RFC 2822, is used to refer to that | |
954 | part of an email address that precedes the @ sign. The part that follows the @ | |
955 | sign is called the domain or mail domain. | |
956 | ||
957 | The terms local delivery and remote delivery are used to distinguish delivery | |
958 | to a file or a pipe on the local host from delivery by SMTP over TCP/IP to | |
959 | another host. As far as Exim is concerned, all hosts other than the host it is | |
960 | running on are remote. | |
961 | ||
962 | Return path is another name that is used for the sender address in a message's | |
963 | envelope. | |
964 | ||
965 | The term queue is used to refer to the set of messages awaiting delivery, | |
966 | because this term is in widespread use in the context of MTAs. However, in | |
967 | Exim's case the reality is more like a pool than a queue, because there is | |
968 | normally no ordering of waiting messages. | |
969 | ||
970 | The term queue runner is used to describe a process that scans the queue and | |
971 | attempts to deliver those messages whose retry times have come. This term is | |
972 | used by other MTAs, and also relates to the command runq, but in Exim the | |
973 | waiting messages are normally processed in an unpredictable order. | |
974 | ||
975 | The term spool directory is used for a directory in which Exim keeps the | |
976 | messages on its queue - that is, those that it is in the process of delivering. | |
977 | This should not be confused with the directory in which local mailboxes are | |
978 | stored, which is called a "spool directory" by some people. In the Exim | |
979 | documentation, "spool" is always used in the first sense. | |
980 | ||
981 | ||
982 | ||
983 | =============================================================================== | |
984 | 2. INCORPORATED CODE | |
985 | ||
986 | A number of pieces of external code are included in the Exim distribution. | |
987 | ||
988 | * Regular expressions are supported in the main Exim program and in the Exim | |
989 | monitor using the freely-distributable PCRE library, copyright (c) | |
990 | University of Cambridge. The source to PCRE is no longer shipped with Exim, | |
991 | so you will need to use the version of PCRE shipped with your system, or | |
992 | obtain and install the full version of the library from ftp:// | |
993 | ftp.csx.cam.ac.uk/pub/software/programming/pcre. | |
994 | ||
995 | * Support for the cdb (Constant DataBase) lookup method is provided by code | |
996 | contributed by Nigel Metheringham of (at the time he contributed it) Planet | |
997 | Online Ltd. The implementation is completely contained within the code of | |
998 | Exim. It does not link against an external cdb library. The code contains | |
999 | the following statements: | |
1000 | ||
1001 | Copyright (c) 1998 Nigel Metheringham, Planet Online Ltd | |
1002 | ||
1003 | This program is free software; you can redistribute it and/or modify it | |
1004 | under the terms of the GNU General Public License as published by the | |
1005 | Free Software Foundation; either version 2 of the License, or (at your | |
1006 | option) any later version. This code implements Dan Bernstein's | |
1007 | Constant DataBase (cdb) spec. Information, the spec and sample code for | |
1008 | cdb can be obtained from http://www.pobox.com/~djb/cdb.html. This | |
1009 | implementation borrows some code from Dan Bernstein's implementation | |
1010 | (which has no license restrictions applied to it). | |
1011 | ||
1012 | * Client support for Microsoft's Secure Password Authentication is provided | |
1013 | by code contributed by Marc Prud'hommeaux. Server support was contributed | |
1014 | by Tom Kistner. This includes code taken from the Samba project, which is | |
1015 | released under the Gnu GPL. | |
1016 | ||
1017 | * Support for calling the Cyrus pwcheck and saslauthd daemons is provided by | |
1018 | code taken from the Cyrus-SASL library and adapted by Alexander S. | |
1019 | Sabourenkov. The permission notice appears below, in accordance with the | |
1020 | conditions expressed therein. | |
1021 | ||
1022 | Copyright (c) 2001 Carnegie Mellon University. All rights reserved. | |
1023 | ||
1024 | Redistribution and use in source and binary forms, with or without | |
1025 | modification, are permitted provided that the following conditions are | |
1026 | met: | |
1027 | ||
1028 | 1. Redistributions of source code must retain the above copyright | |
1029 | notice, this list of conditions and the following disclaimer. | |
1030 | ||
1031 | 2. Redistributions in binary form must reproduce the above copyright | |
1032 | notice, this list of conditions and the following disclaimer in the | |
1033 | documentation and/or other materials provided with the | |
1034 | distribution. | |
1035 | ||
1036 | 3. The name "Carnegie Mellon University" must not be used to endorse | |
1037 | or promote products derived from this software without prior | |
1038 | written permission. For permission or any other legal details, | |
1039 | please contact | |
1040 | ||
1041 | Office of Technology Transfer | |
1042 | Carnegie Mellon University | |
1043 | 5000 Forbes Avenue | |
1044 | Pittsburgh, PA 15213-3890 | |
1045 | (412) 268-4387, fax: (412) 268-7395 | |
1046 | tech-transfer@andrew.cmu.edu | |
1047 | ||
1048 | 4. Redistributions of any form whatsoever must retain the following | |
1049 | acknowledgment: | |
1050 | ||
1051 | "This product includes software developed by Computing Services at | |
1052 | Carnegie Mellon University (http://www.cmu.edu/computing/." | |
1053 | ||
1054 | CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO | |
1055 | THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY | |
1056 | AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE | |
1057 | FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES | |
1058 | WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN | |
1059 | AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING | |
1060 | OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS | |
1061 | SOFTWARE. | |
1062 | ||
1063 | * The Exim Monitor program, which is an X-Window application, includes | |
1064 | modified versions of the Athena StripChart and TextPop widgets. This code | |
1065 | is copyright by DEC and MIT, and their permission notice appears below, in | |
1066 | accordance with the conditions expressed therein. | |
1067 | ||
1068 | Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, | |
1069 | Massachusetts, and the Massachusetts Institute of Technology, | |
1070 | Cambridge, Massachusetts. | |
1071 | ||
1072 | All Rights Reserved | |
1073 | ||
1074 | Permission to use, copy, modify, and distribute this software and its | |
1075 | documentation for any purpose and without fee is hereby granted, | |
1076 | provided that the above copyright notice appear in all copies and that | |
1077 | both that copyright notice and this permission notice appear in | |
1078 | supporting documentation, and that the names of Digital or MIT not be | |
1079 | used in advertising or publicity pertaining to distribution of the | |
1080 | software without specific, written prior permission. | |
1081 | ||
1082 | DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, | |
1083 | INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO | |
1084 | EVENT SHALL DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR | |
1085 | CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF | |
1086 | USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR | |
1087 | OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR | |
1088 | PERFORMANCE OF THIS SOFTWARE. | |
1089 | ||
1090 | * The DMARC implementation uses the OpenDMARC library which is Copyrighted by | |
1091 | The Trusted Domain Project. Portions of Exim source which use OpenDMARC | |
1092 | derived code are indicated in the respective source files. The full | |
1093 | OpenDMARC license is provided in the LICENSE.opendmarc file contained in | |
1094 | the distributed source code. | |
1095 | ||
1096 | * Many people have contributed code fragments, some large, some small, that | |
1097 | were not covered by any specific licence requirements. It is assumed that | |
1098 | the contributors are happy to see their code incorporated into Exim under | |
1099 | the GPL. | |
1100 | ||
1101 | ||
1102 | ||
1103 | =============================================================================== | |
1104 | 3. HOW EXIM RECEIVES AND DELIVERS MAIL | |
1105 | ||
1106 | ||
1107 | 3.1 Overall philosophy | |
1108 | ---------------------- | |
1109 | ||
1110 | Exim is designed to work efficiently on systems that are permanently connected | |
1111 | to the Internet and are handling a general mix of mail. In such circumstances, | |
1112 | most messages can be delivered immediately. Consequently, Exim does not | |
1113 | maintain independent queues of messages for specific domains or hosts, though | |
1114 | it does try to send several messages in a single SMTP connection after a host | |
1115 | has been down, and it also maintains per-host retry information. | |
1116 | ||
1117 | ||
1118 | 3.2 Policy control | |
1119 | ------------------ | |
1120 | ||
1121 | Policy controls are now an important feature of MTAs that are connected to the | |
1122 | Internet. Perhaps their most important job is to stop MTAs being abused as | |
1123 | "open relays" by misguided individuals who send out vast amounts of unsolicited | |
1124 | junk, and want to disguise its source. Exim provides flexible facilities for | |
1125 | specifying policy controls on incoming mail: | |
1126 | ||
1127 | * Exim 4 (unlike previous versions of Exim) implements policy controls on | |
1128 | incoming mail by means of Access Control Lists (ACLs). Each list is a | |
1129 | series of statements that may either grant or deny access. ACLs can be used | |
1130 | at several places in the SMTP dialogue while receiving a message from a | |
1131 | remote host. However, the most common places are after each RCPT command, | |
1132 | and at the very end of the message. The sysadmin can specify conditions for | |
1133 | accepting or rejecting individual recipients or the entire message, | |
1134 | respectively, at these two points (see chapter 42). Denial of access | |
1135 | results in an SMTP error code. | |
1136 | ||
1137 | * An ACL is also available for locally generated, non-SMTP messages. In this | |
1138 | case, the only available actions are to accept or deny the entire message. | |
1139 | ||
1140 | * When Exim is compiled with the content-scanning extension, facilities are | |
1141 | provided in the ACL mechanism for passing the message to external virus and | |
1142 | /or spam scanning software. The result of such a scan is passed back to the | |
1143 | ACL, which can then use it to decide what to do with the message. | |
1144 | ||
1145 | * When a message has been received, either from a remote host or from the | |
1146 | local host, but before the final acknowledgment has been sent, a locally | |
1147 | supplied C function called local_scan() can be run to inspect the message | |
1148 | and decide whether to accept it or not (see chapter 44). If the message is | |
1149 | accepted, the list of recipients can be modified by the function. | |
1150 | ||
1151 | * Using the local_scan() mechanism is another way of calling external scanner | |
1152 | software. The SA-Exim add-on package works this way. It does not require | |
1153 | Exim to be compiled with the content-scanning extension. | |
1154 | ||
1155 | * After a message has been accepted, a further checking mechanism is | |
1156 | available in the form of the system filter (see chapter 45). This runs at | |
1157 | the start of every delivery process. | |
1158 | ||
1159 | ||
1160 | 3.3 User filters | |
1161 | ---------------- | |
1162 | ||
1163 | In a conventional Exim configuration, users are able to run private filters by | |
1164 | setting up appropriate .forward files in their home directories. See chapter 22 | |
1165 | (about the redirect router) for the configuration needed to support this, and | |
1166 | the separate document entitled Exim's interfaces to mail filtering for user | |
1167 | details. Two different kinds of filtering are available: | |
1168 | ||
1169 | * Sieve filters are written in the standard filtering language that is | |
1170 | defined by RFC 3028. | |
1171 | ||
1172 | * Exim filters are written in a syntax that is unique to Exim, but which is | |
1173 | more powerful than Sieve, which it pre-dates. | |
1174 | ||
1175 | User filters are run as part of the routing process, described below. | |
1176 | ||
1177 | ||
1178 | 3.4 Message identification | |
1179 | -------------------------- | |
1180 | ||
1181 | Every message handled by Exim is given a message id which is sixteen characters | |
1182 | long. It is divided into three parts, separated by hyphens, for example | |
1183 | "16VDhn-0001bo-D3". Each part is a sequence of letters and digits, normally | |
1184 | encoding numbers in base 62. However, in the Darwin operating system (Mac OS X) | |
1185 | and when Exim is compiled to run under Cygwin, base 36 (avoiding the use of | |
1186 | lower case letters) is used instead, because the message id is used to | |
1187 | construct file names, and the names of files in those systems are not always | |
1188 | case-sensitive. | |
1189 | ||
1190 | The detail of the contents of the message id have changed as Exim has evolved. | |
1191 | Earlier versions relied on the operating system not re-using a process id (pid) | |
1192 | within one second. On modern operating systems, this assumption can no longer | |
1193 | be made, so the algorithm had to be changed. To retain backward compatibility, | |
1194 | the format of the message id was retained, which is why the following rules are | |
1195 | somewhat eccentric: | |
1196 | ||
1197 | * The first six characters of the message id are the time at which the | |
1198 | message started to be received, to a granularity of one second. That is, | |
1199 | this field contains the number of seconds since the start of the epoch (the | |
1200 | normal Unix way of representing the date and time of day). | |
1201 | ||
1202 | * After the first hyphen, the next six characters are the id of the process | |
1203 | that received the message. | |
1204 | ||
1205 | * There are two different possibilities for the final two characters: | |
1206 | ||
1207 | 1. If localhost_number is not set, this value is the fractional part of | |
1208 | the time of reception, normally in units of 1/2000 of a second, but for | |
1209 | systems that must use base 36 instead of base 62 (because of | |
1210 | case-insensitive file systems), the units are 1/1000 of a second. | |
1211 | ||
1212 | 2. If localhost_number is set, it is multiplied by 200 (100) and added to | |
1213 | the fractional part of the time, which in this case is in units of 1/ | |
1214 | 200 (1/100) of a second. | |
1215 | ||
1216 | After a message has been received, Exim waits for the clock to tick at the | |
1217 | appropriate resolution before proceeding, so that if another message is | |
1218 | received by the same process, or by another process with the same (re-used) | |
1219 | pid, it is guaranteed that the time will be different. In most cases, the clock | |
1220 | will already have ticked while the message was being received. | |
1221 | ||
1222 | ||
1223 | 3.5 Receiving mail | |
1224 | ------------------ | |
1225 | ||
1226 | The only way Exim can receive mail from another host is using SMTP over TCP/IP, | |
1227 | in which case the sender and recipient addresses are transferred using SMTP | |
1228 | commands. However, from a locally running process (such as a user's MUA), there | |
1229 | are several possibilities: | |
1230 | ||
1231 | * If the process runs Exim with the -bm option, the message is read | |
1232 | non-interactively (usually via a pipe), with the recipients taken from the | |
1233 | command line, or from the body of the message if -t is also used. | |
1234 | ||
1235 | * If the process runs Exim with the -bS option, the message is also read | |
1236 | non-interactively, but in this case the recipients are listed at the start | |
1237 | of the message in a series of SMTP RCPT commands, terminated by a DATA | |
1238 | command. This is so-called "batch SMTP" format, but it isn't really SMTP. | |
1239 | The SMTP commands are just another way of passing envelope addresses in a | |
1240 | non-interactive submission. | |
1241 | ||
1242 | * If the process runs Exim with the -bs option, the message is read | |
1243 | interactively, using the SMTP protocol. A two-way pipe is normally used for | |
1244 | passing data between the local process and the Exim process. This is "real" | |
1245 | SMTP and is handled in the same way as SMTP over TCP/IP. For example, the | |
1246 | ACLs for SMTP commands are used for this form of submission. | |
1247 | ||
1248 | * A local process may also make a TCP/IP call to the host's loopback address | |
1249 | (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim | |
1250 | does not treat the loopback address specially. It treats all such | |
1251 | connections in the same way as connections from other hosts. | |
1252 | ||
1253 | In the three cases that do not involve TCP/IP, the sender address is | |
1254 | constructed from the login name of the user that called Exim and a default | |
1255 | qualification domain (which can be set by the qualify_domain configuration | |
1256 | option). For local or batch SMTP, a sender address that is passed using the | |
1257 | SMTP MAIL command is ignored. However, the system administrator may allow | |
1258 | certain users ("trusted users") to specify a different sender address | |
1259 | unconditionally, or all users to specify certain forms of different sender | |
1260 | address. The -f option or the SMTP MAIL command is used to specify these | |
1261 | different addresses. See section 5.2 for details of trusted users, and the | |
1262 | untrusted_set_sender option for a way of allowing untrusted users to change | |
1263 | sender addresses. | |
1264 | ||
1265 | Messages received by either of the non-interactive mechanisms are subject to | |
1266 | checking by the non-SMTP ACL, if one is defined. Messages received using SMTP | |
1267 | (either over TCP/IP, or interacting with a local process) can be checked by a | |
1268 | number of ACLs that operate at different times during the SMTP session. Either | |
1269 | individual recipients, or the entire message, can be rejected if local policy | |
1270 | requirements are not met. The local_scan() function (see chapter 44) is run for | |
1271 | all incoming messages. | |
1272 | ||
1273 | Exim can be configured not to start a delivery process when a message is | |
1274 | received; this can be unconditional, or depend on the number of incoming SMTP | |
1275 | connections or the system load. In these situations, new messages wait on the | |
1276 | queue until a queue runner process picks them up. However, in standard | |
1277 | configurations under normal conditions, delivery is started as soon as a | |
1278 | message is received. | |
1279 | ||
1280 | ||
1281 | 3.6 Handling an incoming message | |
1282 | -------------------------------- | |
1283 | ||
1284 | When Exim accepts a message, it writes two files in its spool directory. The | |
1285 | first contains the envelope information, the current status of the message, and | |
1286 | the header lines, and the second contains the body of the message. The names of | |
1287 | the two spool files consist of the message id, followed by "-H" for the file | |
1288 | containing the envelope and header, and "-D" for the data file. | |
1289 | ||
1290 | By default all these message files are held in a single directory called input | |
1291 | inside the general Exim spool directory. Some operating systems do not perform | |
1292 | very well if the number of files in a directory gets large; to improve | |
1293 | performance in such cases, the split_spool_directory option can be used. This | |
1294 | causes Exim to split up the input files into 62 sub-directories whose names are | |
1295 | single letters or digits. When this is done, the queue is processed one | |
1296 | sub-directory at a time instead of all at once, which can improve overall | |
1297 | performance even when there are not enough files in each directory to affect | |
1298 | file system performance. | |
1299 | ||
1300 | The envelope information consists of the address of the message's sender and | |
1301 | the addresses of the recipients. This information is entirely separate from any | |
1302 | addresses contained in the header lines. The status of the message includes a | |
1303 | list of recipients who have already received the message. The format of the | |
1304 | first spool file is described in chapter 55. | |
1305 | ||
1306 | Address rewriting that is specified in the rewrite section of the configuration | |
1307 | (see chapter 31) is done once and for all on incoming addresses, both in the | |
1308 | header lines and the envelope, at the time the message is accepted. If during | |
1309 | the course of delivery additional addresses are generated (for example, via | |
1310 | aliasing), these new addresses are rewritten as soon as they are generated. At | |
1311 | the time a message is actually delivered (transported) further rewriting can | |
1312 | take place; because this is a transport option, it can be different for | |
1313 | different forms of delivery. It is also possible to specify the addition or | |
1314 | removal of certain header lines at the time the message is delivered (see | |
1315 | chapters 15 and 24). | |
1316 | ||
1317 | ||
1318 | 3.7 Life of a message | |
1319 | --------------------- | |
1320 | ||
1321 | A message remains in the spool directory until it is completely delivered to | |
1322 | its recipients or to an error address, or until it is deleted by an | |
1323 | administrator or by the user who originally created it. In cases when delivery | |
1324 | cannot proceed - for example, when a message can neither be delivered to its | |
1325 | recipients nor returned to its sender, the message is marked "frozen" on the | |
1326 | spool, and no more deliveries are attempted. | |
1327 | ||
1328 | An administrator can "thaw" such messages when the problem has been corrected, | |
1329 | and can also freeze individual messages by hand if necessary. In addition, an | |
1330 | administrator can force a delivery error, causing a bounce message to be sent. | |
1331 | ||
1332 | There are options called ignore_bounce_errors_after and timeout_frozen_after, | |
1333 | which discard frozen messages after a certain time. The first applies only to | |
1334 | frozen bounces, the second to any frozen messages. | |
1335 | ||
1336 | While Exim is working on a message, it writes information about each delivery | |
1337 | attempt to its main log file. This includes successful, unsuccessful, and | |
1338 | delayed deliveries for each recipient (see chapter 51). The log lines are also | |
1339 | written to a separate message log file for each message. These logs are solely | |
1340 | for the benefit of the administrator, and are normally deleted along with the | |
1341 | spool files when processing of a message is complete. The use of individual | |
1342 | message logs can be disabled by setting no_message_logs; this might give an | |
1343 | improvement in performance on very busy systems. | |
1344 | ||
1345 | All the information Exim itself needs to set up a delivery is kept in the first | |
1346 | spool file, along with the header lines. When a successful delivery occurs, the | |
1347 | address is immediately written at the end of a journal file, whose name is the | |
1348 | message id followed by "-J". At the end of a delivery run, if there are some | |
1349 | addresses left to be tried again later, the first spool file (the "-H" file) is | |
1350 | updated to indicate which these are, and the journal file is then deleted. | |
1351 | Updating the spool file is done by writing a new file and renaming it, to | |
1352 | minimize the possibility of data loss. | |
1353 | ||
1354 | Should the system or the program crash after a successful delivery but before | |
1355 | the spool file has been updated, the journal is left lying around. The next | |
1356 | time Exim attempts to deliver the message, it reads the journal file and | |
1357 | updates the spool file before proceeding. This minimizes the chances of double | |
1358 | deliveries caused by crashes. | |
1359 | ||
1360 | ||
1361 | 3.8 Processing an address for delivery | |
1362 | -------------------------------------- | |
1363 | ||
1364 | The main delivery processing elements of Exim are called routers and transports | |
1365 | , and collectively these are known as drivers. Code for a number of them is | |
1366 | provided in the source distribution, and compile-time options specify which | |
1367 | ones are included in the binary. Run time options specify which ones are | |
1368 | actually used for delivering messages. | |
1369 | ||
1370 | Each driver that is specified in the run time configuration is an instance of | |
1371 | that particular driver type. Multiple instances are allowed; for example, you | |
1372 | can set up several different smtp transports, each with different option values | |
1373 | that might specify different ports or different timeouts. Each instance has its | |
1374 | own identifying name. In what follows we will normally use the instance name | |
1375 | when discussing one particular instance (that is, one specific configuration of | |
1376 | the driver), and the generic driver name when discussing the driver's features | |
1377 | in general. | |
1378 | ||
1379 | A router is a driver that operates on an address, either determining how its | |
1380 | delivery should happen, by assigning it to a specific transport, or converting | |
1381 | the address into one or more new addresses (for example, via an alias file). A | |
1382 | router may also explicitly choose to fail an address, causing it to be bounced. | |
1383 | ||
1384 | A transport is a driver that transmits a copy of the message from Exim's spool | |
1385 | to some destination. There are two kinds of transport: for a local transport, | |
1386 | the destination is a file or a pipe on the local host, whereas for a remote | |
1387 | transport the destination is some other host. A message is passed to a specific | |
1388 | transport as a result of successful routing. If a message has several | |
1389 | recipients, it may be passed to a number of different transports. | |
1390 | ||
1391 | An address is processed by passing it to each configured router instance in | |
1392 | turn, subject to certain preconditions, until a router accepts the address or | |
1393 | specifies that it should be bounced. We will describe this process in more | |
1394 | detail shortly. First, as a simple example, we consider how each recipient | |
1395 | address in a message is processed in a small configuration of three routers. | |
1396 | ||
1397 | To make this a more concrete example, it is described in terms of some actual | |
1398 | routers, but remember, this is only an example. You can configure Exim's | |
1399 | routers in many different ways, and there may be any number of routers in a | |
1400 | configuration. | |
1401 | ||
1402 | The first router that is specified in a configuration is often one that handles | |
1403 | addresses in domains that are not recognized specially by the local host. These | |
1404 | are typically addresses for arbitrary domains on the Internet. A precondition | |
1405 | is set up which looks for the special domains known to the host (for example, | |
1406 | its own domain name), and the router is run for addresses that do not match. | |
1407 | Typically, this is a router that looks up domains in the DNS in order to find | |
1408 | the hosts to which this address routes. If it succeeds, the address is assigned | |
1409 | to a suitable SMTP transport; if it does not succeed, the router is configured | |
1410 | to fail the address. | |
1411 | ||
1412 | The second router is reached only when the domain is recognized as one that | |
1413 | "belongs" to the local host. This router does redirection - also known as | |
1414 | aliasing and forwarding. When it generates one or more new addresses from the | |
1415 | original, each of them is routed independently from the start. Otherwise, the | |
1416 | router may cause an address to fail, or it may simply decline to handle the | |
1417 | address, in which case the address is passed to the next router. | |
1418 | ||
1419 | The final router in many configurations is one that checks to see if the | |
1420 | address belongs to a local mailbox. The precondition may involve a check to see | |
1421 | if the local part is the name of a login account, or it may look up the local | |
1422 | part in a file or a database. If its preconditions are not met, or if the | |
1423 | router declines, we have reached the end of the routers. When this happens, the | |
1424 | address is bounced. | |
1425 | ||
1426 | ||
1427 | 3.9 Processing an address for verification | |
1428 | ------------------------------------------ | |
1429 | ||
1430 | As well as being used to decide how to deliver to an address, Exim's routers | |
1431 | are also used for address verification. Verification can be requested as one of | |
1432 | the checks to be performed in an ACL for incoming messages, on both sender and | |
1433 | recipient addresses, and it can be tested using the -bv and -bvs command line | |
1434 | options. | |
1435 | ||
1436 | When an address is being verified, the routers are run in "verify mode". This | |
1437 | does not affect the way the routers work, but it is a state that can be | |
1438 | detected. By this means, a router can be skipped or made to behave differently | |
1439 | when verifying. A common example is a configuration in which the first router | |
1440 | sends all messages to a message-scanning program, unless they have been | |
1441 | previously scanned. Thus, the first router accepts all addresses without any | |
1442 | checking, making it useless for verifying. Normally, the no_verify option would | |
1443 | be set for such a router, causing it to be skipped in verify mode. | |
1444 | ||
1445 | ||
1446 | 3.10 Running an individual router | |
1447 | --------------------------------- | |
1448 | ||
1449 | As explained in the example above, a number of preconditions are checked before | |
1450 | running a router. If any are not met, the router is skipped, and the address is | |
1451 | passed to the next router. When all the preconditions on a router are met, the | |
1452 | router is run. What happens next depends on the outcome, which is one of the | |
1453 | following: | |
1454 | ||
1455 | * accept: The router accepts the address, and either assigns it to a | |
1456 | transport, or generates one or more "child" addresses. Processing the | |
1457 | original address ceases, unless the unseen option is set on the router. | |
1458 | This option can be used to set up multiple deliveries with different | |
1459 | routing (for example, for keeping archive copies of messages). When unseen | |
1460 | is set, the address is passed to the next router. Normally, however, an | |
1461 | accept return marks the end of routing. | |
1462 | ||
1463 | Any child addresses generated by the router are processed independently, | |
1464 | starting with the first router by default. It is possible to change this by | |
1465 | setting the redirect_router option to specify which router to start at for | |
1466 | child addresses. Unlike pass_router (see below) the router specified by | |
1467 | redirect_router may be anywhere in the router configuration. | |
1468 | ||
1469 | * pass: The router recognizes the address, but cannot handle it itself. It | |
1470 | requests that the address be passed to another router. By default the | |
1471 | address is passed to the next router, but this can be changed by setting | |
1472 | the pass_router option. However, (unlike redirect_router) the named router | |
1473 | must be below the current router (to avoid loops). | |
1474 | ||
1475 | * decline: The router declines to accept the address because it does not | |
1476 | recognize it at all. By default, the address is passed to the next router, | |
1477 | but this can be prevented by setting the no_more option. When no_more is | |
1478 | set, all the remaining routers are skipped. In effect, no_more converts | |
1479 | decline into fail. | |
1480 | ||
1481 | * fail: The router determines that the address should fail, and queues it for | |
1482 | the generation of a bounce message. There is no further processing of the | |
1483 | original address unless unseen is set on the router. | |
1484 | ||
1485 | * defer: The router cannot handle the address at the present time. (A | |
1486 | database may be offline, or a DNS lookup may have timed out.) No further | |
1487 | processing of the address happens in this delivery attempt. It is tried | |
1488 | again next time the message is considered for delivery. | |
1489 | ||
1490 | * error: There is some error in the router (for example, a syntax error in | |
1491 | its configuration). The action is as for defer. | |
1492 | ||
1493 | If an address reaches the end of the routers without having been accepted by | |
1494 | any of them, it is bounced as unrouteable. The default error message in this | |
1495 | situation is "unrouteable address", but you can set your own message by making | |
1496 | use of the cannot_route_message option. This can be set for any router; the | |
1497 | value from the last router that "saw" the address is used. | |
1498 | ||
1499 | Sometimes while routing you want to fail a delivery when some conditions are | |
1500 | met but others are not, instead of passing the address on for further routing. | |
1501 | You can do this by having a second router that explicitly fails the delivery | |
1502 | when the relevant conditions are met. The redirect router has a "fail" facility | |
1503 | for this purpose. | |
1504 | ||
1505 | ||
1506 | 3.11 Duplicate addresses | |
1507 | ------------------------ | |
1508 | ||
1509 | Once routing is complete, Exim scans the addresses that are assigned to local | |
1510 | and remote transports, and discards any duplicates that it finds. During this | |
1511 | check, local parts are treated as case-sensitive. This happens only when | |
1512 | actually delivering a message; when testing routers with -bt, all the routed | |
1513 | addresses are shown. | |
1514 | ||
1515 | ||
1516 | 3.12 Router preconditions | |
1517 | ------------------------- | |
1518 | ||
1519 | The preconditions that are tested for each router are listed below, in the | |
1520 | order in which they are tested. The individual configuration options are | |
1521 | described in more detail in chapter 15. | |
1522 | ||
1523 | * The local_part_prefix and local_part_suffix options can specify that the | |
1524 | local parts handled by the router may or must have certain prefixes and/or | |
1525 | suffixes. If a mandatory affix (prefix or suffix) is not present, the | |
1526 | router is skipped. These conditions are tested first. When an affix is | |
1527 | present, it is removed from the local part before further processing, | |
1528 | including the evaluation of any other conditions. | |
1529 | ||
1530 | * Routers can be designated for use only when not verifying an address, that | |
1531 | is, only when routing it for delivery (or testing its delivery routing). If | |
1532 | the verify option is set false, the router is skipped when Exim is | |
1533 | verifying an address. Setting the verify option actually sets two options, | |
1534 | verify_sender and verify_recipient, which independently control the use of | |
1535 | the router for sender and recipient verification. You can set these options | |
1536 | directly if you want a router to be used for only one type of verification. | |
1537 | Note that cutthrough delivery is classed as a recipient verification for | |
1538 | this purpose. | |
1539 | ||
1540 | * If the address_test option is set false, the router is skipped when Exim is | |
1541 | run with the -bt option to test an address routing. This can be helpful | |
1542 | when the first router sends all new messages to a scanner of some sort; it | |
1543 | makes it possible to use -bt to test subsequent delivery routing without | |
1544 | having to simulate the effect of the scanner. | |
1545 | ||
1546 | * Routers can be designated for use only when verifying an address, as | |
1547 | opposed to routing it for delivery. The verify_only option controls this. | |
1548 | Again, cutthrough delivery counts as a verification. | |
1549 | ||
1550 | * Individual routers can be explicitly skipped when running the routers to | |
1551 | check an address given in the SMTP EXPN command (see the expn option). | |
1552 | ||
1553 | * If the domains option is set, the domain of the address must be in the set | |
1554 | of domains that it defines. | |
1555 | ||
1556 | * If the local_parts option is set, the local part of the address must be in | |
1557 | the set of local parts that it defines. If local_part_prefix or | |
1558 | local_part_suffix is in use, the prefix or suffix is removed from the local | |
1559 | part before this check. If you want to do precondition tests on local parts | |
1560 | that include affixes, you can do so by using a condition option (see below) | |
1561 | that uses the variables $local_part, $local_part_prefix, and | |
1562 | $local_part_suffix as necessary. | |
1563 | ||
1564 | * If the check_local_user option is set, the local part must be the name of | |
1565 | an account on the local host. If this check succeeds, the uid and gid of | |
1566 | the local user are placed in $local_user_uid and $local_user_gid and the | |
1567 | user's home directory is placed in $home; these values can be used in the | |
1568 | remaining preconditions. | |
1569 | ||
1570 | * If the router_home_directory option is set, it is expanded at this point, | |
1571 | because it overrides the value of $home. If this expansion were left till | |
1572 | later, the value of $home as set by check_local_user would be used in | |
1573 | subsequent tests. Having two different values of $home in the same router | |
1574 | could lead to confusion. | |
1575 | ||
1576 | * If the senders option is set, the envelope sender address must be in the | |
1577 | set of addresses that it defines. | |
1578 | ||
1579 | * If the require_files option is set, the existence or non-existence of | |
1580 | specified files is tested. | |
1581 | ||
1582 | * If the condition option is set, it is evaluated and tested. This option | |
1583 | uses an expanded string to allow you to set up your own custom | |
1584 | preconditions. Expanded strings are described in chapter 11. | |
1585 | ||
1586 | Note that require_files comes near the end of the list, so you cannot use it to | |
1587 | check for the existence of a file in which to lookup up a domain, local part, | |
1588 | or sender. However, as these options are all expanded, you can use the exists | |
1589 | expansion condition to make such tests within each condition. The require_files | |
1590 | option is intended for checking files that the router may be going to use | |
1591 | internally, or which are needed by a specific transport (for example, | |
1592 | .procmailrc). | |
1593 | ||
1594 | ||
1595 | 3.13 Delivery in detail | |
1596 | ----------------------- | |
1597 | ||
1598 | When a message is to be delivered, the sequence of events is as follows: | |
1599 | ||
1600 | * If a system-wide filter file is specified, the message is passed to it. The | |
1601 | filter may add recipients to the message, replace the recipients, discard | |
1602 | the message, cause a new message to be generated, or cause the message | |
1603 | delivery to fail. The format of the system filter file is the same as for | |
1604 | Exim user filter files, described in the separate document entitled Exim's | |
1605 | interfaces to mail filtering. (Note: Sieve cannot be used for system filter | |
1606 | files.) | |
1607 | ||
1608 | Some additional features are available in system filters - see chapter 45 | |
1609 | for details. Note that a message is passed to the system filter only once | |
1610 | per delivery attempt, however many recipients it has. However, if there are | |
1611 | several delivery attempts because one or more addresses could not be | |
1612 | immediately delivered, the system filter is run each time. The filter | |
1613 | condition first_delivery can be used to detect the first run of the system | |
1614 | filter. | |
1615 | ||
1616 | * Each recipient address is offered to each configured router in turn, | |
1617 | subject to its preconditions, until one is able to handle it. If no router | |
1618 | can handle the address, that is, if they all decline, the address is | |
1619 | failed. Because routers can be targeted at particular domains, several | |
1620 | locally handled domains can be processed entirely independently of each | |
1621 | other. | |
1622 | ||
1623 | * A router that accepts an address may assign it to a local or a remote | |
1624 | transport. However, the transport is not run at this time. Instead, the | |
1625 | address is placed on a list for the particular transport, which will be run | |
1626 | later. Alternatively, the router may generate one or more new addresses | |
1627 | (typically from alias, forward, or filter files). New addresses are fed | |
1628 | back into this process from the top, but in order to avoid loops, a router | |
1629 | ignores any address which has an identically-named ancestor that was | |
1630 | processed by itself. | |
1631 | ||
1632 | * When all the routing has been done, addresses that have been successfully | |
1633 | handled are passed to their assigned transports. When local transports are | |
1634 | doing real local deliveries, they handle only one address at a time, but if | |
1635 | a local transport is being used as a pseudo-remote transport (for example, | |
1636 | to collect batched SMTP messages for transmission by some other means) | |
1637 | multiple addresses can be handled. Remote transports can always handle more | |
1638 | than one address at a time, but can be configured not to do so, or to | |
1639 | restrict multiple addresses to the same domain. | |
1640 | ||
1641 | * Each local delivery to a file or a pipe runs in a separate process under a | |
1642 | non-privileged uid, and these deliveries are run one at a time. Remote | |
1643 | deliveries also run in separate processes, normally under a uid that is | |
1644 | private to Exim ("the Exim user"), but in this case, several remote | |
1645 | deliveries can be run in parallel. The maximum number of simultaneous | |
1646 | remote deliveries for any one message is set by the remote_max_parallel | |
1647 | option. The order in which deliveries are done is not defined, except that | |
1648 | all local deliveries happen before any remote deliveries. | |
1649 | ||
1650 | * When it encounters a local delivery during a queue run, Exim checks its | |
1651 | retry database to see if there has been a previous temporary delivery | |
1652 | failure for the address before running the local transport. If there was a | |
1653 | previous failure, Exim does not attempt a new delivery until the retry time | |
1654 | for the address is reached. However, this happens only for delivery | |
1655 | attempts that are part of a queue run. Local deliveries are always | |
1656 | attempted when delivery immediately follows message reception, even if | |
1657 | retry times are set for them. This makes for better behaviour if one | |
1658 | particular message is causing problems (for example, causing quota | |
1659 | overflow, or provoking an error in a filter file). | |
1660 | ||
1661 | * Remote transports do their own retry handling, since an address may be | |
1662 | deliverable to one of a number of hosts, each of which may have a different | |
1663 | retry time. If there have been previous temporary failures and no host has | |
1664 | reached its retry time, no delivery is attempted, whether in a queue run or | |
1665 | not. See chapter 32 for details of retry strategies. | |
1666 | ||
1667 | * If there were any permanent errors, a bounce message is returned to an | |
1668 | appropriate address (the sender in the common case), with details of the | |
1669 | error for each failing address. Exim can be configured to send copies of | |
1670 | bounce messages to other addresses. | |
1671 | ||
1672 | * If one or more addresses suffered a temporary failure, the message is left | |
1673 | on the queue, to be tried again later. Delivery of these addresses is said | |
1674 | to be deferred. | |
1675 | ||
1676 | * When all the recipient addresses have either been delivered or bounced, | |
1677 | handling of the message is complete. The spool files and message log are | |
1678 | deleted, though the message log can optionally be preserved if required. | |
1679 | ||
1680 | ||
1681 | 3.14 Retry mechanism | |
1682 | -------------------- | |
1683 | ||
1684 | Exim's mechanism for retrying messages that fail to get delivered at the first | |
1685 | attempt is the queue runner process. You must either run an Exim daemon that | |
1686 | uses the -q option with a time interval to start queue runners at regular | |
1687 | intervals, or use some other means (such as cron) to start them. If you do not | |
1688 | arrange for queue runners to be run, messages that fail temporarily at the | |
1689 | first attempt will remain on your queue for ever. A queue runner process works | |
1690 | its way through the queue, one message at a time, trying each delivery that has | |
1691 | passed its retry time. You can run several queue runners at once. | |
1692 | ||
1693 | Exim uses a set of configured rules to determine when next to retry the failing | |
1694 | address (see chapter 32). These rules also specify when Exim should give up | |
1695 | trying to deliver to the address, at which point it generates a bounce message. | |
1696 | If no retry rules are set for a particular host, address, and error | |
1697 | combination, no retries are attempted, and temporary errors are treated as | |
1698 | permanent. | |
1699 | ||
1700 | ||
1701 | 3.15 Temporary delivery failure | |
1702 | ------------------------------- | |
1703 | ||
1704 | There are many reasons why a message may not be immediately deliverable to a | |
1705 | particular address. Failure to connect to a remote machine (because it, or the | |
1706 | connection to it, is down) is one of the most common. Temporary failures may be | |
1707 | detected during routing as well as during the transport stage of delivery. | |
1708 | Local deliveries may be delayed if NFS files are unavailable, or if a mailbox | |
1709 | is on a file system where the user is over quota. Exim can be configured to | |
1710 | impose its own quotas on local mailboxes; where system quotas are set they will | |
1711 | also apply. | |
1712 | ||
1713 | If a host is unreachable for a period of time, a number of messages may be | |
1714 | waiting for it by the time it recovers, and sending them in a single SMTP | |
1715 | connection is clearly beneficial. Whenever a delivery to a remote host is | |
1716 | deferred, Exim makes a note in its hints database, and whenever a successful | |
1717 | SMTP delivery has happened, it looks to see if any other messages are waiting | |
1718 | for the same host. If any are found, they are sent over the same SMTP | |
1719 | connection, subject to a configuration limit as to the maximum number in any | |
1720 | one connection. | |
1721 | ||
1722 | ||
1723 | 3.16 Permanent delivery failure | |
1724 | ------------------------------- | |
1725 | ||
1726 | When a message cannot be delivered to some or all of its intended recipients, a | |
1727 | bounce message is generated. Temporary delivery failures turn into permanent | |
1728 | errors when their timeout expires. All the addresses that fail in a given | |
1729 | delivery attempt are listed in a single message. If the original message has | |
1730 | many recipients, it is possible for some addresses to fail in one delivery | |
1731 | attempt and others to fail subsequently, giving rise to more than one bounce | |
1732 | message. The wording of bounce messages can be customized by the administrator. | |
1733 | See chapter 48 for details. | |
1734 | ||
1735 | Bounce messages contain an X-Failed-Recipients: header line that lists the | |
1736 | failed addresses, for the benefit of programs that try to analyse such messages | |
1737 | automatically. | |
1738 | ||
1739 | A bounce message is normally sent to the sender of the original message, as | |
1740 | obtained from the message's envelope. For incoming SMTP messages, this is the | |
1741 | address given in the MAIL command. However, when an address is expanded via a | |
1742 | forward or alias file, an alternative address can be specified for delivery | |
1743 | failures of the generated addresses. For a mailing list expansion (see section | |
1744 | 49.2) it is common to direct bounce messages to the manager of the list. | |
1745 | ||
1746 | ||
1747 | 3.17 Failures to deliver bounce messages | |
1748 | ---------------------------------------- | |
1749 | ||
1750 | If a bounce message (either locally generated or received from a remote host) | |
1751 | itself suffers a permanent delivery failure, the message is left on the queue, | |
1752 | but it is frozen, awaiting the attention of an administrator. There are options | |
1753 | that can be used to make Exim discard such failed messages, or to keep them for | |
1754 | only a short time (see timeout_frozen_after and ignore_bounce_errors_after). | |
1755 | ||
1756 | ||
1757 | ||
1758 | =============================================================================== | |
1759 | 4. BUILDING AND INSTALLING EXIM | |
1760 | ||
1761 | ||
1762 | 4.1 Unpacking | |
1763 | ------------- | |
1764 | ||
1765 | Exim is distributed as a gzipped or bzipped tar file which, when unpacked, | |
1766 | creates a directory with the name of the current release (for example, | |
188b6fee | 1767 | exim-4.84.2) into which the following files are placed: |
420a0d19 CE |
1768 | |
1769 | ACKNOWLEDGMENTS contains some acknowledgments | |
1770 | CHANGES contains a reference to where changes are documented | |
1771 | LICENCE the GNU General Public Licence | |
1772 | Makefile top-level make file | |
1773 | NOTICE conditions for the use of Exim | |
1774 | README list of files, directories and simple build instructions | |
1775 | ||
1776 | Other files whose names begin with README may also be present. The following | |
1777 | subdirectories are created: | |
1778 | ||
1779 | Local an empty directory for local configuration files | |
1780 | OS OS-specific files | |
1781 | doc documentation files | |
1782 | exim_monitor source files for the Exim monitor | |
1783 | scripts scripts used in the build process | |
1784 | src remaining source files | |
1785 | util independent utilities | |
1786 | ||
1787 | The main utility programs are contained in the src directory, and are built | |
1788 | with the Exim binary. The util directory contains a few optional scripts that | |
1789 | may be useful to some sites. | |
1790 | ||
1791 | ||
1792 | 4.2 Multiple machine architectures and operating systems | |
1793 | -------------------------------------------------------- | |
1794 | ||
1795 | The building process for Exim is arranged to make it easy to build binaries for | |
1796 | a number of different architectures and operating systems from the same set of | |
1797 | source files. Compilation does not take place in the src directory. Instead, a | |
1798 | build directory is created for each architecture and operating system. Symbolic | |
1799 | links to the sources are installed in this directory, which is where the actual | |
1800 | building takes place. In most cases, Exim can discover the machine architecture | |
1801 | and operating system for itself, but the defaults can be overridden if | |
1802 | necessary. | |
1803 | ||
1804 | ||
1805 | 4.3 PCRE library | |
1806 | ---------------- | |
1807 | ||
1808 | Exim no longer has an embedded PCRE library as the vast majority of modern | |
1809 | systems include PCRE as a system library, although you may need to install the | |
1810 | PCRE or PCRE development package for your operating system. If your system has | |
1811 | a normal PCRE installation the Exim build process will need no further | |
1812 | configuration. If the library or the headers are in an unusual location you | |
1813 | will need to either set the PCRE_LIBS and INCLUDE directives appropriately, or | |
1814 | set PCRE_CONFIG=yes to use the installed pcre-config command. If your operating | |
1815 | system has no PCRE support then you will need to obtain and build the current | |
1816 | PCRE from ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/. More | |
1817 | information on PCRE is available at http://www.pcre.org/. | |
1818 | ||
1819 | ||
1820 | 4.4 DBM libraries | |
1821 | ----------------- | |
1822 | ||
1823 | Even if you do not use any DBM files in your configuration, Exim still needs a | |
1824 | DBM library in order to operate, because it uses indexed files for its hints | |
1825 | databases. Unfortunately, there are a number of DBM libraries in existence, and | |
1826 | different operating systems often have different ones installed. | |
1827 | ||
1828 | If you are using Solaris, IRIX, one of the modern BSD systems, or a modern | |
1829 | Linux distribution, the DBM configuration should happen automatically, and you | |
1830 | may be able to ignore this section. Otherwise, you may have to learn more than | |
1831 | you would like about DBM libraries from what follows. | |
1832 | ||
1833 | Licensed versions of Unix normally contain a library of DBM functions operating | |
1834 | via the ndbm interface, and this is what Exim expects by default. Free versions | |
1835 | of Unix seem to vary in what they contain as standard. In particular, some | |
1836 | early versions of Linux have no default DBM library, and different distributors | |
1837 | have chosen to bundle different libraries with their packaged versions. | |
1838 | However, the more recent releases seem to have standardized on the Berkeley DB | |
1839 | library. | |
1840 | ||
1841 | Different DBM libraries have different conventions for naming the files they | |
1842 | use. When a program opens a file called dbmfile, there are several | |
1843 | possibilities: | |
1844 | ||
1845 | 1. A traditional ndbm implementation, such as that supplied as part of | |
1846 | Solaris, operates on two files called dbmfile.dir and dbmfile.pag. | |
1847 | ||
1848 | 2. The GNU library, gdbm, operates on a single file. If used via its ndbm | |
1849 | compatibility interface it makes two different hard links to it with names | |
1850 | dbmfile.dir and dbmfile.pag, but if used via its native interface, the file | |
1851 | name is used unmodified. | |
1852 | ||
1853 | 3. The Berkeley DB package, if called via its ndbm compatibility interface, | |
1854 | operates on a single file called dbmfile.db, but otherwise looks to the | |
1855 | programmer exactly the same as the traditional ndbm implementation. | |
1856 | ||
1857 | 4. If the Berkeley package is used in its native mode, it operates on a single | |
1858 | file called dbmfile; the programmer's interface is somewhat different to | |
1859 | the traditional ndbm interface. | |
1860 | ||
1861 | 5. To complicate things further, there are several very different versions of | |
1862 | the Berkeley DB package. Version 1.85 was stable for a very long time, | |
1863 | releases 2.x and 3.x were current for a while, but the latest versions are | |
1864 | now numbered 4.x. Maintenance of some of the earlier releases has ceased. | |
1865 | All versions of Berkeley DB can be obtained from http://www.sleepycat.com/. | |
1866 | ||
1867 | 6. Yet another DBM library, called tdb, is available from http:// | |
1868 | download.sourceforge.net/tdb. It has its own interface, and also operates | |
1869 | on a single file. | |
1870 | ||
1871 | Exim and its utilities can be compiled to use any of these interfaces. In order | |
1872 | to use any version of the Berkeley DB package in native mode, you must set | |
1873 | USE_DB in an appropriate configuration file (typically Local/Makefile). For | |
1874 | example: | |
1875 | ||
1876 | USE_DB=yes | |
1877 | ||
1878 | Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An error is | |
1879 | diagnosed if you set more than one of these. | |
1880 | ||
1881 | At the lowest level, the build-time configuration sets none of these options, | |
1882 | thereby assuming an interface of type (1). However, some operating system | |
1883 | configuration files (for example, those for the BSD operating systems and | |
1884 | Linux) assume type (4) by setting USE_DB as their default, and the | |
1885 | configuration files for Cygwin set USE_GDBM. Anything you set in Local/Makefile | |
1886 | , however, overrides these system defaults. | |
1887 | ||
1888 | As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be necessary to | |
1889 | set DBMLIB, to cause inclusion of the appropriate library, as in one of these | |
1890 | lines: | |
1891 | ||
1892 | DBMLIB = -ldb | |
1893 | DBMLIB = -ltdb | |
1894 | ||
1895 | Settings like that will work if the DBM library is installed in the standard | |
1896 | place. Sometimes it is not, and the library's header file may also not be in | |
1897 | the default path. You may need to set INCLUDE to specify where the header file | |
1898 | is, and to specify the path to the library more fully in DBMLIB, as in this | |
1899 | example: | |
1900 | ||
1901 | INCLUDE=-I/usr/local/include/db-4.1 | |
1902 | DBMLIB=/usr/local/lib/db-4.1/libdb.a | |
1903 | ||
1904 | There is further detailed discussion about the various DBM libraries in the | |
1905 | file doc/dbm.discuss.txt in the Exim distribution. | |
1906 | ||
1907 | ||
1908 | 4.5 Pre-building configuration | |
1909 | ------------------------------ | |
1910 | ||
1911 | Before building Exim, a local configuration file that specifies options | |
1912 | independent of any operating system has to be created with the name Local/ | |
1913 | Makefile. A template for this file is supplied as the file src/EDITME, and it | |
1914 | contains full descriptions of all the option settings therein. These | |
1915 | descriptions are therefore not repeated here. If you are building Exim for the | |
1916 | first time, the simplest thing to do is to copy src/EDITME to Local/Makefile, | |
1917 | then read it and edit it appropriately. | |
1918 | ||
1919 | There are three settings that you must supply, because Exim will not build | |
1920 | without them. They are the location of the run time configuration file | |
1921 | (CONFIGURE_FILE), the directory in which Exim binaries will be installed | |
1922 | (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and maybe | |
1923 | EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be a | |
1924 | colon-separated list of file names; Exim uses the first of them that exists. | |
1925 | ||
1926 | There are a few other parameters that can be specified either at build time or | |
1927 | at run time, to enable the same binary to be used on a number of different | |
1928 | machines. However, if the locations of Exim's spool directory and log file | |
1929 | directory (if not within the spool directory) are fixed, it is recommended that | |
1930 | you specify them in Local/Makefile instead of at run time, so that errors | |
1931 | detected early in Exim's execution (such as a malformed configuration file) can | |
1932 | be logged. | |
1933 | ||
1934 | Exim's interfaces for calling virus and spam scanning software directly from | |
1935 | access control lists are not compiled by default. If you want to include these | |
1936 | facilities, you need to set | |
1937 | ||
1938 | WITH_CONTENT_SCAN=yes | |
1939 | ||
1940 | in your Local/Makefile. For details of the facilities themselves, see chapter | |
1941 | 43. | |
1942 | ||
1943 | If you are going to build the Exim monitor, a similar configuration process is | |
1944 | required. The file exim_monitor/EDITME must be edited appropriately for your | |
1945 | installation and saved under the name Local/eximon.conf. If you are happy with | |
1946 | the default settings described in exim_monitor/EDITME, Local/eximon.conf can be | |
1947 | empty, but it must exist. | |
1948 | ||
1949 | This is all the configuration that is needed in straightforward cases for known | |
1950 | operating systems. However, the building process is set up so that it is easy | |
1951 | to override options that are set by default or by operating-system-specific | |
1952 | configuration files, for example to change the name of the C compiler, which | |
1953 | defaults to gcc. See section 4.13 below for details of how to do this. | |
1954 | ||
1955 | ||
1956 | 4.6 Support for iconv() | |
1957 | ----------------------- | |
1958 | ||
1959 | The contents of header lines in messages may be encoded according to the rules | |
1960 | described RFC 2047. This makes it possible to transmit characters that are not | |
1961 | in the ASCII character set, and to label them as being in a particular | |
1962 | character set. When Exim is inspecting header lines by means of the $h_ | |
1963 | mechanism, it decodes them, and translates them into a specified character set | |
1964 | (default ISO-8859-1). The translation is possible only if the operating system | |
1965 | supports the iconv() function. | |
1966 | ||
1967 | However, some of the operating systems that supply iconv() do not support very | |
1968 | many conversions. The GNU libiconv library (available from http://www.gnu.org/ | |
1969 | software/libiconv/) can be installed on such systems to remedy this deficiency, | |
1970 | as well as on systems that do not supply iconv() at all. After installing | |
1971 | libiconv, you should add | |
1972 | ||
1973 | HAVE_ICONV=yes | |
1974 | ||
1975 | to your Local/Makefile and rebuild Exim. | |
1976 | ||
1977 | ||
1978 | 4.7 Including TLS/SSL encryption support | |
1979 | ---------------------------------------- | |
1980 | ||
1981 | Exim can be built to support encrypted SMTP connections, using the STARTTLS | |
1982 | command as per RFC 2487. It can also support legacy clients that expect to | |
1983 | start a TLS session immediately on connection to a non-standard port (see the | |
1984 | tls_on_connect_ports runtime option and the -tls-on-connect command line | |
1985 | option). | |
1986 | ||
1987 | If you want to build Exim with TLS support, you must first install either the | |
1988 | OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for | |
1989 | implementing SSL. | |
1990 | ||
1991 | If OpenSSL is installed, you should set | |
1992 | ||
1993 | SUPPORT_TLS=yes | |
1994 | TLS_LIBS=-lssl -lcrypto | |
1995 | ||
1996 | in Local/Makefile. You may also need to specify the locations of the OpenSSL | |
1997 | library and include files. For example: | |
1998 | ||
1999 | SUPPORT_TLS=yes | |
2000 | TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto | |
2001 | TLS_INCLUDE=-I/usr/local/openssl/include/ | |
2002 | ||
2003 | If you have pkg-config available, then instead you can just use: | |
2004 | ||
2005 | SUPPORT_TLS=yes | |
2006 | USE_OPENSSL_PC=openssl | |
2007 | ||
2008 | If GnuTLS is installed, you should set | |
2009 | ||
2010 | SUPPORT_TLS=yes | |
2011 | USE_GNUTLS=yes | |
2012 | TLS_LIBS=-lgnutls -ltasn1 -lgcrypt | |
2013 | ||
2014 | in Local/Makefile, and again you may need to specify the locations of the | |
2015 | library and include files. For example: | |
2016 | ||
2017 | SUPPORT_TLS=yes | |
2018 | USE_GNUTLS=yes | |
2019 | TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt | |
2020 | TLS_INCLUDE=-I/usr/gnu/include | |
2021 | ||
2022 | If you have pkg-config available, then instead you can just use: | |
2023 | ||
2024 | SUPPORT_TLS=yes | |
2025 | USE_GNUTLS=yes | |
2026 | USE_GNUTLS_PC=gnutls | |
2027 | ||
2028 | You do not need to set TLS_INCLUDE if the relevant directory is already | |
2029 | specified in INCLUDE. Details of how to configure Exim to make use of TLS are | |
2030 | given in chapter 41. | |
2031 | ||
2032 | ||
2033 | 4.8 Use of tcpwrappers | |
2034 | ---------------------- | |
2035 | ||
2036 | Exim can be linked with the tcpwrappers library in order to check incoming SMTP | |
2037 | calls using the tcpwrappers control files. This may be a convenient alternative | |
2038 | to Exim's own checking facilities for installations that are already making use | |
2039 | of tcpwrappers for other purposes. To do this, you should set USE_TCP_WRAPPERS | |
2040 | in Local/Makefile, arrange for the file tcpd.h to be available at compile time, | |
2041 | and also ensure that the library libwrap.a is available at link time, typically | |
2042 | by including -lwrap in EXTRALIBS_EXIM. For example, if tcpwrappers is installed | |
2043 | in /usr/local, you might have | |
2044 | ||
2045 | USE_TCP_WRAPPERS=yes | |
2046 | CFLAGS=-O -I/usr/local/include | |
2047 | EXTRALIBS_EXIM=-L/usr/local/lib -lwrap | |
2048 | ||
2049 | in Local/Makefile. The daemon name to use in the tcpwrappers control files is | |
2050 | "exim". For example, the line | |
2051 | ||
2052 | exim : LOCAL 192.168.1. .friendly.domain.example | |
2053 | ||
2054 | in your /etc/hosts.allow file allows connections from the local host, from the | |
2055 | subnet 192.168.1.0/24, and from all hosts in friendly.domain.example. All other | |
2056 | connections are denied. The daemon name used by tcpwrappers can be changed at | |
2057 | build time by setting TCP_WRAPPERS_DAEMON_NAME in Local/Makefile, or by setting | |
2058 | tcp_wrappers_daemon_name in the configure file. Consult the tcpwrappers | |
2059 | documentation for further details. | |
2060 | ||
2061 | ||
2062 | 4.9 Including support for IPv6 | |
2063 | ------------------------------ | |
2064 | ||
2065 | Exim contains code for use on systems that have IPv6 support. Setting | |
2066 | "HAVE_IPV6=YES" in Local/Makefile causes the IPv6 code to be included; it may | |
2067 | also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems where the IPv6 | |
2068 | support is not fully integrated into the normal include and library files. | |
2069 | ||
2070 | Two different types of DNS record for handling IPv6 addresses have been | |
2071 | defined. AAAA records (analogous to A records for IPv4) are in use, and are | |
2072 | currently seen as the mainstream. Another record type called A6 was proposed as | |
2073 | better than AAAA because it had more flexibility. However, it was felt to be | |
2074 | over-complex, and its status was reduced to "experimental". It is not known if | |
2075 | anyone is actually using A6 records. Exim has support for A6 records, but this | |
2076 | is included only if you set "SUPPORT_A6=YES" in Local/Makefile. The support has | |
2077 | not been tested for some time. | |
2078 | ||
2079 | ||
2080 | 4.10 Dynamically loaded lookup module support | |
2081 | --------------------------------------------- | |
2082 | ||
2083 | On some platforms, Exim supports not compiling all lookup types directly into | |
2084 | the main binary, instead putting some into external modules which can be loaded | |
2085 | on demand. This permits packagers to build Exim with support for lookups with | |
2086 | extensive library dependencies without requiring all users to install all of | |
2087 | those dependencies. Most, but not all, lookup types can be built this way. | |
2088 | ||
2089 | Set "LOOKUP_MODULE_DIR" to the directory into which the modules will be | |
2090 | installed; Exim will only load modules from that directory, as a security | |
2091 | measure. You will need to set "CFLAGS_DYNAMIC" if not already defined for your | |
2092 | OS; see OS/Makefile-Linux for an example. Some other requirements for adjusting | |
2093 | "EXTRALIBS" may also be necessary, see src/EDITME for details. | |
2094 | ||
2095 | Then, for each module to be loaded dynamically, define the relevant "LOOKUP_"< | |
2096 | lookup_type> flags to have the value "2" instead of "yes". For example, this | |
2097 | will build in lsearch but load sqlite and mysql support on demand: | |
2098 | ||
2099 | LOOKUP_LSEARCH=yes | |
2100 | LOOKUP_SQLITE=2 | |
2101 | LOOKUP_MYSQL=2 | |
2102 | ||
2103 | ||
2104 | 4.11 The building process | |
2105 | ------------------------- | |
2106 | ||
2107 | Once Local/Makefile (and Local/eximon.conf, if required) have been created, run | |
2108 | make at the top level. It determines the architecture and operating system | |
2109 | types, and creates a build directory if one does not exist. For example, on a | |
2110 | Sun system running Solaris 8, the directory build-SunOS5-5.8-sparc is created. | |
2111 | Symbolic links to relevant source files are installed in the build directory. | |
2112 | ||
2113 | Warning: The -j (parallel) flag must not be used with make; the building | |
2114 | process fails if it is set. | |
2115 | ||
2116 | If this is the first time make has been run, it calls a script that builds a | |
2117 | make file inside the build directory, using the configuration files from the | |
2118 | Local directory. The new make file is then passed to another instance of make. | |
2119 | This does the real work, building a number of utility scripts, and then | |
2120 | compiling and linking the binaries for the Exim monitor (if configured), a | |
2121 | number of utility programs, and finally Exim itself. The command "make | |
2122 | makefile" can be used to force a rebuild of the make file in the build | |
2123 | directory, should this ever be necessary. | |
2124 | ||
2125 | If you have problems building Exim, check for any comments there may be in the | |
2126 | README file concerning your operating system, and also take a look at the FAQ, | |
2127 | where some common problems are covered. | |
2128 | ||
2129 | ||
2130 | 4.12 Output from "make" | |
2131 | ----------------------- | |
2132 | ||
2133 | The output produced by the make process for compile lines is often very | |
2134 | unreadable, because these lines can be very long. For this reason, the normal | |
2135 | output is suppressed by default, and instead output similar to that which | |
2136 | appears when compiling the 2.6 Linux kernel is generated: just a short line for | |
2137 | each module that is being compiled or linked. However, it is still possible to | |
2138 | get the full output, by calling make like this: | |
2139 | ||
2140 | FULLECHO='' make -e | |
2141 | ||
2142 | The value of FULLECHO defaults to "@", the flag character that suppresses | |
2143 | command reflection in make. When you ask for the full output, it is given in | |
2144 | addition to the short output. | |
2145 | ||
2146 | ||
2147 | 4.13 Overriding build-time options for Exim | |
2148 | ------------------------------------------- | |
2149 | ||
2150 | The main make file that is created at the beginning of the building process | |
2151 | consists of the concatenation of a number of files which set configuration | |
2152 | values, followed by a fixed set of make instructions. If a value is set more | |
2153 | than once, the last setting overrides any previous ones. This provides a | |
2154 | convenient way of overriding defaults. The files that are concatenated are, in | |
2155 | order: | |
2156 | ||
2157 | OS/Makefile-Default | |
2158 | OS/Makefile-<ostype> | |
2159 | Local/Makefile | |
2160 | Local/Makefile-<ostype> | |
2161 | Local/Makefile-<archtype> | |
2162 | Local/Makefile-<ostype>-<archtype> | |
2163 | OS/Makefile-Base | |
2164 | ||
2165 | where <ostype> is the operating system type and <archtype> is the architecture | |
2166 | type. Local/Makefile is required to exist, and the building process fails if it | |
2167 | is absent. The other three Local files are optional, and are often not needed. | |
2168 | ||
2169 | The values used for <ostype> and <archtype> are obtained from scripts called | |
2170 | scripts/os-type and scripts/arch-type respectively. If either of the | |
2171 | environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their values are | |
2172 | used, thereby providing a means of forcing particular settings. Otherwise, the | |
2173 | scripts try to get values from the uname command. If this fails, the shell | |
2174 | variables OSTYPE and ARCHTYPE are inspected. A number of ad hoc transformations | |
2175 | are then applied, to produce the standard names that Exim expects. You can run | |
2176 | these scripts directly from the shell in order to find out what values are | |
2177 | being used on your system. | |
2178 | ||
2179 | OS/Makefile-Default contains comments about the variables that are set therein. | |
2180 | Some (but not all) are mentioned below. If there is something that needs | |
2181 | changing, review the contents of this file and the contents of the make file | |
2182 | for your operating system (OS/Makefile-<ostype>) to see what the default values | |
2183 | are. | |
2184 | ||
2185 | If you need to change any of the values that are set in OS/Makefile-Default or | |
2186 | in OS/Makefile-<ostype>, or to add any new definitions, you do not need to | |
2187 | change the original files. Instead, you should make the changes by putting the | |
2188 | new values in an appropriate Local file. For example, when building Exim in | |
2189 | many releases of the Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1) | |
2190 | operating system, it is necessary to specify that the C compiler is called cc | |
2191 | rather than gcc. Also, the compiler must be called with the option -std1, to | |
2192 | make it recognize some of the features of Standard C that Exim uses. (Most | |
2193 | other compilers recognize Standard C by default.) To do this, you should create | |
2194 | a file called Local/Makefile-OSF1 containing the lines | |
2195 | ||
2196 | CC=cc | |
2197 | CFLAGS=-std1 | |
2198 | ||
2199 | If you are compiling for just one operating system, it may be easier to put | |
2200 | these lines directly into Local/Makefile. | |
2201 | ||
2202 | Keeping all your local configuration settings separate from the distributed | |
2203 | files makes it easy to transfer them to new versions of Exim simply by copying | |
2204 | the contents of the Local directory. | |
2205 | ||
2206 | Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file | |
2207 | lookup, but not all systems have these components installed, so the default is | |
2208 | not to include the relevant code in the binary. All the different kinds of file | |
2209 | and database lookup that Exim supports are implemented as separate code modules | |
2210 | which are included only if the relevant compile-time options are set. In the | |
2211 | case of LDAP, NIS, and NIS+, the settings for Local/Makefile are: | |
2212 | ||
2213 | LOOKUP_LDAP=yes | |
2214 | LOOKUP_NIS=yes | |
2215 | LOOKUP_NISPLUS=yes | |
2216 | ||
2217 | and similar settings apply to the other lookup types. They are all listed in | |
2218 | src/EDITME. In many cases the relevant include files and interface libraries | |
2219 | need to be installed before compiling Exim. However, there are some optional | |
2220 | lookup types (such as cdb) for which the code is entirely contained within | |
2221 | Exim, and no external include files or libraries are required. When a lookup | |
2222 | type is not included in the binary, attempts to configure Exim to use it cause | |
2223 | run time configuration errors. | |
2224 | ||
2225 | Many systems now use a tool called pkg-config to encapsulate information about | |
2226 | how to compile against a library; Exim has some initial support for being able | |
2227 | to use pkg-config for lookups and authenticators. For any given makefile | |
2228 | variable which starts "LOOKUP_" or "AUTH_", you can add a new variable with the | |
2229 | "_PC" suffix in the name and assign as the value the name of the package to be | |
2230 | queried. The results of querying via the pkg-config command will be added to | |
2231 | the appropriate Makefile variables with "+=" directives, so your version of | |
2232 | make will need to support that syntax. For instance: | |
2233 | ||
2234 | LOOKUP_SQLITE=yes | |
2235 | LOOKUP_SQLITE_PC=sqlite3 | |
2236 | AUTH_GSASL=yes | |
2237 | AUTH_GSASL_PC=libgsasl | |
2238 | AUTH_HEIMDAL_GSSAPI=yes | |
2239 | AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi | |
2240 | ||
2241 | Exim can be linked with an embedded Perl interpreter, allowing Perl subroutines | |
2242 | to be called during string expansion. To enable this facility, | |
2243 | ||
2244 | EXIM_PERL=perl.o | |
2245 | ||
2246 | must be defined in Local/Makefile. Details of this facility are given in | |
2247 | chapter 12. | |
2248 | ||
2249 | The location of the X11 libraries is something that varies a lot between | |
2250 | operating systems, and there may be different versions of X11 to cope with. | |
2251 | Exim itself makes no use of X11, but if you are compiling the Exim monitor, the | |
2252 | X11 libraries must be available. The following three variables are set in OS/ | |
2253 | Makefile-Default: | |
2254 | ||
2255 | X11=/usr/X11R6 | |
2256 | XINCLUDE=-I$(X11)/include | |
2257 | XLFLAGS=-L$(X11)/lib | |
2258 | ||
2259 | These are overridden in some of the operating-system configuration files. For | |
2260 | example, in OS/Makefile-SunOS5 there is | |
2261 | ||
2262 | X11=/usr/openwin | |
2263 | XINCLUDE=-I$(X11)/include | |
2264 | XLFLAGS=-L$(X11)/lib -R$(X11)/lib | |
2265 | ||
2266 | If you need to override the default setting for your operating system, place a | |
2267 | definition of all three of these variables into your Local/Makefile-<ostype> | |
2268 | file. | |
2269 | ||
2270 | If you need to add any extra libraries to the link steps, these can be put in a | |
2271 | variable called EXTRALIBS, which appears in all the link commands, but by | |
2272 | default is not defined. In contrast, EXTRALIBS_EXIM is used only on the command | |
2273 | for linking the main Exim binary, and not for any associated utilities. | |
2274 | ||
2275 | There is also DBMLIB, which appears in the link commands for binaries that use | |
2276 | DBM functions (see also section 4.4). Finally, there is EXTRALIBS_EXIMON, which | |
2277 | appears only in the link step for the Exim monitor binary, and which can be | |
2278 | used, for example, to include additional X11 libraries. | |
2279 | ||
2280 | The make file copes with rebuilding Exim correctly if any of the configuration | |
2281 | files are edited. However, if an optional configuration file is deleted, it is | |
2282 | necessary to touch the associated non-optional file (that is, Local/Makefile or | |
2283 | Local/eximon.conf) before rebuilding. | |
2284 | ||
2285 | ||
2286 | 4.14 OS-specific header files | |
2287 | ----------------------------- | |
2288 | ||
2289 | The OS directory contains a number of files with names of the form os.h- | |
2290 | <ostype>. These are system-specific C header files that should not normally | |
2291 | need to be changed. There is a list of macro settings that are recognized in | |
2292 | the file OS/os.configuring, which should be consulted if you are porting Exim | |
2293 | to a new operating system. | |
2294 | ||
2295 | ||
2296 | 4.15 Overriding build-time options for the monitor | |
2297 | -------------------------------------------------- | |
2298 | ||
2299 | A similar process is used for overriding things when building the Exim monitor, | |
2300 | where the files that are involved are | |
2301 | ||
2302 | OS/eximon.conf-Default | |
2303 | OS/eximon.conf-<ostype> | |
2304 | Local/eximon.conf | |
2305 | Local/eximon.conf-<ostype> | |
2306 | Local/eximon.conf-<archtype> | |
2307 | Local/eximon.conf-<ostype>-<archtype> | |
2308 | ||
2309 | As with Exim itself, the final three files need not exist, and in this case the | |
2310 | OS/eximon.conf-<ostype> file is also optional. The default values in OS/ | |
2311 | eximon.conf-Default can be overridden dynamically by setting environment | |
2312 | variables of the same name, preceded by EXIMON_. For example, setting | |
2313 | EXIMON_LOG_DEPTH in the environment overrides the value of LOG_DEPTH at run | |
2314 | time. | |
2315 | ||
2316 | ||
2317 | 4.16 Installing Exim binaries and scripts | |
2318 | ----------------------------------------- | |
2319 | ||
2320 | The command "make install" runs the exim_install script with no arguments. The | |
2321 | script copies binaries and utility scripts into the directory whose name is | |
2322 | specified by the BIN_DIRECTORY setting in Local/Makefile. The install script | |
2323 | copies files only if they are newer than the files they are going to replace. | |
2324 | The Exim binary is required to be owned by root and have the setuid bit set, | |
2325 | for normal configurations. Therefore, you must run "make install" as root so | |
2326 | that it can set up the Exim binary in this way. However, in some special | |
2327 | situations (for example, if a host is doing no local deliveries) it may be | |
2328 | possible to run Exim without making the binary setuid root (see chapter 54 for | |
2329 | details). | |
2330 | ||
2331 | Exim's run time configuration file is named by the CONFIGURE_FILE setting in | |
2332 | Local/Makefile. If this names a single file, and the file does not exist, the | |
2333 | default configuration file src/configure.default is copied there by the | |
2334 | installation script. If a run time configuration file already exists, it is | |
2335 | left alone. If CONFIGURE_FILE is a colon-separated list, naming several | |
2336 | alternative files, no default is installed. | |
2337 | ||
2338 | One change is made to the default configuration file when it is installed: the | |
2339 | default configuration contains a router that references a system aliases file. | |
2340 | The path to this file is set to the value specified by SYSTEM_ALIASES_FILE in | |
2341 | Local/Makefile (/etc/aliases by default). If the system aliases file does not | |
2342 | exist, the installation script creates it, and outputs a comment to the user. | |
2343 | ||
2344 | The created file contains no aliases, but it does contain comments about the | |
2345 | aliases a site should normally have. Mail aliases have traditionally been kept | |
2346 | in /etc/aliases. However, some operating systems are now using /etc/mail/ | |
2347 | aliases. You should check if yours is one of these, and change Exim's | |
2348 | configuration if necessary. | |
2349 | ||
2350 | The default configuration uses the local host's name as the only local domain, | |
2351 | and is set up to do local deliveries into the shared directory /var/mail, | |
2352 | running as the local user. System aliases and .forward files in users' home | |
2353 | directories are supported, but no NIS or NIS+ support is configured. Domains | |
2354 | other than the name of the local host are routed using the DNS, with delivery | |
2355 | over SMTP. | |
2356 | ||
2357 | It is possible to install Exim for special purposes (such as building a binary | |
2358 | distribution) in a private part of the file system. You can do this by a | |
2359 | command such as | |
2360 | ||
2361 | make DESTDIR=/some/directory/ install | |
2362 | ||
2363 | This has the effect of pre-pending the specified directory to all the file | |
2364 | paths, except the name of the system aliases file that appears in the default | |
2365 | configuration. (If a default alias file is created, its name is modified.) For | |
2366 | backwards compatibility, ROOT is used if DESTDIR is not set, but this usage is | |
2367 | deprecated. | |
2368 | ||
2369 | Running make install does not copy the Exim 4 conversion script convert4r4. You | |
2370 | will probably run this only once if you are upgrading from Exim 3. None of the | |
2371 | documentation files in the doc directory are copied, except for the info files | |
2372 | when you have set INFO_DIRECTORY, as described in section 4.17 below. | |
2373 | ||
2374 | For the utility programs, old versions are renamed by adding the suffix .O to | |
2375 | their names. The Exim binary itself, however, is handled differently. It is | |
2376 | installed under a name that includes the version number and the compile number, | |
188b6fee | 2377 | for example exim-4.84.2-1. The script then arranges for a symbolic link called |
420a0d19 CE |
2378 | exim to point to the binary. If you are updating a previous version of Exim, |
2379 | the script takes care to ensure that the name exim is never absent from the | |
2380 | directory (as seen by other processes). | |
2381 | ||
2382 | If you want to see what the make install will do before running it for real, | |
2383 | you can pass the -n option to the installation script by this command: | |
2384 | ||
2385 | make INSTALL_ARG=-n install | |
2386 | ||
2387 | The contents of the variable INSTALL_ARG are passed to the installation script. | |
2388 | You do not need to be root to run this test. Alternatively, you can run the | |
2389 | installation script directly, but this must be from within the build directory. | |
2390 | For example, from the top-level Exim directory you could use this command: | |
2391 | ||
2392 | (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n) | |
2393 | ||
2394 | There are two other options that can be supplied to the installation script. | |
2395 | ||
2396 | * -no_chown bypasses the call to change the owner of the installed binary to | |
2397 | root, and the call to make it a setuid binary. | |
2398 | ||
2399 | * -no_symlink bypasses the setting up of the symbolic link exim to the | |
2400 | installed binary. | |
2401 | ||
2402 | INSTALL_ARG can be used to pass these options to the script. For example: | |
2403 | ||
2404 | make INSTALL_ARG=-no_symlink install | |
2405 | ||
2406 | The installation script can also be given arguments specifying which files are | |
2407 | to be copied. For example, to install just the Exim binary, and nothing else, | |
2408 | without creating the symbolic link, you could use: | |
2409 | ||
2410 | make INSTALL_ARG='-no_symlink exim' install | |
2411 | ||
2412 | ||
2413 | 4.17 Installing info documentation | |
2414 | ---------------------------------- | |
2415 | ||
2416 | Not all systems use the GNU info system for documentation, and for this reason, | |
2417 | the Texinfo source of Exim's documentation is not included in the main | |
2418 | distribution. Instead it is available separately from the ftp site (see section | |
2419 | 1.6). | |
2420 | ||
2421 | If you have defined INFO_DIRECTORY in Local/Makefile and the Texinfo source of | |
2422 | the documentation is found in the source tree, running "make install" | |
2423 | automatically builds the info files and installs them. | |
2424 | ||
2425 | ||
2426 | 4.18 Setting up the spool directory | |
2427 | ----------------------------------- | |
2428 | ||
2429 | When it starts up, Exim tries to create its spool directory if it does not | |
2430 | exist. The Exim uid and gid are used for the owner and group of the spool | |
2431 | directory. Sub-directories are automatically created in the spool directory as | |
2432 | necessary. | |
2433 | ||
2434 | ||
2435 | 4.19 Testing | |
2436 | ------------ | |
2437 | ||
2438 | Having installed Exim, you can check that the run time configuration file is | |
2439 | syntactically valid by running the following command, which assumes that the | |
2440 | Exim binary directory is within your PATH environment variable: | |
2441 | ||
2442 | exim -bV | |
2443 | ||
2444 | If there are any errors in the configuration file, Exim outputs error messages. | |
2445 | Otherwise it outputs the version number and build date, the DBM library that is | |
2446 | being used, and information about which drivers and other optional code modules | |
2447 | are included in the binary. Some simple routing tests can be done by using the | |
2448 | address testing option. For example, | |
2449 | ||
2450 | exim -bt <local username> | |
2451 | ||
2452 | should verify that it recognizes a local mailbox, and | |
2453 | ||
2454 | exim -bt <remote address> | |
2455 | ||
2456 | a remote one. Then try getting it to deliver mail, both locally and remotely. | |
2457 | This can be done by passing messages directly to Exim, without going through a | |
2458 | user agent. For example: | |
2459 | ||
2460 | exim -v postmaster@your.domain.example | |
2461 | From: user@your.domain.example | |
2462 | To: postmaster@your.domain.example | |
2463 | Subject: Testing Exim | |
2464 | ||
2465 | This is a test message. | |
2466 | ^D | |
2467 | ||
2468 | The -v option causes Exim to output some verification of what it is doing. In | |
2469 | this case you should see copies of three log lines, one for the message's | |
2470 | arrival, one for its delivery, and one containing "Completed". | |
2471 | ||
2472 | If you encounter problems, look at Exim's log files (mainlog and paniclog) to | |
2473 | see if there is any relevant information there. Another source of information | |
2474 | is running Exim with debugging turned on, by specifying the -d option. If a | |
2475 | message is stuck on Exim's spool, you can force a delivery with debugging | |
2476 | turned on by a command of the form | |
2477 | ||
2478 | exim -d -M <exim-message-id> | |
2479 | ||
2480 | You must be root or an "admin user" in order to do this. The -d option produces | |
2481 | rather a lot of output, but you can cut this down to specific areas. For | |
2482 | example, if you use -d-all+route only the debugging information relevant to | |
2483 | routing is included. (See the -d option in chapter 5 for more details.) | |
2484 | ||
2485 | One specific problem that has shown up on some sites is the inability to do | |
2486 | local deliveries into a shared mailbox directory, because it does not have the | |
2487 | "sticky bit" set on it. By default, Exim tries to create a lock file before | |
2488 | writing to a mailbox file, and if it cannot create the lock file, the delivery | |
2489 | is deferred. You can get round this either by setting the "sticky bit" on the | |
2490 | directory, or by setting a specific group for local deliveries and allowing | |
2491 | that group to create files in the directory (see the comments above the | |
2492 | local_delivery transport in the default configuration file). Another approach | |
2493 | is to configure Exim not to use lock files, but just to rely on fcntl() locking | |
2494 | instead. However, you should do this only if all user agents also use fcntl() | |
2495 | locking. For further discussion of locking issues, see chapter 26. | |
2496 | ||
2497 | One thing that cannot be tested on a system that is already running an MTA is | |
2498 | the receipt of incoming SMTP mail on the standard SMTP port. However, the -oX | |
2499 | option can be used to run an Exim daemon that listens on some other port, or | |
2500 | inetd can be used to do this. The -bh option and the exim_checkaccess utility | |
2501 | can be used to check out policy controls on incoming SMTP mail. | |
2502 | ||
2503 | Testing a new version on a system that is already running Exim can most easily | |
2504 | be done by building a binary with a different CONFIGURE_FILE setting. From | |
2505 | within the run time configuration, all other file and directory names that Exim | |
2506 | uses can be altered, in order to keep it entirely clear of the production | |
2507 | version. | |
2508 | ||
2509 | ||
2510 | 4.20 Replacing another MTA with Exim | |
2511 | ------------------------------------ | |
2512 | ||
2513 | Building and installing Exim for the first time does not of itself put it in | |
2514 | general use. The name by which the system's MTA is called by mail user agents | |
2515 | is either /usr/sbin/sendmail, or /usr/lib/sendmail (depending on the operating | |
2516 | system), and it is necessary to make this name point to the exim binary in | |
2517 | order to get the user agents to pass messages to Exim. This is normally done by | |
2518 | renaming any existing file and making /usr/sbin/sendmail or /usr/lib/sendmail a | |
2519 | symbolic link to the exim binary. It is a good idea to remove any setuid | |
2520 | privilege and executable status from the old MTA. It is then necessary to stop | |
2521 | and restart the mailer daemon, if one is running. | |
2522 | ||
2523 | Some operating systems have introduced alternative ways of switching MTAs. For | |
2524 | example, if you are running FreeBSD, you need to edit the file /etc/mail/ | |
2525 | mailer.conf instead of setting up a symbolic link as just described. A typical | |
2526 | example of the contents of this file for running Exim is as follows: | |
2527 | ||
2528 | sendmail /usr/exim/bin/exim | |
2529 | send-mail /usr/exim/bin/exim | |
2530 | mailq /usr/exim/bin/exim -bp | |
2531 | newaliases /usr/bin/true | |
2532 | ||
2533 | Once you have set up the symbolic link, or edited /etc/mail/mailer.conf, your | |
2534 | Exim installation is "live". Check it by sending a message from your favourite | |
2535 | user agent. | |
2536 | ||
2537 | You should consider what to tell your users about the change of MTA. Exim may | |
2538 | have different capabilities to what was previously running, and there are | |
2539 | various operational differences such as the text of messages produced by | |
2540 | command line options and in bounce messages. If you allow your users to make | |
2541 | use of Exim's filtering capabilities, you should make the document entitled | |
2542 | Exim's interface to mail filtering available to them. | |
2543 | ||
2544 | ||
2545 | 4.21 Upgrading Exim | |
2546 | ------------------- | |
2547 | ||
2548 | If you are already running Exim on your host, building and installing a new | |
2549 | version automatically makes it available to MUAs, or any other programs that | |
2550 | call the MTA directly. However, if you are running an Exim daemon, you do need | |
2551 | to send it a HUP signal, to make it re-execute itself, and thereby pick up the | |
2552 | new binary. You do not need to stop processing mail in order to install a new | |
2553 | version of Exim. The install script does not modify an existing runtime | |
2554 | configuration file. | |
2555 | ||
2556 | ||
2557 | 4.22 Stopping the Exim daemon on Solaris | |
2558 | ---------------------------------------- | |
2559 | ||
2560 | The standard command for stopping the mailer daemon on Solaris is | |
2561 | ||
2562 | /etc/init.d/sendmail stop | |
2563 | ||
2564 | If /usr/lib/sendmail has been turned into a symbolic link, this script fails to | |
2565 | stop Exim because it uses the command ps -e and greps the output for the text | |
2566 | "sendmail"; this is not present because the actual program name (that is, | |
2567 | "exim") is given by the ps command with these options. A solution is to replace | |
2568 | the line that finds the process id with something like | |
2569 | ||
2570 | pid=`cat /var/spool/exim/exim-daemon.pid` | |
2571 | ||
2572 | to obtain the daemon's pid directly from the file that Exim saves it in. | |
2573 | ||
2574 | Note, however, that stopping the daemon does not "stop Exim". Messages can | |
2575 | still be received from local processes, and if automatic delivery is configured | |
2576 | (the normal case), deliveries will still occur. | |
2577 | ||
2578 | ||
2579 | ||
2580 | =============================================================================== | |
2581 | 5. THE EXIM COMMAND LINE | |
2582 | ||
2583 | Exim's command line takes the standard Unix form of a sequence of options, each | |
2584 | starting with a hyphen character, followed by a number of arguments. The | |
2585 | options are compatible with the main options of Sendmail, and there are also | |
2586 | some additional options, some of which are compatible with Smail 3. Certain | |
2587 | combinations of options do not make sense, and provoke an error if used. The | |
2588 | form of the arguments depends on which options are set. | |
2589 | ||
2590 | ||
2591 | 5.1 Setting options by program name | |
2592 | ----------------------------------- | |
2593 | ||
2594 | If Exim is called under the name mailq, it behaves as if the option -bp were | |
2595 | present before any other options. The -bp option requests a listing of the | |
2596 | contents of the mail queue on the standard output. This feature is for | |
2597 | compatibility with some systems that contain a command of that name in one of | |
2598 | the standard libraries, symbolically linked to /usr/sbin/sendmail or /usr/lib/ | |
2599 | sendmail. | |
2600 | ||
2601 | If Exim is called under the name rsmtp it behaves as if the option -bS were | |
2602 | present before any other options, for compatibility with Smail. The -bS option | |
2603 | is used for reading in a number of messages in batched SMTP format. | |
2604 | ||
2605 | If Exim is called under the name rmail it behaves as if the -i and -oee options | |
2606 | were present before any other options, for compatibility with Smail. The name | |
2607 | rmail is used as an interface by some UUCP systems. | |
2608 | ||
2609 | If Exim is called under the name runq it behaves as if the option -q were | |
2610 | present before any other options, for compatibility with Smail. The -q option | |
2611 | causes a single queue runner process to be started. | |
2612 | ||
2613 | If Exim is called under the name newaliases it behaves as if the option -bi | |
2614 | were present before any other options, for compatibility with Sendmail. This | |
2615 | option is used for rebuilding Sendmail's alias file. Exim does not have the | |
2616 | concept of a single alias file, but can be configured to run a given command if | |
2617 | called with the -bi option. | |
2618 | ||
2619 | ||
2620 | 5.2 Trusted and admin users | |
2621 | --------------------------- | |
2622 | ||
2623 | Some Exim options are available only to trusted users and others are available | |
2624 | only to admin users. In the description below, the phrases "Exim user" and | |
2625 | "Exim group" mean the user and group defined by EXIM_USER and EXIM_GROUP in | |
2626 | Local/Makefile or set by the exim_user and exim_group options. These do not | |
2627 | necessarily have to use the name "exim". | |
2628 | ||
2629 | * The trusted users are root, the Exim user, any user listed in the | |
2630 | trusted_users configuration option, and any user whose current group or any | |
2631 | supplementary group is one of those listed in the trusted_groups | |
2632 | configuration option. Note that the Exim group is not automatically | |
2633 | trusted. | |
2634 | ||
2635 | Trusted users are always permitted to use the -f option or a leading | |
2636 | "From " line to specify the envelope sender of a message that is passed to | |
2637 | Exim through the local interface (see the -bm and -f options below). See | |
2638 | the untrusted_set_sender option for a way of permitting non-trusted users | |
2639 | to set envelope senders. | |
2640 | ||
2641 | For a trusted user, there is never any check on the contents of the From: | |
2642 | header line, and a Sender: line is never added. Furthermore, any existing | |
2643 | Sender: line in incoming local (non-TCP/IP) messages is not removed. | |
2644 | ||
2645 | Trusted users may also specify a host name, host address, interface | |
2646 | address, protocol name, ident value, and authentication data when | |
2647 | submitting a message locally. Thus, they are able to insert messages into | |
2648 | Exim's queue locally that have the characteristics of messages received | |
2649 | from a remote host. Untrusted users may in some circumstances use -f, but | |
2650 | can never set the other values that are available to trusted users. | |
2651 | ||
2652 | * The admin users are root, the Exim user, and any user that is a member of | |
2653 | the Exim group or of any group listed in the admin_groups configuration | |
2654 | option. The current group does not have to be one of these groups. | |
2655 | ||
2656 | Admin users are permitted to list the queue, and to carry out certain | |
2657 | operations on messages, for example, to force delivery failures. It is also | |
2658 | necessary to be an admin user in order to see the full information provided | |
2659 | by the Exim monitor, and full debugging output. | |
2660 | ||
2661 | By default, the use of the -M, -q, -R, and -S options to cause Exim to | |
2662 | attempt delivery of messages on its queue is restricted to admin users. | |
2663 | However, this restriction can be relaxed by setting the prod_requires_admin | |
2664 | option false (that is, specifying no_prod_requires_admin). | |
2665 | ||
2666 | Similarly, the use of the -bp option to list all the messages in the queue | |
2667 | is restricted to admin users unless queue_list_requires_admin is set false. | |
2668 | ||
2669 | Warning: If you configure your system so that admin users are able to edit | |
2670 | Exim's configuration file, you are giving those users an easy way of getting | |
2671 | root. There is further discussion of this issue at the start of chapter 6. | |
2672 | ||
2673 | ||
2674 | 5.3 Command line options | |
2675 | ------------------------ | |
2676 | ||
2677 | Exim's command line options are described in alphabetical order below. If none | |
2678 | of the options that specifies a specific action (such as starting the daemon or | |
2679 | a queue runner, or testing an address, or receiving a message in a specific | |
2680 | format, or listing the queue) are present, and there is at least one argument | |
2681 | on the command line, -bm (accept a local message on the standard input, with | |
2682 | the arguments specifying the recipients) is assumed. Otherwise, Exim outputs a | |
2683 | brief message about itself and exits. | |
2684 | ||
2685 | -- | |
2686 | ||
2687 | This is a pseudo-option whose only purpose is to terminate the options and | |
2688 | therefore to cause subsequent command line items to be treated as arguments | |
2689 | rather than options, even if they begin with hyphens. | |
2690 | ||
2691 | --help | |
2692 | ||
2693 | This option causes Exim to output a few sentences stating what it is. The | |
2694 | same output is generated if the Exim binary is called with no options and | |
2695 | no arguments. | |
2696 | ||
2697 | --version | |
2698 | ||
2699 | This option is an alias for -bV and causes version information to be | |
2700 | displayed. | |
2701 | ||
2702 | -Ac, -Am | |
2703 | ||
2704 | These options are used by Sendmail for selecting configuration files and | |
2705 | are ignored by Exim. | |
2706 | ||
2707 | -B<type> | |
2708 | ||
2709 | This is a Sendmail option for selecting 7 or 8 bit processing. Exim is | |
2710 | 8-bit clean; it ignores this option. | |
2711 | ||
2712 | -bd | |
2713 | ||
2714 | This option runs Exim as a daemon, awaiting incoming SMTP connections. | |
2715 | Usually the -bd option is combined with the -q<time> option, to specify | |
2716 | that the daemon should also initiate periodic queue runs. | |
2717 | ||
2718 | The -bd option can be used only by an admin user. If either of the -d | |
2719 | (debugging) or -v (verifying) options are set, the daemon does not | |
2720 | disconnect from the controlling terminal. When running this way, it can be | |
2721 | stopped by pressing ctrl-C. | |
2722 | ||
2723 | By default, Exim listens for incoming connections to the standard SMTP port | |
2724 | on all the host's running interfaces. However, it is possible to listen on | |
2725 | other ports, on multiple ports, and only on specific interfaces. Chapter 13 | |
2726 | contains a description of the options that control this. | |
2727 | ||
2728 | When a listening daemon is started without the use of -oX (that is, without | |
2729 | overriding the normal configuration), it writes its process id to a file | |
2730 | called exim-daemon.pid in Exim's spool directory. This location can be | |
2731 | overridden by setting PID_FILE_PATH in Local/Makefile. The file is written | |
2732 | while Exim is still running as root. | |
2733 | ||
2734 | When -oX is used on the command line to start a listening daemon, the | |
2735 | process id is not written to the normal pid file path. However, -oP can be | |
2736 | used to specify a path on the command line if a pid file is required. | |
2737 | ||
2738 | The SIGHUP signal can be used to cause the daemon to re-execute itself. | |
2739 | This should be done whenever Exim's configuration file, or any file that is | |
2740 | incorporated into it by means of the .include facility, is changed, and | |
2741 | also whenever a new version of Exim is installed. It is not necessary to do | |
2742 | this when other files that are referenced from the configuration (for | |
2743 | example, alias files) are changed, because these are reread each time they | |
2744 | are used. | |
2745 | ||
2746 | -bdf | |
2747 | ||
2748 | This option has the same effect as -bd except that it never disconnects | |
2749 | from the controlling terminal, even when no debugging is specified. | |
2750 | ||
2751 | -be | |
2752 | ||
2753 | Run Exim in expansion testing mode. Exim discards its root privilege, to | |
2754 | prevent ordinary users from using this mode to read otherwise inaccessible | |
2755 | files. If no arguments are given, Exim runs interactively, prompting for | |
2756 | lines of data. Otherwise, it processes each argument in turn. | |
2757 | ||
2758 | If Exim was built with USE_READLINE=yes in Local/Makefile, it tries to load | |
2759 | the libreadline library dynamically whenever the -be option is used without | |
2760 | command line arguments. If successful, it uses the readline() function, | |
2761 | which provides extensive line-editing facilities, for reading the test | |
2762 | data. A line history is supported. | |
2763 | ||
2764 | Long expansion expressions can be split over several lines by using | |
2765 | backslash continuations. As in Exim's run time configuration, white space | |
2766 | at the start of continuation lines is ignored. Each argument or data line | |
2767 | is passed through the string expansion mechanism, and the result is output. | |
2768 | Variable values from the configuration file (for example, $qualify_domain) | |
2769 | are available, but no message-specific values (such as $sender_domain) are | |
2770 | set, because no message is being processed (but see -bem and -Mset). | |
2771 | ||
2772 | Note: If you use this mechanism to test lookups, and you change the data | |
2773 | files or databases you are using, you must exit and restart Exim before | |
2774 | trying the same lookup again. Otherwise, because each Exim process caches | |
2775 | the results of lookups, you will just get the same result as before. | |
2776 | ||
2777 | -bem <filename> | |
2778 | ||
2779 | This option operates like -be except that it must be followed by the name | |
2780 | of a file. For example: | |
2781 | ||
2782 | exim -bem /tmp/testmessage | |
2783 | ||
2784 | The file is read as a message (as if receiving a locally-submitted non-SMTP | |
2785 | message) before any of the test expansions are done. Thus, message-specific | |
2786 | variables such as $message_size and $header_from: are available. However, | |
2787 | no Received: header is added to the message. If the -t option is set, | |
2788 | recipients are read from the headers in the normal way, and are shown in | |
2789 | the $recipients variable. Note that recipients cannot be given on the | |
2790 | command line, because further arguments are taken as strings to expand | |
2791 | (just like -be). | |
2792 | ||
2793 | -bF <filename> | |
2794 | ||
2795 | This option is the same as -bf except that it assumes that the filter being | |
2796 | tested is a system filter. The additional commands that are available only | |
2797 | in system filters are recognized. | |
2798 | ||
2799 | -bf <filename> | |
2800 | ||
2801 | This option runs Exim in user filter testing mode; the file is the filter | |
2802 | file to be tested, and a test message must be supplied on the standard | |
2803 | input. If there are no message-dependent tests in the filter, an empty file | |
2804 | can be supplied. | |
2805 | ||
2806 | If you want to test a system filter file, use -bF instead of -bf. You can | |
2807 | use both -bF and -bf on the same command, in order to test a system filter | |
2808 | and a user filter in the same run. For example: | |
2809 | ||
2810 | exim -bF /system/filter -bf /user/filter </test/message | |
2811 | ||
2812 | This is helpful when the system filter adds header lines or sets filter | |
2813 | variables that are used by the user filter. | |
2814 | ||
2815 | If the test filter file does not begin with one of the special lines | |
2816 | ||
2817 | # Exim filter | |
2818 | # Sieve filter | |
2819 | ||
2820 | it is taken to be a normal .forward file, and is tested for validity under | |
2821 | that interpretation. See sections 22.4 to 22.6 for a description of the | |
2822 | possible contents of non-filter redirection lists. | |
2823 | ||
2824 | The result of an Exim command that uses -bf, provided no errors are | |
2825 | detected, is a list of the actions that Exim would try to take if presented | |
2826 | with the message for real. More details of filter testing are given in the | |
2827 | separate document entitled Exim's interfaces to mail filtering. | |
2828 | ||
2829 | When testing a filter file, the envelope sender can be set by the -f | |
2830 | option, or by a "From " line at the start of the test message. Various | |
2831 | parameters that would normally be taken from the envelope recipient address | |
2832 | of the message can be set by means of additional command line options (see | |
2833 | the next four options). | |
2834 | ||
2835 | -bfd <domain> | |
2836 | ||
2837 | This sets the domain of the recipient address when a filter file is being | |
2838 | tested by means of the -bf option. The default is the value of | |
2839 | $qualify_domain. | |
2840 | ||
2841 | -bfl <local part> | |
2842 | ||
2843 | This sets the local part of the recipient address when a filter file is | |
2844 | being tested by means of the -bf option. The default is the username of the | |
2845 | process that calls Exim. A local part should be specified with any prefix | |
2846 | or suffix stripped, because that is how it appears to the filter when a | |
2847 | message is actually being delivered. | |
2848 | ||
2849 | -bfp <prefix> | |
2850 | ||
2851 | This sets the prefix of the local part of the recipient address when a | |
2852 | filter file is being tested by means of the -bf option. The default is an | |
2853 | empty prefix. | |
2854 | ||
2855 | -bfs <suffix> | |
2856 | ||
2857 | This sets the suffix of the local part of the recipient address when a | |
2858 | filter file is being tested by means of the -bf option. The default is an | |
2859 | empty suffix. | |
2860 | ||
2861 | -bh <IP address> | |
2862 | ||
2863 | This option runs a fake SMTP session as if from the given IP address, using | |
2864 | the standard input and output. The IP address may include a port number at | |
2865 | the end, after a full stop. For example: | |
2866 | ||
2867 | exim -bh 10.9.8.7.1234 | |
2868 | exim -bh fe80::a00:20ff:fe86:a061.5678 | |
2869 | ||
2870 | When an IPv6 address is given, it is converted into canonical form. In the | |
2871 | case of the second example above, the value of $sender_host_address after | |
2872 | conversion to the canonical form is | |
2873 | "fe80:0000:0000:0a00:20ff:fe86:a061.5678". | |
2874 | ||
2875 | Comments as to what is going on are written to the standard error file. | |
2876 | These include lines beginning with "LOG" for anything that would have been | |
2877 | logged. This facility is provided for testing configuration options for | |
2878 | incoming messages, to make sure they implement the required policy. For | |
2879 | example, you can test your relay controls using -bh. | |
2880 | ||
2881 | Warning 1: You can test features of the configuration that rely on ident | |
2882 | (RFC 1413) information by using the -oMt option. However, Exim cannot | |
2883 | actually perform an ident callout when testing using -bh because there is | |
2884 | no incoming SMTP connection. | |
2885 | ||
2886 | Warning 2: Address verification callouts (see section 42.45) are also | |
2887 | skipped when testing using -bh. If you want these callouts to occur, use | |
2888 | -bhc instead. | |
2889 | ||
2890 | Messages supplied during the testing session are discarded, and nothing is | |
2891 | written to any of the real log files. There may be pauses when DNS (and | |
2892 | other) lookups are taking place, and of course these may time out. The -oMi | |
2893 | option can be used to specify a specific IP interface and port if this is | |
2894 | important, and -oMaa and -oMai can be used to set parameters as if the SMTP | |
2895 | session were authenticated. | |
2896 | ||
2897 | The exim_checkaccess utility is a "packaged" version of -bh whose output | |
2898 | just states whether a given recipient address from a given host is | |
2899 | acceptable or not. See section 52.8. | |
2900 | ||
2901 | Features such as authentication and encryption, where the client input is | |
2902 | not plain text, cannot easily be tested with -bh. Instead, you should use a | |
2903 | specialized SMTP test program such as swaks. | |
2904 | ||
2905 | -bhc <IP address> | |
2906 | ||
2907 | This option operates in the same way as -bh, except that address | |
2908 | verification callouts are performed if required. This includes consulting | |
2909 | and updating the callout cache database. | |
2910 | ||
2911 | -bi | |
2912 | ||
2913 | Sendmail interprets the -bi option as a request to rebuild its alias file. | |
2914 | Exim does not have the concept of a single alias file, and so it cannot | |
2915 | mimic this behaviour. However, calls to /usr/lib/sendmail with the -bi | |
2916 | option tend to appear in various scripts such as NIS make files, so the | |
2917 | option must be recognized. | |
2918 | ||
2919 | If -bi is encountered, the command specified by the bi_command | |
2920 | configuration option is run, under the uid and gid of the caller of Exim. | |
2921 | If the -oA option is used, its value is passed to the command as an | |
2922 | argument. The command set by bi_command may not contain arguments. The | |
2923 | command can use the exim_dbmbuild utility, or some other means, to rebuild | |
2924 | alias files if this is required. If the bi_command option is not set, | |
2925 | calling Exim with -bi is a no-op. | |
2926 | ||
2927 | -bI:help | |
2928 | ||
2929 | We shall provide various options starting "-bI:" for querying Exim for | |
2930 | information. The output of many of these will be intended for machine | |
2931 | consumption. This one is not. The -bI:help option asks Exim for a synopsis | |
2932 | of supported options beginning "-bI:". Use of any of these options shall | |
2933 | cause Exim to exit after producing the requested output. | |
2934 | ||
2935 | -bI:dscp | |
2936 | ||
2937 | This option causes Exim to emit an alphabetically sorted list of all | |
2938 | recognised DSCP names. | |
2939 | ||
2940 | -bI:sieve | |
2941 | ||
2942 | This option causes Exim to emit an alphabetically sorted list of all | |
2943 | supported Sieve protocol extensions on stdout, one per line. This is | |
2944 | anticipated to be useful for ManageSieve (RFC 5804) implementations, in | |
2945 | providing that protocol's "SIEVE" capability response line. As the precise | |
2946 | list may depend upon compile-time build options, which this option will | |
2947 | adapt to, this is the only way to guarantee a correct response. | |
2948 | ||
2949 | -bm | |
2950 | ||
2951 | This option runs an Exim receiving process that accepts an incoming, | |
2952 | locally-generated message on the standard input. The recipients are given | |
2953 | as the command arguments (except when -t is also present - see below). Each | |
2954 | argument can be a comma-separated list of RFC 2822 addresses. This is the | |
2955 | default option for selecting the overall action of an Exim call; it is | |
2956 | assumed if no other conflicting option is present. | |
2957 | ||
2958 | If any addresses in the message are unqualified (have no domain), they are | |
2959 | qualified by the values of the qualify_domain or qualify_recipient options, | |
2960 | as appropriate. The -bnq option (see below) provides a way of suppressing | |
2961 | this for special cases. | |
2962 | ||
2963 | Policy checks on the contents of local messages can be enforced by means of | |
2964 | the non-SMTP ACL. See chapter 42 for details. | |
2965 | ||
2966 | The return code is zero if the message is successfully accepted. Otherwise, | |
2967 | the action is controlled by the -oex option setting - see below. | |
2968 | ||
2969 | The format of the message must be as defined in RFC 2822, except that, for | |
2970 | compatibility with Sendmail and Smail, a line in one of the forms | |
2971 | ||
2972 | From sender Fri Jan 5 12:55 GMT 1997 | |
2973 | From sender Fri, 5 Jan 97 12:55:01 | |
2974 | ||
2975 | (with the weekday optional, and possibly with additional text after the | |
2976 | date) is permitted to appear at the start of the message. There appears to | |
2977 | be no authoritative specification of the format of this line. Exim | |
2978 | recognizes it by matching against the regular expression defined by the | |
2979 | uucp_from_pattern option, which can be changed if necessary. | |
2980 | ||
2981 | The specified sender is treated as if it were given as the argument to the | |
2982 | -f option, but if a -f option is also present, its argument is used in | |
2983 | preference to the address taken from the message. The caller of Exim must | |
2984 | be a trusted user for the sender of a message to be set in this way. | |
2985 | ||
2986 | -bmalware <filename> | |
2987 | ||
2988 | This debugging option causes Exim to scan the given file, using the malware | |
2989 | scanning framework. The option of av_scanner influences this option, so if | |
2990 | av_scanner's value is dependent upon an expansion then the expansion should | |
2991 | have defaults which apply to this invocation. ACLs are not invoked, so if | |
2992 | av_scanner references an ACL variable then that variable will never be | |
2993 | populated and -bmalware will fail. | |
2994 | ||
2995 | Exim will have changed working directory before resolving the filename, so | |
2996 | using fully qualified pathnames is advisable. Exim will be running as the | |
2997 | Exim user when it tries to open the file, rather than as the invoking user. | |
2998 | This option requires admin privileges. | |
2999 | ||
3000 | The -bmalware option will not be extended to be more generally useful, | |
3001 | there are better tools for file-scanning. This option exists to help | |
3002 | administrators verify their Exim and AV scanner configuration. | |
3003 | ||
3004 | -bnq | |
3005 | ||
3006 | By default, Exim automatically qualifies unqualified addresses (those | |
3007 | without domains) that appear in messages that are submitted locally (that | |
3008 | is, not over TCP/IP). This qualification applies both to addresses in | |
3009 | envelopes, and addresses in header lines. Sender addresses are qualified | |
3010 | using qualify_domain, and recipient addresses using qualify_recipient | |
3011 | (which defaults to the value of qualify_domain). | |
3012 | ||
3013 | Sometimes, qualification is not wanted. For example, if -bS (batch SMTP) is | |
3014 | being used to re-submit messages that originally came from remote hosts | |
3015 | after content scanning, you probably do not want to qualify unqualified | |
3016 | addresses in header lines. (Such lines will be present only if you have not | |
3017 | enabled a header syntax check in the appropriate ACL.) | |
3018 | ||
3019 | The -bnq option suppresses all qualification of unqualified addresses in | |
3020 | messages that originate on the local host. When this is used, unqualified | |
3021 | addresses in the envelope provoke errors (causing message rejection) and | |
3022 | unqualified addresses in header lines are left alone. | |
3023 | ||
3024 | -bP | |
3025 | ||
3026 | If this option is given with no arguments, it causes the values of all | |
3027 | Exim's main configuration options to be written to the standard output. The | |
3028 | values of one or more specific options can be requested by giving their | |
3029 | names as arguments, for example: | |
3030 | ||
3031 | exim -bP qualify_domain hold_domains | |
3032 | ||
3033 | However, any option setting that is preceded by the word "hide" in the | |
3034 | configuration file is not shown in full, except to an admin user. For other | |
3035 | users, the output is as in this example: | |
3036 | ||
3037 | mysql_servers = <value not displayable> | |
3038 | ||
3039 | If configure_file is given as an argument, the name of the run time | |
3040 | configuration file is output. If a list of configuration files was | |
3041 | supplied, the value that is output here is the name of the file that was | |
3042 | actually used. | |
3043 | ||
3044 | If the -n flag is given, then for most modes of -bP operation the name will | |
3045 | not be output. | |
3046 | ||
3047 | If log_file_path or pid_file_path are given, the names of the directories | |
3048 | where log files and daemon pid files are written are output, respectively. | |
3049 | If these values are unset, log files are written in a sub-directory of the | |
3050 | spool directory called log, and the pid file is written directly into the | |
3051 | spool directory. | |
3052 | ||
3053 | If -bP is followed by a name preceded by "+", for example, | |
3054 | ||
3055 | exim -bP +local_domains | |
3056 | ||
3057 | it searches for a matching named list of any type (domain, host, address, | |
3058 | or local part) and outputs what it finds. | |
3059 | ||
3060 | If one of the words router, transport, or authenticator is given, followed | |
3061 | by the name of an appropriate driver instance, the option settings for that | |
3062 | driver are output. For example: | |
3063 | ||
3064 | exim -bP transport local_delivery | |
3065 | ||
3066 | The generic driver options are output first, followed by the driver's | |
3067 | private options. A list of the names of drivers of a particular type can be | |
3068 | obtained by using one of the words router_list, transport_list, or | |
3069 | authenticator_list, and a complete list of all drivers with their option | |
3070 | settings can be obtained by using routers, transports, or authenticators. | |
3071 | ||
188b6fee CE |
3072 | If environment is given as an argument, the set of environment variables is |
3073 | output, line by line. Using the -n flag supresses the value of the | |
3074 | variables. | |
3075 | ||
420a0d19 CE |
3076 | If invoked by an admin user, then macro, macro_list and macros are |
3077 | available, similarly to the drivers. Because macros are sometimes used for | |
3078 | storing passwords, this option is restricted. The output format is one item | |
3079 | per line. | |
3080 | ||
3081 | -bp | |
3082 | ||
3083 | This option requests a listing of the contents of the mail queue on the | |
3084 | standard output. If the -bp option is followed by a list of message ids, | |
3085 | just those messages are listed. By default, this option can be used only by | |
3086 | an admin user. However, the queue_list_requires_admin option can be set | |
3087 | false to allow any user to see the queue. | |
3088 | ||
3089 | Each message on the queue is displayed as in the following example: | |
3090 | ||
3091 | 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example> | |
3092 | red.king@looking-glass.fict.example | |
3093 | <other addresses> | |
3094 | ||
3095 | The first line contains the length of time the message has been on the | |
3096 | queue (in this case 25 minutes), the size of the message (2.9K), the unique | |
3097 | local identifier for the message, and the message sender, as contained in | |
3098 | the envelope. For bounce messages, the sender address is empty, and appears | |
3099 | as "<>". If the message was submitted locally by an untrusted user who | |
3100 | overrode the default sender address, the user's login name is shown in | |
3101 | parentheses before the sender address. | |
3102 | ||
3103 | If the message is frozen (attempts to deliver it are suspended) then the | |
3104 | text "*** frozen ***" is displayed at the end of this line. | |
3105 | ||
3106 | The recipients of the message (taken from the envelope, not the headers) | |
3107 | are displayed on subsequent lines. Those addresses to which the message has | |
3108 | already been delivered are marked with the letter D. If an original address | |
3109 | gets expanded into several addresses via an alias or forward file, the | |
3110 | original is displayed with a D only when deliveries for all of its child | |
3111 | addresses are complete. | |
3112 | ||
3113 | -bpa | |
3114 | ||
3115 | This option operates like -bp, but in addition it shows delivered addresses | |
3116 | that were generated from the original top level address(es) in each message | |
3117 | by alias or forwarding operations. These addresses are flagged with "+D" | |
3118 | instead of just "D". | |
3119 | ||
3120 | -bpc | |
3121 | ||
3122 | This option counts the number of messages on the queue, and writes the | |
3123 | total to the standard output. It is restricted to admin users, unless | |
3124 | queue_list_requires_admin is set false. | |
3125 | ||
3126 | -bpr | |
3127 | ||
3128 | This option operates like -bp, but the output is not sorted into | |
3129 | chronological order of message arrival. This can speed it up when there are | |
3130 | lots of messages on the queue, and is particularly useful if the output is | |
3131 | going to be post-processed in a way that doesn't need the sorting. | |
3132 | ||
3133 | -bpra | |
3134 | ||
3135 | This option is a combination of -bpr and -bpa. | |
3136 | ||
3137 | -bpru | |
3138 | ||
3139 | This option is a combination of -bpr and -bpu. | |
3140 | ||
3141 | -bpu | |
3142 | ||
3143 | This option operates like -bp but shows only undelivered top-level | |
3144 | addresses for each message displayed. Addresses generated by aliasing or | |
3145 | forwarding are not shown, unless the message was deferred after processing | |
3146 | by a router with the one_time option set. | |
3147 | ||
3148 | -brt | |
3149 | ||
3150 | This option is for testing retry rules, and it must be followed by up to | |
3151 | three arguments. It causes Exim to look for a retry rule that matches the | |
3152 | values and to write it to the standard output. For example: | |
3153 | ||
3154 | exim -brt bach.comp.mus.example | |
3155 | Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m; | |
3156 | ||
3157 | See chapter 32 for a description of Exim's retry rules. The first argument, | |
3158 | which is required, can be a complete address in the form local_part@domain, | |
3159 | or it can be just a domain name. If the second argument contains a dot, it | |
3160 | is interpreted as an optional second domain name; if no retry rule is found | |
3161 | for the first argument, the second is tried. This ties in with Exim's | |
3162 | behaviour when looking for retry rules for remote hosts - if no rule is | |
3163 | found that matches the host, one that matches the mail domain is sought. | |
3164 | Finally, an argument that is the name of a specific delivery error, as used | |
3165 | in setting up retry rules, can be given. For example: | |
3166 | ||
3167 | exim -brt haydn.comp.mus.example quota_3d | |
3168 | Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m | |
3169 | ||
3170 | -brw | |
3171 | ||
3172 | This option is for testing address rewriting rules, and it must be followed | |
3173 | by a single argument, consisting of either a local part without a domain, | |
3174 | or a complete address with a fully qualified domain. Exim outputs how this | |
3175 | address would be rewritten for each possible place it might appear. See | |
3176 | chapter 31 for further details. | |
3177 | ||
3178 | -bS | |
3179 | ||
3180 | This option is used for batched SMTP input, which is an alternative | |
3181 | interface for non-interactive local message submission. A number of | |
3182 | messages can be submitted in a single run. However, despite its name, this | |
3183 | is not really SMTP input. Exim reads each message's envelope from SMTP | |
3184 | commands on the standard input, but generates no responses. If the caller | |
3185 | is trusted, or untrusted_set_sender is set, the senders in the SMTP MAIL | |
3186 | commands are believed; otherwise the sender is always the caller of Exim. | |
3187 | ||
3188 | The message itself is read from the standard input, in SMTP format (leading | |
3189 | dots doubled), terminated by a line containing just a single dot. An error | |
3190 | is provoked if the terminating dot is missing. A further message may then | |
3191 | follow. | |
3192 | ||
3193 | As for other local message submissions, the contents of incoming batch SMTP | |
3194 | messages can be checked using the non-SMTP ACL (see chapter 42). | |
3195 | Unqualified addresses are automatically qualified using qualify_domain and | |
3196 | qualify_recipient, as appropriate, unless the -bnq option is used. | |
3197 | ||
3198 | Some other SMTP commands are recognized in the input. HELO and EHLO act as | |
3199 | RSET; VRFY, EXPN, ETRN, and HELP act as NOOP; QUIT quits, ignoring the rest | |
3200 | of the standard input. | |
3201 | ||
3202 | If any error is encountered, reports are written to the standard output and | |
3203 | error streams, and Exim gives up immediately. The return code is 0 if no | |
3204 | error was detected; it is 1 if one or more messages were accepted before | |
3205 | the error was detected; otherwise it is 2. | |
3206 | ||
3207 | More details of input using batched SMTP are given in section 47.11. | |
3208 | ||
3209 | -bs | |
3210 | ||
3211 | This option causes Exim to accept one or more messages by reading SMTP | |
3212 | commands on the standard input, and producing SMTP replies on the standard | |
3213 | output. SMTP policy controls, as defined in ACLs (see chapter 42) are | |
3214 | applied. Some user agents use this interface as a way of passing | |
3215 | locally-generated messages to the MTA. | |
3216 | ||
3217 | In this usage, if the caller of Exim is trusted, or untrusted_set_sender is | |
3218 | set, the senders of messages are taken from the SMTP MAIL commands. | |
3219 | Otherwise the content of these commands is ignored and the sender is set up | |
3220 | as the calling user. Unqualified addresses are automatically qualified | |
3221 | using qualify_domain and qualify_recipient, as appropriate, unless the -bnq | |
3222 | option is used. | |
3223 | ||
3224 | The -bs option is also used to run Exim from inetd, as an alternative to | |
3225 | using a listening daemon. Exim can distinguish the two cases by checking | |
3226 | whether the standard input is a TCP/IP socket. When Exim is called from | |
3227 | inetd, the source of the mail is assumed to be remote, and the comments | |
3228 | above concerning senders and qualification do not apply. In this situation, | |
3229 | Exim behaves in exactly the same way as it does when receiving a message | |
3230 | via the listening daemon. | |
3231 | ||
3232 | -bt | |
3233 | ||
3234 | This option runs Exim in address testing mode, in which each argument is | |
3235 | taken as a recipient address to be tested for deliverability. The results | |
3236 | are written to the standard output. If a test fails, and the caller is not | |
3237 | an admin user, no details of the failure are output, because these might | |
3238 | contain sensitive information such as usernames and passwords for database | |
3239 | lookups. | |
3240 | ||
3241 | If no arguments are given, Exim runs in an interactive manner, prompting | |
3242 | with a right angle bracket for addresses to be tested. | |
3243 | ||
3244 | Unlike the -be test option, you cannot arrange for Exim to use the readline | |
3245 | () function, because it is running as root and there are security issues. | |
3246 | ||
3247 | Each address is handled as if it were the recipient address of a message | |
3248 | (compare the -bv option). It is passed to the routers and the result is | |
3249 | written to the standard output. However, any router that has | |
3250 | no_address_test set is bypassed. This can make -bt easier to use for | |
3251 | genuine routing tests if your first router passes everything to a scanner | |
3252 | program. | |
3253 | ||
3254 | The return code is 2 if any address failed outright; it is 1 if no address | |
3255 | failed outright but at least one could not be resolved for some reason. | |
3256 | Return code 0 is given only when all addresses succeed. | |
3257 | ||
3258 | Note: When actually delivering a message, Exim removes duplicate recipient | |
3259 | addresses after routing is complete, so that only one delivery takes place. | |
3260 | This does not happen when testing with -bt; the full results of routing are | |
3261 | always shown. | |
3262 | ||
3263 | Warning: -bt can only do relatively simple testing. If any of the routers | |
3264 | in the configuration makes any tests on the sender address of a message, | |
3265 | you can use the -f option to set an appropriate sender when running -bt | |
3266 | tests. Without it, the sender is assumed to be the calling user at the | |
3267 | default qualifying domain. However, if you have set up (for example) | |
3268 | routers whose behaviour depends on the contents of an incoming message, you | |
3269 | cannot test those conditions using -bt. The -N option provides a possible | |
3270 | way of doing such tests. | |
3271 | ||
3272 | -bV | |
3273 | ||
3274 | This option causes Exim to write the current version number, compilation | |
3275 | number, and compilation date of the exim binary to the standard output. It | |
3276 | also lists the DBM library that is being used, the optional modules (such | |
3277 | as specific lookup types), the drivers that are included in the binary, and | |
3278 | the name of the run time configuration file that is in use. | |
3279 | ||
3280 | As part of its operation, -bV causes Exim to read and syntax check its | |
3281 | configuration file. However, this is a static check only. It cannot check | |
3282 | values that are to be expanded. For example, although a misspelt ACL verb | |
3283 | is detected, an error in the verb's arguments is not. You cannot rely on | |
3284 | -bV alone to discover (for example) all the typos in the configuration; | |
3285 | some realistic testing is needed. The -bh and -N options provide more | |
3286 | dynamic testing facilities. | |
3287 | ||
3288 | -bv | |
3289 | ||
3290 | This option runs Exim in address verification mode, in which each argument | |
3291 | is taken as a recipient address to be verified by the routers. (This does | |
3292 | not involve any verification callouts). During normal operation, | |
3293 | verification happens mostly as a consequence processing a verify condition | |
3294 | in an ACL (see chapter 42). If you want to test an entire ACL, possibly | |
3295 | including callouts, see the -bh and -bhc options. | |
3296 | ||
3297 | If verification fails, and the caller is not an admin user, no details of | |
3298 | the failure are output, because these might contain sensitive information | |
3299 | such as usernames and passwords for database lookups. | |
3300 | ||
3301 | If no arguments are given, Exim runs in an interactive manner, prompting | |
3302 | with a right angle bracket for addresses to be verified. | |
3303 | ||
3304 | Unlike the -be test option, you cannot arrange for Exim to use the readline | |
3305 | () function, because it is running as exim and there are security issues. | |
3306 | ||
3307 | Verification differs from address testing (the -bt option) in that routers | |
3308 | that have no_verify set are skipped, and if the address is accepted by a | |
3309 | router that has fail_verify set, verification fails. The address is | |
3310 | verified as a recipient if -bv is used; to test verification for a sender | |
3311 | address, -bvs should be used. | |
3312 | ||
3313 | If the -v option is not set, the output consists of a single line for each | |
3314 | address, stating whether it was verified or not, and giving a reason in the | |
3315 | latter case. Without -v, generating more than one address by redirection | |
3316 | causes verification to end successfully, without considering the generated | |
3317 | addresses. However, if just one address is generated, processing continues, | |
3318 | and the generated address must verify successfully for the overall | |
3319 | verification to succeed. | |
3320 | ||
3321 | When -v is set, more details are given of how the address has been handled, | |
3322 | and in the case of address redirection, all the generated addresses are | |
3323 | also considered. Verification may succeed for some and fail for others. | |
3324 | ||
3325 | The return code is 2 if any address failed outright; it is 1 if no address | |
3326 | failed outright but at least one could not be resolved for some reason. | |
3327 | Return code 0 is given only when all addresses succeed. | |
3328 | ||
3329 | If any of the routers in the configuration makes any tests on the sender | |
3330 | address of a message, you should use the -f option to set an appropriate | |
3331 | sender when running -bv tests. Without it, the sender is assumed to be the | |
3332 | calling user at the default qualifying domain. | |
3333 | ||
3334 | -bvs | |
3335 | ||
3336 | This option acts like -bv, but verifies the address as a sender rather than | |
3337 | a recipient address. This affects any rewriting and qualification that | |
3338 | might happen. | |
3339 | ||
3340 | -bw | |
3341 | ||
3342 | This option runs Exim as a daemon, awaiting incoming SMTP connections, | |
3343 | similarly to the -bd option. All port specifications on the command-line | |
3344 | and in the configuration file are ignored. Queue-running may not be | |
3345 | specified. | |
3346 | ||
3347 | In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is | |
3348 | listening for connections. This permits the system to start up and have | |
3349 | inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for | |
3350 | each port only when the first connection is received. | |
3351 | ||
3352 | If the option is given as -bw<time> then the time is a timeout, after which | |
3353 | the daemon will exit, which should cause inetd to listen once more. | |
3354 | ||
3355 | -C <filelist> | |
3356 | ||
3357 | This option causes Exim to find the run time configuration file from the | |
3358 | given list instead of from the list specified by the CONFIGURE_FILE | |
3359 | compile-time setting. Usually, the list will consist of just a single file | |
3360 | name, but it can be a colon-separated list of names. In this case, the | |
3361 | first file that exists is used. Failure to open an existing file stops Exim | |
3362 | from proceeding any further along the list, and an error is generated. | |
3363 | ||
188b6fee CE |
3364 | The file names need to be absolute names. |
3365 | ||
420a0d19 CE |
3366 | When this option is used by a caller other than root, and the list is |
3367 | different from the compiled-in list, Exim gives up its root privilege | |
3368 | immediately, and runs with the real and effective uid and gid set to those | |
3369 | of the caller. However, if a TRUSTED_CONFIG_LIST file is defined in Local/ | |
3370 | Makefile, that file contains a list of full pathnames, one per line, for | |
3371 | configuration files which are trusted. Root privilege is retained for any | |
3372 | configuration file so listed, as long as the caller is the Exim user (or | |
3373 | the user specified in the CONFIGURE_OWNER option, if any), and as long as | |
3374 | the configuration file is not writeable by inappropriate users or groups. | |
3375 | ||
3376 | Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a | |
3377 | configuration using -C right through message reception and delivery, even | |
3378 | if the caller is root. The reception works, but by that time, Exim is | |
3379 | running as the Exim user, so when it re-executes to regain privilege for | |
3380 | the delivery, the use of -C causes privilege to be lost. However, root can | |
3381 | test reception and delivery using two separate commands (one to put a | |
3382 | message on the queue, using -odq, and another to do the delivery, using -M | |
3383 | ). | |
3384 | ||
3385 | If ALT_CONFIG_PREFIX is defined in Local/Makefile, it specifies a prefix | |
3386 | string with which any file named in a -C command line option must start. In | |
3387 | addition, the file name must not contain the sequence "/../". However, if | |
3388 | the value of the -C option is identical to the value of CONFIGURE_FILE in | |
3389 | Local/Makefile, Exim ignores -C and proceeds as usual. There is no default | |
3390 | setting for ALT_CONFIG_PREFIX; when it is unset, any file name can be used | |
3391 | with -C. | |
3392 | ||
3393 | ALT_CONFIG_PREFIX can be used to confine alternative configuration files to | |
3394 | a directory to which only root has access. This prevents someone who has | |
3395 | broken into the Exim account from running a privileged Exim with an | |
3396 | arbitrary configuration file. | |
3397 | ||
3398 | The -C facility is useful for ensuring that configuration files are | |
3399 | syntactically correct, but cannot be used for test deliveries, unless the | |
3400 | caller is privileged, or unless it is an exotic configuration that does not | |
3401 | require privilege. No check is made on the owner or group of the files | |
3402 | specified by this option. | |
3403 | ||
3404 | -D<macro>=<value> | |
3405 | ||
3406 | This option can be used to override macro definitions in the configuration | |
3407 | file (see section 6.4). However, like -C, if it is used by an unprivileged | |
3408 | caller, it causes Exim to give up its root privilege. If DISABLE_D_OPTION | |
3409 | is defined in Local/Makefile, the use of -D is completely disabled, and its | |
3410 | use causes an immediate error exit. | |
3411 | ||
3412 | If WHITELIST_D_MACROS is defined in Local/Makefile then it should be a | |
3413 | colon-separated list of macros which are considered safe and, if -D only | |
3414 | supplies macros from this list, and the values are acceptable, then Exim | |
3415 | will not give up root privilege if the caller is root, the Exim run-time | |
3416 | user, or the CONFIGURE_OWNER, if set. This is a transition mechanism and is | |
3417 | expected to be removed in the future. Acceptable values for the macros | |
3418 | satisfy the regexp: "^[A-Za-z0-9_/.-]*$" | |
3419 | ||
3420 | The entire option (including equals sign if present) must all be within one | |
3421 | command line item. -D can be used to set the value of a macro to the empty | |
3422 | string, in which case the equals sign is optional. These two commands are | |
3423 | synonymous: | |
3424 | ||
3425 | exim -DABC ... | |
3426 | exim -DABC= ... | |
3427 | ||
3428 | To include spaces in a macro definition item, quotes must be used. If you | |
3429 | use quotes, spaces are permitted around the macro name and the equals sign. | |
3430 | For example: | |
3431 | ||
3432 | exim '-D ABC = something' ... | |
3433 | ||
3434 | -D may be repeated up to 10 times on a command line. | |
3435 | ||
3436 | -d<debug options> | |
3437 | ||
3438 | This option causes debugging information to be written to the standard | |
3439 | error stream. It is restricted to admin users because debugging output may | |
3440 | show database queries that contain password information. Also, the details | |
3441 | of users' filter files should be protected. If a non-admin user uses -d, | |
3442 | Exim writes an error message to the standard error stream and exits with a | |
3443 | non-zero return code. | |
3444 | ||
3445 | When -d is used, -v is assumed. If -d is given on its own, a lot of | |
3446 | standard debugging data is output. This can be reduced, or increased to | |
3447 | include some more rarely needed information, by directly following -d with | |
3448 | a string made up of names preceded by plus or minus characters. These add | |
3449 | or remove sets of debugging data, respectively. For example, -d+filter adds | |
3450 | filter debugging, whereas -d-all+filter selects only filter debugging. Note | |
3451 | that no spaces are allowed in the debug setting. The available debugging | |
3452 | categories are: | |
3453 | ||
3454 | acl ACL interpretation | |
3455 | auth authenticators | |
3456 | deliver general delivery logic | |
3457 | dns DNS lookups (see also resolver) | |
3458 | dnsbl DNS black list (aka RBL) code | |
3459 | exec arguments for execv() calls | |
3460 | expand detailed debugging for string expansions | |
3461 | filter filter handling | |
3462 | hints_lookup hints data lookups | |
3463 | host_lookup all types of name-to-IP address handling | |
3464 | ident ident lookup | |
3465 | interface lists of local interfaces | |
3466 | lists matching things in lists | |
3467 | load system load checks | |
3468 | local_scan can be used by local_scan() (see chapter 44) | |
3469 | lookup general lookup code and all lookups | |
3470 | memory memory handling | |
3471 | pid add pid to debug output lines | |
3472 | process_info setting info for the process log | |
3473 | queue_run queue runs | |
3474 | receive general message reception logic | |
3475 | resolver turn on the DNS resolver's debugging output | |
3476 | retry retry handling | |
3477 | rewrite address rewriting | |
3478 | route address routing | |
3479 | timestamp add timestamp to debug output lines | |
3480 | tls TLS logic | |
3481 | transport transports | |
3482 | uid changes of uid/gid and looking up uid/gid | |
3483 | verify address verification logic | |
3484 | all almost all of the above (see below), and also -v | |
3485 | ||
3486 | The "all" option excludes "memory" when used as "+all", but includes it for | |
3487 | "-all". The reason for this is that "+all" is something that people tend to | |
3488 | use when generating debug output for Exim maintainers. If "+memory" is | |
3489 | included, an awful lot of output that is very rarely of interest is | |
3490 | generated, so it now has to be explicitly requested. However, "-all" does | |
3491 | turn everything off. | |
3492 | ||
3493 | The "resolver" option produces output only if the DNS resolver was compiled | |
3494 | with DEBUG enabled. This is not the case in some operating systems. Also, | |
3495 | unfortunately, debugging output from the DNS resolver is written to stdout | |
3496 | rather than stderr. | |
3497 | ||
3498 | The default (-d with no argument) omits "expand", "filter", "interface", | |
3499 | "load", "memory", "pid", "resolver", and "timestamp". However, the "pid" | |
3500 | selector is forced when debugging is turned on for a daemon, which then | |
3501 | passes it on to any re-executed Exims. Exim also automatically adds the pid | |
3502 | to debug lines when several remote deliveries are run in parallel. | |
3503 | ||
3504 | The "timestamp" selector causes the current time to be inserted at the | |
3505 | start of all debug output lines. This can be useful when trying to track | |
3506 | down delays in processing. | |
3507 | ||
3508 | If the debug_print option is set in any driver, it produces output whenever | |
3509 | any debugging is selected, or if -v is used. | |
3510 | ||
3511 | -dd<debug options> | |
3512 | ||
3513 | This option behaves exactly like -d except when used on a command that | |
3514 | starts a daemon process. In that case, debugging is turned off for the | |
3515 | subprocesses that the daemon creates. Thus, it is useful for monitoring the | |
3516 | behaviour of the daemon without creating as much output as full debugging | |
3517 | does. | |
3518 | ||
3519 | -dropcr | |
3520 | ||
3521 | This is an obsolete option that is now a no-op. It used to affect the way | |
3522 | Exim handled CR and LF characters in incoming messages. What happens now is | |
3523 | described in section 46.2. | |
3524 | ||
3525 | -E | |
3526 | ||
3527 | This option specifies that an incoming message is a locally-generated | |
3528 | delivery failure report. It is used internally by Exim when handling | |
3529 | delivery failures and is not intended for external use. Its only effect is | |
3530 | to stop Exim generating certain messages to the postmaster, as otherwise | |
3531 | message cascades could occur in some situations. As part of the same | |
3532 | option, a message id may follow the characters -E. If it does, the log | |
3533 | entry for the receipt of the new message contains the id, following "R=", | |
3534 | as a cross-reference. | |
3535 | ||
3536 | -ex | |
3537 | ||
3538 | There are a number of Sendmail options starting with -oe which seem to be | |
3539 | called by various programs without the leading o in the option. For | |
3540 | example, the vacation program uses -eq. Exim treats all options of the form | |
3541 | -ex as synonymous with the corresponding -oex options. | |
3542 | ||
3543 | -F <string> | |
3544 | ||
3545 | This option sets the sender's full name for use when a locally-generated | |
3546 | message is being accepted. In the absence of this option, the user's gecos | |
3547 | entry from the password data is used. As users are generally permitted to | |
3548 | alter their gecos entries, no security considerations are involved. White | |
3549 | space between -F and the <string> is optional. | |
3550 | ||
3551 | -f <address> | |
3552 | ||
3553 | This option sets the address of the envelope sender of a locally-generated | |
3554 | message (also known as the return path). The option can normally be used | |
3555 | only by a trusted user, but untrusted_set_sender can be set to allow | |
3556 | untrusted users to use it. | |
3557 | ||
3558 | Processes running as root or the Exim user are always trusted. Other | |
3559 | trusted users are defined by the trusted_users or trusted_groups options. | |
3560 | In the absence of -f, or if the caller is not trusted, the sender of a | |
3561 | local message is set to the caller's login name at the default qualify | |
3562 | domain. | |
3563 | ||
3564 | There is one exception to the restriction on the use of -f: an empty sender | |
3565 | can be specified by any user, trusted or not, to create a message that can | |
3566 | never provoke a bounce. An empty sender can be specified either as an empty | |
3567 | string, or as a pair of angle brackets with nothing between them, as in | |
3568 | these examples of shell commands: | |
3569 | ||
3570 | exim -f '<>' user@domain | |
3571 | exim -f "" user@domain | |
3572 | ||
3573 | In addition, the use of -f is not restricted when testing a filter file | |
3574 | with -bf or when testing or verifying addresses using the -bt or -bv | |
3575 | options. | |
3576 | ||
3577 | Allowing untrusted users to change the sender address does not of itself | |
3578 | make it possible to send anonymous mail. Exim still checks that the From: | |
3579 | header refers to the local user, and if it does not, it adds a Sender: | |
3580 | header, though this can be overridden by setting no_local_from_check. | |
3581 | ||
3582 | White space between -f and the <address> is optional (that is, they can be | |
3583 | given as two arguments or one combined argument). The sender of a | |
3584 | locally-generated message can also be set (when permitted) by an initial | |
3585 | "From " line in the message - see the description of -bm above - but if -f | |
3586 | is also present, it overrides "From ". | |
3587 | ||
3588 | -G | |
3589 | ||
3590 | This option is equivalent to an ACL applying: | |
3591 | ||
3592 | control = suppress_local_fixups | |
3593 | ||
3594 | for every message received. Note that Sendmail will complain about such bad | |
3595 | formatting, where Exim silently just does not fix it up. This may change in | |
3596 | future. | |
3597 | ||
3598 | As this affects audit information, the caller must be a trusted user to use | |
3599 | this option. | |
3600 | ||
3601 | -h <number> | |
3602 | ||
3603 | This option is accepted for compatibility with Sendmail, but has no effect. | |
3604 | (In Sendmail it overrides the "hop count" obtained by counting Received: | |
3605 | headers.) | |
3606 | ||
3607 | -i | |
3608 | ||
3609 | This option, which has the same effect as -oi, specifies that a dot on a | |
3610 | line by itself should not terminate an incoming, non-SMTP message. I can | |
3611 | find no documentation for this option in Solaris 2.4 Sendmail, but the | |
3612 | mailx command in Solaris 2.4 uses it. See also -ti. | |
3613 | ||
3614 | -L <tag> | |
3615 | ||
3616 | This option is equivalent to setting syslog_processname in the config file | |
3617 | and setting log_file_path to "syslog". Its use is restricted to | |
3618 | administrators. The configuration file has to be read and parsed, to | |
3619 | determine access rights, before this is set and takes effect, so early | |
3620 | configuration file errors will not honour this flag. | |
3621 | ||
3622 | The tag should not be longer than 32 characters. | |
3623 | ||
3624 | -M <message id> <message id> ... | |
3625 | ||
3626 | This option requests Exim to run a delivery attempt on each message in | |
3627 | turn. If any of the messages are frozen, they are automatically thawed | |
3628 | before the delivery attempt. The settings of queue_domains, | |
3629 | queue_smtp_domains, and hold_domains are ignored. | |
3630 | ||
3631 | Retry hints for any of the addresses are overridden - Exim tries to deliver | |
3632 | even if the normal retry time has not yet been reached. This option | |
3633 | requires the caller to be an admin user. However, there is an option called | |
3634 | prod_requires_admin which can be set false to relax this restriction (and | |
3635 | also the same requirement for the -q, -R, and -S options). | |
3636 | ||
3637 | The deliveries happen synchronously, that is, the original Exim process | |
3638 | does not terminate until all the delivery attempts have finished. No output | |
3639 | is produced unless there is a serious error. If you want to see what is | |
3640 | happening, use the -v option as well, or inspect Exim's main log. | |
3641 | ||
3642 | -Mar <message id> <address> <address> ... | |
3643 | ||
3644 | This option requests Exim to add the addresses to the list of recipients of | |
3645 | the message ("ar" for "add recipients"). The first argument must be a | |
3646 | message id, and the remaining ones must be email addresses. However, if the | |
3647 | message is active (in the middle of a delivery attempt), it is not altered. | |
3648 | This option can be used only by an admin user. | |
3649 | ||
3650 | -MC <transport> <hostname> <sequence number> <message id> | |
3651 | ||
3652 | This option is not intended for use by external callers. It is used | |
3653 | internally by Exim to invoke another instance of itself to deliver a | |
3654 | waiting message using an existing SMTP connection, which is passed as the | |
3655 | standard input. Details are given in chapter 47. This must be the final | |
3656 | option, and the caller must be root or the Exim user in order to use it. | |
3657 | ||
3658 | -MCA | |
3659 | ||
3660 | This option is not intended for use by external callers. It is used | |
3661 | internally by Exim in conjunction with the -MC option. It signifies that | |
3662 | the connection to the remote host has been authenticated. | |
3663 | ||
3664 | -MCP | |
3665 | ||
3666 | This option is not intended for use by external callers. It is used | |
3667 | internally by Exim in conjunction with the -MC option. It signifies that | |
3668 | the server to which Exim is connected supports pipelining. | |
3669 | ||
3670 | -MCQ <process id> <pipe fd> | |
3671 | ||
3672 | This option is not intended for use by external callers. It is used | |
3673 | internally by Exim in conjunction with the -MC option when the original | |
3674 | delivery was started by a queue runner. It passes on the process id of the | |
3675 | queue runner, together with the file descriptor number of an open pipe. | |
3676 | Closure of the pipe signals the final completion of the sequence of | |
3677 | processes that are passing messages through the same SMTP connection. | |
3678 | ||
3679 | -MCS | |
3680 | ||
3681 | This option is not intended for use by external callers. It is used | |
3682 | internally by Exim in conjunction with the -MC option, and passes on the | |
3683 | fact that the SMTP SIZE option should be used on messages delivered down | |
3684 | the existing connection. | |
3685 | ||
3686 | -MCT | |
3687 | ||
3688 | This option is not intended for use by external callers. It is used | |
3689 | internally by Exim in conjunction with the -MC option, and passes on the | |
3690 | fact that the host to which Exim is connected supports TLS encryption. | |
3691 | ||
3692 | -Mc <message id> <message id> ... | |
3693 | ||
3694 | This option requests Exim to run a delivery attempt on each message in | |
3695 | turn, but unlike the -M option, it does check for retry hints, and respects | |
3696 | any that are found. This option is not very useful to external callers. It | |
3697 | is provided mainly for internal use by Exim when it needs to re-invoke | |
3698 | itself in order to regain root privilege for a delivery (see chapter 54). | |
3699 | However, -Mc can be useful when testing, in order to run a delivery that | |
3700 | respects retry times and other options such as hold_domains that are | |
3701 | overridden when -M is used. Such a delivery does not count as a queue run. | |
3702 | If you want to run a specific delivery as if in a queue run, you should use | |
3703 | -q with a message id argument. A distinction between queue run deliveries | |
3704 | and other deliveries is made in one or two places. | |
3705 | ||
3706 | -Mes <message id> <address> | |
3707 | ||
3708 | This option requests Exim to change the sender address in the message to | |
3709 | the given address, which must be a fully qualified address or "<>" ("es" | |
3710 | for "edit sender"). There must be exactly two arguments. The first argument | |
3711 | must be a message id, and the second one an email address. However, if the | |
3712 | message is active (in the middle of a delivery attempt), its status is not | |
3713 | altered. This option can be used only by an admin user. | |
3714 | ||
3715 | -Mf <message id> <message id> ... | |
3716 | ||
3717 | This option requests Exim to mark each listed message as "frozen". This | |
3718 | prevents any delivery attempts taking place until the message is "thawed", | |
3719 | either manually or as a result of the auto_thaw configuration option. | |
3720 | However, if any of the messages are active (in the middle of a delivery | |
3721 | attempt), their status is not altered. This option can be used only by an | |
3722 | admin user. | |
3723 | ||
3724 | -Mg <message id> <message id> ... | |
3725 | ||
3726 | This option requests Exim to give up trying to deliver the listed messages, | |
3727 | including any that are frozen. However, if any of the messages are active, | |
3728 | their status is not altered. For non-bounce messages, a delivery error | |
3729 | message is sent to the sender, containing the text "cancelled by | |
3730 | administrator". Bounce messages are just discarded. This option can be used | |
3731 | only by an admin user. | |
3732 | ||
3733 | -Mmad <message id> <message id> ... | |
3734 | ||
3735 | This option requests Exim to mark all the recipient addresses in the | |
3736 | messages as already delivered ("mad" for "mark all delivered"). However, if | |
3737 | any message is active (in the middle of a delivery attempt), its status is | |
3738 | not altered. This option can be used only by an admin user. | |
3739 | ||
3740 | -Mmd <message id> <address> <address> ... | |
3741 | ||
3742 | This option requests Exim to mark the given addresses as already delivered | |
3743 | ("md" for "mark delivered"). The first argument must be a message id, and | |
3744 | the remaining ones must be email addresses. These are matched to recipient | |
3745 | addresses in the message in a case-sensitive manner. If the message is | |
3746 | active (in the middle of a delivery attempt), its status is not altered. | |
3747 | This option can be used only by an admin user. | |
3748 | ||
3749 | -Mrm <message id> <message id> ... | |
3750 | ||
3751 | This option requests Exim to remove the given messages from the queue. No | |
3752 | bounce messages are sent; each message is simply forgotten. However, if any | |
3753 | of the messages are active, their status is not altered. This option can be | |
3754 | used only by an admin user or by the user who originally caused the message | |
3755 | to be placed on the queue. | |
3756 | ||
3757 | -Mset <message id> | |
3758 | ||
3759 | This option is useful only in conjunction with -be (that is, when testing | |
3760 | string expansions). Exim loads the given message from its spool before | |
3761 | doing the test expansions, thus setting message-specific variables such as | |
3762 | $message_size and the header variables. The $recipients variable is made | |
3763 | available. This feature is provided to make it easier to test expansions | |
3764 | that make use of these variables. However, this option can be used only by | |
3765 | an admin user. See also -bem. | |
3766 | ||
3767 | -Mt <message id> <message id> ... | |
3768 | ||
3769 | This option requests Exim to "thaw" any of the listed messages that are | |
3770 | "frozen", so that delivery attempts can resume. However, if any of the | |
3771 | messages are active, their status is not altered. This option can be used | |
3772 | only by an admin user. | |
3773 | ||
3774 | -Mvb <message id> | |
3775 | ||
3776 | This option causes the contents of the message body (-D) spool file to be | |
3777 | written to the standard output. This option can be used only by an admin | |
3778 | user. | |
3779 | ||
3780 | -Mvc <message id> | |
3781 | ||
3782 | This option causes a copy of the complete message (header lines plus body) | |
3783 | to be written to the standard output in RFC 2822 format. This option can be | |
3784 | used only by an admin user. | |
3785 | ||
3786 | -Mvh <message id> | |
3787 | ||
3788 | This option causes the contents of the message headers (-H) spool file to | |
3789 | be written to the standard output. This option can be used only by an admin | |
3790 | user. | |
3791 | ||
3792 | -Mvl <message id> | |
3793 | ||
3794 | This option causes the contents of the message log spool file to be written | |
3795 | to the standard output. This option can be used only by an admin user. | |
3796 | ||
3797 | -m | |
3798 | ||
3799 | This is apparently a synonym for -om that is accepted by Sendmail, so Exim | |
3800 | treats it that way too. | |
3801 | ||
3802 | -N | |
3803 | ||
3804 | This is a debugging option that inhibits delivery of a message at the | |
3805 | transport level. It implies -v. Exim goes through many of the motions of | |
3806 | delivery - it just doesn't actually transport the message, but instead | |
3807 | behaves as if it had successfully done so. However, it does not make any | |
3808 | updates to the retry database, and the log entries for deliveries are | |
3809 | flagged with "*>" rather than "=>". | |
3810 | ||
3811 | Because -N discards any message to which it applies, only root or the Exim | |
3812 | user are allowed to use it with -bd, -q, -R or -M. In other words, an | |
3813 | ordinary user can use it only when supplying an incoming message to which | |
3814 | it will apply. Although transportation never fails when -N is set, an | |
3815 | address may be deferred because of a configuration problem on a transport, | |
3816 | or a routing problem. Once -N has been used for a delivery attempt, it | |
3817 | sticks to the message, and applies to any subsequent delivery attempts that | |
3818 | may happen for that message. | |
3819 | ||
3820 | -n | |
3821 | ||
3822 | This option is interpreted by Sendmail to mean "no aliasing". For normal | |
3823 | modes of operation, it is ignored by Exim. When combined with -bP it | |
3824 | suppresses the name of an option from being output. | |
3825 | ||
3826 | -O <data> | |
3827 | ||
3828 | This option is interpreted by Sendmail to mean "set option". It is ignored | |
3829 | by Exim. | |
3830 | ||
3831 | -oA <file name> | |
3832 | ||
3833 | This option is used by Sendmail in conjunction with -bi to specify an | |
3834 | alternative alias file name. Exim handles -bi differently; see the | |
3835 | description above. | |
3836 | ||
3837 | -oB <n> | |
3838 | ||
3839 | This is a debugging option which limits the maximum number of messages that | |
3840 | can be delivered down one SMTP connection, overriding the value set in any | |
3841 | smtp transport. If <n> is omitted, the limit is set to 1. | |
3842 | ||
3843 | -odb | |
3844 | ||
3845 | This option applies to all modes in which Exim accepts incoming messages, | |
3846 | including the listening daemon. It requests "background" delivery of such | |
3847 | messages, which means that the accepting process automatically starts a | |
3848 | delivery process for each message received, but does not wait for the | |
3849 | delivery processes to finish. | |
3850 | ||
3851 | When all the messages have been received, the reception process exits, | |
3852 | leaving the delivery processes to finish in their own time. The standard | |
3853 | output and error streams are closed at the start of each delivery process. | |
3854 | This is the default action if none of the -od options are present. | |
3855 | ||
3856 | If one of the queueing options in the configuration file (queue_only or | |
3857 | queue_only_file, for example) is in effect, -odb overrides it if | |
3858 | queue_only_override is set true, which is the default setting. If | |
3859 | queue_only_override is set false, -odb has no effect. | |
3860 | ||
3861 | -odf | |
3862 | ||
3863 | This option requests "foreground" (synchronous) delivery when Exim has | |
3864 | accepted a locally-generated message. (For the daemon it is exactly the | |
3865 | same as -odb.) A delivery process is automatically started to deliver the | |
3866 | message, and Exim waits for it to complete before proceeding. | |
3867 | ||
3868 | The original Exim reception process does not finish until the delivery | |
3869 | process for the final message has ended. The standard error stream is left | |
3870 | open during deliveries. | |
3871 | ||
3872 | However, like -odb, this option has no effect if queue_only_override is | |
3873 | false and one of the queueing options in the configuration file is in | |
3874 | effect. | |
3875 | ||
3876 | If there is a temporary delivery error during foreground delivery, the | |
3877 | message is left on the queue for later delivery, and the original reception | |
3878 | process exits. See chapter 50 for a way of setting up a restricted | |
3879 | configuration that never queues messages. | |
3880 | ||
3881 | -odi | |
3882 | ||
3883 | This option is synonymous with -odf. It is provided for compatibility with | |
3884 | Sendmail. | |
3885 | ||
3886 | -odq | |
3887 | ||
3888 | This option applies to all modes in which Exim accepts incoming messages, | |
3889 | including the listening daemon. It specifies that the accepting process | |
3890 | should not automatically start a delivery process for each message | |
3891 | received. Messages are placed on the queue, and remain there until a | |
3892 | subsequent queue runner process encounters them. There are several | |
3893 | configuration options (such as queue_only) that can be used to queue | |
3894 | incoming messages under certain conditions. This option overrides all of | |
3895 | them and also -odqs. It always forces queueing. | |
3896 | ||
3897 | -odqs | |
3898 | ||
3899 | This option is a hybrid between -odb/-odi and -odq. However, like -odb and | |
3900 | -odi, this option has no effect if queue_only_override is false and one of | |
3901 | the queueing options in the configuration file is in effect. | |
3902 | ||
3903 | When -odqs does operate, a delivery process is started for each incoming | |
3904 | message, in the background by default, but in the foreground if -odi is | |
3905 | also present. The recipient addresses are routed, and local deliveries are | |
3906 | done in the normal way. However, if any SMTP deliveries are required, they | |
3907 | are not done at this time, so the message remains on the queue until a | |
3908 | subsequent queue runner process encounters it. Because routing was done, | |
3909 | Exim knows which messages are waiting for which hosts, and so a number of | |
3910 | messages for the same host can be sent in a single SMTP connection. The | |
3911 | queue_smtp_domains configuration option has the same effect for specific | |
3912 | domains. See also the -qq option. | |
3913 | ||
3914 | -oee | |
3915 | ||
3916 | If an error is detected while a non-SMTP message is being received (for | |
3917 | example, a malformed address), the error is reported to the sender in a | |
3918 | mail message. | |
3919 | ||
3920 | Provided this error message is successfully sent, the Exim receiving | |
3921 | process exits with a return code of zero. If not, the return code is 2 if | |
3922 | the problem is that the original message has no recipients, or 1 for any | |
3923 | other error. This is the default -oex option if Exim is called as rmail. | |
3924 | ||
3925 | -oem | |
3926 | ||
3927 | This is the same as -oee, except that Exim always exits with a non-zero | |
3928 | return code, whether or not the error message was successfully sent. This | |
3929 | is the default -oex option, unless Exim is called as rmail. | |
3930 | ||
3931 | -oep | |
3932 | ||
3933 | If an error is detected while a non-SMTP message is being received, the | |
3934 | error is reported by writing a message to the standard error file (stderr). | |
3935 | The return code is 1 for all errors. | |
3936 | ||
3937 | -oeq | |
3938 | ||
3939 | This option is supported for compatibility with Sendmail, but has the same | |
3940 | effect as -oep. | |
3941 | ||
3942 | -oew | |
3943 | ||
3944 | This option is supported for compatibility with Sendmail, but has the same | |
3945 | effect as -oem. | |
3946 | ||
3947 | -oi | |
3948 | ||
3949 | This option, which has the same effect as -i, specifies that a dot on a | |
3950 | line by itself should not terminate an incoming, non-SMTP message. | |
3951 | Otherwise, a single dot does terminate, though Exim does no special | |
3952 | processing for other lines that start with a dot. This option is set by | |
3953 | default if Exim is called as rmail. See also -ti. | |
3954 | ||
3955 | -oitrue | |
3956 | ||
3957 | This option is treated as synonymous with -oi. | |
3958 | ||
3959 | -oMa <host address> | |
3960 | ||
3961 | A number of options starting with -oM can be used to set values associated | |
3962 | with remote hosts on locally-submitted messages (that is, messages not | |
3963 | received over TCP/IP). These options can be used by any caller in | |
3964 | conjunction with the -bh, -be, -bf, -bF, -bt, or -bv testing options. In | |
3965 | other circumstances, they are ignored unless the caller is trusted. | |
3966 | ||
3967 | The -oMa option sets the sender host address. This may include a port | |
3968 | number at the end, after a full stop (period). For example: | |
3969 | ||
3970 | exim -bs -oMa 10.9.8.7.1234 | |
3971 | ||
3972 | An alternative syntax is to enclose the IP address in square brackets, | |
3973 | followed by a colon and the port number: | |
3974 | ||
3975 | exim -bs -oMa [10.9.8.7]:1234 | |
3976 | ||
3977 | The IP address is placed in the $sender_host_address variable, and the | |
3978 | port, if present, in $sender_host_port. If both -oMa and -bh are present on | |
3979 | the command line, the sender host IP address is taken from whichever one is | |
3980 | last. | |
3981 | ||
3982 | -oMaa <name> | |
3983 | ||
3984 | See -oMa above for general remarks about the -oM options. The -oMaa option | |
3985 | sets the value of $sender_host_authenticated (the authenticator name). See | |
3986 | chapter 33 for a discussion of SMTP authentication. This option can be used | |
3987 | with -bh and -bs to set up an authenticated SMTP session without actually | |
3988 | using the SMTP AUTH command. | |
3989 | ||
3990 | -oMai <string> | |
3991 | ||
3992 | See -oMa above for general remarks about the -oM options. The -oMai option | |
3993 | sets the value of $authenticated_id (the id that was authenticated). This | |
3994 | overrides the default value (the caller's login id, except with -bh, where | |
3995 | there is no default) for messages from local sources. See chapter 33 for a | |
3996 | discussion of authenticated ids. | |
3997 | ||
3998 | -oMas <address> | |
3999 | ||
4000 | See -oMa above for general remarks about the -oM options. The -oMas option | |
4001 | sets the authenticated sender value in $authenticated_sender. It overrides | |
4002 | the sender address that is created from the caller's login id for messages | |
4003 | from local sources, except when -bh is used, when there is no default. For | |
4004 | both -bh and -bs, an authenticated sender that is specified on a MAIL | |
4005 | command overrides this value. See chapter 33 for a discussion of | |
4006 | authenticated senders. | |
4007 | ||
4008 | -oMi <interface address> | |
4009 | ||
4010 | See -oMa above for general remarks about the -oM options. The -oMi option | |
4011 | sets the IP interface address value. A port number may be included, using | |
4012 | the same syntax as for -oMa. The interface address is placed in | |
4013 | $received_ip_address and the port number, if present, in $received_port. | |
4014 | ||
4015 | -oMm <message reference> | |
4016 | ||
4017 | See -oMa above for general remarks about the -oM options. The -oMm option | |
4018 | sets the message reference, e.g. message-id, and is logged during delivery. | |
4019 | This is useful when some kind of audit trail is required to tie messages | |
4020 | together. The format of the message reference is checked and will abort if | |
4021 | the format is invalid. The option will only be accepted if exim is running | |
4022 | in trusted mode, not as any regular user. | |
4023 | ||
4024 | The best example of a message reference is when Exim sends a bounce | |
4025 | message. The message reference is the message-id of the original message | |
4026 | for which Exim is sending the bounce. | |
4027 | ||
4028 | -oMr <protocol name> | |
4029 | ||
4030 | See -oMa above for general remarks about the -oM options. The -oMr option | |
4031 | sets the received protocol value that is stored in $received_protocol. | |
4032 | However, it does not apply (and is ignored) when -bh or -bs is used. For | |
4033 | -bh, the protocol is forced to one of the standard SMTP protocol names (see | |
4034 | the description of $received_protocol in section 11.9). For -bs, the | |
4035 | protocol is always "local-" followed by one of those same names. For -bS | |
4036 | (batched SMTP) however, the protocol can be set by -oMr. | |
4037 | ||
4038 | -oMs <host name> | |
4039 | ||
4040 | See -oMa above for general remarks about the -oM options. The -oMs option | |
4041 | sets the sender host name in $sender_host_name. When this option is | |
4042 | present, Exim does not attempt to look up a host name from an IP address; | |
4043 | it uses the name it is given. | |
4044 | ||
4045 | -oMt <ident string> | |
4046 | ||
4047 | See -oMa above for general remarks about the -oM options. The -oMt option | |
4048 | sets the sender ident value in $sender_ident. The default setting for local | |
4049 | callers is the login id of the calling process, except when -bh is used, | |
4050 | when there is no default. | |
4051 | ||
4052 | -om | |
4053 | ||
4054 | In Sendmail, this option means "me too", indicating that the sender of a | |
4055 | message should receive a copy of the message if the sender appears in an | |
4056 | alias expansion. Exim always does this, so the option does nothing. | |
4057 | ||
4058 | -oo | |
4059 | ||
4060 | This option is ignored. In Sendmail it specifies "old style headers", | |
4061 | whatever that means. | |
4062 | ||
4063 | -oP <path> | |
4064 | ||
4065 | This option is useful only in conjunction with -bd or -q with a time value. | |
4066 | The option specifies the file to which the process id of the daemon is | |
4067 | written. When -oX is used with -bd, or when -q with a time is used without | |
4068 | -bd, this is the only way of causing Exim to write a pid file, because in | |
4069 | those cases, the normal pid file is not used. | |
4070 | ||
4071 | -or <time> | |
4072 | ||
4073 | This option sets a timeout value for incoming non-SMTP messages. If it is | |
4074 | not set, Exim will wait forever for the standard input. The value can also | |
4075 | be set by the receive_timeout option. The format used for specifying times | |
4076 | is described in section 6.15. | |
4077 | ||
4078 | -os <time> | |
4079 | ||
4080 | This option sets a timeout value for incoming SMTP messages. The timeout | |
4081 | applies to each SMTP command and block of data. The value can also be set | |
4082 | by the smtp_receive_timeout option; it defaults to 5 minutes. The format | |
4083 | used for specifying times is described in section 6.15. | |
4084 | ||
4085 | -ov | |
4086 | ||
4087 | This option has exactly the same effect as -v. | |
4088 | ||
4089 | -oX <number or string> | |
4090 | ||
4091 | This option is relevant only when the -bd (start listening daemon) option | |
4092 | is also given. It controls which ports and interfaces the daemon uses. | |
4093 | Details of the syntax, and how it interacts with configuration file | |
4094 | options, are given in chapter 13. When -oX is used to start a daemon, no | |
4095 | pid file is written unless -oP is also present to specify a pid file name. | |
4096 | ||
4097 | -pd | |
4098 | ||
4099 | This option applies when an embedded Perl interpreter is linked with Exim | |
4100 | (see chapter 12). It overrides the setting of the perl_at_start option, | |
4101 | forcing the starting of the interpreter to be delayed until it is needed. | |
4102 | ||
4103 | -ps | |
4104 | ||
4105 | This option applies when an embedded Perl interpreter is linked with Exim | |
4106 | (see chapter 12). It overrides the setting of the perl_at_start option, | |
4107 | forcing the starting of the interpreter to occur as soon as Exim is | |
4108 | started. | |
4109 | ||
4110 | -p<rval>:<sval> | |
4111 | ||
4112 | For compatibility with Sendmail, this option is equivalent to | |
4113 | ||
4114 | -oMr <rval> -oMs <sval> | |
4115 | ||
4116 | It sets the incoming protocol and host name (for trusted callers). The host | |
4117 | name and its colon can be omitted when only the protocol is to be set. Note | |
4118 | the Exim already has two private options, -pd and -ps, that refer to | |
4119 | embedded Perl. It is therefore impossible to set a protocol value of "d" or | |
4120 | "s" using this option (but that does not seem a real limitation). | |
4121 | ||
4122 | -q | |
4123 | ||
4124 | This option is normally restricted to admin users. However, there is a | |
4125 | configuration option called prod_requires_admin which can be set false to | |
4126 | relax this restriction (and also the same requirement for the -M, -R, and | |
4127 | -S options). | |
4128 | ||
4129 | The -q option starts one queue runner process. This scans the queue of | |
4130 | waiting messages, and runs a delivery process for each one in turn. It | |
4131 | waits for each delivery process to finish before starting the next one. A | |
4132 | delivery process may not actually do any deliveries if the retry times for | |
4133 | the addresses have not been reached. Use -qf (see below) if you want to | |
4134 | override this. | |
4135 | ||
4136 | If the delivery process spawns other processes to deliver other messages | |
4137 | down passed SMTP connections, the queue runner waits for these to finish | |
4138 | before proceeding. | |
4139 | ||
4140 | When all the queued messages have been considered, the original queue | |
4141 | runner process terminates. In other words, a single pass is made over the | |
4142 | waiting mail, one message at a time. Use -q with a time (see below) if you | |
4143 | want this to be repeated periodically. | |
4144 | ||
4145 | Exim processes the waiting messages in an unpredictable order. It isn't | |
4146 | very random, but it is likely to be different each time, which is all that | |
4147 | matters. If one particular message screws up a remote MTA, other messages | |
4148 | to the same MTA have a chance of getting through if they get tried first. | |
4149 | ||
4150 | It is possible to cause the messages to be processed in lexical message id | |
4151 | order, which is essentially the order in which they arrived, by setting the | |
4152 | queue_run_in_order option, but this is not recommended for normal use. | |
4153 | ||
4154 | -q<qflags> | |
4155 | ||
4156 | The -q option may be followed by one or more flag letters that change its | |
4157 | behaviour. They are all optional, but if more than one is present, they | |
4158 | must appear in the correct order. Each flag is described in a separate item | |
4159 | below. | |
4160 | ||
4161 | -qq... | |
4162 | ||
4163 | An option starting with -qq requests a two-stage queue run. In the first | |
4164 | stage, the queue is scanned as if the queue_smtp_domains option matched | |
4165 | every domain. Addresses are routed, local deliveries happen, but no remote | |
4166 | transports are run. | |
4167 | ||
4168 | The hints database that remembers which messages are waiting for specific | |
4169 | hosts is updated, as if delivery to those hosts had been deferred. After | |
4170 | this is complete, a second, normal queue scan happens, with routing and | |
4171 | delivery taking place as normal. Messages that are routed to the same host | |
4172 | should mostly be delivered down a single SMTP connection because of the | |
4173 | hints that were set up during the first queue scan. This option may be | |
4174 | useful for hosts that are connected to the Internet intermittently. | |
4175 | ||
4176 | -q[q]i... | |
4177 | ||
4178 | If the i flag is present, the queue runner runs delivery processes only for | |
4179 | those messages that haven't previously been tried. (i stands for "initial | |
4180 | delivery".) This can be helpful if you are putting messages on the queue | |
4181 | using -odq and want a queue runner just to process the new messages. | |
4182 | ||
4183 | -q[q][i]f... | |
4184 | ||
4185 | If one f flag is present, a delivery attempt is forced for each non-frozen | |
4186 | message, whereas without f only those non-frozen addresses that have passed | |
4187 | their retry times are tried. | |
4188 | ||
4189 | -q[q][i]ff... | |
4190 | ||
4191 | If ff is present, a delivery attempt is forced for every message, whether | |
4192 | frozen or not. | |
4193 | ||
4194 | -q[q][i][f[f]]l | |
4195 | ||
4196 | The l (the letter "ell") flag specifies that only local deliveries are to | |
4197 | be done. If a message requires any remote deliveries, it remains on the | |
4198 | queue for later delivery. | |
4199 | ||
4200 | -q<qflags> <start id> <end id> | |
4201 | ||
4202 | When scanning the queue, Exim can be made to skip over messages whose ids | |
4203 | are lexically less than a given value by following the -q option with a | |
4204 | starting message id. For example: | |
4205 | ||
4206 | exim -q 0t5C6f-0000c8-00 | |
4207 | ||
4208 | Messages that arrived earlier than "0t5C6f-0000c8-00" are not inspected. If | |
4209 | a second message id is given, messages whose ids are lexically greater than | |
4210 | it are also skipped. If the same id is given twice, for example, | |
4211 | ||
4212 | exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00 | |
4213 | ||
4214 | just one delivery process is started, for that message. This differs from | |
4215 | -M in that retry data is respected, and it also differs from -Mc in that it | |
4216 | counts as a delivery from a queue run. Note that the selection mechanism | |
4217 | does not affect the order in which the messages are scanned. There are also | |
4218 | other ways of selecting specific sets of messages for delivery in a queue | |
4219 | run - see -R and -S. | |
4220 | ||
4221 | -q<qflags><time> | |
4222 | ||
4223 | When a time value is present, the -q option causes Exim to run as a daemon, | |
4224 | starting a queue runner process at intervals specified by the given time | |
4225 | value (whose format is described in section 6.15). This form of the -q | |
4226 | option is commonly combined with the -bd option, in which case a single | |
4227 | daemon process handles both functions. A common way of starting up a | |
4228 | combined daemon at system boot time is to use a command such as | |
4229 | ||
4230 | /usr/exim/bin/exim -bd -q30m | |
4231 | ||
4232 | Such a daemon listens for incoming SMTP calls, and also starts a queue | |
4233 | runner process every 30 minutes. | |
4234 | ||
4235 | When a daemon is started by -q with a time value, but without -bd, no pid | |
4236 | file is written unless one is explicitly requested by the -oP option. | |
4237 | ||
4238 | -qR<rsflags> <string> | |
4239 | ||
4240 | This option is synonymous with -R. It is provided for Sendmail | |
4241 | compatibility. | |
4242 | ||
4243 | -qS<rsflags> <string> | |
4244 | ||
4245 | This option is synonymous with -S. | |
4246 | ||
4247 | -R<rsflags> <string> | |
4248 | ||
4249 | The <rsflags> may be empty, in which case the white space before the string | |
4250 | is optional, unless the string is f, ff, r, rf, or rff, which are the | |
4251 | possible values for <rsflags>. White space is required if <rsflags> is not | |
4252 | empty. | |
4253 | ||
4254 | This option is similar to -q with no time value, that is, it causes Exim to | |
4255 | perform a single queue run, except that, when scanning the messages on the | |
4256 | queue, Exim processes only those that have at least one undelivered | |
4257 | recipient address containing the given string, which is checked in a | |
4258 | case-independent way. If the <rsflags> start with r, <string> is | |
4259 | interpreted as a regular expression; otherwise it is a literal string. | |
4260 | ||
4261 | If you want to do periodic queue runs for messages with specific | |
4262 | recipients, you can combine -R with -q and a time value. For example: | |
4263 | ||
4264 | exim -q25m -R @special.domain.example | |
4265 | ||
4266 | This example does a queue run for messages with recipients in the given | |
4267 | domain every 25 minutes. Any additional flags that are specified with -q | |
4268 | are applied to each queue run. | |
4269 | ||
4270 | Once a message is selected for delivery by this mechanism, all its | |
4271 | addresses are processed. For the first selected message, Exim overrides any | |
4272 | retry information and forces a delivery attempt for each undelivered | |
4273 | address. This means that if delivery of any address in the first message is | |
4274 | successful, any existing retry information is deleted, and so delivery | |
4275 | attempts for that address in subsequently selected messages (which are | |
4276 | processed without forcing) will run. However, if delivery of any address | |
4277 | does not succeed, the retry information is updated, and in subsequently | |
4278 | selected messages, the failing address will be skipped. | |
4279 | ||
4280 | If the <rsflags> contain f or ff, the delivery forcing applies to all | |
4281 | selected messages, not just the first; frozen messages are included when ff | |
4282 | is present. | |
4283 | ||
4284 | The -R option makes it straightforward to initiate delivery of all messages | |
4285 | to a given domain after a host has been down for some time. When the SMTP | |
4286 | command ETRN is accepted by its ACL (see chapter 42), its default effect is | |
4287 | to run Exim with the -R option, but it can be configured to run an | |
4288 | arbitrary command instead. | |
4289 | ||
4290 | -r | |
4291 | ||
4292 | This is a documented (for Sendmail) obsolete alternative name for -f. | |
4293 | ||
4294 | -S<rsflags> <string> | |
4295 | ||
4296 | This option acts like -R except that it checks the string against each | |
4297 | message's sender instead of against the recipients. If -R is also set, both | |
4298 | conditions must be met for a message to be selected. If either of the | |
4299 | options has f or ff in its flags, the associated action is taken. | |
4300 | ||
4301 | -Tqt <times> | |
4302 | ||
4303 | This is an option that is exclusively for use by the Exim testing suite. It | |
4304 | is not recognized when Exim is run normally. It allows for the setting up | |
4305 | of explicit "queue times" so that various warning/retry features can be | |
4306 | tested. | |
4307 | ||
4308 | -t | |
4309 | ||
4310 | When Exim is receiving a locally-generated, non-SMTP message on its | |
4311 | standard input, the -t option causes the recipients of the message to be | |
4312 | obtained from the To:, Cc:, and Bcc: header lines in the message instead of | |
4313 | from the command arguments. The addresses are extracted before any | |
4314 | rewriting takes place and the Bcc: header line, if present, is then | |
4315 | removed. | |
4316 | ||
4317 | If the command has any arguments, they specify addresses to which the | |
4318 | message is not to be delivered. That is, the argument addresses are removed | |
4319 | from the recipients list obtained from the headers. This is compatible with | |
4320 | Smail 3 and in accordance with the documented behaviour of several versions | |
4321 | of Sendmail, as described in man pages on a number of operating systems | |
4322 | (e.g. Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail | |
4323 | add argument addresses to those obtained from the headers, and the O'Reilly | |
4324 | Sendmail book documents it that way. Exim can be made to add argument | |
4325 | addresses instead of subtracting them by setting the option | |
4326 | extract_addresses_remove_arguments false. | |
4327 | ||
4328 | If there are any Resent- header lines in the message, Exim extracts | |
4329 | recipients from all Resent-To:, Resent-Cc:, and Resent-Bcc: header lines | |
4330 | instead of from To:, Cc:, and Bcc:. This is for compatibility with Sendmail | |
4331 | and other MTAs. (Prior to release 4.20, Exim gave an error if -t was used | |
4332 | in conjunction with Resent- header lines.) | |
4333 | ||
4334 | RFC 2822 talks about different sets of Resent- header lines (for when a | |
4335 | message is resent several times). The RFC also specifies that they should | |
4336 | be added at the front of the message, and separated by Received: lines. It | |
4337 | is not at all clear how -t should operate in the present of multiple sets, | |
4338 | nor indeed exactly what constitutes a "set". In practice, it seems that | |
4339 | MUAs do not follow the RFC. The Resent- lines are often added at the end of | |
4340 | the header, and if a message is resent more than once, it is common for the | |
4341 | original set of Resent- headers to be renamed as X-Resent- when a new set | |
4342 | is added. This removes any possible ambiguity. | |
4343 | ||
4344 | -ti | |
4345 | ||
4346 | This option is exactly equivalent to -t -i. It is provided for | |
4347 | compatibility with Sendmail. | |
4348 | ||
4349 | -tls-on-connect | |
4350 | ||
4351 | This option is available when Exim is compiled with TLS support. It forces | |
4352 | all incoming SMTP connections to behave as if the incoming port is listed | |
4353 | in the tls_on_connect_ports option. See section 13.4 and chapter 41 for | |
4354 | further details. | |
4355 | ||
4356 | -U | |
4357 | ||
4358 | Sendmail uses this option for "initial message submission", and its | |
4359 | documentation states that in future releases, it may complain about | |
4360 | syntactically invalid messages rather than fixing them when this flag is | |
4361 | not set. Exim ignores this option. | |
4362 | ||
4363 | -v | |
4364 | ||
4365 | This option causes Exim to write information to the standard error stream, | |
4366 | describing what it is doing. In particular, it shows the log lines for | |
4367 | receiving and delivering a message, and if an SMTP connection is made, the | |
4368 | SMTP dialogue is shown. Some of the log lines shown may not actually be | |
4369 | written to the log if the setting of log_selector discards them. Any | |
4370 | relevant selectors are shown with each log line. If none are shown, the | |
4371 | logging is unconditional. | |
4372 | ||
4373 | -x | |
4374 | ||
4375 | AIX uses -x for a private purpose ("mail from a local mail program has | |
4376 | National Language Support extended characters in the body of the mail | |
4377 | item"). It sets -x when calling the MTA from its mail command. Exim ignores | |
4378 | this option. | |
4379 | ||
4380 | -X <logfile> | |
4381 | ||
4382 | This option is interpreted by Sendmail to cause debug information to be | |
4383 | sent to the named file. It is ignored by Exim. | |
4384 | ||
4385 | ||
4386 | ||
4387 | =============================================================================== | |
4388 | 6. THE EXIM RUN TIME CONFIGURATION FILE | |
4389 | ||
4390 | Exim uses a single run time configuration file that is read whenever an Exim | |
4391 | binary is executed. Note that in normal operation, this happens frequently, | |
4392 | because Exim is designed to operate in a distributed manner, without central | |
4393 | control. | |
4394 | ||
4395 | If a syntax error is detected while reading the configuration file, Exim writes | |
4396 | a message on the standard error, and exits with a non-zero return code. The | |
4397 | message is also written to the panic log. Note: Only simple syntax errors can | |
4398 | be detected at this time. The values of any expanded options are not checked | |
4399 | until the expansion happens, even when the expansion does not actually alter | |
4400 | the string. | |
4401 | ||
4402 | The name of the configuration file is compiled into the binary for security | |
4403 | reasons, and is specified by the CONFIGURE_FILE compilation option. In most | |
4404 | configurations, this specifies a single file. However, it is permitted to give | |
4405 | a colon-separated list of file names, in which case Exim uses the first | |
4406 | existing file in the list. | |
4407 | ||
4408 | The run time configuration file must be owned by root or by the user that is | |
4409 | specified at compile time by the CONFIGURE_OWNER option (if set). The | |
4410 | configuration file must not be world-writeable, or group-writeable unless its | |
4411 | group is the root group or the one specified at compile time by the | |
4412 | CONFIGURE_GROUP option. | |
4413 | ||
4414 | Warning: In a conventional configuration, where the Exim binary is setuid to | |
4415 | root, anybody who is able to edit the run time configuration file has an easy | |
4416 | way to run commands as root. If you specify a user or group in the | |
4417 | CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users who | |
4418 | are members of that group will trivially be able to obtain root privileges. | |
4419 | ||
4420 | Up to Exim version 4.72, the run time configuration file was also permitted to | |
4421 | be writeable by the Exim user and/or group. That has been changed in Exim 4.73 | |
4422 | since it offered a simple privilege escalation for any attacker who managed to | |
4423 | compromise the Exim user account. | |
4424 | ||
4425 | A default configuration file, which will work correctly in simple situations, | |
4426 | is provided in the file src/configure.default. If CONFIGURE_FILE defines just | |
4427 | one file name, the installation process copies the default configuration to a | |
4428 | new file of that name if it did not previously exist. If CONFIGURE_FILE is a | |
4429 | list, no default is automatically installed. Chapter 7 is a "walk-through" | |
4430 | discussion of the default configuration. | |
4431 | ||
4432 | ||
4433 | 6.1 Using a different configuration file | |
4434 | ---------------------------------------- | |
4435 | ||
4436 | A one-off alternate configuration can be specified by the -C command line | |
4437 | option, which may specify a single file or a list of files. However, when -C is | |
4438 | used, Exim gives up its root privilege, unless called by root (or unless the | |
4439 | argument for -C is identical to the built-in value from CONFIGURE_FILE), or is | |
4440 | listed in the TRUSTED_CONFIG_LIST file and the caller is the Exim user or the | |
4441 | user specified in the CONFIGURE_OWNER setting. -C is useful mainly for checking | |
4442 | the syntax of configuration files before installing them. No owner or group | |
4443 | checks are done on a configuration file specified by -C, if root privilege has | |
4444 | been dropped. | |
4445 | ||
4446 | Even the Exim user is not trusted to specify an arbitrary configuration file | |
4447 | with the -C option to be used with root privileges, unless that file is listed | |
4448 | in the TRUSTED_CONFIG_LIST file. This locks out the possibility of testing a | |
4449 | configuration using -C right through message reception and delivery, even if | |
4450 | the caller is root. The reception works, but by that time, Exim is running as | |
4451 | the Exim user, so when it re-execs to regain privilege for the delivery, the | |
4452 | use of -C causes privilege to be lost. However, root can test reception and | |
4453 | delivery using two separate commands (one to put a message on the queue, using | |
4454 | -odq, and another to do the delivery, using -M). | |
4455 | ||
4456 | If ALT_CONFIG_PREFIX is defined in Local/Makefile, it specifies a prefix string | |
4457 | with which any file named in a -C command line option must start. In addition, | |
4458 | the file name must not contain the sequence "/../". There is no default setting | |
4459 | for ALT_CONFIG_PREFIX; when it is unset, any file name can be used with -C. | |
4460 | ||
4461 | One-off changes to a configuration can be specified by the -D command line | |
4462 | option, which defines and overrides values for macros used inside the | |
4463 | configuration file. However, like -C, the use of this option by a | |
4464 | non-privileged user causes Exim to discard its root privilege. If | |
4465 | DISABLE_D_OPTION is defined in Local/Makefile, the use of -D is completely | |
4466 | disabled, and its use causes an immediate error exit. | |
4467 | ||
4468 | The WHITELIST_D_MACROS option in Local/Makefile permits the binary builder to | |
4469 | declare certain macro names trusted, such that root privilege will not | |
4470 | necessarily be discarded. WHITELIST_D_MACROS defines a colon-separated list of | |
4471 | macros which are considered safe and, if -D only supplies macros from this | |
4472 | list, and the values are acceptable, then Exim will not give up root privilege | |
4473 | if the caller is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. | |
4474 | This is a transition mechanism and is expected to be removed in the future. | |
4475 | Acceptable values for the macros satisfy the regexp: "^[A-Za-z0-9_/.-]*$" | |
4476 | ||
4477 | Some sites may wish to use the same Exim binary on different machines that | |
4478 | share a file system, but to use different configuration files on each machine. | |
4479 | If CONFIGURE_FILE_USE_NODE is defined in Local/Makefile, Exim first looks for a | |
4480 | file whose name is the configuration file name followed by a dot and the | |
4481 | machine's node name, as obtained from the uname() function. If this file does | |
4482 | not exist, the standard name is tried. This processing occurs for each file | |
4483 | name in the list given by CONFIGURE_FILE or -C. | |
4484 | ||
4485 | In some esoteric situations different versions of Exim may be run under | |
4486 | different effective uids and the CONFIGURE_FILE_USE_EUID is defined to help | |
4487 | with this. See the comments in src/EDITME for details. | |
4488 | ||
4489 | ||
4490 | 6.2 Configuration file format | |
4491 | ----------------------------- | |
4492 | ||
4493 | Exim's configuration file is divided into a number of different parts. General | |
4494 | option settings must always appear at the start of the file. The other parts | |
4495 | are all optional, and may appear in any order. Each part other than the first | |
4496 | is introduced by the word "begin" followed by the name of the part. The | |
4497 | optional parts are: | |
4498 | ||
4499 | * ACL: Access control lists for controlling incoming SMTP mail (see chapter | |
4500 | 42). | |
4501 | ||
4502 | * authenticators: Configuration settings for the authenticator drivers. These | |
4503 | are concerned with the SMTP AUTH command (see chapter 33). | |
4504 | ||
4505 | * routers: Configuration settings for the router drivers. Routers process | |
4506 | addresses and determine how the message is to be delivered (see chapters 15 | |
4507 | -22). | |
4508 | ||
4509 | * transports: Configuration settings for the transport drivers. Transports | |
4510 | define mechanisms for copying messages to destinations (see chapters 24-30 | |
4511 | ). | |
4512 | ||
4513 | * retry: Retry rules, for use when a message cannot be delivered immediately. | |
4514 | If there is no retry section, or if it is empty (that is, no retry rules | |
4515 | are defined), Exim will not retry deliveries. In this situation, temporary | |
4516 | errors are treated the same as permanent errors. Retry rules are discussed | |
4517 | in chapter 32. | |
4518 | ||
4519 | * rewrite: Global address rewriting rules, for use when a message arrives and | |
4520 | when new addresses are generated during delivery. Rewriting is discussed in | |
4521 | chapter 31. | |
4522 | ||
4523 | * local_scan: Private options for the local_scan() function. If you want to | |
4524 | use this feature, you must set | |
4525 | ||
4526 | LOCAL_SCAN_HAS_OPTIONS=yes | |
4527 | ||
4528 | in Local/Makefile before building Exim. Details of the local_scan() | |
4529 | facility are given in chapter 44. | |
4530 | ||
4531 | Leading and trailing white space in configuration lines is always ignored. | |
4532 | ||
4533 | Blank lines in the file, and lines starting with a # character (ignoring | |
4534 | leading white space) are treated as comments and are ignored. Note: A # | |
4535 | character other than at the beginning of a line is not treated specially, and | |
4536 | does not introduce a comment. | |
4537 | ||
4538 | Any non-comment line can be continued by ending it with a backslash. Note that | |
4539 | the general rule for white space means that trailing white space after the | |
4540 | backslash and leading white space at the start of continuation lines is | |
4541 | ignored. Comment lines beginning with # (but not empty lines) may appear in the | |
4542 | middle of a sequence of continuation lines. | |
4543 | ||
4544 | A convenient way to create a configuration file is to start from the default, | |
4545 | which is supplied in src/configure.default, and add, delete, or change settings | |
4546 | as required. | |
4547 | ||
4548 | The ACLs, retry rules, and rewriting rules have their own syntax which is | |
4549 | described in chapters 42, 32, and 31, respectively. The other parts of the | |
4550 | configuration file have some syntactic items in common, and these are described | |
4551 | below, from section 6.10 onwards. Before that, the inclusion, macro, and | |
4552 | conditional facilities are described. | |
4553 | ||
4554 | ||
4555 | 6.3 File inclusions in the configuration file | |
4556 | --------------------------------------------- | |
4557 | ||
4558 | You can include other files inside Exim's run time configuration file by using | |
4559 | this syntax: | |
4560 | ||
4561 | .include <file name> | |
4562 | .include_if_exists <file name> | |
4563 | ||
4564 | on a line by itself. Double quotes round the file name are optional. If you use | |
4565 | the first form, a configuration error occurs if the file does not exist; the | |
4566 | second form does nothing for non-existent files. In all cases, an absolute file | |
4567 | name is required. | |
4568 | ||
4569 | Includes may be nested to any depth, but remember that Exim reads its | |
4570 | configuration file often, so it is a good idea to keep them to a minimum. If | |
4571 | you change the contents of an included file, you must HUP the daemon, because | |
4572 | an included file is read only when the configuration itself is read. | |
4573 | ||
4574 | The processing of inclusions happens early, at a physical line level, so, like | |
4575 | comment lines, an inclusion can be used in the middle of an option setting, for | |
4576 | example: | |
4577 | ||
4578 | hosts_lookup = a.b.c \ | |
4579 | .include /some/file | |
4580 | ||
4581 | Include processing happens after macro processing (see below). Its effect is to | |
4582 | process the lines of the included file as if they occurred inline where the | |
4583 | inclusion appears. | |
4584 | ||
4585 | ||
4586 | 6.4 Macros in the configuration file | |
4587 | ------------------------------------ | |
4588 | ||
4589 | If a line in the main part of the configuration (that is, before the first | |
4590 | "begin" line) begins with an upper case letter, it is taken as a macro | |
4591 | definition, and must be of the form | |
4592 | ||
4593 | <name> = <rest of line> | |
4594 | ||
4595 | The name must consist of letters, digits, and underscores, and need not all be | |
4596 | in upper case, though that is recommended. The rest of the line, including any | |
4597 | continuations, is the replacement text, and has leading and trailing white | |
4598 | space removed. Quotes are not removed. The replacement text can never end with | |
4599 | a backslash character, but this doesn't seem to be a serious limitation. | |
4600 | ||
4601 | Macros may also be defined between router, transport, authenticator, or ACL | |
4602 | definitions. They may not, however, be defined within an individual driver or | |
4603 | ACL, or in the local_scan, retry, or rewrite sections of the configuration. | |
4604 | ||
4605 | ||
4606 | 6.5 Macro substitution | |
4607 | ---------------------- | |
4608 | ||
4609 | Once a macro is defined, all subsequent lines in the file (and any included | |
4610 | files) are scanned for the macro name; if there are several macros, the line is | |
4611 | scanned for each in turn, in the order in which the macros are defined. The | |
4612 | replacement text is not re-scanned for the current macro, though it is scanned | |
4613 | for subsequently defined macros. For this reason, a macro name may not contain | |
4614 | the name of a previously defined macro as a substring. You could, for example, | |
4615 | define | |
4616 | ||
4617 | ABCD_XYZ = <something> | |
4618 | ABCD = <something else> | |
4619 | ||
4620 | but putting the definitions in the opposite order would provoke a configuration | |
4621 | error. Macro expansion is applied to individual physical lines from the file, | |
4622 | before checking for line continuation or file inclusion (see above). If a line | |
4623 | consists solely of a macro name, and the expansion of the macro is empty, the | |
4624 | line is ignored. A macro at the start of a line may turn the line into a | |
4625 | comment line or a ".include" line. | |
4626 | ||
4627 | ||
4628 | 6.6 Redefining macros | |
4629 | --------------------- | |
4630 | ||
4631 | Once defined, the value of a macro can be redefined later in the configuration | |
4632 | (or in an included file). Redefinition is specified by using == instead of =. | |
4633 | For example: | |
4634 | ||
4635 | MAC = initial value | |
4636 | ... | |
4637 | MAC == updated value | |
4638 | ||
4639 | Redefinition does not alter the order in which the macros are applied to the | |
4640 | subsequent lines of the configuration file. It is still the same order in which | |
4641 | the macros were originally defined. All that changes is the macro's value. | |
4642 | Redefinition makes it possible to accumulate values. For example: | |
4643 | ||
4644 | MAC = initial value | |
4645 | ... | |
4646 | MAC == MAC and something added | |
4647 | ||
4648 | This can be helpful in situations where the configuration file is built from a | |
4649 | number of other files. | |
4650 | ||
4651 | ||
4652 | 6.7 Overriding macro values | |
4653 | --------------------------- | |
4654 | ||
4655 | The values set for macros in the configuration file can be overridden by the -D | |
4656 | command line option, but Exim gives up its root privilege when -D is used, | |
4657 | unless called by root or the Exim user. A definition on the command line using | |
4658 | the -D option causes all definitions and redefinitions within the file to be | |
4659 | ignored. | |
4660 | ||
4661 | ||
4662 | 6.8 Example of macro usage | |
4663 | -------------------------- | |
4664 | ||
4665 | As an example of macro usage, consider a configuration where aliases are looked | |
4666 | up in a MySQL database. It helps to keep the file less cluttered if long | |
4667 | strings such as SQL statements are defined separately as macros, for example: | |
4668 | ||
4669 | ALIAS_QUERY = select mailbox from user where \ | |
4670 | login='${quote_mysql:$local_part}'; | |
4671 | ||
4672 | This can then be used in a redirect router setting like this: | |
4673 | ||
4674 | data = ${lookup mysql{ALIAS_QUERY}} | |
4675 | ||
4676 | In earlier versions of Exim macros were sometimes used for domain, host, or | |
4677 | address lists. In Exim 4 these are handled better by named lists - see section | |
4678 | 10.5. | |
4679 | ||
4680 | ||
4681 | 6.9 Conditional skips in the configuration file | |
4682 | ----------------------------------------------- | |
4683 | ||
4684 | You can use the directives ".ifdef", ".ifndef", ".elifdef", ".elifndef", | |
4685 | ".else", and ".endif" to dynamically include or exclude portions of the | |
4686 | configuration file. The processing happens whenever the file is read (that is, | |
4687 | when an Exim binary starts to run). | |
4688 | ||
4689 | The implementation is very simple. Instances of the first four directives must | |
4690 | be followed by text that includes the names of one or macros. The condition | |
4691 | that is tested is whether or not any macro substitution has taken place in the | |
4692 | line. Thus: | |
4693 | ||
4694 | .ifdef AAA | |
4695 | message_size_limit = 50M | |
4696 | .else | |
4697 | message_size_limit = 100M | |
4698 | .endif | |
4699 | ||
4700 | sets a message size limit of 50M if the macro "AAA" is defined, and 100M | |
4701 | otherwise. If there is more than one macro named on the line, the condition is | |
4702 | true if any of them are defined. That is, it is an "or" condition. To obtain an | |
4703 | "and" condition, you need to use nested ".ifdef"s. | |
4704 | ||
4705 | Although you can use a macro expansion to generate one of these directives, it | |
4706 | is not very useful, because the condition "there was a macro substitution in | |
4707 | this line" will always be true. | |
4708 | ||
4709 | Text following ".else" and ".endif" is ignored, and can be used as comment to | |
4710 | clarify complicated nestings. | |
4711 | ||
4712 | ||
4713 | 6.10 Common option syntax | |
4714 | ------------------------- | |
4715 | ||
4716 | For the main set of options, driver options, and local_scan() options, each | |
4717 | setting is on a line by itself, and starts with a name consisting of lower-case | |
4718 | letters and underscores. Many options require a data value, and in these cases | |
4719 | the name must be followed by an equals sign (with optional white space) and | |
4720 | then the value. For example: | |
4721 | ||
4722 | qualify_domain = mydomain.example.com | |
4723 | ||
4724 | Some option settings may contain sensitive data, for example, passwords for | |
4725 | accessing databases. To stop non-admin users from using the -bP command line | |
4726 | option to read these values, you can precede the option settings with the word | |
4727 | "hide". For example: | |
4728 | ||
4729 | hide mysql_servers = localhost/users/admin/secret-password | |
4730 | ||
4731 | For non-admin users, such options are displayed like this: | |
4732 | ||
4733 | mysql_servers = <value not displayable> | |
4734 | ||
4735 | If "hide" is used on a driver option, it hides the value of that option on all | |
4736 | instances of the same driver. | |
4737 | ||
4738 | The following sections describe the syntax used for the different data types | |
4739 | that are found in option settings. | |
4740 | ||
4741 | ||
4742 | 6.11 Boolean options | |
4743 | -------------------- | |
4744 | ||
4745 | Options whose type is given as boolean are on/off switches. There are two | |
4746 | different ways of specifying such options: with and without a data value. If | |
4747 | the option name is specified on its own without data, the switch is turned on; | |
4748 | if it is preceded by "no_" or "not_" the switch is turned off. However, boolean | |
4749 | options may be followed by an equals sign and one of the words "true", "false", | |
4750 | "yes", or "no", as an alternative syntax. For example, the following two | |
4751 | settings have exactly the same effect: | |
4752 | ||
4753 | queue_only | |
4754 | queue_only = true | |
4755 | ||
4756 | The following two lines also have the same (opposite) effect: | |
4757 | ||
4758 | no_queue_only | |
4759 | queue_only = false | |
4760 | ||
4761 | You can use whichever syntax you prefer. | |
4762 | ||
4763 | ||
4764 | 6.12 Integer values | |
4765 | ------------------- | |
4766 | ||
4767 | If an option's type is given as "integer", the value can be given in decimal, | |
4768 | hexadecimal, or octal. If it starts with a digit greater than zero, a decimal | |
4769 | number is assumed. Otherwise, it is treated as an octal number unless it starts | |
4770 | with the characters "0x", in which case the remainder is interpreted as a | |
4771 | hexadecimal number. | |
4772 | ||
4773 | If an integer value is followed by the letter K, it is multiplied by 1024; if | |
4774 | it is followed by the letter M, it is multiplied by 1024x1024. When the values | |
4775 | of integer option settings are output, values which are an exact multiple of | |
4776 | 1024 or 1024x1024 are sometimes, but not always, printed using the letters K | |
4777 | and M. The printing style is independent of the actual input format that was | |
4778 | used. | |
4779 | ||
4780 | ||
4781 | 6.13 Octal integer values | |
4782 | ------------------------- | |
4783 | ||
4784 | If an option's type is given as "octal integer", its value is always | |
4785 | interpreted as an octal number, whether or not it starts with the digit zero. | |
4786 | Such options are always output in octal. | |
4787 | ||
4788 | ||
4789 | 6.14 Fixed point numbers | |
4790 | ------------------------ | |
4791 | ||
4792 | If an option's type is given as "fixed-point", its value must be a decimal | |
4793 | integer, optionally followed by a decimal point and up to three further digits. | |
4794 | ||
4795 | ||
4796 | 6.15 Time intervals | |
4797 | ------------------- | |
4798 | ||
4799 | A time interval is specified as a sequence of numbers, each followed by one of | |
4800 | the following letters, with no intervening white space: | |
4801 | ||
4802 | s seconds | |
4803 | m minutes | |
4804 | h hours | |
4805 | d days | |
4806 | w weeks | |
4807 | ||
4808 | For example, "3h50m" specifies 3 hours and 50 minutes. The values of time | |
4809 | intervals are output in the same format. Exim does not restrict the values; it | |
4810 | is perfectly acceptable, for example, to specify "90m" instead of "1h30m". | |
4811 | ||
4812 | ||
4813 | 6.16 String values | |
4814 | ------------------ | |
4815 | ||
4816 | If an option's type is specified as "string", the value can be specified with | |
4817 | or without double-quotes. If it does not start with a double-quote, the value | |
4818 | consists of the remainder of the line plus any continuation lines, starting at | |
4819 | the first character after any leading white space, with trailing white space | |
4820 | removed, and with no interpretation of the characters in the string. Because | |
4821 | Exim removes comment lines (those beginning with #) at an early stage, they can | |
4822 | appear in the middle of a multi-line string. The following two settings are | |
4823 | therefore equivalent: | |
4824 | ||
4825 | trusted_users = uucp:mail | |
4826 | trusted_users = uucp:\ | |
4827 | # This comment line is ignored | |
4828 | ||
4829 | ||
4830 | If a string does start with a double-quote, it must end with a closing | |
4831 | double-quote, and any backslash characters other than those used for line | |
4832 | continuation are interpreted as escape characters, as follows: | |
4833 | ||
4834 | "\\" single backslash | |
4835 | "\n" newline | |
4836 | "\r" carriage return | |
4837 | "\t" tab | |
4838 | "\"<octal digits> up to 3 octal digits specify one character | |
4839 | "\x"<hex digits> up to 2 hexadecimal digits specify one character | |
4840 | ||
4841 | If a backslash is followed by some other character, including a double-quote | |
4842 | character, that character replaces the pair. | |
4843 | ||
4844 | Quoting is necessary only if you want to make use of the backslash escapes to | |
4845 | insert special characters, or if you need to specify a value with leading or | |
4846 | trailing spaces. These cases are rare, so quoting is almost never needed in | |
4847 | current versions of Exim. In versions of Exim before 3.14, quoting was required | |
4848 | in order to continue lines, so you may come across older configuration files | |
4849 | and examples that apparently quote unnecessarily. | |
4850 | ||
4851 | ||
4852 | 6.17 Expanded strings | |
4853 | --------------------- | |
4854 | ||
4855 | Some strings in the configuration file are subjected to string expansion, by | |
4856 | which means various parts of the string may be changed according to the | |
4857 | circumstances (see chapter 11). The input syntax for such strings is as just | |
4858 | described; in particular, the handling of backslashes in quoted strings is done | |
4859 | as part of the input process, before expansion takes place. However, backslash | |
4860 | is also an escape character for the expander, so any backslashes that are | |
4861 | required for that reason must be doubled if they are within a quoted | |
4862 | configuration string. | |
4863 | ||
4864 | ||
4865 | 6.18 User and group names | |
4866 | ------------------------- | |
4867 | ||
4868 | User and group names are specified as strings, using the syntax described | |
4869 | above, but the strings are interpreted specially. A user or group name must | |
4870 | either consist entirely of digits, or be a name that can be looked up using the | |
4871 | getpwnam() or getgrnam() function, as appropriate. | |
4872 | ||
4873 | ||
4874 | 6.19 List construction | |
4875 | ---------------------- | |
4876 | ||
4877 | The data for some configuration options is a list of items, with colon as the | |
4878 | default separator. Many of these options are shown with type "string list" in | |
4879 | the descriptions later in this document. Others are listed as "domain list", | |
4880 | "host list", "address list", or "local part list". Syntactically, they are all | |
4881 | the same; however, those other than "string list" are subject to particular | |
4882 | kinds of interpretation, as described in chapter 10. | |
4883 | ||
4884 | In all these cases, the entire list is treated as a single string as far as the | |
4885 | input syntax is concerned. The trusted_users setting in section 6.16 above is | |
4886 | an example. If a colon is actually needed in an item in a list, it must be | |
4887 | entered as two colons. Leading and trailing white space on each item in a list | |
4888 | is ignored. This makes it possible to include items that start with a colon, | |
4889 | and in particular, certain forms of IPv6 address. For example, the list | |
4890 | ||
4891 | local_interfaces = 127.0.0.1 : ::::1 | |
4892 | ||
4893 | contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1. | |
4894 | ||
4895 | Note: Although leading and trailing white space is ignored in individual list | |
4896 | items, it is not ignored when parsing the list. The space after the first colon | |
4897 | in the example above is necessary. If it were not there, the list would be | |
4898 | interpreted as the two items 127.0.0.1:: and 1. | |
4899 | ||
4900 | ||
4901 | 6.20 Changing list separators | |
4902 | ----------------------------- | |
4903 | ||
4904 | Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was | |
4905 | introduced to allow the separator character to be changed. If a list begins | |
4906 | with a left angle bracket, followed by any punctuation character, that | |
4907 | character is used instead of colon as the list separator. For example, the list | |
4908 | above can be rewritten to use a semicolon separator like this: | |
4909 | ||
4910 | local_interfaces = <; 127.0.0.1 ; ::1 | |
4911 | ||
4912 | This facility applies to all lists, with the exception of the list in | |
4913 | log_file_path. It is recommended that the use of non-colon separators be | |
4914 | confined to circumstances where they really are needed. | |
4915 | ||
4916 | It is also possible to use newline and other control characters (those with | |
4917 | code values less than 32, plus DEL) as separators in lists. Such separators | |
4918 | must be provided literally at the time the list is processed. For options that | |
4919 | are string-expanded, you can write the separator using a normal escape | |
4920 | sequence. This will be processed by the expander before the string is | |
4921 | interpreted as a list. For example, if a newline-separated list of domains is | |
4922 | generated by a lookup, you can process it directly by a line such as this: | |
4923 | ||
4924 | domains = <\n ${lookup mysql{.....}} | |
4925 | ||
4926 | This avoids having to change the list separator in such data. You are unlikely | |
4927 | to want to use a control character as a separator in an option that is not | |
4928 | expanded, because the value is literal text. However, it can be done by giving | |
4929 | the value in quotes. For example: | |
4930 | ||
4931 | local_interfaces = "<\n 127.0.0.1 \n ::1" | |
4932 | ||
4933 | Unlike printing character separators, which can be included in list items by | |
4934 | doubling, it is not possible to include a control character as data when it is | |
4935 | set as the separator. Two such characters in succession are interpreted as | |
4936 | enclosing an empty list item. | |
4937 | ||
4938 | ||
4939 | 6.21 Empty items in lists | |
4940 | ------------------------- | |
4941 | ||
4942 | An empty item at the end of a list is always ignored. In other words, trailing | |
4943 | separator characters are ignored. Thus, the list in | |
4944 | ||
4945 | senders = user@domain : | |
4946 | ||
4947 | contains only a single item. If you want to include an empty string as one item | |
4948 | in a list, it must not be the last item. For example, this list contains three | |
4949 | items, the second of which is empty: | |
4950 | ||
4951 | senders = user1@domain : : user2@domain | |
4952 | ||
4953 | Note: There must be white space between the two colons, as otherwise they are | |
4954 | interpreted as representing a single colon data character (and the list would | |
4955 | then contain just one item). If you want to specify a list that contains just | |
4956 | one, empty item, you can do it as in this example: | |
4957 | ||
4958 | senders = : | |
4959 | ||
4960 | In this case, the first item is empty, and the second is discarded because it | |
4961 | is at the end of the list. | |
4962 | ||
4963 | ||
4964 | 6.22 Format of driver configurations | |
4965 | ------------------------------------ | |
4966 | ||
4967 | There are separate parts in the configuration for defining routers, transports, | |
4968 | and authenticators. In each part, you are defining a number of driver | |
4969 | instances, each with its own set of options. Each driver instance is defined by | |
4970 | a sequence of lines like this: | |
4971 | ||
4972 | <instance name>: | |
4973 | <option> | |
4974 | ... | |
4975 | <option> | |
4976 | ||
4977 | In the following example, the instance name is localuser, and it is followed by | |
4978 | three options settings: | |
4979 | ||
4980 | localuser: | |
4981 | driver = accept | |
4982 | check_local_user | |
4983 | transport = local_delivery | |
4984 | ||
4985 | For each driver instance, you specify which Exim code module it uses - by the | |
4986 | setting of the driver option - and (optionally) some configuration settings. | |
4987 | For example, in the case of transports, if you want a transport to deliver with | |
4988 | SMTP you would use the smtp driver; if you want to deliver to a local file you | |
4989 | would use the appendfile driver. Each of the drivers is described in detail in | |
4990 | its own separate chapter later in this manual. | |
4991 | ||
4992 | You can have several routers, transports, or authenticators that are based on | |
4993 | the same underlying driver (each must have a different instance name). | |
4994 | ||
4995 | The order in which routers are defined is important, because addresses are | |
4996 | passed to individual routers one by one, in order. The order in which | |
4997 | transports are defined does not matter at all. The order in which | |
4998 | authenticators are defined is used only when Exim, as a client, is searching | |
4999 | them to find one that matches an authentication mechanism offered by the | |
5000 | server. | |
5001 | ||
5002 | Within a driver instance definition, there are two kinds of option: generic and | |
5003 | private. The generic options are those that apply to all drivers of the same | |
5004 | type (that is, all routers, all transports or all authenticators). The driver | |
5005 | option is a generic option that must appear in every definition. The private | |
5006 | options are special for each driver, and none need appear, because they all | |
5007 | have default values. | |
5008 | ||
5009 | The options may appear in any order, except that the driver option must precede | |
5010 | any private options, since these depend on the particular driver. For this | |
5011 | reason, it is recommended that driver always be the first option. | |
5012 | ||
5013 | Driver instance names, which are used for reference in log entries and | |
5014 | elsewhere, can be any sequence of letters, digits, and underscores (starting | |
5015 | with a letter) and must be unique among drivers of the same type. A router and | |
5016 | a transport (for example) can each have the same name, but no two router | |
5017 | instances can have the same name. The name of a driver instance should not be | |
5018 | confused with the name of the underlying driver module. For example, the | |
5019 | configuration lines: | |
5020 | ||
5021 | remote_smtp: | |
5022 | driver = smtp | |
5023 | ||
5024 | create an instance of the smtp transport driver whose name is remote_smtp. The | |
5025 | same driver code can be used more than once, with different instance names and | |
5026 | different option settings each time. A second instance of the smtp transport, | |
5027 | with different options, might be defined thus: | |
5028 | ||
5029 | special_smtp: | |
5030 | driver = smtp | |
5031 | port = 1234 | |
5032 | command_timeout = 10s | |
5033 | ||
5034 | The names remote_smtp and special_smtp would be used to reference these | |
5035 | transport instances from routers, and these names would appear in log lines. | |
5036 | ||
5037 | Comment lines may be present in the middle of driver specifications. The full | |
5038 | list of option settings for any particular driver instance, including all the | |
5039 | defaulted values, can be extracted by making use of the -bP command line | |
5040 | option. | |
5041 | ||
5042 | ||
5043 | ||
5044 | =============================================================================== | |
5045 | 7. THE DEFAULT CONFIGURATION FILE | |
5046 | ||
5047 | The default configuration file supplied with Exim as src/configure.default is | |
5048 | sufficient for a host with simple mail requirements. As an introduction to the | |
5049 | way Exim is configured, this chapter "walks through" the default configuration, | |
5050 | giving brief explanations of the settings. Detailed descriptions of the options | |
5051 | are given in subsequent chapters. The default configuration file itself | |
5052 | contains extensive comments about ways you might want to modify the initial | |
5053 | settings. However, note that there are many options that are not mentioned at | |
5054 | all in the default configuration. | |
5055 | ||
5056 | ||
5057 | 7.1 Main configuration settings | |
5058 | ------------------------------- | |
5059 | ||
5060 | The main (global) configuration option settings must always come first in the | |
5061 | file. The first thing you'll see in the file, after some initial comments, is | |
5062 | the line | |
5063 | ||
5064 | # primary_hostname = | |
5065 | ||
5066 | This is a commented-out setting of the primary_hostname option. Exim needs to | |
5067 | know the official, fully qualified name of your host, and this is where you can | |
5068 | specify it. However, in most cases you do not need to set this option. When it | |
5069 | is unset, Exim uses the uname() system function to obtain the host name. | |
5070 | ||
5071 | The first three non-comment configuration lines are as follows: | |
5072 | ||
5073 | domainlist local_domains = @ | |
5074 | domainlist relay_to_domains = | |
5075 | hostlist relay_from_hosts = 127.0.0.1 | |
5076 | ||
5077 | These are not, in fact, option settings. They are definitions of two named | |
5078 | domain lists and one named host list. Exim allows you to give names to lists of | |
5079 | domains, hosts, and email addresses, in order to make it easier to manage the | |
5080 | configuration file (see section 10.5). | |
5081 | ||
5082 | The first line defines a domain list called local_domains; this is used later | |
5083 | in the configuration to identify domains that are to be delivered on the local | |
5084 | host. | |
5085 | ||
5086 | There is just one item in this list, the string "@". This is a special form of | |
5087 | entry which means "the name of the local host". Thus, if the local host is | |
5088 | called a.host.example, mail to any.user@a.host.example is expected to be | |
5089 | delivered locally. Because the local host's name is referenced indirectly, the | |
5090 | same configuration file can be used on different hosts. | |
5091 | ||
5092 | The second line defines a domain list called relay_to_domains, but the list | |
5093 | itself is empty. Later in the configuration we will come to the part that | |
5094 | controls mail relaying through the local host; it allows relaying to any | |
5095 | domains in this list. By default, therefore, no relaying on the basis of a mail | |
5096 | domain is permitted. | |
5097 | ||
5098 | The third line defines a host list called relay_from_hosts. This list is used | |
5099 | later in the configuration to permit relaying from any host or IP address that | |
5100 | matches the list. The default contains just the IP address of the IPv4 loopback | |
5101 | interface, which means that processes on the local host are able to submit mail | |
5102 | for relaying by sending it over TCP/IP to that interface. No other hosts are | |
5103 | permitted to submit messages for relaying. | |
5104 | ||
5105 | Just to be sure there's no misunderstanding: at this point in the configuration | |
5106 | we aren't actually setting up any controls. We are just defining some domains | |
5107 | and hosts that will be used in the controls that are specified later. | |
5108 | ||
5109 | The next two configuration lines are genuine option settings: | |
5110 | ||
5111 | acl_smtp_rcpt = acl_check_rcpt | |
5112 | acl_smtp_data = acl_check_data | |
5113 | ||
5114 | These options specify Access Control Lists (ACLs) that are to be used during an | |
5115 | incoming SMTP session for every recipient of a message (every RCPT command), | |
5116 | and after the contents of the message have been received, respectively. The | |
5117 | names of the lists are acl_check_rcpt and acl_check_data, and we will come to | |
5118 | their definitions below, in the ACL section of the configuration. The RCPT ACL | |
5119 | controls which recipients are accepted for an incoming message - if a | |
5120 | configuration does not provide an ACL to check recipients, no SMTP mail can be | |
5121 | accepted. The DATA ACL allows the contents of a message to be checked. | |
5122 | ||
5123 | Two commented-out option settings are next: | |
5124 | ||
5125 | # av_scanner = clamd:/tmp/clamd | |
5126 | # spamd_address = 127.0.0.1 783 | |
5127 | ||
5128 | These are example settings that can be used when Exim is compiled with the | |
5129 | content-scanning extension. The first specifies the interface to the virus | |
5130 | scanner, and the second specifies the interface to SpamAssassin. Further | |
5131 | details are given in chapter 43. | |
5132 | ||
5133 | Three more commented-out option settings follow: | |
5134 | ||
5135 | # tls_advertise_hosts = * | |
5136 | # tls_certificate = /etc/ssl/exim.crt | |
5137 | # tls_privatekey = /etc/ssl/exim.pem | |
5138 | ||
5139 | These are example settings that can be used when Exim is compiled with support | |
5140 | for TLS (aka SSL) as described in section 4.7. The first one specifies the list | |
5141 | of clients that are allowed to use TLS when connecting to this server; in this | |
5142 | case the wildcard means all clients. The other options specify where Exim | |
5143 | should find its TLS certificate and private key, which together prove the | |
5144 | server's identity to any clients that connect. More details are given in | |
5145 | chapter 41. | |
5146 | ||
5147 | Another two commented-out option settings follow: | |
5148 | ||
5149 | # daemon_smtp_ports = 25 : 465 : 587 | |
5150 | # tls_on_connect_ports = 465 | |
5151 | ||
5152 | These options provide better support for roaming users who wish to use this | |
5153 | server for message submission. They are not much use unless you have turned on | |
5154 | TLS (as described in the previous paragraph) and authentication (about which | |
5155 | more in section 7.7). The usual SMTP port 25 is often blocked on end-user | |
5156 | networks, so RFC 4409 specifies that message submission should use port 587 | |
5157 | instead. However some software (notably Microsoft Outlook) cannot be configured | |
5158 | to use port 587 correctly, so these settings also enable the non-standard | |
5159 | "smtps" (aka "ssmtp") port 465 (see section 13.4). | |
5160 | ||
5161 | Two more commented-out options settings follow: | |
5162 | ||
5163 | # qualify_domain = | |
5164 | # qualify_recipient = | |
5165 | ||
5166 | The first of these specifies a domain that Exim uses when it constructs a | |
5167 | complete email address from a local login name. This is often needed when Exim | |
5168 | receives a message from a local process. If you do not set qualify_domain, the | |
5169 | value of primary_hostname is used. If you set both of these options, you can | |
5170 | have different qualification domains for sender and recipient addresses. If you | |
5171 | set only the first one, its value is used in both cases. | |
5172 | ||
5173 | The following line must be uncommented if you want Exim to recognize addresses | |
5174 | of the form user@[10.11.12.13] that is, with a "domain literal" (an IP address | |
5175 | within square brackets) instead of a named domain. | |
5176 | ||
5177 | # allow_domain_literals | |
5178 | ||
5179 | The RFCs still require this form, but many people think that in the modern | |
5180 | Internet it makes little sense to permit mail to be sent to specific hosts by | |
5181 | quoting their IP addresses. This ancient format has been used by people who try | |
5182 | to abuse hosts by using them for unwanted relaying. However, some people | |
5183 | believe there are circumstances (for example, messages addressed to postmaster) | |
5184 | where domain literals are still useful. | |
5185 | ||
5186 | The next configuration line is a kind of trigger guard: | |
5187 | ||
5188 | never_users = root | |
5189 | ||
5190 | It specifies that no delivery must ever be run as the root user. The normal | |
5191 | convention is to set up root as an alias for the system administrator. This | |
5192 | setting is a guard against slips in the configuration. The list of users | |
5193 | specified by never_users is not, however, the complete list; the build-time | |
5194 | configuration in Local/Makefile has an option called FIXED_NEVER_USERS | |
5195 | specifying a list that cannot be overridden. The contents of never_users are | |
5196 | added to this list. By default FIXED_NEVER_USERS also specifies root. | |
5197 | ||
5198 | When a remote host connects to Exim in order to send mail, the only information | |
5199 | Exim has about the host's identity is its IP address. The next configuration | |
5200 | line, | |
5201 | ||
5202 | host_lookup = * | |
5203 | ||
5204 | specifies that Exim should do a reverse DNS lookup on all incoming connections, | |
5205 | in order to get a host name. This improves the quality of the logging | |
5206 | information, but if you feel it is too expensive, you can remove it entirely, | |
5207 | or restrict the lookup to hosts on "nearby" networks. Note that it is not | |
5208 | always possible to find a host name from an IP address, because not all DNS | |
5209 | reverse zones are maintained, and sometimes DNS servers are unreachable. | |
5210 | ||
5211 | The next two lines are concerned with ident callbacks, as defined by RFC 1413 | |
5212 | (hence their names): | |
5213 | ||
5214 | rfc1413_hosts = * | |
5215 | rfc1413_query_timeout = 0s | |
5216 | ||
5217 | These settings cause Exim to avoid ident callbacks for all incoming SMTP calls. | |
5218 | Few hosts offer RFC1413 service these days; calls have to be terminated by a | |
5219 | timeout and this needlessly delays the startup of an incoming SMTP connection. | |
5220 | If you have hosts for which you trust RFC1413 and need this information, you | |
5221 | can change this. | |
5222 | ||
5223 | This line enables an efficiency SMTP option. It is negociated by clients and | |
5224 | not expected to cause problems but can be disabled if needed. | |
5225 | ||
5226 | prdr_enable = true | |
5227 | ||
5228 | When Exim receives messages over SMTP connections, it expects all addresses to | |
5229 | be fully qualified with a domain, as required by the SMTP definition. However, | |
5230 | if you are running a server to which simple clients submit messages, you may | |
5231 | find that they send unqualified addresses. The two commented-out options: | |
5232 | ||
5233 | # sender_unqualified_hosts = | |
5234 | # recipient_unqualified_hosts = | |
5235 | ||
5236 | show how you can specify hosts that are permitted to send unqualified sender | |
5237 | and recipient addresses, respectively. | |
5238 | ||
5239 | The percent_hack_domains option is also commented out: | |
5240 | ||
5241 | # percent_hack_domains = | |
5242 | ||
5243 | It provides a list of domains for which the "percent hack" is to operate. This | |
5244 | is an almost obsolete form of explicit email routing. If you do not know | |
5245 | anything about it, you can safely ignore this topic. | |
5246 | ||
5247 | The last two settings in the main part of the default configuration are | |
5248 | concerned with messages that have been "frozen" on Exim's queue. When a message | |
5249 | is frozen, Exim no longer continues to try to deliver it. Freezing occurs when | |
5250 | a bounce message encounters a permanent failure because the sender address of | |
5251 | the original message that caused the bounce is invalid, so the bounce cannot be | |
5252 | delivered. This is probably the most common case, but there are also other | |
5253 | conditions that cause freezing, and frozen messages are not always bounce | |
5254 | messages. | |
5255 | ||
5256 | ignore_bounce_errors_after = 2d | |
5257 | timeout_frozen_after = 7d | |
5258 | ||
5259 | The first of these options specifies that failing bounce messages are to be | |
5260 | discarded after 2 days on the queue. The second specifies that any frozen | |
5261 | message (whether a bounce message or not) is to be timed out (and discarded) | |
5262 | after a week. In this configuration, the first setting ensures that no failing | |
5263 | bounce message ever lasts a week. | |
5264 | ||
5265 | ||
5266 | 7.2 ACL configuration | |
5267 | --------------------- | |
5268 | ||
5269 | In the default configuration, the ACL section follows the main configuration. | |
5270 | It starts with the line | |
5271 | ||
5272 | begin acl | |
5273 | ||
5274 | and it contains the definitions of two ACLs, called acl_check_rcpt and | |
5275 | acl_check_data, that were referenced in the settings of acl_smtp_rcpt and | |
5276 | acl_smtp_data above. | |
5277 | ||
5278 | The first ACL is used for every RCPT command in an incoming SMTP message. Each | |
5279 | RCPT command specifies one of the message's recipients. The ACL statements are | |
5280 | considered in order, until the recipient address is either accepted or | |
5281 | rejected. The RCPT command is then accepted or rejected, according to the | |
5282 | result of the ACL processing. | |
5283 | ||
5284 | acl_check_rcpt: | |
5285 | ||
5286 | This line, consisting of a name terminated by a colon, marks the start of the | |
5287 | ACL, and names it. | |
5288 | ||
5289 | accept hosts = : | |
5290 | ||
5291 | This ACL statement accepts the recipient if the sending host matches the list. | |
5292 | But what does that strange list mean? It doesn't actually contain any host | |
5293 | names or IP addresses. The presence of the colon puts an empty item in the | |
5294 | list; Exim matches this only if the incoming message did not come from a remote | |
5295 | host, because in that case, the remote hostname is empty. The colon is | |
5296 | important. Without it, the list itself is empty, and can never match anything. | |
5297 | ||
5298 | What this statement is doing is to accept unconditionally all recipients in | |
5299 | messages that are submitted by SMTP from local processes using the standard | |
5300 | input and output (that is, not using TCP/IP). A number of MUAs operate in this | |
5301 | manner. | |
5302 | ||
5303 | deny message = Restricted characters in address | |
5304 | domains = +local_domains | |
5305 | local_parts = ^[.] : ^.*[@%!/|] | |
5306 | ||
5307 | deny message = Restricted characters in address | |
5308 | domains = !+local_domains | |
5309 | local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./ | |
5310 | ||
5311 | These statements are concerned with local parts that contain any of the | |
5312 | characters "@", "%", "!", "/", "|", or dots in unusual places. Although these | |
5313 | characters are entirely legal in local parts (in the case of "@" and leading | |
5314 | dots, only if correctly quoted), they do not commonly occur in Internet mail | |
5315 | addresses. | |
5316 | ||
5317 | The first three have in the past been associated with explicitly routed | |
5318 | addresses (percent is still sometimes used - see the percent_hack_domains | |
5319 | option). Addresses containing these characters are regularly tried by spammers | |
5320 | in an attempt to bypass relaying restrictions, and also by open relay testing | |
5321 | programs. Unless you really need them it is safest to reject these characters | |
5322 | at this early stage. This configuration is heavy-handed in rejecting these | |
5323 | characters for all messages it accepts from remote hosts. This is a deliberate | |
5324 | policy of being as safe as possible. | |
5325 | ||
5326 | The first rule above is stricter, and is applied to messages that are addressed | |
5327 | to one of the local domains handled by this host. This is implemented by the | |
5328 | first condition, which restricts it to domains that are listed in the | |
5329 | local_domains domain list. The "+" character is used to indicate a reference to | |
5330 | a named list. In this configuration, there is just one domain in local_domains, | |
5331 | but in general there may be many. | |
5332 | ||
5333 | The second condition on the first statement uses two regular expressions to | |
5334 | block local parts that begin with a dot or contain "@", "%", "!", "/", or "|". | |
5335 | If you have local accounts that include these characters, you will have to | |
5336 | modify this rule. | |
5337 | ||
5338 | Empty components (two dots in a row) are not valid in RFC 2822, but Exim allows | |
5339 | them because they have been encountered in practice. (Consider the common | |
5340 | convention of local parts constructed as " | |
5341 | first-initial.second-initial.family-name" when applied to someone like the | |
5342 | author of Exim, who has no second initial.) However, a local part starting with | |
5343 | a dot or containing "/../" can cause trouble if it is used as part of a file | |
5344 | name (for example, for a mailing list). This is also true for local parts that | |
5345 | contain slashes. A pipe symbol can also be troublesome if the local part is | |
5346 | incorporated unthinkingly into a shell command line. | |
5347 | ||
5348 | The second rule above applies to all other domains, and is less strict. This | |
5349 | allows your own users to send outgoing messages to sites that use slashes and | |
5350 | vertical bars in their local parts. It blocks local parts that begin with a | |
5351 | dot, slash, or vertical bar, but allows these characters within the local part. | |
5352 | However, the sequence "/../" is barred. The use of "@", "%", and "!" is | |
5353 | blocked, as before. The motivation here is to prevent your users (or your | |
5354 | users' viruses) from mounting certain kinds of attack on remote sites. | |
5355 | ||
5356 | accept local_parts = postmaster | |
5357 | domains = +local_domains | |
5358 | ||
5359 | This statement, which has two conditions, accepts an incoming address if the | |
5360 | local part is postmaster and the domain is one of those listed in the | |
5361 | local_domains domain list. The "+" character is used to indicate a reference to | |
5362 | a named list. In this configuration, there is just one domain in local_domains, | |
5363 | but in general there may be many. | |
5364 | ||
5365 | The presence of this statement means that mail to postmaster is never blocked | |
5366 | by any of the subsequent tests. This can be helpful while sorting out problems | |
5367 | in cases where the subsequent tests are incorrectly denying access. | |
5368 | ||
5369 | require verify = sender | |
5370 | ||
5371 | This statement requires the sender address to be verified before any subsequent | |
5372 | ACL statement can be used. If verification fails, the incoming recipient | |
5373 | address is refused. Verification consists of trying to route the address, to | |
5374 | see if a bounce message could be delivered to it. In the case of remote | |
5375 | addresses, basic verification checks only the domain, but callouts can be used | |
5376 | for more verification if required. Section 42.44 discusses the details of | |
5377 | address verification. | |
5378 | ||
5379 | accept hosts = +relay_from_hosts | |
5380 | control = submission | |
5381 | ||
5382 | This statement accepts the address if the message is coming from one of the | |
5383 | hosts that are defined as being allowed to relay through this host. Recipient | |
5384 | verification is omitted here, because in many cases the clients are dumb MUAs | |
5385 | that do not cope well with SMTP error responses. For the same reason, the | |
5386 | second line specifies "submission mode" for messages that are accepted. This is | |
5387 | described in detail in section 46.1; it causes Exim to fix messages that are | |
5388 | deficient in some way, for example, because they lack a Date: header line. If | |
5389 | you are actually relaying out from MTAs, you should probably add recipient | |
5390 | verification here, and disable submission mode. | |
5391 | ||
5392 | accept authenticated = * | |
5393 | control = submission | |
5394 | ||
5395 | This statement accepts the address if the client host has authenticated itself. | |
5396 | Submission mode is again specified, on the grounds that such messages are most | |
5397 | likely to come from MUAs. The default configuration does not define any | |
5398 | authenticators, though it does include some nearly complete commented-out | |
5399 | examples described in 7.7. This means that no client can in fact authenticate | |
5400 | until you complete the authenticator definitions. | |
5401 | ||
5402 | require message = relay not permitted | |
5403 | domains = +local_domains : +relay_to_domains | |
5404 | ||
5405 | This statement rejects the address if its domain is neither a local domain nor | |
5406 | one of the domains for which this host is a relay. | |
5407 | ||
5408 | require verify = recipient | |
5409 | ||
5410 | This statement requires the recipient address to be verified; if verification | |
5411 | fails, the address is rejected. | |
5412 | ||
5413 | # deny message = rejected because $sender_host_address \ | |
5414 | # is in a black list at $dnslist_domain\n\ | |
5415 | # $dnslist_text | |
5416 | # dnslists = black.list.example | |
5417 | # | |
5418 | # warn dnslists = black.list.example | |
5419 | # add_header = X-Warning: $sender_host_address is in \ | |
5420 | # a black list at $dnslist_domain | |
5421 | # log_message = found in $dnslist_domain | |
5422 | ||
5423 | These commented-out lines are examples of how you could configure Exim to check | |
5424 | sending hosts against a DNS black list. The first statement rejects messages | |
5425 | from blacklisted hosts, whereas the second just inserts a warning header line. | |
5426 | ||
5427 | # require verify = csa | |
5428 | ||
5429 | This commented-out line is an example of how you could turn on client SMTP | |
5430 | authorization (CSA) checking. Such checks do DNS lookups for special SRV | |
5431 | records. | |
5432 | ||
5433 | accept | |
5434 | ||
5435 | The final statement in the first ACL unconditionally accepts any recipient | |
5436 | address that has successfully passed all the previous tests. | |
5437 | ||
5438 | acl_check_data: | |
5439 | ||
5440 | This line marks the start of the second ACL, and names it. Most of the contents | |
5441 | of this ACL are commented out: | |
5442 | ||
5443 | # deny malware = * | |
5444 | # message = This message contains a virus \ | |
5445 | # ($malware_name). | |
5446 | ||
5447 | These lines are examples of how to arrange for messages to be scanned for | |
5448 | viruses when Exim has been compiled with the content-scanning extension, and a | |
5449 | suitable virus scanner is installed. If the message is found to contain a | |
5450 | virus, it is rejected with the given custom error message. | |
5451 | ||
5452 | # warn spam = nobody | |
5453 | # message = X-Spam_score: $spam_score\n\ | |
5454 | # X-Spam_score_int: $spam_score_int\n\ | |
5455 | # X-Spam_bar: $spam_bar\n\ | |
5456 | # X-Spam_report: $spam_report | |
5457 | ||
5458 | These lines are an example of how to arrange for messages to be scanned by | |
5459 | SpamAssassin when Exim has been compiled with the content-scanning extension, | |
5460 | and SpamAssassin has been installed. The SpamAssassin check is run with | |
5461 | "nobody" as its user parameter, and the results are added to the message as a | |
5462 | series of extra header line. In this case, the message is not rejected, | |
5463 | whatever the spam score. | |
5464 | ||
5465 | accept | |
5466 | ||
5467 | This final line in the DATA ACL accepts the message unconditionally. | |
5468 | ||
5469 | ||
5470 | 7.3 Router configuration | |
5471 | ------------------------ | |
5472 | ||
5473 | The router configuration comes next in the default configuration, introduced by | |
5474 | the line | |
5475 | ||
5476 | begin routers | |
5477 | ||
5478 | Routers are the modules in Exim that make decisions about where to send | |
5479 | messages. An address is passed to each router in turn, until it is either | |
5480 | accepted, or failed. This means that the order in which you define the routers | |
5481 | matters. Each router is fully described in its own chapter later in this | |
5482 | manual. Here we give only brief overviews. | |
5483 | ||
5484 | # domain_literal: | |
5485 | # driver = ipliteral | |
5486 | # domains = !+local_domains | |
5487 | # transport = remote_smtp | |
5488 | ||
5489 | This router is commented out because the majority of sites do not want to | |
5490 | support domain literal addresses (those of the form user@[10.9.8.7]). If you | |
5491 | uncomment this router, you also need to uncomment the setting of | |
5492 | allow_domain_literals in the main part of the configuration. | |
5493 | ||
5494 | dnslookup: | |
5495 | driver = dnslookup | |
5496 | domains = ! +local_domains | |
5497 | transport = remote_smtp | |
5498 | ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8 | |
5499 | no_more | |
5500 | ||
5501 | The first uncommented router handles addresses that do not involve any local | |
5502 | domains. This is specified by the line | |
5503 | ||
5504 | domains = ! +local_domains | |
5505 | ||
5506 | The domains option lists the domains to which this router applies, but the | |
5507 | exclamation mark is a negation sign, so the router is used only for domains | |
5508 | that are not in the domain list called local_domains (which was defined at the | |
5509 | start of the configuration). The plus sign before local_domains indicates that | |
5510 | it is referring to a named list. Addresses in other domains are passed on to | |
5511 | the following routers. | |
5512 | ||
5513 | The name of the router driver is dnslookup, and is specified by the driver | |
5514 | option. Do not be confused by the fact that the name of this router instance is | |
5515 | the same as the name of the driver. The instance name is arbitrary, but the | |
5516 | name set in the driver option must be one of the driver modules that is in the | |
5517 | Exim binary. | |
5518 | ||
5519 | The dnslookup router routes addresses by looking up their domains in the DNS in | |
5520 | order to obtain a list of hosts to which the address is routed. If the router | |
5521 | succeeds, the address is queued for the remote_smtp transport, as specified by | |
5522 | the transport option. If the router does not find the domain in the DNS, no | |
5523 | further routers are tried because of the no_more setting, so the address fails | |
5524 | and is bounced. | |
5525 | ||
5526 | The ignore_target_hosts option specifies a list of IP addresses that are to be | |
5527 | entirely ignored. This option is present because a number of cases have been | |
5528 | encountered where MX records in the DNS point to host names whose IP addresses | |
5529 | are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1). Completely ignoring | |
5530 | these IP addresses causes Exim to fail to route the email address, so it | |
5531 | bounces. Otherwise, Exim would log a routing problem, and continue to try to | |
5532 | deliver the message periodically until the address timed out. | |
5533 | ||
5534 | system_aliases: | |
5535 | driver = redirect | |
5536 | allow_fail | |
5537 | allow_defer | |
5538 | data = ${lookup{$local_part}lsearch{/etc/aliases}} | |
5539 | # user = exim | |
5540 | file_transport = address_file | |
5541 | pipe_transport = address_pipe | |
5542 | ||
5543 | Control reaches this and subsequent routers only for addresses in the local | |
5544 | domains. This router checks to see whether the local part is defined as an | |
5545 | alias in the /etc/aliases file, and if so, redirects it according to the data | |
5546 | that it looks up from that file. If no data is found for the local part, the | |
5547 | value of the data option is empty, causing the address to be passed to the next | |
5548 | router. | |
5549 | ||
5550 | /etc/aliases is a conventional name for the system aliases file that is often | |
5551 | used. That is why it is referenced by from the default configuration file. | |
5552 | However, you can change this by setting SYSTEM_ALIASES_FILE in Local/Makefile | |
5553 | before building Exim. | |
5554 | ||
5555 | userforward: | |
5556 | driver = redirect | |
5557 | check_local_user | |
5558 | # local_part_suffix = +* : -* | |
5559 | # local_part_suffix_optional | |
5560 | file = $home/.forward | |
5561 | # allow_filter | |
5562 | no_verify | |
5563 | no_expn | |
5564 | check_ancestor | |
5565 | file_transport = address_file | |
5566 | pipe_transport = address_pipe | |
5567 | reply_transport = address_reply | |
5568 | ||
5569 | This is the most complicated router in the default configuration. It is another | |
5570 | redirection router, but this time it is looking for forwarding data set up by | |
5571 | individual users. The check_local_user setting specifies a check that the local | |
5572 | part of the address is the login name of a local user. If it is not, the router | |
5573 | is skipped. The two commented options that follow check_local_user, namely: | |
5574 | ||
5575 | # local_part_suffix = +* : -* | |
5576 | # local_part_suffix_optional | |
5577 | ||
5578 | show how you can specify the recognition of local part suffixes. If the first | |
5579 | is uncommented, a suffix beginning with either a plus or a minus sign, followed | |
5580 | by any sequence of characters, is removed from the local part and placed in the | |
5581 | variable $local_part_suffix. The second suffix option specifies that the | |
5582 | presence of a suffix in the local part is optional. When a suffix is present, | |
5583 | the check for a local login uses the local part with the suffix removed. | |
5584 | ||
5585 | When a local user account is found, the file called .forward in the user's home | |
5586 | directory is consulted. If it does not exist, or is empty, the router declines. | |
5587 | Otherwise, the contents of .forward are interpreted as redirection data (see | |
5588 | chapter 22 for more details). | |
5589 | ||
5590 | Traditional .forward files contain just a list of addresses, pipes, or files. | |
5591 | Exim supports this by default. However, if allow_filter is set (it is commented | |
5592 | out by default), the contents of the file are interpreted as a set of Exim or | |
5593 | Sieve filtering instructions, provided the file begins with "#Exim filter" or " | |
5594 | #Sieve filter", respectively. User filtering is discussed in the separate | |
5595 | document entitled Exim's interfaces to mail filtering. | |
5596 | ||
5597 | The no_verify and no_expn options mean that this router is skipped when | |
5598 | verifying addresses, or when running as a consequence of an SMTP EXPN command. | |
5599 | There are two reasons for doing this: | |
5600 | ||
5601 | 1. Whether or not a local user has a .forward file is not really relevant when | |
5602 | checking an address for validity; it makes sense not to waste resources | |
5603 | doing unnecessary work. | |
5604 | ||
5605 | 2. More importantly, when Exim is verifying addresses or handling an EXPN | |
5606 | command during an SMTP session, it is running as the Exim user, not as | |
5607 | root. The group is the Exim group, and no additional groups are set up. It | |
5608 | may therefore not be possible for Exim to read users' .forward files at | |
5609 | this time. | |
5610 | ||
5611 | The setting of check_ancestor prevents the router from generating a new address | |
5612 | that is the same as any previous address that was redirected. (This works round | |
5613 | a problem concerning a bad interaction between aliasing and forwarding - see | |
5614 | section 22.5). | |
5615 | ||
5616 | The final three option settings specify the transports that are to be used when | |
5617 | forwarding generates a direct delivery to a file, or to a pipe, or sets up an | |
5618 | auto-reply, respectively. For example, if a .forward file contains | |
5619 | ||
5620 | a.nother@elsewhere.example, /home/spqr/archive | |
5621 | ||
5622 | the delivery to /home/spqr/archive is done by running the address_file | |
5623 | transport. | |
5624 | ||
5625 | localuser: | |
5626 | driver = accept | |
5627 | check_local_user | |
5628 | # local_part_suffix = +* : -* | |
5629 | # local_part_suffix_optional | |
5630 | transport = local_delivery | |
5631 | ||
5632 | The final router sets up delivery into local mailboxes, provided that the local | |
5633 | part is the name of a local login, by accepting the address and assigning it to | |
5634 | the local_delivery transport. Otherwise, we have reached the end of the | |
5635 | routers, so the address is bounced. The commented suffix settings fulfil the | |
5636 | same purpose as they do for the userforward router. | |
5637 | ||
5638 | ||
5639 | 7.4 Transport configuration | |
5640 | --------------------------- | |
5641 | ||
5642 | Transports define mechanisms for actually delivering messages. They operate | |
5643 | only when referenced from routers, so the order in which they are defined does | |
5644 | not matter. The transports section of the configuration starts with | |
5645 | ||
5646 | begin transports | |
5647 | ||
5648 | One remote transport and four local transports are defined. | |
5649 | ||
5650 | remote_smtp: | |
5651 | driver = smtp | |
5652 | hosts_try_prdr = * | |
5653 | ||
5654 | This transport is used for delivering messages over SMTP connections. The list | |
5655 | of remote hosts comes from the router. The hosts_try_prdr option enables an | |
5656 | efficiency SMTP option. It is negotiated between client and server and not | |
5657 | expected to cause problems but can be disabled if needed. All other options are | |
5658 | defaulted. | |
5659 | ||
5660 | local_delivery: | |
5661 | driver = appendfile | |
5662 | file = /var/mail/$local_part | |
5663 | delivery_date_add | |
5664 | envelope_to_add | |
5665 | return_path_add | |
5666 | # group = mail | |
5667 | # mode = 0660 | |
5668 | ||
5669 | This appendfile transport is used for local delivery to user mailboxes in | |
5670 | traditional BSD mailbox format. By default it runs under the uid and gid of the | |
5671 | local user, which requires the sticky bit to be set on the /var/mail directory. | |
5672 | Some systems use the alternative approach of running mail deliveries under a | |
5673 | particular group instead of using the sticky bit. The commented options show | |
5674 | how this can be done. | |
5675 | ||
5676 | Exim adds three headers to the message as it delivers it: Delivery-date:, | |
5677 | Envelope-to: and Return-path:. This action is requested by the three | |
5678 | similarly-named options above. | |
5679 | ||
5680 | address_pipe: | |
5681 | driver = pipe | |
5682 | return_output | |
5683 | ||
5684 | This transport is used for handling deliveries to pipes that are generated by | |
5685 | redirection (aliasing or users' .forward files). The return_output option | |
5686 | specifies that any output generated by the pipe is to be returned to the | |
5687 | sender. | |
5688 | ||
5689 | address_file: | |
5690 | driver = appendfile | |
5691 | delivery_date_add | |
5692 | envelope_to_add | |
5693 | return_path_add | |
5694 | ||
5695 | This transport is used for handling deliveries to files that are generated by | |
5696 | redirection. The name of the file is not specified in this instance of | |
5697 | appendfile, because it comes from the redirect router. | |
5698 | ||
5699 | address_reply: | |
5700 | driver = autoreply | |
5701 | ||
5702 | This transport is used for handling automatic replies generated by users' | |
5703 | filter files. | |
5704 | ||
5705 | ||
5706 | 7.5 Default retry rule | |
5707 | ---------------------- | |
5708 | ||
5709 | The retry section of the configuration file contains rules which affect the way | |
5710 | Exim retries deliveries that cannot be completed at the first attempt. It is | |
5711 | introduced by the line | |
5712 | ||
5713 | begin retry | |
5714 | ||
5715 | In the default configuration, there is just one rule, which applies to all | |
5716 | errors: | |
5717 | ||
5718 | * * F,2h,15m; G,16h,1h,1.5; F,4d,6h | |
5719 | ||
5720 | This causes any temporarily failing address to be retried every 15 minutes for | |
5721 | 2 hours, then at intervals starting at one hour and increasing by a factor of | |
5722 | 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address | |
5723 | is not delivered after 4 days of temporary failure, it is bounced. | |
5724 | ||
5725 | If the retry section is removed from the configuration, or is empty (that is, | |
5726 | if no retry rules are defined), Exim will not retry deliveries. This turns | |
5727 | temporary errors into permanent errors. | |
5728 | ||
5729 | ||
5730 | 7.6 Rewriting configuration | |
5731 | --------------------------- | |
5732 | ||
5733 | The rewriting section of the configuration, introduced by | |
5734 | ||
5735 | begin rewrite | |
5736 | ||
5737 | contains rules for rewriting addresses in messages as they arrive. There are no | |
5738 | rewriting rules in the default configuration file. | |
5739 | ||
5740 | ||
5741 | 7.7 Authenticators configuration | |
5742 | -------------------------------- | |
5743 | ||
5744 | The authenticators section of the configuration, introduced by | |
5745 | ||
5746 | begin authenticators | |
5747 | ||
5748 | defines mechanisms for the use of the SMTP AUTH command. The default | |
5749 | configuration file contains two commented-out example authenticators which | |
5750 | support plaintext username/password authentication using the standard PLAIN | |
5751 | mechanism and the traditional but non-standard LOGIN mechanism, with Exim | |
5752 | acting as the server. PLAIN and LOGIN are enough to support most MUA software. | |
5753 | ||
5754 | The example PLAIN authenticator looks like this: | |
5755 | ||
5756 | #PLAIN: | |
5757 | # driver = plaintext | |
5758 | # server_set_id = $auth2 | |
5759 | # server_prompts = : | |
5760 | # server_condition = Authentication is not yet configured | |
5761 | # server_advertise_condition = ${if def:tls_in_cipher } | |
5762 | ||
5763 | And the example LOGIN authenticator looks like this: | |
5764 | ||
5765 | #LOGIN: | |
5766 | # driver = plaintext | |
5767 | # server_set_id = $auth1 | |
5768 | # server_prompts = <| Username: | Password: | |
5769 | # server_condition = Authentication is not yet configured | |
5770 | # server_advertise_condition = ${if def:tls_in_cipher } | |
5771 | ||
5772 | The server_set_id option makes Exim remember the authenticated username in | |
5773 | $authenticated_id, which can be used later in ACLs or routers. The | |
5774 | server_prompts option configures the plaintext authenticator so that it | |
5775 | implements the details of the specific authentication mechanism, i.e. PLAIN or | |
5776 | LOGIN. The server_advertise_condition setting controls when Exim offers | |
5777 | authentication to clients; in the examples, this is only when TLS or SSL has | |
5778 | been started, so to enable the authenticators you also need to add support for | |
5779 | TLS as described in section 7.1. | |
5780 | ||
5781 | The server_condition setting defines how to verify that the username and | |
5782 | password are correct. In the examples it just produces an error message. To | |
5783 | make the authenticators work, you can use a string expansion expression like | |
5784 | one of the examples in chapter 34. | |
5785 | ||
5786 | Beware that the sequence of the parameters to PLAIN and LOGIN differ; the | |
5787 | usercode and password are in different positions. Chapter 34 covers both. | |
5788 | ||
5789 | ||
5790 | ||
5791 | =============================================================================== | |
5792 | 8. REGULAR EXPRESSIONS | |
5793 | ||
5794 | Exim supports the use of regular expressions in many of its options. It uses | |
5795 | the PCRE regular expression library; this provides regular expression matching | |
5796 | that is compatible with Perl 5. The syntax and semantics of regular expressions | |
5797 | is discussed in many Perl reference books, and also in Jeffrey Friedl's | |
5798 | Mastering Regular Expressions, which is published by O'Reilly (see http:// | |
5799 | www.oreilly.com/catalog/regex2/). | |
5800 | ||
5801 | The documentation for the syntax and semantics of the regular expressions that | |
5802 | are supported by PCRE is included in the PCRE distribution, and no further | |
5803 | description is included here. The PCRE functions are called from Exim using the | |
5804 | default option settings (that is, with no PCRE options set), except that the | |
5805 | PCRE_CASELESS option is set when the matching is required to be | |
5806 | case-insensitive. | |
5807 | ||
5808 | In most cases, when a regular expression is required in an Exim configuration, | |
5809 | it has to start with a circumflex, in order to distinguish it from plain text | |
5810 | or an "ends with" wildcard. In this example of a configuration setting, the | |
5811 | second item in the colon-separated list is a regular expression. | |
5812 | ||
5813 | domains = a.b.c : ^\\d{3} : *.y.z : ... | |
5814 | ||
5815 | The doubling of the backslash is required because of string expansion that | |
5816 | precedes interpretation - see section 11.1 for more discussion of this issue, | |
5817 | and a way of avoiding the need for doubling backslashes. The regular expression | |
5818 | that is eventually used in this example contains just one backslash. The | |
5819 | circumflex is included in the regular expression, and has the normal effect of | |
5820 | "anchoring" it to the start of the string that is being matched. | |
5821 | ||
5822 | There are, however, two cases where a circumflex is not required for the | |
5823 | recognition of a regular expression: these are the match condition in a string | |
5824 | expansion, and the matches condition in an Exim filter file. In these cases, | |
5825 | the relevant string is always treated as a regular expression; if it does not | |
5826 | start with a circumflex, the expression is not anchored, and can match anywhere | |
5827 | in the subject string. | |
5828 | ||
5829 | In all cases, if you want a regular expression to match at the end of a string, | |
5830 | you must code the $ metacharacter to indicate this. For example: | |
5831 | ||
5832 | domains = ^\\d{3}\\.example | |
5833 | ||
5834 | matches the domain 123.example, but it also matches 123.example.com. You need | |
5835 | to use: | |
5836 | ||
5837 | domains = ^\\d{3}\\.example\$ | |
5838 | ||
5839 | if you want example to be the top-level domain. The backslash before the $ is | |
5840 | needed because string expansion also interprets dollar characters. | |
5841 | ||
5842 | ||
5843 | ||
5844 | =============================================================================== | |
5845 | 9. FILE AND DATABASE LOOKUPS | |
5846 | ||
5847 | Exim can be configured to look up data in files or databases as it processes | |
5848 | messages. Two different kinds of syntax are used: | |
5849 | ||
5850 | 1. A string that is to be expanded may contain explicit lookup requests. These | |
5851 | cause parts of the string to be replaced by data that is obtained from the | |
5852 | lookup. Lookups of this type are conditional expansion items. Different | |
5853 | results can be defined for the cases of lookup success and failure. See | |
5854 | chapter 11, where string expansions are described in detail. | |
5855 | ||
5856 | 2. Lists of domains, hosts, and email addresses can contain lookup requests as | |
5857 | a way of avoiding excessively long linear lists. In this case, the data | |
5858 | that is returned by the lookup is often (but not always) discarded; whether | |
5859 | the lookup succeeds or fails is what really counts. These kinds of list are | |
5860 | described in chapter 10. | |
5861 | ||
5862 | String expansions, lists, and lookups interact with each other in such a way | |
5863 | that there is no order in which to describe any one of them that does not | |
5864 | involve references to the others. Each of these three chapters makes more sense | |
5865 | if you have read the other two first. If you are reading this for the first | |
5866 | time, be aware that some of it will make a lot more sense after you have read | |
5867 | chapters 10 and 11. | |
5868 | ||
5869 | ||
5870 | 9.1 Examples of different lookup syntax | |
5871 | --------------------------------------- | |
5872 | ||
5873 | It is easy to confuse the two different kinds of lookup, especially as the | |
5874 | lists that may contain the second kind are always expanded before being | |
5875 | processed as lists. Therefore, they may also contain lookups of the first kind. | |
5876 | Be careful to distinguish between the following two examples: | |
5877 | ||
5878 | domains = ${lookup{$sender_host_address}lsearch{/some/file}} | |
5879 | domains = lsearch;/some/file | |
5880 | ||
5881 | The first uses a string expansion, the result of which must be a domain list. | |
5882 | No strings have been specified for a successful or a failing lookup; the | |
5883 | defaults in this case are the looked-up data and an empty string, respectively. | |
5884 | The expansion takes place before the string is processed as a list, and the | |
5885 | file that is searched could contain lines like this: | |
5886 | ||
5887 | 192.168.3.4: domain1:domain2:... | |
5888 | 192.168.1.9: domain3:domain4:... | |
5889 | ||
5890 | When the lookup succeeds, the result of the expansion is a list of domains (and | |
5891 | possibly other types of item that are allowed in domain lists). | |
5892 | ||
5893 | In the second example, the lookup is a single item in a domain list. It causes | |
5894 | Exim to use a lookup to see if the domain that is being processed can be found | |
5895 | in the file. The file could contains lines like this: | |
5896 | ||
5897 | domain1: | |
5898 | domain2: | |
5899 | ||
5900 | Any data that follows the keys is not relevant when checking that the domain | |
5901 | matches the list item. | |
5902 | ||
5903 | It is possible, though no doubt confusing, to use both kinds of lookup at once. | |
5904 | Consider a file containing lines like this: | |
5905 | ||
5906 | 192.168.5.6: lsearch;/another/file | |
5907 | ||
5908 | If the value of $sender_host_address is 192.168.5.6, expansion of the first | |
5909 | domains setting above generates the second setting, which therefore causes a | |
5910 | second lookup to occur. | |
5911 | ||
5912 | The rest of this chapter describes the different lookup types that are | |
5913 | available. Any of them can be used in any part of the configuration where a | |
5914 | lookup is permitted. | |
5915 | ||
5916 | ||
5917 | 9.2 Lookup types | |
5918 | ---------------- | |
5919 | ||
5920 | Two different types of data lookup are implemented: | |
5921 | ||
5922 | * The single-key type requires the specification of a file in which to look, | |
5923 | and a single key to search for. The key must be a non-empty string for the | |
5924 | lookup to succeed. The lookup type determines how the file is searched. | |
5925 | ||
5926 | * The query-style type accepts a generalized database query. No particular | |
5927 | key value is assumed by Exim for query-style lookups. You can use whichever | |
5928 | Exim variables you need to construct the database query. | |
5929 | ||
5930 | The code for each lookup type is in a separate source file that is included in | |
5931 | the binary of Exim only if the corresponding compile-time option is set. The | |
5932 | default settings in src/EDITME are: | |
5933 | ||
5934 | LOOKUP_DBM=yes | |
5935 | LOOKUP_LSEARCH=yes | |
5936 | ||
5937 | which means that only linear searching and DBM lookups are included by default. | |
5938 | For some types of lookup (e.g. SQL databases), you need to install appropriate | |
5939 | libraries and header files before building Exim. | |
5940 | ||
5941 | ||
5942 | 9.3 Single-key lookup types | |
5943 | --------------------------- | |
5944 | ||
5945 | The following single-key lookup types are implemented: | |
5946 | ||
5947 | * cdb: The given file is searched as a Constant DataBase file, using the key | |
5948 | string without a terminating binary zero. The cdb format is designed for | |
5949 | indexed files that are read frequently and never updated, except by total | |
5950 | re-creation. As such, it is particularly suitable for large files | |
5951 | containing aliases or other indexed data referenced by an MTA. Information | |
5952 | about cdb can be found in several places: | |
5953 | ||
5954 | http://www.pobox.com/~djb/cdb.html | |
5955 | ftp://ftp.corpit.ru/pub/tinycdb/ | |
5956 | http://packages.debian.org/stable/utils/freecdb.html | |
5957 | ||
5958 | A cdb distribution is not needed in order to build Exim with cdb support, | |
5959 | because the code for reading cdb files is included directly in Exim itself. | |
5960 | However, no means of building or testing cdb files is provided with Exim, | |
5961 | so you need to obtain a cdb distribution in order to do this. | |
5962 | ||
5963 | * dbm: Calls to DBM library functions are used to extract data from the given | |
5964 | DBM file by looking up the record with the given key. A terminating binary | |
5965 | zero is included in the key that is passed to the DBM library. See section | |
5966 | 4.4 for a discussion of DBM libraries. | |
5967 | ||
5968 | For all versions of Berkeley DB, Exim uses the DB_HASH style of database | |
5969 | when building DBM files using the exim_dbmbuild utility. However, when | |
5970 | using Berkeley DB versions 3 or 4, it opens existing databases for reading | |
5971 | with the DB_UNKNOWN option. This enables it to handle any of the types of | |
5972 | database that the library supports, and can be useful for accessing DBM | |
5973 | files created by other applications. (For earlier DB versions, DB_HASH is | |
5974 | always used.) | |
5975 | ||
5976 | * dbmjz: This is the same as dbm, except that the lookup key is interpreted | |
5977 | as an Exim list; the elements of the list are joined together with ASCII | |
5978 | NUL characters to form the lookup key. An example usage would be to | |
5979 | authenticate incoming SMTP calls using the passwords from Cyrus SASL's /etc | |
5980 | /sasldb2 file with the gsasl authenticator or Exim's own cram_md5 | |
5981 | authenticator. | |
5982 | ||
5983 | * dbmnz: This is the same as dbm, except that a terminating binary zero is | |
5984 | not included in the key that is passed to the DBM library. You may need | |
5985 | this if you want to look up data in files that are created by or shared | |
5986 | with some other application that does not use terminating zeros. For | |
5987 | example, you need to use dbmnz rather than dbm if you want to authenticate | |
5988 | incoming SMTP calls using the passwords from Courier's /etc/ | |
5989 | userdbshadow.dat file. Exim's utility program for creating DBM files ( | |
5990 | exim_dbmbuild) includes the zeros by default, but has an option to omit | |
5991 | them (see section 52.9). | |
5992 | ||
5993 | * dsearch: The given file must be a directory; this is searched for an entry | |
5994 | whose name is the key by calling the lstat() function. The key may not | |
5995 | contain any forward slash characters. If lstat() succeeds, the result of | |
5996 | the lookup is the name of the entry, which may be a file, directory, | |
5997 | symbolic link, or any other kind of directory entry. An example of how this | |
5998 | lookup can be used to support virtual domains is given in section 49.7. | |
5999 | ||
6000 | * iplsearch: The given file is a text file containing keys and data. A key is | |
6001 | terminated by a colon or white space or the end of the line. The keys in | |
6002 | the file must be IP addresses, or IP addresses with CIDR masks. Keys that | |
6003 | involve IPv6 addresses must be enclosed in quotes to prevent the first | |
6004 | internal colon being interpreted as a key terminator. For example: | |
6005 | ||
6006 | 1.2.3.4: data for 1.2.3.4 | |
6007 | 192.168.0.0/16: data for 192.168.0.0/16 | |
6008 | "abcd::cdab": data for abcd::cdab | |
6009 | "abcd:abcd::/32" data for abcd:abcd::/32 | |
6010 | ||
6011 | The key for an iplsearch lookup must be an IP address (without a mask). The | |
6012 | file is searched linearly, using the CIDR masks where present, until a | |
6013 | matching key is found. The first key that matches is used; there is no | |
6014 | attempt to find a "best" match. Apart from the way the keys are matched, | |
6015 | the processing for iplsearch is the same as for lsearch. | |
6016 | ||
6017 | Warning 1: Unlike most other single-key lookup types, a file of data for | |
6018 | iplsearch can not be turned into a DBM or cdb file, because those lookup | |
6019 | types support only literal keys. | |
6020 | ||
6021 | Warning 2: In a host list, you must always use net-iplsearch so that the | |
6022 | implicit key is the host's IP address rather than its name (see section | |
6023 | 10.12). | |
6024 | ||
6025 | * lsearch: The given file is a text file that is searched linearly for a line | |
6026 | beginning with the search key, terminated by a colon or white space or the | |
6027 | end of the line. The search is case-insensitive; that is, upper and lower | |
6028 | case letters are treated as the same. The first occurrence of the key that | |
6029 | is found in the file is used. | |
6030 | ||
6031 | White space between the key and the colon is permitted. The remainder of | |
6032 | the line, with leading and trailing white space removed, is the data. This | |
6033 | can be continued onto subsequent lines by starting them with any amount of | |
6034 | white space, but only a single space character is included in the data at | |
6035 | such a junction. If the data begins with a colon, the key must be | |
6036 | terminated by a colon, for example: | |
6037 | ||
6038 | baduser: :fail: | |
6039 | ||
6040 | Empty lines and lines beginning with # are ignored, even if they occur in | |
6041 | the middle of an item. This is the traditional textual format of alias | |
6042 | files. Note that the keys in an lsearch file are literal strings. There is | |
6043 | no wildcarding of any kind. | |
6044 | ||
6045 | In most lsearch files, keys are not required to contain colons or # | |
6046 | characters, or white space. However, if you need this feature, it is | |
6047 | available. If a key begins with a doublequote character, it is terminated | |
6048 | only by a matching quote (or end of line), and the normal escaping rules | |
6049 | apply to its contents (see section 6.16). An optional colon is permitted | |
6050 | after quoted keys (exactly as for unquoted keys). There is no special | |
6051 | handling of quotes for the data part of an lsearch line. | |
6052 | ||
6053 | * nis: The given file is the name of a NIS map, and a NIS lookup is done with | |
6054 | the given key, without a terminating binary zero. There is a variant called | |
6055 | nis0 which does include the terminating binary zero in the key. This is | |
6056 | reportedly needed for Sun-style alias files. Exim does not recognize NIS | |
6057 | aliases; the full map names must be used. | |
6058 | ||
6059 | * wildlsearch or nwildlsearch: These search a file linearly, like lsearch, | |
6060 | but instead of being interpreted as a literal string, each key in the file | |
6061 | may be wildcarded. The difference between these two lookup types is that | |
6062 | for wildlsearch, each key in the file is string-expanded before being used, | |
6063 | whereas for nwildlsearch, no expansion takes place. | |
6064 | ||
6065 | Like lsearch, the testing is done case-insensitively. However, keys in the | |
6066 | file that are regular expressions can be made case-sensitive by the use of | |
6067 | "(-i)" within the pattern. The following forms of wildcard are recognized: | |
6068 | ||
6069 | 1. The string may begin with an asterisk to mean "ends with". For example: | |
6070 | ||
6071 | *.a.b.c data for anything.a.b.c | |
6072 | *fish data for anythingfish | |
6073 | ||
6074 | 2. The string may begin with a circumflex to indicate a regular | |
6075 | expression. For example, for wildlsearch: | |
6076 | ||
6077 | ^\N\d+\.a\.b\N data for <digits>.a.b | |
6078 | ||
6079 | Note the use of "\N" to disable expansion of the contents of the | |
6080 | regular expression. If you are using nwildlsearch, where the keys are | |
6081 | not string-expanded, the equivalent entry is: | |
6082 | ||
6083 | ^\d+\.a\.b data for <digits>.a.b | |
6084 | ||
6085 | The case-insensitive flag is set at the start of compiling the regular | |
6086 | expression, but it can be turned off by using "(-i)" at an appropriate | |
6087 | point. For example, to make the entire pattern case-sensitive: | |
6088 | ||
6089 | ^(?-i)\d+\.a\.b data for <digits>.a.b | |
6090 | ||
6091 | If the regular expression contains white space or colon characters, you | |
6092 | must either quote it (see lsearch above), or represent these characters | |
6093 | in other ways. For example, "\s" can be used for white space and "\x3A" | |
6094 | for a colon. This may be easier than quoting, because if you quote, you | |
6095 | have to escape all the backslashes inside the quotes. | |
6096 | ||
6097 | Note: It is not possible to capture substrings in a regular expression | |
6098 | match for later use, because the results of all lookups are cached. If | |
6099 | a lookup is repeated, the result is taken from the cache, and no actual | |
6100 | pattern matching takes place. The values of all the numeric variables | |
6101 | are unset after a (n)wildlsearch match. | |
6102 | ||
6103 | 3. Although I cannot see it being of much use, the general matching | |
6104 | function that is used to implement (n)wildlsearch means that the string | |
6105 | may begin with a lookup name terminated by a semicolon, and followed by | |
6106 | lookup data. For example: | |
6107 | ||
6108 | cdb;/some/file data for keys that match the file | |
6109 | ||
6110 | The data that is obtained from the nested lookup is discarded. | |
6111 | ||
6112 | Keys that do not match any of these patterns are interpreted literally. The | |
6113 | continuation rules for the data are the same as for lsearch, and keys may | |
6114 | be followed by optional colons. | |
6115 | ||
6116 | Warning: Unlike most other single-key lookup types, a file of data for (n) | |
6117 | wildlsearch can not be turned into a DBM or cdb file, because those lookup | |
6118 | types support only literal keys. | |
6119 | ||
6120 | ||
6121 | 9.4 Query-style lookup types | |
6122 | ---------------------------- | |
6123 | ||
6124 | The supported query-style lookup types are listed below. Further details about | |
6125 | many of them are given in later sections. | |
6126 | ||
6127 | * dnsdb: This does a DNS search for one or more records whose domain names | |
6128 | are given in the supplied query. The resulting data is the contents of the | |
6129 | records. See section 9.10. | |
6130 | ||
6131 | * ibase: This does a lookup in an InterBase database. | |
6132 | ||
6133 | * ldap: This does an LDAP lookup using a query in the form of a URL, and | |
6134 | returns attributes from a single entry. There is a variant called ldapm | |
6135 | that permits values from multiple entries to be returned. A third variant | |
6136 | called ldapdn returns the Distinguished Name of a single entry instead of | |
6137 | any attribute values. See section 9.13. | |
6138 | ||
6139 | * mysql: The format of the query is an SQL statement that is passed to a | |
6140 | MySQL database. See section 9.20. | |
6141 | ||
6142 | * nisplus: This does a NIS+ lookup using a query that can specify the name of | |
6143 | the field to be returned. See section 9.19. | |
6144 | ||
6145 | * oracle: The format of the query is an SQL statement that is passed to an | |
6146 | Oracle database. See section 9.20. | |
6147 | ||
6148 | * passwd is a query-style lookup with queries that are just user names. The | |
6149 | lookup calls getpwnam() to interrogate the system password data, and on | |
6150 | success, the result string is the same as you would get from an lsearch | |
6151 | lookup on a traditional /etc/passwd file, though with "*" for the password | |
6152 | value. For example: | |
6153 | ||
6154 | *:42:42:King Rat:/home/kr:/bin/bash | |
6155 | ||
6156 | * pgsql: The format of the query is an SQL statement that is passed to a | |
6157 | PostgreSQL database. See section 9.20. | |
6158 | ||
6159 | * sqlite: The format of the query is a file name followed by an SQL statement | |
6160 | that is passed to an SQLite database. See section 9.25. | |
6161 | ||
6162 | * testdb: This is a lookup type that is used for testing Exim. It is not | |
6163 | likely to be useful in normal operation. | |
6164 | ||
6165 | * whoson: Whoson (http://whoson.sourceforge.net) is a protocol that allows a | |
6166 | server to check whether a particular (dynamically allocated) IP address is | |
6167 | currently allocated to a known (trusted) user and, optionally, to obtain | |
6168 | the identity of the said user. For SMTP servers, Whoson was popular at one | |
6169 | time for "POP before SMTP" authentication, but that approach has been | |
6170 | superseded by SMTP authentication. In Exim, Whoson can be used to implement | |
6171 | "POP before SMTP" checking using ACL statements such as | |
6172 | ||
6173 | require condition = \ | |
6174 | ${lookup whoson {$sender_host_address}{yes}{no}} | |
6175 | ||
6176 | The query consists of a single IP address. The value returned is the name | |
6177 | of the authenticated user, which is stored in the variable $value. However, | |
6178 | in this example, the data in $value is not used; the result of the lookup | |
6179 | is one of the fixed strings "yes" or "no". | |
6180 | ||
6181 | ||
6182 | 9.5 Temporary errors in lookups | |
6183 | ------------------------------- | |
6184 | ||
6185 | Lookup functions can return temporary error codes if the lookup cannot be | |
6186 | completed. For example, an SQL or LDAP database might be unavailable. For this | |
6187 | reason, it is not advisable to use a lookup that might do this for critical | |
6188 | options such as a list of local domains. | |
6189 | ||
6190 | When a lookup cannot be completed in a router or transport, delivery of the | |
6191 | message (to the relevant address) is deferred, as for any other temporary | |
6192 | error. In other circumstances Exim may assume the lookup has failed, or may | |
6193 | give up altogether. | |
6194 | ||
6195 | ||
6196 | 9.6 Default values in single-key lookups | |
6197 | ---------------------------------------- | |
6198 | ||
6199 | In this context, a "default value" is a value specified by the administrator | |
6200 | that is to be used if a lookup fails. | |
6201 | ||
6202 | Note: This section applies only to single-key lookups. For query-style lookups, | |
6203 | the facilities of the query language must be used. An attempt to specify a | |
6204 | default for a query-style lookup provokes an error. | |
6205 | ||
6206 | If "*" is added to a single-key lookup type (for example, lsearch*) and the | |
6207 | initial lookup fails, the key "*" is looked up in the file to provide a default | |
6208 | value. See also the section on partial matching below. | |
6209 | ||
6210 | Alternatively, if "*@" is added to a single-key lookup type (for example dbm*@) | |
6211 | then, if the initial lookup fails and the key contains an @ character, a second | |
6212 | lookup is done with everything before the last @ replaced by *. This makes it | |
6213 | possible to provide per-domain defaults in alias files that include the domains | |
6214 | in the keys. If the second lookup fails (or doesn't take place because there is | |
6215 | no @ in the key), "*" is looked up. For example, a redirect router might | |
6216 | contain: | |
6217 | ||
6218 | data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}} | |
6219 | ||
6220 | Suppose the address that is being processed is jane@eyre.example. Exim looks up | |
6221 | these keys, in this order: | |
6222 | ||
6223 | jane@eyre.example | |
6224 | *@eyre.example | |
6225 | * | |
6226 | ||
6227 | The data is taken from whichever key it finds first. Note: In an lsearch file, | |
6228 | this does not mean the first of these keys in the file. A complete scan is done | |
6229 | for each key, and only if it is not found at all does Exim move on to try the | |
6230 | next key. | |
6231 | ||
6232 | ||
6233 | 9.7 Partial matching in single-key lookups | |
6234 | ------------------------------------------ | |
6235 | ||
6236 | The normal operation of a single-key lookup is to search the file for an exact | |
6237 | match with the given key. However, in a number of situations where domains are | |
6238 | being looked up, it is useful to be able to do partial matching. In this case, | |
6239 | information in the file that has a key starting with "*." is matched by any | |
6240 | domain that ends with the components that follow the full stop. For example, if | |
6241 | a key in a DBM file is | |
6242 | ||
6243 | *.dates.fict.example | |
6244 | ||
6245 | then when partial matching is enabled this is matched by (amongst others) | |
6246 | 2001.dates.fict.example and 1984.dates.fict.example. It is also matched by | |
6247 | dates.fict.example, if that does not appear as a separate key in the file. | |
6248 | ||
6249 | Note: Partial matching is not available for query-style lookups. It is also not | |
6250 | available for any lookup items in address lists (see section 10.19). | |
6251 | ||
6252 | Partial matching is implemented by doing a series of separate lookups using | |
6253 | keys constructed by modifying the original subject key. This means that it can | |
6254 | be used with any of the single-key lookup types, provided that partial matching | |
6255 | keys beginning with a special prefix (default "*.") are included in the data | |
6256 | file. Keys in the file that do not begin with the prefix are matched only by | |
6257 | unmodified subject keys when partial matching is in use. | |
6258 | ||
6259 | Partial matching is requested by adding the string "partial-" to the front of | |
6260 | the name of a single-key lookup type, for example, partial-dbm. When this is | |
6261 | done, the subject key is first looked up unmodified; if that fails, "*." is | |
6262 | added at the start of the subject key, and it is looked up again. If that | |
6263 | fails, further lookups are tried with dot-separated components removed from the | |
6264 | start of the subject key, one-by-one, and "*." added on the front of what | |
6265 | remains. | |
6266 | ||
6267 | A minimum number of two non-* components are required. This can be adjusted by | |
6268 | including a number before the hyphen in the search type. For example, | |
6269 | partial3-lsearch specifies a minimum of three non-* components in the modified | |
6270 | keys. Omitting the number is equivalent to "partial2-". If the subject key is | |
6271 | 2250.dates.fict.example then the following keys are looked up when the minimum | |
6272 | number of non-* components is two: | |
6273 | ||
6274 | 2250.dates.fict.example | |
6275 | *.2250.dates.fict.example | |
6276 | *.dates.fict.example | |
6277 | *.fict.example | |
6278 | ||
6279 | As soon as one key in the sequence is successfully looked up, the lookup | |
6280 | finishes. | |
6281 | ||
6282 | The use of "*." as the partial matching prefix is a default that can be | |
6283 | changed. The motivation for this feature is to allow Exim to operate with file | |
6284 | formats that are used by other MTAs. A different prefix can be supplied in | |
6285 | parentheses instead of the hyphen after "partial". For example: | |
6286 | ||
6287 | domains = partial(.)lsearch;/some/file | |
6288 | ||
6289 | In this example, if the domain is a.b.c, the sequence of lookups is "a.b.c", | |
6290 | ".a.b.c", and ".b.c" (the default minimum of 2 non-wild components is | |
6291 | unchanged). The prefix may consist of any punctuation characters other than a | |
6292 | closing parenthesis. It may be empty, for example: | |
6293 | ||
6294 | domains = partial1()cdb;/some/file | |
6295 | ||
6296 | For this example, if the domain is a.b.c, the sequence of lookups is "a.b.c", | |
6297 | "b.c", and "c". | |
6298 | ||
6299 | If "partial0" is specified, what happens at the end (when the lookup with just | |
6300 | one non-wild component has failed, and the original key is shortened right down | |
6301 | to the null string) depends on the prefix: | |
6302 | ||
6303 | * If the prefix has zero length, the whole lookup fails. | |
6304 | ||
6305 | * If the prefix has length 1, a lookup for just the prefix is done. For | |
6306 | example, the final lookup for "partial0(.)" is for "." alone. | |
6307 | ||
6308 | * Otherwise, if the prefix ends in a dot, the dot is removed, and the | |
6309 | remainder is looked up. With the default prefix, therefore, the final | |
6310 | lookup is for "*" on its own. | |
6311 | ||
6312 | * Otherwise, the whole prefix is looked up. | |
6313 | ||
6314 | If the search type ends in "*" or "*@" (see section 9.6 above), the search for | |
6315 | an ultimate default that this implies happens after all partial lookups have | |
6316 | failed. If "partial0" is specified, adding "*" to the search type has no effect | |
6317 | with the default prefix, because the "*" key is already included in the | |
6318 | sequence of partial lookups. However, there might be a use for lookup types | |
6319 | such as "partial0(.)lsearch*". | |
6320 | ||
6321 | The use of "*" in lookup partial matching differs from its use as a wildcard in | |
6322 | domain lists and the like. Partial matching works only in terms of | |
6323 | dot-separated components; a key such as "*fict.example" in a database file is | |
6324 | useless, because the asterisk in a partial matching subject key is always | |
6325 | followed by a dot. | |
6326 | ||
6327 | ||
6328 | 9.8 Lookup caching | |
6329 | ------------------ | |
6330 | ||
6331 | Exim caches all lookup results in order to avoid needless repetition of | |
6332 | lookups. However, because (apart from the daemon) Exim operates as a collection | |
6333 | of independent, short-lived processes, this caching applies only within a | |
6334 | single Exim process. There is no inter-process lookup caching facility. | |
6335 | ||
6336 | For single-key lookups, Exim keeps the relevant files open in case there is | |
6337 | another lookup that needs them. In some types of configuration this can lead to | |
6338 | many files being kept open for messages with many recipients. To avoid hitting | |
6339 | the operating system limit on the number of simultaneously open files, Exim | |
6340 | closes the least recently used file when it needs to open more files than its | |
6341 | own internal limit, which can be changed via the lookup_open_max option. | |
6342 | ||
6343 | The single-key lookup files are closed and the lookup caches are flushed at | |
6344 | strategic points during delivery - for example, after all routing is complete. | |
6345 | ||
6346 | ||
6347 | 9.9 Quoting lookup data | |
6348 | ----------------------- | |
6349 | ||
6350 | When data from an incoming message is included in a query-style lookup, there | |
6351 | is the possibility of special characters in the data messing up the syntax of | |
6352 | the query. For example, a NIS+ query that contains | |
6353 | ||
6354 | [name=$local_part] | |
6355 | ||
6356 | will be broken if the local part happens to contain a closing square bracket. | |
6357 | For NIS+, data can be enclosed in double quotes like this: | |
6358 | ||
6359 | [name="$local_part"] | |
6360 | ||
6361 | but this still leaves the problem of a double quote in the data. The rule for | |
6362 | NIS+ is that double quotes must be doubled. Other lookup types have different | |
6363 | rules, and to cope with the differing requirements, an expansion operator of | |
6364 | the following form is provided: | |
6365 | ||
6366 | ${quote_<lookup-type>:<string>} | |
6367 | ||
6368 | For example, the safest way to write the NIS+ query is | |
6369 | ||
6370 | [name="${quote_nisplus:$local_part}"] | |
6371 | ||
6372 | See chapter 11 for full coverage of string expansions. The quote operator can | |
6373 | be used for all lookup types, but has no effect for single-key lookups, since | |
6374 | no quoting is ever needed in their key strings. | |
6375 | ||
6376 | ||
6377 | 9.10 More about dnsdb | |
6378 | --------------------- | |
6379 | ||
6380 | The dnsdb lookup type uses the DNS as its database. A simple query consists of | |
6381 | a record type and a domain name, separated by an equals sign. For example, an | |
6382 | expansion string could contain: | |
6383 | ||
6384 | ${lookup dnsdb{mx=a.b.example}{$value}fail} | |
6385 | ||
6386 | If the lookup succeeds, the result is placed in $value, which in this case is | |
6387 | used on its own as the result. If the lookup does not succeed, the "fail" | |
6388 | keyword causes a forced expansion failure - see section 11.4 for an explanation | |
6389 | of what this means. | |
6390 | ||
6391 | The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, TLSA and | |
6392 | TXT, and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also | |
6393 | configured). If no type is given, TXT is assumed. When the type is PTR, the | |
6394 | data can be an IP address, written as normal; inversion and the addition of | |
6395 | in-addr.arpa or ip6.arpa happens automatically. For example: | |
6396 | ||
6397 | ${lookup dnsdb{ptr=192.168.4.5}{$value}fail} | |
6398 | ||
6399 | If the data for a PTR record is not a syntactically valid IP address, it is not | |
6400 | altered and nothing is added. | |
6401 | ||
6402 | For an MX lookup, both the preference value and the host name are returned for | |
6403 | each record, separated by a space. For an SRV lookup, the priority, weight, | |
6404 | port, and host name are returned for each record, separated by spaces. | |
6405 | ||
6406 | For any record type, if multiple records are found (or, for A6 lookups, if a | |
6407 | single record leads to multiple addresses), the data is returned as a | |
6408 | concatenation, with newline as the default separator. The order, of course, | |
6409 | depends on the DNS resolver. You can specify a different separator character | |
6410 | between multiple records by putting a right angle-bracket followed immediately | |
6411 | by the new separator at the start of the query. For example: | |
6412 | ||
6413 | ${lookup dnsdb{>: a=host1.example}} | |
6414 | ||
6415 | It is permitted to specify a space as the separator character. Further white | |
6416 | space is ignored. | |
6417 | ||
6418 | For TXT records with multiple items of data, only the first item is returned, | |
6419 | unless a separator for them is specified using a comma after the separator | |
6420 | character followed immediately by the TXT record item separator. To concatenate | |
6421 | items without a separator, use a semicolon instead. For SPF records the default | |
6422 | behaviour is to concatenate multiple items without using a separator. | |
6423 | ||
6424 | ${lookup dnsdb{>\n,: txt=a.b.example}} | |
6425 | ${lookup dnsdb{>\n; txt=a.b.example}} | |
6426 | ${lookup dnsdb{spf=example.org}} | |
6427 | ||
6428 | It is permitted to specify a space as the separator character. Further white | |
6429 | space is ignored. | |
6430 | ||
6431 | ||
6432 | 9.11 Pseudo dnsdb record types | |
6433 | ------------------------------ | |
6434 | ||
6435 | By default, both the preference value and the host name are returned for each | |
6436 | MX record, separated by a space. If you want only host names, you can use the | |
6437 | pseudo-type MXH: | |
6438 | ||
6439 | ${lookup dnsdb{mxh=a.b.example}} | |
6440 | ||
6441 | In this case, the preference values are omitted, and just the host names are | |
6442 | returned. | |
6443 | ||
6444 | Another pseudo-type is ZNS (for "zone NS"). It performs a lookup for NS records | |
6445 | on the given domain, but if none are found, it removes the first component of | |
6446 | the domain name, and tries again. This process continues until NS records are | |
6447 | found or there are no more components left (or there is a DNS error). In other | |
6448 | words, it may return the name servers for a top-level domain, but it never | |
6449 | returns the root name servers. If there are no NS records for the top-level | |
6450 | domain, the lookup fails. Consider these examples: | |
6451 | ||
6452 | ${lookup dnsdb{zns=xxx.quercite.com}} | |
6453 | ${lookup dnsdb{zns=xxx.edu}} | |
6454 | ||
6455 | Assuming that in each case there are no NS records for the full domain name, | |
6456 | the first returns the name servers for quercite.com, and the second returns the | |
6457 | name servers for edu. | |
6458 | ||
6459 | You should be careful about how you use this lookup because, unless the | |
6460 | top-level domain does not exist, the lookup always returns some host names. The | |
6461 | sort of use to which this might be put is for seeing if the name servers for a | |
6462 | given domain are on a blacklist. You can probably assume that the name servers | |
6463 | for the high-level domains such as com or co.uk are not going to be on such a | |
6464 | list. | |
6465 | ||
6466 | A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV | |
6467 | records according to the CSA rules, which are described in section 42.50. | |
6468 | Although dnsdb supports SRV lookups directly, this is not sufficient because of | |
6469 | the extra parent domain search behaviour of CSA. The result of a successful | |
6470 | lookup such as: | |
6471 | ||
6472 | ${lookup dnsdb {csa=$sender_helo_name}} | |
6473 | ||
6474 | has two space-separated fields: an authorization code and a target host name. | |
6475 | The authorization code can be "Y" for yes, "N" for no, "X" for explicit | |
6476 | authorization required but absent, or "?" for unknown. | |
6477 | ||
6478 | The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA | |
6479 | and then an A lookup. All results are returned; defer processing (see below) is | |
6480 | handled separately for each lookup. Example: | |
6481 | ||
6482 | ${lookup dnsdb {>; a+=$sender_helo_name}} | |
6483 | ||
6484 | ||
6485 | 9.12 Multiple dnsdb lookups | |
6486 | --------------------------- | |
6487 | ||
6488 | In the previous sections, dnsdb lookups for a single domain are described. | |
6489 | However, you can specify a list of domains or IP addresses in a single dnsdb | |
6490 | lookup. The list is specified in the normal Exim way, with colon as the default | |
6491 | separator, but with the ability to change this. For example: | |
6492 | ||
6493 | ${lookup dnsdb{one.domain.com:two.domain.com}} | |
6494 | ${lookup dnsdb{a=one.host.com:two.host.com}} | |
6495 | ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}} | |
6496 | ||
6497 | In order to retain backwards compatibility, there is one special case: if the | |
6498 | lookup type is PTR and no change of separator is specified, Exim looks to see | |
6499 | if the rest of the string is precisely one IPv6 address. In this case, it does | |
6500 | not treat it as a list. | |
6501 | ||
6502 | The data from each lookup is concatenated, with newline separators by default, | |
6503 | in the same way that multiple DNS records for a single item are handled. A | |
6504 | different separator can be specified, as described above. | |
6505 | ||
6506 | Modifiers for dnsdb lookups are givien by optional keywords, each followed by a | |
6507 | comma, that may appear before the record type. | |
6508 | ||
6509 | The dnsdb lookup fails only if all the DNS lookups fail. If there is a | |
6510 | temporary DNS error for any of them, the behaviour is controlled by a | |
6511 | defer-option modifier. The possible keywords are "defer_strict", "defer_never", | |
6512 | and "defer_lax". With "strict" behaviour, any temporary DNS error causes the | |
6513 | whole lookup to defer. With "never" behaviour, a temporary DNS error is | |
6514 | ignored, and the behaviour is as if the DNS lookup failed to find anything. | |
6515 | With "lax" behaviour, all the queries are attempted, but a temporary DNS error | |
6516 | causes the whole lookup to defer only if none of the other lookups succeed. The | |
6517 | default is "lax", so the following lookups are equivalent: | |
6518 | ||
6519 | ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}} | |
6520 | ${lookup dnsdb{a=one.host.com:two.host.com}} | |
6521 | ||
6522 | Thus, in the default case, as long as at least one of the DNS lookups yields | |
6523 | some data, the lookup succeeds. | |
6524 | ||
6525 | Use of DNSSEC is controlled by a dnssec modifier. The possible keywords are | |
6526 | "dnssec_strict", "dnssec_lax", and "dnssec_never". With "strict" or "lax" | |
6527 | DNSSEC information is requested with the lookup. With "strict" a response from | |
6528 | the DNS resolver that is not labelled as authenticated data is treated as | |
6529 | equivalent to a temporary DNS error. The default is "never". | |
6530 | ||
6531 | See also the $lookup_dnssec_authenticated variable. | |
6532 | ||
6533 | ||
6534 | 9.13 More about LDAP | |
6535 | -------------------- | |
6536 | ||
6537 | The original LDAP implementation came from the University of Michigan; this has | |
6538 | become "Open LDAP", and there are now two different releases. Another | |
6539 | implementation comes from Netscape, and Solaris 7 and subsequent releases | |
6540 | contain inbuilt LDAP support. Unfortunately, though these are all compatible at | |
6541 | the lookup function level, their error handling is different. For this reason | |
6542 | it is necessary to set a compile-time variable when building Exim with LDAP, to | |
6543 | indicate which LDAP library is in use. One of the following should appear in | |
6544 | your Local/Makefile: | |
6545 | ||
6546 | LDAP_LIB_TYPE=UMICHIGAN | |
6547 | LDAP_LIB_TYPE=OPENLDAP1 | |
6548 | LDAP_LIB_TYPE=OPENLDAP2 | |
6549 | LDAP_LIB_TYPE=NETSCAPE | |
6550 | LDAP_LIB_TYPE=SOLARIS | |
6551 | ||
6552 | If LDAP_LIB_TYPE is not set, Exim assumes "OPENLDAP1", which has the same | |
6553 | interface as the University of Michigan version. | |
6554 | ||
6555 | There are three LDAP lookup types in Exim. These behave slightly differently in | |
6556 | the way they handle the results of a query: | |
6557 | ||
6558 | * ldap requires the result to contain just one entry; if there are more, it | |
6559 | gives an error. | |
6560 | ||
6561 | * ldapdn also requires the result to contain just one entry, but it is the | |
6562 | Distinguished Name that is returned rather than any attribute values. | |
6563 | ||
6564 | * ldapm permits the result to contain more than one entry; the attributes | |
6565 | from all of them are returned. | |
6566 | ||
6567 | For ldap and ldapm, if a query finds only entries with no attributes, Exim | |
6568 | behaves as if the entry did not exist, and the lookup fails. The format of the | |
6569 | data returned by a successful lookup is described in the next section. First we | |
6570 | explain how LDAP queries are coded. | |
6571 | ||
6572 | ||
6573 | 9.14 Format of LDAP queries | |
6574 | --------------------------- | |
6575 | ||
6576 | An LDAP query takes the form of a URL as defined in RFC 2255. For example, in | |
6577 | the configuration of a redirect router one might have this setting: | |
6578 | ||
6579 | data = ${lookup ldap \ | |
6580 | {ldap:///cn=$local_part,o=University%20of%20Cambridge,\ | |
6581 | c=UK?mailbox?base?}} | |
6582 | ||
6583 | The URL may begin with "ldap" or "ldaps" if your LDAP library supports secure | |
6584 | (encrypted) LDAP connections. The second of these ensures that an encrypted TLS | |
6585 | connection is used. | |
6586 | ||
6587 | With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular | |
6588 | LDAP connections, rather than the SSL-on-connect "ldaps". See the | |
6589 | ldap_start_tls option. | |
6590 | ||
6591 | Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly | |
6592 | controlled. Every part of the TLS configuration can be configured by settings | |
6593 | in exim.conf. Depending on the version of the client libraries installed on | |
6594 | your system, some of the initialization may have required setting options in / | |
6595 | etc/ldap.conf or ~/.ldaprc to get TLS working with self-signed certificates. | |
6596 | This revealed a nuance where the current UID that exim was running as could | |
6597 | affect which config files it read. With Exim 4.83, these methods become | |
6598 | optional, only taking effect if not specifically set in exim.conf. | |
6599 | ||
6600 | ||
6601 | 9.15 LDAP quoting | |
6602 | ----------------- | |
6603 | ||
6604 | Two levels of quoting are required in LDAP queries, the first for LDAP itself | |
6605 | and the second because the LDAP query is represented as a URL. Furthermore, | |
6606 | within an LDAP query, two different kinds of quoting are required. For this | |
6607 | reason, there are two different LDAP-specific quoting operators. | |
6608 | ||
6609 | The quote_ldap operator is designed for use on strings that are part of filter | |
6610 | specifications. Conceptually, it first does the following conversions on the | |
6611 | string: | |
6612 | ||
6613 | * => \2A | |
6614 | ( => \28 | |
6615 | ) => \29 | |
6616 | \ => \5C | |
6617 | ||
6618 | in accordance with RFC 2254. The resulting string is then quoted according to | |
6619 | the rules for URLs, that is, all non-alphanumeric characters except | |
6620 | ||
6621 | ! $ ' - . _ ( ) * + | |
6622 | ||
6623 | are converted to their hex values, preceded by a percent sign. For example: | |
6624 | ||
6625 | ${quote_ldap: a(bc)*, a<yz>; } | |
6626 | ||
6627 | yields | |
6628 | ||
6629 | %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20 | |
6630 | ||
6631 | Removing the URL quoting, this is (with a leading and a trailing space): | |
6632 | ||
6633 | a\28bc\29\2A, a<yz>; | |
6634 | ||
6635 | The quote_ldap_dn operator is designed for use on strings that are part of base | |
6636 | DN specifications in queries. Conceptually, it first converts the string by | |
6637 | inserting a backslash in front of any of the following characters: | |
6638 | ||
6639 | , + " \ < > ; | |
6640 | ||
6641 | It also inserts a backslash before any leading spaces or # characters, and | |
6642 | before any trailing spaces. (These rules are in RFC 2253.) The resulting string | |
6643 | is then quoted according to the rules for URLs. For example: | |
6644 | ||
6645 | ${quote_ldap_dn: a(bc)*, a<yz>; } | |
6646 | ||
6647 | yields | |
6648 | ||
6649 | %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20 | |
6650 | ||
6651 | Removing the URL quoting, this is (with a trailing space): | |
6652 | ||
6653 | \ a(bc)*\, a\<yz\>\;\ | |
6654 | ||
6655 | There are some further comments about quoting in the section on LDAP | |
6656 | authentication below. | |
6657 | ||
6658 | ||
6659 | 9.16 LDAP connections | |
6660 | --------------------- | |
6661 | ||
6662 | The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP | |
6663 | is in use, via a Unix domain socket. The example given above does not specify | |
6664 | an LDAP server. A server that is reached by TCP/IP can be specified in a query | |
6665 | by starting it with | |
6666 | ||
6667 | ldap://<hostname>:<port>/... | |
6668 | ||
6669 | If the port (and preceding colon) are omitted, the standard LDAP port (389) is | |
6670 | used. When no server is specified in a query, a list of default servers is | |
6671 | taken from the ldap_default_servers configuration option. This supplies a | |
6672 | colon-separated list of servers which are tried in turn until one successfully | |
6673 | handles a query, or there is a serious error. Successful handling either | |
6674 | returns the requested data, or indicates that it does not exist. Serious errors | |
6675 | are syntactical, or multiple values when only a single value is expected. | |
6676 | Errors which cause the next server to be tried are connection failures, bind | |
6677 | failures, and timeouts. | |
6678 | ||
6679 | For each server name in the list, a port number can be given. The standard way | |
6680 | of specifying a host and port is to use a colon separator (RFC 1738). Because | |
6681 | ldap_default_servers is a colon-separated list, such colons have to be doubled. | |
6682 | For example | |
6683 | ||
6684 | ldap_default_servers = ldap1.example.com::145:ldap2.example.com | |
6685 | ||
6686 | If ldap_default_servers is unset, a URL with no server name is passed to the | |
6687 | LDAP library with no server name, and the library's default (normally the local | |
6688 | host) is used. | |
6689 | ||
6690 | If you are using the OpenLDAP library, you can connect to an LDAP server using | |
6691 | a Unix domain socket instead of a TCP/IP connection. This is specified by using | |
6692 | "ldapi" instead of "ldap" in LDAP queries. What follows here applies only to | |
6693 | OpenLDAP. If Exim is compiled with a different LDAP library, this feature is | |
6694 | not available. | |
6695 | ||
6696 | For this type of connection, instead of a host name for the server, a pathname | |
6697 | for the socket is required, and the port number is not relevant. The pathname | |
6698 | can be specified either as an item in ldap_default_servers, or inline in the | |
6699 | query. In the former case, you can have settings such as | |
6700 | ||
6701 | ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain | |
6702 | ||
6703 | When the pathname is given in the query, you have to escape the slashes as | |
6704 | "%2F" to fit in with the LDAP URL syntax. For example: | |
6705 | ||
6706 | ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=... | |
6707 | ||
6708 | When Exim processes an LDAP lookup and finds that the "hostname" is really a | |
6709 | pathname, it uses the Unix domain socket code, even if the query actually | |
6710 | specifies "ldap" or "ldaps". In particular, no encryption is used for a socket | |
6711 | connection. This behaviour means that you can use a setting of | |
6712 | ldap_default_servers such as in the example above with traditional "ldap" or | |
6713 | "ldaps" queries, and it will work. First, Exim tries a connection via the Unix | |
6714 | domain socket; if that fails, it tries a TCP/IP connection to the backup host. | |
6715 | ||
6716 | If an explicit "ldapi" type is given in a query when a host name is specified, | |
6717 | an error is diagnosed. However, if there are more items in ldap_default_servers | |
6718 | , they are tried. In other words: | |
6719 | ||
6720 | * Using a pathname with "ldap" or "ldaps" forces the use of the Unix domain | |
6721 | interface. | |
6722 | ||
6723 | * Using "ldapi" with a host name causes an error. | |
6724 | ||
6725 | Using "ldapi" with no host or path in the query, and no setting of | |
6726 | ldap_default_servers, does whatever the library does by default. | |
6727 | ||
6728 | ||
6729 | 9.17 LDAP authentication and control information | |
6730 | ------------------------------------------------ | |
6731 | ||
6732 | The LDAP URL syntax provides no way of passing authentication and other control | |
6733 | information to the server. To make this possible, the URL in an LDAP query may | |
6734 | be preceded by any number of <name>=<value> settings, separated by spaces. If a | |
6735 | value contains spaces it must be enclosed in double quotes, and when double | |
6736 | quotes are used, backslash is interpreted in the usual way inside them. The | |
6737 | following names are recognized: | |
6738 | ||
6739 | DEREFERENCE set the dereferencing parameter | |
6740 | NETTIME set a timeout for a network operation | |
6741 | USER set the DN, for authenticating the LDAP bind | |
6742 | PASS set the password, likewise | |
6743 | REFERRALS set the referrals parameter | |
6744 | SERVERS set alternate server list for this query only | |
6745 | SIZE set the limit for the number of entries returned | |
6746 | TIME set the maximum waiting time for a query | |
6747 | ||
6748 | The value of the DEREFERENCE parameter must be one of the words "never", | |
6749 | "searching", "finding", or "always". The value of the REFERRALS parameter must | |
6750 | be "follow" (the default) or "nofollow". The latter stops the LDAP library from | |
6751 | trying to follow referrals issued by the LDAP server. | |
6752 | ||
6753 | The name CONNECT is an obsolete name for NETTIME, retained for backwards | |
6754 | compatibility. This timeout (specified as a number of seconds) is enforced from | |
6755 | the client end for operations that can be carried out over a network. | |
6756 | Specifically, it applies to network connections and calls to the ldap_result() | |
6757 | function. If the value is greater than zero, it is used if | |
6758 | LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or if | |
6759 | LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape SDK 4.1). A | |
6760 | value of zero forces an explicit setting of "no timeout" for Netscape SDK; for | |
6761 | OpenLDAP no action is taken. | |
6762 | ||
6763 | The TIME parameter (also a number of seconds) is passed to the server to set a | |
6764 | server-side limit on the time taken to complete a search. | |
6765 | ||
6766 | The SERVERS parameter allows you to specify an alternate list of ldap servers | |
6767 | to use for an individual lookup. The global ldap_servers option provides a | |
6768 | default list of ldap servers, and a single lookup can specify a single ldap | |
6769 | server to use. But when you need to do a lookup with a list of servers that is | |
6770 | different than the default list (maybe different order, maybe a completely | |
6771 | different set of servers), the SERVERS parameter allows you to specify this | |
6772 | alternate list. | |
6773 | ||
6774 | Here is an example of an LDAP query in an Exim lookup that uses some of these | |
6775 | values. This is a single line, folded to fit on the page: | |
6776 | ||
6777 | ${lookup ldap | |
6778 | {user="cn=manager,o=University of Cambridge,c=UK" pass=secret | |
6779 | ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)} | |
6780 | {$value}fail} | |
6781 | ||
6782 | The encoding of spaces as "%20" is a URL thing which should not be done for any | |
6783 | of the auxiliary data. Exim configuration settings that include lookups which | |
6784 | contain password information should be preceded by "hide" to prevent non-admin | |
6785 | users from using the -bP option to see their values. | |
6786 | ||
6787 | The auxiliary data items may be given in any order. The default is no | |
6788 | connection timeout (the system timeout is used), no user or password, no limit | |
6789 | on the number of entries returned, and no time limit on queries. | |
6790 | ||
6791 | When a DN is quoted in the USER= setting for LDAP authentication, Exim removes | |
6792 | any URL quoting that it may contain before passing it LDAP. Apparently some | |
6793 | libraries do this for themselves, but some do not. Removing the URL quoting has | |
6794 | two advantages: | |
6795 | ||
6796 | * It makes it possible to use the same quote_ldap_dn expansion for USER= DNs | |
6797 | as with DNs inside actual queries. | |
6798 | ||
6799 | * It permits spaces inside USER= DNs. | |
6800 | ||
6801 | For example, a setting such as | |
6802 | ||
6803 | USER=cn=${quote_ldap_dn:$1} | |
6804 | ||
6805 | should work even if $1 contains spaces. | |
6806 | ||
6807 | Expanded data for the PASS= value should be quoted using the quote expansion | |
6808 | operator, rather than the LDAP quote operators. The only reason this field | |
6809 | needs quoting is to ensure that it conforms to the Exim syntax, which does not | |
6810 | allow unquoted spaces. For example: | |
6811 | ||
6812 | PASS=${quote:$3} | |
6813 | ||
6814 | The LDAP authentication mechanism can be used to check passwords as part of | |
6815 | SMTP authentication. See the ldapauth expansion string condition in chapter 11. | |
6816 | ||
6817 | ||
6818 | 9.18 Format of data returned by LDAP | |
6819 | ------------------------------------ | |
6820 | ||
6821 | The ldapdn lookup type returns the Distinguished Name from a single entry as a | |
6822 | sequence of values, for example | |
6823 | ||
6824 | cn=manager, o=University of Cambridge, c=UK | |
6825 | ||
6826 | The ldap lookup type generates an error if more than one entry matches the | |
6827 | search filter, whereas ldapm permits this case, and inserts a newline in the | |
6828 | result between the data from different entries. It is possible for multiple | |
6829 | values to be returned for both ldap and ldapm, but in the former case you know | |
6830 | that whatever values are returned all came from a single entry in the | |
6831 | directory. | |
6832 | ||
6833 | In the common case where you specify a single attribute in your LDAP query, the | |
6834 | result is not quoted, and does not contain the attribute name. If the attribute | |
6835 | has multiple values, they are separated by commas. | |
6836 | ||
6837 | If you specify multiple attributes, the result contains space-separated, quoted | |
6838 | strings, each preceded by the attribute name and an equals sign. Within the | |
6839 | quotes, the quote character, backslash, and newline are escaped with | |
6840 | backslashes, and commas are used to separate multiple values for the attribute. | |
6841 | Apart from the escaping, the string within quotes takes the same form as the | |
6842 | output when a single attribute is requested. Specifying no attributes is the | |
6843 | same as specifying all of an entry's attributes. | |
6844 | ||
6845 | Here are some examples of the output format. The first line of each pair is an | |
6846 | LDAP query, and the second is the data that is returned. The attribute called | |
6847 | attr1 has two values, whereas attr2 has only one value: | |
6848 | ||
6849 | ldap:///o=base?attr1?sub?(uid=fred) | |
6850 | value1.1, value1.2 | |
6851 | ||
6852 | ldap:///o=base?attr2?sub?(uid=fred) | |
6853 | value two | |
6854 | ||
6855 | ldap:///o=base?attr1,attr2?sub?(uid=fred) | |
6856 | attr1="value1.1, value1.2" attr2="value two" | |
6857 | ||
6858 | ldap:///o=base??sub?(uid=fred) | |
6859 | objectClass="top" attr1="value1.1, value1.2" attr2="value two" | |
6860 | ||
6861 | The extract operator in string expansions can be used to pick out individual | |
6862 | fields from data that consists of key=value pairs. You can make use of Exim's | |
6863 | -be option to run expansion tests and thereby check the results of LDAP | |
6864 | lookups. | |
6865 | ||
6866 | ||
6867 | 9.19 More about NIS+ | |
6868 | -------------------- | |
6869 | ||
6870 | NIS+ queries consist of a NIS+ indexed name followed by an optional colon and | |
6871 | field name. If this is given, the result of a successful query is the contents | |
6872 | of the named field; otherwise the result consists of a concatenation of | |
6873 | field-name=field-value pairs, separated by spaces. Empty values and values | |
6874 | containing spaces are quoted. For example, the query | |
6875 | ||
6876 | [name=mg1456],passwd.org_dir | |
6877 | ||
6878 | might return the string | |
6879 | ||
6880 | name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre" | |
6881 | home=/home/mg1456 shell=/bin/bash shadow="" | |
6882 | ||
6883 | (split over two lines here to fit on the page), whereas | |
6884 | ||
6885 | [name=mg1456],passwd.org_dir:gcos | |
6886 | ||
6887 | would just return | |
6888 | ||
6889 | Martin Guerre | |
6890 | ||
6891 | with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry | |
6892 | for the given indexed key. The effect of the quote_nisplus expansion operator | |
6893 | is to double any quote characters within the text. | |
6894 | ||
6895 | ||
6896 | 9.20 SQL lookups | |
6897 | ---------------- | |
6898 | ||
6899 | Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite | |
6900 | databases. Queries for these databases contain SQL statements, so an example | |
6901 | might be | |
6902 | ||
6903 | ${lookup mysql{select mailbox from users where id='userx'}\ | |
6904 | {$value}fail} | |
6905 | ||
6906 | If the result of the query contains more than one field, the data for each | |
6907 | field in the row is returned, preceded by its name, so the result of | |
6908 | ||
6909 | ${lookup pgsql{select home,name from users where id='userx'}\ | |
6910 | {$value}} | |
6911 | ||
6912 | might be | |
6913 | ||
6914 | home=/home/userx name="Mister X" | |
6915 | ||
6916 | Empty values and values containing spaces are double quoted, with embedded | |
6917 | quotes escaped by a backslash. If the result of the query contains just one | |
6918 | field, the value is passed back verbatim, without a field name, for example: | |
6919 | ||
6920 | Mister X | |
6921 | ||
6922 | If the result of the query yields more than one row, it is all concatenated, | |
6923 | with a newline between the data for each row. | |
6924 | ||
6925 | ||
6926 | 9.21 More about MySQL, PostgreSQL, Oracle, and InterBase | |
6927 | -------------------------------------------------------- | |
6928 | ||
6929 | If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the | |
6930 | mysql_servers, pgsql_servers, oracle_servers, or ibase_servers option (as | |
6931 | appropriate) must be set to a colon-separated list of server information. (For | |
6932 | MySQL and PostgreSQL only, the global option need not be set if all queries | |
6933 | contain their own server information - see section 9.22.) Each item in the list | |
6934 | is a slash-separated list of four items: host name, database name, user name, | |
6935 | and password. In the case of Oracle, the host name field is used for the | |
6936 | "service name", and the database name field is not used and should be empty. | |
6937 | For example: | |
6938 | ||
6939 | hide oracle_servers = oracle.plc.example//userx/abcdwxyz | |
6940 | ||
6941 | Because password data is sensitive, you should always precede the setting with | |
6942 | "hide", to prevent non-admin users from obtaining the setting via the -bP | |
6943 | option. Here is an example where two MySQL servers are listed: | |
6944 | ||
6945 | hide mysql_servers = localhost/users/root/secret:\ | |
6946 | otherhost/users/root/othersecret | |
6947 | ||
6948 | For MySQL and PostgreSQL, a host may be specified as <name>:<port> but because | |
6949 | this is a colon-separated list, the colon has to be doubled. For each query, | |
6950 | these parameter groups are tried in order until a connection is made and a | |
6951 | query is successfully processed. The result of a query may be that no data is | |
6952 | found, but that is still a successful query. In other words, the list of | |
6953 | servers provides a backup facility, not a list of different places to look. | |
6954 | ||
6955 | The quote_mysql, quote_pgsql, and quote_oracle expansion operators convert | |
6956 | newline, tab, carriage return, and backspace to \n, \t, \r, and \b | |
6957 | respectively, and the characters single-quote, double-quote, and backslash | |
6958 | itself are escaped with backslashes. The quote_pgsql expansion operator, in | |
6959 | addition, escapes the percent and underscore characters. This cannot be done | |
6960 | for MySQL because these escapes are not recognized in contexts where these | |
6961 | characters are not special. | |
6962 | ||
6963 | ||
6964 | 9.22 Specifying the server in the query | |
6965 | --------------------------------------- | |
6966 | ||
6967 | For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase), | |
6968 | it is possible to specify a list of servers with an individual query. This is | |
6969 | done by starting the query with | |
6970 | ||
6971 | servers=server1:server2:server3:...; | |
6972 | ||
6973 | Each item in the list may take one of two forms: | |
6974 | ||
6975 | 1. If it contains no slashes it is assumed to be just a host name. The | |
6976 | appropriate global option (mysql_servers or pgsql_servers) is searched for | |
6977 | a host of the same name, and the remaining parameters (database, user, | |
6978 | password) are taken from there. | |
6979 | ||
6980 | 2. If it contains any slashes, it is taken as a complete parameter set. | |
6981 | ||
6982 | The list of servers is used in exactly the same way as the global list. Once a | |
6983 | connection to a server has happened and a query has been successfully executed, | |
6984 | processing of the lookup ceases. | |
6985 | ||
6986 | This feature is intended for use in master/slave situations where updates are | |
6987 | occurring and you want to update the master rather than a slave. If the master | |
6988 | is in the list as a backup for reading, you might have a global setting like | |
6989 | this: | |
6990 | ||
6991 | mysql_servers = slave1/db/name/pw:\ | |
6992 | slave2/db/name/pw:\ | |
6993 | master/db/name/pw | |
6994 | ||
6995 | In an updating lookup, you could then write: | |
6996 | ||
6997 | ${lookup mysql{servers=master; UPDATE ...} } | |
6998 | ||
6999 | That query would then be sent only to the master server. If, on the other hand, | |
7000 | the master is not to be used for reading, and so is not present in the global | |
7001 | option, you can still update it by a query of this form: | |
7002 | ||
7003 | ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} } | |
7004 | ||
7005 | ||
7006 | 9.23 Special MySQL features | |
7007 | --------------------------- | |
7008 | ||
7009 | For MySQL, an empty host name or the use of "localhost" in mysql_servers causes | |
7010 | a connection to the server on the local host by means of a Unix domain socket. | |
7011 | An alternate socket can be specified in parentheses. The full syntax of each | |
7012 | item in mysql_servers is: | |
7013 | ||
7014 | <hostname>::<port>(<socket name>)/<database>/<user>/<password> | |
7015 | ||
7016 | Any of the three sub-parts of the first field can be omitted. For normal use on | |
7017 | the local host it can be left blank or set to just "localhost". | |
7018 | ||
7019 | No database need be supplied - but if it is absent here, it must be given in | |
7020 | the queries. | |
7021 | ||
7022 | If a MySQL query is issued that does not request any data (an insert, update, | |
7023 | or delete command), the result of the lookup is the number of rows affected. | |
7024 | ||
7025 | Warning: This can be misleading. If an update does not actually change anything | |
7026 | (for example, setting a field to the value it already has), the result is zero | |
7027 | because no rows are affected. | |
7028 | ||
7029 | ||
7030 | 9.24 Special PostgreSQL features | |
7031 | -------------------------------- | |
7032 | ||
7033 | PostgreSQL lookups can also use Unix domain socket connections to the database. | |
7034 | This is usually faster and costs less CPU time than a TCP/IP connection. | |
7035 | However it can be used only if the mail server runs on the same machine as the | |
7036 | database server. A configuration line for PostgreSQL via Unix domain sockets | |
7037 | looks like this: | |
7038 | ||
7039 | hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ... | |
7040 | ||
7041 | In other words, instead of supplying a host name, a path to the socket is | |
7042 | given. The path name is enclosed in parentheses so that its slashes aren't | |
7043 | visually confused with the delimiters for the other server parameters. | |
7044 | ||
7045 | If a PostgreSQL query is issued that does not request any data (an insert, | |
7046 | update, or delete command), the result of the lookup is the number of rows | |
7047 | affected. | |
7048 | ||
7049 | ||
7050 | 9.25 More about SQLite | |
7051 | ---------------------- | |
7052 | ||
7053 | SQLite is different to the other SQL lookups because a file name is required in | |
7054 | addition to the SQL query. An SQLite database is a single file, and there is no | |
7055 | daemon as in the other SQL databases. The interface to Exim requires the name | |
7056 | of the file, as an absolute path, to be given at the start of the query. It is | |
7057 | separated from the query by white space. This means that the path name cannot | |
7058 | contain white space. Here is a lookup expansion example: | |
7059 | ||
7060 | ${lookup sqlite {/some/thing/sqlitedb \ | |
7061 | select name from aliases where id='userx';}} | |
7062 | ||
7063 | In a list, the syntax is similar. For example: | |
7064 | ||
7065 | domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \ | |
7066 | select * from relays where ip='$sender_host_address'; | |
7067 | ||
7068 | The only character affected by the quote_sqlite operator is a single quote, | |
7069 | which it doubles. | |
7070 | ||
7071 | The SQLite library handles multiple simultaneous accesses to the database | |
7072 | internally. Multiple readers are permitted, but only one process can update at | |
7073 | once. Attempts to access the database while it is being updated are rejected | |
7074 | after a timeout period, during which the SQLite library waits for the lock to | |
7075 | be released. In Exim, the default timeout is set to 5 seconds, but it can be | |
7076 | changed by means of the sqlite_lock_timeout option. | |
7077 | ||
7078 | ||
7079 | ||
7080 | =============================================================================== | |
7081 | 10. DOMAIN, HOST, ADDRESS, AND LOCAL PART LISTS | |
7082 | ||
7083 | A number of Exim configuration options contain lists of domains, hosts, email | |
7084 | addresses, or local parts. For example, the hold_domains option contains a list | |
7085 | of domains whose delivery is currently suspended. These lists are also used as | |
7086 | data in ACL statements (see chapter 42), and as arguments to expansion | |
7087 | conditions such as match_domain. | |
7088 | ||
7089 | Each item in one of these lists is a pattern to be matched against a domain, | |
7090 | host, email address, or local part, respectively. In the sections below, the | |
7091 | different types of pattern for each case are described, but first we cover some | |
7092 | general facilities that apply to all four kinds of list. | |
7093 | ||
7094 | ||
7095 | 10.1 Expansion of lists | |
7096 | ----------------------- | |
7097 | ||
7098 | Each list is expanded as a single string before it is used. The result of | |
7099 | expansion must be a list, possibly containing empty items, which is split up | |
7100 | into separate items for matching. By default, colon is the separator character, | |
7101 | but this can be varied if necessary. See sections 6.19 and 6.21 for details of | |
7102 | the list syntax; the second of these discusses the way to specify empty list | |
7103 | items. | |
7104 | ||
7105 | If the string expansion is forced to fail, Exim behaves as if the item it is | |
7106 | testing (domain, host, address, or local part) is not in the list. Other | |
7107 | expansion failures cause temporary errors. | |
7108 | ||
7109 | If an item in a list is a regular expression, backslashes, dollars and possibly | |
7110 | other special characters in the expression must be protected against | |
7111 | misinterpretation by the string expander. The easiest way to do this is to use | |
7112 | the "\N" expansion feature to indicate that the contents of the regular | |
7113 | expression should not be expanded. For example, in an ACL you might have: | |
7114 | ||
7115 | deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \ | |
7116 | ${lookup{$domain}lsearch{/badsenders/bydomain}} | |
7117 | ||
7118 | The first item is a regular expression that is protected from expansion by "\ | |
7119 | N", whereas the second uses the expansion to obtain a list of unwanted senders | |
7120 | based on the receiving domain. | |
7121 | ||
7122 | ||
7123 | 10.2 Negated items in lists | |
7124 | --------------------------- | |
7125 | ||
7126 | Items in a list may be positive or negative. Negative items are indicated by a | |
7127 | leading exclamation mark, which may be followed by optional white space. A list | |
7128 | defines a set of items (domains, etc). When Exim processes one of these lists, | |
7129 | it is trying to find out whether a domain, host, address, or local part | |
7130 | (respectively) is in the set that is defined by the list. It works like this: | |
7131 | ||
7132 | The list is scanned from left to right. If a positive item is matched, the | |
7133 | subject that is being checked is in the set; if a negative item is matched, the | |
7134 | subject is not in the set. If the end of the list is reached without the | |
7135 | subject having matched any of the patterns, it is in the set if the last item | |
7136 | was a negative one, but not if it was a positive one. For example, the list in | |
7137 | ||
7138 | domainlist relay_to_domains = !a.b.c : *.b.c | |
7139 | ||
7140 | matches any domain ending in .b.c except for a.b.c. Domains that match neither | |
7141 | a.b.c nor *.b.c do not match, because the last item in the list is positive. | |
7142 | However, if the setting were | |
7143 | ||
7144 | domainlist relay_to_domains = !a.b.c | |
7145 | ||
7146 | then all domains other than a.b.c would match because the last item in the list | |
7147 | is negative. In other words, a list that ends with a negative item behaves as | |
7148 | if it had an extra item ":*" on the end. | |
7149 | ||
7150 | Another way of thinking about positive and negative items in lists is to read | |
7151 | the connector as "or" after a positive item and as "and" after a negative item. | |
7152 | ||
7153 | ||
7154 | 10.3 File names in lists | |
7155 | ------------------------ | |
7156 | ||
7157 | If an item in a domain, host, address, or local part list is an absolute file | |
7158 | name (beginning with a slash character), each line of the file is read and | |
7159 | processed as if it were an independent item in the list, except that further | |
7160 | file names are not allowed, and no expansion of the data from the file takes | |
7161 | place. Empty lines in the file are ignored, and the file may also contain | |
7162 | comment lines: | |
7163 | ||
7164 | * For domain and host lists, if a # character appears anywhere in a line of | |
7165 | the file, it and all following characters are ignored. | |
7166 | ||
7167 | * Because local parts may legitimately contain # characters, a comment in an | |
7168 | address list or local part list file is recognized only if # is preceded by | |
7169 | white space or the start of the line. For example: | |
7170 | ||
7171 | not#comment@x.y.z # but this is a comment | |
7172 | ||
7173 | Putting a file name in a list has the same effect as inserting each line of the | |
7174 | file as an item in the list (blank lines and comments excepted). However, there | |
7175 | is one important difference: the file is read each time the list is processed, | |
7176 | so if its contents vary over time, Exim's behaviour changes. | |
7177 | ||
7178 | If a file name is preceded by an exclamation mark, the sense of any match | |
7179 | within the file is inverted. For example, if | |
7180 | ||
7181 | hold_domains = !/etc/nohold-domains | |
7182 | ||
7183 | and the file contains the lines | |
7184 | ||
7185 | !a.b.c | |
7186 | *.b.c | |
7187 | ||
7188 | then a.b.c is in the set of domains defined by hold_domains, whereas any domain | |
7189 | matching "*.b.c" is not. | |
7190 | ||
7191 | ||
7192 | 10.4 An lsearch file is not an out-of-line list | |
7193 | ----------------------------------------------- | |
7194 | ||
7195 | As will be described in the sections that follow, lookups can be used in lists | |
7196 | to provide indexed methods of checking list membership. There has been some | |
7197 | confusion about the way lsearch lookups work in lists. Because an lsearch file | |
7198 | contains plain text and is scanned sequentially, it is sometimes thought that | |
7199 | it is allowed to contain wild cards and other kinds of non-constant pattern. | |
7200 | This is not the case. The keys in an lsearch file are always fixed strings, | |
7201 | just as for any other single-key lookup type. | |
7202 | ||
7203 | If you want to use a file to contain wild-card patterns that form part of a | |
7204 | list, just give the file name on its own, without a search type, as described | |
7205 | in the previous section. You could also use the wildlsearch or nwildlsearch, | |
7206 | but there is no advantage in doing this. | |
7207 | ||
7208 | ||
7209 | 10.5 Named lists | |
7210 | ---------------- | |
7211 | ||
7212 | A list of domains, hosts, email addresses, or local parts can be given a name | |
7213 | which is then used to refer to the list elsewhere in the configuration. This is | |
7214 | particularly convenient if the same list is required in several different | |
7215 | places. It also allows lists to be given meaningful names, which can improve | |
7216 | the readability of the configuration. For example, it is conventional to define | |
7217 | a domain list called local_domains for all the domains that are handled locally | |
7218 | on a host, using a configuration line such as | |
7219 | ||
7220 | domainlist local_domains = localhost:my.dom.example | |
7221 | ||
7222 | Named lists are referenced by giving their name preceded by a plus sign, so, | |
7223 | for example, a router that is intended to handle local domains would be | |
7224 | configured with the line | |
7225 | ||
7226 | domains = +local_domains | |
7227 | ||
7228 | The first router in a configuration is often one that handles all domains | |
7229 | except the local ones, using a configuration with a negated item like this: | |
7230 | ||
7231 | dnslookup: | |
7232 | driver = dnslookup | |
7233 | domains = ! +local_domains | |
7234 | transport = remote_smtp | |
7235 | no_more | |
7236 | ||
7237 | The four kinds of named list are created by configuration lines starting with | |
7238 | the words domainlist, hostlist, addresslist, or localpartlist, respectively. | |
7239 | Then there follows the name that you are defining, followed by an equals sign | |
7240 | and the list itself. For example: | |
7241 | ||
7242 | hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example | |
7243 | addresslist bad_senders = cdb;/etc/badsenders | |
7244 | ||
7245 | A named list may refer to other named lists: | |
7246 | ||
7247 | domainlist dom1 = first.example : second.example | |
7248 | domainlist dom2 = +dom1 : third.example | |
7249 | domainlist dom3 = fourth.example : +dom2 : fifth.example | |
7250 | ||
7251 | Warning: If the last item in a referenced list is a negative one, the effect | |
7252 | may not be what you intended, because the negation does not propagate out to | |
7253 | the higher level. For example, consider: | |
7254 | ||
7255 | domainlist dom1 = !a.b | |
7256 | domainlist dom2 = +dom1 : *.b | |
7257 | ||
7258 | The second list specifies "either in the dom1 list or *.b". The first list | |
7259 | specifies just "not a.b", so the domain x.y matches it. That means it matches | |
7260 | the second list as well. The effect is not the same as | |
7261 | ||
7262 | domainlist dom2 = !a.b : *.b | |
7263 | ||
7264 | where x.y does not match. It's best to avoid negation altogether in referenced | |
7265 | lists if you can. | |
7266 | ||
7267 | Named lists may have a performance advantage. When Exim is routing an address | |
7268 | or checking an incoming message, it caches the result of tests on named lists. | |
7269 | So, if you have a setting such as | |
7270 | ||
7271 | domains = +local_domains | |
7272 | ||
7273 | on several of your routers or in several ACL statements, the actual test is | |
7274 | done only for the first one. However, the caching works only if there are no | |
7275 | expansions within the list itself or any sublists that it references. In other | |
7276 | words, caching happens only for lists that are known to be the same each time | |
7277 | they are referenced. | |
7278 | ||
7279 | By default, there may be up to 16 named lists of each type. This limit can be | |
7280 | extended by changing a compile-time variable. The use of domain and host lists | |
7281 | is recommended for concepts such as local domains, relay domains, and relay | |
7282 | hosts. The default configuration is set up like this. | |
7283 | ||
7284 | ||
7285 | 10.6 Named lists compared with macros | |
7286 | ------------------------------------- | |
7287 | ||
7288 | At first sight, named lists might seem to be no different from macros in the | |
7289 | configuration file. However, macros are just textual substitutions. If you | |
7290 | write | |
7291 | ||
7292 | ALIST = host1 : host2 | |
7293 | auth_advertise_hosts = !ALIST | |
7294 | ||
7295 | it probably won't do what you want, because that is exactly the same as | |
7296 | ||
7297 | auth_advertise_hosts = !host1 : host2 | |
7298 | ||
7299 | Notice that the second host name is not negated. However, if you use a host | |
7300 | list, and write | |
7301 | ||
7302 | hostlist alist = host1 : host2 | |
7303 | auth_advertise_hosts = ! +alist | |
7304 | ||
7305 | the negation applies to the whole list, and so that is equivalent to | |
7306 | ||
7307 | auth_advertise_hosts = !host1 : !host2 | |
7308 | ||
7309 | ||
7310 | 10.7 Named list caching | |
7311 | ----------------------- | |
7312 | ||
7313 | While processing a message, Exim caches the result of checking a named list if | |
7314 | it is sure that the list is the same each time. In practice, this means that | |
7315 | the cache operates only if the list contains no $ characters, which guarantees | |
7316 | that it will not change when it is expanded. Sometimes, however, you may have | |
7317 | an expanded list that you know will be the same each time within a given | |
7318 | message. For example: | |
7319 | ||
7320 | domainlist special_domains = \ | |
7321 | ${lookup{$sender_host_address}cdb{/some/file}} | |
7322 | ||
7323 | This provides a list of domains that depends only on the sending host's IP | |
7324 | address. If this domain list is referenced a number of times (for example, in | |
7325 | several ACL lines, or in several routers) the result of the check is not cached | |
7326 | by default, because Exim does not know that it is going to be the same list | |
7327 | each time. | |
7328 | ||
7329 | By appending "_cache" to "domainlist" you can tell Exim to go ahead and cache | |
7330 | the result anyway. For example: | |
7331 | ||
7332 | domainlist_cache special_domains = ${lookup{... | |
7333 | ||
7334 | If you do this, you should be absolutely sure that caching is going to do the | |
7335 | right thing in all cases. When in doubt, leave it out. | |
7336 | ||
7337 | ||
7338 | 10.8 Domain lists | |
7339 | ----------------- | |
7340 | ||
7341 | Domain lists contain patterns that are to be matched against a mail domain. The | |
7342 | following types of item may appear in domain lists: | |
7343 | ||
7344 | * If a pattern consists of a single @ character, it matches the local host | |
7345 | name, as set by the primary_hostname option (or defaulted). This makes it | |
7346 | possible to use the same configuration file on several different hosts that | |
7347 | differ only in their names. | |
7348 | ||
7349 | * If a pattern consists of the string "@[]" it matches an IP address enclosed | |
7350 | in square brackets (as in an email address that contains a domain literal), | |
7351 | but only if that IP address is recognized as local for email routing | |
7352 | purposes. The local_interfaces and extra_local_interfaces options can be | |
7353 | used to control which of a host's several IP addresses are treated as | |
7354 | local. In today's Internet, the use of domain literals is controversial. | |
7355 | ||
7356 | * If a pattern consists of the string "@mx_any" it matches any domain that | |
7357 | has an MX record pointing to the local host or to any host that is listed | |
7358 | in hosts_treat_as_local. The items "@mx_primary" and "@mx_secondary" are | |
7359 | similar, except that the first matches only when a primary MX target is the | |
7360 | local host, and the second only when no primary MX target is the local | |
7361 | host, but a secondary MX target is. "Primary" means an MX record with the | |
7362 | lowest preference value - there may of course be more than one of them. | |
7363 | ||
7364 | The MX lookup that takes place when matching a pattern of this type is | |
7365 | performed with the resolver options for widening names turned off. Thus, | |
7366 | for example, a single-component domain will not be expanded by adding the | |
7367 | resolver's default domain. See the qualify_single and search_parents | |
7368 | options of the dnslookup router for a discussion of domain widening. | |
7369 | ||
7370 | Sometimes you may want to ignore certain IP addresses when using one of | |
7371 | these patterns. You can specify this by following the pattern with "/ignore | |
7372 | ="<ip list>, where <ip list> is a list of IP addresses. These addresses are | |
7373 | ignored when processing the pattern (compare the ignore_target_hosts option | |
7374 | on a router). For example: | |
7375 | ||
7376 | domains = @mx_any/ignore=127.0.0.1 | |
7377 | ||
7378 | This example matches any domain that has an MX record pointing to one of | |
7379 | the local host's IP addresses other than 127.0.0.1. | |
7380 | ||
7381 | The list of IP addresses is in fact processed by the same code that | |
7382 | processes host lists, so it may contain CIDR-coded network specifications | |
7383 | and it may also contain negative items. | |
7384 | ||
7385 | Because the list of IP addresses is a sublist within a domain list, you | |
7386 | have to be careful about delimiters if there is more than one address. Like | |
7387 | any other list, the default delimiter can be changed. Thus, you might have: | |
7388 | ||
7389 | domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \ | |
7390 | an.other.domain : ... | |
7391 | ||
7392 | so that the sublist uses semicolons for delimiters. When IPv6 addresses are | |
7393 | involved, it is easiest to change the delimiter for the main list as well: | |
7394 | ||
7395 | domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \ | |
7396 | an.other.domain ? ... | |
7397 | ||
7398 | * If a pattern starts with an asterisk, the remaining characters of the | |
7399 | pattern are compared with the terminating characters of the domain. The use | |
7400 | of "*" in domain lists differs from its use in partial matching lookups. In | |
7401 | a domain list, the character following the asterisk need not be a dot, | |
7402 | whereas partial matching works only in terms of dot-separated components. | |
7403 | For example, a domain list item such as "*key.ex" matches donkey.ex as well | |
7404 | as cipher.key.ex. | |
7405 | ||
7406 | * If a pattern starts with a circumflex character, it is treated as a regular | |
7407 | expression, and matched against the domain using a regular expression | |
7408 | matching function. The circumflex is treated as part of the regular | |
7409 | expression. Email domains are case-independent, so this regular expression | |
7410 | match is by default case-independent, but you can make it case-dependent by | |
7411 | starting it with "(?-i)". References to descriptions of the syntax of | |
7412 | regular expressions are given in chapter 8. | |
7413 | ||
7414 | Warning: Because domain lists are expanded before being processed, you must | |
7415 | escape any backslash and dollar characters in the regular expression, or | |
7416 | use the special "\N" sequence (see chapter 11) to specify that it is not to | |
7417 | be expanded (unless you really do want to build a regular expression by | |
7418 | expansion, of course). | |
7419 | ||
7420 | * If a pattern starts with the name of a single-key lookup type followed by a | |
7421 | semicolon (for example, "dbm;" or "lsearch;"), the remainder of the pattern | |
7422 | must be a file name in a suitable format for the lookup type. For example, | |
7423 | for "cdb;" it must be an absolute path: | |
7424 | ||
7425 | domains = cdb;/etc/mail/local_domains.cdb | |
7426 | ||
7427 | The appropriate type of lookup is done on the file using the domain name as | |
7428 | the key. In most cases, the data that is looked up is not used; Exim is | |
7429 | interested only in whether or not the key is present in the file. However, | |
7430 | when a lookup is used for the domains option on a router or a domains | |
7431 | condition in an ACL statement, the data is preserved in the $domain_data | |
7432 | variable and can be referred to in other router options or other statements | |
7433 | in the same ACL. | |
7434 | ||
7435 | * Any of the single-key lookup type names may be preceded by "partial"<n>"-", | |
7436 | where the <n> is optional, for example, | |
7437 | ||
7438 | domains = partial-dbm;/partial/domains | |
7439 | ||
7440 | This causes partial matching logic to be invoked; a description of how this | |
7441 | works is given in section 9.7. | |
7442 | ||
7443 | * Any of the single-key lookup types may be followed by an asterisk. This | |
7444 | causes a default lookup for a key consisting of a single asterisk to be | |
7445 | done if the original lookup fails. This is not a useful feature when using | |
7446 | a domain list to select particular domains (because any domain would | |
7447 | match), but it might have value if the result of the lookup is being used | |
7448 | via the $domain_data expansion variable. | |
7449 | ||
7450 | * If the pattern starts with the name of a query-style lookup type followed | |
7451 | by a semicolon (for example, "nisplus;" or "ldap;"), the remainder of the | |
7452 | pattern must be an appropriate query for the lookup type, as described in | |
7453 | chapter 9. For example: | |
7454 | ||
7455 | hold_domains = mysql;select domain from holdlist \ | |
7456 | where domain = '${quote_mysql:$domain}'; | |
7457 | ||
7458 | In most cases, the data that is looked up is not used (so for an SQL query, | |
7459 | for example, it doesn't matter what field you select). Exim is interested | |
7460 | only in whether or not the query succeeds. However, when a lookup is used | |
7461 | for the domains option on a router, the data is preserved in the | |
7462 | $domain_data variable and can be referred to in other options. | |
7463 | ||
7464 | * If none of the above cases apply, a caseless textual comparison is made | |
7465 | between the pattern and the domain. | |
7466 | ||
7467 | Here is an example that uses several different kinds of pattern: | |
7468 | ||
7469 | domainlist funny_domains = \ | |
7470 | @ : \ | |
7471 | lib.unseen.edu : \ | |
7472 | *.foundation.fict.example : \ | |
7473 | \N^[1-2]\d{3}\.fict\.example$\N : \ | |
7474 | partial-dbm;/opt/data/penguin/book : \ | |
7475 | nis;domains.byname : \ | |
7476 | nisplus;[name=$domain,status=local],domains.org_dir | |
7477 | ||
7478 | There are obvious processing trade-offs among the various matching modes. Using | |
7479 | an asterisk is faster than a regular expression, and listing a few names | |
7480 | explicitly probably is too. The use of a file or database lookup is expensive, | |
7481 | but may be the only option if hundreds of names are required. Because the | |
7482 | patterns are tested in order, it makes sense to put the most commonly matched | |
7483 | patterns earlier. | |
7484 | ||
7485 | ||
7486 | 10.9 Host lists | |
7487 | --------------- | |
7488 | ||
7489 | Host lists are used to control what remote hosts are allowed to do. For | |
7490 | example, some hosts may be allowed to use the local host as a relay, and some | |
7491 | may be permitted to use the SMTP ETRN command. Hosts can be identified in two | |
7492 | different ways, by name or by IP address. In a host list, some types of pattern | |
7493 | are matched to a host name, and some are matched to an IP address. You need to | |
7494 | be particularly careful with this when single-key lookups are involved, to | |
7495 | ensure that the right value is being used as the key. | |
7496 | ||
7497 | ||
7498 | 10.10 Special host list patterns | |
7499 | -------------------------------- | |
7500 | ||
7501 | If a host list item is the empty string, it matches only when no remote host is | |
7502 | involved. This is the case when a message is being received from a local | |
7503 | process using SMTP on the standard input, that is, when a TCP/IP connection is | |
7504 | not used. | |
7505 | ||
7506 | The special pattern "*" in a host list matches any host or no host. Neither the | |
7507 | IP address nor the name is actually inspected. | |
7508 | ||
7509 | ||
7510 | 10.11 Host list patterns that match by IP address | |
7511 | ------------------------------------------------- | |
7512 | ||
7513 | If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket, | |
7514 | the incoming address actually appears in the IPv6 host as "::ffff:"<v4address>. | |
7515 | When such an address is tested against a host list, it is converted into a | |
7516 | traditional IPv4 address first. (Not all operating systems accept IPv4 calls on | |
7517 | IPv6 sockets, as there have been some security concerns.) | |
7518 | ||
7519 | The following types of pattern in a host list check the remote host by | |
7520 | inspecting its IP address: | |
7521 | ||
7522 | * If the pattern is a plain domain name (not a regular expression, not | |
7523 | starting with *, not a lookup of any kind), Exim calls the operating system | |
7524 | function to find the associated IP address(es). Exim uses the newer | |
7525 | getipnodebyname() function when available, otherwise gethostbyname(). This | |
7526 | typically causes a forward DNS lookup of the name. The result is compared | |
7527 | with the IP address of the subject host. | |
7528 | ||
7529 | If there is a temporary problem (such as a DNS timeout) with the host name | |
7530 | lookup, a temporary error occurs. For example, if the list is being used in | |
7531 | an ACL condition, the ACL gives a "defer" response, usually leading to a | |
7532 | temporary SMTP error code. If no IP address can be found for the host name, | |
7533 | what happens is described in section 10.14 below. | |
7534 | ||
7535 | * If the pattern is "@", the primary host name is substituted and used as a | |
7536 | domain name, as just described. | |
7537 | ||
7538 | * If the pattern is an IP address, it is matched against the IP address of | |
7539 | the subject host. IPv4 addresses are given in the normal "dotted-quad" | |
7540 | notation. IPv6 addresses can be given in colon-separated format, but the | |
7541 | colons have to be doubled so as not to be taken as item separators when the | |
7542 | default list separator is used. IPv6 addresses are recognized even when | |
7543 | Exim is compiled without IPv6 support. This means that if they appear in a | |
7544 | host list on an IPv4-only host, Exim will not treat them as host names. | |
7545 | They are just addresses that can never match a client host. | |
7546 | ||
7547 | * If the pattern is "@[]", it matches the IP address of any IP interface on | |
7548 | the local host. For example, if the local host is an IPv4 host with one | |
7549 | interface address 10.45.23.56, these two ACL statements have the same | |
7550 | effect: | |
7551 | ||
7552 | accept hosts = 127.0.0.1 : 10.45.23.56 | |
7553 | accept hosts = @[] | |
7554 | ||
7555 | * If the pattern is an IP address followed by a slash and a mask length (for | |
7556 | example 10.11.42.0/24), it is matched against the IP address of the subject | |
7557 | host under the given mask. This allows, an entire network of hosts to be | |
7558 | included (or excluded) by a single item. The mask uses CIDR notation; it | |
7559 | specifies the number of address bits that must match, starting from the | |
7560 | most significant end of the address. | |
7561 | ||
7562 | Note: The mask is not a count of addresses, nor is it the high number of a | |
7563 | range of addresses. It is the number of bits in the network portion of the | |
7564 | address. The above example specifies a 24-bit netmask, so it matches all | |
7565 | 256 addresses in the 10.11.42.0 network. An item such as | |
7566 | ||
7567 | 192.168.23.236/31 | |
7568 | ||
7569 | matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value | |
7570 | of 32 for an IPv4 address is the same as no mask at all; just a single | |
7571 | address matches. | |
7572 | ||
7573 | Here is another example which shows an IPv4 and an IPv6 network: | |
7574 | ||
7575 | recipient_unqualified_hosts = 192.168.0.0/16: \ | |
7576 | 3ffe::ffff::836f::::/48 | |
7577 | ||
7578 | The doubling of list separator characters applies only when these items | |
7579 | appear inline in a host list. It is not required when indirecting via a | |
7580 | file. For example: | |
7581 | ||
7582 | recipient_unqualified_hosts = /opt/exim/unqualnets | |
7583 | ||
7584 | could make use of a file containing | |
7585 | ||
7586 | 172.16.0.0/12 | |
7587 | 3ffe:ffff:836f::/48 | |
7588 | ||
7589 | to have exactly the same effect as the previous example. When listing IPv6 | |
7590 | addresses inline, it is usually more convenient to use the facility for | |
7591 | changing separator characters. This list contains the same two networks: | |
7592 | ||
7593 | recipient_unqualified_hosts = <; 172.16.0.0/12; \ | |
7594 | 3ffe:ffff:836f::/48 | |
7595 | ||
7596 | The separator is changed to semicolon by the leading "<;" at the start of | |
7597 | the list. | |
7598 | ||
7599 | ||
7600 | 10.12 Host list patterns for single-key lookups by host address | |
7601 | --------------------------------------------------------------- | |
7602 | ||
7603 | When a host is to be identified by a single-key lookup of its complete IP | |
7604 | address, the pattern takes this form: | |
7605 | ||
7606 | net-<single-key-search-type>;<search-data> | |
7607 | ||
7608 | For example: | |
7609 | ||
7610 | hosts_lookup = net-cdb;/hosts-by-ip.db | |
7611 | ||
7612 | The text form of the IP address of the subject host is used as the lookup key. | |
7613 | IPv6 addresses are converted to an unabbreviated form, using lower case | |
7614 | letters, with dots as separators because colon is the key terminator in lsearch | |
7615 | files. [Colons can in fact be used in keys in lsearch files by quoting the | |
7616 | keys, but this is a facility that was added later.] The data returned by the | |
7617 | lookup is not used. | |
7618 | ||
7619 | Single-key lookups can also be performed using masked IP addresses, using | |
7620 | patterns of this form: | |
7621 | ||
7622 | net<number>-<single-key-search-type>;<search-data> | |
7623 | ||
7624 | For example: | |
7625 | ||
7626 | net24-dbm;/networks.db | |
7627 | ||
7628 | The IP address of the subject host is masked using <number> as the mask length. | |
7629 | A textual string is constructed from the masked value, followed by the mask, | |
7630 | and this is used as the lookup key. For example, if the host's IP address is | |
7631 | 192.168.34.6, the key that is looked up for the above example is "192.168.34.0/ | |
7632 | 24". | |
7633 | ||
7634 | When an IPv6 address is converted to a string, dots are normally used instead | |
7635 | of colons, so that keys in lsearch files need not contain colons (which | |
7636 | terminate lsearch keys). This was implemented some time before the ability to | |
7637 | quote keys was made available in lsearch files. However, the more recently | |
7638 | implemented iplsearch files do require colons in IPv6 keys (notated using the | |
7639 | quoting facility) so as to distinguish them from IPv4 keys. For this reason, | |
7640 | when the lookup type is iplsearch, IPv6 addresses are converted using colons | |
7641 | and not dots. In all cases, full, unabbreviated IPv6 addresses are always used. | |
7642 | ||
7643 | Ideally, it would be nice to tidy up this anomalous situation by changing to | |
7644 | colons in all cases, given that quoting is now available for lsearch. However, | |
7645 | this would be an incompatible change that might break some existing | |
7646 | configurations. | |
7647 | ||
7648 | Warning: Specifying net32- (for an IPv4 address) or net128- (for an IPv6 | |
7649 | address) is not the same as specifying just net- without a number. In the | |
7650 | former case the key strings include the mask value, whereas in the latter case | |
7651 | the IP address is used on its own. | |
7652 | ||
7653 | ||
7654 | 10.13 Host list patterns that match by host name | |
7655 | ------------------------------------------------ | |
7656 | ||
7657 | There are several types of pattern that require Exim to know the name of the | |
7658 | remote host. These are either wildcard patterns or lookups by name. (If a | |
7659 | complete hostname is given without any wildcarding, it is used to find an IP | |
7660 | address to match against, as described in section 10.11 above.) | |
7661 | ||
7662 | If the remote host name is not already known when Exim encounters one of these | |
7663 | patterns, it has to be found from the IP address. Although many sites on the | |
7664 | Internet are conscientious about maintaining reverse DNS data for their hosts, | |
7665 | there are also many that do not do this. Consequently, a name cannot always be | |
7666 | found, and this may lead to unwanted effects. Take care when configuring host | |
7667 | lists with wildcarded name patterns. Consider what will happen if a name cannot | |
7668 | be found. | |
7669 | ||
7670 | Because of the problems of determining host names from IP addresses, matching | |
7671 | against host names is not as common as matching against IP addresses. | |
7672 | ||
7673 | By default, in order to find a host name, Exim first does a reverse DNS lookup; | |
7674 | if no name is found in the DNS, the system function (gethostbyaddr() or | |
7675 | getipnodebyaddr() if available) is tried. The order in which these lookups are | |
7676 | done can be changed by setting the host_lookup_order option. For security, once | |
7677 | Exim has found one or more names, it looks up the IP addresses for these names | |
7678 | and compares them with the IP address that it started with. Only those names | |
7679 | whose IP addresses match are accepted. Any other names are discarded. If no | |
7680 | names are left, Exim behaves as if the host name cannot be found. In the most | |
7681 | common case there is only one name and one IP address. | |
7682 | ||
7683 | There are some options that control what happens if a host name cannot be | |
7684 | found. These are described in section 10.14 below. | |
7685 | ||
7686 | As a result of aliasing, hosts may have more than one name. When processing any | |
7687 | of the following types of pattern, all the host's names are checked: | |
7688 | ||
7689 | * If a pattern starts with "*" the remainder of the item must match the end | |
7690 | of the host name. For example, "*.b.c" matches all hosts whose names end in | |
7691 | .b.c. This special simple form is provided because this is a very common | |
7692 | requirement. Other kinds of wildcarding require the use of a regular | |
7693 | expression. | |
7694 | ||
7695 | * If the item starts with "^" it is taken to be a regular expression which is | |
7696 | matched against the host name. Host names are case-independent, so this | |
7697 | regular expression match is by default case-independent, but you can make | |
7698 | it case-dependent by starting it with "(?-i)". References to descriptions | |
7699 | of the syntax of regular expressions are given in chapter 8. For example, | |
7700 | ||
7701 | ^(a|b)\.c\.d$ | |
7702 | ||
7703 | is a regular expression that matches either of the two hosts a.c.d or b.c.d | |
7704 | . When a regular expression is used in a host list, you must take care that | |
7705 | backslash and dollar characters are not misinterpreted as part of the | |
7706 | string expansion. The simplest way to do this is to use "\N" to mark that | |
7707 | part of the string as non-expandable. For example: | |
7708 | ||
7709 | sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : .... | |
7710 | ||
7711 | Warning: If you want to match a complete host name, you must include the | |
7712 | "$" terminating metacharacter in the regular expression, as in the above | |
7713 | example. Without it, a match at the start of the host name is all that is | |
7714 | required. | |
7715 | ||
7716 | ||
7717 | 10.14 Behaviour when an IP address or name cannot be found | |
7718 | ---------------------------------------------------------- | |
7719 | ||
7720 | While processing a host list, Exim may need to look up an IP address from a | |
7721 | name (see section 10.11), or it may need to look up a host name from an IP | |
7722 | address (see section 10.13). In either case, the behaviour when it fails to | |
7723 | find the information it is seeking is the same. | |
7724 | ||
7725 | Note: This section applies to permanent lookup failures. It does not apply to | |
7726 | temporary DNS errors, whose handling is described in the next section. | |
7727 | ||
7728 | Exim parses a host list from left to right. If it encounters a permanent lookup | |
7729 | failure in any item in the host list before it has found a match, Exim treats | |
7730 | it as a failure and the default behavior is as if the host does not match the | |
7731 | list. This may not always be what you want to happen. To change Exim's | |
7732 | behaviour, the special items "+include_unknown" or "+ignore_unknown" may appear | |
7733 | in the list (at top level - they are not recognized in an indirected file). | |
7734 | ||
7735 | * If any item that follows "+include_unknown" requires information that | |
7736 | cannot found, Exim behaves as if the host does match the list. For example, | |
7737 | ||
7738 | host_reject_connection = +include_unknown:*.enemy.ex | |
7739 | ||
7740 | rejects connections from any host whose name matches "*.enemy.ex", and also | |
7741 | any hosts whose name it cannot find. | |
7742 | ||
7743 | * If any item that follows "+ignore_unknown" requires information that cannot | |
7744 | be found, Exim ignores that item and proceeds to the rest of the list. For | |
7745 | example: | |
7746 | ||
7747 | accept hosts = +ignore_unknown : friend.example : \ | |
7748 | 192.168.4.5 | |
7749 | ||
7750 | accepts from any host whose name is friend.example and from 192.168.4.5, | |
7751 | whether or not its host name can be found. Without "+ignore_unknown", if no | |
7752 | name can be found for 192.168.4.5, it is rejected. | |
7753 | ||
7754 | Both "+include_unknown" and "+ignore_unknown" may appear in the same list. The | |
7755 | effect of each one lasts until the next, or until the end of the list. | |
7756 | ||
7757 | ||
7758 | 10.15 Mixing wildcarded host names and addresses in host lists | |
7759 | -------------------------------------------------------------- | |
7760 | ||
7761 | This section explains the host/ip processing logic with the same concepts as | |
7762 | the previous section, but specifically addresses what happens when a wildcarded | |
7763 | hostname is one of the items in the hostlist. | |
7764 | ||
7765 | * If you have name lookups or wildcarded host names and IP addresses in the | |
7766 | same host list, you should normally put the IP addresses first. For | |
7767 | example, in an ACL you could have: | |
7768 | ||
7769 | accept hosts = 10.9.8.7 : *.friend.example | |
7770 | ||
7771 | The reason you normally would order it this way lies in the left-to-right | |
7772 | way that Exim processes lists. It can test IP addresses without doing any | |
7773 | DNS lookups, but when it reaches an item that requires a host name, it | |
7774 | fails if it cannot find a host name to compare with the pattern. If the | |
7775 | above list is given in the opposite order, the accept statement fails for a | |
7776 | host whose name cannot be found, even if its IP address is 10.9.8.7. | |
7777 | ||
7778 | * If you really do want to do the name check first, and still recognize the | |
7779 | IP address, you can rewrite the ACL like this: | |
7780 | ||
7781 | accept hosts = *.friend.example | |
7782 | accept hosts = 10.9.8.7 | |
7783 | ||
7784 | If the first accept fails, Exim goes on to try the second one. See chapter | |
7785 | 42 for details of ACLs. Alternatively, you can use "+ignore_unknown", which | |
7786 | was discussed in depth in the first example in this section. | |
7787 | ||
7788 | ||
7789 | 10.16 Temporary DNS errors when looking up host information | |
7790 | ----------------------------------------------------------- | |
7791 | ||
7792 | A temporary DNS lookup failure normally causes a defer action (except when | |
7793 | dns_again_means_nonexist converts it into a permanent error). However, host | |
7794 | lists can include "+ignore_defer" and "+include_defer", analagous to | |
7795 | "+ignore_unknown" and "+include_unknown", as described in the previous section. | |
7796 | These options should be used with care, probably only in non-critical host | |
7797 | lists such as whitelists. | |
7798 | ||
7799 | ||
7800 | 10.17 Host list patterns for single-key lookups by host name | |
7801 | ------------------------------------------------------------ | |
7802 | ||
7803 | If a pattern is of the form | |
7804 | ||
7805 | <single-key-search-type>;<search-data> | |
7806 | ||
7807 | for example | |
7808 | ||
7809 | dbm;/host/accept/list | |
7810 | ||
7811 | a single-key lookup is performed, using the host name as its key. If the lookup | |
7812 | succeeds, the host matches the item. The actual data that is looked up is not | |
7813 | used. | |
7814 | ||
7815 | Reminder: With this kind of pattern, you must have host names as keys in the | |
7816 | file, not IP addresses. If you want to do lookups based on IP addresses, you | |
7817 | must precede the search type with "net-" (see section 10.12). There is, | |
7818 | however, no reason why you could not use two items in the same list, one doing | |
7819 | an address lookup and one doing a name lookup, both using the same file. | |
7820 | ||
7821 | ||
7822 | 10.18 Host list patterns for query-style lookups | |
7823 | ------------------------------------------------ | |
7824 | ||
7825 | If a pattern is of the form | |
7826 | ||
7827 | <query-style-search-type>;<query> | |
7828 | ||
7829 | the query is obeyed, and if it succeeds, the host matches the item. The actual | |
7830 | data that is looked up is not used. The variables $sender_host_address and | |
7831 | $sender_host_name can be used in the query. For example: | |
7832 | ||
7833 | hosts_lookup = pgsql;\ | |
7834 | select ip from hostlist where ip='$sender_host_address' | |
7835 | ||
7836 | The value of $sender_host_address for an IPv6 address contains colons. You can | |
7837 | use the sg expansion item to change this if you need to. If you want to use | |
7838 | masked IP addresses in database queries, you can use the mask expansion | |
7839 | operator. | |
7840 | ||
7841 | If the query contains a reference to $sender_host_name, Exim automatically | |
7842 | looks up the host name if it has not already done so. (See section 10.13 for | |
7843 | comments on finding host names.) | |
7844 | ||
7845 | Historical note: prior to release 4.30, Exim would always attempt to find a | |
7846 | host name before running the query, unless the search type was preceded by | |
7847 | "net-". This is no longer the case. For backwards compatibility, "net-" is | |
7848 | still recognized for query-style lookups, but its presence or absence has no | |
7849 | effect. (Of course, for single-key lookups, "net-" is important. See section | |
7850 | 10.12.) | |
7851 | ||
7852 | ||
7853 | 10.19 Address lists | |
7854 | ------------------- | |
7855 | ||
7856 | Address lists contain patterns that are matched against mail addresses. There | |
7857 | is one special case to be considered: the sender address of a bounce message is | |
7858 | always empty. You can test for this by providing an empty item in an address | |
7859 | list. For example, you can set up a router to process bounce messages by using | |
7860 | this option setting: | |
7861 | ||
7862 | senders = : | |
7863 | ||
7864 | The presence of the colon creates an empty item. If you do not provide any | |
7865 | data, the list is empty and matches nothing. The empty sender can also be | |
7866 | detected by a regular expression that matches an empty string, and by a | |
7867 | query-style lookup that succeeds when $sender_address is empty. | |
7868 | ||
7869 | Non-empty items in an address list can be straightforward email addresses. For | |
7870 | example: | |
7871 | ||
7872 | senders = jbc@askone.example : hs@anacreon.example | |
7873 | ||
7874 | A certain amount of wildcarding is permitted. If a pattern contains an @ | |
7875 | character, but is not a regular expression and does not begin with a | |
7876 | semicolon-terminated lookup type (described below), the local part of the | |
7877 | subject address is compared with the local part of the pattern, which may start | |
7878 | with an asterisk. If the local parts match, the domain is checked in exactly | |
7879 | the same way as for a pattern in a domain list. For example, the domain can be | |
7880 | wildcarded, refer to a named list, or be a lookup: | |
7881 | ||
7882 | deny senders = *@*.spamming.site:\ | |
7883 | *@+hostile_domains:\ | |
7884 | bozo@partial-lsearch;/list/of/dodgy/sites:\ | |
7885 | *@dbm;/bad/domains.db | |
7886 | ||
7887 | If a local part that begins with an exclamation mark is required, it has to be | |
7888 | specified using a regular expression, because otherwise the exclamation mark is | |
7889 | treated as a sign of negation, as is standard in lists. | |
7890 | ||
7891 | If a non-empty pattern that is not a regular expression or a lookup does not | |
7892 | contain an @ character, it is matched against the domain part of the subject | |
7893 | address. The only two formats that are recognized this way are a literal | |
7894 | domain, or a domain pattern that starts with *. In both these cases, the effect | |
7895 | is the same as if "*@" preceded the pattern. For example: | |
7896 | ||
7897 | deny senders = enemy.domain : *.enemy.domain | |
7898 | ||
7899 | The following kinds of more complicated address list pattern can match any | |
7900 | address, including the empty address that is characteristic of bounce message | |
7901 | senders: | |
7902 | ||
7903 | * If (after expansion) a pattern starts with "^", a regular expression match | |
7904 | is done against the complete address, with the pattern as the regular | |
7905 | expression. You must take care that backslash and dollar characters are not | |
7906 | misinterpreted as part of the string expansion. The simplest way to do this | |
7907 | is to use "\N" to mark that part of the string as non-expandable. For | |
7908 | example: | |
7909 | ||
7910 | deny senders = \N^.*this.*@example\.com$\N : \ | |
7911 | \N^\d{8}.+@spamhaus.example$\N : ... | |
7912 | ||
7913 | The "\N" sequences are removed by the expansion, so these items do indeed | |
7914 | start with "^" by the time they are being interpreted as address patterns. | |
7915 | ||
7916 | * Complete addresses can be looked up by using a pattern that starts with a | |
7917 | lookup type terminated by a semicolon, followed by the data for the lookup. | |
7918 | For example: | |
7919 | ||
7920 | deny senders = cdb;/etc/blocked.senders : \ | |
7921 | mysql;select address from blocked where \ | |
7922 | address='${quote_mysql:$sender_address}' | |
7923 | ||
7924 | Both query-style and single-key lookup types can be used. For a single-key | |
7925 | lookup type, Exim uses the complete address as the key. However, empty keys | |
7926 | are not supported for single-key lookups, so a match against the empty | |
7927 | address always fails. This restriction does not apply to query-style | |
7928 | lookups. | |
7929 | ||
7930 | Partial matching for single-key lookups (section 9.7) cannot be used, and | |
7931 | is ignored if specified, with an entry being written to the panic log. | |
7932 | However, you can configure lookup defaults, as described in section 9.6, | |
7933 | but this is useful only for the "*@" type of default. For example, with | |
7934 | this lookup: | |
7935 | ||
7936 | accept senders = lsearch*@;/some/file | |
7937 | ||
7938 | the file could contains lines like this: | |
7939 | ||
7940 | user1@domain1.example | |
7941 | *@domain2.example | |
7942 | ||
7943 | and for the sender address nimrod@jaeger.example, the sequence of keys that | |
7944 | are tried is: | |
7945 | ||
7946 | nimrod@jaeger.example | |
7947 | *@jaeger.example | |
7948 | * | |
7949 | ||
7950 | Warning 1: Do not include a line keyed by "*" in the file, because that | |
7951 | would mean that every address matches, thus rendering the test useless. | |
7952 | ||
7953 | Warning 2: Do not confuse these two kinds of item: | |
7954 | ||
7955 | deny recipients = dbm*@;/some/file | |
7956 | deny recipients = *@dbm;/some/file | |
7957 | ||
7958 | The first does a whole address lookup, with defaulting, as just described, | |
7959 | because it starts with a lookup type. The second matches the local part and | |
7960 | domain independently, as described in a bullet point below. | |
7961 | ||
7962 | The following kinds of address list pattern can match only non-empty addresses. | |
7963 | If the subject address is empty, a match against any of these pattern types | |
7964 | always fails. | |
7965 | ||
7966 | * If a pattern starts with "@@" followed by a single-key lookup item (for | |
7967 | example, "@@lsearch;/some/file"), the address that is being checked is | |
7968 | split into a local part and a domain. The domain is looked up in the file. | |
7969 | If it is not found, there is no match. If it is found, the data that is | |
7970 | looked up from the file is treated as a colon-separated list of local part | |
7971 | patterns, each of which is matched against the subject local part in turn. | |
7972 | ||
7973 | The lookup may be a partial one, and/or one involving a search for a | |
7974 | default keyed by "*" (see section 9.6). The local part patterns that are | |
7975 | looked up can be regular expressions or begin with "*", or even be further | |
7976 | lookups. They may also be independently negated. For example, with | |
7977 | ||
7978 | deny senders = @@dbm;/etc/reject-by-domain | |
7979 | ||
7980 | the data from which the DBM file is built could contain lines like | |
7981 | ||
7982 | baddomain.com: !postmaster : * | |
7983 | ||
7984 | to reject all senders except postmaster from that domain. | |
7985 | ||
7986 | If a local part that actually begins with an exclamation mark is required, | |
7987 | it has to be specified using a regular expression. In lsearch files, an | |
7988 | entry may be split over several lines by indenting the second and | |
7989 | subsequent lines, but the separating colon must still be included at line | |
7990 | breaks. White space surrounding the colons is ignored. For example: | |
7991 | ||
7992 | aol.com: spammer1 : spammer2 : ^[0-9]+$ : | |
7993 | spammer3 : spammer4 | |
7994 | ||
7995 | As in all colon-separated lists in Exim, a colon can be included in an item | |
7996 | by doubling. | |
7997 | ||
7998 | If the last item in the list starts with a right angle-bracket, the | |
7999 | remainder of the item is taken as a new key to look up in order to obtain a | |
8000 | continuation list of local parts. The new key can be any sequence of | |
8001 | characters. Thus one might have entries like | |
8002 | ||
8003 | aol.com: spammer1 : spammer 2 : >* | |
8004 | xyz.com: spammer3 : >* | |
8005 | *: ^\d{8}$ | |
8006 | ||
8007 | in a file that was searched with @@dbm*, to specify a match for 8-digit | |
8008 | local parts for all domains, in addition to the specific local parts listed | |
8009 | for each domain. Of course, using this feature costs another lookup each | |
8010 | time a chain is followed, but the effort needed to maintain the data is | |
8011 | reduced. | |
8012 | ||
8013 | It is possible to construct loops using this facility, and in order to | |
8014 | catch them, the chains may be no more than fifty items long. | |
8015 | ||
8016 | * The @@<lookup> style of item can also be used with a query-style lookup, | |
8017 | but in this case, the chaining facility is not available. The lookup can | |
8018 | only return a single list of local parts. | |
8019 | ||
8020 | Warning: There is an important difference between the address list items in | |
8021 | these two examples: | |
8022 | ||
8023 | senders = +my_list | |
8024 | senders = *@+my_list | |
8025 | ||
8026 | In the first one, "my_list" is a named address list, whereas in the second | |
8027 | example it is a named domain list. | |
8028 | ||
8029 | ||
8030 | 10.20 Case of letters in address lists | |
8031 | -------------------------------------- | |
8032 | ||
8033 | Domains in email addresses are always handled caselessly, but for local parts | |
8034 | case may be significant on some systems (see caseful_local_part for how Exim | |
8035 | deals with this when routing addresses). However, RFC 2505 (Anti-Spam | |
8036 | Recommendations for SMTP MTAs) suggests that matching of addresses to blocking | |
8037 | lists should be done in a case-independent manner. Since most address lists in | |
8038 | Exim are used for this kind of control, Exim attempts to do this by default. | |
8039 | ||
8040 | The domain portion of an address is always lowercased before matching it to an | |
8041 | address list. The local part is lowercased by default, and any string | |
8042 | comparisons that take place are done caselessly. This means that the data in | |
8043 | the address list itself, in files included as plain file names, and in any file | |
8044 | that is looked up using the "@@" mechanism, can be in any case. However, the | |
8045 | keys in files that are looked up by a search type other than lsearch (which | |
8046 | works caselessly) must be in lower case, because these lookups are not | |
8047 | case-independent. | |
8048 | ||
8049 | To allow for the possibility of caseful address list matching, if an item in an | |
8050 | address list is the string "+caseful", the original case of the local part is | |
8051 | restored for any comparisons that follow, and string comparisons are no longer | |
8052 | case-independent. This does not affect the domain, which remains in lower case. | |
8053 | However, although independent matches on the domain alone are still performed | |
8054 | caselessly, regular expressions that match against an entire address become | |
8055 | case-sensitive after "+caseful" has been seen. | |
8056 | ||
8057 | ||
8058 | 10.21 Local part lists | |
8059 | ---------------------- | |
8060 | ||
8061 | Case-sensitivity in local part lists is handled in the same way as for address | |
8062 | lists, as just described. The "+caseful" item can be used if required. In a | |
8063 | setting of the local_parts option in a router with caseful_local_part set | |
8064 | false, the subject is lowercased and the matching is initially | |
8065 | case-insensitive. In this case, "+caseful" will restore case-sensitive matching | |
8066 | in the local part list, but not elsewhere in the router. If caseful_local_part | |
8067 | is set true in a router, matching in the local_parts option is case-sensitive | |
8068 | from the start. | |
8069 | ||
8070 | If a local part list is indirected to a file (see section 10.3), comments are | |
8071 | handled in the same way as address lists - they are recognized only if the # is | |
8072 | preceded by white space or the start of the line. Otherwise, local part lists | |
8073 | are matched in the same way as domain lists, except that the special items that | |
8074 | refer to the local host ("@", "@[]", "@mx_any", "@mx_primary", and | |
8075 | "@mx_secondary") are not recognized. Refer to section 10.8 for details of the | |
8076 | other available item types. | |
8077 | ||
8078 | ||
8079 | ||
8080 | =============================================================================== | |
8081 | 11. STRING EXPANSIONS | |
8082 | ||
8083 | Many strings in Exim's run time configuration are expanded before use. Some of | |
8084 | them are expanded every time they are used; others are expanded only once. | |
8085 | ||
8086 | When a string is being expanded it is copied verbatim from left to right except | |
8087 | when a dollar or backslash character is encountered. A dollar specifies the | |
8088 | start of a portion of the string that is interpreted and replaced as described | |
8089 | below in section 11.5 onwards. Backslash is used as an escape character, as | |
8090 | described in the following section. | |
8091 | ||
8092 | Whether a string is expanded depends upon the context. Usually this is solely | |
8093 | dependent upon the option for which a value is sought; in this documentation, | |
8094 | options for which string expansion is performed are marked with * after the | |
8095 | data type. ACL rules always expand strings. A couple of expansion conditions do | |
8096 | not expand some of the brace-delimited branches, for security reasons. | |
8097 | ||
8098 | ||
8099 | 11.1 Literal text in expanded strings | |
8100 | ------------------------------------- | |
8101 | ||
8102 | An uninterpreted dollar can be included in an expanded string by putting a | |
8103 | backslash in front of it. A backslash can be used to prevent any special | |
8104 | character being treated specially in an expansion, including backslash itself. | |
8105 | If the string appears in quotes in the configuration file, two backslashes are | |
8106 | required because the quotes themselves cause interpretation of backslashes when | |
8107 | the string is read in (see section 6.16). | |
8108 | ||
8109 | A portion of the string can specified as non-expandable by placing it between | |
8110 | two occurrences of "\N". This is particularly useful for protecting regular | |
8111 | expressions, which often contain backslashes and dollar signs. For example: | |
8112 | ||
8113 | deny senders = \N^\d{8}[a-z]@some\.site\.example$\N | |
8114 | ||
8115 | On encountering the first "\N", the expander copies subsequent characters | |
8116 | without interpretation until it reaches the next "\N" or the end of the string. | |
8117 | ||
8118 | ||
8119 | 11.2 Character escape sequences in expanded strings | |
8120 | --------------------------------------------------- | |
8121 | ||
8122 | A backslash followed by one of the letters "n", "r", or "t" in an expanded | |
8123 | string is recognized as an escape sequence for the character newline, carriage | |
8124 | return, or tab, respectively. A backslash followed by up to three octal digits | |
8125 | is recognized as an octal encoding for a single character, and a backslash | |
8126 | followed by "x" and up to two hexadecimal digits is a hexadecimal encoding. | |
8127 | ||
8128 | These escape sequences are also recognized in quoted strings when they are read | |
8129 | in. Their interpretation in expansions as well is useful for unquoted strings, | |
8130 | and for other cases such as looked-up strings that are then expanded. | |
8131 | ||
8132 | ||
8133 | 11.3 Testing string expansions | |
8134 | ------------------------------ | |
8135 | ||
8136 | Many expansions can be tested by calling Exim with the -be option. This takes | |
8137 | the command arguments, or lines from the standard input if there are no | |
8138 | arguments, runs them through the string expansion code, and writes the results | |
8139 | to the standard output. Variables based on configuration values are set up, but | |
8140 | since no message is being processed, variables such as $local_part have no | |
8141 | value. Nevertheless the -be option can be useful for checking out file and | |
8142 | database lookups, and the use of expansion operators such as sg, substr and | |
8143 | nhash. | |
8144 | ||
8145 | Exim gives up its root privilege when it is called with the -be option, and | |
8146 | instead runs under the uid and gid it was called with, to prevent users from | |
8147 | using -be for reading files to which they do not have access. | |
8148 | ||
8149 | If you want to test expansions that include variables whose values are taken | |
8150 | from a message, there are two other options that can be used. The -bem option | |
8151 | is like -be except that it is followed by a file name. The file is read as a | |
8152 | message before doing the test expansions. For example: | |
8153 | ||
8154 | exim -bem /tmp/test.message '$h_subject:' | |
8155 | ||
8156 | The -Mset option is used in conjunction with -be and is followed by an Exim | |
8157 | message identifier. For example: | |
8158 | ||
8159 | exim -be -Mset 1GrA8W-0004WS-LQ '$recipients' | |
8160 | ||
8161 | This loads the message from Exim's spool before doing the test expansions, and | |
8162 | is therefore restricted to admin users. | |
8163 | ||
8164 | ||
8165 | 11.4 Forced expansion failure | |
8166 | ----------------------------- | |
8167 | ||
8168 | A number of expansions that are described in the following section have | |
8169 | alternative "true" and "false" substrings, enclosed in brace characters (which | |
8170 | are sometimes called "curly brackets"). Which of the two strings is used | |
8171 | depends on some condition that is evaluated as part of the expansion. If, | |
8172 | instead of a "false" substring, the word "fail" is used (not in braces), the | |
8173 | entire string expansion fails in a way that can be detected by the code that | |
8174 | requested the expansion. This is called "forced expansion failure", and its | |
8175 | consequences depend on the circumstances. In some cases it is no different from | |
8176 | any other expansion failure, but in others a different action may be taken. | |
8177 | Such variations are mentioned in the documentation of the option that is being | |
8178 | expanded. | |
8179 | ||
8180 | ||
8181 | 11.5 Expansion items | |
8182 | -------------------- | |
8183 | ||
8184 | The following items are recognized in expanded strings. White space may be used | |
8185 | between sub-items that are keywords or substrings enclosed in braces inside an | |
8186 | outer set of braces, to improve readability. Warning: Within braces, white | |
8187 | space is significant. | |
8188 | ||
8189 | $<variable name> or ${<variable name>} | |
8190 | ||
8191 | Substitute the contents of the named variable, for example: | |
8192 | ||
8193 | $local_part | |
8194 | ${domain} | |
8195 | ||
8196 | The second form can be used to separate the name from subsequent | |
8197 | alphanumeric characters. This form (using braces) is available only for | |
8198 | variables; it does not apply to message headers. The names of the variables | |
8199 | are given in section 11.9 below. If the name of a non-existent variable is | |
8200 | given, the expansion fails. | |
8201 | ||
8202 | ${<op>:<string>} | |
8203 | ||
8204 | The string is first itself expanded, and then the operation specified by < | |
8205 | op> is applied to it. For example: | |
8206 | ||
8207 | ${lc:$local_part} | |
8208 | ||
8209 | The string starts with the first character after the colon, which may be | |
8210 | leading white space. A list of operators is given in section 11.6 below. | |
8211 | The operator notation is used for simple expansion items that have just one | |
8212 | argument, because it reduces the number of braces and therefore makes the | |
8213 | string easier to understand. | |
8214 | ||
8215 | $bheader_<header name>: or $bh_<header name>: | |
8216 | ||
8217 | This item inserts "basic" header lines. It is described with the header | |
8218 | expansion item below. | |
8219 | ||
8220 | ${acl{<name>}{<arg>}...} | |
8221 | ||
8222 | The name and zero to nine argument strings are first expanded separately. | |
8223 | The expanded arguments are assigned to the variables $acl_arg1 to $acl_arg9 | |
8224 | in order. Any unused are made empty. The variable $acl_narg is set to the | |
8225 | number of arguments. The named ACL (see chapter 42) is called and may use | |
8226 | the variables; if another acl expansion is used the values are restored | |
8227 | after it returns. If the ACL sets a value using a "message =" modifier and | |
8228 | returns accept or deny, the value becomes the result of the expansion. If | |
8229 | no message is set and the ACL returns accept or deny the expansion result | |
8230 | is an empty string. If the ACL returns defer the result is a forced-fail. | |
8231 | Otherwise the expansion fails. | |
8232 | ||
8233 | ${certextract{<field>}{<certificate>}{<string2>}{<string3>}} | |
8234 | ||
8235 | The <certificate> must be a variable of type certificate. The field name is | |
8236 | expanded and used to retrive the relevant field from the certificate. | |
8237 | Supported fields are: | |
8238 | ||
8239 | version | |
8240 | serial_number | |
8241 | subject RFC4514 DN | |
8242 | issuer RFC4514 DN | |
8243 | notbefore time | |
8244 | notafter time | |
8245 | sig_algorithm | |
8246 | signature | |
8247 | subj_altname tagged list | |
8248 | ocsp_uri list | |
8249 | crl_uri list | |
8250 | ||
8251 | If the field is found, <string2> is expanded, and replaces the whole item; | |
8252 | otherwise <string3> is used. During the expansion of <string2> the variable | |
8253 | $value contains the value that has been extracted. Afterwards, it is | |
8254 | restored to any previous value it might have had. | |
8255 | ||
8256 | If {<string3>} is omitted, the item is replaced by an empty string if the | |
8257 | key is not found. If {<string2>} is also omitted, the value that was | |
8258 | extracted is used. | |
8259 | ||
8260 | Some field names take optional modifiers, appended and separated by commas. | |
8261 | ||
8262 | The field selectors marked as "RFC4514" above output a Distinguished Name | |
8263 | string which is not quite parseable by Exim as a comma-separated tagged | |
8264 | list (the exceptions being elements containin commas). RDN elements of a | |
8265 | single type may be selected by a modifier of the type label; if so the | |
8266 | expansion result is a list (newline-separated by default). The separator | |
8267 | may be changed by another modifer of a right angle-bracket followed | |
8268 | immediately by the new separator. Recognised RDN type labels include "CN", | |
8269 | "O", "OU" and "DC". | |
8270 | ||
8271 | The field selectors marked as "time" above may output a number of seconds | |
8272 | since epoch if the modifier "int" is used. | |
8273 | ||
8274 | The field selectors marked as "list" above return a list, newline-separated | |
8275 | by default, (embedded separator characters in elements are doubled). The | |
8276 | separator may be changed by a modifier of a right angle-bracket followed | |
8277 | immediately by the new separator. | |
8278 | ||
8279 | The field selectors marked as "tagged" above prefix each list element with | |
8280 | a type string and an equals sign. Elements of only one type may be selected | |
8281 | by a modifier which is one of "dns", "uri" or "mail"; if so the elenment | |
8282 | tags are omitted. | |
8283 | ||
8284 | If not otherwise noted field values are presented in human-readable form. | |
8285 | ||
8286 | ${dlfunc{<file>}{<function>}{<arg>}{<arg>}...} | |
8287 | ||
8288 | This expansion dynamically loads and then calls a locally-written C | |
8289 | function. This functionality is available only if Exim is compiled with | |
8290 | ||
8291 | EXPAND_DLFUNC=yes | |
8292 | ||
8293 | set in Local/Makefile. Once loaded, Exim remembers the dynamically loaded | |
8294 | object so that it doesn't reload the same object file in the same Exim | |
8295 | process (but of course Exim does start new processes frequently). | |
8296 | ||
8297 | There may be from zero to eight arguments to the function. When compiling a | |
8298 | local function that is to be called in this way, local_scan.h should be | |
8299 | included. The Exim variables and functions that are defined by that API are | |
8300 | also available for dynamically loaded functions. The function itself must | |
8301 | have the following type: | |
8302 | ||
8303 | int dlfunction(uschar **yield, int argc, uschar *argv[]) | |
8304 | ||
8305 | Where "uschar" is a typedef for "unsigned char" in local_scan.h. The | |
8306 | function should return one of the following values: | |
8307 | ||
8308 | "OK": Success. The string that is placed in the variable yield is put into | |
8309 | the expanded string that is being built. | |
8310 | ||
8311 | "FAIL": A non-forced expansion failure occurs, with the error message taken | |
8312 | from yield, if it is set. | |
8313 | ||
8314 | "FAIL_FORCED": A forced expansion failure occurs, with the error message | |
8315 | taken from yield if it is set. | |
8316 | ||
8317 | "ERROR": Same as "FAIL", except that a panic log entry is written. | |
8318 | ||
8319 | When compiling a function that is to be used in this way with gcc, you need | |
8320 | to add -shared to the gcc command. Also, in the Exim build-time | |
8321 | configuration, you must add -export-dynamic to EXTRALIBS. | |
8322 | ||
8323 | ${extract{<key>}{<string1>}{<string2>}{<string3>}} | |
8324 | ||
8325 | The key and <string1> are first expanded separately. Leading and trailing | |
8326 | white space is removed from the key (but not from any of the strings). The | |
8327 | key must not consist entirely of digits. The expanded <string1> must be of | |
8328 | the form: | |
8329 | ||
8330 | <key1> = <value1> <key2> = <value2> ... | |
8331 | ||
8332 | where the equals signs and spaces (but not both) are optional. If any of | |
8333 | the values contain white space, they must be enclosed in double quotes, and | |
8334 | any values that are enclosed in double quotes are subject to escape | |
8335 | processing as described in section 6.16. The expanded <string1> is searched | |
8336 | for the value that corresponds to the key. The search is case-insensitive. | |
8337 | If the key is found, <string2> is expanded, and replaces the whole item; | |
8338 | otherwise <string3> is used. During the expansion of <string2> the variable | |
8339 | $value contains the value that has been extracted. Afterwards, it is | |
8340 | restored to any previous value it might have had. | |
8341 | ||
8342 | If {<string3>} is omitted, the item is replaced by an empty string if the | |
8343 | key is not found. If {<string2>} is also omitted, the value that was | |
8344 | extracted is used. Thus, for example, these two expansions are identical, | |
8345 | and yield "2001": | |
8346 | ||
8347 | ${extract{gid}{uid=1984 gid=2001}} | |
8348 | ${extract{gid}{uid=1984 gid=2001}{$value}} | |
8349 | ||
8350 | Instead of {<string3>} the word "fail" (not in curly brackets) can appear, | |
8351 | for example: | |
8352 | ||
8353 | ${extract{Z}{A=... B=...}{$value} fail } | |
8354 | ||
8355 | This forces an expansion failure (see section 11.4); {<string2>} must be | |
8356 | present for "fail" to be recognized. | |
8357 | ||
8358 | ${extract{<number>}{<separators>}{<string1>}{<string2>}{<string3>}} | |
8359 | ||
8360 | The <number> argument must consist entirely of decimal digits, apart from | |
8361 | leading and trailing white space, which is ignored. This is what | |
8362 | distinguishes this form of extract from the previous kind. It behaves in | |
8363 | the same way, except that, instead of extracting a named field, it extracts | |
8364 | from <string1> the field whose number is given as the first argument. You | |
8365 | can use $value in <string2> or "fail" instead of <string3> as before. | |
8366 | ||
8367 | The fields in the string are separated by any one of the characters in the | |
8368 | separator string. These may include space or tab characters. The first | |
8369 | field is numbered one. If the number is negative, the fields are counted | |
8370 | from the end of the string, with the rightmost one numbered -1. If the | |
8371 | number given is zero, the entire string is returned. If the modulus of the | |
8372 | number is greater than the number of fields in the string, the result is | |
8373 | the expansion of <string3>, or the empty string if <string3> is not | |
8374 | provided. For example: | |
8375 | ||
8376 | ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}} | |
8377 | ||
8378 | yields "42", and | |
8379 | ||
8380 | ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}} | |
8381 | ||
8382 | yields "99". Two successive separators mean that the field between them is | |
8383 | empty (for example, the fifth field above). | |
8384 | ||
8385 | ${filter{<string>}{<condition>}} | |
8386 | ||
8387 | After expansion, <string> is interpreted as a list, colon-separated by | |
8388 | default, but the separator can be changed in the usual way. For each item | |
8389 | in this list, its value is place in $item, and then the condition is | |
8390 | evaluated. If the condition is true, $item is added to the output as an | |
8391 | item in a new list; if the condition is false, the item is discarded. The | |
8392 | separator used for the output list is the same as the one used for the | |
8393 | input, but a separator setting is not included in the output. For example: | |
8394 | ||
8395 | ${filter{a:b:c}{!eq{$item}{b}} | |
8396 | ||
8397 | yields "a:c". At the end of the expansion, the value of $item is restored | |
8398 | to what it was before. See also the map and reduce expansion items. | |
8399 | ||
8400 | ${hash{<string1>}{<string2>}{<string3>}} | |
8401 | ||
8402 | This is a textual hashing function, and was the first to be implemented in | |
8403 | early versions of Exim. In current releases, there are other hashing | |
8404 | functions (numeric, MD5, and SHA-1), which are described below. | |
8405 | ||
8406 | The first two strings, after expansion, must be numbers. Call them <m> and | |
8407 | <n>. If you are using fixed values for these numbers, that is, if <string1> | |
8408 | and <string2> do not change when they are expanded, you can use the simpler | |
8409 | operator notation that avoids some of the braces: | |
8410 | ||
8411 | ${hash_<n>_<m>:<string>} | |
8412 | ||
8413 | The second number is optional (in both notations). If <n> is greater than | |
8414 | or equal to the length of the string, the expansion item returns the | |
8415 | string. Otherwise it computes a new string of length <n> by applying a | |
8416 | hashing function to the string. The new string consists of characters taken | |
8417 | from the first <m> characters of the string | |
8418 | ||
8419 | abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789 | |
8420 | ||
8421 | If <m> is not present the value 26 is used, so that only lower case letters | |
8422 | appear. For example: | |
8423 | ||
8424 | $hash{3}{monty}} yields jmg | |
8425 | $hash{5}{monty}} yields monty | |
8426 | $hash{4}{62}{monty python}} yields fbWx | |
8427 | ||
8428 | $header_<header name>: or $h_<header name>:, $bheader_<header name>: or $bh_< | |
8429 | header name>:, $rheader_<header name>: or $rh_<header name>: | |
8430 | ||
8431 | Substitute the contents of the named message header line, for example | |
8432 | ||
8433 | $header_reply-to: | |
8434 | ||
8435 | The newline that terminates a header line is not included in the expansion, | |
8436 | but internal newlines (caused by splitting the header line over several | |
8437 | physical lines) may be present. | |
8438 | ||
8439 | The difference between rheader, bheader, and header is in the way the data | |
8440 | in the header line is interpreted. | |
8441 | ||
8442 | * rheader gives the original "raw" content of the header line, with no | |
8443 | processing at all, and without the removal of leading and trailing | |
8444 | white space. | |
8445 | ||
8446 | * bheader removes leading and trailing white space, and then decodes | |
8447 | base64 or quoted-printable MIME "words" within the header text, but | |
8448 | does no character set translation. If decoding of what looks | |
8449 | superficially like a MIME "word" fails, the raw string is returned. If | |
8450 | decoding produces a binary zero character, it is replaced by a question | |
8451 | mark - this is what Exim does for binary zeros that are actually | |
8452 | received in header lines. | |
8453 | ||
8454 | * header tries to translate the string as decoded by bheader to a | |
8455 | standard character set. This is an attempt to produce the same string | |
8456 | as would be displayed on a user's MUA. If translation fails, the | |
8457 | bheader string is returned. Translation is attempted only on operating | |
8458 | systems that support the iconv() function. This is indicated by the | |
8459 | compile-time macro HAVE_ICONV in a system Makefile or in Local/Makefile | |
8460 | . | |
8461 | ||
8462 | In a filter file, the target character set for header can be specified by a | |
8463 | command of the following form: | |
8464 | ||
8465 | headers charset "UTF-8" | |
8466 | ||
8467 | This command affects all references to $h_ (or $header_) expansions in | |
8468 | subsequently obeyed filter commands. In the absence of this command, the | |
8469 | target character set in a filter is taken from the setting of the | |
8470 | headers_charset option in the runtime configuration. The value of this | |
8471 | option defaults to the value of HEADERS_CHARSET in Local/Makefile. The | |
8472 | ultimate default is ISO-8859-1. | |
8473 | ||
8474 | Header names follow the syntax of RFC 2822, which states that they may | |
8475 | contain any printing characters except space and colon. Consequently, curly | |
8476 | brackets do not terminate header names, and should not be used to enclose | |
8477 | them as if they were variables. Attempting to do so causes a syntax error. | |
8478 | ||
8479 | Only header lines that are common to all copies of a message are visible to | |
8480 | this mechanism. These are the original header lines that are received with | |
8481 | the message, and any that are added by an ACL statement or by a system | |
8482 | filter. Header lines that are added to a particular copy of a message by a | |
8483 | router or transport are not accessible. | |
8484 | ||
8485 | For incoming SMTP messages, no header lines are visible in ACLs that are | |
8486 | obeyed before the DATA ACL, because the header structure is not set up | |
8487 | until the message is received. Header lines that are added in a RCPT ACL | |
8488 | (for example) are saved until the message's incoming header lines are | |
8489 | available, at which point they are added. When a DATA ACL is running, | |
8490 | however, header lines added by earlier ACLs are visible. | |
8491 | ||
8492 | Upper case and lower case letters are synonymous in header names. If the | |
8493 | following character is white space, the terminating colon may be omitted, | |
8494 | but this is not recommended, because you may then forget it when it is | |
8495 | needed. When white space terminates the header name, it is included in the | |
8496 | expanded string. If the message does not contain the given header, the | |
8497 | expansion item is replaced by an empty string. (See the def condition in | |
8498 | section 11.7 for a means of testing for the existence of a header.) | |
8499 | ||
8500 | If there is more than one header with the same name, they are all | |
8501 | concatenated to form the substitution string, up to a maximum length of | |
8502 | 64K. Unless rheader is being used, leading and trailing white space is | |
8503 | removed from each header before concatenation, and a completely empty | |
8504 | header is ignored. A newline character is then inserted between non-empty | |
8505 | headers, but there is no newline at the very end. For the header and | |
8506 | bheader expansion, for those headers that contain lists of addresses, a | |
8507 | comma is also inserted at the junctions between headers. This does not | |
8508 | happen for the rheader expansion. | |
8509 | ||
8510 | ${hmac{<hashname>}{<secret>}{<string>}} | |
8511 | ||
8512 | This function uses cryptographic hashing (either MD5 or SHA-1) to convert a | |
8513 | shared secret and some text into a message authentication code, as | |
8514 | specified in RFC 2104. This differs from "${md5:secret_text...}" or "$ | |
8515 | {sha1:secret_text...}" in that the hmac step adds a signature to the | |
8516 | cryptographic hash, allowing for authentication that is not possible with | |
8517 | MD5 or SHA-1 alone. The hash name must expand to either "md5" or "sha1" at | |
8518 | present. For example: | |
8519 | ||
8520 | ${hmac{md5}{somesecret}{$primary_hostname $tod_log}} | |
8521 | ||
8522 | For the hostname mail.example.com and time 2002-10-17 11:30:59, this | |
8523 | produces: | |
8524 | ||
8525 | dd97e3ba5d1a61b5006108f8c8252953 | |
8526 | ||
8527 | As an example of how this might be used, you might put in the main part of | |
8528 | an Exim configuration: | |
8529 | ||
8530 | SPAMSCAN_SECRET=cohgheeLei2thahw | |
8531 | ||
8532 | In a router or a transport you could then have: | |
8533 | ||
8534 | headers_add = \ | |
8535 | X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \ | |
8536 | ${hmac{md5}{SPAMSCAN_SECRET}\ | |
8537 | {${primary_hostname},${message_exim_id},$h_message-id:}} | |
8538 | ||
8539 | Then given a message, you can check where it was scanned by looking at the | |
8540 | X-Spam-Scanned: header line. If you know the secret, you can check that | |
8541 | this header line is authentic by recomputing the authentication code from | |
8542 | the host name, message ID and the Message-id: header line. This can be done | |
8543 | using Exim's -be option, or by other means, for example by using the | |
8544 | hmac_md5_hex() function in Perl. | |
8545 | ||
8546 | ${if <condition> {<string1>}{<string2>}} | |
8547 | ||
8548 | If <condition> is true, <string1> is expanded and replaces the whole item; | |
8549 | otherwise <string2> is used. The available conditions are described in | |
8550 | section 11.7 below. For example: | |
8551 | ||
8552 | ${if eq {$local_part}{postmaster} {yes}{no} } | |
8553 | ||
8554 | The second string need not be present; if it is not and the condition is | |
8555 | not true, the item is replaced with nothing. Alternatively, the word "fail" | |
8556 | may be present instead of the second string (without any curly brackets). | |
8557 | In this case, the expansion is forced to fail if the condition is not true | |
8558 | (see section 11.4). | |
8559 | ||
8560 | If both strings are omitted, the result is the string "true" if the | |
8561 | condition is true, and the empty string if the condition is false. This | |
8562 | makes it less cumbersome to write custom ACL and router conditions. For | |
8563 | example, instead of | |
8564 | ||
8565 | condition = ${if >{$acl_m4}{3}{true}{false}} | |
8566 | ||
8567 | you can use | |
8568 | ||
8569 | condition = ${if >{$acl_m4}{3}} | |
8570 | ||
8571 | ${length{<string1>}{<string2>}} | |
8572 | ||
8573 | The length item is used to extract the initial portion of a string. Both | |
8574 | strings are expanded, and the first one must yield a number, <n>, say. If | |
8575 | you are using a fixed value for the number, that is, if <string1> does not | |
8576 | change when expanded, you can use the simpler operator notation that avoids | |
8577 | some of the braces: | |
8578 | ||
8579 | ${length_<n>:<string>} | |
8580 | ||
8581 | The result of this item is either the first <n> characters or the whole of | |
8582 | <string2>, whichever is the shorter. Do not confuse length with strlen, | |
8583 | which gives the length of a string. | |
8584 | ||
8585 | ${listextract{<number>}{<string1>}{<string2>}{<string3>}} | |
8586 | ||
8587 | The <number> argument must consist entirely of decimal digits, apart from | |
8588 | an optional leading minus, and leading and trailing white space (which is | |
8589 | ignored). | |
8590 | ||
8591 | After expansion, <string1> is interpreted as a list, colon-separated by | |
8592 | default, but the separator can be changed in the usual way. | |
8593 | ||
8594 | The first field of the list is numbered one. If the number is negative, the | |
8595 | fields are counted from the end of the list, with the rightmost one | |
8596 | numbered -1. The numbered element of the list is extracted and placed in | |
8597 | $value, then <string2> is expanded as the result. | |
8598 | ||
8599 | If the modulus of the number is zero or greater than the number of fields | |
8600 | in the string, the result is the expansion of <string3>. | |
8601 | ||
8602 | For example: | |
8603 | ||
8604 | ${listextract{2}{x:42:99}} | |
8605 | ||
8606 | yields "42", and | |
8607 | ||
8608 | ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}} | |
8609 | ||
8610 | yields "result: 99". | |
8611 | ||
8612 | If {<string3>} is omitted, an empty string is used for string3. If {< | |
8613 | string2>} is also omitted, the value that was extracted is used. You can | |
8614 | use "fail" instead of {<string3>} as in a string extract. | |
8615 | ||
8616 | ${lookup{<key>} <search type> {<file>} {<string1>} {<string2>}} | |
8617 | ||
8618 | This is the first of one of two different types of lookup item, which are | |
8619 | both described in the next item. | |
8620 | ||
8621 | ${lookup <search type> {<query>} {<string1>} {<string2>}} | |
8622 | ||
8623 | The two forms of lookup item specify data lookups in files and databases, | |
8624 | as discussed in chapter 9. The first form is used for single-key lookups, | |
8625 | and the second is used for query-style lookups. The <key>, <file>, and < | |
8626 | query> strings are expanded before use. | |
8627 | ||
8628 | If there is any white space in a lookup item which is part of a filter | |
8629 | command, a retry or rewrite rule, a routing rule for the manualroute | |
8630 | router, or any other place where white space is significant, the lookup | |
8631 | item must be enclosed in double quotes. The use of data lookups in users' | |
8632 | filter files may be locked out by the system administrator. | |
8633 | ||
8634 | If the lookup succeeds, <string1> is expanded and replaces the entire item. | |
8635 | During its expansion, the variable $value contains the data returned by the | |
8636 | lookup. Afterwards it reverts to the value it had previously (at the outer | |
8637 | level it is empty). If the lookup fails, <string2> is expanded and replaces | |
8638 | the entire item. If {<string2>} is omitted, the replacement is the empty | |
8639 | string on failure. If <string2> is provided, it can itself be a nested | |
8640 | lookup, thus providing a mechanism for looking up a default value when the | |
8641 | original lookup fails. | |
8642 | ||
8643 | If a nested lookup is used as part of <string1>, $value contains the data | |
8644 | for the outer lookup while the parameters of the second lookup are | |
8645 | expanded, and also while <string2> of the second lookup is expanded, should | |
8646 | the second lookup fail. Instead of {<string2>} the word "fail" can appear, | |
8647 | and in this case, if the lookup fails, the entire expansion is forced to | |
8648 | fail (see section 11.4). If both {<string1>} and {<string2>} are omitted, | |
8649 | the result is the looked up value in the case of a successful lookup, and | |
8650 | nothing in the case of failure. | |
8651 | ||
8652 | For single-key lookups, the string "partial" is permitted to precede the | |
8653 | search type in order to do partial matching, and * or *@ may follow a | |
8654 | search type to request default lookups if the key does not match (see | |
8655 | sections 9.6 and 9.7 for details). | |
8656 | ||
8657 | If a partial search is used, the variables $1 and $2 contain the wild and | |
8658 | non-wild parts of the key during the expansion of the replacement text. | |
8659 | They return to their previous values at the end of the lookup item. | |
8660 | ||
8661 | This example looks up the postmaster alias in the conventional alias file: | |
8662 | ||
8663 | ${lookup {postmaster} lsearch {/etc/aliases} {$value}} | |
8664 | ||
8665 | This example uses NIS+ to look up the full name of the user corresponding | |
8666 | to the local part of an address, forcing the expansion to fail if it is not | |
8667 | found: | |
8668 | ||
8669 | ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \ | |
8670 | {$value}fail} | |
8671 | ||
8672 | ${map{<string1>}{<string2>}} | |
8673 | ||
8674 | After expansion, <string1> is interpreted as a list, colon-separated by | |
8675 | default, but the separator can be changed in the usual way. For each item | |
8676 | in this list, its value is place in $item, and then <string2> is expanded | |
8677 | and added to the output as an item in a new list. The separator used for | |
8678 | the output list is the same as the one used for the input, but a separator | |
8679 | setting is not included in the output. For example: | |
8680 | ||
8681 | ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}} | |
8682 | ||
8683 | expands to "[a]:[b]:[c] (x)-(y)-(z)". At the end of the expansion, the | |
8684 | value of $item is restored to what it was before. See also the filter and | |
8685 | reduce expansion items. | |
8686 | ||
8687 | ${nhash{<string1>}{<string2>}{<string3>}} | |
8688 | ||
8689 | The three strings are expanded; the first two must yield numbers. Call them | |
8690 | <n> and <m>. If you are using fixed values for these numbers, that is, if < | |
8691 | string1> and <string2> do not change when they are expanded, you can use | |
8692 | the simpler operator notation that avoids some of the braces: | |
8693 | ||
8694 | ${nhash_<n>_<m>:<string>} | |
8695 | ||
8696 | The second number is optional (in both notations). If there is only one | |
8697 | number, the result is a number in the range 0-<n>-1. Otherwise, the string | |
8698 | is processed by a div/mod hash function that returns two numbers, separated | |
8699 | by a slash, in the ranges 0 to <n>-1 and 0 to <m>-1, respectively. For | |
8700 | example, | |
8701 | ||
8702 | ${nhash{8}{64}{supercalifragilisticexpialidocious}} | |
8703 | ||
8704 | returns the string "6/33". | |
8705 | ||
8706 | ${perl{<subroutine>}{<arg>}{<arg>}...} | |
8707 | ||
8708 | This item is available only if Exim has been built to include an embedded | |
8709 | Perl interpreter. The subroutine name and the arguments are first | |
8710 | separately expanded, and then the Perl subroutine is called with those | |
8711 | arguments. No additional arguments need be given; the maximum number | |
8712 | permitted, including the name of the subroutine, is nine. | |
8713 | ||
8714 | The return value of the subroutine is inserted into the expanded string, | |
8715 | unless the return value is undef. In that case, the expansion fails in the | |
8716 | same way as an explicit "fail" on a lookup item. The return value is a | |
8717 | scalar. Whatever you return is evaluated in a scalar context. For example, | |
8718 | if you return the name of a Perl vector, the return value is the size of | |
8719 | the vector, not its contents. | |
8720 | ||
8721 | If the subroutine exits by calling Perl's die function, the expansion fails | |
8722 | with the error message that was passed to die. More details of the embedded | |
8723 | Perl facility are given in chapter 12. | |
8724 | ||
8725 | The redirect router has an option called forbid_filter_perl which locks out | |
8726 | the use of this expansion item in filter files. | |
8727 | ||
8728 | ${prvs{<address>}{<secret>}{<keynumber>}} | |
8729 | ||
8730 | The first argument is a complete email address and the second is secret | |
8731 | keystring. The third argument, specifying a key number, is optional. If | |
8732 | absent, it defaults to 0. The result of the expansion is a prvs-signed | |
8733 | email address, to be typically used with the return_path option on an smtp | |
8734 | transport as part of a bounce address tag validation (BATV) scheme. For | |
8735 | more discussion and an example, see section 42.51. | |
8736 | ||
8737 | ${prvscheck{<address>}{<secret>}{<string>}} | |
8738 | ||
8739 | This expansion item is the complement of the prvs item. It is used for | |
8740 | checking prvs-signed addresses. If the expansion of the first argument does | |
8741 | not yield a syntactically valid prvs-signed address, the whole item expands | |
8742 | to the empty string. When the first argument does expand to a syntactically | |
8743 | valid prvs-signed address, the second argument is expanded, with the | |
8744 | prvs-decoded version of the address and the key number extracted from the | |
8745 | address in the variables $prvscheck_address and $prvscheck_keynum, | |
8746 | respectively. | |
8747 | ||
8748 | These two variables can be used in the expansion of the second argument to | |
8749 | retrieve the secret. The validity of the prvs-signed address is then | |
8750 | checked against the secret. The result is stored in the variable | |
8751 | $prvscheck_result, which is empty for failure or "1" for success. | |
8752 | ||
8753 | The third argument is optional; if it is missing, it defaults to an empty | |
8754 | string. This argument is now expanded. If the result is an empty string, | |
8755 | the result of the expansion is the decoded version of the address. This is | |
8756 | the case whether or not the signature was valid. Otherwise, the result of | |
8757 | the expansion is the expansion of the third argument. | |
8758 | ||
8759 | All three variables can be used in the expansion of the third argument. | |
8760 | However, once the expansion is complete, only $prvscheck_result remains | |
8761 | set. For more discussion and an example, see section 42.51. | |
8762 | ||
8763 | ${readfile{<file name>}{<eol string>}} | |
8764 | ||
8765 | The file name and end-of-line string are first expanded separately. The | |
8766 | file is then read, and its contents replace the entire item. All newline | |
8767 | characters in the file are replaced by the end-of-line string if it is | |
8768 | present. Otherwise, newlines are left in the string. String expansion is | |
8769 | not applied to the contents of the file. If you want this, you must wrap | |
8770 | the item in an expand operator. If the file cannot be read, the string | |
8771 | expansion fails. | |
8772 | ||
8773 | The redirect router has an option called forbid_filter_readfile which locks | |
8774 | out the use of this expansion item in filter files. | |
8775 | ||
8776 | ${readsocket{<name>}{<request>}{<timeout>}{<eol string>}{<fail string>}} | |
8777 | ||
8778 | This item inserts data from a Unix domain or Internet socket into the | |
8779 | expanded string. The minimal way of using it uses just two arguments, as in | |
8780 | these examples: | |
8781 | ||
8782 | ${readsocket{/socket/name}{request string}} | |
8783 | ${readsocket{inet:some.host:1234}{request string}} | |
8784 | ||
8785 | For a Unix domain socket, the first substring must be the path to the | |
8786 | socket. For an Internet socket, the first substring must contain "inet:" | |
8787 | followed by a host name or IP address, followed by a colon and a port, | |
8788 | which can be a number or the name of a TCP port in /etc/services. An IP | |
8789 | address may optionally be enclosed in square brackets. This is best for | |
8790 | IPv6 addresses. For example: | |
8791 | ||
8792 | ${readsocket{inet:[::1]:1234}{request string}} | |
8793 | ||
8794 | Only a single host name may be given, but if looking it up yields more than | |
8795 | one IP address, they are each tried in turn until a connection is made. For | |
8796 | both kinds of socket, Exim makes a connection, writes the request string | |
8797 | (unless it is an empty string) and reads from the socket until an | |
8798 | end-of-file is read. A timeout of 5 seconds is applied. Additional, | |
8799 | optional arguments extend what can be done. Firstly, you can vary the | |
8800 | timeout. For example: | |
8801 | ||
8802 | ${readsocket{/socket/name}{request string}{3s}} | |
8803 | ||
8804 | A fourth argument allows you to change any newlines that are in the data | |
8805 | that is read, in the same way as for readfile (see above). This example | |
8806 | turns them into spaces: | |
8807 | ||
8808 | ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }} | |
8809 | ||
8810 | As with all expansions, the substrings are expanded before the processing | |
8811 | happens. Errors in these sub-expansions cause the expansion to fail. In | |
8812 | addition, the following errors can occur: | |
8813 | ||
8814 | * Failure to create a socket file descriptor; | |
8815 | ||
8816 | * Failure to connect the socket; | |
8817 | ||
8818 | * Failure to write the request string; | |
8819 | ||
8820 | * Timeout on reading from the socket. | |
8821 | ||
8822 | By default, any of these errors causes the expansion to fail. However, if | |
8823 | you supply a fifth substring, it is expanded and used when any of the above | |
8824 | errors occurs. For example: | |
8825 | ||
8826 | ${readsocket{/socket/name}{request string}{3s}{\n}\ | |
8827 | {socket failure}} | |
8828 | ||
8829 | You can test for the existence of a Unix domain socket by wrapping this | |
8830 | expansion in "${if exists", but there is a race condition between that test | |
8831 | and the actual opening of the socket, so it is safer to use the fifth | |
8832 | argument if you want to be absolutely sure of avoiding an expansion error | |
8833 | for a non-existent Unix domain socket, or a failure to connect to an | |
8834 | Internet socket. | |
8835 | ||
8836 | The redirect router has an option called forbid_filter_readsocket which | |
8837 | locks out the use of this expansion item in filter files. | |
8838 | ||
8839 | ${reduce{<string1>}{<string2>}{<string3>}} | |
8840 | ||
8841 | This operation reduces a list to a single, scalar string. After expansion, | |
8842 | <string1> is interpreted as a list, colon-separated by default, but the | |
8843 | separator can be changed in the usual way. Then <string2> is expanded and | |
8844 | assigned to the $value variable. After this, each item in the <string1> | |
8845 | list is assigned to $item in turn, and <string3> is expanded for each of | |
8846 | them. The result of that expansion is assigned to $value before the next | |
8847 | iteration. When the end of the list is reached, the final value of $value | |
8848 | is added to the expansion output. The reduce expansion item can be used in | |
8849 | a number of ways. For example, to add up a list of numbers: | |
8850 | ||
8851 | ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}} | |
8852 | ||
8853 | The result of that expansion would be "6". The maximum of a list of numbers | |
8854 | can be found: | |
8855 | ||
8856 | ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}} | |
8857 | ||
8858 | At the end of a reduce expansion, the values of $item and $value are | |
8859 | restored to what they were before. See also the filter and map expansion | |
8860 | items. | |
8861 | ||
8862 | $rheader_<header name>: or $rh_<header name>: | |
8863 | ||
8864 | This item inserts "raw" header lines. It is described with the header | |
8865 | expansion item above. | |
8866 | ||
8867 | ${run{<command> <args>}{<string1>}{<string2>}} | |
8868 | ||
8869 | The command and its arguments are first expanded as one string. The string | |
8870 | is split apart into individual arguments by spaces, and then the command is | |
8871 | run in a separate process, but under the same uid and gid. As in other | |
8872 | command executions from Exim, a shell is not used by default. If the | |
8873 | command requires a shell, you must explicitly code it. | |
8874 | ||
8875 | Since the arguments are split by spaces, when there is a variable expansion | |
8876 | which has an empty result, it will cause the situation that the argument | |
8877 | will simply be omitted when the program is actually executed by Exim. If | |
8878 | the script/program requires a specific number of arguments and the expanded | |
8879 | variable could possibly result in this empty expansion, the variable must | |
8880 | be quoted. This is more difficult if the expanded variable itself could | |
8881 | result in a string containing quotes, because it would interfere with the | |
8882 | quotes around the command arguments. A possible guard against this is to | |
8883 | wrap the variable in the sg operator to change any quote marks to some | |
8884 | other character. | |
8885 | ||
8886 | The standard input for the command exists, but is empty. The standard | |
8887 | output and standard error are set to the same file descriptor. If the | |
8888 | command succeeds (gives a zero return code) <string1> is expanded and | |
8889 | replaces the entire item; during this expansion, the standard output/error | |
8890 | from the command is in the variable $value. If the command fails, <string2 | |
8891 | >, if present, is expanded and used. Once again, during the expansion, the | |
8892 | standard output/error from the command is in the variable $value. | |
8893 | ||
8894 | If <string2> is absent, the result is empty. Alternatively, <string2> can | |
8895 | be the word "fail" (not in braces) to force expansion failure if the | |
8896 | command does not succeed. If both strings are omitted, the result is | |
8897 | contents of the standard output/error on success, and nothing on failure. | |
8898 | ||
8899 | The standard output/error of the command is put in the variable $value. In | |
8900 | this ACL example, the output of a command is logged for the admin to | |
8901 | troubleshoot: | |
8902 | ||
8903 | warn condition = ${run{/usr/bin/id}{yes}{no}} | |
8904 | log_message = Output of id: $value | |
8905 | ||
8906 | If the command requires shell idioms, such as the > redirect operator, the | |
8907 | shell must be invoked directly, such as with: | |
8908 | ||
8909 | ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}} | |
8910 | ||
8911 | The return code from the command is put in the variable $runrc, and this | |
8912 | remains set afterwards, so in a filter file you can do things like this: | |
8913 | ||
8914 | if "${run{x y z}{}}$runrc" is 1 then ... | |
8915 | elif $runrc is 2 then ... | |
8916 | ... | |
8917 | endif | |
8918 | ||
8919 | If execution of the command fails (for example, the command does not | |
8920 | exist), the return code is 127 - the same code that shells use for | |
8921 | non-existent commands. | |
8922 | ||
8923 | Warning: In a router or transport, you cannot assume the order in which | |
8924 | option values are expanded, except for those preconditions whose order of | |
8925 | testing is documented. Therefore, you cannot reliably expect to set $runrc | |
8926 | by the expansion of one option, and use it in another. | |
8927 | ||
8928 | The redirect router has an option called forbid_filter_run which locks out | |
8929 | the use of this expansion item in filter files. | |
8930 | ||
8931 | ${sg{<subject>}{<regex>}{<replacement>}} | |
8932 | ||
8933 | This item works like Perl's substitution operator (s) with the global (/g) | |
8934 | option; hence its name. However, unlike the Perl equivalent, Exim does not | |
8935 | modify the subject string; instead it returns the modified string for | |
8936 | insertion into the overall expansion. The item takes three arguments: the | |
8937 | subject string, a regular expression, and a substitution string. For | |
8938 | example: | |
8939 | ||
8940 | ${sg{abcdefabcdef}{abc}{xyz}} | |
8941 | ||
8942 | yields "xyzdefxyzdef". Because all three arguments are expanded before use, | |
8943 | if any $ or \ characters are required in the regular expression or in the | |
8944 | substitution string, they have to be escaped. For example: | |
8945 | ||
8946 | ${sg{abcdef}{^(...)(...)\$}{\$2\$1}} | |
8947 | ||
8948 | yields "defabc", and | |
8949 | ||
8950 | ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}} | |
8951 | ||
8952 | yields "K1=A K4=D K3=C". Note the use of "\N" to protect the contents of | |
8953 | the regular expression from string expansion. | |
8954 | ||
8955 | ${substr{<string1>}{<string2>}{<string3>}} | |
8956 | ||
8957 | The three strings are expanded; the first two must yield numbers. Call them | |
8958 | <n> and <m>. If you are using fixed values for these numbers, that is, if < | |
8959 | string1> and <string2> do not change when they are expanded, you can use | |
8960 | the simpler operator notation that avoids some of the braces: | |
8961 | ||
8962 | ${substr_<n>_<m>:<string>} | |
8963 | ||
8964 | The second number is optional (in both notations). If it is absent in the | |
8965 | simpler format, the preceding underscore must also be omitted. | |
8966 | ||
8967 | The substr item can be used to extract more general substrings than length. | |
8968 | The first number, <n>, is a starting offset, and <m> is the length | |
8969 | required. For example | |
8970 | ||
8971 | ${substr{3}{2}{$local_part}} | |
8972 | ||
8973 | If the starting offset is greater than the string length the result is the | |
8974 | null string; if the length plus starting offset is greater than the string | |
8975 | length, the result is the right-hand part of the string, starting from the | |
8976 | given offset. The first character in the string has offset zero. | |
8977 | ||
8978 | The substr expansion item can take negative offset values to count from the | |
8979 | right-hand end of its operand. The last character is offset -1, the | |
8980 | second-last is offset -2, and so on. Thus, for example, | |
8981 | ||
8982 | ${substr{-5}{2}{1234567}} | |
8983 | ||
8984 | yields "34". If the absolute value of a negative offset is greater than the | |
8985 | length of the string, the substring starts at the beginning of the string, | |
8986 | and the length is reduced by the amount of overshoot. Thus, for example, | |
8987 | ||
8988 | ${substr{-5}{2}{12}} | |
8989 | ||
8990 | yields an empty string, but | |
8991 | ||
8992 | ${substr{-3}{2}{12}} | |
8993 | ||
8994 | yields "1". | |
8995 | ||
8996 | When the second number is omitted from substr, the remainder of the string | |
8997 | is taken if the offset is positive. If it is negative, all characters in | |
8998 | the string preceding the offset point are taken. For example, an offset of | |
8999 | -1 and no length, as in these semantically identical examples: | |
9000 | ||
9001 | ${substr_-1:abcde} | |
9002 | ${substr{-1}{abcde}} | |
9003 | ||
9004 | yields all but the last character of the string, that is, "abcd". | |
9005 | ||
9006 | ${tr{<subject>}{<characters>}{<replacements>}} | |
9007 | ||
9008 | This item does single-character translation on its subject string. The | |
9009 | second argument is a list of characters to be translated in the subject | |
9010 | string. Each matching character is replaced by the corresponding character | |
9011 | from the replacement list. For example | |
9012 | ||
9013 | ${tr{abcdea}{ac}{13}} | |
9014 | ||
9015 | yields "1b3de1". If there are duplicates in the second character string, | |
9016 | the last occurrence is used. If the third string is shorter than the | |
9017 | second, its last character is replicated. However, if it is empty, no | |
9018 | translation takes place. | |
9019 | ||
9020 | ||
9021 | 11.6 Expansion operators | |
9022 | ------------------------ | |
9023 | ||
9024 | For expansion items that perform transformations on a single argument string, | |
9025 | the "operator" notation is used because it is simpler and uses fewer braces. | |
9026 | The substring is first expanded before the operation is applied to it. The | |
9027 | following operations can be performed: | |
9028 | ||
9029 | ${address:<string>} | |
9030 | ||
9031 | The string is interpreted as an RFC 2822 address, as it might appear in a | |
9032 | header line, and the effective address is extracted from it. If the string | |
9033 | does not parse successfully, the result is empty. | |
9034 | ||
9035 | ${addresses:<string>} | |
9036 | ||
9037 | The string (after expansion) is interpreted as a list of addresses in RFC | |
9038 | 2822 format, such as can be found in a To: or Cc: header line. The | |
9039 | operative address (local-part@domain) is extracted from each item, and the | |
9040 | result of the expansion is a colon-separated list, with appropriate | |
9041 | doubling of colons should any happen to be present in the email addresses. | |
9042 | Syntactically invalid RFC2822 address items are omitted from the output. | |
9043 | ||
9044 | It is possible to specify a character other than colon for the output | |
9045 | separator by starting the string with > followed by the new separator | |
9046 | character. For example: | |
9047 | ||
9048 | ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)} | |
9049 | ||
9050 | expands to "ceo@up.stairs&sec@base.ment". Compare the address (singular) | |
9051 | expansion item, which extracts the working address from a single RFC2822 | |
9052 | address. See the filter, map, and reduce items for ways of processing | |
9053 | lists. | |
9054 | ||
9055 | To clarify "list of addresses in RFC 2822 format" mentioned above, Exim | |
9056 | follows a strict interpretation of header line formatting. Exim parses the | |
9057 | bare, unquoted portion of an email address and if it finds a comma, treats | |
9058 | it as an email address seperator. For the example header line: | |
9059 | ||
9060 | From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com> | |
9061 | ||
9062 | The first example below demonstrates that Q-encoded email addresses are | |
9063 | parsed properly if it is given the raw header (in this example, | |
9064 | "$rheader_from:"). It does not see the comma because it's still encoded as | |
9065 | "=2C". The second example below is passed the contents of "$header_from:", | |
9066 | meaning it gets de-mimed. Exim sees the decoded "," so it treats it as two | |
9067 | email addresses. The third example shows that the presence of a comma is | |
9068 | skipped when it is quoted. | |
9069 | ||
9070 | # exim -be '${addresses:From: \ | |
9071 | =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}' | |
9072 | user@example.com | |
9073 | # exim -be '${addresses:From: Last, First <user@example.com>}' | |
9074 | Last:user@example.com | |
9075 | # exim -be '${addresses:From: "Last, First" <user@example.com>}' | |
9076 | user@example.com | |
9077 | ||
9078 | ${base62:<digits>} | |
9079 | ||
9080 | The string must consist entirely of decimal digits. The number is converted | |
9081 | to base 62 and output as a string of six characters, including leading | |
9082 | zeros. In the few operating environments where Exim uses base 36 instead of | |
9083 | base 62 for its message identifiers (because those systems do not have | |
9084 | case-sensitive file names), base 36 is used by this operator, despite its | |
9085 | name. Note: Just to be absolutely clear: this is not base64 encoding. | |
9086 | ||
9087 | ${base62d:<base-62 digits>} | |
9088 | ||
9089 | The string must consist entirely of base-62 digits, or, in operating | |
9090 | environments where Exim uses base 36 instead of base 62 for its message | |
9091 | identifiers, base-36 digits. The number is converted to decimal and output | |
9092 | as a string. | |
9093 | ||
9094 | ${domain:<string>} | |
9095 | ||
9096 | The string is interpreted as an RFC 2822 address and the domain is | |
9097 | extracted from it. If the string does not parse successfully, the result is | |
9098 | empty. | |
9099 | ||
9100 | ${escape:<string>} | |
9101 | ||
9102 | If the string contains any non-printing characters, they are converted to | |
9103 | escape sequences starting with a backslash. Whether characters with the | |
9104 | most significant bit set (so-called "8-bit characters") count as printing | |
9105 | or not is controlled by the print_topbitchars option. | |
9106 | ||
9107 | ${eval:<string>} and ${eval10:<string>} | |
9108 | ||
9109 | These items supports simple arithmetic and bitwise logical operations in | |
9110 | expansion strings. The string (after expansion) must be a conventional | |
9111 | arithmetic expression, but it is limited to basic arithmetic operators, | |
9112 | bitwise logical operators, and parentheses. All operations are carried out | |
9113 | using integer arithmetic. The operator priorities are as follows (the same | |
9114 | as in the C programming language): | |
9115 | ||
9116 | highest: not (~), negate (-) | |
9117 | multiply (*), divide (/), remainder (%) | |
9118 | plus (+), minus (-) | |
9119 | shift-left (<<), shift-right (>>) | |
9120 | and (&) | |
9121 | xor (^) | |
9122 | lowest: or (|) | |
9123 | ||
9124 | Binary operators with the same priority are evaluated from left to right. | |
9125 | White space is permitted before or after operators. | |
9126 | ||
9127 | For eval, numbers may be decimal, octal (starting with "0") or hexadecimal | |
9128 | (starting with "0x"). For eval10, all numbers are taken as decimal, even if | |
9129 | they start with a leading zero; hexadecimal numbers are not permitted. This | |
9130 | can be useful when processing numbers extracted from dates or times, which | |
9131 | often do have leading zeros. | |
9132 | ||
9133 | A number may be followed by "K", "M" or "G" to multiply it by 1024, | |
9134 | 1024*1024 or 1024*1024*1024, respectively. Negative numbers are supported. | |
9135 | The result of the computation is a decimal representation of the answer | |
9136 | (without "K", "M" or "G"). For example: | |
9137 | ||
9138 | ${eval:1+1} yields 2 | |
9139 | ${eval:1+2*3} yields 7 | |
9140 | ${eval:(1+2)*3} yields 9 | |
9141 | ${eval:2+42%5} yields 4 | |
9142 | ${eval:0xc&5} yields 4 | |
9143 | ${eval:0xc|5} yields 13 | |
9144 | ${eval:0xc^5} yields 9 | |
9145 | ${eval:0xc>>1} yields 6 | |
9146 | ${eval:0xc<<1} yields 24 | |
9147 | ${eval:~255&0x1234} yields 4608 | |
9148 | ${eval:-(~255&0x1234)} yields -4608 | |
9149 | ||
9150 | As a more realistic example, in an ACL you might have | |
9151 | ||
9152 | deny message = Too many bad recipients | |
9153 | condition = \ | |
9154 | ${if and { \ | |
9155 | {>{$rcpt_count}{10}} \ | |
9156 | { \ | |
9157 | < \ | |
9158 | {$recipients_count} \ | |
9159 | {${eval:$rcpt_count/2}} \ | |
9160 | } \ | |
9161 | }{yes}{no}} | |
9162 | ||
9163 | The condition is true if there have been more than 10 RCPT commands and | |
9164 | fewer than half of them have resulted in a valid recipient. | |
9165 | ||
9166 | ${expand:<string>} | |
9167 | ||
9168 | The expand operator causes a string to be expanded for a second time. For | |
9169 | example, | |
9170 | ||
9171 | ${expand:${lookup{$domain}dbm{/some/file}{$value}}} | |
9172 | ||
9173 | first looks up a string in a file while expanding the operand for expand, | |
9174 | and then re-expands what it has found. | |
9175 | ||
9176 | ${from_utf8:<string>} | |
9177 | ||
9178 | The world is slowly moving towards Unicode, although there are no standards | |
9179 | for email yet. However, other applications (including some databases) are | |
9180 | starting to store data in Unicode, using UTF-8 encoding. This operator | |
9181 | converts from a UTF-8 string to an ISO-8859-1 string. UTF-8 code values | |
9182 | greater than 255 are converted to underscores. The input must be a valid | |
9183 | UTF-8 string. If it is not, the result is an undefined sequence of bytes. | |
9184 | ||
9185 | Unicode code points with values less than 256 are compatible with ASCII and | |
9186 | ISO-8859-1 (also known as Latin-1). For example, character 169 is the | |
9187 | copyright symbol in both cases, though the way it is encoded is different. | |
9188 | In UTF-8, more than one byte is needed for characters with code values | |
9189 | greater than 127, whereas ISO-8859-1 is a single-byte encoding (but thereby | |
9190 | limited to 256 characters). This makes translation from UTF-8 to ISO-8859-1 | |
9191 | straightforward. | |
9192 | ||
9193 | ${hash_<n>_<m>:<string>} | |
9194 | ||
9195 | The hash operator is a simpler interface to the hashing function that can | |
9196 | be used when the two parameters are fixed numbers (as opposed to strings | |
9197 | that change when expanded). The effect is the same as | |
9198 | ||
9199 | ${hash{<n>}{<m>}{<string>}} | |
9200 | ||
9201 | See the description of the general hash item above for details. The | |
9202 | abbreviation h can be used when hash is used as an operator. | |
9203 | ||
9204 | ${hex2b64:<hexstring>} | |
9205 | ||
9206 | This operator converts a hex string into one that is base64 encoded. This | |
9207 | can be useful for processing the output of the MD5 and SHA-1 hashing | |
9208 | functions. | |
9209 | ||
9210 | ${hexquote:<string>} | |
9211 | ||
9212 | This operator converts non-printable characters in a string into a hex | |
9213 | escape form. Byte values between 33 (!) and 126 (~) inclusive are left as | |
9214 | is, and other byte values are converted to "\xNN", for example a byte value | |
9215 | 127 is converted to "\x7f". | |
9216 | ||
9217 | ${lc:<string>} | |
9218 | ||
9219 | This forces the letters in the string into lower-case, for example: | |
9220 | ||
9221 | ${lc:$local_part} | |
9222 | ||
9223 | ${length_<number>:<string>} | |
9224 | ||
9225 | The length operator is a simpler interface to the length function that can | |
9226 | be used when the parameter is a fixed number (as opposed to a string that | |
9227 | changes when expanded). The effect is the same as | |
9228 | ||
9229 | ${length{<number>}{<string>}} | |
9230 | ||
9231 | See the description of the general length item above for details. Note that | |
9232 | length is not the same as strlen. The abbreviation l can be used when | |
9233 | length is used as an operator. | |
9234 | ||
9235 | ${listcount:<string>} | |
9236 | ||
9237 | The string is interpreted as a list and the number of items is returned. | |
9238 | ||
9239 | ${listnamed:<name>} and ${listnamed_<type>:<name>} | |
9240 | ||
9241 | The name is interpreted as a named list and the content of the list is | |
9242 | returned, expanding any referenced lists, re-quoting as needed for | |
9243 | colon-separation. If the optional type is given it must be one of "a", "d", | |
9244 | "h" or "l" and selects address-, domain-, host- or localpart- lists to | |
9245 | search among respectively. Otherwise all types are searched in an undefined | |
9246 | order and the first matching list is returned. | |
9247 | ||
9248 | ${local_part:<string>} | |
9249 | ||
9250 | The string is interpreted as an RFC 2822 address and the local part is | |
9251 | extracted from it. If the string does not parse successfully, the result is | |
9252 | empty. | |
9253 | ||
9254 | ${mask:<IP address>/<bit count>} | |
9255 | ||
9256 | If the form of the string to be operated on is not an IP address followed | |
9257 | by a slash and an integer (that is, a network address in CIDR notation), | |
9258 | the expansion fails. Otherwise, this operator converts the IP address to | |
9259 | binary, masks off the least significant bits according to the bit count, | |
9260 | and converts the result back to text, with mask appended. For example, | |
9261 | ||
9262 | ${mask:10.111.131.206/28} | |
9263 | ||
9264 | returns the string "10.111.131.192/28". Since this operation is expected to | |
9265 | be mostly used for looking up masked addresses in files, the result for an | |
9266 | IPv6 address uses dots to separate components instead of colons, because | |
9267 | colon terminates a key string in lsearch files. So, for example, | |
9268 | ||
9269 | ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99} | |
9270 | ||
9271 | returns the string | |
9272 | ||
9273 | 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99 | |
9274 | ||
9275 | Letters in IPv6 addresses are always output in lower case. | |
9276 | ||
9277 | ${md5:<string>} | |
9278 | ||
9279 | The md5 operator computes the MD5 hash value of the string, and returns it | |
9280 | as a 32-digit hexadecimal number, in which any letters are in lower case. | |
9281 | ||
9282 | ${nhash_<n>_<m>:<string>} | |
9283 | ||
9284 | The nhash operator is a simpler interface to the numeric hashing function | |
9285 | that can be used when the two parameters are fixed numbers (as opposed to | |
9286 | strings that change when expanded). The effect is the same as | |
9287 | ||
9288 | ${nhash{<n>}{<m>}{<string>}} | |
9289 | ||
9290 | See the description of the general nhash item above for details. | |
9291 | ||
9292 | ${quote:<string>} | |
9293 | ||
9294 | The quote operator puts its argument into double quotes if it is an empty | |
9295 | string or contains anything other than letters, digits, underscores, dots, | |
9296 | and hyphens. Any occurrences of double quotes and backslashes are escaped | |
9297 | with a backslash. Newlines and carriage returns are converted to "\n" and " | |
9298 | \r", respectively For example, | |
9299 | ||
9300 | ${quote:ab"*"cd} | |
9301 | ||
9302 | becomes | |
9303 | ||
9304 | "ab\"*\"cd" | |
9305 | ||
9306 | The place where this is useful is when the argument is a substitution from | |
9307 | a variable or a message header. | |
9308 | ||
9309 | ${quote_local_part:<string>} | |
9310 | ||
9311 | This operator is like quote, except that it quotes the string only if | |
9312 | required to do so by the rules of RFC 2822 for quoting local parts. For | |
9313 | example, a plus sign would not cause quoting (but it would for quote). If | |
9314 | you are creating a new email address from the contents of $local_part (or | |
9315 | any other unknown data), you should always use this operator. | |
9316 | ||
9317 | ${quote_<lookup-type>:<string>} | |
9318 | ||
9319 | This operator applies lookup-specific quoting rules to the string. Each | |
9320 | query-style lookup type has its own quoting rules which are described with | |
9321 | the lookups in chapter 9. For example, | |
9322 | ||
9323 | ${quote_ldap:two * two} | |
9324 | ||
9325 | returns | |
9326 | ||
9327 | two%20%5C2A%20two | |
9328 | ||
9329 | For single-key lookup types, no quoting is ever necessary and this operator | |
9330 | yields an unchanged string. | |
9331 | ||
9332 | ${randint:<n>} | |
9333 | ||
9334 | This operator returns a somewhat random number which is less than the | |
9335 | supplied number and is at least 0. The quality of this randomness depends | |
9336 | on how Exim was built; the values are not suitable for keying material. If | |
9337 | Exim is linked against OpenSSL then RAND_pseudo_bytes() is used. If Exim is | |
9338 | linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used, for | |
9339 | versions of GnuTLS with that function. Otherwise, the implementation may be | |
9340 | arc4random(), random() seeded by srandomdev() or srandom(), or a custom | |
9341 | implementation even weaker than random(). | |
9342 | ||
9343 | ${reverse_ip:<ipaddr>} | |
9344 | ||
9345 | This operator reverses an IP address; for IPv4 addresses, the result is in | |
9346 | dotted-quad decimal form, while for IPv6 addreses the result is in | |
9347 | dotted-nibble hexadecimal form. In both cases, this is the "natural" form | |
9348 | for DNS. For example, | |
9349 | ||
9350 | ${reverse_ip:192.0.2.4} | |
9351 | ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127} | |
9352 | ||
9353 | returns | |
9354 | ||
9355 | 4.2.0.192 | |
9356 | f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2 | |
9357 | ||
9358 | ${rfc2047:<string>} | |
9359 | ||
9360 | This operator encodes text according to the rules of RFC 2047. This is an | |
9361 | encoding that is used in header lines to encode non-ASCII characters. It is | |
9362 | assumed that the input string is in the encoding specified by the | |
9363 | headers_charset option, which defaults to ISO-8859-1. If the string | |
9364 | contains only characters in the range 33-126, and no instances of the | |
9365 | characters | |
9366 | ||
9367 | ? = ( ) < > @ , ; : \ " . [ ] _ | |
9368 | ||
9369 | it is not modified. Otherwise, the result is the RFC 2047 encoding of the | |
9370 | string, using as many "encoded words" as necessary to encode all the | |
9371 | characters. | |
9372 | ||
9373 | ${rfc2047d:<string>} | |
9374 | ||
9375 | This operator decodes strings that are encoded as per RFC 2047. Binary zero | |
9376 | bytes are replaced by question marks. Characters are converted into the | |
9377 | character set defined by headers_charset. Overlong RFC 2047 "words" are not | |
9378 | recognized unless check_rfc2047_length is set false. | |
9379 | ||
9380 | Note: If you use $header_xxx: (or $h_xxx:) to access a header line, RFC | |
9381 | 2047 decoding is done automatically. You do not need to use this operator | |
9382 | as well. | |
9383 | ||
9384 | ${rxquote:<string>} | |
9385 | ||
9386 | The rxquote operator inserts a backslash before any non-alphanumeric | |
9387 | characters in its argument. This is useful when substituting the values of | |
9388 | variables or headers inside regular expressions. | |
9389 | ||
9390 | ${sha1:<string>} | |
9391 | ||
9392 | The sha1 operator computes the SHA-1 hash value of the string, and returns | |
9393 | it as a 40-digit hexadecimal number, in which any letters are in upper | |
9394 | case. | |
9395 | ||
9396 | ${sha256:<certificate>} | |
9397 | ||
9398 | The sha256 operator computes the SHA-256 hash fingerprint of the | |
9399 | certificate, and returns it as a 64-digit hexadecimal number, in which any | |
9400 | letters are in upper case. Only arguments which are a single variable of | |
9401 | certificate type are supported. | |
9402 | ||
9403 | ${stat:<string>} | |
9404 | ||
9405 | The string, after expansion, must be a file path. A call to the stat() | |
9406 | function is made for this path. If stat() fails, an error occurs and the | |
9407 | expansion fails. If it succeeds, the data from the stat replaces the item, | |
9408 | as a series of <name>=<value> pairs, where the values are all numerical, | |
9409 | except for the value of "smode". The names are: "mode" (giving the mode as | |
9410 | a 4-digit octal number), "smode" (giving the mode in symbolic format as a | |
9411 | 10-character string, as for the ls command), "inode", "device", "links", | |
9412 | "uid", "gid", "size", "atime", "mtime", and "ctime". You can extract | |
9413 | individual fields using the extract expansion item. | |
9414 | ||
9415 | The use of the stat expansion in users' filter files can be locked out by | |
9416 | the system administrator. Warning: The file size may be incorrect on 32-bit | |
9417 | systems for files larger than 2GB. | |
9418 | ||
9419 | ${str2b64:<string>} | |
9420 | ||
9421 | This operator converts a string into one that is base64 encoded. | |
9422 | ||
9423 | ${strlen:<string>} | |
9424 | ||
9425 | The item is replace by the length of the expanded string, expressed as a | |
9426 | decimal number. Note: Do not confuse strlen with length. | |
9427 | ||
9428 | ${substr_<start>_<length>:<string>} | |
9429 | ||
9430 | The substr operator is a simpler interface to the substr function that can | |
9431 | be used when the two parameters are fixed numbers (as opposed to strings | |
9432 | that change when expanded). The effect is the same as | |
9433 | ||
9434 | ${substr{<start>}{<length>}{<string>}} | |
9435 | ||
9436 | See the description of the general substr item above for details. The | |
9437 | abbreviation s can be used when substr is used as an operator. | |
9438 | ||
9439 | ${time_eval:<string>} | |
9440 | ||
9441 | This item converts an Exim time interval such as "2d4h5m" into a number of | |
9442 | seconds. | |
9443 | ||
9444 | ${time_interval:<string>} | |
9445 | ||
9446 | The argument (after sub-expansion) must be a sequence of decimal digits | |
9447 | that represents an interval of time as a number of seconds. It is converted | |
9448 | into a number of larger units and output in Exim's normal time format, for | |
9449 | example, "1w3d4h2m6s". | |
9450 | ||
9451 | ${uc:<string>} | |
9452 | ||
9453 | This forces the letters in the string into upper-case. | |
9454 | ||
9455 | ${utf8clean:<string>} | |
9456 | ||
9457 | This replaces any invalid utf-8 sequence in the string by the character "? | |
9458 | ". | |
9459 | ||
9460 | ||
9461 | 11.7 Expansion conditions | |
9462 | ------------------------- | |
9463 | ||
9464 | The following conditions are available for testing by the ${if construct while | |
9465 | expanding strings: | |
9466 | ||
9467 | !<condition> | |
9468 | ||
9469 | Preceding any condition with an exclamation mark negates the result of the | |
9470 | condition. | |
9471 | ||
9472 | <symbolic operator> {<string1>}{<string2>} | |
9473 | ||
9474 | There are a number of symbolic operators for doing numeric comparisons. | |
9475 | They are: | |
9476 | ||
9477 | = equal | |
9478 | == equal | |
9479 | > greater | |
9480 | >= greater or equal | |
9481 | < less | |
9482 | <= less or equal | |
9483 | ||
9484 | For example: | |
9485 | ||
9486 | ${if >{$message_size}{10M} ... | |
9487 | ||
9488 | Note that the general negation operator provides for inequality testing. | |
9489 | The two strings must take the form of optionally signed decimal integers, | |
9490 | optionally followed by one of the letters "K", "M" or "G" (in either upper | |
9491 | or lower case), signifying multiplication by 1024, 1024*1024 or | |
9492 | 1024*1024*1024, respectively. As a special case, the numerical value of an | |
9493 | empty string is taken as zero. | |
9494 | ||
9495 | In all cases, a relative comparator OP is testing if <string1> OP <string2 | |
9496 | >; the above example is checking if $message_size is larger than 10M, not | |
9497 | if 10M is larger than $message_size. | |
9498 | ||
9499 | acl {{<name>}{<arg1>}{<arg2>}...} | |
9500 | ||
9501 | The name and zero to nine argument strings are first expanded separately. | |
9502 | The expanded arguments are assigned to the variables $acl_arg1 to $acl_arg9 | |
9503 | in order. Any unused are made empty. The variable $acl_narg is set to the | |
9504 | number of arguments. The named ACL (see chapter 42) is called and may use | |
9505 | the variables; if another acl expansion is used the values are restored | |
9506 | after it returns. If the ACL sets a value using a "message =" modifier the | |
9507 | variable $value becomes the result of the expansion, otherwise it is empty. | |
9508 | If the ACL returns accept the condition is true; if deny, false. If the ACL | |
9509 | returns defer the result is a forced-fail. | |
9510 | ||
9511 | bool {<string>} | |
9512 | ||
9513 | This condition turns a string holding a true or false representation into a | |
9514 | boolean state. It parses "true", "false", "yes" and "no" | |
9515 | (case-insensitively); also integer numbers map to true if non-zero, false | |
9516 | if zero. An empty string is treated as false. Leading and trailing | |
9517 | whitespace is ignored; thus a string consisting only of whitespace is | |
9518 | false. All other string values will result in expansion failure. | |
9519 | ||
9520 | When combined with ACL variables, this expansion condition will let you | |
9521 | make decisions in one place and act on those decisions in another place. | |
9522 | For example: | |
9523 | ||
9524 | ${if bool{$acl_m_privileged_sender} ... | |
9525 | ||
9526 | bool_lax {<string>} | |
9527 | ||
9528 | Like bool, this condition turns a string into a boolean state. But where | |
9529 | bool accepts a strict set of strings, bool_lax uses the same loose | |
9530 | definition that the Router condition option uses. The empty string and the | |
9531 | values "false", "no" and "0" map to false, all others map to true. Leading | |
9532 | and trailing whitespace is ignored. | |
9533 | ||
9534 | Note that where "bool{00}" is false, "bool_lax{00}" is true. | |
9535 | ||
9536 | crypteq {<string1>}{<string2>} | |
9537 | ||
9538 | This condition is included in the Exim binary if it is built to support any | |
9539 | authentication mechanisms (see chapter 33). Otherwise, it is necessary to | |
9540 | define SUPPORT_CRYPTEQ in Local/Makefile to get crypteq included in the | |
9541 | binary. | |
9542 | ||
9543 | The crypteq condition has two arguments. The first is encrypted and | |
9544 | compared against the second, which is already encrypted. The second string | |
9545 | may be in the LDAP form for storing encrypted strings, which starts with | |
9546 | the encryption type in curly brackets, followed by the data. If the second | |
9547 | string does not begin with "{" it is assumed to be encrypted with crypt() | |
9548 | or crypt16() (see below), since such strings cannot begin with "{". | |
9549 | Typically this will be a field from a password file. An example of an | |
9550 | encrypted string in LDAP form is: | |
9551 | ||
9552 | {md5}CY9rzUYh03PK3k6DJie09g== | |
9553 | ||
9554 | If such a string appears directly in an expansion, the curly brackets have | |
9555 | to be quoted, because they are part of the expansion syntax. For example: | |
9556 | ||
9557 | ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}} | |
9558 | ||
9559 | The following encryption types (whose names are matched case-independently) | |
9560 | are supported: | |
9561 | ||
9562 | * {md5} computes the MD5 digest of the first string, and expresses this | |
9563 | as printable characters to compare with the remainder of the second | |
9564 | string. If the length of the comparison string is 24, Exim assumes that | |
9565 | it is base64 encoded (as in the above example). If the length is 32, | |
9566 | Exim assumes that it is a hexadecimal encoding of the MD5 digest. If | |
9567 | the length not 24 or 32, the comparison fails. | |
9568 | ||
9569 | * {sha1} computes the SHA-1 digest of the first string, and expresses | |
9570 | this as printable characters to compare with the remainder of the | |
9571 | second string. If the length of the comparison string is 28, Exim | |
9572 | assumes that it is base64 encoded. If the length is 40, Exim assumes | |
9573 | that it is a hexadecimal encoding of the SHA-1 digest. If the length is | |
9574 | not 28 or 40, the comparison fails. | |
9575 | ||
9576 | * {crypt} calls the crypt() function, which traditionally used to use | |
9577 | only the first eight characters of the password. However, in modern | |
9578 | operating systems this is no longer true, and in many cases the entire | |
9579 | password is used, whatever its length. | |
9580 | ||
9581 | * {crypt16} calls the crypt16() function, which was originally created to | |
9582 | use up to 16 characters of the password in some operating systems. | |
9583 | Again, in modern operating systems, more characters may be used. | |
9584 | ||
9585 | Exim has its own version of crypt16(), which is just a double call to crypt | |
9586 | (). For operating systems that have their own version, setting HAVE_CRYPT16 | |
9587 | in Local/Makefile when building Exim causes it to use the operating system | |
9588 | version instead of its own. This option is set by default in the | |
9589 | OS-dependent Makefile for those operating systems that are known to support | |
9590 | crypt16(). | |
9591 | ||
9592 | Some years after Exim's crypt16() was implemented, a user discovered that | |
9593 | it was not using the same algorithm as some operating systems' versions. It | |
9594 | turns out that as well as crypt16() there is a function called bigcrypt() | |
9595 | in some operating systems. This may or may not use the same algorithm, and | |
9596 | both of them may be different to Exim's built-in crypt16(). | |
9597 | ||
9598 | However, since there is now a move away from the traditional crypt() | |
9599 | functions towards using SHA1 and other algorithms, tidying up this area of | |
9600 | Exim is seen as very low priority. | |
9601 | ||
9602 | If you do not put a encryption type (in curly brackets) in a crypteq | |
9603 | comparison, the default is usually either "{crypt}" or "{crypt16}", as | |
9604 | determined by the setting of DEFAULT_CRYPT in Local/Makefile. The default | |
9605 | default is "{crypt}". Whatever the default, you can always use either | |
9606 | function by specifying it explicitly in curly brackets. | |
9607 | ||
9608 | def:<variable name> | |
9609 | ||
9610 | The def condition must be followed by the name of one of the expansion | |
9611 | variables defined in section 11.9. The condition is true if the variable | |
9612 | does not contain the empty string. For example: | |
9613 | ||
9614 | ${if def:sender_ident {from $sender_ident}} | |
9615 | ||
9616 | Note that the variable name is given without a leading $ character. If the | |
9617 | variable does not exist, the expansion fails. | |
9618 | ||
9619 | def:header_<header name>: or def:h_<header name>: | |
9620 | ||
9621 | This condition is true if a message is being processed and the named header | |
9622 | exists in the message. For example, | |
9623 | ||
9624 | ${if def:header_reply-to:{$h_reply-to:}{$h_from:}} | |
9625 | ||
9626 | Note: No $ appears before header_ or h_ in the condition, and the header | |
9627 | name must be terminated by a colon if white space does not follow. | |
9628 | ||
9629 | eq {<string1>}{<string2>}, eqi {<string1>}{<string2>} | |
9630 | ||
9631 | The two substrings are first expanded. The condition is true if the two | |
9632 | resulting strings are identical. For eq the comparison includes the case of | |
9633 | letters, whereas for eqi the comparison is case-independent. | |
9634 | ||
9635 | exists {<file name>} | |
9636 | ||
9637 | The substring is first expanded and then interpreted as an absolute path. | |
9638 | The condition is true if the named file (or directory) exists. The | |
9639 | existence test is done by calling the stat() function. The use of the | |
9640 | exists test in users' filter files may be locked out by the system | |
9641 | administrator. | |
9642 | ||
9643 | first_delivery | |
9644 | ||
9645 | This condition, which has no data, is true during a message's first | |
9646 | delivery attempt. It is false during any subsequent delivery attempts. | |
9647 | ||
9648 | forall{<a list>}{<a condition>}, forany{<a list>}{<a condition>} | |
9649 | ||
9650 | These conditions iterate over a list. The first argument is expanded to | |
9651 | form the list. By default, the list separator is a colon, but it can be | |
9652 | changed by the normal method. The second argument is interpreted as a | |
9653 | condition that is to be applied to each item in the list in turn. During | |
9654 | the interpretation of the condition, the current list item is placed in a | |
9655 | variable called $item. | |
9656 | ||
9657 | * For forany, interpretation stops if the condition is true for any item, | |
9658 | and the result of the whole condition is true. If the condition is | |
9659 | false for all items in the list, the overall condition is false. | |
9660 | ||
9661 | * For forall, interpretation stops if the condition is false for any | |
9662 | item, and the result of the whole condition is false. If the condition | |
9663 | is true for all items in the list, the overall condition is true. | |
9664 | ||
9665 | Note that negation of forany means that the condition must be false for all | |
9666 | items for the overall condition to succeed, and negation of forall means | |
9667 | that the condition must be false for at least one item. In this example, | |
9668 | the list separator is changed to a comma: | |
9669 | ||
9670 | ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}} | |
9671 | ||
9672 | The value of $item is saved and restored while forany or forall is being | |
9673 | processed, to enable these expansion items to be nested. | |
9674 | ||
9675 | To scan a named list, expand it with the listnamed operator. | |
9676 | ||
9677 | ge {<string1>}{<string2>}, gei {<string1>}{<string2>} | |
9678 | ||
9679 | The two substrings are first expanded. The condition is true if the first | |
9680 | string is lexically greater than or equal to the second string. For ge the | |
9681 | comparison includes the case of letters, whereas for gei the comparison is | |
9682 | case-independent. | |
9683 | ||
9684 | gt {<string1>}{<string2>}, gti {<string1>}{<string2>} | |
9685 | ||
9686 | The two substrings are first expanded. The condition is true if the first | |
9687 | string is lexically greater than the second string. For gt the comparison | |
9688 | includes the case of letters, whereas for gti the comparison is | |
9689 | case-independent. | |
9690 | ||
9691 | inlist {<string1>}{<string2>}, inlisti {<string1>}{<string2>} | |
9692 | ||
9693 | Both strings are expanded; the second string is treated as a list of simple | |
9694 | strings; if the first string is a member of the second, then the condition | |
9695 | is true. | |
9696 | ||
9697 | These are simpler to use versions of the more powerful forany condition. | |
9698 | Examples, and the forany equivalents: | |
9699 | ||
9700 | ${if inlist{needle}{foo:needle:bar}} | |
9701 | ${if forany{foo:needle:bar}{eq{$item}{needle}}} | |
9702 | ${if inlisti{Needle}{fOo:NeeDLE:bAr}} | |
9703 | ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}} | |
9704 | ||
9705 | isip {<string>}, isip4 {<string>}, isip6 {<string>} | |
9706 | ||
9707 | The substring is first expanded, and then tested to see if it has the form | |
9708 | of an IP address. Both IPv4 and IPv6 addresses are valid for isip, whereas | |
9709 | isip4 and isip6 test specifically for IPv4 or IPv6 addresses. | |
9710 | ||
9711 | For an IPv4 address, the test is for four dot-separated components, each of | |
9712 | which consists of from one to three digits. For an IPv6 address, up to | |
9713 | eight colon-separated components are permitted, each containing from one to | |
9714 | four hexadecimal digits. There may be fewer than eight components if an | |
9715 | empty component (adjacent colons) is present. Only one empty component is | |
9716 | permitted. | |
9717 | ||
9718 | Note: The checks are just on the form of the address; actual numerical | |
9719 | values are not considered. Thus, for example, 999.999.999.999 passes the | |
9720 | IPv4 check. The main use of these tests is to distinguish between IP | |
9721 | addresses and host names, or between IPv4 and IPv6 addresses. For example, | |
9722 | you could use | |
9723 | ||
9724 | ${if isip4{$sender_host_address}... | |
9725 | ||
9726 | to test which IP version an incoming SMTP connection is using. | |
9727 | ||
9728 | ldapauth {<ldap query>} | |
9729 | ||
9730 | This condition supports user authentication using LDAP. See section 9.13 | |
9731 | for details of how to use LDAP in lookups and the syntax of queries. For | |
9732 | this use, the query must contain a user name and password. The query itself | |
9733 | is not used, and can be empty. The condition is true if the password is not | |
9734 | empty, and the user name and password are accepted by the LDAP server. An | |
9735 | empty password is rejected without calling LDAP because LDAP binds with an | |
9736 | empty password are considered anonymous regardless of the username, and | |
9737 | will succeed in most configurations. See chapter 33 for details of SMTP | |
9738 | authentication, and chapter 34 for an example of how this can be used. | |
9739 | ||
9740 | le {<string1>}{<string2>}, lei {<string1>}{<string2>} | |
9741 | ||
9742 | The two substrings are first expanded. The condition is true if the first | |
9743 | string is lexically less than or equal to the second string. For le the | |
9744 | comparison includes the case of letters, whereas for lei the comparison is | |
9745 | case-independent. | |
9746 | ||
9747 | lt {<string1>}{<string2>}, lti {<string1>}{<string2>} | |
9748 | ||
9749 | The two substrings are first expanded. The condition is true if the first | |
9750 | string is lexically less than the second string. For lt the comparison | |
9751 | includes the case of letters, whereas for lti the comparison is | |
9752 | case-independent. | |
9753 | ||
9754 | match {<string1>}{<string2>} | |
9755 | ||
9756 | The two substrings are first expanded. The second is then treated as a | |
9757 | regular expression and applied to the first. Because of the pre-expansion, | |
9758 | if the regular expression contains dollar, or backslash characters, they | |
9759 | must be escaped. Care must also be taken if the regular expression contains | |
9760 | braces (curly brackets). A closing brace must be escaped so that it is not | |
9761 | taken as a premature termination of <string2>. The easiest approach is to | |
9762 | use the "\N" feature to disable expansion of the regular expression. For | |
9763 | example, | |
9764 | ||
9765 | ${if match {$local_part}{\N^\d{3}\N} ... | |
9766 | ||
9767 | If the whole expansion string is in double quotes, further escaping of | |
9768 | backslashes is also required. | |
9769 | ||
9770 | The condition is true if the regular expression match succeeds. The regular | |
9771 | expression is not required to begin with a circumflex metacharacter, but if | |
9772 | there is no circumflex, the expression is not anchored, and it may match | |
9773 | anywhere in the subject, not just at the start. If you want the pattern to | |
9774 | match at the end of the subject, you must include the "$" metacharacter at | |
9775 | an appropriate point. | |
9776 | ||
9777 | At the start of an if expansion the values of the numeric variable | |
9778 | substitutions $1 etc. are remembered. Obeying a match condition that | |
9779 | succeeds causes them to be reset to the substrings of that condition and | |
9780 | they will have these values during the expansion of the success string. At | |
9781 | the end of the if expansion, the previous values are restored. After | |
9782 | testing a combination of conditions using or, the subsequent values of the | |
9783 | numeric variables are those of the condition that succeeded. | |
9784 | ||
9785 | match_address {<string1>}{<string2>} | |
9786 | ||
9787 | See match_local_part. | |
9788 | ||
9789 | match_domain {<string1>}{<string2>} | |
9790 | ||
9791 | See match_local_part. | |
9792 | ||
9793 | match_ip {<string1>}{<string2>} | |
9794 | ||
9795 | This condition matches an IP address to a list of IP address patterns. It | |
9796 | must be followed by two argument strings. The first (after expansion) must | |
9797 | be an IP address or an empty string. The second (not expanded) is a | |
9798 | restricted host list that can match only an IP address, not a host name. | |
9799 | For example: | |
9800 | ||
9801 | ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}} | |
9802 | ||
9803 | The specific types of host list item that are permitted in the list are: | |
9804 | ||
9805 | * An IP address, optionally with a CIDR mask. | |
9806 | ||
9807 | * A single asterisk, which matches any IP address. | |
9808 | ||
9809 | * An empty item, which matches only if the IP address is empty. This | |
9810 | could be useful for testing for a locally submitted message or one from | |
9811 | specific hosts in a single test such as | |
9812 | ||
9813 | ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}} | |
9814 | ||
9815 | where the first item in the list is the empty string. | |
9816 | ||
9817 | * The item @[] matches any of the local host's interface addresses. | |
9818 | ||
9819 | * Single-key lookups are assumed to be like "net-" style lookups in host | |
9820 | lists, even if "net-" is not specified. There is never any attempt to | |
9821 | turn the IP address into a host name. The most common type of linear | |
9822 | search for match_ip is likely to be iplsearch, in which the file can | |
9823 | contain CIDR masks. For example: | |
9824 | ||
9825 | ${if match_ip{$sender_host_address}{iplsearch;/some/file}... | |
9826 | ||
9827 | It is of course possible to use other kinds of lookup, and in such a | |
9828 | case, you do need to specify the "net-" prefix if you want to specify a | |
9829 | specific address mask, for example: | |
9830 | ||
9831 | ${if match_ip{$sender_host_address}{net24-dbm;/some/file}... | |
9832 | ||
9833 | However, unless you are combining a match_ip condition with others, it | |
9834 | is just as easy to use the fact that a lookup is itself a condition, | |
9835 | and write: | |
9836 | ||
9837 | ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}... | |
9838 | ||
9839 | Note that <string2> is not itself subject to string expansion, unless Exim | |
9840 | was built with the EXPAND_LISTMATCH_RHS option. | |
9841 | ||
9842 | Consult section 10.11 for further details of these patterns. | |
9843 | ||
9844 | match_local_part {<string1>}{<string2>} | |
9845 | ||
9846 | This condition, together with match_address and match_domain, make it | |
9847 | possible to test domain, address, and local part lists within expansions. | |
9848 | Each condition requires two arguments: an item and a list to match. A | |
9849 | trivial example is: | |
9850 | ||
9851 | ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}} | |
9852 | ||
9853 | In each case, the second argument may contain any of the allowable items | |
9854 | for a list of the appropriate type. Also, because the second argument | |
9855 | (after expansion) is a standard form of list, it is possible to refer to a | |
9856 | named list. Thus, you can use conditions like this: | |
9857 | ||
9858 | ${if match_domain{$domain}{+local_domains}{... | |
9859 | ||
9860 | For address lists, the matching starts off caselessly, but the "+caseful" | |
9861 | item can be used, as in all address lists, to cause subsequent items to | |
9862 | have their local parts matched casefully. Domains are always matched | |
9863 | caselessly. | |
9864 | ||
9865 | Note that <string2> is not itself subject to string expansion, unless Exim | |
9866 | was built with the EXPAND_LISTMATCH_RHS option. | |
9867 | ||
9868 | Note: Host lists are not supported in this way. This is because hosts have | |
9869 | two identities: a name and an IP address, and it is not clear how to | |
9870 | specify cleanly how such a test would work. However, IP addresses can be | |
9871 | matched using match_ip. | |
9872 | ||
9873 | pam {<string1>:<string2>:...} | |
9874 | ||
9875 | Pluggable Authentication Modules (http://www.kernel.org/pub/linux/libs/pam/ | |
9876 | ) are a facility that is available in the latest releases of Solaris and in | |
9877 | some GNU/Linux distributions. The Exim support, which is intended for use | |
9878 | in conjunction with the SMTP AUTH command, is available only if Exim is | |
9879 | compiled with | |
9880 | ||
9881 | SUPPORT_PAM=yes | |
9882 | ||
9883 | in Local/Makefile. You probably need to add -lpam to EXTRALIBS, and in some | |
9884 | releases of GNU/Linux -ldl is also needed. | |
9885 | ||
9886 | The argument string is first expanded, and the result must be a | |
9887 | colon-separated list of strings. Leading and trailing white space is | |
9888 | ignored. The PAM module is initialized with the service name "exim" and the | |
9889 | user name taken from the first item in the colon-separated data string (< | |
9890 | string1>). The remaining items in the data string are passed over in | |
9891 | response to requests from the authentication function. In the simple case | |
9892 | there will only be one request, for a password, so the data consists of | |
9893 | just two strings. | |
9894 | ||
9895 | There can be problems if any of the strings are permitted to contain colon | |
9896 | characters. In the usual way, these have to be doubled to avoid being taken | |
9897 | as separators. If the data is being inserted from a variable, the sg | |
9898 | expansion item can be used to double any existing colons. For example, the | |
9899 | configuration of a LOGIN authenticator might contain this setting: | |
9900 | ||
9901 | server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}} | |
9902 | ||
9903 | For a PLAIN authenticator you could use: | |
9904 | ||
9905 | server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}} | |
9906 | ||
9907 | In some operating systems, PAM authentication can be done only from a | |
9908 | process running as root. Since Exim is running as the Exim user when | |
9909 | receiving messages, this means that PAM cannot be used directly in those | |
9910 | systems. A patched version of the pam_unix module that comes with the Linux | |
9911 | PAM package is available from http://www.e-admin.de/pam_exim/. The patched | |
9912 | module allows one special uid/gid combination, in addition to root, to | |
9913 | authenticate. If you build the patched module to allow the Exim user and | |
9914 | group, PAM can then be used from an Exim authenticator. | |
9915 | ||
9916 | pwcheck {<string1>:<string2>} | |
9917 | ||
9918 | This condition supports user authentication using the Cyrus pwcheck daemon. | |
9919 | This is one way of making it possible for passwords to be checked by a | |
9920 | process that is not running as root. Note: The use of pwcheck is now | |
9921 | deprecated. Its replacement is saslauthd (see below). | |
9922 | ||
9923 | The pwcheck support is not included in Exim by default. You need to specify | |
9924 | the location of the pwcheck daemon's socket in Local/Makefile before | |
9925 | building Exim. For example: | |
9926 | ||
9927 | CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck | |
9928 | ||
9929 | You do not need to install the full Cyrus software suite in order to use | |
9930 | the pwcheck daemon. You can compile and install just the daemon alone from | |
9931 | the Cyrus SASL library. Ensure that exim is the only user that has access | |
9932 | to the /var/pwcheck directory. | |
9933 | ||
9934 | The pwcheck condition takes one argument, which must be the user name and | |
9935 | password, separated by a colon. For example, in a LOGIN authenticator | |
9936 | configuration, you might have this: | |
9937 | ||
9938 | server_condition = ${if pwcheck{$auth1:$auth2}} | |
9939 | ||
9940 | Again, for a PLAIN authenticator configuration, this would be: | |
9941 | ||
9942 | server_condition = ${if pwcheck{$auth2:$auth3}} | |
9943 | ||
9944 | queue_running | |
9945 | ||
9946 | This condition, which has no data, is true during delivery attempts that | |
9947 | are initiated by queue runner processes, and false otherwise. | |
9948 | ||
9949 | radius {<authentication string>} | |
9950 | ||
9951 | Radius authentication (RFC 2865) is supported in a similar way to PAM. You | |
9952 | must set RADIUS_CONFIG_FILE in Local/Makefile to specify the location of | |
9953 | the Radius client configuration file in order to build Exim with Radius | |
9954 | support. | |
9955 | ||
9956 | With just that one setting, Exim expects to be linked with the radiusclient | |
9957 | library, using the original API. If you are using release 0.4.0 or later of | |
9958 | this library, you need to set | |
9959 | ||
9960 | RADIUS_LIB_TYPE=RADIUSCLIENTNEW | |
9961 | ||
9962 | in Local/Makefile when building Exim. You can also link Exim with the | |
9963 | libradius library that comes with FreeBSD. To do this, set | |
9964 | ||
9965 | RADIUS_LIB_TYPE=RADLIB | |
9966 | ||
9967 | in Local/Makefile, in addition to setting RADIUS_CONFIGURE_FILE. You may | |
9968 | also have to supply a suitable setting in EXTRALIBS so that the Radius | |
9969 | library can be found when Exim is linked. | |
9970 | ||
9971 | The string specified by RADIUS_CONFIG_FILE is expanded and passed to the | |
9972 | Radius client library, which calls the Radius server. The condition is true | |
9973 | if the authentication is successful. For example: | |
9974 | ||
9975 | server_condition = ${if radius{<arguments>}} | |
9976 | ||
9977 | saslauthd {{<user>}{<password>}{<service>}{<realm>}} | |
9978 | ||
9979 | This condition supports user authentication using the Cyrus saslauthd | |
9980 | daemon. This replaces the older pwcheck daemon, which is now deprecated. | |
9981 | Using this daemon is one way of making it possible for passwords to be | |
9982 | checked by a process that is not running as root. | |
9983 | ||
9984 | The saslauthd support is not included in Exim by default. You need to | |
9985 | specify the location of the saslauthd daemon's socket in Local/Makefile | |
9986 | before building Exim. For example: | |
9987 | ||
9988 | CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux | |
9989 | ||
9990 | You do not need to install the full Cyrus software suite in order to use | |
9991 | the saslauthd daemon. You can compile and install just the daemon alone | |
9992 | from the Cyrus SASL library. | |
9993 | ||
9994 | Up to four arguments can be supplied to the saslauthd condition, but only | |
9995 | two are mandatory. For example: | |
9996 | ||
9997 | server_condition = ${if saslauthd{{$auth1}{$auth2}}} | |
9998 | ||
9999 | The service and the realm are optional (which is why the arguments are | |
10000 | enclosed in their own set of braces). For details of the meaning of the | |
10001 | service and realm, and how to run the daemon, consult the Cyrus | |
10002 | documentation. | |
10003 | ||
10004 | ||
10005 | 11.8 Combining expansion conditions | |
10006 | ----------------------------------- | |
10007 | ||
10008 | Several conditions can be tested at once by combining them using the and and or | |
10009 | combination conditions. Note that and and or are complete conditions on their | |
10010 | own, and precede their lists of sub-conditions. Each sub-condition must be | |
10011 | enclosed in braces within the overall braces that contain the list. No | |
10012 | repetition of if is used. | |
10013 | ||
10014 | or {{<cond1>}{<cond2>}...} | |
10015 | ||
10016 | The sub-conditions are evaluated from left to right. The condition is true | |
10017 | if any one of the sub-conditions is true. For example, | |
10018 | ||
10019 | ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}... | |
10020 | ||
10021 | When a true sub-condition is found, the following ones are parsed but not | |
10022 | evaluated. If there are several "match" sub-conditions the values of the | |
10023 | numeric variables afterwards are taken from the first one that succeeds. | |
10024 | ||
10025 | and {{<cond1>}{<cond2>}...} | |
10026 | ||
10027 | The sub-conditions are evaluated from left to right. The condition is true | |
10028 | if all of the sub-conditions are true. If there are several "match" | |
10029 | sub-conditions, the values of the numeric variables afterwards are taken | |
10030 | from the last one. When a false sub-condition is found, the following ones | |
10031 | are parsed but not evaluated. | |
10032 | ||
10033 | ||
10034 | 11.9 Expansion variables | |
10035 | ------------------------ | |
10036 | ||
10037 | This section contains an alphabetical list of all the expansion variables. Some | |
10038 | of them are available only when Exim is compiled with specific options such as | |
10039 | support for TLS or the content scanning extension. | |
10040 | ||
10041 | $0, $1, etc | |
10042 | ||
10043 | When a match expansion condition succeeds, these variables contain the | |
10044 | captured substrings identified by the regular expression during subsequent | |
10045 | processing of the success string of the containing if expansion item. | |
10046 | However, they do not retain their values afterwards; in fact, their | |
10047 | previous values are restored at the end of processing an if item. The | |
10048 | numerical variables may also be set externally by some other matching | |
10049 | process which precedes the expansion of the string. For example, the | |
10050 | commands available in Exim filter files include an if command with its own | |
10051 | regular expression matching condition. | |
10052 | ||
10053 | $acl_arg1, $acl_arg2, etc | |
10054 | ||
10055 | Within an acl condition, expansion condition or expansion item any | |
10056 | arguments are copied to these variables, any unused variables being made | |
10057 | empty. | |
10058 | ||
10059 | $acl_c... | |
10060 | ||
10061 | Values can be placed in these variables by the set modifier in an ACL. They | |
10062 | can be given any name that starts with $acl_c and is at least six | |
10063 | characters long, but the sixth character must be either a digit or an | |
10064 | underscore. For example: $acl_c5, $acl_c_mycount. The values of the | |
10065 | $acl_c... variables persist throughout the lifetime of an SMTP connection. | |
10066 | They can be used to pass information between ACLs and between different | |
10067 | invocations of the same ACL. When a message is received, the values of | |
10068 | these variables are saved with the message, and can be accessed by filters, | |
10069 | routers, and transports during subsequent delivery. | |
10070 | ||
10071 | $acl_m... | |
10072 | ||
10073 | These variables are like the $acl_c... variables, except that their values | |
10074 | are reset after a message has been received. Thus, if several messages are | |
10075 | received in one SMTP connection, $acl_m... values are not passed on from | |
10076 | one message to the next, as $acl_c... values are. The $acl_m... variables | |
10077 | are also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. | |
10078 | When a message is received, the values of these variables are saved with | |
10079 | the message, and can be accessed by filters, routers, and transports during | |
10080 | subsequent delivery. | |
10081 | ||
10082 | $acl_narg | |
10083 | ||
10084 | Within an acl condition, expansion condition or expansion item this | |
10085 | variable has the number of arguments. | |
10086 | ||
10087 | $acl_verify_message | |
10088 | ||
10089 | After an address verification has failed, this variable contains the | |
10090 | failure message. It retains its value for use in subsequent modifiers. The | |
10091 | message can be preserved by coding like this: | |
10092 | ||
10093 | warn !verify = sender | |
10094 | set acl_m0 = $acl_verify_message | |
10095 | ||
10096 | You can use $acl_verify_message during the expansion of the message or | |
10097 | log_message modifiers, to include information about the verification | |
10098 | failure. | |
10099 | ||
10100 | $address_data | |
10101 | ||
10102 | This variable is set by means of the address_data option in routers. The | |
10103 | value then remains with the address while it is processed by subsequent | |
10104 | routers and eventually a transport. If the transport is handling multiple | |
10105 | addresses, the value from the first address is used. See chapter 15 for | |
10106 | more details. Note: The contents of $address_data are visible in user | |
10107 | filter files. | |
10108 | ||
10109 | If $address_data is set when the routers are called from an ACL to verify a | |
10110 | recipient address, the final value is still in the variable for subsequent | |
10111 | conditions and modifiers of the ACL statement. If routing the address | |
10112 | caused it to be redirected to just one address, the child address is also | |
10113 | routed as part of the verification, and in this case the final value of | |
10114 | $address_data is from the child's routing. | |
10115 | ||
10116 | If $address_data is set when the routers are called from an ACL to verify a | |
10117 | sender address, the final value is also preserved, but this time in | |
10118 | $sender_address_data, to distinguish it from data from a recipient address. | |
10119 | ||
10120 | In both cases (recipient and sender verification), the value does not | |
10121 | persist after the end of the current ACL statement. If you want to preserve | |
10122 | these values for longer, you can save them in ACL variables. | |
10123 | ||
10124 | $address_file | |
10125 | ||
10126 | When, as a result of aliasing, forwarding, or filtering, a message is | |
10127 | directed to a specific file, this variable holds the name of the file when | |
10128 | the transport is running. At other times, the variable is empty. For | |
10129 | example, using the default configuration, if user r2d2 has a .forward file | |
10130 | containing | |
10131 | ||
10132 | /home/r2d2/savemail | |
10133 | ||
10134 | then when the address_file transport is running, $address_file contains the | |
10135 | text string "/home/r2d2/savemail". For Sieve filters, the value may be | |
10136 | "inbox" or a relative folder name. It is then up to the transport | |
10137 | configuration to generate an appropriate absolute path to the relevant | |
10138 | file. | |
10139 | ||
10140 | $address_pipe | |
10141 | ||
10142 | When, as a result of aliasing or forwarding, a message is directed to a | |
10143 | pipe, this variable holds the pipe command when the transport is running. | |
10144 | ||
10145 | $auth1 - $auth3 | |
10146 | ||
10147 | These variables are used in SMTP authenticators (see chapters 34-40). | |
10148 | Elsewhere, they are empty. | |
10149 | ||
10150 | $authenticated_id | |
10151 | ||
10152 | When a server successfully authenticates a client it may be configured to | |
10153 | preserve some of the authentication information in the variable | |
10154 | $authenticated_id (see chapter 33). For example, a user/password | |
10155 | authenticator configuration might preserve the user name for use in the | |
10156 | routers. Note that this is not the same information that is saved in | |
10157 | $sender_host_authenticated. When a message is submitted locally (that is, | |
10158 | not over a TCP connection) the value of $authenticated_id is normally the | |
10159 | login name of the calling process. However, a trusted user can override | |
10160 | this by means of the -oMai command line option. | |
10161 | ||
10162 | $authenticated_fail_id | |
10163 | ||
10164 | When an authentication attempt fails, the variable $authenticated_fail_id | |
10165 | will contain the failed authentication id. If more than one authentication | |
10166 | id is attempted, it will contain only the last one. The variable is | |
10167 | available for processing in the ACL's, generally the quit or notquit ACL. A | |
10168 | message to a local recipient could still be accepted without requiring | |
10169 | authentication, which means this variable could also be visible in all of | |
10170 | the ACL's as well. | |
10171 | ||
10172 | $authenticated_sender | |
10173 | ||
10174 | When acting as a server, Exim takes note of the AUTH= parameter on an | |
10175 | incoming SMTP MAIL command if it believes the sender is sufficiently | |
10176 | trusted, as described in section 33.2. Unless the data is the string "<>", | |
10177 | it is set as the authenticated sender of the message, and the value is | |
10178 | available during delivery in the $authenticated_sender variable. If the | |
10179 | sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the | |
10180 | data. | |
10181 | ||
10182 | When a message is submitted locally (that is, not over a TCP connection), | |
10183 | the value of $authenticated_sender is an address constructed from the login | |
10184 | name of the calling process and $qualify_domain, except that a trusted user | |
10185 | can override this by means of the -oMas command line option. | |
10186 | ||
10187 | $authentication_failed | |
10188 | ||
10189 | This variable is set to "1" in an Exim server if a client issues an AUTH | |
10190 | command that does not succeed. Otherwise it is set to "0". This makes it | |
10191 | possible to distinguish between "did not try to authenticate" ( | |
10192 | $sender_host_authenticated is empty and $authentication_failed is set to | |
10193 | "0") and "tried to authenticate but failed" ($sender_host_authenticated is | |
10194 | empty and $authentication_failed is set to "1"). Failure includes any | |
10195 | negative response to an AUTH command, including (for example) an attempt to | |
10196 | use an undefined mechanism. | |
10197 | ||
10198 | $av_failed | |
10199 | ||
10200 | This variable is available when Exim is compiled with the content-scanning | |
10201 | extension. It is set to "0" by default, but will be set to "1" if any | |
10202 | problem occurs with the virus scanner (specified by av_scanner) during the | |
10203 | ACL malware condition. | |
10204 | ||
10205 | $body_linecount | |
10206 | ||
10207 | When a message is being received or delivered, this variable contains the | |
10208 | number of lines in the message's body. See also $message_linecount. | |
10209 | ||
10210 | $body_zerocount | |
10211 | ||
10212 | When a message is being received or delivered, this variable contains the | |
10213 | number of binary zero bytes (ASCII NULs) in the message's body. | |
10214 | ||
10215 | $bounce_recipient | |
10216 | ||
10217 | This is set to the recipient address of a bounce message while Exim is | |
10218 | creating it. It is useful if a customized bounce message text file is in | |
10219 | use (see chapter 48). | |
10220 | ||
10221 | $bounce_return_size_limit | |
10222 | ||
10223 | This contains the value set in the bounce_return_size_limit option, rounded | |
10224 | up to a multiple of 1000. It is useful when a customized error message text | |
10225 | file is in use (see chapter 48). | |
10226 | ||
10227 | $caller_gid | |
10228 | ||
10229 | The real group id under which the process that called Exim was running. | |
10230 | This is not the same as the group id of the originator of a message (see | |
10231 | $originator_gid). If Exim re-execs itself, this variable in the new | |
10232 | incarnation normally contains the Exim gid. | |
10233 | ||
10234 | $caller_uid | |
10235 | ||
10236 | The real user id under which the process that called Exim was running. This | |
10237 | is not the same as the user id of the originator of a message (see | |
10238 | $originator_uid). If Exim re-execs itself, this variable in the new | |
10239 | incarnation normally contains the Exim uid. | |
10240 | ||
10241 | $compile_date | |
10242 | ||
10243 | The date on which the Exim binary was compiled. | |
10244 | ||
10245 | $compile_number | |
10246 | ||
10247 | The building process for Exim keeps a count of the number of times it has | |
10248 | been compiled. This serves to distinguish different compilations of the | |
10249 | same version of the program. | |
10250 | ||
10251 | $demime_errorlevel | |
10252 | ||
10253 | This variable is available when Exim is compiled with the content-scanning | |
10254 | extension and the obsolete demime condition. For details, see section 43.6. | |
10255 | ||
10256 | $demime_reason | |
10257 | ||
10258 | This variable is available when Exim is compiled with the content-scanning | |
10259 | extension and the obsolete demime condition. For details, see section 43.6. | |
10260 | ||
10261 | $dnslist_domain, $dnslist_matched, $dnslist_text, $dnslist_value | |
10262 | ||
10263 | When a DNS (black) list lookup succeeds, these variables are set to contain | |
10264 | the following data from the lookup: the list's domain name, the key that | |
10265 | was looked up, the contents of any associated TXT record, and the value | |
10266 | from the main A record. See section 42.32 for more details. | |
10267 | ||
10268 | $domain | |
10269 | ||
10270 | When an address is being routed, or delivered on its own, this variable | |
10271 | contains the domain. Uppercase letters in the domain are converted into | |
10272 | lower case for $domain. | |
10273 | ||
10274 | Global address rewriting happens when a message is received, so the value | |
10275 | of $domain during routing and delivery is the value after rewriting. | |
10276 | $domain is set during user filtering, but not during system filtering, | |
10277 | because a message may have many recipients and the system filter is called | |
10278 | just once. | |
10279 | ||
10280 | When more than one address is being delivered at once (for example, several | |
10281 | RCPT commands in one SMTP delivery), $domain is set only if they all have | |
10282 | the same domain. Transports can be restricted to handling only one domain | |
10283 | at a time if the value of $domain is required at transport time - this is | |
10284 | the default for local transports. For further details of the environment in | |
10285 | which local transports are run, see chapter 23. | |
10286 | ||
10287 | At the end of a delivery, if all deferred addresses have the same domain, | |
10288 | it is set in $domain during the expansion of delay_warning_condition. | |
10289 | ||
10290 | The $domain variable is also used in some other circumstances: | |
10291 | ||
10292 | * When an ACL is running for a RCPT command, $domain contains the domain | |
10293 | of the recipient address. The domain of the sender address is in | |
10294 | $sender_address_domain at both MAIL time and at RCPT time. $domain is | |
10295 | not normally set during the running of the MAIL ACL. However, if the | |
10296 | sender address is verified with a callout during the MAIL ACL, the | |
10297 | sender domain is placed in $domain during the expansions of hosts, | |
10298 | interface, and port in the smtp transport. | |
10299 | ||
10300 | * When a rewrite item is being processed (see chapter 31), $domain | |
10301 | contains the domain portion of the address that is being rewritten; it | |
10302 | can be used in the expansion of the replacement address, for example, | |
10303 | to rewrite domains by file lookup. | |
10304 | ||
10305 | * With one important exception, whenever a domain list is being scanned, | |
10306 | $domain contains the subject domain. Exception: When a domain list in a | |
10307 | sender_domains condition in an ACL is being processed, the subject | |
10308 | domain is in $sender_address_domain and not in $domain. It works this | |
10309 | way so that, in a RCPT ACL, the sender domain list can be dependent on | |
10310 | the recipient domain (which is what is in $domain at this time). | |
10311 | ||
10312 | * When the smtp_etrn_command option is being expanded, $domain contains | |
10313 | the complete argument of the ETRN command (see section 47.8). | |
10314 | ||
10315 | $domain_data | |
10316 | ||
10317 | When the domains option on a router matches a domain by means of a lookup, | |
10318 | the data read by the lookup is available during the running of the router | |
10319 | as $domain_data. In addition, if the driver routes the address to a | |
10320 | transport, the value is available in that transport. If the transport is | |
10321 | handling multiple addresses, the value from the first address is used. | |
10322 | ||
10323 | $domain_data is also set when the domains condition in an ACL matches a | |
10324 | domain by means of a lookup. The data read by the lookup is available | |
10325 | during the rest of the ACL statement. In all other situations, this | |
10326 | variable expands to nothing. | |
10327 | ||
10328 | $exim_gid | |
10329 | ||
10330 | This variable contains the numerical value of the Exim group id. | |
10331 | ||
10332 | $exim_path | |
10333 | ||
10334 | This variable contains the path to the Exim binary. | |
10335 | ||
10336 | $exim_uid | |
10337 | ||
10338 | This variable contains the numerical value of the Exim user id. | |
10339 | ||
10340 | $found_extension | |
10341 | ||
10342 | This variable is available when Exim is compiled with the content-scanning | |
10343 | extension and the obsolete demime condition. For details, see section 43.6. | |
10344 | ||
10345 | $header_<name> | |
10346 | ||
10347 | This is not strictly an expansion variable. It is expansion syntax for | |
10348 | inserting the message header line with the given name. Note that the name | |
10349 | must be terminated by colon or white space, because it may contain a wide | |
10350 | variety of characters. Note also that braces must not be used. | |
10351 | ||
10352 | $headers_added | |
10353 | ||
10354 | Within an ACL this variable contains the headers added so far by the ACL | |
10355 | modifier add_header (section 42.24). The headers are a newline-separated | |
10356 | list. | |
10357 | ||
10358 | $home | |
10359 | ||
10360 | When the check_local_user option is set for a router, the user's home | |
10361 | directory is placed in $home when the check succeeds. In particular, this | |
10362 | means it is set during the running of users' filter files. A router may | |
10363 | also explicitly set a home directory for use by a transport; this can be | |
10364 | overridden by a setting on the transport itself. | |
10365 | ||
10366 | When running a filter test via the -bf option, $home is set to the value of | |
10367 | the environment variable HOME. | |
10368 | ||
10369 | $host | |
10370 | ||
10371 | If a router assigns an address to a transport (any transport), and passes a | |
10372 | list of hosts with the address, the value of $host when the transport | |
10373 | starts to run is the name of the first host on the list. Note that this | |
10374 | applies both to local and remote transports. | |
10375 | ||
10376 | For the smtp transport, if there is more than one host, the value of $host | |
10377 | changes as the transport works its way through the list. In particular, | |
10378 | when the smtp transport is expanding its options for encryption using TLS, | |
10379 | or for specifying a transport filter (see chapter 24), $host contains the | |
10380 | name of the host to which it is connected. | |
10381 | ||
10382 | When used in the client part of an authenticator configuration (see chapter | |
10383 | 33), $host contains the name of the server to which the client is | |
10384 | connected. | |
10385 | ||
10386 | $host_address | |
10387 | ||
10388 | This variable is set to the remote host's IP address whenever $host is set | |
10389 | for a remote connection. It is also set to the IP address that is being | |
10390 | checked when the ignore_target_hosts option is being processed. | |
10391 | ||
10392 | $host_data | |
10393 | ||
10394 | If a hosts condition in an ACL is satisfied by means of a lookup, the | |
10395 | result of the lookup is made available in the $host_data variable. This | |
10396 | allows you, for example, to do things like this: | |
10397 | ||
10398 | deny hosts = net-lsearch;/some/file | |
10399 | message = $host_data | |
10400 | ||
10401 | $host_lookup_deferred | |
10402 | ||
10403 | This variable normally contains "0", as does $host_lookup_failed. When a | |
10404 | message comes from a remote host and there is an attempt to look up the | |
10405 | host's name from its IP address, and the attempt is not successful, one of | |
10406 | these variables is set to "1". | |
10407 | ||
10408 | * If the lookup receives a definite negative response (for example, a DNS | |
10409 | lookup succeeded, but no records were found), $host_lookup_failed is | |
10410 | set to "1". | |
10411 | ||
10412 | * If there is any kind of problem during the lookup, such that Exim | |
10413 | cannot tell whether or not the host name is defined (for example, a | |
10414 | timeout for a DNS lookup), $host_lookup_deferred is set to "1". | |
10415 | ||
10416 | Looking up a host's name from its IP address consists of more than just a | |
10417 | single reverse lookup. Exim checks that a forward lookup of at least one of | |
10418 | the names it receives from a reverse lookup yields the original IP address. | |
10419 | If this is not the case, Exim does not accept the looked up name(s), and | |
10420 | $host_lookup_failed is set to "1". Thus, being able to find a name from an | |
10421 | IP address (for example, the existence of a PTR record in the DNS) is not | |
10422 | sufficient on its own for the success of a host name lookup. If the reverse | |
10423 | lookup succeeds, but there is a lookup problem such as a timeout when | |
10424 | checking the result, the name is not accepted, and $host_lookup_deferred is | |
10425 | set to "1". See also $sender_host_name. | |
10426 | ||
10427 | $host_lookup_failed | |
10428 | ||
10429 | See $host_lookup_deferred. | |
10430 | ||
10431 | $inode | |
10432 | ||
10433 | The only time this variable is set is while expanding the directory_file | |
10434 | option in the appendfile transport. The variable contains the inode number | |
10435 | of the temporary file which is about to be renamed. It can be used to | |
10436 | construct a unique name for the file. | |
10437 | ||
10438 | $interface_address | |
10439 | ||
10440 | This is an obsolete name for $received_ip_address. | |
10441 | ||
10442 | $interface_port | |
10443 | ||
10444 | This is an obsolete name for $received_port. | |
10445 | ||
10446 | $item | |
10447 | ||
10448 | This variable is used during the expansion of forall and forany conditions | |
10449 | (see section 11.7), and filter, map, and reduce items (see section 11.7). | |
10450 | In other circumstances, it is empty. | |
10451 | ||
10452 | $ldap_dn | |
10453 | ||
10454 | This variable, which is available only when Exim is compiled with LDAP | |
10455 | support, contains the DN from the last entry in the most recently | |
10456 | successful LDAP lookup. | |
10457 | ||
10458 | $load_average | |
10459 | ||
10460 | This variable contains the system load average, multiplied by 1000 so that | |
10461 | it is an integer. For example, if the load average is 0.21, the value of | |
10462 | the variable is 210. The value is recomputed every time the variable is | |
10463 | referenced. | |
10464 | ||
10465 | $local_part | |
10466 | ||
10467 | When an address is being routed, or delivered on its own, this variable | |
10468 | contains the local part. When a number of addresses are being delivered | |
10469 | together (for example, multiple RCPT commands in an SMTP session), | |
10470 | $local_part is not set. | |
10471 | ||
10472 | Global address rewriting happens when a message is received, so the value | |
10473 | of $local_part during routing and delivery is the value after rewriting. | |
10474 | $local_part is set during user filtering, but not during system filtering, | |
10475 | because a message may have many recipients and the system filter is called | |
10476 | just once. | |
10477 | ||
10478 | If a local part prefix or suffix has been recognized, it is not included in | |
10479 | the value of $local_part during routing and subsequent delivery. The values | |
10480 | of any prefix or suffix are in $local_part_prefix and $local_part_suffix, | |
10481 | respectively. | |
10482 | ||
10483 | When a message is being delivered to a file, pipe, or autoreply transport | |
10484 | as a result of aliasing or forwarding, $local_part is set to the local part | |
10485 | of the parent address, not to the file name or command (see $address_file | |
10486 | and $address_pipe). | |
10487 | ||
10488 | When an ACL is running for a RCPT command, $local_part contains the local | |
10489 | part of the recipient address. | |
10490 | ||
10491 | When a rewrite item is being processed (see chapter 31), $local_part | |
10492 | contains the local part of the address that is being rewritten; it can be | |
10493 | used in the expansion of the replacement address, for example. | |
10494 | ||
10495 | In all cases, all quoting is removed from the local part. For example, for | |
10496 | both the addresses | |
10497 | ||
10498 | "abc:xyz"@test.example | |
10499 | abc\:xyz@test.example | |
10500 | ||
10501 | the value of $local_part is | |
10502 | ||
10503 | abc:xyz | |
10504 | ||
10505 | If you use $local_part to create another address, you should always wrap it | |
10506 | inside a quoting operator. For example, in a redirect router you could | |
10507 | have: | |
10508 | ||
10509 | data = ${quote_local_part:$local_part}@new.domain.example | |
10510 | ||
10511 | Note: The value of $local_part is normally lower cased. If you want to | |
10512 | process local parts in a case-dependent manner in a router, you can set the | |
10513 | caseful_local_part option (see chapter 15). | |
10514 | ||
10515 | $local_part_data | |
10516 | ||
10517 | When the local_parts option on a router matches a local part by means of a | |
10518 | lookup, the data read by the lookup is available during the running of the | |
10519 | router as $local_part_data. In addition, if the driver routes the address | |
10520 | to a transport, the value is available in that transport. If the transport | |
10521 | is handling multiple addresses, the value from the first address is used. | |
10522 | ||
10523 | $local_part_data is also set when the local_parts condition in an ACL | |
10524 | matches a local part by means of a lookup. The data read by the lookup is | |
10525 | available during the rest of the ACL statement. In all other situations, | |
10526 | this variable expands to nothing. | |
10527 | ||
10528 | $local_part_prefix | |
10529 | ||
10530 | When an address is being routed or delivered, and a specific prefix for the | |
10531 | local part was recognized, it is available in this variable, having been | |
10532 | removed from $local_part. | |
10533 | ||
10534 | $local_part_suffix | |
10535 | ||
10536 | When an address is being routed or delivered, and a specific suffix for the | |
10537 | local part was recognized, it is available in this variable, having been | |
10538 | removed from $local_part. | |
10539 | ||
10540 | $local_scan_data | |
10541 | ||
10542 | This variable contains the text returned by the local_scan() function when | |
10543 | a message is received. See chapter 44 for more details. | |
10544 | ||
10545 | $local_user_gid | |
10546 | ||
10547 | See $local_user_uid. | |
10548 | ||
10549 | $local_user_uid | |
10550 | ||
10551 | This variable and $local_user_gid are set to the uid and gid after the | |
10552 | check_local_user router precondition succeeds. This means that their values | |
10553 | are available for the remaining preconditions (senders, require_files, and | |
10554 | condition), for the address_data expansion, and for any router-specific | |
10555 | expansions. At all other times, the values in these variables are "(uid_t) | |
10556 | (-1)" and "(gid_t)(-1)", respectively. | |
10557 | ||
10558 | $localhost_number | |
10559 | ||
10560 | This contains the expanded value of the localhost_number option. The | |
10561 | expansion happens after the main options have been read. | |
10562 | ||
10563 | $log_inodes | |
10564 | ||
10565 | The number of free inodes in the disk partition where Exim's log files are | |
10566 | being written. The value is recalculated whenever the variable is | |
10567 | referenced. If the relevant file system does not have the concept of | |
10568 | inodes, the value of is -1. See also the check_log_inodes option. | |
10569 | ||
10570 | $log_space | |
10571 | ||
10572 | The amount of free space (as a number of kilobytes) in the disk partition | |
10573 | where Exim's log files are being written. The value is recalculated | |
10574 | whenever the variable is referenced. If the operating system does not have | |
10575 | the ability to find the amount of free space (only true for experimental | |
10576 | systems), the space value is -1. See also the check_log_space option. | |
10577 | ||
10578 | $lookup_dnssec_authenticated | |
10579 | ||
10580 | This variable is set after a DNS lookup done by a dnsdb lookup expansion, | |
10581 | dnslookup router or smtp transport. It will be empty if DNSSEC was not | |
10582 | requested, "no" if the result was not labelled as authenticated data and | |
10583 | "yes" if it was. | |
10584 | ||
10585 | $mailstore_basename | |
10586 | ||
10587 | This variable is set only when doing deliveries in "mailstore" format in | |
10588 | the appendfile transport. During the expansion of the mailstore_prefix, | |
10589 | mailstore_suffix, message_prefix, and message_suffix options, it contains | |
10590 | the basename of the files that are being written, that is, the name without | |
10591 | the ".tmp", ".env", or ".msg" suffix. At all other times, this variable is | |
10592 | empty. | |
10593 | ||
10594 | $malware_name | |
10595 | ||
10596 | This variable is available when Exim is compiled with the content-scanning | |
10597 | extension. It is set to the name of the virus that was found when the ACL | |
10598 | malware condition is true (see section 43.1). | |
10599 | ||
10600 | $max_received_linelength | |
10601 | ||
10602 | This variable contains the number of bytes in the longest line that was | |
10603 | received as part of the message, not counting the line termination | |
10604 | character(s). | |
10605 | ||
10606 | $message_age | |
10607 | ||
10608 | This variable is set at the start of a delivery attempt to contain the | |
10609 | number of seconds since the message was received. It does not change during | |
10610 | a single delivery attempt. | |
10611 | ||
10612 | $message_body | |
10613 | ||
10614 | This variable contains the initial portion of a message's body while it is | |
10615 | being delivered, and is intended mainly for use in filter files. The | |
10616 | maximum number of characters of the body that are put into the variable is | |
10617 | set by the message_body_visible configuration option; the default is 500. | |
10618 | ||
10619 | By default, newlines are converted into spaces in $message_body, to make it | |
10620 | easier to search for phrases that might be split over a line break. | |
10621 | However, this can be disabled by setting message_body_newlines to be true. | |
10622 | Binary zeros are always converted into spaces. | |
10623 | ||
10624 | $message_body_end | |
10625 | ||
10626 | This variable contains the final portion of a message's body while it is | |
10627 | being delivered. The format and maximum size are as for $message_body. | |
10628 | ||
10629 | $message_body_size | |
10630 | ||
10631 | When a message is being delivered, this variable contains the size of the | |
10632 | body in bytes. The count starts from the character after the blank line | |
10633 | that separates the body from the header. Newlines are included in the | |
10634 | count. See also $message_size, $body_linecount, and $body_zerocount. | |
10635 | ||
10636 | $message_exim_id | |
10637 | ||
10638 | When a message is being received or delivered, this variable contains the | |
10639 | unique message id that is generated and used by Exim to identify the | |
10640 | message. An id is not created for a message until after its header has been | |
10641 | successfully received. Note: This is not the contents of the Message-ID: | |
10642 | header line; it is the local id that Exim assigns to the message, for | |
10643 | example: "1BXTIK-0001yO-VA". | |
10644 | ||
10645 | $message_headers | |
10646 | ||
10647 | This variable contains a concatenation of all the header lines when a | |
10648 | message is being processed, except for lines added by routers or | |
10649 | transports. The header lines are separated by newline characters. Their | |
10650 | contents are decoded in the same way as a header line that is inserted by | |
10651 | bheader. | |
10652 | ||
10653 | $message_headers_raw | |
10654 | ||
10655 | This variable is like $message_headers except that no processing of the | |
10656 | contents of header lines is done. | |
10657 | ||
10658 | $message_id | |
10659 | ||
10660 | This is an old name for $message_exim_id, which is now deprecated. | |
10661 | ||
10662 | $message_linecount | |
10663 | ||
10664 | This variable contains the total number of lines in the header and body of | |
10665 | the message. Compare $body_linecount, which is the count for the body only. | |
10666 | During the DATA and content-scanning ACLs, $message_linecount contains the | |
10667 | number of lines received. Before delivery happens (that is, before filters, | |
10668 | routers, and transports run) the count is increased to include the | |
10669 | Received: header line that Exim standardly adds, and also any other header | |
10670 | lines that are added by ACLs. The blank line that separates the message | |
10671 | header from the body is not counted. | |
10672 | ||
10673 | As with the special case of $message_size, during the expansion of the | |
10674 | appendfile transport's maildir_tag option in maildir format, the value of | |
10675 | $message_linecount is the precise size of the number of newlines in the | |
10676 | file that has been written (minus one for the blank line between the header | |
10677 | and the body). | |
10678 | ||
10679 | Here is an example of the use of this variable in a DATA ACL: | |
10680 | ||
10681 | deny message = Too many lines in message header | |
10682 | condition = \ | |
10683 | ${if <{250}{${eval:$message_linecount - $body_linecount}}} | |
10684 | ||
10685 | In the MAIL and RCPT ACLs, the value is zero because at that stage the | |
10686 | message has not yet been received. | |
10687 | ||
10688 | $message_size | |
10689 | ||
10690 | When a message is being processed, this variable contains its size in | |
10691 | bytes. In most cases, the size includes those headers that were received | |
10692 | with the message, but not those (such as Envelope-to:) that are added to | |
10693 | individual deliveries as they are written. However, there is one special | |
10694 | case: during the expansion of the maildir_tag option in the appendfile | |
10695 | transport while doing a delivery in maildir format, the value of | |
10696 | $message_size is the precise size of the file that has been written. See | |
10697 | also $message_body_size, $body_linecount, and $body_zerocount. | |
10698 | ||
10699 | While running a per message ACL (mail/rcpt/predata), $message_size contains | |
10700 | the size supplied on the MAIL command, or -1 if no size was given. The | |
10701 | value may not, of course, be truthful. | |
10702 | ||
10703 | $mime_xxx | |
10704 | ||
10705 | A number of variables whose names start with $mime are available when Exim | |
10706 | is compiled with the content-scanning extension. For details, see section | |
10707 | 43.4. | |
10708 | ||
10709 | $n0 - $n9 | |
10710 | ||
10711 | These variables are counters that can be incremented by means of the add | |
10712 | command in filter files. | |
10713 | ||
10714 | $original_domain | |
10715 | ||
10716 | When a top-level address is being processed for delivery, this contains the | |
10717 | same value as $domain. However, if a "child" address (for example, | |
10718 | generated by an alias, forward, or filter file) is being processed, this | |
10719 | variable contains the domain of the original address (lower cased). This | |
10720 | differs from $parent_domain only when there is more than one level of | |
10721 | aliasing or forwarding. When more than one address is being delivered in a | |
10722 | single transport run, $original_domain is not set. | |
10723 | ||
10724 | If a new address is created by means of a deliver command in a system | |
10725 | filter, it is set up with an artificial "parent" address. This has the | |
10726 | local part system-filter and the default qualify domain. | |
10727 | ||
10728 | $original_local_part | |
10729 | ||
10730 | When a top-level address is being processed for delivery, this contains the | |
10731 | same value as $local_part, unless a prefix or suffix was removed from the | |
10732 | local part, because $original_local_part always contains the full local | |
10733 | part. When a "child" address (for example, generated by an alias, forward, | |
10734 | or filter file) is being processed, this variable contains the full local | |
10735 | part of the original address. | |
10736 | ||
10737 | If the router that did the redirection processed the local part | |
10738 | case-insensitively, the value in $original_local_part is in lower case. | |
10739 | This variable differs from $parent_local_part only when there is more than | |
10740 | one level of aliasing or forwarding. When more than one address is being | |
10741 | delivered in a single transport run, $original_local_part is not set. | |
10742 | ||
10743 | If a new address is created by means of a deliver command in a system | |
10744 | filter, it is set up with an artificial "parent" address. This has the | |
10745 | local part system-filter and the default qualify domain. | |
10746 | ||
10747 | $originator_gid | |
10748 | ||
10749 | This variable contains the value of $caller_gid that was set when the | |
10750 | message was received. For messages received via the command line, this is | |
10751 | the gid of the sending user. For messages received by SMTP over TCP/IP, | |
10752 | this is normally the gid of the Exim user. | |
10753 | ||
10754 | $originator_uid | |
10755 | ||
10756 | The value of $caller_uid that was set when the message was received. For | |
10757 | messages received via the command line, this is the uid of the sending | |
10758 | user. For messages received by SMTP over TCP/IP, this is normally the uid | |
10759 | of the Exim user. | |
10760 | ||
10761 | $parent_domain | |
10762 | ||
10763 | This variable is similar to $original_domain (see above), except that it | |
10764 | refers to the immediately preceding parent address. | |
10765 | ||
10766 | $parent_local_part | |
10767 | ||
10768 | This variable is similar to $original_local_part (see above), except that | |
10769 | it refers to the immediately preceding parent address. | |
10770 | ||
10771 | $pid | |
10772 | ||
10773 | This variable contains the current process id. | |
10774 | ||
10775 | $pipe_addresses | |
10776 | ||
10777 | This is not an expansion variable, but is mentioned here because the string | |
10778 | "$pipe_addresses" is handled specially in the command specification for the | |
10779 | pipe transport (chapter 29) and in transport filters (described under | |
10780 | transport_filter in chapter 24). It cannot be used in general expansion | |
10781 | strings, and provokes an "unknown variable" error if encountered. | |
10782 | ||
10783 | $primary_hostname | |
10784 | ||
10785 | This variable contains the value set by primary_hostname in the | |
10786 | configuration file, or read by the uname() function. If uname() returns a | |
10787 | single-component name, Exim calls gethostbyname() (or getipnodebyname() | |
10788 | where available) in an attempt to acquire a fully qualified host name. See | |
10789 | also $smtp_active_hostname. | |
10790 | ||
10791 | $prvscheck_address | |
10792 | ||
10793 | This variable is used in conjunction with the prvscheck expansion item, | |
10794 | which is described in sections 11.5 and 42.51. | |
10795 | ||
10796 | $prvscheck_keynum | |
10797 | ||
10798 | This variable is used in conjunction with the prvscheck expansion item, | |
10799 | which is described in sections 11.5 and 42.51. | |
10800 | ||
10801 | $prvscheck_result | |
10802 | ||
10803 | This variable is used in conjunction with the prvscheck expansion item, | |
10804 | which is described in sections 11.5 and 42.51. | |
10805 | ||
10806 | $qualify_domain | |
10807 | ||
10808 | The value set for the qualify_domain option in the configuration file. | |
10809 | ||
10810 | $qualify_recipient | |
10811 | ||
10812 | The value set for the qualify_recipient option in the configuration file, | |
10813 | or if not set, the value of $qualify_domain. | |
10814 | ||
10815 | $rcpt_count | |
10816 | ||
10817 | When a message is being received by SMTP, this variable contains the number | |
10818 | of RCPT commands received for the current message. If this variable is used | |
10819 | in a RCPT ACL, its value includes the current command. | |
10820 | ||
10821 | $rcpt_defer_count | |
10822 | ||
10823 | When a message is being received by SMTP, this variable contains the number | |
10824 | of RCPT commands in the current message that have previously been rejected | |
10825 | with a temporary (4xx) response. | |
10826 | ||
10827 | $rcpt_fail_count | |
10828 | ||
10829 | When a message is being received by SMTP, this variable contains the number | |
10830 | of RCPT commands in the current message that have previously been rejected | |
10831 | with a permanent (5xx) response. | |
10832 | ||
10833 | $received_count | |
10834 | ||
10835 | This variable contains the number of Received: header lines in the message, | |
10836 | including the one added by Exim (so its value is always greater than zero). | |
10837 | It is available in the DATA ACL, the non-SMTP ACL, and while routing and | |
10838 | delivering. | |
10839 | ||
10840 | $received_for | |
10841 | ||
10842 | If there is only a single recipient address in an incoming message, this | |
10843 | variable contains that address when the Received: header line is being | |
10844 | built. The value is copied after recipient rewriting has happened, but | |
10845 | before the local_scan() function is run. | |
10846 | ||
10847 | $received_ip_address | |
10848 | ||
10849 | As soon as an Exim server starts processing an incoming TCP/IP connection, | |
10850 | this variable is set to the address of the local IP interface, and | |
10851 | $received_port is set to the local port number. (The remote IP address and | |
10852 | port are in $sender_host_address and $sender_host_port.) When testing with | |
10853 | -bh, the port value is -1 unless it has been set using the -oMi command | |
10854 | line option. | |
10855 | ||
10856 | As well as being useful in ACLs (including the "connect" ACL), these | |
10857 | variable could be used, for example, to make the file name for a TLS | |
10858 | certificate depend on which interface and/or port is being used for the | |
10859 | incoming connection. The values of $received_ip_address and $received_port | |
10860 | are saved with any messages that are received, thus making these variables | |
10861 | available at delivery time. | |
10862 | ||
10863 | Note: There are no equivalent variables for outgoing connections, because | |
10864 | the values are unknown (unless they are explicitly set by options of the | |
10865 | smtp transport). | |
10866 | ||
10867 | $received_port | |
10868 | ||
10869 | See $received_ip_address. | |
10870 | ||
10871 | $received_protocol | |
10872 | ||
10873 | When a message is being processed, this variable contains the name of the | |
10874 | protocol by which it was received. Most of the names used by Exim are | |
10875 | defined by RFCs 821, 2821, and 3848. They start with "smtp" (the client | |
10876 | used HELO) or "esmtp" (the client used EHLO). This can be followed by "s" | |
10877 | for secure (encrypted) and/or "a" for authenticated. Thus, for example, if | |
10878 | the protocol is set to "esmtpsa", the message was received over an | |
10879 | encrypted SMTP connection and the client was successfully authenticated. | |
10880 | ||
10881 | Exim uses the protocol name "smtps" for the case when encryption is | |
10882 | automatically set up on connection without the use of STARTTLS (see | |
10883 | tls_on_connect_ports), and the client uses HELO to initiate the encrypted | |
10884 | SMTP session. The name "smtps" is also used for the rare situation where | |
10885 | the client initially uses EHLO, sets up an encrypted connection using | |
10886 | STARTTLS, and then uses HELO afterwards. | |
10887 | ||
10888 | The -oMr option provides a way of specifying a custom protocol name for | |
10889 | messages that are injected locally by trusted callers. This is commonly | |
10890 | used to identify messages that are being re-injected after some kind of | |
10891 | scanning. | |
10892 | ||
10893 | $received_time | |
10894 | ||
10895 | This variable contains the date and time when the current message was | |
10896 | received, as a number of seconds since the start of the Unix epoch. | |
10897 | ||
10898 | $recipient_data | |
10899 | ||
10900 | This variable is set after an indexing lookup success in an ACL recipients | |
10901 | condition. It contains the data from the lookup, and the value remains set | |
10902 | until the next recipients test. Thus, you can do things like this: | |
10903 | ||
10904 | require recipients = cdb*@;/some/file | |
10905 | deny some further test involving $recipient_data | |
10906 | ||
10907 | Warning: This variable is set only when a lookup is used as an indexing | |
10908 | method in the address list, using the semicolon syntax as in the example | |
10909 | above. The variable is not set for a lookup that is used as part of the | |
10910 | string expansion that all such lists undergo before being interpreted. | |
10911 | ||
10912 | $recipient_verify_failure | |
10913 | ||
10914 | In an ACL, when a recipient verification fails, this variable contains | |
10915 | information about the failure. It is set to one of the following words: | |
10916 | ||
10917 | * "qualify": The address was unqualified (no domain), and the message was | |
10918 | neither local nor came from an exempted host. | |
10919 | ||
10920 | * "route": Routing failed. | |
10921 | ||
10922 | * "mail": Routing succeeded, and a callout was attempted; rejection | |
10923 | occurred at or before the MAIL command (that is, on initial connection, | |
10924 | HELO, or MAIL). | |
10925 | ||
10926 | * "recipient": The RCPT command in a callout was rejected. | |
10927 | ||
10928 | * "postmaster": The postmaster check in a callout was rejected. | |
10929 | ||
10930 | The main use of this variable is expected to be to distinguish between | |
10931 | rejections of MAIL and rejections of RCPT. | |
10932 | ||
10933 | $recipients | |
10934 | ||
10935 | This variable contains a list of envelope recipients for a message. A comma | |
10936 | and a space separate the addresses in the replacement text. However, the | |
10937 | variable is not generally available, to prevent exposure of Bcc recipients | |
10938 | in unprivileged users' filter files. You can use $recipients only in these | |
10939 | cases: | |
10940 | ||
10941 | 1. In a system filter file. | |
10942 | ||
10943 | 2. In the ACLs associated with the DATA command and with non-SMTP | |
10944 | messages, that is, the ACLs defined by acl_smtp_predata, acl_smtp_data, | |
10945 | acl_smtp_mime, acl_not_smtp_start, acl_not_smtp, and acl_not_smtp_mime. | |
10946 | ||
10947 | 3. From within a local_scan() function. | |
10948 | ||
10949 | $recipients_count | |
10950 | ||
10951 | When a message is being processed, this variable contains the number of | |
10952 | envelope recipients that came with the message. Duplicates are not excluded | |
10953 | from the count. While a message is being received over SMTP, the number | |
10954 | increases for each accepted recipient. It can be referenced in an ACL. | |
10955 | ||
10956 | $regex_match_string | |
10957 | ||
10958 | This variable is set to contain the matching regular expression after a | |
10959 | regex ACL condition has matched (see section 43.5). | |
10960 | ||
10961 | $reply_address | |
10962 | ||
10963 | When a message is being processed, this variable contains the contents of | |
10964 | the Reply-To: header line if one exists and it is not empty, or otherwise | |
10965 | the contents of the From: header line. Apart from the removal of leading | |
10966 | white space, the value is not processed in any way. In particular, no RFC | |
10967 | 2047 decoding or character code translation takes place. | |
10968 | ||
10969 | $return_path | |
10970 | ||
10971 | When a message is being delivered, this variable contains the return path - | |
10972 | the sender field that will be sent as part of the envelope. It is not | |
10973 | enclosed in <> characters. At the start of routing an address, $return_path | |
10974 | has the same value as $sender_address, but if, for example, an incoming | |
10975 | message to a mailing list has been expanded by a router which specifies a | |
10976 | different address for bounce messages, $return_path subsequently contains | |
10977 | the new bounce address, whereas $sender_address always contains the | |
10978 | original sender address that was received with the message. In other words, | |
10979 | $sender_address contains the incoming envelope sender, and $return_path | |
10980 | contains the outgoing envelope sender. | |
10981 | ||
10982 | $return_size_limit | |
10983 | ||
10984 | This is an obsolete name for $bounce_return_size_limit. | |
10985 | ||
10986 | $router_name | |
10987 | ||
10988 | During the running of a router this variable contains its name. | |
10989 | ||
10990 | $runrc | |
10991 | ||
10992 | This variable contains the return code from a command that is run by the $ | |
10993 | {run...} expansion item. Warning: In a router or transport, you cannot | |
10994 | assume the order in which option values are expanded, except for those | |
10995 | preconditions whose order of testing is documented. Therefore, you cannot | |
10996 | reliably expect to set $runrc by the expansion of one option, and use it in | |
10997 | another. | |
10998 | ||
10999 | $self_hostname | |
11000 | ||
11001 | When an address is routed to a supposedly remote host that turns out to be | |
11002 | the local host, what happens is controlled by the self generic router | |
11003 | option. One of its values causes the address to be passed to another | |
11004 | router. When this happens, $self_hostname is set to the name of the local | |
11005 | host that the original router encountered. In other circumstances its | |
11006 | contents are null. | |
11007 | ||
11008 | $sender_address | |
11009 | ||
11010 | When a message is being processed, this variable contains the sender's | |
11011 | address that was received in the message's envelope. The case of letters in | |
11012 | the address is retained, in both the local part and the domain. For bounce | |
11013 | messages, the value of this variable is the empty string. See also | |
11014 | $return_path. | |
11015 | ||
11016 | $sender_address_data | |
11017 | ||
11018 | If $address_data is set when the routers are called from an ACL to verify a | |
11019 | sender address, the final value is preserved in $sender_address_data, to | |
11020 | distinguish it from data from a recipient address. The value does not | |
11021 | persist after the end of the current ACL statement. If you want to preserve | |
11022 | it for longer, you can save it in an ACL variable. | |
11023 | ||
11024 | $sender_address_domain | |
11025 | ||
11026 | The domain portion of $sender_address. | |
11027 | ||
11028 | $sender_address_local_part | |
11029 | ||
11030 | The local part portion of $sender_address. | |
11031 | ||
11032 | $sender_data | |
11033 | ||
11034 | This variable is set after a lookup success in an ACL senders condition or | |
11035 | in a router senders option. It contains the data from the lookup, and the | |
11036 | value remains set until the next senders test. Thus, you can do things like | |
11037 | this: | |
11038 | ||
11039 | require senders = cdb*@;/some/file | |
11040 | deny some further test involving $sender_data | |
11041 | ||
11042 | Warning: This variable is set only when a lookup is used as an indexing | |
11043 | method in the address list, using the semicolon syntax as in the example | |
11044 | above. The variable is not set for a lookup that is used as part of the | |
11045 | string expansion that all such lists undergo before being interpreted. | |
11046 | ||
11047 | $sender_fullhost | |
11048 | ||
11049 | When a message is received from a remote host, this variable contains the | |
11050 | host name and IP address in a single string. It ends with the IP address in | |
11051 | square brackets, followed by a colon and a port number if the logging of | |
11052 | ports is enabled. The format of the rest of the string depends on whether | |
11053 | the host issued a HELO or EHLO SMTP command, and whether the host name was | |
11054 | verified by looking up its IP address. (Looking up the IP address can be | |
11055 | forced by the host_lookup option, independent of verification.) A plain | |
11056 | host name at the start of the string is a verified host name; if this is | |
11057 | not present, verification either failed or was not requested. A host name | |
11058 | in parentheses is the argument of a HELO or EHLO command. This is omitted | |
11059 | if it is identical to the verified host name or to the host's IP address in | |
11060 | square brackets. | |
11061 | ||
11062 | $sender_helo_name | |
11063 | ||
11064 | When a message is received from a remote host that has issued a HELO or | |
11065 | EHLO command, the argument of that command is placed in this variable. It | |
11066 | is also set if HELO or EHLO is used when a message is received using SMTP | |
11067 | locally via the -bs or -bS options. | |
11068 | ||
11069 | $sender_host_address | |
11070 | ||
11071 | When a message is received from a remote host, this variable contains that | |
11072 | host's IP address. For locally submitted messages, it is empty. | |
11073 | ||
11074 | $sender_host_authenticated | |
11075 | ||
11076 | This variable contains the name (not the public name) of the authenticator | |
11077 | driver that successfully authenticated the client from which the message | |
11078 | was received. It is empty if there was no successful authentication. See | |
11079 | also $authenticated_id. | |
11080 | ||
11081 | $sender_host_dnssec | |
11082 | ||
11083 | If an attempt to populate $sender_host_name has been made (by reference, | |
11084 | hosts_lookup or otherwise) then this boolean will have been set true if, | |
11085 | and only if, the resolver library states that the reverse DNS was | |
11086 | authenticated data. At all other times, this variable is false. | |
11087 | ||
11088 | It is likely that you will need to coerce DNSSEC support on in the resolver | |
11089 | library, by setting: | |
11090 | ||
11091 | dns_dnssec_ok = 1 | |
11092 | ||
11093 | Exim does not perform DNSSEC validation itself, instead leaving that to a | |
11094 | validating resolver (eg, unbound, or bind with suitable configuration). | |
11095 | ||
11096 | Exim does not (currently) check to see if the forward DNS was also secured | |
11097 | with DNSSEC, only the reverse DNS. | |
11098 | ||
11099 | If you have changed host_lookup_order so that "bydns" is not the first | |
11100 | mechanism in the list, then this variable will be false. | |
11101 | ||
11102 | $sender_host_name | |
11103 | ||
11104 | When a message is received from a remote host, this variable contains the | |
11105 | host's name as obtained by looking up its IP address. For messages received | |
11106 | by other means, this variable is empty. | |
11107 | ||
11108 | If the host name has not previously been looked up, a reference to | |
11109 | $sender_host_name triggers a lookup (for messages from remote hosts). A | |
11110 | looked up name is accepted only if it leads back to the original IP address | |
11111 | via a forward lookup. If either the reverse or the forward lookup fails to | |
11112 | find any data, or if the forward lookup does not yield the original IP | |
11113 | address, $sender_host_name remains empty, and $host_lookup_failed is set to | |
11114 | "1". | |
11115 | ||
11116 | However, if either of the lookups cannot be completed (for example, there | |
11117 | is a DNS timeout), $host_lookup_deferred is set to "1", and | |
11118 | $host_lookup_failed remains set to "0". | |
11119 | ||
11120 | Once $host_lookup_failed is set to "1", Exim does not try to look up the | |
11121 | host name again if there is a subsequent reference to $sender_host_name in | |
11122 | the same Exim process, but it does try again if $host_lookup_deferred is | |
11123 | set to "1". | |
11124 | ||
11125 | Exim does not automatically look up every calling host's name. If you want | |
11126 | maximum efficiency, you should arrange your configuration so that it avoids | |
11127 | these lookups altogether. The lookup happens only if one or more of the | |
11128 | following are true: | |
11129 | ||
11130 | * A string containing $sender_host_name is expanded. | |
11131 | ||
11132 | * The calling host matches the list in host_lookup. In the default | |
11133 | configuration, this option is set to *, so it must be changed if | |
11134 | lookups are to be avoided. (In the code, the default for host_lookup is | |
11135 | unset.) | |
11136 | ||
11137 | * Exim needs the host name in order to test an item in a host list. The | |
11138 | items that require this are described in sections 10.13 and 10.17. | |
11139 | ||
11140 | * The calling host matches helo_try_verify_hosts or helo_verify_hosts. In | |
11141 | this case, the host name is required to compare with the name quoted in | |
11142 | any EHLO or HELO commands that the client issues. | |
11143 | ||
11144 | * The remote host issues a EHLO or HELO command that quotes one of the | |
11145 | domains in helo_lookup_domains. The default value of this option is | |
11146 | ||
11147 | helo_lookup_domains = @ : @[] | |
11148 | ||
11149 | which causes a lookup if a remote host (incorrectly) gives the server's | |
11150 | name or IP address in an EHLO or HELO command. | |
11151 | ||
11152 | $sender_host_port | |
11153 | ||
11154 | When a message is received from a remote host, this variable contains the | |
11155 | port number that was used on the remote host. | |
11156 | ||
11157 | $sender_ident | |
11158 | ||
11159 | When a message is received from a remote host, this variable contains the | |
11160 | identification received in response to an RFC 1413 request. When a message | |
11161 | has been received locally, this variable contains the login name of the | |
11162 | user that called Exim. | |
11163 | ||
11164 | $sender_rate_xxx | |
11165 | ||
11166 | A number of variables whose names begin $sender_rate_ are set as part of | |
11167 | the ratelimit ACL condition. Details are given in section 42.38. | |
11168 | ||
11169 | $sender_rcvhost | |
11170 | ||
11171 | This is provided specifically for use in Received: headers. It starts with | |
11172 | either the verified host name (as obtained from a reverse DNS lookup) or, | |
11173 | if there is no verified host name, the IP address in square brackets. After | |
11174 | that there may be text in parentheses. When the first item is a verified | |
11175 | host name, the first thing in the parentheses is the IP address in square | |
11176 | brackets, followed by a colon and a port number if port logging is enabled. | |
11177 | When the first item is an IP address, the port is recorded as "port=xxxx" | |
11178 | inside the parentheses. | |
11179 | ||
11180 | There may also be items of the form "helo=xxxx" if HELO or EHLO was used | |
11181 | and its argument was not identical to the real host name or IP address, and | |
11182 | "ident=xxxx" if an RFC 1413 ident string is available. If all three items | |
11183 | are present in the parentheses, a newline and tab are inserted into the | |
11184 | string, to improve the formatting of the Received: header. | |
11185 | ||
11186 | $sender_verify_failure | |
11187 | ||
11188 | In an ACL, when a sender verification fails, this variable contains | |
11189 | information about the failure. The details are the same as for | |
11190 | $recipient_verify_failure. | |
11191 | ||
11192 | $sending_ip_address | |
11193 | ||
11194 | This variable is set whenever an outgoing SMTP connection to another host | |
11195 | has been set up. It contains the IP address of the local interface that is | |
11196 | being used. This is useful if a host that has more than one IP address | |
11197 | wants to take on different personalities depending on which one is being | |
11198 | used. For incoming connections, see $received_ip_address. | |
11199 | ||
11200 | $sending_port | |
11201 | ||
11202 | This variable is set whenever an outgoing SMTP connection to another host | |
11203 | has been set up. It contains the local port that is being used. For | |
11204 | incoming connections, see $received_port. | |
11205 | ||
11206 | $smtp_active_hostname | |
11207 | ||
11208 | During an incoming SMTP session, this variable contains the value of the | |
11209 | active host name, as specified by the smtp_active_hostname option. The | |
11210 | value of $smtp_active_hostname is saved with any message that is received, | |
11211 | so its value can be consulted during routing and delivery. | |
11212 | ||
11213 | $smtp_command | |
11214 | ||
11215 | During the processing of an incoming SMTP command, this variable contains | |
11216 | the entire command. This makes it possible to distinguish between HELO and | |
11217 | EHLO in the HELO ACL, and also to distinguish between commands such as | |
11218 | these: | |
11219 | ||
11220 | MAIL FROM:<> | |
11221 | MAIL FROM: <> | |
11222 | ||
11223 | For a MAIL command, extra parameters such as SIZE can be inspected. For a | |
11224 | RCPT command, the address in $smtp_command is the original address before | |
11225 | any rewriting, whereas the values in $local_part and $domain are taken from | |
11226 | the address after SMTP-time rewriting. | |
11227 | ||
11228 | $smtp_command_argument | |
11229 | ||
11230 | While an ACL is running to check an SMTP command, this variable contains | |
11231 | the argument, that is, the text that follows the command name, with leading | |
11232 | white space removed. Following the introduction of $smtp_command, this | |
11233 | variable is somewhat redundant, but is retained for backwards | |
11234 | compatibility. | |
11235 | ||
11236 | $smtp_count_at_connection_start | |
11237 | ||
11238 | This variable is set greater than zero only in processes spawned by the | |
11239 | Exim daemon for handling incoming SMTP connections. The name is | |
11240 | deliberately long, in order to emphasize what the contents are. When the | |
11241 | daemon accepts a new connection, it increments this variable. A copy of the | |
11242 | variable is passed to the child process that handles the connection, but | |
11243 | its value is fixed, and never changes. It is only an approximation of how | |
11244 | many incoming connections there actually are, because many other | |
11245 | connections may come and go while a single connection is being processed. | |
11246 | When a child process terminates, the daemon decrements its copy of the | |
11247 | variable. | |
11248 | ||
11249 | $sn0 - $sn9 | |
11250 | ||
11251 | These variables are copies of the values of the $n0 - $n9 accumulators that | |
11252 | were current at the end of the system filter file. This allows a system | |
11253 | filter file to set values that can be tested in users' filter files. For | |
11254 | example, a system filter could set a value indicating how likely it is that | |
11255 | a message is junk mail. | |
11256 | ||
11257 | $spam_xxx | |
11258 | ||
11259 | A number of variables whose names start with $spam are available when Exim | |
11260 | is compiled with the content-scanning extension. For details, see section | |
11261 | 43.2. | |
11262 | ||
11263 | $spool_directory | |
11264 | ||
11265 | The name of Exim's spool directory. | |
11266 | ||
11267 | $spool_inodes | |
11268 | ||
11269 | The number of free inodes in the disk partition where Exim's spool files | |
11270 | are being written. The value is recalculated whenever the variable is | |
11271 | referenced. If the relevant file system does not have the concept of | |
11272 | inodes, the value of is -1. See also the check_spool_inodes option. | |
11273 | ||
11274 | $spool_space | |
11275 | ||
11276 | The amount of free space (as a number of kilobytes) in the disk partition | |
11277 | where Exim's spool files are being written. The value is recalculated | |
11278 | whenever the variable is referenced. If the operating system does not have | |
11279 | the ability to find the amount of free space (only true for experimental | |
11280 | systems), the space value is -1. For example, to check in an ACL that there | |
11281 | is at least 50 megabytes free on the spool, you could write: | |
11282 | ||
11283 | condition = ${if > {$spool_space}{50000}} | |
11284 | ||
11285 | See also the check_spool_space option. | |
11286 | ||
11287 | $thisaddress | |
11288 | ||
11289 | This variable is set only during the processing of the foranyaddress | |
11290 | command in a filter file. Its use is explained in the description of that | |
11291 | command, which can be found in the separate document entitled Exim's | |
11292 | interfaces to mail filtering. | |
11293 | ||
11294 | $tls_in_bits | |
11295 | ||
11296 | Contains an approximation of the TLS cipher's bit-strength on the inbound | |
11297 | connection; the meaning of this depends upon the TLS implementation used. | |
11298 | If TLS has not been negotiated, the value will be 0. The value of this is | |
11299 | automatically fed into the Cyrus SASL authenticator when acting as a | |
11300 | server, to specify the "external SSF" (a SASL term). | |
11301 | ||
11302 | The deprecated $tls_bits variable refers to the inbound side except when | |
11303 | used in the context of an outbound SMTP delivery, when it refers to the | |
11304 | outbound. | |
11305 | ||
11306 | $tls_out_bits | |
11307 | ||
11308 | Contains an approximation of the TLS cipher's bit-strength on an outbound | |
11309 | SMTP connection; the meaning of this depends upon the TLS implementation | |
11310 | used. If TLS has not been negotiated, the value will be 0. | |
11311 | ||
11312 | $tls_in_ourcert | |
11313 | ||
11314 | This variable refers to the certificate presented to the peer of an inbound | |
11315 | connection when the message was received. It is only useful as the argument | |
11316 | of a certextract expansion item, md5 or sha1 operator, or a def condition. | |
11317 | ||
11318 | $tls_in_peercert | |
11319 | ||
11320 | This variable refers to the certificate presented by the peer of an inbound | |
11321 | connection when the message was received. It is only useful as the argument | |
11322 | of a certextract expansion item, md5 or sha1 operator, or a def condition. | |
11323 | ||
11324 | $tls_out_ourcert | |
11325 | ||
11326 | This variable refers to the certificate presented to the peer of an | |
11327 | outbound connection. It is only useful as the argument of a certextract | |
11328 | expansion item, md5 or sha1 operator, or a def condition. | |
11329 | ||
11330 | $tls_out_peercert | |
11331 | ||
11332 | This variable refers to the certificate presented by the peer of an | |
11333 | outbound connection. It is only useful as the argument of a certextract | |
11334 | expansion item, md5 or sha1 operator, or a def condition. | |
11335 | ||
11336 | $tls_in_certificate_verified | |
11337 | ||
11338 | This variable is set to "1" if a TLS certificate was verified when the | |
11339 | message was received, and "0" otherwise. | |
11340 | ||
11341 | The deprecated $tls_certificate_verfied variable refers to the inbound side | |
11342 | except when used in the context of an outbound SMTP delivery, when it | |
11343 | refers to the outbound. | |
11344 | ||
11345 | $tls_out_certificate_verified | |
11346 | ||
11347 | This variable is set to "1" if a TLS certificate was verified when an | |
11348 | outbound SMTP connection was made, and "0" otherwise. | |
11349 | ||
11350 | $tls_in_cipher | |
11351 | ||
11352 | When a message is received from a remote host over an encrypted SMTP | |
11353 | connection, this variable is set to the cipher suite that was negotiated, | |
11354 | for example DES-CBC3-SHA. In other circumstances, in particular, for | |
11355 | message received over unencrypted connections, the variable is empty. | |
11356 | Testing $tls_cipher for emptiness is one way of distinguishing between | |
11357 | encrypted and non-encrypted connections during ACL processing. | |
11358 | ||
11359 | The deprecated $tls_cipher variable is the same as $tls_in_cipher during | |
11360 | message reception, but in the context of an outward SMTP delivery taking | |
11361 | place via the smtp transport becomes the same as $tls_out_cipher. | |
11362 | ||
11363 | $tls_out_cipher | |
11364 | ||
11365 | This variable is cleared before any outgoing SMTP connection is made, and | |
11366 | then set to the outgoing cipher suite if one is negotiated. See chapter 41 | |
11367 | for details of TLS support and chapter 30 for details of the smtp | |
11368 | transport. | |
11369 | ||
11370 | $tls_in_ocsp | |
11371 | ||
11372 | When a message is received from a remote client connection the result of | |
11373 | any OCSP request from the client is encoded in this variable: | |
11374 | ||
11375 | 0 OCSP proof was not requested (default value) | |
11376 | 1 No response to request | |
11377 | 2 Response not verified | |
11378 | 3 Verification failed | |
11379 | 4 Verification succeeded | |
11380 | ||
11381 | $tls_out_ocsp | |
11382 | ||
11383 | When a message is sent to a remote host connection the result of any OCSP | |
11384 | request made is encoded in this variable. See $tls_in_ocsp for values. | |
11385 | ||
11386 | $tls_in_peerdn | |
11387 | ||
11388 | When a message is received from a remote host over an encrypted SMTP | |
11389 | connection, and Exim is configured to request a certificate from the | |
11390 | client, the value of the Distinguished Name of the certificate is made | |
11391 | available in the $tls_in_peerdn during subsequent processing. | |
11392 | ||
11393 | The deprecated $tls_peerdn variable refers to the inbound side except when | |
11394 | used in the context of an outbound SMTP delivery, when it refers to the | |
11395 | outbound. | |
11396 | ||
11397 | $tls_out_peerdn | |
11398 | ||
11399 | When a message is being delivered to a remote host over an encrypted SMTP | |
11400 | connection, and Exim is configured to request a certificate from the | |
11401 | server, the value of the Distinguished Name of the certificate is made | |
11402 | available in the $tls_out_peerdn during subsequent processing. | |
11403 | ||
11404 | $tls_in_sni | |
11405 | ||
11406 | When a TLS session is being established, if the client sends the Server | |
11407 | Name Indication extension, the value will be placed in this variable. If | |
11408 | the variable appears in tls_certificate then this option and some others, | |
11409 | described in 41.10, will be re-expanded early in the TLS session, to permit | |
11410 | a different certificate to be presented (and optionally a different key to | |
11411 | be used) to the client, based upon the value of the SNI extension. | |
11412 | ||
11413 | The deprecated $tls_sni variable refers to the inbound side except when | |
11414 | used in the context of an outbound SMTP delivery, when it refers to the | |
11415 | outbound. | |
11416 | ||
11417 | $tls_out_sni | |
11418 | ||
11419 | During outbound SMTP deliveries, this variable reflects the value of the | |
11420 | tls_sni option on the transport. | |
11421 | ||
11422 | $tod_bsdinbox | |
11423 | ||
11424 | The time of day and the date, in the format required for BSD-style mailbox | |
11425 | files, for example: Thu Oct 17 17:14:09 1995. | |
11426 | ||
11427 | $tod_epoch | |
11428 | ||
11429 | The time and date as a number of seconds since the start of the Unix epoch. | |
11430 | ||
11431 | $tod_epoch_l | |
11432 | ||
11433 | The time and date as a number of microseconds since the start of the Unix | |
11434 | epoch. | |
11435 | ||
11436 | $tod_full | |
11437 | ||
11438 | A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40 | |
11439 | +0100. The timezone is always given as a numerical offset from UTC, with | |
11440 | positive values used for timezones that are ahead (east) of UTC, and | |
11441 | negative values for those that are behind (west). | |
11442 | ||
11443 | $tod_log | |
11444 | ||
11445 | The time and date in the format used for writing Exim's log files, for | |
11446 | example: 1995-10-12 15:32:29, but without a timezone. | |
11447 | ||
11448 | $tod_logfile | |
11449 | ||
11450 | This variable contains the date in the format yyyymmdd. This is the format | |
11451 | that is used for datestamping log files when log_file_path contains the | |
11452 | "%D" flag. | |
11453 | ||
11454 | $tod_zone | |
11455 | ||
11456 | This variable contains the numerical value of the local timezone, for | |
11457 | example: -0500. | |
11458 | ||
11459 | $tod_zulu | |
11460 | ||
11461 | This variable contains the UTC date and time in "Zulu" format, as specified | |
11462 | by ISO 8601, for example: 20030221154023Z. | |
11463 | ||
11464 | $transport_name | |
11465 | ||
11466 | During the running of a transport, this variable contains its name. | |
11467 | ||
11468 | $value | |
11469 | ||
11470 | This variable contains the result of an expansion lookup, extraction | |
11471 | operation, or external command, as described above. It is also used during | |
11472 | a reduce expansion. | |
11473 | ||
11474 | $version_number | |
11475 | ||
11476 | The version number of Exim. | |
11477 | ||
11478 | $warn_message_delay | |
11479 | ||
11480 | This variable is set only during the creation of a message warning about a | |
11481 | delivery delay. Details of its use are explained in section 48.2. | |
11482 | ||
11483 | $warn_message_recipients | |
11484 | ||
11485 | This variable is set only during the creation of a message warning about a | |
11486 | delivery delay. Details of its use are explained in section 48.2. | |
11487 | ||
11488 | ||
11489 | ||
11490 | =============================================================================== | |
11491 | 12. EMBEDDED PERL | |
11492 | ||
11493 | Exim can be built to include an embedded Perl interpreter. When this is done, | |
11494 | Perl subroutines can be called as part of the string expansion process. To make | |
11495 | use of the Perl support, you need version 5.004 or later of Perl installed on | |
11496 | your system. To include the embedded interpreter in the Exim binary, include | |
11497 | the line | |
11498 | ||
11499 | EXIM_PERL = perl.o | |
11500 | ||
11501 | in your Local/Makefile and then build Exim in the normal way. | |
11502 | ||
11503 | ||
11504 | 12.1 Setting up so Perl can be used | |
11505 | ----------------------------------- | |
11506 | ||
11507 | Access to Perl subroutines is via a global configuration option called | |
11508 | perl_startup and an expansion string operator ${perl ...}. If there is no | |
11509 | perl_startup option in the Exim configuration file then no Perl interpreter is | |
11510 | started and there is almost no overhead for Exim (since none of the Perl | |
11511 | library will be paged in unless used). If there is a perl_startup option then | |
11512 | the associated value is taken to be Perl code which is executed in a newly | |
11513 | created Perl interpreter. | |
11514 | ||
11515 | The value of perl_startup is not expanded in the Exim sense, so you do not need | |
11516 | backslashes before any characters to escape special meanings. The option should | |
11517 | usually be something like | |
11518 | ||
11519 | perl_startup = do '/etc/exim.pl' | |
11520 | ||
11521 | where /etc/exim.pl is Perl code which defines any subroutines you want to use | |
11522 | from Exim. Exim can be configured either to start up a Perl interpreter as soon | |
11523 | as it is entered, or to wait until the first time it is needed. Starting the | |
11524 | interpreter at the beginning ensures that it is done while Exim still has its | |
11525 | setuid privilege, but can impose an unnecessary overhead if Perl is not in fact | |
11526 | used in a particular run. Also, note that this does not mean that Exim is | |
11527 | necessarily running as root when Perl is called at a later time. By default, | |
11528 | the interpreter is started only when it is needed, but this can be changed in | |
11529 | two ways: | |
11530 | ||
11531 | * Setting perl_at_start (a boolean option) in the configuration requests a | |
11532 | startup when Exim is entered. | |
11533 | ||
11534 | * The command line option -ps also requests a startup when Exim is entered, | |
11535 | overriding the setting of perl_at_start. | |
11536 | ||
11537 | There is also a command line option -pd (for delay) which suppresses the | |
11538 | initial startup, even if perl_at_start is set. | |
11539 | ||
11540 | ||
11541 | 12.2 Calling Perl subroutines | |
11542 | ----------------------------- | |
11543 | ||
11544 | When the configuration file includes a perl_startup option you can make use of | |
11545 | the string expansion item to call the Perl subroutines that are defined by the | |
11546 | perl_startup code. The operator is used in any of the following forms: | |
11547 | ||
11548 | ${perl{foo}} | |
11549 | ${perl{foo}{argument}} | |
11550 | ${perl{foo}{argument1}{argument2} ... } | |
11551 | ||
11552 | which calls the subroutine foo with the given arguments. A maximum of eight | |
11553 | arguments may be passed. Passing more than this results in an expansion failure | |
11554 | with an error message of the form | |
11555 | ||
11556 | Too many arguments passed to Perl subroutine "foo" (max is 8) | |
11557 | ||
11558 | The return value of the Perl subroutine is evaluated in a scalar context before | |
11559 | it is passed back to Exim to be inserted into the expanded string. If the | |
11560 | return value is undef, the expansion is forced to fail in the same way as an | |
11561 | explicit "fail" on an if or lookup item. If the subroutine aborts by obeying | |
11562 | Perl's die function, the expansion fails with the error message that was passed | |
11563 | to die. | |
11564 | ||
11565 | ||
11566 | 12.3 Calling Exim functions from Perl | |
11567 | ------------------------------------- | |
11568 | ||
11569 | Within any Perl code called from Exim, the function Exim::expand_string() is | |
11570 | available to call back into Exim's string expansion function. For example, the | |
11571 | Perl code | |
11572 | ||
11573 | my $lp = Exim::expand_string('$local_part'); | |
11574 | ||
11575 | makes the current Exim $local_part available in the Perl variable $lp. Note | |
11576 | those are single quotes and not double quotes to protect against $local_part | |
11577 | being interpolated as a Perl variable. | |
11578 | ||
11579 | If the string expansion is forced to fail by a "fail" item, the result of | |
11580 | Exim::expand_string() is undef. If there is a syntax error in the expansion | |
11581 | string, the Perl call from the original expansion string fails with an | |
11582 | appropriate error message, in the same way as if die were used. | |
11583 | ||
11584 | Two other Exim functions are available for use from within Perl code. | |
11585 | Exim::debug_write() writes a string to the standard error stream if Exim's | |
11586 | debugging is enabled. If you want a newline at the end, you must supply it. | |
11587 | Exim::log_write() writes a string to Exim's main log, adding a leading | |
11588 | timestamp. In this case, you should not supply a terminating newline. | |
11589 | ||
11590 | ||
11591 | 12.4 Use of standard output and error by Perl | |
11592 | --------------------------------------------- | |
11593 | ||
11594 | You should not write to the standard error or output streams from within your | |
11595 | Perl code, as it is not defined how these are set up. In versions of Exim | |
11596 | before 4.50, it is possible for the standard output or error to refer to the | |
11597 | SMTP connection during message reception via the daemon. Writing to this stream | |
11598 | is certain to cause chaos. From Exim 4.50 onwards, the standard output and | |
11599 | error streams are connected to /dev/null in the daemon. The chaos is avoided, | |
11600 | but the output is lost. | |
11601 | ||
11602 | The Perl warn statement writes to the standard error stream by default. Calls | |
11603 | to warn may be embedded in Perl modules that you use, but over which you have | |
11604 | no control. When Exim starts up the Perl interpreter, it arranges for output | |
11605 | from the warn statement to be written to the Exim main log. You can change this | |
11606 | by including appropriate Perl magic somewhere in your Perl code. For example, | |
11607 | to discard warn output completely, you need this: | |
11608 | ||
11609 | $SIG{__WARN__} = sub { }; | |
11610 | ||
11611 | Whenever a warn is obeyed, the anonymous subroutine is called. In this example, | |
11612 | the code for the subroutine is empty, so it does nothing, but you can include | |
11613 | any Perl code that you like. The text of the warn message is passed as the | |
11614 | first subroutine argument. | |
11615 | ||
11616 | ||
11617 | ||
11618 | =============================================================================== | |
11619 | 13. STARTING THE DAEMON AND THE USE OF NETWORK INTERFACES | |
11620 | ||
11621 | A host that is connected to a TCP/IP network may have one or more physical | |
11622 | hardware network interfaces. Each of these interfaces may be configured as one | |
11623 | or more "logical" interfaces, which are the entities that a program actually | |
11624 | works with. Each of these logical interfaces is associated with an IP address. | |
11625 | In addition, TCP/IP software supports "loopback" interfaces (127.0.0.1 in IPv4 | |
11626 | and ::1 in IPv6), which do not use any physical hardware. Exim requires | |
11627 | knowledge about the host's interfaces for use in three different circumstances: | |
11628 | ||
11629 | 1. When a listening daemon is started, Exim needs to know which interfaces and | |
11630 | ports to listen on. | |
11631 | ||
11632 | 2. When Exim is routing an address, it needs to know which IP addresses are | |
11633 | associated with local interfaces. This is required for the correct | |
11634 | processing of MX lists by removing the local host and others with the same | |
11635 | or higher priority values. Also, Exim needs to detect cases when an address | |
11636 | is routed to an IP address that in fact belongs to the local host. Unless | |
11637 | the self router option or the allow_localhost option of the smtp transport | |
11638 | is set (as appropriate), this is treated as an error situation. | |
11639 | ||
11640 | 3. When Exim connects to a remote host, it may need to know which interface to | |
11641 | use for the outgoing connection. | |
11642 | ||
11643 | Exim's default behaviour is likely to be appropriate in the vast majority of | |
11644 | cases. If your host has only one interface, and you want all its IP addresses | |
11645 | to be treated in the same way, and you are using only the standard SMTP port, | |
11646 | you should not need to take any special action. The rest of this chapter does | |
11647 | not apply to you. | |
11648 | ||
11649 | In a more complicated situation you may want to listen only on certain | |
11650 | interfaces, or on different ports, and for this reason there are a number of | |
11651 | options that can be used to influence Exim's behaviour. The rest of this | |
11652 | chapter describes how they operate. | |
11653 | ||
11654 | When a message is received over TCP/IP, the interface and port that were | |
11655 | actually used are set in $received_ip_address and $received_port. | |
11656 | ||
11657 | ||
11658 | 13.1 Starting a listening daemon | |
11659 | -------------------------------- | |
11660 | ||
11661 | When a listening daemon is started (by means of the -bd command line option), | |
11662 | the interfaces and ports on which it listens are controlled by the following | |
11663 | options: | |
11664 | ||
11665 | * daemon_smtp_ports contains a list of default ports or service names. (For | |
11666 | backward compatibility, this option can also be specified in the singular.) | |
11667 | ||
11668 | * local_interfaces contains list of interface IP addresses on which to | |
11669 | listen. Each item may optionally also specify a port. | |
11670 | ||
11671 | The default list separator in both cases is a colon, but this can be changed as | |
11672 | described in section 6.19. When IPv6 addresses are involved, it is usually best | |
11673 | to change the separator to avoid having to double all the colons. For example: | |
11674 | ||
11675 | local_interfaces = <; 127.0.0.1 ; \ | |
11676 | 192.168.23.65 ; \ | |
11677 | ::1 ; \ | |
11678 | 3ffe:ffff:836f::fe86:a061 | |
11679 | ||
11680 | There are two different formats for specifying a port along with an IP address | |
11681 | in local_interfaces: | |
11682 | ||
11683 | 1. The port is added onto the address with a dot separator. For example, to | |
11684 | listen on port 1234 on two different IP addresses: | |
11685 | ||
11686 | local_interfaces = <; 192.168.23.65.1234 ; \ | |
11687 | 3ffe:ffff:836f::fe86:a061.1234 | |
11688 | ||
11689 | 2. The IP address is enclosed in square brackets, and the port is added with a | |
11690 | colon separator, for example: | |
11691 | ||
11692 | local_interfaces = <; [192.168.23.65]:1234 ; \ | |
11693 | [3ffe:ffff:836f::fe86:a061]:1234 | |
11694 | ||
11695 | When a port is not specified, the value of daemon_smtp_ports is used. The | |
11696 | default setting contains just one port: | |
11697 | ||
11698 | daemon_smtp_ports = smtp | |
11699 | ||
11700 | If more than one port is listed, each interface that does not have its own port | |
11701 | specified listens on all of them. Ports that are listed in daemon_smtp_ports | |
11702 | can be identified either by name (defined in /etc/services) or by number. | |
11703 | However, when ports are given with individual IP addresses in local_interfaces, | |
11704 | only numbers (not names) can be used. | |
11705 | ||
11706 | ||
11707 | 13.2 Special IP listening addresses | |
11708 | ----------------------------------- | |
11709 | ||
11710 | The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted as | |
11711 | "all IPv4 interfaces" and "all IPv6 interfaces", respectively. In each case, | |
11712 | Exim tells the TCP/IP stack to "listen on all IPvx interfaces" instead of | |
11713 | setting up separate listening sockets for each interface. The default value of | |
11714 | local_interfaces is | |
11715 | ||
11716 | local_interfaces = 0.0.0.0 | |
11717 | ||
11718 | when Exim is built without IPv6 support; otherwise it is: | |
11719 | ||
11720 | local_interfaces = <; ::0 ; 0.0.0.0 | |
11721 | ||
11722 | Thus, by default, Exim listens on all available interfaces, on the SMTP port. | |
11723 | ||
11724 | ||
11725 | 13.3 Overriding local_interfaces and daemon_smtp_ports | |
11726 | ------------------------------------------------------ | |
11727 | ||
11728 | The -oX command line option can be used to override the values of | |
11729 | daemon_smtp_ports and/or local_interfaces for a particular daemon instance. | |
11730 | Another way of doing this would be to use macros and the -D option. However, | |
11731 | -oX can be used by any admin user, whereas modification of the runtime | |
11732 | configuration by -D is allowed only when the caller is root or exim. | |
11733 | ||
11734 | The value of -oX is a list of items. The default colon separator can be changed | |
11735 | in the usual way if required. If there are any items that do not contain dots | |
11736 | or colons (that is, are not IP addresses), the value of daemon_smtp_ports is | |
11737 | replaced by the list of those items. If there are any items that do contain | |
11738 | dots or colons, the value of local_interfaces is replaced by those items. Thus, | |
11739 | for example, | |
11740 | ||
11741 | -oX 1225 | |
11742 | ||
11743 | overrides daemon_smtp_ports, but leaves local_interfaces unchanged, whereas | |
11744 | ||
11745 | -oX 192.168.34.5.1125 | |
11746 | ||
11747 | overrides local_interfaces, leaving daemon_smtp_ports unchanged. (However, | |
11748 | since local_interfaces now contains no items without ports, the value of | |
11749 | daemon_smtp_ports is no longer relevant in this example.) | |
11750 | ||
11751 | ||
11752 | 13.4 Support for the obsolete SSMTP (or SMTPS) protocol | |
11753 | ------------------------------------------------------- | |
11754 | ||
11755 | Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used | |
11756 | before the STARTTLS command was standardized for SMTP. Some legacy clients | |
11757 | still use this protocol. If the tls_on_connect_ports option is set to a list of | |
11758 | port numbers or service names, connections to those ports must use SSMTP. The | |
11759 | most common use of this option is expected to be | |
11760 | ||
11761 | tls_on_connect_ports = 465 | |
11762 | ||
11763 | because 465 is the usual port number used by the legacy clients. There is also | |
11764 | a command line option -tls-on-connect, which forces all ports to behave in this | |
11765 | way when a daemon is started. | |
11766 | ||
11767 | Warning: Setting tls_on_connect_ports does not of itself cause the daemon to | |
11768 | listen on those ports. You must still specify them in daemon_smtp_ports, | |
11769 | local_interfaces, or the -oX option. (This is because tls_on_connect_ports | |
11770 | applies to inetd connections as well as to connections via the daemon.) | |
11771 | ||
11772 | ||
11773 | 13.5 IPv6 address scopes | |
11774 | ------------------------ | |
11775 | ||
11776 | IPv6 addresses have "scopes", and a host with multiple hardware interfaces can, | |
11777 | in principle, have the same link-local IPv6 address on different interfaces. | |
11778 | Thus, additional information is needed, over and above the IP address, to | |
11779 | distinguish individual interfaces. A convention of using a percent sign | |
11780 | followed by something (often the interface name) has been adopted in some | |
11781 | cases, leading to addresses like this: | |
11782 | ||
11783 | fe80::202:b3ff:fe03:45c1%eth0 | |
11784 | ||
11785 | To accommodate this usage, a percent sign followed by an arbitrary string is | |
11786 | allowed at the end of an IPv6 address. By default, Exim calls getaddrinfo() to | |
11787 | convert a textual IPv6 address for actual use. This function recognizes the | |
11788 | percent convention in operating systems that support it, and it processes the | |
11789 | address appropriately. Unfortunately, some older libraries have problems with | |
11790 | getaddrinfo(). If | |
11791 | ||
11792 | IPV6_USE_INET_PTON=yes | |
11793 | ||
11794 | is set in Local/Makefile (or an OS-dependent Makefile) when Exim is built, Exim | |
11795 | uses inet_pton() to convert a textual IPv6 address for actual use, instead of | |
11796 | getaddrinfo(). (Before version 4.14, it always used this function.) Of course, | |
11797 | this means that the additional functionality of getaddrinfo() - recognizing | |
11798 | scoped addresses - is lost. | |
11799 | ||
11800 | ||
11801 | 13.6 Disabling IPv6 | |
11802 | ------------------- | |
11803 | ||
11804 | Sometimes it happens that an Exim binary that was compiled with IPv6 support is | |
11805 | run on a host whose kernel does not support IPv6. The binary will fall back to | |
11806 | using IPv4, but it may waste resources looking up AAAA records, and trying to | |
11807 | connect to IPv6 addresses, causing delays to mail delivery. If you set the | |
11808 | disable_ipv6 option true, even if the Exim binary has IPv6 support, no IPv6 | |
11809 | activities take place. AAAA records are never looked up, and any IPv6 addresses | |
11810 | that are listed in local_interfaces, data for the manualroute router, etc. are | |
11811 | ignored. If IP literals are enabled, the ipliteral router declines to handle | |
11812 | IPv6 literal addresses. | |
11813 | ||
11814 | On the other hand, when IPv6 is in use, there may be times when you want to | |
11815 | disable it for certain hosts or domains. You can use the dns_ipv4_lookup option | |
11816 | to globally suppress the lookup of AAAA records for specified domains, and you | |
11817 | can use the ignore_target_hosts generic router option to ignore IPv6 addresses | |
11818 | in an individual router. | |
11819 | ||
11820 | ||
11821 | 13.7 Examples of starting a listening daemon | |
11822 | -------------------------------------------- | |
11823 | ||
11824 | The default case in an IPv6 environment is | |
11825 | ||
11826 | daemon_smtp_ports = smtp | |
11827 | local_interfaces = <; ::0 ; 0.0.0.0 | |
11828 | ||
11829 | This specifies listening on the smtp port on all IPv6 and IPv4 interfaces. | |
11830 | Either one or two sockets may be used, depending on the characteristics of the | |
11831 | TCP/IP stack. (This is complicated and messy; for more information, read the | |
11832 | comments in the daemon.c source file.) | |
11833 | ||
11834 | To specify listening on ports 25 and 26 on all interfaces: | |
11835 | ||
11836 | daemon_smtp_ports = 25 : 26 | |
11837 | ||
11838 | (leaving local_interfaces at the default setting) or, more explicitly: | |
11839 | ||
11840 | local_interfaces = <; ::0.25 ; ::0.26 \ | |
11841 | 0.0.0.0.25 ; 0.0.0.0.26 | |
11842 | ||
11843 | To listen on the default port on all IPv4 interfaces, and on port 26 on the | |
11844 | IPv4 loopback address only: | |
11845 | ||
11846 | local_interfaces = 0.0.0.0 : 127.0.0.1.26 | |
11847 | ||
11848 | To specify listening on the default port on specific interfaces only: | |
11849 | ||
11850 | local_interfaces = 10.0.0.67 : 192.168.34.67 | |
11851 | ||
11852 | Warning: Such a setting excludes listening on the loopback interfaces. | |
11853 | ||
11854 | ||
11855 | 13.8 Recognizing the local host | |
11856 | ------------------------------- | |
11857 | ||
11858 | The local_interfaces option is also used when Exim needs to determine whether | |
11859 | or not an IP address refers to the local host. That is, the IP addresses of all | |
11860 | the interfaces on which a daemon is listening are always treated as local. | |
11861 | ||
11862 | For this usage, port numbers in local_interfaces are ignored. If either of the | |
11863 | items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of available | |
11864 | interfaces from the operating system, and extracts the relevant (that is, IPv4 | |
11865 | or IPv6) addresses to use for checking. | |
11866 | ||
11867 | Some systems set up large numbers of virtual interfaces in order to provide | |
11868 | many virtual web servers. In this situation, you may want to listen for email | |
11869 | on only a few of the available interfaces, but nevertheless treat all | |
11870 | interfaces as local when routing. You can do this by setting | |
11871 | extra_local_interfaces to a list of IP addresses, possibly including the "all" | |
11872 | wildcard values. These addresses are recognized as local, but are not used for | |
11873 | listening. Consider this example: | |
11874 | ||
11875 | local_interfaces = <; 127.0.0.1 ; ::1 ; \ | |
11876 | 192.168.53.235 ; \ | |
11877 | 3ffe:2101:12:1:a00:20ff:fe86:a061 | |
11878 | ||
11879 | extra_local_interfaces = <; ::0 ; 0.0.0.0 | |
11880 | ||
11881 | The daemon listens on the loopback interfaces and just one IPv4 and one IPv6 | |
11882 | address, but all available interface addresses are treated as local when Exim | |
11883 | is routing. | |
11884 | ||
11885 | In some environments the local host name may be in an MX list, but with an IP | |
11886 | address that is not assigned to any local interface. In other cases it may be | |
11887 | desirable to treat other host names as if they referred to the local host. Both | |
11888 | these cases can be handled by setting the hosts_treat_as_local option. This | |
11889 | contains host names rather than IP addresses. When a host is referenced during | |
11890 | routing, either via an MX record or directly, it is treated as the local host | |
11891 | if its name matches hosts_treat_as_local, or if any of its IP addresses match | |
11892 | local_interfaces or extra_local_interfaces. | |
11893 | ||
11894 | ||
11895 | 13.9 Delivering to a remote host | |
11896 | -------------------------------- | |
11897 | ||
11898 | Delivery to a remote host is handled by the smtp transport. By default, it | |
11899 | allows the system's TCP/IP functions to choose which interface to use (if there | |
11900 | is more than one) when connecting to a remote host. However, the interface | |
11901 | option can be set to specify which interface is used. See the description of | |
11902 | the smtp transport in chapter 30 for more details. | |
11903 | ||
11904 | ||
11905 | ||
11906 | =============================================================================== | |
11907 | 14. MAIN CONFIGURATION | |
11908 | ||
11909 | The first part of the run time configuration file contains three types of item: | |
11910 | ||
11911 | * Macro definitions: These lines start with an upper case letter. See section | |
11912 | 6.4 for details of macro processing. | |
11913 | ||
11914 | * Named list definitions: These lines start with one of the words | |
11915 | "domainlist", "hostlist", "addresslist", or "localpartlist". Their use is | |
11916 | described in section 10.5. | |
11917 | ||
11918 | * Main configuration settings: Each setting occupies one line of the file | |
11919 | (with possible continuations). If any setting is preceded by the word | |
11920 | "hide", the -bP command line option displays its value to admin users only. | |
11921 | See section 6.10 for a description of the syntax of these option settings. | |
11922 | ||
11923 | This chapter specifies all the main configuration options, along with their | |
11924 | types and default values. For ease of finding a particular option, they appear | |
11925 | in alphabetical order in section 14.23 below. However, because there are now so | |
11926 | many options, they are first listed briefly in functional groups, as an aid to | |
11927 | finding the name of the option you are looking for. Some options are listed in | |
11928 | more than one group. | |
11929 | ||
11930 | ||
11931 | 14.1 Miscellaneous | |
11932 | ------------------ | |
11933 | ||
11934 | bi_command to run for -bi command line option | |
11935 | disable_ipv6 do no IPv6 processing | |
11936 | keep_malformed for broken files - should not happen | |
11937 | localhost_number for unique message ids in clusters | |
11938 | message_body_newlines retain newlines in $message_body | |
11939 | message_body_visible how much to show in $message_body | |
11940 | mua_wrapper run in "MUA wrapper" mode | |
11941 | print_topbitchars top-bit characters are printing | |
11942 | timezone force time zone | |
11943 | ||
11944 | ||
11945 | 14.2 Exim parameters | |
11946 | -------------------- | |
11947 | ||
11948 | exim_group override compiled-in value | |
11949 | exim_path override compiled-in value | |
11950 | exim_user override compiled-in value | |
11951 | primary_hostname default from uname() | |
11952 | split_spool_directory use multiple directories | |
11953 | spool_directory override compiled-in value | |
11954 | ||
11955 | ||
11956 | 14.3 Privilege controls | |
11957 | ----------------------- | |
11958 | ||
11959 | admin_groups groups that are Exim admin users | |
11960 | deliver_drop_privilege drop root for delivery processes | |
11961 | local_from_check insert Sender: if necessary | |
11962 | local_from_prefix for testing From: for local sender | |
11963 | local_from_suffix for testing From: for local sender | |
11964 | local_sender_retain keep Sender: from untrusted user | |
11965 | never_users do not run deliveries as these | |
11966 | prod_requires_admin forced delivery requires admin user | |
11967 | queue_list_requires_admin queue listing requires admin user | |
11968 | trusted_groups groups that are trusted | |
11969 | trusted_users users that are trusted | |
11970 | ||
11971 | ||
11972 | 14.4 Logging | |
11973 | ------------ | |
11974 | ||
11975 | hosts_connection_nolog exemption from connect logging | |
11976 | log_file_path override compiled-in value | |
11977 | log_selector set/unset optional logging | |
11978 | log_timezone add timezone to log lines | |
11979 | message_logs create per-message logs | |
11980 | preserve_message_logs after message completion | |
11981 | process_log_path for SIGUSR1 and exiwhat | |
11982 | syslog_duplication controls duplicate log lines on syslog | |
11983 | syslog_facility set syslog "facility" field | |
11984 | syslog_processname set syslog "ident" field | |
11985 | syslog_timestamp timestamp syslog lines | |
11986 | write_rejectlog control use of message log | |
11987 | ||
11988 | ||
11989 | 14.5 Frozen messages | |
11990 | -------------------- | |
11991 | ||
11992 | auto_thaw sets time for retrying frozen messages | |
11993 | freeze_tell send message when freezing | |
11994 | move_frozen_messages to another directory | |
11995 | timeout_frozen_after keep frozen messages only so long | |
11996 | ||
11997 | ||
11998 | 14.6 Data lookups | |
11999 | ----------------- | |
12000 | ||
12001 | ibase_servers InterBase servers | |
12002 | ldap_ca_cert_dir dir of CA certs to verify LDAP server's | |
12003 | ldap_ca_cert_file file of CA certs to verify LDAP server's | |
12004 | ldap_cert_file client cert file for LDAP | |
12005 | ldap_cert_key client key file for LDAP | |
12006 | ldap_cipher_suite TLS negotiation preference control | |
12007 | ldap_default_servers used if no server in query | |
12008 | ldap_require_cert action to take without LDAP server cert | |
12009 | ldap_start_tls require TLS within LDAP | |
12010 | ldap_version set protocol version | |
12011 | lookup_open_max lookup files held open | |
12012 | mysql_servers default MySQL servers | |
12013 | oracle_servers Oracle servers | |
12014 | pgsql_servers default PostgreSQL servers | |
12015 | sqlite_lock_timeout as it says | |
12016 | ||
12017 | ||
12018 | 14.7 Message ids | |
12019 | ---------------- | |
12020 | ||
12021 | message_id_header_domain used to build Message-ID: header | |
12022 | message_id_header_text ditto | |
12023 | ||
12024 | ||
12025 | 14.8 Embedded Perl Startup | |
12026 | -------------------------- | |
12027 | ||
12028 | perl_at_start always start the interpreter | |
12029 | perl_startup code to obey when starting Perl | |
12030 | ||
12031 | ||
12032 | 14.9 Daemon | |
12033 | ----------- | |
12034 | ||
12035 | daemon_smtp_ports default ports | |
12036 | daemon_startup_retries number of times to retry | |
12037 | daemon_startup_sleep time to sleep between tries | |
12038 | extra_local_interfaces not necessarily listened on | |
12039 | local_interfaces on which to listen, with optional ports | |
12040 | pid_file_path override compiled-in value | |
12041 | queue_run_max maximum simultaneous queue runners | |
12042 | ||
12043 | ||
12044 | 14.10 Resource control | |
12045 | ---------------------- | |
12046 | ||
12047 | check_log_inodes before accepting a message | |
12048 | check_log_space before accepting a message | |
12049 | check_spool_inodes before accepting a message | |
12050 | check_spool_space before accepting a message | |
12051 | deliver_queue_load_max no queue deliveries if load high | |
12052 | queue_only_load queue incoming if load high | |
12053 | queue_only_load_latch don't re-evaluate load for each message | |
12054 | queue_run_max maximum simultaneous queue runners | |
12055 | remote_max_parallel parallel SMTP delivery per message | |
12056 | smtp_accept_max simultaneous incoming connections | |
12057 | smtp_accept_max_nonmail non-mail commands | |
12058 | smtp_accept_max_nonmail_hosts hosts to which the limit applies | |
12059 | smtp_accept_max_per_connection messages per connection | |
12060 | smtp_accept_max_per_host connections from one host | |
12061 | smtp_accept_queue queue mail if more connections | |
12062 | smtp_accept_queue_per_connection queue if more messages per connection | |
12063 | smtp_accept_reserve only reserve hosts if more connections | |
12064 | smtp_check_spool_space from SIZE on MAIL command | |
12065 | smtp_connect_backlog passed to TCP/IP stack | |
12066 | smtp_load_reserve SMTP from reserved hosts if load high | |
12067 | smtp_reserve_hosts these are the reserve hosts | |
12068 | ||
12069 | ||
12070 | 14.11 Policy controls | |
12071 | --------------------- | |
12072 | ||
12073 | acl_not_smtp ACL for non-SMTP messages | |
12074 | acl_not_smtp_mime ACL for non-SMTP MIME parts | |
12075 | acl_not_smtp_start ACL for start of non-SMTP message | |
12076 | acl_smtp_auth ACL for AUTH | |
12077 | acl_smtp_connect ACL for connection | |
12078 | acl_smtp_data ACL for DATA | |
12079 | acl_smtp_data_prdr ACL for DATA, per-recipient | |
12080 | acl_smtp_dkim ACL for DKIM verification | |
12081 | acl_smtp_etrn ACL for ETRN | |
12082 | acl_smtp_expn ACL for EXPN | |
12083 | acl_smtp_helo ACL for EHLO or HELO | |
12084 | acl_smtp_mail ACL for MAIL | |
12085 | acl_smtp_mailauth ACL for AUTH on MAIL command | |
12086 | acl_smtp_mime ACL for MIME parts | |
12087 | acl_smtp_predata ACL for start of data | |
12088 | acl_smtp_quit ACL for QUIT | |
12089 | acl_smtp_rcpt ACL for RCPT | |
12090 | acl_smtp_starttls ACL for STARTTLS | |
12091 | acl_smtp_vrfy ACL for VRFY | |
12092 | av_scanner specify virus scanner | |
12093 | check_rfc2047_length check length of RFC 2047 "encoded words" | |
12094 | dns_csa_search_limit control CSA parent search depth | |
12095 | dns_csa_use_reverse en/disable CSA IP reverse search | |
12096 | header_maxsize total size of message header | |
12097 | header_line_maxsize individual header line limit | |
12098 | helo_accept_junk_hosts allow syntactic junk from these hosts | |
12099 | helo_allow_chars allow illegal chars in HELO names | |
12100 | helo_lookup_domains lookup hostname for these HELO names | |
12101 | helo_try_verify_hosts HELO soft-checked for these hosts | |
12102 | helo_verify_hosts HELO hard-checked for these hosts | |
12103 | host_lookup host name looked up for these hosts | |
12104 | host_lookup_order order of DNS and local name lookups | |
12105 | host_reject_connection reject connection from these hosts | |
12106 | hosts_treat_as_local useful in some cluster configurations | |
12107 | local_scan_timeout timeout for local_scan() | |
12108 | message_size_limit for all messages | |
12109 | percent_hack_domains recognize %-hack for these domains | |
12110 | spamd_address set interface to SpamAssassin | |
12111 | strict_acl_vars object to unset ACL variables | |
12112 | ||
12113 | ||
12114 | 14.12 Callout cache | |
12115 | ------------------- | |
12116 | ||
12117 | callout_domain_negative_expire timeout for negative domain cache item | |
12118 | callout_domain_positive_expire timeout for positive domain cache item | |
12119 | callout_negative_expire timeout for negative address cache item | |
12120 | callout_positive_expire timeout for positive address cache item | |
12121 | callout_random_local_part string to use for "random" testing | |
12122 | ||
12123 | ||
12124 | 14.13 TLS | |
12125 | --------- | |
12126 | ||
12127 | gnutls_compat_mode use GnuTLS compatibility mode | |
12128 | gnutls_allow_auto_pkcs11 allow GnuTLS to autoload PKCS11 modules | |
12129 | openssl_options adjust OpenSSL compatibility options | |
12130 | tls_advertise_hosts advertise TLS to these hosts | |
12131 | tls_certificate location of server certificate | |
12132 | tls_crl certificate revocation list | |
12133 | tls_dh_max_bits clamp D-H bit count suggestion | |
12134 | tls_dhparam DH parameters for server | |
12135 | tls_ocsp_file location of server certificate status proof | |
12136 | tls_on_connect_ports specify SSMTP (SMTPS) ports | |
12137 | tls_privatekey location of server private key | |
12138 | tls_remember_esmtp don't reset after starting TLS | |
12139 | tls_require_ciphers specify acceptable ciphers | |
12140 | tls_try_verify_hosts try to verify client certificate | |
12141 | tls_verify_certificates expected client certificates | |
12142 | tls_verify_hosts insist on client certificate verify | |
12143 | ||
12144 | ||
12145 | 14.14 Local user handling | |
12146 | ------------------------- | |
12147 | ||
12148 | finduser_retries useful in NIS environments | |
12149 | gecos_name used when creating Sender: | |
12150 | gecos_pattern ditto | |
12151 | max_username_length for systems that truncate | |
12152 | unknown_login used when no login name found | |
12153 | unknown_username ditto | |
12154 | uucp_from_pattern for recognizing "From " lines | |
12155 | uucp_from_sender ditto | |
12156 | ||
12157 | ||
12158 | 14.15 All incoming messages (SMTP and non-SMTP) | |
12159 | ----------------------------------------------- | |
12160 | ||
12161 | header_maxsize total size of message header | |
12162 | header_line_maxsize individual header line limit | |
12163 | message_size_limit applies to all messages | |
12164 | percent_hack_domains recognize %-hack for these domains | |
12165 | received_header_text expanded to make Received: | |
12166 | received_headers_max for mail loop detection | |
12167 | recipients_max limit per message | |
12168 | recipients_max_reject permanently reject excess recipients | |
12169 | ||
12170 | ||
12171 | 14.16 Non-SMTP incoming messages | |
12172 | -------------------------------- | |
12173 | ||
12174 | receive_timeout for non-SMTP messages | |
12175 | ||
12176 | ||
12177 | 14.17 Incoming SMTP messages | |
12178 | ---------------------------- | |
12179 | ||
12180 | See also the Policy controls section above. | |
12181 | ||
12182 | host_lookup host name looked up for these hosts | |
12183 | host_lookup_order order of DNS and local name lookups | |
12184 | recipient_unqualified_hosts may send unqualified recipients | |
12185 | rfc1413_hosts make ident calls to these hosts | |
12186 | rfc1413_query_timeout zero disables ident calls | |
12187 | sender_unqualified_hosts may send unqualified senders | |
12188 | smtp_accept_keepalive some TCP/IP magic | |
12189 | smtp_accept_max simultaneous incoming connections | |
12190 | smtp_accept_max_nonmail non-mail commands | |
12191 | smtp_accept_max_nonmail_hosts hosts to which the limit applies | |
12192 | smtp_accept_max_per_connection messages per connection | |
12193 | smtp_accept_max_per_host connections from one host | |
12194 | smtp_accept_queue queue mail if more connections | |
12195 | smtp_accept_queue_per_connection queue if more messages per connection | |
12196 | smtp_accept_reserve only reserve hosts if more connections | |
12197 | smtp_active_hostname host name to use in messages | |
12198 | smtp_banner text for welcome banner | |
12199 | smtp_check_spool_space from SIZE on MAIL command | |
12200 | smtp_connect_backlog passed to TCP/IP stack | |
12201 | smtp_enforce_sync of SMTP command/responses | |
12202 | smtp_etrn_command what to run for ETRN | |
12203 | smtp_etrn_serialize only one at once | |
12204 | smtp_load_reserve only reserve hosts if this load | |
12205 | smtp_max_unknown_commands before dropping connection | |
12206 | smtp_ratelimit_hosts apply ratelimiting to these hosts | |
12207 | smtp_ratelimit_mail ratelimit for MAIL commands | |
12208 | smtp_ratelimit_rcpt ratelimit for RCPT commands | |
12209 | smtp_receive_timeout per command or data line | |
12210 | smtp_reserve_hosts these are the reserve hosts | |
12211 | smtp_return_error_details give detail on rejections | |
12212 | ||
12213 | ||
12214 | 14.18 SMTP extensions | |
12215 | --------------------- | |
12216 | ||
12217 | accept_8bitmime advertise 8BITMIME | |
12218 | auth_advertise_hosts advertise AUTH to these hosts | |
12219 | ignore_fromline_hosts allow "From " from these hosts | |
12220 | ignore_fromline_local allow "From " from local SMTP | |
12221 | pipelining_advertise_hosts advertise pipelining to these hosts | |
12222 | prdr_enable advertise PRDR to all hosts | |
12223 | tls_advertise_hosts advertise TLS to these hosts | |
12224 | ||
12225 | ||
12226 | 14.19 Processing messages | |
12227 | ------------------------- | |
12228 | ||
12229 | allow_domain_literals recognize domain literal syntax | |
12230 | allow_mx_to_ip allow MX to point to IP address | |
12231 | allow_utf8_domains in addresses | |
12232 | check_rfc2047_length check length of RFC 2047 "encoded words" | |
12233 | delivery_date_remove from incoming messages | |
12234 | envelope_to_remove from incoming messages | |
12235 | extract_addresses_remove_arguments affects -t processing | |
12236 | headers_charset default for translations | |
12237 | qualify_domain default for senders | |
12238 | qualify_recipient default for recipients | |
12239 | return_path_remove from incoming messages | |
12240 | strip_excess_angle_brackets in addresses | |
12241 | strip_trailing_dot at end of addresses | |
12242 | untrusted_set_sender untrusted can set envelope sender | |
12243 | ||
12244 | ||
12245 | 14.20 System filter | |
12246 | ------------------- | |
12247 | ||
12248 | system_filter locate system filter | |
12249 | system_filter_directory_transport transport for delivery to a directory | |
12250 | system_filter_file_transport transport for delivery to a file | |
12251 | system_filter_group group for filter running | |
12252 | system_filter_pipe_transport transport for delivery to a pipe | |
12253 | system_filter_reply_transport transport for autoreply delivery | |
12254 | system_filter_user user for filter running | |
12255 | ||
12256 | ||
12257 | 14.21 Routing and delivery | |
12258 | -------------------------- | |
12259 | ||
12260 | disable_ipv6 do no IPv6 processing | |
12261 | dns_again_means_nonexist for broken domains | |
12262 | dns_check_names_pattern pre-DNS syntax check | |
12263 | dns_dnssec_ok parameter for resolver | |
12264 | dns_ipv4_lookup only v4 lookup for these domains | |
12265 | dns_retrans parameter for resolver | |
12266 | dns_retry parameter for resolver | |
12267 | dns_use_edns0 parameter for resolver | |
12268 | hold_domains hold delivery for these domains | |
12269 | local_interfaces for routing checks | |
12270 | queue_domains no immediate delivery for these | |
12271 | queue_only no immediate delivery at all | |
12272 | queue_only_file no immediate delivery if file exists | |
12273 | queue_only_load no immediate delivery if load is high | |
12274 | queue_only_load_latch don't re-evaluate load for each message | |
12275 | queue_only_override allow command line to override | |
12276 | queue_run_in_order order of arrival | |
12277 | queue_run_max of simultaneous queue runners | |
12278 | queue_smtp_domains no immediate SMTP delivery for these | |
12279 | remote_max_parallel parallel SMTP delivery per message | |
12280 | remote_sort_domains order of remote deliveries | |
12281 | retry_data_expire timeout for retry data | |
12282 | retry_interval_max safety net for retry rules | |
12283 | ||
12284 | ||
12285 | 14.22 Bounce and warning messages | |
12286 | --------------------------------- | |
12287 | ||
12288 | bounce_message_file content of bounce | |
12289 | bounce_message_text content of bounce | |
12290 | bounce_return_body include body if returning message | |
12291 | bounce_return_message include original message in bounce | |
12292 | bounce_return_size_limit limit on returned message | |
12293 | bounce_sender_authentication send authenticated sender with bounce | |
12294 | dsn_from set From: contents in bounces | |
12295 | errors_copy copy bounce messages | |
12296 | errors_reply_to Reply-to: in bounces | |
12297 | delay_warning time schedule | |
12298 | delay_warning_condition condition for warning messages | |
12299 | ignore_bounce_errors_after discard undeliverable bounces | |
12300 | smtp_return_error_details give detail on rejections | |
12301 | warn_message_file content of warning message | |
12302 | ||
12303 | ||
12304 | 14.23 Alphabetical list of main options | |
12305 | --------------------------------------- | |
12306 | ||
12307 | Those options that undergo string expansion before use are marked with *. | |
12308 | ||
12309 | +---------------+---------+-------------+-------------+ | |
12310 | |accept_8bitmime|Use: main|Type: boolean|Default: true| | |
12311 | +---------------+---------+-------------+-------------+ | |
12312 | ||
12313 | This option causes Exim to send 8BITMIME in its response to an SMTP EHLO | |
12314 | command, and to accept the BODY= parameter on MAIL commands. However, though | |
12315 | Exim is 8-bit clean, it is not a protocol converter, and it takes no steps to | |
12316 | do anything special with messages received by this route. | |
12317 | ||
12318 | Historically Exim kept this option off by default, but the maintainers feel | |
12319 | that in today's Internet, this causes more problems than it solves. It now | |
12320 | defaults to true. A more detailed analysis of the issues is provided by Dan | |
12321 | Bernstein: | |
12322 | ||
12323 | http://cr.yp.to/smtp/8bitmime.html | |
12324 | ||
12325 | To log received 8BITMIME status use | |
12326 | ||
12327 | log_selector = +8bitmime | |
12328 | ||
12329 | +------------+---------+-------------+--------------+ | |
12330 | |acl_not_smtp|Use: main|Type: string*|Default: unset| | |
12331 | +------------+---------+-------------+--------------+ | |
12332 | ||
12333 | This option defines the ACL that is run when a non-SMTP message has been read | |
12334 | and is on the point of being accepted. See chapter 42 for further details. | |
12335 | ||
12336 | +-----------------+---------+-------------+--------------+ | |
12337 | |acl_not_smtp_mime|Use: main|Type: string*|Default: unset| | |
12338 | +-----------------+---------+-------------+--------------+ | |
12339 | ||
12340 | This option defines the ACL that is run for individual MIME parts of non-SMTP | |
12341 | messages. It operates in exactly the same way as acl_smtp_mime operates for | |
12342 | SMTP messages. | |
12343 | ||
12344 | +------------------+---------+-------------+--------------+ | |
12345 | |acl_not_smtp_start|Use: main|Type: string*|Default: unset| | |
12346 | +------------------+---------+-------------+--------------+ | |
12347 | ||
12348 | This option defines the ACL that is run before Exim starts reading a non-SMTP | |
12349 | message. See chapter 42 for further details. | |
12350 | ||
12351 | +-------------+---------+-------------+--------------+ | |
12352 | |acl_smtp_auth|Use: main|Type: string*|Default: unset| | |
12353 | +-------------+---------+-------------+--------------+ | |
12354 | ||
12355 | This option defines the ACL that is run when an SMTP AUTH command is received. | |
12356 | See chapter 42 for further details. | |
12357 | ||
12358 | +----------------+---------+-------------+--------------+ | |
12359 | |acl_smtp_connect|Use: main|Type: string*|Default: unset| | |
12360 | +----------------+---------+-------------+--------------+ | |
12361 | ||
12362 | This option defines the ACL that is run when an SMTP connection is received. | |
12363 | See chapter 42 for further details. | |
12364 | ||
12365 | +-------------+---------+-------------+--------------+ | |
12366 | |acl_smtp_data|Use: main|Type: string*|Default: unset| | |
12367 | +-------------+---------+-------------+--------------+ | |
12368 | ||
12369 | This option defines the ACL that is run after an SMTP DATA command has been | |
12370 | processed and the message itself has been received, but before the final | |
12371 | acknowledgment is sent. See chapter 42 for further details. | |
12372 | ||
12373 | +------------------+---------+-------------+--------------+ | |
12374 | |acl_smtp_data_prdr|Use: main|Type: string*|Default: unset| | |
12375 | +------------------+---------+-------------+--------------+ | |
12376 | ||
12377 | This option defines the ACL that, if the PRDR feature has been negotiated, is | |
12378 | run for each recipient after an SMTP DATA command has been processed and the | |
12379 | message itself has been received, but before the acknowledgment is sent. See | |
12380 | chapter 42 for further details. | |
12381 | ||
12382 | +-------------+---------+-------------+--------------+ | |
12383 | |acl_smtp_etrn|Use: main|Type: string*|Default: unset| | |
12384 | +-------------+---------+-------------+--------------+ | |
12385 | ||
12386 | This option defines the ACL that is run when an SMTP ETRN command is received. | |
12387 | See chapter 42 for further details. | |
12388 | ||
12389 | +-------------+---------+-------------+--------------+ | |
12390 | |acl_smtp_expn|Use: main|Type: string*|Default: unset| | |
12391 | +-------------+---------+-------------+--------------+ | |
12392 | ||
12393 | This option defines the ACL that is run when an SMTP EXPN command is received. | |
12394 | See chapter 42 for further details. | |
12395 | ||
12396 | +-------------+---------+-------------+--------------+ | |
12397 | |acl_smtp_helo|Use: main|Type: string*|Default: unset| | |
12398 | +-------------+---------+-------------+--------------+ | |
12399 | ||
12400 | This option defines the ACL that is run when an SMTP EHLO or HELO command is | |
12401 | received. See chapter 42 for further details. | |
12402 | ||
12403 | +-------------+---------+-------------+--------------+ | |
12404 | |acl_smtp_mail|Use: main|Type: string*|Default: unset| | |
12405 | +-------------+---------+-------------+--------------+ | |
12406 | ||
12407 | This option defines the ACL that is run when an SMTP MAIL command is received. | |
12408 | See chapter 42 for further details. | |
12409 | ||
12410 | +-----------------+---------+-------------+--------------+ | |
12411 | |acl_smtp_mailauth|Use: main|Type: string*|Default: unset| | |
12412 | +-----------------+---------+-------------+--------------+ | |
12413 | ||
12414 | This option defines the ACL that is run when there is an AUTH parameter on a | |
12415 | MAIL command. See chapter 42 for details of ACLs, and chapter 33 for details of | |
12416 | authentication. | |
12417 | ||
12418 | +-------------+---------+-------------+--------------+ | |
12419 | |acl_smtp_mime|Use: main|Type: string*|Default: unset| | |
12420 | +-------------+---------+-------------+--------------+ | |
12421 | ||
12422 | This option is available when Exim is built with the content-scanning | |
12423 | extension. It defines the ACL that is run for each MIME part in a message. See | |
12424 | section 43.4 for details. | |
12425 | ||
12426 | +----------------+---------+-------------+--------------+ | |
12427 | |acl_smtp_predata|Use: main|Type: string*|Default: unset| | |
12428 | +----------------+---------+-------------+--------------+ | |
12429 | ||
12430 | This option defines the ACL that is run when an SMTP DATA command is received, | |
12431 | before the message itself is received. See chapter 42 for further details. | |
12432 | ||
12433 | +-------------+---------+-------------+--------------+ | |
12434 | |acl_smtp_quit|Use: main|Type: string*|Default: unset| | |
12435 | +-------------+---------+-------------+--------------+ | |
12436 | ||
12437 | This option defines the ACL that is run when an SMTP QUIT command is received. | |
12438 | See chapter 42 for further details. | |
12439 | ||
12440 | +-------------+---------+-------------+--------------+ | |
12441 | |acl_smtp_rcpt|Use: main|Type: string*|Default: unset| | |
12442 | +-------------+---------+-------------+--------------+ | |
12443 | ||
12444 | This option defines the ACL that is run when an SMTP RCPT command is received. | |
12445 | See chapter 42 for further details. | |
12446 | ||
12447 | +-----------------+---------+-------------+--------------+ | |
12448 | |acl_smtp_starttls|Use: main|Type: string*|Default: unset| | |
12449 | +-----------------+---------+-------------+--------------+ | |
12450 | ||
12451 | This option defines the ACL that is run when an SMTP STARTTLS command is | |
12452 | received. See chapter 42 for further details. | |
12453 | ||
12454 | +-------------+---------+-------------+--------------+ | |
12455 | |acl_smtp_vrfy|Use: main|Type: string*|Default: unset| | |
12456 | +-------------+---------+-------------+--------------+ | |
12457 | ||
12458 | This option defines the ACL that is run when an SMTP VRFY command is received. | |
12459 | See chapter 42 for further details. | |
12460 | ||
188b6fee CE |
12461 | +---------------+---------+-----------------+--------------+ |
12462 | |add_environment|Use: main|Type: string list|Default: empty| | |
12463 | +---------------+---------+-----------------+--------------+ | |
12464 | ||
12465 | This option allows to set individual environment variables that the currently | |
12466 | linked libraries and programs in child processes use. The default list is | |
12467 | empty, | |
12468 | ||
420a0d19 CE |
12469 | +------------+---------+------------------+--------------+ |
12470 | |admin_groups|Use: main|Type: string list*|Default: unset| | |
12471 | +------------+---------+------------------+--------------+ | |
12472 | ||
12473 | This option is expanded just once, at the start of Exim's processing. If the | |
12474 | current group or any of the supplementary groups of an Exim caller is in this | |
12475 | colon-separated list, the caller has admin privileges. If all your system | |
12476 | programmers are in a specific group, for example, you can give them all Exim | |
12477 | admin privileges by putting that group in admin_groups. However, this does not | |
12478 | permit them to read Exim's spool files (whose group owner is the Exim gid). To | |
12479 | permit this, you have to add individuals to the Exim group. | |
12480 | ||
12481 | +---------------------+---------+-------------+--------------+ | |
12482 | |allow_domain_literals|Use: main|Type: boolean|Default: false| | |
12483 | +---------------------+---------+-------------+--------------+ | |
12484 | ||
12485 | If this option is set, the RFC 2822 domain literal format is permitted in email | |
12486 | addresses. The option is not set by default, because the domain literal format | |
12487 | is not normally required these days, and few people know about it. It has, | |
12488 | however, been exploited by mail abusers. | |
12489 | ||
12490 | Unfortunately, it seems that some DNS black list maintainers are using this | |
12491 | format to report black listing to postmasters. If you want to accept messages | |
12492 | addressed to your hosts by IP address, you need to set allow_domain_literals | |
12493 | true, and also to add "@[]" to the list of local domains (defined in the named | |
12494 | domain list local_domains in the default configuration). This "magic string" | |
12495 | matches the domain literal form of all the local host's IP addresses. | |
12496 | ||
12497 | +--------------+---------+-------------+--------------+ | |
12498 | |allow_mx_to_ip|Use: main|Type: boolean|Default: false| | |
12499 | +--------------+---------+-------------+--------------+ | |
12500 | ||
12501 | It appears that more and more DNS zone administrators are breaking the rules | |
12502 | and putting domain names that look like IP addresses on the right hand side of | |
12503 | MX records. Exim follows the rules and rejects this, giving an error message | |
12504 | that explains the mis-configuration. However, some other MTAs support this | |
12505 | practice, so to avoid "Why can't Exim do this?" complaints, allow_mx_to_ip | |
12506 | exists, in order to enable this heinous activity. It is not recommended, except | |
12507 | when you have no other choice. | |
12508 | ||
12509 | +------------------+---------+-------------+--------------+ | |
12510 | |allow_utf8_domains|Use: main|Type: boolean|Default: false| | |
12511 | +------------------+---------+-------------+--------------+ | |
12512 | ||
12513 | Lots of discussion is going on about internationalized domain names. One camp | |
12514 | is strongly in favour of just using UTF-8 characters, and it seems that at | |
12515 | least two other MTAs permit this. This option allows Exim users to experiment | |
12516 | if they wish. | |
12517 | ||
12518 | If it is set true, Exim's domain parsing function allows valid UTF-8 | |
12519 | multicharacters to appear in domain name components, in addition to letters, | |
12520 | digits, and hyphens. However, just setting this option is not enough; if you | |
12521 | want to look up these domain names in the DNS, you must also adjust the value | |
12522 | of dns_check_names_pattern to match the extended form. A suitable setting is: | |
12523 | ||
12524 | dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\ | |
12525 | (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$ | |
12526 | ||
12527 | Alternatively, you can just disable this feature by setting | |
12528 | ||
12529 | dns_check_names_pattern = | |
12530 | ||
12531 | That is, set the option to an empty string so that no check is done. | |
12532 | ||
12533 | +--------------------+---------+----------------+----------+ | |
12534 | |auth_advertise_hosts|Use: main|Type: host list*|Default: *| | |
12535 | +--------------------+---------+----------------+----------+ | |
12536 | ||
12537 | If any server authentication mechanisms are configured, Exim advertises them in | |
12538 | response to an EHLO command only if the calling host matches this list. | |
12539 | Otherwise, Exim does not advertise AUTH. Exim does not accept AUTH commands | |
12540 | from clients to which it has not advertised the availability of AUTH. The | |
12541 | advertising of individual authentication mechanisms can be controlled by the | |
12542 | use of the server_advertise_condition generic authenticator option on the | |
12543 | individual authenticators. See chapter 33 for further details. | |
12544 | ||
12545 | Certain mail clients (for example, Netscape) require the user to provide a name | |
12546 | and password for authentication if AUTH is advertised, even though it may not | |
12547 | be needed (the host may accept messages from hosts on its local LAN without | |
12548 | authentication, for example). The auth_advertise_hosts option can be used to | |
12549 | make these clients more friendly by excluding them from the set of hosts to | |
12550 | which Exim advertises AUTH. | |
12551 | ||
12552 | If you want to advertise the availability of AUTH only when the connection is | |
12553 | encrypted using TLS, you can make use of the fact that the value of this option | |
12554 | is expanded, with a setting like this: | |
12555 | ||
12556 | auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}} | |
12557 | ||
12558 | If $tls_in_cipher is empty, the session is not encrypted, and the result of the | |
12559 | expansion is empty, thus matching no hosts. Otherwise, the result of the | |
12560 | expansion is *, which matches all hosts. | |
12561 | ||
12562 | +---------+---------+----------+-----------+ | |
12563 | |auto_thaw|Use: main|Type: time|Default: 0s| | |
12564 | +---------+---------+----------+-----------+ | |
12565 | ||
12566 | If this option is set to a time greater than zero, a queue runner will try a | |
12567 | new delivery attempt on any frozen message, other than a bounce message, if | |
12568 | this much time has passed since it was frozen. This may result in the message | |
12569 | being re-frozen if nothing has changed since the last attempt. It is a way of | |
12570 | saying "keep on trying, even though there are big problems". | |
12571 | ||
12572 | Note: This is an old option, which predates timeout_frozen_after and | |
12573 | ignore_bounce_errors_after. It is retained for compatibility, but it is not | |
12574 | thought to be very useful any more, and its use should probably be avoided. | |
12575 | ||
12576 | +----------+---------+------------+------------------+ | |
12577 | |av_scanner|Use: main|Type: string|Default: see below| | |
12578 | +----------+---------+------------+------------------+ | |
12579 | ||
12580 | This option is available if Exim is built with the content-scanning extension. | |
12581 | It specifies which anti-virus scanner to use. The default value is: | |
12582 | ||
12583 | sophie:/var/run/sophie | |
12584 | ||
12585 | If the value of av_scanner starts with a dollar character, it is expanded | |
12586 | before use. See section 43.1 for further details. | |
12587 | ||
12588 | +----------+---------+------------+--------------+ | |
12589 | |bi_command|Use: main|Type: string|Default: unset| | |
12590 | +----------+---------+------------+--------------+ | |
12591 | ||
12592 | This option supplies the name of a command that is run when Exim is called with | |
12593 | the -bi option (see chapter 5). The string value is just the command name, it | |
12594 | is not a complete command line. If an argument is required, it must come from | |
12595 | the -oA command line option. | |
12596 | ||
12597 | +-------------------+---------+------------+--------------+ | |
12598 | |bounce_message_file|Use: main|Type: string|Default: unset| | |
12599 | +-------------------+---------+------------+--------------+ | |
12600 | ||
12601 | This option defines a template file containing paragraphs of text to be used | |
12602 | for constructing bounce messages. Details of the file's contents are given in | |
12603 | chapter 48. See also warn_message_file. | |
12604 | ||
12605 | +-------------------+---------+------------+--------------+ | |
12606 | |bounce_message_text|Use: main|Type: string|Default: unset| | |
12607 | +-------------------+---------+------------+--------------+ | |
12608 | ||
12609 | When this option is set, its contents are included in the default bounce | |
12610 | message immediately after "This message was created automatically by mail | |
12611 | delivery software." It is not used if bounce_message_file is set. | |
12612 | ||
12613 | +------------------+---------+-------------+-------------+ | |
12614 | |bounce_return_body|Use: main|Type: boolean|Default: true| | |
12615 | +------------------+---------+-------------+-------------+ | |
12616 | ||
12617 | This option controls whether the body of an incoming message is included in a | |
12618 | bounce message when bounce_return_message is true. The default setting causes | |
12619 | the entire message, both header and body, to be returned (subject to the value | |
12620 | of bounce_return_size_limit). If this option is false, only the message header | |
12621 | is included. In the case of a non-SMTP message containing an error that is | |
12622 | detected during reception, only those header lines preceding the point at which | |
12623 | the error was detected are returned. | |
12624 | ||
12625 | +---------------------+---------+-------------+-------------+ | |
12626 | |bounce_return_message|Use: main|Type: boolean|Default: true| | |
12627 | +---------------------+---------+-------------+-------------+ | |
12628 | ||
12629 | If this option is set false, none of the original message is included in bounce | |
12630 | messages generated by Exim. See also bounce_return_size_limit and | |
12631 | bounce_return_body. | |
12632 | ||
12633 | +------------------------+---------+-------------+-------------+ | |
12634 | |bounce_return_size_limit|Use: main|Type: integer|Default: 100K| | |
12635 | +------------------------+---------+-------------+-------------+ | |
12636 | ||
12637 | This option sets a limit in bytes on the size of messages that are returned to | |
12638 | senders as part of bounce messages when bounce_return_message is true. The | |
12639 | limit should be less than the value of the global message_size_limit and of any | |
12640 | message_size_limit settings on transports, to allow for the bounce text that | |
12641 | Exim generates. If this option is set to zero there is no limit. | |
12642 | ||
12643 | When the body of any message that is to be included in a bounce message is | |
12644 | greater than the limit, it is truncated, and a comment pointing this out is | |
12645 | added at the top. The actual cutoff may be greater than the value given, owing | |
12646 | to the use of buffering for transferring the message in chunks (typically 8K in | |
12647 | size). The idea is to save bandwidth on those undeliverable 15-megabyte | |
12648 | messages. | |
12649 | ||
12650 | +----------------------------+---------+------------+--------------+ | |
12651 | |bounce_sender_authentication|Use: main|Type: string|Default: unset| | |
12652 | +----------------------------+---------+------------+--------------+ | |
12653 | ||
12654 | This option provides an authenticated sender address that is sent with any | |
12655 | bounce messages generated by Exim that are sent over an authenticated SMTP | |
12656 | connection. A typical setting might be: | |
12657 | ||
12658 | bounce_sender_authentication = mailer-daemon@my.domain.example | |
12659 | ||
12660 | which would cause bounce messages to be sent using the SMTP command: | |
12661 | ||
12662 | MAIL FROM:<> AUTH=mailer-daemon@my.domain.example | |
12663 | ||
12664 | The value of bounce_sender_authentication must always be a complete email | |
12665 | address. | |
12666 | ||
12667 | +------------------------------+---------+----------+-----------+ | |
12668 | |callout_domain_negative_expire|Use: main|Type: time|Default: 3h| | |
12669 | +------------------------------+---------+----------+-----------+ | |
12670 | ||
12671 | This option specifies the expiry time for negative callout cache data for a | |
12672 | domain. See section 42.45 for details of callout verification, and section | |
12673 | 42.47 for details of the caching. | |
12674 | ||
12675 | +------------------------------+---------+----------+-----------+ | |
12676 | |callout_domain_positive_expire|Use: main|Type: time|Default: 7d| | |
12677 | +------------------------------+---------+----------+-----------+ | |
12678 | ||
12679 | This option specifies the expiry time for positive callout cache data for a | |
12680 | domain. See section 42.45 for details of callout verification, and section | |
12681 | 42.47 for details of the caching. | |
12682 | ||
12683 | +-----------------------+---------+----------+-----------+ | |
12684 | |callout_negative_expire|Use: main|Type: time|Default: 2h| | |
12685 | +-----------------------+---------+----------+-----------+ | |
12686 | ||
12687 | This option specifies the expiry time for negative callout cache data for an | |
12688 | address. See section 42.45 for details of callout verification, and section | |
12689 | 42.47 for details of the caching. | |
12690 | ||
12691 | +-----------------------+---------+----------+------------+ | |
12692 | |callout_positive_expire|Use: main|Type: time|Default: 24h| | |
12693 | +-----------------------+---------+----------+------------+ | |
12694 | ||
12695 | This option specifies the expiry time for positive callout cache data for an | |
12696 | address. See section 42.45 for details of callout verification, and section | |
12697 | 42.47 for details of the caching. | |
12698 | ||
12699 | +-------------------------+---------+-------------+------------------+ | |
12700 | |callout_random_local_part|Use: main|Type: string*|Default: see below| | |
12701 | +-------------------------+---------+-------------+------------------+ | |
12702 | ||
12703 | This option defines the "random" local part that can be used as part of callout | |
12704 | verification. The default value is | |
12705 | ||
12706 | $primary_hostname-$tod_epoch-testing | |
12707 | ||
12708 | See section 42.46 for details of how this value is used. | |
12709 | ||
12710 | +----------------+---------+-------------+----------+ | |
12711 | |check_log_inodes|Use: main|Type: integer|Default: 0| | |
12712 | +----------------+---------+-------------+----------+ | |
12713 | ||
12714 | See check_spool_space below. | |
12715 | ||
12716 | +---------------+---------+-------------+----------+ | |
12717 | |check_log_space|Use: main|Type: integer|Default: 0| | |
12718 | +---------------+---------+-------------+----------+ | |
12719 | ||
12720 | See check_spool_space below. | |
12721 | ||
12722 | +--------------------+---------+-------------+-------------+ | |
12723 | |check_rfc2047_length|Use: main|Type: boolean|Default: true| | |
12724 | +--------------------+---------+-------------+-------------+ | |
12725 | ||
12726 | RFC 2047 defines a way of encoding non-ASCII characters in headers using a | |
12727 | system of "encoded words". The RFC specifies a maximum length for an encoded | |
12728 | word; strings to be encoded that exceed this length are supposed to use | |
12729 | multiple encoded words. By default, Exim does not recognize encoded words that | |
12730 | exceed the maximum length. However, it seems that some software, in violation | |
12731 | of the RFC, generates overlong encoded words. If check_rfc2047_length is set | |
12732 | false, Exim recognizes encoded words of any length. | |
12733 | ||
12734 | +------------------+---------+-------------+----------+ | |
12735 | |check_spool_inodes|Use: main|Type: integer|Default: 0| | |
12736 | +------------------+---------+-------------+----------+ | |
12737 | ||
12738 | See check_spool_space below. | |
12739 | ||
12740 | +-----------------+---------+-------------+----------+ | |
12741 | |check_spool_space|Use: main|Type: integer|Default: 0| | |
12742 | +-----------------+---------+-------------+----------+ | |
12743 | ||
12744 | The four check_... options allow for checking of disk resources before a | |
12745 | message is accepted. | |
12746 | ||
12747 | When any of these options are set, they apply to all incoming messages. If you | |
12748 | want to apply different checks to different kinds of message, you can do so by | |
12749 | testing the variables $log_inodes, $log_space, $spool_inodes, and $spool_space | |
12750 | in an ACL with appropriate additional conditions. | |
12751 | ||
12752 | check_spool_space and check_spool_inodes check the spool partition if either | |
12753 | value is greater than zero, for example: | |
12754 | ||
12755 | check_spool_space = 10M | |
12756 | check_spool_inodes = 100 | |
12757 | ||
12758 | The spool partition is the one that contains the directory defined by | |
12759 | SPOOL_DIRECTORY in Local/Makefile. It is used for holding messages in transit. | |
12760 | ||
12761 | check_log_space and check_log_inodes check the partition in which log files are | |
12762 | written if either is greater than zero. These should be set only if | |
12763 | log_file_path and spool_directory refer to different partitions. | |
12764 | ||
12765 | If there is less space or fewer inodes than requested, Exim refuses to accept | |
12766 | incoming mail. In the case of SMTP input this is done by giving a 452 temporary | |
12767 | error response to the MAIL command. If ESMTP is in use and there was a SIZE | |
12768 | parameter on the MAIL command, its value is added to the check_spool_space | |
12769 | value, and the check is performed even if check_spool_space is zero, unless | |
12770 | no_smtp_check_spool_space is set. | |
12771 | ||
12772 | The values for check_spool_space and check_log_space are held as a number of | |
12773 | kilobytes. If a non-multiple of 1024 is specified, it is rounded up. | |
12774 | ||
12775 | For non-SMTP input and for batched SMTP input, the test is done at start-up; on | |
12776 | failure a message is written to stderr and Exim exits with a non-zero code, as | |
12777 | it obviously cannot send an error message of any kind. | |
12778 | ||
12779 | +-----------------+---------+------------+---------------+ | |
12780 | |daemon_smtp_ports|Use: main|Type: string|Default: "smtp"| | |
12781 | +-----------------+---------+------------+---------------+ | |
12782 | ||
12783 | This option specifies one or more default SMTP ports on which the Exim daemon | |
12784 | listens. See chapter 13 for details of how it is used. For backward | |
12785 | compatibility, daemon_smtp_port (singular) is a synonym. | |
12786 | ||
12787 | +----------------------+---------+-------------+----------+ | |
12788 | |daemon_startup_retries|Use: main|Type: integer|Default: 9| | |
12789 | +----------------------+---------+-------------+----------+ | |
12790 | ||
12791 | This option, along with daemon_startup_sleep, controls the retrying done by the | |
12792 | daemon at startup when it cannot immediately bind a listening socket (typically | |
12793 | because the socket is already in use): daemon_startup_retries defines the | |
12794 | number of retries after the first failure, and daemon_startup_sleep defines the | |
12795 | length of time to wait between retries. | |
12796 | ||
12797 | +--------------------+---------+----------+------------+ | |
12798 | |daemon_startup_sleep|Use: main|Type: time|Default: 30s| | |
12799 | +--------------------+---------+----------+------------+ | |
12800 | ||
12801 | See daemon_startup_retries. | |
12802 | ||
12803 | +-------------+---------+---------------+------------+ | |
12804 | |delay_warning|Use: main|Type: time list|Default: 24h| | |
12805 | +-------------+---------+---------------+------------+ | |
12806 | ||
12807 | When a message is delayed, Exim sends a warning message to the sender at | |
12808 | intervals specified by this option. The data is a colon-separated list of times | |
12809 | after which to send warning messages. If the value of the option is an empty | |
12810 | string or a zero time, no warnings are sent. Up to 10 times may be given. If a | |
12811 | message has been on the queue for longer than the last time, the last interval | |
12812 | between the times is used to compute subsequent warning times. For example, | |
12813 | with | |
12814 | ||
12815 | delay_warning = 4h:8h:24h | |
12816 | ||
12817 | the first message is sent after 4 hours, the second after 8 hours, and the | |
12818 | third one after 24 hours. After that, messages are sent every 16 hours, because | |
12819 | that is the interval between the last two times on the list. If you set just | |
12820 | one time, it specifies the repeat interval. For example, with: | |
12821 | ||
12822 | delay_warning = 6h | |
12823 | ||
12824 | messages are repeated every six hours. To stop warnings after a given time, set | |
12825 | a very large time at the end of the list. For example: | |
12826 | ||
12827 | delay_warning = 2h:12h:99d | |
12828 | ||
12829 | Note that the option is only evaluated at the time a delivery attempt fails, | |
12830 | which depends on retry and queue-runner configuration. Typically retries will | |
12831 | be configured more frequently than warning messages. | |
12832 | ||
12833 | +-----------------------+---------+-------------+------------------+ | |
12834 | |delay_warning_condition|Use: main|Type: string*|Default: see below| | |
12835 | +-----------------------+---------+-------------+------------------+ | |
12836 | ||
12837 | The string is expanded at the time a warning message might be sent. If all the | |
12838 | deferred addresses have the same domain, it is set in $domain during the | |
12839 | expansion. Otherwise $domain is empty. If the result of the expansion is a | |
12840 | forced failure, an empty string, or a string matching any of "0", "no" or | |
12841 | "false" (the comparison being done caselessly) then the warning message is not | |
12842 | sent. The default is: | |
12843 | ||
12844 | delay_warning_condition = ${if or {\ | |
12845 | { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\ | |
12846 | { match{$h_precedence:}{(?i)bulk|list|junk} }\ | |
12847 | { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\ | |
12848 | } {no}{yes}} | |
12849 | ||
12850 | This suppresses the sending of warnings for messages that contain List-ID:, | |
12851 | List-Post:, or List-Subscribe: headers, or have "bulk", "list" or "junk" in a | |
12852 | Precedence: header, or have "auto-generated" or "auto-replied" in an | |
12853 | Auto-Submitted: header. | |
12854 | ||
12855 | +----------------------+---------+-------------+--------------+ | |
12856 | |deliver_drop_privilege|Use: main|Type: boolean|Default: false| | |
12857 | +----------------------+---------+-------------+--------------+ | |
12858 | ||
12859 | If this option is set true, Exim drops its root privilege at the start of a | |
12860 | delivery process, and runs as the Exim user throughout. This severely restricts | |
12861 | the kinds of local delivery that are possible, but is viable in certain types | |
12862 | of configuration. There is a discussion about the use of root privilege in | |
12863 | chapter 54. | |
12864 | ||
12865 | +----------------------+---------+-----------------+--------------+ | |
12866 | |deliver_queue_load_max|Use: main|Type: fixed-point|Default: unset| | |
12867 | +----------------------+---------+-----------------+--------------+ | |
12868 | ||
12869 | When this option is set, a queue run is abandoned if the system load average | |
12870 | becomes greater than the value of the option. The option has no effect on | |
12871 | ancient operating systems on which Exim cannot determine the load average. See | |
12872 | also queue_only_load and smtp_load_reserve. | |
12873 | ||
12874 | +--------------------+---------+-------------+-------------+ | |
12875 | |delivery_date_remove|Use: main|Type: boolean|Default: true| | |
12876 | +--------------------+---------+-------------+-------------+ | |
12877 | ||
12878 | Exim's transports have an option for adding a Delivery-date: header to a | |
12879 | message when it is delivered, in exactly the same way as Return-path: is | |
12880 | handled. Delivery-date: records the actual time of delivery. Such headers | |
12881 | should not be present in incoming messages, and this option causes them to be | |
12882 | removed at the time the message is received, to avoid any problems that might | |
12883 | occur when a delivered message is subsequently sent on to some other recipient. | |
12884 | ||
12885 | +-------------+---------+-------------+--------------+ | |
12886 | |disable_fsync|Use: main|Type: boolean|Default: false| | |
12887 | +-------------+---------+-------------+--------------+ | |
12888 | ||
12889 | This option is available only if Exim was built with the compile-time option | |
12890 | ENABLE_DISABLE_FSYNC. When this is not set, a reference to disable_fsync in a | |
12891 | runtime configuration generates an "unknown option" error. You should not build | |
12892 | Exim with ENABLE_DISABLE_FSYNC or set disable_fsync unless you really, really, | |
12893 | really understand what you are doing. No pre-compiled distributions of Exim | |
12894 | should ever make this option available. | |
12895 | ||
12896 | When disable_fsync is set true, Exim no longer calls fsync() to force updated | |
12897 | files' data to be written to disc before continuing. Unexpected events such as | |
12898 | crashes and power outages may cause data to be lost or scrambled. Here be | |
12899 | Dragons. Beware. | |
12900 | ||
12901 | +------------+---------+-------------+--------------+ | |
12902 | |disable_ipv6|Use: main|Type: boolean|Default: false| | |
12903 | +------------+---------+-------------+--------------+ | |
12904 | ||
12905 | If this option is set true, even if the Exim binary has IPv6 support, no IPv6 | |
12906 | activities take place. AAAA records are never looked up, and any IPv6 addresses | |
12907 | that are listed in local_interfaces, data for the manualroute router, etc. are | |
12908 | ignored. If IP literals are enabled, the ipliteral router declines to handle | |
12909 | IPv6 literal addresses. | |
12910 | ||
12911 | +------------------------+---------+------------------+--------------+ | |
12912 | |dns_again_means_nonexist|Use: main|Type: domain list*|Default: unset| | |
12913 | +------------------------+---------+------------------+--------------+ | |
12914 | ||
12915 | DNS lookups give a "try again" response for the DNS errors "non-authoritative | |
12916 | host not found" and "SERVERFAIL". This can cause Exim to keep trying to deliver | |
12917 | a message, or to give repeated temporary errors to incoming mail. Sometimes the | |
12918 | effect is caused by a badly set up name server and may persist for a long time. | |
12919 | If a domain which exhibits this problem matches anything in | |
12920 | dns_again_means_nonexist, it is treated as if it did not exist. This option | |
12921 | should be used with care. You can make it apply to reverse lookups by a setting | |
12922 | such as this: | |
12923 | ||
12924 | dns_again_means_nonexist = *.in-addr.arpa | |
12925 | ||
12926 | This option applies to all DNS lookups that Exim does. It also applies when the | |
12927 | gethostbyname() or getipnodebyname() functions give temporary errors, since | |
12928 | these are most likely to be caused by DNS lookup problems. The dnslookup router | |
12929 | has some options of its own for controlling what happens when lookups for MX or | |
12930 | SRV records give temporary errors. These more specific options are applied | |
12931 | after this global option. | |
12932 | ||
12933 | +-----------------------+---------+------------+------------------+ | |
12934 | |dns_check_names_pattern|Use: main|Type: string|Default: see below| | |
12935 | +-----------------------+---------+------------+------------------+ | |
12936 | ||
12937 | When this option is set to a non-empty string, it causes Exim to check domain | |
12938 | names for characters that are not allowed in host names before handing them to | |
12939 | the DNS resolver, because some resolvers give temporary errors for names that | |
12940 | contain unusual characters. If a domain name contains any unwanted characters, | |
12941 | a "not found" result is forced, and the resolver is not called. The check is | |
12942 | done by matching the domain name against a regular expression, which is the | |
12943 | value of this option. The default pattern is | |
12944 | ||
12945 | dns_check_names_pattern = \ | |
12946 | (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$ | |
12947 | ||
12948 | which permits only letters, digits, slashes, and hyphens in components, but | |
12949 | they must start and end with a letter or digit. Slashes are not, in fact, | |
12950 | permitted in host names, but they are found in certain NS records (which can be | |
12951 | accessed in Exim by using a dnsdb lookup). If you set allow_utf8_domains, you | |
12952 | must modify this pattern, or set the option to an empty string. | |
12953 | ||
12954 | +--------------------+---------+-------------+----------+ | |
12955 | |dns_csa_search_limit|Use: main|Type: integer|Default: 5| | |
12956 | +--------------------+---------+-------------+----------+ | |
12957 | ||
12958 | This option controls the depth of parental searching for CSA SRV records in the | |
12959 | DNS, as described in more detail in section 42.50. | |
12960 | ||
12961 | +-------------------+---------+-------------+-------------+ | |
12962 | |dns_csa_use_reverse|Use: main|Type: boolean|Default: true| | |
12963 | +-------------------+---------+-------------+-------------+ | |
12964 | ||
12965 | This option controls whether or not an IP address, given as a CSA domain, is | |
12966 | reversed and looked up in the reverse DNS, as described in more detail in | |
12967 | section 42.50. | |
12968 | ||
12969 | +-------------+---------+-------------+-----------+ | |
12970 | |dns_dnssec_ok|Use: main|Type: integer|Default: -1| | |
12971 | +-------------+---------+-------------+-----------+ | |
12972 | ||
12973 | If this option is set to a non-negative number then Exim will initialise the | |
12974 | DNS resolver library to either use or not use DNSSEC, overriding the system | |
12975 | default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on. | |
12976 | ||
12977 | If the resolver library does not support DNSSEC then this option has no effect. | |
12978 | ||
12979 | +---------------+---------+------------------+--------------+ | |
12980 | |dns_ipv4_lookup|Use: main|Type: domain list*|Default: unset| | |
12981 | +---------------+---------+------------------+--------------+ | |
12982 | ||
12983 | When Exim is compiled with IPv6 support and disable_ipv6 is not set, it looks | |
12984 | for IPv6 address records (AAAA records) as well as IPv4 address records (A | |
12985 | records) when trying to find IP addresses for hosts, unless the host's domain | |
12986 | matches this list. | |
12987 | ||
12988 | This is a fudge to help with name servers that give big delays or otherwise do | |
12989 | not work for the AAAA record type. In due course, when the world's name servers | |
12990 | have all been upgraded, there should be no need for this option. | |
12991 | ||
12992 | +-----------+---------+----------+-----------+ | |
12993 | |dns_retrans|Use: main|Type: time|Default: 0s| | |
12994 | +-----------+---------+----------+-----------+ | |
12995 | ||
12996 | The options dns_retrans and dns_retry can be used to set the retransmission and | |
12997 | retry parameters for DNS lookups. Values of zero (the defaults) leave the | |
12998 | system default settings unchanged. The first value is the time between retries, | |
12999 | and the second is the number of retries. It isn't totally clear exactly how | |
13000 | these settings affect the total time a DNS lookup may take. I haven't found any | |
13001 | documentation about timeouts on DNS lookups; these parameter values are | |
13002 | available in the external resolver interface structure, but nowhere does it | |
13003 | seem to describe how they are used or what you might want to set in them. | |
13004 | ||
13005 | +---------+---------+-------------+----------+ | |
13006 | |dns_retry|Use: main|Type: integer|Default: 0| | |
13007 | +---------+---------+-------------+----------+ | |
13008 | ||
13009 | See dns_retrans above. | |
13010 | ||
13011 | +-------------+---------+-------------+-----------+ | |
13012 | |dns_use_edns0|Use: main|Type: integer|Default: -1| | |
13013 | +-------------+---------+-------------+-----------+ | |
13014 | ||
13015 | If this option is set to a non-negative number then Exim will initialise the | |
13016 | DNS resolver library to either use or not use EDNS0 extensions, overriding the | |
13017 | system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0 on. | |
13018 | ||
13019 | If the resolver library does not support EDNS0 then this option has no effect. | |
13020 | ||
13021 | +-------+---------+-------------+--------------+ | |
13022 | |drop_cr|Use: main|Type: boolean|Default: false| | |
13023 | +-------+---------+-------------+--------------+ | |
13024 | ||
13025 | This is an obsolete option that is now a no-op. It used to affect the way Exim | |
13026 | handled CR and LF characters in incoming messages. What happens now is | |
13027 | described in section 46.2. | |
13028 | ||
13029 | +--------+---------+-------------+------------------+ | |
13030 | |dsn_from|Use: main|Type: string*|Default: see below| | |
13031 | +--------+---------+-------------+------------------+ | |
13032 | ||
13033 | This option can be used to vary the contents of From: header lines in bounces | |
13034 | and other automatically generated messages ("Delivery Status Notifications" - | |
13035 | hence the name of the option). The default setting is: | |
13036 | ||
13037 | dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain> | |
13038 | ||
13039 | The value is expanded every time it is needed. If the expansion fails, a panic | |
13040 | is logged, and the default value is used. | |
13041 | ||
13042 | +------------------+---------+-------------+-------------+ | |
13043 | |envelope_to_remove|Use: main|Type: boolean|Default: true| | |
13044 | +------------------+---------+-------------+-------------+ | |
13045 | ||
13046 | Exim's transports have an option for adding an Envelope-to: header to a message | |
13047 | when it is delivered, in exactly the same way as Return-path: is handled. | |
13048 | Envelope-to: records the original recipient address from the messages's | |
13049 | envelope that caused the delivery to happen. Such headers should not be present | |
13050 | in incoming messages, and this option causes them to be removed at the time the | |
13051 | message is received, to avoid any problems that might occur when a delivered | |
13052 | message is subsequently sent on to some other recipient. | |
13053 | ||
13054 | +-----------+---------+------------------+--------------+ | |
13055 | |errors_copy|Use: main|Type: string list*|Default: unset| | |
13056 | +-----------+---------+------------------+--------------+ | |
13057 | ||
13058 | Setting this option causes Exim to send bcc copies of bounce messages that it | |
13059 | generates to other addresses. Note: This does not apply to bounce messages | |
13060 | coming from elsewhere. The value of the option is a colon-separated list of | |
13061 | items. Each item consists of a pattern, terminated by white space, followed by | |
13062 | a comma-separated list of email addresses. If a pattern contains spaces, it | |
13063 | must be enclosed in double quotes. | |
13064 | ||
13065 | Each pattern is processed in the same way as a single item in an address list | |
13066 | (see section 10.19). When a pattern matches the recipient of the bounce | |
13067 | message, the message is copied to the addresses on the list. The items are | |
13068 | scanned in order, and once a matching one is found, no further items are | |
13069 | examined. For example: | |
13070 | ||
13071 | errors_copy = spqr@mydomain postmaster@mydomain.example :\ | |
13072 | rqps@mydomain hostmaster@mydomain.example,\ | |
13073 | postmaster@mydomain.example | |
13074 | ||
13075 | The address list is expanded before use. The expansion variables $local_part | |
13076 | and $domain are set from the original recipient of the error message, and if | |
13077 | there was any wildcard matching in the pattern, the expansion variables $0, $1, | |
13078 | etc. are set in the normal way. | |
13079 | ||
13080 | +---------------+---------+------------+--------------+ | |
13081 | |errors_reply_to|Use: main|Type: string|Default: unset| | |
13082 | +---------------+---------+------------+--------------+ | |
13083 | ||
13084 | By default, Exim's bounce and delivery warning messages contain the header line | |
13085 | ||
13086 | From: Mail Delivery System <Mailer-Daemon@qualify-domain> | |
13087 | ||
13088 | where qualify-domain is the value of the qualify_domain option. A warning | |
13089 | message that is generated by the quota_warn_message option in an appendfile | |
13090 | transport may contain its own From: header line that overrides the default. | |
13091 | ||
13092 | Experience shows that people reply to bounce messages. If the errors_reply_to | |
13093 | option is set, a Reply-To: header is added to bounce and warning messages. For | |
13094 | example: | |
13095 | ||
13096 | errors_reply_to = postmaster@my.domain.example | |
13097 | ||
13098 | The value of the option is not expanded. It must specify a valid RFC 2822 | |
13099 | address. However, if a warning message that is generated by the | |
13100 | quota_warn_message option in an appendfile transport contain its own Reply-To: | |
13101 | header line, the value of the errors_reply_to option is not used. | |
13102 | ||
13103 | +----------+---------+------------+--------------------------------+ | |
13104 | |exim_group|Use: main|Type: string|Default: compile-time configured| | |
13105 | +----------+---------+------------+--------------------------------+ | |
13106 | ||
13107 | This option changes the gid under which Exim runs when it gives up root | |
13108 | privilege. The default value is compiled into the binary. The value of this | |
13109 | option is used only when exim_user is also set. Unless it consists entirely of | |
13110 | digits, the string is looked up using getgrnam(), and failure causes a | |
13111 | configuration error. See chapter 54 for a discussion of security issues. | |
13112 | ||
13113 | +---------+---------+------------+------------------+ | |
13114 | |exim_path|Use: main|Type: string|Default: see below| | |
13115 | +---------+---------+------------+------------------+ | |
13116 | ||
13117 | This option specifies the path name of the Exim binary, which is used when Exim | |
13118 | needs to re-exec itself. The default is set up to point to the file exim in the | |
13119 | directory configured at compile time by the BIN_DIRECTORY setting. It is | |
13120 | necessary to change exim_path if, exceptionally, Exim is run from some other | |
13121 | place. Warning: Do not use a macro to define the value of this option, because | |
13122 | you will break those Exim utilities that scan the configuration file to find | |
13123 | where the binary is. (They then use the -bP option to extract option settings | |
13124 | such as the value of spool_directory.) | |
13125 | ||
13126 | +---------+---------+------------+--------------------------------+ | |
13127 | |exim_user|Use: main|Type: string|Default: compile-time configured| | |
13128 | +---------+---------+------------+--------------------------------+ | |
13129 | ||
13130 | This option changes the uid under which Exim runs when it gives up root | |
13131 | privilege. The default value is compiled into the binary. Ownership of the run | |
13132 | time configuration file and the use of the -C and -D command line options is | |
13133 | checked against the values in the binary, not what is set here. | |
13134 | ||
13135 | Unless it consists entirely of digits, the string is looked up using getpwnam() | |
13136 | , and failure causes a configuration error. If exim_group is not also supplied, | |
13137 | the gid is taken from the result of getpwnam() if it is used. See chapter 54 | |
13138 | for a discussion of security issues. | |
13139 | ||
13140 | +----------------------+---------+-----------------+--------------+ | |
13141 | |extra_local_interfaces|Use: main|Type: string list|Default: unset| | |
13142 | +----------------------+---------+-----------------+--------------+ | |
13143 | ||
13144 | This option defines network interfaces that are to be considered local when | |
13145 | routing, but which are not used for listening by the daemon. See section 13.8 | |
13146 | for details. | |
13147 | ||
13148 | +-------------------------------------+---------+-------------+-------------+ | |
13149 | |extract_addresses_remove_ arguments|Use: main|Type: boolean|Default: true| | |
13150 | +-------------------------------------+---------+-------------+-------------+ | |
13151 | ||
13152 | According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses | |
13153 | are present on the command line when the -t option is used to build an envelope | |
13154 | from a message's To:, Cc: and Bcc: headers, the command line addresses are | |
13155 | removed from the recipients list. This is also how Smail behaves. However, | |
13156 | other Sendmail documentation (the O'Reilly book) states that command line | |
13157 | addresses are added to those obtained from the header lines. When | |
13158 | extract_addresses_remove_arguments is true (the default), Exim subtracts | |
13159 | argument headers. If it is set false, Exim adds rather than removes argument | |
13160 | addresses. | |
13161 | ||
13162 | +----------------+---------+-------------+----------+ | |
13163 | |finduser_retries|Use: main|Type: integer|Default: 0| | |
13164 | +----------------+---------+-------------+----------+ | |
13165 | ||
13166 | On systems running NIS or other schemes in which user and group information is | |
13167 | distributed from a remote system, there can be times when getpwnam() and | |
13168 | related functions fail, even when given valid data, because things time out. | |
13169 | Unfortunately these failures cannot be distinguished from genuine "not found" | |
13170 | errors. If finduser_retries is set greater than zero, Exim will try that many | |
13171 | extra times to find a user or a group, waiting for one second between retries. | |
13172 | ||
13173 | You should not set this option greater than zero if your user information is in | |
13174 | a traditional /etc/passwd file, because it will cause Exim needlessly to search | |
13175 | the file multiple times for non-existent users, and also cause delay. | |
13176 | ||
13177 | +-----------+---------+----------------------------------+--------------+ | |
13178 | |freeze_tell|Use: main|Type: string list, comma separated|Default: unset| | |
13179 | +-----------+---------+----------------------------------+--------------+ | |
13180 | ||
13181 | On encountering certain errors, or when configured to do so in a system filter, | |
13182 | ACL, or special router, Exim freezes a message. This means that no further | |
13183 | delivery attempts take place until an administrator thaws the message, or the | |
13184 | auto_thaw, ignore_bounce_errors_after, or timeout_frozen_after feature cause it | |
13185 | to be processed. If freeze_tell is set, Exim generates a warning message | |
13186 | whenever it freezes something, unless the message it is freezing is a | |
13187 | locally-generated bounce message. (Without this exception there is the | |
13188 | possibility of looping.) The warning message is sent to the addresses supplied | |
13189 | as the comma-separated value of this option. If several of the message's | |
13190 | addresses cause freezing, only a single message is sent. If the freezing was | |
13191 | automatic, the reason(s) for freezing can be found in the message log. If you | |
13192 | configure freezing in a filter or ACL, you must arrange for any logging that | |
13193 | you require. | |
13194 | ||
13195 | +----------+---------+-------------+--------------+ | |
13196 | |gecos_name|Use: main|Type: string*|Default: unset| | |
13197 | +----------+---------+-------------+--------------+ | |
13198 | ||
13199 | Some operating systems, notably HP-UX, use the "gecos" field in the system | |
13200 | password file to hold other information in addition to users' real names. Exim | |
13201 | looks up this field for use when it is creating Sender: or From: headers. If | |
13202 | either gecos_pattern or gecos_name are unset, the contents of the field are | |
13203 | used unchanged, except that, if an ampersand is encountered, it is replaced by | |
13204 | the user's login name with the first character forced to upper case, since this | |
13205 | is a convention that is observed on many systems. | |
13206 | ||
13207 | When these options are set, gecos_pattern is treated as a regular expression | |
13208 | that is to be applied to the field (again with & replaced by the login name), | |
13209 | and if it matches, gecos_name is expanded and used as the user's name. | |
13210 | ||
13211 | Numeric variables such as $1, $2, etc. can be used in the expansion to pick up | |
13212 | sub-fields that were matched by the pattern. In HP-UX, where the user's name | |
13213 | terminates at the first comma, the following can be used: | |
13214 | ||
13215 | gecos_pattern = ([^,]*) | |
13216 | gecos_name = $1 | |
13217 | ||
13218 | +-------------+---------+------------+--------------+ | |
13219 | |gecos_pattern|Use: main|Type: string|Default: unset| | |
13220 | +-------------+---------+------------+--------------+ | |
13221 | ||
13222 | See gecos_name above. | |
13223 | ||
13224 | +------------------+---------+-------------+--------------+ | |
13225 | |gnutls_compat_mode|Use: main|Type: boolean|Default: unset| | |
13226 | +------------------+---------+-------------+--------------+ | |
13227 | ||
13228 | This option controls whether GnuTLS is used in compatibility mode in an Exim | |
13229 | server. This reduces security slightly, but improves interworking with older | |
13230 | implementations of TLS. | |
13231 | ||
13232 | option gnutls_allow_auto_pkcs11 main boolean unset This option will let GnuTLS | |
13233 | (2.12.0 or later) autoload PKCS11 modules with the p11-kit configuration files | |
13234 | in /etc/pkcs11/modules/. | |
13235 | ||
13236 | See http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs for | |
13237 | documentation. | |
13238 | ||
13239 | +---------------+---------+------------+------------------+ | |
13240 | |headers_charset|Use: main|Type: string|Default: see below| | |
13241 | +---------------+---------+------------+------------------+ | |
13242 | ||
13243 | This option sets a default character set for translating from encoded MIME | |
13244 | "words" in header lines, when referenced by an $h_xxx expansion item. The | |
13245 | default is the value of HEADERS_CHARSET in Local/Makefile. The ultimate default | |
13246 | is ISO-8859-1. For more details see the description of header insertions in | |
13247 | section 11.5. | |
13248 | ||
13249 | +--------------+---------+-------------+------------------+ | |
13250 | |header_maxsize|Use: main|Type: integer|Default: see below| | |
13251 | +--------------+---------+-------------+------------------+ | |
13252 | ||
13253 | This option controls the overall maximum size of a message's header section. | |
13254 | The default is the value of HEADER_MAXSIZE in Local/Makefile; the default for | |
13255 | that is 1M. Messages with larger header sections are rejected. | |
13256 | ||
13257 | +-------------------+---------+-------------+----------+ | |
13258 | |header_line_maxsize|Use: main|Type: integer|Default: 0| | |
13259 | +-------------------+---------+-------------+----------+ | |
13260 | ||
13261 | This option limits the length of any individual header line in a message, after | |
13262 | all the continuations have been joined together. Messages with individual | |
13263 | header lines that are longer than the limit are rejected. The default value of | |
13264 | zero means "no limit". | |
13265 | ||
13266 | +----------------------+---------+----------------+--------------+ | |
13267 | |helo_accept_junk_hosts|Use: main|Type: host list*|Default: unset| | |
13268 | +----------------------+---------+----------------+--------------+ | |
13269 | ||
13270 | Exim checks the syntax of HELO and EHLO commands for incoming SMTP mail, and | |
13271 | gives an error response for invalid data. Unfortunately, there are some SMTP | |
13272 | clients that send syntactic junk. They can be accommodated by setting this | |
13273 | option. Note that this is a syntax check only. See helo_verify_hosts if you | |
13274 | want to do semantic checking. See also helo_allow_chars for a way of extending | |
13275 | the permitted character set. | |
13276 | ||
13277 | +----------------+---------+------------+--------------+ | |
13278 | |helo_allow_chars|Use: main|Type: string|Default: unset| | |
13279 | +----------------+---------+------------+--------------+ | |
13280 | ||
13281 | This option can be set to a string of rogue characters that are permitted in | |
13282 | all EHLO and HELO names in addition to the standard letters, digits, hyphens, | |
13283 | and dots. If you really must allow underscores, you can set | |
13284 | ||
13285 | helo_allow_chars = _ | |
13286 | ||
13287 | Note that the value is one string, not a list. | |
13288 | ||
13289 | +-------------------+---------+------------------+----------------+ | |
13290 | |helo_lookup_domains|Use: main|Type: domain list*|Default: "@:@[]"| | |
13291 | +-------------------+---------+------------------+----------------+ | |
13292 | ||
13293 | If the domain given by a client in a HELO or EHLO command matches this list, a | |
13294 | reverse lookup is done in order to establish the host's true name. The default | |
13295 | forces a lookup if the client host gives the server's name or any of its IP | |
13296 | addresses (in brackets), something that broken clients have been seen to do. | |
13297 | ||
13298 | +---------------------+---------+----------------+--------------+ | |
13299 | |helo_try_verify_hosts|Use: main|Type: host list*|Default: unset| | |
13300 | +---------------------+---------+----------------+--------------+ | |
13301 | ||
13302 | By default, Exim just checks the syntax of HELO and EHLO commands (see | |
13303 | helo_accept_junk_hosts and helo_allow_chars). However, some sites like to do | |
13304 | more extensive checking of the data supplied by these commands. The ACL | |
13305 | condition "verify = helo" is provided to make this possible. Formerly, it was | |
13306 | necessary also to set this option (helo_try_verify_hosts) to force the check to | |
13307 | occur. From release 4.53 onwards, this is no longer necessary. If the check has | |
13308 | not been done before "verify = helo" is encountered, it is done at that time. | |
13309 | Consequently, this option is obsolete. Its specification is retained here for | |
13310 | backwards compatibility. | |
13311 | ||
13312 | When an EHLO or HELO command is received, if the calling host matches | |
13313 | helo_try_verify_hosts, Exim checks that the host name given in the HELO or EHLO | |
13314 | command either: | |
13315 | ||
13316 | * is an IP literal matching the calling address of the host, or | |
13317 | ||
13318 | * matches the host name that Exim obtains by doing a reverse lookup of the | |
13319 | calling host address, or | |
13320 | ||
13321 | * when looked up using gethostbyname() (or getipnodebyname() when available) | |
13322 | yields the calling host address. | |
13323 | ||
13324 | However, the EHLO or HELO command is not rejected if any of the checks fail. | |
13325 | Processing continues, but the result of the check is remembered, and can be | |
13326 | detected later in an ACL by the "verify = helo" condition. | |
13327 | ||
13328 | +-----------------+---------+----------------+--------------+ | |
13329 | |helo_verify_hosts|Use: main|Type: host list*|Default: unset| | |
13330 | +-----------------+---------+----------------+--------------+ | |
13331 | ||
13332 | Like helo_try_verify_hosts, this option is obsolete, and retained only for | |
13333 | backwards compatibility. For hosts that match this option, Exim checks the host | |
13334 | name given in the HELO or EHLO in the same way as for helo_try_verify_hosts. If | |
13335 | the check fails, the HELO or EHLO command is rejected with a 550 error, and | |
13336 | entries are written to the main and reject logs. If a MAIL command is received | |
13337 | before EHLO or HELO, it is rejected with a 503 error. | |
13338 | ||
13339 | +------------+---------+------------------+--------------+ | |
13340 | |hold_domains|Use: main|Type: domain list*|Default: unset| | |
13341 | +------------+---------+------------------+--------------+ | |
13342 | ||
13343 | This option allows mail for particular domains to be held on the queue | |
13344 | manually. The option is overridden if a message delivery is forced with the -M, | |
13345 | -qf, -Rf or -Sf options, and also while testing or verifying addresses using | |
13346 | -bt or -bv. Otherwise, if a domain matches an item in hold_domains, no routing | |
13347 | or delivery for that address is done, and it is deferred every time the message | |
13348 | is looked at. | |
13349 | ||
13350 | This option is intended as a temporary operational measure for delaying the | |
13351 | delivery of mail while some problem is being sorted out, or some new | |
13352 | configuration tested. If you just want to delay the processing of some domains | |
13353 | until a queue run occurs, you should use queue_domains or queue_smtp_domains, | |
13354 | not hold_domains. | |
13355 | ||
13356 | A setting of hold_domains does not override Exim's code for removing messages | |
13357 | from the queue if they have been there longer than the longest retry time in | |
13358 | any retry rule. If you want to hold messages for longer than the normal retry | |
13359 | times, insert a dummy retry rule with a long retry time. | |
13360 | ||
13361 | +-----------+---------+----------------+--------------+ | |
13362 | |host_lookup|Use: main|Type: host list*|Default: unset| | |
13363 | +-----------+---------+----------------+--------------+ | |
13364 | ||
13365 | Exim does not look up the name of a calling host from its IP address unless it | |
13366 | is required to compare against some host list, or the host matches | |
13367 | helo_try_verify_hosts or helo_verify_hosts, or the host matches this option | |
13368 | (which normally contains IP addresses rather than host names). The default | |
13369 | configuration file contains | |
13370 | ||
13371 | host_lookup = * | |
13372 | ||
13373 | which causes a lookup to happen for all hosts. If the expense of these lookups | |
13374 | is felt to be too great, the setting can be changed or removed. | |
13375 | ||
13376 | After a successful reverse lookup, Exim does a forward lookup on the name it | |
13377 | has obtained, to verify that it yields the IP address that it started with. If | |
13378 | this check fails, Exim behaves as if the name lookup failed. | |
13379 | ||
13380 | After any kind of failure, the host name (in $sender_host_name) remains unset, | |
13381 | and $host_lookup_failed is set to the string "1". See also | |
13382 | dns_again_means_nonexist, helo_lookup_domains, and "verify = | |
13383 | reverse_host_lookup" in ACLs. | |
13384 | ||
13385 | +-----------------+---------+-----------------+-----------------------+ | |
13386 | |host_lookup_order|Use: main|Type: string list|Default: "bydns:byaddr"| | |
13387 | +-----------------+---------+-----------------+-----------------------+ | |
13388 | ||
13389 | This option specifies the order of different lookup methods when Exim is trying | |
13390 | to find a host name from an IP address. The default is to do a DNS lookup | |
13391 | first, and then to try a local lookup (using gethostbyaddr() or equivalent) if | |
13392 | that fails. You can change the order of these lookups, or omit one entirely, if | |
13393 | you want. | |
13394 | ||
13395 | Warning: The "byaddr" method does not always yield aliases when there are | |
13396 | multiple PTR records in the DNS and the IP address is not listed in /etc/hosts. | |
13397 | Different operating systems give different results in this case. That is why | |
13398 | the default tries a DNS lookup first. | |
13399 | ||
13400 | +----------------------+---------+----------------+--------------+ | |
13401 | |host_reject_connection|Use: main|Type: host list*|Default: unset| | |
13402 | +----------------------+---------+----------------+--------------+ | |
13403 | ||
13404 | If this option is set, incoming SMTP calls from the hosts listed are rejected | |
13405 | as soon as the connection is made. This option is obsolete, and retained only | |
13406 | for backward compatibility, because nowadays the ACL specified by | |
13407 | acl_smtp_connect can also reject incoming connections immediately. | |
13408 | ||
13409 | The ability to give an immediate rejection (either by this option or using an | |
13410 | ACL) is provided for use in unusual cases. Many hosts will just try again, | |
13411 | sometimes without much delay. Normally, it is better to use an ACL to reject | |
13412 | incoming messages at a later stage, such as after RCPT commands. See chapter 42 | |
13413 | . | |
13414 | ||
13415 | +----------------------+---------+----------------+--------------+ | |
13416 | |hosts_connection_nolog|Use: main|Type: host list*|Default: unset| | |
13417 | +----------------------+---------+----------------+--------------+ | |
13418 | ||
13419 | This option defines a list of hosts for which connection logging does not | |
13420 | happen, even though the smtp_connection log selector is set. For example, you | |
13421 | might want not to log SMTP connections from local processes, or from 127.0.0.1, | |
13422 | or from your local LAN. This option is consulted in the main loop of the | |
13423 | daemon; you should therefore strive to restrict its value to a short inline | |
13424 | list of IP addresses and networks. To disable logging SMTP connections from | |
13425 | local processes, you must create a host list with an empty item. For example: | |
13426 | ||
13427 | hosts_connection_nolog = : | |
13428 | ||
13429 | If the smtp_connection log selector is not set, this option has no effect. | |
13430 | ||
13431 | +--------------------+---------+------------------+--------------+ | |
13432 | |hosts_treat_as_local|Use: main|Type: domain list*|Default: unset| | |
13433 | +--------------------+---------+------------------+--------------+ | |
13434 | ||
13435 | If this option is set, any host names that match the domain list are treated as | |
13436 | if they were the local host when Exim is scanning host lists obtained from MX | |
13437 | records or other sources. Note that the value of this option is a domain list, | |
13438 | not a host list, because it is always used to check host names, not IP | |
13439 | addresses. | |
13440 | ||
13441 | This option also applies when Exim is matching the special items "@mx_any", | |
13442 | "@mx_primary", and "@mx_secondary" in a domain list (see section 10.8), and | |
13443 | when checking the hosts option in the smtp transport for the local host (see | |
13444 | the allow_localhost option in that transport). See also local_interfaces, | |
13445 | extra_local_interfaces, and chapter 13, which contains a discussion about local | |
13446 | network interfaces and recognizing the local host. | |
13447 | ||
13448 | +-------------+---------+-----------------+--------------+ | |
13449 | |ibase_servers|Use: main|Type: string list|Default: unset| | |
13450 | +-------------+---------+-----------------+--------------+ | |
13451 | ||
13452 | This option provides a list of InterBase servers and associated connection | |
13453 | data, to be used in conjunction with ibase lookups (see section 9.21). The | |
13454 | option is available only if Exim has been built with InterBase support. | |
13455 | ||
13456 | +--------------------------+---------+----------+------------+ | |
13457 | |ignore_bounce_errors_after|Use: main|Type: time|Default: 10w| | |
13458 | +--------------------------+---------+----------+------------+ | |
13459 | ||
13460 | This option affects the processing of bounce messages that cannot be delivered, | |
13461 | that is, those that suffer a permanent delivery failure. (Bounce messages that | |
13462 | suffer temporary delivery failures are of course retried in the usual way.) | |
13463 | ||
13464 | After a permanent delivery failure, bounce messages are frozen, because there | |
13465 | is no sender to whom they can be returned. When a frozen bounce message has | |
13466 | been on the queue for more than the given time, it is unfrozen at the next | |
13467 | queue run, and a further delivery is attempted. If delivery fails again, the | |
13468 | bounce message is discarded. This makes it possible to keep failed bounce | |
13469 | messages around for a shorter time than the normal maximum retry time for | |
13470 | frozen messages. For example, | |
13471 | ||
13472 | ignore_bounce_errors_after = 12h | |
13473 | ||
13474 | retries failed bounce message deliveries after 12 hours, discarding any further | |
13475 | failures. If the value of this option is set to a zero time period, bounce | |
13476 | failures are discarded immediately. Setting a very long time (as in the default | |
13477 | value) has the effect of disabling this option. For ways of automatically | |
13478 | dealing with other kinds of frozen message, see auto_thaw and | |
13479 | timeout_frozen_after. | |
13480 | ||
13481 | +---------------------+---------+----------------+--------------+ | |
13482 | |ignore_fromline_hosts|Use: main|Type: host list*|Default: unset| | |
13483 | +---------------------+---------+----------------+--------------+ | |
13484 | ||
13485 | Some broken SMTP clients insist on sending a UUCP-like "From " line before the | |
13486 | headers of a message. By default this is treated as the start of the message's | |
13487 | body, which means that any following headers are not recognized as such. Exim | |
13488 | can be made to ignore it by setting ignore_fromline_hosts to match those hosts | |
13489 | that insist on sending it. If the sender is actually a local process rather | |
13490 | than a remote host, and is using -bs to inject the messages, | |
13491 | ignore_fromline_local must be set to achieve this effect. | |
13492 | ||
13493 | +---------------------+---------+-------------+--------------+ | |
13494 | |ignore_fromline_local|Use: main|Type: boolean|Default: false| | |
13495 | +---------------------+---------+-------------+--------------+ | |
13496 | ||
13497 | See ignore_fromline_hosts above. | |
13498 | ||
188b6fee CE |
13499 | +----------------+---------+-----------------+--------------+ |
13500 | |keep_environment|Use: main|Type: string list|Default: unset| | |
13501 | +----------------+---------+-----------------+--------------+ | |
13502 | ||
13503 | This option contains a string list of environment variables to keep. You have | |
13504 | to trust these variables or you have to be sure that these variables do not | |
13505 | impose any security risk. Keep in mind that during the startup phase Exim is | |
13506 | running with an effective UID 0 in most installations. As the default value is | |
13507 | an empty list, the default environment for using libraries, running embedded | |
13508 | Perl code, or running external binaries is empty, and does not not even contain | |
13509 | PATH or HOME. | |
13510 | ||
13511 | Actually the list is interpreted as a list of patterns (10.1), except that it | |
13512 | is not expanded first. | |
13513 | ||
13514 | WARNING: Macro substitution is still done first, so having a macro FOO and | |
13515 | having FOO_HOME in your keep_environment option may have unexpected results. | |
13516 | You may work around this using a regular expression that does not match the | |
13517 | macro name: ^[F]OO_HOME$. | |
13518 | ||
13519 | Current versions of Exim issue a warning during startupif you do not mention | |
13520 | keep_environment or add_environment in your runtime configuration file. | |
13521 | ||
420a0d19 CE |
13522 | +--------------+---------+----------+-----------+ |
13523 | |keep_malformed|Use: main|Type: time|Default: 4d| | |
13524 | +--------------+---------+----------+-----------+ | |
13525 | ||
13526 | This option specifies the length of time to keep messages whose spool files | |
13527 | have been corrupted in some way. This should, of course, never happen. At the | |
13528 | next attempt to deliver such a message, it gets removed. The incident is | |
13529 | logged. | |
13530 | ||
13531 | +----------------+---------+------------+--------------+ | |
13532 | |ldap_ca_cert_dir|Use: main|Type: string|Default: unset| | |
13533 | +----------------+---------+------------+--------------+ | |
13534 | ||
13535 | This option indicates which directory contains CA certificates for verifying a | |
13536 | TLS certificate presented by an LDAP server. While Exim does not provide a | |
13537 | default value, your SSL library may. Analogous to tls_verify_certificates but | |
13538 | as a client-side option for LDAP and constrained to be a directory. | |
13539 | ||
13540 | +-----------------+---------+------------+--------------+ | |
13541 | |ldap_ca_cert_file|Use: main|Type: string|Default: unset| | |
13542 | +-----------------+---------+------------+--------------+ | |
13543 | ||
13544 | This option indicates which file contains CA certificates for verifying a TLS | |
13545 | certificate presented by an LDAP server. While Exim does not provide a default | |
13546 | value, your SSL library may. Analogous to tls_verify_certificates but as a | |
13547 | client-side option for LDAP and constrained to be a file. | |
13548 | ||
13549 | +--------------+---------+------------+--------------+ | |
13550 | |ldap_cert_file|Use: main|Type: string|Default: unset| | |
13551 | +--------------+---------+------------+--------------+ | |
13552 | ||
13553 | This option indicates which file contains an TLS client certificate which Exim | |
13554 | should present to the LDAP server during TLS negotiation. Should be used | |
13555 | together with ldap_cert_key. | |
13556 | ||
13557 | +-------------+---------+------------+--------------+ | |
13558 | |ldap_cert_key|Use: main|Type: string|Default: unset| | |
13559 | +-------------+---------+------------+--------------+ | |
13560 | ||
13561 | This option indicates which file contains the secret/private key to use to | |
13562 | prove identity to the LDAP server during TLS negotiation. Should be used | |
13563 | together with ldap_cert_file, which contains the identity to be proven. | |
13564 | ||
13565 | +-----------------+---------+------------+--------------+ | |
13566 | |ldap_cipher_suite|Use: main|Type: string|Default: unset| | |
13567 | +-----------------+---------+------------+--------------+ | |
13568 | ||
13569 | This controls the TLS cipher-suite negotiation during TLS negotiation with the | |
13570 | LDAP server. See 41.4 for more details of the format of cipher-suite options | |
13571 | with OpenSSL (as used by LDAP client libraries). | |
13572 | ||
13573 | +--------------------+---------+-----------------+--------------+ | |
13574 | |ldap_default_servers|Use: main|Type: string list|Default: unset| | |
13575 | +--------------------+---------+-----------------+--------------+ | |
13576 | ||
13577 | This option provides a list of LDAP servers which are tried in turn when an | |
13578 | LDAP query does not contain a server. See section 9.14 for details of LDAP | |
13579 | queries. This option is available only when Exim has been built with LDAP | |
13580 | support. | |
13581 | ||
13582 | +-----------------+---------+------------+---------------+ | |
13583 | |ldap_require_cert|Use: main|Type: string|Default: unset.| | |
13584 | +-----------------+---------+------------+---------------+ | |
13585 | ||
13586 | This should be one of the values "hard", "demand", "allow", "try" or "never". A | |
13587 | value other than one of these is interpreted as "never". See the entry | |
13588 | "TLS_REQCERT" in your system man page for ldap.conf(5). Although Exim does not | |
13589 | set a default, the LDAP library probably defaults to hard/demand. | |
13590 | ||
13591 | +--------------+---------+-------------+--------------+ | |
13592 | |ldap_start_tls|Use: main|Type: boolean|Default: false| | |
13593 | +--------------+---------+-------------+--------------+ | |
13594 | ||
13595 | If set, Exim will attempt to negotiate TLS with the LDAP server when connecting | |
13596 | on a regular LDAP port. This is the LDAP equivalent of SMTP's "STARTTLS". This | |
13597 | is distinct from using "ldaps", which is the LDAP form of SSL-on-connect. In | |
13598 | the event of failure to negotiate TLS, the action taken is controlled by | |
13599 | ldap_require_cert. | |
13600 | ||
13601 | +------------+---------+-------------+--------------+ | |
13602 | |ldap_version|Use: main|Type: integer|Default: unset| | |
13603 | +------------+---------+-------------+--------------+ | |
13604 | ||
13605 | This option can be used to force Exim to set a specific protocol version for | |
13606 | LDAP. If it option is unset, it is shown by the -bP command line option as -1. | |
13607 | When this is the case, the default is 3 if LDAP_VERSION3 is defined in the LDAP | |
13608 | headers; otherwise it is 2. This option is available only when Exim has been | |
13609 | built with LDAP support. | |
13610 | ||
13611 | +----------------+---------+-------------+-------------+ | |
13612 | |local_from_check|Use: main|Type: boolean|Default: true| | |
13613 | +----------------+---------+-------------+-------------+ | |
13614 | ||
13615 | When a message is submitted locally (that is, not over a TCP/IP connection) by | |
13616 | an untrusted user, Exim removes any existing Sender: header line, and checks | |
13617 | that the From: header line matches the login of the calling user and the domain | |
13618 | specified by qualify_domain. | |
13619 | ||
13620 | Note: An unqualified address (no domain) in the From: header in a locally | |
13621 | submitted message is automatically qualified by Exim, unless the -bnq command | |
13622 | line option is used. | |
13623 | ||
13624 | You can use local_from_prefix and local_from_suffix to permit affixes on the | |
13625 | local part. If the From: header line does not match, Exim adds a Sender: header | |
13626 | with an address constructed from the calling user's login and the default | |
13627 | qualify domain. | |
13628 | ||
13629 | If local_from_check is set false, the From: header check is disabled, and no | |
13630 | Sender: header is ever added. If, in addition, you want to retain Sender: | |
13631 | header lines supplied by untrusted users, you must also set local_sender_retain | |
13632 | to be true. | |
13633 | ||
13634 | These options affect only the header lines in the message. The envelope sender | |
13635 | is still forced to be the login id at the qualify domain unless | |
13636 | untrusted_set_sender permits the user to supply an envelope sender. | |
13637 | ||
13638 | For messages received over TCP/IP, an ACL can specify "submission mode" to | |
13639 | request similar header line checking. See section 46.16, which has more details | |
13640 | about Sender: processing. | |
13641 | ||
13642 | +-----------------+---------+------------+--------------+ | |
13643 | |local_from_prefix|Use: main|Type: string|Default: unset| | |
13644 | +-----------------+---------+------------+--------------+ | |
13645 | ||
13646 | When Exim checks the From: header line of locally submitted messages for | |
13647 | matching the login id (see local_from_check above), it can be configured to | |
13648 | ignore certain prefixes and suffixes in the local part of the address. This is | |
13649 | done by setting local_from_prefix and/or local_from_suffix to appropriate | |
13650 | lists, in the same form as the local_part_prefix and local_part_suffix router | |
13651 | options (see chapter 15). For example, if | |
13652 | ||
13653 | local_from_prefix = *- | |
13654 | ||
13655 | is set, a From: line containing | |
13656 | ||
13657 | From: anything-user@your.domain.example | |
13658 | ||
13659 | will not cause a Sender: header to be added if user@your.domain.example matches | |
13660 | the actual sender address that is constructed from the login name and qualify | |
13661 | domain. | |
13662 | ||
13663 | +-----------------+---------+------------+--------------+ | |
13664 | |local_from_suffix|Use: main|Type: string|Default: unset| | |
13665 | +-----------------+---------+------------+--------------+ | |
13666 | ||
13667 | See local_from_prefix above. | |
13668 | ||
13669 | +----------------+---------+-----------------+------------------+ | |
13670 | |local_interfaces|Use: main|Type: string list|Default: see below| | |
13671 | +----------------+---------+-----------------+------------------+ | |
13672 | ||
13673 | This option controls which network interfaces are used by the daemon for | |
13674 | listening; they are also used to identify the local host when routing. Chapter | |
13675 | 13 contains a full description of this option and the related options | |
13676 | daemon_smtp_ports, extra_local_interfaces, hosts_treat_as_local, and | |
13677 | tls_on_connect_ports. The default value for local_interfaces is | |
13678 | ||
13679 | local_interfaces = 0.0.0.0 | |
13680 | ||
13681 | when Exim is built without IPv6 support; otherwise it is | |
13682 | ||
13683 | local_interfaces = <; ::0 ; 0.0.0.0 | |
13684 | ||
13685 | +------------------+---------+----------+-----------+ | |
13686 | |local_scan_timeout|Use: main|Type: time|Default: 5m| | |
13687 | +------------------+---------+----------+-----------+ | |
13688 | ||
13689 | This timeout applies to the local_scan() function (see chapter 44). Zero means | |
13690 | "no timeout". If the timeout is exceeded, the incoming message is rejected with | |
13691 | a temporary error if it is an SMTP message. For a non-SMTP message, the message | |
13692 | is dropped and Exim ends with a non-zero code. The incident is logged on the | |
13693 | main and reject logs. | |
13694 | ||
13695 | +-------------------+---------+-------------+--------------+ | |
13696 | |local_sender_retain|Use: main|Type: boolean|Default: false| | |
13697 | +-------------------+---------+-------------+--------------+ | |
13698 | ||
13699 | When a message is submitted locally (that is, not over a TCP/IP connection) by | |
13700 | an untrusted user, Exim removes any existing Sender: header line. If you do not | |
13701 | want this to happen, you must set local_sender_retain, and you must also set | |
13702 | local_from_check to be false (Exim will complain if you do not). See also the | |
13703 | ACL modifier "control = suppress_local_fixups". Section 46.16 has more details | |
13704 | about Sender: processing. | |
13705 | ||
13706 | +----------------+---------+-------------+--------------+ | |
13707 | |localhost_number|Use: main|Type: string*|Default: unset| | |
13708 | +----------------+---------+-------------+--------------+ | |
13709 | ||
13710 | Exim's message ids are normally unique only within the local host. If | |
13711 | uniqueness among a set of hosts is required, each host must set a different | |
13712 | value for the localhost_number option. The string is expanded immediately after | |
13713 | reading the configuration file (so that a number can be computed from the host | |
13714 | name, for example) and the result of the expansion must be a number in the | |
13715 | range 0-16 (or 0-10 on operating systems with case-insensitive file systems). | |
13716 | This is available in subsequent string expansions via the variable | |
13717 | $localhost_number. When localhost_number is set, the final two characters of | |
13718 | the message id, instead of just being a fractional part of the time, are | |
13719 | computed from the time and the local host number as described in section 3.4. | |
13720 | ||
13721 | +-------------+---------+------------------+----------------------------+ | |
13722 | |log_file_path|Use: main|Type: string list*|Default: set at compile time| | |
13723 | +-------------+---------+------------------+----------------------------+ | |
13724 | ||
13725 | This option sets the path which is used to determine the names of Exim's log | |
13726 | files, or indicates that logging is to be to syslog, or both. It is expanded | |
13727 | when Exim is entered, so it can, for example, contain a reference to the host | |
13728 | name. If no specific path is set for the log files at compile or run time, they | |
13729 | are written in a sub-directory called log in Exim's spool directory. Chapter 51 | |
13730 | contains further details about Exim's logging, and section 51.1 describes how | |
13731 | the contents of log_file_path are used. If this string is fixed at your | |
13732 | installation (contains no expansion variables) it is recommended that you do | |
13733 | not set this option in the configuration file, but instead supply the path | |
13734 | using LOG_FILE_PATH in Local/Makefile so that it is available to Exim for | |
13735 | logging errors detected early on - in particular, failure to read the | |
13736 | configuration file. | |
13737 | ||
13738 | +------------+---------+------------+--------------+ | |
13739 | |log_selector|Use: main|Type: string|Default: unset| | |
13740 | +------------+---------+------------+--------------+ | |
13741 | ||
13742 | This option can be used to reduce or increase the number of things that Exim | |
13743 | writes to its log files. Its argument is made up of names preceded by plus or | |
13744 | minus characters. For example: | |
13745 | ||
13746 | log_selector = +arguments -retry_defer | |
13747 | ||
13748 | A list of possible names and what they control is given in the chapter on | |
13749 | logging, in section 51.15. | |
13750 | ||
13751 | +------------+---------+-------------+--------------+ | |
13752 | |log_timezone|Use: main|Type: boolean|Default: false| | |
13753 | +------------+---------+-------------+--------------+ | |
13754 | ||
13755 | By default, the timestamps on log lines are in local time without the timezone. | |
13756 | This means that if your timezone changes twice a year, the timestamps in log | |
13757 | lines are ambiguous for an hour when the clocks go back. One way of avoiding | |
13758 | this problem is to set the timezone to UTC. An alternative is to set | |
13759 | log_timezone true. This turns on the addition of the timezone offset to | |
13760 | timestamps in log lines. Turning on this option can add quite a lot to the size | |
13761 | of log files because each line is extended by 6 characters. Note that the | |
13762 | $tod_log variable contains the log timestamp without the zone, but there is | |
13763 | another variable called $tod_zone that contains just the timezone offset. | |
13764 | ||
13765 | +---------------+---------+-------------+-----------+ | |
13766 | |lookup_open_max|Use: main|Type: integer|Default: 25| | |
13767 | +---------------+---------+-------------+-----------+ | |
13768 | ||
13769 | This option limits the number of simultaneously open files for single-key | |
13770 | lookups that use regular files (that is, lsearch, dbm, and cdb). Exim normally | |
13771 | keeps these files open during routing, because often the same file is required | |
13772 | several times. If the limit is reached, Exim closes the least recently used | |
13773 | file. Note that if you are using the ndbm library, it actually opens two files | |
13774 | for each logical DBM database, though it still counts as one for the purposes | |
13775 | of lookup_open_max. If you are getting "too many open files" errors with NDBM, | |
13776 | you need to reduce the value of lookup_open_max. | |
13777 | ||
13778 | +-------------------+---------+-------------+----------+ | |
13779 | |max_username_length|Use: main|Type: integer|Default: 0| | |
13780 | +-------------------+---------+-------------+----------+ | |
13781 | ||
13782 | Some operating systems are broken in that they truncate long arguments to | |
13783 | getpwnam() to eight characters, instead of returning "no such user". If this | |
13784 | option is set greater than zero, any attempt to call getpwnam() with an | |
13785 | argument that is longer behaves as if getpwnam() failed. | |
13786 | ||
13787 | +---------------------+---------+----------+--------------+ | |
13788 | |message_body_newlines|Use: main|Type: bool|Default: false| | |
13789 | +---------------------+---------+----------+--------------+ | |
13790 | ||
13791 | By default, newlines in the message body are replaced by spaces when setting | |
13792 | the $message_body and $message_body_end expansion variables. If this option is | |
13793 | set true, this no longer happens. | |
13794 | ||
13795 | +--------------------+---------+-------------+------------+ | |
13796 | |message_body_visible|Use: main|Type: integer|Default: 500| | |
13797 | +--------------------+---------+-------------+------------+ | |
13798 | ||
13799 | This option specifies how much of a message's body is to be included in the | |
13800 | $message_body and $message_body_end expansion variables. | |
13801 | ||
13802 | +------------------------+---------+-------------+--------------+ | |
13803 | |message_id_header_domain|Use: main|Type: string*|Default: unset| | |
13804 | +------------------------+---------+-------------+--------------+ | |
13805 | ||
13806 | If this option is set, the string is expanded and used as the right hand side | |
13807 | (domain) of the Message-ID: header that Exim creates if a locally-originated | |
13808 | incoming message does not have one. "Locally-originated" means "not received | |
13809 | over TCP/IP." Otherwise, the primary host name is used. Only letters, digits, | |
13810 | dot and hyphen are accepted; any other characters are replaced by hyphens. If | |
13811 | the expansion is forced to fail, or if the result is an empty string, the | |
13812 | option is ignored. | |
13813 | ||
13814 | +----------------------+---------+-------------+--------------+ | |
13815 | |message_id_header_text|Use: main|Type: string*|Default: unset| | |
13816 | +----------------------+---------+-------------+--------------+ | |
13817 | ||
13818 | If this variable is set, the string is expanded and used to augment the text of | |
13819 | the Message-id: header that Exim creates if a locally-originated incoming | |
13820 | message does not have one. The text of this header is required by RFC 2822 to | |
13821 | take the form of an address. By default, Exim uses its internal message id as | |
13822 | the local part, and the primary host name as the domain. If this option is set, | |
13823 | it is expanded, and provided the expansion is not forced to fail, and does not | |
13824 | yield an empty string, the result is inserted into the header immediately | |
13825 | before the @, separated from the internal message id by a dot. Any characters | |
13826 | that are illegal in an address are automatically converted into hyphens. This | |
13827 | means that variables such as $tod_log can be used, because the spaces and | |
13828 | colons will become hyphens. | |
13829 | ||
13830 | +------------+---------+-------------+-------------+ | |
13831 | |message_logs|Use: main|Type: boolean|Default: true| | |
13832 | +------------+---------+-------------+-------------+ | |
13833 | ||
13834 | If this option is turned off, per-message log files are not created in the | |
13835 | msglog spool sub-directory. This reduces the amount of disk I/O required by | |
13836 | Exim, by reducing the number of files involved in handling a message from a | |
13837 | minimum of four (header spool file, body spool file, delivery journal, and | |
13838 | per-message log) to three. The other major I/O activity is Exim's main log, | |
13839 | which is not affected by this option. | |
13840 | ||
13841 | +------------------+---------+-------------+------------+ | |
13842 | |message_size_limit|Use: main|Type: string*|Default: 50M| | |
13843 | +------------------+---------+-------------+------------+ | |
13844 | ||
13845 | This option limits the maximum size of message that Exim will process. The | |
13846 | value is expanded for each incoming connection so, for example, it can be made | |
13847 | to depend on the IP address of the remote host for messages arriving via TCP/ | |
13848 | IP. After expansion, the value must be a sequence of decimal digits, optionally | |
13849 | followed by K or M. | |
13850 | ||
13851 | Note: This limit cannot be made to depend on a message's sender or any other | |
13852 | properties of an individual message, because it has to be advertised in the | |
13853 | server's response to EHLO. String expansion failure causes a temporary error. A | |
13854 | value of zero means no limit, but its use is not recommended. See also | |
13855 | bounce_return_size_limit. | |
13856 | ||
13857 | Incoming SMTP messages are failed with a 552 error if the limit is exceeded; | |
13858 | locally-generated messages either get a stderr message or a delivery failure | |
13859 | message to the sender, depending on the -oe setting. Rejection of an oversized | |
13860 | message is logged in both the main and the reject logs. See also the generic | |
13861 | transport option message_size_limit, which limits the size of message that an | |
13862 | individual transport can process. | |
13863 | ||
13864 | If you use a virus-scanner and set this option to to a value larger than the | |
13865 | maximum size that your virus-scanner is configured to support, you may get | |
13866 | failures triggered by large mails. The right size to configure for the | |
13867 | virus-scanner depends upon what data is passed and the options in use but it's | |
13868 | probably safest to just set it to a little larger than this value. Eg, with a | |
13869 | default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M, | |
13870 | some problems may result. | |
13871 | ||
13872 | A value of 0 will disable size limit checking; Exim will still advertise the | |
13873 | SIZE extension in an EHLO response, but without a limit, so as to permit SMTP | |
13874 | clients to still indicate the message size along with the MAIL verb. | |
13875 | ||
13876 | +--------------------+---------+-------------+--------------+ | |
13877 | |move_frozen_messages|Use: main|Type: boolean|Default: false| | |
13878 | +--------------------+---------+-------------+--------------+ | |
13879 | ||
13880 | This option, which is available only if Exim has been built with the setting | |
13881 | ||
13882 | SUPPORT_MOVE_FROZEN_MESSAGES=yes | |
13883 | ||
13884 | in Local/Makefile, causes frozen messages and their message logs to be moved | |
13885 | from the input and msglog directories on the spool to Finput and Fmsglog, | |
13886 | respectively. There is currently no support in Exim or the standard utilities | |
13887 | for handling such moved messages, and they do not show up in lists generated by | |
13888 | -bp or by the Exim monitor. | |
13889 | ||
13890 | +-----------+---------+-------------+--------------+ | |
13891 | |mua_wrapper|Use: main|Type: boolean|Default: false| | |
13892 | +-----------+---------+-------------+--------------+ | |
13893 | ||
13894 | Setting this option true causes Exim to run in a very restrictive mode in which | |
13895 | it passes messages synchronously to a smart host. Chapter 50 contains a full | |
13896 | description of this facility. | |
13897 | ||
13898 | +-------------+---------+-----------------+--------------+ | |
13899 | |mysql_servers|Use: main|Type: string list|Default: unset| | |
13900 | +-------------+---------+-----------------+--------------+ | |
13901 | ||
13902 | This option provides a list of MySQL servers and associated connection data, to | |
13903 | be used in conjunction with mysql lookups (see section 9.21). The option is | |
13904 | available only if Exim has been built with MySQL support. | |
13905 | ||
13906 | +-----------+---------+------------------+--------------+ | |
13907 | |never_users|Use: main|Type: string list*|Default: unset| | |
13908 | +-----------+---------+------------------+--------------+ | |
13909 | ||
13910 | This option is expanded just once, at the start of Exim's processing. Local | |
13911 | message deliveries are normally run in processes that are setuid to the | |
13912 | recipient, and remote deliveries are normally run under Exim's own uid and gid. | |
13913 | It is usually desirable to prevent any deliveries from running as root, as a | |
13914 | safety precaution. | |
13915 | ||
13916 | When Exim is built, an option called FIXED_NEVER_USERS can be set to a list of | |
13917 | users that must not be used for local deliveries. This list is fixed in the | |
13918 | binary and cannot be overridden by the configuration file. By default, it | |
13919 | contains just the single user name "root". The never_users runtime option can | |
13920 | be used to add more users to the fixed list. | |
13921 | ||
13922 | If a message is to be delivered as one of the users on the fixed list or the | |
13923 | never_users list, an error occurs, and delivery is deferred. A common example | |
13924 | is | |
13925 | ||
13926 | never_users = root:daemon:bin | |
13927 | ||
13928 | Including root is redundant if it is also on the fixed list, but it does no | |
13929 | harm. This option overrides the pipe_as_creator option of the pipe transport | |
13930 | driver. | |
13931 | ||
13932 | +---------------+---------+-----------------+------------------+ | |
13933 | |openssl_options|Use: main|Type: string list|Default: +no_sslv2| | |
13934 | +---------------+---------+-----------------+------------------+ | |
13935 | ||
13936 | This option allows an administrator to adjust the SSL options applied by | |
13937 | OpenSSL to connections. It is given as a space-separated list of items, each | |
13938 | one to be +added or -subtracted from the current value. | |
13939 | ||
13940 | This option is only available if Exim is built against OpenSSL. The values | |
13941 | available for this option vary according to the age of your OpenSSL install. | |
13942 | The "all" value controls a subset of flags which are available, typically the | |
13943 | bug workaround options. The SSL_CTX_set_options man page will list the values | |
13944 | known on your system and Exim should support all the "bug workaround" options | |
13945 | and many of the "modifying" options. The Exim names lose the leading "SSL_OP_" | |
13946 | and are lower-cased. | |
13947 | ||
13948 | Note that adjusting the options can have severe impact upon the security of SSL | |
13949 | as used by Exim. It is possible to disable safety checks and shoot yourself in | |
13950 | the foot in various unpleasant ways. This option should not be adjusted | |
13951 | lightly. An unrecognised item will be detected at startup, by invoking Exim | |
13952 | with the -bV flag. | |
13953 | ||
13954 | Historical note: prior to release 4.80, Exim defaulted this value to | |
13955 | "+dont_insert_empty_fragments", which may still be needed for compatibility | |
13956 | with some clients, but which lowers security by increasing exposure to some now | |
13957 | infamous attacks. | |
13958 | ||
13959 | An example: | |
13960 | ||
13961 | # Make both old MS and old Eudora happy: | |
13962 | openssl_options = -all +microsoft_big_sslv3_buffer \ | |
13963 | +dont_insert_empty_fragments | |
13964 | ||
13965 | Possible options may include: | |
13966 | ||
13967 | * "all" | |
13968 | ||
13969 | * "allow_unsafe_legacy_renegotiation" | |
13970 | ||
13971 | * "cipher_server_preference" | |
13972 | ||
13973 | * "dont_insert_empty_fragments" | |
13974 | ||
13975 | * "ephemeral_rsa" | |
13976 | ||
13977 | * "legacy_server_connect" | |
13978 | ||
13979 | * "microsoft_big_sslv3_buffer" | |
13980 | ||
13981 | * "microsoft_sess_id_bug" | |
13982 | ||
13983 | * "msie_sslv2_rsa_padding" | |
13984 | ||
13985 | * "netscape_challenge_bug" | |
13986 | ||
13987 | * "netscape_reuse_cipher_change_bug" | |
13988 | ||
13989 | * "no_compression" | |
13990 | ||
13991 | * "no_session_resumption_on_renegotiation" | |
13992 | ||
13993 | * "no_sslv2" | |
13994 | ||
13995 | * "no_sslv3" | |
13996 | ||
13997 | * "no_ticket" | |
13998 | ||
13999 | * "no_tlsv1" | |
14000 | ||
14001 | * "no_tlsv1_1" | |
14002 | ||
14003 | * "no_tlsv1_2" | |
14004 | ||
14005 | * "safari_ecdhe_ecdsa_bug" | |
14006 | ||
14007 | * "single_dh_use" | |
14008 | ||
14009 | * "single_ecdh_use" | |
14010 | ||
14011 | * "ssleay_080_client_dh_bug" | |
14012 | ||
14013 | * "sslref2_reuse_cert_type_bug" | |
14014 | ||
14015 | * "tls_block_padding_bug" | |
14016 | ||
14017 | * "tls_d5_bug" | |
14018 | ||
14019 | * "tls_rollback_bug" | |
14020 | ||
14021 | As an aside, the "safari_ecdhe_ecdsa_bug" item is a misnomer and affects all | |
14022 | clients connecting using the MacOS SecureTransport TLS facility prior to MacOS | |
14023 | 10.8.4, including email clients. If you see old MacOS clients failing to | |
14024 | negotiate TLS then this option value might help, provided that your OpenSSL | |
14025 | release is new enough to contain this work-around. This may be a situation | |
14026 | where you have to upgrade OpenSSL to get buggy clients working. | |
14027 | ||
14028 | +--------------+---------+-----------------+--------------+ | |
14029 | |oracle_servers|Use: main|Type: string list|Default: unset| | |
14030 | +--------------+---------+-----------------+--------------+ | |
14031 | ||
14032 | This option provides a list of Oracle servers and associated connection data, | |
14033 | to be used in conjunction with oracle lookups (see section 9.21). The option is | |
14034 | available only if Exim has been built with Oracle support. | |
14035 | ||
14036 | +--------------------+---------+------------------+--------------+ | |
14037 | |percent_hack_domains|Use: main|Type: domain list*|Default: unset| | |
14038 | +--------------------+---------+------------------+--------------+ | |
14039 | ||
14040 | The "percent hack" is the convention whereby a local part containing a percent | |
14041 | sign is re-interpreted as a new email address, with the percent replaced by @. | |
14042 | This is sometimes called "source routing", though that term is also applied to | |
14043 | RFC 2822 addresses that begin with an @ character. If this option is set, Exim | |
14044 | implements the percent facility for those domains listed, but no others. This | |
14045 | happens before an incoming SMTP address is tested against an ACL. | |
14046 | ||
14047 | Warning: The "percent hack" has often been abused by people who are trying to | |
14048 | get round relaying restrictions. For this reason, it is best avoided if at all | |
14049 | possible. Unfortunately, a number of less security-conscious MTAs implement it | |
14050 | unconditionally. If you are running Exim on a gateway host, and routing mail | |
14051 | through to internal MTAs without processing the local parts, it is a good idea | |
14052 | to reject recipient addresses with percent characters in their local parts. | |
14053 | Exim's default configuration does this. | |
14054 | ||
14055 | +-------------+---------+-------------+--------------+ | |
14056 | |perl_at_start|Use: main|Type: boolean|Default: false| | |
14057 | +-------------+---------+-------------+--------------+ | |
14058 | ||
14059 | This option is available only when Exim is built with an embedded Perl | |
14060 | interpreter. See chapter 12 for details of its use. | |
14061 | ||
14062 | +------------+---------+------------+--------------+ | |
14063 | |perl_startup|Use: main|Type: string|Default: unset| | |
14064 | +------------+---------+------------+--------------+ | |
14065 | ||
14066 | This option is available only when Exim is built with an embedded Perl | |
14067 | interpreter. See chapter 12 for details of its use. | |
14068 | ||
14069 | +-------------+---------+-----------------+--------------+ | |
14070 | |pgsql_servers|Use: main|Type: string list|Default: unset| | |
14071 | +-------------+---------+-----------------+--------------+ | |
14072 | ||
14073 | This option provides a list of PostgreSQL servers and associated connection | |
14074 | data, to be used in conjunction with pgsql lookups (see section 9.21). The | |
14075 | option is available only if Exim has been built with PostgreSQL support. | |
14076 | ||
14077 | +-------------+---------+-------------+----------------------------+ | |
14078 | |pid_file_path|Use: main|Type: string*|Default: set at compile time| | |
14079 | +-------------+---------+-------------+----------------------------+ | |
14080 | ||
14081 | This option sets the name of the file to which the Exim daemon writes its | |
14082 | process id. The string is expanded, so it can contain, for example, references | |
14083 | to the host name: | |
14084 | ||
14085 | pid_file_path = /var/log/$primary_hostname/exim.pid | |
14086 | ||
14087 | If no path is set, the pid is written to the file exim-daemon.pid in Exim's | |
14088 | spool directory. The value set by the option can be overridden by the -oP | |
14089 | command line option. A pid file is not written if a "non-standard" daemon is | |
14090 | run by means of the -oX option, unless a path is explicitly supplied by -oP. | |
14091 | ||
14092 | +--------------------------+---------+----------------+----------+ | |
14093 | |pipelining_advertise_hosts|Use: main|Type: host list*|Default: *| | |
14094 | +--------------------------+---------+----------------+----------+ | |
14095 | ||
14096 | This option can be used to suppress the advertisement of the SMTP PIPELINING | |
14097 | extension to specific hosts. See also the no_pipelining control in section | |
14098 | 42.22. When PIPELINING is not advertised and smtp_enforce_sync is true, an Exim | |
14099 | server enforces strict synchronization for each SMTP command and response. When | |
14100 | PIPELINING is advertised, Exim assumes that clients will use it; "out of order" | |
14101 | commands that are "expected" do not count as protocol errors (see | |
14102 | smtp_max_synprot_errors). | |
14103 | ||
14104 | +-----------+---------+-------------+--------------+ | |
14105 | |prdr_enable|Use: main|Type: boolean|Default: false| | |
14106 | +-----------+---------+-------------+--------------+ | |
14107 | ||
14108 | This option can be used to enable the Per-Recipient Data Response extension to | |
14109 | SMTP, defined by Eric Hall. If the option is set, PRDR is advertised by Exim | |
14110 | when operating as a server. If the client requests PRDR, and more than one | |
14111 | recipient, for a message an additional ACL is called for each recipient after | |
14112 | the message content is recieved. See section 42.9. | |
14113 | ||
14114 | +---------------------+---------+-------------+--------------+ | |
14115 | |preserve_message_logs|Use: main|Type: boolean|Default: false| | |
14116 | +---------------------+---------+-------------+--------------+ | |
14117 | ||
14118 | If this option is set, message log files are not deleted when messages are | |
14119 | completed. Instead, they are moved to a sub-directory of the spool directory | |
14120 | called msglog.OLD, where they remain available for statistical or debugging | |
14121 | purposes. This is a dangerous option to set on systems with any appreciable | |
14122 | volume of mail. Use with care! | |
14123 | ||
14124 | +----------------+---------+------------+------------------+ | |
14125 | |primary_hostname|Use: main|Type: string|Default: see below| | |
14126 | +----------------+---------+------------+------------------+ | |
14127 | ||
14128 | This specifies the name of the current host. It is used in the default EHLO or | |
14129 | HELO command for outgoing SMTP messages (changeable via the helo_data option in | |
14130 | the smtp transport), and as the default for qualify_domain. The value is also | |
14131 | used by default in some SMTP response messages from an Exim server. This can be | |
14132 | changed dynamically by setting smtp_active_hostname. | |
14133 | ||
14134 | If primary_hostname is not set, Exim calls uname() to find the host name. If | |
14135 | this fails, Exim panics and dies. If the name returned by uname() contains only | |
14136 | one component, Exim passes it to gethostbyname() (or getipnodebyname() when | |
14137 | available) in order to obtain the fully qualified version. The variable | |
14138 | $primary_hostname contains the host name, whether set explicitly by this | |
14139 | option, or defaulted. | |
14140 | ||
14141 | +-----------------+---------+-------------+--------------+ | |
14142 | |print_topbitchars|Use: main|Type: boolean|Default: false| | |
14143 | +-----------------+---------+-------------+--------------+ | |
14144 | ||
14145 | By default, Exim considers only those characters whose codes lie in the range | |
14146 | 32-126 to be printing characters. In a number of circumstances (for example, | |
14147 | when writing log entries) non-printing characters are converted into escape | |
14148 | sequences, primarily to avoid messing up the layout. If print_topbitchars is | |
14149 | set, code values of 128 and above are also considered to be printing | |
14150 | characters. | |
14151 | ||
14152 | This option also affects the header syntax checks performed by the autoreply | |
14153 | transport, and whether Exim uses RFC 2047 encoding of the user's full name when | |
14154 | constructing From: and Sender: addresses (as described in section 46.18). | |
14155 | Setting this option can cause Exim to generate eight bit message headers that | |
14156 | do not conform to the standards. | |
14157 | ||
14158 | +----------------+---------+------------+--------------+ | |
14159 | |process_log_path|Use: main|Type: string|Default: unset| | |
14160 | +----------------+---------+------------+--------------+ | |
14161 | ||
14162 | This option sets the name of the file to which an Exim process writes its | |
14163 | "process log" when sent a USR1 signal. This is used by the exiwhat utility | |
14164 | script. If this option is unset, the file called exim-process.info in Exim's | |
14165 | spool directory is used. The ability to specify the name explicitly can be | |
14166 | useful in environments where two different Exims are running, using different | |
14167 | spool directories. | |
14168 | ||
14169 | +-------------------+---------+-------------+-------------+ | |
14170 | |prod_requires_admin|Use: main|Type: boolean|Default: true| | |
14171 | +-------------------+---------+-------------+-------------+ | |
14172 | ||
14173 | The -M, -R, and -q command-line options require the caller to be an admin user | |
14174 | unless prod_requires_admin is set false. See also queue_list_requires_admin. | |
14175 | ||
14176 | +--------------+---------+------------+------------------+ | |
14177 | |qualify_domain|Use: main|Type: string|Default: see below| | |
14178 | +--------------+---------+------------+------------------+ | |
14179 | ||
14180 | This option specifies the domain name that is added to any envelope sender | |
14181 | addresses that do not have a domain qualification. It also applies to recipient | |
14182 | addresses if qualify_recipient is not set. Unqualified addresses are accepted | |
14183 | by default only for locally-generated messages. Qualification is also applied | |
14184 | to addresses in header lines such as From: and To: for locally-generated | |
14185 | messages, unless the -bnq command line option is used. | |
14186 | ||
14187 | Messages from external sources must always contain fully qualified addresses, | |
14188 | unless the sending host matches sender_unqualified_hosts or | |
14189 | recipient_unqualified_hosts (as appropriate), in which case incoming addresses | |
14190 | are qualified with qualify_domain or qualify_recipient as necessary. | |
14191 | Internally, Exim always works with fully qualified envelope addresses. If | |
14192 | qualify_domain is not set, it defaults to the primary_hostname value. | |
14193 | ||
14194 | +-----------------+---------+------------+------------------+ | |
14195 | |qualify_recipient|Use: main|Type: string|Default: see below| | |
14196 | +-----------------+---------+------------+------------------+ | |
14197 | ||
14198 | This option allows you to specify a different domain for qualifying recipient | |
14199 | addresses to the one that is used for senders. See qualify_domain above. | |
14200 | ||
14201 | +-------------+---------+------------------+--------------+ | |
14202 | |queue_domains|Use: main|Type: domain list*|Default: unset| | |
14203 | +-------------+---------+------------------+--------------+ | |
14204 | ||
14205 | This option lists domains for which immediate delivery is not required. A | |
14206 | delivery process is started whenever a message is received, but only those | |
14207 | domains that do not match are processed. All other deliveries wait until the | |
14208 | next queue run. See also hold_domains and queue_smtp_domains. | |
14209 | ||
14210 | +-------------------------+---------+-------------+-------------+ | |
14211 | |queue_list_requires_admin|Use: main|Type: boolean|Default: true| | |
14212 | +-------------------------+---------+-------------+-------------+ | |
14213 | ||
14214 | The -bp command-line option, which lists the messages that are on the queue, | |
14215 | requires the caller to be an admin user unless queue_list_requires_admin is set | |
14216 | false. See also prod_requires_admin. | |
14217 | ||
14218 | +----------+---------+-------------+--------------+ | |
14219 | |queue_only|Use: main|Type: boolean|Default: false| | |
14220 | +----------+---------+-------------+--------------+ | |
14221 | ||
14222 | If queue_only is set, a delivery process is not automatically started whenever | |
14223 | a message is received. Instead, the message waits on the queue for the next | |
14224 | queue run. Even if queue_only is false, incoming messages may not get delivered | |
14225 | immediately when certain conditions (such as heavy load) occur. | |
14226 | ||
14227 | The -odq command line has the same effect as queue_only. The -odb and -odi | |
14228 | command line options override queue_only unless queue_only_override is set | |
14229 | false. See also queue_only_file, queue_only_load, and smtp_accept_queue. | |
14230 | ||
14231 | +---------------+---------+------------+--------------+ | |
14232 | |queue_only_file|Use: main|Type: string|Default: unset| | |
14233 | +---------------+---------+------------+--------------+ | |
14234 | ||
14235 | This option can be set to a colon-separated list of absolute path names, each | |
14236 | one optionally preceded by "smtp". When Exim is receiving a message, it tests | |
14237 | for the existence of each listed path using a call to stat(). For each path | |
14238 | that exists, the corresponding queueing option is set. For paths with no | |
14239 | prefix, queue_only is set; for paths prefixed by "smtp", queue_smtp_domains is | |
14240 | set to match all domains. So, for example, | |
14241 | ||
14242 | queue_only_file = smtp/some/file | |
14243 | ||
14244 | causes Exim to behave as if queue_smtp_domains were set to "*" whenever /some/ | |
14245 | file exists. | |
14246 | ||
14247 | +---------------+---------+-----------------+--------------+ | |
14248 | |queue_only_load|Use: main|Type: fixed-point|Default: unset| | |
14249 | +---------------+---------+-----------------+--------------+ | |
14250 | ||
14251 | If the system load average is higher than this value, incoming messages from | |
14252 | all sources are queued, and no automatic deliveries are started. If this | |
14253 | happens during local or remote SMTP input, all subsequent messages received on | |
14254 | the same SMTP connection are queued by default, whatever happens to the load in | |
14255 | the meantime, but this can be changed by setting queue_only_load_latch false. | |
14256 | ||
14257 | Deliveries will subsequently be performed by queue runner processes. This | |
14258 | option has no effect on ancient operating systems on which Exim cannot | |
14259 | determine the load average. See also deliver_queue_load_max and | |
14260 | smtp_load_reserve. | |
14261 | ||
14262 | +---------------------+---------+-------------+-------------+ | |
14263 | |queue_only_load_latch|Use: main|Type: boolean|Default: true| | |
14264 | +---------------------+---------+-------------+-------------+ | |
14265 | ||
14266 | When this option is true (the default), once one message has been queued | |
14267 | because the load average is higher than the value set by queue_only_load, all | |
14268 | subsequent messages received on the same SMTP connection are also queued. This | |
14269 | is a deliberate choice; even though the load average may fall below the | |
14270 | threshold, it doesn't seem right to deliver later messages on the same | |
14271 | connection when not delivering earlier ones. However, there are special | |
14272 | circumstances such as very long-lived connections from scanning appliances | |
14273 | where this is not the best strategy. In such cases, queue_only_load_latch | |
14274 | should be set false. This causes the value of the load average to be | |
14275 | re-evaluated for each message. | |
14276 | ||
14277 | +-------------------+---------+-------------+-------------+ | |
14278 | |queue_only_override|Use: main|Type: boolean|Default: true| | |
14279 | +-------------------+---------+-------------+-------------+ | |
14280 | ||
14281 | When this option is true, the -odx command line options override the setting of | |
14282 | queue_only or queue_only_file in the configuration file. If queue_only_override | |
14283 | is set false, the -odx options cannot be used to override; they are accepted, | |
14284 | but ignored. | |
14285 | ||
14286 | +------------------+---------+-------------+--------------+ | |
14287 | |queue_run_in_order|Use: main|Type: boolean|Default: false| | |
14288 | +------------------+---------+-------------+--------------+ | |
14289 | ||
14290 | If this option is set, queue runs happen in order of message arrival instead of | |
14291 | in an arbitrary order. For this to happen, a complete list of the entire queue | |
14292 | must be set up before the deliveries start. When the queue is all held in a | |
14293 | single directory (the default), a single list is created for both the ordered | |
14294 | and the non-ordered cases. However, if split_spool_directory is set, a single | |
14295 | list is not created when queue_run_in_order is false. In this case, the | |
14296 | sub-directories are processed one at a time (in a random order), and this | |
14297 | avoids setting up one huge list for the whole queue. Thus, setting | |
14298 | queue_run_in_order with split_spool_directory may degrade performance when the | |
14299 | queue is large, because of the extra work in setting up the single, large list. | |
14300 | In most situations, queue_run_in_order should not be set. | |
14301 | ||
14302 | +-------------+---------+-------------+----------+ | |
14303 | |queue_run_max|Use: main|Type: integer|Default: 5| | |
14304 | +-------------+---------+-------------+----------+ | |
14305 | ||
14306 | This controls the maximum number of queue runner processes that an Exim daemon | |
14307 | can run simultaneously. This does not mean that it starts them all at once, but | |
14308 | rather that if the maximum number are still running when the time comes to | |
14309 | start another one, it refrains from starting another one. This can happen with | |
14310 | very large queues and/or very sluggish deliveries. This option does not, | |
14311 | however, interlock with other processes, so additional queue runners can be | |
14312 | started by other means, or by killing and restarting the daemon. | |
14313 | ||
14314 | Setting this option to zero does not suppress queue runs; rather, it disables | |
14315 | the limit, allowing any number of simultaneous queue runner processes to be | |
14316 | run. If you do not want queue runs to occur, omit the -qxx setting on the | |
14317 | daemon's command line. | |
14318 | ||
14319 | +------------------+---------+------------------+--------------+ | |
14320 | |queue_smtp_domains|Use: main|Type: domain list*|Default: unset| | |
14321 | +------------------+---------+------------------+--------------+ | |
14322 | ||
14323 | When this option is set, a delivery process is started whenever a message is | |
14324 | received, routing is performed, and local deliveries take place. However, if | |
14325 | any SMTP deliveries are required for domains that match queue_smtp_domains, | |
14326 | they are not immediately delivered, but instead the message waits on the queue | |
14327 | for the next queue run. Since routing of the message has taken place, Exim | |
14328 | knows to which remote hosts it must be delivered, and so when the queue run | |
14329 | happens, multiple messages for the same host are delivered over a single SMTP | |
14330 | connection. The -odqs command line option causes all SMTP deliveries to be | |
14331 | queued in this way, and is equivalent to setting queue_smtp_domains to "*". See | |
14332 | also hold_domains and queue_domains. | |
14333 | ||
14334 | +---------------+---------+----------+-----------+ | |
14335 | |receive_timeout|Use: main|Type: time|Default: 0s| | |
14336 | +---------------+---------+----------+-----------+ | |
14337 | ||
14338 | This option sets the timeout for accepting a non-SMTP message, that is, the | |
14339 | maximum time that Exim waits when reading a message on the standard input. If | |
14340 | the value is zero, it will wait for ever. This setting is overridden by the -or | |
14341 | command line option. The timeout for incoming SMTP messages is controlled by | |
14342 | smtp_receive_timeout. | |
14343 | ||
14344 | +--------------------+---------+-------------+------------------+ | |
14345 | |received_header_text|Use: main|Type: string*|Default: see below| | |
14346 | +--------------------+---------+-------------+------------------+ | |
14347 | ||
14348 | This string defines the contents of the Received: message header that is added | |
14349 | to each message, except for the timestamp, which is automatically added on at | |
14350 | the end (preceded by a semicolon). The string is expanded each time it is used. | |
14351 | If the expansion yields an empty string, no Received: header line is added to | |
14352 | the message. Otherwise, the string should start with the text "Received:" and | |
14353 | conform to the RFC 2822 specification for Received: header lines. The default | |
14354 | setting is: | |
14355 | ||
14356 | received_header_text = Received: \ | |
14357 | ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\ | |
14358 | {${if def:sender_ident \ | |
14359 | {from ${quote_local_part:$sender_ident} }}\ | |
14360 | ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\ | |
14361 | by $primary_hostname \ | |
14362 | ${if def:received_protocol {with $received_protocol}} \ | |
14363 | ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\ | |
14364 | (Exim $version_number)\n\t\ | |
14365 | ${if def:sender_address \ | |
14366 | {(envelope-from <$sender_address>)\n\t}}\ | |
14367 | id $message_exim_id\ | |
14368 | ${if def:received_for {\n\tfor $received_for}} | |
14369 | ||
14370 | The reference to the TLS cipher is omitted when Exim is built without TLS | |
14371 | support. The use of conditional expansions ensures that this works for both | |
14372 | locally generated messages and messages received from remote hosts, giving | |
14373 | header lines such as the following: | |
14374 | ||
14375 | Received: from scrooge.carol.example ([192.168.12.25] ident=root) | |
14376 | by marley.carol.example with esmtp (Exim 4.00) | |
14377 | (envelope-from <bob@carol.example>) | |
14378 | id 16IOWa-00019l-00 | |
14379 | for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000 | |
14380 | Received: by scrooge.carol.example with local (Exim 4.00) | |
14381 | id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000 | |
14382 | ||
14383 | Until the body of the message has been received, the timestamp is the time when | |
14384 | the message started to be received. Once the body has arrived, and all policy | |
14385 | checks have taken place, the timestamp is updated to the time at which the | |
14386 | message was accepted. | |
14387 | ||
14388 | +--------------------+---------+-------------+-----------+ | |
14389 | |received_headers_max|Use: main|Type: integer|Default: 30| | |
14390 | +--------------------+---------+-------------+-----------+ | |
14391 | ||
14392 | When a message is to be delivered, the number of Received: headers is counted, | |
14393 | and if it is greater than this parameter, a mail loop is assumed to have | |
14394 | occurred, the delivery is abandoned, and an error message is generated. This | |
14395 | applies to both local and remote deliveries. | |
14396 | ||
14397 | +---------------------------+---------+----------------+--------------+ | |
14398 | |recipient_unqualified_hosts|Use: main|Type: host list*|Default: unset| | |
14399 | +---------------------------+---------+----------------+--------------+ | |
14400 | ||
14401 | This option lists those hosts from which Exim is prepared to accept unqualified | |
14402 | recipient addresses in message envelopes. The addresses are made fully | |
14403 | qualified by the addition of the qualify_recipient value. This option also | |
14404 | affects message header lines. Exim does not reject unqualified recipient | |
14405 | addresses in headers, but it qualifies them only if the message came from a | |
14406 | host that matches recipient_unqualified_hosts, or if the message was submitted | |
14407 | locally (not using TCP/IP), and the -bnq option was not set. | |
14408 | ||
14409 | +--------------+---------+-------------+----------+ | |
14410 | |recipients_max|Use: main|Type: integer|Default: 0| | |
14411 | +--------------+---------+-------------+----------+ | |
14412 | ||
14413 | If this option is set greater than zero, it specifies the maximum number of | |
14414 | original recipients for any message. Additional recipients that are generated | |
14415 | by aliasing or forwarding do not count. SMTP messages get a 452 response for | |
14416 | all recipients over the limit; earlier recipients are delivered as normal. | |
14417 | Non-SMTP messages with too many recipients are failed, and no deliveries are | |
14418 | done. | |
14419 | ||
14420 | Note: The RFCs specify that an SMTP server should accept at least 100 RCPT | |
14421 | commands in a single message. | |
14422 | ||
14423 | +---------------------+---------+-------------+--------------+ | |
14424 | |recipients_max_reject|Use: main|Type: boolean|Default: false| | |
14425 | +---------------------+---------+-------------+--------------+ | |
14426 | ||
14427 | If this option is set true, Exim rejects SMTP messages containing too many | |
14428 | recipients by giving 552 errors to the surplus RCPT commands, and a 554 error | |
14429 | to the eventual DATA command. Otherwise (the default) it gives a 452 error to | |
14430 | the surplus RCPT commands and accepts the message on behalf of the initial set | |
14431 | of recipients. The remote server should then re-send the message for the | |
14432 | remaining recipients at a later time. | |
14433 | ||
14434 | +-------------------+---------+-------------+----------+ | |
14435 | |remote_max_parallel|Use: main|Type: integer|Default: 2| | |
14436 | +-------------------+---------+-------------+----------+ | |
14437 | ||
14438 | This option controls parallel delivery of one message to a number of remote | |
14439 | hosts. If the value is less than 2, parallel delivery is disabled, and Exim | |
14440 | does all the remote deliveries for a message one by one. Otherwise, if a single | |
14441 | message has to be delivered to more than one remote host, or if several copies | |
14442 | have to be sent to the same remote host, up to remote_max_parallel deliveries | |
14443 | are done simultaneously. If more than remote_max_parallel deliveries are | |
14444 | required, the maximum number of processes are started, and as each one | |
14445 | finishes, another is begun. The order of starting processes is the same as if | |
14446 | sequential delivery were being done, and can be controlled by the | |
14447 | remote_sort_domains option. If parallel delivery takes place while running with | |
14448 | debugging turned on, the debugging output from each delivery process is tagged | |
14449 | with its process id. | |
14450 | ||
14451 | This option controls only the maximum number of parallel deliveries for one | |
14452 | message in one Exim delivery process. Because Exim has no central queue | |
14453 | manager, there is no way of controlling the total number of simultaneous | |
14454 | deliveries if the configuration allows a delivery attempt as soon as a message | |
14455 | is received. | |
14456 | ||
14457 | If you want to control the total number of deliveries on the system, you need | |
14458 | to set the queue_only option. This ensures that all incoming messages are added | |
14459 | to the queue without starting a delivery process. Then set up an Exim daemon to | |
14460 | start queue runner processes at appropriate intervals (probably fairly often, | |
14461 | for example, every minute), and limit the total number of queue runners by | |
14462 | setting the queue_run_max parameter. Because each queue runner delivers only | |
14463 | one message at a time, the maximum number of deliveries that can then take | |
14464 | place at once is queue_run_max multiplied by remote_max_parallel. | |
14465 | ||
14466 | If it is purely remote deliveries you want to control, use queue_smtp_domains | |
14467 | instead of queue_only. This has the added benefit of doing the SMTP routing | |
14468 | before queueing, so that several messages for the same host will eventually get | |
14469 | delivered down the same connection. | |
14470 | ||
14471 | +-------------------+---------+------------------+--------------+ | |
14472 | |remote_sort_domains|Use: main|Type: domain list*|Default: unset| | |
14473 | +-------------------+---------+------------------+--------------+ | |
14474 | ||
14475 | When there are a number of remote deliveries for a message, they are sorted by | |
14476 | domain into the order given by this list. For example, | |
14477 | ||
14478 | remote_sort_domains = *.cam.ac.uk:*.uk | |
14479 | ||
14480 | would attempt to deliver to all addresses in the cam.ac.uk domain first, then | |
14481 | to those in the uk domain, then to any others. | |
14482 | ||
14483 | +-----------------+---------+----------+-----------+ | |
14484 | |retry_data_expire|Use: main|Type: time|Default: 7d| | |
14485 | +-----------------+---------+----------+-----------+ | |
14486 | ||
14487 | This option sets a "use before" time on retry information in Exim's hints | |
14488 | database. Any older retry data is ignored. This means that, for example, once a | |
14489 | host has not been tried for 7 days, Exim behaves as if it has no knowledge of | |
14490 | past failures. | |
14491 | ||
14492 | +------------------+---------+----------+------------+ | |
14493 | |retry_interval_max|Use: main|Type: time|Default: 24h| | |
14494 | +------------------+---------+----------+------------+ | |
14495 | ||
14496 | Chapter 32 describes Exim's mechanisms for controlling the intervals between | |
14497 | delivery attempts for messages that cannot be delivered straight away. This | |
14498 | option sets an overall limit to the length of time between retries. It cannot | |
14499 | be set greater than 24 hours; any attempt to do so forces the default value. | |
14500 | ||
14501 | +------------------+---------+-------------+-------------+ | |
14502 | |return_path_remove|Use: main|Type: boolean|Default: true| | |
14503 | +------------------+---------+-------------+-------------+ | |
14504 | ||
14505 | RFC 2821, section 4.4, states that an SMTP server must insert a Return-path: | |
14506 | header line into a message when it makes a "final delivery". The Return-path: | |
14507 | header preserves the sender address as received in the MAIL command. This | |
14508 | description implies that this header should not be present in an incoming | |
14509 | message. If return_path_remove is true, any existing Return-path: headers are | |
14510 | removed from messages at the time they are received. Exim's transports have | |
14511 | options for adding Return-path: headers at the time of delivery. They are | |
14512 | normally used only for final local deliveries. | |
14513 | ||
14514 | +-----------------+---------+-------------+-------------+ | |
14515 | |return_size_limit|Use: main|Type: integer|Default: 100K| | |
14516 | +-----------------+---------+-------------+-------------+ | |
14517 | ||
14518 | This option is an obsolete synonym for bounce_return_size_limit. | |
14519 | ||
14520 | +-------------+---------+----------------+----------+ | |
14521 | |rfc1413_hosts|Use: main|Type: host list*|Default: *| | |
14522 | +-------------+---------+----------------+----------+ | |
14523 | ||
14524 | RFC 1413 identification calls are made to any client host which matches an item | |
14525 | in the list. | |
14526 | ||
14527 | +---------------------+---------+----------+-----------+ | |
14528 | |rfc1413_query_timeout|Use: main|Type: time|Default: 5s| | |
14529 | +---------------------+---------+----------+-----------+ | |
14530 | ||
14531 | This sets the timeout on RFC 1413 identification calls. If it is set to zero, | |
14532 | no RFC 1413 calls are ever made. | |
14533 | ||
14534 | +------------------------+---------+----------------+--------------+ | |
14535 | |sender_unqualified_hosts|Use: main|Type: host list*|Default: unset| | |
14536 | +------------------------+---------+----------------+--------------+ | |
14537 | ||
14538 | This option lists those hosts from which Exim is prepared to accept unqualified | |
14539 | sender addresses. The addresses are made fully qualified by the addition of | |
14540 | qualify_domain. This option also affects message header lines. Exim does not | |
14541 | reject unqualified addresses in headers that contain sender addresses, but it | |
14542 | qualifies them only if the message came from a host that matches | |
14543 | sender_unqualified_hosts, or if the message was submitted locally (not using | |
14544 | TCP/IP), and the -bnq option was not set. | |
14545 | ||
188b6fee CE |
14546 | +---------------+---------+-----------------+--------------+ |
14547 | |set_environment|Use: main|Type: string list|Default: empty| | |
14548 | +---------------+---------+-----------------+--------------+ | |
14549 | ||
14550 | This option allows to set individual environment variables that the currently | |
14551 | linked libraries and programs in child processes use. The default list is | |
14552 | empty, | |
14553 | ||
420a0d19 CE |
14554 | +---------------------+---------+-------------+-------------+ |
14555 | |smtp_accept_keepalive|Use: main|Type: boolean|Default: true| | |
14556 | +---------------------+---------+-------------+-------------+ | |
14557 | ||
14558 | This option controls the setting of the SO_KEEPALIVE option on incoming TCP/IP | |
14559 | socket connections. When set, it causes the kernel to probe idle connections | |
14560 | periodically, by sending packets with "old" sequence numbers. The other end of | |
14561 | the connection should send an acknowledgment if the connection is still okay or | |
14562 | a reset if the connection has been aborted. The reason for doing this is that | |
14563 | it has the beneficial effect of freeing up certain types of connection that can | |
14564 | get stuck when the remote host is disconnected without tidying up the TCP/IP | |
14565 | call properly. The keepalive mechanism takes several hours to detect | |
14566 | unreachable hosts. | |
14567 | ||
14568 | +---------------+---------+-------------+-----------+ | |
14569 | |smtp_accept_max|Use: main|Type: integer|Default: 20| | |
14570 | +---------------+---------+-------------+-----------+ | |
14571 | ||
14572 | This option specifies the maximum number of simultaneous incoming SMTP calls | |
14573 | that Exim will accept. It applies only to the listening daemon; there is no | |
14574 | control (in Exim) when incoming SMTP is being handled by inetd. If the value is | |
14575 | set to zero, no limit is applied. However, it is required to be non-zero if | |
14576 | either smtp_accept_max_per_host or smtp_accept_queue is set. See also | |
14577 | smtp_accept_reserve and smtp_load_reserve. | |
14578 | ||
14579 | A new SMTP connection is immediately rejected if the smtp_accept_max limit has | |
14580 | been reached. If not, Exim first checks smtp_accept_max_per_host. If that limit | |
14581 | has not been reached for the client host, smtp_accept_reserve and | |
14582 | smtp_load_reserve are then checked before accepting the connection. | |
14583 | ||
14584 | +-----------------------+---------+-------------+-----------+ | |
14585 | |smtp_accept_max_nonmail|Use: main|Type: integer|Default: 10| | |
14586 | +-----------------------+---------+-------------+-----------+ | |
14587 | ||
14588 | Exim counts the number of "non-mail" commands in an SMTP session, and drops the | |
14589 | connection if there are too many. This option defines "too many". The check | |
14590 | catches some denial-of-service attacks, repeated failing AUTHs, or a mad client | |
14591 | looping sending EHLO, for example. The check is applied only if the client host | |
14592 | matches smtp_accept_max_nonmail_hosts. | |
14593 | ||
14594 | When a new message is expected, one occurrence of RSET is not counted. This | |
14595 | allows a client to send one RSET between messages (this is not necessary, but | |
14596 | some clients do it). Exim also allows one uncounted occurrence of HELO or EHLO, | |
14597 | and one occurrence of STARTTLS between messages. After starting up a TLS | |
14598 | session, another EHLO is expected, and so it too is not counted. The first | |
14599 | occurrence of AUTH in a connection, or immediately following STARTTLS is not | |
14600 | counted. Otherwise, all commands other than MAIL, RCPT, DATA, and QUIT are | |
14601 | counted. | |
14602 | ||
14603 | +-----------------------------+---------+----------------+----------+ | |
14604 | |smtp_accept_max_nonmail_hosts|Use: main|Type: host list*|Default: *| | |
14605 | +-----------------------------+---------+----------------+----------+ | |
14606 | ||
14607 | You can control which hosts are subject to the smtp_accept_max_nonmail check by | |
14608 | setting this option. The default value makes it apply to all hosts. By changing | |
14609 | the value, you can exclude any badly-behaved hosts that you have to live with. | |
14610 | ||
14611 | +------------------------------+---------+-------------+-------------+ | |
14612 | |smtp_accept_max_per_connection|Use: main|Type: integer|Default: 1000| | |
14613 | +------------------------------+---------+-------------+-------------+ | |
14614 | ||
14615 | The value of this option limits the number of MAIL commands that Exim is | |
14616 | prepared to accept over a single SMTP connection, whether or not each command | |
14617 | results in the transfer of a message. After the limit is reached, a 421 | |
14618 | response is given to subsequent MAIL commands. This limit is a safety | |
14619 | precaution against a client that goes mad (incidents of this type have been | |
14620 | seen). | |
14621 | ||
14622 | +------------------------+---------+-------------+--------------+ | |
14623 | |smtp_accept_max_per_host|Use: main|Type: string*|Default: unset| | |
14624 | +------------------------+---------+-------------+--------------+ | |
14625 | ||
14626 | This option restricts the number of simultaneous IP connections from a single | |
14627 | host (strictly, from a single IP address) to the Exim daemon. The option is | |
14628 | expanded, to enable different limits to be applied to different hosts by | |
14629 | reference to $sender_host_address. Once the limit is reached, additional | |
14630 | connection attempts from the same host are rejected with error code 421. This | |
14631 | is entirely independent of smtp_accept_reserve. The option's default value of | |
14632 | zero imposes no limit. If this option is set greater than zero, it is required | |
14633 | that smtp_accept_max be non-zero. | |
14634 | ||
14635 | Warning: When setting this option you should not use any expansion | |
14636 | constructions that take an appreciable amount of time. The expansion and test | |
14637 | happen in the main daemon loop, in order to reject additional connections | |
14638 | without forking additional processes (otherwise a denial-of-service attack | |
14639 | could cause a vast number or processes to be created). While the daemon is | |
14640 | doing this processing, it cannot accept any other incoming connections. | |
14641 | ||
14642 | +-----------------+---------+-------------+----------+ | |
14643 | |smtp_accept_queue|Use: main|Type: integer|Default: 0| | |
14644 | +-----------------+---------+-------------+----------+ | |
14645 | ||
14646 | If the number of simultaneous incoming SMTP connections being handled via the | |
14647 | listening daemon exceeds this value, messages received by SMTP are just placed | |
14648 | on the queue; no delivery processes are started automatically. The count is | |
14649 | fixed at the start of an SMTP connection. It cannot be updated in the | |
14650 | subprocess that receives messages, and so the queueing or not queueing applies | |
14651 | to all messages received in the same connection. | |
14652 | ||
14653 | A value of zero implies no limit, and clearly any non-zero value is useful only | |
14654 | if it is less than the smtp_accept_max value (unless that is zero). See also | |
14655 | queue_only, queue_only_load, queue_smtp_domains, and the various -odx command | |
14656 | line options. | |
14657 | ||
14658 | +--------------------------------+---------+-------------+-----------+ | |
14659 | |smtp_accept_queue_per_connection|Use: main|Type: integer|Default: 10| | |
14660 | +--------------------------------+---------+-------------+-----------+ | |
14661 | ||
14662 | This option limits the number of delivery processes that Exim starts | |
14663 | automatically when receiving messages via SMTP, whether via the daemon or by | |
14664 | the use of -bs or -bS. If the value of the option is greater than zero, and the | |
14665 | number of messages received in a single SMTP session exceeds this number, | |
14666 | subsequent messages are placed on the queue, but no delivery processes are | |
14667 | started. This helps to limit the number of Exim processes when a server | |
14668 | restarts after downtime and there is a lot of mail waiting for it on other | |
14669 | systems. On large systems, the default should probably be increased, and on | |
14670 | dial-in client systems it should probably be set to zero (that is, disabled). | |
14671 | ||
14672 | +-------------------+---------+-------------+----------+ | |
14673 | |smtp_accept_reserve|Use: main|Type: integer|Default: 0| | |
14674 | +-------------------+---------+-------------+----------+ | |
14675 | ||
14676 | When smtp_accept_max is set greater than zero, this option specifies a number | |
14677 | of SMTP connections that are reserved for connections from the hosts that are | |
14678 | specified in smtp_reserve_hosts. The value set in smtp_accept_max includes this | |
14679 | reserve pool. The specified hosts are not restricted to this number of | |
14680 | connections; the option specifies a minimum number of connection slots for | |
14681 | them, not a maximum. It is a guarantee that this group of hosts can always get | |
14682 | at least smtp_accept_reserve connections. However, the limit specified by | |
14683 | smtp_accept_max_per_host is still applied to each individual host. | |
14684 | ||
14685 | For example, if smtp_accept_max is set to 50 and smtp_accept_reserve is set to | |
14686 | 5, once there are 45 active connections (from any hosts), new connections are | |
14687 | accepted only from hosts listed in smtp_reserve_hosts, provided the other | |
14688 | criteria for acceptance are met. | |
14689 | ||
14690 | +--------------------+---------+-------------+--------------+ | |
14691 | |smtp_active_hostname|Use: main|Type: string*|Default: unset| | |
14692 | +--------------------+---------+-------------+--------------+ | |
14693 | ||
14694 | This option is provided for multi-homed servers that want to masquerade as | |
14695 | several different hosts. At the start of an incoming SMTP connection, its value | |
14696 | is expanded and used instead of the value of $primary_hostname in SMTP | |
14697 | responses. For example, it is used as domain name in the response to an | |
14698 | incoming HELO or EHLO command. | |
14699 | ||
14700 | The active hostname is placed in the $smtp_active_hostname variable, which is | |
14701 | saved with any messages that are received. It is therefore available for use in | |
14702 | routers and transports when the message is later delivered. | |
14703 | ||
14704 | If this option is unset, or if its expansion is forced to fail, or if the | |
14705 | expansion results in an empty string, the value of $primary_hostname is used. | |
14706 | Other expansion failures cause a message to be written to the main and panic | |
14707 | logs, and the SMTP command receives a temporary error. Typically, the value of | |
14708 | smtp_active_hostname depends on the incoming interface address. For example: | |
14709 | ||
14710 | smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\ | |
14711 | {cox.mydomain}{box.mydomain}} | |
14712 | ||
14713 | Although $smtp_active_hostname is primarily concerned with incoming messages, | |
14714 | it is also used as the default for HELO commands in callout verification if | |
14715 | there is no remote transport from which to obtain a helo_data value. | |
14716 | ||
14717 | +-----------+---------+-------------+------------------+ | |
14718 | |smtp_banner|Use: main|Type: string*|Default: see below| | |
14719 | +-----------+---------+-------------+------------------+ | |
14720 | ||
14721 | This string, which is expanded every time it is used, is output as the initial | |
14722 | positive response to an SMTP connection. The default setting is: | |
14723 | ||
14724 | smtp_banner = $smtp_active_hostname ESMTP Exim \ | |
14725 | $version_number $tod_full | |
14726 | ||
14727 | Failure to expand the string causes a panic error. If you want to create a | |
14728 | multiline response to the initial SMTP connection, use "\n" in the string at | |
14729 | appropriate points, but not at the end. Note that the 220 code is not included | |
14730 | in this string. Exim adds it automatically (several times in the case of a | |
14731 | multiline response). | |
14732 | ||
14733 | +----------------------+---------+-------------+-------------+ | |
14734 | |smtp_check_spool_space|Use: main|Type: boolean|Default: true| | |
14735 | +----------------------+---------+-------------+-------------+ | |
14736 | ||
14737 | When this option is set, if an incoming SMTP session encounters the SIZE option | |
14738 | on a MAIL command, it checks that there is enough space in the spool | |
14739 | directory's partition to accept a message of that size, while still leaving | |
14740 | free the amount specified by check_spool_space (even if that value is zero). If | |
14741 | there isn't enough space, a temporary error code is returned. | |
14742 | ||
14743 | +--------------------+---------+-------------+-----------+ | |
14744 | |smtp_connect_backlog|Use: main|Type: integer|Default: 20| | |
14745 | +--------------------+---------+-------------+-----------+ | |
14746 | ||
14747 | This option specifies a maximum number of waiting SMTP connections. Exim passes | |
14748 | this value to the TCP/IP system when it sets up its listener. Once this number | |
14749 | of connections are waiting for the daemon's attention, subsequent connection | |
14750 | attempts are refused at the TCP/IP level. At least, that is what the manuals | |
14751 | say; in some circumstances such connection attempts have been observed to time | |
14752 | out instead. For large systems it is probably a good idea to increase the value | |
14753 | (to 50, say). It also gives some protection against denial-of-service attacks | |
14754 | by SYN flooding. | |
14755 | ||
14756 | +-----------------+---------+-------------+-------------+ | |
14757 | |smtp_enforce_sync|Use: main|Type: boolean|Default: true| | |
14758 | +-----------------+---------+-------------+-------------+ | |
14759 | ||
14760 | The SMTP protocol specification requires the client to wait for a response from | |
14761 | the server at certain points in the dialogue. Without PIPELINING these | |
14762 | synchronization points are after every command; with PIPELINING they are fewer, | |
14763 | but they still exist. | |
14764 | ||
14765 | Some spamming sites send out a complete set of SMTP commands without waiting | |
14766 | for any response. Exim protects against this by rejecting a message if the | |
14767 | client has sent further input when it should not have. The error response "554 | |
14768 | SMTP synchronization error" is sent, and the connection is dropped. Testing for | |
14769 | this error cannot be perfect because of transmission delays (unexpected input | |
14770 | may be on its way but not yet received when Exim checks). However, it does | |
14771 | detect many instances. | |
14772 | ||
14773 | The check can be globally disabled by setting smtp_enforce_sync false. If you | |
14774 | want to disable the check selectively (for example, only for certain hosts), | |
14775 | you can do so by an appropriate use of a control modifier in an ACL (see | |
14776 | section 42.22). See also pipelining_advertise_hosts. | |
14777 | ||
14778 | +-----------------+---------+-------------+--------------+ | |
14779 | |smtp_etrn_command|Use: main|Type: string*|Default: unset| | |
14780 | +-----------------+---------+-------------+--------------+ | |
14781 | ||
14782 | If this option is set, the given command is run whenever an SMTP ETRN command | |
14783 | is received from a host that is permitted to issue such commands (see chapter | |
14784 | 42). The string is split up into separate arguments which are independently | |
14785 | expanded. The expansion variable $domain is set to the argument of the ETRN | |
14786 | command, and no syntax checking is done on it. For example: | |
14787 | ||
14788 | smtp_etrn_command = /etc/etrn_command $domain \ | |
14789 | $sender_host_address | |
14790 | ||
14791 | A new process is created to run the command, but Exim does not wait for it to | |
14792 | complete. Consequently, its status cannot be checked. If the command cannot be | |
14793 | run, a line is written to the panic log, but the ETRN caller still receives a | |
14794 | 250 success response. Exim is normally running under its own uid when receiving | |
14795 | SMTP, so it is not possible for it to change the uid before running the | |
14796 | command. | |
14797 | ||
14798 | +-------------------+---------+-------------+-------------+ | |
14799 | |smtp_etrn_serialize|Use: main|Type: boolean|Default: true| | |
14800 | +-------------------+---------+-------------+-------------+ | |
14801 | ||
14802 | When this option is set, it prevents the simultaneous execution of more than | |
14803 | one identical command as a result of ETRN in an SMTP connection. See section | |
14804 | 47.8 for details. | |
14805 | ||
14806 | +-----------------+---------+-----------------+--------------+ | |
14807 | |smtp_load_reserve|Use: main|Type: fixed-point|Default: unset| | |
14808 | +-----------------+---------+-----------------+--------------+ | |
14809 | ||
14810 | If the system load average ever gets higher than this, incoming SMTP calls are | |
14811 | accepted only from those hosts that match an entry in smtp_reserve_hosts. If | |
14812 | smtp_reserve_hosts is not set, no incoming SMTP calls are accepted when the | |
14813 | load is over the limit. The option has no effect on ancient operating systems | |
14814 | on which Exim cannot determine the load average. See also | |
14815 | deliver_queue_load_max and queue_only_load. | |
14816 | ||
14817 | +-----------------------+---------+-------------+----------+ | |
14818 | |smtp_max_synprot_errors|Use: main|Type: integer|Default: 3| | |
14819 | +-----------------------+---------+-------------+----------+ | |
14820 | ||
14821 | Exim rejects SMTP commands that contain syntax or protocol errors. In | |
14822 | particular, a syntactically invalid email address, as in this command: | |
14823 | ||
14824 | RCPT TO:<abc xyz@a.b.c> | |
14825 | ||
14826 | causes immediate rejection of the command, before any other tests are done. | |
14827 | (The ACL cannot be run if there is no valid address to set up for it.) An | |
14828 | example of a protocol error is receiving RCPT before MAIL. If there are too | |
14829 | many syntax or protocol errors in one SMTP session, the connection is dropped. | |
14830 | The limit is set by this option. | |
14831 | ||
14832 | When the PIPELINING extension to SMTP is in use, some protocol errors are | |
14833 | "expected", for instance, a RCPT command after a rejected MAIL command. Exim | |
14834 | assumes that PIPELINING will be used if it advertises it (see | |
14835 | pipelining_advertise_hosts), and in this situation, "expected" errors do not | |
14836 | count towards the limit. | |
14837 | ||
14838 | +-------------------------+---------+-------------+----------+ | |
14839 | |smtp_max_unknown_commands|Use: main|Type: integer|Default: 3| | |
14840 | +-------------------------+---------+-------------+----------+ | |
14841 | ||
14842 | If there are too many unrecognized commands in an incoming SMTP session, an | |
14843 | Exim server drops the connection. This is a defence against some kinds of abuse | |
14844 | that subvert web clients into making connections to SMTP ports; in these | |
14845 | circumstances, a number of non-SMTP command lines are sent first. | |
14846 | ||
14847 | +--------------------+---------+----------------+--------------+ | |
14848 | |smtp_ratelimit_hosts|Use: main|Type: host list*|Default: unset| | |
14849 | +--------------------+---------+----------------+--------------+ | |
14850 | ||
14851 | Some sites find it helpful to be able to limit the rate at which certain hosts | |
14852 | can send them messages, and the rate at which an individual message can specify | |
14853 | recipients. | |
14854 | ||
14855 | Exim has two rate-limiting facilities. This section describes the older | |
14856 | facility, which can limit rates within a single connection. The newer ratelimit | |
14857 | ACL condition can limit rates across all connections. See section 42.38 for | |
14858 | details of the newer facility. | |
14859 | ||
14860 | When a host matches smtp_ratelimit_hosts, the values of smtp_ratelimit_mail and | |
14861 | smtp_ratelimit_rcpt are used to control the rate of acceptance of MAIL and RCPT | |
14862 | commands in a single SMTP session, respectively. Each option, if set, must | |
14863 | contain a set of four comma-separated values: | |
14864 | ||
14865 | * A threshold, before which there is no rate limiting. | |
14866 | ||
14867 | * An initial time delay. Unlike other times in Exim, numbers with decimal | |
14868 | fractional parts are allowed here. | |
14869 | ||
14870 | * A factor by which to increase the delay each time. | |
14871 | ||
14872 | * A maximum value for the delay. This should normally be less than 5 minutes, | |
14873 | because after that time, the client is liable to timeout the SMTP command. | |
14874 | ||
14875 | For example, these settings have been used successfully at the site which first | |
14876 | suggested this feature, for controlling mail from their customers: | |
14877 | ||
14878 | smtp_ratelimit_mail = 2,0.5s,1.05,4m | |
14879 | smtp_ratelimit_rcpt = 4,0.25s,1.015,4m | |
14880 | ||
14881 | The first setting specifies delays that are applied to MAIL commands after two | |
14882 | have been received over a single connection. The initial delay is 0.5 seconds, | |
14883 | increasing by a factor of 1.05 each time. The second setting applies delays to | |
14884 | RCPT commands when more than four occur in a single message. | |
14885 | ||
14886 | +-------------------+---------+------------+--------------+ | |
14887 | |smtp_ratelimit_mail|Use: main|Type: string|Default: unset| | |
14888 | +-------------------+---------+------------+--------------+ | |
14889 | ||
14890 | See smtp_ratelimit_hosts above. | |
14891 | ||
14892 | +-------------------+---------+------------+--------------+ | |
14893 | |smtp_ratelimit_rcpt|Use: main|Type: string|Default: unset| | |
14894 | +-------------------+---------+------------+--------------+ | |
14895 | ||
14896 | See smtp_ratelimit_hosts above. | |
14897 | ||
14898 | +--------------------+---------+----------+-----------+ | |
14899 | |smtp_receive_timeout|Use: main|Type: time|Default: 5m| | |
14900 | +--------------------+---------+----------+-----------+ | |
14901 | ||
14902 | This sets a timeout value for SMTP reception. It applies to all forms of SMTP | |
14903 | input, including batch SMTP. If a line of input (either an SMTP command or a | |
14904 | data line) is not received within this time, the SMTP connection is dropped and | |
14905 | the message is abandoned. A line is written to the log containing one of the | |
14906 | following messages: | |
14907 | ||
14908 | SMTP command timeout on connection from... | |
14909 | SMTP data timeout on connection from... | |
14910 | ||
14911 | The former means that Exim was expecting to read an SMTP command; the latter | |
14912 | means that it was in the DATA phase, reading the contents of a message. | |
14913 | ||
14914 | The value set by this option can be overridden by the -os command-line option. | |
14915 | A setting of zero time disables the timeout, but this should never be used for | |
14916 | SMTP over TCP/IP. (It can be useful in some cases of local input using -bs or | |
14917 | -bS.) For non-SMTP input, the reception timeout is controlled by | |
14918 | receive_timeout and -or. | |
14919 | ||
14920 | +------------------+---------+----------------+--------------+ | |
14921 | |smtp_reserve_hosts|Use: main|Type: host list*|Default: unset| | |
14922 | +------------------+---------+----------------+--------------+ | |
14923 | ||
14924 | This option defines hosts for which SMTP connections are reserved; see | |
14925 | smtp_accept_reserve and smtp_load_reserve above. | |
14926 | ||
14927 | +-------------------------+---------+-------------+--------------+ | |
14928 | |smtp_return_error_details|Use: main|Type: boolean|Default: false| | |
14929 | +-------------------------+---------+-------------+--------------+ | |
14930 | ||
14931 | In the default state, Exim uses bland messages such as "Administrative | |
14932 | prohibition" when it rejects SMTP commands for policy reasons. Many sysadmins | |
14933 | like this because it gives away little information to spammers. However, some | |
14934 | other sysadmins who are applying strict checking policies want to give out much | |
14935 | fuller information about failures. Setting smtp_return_error_details true | |
14936 | causes Exim to be more forthcoming. For example, instead of "Administrative | |
14937 | prohibition", it might give: | |
14938 | ||
14939 | 550-Rejected after DATA: '>' missing at end of address: | |
14940 | 550 failing address in "From" header is: <user@dom.ain | |
14941 | ||
14942 | +-------------+---------+------------+------------------+ | |
14943 | |spamd_address|Use: main|Type: string|Default: see below| | |
14944 | +-------------+---------+------------+------------------+ | |
14945 | ||
14946 | This option is available when Exim is compiled with the content-scanning | |
14947 | extension. It specifies how Exim connects to SpamAssassin's spamd daemon. The | |
14948 | default value is | |
14949 | ||
14950 | 127.0.0.1 783 | |
14951 | ||
14952 | See section 43.2 for more details. | |
14953 | ||
14954 | +---------------------+---------+-------------+--------------+ | |
14955 | |split_spool_directory|Use: main|Type: boolean|Default: false| | |
14956 | +---------------------+---------+-------------+--------------+ | |
14957 | ||
14958 | If this option is set, it causes Exim to split its input directory into 62 | |
14959 | subdirectories, each with a single alphanumeric character as its name. The | |
14960 | sixth character of the message id is used to allocate messages to | |
14961 | subdirectories; this is the least significant base-62 digit of the time of | |
14962 | arrival of the message. | |
14963 | ||
14964 | Splitting up the spool in this way may provide better performance on systems | |
14965 | where there are long mail queues, by reducing the number of files in any one | |
14966 | directory. The msglog directory is also split up in a similar way to the input | |
14967 | directory; however, if preserve_message_logs is set, all old msglog files are | |
14968 | still placed in the single directory msglog.OLD. | |
14969 | ||
14970 | It is not necessary to take any special action for existing messages when | |
14971 | changing split_spool_directory. Exim notices messages that are in the "wrong" | |
14972 | place, and continues to process them. If the option is turned off after a | |
14973 | period of being on, the subdirectories will eventually empty and be | |
14974 | automatically deleted. | |
14975 | ||
14976 | When split_spool_directory is set, the behaviour of queue runner processes | |
14977 | changes. Instead of creating a list of all messages in the queue, and then | |
14978 | trying to deliver each one in turn, it constructs a list of those in one | |
14979 | sub-directory and tries to deliver them, before moving on to the next | |
14980 | sub-directory. The sub-directories are processed in a random order. This | |
14981 | spreads out the scanning of the input directories, and uses less memory. It is | |
14982 | particularly beneficial when there are lots of messages on the queue. However, | |
14983 | if queue_run_in_order is set, none of this new processing happens. The entire | |
14984 | queue has to be scanned and sorted before any deliveries can start. | |
14985 | ||
14986 | +---------------+---------+-------------+----------------------------+ | |
14987 | |spool_directory|Use: main|Type: string*|Default: set at compile time| | |
14988 | +---------------+---------+-------------+----------------------------+ | |
14989 | ||
14990 | This defines the directory in which Exim keeps its spool, that is, the messages | |
14991 | it is waiting to deliver. The default value is taken from the compile-time | |
14992 | configuration setting, if there is one. If not, this option must be set. The | |
14993 | string is expanded, so it can contain, for example, a reference to | |
14994 | $primary_hostname. | |
14995 | ||
14996 | If the spool directory name is fixed on your installation, it is recommended | |
14997 | that you set it at build time rather than from this option, particularly if the | |
14998 | log files are being written to the spool directory (see log_file_path). | |
14999 | Otherwise log files cannot be used for errors that are detected early on, such | |
15000 | as failures in the configuration file. | |
15001 | ||
15002 | By using this option to override the compiled-in path, it is possible to run | |
15003 | tests of Exim without using the standard spool. | |
15004 | ||
15005 | +-------------------+---------+----------+-----------+ | |
15006 | |sqlite_lock_timeout|Use: main|Type: time|Default: 5s| | |
15007 | +-------------------+---------+----------+-----------+ | |
15008 | ||
15009 | This option controls the timeout that the sqlite lookup uses when trying to | |
15010 | access an SQLite database. See section 9.25 for more details. | |
15011 | ||
15012 | +---------------+---------+-------------+--------------+ | |
15013 | |strict_acl_vars|Use: main|Type: boolean|Default: false| | |
15014 | +---------------+---------+-------------+--------------+ | |
15015 | ||
15016 | This option controls what happens if a syntactically valid but undefined ACL | |
15017 | variable is referenced. If it is false (the default), an empty string is | |
15018 | substituted; if it is true, an error is generated. See section 42.19 for | |
15019 | details of ACL variables. | |
15020 | ||
15021 | +---------------------------+---------+-------------+--------------+ | |
15022 | |strip_excess_angle_brackets|Use: main|Type: boolean|Default: false| | |
15023 | +---------------------------+---------+-------------+--------------+ | |
15024 | ||
15025 | If this option is set, redundant pairs of angle brackets round "route-addr" | |
15026 | items in addresses are stripped. For example, <<xxx@a.b.c.d>> is treated as | |
15027 | <xxx@a.b.c.d>. If this is in the envelope and the message is passed on to | |
15028 | another MTA, the excess angle brackets are not passed on. If this option is not | |
15029 | set, multiple pairs of angle brackets cause a syntax error. | |
15030 | ||
15031 | +------------------+---------+-------------+--------------+ | |
15032 | |strip_trailing_dot|Use: main|Type: boolean|Default: false| | |
15033 | +------------------+---------+-------------+--------------+ | |
15034 | ||
15035 | If this option is set, a trailing dot at the end of a domain in an address is | |
15036 | ignored. If this is in the envelope and the message is passed on to another | |
15037 | MTA, the dot is not passed on. If this option is not set, a dot at the end of a | |
15038 | domain causes a syntax error. However, addresses in header lines are checked | |
15039 | only when an ACL requests header syntax checking. | |
15040 | ||
15041 | +------------------+---------+-------------+-------------+ | |
15042 | |syslog_duplication|Use: main|Type: boolean|Default: true| | |
15043 | +------------------+---------+-------------+-------------+ | |
15044 | ||
15045 | When Exim is logging to syslog, it writes the log lines for its three separate | |
15046 | logs at different syslog priorities so that they can in principle be separated | |
15047 | on the logging hosts. Some installations do not require this separation, and in | |
15048 | those cases, the duplication of certain log lines is a nuisance. If | |
15049 | syslog_duplication is set false, only one copy of any particular log line is | |
15050 | written to syslog. For lines that normally go to both the main log and the | |
15051 | reject log, the reject log version (possibly containing message header lines) | |
15052 | is written, at LOG_NOTICE priority. Lines that normally go to both the main and | |
15053 | the panic log are written at the LOG_ALERT priority. | |
15054 | ||
15055 | +---------------+---------+------------+--------------+ | |
15056 | |syslog_facility|Use: main|Type: string|Default: unset| | |
15057 | +---------------+---------+------------+--------------+ | |
15058 | ||
15059 | This option sets the syslog "facility" name, used when Exim is logging to | |
15060 | syslog. The value must be one of the strings "mail", "user", "news", "uucp", | |
15061 | "daemon", or "localx" where x is a digit between 0 and 7. If this option is | |
15062 | unset, "mail" is used. See chapter 51 for details of Exim's logging. | |
15063 | ||
15064 | +------------------+---------+------------+---------------+ | |
15065 | |syslog_processname|Use: main|Type: string|Default: "exim"| | |
15066 | +------------------+---------+------------+---------------+ | |
15067 | ||
15068 | This option sets the syslog "ident" name, used when Exim is logging to syslog. | |
15069 | The value must be no longer than 32 characters. See chapter 51 for details of | |
15070 | Exim's logging. | |
15071 | ||
15072 | +----------------+---------+-------------+-------------+ | |
15073 | |syslog_timestamp|Use: main|Type: boolean|Default: true| | |
15074 | +----------------+---------+-------------+-------------+ | |
15075 | ||
15076 | If syslog_timestamp is set false, the timestamps on Exim's log lines are | |
15077 | omitted when these lines are sent to syslog. See chapter 51 for details of | |
15078 | Exim's logging. | |
15079 | ||
15080 | +-------------+---------+-------------+--------------+ | |
15081 | |system_filter|Use: main|Type: string*|Default: unset| | |
15082 | +-------------+---------+-------------+--------------+ | |
15083 | ||
15084 | This option specifies an Exim filter file that is applied to all messages at | |
15085 | the start of each delivery attempt, before any routing is done. System filters | |
15086 | must be Exim filters; they cannot be Sieve filters. If the system filter | |
15087 | generates any deliveries to files or pipes, or any new mail messages, the | |
15088 | appropriate system_filter_..._transport option(s) must be set, to define which | |
15089 | transports are to be used. Details of this facility are given in chapter 45. | |
15090 | ||
15091 | +---------------------------------+---------+-------------+--------------+ | |
15092 | |system_filter_directory_transport|Use: main|Type: string*|Default: unset| | |
15093 | +---------------------------------+---------+-------------+--------------+ | |
15094 | ||
15095 | This sets the name of the transport driver that is to be used when the save | |
15096 | command in a system message filter specifies a path ending in "/", implying | |
15097 | delivery of each message into a separate file in some directory. During the | |
15098 | delivery, the variable $address_file contains the path name. | |
15099 | ||
15100 | +----------------------------+---------+-------------+--------------+ | |
15101 | |system_filter_file_transport|Use: main|Type: string*|Default: unset| | |
15102 | +----------------------------+---------+-------------+--------------+ | |
15103 | ||
15104 | This sets the name of the transport driver that is to be used when the save | |
15105 | command in a system message filter specifies a path not ending in "/". During | |
15106 | the delivery, the variable $address_file contains the path name. | |
15107 | ||
15108 | +-------------------+---------+------------+--------------+ | |
15109 | |system_filter_group|Use: main|Type: string|Default: unset| | |
15110 | +-------------------+---------+------------+--------------+ | |
15111 | ||
15112 | This option is used only when system_filter_user is also set. It sets the gid | |
15113 | under which the system filter is run, overriding any gid that is associated | |
15114 | with the user. The value may be numerical or symbolic. | |
15115 | ||
15116 | +----------------------------+---------+-------------+--------------+ | |
15117 | |system_filter_pipe_transport|Use: main|Type: string*|Default: unset| | |
15118 | +----------------------------+---------+-------------+--------------+ | |
15119 | ||
15120 | This specifies the transport driver that is to be used when a pipe command is | |
15121 | used in a system filter. During the delivery, the variable $address_pipe | |
15122 | contains the pipe command. | |
15123 | ||
15124 | +-----------------------------+---------+-------------+--------------+ | |
15125 | |system_filter_reply_transport|Use: main|Type: string*|Default: unset| | |
15126 | +-----------------------------+---------+-------------+--------------+ | |
15127 | ||
15128 | This specifies the transport driver that is to be used when a mail command is | |
15129 | used in a system filter. | |
15130 | ||
15131 | +------------------+---------+------------+--------------+ | |
15132 | |system_filter_user|Use: main|Type: string|Default: unset| | |
15133 | +------------------+---------+------------+--------------+ | |
15134 | ||
15135 | If this option is set to root, the system filter is run in the main Exim | |
15136 | delivery process, as root. Otherwise, the system filter runs in a separate | |
15137 | process, as the given user, defaulting to the Exim run-time user. Unless the | |
15138 | string consists entirely of digits, it is looked up in the password data. | |
15139 | Failure to find the named user causes a configuration error. The gid is either | |
15140 | taken from the password data, or specified by system_filter_group. When the uid | |
15141 | is specified numerically, system_filter_group is required to be set. | |
15142 | ||
15143 | If the system filter generates any pipe, file, or reply deliveries, the uid | |
15144 | under which the filter is run is used when transporting them, unless a | |
15145 | transport option overrides. | |
15146 | ||
15147 | +-----------+---------+-------------+-------------+ | |
15148 | |tcp_nodelay|Use: main|Type: boolean|Default: true| | |
15149 | +-----------+---------+-------------+-------------+ | |
15150 | ||
15151 | If this option is set false, it stops the Exim daemon setting the TCP_NODELAY | |
15152 | option on its listening sockets. Setting TCP_NODELAY turns off the "Nagle | |
15153 | algorithm", which is a way of improving network performance in interactive | |
15154 | (character-by-character) situations. Turning it off should improve Exim's | |
15155 | performance a bit, so that is what happens by default. However, it appears that | |
15156 | some broken clients cannot cope, and time out. Hence this option. It affects | |
15157 | only those sockets that are set up for listening by the daemon. Sockets created | |
15158 | by the smtp transport for delivering mail always set TCP_NODELAY. | |
15159 | ||
15160 | +--------------------+---------+----------+-----------+ | |
15161 | |timeout_frozen_after|Use: main|Type: time|Default: 0s| | |
15162 | +--------------------+---------+----------+-----------+ | |
15163 | ||
15164 | If timeout_frozen_after is set to a time greater than zero, a frozen message of | |
15165 | any kind that has been on the queue for longer than the given time is | |
15166 | automatically cancelled at the next queue run. If the frozen message is a | |
15167 | bounce message, it is just discarded; otherwise, a bounce is sent to the | |
15168 | sender, in a similar manner to cancellation by the -Mg command line option. If | |
15169 | you want to timeout frozen bounce messages earlier than other kinds of frozen | |
15170 | message, see ignore_bounce_errors_after. | |
15171 | ||
15172 | Note: the default value of zero means no timeouts; with this setting, frozen | |
15173 | messages remain on the queue forever (except for any frozen bounce messages | |
15174 | that are released by ignore_bounce_errors_after). | |
15175 | ||
15176 | +--------+---------+------------+--------------+ | |
15177 | |timezone|Use: main|Type: string|Default: unset| | |
15178 | +--------+---------+------------+--------------+ | |
15179 | ||
15180 | The value of timezone is used to set the environment variable TZ while running | |
15181 | Exim (if it is different on entry). This ensures that all timestamps created by | |
15182 | Exim are in the required timezone. If you want all your timestamps to be in UTC | |
15183 | (aka GMT) you should set | |
15184 | ||
15185 | timezone = UTC | |
15186 | ||
15187 | The default value is taken from TIMEZONE_DEFAULT in Local/Makefile, or, if that | |
15188 | is not set, from the value of the TZ environment variable when Exim is built. | |
15189 | If timezone is set to the empty string, either at build or run time, any | |
15190 | existing TZ variable is removed from the environment when Exim runs. This is | |
15191 | appropriate behaviour for obtaining wall-clock time on some, but unfortunately | |
15192 | not all, operating systems. | |
15193 | ||
15194 | +-------------------+---------+----------------+--------------+ | |
15195 | |tls_advertise_hosts|Use: main|Type: host list*|Default: unset| | |
15196 | +-------------------+---------+----------------+--------------+ | |
15197 | ||
15198 | When Exim is built with support for TLS encrypted connections, the availability | |
15199 | of the STARTTLS command to set up an encrypted session is advertised in | |
15200 | response to EHLO only to those client hosts that match this option. See chapter | |
15201 | 41 for details of Exim's support for TLS. | |
15202 | ||
15203 | +---------------+---------+-------------+--------------+ | |
15204 | |tls_certificate|Use: main|Type: string*|Default: unset| | |
15205 | +---------------+---------+-------------+--------------+ | |
15206 | ||
15207 | The value of this option is expanded, and must then be the absolute path to a | |
15208 | file which contains the server's certificates. The server's private key is also | |
15209 | assumed to be in this file if tls_privatekey is unset. See chapter 41 for | |
15210 | further details. | |
15211 | ||
15212 | Note: The certificates defined by this option are used only when Exim is | |
15213 | receiving incoming messages as a server. If you want to supply certificates for | |
15214 | use when sending messages as a client, you must set the tls_certificate option | |
15215 | in the relevant smtp transport. | |
15216 | ||
15217 | If the option contains $tls_out_sni and Exim is built against OpenSSL, then if | |
15218 | the OpenSSL build supports TLS extensions and the TLS client sends the Server | |
15219 | Name Indication extension, then this option and others documented in 41.10 will | |
15220 | be re-expanded. | |
15221 | ||
15222 | +-------+---------+-------------+--------------+ | |
15223 | |tls_crl|Use: main|Type: string*|Default: unset| | |
15224 | +-------+---------+-------------+--------------+ | |
15225 | ||
15226 | This option specifies a certificate revocation list. The expanded value must be | |
15227 | the name of a file that contains a CRL in PEM format. | |
15228 | ||
15229 | See 41.10 for discussion of when this option might be re-expanded. | |
15230 | ||
15231 | +---------------+---------+-------------+-------------+ | |
15232 | |tls_dh_max_bits|Use: main|Type: integer|Default: 2236| | |
15233 | +---------------+---------+-------------+-------------+ | |
15234 | ||
15235 | The number of bits used for Diffie-Hellman key-exchange may be suggested by the | |
15236 | chosen TLS library. That value might prove to be too high for interoperability. | |
15237 | This option provides a maximum clamp on the value suggested, trading off | |
15238 | security for interoperability. | |
15239 | ||
15240 | The value must be at least 1024. | |
15241 | ||
15242 | The value 2236 was chosen because, at time of adding the option, it was the | |
15243 | hard-coded maximum value supported by the NSS cryptographic library, as used by | |
15244 | Thunderbird, while GnuTLS was suggesting 2432 bits as normal. | |
15245 | ||
15246 | If you prefer more security and are willing to break some clients, raise this | |
15247 | number. | |
15248 | ||
15249 | Note that the value passed to GnuTLS for *generating* a new prime may be a | |
15250 | little less than this figure, because GnuTLS is inexact and may produce a | |
15251 | larger prime than requested. | |
15252 | ||
15253 | +-----------+---------+-------------+--------------+ | |
15254 | |tls_dhparam|Use: main|Type: string*|Default: unset| | |
15255 | +-----------+---------+-------------+--------------+ | |
15256 | ||
15257 | The value of this option is expanded and indicates the source of DH parameters | |
15258 | to be used by Exim. | |
15259 | ||
15260 | If it is a filename starting with a "/", then it names a file from which DH | |
15261 | parameters should be loaded. If the file exists, it should hold a PEM-encoded | |
15262 | PKCS#3 representation of the DH prime. If the file does not exist, for OpenSSL | |
15263 | it is an error. For GnuTLS, Exim will attempt to create the file and fill it | |
15264 | with a generated DH prime. For OpenSSL, if the DH bit-count from loading the | |
15265 | file is greater than tls_dh_max_bits then it will be ignored, and treated as | |
15266 | though the tls_dhparam were set to "none". | |
15267 | ||
15268 | If this option expands to the string "none", then no DH parameters will be | |
15269 | loaded by Exim. | |
15270 | ||
15271 | If this option expands to the string "historic" and Exim is using GnuTLS, then | |
15272 | Exim will attempt to load a file from inside the spool directory. If the file | |
15273 | does not exist, Exim will attempt to create it. See section 41.3 for further | |
15274 | details. | |
15275 | ||
15276 | If Exim is using OpenSSL and this option is empty or unset, then Exim will load | |
15277 | a default DH prime; the default is the 2048 bit prime described in section 2.2 | |
15278 | of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which in | |
15279 | IKE is assigned number 23. | |
15280 | ||
15281 | Otherwise, the option must expand to the name used by Exim for any of a number | |
15282 | of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses | |
15283 | "ike" followed by the number used by IKE, of "default" which corresponds to | |
15284 | "ike23". | |
15285 | ||
15286 | The available primes are: "ike1", "ike2", "ike5", "ike14", "ike15", "ike16", | |
15287 | "ike17", "ike18", "ike22", "ike23" (aka "default") and "ike24". | |
15288 | ||
15289 | Some of these will be too small to be accepted by clients. Some may be too | |
15290 | large to be accepted by clients. | |
15291 | ||
15292 | The TLS protocol does not negotiate an acceptable size for this; clients tend | |
15293 | to hard-drop connections if what is offered by the server is unacceptable, | |
15294 | whether too large or too small, and there's no provision for the client to tell | |
15295 | the server what these constraints are. Thus, as a server operator, you need to | |
15296 | make an educated guess as to what is most likely to work for your userbase. | |
15297 | ||
15298 | Some known size constraints suggest that a bit-size in the range 2048 to 2236 | |
15299 | is most likely to maximise interoperability. The upper bound comes from | |
15300 | applications using the Mozilla Network Security Services (NSS) library, which | |
15301 | used to set its "DH_MAX_P_BITS" upper-bound to 2236. This affects many mail | |
15302 | user agents (MUAs). The lower bound comes from Debian installs of Exim4 prior | |
15303 | to the 4.80 release, as Debian used to patch Exim to raise the minimum | |
15304 | acceptable bound from 1024 to 2048. | |
15305 | ||
15306 | +-------------+---------+-------------+--------------+ | |
15307 | |tls_ocsp_file|Use: main|Type: string*|Default: unset| | |
15308 | +-------------+---------+-------------+--------------+ | |
15309 | ||
15310 | This option must if set expand to the absolute path to a file which contains a | |
15311 | current status proof for the server's certificate, as obtained from the | |
15312 | Certificate Authority. | |
15313 | ||
15314 | +--------------------+---------+-----------------+--------------+ | |
15315 | |tls_on_connect_ports|Use: main|Type: string list|Default: unset| | |
15316 | +--------------------+---------+-----------------+--------------+ | |
15317 | ||
15318 | This option specifies a list of incoming SSMTP (aka SMTPS) ports that should | |
15319 | operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately | |
15320 | set up without waiting for the client to issue a STARTTLS command. For further | |
15321 | details, see section 13.4. | |
15322 | ||
15323 | +--------------+---------+-------------+--------------+ | |
15324 | |tls_privatekey|Use: main|Type: string*|Default: unset| | |
15325 | +--------------+---------+-------------+--------------+ | |
15326 | ||
15327 | The value of this option is expanded, and must then be the absolute path to a | |
15328 | file which contains the server's private key. If this option is unset, or if | |
15329 | the expansion is forced to fail, or the result is an empty string, the private | |
15330 | key is assumed to be in the same file as the server's certificates. See chapter | |
15331 | 41 for further details. | |
15332 | ||
15333 | See 41.10 for discussion of when this option might be re-expanded. | |
15334 | ||
15335 | +------------------+---------+-------------+--------------+ | |
15336 | |tls_remember_esmtp|Use: main|Type: boolean|Default: false| | |
15337 | +------------------+---------+-------------+--------------+ | |
15338 | ||
15339 | If this option is set true, Exim violates the RFCs by remembering that it is in | |
15340 | "esmtp" state after successfully negotiating a TLS session. This provides | |
15341 | support for broken clients that fail to send a new EHLO after starting a TLS | |
15342 | session. | |
15343 | ||
15344 | +-------------------+---------+-------------+--------------+ | |
15345 | |tls_require_ciphers|Use: main|Type: string*|Default: unset| | |
15346 | +-------------------+---------+-------------+--------------+ | |
15347 | ||
15348 | This option controls which ciphers can be used for incoming TLS connections. | |
15349 | The smtp transport has an option of the same name for controlling outgoing | |
15350 | connections. This option is expanded for each connection, so can be varied for | |
15351 | different clients if required. The value of this option must be a list of | |
15352 | permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control | |
15353 | in somewhat different ways. If GnuTLS is being used, the client controls the | |
15354 | preference order of the available ciphers. Details are given in sections 41.4 | |
15355 | and 41.5. | |
15356 | ||
15357 | +--------------------+---------+----------------+--------------+ | |
15358 | |tls_try_verify_hosts|Use: main|Type: host list*|Default: unset| | |
15359 | +--------------------+---------+----------------+--------------+ | |
15360 | ||
15361 | See tls_verify_hosts below. | |
15362 | ||
15363 | +-----------------------+---------+-------------+--------------+ | |
15364 | |tls_verify_certificates|Use: main|Type: string*|Default: unset| | |
15365 | +-----------------------+---------+-------------+--------------+ | |
15366 | ||
15367 | The value of this option is expanded, and must then be the absolute path to a | |
15368 | file containing permitted certificates for clients that match tls_verify_hosts | |
15369 | or tls_try_verify_hosts. Alternatively, if you are using OpenSSL, you can set | |
15370 | tls_verify_certificates to the name of a directory containing certificate | |
15371 | files. This does not work with GnuTLS; the option must be set to the name of a | |
15372 | single file if you are using GnuTLS. | |
15373 | ||
15374 | These certificates should be for the certificate authorities trusted, rather | |
15375 | than the public cert of individual clients. With both OpenSSL and GnuTLS, if | |
15376 | the value is a file then the certificates are sent by Exim as a server to | |
15377 | connecting clients, defining the list of accepted certificate authorities. Thus | |
15378 | the values defined should be considered public data. To avoid this, use OpenSSL | |
15379 | with a directory. | |
15380 | ||
15381 | See 41.10 for discussion of when this option might be re-expanded. | |
15382 | ||
15383 | A forced expansion failure or setting to an empty string is equivalent to being | |
15384 | unset. | |
15385 | ||
15386 | +----------------+---------+----------------+--------------+ | |
15387 | |tls_verify_hosts|Use: main|Type: host list*|Default: unset| | |
15388 | +----------------+---------+----------------+--------------+ | |
15389 | ||
15390 | This option, along with tls_try_verify_hosts, controls the checking of | |
15391 | certificates from clients. The expected certificates are defined by | |
15392 | tls_verify_certificates, which must be set. A configuration error occurs if | |
15393 | either tls_verify_hosts or tls_try_verify_hosts is set and | |
15394 | tls_verify_certificates is not set. | |
15395 | ||
15396 | Any client that matches tls_verify_hosts is constrained by | |
15397 | tls_verify_certificates. When the client initiates a TLS session, it must | |
15398 | present one of the listed certificates. If it does not, the connection is | |
15399 | aborted. Warning: Including a host in tls_verify_hosts does not require the | |
15400 | host to use TLS. It can still send SMTP commands through unencrypted | |
15401 | connections. Forcing a client to use TLS has to be done separately using an ACL | |
15402 | to reject inappropriate commands when the connection is not encrypted. | |
15403 | ||
15404 | A weaker form of checking is provided by tls_try_verify_hosts. If a client | |
15405 | matches this option (but not tls_verify_hosts), Exim requests a certificate and | |
15406 | checks it against tls_verify_certificates, but does not abort the connection if | |
15407 | there is no certificate or if it does not match. This state can be detected in | |
15408 | an ACL, which makes it possible to implement policies such as "accept for relay | |
15409 | only if a verified certificate has been received, but accept for local delivery | |
15410 | if encrypted, even without a verified certificate". | |
15411 | ||
15412 | Client hosts that match neither of these lists are not asked to present | |
15413 | certificates. | |
15414 | ||
15415 | +--------------+---------+------------------+--------------+ | |
15416 | |trusted_groups|Use: main|Type: string list*|Default: unset| | |
15417 | +--------------+---------+------------------+--------------+ | |
15418 | ||
15419 | This option is expanded just once, at the start of Exim's processing. If this | |
15420 | option is set, any process that is running in one of the listed groups, or | |
15421 | which has one of them as a supplementary group, is trusted. The groups can be | |
15422 | specified numerically or by name. See section 5.2 for details of what trusted | |
15423 | callers are permitted to do. If neither trusted_groups nor trusted_users is | |
15424 | set, only root and the Exim user are trusted. | |
15425 | ||
15426 | +-------------+---------+------------------+--------------+ | |
15427 | |trusted_users|Use: main|Type: string list*|Default: unset| | |
15428 | +-------------+---------+------------------+--------------+ | |
15429 | ||
15430 | This option is expanded just once, at the start of Exim's processing. If this | |
15431 | option is set, any process that is running as one of the listed users is | |
15432 | trusted. The users can be specified numerically or by name. See section 5.2 for | |
15433 | details of what trusted callers are permitted to do. If neither trusted_groups | |
15434 | nor trusted_users is set, only root and the Exim user are trusted. | |
15435 | ||
15436 | +-------------+---------+-------------+--------------+ | |
15437 | |unknown_login|Use: main|Type: string*|Default: unset| | |
15438 | +-------------+---------+-------------+--------------+ | |
15439 | ||
15440 | This is a specialized feature for use in unusual configurations. By default, if | |
15441 | the uid of the caller of Exim cannot be looked up using getpwuid(), Exim gives | |
15442 | up. The unknown_login option can be used to set a login name to be used in this | |
15443 | circumstance. It is expanded, so values like user$caller_uid can be set. When | |
15444 | unknown_login is used, the value of unknown_username is used for the user's | |
15445 | real name (gecos field), unless this has been set by the -F option. | |
15446 | ||
15447 | +----------------+---------+------------+--------------+ | |
15448 | |unknown_username|Use: main|Type: string|Default: unset| | |
15449 | +----------------+---------+------------+--------------+ | |
15450 | ||
15451 | See unknown_login. | |
15452 | ||
15453 | +--------------------+---------+-------------------+--------------+ | |
15454 | |untrusted_set_sender|Use: main|Type: address list*|Default: unset| | |
15455 | +--------------------+---------+-------------------+--------------+ | |
15456 | ||
15457 | When an untrusted user submits a message to Exim using the standard input, Exim | |
15458 | normally creates an envelope sender address from the user's login and the | |
15459 | default qualification domain. Data from the -f option (for setting envelope | |
15460 | senders on non-SMTP messages) or the SMTP MAIL command (if -bs or -bS is used) | |
15461 | is ignored. | |
15462 | ||
15463 | However, untrusted users are permitted to set an empty envelope sender address, | |
15464 | to declare that a message should never generate any bounces. For example: | |
15465 | ||
15466 | exim -f '<>' user@domain.example | |
15467 | ||
15468 | The untrusted_set_sender option allows you to permit untrusted users to set | |
15469 | other envelope sender addresses in a controlled way. When it is set, untrusted | |
15470 | users are allowed to set envelope sender addresses that match any of the | |
15471 | patterns in the list. Like all address lists, the string is expanded. The | |
15472 | identity of the user is in $sender_ident, so you can, for example, restrict | |
15473 | users to setting senders that start with their login ids followed by a hyphen | |
15474 | by a setting like this: | |
15475 | ||
15476 | untrusted_set_sender = ^$sender_ident- | |
15477 | ||
15478 | If you want to allow untrusted users to set envelope sender addresses without | |
15479 | restriction, you can use | |
15480 | ||
15481 | untrusted_set_sender = * | |
15482 | ||
15483 | The untrusted_set_sender option applies to all forms of local input, but only | |
15484 | to the setting of the envelope sender. It does not permit untrusted users to | |
15485 | use the other options which trusted user can use to override message | |
15486 | parameters. Furthermore, it does not stop Exim from removing an existing | |
15487 | Sender: header in the message, or from adding a Sender: header if necessary. | |
15488 | See local_sender_retain and local_from_check for ways of overriding these | |
15489 | actions. The handling of the Sender: header is also described in section 46.16. | |
15490 | ||
15491 | The log line for a message's arrival shows the envelope sender following "<=". | |
15492 | For local messages, the user's login always follows, after "U=". In -bp | |
15493 | displays, and in the Exim monitor, if an untrusted user sets an envelope sender | |
15494 | address, the user's login is shown in parentheses after the sender address. | |
15495 | ||
15496 | +-----------------+---------+------------+------------------+ | |
15497 | |uucp_from_pattern|Use: main|Type: string|Default: see below| | |
15498 | +-----------------+---------+------------+------------------+ | |
15499 | ||
15500 | Some applications that pass messages to an MTA via a command line interface use | |
15501 | an initial line starting with "From " to pass the envelope sender. In | |
15502 | particular, this is used by UUCP software. Exim recognizes such a line by means | |
15503 | of a regular expression that is set in uucp_from_pattern. When the pattern | |
15504 | matches, the sender address is constructed by expanding the contents of | |
15505 | uucp_from_sender, provided that the caller of Exim is a trusted user. The | |
15506 | default pattern recognizes lines in the following two forms: | |
15507 | ||
15508 | From ph10 Fri Jan 5 12:35 GMT 1996 | |
15509 | From ph10 Fri, 7 Jan 97 14:00:00 GMT | |
15510 | ||
15511 | The pattern can be seen by running | |
15512 | ||
15513 | exim -bP uucp_from_pattern | |
15514 | ||
15515 | It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit | |
15516 | year in the second case. The first word after "From " is matched in the regular | |
15517 | expression by a parenthesized subpattern. The default value for | |
15518 | uucp_from_sender is "$1", which therefore just uses this first word ("ph10" in | |
15519 | the example above) as the message's sender. See also ignore_fromline_hosts. | |
15520 | ||
15521 | +----------------+---------+-------------+-------------+ | |
15522 | |uucp_from_sender|Use: main|Type: string*|Default: "$1"| | |
15523 | +----------------+---------+-------------+-------------+ | |
15524 | ||
15525 | See uucp_from_pattern above. | |
15526 | ||
15527 | +-----------------+---------+------------+--------------+ | |
15528 | |warn_message_file|Use: main|Type: string|Default: unset| | |
15529 | +-----------------+---------+------------+--------------+ | |
15530 | ||
15531 | This option defines a template file containing paragraphs of text to be used | |
15532 | for constructing the warning message which is sent by Exim when a message has | |
15533 | been on the queue for a specified amount of time, as specified by delay_warning | |
15534 | . Details of the file's contents are given in chapter 48. See also | |
15535 | bounce_message_file. | |
15536 | ||
15537 | +---------------+---------+-------------+-------------+ | |
15538 | |write_rejectlog|Use: main|Type: boolean|Default: true| | |
15539 | +---------------+---------+-------------+-------------+ | |
15540 | ||
15541 | If this option is set false, Exim no longer writes anything to the reject log. | |
15542 | See chapter 51 for details of what Exim writes to its logs. | |
15543 | ||
15544 | ||
15545 | ||
15546 | =============================================================================== | |
15547 | 15. GENERIC OPTIONS FOR ROUTERS | |
15548 | ||
15549 | This chapter describes the generic options that apply to all routers. Those | |
15550 | that are preconditions are marked with ** in the "use" field. | |
15551 | ||
15552 | For a general description of how a router operates, see sections 3.10 and 3.12. | |
15553 | The latter specifies the order in which the preconditions are tested. The order | |
15554 | of expansion of the options that provide data for a transport is: errors_to, | |
15555 | headers_add, headers_remove, transport. | |
15556 | ||
15557 | +------------+------------+-------------+--------------+ | |
15558 | |address_data|Use: routers|Type: string*|Default: unset| | |
15559 | +------------+------------+-------------+--------------+ | |
15560 | ||
15561 | The string is expanded just before the router is run, that is, after all the | |
15562 | precondition tests have succeeded. If the expansion is forced to fail, the | |
15563 | router declines, the value of address_data remains unchanged, and the more | |
15564 | option controls what happens next. Other expansion failures cause delivery of | |
15565 | the address to be deferred. | |
15566 | ||
15567 | When the expansion succeeds, the value is retained with the address, and can be | |
15568 | accessed using the variable $address_data in the current router, subsequent | |
15569 | routers, and the eventual transport. | |
15570 | ||
15571 | Warning: If the current or any subsequent router is a redirect router that runs | |
15572 | a user's filter file, the contents of $address_data are accessible in the | |
15573 | filter. This is not normally a problem, because such data is usually either not | |
15574 | confidential or it "belongs" to the current user, but if you do put | |
15575 | confidential data into $address_data you need to remember this point. | |
15576 | ||
15577 | Even if the router declines or passes, the value of $address_data remains with | |
15578 | the address, though it can be changed by another address_data setting on a | |
15579 | subsequent router. If a router generates child addresses, the value of | |
15580 | $address_data propagates to them. This also applies to the special kind of | |
15581 | "child" that is generated by a router with the unseen option. | |
15582 | ||
15583 | The idea of address_data is that you can use it to look up a lot of data for | |
15584 | the address once, and then pick out parts of the data later. For example, you | |
15585 | could use a single LDAP lookup to return a string of the form | |
15586 | ||
15587 | uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward | |
15588 | ||
15589 | In the transport you could pick out the mailbox by a setting such as | |
15590 | ||
15591 | file = ${extract{mailbox}{$address_data}} | |
15592 | ||
15593 | This makes the configuration file less messy, and also reduces the number of | |
15594 | lookups (though Exim does cache lookups). | |
15595 | ||
15596 | The address_data facility is also useful as a means of passing information from | |
15597 | one router to another, and from a router to a transport. In addition, if | |
15598 | $address_data is set by a router when verifying a recipient address from an | |
15599 | ACL, it remains available for use in the rest of the ACL statement. After | |
15600 | verifying a sender, the value is transferred to $sender_address_data. | |
15601 | ||
15602 | +------------+--------------+-------------+-------------+ | |
15603 | |address_test|Use: routers**|Type: boolean|Default: true| | |
15604 | +------------+--------------+-------------+-------------+ | |
15605 | ||
15606 | If this option is set false, the router is skipped when routing is being tested | |
15607 | by means of the -bt command line option. This can be a convenience when your | |
15608 | first router sends messages to an external scanner, because it saves you having | |
15609 | to set the "already scanned" indicator when testing real address routing. | |
15610 | ||
15611 | +--------------------+------------+-------------+--------------+ | |
15612 | |cannot_route_message|Use: routers|Type: string*|Default: unset| | |
15613 | +--------------------+------------+-------------+--------------+ | |
15614 | ||
15615 | This option specifies a text message that is used when an address cannot be | |
15616 | routed because Exim has run out of routers. The default message is "Unrouteable | |
15617 | address". This option is useful only on routers that have more set false, or on | |
15618 | the very last router in a configuration, because the value that is used is | |
15619 | taken from the last router that is considered. This includes a router that is | |
15620 | skipped because its preconditions are not met, as well as a router that | |
15621 | declines. For example, using the default configuration, you could put: | |
15622 | ||
15623 | cannot_route_message = Remote domain not found in DNS | |
15624 | ||
15625 | on the first router, which is a dnslookup router with more set false, and | |
15626 | ||
15627 | cannot_route_message = Unknown local user | |
15628 | ||
15629 | on the final router that checks for local users. If string expansion fails for | |
15630 | this option, the default message is used. Unless the expansion failure was | |
15631 | explicitly forced, a message about the failure is written to the main and panic | |
15632 | logs, in addition to the normal message about the routing failure. | |
15633 | ||
15634 | +------------------+------------+-------------+--------------+ | |
15635 | |caseful_local_part|Use: routers|Type: boolean|Default: false| | |
15636 | +------------------+------------+-------------+--------------+ | |
15637 | ||
15638 | By default, routers handle the local parts of addresses in a case-insensitive | |
15639 | manner, though the actual case is preserved for transmission with the message. | |
15640 | If you want the case of letters to be significant in a router, you must set | |
15641 | this option true. For individual router options that contain address or local | |
15642 | part lists (for example, local_parts), case-sensitive matching can be turned on | |
15643 | by "+caseful" as a list item. See section 10.20 for more details. | |
15644 | ||
15645 | The value of the $local_part variable is forced to lower case while a router is | |
15646 | running unless caseful_local_part is set. When a router assigns an address to a | |
15647 | transport, the value of $local_part when the transport runs is the same as it | |
15648 | was in the router. Similarly, when a router generates child addresses by | |
15649 | aliasing or forwarding, the values of $original_local_part and | |
15650 | $parent_local_part are those that were used by the redirecting router. | |
15651 | ||
15652 | This option applies to the processing of an address by a router. When a | |
15653 | recipient address is being processed in an ACL, there is a separate control | |
15654 | modifier that can be used to specify case-sensitive processing within the ACL | |
15655 | (see section 42.22). | |
15656 | ||
15657 | +----------------+--------------+-------------+--------------+ | |
15658 | |check_local_user|Use: routers**|Type: boolean|Default: false| | |
15659 | +----------------+--------------+-------------+--------------+ | |
15660 | ||
15661 | When this option is true, Exim checks that the local part of the recipient | |
15662 | address (with affixes removed if relevant) is the name of an account on the | |
15663 | local system. The check is done by calling the getpwnam() function rather than | |
15664 | trying to read /etc/passwd directly. This means that other methods of holding | |
15665 | password data (such as NIS) are supported. If the local part is a local user, | |
15666 | $home is set from the password data, and can be tested in other preconditions | |
15667 | that are evaluated after this one (the order of evaluation is given in section | |
15668 | 3.12). However, the value of $home can be overridden by router_home_directory. | |
15669 | If the local part is not a local user, the router is skipped. | |
15670 | ||
15671 | If you want to check that the local part is either the name of a local user or | |
15672 | matches something else, you cannot combine check_local_user with a setting of | |
15673 | local_parts, because that specifies the logical and of the two conditions. | |
15674 | However, you can use a passwd lookup in a local_parts setting to achieve this. | |
15675 | For example: | |
15676 | ||
15677 | local_parts = passwd;$local_part : lsearch;/etc/other/users | |
15678 | ||
15679 | Note, however, that the side effects of check_local_user (such as setting up a | |
15680 | home directory) do not occur when a passwd lookup is used in a local_parts (or | |
15681 | any other) precondition. | |
15682 | ||
15683 | +---------+--------------+-------------+--------------+ | |
15684 | |condition|Use: routers**|Type: string*|Default: unset| | |
15685 | +---------+--------------+-------------+--------------+ | |
15686 | ||
15687 | This option specifies a general precondition test that has to succeed for the | |
15688 | router to be called. The condition option is the last precondition to be | |
15689 | evaluated (see section 3.12). The string is expanded, and if the result is a | |
15690 | forced failure, or an empty string, or one of the strings "0" or "no" or | |
15691 | "false" (checked without regard to the case of the letters), the router is | |
15692 | skipped, and the address is offered to the next one. | |
15693 | ||
15694 | If the result is any other value, the router is run (as this is the last | |
15695 | precondition to be evaluated, all the other preconditions must be true). | |
15696 | ||
15697 | This option is unusual in that multiple condition options may be present. All | |
15698 | condition options must succeed. | |
15699 | ||
15700 | The condition option provides a means of applying custom conditions to the | |
15701 | running of routers. Note that in the case of a simple conditional expansion, | |
15702 | the default expansion values are exactly what is wanted. For example: | |
15703 | ||
15704 | condition = ${if >{$message_age}{600}} | |
15705 | ||
15706 | Because of the default behaviour of the string expansion, this is equivalent to | |
15707 | ||
15708 | condition = ${if >{$message_age}{600}{true}{}} | |
15709 | ||
15710 | A multiple condition example, which succeeds: | |
15711 | ||
15712 | condition = ${if >{$message_age}{600}} | |
15713 | condition = ${if !eq{${lc:$local_part}}{postmaster}} | |
15714 | condition = foobar | |
15715 | ||
15716 | If the expansion fails (other than forced failure) delivery is deferred. Some | |
15717 | of the other precondition options are common special cases that could in fact | |
15718 | be specified using condition. | |
15719 | ||
15720 | +-----------+------------+-------------+--------------+ | |
15721 | |debug_print|Use: routers|Type: string*|Default: unset| | |
15722 | +-----------+------------+-------------+--------------+ | |
15723 | ||
15724 | If this option is set and debugging is enabled (see the -d command line option) | |
15725 | or in address-testing mode (see the -bt command line option), the string is | |
15726 | expanded and included in the debugging output. If expansion of the string | |
15727 | fails, the error message is written to the debugging output, and Exim carries | |
15728 | on processing. This option is provided to help with checking out the values of | |
15729 | variables and so on when debugging router configurations. For example, if a | |
15730 | condition option appears not to be working, debug_print can be used to output | |
15731 | the variables it references. The output happens after checks for domains, | |
15732 | local_parts, and check_local_user but before any other preconditions are | |
15733 | tested. A newline is added to the text if it does not end with one. The | |
15734 | variable $router_name contains the name of the router. | |
15735 | ||
15736 | +---------------+------------+-------------+--------------+ | |
15737 | |disable_logging|Use: routers|Type: boolean|Default: false| | |
15738 | +---------------+------------+-------------+--------------+ | |
15739 | ||
15740 | If this option is set true, nothing is logged for any routing errors or for any | |
15741 | deliveries caused by this router. You should not set this option unless you | |
15742 | really, really know what you are doing. See also the generic transport option | |
15743 | of the same name. | |
15744 | ||
15745 | +-------+--------------+------------------+--------------+ | |
15746 | |domains|Use: routers**|Type: domain list*|Default: unset| | |
15747 | +-------+--------------+------------------+--------------+ | |
15748 | ||
15749 | If this option is set, the router is skipped unless the current domain matches | |
15750 | the list. If the match is achieved by means of a file lookup, the data that the | |
15751 | lookup returned for the domain is placed in $domain_data for use in string | |
15752 | expansions of the driver's private options. See section 3.12 for a list of the | |
15753 | order in which preconditions are evaluated. | |
15754 | ||
15755 | +------+------------+------------+--------------+ | |
15756 | |driver|Use: routers|Type: string|Default: unset| | |
15757 | +------+------------+------------+--------------+ | |
15758 | ||
15759 | This option must always be set. It specifies which of the available routers is | |
15760 | to be used. | |
15761 | ||
15762 | +---------+------------+-------------+--------------+ | |
15763 | |errors_to|Use: routers|Type: string*|Default: unset| | |
15764 | +---------+------------+-------------+--------------+ | |
15765 | ||
15766 | If a router successfully handles an address, it may assign the address to a | |
15767 | transport for delivery or it may generate child addresses. In both cases, if | |
15768 | there is a delivery problem during later processing, the resulting bounce | |
15769 | message is sent to the address that results from expanding this string, | |
15770 | provided that the address verifies successfully. The errors_to option is | |
15771 | expanded before headers_add, headers_remove, and transport. | |
15772 | ||
15773 | The errors_to setting associated with an address can be overridden if it | |
15774 | subsequently passes through other routers that have their own errors_to | |
15775 | settings, or if the message is delivered by a transport with a return_path | |
15776 | setting. | |
15777 | ||
15778 | If errors_to is unset, or the expansion is forced to fail, or the result of the | |
15779 | expansion fails to verify, the errors address associated with the incoming | |
15780 | address is used. At top level, this is the envelope sender. A non-forced | |
15781 | expansion failure causes delivery to be deferred. | |
15782 | ||
15783 | If an address for which errors_to has been set ends up being delivered over | |
15784 | SMTP, the envelope sender for that delivery is the errors_to value, so that any | |
15785 | bounces that are generated by other MTAs on the delivery route are also sent | |
15786 | there. You can set errors_to to the empty string by either of these settings: | |
15787 | ||
15788 | errors_to = | |
15789 | errors_to = "" | |
15790 | ||
15791 | An expansion item that yields an empty string has the same effect. If you do | |
15792 | this, a locally detected delivery error for addresses processed by this router | |
15793 | no longer gives rise to a bounce message; the error is discarded. If the | |
15794 | address is delivered to a remote host, the return path is set to "<>", unless | |
15795 | overridden by the return_path option on the transport. | |
15796 | ||
15797 | If for some reason you want to discard local errors, but use a non-empty MAIL | |
15798 | command for remote delivery, you can preserve the original return path in | |
15799 | $address_data in the router, and reinstate it in the transport by setting | |
15800 | return_path. | |
15801 | ||
15802 | The most common use of errors_to is to direct mailing list bounces to the | |
15803 | manager of the list, as described in section 49.2, or to implement VERP | |
15804 | (Variable Envelope Return Paths) (see section 49.6). | |
15805 | ||
15806 | +----+--------------+-------------+-------------+ | |
15807 | |expn|Use: routers**|Type: boolean|Default: true| | |
15808 | +----+--------------+-------------+-------------+ | |
15809 | ||
15810 | If this option is turned off, the router is skipped when testing an address as | |
15811 | a result of processing an SMTP EXPN command. You might, for example, want to | |
15812 | turn it off on a router for users' .forward files, while leaving it on for the | |
15813 | system alias file. See section 3.12 for a list of the order in which | |
15814 | preconditions are evaluated. | |
15815 | ||
15816 | The use of the SMTP EXPN command is controlled by an ACL (see chapter 42). When | |
15817 | Exim is running an EXPN command, it is similar to testing an address with -bt. | |
15818 | Compare VRFY, whose counterpart is -bv. | |
15819 | ||
15820 | +-----------+------------+-------------+--------------+ | |
15821 | |fail_verify|Use: routers|Type: boolean|Default: false| | |
15822 | +-----------+------------+-------------+--------------+ | |
15823 | ||
15824 | Setting this option has the effect of setting both fail_verify_sender and | |
15825 | fail_verify_recipient to the same value. | |
15826 | ||
15827 | +---------------------+------------+-------------+--------------+ | |
15828 | |fail_verify_recipient|Use: routers|Type: boolean|Default: false| | |
15829 | +---------------------+------------+-------------+--------------+ | |
15830 | ||
15831 | If this option is true and an address is accepted by this router when verifying | |
15832 | a recipient, verification fails. | |
15833 | ||
15834 | +------------------+------------+-------------+--------------+ | |
15835 | |fail_verify_sender|Use: routers|Type: boolean|Default: false| | |
15836 | +------------------+------------+-------------+--------------+ | |
15837 | ||
15838 | If this option is true and an address is accepted by this router when verifying | |
15839 | a sender, verification fails. | |
15840 | ||
15841 | +--------------+------------+-----------------+--------------+ | |
15842 | |fallback_hosts|Use: routers|Type: string list|Default: unset| | |
15843 | +--------------+------------+-----------------+--------------+ | |
15844 | ||
15845 | String expansion is not applied to this option. The argument must be a | |
15846 | colon-separated list of host names or IP addresses. The list separator can be | |
15847 | changed (see section 6.19), and a port can be specified with each name or | |
15848 | address. In fact, the format of each item is exactly the same as defined for | |
15849 | the list of hosts in a manualroute router (see section 20.5). | |
15850 | ||
15851 | If a router queues an address for a remote transport, this host list is | |
15852 | associated with the address, and used instead of the transport's fallback host | |
15853 | list. If hosts_randomize is set on the transport, the order of the list is | |
15854 | randomized for each use. See the fallback_hosts option of the smtp transport | |
15855 | for further details. | |
15856 | ||
15857 | +-----+------------+-------------+------------------+ | |
15858 | |group|Use: routers|Type: string*|Default: see below| | |
15859 | +-----+------------+-------------+------------------+ | |
15860 | ||
15861 | When a router queues an address for a transport, and the transport does not | |
15862 | specify a group, the group given here is used when running the delivery | |
15863 | process. The group may be specified numerically or by name. If expansion fails, | |
15864 | the error is logged and delivery is deferred. The default is unset, unless | |
15865 | check_local_user is set, when the default is taken from the password | |
15866 | information. See also initgroups and user and the discussion in chapter 23. | |
15867 | ||
15868 | +-----------+------------+-----------+--------------+ | |
15869 | |headers_add|Use: routers|Type: list*|Default: unset| | |
15870 | +-----------+------------+-----------+--------------+ | |
15871 | ||
15872 | This option specifies a list of text headers, newline-separated, that is | |
15873 | associated with any addresses that are accepted by the router. Each item is | |
15874 | separately expanded, at routing time. However, this option has no effect when | |
15875 | an address is just being verified. The way in which the text is used to add | |
15876 | header lines at transport time is described in section 46.17. New header lines | |
15877 | are not actually added until the message is in the process of being | |
15878 | transported. This means that references to header lines in string expansions in | |
15879 | the transport's configuration do not "see" the added header lines. | |
15880 | ||
15881 | The headers_add option is expanded after errors_to, but before headers_remove | |
15882 | and transport. If an item is empty, or if an item expansion is forced to fail, | |
15883 | the item has no effect. Other expansion failures are treated as configuration | |
15884 | errors. | |
15885 | ||
15886 | Unlike most options, headers_add can be specified multiple times for a router; | |
15887 | all listed headers are added. | |
15888 | ||
15889 | Warning 1: The headers_add option cannot be used for a redirect router that has | |
15890 | the one_time option set. | |
15891 | ||
15892 | Warning 2: If the unseen option is set on the router, all header additions are | |
15893 | deleted when the address is passed on to subsequent routers. For a redirect | |
15894 | router, if a generated address is the same as the incoming address, this can | |
15895 | lead to duplicate addresses with different header modifications. Exim does not | |
15896 | do duplicate deliveries (except, in certain circumstances, to pipes -- see | |
15897 | section 22.7), but it is undefined which of the duplicates is discarded, so | |
15898 | this ambiguous situation should be avoided. The repeat_use option of the | |
15899 | redirect router may be of help. | |
15900 | ||
15901 | +--------------+------------+-----------+--------------+ | |
15902 | |headers_remove|Use: routers|Type: list*|Default: unset| | |
15903 | +--------------+------------+-----------+--------------+ | |
15904 | ||
15905 | This option specifies a list of text headers, colon-separated, that is | |
15906 | associated with any addresses that are accepted by the router. Each item is | |
15907 | separately expanded, at routing time. However, this option has no effect when | |
15908 | an address is just being verified. The way in which the text is used to remove | |
15909 | header lines at transport time is described in section 46.17. Header lines are | |
15910 | not actually removed until the message is in the process of being transported. | |
15911 | This means that references to header lines in string expansions in the | |
15912 | transport's configuration still "see" the original header lines. | |
15913 | ||
15914 | The headers_remove option is expanded after errors_to and headers_add, but | |
15915 | before transport. If an item expansion is forced to fail, the item has no | |
15916 | effect. Other expansion failures are treated as configuration errors. | |
15917 | ||
15918 | Unlike most options, headers_remove can be specified multiple times for a | |
15919 | router; all listed headers are removed. | |
15920 | ||
15921 | Warning 1: The headers_remove option cannot be used for a redirect router that | |
15922 | has the one_time option set. | |
15923 | ||
15924 | Warning 2: If the unseen option is set on the router, all header removal | |
15925 | requests are deleted when the address is passed on to subsequent routers, and | |
15926 | this can lead to problems with duplicates -- see the similar warning for | |
15927 | headers_add above. | |
15928 | ||
15929 | +-------------------+------------+----------------+--------------+ | |
15930 | |ignore_target_hosts|Use: routers|Type: host list*|Default: unset| | |
15931 | +-------------------+------------+----------------+--------------+ | |
15932 | ||
15933 | Although this option is a host list, it should normally contain IP address | |
15934 | entries rather than names. If any host that is looked up by the router has an | |
15935 | IP address that matches an item in this list, Exim behaves as if that IP | |
15936 | address did not exist. This option allows you to cope with rogue DNS entries | |
15937 | like | |
15938 | ||
15939 | remote.domain.example. A 127.0.0.1 | |
15940 | ||
15941 | by setting | |
15942 | ||
15943 | ignore_target_hosts = 127.0.0.1 | |
15944 | ||
15945 | on the relevant router. If all the hosts found by a dnslookup router are | |
15946 | discarded in this way, the router declines. In a conventional configuration, an | |
15947 | attempt to mail to such a domain would normally provoke the "unrouteable | |
15948 | domain" error, and an attempt to verify an address in the domain would fail. | |
15949 | Similarly, if ignore_target_hosts is set on an ipliteral router, the router | |
15950 | declines if presented with one of the listed addresses. | |
15951 | ||
15952 | You can use this option to disable the use of IPv4 or IPv6 for mail delivery by | |
15953 | means of the first or the second of the following settings, respectively: | |
15954 | ||
15955 | ignore_target_hosts = 0.0.0.0/0 | |
15956 | ignore_target_hosts = <; 0::0/0 | |
15957 | ||
15958 | The pattern in the first line matches all IPv4 addresses, whereas the pattern | |
15959 | in the second line matches all IPv6 addresses. | |
15960 | ||
15961 | This option may also be useful for ignoring link-local and site-local IPv6 | |
15962 | addresses. Because, like all host lists, the value of ignore_target_hosts is | |
15963 | expanded before use as a list, it is possible to make it dependent on the | |
15964 | domain that is being routed. | |
15965 | ||
15966 | During its expansion, $host_address is set to the IP address that is being | |
15967 | checked. | |
15968 | ||
15969 | +----------+------------+-------------+--------------+ | |
15970 | |initgroups|Use: routers|Type: boolean|Default: false| | |
15971 | +----------+------------+-------------+--------------+ | |
15972 | ||
15973 | If the router queues an address for a transport, and this option is true, and | |
15974 | the uid supplied by the router is not overridden by the transport, the | |
15975 | initgroups() function is called when running the transport to ensure that any | |
15976 | additional groups associated with the uid are set up. See also group and user | |
15977 | and the discussion in chapter 23. | |
15978 | ||
15979 | +-----------------+--------------+-----------------+--------------+ | |
15980 | |local_part_prefix|Use: routers**|Type: string list|Default: unset| | |
15981 | +-----------------+--------------+-----------------+--------------+ | |
15982 | ||
15983 | If this option is set, the router is skipped unless the local part starts with | |
15984 | one of the given strings, or local_part_prefix_optional is true. See section | |
15985 | 3.12 for a list of the order in which preconditions are evaluated. | |
15986 | ||
15987 | The list is scanned from left to right, and the first prefix that matches is | |
15988 | used. A limited form of wildcard is available; if the prefix begins with an | |
15989 | asterisk, it matches the longest possible sequence of arbitrary characters at | |
15990 | the start of the local part. An asterisk should therefore always be followed by | |
15991 | some character that does not occur in normal local parts. Wildcarding can be | |
15992 | used to set up multiple user mailboxes, as described in section 49.8. | |
15993 | ||
15994 | During the testing of the local_parts option, and while the router is running, | |
15995 | the prefix is removed from the local part, and is available in the expansion | |
15996 | variable $local_part_prefix. When a message is being delivered, if the router | |
15997 | accepts the address, this remains true during subsequent delivery by a | |
15998 | transport. In particular, the local part that is transmitted in the RCPT | |
15999 | command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default. | |
16000 | This behaviour can be overridden by setting rcpt_include_affixes true on the | |
16001 | relevant transport. | |
16002 | ||
16003 | When an address is being verified, local_part_prefix affects only the behaviour | |
16004 | of the router. If the callout feature of verification is in use, this means | |
16005 | that the full address, including the prefix, will be used during the callout. | |
16006 | ||
16007 | The prefix facility is commonly used to handle local parts of the form | |
16008 | owner-something. Another common use is to support local parts of the form | |
16009 | real-username to bypass a user's .forward file - helpful when trying to tell a | |
16010 | user their forwarding is broken - by placing a router like this one immediately | |
16011 | before the router that handles .forward files: | |
16012 | ||
16013 | real_localuser: | |
16014 | driver = accept | |
16015 | local_part_prefix = real- | |
16016 | check_local_user | |
16017 | transport = local_delivery | |
16018 | ||
16019 | For security, it would probably be a good idea to restrict the use of this | |
16020 | router to locally-generated messages, using a condition such as this: | |
16021 | ||
16022 | condition = ${if match {$sender_host_address}\ | |
16023 | {\N^(|127\.0\.0\.1)$\N}} | |
16024 | ||
16025 | If both local_part_prefix and local_part_suffix are set for a router, both | |
16026 | conditions must be met if not optional. Care must be taken if wildcards are | |
16027 | used in both a prefix and a suffix on the same router. Different separator | |
16028 | characters must be used to avoid ambiguity. | |
16029 | ||
16030 | +--------------------------+------------+-------------+--------------+ | |
16031 | |local_part_prefix_optional|Use: routers|Type: boolean|Default: false| | |
16032 | +--------------------------+------------+-------------+--------------+ | |
16033 | ||
16034 | See local_part_prefix above. | |
16035 | ||
16036 | +-----------------+--------------+-----------------+--------------+ | |
16037 | |local_part_suffix|Use: routers**|Type: string list|Default: unset| | |
16038 | +-----------------+--------------+-----------------+--------------+ | |
16039 | ||
16040 | This option operates in the same way as local_part_prefix, except that the | |
16041 | local part must end (rather than start) with the given string, the | |
16042 | local_part_suffix_optional option determines whether the suffix is mandatory, | |
16043 | and the wildcard * character, if present, must be the last character of the | |
16044 | suffix. This option facility is commonly used to handle local parts of the form | |
16045 | something-request and multiple user mailboxes of the form username-foo. | |
16046 | ||
16047 | +--------------------------+------------+-------------+--------------+ | |
16048 | |local_part_suffix_optional|Use: routers|Type: boolean|Default: false| | |
16049 | +--------------------------+------------+-------------+--------------+ | |
16050 | ||
16051 | See local_part_suffix above. | |
16052 | ||
16053 | +-----------+--------------+----------------------+--------------+ | |
16054 | |local_parts|Use: routers**|Type: local part list*|Default: unset| | |
16055 | +-----------+--------------+----------------------+--------------+ | |
16056 | ||
16057 | The router is run only if the local part of the address matches the list. See | |
16058 | section 3.12 for a list of the order in which preconditions are evaluated, and | |
16059 | section 10.21 for a discussion of local part lists. Because the string is | |
16060 | expanded, it is possible to make it depend on the domain, for example: | |
16061 | ||
16062 | local_parts = dbm;/usr/local/specials/$domain | |
16063 | ||
16064 | If the match is achieved by a lookup, the data that the lookup returned for the | |
16065 | local part is placed in the variable $local_part_data for use in expansions of | |
16066 | the router's private options. You might use this option, for example, if you | |
16067 | have a large number of local virtual domains, and you want to send all | |
16068 | postmaster mail to the same place without having to set up an alias in each | |
16069 | virtual domain: | |
16070 | ||
16071 | postmaster: | |
16072 | driver = redirect | |
16073 | local_parts = postmaster | |
16074 | data = postmaster@real.domain.example | |
16075 | ||
16076 | +------------+------------+-------------+------------------+ | |
16077 | |log_as_local|Use: routers|Type: boolean|Default: see below| | |
16078 | +------------+------------+-------------+------------------+ | |
16079 | ||
16080 | Exim has two logging styles for delivery, the idea being to make local | |
16081 | deliveries stand out more visibly from remote ones. In the "local" style, the | |
16082 | recipient address is given just as the local part, without a domain. The use of | |
16083 | this style is controlled by this option. It defaults to true for the accept | |
16084 | router, and false for all the others. This option applies only when a router | |
16085 | assigns an address to a transport. It has no effect on routers that redirect | |
16086 | addresses. | |
16087 | ||
16088 | +----+------------+--------------+-------------+ | |
16089 | |more|Use: routers|Type: boolean*|Default: true| | |
16090 | +----+------------+--------------+-------------+ | |
16091 | ||
16092 | The result of string expansion for this option must be a valid boolean value, | |
16093 | that is, one of the strings "yes", "no", "true", or "false". Any other result | |
16094 | causes an error, and delivery is deferred. If the expansion is forced to fail, | |
16095 | the default value for the option (true) is used. Other failures cause delivery | |
16096 | to be deferred. | |
16097 | ||
16098 | If this option is set false, and the router declines to handle the address, no | |
16099 | further routers are tried, routing fails, and the address is bounced. However, | |
16100 | if the router explicitly passes an address to the following router by means of | |
16101 | the setting | |
16102 | ||
16103 | self = pass | |
16104 | ||
16105 | or otherwise, the setting of more is ignored. Also, the setting of more does | |
16106 | not affect the behaviour if one of the precondition tests fails. In that case, | |
16107 | the address is always passed to the next router. | |
16108 | ||
16109 | Note that address_data is not considered to be a precondition. If its expansion | |
16110 | is forced to fail, the router declines, and the value of more controls what | |
16111 | happens next. | |
16112 | ||
16113 | +---------------+------------+-------------+--------------+ | |
16114 | |pass_on_timeout|Use: routers|Type: boolean|Default: false| | |
16115 | +---------------+------------+-------------+--------------+ | |
16116 | ||
16117 | If a router times out during a host lookup, it normally causes deferral of the | |
16118 | address. If pass_on_timeout is set, the address is passed on to the next | |
16119 | router, overriding no_more. This may be helpful for systems that are | |
16120 | intermittently connected to the Internet, or those that want to pass to a smart | |
16121 | host any messages that cannot immediately be delivered. | |
16122 | ||
16123 | There are occasional other temporary errors that can occur while doing DNS | |
16124 | lookups. They are treated in the same way as a timeout, and this option applies | |
16125 | to all of them. | |
16126 | ||
16127 | +-----------+------------+------------+--------------+ | |
16128 | |pass_router|Use: routers|Type: string|Default: unset| | |
16129 | +-----------+------------+------------+--------------+ | |
16130 | ||
16131 | Routers that recognize the generic self option (dnslookup, ipliteral, and | |
16132 | manualroute) are able to return "pass", forcing routing to continue, and | |
16133 | overriding a false setting of more. When one of these routers returns "pass", | |
16134 | the address is normally handed on to the next router in sequence. This can be | |
16135 | changed by setting pass_router to the name of another router. However (unlike | |
16136 | redirect_router) the named router must be below the current router, to avoid | |
16137 | loops. Note that this option applies only to the special case of "pass". It | |
16138 | does not apply when a router returns "decline" because it cannot handle an | |
16139 | address. | |
16140 | ||
16141 | +---------------+------------+------------+--------------+ | |
16142 | |redirect_router|Use: routers|Type: string|Default: unset| | |
16143 | +---------------+------------+------------+--------------+ | |
16144 | ||
16145 | Sometimes an administrator knows that it is pointless to reprocess addresses | |
16146 | generated from alias or forward files with the same router again. For example, | |
16147 | if an alias file translates real names into login ids there is no point | |
16148 | searching the alias file a second time, especially if it is a large file. | |
16149 | ||
16150 | The redirect_router option can be set to the name of any router instance. It | |
16151 | causes the routing of any generated addresses to start at the named router | |
16152 | instead of at the first router. This option has no effect if the router in | |
16153 | which it is set does not generate new addresses. | |
16154 | ||
16155 | +-------------+--------------+------------------+--------------+ | |
16156 | |require_files|Use: routers**|Type: string list*|Default: unset| | |
16157 | +-------------+--------------+------------------+--------------+ | |
16158 | ||
16159 | This option provides a general mechanism for predicating the running of a | |
16160 | router on the existence or non-existence of certain files or directories. | |
16161 | Before running a router, as one of its precondition tests, Exim works its way | |
16162 | through the require_files list, expanding each item separately. | |
16163 | ||
16164 | Because the list is split before expansion, any colons in expansion items must | |
16165 | be doubled, or the facility for using a different list separator must be used. | |
16166 | If any expansion is forced to fail, the item is ignored. Other expansion | |
16167 | failures cause routing of the address to be deferred. | |
16168 | ||
16169 | If any expanded string is empty, it is ignored. Otherwise, except as described | |
16170 | below, each string must be a fully qualified file path, optionally preceded by | |
16171 | "!". The paths are passed to the stat() function to test for the existence of | |
16172 | the files or directories. The router is skipped if any paths not preceded by "! | |
16173 | " do not exist, or if any paths preceded by "!" do exist. | |
16174 | ||
16175 | If stat() cannot determine whether a file exists or not, delivery of the | |
16176 | message is deferred. This can happen when NFS-mounted filesystems are | |
16177 | unavailable. | |
16178 | ||
16179 | This option is checked after the domains, local_parts, and senders options, so | |
16180 | you cannot use it to check for the existence of a file in which to look up a | |
16181 | domain, local part, or sender. (See section 3.12 for a full list of the order | |
16182 | in which preconditions are evaluated.) However, as these options are all | |
16183 | expanded, you can use the exists expansion condition to make such tests. The | |
16184 | require_files option is intended for checking files that the router may be | |
16185 | going to use internally, or which are needed by a transport (for example | |
16186 | .procmailrc). | |
16187 | ||
16188 | During delivery, the stat() function is run as root, but there is a facility | |
16189 | for some checking of the accessibility of a file by another user. This is not a | |
16190 | proper permissions check, but just a "rough" check that operates as follows: | |
16191 | ||
16192 | If an item in a require_files list does not contain any forward slash | |
16193 | characters, it is taken to be the user (and optional group, separated by a | |
16194 | comma) to be checked for subsequent files in the list. If no group is specified | |
16195 | but the user is specified symbolically, the gid associated with the uid is | |
16196 | used. For example: | |
16197 | ||
16198 | require_files = mail:/some/file | |
16199 | require_files = $local_part:$home/.procmailrc | |
16200 | ||
16201 | If a user or group name in a require_files list does not exist, the | |
16202 | require_files condition fails. | |
16203 | ||
16204 | Exim performs the check by scanning along the components of the file path, and | |
16205 | checking the access for the given uid and gid. It checks for "x" access on | |
16206 | directories, and "r" access on the final file. Note that this means that file | |
16207 | access control lists, if the operating system has them, are ignored. | |
16208 | ||
16209 | Warning 1: When the router is being run to verify addresses for an incoming | |
16210 | SMTP message, Exim is not running as root, but under its own uid. This may | |
16211 | affect the result of a require_files check. In particular, stat() may yield the | |
16212 | error EACCES ("Permission denied"). This means that the Exim user is not | |
16213 | permitted to read one of the directories on the file's path. | |
16214 | ||
16215 | Warning 2: Even when Exim is running as root while delivering a message, stat() | |
16216 | can yield EACCES for a file in an NFS directory that is mounted without root | |
16217 | access. In this case, if a check for access by a particular user is requested, | |
16218 | Exim creates a subprocess that runs as that user, and tries the check again in | |
16219 | that process. | |
16220 | ||
16221 | The default action for handling an unresolved EACCES is to consider it to be | |
16222 | caused by a configuration error, and routing is deferred because the existence | |
16223 | or non-existence of the file cannot be determined. However, in some | |
16224 | circumstances it may be desirable to treat this condition as if the file did | |
16225 | not exist. If the file name (or the exclamation mark that precedes the file | |
16226 | name for non-existence) is preceded by a plus sign, the EACCES error is treated | |
16227 | as if the file did not exist. For example: | |
16228 | ||
16229 | require_files = +/some/file | |
16230 | ||
16231 | If the router is not an essential part of verification (for example, it handles | |
16232 | users' .forward files), another solution is to set the verify option false so | |
16233 | that the router is skipped when verifying. | |
16234 | ||
16235 | +--------------------+------------+-------------+------------------+ | |
16236 | |retry_use_local_part|Use: routers|Type: boolean|Default: see below| | |
16237 | +--------------------+------------+-------------+------------------+ | |
16238 | ||
16239 | When a delivery suffers a temporary routing failure, a retry record is created | |
16240 | in Exim's hints database. For addresses whose routing depends only on the | |
16241 | domain, the key for the retry record should not involve the local part, but for | |
16242 | other addresses, both the domain and the local part should be included. | |
16243 | Usually, remote routing is of the former kind, and local routing is of the | |
16244 | latter kind. | |
16245 | ||
16246 | This option controls whether the local part is used to form the key for retry | |
16247 | hints for addresses that suffer temporary errors while being handled by this | |
16248 | router. The default value is true for any router that has check_local_user set, | |
16249 | and false otherwise. Note that this option does not apply to hints keys for | |
16250 | transport delays; they are controlled by a generic transport option of the same | |
16251 | name. | |
16252 | ||
16253 | The setting of retry_use_local_part applies only to the router on which it | |
16254 | appears. If the router generates child addresses, they are routed | |
16255 | independently; this setting does not become attached to them. | |
16256 | ||
16257 | +---------------------+------------+-------------+--------------+ | |
16258 | |router_home_directory|Use: routers|Type: string*|Default: unset| | |
16259 | +---------------------+------------+-------------+--------------+ | |
16260 | ||
16261 | This option sets a home directory for use while the router is running. (Compare | |
16262 | transport_home_directory, which sets a home directory for later transporting.) | |
16263 | In particular, if used on a redirect router, this option sets a value for $home | |
16264 | while a filter is running. The value is expanded; forced expansion failure | |
16265 | causes the option to be ignored - other failures cause the router to defer. | |
16266 | ||
16267 | Expansion of router_home_directory happens immediately after the | |
16268 | check_local_user test (if configured), before any further expansions take | |
16269 | place. (See section 3.12 for a list of the order in which preconditions are | |
16270 | evaluated.) While the router is running, router_home_directory overrides the | |
16271 | value of $home that came from check_local_user. | |
16272 | ||
16273 | When a router accepts an address and assigns it to a local transport (including | |
16274 | the cases when a redirect router generates a pipe, file, or autoreply | |
16275 | delivery), the home directory setting for the transport is taken from the first | |
16276 | of these values that is set: | |
16277 | ||
16278 | * The home_directory option on the transport; | |
16279 | ||
16280 | * The transport_home_directory option on the router; | |
16281 | ||
16282 | * The password data if check_local_user is set on the router; | |
16283 | ||
16284 | * The router_home_directory option on the router. | |
16285 | ||
16286 | In other words, router_home_directory overrides the password data for the | |
16287 | router, but not for the transport. | |
16288 | ||
16289 | +----+------------+------------+---------------+ | |
16290 | |self|Use: routers|Type: string|Default: freeze| | |
16291 | +----+------------+------------+---------------+ | |
16292 | ||
16293 | This option applies to those routers that use a recipient address to find a | |
16294 | list of remote hosts. Currently, these are the dnslookup, ipliteral, and | |
16295 | manualroute routers. Certain configurations of the queryprogram router can also | |
16296 | specify a list of remote hosts. Usually such routers are configured to send the | |
16297 | message to a remote host via an smtp transport. The self option specifies what | |
16298 | happens when the first host on the list turns out to be the local host. The way | |
16299 | in which Exim checks for the local host is described in section 13.8. | |
16300 | ||
16301 | Normally this situation indicates either an error in Exim's configuration (for | |
16302 | example, the router should be configured not to process this domain), or an | |
16303 | error in the DNS (for example, the MX should not point to this host). For this | |
16304 | reason, the default action is to log the incident, defer the address, and | |
16305 | freeze the message. The following alternatives are provided for use in special | |
16306 | cases: | |
16307 | ||
16308 | defer | |
16309 | ||
16310 | Delivery of the message is tried again later, but the message is not | |
16311 | frozen. | |
16312 | ||
16313 | reroute: <domain> | |
16314 | ||
16315 | The domain is changed to the given domain, and the address is passed back | |
16316 | to be reprocessed by the routers. No rewriting of headers takes place. This | |
16317 | behaviour is essentially a redirection. | |
16318 | ||
16319 | reroute: rewrite: <domain> | |
16320 | ||
16321 | The domain is changed to the given domain, and the address is passed back | |
16322 | to be reprocessed by the routers. Any headers that contain the original | |
16323 | domain are rewritten. | |
16324 | ||
16325 | pass | |
16326 | ||
16327 | The router passes the address to the next router, or to the router named in | |
16328 | the pass_router option if it is set. This overrides no_more. During | |
16329 | subsequent routing and delivery, the variable $self_hostname contains the | |
16330 | name of the local host that the router encountered. This can be used to | |
16331 | distinguish between different cases for hosts with multiple names. The | |
16332 | combination | |
16333 | ||
16334 | self = pass | |
16335 | no_more | |
16336 | ||
16337 | ensures that only those addresses that routed to the local host are passed | |
16338 | on. Without no_more, addresses that were declined for other reasons would | |
16339 | also be passed to the next router. | |
16340 | ||
16341 | fail | |
16342 | ||
16343 | Delivery fails and an error report is generated. | |
16344 | ||
16345 | send | |
16346 | ||
16347 | The anomaly is ignored and the address is queued for the transport. This | |
16348 | setting should be used with extreme caution. For an smtp transport, it | |
16349 | makes sense only in cases where the program that is listening on the SMTP | |
16350 | port is not this version of Exim. That is, it must be some other MTA, or | |
16351 | Exim with a different configuration file that handles the domain in another | |
16352 | way. | |
16353 | ||
16354 | +-------+--------------+-------------------+--------------+ | |
16355 | |senders|Use: routers**|Type: address list*|Default: unset| | |
16356 | +-------+--------------+-------------------+--------------+ | |
16357 | ||
16358 | If this option is set, the router is skipped unless the message's sender | |
16359 | address matches something on the list. See section 3.12 for a list of the order | |
16360 | in which preconditions are evaluated. | |
16361 | ||
16362 | There are issues concerning verification when the running of routers is | |
16363 | dependent on the sender. When Exim is verifying the address in an errors_to | |
16364 | setting, it sets the sender to the null string. When using the -bt option to | |
16365 | check a configuration file, it is necessary also to use the -f option to set an | |
16366 | appropriate sender. For incoming mail, the sender is unset when verifying the | |
16367 | sender, but is available when verifying any recipients. If the SMTP VRFY | |
16368 | command is enabled, it must be used after MAIL if the sender address matters. | |
16369 | ||
16370 | +--------------------+------------+-------------+--------------+ | |
16371 | |translate_ip_address|Use: routers|Type: string*|Default: unset| | |
16372 | +--------------------+------------+-------------+--------------+ | |
16373 | ||
16374 | There exist some rare networking situations (for example, packet radio) where | |
16375 | it is helpful to be able to translate IP addresses generated by normal routing | |
16376 | mechanisms into other IP addresses, thus performing a kind of manual IP | |
16377 | routing. This should be done only if the normal IP routing of the TCP/IP stack | |
16378 | is inadequate or broken. Because this is an extremely uncommon requirement, the | |
16379 | code to support this option is not included in the Exim binary unless | |
16380 | SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in Local/Makefile. | |
16381 | ||
16382 | The translate_ip_address string is expanded for every IP address generated by | |
16383 | the router, with the generated address set in $host_address. If the expansion | |
16384 | is forced to fail, no action is taken. For any other expansion error, delivery | |
16385 | of the message is deferred. If the result of the expansion is an IP address, | |
16386 | that replaces the original address; otherwise the result is assumed to be a | |
16387 | host name - this is looked up using gethostbyname() (or getipnodebyname() when | |
16388 | available) to produce one or more replacement IP addresses. For example, to | |
16389 | subvert all IP addresses in some specific networks, this could be added to a | |
16390 | router: | |
16391 | ||
16392 | translate_ip_address = \ | |
16393 | ${lookup{${mask:$host_address/26}}lsearch{/some/file}\ | |
16394 | {$value}fail}} | |
16395 | ||
16396 | The file would contain lines like | |
16397 | ||
16398 | 10.2.3.128/26 some.host | |
16399 | 10.8.4.34/26 10.44.8.15 | |
16400 | ||
16401 | You should not make use of this facility unless you really understand what you | |
16402 | are doing. | |
16403 | ||
16404 | +---------+------------+-------------+--------------+ | |
16405 | |transport|Use: routers|Type: string*|Default: unset| | |
16406 | +---------+------------+-------------+--------------+ | |
16407 | ||
16408 | This option specifies the transport to be used when a router accepts an address | |
16409 | and sets it up for delivery. A transport is never needed if a router is used | |
16410 | only for verification. The value of the option is expanded at routing time, | |
16411 | after the expansion of errors_to, headers_add, and headers_remove, and result | |
16412 | must be the name of one of the configured transports. If it is not, delivery is | |
16413 | deferred. | |
16414 | ||
16415 | The transport option is not used by the redirect router, but it does have some | |
16416 | private options that set up transports for pipe and file deliveries (see | |
16417 | chapter 22). | |
16418 | ||
16419 | +---------------------------+------------+-------------+--------------+ | |
16420 | |transport_current_directory|Use: routers|Type: string*|Default: unset| | |
16421 | +---------------------------+------------+-------------+--------------+ | |
16422 | ||
16423 | This option associates a current directory with any address that is routed to a | |
16424 | local transport. This can happen either because a transport is explicitly | |
16425 | configured for the router, or because it generates a delivery to a file or a | |
16426 | pipe. During the delivery process (that is, at transport time), this option | |
16427 | string is expanded and is set as the current directory, unless overridden by a | |
16428 | setting on the transport. If the expansion fails for any reason, including | |
16429 | forced failure, an error is logged, and delivery is deferred. See chapter 23 | |
16430 | for details of the local delivery environment. | |
16431 | ||
16432 | +------------------------+------------+-------------+------------------+ | |
16433 | |transport_home_directory|Use: routers|Type: string*|Default: see below| | |
16434 | +------------------------+------------+-------------+------------------+ | |
16435 | ||
16436 | This option associates a home directory with any address that is routed to a | |
16437 | local transport. This can happen either because a transport is explicitly | |
16438 | configured for the router, or because it generates a delivery to a file or a | |
16439 | pipe. During the delivery process (that is, at transport time), the option | |
16440 | string is expanded and is set as the home directory, unless overridden by a | |
16441 | setting of home_directory on the transport. If the expansion fails for any | |
16442 | reason, including forced failure, an error is logged, and delivery is deferred. | |
16443 | ||
16444 | If the transport does not specify a home directory, and | |
16445 | transport_home_directory is not set for the router, the home directory for the | |
16446 | transport is taken from the password data if check_local_user is set for the | |
16447 | router. Otherwise it is taken from router_home_directory if that option is set; | |
16448 | if not, no home directory is set for the transport. | |
16449 | ||
16450 | See chapter 23 for further details of the local delivery environment. | |
16451 | ||
16452 | +------+------------+--------------+--------------+ | |
16453 | |unseen|Use: routers|Type: boolean*|Default: false| | |
16454 | +------+------------+--------------+--------------+ | |
16455 | ||
16456 | The result of string expansion for this option must be a valid boolean value, | |
16457 | that is, one of the strings "yes", "no", "true", or "false". Any other result | |
16458 | causes an error, and delivery is deferred. If the expansion is forced to fail, | |
16459 | the default value for the option (false) is used. Other failures cause delivery | |
16460 | to be deferred. | |
16461 | ||
16462 | When this option is set true, routing does not cease if the router accepts the | |
16463 | address. Instead, a copy of the incoming address is passed to the next router, | |
16464 | overriding a false setting of more. There is little point in setting more false | |
16465 | if unseen is always true, but it may be useful in cases when the value of | |
16466 | unseen contains expansion items (and therefore, presumably, is sometimes true | |
16467 | and sometimes false). | |
16468 | ||
16469 | Setting the unseen option has a similar effect to the unseen command qualifier | |
16470 | in filter files. It can be used to cause copies of messages to be delivered to | |
16471 | some other destination, while also carrying out a normal delivery. In effect, | |
16472 | the current address is made into a "parent" that has two children - one that is | |
16473 | delivered as specified by this router, and a clone that goes on to be routed | |
16474 | further. For this reason, unseen may not be combined with the one_time option | |
16475 | in a redirect router. | |
16476 | ||
16477 | Warning: Header lines added to the address (or specified for removal) by this | |
16478 | router or by previous routers affect the "unseen" copy of the message only. The | |
16479 | clone that continues to be processed by further routers starts with no added | |
16480 | headers and none specified for removal. For a redirect router, if a generated | |
16481 | address is the same as the incoming address, this can lead to duplicate | |
16482 | addresses with different header modifications. Exim does not do duplicate | |
16483 | deliveries (except, in certain circumstances, to pipes -- see section 22.7), | |
16484 | but it is undefined which of the duplicates is discarded, so this ambiguous | |
16485 | situation should be avoided. The repeat_use option of the redirect router may | |
16486 | be of help. | |
16487 | ||
16488 | Unlike the handling of header modifications, any data that was set by the | |
16489 | address_data option in the current or previous routers is passed on to | |
16490 | subsequent routers. | |
16491 | ||
16492 | +----+------------+-------------+------------------+ | |
16493 | |user|Use: routers|Type: string*|Default: see below| | |
16494 | +----+------------+-------------+------------------+ | |
16495 | ||
16496 | When a router queues an address for a transport, and the transport does not | |
16497 | specify a user, the user given here is used when running the delivery process. | |
16498 | The user may be specified numerically or by name. If expansion fails, the error | |
16499 | is logged and delivery is deferred. This user is also used by the redirect | |
16500 | router when running a filter file. The default is unset, except when | |
16501 | check_local_user is set. In this case, the default is taken from the password | |
16502 | information. If the user is specified as a name, and group is not set, the | |
16503 | group associated with the user is used. See also initgroups and group and the | |
16504 | discussion in chapter 23. | |
16505 | ||
16506 | +------+--------------+-------------+-------------+ | |
16507 | |verify|Use: routers**|Type: boolean|Default: true| | |
16508 | +------+--------------+-------------+-------------+ | |
16509 | ||
16510 | Setting this option has the effect of setting verify_sender and | |
16511 | verify_recipient to the same value. | |
16512 | ||
16513 | +-----------+--------------+-------------+--------------+ | |
16514 | |verify_only|Use: routers**|Type: boolean|Default: false| | |
16515 | +-----------+--------------+-------------+--------------+ | |
16516 | ||
16517 | If this option is set, the router is used only when verifying an address, | |
16518 | delivering in cutthrough mode or testing with the -bv option, not when actually | |
16519 | doing a delivery, testing with the -bt option, or running the SMTP EXPN | |
16520 | command. It can be further restricted to verifying only senders or recipients | |
16521 | by means of verify_sender and verify_recipient. | |
16522 | ||
16523 | Warning: When the router is being run to verify addresses for an incoming SMTP | |
16524 | message, Exim is not running as root, but under its own uid. If the router | |
16525 | accesses any files, you need to make sure that they are accessible to the Exim | |
16526 | user or group. | |
16527 | ||
16528 | +----------------+--------------+-------------+-------------+ | |
16529 | |verify_recipient|Use: routers**|Type: boolean|Default: true| | |
16530 | +----------------+--------------+-------------+-------------+ | |
16531 | ||
16532 | If this option is false, the router is skipped when verifying recipient | |
16533 | addresses, delivering in cutthrough mode or testing recipient verification | |
16534 | using -bv. See section 3.12 for a list of the order in which preconditions are | |
16535 | evaluated. | |
16536 | ||
16537 | +-------------+--------------+-------------+-------------+ | |
16538 | |verify_sender|Use: routers**|Type: boolean|Default: true| | |
16539 | +-------------+--------------+-------------+-------------+ | |
16540 | ||
16541 | If this option is false, the router is skipped when verifying sender addresses | |
16542 | or testing sender verification using -bvs. See section 3.12 for a list of the | |
16543 | order in which preconditions are evaluated. | |
16544 | ||
16545 | ||
16546 | ||
16547 | =============================================================================== | |
16548 | 16. THE ACCEPT ROUTER | |
16549 | ||
16550 | The accept router has no private options of its own. Unless it is being used | |
16551 | purely for verification (see verify_only) a transport is required to be defined | |
16552 | by the generic transport option. If the preconditions that are specified by | |
16553 | generic options are met, the router accepts the address and queues it for the | |
16554 | given transport. The most common use of this router is for setting up | |
16555 | deliveries to local mailboxes. For example: | |
16556 | ||
16557 | localusers: | |
16558 | driver = accept | |
16559 | domains = mydomain.example | |
16560 | check_local_user | |
16561 | transport = local_delivery | |
16562 | ||
16563 | The domains condition in this example checks the domain of the address, and | |
16564 | check_local_user checks that the local part is the login of a local user. When | |
16565 | both preconditions are met, the accept router runs, and queues the address for | |
16566 | the local_delivery transport. | |
16567 | ||
16568 | ||
16569 | ||
16570 | =============================================================================== | |
16571 | 17. THE DNSLOOKUP ROUTER | |
16572 | ||
16573 | The dnslookup router looks up the hosts that handle mail for the recipient's | |
16574 | domain in the DNS. A transport must always be set for this router, unless | |
16575 | verify_only is set. | |
16576 | ||
16577 | If SRV support is configured (see check_srv below), Exim first searches for SRV | |
16578 | records. If none are found, or if SRV support is not configured, MX records are | |
16579 | looked up. If no MX records exist, address records are sought. However, | |
16580 | mx_domains can be set to disable the direct use of address records. | |
16581 | ||
16582 | MX records of equal priority are sorted by Exim into a random order. Exim then | |
16583 | looks for address records for the host names obtained from MX or SRV records. | |
16584 | When a host has more than one IP address, they are sorted into a random order, | |
16585 | except that IPv6 addresses are always sorted before IPv4 addresses. If all the | |
16586 | IP addresses found are discarded by a setting of the ignore_target_hosts | |
16587 | generic option, the router declines. | |
16588 | ||
16589 | Unless they have the highest priority (lowest MX value), MX records that point | |
16590 | to the local host, or to any host name that matches hosts_treat_as_local, are | |
16591 | discarded, together with any other MX records of equal or lower priority. | |
16592 | ||
16593 | If the host pointed to by the highest priority MX record, or looked up as an | |
16594 | address record, is the local host, or matches hosts_treat_as_local, what | |
16595 | happens is controlled by the generic self option. | |
16596 | ||
16597 | ||
16598 | 17.1 Problems with DNS lookups | |
16599 | ------------------------------ | |
16600 | ||
16601 | There have been problems with DNS servers when SRV records are looked up. Some | |
16602 | mis-behaving servers return a DNS error or timeout when a non-existent SRV | |
16603 | record is sought. Similar problems have in the past been reported for MX | |
16604 | records. The global dns_again_means_nonexist option can help with this problem, | |
16605 | but it is heavy-handed because it is a global option. | |
16606 | ||
16607 | For this reason, there are two options, srv_fail_domains and mx_fail_domains, | |
16608 | that control what happens when a DNS lookup in a dnslookup router results in a | |
16609 | DNS failure or a "try again" response. If an attempt to look up an SRV or MX | |
16610 | record causes one of these results, and the domain matches the relevant list, | |
16611 | Exim behaves as if the DNS had responded "no such record". In the case of an | |
16612 | SRV lookup, this means that the router proceeds to look for MX records; in the | |
16613 | case of an MX lookup, it proceeds to look for A or AAAA records, unless the | |
16614 | domain matches mx_domains, in which case routing fails. | |
16615 | ||
16616 | ||
16617 | 17.2 Declining addresses by dnslookup | |
16618 | ------------------------------------- | |
16619 | ||
16620 | There are a few cases where a dnslookup router will decline to accept an | |
16621 | address; if such a router is expected to handle "all remaining non-local | |
16622 | domains", then it is important to set no_more. | |
16623 | ||
16624 | Reasons for a dnslookup router to decline currently include: | |
16625 | ||
16626 | * The domain does not exist in DNS | |
16627 | ||
16628 | * The domain exists but the MX record's host part is just "."; this is a | |
16629 | common convention (borrowed from SRV) used to indicate that there is no | |
16630 | such service for this domain and to not fall back to trying A/AAAA records. | |
16631 | ||
16632 | * Ditto, but for SRV records, when check_srv is set on this router. | |
16633 | ||
16634 | * MX record points to a non-existent host. | |
16635 | ||
16636 | * MX record points to an IP address and the main section option | |
16637 | allow_mx_to_ip is not set. | |
16638 | ||
16639 | * MX records exist and point to valid hosts, but all hosts resolve only to | |
16640 | addresses blocked by the ignore_target_hosts generic option on this router. | |
16641 | ||
16642 | * The domain is not syntactically valid (see also allow_utf8_domains and | |
16643 | dns_check_names_pattern for handling one variant of this) | |
16644 | ||
16645 | * check_secondary_mx is set on this router but the local host can not be | |
16646 | found in the MX records (see below) | |
16647 | ||
16648 | ||
16649 | 17.3 Private options for dnslookup | |
16650 | ---------------------------------- | |
16651 | ||
16652 | The private options for the dnslookup router are as follows: | |
16653 | ||
16654 | +------------------+--------------+-------------+--------------+ | |
16655 | |check_secondary_mx|Use: dnslookup|Type: boolean|Default: false| | |
16656 | +------------------+--------------+-------------+--------------+ | |
16657 | ||
16658 | If this option is set, the router declines unless the local host is found in | |
16659 | (and removed from) the list of hosts obtained by MX lookup. This can be used to | |
16660 | process domains for which the local host is a secondary mail exchanger | |
16661 | differently to other domains. The way in which Exim decides whether a host is | |
16662 | the local host is described in section 13.8. | |
16663 | ||
16664 | +---------+--------------+-------------+--------------+ | |
16665 | |check_srv|Use: dnslookup|Type: string*|Default: unset| | |
16666 | +---------+--------------+-------------+--------------+ | |
16667 | ||
16668 | The dnslookup router supports the use of SRV records (see RFC 2782) in addition | |
16669 | to MX and address records. The support is disabled by default. To enable SRV | |
16670 | support, set the check_srv option to the name of the service required. For | |
16671 | example, | |
16672 | ||
16673 | check_srv = smtp | |
16674 | ||
16675 | looks for SRV records that refer to the normal smtp service. The option is | |
16676 | expanded, so the service name can vary from message to message or address to | |
16677 | address. This might be helpful if SRV records are being used for a submission | |
16678 | service. If the expansion is forced to fail, the check_srv option is ignored, | |
16679 | and the router proceeds to look for MX records in the normal way. | |
16680 | ||
16681 | When the expansion succeeds, the router searches first for SRV records for the | |
16682 | given service (it assumes TCP protocol). A single SRV record with a host name | |
16683 | that consists of just a single dot indicates "no such service for this domain"; | |
16684 | if this is encountered, the router declines. If other kinds of SRV record are | |
16685 | found, they are used to construct a host list for delivery according to the | |
16686 | rules of RFC 2782. MX records are not sought in this case. | |
16687 | ||
16688 | When no SRV records are found, MX records (and address records) are sought in | |
16689 | the traditional way. In other words, SRV records take precedence over MX | |
16690 | records, just as MX records take precedence over address records. Note that | |
16691 | this behaviour is not sanctioned by RFC 2782, though a previous draft RFC | |
16692 | defined it. It is apparently believed that MX records are sufficient for email | |
16693 | and that SRV records should not be used for this purpose. However, SRV records | |
16694 | have an additional "weight" feature which some people might find useful when | |
16695 | trying to split an SMTP load between hosts of different power. | |
16696 | ||
16697 | See section 17.1 above for a discussion of Exim's behaviour when there is a DNS | |
16698 | lookup error. | |
16699 | ||
16700 | +----------------------+--------------+------------------+--------------+ | |
16701 | |dnssec_request_domains|Use: dnslookup|Type: domain list*|Default: unset| | |
16702 | +----------------------+--------------+------------------+--------------+ | |
16703 | ||
16704 | DNS lookups for domains matching dnssec_request_domains will be done with the | |
16705 | dnssec request bit set. This applies to all of the SRV, MX A6, AAAA, A lookup | |
16706 | sequence. | |
16707 | ||
16708 | +----------------------+--------------+------------------+--------------+ | |
16709 | |dnssec_require_domains|Use: dnslookup|Type: domain list*|Default: unset| | |
16710 | +----------------------+--------------+------------------+--------------+ | |
16711 | ||
16712 | DNS lookups for domains matching dnssec_request_domains will be done with the | |
16713 | dnssec request bit set. Any returns not having the Authenticated Data bit (AD | |
16714 | bit) set wil be ignored and logged as a host-lookup failure. This applies to | |
16715 | all of the SRV, MX A6, AAAA, A lookup sequence. | |
16716 | ||
16717 | +----------+--------------+------------------+--------------+ | |
16718 | |mx_domains|Use: dnslookup|Type: domain list*|Default: unset| | |
16719 | +----------+--------------+------------------+--------------+ | |
16720 | ||
16721 | A domain that matches mx_domains is required to have either an MX or an SRV | |
16722 | record in order to be recognized. (The name of this option could be improved.) | |
16723 | For example, if all the mail hosts in fict.example are known to have MX | |
16724 | records, except for those in discworld.fict.example, you could use this | |
16725 | setting: | |
16726 | ||
16727 | mx_domains = ! *.discworld.fict.example : *.fict.example | |
16728 | ||
16729 | This specifies that messages addressed to a domain that matches the list but | |
16730 | has no MX record should be bounced immediately instead of being routed using | |
16731 | the address record. | |
16732 | ||
16733 | +---------------+--------------+------------------+--------------+ | |
16734 | |mx_fail_domains|Use: dnslookup|Type: domain list*|Default: unset| | |
16735 | +---------------+--------------+------------------+--------------+ | |
16736 | ||
16737 | If the DNS lookup for MX records for one of the domains in this list causes a | |
16738 | DNS lookup error, Exim behaves as if no MX records were found. See section 17.1 | |
16739 | for more discussion. | |
16740 | ||
16741 | +--------------+--------------+-------------+-------------+ | |
16742 | |qualify_single|Use: dnslookup|Type: boolean|Default: true| | |
16743 | +--------------+--------------+-------------+-------------+ | |
16744 | ||
16745 | When this option is true, the resolver option RES_DEFNAMES is set for DNS | |
16746 | lookups. Typically, but not standardly, this causes the resolver to qualify | |
16747 | single-component names with the default domain. For example, on a machine | |
16748 | called dictionary.ref.example, the domain thesaurus would be changed to | |
16749 | thesaurus.ref.example inside the resolver. For details of what your resolver | |
16750 | actually does, consult your man pages for resolver and resolv.conf. | |
16751 | ||
16752 | +---------------+--------------+-------------+-------------+ | |
16753 | |rewrite_headers|Use: dnslookup|Type: boolean|Default: true| | |
16754 | +---------------+--------------+-------------+-------------+ | |
16755 | ||
16756 | If the domain name in the address that is being processed is not fully | |
16757 | qualified, it may be expanded to its full form by a DNS lookup. For example, if | |
16758 | an address is specified as dormouse@teaparty, the domain might be expanded to | |
16759 | teaparty.wonderland.fict.example. Domain expansion can also occur as a result | |
16760 | of setting the widen_domains option. If rewrite_headers is true, all | |
16761 | occurrences of the abbreviated domain name in any Bcc:, Cc:, From:, Reply-to:, | |
16762 | Sender:, and To: header lines of the message are rewritten with the full domain | |
16763 | name. | |
16764 | ||
16765 | This option should be turned off only when it is known that no message is ever | |
16766 | going to be sent outside an environment where the abbreviation makes sense. | |
16767 | ||
16768 | When an MX record is looked up in the DNS and matches a wildcard record, name | |
16769 | servers normally return a record containing the name that has been looked up, | |
16770 | making it impossible to detect whether a wildcard was present or not. However, | |
16771 | some name servers have recently been seen to return the wildcard entry. If the | |
16772 | name returned by a DNS lookup begins with an asterisk, it is not used for | |
16773 | header rewriting. | |
16774 | ||
16775 | +------------------------+--------------+-------------+--------------+ | |
16776 | |same_domain_copy_routing|Use: dnslookup|Type: boolean|Default: false| | |
16777 | +------------------------+--------------+-------------+--------------+ | |
16778 | ||
16779 | Addresses with the same domain are normally routed by the dnslookup router to | |
16780 | the same list of hosts. However, this cannot be presumed, because the router | |
16781 | options and preconditions may refer to the local part of the address. By | |
16782 | default, therefore, Exim routes each address in a message independently. DNS | |
16783 | servers run caches, so repeated DNS lookups are not normally expensive, and in | |
16784 | any case, personal messages rarely have more than a few recipients. | |
16785 | ||
16786 | If you are running mailing lists with large numbers of subscribers at the same | |
16787 | domain, and you are using a dnslookup router which is independent of the local | |
16788 | part, you can set same_domain_copy_routing to bypass repeated DNS lookups for | |
16789 | identical domains in one message. In this case, when dnslookup routes an | |
16790 | address to a remote transport, any other unrouted addresses in the message that | |
16791 | have the same domain are automatically given the same routing without | |
16792 | processing them independently, provided the following conditions are met: | |
16793 | ||
16794 | * No router that processed the address specified headers_add or | |
16795 | headers_remove. | |
16796 | ||
16797 | * The router did not change the address in any way, for example, by | |
16798 | "widening" the domain. | |
16799 | ||
16800 | +--------------+--------------+-------------+--------------+ | |
16801 | |search_parents|Use: dnslookup|Type: boolean|Default: false| | |
16802 | +--------------+--------------+-------------+--------------+ | |
16803 | ||
16804 | When this option is true, the resolver option RES_DNSRCH is set for DNS | |
16805 | lookups. This is different from the qualify_single option in that it applies to | |
16806 | domains containing dots. Typically, but not standardly, it causes the resolver | |
16807 | to search for the name in the current domain and in parent domains. For | |
16808 | example, on a machine in the fict.example domain, if looking up | |
16809 | teaparty.wonderland failed, the resolver would try | |
16810 | teaparty.wonderland.fict.example. For details of what your resolver actually | |
16811 | does, consult your man pages for resolver and resolv.conf. | |
16812 | ||
16813 | Setting this option true can cause problems in domains that have a wildcard MX | |
16814 | record, because any domain that does not have its own MX record matches the | |
16815 | local wildcard. | |
16816 | ||
16817 | +----------------+--------------+------------------+--------------+ | |
16818 | |srv_fail_domains|Use: dnslookup|Type: domain list*|Default: unset| | |
16819 | +----------------+--------------+------------------+--------------+ | |
16820 | ||
16821 | If the DNS lookup for SRV records for one of the domains in this list causes a | |
16822 | DNS lookup error, Exim behaves as if no SRV records were found. See section | |
16823 | 17.1 for more discussion. | |
16824 | ||
16825 | +-------------+--------------+-----------------+--------------+ | |
16826 | |widen_domains|Use: dnslookup|Type: string list|Default: unset| | |
16827 | +-------------+--------------+-----------------+--------------+ | |
16828 | ||
16829 | If a DNS lookup fails and this option is set, each of its strings in turn is | |
16830 | added onto the end of the domain, and the lookup is tried again. For example, | |
16831 | if | |
16832 | ||
16833 | widen_domains = fict.example:ref.example | |
16834 | ||
16835 | is set and a lookup of klingon.dictionary fails, | |
16836 | klingon.dictionary.fict.example is looked up, and if this fails, | |
16837 | klingon.dictionary.ref.example is tried. Note that the qualify_single and | |
16838 | search_parents options can cause some widening to be undertaken inside the DNS | |
16839 | resolver. widen_domains is not applied to sender addresses when verifying, | |
16840 | unless rewrite_headers is false (not the default). | |
16841 | ||
16842 | ||
16843 | 17.4 Effect of qualify_single and search_parents | |
16844 | ------------------------------------------------ | |
16845 | ||
16846 | When a domain from an envelope recipient is changed by the resolver as a result | |
16847 | of the qualify_single or search_parents options, Exim rewrites the | |
16848 | corresponding address in the message's header lines unless rewrite_headers is | |
16849 | set false. Exim then re-routes the address, using the full domain. | |
16850 | ||
16851 | These two options affect only the DNS lookup that takes place inside the router | |
16852 | for the domain of the address that is being routed. They do not affect lookups | |
16853 | such as that implied by | |
16854 | ||
16855 | domains = @mx_any | |
16856 | ||
16857 | that may happen while processing a router precondition before the router is | |
16858 | entered. No widening ever takes place for these lookups. | |
16859 | ||
16860 | ||
16861 | ||
16862 | =============================================================================== | |
16863 | 18. THE IPLITERAL ROUTER | |
16864 | ||
16865 | This router has no private options. Unless it is being used purely for | |
16866 | verification (see verify_only) a transport is required to be defined by the | |
16867 | generic transport option. The router accepts the address if its domain part | |
16868 | takes the form of an RFC 2822 domain literal. For example, the ipliteral router | |
16869 | handles the address | |
16870 | ||
16871 | root@[192.168.1.1] | |
16872 | ||
16873 | by setting up delivery to the host with that IP address. IPv4 domain literals | |
16874 | consist of an IPv4 address enclosed in square brackets. IPv6 domain literals | |
16875 | are similar, but the address is preceded by "ipv6:". For example: | |
16876 | ||
16877 | postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678] | |
16878 | ||
16879 | Exim allows "ipv4:" before IPv4 addresses, for consistency, and on the grounds | |
16880 | that sooner or later somebody will try it. | |
16881 | ||
16882 | If the IP address matches something in ignore_target_hosts, the router | |
16883 | declines. If an IP literal turns out to refer to the local host, the generic | |
16884 | self option determines what happens. | |
16885 | ||
16886 | The RFCs require support for domain literals; however, their use is | |
16887 | controversial in today's Internet. If you want to use this router, you must | |
16888 | also set the main configuration option allow_domain_literals. Otherwise, Exim | |
16889 | will not recognize the domain literal syntax in addresses. | |
16890 | ||
16891 | ||
16892 | ||
16893 | =============================================================================== | |
16894 | 19. THE IPLOOKUP ROUTER | |
16895 | ||
16896 | The iplookup router was written to fulfil a specific requirement in Cambridge | |
16897 | University (which in fact no longer exists). For this reason, it is not | |
16898 | included in the binary of Exim by default. If you want to include it, you must | |
16899 | set | |
16900 | ||
16901 | ROUTER_IPLOOKUP=yes | |
16902 | ||
16903 | in your Local/Makefile configuration file. | |
16904 | ||
16905 | The iplookup router routes an address by sending it over a TCP or UDP | |
16906 | connection to one or more specific hosts. The host can then return the same or | |
16907 | a different address - in effect rewriting the recipient address in the | |
16908 | message's envelope. The new address is then passed on to subsequent routers. If | |
16909 | this process fails, the address can be passed on to other routers, or delivery | |
16910 | can be deferred. Since iplookup is just a rewriting router, a transport must | |
16911 | not be specified for it. | |
16912 | ||
16913 | +-----+-------------+------------+--------------+ | |
16914 | |hosts|Use: iplookup|Type: string|Default: unset| | |
16915 | +-----+-------------+------------+--------------+ | |
16916 | ||
16917 | This option must be supplied. Its value is a colon-separated list of host | |
16918 | names. The hosts are looked up using gethostbyname() (or getipnodebyname() when | |
16919 | available) and are tried in order until one responds to the query. If none | |
16920 | respond, what happens is controlled by optional. | |
16921 | ||
16922 | +--------+-------------+-------------+--------------+ | |
16923 | |optional|Use: iplookup|Type: boolean|Default: false| | |
16924 | +--------+-------------+-------------+--------------+ | |
16925 | ||
16926 | If optional is true, if no response is obtained from any host, the address is | |
16927 | passed to the next router, overriding no_more. If optional is false, delivery | |
16928 | to the address is deferred. | |
16929 | ||
16930 | +----+-------------+-------------+----------+ | |
16931 | |port|Use: iplookup|Type: integer|Default: 0| | |
16932 | +----+-------------+-------------+----------+ | |
16933 | ||
16934 | This option must be supplied. It specifies the port number for the TCP or UDP | |
16935 | call. | |
16936 | ||
16937 | +--------+-------------+------------+------------+ | |
16938 | |protocol|Use: iplookup|Type: string|Default: udp| | |
16939 | +--------+-------------+------------+------------+ | |
16940 | ||
16941 | This option can be set to "udp" or "tcp" to specify which of the two protocols | |
16942 | is to be used. | |
16943 | ||
16944 | +-----+-------------+-------------+------------------+ | |
16945 | |query|Use: iplookup|Type: string*|Default: see below| | |
16946 | +-----+-------------+-------------+------------------+ | |
16947 | ||
16948 | This defines the content of the query that is sent to the remote hosts. The | |
16949 | default value is: | |
16950 | ||
16951 | $local_part@$domain $local_part@$domain | |
16952 | ||
16953 | The repetition serves as a way of checking that a response is to the correct | |
16954 | query in the default case (see response_pattern below). | |
16955 | ||
16956 | +-------+-------------+-------------+--------------+ | |
16957 | |reroute|Use: iplookup|Type: string*|Default: unset| | |
16958 | +-------+-------------+-------------+--------------+ | |
16959 | ||
16960 | If this option is not set, the rerouted address is precisely the byte string | |
16961 | returned by the remote host, up to the first white space, if any. If set, the | |
16962 | string is expanded to form the rerouted address. It can include parts matched | |
16963 | in the response by response_pattern by means of numeric variables such as $1, | |
16964 | $2, etc. The variable $0 refers to the entire input string, whether or not a | |
16965 | pattern is in use. In all cases, the rerouted address must end up in the form | |
16966 | local_part@domain. | |
16967 | ||
16968 | +----------------+-------------+------------+--------------+ | |
16969 | |response_pattern|Use: iplookup|Type: string|Default: unset| | |
16970 | +----------------+-------------+------------+--------------+ | |
16971 | ||
16972 | This option can be set to a regular expression that is applied to the string | |
16973 | returned from the remote host. If the pattern does not match the response, the | |
16974 | router declines. If response_pattern is not set, no checking of the response is | |
16975 | done, unless the query was defaulted, in which case there is a check that the | |
16976 | text returned after the first white space is the original address. This checks | |
16977 | that the answer that has been received is in response to the correct question. | |
16978 | For example, if the response is just a new domain, the following could be used: | |
16979 | ||
16980 | response_pattern = ^([^@]+)$ | |
16981 | reroute = $local_part@$1 | |
16982 | ||
16983 | +-------+-------------+----------+-----------+ | |
16984 | |timeout|Use: iplookup|Type: time|Default: 5s| | |
16985 | +-------+-------------+----------+-----------+ | |
16986 | ||
16987 | This specifies the amount of time to wait for a response from the remote | |
16988 | machine. The same timeout is used for the connect() function for a TCP call. It | |
16989 | does not apply to UDP. | |
16990 | ||
16991 | ||
16992 | ||
16993 | =============================================================================== | |
16994 | 20. THE MANUALROUTE ROUTER | |
16995 | ||
16996 | The manualroute router is so-called because it provides a way of manually | |
16997 | routing an address according to its domain. It is mainly used when you want to | |
16998 | route addresses to remote hosts according to your own rules, bypassing the | |
16999 | normal DNS routing that looks up MX records. However, manualroute can also | |
17000 | route to local transports, a facility that may be useful if you want to save | |
17001 | messages for dial-in hosts in local files. | |
17002 | ||
17003 | The manualroute router compares a list of domain patterns with the domain it is | |
17004 | trying to route. If there is no match, the router declines. Each pattern has | |
17005 | associated with it a list of hosts and some other optional data, which may | |
17006 | include a transport. The combination of a pattern and its data is called a | |
17007 | "routing rule". For patterns that do not have an associated transport, the | |
17008 | generic transport option must specify a transport, unless the router is being | |
17009 | used purely for verification (see verify_only). | |
17010 | ||
17011 | In the case of verification, matching the domain pattern is sufficient for the | |
17012 | router to accept the address. When actually routing an address for delivery, an | |
17013 | address that matches a domain pattern is queued for the associated transport. | |
17014 | If the transport is not a local one, a host list must be associated with the | |
17015 | pattern; IP addresses are looked up for the hosts, and these are passed to the | |
17016 | transport along with the mail address. For local transports, a host list is | |
17017 | optional. If it is present, it is passed in $host as a single text string. | |
17018 | ||
17019 | The list of routing rules can be provided as an inline string in route_list, or | |
17020 | the data can be obtained by looking up the domain in a file or database by | |
17021 | setting route_data. Only one of these settings may appear in any one instance | |
17022 | of manualroute. The format of routing rules is described below, following the | |
17023 | list of private options. | |
17024 | ||
17025 | ||
17026 | 20.1 Private options for manualroute | |
17027 | ------------------------------------ | |
17028 | ||
17029 | The private options for the manualroute router are as follows: | |
17030 | ||
17031 | +----------------+----------------+------------+--------------+ | |
17032 | |host_all_ignored|Use: manualroute|Type: string|Default: defer| | |
17033 | +----------------+----------------+------------+--------------+ | |
17034 | ||
17035 | See host_find_failed. | |
17036 | ||
17037 | +----------------+----------------+------------+---------------+ | |
17038 | |host_find_failed|Use: manualroute|Type: string|Default: freeze| | |
17039 | +----------------+----------------+------------+---------------+ | |
17040 | ||
17041 | This option controls what happens when manualroute tries to find an IP address | |
17042 | for a host, and the host does not exist. The option can be set to one of the | |
17043 | following values: | |
17044 | ||
17045 | decline | |
17046 | defer | |
17047 | fail | |
17048 | freeze | |
17049 | ignore | |
17050 | pass | |
17051 | ||
17052 | The default ("freeze") assumes that this state is a serious configuration | |
17053 | error. The difference between "pass" and "decline" is that the former forces | |
17054 | the address to be passed to the next router (or the router defined by | |
17055 | pass_router), overriding no_more, whereas the latter passes the address to the | |
17056 | next router only if more is true. | |
17057 | ||
17058 | The value "ignore" causes Exim to completely ignore a host whose IP address | |
17059 | cannot be found. If all the hosts in the list are ignored, the behaviour is | |
17060 | controlled by the host_all_ignored option. This takes the same values as | |
17061 | host_find_failed, except that it cannot be set to "ignore". | |
17062 | ||
17063 | The host_find_failed option applies only to a definite "does not exist" state; | |
17064 | if a host lookup gets a temporary error, delivery is deferred unless the | |
17065 | generic pass_on_timeout option is set. | |
17066 | ||
17067 | +---------------+----------------+-------------+--------------+ | |
17068 | |hosts_randomize|Use: manualroute|Type: boolean|Default: false| | |
17069 | +---------------+----------------+-------------+--------------+ | |
17070 | ||
17071 | If this option is set, the order of the items in a host list in a routing rule | |
17072 | is randomized each time the list is used, unless an option in the routing rule | |
17073 | overrides (see below). Randomizing the order of a host list can be used to do | |
17074 | crude load sharing. However, if more than one mail address is routed by the | |
17075 | same router to the same host list, the host lists are considered to be the same | |
17076 | (even though they may be randomized into different orders) for the purpose of | |
17077 | deciding whether to batch the deliveries into a single SMTP transaction. | |
17078 | ||
17079 | When hosts_randomize is true, a host list may be split into groups whose order | |
17080 | is separately randomized. This makes it possible to set up MX-like behaviour. | |
17081 | The boundaries between groups are indicated by an item that is just "+" in the | |
17082 | host list. For example: | |
17083 | ||
17084 | route_list = * host1:host2:host3:+:host4:host5 | |
17085 | ||
17086 | The order of the first three hosts and the order of the last two hosts is | |
17087 | randomized for each use, but the first three always end up before the last two. | |
17088 | If hosts_randomize is not set, a "+" item in the list is ignored. If a | |
17089 | randomized host list is passed to an smtp transport that also has | |
17090 | hosts_randomize set, the list is not re-randomized. | |
17091 | ||
17092 | +----------+----------------+-------------+--------------+ | |
17093 | |route_data|Use: manualroute|Type: string*|Default: unset| | |
17094 | +----------+----------------+-------------+--------------+ | |
17095 | ||
17096 | If this option is set, it must expand to yield the data part of a routing rule. | |
17097 | Typically, the expansion string includes a lookup based on the domain. For | |
17098 | example: | |
17099 | ||
17100 | route_data = ${lookup{$domain}dbm{/etc/routes}} | |
17101 | ||
17102 | If the expansion is forced to fail, or the result is an empty string, the | |
17103 | router declines. Other kinds of expansion failure cause delivery to be | |
17104 | deferred. | |
17105 | ||
17106 | +----------+----------------+-----------------+--------------+ | |
17107 | |route_list|Use: manualroute|Type: string list|Default: unset| | |
17108 | +----------+----------------+-----------------+--------------+ | |
17109 | ||
17110 | This string is a list of routing rules, in the form defined below. Note that, | |
17111 | unlike most string lists, the items are separated by semicolons. This is so | |
17112 | that they may contain colon-separated host lists. | |
17113 | ||
17114 | +------------------------+----------------+-------------+--------------+ | |
17115 | |same_domain_copy_routing|Use: manualroute|Type: boolean|Default: false| | |
17116 | +------------------------+----------------+-------------+--------------+ | |
17117 | ||
17118 | Addresses with the same domain are normally routed by the manualroute router to | |
17119 | the same list of hosts. However, this cannot be presumed, because the router | |
17120 | options and preconditions may refer to the local part of the address. By | |
17121 | default, therefore, Exim routes each address in a message independently. DNS | |
17122 | servers run caches, so repeated DNS lookups are not normally expensive, and in | |
17123 | any case, personal messages rarely have more than a few recipients. | |
17124 | ||
17125 | If you are running mailing lists with large numbers of subscribers at the same | |
17126 | domain, and you are using a manualroute router which is independent of the | |
17127 | local part, you can set same_domain_copy_routing to bypass repeated DNS lookups | |
17128 | for identical domains in one message. In this case, when manualroute routes an | |
17129 | address to a remote transport, any other unrouted addresses in the message that | |
17130 | have the same domain are automatically given the same routing without | |
17131 | processing them independently. However, this is only done if headers_add and | |
17132 | headers_remove are unset. | |
17133 | ||
17134 | ||
17135 | 20.2 Routing rules in route_list | |
17136 | -------------------------------- | |
17137 | ||
17138 | The value of route_list is a string consisting of a sequence of routing rules, | |
17139 | separated by semicolons. If a semicolon is needed in a rule, it can be entered | |
17140 | as two semicolons. Alternatively, the list separator can be changed as | |
17141 | described (for colon-separated lists) in section 6.19. Empty rules are ignored. | |
17142 | The format of each rule is | |
17143 | ||
17144 | <domain pattern> <list of hosts> <options> | |
17145 | ||
17146 | The following example contains two rules, each with a simple domain pattern and | |
17147 | no options: | |
17148 | ||
17149 | route_list = \ | |
17150 | dict.ref.example mail-1.ref.example:mail-2.ref.example ; \ | |
17151 | thes.ref.example mail-3.ref.example:mail-4.ref.example | |
17152 | ||
17153 | The three parts of a rule are separated by white space. The pattern and the | |
17154 | list of hosts can be enclosed in quotes if necessary, and if they are, the | |
17155 | usual quoting rules apply. Each rule in a route_list must start with a single | |
17156 | domain pattern, which is the only mandatory item in the rule. The pattern is in | |
17157 | the same format as one item in a domain list (see section 10.8), except that it | |
17158 | may not be the name of an interpolated file. That is, it may be wildcarded, or | |
17159 | a regular expression, or a file or database lookup (with semicolons doubled, | |
17160 | because of the use of semicolon as a separator in a route_list). | |
17161 | ||
17162 | The rules in route_list are searched in order until one of the patterns matches | |
17163 | the domain that is being routed. The list of hosts and then options are then | |
17164 | used as described below. If there is no match, the router declines. When | |
17165 | route_list is set, route_data must not be set. | |
17166 | ||
17167 | ||
17168 | 20.3 Routing rules in route_data | |
17169 | -------------------------------- | |
17170 | ||
17171 | The use of route_list is convenient when there are only a small number of | |
17172 | routing rules. For larger numbers, it is easier to use a file or database to | |
17173 | hold the routing information, and use the route_data option instead. The value | |
17174 | of route_data is a list of hosts, followed by (optional) options. Most | |
17175 | commonly, route_data is set as a string that contains an expansion lookup. For | |
17176 | example, suppose we place two routing rules in a file like this: | |
17177 | ||
17178 | dict.ref.example: mail-1.ref.example:mail-2.ref.example | |
17179 | thes.ref.example: mail-3.ref.example:mail-4.ref.example | |
17180 | ||
17181 | This data can be accessed by setting | |
17182 | ||
17183 | route_data = ${lookup{$domain}lsearch{/the/file/name}} | |
17184 | ||
17185 | Failure of the lookup results in an empty string, causing the router to | |
17186 | decline. However, you do not have to use a lookup in route_data. The only | |
17187 | requirement is that the result of expanding the string is a list of hosts, | |
17188 | possibly followed by options, separated by white space. The list of hosts must | |
17189 | be enclosed in quotes if it contains white space. | |
17190 | ||
17191 | ||
17192 | 20.4 Format of the list of hosts | |
17193 | -------------------------------- | |
17194 | ||
17195 | A list of hosts, whether obtained via route_data or route_list, is always | |
17196 | separately expanded before use. If the expansion fails, the router declines. | |
17197 | The result of the expansion must be a colon-separated list of names and/or IP | |
17198 | addresses, optionally also including ports. The format of each item in the list | |
17199 | is described in the next section. The list separator can be changed as | |
17200 | described in section 6.19. | |
17201 | ||
17202 | If the list of hosts was obtained from a route_list item, the following | |
17203 | variables are set during its expansion: | |
17204 | ||
17205 | * If the domain was matched against a regular expression, the numeric | |
17206 | variables $1, $2, etc. may be set. For example: | |
17207 | ||
17208 | route_list = ^domain(\d+) host-$1.text.example | |
17209 | ||
17210 | * $0 is always set to the entire domain. | |
17211 | ||
17212 | * $1 is also set when partial matching is done in a file lookup. | |
17213 | ||
17214 | * If the pattern that matched the domain was a lookup item, the data that was | |
17215 | looked up is available in the expansion variable $value. For example: | |
17216 | ||
17217 | route_list = lsearch;;/some/file.routes $value | |
17218 | ||
17219 | Note the doubling of the semicolon in the pattern that is necessary because | |
17220 | semicolon is the default route list separator. | |
17221 | ||
17222 | ||
17223 | 20.5 Format of one host item | |
17224 | ---------------------------- | |
17225 | ||
17226 | Each item in the list of hosts is either a host name or an IP address, | |
17227 | optionally with an attached port number. When no port is given, an IP address | |
17228 | is not enclosed in brackets. When a port is specified, it overrides the port | |
17229 | specification on the transport. The port is separated from the name or address | |
17230 | by a colon. This leads to some complications: | |
17231 | ||
17232 | * Because colon is the default separator for the list of hosts, either the | |
17233 | colon that specifies a port must be doubled, or the list separator must be | |
17234 | changed. The following two examples have the same effect: | |
17235 | ||
17236 | route_list = * "host1.tld::1225 : host2.tld::1226" | |
17237 | route_list = * "<+ host1.tld:1225 + host2.tld:1226" | |
17238 | ||
17239 | * When IPv6 addresses are involved, it gets worse, because they contain | |
17240 | colons of their own. To make this case easier, it is permitted to enclose | |
17241 | an IP address (either v4 or v6) in square brackets if a port number | |
17242 | follows. For example: | |
17243 | ||
17244 | route_list = * "</ [10.1.1.1]:1225 / [::1]:1226" | |
17245 | ||
17246 | ||
17247 | 20.6 How the list of hosts is used | |
17248 | ---------------------------------- | |
17249 | ||
17250 | When an address is routed to an smtp transport by manualroute, each of the | |
17251 | hosts is tried, in the order specified, when carrying out the SMTP delivery. | |
17252 | However, the order can be changed by setting the hosts_randomize option, either | |
17253 | on the router (see section 20.1 above), or on the transport. | |
17254 | ||
17255 | Hosts may be listed by name or by IP address. An unadorned name in the list of | |
17256 | hosts is interpreted as a host name. A name that is followed by "/MX" is | |
17257 | interpreted as an indirection to a sublist of hosts obtained by looking up MX | |
17258 | records in the DNS. For example: | |
17259 | ||
17260 | route_list = * x.y.z:p.q.r/MX:e.f.g | |
17261 | ||
17262 | If this feature is used with a port specifier, the port must come last. For | |
17263 | example: | |
17264 | ||
17265 | route_list = * dom1.tld/mx::1225 | |
17266 | ||
17267 | If the hosts_randomize option is set, the order of the items in the list is | |
17268 | randomized before any lookups are done. Exim then scans the list; for any name | |
17269 | that is not followed by "/MX" it looks up an IP address. If this turns out to | |
17270 | be an interface on the local host and the item is not the first in the list, | |
17271 | Exim discards it and any subsequent items. If it is the first item, what | |
17272 | happens is controlled by the self option of the router. | |
17273 | ||
17274 | A name on the list that is followed by "/MX" is replaced with the list of hosts | |
17275 | obtained by looking up MX records for the name. This is always a DNS lookup; | |
17276 | the bydns and byname options (see section 20.7 below) are not relevant here. | |
17277 | The order of these hosts is determined by the preference values in the MX | |
17278 | records, according to the usual rules. Because randomizing happens before the | |
17279 | MX lookup, it does not affect the order that is defined by MX preferences. | |
17280 | ||
17281 | If the local host is present in the sublist obtained from MX records, but is | |
17282 | not the most preferred host in that list, it and any equally or less preferred | |
17283 | hosts are removed before the sublist is inserted into the main list. | |
17284 | ||
17285 | If the local host is the most preferred host in the MX list, what happens | |
17286 | depends on where in the original list of hosts the "/MX" item appears. If it is | |
17287 | not the first item (that is, there are previous hosts in the main list), Exim | |
17288 | discards this name and any subsequent items in the main list. | |
17289 | ||
17290 | If the MX item is first in the list of hosts, and the local host is the most | |
17291 | preferred host, what happens is controlled by the self option of the router. | |
17292 | ||
17293 | DNS failures when lookup up the MX records are treated in the same way as DNS | |
17294 | failures when looking up IP addresses: pass_on_timeout and host_find_failed are | |
17295 | used when relevant. | |
17296 | ||
17297 | The generic ignore_target_hosts option applies to all hosts in the list, | |
17298 | whether obtained from an MX lookup or not. | |
17299 | ||
17300 | ||
17301 | 20.7 How the options are used | |
17302 | ----------------------------- | |
17303 | ||
17304 | The options are a sequence of words; in practice no more than three are ever | |
17305 | present. One of the words can be the name of a transport; this overrides the | |
17306 | transport option on the router for this particular routing rule only. The other | |
17307 | words (if present) control randomization of the list of hosts on a per-rule | |
17308 | basis, and how the IP addresses of the hosts are to be found when routing to a | |
17309 | remote transport. These options are as follows: | |
17310 | ||
17311 | * randomize: randomize the order of the hosts in this list, overriding the | |
17312 | setting of hosts_randomize for this routing rule only. | |
17313 | ||
17314 | * no_randomize: do not randomize the order of the hosts in this list, | |
17315 | overriding the setting of hosts_randomize for this routing rule only. | |
17316 | ||
17317 | * byname: use getipnodebyname() (gethostbyname() on older systems) to find IP | |
17318 | addresses. This function may ultimately cause a DNS lookup, but it may also | |
17319 | look in /etc/hosts or other sources of information. | |
17320 | ||
17321 | * bydns: look up address records for the hosts directly in the DNS; fail if | |
17322 | no address records are found. If there is a temporary DNS error (such as a | |
17323 | timeout), delivery is deferred. | |
17324 | ||
17325 | For example: | |
17326 | ||
17327 | route_list = domain1 host1:host2:host3 randomize bydns;\ | |
17328 | domain2 host4:host5 | |
17329 | ||
17330 | If neither byname nor bydns is given, Exim behaves as follows: First, a DNS | |
17331 | lookup is done. If this yields anything other than HOST_NOT_FOUND, that result | |
17332 | is used. Otherwise, Exim goes on to try a call to getipnodebyname() or | |
17333 | gethostbyname(), and the result of the lookup is the result of that call. | |
17334 | ||
17335 | Warning: It has been discovered that on some systems, if a DNS lookup called | |
17336 | via getipnodebyname() times out, HOST_NOT_FOUND is returned instead of | |
17337 | TRY_AGAIN. That is why the default action is to try a DNS lookup first. Only if | |
17338 | that gives a definite "no such host" is the local function called. | |
17339 | ||
17340 | If no IP address for a host can be found, what happens is controlled by the | |
17341 | host_find_failed option. | |
17342 | ||
17343 | When an address is routed to a local transport, IP addresses are not looked up. | |
17344 | The host list is passed to the transport in the $host variable. | |
17345 | ||
17346 | ||
17347 | 20.8 Manualroute examples | |
17348 | ------------------------- | |
17349 | ||
17350 | In some of the examples that follow, the presence of the remote_smtp transport, | |
17351 | as defined in the default configuration file, is assumed: | |
17352 | ||
17353 | * The manualroute router can be used to forward all external mail to a smart | |
17354 | host. If you have set up, in the main part of the configuration, a named | |
17355 | domain list that contains your local domains, for example: | |
17356 | ||
17357 | domainlist local_domains = my.domain.example | |
17358 | ||
17359 | You can arrange for all other domains to be routed to a smart host by | |
17360 | making your first router something like this: | |
17361 | ||
17362 | smart_route: | |
17363 | driver = manualroute | |
17364 | domains = !+local_domains | |
17365 | transport = remote_smtp | |
17366 | route_list = * smarthost.ref.example | |
17367 | ||
17368 | This causes all non-local addresses to be sent to the single host | |
17369 | smarthost.ref.example. If a colon-separated list of smart hosts is given, | |
17370 | they are tried in order (but you can use hosts_randomize to vary the order | |
17371 | each time). Another way of configuring the same thing is this: | |
17372 | ||
17373 | smart_route: | |
17374 | driver = manualroute | |
17375 | transport = remote_smtp | |
17376 | route_list = !+local_domains smarthost.ref.example | |
17377 | ||
17378 | There is no difference in behaviour between these two routers as they | |
17379 | stand. However, they behave differently if no_more is added to them. In the | |
17380 | first example, the router is skipped if the domain does not match the | |
17381 | domains precondition; the following router is always tried. If the router | |
17382 | runs, it always matches the domain and so can never decline. Therefore, | |
17383 | no_more would have no effect. In the second case, the router is never | |
17384 | skipped; it always runs. However, if it doesn't match the domain, it | |
17385 | declines. In this case no_more would prevent subsequent routers from | |
17386 | running. | |
17387 | ||
17388 | * A mail hub is a host which receives mail for a number of domains via MX | |
17389 | records in the DNS and delivers it via its own private routing mechanism. | |
17390 | Often the final destinations are behind a firewall, with the mail hub being | |
17391 | the one machine that can connect to machines both inside and outside the | |
17392 | firewall. The manualroute router is usually used on a mail hub to route | |
17393 | incoming messages to the correct hosts. For a small number of domains, the | |
17394 | routing can be inline, using the route_list option, but for a larger number | |
17395 | a file or database lookup is easier to manage. | |
17396 | ||
17397 | If the domain names are in fact the names of the machines to which the mail | |
17398 | is to be sent by the mail hub, the configuration can be quite simple. For | |
17399 | example: | |
17400 | ||
17401 | hub_route: | |
17402 | driver = manualroute | |
17403 | transport = remote_smtp | |
17404 | route_list = *.rhodes.tvs.example $domain | |
17405 | ||
17406 | This configuration routes domains that match "*.rhodes.tvs.example" to | |
17407 | hosts whose names are the same as the mail domains. A similar approach can | |
17408 | be taken if the host name can be obtained from the domain name by a string | |
17409 | manipulation that the expansion facilities can handle. Otherwise, a lookup | |
17410 | based on the domain can be used to find the host: | |
17411 | ||
17412 | through_firewall: | |
17413 | driver = manualroute | |
17414 | transport = remote_smtp | |
17415 | route_data = ${lookup {$domain} cdb {/internal/host/routes}} | |
17416 | ||
17417 | The result of the lookup must be the name or IP address of the host (or | |
17418 | hosts) to which the address is to be routed. If the lookup fails, the route | |
17419 | data is empty, causing the router to decline. The address then passes to | |
17420 | the next router. | |
17421 | ||
17422 | * You can use manualroute to deliver messages to pipes or files in batched | |
17423 | SMTP format for onward transportation by some other means. This is one way | |
17424 | of storing mail for a dial-up host when it is not connected. The route list | |
17425 | entry can be as simple as a single domain name in a configuration like | |
17426 | this: | |
17427 | ||
17428 | save_in_file: | |
17429 | driver = manualroute | |
17430 | transport = batchsmtp_appendfile | |
17431 | route_list = saved.domain.example | |
17432 | ||
17433 | though often a pattern is used to pick up more than one domain. If there | |
17434 | are several domains or groups of domains with different transport | |
17435 | requirements, different transports can be listed in the routing | |
17436 | information: | |
17437 | ||
17438 | save_in_file: | |
17439 | driver = manualroute | |
17440 | route_list = \ | |
17441 | *.saved.domain1.example $domain batch_appendfile; \ | |
17442 | *.saved.domain2.example \ | |
17443 | ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \ | |
17444 | batch_pipe | |
17445 | ||
17446 | The first of these just passes the domain in the $host variable, which | |
17447 | doesn't achieve much (since it is also in $domain), but the second does a | |
17448 | file lookup to find a value to pass, causing the router to decline to | |
17449 | handle the address if the lookup fails. | |
17450 | ||
17451 | * Routing mail directly to UUCP software is a specific case of the use of | |
17452 | manualroute in a gateway to another mail environment. This is an example of | |
17453 | one way it can be done: | |
17454 | ||
17455 | # Transport | |
17456 | uucp: | |
17457 | driver = pipe | |
17458 | user = nobody | |
17459 | command = /usr/local/bin/uux -r - \ | |
17460 | ${substr_-5:$host}!rmail ${local_part} | |
17461 | return_fail_output = true | |
17462 | ||
17463 | # Router | |
17464 | uucphost: | |
17465 | transport = uucp | |
17466 | driver = manualroute | |
17467 | route_data = \ | |
17468 | ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}} | |
17469 | ||
17470 | The file /usr/local/exim/uucphosts contains entries like | |
17471 | ||
17472 | darksite.ethereal.example: darksite.UUCP | |
17473 | ||
17474 | It can be set up more simply without adding and removing ".UUCP" but this | |
17475 | way makes clear the distinction between the domain name | |
17476 | darksite.ethereal.example and the UUCP host name darksite. | |
17477 | ||
17478 | ||
17479 | ||
17480 | =============================================================================== | |
17481 | 21. THE QUERYPROGRAM ROUTER | |
17482 | ||
17483 | The queryprogram router routes an address by running an external command and | |
17484 | acting on its output. This is an expensive way to route, and is intended mainly | |
17485 | for use in lightly-loaded systems, or for performing experiments. However, if | |
17486 | it is possible to use the precondition options (domains, local_parts, etc) to | |
17487 | skip this router for most addresses, it could sensibly be used in special | |
17488 | cases, even on a busy host. There are the following private options: | |
17489 | ||
17490 | +-------+-----------------+-------------+--------------+ | |
17491 | |command|Use: queryprogram|Type: string*|Default: unset| | |
17492 | +-------+-----------------+-------------+--------------+ | |
17493 | ||
17494 | This option must be set. It specifies the command that is to be run. The | |
17495 | command is split up into a command name and arguments, and then each is | |
17496 | expanded separately (exactly as for a pipe transport, described in chapter 29). | |
17497 | ||
17498 | +-------------+-----------------+------------+--------------+ | |
17499 | |command_group|Use: queryprogram|Type: string|Default: unset| | |
17500 | +-------------+-----------------+------------+--------------+ | |
17501 | ||
17502 | This option specifies a gid to be set when running the command while routing an | |
17503 | address for deliver. It must be set if command_user specifies a numerical uid. | |
17504 | If it begins with a digit, it is interpreted as the numerical value of the gid. | |
17505 | Otherwise it is looked up using getgrnam(). | |
17506 | ||
17507 | +------------+-----------------+------------+--------------+ | |
17508 | |command_user|Use: queryprogram|Type: string|Default: unset| | |
17509 | +------------+-----------------+------------+--------------+ | |
17510 | ||
17511 | This option must be set. It specifies the uid which is set when running the | |
17512 | command while routing an address for delivery. If the value begins with a | |
17513 | digit, it is interpreted as the numerical value of the uid. Otherwise, it is | |
17514 | looked up using getpwnam() to obtain a value for the uid and, if command_group | |
17515 | is not set, a value for the gid also. | |
17516 | ||
17517 | Warning: Changing uid and gid is possible only when Exim is running as root, | |
17518 | which it does during a normal delivery in a conventional configuration. | |
17519 | However, when an address is being verified during message reception, Exim is | |
17520 | usually running as the Exim user, not as root. If the queryprogram router is | |
17521 | called from a non-root process, Exim cannot change uid or gid before running | |
17522 | the command. In this circumstance the command runs under the current uid and | |
17523 | gid. | |
17524 | ||
17525 | +-----------------+-----------------+------------+----------+ | |
17526 | |current_directory|Use: queryprogram|Type: string|Default: /| | |
17527 | +-----------------+-----------------+------------+----------+ | |
17528 | ||
17529 | This option specifies an absolute path which is made the current directory | |
17530 | before running the command. | |
17531 | ||
17532 | +-------+-----------------+----------+-----------+ | |
17533 | |timeout|Use: queryprogram|Type: time|Default: 1h| | |
17534 | +-------+-----------------+----------+-----------+ | |
17535 | ||
17536 | If the command does not complete within the timeout period, its process group | |
17537 | is killed and the message is frozen. A value of zero time specifies no timeout. | |
17538 | ||
17539 | The standard output of the command is connected to a pipe, which is read when | |
17540 | the command terminates. It should consist of a single line of output, | |
17541 | containing up to five fields, separated by white space. The maximum length of | |
17542 | the line is 1023 characters. Longer lines are silently truncated. The first | |
17543 | field is one of the following words (case-insensitive): | |
17544 | ||
17545 | * Accept: routing succeeded; the remaining fields specify what to do (see | |
17546 | below). | |
17547 | ||
17548 | * Decline: the router declines; pass the address to the next router, unless | |
17549 | no_more is set. | |
17550 | ||
17551 | * Fail: routing failed; do not pass the address to any more routers. Any | |
17552 | subsequent text on the line is an error message. If the router is run as | |
17553 | part of address verification during an incoming SMTP message, the message | |
17554 | is included in the SMTP response. | |
17555 | ||
17556 | * Defer: routing could not be completed at this time; try again later. Any | |
17557 | subsequent text on the line is an error message which is logged. It is not | |
17558 | included in any SMTP response. | |
17559 | ||
17560 | * Freeze: the same as defer, except that the message is frozen. | |
17561 | ||
17562 | * Pass: pass the address to the next router (or the router specified by | |
17563 | pass_router), overriding no_more. | |
17564 | ||
17565 | * Redirect: the message is redirected. The remainder of the line is a list of | |
17566 | new addresses, which are routed independently, starting with the first | |
17567 | router, or the router specified by redirect_router, if set. | |
17568 | ||
17569 | When the first word is accept, the remainder of the line consists of a number | |
17570 | of keyed data values, as follows (split into two lines here, to fit on the | |
17571 | page): | |
17572 | ||
17573 | ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts> | |
17574 | LOOKUP=byname|bydns DATA=<text> | |
17575 | ||
17576 | The data items can be given in any order, and all are optional. If no transport | |
17577 | is included, the transport specified by the generic transport option is used. | |
17578 | The list of hosts and the lookup type are needed only if the transport is an | |
17579 | smtp transport that does not itself supply a list of hosts. | |
17580 | ||
17581 | The format of the list of hosts is the same as for the manualroute router. As | |
17582 | well as host names and IP addresses with optional port numbers, as described in | |
17583 | section 20.5, it may contain names followed by "/MX" to specify sublists of | |
17584 | hosts that are obtained by looking up MX records (see section 20.6). | |
17585 | ||
17586 | If the lookup type is not specified, Exim behaves as follows when trying to | |
17587 | find an IP address for each host: First, a DNS lookup is done. If this yields | |
17588 | anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim goes | |
17589 | on to try a call to getipnodebyname() or gethostbyname(), and the result of the | |
17590 | lookup is the result of that call. | |
17591 | ||
17592 | If the DATA field is set, its value is placed in the $address_data variable. | |
17593 | For example, this return line | |
17594 | ||
17595 | accept hosts=x1.y.example:x2.y.example data="rule1" | |
17596 | ||
17597 | routes the address to the default transport, passing a list of two hosts. When | |
17598 | the transport runs, the string "rule1" is in $address_data. | |
17599 | ||
17600 | ||
17601 | ||
17602 | =============================================================================== | |
17603 | 22. THE REDIRECT ROUTER | |
17604 | ||
17605 | The redirect router handles several kinds of address redirection. Its most | |
17606 | common uses are for resolving local part aliases from a central alias file | |
17607 | (usually called /etc/aliases) and for handling users' personal .forward files, | |
17608 | but it has many other potential uses. The incoming address can be redirected in | |
17609 | several different ways: | |
17610 | ||
17611 | * It can be replaced by one or more new addresses which are themselves routed | |
17612 | independently. | |
17613 | ||
17614 | * It can be routed to be delivered to a given file or directory. | |
17615 | ||
17616 | * It can be routed to be delivered to a specified pipe command. | |
17617 | ||
17618 | * It can cause an automatic reply to be generated. | |
17619 | ||
17620 | * It can be forced to fail, optionally with a custom error message. | |
17621 | ||
17622 | * It can be temporarily deferred, optionally with a custom message. | |
17623 | ||
17624 | * It can be discarded. | |
17625 | ||
17626 | The generic transport option must not be set for redirect routers. However, | |
17627 | there are some private options which define transports for delivery to files | |
17628 | and pipes, and for generating autoreplies. See the file_transport, | |
17629 | pipe_transport and reply_transport descriptions below. | |
17630 | ||
17631 | ||
17632 | 22.1 Redirection data | |
17633 | --------------------- | |
17634 | ||
17635 | The router operates by interpreting a text string which it obtains either by | |
17636 | expanding the contents of the data option, or by reading the entire contents of | |
17637 | a file whose name is given in the file option. These two options are mutually | |
17638 | exclusive. The first is commonly used for handling system aliases, in a | |
17639 | configuration like this: | |
17640 | ||
17641 | system_aliases: | |
17642 | driver = redirect | |
17643 | data = ${lookup{$local_part}lsearch{/etc/aliases}} | |
17644 | ||
17645 | If the lookup fails, the expanded string in this example is empty. When the | |
17646 | expansion of data results in an empty string, the router declines. A forced | |
17647 | expansion failure also causes the router to decline; other expansion failures | |
17648 | cause delivery to be deferred. | |
17649 | ||
17650 | A configuration using file is commonly used for handling users' .forward files, | |
17651 | like this: | |
17652 | ||
17653 | userforward: | |
17654 | driver = redirect | |
17655 | check_local_user | |
17656 | file = $home/.forward | |
17657 | no_verify | |
17658 | ||
17659 | If the file does not exist, or causes no action to be taken (for example, it is | |
17660 | empty or consists only of comments), the router declines. Warning: This is not | |
17661 | the case when the file contains syntactically valid items that happen to yield | |
17662 | empty addresses, for example, items containing only RFC 2822 address comments. | |
17663 | ||
17664 | ||
17665 | 22.2 Forward files and address verification | |
17666 | ------------------------------------------- | |
17667 | ||
17668 | It is usual to set no_verify on redirect routers which handle users' .forward | |
17669 | files, as in the example above. There are two reasons for this: | |
17670 | ||
17671 | * When Exim is receiving an incoming SMTP message from a remote host, it is | |
17672 | running under the Exim uid, not as root. Exim is unable to change uid to | |
17673 | read the file as the user, and it may not be able to read it as the Exim | |
17674 | user. So in practice the router may not be able to operate. | |
17675 | ||
17676 | * However, even when the router can operate, the existence of a .forward file | |
17677 | is unimportant when verifying an address. What should be checked is whether | |
17678 | the local part is a valid user name or not. Cutting out the redirection | |
17679 | processing saves some resources. | |
17680 | ||
17681 | ||
17682 | 22.3 Interpreting redirection data | |
17683 | ---------------------------------- | |
17684 | ||
17685 | The contents of the data string, whether obtained from data or file, can be | |
17686 | interpreted in two different ways: | |
17687 | ||
17688 | * If the allow_filter option is set true, and the data begins with the text " | |
17689 | #Exim filter" or "#Sieve filter", it is interpreted as a list of filtering | |
17690 | instructions in the form of an Exim or Sieve filter file, respectively. | |
17691 | Details of the syntax and semantics of filter files are described in a | |
17692 | separate document entitled Exim's interfaces to mail filtering; this | |
17693 | document is intended for use by end users. | |
17694 | ||
17695 | * Otherwise, the data must be a comma-separated list of redirection items, as | |
17696 | described in the next section. | |
17697 | ||
17698 | When a message is redirected to a file (a "mail folder"), the file name given | |
17699 | in a non-filter redirection list must always be an absolute path. A filter may | |
17700 | generate a relative path - how this is handled depends on the transport's | |
17701 | configuration. See section 26.1 for a discussion of this issue for the | |
17702 | appendfile transport. | |
17703 | ||
17704 | ||
17705 | 22.4 Items in a non-filter redirection list | |
17706 | ------------------------------------------- | |
17707 | ||
17708 | When the redirection data is not an Exim or Sieve filter, for example, if it | |
17709 | comes from a conventional alias or forward file, it consists of a list of | |
17710 | addresses, file names, pipe commands, or certain special items (see section | |
17711 | 22.6 below). The special items can be individually enabled or disabled by means | |
17712 | of options whose names begin with allow_ or forbid_, depending on their default | |
17713 | values. The items in the list are separated by commas or newlines. If a comma | |
17714 | is required in an item, the entire item must be enclosed in double quotes. | |
17715 | ||
17716 | Lines starting with a # character are comments, and are ignored, and # may also | |
17717 | appear following a comma, in which case everything between the # and the next | |
17718 | newline character is ignored. | |
17719 | ||
17720 | If an item is entirely enclosed in double quotes, these are removed. Otherwise | |
17721 | double quotes are retained because some forms of mail address require their use | |
17722 | (but never to enclose the entire address). In the following description, "item" | |
17723 | refers to what remains after any surrounding double quotes have been removed. | |
17724 | ||
17725 | Warning: If you use an Exim expansion to construct a redirection address, and | |
17726 | the expansion contains a reference to $local_part, you should make use of the | |
17727 | quote_local_part expansion operator, in case the local part contains special | |
17728 | characters. For example, to redirect all mail for the domain obsolete.example, | |
17729 | retaining the existing local part, you could use this setting: | |
17730 | ||
17731 | data = ${quote_local_part:$local_part}@newdomain.example | |
17732 | ||
17733 | ||
17734 | 22.5 Redirecting to a local mailbox | |
17735 | ----------------------------------- | |
17736 | ||
17737 | A redirection item may safely be the same as the address currently under | |
17738 | consideration. This does not cause a routing loop, because a router is | |
17739 | automatically skipped if any ancestor of the address that is being processed is | |
17740 | the same as the current address and was processed by the current router. Such | |
17741 | an address is therefore passed to the following routers, so it is handled as if | |
17742 | there were no redirection. When making this loop-avoidance test, the complete | |
17743 | local part, including any prefix or suffix, is used. | |
17744 | ||
17745 | Specifying the same local part without a domain is a common usage in personal | |
17746 | filter files when the user wants to have messages delivered to the local | |
17747 | mailbox and also forwarded elsewhere. For example, the user whose login is cleo | |
17748 | might have a .forward file containing this: | |
17749 | ||
17750 | cleo, cleopatra@egypt.example | |
17751 | ||
17752 | For compatibility with other MTAs, such unqualified local parts may be preceded | |
17753 | by "\", but this is not a requirement for loop prevention. However, it does | |
17754 | make a difference if more than one domain is being handled synonymously. | |
17755 | ||
17756 | If an item begins with "\" and the rest of the item parses as a valid RFC 2822 | |
17757 | address that does not include a domain, the item is qualified using the domain | |
17758 | of the incoming address. In the absence of a leading "\", unqualified addresses | |
17759 | are qualified using the value in qualify_recipient, but you can force the | |
17760 | incoming domain to be used by setting qualify_preserve_domain. | |
17761 | ||
17762 | Care must be taken if there are alias names for local users. Consider an MTA | |
17763 | handling a single local domain where the system alias file contains: | |
17764 | ||
17765 | Sam.Reman: spqr | |
17766 | ||
17767 | Now suppose that Sam (whose login id is spqr) wants to save copies of messages | |
17768 | in the local mailbox, and also forward copies elsewhere. He creates this | |
17769 | forward file: | |
17770 | ||
17771 | Sam.Reman, spqr@reme.elsewhere.example | |
17772 | ||
17773 | With these settings, an incoming message addressed to Sam.Reman fails. The | |
17774 | redirect router for system aliases does not process Sam.Reman the second time | |
17775 | round, because it has previously routed it, and the following routers | |
17776 | presumably cannot handle the alias. The forward file should really contain | |
17777 | ||
17778 | spqr, spqr@reme.elsewhere.example | |
17779 | ||
17780 | but because this is such a common error, the check_ancestor option (see below) | |
17781 | exists to provide a way to get round it. This is normally set on a redirect | |
17782 | router that is handling users' .forward files. | |
17783 | ||
17784 | ||
17785 | 22.6 Special items in redirection lists | |
17786 | --------------------------------------- | |
17787 | ||
17788 | In addition to addresses, the following types of item may appear in redirection | |
17789 | lists (that is, in non-filter redirection data): | |
17790 | ||
17791 | * An item is treated as a pipe command if it begins with "|" and does not | |
17792 | parse as a valid RFC 2822 address that includes a domain. A transport for | |
17793 | running the command must be specified by the pipe_transport option. | |
17794 | Normally, either the router or the transport specifies a user and a group | |
17795 | under which to run the delivery. The default is to use the Exim user and | |
17796 | group. | |
17797 | ||
17798 | Single or double quotes can be used for enclosing the individual arguments | |
17799 | of the pipe command; no interpretation of escapes is done for single | |
17800 | quotes. If the command contains a comma character, it is necessary to put | |
17801 | the whole item in double quotes, for example: | |
17802 | ||
17803 | "|/some/command ready,steady,go" | |
17804 | ||
17805 | since items in redirection lists are terminated by commas. Do not, however, | |
17806 | quote just the command. An item such as | |
17807 | ||
17808 | |"/some/command ready,steady,go" | |
17809 | ||
17810 | is interpreted as a pipe with a rather strange command name, and no | |
17811 | arguments. | |
17812 | ||
17813 | Note that the above example assumes that the text comes from a lookup | |
17814 | source of some sort, so that the quotes are part of the data. If composing | |
17815 | a redirect router with a data option directly specifying this command, the | |
17816 | quotes will be used by the configuration parser to define the extent of one | |
17817 | string, but will not be passed down into the redirect router itself. There | |
17818 | are two main approaches to get around this: escape quotes to be part of the | |
17819 | data itself, or avoid using this mechanism and instead create a custom | |
17820 | transport with the command option set and reference that transport from an | |
17821 | accept router. | |
17822 | ||
17823 | * An item is interpreted as a path name if it begins with "/" and does not | |
17824 | parse as a valid RFC 2822 address that includes a domain. For example, | |
17825 | ||
17826 | /home/world/minbari | |
17827 | ||
17828 | is treated as a file name, but | |
17829 | ||
17830 | /s=molari/o=babylon/@x400gate.way | |
17831 | ||
17832 | is treated as an address. For a file name, a transport must be specified | |
17833 | using the file_transport option. However, if the generated path name ends | |
17834 | with a forward slash character, it is interpreted as a directory name | |
17835 | rather than a file name, and directory_transport is used instead. | |
17836 | ||
17837 | Normally, either the router or the transport specifies a user and a group | |
17838 | under which to run the delivery. The default is to use the Exim user and | |
17839 | group. | |
17840 | ||
17841 | However, if a redirection item is the path /dev/null, delivery to it is | |
17842 | bypassed at a high level, and the log entry shows "**bypassed**" instead of | |
17843 | a transport name. In this case the user and group are not used. | |
17844 | ||
17845 | * If an item is of the form | |
17846 | ||
17847 | :include:<path name> | |
17848 | ||
17849 | a list of further items is taken from the given file and included at that | |
17850 | point. Note: Such a file can not be a filter file; it is just an | |
17851 | out-of-line addition to the list. The items in the included list are | |
17852 | separated by commas or newlines and are not subject to expansion. If this | |
17853 | is the first item in an alias list in an lsearch file, a colon must be used | |
17854 | to terminate the alias name. This example is incorrect: | |
17855 | ||
17856 | list1 :include:/opt/lists/list1 | |
17857 | ||
17858 | It must be given as | |
17859 | ||
17860 | list1: :include:/opt/lists/list1 | |
17861 | ||
17862 | * Sometimes you want to throw away mail to a particular local part. Making | |
17863 | the data option expand to an empty string does not work, because that | |
17864 | causes the router to decline. Instead, the alias item :blackhole: can be | |
17865 | used. It does what its name implies. No delivery is done, and no error | |
17866 | message is generated. This has the same effect as specifing /dev/null as a | |
17867 | destination, but it can be independently disabled. | |
17868 | ||
17869 | Warning: If :blackhole: appears anywhere in a redirection list, no delivery | |
17870 | is done for the original local part, even if other redirection items are | |
17871 | present. If you are generating a multi-item list (for example, by reading a | |
17872 | database) and need the ability to provide a no-op item, you must use /dev/ | |
17873 | null. | |
17874 | ||
17875 | * An attempt to deliver a particular address can be deferred or forced to | |
17876 | fail by redirection items of the form | |
17877 | ||
17878 | :defer: | |
17879 | :fail: | |
17880 | ||
17881 | respectively. When a redirection list contains such an item, it applies to | |
17882 | the entire redirection; any other items in the list are ignored. Any text | |
17883 | following :fail: or :defer: is placed in the error text associated with the | |
17884 | failure. For example, an alias file might contain: | |
17885 | ||
17886 | X.Employee: :fail: Gone away, no forwarding address | |
17887 | ||
17888 | In the case of an address that is being verified from an ACL or as the | |
17889 | subject of a VRFY command, the text is included in the SMTP error response | |
17890 | by default. The text is not included in the response to an EXPN command. In | |
17891 | non-SMTP cases the text is included in the error message that Exim | |
17892 | generates. | |
17893 | ||
17894 | By default, Exim sends a 451 SMTP code for a :defer:, and 550 for :fail:. | |
17895 | However, if the message starts with three digits followed by a space, | |
17896 | optionally followed by an extended code of the form n.n.n, also followed by | |
17897 | a space, and the very first digit is the same as the default error code, | |
17898 | the code from the message is used instead. If the very first digit is | |
17899 | incorrect, a panic error is logged, and the default code is used. You can | |
17900 | suppress the use of the supplied code in a redirect router by setting the | |
17901 | forbid_smtp_code option true. In this case, any SMTP code is quietly | |
17902 | ignored. | |
17903 | ||
17904 | In an ACL, an explicitly provided message overrides the default, but the | |
17905 | default message is available in the variable $acl_verify_message and can | |
17906 | therefore be included in a custom message if this is desired. | |
17907 | ||
17908 | Normally the error text is the rest of the redirection list - a comma does | |
17909 | not terminate it - but a newline does act as a terminator. Newlines are not | |
17910 | normally present in alias expansions. In lsearch lookups they are removed | |
17911 | as part of the continuation process, but they may exist in other kinds of | |
17912 | lookup and in :include: files. | |
17913 | ||
17914 | During routing for message delivery (as opposed to verification), a | |
17915 | redirection containing :fail: causes an immediate failure of the incoming | |
17916 | address, whereas :defer: causes the message to remain on the queue so that | |
17917 | a subsequent delivery attempt can happen at a later time. If an address is | |
17918 | deferred for too long, it will ultimately fail, because the normal retry | |
17919 | rules still apply. | |
17920 | ||
17921 | * Sometimes it is useful to use a single-key search type with a default (see | |
17922 | chapter 9) to look up aliases. However, there may be a need for exceptions | |
17923 | to the default. These can be handled by aliasing them to :unknown:. This | |
17924 | differs from :fail: in that it causes the redirect router to decline, | |
17925 | whereas :fail: forces routing to fail. A lookup which results in an empty | |
17926 | redirection list has the same effect. | |
17927 | ||
17928 | ||
17929 | 22.7 Duplicate addresses | |
17930 | ------------------------ | |
17931 | ||
17932 | Exim removes duplicate addresses from the list to which it is delivering, so as | |
17933 | to deliver just one copy to each address. This does not apply to deliveries | |
17934 | routed to pipes by different immediate parent addresses, but an indirect | |
17935 | aliasing scheme of the type | |
17936 | ||
17937 | pipe: |/some/command $local_part | |
17938 | localpart1: pipe | |
17939 | localpart2: pipe | |
17940 | ||
17941 | does not work with a message that is addressed to both local parts, because | |
17942 | when the second is aliased to the intermediate local part "pipe" it gets | |
17943 | discarded as being the same as a previously handled address. However, a scheme | |
17944 | such as | |
17945 | ||
17946 | localpart1: |/some/command $local_part | |
17947 | localpart2: |/some/command $local_part | |
17948 | ||
17949 | does result in two different pipe deliveries, because the immediate parents of | |
17950 | the pipes are distinct. | |
17951 | ||
17952 | ||
17953 | 22.8 Repeated redirection expansion | |
17954 | ----------------------------------- | |
17955 | ||
17956 | When a message cannot be delivered to all of its recipients immediately, | |
17957 | leading to two or more delivery attempts, redirection expansion is carried out | |
17958 | afresh each time for those addresses whose children were not all previously | |
17959 | delivered. If redirection is being used as a mailing list, this can lead to new | |
17960 | members of the list receiving copies of old messages. The one_time option can | |
17961 | be used to avoid this. | |
17962 | ||
17963 | ||
17964 | 22.9 Errors in redirection lists | |
17965 | -------------------------------- | |
17966 | ||
17967 | If skip_syntax_errors is set, a malformed address that causes a parsing error | |
17968 | is skipped, and an entry is written to the main log. This may be useful for | |
17969 | mailing lists that are automatically managed. Otherwise, if an error is | |
17970 | detected while generating the list of new addresses, the original address is | |
17971 | deferred. See also syntax_errors_to. | |
17972 | ||
17973 | ||
17974 | 22.10 Private options for the redirect router | |
17975 | --------------------------------------------- | |
17976 | ||
17977 | The private options for the redirect router are as follows: | |
17978 | ||
17979 | +-----------+-------------+-------------+--------------+ | |
17980 | |allow_defer|Use: redirect|Type: boolean|Default: false| | |
17981 | +-----------+-------------+-------------+--------------+ | |
17982 | ||
17983 | Setting this option allows the use of :defer: in non-filter redirection data, | |
17984 | or the defer command in an Exim filter file. | |
17985 | ||
17986 | +----------+-------------+-------------+--------------+ | |
17987 | |allow_fail|Use: redirect|Type: boolean|Default: false| | |
17988 | +----------+-------------+-------------+--------------+ | |
17989 | ||
17990 | If this option is true, the :fail: item can be used in a redirection list, and | |
17991 | the fail command may be used in an Exim filter file. | |
17992 | ||
17993 | +------------+-------------+-------------+--------------+ | |
17994 | |allow_filter|Use: redirect|Type: boolean|Default: false| | |
17995 | +------------+-------------+-------------+--------------+ | |
17996 | ||
17997 | Setting this option allows Exim to interpret redirection data that starts with | |
17998 | "#Exim filter" or "#Sieve filter" as a set of filtering instructions. There are | |
17999 | some features of Exim filter files that some administrators may wish to lock | |
18000 | out; see the forbid_filter_xxx options below. | |
18001 | ||
18002 | It is also possible to lock out Exim filters or Sieve filters while allowing | |
18003 | the other type; see forbid_exim_filter and forbid_sieve_filter. | |
18004 | ||
18005 | The filter is run using the uid and gid set by the generic user and group | |
18006 | options. These take their defaults from the password data if check_local_user | |
18007 | is set, so in the normal case of users' personal filter files, the filter is | |
18008 | run as the relevant user. When allow_filter is set true, Exim insists that | |
18009 | either check_local_user or user is set. | |
18010 | ||
18011 | +------------+-------------+-------------+--------------+ | |
18012 | |allow_freeze|Use: redirect|Type: boolean|Default: false| | |
18013 | +------------+-------------+-------------+--------------+ | |
18014 | ||
18015 | Setting this option allows the use of the freeze command in an Exim filter. | |
18016 | This command is more normally encountered in system filters, and is disabled by | |
18017 | default for redirection filters because it isn't something you usually want to | |
18018 | let ordinary users do. | |
18019 | ||
18020 | +--------------+-------------+-------------+--------------+ | |
18021 | |check_ancestor|Use: redirect|Type: boolean|Default: false| | |
18022 | +--------------+-------------+-------------+--------------+ | |
18023 | ||
18024 | This option is concerned with handling generated addresses that are the same as | |
18025 | some address in the list of redirection ancestors of the current address. | |
18026 | Although it is turned off by default in the code, it is set in the default | |
18027 | configuration file for handling users' .forward files. It is recommended for | |
18028 | this use of the redirect router. | |
18029 | ||
18030 | When check_ancestor is set, if a generated address (including the domain) is | |
18031 | the same as any ancestor of the current address, it is replaced by a copy of | |
18032 | the current address. This helps in the case where local part A is aliased to B, | |
18033 | and B has a .forward file pointing back to A. For example, within a single | |
18034 | domain, the local part "Joe.Bloggs" is aliased to "jb" and jb/.forward | |
18035 | contains: | |
18036 | ||
18037 | \Joe.Bloggs, <other item(s)> | |
18038 | ||
18039 | Without the check_ancestor setting, either local part ("jb" or "joe.bloggs") | |
18040 | gets processed once by each router and so ends up as it was originally. If "jb" | |
18041 | is the real mailbox name, mail to "jb" gets delivered (having been turned into | |
18042 | "joe.bloggs" by the .forward file and back to "jb" by the alias), but mail to | |
18043 | "joe.bloggs" fails. Setting check_ancestor on the redirect router that handles | |
18044 | the .forward file prevents it from turning "jb" back into "joe.bloggs" when | |
18045 | that was the original address. See also the repeat_use option below. | |
18046 | ||
18047 | +-----------+-------------+-------------+------------------+ | |
18048 | |check_group|Use: redirect|Type: boolean|Default: see below| | |
18049 | +-----------+-------------+-------------+------------------+ | |
18050 | ||
18051 | When the file option is used, the group owner of the file is checked only when | |
18052 | this option is set. The permitted groups are those listed in the owngroups | |
18053 | option, together with the user's default group if check_local_user is set. If | |
18054 | the file has the wrong group, routing is deferred. The default setting for this | |
18055 | option is true if check_local_user is set and the modemask option permits the | |
18056 | group write bit, or if the owngroups option is set. Otherwise it is false, and | |
18057 | no group check occurs. | |
18058 | ||
18059 | +-----------+-------------+-------------+------------------+ | |
18060 | |check_owner|Use: redirect|Type: boolean|Default: see below| | |
18061 | +-----------+-------------+-------------+------------------+ | |
18062 | ||
18063 | When the file option is used, the owner of the file is checked only when this | |
18064 | option is set. If check_local_user is set, the local user is permitted; | |
18065 | otherwise the owner must be one of those listed in the owners option. The | |
18066 | default value for this option is true if check_local_user or owners is set. | |
18067 | Otherwise the default is false, and no owner check occurs. | |
18068 | ||
18069 | +----+-------------+-------------+--------------+ | |
18070 | |data|Use: redirect|Type: string*|Default: unset| | |
18071 | +----+-------------+-------------+--------------+ | |
18072 | ||
18073 | This option is mutually exclusive with file. One or other of them must be set, | |
18074 | but not both. The contents of data are expanded, and then used as the list of | |
18075 | forwarding items, or as a set of filtering instructions. If the expansion is | |
18076 | forced to fail, or the result is an empty string or a string that has no effect | |
18077 | (consists entirely of comments), the router declines. | |
18078 | ||
18079 | When filtering instructions are used, the string must begin with "#Exim | |
18080 | filter", and all comments in the string, including this initial one, must be | |
18081 | terminated with newline characters. For example: | |
18082 | ||
18083 | data = #Exim filter\n\ | |
18084 | if $h_to: contains Exim then save $home/mail/exim endif | |
18085 | ||
18086 | If you are reading the data from a database where newlines cannot be included, | |
18087 | you can use the ${sg} expansion item to turn the escape string of your choice | |
18088 | into a newline. | |
18089 | ||
18090 | +-------------------+-------------+-------------+--------------+ | |
18091 | |directory_transport|Use: redirect|Type: string*|Default: unset| | |
18092 | +-------------------+-------------+-------------+--------------+ | |
18093 | ||
18094 | A redirect router sets up a direct delivery to a directory when a path name | |
18095 | ending with a slash is specified as a new "address". The transport used is | |
18096 | specified by this option, which, after expansion, must be the name of a | |
18097 | configured transport. This should normally be an appendfile transport. | |
18098 | ||
18099 | +----+-------------+-------------+--------------+ | |
18100 | |file|Use: redirect|Type: string*|Default: unset| | |
18101 | +----+-------------+-------------+--------------+ | |
18102 | ||
18103 | This option specifies the name of a file that contains the redirection data. It | |
18104 | is mutually exclusive with the data option. The string is expanded before use; | |
18105 | if the expansion is forced to fail, the router declines. Other expansion | |
18106 | failures cause delivery to be deferred. The result of a successful expansion | |
18107 | must be an absolute path. The entire file is read and used as the redirection | |
18108 | data. If the data is an empty string or a string that has no effect (consists | |
18109 | entirely of comments), the router declines. | |
18110 | ||
18111 | If the attempt to open the file fails with a "does not exist" error, Exim runs | |
18112 | a check on the containing directory, unless ignore_enotdir is true (see below). | |
18113 | If the directory does not appear to exist, delivery is deferred. This can | |
18114 | happen when users' .forward files are in NFS-mounted directories, and there is | |
18115 | a mount problem. If the containing directory does exist, but the file does not, | |
18116 | the router declines. | |
18117 | ||
18118 | +--------------+-------------+-------------+--------------+ | |
18119 | |file_transport|Use: redirect|Type: string*|Default: unset| | |
18120 | +--------------+-------------+-------------+--------------+ | |
18121 | ||
18122 | A redirect router sets up a direct delivery to a file when a path name not | |
18123 | ending in a slash is specified as a new "address". The transport used is | |
18124 | specified by this option, which, after expansion, must be the name of a | |
18125 | configured transport. This should normally be an appendfile transport. When it | |
18126 | is running, the file name is in $address_file. | |
18127 | ||
18128 | +-------------------+-------------+-------------+-------------+ | |
18129 | |filter_prepend_home|Use: redirect|Type: boolean|Default: true| | |
18130 | +-------------------+-------------+-------------+-------------+ | |
18131 | ||
18132 | When this option is true, if a save command in an Exim filter specifies a | |
18133 | relative path, and $home is defined, it is automatically prepended to the | |
18134 | relative path. If this option is set false, this action does not happen. The | |
18135 | relative path is then passed to the transport unmodified. | |
18136 | ||
18137 | +----------------+-------------+-------------+--------------+ | |
18138 | |forbid_blackhole|Use: redirect|Type: boolean|Default: false| | |
18139 | +----------------+-------------+-------------+--------------+ | |
18140 | ||
18141 | If this option is true, the :blackhole: item may not appear in a redirection | |
18142 | list. | |
18143 | ||
18144 | +------------------+-------------+-------------+--------------+ | |
18145 | |forbid_exim_filter|Use: redirect|Type: boolean|Default: false| | |
18146 | +------------------+-------------+-------------+--------------+ | |
18147 | ||
18148 | If this option is set true, only Sieve filters are permitted when allow_filter | |
18149 | is true. | |
18150 | ||
18151 | +-----------+-------------+-------------+--------------+ | |
18152 | |forbid_file|Use: redirect|Type: boolean|Default: false| | |
18153 | +-----------+-------------+-------------+--------------+ | |
18154 | ||
18155 | If this option is true, this router may not generate a new address that | |
18156 | specifies delivery to a local file or directory, either from a filter or from a | |
18157 | conventional forward file. This option is forced to be true if one_time is set. | |
18158 | It applies to Sieve filters as well as to Exim filters, but if true, it locks | |
18159 | out the Sieve's "keep" facility. | |
18160 | ||
18161 | +--------------------+-------------+-------------+--------------+ | |
18162 | |forbid_filter_dlfunc|Use: redirect|Type: boolean|Default: false| | |
18163 | +--------------------+-------------+-------------+--------------+ | |
18164 | ||
18165 | If this option is true, string expansions in Exim filters are not allowed to | |
18166 | make use of the dlfunc expansion facility to run dynamically loaded functions. | |
18167 | ||
18168 | +------------------------+-------------+-------------+--------------+ | |
18169 | |forbid_filter_existstest|Use: redirect|Type: boolean|Default: false| | |
18170 | +------------------------+-------------+-------------+--------------+ | |
18171 | ||
18172 | If this option is true, string expansions in Exim filters are not allowed to | |
18173 | make use of the exists condition or the stat expansion item. | |
18174 | ||
18175 | +----------------------+-------------+-------------+--------------+ | |
18176 | |forbid_filter_logwrite|Use: redirect|Type: boolean|Default: false| | |
18177 | +----------------------+-------------+-------------+--------------+ | |
18178 | ||
18179 | If this option is true, use of the logging facility in Exim filters is not | |
18180 | permitted. Logging is in any case available only if the filter is being run | |
18181 | under some unprivileged uid (which is normally the case for ordinary users' | |
18182 | .forward files). | |
18183 | ||
18184 | +--------------------+-------------+-------------+--------------+ | |
18185 | |forbid_filter_lookup|Use: redirect|Type: boolean|Default: false| | |
18186 | +--------------------+-------------+-------------+--------------+ | |
18187 | ||
18188 | If this option is true, string expansions in Exim filter files are not allowed | |
18189 | to make use of lookup items. | |
18190 | ||
18191 | +------------------+-------------+-------------+--------------+ | |
18192 | |forbid_filter_perl|Use: redirect|Type: boolean|Default: false| | |
18193 | +------------------+-------------+-------------+--------------+ | |
18194 | ||
18195 | This option has an effect only if Exim is built with embedded Perl support. If | |
18196 | it is true, string expansions in Exim filter files are not allowed to make use | |
18197 | of the embedded Perl support. | |
18198 | ||
18199 | +----------------------+-------------+-------------+--------------+ | |
18200 | |forbid_filter_readfile|Use: redirect|Type: boolean|Default: false| | |
18201 | +----------------------+-------------+-------------+--------------+ | |
18202 | ||
18203 | If this option is true, string expansions in Exim filter files are not allowed | |
18204 | to make use of readfile items. | |
18205 | ||
18206 | +------------------------+-------------+-------------+--------------+ | |
18207 | |forbid_filter_readsocket|Use: redirect|Type: boolean|Default: false| | |
18208 | +------------------------+-------------+-------------+--------------+ | |
18209 | ||
18210 | If this option is true, string expansions in Exim filter files are not allowed | |
18211 | to make use of readsocket items. | |
18212 | ||
18213 | +-------------------+-------------+-------------+--------------+ | |
18214 | |forbid_filter_reply|Use: redirect|Type: boolean|Default: false| | |
18215 | +-------------------+-------------+-------------+--------------+ | |
18216 | ||
18217 | If this option is true, this router may not generate an automatic reply | |
18218 | message. Automatic replies can be generated only from Exim or Sieve filter | |
18219 | files, not from traditional forward files. This option is forced to be true if | |
18220 | one_time is set. | |
18221 | ||
18222 | +-----------------+-------------+-------------+--------------+ | |
18223 | |forbid_filter_run|Use: redirect|Type: boolean|Default: false| | |
18224 | +-----------------+-------------+-------------+--------------+ | |
18225 | ||
18226 | If this option is true, string expansions in Exim filter files are not allowed | |
18227 | to make use of run items. | |
18228 | ||
18229 | +--------------+-------------+-------------+--------------+ | |
18230 | |forbid_include|Use: redirect|Type: boolean|Default: false| | |
18231 | +--------------+-------------+-------------+--------------+ | |
18232 | ||
18233 | If this option is true, items of the form | |
18234 | ||
18235 | :include:<path name> | |
18236 | ||
18237 | are not permitted in non-filter redirection lists. | |
18238 | ||
18239 | +-----------+-------------+-------------+--------------+ | |
18240 | |forbid_pipe|Use: redirect|Type: boolean|Default: false| | |
18241 | +-----------+-------------+-------------+--------------+ | |
18242 | ||
18243 | If this option is true, this router may not generate a new address which | |
18244 | specifies delivery to a pipe, either from an Exim filter or from a conventional | |
18245 | forward file. This option is forced to be true if one_time is set. | |
18246 | ||
18247 | +-------------------+-------------+-------------+--------------+ | |
18248 | |forbid_sieve_filter|Use: redirect|Type: boolean|Default: false| | |
18249 | +-------------------+-------------+-------------+--------------+ | |
18250 | ||
18251 | If this option is set true, only Exim filters are permitted when allow_filter | |
18252 | is true. | |
18253 | ||
18254 | +----------------+-------------+-------------+--------------+ | |
18255 | |forbid_smtp_code|Use: redirect|Type: boolean|Default: false| | |
18256 | +----------------+-------------+-------------+--------------+ | |
18257 | ||
18258 | If this option is set true, any SMTP error codes that are present at the start | |
18259 | of messages specified for ":defer:" or ":fail:" are quietly ignored, and the | |
18260 | default codes (451 and 550, respectively) are always used. | |
18261 | ||
18262 | +--------------------+-------------+-------------+--------------+ | |
18263 | |hide_child_in_errmsg|Use: redirect|Type: boolean|Default: false| | |
18264 | +--------------------+-------------+-------------+--------------+ | |
18265 | ||
18266 | If this option is true, it prevents Exim from quoting a child address if it | |
18267 | generates a bounce or delay message for it. Instead it says "an address | |
18268 | generated from <the top level address>". Of course, this applies only to | |
18269 | bounces generated locally. If a message is forwarded to another host, its | |
18270 | bounce may well quote the generated address. | |
18271 | ||
18272 | +-------------+-------------+-------------+--------------+ | |
18273 | |ignore_eacces|Use: redirect|Type: boolean|Default: false| | |
18274 | +-------------+-------------+-------------+--------------+ | |
18275 | ||
18276 | If this option is set and an attempt to open a redirection file yields the | |
18277 | EACCES error (permission denied), the redirect router behaves as if the file | |
18278 | did not exist. | |
18279 | ||
18280 | +--------------+-------------+-------------+--------------+ | |
18281 | |ignore_enotdir|Use: redirect|Type: boolean|Default: false| | |
18282 | +--------------+-------------+-------------+--------------+ | |
18283 | ||
18284 | If this option is set and an attempt to open a redirection file yields the | |
18285 | ENOTDIR error (something on the path is not a directory), the redirect router | |
18286 | behaves as if the file did not exist. | |
18287 | ||
18288 | Setting ignore_enotdir has another effect as well: When a redirect router that | |
18289 | has the file option set discovers that the file does not exist (the ENOENT | |
18290 | error), it tries to stat() the parent directory, as a check against unmounted | |
18291 | NFS directories. If the parent can not be statted, delivery is deferred. | |
18292 | However, it seems wrong to do this check when ignore_enotdir is set, because | |
18293 | that option tells Exim to ignore "something on the path is not a directory" | |
18294 | (the ENOTDIR error). This is a confusing area, because it seems that some | |
18295 | operating systems give ENOENT where others give ENOTDIR. | |
18296 | ||
18297 | +-----------------+-------------+------------+--------------+ | |
18298 | |include_directory|Use: redirect|Type: string|Default: unset| | |
18299 | +-----------------+-------------+------------+--------------+ | |
18300 | ||
18301 | If this option is set, the path names of any :include: items in a redirection | |
18302 | list must start with this directory. | |
18303 | ||
18304 | +--------+-------------+-------------------+------------+ | |
18305 | |modemask|Use: redirect|Type: octal integer|Default: 022| | |
18306 | +--------+-------------+-------------------+------------+ | |
18307 | ||
18308 | This specifies mode bits which must not be set for a file specified by the file | |
18309 | option. If any of the forbidden bits are set, delivery is deferred. | |
18310 | ||
18311 | +--------+-------------+-------------+--------------+ | |
18312 | |one_time|Use: redirect|Type: boolean|Default: false| | |
18313 | +--------+-------------+-------------+--------------+ | |
18314 | ||
18315 | Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection | |
18316 | files each time it tries to deliver a message causes a problem when one or more | |
18317 | of the generated addresses fails be delivered at the first attempt. The problem | |
18318 | is not one of duplicate delivery - Exim is clever enough to handle that - but | |
18319 | of what happens when the redirection list changes during the time that the | |
18320 | message is on Exim's queue. This is particularly true in the case of mailing | |
18321 | lists, where new subscribers might receive copies of messages that were posted | |
18322 | before they subscribed. | |
18323 | ||
18324 | If one_time is set and any addresses generated by the router fail to deliver at | |
18325 | the first attempt, the failing addresses are added to the message as "top | |
18326 | level" addresses, and the parent address that generated them is marked | |
18327 | "delivered". Thus, redirection does not happen again at the next delivery | |
18328 | attempt. | |
18329 | ||
18330 | Warning 1: Any header line addition or removal that is specified by this router | |
18331 | would be lost if delivery did not succeed at the first attempt. For this | |
18332 | reason, the headers_add and headers_remove generic options are not permitted | |
18333 | when one_time is set. | |
18334 | ||
18335 | Warning 2: To ensure that the router generates only addresses (as opposed to | |
18336 | pipe or file deliveries or auto-replies) forbid_file, forbid_pipe, and | |
18337 | forbid_filter_reply are forced to be true when one_time is set. | |
18338 | ||
18339 | Warning 3: The unseen generic router option may not be set with one_time. | |
18340 | ||
18341 | The original top-level address is remembered with each of the generated | |
18342 | addresses, and is output in any log messages. However, any intermediate parent | |
18343 | addresses are not recorded. This makes a difference to the log only if | |
18344 | all_parents log selector is set. It is expected that one_time will typically be | |
18345 | used for mailing lists, where there is normally just one level of expansion. | |
18346 | ||
18347 | +------+-------------+-----------------+--------------+ | |
18348 | |owners|Use: redirect|Type: string list|Default: unset| | |
18349 | +------+-------------+-----------------+--------------+ | |
18350 | ||
18351 | This specifies a list of permitted owners for the file specified by file. This | |
18352 | list is in addition to the local user when check_local_user is set. See | |
18353 | check_owner above. | |
18354 | ||
18355 | +---------+-------------+-----------------+--------------+ | |
18356 | |owngroups|Use: redirect|Type: string list|Default: unset| | |
18357 | +---------+-------------+-----------------+--------------+ | |
18358 | ||
18359 | This specifies a list of permitted groups for the file specified by file. The | |
18360 | list is in addition to the local user's primary group when check_local_user is | |
18361 | set. See check_group above. | |
18362 | ||
18363 | +--------------+-------------+-------------+--------------+ | |
18364 | |pipe_transport|Use: redirect|Type: string*|Default: unset| | |
18365 | +--------------+-------------+-------------+--------------+ | |
18366 | ||
18367 | A redirect router sets up a direct delivery to a pipe when a string starting | |
18368 | with a vertical bar character is specified as a new "address". The transport | |
18369 | used is specified by this option, which, after expansion, must be the name of a | |
18370 | configured transport. This should normally be a pipe transport. When the | |
18371 | transport is run, the pipe command is in $address_pipe. | |
18372 | ||
18373 | +--------------+-------------+-------------+--------------+ | |
18374 | |qualify_domain|Use: redirect|Type: string*|Default: unset| | |
18375 | +--------------+-------------+-------------+--------------+ | |
18376 | ||
18377 | If this option is set, and an unqualified address (one without a domain) is | |
18378 | generated, and that address would normally be qualified by the global setting | |
18379 | in qualify_recipient, it is instead qualified with the domain specified by | |
18380 | expanding this string. If the expansion fails, the router declines. If you want | |
18381 | to revert to the default, you can have the expansion generate | |
18382 | $qualify_recipient. | |
18383 | ||
18384 | This option applies to all unqualified addresses generated by Exim filters, but | |
18385 | for traditional .forward files, it applies only to addresses that are not | |
18386 | preceded by a backslash. Sieve filters cannot generate unqualified addresses. | |
18387 | ||
18388 | +-----------------------+-------------+-------------+--------------+ | |
18389 | |qualify_preserve_domain|Use: redirect|Type: boolean|Default: false| | |
18390 | +-----------------------+-------------+-------------+--------------+ | |
18391 | ||
18392 | If this option is set, the router's local qualify_domain option must not be set | |
18393 | (a configuration error occurs if it is). If an unqualified address (one without | |
18394 | a domain) is generated, it is qualified with the domain of the parent address | |
18395 | (the immediately preceding ancestor) instead of the global qualify_recipient | |
18396 | value. In the case of a traditional .forward file, this applies whether or not | |
18397 | the address is preceded by a backslash. | |
18398 | ||
18399 | +----------+-------------+-------------+-------------+ | |
18400 | |repeat_use|Use: redirect|Type: boolean|Default: true| | |
18401 | +----------+-------------+-------------+-------------+ | |
18402 | ||
18403 | If this option is set false, the router is skipped for a child address that has | |
18404 | any ancestor that was routed by this router. This test happens before any of | |
18405 | the other preconditions are tested. Exim's default anti-looping rules skip only | |
18406 | when the ancestor is the same as the current address. See also check_ancestor | |
18407 | above and the generic redirect_router option. | |
18408 | ||
18409 | +---------------+-------------+-------------+--------------+ | |
18410 | |reply_transport|Use: redirect|Type: string*|Default: unset| | |
18411 | +---------------+-------------+-------------+--------------+ | |
18412 | ||
18413 | A redirect router sets up an automatic reply when a mail or vacation command is | |
18414 | used in a filter file. The transport used is specified by this option, which, | |
18415 | after expansion, must be the name of a configured transport. This should | |
18416 | normally be an autoreply transport. Other transports are unlikely to do | |
18417 | anything sensible or useful. | |
18418 | ||
18419 | +-------+-------------+-------------+-------------+ | |
18420 | |rewrite|Use: redirect|Type: boolean|Default: true| | |
18421 | +-------+-------------+-------------+-------------+ | |
18422 | ||
18423 | If this option is set false, addresses generated by the router are not subject | |
18424 | to address rewriting. Otherwise, they are treated like new addresses and are | |
18425 | rewritten according to the global rewriting rules. | |
18426 | ||
18427 | +----------------+-------------+-------------+--------------+ | |
18428 | |sieve_subaddress|Use: redirect|Type: string*|Default: unset| | |
18429 | +----------------+-------------+-------------+--------------+ | |
18430 | ||
18431 | The value of this option is passed to a Sieve filter to specify the :subaddress | |
18432 | part of an address. | |
18433 | ||
18434 | +-----------------+-------------+-------------+--------------+ | |
18435 | |sieve_useraddress|Use: redirect|Type: string*|Default: unset| | |
18436 | +-----------------+-------------+-------------+--------------+ | |
18437 | ||
18438 | The value of this option is passed to a Sieve filter to specify the :user part | |
18439 | of an address. However, if it is unset, the entire original local part | |
18440 | (including any prefix or suffix) is used for :user. | |
18441 | ||
18442 | +------------------------+-------------+-------------+--------------+ | |
18443 | |sieve_vacation_directory|Use: redirect|Type: string*|Default: unset| | |
18444 | +------------------------+-------------+-------------+--------------+ | |
18445 | ||
18446 | To enable the "vacation" extension for Sieve filters, you must set | |
18447 | sieve_vacation_directory to the directory where vacation databases are held (do | |
18448 | not put anything else in that directory), and ensure that the reply_transport | |
18449 | option refers to an autoreply transport. Each user needs their own directory; | |
18450 | Exim will create it if necessary. | |
18451 | ||
18452 | +------------------+-------------+-------------+--------------+ | |
18453 | |skip_syntax_errors|Use: redirect|Type: boolean|Default: false| | |
18454 | +------------------+-------------+-------------+--------------+ | |
18455 | ||
18456 | If skip_syntax_errors is set, syntactically malformed addresses in non-filter | |
18457 | redirection data are skipped, and each failing address is logged. If | |
18458 | syntax_errors_to is set, a message is sent to the address it defines, giving | |
18459 | details of the failures. If syntax_errors_text is set, its contents are | |
18460 | expanded and placed at the head of the error message generated by | |
18461 | syntax_errors_to. Usually it is appropriate to set syntax_errors_to to be the | |
18462 | same address as the generic errors_to option. The skip_syntax_errors option is | |
18463 | often used when handling mailing lists. | |
18464 | ||
18465 | If all the addresses in a redirection list are skipped because of syntax | |
18466 | errors, the router declines to handle the original address, and it is passed to | |
18467 | the following routers. | |
18468 | ||
18469 | If skip_syntax_errors is set when an Exim filter is interpreted, any syntax | |
18470 | error in the filter causes filtering to be abandoned without any action being | |
18471 | taken. The incident is logged, and the router declines to handle the address, | |
18472 | so it is passed to the following routers. | |
18473 | ||
18474 | Syntax errors in a Sieve filter file cause the "keep" action to occur. This | |
18475 | action is specified by RFC 3028. The values of skip_syntax_errors, | |
18476 | syntax_errors_to, and syntax_errors_text are not used. | |
18477 | ||
18478 | skip_syntax_errors can be used to specify that errors in users' forward lists | |
18479 | or filter files should not prevent delivery. The syntax_errors_to option, used | |
18480 | with an address that does not get redirected, can be used to notify users of | |
18481 | these errors, by means of a router like this: | |
18482 | ||
18483 | userforward: | |
18484 | driver = redirect | |
18485 | allow_filter | |
18486 | check_local_user | |
18487 | file = $home/.forward | |
18488 | file_transport = address_file | |
18489 | pipe_transport = address_pipe | |
18490 | reply_transport = address_reply | |
18491 | no_verify | |
18492 | skip_syntax_errors | |
18493 | syntax_errors_to = real-$local_part@$domain | |
18494 | syntax_errors_text = \ | |
18495 | This is an automatically generated message. An error has\n\ | |
18496 | been found in your .forward file. Details of the error are\n\ | |
18497 | reported below. While this error persists, you will receive\n\ | |
18498 | a copy of this message for every message that is addressed\n\ | |
18499 | to you. If your .forward file is a filter file, or if it is\n\ | |
18500 | a non-filter file containing no valid forwarding addresses,\n\ | |
18501 | a copy of each incoming message will be put in your normal\n\ | |
18502 | mailbox. If a non-filter file contains at least one valid\n\ | |
18503 | forwarding address, forwarding to the valid addresses will\n\ | |
18504 | happen, and those will be the only deliveries that occur. | |
18505 | ||
18506 | You also need a router to ensure that local addresses that are prefixed by | |
18507 | "real-" are recognized, but not forwarded or filtered. For example, you could | |
18508 | put this immediately before the userforward router: | |
18509 | ||
18510 | real_localuser: | |
18511 | driver = accept | |
18512 | check_local_user | |
18513 | local_part_prefix = real- | |
18514 | transport = local_delivery | |
18515 | ||
18516 | For security, it would probably be a good idea to restrict the use of this | |
18517 | router to locally-generated messages, using a condition such as this: | |
18518 | ||
18519 | condition = ${if match {$sender_host_address}\ | |
18520 | {\N^(|127\.0\.0\.1)$\N}} | |
18521 | ||
18522 | +------------------+-------------+-------------+--------------+ | |
18523 | |syntax_errors_text|Use: redirect|Type: string*|Default: unset| | |
18524 | +------------------+-------------+-------------+--------------+ | |
18525 | ||
18526 | See skip_syntax_errors above. | |
18527 | ||
18528 | +----------------+-------------+------------+--------------+ | |
18529 | |syntax_errors_to|Use: redirect|Type: string|Default: unset| | |
18530 | +----------------+-------------+------------+--------------+ | |
18531 | ||
18532 | See skip_syntax_errors above. | |
18533 | ||
18534 | ||
18535 | ||
18536 | =============================================================================== | |
18537 | 23. ENVIRONMENT FOR RUNNING LOCAL TRANSPORTS | |
18538 | ||
18539 | Local transports handle deliveries to files and pipes. (The autoreply transport | |
18540 | can be thought of as similar to a pipe.) Exim always runs transports in | |
18541 | subprocesses, under specified uids and gids. Typical deliveries to local | |
18542 | mailboxes run under the uid and gid of the local user. | |
18543 | ||
18544 | Exim also sets a specific current directory while running the transport; for | |
18545 | some transports a home directory setting is also relevant. The pipe transport | |
18546 | is the only one that sets up environment variables; see section 29.4 for | |
18547 | details. | |
18548 | ||
18549 | The values used for the uid, gid, and the directories may come from several | |
18550 | different places. In many cases, the router that handles the address associates | |
18551 | settings with that address as a result of its check_local_user, group, or user | |
18552 | options. However, values may also be given in the transport's own | |
18553 | configuration, and these override anything that comes from the router. | |
18554 | ||
18555 | ||
18556 | 23.1 Concurrent deliveries | |
18557 | -------------------------- | |
18558 | ||
18559 | If two different messages for the same local recipient arrive more or less | |
18560 | simultaneously, the two delivery processes are likely to run concurrently. When | |
18561 | the appendfile transport is used to write to a file, Exim applies locking rules | |
18562 | to stop concurrent processes from writing to the same file at the same time. | |
18563 | ||
18564 | However, when you use a pipe transport, it is up to you to arrange any locking | |
18565 | that is needed. Here is a silly example: | |
18566 | ||
18567 | my_transport: | |
18568 | driver = pipe | |
18569 | command = /bin/sh -c 'cat >>/some/file' | |
18570 | ||
18571 | This is supposed to write the message at the end of the file. However, if two | |
18572 | messages arrive at the same time, the file will be scrambled. You can use the | |
18573 | exim_lock utility program (see section 52.15) to lock a file using the same | |
18574 | algorithm that Exim itself uses. | |
18575 | ||
18576 | ||
18577 | 23.2 Uids and gids | |
18578 | ------------------ | |
18579 | ||
18580 | All transports have the options group and user. If group is set, it overrides | |
18581 | any group that the router set in the address, even if user is not set for the | |
18582 | transport. This makes it possible, for example, to run local mail delivery | |
18583 | under the uid of the recipient (set by the router), but in a special group (set | |
18584 | by the transport). For example: | |
18585 | ||
18586 | # Routers ... | |
18587 | # User/group are set by check_local_user in this router | |
18588 | local_users: | |
18589 | driver = accept | |
18590 | check_local_user | |
18591 | transport = group_delivery | |
18592 | ||
18593 | # Transports ... | |
18594 | # This transport overrides the group | |
18595 | group_delivery: | |
18596 | driver = appendfile | |
18597 | file = /var/spool/mail/$local_part | |
18598 | group = mail | |
18599 | ||
18600 | If user is set for a transport, its value overrides what is set in the address | |
18601 | by the router. If user is non-numeric and group is not set, the gid associated | |
18602 | with the user is used. If user is numeric, group must be set. | |
18603 | ||
18604 | When the uid is taken from the transport's configuration, the initgroups() | |
18605 | function is called for the groups associated with that uid if the initgroups | |
18606 | option is set for the transport. When the uid is not specified by the | |
18607 | transport, but is associated with the address by a router, the option for | |
18608 | calling initgroups() is taken from the router configuration. | |
18609 | ||
18610 | The pipe transport contains the special option pipe_as_creator. If this is set | |
18611 | and user is not set, the uid of the process that called Exim to receive the | |
18612 | message is used, and if group is not set, the corresponding original gid is | |
18613 | also used. | |
18614 | ||
18615 | This is the detailed preference order for obtaining a gid; the first of the | |
18616 | following that is set is used: | |
18617 | ||
18618 | * A group setting of the transport; | |
18619 | ||
18620 | * A group setting of the router; | |
18621 | ||
18622 | * A gid associated with a user setting of the router, either as a result of | |
18623 | check_local_user or an explicit non-numeric user setting; | |
18624 | ||
18625 | * The group associated with a non-numeric user setting of the transport; | |
18626 | ||
18627 | * In a pipe transport, the creator's gid if deliver_as_creator is set and the | |
18628 | uid is the creator's uid; | |
18629 | ||
18630 | * The Exim gid if the Exim uid is being used as a default. | |
18631 | ||
18632 | If, for example, the user is specified numerically on the router and there are | |
18633 | no group settings, no gid is available. In this situation, an error occurs. | |
18634 | This is different for the uid, for which there always is an ultimate default. | |
18635 | The first of the following that is set is used: | |
18636 | ||
18637 | * A user setting of the transport; | |
18638 | ||
18639 | * In a pipe transport, the creator's uid if deliver_as_creator is set; | |
18640 | ||
18641 | * A user setting of the router; | |
18642 | ||
18643 | * A check_local_user setting of the router; | |
18644 | ||
18645 | * The Exim uid. | |
18646 | ||
18647 | Of course, an error will still occur if the uid that is chosen is on the | |
18648 | never_users list. | |
18649 | ||
18650 | ||
18651 | 23.3 Current and home directories | |
18652 | --------------------------------- | |
18653 | ||
18654 | Routers may set current and home directories for local transports by means of | |
18655 | the transport_current_directory and transport_home_directory options. However, | |
18656 | if the transport's current_directory or home_directory options are set, they | |
18657 | override the router's values. In detail, the home directory for a local | |
18658 | transport is taken from the first of these values that is set: | |
18659 | ||
18660 | * The home_directory option on the transport; | |
18661 | ||
18662 | * The transport_home_directory option on the router; | |
18663 | ||
18664 | * The password data if check_local_user is set on the router; | |
18665 | ||
18666 | * The router_home_directory option on the router. | |
18667 | ||
18668 | The current directory is taken from the first of these values that is set: | |
18669 | ||
18670 | * The current_directory option on the transport; | |
18671 | ||
18672 | * The transport_current_directory option on the router. | |
18673 | ||
18674 | If neither the router nor the transport sets a current directory, Exim uses the | |
18675 | value of the home directory, if it is set. Otherwise it sets the current | |
18676 | directory to / before running a local transport. | |
18677 | ||
18678 | ||
18679 | 23.4 Expansion variables derived from the address | |
18680 | ------------------------------------------------- | |
18681 | ||
18682 | Normally a local delivery is handling a single address, and in that case the | |
18683 | variables such as $domain and $local_part are set during local deliveries. | |
18684 | However, in some circumstances more than one address may be handled at once | |
18685 | (for example, while writing batch SMTP for onward transmission by some other | |
18686 | means). In this case, the variables associated with the local part are never | |
18687 | set, $domain is set only if all the addresses have the same domain, and | |
18688 | $original_domain is never set. | |
18689 | ||
18690 | ||
18691 | ||
18692 | =============================================================================== | |
18693 | 24. GENERIC OPTIONS FOR TRANSPORTS | |
18694 | ||
18695 | The following generic options apply to all transports: | |
18696 | ||
18697 | +---------+---------------+-------------+--------------+ | |
18698 | |body_only|Use: transports|Type: boolean|Default: false| | |
18699 | +---------+---------------+-------------+--------------+ | |
18700 | ||
18701 | If this option is set, the message's headers are not transported. It is | |
18702 | mutually exclusive with headers_only. If it is used with the appendfile or pipe | |
18703 | transports, the settings of message_prefix and message_suffix should be | |
18704 | checked, because this option does not automatically suppress them. | |
18705 | ||
18706 | +-----------------+---------------+-------------+--------------+ | |
18707 | |current_directory|Use: transports|Type: string*|Default: unset| | |
18708 | +-----------------+---------------+-------------+--------------+ | |
18709 | ||
18710 | This specifies the current directory that is to be set while running the | |
18711 | transport, overriding any value that may have been set by the router. If the | |
18712 | expansion fails for any reason, including forced failure, an error is logged, | |
18713 | and delivery is deferred. | |
18714 | ||
18715 | +---------------+---------------+-------------+--------------+ | |
18716 | |disable_logging|Use: transports|Type: boolean|Default: false| | |
18717 | +---------------+---------------+-------------+--------------+ | |
18718 | ||
18719 | If this option is set true, nothing is logged for any deliveries by the | |
18720 | transport or for any transport errors. You should not set this option unless | |
18721 | you really, really know what you are doing. | |
18722 | ||
18723 | +-----------+---------------+-------------+--------------+ | |
18724 | |debug_print|Use: transports|Type: string*|Default: unset| | |
18725 | +-----------+---------------+-------------+--------------+ | |
18726 | ||
18727 | If this option is set and debugging is enabled (see the -d command line | |
18728 | option), the string is expanded and included in the debugging output when the | |
18729 | transport is run. If expansion of the string fails, the error message is | |
18730 | written to the debugging output, and Exim carries on processing. This facility | |
18731 | is provided to help with checking out the values of variables and so on when | |
18732 | debugging driver configurations. For example, if a headers_add option is not | |
18733 | working properly, debug_print could be used to output the variables it | |
18734 | references. A newline is added to the text if it does not end with one. The | |
18735 | variables $transport_name and $router_name contain the name of the transport | |
18736 | and the router that called it. | |
18737 | ||
18738 | +-----------------+---------------+-------------+--------------+ | |
18739 | |delivery_date_add|Use: transports|Type: boolean|Default: false| | |
18740 | +-----------------+---------------+-------------+--------------+ | |
18741 | ||
18742 | If this option is true, a Delivery-date: header is added to the message. This | |
18743 | gives the actual time the delivery was made. As this is not a standard header, | |
18744 | Exim has a configuration option (delivery_date_remove) which requests its | |
18745 | removal from incoming messages, so that delivered messages can safely be resent | |
18746 | to other recipients. | |
18747 | ||
18748 | +------+---------------+------------+--------------+ | |
18749 | |driver|Use: transports|Type: string|Default: unset| | |
18750 | +------+---------------+------------+--------------+ | |
18751 | ||
18752 | This specifies which of the available transport drivers is to be used. There is | |
18753 | no default, and this option must be set for every transport. | |
18754 | ||
18755 | +---------------+---------------+-------------+--------------+ | |
18756 | |envelope_to_add|Use: transports|Type: boolean|Default: false| | |
18757 | +---------------+---------------+-------------+--------------+ | |
18758 | ||
18759 | If this option is true, an Envelope-to: header is added to the message. This | |
18760 | gives the original address(es) in the incoming envelope that caused this | |
18761 | delivery to happen. More than one address may be present if the transport is | |
18762 | configured to handle several addresses at once, or if more than one original | |
18763 | address was redirected to the same final address. As this is not a standard | |
18764 | header, Exim has a configuration option (envelope_to_remove) which requests its | |
18765 | removal from incoming messages, so that delivered messages can safely be resent | |
18766 | to other recipients. | |
18767 | ||
18768 | +-----+---------------+-------------+-------------------+ | |
18769 | |group|Use: transports|Type: string*|Default: Exim group| | |
18770 | +-----+---------------+-------------+-------------------+ | |
18771 | ||
18772 | This option specifies a gid for running the transport process, overriding any | |
18773 | value that the router supplies, and also overriding any value associated with | |
18774 | user (see below). | |
18775 | ||
18776 | +-----------+---------------+-----------+--------------+ | |
18777 | |headers_add|Use: transports|Type: list*|Default: unset| | |
18778 | +-----------+---------------+-----------+--------------+ | |
18779 | ||
18780 | This option specifies a list of text headers, newline-separated, which are | |
18781 | (separately) expanded and added to the header portion of a message as it is | |
18782 | transported, as described in section 46.17. Additional header lines can also be | |
18783 | specified by routers. If the result of the expansion is an empty string, or if | |
18784 | the expansion is forced to fail, no action is taken. Other expansion failures | |
18785 | are treated as errors and cause the delivery to be deferred. | |
18786 | ||
18787 | Unlike most options, headers_add can be specified multiple times for a | |
18788 | transport; all listed headers are added. | |
18789 | ||
18790 | +------------+---------------+-------------+--------------+ | |
18791 | |headers_only|Use: transports|Type: boolean|Default: false| | |
18792 | +------------+---------------+-------------+--------------+ | |
18793 | ||
18794 | If this option is set, the message's body is not transported. It is mutually | |
18795 | exclusive with body_only. If it is used with the appendfile or pipe transports, | |
18796 | the settings of message_prefix and message_suffix should be checked, since this | |
18797 | option does not automatically suppress them. | |
18798 | ||
18799 | +--------------+---------------+-----------+--------------+ | |
18800 | |headers_remove|Use: transports|Type: list*|Default: unset| | |
18801 | +--------------+---------------+-----------+--------------+ | |
18802 | ||
18803 | This option specifies a list of header names, colon-separated; these headers | |
18804 | are omitted from the message as it is transported, as described in section | |
18805 | 46.17. Header removal can also be specified by routers. Each list item is | |
18806 | separately expanded. If the result of the expansion is an empty string, or if | |
18807 | the expansion is forced to fail, no action is taken. Other expansion failures | |
18808 | are treated as errors and cause the delivery to be deferred. | |
18809 | ||
18810 | Unlike most options, headers_remove can be specified multiple times for a | |
18811 | router; all listed headers are removed. | |
18812 | ||
18813 | +---------------+---------------+------------+--------------+ | |
18814 | |headers_rewrite|Use: transports|Type: string|Default: unset| | |
18815 | +---------------+---------------+------------+--------------+ | |
18816 | ||
18817 | This option allows addresses in header lines to be rewritten at transport time, | |
18818 | that is, as the message is being copied to its destination. The contents of the | |
18819 | option are a colon-separated list of rewriting rules. Each rule is in exactly | |
18820 | the same form as one of the general rewriting rules that are applied when a | |
18821 | message is received. These are described in chapter 31. For example, | |
18822 | ||
18823 | headers_rewrite = a@b c@d f : \ | |
18824 | x@y w@z | |
18825 | ||
18826 | changes a@b into c@d in From: header lines, and x@y into w@z in all | |
18827 | address-bearing header lines. The rules are applied to the header lines just | |
18828 | before they are written out at transport time, so they affect only those copies | |
18829 | of the message that pass through the transport. However, only the message's | |
18830 | original header lines, and any that were added by a system filter, are | |
18831 | rewritten. If a router or transport adds header lines, they are not affected by | |
18832 | this option. These rewriting rules are not applied to the envelope. You can | |
18833 | change the return path using return_path, but you cannot change envelope | |
18834 | recipients at this time. | |
18835 | ||
18836 | +--------------+---------------+-------------+--------------+ | |
18837 | |home_directory|Use: transports|Type: string*|Default: unset| | |
18838 | +--------------+---------------+-------------+--------------+ | |
18839 | ||
18840 | This option specifies a home directory setting for a local transport, | |
18841 | overriding any value that may be set by the router. The home directory is | |
18842 | placed in $home while expanding the transport's private options. It is also | |
18843 | used as the current directory if no current directory is set by the | |
18844 | current_directory option on the transport or the transport_current_directory | |
18845 | option on the router. If the expansion fails for any reason, including forced | |
18846 | failure, an error is logged, and delivery is deferred. | |
18847 | ||
18848 | +----------+---------------+-------------+--------------+ | |
18849 | |initgroups|Use: transports|Type: boolean|Default: false| | |
18850 | +----------+---------------+-------------+--------------+ | |
18851 | ||
18852 | If this option is true and the uid for the delivery process is provided by the | |
18853 | transport, the initgroups() function is called when running the transport to | |
18854 | ensure that any additional groups associated with the uid are set up. | |
18855 | ||
18856 | +------------------+---------------+-------------+----------+ | |
18857 | |message_size_limit|Use: transports|Type: string*|Default: 0| | |
18858 | +------------------+---------------+-------------+----------+ | |
18859 | ||
18860 | This option controls the size of messages passed through the transport. It is | |
18861 | expanded before use; the result of the expansion must be a sequence of decimal | |
18862 | digits, optionally followed by K or M. If the expansion fails for any reason, | |
18863 | including forced failure, or if the result is not of the required form, | |
18864 | delivery is deferred. If the value is greater than zero and the size of a | |
18865 | message exceeds this limit, the address is failed. If there is any chance that | |
18866 | the resulting bounce message could be routed to the same transport, you should | |
18867 | ensure that return_size_limit is less than the transport's message_size_limit, | |
18868 | as otherwise the bounce message will fail to get delivered. | |
18869 | ||
18870 | +--------------------+---------------+-------------+--------------+ | |
18871 | |rcpt_include_affixes|Use: transports|Type: boolean|Default: false| | |
18872 | +--------------------+---------------+-------------+--------------+ | |
18873 | ||
18874 | When this option is false (the default), and an address that has had any | |
18875 | affixes (prefixes or suffixes) removed from the local part is delivered by any | |
18876 | form of SMTP or LMTP, the affixes are not included. For example, if a router | |
18877 | that contains | |
18878 | ||
18879 | local_part_prefix = *- | |
18880 | ||
18881 | routes the address abc-xyz@some.domain to an SMTP transport, the envelope is | |
18882 | delivered with | |
18883 | ||
18884 | RCPT TO:<xyz@some.domain> | |
18885 | ||
18886 | This is also the case when an ACL-time callout is being used to verify a | |
18887 | recipient address. However, if rcpt_include_affixes is set true, the whole | |
18888 | local part is included in the RCPT command. This option applies to BSMTP | |
18889 | deliveries by the appendfile and pipe transports as well as to the lmtp and | |
18890 | smtp transports. | |
18891 | ||
18892 | +--------------------+---------------+-------------+------------------+ | |
18893 | |retry_use_local_part|Use: transports|Type: boolean|Default: see below| | |
18894 | +--------------------+---------------+-------------+------------------+ | |
18895 | ||
18896 | When a delivery suffers a temporary failure, a retry record is created in | |
18897 | Exim's hints database. For remote deliveries, the key for the retry record is | |
18898 | based on the name and/or IP address of the failing remote host. For local | |
18899 | deliveries, the key is normally the entire address, including both the local | |
18900 | part and the domain. This is suitable for most common cases of local delivery | |
18901 | temporary failure - for example, exceeding a mailbox quota should delay only | |
18902 | deliveries to that mailbox, not to the whole domain. | |
18903 | ||
18904 | However, in some special cases you may want to treat a temporary local delivery | |
18905 | as a failure associated with the domain, and not with a particular local part. | |
18906 | (For example, if you are storing all mail for some domain in files.) You can do | |
18907 | this by setting retry_use_local_part false. | |
18908 | ||
18909 | For all the local transports, its default value is true. For remote transports, | |
18910 | the default value is false for tidiness, but changing the value has no effect | |
18911 | on a remote transport in the current implementation. | |
18912 | ||
18913 | +-----------+---------------+-------------+--------------+ | |
18914 | |return_path|Use: transports|Type: string*|Default: unset| | |
18915 | +-----------+---------------+-------------+--------------+ | |
18916 | ||
18917 | If this option is set, the string is expanded at transport time and replaces | |
18918 | the existing return path (envelope sender) value in the copy of the message | |
18919 | that is being delivered. An empty return path is permitted. This feature is | |
18920 | designed for remote deliveries, where the value of this option is used in the | |
18921 | SMTP MAIL command. If you set return_path for a local transport, the only | |
18922 | effect is to change the address that is placed in the Return-path: header line, | |
18923 | if one is added to the message (see the next option). | |
18924 | ||
18925 | Note: A changed return path is not logged unless you add | |
18926 | return_path_on_delivery to the log selector. | |
18927 | ||
18928 | The expansion can refer to the existing value via $return_path. This is either | |
18929 | the message's envelope sender, or an address set by the errors_to option on a | |
18930 | router. If the expansion is forced to fail, no replacement occurs; if it fails | |
18931 | for another reason, delivery is deferred. This option can be used to support | |
18932 | VERP (Variable Envelope Return Paths) - see section 49.6. | |
18933 | ||
18934 | Note: If a delivery error is detected locally, including the case when a remote | |
18935 | server rejects a message at SMTP time, the bounce message is not sent to the | |
18936 | value of this option. It is sent to the previously set errors address. This | |
18937 | defaults to the incoming sender address, but can be changed by setting | |
18938 | errors_to in a router. | |
18939 | ||
18940 | +---------------+---------------+-------------+--------------+ | |
18941 | |return_path_add|Use: transports|Type: boolean|Default: false| | |
18942 | +---------------+---------------+-------------+--------------+ | |
18943 | ||
18944 | If this option is true, a Return-path: header is added to the message. Although | |
18945 | the return path is normally available in the prefix line of BSD mailboxes, this | |
18946 | is commonly not displayed by MUAs, and so the user does not have easy access to | |
18947 | it. | |
18948 | ||
18949 | RFC 2821 states that the Return-path: header is added to a message "when the | |
18950 | delivery SMTP server makes the final delivery". This implies that this header | |
18951 | should not be present in incoming messages. Exim has a configuration option, | |
18952 | return_path_remove, which requests removal of this header from incoming | |
18953 | messages, so that delivered messages can safely be resent to other recipients. | |
18954 | ||
18955 | +----------------+---------------+-------------+--------------+ | |
18956 | |shadow_condition|Use: transports|Type: string*|Default: unset| | |
18957 | +----------------+---------------+-------------+--------------+ | |
18958 | ||
18959 | See shadow_transport below. | |
18960 | ||
18961 | +----------------+---------------+------------+--------------+ | |
18962 | |shadow_transport|Use: transports|Type: string|Default: unset| | |
18963 | +----------------+---------------+------------+--------------+ | |
18964 | ||
18965 | A local transport may set the shadow_transport option to the name of another | |
18966 | local transport. Shadow remote transports are not supported. | |
18967 | ||
18968 | Whenever a delivery to the main transport succeeds, and either shadow_condition | |
18969 | is unset, or its expansion does not result in the empty string or one of the | |
18970 | strings "0" or "no" or "false", the message is also passed to the shadow | |
18971 | transport, with the same delivery address or addresses. If expansion fails, no | |
18972 | action is taken except that non-forced expansion failures cause a log line to | |
18973 | be written. | |
18974 | ||
18975 | The result of the shadow transport is discarded and does not affect the | |
18976 | subsequent processing of the message. Only a single level of shadowing is | |
18977 | provided; the shadow_transport option is ignored on any transport when it is | |
18978 | running as a shadow. Options concerned with output from pipes are also ignored. | |
18979 | The log line for the successful delivery has an item added on the end, of the | |
18980 | form | |
18981 | ||
18982 | ST=<shadow transport name> | |
18983 | ||
18984 | If the shadow transport did not succeed, the error message is put in | |
18985 | parentheses afterwards. Shadow transports can be used for a number of different | |
18986 | purposes, including keeping more detailed log information than Exim normally | |
18987 | provides, and implementing automatic acknowledgment policies based on message | |
18988 | headers that some sites insist on. | |
18989 | ||
18990 | +----------------+---------------+-------------+--------------+ | |
18991 | |transport_filter|Use: transports|Type: string*|Default: unset| | |
18992 | +----------------+---------------+-------------+--------------+ | |
18993 | ||
18994 | This option sets up a filtering (in the Unix shell sense) process for messages | |
18995 | at transport time. It should not be confused with mail filtering as set up by | |
18996 | individual users or via a system filter. | |
18997 | ||
18998 | When the message is about to be written out, the command specified by | |
18999 | transport_filter is started up in a separate, parallel process, and the entire | |
19000 | message, including the header lines, is passed to it on its standard input | |
19001 | (this in fact is done from a third process, to avoid deadlock). The command | |
19002 | must be specified as an absolute path. | |
19003 | ||
19004 | The lines of the message that are written to the transport filter are | |
19005 | terminated by newline ("\n"). The message is passed to the filter before any | |
19006 | SMTP-specific processing, such as turning "\n" into "\r\n" and escaping lines | |
19007 | beginning with a dot, and also before any processing implied by the settings of | |
19008 | check_string and escape_string in the appendfile or pipe transports. | |
19009 | ||
19010 | The standard error for the filter process is set to the same destination as its | |
19011 | standard output; this is read and written to the message's ultimate | |
19012 | destination. The process that writes the message to the filter, the filter | |
19013 | itself, and the original process that reads the result and delivers it are all | |
19014 | run in parallel, like a shell pipeline. | |
19015 | ||
19016 | The filter can perform any transformations it likes, but of course should take | |
19017 | care not to break RFC 2822 syntax. Exim does not check the result, except to | |
19018 | test for a final newline when SMTP is in use. All messages transmitted over | |
19019 | SMTP must end with a newline, so Exim supplies one if it is missing. | |
19020 | ||
19021 | A transport filter can be used to provide content-scanning on a per-user basis | |
19022 | at delivery time if the only required effect of the scan is to modify the | |
19023 | message. For example, a content scan could insert a new header line containing | |
19024 | a spam score. This could be interpreted by a filter in the user's MUA. It is | |
19025 | not possible to discard a message at this stage. | |
19026 | ||
19027 | A problem might arise if the filter increases the size of a message that is | |
19028 | being sent down an SMTP connection. If the receiving SMTP server has indicated | |
19029 | support for the SIZE parameter, Exim will have sent the size of the message at | |
19030 | the start of the SMTP session. If what is actually sent is substantially more, | |
19031 | the server might reject the message. This can be worked round by setting the | |
19032 | size_addition option on the smtp transport, either to allow for additions to | |
19033 | the message, or to disable the use of SIZE altogether. | |
19034 | ||
19035 | The value of the transport_filter option is the command string for starting the | |
19036 | filter, which is run directly from Exim, not under a shell. The string is | |
19037 | parsed by Exim in the same way as a command string for the pipe transport: Exim | |
19038 | breaks it up into arguments and then expands each argument separately (see | |
19039 | section 29.3). Any kind of expansion failure causes delivery to be deferred. | |
19040 | The special argument $pipe_addresses is replaced by a number of arguments, one | |
19041 | for each address that applies to this delivery. (This isn't an ideal name for | |
19042 | this feature here, but as it was already implemented for the pipe transport, it | |
19043 | seemed sensible not to change it.) | |
19044 | ||
19045 | The expansion variables $host and $host_address are available when the | |
19046 | transport is a remote one. They contain the name and IP address of the host to | |
19047 | which the message is being sent. For example: | |
19048 | ||
19049 | transport_filter = /some/directory/transport-filter.pl \ | |
19050 | $host $host_address $sender_address $pipe_addresses | |
19051 | ||
19052 | Two problems arise if you want to use more complicated expansion items to | |
19053 | generate transport filter commands, both of which due to the fact that the | |
19054 | command is split up before expansion. | |
19055 | ||
19056 | * If an expansion item contains white space, you must quote it, so that it is | |
19057 | all part of the same command item. If the entire option setting is one such | |
19058 | expansion item, you have to take care what kind of quoting you use. For | |
19059 | example: | |
19060 | ||
19061 | transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}' | |
19062 | ||
19063 | This runs the command /bin/cmd1 if the host name is a.b.c, and /bin/cmd2 | |
19064 | otherwise. If double quotes had been used, they would have been stripped by | |
19065 | Exim when it read the option's value. When the value is used, if the single | |
19066 | quotes were missing, the line would be split into two items, "/bin/cmd${if" | |
19067 | and "eq{$host}{a.b.c}{1}{2}", and an error would occur when Exim tried to | |
19068 | expand the first one. | |
19069 | ||
19070 | * Except for the special case of $pipe_addresses that is mentioned above, an | |
19071 | expansion cannot generate multiple arguments, or a command name followed by | |
19072 | arguments. Consider this example: | |
19073 | ||
19074 | transport_filter = ${lookup{$host}lsearch{/a/file}\ | |
19075 | {$value}{/bin/cat}} | |
19076 | ||
19077 | The result of the lookup is interpreted as the name of the command, even if | |
19078 | it contains white space. The simplest way round this is to use a shell: | |
19079 | ||
19080 | transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\ | |
19081 | {$value}{/bin/cat}} | |
19082 | ||
19083 | The filter process is run under the same uid and gid as the normal delivery. | |
19084 | For remote deliveries this is the Exim uid/gid by default. The command should | |
19085 | normally yield a zero return code. Transport filters are not supposed to fail. | |
19086 | A non-zero code is taken to mean that the transport filter encountered some | |
19087 | serious problem. Delivery of the message is deferred; the message remains on | |
19088 | the queue and is tried again later. It is not possible to cause a message to be | |
19089 | bounced from a transport filter. | |
19090 | ||
19091 | If a transport filter is set on an autoreply transport, the original message is | |
19092 | passed through the filter as it is being copied into the newly generated | |
19093 | message, which happens if the return_message option is set. | |
19094 | ||
19095 | +------------------------+---------------+----------+-----------+ | |
19096 | |transport_filter_timeout|Use: transports|Type: time|Default: 5m| | |
19097 | +------------------------+---------------+----------+-----------+ | |
19098 | ||
19099 | When Exim is reading the output of a transport filter, it applies a timeout | |
19100 | that can be set by this option. Exceeding the timeout is normally treated as a | |
19101 | temporary delivery failure. However, if a transport filter is used with a pipe | |
19102 | transport, a timeout in the transport filter is treated in the same way as a | |
19103 | timeout in the pipe command itself. By default, a timeout is a hard error, but | |
19104 | if the pipe transport's timeout_defer option is set true, it becomes a | |
19105 | temporary error. | |
19106 | ||
19107 | +----+---------------+-------------+------------------+ | |
19108 | |user|Use: transports|Type: string*|Default: Exim user| | |
19109 | +----+---------------+-------------+------------------+ | |
19110 | ||
19111 | This option specifies the user under whose uid the delivery process is to be | |
19112 | run, overriding any uid that may have been set by the router. If the user is | |
19113 | given as a name, the uid is looked up from the password data, and the | |
19114 | associated group is taken as the value of the gid to be used if the group | |
19115 | option is not set. | |
19116 | ||
19117 | For deliveries that use local transports, a user and group are normally | |
19118 | specified explicitly or implicitly (for example, as a result of | |
19119 | check_local_user) by the router or transport. | |
19120 | ||
19121 | For remote transports, you should leave this option unset unless you really are | |
19122 | sure you know what you are doing. When a remote transport is running, it needs | |
19123 | to be able to access Exim's hints databases, because each host may have its own | |
19124 | retry data. | |
19125 | ||
19126 | ||
19127 | ||
19128 | =============================================================================== | |
19129 | 25. ADDRESS BATCHING IN LOCAL TRANSPORTS | |
19130 | ||
19131 | The only remote transport (smtp) is normally configured to handle more than one | |
19132 | address at a time, so that when several addresses are routed to the same remote | |
19133 | host, just one copy of the message is sent. Local transports, however, normally | |
19134 | handle one address at a time. That is, a separate instance of the transport is | |
19135 | run for each address that is routed to the transport. A separate copy of the | |
19136 | message is delivered each time. | |
19137 | ||
19138 | In special cases, it may be desirable to handle several addresses at once in a | |
19139 | local transport, for example: | |
19140 | ||
19141 | * In an appendfile transport, when storing messages in files for later | |
19142 | delivery by some other means, a single copy of the message with multiple | |
19143 | recipients saves space. | |
19144 | ||
19145 | * In an lmtp transport, when delivering over "local SMTP" to some process, a | |
19146 | single copy saves time, and is the normal way LMTP is expected to work. | |
19147 | ||
19148 | * In a pipe transport, when passing the message to a scanner program or to | |
19149 | some other delivery mechanism such as UUCP, multiple recipients may be | |
19150 | acceptable. | |
19151 | ||
19152 | These three local transports all have the same options for controlling multiple | |
19153 | ("batched") deliveries, namely batch_max and batch_id. To save repeating the | |
19154 | information for each transport, these options are described here. | |
19155 | ||
19156 | The batch_max option specifies the maximum number of addresses that can be | |
19157 | delivered together in a single run of the transport. Its default value is one | |
19158 | (no batching). When more than one address is routed to a transport that has a | |
19159 | batch_max value greater than one, the addresses are delivered in a batch (that | |
19160 | is, in a single run of the transport with multiple recipients), subject to | |
19161 | certain conditions: | |
19162 | ||
19163 | * If any of the transport's options contain a reference to $local_part, no | |
19164 | batching is possible. | |
19165 | ||
19166 | * If any of the transport's options contain a reference to $domain, only | |
19167 | addresses with the same domain are batched. | |
19168 | ||
19169 | * If batch_id is set, it is expanded for each address, and only those | |
19170 | addresses with the same expanded value are batched. This allows you to | |
19171 | specify customized batching conditions. Failure of the expansion for any | |
19172 | reason, including forced failure, disables batching, but it does not stop | |
19173 | the delivery from taking place. | |
19174 | ||
19175 | * Batched addresses must also have the same errors address (where to send | |
19176 | delivery errors), the same header additions and removals, the same user and | |
19177 | group for the transport, and if a host list is present, the first host must | |
19178 | be the same. | |
19179 | ||
19180 | In the case of the appendfile and pipe transports, batching applies both when | |
19181 | the file or pipe command is specified in the transport, and when it is | |
19182 | specified by a redirect router, but all the batched addresses must of course be | |
19183 | routed to the same file or pipe command. These two transports have an option | |
19184 | called use_bsmtp, which causes them to deliver the message in "batched SMTP" | |
19185 | format, with the envelope represented as SMTP commands. The check_string and | |
19186 | escape_string options are forced to the values | |
19187 | ||
19188 | check_string = "." | |
19189 | escape_string = ".." | |
19190 | ||
19191 | when batched SMTP is in use. A full description of the batch SMTP mechanism is | |
19192 | given in section 47.10. The lmtp transport does not have a use_bsmtp option, | |
19193 | because it always delivers using the SMTP protocol. | |
19194 | ||
19195 | If the generic envelope_to_add option is set for a batching transport, the | |
19196 | Envelope-to: header that is added to the message contains all the addresses | |
19197 | that are being processed together. If you are using a batching appendfile | |
19198 | transport without use_bsmtp, the only way to preserve the recipient addresses | |
19199 | is to set the envelope_to_add option. | |
19200 | ||
19201 | If you are using a pipe transport without BSMTP, and setting the transport's | |
19202 | command option, you can include $pipe_addresses as part of the command. This is | |
19203 | not a true variable; it is a bit of magic that causes each of the recipient | |
19204 | addresses to be inserted into the command as a separate argument. This provides | |
19205 | a way of accessing all the addresses that are being delivered in the batch. | |
19206 | Note: This is not possible for pipe commands that are specified by a redirect | |
19207 | router. | |
19208 | ||
19209 | ||
19210 | ||
19211 | =============================================================================== | |
19212 | 26. THE APPENDFILE TRANSPORT | |
19213 | ||
19214 | The appendfile transport delivers a message by appending it to an existing | |
19215 | file, or by creating an entirely new file in a specified directory. Single | |
19216 | files to which messages are appended can be in the traditional Unix mailbox | |
19217 | format, or optionally in the MBX format supported by the Pine MUA and | |
19218 | University of Washington IMAP daemon, inter alia. When each message is being | |
19219 | delivered as a separate file, "maildir" format can optionally be used to give | |
19220 | added protection against failures that happen part-way through the delivery. A | |
19221 | third form of separate-file delivery known as "mailstore" is also supported. | |
19222 | For all file formats, Exim attempts to create as many levels of directory as | |
19223 | necessary, provided that create_directory is set. | |
19224 | ||
19225 | The code for the optional formats is not included in the Exim binary by | |
19226 | default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or | |
19227 | SUPPORT_MAILSTORE in Local/Makefile to have the appropriate code included. | |
19228 | ||
19229 | Exim recognizes system quota errors, and generates an appropriate message. Exim | |
19230 | also supports its own quota control within the transport, for use when the | |
19231 | system facility is unavailable or cannot be used for some reason. | |
19232 | ||
19233 | If there is an error while appending to a file (for example, quota exceeded or | |
19234 | partition filled), Exim attempts to reset the file's length and last | |
19235 | modification time back to what they were before. If there is an error while | |
19236 | creating an entirely new file, the new file is removed. | |
19237 | ||
19238 | Before appending to a file, a number of security checks are made, and the file | |
19239 | is locked. A detailed description is given below, after the list of private | |
19240 | options. | |
19241 | ||
19242 | The appendfile transport is most commonly used for local deliveries to users' | |
19243 | mailboxes. However, it can also be used as a pseudo-remote transport for | |
19244 | putting messages into files for remote delivery by some means other than Exim. | |
19245 | "Batch SMTP" format is often used in this case (see the use_bsmtp option). | |
19246 | ||
19247 | ||
19248 | 26.1 The file and directory options | |
19249 | ----------------------------------- | |
19250 | ||
19251 | The file option specifies a single file, to which the message is appended; the | |
19252 | directory option specifies a directory, in which a new file containing the | |
19253 | message is created. Only one of these two options can be set, and for normal | |
19254 | deliveries to mailboxes, one of them must be set. | |
19255 | ||
19256 | However, appendfile is also used for delivering messages to files or | |
19257 | directories whose names (or parts of names) are obtained from alias, | |
19258 | forwarding, or filtering operations (for example, a save command in a user's | |
19259 | Exim filter). When such a transport is running, $local_part contains the local | |
19260 | part that was aliased or forwarded, and $address_file contains the name (or | |
19261 | partial name) of the file or directory generated by the redirection operation. | |
19262 | There are two cases: | |
19263 | ||
19264 | * If neither file nor directory is set, the redirection operation must | |
19265 | specify an absolute path (one that begins with "/"). This is the most | |
19266 | common case when users with local accounts use filtering to sort mail into | |
19267 | different folders. See for example, the address_file transport in the | |
19268 | default configuration. If the path ends with a slash, it is assumed to be | |
19269 | the name of a directory. A delivery to a directory can also be forced by | |
19270 | setting maildir_format or mailstore_format. | |
19271 | ||
19272 | * If file or directory is set for a delivery from a redirection, it is used | |
19273 | to determine the file or directory name for the delivery. Normally, the | |
19274 | contents of $address_file are used in some way in the string expansion. | |
19275 | ||
19276 | As an example of the second case, consider an environment where users do not | |
19277 | have home directories. They may be permitted to use Exim filter commands of the | |
19278 | form: | |
19279 | ||
19280 | save folder23 | |
19281 | ||
19282 | or Sieve filter commands of the form: | |
19283 | ||
19284 | require "fileinto"; | |
19285 | fileinto "folder23"; | |
19286 | ||
19287 | In this situation, the expansion of file or directory in the transport must | |
19288 | transform the relative path into an appropriate absolute file name. In the case | |
19289 | of Sieve filters, the name inbox must be handled. It is the name that is used | |
19290 | as a result of a "keep" action in the filter. This example shows one way of | |
19291 | handling this requirement: | |
19292 | ||
19293 | file = ${if eq{$address_file}{inbox} \ | |
19294 | {/var/mail/$local_part} \ | |
19295 | {${if eq{${substr_0_1:$address_file}}{/} \ | |
19296 | {$address_file} \ | |
19297 | {$home/mail/$address_file} \ | |
19298 | }} \ | |
19299 | } | |
19300 | ||
19301 | With this setting of file, inbox refers to the standard mailbox location, | |
19302 | absolute paths are used without change, and other folders are in the mail | |
19303 | directory within the home directory. | |
19304 | ||
19305 | Note 1: While processing an Exim filter, a relative path such as folder23 is | |
19306 | turned into an absolute path if a home directory is known to the router. In | |
19307 | particular, this is the case if check_local_user is set. If you want to prevent | |
19308 | this happening at routing time, you can set router_home_directory empty. This | |
19309 | forces the router to pass the relative path to the transport. | |
19310 | ||
19311 | Note 2: An absolute path in $address_file is not treated specially; the file or | |
19312 | directory option is still used if it is set. | |
19313 | ||
19314 | ||
19315 | 26.2 Private options for appendfile | |
19316 | ----------------------------------- | |
19317 | ||
19318 | +----------+---------------+-------------+--------------+ | |
19319 | |allow_fifo|Use: appendfile|Type: boolean|Default: false| | |
19320 | +----------+---------------+-------------+--------------+ | |
19321 | ||
19322 | Setting this option permits delivery to named pipes (FIFOs) as well as to | |
19323 | regular files. If no process is reading the named pipe at delivery time, the | |
19324 | delivery is deferred. | |
19325 | ||
19326 | +-------------+---------------+-------------+--------------+ | |
19327 | |allow_symlink|Use: appendfile|Type: boolean|Default: false| | |
19328 | +-------------+---------------+-------------+--------------+ | |
19329 | ||
19330 | By default, appendfile will not deliver if the path name for the file is that | |
19331 | of a symbolic link. Setting this option relaxes that constraint, but there are | |
19332 | security issues involved in the use of symbolic links. Be sure you know what | |
19333 | you are doing if you set this. Details of exactly what this option affects are | |
19334 | included in the discussion which follows this list of options. | |
19335 | ||
19336 | +--------+---------------+-------------+--------------+ | |
19337 | |batch_id|Use: appendfile|Type: string*|Default: unset| | |
19338 | +--------+---------------+-------------+--------------+ | |
19339 | ||
19340 | See the description of local delivery batching in chapter 25. However, batching | |
19341 | is automatically disabled for appendfile deliveries that happen as a result of | |
19342 | forwarding or aliasing or other redirection directly to a file. | |
19343 | ||
19344 | +---------+---------------+-------------+----------+ | |
19345 | |batch_max|Use: appendfile|Type: integer|Default: 1| | |
19346 | +---------+---------------+-------------+----------+ | |
19347 | ||
19348 | See the description of local delivery batching in chapter 25. | |
19349 | ||
19350 | +-----------+---------------+-------------+--------------+ | |
19351 | |check_group|Use: appendfile|Type: boolean|Default: false| | |
19352 | +-----------+---------------+-------------+--------------+ | |
19353 | ||
19354 | When this option is set, the group owner of the file defined by the file option | |
19355 | is checked to see that it is the same as the group under which the delivery | |
19356 | process is running. The default setting is false because the default file mode | |
19357 | is 0600, which means that the group is irrelevant. | |
19358 | ||
19359 | +-----------+---------------+-------------+-------------+ | |
19360 | |check_owner|Use: appendfile|Type: boolean|Default: true| | |
19361 | +-----------+---------------+-------------+-------------+ | |
19362 | ||
19363 | When this option is set, the owner of the file defined by the file option is | |
19364 | checked to ensure that it is the same as the user under which the delivery | |
19365 | process is running. | |
19366 | ||
19367 | +------------+---------------+------------+------------------+ | |
19368 | |check_string|Use: appendfile|Type: string|Default: see below| | |
19369 | +------------+---------------+------------+------------------+ | |
19370 | ||
19371 | As appendfile writes the message, the start of each line is tested for matching | |
19372 | check_string, and if it does, the initial matching characters are replaced by | |
19373 | the contents of escape_string. The value of check_string is a literal string, | |
19374 | not a regular expression, and the case of any letters it contains is | |
19375 | significant. | |
19376 | ||
19377 | If use_bsmtp is set the values of check_string and escape_string are forced to | |
19378 | "." and ".." respectively, and any settings in the configuration are ignored. | |
19379 | Otherwise, they default to "From " and ">From " when the file option is set, | |
19380 | and unset when any of the directory, maildir, or mailstore options are set. | |
19381 | ||
19382 | The default settings, along with message_prefix and message_suffix, are | |
19383 | suitable for traditional "BSD" mailboxes, where a line beginning with "From " | |
19384 | indicates the start of a new message. All four options need changing if another | |
19385 | format is used. For example, to deliver to mailboxes in MMDF format: | |
19386 | ||
19387 | check_string = "\1\1\1\1\n" | |
19388 | escape_string = "\1\1\1\1 \n" | |
19389 | message_prefix = "\1\1\1\1\n" | |
19390 | message_suffix = "\1\1\1\1\n" | |
19391 | ||
19392 | +----------------+---------------+-------------+-------------+ | |
19393 | |create_directory|Use: appendfile|Type: boolean|Default: true| | |
19394 | +----------------+---------------+-------------+-------------+ | |
19395 | ||
19396 | When this option is true, Exim attempts to create any missing superior | |
19397 | directories for the file that it is about to write. A created directory's mode | |
19398 | is given by the directory_mode option. | |
19399 | ||
19400 | The group ownership of a newly created directory is highly dependent on the | |
19401 | operating system (and possibly the file system) that is being used. For | |
19402 | example, in Solaris, if the parent directory has the setgid bit set, its group | |
19403 | is propagated to the child; if not, the currently set group is used. However, | |
19404 | in FreeBSD, the parent's group is always used. | |
19405 | ||
19406 | +-----------+---------------+------------+-----------------+ | |
19407 | |create_file|Use: appendfile|Type: string|Default: anywhere| | |
19408 | +-----------+---------------+------------+-----------------+ | |
19409 | ||
19410 | This option constrains the location of files and directories that are created | |
19411 | by this transport. It applies to files defined by the file option and | |
19412 | directories defined by the directory option. In the case of maildir delivery, | |
19413 | it applies to the top level directory, not the maildir directories beneath. | |
19414 | ||
19415 | The option must be set to one of the words "anywhere", "inhome", or | |
19416 | "belowhome". In the second and third cases, a home directory must have been set | |
19417 | for the transport. This option is not useful when an explicit file name is | |
19418 | given for normal mailbox deliveries. It is intended for the case when file | |
19419 | names are generated from users' .forward files. These are usually handled by an | |
19420 | appendfile transport called address_file. See also file_must_exist. | |
19421 | ||
19422 | +---------+---------------+-------------+--------------+ | |
19423 | |directory|Use: appendfile|Type: string*|Default: unset| | |
19424 | +---------+---------------+-------------+--------------+ | |
19425 | ||
19426 | This option is mutually exclusive with the file option, but one of file or | |
19427 | directory must be set, unless the delivery is the direct result of a | |
19428 | redirection (see section 26.1). | |
19429 | ||
19430 | When directory is set, the string is expanded, and the message is delivered | |
19431 | into a new file or files in or below the given directory, instead of being | |
19432 | appended to a single mailbox file. A number of different formats are provided | |
19433 | (see maildir_format and mailstore_format), and see section 26.4 for further | |
19434 | details of this form of delivery. | |
19435 | ||
19436 | +--------------+---------------+-------------+------------------+ | |
19437 | |directory_file|Use: appendfile|Type: string*|Default: see below| | |
19438 | +--------------+---------------+-------------+------------------+ | |
19439 | ||
19440 | When directory is set, but neither maildir_format nor mailstore_format is set, | |
19441 | appendfile delivers each message into a file whose name is obtained by | |
19442 | expanding this string. The default value is: | |
19443 | ||
19444 | q${base62:$tod_epoch}-$inode | |
19445 | ||
19446 | This generates a unique name from the current time, in base 62 form, and the | |
19447 | inode of the file. The variable $inode is available only when expanding this | |
19448 | option. | |
19449 | ||
19450 | +--------------+---------------+-------------------+-------------+ | |
19451 | |directory_mode|Use: appendfile|Type: octal integer|Default: 0700| | |
19452 | +--------------+---------------+-------------------+-------------+ | |
19453 | ||
19454 | If appendfile creates any directories as a result of the create_directory | |
19455 | option, their mode is specified by this option. | |
19456 | ||
19457 | +-------------+---------------+------------+------------------------+ | |
19458 | |escape_string|Use: appendfile|Type: string|Default: see description| | |
19459 | +-------------+---------------+------------+------------------------+ | |
19460 | ||
19461 | See check_string above. | |
19462 | ||
19463 | +----+---------------+-------------+--------------+ | |
19464 | |file|Use: appendfile|Type: string*|Default: unset| | |
19465 | +----+---------------+-------------+--------------+ | |
19466 | ||
19467 | This option is mutually exclusive with the directory option, but one of file or | |
19468 | directory must be set, unless the delivery is the direct result of a | |
19469 | redirection (see section 26.1). The file option specifies a single file, to | |
19470 | which the message is appended. One or more of use_fcntl_lock, use_flock_lock, | |
19471 | or use_lockfile must be set with file. | |
19472 | ||
19473 | If you are using more than one host to deliver over NFS into the same | |
19474 | mailboxes, you should always use lock files. | |
19475 | ||
19476 | The string value is expanded for each delivery, and must yield an absolute | |
19477 | path. The most common settings of this option are variations on one of these | |
19478 | examples: | |
19479 | ||
19480 | file = /var/spool/mail/$local_part | |
19481 | file = /home/$local_part/inbox | |
19482 | file = $home/inbox | |
19483 | ||
19484 | In the first example, all deliveries are done into the same directory. If Exim | |
19485 | is configured to use lock files (see use_lockfile below) it must be able to | |
19486 | create a file in the directory, so the "sticky" bit must be turned on for | |
19487 | deliveries to be possible, or alternatively the group option can be used to run | |
19488 | the delivery under a group id which has write access to the directory. | |
19489 | ||
19490 | +-----------+---------------+------------+--------------+ | |
19491 | |file_format|Use: appendfile|Type: string|Default: unset| | |
19492 | +-----------+---------------+------------+--------------+ | |
19493 | ||
19494 | This option requests the transport to check the format of an existing file | |
19495 | before adding to it. The check consists of matching a specific string at the | |
19496 | start of the file. The value of the option consists of an even number of | |
19497 | colon-separated strings. The first of each pair is the test string, and the | |
19498 | second is the name of a transport. If the transport associated with a matched | |
19499 | string is not the current transport, control is passed over to the other | |
19500 | transport. For example, suppose the standard local_delivery transport has this | |
19501 | added to it: | |
19502 | ||
19503 | file_format = "From : local_delivery :\ | |
19504 | \1\1\1\1\n : local_mmdf_delivery" | |
19505 | ||
19506 | Mailboxes that begin with "From" are still handled by this transport, but if a | |
19507 | mailbox begins with four binary ones followed by a newline, control is passed | |
19508 | to a transport called local_mmdf_delivery, which presumably is configured to do | |
19509 | the delivery in MMDF format. If a mailbox does not exist or is empty, it is | |
19510 | assumed to match the current transport. If the start of a mailbox doesn't match | |
19511 | any string, or if the transport named for a given string is not defined, | |
19512 | delivery is deferred. | |
19513 | ||
19514 | +---------------+---------------+-------------+--------------+ | |
19515 | |file_must_exist|Use: appendfile|Type: boolean|Default: false| | |
19516 | +---------------+---------------+-------------+--------------+ | |
19517 | ||
19518 | If this option is true, the file specified by the file option must exist. A | |
19519 | temporary error occurs if it does not, causing delivery to be deferred. If this | |
19520 | option is false, the file is created if it does not exist. | |
19521 | ||
19522 | +------------------+---------------+----------+-----------+ | |
19523 | |lock_fcntl_timeout|Use: appendfile|Type: time|Default: 0s| | |
19524 | +------------------+---------------+----------+-----------+ | |
19525 | ||
19526 | By default, the appendfile transport uses non-blocking calls to fcntl() when | |
19527 | locking an open mailbox file. If the call fails, the delivery process sleeps | |
19528 | for lock_interval and tries again, up to lock_retries times. Non-blocking calls | |
19529 | are used so that the file is not kept open during the wait for the lock; the | |
19530 | reason for this is to make it as safe as possible for deliveries over NFS in | |
19531 | the case when processes might be accessing an NFS mailbox without using a lock | |
19532 | file. This should not be done, but misunderstandings and hence | |
19533 | misconfigurations are not unknown. | |
19534 | ||
19535 | On a busy system, however, the performance of a non-blocking lock approach is | |
19536 | not as good as using a blocking lock with a timeout. In this case, the waiting | |
19537 | is done inside the system call, and Exim's delivery process acquires the lock | |
19538 | and can proceed as soon as the previous lock holder releases it. | |
19539 | ||
19540 | If lock_fcntl_timeout is set to a non-zero time, blocking locks, with that | |
19541 | timeout, are used. There may still be some retrying: the maximum number of | |
19542 | retries is | |
19543 | ||
19544 | (lock_retries * lock_interval) / lock_fcntl_timeout | |
19545 | ||
19546 | rounded up to the next whole number. In other words, the total time during | |
19547 | which appendfile is trying to get a lock is roughly the same, unless | |
19548 | lock_fcntl_timeout is set very large. | |
19549 | ||
19550 | You should consider setting this option if you are getting a lot of delayed | |
19551 | local deliveries because of errors of the form | |
19552 | ||
19553 | failed to lock mailbox /some/file (fcntl) | |
19554 | ||
19555 | +------------------+---------------+----------+-----------+ | |
19556 | |lock_flock_timeout|Use: appendfile|Type: time|Default: 0s| | |
19557 | +------------------+---------------+----------+-----------+ | |
19558 | ||
19559 | This timeout applies to file locking when using flock() (see use_flock); the | |
19560 | timeout operates in a similar manner to lock_fcntl_timeout. | |
19561 | ||
19562 | +-------------+---------------+----------+-----------+ | |
19563 | |lock_interval|Use: appendfile|Type: time|Default: 3s| | |
19564 | +-------------+---------------+----------+-----------+ | |
19565 | ||
19566 | This specifies the time to wait between attempts to lock the file. See below | |
19567 | for details of locking. | |
19568 | ||
19569 | +------------+---------------+-------------+-----------+ | |
19570 | |lock_retries|Use: appendfile|Type: integer|Default: 10| | |
19571 | +------------+---------------+-------------+-----------+ | |
19572 | ||
19573 | This specifies the maximum number of attempts to lock the file. A value of zero | |
19574 | is treated as 1. See below for details of locking. | |
19575 | ||
19576 | +-------------+---------------+-------------------+-------------+ | |
19577 | |lockfile_mode|Use: appendfile|Type: octal integer|Default: 0600| | |
19578 | +-------------+---------------+-------------------+-------------+ | |
19579 | ||
19580 | This specifies the mode of the created lock file, when a lock file is being | |
19581 | used (see use_lockfile and use_mbx_lock). | |
19582 | ||
19583 | +----------------+---------------+----------+------------+ | |
19584 | |lockfile_timeout|Use: appendfile|Type: time|Default: 30m| | |
19585 | +----------------+---------------+----------+------------+ | |
19586 | ||
19587 | When a lock file is being used (see use_lockfile), if a lock file already | |
19588 | exists and is older than this value, it is assumed to have been left behind by | |
19589 | accident, and Exim attempts to remove it. | |
19590 | ||
19591 | +-----------------+---------------+-------------+--------------+ | |
19592 | |mailbox_filecount|Use: appendfile|Type: string*|Default: unset| | |
19593 | +-----------------+---------------+-------------+--------------+ | |
19594 | ||
19595 | If this option is set, it is expanded, and the result is taken as the current | |
19596 | number of files in the mailbox. It must be a decimal number, optionally | |
19597 | followed by K or M. This provides a way of obtaining this information from an | |
19598 | external source that maintains the data. | |
19599 | ||
19600 | +------------+---------------+-------------+--------------+ | |
19601 | |mailbox_size|Use: appendfile|Type: string*|Default: unset| | |
19602 | +------------+---------------+-------------+--------------+ | |
19603 | ||
19604 | If this option is set, it is expanded, and the result is taken as the current | |
19605 | size the mailbox. It must be a decimal number, optionally followed by K or M. | |
19606 | This provides a way of obtaining this information from an external source that | |
19607 | maintains the data. This is likely to be helpful for maildir deliveries where | |
19608 | it is computationally expensive to compute the size of a mailbox. | |
19609 | ||
19610 | +--------------+---------------+-------------+--------------+ | |
19611 | |maildir_format|Use: appendfile|Type: boolean|Default: false| | |
19612 | +--------------+---------------+-------------+--------------+ | |
19613 | ||
19614 | If this option is set with the directory option, the delivery is into a new | |
19615 | file, in the "maildir" format that is used by other mail software. When the | |
19616 | transport is activated directly from a redirect router (for example, the | |
19617 | address_file transport in the default configuration), setting maildir_format | |
19618 | causes the path received from the router to be treated as a directory, whether | |
19619 | or not it ends with "/". This option is available only if SUPPORT_MAILDIR is | |
19620 | present in Local/Makefile. See section 26.5 below for further details. | |
19621 | ||
19622 | +-----------------------------+---------------+------------+------------------+ | |
19623 | |maildir_quota_directory_regex|Use: appendfile|Type: string|Default: See below| | |
19624 | +-----------------------------+---------------+------------+------------------+ | |
19625 | ||
19626 | This option is relevant only when maildir_use_size_file is set. It defines a | |
19627 | regular expression for specifying directories, relative to the quota directory | |
19628 | (see quota_directory), that should be included in the quota calculation. The | |
19629 | default value is: | |
19630 | ||
19631 | maildir_quota_directory_regex = ^(?:cur|new|\..*)$ | |
19632 | ||
19633 | This includes the cur and new directories, and any maildir++ folders | |
19634 | (directories whose names begin with a dot). If you want to exclude the Trash | |
19635 | folder from the count (as some sites do), you need to change this setting to | |
19636 | ||
19637 | maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$ | |
19638 | ||
19639 | This uses a negative lookahead in the regular expression to exclude the | |
19640 | directory whose name is .Trash. When a directory is excluded from quota | |
19641 | calculations, quota processing is bypassed for any messages that are delivered | |
19642 | directly into that directory. | |
19643 | ||
19644 | +---------------+---------------+-------------+-----------+ | |
19645 | |maildir_retries|Use: appendfile|Type: integer|Default: 10| | |
19646 | +---------------+---------------+-------------+-----------+ | |
19647 | ||
19648 | This option specifies the number of times to retry when writing a file in | |
19649 | "maildir" format. See section 26.5 below. | |
19650 | ||
19651 | +-----------+---------------+-------------+--------------+ | |
19652 | |maildir_tag|Use: appendfile|Type: string*|Default: unset| | |
19653 | +-----------+---------------+-------------+--------------+ | |
19654 | ||
19655 | This option applies only to deliveries in maildir format, and is described in | |
19656 | section 26.5 below. | |
19657 | ||
19658 | +---------------------+----------------+-------------+--------------+ | |
19659 | |maildir_use_size_file|Use: appendfile*|Type: boolean|Default: false| | |
19660 | +---------------------+----------------+-------------+--------------+ | |
19661 | ||
19662 | The result of string expansion for this option must be a valid boolean value. | |
19663 | If it is true, it enables support for maildirsize files. Exim creates a | |
19664 | maildirsize file in a maildir if one does not exist, taking the quota from the | |
19665 | quota option of the transport. If quota is unset, the value is zero. See | |
19666 | maildir_quota_directory_regex above and section 26.5 below for further details. | |
19667 | ||
19668 | +--------------------------+---------------+------------+--------------+ | |
19669 | |maildirfolder_create_regex|Use: appendfile|Type: string|Default: unset| | |
19670 | +--------------------------+---------------+------------+--------------+ | |
19671 | ||
19672 | The value of this option is a regular expression. If it is unset, it has no | |
19673 | effect. Otherwise, before a maildir delivery takes place, the pattern is | |
19674 | matched against the name of the maildir directory, that is, the directory | |
19675 | containing the new and tmp subdirectories that will be used for the delivery. | |
19676 | If there is a match, Exim checks for the existence of a file called | |
19677 | maildirfolder in the directory, and creates it if it does not exist. See | |
19678 | section 26.5 for more details. | |
19679 | ||
19680 | +----------------+---------------+-------------+--------------+ | |
19681 | |mailstore_format|Use: appendfile|Type: boolean|Default: false| | |
19682 | +----------------+---------------+-------------+--------------+ | |
19683 | ||
19684 | If this option is set with the directory option, the delivery is into two new | |
19685 | files in "mailstore" format. The option is available only if SUPPORT_MAILSTORE | |
19686 | is present in Local/Makefile. See section 26.4 below for further details. | |
19687 | ||
19688 | +----------------+---------------+-------------+--------------+ | |
19689 | |mailstore_prefix|Use: appendfile|Type: string*|Default: unset| | |
19690 | +----------------+---------------+-------------+--------------+ | |
19691 | ||
19692 | This option applies only to deliveries in mailstore format, and is described in | |
19693 | section 26.4 below. | |
19694 | ||
19695 | +----------------+---------------+-------------+--------------+ | |
19696 | |mailstore_suffix|Use: appendfile|Type: string*|Default: unset| | |
19697 | +----------------+---------------+-------------+--------------+ | |
19698 | ||
19699 | This option applies only to deliveries in mailstore format, and is described in | |
19700 | section 26.4 below. | |
19701 | ||
19702 | +----------+---------------+-------------+--------------+ | |
19703 | |mbx_format|Use: appendfile|Type: boolean|Default: false| | |
19704 | +----------+---------------+-------------+--------------+ | |
19705 | ||
19706 | This option is available only if Exim has been compiled with SUPPORT_MBX set in | |
19707 | Local/Makefile. If mbx_format is set with the file option, the message is | |
19708 | appended to the mailbox file in MBX format instead of traditional Unix format. | |
19709 | This format is supported by Pine4 and its associated IMAP and POP daemons, by | |
19710 | means of the c-client library that they all use. | |
19711 | ||
19712 | Note: The message_prefix and message_suffix options are not automatically | |
19713 | changed by the use of mbx_format. They should normally be set empty when using | |
19714 | MBX format, so this option almost always appears in this combination: | |
19715 | ||
19716 | mbx_format = true | |
19717 | message_prefix = | |
19718 | message_suffix = | |
19719 | ||
19720 | If none of the locking options are mentioned in the configuration, use_mbx_lock | |
19721 | is assumed and the other locking options default to false. It is possible to | |
19722 | specify the other kinds of locking with mbx_format, but use_fcntl_lock and | |
19723 | use_mbx_lock are mutually exclusive. MBX locking interworks with c-client, | |
19724 | providing for shared access to the mailbox. It should not be used if any | |
19725 | program that does not use this form of locking is going to access the mailbox, | |
19726 | nor should it be used if the mailbox file is NFS mounted, because it works only | |
19727 | when the mailbox is accessed from a single host. | |
19728 | ||
19729 | If you set use_fcntl_lock with an MBX-format mailbox, you cannot use the | |
19730 | standard version of c-client, because as long as it has a mailbox open (this | |
19731 | means for the whole of a Pine or IMAP session), Exim will not be able to append | |
19732 | messages to it. | |
19733 | ||
19734 | +--------------+---------------+-------------+------------------+ | |
19735 | |message_prefix|Use: appendfile|Type: string*|Default: see below| | |
19736 | +--------------+---------------+-------------+------------------+ | |
19737 | ||
19738 | The string specified here is expanded and output at the start of every message. | |
19739 | The default is unset unless file is specified and use_bsmtp is not set, in | |
19740 | which case it is: | |
19741 | ||
19742 | message_prefix = "From ${if def:return_path{$return_path}\ | |
19743 | {MAILER-DAEMON}} $tod_bsdinbox\n" | |
19744 | ||
19745 | Note: If you set use_crlf true, you must change any occurrences of "\n" to "\r\ | |
19746 | n" in message_prefix. | |
19747 | ||
19748 | +--------------+---------------+-------------+------------------+ | |
19749 | |message_suffix|Use: appendfile|Type: string*|Default: see below| | |
19750 | +--------------+---------------+-------------+------------------+ | |
19751 | ||
19752 | The string specified here is expanded and output at the end of every message. | |
19753 | The default is unset unless file is specified and use_bsmtp is not set, in | |
19754 | which case it is a single newline character. The suffix can be suppressed by | |
19755 | setting | |
19756 | ||
19757 | message_suffix = | |
19758 | ||
19759 | Note: If you set use_crlf true, you must change any occurrences of "\n" to "\r\ | |
19760 | n" in message_suffix. | |
19761 | ||
19762 | +----+---------------+-------------------+-------------+ | |
19763 | |mode|Use: appendfile|Type: octal integer|Default: 0600| | |
19764 | +----+---------------+-------------------+-------------+ | |
19765 | ||
19766 | If the output file is created, it is given this mode. If it already exists and | |
19767 | has wider permissions, they are reduced to this mode. If it has narrower | |
19768 | permissions, an error occurs unless mode_fail_narrower is false. However, if | |
19769 | the delivery is the result of a save command in a filter file specifying a | |
19770 | particular mode, the mode of the output file is always forced to take that | |
19771 | value, and this option is ignored. | |
19772 | ||
19773 | +------------------+---------------+-------------+-------------+ | |
19774 | |mode_fail_narrower|Use: appendfile|Type: boolean|Default: true| | |
19775 | +------------------+---------------+-------------+-------------+ | |
19776 | ||
19777 | This option applies in the case when an existing mailbox file has a narrower | |
19778 | mode than that specified by the mode option. If mode_fail_narrower is true, the | |
19779 | delivery is deferred ("mailbox has the wrong mode"); otherwise Exim continues | |
19780 | with the delivery attempt, using the existing mode of the file. | |
19781 | ||
19782 | +-------------+---------------+-------------+--------------+ | |
19783 | |notify_comsat|Use: appendfile|Type: boolean|Default: false| | |
19784 | +-------------+---------------+-------------+--------------+ | |
19785 | ||
19786 | If this option is true, the comsat daemon is notified after every successful | |
19787 | delivery to a user mailbox. This is the daemon that notifies logged on users | |
19788 | about incoming mail. | |
19789 | ||
19790 | +-----+---------------+-------------+--------------+ | |
19791 | |quota|Use: appendfile|Type: string*|Default: unset| | |
19792 | +-----+---------------+-------------+--------------+ | |
19793 | ||
19794 | This option imposes a limit on the size of the file to which Exim is appending, | |
19795 | or to the total space used in the directory tree when the directory option is | |
19796 | set. In the latter case, computation of the space used is expensive, because | |
19797 | all the files in the directory (and any sub-directories) have to be | |
19798 | individually inspected and their sizes summed. (See quota_size_regex and | |
19799 | maildir_use_size_file for ways to avoid this in environments where users have | |
19800 | no shell access to their mailboxes). | |
19801 | ||
19802 | As there is no interlock against two simultaneous deliveries into a multi-file | |
19803 | mailbox, it is possible for the quota to be overrun in this case. For | |
19804 | single-file mailboxes, of course, an interlock is a necessity. | |
19805 | ||
19806 | A file's size is taken as its used value. Because of blocking effects, this may | |
19807 | be a lot less than the actual amount of disk space allocated to the file. If | |
19808 | the sizes of a number of files are being added up, the rounding effect can | |
19809 | become quite noticeable, especially on systems that have large block sizes. | |
19810 | Nevertheless, it seems best to stick to the used figure, because this is the | |
19811 | obvious value which users understand most easily. | |
19812 | ||
19813 | The value of the option is expanded, and must then be a numerical value | |
19814 | (decimal point allowed), optionally followed by one of the letters K, M, or G, | |
19815 | for kilobytes, megabytes, or gigabytes. If Exim is running on a system with | |
19816 | large file support (Linux and FreeBSD have this), mailboxes larger than 2G can | |
19817 | be handled. | |
19818 | ||
19819 | Note: A value of zero is interpreted as "no quota". | |
19820 | ||
19821 | The expansion happens while Exim is running as root, before it changes uid for | |
19822 | the delivery. This means that files that are inaccessible to the end user can | |
19823 | be used to hold quota values that are looked up in the expansion. When delivery | |
19824 | fails because this quota is exceeded, the handling of the error is as for | |
19825 | system quota failures. | |
19826 | ||
19827 | By default, Exim's quota checking mimics system quotas, and restricts the | |
19828 | mailbox to the specified maximum size, though the value is not accurate to the | |
19829 | last byte, owing to separator lines and additional headers that may get added | |
19830 | during message delivery. When a mailbox is nearly full, large messages may get | |
19831 | refused even though small ones are accepted, because the size of the current | |
19832 | message is added to the quota when the check is made. This behaviour can be | |
19833 | changed by setting quota_is_inclusive false. When this is done, the check for | |
19834 | exceeding the quota does not include the current message. Thus, deliveries | |
19835 | continue until the quota has been exceeded; thereafter, no further messages are | |
19836 | delivered. See also quota_warn_threshold. | |
19837 | ||
19838 | +---------------+---------------+-------------+--------------+ | |
19839 | |quota_directory|Use: appendfile|Type: string*|Default: unset| | |
19840 | +---------------+---------------+-------------+--------------+ | |
19841 | ||
19842 | This option defines the directory to check for quota purposes when delivering | |
19843 | into individual files. The default is the delivery directory, or, if a file | |
19844 | called maildirfolder exists in a maildir directory, the parent of the delivery | |
19845 | directory. | |
19846 | ||
19847 | +---------------+---------------+-------------+----------+ | |
19848 | |quota_filecount|Use: appendfile|Type: string*|Default: 0| | |
19849 | +---------------+---------------+-------------+----------+ | |
19850 | ||
19851 | This option applies when the directory option is set. It limits the total | |
19852 | number of files in the directory (compare the inode limit in system quotas). It | |
19853 | can only be used if quota is also set. The value is expanded; an expansion | |
19854 | failure causes delivery to be deferred. A value of zero is interpreted as "no | |
19855 | quota". | |
19856 | ||
19857 | +------------------+---------------+-------------+-------------+ | |
19858 | |quota_is_inclusive|Use: appendfile|Type: boolean|Default: true| | |
19859 | +------------------+---------------+-------------+-------------+ | |
19860 | ||
19861 | See quota above. | |
19862 | ||
19863 | +----------------+---------------+------------+--------------+ | |
19864 | |quota_size_regex|Use: appendfile|Type: string|Default: unset| | |
19865 | +----------------+---------------+------------+--------------+ | |
19866 | ||
19867 | This option applies when one of the delivery modes that writes a separate file | |
19868 | for each message is being used. When Exim wants to find the size of one of | |
19869 | these files in order to test the quota, it first checks quota_size_regex. If | |
19870 | this is set to a regular expression that matches the file name, and it captures | |
19871 | one string, that string is interpreted as a representation of the file's size. | |
19872 | The value of quota_size_regex is not expanded. | |
19873 | ||
19874 | This feature is useful only when users have no shell access to their mailboxes | |
19875 | - otherwise they could defeat the quota simply by renaming the files. This | |
19876 | facility can be used with maildir deliveries, by setting maildir_tag to add the | |
19877 | file length to the file name. For example: | |
19878 | ||
19879 | maildir_tag = ,S=$message_size | |
19880 | quota_size_regex = ,S=(\d+) | |
19881 | ||
19882 | An alternative to $message_size is $message_linecount, which contains the | |
19883 | number of lines in the message. | |
19884 | ||
19885 | The regular expression should not assume that the length is at the end of the | |
19886 | file name (even though maildir_tag puts it there) because maildir MUAs | |
19887 | sometimes add other information onto the ends of message file names. | |
19888 | ||
19889 | Section 26.7 contains further information. | |
19890 | ||
19891 | +------------------+---------------+-------------+------------------+ | |
19892 | |quota_warn_message|Use: appendfile|Type: string*|Default: see below| | |
19893 | +------------------+---------------+-------------+------------------+ | |
19894 | ||
19895 | See below for the use of this option. If it is not set when | |
19896 | quota_warn_threshold is set, it defaults to | |
19897 | ||
19898 | quota_warn_message = "\ | |
19899 | To: $local_part@$domain\n\ | |
19900 | Subject: Your mailbox\n\n\ | |
19901 | This message is automatically created \ | |
19902 | by mail delivery software.\n\n\ | |
19903 | The size of your mailbox has exceeded \ | |
19904 | a warning threshold that is\n\ | |
19905 | set by the system administrator.\n" | |
19906 | ||
19907 | +--------------------+---------------+-------------+----------+ | |
19908 | |quota_warn_threshold|Use: appendfile|Type: string*|Default: 0| | |
19909 | +--------------------+---------------+-------------+----------+ | |
19910 | ||
19911 | This option is expanded in the same way as quota (see above). If the resulting | |
19912 | value is greater than zero, and delivery of the message causes the size of the | |
19913 | file or total space in the directory tree to cross the given threshold, a | |
19914 | warning message is sent. If quota is also set, the threshold may be specified | |
19915 | as a percentage of it by following the value with a percent sign. For example: | |
19916 | ||
19917 | quota = 10M | |
19918 | quota_warn_threshold = 75% | |
19919 | ||
19920 | If quota is not set, a setting of quota_warn_threshold that ends with a percent | |
19921 | sign is ignored. | |
19922 | ||
19923 | The warning message itself is specified by the quota_warn_message option, and | |
19924 | it must start with a To: header line containing the recipient(s) of the warning | |
19925 | message. These do not necessarily have to include the recipient(s) of the | |
19926 | original message. A Subject: line should also normally be supplied. You can | |
19927 | include any other header lines that you want. If you do not include a From: | |
19928 | line, the default is: | |
19929 | ||
19930 | From: Mail Delivery System <mailer-daemon@$qualify_domain_sender> | |
19931 | ||
19932 | If you supply a Reply-To: line, it overrides the global errors_reply_to option. | |
19933 | ||
19934 | The quota option does not have to be set in order to use this option; they are | |
19935 | independent of one another except when the threshold is specified as a | |
19936 | percentage. | |
19937 | ||
19938 | +---------+---------------+-------------+--------------+ | |
19939 | |use_bsmtp|Use: appendfile|Type: boolean|Default: false| | |
19940 | +---------+---------------+-------------+--------------+ | |
19941 | ||
19942 | If this option is set true, appendfile writes messages in "batch SMTP" format, | |
19943 | with the envelope sender and recipient(s) included as SMTP commands. If you | |
19944 | want to include a leading HELO command with such messages, you can do so by | |
19945 | setting the message_prefix option. See section 47.10 for details of batch SMTP. | |
19946 | ||
19947 | +--------+---------------+-------------+--------------+ | |
19948 | |use_crlf|Use: appendfile|Type: boolean|Default: false| | |
19949 | +--------+---------------+-------------+--------------+ | |
19950 | ||
19951 | This option causes lines to be terminated with the two-character CRLF sequence | |
19952 | (carriage return, linefeed) instead of just a linefeed character. In the case | |
19953 | of batched SMTP, the byte sequence written to the file is then an exact image | |
19954 | of what would be sent down a real SMTP connection. | |
19955 | ||
19956 | Note: The contents of the message_prefix and message_suffix options (which are | |
19957 | used to supply the traditional "From " and blank line separators in | |
19958 | Berkeley-style mailboxes) are written verbatim, so must contain their own | |
19959 | carriage return characters if these are needed. In cases where these options | |
19960 | have non-empty defaults, the values end with a single linefeed, so they must be | |
19961 | changed to end with "\r\n" if use_crlf is set. | |
19962 | ||
19963 | +--------------+---------------+-------------+------------------+ | |
19964 | |use_fcntl_lock|Use: appendfile|Type: boolean|Default: see below| | |
19965 | +--------------+---------------+-------------+------------------+ | |
19966 | ||
19967 | This option controls the use of the fcntl() function to lock a file for | |
19968 | exclusive use when a message is being appended. It is set by default unless | |
19969 | use_flock_lock is set. Otherwise, it should be turned off only if you know that | |
19970 | all your MUAs use lock file locking. When both use_fcntl_lock and | |
19971 | use_flock_lock are unset, use_lockfile must be set. | |
19972 | ||
19973 | +--------------+---------------+-------------+--------------+ | |
19974 | |use_flock_lock|Use: appendfile|Type: boolean|Default: false| | |
19975 | +--------------+---------------+-------------+--------------+ | |
19976 | ||
19977 | This option is provided to support the use of flock() for file locking, for the | |
19978 | few situations where it is needed. Most modern operating systems support fcntl | |
19979 | () and lockf() locking, and these two functions interwork with each other. Exim | |
19980 | uses fcntl() locking by default. | |
19981 | ||
19982 | This option is required only if you are using an operating system where flock() | |
19983 | is used by programs that access mailboxes (typically MUAs), and where flock() | |
19984 | does not correctly interwork with fcntl(). You can use both fcntl() and flock() | |
19985 | locking simultaneously if you want. | |
19986 | ||
19987 | Not all operating systems provide flock(). Some versions of Solaris do not have | |
19988 | it (and some, I think, provide a not quite right version built on top of lockf | |
19989 | ()). If the OS does not have flock(), Exim will be built without the ability to | |
19990 | use it, and any attempt to do so will cause a configuration error. | |
19991 | ||
19992 | Warning: flock() locks do not work on NFS files (unless flock() is just being | |
19993 | mapped onto fcntl() by the OS). | |
19994 | ||
19995 | +------------+---------------+-------------+------------------+ | |
19996 | |use_lockfile|Use: appendfile|Type: boolean|Default: see below| | |
19997 | +------------+---------------+-------------+------------------+ | |
19998 | ||
19999 | If this option is turned off, Exim does not attempt to create a lock file when | |
20000 | appending to a mailbox file. In this situation, the only locking is by fcntl(). | |
20001 | You should only turn use_lockfile off if you are absolutely sure that every MUA | |
20002 | that is ever going to look at your users' mailboxes uses fcntl() rather than a | |
20003 | lock file, and even then only when you are not delivering over NFS from more | |
20004 | than one host. | |
20005 | ||
20006 | In order to append to an NFS file safely from more than one host, it is | |
20007 | necessary to take out a lock before opening the file, and the lock file | |
20008 | achieves this. Otherwise, even with fcntl() locking, there is a risk of file | |
20009 | corruption. | |
20010 | ||
20011 | The use_lockfile option is set by default unless use_mbx_lock is set. It is not | |
20012 | possible to turn both use_lockfile and use_fcntl_lock off, except when | |
20013 | mbx_format is set. | |
20014 | ||
20015 | +------------+---------------+-------------+------------------+ | |
20016 | |use_mbx_lock|Use: appendfile|Type: boolean|Default: see below| | |
20017 | +------------+---------------+-------------+------------------+ | |
20018 | ||
20019 | This option is available only if Exim has been compiled with SUPPORT_MBX set in | |
20020 | Local/Makefile. Setting the option specifies that special MBX locking rules be | |
20021 | used. It is set by default if mbx_format is set and none of the locking options | |
20022 | are mentioned in the configuration. The locking rules are the same as are used | |
20023 | by the c-client library that underlies Pine and the IMAP4 and POP daemons that | |
20024 | come with it (see the discussion below). The rules allow for shared access to | |
20025 | the mailbox. However, this kind of locking does not work when the mailbox is | |
20026 | NFS mounted. | |
20027 | ||
20028 | You can set use_mbx_lock with either (or both) of use_fcntl_lock and | |
20029 | use_flock_lock to control what kind of locking is used in implementing the MBX | |
20030 | locking rules. The default is to use fcntl() if use_mbx_lock is set without | |
20031 | use_fcntl_lock or use_flock_lock. | |
20032 | ||
20033 | ||
20034 | 26.3 Operational details for appending | |
20035 | -------------------------------------- | |
20036 | ||
20037 | Before appending to a file, the following preparations are made: | |
20038 | ||
20039 | * If the name of the file is /dev/null, no action is taken, and a success | |
20040 | return is given. | |
20041 | ||
20042 | * If any directories on the file's path are missing, Exim creates them if the | |
20043 | create_directory option is set. A created directory's mode is given by the | |
20044 | directory_mode option. | |
20045 | ||
20046 | * If file_format is set, the format of an existing file is checked. If this | |
20047 | indicates that a different transport should be used, control is passed to | |
20048 | that transport. | |
20049 | ||
20050 | * If use_lockfile is set, a lock file is built in a way that will work | |
20051 | reliably over NFS, as follows: | |
20052 | ||
20053 | 1. Create a "hitching post" file whose name is that of the lock file with | |
20054 | the current time, primary host name, and process id added, by opening | |
20055 | for writing as a new file. If this fails with an access error, delivery | |
20056 | is deferred. | |
20057 | ||
20058 | 2. Close the hitching post file, and hard link it to the lock file name. | |
20059 | ||
20060 | 3. If the call to link() succeeds, creation of the lock file has | |
20061 | succeeded. Unlink the hitching post name. | |
20062 | ||
20063 | 4. Otherwise, use stat() to get information about the hitching post file, | |
20064 | and then unlink hitching post name. If the number of links is exactly | |
20065 | two, creation of the lock file succeeded but something (for example, an | |
20066 | NFS server crash and restart) caused this fact not to be communicated | |
20067 | to the link() call. | |
20068 | ||
20069 | 5. If creation of the lock file failed, wait for lock_interval and try | |
20070 | again, up to lock_retries times. However, since any program that writes | |
20071 | to a mailbox should complete its task very quickly, it is reasonable to | |
20072 | time out old lock files that are normally the result of user agent and | |
20073 | system crashes. If an existing lock file is older than lockfile_timeout | |
20074 | Exim attempts to unlink it before trying again. | |
20075 | ||
20076 | * A call is made to lstat() to discover whether the main file exists, and if | |
20077 | so, what its characteristics are. If lstat() fails for any reason other | |
20078 | than non-existence, delivery is deferred. | |
20079 | ||
20080 | * If the file does exist and is a symbolic link, delivery is deferred, unless | |
20081 | the allow_symlink option is set, in which case the ownership of the link is | |
20082 | checked, and then stat() is called to find out about the real file, which | |
20083 | is then subjected to the checks below. The check on the top-level link | |
20084 | ownership prevents one user creating a link for another's mailbox in a | |
20085 | sticky directory, though allowing symbolic links in this case is definitely | |
20086 | not a good idea. If there is a chain of symbolic links, the intermediate | |
20087 | ones are not checked. | |
20088 | ||
20089 | * If the file already exists but is not a regular file, or if the file's | |
20090 | owner and group (if the group is being checked - see check_group above) are | |
20091 | different from the user and group under which the delivery is running, | |
20092 | delivery is deferred. | |
20093 | ||
20094 | * If the file's permissions are more generous than specified, they are | |
20095 | reduced. If they are insufficient, delivery is deferred, unless | |
20096 | mode_fail_narrower is set false, in which case the delivery is tried using | |
20097 | the existing permissions. | |
20098 | ||
20099 | * The file's inode number is saved, and the file is then opened for | |
20100 | appending. If this fails because the file has vanished, appendfile behaves | |
20101 | as if it hadn't existed (see below). For any other failures, delivery is | |
20102 | deferred. | |
20103 | ||
20104 | * If the file is opened successfully, check that the inode number hasn't | |
20105 | changed, that it is still a regular file, and that the owner and | |
20106 | permissions have not changed. If anything is wrong, defer delivery and | |
20107 | freeze the message. | |
20108 | ||
20109 | * If the file did not exist originally, defer delivery if the file_must_exist | |
20110 | option is set. Otherwise, check that the file is being created in a | |
20111 | permitted directory if the create_file option is set (deferring on | |
20112 | failure), and then open for writing as a new file, with the O_EXCL and | |
20113 | O_CREAT options, except when dealing with a symbolic link (the | |
20114 | allow_symlink option must be set). In this case, which can happen if the | |
20115 | link points to a non-existent file, the file is opened for writing using | |
20116 | O_CREAT but not O_EXCL, because that prevents link following. | |
20117 | ||
20118 | * If opening fails because the file exists, obey the tests given above for | |
20119 | existing files. However, to avoid looping in a situation where the file is | |
20120 | being continuously created and destroyed, the exists/not-exists loop is | |
20121 | broken after 10 repetitions, and the message is then frozen. | |
20122 | ||
20123 | * If opening fails with any other error, defer delivery. | |
20124 | ||
20125 | * Once the file is open, unless both use_fcntl_lock and use_flock_lock are | |
20126 | false, it is locked using fcntl() or flock() or both. If use_mbx_lock is | |
20127 | false, an exclusive lock is requested in each case. However, if | |
20128 | use_mbx_lock is true, Exim takes out a shared lock on the open file, and an | |
20129 | exclusive lock on the file whose name is | |
20130 | ||
20131 | /tmp/.<device-number>.<inode-number> | |
20132 | ||
20133 | using the device and inode numbers of the open mailbox file, in accordance | |
20134 | with the MBX locking rules. This file is created with a mode that is | |
20135 | specified by the lockfile_mode option. | |
20136 | ||
20137 | If Exim fails to lock the file, there are two possible courses of action, | |
20138 | depending on the value of the locking timeout. This is obtained from | |
20139 | lock_fcntl_timeout or lock_flock_timeout, as appropriate. | |
20140 | ||
20141 | If the timeout value is zero, the file is closed, Exim waits for | |
20142 | lock_interval, and then goes back and re-opens the file as above and tries | |
20143 | to lock it again. This happens up to lock_retries times, after which the | |
20144 | delivery is deferred. | |
20145 | ||
20146 | If the timeout has a value greater than zero, blocking calls to fcntl() or | |
20147 | flock() are used (with the given timeout), so there has already been some | |
20148 | waiting involved by the time locking fails. Nevertheless, Exim does not | |
20149 | give up immediately. It retries up to | |
20150 | ||
20151 | (lock_retries * lock_interval) / <timeout> | |
20152 | ||
20153 | times (rounded up). | |
20154 | ||
20155 | At the end of delivery, Exim closes the file (which releases the fcntl() and/or | |
20156 | flock() locks) and then deletes the lock file if one was created. | |
20157 | ||
20158 | ||
20159 | 26.4 Operational details for delivery to a new file | |
20160 | --------------------------------------------------- | |
20161 | ||
20162 | When the directory option is set instead of file, each message is delivered | |
20163 | into a newly-created file or set of files. When appendfile is activated | |
20164 | directly from a redirect router, neither file nor directory is normally set, | |
20165 | because the path for delivery is supplied by the router. (See for example, the | |
20166 | address_file transport in the default configuration.) In this case, delivery is | |
20167 | to a new file if either the path name ends in "/", or the maildir_format or | |
20168 | mailstore_format option is set. | |
20169 | ||
20170 | No locking is required while writing the message to a new file, so the various | |
20171 | locking options of the transport are ignored. The "From" line that by default | |
20172 | separates messages in a single file is not normally needed, nor is the escaping | |
20173 | of message lines that start with "From", and there is no need to ensure a | |
20174 | newline at the end of each message. Consequently, the default values for | |
20175 | check_string, message_prefix, and message_suffix are all unset when any of | |
20176 | directory, maildir_format, or mailstore_format is set. | |
20177 | ||
20178 | If Exim is required to check a quota setting, it adds up the sizes of all the | |
20179 | files in the delivery directory by default. However, you can specify a | |
20180 | different directory by setting quota_directory. Also, for maildir deliveries | |
20181 | (see below) the maildirfolder convention is honoured. | |
20182 | ||
20183 | There are three different ways in which delivery to individual files can be | |
20184 | done, controlled by the settings of the maildir_format and mailstore_format | |
20185 | options. Note that code to support maildir or mailstore formats is not included | |
20186 | in the binary unless SUPPORT_MAILDIR or SUPPORT_MAILSTORE, respectively, is set | |
20187 | in Local/Makefile. | |
20188 | ||
20189 | In all three cases an attempt is made to create the directory and any necessary | |
20190 | sub-directories if they do not exist, provided that the create_directory option | |
20191 | is set (the default). The location of a created directory can be constrained by | |
20192 | setting create_file. A created directory's mode is given by the directory_mode | |
20193 | option. If creation fails, or if the create_directory option is not set when | |
20194 | creation is required, delivery is deferred. | |
20195 | ||
20196 | ||
20197 | 26.5 Maildir delivery | |
20198 | --------------------- | |
20199 | ||
20200 | If the maildir_format option is true, Exim delivers each message by writing it | |
20201 | to a file whose name is tmp/<stime>.H<mtime>P<pid>.<host> in the directory that | |
20202 | is defined by the directory option (the "delivery directory"). If the delivery | |
20203 | is successful, the file is renamed into the new subdirectory. | |
20204 | ||
20205 | In the file name, <stime> is the current time of day in seconds, and <mtime> is | |
20206 | the microsecond fraction of the time. After a maildir delivery, Exim checks | |
20207 | that the time-of-day clock has moved on by at least one microsecond before | |
20208 | terminating the delivery process. This guarantees uniqueness for the file name. | |
20209 | However, as a precaution, Exim calls stat() for the file before opening it. If | |
20210 | any response other than ENOENT (does not exist) is given, Exim waits 2 seconds | |
20211 | and tries again, up to maildir_retries times. | |
20212 | ||
20213 | Before Exim carries out a maildir delivery, it ensures that subdirectories | |
20214 | called new, cur, and tmp exist in the delivery directory. If they do not exist, | |
20215 | Exim tries to create them and any superior directories in their path, subject | |
20216 | to the create_directory and create_file options. If the | |
20217 | maildirfolder_create_regex option is set, and the regular expression it | |
20218 | contains matches the delivery directory, Exim also ensures that a file called | |
20219 | maildirfolder exists in the delivery directory. If a missing directory or | |
20220 | maildirfolder file cannot be created, delivery is deferred. | |
20221 | ||
20222 | These features make it possible to use Exim to create all the necessary files | |
20223 | and directories in a maildir mailbox, including subdirectories for maildir++ | |
20224 | folders. Consider this example: | |
20225 | ||
20226 | maildir_format = true | |
20227 | directory = /var/mail/$local_part\ | |
20228 | ${if eq{$local_part_suffix}{}{}\ | |
20229 | {/.${substr_1:$local_part_suffix}}} | |
20230 | maildirfolder_create_regex = /\.[^/]+$ | |
20231 | ||
20232 | If $local_part_suffix is empty (there was no suffix for the local part), | |
20233 | delivery is into a toplevel maildir with a name like /var/mail/pimbo (for the | |
20234 | user called pimbo). The pattern in maildirfolder_create_regex does not match | |
20235 | this name, so Exim will not look for or create the file /var/mail/pimbo/ | |
20236 | maildirfolder, though it will create /var/mail/pimbo/{cur,new,tmp} if | |
20237 | necessary. | |
20238 | ||
20239 | However, if $local_part_suffix contains "-eximusers" (for example), delivery is | |
20240 | into the maildir++ folder /var/mail/pimbo/.eximusers, which does match | |
20241 | maildirfolder_create_regex. In this case, Exim will create /var/mail/pimbo | |
20242 | /.eximusers/maildirfolder as well as the three maildir directories /var/mail/ | |
20243 | pimbo/.eximusers/{cur,new,tmp}. | |
20244 | ||
20245 | Warning: Take care when setting maildirfolder_create_regex that it does not | |
20246 | inadvertently match the toplevel maildir directory, because a maildirfolder | |
20247 | file at top level would completely break quota calculations. | |
20248 | ||
20249 | If Exim is required to check a quota setting before a maildir delivery, and | |
20250 | quota_directory is not set, it looks for a file called maildirfolder in the | |
20251 | maildir directory (alongside new, cur, tmp). If this exists, Exim assumes the | |
20252 | directory is a maildir++ folder directory, which is one level down from the | |
20253 | user's top level mailbox directory. This causes it to start at the parent | |
20254 | directory instead of the current directory when calculating the amount of space | |
20255 | used. | |
20256 | ||
20257 | One problem with delivering into a multi-file mailbox is that it is | |
20258 | computationally expensive to compute the size of the mailbox for quota | |
20259 | checking. Various approaches have been taken to reduce the amount of work | |
20260 | needed. The next two sections describe two of them. A third alternative is to | |
20261 | use some external process for maintaining the size data, and use the expansion | |
20262 | of the mailbox_size option as a way of importing it into Exim. | |
20263 | ||
20264 | ||
20265 | 26.6 Using tags to record message sizes | |
20266 | --------------------------------------- | |
20267 | ||
20268 | If maildir_tag is set, the string is expanded for each delivery. When the | |
20269 | maildir file is renamed into the new sub-directory, the tag is added to its | |
20270 | name. However, if adding the tag takes the length of the name to the point | |
20271 | where the test stat() call fails with ENAMETOOLONG, the tag is dropped and the | |
20272 | maildir file is created with no tag. | |
20273 | ||
20274 | Tags can be used to encode the size of files in their names; see | |
20275 | quota_size_regex above for an example. The expansion of maildir_tag happens | |
20276 | after the message has been written. The value of the $message_size variable is | |
20277 | set to the number of bytes actually written. If the expansion is forced to | |
20278 | fail, the tag is ignored, but a non-forced failure causes delivery to be | |
20279 | deferred. The expanded tag may contain any printing characters except "/". | |
20280 | Non-printing characters in the string are ignored; if the resulting string is | |
20281 | empty, it is ignored. If it starts with an alphanumeric character, a leading | |
20282 | colon is inserted; this default has not proven to be the path that popular | |
20283 | maildir implementations have chosen (but changing it in Exim would break | |
20284 | backwards compatibility). | |
20285 | ||
20286 | For one common implementation, you might set: | |
20287 | ||
20288 | maildir_tag = ,S=${message_size} | |
20289 | ||
20290 | but you should check the documentation of the other software to be sure. | |
20291 | ||
20292 | It is advisable to also set quota_size_regex when setting maildir_tag as this | |
20293 | allows Exim to extract the size from your tag, instead of having to stat() each | |
20294 | message file. | |
20295 | ||
20296 | ||
20297 | 26.7 Using a maildirsize file | |
20298 | ----------------------------- | |
20299 | ||
20300 | If maildir_use_size_file is true, Exim implements the maildir++ rules for | |
20301 | storing quota and message size information in a file called maildirsize within | |
20302 | the toplevel maildir directory. If this file does not exist, Exim creates it, | |
20303 | setting the quota from the quota option of the transport. If the maildir | |
20304 | directory itself does not exist, it is created before any attempt to write a | |
20305 | maildirsize file. | |
20306 | ||
20307 | The maildirsize file is used to hold information about the sizes of messages in | |
20308 | the maildir, thus speeding up quota calculations. The quota value in the file | |
20309 | is just a cache; if the quota is changed in the transport, the new value | |
20310 | overrides the cached value when the next message is delivered. The cache is | |
20311 | maintained for the benefit of other programs that access the maildir and need | |
20312 | to know the quota. | |
20313 | ||
20314 | If the quota option in the transport is unset or zero, the maildirsize file is | |
20315 | maintained (with a zero quota setting), but no quota is imposed. | |
20316 | ||
20317 | A regular expression is available for controlling which directories in the | |
20318 | maildir participate in quota calculations when a maildirsizefile is in use. See | |
20319 | the description of the maildir_quota_directory_regex option above for details. | |
20320 | ||
20321 | ||
20322 | 26.8 Mailstore delivery | |
20323 | ----------------------- | |
20324 | ||
20325 | If the mailstore_format option is true, each message is written as two files in | |
20326 | the given directory. A unique base name is constructed from the message id and | |
20327 | the current delivery process, and the files that are written use this base name | |
20328 | plus the suffixes .env and .msg. The .env file contains the message's envelope, | |
20329 | and the .msg file contains the message itself. The base name is placed in the | |
20330 | variable $mailstore_basename. | |
20331 | ||
20332 | During delivery, the envelope is first written to a file with the suffix .tmp. | |
20333 | The .msg file is then written, and when it is complete, the .tmp file is | |
20334 | renamed as the .env file. Programs that access messages in mailstore format | |
20335 | should wait for the presence of both a .msg and a .env file before accessing | |
20336 | either of them. An alternative approach is to wait for the absence of a .tmp | |
20337 | file. | |
20338 | ||
20339 | The envelope file starts with any text defined by the mailstore_prefix option, | |
20340 | expanded and terminated by a newline if there isn't one. Then follows the | |
20341 | sender address on one line, then all the recipient addresses, one per line. | |
20342 | There can be more than one recipient only if the batch_max option is set | |
20343 | greater than one. Finally, mailstore_suffix is expanded and the result appended | |
20344 | to the file, followed by a newline if it does not end with one. | |
20345 | ||
20346 | If expansion of mailstore_prefix or mailstore_suffix ends with a forced | |
20347 | failure, it is ignored. Other expansion errors are treated as serious | |
20348 | configuration errors, and delivery is deferred. The variable | |
20349 | $mailstore_basename is available for use during these expansions. | |
20350 | ||
20351 | ||
20352 | 26.9 Non-special new file delivery | |
20353 | ---------------------------------- | |
20354 | ||
20355 | If neither maildir_format nor mailstore_format is set, a single new file is | |
20356 | created directly in the named directory. For example, when delivering messages | |
20357 | into files in batched SMTP format for later delivery to some host (see section | |
20358 | 47.10), a setting such as | |
20359 | ||
20360 | directory = /var/bsmtp/$host | |
20361 | ||
20362 | might be used. A message is written to a file with a temporary name, which is | |
20363 | then renamed when the delivery is complete. The final name is obtained by | |
20364 | expanding the contents of the directory_file option. | |
20365 | ||
20366 | ||
20367 | ||
20368 | =============================================================================== | |
20369 | 27. THE AUTOREPLY TRANSPORT | |
20370 | ||
20371 | The autoreply transport is not a true transport in that it does not cause the | |
20372 | message to be transmitted. Instead, it generates a new mail message as an | |
20373 | automatic reply to the incoming message. References: and Auto-Submitted: header | |
20374 | lines are included. These are constructed according to the rules in RFCs 2822 | |
20375 | and 3834, respectively. | |
20376 | ||
20377 | If the router that passes the message to this transport does not have the | |
20378 | unseen option set, the original message (for the current recipient) is not | |
20379 | delivered anywhere. However, when the unseen option is set on the router that | |
20380 | passes the message to this transport, routing of the address continues, so | |
20381 | another router can set up a normal message delivery. | |
20382 | ||
20383 | The autoreply transport is usually run as the result of mail filtering, a | |
20384 | "vacation" message being the standard example. However, it can also be run | |
20385 | directly from a router like any other transport. To reduce the possibility of | |
20386 | message cascades, messages created by the autoreply transport always have empty | |
20387 | envelope sender addresses, like bounce messages. | |
20388 | ||
20389 | The parameters of the message to be sent can be specified in the configuration | |
20390 | by options described below. However, these are used only when the address | |
20391 | passed to the transport does not contain its own reply information. When the | |
20392 | transport is run as a consequence of a mail or vacation command in a filter | |
20393 | file, the parameters of the message are supplied by the filter, and passed with | |
20394 | the address. The transport's options that define the message are then ignored | |
20395 | (so they are not usually set in this case). The message is specified entirely | |
20396 | by the filter or by the transport; it is never built from a mixture of options. | |
20397 | However, the file_optional, mode, and return_message options apply in all | |
20398 | cases. | |
20399 | ||
20400 | Autoreply is implemented as a local transport. When used as a result of a | |
20401 | command in a user's filter file, autoreply normally runs under the uid and gid | |
20402 | of the user, and with appropriate current and home directories (see chapter 23 | |
20403 | ). | |
20404 | ||
20405 | There is a subtle difference between routing a message to a pipe transport that | |
20406 | generates some text to be returned to the sender, and routing it to an | |
20407 | autoreply transport. This difference is noticeable only if more than one | |
20408 | address from the same message is so handled. In the case of a pipe, the | |
20409 | separate outputs from the different addresses are gathered up and returned to | |
20410 | the sender in a single message, whereas if autoreply is used, a separate | |
20411 | message is generated for each address that is passed to it. | |
20412 | ||
20413 | Non-printing characters are not permitted in the header lines generated for the | |
20414 | message that autoreply creates, with the exception of newlines that are | |
20415 | immediately followed by white space. If any non-printing characters are found, | |
20416 | the transport defers. Whether characters with the top bit set count as printing | |
20417 | characters or not is controlled by the print_topbitchars global option. | |
20418 | ||
20419 | If any of the generic options for manipulating headers (for example, | |
20420 | headers_add) are set on an autoreply transport, they apply to the copy of the | |
20421 | original message that is included in the generated message when return_message | |
20422 | is set. They do not apply to the generated message itself. | |
20423 | ||
20424 | If the autoreply transport receives return code 2 from Exim when it submits the | |
20425 | message, indicating that there were no recipients, it does not treat this as an | |
20426 | error. This means that autoreplies sent to $sender_address when this is empty | |
20427 | (because the incoming message is a bounce message) do not cause problems. They | |
20428 | are just discarded. | |
20429 | ||
20430 | ||
20431 | 27.1 Private options for autoreply | |
20432 | ---------------------------------- | |
20433 | ||
20434 | +---+--------------+-------------+--------------+ | |
20435 | |bcc|Use: autoreply|Type: string*|Default: unset| | |
20436 | +---+--------------+-------------+--------------+ | |
20437 | ||
20438 | This specifies the addresses that are to receive "blind carbon copies" of the | |
20439 | message when the message is specified by the transport. | |
20440 | ||
20441 | +--+--------------+-------------+--------------+ | |
20442 | |cc|Use: autoreply|Type: string*|Default: unset| | |
20443 | +--+--------------+-------------+--------------+ | |
20444 | ||
20445 | This specifies recipients of the message and the contents of the Cc: header | |
20446 | when the message is specified by the transport. | |
20447 | ||
20448 | +----+--------------+-------------+--------------+ | |
20449 | |file|Use: autoreply|Type: string*|Default: unset| | |
20450 | +----+--------------+-------------+--------------+ | |
20451 | ||
20452 | The contents of the file are sent as the body of the message when the message | |
20453 | is specified by the transport. If both file and text are set, the text string | |
20454 | comes first. | |
20455 | ||
20456 | +-----------+--------------+-------------+--------------+ | |
20457 | |file_expand|Use: autoreply|Type: boolean|Default: false| | |
20458 | +-----------+--------------+-------------+--------------+ | |
20459 | ||
20460 | If this is set, the contents of the file named by the file option are subjected | |
20461 | to string expansion as they are added to the message. | |
20462 | ||
20463 | +-------------+--------------+-------------+--------------+ | |
20464 | |file_optional|Use: autoreply|Type: boolean|Default: false| | |
20465 | +-------------+--------------+-------------+--------------+ | |
20466 | ||
20467 | If this option is true, no error is generated if the file named by the file | |
20468 | option or passed with the address does not exist or cannot be read. | |
20469 | ||
20470 | +----+--------------+-------------+--------------+ | |
20471 | |from|Use: autoreply|Type: string*|Default: unset| | |
20472 | +----+--------------+-------------+--------------+ | |
20473 | ||
20474 | This specifies the contents of the From: header when the message is specified | |
20475 | by the transport. | |
20476 | ||
20477 | +-------+--------------+-------------+--------------+ | |
20478 | |headers|Use: autoreply|Type: string*|Default: unset| | |
20479 | +-------+--------------+-------------+--------------+ | |
20480 | ||
20481 | This specifies additional RFC 2822 headers that are to be added to the message | |
20482 | when the message is specified by the transport. Several can be given by using " | |
20483 | \n" to separate them. There is no check on the format. | |
20484 | ||
20485 | +---+--------------+-------------+--------------+ | |
20486 | |log|Use: autoreply|Type: string*|Default: unset| | |
20487 | +---+--------------+-------------+--------------+ | |
20488 | ||
20489 | This option names a file in which a record of every message sent is logged when | |
20490 | the message is specified by the transport. | |
20491 | ||
20492 | +----+--------------+-------------------+-------------+ | |
20493 | |mode|Use: autoreply|Type: octal integer|Default: 0600| | |
20494 | +----+--------------+-------------------+-------------+ | |
20495 | ||
20496 | If either the log file or the "once" file has to be created, this mode is used. | |
20497 | ||
20498 | +----------+--------------+-------------------+--------------+ | |
20499 | |never_mail|Use: autoreply|Type: address list*|Default: unset| | |
20500 | +----------+--------------+-------------------+--------------+ | |
20501 | ||
20502 | If any run of the transport creates a message with a recipient that matches any | |
20503 | item in the list, that recipient is quietly discarded. If all recipients are | |
20504 | discarded, no message is created. This applies both when the recipients are | |
20505 | generated by a filter and when they are specified in the transport. | |
20506 | ||
20507 | +----+--------------+-------------+--------------+ | |
20508 | |once|Use: autoreply|Type: string*|Default: unset| | |
20509 | +----+--------------+-------------+--------------+ | |
20510 | ||
20511 | This option names a file or DBM database in which a record of each To: | |
20512 | recipient is kept when the message is specified by the transport. Note: This | |
20513 | does not apply to Cc: or Bcc: recipients. | |
20514 | ||
20515 | If once is unset, or is set to an empty string, the message is always sent. By | |
20516 | default, if once is set to a non-empty file name, the message is not sent if a | |
20517 | potential recipient is already listed in the database. However, if the | |
20518 | once_repeat option specifies a time greater than zero, the message is sent if | |
20519 | that much time has elapsed since a message was last sent to this recipient. A | |
20520 | setting of zero time for once_repeat (the default) prevents a message from | |
20521 | being sent a second time - in this case, zero means infinity. | |
20522 | ||
20523 | If once_file_size is zero, a DBM database is used to remember recipients, and | |
20524 | it is allowed to grow as large as necessary. If once_file_size is set greater | |
20525 | than zero, it changes the way Exim implements the once option. Instead of using | |
20526 | a DBM file to record every recipient it sends to, it uses a regular file, whose | |
20527 | size will never get larger than the given value. | |
20528 | ||
20529 | In the file, Exim keeps a linear list of recipient addresses and the times at | |
20530 | which they were sent messages. If the file is full when a new address needs to | |
20531 | be added, the oldest address is dropped. If once_repeat is not set, this means | |
20532 | that a given recipient may receive multiple messages, but at unpredictable | |
20533 | intervals that depend on the rate of turnover of addresses in the file. If | |
20534 | once_repeat is set, it specifies a maximum time between repeats. | |
20535 | ||
20536 | +--------------+--------------+-------------+----------+ | |
20537 | |once_file_size|Use: autoreply|Type: integer|Default: 0| | |
20538 | +--------------+--------------+-------------+----------+ | |
20539 | ||
20540 | See once above. | |
20541 | ||
20542 | +-----------+--------------+-----------+-----------+ | |
20543 | |once_repeat|Use: autoreply|Type: time*|Default: 0s| | |
20544 | +-----------+--------------+-----------+-----------+ | |
20545 | ||
20546 | See once above. After expansion, the value of this option must be a valid time | |
20547 | value. | |
20548 | ||
20549 | +--------+--------------+-------------+--------------+ | |
20550 | |reply_to|Use: autoreply|Type: string*|Default: unset| | |
20551 | +--------+--------------+-------------+--------------+ | |
20552 | ||
20553 | This specifies the contents of the Reply-To: header when the message is | |
20554 | specified by the transport. | |
20555 | ||
20556 | +--------------+--------------+-------------+--------------+ | |
20557 | |return_message|Use: autoreply|Type: boolean|Default: false| | |
20558 | +--------------+--------------+-------------+--------------+ | |
20559 | ||
20560 | If this is set, a copy of the original message is returned with the new | |
20561 | message, subject to the maximum size set in the return_size_limit global | |
20562 | configuration option. | |
20563 | ||
20564 | +-------+--------------+-------------+--------------+ | |
20565 | |subject|Use: autoreply|Type: string*|Default: unset| | |
20566 | +-------+--------------+-------------+--------------+ | |
20567 | ||
20568 | This specifies the contents of the Subject: header when the message is | |
20569 | specified by the transport. It is tempting to quote the original subject in | |
20570 | automatic responses. For example: | |
20571 | ||
20572 | subject = Re: $h_subject: | |
20573 | ||
20574 | There is a danger in doing this, however. It may allow a third party to | |
20575 | subscribe your users to an opt-in mailing list, provided that the list accepts | |
20576 | bounce messages as subscription confirmations. Well-managed lists require a | |
20577 | non-bounce message to confirm a subscription, so the danger is relatively | |
20578 | small. | |
20579 | ||
20580 | +----+--------------+-------------+--------------+ | |
20581 | |text|Use: autoreply|Type: string*|Default: unset| | |
20582 | +----+--------------+-------------+--------------+ | |
20583 | ||
20584 | This specifies a single string to be used as the body of the message when the | |
20585 | message is specified by the transport. If both text and file are set, the text | |
20586 | comes first. | |
20587 | ||
20588 | +--+--------------+-------------+--------------+ | |
20589 | |to|Use: autoreply|Type: string*|Default: unset| | |
20590 | +--+--------------+-------------+--------------+ | |
20591 | ||
20592 | This specifies recipients of the message and the contents of the To: header | |
20593 | when the message is specified by the transport. | |
20594 | ||
20595 | ||
20596 | ||
20597 | =============================================================================== | |
20598 | 28. THE LMTP TRANSPORT | |
20599 | ||
20600 | The lmtp transport runs the LMTP protocol (RFC 2033) over a pipe to a specified | |
20601 | command or by interacting with a Unix domain socket. This transport is | |
20602 | something of a cross between the pipe and smtp transports. Exim also has | |
20603 | support for using LMTP over TCP/IP; this is implemented as an option for the | |
20604 | smtp transport. Because LMTP is expected to be of minority interest, the | |
20605 | default build-time configure in src/EDITME has it commented out. You need to | |
20606 | ensure that | |
20607 | ||
20608 | TRANSPORT_LMTP=yes | |
20609 | ||
20610 | is present in your Local/Makefile in order to have the lmtp transport included | |
20611 | in the Exim binary. The private options of the lmtp transport are as follows: | |
20612 | ||
20613 | +--------+---------+-------------+--------------+ | |
20614 | |batch_id|Use: lmtp|Type: string*|Default: unset| | |
20615 | +--------+---------+-------------+--------------+ | |
20616 | ||
20617 | See the description of local delivery batching in chapter 25. | |
20618 | ||
20619 | +---------+---------+-------------+----------+ | |
20620 | |batch_max|Use: lmtp|Type: integer|Default: 1| | |
20621 | +---------+---------+-------------+----------+ | |
20622 | ||
20623 | This limits the number of addresses that can be handled in a single delivery. | |
20624 | Most LMTP servers can handle several addresses at once, so it is normally a | |
20625 | good idea to increase this value. See the description of local delivery | |
20626 | batching in chapter 25. | |
20627 | ||
20628 | +-------+---------+-------------+--------------+ | |
20629 | |command|Use: lmtp|Type: string*|Default: unset| | |
20630 | +-------+---------+-------------+--------------+ | |
20631 | ||
20632 | This option must be set if socket is not set. The string is a command which is | |
20633 | run in a separate process. It is split up into a command name and list of | |
20634 | arguments, each of which is separately expanded (so expansion cannot change the | |
20635 | number of arguments). The command is run directly, not via a shell. The message | |
20636 | is passed to the new process using the standard input and output to operate the | |
20637 | LMTP protocol. | |
20638 | ||
20639 | +------------+---------+-------------+--------------+ | |
20640 | |ignore_quota|Use: lmtp|Type: boolean|Default: false| | |
20641 | +------------+---------+-------------+--------------+ | |
20642 | ||
20643 | If this option is set true, the string "IGNOREQUOTA" is added to RCPT commands, | |
20644 | provided that the LMTP server has advertised support for IGNOREQUOTA in its | |
20645 | response to the LHLO command. | |
20646 | ||
20647 | +------+---------+-------------+--------------+ | |
20648 | |socket|Use: lmtp|Type: string*|Default: unset| | |
20649 | +------+---------+-------------+--------------+ | |
20650 | ||
20651 | This option must be set if command is not set. The result of expansion must be | |
20652 | the name of a Unix domain socket. The transport connects to the socket and | |
20653 | delivers the message to it using the LMTP protocol. | |
20654 | ||
20655 | +-------+---------+----------+-----------+ | |
20656 | |timeout|Use: lmtp|Type: time|Default: 5m| | |
20657 | +-------+---------+----------+-----------+ | |
20658 | ||
20659 | The transport is aborted if the created process or Unix domain socket does not | |
20660 | respond to LMTP commands or message input within this timeout. Delivery is | |
20661 | deferred, and will be tried again later. Here is an example of a typical LMTP | |
20662 | transport: | |
20663 | ||
20664 | lmtp: | |
20665 | driver = lmtp | |
20666 | command = /some/local/lmtp/delivery/program | |
20667 | batch_max = 20 | |
20668 | user = exim | |
20669 | ||
20670 | This delivers up to 20 addresses at a time, in a mixture of domains if | |
20671 | necessary, running as the user exim. | |
20672 | ||
20673 | ||
20674 | ||
20675 | =============================================================================== | |
20676 | 29. THE PIPE TRANSPORT | |
20677 | ||
20678 | The pipe transport is used to deliver messages via a pipe to a command running | |
20679 | in another process. One example is the use of pipe as a pseudo-remote transport | |
20680 | for passing messages to some other delivery mechanism (such as UUCP). Another | |
20681 | is the use by individual users to automatically process their incoming | |
20682 | messages. The pipe transport can be used in one of the following ways: | |
20683 | ||
20684 | * A router routes one address to a transport in the normal way, and the | |
20685 | transport is configured as a pipe transport. In this case, $local_part | |
20686 | contains the local part of the address (as usual), and the command that is | |
20687 | run is specified by the command option on the transport. | |
20688 | ||
20689 | * If the batch_max option is set greater than 1 (the default is 1), the | |
20690 | transport can handle more than one address in a single run. In this case, | |
20691 | when more than one address is routed to the transport, $local_part is not | |
20692 | set (because it is not unique). However, the pseudo-variable | |
20693 | $pipe_addresses (described in section 29.3 below) contains all the | |
20694 | addresses that are routed to the transport. | |
20695 | ||
20696 | * A router redirects an address directly to a pipe command (for example, from | |
20697 | an alias or forward file). In this case, $address_pipe contains the text of | |
20698 | the pipe command, and the command option on the transport is ignored unless | |
20699 | force_command is set. If only one address is being transported (batch_max | |
20700 | is not greater than one, or only one address was redirected to this pipe | |
20701 | command), $local_part contains the local part that was redirected. | |
20702 | ||
20703 | The pipe transport is a non-interactive delivery method. Exim can also deliver | |
20704 | messages over pipes using the LMTP interactive protocol. This is implemented by | |
20705 | the lmtp transport. | |
20706 | ||
20707 | In the case when pipe is run as a consequence of an entry in a local user's | |
20708 | .forward file, the command runs under the uid and gid of that user. In other | |
20709 | cases, the uid and gid have to be specified explicitly, either on the transport | |
20710 | or on the router that handles the address. Current and "home" directories are | |
20711 | also controllable. See chapter 23 for details of the local delivery environment | |
20712 | and chapter 25 for a discussion of local delivery batching. | |
20713 | ||
20714 | ||
20715 | 29.1 Concurrent delivery | |
20716 | ------------------------ | |
20717 | ||
20718 | If two messages arrive at almost the same time, and both are routed to a pipe | |
20719 | delivery, the two pipe transports may be run concurrently. You must ensure that | |
20720 | any pipe commands you set up are robust against this happening. If the commands | |
20721 | write to a file, the exim_lock utility might be of use. | |
20722 | ||
20723 | ||
20724 | 29.2 Returned status and data | |
20725 | ----------------------------- | |
20726 | ||
20727 | If the command exits with a non-zero return code, the delivery is deemed to | |
20728 | have failed, unless either the ignore_status option is set (in which case the | |
20729 | return code is treated as zero), or the return code is one of those listed in | |
20730 | the temp_errors option, which are interpreted as meaning "try again later". In | |
20731 | this case, delivery is deferred. Details of a permanent failure are logged, but | |
20732 | are not included in the bounce message, which merely contains "local delivery | |
20733 | failed". | |
20734 | ||
20735 | If the command exits on a signal and the freeze_signal option is set then the | |
20736 | message will be frozen in the queue. If that option is not set, a bounce will | |
20737 | be sent as normal. | |
20738 | ||
20739 | If the return code is greater than 128 and the command being run is a shell | |
20740 | script, it normally means that the script was terminated by a signal whose | |
20741 | value is the return code minus 128. The freeze_signal option does not apply in | |
20742 | this case. | |
20743 | ||
20744 | If Exim is unable to run the command (that is, if execve() fails), the return | |
20745 | code is set to 127. This is the value that a shell returns if it is asked to | |
20746 | run a non-existent command. The wording for the log line suggests that a | |
20747 | non-existent command may be the problem. | |
20748 | ||
20749 | The return_output option can affect the result of a pipe delivery. If it is set | |
20750 | and the command produces any output on its standard output or standard error | |
20751 | streams, the command is considered to have failed, even if it gave a zero | |
20752 | return code or if ignore_status is set. The output from the command is included | |
20753 | as part of the bounce message. The return_fail_output option is similar, except | |
20754 | that output is returned only when the command exits with a failure return code, | |
20755 | that is, a value other than zero or a code that matches temp_errors. | |
20756 | ||
20757 | ||
20758 | 29.3 How the command is run | |
20759 | --------------------------- | |
20760 | ||
20761 | The command line is (by default) broken down into a command name and arguments | |
20762 | by the pipe transport itself. The allow_commands and restrict_to_path options | |
20763 | can be used to restrict the commands that may be run. | |
20764 | ||
20765 | Unquoted arguments are delimited by white space. If an argument appears in | |
20766 | double quotes, backslash is interpreted as an escape character in the usual | |
20767 | way. If an argument appears in single quotes, no escaping is done. | |
20768 | ||
20769 | String expansion is applied to the command line except when it comes from a | |
20770 | traditional .forward file (commands from a filter file are expanded). The | |
20771 | expansion is applied to each argument in turn rather than to the whole line. | |
20772 | For this reason, any string expansion item that contains white space must be | |
20773 | quoted so as to be contained within a single argument. A setting such as | |
20774 | ||
20775 | command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}} | |
20776 | ||
20777 | will not work, because the expansion item gets split between several arguments. | |
20778 | You have to write | |
20779 | ||
20780 | command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}" | |
20781 | ||
20782 | to ensure that it is all in one argument. The expansion is done in this way, | |
20783 | argument by argument, so that the number of arguments cannot be changed as a | |
20784 | result of expansion, and quotes or backslashes in inserted variables do not | |
20785 | interact with external quoting. However, this leads to problems if you want to | |
20786 | generate multiple arguments (or the command name plus arguments) from a single | |
20787 | expansion. In this situation, the simplest solution is to use a shell. For | |
20788 | example: | |
20789 | ||
20790 | command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}} | |
20791 | ||
20792 | Special handling takes place when an argument consists of precisely the text | |
20793 | "$pipe_addresses". This is not a general expansion variable; the only place | |
20794 | this string is recognized is when it appears as an argument for a pipe or | |
20795 | transport filter command. It causes each address that is being handled to be | |
20796 | inserted in the argument list at that point as a separate argument. This avoids | |
20797 | any problems with spaces or shell metacharacters, and is of use when a pipe | |
20798 | transport is handling groups of addresses in a batch. | |
20799 | ||
20800 | If force_command is enabled on the transport, Special handling takes place for | |
20801 | an argument that consists of precisely the text "$address_pipe". It is handled | |
20802 | similarly to $pipe_addresses above. It is expanded and each argument is | |
20803 | inserted in the argument list at that point as a separate argument. The | |
20804 | "$address_pipe" item does not need to be the only item in the argument; in | |
20805 | fact, if it were then force_command should behave as a no-op. Rather, it should | |
20806 | be used to adjust the command run while preserving the argument vector | |
20807 | separation. | |
20808 | ||
20809 | After splitting up into arguments and expansion, the resulting command is run | |
20810 | in a subprocess directly from the transport, not under a shell. The message | |
20811 | that is being delivered is supplied on the standard input, and the standard | |
20812 | output and standard error are both connected to a single pipe that is read by | |
20813 | Exim. The max_output option controls how much output the command may produce, | |
20814 | and the return_output and return_fail_output options control what is done with | |
20815 | it. | |
20816 | ||
20817 | Not running the command under a shell (by default) lessens the security risks | |
20818 | in cases when a command from a user's filter file is built out of data that was | |
20819 | taken from an incoming message. If a shell is required, it can of course be | |
20820 | explicitly specified as the command to be run. However, there are circumstances | |
20821 | where existing commands (for example, in .forward files) expect to be run under | |
20822 | a shell and cannot easily be modified. To allow for these cases, there is an | |
20823 | option called use_shell, which changes the way the pipe transport works. | |
20824 | Instead of breaking up the command line as just described, it expands it as a | |
20825 | single string and passes the result to /bin/sh. The restrict_to_path option and | |
20826 | the $pipe_addresses facility cannot be used with use_shell, and the whole | |
20827 | mechanism is inherently less secure. | |
20828 | ||
20829 | ||
20830 | 29.4 Environment variables | |
20831 | -------------------------- | |
20832 | ||
20833 | The environment variables listed below are set up when the command is invoked. | |
20834 | This list is a compromise for maximum compatibility with other MTAs. Note that | |
20835 | the environment option can be used to add additional variables to this | |
20836 | environment. | |
20837 | ||
20838 | DOMAIN the domain of the address | |
20839 | HOME the home directory, if set | |
20840 | HOST the host name when called from a router (see below) | |
20841 | LOCAL_PART see below | |
20842 | LOCAL_PART_PREFIX see below | |
20843 | LOCAL_PART_SUFFIX see below | |
20844 | LOGNAME see below | |
20845 | MESSAGE_ID Exim's local ID for the message | |
20846 | PATH as specified by the path option below | |
20847 | QUALIFY_DOMAIN the sender qualification domain | |
20848 | RECIPIENT the complete recipient address | |
20849 | SENDER the sender of the message (empty if a bounce) | |
20850 | SHELL /bin/sh | |
20851 | TZ the value of the timezone option, if set | |
20852 | USER see below | |
20853 | ||
20854 | When a pipe transport is called directly from (for example) an accept router, | |
20855 | LOCAL_PART is set to the local part of the address. When it is called as a | |
20856 | result of a forward or alias expansion, LOCAL_PART is set to the local part of | |
20857 | the address that was expanded. In both cases, any affixes are removed from the | |
20858 | local part, and made available in LOCAL_PART_PREFIX and LOCAL_PART_SUFFIX, | |
20859 | respectively. LOGNAME and USER are set to the same value as LOCAL_PART for | |
20860 | compatibility with other MTAs. | |
20861 | ||
20862 | HOST is set only when a pipe transport is called from a router that associates | |
20863 | hosts with an address, typically when using pipe as a pseudo-remote transport. | |
20864 | HOST is set to the first host name specified by the router. | |
20865 | ||
20866 | If the transport's generic home_directory option is set, its value is used for | |
20867 | the HOME environment variable. Otherwise, a home directory may be set by the | |
20868 | router's transport_home_directory option, which defaults to the user's home | |
20869 | directory if check_local_user is set. | |
20870 | ||
20871 | ||
20872 | 29.5 Private options for pipe | |
20873 | ----------------------------- | |
20874 | ||
20875 | +--------------+---------+------------------+--------------+ | |
20876 | |allow_commands|Use: pipe|Type: string list*|Default: unset| | |
20877 | +--------------+---------+------------------+--------------+ | |
20878 | ||
20879 | The string is expanded, and is then interpreted as a colon-separated list of | |
20880 | permitted commands. If restrict_to_path is not set, the only commands permitted | |
20881 | are those in the allow_commands list. They need not be absolute paths; the path | |
20882 | option is still used for relative paths. If restrict_to_path is set with | |
20883 | allow_commands, the command must either be in the allow_commands list, or a | |
20884 | name without any slashes that is found on the path. In other words, if neither | |
20885 | allow_commands nor restrict_to_path is set, there is no restriction on the | |
20886 | command, but otherwise only commands that are permitted by one or the other are | |
20887 | allowed. For example, if | |
20888 | ||
20889 | allow_commands = /usr/bin/vacation | |
20890 | ||
20891 | and restrict_to_path is not set, the only permitted command is /usr/bin/ | |
20892 | vacation. The allow_commands option may not be set if use_shell is set. | |
20893 | ||
20894 | +--------+---------+-------------+--------------+ | |
20895 | |batch_id|Use: pipe|Type: string*|Default: unset| | |
20896 | +--------+---------+-------------+--------------+ | |
20897 | ||
20898 | See the description of local delivery batching in chapter 25. | |
20899 | ||
20900 | +---------+---------+-------------+----------+ | |
20901 | |batch_max|Use: pipe|Type: integer|Default: 1| | |
20902 | +---------+---------+-------------+----------+ | |
20903 | ||
20904 | This limits the number of addresses that can be handled in a single delivery. | |
20905 | See the description of local delivery batching in chapter 25. | |
20906 | ||
20907 | +------------+---------+------------+--------------+ | |
20908 | |check_string|Use: pipe|Type: string|Default: unset| | |
20909 | +------------+---------+------------+--------------+ | |
20910 | ||
20911 | As pipe writes the message, the start of each line is tested for matching | |
20912 | check_string, and if it does, the initial matching characters are replaced by | |
20913 | the contents of escape_string, provided both are set. The value of check_string | |
20914 | is a literal string, not a regular expression, and the case of any letters it | |
20915 | contains is significant. When use_bsmtp is set, the contents of check_string | |
20916 | and escape_string are forced to values that implement the SMTP escaping | |
20917 | protocol. Any settings made in the configuration file are ignored. | |
20918 | ||
20919 | +-------+---------+-------------+--------------+ | |
20920 | |command|Use: pipe|Type: string*|Default: unset| | |
20921 | +-------+---------+-------------+--------------+ | |
20922 | ||
20923 | This option need not be set when pipe is being used to deliver to pipes | |
20924 | obtained directly from address redirections. In other cases, the option must be | |
20925 | set, to provide a command to be run. It need not yield an absolute path (see | |
20926 | the path option below). The command is split up into separate arguments by | |
20927 | Exim, and each argument is separately expanded, as described in section 29.3 | |
20928 | above. | |
20929 | ||
20930 | +-----------+---------+-------------+--------------+ | |
20931 | |environment|Use: pipe|Type: string*|Default: unset| | |
20932 | +-----------+---------+-------------+--------------+ | |
20933 | ||
20934 | This option is used to add additional variables to the environment in which the | |
20935 | command runs (see section 29.4 for the default list). Its value is a string | |
20936 | which is expanded, and then interpreted as a colon-separated list of | |
20937 | environment settings of the form <name>=<value>. | |
20938 | ||
20939 | +-------------+---------+------------+--------------+ | |
20940 | |escape_string|Use: pipe|Type: string|Default: unset| | |
20941 | +-------------+---------+------------+--------------+ | |
20942 | ||
20943 | See check_string above. | |
20944 | ||
20945 | +----------------+---------+-------------+--------------+ | |
20946 | |freeze_exec_fail|Use: pipe|Type: boolean|Default: false| | |
20947 | +----------------+---------+-------------+--------------+ | |
20948 | ||
20949 | Failure to exec the command in a pipe transport is by default treated like any | |
20950 | other failure while running the command. However, if freeze_exec_fail is set, | |
20951 | failure to exec is treated specially, and causes the message to be frozen, | |
20952 | whatever the setting of ignore_status. | |
20953 | ||
20954 | +-------------+---------+-------------+--------------+ | |
20955 | |freeze_signal|Use: pipe|Type: boolean|Default: false| | |
20956 | +-------------+---------+-------------+--------------+ | |
20957 | ||
20958 | Normally if the process run by a command in a pipe transport exits on a signal, | |
20959 | a bounce message is sent. If freeze_signal is set, the message will be frozen | |
20960 | in Exim's queue instead. | |
20961 | ||
20962 | +-------------+---------+-------------+--------------+ | |
20963 | |force_command|Use: pipe|Type: boolean|Default: false| | |
20964 | +-------------+---------+-------------+--------------+ | |
20965 | ||
20966 | Normally when a router redirects an address directly to a pipe command the | |
20967 | command option on the transport is ignored. If force_command is set, the | |
20968 | command option will used. This is especially useful for forcing a wrapper or | |
20969 | additional argument to be added to the command. For example: | |
20970 | ||
20971 | command = /usr/bin/remote_exec myhost -- $address_pipe | |
20972 | force_command | |
20973 | ||
20974 | Note that $address_pipe is handled specially in command when force_command is | |
20975 | set, expanding out to the original argument vector as separate items, similarly | |
20976 | to a Unix shell ""$@"" construct. | |
20977 | ||
20978 | +-------------+---------+-------------+--------------+ | |
20979 | |ignore_status|Use: pipe|Type: boolean|Default: false| | |
20980 | +-------------+---------+-------------+--------------+ | |
20981 | ||
20982 | If this option is true, the status returned by the subprocess that is set up to | |
20983 | run the command is ignored, and Exim behaves as if zero had been returned. | |
20984 | Otherwise, a non-zero status or termination by signal causes an error return | |
20985 | from the transport unless the status value is one of those listed in | |
20986 | temp_errors; these cause the delivery to be deferred and tried again later. | |
20987 | ||
20988 | Note: This option does not apply to timeouts, which do not return a status. See | |
20989 | the timeout_defer option for how timeouts are handled. | |
20990 | ||
20991 | +----------------+---------+-------------+--------------+ | |
20992 | |log_defer_output|Use: pipe|Type: boolean|Default: false| | |
20993 | +----------------+---------+-------------+--------------+ | |
20994 | ||
20995 | If this option is set, and the status returned by the command is one of the | |
20996 | codes listed in temp_errors (that is, delivery was deferred), and any output | |
20997 | was produced, the first line of it is written to the main log. | |
20998 | ||
20999 | +---------------+---------+-------------+--------------+ | |
21000 | |log_fail_output|Use: pipe|Type: boolean|Default: false| | |
21001 | +---------------+---------+-------------+--------------+ | |
21002 | ||
21003 | If this option is set, and the command returns any output, and also ends with a | |
21004 | return code that is neither zero nor one of the return codes listed in | |
21005 | temp_errors (that is, the delivery failed), the first line of output is written | |
21006 | to the main log. This option and log_output are mutually exclusive. Only one of | |
21007 | them may be set. | |
21008 | ||
21009 | +----------+---------+-------------+--------------+ | |
21010 | |log_output|Use: pipe|Type: boolean|Default: false| | |
21011 | +----------+---------+-------------+--------------+ | |
21012 | ||
21013 | If this option is set and the command returns any output, the first line of | |
21014 | output is written to the main log, whatever the return code. This option and | |
21015 | log_fail_output are mutually exclusive. Only one of them may be set. | |
21016 | ||
21017 | +----------+---------+-------------+------------+ | |
21018 | |max_output|Use: pipe|Type: integer|Default: 20K| | |
21019 | +----------+---------+-------------+------------+ | |
21020 | ||
21021 | This specifies the maximum amount of output that the command may produce on its | |
21022 | standard output and standard error file combined. If the limit is exceeded, the | |
21023 | process running the command is killed. This is intended as a safety measure to | |
21024 | catch runaway processes. The limit is applied independently of the settings of | |
21025 | the options that control what is done with such output (for example, | |
21026 | return_output). Because of buffering effects, the amount of output may exceed | |
21027 | the limit by a small amount before Exim notices. | |
21028 | ||
21029 | +--------------+---------+-------------+------------------+ | |
21030 | |message_prefix|Use: pipe|Type: string*|Default: see below| | |
21031 | +--------------+---------+-------------+------------------+ | |
21032 | ||
21033 | The string specified here is expanded and output at the start of every message. | |
21034 | The default is unset if use_bsmtp is set. Otherwise it is | |
21035 | ||
21036 | message_prefix = \ | |
21037 | From ${if def:return_path{$return_path}{MAILER-DAEMON}}\ | |
21038 | ${tod_bsdinbox}\n | |
21039 | ||
21040 | This is required by the commonly used /usr/bin/vacation program. However, it | |
21041 | must not be present if delivery is to the Cyrus IMAP server, or to the tmail | |
21042 | local delivery agent. The prefix can be suppressed by setting | |
21043 | ||
21044 | message_prefix = | |
21045 | ||
21046 | Note: If you set use_crlf true, you must change any occurrences of "\n" to "\r\ | |
21047 | n" in message_prefix. | |
21048 | ||
21049 | +--------------+---------+-------------+------------------+ | |
21050 | |message_suffix|Use: pipe|Type: string*|Default: see below| | |
21051 | +--------------+---------+-------------+------------------+ | |
21052 | ||
21053 | The string specified here is expanded and output at the end of every message. | |
21054 | The default is unset if use_bsmtp is set. Otherwise it is a single newline. The | |
21055 | suffix can be suppressed by setting | |
21056 | ||
21057 | message_suffix = | |
21058 | ||
21059 | Note: If you set use_crlf true, you must change any occurrences of "\n" to "\r\ | |
21060 | n" in message_suffix. | |
21061 | ||
21062 | +----+---------+------------+------------------+ | |
21063 | |path|Use: pipe|Type: string|Default: see below| | |
21064 | +----+---------+------------+------------------+ | |
21065 | ||
21066 | This option specifies the string that is set up in the PATH environment | |
21067 | variable of the subprocess. The default is: | |
21068 | ||
21069 | /bin:/usr/bin | |
21070 | ||
21071 | If the command option does not yield an absolute path name, the command is | |
21072 | sought in the PATH directories, in the usual way. Warning: This does not apply | |
21073 | to a command specified as a transport filter. | |
21074 | ||
21075 | +---------------+---------+-------------+--------------+ | |
21076 | |permit_coredump|Use: pipe|Type: boolean|Default: false| | |
21077 | +---------------+---------+-------------+--------------+ | |
21078 | ||
21079 | Normally Exim inhibits core-dumps during delivery. If you have a need to get a | |
21080 | core-dump of a pipe command, enable this command. This enables core-dumps | |
21081 | during delivery and affects both the Exim binary and the pipe command run. It | |
21082 | is recommended that this option remain off unless and until you have a need for | |
21083 | it and that this only be enabled when needed, as the risk of excessive resource | |
21084 | consumption can be quite high. Note also that Exim is typically installed as a | |
21085 | setuid binary and most operating systems will inhibit coredumps of these by | |
21086 | default, so further OS-specific action may be required. | |
21087 | ||
21088 | +---------------+---------+-------------+--------------+ | |
21089 | |pipe_as_creator|Use: pipe|Type: boolean|Default: false| | |
21090 | +---------------+---------+-------------+--------------+ | |
21091 | ||
21092 | If the generic user option is not set and this option is true, the delivery | |
21093 | process is run under the uid that was in force when Exim was originally called | |
21094 | to accept the message. If the group id is not otherwise set (via the generic | |
21095 | group option), the gid that was in force when Exim was originally called to | |
21096 | accept the message is used. | |
21097 | ||
21098 | +----------------+---------+-------------+--------------+ | |
21099 | |restrict_to_path|Use: pipe|Type: boolean|Default: false| | |
21100 | +----------------+---------+-------------+--------------+ | |
21101 | ||
21102 | When this option is set, any command name not listed in allow_commands must | |
21103 | contain no slashes. The command is searched for only in the directories listed | |
21104 | in the path option. This option is intended for use in the case when a pipe | |
21105 | command has been generated from a user's .forward file. This is usually handled | |
21106 | by a pipe transport called address_pipe. | |
21107 | ||
21108 | +------------------+---------+-------------+--------------+ | |
21109 | |return_fail_output|Use: pipe|Type: boolean|Default: false| | |
21110 | +------------------+---------+-------------+--------------+ | |
21111 | ||
21112 | If this option is true, and the command produced any output and ended with a | |
21113 | return code other than zero or one of the codes listed in temp_errors (that is, | |
21114 | the delivery failed), the output is returned in the bounce message. However, if | |
21115 | the message has a null sender (that is, it is itself a bounce message), output | |
21116 | from the command is discarded. This option and return_output are mutually | |
21117 | exclusive. Only one of them may be set. | |
21118 | ||
21119 | +-------------+---------+-------------+--------------+ | |
21120 | |return_output|Use: pipe|Type: boolean|Default: false| | |
21121 | +-------------+---------+-------------+--------------+ | |
21122 | ||
21123 | If this option is true, and the command produced any output, the delivery is | |
21124 | deemed to have failed whatever the return code from the command, and the output | |
21125 | is returned in the bounce message. Otherwise, the output is just discarded. | |
21126 | However, if the message has a null sender (that is, it is a bounce message), | |
21127 | output from the command is always discarded, whatever the setting of this | |
21128 | option. This option and return_fail_output are mutually exclusive. Only one of | |
21129 | them may be set. | |
21130 | ||
21131 | +-----------+---------+-----------------+------------------+ | |
21132 | |temp_errors|Use: pipe|Type: string list|Default: see below| | |
21133 | +-----------+---------+-----------------+------------------+ | |
21134 | ||
21135 | This option contains either a colon-separated list of numbers, or a single | |
21136 | asterisk. If ignore_status is false and return_output is not set, and the | |
21137 | command exits with a non-zero return code, the failure is treated as temporary | |
21138 | and the delivery is deferred if the return code matches one of the numbers, or | |
21139 | if the setting is a single asterisk. Otherwise, non-zero return codes are | |
21140 | treated as permanent errors. The default setting contains the codes defined by | |
21141 | EX_TEMPFAIL and EX_CANTCREAT in sysexits.h. If Exim is compiled on a system | |
21142 | that does not define these macros, it assumes values of 75 and 73, | |
21143 | respectively. | |
21144 | ||
21145 | +-------+---------+----------+-----------+ | |
21146 | |timeout|Use: pipe|Type: time|Default: 1h| | |
21147 | +-------+---------+----------+-----------+ | |
21148 | ||
21149 | If the command fails to complete within this time, it is killed. This normally | |
21150 | causes the delivery to fail (but see timeout_defer). A zero time interval | |
21151 | specifies no timeout. In order to ensure that any subprocesses created by the | |
21152 | command are also killed, Exim makes the initial process a process group leader, | |
21153 | and kills the whole process group on a timeout. However, this can be defeated | |
21154 | if one of the processes starts a new process group. | |
21155 | ||
21156 | +-------------+---------+-------------+--------------+ | |
21157 | |timeout_defer|Use: pipe|Type: boolean|Default: false| | |
21158 | +-------------+---------+-------------+--------------+ | |
21159 | ||
21160 | A timeout in a pipe transport, either in the command that the transport runs, | |
21161 | or in a transport filter that is associated with it, is by default treated as a | |
21162 | hard error, and the delivery fails. However, if timeout_defer is set true, both | |
21163 | kinds of timeout become temporary errors, causing the delivery to be deferred. | |
21164 | ||
21165 | +-----+---------+-------------------+------------+ | |
21166 | |umask|Use: pipe|Type: octal integer|Default: 022| | |
21167 | +-----+---------+-------------------+------------+ | |
21168 | ||
21169 | This specifies the umask setting for the subprocess that runs the command. | |
21170 | ||
21171 | +---------+---------+-------------+--------------+ | |
21172 | |use_bsmtp|Use: pipe|Type: boolean|Default: false| | |
21173 | +---------+---------+-------------+--------------+ | |
21174 | ||
21175 | If this option is set true, the pipe transport writes messages in "batch SMTP" | |
21176 | format, with the envelope sender and recipient(s) included as SMTP commands. If | |
21177 | you want to include a leading HELO command with such messages, you can do so by | |
21178 | setting the message_prefix option. See section 47.10 for details of batch SMTP. | |
21179 | ||
21180 | +------------------+---------+-------------+--------------+ | |
21181 | |use_classresources|Use: pipe|Type: boolean|Default: false| | |
21182 | +------------------+---------+-------------+--------------+ | |
21183 | ||
21184 | This option is available only when Exim is running on FreeBSD, NetBSD, or BSD/ | |
21185 | OS. If it is set true, the setclassresources() function is used to set resource | |
21186 | limits when a pipe transport is run to perform a delivery. The limits for the | |
21187 | uid under which the pipe is to run are obtained from the login class database. | |
21188 | ||
21189 | +--------+---------+-------------+--------------+ | |
21190 | |use_crlf|Use: pipe|Type: boolean|Default: false| | |
21191 | +--------+---------+-------------+--------------+ | |
21192 | ||
21193 | This option causes lines to be terminated with the two-character CRLF sequence | |
21194 | (carriage return, linefeed) instead of just a linefeed character. In the case | |
21195 | of batched SMTP, the byte sequence written to the pipe is then an exact image | |
21196 | of what would be sent down a real SMTP connection. | |
21197 | ||
21198 | The contents of the message_prefix and message_suffix options are written | |
21199 | verbatim, so must contain their own carriage return characters if these are | |
21200 | needed. When use_bsmtp is not set, the default values for both message_prefix | |
21201 | and message_suffix end with a single linefeed, so their values must be changed | |
21202 | to end with "\r\n" if use_crlf is set. | |
21203 | ||
21204 | +---------+---------+-------------+--------------+ | |
21205 | |use_shell|Use: pipe|Type: boolean|Default: false| | |
21206 | +---------+---------+-------------+--------------+ | |
21207 | ||
21208 | If this option is set, it causes the command to be passed to /bin/sh instead of | |
21209 | being run directly from the transport, as described in section 29.3. This is | |
21210 | less secure, but is needed in some situations where the command is expected to | |
21211 | be run under a shell and cannot easily be modified. The allow_commands and | |
21212 | restrict_to_path options, and the "$pipe_addresses" facility are incompatible | |
21213 | with use_shell. The command is expanded as a single string, and handed to /bin/ | |
21214 | sh as data for its -c option. | |
21215 | ||
21216 | ||
21217 | 29.6 Using an external local delivery agent | |
21218 | ------------------------------------------- | |
21219 | ||
21220 | The pipe transport can be used to pass all messages that require local delivery | |
21221 | to a separate local delivery agent such as procmail. When doing this, care must | |
21222 | be taken to ensure that the pipe is run under an appropriate uid and gid. In | |
21223 | some configurations one wants this to be a uid that is trusted by the delivery | |
21224 | agent to supply the correct sender of the message. It may be necessary to | |
21225 | recompile or reconfigure the delivery agent so that it trusts an appropriate | |
21226 | user. The following is an example transport and router configuration for | |
21227 | procmail: | |
21228 | ||
21229 | # transport | |
21230 | procmail_pipe: | |
21231 | driver = pipe | |
21232 | command = /usr/local/bin/procmail -d $local_part | |
21233 | return_path_add | |
21234 | delivery_date_add | |
21235 | envelope_to_add | |
21236 | check_string = "From " | |
21237 | escape_string = ">From " | |
21238 | umask = 077 | |
21239 | user = $local_part | |
21240 | group = mail | |
21241 | ||
21242 | # router | |
21243 | procmail: | |
21244 | driver = accept | |
21245 | check_local_user | |
21246 | transport = procmail_pipe | |
21247 | ||
21248 | In this example, the pipe is run as the local user, but with the group set to | |
21249 | mail. An alternative is to run the pipe as a specific user such as mail or exim | |
21250 | , but in this case you must arrange for procmail to trust that user to supply a | |
21251 | correct sender address. If you do not specify either a group or a user option, | |
21252 | the pipe command is run as the local user. The home directory is the user's | |
21253 | home directory by default. | |
21254 | ||
21255 | Note: The command that the pipe transport runs does not begin with | |
21256 | ||
21257 | IFS=" " | |
21258 | ||
21259 | as shown in some procmail documentation, because Exim does not by default use a | |
21260 | shell to run pipe commands. | |
21261 | ||
21262 | The next example shows a transport and a router for a system where local | |
21263 | deliveries are handled by the Cyrus IMAP server. | |
21264 | ||
21265 | # transport | |
21266 | local_delivery_cyrus: | |
21267 | driver = pipe | |
21268 | command = /usr/cyrus/bin/deliver \ | |
21269 | -m ${substr_1:$local_part_suffix} -- $local_part | |
21270 | user = cyrus | |
21271 | group = mail | |
21272 | return_output | |
21273 | log_output | |
21274 | message_prefix = | |
21275 | message_suffix = | |
21276 | ||
21277 | # router | |
21278 | local_user_cyrus: | |
21279 | driver = accept | |
21280 | check_local_user | |
21281 | local_part_suffix = .* | |
21282 | transport = local_delivery_cyrus | |
21283 | ||
21284 | Note the unsetting of message_prefix and message_suffix, and the use of | |
21285 | return_output to cause any text written by Cyrus to be returned to the sender. | |
21286 | ||
21287 | ||
21288 | ||
21289 | =============================================================================== | |
21290 | 30. THE SMTP TRANSPORT | |
21291 | ||
21292 | The smtp transport delivers messages over TCP/IP connections using the SMTP or | |
21293 | LMTP protocol. The list of hosts to try can either be taken from the address | |
21294 | that is being processed (having been set up by the router), or specified | |
21295 | explicitly for the transport. Timeout and retry processing (see chapter 32) is | |
21296 | applied to each IP address independently. | |
21297 | ||
21298 | ||
21299 | 30.1 Multiple messages on a single connection | |
21300 | --------------------------------------------- | |
21301 | ||
21302 | The sending of multiple messages over a single TCP/IP connection can arise in | |
21303 | two ways: | |
21304 | ||
21305 | * If a message contains more than max_rcpt (see below) addresses that are | |
21306 | routed to the same host, more than one copy of the message has to be sent | |
21307 | to that host. In this situation, multiple copies may be sent in a single | |
21308 | run of the smtp transport over a single TCP/IP connection. (What Exim | |
21309 | actually does when it has too many addresses to send in one message also | |
21310 | depends on the value of the global remote_max_parallel option. Details are | |
21311 | given in section 47.1.) | |
21312 | ||
21313 | * When a message has been successfully delivered over a TCP/IP connection, | |
21314 | Exim looks in its hints database to see if there are any other messages | |
21315 | awaiting a connection to the same host. If there are, a new delivery | |
21316 | process is started for one of them, and the current TCP/IP connection is | |
21317 | passed on to it. The new process may in turn send multiple copies and | |
21318 | possibly create yet another process. | |
21319 | ||
21320 | For each copy sent over the same TCP/IP connection, a sequence counter is | |
21321 | incremented, and if it ever gets to the value of connection_max_messages, no | |
21322 | further messages are sent over that connection. | |
21323 | ||
21324 | ||
21325 | 30.2 Use of the $host and $host_address variables | |
21326 | ------------------------------------------------- | |
21327 | ||
21328 | At the start of a run of the smtp transport, the values of $host and | |
21329 | $host_address are the name and IP address of the first host on the host list | |
21330 | passed by the router. However, when the transport is about to connect to a | |
21331 | specific host, and while it is connected to that host, $host and $host_address | |
21332 | are set to the values for that host. These are the values that are in force | |
21333 | when the helo_data, hosts_try_auth, interface, serialize_hosts, and the various | |
21334 | TLS options are expanded. | |
21335 | ||
21336 | ||
21337 | 30.3 Use of $tls_cipher and $tls_peerdn | |
21338 | --------------------------------------- | |
21339 | ||
21340 | At the start of a run of the smtp transport, the values of $tls_bits, | |
21341 | $tls_cipher, $tls_peerdn and $tls_sni are the values that were set when the | |
21342 | message was received. These are the values that are used for options that are | |
21343 | expanded before any SMTP connections are made. Just before each connection is | |
21344 | made, these four variables are emptied. If TLS is subsequently started, they | |
21345 | are set to the appropriate values for the outgoing connection, and these are | |
21346 | the values that are in force when any authenticators are run and when the | |
21347 | authenticated_sender option is expanded. | |
21348 | ||
21349 | These variables are deprecated in favour of $tls_in_cipher et. al. and will be | |
21350 | removed in a future release. | |
21351 | ||
21352 | ||
21353 | 30.4 Private options for smtp | |
21354 | ----------------------------- | |
21355 | ||
21356 | The private options of the smtp transport are as follows: | |
21357 | ||
21358 | +----------------------------+---------+-------------+-------------+ | |
21359 | |address_retry_include_sender|Use: smtp|Type: boolean|Default: true| | |
21360 | +----------------------------+---------+-------------+-------------+ | |
21361 | ||
21362 | When an address is delayed because of a 4xx response to a RCPT command, it is | |
21363 | the combination of sender and recipient that is delayed in subsequent queue | |
21364 | runs until the retry time is reached. You can delay the recipient without | |
21365 | reference to the sender (which is what earlier versions of Exim did), by | |
21366 | setting address_retry_include_sender false. However, this can lead to problems | |
21367 | with servers that regularly issue 4xx responses to RCPT commands. | |
21368 | ||
21369 | +---------------+---------+-------------+--------------+ | |
21370 | |allow_localhost|Use: smtp|Type: boolean|Default: false| | |
21371 | +---------------+---------+-------------+--------------+ | |
21372 | ||
21373 | When a host specified in hosts or fallback_hosts (see below) turns out to be | |
21374 | the local host, or is listed in hosts_treat_as_local, delivery is deferred by | |
21375 | default. However, if allow_localhost is set, Exim goes on to do the delivery | |
21376 | anyway. This should be used only in special cases when the configuration | |
21377 | ensures that no looping will result (for example, a differently configured Exim | |
21378 | is listening on the port to which the message is sent). | |
21379 | ||
21380 | +--------------------+---------+-------------+--------------+ | |
21381 | |authenticated_sender|Use: smtp|Type: string*|Default: unset| | |
21382 | +--------------------+---------+-------------+--------------+ | |
21383 | ||
21384 | When Exim has authenticated as a client, or if authenticated_sender_force is | |
21385 | true, this option sets a value for the AUTH= item on outgoing MAIL commands, | |
21386 | overriding any existing authenticated sender value. If the string expansion is | |
21387 | forced to fail, the option is ignored. Other expansion failures cause delivery | |
21388 | to be deferred. If the result of expansion is an empty string, that is also | |
21389 | ignored. | |
21390 | ||
21391 | The expansion happens after the outgoing connection has been made and TLS | |
21392 | started, if required. This means that the $host, $host_address, $tls_out_cipher | |
21393 | , and $tls_out_peerdn variables are set according to the particular connection. | |
21394 | ||
21395 | If the SMTP session is not authenticated, the expansion of authenticated_sender | |
21396 | still happens (and can cause the delivery to be deferred if it fails), but no | |
21397 | AUTH= item is added to MAIL commands unless authenticated_sender_force is true. | |
21398 | ||
21399 | This option allows you to use the smtp transport in LMTP mode to deliver mail | |
21400 | to Cyrus IMAP and provide the proper local part as the "authenticated sender", | |
21401 | via a setting such as: | |
21402 | ||
21403 | authenticated_sender = $local_part | |
21404 | ||
21405 | This removes the need for IMAP subfolders to be assigned special ACLs to allow | |
21406 | direct delivery to those subfolders. | |
21407 | ||
21408 | Because of expected uses such as that just described for Cyrus (when no domain | |
21409 | is involved), there is no checking on the syntax of the provided value. | |
21410 | ||
21411 | +--------------------------+---------+-------------+--------------+ | |
21412 | |authenticated_sender_force|Use: smtp|Type: boolean|Default: false| | |
21413 | +--------------------------+---------+-------------+--------------+ | |
21414 | ||
21415 | If this option is set true, the authenticated_sender option's value is used for | |
21416 | the AUTH= item on outgoing MAIL commands, even if Exim has not authenticated as | |
21417 | a client. | |
21418 | ||
21419 | +---------------+---------+----------+-----------+ | |
21420 | |command_timeout|Use: smtp|Type: time|Default: 5m| | |
21421 | +---------------+---------+----------+-----------+ | |
21422 | ||
21423 | This sets a timeout for receiving a response to an SMTP command that has been | |
21424 | sent out. It is also used when waiting for the initial banner line from the | |
21425 | remote host. Its value must not be zero. | |
21426 | ||
21427 | +---------------+---------+----------+-----------+ | |
21428 | |connect_timeout|Use: smtp|Type: time|Default: 5m| | |
21429 | +---------------+---------+----------+-----------+ | |
21430 | ||
21431 | This sets a timeout for the connect() function, which sets up a TCP/IP call to | |
21432 | a remote host. A setting of zero allows the system timeout (typically several | |
21433 | minutes) to act. To have any effect, the value of this option must be less than | |
21434 | the system timeout. However, it has been observed that on some systems there is | |
21435 | no system timeout, which is why the default value for this option is 5 minutes, | |
21436 | a value recommended by RFC 1123. | |
21437 | ||
21438 | +-----------------------+---------+-------------+------------+ | |
21439 | |connection_max_messages|Use: smtp|Type: integer|Default: 500| | |
21440 | +-----------------------+---------+-------------+------------+ | |
21441 | ||
21442 | This controls the maximum number of separate message deliveries that are sent | |
21443 | over a single TCP/IP connection. If the value is zero, there is no limit. For | |
21444 | testing purposes, this value can be overridden by the -oB command line option. | |
21445 | ||
21446 | +------------+---------+----------+-----------+ | |
21447 | |data_timeout|Use: smtp|Type: time|Default: 5m| | |
21448 | +------------+---------+----------+-----------+ | |
21449 | ||
21450 | This sets a timeout for the transmission of each block in the data portion of | |
21451 | the message. As a result, the overall timeout for a message depends on the size | |
21452 | of the message. Its value must not be zero. See also final_timeout. | |
21453 | ||
21454 | +------------------+---------+-------------+-------------+ | |
21455 | |delay_after_cutoff|Use: smtp|Type: boolean|Default: true| | |
21456 | +------------------+---------+-------------+-------------+ | |
21457 | ||
21458 | This option controls what happens when all remote IP addresses for a given | |
21459 | domain have been inaccessible for so long that they have passed their retry | |
21460 | cutoff times. | |
21461 | ||
21462 | In the default state, if the next retry time has not been reached for any of | |
21463 | them, the address is bounced without trying any deliveries. In other words, | |
21464 | Exim delays retrying an IP address after the final cutoff time until a new | |
21465 | retry time is reached, and can therefore bounce an address without ever trying | |
21466 | a delivery, when machines have been down for a long time. Some people are | |
21467 | unhappy at this prospect, so... | |
21468 | ||
21469 | If delay_after_cutoff is set false, Exim behaves differently. If all IP | |
21470 | addresses are past their final cutoff time, Exim tries to deliver to those IP | |
21471 | addresses that have not been tried since the message arrived. If there are | |
21472 | none, of if they all fail, the address is bounced. In other words, it does not | |
21473 | delay when a new message arrives, but immediately tries those expired IP | |
21474 | addresses that haven't been tried since the message arrived. If there is a | |
21475 | continuous stream of messages for the dead hosts, unsetting delay_after_cutoff | |
21476 | means that there will be many more attempts to deliver to them. | |
21477 | ||
21478 | +------------------+---------+-------------+-------------+ | |
21479 | |dns_qualify_single|Use: smtp|Type: boolean|Default: true| | |
21480 | +------------------+---------+-------------+-------------+ | |
21481 | ||
21482 | If the hosts or fallback_hosts option is being used, and the gethostbyname | |
21483 | option is false, the RES_DEFNAMES resolver option is set. See the | |
21484 | qualify_single option in chapter 17 for more details. | |
21485 | ||
21486 | +------------------+---------+-------------+--------------+ | |
21487 | |dns_search_parents|Use: smtp|Type: boolean|Default: false| | |
21488 | +------------------+---------+-------------+--------------+ | |
21489 | ||
21490 | If the hosts or fallback_hosts option is being used, and the gethostbyname | |
21491 | option is false, the RES_DNSRCH resolver option is set. See the search_parents | |
21492 | option in chapter 17 for more details. | |
21493 | ||
21494 | +----------------------+---------+------------------+--------------+ | |
21495 | |dnssec_request_domains|Use: smtp|Type: domain list*|Default: unset| | |
21496 | +----------------------+---------+------------------+--------------+ | |
21497 | ||
21498 | DNS lookups for domains matching dnssec_request_domains will be done with the | |
21499 | dnssec request bit set. This applies to all of the SRV, MX A6, AAAA, A lookup | |
21500 | sequence. | |
21501 | ||
21502 | +----------------------+---------+------------------+--------------+ | |
21503 | |dnssec_require_domains|Use: smtp|Type: domain list*|Default: unset| | |
21504 | +----------------------+---------+------------------+--------------+ | |
21505 | ||
21506 | DNS lookups for domains matching dnssec_request_domains will be done with the | |
21507 | dnssec request bit set. Any returns not having the Authenticated Data bit (AD | |
21508 | bit) set wil be ignored and logged as a host-lookup failure. This applies to | |
21509 | all of the SRV, MX A6, AAAA, A lookup sequence. | |
21510 | ||
21511 | +----+---------+-------------+--------------+ | |
21512 | |dscp|Use: smtp|Type: string*|Default: unset| | |
21513 | +----+---------+-------------+--------------+ | |
21514 | ||
21515 | This option causes the DSCP value associated with a socket to be set to one of | |
21516 | a number of fixed strings or to numeric value. The -bI:dscp option may be used | |
21517 | to ask Exim which names it knows of. Common values include "throughput", | |
21518 | "mincost", and on newer systems "ef", "af41", etc. Numeric values may be in the | |
21519 | range 0 to 0x3F. | |
21520 | ||
21521 | The outbound packets from Exim will be marked with this value in the header | |
21522 | (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee | |
21523 | that these values will have any effect, not be stripped by networking | |
21524 | equipment, or do much of anything without cooperation with your Network | |
21525 | Engineer and those of all network operators between the source and destination. | |
21526 | ||
21527 | +--------------+---------+-----------------+--------------+ | |
21528 | |fallback_hosts|Use: smtp|Type: string list|Default: unset| | |
21529 | +--------------+---------+-----------------+--------------+ | |
21530 | ||
21531 | String expansion is not applied to this option. The argument must be a | |
21532 | colon-separated list of host names or IP addresses, optionally also including | |
21533 | port numbers, though the separator can be changed, as described in section 6.19 | |
21534 | . Each individual item in the list is the same as an item in a route_list | |
21535 | setting for the manualroute router, as described in section 20.5. | |
21536 | ||
21537 | Fallback hosts can also be specified on routers, which associate them with the | |
21538 | addresses they process. As for the hosts option without hosts_override, | |
21539 | fallback_hosts specified on the transport is used only if the address does not | |
21540 | have its own associated fallback host list. Unlike hosts, a setting of | |
21541 | fallback_hosts on an address is not overridden by hosts_override. However, | |
21542 | hosts_randomize does apply to fallback host lists. | |
21543 | ||
21544 | If Exim is unable to deliver to any of the hosts for a particular address, and | |
21545 | the errors are not permanent rejections, the address is put on a separate | |
21546 | transport queue with its host list replaced by the fallback hosts, unless the | |
21547 | address was routed via MX records and the current host was in the original MX | |
21548 | list. In that situation, the fallback host list is not used. | |
21549 | ||
21550 | Once normal deliveries are complete, the fallback queue is delivered by | |
21551 | re-running the same transports with the new host lists. If several failing | |
21552 | addresses have the same fallback hosts (and max_rcpt permits it), a single copy | |
21553 | of the message is sent. | |
21554 | ||
21555 | The resolution of the host names on the fallback list is controlled by the | |
21556 | gethostbyname option, as for the hosts option. Fallback hosts apply both to | |
21557 | cases when the host list comes with the address and when it is taken from hosts | |
21558 | . This option provides a "use a smart host only if delivery fails" facility. | |
21559 | ||
21560 | +-------------+---------+----------+------------+ | |
21561 | |final_timeout|Use: smtp|Type: time|Default: 10m| | |
21562 | +-------------+---------+----------+------------+ | |
21563 | ||
21564 | This is the timeout that applies while waiting for the response to the final | |
21565 | line containing just "." that terminates a message. Its value must not be zero. | |
21566 | ||
21567 | +-------------+---------+-------------+--------------+ | |
21568 | |gethostbyname|Use: smtp|Type: boolean|Default: false| | |
21569 | +-------------+---------+-------------+--------------+ | |
21570 | ||
21571 | If this option is true when the hosts and/or fallback_hosts options are being | |
21572 | used, names are looked up using gethostbyname() (or getipnodebyname() when | |
21573 | available) instead of using the DNS. Of course, that function may in fact use | |
21574 | the DNS, but it may also consult other sources of information such as /etc/ | |
21575 | hosts. | |
21576 | ||
21577 | +------------------+---------+-------------+--------------+ | |
21578 | |gnutls_compat_mode|Use: smtp|Type: boolean|Default: unset| | |
21579 | +------------------+---------+-------------+--------------+ | |
21580 | ||
21581 | This option controls whether GnuTLS is used in compatibility mode in an Exim | |
21582 | server. This reduces security slightly, but improves interworking with older | |
21583 | implementations of TLS. | |
21584 | ||
21585 | +---------+---------+-------------+------------------+ | |
21586 | |helo_data|Use: smtp|Type: string*|Default: see below| | |
21587 | +---------+---------+-------------+------------------+ | |
21588 | ||
21589 | The value of this option is expanded after a connection to a another host has | |
21590 | been set up. The result is used as the argument for the EHLO, HELO, or LHLO | |
21591 | command that starts the outgoing SMTP or LMTP session. The default value of the | |
21592 | option is: | |
21593 | ||
21594 | $primary_hostname | |
21595 | ||
21596 | During the expansion, the variables $host and $host_address are set to the | |
21597 | identity of the remote host, and the variables $sending_ip_address and | |
21598 | $sending_port are set to the local IP address and port number that are being | |
21599 | used. These variables can be used to generate different values for different | |
21600 | servers or different local IP addresses. For example, if you want the string | |
21601 | that is used for helo_data to be obtained by a DNS lookup of the outgoing | |
21602 | interface address, you could use this: | |
21603 | ||
21604 | helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\ | |
21605 | {$primary_hostname}} | |
21606 | ||
21607 | The use of helo_data applies both to sending messages and when doing callouts. | |
21608 | ||
21609 | +-----+---------+------------------+--------------+ | |
21610 | |hosts|Use: smtp|Type: string list*|Default: unset| | |
21611 | +-----+---------+------------------+--------------+ | |
21612 | ||
21613 | Hosts are associated with an address by a router such as dnslookup, which finds | |
21614 | the hosts by looking up the address domain in the DNS, or by manualroute, which | |
21615 | has lists of hosts in its configuration. However, email addresses can be passed | |
21616 | to the smtp transport by any router, and not all of them can provide an | |
21617 | associated list of hosts. | |
21618 | ||
21619 | The hosts option specifies a list of hosts to be used if the address being | |
21620 | processed does not have any hosts associated with it. The hosts specified by | |
21621 | hosts are also used, whether or not the address has its own hosts, if | |
21622 | hosts_override is set. | |
21623 | ||
21624 | The string is first expanded, before being interpreted as a colon-separated | |
21625 | list of host names or IP addresses, possibly including port numbers. The | |
21626 | separator may be changed to something other than colon, as described in section | |
21627 | 6.19. Each individual item in the list is the same as an item in a route_list | |
21628 | setting for the manualroute router, as described in section 20.5. However, note | |
21629 | that the "/MX" facility of the manualroute router is not available here. | |
21630 | ||
21631 | If the expansion fails, delivery is deferred. Unless the failure was caused by | |
21632 | the inability to complete a lookup, the error is logged to the panic log as | |
21633 | well as the main log. Host names are looked up either by searching directly for | |
21634 | address records in the DNS or by calling gethostbyname() (or getipnodebyname() | |
21635 | when available), depending on the setting of the gethostbyname option. When | |
21636 | Exim is compiled with IPv6 support, if a host that is looked up in the DNS has | |
21637 | both IPv4 and IPv6 addresses, both types of address are used. | |
21638 | ||
21639 | During delivery, the hosts are tried in order, subject to their retry status, | |
21640 | unless hosts_randomize is set. | |
21641 | ||
21642 | +-----------------+---------+----------------+--------------+ | |
21643 | |hosts_avoid_esmtp|Use: smtp|Type: host list*|Default: unset| | |
21644 | +-----------------+---------+----------------+--------------+ | |
21645 | ||
21646 | This option is for use with broken hosts that announce ESMTP facilities (for | |
21647 | example, PIPELINING) and then fail to implement them properly. When a host | |
21648 | matches hosts_avoid_esmtp, Exim sends HELO rather than EHLO at the start of the | |
21649 | SMTP session. This means that it cannot use any of the ESMTP facilities such as | |
21650 | AUTH, PIPELINING, SIZE, and STARTTLS. | |
21651 | ||
21652 | +----------------------+---------+----------------+--------------+ | |
21653 | |hosts_avoid_pipelining|Use: smtp|Type: host list*|Default: unset| | |
21654 | +----------------------+---------+----------------+--------------+ | |
21655 | ||
21656 | Exim will not use the SMTP PIPELINING extension when delivering to any host | |
21657 | that matches this list, even if the server host advertises PIPELINING support. | |
21658 | ||
21659 | +---------------+---------+----------------+--------------+ | |
21660 | |hosts_avoid_tls|Use: smtp|Type: host list*|Default: unset| | |
21661 | +---------------+---------+----------------+--------------+ | |
21662 | ||
21663 | Exim will not try to start a TLS session when delivering to any host that | |
21664 | matches this list. See chapter 41 for details of TLS. | |
21665 | ||
21666 | +----------------------+---------+----------------+----------+ | |
21667 | |hosts_verify_avoid_tls|Use: smtp|Type: host list*|Default: *| | |
21668 | +----------------------+---------+----------------+----------+ | |
21669 | ||
21670 | Exim will not try to start a TLS session for a verify callout, or when | |
21671 | delivering in cutthrough mode, to any host that matches this list. Note that | |
21672 | the default is to not use TLS. | |
21673 | ||
21674 | +-------------+---------+-------------+----------+ | |
21675 | |hosts_max_try|Use: smtp|Type: integer|Default: 5| | |
21676 | +-------------+---------+-------------+----------+ | |
21677 | ||
21678 | This option limits the number of IP addresses that are tried for any one | |
21679 | delivery in cases where there are temporary delivery errors. Section 30.5 | |
21680 | describes in detail how the value of this option is used. | |
21681 | ||
21682 | +-----------------------+---------+-------------+-----------+ | |
21683 | |hosts_max_try_hardlimit|Use: smtp|Type: integer|Default: 50| | |
21684 | +-----------------------+---------+-------------+-----------+ | |
21685 | ||
21686 | This is an additional check on the maximum number of IP addresses that Exim | |
21687 | tries for any one delivery. Section 30.5 describes its use and why it exists. | |
21688 | ||
21689 | +----------------+---------+----------------+--------------+ | |
21690 | |hosts_nopass_tls|Use: smtp|Type: host list*|Default: unset| | |
21691 | +----------------+---------+----------------+--------------+ | |
21692 | ||
21693 | For any host that matches this list, a connection on which a TLS session has | |
21694 | been started will not be passed to a new delivery process for sending another | |
21695 | message on the same connection. See section 41.11 for an explanation of when | |
21696 | this might be needed. | |
21697 | ||
21698 | +--------------+---------+-------------+--------------+ | |
21699 | |hosts_override|Use: smtp|Type: boolean|Default: false| | |
21700 | +--------------+---------+-------------+--------------+ | |
21701 | ||
21702 | If this option is set and the hosts option is also set, any hosts that are | |
21703 | attached to the address are ignored, and instead the hosts specified by the | |
21704 | hosts option are always used. This option does not apply to fallback_hosts. | |
21705 | ||
21706 | +---------------+---------+-------------+--------------+ | |
21707 | |hosts_randomize|Use: smtp|Type: boolean|Default: false| | |
21708 | +---------------+---------+-------------+--------------+ | |
21709 | ||
21710 | If this option is set, and either the list of hosts is taken from the hosts or | |
21711 | the fallback_hosts option, or the hosts supplied by the router were not | |
21712 | obtained from MX records (this includes fallback hosts from the router), and | |
21713 | were not randomized by the router, the order of trying the hosts is randomized | |
21714 | each time the transport runs. Randomizing the order of a host list can be used | |
21715 | to do crude load sharing. | |
21716 | ||
21717 | When hosts_randomize is true, a host list may be split into groups whose order | |
21718 | is separately randomized. This makes it possible to set up MX-like behaviour. | |
21719 | The boundaries between groups are indicated by an item that is just "+" in the | |
21720 | host list. For example: | |
21721 | ||
21722 | hosts = host1:host2:host3:+:host4:host5 | |
21723 | ||
21724 | The order of the first three hosts and the order of the last two hosts is | |
21725 | randomized for each use, but the first three always end up before the last two. | |
21726 | If hosts_randomize is not set, a "+" item in the list is ignored. | |
21727 | ||
21728 | +------------------+---------+----------------+--------------+ | |
21729 | |hosts_require_auth|Use: smtp|Type: host list*|Default: unset| | |
21730 | +------------------+---------+----------------+--------------+ | |
21731 | ||
21732 | This option provides a list of servers for which authentication must succeed | |
21733 | before Exim will try to transfer a message. If authentication fails for servers | |
21734 | which are not in this list, Exim tries to send unauthenticated. If | |
21735 | authentication fails for one of these servers, delivery is deferred. This | |
21736 | temporary error is detectable in the retry rules, so it can be turned into a | |
21737 | hard failure if required. See also hosts_try_auth, and chapter 33 for details | |
21738 | of authentication. | |
21739 | ||
21740 | +------------------+---------+----------------+----------+ | |
21741 | |hosts_request_ocsp|Use: smtp|Type: host list*|Default: *| | |
21742 | +------------------+---------+----------------+----------+ | |
21743 | ||
21744 | Exim will request a Certificate Status on a TLS session for any host that | |
21745 | matches this list. tls_verify_certificates should also be set for the | |
21746 | transport. | |
21747 | ||
21748 | +------------------+---------+----------------+--------------+ | |
21749 | |hosts_require_ocsp|Use: smtp|Type: host list*|Default: unset| | |
21750 | +------------------+---------+----------------+--------------+ | |
21751 | ||
21752 | Exim will request, and check for a valid Certificate Status being given, on a | |
21753 | TLS session for any host that matches this list. tls_verify_certificates should | |
21754 | also be set for the transport. | |
21755 | ||
21756 | +-----------------+---------+----------------+--------------+ | |
21757 | |hosts_require_tls|Use: smtp|Type: host list*|Default: unset| | |
21758 | +-----------------+---------+----------------+--------------+ | |
21759 | ||
21760 | Exim will insist on using a TLS session when delivering to any host that | |
21761 | matches this list. See chapter 41 for details of TLS. Note: This option affects | |
21762 | outgoing mail only. To insist on TLS for incoming messages, use an appropriate | |
21763 | ACL. | |
21764 | ||
21765 | +--------------+---------+----------------+--------------+ | |
21766 | |hosts_try_auth|Use: smtp|Type: host list*|Default: unset| | |
21767 | +--------------+---------+----------------+--------------+ | |
21768 | ||
21769 | This option provides a list of servers to which, provided they announce | |
21770 | authentication support, Exim will attempt to authenticate as a client when it | |
21771 | connects. If authentication fails, Exim will try to transfer the message | |
21772 | unauthenticated. See also hosts_require_auth, and chapter 33 for details of | |
21773 | authentication. | |
21774 | ||
21775 | +--------------+---------+----------------+--------------+ | |
21776 | |hosts_try_prdr|Use: smtp|Type: host list*|Default: unset| | |
21777 | +--------------+---------+----------------+--------------+ | |
21778 | ||
21779 | This option provides a list of servers to which, provided they announce PRDR | |
21780 | support, Exim will attempt to negotiate PRDR for multi-recipient messages. | |
21781 | ||
21782 | +---------+---------+------------------+--------------+ | |
21783 | |interface|Use: smtp|Type: string list*|Default: unset| | |
21784 | +---------+---------+------------------+--------------+ | |
21785 | ||
21786 | This option specifies which interface to bind to when making an outgoing SMTP | |
21787 | call. The value is an IP address, not an interface name such as "eth0". Do not | |
21788 | confuse this with the interface address that was used when a message was | |
21789 | received, which is in $received_ip_address, formerly known as | |
21790 | $interface_address. The name was changed to minimize confusion with the | |
21791 | outgoing interface address. There is no variable that contains an outgoing | |
21792 | interface address because, unless it is set by this option, its value is | |
21793 | unknown. | |
21794 | ||
21795 | During the expansion of the interface option the variables $host and | |
21796 | $host_address refer to the host to which a connection is about to be made | |
21797 | during the expansion of the string. Forced expansion failure, or an empty | |
21798 | string result causes the option to be ignored. Otherwise, after expansion, the | |
21799 | string must be a list of IP addresses, colon-separated by default, but the | |
21800 | separator can be changed in the usual way. For example: | |
21801 | ||
21802 | interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061 | |
21803 | ||
21804 | The first interface of the correct type (IPv4 or IPv6) is used for the outgoing | |
21805 | connection. If none of them are the correct type, the option is ignored. If | |
21806 | interface is not set, or is ignored, the system's IP functions choose which | |
21807 | interface to use if the host has more than one. | |
21808 | ||
21809 | +---------+---------+-------------+-------------+ | |
21810 | |keepalive|Use: smtp|Type: boolean|Default: true| | |
21811 | +---------+---------+-------------+-------------+ | |
21812 | ||
21813 | This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket | |
21814 | connections. When set, it causes the kernel to probe idle connections | |
21815 | periodically, by sending packets with "old" sequence numbers. The other end of | |
21816 | the connection should send a acknowledgment if the connection is still okay or | |
21817 | a reset if the connection has been aborted. The reason for doing this is that | |
21818 | it has the beneficial effect of freeing up certain types of connection that can | |
21819 | get stuck when the remote host is disconnected without tidying up the TCP/IP | |
21820 | call properly. The keepalive mechanism takes several hours to detect | |
21821 | unreachable hosts. | |
21822 | ||
21823 | +-----------------+---------+-------------+--------------+ | |
21824 | |lmtp_ignore_quota|Use: smtp|Type: boolean|Default: false| | |
21825 | +-----------------+---------+-------------+--------------+ | |
21826 | ||
21827 | If this option is set true when the protocol option is set to "lmtp", the | |
21828 | string "IGNOREQUOTA" is added to RCPT commands, provided that the LMTP server | |
21829 | has advertised support for IGNOREQUOTA in its response to the LHLO command. | |
21830 | ||
21831 | +--------+---------+-------------+------------+ | |
21832 | |max_rcpt|Use: smtp|Type: integer|Default: 100| | |
21833 | +--------+---------+-------------+------------+ | |
21834 | ||
21835 | This option limits the number of RCPT commands that are sent in a single SMTP | |
21836 | message transaction. Each set of addresses is treated independently, and so can | |
21837 | cause parallel connections to the same host if remote_max_parallel permits | |
21838 | this. | |
21839 | ||
21840 | +------------+---------+-------------+-------------+ | |
21841 | |multi_domain|Use: smtp|Type: boolean|Default: true| | |
21842 | +------------+---------+-------------+-------------+ | |
21843 | ||
21844 | When this option is set, the smtp transport can handle a number of addresses | |
21845 | containing a mixture of different domains provided they all resolve to the same | |
21846 | list of hosts. Turning the option off restricts the transport to handling only | |
21847 | one domain at a time. This is useful if you want to use $domain in an expansion | |
21848 | for the transport, because it is set only when there is a single domain | |
21849 | involved in a remote delivery. | |
21850 | ||
21851 | +----+---------+-------------+------------------+ | |
21852 | |port|Use: smtp|Type: string*|Default: see below| | |
21853 | +----+---------+-------------+------------------+ | |
21854 | ||
21855 | This option specifies the TCP/IP port on the server to which Exim connects. | |
21856 | Note: Do not confuse this with the port that was used when a message was | |
21857 | received, which is in $received_port, formerly known as $interface_port. The | |
21858 | name was changed to minimize confusion with the outgoing port. There is no | |
21859 | variable that contains an outgoing port. | |
21860 | ||
21861 | If the value of this option begins with a digit it is taken as a port number; | |
21862 | otherwise it is looked up using getservbyname(). The default value is normally | |
21863 | "smtp", but if protocol is set to "lmtp", the default is "lmtp". If the | |
21864 | expansion fails, or if a port number cannot be found, delivery is deferred. | |
21865 | ||
21866 | +--------+---------+------------+-------------+ | |
21867 | |protocol|Use: smtp|Type: string|Default: smtp| | |
21868 | +--------+---------+------------+-------------+ | |
21869 | ||
21870 | If this option is set to "lmtp" instead of "smtp", the default value for the | |
21871 | port option changes to "lmtp", and the transport operates the LMTP protocol | |
21872 | (RFC 2033) instead of SMTP. This protocol is sometimes used for local | |
21873 | deliveries into closed message stores. Exim also has support for running LMTP | |
21874 | over a pipe to a local process - see chapter 28. | |
21875 | ||
21876 | If this option is set to "smtps", the default vaule for the port option changes | |
21877 | to "smtps", and the transport initiates TLS immediately after connecting, as an | |
21878 | outbound SSL-on-connect, instead of using STARTTLS to upgrade. The Internet | |
21879 | standards bodies strongly discourage use of this mode. | |
21880 | ||
21881 | +------------------------+---------+-------------+-------------+ | |
21882 | |retry_include_ip_address|Use: smtp|Type: boolean|Default: true| | |
21883 | +------------------------+---------+-------------+-------------+ | |
21884 | ||
21885 | Exim normally includes both the host name and the IP address in the key it | |
21886 | constructs for indexing retry data after a temporary delivery failure. This | |
21887 | means that when one of several IP addresses for a host is failing, it gets | |
21888 | tried periodically (controlled by the retry rules), but use of the other IP | |
21889 | addresses is not affected. | |
21890 | ||
21891 | However, in some dialup environments hosts are assigned a different IP address | |
21892 | each time they connect. In this situation the use of the IP address as part of | |
21893 | the retry key leads to undesirable behaviour. Setting this option false causes | |
21894 | Exim to use only the host name. This should normally be done on a separate | |
21895 | instance of the smtp transport, set up specially to handle the dialup hosts. | |
21896 | ||
21897 | +---------------+---------+----------------+--------------+ | |
21898 | |serialize_hosts|Use: smtp|Type: host list*|Default: unset| | |
21899 | +---------------+---------+----------------+--------------+ | |
21900 | ||
21901 | Because Exim operates in a distributed manner, if several messages for the same | |
21902 | host arrive at around the same time, more than one simultaneous connection to | |
21903 | the remote host can occur. This is not usually a problem except when there is a | |
21904 | slow link between the hosts. In that situation it may be helpful to restrict | |
21905 | Exim to one connection at a time. This can be done by setting serialize_hosts | |
21906 | to match the relevant hosts. | |
21907 | ||
21908 | Exim implements serialization by means of a hints database in which a record is | |
21909 | written whenever a process connects to one of the restricted hosts. The record | |
21910 | is deleted when the connection is completed. Obviously there is scope for | |
21911 | records to get left lying around if there is a system or program crash. To | |
21912 | guard against this, Exim ignores any records that are more than six hours old. | |
21913 | ||
21914 | If you set up this kind of serialization, you should also arrange to delete the | |
21915 | relevant hints database whenever your system reboots. The names of the files | |
21916 | start with misc and they are kept in the spool/db directory. There may be one | |
21917 | or two files, depending on the type of DBM in use. The same files are used for | |
21918 | ETRN serialization. | |
21919 | ||
21920 | +-------------+---------+-------------+-------------+ | |
21921 | |size_addition|Use: smtp|Type: integer|Default: 1024| | |
21922 | +-------------+---------+-------------+-------------+ | |
21923 | ||
21924 | If a remote SMTP server indicates that it supports the SIZE option of the MAIL | |
21925 | command, Exim uses this to pass over the message size at the start of an SMTP | |
21926 | transaction. It adds the value of size_addition to the value it sends, to allow | |
21927 | for headers and other text that may be added during delivery by configuration | |
21928 | options or in a transport filter. It may be necessary to increase this if a lot | |
21929 | of text is added to messages. | |
21930 | ||
21931 | Alternatively, if the value of size_addition is set negative, it disables the | |
21932 | use of the SIZE option altogether. | |
21933 | ||
21934 | +---------------+---------+-------------+--------------+ | |
21935 | |tls_certificate|Use: smtp|Type: string*|Default: unset| | |
21936 | +---------------+---------+-------------+--------------+ | |
21937 | ||
21938 | The value of this option must be the absolute path to a file which contains the | |
21939 | client's certificate, for possible use when sending a message over an encrypted | |
21940 | connection. The values of $host and $host_address are set to the name and | |
21941 | address of the server during the expansion. See chapter 41 for details of TLS. | |
21942 | ||
21943 | Note: This option must be set if you want Exim to be able to use a TLS | |
21944 | certificate when sending messages as a client. The global option of the same | |
21945 | name specifies the certificate for Exim as a server; it is not automatically | |
21946 | assumed that the same certificate should be used when Exim is operating as a | |
21947 | client. | |
21948 | ||
21949 | +-------+---------+-------------+--------------+ | |
21950 | |tls_crl|Use: smtp|Type: string*|Default: unset| | |
21951 | +-------+---------+-------------+--------------+ | |
21952 | ||
21953 | This option specifies a certificate revocation list. The expanded value must be | |
21954 | the name of a file that contains a CRL in PEM format. | |
21955 | ||
21956 | +---------------+---------+-------------+-------------+ | |
21957 | |tls_dh_min_bits|Use: smtp|Type: integer|Default: 1024| | |
21958 | +---------------+---------+-------------+-------------+ | |
21959 | ||
21960 | When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman key | |
21961 | agreement is negotiated, the server will provide a large prime number for use. | |
21962 | This option establishes the minimum acceptable size of that number. If the | |
21963 | parameter offered by the server is too small, then the TLS handshake will fail. | |
21964 | ||
21965 | Only supported when using GnuTLS. | |
21966 | ||
21967 | +--------------+---------+-------------+--------------+ | |
21968 | |tls_privatekey|Use: smtp|Type: string*|Default: unset| | |
21969 | +--------------+---------+-------------+--------------+ | |
21970 | ||
21971 | The value of this option must be the absolute path to a file which contains the | |
21972 | client's private key. This is used when sending a message over an encrypted | |
21973 | connection using a client certificate. The values of $host and $host_address | |
21974 | are set to the name and address of the server during the expansion. If this | |
21975 | option is unset, or the expansion is forced to fail, or the result is an empty | |
21976 | string, the private key is assumed to be in the same file as the certificate. | |
21977 | See chapter 41 for details of TLS. | |
21978 | ||
21979 | +-------------------+---------+-------------+--------------+ | |
21980 | |tls_require_ciphers|Use: smtp|Type: string*|Default: unset| | |
21981 | +-------------------+---------+-------------+--------------+ | |
21982 | ||
21983 | The value of this option must be a list of permitted cipher suites, for use | |
21984 | when setting up an outgoing encrypted connection. (There is a global option of | |
21985 | the same name for controlling incoming connections.) The values of $host and | |
21986 | $host_address are set to the name and address of the server during the | |
21987 | expansion. See chapter 41 for details of TLS; note that this option is used in | |
21988 | different ways by OpenSSL and GnuTLS (see sections 41.4 and 41.5). For GnuTLS, | |
21989 | the order of the ciphers is a preference order. | |
21990 | ||
21991 | +-------+---------+-------------+--------------+ | |
21992 | |tls_sni|Use: smtp|Type: string*|Default: unset| | |
21993 | +-------+---------+-------------+--------------+ | |
21994 | ||
21995 | If this option is set then it sets the $tls_out_sni variable and causes any TLS | |
21996 | session to pass this value as the Server Name Indication extension to the | |
21997 | remote side, which can be used by the remote side to select an appropriate | |
21998 | certificate and private key for the session. | |
21999 | ||
22000 | See 41.10 for more information. | |
22001 | ||
22002 | Note that for OpenSSL, this feature requires a build of OpenSSL that supports | |
22003 | TLS extensions. | |
22004 | ||
22005 | +---------------------+---------+-------------+-------------+ | |
22006 | |tls_tempfail_tryclear|Use: smtp|Type: boolean|Default: true| | |
22007 | +---------------------+---------+-------------+-------------+ | |
22008 | ||
22009 | When the server host is not in hosts_require_tls, and there is a problem in | |
22010 | setting up a TLS session, this option determines whether or not Exim should try | |
22011 | to deliver the message unencrypted. If it is set false, delivery to the current | |
22012 | host is deferred; if there are other hosts, they are tried. If this option is | |
22013 | set true, Exim attempts to deliver unencrypted after a 4xx response to | |
22014 | STARTTLS. Also, if STARTTLS is accepted, but the subsequent TLS negotiation | |
22015 | fails, Exim closes the current connection (because it is in an unknown state), | |
22016 | opens a new one to the same host, and then tries the delivery in clear. | |
22017 | ||
22018 | +--------------------+---------+----------------------+--------+ | |
22019 | |tls_try_verify_hosts|Use: smtp|Type: host list* unset|Default:| | |
22020 | +--------------------+---------+----------------------+--------+ | |
22021 | ||
22022 | This option gives a list of hosts for which, on encrypted connections, | |
22023 | certificate verification will be tried but need not succeed. The | |
22024 | tls_verify_certificates option must also be set. Note that unless the host is | |
22025 | in this list TLS connections will be denied to hosts using self-signed | |
22026 | certificates when tls_verify_certificates is set. The | |
22027 | $tls_out_certificate_verified variable is set when certificate verification | |
22028 | succeeds. | |
22029 | ||
22030 | +-----------------------+---------+-------------+--------------+ | |
22031 | |tls_verify_certificates|Use: smtp|Type: string*|Default: unset| | |
22032 | +-----------------------+---------+-------------+--------------+ | |
22033 | ||
22034 | The value of this option must be the absolute path to a file containing | |
22035 | permitted server certificates, for use when setting up an encrypted connection. | |
22036 | Alternatively, if you are using OpenSSL, you can set tls_verify_certificates to | |
22037 | the name of a directory containing certificate files. This does not work with | |
22038 | GnuTLS; the option must be set to the name of a single file if you are using | |
22039 | GnuTLS. The values of $host and $host_address are set to the name and address | |
22040 | of the server during the expansion of this option. See chapter 41 for details | |
22041 | of TLS. | |
22042 | ||
22043 | For back-compatability, if neither tls_verify_hosts nor tls_try_verify_hosts | |
22044 | are set and certificate verification fails the TLS connection is closed. | |
22045 | ||
22046 | +----------------+---------+----------------------+--------+ | |
22047 | |tls_verify_hosts|Use: smtp|Type: host list* unset|Default:| | |
22048 | +----------------+---------+----------------------+--------+ | |
22049 | ||
22050 | This option gives a list of hosts for which. on encrypted connections, | |
22051 | certificate verification must succeed. The tls_verify_certificates option must | |
22052 | also be set. If both this option and tls_try_verify_hosts are unset operation | |
22053 | is as if this option selected all hosts. | |
22054 | ||
22055 | ||
22056 | 30.5 How the limits for the number of hosts to try are used | |
22057 | ----------------------------------------------------------- | |
22058 | ||
22059 | There are two options that are concerned with the number of hosts that are | |
22060 | tried when an SMTP delivery takes place. They are hosts_max_try and | |
22061 | hosts_max_try_hardlimit. | |
22062 | ||
22063 | The hosts_max_try option limits the number of hosts that are tried for a single | |
22064 | delivery. However, despite the term "host" in its name, the option actually | |
22065 | applies to each IP address independently. In other words, a multihomed host is | |
22066 | treated as several independent hosts, just as it is for retrying. | |
22067 | ||
22068 | Many of the larger ISPs have multiple MX records which often point to | |
22069 | multihomed hosts. As a result, a list of a dozen or more IP addresses may be | |
22070 | created as a result of routing one of these domains. | |
22071 | ||
22072 | Trying every single IP address on such a long list does not seem sensible; if | |
22073 | several at the top of the list fail, it is reasonable to assume there is some | |
22074 | problem that is likely to affect all of them. Roughly speaking, the value of | |
22075 | hosts_max_try is the maximum number that are tried before deferring the | |
22076 | delivery. However, the logic cannot be quite that simple. | |
22077 | ||
22078 | Firstly, IP addresses that are skipped because their retry times have not | |
22079 | arrived do not count, and in addition, addresses that are past their retry | |
22080 | limits are also not counted, even when they are tried. This means that when | |
22081 | some IP addresses are past their retry limits, more than the value of | |
22082 | hosts_max_retry may be tried. The reason for this behaviour is to ensure that | |
22083 | all IP addresses are considered before timing out an email address (but see | |
22084 | below for an exception). | |
22085 | ||
22086 | Secondly, when the hosts_max_try limit is reached, Exim looks down the host | |
22087 | list to see if there is a subsequent host with a different (higher valued) MX. | |
22088 | If there is, that host is considered next, and the current IP address is used | |
22089 | but not counted. This behaviour helps in the case of a domain with a retry rule | |
22090 | that hardly ever delays any hosts, as is now explained: | |
22091 | ||
22092 | Consider the case of a long list of hosts with one MX value, and a few with a | |
22093 | higher MX value. If hosts_max_try is small (the default is 5) only a few hosts | |
22094 | at the top of the list are tried at first. With the default retry rule, which | |
22095 | specifies increasing retry times, the higher MX hosts are eventually tried when | |
22096 | those at the top of the list are skipped because they have not reached their | |
22097 | retry times. | |
22098 | ||
22099 | However, it is common practice to put a fixed short retry time on domains for | |
22100 | large ISPs, on the grounds that their servers are rarely down for very long. | |
22101 | Unfortunately, these are exactly the domains that tend to resolve to long lists | |
22102 | of hosts. The short retry time means that the lowest MX hosts are tried every | |
22103 | time. The attempts may be in a different order because of random sorting, but | |
22104 | without the special MX check, the higher MX hosts would never be tried until | |
22105 | all the lower MX hosts had timed out (which might be several days), because | |
22106 | there are always some lower MX hosts that have reached their retry times. With | |
22107 | the special check, Exim considers at least one IP address from each MX value at | |
22108 | every delivery attempt, even if the hosts_max_try limit has already been | |
22109 | reached. | |
22110 | ||
22111 | The above logic means that hosts_max_try is not a hard limit, and in | |
22112 | particular, Exim normally eventually tries all the IP addresses before timing | |
22113 | out an email address. When hosts_max_try was implemented, this seemed a | |
22114 | reasonable thing to do. Recently, however, some lunatic DNS configurations have | |
22115 | been set up with hundreds of IP addresses for some domains. It can take a very | |
22116 | long time indeed for an address to time out in these cases. | |
22117 | ||
22118 | The hosts_max_try_hardlimit option was added to help with this problem. Exim | |
22119 | never tries more than this number of IP addresses; if it hits this limit and | |
22120 | they are all timed out, the email address is bounced, even though not all | |
22121 | possible IP addresses have been tried. | |
22122 | ||
22123 | ||
22124 | ||
22125 | =============================================================================== | |
22126 | 31. ADDRESS REWRITING | |
22127 | ||
22128 | There are some circumstances in which Exim automatically rewrites domains in | |
22129 | addresses. The two most common are when an address is given without a domain | |
22130 | (referred to as an "unqualified address") or when an address contains an | |
22131 | abbreviated domain that is expanded by DNS lookup. | |
22132 | ||
22133 | Unqualified envelope addresses are accepted only for locally submitted | |
22134 | messages, or for messages that are received from hosts matching | |
22135 | sender_unqualified_hosts or recipient_unqualified_hosts, as appropriate. | |
22136 | Unqualified addresses in header lines are qualified if they are in locally | |
22137 | submitted messages, or messages from hosts that are permitted to send | |
22138 | unqualified envelope addresses. Otherwise, unqualified addresses in header | |
22139 | lines are neither qualified nor rewritten. | |
22140 | ||
22141 | One situation in which Exim does not automatically rewrite a domain is when it | |
22142 | is the name of a CNAME record in the DNS. The older RFCs suggest that such a | |
22143 | domain should be rewritten using the "canonical" name, and some MTAs do this. | |
22144 | The new RFCs do not contain this suggestion. | |
22145 | ||
22146 | ||
22147 | 31.1 Explicitly configured address rewriting | |
22148 | -------------------------------------------- | |
22149 | ||
22150 | This chapter describes the rewriting rules that can be used in the main rewrite | |
22151 | section of the configuration file, and also in the generic headers_rewrite | |
22152 | option that can be set on any transport. | |
22153 | ||
22154 | Some people believe that configured address rewriting is a Mortal Sin. Others | |
22155 | believe that life is not possible without it. Exim provides the facility; you | |
22156 | do not have to use it. | |
22157 | ||
22158 | The main rewriting rules that appear in the "rewrite" section of the | |
22159 | configuration file are applied to addresses in incoming messages, both envelope | |
22160 | addresses and addresses in header lines. Each rule specifies the types of | |
22161 | address to which it applies. | |
22162 | ||
22163 | Whether or not addresses in header lines are rewritten depends on the origin of | |
22164 | the headers and the type of rewriting. Global rewriting, that is, rewriting | |
22165 | rules from the rewrite section of the configuration file, is applied only to | |
22166 | those headers that were received with the message. Header lines that are added | |
22167 | by ACLs or by a system filter or by individual routers or transports (which are | |
22168 | specific to individual recipient addresses) are not rewritten by the global | |
22169 | rules. | |
22170 | ||
22171 | Rewriting at transport time, by means of the headers_rewrite option, applies | |
22172 | all headers except those added by routers and transports. That is, as well as | |
22173 | the headers that were received with the message, it also applies to headers | |
22174 | that were added by an ACL or a system filter. | |
22175 | ||
22176 | In general, rewriting addresses from your own system or domain has some | |
22177 | legitimacy. Rewriting other addresses should be done only with great care and | |
22178 | in special circumstances. The author of Exim believes that rewriting should be | |
22179 | used sparingly, and mainly for "regularizing" addresses in your own domains. | |
22180 | Although it can sometimes be used as a routing tool, this is very strongly | |
22181 | discouraged. | |
22182 | ||
22183 | There are two commonly encountered circumstances where rewriting is used, as | |
22184 | illustrated by these examples: | |
22185 | ||
22186 | * The company whose domain is hitch.fict.example has a number of hosts that | |
22187 | exchange mail with each other behind a firewall, but there is only a single | |
22188 | gateway to the outer world. The gateway rewrites *.hitch.fict.example as | |
22189 | hitch.fict.example when sending mail off-site. | |
22190 | ||
22191 | * A host rewrites the local parts of its own users so that, for example, | |
22192 | fp42@hitch.fict.example becomes Ford.Prefect@hitch.fict.example. | |
22193 | ||
22194 | ||
22195 | 31.2 When does rewriting happen? | |
22196 | -------------------------------- | |
22197 | ||
22198 | Configured address rewriting can take place at several different stages of a | |
22199 | message's processing. | |
22200 | ||
22201 | At the start of an ACL for MAIL, the sender address may have been rewritten by | |
22202 | a special SMTP-time rewrite rule (see section 31.9), but no ordinary rewrite | |
22203 | rules have yet been applied. If, however, the sender address is verified in the | |
22204 | ACL, it is rewritten before verification, and remains rewritten thereafter. The | |
22205 | subsequent value of $sender_address is the rewritten address. This also applies | |
22206 | if sender verification happens in a RCPT ACL. Otherwise, when the sender | |
22207 | address is not verified, it is rewritten as soon as a message's header lines | |
22208 | have been received. | |
22209 | ||
22210 | Similarly, at the start of an ACL for RCPT, the current recipient's address may | |
22211 | have been rewritten by a special SMTP-time rewrite rule, but no ordinary | |
22212 | rewrite rules have yet been applied to it. However, the behaviour is different | |
22213 | from the sender address when a recipient is verified. The address is rewritten | |
22214 | for the verification, but the rewriting is not remembered at this stage. The | |
22215 | value of $local_part and $domain after verification are always the same as they | |
22216 | were before (that is, they contain the unrewritten - except for SMTP-time | |
22217 | rewriting - address). | |
22218 | ||
22219 | As soon as a message's header lines have been received, all the envelope | |
22220 | recipient addresses are permanently rewritten, and rewriting is also applied to | |
22221 | the addresses in the header lines (if configured). This happens before adding | |
22222 | any header lines that were specified in MAIL or RCPT ACLs, and before the DATA | |
22223 | ACL and local_scan() functions are run. | |
22224 | ||
22225 | When an address is being routed, either for delivery or for verification, | |
22226 | rewriting is applied immediately to child addresses that are generated by | |
22227 | redirection, unless no_rewrite is set on the router. | |
22228 | ||
22229 | At transport time, additional rewriting of addresses in header lines can be | |
22230 | specified by setting the generic headers_rewrite option on a transport. This | |
22231 | option contains rules that are identical in form to those in the rewrite | |
22232 | section of the configuration file. They are applied to the original message | |
22233 | header lines and any that were added by ACLs or a system filter. They are not | |
22234 | applied to header lines that are added by routers or the transport. | |
22235 | ||
22236 | The outgoing envelope sender can be rewritten by means of the return_path | |
22237 | transport option. However, it is not possible to rewrite envelope recipients at | |
22238 | transport time. | |
22239 | ||
22240 | ||
22241 | 31.3 Testing the rewriting rules that apply on input | |
22242 | ---------------------------------------------------- | |
22243 | ||
22244 | Exim's input rewriting configuration appears in a part of the run time | |
22245 | configuration file headed by "begin rewrite". It can be tested by the -brw | |
22246 | command line option. This takes an address (which can be a full RFC 2822 | |
22247 | address) as its argument. The output is a list of how the address would be | |
22248 | transformed by the rewriting rules for each of the different places it might | |
22249 | appear in an incoming message, that is, for each different header and for the | |
22250 | envelope sender and recipient fields. For example, | |
22251 | ||
22252 | exim -brw ph10@exim.workshop.example | |
22253 | ||
22254 | might produce the output | |
22255 | ||
22256 | sender: Philip.Hazel@exim.workshop.example | |
22257 | from: Philip.Hazel@exim.workshop.example | |
22258 | to: ph10@exim.workshop.example | |
22259 | cc: ph10@exim.workshop.example | |
22260 | bcc: ph10@exim.workshop.example | |
22261 | reply-to: Philip.Hazel@exim.workshop.example | |
22262 | env-from: Philip.Hazel@exim.workshop.example | |
22263 | env-to: ph10@exim.workshop.example | |
22264 | ||
22265 | which shows that rewriting has been set up for that address when used in any of | |
22266 | the source fields, but not when it appears as a recipient address. At the | |
22267 | present time, there is no equivalent way of testing rewriting rules that are | |
22268 | set for a particular transport. | |
22269 | ||
22270 | ||
22271 | 31.4 Rewriting rules | |
22272 | -------------------- | |
22273 | ||
22274 | The rewrite section of the configuration file consists of lines of rewriting | |
22275 | rules in the form | |
22276 | ||
22277 | <source pattern> <replacement> <flags> | |
22278 | ||
22279 | Rewriting rules that are specified for the headers_rewrite generic transport | |
22280 | option are given as a colon-separated list. Each item in the list takes the | |
22281 | same form as a line in the main rewriting configuration (except that any colons | |
22282 | must be doubled, of course). | |
22283 | ||
22284 | The formats of source patterns and replacement strings are described below. | |
22285 | Each is terminated by white space, unless enclosed in double quotes, in which | |
22286 | case normal quoting conventions apply inside the quotes. The flags are single | |
22287 | characters which may appear in any order. Spaces and tabs between them are | |
22288 | ignored. | |
22289 | ||
22290 | For each address that could potentially be rewritten, the rules are scanned in | |
22291 | order, and replacements for the address from earlier rules can themselves be | |
22292 | replaced by later rules (but see the "q" and "R" flags). | |
22293 | ||
22294 | The order in which addresses are rewritten is undefined, may change between | |
22295 | releases, and must not be relied on, with one exception: when a message is | |
22296 | received, the envelope sender is always rewritten first, before any header | |
22297 | lines are rewritten. For example, the replacement string for a rewrite of an | |
22298 | address in To: must not assume that the message's address in From: has (or has | |
22299 | not) already been rewritten. However, a rewrite of From: may assume that the | |
22300 | envelope sender has already been rewritten. | |
22301 | ||
22302 | The variables $local_part and $domain can be used in the replacement string to | |
22303 | refer to the address that is being rewritten. Note that lookup-driven rewriting | |
22304 | can be done by a rule of the form | |
22305 | ||
22306 | *@* ${lookup ... | |
22307 | ||
22308 | where the lookup key uses $1 and $2 or $local_part and $domain to refer to the | |
22309 | address that is being rewritten. | |
22310 | ||
22311 | ||
22312 | 31.5 Rewriting patterns | |
22313 | ----------------------- | |
22314 | ||
22315 | The source pattern in a rewriting rule is any item which may appear in an | |
22316 | address list (see section 10.19). It is in fact processed as a single-item | |
22317 | address list, which means that it is expanded before being tested against the | |
22318 | address. As always, if you use a regular expression as a pattern, you must take | |
22319 | care to escape dollar and backslash characters, or use the "\N" facility to | |
22320 | suppress string expansion within the regular expression. | |
22321 | ||
22322 | Domains in patterns should be given in lower case. Local parts in patterns are | |
22323 | case-sensitive. If you want to do case-insensitive matching of local parts, you | |
22324 | can use a regular expression that starts with "^(?i)". | |
22325 | ||
22326 | After matching, the numerical variables $1, $2, etc. may be set, depending on | |
22327 | the type of match which occurred. These can be used in the replacement string | |
22328 | to insert portions of the incoming address. $0 always refers to the complete | |
22329 | incoming address. When a regular expression is used, the numerical variables | |
22330 | are set from its capturing subexpressions. For other types of pattern they are | |
22331 | set as follows: | |
22332 | ||
22333 | * If a local part or domain starts with an asterisk, the numerical variables | |
22334 | refer to the character strings matched by asterisks, with $1 associated | |
22335 | with the first asterisk, and $2 with the second, if present. For example, | |
22336 | if the pattern | |
22337 | ||
22338 | *queen@*.fict.example | |
22339 | ||
22340 | is matched against the address hearts-queen@wonderland.fict.example then | |
22341 | ||
22342 | $0 = hearts-queen@wonderland.fict.example | |
22343 | $1 = hearts- | |
22344 | $2 = wonderland | |
22345 | ||
22346 | Note that if the local part does not start with an asterisk, but the domain | |
22347 | does, it is $1 that contains the wild part of the domain. | |
22348 | ||
22349 | * If the domain part of the pattern is a partial lookup, the wild and fixed | |
22350 | parts of the domain are placed in the next available numerical variables. | |
22351 | Suppose, for example, that the address foo@bar.baz.example is processed by | |
22352 | a rewriting rule of the form | |
22353 | ||
22354 | *@partial-dbm;/some/dbm/file <replacement string> | |
22355 | ||
22356 | and the key in the file that matches the domain is "*.baz.example". Then | |
22357 | ||
22358 | $1 = foo | |
22359 | $2 = bar | |
22360 | $3 = baz.example | |
22361 | ||
22362 | If the address foo@baz.example is looked up, this matches the same wildcard | |
22363 | file entry, and in this case $2 is set to the empty string, but $3 is still | |
22364 | set to baz.example. If a non-wild key is matched in a partial lookup, $2 is | |
22365 | again set to the empty string and $3 is set to the whole domain. For | |
22366 | non-partial domain lookups, no numerical variables are set. | |
22367 | ||
22368 | ||
22369 | 31.6 Rewriting replacements | |
22370 | --------------------------- | |
22371 | ||
22372 | If the replacement string for a rule is a single asterisk, addresses that match | |
22373 | the pattern and the flags are not rewritten, and no subsequent rewriting rules | |
22374 | are scanned. For example, | |
22375 | ||
22376 | hatta@lookingglass.fict.example * f | |
22377 | ||
22378 | specifies that hatta@lookingglass.fict.example is never to be rewritten in | |
22379 | From: headers. | |
22380 | ||
22381 | If the replacement string is not a single asterisk, it is expanded, and must | |
22382 | yield a fully qualified address. Within the expansion, the variables | |
22383 | $local_part and $domain refer to the address that is being rewritten. Any | |
22384 | letters they contain retain their original case - they are not lower cased. The | |
22385 | numerical variables are set up according to the type of pattern that matched | |
22386 | the address, as described above. If the expansion is forced to fail by the | |
22387 | presence of "fail" in a conditional or lookup item, rewriting by the current | |
22388 | rule is abandoned, but subsequent rules may take effect. Any other expansion | |
22389 | failure causes the entire rewriting operation to be abandoned, and an entry | |
22390 | written to the panic log. | |
22391 | ||
22392 | ||
22393 | 31.7 Rewriting flags | |
22394 | -------------------- | |
22395 | ||
22396 | There are three different kinds of flag that may appear on rewriting rules: | |
22397 | ||
22398 | * Flags that specify which headers and envelope addresses to rewrite: E, F, | |
22399 | T, b, c, f, h, r, s, t. | |
22400 | ||
22401 | * A flag that specifies rewriting at SMTP time: S. | |
22402 | ||
22403 | * Flags that control the rewriting process: Q, q, R, w. | |
22404 | ||
22405 | For rules that are part of the headers_rewrite generic transport option, E, F, | |
22406 | T, and S are not permitted. | |
22407 | ||
22408 | ||
22409 | 31.8 Flags specifying which headers and envelope addresses to rewrite | |
22410 | --------------------------------------------------------------------- | |
22411 | ||
22412 | If none of the following flag letters, nor the "S" flag (see section 31.9) are | |
22413 | present, a main rewriting rule applies to all headers and to both the sender | |
22414 | and recipient fields of the envelope, whereas a transport-time rewriting rule | |
22415 | just applies to all headers. Otherwise, the rewriting rule is skipped unless | |
22416 | the relevant addresses are being processed. | |
22417 | ||
22418 | E rewrite all envelope fields | |
22419 | F rewrite the envelope From field | |
22420 | T rewrite the envelope To field | |
22421 | b rewrite the Bcc: header | |
22422 | c rewrite the Cc: header | |
22423 | f rewrite the From: header | |
22424 | h rewrite all headers | |
22425 | r rewrite the Reply-To: header | |
22426 | s rewrite the Sender: header | |
22427 | t rewrite the To: header | |
22428 | ||
22429 | "All headers" means all of the headers listed above that can be selected | |
22430 | individually, plus their Resent- versions. It does not include other headers | |
22431 | such as Subject: etc. | |
22432 | ||
22433 | You should be particularly careful about rewriting Sender: headers, and | |
22434 | restrict this to special known cases in your own domains. | |
22435 | ||
22436 | ||
22437 | 31.9 The SMTP-time rewriting flag | |
22438 | --------------------------------- | |
22439 | ||
22440 | The rewrite flag "S" specifies a rewrite of incoming envelope addresses at SMTP | |
22441 | time, as soon as an address is received in a MAIL or RCPT command, and before | |
22442 | any other processing; even before syntax checking. The pattern is required to | |
22443 | be a regular expression, and it is matched against the whole of the data for | |
22444 | the command, including any surrounding angle brackets. | |
22445 | ||
22446 | This form of rewrite rule allows for the handling of addresses that are not | |
22447 | compliant with RFCs 2821 and 2822 (for example, "bang paths" in batched SMTP | |
22448 | input). Because the input is not required to be a syntactically valid address, | |
22449 | the variables $local_part and $domain are not available during the expansion of | |
22450 | the replacement string. The result of rewriting replaces the original address | |
22451 | in the MAIL or RCPT command. | |
22452 | ||
22453 | ||
22454 | 31.10 Flags controlling the rewriting process | |
22455 | --------------------------------------------- | |
22456 | ||
22457 | There are four flags which control the way the rewriting process works. These | |
22458 | take effect only when a rule is invoked, that is, when the address is of the | |
22459 | correct type (matches the flags) and matches the pattern: | |
22460 | ||
22461 | * If the "Q" flag is set on a rule, the rewritten address is permitted to be | |
22462 | an unqualified local part. It is qualified with qualify_recipient. In the | |
22463 | absence of "Q" the rewritten address must always include a domain. | |
22464 | ||
22465 | * If the "q" flag is set on a rule, no further rewriting rules are | |
22466 | considered, even if no rewriting actually takes place because of a "fail" | |
22467 | in the expansion. The "q" flag is not effective if the address is of the | |
22468 | wrong type (does not match the flags) or does not match the pattern. | |
22469 | ||
22470 | * The "R" flag causes a successful rewriting rule to be re-applied to the new | |
22471 | address, up to ten times. It can be combined with the "q" flag, to stop | |
22472 | rewriting once it fails to match (after at least one successful rewrite). | |
22473 | ||
22474 | * When an address in a header is rewritten, the rewriting normally applies | |
22475 | only to the working part of the address, with any comments and RFC 2822 | |
22476 | "phrase" left unchanged. For example, rewriting might change | |
22477 | ||
22478 | From: Ford Prefect <fp42@restaurant.hitch.fict.example> | |
22479 | ||
22480 | into | |
22481 | ||
22482 | From: Ford Prefect <prefectf@hitch.fict.example> | |
22483 | ||
22484 | Sometimes there is a need to replace the whole address item, and this can | |
22485 | be done by adding the flag letter "w" to a rule. If this is set on a rule | |
22486 | that causes an address in a header line to be rewritten, the entire address | |
22487 | is replaced, not just the working part. The replacement must be a complete | |
22488 | RFC 2822 address, including the angle brackets if necessary. If text | |
22489 | outside angle brackets contains a character whose value is greater than 126 | |
22490 | or less than 32 (except for tab), the text is encoded according to RFC | |
22491 | 2047. The character set is taken from headers_charset, which defaults to | |
22492 | ISO-8859-1. | |
22493 | ||
22494 | When the "w" flag is set on a rule that causes an envelope address to be | |
22495 | rewritten, all but the working part of the replacement address is | |
22496 | discarded. | |
22497 | ||
22498 | ||
22499 | 31.11 Rewriting examples | |
22500 | ------------------------ | |
22501 | ||
22502 | Here is an example of the two common rewriting paradigms: | |
22503 | ||
22504 | *@*.hitch.fict.example $1@hitch.fict.example | |
22505 | *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\ | |
22506 | {$value}fail}@hitch.fict.example bctfrF | |
22507 | ||
22508 | Note the use of "fail" in the lookup expansion in the second rule, forcing the | |
22509 | string expansion to fail if the lookup does not succeed. In this context it has | |
22510 | the effect of leaving the original address unchanged, but Exim goes on to | |
22511 | consider subsequent rewriting rules, if any, because the "q" flag is not | |
22512 | present in that rule. An alternative to "fail" would be to supply $1 | |
22513 | explicitly, which would cause the rewritten address to be the same as before, | |
22514 | at the cost of a small bit of processing. Not supplying either of these is an | |
22515 | error, since the rewritten address would then contain no local part. | |
22516 | ||
22517 | The first example above replaces the domain with a superior, more general | |
22518 | domain. This may not be desirable for certain local parts. If the rule | |
22519 | ||
22520 | root@*.hitch.fict.example * | |
22521 | ||
22522 | were inserted before the first rule, rewriting would be suppressed for the | |
22523 | local part root at any domain ending in hitch.fict.example. | |
22524 | ||
22525 | Rewriting can be made conditional on a number of tests, by making use of ${if | |
22526 | in the expansion item. For example, to apply a rewriting rule only to messages | |
22527 | that originate outside the local host: | |
22528 | ||
22529 | *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\ | |
22530 | {$1@hitch.fict.example}fail}" | |
22531 | ||
22532 | The replacement string is quoted in this example because it contains white | |
22533 | space. | |
22534 | ||
22535 | Exim does not handle addresses in the form of "bang paths". If it sees such an | |
22536 | address it treats it as an unqualified local part which it qualifies with the | |
22537 | local qualification domain (if the source of the message is local or if the | |
22538 | remote host is permitted to send unqualified addresses). Rewriting can | |
22539 | sometimes be used to handle simple bang paths with a fixed number of | |
22540 | components. For example, the rule | |
22541 | ||
22542 | \N^([^!]+)!(.*)@your.domain.example$\N $2@$1 | |
22543 | ||
22544 | rewrites a two-component bang path host.name!user as the domain address | |
22545 | user@host.name. However, there is a security implication in using this as a | |
22546 | global rewriting rule for envelope addresses. It can provide a backdoor method | |
22547 | for using your system as a relay, because the incoming addresses appear to be | |
22548 | local. If the bang path addresses are received via SMTP, it is safer to use the | |
22549 | "S" flag to rewrite them as they are received, so that relay checking can be | |
22550 | done on the rewritten addresses. | |
22551 | ||
22552 | ||
22553 | ||
22554 | =============================================================================== | |
22555 | 32. RETRY CONFIGURATION | |
22556 | ||
22557 | The "retry" section of the runtime configuration file contains a list of retry | |
22558 | rules that control how often Exim tries to deliver messages that cannot be | |
22559 | delivered at the first attempt. If there are no retry rules (the section is | |
22560 | empty or not present), there are no retries. In this situation, temporary | |
22561 | errors are treated as permanent. The default configuration contains a single, | |
22562 | general-purpose retry rule (see section 7.5). The -brt command line option can | |
22563 | be used to test which retry rule will be used for a given address, domain and | |
22564 | error. | |
22565 | ||
22566 | The most common cause of retries is temporary failure to deliver to a remote | |
22567 | host because the host is down, or inaccessible because of a network problem. | |
22568 | Exim's retry processing in this case is applied on a per-host (strictly, per IP | |
22569 | address) basis, not on a per-message basis. Thus, if one message has recently | |
22570 | been delayed, delivery of a new message to the same host is not immediately | |
22571 | tried, but waits for the host's retry time to arrive. If the retry_defer log | |
22572 | selector is set, the message "retry time not reached" is written to the main | |
22573 | log whenever a delivery is skipped for this reason. Section 47.2 contains more | |
22574 | details of the handling of errors during remote deliveries. | |
22575 | ||
22576 | Retry processing applies to routing as well as to delivering, except as covered | |
22577 | in the next paragraph. The retry rules do not distinguish between these | |
22578 | actions. It is not possible, for example, to specify different behaviour for | |
22579 | failures to route the domain snark.fict.example and failures to deliver to the | |
22580 | host snark.fict.example. I didn't think anyone would ever need this added | |
22581 | complication, so did not implement it. However, although they share the same | |
22582 | retry rule, the actual retry times for routing and transporting a given domain | |
22583 | are maintained independently. | |
22584 | ||
22585 | When a delivery is not part of a queue run (typically an immediate delivery on | |
22586 | receipt of a message), the routers are always run, and local deliveries are | |
22587 | always attempted, even if retry times are set for them. This makes for better | |
22588 | behaviour if one particular message is causing problems (for example, causing | |
22589 | quota overflow, or provoking an error in a filter file). If such a delivery | |
22590 | suffers a temporary failure, the retry data is updated as normal, and | |
22591 | subsequent delivery attempts from queue runs occur only when the retry time for | |
22592 | the local address is reached. | |
22593 | ||
22594 | ||
22595 | 32.1 Changing retry rules | |
22596 | ------------------------- | |
22597 | ||
22598 | If you change the retry rules in your configuration, you should consider | |
22599 | whether or not to delete the retry data that is stored in Exim's spool area in | |
22600 | files with names like db/retry. Deleting any of Exim's hints files is always | |
22601 | safe; that is why they are called "hints". | |
22602 | ||
22603 | The hints retry data contains suggested retry times based on the previous | |
22604 | rules. In the case of a long-running problem with a remote host, it might | |
22605 | record the fact that the host has timed out. If your new rules increase the | |
22606 | timeout time for such a host, you should definitely remove the old retry data | |
22607 | and let Exim recreate it, based on the new rules. Otherwise Exim might bounce | |
22608 | messages that it should now be retaining. | |
22609 | ||
22610 | ||
22611 | 32.2 Format of retry rules | |
22612 | -------------------------- | |
22613 | ||
22614 | Each retry rule occupies one line and consists of three or four parts, | |
22615 | separated by white space: a pattern, an error name, an optional list of sender | |
22616 | addresses, and a list of retry parameters. The pattern and sender lists must be | |
22617 | enclosed in double quotes if they contain white space. The rules are searched | |
22618 | in order until one is found where the pattern, error name, and sender list (if | |
22619 | present) match the failing host or address, the error that occurred, and the | |
22620 | message's sender, respectively. | |
22621 | ||
22622 | The pattern is any single item that may appear in an address list (see section | |
22623 | 10.19). It is in fact processed as a one-item address list, which means that it | |
22624 | is expanded before being tested against the address that has been delayed. A | |
22625 | negated address list item is permitted. Address list processing treats a plain | |
22626 | domain name as if it were preceded by "*@", which makes it possible for many | |
22627 | retry rules to start with just a domain. For example, | |
22628 | ||
22629 | lookingglass.fict.example * F,24h,30m; | |
22630 | ||
22631 | provides a rule for any address in the lookingglass.fict.example domain, | |
22632 | whereas | |
22633 | ||
22634 | alice@lookingglass.fict.example * F,24h,30m; | |
22635 | ||
22636 | applies only to temporary failures involving the local part alice. In practice, | |
22637 | almost all rules start with a domain name pattern without a local part. | |
22638 | ||
22639 | Warning: If you use a regular expression in a retry rule pattern, it must match | |
22640 | a complete address, not just a domain, because that is how regular expressions | |
22641 | work in address lists. | |
22642 | ||
22643 | ^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2 Wrong | |
22644 | ^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2 Right | |
22645 | ||
22646 | ||
22647 | 32.3 Choosing which retry rule to use for address errors | |
22648 | -------------------------------------------------------- | |
22649 | ||
22650 | When Exim is looking for a retry rule after a routing attempt has failed (for | |
22651 | example, after a DNS timeout), each line in the retry configuration is tested | |
22652 | against the complete address only if retry_use_local_part is set for the | |
22653 | router. Otherwise, only the domain is used, except when matching against a | |
22654 | regular expression, when the local part of the address is replaced with "*". A | |
22655 | domain on its own can match a domain pattern, or a pattern that starts with | |
22656 | "*@". By default, retry_use_local_part is true for routers where | |
22657 | check_local_user is true, and false for other routers. | |
22658 | ||
22659 | Similarly, when Exim is looking for a retry rule after a local delivery has | |
22660 | failed (for example, after a mailbox full error), each line in the retry | |
22661 | configuration is tested against the complete address only if | |
22662 | retry_use_local_part is set for the transport (it defaults true for all local | |
22663 | transports). | |
22664 | ||
22665 | However, when Exim is looking for a retry rule after a remote delivery attempt | |
22666 | suffers an address error (a 4xx SMTP response for a recipient address), the | |
22667 | whole address is always used as the key when searching the retry rules. The | |
22668 | rule that is found is used to create a retry time for the combination of the | |
22669 | failing address and the message's sender. It is the combination of sender and | |
22670 | recipient that is delayed in subsequent queue runs until its retry time is | |
22671 | reached. You can delay the recipient without regard to the sender by setting | |
22672 | address_retry_include_sender false in the smtp transport but this can lead to | |
22673 | problems with servers that regularly issue 4xx responses to RCPT commands. | |
22674 | ||
22675 | ||
22676 | 32.4 Choosing which retry rule to use for host and message errors | |
22677 | ----------------------------------------------------------------- | |
22678 | ||
22679 | For a temporary error that is not related to an individual address (for | |
22680 | example, a connection timeout), each line in the retry configuration is checked | |
22681 | twice. First, the name of the remote host is used as a domain name (preceded by | |
22682 | "*@" when matching a regular expression). If this does not match the line, the | |
22683 | domain from the email address is tried in a similar fashion. For example, | |
22684 | suppose the MX records for a.b.c.example are | |
22685 | ||
22686 | a.b.c.example MX 5 x.y.z.example | |
22687 | MX 6 p.q.r.example | |
22688 | MX 7 m.n.o.example | |
22689 | ||
22690 | and the retry rules are | |
22691 | ||
22692 | p.q.r.example * F,24h,30m; | |
22693 | a.b.c.example * F,4d,45m; | |
22694 | ||
22695 | and a delivery to the host x.y.z.example suffers a connection failure. The | |
22696 | first rule matches neither the host nor the domain, so Exim looks at the second | |
22697 | rule. This does not match the host, but it does match the domain, so it is used | |
22698 | to calculate the retry time for the host x.y.z.example. Meanwhile, Exim tries | |
22699 | to deliver to p.q.r.example. If this also suffers a host error, the first retry | |
22700 | rule is used, because it matches the host. | |
22701 | ||
22702 | In other words, temporary failures to deliver to host p.q.r.example use the | |
22703 | first rule to determine retry times, but for all the other hosts for the domain | |
22704 | a.b.c.example, the second rule is used. The second rule is also used if routing | |
22705 | to a.b.c.example suffers a temporary failure. | |
22706 | ||
22707 | Note: The host name is used when matching the patterns, not its IP address. | |
22708 | However, if a message is routed directly to an IP address without the use of a | |
22709 | host name, for example, if a manualroute router contains a setting such as: | |
22710 | ||
22711 | route_list = *.a.example 192.168.34.23 | |
22712 | ||
22713 | then the "host name" that is used when searching for a retry rule is the | |
22714 | textual form of the IP address. | |
22715 | ||
22716 | ||
22717 | 32.5 Retry rules for specific errors | |
22718 | ------------------------------------ | |
22719 | ||
22720 | The second field in a retry rule is the name of a particular error, or an | |
22721 | asterisk, which matches any error. The errors that can be tested for are: | |
22722 | ||
22723 | auth_failed | |
22724 | ||
22725 | Authentication failed when trying to send to a host in the | |
22726 | hosts_require_auth list in an smtp transport. | |
22727 | ||
22728 | data_4xx | |
22729 | ||
22730 | A 4xx error was received for an outgoing DATA command, either immediately | |
22731 | after the command, or after sending the message's data. | |
22732 | ||
22733 | mail_4xx | |
22734 | ||
22735 | A 4xx error was received for an outgoing MAIL command. | |
22736 | ||
22737 | rcpt_4xx | |
22738 | ||
22739 | A 4xx error was received for an outgoing RCPT command. | |
22740 | ||
22741 | For the three 4xx errors, either the first or both of the x's can be given as | |
22742 | specific digits, for example: "mail_45x" or "rcpt_436". For example, to | |
22743 | recognize 452 errors given to RCPT commands for addresses in a certain domain, | |
22744 | and have retries every ten minutes with a one-hour timeout, you could set up a | |
22745 | retry rule of this form: | |
22746 | ||
22747 | the.domain.name rcpt_452 F,1h,10m | |
22748 | ||
22749 | These errors apply to both outgoing SMTP (the smtp transport) and outgoing LMTP | |
22750 | (either the lmtp transport, or the smtp transport in LMTP mode). | |
22751 | ||
22752 | lost_connection | |
22753 | ||
22754 | A server unexpectedly closed the SMTP connection. There may, of course, | |
22755 | legitimate reasons for this (host died, network died), but if it repeats a | |
22756 | lot for the same host, it indicates something odd. | |
22757 | ||
22758 | refused_MX | |
22759 | ||
22760 | A connection to a host obtained from an MX record was refused. | |
22761 | ||
22762 | refused_A | |
22763 | ||
22764 | A connection to a host not obtained from an MX record was refused. | |
22765 | ||
22766 | refused | |
22767 | ||
22768 | A connection was refused. | |
22769 | ||
22770 | timeout_connect_MX | |
22771 | ||
22772 | A connection attempt to a host obtained from an MX record timed out. | |
22773 | ||
22774 | timeout_connect_A | |
22775 | ||
22776 | A connection attempt to a host not obtained from an MX record timed out. | |
22777 | ||
22778 | timeout_connect | |
22779 | ||
22780 | A connection attempt timed out. | |
22781 | ||
22782 | timeout_MX | |
22783 | ||
22784 | There was a timeout while connecting or during an SMTP session with a host | |
22785 | obtained from an MX record. | |
22786 | ||
22787 | timeout_A | |
22788 | ||
22789 | There was a timeout while connecting or during an SMTP session with a host | |
22790 | not obtained from an MX record. | |
22791 | ||
22792 | timeout | |
22793 | ||
22794 | There was a timeout while connecting or during an SMTP session. | |
22795 | ||
22796 | tls_required | |
22797 | ||
22798 | The server was required to use TLS (it matched hosts_require_tls in the | |
22799 | smtp transport), but either did not offer TLS, or it responded with 4xx to | |
22800 | STARTTLS, or there was a problem setting up the TLS connection. | |
22801 | ||
22802 | quota | |
22803 | ||
22804 | A mailbox quota was exceeded in a local delivery by the appendfile | |
22805 | transport. | |
22806 | ||
22807 | quota_<time> | |
22808 | ||
22809 | A mailbox quota was exceeded in a local delivery by the appendfile | |
22810 | transport, and the mailbox has not been accessed for <time>. For example, | |
22811 | quota_4d applies to a quota error when the mailbox has not been accessed | |
22812 | for four days. | |
22813 | ||
22814 | The idea of quota_<time> is to make it possible to have shorter timeouts when | |
22815 | the mailbox is full and is not being read by its owner. Ideally, it should be | |
22816 | based on the last time that the user accessed the mailbox. However, it is not | |
22817 | always possible to determine this. Exim uses the following heuristic rules: | |
22818 | ||
22819 | * If the mailbox is a single file, the time of last access (the "atime") is | |
22820 | used. As no new messages are being delivered (because the mailbox is over | |
22821 | quota), Exim does not access the file, so this is the time of last user | |
22822 | access. | |
22823 | ||
22824 | * For a maildir delivery, the time of last modification of the new | |
22825 | subdirectory is used. As the mailbox is over quota, no new files are | |
22826 | created in the new subdirectory, because no new messages are being | |
22827 | delivered. Any change to the new subdirectory is therefore assumed to be | |
22828 | the result of an MUA moving a new message to the cur directory when it is | |
22829 | first read. The time that is used is therefore the last time that the user | |
22830 | read a new message. | |
22831 | ||
22832 | * For other kinds of multi-file mailbox, the time of last access cannot be | |
22833 | obtained, so a retry rule that uses this type of error field is never | |
22834 | matched. | |
22835 | ||
22836 | The quota errors apply both to system-enforced quotas and to Exim's own quota | |
22837 | mechanism in the appendfile transport. The quota error also applies when a | |
22838 | local delivery is deferred because a partition is full (the ENOSPC error). | |
22839 | ||
22840 | ||
22841 | 32.6 Retry rules for specified senders | |
22842 | -------------------------------------- | |
22843 | ||
22844 | You can specify retry rules that apply only when the failing message has a | |
22845 | specific sender. In particular, this can be used to define retry rules that | |
22846 | apply only to bounce messages. The third item in a retry rule can be of this | |
22847 | form: | |
22848 | ||
22849 | senders=<address list> | |
22850 | ||
22851 | The retry timings themselves are then the fourth item. For example: | |
22852 | ||
22853 | * rcpt_4xx senders=: F,1h,30m | |
22854 | ||
22855 | matches recipient 4xx errors for bounce messages sent to any address at any | |
22856 | host. If the address list contains white space, it must be enclosed in quotes. | |
22857 | For example: | |
22858 | ||
22859 | a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5 | |
22860 | ||
22861 | Warning: This facility can be unhelpful if it is used for host errors (which do | |
22862 | not depend on the recipient). The reason is that the sender is used only to | |
22863 | match the retry rule. Once the rule has been found for a host error, its | |
22864 | contents are used to set a retry time for the host, and this will apply to all | |
22865 | messages, not just those with specific senders. | |
22866 | ||
22867 | When testing retry rules using -brt, you can supply a sender using the -f | |
22868 | command line option, like this: | |
22869 | ||
22870 | exim -f "" -brt user@dom.ain | |
22871 | ||
22872 | If you do not set -f with -brt, a retry rule that contains a senders list is | |
22873 | never matched. | |
22874 | ||
22875 | ||
22876 | 32.7 Retry parameters | |
22877 | --------------------- | |
22878 | ||
22879 | The third (or fourth, if a senders list is present) field in a retry rule is a | |
22880 | sequence of retry parameter sets, separated by semicolons. Each set consists of | |
22881 | ||
22882 | <letter>,<cutoff time>,<arguments> | |
22883 | ||
22884 | The letter identifies the algorithm for computing a new retry time; the cutoff | |
22885 | time is the time beyond which this algorithm no longer applies, and the | |
22886 | arguments vary the algorithm's action. The cutoff time is measured from the | |
22887 | time that the first failure for the domain (combined with the local part if | |
22888 | relevant) was detected, not from the time the message was received. | |
22889 | ||
22890 | The available algorithms are: | |
22891 | ||
22892 | * F: retry at fixed intervals. There is a single time parameter specifying | |
22893 | the interval. | |
22894 | ||
22895 | * G: retry at geometrically increasing intervals. The first argument | |
22896 | specifies a starting value for the interval, and the second a multiplier, | |
22897 | which is used to increase the size of the interval at each retry. | |
22898 | ||
22899 | * H: retry at randomized intervals. The arguments are as for G. For each | |
22900 | retry, the previous interval is multiplied by the factor in order to get a | |
22901 | maximum for the next interval. The minimum interval is the first argument | |
22902 | of the parameter, and an actual interval is chosen randomly between them. | |
22903 | Such a rule has been found to be helpful in cluster configurations when all | |
22904 | the members of the cluster restart at once, and may therefore synchronize | |
22905 | their queue processing times. | |
22906 | ||
22907 | When computing the next retry time, the algorithm definitions are scanned in | |
22908 | order until one whose cutoff time has not yet passed is reached. This is then | |
22909 | used to compute a new retry time that is later than the current time. In the | |
22910 | case of fixed interval retries, this simply means adding the interval to the | |
22911 | current time. For geometrically increasing intervals, retry intervals are | |
22912 | computed from the rule's parameters until one that is greater than the previous | |
22913 | interval is found. The main configuration variable retry_interval_max limits | |
22914 | the maximum interval between retries. It cannot be set greater than "24h", | |
22915 | which is its default value. | |
22916 | ||
22917 | A single remote domain may have a number of hosts associated with it, and each | |
22918 | host may have more than one IP address. Retry algorithms are selected on the | |
22919 | basis of the domain name, but are applied to each IP address independently. If, | |
22920 | for example, a host has two IP addresses and one is unusable, Exim will | |
22921 | generate retry times for it and will not try to use it until its next retry | |
22922 | time comes. Thus the good IP address is likely to be tried first most of the | |
22923 | time. | |
22924 | ||
22925 | Retry times are hints rather than promises. Exim does not make any attempt to | |
22926 | run deliveries exactly at the computed times. Instead, a queue runner process | |
22927 | starts delivery processes for delayed messages periodically, and these attempt | |
22928 | new deliveries only for those addresses that have passed their next retry time. | |
22929 | If a new message arrives for a deferred address, an immediate delivery attempt | |
22930 | occurs only if the address has passed its retry time. In the absence of new | |
22931 | messages, the minimum time between retries is the interval between queue runner | |
22932 | processes. There is not much point in setting retry times of five minutes if | |
22933 | your queue runners happen only once an hour, unless there are a significant | |
22934 | number of incoming messages (which might be the case on a system that is | |
22935 | sending everything to a smart host, for example). | |
22936 | ||
22937 | The data in the retry hints database can be inspected by using the exim_dumpdb | |
22938 | or exim_fixdb utility programs (see chapter 52). The latter utility can also be | |
22939 | used to change the data. The exinext utility script can be used to find out | |
22940 | what the next retry times are for the hosts associated with a particular mail | |
22941 | domain, and also for local deliveries that have been deferred. | |
22942 | ||
22943 | ||
22944 | 32.8 Retry rule examples | |
22945 | ------------------------ | |
22946 | ||
22947 | Here are some example retry rules: | |
22948 | ||
22949 | alice@wonderland.fict.example quota_5d F,7d,3h | |
22950 | wonderland.fict.example quota_5d | |
22951 | wonderland.fict.example * F,1h,15m; G,2d,1h,2; | |
22952 | lookingglass.fict.example * F,24h,30m; | |
22953 | * refused_A F,2h,20m; | |
22954 | * * F,2h,15m; G,16h,1h,1.5; F,5d,8h | |
22955 | ||
22956 | The first rule sets up special handling for mail to | |
22957 | alice@wonderland.fict.example when there is an over-quota error and the mailbox | |
22958 | has not been read for at least 5 days. Retries continue every three hours for 7 | |
22959 | days. The second rule handles over-quota errors for all other local parts at | |
22960 | wonderland.fict.example; the absence of a local part has the same effect as | |
22961 | supplying "*@". As no retry algorithms are supplied, messages that fail are | |
22962 | bounced immediately if the mailbox has not been read for at least 5 days. | |
22963 | ||
22964 | The third rule handles all other errors at wonderland.fict.example; retries | |
22965 | happen every 15 minutes for an hour, then with geometrically increasing | |
22966 | intervals until two days have passed since a delivery first failed. After the | |
22967 | first hour there is a delay of one hour, then two hours, then four hours, and | |
22968 | so on (this is a rather extreme example). | |
22969 | ||
22970 | The fourth rule controls retries for the domain lookingglass.fict.example. They | |
22971 | happen every 30 minutes for 24 hours only. The remaining two rules handle all | |
22972 | other domains, with special action for connection refusal from hosts that were | |
22973 | not obtained from an MX record. | |
22974 | ||
22975 | The final rule in a retry configuration should always have asterisks in the | |
22976 | first two fields so as to provide a general catch-all for any addresses that do | |
22977 | not have their own special handling. This example tries every 15 minutes for 2 | |
22978 | hours, then with intervals starting at one hour and increasing by a factor of | |
22979 | 1.5 up to 16 hours, then every 8 hours up to 5 days. | |
22980 | ||
22981 | ||
22982 | 32.9 Timeout of retry data | |
22983 | -------------------------- | |
22984 | ||
22985 | Exim timestamps the data that it writes to its retry hints database. When it | |
22986 | consults the data during a delivery it ignores any that is older than the value | |
22987 | set in retry_data_expire (default 7 days). If, for example, a host hasn't been | |
22988 | tried for 7 days, Exim will try to deliver to it immediately a message arrives, | |
22989 | and if that fails, it will calculate a retry time as if it were failing for the | |
22990 | first time. | |
22991 | ||
22992 | This improves the behaviour for messages routed to rarely-used hosts such as MX | |
22993 | backups. If such a host was down at one time, and happens to be down again when | |
22994 | Exim tries a month later, using the old retry data would imply that it had been | |
22995 | down all the time, which is not a justified assumption. | |
22996 | ||
22997 | If a host really is permanently dead, this behaviour causes a burst of retries | |
22998 | every now and again, but only if messages routed to it are rare. If there is a | |
22999 | message at least once every 7 days the retry data never expires. | |
23000 | ||
23001 | ||
23002 | 32.10 Long-term failures | |
23003 | ------------------------ | |
23004 | ||
23005 | Special processing happens when an email address has been failing for so long | |
23006 | that the cutoff time for the last algorithm is reached. For example, using the | |
23007 | default retry rule: | |
23008 | ||
23009 | * * F,2h,15m; G,16h,1h,1.5; F,4d,6h | |
23010 | ||
23011 | the cutoff time is four days. Reaching the retry cutoff is independent of how | |
23012 | long any specific message has been failing; it is the length of continuous | |
23013 | failure for the recipient address that counts. | |
23014 | ||
23015 | When the cutoff time is reached for a local delivery, or for all the IP | |
23016 | addresses associated with a remote delivery, a subsequent delivery failure | |
23017 | causes Exim to give up on the address, and a bounce message is generated. In | |
23018 | order to cater for new messages that use the failing address, a next retry time | |
23019 | is still computed from the final algorithm, and is used as follows: | |
23020 | ||
23021 | For local deliveries, one delivery attempt is always made for any subsequent | |
23022 | messages. If this delivery fails, the address fails immediately. The | |
23023 | post-cutoff retry time is not used. | |
23024 | ||
23025 | If the delivery is remote, there are two possibilities, controlled by the | |
23026 | delay_after_cutoff option of the smtp transport. The option is true by default. | |
23027 | Until the post-cutoff retry time for one of the IP addresses is reached, the | |
23028 | failing email address is bounced immediately, without a delivery attempt taking | |
23029 | place. After that time, one new delivery attempt is made to those IP addresses | |
23030 | that are past their retry times, and if that still fails, the address is | |
23031 | bounced and new retry times are computed. | |
23032 | ||
23033 | In other words, when all the hosts for a given email address have been failing | |
23034 | for a long time, Exim bounces rather then defers until one of the hosts' retry | |
23035 | times is reached. Then it tries once, and bounces if that attempt fails. This | |
23036 | behaviour ensures that few resources are wasted in repeatedly trying to deliver | |
23037 | to a broken destination, but if the host does recover, Exim will eventually | |
23038 | notice. | |
23039 | ||
23040 | If delay_after_cutoff is set false, Exim behaves differently. If all IP | |
23041 | addresses are past their final cutoff time, Exim tries to deliver to those IP | |
23042 | addresses that have not been tried since the message arrived. If there are no | |
23043 | suitable IP addresses, or if they all fail, the address is bounced. In other | |
23044 | words, it does not delay when a new message arrives, but tries the expired | |
23045 | addresses immediately, unless they have been tried since the message arrived. | |
23046 | If there is a continuous stream of messages for the failing domains, setting | |
23047 | delay_after_cutoff false means that there will be many more attempts to deliver | |
23048 | to permanently failing IP addresses than when delay_after_cutoff is true. | |
23049 | ||
23050 | ||
23051 | 32.11 Deliveries that work intermittently | |
23052 | ----------------------------------------- | |
23053 | ||
23054 | Some additional logic is needed to cope with cases where a host is | |
23055 | intermittently available, or when a message has some attribute that prevents | |
23056 | its delivery when others to the same address get through. In this situation, | |
23057 | because some messages are successfully delivered, the "retry clock" for the | |
23058 | host or address keeps getting reset by the successful deliveries, and so | |
23059 | failing messages remain on the queue for ever because the cutoff time is never | |
23060 | reached. | |
23061 | ||
23062 | Two exceptional actions are applied to prevent this happening. The first | |
23063 | applies to errors that are related to a message rather than a remote host. | |
23064 | Section 47.2 has a discussion of the different kinds of error; examples of | |
23065 | message-related errors are 4xx responses to MAIL or DATA commands, and quota | |
23066 | failures. For this type of error, if a message's arrival time is earlier than | |
23067 | the "first failed" time for the error, the earlier time is used when scanning | |
23068 | the retry rules to decide when to try next and when to time out the address. | |
23069 | ||
23070 | The exceptional second action applies in all cases. If a message has been on | |
23071 | the queue for longer than the cutoff time of any applicable retry rule for a | |
23072 | given address, a delivery is attempted for that address, even if it is not yet | |
23073 | time, and if this delivery fails, the address is timed out. A new retry time is | |
23074 | not computed in this case, so that other messages for the same address are | |
23075 | considered immediately. | |
23076 | ||
23077 | ||
23078 | ||
23079 | =============================================================================== | |
23080 | 33. SMTP AUTHENTICATION | |
23081 | ||
23082 | The "authenticators" section of Exim's run time configuration is concerned with | |
23083 | SMTP authentication. This facility is an extension to the SMTP protocol, | |
23084 | described in RFC 2554, which allows a client SMTP host to authenticate itself | |
23085 | to a server. This is a common way for a server to recognize clients that are | |
23086 | permitted to use it as a relay. SMTP authentication is not of relevance to the | |
23087 | transfer of mail between servers that have no managerial connection with each | |
23088 | other. | |
23089 | ||
23090 | Very briefly, the way SMTP authentication works is as follows: | |
23091 | ||
23092 | * The server advertises a number of authentication mechanisms in response to | |
23093 | the client's EHLO command. | |
23094 | ||
23095 | * The client issues an AUTH command, naming a specific mechanism. The command | |
23096 | may, optionally, contain some authentication data. | |
23097 | ||
23098 | * The server may issue one or more challenges, to which the client must send | |
23099 | appropriate responses. In simple authentication mechanisms, the challenges | |
23100 | are just prompts for user names and passwords. The server does not have to | |
23101 | issue any challenges - in some mechanisms the relevant data may all be | |
23102 | transmitted with the AUTH command. | |
23103 | ||
23104 | * The server either accepts or denies authentication. | |
23105 | ||
23106 | * If authentication succeeds, the client may optionally make use of the AUTH | |
23107 | option on the MAIL command to pass an authenticated sender in subsequent | |
23108 | mail transactions. Authentication lasts for the remainder of the SMTP | |
23109 | connection. | |
23110 | ||
23111 | * If authentication fails, the client may give up, or it may try a different | |
23112 | authentication mechanism, or it may try transferring mail over the | |
23113 | unauthenticated connection. | |
23114 | ||
23115 | If you are setting up a client, and want to know which authentication | |
23116 | mechanisms the server supports, you can use Telnet to connect to port 25 (the | |
23117 | SMTP port) on the server, and issue an EHLO command. The response to this | |
23118 | includes the list of supported mechanisms. For example: | |
23119 | ||
23120 | $ telnet server.example 25 | |
23121 | Trying 192.168.34.25... | |
23122 | Connected to server.example. | |
23123 | Escape character is '^]'. | |
23124 | 220 server.example ESMTP Exim 4.20 ... | |
23125 | ehlo client.example | |
23126 | 250-server.example Hello client.example [10.8.4.5] | |
23127 | 250-SIZE 52428800 | |
23128 | 250-PIPELINING | |
23129 | 250-AUTH PLAIN | |
23130 | 250 HELP | |
23131 | ||
23132 | The second-last line of this example output shows that the server supports | |
23133 | authentication using the PLAIN mechanism. In Exim, the different authentication | |
23134 | mechanisms are configured by specifying authenticator drivers. Like the routers | |
23135 | and transports, which authenticators are included in the binary is controlled | |
23136 | by build-time definitions. The following are currently available, included by | |
23137 | setting | |
23138 | ||
23139 | AUTH_CRAM_MD5=yes | |
23140 | AUTH_CYRUS_SASL=yes | |
23141 | AUTH_DOVECOT=yes | |
23142 | AUTH_GSASL=yes | |
23143 | AUTH_HEIMDAL_GSSAPI=yes | |
23144 | AUTH_PLAINTEXT=yes | |
23145 | AUTH_SPA=yes | |
23146 | ||
23147 | in Local/Makefile, respectively. The first of these supports the CRAM-MD5 | |
23148 | authentication mechanism (RFC 2195), and the second provides an interface to | |
23149 | the Cyrus SASL authentication library. The third is an interface to Dovecot's | |
23150 | authentication system, delegating the work via a socket interface. The fourth | |
23151 | provides an interface to the GNU SASL authentication library, which provides | |
23152 | mechanisms but typically not data sources. The fifth provides direct access to | |
23153 | Heimdal GSSAPI, geared for Kerberos, but supporting setting a server keytab. | |
23154 | The sixth can be configured to support the PLAIN authentication mechanism (RFC | |
23155 | 2595) or the LOGIN mechanism, which is not formally documented, but used by | |
23156 | several MUAs. The seventh authenticator supports Microsoft's Secure Password | |
23157 | Authentication mechanism. | |
23158 | ||
23159 | The authenticators are configured using the same syntax as other drivers (see | |
23160 | section 6.22). If no authenticators are required, no authentication section | |
23161 | need be present in the configuration file. Each authenticator can in principle | |
23162 | have both server and client functions. When Exim is receiving SMTP mail, it is | |
23163 | acting as a server; when it is sending out messages over SMTP, it is acting as | |
23164 | a client. Authenticator configuration options are provided for use in both | |
23165 | these circumstances. | |
23166 | ||
23167 | To make it clear which options apply to which situation, the prefixes server_ | |
23168 | and client_ are used on option names that are specific to either the server or | |
23169 | the client function, respectively. Server and client functions are disabled if | |
23170 | none of their options are set. If an authenticator is to be used for both | |
23171 | server and client functions, a single definition, using both sets of options, | |
23172 | is required. For example: | |
23173 | ||
23174 | cram: | |
23175 | driver = cram_md5 | |
23176 | public_name = CRAM-MD5 | |
23177 | server_secret = ${if eq{$auth1}{ph10}{secret1}fail} | |
23178 | client_name = ph10 | |
23179 | client_secret = secret2 | |
23180 | ||
23181 | The server_ option is used when Exim is acting as a server, and the client_ | |
23182 | options when it is acting as a client. | |
23183 | ||
23184 | Descriptions of the individual authenticators are given in subsequent chapters. | |
23185 | The remainder of this chapter covers the generic options for the | |
23186 | authenticators, followed by general discussion of the way authentication works | |
23187 | in Exim. | |
23188 | ||
23189 | Beware: the meaning of $auth1, $auth2, ... varies on a per-driver and | |
23190 | per-mechanism basis. Please read carefully to determine which variables hold | |
23191 | account labels such as usercodes and which hold passwords or other | |
23192 | authenticating data. | |
23193 | ||
23194 | Note that some mechanisms support two different identifiers for accounts: the | |
23195 | authentication id and the authorization id. The contractions authn and authz | |
23196 | are commonly encountered. The American spelling is standard here. Conceptually, | |
23197 | authentication data such as passwords are tied to the identifier used to | |
23198 | authenticate; servers may have rules to permit one user to act as a second | |
23199 | user, so that after login the session is treated as though that second user had | |
23200 | logged in. That second user is the authorization id. A robust configuration | |
23201 | might confirm that the authz field is empty or matches the authn field. Often | |
23202 | this is just ignored. The authn can be considered as verified data, the authz | |
23203 | as an unverified request which the server might choose to honour. | |
23204 | ||
23205 | A realm is a text string, typically a domain name, presented by a server to a | |
23206 | client to help it select an account and credentials to use. In some mechanisms, | |
23207 | the client and server provably agree on the realm, but clients typically can | |
23208 | not treat the realm as secure data to be blindly trusted. | |
23209 | ||
23210 | ||
23211 | 33.1 Generic options for authenticators | |
23212 | --------------------------------------- | |
23213 | ||
23214 | +----------------+-------------------+-------------+--------------+ | |
23215 | |client_condition|Use: authenticators|Type: string*|Default: unset| | |
23216 | +----------------+-------------------+-------------+--------------+ | |
23217 | ||
23218 | When Exim is authenticating as a client, it skips any authenticator whose | |
23219 | client_condition expansion yields "0", "no", or "false". This can be used, for | |
23220 | example, to skip plain text authenticators when the connection is not encrypted | |
23221 | by a setting such as: | |
23222 | ||
23223 | client_condition = ${if !eq{$tls_out_cipher}{}} | |
23224 | ||
23225 | +-------------+-------------------+-------------+--------------+ | |
23226 | |client_set_id|Use: authenticators|Type: string*|Default: unset| | |
23227 | +-------------+-------------------+-------------+--------------+ | |
23228 | ||
23229 | When client authentication succeeds, this condition is expanded; the result is | |
23230 | used in the log lines for outbound messasges. Typically it will be the user | |
23231 | name used for authentication. | |
23232 | ||
23233 | +------+-------------------+------------+--------------+ | |
23234 | |driver|Use: authenticators|Type: string|Default: unset| | |
23235 | +------+-------------------+------------+--------------+ | |
23236 | ||
23237 | This option must always be set. It specifies which of the available | |
23238 | authenticators is to be used. | |
23239 | ||
23240 | +-----------+-------------------+------------+--------------+ | |
23241 | |public_name|Use: authenticators|Type: string|Default: unset| | |
23242 | +-----------+-------------------+------------+--------------+ | |
23243 | ||
23244 | This option specifies the name of the authentication mechanism that the driver | |
23245 | implements, and by which it is known to the outside world. These names should | |
23246 | contain only upper case letters, digits, underscores, and hyphens (RFC 2222), | |
23247 | but Exim in fact matches them caselessly. If public_name is not set, it | |
23248 | defaults to the driver's instance name. | |
23249 | ||
23250 | +--------------------------+-------------------+-------------+--------------+ | |
23251 | |server_advertise_condition|Use: authenticators|Type: string*|Default: unset| | |
23252 | +--------------------------+-------------------+-------------+--------------+ | |
23253 | ||
23254 | When a server is about to advertise an authentication mechanism, the condition | |
23255 | is expanded. If it yields the empty string, "0", "no", or "false", the | |
23256 | mechanism is not advertised. If the expansion fails, the mechanism is not | |
23257 | advertised. If the failure was not forced, and was not caused by a lookup | |
23258 | defer, the incident is logged. See section 33.3 below for further discussion. | |
23259 | ||
23260 | +----------------+-------------------+-------------+--------------+ | |
23261 | |server_condition|Use: authenticators|Type: string*|Default: unset| | |
23262 | +----------------+-------------------+-------------+--------------+ | |
23263 | ||
23264 | This option must be set for a plaintext server authenticator, where it is used | |
23265 | directly to control authentication. See section 34.2 for details. | |
23266 | ||
23267 | For the gsasl authenticator, this option is required for various mechanisms; | |
23268 | see chapter 38 for details. | |
23269 | ||
23270 | For the other authenticators, server_condition can be used as an additional | |
23271 | authentication or authorization mechanism that is applied after the other | |
23272 | authenticator conditions succeed. If it is set, it is expanded when the | |
23273 | authenticator would otherwise return a success code. If the expansion is forced | |
23274 | to fail, authentication fails. Any other expansion failure causes a temporary | |
23275 | error code to be returned. If the result of a successful expansion is an empty | |
23276 | string, "0", "no", or "false", authentication fails. If the result of the | |
23277 | expansion is "1", "yes", or "true", authentication succeeds. For any other | |
23278 | result, a temporary error code is returned, with the expanded string as the | |
23279 | error text. | |
23280 | ||
23281 | +------------------+-------------------+-------------+--------------+ | |
23282 | |server_debug_print|Use: authenticators|Type: string*|Default: unset| | |
23283 | +------------------+-------------------+-------------+--------------+ | |
23284 | ||
23285 | If this option is set and authentication debugging is enabled (see the -d | |
23286 | command line option), the string is expanded and included in the debugging | |
23287 | output when the authenticator is run as a server. This can help with checking | |
23288 | out the values of variables. If expansion of the string fails, the error | |
23289 | message is written to the debugging output, and Exim carries on processing. | |
23290 | ||
23291 | +-------------+-------------------+-------------+--------------+ | |
23292 | |server_set_id|Use: authenticators|Type: string*|Default: unset| | |
23293 | +-------------+-------------------+-------------+--------------+ | |
23294 | ||
23295 | When an Exim server successfully authenticates a client, this string is | |
23296 | expanded using data from the authentication, and preserved for any incoming | |
23297 | messages in the variable $authenticated_id. It is also included in the log | |
23298 | lines for incoming messages. For example, a user/password authenticator | |
23299 | configuration might preserve the user name that was used to authenticate, and | |
23300 | refer to it subsequently during delivery of the message. If expansion fails, | |
23301 | the option is ignored. | |
23302 | ||
23303 | +--------------------------+-------------------+-------------+--------------+ | |
23304 | |server_mail_auth_condition|Use: authenticators|Type: string*|Default: unset| | |
23305 | +--------------------------+-------------------+-------------+--------------+ | |
23306 | ||
23307 | This option allows a server to discard authenticated sender addresses supplied | |
23308 | as part of MAIL commands in SMTP connections that are authenticated by the | |
23309 | driver on which server_mail_auth_condition is set. The option is not used as | |
23310 | part of the authentication process; instead its (unexpanded) value is | |
23311 | remembered for later use. How it is used is described in the following section. | |
23312 | ||
23313 | ||
23314 | 33.2 The AUTH parameter on MAIL commands | |
23315 | ---------------------------------------- | |
23316 | ||
23317 | When a client supplied an AUTH= item on a MAIL command, Exim applies the | |
23318 | following checks before accepting it as the authenticated sender of the | |
23319 | message: | |
23320 | ||
23321 | * If the connection is not using extended SMTP (that is, HELO was used rather | |
23322 | than EHLO), the use of AUTH= is a syntax error. | |
23323 | ||
23324 | * If the value of the AUTH= parameter is "<>", it is ignored. | |
23325 | ||
23326 | * If acl_smtp_mailauth is defined, the ACL it specifies is run. While it is | |
23327 | running, the value of $authenticated_sender is set to the value obtained | |
23328 | from the AUTH= parameter. If the ACL does not yield "accept", the value of | |
23329 | $authenticated_sender is deleted. The acl_smtp_mailauth ACL may not return | |
23330 | "drop" or "discard". If it defers, a temporary error code (451) is given | |
23331 | for the MAIL command. | |
23332 | ||
23333 | * If acl_smtp_mailauth is not defined, the value of the AUTH= parameter is | |
23334 | accepted and placed in $authenticated_sender only if the client has | |
23335 | authenticated. | |
23336 | ||
23337 | * If the AUTH= value was accepted by either of the two previous rules, and | |
23338 | the client has authenticated, and the authenticator has a setting for the | |
23339 | server_mail_auth_condition, the condition is checked at this point. The | |
23340 | valued that was saved from the authenticator is expanded. If the expansion | |
23341 | fails, or yields an empty string, "0", "no", or "false", the value of | |
23342 | $authenticated_sender is deleted. If the expansion yields any other value, | |
23343 | the value of $authenticated_sender is retained and passed on with the | |
23344 | message. | |
23345 | ||
23346 | When $authenticated_sender is set for a message, it is passed on to other hosts | |
23347 | to which Exim authenticates as a client. Do not confuse this value with | |
23348 | $authenticated_id, which is a string obtained from the authentication process, | |
23349 | and which is not usually a complete email address. | |
23350 | ||
23351 | Whenever an AUTH= value is ignored, the incident is logged. The ACL for MAIL, | |
23352 | if defined, is run after AUTH= is accepted or ignored. It can therefore make | |
23353 | use of $authenticated_sender. The converse is not true: the value of | |
23354 | $sender_address is not yet set up when the acl_smtp_mailauth ACL is run. | |
23355 | ||
23356 | ||
23357 | 33.3 Authentication on an Exim server | |
23358 | ------------------------------------- | |
23359 | ||
23360 | When Exim receives an EHLO command, it advertises the public names of those | |
23361 | authenticators that are configured as servers, subject to the following | |
23362 | conditions: | |
23363 | ||
23364 | * The client host must match auth_advertise_hosts (default *). | |
23365 | ||
23366 | * It the server_advertise_condition option is set, its expansion must not | |
23367 | yield the empty string, "0", "no", or "false". | |
23368 | ||
23369 | The order in which the authenticators are defined controls the order in which | |
23370 | the mechanisms are advertised. | |
23371 | ||
23372 | Some mail clients (for example, some versions of Netscape) require the user to | |
23373 | provide a name and password for authentication whenever AUTH is advertised, | |
23374 | even though authentication may not in fact be needed (for example, Exim may be | |
23375 | set up to allow unconditional relaying from the client by an IP address check). | |
23376 | You can make such clients more friendly by not advertising AUTH to them. For | |
23377 | example, if clients on the 10.9.8.0/24 network are permitted (by the ACL that | |
23378 | runs for RCPT) to relay without authentication, you should set | |
23379 | ||
23380 | auth_advertise_hosts = ! 10.9.8.0/24 | |
23381 | ||
23382 | so that no authentication mechanisms are advertised to them. | |
23383 | ||
23384 | The server_advertise_condition controls the advertisement of individual | |
23385 | authentication mechanisms. For example, it can be used to restrict the | |
23386 | advertisement of a particular mechanism to encrypted connections, by a setting | |
23387 | such as: | |
23388 | ||
23389 | server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}} | |
23390 | ||
23391 | If the session is encrypted, $tls_in_cipher is not empty, and so the expansion | |
23392 | yields "yes", which allows the advertisement to happen. | |
23393 | ||
23394 | When an Exim server receives an AUTH command from a client, it rejects it | |
23395 | immediately if AUTH was not advertised in response to an earlier EHLO command. | |
23396 | This is the case if | |
23397 | ||
23398 | * The client host does not match auth_advertise_hosts; or | |
23399 | ||
23400 | * No authenticators are configured with server options; or | |
23401 | ||
23402 | * Expansion of server_advertise_condition blocked the advertising of all the | |
23403 | server authenticators. | |
23404 | ||
23405 | Otherwise, Exim runs the ACL specified by acl_smtp_auth in order to decide | |
23406 | whether to accept the command. If acl_smtp_auth is not set, AUTH is accepted | |
23407 | from any client host. | |
23408 | ||
23409 | If AUTH is not rejected by the ACL, Exim searches its configuration for a | |
23410 | server authentication mechanism that was advertised in response to EHLO and | |
23411 | that matches the one named in the AUTH command. If it finds one, it runs the | |
23412 | appropriate authentication protocol, and authentication either succeeds or | |
23413 | fails. If there is no matching advertised mechanism, the AUTH command is | |
23414 | rejected with a 504 error. | |
23415 | ||
23416 | When a message is received from an authenticated host, the value of | |
23417 | $received_protocol is set to "esmtpa" or "esmtpsa" instead of "esmtp" or | |
23418 | "esmtps", and $sender_host_authenticated contains the name (not the public | |
23419 | name) of the authenticator driver that successfully authenticated the client | |
23420 | from which the message was received. This variable is empty if there was no | |
23421 | successful authentication. | |
23422 | ||
23423 | ||
23424 | 33.4 Testing server authentication | |
23425 | ---------------------------------- | |
23426 | ||
23427 | Exim's -bh option can be useful for testing server authentication | |
23428 | configurations. The data for the AUTH command has to be sent using base64 | |
23429 | encoding. A quick way to produce such data for testing is the following Perl | |
23430 | script: | |
23431 | ||
23432 | use MIME::Base64; | |
23433 | printf ("%s", encode_base64(eval "\"$ARGV[0]\"")); | |
23434 | ||
23435 | This interprets its argument as a Perl string, and then encodes it. The | |
23436 | interpretation as a Perl string allows binary zeros, which are required for | |
23437 | some kinds of authentication, to be included in the data. For example, a | |
23438 | command line to run this script on such data might be | |
23439 | ||
23440 | encode '\0user\0password' | |
23441 | ||
23442 | Note the use of single quotes to prevent the shell interpreting the | |
23443 | backslashes, so that they can be interpreted by Perl to specify characters | |
23444 | whose code value is zero. | |
23445 | ||
23446 | Warning 1: If either of the user or password strings starts with an octal | |
23447 | digit, you must use three zeros instead of one after the leading backslash. If | |
23448 | you do not, the octal digit that starts your string will be incorrectly | |
23449 | interpreted as part of the code for the first character. | |
23450 | ||
23451 | Warning 2: If there are characters in the strings that Perl interprets | |
23452 | specially, you must use a Perl escape to prevent them being misinterpreted. For | |
23453 | example, a command such as | |
23454 | ||
23455 | encode '\0user@domain.com\0pas$$word' | |
23456 | ||
23457 | gives an incorrect answer because of the unescaped "@" and "$" characters. | |
23458 | ||
23459 | If you have the mimencode command installed, another way to do produce | |
23460 | base64-encoded strings is to run the command | |
23461 | ||
23462 | echo -e -n `\0user\0password' | mimencode | |
23463 | ||
23464 | The -e option of echo enables the interpretation of backslash escapes in the | |
23465 | argument, and the -n option specifies no newline at the end of its output. | |
23466 | However, not all versions of echo recognize these options, so you should check | |
23467 | your version before relying on this suggestion. | |
23468 | ||
23469 | ||
23470 | 33.5 Authentication by an Exim client | |
23471 | ------------------------------------- | |
23472 | ||
23473 | The smtp transport has two options called hosts_require_auth and hosts_try_auth | |
23474 | . When the smtp transport connects to a server that announces support for | |
23475 | authentication, and the host matches an entry in either of these options, Exim | |
23476 | (as a client) tries to authenticate as follows: | |
23477 | ||
23478 | * For each authenticator that is configured as a client, in the order in | |
23479 | which they are defined in the configuration, it searches the authentication | |
23480 | mechanisms announced by the server for one whose name matches the public | |
23481 | name of the authenticator. | |
23482 | ||
23483 | * When it finds one that matches, it runs the authenticator's client code. | |
23484 | The variables $host and $host_address are available for any string | |
23485 | expansions that the client might do. They are set to the server's name and | |
23486 | IP address. If any expansion is forced to fail, the authentication attempt | |
23487 | is abandoned, and Exim moves on to the next authenticator. Otherwise an | |
23488 | expansion failure causes delivery to be deferred. | |
23489 | ||
23490 | * If the result of the authentication attempt is a temporary error or a | |
23491 | timeout, Exim abandons trying to send the message to the host for the | |
23492 | moment. It will try again later. If there are any backup hosts available, | |
23493 | they are tried in the usual way. | |
23494 | ||
23495 | * If the response to authentication is a permanent error (5xx code), Exim | |
23496 | carries on searching the list of authenticators and tries another one if | |
23497 | possible. If all authentication attempts give permanent errors, or if there | |
23498 | are no attempts because no mechanisms match (or option expansions force | |
23499 | failure), what happens depends on whether the host matches | |
23500 | hosts_require_auth or hosts_try_auth. In the first case, a temporary error | |
23501 | is generated, and delivery is deferred. The error can be detected in the | |
23502 | retry rules, and thereby turned into a permanent error if you wish. In the | |
23503 | second case, Exim tries to deliver the message unauthenticated. | |
23504 | ||
23505 | When Exim has authenticated itself to a remote server, it adds the AUTH | |
23506 | parameter to the MAIL commands it sends, if it has an authenticated sender for | |
23507 | the message. If the message came from a remote host, the authenticated sender | |
23508 | is the one that was receiving on an incoming MAIL command, provided that the | |
23509 | incoming connection was authenticated and the server_mail_auth condition | |
23510 | allowed the authenticated sender to be retained. If a local process calls Exim | |
23511 | to send a message, the sender address that is built from the login name and | |
23512 | qualify_domain is treated as authenticated. However, if the | |
23513 | authenticated_sender option is set on the smtp transport, it overrides the | |
23514 | authenticated sender that was received with the message. | |
23515 | ||
23516 | ||
23517 | ||
23518 | =============================================================================== | |
23519 | 34. THE PLAINTEXT AUTHENTICATOR | |
23520 | ||
23521 | The plaintext authenticator can be configured to support the PLAIN and LOGIN | |
23522 | authentication mechanisms, both of which transfer authentication data as plain | |
23523 | (unencrypted) text (though base64 encoded). The use of plain text is a security | |
23524 | risk; you are strongly advised to insist on the use of SMTP encryption (see | |
23525 | chapter 41) if you use the PLAIN or LOGIN mechanisms. If you do use unencrypted | |
23526 | plain text, you should not use the same passwords for SMTP connections as you | |
23527 | do for login accounts. | |
23528 | ||
23529 | ||
23530 | 34.1 Plaintext options | |
23531 | ---------------------- | |
23532 | ||
23533 | When configured as a server, plaintext uses the following options: | |
23534 | ||
23535 | +----------------+-------------------+-------------+--------------+ | |
23536 | |server_condition|Use: authenticators|Type: string*|Default: unset| | |
23537 | +----------------+-------------------+-------------+--------------+ | |
23538 | ||
23539 | This is actually a global authentication option, but it must be set in order to | |
23540 | configure the plaintext driver as a server. Its use is described below. | |
23541 | ||
23542 | +--------------+--------------+-------------+--------------+ | |
23543 | |server_prompts|Use: plaintext|Type: string*|Default: unset| | |
23544 | +--------------+--------------+-------------+--------------+ | |
23545 | ||
23546 | The contents of this option, after expansion, must be a colon-separated list of | |
23547 | prompt strings. If expansion fails, a temporary authentication rejection is | |
23548 | given. | |
23549 | ||
23550 | ||
23551 | 34.2 Using plaintext in a server | |
23552 | -------------------------------- | |
23553 | ||
23554 | When running as a server, plaintext performs the authentication test by | |
23555 | expanding a string. The data sent by the client with the AUTH command, or in | |
23556 | response to subsequent prompts, is base64 encoded, and so may contain any byte | |
23557 | values when decoded. If any data is supplied with the command, it is treated as | |
23558 | a list of strings, separated by NULs (binary zeros), the first three of which | |
23559 | are placed in the expansion variables $auth1, $auth2, and $auth3 (neither LOGIN | |
23560 | nor PLAIN uses more than three strings). | |
23561 | ||
23562 | For compatibility with previous releases of Exim, the values are also placed in | |
23563 | the expansion variables $1, $2, and $3. However, the use of these variables for | |
23564 | this purpose is now deprecated, as it can lead to confusion in string | |
23565 | expansions that also use them for other things. | |
23566 | ||
23567 | If there are more strings in server_prompts than the number of strings supplied | |
23568 | with the AUTH command, the remaining prompts are used to obtain more data. Each | |
23569 | response from the client may be a list of NUL-separated strings. | |
23570 | ||
23571 | Once a sufficient number of data strings have been received, server_condition | |
23572 | is expanded. If the expansion is forced to fail, authentication fails. Any | |
23573 | other expansion failure causes a temporary error code to be returned. If the | |
23574 | result of a successful expansion is an empty string, "0", "no", or "false", | |
23575 | authentication fails. If the result of the expansion is "1", "yes", or "true", | |
23576 | authentication succeeds and the generic server_set_id option is expanded and | |
23577 | saved in $authenticated_id. For any other result, a temporary error code is | |
23578 | returned, with the expanded string as the error text | |
23579 | ||
23580 | Warning: If you use a lookup in the expansion to find the user's password, be | |
23581 | sure to make the authentication fail if the user is unknown. There are good and | |
23582 | bad examples at the end of the next section. | |
23583 | ||
23584 | ||
23585 | 34.3 The PLAIN authentication mechanism | |
23586 | --------------------------------------- | |
23587 | ||
23588 | The PLAIN authentication mechanism (RFC 2595) specifies that three strings be | |
23589 | sent as one item of data (that is, one combined string containing two NUL | |
23590 | separators). The data is sent either as part of the AUTH command, or | |
23591 | subsequently in response to an empty prompt from the server. | |
23592 | ||
23593 | The second and third strings are a user name and a corresponding password. | |
23594 | Using a single fixed user name and password as an example, this could be | |
23595 | configured as follows: | |
23596 | ||
23597 | fixed_plain: | |
23598 | driver = plaintext | |
23599 | public_name = PLAIN | |
23600 | server_prompts = : | |
23601 | server_condition = \ | |
23602 | ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}} | |
23603 | server_set_id = $auth2 | |
23604 | ||
23605 | Note that the default result strings from if ("true" or an empty string) are | |
23606 | exactly what we want here, so they need not be specified. Obviously, if the | |
23607 | password contains expansion-significant characters such as dollar, backslash, | |
23608 | or closing brace, they have to be escaped. | |
23609 | ||
23610 | The server_prompts setting specifies a single, empty prompt (empty items at the | |
23611 | end of a string list are ignored). If all the data comes as part of the AUTH | |
23612 | command, as is commonly the case, the prompt is not used. This authenticator is | |
23613 | advertised in the response to EHLO as | |
23614 | ||
23615 | 250-AUTH PLAIN | |
23616 | ||
23617 | and a client host can authenticate itself by sending the command | |
23618 | ||
23619 | AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0 | |
23620 | ||
23621 | As this contains three strings (more than the number of prompts), no further | |
23622 | data is required from the client. Alternatively, the client may just send | |
23623 | ||
23624 | AUTH PLAIN | |
23625 | ||
23626 | to initiate authentication, in which case the server replies with an empty | |
23627 | prompt. The client must respond with the combined data string. | |
23628 | ||
23629 | The data string is base64 encoded, as required by the RFC. This example, when | |
23630 | decoded, is <NUL>"username"<NUL>"mysecret", where <NUL> represents a zero byte. | |
23631 | This is split up into three strings, the first of which is empty. The | |
23632 | server_condition option in the authenticator checks that the second two are | |
23633 | "username" and "mysecret" respectively. | |
23634 | ||
23635 | Having just one fixed user name and password, as in this example, is not very | |
23636 | realistic, though for a small organization with only a handful of | |
23637 | authenticating clients it could make sense. | |
23638 | ||
23639 | A more sophisticated instance of this authenticator could use the user name in | |
23640 | $auth2 to look up a password in a file or database, and maybe do an encrypted | |
23641 | comparison (see crypteq in chapter 11). Here is a example of this approach, | |
23642 | where the passwords are looked up in a DBM file. Warning: This is an incorrect | |
23643 | example: | |
23644 | ||
23645 | server_condition = \ | |
23646 | ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}} | |
23647 | ||
23648 | The expansion uses the user name ($auth2) as the key to look up a password, | |
23649 | which it then compares to the supplied password ($auth3). Why is this example | |
23650 | incorrect? It works fine for existing users, but consider what happens if a | |
23651 | non-existent user name is given. The lookup fails, but as no success/failure | |
23652 | strings are given for the lookup, it yields an empty string. Thus, to defeat | |
23653 | the authentication, all a client has to do is to supply a non-existent user | |
23654 | name and an empty password. The correct way of writing this test is: | |
23655 | ||
23656 | server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\ | |
23657 | {${if eq{$value}{$auth3}}} {false}} | |
23658 | ||
23659 | In this case, if the lookup succeeds, the result is checked; if the lookup | |
23660 | fails, "false" is returned and authentication fails. If crypteq is being used | |
23661 | instead of eq, the first example is in fact safe, because crypteq always fails | |
23662 | if its second argument is empty. However, the second way of writing the test | |
23663 | makes the logic clearer. | |
23664 | ||
23665 | ||
23666 | 34.4 The LOGIN authentication mechanism | |
23667 | --------------------------------------- | |
23668 | ||
23669 | The LOGIN authentication mechanism is not documented in any RFC, but is in use | |
23670 | in a number of programs. No data is sent with the AUTH command. Instead, a user | |
23671 | name and password are supplied separately, in response to prompts. The | |
23672 | plaintext authenticator can be configured to support this as in this example: | |
23673 | ||
23674 | fixed_login: | |
23675 | driver = plaintext | |
23676 | public_name = LOGIN | |
23677 | server_prompts = User Name : Password | |
23678 | server_condition = \ | |
23679 | ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}} | |
23680 | server_set_id = $auth1 | |
23681 | ||
23682 | Because of the way plaintext operates, this authenticator accepts data supplied | |
23683 | with the AUTH command (in contravention of the specification of LOGIN), but if | |
23684 | the client does not supply it (as is the case for LOGIN clients), the prompt | |
23685 | strings are used to obtain two data items. | |
23686 | ||
23687 | Some clients are very particular about the precise text of the prompts. For | |
23688 | example, Outlook Express is reported to recognize only "Username:" and | |
23689 | "Password:". Here is an example of a LOGIN authenticator that uses those | |
23690 | strings. It uses the ldapauth expansion condition to check the user name and | |
23691 | password by binding to an LDAP server: | |
23692 | ||
23693 | login: | |
23694 | driver = plaintext | |
23695 | public_name = LOGIN | |
23696 | server_prompts = Username:: : Password:: | |
23697 | server_condition = ${if and{{ \ | |
23698 | !eq{}{$auth1} }{ \ | |
23699 | ldapauth{\ | |
23700 | user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \ | |
23701 | pass=${quote:$auth2} \ | |
23702 | ldap://ldap.example.org/} }} } | |
23703 | server_set_id = uid=$auth1,ou=people,o=example.org | |
23704 | ||
23705 | We have to check that the username is not empty before using it, because LDAP | |
23706 | does not permit empty DN components. We must also use the quote_ldap_dn | |
23707 | operator to correctly quote the DN for authentication. However, the basic quote | |
23708 | operator, rather than any of the LDAP quoting operators, is the correct one to | |
23709 | use for the password, because quoting is needed only to make the password | |
23710 | conform to the Exim syntax. At the LDAP level, the password is an uninterpreted | |
23711 | string. | |
23712 | ||
23713 | ||
23714 | 34.5 Support for different kinds of authentication | |
23715 | -------------------------------------------------- | |
23716 | ||
23717 | A number of string expansion features are provided for the purpose of | |
23718 | interfacing to different ways of user authentication. These include checking | |
23719 | traditionally encrypted passwords from /etc/passwd (or equivalent), PAM, | |
23720 | Radius, ldapauth, pwcheck, and saslauthd. For details see section 11.7. | |
23721 | ||
23722 | ||
23723 | 34.6 Using plaintext in a client | |
23724 | -------------------------------- | |
23725 | ||
23726 | The plaintext authenticator has two client options: | |
23727 | ||
23728 | +----------------------------+--------------+-------------+--------------+ | |
23729 | |client_ignore_invalid_base64|Use: plaintext|Type: boolean|Default: false| | |
23730 | +----------------------------+--------------+-------------+--------------+ | |
23731 | ||
23732 | If the client receives a server prompt that is not a valid base64 string, | |
23733 | authentication is abandoned by default. However, if this option is set true, | |
23734 | the error in the challenge is ignored and the client sends the response as | |
23735 | usual. | |
23736 | ||
23737 | +-----------+--------------+-------------+--------------+ | |
23738 | |client_send|Use: plaintext|Type: string*|Default: unset| | |
23739 | +-----------+--------------+-------------+--------------+ | |
23740 | ||
23741 | The string is a colon-separated list of authentication data strings. Each | |
23742 | string is independently expanded before being sent to the server. The first | |
23743 | string is sent with the AUTH command; any more strings are sent in response to | |
23744 | prompts from the server. Before each string is expanded, the value of the most | |
23745 | recent prompt is placed in the next $auth<n> variable, starting with $auth1 for | |
23746 | the first prompt. Up to three prompts are stored in this way. Thus, the prompt | |
23747 | that is received in response to sending the first string (with the AUTH | |
23748 | command) can be used in the expansion of the second string, and so on. If an | |
23749 | invalid base64 string is received when client_ignore_invalid_base64 is set, an | |
23750 | empty string is put in the $auth<n> variable. | |
23751 | ||
23752 | Note: You cannot use expansion to create multiple strings, because splitting | |
23753 | takes priority and happens first. | |
23754 | ||
23755 | Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in | |
23756 | the data, further processing is applied to each string before it is sent. If | |
23757 | there are any single circumflex characters in the string, they are converted to | |
23758 | NULs. Should an actual circumflex be required as data, it must be doubled in | |
23759 | the string. | |
23760 | ||
23761 | This is an example of a client configuration that implements the PLAIN | |
23762 | authentication mechanism with a fixed user name and password: | |
23763 | ||
23764 | fixed_plain: | |
23765 | driver = plaintext | |
23766 | public_name = PLAIN | |
23767 | client_send = ^username^mysecret | |
23768 | ||
23769 | The lack of colons means that the entire text is sent with the AUTH command, | |
23770 | with the circumflex characters converted to NULs. A similar example that uses | |
23771 | the LOGIN mechanism is: | |
23772 | ||
23773 | fixed_login: | |
23774 | driver = plaintext | |
23775 | public_name = LOGIN | |
23776 | client_send = : username : mysecret | |
23777 | ||
23778 | The initial colon means that the first string is empty, so no data is sent with | |
23779 | the AUTH command itself. The remaining strings are sent in response to prompts. | |
23780 | ||
23781 | ||
23782 | ||
23783 | =============================================================================== | |
23784 | 35. THE CRAM_MD5 AUTHENTICATOR | |
23785 | ||
23786 | The CRAM-MD5 authentication mechanism is described in RFC 2195. The server | |
23787 | sends a challenge string to the client, and the response consists of a user | |
23788 | name and the CRAM-MD5 digest of the challenge string combined with a secret | |
23789 | string (password) which is known to both server and client. Thus, the secret is | |
23790 | not sent over the network as plain text, which makes this authenticator more | |
23791 | secure than plaintext. However, the downside is that the secret has to be | |
23792 | available in plain text at either end. | |
23793 | ||
23794 | ||
23795 | 35.1 Using cram_md5 as a server | |
23796 | ------------------------------- | |
23797 | ||
23798 | This authenticator has one server option, which must be set to configure the | |
23799 | authenticator as a server: | |
23800 | ||
23801 | +-------------+-------------+-------------+--------------+ | |
23802 | |server_secret|Use: cram_md5|Type: string*|Default: unset| | |
23803 | +-------------+-------------+-------------+--------------+ | |
23804 | ||
23805 | When the server receives the client's response, the user name is placed in the | |
23806 | expansion variable $auth1, and server_secret is expanded to obtain the password | |
23807 | for that user. The server then computes the CRAM-MD5 digest that the client | |
23808 | should have sent, and checks that it received the correct string. If the | |
23809 | expansion of server_secret is forced to fail, authentication fails. If the | |
23810 | expansion fails for some other reason, a temporary error code is returned to | |
23811 | the client. | |
23812 | ||
23813 | For compatibility with previous releases of Exim, the user name is also placed | |
23814 | in $1. However, the use of this variables for this purpose is now deprecated, | |
23815 | as it can lead to confusion in string expansions that also use numeric | |
23816 | variables for other things. | |
23817 | ||
23818 | For example, the following authenticator checks that the user name given by the | |
23819 | client is "ph10", and if so, uses "secret" as the password. For any other user | |
23820 | name, authentication fails. | |
23821 | ||
23822 | fixed_cram: | |
23823 | driver = cram_md5 | |
23824 | public_name = CRAM-MD5 | |
23825 | server_secret = ${if eq{$auth1}{ph10}{secret}fail} | |
23826 | server_set_id = $auth1 | |
23827 | ||
23828 | If authentication succeeds, the setting of server_set_id preserves the user | |
23829 | name in $authenticated_id. A more typical configuration might look up the | |
23830 | secret string in a file, using the user name as the key. For example: | |
23831 | ||
23832 | lookup_cram: | |
23833 | driver = cram_md5 | |
23834 | public_name = CRAM-MD5 | |
23835 | server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\ | |
23836 | {$value}fail} | |
23837 | server_set_id = $auth1 | |
23838 | ||
23839 | Note that this expansion explicitly forces failure if the lookup fails because | |
23840 | $auth1 contains an unknown user name. | |
23841 | ||
23842 | As another example, if you wish to re-use a Cyrus SASL sasldb2 file without | |
23843 | using the relevant libraries, you need to know the realm to specify in the | |
23844 | lookup and then ask for the "userPassword" attribute for that user in that | |
23845 | realm, with: | |
23846 | ||
23847 | cyrusless_crammd5: | |
23848 | driver = cram_md5 | |
23849 | public_name = CRAM-MD5 | |
23850 | server_secret = ${lookup{$auth1:mail.example.org:userPassword}\ | |
23851 | dbmjz{/etc/sasldb2}} | |
23852 | server_set_id = $auth1 | |
23853 | ||
23854 | ||
23855 | 35.2 Using cram_md5 as a client | |
23856 | ------------------------------- | |
23857 | ||
23858 | When used as a client, the cram_md5 authenticator has two options: | |
23859 | ||
23860 | +-----------+-------------+-------------+------------------------------+ | |
23861 | |client_name|Use: cram_md5|Type: string*|Default: the primary host name| | |
23862 | +-----------+-------------+-------------+------------------------------+ | |
23863 | ||
23864 | This string is expanded, and the result used as the user name data when | |
23865 | computing the response to the server's challenge. | |
23866 | ||
23867 | +-------------+-------------+-------------+--------------+ | |
23868 | |client_secret|Use: cram_md5|Type: string*|Default: unset| | |
23869 | +-------------+-------------+-------------+--------------+ | |
23870 | ||
23871 | This option must be set for the authenticator to work as a client. Its value is | |
23872 | expanded and the result used as the secret string when computing the response. | |
23873 | ||
23874 | Different user names and secrets can be used for different servers by referring | |
23875 | to $host or $host_address in the options. Forced failure of either expansion | |
23876 | string is treated as an indication that this authenticator is not prepared to | |
23877 | handle this case. Exim moves on to the next configured client authenticator. | |
23878 | Any other expansion failure causes Exim to give up trying to send the message | |
23879 | to the current server. | |
23880 | ||
23881 | A simple example configuration of a cram_md5 authenticator, using fixed | |
23882 | strings, is: | |
23883 | ||
23884 | fixed_cram: | |
23885 | driver = cram_md5 | |
23886 | public_name = CRAM-MD5 | |
23887 | client_name = ph10 | |
23888 | client_secret = secret | |
23889 | ||
23890 | ||
23891 | ||
23892 | =============================================================================== | |
23893 | 36. THE CYRUS_SASL AUTHENTICATOR | |
23894 | ||
23895 | The code for this authenticator was provided by Matthew Byng-Maddick of A L | |
23896 | Digital Ltd (http://www.aldigital.co.uk). | |
23897 | ||
23898 | The cyrus_sasl authenticator provides server support for the Cyrus SASL library | |
23899 | implementation of the RFC 2222 ("Simple Authentication and Security Layer"). | |
23900 | This library supports a number of authentication mechanisms, including PLAIN | |
23901 | and LOGIN, but also several others that Exim does not support directly. In | |
23902 | particular, there is support for Kerberos authentication. | |
23903 | ||
23904 | The cyrus_sasl authenticator provides a gatewaying mechanism directly to the | |
23905 | Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5, then | |
23906 | so can the cyrus_sasl authenticator. By default it uses the public name of the | |
23907 | driver to determine which mechanism to support. | |
23908 | ||
23909 | Where access to some kind of secret file is required, for example in GSSAPI or | |
23910 | CRAM-MD5, it is worth noting that the authenticator runs as the Exim user, and | |
23911 | that the Cyrus SASL library has no way of escalating privileges by default. You | |
23912 | may also find you need to set environment variables, depending on the driver | |
23913 | you are using. | |
23914 | ||
23915 | The application name provided by Exim is "exim", so various SASL options may be | |
23916 | set in exim.conf in your SASL directory. If you are using GSSAPI for Kerberos, | |
23917 | note that because of limitations in the GSSAPI interface, changing the server | |
23918 | keytab might need to be communicated down to the Kerberos layer independently. | |
23919 | The mechanism for doing so is dependent upon the Kerberos implementation. | |
23920 | ||
23921 | For example, for older releases of Heimdal, the environment variable | |
23922 | KRB5_KTNAME may be set to point to an alternative keytab file. Exim will pass | |
23923 | this variable through from its own inherited environment when started as root | |
23924 | or the Exim user. The keytab file needs to be readable by the Exim user. With | |
23925 | newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the | |
23926 | environment variable. In practice, for those releases, the Cyrus authenticator | |
23927 | is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider | |
23928 | the heimdal_gssapi authenticator, described in chapter 39 | |
23929 | ||
23930 | ||
23931 | 36.1 Using cyrus_sasl as a server | |
23932 | --------------------------------- | |
23933 | ||
23934 | The cyrus_sasl authenticator has four private options. It puts the username (on | |
23935 | a successful authentication) into $auth1. For compatibility with previous | |
23936 | releases of Exim, the username is also placed in $1. However, the use of this | |
23937 | variable for this purpose is now deprecated, as it can lead to confusion in | |
23938 | string expansions that also use numeric variables for other things. | |
23939 | ||
23940 | +---------------+---------------+-------------+------------------+ | |
23941 | |server_hostname|Use: cyrus_sasl|Type: string*|Default: see below| | |
23942 | +---------------+---------------+-------------+------------------+ | |
23943 | ||
23944 | This option selects the hostname that is used when communicating with the | |
23945 | library. The default value is "$primary_hostname". It is up to the underlying | |
23946 | SASL plug-in what it does with this data. | |
23947 | ||
23948 | +-----------+---------------+------------+------------------+ | |
23949 | |server_mech|Use: cyrus_sasl|Type: string|Default: see below| | |
23950 | +-----------+---------------+------------+------------------+ | |
23951 | ||
23952 | This option selects the authentication mechanism this driver should use. The | |
23953 | default is the value of the generic public_name option. This option allows you | |
23954 | to use a different underlying mechanism from the advertised name. For example: | |
23955 | ||
23956 | sasl: | |
23957 | driver = cyrus_sasl | |
23958 | public_name = X-ANYTHING | |
23959 | server_mech = CRAM-MD5 | |
23960 | server_set_id = $auth1 | |
23961 | ||
23962 | +------------+---------------+-------------+--------------+ | |
23963 | |server_realm|Use: cyrus_sasl|Type: string*|Default: unset| | |
23964 | +------------+---------------+-------------+--------------+ | |
23965 | ||
23966 | This specifies the SASL realm that the server claims to be in. | |
23967 | ||
23968 | +--------------+---------------+------------+---------------+ | |
23969 | |server_service|Use: cyrus_sasl|Type: string|Default: "smtp"| | |
23970 | +--------------+---------------+------------+---------------+ | |
23971 | ||
23972 | This is the SASL service that the server claims to implement. | |
23973 | ||
23974 | For straightforward cases, you do not need to set any of the authenticator's | |
23975 | private options. All you need to do is to specify an appropriate mechanism as | |
23976 | the public name. Thus, if you have a SASL library that supports CRAM-MD5 and | |
23977 | PLAIN, you could have two authenticators as follows: | |
23978 | ||
23979 | sasl_cram_md5: | |
23980 | driver = cyrus_sasl | |
23981 | public_name = CRAM-MD5 | |
23982 | server_set_id = $auth1 | |
23983 | ||
23984 | sasl_plain: | |
23985 | driver = cyrus_sasl | |
23986 | public_name = PLAIN | |
23987 | server_set_id = $auth2 | |
23988 | ||
23989 | Cyrus SASL does implement the LOGIN authentication method, even though it is | |
23990 | not a standard method. It is disabled by default in the source distribution, | |
23991 | but it is present in many binary distributions. | |
23992 | ||
23993 | ||
23994 | ||
23995 | =============================================================================== | |
23996 | 37. THE DOVECOT AUTHENTICATOR | |
23997 | ||
23998 | This authenticator is an interface to the authentication facility of the | |
23999 | Dovecot POP/IMAP server, which can support a number of authentication methods. | |
24000 | ||
24001 | Note that Dovecot must be configured to use auth-client not auth-userdb. | |
24002 | ||
24003 | If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful | |
24004 | to use the same mechanisms for SMTP authentication. This is a server | |
24005 | authenticator only. There is only one option: | |
24006 | ||
24007 | +-------------+------------+------------+--------------+ | |
24008 | |server_socket|Use: dovecot|Type: string|Default: unset| | |
24009 | +-------------+------------+------------+--------------+ | |
24010 | ||
24011 | This option must specify the socket that is the interface to Dovecot | |
24012 | authentication. The public_name option must specify an authentication mechanism | |
24013 | that Dovecot is configured to support. You can have several authenticators for | |
24014 | different mechanisms. For example: | |
24015 | ||
24016 | dovecot_plain: | |
24017 | driver = dovecot | |
24018 | public_name = PLAIN | |
24019 | server_socket = /var/run/dovecot/auth-client | |
24020 | server_set_id = $auth1 | |
24021 | ||
24022 | dovecot_ntlm: | |
24023 | driver = dovecot | |
24024 | public_name = NTLM | |
24025 | server_socket = /var/run/dovecot/auth-client | |
24026 | server_set_id = $auth1 | |
24027 | ||
24028 | If the SMTP connection is encrypted, or if $sender_host_address is equal to | |
24029 | $received_ip_address (that is, the connection is local), the "secured" option | |
24030 | is passed in the Dovecot authentication command. If, for a TLS connection, a | |
24031 | client certificate has been verified, the "valid-client-cert" option is passed. | |
24032 | When authentication succeeds, the identity of the user who authenticated is | |
24033 | placed in $auth1. | |
24034 | ||
24035 | ||
24036 | ||
24037 | =============================================================================== | |
24038 | 38. THE GSASL AUTHENTICATOR | |
24039 | ||
24040 | The gsasl authenticator provides server integration for the GNU SASL library | |
24041 | and the mechanisms it provides. This is new as of the 4.80 release and there | |
24042 | are a few areas where the library does not let Exim smoothly scale to handle | |
24043 | future authentication mechanisms, so no guarantee can be made that any | |
24044 | particular new authentication mechanism will be supported without code changes | |
24045 | in Exim. | |
24046 | ||
24047 | +---------------------+----------+-------------+--------------+ | |
24048 | |server_channelbinding|Use: gsasl|Type: boolean|Default: false| | |
24049 | +---------------------+----------+-------------+--------------+ | |
24050 | ||
24051 | Some authentication mechanisms are able to use external context at both ends of | |
24052 | the session to bind the authentication to that context, and fail the | |
24053 | authentication process if that context differs. Specifically, some TLS | |
24054 | ciphersuites can provide identifying information about the cryptographic | |
24055 | context. | |
24056 | ||
24057 | This means that certificate identity and verification becomes a non-issue, as a | |
24058 | man-in-the-middle attack will cause the correct client and server to see | |
24059 | different identifiers and authentication will fail. | |
24060 | ||
24061 | This is currently only supported when using the GnuTLS library. This is only | |
24062 | usable by mechanisms which support "channel binding"; at time of writing, | |
24063 | that's the SCRAM family. | |
24064 | ||
24065 | This defaults off to ensure smooth upgrade across Exim releases, in case this | |
24066 | option causes some clients to start failing. Some future release of Exim may | |
24067 | switch the default to be true. | |
24068 | ||
24069 | +---------------+----------+-------------+------------------+ | |
24070 | |server_hostname|Use: gsasl|Type: string*|Default: see below| | |
24071 | +---------------+----------+-------------+------------------+ | |
24072 | ||
24073 | This option selects the hostname that is used when communicating with the | |
24074 | library. The default value is "$primary_hostname". Some mechanisms will use | |
24075 | this data. | |
24076 | ||
24077 | +-----------+----------+------------+------------------+ | |
24078 | |server_mech|Use: gsasl|Type: string|Default: see below| | |
24079 | +-----------+----------+------------+------------------+ | |
24080 | ||
24081 | This option selects the authentication mechanism this driver should use. The | |
24082 | default is the value of the generic public_name option. This option allows you | |
24083 | to use a different underlying mechanism from the advertised name. For example: | |
24084 | ||
24085 | sasl: | |
24086 | driver = gsasl | |
24087 | public_name = X-ANYTHING | |
24088 | server_mech = CRAM-MD5 | |
24089 | server_set_id = $auth1 | |
24090 | ||
24091 | +---------------+----------+-------------+--------------+ | |
24092 | |server_password|Use: gsasl|Type: string*|Default: unset| | |
24093 | +---------------+----------+-------------+--------------+ | |
24094 | ||
24095 | Various mechanisms need access to the cleartext password on the server, so that | |
24096 | proof-of-possession can be demonstrated on the wire, without sending the | |
24097 | password itself. | |
24098 | ||
24099 | The data available for lookup varies per mechanism. In all cases, $auth1 is set | |
24100 | to the authentication id. The $auth2 variable will always be the authorization | |
24101 | id (authz) if available, else the empty string. The $auth3 variable will always | |
24102 | be the realm if available, else the empty string. | |
24103 | ||
24104 | A forced failure will cause authentication to defer. | |
24105 | ||
24106 | If using this option, it may make sense to set the server_condition option to | |
24107 | be simply "true". | |
24108 | ||
24109 | +------------+----------+-------------+--------------+ | |
24110 | |server_realm|Use: gsasl|Type: string*|Default: unset| | |
24111 | +------------+----------+-------------+--------------+ | |
24112 | ||
24113 | This specifies the SASL realm that the server claims to be in. Some mechanisms | |
24114 | will use this data. | |
24115 | ||
24116 | +-----------------+----------+-------------+--------------+ | |
24117 | |server_scram_iter|Use: gsasl|Type: string*|Default: unset| | |
24118 | +-----------------+----------+-------------+--------------+ | |
24119 | ||
24120 | This option provides data for the SCRAM family of mechanisms. $auth1 is not | |
24121 | available at evaluation time. (This may change, as we receive feedback on use) | |
24122 | ||
24123 | +-----------------+----------+-------------+--------------+ | |
24124 | |server_scram_salt|Use: gsasl|Type: string*|Default: unset| | |
24125 | +-----------------+----------+-------------+--------------+ | |
24126 | ||
24127 | This option provides data for the SCRAM family of mechanisms. $auth1 is not | |
24128 | available at evaluation time. (This may change, as we receive feedback on use) | |
24129 | ||
24130 | +--------------+----------+------------+---------------+ | |
24131 | |server_service|Use: gsasl|Type: string|Default: "smtp"| | |
24132 | +--------------+----------+------------+---------------+ | |
24133 | ||
24134 | This is the SASL service that the server claims to implement. Some mechanisms | |
24135 | will use this data. | |
24136 | ||
24137 | ||
24138 | 38.1 gsasl auth variables | |
24139 | ------------------------- | |
24140 | ||
24141 | These may be set when evaluating specific options, as detailed above. They will | |
24142 | also be set when evaluating server_condition. | |
24143 | ||
24144 | Unless otherwise stated below, the gsasl integration will use the following | |
24145 | meanings for these variables: | |
24146 | ||
24147 | * $auth1: the authentication id | |
24148 | ||
24149 | * $auth2: the authorization id | |
24150 | ||
24151 | * $auth3: the realm | |
24152 | ||
24153 | On a per-mechanism basis: | |
24154 | ||
24155 | * EXTERNAL: only $auth1 is set, to the possibly empty authorization id; the | |
24156 | server_condition option must be present. | |
24157 | ||
24158 | * ANONYMOUS: only $auth1 is set, to the possibly empty anonymous token; the | |
24159 | server_condition option must be present. | |
24160 | ||
24161 | * GSSAPI: $auth1 will be set to the GSSAPI Display Name; $auth2 will be set | |
24162 | to the authorization id, the server_condition option must be present. | |
24163 | ||
24164 | An anonymous token is something passed along as an unauthenticated identifier; | |
24165 | this is analogous to FTP anonymous authentication passing an email address, or | |
24166 | software-identifier@, as the "password". | |
24167 | ||
24168 | An example showing the password having the realm specified in the callback and | |
24169 | demonstrating a Cyrus SASL to GSASL migration approach is: | |
24170 | ||
24171 | gsasl_cyrusless_crammd5: | |
24172 | driver = gsasl | |
24173 | public_name = CRAM-MD5 | |
24174 | server_realm = imap.example.org | |
24175 | server_password = ${lookup{$auth1:$auth3:userPassword}\ | |
24176 | dbmjz{/etc/sasldb2}{$value}fail} | |
24177 | server_set_id = ${quote:$auth1} | |
24178 | server_condition = yes | |
24179 | ||
24180 | ||
24181 | ||
24182 | =============================================================================== | |
24183 | 39. THE HEIMDAL_GSSAPI AUTHENTICATOR | |
24184 | ||
24185 | The heimdal_gssapi authenticator provides server integration for the Heimdal | |
24186 | GSSAPI/Kerberos library, permitting Exim to set a keytab pathname reliably. | |
24187 | ||
24188 | +---------------+-------------------+-------------+------------------+ | |
24189 | |server_hostname|Use: heimdal_gssapi|Type: string*|Default: see below| | |
24190 | +---------------+-------------------+-------------+------------------+ | |
24191 | ||
24192 | This option selects the hostname that is used, with server_service, for | |
24193 | constructing the GSS server name, as a GSS_C_NT_HOSTBASED_SERVICE identifier. | |
24194 | The default value is "$primary_hostname". | |
24195 | ||
24196 | +-------------+-------------------+-------------+--------------+ | |
24197 | |server_keytab|Use: heimdal_gssapi|Type: string*|Default: unset| | |
24198 | +-------------+-------------------+-------------+--------------+ | |
24199 | ||
24200 | If set, then Heimdal will not use the system default keytab (typically /etc/ | |
24201 | krb5.keytab) but instead the pathname given in this option. The value should be | |
24202 | a pathname, with no "file:" prefix. | |
24203 | ||
24204 | +--------------+-------------------+-------------+-------------+ | |
24205 | |server_service|Use: heimdal_gssapi|Type: string*|Default: smtp| | |
24206 | +--------------+-------------------+-------------+-------------+ | |
24207 | ||
24208 | This option specifies the service identifier used, in conjunction with | |
24209 | server_hostname, for building the identifer for finding credentials from the | |
24210 | keytab. | |
24211 | ||
24212 | ||
24213 | 39.1 heimdal_gssapi auth variables | |
24214 | ---------------------------------- | |
24215 | ||
24216 | Beware that these variables will typically include a realm, thus will appear to | |
24217 | be roughly like an email address already. The authzid in $auth2 is not | |
24218 | verified, so a malicious client can set it to anything. | |
24219 | ||
24220 | The $auth1 field should be safely trustable as a value from the Key | |
24221 | Distribution Center. Note that these are not quite email addresses. Each | |
24222 | identifier is for a role, and so the left-hand-side may include a role suffix. | |
24223 | For instance, "joe/admin@EXAMPLE.ORG". | |
24224 | ||
24225 | * $auth1: the authentication id, set to the GSS Display Name. | |
24226 | ||
24227 | * $auth2: the authorization id, sent within SASL encapsulation after | |
24228 | authentication. If that was empty, this will also be set to the GSS Display | |
24229 | Name. | |
24230 | ||
24231 | ||
24232 | ||
24233 | =============================================================================== | |
24234 | 40. THE SPA AUTHENTICATOR | |
24235 | ||
24236 | The spa authenticator provides client support for Microsoft's Secure Password | |
24237 | Authentication mechanism, which is also sometimes known as NTLM (NT LanMan). | |
24238 | The code for client side of this authenticator was contributed by Marc | |
24239 | Prud'hommeaux, and much of it is taken from the Samba project (http:// | |
24240 | www.samba.org). The code for the server side was subsequently contributed by | |
24241 | Tom Kistner. The mechanism works as follows: | |
24242 | ||
24243 | * After the AUTH command has been accepted, the client sends an SPA | |
24244 | authentication request based on the user name and optional domain. | |
24245 | ||
24246 | * The server sends back a challenge. | |
24247 | ||
24248 | * The client builds a challenge response which makes use of the user's | |
24249 | password and sends it to the server, which then accepts or rejects it. | |
24250 | ||
24251 | Encryption is used to protect the password in transit. | |
24252 | ||
24253 | ||
24254 | 40.1 Using spa as a server | |
24255 | -------------------------- | |
24256 | ||
24257 | The spa authenticator has just one server option: | |
24258 | ||
24259 | +---------------+--------+-------------+--------------+ | |
24260 | |server_password|Use: spa|Type: string*|Default: unset| | |
24261 | +---------------+--------+-------------+--------------+ | |
24262 | ||
24263 | This option is expanded, and the result must be the cleartext password for the | |
24264 | authenticating user, whose name is at this point in $auth1. For compatibility | |
24265 | with previous releases of Exim, the user name is also placed in $1. However, | |
24266 | the use of this variable for this purpose is now deprecated, as it can lead to | |
24267 | confusion in string expansions that also use numeric variables for other | |
24268 | things. For example: | |
24269 | ||
24270 | spa: | |
24271 | driver = spa | |
24272 | public_name = NTLM | |
24273 | server_password = \ | |
24274 | ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail} | |
24275 | ||
24276 | If the expansion is forced to fail, authentication fails. Any other expansion | |
24277 | failure causes a temporary error code to be returned. | |
24278 | ||
24279 | ||
24280 | 40.2 Using spa as a client | |
24281 | -------------------------- | |
24282 | ||
24283 | The spa authenticator has the following client options: | |
24284 | ||
24285 | +-------------+--------+-------------+--------------+ | |
24286 | |client_domain|Use: spa|Type: string*|Default: unset| | |
24287 | +-------------+--------+-------------+--------------+ | |
24288 | ||
24289 | This option specifies an optional domain for the authentication. | |
24290 | ||
24291 | +---------------+--------+-------------+--------------+ | |
24292 | |client_password|Use: spa|Type: string*|Default: unset| | |
24293 | +---------------+--------+-------------+--------------+ | |
24294 | ||
24295 | This option specifies the user's password, and must be set. | |
24296 | ||
24297 | +---------------+--------+-------------+--------------+ | |
24298 | |client_username|Use: spa|Type: string*|Default: unset| | |
24299 | +---------------+--------+-------------+--------------+ | |
24300 | ||
24301 | This option specifies the user name, and must be set. Here is an example of a | |
24302 | configuration of this authenticator for use with the mail servers at msn.com: | |
24303 | ||
24304 | msn: | |
24305 | driver = spa | |
24306 | public_name = MSN | |
24307 | client_username = msn/msn_username | |
24308 | client_password = msn_plaintext_password | |
24309 | client_domain = DOMAIN_OR_UNSET | |
24310 | ||
24311 | ||
24312 | ||
24313 | =============================================================================== | |
24314 | 41. ENCRYPTED SMTP CONNECTIONS USING TLS/SSL | |
24315 | ||
24316 | Support for TLS (Transport Layer Security), formerly known as SSL (Secure | |
24317 | Sockets Layer), is implemented by making use of the OpenSSL library or the | |
24318 | GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no | |
24319 | cryptographic code in the Exim distribution itself for implementing TLS. In | |
24320 | order to use this feature you must install OpenSSL or GnuTLS, and then build a | |
24321 | version of Exim that includes TLS support (see section 4.7). You also need to | |
24322 | understand the basic concepts of encryption at a managerial level, and in | |
24323 | particular, the way that public keys, private keys, and certificates are used. | |
24324 | ||
24325 | RFC 3207 defines how SMTP connections can make use of encryption. Once a | |
24326 | connection is established, the client issues a STARTTLS command. If the server | |
24327 | accepts this, the client and the server negotiate an encryption mechanism. If | |
24328 | the negotiation succeeds, the data that subsequently passes between them is | |
24329 | encrypted. | |
24330 | ||
24331 | Exim's ACLs can detect whether the current SMTP session is encrypted or not, | |
24332 | and if so, what cipher suite is in use, whether the client supplied a | |
24333 | certificate, and whether or not that certificate was verified. This makes it | |
24334 | possible for an Exim server to deny or accept certain commands based on the | |
24335 | encryption state. | |
24336 | ||
24337 | Warning: Certain types of firewall and certain anti-virus products can disrupt | |
24338 | TLS connections. You need to turn off SMTP scanning for these products in order | |
24339 | to get TLS to work. | |
24340 | ||
24341 | ||
24342 | 41.1 Support for the legacy "ssmtp" (aka "smtps") protocol | |
24343 | ---------------------------------------------------------- | |
24344 | ||
24345 | Early implementations of encrypted SMTP used a different TCP port from normal | |
24346 | SMTP, and expected an encryption negotiation to start immediately, instead of | |
24347 | waiting for a STARTTLS command from the client using the standard SMTP port. | |
24348 | The protocol was called "ssmtp" or "smtps", and port 465 was allocated for this | |
24349 | purpose. | |
24350 | ||
24351 | This approach was abandoned when encrypted SMTP was standardized, but there are | |
24352 | still some legacy clients that use it. Exim supports these clients by means of | |
24353 | the tls_on_connect_ports global option. Its value must be a list of port | |
24354 | numbers; the most common use is expected to be: | |
24355 | ||
24356 | tls_on_connect_ports = 465 | |
24357 | ||
24358 | The port numbers specified by this option apply to all SMTP connections, both | |
24359 | via the daemon and via inetd. You still need to specify all the ports that the | |
24360 | daemon uses (by setting daemon_smtp_ports or local_interfaces or the -oX | |
24361 | command line option) because tls_on_connect_ports does not add an extra port - | |
24362 | rather, it specifies different behaviour on a port that is defined elsewhere. | |
24363 | ||
24364 | There is also a -tls-on-connect command line option. This overrides | |
24365 | tls_on_connect_ports; it forces the legacy behaviour for all ports. | |
24366 | ||
24367 | ||
24368 | 41.2 OpenSSL vs GnuTLS | |
24369 | ---------------------- | |
24370 | ||
24371 | The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS | |
24372 | followed later, when the first versions of GnuTLS were released. To build Exim | |
24373 | to use GnuTLS, you need to set | |
24374 | ||
24375 | USE_GNUTLS=yes | |
24376 | ||
24377 | in Local/Makefile, in addition to | |
24378 | ||
24379 | SUPPORT_TLS=yes | |
24380 | ||
24381 | You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the include | |
24382 | files and libraries for GnuTLS can be found. | |
24383 | ||
24384 | There are some differences in usage when using GnuTLS instead of OpenSSL: | |
24385 | ||
24386 | * The tls_verify_certificates option must contain the name of a file, not the | |
24387 | name of a directory (for OpenSSL it can be either). | |
24388 | ||
24389 | * The default value for tls_dhparam differs for historical reasons. | |
24390 | ||
24391 | * Distinguished Name (DN) strings reported by the OpenSSL library use a slash | |
24392 | for separating fields; GnuTLS uses commas, in accordance with RFC 2253. | |
24393 | This affects the value of the $tls_in_peerdn and $tls_out_peerdn variables. | |
24394 | ||
24395 | * OpenSSL identifies cipher suites using hyphens as separators, for example: | |
24396 | DES-CBC3-SHA. GnuTLS historically used underscores, for example: | |
24397 | RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present | |
24398 | in a cipher list. To make life simpler, Exim changes underscores to hyphens | |
24399 | for OpenSSL and passes the string unchanged to GnuTLS (expecting the | |
24400 | library to handle its own older variants) when processing lists of cipher | |
24401 | suites in the tls_require_ciphers options (the global option and the smtp | |
24402 | transport option). | |
24403 | ||
24404 | * The tls_require_ciphers options operate differently, as described in the | |
24405 | sections 41.4 and 41.5. | |
24406 | ||
24407 | * The tls_dh_min_bits SMTP transport option is only honoured by GnuTLS. When | |
24408 | using OpenSSL, this option is ignored. (If an API is found to let OpenSSL | |
24409 | be configured in this way, let the Exim Maintainers know and we'll likely | |
24410 | use it). | |
24411 | ||
24412 | * Some other recently added features may only be available in one or the | |
24413 | other. This should be documented with the feature. If the documentation | |
24414 | does not explicitly state that the feature is infeasible in the other TLS | |
24415 | implementation, then patches are welcome. | |
24416 | ||
24417 | ||
24418 | 41.3 GnuTLS parameter computation | |
24419 | --------------------------------- | |
24420 | ||
24421 | This section only applies if tls_dhparam is set to "historic" or to an explicit | |
24422 | path; if the latter, then the text about generation still applies, but not the | |
24423 | chosen filename. By default, as of Exim 4.80 a hard-coded D-H prime is used. | |
24424 | See the documentation of tls_dhparam for more information. | |
24425 | ||
24426 | GnuTLS uses D-H parameters that may take a substantial amount of time to | |
24427 | compute. It is unreasonable to re-compute them for every TLS session. | |
24428 | Therefore, Exim keeps this data in a file in its spool directory, called | |
24429 | gnutls-params-NNNN for some value of NNNN, corresponding to the number of bits | |
24430 | requested. The file is owned by the Exim user and is readable only by its | |
24431 | owner. Every Exim process that start up GnuTLS reads the D-H parameters from | |
24432 | this file. If the file does not exist, the first Exim process that needs it | |
24433 | computes the data and writes it to a temporary file which is renamed once it is | |
24434 | complete. It does not matter if several Exim processes do this simultaneously | |
24435 | (apart from wasting a few resources). Once a file is in place, new Exim | |
24436 | processes immediately start using it. | |
24437 | ||
24438 | For maximum security, the parameters that are stored in this file should be | |
24439 | recalculated periodically, the frequency depending on your paranoia level. If | |
24440 | you are avoiding using the fixed D-H primes published in RFCs, then you are | |
24441 | concerned about some advanced attacks and will wish to do this; if you do not | |
24442 | regenerate then you might as well stick to the standard primes. | |
24443 | ||
24444 | Arranging this is easy in principle; just delete the file when you want new | |
24445 | values to be computed. However, there may be a problem. The calculation of new | |
24446 | parameters needs random numbers, and these are obtained from /dev/random. If | |
24447 | the system is not very active, /dev/random may delay returning data until | |
24448 | enough randomness (entropy) is available. This may cause Exim to hang for a | |
24449 | substantial amount of time, causing timeouts on incoming connections. | |
24450 | ||
24451 | The solution is to generate the parameters externally to Exim. They are stored | |
24452 | in gnutls-params-N in PEM format, which means that they can be generated | |
24453 | externally using the certtool command that is part of GnuTLS. | |
24454 | ||
24455 | To replace the parameters with new ones, instead of deleting the file and | |
24456 | letting Exim re-create it, you can generate new parameters using certtool and, | |
24457 | when this has been done, replace Exim's cache file by renaming. The relevant | |
24458 | commands are something like this: | |
24459 | ||
24460 | # ls | |
24461 | [ look for file; assume gnutls-params-2236 is the most recent ] | |
24462 | # rm -f new-params | |
24463 | # touch new-params | |
24464 | # chown exim:exim new-params | |
24465 | # chmod 0600 new-params | |
24466 | # certtool --generate-dh-params --bits 2236 >>new-params | |
24467 | # openssl dhparam -noout -text -in new-params | head | |
24468 | [ check the first line, make sure it's not more than 2236; | |
24469 | if it is, then go back to the start ("rm") and repeat | |
24470 | until the size generated is at most the size requested ] | |
24471 | # chmod 0400 new-params | |
24472 | # mv new-params gnutls-params-2236 | |
24473 | ||
24474 | If Exim never has to generate the parameters itself, the possibility of | |
24475 | stalling is removed. | |
24476 | ||
24477 | The filename changed in Exim 4.80, to gain the -bits suffix. The value which | |
24478 | Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS, | |
24479 | the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is a | |
24480 | way for Exim to ask for the "normal" number of bits for D-H public-key usage, | |
24481 | and Exim does so. This attempt to remove Exim from TLS policy decisions failed, | |
24482 | as GnuTLS 2.12 returns a value higher than the current hard-coded limit of the | |
24483 | NSS library. Thus Exim gains the tls_dh_max_bits global option, which applies | |
24484 | to all D-H usage, client or server. If the value returned by GnuTLS is greater | |
24485 | than tls_dh_max_bits then the value will be clamped down to tls_dh_max_bits. | |
24486 | The default value has been set at the current NSS limit, which is still much | |
24487 | higher than Exim historically used. | |
24488 | ||
24489 | The filename and bits used will change as the GnuTLS maintainers change the | |
24490 | value for their parameter "GNUTLS_SEC_PARAM_NORMAL", as clamped by | |
24491 | tls_dh_max_bits. At the time of writing (mid 2012), GnuTLS 2.12 recommends 2432 | |
24492 | bits, while NSS is limited to 2236 bits. | |
24493 | ||
24494 | In fact, the requested value will be *lower* than tls_dh_max_bits, to increase | |
24495 | the chance of the generated prime actually being within acceptable bounds, as | |
24496 | GnuTLS has been observed to overshoot. Note the check step in the procedure | |
24497 | above. There is no sane procedure available to Exim to double-check the size of | |
24498 | the generated prime, so it might still be too large. | |
24499 | ||
24500 | ||
24501 | 41.4 Requiring specific ciphers in OpenSSL | |
24502 | ------------------------------------------ | |
24503 | ||
24504 | There is a function in the OpenSSL library that can be passed a list of cipher | |
24505 | suites before the cipher negotiation takes place. This specifies which ciphers | |
24506 | are acceptable. The list is colon separated and may contain names like | |
24507 | DES-CBC3-SHA. Exim passes the expanded value of tls_require_ciphers directly to | |
24508 | this function call. Many systems will install the OpenSSL manual-pages, so you | |
24509 | may have ciphers(1) available to you. The following quotation from the OpenSSL | |
24510 | documentation specifies what forms of item are allowed in the cipher string: | |
24511 | ||
24512 | * It can consist of a single cipher suite such as RC4-SHA. | |
24513 | ||
24514 | * It can represent a list of cipher suites containing a certain algorithm, or | |
24515 | cipher suites of a certain type. For example SHA1 represents all ciphers | |
24516 | suites using the digest algorithm SHA1 and SSLv3 represents all SSL v3 | |
24517 | algorithms. | |
24518 | ||
24519 | * Lists of cipher suites can be combined in a single cipher string using the | |
24520 | + character. This is used as a logical and operation. For example SHA1+DES | |
24521 | represents all cipher suites containing the SHA1 and the DES algorithms. | |
24522 | ||
24523 | Each cipher string can be optionally preceded by one of the characters "!", "-" | |
24524 | or "+". | |
24525 | ||
24526 | * If "!" is used, the ciphers are permanently deleted from the list. The | |
24527 | ciphers deleted can never reappear in the list even if they are explicitly | |
24528 | stated. | |
24529 | ||
24530 | * If "-" is used, the ciphers are deleted from the list, but some or all of | |
24531 | the ciphers can be added again by later options. | |
24532 | ||
24533 | * If "+" is used, the ciphers are moved to the end of the list. This option | |
24534 | does not add any new ciphers; it just moves matching existing ones. | |
24535 | ||
24536 | If none of these characters is present, the string is interpreted as a list of | |
24537 | ciphers to be appended to the current preference list. If the list includes any | |
24538 | ciphers already present they will be ignored: that is, they will not be moved | |
24539 | to the end of the list. | |
24540 | ||
24541 | The OpenSSL ciphers(1) command may be used to test the results of a given | |
24542 | string: | |
24543 | ||
24544 | # note single-quotes to get ! past any shell history expansion | |
24545 | $ openssl ciphers 'HIGH:!MD5:!SHA1' | |
24546 | ||
24547 | This example will let the library defaults be permitted on the MX port, where | |
24548 | there's probably no identity verification anyway, but ups the ante on the | |
24549 | submission ports where the administrator might have some influence on the | |
24550 | choice of clients used: | |
24551 | ||
24552 | # OpenSSL variant; see man ciphers(1) | |
24553 | tls_require_ciphers = ${if =={$received_port}{25}\ | |
24554 | {DEFAULT}\ | |
24555 | {HIGH:!MD5:!SHA1}} | |
24556 | ||
24557 | ||
24558 | 41.5 Requiring specific ciphers or other parameters in GnuTLS | |
24559 | ------------------------------------------------------------- | |
24560 | ||
24561 | The GnuTLS library allows the caller to provide a "priority string", documented | |
24562 | as part of the gnutls_priority_init function. This is very similar to the | |
24563 | ciphersuite specification in OpenSSL. | |
24564 | ||
24565 | The tls_require_ciphers option is treated as the GnuTLS priority string. | |
24566 | ||
24567 | The tls_require_ciphers option is available both as an global option, | |
24568 | controlling how Exim behaves as a server, and also as an option of the smtp | |
24569 | transport, controlling how Exim behaves as a client. In both cases the value is | |
24570 | string expanded. The resulting string is not an Exim list and the string is | |
24571 | given to the GnuTLS library, so that Exim does not need to be aware of future | |
24572 | feature enhancements of GnuTLS. | |
24573 | ||
24574 | Documentation of the strings accepted may be found in the GnuTLS manual, under | |
24575 | "Priority strings". This is online as http://www.gnutls.org/manual/html_node/ | |
24576 | Priority-Strings.html, but beware that this relates to GnuTLS 3, which may be | |
24577 | newer than the version installed on your system. If you are using GnuTLS 3, | |
24578 | then the example code on that site can be used to test a given string. | |
24579 | ||
24580 | Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three | |
24581 | additional options, "gnutls_require_kx", "gnutls_require_mac" and " | |
24582 | gnutls_require_protocols". tls_require_ciphers was an Exim list. | |
24583 | ||
24584 | This example will let the library defaults be permitted on the MX port, where | |
24585 | there's probably no identity verification anyway, and lowers security further | |
24586 | by increasing compatibility; but this ups the ante on the submission ports | |
24587 | where the administrator might have some influence on the choice of clients | |
24588 | used: | |
24589 | ||
24590 | # GnuTLS variant | |
24591 | tls_require_ciphers = ${if =={$received_port}{25}\ | |
24592 | {NORMAL:%COMPAT}\ | |
24593 | {SECURE128}} | |
24594 | ||
24595 | ||
24596 | 41.6 Configuring an Exim server to use TLS | |
24597 | ------------------------------------------ | |
24598 | ||
24599 | When Exim has been built with TLS support, it advertises the availability of | |
24600 | the STARTTLS command to client hosts that match tls_advertise_hosts, but not to | |
24601 | any others. The default value of this option is unset, which means that | |
24602 | STARTTLS is not advertised at all. This default is chosen because you need to | |
24603 | set some other options in order to make TLS available, and also it is sensible | |
24604 | for systems that want to use TLS only as a client. | |
24605 | ||
24606 | If a client issues a STARTTLS command and there is some configuration problem | |
24607 | in the server, the command is rejected with a 454 error. If the client persists | |
24608 | in trying to issue SMTP commands, all except QUIT are rejected with the error | |
24609 | ||
24610 | 554 Security failure | |
24611 | ||
24612 | If a STARTTLS command is issued within an existing TLS session, it is rejected | |
24613 | with a 554 error code. | |
24614 | ||
24615 | To enable TLS operations on a server, you must set tls_advertise_hosts to match | |
24616 | some hosts. You can, of course, set it to * to match all hosts. However, this | |
24617 | is not all you need to do. TLS sessions to a server won't work without some | |
24618 | further configuration at the server end. | |
24619 | ||
24620 | It is rumoured that all existing clients that support TLS/SSL use RSA | |
24621 | encryption. To make this work you need to set, in the server, | |
24622 | ||
24623 | tls_certificate = /some/file/name | |
24624 | tls_privatekey = /some/file/name | |
24625 | ||
24626 | These options are, in fact, expanded strings, so you can make them depend on | |
24627 | the identity of the client that is connected if you wish. The first file | |
24628 | contains the server's X509 certificate, and the second contains the private key | |
24629 | that goes with it. These files need to be readable by the Exim user, and must | |
24630 | always be given as full path names. They can be the same file if both the | |
24631 | certificate and the key are contained within it. If tls_privatekey is not set, | |
24632 | or if its expansion is forced to fail or results in an empty string, this is | |
24633 | assumed to be the case. The certificate file may also contain intermediate | |
24634 | certificates that need to be sent to the client to enable it to authenticate | |
24635 | the server's certificate. | |
24636 | ||
24637 | If you do not understand about certificates and keys, please try to find a | |
24638 | source of this background information, which is not Exim-specific. (There are a | |
24639 | few comments below in section 41.12.) | |
24640 | ||
24641 | Note: These options do not apply when Exim is operating as a client - they | |
24642 | apply only in the case of a server. If you need to use a certificate in an Exim | |
24643 | client, you must set the options of the same names in an smtp transport. | |
24644 | ||
24645 | With just these options, an Exim server will be able to use TLS. It does not | |
24646 | require the client to have a certificate (but see below for how to insist on | |
24647 | this). There is one other option that may be needed in other situations. If | |
24648 | ||
24649 | tls_dhparam = /some/file/name | |
24650 | ||
24651 | is set, the SSL library is initialized for the use of Diffie-Hellman ciphers | |
24652 | with the parameters contained in the file. Set this to "none" to disable use of | |
24653 | DH entirely, by making no prime available: | |
24654 | ||
24655 | tls_dhparam = none | |
24656 | ||
24657 | This may also be set to a string identifying a standard prime to be used for | |
24658 | DH; if it is set to "default" or, for OpenSSL, is unset, then the prime used is | |
24659 | "ike23". There are a few standard primes available, see the documentation for | |
24660 | tls_dhparam for the complete list. | |
24661 | ||
24662 | See the command | |
24663 | ||
24664 | openssl dhparam | |
24665 | ||
24666 | for a way of generating file data. | |
24667 | ||
24668 | The strings supplied for these three options are expanded every time a client | |
24669 | host connects. It is therefore possible to use different certificates and keys | |
24670 | for different hosts, if you so wish, by making use of the client's IP address | |
24671 | in $sender_host_address to control the expansion. If a string expansion is | |
24672 | forced to fail, Exim behaves as if the option is not set. | |
24673 | ||
24674 | The variable $tls_in_cipher is set to the cipher suite that was negotiated for | |
24675 | an incoming TLS connection. It is included in the Received: header of an | |
24676 | incoming message (by default - you can, of course, change this), and it is also | |
24677 | included in the log line that records a message's arrival, keyed by "X=", | |
24678 | unless the tls_cipher log selector is turned off. The encrypted condition can | |
24679 | be used to test for specific cipher suites in ACLs. | |
24680 | ||
24681 | Once TLS has been established, the ACLs that run for subsequent SMTP commands | |
24682 | can check the name of the cipher suite and vary their actions accordingly. The | |
24683 | cipher suite names vary, depending on which TLS library is being used. For | |
24684 | example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other | |
24685 | contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS | |
24686 | documentation for more details. | |
24687 | ||
24688 | For outgoing SMTP deliveries, $tls_out_cipher is used and logged (again | |
24689 | depending on the tls_cipher log selector). | |
24690 | ||
24691 | ||
24692 | 41.7 Requesting and verifying client certificates | |
24693 | ------------------------------------------------- | |
24694 | ||
24695 | If you want an Exim server to request a certificate when negotiating a TLS | |
24696 | session with a client, you must set either tls_verify_hosts or | |
24697 | tls_try_verify_hosts. You can, of course, set either of them to * to apply to | |
24698 | all TLS connections. For any host that matches one of these options, Exim | |
24699 | requests a certificate as part of the setup of the TLS session. The contents of | |
24700 | the certificate are verified by comparing it with a list of expected | |
24701 | certificates. These must be available in a file or, for OpenSSL only (not | |
24702 | GnuTLS), a directory, identified by tls_verify_certificates. | |
24703 | ||
24704 | A file can contain multiple certificates, concatenated end to end. If a | |
24705 | directory is used (OpenSSL only), each certificate must be in a separate file, | |
24706 | with a name (or a symbolic link) of the form <hash>.0, where <hash> is a hash | |
24707 | value constructed from the certificate. You can compute the relevant hash by | |
24708 | running the command | |
24709 | ||
24710 | openssl x509 -hash -noout -in /cert/file | |
24711 | ||
24712 | where /cert/file contains a single certificate. | |
24713 | ||
24714 | The difference between tls_verify_hosts and tls_try_verify_hosts is what | |
24715 | happens if the client does not supply a certificate, or if the certificate does | |
24716 | not match any of the certificates in the collection named by | |
24717 | tls_verify_certificates. If the client matches tls_verify_hosts, the attempt to | |
24718 | set up a TLS session is aborted, and the incoming connection is dropped. If the | |
24719 | client matches tls_try_verify_hosts, the (encrypted) SMTP session continues. | |
24720 | ACLs that run for subsequent SMTP commands can detect the fact that no | |
24721 | certificate was verified, and vary their actions accordingly. For example, you | |
24722 | can insist on a certificate before accepting a message for relaying, but not | |
24723 | when the message is destined for local delivery. | |
24724 | ||
24725 | When a client supplies a certificate (whether it verifies or not), the value of | |
24726 | the Distinguished Name of the certificate is made available in the variable | |
24727 | $tls_in_peerdn during subsequent processing of the message. | |
24728 | ||
24729 | Because it is often a long text string, it is not included in the log line or | |
24730 | Received: header by default. You can arrange for it to be logged, keyed by "DN= | |
24731 | ", by setting the tls_peerdn log selector, and you can use received_header_text | |
24732 | to change the Received: header. When no certificate is supplied, $tls_in_peerdn | |
24733 | is empty. | |
24734 | ||
24735 | ||
24736 | 41.8 Revoked certificates | |
24737 | ------------------------- | |
24738 | ||
24739 | Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when | |
24740 | certificates are revoked. If you have such a list, you can pass it to an Exim | |
24741 | server using the global option called tls_crl and to an Exim client using an | |
24742 | identically named option for the smtp transport. In each case, the value of the | |
24743 | option is expanded and must then be the name of a file that contains a CRL in | |
24744 | PEM format. The downside is that clients have to periodically re-download a | |
24745 | potentially huge file from every certificate authority the know of. | |
24746 | ||
24747 | The way with most moving parts at query time is Online Certificate Status | |
24748 | Protocol (OCSP), where the client verifies the certificate against an OCSP | |
24749 | server run by the CA. This lets the CA track all usage of the certs. It | |
24750 | requires running software with access to the private key of the CA, to sign the | |
24751 | responses to the OCSP queries. OCSP is based on HTTP and can be proxied | |
24752 | accordingly. | |
24753 | ||
24754 | The only widespread OCSP server implementation (known to this writer) comes as | |
24755 | part of OpenSSL and aborts on an invalid request, such as connecting to the | |
24756 | port and then disconnecting. This requires re-entering the passphrase each time | |
24757 | some random client does this. | |
24758 | ||
24759 | The third way is OCSP Stapling; in this, the server using a certificate issued | |
24760 | by the CA periodically requests an OCSP proof of validity from the OCSP server, | |
24761 | then serves it up inline as part of the TLS negotiation. This approach adds no | |
24762 | extra round trips, does not let the CA track users, scales well with number of | |
24763 | certs issued by the CA and is resilient to temporary OCSP server failures, as | |
24764 | long as the server starts retrying to fetch an OCSP proof some time before its | |
24765 | current proof expires. The downside is that it requires server support. | |
24766 | ||
24767 | Unless Exim is built with the support disabled, or with GnuTLS earlier than | |
24768 | version 3.1.3, support for OCSP stapling is included. | |
24769 | ||
24770 | There is a global option called tls_ocsp_file. The file specified therein is | |
24771 | expected to be in DER format, and contain an OCSP proof. Exim will serve it as | |
24772 | part of the TLS handshake. This option will be re-expanded for SNI, if the | |
24773 | tls_certificate option contains "tls_in_sni", as per other TLS options. | |
24774 | ||
24775 | Exim does not at this time implement any support for fetching a new OCSP proof. | |
24776 | The burden is on the administrator to handle this, outside of Exim. The file | |
24777 | specified should be replaced atomically, so that the contents are always valid. | |
24778 | Exim will expand the tls_ocsp_file option on each connection, so a new file | |
24779 | will be handled transparently on the next connection. | |
24780 | ||
24781 | When built with OpenSSL Exim will check for a valid next update timestamp in | |
24782 | the OCSP proof; if not present, or if the proof has expired, it will be | |
24783 | ignored. | |
24784 | ||
24785 | For the client to be able to verify the stapled OCSP the server must also | |
24786 | supply, in its stapled information, any intermediate certificates for the chain | |
24787 | leading to the OCSP proof from the signer of the server certificate. There may | |
24788 | be zero or one such. These intermediate certificates should be added to the | |
24789 | server OCSP stapling file named by tls_ocsp_file. | |
24790 | ||
24791 | Note that the proof only covers the terminal server certificate, not any of the | |
24792 | chain from CA to it. | |
24793 | ||
24794 | There is no current way to staple a proof for a client certificate. | |
24795 | ||
24796 | A helper script "ocsp_fetch.pl" for fetching a proof from a CA | |
24797 | OCSP server is supplied. The server URL may be included in the | |
24798 | server certificate, if the CA is helpful. | |
24799 | ||
24800 | One failure mode seen was the OCSP Signer cert expiring before the end | |
24801 | of validity of the OCSP proof. The checking done by Exim/OpenSSL | |
24802 | noted this as invalid overall, but the re-fetch script did not. | |
24803 | ||
24804 | ||
24805 | 41.9 Configuring an Exim client to use TLS | |
24806 | ------------------------------------------ | |
24807 | ||
24808 | The tls_cipher and tls_peerdn log selectors apply to outgoing SMTP deliveries | |
24809 | as well as to incoming, the latter one causing logging of the server | |
24810 | certificate's DN. The remaining client configuration for TLS is all within the | |
24811 | smtp transport. | |
24812 | ||
24813 | It is not necessary to set any options to have TLS work in the smtp transport. | |
24814 | If Exim is built with TLS support, and TLS is advertised by a server, the smtp | |
24815 | transport always tries to start a TLS session. However, this can be prevented | |
24816 | by setting hosts_avoid_tls (an option of the transport) to a list of server | |
24817 | hosts for which TLS should not be used. | |
24818 | ||
24819 | If you do not want Exim to attempt to send messages unencrypted when an attempt | |
24820 | to set up an encrypted connection fails in any way, you can set | |
24821 | hosts_require_tls to a list of hosts for which encryption is mandatory. For | |
24822 | those hosts, delivery is always deferred if an encrypted connection cannot be | |
24823 | set up. If there are any other hosts for the address, they are tried in the | |
24824 | usual way. | |
24825 | ||
24826 | When the server host is not in hosts_require_tls, Exim may try to deliver the | |
24827 | message unencrypted. It always does this if the response to STARTTLS is a 5xx | |
24828 | code. For a temporary error code, or for a failure to negotiate a TLS session | |
24829 | after a success response code, what happens is controlled by the | |
24830 | tls_tempfail_tryclear option of the smtp transport. If it is false, delivery to | |
24831 | this host is deferred, and other hosts (if available) are tried. If it is true, | |
24832 | Exim attempts to deliver unencrypted after a 4xx response to STARTTLS, and if | |
24833 | STARTTLS is accepted, but the subsequent TLS negotiation fails, Exim closes the | |
24834 | current connection (because it is in an unknown state), opens a new one to the | |
24835 | same host, and then tries the delivery unencrypted. | |
24836 | ||
24837 | The tls_certificate and tls_privatekey options of the smtp transport provide | |
24838 | the client with a certificate, which is passed to the server if it requests it. | |
24839 | If the server is Exim, it will request a certificate only if tls_verify_hosts | |
24840 | or tls_try_verify_hosts matches the client. | |
24841 | ||
24842 | If the tls_verify_certificates option is set on the smtp transport, it must | |
24843 | name a file or, for OpenSSL only (not GnuTLS), a directory, that contains a | |
24844 | collection of expected server certificates. The client verifies the server's | |
24845 | certificate against this collection, taking into account any revoked | |
24846 | certificates that are in the list defined by tls_crl. Failure to verify fails | |
24847 | the TLS connection unless either of the tls_verify_hosts or | |
24848 | tls_try_verify_hosts options are set. | |
24849 | ||
24850 | The tls_verify_hosts and tls_try_verify_hosts options restrict certificate | |
24851 | verification to the listed servers. Verification either must or need not | |
24852 | succeed respectively. | |
24853 | ||
24854 | The smtp transport has two OCSP-related options: hosts_require_ocsp; a | |
24855 | host-list for which a Certificate Status is requested and required for the | |
24856 | connection to proceed. The default value is empty. hosts_request_ocsp; a | |
24857 | host-list for which (additionally) a Certificate Status is requested (but not | |
24858 | necessarily verified). The default value is "*" meaning that requests are made | |
24859 | unless configured otherwise. | |
24860 | ||
24861 | The host(s) should also be in hosts_require_tls, and tls_verify_certificates | |
24862 | configured for the transport, for OCSP to be relevant. | |
24863 | ||
24864 | If tls_require_ciphers is set on the smtp transport, it must contain a list of | |
24865 | permitted cipher suites. If either of these checks fails, delivery to the | |
24866 | current host is abandoned, and the smtp transport tries to deliver to | |
24867 | alternative hosts, if any. | |
24868 | ||
24869 | Note: These options must be set in the smtp transport for Exim to use TLS when | |
24870 | it is operating as a client. Exim does not assume that a server certificate | |
24871 | (set by the global options of the same name) should also be used when operating | |
24872 | as a client. | |
24873 | ||
24874 | All the TLS options in the smtp transport are expanded before use, with $host | |
24875 | and $host_address containing the name and address of the server to which the | |
24876 | client is connected. Forced failure of an expansion causes Exim to behave as if | |
24877 | the relevant option were unset. | |
24878 | ||
24879 | Before an SMTP connection is established, the $tls_out_bits, $tls_out_cipher, | |
24880 | $tls_out_peerdn and $tls_out_sni variables are emptied. (Until the first | |
24881 | connection, they contain the values that were set when the message was | |
24882 | received.) If STARTTLS is subsequently successfully obeyed, these variables are | |
24883 | set to the relevant values for the outgoing connection. | |
24884 | ||
24885 | ||
24886 | 41.10 Use of TLS Server Name Indication | |
24887 | --------------------------------------- | |
24888 | ||
24889 | With TLS1.0 or above, there is an extension mechanism by which extra | |
24890 | information can be included at various points in the protocol. One of these | |
24891 | extensions, documented in RFC 6066 (and before that RFC 4366) is "Server Name | |
24892 | Indication", commonly "SNI". This extension is sent by the client in the | |
24893 | initial handshake, so that the server can examine the servername within and | |
24894 | possibly choose to use different certificates and keys (and more) for this | |
24895 | session. | |
24896 | ||
24897 | This is analagous to HTTP's "Host:" header, and is the main mechanism by which | |
24898 | HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP address. | |
24899 | ||
24900 | With SMTP to MX, there are the same problems here as in choosing the identity | |
24901 | against which to validate a certificate: you can't rely on insecure DNS to | |
24902 | provide the identity which you then cryptographically verify. So this will be | |
24903 | of limited use in that environment. | |
24904 | ||
24905 | With SMTP to Submission, there is a well-defined hostname which clients are | |
24906 | connecting to and can validate certificates against. Thus clients can choose to | |
24907 | include this information in the TLS negotiation. If this becomes wide-spread, | |
24908 | then hosters can choose to present different certificates to different clients. | |
24909 | Or even negotiate different cipher suites. | |
24910 | ||
24911 | The tls_sni option on an SMTP transport is an expanded string; the result, if | |
24912 | not empty, will be sent on a TLS session as part of the handshake. There's | |
24913 | nothing more to it. Choosing a sensible value not derived insecurely is the | |
24914 | only point of caution. The $tls_out_sni variable will be set to this string for | |
24915 | the lifetime of the client connection (including during authentication). | |
24916 | ||
24917 | Except during SMTP client sessions, if $tls_in_sni is set then it is a string | |
24918 | received from a client. It can be logged with the log_selector item "+tls_sni". | |
24919 | ||
24920 | If the string "tls_in_sni" appears in the main section's tls_certificate option | |
24921 | (prior to expansion) then the following options will be re-expanded during TLS | |
24922 | session handshake, to permit alternative values to be chosen: | |
24923 | ||
24924 | * tls_certificate | |
24925 | ||
24926 | * tls_crl | |
24927 | ||
24928 | * tls_privatekey | |
24929 | ||
24930 | * tls_verify_certificates | |
24931 | ||
24932 | * tls_verify_certificates | |
24933 | ||
24934 | Great care should be taken to deal with matters of case, various injection | |
24935 | attacks in the string ("../" or SQL), and ensuring that a valid filename can | |
24936 | always be referenced; it is important to remember that $tls_sni is arbitrary | |
24937 | unverified data provided prior to authentication. | |
24938 | ||
24939 | The Exim developers are proceeding cautiously and so far no other TLS options | |
24940 | are re-expanded. | |
24941 | ||
24942 | When Exim is built againt OpenSSL, OpenSSL must have been built with support | |
24943 | for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with | |
24944 | enable-tlsext in EXTRACONFIGURE. If you invoke openssl s_client -h and see | |
24945 | "-servername" in the output, then OpenSSL has support. | |
24946 | ||
24947 | When Exim is built against GnuTLS, SNI support is available as of GnuTLS | |
24948 | 0.5.10. (Its presence predates the current API which Exim uses, so if Exim | |
24949 | built, then you have SNI support). | |
24950 | ||
24951 | ||
24952 | 41.11 Multiple messages on the same encrypted TCP/IP connection | |
24953 | --------------------------------------------------------------- | |
24954 | ||
24955 | Exim sends multiple messages down the same TCP/IP connection by starting up an | |
24956 | entirely new delivery process for each message, passing the socket from one | |
24957 | process to the next. This implementation does not fit well with the use of TLS, | |
24958 | because there is quite a lot of state information associated with a TLS | |
24959 | connection, not just a socket identification. Passing all the state information | |
24960 | to a new process is not feasible. Consequently, Exim shuts down an existing TLS | |
24961 | session before passing the socket to a new process. The new process may then | |
24962 | try to start a new TLS session, and if successful, may try to re-authenticate | |
24963 | if AUTH is in use, before sending the next message. | |
24964 | ||
24965 | The RFC is not clear as to whether or not an SMTP session continues in clear | |
24966 | after TLS has been shut down, or whether TLS may be restarted again later, as | |
24967 | just described. However, if the server is Exim, this shutdown and | |
24968 | reinitialization works. It is not known which (if any) other servers operate | |
24969 | successfully if the client closes a TLS session and continues with unencrypted | |
24970 | SMTP, but there are certainly some that do not work. For such servers, Exim | |
24971 | should not pass the socket to another process, because the failure of the | |
24972 | subsequent attempt to use it would cause Exim to record a temporary host error, | |
24973 | and delay other deliveries to that host. | |
24974 | ||
24975 | To test for this case, Exim sends an EHLO command to the server after closing | |
24976 | down the TLS session. If this fails in any way, the connection is closed | |
24977 | instead of being passed to a new delivery process, but no retry information is | |
24978 | recorded. | |
24979 | ||
24980 | There is also a manual override; you can set hosts_nopass_tls on the smtp | |
24981 | transport to match those hosts for which Exim should not pass connections to | |
24982 | new processes if TLS has been used. | |
24983 | ||
24984 | ||
24985 | 41.12 Certificates and all that | |
24986 | ------------------------------- | |
24987 | ||
24988 | In order to understand fully how TLS works, you need to know about | |
24989 | certificates, certificate signing, and certificate authorities. This is not the | |
24990 | place to give a tutorial, especially as I do not know very much about it | |
24991 | myself. Some helpful introduction can be found in the FAQ for the SSL addition | |
24992 | to Apache, currently at | |
24993 | ||
24994 | http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24 | |
24995 | ||
24996 | Other parts of the modssl documentation are also helpful, and have links to | |
24997 | further files. Eric Rescorla's book, SSL and TLS, published by Addison-Wesley | |
24998 | (ISBN 0-201-61598-3), contains both introductory and more in-depth | |
24999 | descriptions. Some sample programs taken from the book are available from | |
25000 | ||
25001 | http://www.rtfm.com/openssl-examples/ | |
25002 | ||
25003 | ||
25004 | 41.13 Certificate chains | |
25005 | ------------------------ | |
25006 | ||
25007 | The file named by tls_certificate may contain more than one certificate. This | |
25008 | is useful in the case where the certificate that is being sent is validated by | |
25009 | an intermediate certificate which the other end does not have. Multiple | |
25010 | certificates must be in the correct order in the file. First the host's | |
25011 | certificate itself, then the first intermediate certificate to validate the | |
25012 | issuer of the host certificate, then the next intermediate certificate to | |
25013 | validate the issuer of the first intermediate certificate, and so on, until | |
25014 | finally (optionally) the root certificate. The root certificate must already be | |
25015 | trusted by the recipient for validation to succeed, of course, but if it's not | |
25016 | preinstalled, sending the root certificate along with the rest makes it | |
25017 | available for the user to install if the receiving end is a client MUA that can | |
25018 | interact with a user. | |
25019 | ||
25020 | Note that certificates using MD5 are unlikely to work on today's Internet; even | |
25021 | if your libraries allow loading them for use in Exim when acting as a server, | |
25022 | increasingly clients will not accept such certificates. The error diagnostics | |
25023 | in such a case can be frustratingly vague. | |
25024 | ||
25025 | ||
25026 | 41.14 Self-signed certificates | |
25027 | ------------------------------ | |
25028 | ||
25029 | You can create a self-signed certificate using the req command provided with | |
25030 | OpenSSL, like this: | |
25031 | ||
25032 | openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \ | |
25033 | -days 9999 -nodes | |
25034 | ||
25035 | file1 and file2 can be the same file; the key and the certificate are delimited | |
25036 | and so can be identified independently. The -days option specifies a period for | |
25037 | which the certificate is valid. The -nodes option is important: if you do not | |
25038 | set it, the key is encrypted with a passphrase that you are prompted for, and | |
25039 | any use that is made of the key causes more prompting for the passphrase. This | |
25040 | is not helpful if you are going to use this certificate and key in an MTA, | |
25041 | where prompting is not possible. | |
25042 | ||
25043 | NB: we are now past the point where 9999 days takes us past the 32-bit Unix | |
25044 | epoch. If your system uses unsigned time_t (most do) and is 32-bit, then the | |
25045 | above command might produce a date in the past. Think carefully about the | |
25046 | lifetime of the systems you're deploying, and either reduce the duration of the | |
25047 | certificate or reconsider your platform deployment. (At time of writing, | |
25048 | reducing the duration is the most likely choice, but the inexorable progression | |
25049 | of time takes us steadily towards an era where this will not be a sensible | |
25050 | resolution). | |
25051 | ||
25052 | A self-signed certificate made in this way is sufficient for testing, and may | |
25053 | be adequate for all your requirements if you are mainly interested in | |
25054 | encrypting transfers, and not in secure identification. | |
25055 | ||
25056 | However, many clients require that the certificate presented by the server be a | |
25057 | user (also called "leaf" or "site") certificate, and not a self-signed | |
25058 | certificate. In this situation, the self-signed certificate described above | |
25059 | must be installed on the client host as a trusted root certification authority | |
25060 | (CA), and the certificate used by Exim must be a user certificate signed with | |
25061 | that self-signed certificate. | |
25062 | ||
25063 | For information on creating self-signed CA certificates and using them to sign | |
25064 | user certificates, see the General implementation overview chapter of the | |
25065 | Open-source PKI book, available online at http://ospkibook.sourceforge.net/. | |
25066 | ||
25067 | ||
25068 | ||
25069 | =============================================================================== | |
25070 | 42. ACCESS CONTROL LISTS | |
25071 | ||
25072 | Access Control Lists (ACLs) are defined in a separate section of the run time | |
25073 | configuration file, headed by "begin acl". Each ACL definition starts with a | |
25074 | name, terminated by a colon. Here is a complete ACL section that contains just | |
25075 | one very small ACL: | |
25076 | ||
25077 | begin acl | |
25078 | small_acl: | |
25079 | accept hosts = one.host.only | |
25080 | ||
25081 | You can have as many lists as you like in the ACL section, and the order in | |
25082 | which they appear does not matter. The lists are self-terminating. | |
25083 | ||
25084 | The majority of ACLs are used to control Exim's behaviour when it receives | |
25085 | certain SMTP commands. This applies both to incoming TCP/IP connections, and | |
25086 | when a local process submits a message using SMTP by specifying the -bs option. | |
25087 | The most common use is for controlling which recipients are accepted in | |
25088 | incoming messages. In addition, you can define an ACL that is used to check | |
25089 | local non-SMTP messages. The default configuration file contains an example of | |
25090 | a realistic ACL for checking RCPT commands. This is discussed in chapter 7. | |
25091 | ||
25092 | ||
25093 | 42.1 Testing ACLs | |
25094 | ----------------- | |
25095 | ||
25096 | The -bh command line option provides a way of testing your ACL configuration | |
25097 | locally by running a fake SMTP session with which you interact. The host | |
25098 | relay-test.mail-abuse.org provides a service for checking your relaying | |
25099 | configuration (see section 42.53 for more details). | |
25100 | ||
25101 | ||
25102 | 42.2 Specifying when ACLs are used | |
25103 | ---------------------------------- | |
25104 | ||
25105 | In order to cause an ACL to be used, you have to name it in one of the relevant | |
25106 | options in the main part of the configuration. These options are: | |
25107 | ||
25108 | acl_not_smtp ACL for non-SMTP messages | |
25109 | acl_not_smtp_mime ACL for non-SMTP MIME parts | |
25110 | acl_not_smtp_start ACL at start of non-SMTP message | |
25111 | acl_smtp_auth ACL for AUTH | |
25112 | acl_smtp_connect ACL for start of SMTP connection | |
25113 | acl_smtp_data ACL after DATA is complete | |
25114 | acl_smtp_data_prdr ACL for each recipient, after DATA is complete | |
25115 | acl_smtp_etrn ACL for ETRN | |
25116 | acl_smtp_expn ACL for EXPN | |
25117 | acl_smtp_helo ACL for HELO or EHLO | |
25118 | acl_smtp_mail ACL for MAIL | |
25119 | acl_smtp_mailauth ACL for the AUTH parameter of MAIL | |
25120 | acl_smtp_mime ACL for content-scanning MIME parts | |
25121 | acl_smtp_notquit ACL for non-QUIT terminations | |
25122 | acl_smtp_predata ACL at start of DATA command | |
25123 | acl_smtp_quit ACL for QUIT | |
25124 | acl_smtp_rcpt ACL for RCPT | |
25125 | acl_smtp_starttls ACL for STARTTLS | |
25126 | acl_smtp_vrfy ACL for VRFY | |
25127 | ||
25128 | For example, if you set | |
25129 | ||
25130 | acl_smtp_rcpt = small_acl | |
25131 | ||
25132 | the little ACL defined above is used whenever Exim receives a RCPT command in | |
25133 | an SMTP dialogue. The majority of policy tests on incoming messages can be done | |
25134 | when RCPT commands arrive. A rejection of RCPT should cause the sending MTA to | |
25135 | give up on the recipient address contained in the RCPT command, whereas | |
25136 | rejection at other times may cause the client MTA to keep on trying to deliver | |
25137 | the message. It is therefore recommended that you do as much testing as | |
25138 | possible at RCPT time. | |
25139 | ||
25140 | ||
25141 | 42.3 The non-SMTP ACLs | |
25142 | ---------------------- | |
25143 | ||
25144 | The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they | |
25145 | apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not | |
25146 | really SMTP.) Many of the ACL conditions (for example, host tests, and tests on | |
25147 | the state of the SMTP connection such as encryption and authentication) are not | |
25148 | relevant and are forbidden in these ACLs. However, the sender and recipients | |
25149 | are known, so the senders and sender_domains conditions and the $sender_address | |
25150 | and $recipients variables can be used. Variables such as $authenticated_sender | |
25151 | are also available. You can specify added header lines in any of these ACLs. | |
25152 | ||
25153 | The acl_not_smtp_start ACL is run right at the start of receiving a non-SMTP | |
25154 | message, before any of the message has been read. (This is the analogue of the | |
25155 | acl_smtp_predata ACL for SMTP input.) In the case of batched SMTP input, it | |
25156 | runs after the DATA command has been reached. The result of this ACL is | |
25157 | ignored; it cannot be used to reject a message. If you really need to, you | |
25158 | could set a value in an ACL variable here and reject based on that in the | |
25159 | acl_not_smtp ACL. However, this ACL can be used to set controls, and in | |
25160 | particular, it can be used to set | |
25161 | ||
25162 | control = suppress_local_fixups | |
25163 | ||
25164 | This cannot be used in the other non-SMTP ACLs because by the time they are | |
25165 | run, it is too late. | |
25166 | ||
25167 | The acl_not_smtp_mime ACL is available only when Exim is compiled with the | |
25168 | content-scanning extension. For details, see chapter 43. | |
25169 | ||
25170 | The acl_not_smtp ACL is run just before the local_scan() function. Any kind of | |
25171 | rejection is treated as permanent, because there is no way of sending a | |
25172 | temporary error for these kinds of message. | |
25173 | ||
25174 | ||
25175 | 42.4 The SMTP connect ACL | |
25176 | ------------------------- | |
25177 | ||
25178 | The ACL test specified by acl_smtp_connect happens at the start of an SMTP | |
25179 | session, after the test specified by host_reject_connection (which is now an | |
25180 | anomaly) and any TCP Wrappers testing (if configured). If the connection is | |
25181 | accepted by an accept verb that has a message modifier, the contents of the | |
25182 | message override the banner message that is otherwise specified by the | |
25183 | smtp_banner option. | |
25184 | ||
25185 | ||
25186 | 42.5 The EHLO/HELO ACL | |
25187 | ---------------------- | |
25188 | ||
25189 | The ACL test specified by acl_smtp_helo happens when the client issues an EHLO | |
25190 | or HELO command, after the tests specified by helo_accept_junk_hosts, | |
25191 | helo_allow_chars, helo_verify_hosts, and helo_try_verify_hosts. Note that a | |
25192 | client may issue more than one EHLO or HELO command in an SMTP session, and | |
25193 | indeed is required to issue a new EHLO or HELO after successfully setting up | |
25194 | encryption following a STARTTLS command. | |
25195 | ||
25196 | If the command is accepted by an accept verb that has a message modifier, the | |
25197 | message may not contain more than one line (it will be truncated at the first | |
25198 | newline and a panic logged if it does). Such a message cannot affect the EHLO | |
25199 | options that are listed on the second and subsequent lines of an EHLO response. | |
25200 | ||
25201 | ||
25202 | 42.6 The DATA ACLs | |
25203 | ------------------ | |
25204 | ||
25205 | Two ACLs are associated with the DATA command, because it is two-stage command, | |
25206 | with two responses being sent to the client. When the DATA command is received, | |
25207 | the ACL defined by acl_smtp_predata is obeyed. This gives you control after all | |
25208 | the RCPT commands, but before the message itself is received. It offers the | |
25209 | opportunity to give a negative response to the DATA command before the data is | |
25210 | transmitted. Header lines added by MAIL or RCPT ACLs are not visible at this | |
25211 | time, but any that are defined here are visible when the acl_smtp_data ACL is | |
25212 | run. | |
25213 | ||
25214 | You cannot test the contents of the message, for example, to verify addresses | |
25215 | in the headers, at RCPT time or when the DATA command is received. Such tests | |
25216 | have to appear in the ACL that is run after the message itself has been | |
25217 | received, before the final response to the DATA command is sent. This is the | |
25218 | ACL specified by acl_smtp_data, which is the second ACL that is associated with | |
25219 | the DATA command. | |
25220 | ||
25221 | For both of these ACLs, it is not possible to reject individual recipients. An | |
25222 | error response rejects the entire message. Unfortunately, it is known that some | |
25223 | MTAs do not treat hard (5xx) responses to the DATA command (either before or | |
25224 | after the data) correctly - they keep the message on their queues and try again | |
25225 | later, but that is their problem, though it does waste some of your resources. | |
25226 | ||
25227 | The acl_smtp_data ACL is run after the acl_smtp_data_prdr, the acl_smtp_dkim | |
25228 | and the acl_smtp_mime ACLs. | |
25229 | ||
25230 | ||
25231 | 42.7 The SMTP DKIM ACL | |
25232 | ---------------------- | |
25233 | ||
25234 | The acl_smtp_dkim ACL is available only when Exim is compiled with DKIM support | |
25235 | enabled (which is the default). | |
25236 | ||
25237 | The ACL test specified by acl_smtp_dkim happens after a message has been | |
25238 | received, and is executed for each DKIM signature found in a message. If not | |
25239 | otherwise specified, the default action is to accept. | |
25240 | ||
25241 | This ACL is evaluated before acl_smtp_mime and acl_smtp_data. | |
25242 | ||
25243 | For details on the operation of DKIM, see chapter 56. | |
25244 | ||
25245 | ||
25246 | 42.8 The SMTP MIME ACL | |
25247 | ---------------------- | |
25248 | ||
25249 | The acl_smtp_mime option is available only when Exim is compiled with the | |
25250 | content-scanning extension. For details, see chapter 43. | |
25251 | ||
25252 | This ACL is evaluated after acl_smtp_dkim but before acl_smtp_data. | |
25253 | ||
25254 | ||
25255 | 42.9 The SMTP PRDR ACL | |
25256 | ---------------------- | |
25257 | ||
25258 | The acl_smtp_data_prdr ACL is available only when Exim is compiled with PRDR | |
25259 | support enabled (which is the default). It becomes active only when the PRDR | |
25260 | feature is negotiated between client and server for a message, and more than | |
25261 | one recipient has been accepted. | |
25262 | ||
25263 | The ACL test specfied by acl_smtp_data_prdr happens after a message has been | |
25264 | recieved, and is executed for each recipient of the message. The test may | |
25265 | accept or deny for inividual recipients. The acl_smtp_data will still be called | |
25266 | after this ACL and can reject the message overall, even if this ACL has | |
25267 | accepted it for some or all recipients. | |
25268 | ||
25269 | PRDR may be used to support per-user content filtering. Without it one must | |
25270 | defer any recipient after the first that has a different content-filter | |
25271 | configuration. With PRDR, the RCPT-time check for this can be disabled when the | |
25272 | MAIL-time $smtp_command included "PRDR". Any required difference in behaviour | |
25273 | of the main DATA-time ACL should however depend on the PRDR-time ACL having | |
25274 | run, as Exim will avoid doing so in some situations (eg. single-recipient | |
25275 | mails). | |
25276 | ||
25277 | See also the prdr_enable global option and the hosts_try_prdr smtp transport | |
25278 | option. | |
25279 | ||
25280 | This ACL is evaluated after acl_smtp_dkim but before acl_smtp_data. If the ACL | |
25281 | is not defined, processing completes as if the feature was not requested by the | |
25282 | client. | |
25283 | ||
25284 | ||
25285 | 42.10 The QUIT ACL | |
25286 | ------------------ | |
25287 | ||
25288 | The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL | |
25289 | does not affect the response code to QUIT, which is always 221. Thus, the ACL | |
25290 | does not in fact control any access. For this reason, the only verbs that are | |
25291 | permitted are accept and warn. | |
25292 | ||
25293 | This ACL can be used for tasks such as custom logging at the end of an SMTP | |
25294 | session. For example, you can use ACL variables in other ACLs to count | |
25295 | messages, recipients, etc., and log the totals at QUIT time using one or more | |
25296 | logwrite modifiers on a warn verb. | |
25297 | ||
25298 | Warning: Only the $acl_cx variables can be used for this, because the $acl_mx | |
25299 | variables are reset at the end of each incoming message. | |
25300 | ||
25301 | You do not need to have a final accept, but if you do, you can use a message | |
25302 | modifier to specify custom text that is sent as part of the 221 response to | |
25303 | QUIT. | |
25304 | ||
25305 | This ACL is run only for a "normal" QUIT. For certain kinds of disastrous | |
25306 | failure (for example, failure to open a log file, or when Exim is bombing out | |
25307 | because it has detected an unrecoverable error), all SMTP commands from the | |
25308 | client are given temporary error responses until QUIT is received or the | |
25309 | connection is closed. In these special cases, the QUIT ACL does not run. | |
25310 | ||
25311 | ||
25312 | 42.11 The not-QUIT ACL | |
25313 | ---------------------- | |
25314 | ||
25315 | The not-QUIT ACL, specified by acl_smtp_notquit, is run in most cases when an | |
25316 | SMTP session ends without sending QUIT. However, when Exim itself is in bad | |
25317 | trouble, such as being unable to write to its log files, this ACL is not run, | |
25318 | because it might try to do things (such as write to log files) that make the | |
25319 | situation even worse. | |
25320 | ||
25321 | Like the QUIT ACL, this ACL is provided to make it possible to do customized | |
25322 | logging or to gather statistics, and its outcome is ignored. The delay modifier | |
25323 | is forbidden in this ACL, and the only permitted verbs are accept and warn. | |
25324 | ||
25325 | When the not-QUIT ACL is running, the variable $smtp_notquit_reason is set to a | |
25326 | string that indicates the reason for the termination of the SMTP connection. | |
25327 | The possible values are: | |
25328 | ||
25329 | "acl-drop" Another ACL issued a drop command | |
25330 | "bad-commands" Too many unknown or non-mail commands | |
25331 | "command-timeout" Timeout while reading SMTP commands | |
25332 | "connection-lost" The SMTP connection has been lost | |
25333 | "data-timeout" Timeout while reading message data | |
25334 | "local-scan-error" The local_scan() function crashed | |
25335 | "local-scan-timeout" The local_scan() function timed out | |
25336 | "signal-exit" SIGTERM or SIGINT | |
25337 | "synchronization-error" SMTP synchronization error | |
25338 | "tls-failed" TLS failed to start | |
25339 | ||
25340 | In most cases when an SMTP connection is closed without having received QUIT, | |
25341 | Exim sends an SMTP response message before actually closing the connection. | |
25342 | With the exception of the "acl-drop" case, the default message can be | |
25343 | overridden by the message modifier in the not-QUIT ACL. In the case of a drop | |
25344 | verb in another ACL, it is the message from the other ACL that is used. | |
25345 | ||
25346 | ||
25347 | 42.12 Finding an ACL to use | |
25348 | --------------------------- | |
25349 | ||
25350 | The value of an acl_smtp_xxx option is expanded before use, so you can use | |
25351 | different ACLs in different circumstances. For example, | |
25352 | ||
25353 | acl_smtp_rcpt = ${if ={25}{$interface_port} \ | |
25354 | {acl_check_rcpt} {acl_check_rcpt_submit} } | |
25355 | ||
25356 | In the default configuration file there are some example settings for providing | |
25357 | an RFC 4409 message submission service on port 587 and a non-standard "smtps" | |
25358 | service on port 465. You can use a string expansion like this to choose an ACL | |
25359 | for MUAs on these ports which is more appropriate for this purpose than the | |
25360 | default ACL on port 25. | |
25361 | ||
25362 | The expanded string does not have to be the name of an ACL in the configuration | |
25363 | file; there are other possibilities. Having expanded the string, Exim searches | |
25364 | for an ACL as follows: | |
25365 | ||
25366 | * If the string begins with a slash, Exim uses it as a file name, and reads | |
25367 | its contents as an ACL. The lines are processed in the same way as lines in | |
25368 | the Exim configuration file. In particular, continuation lines are | |
25369 | supported, blank lines are ignored, as are lines whose first non-whitespace | |
25370 | character is "#". If the file does not exist or cannot be read, an error | |
25371 | occurs (typically causing a temporary failure of whatever caused the ACL to | |
25372 | be run). For example: | |
25373 | ||
25374 | acl_smtp_data = /etc/acls/\ | |
25375 | ${lookup{$sender_host_address}lsearch\ | |
25376 | {/etc/acllist}{$value}{default}} | |
25377 | ||
25378 | This looks up an ACL file to use on the basis of the host's IP address, | |
25379 | falling back to a default if the lookup fails. If an ACL is successfully | |
25380 | read from a file, it is retained in memory for the duration of the Exim | |
25381 | process, so that it can be re-used without having to re-read the file. | |
25382 | ||
25383 | * If the string does not start with a slash, and does not contain any spaces, | |
25384 | Exim searches the ACL section of the configuration for an ACL whose name | |
25385 | matches the string. | |
25386 | ||
25387 | * If no named ACL is found, or if the string contains spaces, Exim parses the | |
25388 | string as an inline ACL. This can save typing in cases where you just want | |
25389 | to have something like | |
25390 | ||
25391 | acl_smtp_vrfy = accept | |
25392 | ||
25393 | in order to allow free use of the VRFY command. Such a string may contain | |
25394 | newlines; it is processed in the same way as an ACL that is read from a | |
25395 | file. | |
25396 | ||
25397 | ||
25398 | 42.13 ACL return codes | |
25399 | ---------------------- | |
25400 | ||
25401 | Except for the QUIT ACL, which does not affect the SMTP return code (see | |
25402 | section 42.10 above), the result of running an ACL is either "accept" or | |
25403 | "deny", or, if some test cannot be completed (for example, if a database is | |
25404 | down), "defer". These results cause 2xx, 5xx, and 4xx return codes, | |
25405 | respectively, to be used in the SMTP dialogue. A fourth return, "error", occurs | |
25406 | when there is an error such as invalid syntax in the ACL. This also causes a 4 | |
25407 | xx return code. | |
25408 | ||
25409 | For the non-SMTP ACL, "defer" and "error" are treated in the same way as | |
25410 | "deny", because there is no mechanism for passing temporary errors to the | |
25411 | submitters of non-SMTP messages. | |
25412 | ||
25413 | ACLs that are relevant to message reception may also return "discard". This has | |
25414 | the effect of "accept", but causes either the entire message or an individual | |
25415 | recipient address to be discarded. In other words, it is a blackholing | |
25416 | facility. Use it with care. | |
25417 | ||
25418 | If the ACL for MAIL returns "discard", all recipients are discarded, and no ACL | |
25419 | is run for subsequent RCPT commands. The effect of "discard" in a RCPT ACL is | |
25420 | to discard just the one recipient address. If there are no recipients left when | |
25421 | the message's data is received, the DATA ACL is not run. A "discard" return | |
25422 | from the DATA or the non-SMTP ACL discards all the remaining recipients. The | |
25423 | "discard" return is not permitted for the acl_smtp_predata ACL. | |
25424 | ||
25425 | The local_scan() function is always run, even if there are no remaining | |
25426 | recipients; it may create new recipients. | |
25427 | ||
25428 | ||
25429 | 42.14 Unset ACL options | |
25430 | ----------------------- | |
25431 | ||
25432 | The default actions when any of the acl_xxx options are unset are not all the | |
25433 | same. Note: These defaults apply only when the relevant ACL is not defined at | |
25434 | all. For any defined ACL, the default action when control reaches the end of | |
25435 | the ACL statements is "deny". | |
25436 | ||
25437 | For acl_smtp_quit and acl_not_smtp_start there is no default because these two | |
25438 | are ACLs that are used only for their side effects. They cannot be used to | |
25439 | accept or reject anything. | |
25440 | ||
25441 | For acl_not_smtp, acl_smtp_auth, acl_smtp_connect, acl_smtp_data, acl_smtp_helo | |
25442 | , acl_smtp_mail, acl_smtp_mailauth, acl_smtp_mime, acl_smtp_predata, and | |
25443 | acl_smtp_starttls, the action when the ACL is not defined is "accept". | |
25444 | ||
25445 | For the others (acl_smtp_etrn, acl_smtp_expn, acl_smtp_rcpt, and acl_smtp_vrfy | |
25446 | ), the action when the ACL is not defined is "deny". This means that | |
25447 | acl_smtp_rcpt must be defined in order to receive any messages over an SMTP | |
25448 | connection. For an example, see the ACL in the default configuration file. | |
25449 | ||
25450 | ||
25451 | 42.15 Data for message ACLs | |
25452 | --------------------------- | |
25453 | ||
25454 | When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables | |
25455 | that contain information about the host and the message's sender (for example, | |
25456 | $sender_host_address and $sender_address) are set, and can be used in ACL | |
25457 | statements. In the case of RCPT (but not MAIL or DATA), $domain and $local_part | |
25458 | are set from the argument address. The entire SMTP command is available in | |
25459 | $smtp_command. | |
25460 | ||
25461 | When an ACL for the AUTH parameter of MAIL is running, the variables that | |
25462 | contain information about the host are set, but $sender_address is not yet set. | |
25463 | Section 33.2 contains a discussion of this parameter and how it is used. | |
25464 | ||
25465 | The $message_size variable is set to the value of the SIZE parameter on the | |
25466 | MAIL command at MAIL, RCPT and pre-data time, or to -1 if that parameter is not | |
25467 | given. The value is updated to the true message size by the time the final DATA | |
25468 | ACL is run (after the message data has been received). | |
25469 | ||
25470 | The $rcpt_count variable increases by one for each RCPT command received. The | |
25471 | $recipients_count variable increases by one each time a RCPT command is | |
25472 | accepted, so while an ACL for RCPT is being processed, it contains the number | |
25473 | of previously accepted recipients. At DATA time (for both the DATA ACLs), | |
25474 | $rcpt_count contains the total number of RCPT commands, and $recipients_count | |
25475 | contains the total number of accepted recipients. | |
25476 | ||
25477 | ||
25478 | 42.16 Data for non-message ACLs | |
25479 | ------------------------------- | |
25480 | ||
25481 | When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY, | |
25482 | the remainder of the SMTP command line is placed in $smtp_command_argument, and | |
25483 | the entire SMTP command is available in $smtp_command. These variables can be | |
25484 | tested using a condition condition. For example, here is an ACL for use with | |
25485 | AUTH, which insists that either the session is encrypted, or the CRAM-MD5 | |
25486 | authentication method is used. In other words, it does not permit | |
25487 | authentication methods that use cleartext passwords on unencrypted connections. | |
25488 | ||
25489 | acl_check_auth: | |
25490 | accept encrypted = * | |
25491 | accept condition = ${if eq{${uc:$smtp_command_argument}}\ | |
25492 | {CRAM-MD5}} | |
25493 | deny message = TLS encryption or CRAM-MD5 required | |
25494 | ||
25495 | (Another way of applying this restriction is to arrange for the authenticators | |
25496 | that use cleartext passwords not to be advertised when the connection is not | |
25497 | encrypted. You can use the generic server_advertise_condition authenticator | |
25498 | option to do this.) | |
25499 | ||
25500 | ||
25501 | 42.17 Format of an ACL | |
25502 | ---------------------- | |
25503 | ||
25504 | An individual ACL consists of a number of statements. Each statement starts | |
25505 | with a verb, optionally followed by a number of conditions and "modifiers". | |
25506 | Modifiers can change the way the verb operates, define error and log messages, | |
25507 | set variables, insert delays, and vary the processing of accepted messages. | |
25508 | ||
25509 | If all the conditions are met, the verb is obeyed. The same condition may be | |
25510 | used (with different arguments) more than once in the same statement. This | |
25511 | provides a means of specifying an "and" conjunction between conditions. For | |
25512 | example: | |
25513 | ||
25514 | deny dnslists = list1.example | |
25515 | dnslists = list2.example | |
25516 | ||
25517 | If there are no conditions, the verb is always obeyed. Exim stops evaluating | |
25518 | the conditions and modifiers when it reaches a condition that fails. What | |
25519 | happens then depends on the verb (and in one case, on a special modifier). Not | |
25520 | all the conditions make sense at every testing point. For example, you cannot | |
25521 | test a sender address in the ACL that is run for a VRFY command. | |
25522 | ||
25523 | ||
25524 | 42.18 ACL verbs | |
25525 | --------------- | |
25526 | ||
25527 | The ACL verbs are as follows: | |
25528 | ||
25529 | * accept: If all the conditions are met, the ACL returns "accept". If any of | |
25530 | the conditions are not met, what happens depends on whether endpass appears | |
25531 | among the conditions (for syntax see below). If the failing condition is | |
25532 | before endpass, control is passed to the next ACL statement; if it is after | |
25533 | endpass, the ACL returns "deny". Consider this statement, used to check a | |
25534 | RCPT command: | |
25535 | ||
25536 | accept domains = +local_domains | |
25537 | endpass | |
25538 | verify = recipient | |
25539 | ||
25540 | If the recipient domain does not match the domains condition, control | |
25541 | passes to the next statement. If it does match, the recipient is verified, | |
25542 | and the command is accepted if verification succeeds. However, if | |
25543 | verification fails, the ACL yields "deny", because the failing condition is | |
25544 | after endpass. | |
25545 | ||
25546 | The endpass feature has turned out to be confusing to many people, so its | |
25547 | use is not recommended nowadays. It is always possible to rewrite an ACL so | |
25548 | that endpass is not needed, and it is no longer used in the default | |
25549 | configuration. | |
25550 | ||
25551 | If a message modifier appears on an accept statement, its action depends on | |
25552 | whether or not endpass is present. In the absence of endpass (when an | |
25553 | accept verb either accepts or passes control to the next statement), | |
25554 | message can be used to vary the message that is sent when an SMTP command | |
25555 | is accepted. For example, in a RCPT ACL you could have: | |
25556 | ||
25557 | accept <some conditions> | |
25558 | message = OK, I will allow you through today | |
25559 | ||
25560 | You can specify an SMTP response code, optionally followed by an "extended | |
25561 | response code" at the start of the message, but the first digit must be the | |
25562 | same as would be sent by default, which is 2 for an accept verb. | |
25563 | ||
25564 | If endpass is present in an accept statement, message specifies an error | |
25565 | message that is used when access is denied. This behaviour is retained for | |
25566 | backward compatibility, but current "best practice" is to avoid the use of | |
25567 | endpass. | |
25568 | ||
25569 | * defer: If all the conditions are true, the ACL returns "defer" which, in an | |
25570 | SMTP session, causes a 4xx response to be given. For a non-SMTP ACL, defer | |
25571 | is the same as deny, because there is no way of sending a temporary error. | |
25572 | For a RCPT command, defer is much the same as using a redirect router and | |
25573 | ":defer:" while verifying, but the defer verb can be used in any ACL, and | |
25574 | even for a recipient it might be a simpler approach. | |
25575 | ||
25576 | * deny: If all the conditions are met, the ACL returns "deny". If any of the | |
25577 | conditions are not met, control is passed to the next ACL statement. For | |
25578 | example, | |
25579 | ||
25580 | deny dnslists = blackholes.mail-abuse.org | |
25581 | ||
25582 | rejects commands from hosts that are on a DNS black list. | |
25583 | ||
25584 | * discard: This verb behaves like accept, except that it returns "discard" | |
25585 | from the ACL instead of "accept". It is permitted only on ACLs that are | |
25586 | concerned with receiving messages. When all the conditions are true, the | |
25587 | sending entity receives a "success" response. However, discard causes | |
25588 | recipients to be discarded. If it is used in an ACL for RCPT, just the one | |
25589 | recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all | |
25590 | the message's recipients are discarded. Recipients that are discarded | |
25591 | before DATA do not appear in the log line when the received_recipients log | |
25592 | selector is set. | |
25593 | ||
25594 | If the log_message modifier is set when discard operates, its contents are | |
25595 | added to the line that is automatically written to the log. The message | |
25596 | modifier operates exactly as it does for accept. | |
25597 | ||
25598 | * drop: This verb behaves like deny, except that an SMTP connection is | |
25599 | forcibly closed after the 5xx error message has been sent. For example: | |
25600 | ||
25601 | drop message = I don't take more than 20 RCPTs | |
25602 | condition = ${if > {$rcpt_count}{20}} | |
25603 | ||
25604 | There is no difference between deny and drop for the connect-time ACL. The | |
25605 | connection is always dropped after sending a 550 response. | |
25606 | ||
25607 | * require: If all the conditions are met, control is passed to the next ACL | |
25608 | statement. If any of the conditions are not met, the ACL returns "deny". | |
25609 | For example, when checking a RCPT command, | |
25610 | ||
25611 | require message = Sender did not verify | |
25612 | verify = sender | |
25613 | ||
25614 | passes control to subsequent statements only if the message's sender can be | |
25615 | verified. Otherwise, it rejects the command. Note the positioning of the | |
25616 | message modifier, before the verify condition. The reason for this is | |
25617 | discussed in section 42.20. | |
25618 | ||
25619 | * warn: If all the conditions are true, a line specified by the log_message | |
25620 | modifier is written to Exim's main log. Control always passes to the next | |
25621 | ACL statement. If any condition is false, the log line is not written. If | |
25622 | an identical log line is requested several times in the same message, only | |
25623 | one copy is actually written to the log. If you want to force duplicates to | |
25624 | be written, use the logwrite modifier instead. | |
25625 | ||
25626 | If log_message is not present, a warn verb just checks its conditions and | |
25627 | obeys any "immediate" modifiers (such as control, set, logwrite, add_header | |
25628 | , and remove_header) that appear before the first failing condition. There | |
25629 | is more about adding header lines in section 42.24. | |
25630 | ||
25631 | If any condition on a warn statement cannot be completed (that is, there is | |
25632 | some sort of defer), the log line specified by log_message is not written. | |
25633 | This does not include the case of a forced failure from a lookup, which is | |
25634 | considered to be a successful completion. After a defer, no further | |
25635 | conditions or modifiers in the warn statement are processed. The incident | |
25636 | is logged, and the ACL continues to be processed, from the next statement | |
25637 | onwards. | |
25638 | ||
25639 | When one of the warn conditions is an address verification that fails, the | |
25640 | text of the verification failure message is in $acl_verify_message. If you | |
25641 | want this logged, you must set it up explicitly. For example: | |
25642 | ||
25643 | warn !verify = sender | |
25644 | log_message = sender verify failed: $acl_verify_message | |
25645 | ||
25646 | At the end of each ACL there is an implicit unconditional deny. | |
25647 | ||
25648 | As you can see from the examples above, the conditions and modifiers are | |
25649 | written one to a line, with the first one on the same line as the verb, and | |
25650 | subsequent ones on following lines. If you have a very long condition, you can | |
25651 | continue it onto several physical lines by the usual backslash continuation | |
25652 | mechanism. It is conventional to align the conditions vertically. | |
25653 | ||
25654 | ||
25655 | 42.19 ACL variables | |
25656 | ------------------- | |
25657 | ||
25658 | There are some special variables that can be set during ACL processing. They | |
25659 | can be used to pass information between different ACLs, different invocations | |
25660 | of the same ACL in the same SMTP connection, and between ACLs and the routers, | |
25661 | transports, and filters that are used to deliver a message. The names of these | |
25662 | variables must begin with $acl_c or $acl_m, followed either by a digit or an | |
25663 | underscore, but the remainder of the name can be any sequence of alphanumeric | |
25664 | characters and underscores that you choose. There is no limit on the number of | |
25665 | ACL variables. The two sets act as follows: | |
25666 | ||
25667 | * The values of those variables whose names begin with $acl_c persist | |
25668 | throughout an SMTP connection. They are never reset. Thus, a value that is | |
25669 | set while receiving one message is still available when receiving the next | |
25670 | message on the same SMTP connection. | |
25671 | ||
25672 | * The values of those variables whose names begin with $acl_m persist only | |
25673 | while a message is being received. They are reset afterwards. They are also | |
25674 | reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session. | |
25675 | ||
25676 | When a message is accepted, the current values of all the ACL variables are | |
25677 | preserved with the message and are subsequently made available at delivery | |
25678 | time. The ACL variables are set by a modifier called set. For example: | |
25679 | ||
25680 | accept hosts = whatever | |
25681 | set acl_m4 = some value | |
25682 | accept authenticated = * | |
25683 | set acl_c_auth = yes | |
25684 | ||
25685 | Note: A leading dollar sign is not used when naming a variable that is to be | |
25686 | set. If you want to set a variable without taking any action, you can use a | |
25687 | warn verb without any other modifiers or conditions. | |
25688 | ||
25689 | What happens if a syntactically valid but undefined ACL variable is referenced | |
25690 | depends on the setting of the strict_acl_vars option. If it is false (the | |
25691 | default), an empty string is substituted; if it is true, an error is generated. | |
25692 | ||
25693 | Versions of Exim before 4.64 have a limited set of numbered variables, but | |
25694 | their names are compatible, so there is no problem with upgrading. | |
25695 | ||
25696 | ||
25697 | 42.20 Condition and modifier processing | |
25698 | --------------------------------------- | |
25699 | ||
25700 | An exclamation mark preceding a condition negates its result. For example: | |
25701 | ||
25702 | deny domains = *.dom.example | |
25703 | !verify = recipient | |
25704 | ||
25705 | causes the ACL to return "deny" if the recipient domain ends in dom.example and | |
25706 | the recipient address cannot be verified. Sometimes negation can be used on the | |
25707 | right-hand side of a condition. For example, these two statements are | |
25708 | equivalent: | |
25709 | ||
25710 | deny hosts = !192.168.3.4 | |
25711 | deny !hosts = 192.168.3.4 | |
25712 | ||
25713 | However, for many conditions (verify being a good example), only left-hand side | |
25714 | negation of the whole condition is possible. | |
25715 | ||
25716 | The arguments of conditions and modifiers are expanded. A forced failure of an | |
25717 | expansion causes a condition to be ignored, that is, it behaves as if the | |
25718 | condition is true. Consider these two statements: | |
25719 | ||
25720 | accept senders = ${lookup{$host_name}lsearch\ | |
25721 | {/some/file}{$value}fail} | |
25722 | accept senders = ${lookup{$host_name}lsearch\ | |
25723 | {/some/file}{$value}{}} | |
25724 | ||
25725 | Each attempts to look up a list of acceptable senders. If the lookup succeeds, | |
25726 | the returned list is searched, but if the lookup fails the behaviour is | |
25727 | different in the two cases. The fail in the first statement causes the | |
25728 | condition to be ignored, leaving no further conditions. The accept verb | |
25729 | therefore succeeds. The second statement, however, generates an empty list when | |
25730 | the lookup fails. No sender can match an empty list, so the condition fails, | |
25731 | and therefore the accept also fails. | |
25732 | ||
25733 | ACL modifiers appear mixed in with conditions in ACL statements. Some of them | |
25734 | specify actions that are taken as the conditions for a statement are checked; | |
25735 | others specify text for messages that are used when access is denied or a | |
25736 | warning is generated. The control modifier affects the way an incoming message | |
25737 | is handled. | |
25738 | ||
25739 | The positioning of the modifiers in an ACL statement is important, because the | |
25740 | processing of a verb ceases as soon as its outcome is known. Only those | |
25741 | modifiers that have already been encountered will take effect. For example, | |
25742 | consider this use of the message modifier: | |
25743 | ||
25744 | require message = Can't verify sender | |
25745 | verify = sender | |
25746 | message = Can't verify recipient | |
25747 | verify = recipient | |
25748 | message = This message cannot be used | |
25749 | ||
25750 | If sender verification fails, Exim knows that the result of the statement is | |
25751 | "deny", so it goes no further. The first message modifier has been seen, so its | |
25752 | text is used as the error message. If sender verification succeeds, but | |
25753 | recipient verification fails, the second message is used. If recipient | |
25754 | verification succeeds, the third message becomes "current", but is never used | |
25755 | because there are no more conditions to cause failure. | |
25756 | ||
25757 | For the deny verb, on the other hand, it is always the last message modifier | |
25758 | that is used, because all the conditions must be true for rejection to happen. | |
25759 | Specifying more than one message modifier does not make sense, and the message | |
25760 | can even be specified after all the conditions. For example: | |
25761 | ||
25762 | deny hosts = ... | |
25763 | !senders = *@my.domain.example | |
25764 | message = Invalid sender from client host | |
25765 | ||
25766 | The "deny" result does not happen until the end of the statement is reached, by | |
25767 | which time Exim has set up the message. | |
25768 | ||
25769 | ||
25770 | 42.21 ACL modifiers | |
25771 | ------------------- | |
25772 | ||
25773 | The ACL modifiers are as follows: | |
25774 | ||
25775 | add_header = <text> | |
25776 | ||
25777 | This modifier specifies one or more header lines that are to be added to an | |
25778 | incoming message, assuming, of course, that the message is ultimately | |
25779 | accepted. For details, see section 42.24. | |
25780 | ||
25781 | continue = <text> | |
25782 | ||
25783 | This modifier does nothing of itself, and processing of the ACL always | |
25784 | continues with the next condition or modifier. The value of continue is in | |
25785 | the side effects of expanding its argument. Typically this could be used to | |
25786 | update a database. It is really just a syntactic tidiness, to avoid having | |
25787 | to write rather ugly lines like this: | |
25788 | ||
25789 | condition = ${if eq{0}{<some expansion>}{true}{true}} | |
25790 | ||
25791 | Instead, all you need is | |
25792 | ||
25793 | continue = <some expansion> | |
25794 | ||
25795 | control = <text> | |
25796 | ||
25797 | This modifier affects the subsequent processing of the SMTP connection or | |
25798 | of an incoming message that is accepted. The effect of the first type of | |
25799 | control lasts for the duration of the connection, whereas the effect of the | |
25800 | second type lasts only until the current message has been received. The | |
25801 | message-specific controls always apply to the whole message, not to | |
25802 | individual recipients, even if the control modifier appears in a RCPT ACL. | |
25803 | ||
25804 | As there are now quite a few controls that can be applied, they are | |
25805 | described separately in section 42.22. The control modifier can be used in | |
25806 | several different ways. For example: | |
25807 | ||
25808 | * It can be at the end of an accept statement: | |
25809 | ||
25810 | accept ...some conditions | |
25811 | control = queue_only | |
25812 | ||
25813 | In this case, the control is applied when this statement yields | |
25814 | "accept", in other words, when the conditions are all true. | |
25815 | ||
25816 | * It can be in the middle of an accept statement: | |
25817 | ||
25818 | accept ...some conditions... | |
25819 | control = queue_only | |
25820 | ...some more conditions... | |
25821 | ||
25822 | If the first set of conditions are true, the control is applied, even | |
25823 | if the statement does not accept because one of the second set of | |
25824 | conditions is false. In this case, some subsequent statement must yield | |
25825 | "accept" for the control to be relevant. | |
25826 | ||
25827 | * It can be used with warn to apply the control, leaving the decision | |
25828 | about accepting or denying to a subsequent verb. For example: | |
25829 | ||
25830 | warn ...some conditions... | |
25831 | control = freeze | |
25832 | accept ... | |
25833 | ||
25834 | This example of warn does not contain message, log_message, or logwrite | |
25835 | , so it does not add anything to the message and does not write a log | |
25836 | entry. | |
25837 | ||
25838 | * If you want to apply a control unconditionally, you can use it with a | |
25839 | require verb. For example: | |
25840 | ||
25841 | require control = no_multiline_responses | |
25842 | ||
25843 | delay = <time> | |
25844 | ||
25845 | This modifier may appear in any ACL except notquit. It causes Exim to wait | |
25846 | for the time interval before proceeding. However, when testing Exim using | |
25847 | the -bh option, the delay is not actually imposed (an appropriate message | |
25848 | is output instead). The time is given in the usual Exim notation, and the | |
25849 | delay happens as soon as the modifier is processed. In an SMTP session, | |
25850 | pending output is flushed before the delay is imposed. | |
25851 | ||
25852 | Like control, delay can be used with accept or deny, for example: | |
25853 | ||
25854 | deny ...some conditions... | |
25855 | delay = 30s | |
25856 | ||
25857 | The delay happens if all the conditions are true, before the statement | |
25858 | returns "deny". Compare this with: | |
25859 | ||
25860 | deny delay = 30s | |
25861 | ...some conditions... | |
25862 | ||
25863 | which waits for 30s before processing the conditions. The delay modifier | |
25864 | can also be used with warn and together with control: | |
25865 | ||
25866 | warn ...some conditions... | |
25867 | delay = 2m | |
25868 | control = freeze | |
25869 | accept ... | |
25870 | ||
25871 | If delay is encountered when the SMTP PIPELINING extension is in use, | |
25872 | responses to several commands are no longer buffered and sent in one packet | |
25873 | (as they would normally be) because all output is flushed before imposing | |
25874 | the delay. This optimization is disabled so that a number of small delays | |
25875 | do not appear to the client as one large aggregated delay that might | |
25876 | provoke an unwanted timeout. You can, however, disable output flushing for | |
25877 | delay by using a control modifier to set no_delay_flush. | |
25878 | ||
25879 | endpass | |
25880 | ||
25881 | This modifier, which has no argument, is recognized only in accept and | |
25882 | discard statements. It marks the boundary between the conditions whose | |
25883 | failure causes control to pass to the next statement, and the conditions | |
25884 | whose failure causes the ACL to return "deny". This concept has proved to | |
25885 | be confusing to some people, so the use of endpass is no longer recommended | |
25886 | as "best practice". See the description of accept above for more details. | |
25887 | ||
25888 | log_message = <text> | |
25889 | ||
25890 | This modifier sets up a message that is used as part of the log message if | |
25891 | the ACL denies access or a warn statement's conditions are true. For | |
25892 | example: | |
25893 | ||
25894 | require log_message = wrong cipher suite $tls_in_cipher | |
25895 | encrypted = DES-CBC3-SHA | |
25896 | ||
25897 | log_message is also used when recipients are discarded by discard. For | |
25898 | example: | |
25899 | ||
25900 | discard <some conditions> | |
25901 | log_message = Discarded $local_part@$domain because... | |
25902 | ||
25903 | When access is denied, log_message adds to any underlying error message | |
25904 | that may exist because of a condition failure. For example, while verifying | |
25905 | a recipient address, a :fail: redirection might have already set up a | |
25906 | message. | |
25907 | ||
25908 | The message may be defined before the conditions to which it applies, | |
25909 | because the string expansion does not happen until Exim decides that access | |
25910 | is to be denied. This means that any variables that are set by the | |
25911 | condition are available for inclusion in the message. For example, the | |
25912 | $dnslist_<xxx> variables are set after a DNS black list lookup succeeds. If | |
25913 | the expansion of log_message fails, or if the result is an empty string, | |
25914 | the modifier is ignored. | |
25915 | ||
25916 | If you want to use a warn statement to log the result of an address | |
25917 | verification, you can use $acl_verify_message to include the verification | |
25918 | error message. | |
25919 | ||
25920 | If log_message is used with a warn statement, "Warning:" is added to the | |
25921 | start of the logged message. If the same warning log message is requested | |
25922 | more than once while receiving a single email message, only one copy is | |
25923 | actually logged. If you want to log multiple copies, use logwrite instead | |
25924 | of log_message. In the absence of log_message and logwrite, nothing is | |
25925 | logged for a successful warn statement. | |
25926 | ||
25927 | If log_message is not present and there is no underlying error message (for | |
25928 | example, from the failure of address verification), but message is present, | |
25929 | the message text is used for logging rejections. However, if any text for | |
25930 | logging contains newlines, only the first line is logged. In the absence of | |
25931 | both log_message and message, a default built-in message is used for | |
25932 | logging rejections. | |
25933 | ||
25934 | log_reject_target = <log name list> | |
25935 | ||
25936 | This modifier makes it possible to specify which logs are used for messages | |
25937 | about ACL rejections. Its argument is a colon-separated list of words that | |
25938 | can be "main", "reject", or "panic". The default is "main:reject". The list | |
25939 | may be empty, in which case a rejection is not logged at all. For example, | |
25940 | this ACL fragment writes no logging information when access is denied: | |
25941 | ||
25942 | deny <some conditions> | |
25943 | log_reject_target = | |
25944 | ||
25945 | This modifier can be used in SMTP and non-SMTP ACLs. It applies to both | |
25946 | permanent and temporary rejections. Its effect lasts for the rest of the | |
25947 | current ACL. | |
25948 | ||
25949 | logwrite = <text> | |
25950 | ||
25951 | This modifier writes a message to a log file as soon as it is encountered | |
25952 | when processing an ACL. (Compare log_message, which, except in the case of | |
25953 | warn and discard, is used only if the ACL statement denies access.) The | |
25954 | logwrite modifier can be used to log special incidents in ACLs. For | |
25955 | example: | |
25956 | ||
25957 | accept <some special conditions> | |
25958 | control = freeze | |
25959 | logwrite = froze message because ... | |
25960 | ||
25961 | By default, the message is written to the main log. However, it may begin | |
25962 | with a colon, followed by a comma-separated list of log names, and then | |
25963 | another colon, to specify exactly which logs are to be written. For | |
25964 | example: | |
25965 | ||
25966 | logwrite = :main,reject: text for main and reject logs | |
25967 | logwrite = :panic: text for panic log only | |
25968 | ||
25969 | message = <text> | |
25970 | ||
25971 | This modifier sets up a text string that is expanded and used as a response | |
25972 | message when an ACL statement terminates the ACL with an "accept", "deny", | |
25973 | or "defer" response. (In the case of the accept and discard verbs, there is | |
25974 | some complication if endpass is involved; see the description of accept for | |
25975 | details.) | |
25976 | ||
25977 | The expansion of the message happens at the time Exim decides that the ACL | |
25978 | is to end, not at the time it processes message. If the expansion fails, or | |
25979 | generates an empty string, the modifier is ignored. Here is an example | |
25980 | where message must be specified first, because the ACL ends with a | |
25981 | rejection if the hosts condition fails: | |
25982 | ||
25983 | require message = Host not recognized | |
25984 | hosts = 10.0.0.0/8 | |
25985 | ||
25986 | (Once a condition has failed, no further conditions or modifiers are | |
25987 | processed.) | |
25988 | ||
25989 | For ACLs that are triggered by SMTP commands, the message is returned as | |
25990 | part of the SMTP response. The use of message with accept (or discard) is | |
25991 | meaningful only for SMTP, as no message is returned when a non-SMTP message | |
25992 | is accepted. In the case of the connect ACL, accepting with a message | |
25993 | modifier overrides the value of smtp_banner. For the EHLO/HELO ACL, a | |
25994 | customized accept message may not contain more than one line (otherwise it | |
25995 | will be truncated at the first newline and a panic logged), and it cannot | |
25996 | affect the EHLO options. | |
25997 | ||
25998 | When SMTP is involved, the message may begin with an overriding response | |
25999 | code, consisting of three digits optionally followed by an "extended | |
26000 | response code" of the form n.n.n, each code being followed by a space. For | |
26001 | example: | |
26002 | ||
26003 | deny message = 599 1.2.3 Host not welcome | |
26004 | hosts = 192.168.34.0/24 | |
26005 | ||
26006 | The first digit of the supplied response code must be the same as would be | |
26007 | sent by default. A panic occurs if it is not. Exim uses a 550 code when it | |
26008 | denies access, but for the predata ACL, note that the default success code | |
26009 | is 354, not 2xx. | |
26010 | ||
26011 | Notwithstanding the previous paragraph, for the QUIT ACL, unlike the | |
26012 | others, the message modifier cannot override the 221 response code. | |
26013 | ||
26014 | The text in a message modifier is literal; any quotes are taken as | |
26015 | literals, but because the string is expanded, backslash escapes are | |
26016 | processed anyway. If the message contains newlines, this gives rise to a | |
26017 | multi-line SMTP response. | |
26018 | ||
26019 | If message is used on a statement that verifies an address, the message | |
26020 | specified overrides any message that is generated by the verification | |
26021 | process. However, the original message is available in the variable | |
26022 | $acl_verify_message, so you can incorporate it into your message if you | |
26023 | wish. In particular, if you want the text from :fail: items in redirect | |
26024 | routers to be passed back as part of the SMTP response, you should either | |
26025 | not use a message modifier, or make use of $acl_verify_message. | |
26026 | ||
26027 | For compatibility with previous releases of Exim, a message modifier that | |
26028 | is used with a warn verb behaves in a similar way to the add_header | |
26029 | modifier, but this usage is now deprecated. However, message acts only when | |
26030 | all the conditions are true, wherever it appears in an ACL command, whereas | |
26031 | add_header acts as soon as it is encountered. If message is used with warn | |
26032 | in an ACL that is not concerned with receiving a message, it has no effect. | |
26033 | ||
26034 | remove_header = <text> | |
26035 | ||
26036 | This modifier specifies one or more header names in a colon-separated list | |
26037 | that are to be removed from an incoming message, assuming, of course, that | |
26038 | the message is ultimately accepted. For details, see section 42.25. | |
26039 | ||
26040 | set <acl_name> = <value> | |
26041 | ||
26042 | This modifier puts a value into one of the ACL variables (see section 42.19 | |
26043 | ). | |
26044 | ||
26045 | udpsend = <parameters> | |
26046 | ||
26047 | This modifier sends a UDP packet, for purposes such as statistics | |
26048 | collection or behaviour monitoring. The parameters are expanded, and the | |
26049 | result of the expansion must be a colon-separated list consisting of a | |
26050 | destination server, port number, and the packet contents. The server can be | |
26051 | specified as a host name or IPv4 or IPv6 address. The separator can be | |
26052 | changed with the usual angle bracket syntax. For example, you might want to | |
26053 | collect information on which hosts connect when: | |
26054 | ||
26055 | udpsend = <; 2001:dB8::dead:beef ; 1234 ;\ | |
26056 | $tod_zulu $sender_host_address | |
26057 | ||
26058 | ||
26059 | 42.22 Use of the control modifier | |
26060 | --------------------------------- | |
26061 | ||
26062 | The control modifier supports the following settings: | |
26063 | ||
26064 | control = allow_auth_unadvertised | |
26065 | ||
26066 | This modifier allows a client host to use the SMTP AUTH command even when | |
26067 | it has not been advertised in response to EHLO. Furthermore, because there | |
26068 | are apparently some really broken clients that do this, Exim will accept | |
26069 | AUTH after HELO (rather than EHLO) when this control is set. It should be | |
26070 | used only if you really need it, and you should limit its use to those | |
26071 | broken clients that do not work without it. For example: | |
26072 | ||
26073 | warn hosts = 192.168.34.25 | |
26074 | control = allow_auth_unadvertised | |
26075 | ||
26076 | Normally, when an Exim server receives an AUTH command, it checks the name | |
26077 | of the authentication mechanism that is given in the command to ensure that | |
26078 | it matches an advertised mechanism. When this control is set, the check | |
26079 | that a mechanism has been advertised is bypassed. Any configured mechanism | |
26080 | can be used by the client. This control is permitted only in the connection | |
26081 | and HELO ACLs. | |
26082 | ||
26083 | control = caseful_local_part, control = caselower_local_part | |
26084 | ||
26085 | These two controls are permitted only in the ACL specified by acl_smtp_rcpt | |
26086 | (that is, during RCPT processing). By default, the contents of $local_part | |
26087 | are lower cased before ACL processing. If "caseful_local_part" is | |
26088 | specified, any uppercase letters in the original local part are restored in | |
26089 | $local_part for the rest of the ACL, or until a control that sets | |
26090 | "caselower_local_part" is encountered. | |
26091 | ||
26092 | These controls affect only the current recipient. Moreover, they apply only | |
26093 | to local part handling that takes place directly in the ACL (for example, | |
26094 | as a key in lookups). If a test to verify the recipient is obeyed, the | |
26095 | case-related handling of the local part during the verification is | |
26096 | controlled by the router configuration (see the caseful_local_part generic | |
26097 | router option). | |
26098 | ||
26099 | This facility could be used, for example, to add a spam score to local | |
26100 | parts containing upper case letters. For example, using $acl_m4 to | |
26101 | accumulate the spam score: | |
26102 | ||
26103 | warn control = caseful_local_part | |
26104 | set acl_m4 = ${eval:\ | |
26105 | $acl_m4 + \ | |
26106 | ${if match{$local_part}{[A-Z]}{1}{0}}\ | |
26107 | } | |
26108 | control = caselower_local_part | |
26109 | ||
26110 | Notice that we put back the lower cased version afterwards, assuming that | |
26111 | is what is wanted for subsequent tests. | |
26112 | ||
26113 | control = cutthrough_delivery | |
26114 | ||
26115 | This option requests delivery be attempted while the item is being | |
26116 | received. It is usable in the RCPT ACL and valid only for single-recipient | |
26117 | mails forwarded from one SMTP connection to another. If a recipient-verify | |
26118 | callout connection is requested in the same ACL it is held open and used | |
26119 | for the data, otherwise one is made after the ACL completes. | |
26120 | ||
26121 | Note that routers are used in verify mode, and cannot depend on content of | |
26122 | received headers. Note also that headers cannot be modified by any of the | |
26123 | post-data ACLs (DATA, MIME and DKIM). Headers may be modified by routers | |
26124 | (subject to the above) and transports. | |
26125 | ||
26126 | Cutthrough delivery is not supported via transport-filters or when DKIM | |
26127 | signing of outgoing messages is done, because it sends data to the ultimate | |
26128 | destination before the entire message has been received from the source. | |
26129 | ||
26130 | Should the ultimate destination system positively accept or reject the | |
26131 | mail, a corresponding indication is given to the source system and nothing | |
26132 | is queued. If there is a temporary error the item is queued for later | |
26133 | delivery in the usual fashion. If the item is successfully delivered in | |
26134 | cutthrough mode the log line is tagged with ">>" rather than "=>" and | |
26135 | appears before the acceptance "<=" line. | |
26136 | ||
26137 | Delivery in this mode avoids the generation of a bounce mail to a (possibly | |
26138 | faked) sender when the destination system is doing content-scan based | |
26139 | rejection. | |
26140 | ||
26141 | control = debug/<options> | |
26142 | ||
26143 | This control turns on debug logging, almost as though Exim had been invoked | |
26144 | with "-d", with the output going to a new logfile, by default called | |
26145 | debuglog. The filename can be adjusted with the tag option, which may | |
26146 | access any variables already defined. The logging may be adjusted with the | |
26147 | opts option, which takes the same values as the "-d" command-line option. | |
26148 | Some examples (which depend on variables that don't exist in all contexts): | |
26149 | ||
26150 | control = debug | |
26151 | control = debug/tag=.$sender_host_address | |
26152 | control = debug/opts=+expand+acl | |
26153 | control = debug/tag=.$message_exim_id/opts=+expand | |
26154 | ||
26155 | control = dkim_disable_verify | |
26156 | ||
26157 | This control turns off DKIM verification processing entirely. For details | |
26158 | on the operation and configuration of DKIM, see chapter 56. | |
26159 | ||
26160 | control = dscp/<value> | |
26161 | ||
26162 | This option causes the DSCP value associated with the socket for the | |
26163 | inbound connection to be adjusted to a given value, given as one of a | |
26164 | number of fixed strings or to numeric value. The -bI:dscp option may be | |
26165 | used to ask Exim which names it knows of. Common values include | |
26166 | "throughput", "mincost", and on newer systems "ef", "af41", etc. Numeric | |
26167 | values may be in the range 0 to 0x3F. | |
26168 | ||
26169 | The outbound packets from Exim will be marked with this value in the header | |
26170 | (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no | |
26171 | guarantee that these values will have any effect, not be stripped by | |
26172 | networking equipment, or do much of anything without cooperation with your | |
26173 | Network Engineer and those of all network operators between the source and | |
26174 | destination. | |
26175 | ||
26176 | control = enforce_sync, control = no_enforce_sync | |
26177 | ||
26178 | These controls make it possible to be selective about when SMTP | |
26179 | synchronization is enforced. The global option smtp_enforce_sync specifies | |
26180 | the initial state of the switch (it is true by default). See the | |
26181 | description of this option in chapter 14 for details of SMTP | |
26182 | synchronization checking. | |
26183 | ||
26184 | The effect of these two controls lasts for the remainder of the SMTP | |
26185 | connection. They can appear in any ACL except the one for the non-SMTP | |
26186 | messages. The most straightforward place to put them is in the ACL defined | |
26187 | by acl_smtp_connect, which is run at the start of an incoming SMTP | |
26188 | connection, before the first synchronization check. The expected use is to | |
26189 | turn off the synchronization checks for badly-behaved hosts that you | |
26190 | nevertheless need to work with. | |
26191 | ||
26192 | control = fakedefer/<message> | |
26193 | ||
26194 | This control works in exactly the same way as fakereject (described below) | |
26195 | except that it causes an SMTP 450 response after the message data instead | |
26196 | of a 550 response. You must take care when using fakedefer because it | |
26197 | causes the messages to be duplicated when the sender retries. Therefore, | |
26198 | you should not use fakedefer if the message is to be delivered normally. | |
26199 | ||
26200 | control = fakereject/<message> | |
26201 | ||
26202 | This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other | |
26203 | words, only when an SMTP message is being received. If Exim accepts the | |
26204 | message, instead the final 250 response, a 550 rejection message is sent. | |
26205 | However, Exim proceeds to deliver the message as normal. The control | |
26206 | applies only to the current message, not to any subsequent ones that may be | |
26207 | received in the same SMTP connection. | |
26208 | ||
26209 | The text for the 550 response is taken from the control modifier. If no | |
26210 | message is supplied, the following is used: | |
26211 | ||
26212 | 550-Your message has been rejected but is being | |
26213 | 550-kept for evaluation. | |
26214 | 550-If it was a legitimate message, it may still be | |
26215 | 550 delivered to the target recipient(s). | |
26216 | ||
26217 | This facility should be used with extreme caution. | |
26218 | ||
26219 | control = freeze | |
26220 | ||
26221 | This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, | |
26222 | in other words, only when a message is being received. If the message is | |
26223 | accepted, it is placed on Exim's queue and frozen. The control applies only | |
26224 | to the current message, not to any subsequent ones that may be received in | |
26225 | the same SMTP connection. | |
26226 | ||
26227 | This modifier can optionally be followed by "/no_tell". If the global | |
26228 | option freeze_tell is set, it is ignored for the current message (that is, | |
26229 | nobody is told about the freezing), provided all the control=freeze | |
26230 | modifiers that are obeyed for the current message have the "/no_tell" | |
26231 | option. | |
26232 | ||
26233 | control = no_delay_flush | |
26234 | ||
26235 | Exim normally flushes SMTP output before implementing a delay in an ACL, to | |
26236 | avoid unexpected timeouts in clients when the SMTP PIPELINING extension is | |
26237 | in use. This control, as long as it is encountered before the delay | |
26238 | modifier, disables such output flushing. | |
26239 | ||
26240 | control = no_callout_flush | |
26241 | ||
26242 | Exim normally flushes SMTP output before performing a callout in an ACL, to | |
26243 | avoid unexpected timeouts in clients when the SMTP PIPELINING extension is | |
26244 | in use. This control, as long as it is encountered before the verify | |
26245 | condition that causes the callout, disables such output flushing. | |
26246 | ||
26247 | control = no_mbox_unspool | |
26248 | ||
26249 | This control is available when Exim is compiled with the content scanning | |
26250 | extension. Content scanning may require a copy of the current message, or | |
26251 | parts of it, to be written in "mbox format" to a spool file, for passing to | |
26252 | a virus or spam scanner. Normally, such copies are deleted when they are no | |
26253 | longer needed. If this control is set, the copies are not deleted. The | |
26254 | control applies only to the current message, not to any subsequent ones | |
26255 | that may be received in the same SMTP connection. It is provided for | |
26256 | debugging purposes and is unlikely to be useful in production. | |
26257 | ||
26258 | control = no_multiline_responses | |
26259 | ||
26260 | This control is permitted for any ACL except the one for non-SMTP messages. | |
26261 | It seems that there are broken clients in use that cannot handle multiline | |
26262 | SMTP responses, despite the fact that RFC 821 defined them over 20 years | |
26263 | ago. | |
26264 | ||
26265 | If this control is set, multiline SMTP responses from ACL rejections are | |
26266 | suppressed. One way of doing this would have been to put out these | |
26267 | responses as one long line. However, RFC 2821 specifies a maximum of 512 | |
26268 | bytes per response ("use multiline responses for more" it says - ha!), and | |
26269 | some of the responses might get close to that. So this facility, which is | |
26270 | after all only a sop to broken clients, is implemented by doing two very | |
26271 | easy things: | |
26272 | ||
26273 | * Extra information that is normally output as part of a rejection caused | |
26274 | by sender verification failure is omitted. Only the final line | |
26275 | (typically "sender verification failed") is sent. | |
26276 | ||
26277 | * If a message modifier supplies a multiline response, only the first | |
26278 | line is output. | |
26279 | ||
26280 | The setting of the switch can, of course, be made conditional on the | |
26281 | calling host. Its effect lasts until the end of the SMTP connection. | |
26282 | ||
26283 | control = no_pipelining | |
26284 | ||
26285 | This control turns off the advertising of the PIPELINING extension to SMTP | |
26286 | in the current session. To be useful, it must be obeyed before Exim sends | |
26287 | its response to an EHLO command. Therefore, it should normally appear in an | |
26288 | ACL controlled by acl_smtp_connect or acl_smtp_helo. See also | |
26289 | pipelining_advertise_hosts. | |
26290 | ||
26291 | control = queue_only | |
26292 | ||
26293 | This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, | |
26294 | in other words, only when a message is being received. If the message is | |
26295 | accepted, it is placed on Exim's queue and left there for delivery by a | |
26296 | subsequent queue runner. No immediate delivery process is started. In other | |
26297 | words, it has the effect as the queue_only global option. However, the | |
26298 | control applies only to the current message, not to any subsequent ones | |
26299 | that may be received in the same SMTP connection. | |
26300 | ||
26301 | control = submission/<options> | |
26302 | ||
26303 | This control is permitted only for the MAIL, RCPT, and start of data ACLs | |
26304 | (the latter is the one defined by acl_smtp_predata). Setting it tells Exim | |
26305 | that the current message is a submission from a local MUA. In this case, | |
26306 | Exim operates in "submission mode", and applies certain fixups to the | |
26307 | message if necessary. For example, it adds a Date: header line if one is | |
26308 | not present. This control is not permitted in the acl_smtp_data ACL, | |
26309 | because that is too late (the message has already been created). | |
26310 | ||
26311 | Chapter 46 describes the processing that Exim applies to messages. Section | |
26312 | 46.1 covers the processing that happens in submission mode; the available | |
26313 | options for this control are described there. The control applies only to | |
26314 | the current message, not to any subsequent ones that may be received in the | |
26315 | same SMTP connection. | |
26316 | ||
26317 | control = suppress_local_fixups | |
26318 | ||
26319 | This control applies to locally submitted (non TCP/IP) messages, and is the | |
26320 | complement of "control = submission". It disables the fixups that are | |
26321 | normally applied to locally-submitted messages. Specifically: | |
26322 | ||
26323 | * Any Sender: header line is left alone (in this respect, it is a dynamic | |
26324 | version of local_sender_retain). | |
26325 | ||
26326 | * No Message-ID:, From:, or Date: header lines are added. | |
26327 | ||
26328 | * There is no check that From: corresponds to the actual sender. | |
26329 | ||
26330 | This control may be useful when a remotely-originated message is accepted, | |
26331 | passed to some scanning program, and then re-submitted for delivery. It can | |
26332 | be used only in the acl_smtp_mail, acl_smtp_rcpt, acl_smtp_predata, and | |
26333 | acl_not_smtp_start ACLs, because it has to be set before the message's data | |
26334 | is read. | |
26335 | ||
26336 | Note: This control applies only to the current message, not to any others | |
26337 | that are being submitted at the same time using -bs or -bS. | |
26338 | ||
26339 | ||
26340 | 42.23 Summary of message fixup control | |
26341 | -------------------------------------- | |
26342 | ||
26343 | All four possibilities for message fixups can be specified: | |
26344 | ||
26345 | * Locally submitted, fixups applied: the default. | |
26346 | ||
26347 | * Locally submitted, no fixups applied: use "control = | |
26348 | suppress_local_fixups". | |
26349 | ||
26350 | * Remotely submitted, no fixups applied: the default. | |
26351 | ||
26352 | * Remotely submitted, fixups applied: use "control = submission". | |
26353 | ||
26354 | ||
26355 | 42.24 Adding header lines in ACLs | |
26356 | --------------------------------- | |
26357 | ||
26358 | The add_header modifier can be used to add one or more extra header lines to an | |
26359 | incoming message, as in this example: | |
26360 | ||
26361 | warn dnslists = sbl.spamhaus.org : \ | |
26362 | dialup.mail-abuse.org | |
26363 | add_header = X-blacklisted-at: $dnslist_domain | |
26364 | ||
26365 | The add_header modifier is permitted in the MAIL, RCPT, PREDATA, DATA, MIME, | |
26366 | DKIM, and non-SMTP ACLs (in other words, those that are concerned with | |
26367 | receiving a message). The message must ultimately be accepted for add_header to | |
26368 | have any significant effect. You can use add_header with any ACL verb, | |
26369 | including deny (though this is potentially useful only in a RCPT ACL). | |
26370 | ||
26371 | Headers will not be added to the message if the modifier is used in DATA, MIME | |
26372 | or DKIM ACLs for messages delivered by cutthrough routing. | |
26373 | ||
26374 | Leading and trailing newlines are removed from the data for the add_header | |
26375 | modifier; if it then contains one or more newlines that are not followed by a | |
26376 | space or a tab, it is assumed to contain multiple header lines. Each one is | |
26377 | checked for valid syntax; "X-ACL-Warn:" is added to the front of any line that | |
26378 | is not a valid header line. | |
26379 | ||
26380 | Added header lines are accumulated during the MAIL, RCPT, and predata ACLs. | |
26381 | They are added to the message before processing the DATA and MIME ACLs. | |
26382 | However, if an identical header line is requested more than once, only one copy | |
26383 | is actually added to the message. Further header lines may be accumulated | |
26384 | during the DATA and MIME ACLs, after which they are added to the message, again | |
26385 | with duplicates suppressed. Thus, it is possible to add two identical header | |
26386 | lines to an SMTP message, but only if one is added before DATA and one after. | |
26387 | In the case of non-SMTP messages, new headers are accumulated during the | |
26388 | non-SMTP ACLs, and are added to the message after all the ACLs have run. If a | |
26389 | message is rejected after DATA or by the non-SMTP ACL, all added header lines | |
26390 | are included in the entry that is written to the reject log. | |
26391 | ||
26392 | Header lines are not visible in string expansions of message headers until they | |
26393 | are added to the message. It follows that header lines defined in the MAIL, | |
26394 | RCPT, and predata ACLs are not visible until the DATA ACL and MIME ACLs are | |
26395 | run. Similarly, header lines that are added by the DATA or MIME ACLs are not | |
26396 | visible in those ACLs. Because of this restriction, you cannot use header lines | |
26397 | as a way of passing data between (for example) the MAIL and RCPT ACLs. If you | |
26398 | want to do this, you can use ACL variables, as described in section 42.19. | |
26399 | ||
26400 | The list of headers yet to be added is given by the $headers_added variable. | |
26401 | ||
26402 | The add_header modifier acts immediately as it is encountered during the | |
26403 | processing of an ACL. Notice the difference between these two cases: | |
26404 | ||
26405 | accept add_header = ADDED: some text | |
26406 | <some condition> | |
26407 | ||
26408 | accept <some condition> | |
26409 | add_header = ADDED: some text | |
26410 | ||
26411 | In the first case, the header line is always added, whether or not the | |
26412 | condition is true. In the second case, the header line is added only if the | |
26413 | condition is true. Multiple occurrences of add_header may occur in the same ACL | |
26414 | statement. All those that are encountered before a condition fails are | |
26415 | honoured. | |
26416 | ||
26417 | For compatibility with previous versions of Exim, a message modifier for a warn | |
26418 | verb acts in the same way as add_header, except that it takes effect only if | |
26419 | all the conditions are true, even if it appears before some of them. | |
26420 | Furthermore, only the last occurrence of message is honoured. This usage of | |
26421 | message is now deprecated. If both add_header and message are present on a warn | |
26422 | verb, both are processed according to their specifications. | |
26423 | ||
26424 | By default, new header lines are added to a message at the end of the existing | |
26425 | header lines. However, you can specify that any particular header line should | |
26426 | be added right at the start (before all the Received: lines), immediately after | |
26427 | the first block of Received: lines, or immediately before any line that is not | |
26428 | a Received: or Resent-something: header. | |
26429 | ||
26430 | This is done by specifying ":at_start:", ":after_received:", or | |
26431 | ":at_start_rfc:" (or, for completeness, ":at_end:") before the text of the | |
26432 | header line, respectively. (Header text cannot start with a colon, as there has | |
26433 | to be a header name first.) For example: | |
26434 | ||
26435 | warn add_header = \ | |
26436 | :after_received:X-My-Header: something or other... | |
26437 | ||
26438 | If more than one header line is supplied in a single add_header modifier, each | |
26439 | one is treated independently and can therefore be placed differently. If you | |
26440 | add more than one line at the start, or after the Received: block, they end up | |
26441 | in reverse order. | |
26442 | ||
26443 | Warning: This facility currently applies only to header lines that are added in | |
26444 | an ACL. It does NOT work for header lines that are added in a system filter or | |
26445 | in a router or transport. | |
26446 | ||
26447 | ||
26448 | 42.25 Removing header lines in ACLs | |
26449 | ----------------------------------- | |
26450 | ||
26451 | The remove_header modifier can be used to remove one or more header lines from | |
26452 | an incoming message, as in this example: | |
26453 | ||
26454 | warn message = Remove internal headers | |
26455 | remove_header = x-route-mail1 : x-route-mail2 | |
26456 | ||
26457 | The remove_header modifier is permitted in the MAIL, RCPT, PREDATA, DATA, MIME, | |
26458 | DKIM, and non-SMTP ACLs (in other words, those that are concerned with | |
26459 | receiving a message). The message must ultimately be accepted for remove_header | |
26460 | to have any significant effect. You can use remove_header with any ACL verb, | |
26461 | including deny, though this is really not useful for any verb that doesn't | |
26462 | result in a delivered message. | |
26463 | ||
26464 | Headers will not be removed to the message if the modifier is used in DATA, | |
26465 | MIME or DKIM ACLs for messages delivered by cutthrough routing. | |
26466 | ||
26467 | More than one header can be removed at the same time by using a colon separated | |
26468 | list of header names. The header matching is case insensitive. Wildcards are | |
26469 | not permitted, nor is list expansion performed, so you cannot use hostlists to | |
26470 | create a list of headers, however both connection and message variable | |
26471 | expansion are performed ($acl_c_* and $acl_m_*), illustrated in this example: | |
26472 | ||
26473 | warn hosts = +internal_hosts | |
26474 | set acl_c_ihdrs = x-route-mail1 : x-route-mail2 | |
26475 | warn message = Remove internal headers | |
26476 | remove_header = $acl_c_ihdrs | |
26477 | ||
26478 | Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs. | |
26479 | They are removed from the message before processing the DATA and MIME ACLs. | |
26480 | There is no harm in attempting to remove the same header twice nor is removing | |
26481 | a non-existent header. Further header lines to be removed may be accumulated | |
26482 | during the DATA and MIME ACLs, after which they are removed from the message, | |
26483 | if present. In the case of non-SMTP messages, headers to be removed are | |
26484 | accumulated during the non-SMTP ACLs, and are removed from the message after | |
26485 | all the ACLs have run. If a message is rejected after DATA or by the non-SMTP | |
26486 | ACL, there really is no effect because there is no logging of what headers | |
26487 | would have been removed. | |
26488 | ||
26489 | Header lines are not visible in string expansions until the DATA phase when it | |
26490 | is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are | |
26491 | not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are | |
26492 | removed by the DATA or MIME ACLs are still visible in those ACLs. Because of | |
26493 | this restriction, you cannot use header lines as a way of controlling data | |
26494 | passed between (for example) the MAIL and RCPT ACLs. If you want to do this, | |
26495 | you should instead use ACL variables, as described in section 42.19. | |
26496 | ||
26497 | The remove_header modifier acts immediately as it is encountered during the | |
26498 | processing of an ACL. Notice the difference between these two cases: | |
26499 | ||
26500 | accept remove_header = X-Internal | |
26501 | <some condition> | |
26502 | ||
26503 | accept <some condition> | |
26504 | remove_header = X-Internal | |
26505 | ||
26506 | In the first case, the header line is always removed, whether or not the | |
26507 | condition is true. In the second case, the header line is removed only if the | |
26508 | condition is true. Multiple occurrences of remove_header may occur in the same | |
26509 | ACL statement. All those that are encountered before a condition fails are | |
26510 | honoured. | |
26511 | ||
26512 | Warning: This facility currently applies only to header lines that are present | |
26513 | during ACL processing. It does NOT remove header lines that are added in a | |
26514 | system filter or in a router or transport. | |
26515 | ||
26516 | ||
26517 | 42.26 ACL conditions | |
26518 | -------------------- | |
26519 | ||
26520 | Some of the conditions listed in this section are available only when Exim is | |
26521 | compiled with the content-scanning extension. They are included here briefly | |
26522 | for completeness. More detailed descriptions can be found in the discussion on | |
26523 | content scanning in chapter 43. | |
26524 | ||
26525 | Not all conditions are relevant in all circumstances. For example, testing | |
26526 | senders and recipients does not make sense in an ACL that is being run as the | |
26527 | result of the arrival of an ETRN command, and checks on message headers can be | |
26528 | done only in the ACLs specified by acl_smtp_data and acl_not_smtp. You can use | |
26529 | the same condition (with different parameters) more than once in the same ACL | |
26530 | statement. This provides a way of specifying an "and" conjunction. The | |
26531 | conditions are as follows: | |
26532 | ||
26533 | acl = <name of acl or ACL string or file name > | |
26534 | ||
26535 | The possible values of the argument are the same as for the acl_smtp_xxx | |
26536 | options. The named or inline ACL is run. If it returns "accept" the | |
26537 | condition is true; if it returns "deny" the condition is false. If it | |
26538 | returns "defer", the current ACL returns "defer" unless the condition is on | |
26539 | a warn verb. In that case, a "defer" return makes the condition false. This | |
26540 | means that further processing of the warn verb ceases, but processing of | |
26541 | the ACL continues. | |
26542 | ||
26543 | If the argument is a named ACL, up to nine space-separated optional values | |
26544 | can be appended; they appear within the called ACL in $acl_arg1 to | |
26545 | $acl_arg9, and $acl_narg is set to the count of values. Previous values of | |
26546 | these variables are restored after the call returns. The name and values | |
26547 | are expanded separately. | |
26548 | ||
26549 | If the nested acl returns "drop" and the outer condition denies access, the | |
26550 | connection is dropped. If it returns "discard", the verb must be accept or | |
26551 | discard, and the action is taken immediately - no further conditions are | |
26552 | tested. | |
26553 | ||
26554 | ACLs may be nested up to 20 deep; the limit exists purely to catch runaway | |
26555 | loops. This condition allows you to use different ACLs in different | |
26556 | circumstances. For example, different ACLs can be used to handle RCPT | |
26557 | commands for different local users or different local domains. | |
26558 | ||
26559 | authenticated = <string list> | |
26560 | ||
26561 | If the SMTP connection is not authenticated, the condition is false. | |
26562 | Otherwise, the name of the authenticator is tested against the list. To | |
26563 | test for authentication by any authenticator, you can set | |
26564 | ||
26565 | authenticated = * | |
26566 | ||
26567 | condition = <string> | |
26568 | ||
26569 | This feature allows you to make up custom conditions. If the result of | |
26570 | expanding the string is an empty string, the number zero, or one of the | |
26571 | strings "no" or "false", the condition is false. If the result is any | |
26572 | non-zero number, or one of the strings "yes" or "true", the condition is | |
26573 | true. For any other value, some error is assumed to have occurred, and the | |
26574 | ACL returns "defer". However, if the expansion is forced to fail, the | |
26575 | condition is ignored. The effect is to treat it as true, whether it is | |
26576 | positive or negative. | |
26577 | ||
26578 | decode = <location> | |
26579 | ||
26580 | This condition is available only when Exim is compiled with the | |
26581 | content-scanning extension, and it is allowed only in the ACL defined by | |
26582 | acl_smtp_mime. It causes the current MIME part to be decoded into a file. | |
26583 | If all goes well, the condition is true. It is false only if there are | |
26584 | problems such as a syntax error or a memory shortage. For more details, see | |
26585 | chapter 43. | |
26586 | ||
26587 | demime = <extension list> | |
26588 | ||
26589 | This condition is available only when Exim is compiled with the | |
26590 | content-scanning extension. Its use is described in section 43.6. | |
26591 | ||
26592 | dnslists = <list of domain names and other data> | |
26593 | ||
26594 | This condition checks for entries in DNS black lists. These are also known | |
26595 | as "RBL lists", after the original Realtime Blackhole List, but note that | |
26596 | the use of the lists at mail-abuse.org now carries a charge. There are too | |
26597 | many different variants of this condition to describe briefly here. See | |
26598 | sections 42.27-42.37 for details. | |
26599 | ||
26600 | domains = <domain list> | |
26601 | ||
26602 | This condition is relevant only after a RCPT command. It checks that the | |
26603 | domain of the recipient address is in the domain list. If percent-hack | |
26604 | processing is enabled, it is done before this test is done. If the check | |
26605 | succeeds with a lookup, the result of the lookup is placed in $domain_data | |
26606 | until the next domains test. | |
26607 | ||
26608 | Note carefully (because many people seem to fall foul of this): you cannot | |
26609 | use domains in a DATA ACL. | |
26610 | ||
26611 | encrypted = <string list> | |
26612 | ||
26613 | If the SMTP connection is not encrypted, the condition is false. Otherwise, | |
26614 | the name of the cipher suite in use is tested against the list. To test for | |
26615 | encryption without testing for any specific cipher suite(s), set | |
26616 | ||
26617 | encrypted = * | |
26618 | ||
26619 | hosts = <host list> | |
26620 | ||
26621 | This condition tests that the calling host matches the host list. If you | |
26622 | have name lookups or wildcarded host names and IP addresses in the same | |
26623 | host list, you should normally put the IP addresses first. For example, you | |
26624 | could have: | |
26625 | ||
26626 | accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts | |
26627 | ||
26628 | The lookup in this example uses the host name for its key. This is implied | |
26629 | by the lookup type "dbm". (For a host address lookup you would use | |
26630 | "net-dbm" and it wouldn't matter which way round you had these two items.) | |
26631 | ||
26632 | The reason for the problem with host names lies in the left-to-right way | |
26633 | that Exim processes lists. It can test IP addresses without doing any DNS | |
26634 | lookups, but when it reaches an item that requires a host name, it fails if | |
26635 | it cannot find a host name to compare with the pattern. If the above list | |
26636 | is given in the opposite order, the accept statement fails for a host whose | |
26637 | name cannot be found, even if its IP address is 10.9.8.7. | |
26638 | ||
26639 | If you really do want to do the name check first, and still recognize the | |
26640 | IP address even if the name lookup fails, you can rewrite the ACL like | |
26641 | this: | |
26642 | ||
26643 | accept hosts = dbm;/etc/friendly/hosts | |
26644 | accept hosts = 10.9.8.7 | |
26645 | ||
26646 | The default action on failing to find the host name is to assume that the | |
26647 | host is not in the list, so the first accept statement fails. The second | |
26648 | statement can then check the IP address. | |
26649 | ||
26650 | If a hosts condition is satisfied by means of a lookup, the result of the | |
26651 | lookup is made available in the $host_data variable. This allows you, for | |
26652 | example, to set up a statement like this: | |
26653 | ||
26654 | deny hosts = net-lsearch;/some/file | |
26655 | message = $host_data | |
26656 | ||
26657 | which gives a custom error message for each denied host. | |
26658 | ||
26659 | local_parts = <local part list> | |
26660 | ||
26661 | This condition is relevant only after a RCPT command. It checks that the | |
26662 | local part of the recipient address is in the list. If percent-hack | |
26663 | processing is enabled, it is done before this test. If the check succeeds | |
26664 | with a lookup, the result of the lookup is placed in $local_part_data, | |
26665 | which remains set until the next local_parts test. | |
26666 | ||
26667 | malware = <option> | |
26668 | ||
26669 | This condition is available only when Exim is compiled with the | |
26670 | content-scanning extension. It causes the incoming message to be scanned | |
26671 | for viruses. For details, see chapter 43. | |
26672 | ||
26673 | mime_regex = <list of regular expressions> | |
26674 | ||
26675 | This condition is available only when Exim is compiled with the | |
26676 | content-scanning extension, and it is allowed only in the ACL defined by | |
26677 | acl_smtp_mime. It causes the current MIME part to be scanned for a match | |
26678 | with any of the regular expressions. For details, see chapter 43. | |
26679 | ||
26680 | ratelimit = <parameters> | |
26681 | ||
26682 | This condition can be used to limit the rate at which a user or host | |
26683 | submits messages. Details are given in section 42.38. | |
26684 | ||
26685 | recipients = <address list> | |
26686 | ||
26687 | This condition is relevant only after a RCPT command. It checks the entire | |
26688 | recipient address against a list of recipients. | |
26689 | ||
26690 | regex = <list of regular expressions> | |
26691 | ||
26692 | This condition is available only when Exim is compiled with the | |
26693 | content-scanning extension, and is available only in the DATA, MIME, and | |
26694 | non-SMTP ACLs. It causes the incoming message to be scanned for a match | |
26695 | with any of the regular expressions. For details, see chapter 43. | |
26696 | ||
26697 | sender_domains = <domain list> | |
26698 | ||
26699 | This condition tests the domain of the sender of the message against the | |
26700 | given domain list. Note: The domain of the sender address is in | |
26701 | $sender_address_domain. It is not put in $domain during the testing of this | |
26702 | condition. This is an exception to the general rule for testing domain | |
26703 | lists. It is done this way so that, if this condition is used in an ACL for | |
26704 | a RCPT command, the recipient's domain (which is in $domain) can be used to | |
26705 | influence the sender checking. | |
26706 | ||
26707 | Warning: It is a bad idea to use this condition on its own as a control on | |
26708 | relaying, because sender addresses are easily, and commonly, forged. | |
26709 | ||
26710 | senders = <address list> | |
26711 | ||
26712 | This condition tests the sender of the message against the given list. To | |
26713 | test for a bounce message, which has an empty sender, set | |
26714 | ||
26715 | senders = : | |
26716 | ||
26717 | Warning: It is a bad idea to use this condition on its own as a control on | |
26718 | relaying, because sender addresses are easily, and commonly, forged. | |
26719 | ||
26720 | spam = <username> | |
26721 | ||
26722 | This condition is available only when Exim is compiled with the | |
26723 | content-scanning extension. It causes the incoming message to be scanned by | |
26724 | SpamAssassin. For details, see chapter 43. | |
26725 | ||
26726 | verify = certificate | |
26727 | ||
26728 | This condition is true in an SMTP session if the session is encrypted, and | |
26729 | a certificate was received from the client, and the certificate was | |
26730 | verified. The server requests a certificate only if the client matches | |
26731 | tls_verify_hosts or tls_try_verify_hosts (see chapter 41). | |
26732 | ||
26733 | verify = csa | |
26734 | ||
26735 | This condition checks whether the sending host (the client) is authorized | |
26736 | to send email. Details of how this works are given in section 42.50. | |
26737 | ||
26738 | verify = header_names_ascii | |
26739 | ||
26740 | This condition is relevant only in an ACL that is run after a message has | |
26741 | been received, that is, in an ACL specified by acl_smtp_data or | |
26742 | acl_not_smtp. It checks all header names (not the content) to make sure | |
26743 | there are no non-ASCII characters, also excluding control characters. The | |
26744 | allowable characters are decimal ASCII values 33 through 126. | |
26745 | ||
26746 | Exim itself will handle headers with non-ASCII characters, but it can cause | |
26747 | problems for downstream applications, so this option will allow their | |
26748 | detection and rejection in the DATA ACL's. | |
26749 | ||
26750 | verify = header_sender/<options> | |
26751 | ||
26752 | This condition is relevant only in an ACL that is run after a message has | |
26753 | been received, that is, in an ACL specified by acl_smtp_data or | |
26754 | acl_not_smtp. It checks that there is a verifiable address in at least one | |
26755 | of the Sender:, Reply-To:, or From: header lines. Such an address is | |
26756 | loosely thought of as a "sender" address (hence the name of the test). | |
26757 | However, an address that appears in one of these headers need not be an | |
26758 | address that accepts bounce messages; only sender addresses in envelopes | |
26759 | are required to accept bounces. Therefore, if you use the callout option on | |
26760 | this check, you might want to arrange for a non-empty address in the MAIL | |
26761 | command. | |
26762 | ||
26763 | Details of address verification and the options are given later, starting | |
26764 | at section 42.44 (callouts are described in section 42.45). You can combine | |
26765 | this condition with the senders condition to restrict it to bounce messages | |
26766 | only: | |
26767 | ||
26768 | deny senders = : | |
26769 | message = A valid sender header is required for bounces | |
26770 | !verify = header_sender | |
26771 | ||
26772 | verify = header_syntax | |
26773 | ||
26774 | This condition is relevant only in an ACL that is run after a message has | |
26775 | been received, that is, in an ACL specified by acl_smtp_data or | |
26776 | acl_not_smtp. It checks the syntax of all header lines that can contain | |
26777 | lists of addresses (Sender:, From:, Reply-To:, To:, Cc:, and Bcc:). | |
26778 | Unqualified addresses (local parts without domains) are permitted only in | |
26779 | locally generated messages and from hosts that match | |
26780 | sender_unqualified_hosts or recipient_unqualified_hosts, as appropriate. | |
26781 | ||
26782 | Note that this condition is a syntax check only. However, a common spamming | |
26783 | ploy used to be to send syntactically invalid headers such as | |
26784 | ||
26785 | To: @ | |
26786 | ||
26787 | and this condition can be used to reject such messages, though they are not | |
26788 | as common as they used to be. | |
26789 | ||
26790 | verify = helo | |
26791 | ||
26792 | This condition is true if a HELO or EHLO command has been received from the | |
26793 | client host, and its contents have been verified. If there has been no | |
26794 | previous attempt to verify the HELO/EHLO contents, it is carried out when | |
26795 | this condition is encountered. See the description of the helo_verify_hosts | |
26796 | and helo_try_verify_hosts options for details of how to request | |
26797 | verification independently of this condition. | |
26798 | ||
26799 | For SMTP input that does not come over TCP/IP (the -bs command line | |
26800 | option), this condition is always true. | |
26801 | ||
26802 | verify = not_blind | |
26803 | ||
26804 | This condition checks that there are no blind (bcc) recipients in the | |
26805 | message. Every envelope recipient must appear either in a To: header line | |
26806 | or in a Cc: header line for this condition to be true. Local parts are | |
26807 | checked case-sensitively; domains are checked case-insensitively. If | |
26808 | Resent-To: or Resent-Cc: header lines exist, they are also checked. This | |
26809 | condition can be used only in a DATA or non-SMTP ACL. | |
26810 | ||
26811 | There are, of course, many legitimate messages that make use of blind (bcc) | |
26812 | recipients. This check should not be used on its own for blocking messages. | |
26813 | ||
26814 | verify = recipient/<options> | |
26815 | ||
26816 | This condition is relevant only after a RCPT command. It verifies the | |
26817 | current recipient. Details of address verification are given later, | |
26818 | starting at section 42.44. After a recipient has been verified, the value | |
26819 | of $address_data is the last value that was set while routing the address. | |
26820 | This applies even if the verification fails. When an address that is being | |
26821 | verified is redirected to a single address, verification continues with the | |
26822 | new address, and in that case, the subsequent value of $address_data is the | |
26823 | value for the child address. | |
26824 | ||
26825 | verify = reverse_host_lookup | |
26826 | ||
26827 | This condition ensures that a verified host name has been looked up from | |
26828 | the IP address of the client host. (This may have happened already if the | |
26829 | host name was needed for checking a host list, or if the host matched | |
26830 | host_lookup.) Verification ensures that the host name obtained from a | |
26831 | reverse DNS lookup, or one of its aliases, does, when it is itself looked | |
26832 | up in the DNS, yield the original IP address. | |
26833 | ||
26834 | If this condition is used for a locally generated message (that is, when | |
26835 | there is no client host involved), it always succeeds. | |
26836 | ||
26837 | verify = sender/<options> | |
26838 | ||
26839 | This condition is relevant only after a MAIL or RCPT command, or after a | |
26840 | message has been received (the acl_smtp_data or acl_not_smtp ACLs). If the | |
26841 | message's sender is empty (that is, this is a bounce message), the | |
26842 | condition is true. Otherwise, the sender address is verified. | |
26843 | ||
26844 | If there is data in the $address_data variable at the end of routing, its | |
26845 | value is placed in $sender_address_data at the end of verification. This | |
26846 | value can be used in subsequent conditions and modifiers in the same ACL | |
26847 | statement. It does not persist after the end of the current statement. If | |
26848 | you want to preserve the value for longer, you can save it in an ACL | |
26849 | variable. | |
26850 | ||
26851 | Details of verification are given later, starting at section 42.44. Exim | |
26852 | caches the result of sender verification, to avoid doing it more than once | |
26853 | per message. | |
26854 | ||
26855 | verify = sender=<address>/<options> | |
26856 | ||
26857 | This is a variation of the previous option, in which a modified address is | |
26858 | verified as a sender. | |
26859 | ||
26860 | ||
26861 | 42.27 Using DNS lists | |
26862 | --------------------- | |
26863 | ||
26864 | In its simplest form, the dnslists condition tests whether the calling host is | |
26865 | on at least one of a number of DNS lists by looking up the inverted IP address | |
26866 | in one or more DNS domains. (Note that DNS list domains are not mail domains, | |
26867 | so the "+" syntax for named lists doesn't work - it is used for special options | |
26868 | instead.) For example, if the calling host's IP address is 192.168.62.43, and | |
26869 | the ACL statement is | |
26870 | ||
26871 | deny dnslists = blackholes.mail-abuse.org : \ | |
26872 | dialups.mail-abuse.org | |
26873 | ||
26874 | the following records are looked up: | |
26875 | ||
26876 | 43.62.168.192.blackholes.mail-abuse.org | |
26877 | 43.62.168.192.dialups.mail-abuse.org | |
26878 | ||
26879 | As soon as Exim finds an existing DNS record, processing of the list stops. | |
26880 | Thus, multiple entries on the list provide an "or" conjunction. If you want to | |
26881 | test that a host is on more than one list (an "and" conjunction), you can use | |
26882 | two separate conditions: | |
26883 | ||
26884 | deny dnslists = blackholes.mail-abuse.org | |
26885 | dnslists = dialups.mail-abuse.org | |
26886 | ||
26887 | If a DNS lookup times out or otherwise fails to give a decisive answer, Exim | |
26888 | behaves as if the host does not match the list item, that is, as if the DNS | |
26889 | record does not exist. If there are further items in the DNS list, they are | |
26890 | processed. | |
26891 | ||
26892 | This is usually the required action when dnslists is used with deny (which is | |
26893 | the most common usage), because it prevents a DNS failure from blocking mail. | |
26894 | However, you can change this behaviour by putting one of the following special | |
26895 | items in the list: | |
26896 | ||
26897 | +include_unknown behave as if the item is on the list | |
26898 | +exclude_unknown behave as if the item is not on the list (default) | |
26899 | +defer_unknown give a temporary error | |
26900 | ||
26901 | Each of these applies to any subsequent items on the list. For example: | |
26902 | ||
26903 | deny dnslists = +defer_unknown : foo.bar.example | |
26904 | ||
26905 | Testing the list of domains stops as soon as a match is found. If you want to | |
26906 | warn for one list and block for another, you can use two different statements: | |
26907 | ||
26908 | deny dnslists = blackholes.mail-abuse.org | |
26909 | warn message = X-Warn: sending host is on dialups list | |
26910 | dnslists = dialups.mail-abuse.org | |
26911 | ||
26912 | DNS list lookups are cached by Exim for the duration of the SMTP session, so a | |
26913 | lookup based on the IP address is done at most once for any incoming | |
26914 | connection. Exim does not share information between multiple incoming | |
26915 | connections (but your local name server cache should be active). | |
26916 | ||
26917 | ||
26918 | 42.28 Specifying the IP address for a DNS list lookup | |
26919 | ----------------------------------------------------- | |
26920 | ||
26921 | By default, the IP address that is used in a DNS list lookup is the IP address | |
26922 | of the calling host. However, you can specify another IP address by listing it | |
26923 | after the domain name, introduced by a slash. For example: | |
26924 | ||
26925 | deny dnslists = black.list.tld/192.168.1.2 | |
26926 | ||
26927 | This feature is not very helpful with explicit IP addresses; it is intended for | |
26928 | use with IP addresses that are looked up, for example, the IP addresses of the | |
26929 | MX hosts or nameservers of an email sender address. For an example, see section | |
26930 | 42.30 below. | |
26931 | ||
26932 | ||
26933 | 42.29 DNS lists keyed on domain names | |
26934 | ------------------------------------- | |
26935 | ||
26936 | There are some lists that are keyed on domain names rather than inverted IP | |
26937 | addresses (see for example the domain based zones link at http:// | |
26938 | www.rfc-ignorant.org/). No reversing of components is used with these lists. | |
26939 | You can change the name that is looked up in a DNS list by listing it after the | |
26940 | domain name, introduced by a slash. For example, | |
26941 | ||
26942 | deny message = Sender's domain is listed at $dnslist_domain | |
26943 | dnslists = dsn.rfc-ignorant.org/$sender_address_domain | |
26944 | ||
26945 | This particular example is useful only in ACLs that are obeyed after the RCPT | |
26946 | or DATA commands, when a sender address is available. If (for example) the | |
26947 | message's sender is user@tld.example the name that is looked up by this example | |
26948 | is | |
26949 | ||
26950 | tld.example.dsn.rfc-ignorant.org | |
26951 | ||
26952 | A single dnslists condition can contain entries for both names and IP | |
26953 | addresses. For example: | |
26954 | ||
26955 | deny dnslists = sbl.spamhaus.org : \ | |
26956 | dsn.rfc-ignorant.org/$sender_address_domain | |
26957 | ||
26958 | The first item checks the sending host's IP address; the second checks a domain | |
26959 | name. The whole condition is true if either of the DNS lookups succeeds. | |
26960 | ||
26961 | ||
26962 | 42.30 Multiple explicit keys for a DNS list | |
26963 | ------------------------------------------- | |
26964 | ||
26965 | The syntax described above for looking up explicitly-defined values (either | |
26966 | names or IP addresses) in a DNS blacklist is a simplification. After the domain | |
26967 | name for the DNS list, what follows the slash can in fact be a list of items. | |
26968 | As with all lists in Exim, the default separator is a colon. However, because | |
26969 | this is a sublist within the list of DNS blacklist domains, it is necessary | |
26970 | either to double the separators like this: | |
26971 | ||
26972 | dnslists = black.list.tld/name.1::name.2 | |
26973 | ||
26974 | or to change the separator character, like this: | |
26975 | ||
26976 | dnslists = black.list.tld/<;name.1;name.2 | |
26977 | ||
26978 | If an item in the list is an IP address, it is inverted before the DNS | |
26979 | blacklist domain is appended. If it is not an IP address, no inversion occurs. | |
26980 | Consider this condition: | |
26981 | ||
26982 | dnslists = black.list.tld/<;192.168.1.2;a.domain | |
26983 | ||
26984 | The DNS lookups that occur are: | |
26985 | ||
26986 | 2.1.168.192.black.list.tld | |
26987 | a.domain.black.list.tld | |
26988 | ||
26989 | Once a DNS record has been found (that matches a specific IP return address, if | |
26990 | specified - see section 42.33), no further lookups are done. If there is a | |
26991 | temporary DNS error, the rest of the sublist of domains or IP addresses is | |
26992 | tried. A temporary error for the whole dnslists item occurs only if no other | |
26993 | DNS lookup in this sublist succeeds. In other words, a successful lookup for | |
26994 | any of the items in the sublist overrides a temporary error for a previous | |
26995 | item. | |
26996 | ||
26997 | The ability to supply a list of items after the slash is in some sense just a | |
26998 | syntactic convenience. These two examples have the same effect: | |
26999 | ||
27000 | dnslists = black.list.tld/a.domain : black.list.tld/b.domain | |
27001 | dnslists = black.list.tld/a.domain::b.domain | |
27002 | ||
27003 | However, when the data for the list is obtained from a lookup, the second form | |
27004 | is usually much more convenient. Consider this example: | |
27005 | ||
27006 | deny message = The mail servers for the domain \ | |
27007 | $sender_address_domain \ | |
27008 | are listed at $dnslist_domain ($dnslist_value); \ | |
27009 | see $dnslist_text. | |
27010 | dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\ | |
27011 | ${lookup dnsdb {>|mxh=\ | |
27012 | $sender_address_domain} }} } | |
27013 | ||
27014 | Note the use of ">|" in the dnsdb lookup to specify the separator for multiple | |
27015 | DNS records. The inner dnsdb lookup produces a list of MX hosts and the outer | |
27016 | dnsdb lookup finds the IP addresses for these hosts. The result of expanding | |
27017 | the condition might be something like this: | |
27018 | ||
27019 | dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|... | |
27020 | ||
27021 | Thus, this example checks whether or not the IP addresses of the sender | |
27022 | domain's mail servers are on the Spamhaus black list. | |
27023 | ||
27024 | The key that was used for a successful DNS list lookup is put into the variable | |
27025 | $dnslist_matched (see section 42.32). | |
27026 | ||
27027 | ||
27028 | 42.31 Data returned by DNS lists | |
27029 | -------------------------------- | |
27030 | ||
27031 | DNS lists are constructed using address records in the DNS. The original RBL | |
27032 | just used the address 127.0.0.1 on the right hand side of each record, but the | |
27033 | RBL+ list and some other lists use a number of values with different meanings. | |
27034 | The values used on the RBL+ list are: | |
27035 | ||
27036 | 127.1.0.1 RBL | |
27037 | 127.1.0.2 DUL | |
27038 | 127.1.0.3 DUL and RBL | |
27039 | 127.1.0.4 RSS | |
27040 | 127.1.0.5 RSS and RBL | |
27041 | 127.1.0.6 RSS and DUL | |
27042 | 127.1.0.7 RSS and DUL and RBL | |
27043 | ||
27044 | Section 42.33 below describes how you can distinguish between different values. | |
27045 | Some DNS lists may return more than one address record; see section 42.35 for | |
27046 | details of how they are checked. | |
27047 | ||
27048 | ||
27049 | 42.32 Variables set from DNS lists | |
27050 | ---------------------------------- | |
27051 | ||
27052 | When an entry is found in a DNS list, the variable $dnslist_domain contains the | |
27053 | name of the overall domain that matched (for example, "spamhaus.example"), | |
27054 | $dnslist_matched contains the key within that domain (for example, | |
27055 | "192.168.5.3"), and $dnslist_value contains the data from the DNS record. When | |
27056 | the key is an IP address, it is not reversed in $dnslist_matched (though it is, | |
27057 | of course, in the actual lookup). In simple cases, for example: | |
27058 | ||
27059 | deny dnslists = spamhaus.example | |
27060 | ||
27061 | the key is also available in another variable (in this case, | |
27062 | $sender_host_address). In more complicated cases, however, this is not true. | |
27063 | For example, using a data lookup (as described in section 42.30) might generate | |
27064 | a dnslists lookup like this: | |
27065 | ||
27066 | deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|... | |
27067 | ||
27068 | If this condition succeeds, the value in $dnslist_matched might be | |
27069 | "192.168.6.7" (for example). | |
27070 | ||
27071 | If more than one address record is returned by the DNS lookup, all the IP | |
27072 | addresses are included in $dnslist_value, separated by commas and spaces. The | |
27073 | variable $dnslist_text contains the contents of any associated TXT record. For | |
27074 | lists such as RBL+ the TXT record for a merged entry is often not very | |
27075 | meaningful. See section 42.36 for a way of obtaining more information. | |
27076 | ||
27077 | You can use the DNS list variables in message or log_message modifiers - | |
27078 | although these appear before the condition in the ACL, they are not expanded | |
27079 | until after it has failed. For example: | |
27080 | ||
27081 | deny hosts = !+local_networks | |
27082 | message = $sender_host_address is listed \ | |
27083 | at $dnslist_domain | |
27084 | dnslists = rbl-plus.mail-abuse.example | |
27085 | ||
27086 | ||
27087 | 42.33 Additional matching conditions for DNS lists | |
27088 | -------------------------------------------------- | |
27089 | ||
27090 | You can add an equals sign and an IP address after a dnslists domain name in | |
27091 | order to restrict its action to DNS records with a matching right hand side. | |
27092 | For example, | |
27093 | ||
27094 | deny dnslists = rblplus.mail-abuse.org=127.0.0.2 | |
27095 | ||
27096 | rejects only those hosts that yield 127.0.0.2. Without this additional data, | |
27097 | any address record is considered to be a match. For the moment, we assume that | |
27098 | the DNS lookup returns just one record. Section 42.35 describes how multiple | |
27099 | records are handled. | |
27100 | ||
27101 | More than one IP address may be given for checking, using a comma as a | |
27102 | separator. These are alternatives - if any one of them matches, the dnslists | |
27103 | condition is true. For example: | |
27104 | ||
27105 | deny dnslists = a.b.c=127.0.0.2,127.0.0.3 | |
27106 | ||
27107 | If you want to specify a constraining address list and also specify names or IP | |
27108 | addresses to be looked up, the constraining address list must be specified | |
27109 | first. For example: | |
27110 | ||
27111 | deny dnslists = dsn.rfc-ignorant.org\ | |
27112 | =127.0.0.2/$sender_address_domain | |
27113 | ||
27114 | If the character "&" is used instead of "=", the comparison for each listed IP | |
27115 | address is done by a bitwise "and" instead of by an equality test. In other | |
27116 | words, the listed addresses are used as bit masks. The comparison is true if | |
27117 | all the bits in the mask are present in the address that is being tested. For | |
27118 | example: | |
27119 | ||
27120 | dnslists = a.b.c&0.0.0.3 | |
27121 | ||
27122 | matches if the address is x.x.x.3, x.x.x.7, x.x.x.11, etc. If you want to test | |
27123 | whether one bit or another bit is present (as opposed to both being present), | |
27124 | you must use multiple values. For example: | |
27125 | ||
27126 | dnslists = a.b.c&0.0.0.1,0.0.0.2 | |
27127 | ||
27128 | matches if the final component of the address is an odd number or two times an | |
27129 | odd number. | |
27130 | ||
27131 | ||
27132 | 42.34 Negated DNS matching conditions | |
27133 | ------------------------------------- | |
27134 | ||
27135 | You can supply a negative list of IP addresses as part of a dnslists condition. | |
27136 | Whereas | |
27137 | ||
27138 | deny dnslists = a.b.c=127.0.0.2,127.0.0.3 | |
27139 | ||
27140 | means "deny if the host is in the black list at the domain a.b.c and the IP | |
27141 | address yielded by the list is either 127.0.0.2 or 127.0.0.3", | |
27142 | ||
27143 | deny dnslists = a.b.c!=127.0.0.2,127.0.0.3 | |
27144 | ||
27145 | means "deny if the host is in the black list at the domain a.b.c and the IP | |
27146 | address yielded by the list is not 127.0.0.2 and not 127.0.0.3". In other | |
27147 | words, the result of the test is inverted if an exclamation mark appears before | |
27148 | the "=" (or the "&") sign. | |
27149 | ||
27150 | Note: This kind of negation is not the same as negation in a domain, host, or | |
27151 | address list (which is why the syntax is different). | |
27152 | ||
27153 | If you are using just one list, the negation syntax does not gain you much. The | |
27154 | previous example is precisely equivalent to | |
27155 | ||
27156 | deny dnslists = a.b.c | |
27157 | !dnslists = a.b.c=127.0.0.2,127.0.0.3 | |
27158 | ||
27159 | However, if you are using multiple lists, the negation syntax is clearer. | |
27160 | Consider this example: | |
27161 | ||
27162 | deny dnslists = sbl.spamhaus.org : \ | |
27163 | list.dsbl.org : \ | |
27164 | dnsbl.njabl.org!=127.0.0.3 : \ | |
27165 | relays.ordb.org | |
27166 | ||
27167 | Using only positive lists, this would have to be: | |
27168 | ||
27169 | deny dnslists = sbl.spamhaus.org : \ | |
27170 | list.dsbl.org | |
27171 | deny dnslists = dnsbl.njabl.org | |
27172 | !dnslists = dnsbl.njabl.org=127.0.0.3 | |
27173 | deny dnslists = relays.ordb.org | |
27174 | ||
27175 | which is less clear, and harder to maintain. | |
27176 | ||
27177 | ||
27178 | 42.35 Handling multiple DNS records from a DNS list | |
27179 | --------------------------------------------------- | |
27180 | ||
27181 | A DNS lookup for a dnslists condition may return more than one DNS record, | |
27182 | thereby providing more than one IP address. When an item in a dnslists list is | |
27183 | followed by "=" or "&" and a list of IP addresses, in order to restrict the | |
27184 | match to specific results from the DNS lookup, there are two ways in which the | |
27185 | checking can be handled. For example, consider the condition: | |
27186 | ||
27187 | dnslists = a.b.c=127.0.0.1 | |
27188 | ||
27189 | What happens if the DNS lookup for the incoming IP address yields both | |
27190 | 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the condition | |
27191 | true because at least one given value was found, or is it false because at | |
27192 | least one of the found values was not listed? And how does this affect negated | |
27193 | conditions? Both possibilities are provided for with the help of additional | |
27194 | separators "==" and "=&". | |
27195 | ||
27196 | * If "=" or "&" is used, the condition is true if any one of the looked up IP | |
27197 | addresses matches one of the listed addresses. For the example above, the | |
27198 | condition is true because 127.0.0.1 matches. | |
27199 | ||
27200 | * If "==" or "=&" is used, the condition is true only if every one of the | |
27201 | looked up IP addresses matches one of the listed addresses. If the | |
27202 | condition is changed to: | |
27203 | ||
27204 | dnslists = a.b.c==127.0.0.1 | |
27205 | ||
27206 | and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is | |
27207 | false because 127.0.0.2 is not listed. You would need to have: | |
27208 | ||
27209 | dnslists = a.b.c==127.0.0.1,127.0.0.2 | |
27210 | ||
27211 | for the condition to be true. | |
27212 | ||
27213 | When "!" is used to negate IP address matching, it inverts the result, giving | |
27214 | the precise opposite of the behaviour above. Thus: | |
27215 | ||
27216 | * If "!=" or "!&" is used, the condition is true if none of the looked up IP | |
27217 | addresses matches one of the listed addresses. Consider: | |
27218 | ||
27219 | dnslists = a.b.c!&0.0.0.1 | |
27220 | ||
27221 | If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is | |
27222 | false because 127.0.0.1 matches. | |
27223 | ||
27224 | * If "!==" or "!=&" is used, the condition is true if there is at least one | |
27225 | looked up IP address that does not match. Consider: | |
27226 | ||
27227 | dnslists = a.b.c!=&0.0.0.1 | |
27228 | ||
27229 | If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is | |
27230 | true, because 127.0.0.2 does not match. You would need to have: | |
27231 | ||
27232 | dnslists = a.b.c!=&0.0.0.1,0.0.0.2 | |
27233 | ||
27234 | for the condition to be false. | |
27235 | ||
27236 | When the DNS lookup yields only a single IP address, there is no difference | |
27237 | between "=" and "==" and between "&" and "=&". | |
27238 | ||
27239 | ||
27240 | 42.36 Detailed information from merged DNS lists | |
27241 | ------------------------------------------------ | |
27242 | ||
27243 | When the facility for restricting the matching IP values in a DNS list is used, | |
27244 | the text from the TXT record that is set in $dnslist_text may not reflect the | |
27245 | true reason for rejection. This happens when lists are merged and the IP | |
27246 | address in the A record is used to distinguish them; unfortunately there is | |
27247 | only one TXT record. One way round this is not to use merged lists, but that | |
27248 | can be inefficient because it requires multiple DNS lookups where one would do | |
27249 | in the vast majority of cases when the host of interest is not on any of the | |
27250 | lists. | |
27251 | ||
27252 | A less inefficient way of solving this problem is available. If two domain | |
27253 | names, comma-separated, are given, the second is used first to do an initial | |
27254 | check, making use of any IP value restrictions that are set. If there is a | |
27255 | match, the first domain is used, without any IP value restrictions, to get the | |
27256 | TXT record. As a byproduct of this, there is also a check that the IP being | |
27257 | tested is indeed on the first list. The first domain is the one that is put in | |
27258 | $dnslist_domain. For example: | |
27259 | ||
27260 | reject message = \ | |
27261 | rejected because $sender_host_address is blacklisted \ | |
27262 | at $dnslist_domain\n$dnslist_text | |
27263 | dnslists = \ | |
27264 | sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \ | |
27265 | dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10 | |
27266 | ||
27267 | For the first blacklist item, this starts by doing a lookup in | |
27268 | sbl-xbl.spamhaus.org and testing for a 127.0.0.2 return. If there is a match, | |
27269 | it then looks in sbl.spamhaus.org, without checking the return value, and as | |
27270 | long as something is found, it looks for the corresponding TXT record. If there | |
27271 | is no match in sbl-xbl.spamhaus.org, nothing more is done. The second blacklist | |
27272 | item is processed similarly. | |
27273 | ||
27274 | If you are interested in more than one merged list, the same list must be given | |
27275 | several times, but because the results of the DNS lookups are cached, the DNS | |
27276 | calls themselves are not repeated. For example: | |
27277 | ||
27278 | reject dnslists = \ | |
27279 | http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \ | |
27280 | socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \ | |
27281 | misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \ | |
27282 | dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10 | |
27283 | ||
27284 | In this case there is one lookup in dnsbl.sorbs.net, and if none of the IP | |
27285 | values matches (or if no record is found), this is the only lookup that is | |
27286 | done. Only if there is a match is one of the more specific lists consulted. | |
27287 | ||
27288 | ||
27289 | 42.37 DNS lists and IPv6 | |
27290 | ------------------------ | |
27291 | ||
27292 | If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it | |
27293 | nibble by nibble. For example, if the calling host's IP address is | |
27294 | 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up | |
27295 | ||
27296 | 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8. | |
27297 | f.f.f.f.e.f.f.3.blackholes.mail-abuse.org | |
27298 | ||
27299 | (split over two lines here to fit on the page). Unfortunately, some of the DNS | |
27300 | lists contain wildcard records, intended for IPv4, that interact badly with | |
27301 | IPv6. For example, the DNS entry | |
27302 | ||
27303 | *.3.some.list.example. A 127.0.0.1 | |
27304 | ||
27305 | is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list. | |
27306 | Unfortunately, it also matches the entire 3::/4 IPv6 network. | |
27307 | ||
27308 | You can exclude IPv6 addresses from DNS lookups by making use of a suitable | |
27309 | condition condition, as in this example: | |
27310 | ||
27311 | deny condition = ${if isip4{$sender_host_address}} | |
27312 | dnslists = some.list.example | |
27313 | ||
27314 | If an explicit key is being used for a DNS lookup and it may be an IPv6 address | |
27315 | you should specify alternate list separators for both the outer (DNS list name) | |
27316 | list and inner (lookup keys) list: | |
27317 | ||
27318 | dnslists = <; dnsbl.example.com/<|$acl_m_addrslist | |
27319 | ||
27320 | ||
27321 | 42.38 Rate limiting incoming messages | |
27322 | ------------------------------------- | |
27323 | ||
27324 | The ratelimit ACL condition can be used to measure and control the rate at | |
27325 | which clients can send email. This is more powerful than the smtp_ratelimit_* | |
27326 | options, because those options control the rate of commands in a single SMTP | |
27327 | session only, whereas the ratelimit condition works across all connections | |
27328 | (concurrent and sequential) from the same client host. The syntax of the | |
27329 | ratelimit condition is: | |
27330 | ||
27331 | ratelimit = <m> / <p> / <options> / <key> | |
27332 | ||
27333 | If the average client sending rate is less than m messages per time period p | |
27334 | then the condition is false; otherwise it is true. | |
27335 | ||
27336 | As a side-effect, the ratelimit condition sets the expansion variable | |
27337 | $sender_rate to the client's computed rate, $sender_rate_limit to the | |
27338 | configured value of m, and $sender_rate_period to the configured value of p. | |
27339 | ||
27340 | The parameter p is the smoothing time constant, in the form of an Exim time | |
27341 | interval, for example, "8h" for eight hours. A larger time constant means that | |
27342 | it takes Exim longer to forget a client's past behaviour. The parameter m is | |
27343 | the maximum number of messages that a client is permitted to send in each time | |
27344 | interval. It also specifies the number of messages permitted in a fast burst. | |
27345 | By increasing both m and p but keeping m/p constant, you can allow a client to | |
27346 | send more messages in a burst without changing its long-term sending rate | |
27347 | limit. Conversely, if m and p are both small, messages must be sent at an even | |
27348 | rate. | |
27349 | ||
27350 | There is a script in util/ratelimit.pl which extracts sending rates from log | |
27351 | files, to assist with choosing appropriate settings for m and p when deploying | |
27352 | the ratelimit ACL condition. The script prints usage instructions when it is | |
27353 | run with no arguments. | |
27354 | ||
27355 | The key is used to look up the data for calculating the client's average | |
27356 | sending rate. This data is stored in Exim's spool directory, alongside the | |
27357 | retry and other hints databases. The default key is $sender_host_address, which | |
27358 | means Exim computes the sending rate of each client host IP address. By | |
27359 | changing the key you can change how Exim identifies clients for the purpose of | |
27360 | ratelimiting. For example, to limit the sending rate of each authenticated | |
27361 | user, independent of the computer they are sending from, set the key to | |
27362 | $authenticated_id. You must ensure that the lookup key is meaningful; for | |
27363 | example, $authenticated_id is only meaningful if the client has authenticated | |
27364 | (which you can check with the authenticated ACL condition). | |
27365 | ||
27366 | The lookup key does not have to identify clients: If you want to limit the rate | |
27367 | at which a recipient receives messages, you can use the key | |
27368 | "$local_part@$domain" with the per_rcpt option (see below) in a RCPT ACL. | |
27369 | ||
27370 | Each ratelimit condition can have up to four options. A per_* option specifies | |
27371 | what Exim measures the rate of, for example messages or recipients or bytes. | |
27372 | You can adjust the measurement using the unique= and/or count= options. You can | |
27373 | also control when Exim updates the recorded rate using a strict, leaky, or | |
27374 | readonly option. The options are separated by a slash, like the other | |
27375 | parameters. They may appear in any order. | |
27376 | ||
27377 | Internally, Exim appends the smoothing constant p onto the lookup key with any | |
27378 | options that alter the meaning of the stored data. The limit m is not stored, | |
27379 | so you can alter the configured maximum rate and Exim will still remember | |
27380 | clients' past behaviour. If you change the per_* mode or add or remove the | |
27381 | unique= option, the lookup key changes so Exim will forget past behaviour. The | |
27382 | lookup key is not affected by changes to the update mode and the count= option. | |
27383 | ||
27384 | ||
27385 | 42.39 Ratelimit options for what is being measured | |
27386 | -------------------------------------------------- | |
27387 | ||
27388 | The per_conn option limits the client's connection rate. It is not normally | |
27389 | used in the acl_not_smtp, acl_not_smtp_mime, or acl_not_smtp_start ACLs. | |
27390 | ||
27391 | The per_mail option limits the client's rate of sending messages. This is the | |
27392 | default if none of the per_* options is specified. It can be used in | |
27393 | acl_smtp_mail, acl_smtp_rcpt, acl_smtp_predata, acl_smtp_mime, acl_smtp_data, | |
27394 | or acl_not_smtp. | |
27395 | ||
27396 | The per_byte option limits the sender's email bandwidth. It can be used in the | |
27397 | same ACLs as the per_mail option, though it is best to use this option in the | |
27398 | acl_smtp_mime, acl_smtp_data or acl_not_smtp ACLs; if it is used in an earlier | |
27399 | ACL, Exim relies on the SIZE parameter given by the client in its MAIL command, | |
27400 | which may be inaccurate or completely missing. You can follow the limit m in | |
27401 | the configuration with K, M, or G to specify limits in kilobytes, megabytes, or | |
27402 | gigabytes, respectively. | |
27403 | ||
27404 | The per_rcpt option causes Exim to limit the rate at which recipients are | |
27405 | accepted. It can be used in the acl_smtp_rcpt, acl_smtp_predata, acl_smtp_mime, | |
27406 | acl_smtp_data, or acl_smtp_rcpt ACLs. In acl_smtp_rcpt the rate is updated one | |
27407 | recipient at a time; in the other ACLs the rate is updated with the total | |
27408 | recipient count in one go. Note that in either case the rate limiting engine | |
27409 | will see a message with many recipients as a large high-speed burst. | |
27410 | ||
27411 | The per_addr option is like the per_rcpt option, except it counts the number of | |
27412 | different recipients that the client has sent messages to in the last time | |
27413 | period. That is, if the client repeatedly sends messages to the same recipient, | |
27414 | its measured rate is not increased. This option can only be used in | |
27415 | acl_smtp_rcpt. | |
27416 | ||
27417 | The per_cmd option causes Exim to recompute the rate every time the condition | |
27418 | is processed. This can be used to limit the rate of any SMTP command. If it is | |
27419 | used in multiple ACLs it can limit the aggregate rate of multiple different | |
27420 | commands. | |
27421 | ||
27422 | The count= option can be used to alter how much Exim adds to the client's | |
27423 | measured rate. For example, the per_byte option is equivalent to "per_mail/ | |
27424 | count=$message_size". If there is no count= option, Exim increases the measured | |
27425 | rate by one (except for the per_rcpt option in ACLs other than acl_smtp_rcpt). | |
27426 | The count does not have to be an integer. | |
27427 | ||
27428 | The unique= option is described in section 42.42 below. | |
27429 | ||
27430 | ||
27431 | 42.40 Ratelimit update modes | |
27432 | ---------------------------- | |
27433 | ||
27434 | You can specify one of three options with the ratelimit condition to control | |
27435 | when its database is updated. This section describes the readonly mode, and the | |
27436 | next section describes the strict and leaky modes. | |
27437 | ||
27438 | If the ratelimit condition is used in readonly mode, Exim looks up a | |
27439 | previously-computed rate to check against the limit. | |
27440 | ||
27441 | For example, you can test the client's sending rate and deny it access (when it | |
27442 | is too fast) in the connect ACL. If the client passes this check then it can go | |
27443 | on to send a message, in which case its recorded rate will be updated in the | |
27444 | MAIL ACL. Subsequent connections from the same client will check this new rate. | |
27445 | ||
27446 | acl_check_connect: | |
27447 | deny ratelimit = 100 / 5m / readonly | |
27448 | log_message = RATE CHECK: $sender_rate/$sender_rate_period \ | |
27449 | (max $sender_rate_limit) | |
27450 | # ... | |
27451 | acl_check_mail: | |
27452 | warn ratelimit = 100 / 5m / strict | |
27453 | log_message = RATE UPDATE: $sender_rate/$sender_rate_period \ | |
27454 | (max $sender_rate_limit) | |
27455 | ||
27456 | If Exim encounters multiple ratelimit conditions with the same key when | |
27457 | processing a message then it may increase the client's measured rate more than | |
27458 | it should. For example, this will happen if you check the per_rcpt option in | |
27459 | both acl_smtp_rcpt and acl_smtp_data. However it's OK to check the same | |
27460 | ratelimit condition multiple times in the same ACL. You can avoid any multiple | |
27461 | update problems by using the readonly option on later ratelimit checks. | |
27462 | ||
27463 | The per_* options described above do not make sense in some ACLs. If you use a | |
27464 | per_* option in an ACL where it is not normally permitted then the update mode | |
27465 | defaults to readonly and you cannot specify the strict or leaky modes. In other | |
27466 | ACLs the default update mode is leaky (see the next section) so you must | |
27467 | specify the readonly option explicitly. | |
27468 | ||
27469 | ||
27470 | 42.41 Ratelimit options for handling fast clients | |
27471 | ------------------------------------------------- | |
27472 | ||
27473 | If a client's average rate is greater than the maximum, the rate limiting | |
27474 | engine can react in two possible ways, depending on the presence of the strict | |
27475 | or leaky update modes. This is independent of the other counter-measures (such | |
27476 | as rejecting the message) that may be specified by the rest of the ACL. | |
27477 | ||
27478 | The leaky (default) option means that the client's recorded rate is not updated | |
27479 | if it is above the limit. The effect of this is that Exim measures the client's | |
27480 | average rate of successfully sent email, which cannot be greater than the | |
27481 | maximum allowed. If the client is over the limit it may suffer some | |
27482 | counter-measures (as specified in the ACL), but it will still be able to send | |
27483 | email at the configured maximum rate, whatever the rate of its attempts. This | |
27484 | is generally the better choice if you have clients that retry automatically. | |
27485 | For example, it does not prevent a sender with an over-aggressive retry rate | |
27486 | from getting any email through. | |
27487 | ||
27488 | The strict option means that the client's recorded rate is always updated. The | |
27489 | effect of this is that Exim measures the client's average rate of attempts to | |
27490 | send email, which can be much higher than the maximum it is actually allowed. | |
27491 | If the client is over the limit it may be subjected to counter-measures by the | |
27492 | ACL. It must slow down and allow sufficient time to pass that its computed rate | |
27493 | falls below the maximum before it can send email again. The time (the number of | |
27494 | smoothing periods) it must wait and not attempt to send mail can be calculated | |
27495 | with this formula: | |
27496 | ||
27497 | ln(peakrate/maxrate) | |
27498 | ||
27499 | ||
27500 | 42.42 Limiting the rate of different events | |
27501 | ------------------------------------------- | |
27502 | ||
27503 | The ratelimit unique= option controls a mechanism for counting the rate of | |
27504 | different events. For example, the per_addr option uses this mechanism to count | |
27505 | the number of different recipients that the client has sent messages to in the | |
27506 | last time period; it is equivalent to "per_rcpt/unique=$local_part@$domain". | |
27507 | You could use this feature to measure the rate that a client uses different | |
27508 | sender addresses with the options "per_mail/unique=$sender_address". | |
27509 | ||
27510 | For each ratelimit key Exim stores the set of unique= values that it has seen | |
27511 | for that key. The whole set is thrown away when it is older than the rate | |
27512 | smoothing period p, so each different event is counted at most once per period. | |
27513 | In the leaky update mode, an event that causes the client to go over the limit | |
27514 | is not added to the set, in the same way that the client's recorded rate is not | |
27515 | updated in the same situation. | |
27516 | ||
27517 | When you combine the unique= and readonly options, the specific unique= value | |
27518 | is ignored, and Exim just retrieves the client's stored rate. | |
27519 | ||
27520 | The unique= mechanism needs more space in the ratelimit database than the other | |
27521 | ratelimit options in order to store the event set. The number of unique values | |
27522 | is potentially as large as the rate limit, so the extra space required | |
27523 | increases with larger limits. | |
27524 | ||
27525 | The uniqueification is not perfect: there is a small probability that Exim will | |
27526 | think a new event has happened before. If the sender's rate is less than the | |
27527 | limit, Exim should be more than 99.9% correct. However in strict mode the | |
27528 | measured rate can go above the limit, in which case Exim may under-count events | |
27529 | by a significant margin. Fortunately, if the rate is high enough (2.7 times the | |
27530 | limit) that the false positive rate goes above 9%, then Exim will throw away | |
27531 | the over-full event set before the measured rate falls below the limit. | |
27532 | Therefore the only harm should be that exceptionally high sending rates are | |
27533 | logged incorrectly; any countermeasures you configure will be as effective as | |
27534 | intended. | |
27535 | ||
27536 | ||
27537 | 42.43 Using rate limiting | |
27538 | ------------------------- | |
27539 | ||
27540 | Exim's other ACL facilities are used to define what counter-measures are taken | |
27541 | when the rate limit is exceeded. This might be anything from logging a warning | |
27542 | (for example, while measuring existing sending rates in order to define | |
27543 | policy), through time delays to slow down fast senders, up to rejecting the | |
27544 | message. For example: | |
27545 | ||
27546 | # Log all senders' rates | |
27547 | warn ratelimit = 0 / 1h / strict | |
27548 | log_message = Sender rate $sender_rate / $sender_rate_period | |
27549 | ||
27550 | # Slow down fast senders; note the need to truncate $sender_rate | |
27551 | # at the decimal point. | |
27552 | warn ratelimit = 100 / 1h / per_rcpt / strict | |
27553 | delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \ | |
27554 | $sender_rate_limit }s | |
27555 | ||
27556 | # Keep authenticated users under control | |
27557 | deny authenticated = * | |
27558 | ratelimit = 100 / 1d / strict / $authenticated_id | |
27559 | ||
27560 | # System-wide rate limit | |
27561 | defer message = Sorry, too busy. Try again later. | |
27562 | ratelimit = 10 / 1s / $primary_hostname | |
27563 | ||
27564 | # Restrict incoming rate from each host, with a default | |
27565 | # set using a macro and special cases looked up in a table. | |
27566 | defer message = Sender rate exceeds $sender_rate_limit \ | |
27567 | messages per $sender_rate_period | |
27568 | ratelimit = ${lookup {$sender_host_address} \ | |
27569 | cdb {DB/ratelimits.cdb} \ | |
27570 | {$value} {RATELIMIT} } | |
27571 | ||
27572 | Warning: If you have a busy server with a lot of ratelimit tests, especially | |
27573 | with the per_rcpt option, you may suffer from a performance bottleneck caused | |
27574 | by locking on the ratelimit hints database. Apart from making your ACLs less | |
27575 | complicated, you can reduce the problem by using a RAM disk for Exim's hints | |
27576 | directory (usually /var/spool/exim/db/). However this means that Exim will lose | |
27577 | its hints data after a reboot (including retry hints, the callout cache, and | |
27578 | ratelimit data). | |
27579 | ||
27580 | ||
27581 | 42.44 Address verification | |
27582 | -------------------------- | |
27583 | ||
27584 | Several of the verify conditions described in section 42.26 cause addresses to | |
27585 | be verified. Section 42.48 discusses the reporting of sender verification | |
27586 | failures. The verification conditions can be followed by options that modify | |
27587 | the verification process. The options are separated from the keyword and from | |
27588 | each other by slashes, and some of them contain parameters. For example: | |
27589 | ||
27590 | verify = sender/callout | |
27591 | verify = recipient/defer_ok/callout=10s,defer_ok | |
27592 | ||
27593 | The first stage of address verification, which always happens, is to run the | |
27594 | address through the routers, in "verify mode". Routers can detect the | |
27595 | difference between verification and routing for delivery, and their actions can | |
27596 | be varied by a number of generic options such as verify and verify_only (see | |
27597 | chapter 15). If routing fails, verification fails. The available options are as | |
27598 | follows: | |
27599 | ||
27600 | * If the callout option is specified, successful routing to one or more | |
27601 | remote hosts is followed by a "callout" to those hosts as an additional | |
27602 | check. Callouts and their sub-options are discussed in the next section. | |
27603 | ||
27604 | * If there is a defer error while doing verification routing, the ACL | |
27605 | normally returns "defer". However, if you include defer_ok in the options, | |
27606 | the condition is forced to be true instead. Note that this is a main | |
27607 | verification option as well as a suboption for callouts. | |
27608 | ||
27609 | * The no_details option is covered in section 42.48, which discusses the | |
27610 | reporting of sender address verification failures. | |
27611 | ||
27612 | * The success_on_redirect option causes verification always to succeed | |
27613 | immediately after a successful redirection. By default, if a redirection | |
27614 | generates just one address, that address is also verified. See further | |
27615 | discussion in section 42.49. | |
27616 | ||
27617 | After an address verification failure, $acl_verify_message contains the error | |
27618 | message that is associated with the failure. It can be preserved by coding like | |
27619 | this: | |
27620 | ||
27621 | warn !verify = sender | |
27622 | set acl_m0 = $acl_verify_message | |
27623 | ||
27624 | If you are writing your own custom rejection message or log message when | |
27625 | denying access, you can use this variable to include information about the | |
27626 | verification failure. | |
27627 | ||
27628 | In addition, $sender_verify_failure or $recipient_verify_failure (as | |
27629 | appropriate) contains one of the following words: | |
27630 | ||
27631 | * qualify: The address was unqualified (no domain), and the message was | |
27632 | neither local nor came from an exempted host. | |
27633 | ||
27634 | * route: Routing failed. | |
27635 | ||
27636 | * mail: Routing succeeded, and a callout was attempted; rejection occurred at | |
27637 | or before the MAIL command (that is, on initial connection, HELO, or MAIL). | |
27638 | ||
27639 | * recipient: The RCPT command in a callout was rejected. | |
27640 | ||
27641 | * postmaster: The postmaster check in a callout was rejected. | |
27642 | ||
27643 | The main use of these variables is expected to be to distinguish between | |
27644 | rejections of MAIL and rejections of RCPT in callouts. | |
27645 | ||
27646 | ||
27647 | 42.45 Callout verification | |
27648 | -------------------------- | |
27649 | ||
27650 | For non-local addresses, routing verifies the domain, but is unable to do any | |
27651 | checking of the local part. There are situations where some means of verifying | |
27652 | the local part is desirable. One way this can be done is to make an SMTP | |
27653 | callback to a delivery host for the sender address or a callforward to a | |
27654 | subsequent host for a recipient address, to see if the host accepts the | |
27655 | address. We use the term callout to cover both cases. Note that for a sender | |
27656 | address, the callback is not to the client host that is trying to deliver the | |
27657 | message, but to one of the hosts that accepts incoming mail for the sender's | |
27658 | domain. | |
27659 | ||
27660 | Exim does not do callouts by default. If you want them to happen, you must | |
27661 | request them by setting appropriate options on the verify condition, as | |
27662 | described below. This facility should be used with care, because it can add a | |
27663 | lot of resource usage to the cost of verifying an address. However, Exim does | |
27664 | cache the results of callouts, which helps to reduce the cost. Details of | |
27665 | caching are in section 42.47. | |
27666 | ||
27667 | Recipient callouts are usually used only between hosts that are controlled by | |
27668 | the same administration. For example, a corporate gateway host could use | |
27669 | callouts to check for valid recipients on an internal mailserver. A successful | |
27670 | callout does not guarantee that a real delivery to the address would succeed; | |
27671 | on the other hand, a failing callout does guarantee that a delivery would fail. | |
27672 | ||
27673 | If the callout option is present on a condition that verifies an address, a | |
27674 | second stage of verification occurs if the address is successfully routed to | |
27675 | one or more remote hosts. The usual case is routing by a dnslookup or a | |
27676 | manualroute router, where the router specifies the hosts. However, if a router | |
27677 | that does not set up hosts routes to an smtp transport with a hosts setting, | |
27678 | the transport's hosts are used. If an smtp transport has hosts_override set, | |
27679 | its hosts are always used, whether or not the router supplies a host list. | |
27680 | Callouts are only supported on smtp transports. | |
27681 | ||
27682 | The port that is used is taken from the transport, if it is specified and is a | |
27683 | remote transport. (For routers that do verification only, no transport need be | |
27684 | specified.) Otherwise, the default SMTP port is used. If a remote transport | |
27685 | specifies an outgoing interface, this is used; otherwise the interface is not | |
27686 | specified. Likewise, the text that is used for the HELO command is taken from | |
27687 | the transport's helo_data option; if there is no transport, the value of | |
27688 | $smtp_active_hostname is used. | |
27689 | ||
27690 | For a sender callout check, Exim makes SMTP connections to the remote hosts, to | |
27691 | test whether a bounce message could be delivered to the sender address. The | |
27692 | following SMTP commands are sent: | |
27693 | ||
27694 | HELO <local host name> | |
27695 | MAIL FROM:<> | |
27696 | RCPT TO:<the address to be tested> | |
27697 | QUIT | |
27698 | ||
27699 | LHLO is used instead of HELO if the transport's protocol option is set to | |
27700 | "lmtp". | |
27701 | ||
27702 | The callout may use EHLO, AUTH and/or STARTTLS given appropriate option | |
27703 | settings. | |
27704 | ||
27705 | A recipient callout check is similar. By default, it also uses an empty address | |
27706 | for the sender. This default is chosen because most hosts do not make use of | |
27707 | the sender address when verifying a recipient. Using the same address means | |
27708 | that a single cache entry can be used for each recipient. Some sites, however, | |
27709 | do make use of the sender address when verifying. These are catered for by the | |
27710 | use_sender and use_postmaster options, described in the next section. | |
27711 | ||
27712 | If the response to the RCPT command is a 2xx code, the verification succeeds. | |
27713 | If it is 5xx, the verification fails. For any other condition, Exim tries the | |
27714 | next host, if any. If there is a problem with all the remote hosts, the ACL | |
27715 | yields "defer", unless the defer_ok parameter of the callout option is given, | |
27716 | in which case the condition is forced to succeed. | |
27717 | ||
27718 | A callout may take a little time. For this reason, Exim normally flushes SMTP | |
27719 | output before performing a callout in an ACL, to avoid unexpected timeouts in | |
27720 | clients when the SMTP PIPELINING extension is in use. The flushing can be | |
27721 | disabled by using a control modifier to set no_callout_flush. | |
27722 | ||
27723 | ||
27724 | 42.46 Additional parameters for callouts | |
27725 | ---------------------------------------- | |
27726 | ||
27727 | The callout option can be followed by an equals sign and a number of optional | |
27728 | parameters, separated by commas. For example: | |
27729 | ||
27730 | verify = recipient/callout=10s,defer_ok | |
27731 | ||
27732 | The old syntax, which had callout_defer_ok and check_postmaster as separate | |
27733 | verify options, is retained for backwards compatibility, but is now deprecated. | |
27734 | The additional parameters for callout are as follows: | |
27735 | ||
27736 | <a time interval> | |
27737 | ||
27738 | This specifies the timeout that applies for the callout attempt to each | |
27739 | host. For example: | |
27740 | ||
27741 | verify = sender/callout=5s | |
27742 | ||
27743 | The default is 30 seconds. The timeout is used for each response from the | |
27744 | remote host. It is also used for the initial connection, unless overridden | |
27745 | by the connect parameter. | |
27746 | ||
27747 | connect = <time interval> | |
27748 | ||
27749 | This parameter makes it possible to set a different (usually smaller) | |
27750 | timeout for making the SMTP connection. For example: | |
27751 | ||
27752 | verify = sender/callout=5s,connect=1s | |
27753 | ||
27754 | If not specified, this timeout defaults to the general timeout value. | |
27755 | ||
27756 | defer_ok | |
27757 | ||
27758 | When this parameter is present, failure to contact any host, or any other | |
27759 | kind of temporary error, is treated as success by the ACL. However, the | |
27760 | cache is not updated in this circumstance. | |
27761 | ||
27762 | fullpostmaster | |
27763 | ||
27764 | This operates like the postmaster option (see below), but if the check for | |
27765 | postmaster@domain fails, it tries just postmaster, without a domain, in | |
27766 | accordance with the specification in RFC 2821. The RFC states that the | |
27767 | unqualified address postmaster should be accepted. | |
27768 | ||
27769 | mailfrom = <email address> | |
27770 | ||
27771 | When verifying addresses in header lines using the header_sender | |
27772 | verification option, Exim behaves by default as if the addresses are | |
27773 | envelope sender addresses from a message. Callout verification therefore | |
27774 | tests to see whether a bounce message could be delivered, by using an empty | |
27775 | address in the MAIL command. However, it is arguable that these addresses | |
27776 | might never be used as envelope senders, and could therefore justifiably | |
27777 | reject bounce messages (empty senders). The mailfrom callout parameter | |
27778 | allows you to specify what address to use in the MAIL command. For example: | |
27779 | ||
27780 | require verify = header_sender/callout=mailfrom=abcd@x.y.z | |
27781 | ||
27782 | This parameter is available only for the header_sender verification option. | |
27783 | ||
27784 | maxwait = <time interval> | |
27785 | ||
27786 | This parameter sets an overall timeout for performing a callout | |
27787 | verification. For example: | |
27788 | ||
27789 | verify = sender/callout=5s,maxwait=30s | |
27790 | ||
27791 | This timeout defaults to four times the callout timeout for individual SMTP | |
27792 | commands. The overall timeout applies when there is more than one host that | |
27793 | can be tried. The timeout is checked before trying the next host. This | |
27794 | prevents very long delays if there are a large number of hosts and all are | |
27795 | timing out (for example, when network connections are timing out). | |
27796 | ||
27797 | no_cache | |
27798 | ||
27799 | When this parameter is given, the callout cache is neither read nor | |
27800 | updated. | |
27801 | ||
27802 | postmaster | |
27803 | ||
27804 | When this parameter is set, a successful callout check is followed by a | |
27805 | similar check for the local part postmaster at the same domain. If this | |
27806 | address is rejected, the callout fails (but see fullpostmaster above). The | |
27807 | result of the postmaster check is recorded in a cache record; if it is a | |
27808 | failure, this is used to fail subsequent callouts for the domain without a | |
27809 | connection being made, until the cache record expires. | |
27810 | ||
27811 | postmaster_mailfrom = <email address> | |
27812 | ||
27813 | The postmaster check uses an empty sender in the MAIL command by default. | |
27814 | You can use this parameter to do a postmaster check using a different | |
27815 | address. For example: | |
27816 | ||
27817 | require verify = sender/callout=postmaster_mailfrom=abc@x.y.z | |
27818 | ||
27819 | If both postmaster and postmaster_mailfrom are present, the rightmost one | |
27820 | overrides. The postmaster parameter is equivalent to this example: | |
27821 | ||
27822 | require verify = sender/callout=postmaster_mailfrom= | |
27823 | ||
27824 | Warning: The caching arrangements for postmaster checking do not take | |
27825 | account of the sender address. It is assumed that either the empty address | |
27826 | or a fixed non-empty address will be used. All that Exim remembers is that | |
27827 | the postmaster check for the domain succeeded or failed. | |
27828 | ||
27829 | random | |
27830 | ||
27831 | When this parameter is set, before doing the normal callout check, Exim | |
27832 | does a check for a "random" local part at the same domain. The local part | |
27833 | is not really random - it is defined by the expansion of the option | |
27834 | callout_random_local_part, which defaults to | |
27835 | ||
27836 | $primary_hostname-$tod_epoch-testing | |
27837 | ||
27838 | The idea here is to try to determine whether the remote host accepts all | |
27839 | local parts without checking. If it does, there is no point in doing | |
27840 | callouts for specific local parts. If the "random" check succeeds, the | |
27841 | result is saved in a cache record, and used to force the current and | |
27842 | subsequent callout checks to succeed without a connection being made, until | |
27843 | the cache record expires. | |
27844 | ||
27845 | use_postmaster | |
27846 | ||
27847 | This parameter applies to recipient callouts only. For example: | |
27848 | ||
27849 | deny !verify = recipient/callout=use_postmaster | |
27850 | ||
27851 | It causes a non-empty postmaster address to be used in the MAIL command | |
27852 | when performing the callout for the recipient, and also for a "random" | |
27853 | check if that is configured. The local part of the address is "postmaster" | |
27854 | and the domain is the contents of $qualify_domain. | |
27855 | ||
27856 | use_sender | |
27857 | ||
27858 | This option applies to recipient callouts only. For example: | |
27859 | ||
27860 | require verify = recipient/callout=use_sender | |
27861 | ||
27862 | It causes the message's actual sender address to be used in the MAIL | |
27863 | command when performing the callout, instead of an empty address. There is | |
27864 | no need to use this option unless you know that the called hosts make use | |
27865 | of the sender when checking recipients. If used indiscriminately, it | |
27866 | reduces the usefulness of callout caching. | |
27867 | ||
27868 | If you use any of the parameters that set a non-empty sender for the MAIL | |
27869 | command (mailfrom, postmaster_mailfrom, use_postmaster, or use_sender), you | |
27870 | should think about possible loops. Recipient checking is usually done between | |
27871 | two hosts that are under the same management, and the host that receives the | |
27872 | callouts is not normally configured to do callouts itself. Therefore, it is | |
27873 | normally safe to use use_postmaster or use_sender in these circumstances. | |
27874 | ||
27875 | However, if you use a non-empty sender address for a callout to an arbitrary | |
27876 | host, there is the likelihood that the remote host will itself initiate a | |
27877 | callout check back to your host. As it is checking what appears to be a message | |
27878 | sender, it is likely to use an empty address in MAIL, thus avoiding a callout | |
27879 | loop. However, to be on the safe side it would be best to set up your own ACLs | |
27880 | so that they do not do sender verification checks when the recipient is the | |
27881 | address you use for header sender or postmaster callout checking. | |
27882 | ||
27883 | Another issue to think about when using non-empty senders for callouts is | |
27884 | caching. When you set mailfrom or use_sender, the cache record is keyed by the | |
27885 | sender/recipient combination; thus, for any given recipient, many more actual | |
27886 | callouts are performed than when an empty sender or postmaster is used. | |
27887 | ||
27888 | ||
27889 | 42.47 Callout caching | |
27890 | --------------------- | |
27891 | ||
27892 | Exim caches the results of callouts in order to reduce the amount of resources | |
27893 | used, unless you specify the no_cache parameter with the callout option. A | |
27894 | hints database called "callout" is used for the cache. Two different record | |
27895 | types are used: one records the result of a callout check for a specific | |
27896 | address, and the other records information that applies to the entire domain | |
27897 | (for example, that it accepts the local part postmaster). | |
27898 | ||
27899 | When an original callout fails, a detailed SMTP error message is given about | |
27900 | the failure. However, for subsequent failures use the cache data, this message | |
27901 | is not available. | |
27902 | ||
27903 | The expiry times for negative and positive address cache records are | |
27904 | independent, and can be set by the global options callout_negative_expire | |
27905 | (default 2h) and callout_positive_expire (default 24h), respectively. | |
27906 | ||
27907 | If a host gives a negative response to an SMTP connection, or rejects any | |
27908 | commands up to and including | |
27909 | ||
27910 | MAIL FROM:<> | |
27911 | ||
27912 | (but not including the MAIL command with a non-empty address), any callout | |
27913 | attempt is bound to fail. Exim remembers such failures in a domain cache | |
27914 | record, which it uses to fail callouts for the domain without making new | |
27915 | connections, until the domain record times out. There are two separate expiry | |
27916 | times for domain cache records: callout_domain_negative_expire (default 3h) and | |
27917 | callout_domain_positive_expire (default 7d). | |
27918 | ||
27919 | Domain records expire when the negative expiry time is reached if callouts | |
27920 | cannot be made for the domain, or if the postmaster check failed. Otherwise, | |
27921 | they expire when the positive expiry time is reached. This ensures that, for | |
27922 | example, a host that stops accepting "random" local parts will eventually be | |
27923 | noticed. | |
27924 | ||
27925 | The callout caching mechanism is based on the domain of the address that is | |
27926 | being tested. If the domain routes to several hosts, it is assumed that their | |
27927 | behaviour will be the same. | |
27928 | ||
27929 | ||
27930 | 42.48 Sender address verification reporting | |
27931 | ------------------------------------------- | |
27932 | ||
27933 | See section 42.44 for a general discussion of verification. When sender | |
27934 | verification fails in an ACL, the details of the failure are given as | |
27935 | additional output lines before the 550 response to the relevant SMTP command | |
27936 | (RCPT or DATA). For example, if sender callout is in use, you might see: | |
27937 | ||
27938 | MAIL FROM:<xyz@abc.example> | |
27939 | 250 OK | |
27940 | RCPT TO:<pqr@def.example> | |
27941 | 550-Verification failed for <xyz@abc.example> | |
27942 | 550-Called: 192.168.34.43 | |
27943 | 550-Sent: RCPT TO:<xyz@abc.example> | |
27944 | 550-Response: 550 Unknown local part xyz in <xyz@abc.example> | |
27945 | 550 Sender verification failed | |
27946 | ||
27947 | If more than one RCPT command fails in the same way, the details are given only | |
27948 | for the first of them. However, some administrators do not want to send out | |
27949 | this much information. You can suppress the details by adding "/no_details" to | |
27950 | the ACL statement that requests sender verification. For example: | |
27951 | ||
27952 | verify = sender/no_details | |
27953 | ||
27954 | ||
27955 | 42.49 Redirection while verifying | |
27956 | --------------------------------- | |
27957 | ||
27958 | A dilemma arises when a local address is redirected by aliasing or forwarding | |
27959 | during verification: should the generated addresses themselves be verified, or | |
27960 | should the successful expansion of the original address be enough to verify it? | |
27961 | By default, Exim takes the following pragmatic approach: | |
27962 | ||
27963 | * When an incoming address is redirected to just one child address, | |
27964 | verification continues with the child address, and if that fails to verify, | |
27965 | the original verification also fails. | |
27966 | ||
27967 | * When an incoming address is redirected to more than one child address, | |
27968 | verification does not continue. A success result is returned. | |
27969 | ||
27970 | This seems the most reasonable behaviour for the common use of aliasing as a | |
27971 | way of redirecting different local parts to the same mailbox. It means, for | |
27972 | example, that a pair of alias entries of the form | |
27973 | ||
27974 | A.Wol: aw123 | |
27975 | aw123: :fail: Gone away, no forwarding address | |
27976 | ||
27977 | work as expected, with both local parts causing verification failure. When a | |
27978 | redirection generates more than one address, the behaviour is more like a | |
27979 | mailing list, where the existence of the alias itself is sufficient for | |
27980 | verification to succeed. | |
27981 | ||
27982 | It is possible, however, to change the default behaviour so that all successful | |
27983 | redirections count as successful verifications, however many new addresses are | |
27984 | generated. This is specified by the success_on_redirect verification option. | |
27985 | For example: | |
27986 | ||
27987 | require verify = recipient/success_on_redirect/callout=10s | |
27988 | ||
27989 | In this example, verification succeeds if a router generates a new address, and | |
27990 | the callout does not occur, because no address was routed to a remote host. | |
27991 | ||
27992 | When verification is being tested via the -bv option, the treatment of | |
27993 | redirections is as just described, unless the -v or any debugging option is | |
27994 | also specified. In that case, full verification is done for every generated | |
27995 | address and a report is output for each of them. | |
27996 | ||
27997 | ||
27998 | 42.50 Client SMTP authorization (CSA) | |
27999 | ------------------------------------- | |
28000 | ||
28001 | Client SMTP Authorization is a system that allows a site to advertise which | |
28002 | machines are and are not permitted to send email. This is done by placing | |
28003 | special SRV records in the DNS; these are looked up using the client's HELO | |
28004 | domain. At the time of writing, CSA is still an Internet Draft. Client SMTP | |
28005 | Authorization checks in Exim are performed by the ACL condition: | |
28006 | ||
28007 | verify = csa | |
28008 | ||
28009 | This fails if the client is not authorized. If there is a DNS problem, or if no | |
28010 | valid CSA SRV record is found, or if the client is authorized, the condition | |
28011 | succeeds. These three cases can be distinguished using the expansion variable | |
28012 | $csa_status, which can take one of the values "fail", "defer", "unknown", or | |
28013 | "ok". The condition does not itself defer because that would be likely to cause | |
28014 | problems for legitimate email. | |
28015 | ||
28016 | The error messages produced by the CSA code include slightly more detail. If | |
28017 | $csa_status is "defer", this may be because of problems looking up the CSA SRV | |
28018 | record, or problems looking up the CSA target address record. There are four | |
28019 | reasons for $csa_status being "fail": | |
28020 | ||
28021 | * The client's host name is explicitly not authorized. | |
28022 | ||
28023 | * The client's IP address does not match any of the CSA target IP addresses. | |
28024 | ||
28025 | * The client's host name is authorized but it has no valid target IP | |
28026 | addresses (for example, the target's addresses are IPv6 and the client is | |
28027 | using IPv4). | |
28028 | ||
28029 | * The client's host name has no CSA SRV record but a parent domain has | |
28030 | asserted that all subdomains must be explicitly authorized. | |
28031 | ||
28032 | The csa verification condition can take an argument which is the domain to use | |
28033 | for the DNS query. The default is: | |
28034 | ||
28035 | verify = csa/$sender_helo_name | |
28036 | ||
28037 | This implementation includes an extension to CSA. If the query domain is an | |
28038 | address literal such as [192.0.2.95], or if it is a bare IP address, Exim | |
28039 | searches for CSA SRV records in the reverse DNS as if the HELO domain was (for | |
28040 | example) 95.2.0.192.in-addr.arpa. Therefore it is meaningful to say: | |
28041 | ||
28042 | verify = csa/$sender_host_address | |
28043 | ||
28044 | In fact, this is the check that Exim performs if the client does not say HELO. | |
28045 | This extension can be turned off by setting the main configuration option | |
28046 | dns_csa_use_reverse to be false. | |
28047 | ||
28048 | If a CSA SRV record is not found for the domain itself, a search is performed | |
28049 | through its parent domains for a record which might be making assertions about | |
28050 | subdomains. The maximum depth of this search is limited using the main | |
28051 | configuration option dns_csa_search_limit, which is 5 by default. Exim does not | |
28052 | look for CSA SRV records in a top level domain, so the default settings handle | |
28053 | HELO domains as long as seven (hostname.five.four.three.two.one.com). This | |
28054 | encompasses the vast majority of legitimate HELO domains. | |
28055 | ||
28056 | The dnsdb lookup also has support for CSA. Although dnsdb also supports direct | |
28057 | SRV lookups, this is not sufficient because of the extra parent domain search | |
28058 | behaviour of CSA, and (as with PTR lookups) dnsdb also turns IP addresses into | |
28059 | lookups in the reverse DNS space. The result of a successful lookup such as: | |
28060 | ||
28061 | ${lookup dnsdb {csa=$sender_helo_name}} | |
28062 | ||
28063 | has two space-separated fields: an authorization code and a target host name. | |
28064 | The authorization code can be "Y" for yes, "N" for no, "X" for explicit | |
28065 | authorization required but absent, or "?" for unknown. | |
28066 | ||
28067 | ||
28068 | 42.51 Bounce address tag validation | |
28069 | ----------------------------------- | |
28070 | ||
28071 | Bounce address tag validation (BATV) is a scheme whereby the envelope senders | |
28072 | of outgoing messages have a cryptographic, timestamped "tag" added to them. | |
28073 | Genuine incoming bounce messages should therefore always be addressed to | |
28074 | recipients that have a valid tag. This scheme is a way of detecting unwanted | |
28075 | bounce messages caused by sender address forgeries (often called "collateral | |
28076 | spam"), because the recipients of such messages do not include valid tags. | |
28077 | ||
28078 | There are two expansion items to help with the implementation of the BATV | |
28079 | "prvs" (private signature) scheme in an Exim configuration. This scheme signs | |
28080 | the original envelope sender address by using a simple key to add a hash of the | |
28081 | address and some time-based randomizing information. The prvs expansion item | |
28082 | creates a signed address, and the prvscheck expansion item checks one. The | |
28083 | syntax of these expansion items is described in section 11.5. | |
28084 | ||
28085 | As an example, suppose the secret per-address keys are stored in an MySQL | |
28086 | database. A query to look up the key for an address could be defined as a macro | |
28087 | like this: | |
28088 | ||
28089 | PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \ | |
28090 | WHERE sender='${quote_mysql:$prvscheck_address}'\ | |
28091 | }{$value}} | |
28092 | ||
28093 | Suppose also that the senders who make use of BATV are defined by an address | |
28094 | list called batv_senders. Then, in the ACL for RCPT commands, you could use | |
28095 | this: | |
28096 | ||
28097 | # Bounces: drop unsigned addresses for BATV senders | |
28098 | deny message = This address does not send an unsigned reverse path | |
28099 | senders = : | |
28100 | recipients = +batv_senders | |
28101 | ||
28102 | # Bounces: In case of prvs-signed address, check signature. | |
28103 | deny message = Invalid reverse path signature. | |
28104 | senders = : | |
28105 | condition = ${prvscheck {$local_part@$domain}\ | |
28106 | {PRVSCHECK_SQL}{1}} | |
28107 | !condition = $prvscheck_result | |
28108 | ||
28109 | The first statement rejects recipients for bounce messages that are addressed | |
28110 | to plain BATV sender addresses, because it is known that BATV senders do not | |
28111 | send out messages with plain sender addresses. The second statement rejects | |
28112 | recipients that are prvs-signed, but with invalid signatures (either because | |
28113 | the key is wrong, or the signature has timed out). | |
28114 | ||
28115 | A non-prvs-signed address is not rejected by the second statement, because the | |
28116 | prvscheck expansion yields an empty string if its first argument is not a | |
28117 | prvs-signed address, thus causing the condition condition to be false. If the | |
28118 | first argument is a syntactically valid prvs-signed address, the yield is the | |
28119 | third string (in this case "1"), whether or not the cryptographic and timeout | |
28120 | checks succeed. The $prvscheck_result variable contains the result of the | |
28121 | checks (empty for failure, "1" for success). | |
28122 | ||
28123 | There is one more issue you must consider when implementing prvs-signing: you | |
28124 | have to ensure that the routers accept prvs-signed addresses and deliver them | |
28125 | correctly. The easiest way to handle this is to use a redirect router to remove | |
28126 | the signature with a configuration along these lines: | |
28127 | ||
28128 | batv_redirect: | |
28129 | driver = redirect | |
28130 | data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}} | |
28131 | ||
28132 | This works because, if the third argument of prvscheck is empty, the result of | |
28133 | the expansion of a prvs-signed address is the decoded value of the original | |
28134 | address. This router should probably be the first of your routers that handles | |
28135 | local addresses. | |
28136 | ||
28137 | To create BATV-signed addresses in the first place, a transport of this form | |
28138 | can be used: | |
28139 | ||
28140 | external_smtp_batv: | |
28141 | driver = smtp | |
28142 | return_path = ${prvs {$return_path} \ | |
28143 | {${lookup mysql{SELECT \ | |
28144 | secret FROM batv_prvs WHERE \ | |
28145 | sender='${quote_mysql:$sender_address}'} \ | |
28146 | {$value}fail}}} | |
28147 | ||
28148 | If no key can be found for the existing return path, no signing takes place. | |
28149 | ||
28150 | ||
28151 | 42.52 Using an ACL to control relaying | |
28152 | -------------------------------------- | |
28153 | ||
28154 | An MTA is said to relay a message if it receives it from some host and delivers | |
28155 | it directly to another host as a result of a remote address contained within | |
28156 | it. Redirecting a local address via an alias or forward file and then passing | |
28157 | the message on to another host is not relaying, but a redirection as a result | |
28158 | of the "percent hack" is. | |
28159 | ||
28160 | Two kinds of relaying exist, which are termed "incoming" and "outgoing". A host | |
28161 | which is acting as a gateway or an MX backup is concerned with incoming | |
28162 | relaying from arbitrary hosts to a specific set of domains. On the other hand, | |
28163 | a host which is acting as a smart host for a number of clients is concerned | |
28164 | with outgoing relaying from those clients to the Internet at large. Often the | |
28165 | same host is fulfilling both functions, but in principle these two kinds of | |
28166 | relaying are entirely independent. What is not wanted is the transmission of | |
28167 | mail from arbitrary remote hosts through your system to arbitrary domains. | |
28168 | ||
28169 | You can implement relay control by means of suitable statements in the ACL that | |
28170 | runs for each RCPT command. For convenience, it is often easiest to use Exim's | |
28171 | named list facility to define the domains and hosts involved. For example, | |
28172 | suppose you want to do the following: | |
28173 | ||
28174 | * Deliver a number of domains to mailboxes on the local host (or process them | |
28175 | locally in some other way). Let's say these are my.dom1.example and | |
28176 | my.dom2.example. | |
28177 | ||
28178 | * Relay mail for a number of other domains for which you are the secondary | |
28179 | MX. These might be friend1.example and friend2.example. | |
28180 | ||
28181 | * Relay mail from the hosts on your local LAN, to whatever domains are | |
28182 | involved. Suppose your LAN is 192.168.45.0/24. | |
28183 | ||
28184 | In the main part of the configuration, you put the following definitions: | |
28185 | ||
28186 | domainlist local_domains = my.dom1.example : my.dom2.example | |
28187 | domainlist relay_to_domains = friend1.example : friend2.example | |
28188 | hostlist relay_from_hosts = 192.168.45.0/24 | |
28189 | ||
28190 | Now you can use these definitions in the ACL that is run for every RCPT | |
28191 | command: | |
28192 | ||
28193 | acl_check_rcpt: | |
28194 | accept domains = +local_domains : +relay_to_domains | |
28195 | accept hosts = +relay_from_hosts | |
28196 | ||
28197 | The first statement accepts any RCPT command that contains an address in the | |
28198 | local or relay domains. For any other domain, control passes to the second | |
28199 | statement, which accepts the command only if it comes from one of the relay | |
28200 | hosts. In practice, you will probably want to make your ACL more sophisticated | |
28201 | than this, for example, by including sender and recipient verification. The | |
28202 | default configuration includes a more comprehensive example, which is described | |
28203 | in chapter 7. | |
28204 | ||
28205 | ||
28206 | 42.53 Checking a relay configuration | |
28207 | ------------------------------------ | |
28208 | ||
28209 | You can check the relay characteristics of your configuration in the same way | |
28210 | that you can test any ACL behaviour for an incoming SMTP connection, by using | |
28211 | the -bh option to run a fake SMTP session with which you interact. | |
28212 | ||
28213 | For specifically testing for unwanted relaying, the host | |
28214 | relay-test.mail-abuse.org provides a useful service. If you telnet to this host | |
28215 | from the host on which Exim is running, using the normal telnet port, you will | |
28216 | see a normal telnet connection message and then quite a long delay. Be patient. | |
28217 | The remote host is making an SMTP connection back to your host, and trying a | |
28218 | number of common probes to test for open relay vulnerability. The results of | |
28219 | the tests will eventually appear on your terminal. | |
28220 | ||
28221 | ||
28222 | ||
28223 | =============================================================================== | |
28224 | 43. CONTENT SCANNING AT ACL TIME | |
28225 | ||
28226 | The extension of Exim to include content scanning at ACL time, formerly known | |
28227 | as "exiscan", was originally implemented as a patch by Tom Kistner. The code | |
28228 | was integrated into the main source for Exim release 4.50, and Tom continues to | |
28229 | maintain it. Most of the wording of this chapter is taken from Tom's | |
28230 | specification. | |
28231 | ||
28232 | It is also possible to scan the content of messages at other times. The | |
28233 | local_scan() function (see chapter 44) allows for content scanning after all | |
28234 | the ACLs have run. A transport filter can be used to scan messages at delivery | |
28235 | time (see the transport_filter option, described in chapter 24). | |
28236 | ||
28237 | If you want to include the ACL-time content-scanning features when you compile | |
28238 | Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your Local/ | |
28239 | Makefile. When you do that, the Exim binary is built with: | |
28240 | ||
28241 | * Two additional ACLs (acl_smtp_mime and acl_not_smtp_mime) that are run for | |
28242 | all MIME parts for SMTP and non-SMTP messages, respectively. | |
28243 | ||
28244 | * Additional ACL conditions and modifiers: decode, malware, mime_regex, regex | |
28245 | , and spam. These can be used in the ACL that is run at the end of message | |
28246 | reception (the acl_smtp_data ACL). | |
28247 | ||
28248 | * An additional control feature ("no_mbox_unspool") that saves spooled copies | |
28249 | of messages, or parts of messages, for debugging purposes. | |
28250 | ||
28251 | * Additional expansion variables that are set in the new ACL and by the new | |
28252 | conditions. | |
28253 | ||
28254 | * Two new main configuration options: av_scanner and spamd_address. | |
28255 | ||
28256 | There is another content-scanning configuration option for Local/Makefile, | |
28257 | called WITH_OLD_DEMIME. If this is set, the old, deprecated demime ACL | |
28258 | condition is compiled, in addition to all the other content-scanning features. | |
28259 | ||
28260 | Content-scanning is continually evolving, and new features are still being | |
28261 | added. While such features are still unstable and liable to incompatible | |
28262 | changes, they are made available in Exim by setting options whose names begin | |
28263 | EXPERIMENTAL_ in Local/Makefile. Such features are not documented in this | |
28264 | manual. You can find out about them by reading the file called doc/ | |
28265 | experimental.txt. | |
28266 | ||
28267 | All the content-scanning facilities work on a MBOX copy of the message that is | |
28268 | temporarily created in a file called: | |
28269 | ||
28270 | <spool_directory>/scan/<message_id>/<message_id>.eml | |
28271 | ||
28272 | The .eml extension is a friendly hint to virus scanners that they can expect an | |
28273 | MBOX-like structure inside that file. The file is created when the first | |
28274 | content scanning facility is called. Subsequent calls to content scanning | |
28275 | conditions open the same file again. The directory is recursively removed when | |
28276 | the acl_smtp_data ACL has finished running, unless | |
28277 | ||
28278 | control = no_mbox_unspool | |
28279 | ||
28280 | has been encountered. When the MIME ACL decodes files, they are put into the | |
28281 | same directory by default. | |
28282 | ||
28283 | ||
28284 | 43.1 Scanning for viruses | |
28285 | ------------------------- | |
28286 | ||
28287 | The malware ACL condition lets you connect virus scanner software to Exim. It | |
28288 | supports a "generic" interface to scanners called via the shell, and | |
28289 | specialized interfaces for "daemon" type virus scanners, which are resident in | |
28290 | memory and thus are much faster. | |
28291 | ||
28292 | You can set the av_scanner option in first part of the Exim configuration file | |
28293 | to specify which scanner to use, together with any additional options that are | |
28294 | needed. The basic syntax is as follows: | |
28295 | ||
28296 | av_scanner = <scanner-type>:<option1>:<option2>:[...] | |
28297 | ||
28298 | If you do not set av_scanner, it defaults to | |
28299 | ||
28300 | av_scanner = sophie:/var/run/sophie | |
28301 | ||
28302 | If the value of av_scanner starts with a dollar character, it is expanded | |
28303 | before use. The usual list-parsing of the content (see 6.19) applies. The | |
28304 | following scanner types are supported in this release: | |
28305 | ||
28306 | aveserver | |
28307 | ||
28308 | This is the scanner daemon of Kaspersky Version 5. You can get a trial | |
28309 | version at http://www.kaspersky.com. This scanner type takes one option, | |
28310 | which is the path to the daemon's UNIX socket. The default is shown in this | |
28311 | example: | |
28312 | ||
28313 | av_scanner = aveserver:/var/run/aveserver | |
28314 | ||
28315 | clamd | |
28316 | ||
28317 | This daemon-type scanner is GPL and free. You can get it at http:// | |
28318 | www.clamav.net/. Some older versions of clamd do not seem to unpack MIME | |
28319 | containers, so it used to be recommended to unpack MIME attachments in the | |
28320 | MIME ACL. This no longer believed to be necessary. One option is required: | |
28321 | either the path and name of a UNIX socket file, or a hostname or IP number, | |
28322 | and a port, separated by space, as in the second of these examples: | |
28323 | ||
28324 | av_scanner = clamd:/opt/clamd/socket | |
28325 | av_scanner = clamd:192.0.2.3 1234 | |
28326 | av_scanner = clamd:192.0.2.3 1234:local | |
28327 | av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234 | |
28328 | ||
28329 | If the value of av_scanner points to a UNIX socket file or contains the | |
28330 | local keyword, then the ClamAV interface will pass a filename containing | |
28331 | the data to be scanned, which will should normally result in less I/O | |
28332 | happening and be more efficient. Normally in the TCP case, the data is | |
28333 | streamed to ClamAV as Exim does not assume that there is a common | |
28334 | filesystem with the remote host. There is an option WITH_OLD_CLAMAV_STREAM | |
28335 | in src/EDITME available, should you be running a version of ClamAV prior to | |
28336 | 0.95. | |
28337 | ||
28338 | The final example shows that multiple TCP targets can be specified. Exim | |
28339 | will randomly use one for each incoming email (i.e. it load balances them). | |
28340 | Note that only TCP targets may be used if specifying a list of scanners; a | |
28341 | UNIX socket cannot be mixed in with TCP targets. If one of the servers | |
28342 | becomes unavailable, Exim will try the remaining one(s) until it finds one | |
28343 | that works. When a clamd server becomes unreachable, Exim will log a | |
28344 | message. Exim does not keep track of scanner state between multiple | |
28345 | messages, and the scanner selection is random, so the message will get | |
28346 | logged in the mainlog for each email that the down scanner gets chosen | |
28347 | first (message wrapped to be readable): | |
28348 | ||
28349 | 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition: | |
28350 | clamd: connection to localhost, port 3310 failed | |
28351 | (Connection refused) | |
28352 | ||
28353 | If the option is unset, the default is /tmp/clamd. Thanks to David Saez for | |
28354 | contributing the code for this scanner. | |
28355 | ||
28356 | cmdline | |
28357 | ||
28358 | This is the keyword for the generic command line scanner interface. It can | |
28359 | be used to attach virus scanners that are invoked from the shell. This | |
28360 | scanner type takes 3 mandatory options: | |
28361 | ||
28362 | 1. The full path and name of the scanner binary, with all command line | |
28363 | options, and a placeholder ("%s") for the directory to scan. | |
28364 | ||
28365 | 2. A regular expression to match against the STDOUT and STDERR output of | |
28366 | the virus scanner. If the expression matches, a virus was found. You | |
28367 | must make absolutely sure that this expression matches on "virus | |
28368 | found". This is called the "trigger" expression. | |
28369 | ||
28370 | 3. Another regular expression, containing exactly one pair of parentheses, | |
28371 | to match the name of the virus found in the scanners output. This is | |
28372 | called the "name" expression. | |
28373 | ||
28374 | For example, Sophos Sweep reports a virus on a line like this: | |
28375 | ||
28376 | Virus 'W32/Magistr-B' found in file ./those.bat | |
28377 | ||
28378 | For the trigger expression, we can match the phrase "found in file". For | |
28379 | the name expression, we want to extract the W32/Magistr-B string, so we can | |
28380 | match for the single quotes left and right of it. Altogether, this makes | |
28381 | the configuration setting: | |
28382 | ||
28383 | av_scanner = cmdline:\ | |
28384 | /path/to/sweep -ss -all -rec -archive %s:\ | |
28385 | found in file:'(.+)' | |
28386 | ||
28387 | drweb | |
28388 | ||
28389 | The DrWeb daemon scanner (http://www.sald.com/) interface takes one | |
28390 | argument, either a full path to a UNIX socket, or an IP address and port | |
28391 | separated by white space, as in these examples: | |
28392 | ||
28393 | av_scanner = drweb:/var/run/drwebd.sock | |
28394 | av_scanner = drweb:192.168.2.20 31337 | |
28395 | ||
28396 | If you omit the argument, the default path /usr/local/drweb/run/drwebd.sock | |
28397 | is used. Thanks to Alex Miller for contributing the code for this scanner. | |
28398 | ||
28399 | fsecure | |
28400 | ||
28401 | The F-Secure daemon scanner (http://www.f-secure.com) takes one argument | |
28402 | which is the path to a UNIX socket. For example: | |
28403 | ||
28404 | av_scanner = fsecure:/path/to/.fsav | |
28405 | ||
28406 | If no argument is given, the default is /var/run/.fsav. Thanks to Johan | |
28407 | Thelmen for contributing the code for this scanner. | |
28408 | ||
28409 | kavdaemon | |
28410 | ||
28411 | This is the scanner daemon of Kaspersky Version 4. This version of the | |
28412 | Kaspersky scanner is outdated. Please upgrade (see aveserver above). This | |
28413 | scanner type takes one option, which is the path to the daemon's UNIX | |
28414 | socket. For example: | |
28415 | ||
28416 | av_scanner = kavdaemon:/opt/AVP/AvpCtl | |
28417 | ||
28418 | The default path is /var/run/AvpCtl. | |
28419 | ||
28420 | mksd | |
28421 | ||
28422 | This is a daemon type scanner that is aimed mainly at Polish users, though | |
28423 | some parts of documentation are now available in English. You can get it at | |
28424 | http://linux.mks.com.pl/. The only option for this scanner type is the | |
28425 | maximum number of processes used simultaneously to scan the attachments, | |
28426 | provided that the demime facility is employed and also provided that mksd | |
28427 | has been run with at least the same number of child processes. For example: | |
28428 | ||
28429 | av_scanner = mksd:2 | |
28430 | ||
28431 | You can safely omit this option (the default value is 1). | |
28432 | ||
28433 | sock | |
28434 | ||
28435 | This is a general-purpose way of talking to simple scanner daemons running | |
28436 | on the local machine. There are four options: an address (which may be an | |
28437 | IP addres and port, or the path of a Unix socket), a commandline to send | |
28438 | (may include a single %s which will be replaced with the path to the mail | |
28439 | file to be scanned), an RE to trigger on from the returned data, an RE to | |
28440 | extract malware_name from the returned data. For example: | |
28441 | ||
28442 | av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$ | |
28443 | ||
28444 | Default for the socket specifier is /tmp/malware.sock. Default for the | |
28445 | commandline is %s\n. Both regular-expressions are required. | |
28446 | ||
28447 | sophie | |
28448 | ||
28449 | Sophie is a daemon that uses Sophos' libsavi library to scan for viruses. | |
28450 | You can get Sophie at http://www.clanfield.info/sophie/. The only option | |
28451 | for this scanner type is the path to the UNIX socket that Sophie uses for | |
28452 | client communication. For example: | |
28453 | ||
28454 | av_scanner = sophie:/tmp/sophie | |
28455 | ||
28456 | The default path is /var/run/sophie, so if you are using this, you can omit | |
28457 | the option. | |
28458 | ||
28459 | When av_scanner is correctly set, you can use the malware condition in the DATA | |
28460 | ACL. Note: You cannot use the malware condition in the MIME ACL. | |
28461 | ||
28462 | The av_scanner option is expanded each time malware is called. This makes it | |
28463 | possible to use different scanners. See further below for an example. The | |
28464 | malware condition caches its results, so when you use it multiple times for the | |
28465 | same message, the actual scanning process is only carried out once. However, | |
28466 | using expandable items in av_scanner disables this caching, in which case each | |
28467 | use of the malware condition causes a new scan of the message. | |
28468 | ||
28469 | The malware condition takes a right-hand argument that is expanded before use. | |
28470 | It can then be one of | |
28471 | ||
28472 | * "true", "*", or "1", in which case the message is scanned for viruses. The | |
28473 | condition succeeds if a virus was found, and fail otherwise. This is the | |
28474 | recommended usage. | |
28475 | ||
28476 | * "false" or "0" or an empty string, in which case no scanning is done and | |
28477 | the condition fails immediately. | |
28478 | ||
28479 | * A regular expression, in which case the message is scanned for viruses. The | |
28480 | condition succeeds if a virus is found and its name matches the regular | |
28481 | expression. This allows you to take special actions on certain types of | |
28482 | virus. | |
28483 | ||
28484 | You can append "/defer_ok" to the malware condition to accept messages even if | |
28485 | there is a problem with the virus scanner. Otherwise, such a problem causes the | |
28486 | ACL to defer. | |
28487 | ||
28488 | When a virus is found, the condition sets up an expansion variable called | |
28489 | $malware_name that contains the name of the virus. You can use it in a message | |
28490 | modifier that specifies the error returned to the sender, and/or in logging | |
28491 | data. | |
28492 | ||
28493 | If your virus scanner cannot unpack MIME and TNEF containers itself, you should | |
28494 | use the demime condition (see section 43.6) before the malware condition. | |
28495 | ||
28496 | Beware the interaction of Exim's message_size_limit with any size limits | |
28497 | imposed by your anti-virus scanner. | |
28498 | ||
28499 | Here is a very simple scanning example: | |
28500 | ||
28501 | deny message = This message contains malware ($malware_name) | |
28502 | demime = * | |
28503 | malware = * | |
28504 | ||
28505 | The next example accepts messages when there is a problem with the scanner: | |
28506 | ||
28507 | deny message = This message contains malware ($malware_name) | |
28508 | demime = * | |
28509 | malware = */defer_ok | |
28510 | ||
28511 | The next example shows how to use an ACL variable to scan with both sophie and | |
28512 | aveserver. It assumes you have set: | |
28513 | ||
28514 | av_scanner = $acl_m0 | |
28515 | ||
28516 | in the main Exim configuration. | |
28517 | ||
28518 | deny message = This message contains malware ($malware_name) | |
28519 | set acl_m0 = sophie | |
28520 | malware = * | |
28521 | ||
28522 | deny message = This message contains malware ($malware_name) | |
28523 | set acl_m0 = aveserver | |
28524 | malware = * | |
28525 | ||
28526 | ||
28527 | 43.2 Scanning with SpamAssassin | |
28528 | ------------------------------- | |
28529 | ||
28530 | The spam ACL condition calls SpamAssassin's spamd daemon to get a spam score | |
28531 | and a report for the message. You can get SpamAssassin at http:// | |
28532 | www.spamassassin.org, or, if you have a working Perl installation, you can use | |
28533 | CPAN by running: | |
28534 | ||
28535 | perl -MCPAN -e 'install Mail::SpamAssassin' | |
28536 | ||
28537 | SpamAssassin has its own set of configuration files. Please review its | |
28538 | documentation to see how you can tweak it. The default installation should work | |
28539 | nicely, however. | |
28540 | ||
28541 | After having installed and configured SpamAssassin, start the spamd daemon. By | |
28542 | default, it listens on 127.0.0.1, TCP port 783. If you use another host or port | |
28543 | for spamd, you must set the spamd_address option in the global part of the Exim | |
28544 | configuration as follows (example): | |
28545 | ||
28546 | spamd_address = 192.168.99.45 387 | |
28547 | ||
28548 | You do not need to set this option if you use the default. As of version 2.60, | |
28549 | spamd also supports communication over UNIX sockets. If you want to use these, | |
28550 | supply spamd_address with an absolute file name instead of a address/port pair: | |
28551 | ||
28552 | spamd_address = /var/run/spamd_socket | |
28553 | ||
28554 | You can have multiple spamd servers to improve scalability. These can reside on | |
28555 | other hardware reachable over the network. To specify multiple spamd servers, | |
28556 | put multiple address/port pairs in the spamd_address option, separated with | |
28557 | colons: | |
28558 | ||
28559 | spamd_address = 192.168.2.10 783 : \ | |
28560 | 192.168.2.11 783 : \ | |
28561 | 192.168.2.12 783 | |
28562 | ||
28563 | Up to 32 spamd servers are supported. The servers are queried in a random | |
28564 | fashion. When a server fails to respond to the connection attempt, all other | |
28565 | servers are tried until one succeeds. If no server responds, the spam condition | |
28566 | defers. | |
28567 | ||
28568 | Warning: It is not possible to use the UNIX socket connection method with | |
28569 | multiple spamd servers. | |
28570 | ||
28571 | The spamd_address variable is expanded before use if it starts with a dollar | |
28572 | sign. In this case, the expansion may return a string that is used as the list | |
28573 | so that multiple spamd servers can be the result of an expansion. | |
28574 | ||
28575 | ||
28576 | 43.3 Calling SpamAssassin from an Exim ACL | |
28577 | ------------------------------------------ | |
28578 | ||
28579 | Here is a simple example of the use of the spam condition in a DATA ACL: | |
28580 | ||
28581 | deny message = This message was classified as SPAM | |
28582 | spam = joe | |
28583 | ||
28584 | The right-hand side of the spam condition specifies a name. This is relevant if | |
28585 | you have set up multiple SpamAssassin profiles. If you do not want to scan | |
28586 | using a specific profile, but rather use the SpamAssassin system-wide default | |
28587 | profile, you can scan for an unknown name, or simply use "nobody". However, you | |
28588 | must put something on the right-hand side. | |
28589 | ||
28590 | The name allows you to use per-domain or per-user antispam profiles in | |
28591 | principle, but this is not straightforward in practice, because a message may | |
28592 | have multiple recipients, not necessarily all in the same domain. Because the | |
28593 | spam condition has to be called from a DATA ACL in order to be able to read the | |
28594 | contents of the message, the variables $local_part and $domain are not set. | |
28595 | ||
28596 | The right-hand side of the spam condition is expanded before being used, so you | |
28597 | can put lookups or conditions there. When the right-hand side evaluates to "0" | |
28598 | or "false", no scanning is done and the condition fails immediately. | |
28599 | ||
28600 | Scanning with SpamAssassin uses a lot of resources. If you scan every message, | |
28601 | large ones may cause significant performance degradation. As most spam messages | |
28602 | are quite small, it is recommended that you do not scan the big ones. For | |
28603 | example: | |
28604 | ||
28605 | deny message = This message was classified as SPAM | |
28606 | condition = ${if < {$message_size}{10K}} | |
28607 | spam = nobody | |
28608 | ||
28609 | The spam condition returns true if the threshold specified in the user's | |
28610 | SpamAssassin profile has been matched or exceeded. If you want to use the spam | |
28611 | condition for its side effects (see the variables below), you can make it | |
28612 | always return "true" by appending ":true" to the username. | |
28613 | ||
28614 | When the spam condition is run, it sets up a number of expansion variables. | |
28615 | These variables are saved with the received message, thus they are available | |
28616 | for use at delivery time. | |
28617 | ||
28618 | $spam_score | |
28619 | ||
28620 | The spam score of the message, for example "3.4" or "30.5". This is useful | |
28621 | for inclusion in log or reject messages. | |
28622 | ||
28623 | $spam_score_int | |
28624 | ||
28625 | The spam score of the message, multiplied by ten, as an integer value. For | |
28626 | example "34" or "305". It may appear to disagree with $spam_score because | |
28627 | $spam_score is rounded and $spam_score_int is truncated. The integer value | |
28628 | is useful for numeric comparisons in conditions. | |
28629 | ||
28630 | $spam_bar | |
28631 | ||
28632 | A string consisting of a number of "+" or "-" characters, representing the | |
28633 | integer part of the spam score value. A spam score of 4.4 would have a | |
28634 | $spam_bar value of "++++". This is useful for inclusion in warning headers, | |
28635 | since MUAs can match on such strings. | |
28636 | ||
28637 | $spam_report | |
28638 | ||
28639 | A multiline text table, containing the full SpamAssassin report for the | |
28640 | message. Useful for inclusion in headers or reject messages. | |
28641 | ||
28642 | The spam condition caches its results unless expansion in spamd_address was | |
28643 | used. If you call it again with the same user name, it does not scan again, but | |
28644 | rather returns the same values as before. | |
28645 | ||
28646 | The spam condition returns DEFER if there is any error while running the | |
28647 | message through SpamAssassin or if the expansion of spamd_address failed. If | |
28648 | you want to treat DEFER as FAIL (to pass on to the next ACL statement block), | |
28649 | append "/defer_ok" to the right-hand side of the spam condition, like this: | |
28650 | ||
28651 | deny message = This message was classified as SPAM | |
28652 | spam = joe/defer_ok | |
28653 | ||
28654 | This causes messages to be accepted even if there is a problem with spamd. | |
28655 | ||
28656 | Here is a longer, commented example of the use of the spam condition: | |
28657 | ||
28658 | # put headers in all messages (no matter if spam or not) | |
28659 | warn spam = nobody:true | |
28660 | add_header = X-Spam-Score: $spam_score ($spam_bar) | |
28661 | add_header = X-Spam-Report: $spam_report | |
28662 | ||
28663 | # add second subject line with *SPAM* marker when message | |
28664 | # is over threshold | |
28665 | warn spam = nobody | |
28666 | add_header = Subject: *SPAM* $h_Subject: | |
28667 | ||
28668 | # reject spam at high scores (> 12) | |
28669 | deny message = This message scored $spam_score spam points. | |
28670 | spam = nobody:true | |
28671 | condition = ${if >{$spam_score_int}{120}{1}{0}} | |
28672 | ||
28673 | ||
28674 | 43.4 Scanning MIME parts | |
28675 | ------------------------ | |
28676 | ||
28677 | The acl_smtp_mime global option specifies an ACL that is called once for each | |
28678 | MIME part of an SMTP message, including multipart types, in the sequence of | |
28679 | their position in the message. Similarly, the acl_not_smtp_mime option | |
28680 | specifies an ACL that is used for the MIME parts of non-SMTP messages. These | |
28681 | options may both refer to the same ACL if you want the same processing in both | |
28682 | cases. | |
28683 | ||
28684 | These ACLs are called (possibly many times) just before the acl_smtp_data ACL | |
28685 | in the case of an SMTP message, or just before the acl_not_smtp ACL in the case | |
28686 | of a non-SMTP message. However, a MIME ACL is called only if the message | |
28687 | contains a Content-Type: header line. When a call to a MIME ACL does not yield | |
28688 | "accept", ACL processing is aborted and the appropriate result code is sent to | |
28689 | the client. In the case of an SMTP message, the acl_smtp_data ACL is not called | |
28690 | when this happens. | |
28691 | ||
28692 | You cannot use the malware or spam conditions in a MIME ACL; these can only be | |
28693 | used in the DATA or non-SMTP ACLs. However, you can use the regex condition to | |
28694 | match against the raw MIME part. You can also use the mime_regex condition to | |
28695 | match against the decoded MIME part (see section 43.5). | |
28696 | ||
28697 | At the start of a MIME ACL, a number of variables are set from the header | |
28698 | information for the relevant MIME part. These are described below. The contents | |
28699 | of the MIME part are not by default decoded into a disk file except for MIME | |
28700 | parts whose content-type is "message/rfc822". If you want to decode a MIME part | |
28701 | into a disk file, you can use the decode condition. The general syntax is: | |
28702 | ||
28703 | decode = [/<path>/]<filename> | |
28704 | ||
28705 | The right hand side is expanded before use. After expansion, the value can be: | |
28706 | ||
28707 | 1. "0" or "false", in which case no decoding is done. | |
28708 | ||
28709 | 2. The string "default". In that case, the file is put in the temporary | |
28710 | "default" directory <spool_directory>/scan/<message_id>/ with a sequential | |
28711 | file name consisting of the message id and a sequence number. The full path | |
28712 | and name is available in $mime_decoded_filename after decoding. | |
28713 | ||
28714 | 3. A full path name starting with a slash. If the full name is an existing | |
28715 | directory, it is used as a replacement for the default directory. The | |
28716 | filename is then sequentially assigned. If the path does not exist, it is | |
28717 | used as the full path and file name. | |
28718 | ||
28719 | 4. If the string does not start with a slash, it is used as the filename, and | |
28720 | the default path is then used. | |
28721 | ||
28722 | The decode condition normally succeeds. It is only false for syntax errors or | |
28723 | unusual circumstances such as memory shortages. You can easily decode a file | |
28724 | with its original, proposed filename using | |
28725 | ||
28726 | decode = $mime_filename | |
28727 | ||
28728 | However, you should keep in mind that $mime_filename might contain anything. If | |
28729 | you place files outside of the default path, they are not automatically | |
28730 | unlinked. | |
28731 | ||
28732 | For RFC822 attachments (these are messages attached to messages, with a | |
28733 | content-type of "message/rfc822"), the ACL is called again in the same manner | |
28734 | as for the primary message, only that the $mime_is_rfc822 expansion variable is | |
28735 | set (see below). Attached messages are always decoded to disk before being | |
28736 | checked, and the files are unlinked once the check is done. | |
28737 | ||
28738 | The MIME ACL supports the regex and mime_regex conditions. These can be used to | |
28739 | match regular expressions against raw and decoded MIME parts, respectively. | |
28740 | They are described in section 43.5. | |
28741 | ||
28742 | The following list describes all expansion variables that are available in the | |
28743 | MIME ACL: | |
28744 | ||
28745 | $mime_boundary | |
28746 | ||
28747 | If the current part is a multipart (see $mime_is_multipart) below, it | |
28748 | should have a boundary string, which is stored in this variable. If the | |
28749 | current part has no boundary parameter in the Content-Type: header, this | |
28750 | variable contains the empty string. | |
28751 | ||
28752 | $mime_charset | |
28753 | ||
28754 | This variable contains the character set identifier, if one was found in | |
28755 | the Content-Type: header. Examples for charset identifiers are: | |
28756 | ||
28757 | us-ascii | |
28758 | gb2312 (Chinese) | |
28759 | iso-8859-1 | |
28760 | ||
28761 | Please note that this value is not normalized, so you should do matches | |
28762 | case-insensitively. | |
28763 | ||
28764 | $mime_content_description | |
28765 | ||
28766 | This variable contains the normalized content of the Content-Description: | |
28767 | header. It can contain a human-readable description of the parts content. | |
28768 | Some implementations repeat the filename for attachments here, but they are | |
28769 | usually only used for display purposes. | |
28770 | ||
28771 | $mime_content_disposition | |
28772 | ||
28773 | This variable contains the normalized content of the Content-Disposition: | |
28774 | header. You can expect strings like "attachment" or "inline" here. | |
28775 | ||
28776 | $mime_content_id | |
28777 | ||
28778 | This variable contains the normalized content of the Content-ID: header. | |
28779 | This is a unique ID that can be used to reference a part from another part. | |
28780 | ||
28781 | $mime_content_size | |
28782 | ||
28783 | This variable is set only after the decode modifier (see above) has been | |
28784 | successfully run. It contains the size of the decoded part in kilobytes. | |
28785 | The size is always rounded up to full kilobytes, so only a completely empty | |
28786 | part has a $mime_content_size of zero. | |
28787 | ||
28788 | $mime_content_transfer_encoding | |
28789 | ||
28790 | This variable contains the normalized content of the | |
28791 | Content-transfer-encoding: header. This is a symbolic name for an encoding | |
28792 | type. Typical values are "base64" and "quoted-printable". | |
28793 | ||
28794 | $mime_content_type | |
28795 | ||
28796 | If the MIME part has a Content-Type: header, this variable contains its | |
28797 | value, lowercased, and without any options (like "name" or "charset"). Here | |
28798 | are some examples of popular MIME types, as they may appear in this | |
28799 | variable: | |
28800 | ||
28801 | text/plain | |
28802 | text/html | |
28803 | application/octet-stream | |
28804 | image/jpeg | |
28805 | audio/midi | |
28806 | ||
28807 | If the MIME part has no Content-Type: header, this variable contains the | |
28808 | empty string. | |
28809 | ||
28810 | $mime_decoded_filename | |
28811 | ||
28812 | This variable is set only after the decode modifier (see above) has been | |
28813 | successfully run. It contains the full path and file name of the file | |
28814 | containing the decoded data. | |
28815 | ||
28816 | $mime_filename | |
28817 | ||
28818 | This is perhaps the most important of the MIME variables. It contains a | |
28819 | proposed filename for an attachment, if one was found in either the | |
28820 | Content-Type: or Content-Disposition: headers. The filename will be RFC2047 | |
28821 | decoded, but no additional sanity checks are done. If no filename was | |
28822 | found, this variable contains the empty string. | |
28823 | ||
28824 | $mime_is_coverletter | |
28825 | ||
28826 | This variable attempts to differentiate the "cover letter" of an e-mail | |
28827 | from attached data. It can be used to clamp down on flashy or unnecessarily | |
28828 | encoded content in the cover letter, while not restricting attachments at | |
28829 | all. | |
28830 | ||
28831 | The variable contains 1 (true) for a MIME part believed to be part of the | |
28832 | cover letter, and 0 (false) for an attachment. At present, the algorithm is | |
28833 | as follows: | |
28834 | ||
28835 | 1. The outermost MIME part of a message is always a cover letter. | |
28836 | ||
28837 | 2. If a multipart/alternative or multipart/related MIME part is a cover | |
28838 | letter, so are all MIME subparts within that multipart. | |
28839 | ||
28840 | 3. If any other multipart is a cover letter, the first subpart is a cover | |
28841 | letter, and the rest are attachments. | |
28842 | ||
28843 | 4. All parts contained within an attachment multipart are attachments. | |
28844 | ||
28845 | As an example, the following will ban "HTML mail" (including that sent with | |
28846 | alternative plain text), while allowing HTML files to be attached. HTML | |
28847 | coverletter mail attached to non-HMTL coverletter mail will also be | |
28848 | allowed: | |
28849 | ||
28850 | deny message = HTML mail is not accepted here | |
28851 | !condition = $mime_is_rfc822 | |
28852 | condition = $mime_is_coverletter | |
28853 | condition = ${if eq{$mime_content_type}{text/html}{1}{0}} | |
28854 | ||
28855 | $mime_is_multipart | |
28856 | ||
28857 | This variable has the value 1 (true) when the current part has the main | |
28858 | type "multipart", for example "multipart/alternative" or "multipart/mixed". | |
28859 | Since multipart entities only serve as containers for other parts, you may | |
28860 | not want to carry out specific actions on them. | |
28861 | ||
28862 | $mime_is_rfc822 | |
28863 | ||
28864 | This variable has the value 1 (true) if the current part is not a part of | |
28865 | the checked message itself, but part of an attached message. Attached | |
28866 | message decoding is fully recursive. | |
28867 | ||
28868 | $mime_part_count | |
28869 | ||
28870 | This variable is a counter that is raised for each processed MIME part. It | |
28871 | starts at zero for the very first part (which is usually a multipart). The | |
28872 | counter is per-message, so it is reset when processing RFC822 attachments | |
28873 | (see $mime_is_rfc822). The counter stays set after acl_smtp_mime is | |
28874 | complete, so you can use it in the DATA ACL to determine the number of MIME | |
28875 | parts of a message. For non-MIME messages, this variable contains the value | |
28876 | -1. | |
28877 | ||
28878 | ||
28879 | 43.5 Scanning with regular expressions | |
28880 | -------------------------------------- | |
28881 | ||
28882 | You can specify your own custom regular expression matches on the full body of | |
28883 | the message, or on individual MIME parts. | |
28884 | ||
28885 | The regex condition takes one or more regular expressions as arguments and | |
28886 | matches them against the full message (when called in the DATA ACL) or a raw | |
28887 | MIME part (when called in the MIME ACL). The regex condition matches linewise, | |
28888 | with a maximum line length of 32K characters. That means you cannot have | |
28889 | multiline matches with the regex condition. | |
28890 | ||
28891 | The mime_regex condition can be called only in the MIME ACL. It matches up to | |
28892 | 32K of decoded content (the whole content at once, not linewise). If the part | |
28893 | has not been decoded with the decode modifier earlier in the ACL, it is decoded | |
28894 | automatically when mime_regex is executed (using default path and filename | |
28895 | values). If the decoded data is larger than 32K, only the first 32K characters | |
28896 | are checked. | |
28897 | ||
28898 | The regular expressions are passed as a colon-separated list. To include a | |
28899 | literal colon, you must double it. Since the whole right-hand side string is | |
28900 | expanded before being used, you must also escape dollar signs and backslashes | |
28901 | with more backslashes, or use the "\N" facility to disable expansion. Here is a | |
28902 | simple example that contains two regular expressions: | |
28903 | ||
28904 | deny message = contains blacklisted regex ($regex_match_string) | |
28905 | regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL | |
28906 | ||
28907 | The conditions returns true if any one of the regular expressions matches. The | |
28908 | $regex_match_string expansion variable is then set up and contains the matching | |
28909 | regular expression. | |
28910 | ||
28911 | Warning: With large messages, these conditions can be fairly CPU-intensive. | |
28912 | ||
28913 | ||
28914 | 43.6 The demime condition | |
28915 | ------------------------- | |
28916 | ||
28917 | The demime ACL condition provides MIME unpacking, sanity checking and file | |
28918 | extension blocking. It is usable only in the DATA and non-SMTP ACLs. The demime | |
28919 | condition uses a simpler interface to MIME decoding than the MIME ACL | |
28920 | functionality, but provides no additional facilities. Please note that this | |
28921 | condition is deprecated and kept only for backward compatibility. You must set | |
28922 | the WITH_OLD_DEMIME option in Local/Makefile at build time to be able to use | |
28923 | the demime condition. | |
28924 | ||
28925 | The demime condition unpacks MIME containers in the message. It detects errors | |
28926 | in MIME containers and can match file extensions found in the message against a | |
28927 | list. Using this facility produces files containing the unpacked MIME parts of | |
28928 | the message in the temporary scan directory. If you do antivirus scanning, it | |
28929 | is recommended that you use the demime condition before the antivirus (malware) | |
28930 | condition. | |
28931 | ||
28932 | On the right-hand side of the demime condition you can pass a colon-separated | |
28933 | list of file extensions that it should match against. For example: | |
28934 | ||
28935 | deny message = Found blacklisted file attachment | |
28936 | demime = vbs:com:bat:pif:prf:lnk | |
28937 | ||
28938 | If one of the file extensions is found, the condition is true, otherwise it is | |
28939 | false. If there is a temporary error while demimeing (for example, "disk | |
28940 | full"), the condition defers, and the message is temporarily rejected (unless | |
28941 | the condition is on a warn verb). | |
28942 | ||
28943 | The right-hand side is expanded before being treated as a list, so you can have | |
28944 | conditions and lookups there. If it expands to an empty string, "false", or | |
28945 | zero ("0"), no demimeing is done and the condition is false. | |
28946 | ||
28947 | The demime condition set the following variables: | |
28948 | ||
28949 | $demime_errorlevel | |
28950 | ||
28951 | When an error is detected in a MIME container, this variable contains the | |
28952 | severity of the error, as an integer number. The higher the value, the more | |
28953 | severe the error (the current maximum value is 3). If this variable is | |
28954 | unset or zero, no error occurred. | |
28955 | ||
28956 | $demime_reason | |
28957 | ||
28958 | When $demime_errorlevel is greater than zero, this variable contains a | |
28959 | human-readable text string describing the MIME error that occurred. | |
28960 | ||
28961 | $found_extension | |
28962 | ||
28963 | When the demime condition is true, this variable contains the file | |
28964 | extension it found. | |
28965 | ||
28966 | Both $demime_errorlevel and $demime_reason are set by the first call of the | |
28967 | demime condition, and are not changed on subsequent calls. | |
28968 | ||
28969 | If you do not want to check for file extensions, but rather use the demime | |
28970 | condition for unpacking or error checking purposes, pass "*" as the right-hand | |
28971 | side value. Here is a more elaborate example of how to use this facility: | |
28972 | ||
28973 | # Reject messages with serious MIME container errors | |
28974 | deny message = Found MIME error ($demime_reason). | |
28975 | demime = * | |
28976 | condition = ${if >{$demime_errorlevel}{2}{1}{0}} | |
28977 | ||
28978 | # Reject known virus spreading file extensions. | |
28979 | # Accepting these is pretty much braindead. | |
28980 | deny message = contains $found_extension file (blacklisted). | |
28981 | demime = com:vbs:bat:pif:scr | |
28982 | ||
28983 | # Freeze .exe and .doc files. Postmaster can | |
28984 | # examine them and eventually thaw them. | |
28985 | deny log_message = Another $found_extension file. | |
28986 | demime = exe:doc | |
28987 | control = freeze | |
28988 | ||
28989 | ||
28990 | ||
28991 | =============================================================================== | |
28992 | 44. ADDING A LOCAL SCAN FUNCTION TO EXIM | |
28993 | ||
28994 | In these days of email worms, viruses, and ever-increasing spam, some sites | |
28995 | want to apply a lot of checking to messages before accepting them. | |
28996 | ||
28997 | The content scanning extension (chapter 43) has facilities for passing messages | |
28998 | to external virus and spam scanning software. You can also do a certain amount | |
28999 | in Exim itself through string expansions and the condition condition in the ACL | |
29000 | that runs after the SMTP DATA command or the ACL for non-SMTP messages (see | |
29001 | chapter 42), but this has its limitations. | |
29002 | ||
29003 | To allow for further customization to a site's own requirements, there is the | |
29004 | possibility of linking Exim with a private message scanning function, written | |
29005 | in C. If you want to run code that is written in something other than C, you | |
29006 | can of course use a little C stub to call it. | |
29007 | ||
29008 | The local scan function is run once for every incoming message, at the point | |
29009 | when Exim is just about to accept the message. It can therefore be used to | |
29010 | control non-SMTP messages from local processes as well as messages arriving via | |
29011 | SMTP. | |
29012 | ||
29013 | Exim applies a timeout to calls of the local scan function, and there is an | |
29014 | option called local_scan_timeout for setting it. The default is 5 minutes. Zero | |
29015 | means "no timeout". Exim also sets up signal handlers for SIGSEGV, SIGILL, | |
29016 | SIGFPE, and SIGBUS before calling the local scan function, so that the most | |
29017 | common types of crash are caught. If the timeout is exceeded or one of those | |
29018 | signals is caught, the incoming message is rejected with a temporary error if | |
29019 | it is an SMTP message. For a non-SMTP message, the message is dropped and Exim | |
29020 | ends with a non-zero code. The incident is logged on the main and reject logs. | |
29021 | ||
29022 | ||
29023 | 44.1 Building Exim to use a local scan function | |
29024 | ----------------------------------------------- | |
29025 | ||
29026 | To make use of the local scan function feature, you must tell Exim where your | |
29027 | function is before building Exim, by setting LOCAL_SCAN_SOURCE in your Local/ | |
29028 | Makefile. A recommended place to put it is in the Local directory, so you might | |
29029 | set | |
29030 | ||
29031 | LOCAL_SCAN_SOURCE=Local/local_scan.c | |
29032 | ||
29033 | for example. The function must be called local_scan(). It is called by Exim | |
29034 | after it has received a message, when the success return code is about to be | |
29035 | sent. This is after all the ACLs have been run. The return code from your | |
29036 | function controls whether the message is actually accepted or not. There is a | |
29037 | commented template function (that just accepts the message) in the file _src/ | |
29038 | local_scan.c_. | |
29039 | ||
29040 | If you want to make use of Exim's run time configuration file to set options | |
29041 | for your local_scan() function, you must also set | |
29042 | ||
29043 | LOCAL_SCAN_HAS_OPTIONS=yes | |
29044 | ||
29045 | in Local/Makefile (see section 44.3 below). | |
29046 | ||
29047 | ||
29048 | 44.2 API for local_scan() | |
29049 | ------------------------- | |
29050 | ||
29051 | You must include this line near the start of your code: | |
29052 | ||
29053 | #include "local_scan.h" | |
29054 | ||
29055 | This header file defines a number of variables and other values, and the | |
29056 | prototype for the function itself. Exim is coded to use unsigned char values | |
29057 | almost exclusively, and one of the things this header defines is a shorthand | |
29058 | for "unsigned char" called "uschar". It also contains the following macro | |
29059 | definitions, to simplify casting character strings and pointers to character | |
29060 | strings: | |
29061 | ||
29062 | #define CS (char *) | |
29063 | #define CCS (const char *) | |
29064 | #define CSS (char **) | |
29065 | #define US (unsigned char *) | |
29066 | #define CUS (const unsigned char *) | |
29067 | #define USS (unsigned char **) | |
29068 | ||
29069 | The function prototype for local_scan() is: | |
29070 | ||
29071 | extern int local_scan(int fd, uschar **return_text); | |
29072 | ||
29073 | The arguments are as follows: | |
29074 | ||
29075 | * fd is a file descriptor for the file that contains the body of the message | |
29076 | (the -D file). The file is open for reading and writing, but updating it is | |
29077 | not recommended. Warning: You must not close this file descriptor. | |
29078 | ||
29079 | The descriptor is positioned at character 19 of the file, which is the | |
29080 | first character of the body itself, because the first 19 characters are the | |
29081 | message id followed by "-D" and a newline. If you rewind the file, you | |
29082 | should use the macro SPOOL_DATA_START_OFFSET to reset to the start of the | |
29083 | data, just in case this changes in some future version. | |
29084 | ||
29085 | * return_text is an address which you can use to return a pointer to a text | |
29086 | string at the end of the function. The value it points to on entry is NULL. | |
29087 | ||
29088 | The function must return an int value which is one of the following macros: | |
29089 | ||
29090 | "LOCAL_SCAN_ACCEPT" | |
29091 | ||
29092 | The message is accepted. If you pass back a string of text, it is saved | |
29093 | with the message, and made available in the variable $local_scan_data. No | |
29094 | newlines are permitted (if there are any, they are turned into spaces) and | |
29095 | the maximum length of text is 1000 characters. | |
29096 | ||
29097 | "LOCAL_SCAN_ACCEPT_FREEZE" | |
29098 | ||
29099 | This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is | |
29100 | queued without immediate delivery, and is frozen. | |
29101 | ||
29102 | "LOCAL_SCAN_ACCEPT_QUEUE" | |
29103 | ||
29104 | This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is | |
29105 | queued without immediate delivery. | |
29106 | ||
29107 | "LOCAL_SCAN_REJECT" | |
29108 | ||
29109 | The message is rejected; the returned text is used as an error message | |
29110 | which is passed back to the sender and which is also logged. Newlines are | |
29111 | permitted - they cause a multiline response for SMTP rejections, but are | |
29112 | converted to "\n" in log lines. If no message is given, "Administrative | |
29113 | prohibition" is used. | |
29114 | ||
29115 | "LOCAL_SCAN_TEMPREJECT" | |
29116 | ||
29117 | The message is temporarily rejected; the returned text is used as an error | |
29118 | message as for LOCAL_SCAN_REJECT. If no message is given, "Temporary local | |
29119 | problem" is used. | |
29120 | ||
29121 | "LOCAL_SCAN_REJECT_NOLOGHDR" | |
29122 | ||
29123 | This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected | |
29124 | message is not written to the reject log. It has the effect of unsetting | |
29125 | the rejected_header log selector for just this rejection. If | |
29126 | rejected_header is already unset (see the discussion of the log_selection | |
29127 | option in section 51.15), this code is the same as LOCAL_SCAN_REJECT. | |
29128 | ||
29129 | "LOCAL_SCAN_TEMPREJECT_NOLOGHDR" | |
29130 | ||
29131 | This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that | |
29132 | LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT. | |
29133 | ||
29134 | If the message is not being received by interactive SMTP, rejections are | |
29135 | reported by writing to stderr or by sending an email, as configured by the -oe | |
29136 | command line options. | |
29137 | ||
29138 | ||
29139 | 44.3 Configuration options for local_scan() | |
29140 | ------------------------------------------- | |
29141 | ||
29142 | It is possible to have option settings in the main configuration file that set | |
29143 | values in static variables in the local_scan() module. If you want to do this, | |
29144 | you must have the line | |
29145 | ||
29146 | LOCAL_SCAN_HAS_OPTIONS=yes | |
29147 | ||
29148 | in your Local/Makefile when you build Exim. (This line is in OS/ | |
29149 | Makefile-Default, commented out). Then, in the local_scan() source file, you | |
29150 | must define static variables to hold the option values, and a table to define | |
29151 | them. | |
29152 | ||
29153 | The table must be a vector called local_scan_options, of type "optionlist". | |
29154 | Each entry is a triplet, consisting of a name, an option type, and a pointer to | |
29155 | the variable that holds the value. The entries must appear in alphabetical | |
29156 | order. Following local_scan_options you must also define a variable called | |
29157 | local_scan_options_count that contains the number of entries in the table. Here | |
29158 | is a short example, showing two kinds of option: | |
29159 | ||
29160 | static int my_integer_option = 42; | |
29161 | static uschar *my_string_option = US"a default string"; | |
29162 | ||
29163 | optionlist local_scan_options[] = { | |
29164 | { "my_integer", opt_int, &my_integer_option }, | |
29165 | { "my_string", opt_stringptr, &my_string_option } | |
29166 | }; | |
29167 | ||
29168 | int local_scan_options_count = | |
29169 | sizeof(local_scan_options)/sizeof(optionlist); | |
29170 | ||
29171 | The values of the variables can now be changed from Exim's runtime | |
29172 | configuration file by including a local scan section as in this example: | |
29173 | ||
29174 | begin local_scan | |
29175 | my_integer = 99 | |
29176 | my_string = some string of text... | |
29177 | ||
29178 | The available types of option data are as follows: | |
29179 | ||
29180 | opt_bool | |
29181 | ||
29182 | This specifies a boolean (true/false) option. The address should point to a | |
29183 | variable of type "BOOL", which will be set to TRUE or FALSE, which are | |
29184 | macros that are defined as "1" and "0", respectively. If you want to detect | |
29185 | whether such a variable has been set at all, you can initialize it to | |
29186 | TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than | |
29187 | two values.) | |
29188 | ||
29189 | opt_fixed | |
29190 | ||
29191 | This specifies a fixed point number, such as is used for load averages. The | |
29192 | address should point to a variable of type "int". The value is stored | |
29193 | multiplied by 1000, so, for example, 1.4142 is truncated and stored as | |
29194 | 1414. | |
29195 | ||
29196 | opt_int | |
29197 | ||
29198 | This specifies an integer; the address should point to a variable of type | |
29199 | "int". The value may be specified in any of the integer formats accepted by | |
29200 | Exim. | |
29201 | ||
29202 | opt_mkint | |
29203 | ||
29204 | This is the same as opt_int, except that when such a value is output in a | |
29205 | -bP listing, if it is an exact number of kilobytes or megabytes, it is | |
29206 | printed with the suffix K or M. | |
29207 | ||
29208 | opt_octint | |
29209 | ||
29210 | This also specifies an integer, but the value is always interpreted as an | |
29211 | octal integer, whether or not it starts with the digit zero, and it is | |
29212 | always output in octal. | |
29213 | ||
29214 | opt_stringptr | |
29215 | ||
29216 | This specifies a string value; the address must be a pointer to a variable | |
29217 | that points to a string (for example, of type "uschar *"). | |
29218 | ||
29219 | opt_time | |
29220 | ||
29221 | This specifies a time interval value. The address must point to a variable | |
29222 | of type "int". The value that is placed there is a number of seconds. | |
29223 | ||
29224 | If the -bP command line option is followed by "local_scan", Exim prints out the | |
29225 | values of all the local_scan() options. | |
29226 | ||
29227 | ||
29228 | 44.4 Available Exim variables | |
29229 | ----------------------------- | |
29230 | ||
29231 | The header local_scan.h gives you access to a number of C variables. These are | |
29232 | the only ones that are guaranteed to be maintained from release to release. | |
29233 | Note, however, that you can obtain the value of any Exim expansion variable, | |
29234 | including $recipients, by calling expand_string(). The exported C variables are | |
29235 | as follows: | |
29236 | ||
29237 | int body_linecount | |
29238 | ||
29239 | This variable contains the number of lines in the message's body. | |
29240 | ||
29241 | int body_zerocount | |
29242 | ||
29243 | This variable contains the number of binary zero bytes in the message's | |
29244 | body. | |
29245 | ||
29246 | unsigned int debug_selector | |
29247 | ||
29248 | This variable is set to zero when no debugging is taking place. Otherwise, | |
29249 | it is a bitmap of debugging selectors. Two bits are identified for use in | |
29250 | local_scan(); they are defined as macros: | |
29251 | ||
29252 | * The "D_v" bit is set when -v was present on the command line. This is a | |
29253 | testing option that is not privileged - any caller may set it. All the | |
29254 | other selector bits can be set only by admin users. | |
29255 | ||
29256 | * The "D_local_scan" bit is provided for use by local_scan(); it is set | |
29257 | by the "+local_scan" debug selector. It is not included in the default | |
29258 | set of debugging bits. | |
29259 | ||
29260 | Thus, to write to the debugging output only when "+local_scan" has been | |
29261 | selected, you should use code like this: | |
29262 | ||
29263 | if ((debug_selector & D_local_scan) != 0) | |
29264 | debug_printf("xxx", ...); | |
29265 | ||
29266 | uschar *expand_string_message | |
29267 | ||
29268 | After a failing call to expand_string() (returned value NULL), the variable | |
29269 | expand_string_message contains the error message, zero-terminated. | |
29270 | ||
29271 | header_line *header_list | |
29272 | ||
29273 | A pointer to a chain of header lines. The header_line structure is | |
29274 | discussed below. | |
29275 | ||
29276 | header_line *header_last | |
29277 | ||
29278 | A pointer to the last of the header lines. | |
29279 | ||
29280 | uschar *headers_charset | |
29281 | ||
29282 | The value of the headers_charset configuration option. | |
29283 | ||
29284 | BOOL host_checking | |
29285 | ||
29286 | This variable is TRUE during a host checking session that is initiated by | |
29287 | the -bh command line option. | |
29288 | ||
29289 | uschar *interface_address | |
29290 | ||
29291 | The IP address of the interface that received the message, as a string. | |
29292 | This is NULL for locally submitted messages. | |
29293 | ||
29294 | int interface_port | |
29295 | ||
29296 | The port on which this message was received. When testing with the -bh | |
29297 | command line option, the value of this variable is -1 unless a port has | |
29298 | been specified via the -oMi option. | |
29299 | ||
29300 | uschar *message_id | |
29301 | ||
29302 | This variable contains Exim's message id for the incoming message (the | |
29303 | value of $message_exim_id) as a zero-terminated string. | |
29304 | ||
29305 | uschar *received_protocol | |
29306 | ||
29307 | The name of the protocol by which the message was received. | |
29308 | ||
29309 | int recipients_count | |
29310 | ||
29311 | The number of accepted recipients. | |
29312 | ||
29313 | recipient_item *recipients_list | |
29314 | ||
29315 | The list of accepted recipients, held in a vector of length | |
29316 | recipients_count. The recipient_item structure is discussed below. You can | |
29317 | add additional recipients by calling receive_add_recipient() (see below). | |
29318 | You can delete recipients by removing them from the vector and adjusting | |
29319 | the value in recipients_count. In particular, by setting recipients_count | |
29320 | to zero you remove all recipients. If you then return the value | |
29321 | "LOCAL_SCAN_ACCEPT", the message is accepted, but immediately blackholed. | |
29322 | To replace the recipients, you can set recipients_count to zero and then | |
29323 | call receive_add_recipient() as often as needed. | |
29324 | ||
29325 | uschar *sender_address | |
29326 | ||
29327 | The envelope sender address. For bounce messages this is the empty string. | |
29328 | ||
29329 | uschar *sender_host_address | |
29330 | ||
29331 | The IP address of the sending host, as a string. This is NULL for | |
29332 | locally-submitted messages. | |
29333 | ||
29334 | uschar *sender_host_authenticated | |
29335 | ||
29336 | The name of the authentication mechanism that was used, or NULL if the | |
29337 | message was not received over an authenticated SMTP connection. | |
29338 | ||
29339 | uschar *sender_host_name | |
29340 | ||
29341 | The name of the sending host, if known. | |
29342 | ||
29343 | int sender_host_port | |
29344 | ||
29345 | The port on the sending host. | |
29346 | ||
29347 | BOOL smtp_input | |
29348 | ||
29349 | This variable is TRUE for all SMTP input, including BSMTP. | |
29350 | ||
29351 | BOOL smtp_batched_input | |
29352 | ||
29353 | This variable is TRUE for BSMTP input. | |
29354 | ||
29355 | int store_pool | |
29356 | ||
29357 | The contents of this variable control which pool of memory is used for new | |
29358 | requests. See section 44.8 for details. | |
29359 | ||
29360 | ||
29361 | 44.5 Structure of header lines | |
29362 | ------------------------------ | |
29363 | ||
29364 | The header_line structure contains the members listed below. You can add | |
29365 | additional header lines by calling the header_add() function (see below). You | |
29366 | can cause header lines to be ignored (deleted) by setting their type to *. | |
29367 | ||
29368 | struct header_line *next | |
29369 | ||
29370 | A pointer to the next header line, or NULL for the last line. | |
29371 | ||
29372 | int type | |
29373 | ||
29374 | A code identifying certain headers that Exim recognizes. The codes are | |
29375 | printing characters, and are documented in chapter 55 of this manual. | |
29376 | Notice in particular that any header line whose type is * is not | |
29377 | transmitted with the message. This flagging is used for header lines that | |
29378 | have been rewritten, or are to be removed (for example, Envelope-sender: | |
29379 | header lines.) Effectively, * means "deleted". | |
29380 | ||
29381 | int slen | |
29382 | ||
29383 | The number of characters in the header line, including the terminating and | |
29384 | any internal newlines. | |
29385 | ||
29386 | uschar *text | |
29387 | ||
29388 | A pointer to the text of the header. It always ends with a newline, | |
29389 | followed by a zero byte. Internal newlines are preserved. | |
29390 | ||
29391 | ||
29392 | 44.6 Structure of recipient items | |
29393 | --------------------------------- | |
29394 | ||
29395 | The recipient_item structure contains these members: | |
29396 | ||
29397 | uschar *address | |
29398 | ||
29399 | This is a pointer to the recipient address as it was received. | |
29400 | ||
29401 | int pno | |
29402 | ||
29403 | This is used in later Exim processing when top level addresses are created | |
29404 | by the one_time option. It is not relevant at the time local_scan() is run | |
29405 | and must always contain -1 at this stage. | |
29406 | ||
29407 | uschar *errors_to | |
29408 | ||
29409 | If this value is not NULL, bounce messages caused by failing to deliver to | |
29410 | the recipient are sent to the address it contains. In other words, it | |
29411 | overrides the envelope sender for this one recipient. (Compare the | |
29412 | errors_to generic router option.) If a local_scan() function sets an | |
29413 | errors_to field to an unqualified address, Exim qualifies it using the | |
29414 | domain from qualify_recipient. When local_scan() is called, the errors_to | |
29415 | field is NULL for all recipients. | |
29416 | ||
29417 | ||
29418 | 44.7 Available Exim functions | |
29419 | ----------------------------- | |
29420 | ||
29421 | The header local_scan.h gives you access to a number of Exim functions. These | |
29422 | are the only ones that are guaranteed to be maintained from release to release: | |
29423 | ||
29424 | pid_t child_open | |
29425 | (uschar **argv, uschar **envp, int newumask, int *infdptr, int *outfdptr, | |
29426 | BOOL make_leader) | |
29427 | ||
29428 | This function creates a child process that runs the command specified by | |
29429 | argv. The environment for the process is specified by envp, which can be | |
29430 | NULL if no environment variables are to be passed. A new umask is supplied | |
29431 | for the process in newumask. | |
29432 | ||
29433 | Pipes to the standard input and output of the new process are set up and | |
29434 | returned to the caller via the infdptr and outfdptr arguments. The standard | |
29435 | error is cloned to the standard output. If there are any file descriptors | |
29436 | "in the way" in the new process, they are closed. If the final argument is | |
29437 | TRUE, the new process is made into a process group leader. | |
29438 | ||
29439 | The function returns the pid of the new process, or -1 if things go wrong. | |
29440 | ||
29441 | int child_close(pid_t pid, int timeout) | |
29442 | ||
29443 | This function waits for a child process to terminate, or for a timeout (in | |
29444 | seconds) to expire. A timeout value of zero means wait as long as it takes. | |
29445 | The return value is as follows: | |
29446 | ||
29447 | * >= 0 | |
29448 | ||
29449 | The process terminated by a normal exit and the value is the process | |
29450 | ending status. | |
29451 | ||
29452 | * < 0 and > -256 | |
29453 | ||
29454 | The process was terminated by a signal and the value is the negation of | |
29455 | the signal number. | |
29456 | ||
29457 | * -256 | |
29458 | ||
29459 | The process timed out. | |
29460 | ||
29461 | * -257 | |
29462 | ||
29463 | The was some other error in wait(); errno is still set. | |
29464 | ||
29465 | pid_t child_open_exim(int *fd) | |
29466 | ||
29467 | This function provide you with a means of submitting a new message to Exim. | |
29468 | (Of course, you can also call /usr/sbin/sendmail yourself if you want, but | |
29469 | this packages it all up for you.) The function creates a pipe, forks a | |
29470 | subprocess that is running | |
29471 | ||
29472 | exim -t -oem -oi -f <> | |
29473 | ||
29474 | and returns to you (via the "int *" argument) a file descriptor for the | |
29475 | pipe that is connected to the standard input. The yield of the function is | |
29476 | the PID of the subprocess. You can then write a message to the file | |
29477 | descriptor, with recipients in To:, Cc:, and/or Bcc: header lines. | |
29478 | ||
29479 | When you have finished, call child_close() to wait for the process to | |
29480 | finish and to collect its ending status. A timeout value of zero is usually | |
29481 | fine in this circumstance. Unless you have made a mistake with the | |
29482 | recipient addresses, you should get a return code of zero. | |
29483 | ||
29484 | pid_t child_open_exim2(int *fd, uschar *sender, uschar *sender_authentication) | |
29485 | ||
29486 | This function is a more sophisticated version of child_open(). The command | |
29487 | that it runs is: | |
29488 | ||
29489 | exim -t -oem -oi -f sender -oMas sender_authentication | |
29490 | ||
29491 | The third argument may be NULL, in which case the -oMas option is omitted. | |
29492 | ||
29493 | void debug_printf(char *, ...) | |
29494 | ||
29495 | This is Exim's debugging function, with arguments as for (printf(). The | |
29496 | output is written to the standard error stream. If no debugging is | |
29497 | selected, calls to debug_printf() have no effect. Normally, you should make | |
29498 | calls conditional on the "local_scan" debug selector by coding like this: | |
29499 | ||
29500 | if ((debug_selector & D_local_scan) != 0) | |
29501 | debug_printf("xxx", ...); | |
29502 | ||
29503 | uschar *expand_string(uschar *string) | |
29504 | ||
29505 | This is an interface to Exim's string expansion code. The return value is | |
29506 | the expanded string, or NULL if there was an expansion failure. The C | |
29507 | variable expand_string_message contains an error message after an expansion | |
29508 | failure. If expansion does not change the string, the return value is the | |
29509 | pointer to the input string. Otherwise, the return value points to a new | |
29510 | block of memory that was obtained by a call to store_get(). See section | |
29511 | 44.8 below for a discussion of memory handling. | |
29512 | ||
29513 | void header_add(int type, char *format, ...) | |
29514 | ||
29515 | This function allows you to an add additional header line at the end of the | |
29516 | existing ones. The first argument is the type, and should normally be a | |
29517 | space character. The second argument is a format string and any number of | |
29518 | substitution arguments as for sprintf(). You may include internal newlines | |
29519 | if you want, and you must ensure that the string ends with a newline. | |
29520 | ||
29521 | void header_add_at_position | |
29522 | (BOOL after, uschar *name, BOOL topnot, int type, char *format, ...) | |
29523 | ||
29524 | This function adds a new header line at a specified point in the header | |
29525 | chain. The header itself is specified as for header_add(). | |
29526 | ||
29527 | If name is NULL, the new header is added at the end of the chain if after | |
29528 | is true, or at the start if after is false. If name is not NULL, the header | |
29529 | lines are searched for the first non-deleted header that matches the name. | |
29530 | If one is found, the new header is added before it if after is false. If | |
29531 | after is true, the new header is added after the found header and any | |
29532 | adjacent subsequent ones with the same name (even if marked "deleted"). If | |
29533 | no matching non-deleted header is found, the topnot option controls where | |
29534 | the header is added. If it is true, addition is at the top; otherwise at | |
29535 | the bottom. Thus, to add a header after all the Received: headers, or at | |
29536 | the top if there are no Received: headers, you could use | |
29537 | ||
29538 | header_add_at_position(TRUE, US"Received", TRUE, | |
29539 | ' ', "X-xxx: ..."); | |
29540 | ||
29541 | Normally, there is always at least one non-deleted Received: header, but | |
29542 | there may not be if received_header_text expands to an empty string. | |
29543 | ||
29544 | void header_remove(int occurrence, uschar *name) | |
29545 | ||
29546 | This function removes header lines. If occurrence is zero or negative, all | |
29547 | occurrences of the header are removed. If occurrence is greater than zero, | |
29548 | that particular instance of the header is removed. If no header(s) can be | |
29549 | found that match the specification, the function does nothing. | |
29550 | ||
29551 | BOOL header_testname(header_line *hdr, uschar *name, int length, BOOL notdel) | |
29552 | ||
29553 | This function tests whether the given header has the given name. It is not | |
29554 | just a string comparison, because white space is permitted between the name | |
29555 | and the colon. If the notdel argument is true, a false return is forced for | |
29556 | all "deleted" headers; otherwise they are not treated specially. For | |
29557 | example: | |
29558 | ||
29559 | if (header_testname(h, US"X-Spam", 6, TRUE)) ... | |
29560 | ||
29561 | uschar *lss_b64encode(uschar *cleartext, int length) | |
29562 | ||
29563 | This function base64-encodes a string, which is passed by address and | |
29564 | length. The text may contain bytes of any value, including zero. The result | |
29565 | is passed back in dynamic memory that is obtained by calling store_get(). | |
29566 | It is zero-terminated. | |
29567 | ||
29568 | int lss_b64decode(uschar *codetext, uschar **cleartext) | |
29569 | ||
29570 | This function decodes a base64-encoded string. Its arguments are a | |
29571 | zero-terminated base64-encoded string and the address of a variable that is | |
29572 | set to point to the result, which is in dynamic memory. The length of the | |
29573 | decoded string is the yield of the function. If the input is invalid base64 | |
29574 | data, the yield is -1. A zero byte is added to the end of the output string | |
29575 | to make it easy to interpret as a C string (assuming it contains no zeros | |
29576 | of its own). The added zero byte is not included in the returned count. | |
29577 | ||
29578 | int lss_match_domain(uschar *domain, uschar *list) | |
29579 | ||
29580 | This function checks for a match in a domain list. Domains are always | |
29581 | matched caselessly. The return value is one of the following: | |
29582 | ||
29583 | OK match succeeded | |
29584 | FAIL match failed | |
29585 | DEFER match deferred | |
29586 | ||
29587 | DEFER is usually caused by some kind of lookup defer, such as the inability | |
29588 | to contact a database. | |
29589 | ||
29590 | int lss_match_local_part(uschar *localpart, uschar *list, BOOL caseless) | |
29591 | ||
29592 | This function checks for a match in a local part list. The third argument | |
29593 | controls case-sensitivity. The return values are as for lss_match_domain(). | |
29594 | ||
29595 | int lss_match_address(uschar *address, uschar *list, BOOL caseless) | |
29596 | ||
29597 | This function checks for a match in an address list. The third argument | |
29598 | controls the case-sensitivity of the local part match. The domain is always | |
29599 | matched caselessly. The return values are as for lss_match_domain(). | |
29600 | ||
29601 | int lss_match_host(uschar *host_name, uschar *host_address, uschar *list) | |
29602 | ||
29603 | This function checks for a match in a host list. The most common usage is | |
29604 | expected to be | |
29605 | ||
29606 | lss_match_host(sender_host_name, sender_host_address, ...) | |
29607 | ||
29608 | An empty address field matches an empty item in the host list. If the host | |
29609 | name is NULL, the name corresponding to $sender_host_address is | |
29610 | automatically looked up if a host name is required to match an item in the | |
29611 | list. The return values are as for lss_match_domain(), but in addition, | |
29612 | lss_match_host() returns ERROR in the case when it had to look up a host | |
29613 | name, but the lookup failed. | |
29614 | ||
29615 | void log_write(unsigned int selector, int which, char *format, ...) | |
29616 | ||
29617 | This function writes to Exim's log files. The first argument should be zero | |
29618 | (it is concerned with log_selector). The second argument can be "LOG_MAIN" | |
29619 | or "LOG_REJECT" or "LOG_PANIC" or the inclusive "or" of any combination of | |
29620 | them. It specifies to which log or logs the message is written. The | |
29621 | remaining arguments are a format and relevant insertion arguments. The | |
29622 | string should not contain any newlines, not even at the end. | |
29623 | ||
29624 | void receive_add_recipient(uschar *address, int pno) | |
29625 | ||
29626 | This function adds an additional recipient to the message. The first | |
29627 | argument is the recipient address. If it is unqualified (has no domain), it | |
29628 | is qualified with the qualify_recipient domain. The second argument must | |
29629 | always be -1. | |
29630 | ||
29631 | This function does not allow you to specify a private errors_to address (as | |
29632 | described with the structure of recipient_item above), because it pre-dates | |
29633 | the addition of that field to the structure. However, it is easy to add | |
29634 | such a value afterwards. For example: | |
29635 | ||
29636 | receive_add_recipient(US"monitor@mydom.example", -1); | |
29637 | recipients_list[recipients_count-1].errors_to = | |
29638 | US"postmaster@mydom.example"; | |
29639 | ||
29640 | BOOL receive_remove_recipient(uschar *recipient) | |
29641 | ||
29642 | This is a convenience function to remove a named recipient from the list of | |
29643 | recipients. It returns true if a recipient was removed, and false if no | |
29644 | matching recipient could be found. The argument must be a complete email | |
29645 | address. | |
29646 | ||
29647 | uschar rfc2047_decode | |
29648 | (uschar *string, BOOL lencheck, uschar *target, int zeroval, int *lenptr, | |
29649 | uschar **error) | |
29650 | ||
29651 | This function decodes strings that are encoded according to RFC 2047. | |
29652 | Typically these are the contents of header lines. First, each "encoded | |
29653 | word" is decoded from the Q or B encoding into a byte-string. Then, if | |
29654 | provided with the name of a charset encoding, and if the iconv() function | |
29655 | is available, an attempt is made to translate the result to the named | |
29656 | character set. If this fails, the binary string is returned with an error | |
29657 | message. | |
29658 | ||
29659 | The first argument is the string to be decoded. If lencheck is TRUE, the | |
29660 | maximum MIME word length is enforced. The third argument is the target | |
29661 | encoding, or NULL if no translation is wanted. | |
29662 | ||
29663 | If a binary zero is encountered in the decoded string, it is replaced by | |
29664 | the contents of the zeroval argument. For use with Exim headers, the value | |
29665 | must not be 0 because header lines are handled as zero-terminated strings. | |
29666 | ||
29667 | The function returns the result of processing the string, zero-terminated; | |
29668 | if lenptr is not NULL, the length of the result is set in the variable to | |
29669 | which it points. When zeroval is 0, lenptr should not be NULL. | |
29670 | ||
29671 | If an error is encountered, the function returns NULL and uses the error | |
29672 | argument to return an error message. The variable pointed to by error is | |
29673 | set to NULL if there is no error; it may be set non-NULL even when the | |
29674 | function returns a non-NULL value if decoding was successful, but there was | |
29675 | a problem with translation. | |
29676 | ||
29677 | int smtp_fflush(void) | |
29678 | ||
29679 | This function is used in conjunction with smtp_printf(), as described | |
29680 | below. | |
29681 | ||
29682 | void smtp_printf(char *, ...) | |
29683 | ||
29684 | The arguments of this function are like printf(); it writes to the SMTP | |
29685 | output stream. You should use this function only when there is an SMTP | |
29686 | output stream, that is, when the incoming message is being received via | |
29687 | interactive SMTP. This is the case when smtp_input is TRUE and | |
29688 | smtp_batched_input is FALSE. If you want to test for an incoming message | |
29689 | from another host (as opposed to a local process that used the -bs command | |
29690 | line option), you can test the value of sender_host_address, which is | |
29691 | non-NULL when a remote host is involved. | |
29692 | ||
29693 | If an SMTP TLS connection is established, smtp_printf() uses the TLS output | |
29694 | function, so it can be used for all forms of SMTP connection. | |
29695 | ||
29696 | Strings that are written by smtp_printf() from within local_scan() must | |
29697 | start with an appropriate response code: 550 if you are going to return | |
29698 | LOCAL_SCAN_REJECT, 451 if you are going to return LOCAL_SCAN_TEMPREJECT, | |
29699 | and 250 otherwise. Because you are writing the initial lines of a | |
29700 | multi-line response, the code must be followed by a hyphen to indicate that | |
29701 | the line is not the final response line. You must also ensure that the | |
29702 | lines you write terminate with CRLF. For example: | |
29703 | ||
29704 | smtp_printf("550-this is some extra info\r\n"); | |
29705 | return LOCAL_SCAN_REJECT; | |
29706 | ||
29707 | Note that you can also create multi-line responses by including newlines in | |
29708 | the data returned via the return_text argument. The added value of using | |
29709 | smtp_printf() is that, for instance, you could introduce delays between | |
29710 | multiple output lines. | |
29711 | ||
29712 | The smtp_printf() function does not return any error indication, because it | |
29713 | does not automatically flush pending output, and therefore does not test | |
29714 | the state of the stream. (In the main code of Exim, flushing and error | |
29715 | detection is done when Exim is ready for the next SMTP input command.) If | |
29716 | you want to flush the output and check for an error (for example, the | |
29717 | dropping of a TCP/IP connection), you can call smtp_fflush(), which has no | |
29718 | arguments. It flushes the output stream, and returns a non-zero value if | |
29719 | there is an error. | |
29720 | ||
29721 | void *store_get(int) | |
29722 | ||
29723 | This function accesses Exim's internal store (memory) manager. It gets a | |
29724 | new chunk of memory whose size is given by the argument. Exim bombs out if | |
29725 | it ever runs out of memory. See the next section for a discussion of memory | |
29726 | handling. | |
29727 | ||
29728 | void *store_get_perm(int) | |
29729 | ||
29730 | This function is like store_get(), but it always gets memory from the | |
29731 | permanent pool. See the next section for a discussion of memory handling. | |
29732 | ||
29733 | uschar *string_copy(uschar *string) | |
29734 | ||
29735 | See below. | |
29736 | ||
29737 | uschar *string_copyn(uschar *string, int length) | |
29738 | ||
29739 | See below. | |
29740 | ||
29741 | uschar *string_sprintf(char *format, ...) | |
29742 | ||
29743 | These three functions create strings using Exim's dynamic memory | |
29744 | facilities. The first makes a copy of an entire string. The second copies | |
29745 | up to a maximum number of characters, indicated by the second argument. The | |
29746 | third uses a format and insertion arguments to create a new string. In each | |
29747 | case, the result is a pointer to a new string in the current memory pool. | |
29748 | See the next section for more discussion. | |
29749 | ||
29750 | ||
29751 | 44.8 More about Exim's memory handling | |
29752 | -------------------------------------- | |
29753 | ||
29754 | No function is provided for freeing memory, because that is never needed. The | |
29755 | dynamic memory that Exim uses when receiving a message is automatically | |
29756 | recycled if another message is received by the same process (this applies only | |
29757 | to incoming SMTP connections - other input methods can supply only one message | |
29758 | at a time). After receiving the last message, a reception process terminates. | |
29759 | ||
29760 | Because it is recycled, the normal dynamic memory cannot be used for holding | |
29761 | data that must be preserved over a number of incoming messages on the same SMTP | |
29762 | connection. However, Exim in fact uses two pools of dynamic memory; the second | |
29763 | one is not recycled, and can be used for this purpose. | |
29764 | ||
29765 | If you want to allocate memory that remains available for subsequent messages | |
29766 | in the same SMTP connection, you should set | |
29767 | ||
29768 | store_pool = POOL_PERM | |
29769 | ||
29770 | before calling the function that does the allocation. There is no need to | |
29771 | restore the value if you do not need to; however, if you do want to revert to | |
29772 | the normal pool, you can either restore the previous value of store_pool or set | |
29773 | it explicitly to POOL_MAIN. | |
29774 | ||
29775 | The pool setting applies to all functions that get dynamic memory, including | |
29776 | expand_string(), store_get(), and the string_xxx() functions. There is also a | |
29777 | convenience function called store_get_perm() that gets a block of memory from | |
29778 | the permanent pool while preserving the value of store_pool. | |
29779 | ||
29780 | ||
29781 | ||
29782 | =============================================================================== | |
29783 | 45. SYSTEM-WIDE MESSAGE FILTERING | |
29784 | ||
29785 | The previous chapters (on ACLs and the local scan function) describe checks | |
29786 | that can be applied to messages before they are accepted by a host. There is | |
29787 | also a mechanism for checking messages once they have been received, but before | |
29788 | they are delivered. This is called the system filter. | |
29789 | ||
29790 | The system filter operates in a similar manner to users' filter files, but it | |
29791 | is run just once per message (however many recipients the message has). It | |
29792 | should not normally be used as a substitute for routing, because deliver | |
29793 | commands in a system router provide new envelope recipient addresses. The | |
29794 | system filter must be an Exim filter. It cannot be a Sieve filter. | |
29795 | ||
29796 | The system filter is run at the start of a delivery attempt, before any routing | |
29797 | is done. If a message fails to be completely delivered at the first attempt, | |
29798 | the system filter is run again at the start of every retry. If you want your | |
29799 | filter to do something only once per message, you can make use of the | |
29800 | first_delivery condition in an if command in the filter to prevent it happening | |
29801 | on retries. | |
29802 | ||
29803 | Warning: Because the system filter runs just once, variables that are specific | |
29804 | to individual recipient addresses, such as $local_part and $domain, are not | |
29805 | set, and the "personal" condition is not meaningful. If you want to run a | |
29806 | centrally-specified filter for each recipient address independently, you can do | |
29807 | so by setting up a suitable redirect router, as described in section 45.8 | |
29808 | below. | |
29809 | ||
29810 | ||
29811 | 45.1 Specifying a system filter | |
29812 | ------------------------------- | |
29813 | ||
29814 | The name of the file that contains the system filter must be specified by | |
29815 | setting system_filter. If you want the filter to run under a uid and gid other | |
29816 | than root, you must also set system_filter_user and system_filter_group as | |
29817 | appropriate. For example: | |
29818 | ||
29819 | system_filter = /etc/mail/exim.filter | |
29820 | system_filter_user = exim | |
29821 | ||
29822 | If a system filter generates any deliveries directly to files or pipes (via the | |
29823 | save or pipe commands), transports to handle these deliveries must be specified | |
29824 | by setting system_filter_file_transport and system_filter_pipe_transport, | |
29825 | respectively. Similarly, system_filter_reply_transport must be set to handle | |
29826 | any messages generated by the reply command. | |
29827 | ||
29828 | ||
29829 | 45.2 Testing a system filter | |
29830 | ---------------------------- | |
29831 | ||
29832 | You can run simple tests of a system filter in the same way as for a user | |
29833 | filter, but you should use -bF rather than -bf, so that features that are | |
29834 | permitted only in system filters are recognized. | |
29835 | ||
29836 | If you want to test the combined effect of a system filter and a user filter, | |
29837 | you can use both -bF and -bf on the same command line. | |
29838 | ||
29839 | ||
29840 | 45.3 Contents of a system filter | |
29841 | -------------------------------- | |
29842 | ||
29843 | The language used to specify system filters is the same as for users' filter | |
29844 | files. It is described in the separate end-user document Exim's interface to | |
29845 | mail filtering. However, there are some additional features that are available | |
29846 | only in system filters; these are described in subsequent sections. If they are | |
29847 | encountered in a user's filter file or when testing with -bf, they cause | |
29848 | errors. | |
29849 | ||
29850 | There are two special conditions which, though available in users' filter | |
29851 | files, are designed for use in system filters. The condition first_delivery is | |
29852 | true only for the first attempt at delivering a message, and manually_thawed is | |
29853 | true only if the message has been frozen, and subsequently thawed by an admin | |
29854 | user. An explicit forced delivery counts as a manual thaw, but thawing as a | |
29855 | result of the auto_thaw setting does not. | |
29856 | ||
29857 | Warning: If a system filter uses the first_delivery condition to specify an | |
29858 | "unseen" (non-significant) delivery, and that delivery does not succeed, it | |
29859 | will not be tried again. If you want Exim to retry an unseen delivery until it | |
29860 | succeeds, you should arrange to set it up every time the filter runs. | |
29861 | ||
29862 | When a system filter finishes running, the values of the variables $n0 - $n9 | |
29863 | are copied into $sn0 - $sn9 and are thereby made available to users' filter | |
29864 | files. Thus a system filter can, for example, set up "scores" to which users' | |
29865 | filter files can refer. | |
29866 | ||
29867 | ||
29868 | 45.4 Additional variable for system filters | |
29869 | ------------------------------------------- | |
29870 | ||
29871 | The expansion variable $recipients, containing a list of all the recipients of | |
29872 | the message (separated by commas and white space), is available in system | |
29873 | filters. It is not available in users' filters for privacy reasons. | |
29874 | ||
29875 | ||
29876 | 45.5 Defer, freeze, and fail commands for system filters | |
29877 | -------------------------------------------------------- | |
29878 | ||
29879 | There are three extra commands (defer, freeze and fail) which are always | |
29880 | available in system filters, but are not normally enabled in users' filters. | |
29881 | (See the allow_defer, allow_freeze and allow_fail options for the redirect | |
29882 | router.) These commands can optionally be followed by the word text and a | |
29883 | string containing an error message, for example: | |
29884 | ||
29885 | fail text "this message looks like spam to me" | |
29886 | ||
29887 | The keyword text is optional if the next character is a double quote. | |
29888 | ||
29889 | The defer command defers delivery of the original recipients of the message. | |
29890 | The fail command causes all the original recipients to be failed, and a bounce | |
29891 | message to be created. The freeze command suspends all delivery attempts for | |
29892 | the original recipients. In all cases, any new deliveries that are specified by | |
29893 | the filter are attempted as normal after the filter has run. | |
29894 | ||
29895 | The freeze command is ignored if the message has been manually unfrozen and not | |
29896 | manually frozen since. This means that automatic freezing by a system filter | |
29897 | can be used as a way of checking out suspicious messages. If a message is found | |
29898 | to be all right, manually unfreezing it allows it to be delivered. | |
29899 | ||
29900 | The text given with a fail command is used as part of the bounce message as | |
29901 | well as being written to the log. If the message is quite long, this can fill | |
29902 | up a lot of log space when such failures are common. To reduce the size of the | |
29903 | log message, Exim interprets the text in a special way if it starts with the | |
29904 | two characters "<<" and contains ">>" later. The text between these two strings | |
29905 | is written to the log, and the rest of the text is used in the bounce message. | |
29906 | For example: | |
29907 | ||
29908 | fail "<<filter test 1>>Your message is rejected \ | |
29909 | because it contains attachments that we are \ | |
29910 | not prepared to receive." | |
29911 | ||
29912 | Take great care with the fail command when basing the decision to fail on the | |
29913 | contents of the message, because the bounce message will of course include the | |
29914 | contents of the original message and will therefore trigger the fail command | |
29915 | again (causing a mail loop) unless steps are taken to prevent this. Testing the | |
29916 | error_message condition is one way to prevent this. You could use, for example | |
29917 | ||
29918 | if $message_body contains "this is spam" and not error_message | |
29919 | then fail text "spam is not wanted here" endif | |
29920 | ||
29921 | though of course that might let through unwanted bounce messages. The | |
29922 | alternative is clever checking of the body and/or headers to detect bounces | |
29923 | generated by the filter. | |
29924 | ||
29925 | The interpretation of a system filter file ceases after a defer, freeze, or | |
29926 | fail command is obeyed. However, any deliveries that were set up earlier in the | |
29927 | filter file are honoured, so you can use a sequence such as | |
29928 | ||
29929 | mail ... | |
29930 | freeze | |
29931 | ||
29932 | to send a specified message when the system filter is freezing (or deferring or | |
29933 | failing) a message. The normal deliveries for the message do not, of course, | |
29934 | take place. | |
29935 | ||
29936 | ||
29937 | 45.6 Adding and removing headers in a system filter | |
29938 | --------------------------------------------------- | |
29939 | ||
29940 | Two filter commands that are available only in system filters are: | |
29941 | ||
29942 | headers add <string> | |
29943 | headers remove <string> | |
29944 | ||
29945 | The argument for the headers add is a string that is expanded and then added to | |
29946 | the end of the message's headers. It is the responsibility of the filter | |
29947 | maintainer to make sure it conforms to RFC 2822 syntax. Leading white space is | |
29948 | ignored, and if the string is otherwise empty, or if the expansion is forced to | |
29949 | fail, the command has no effect. | |
29950 | ||
29951 | You can use "\n" within the string, followed by white space, to specify | |
29952 | continued header lines. More than one header may be added in one command by | |
29953 | including "\n" within the string without any following white space. For | |
29954 | example: | |
29955 | ||
29956 | headers add "X-header-1: ....\n \ | |
29957 | continuation of X-header-1 ...\n\ | |
29958 | X-header-2: ...." | |
29959 | ||
29960 | Note that the header line continuation white space after the first newline must | |
29961 | be placed before the backslash that continues the input string, because white | |
29962 | space after input continuations is ignored. | |
29963 | ||
29964 | The argument for headers remove is a colon-separated list of header names. This | |
29965 | command applies only to those headers that are stored with the message; those | |
29966 | that are added at delivery time (such as Envelope-To: and Return-Path:) cannot | |
29967 | be removed by this means. If there is more than one header with the same name, | |
29968 | they are all removed. | |
29969 | ||
29970 | The headers command in a system filter makes an immediate change to the set of | |
29971 | header lines that was received with the message (with possible additions from | |
29972 | ACL processing). Subsequent commands in the system filter operate on the | |
29973 | modified set, which also forms the basis for subsequent message delivery. | |
29974 | Unless further modified during routing or transporting, this set of headers is | |
29975 | used for all recipients of the message. | |
29976 | ||
29977 | During routing and transporting, the variables that refer to the contents of | |
29978 | header lines refer only to those lines that are in this set. Thus, header lines | |
29979 | that are added by a system filter are visible to users' filter files and to all | |
29980 | routers and transports. This contrasts with the manipulation of header lines by | |
29981 | routers and transports, which is not immediate, but which instead is saved up | |
29982 | until the message is actually being written (see section 46.17). | |
29983 | ||
29984 | If the message is not delivered at the first attempt, header lines that were | |
29985 | added by the system filter are stored with the message, and so are still | |
29986 | present at the next delivery attempt. Header lines that were removed are still | |
29987 | present, but marked "deleted" so that they are not transported with the | |
29988 | message. For this reason, it is usual to make the headers command conditional | |
29989 | on first_delivery so that the set of header lines is not modified more than | |
29990 | once. | |
29991 | ||
29992 | Because header modification in a system filter acts immediately, you have to | |
29993 | use an indirect approach if you want to modify the contents of a header line. | |
29994 | For example: | |
29995 | ||
29996 | headers add "Old-Subject: $h_subject:" | |
29997 | headers remove "Subject" | |
29998 | headers add "Subject: new subject (was: $h_old-subject:)" | |
29999 | headers remove "Old-Subject" | |
30000 | ||
30001 | ||
30002 | 45.7 Setting an errors address in a system filter | |
30003 | ------------------------------------------------- | |
30004 | ||
30005 | In a system filter, if a deliver command is followed by | |
30006 | ||
30007 | errors_to <some address> | |
30008 | ||
30009 | in order to change the envelope sender (and hence the error reporting) for that | |
30010 | delivery, any address may be specified. (In a user filter, only the current | |
30011 | user's address can be set.) For example, if some mail is being monitored, you | |
30012 | might use | |
30013 | ||
30014 | unseen deliver monitor@spying.example errors_to root@local.example | |
30015 | ||
30016 | to take a copy which would not be sent back to the normal error reporting | |
30017 | address if its delivery failed. | |
30018 | ||
30019 | ||
30020 | 45.8 Per-address filtering | |
30021 | -------------------------- | |
30022 | ||
30023 | In contrast to the system filter, which is run just once per message for each | |
30024 | delivery attempt, it is also possible to set up a system-wide filtering | |
30025 | operation that runs once for each recipient address. In this case, variables | |
30026 | such as $local_part and $domain can be used, and indeed, the choice of filter | |
30027 | file could be made dependent on them. This is an example of a router which | |
30028 | implements such a filter: | |
30029 | ||
30030 | central_filter: | |
30031 | check_local_user | |
30032 | driver = redirect | |
30033 | domains = +local_domains | |
30034 | file = /central/filters/$local_part | |
30035 | no_verify | |
30036 | allow_filter | |
30037 | allow_freeze | |
30038 | ||
30039 | The filter is run in a separate process under its own uid. Therefore, either | |
30040 | check_local_user must be set (as above), in which case the filter is run as the | |
30041 | local user, or the user option must be used to specify which user to use. If | |
30042 | both are set, user overrides. | |
30043 | ||
30044 | Care should be taken to ensure that none of the commands in the filter file | |
30045 | specify a significant delivery if the message is to go on to be delivered to | |
30046 | its intended recipient. The router will not then claim to have dealt with the | |
30047 | address, so it will be passed on to subsequent routers to be delivered in the | |
30048 | normal way. | |
30049 | ||
30050 | ||
30051 | ||
30052 | =============================================================================== | |
30053 | 46. MESSAGE PROCESSING | |
30054 | ||
30055 | Exim performs various transformations on the sender and recipient addresses of | |
30056 | all messages that it handles, and also on the messages' header lines. Some of | |
30057 | these are optional and configurable, while others always take place. All of | |
30058 | this processing, except rewriting as a result of routing, and the addition or | |
30059 | removal of header lines while delivering, happens when a message is received, | |
30060 | before it is placed on Exim's queue. | |
30061 | ||
30062 | Some of the automatic processing takes place by default only for | |
30063 | "locally-originated" messages. This adjective is used to describe messages that | |
30064 | are not received over TCP/IP, but instead are passed to an Exim process on its | |
30065 | standard input. This includes the interactive "local SMTP" case that is set up | |
30066 | by the -bs command line option. | |
30067 | ||
30068 | Note: Messages received over TCP/IP on the loopback interface (127.0.0.1 or | |
30069 | ::1) are not considered to be locally-originated. Exim does not treat the | |
30070 | loopback interface specially in any way. | |
30071 | ||
30072 | If you want the loopback interface to be treated specially, you must ensure | |
30073 | that there are appropriate entries in your ACLs. | |
30074 | ||
30075 | ||
30076 | 46.1 Submission mode for non-local messages | |
30077 | ------------------------------------------- | |
30078 | ||
30079 | Processing that happens automatically for locally-originated messages (unless | |
30080 | suppress_local_fixups is set) can also be requested for messages that are | |
30081 | received over TCP/IP. The term "submission mode" is used to describe this | |
30082 | state. Submission mode is set by the modifier | |
30083 | ||
30084 | control = submission | |
30085 | ||
30086 | in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections 42.21 | |
30087 | and 42.22). This makes Exim treat the message as a local submission, and is | |
30088 | normally used when the source of the message is known to be an MUA running on a | |
30089 | client host (as opposed to an MTA). For example, to set submission mode for | |
30090 | messages originating on the IPv4 loopback interface, you could include the | |
30091 | following in the MAIL ACL: | |
30092 | ||
30093 | warn hosts = 127.0.0.1 | |
30094 | control = submission | |
30095 | ||
30096 | There are some options that can be used when setting submission mode. A slash | |
30097 | is used to separate options. For example: | |
30098 | ||
30099 | control = submission/sender_retain | |
30100 | ||
30101 | Specifying sender_retain has the effect of setting local_sender_retain true and | |
30102 | local_from_check false for the current incoming message. The first of these | |
30103 | allows an existing Sender: header in the message to remain, and the second | |
30104 | suppresses the check to ensure that From: matches the authenticated sender. | |
30105 | With this setting, Exim still fixes up messages by adding Date: and Message-ID: | |
30106 | header lines if they are missing, but makes no attempt to check sender | |
30107 | authenticity in header lines. | |
30108 | ||
30109 | When sender_retain is not set, a submission mode setting may specify a domain | |
30110 | to be used when generating a From: or Sender: header line. For example: | |
30111 | ||
30112 | control = submission/domain=some.domain | |
30113 | ||
30114 | The domain may be empty. How this value is used is described in sections 46.11 | |
30115 | and 46.16. There is also a name option that allows you to specify the user's | |
30116 | full name for inclusion in a created Sender: or From: header line. For example: | |
30117 | ||
30118 | accept authenticated = * | |
30119 | control = submission/domain=wonderland.example/\ | |
30120 | name=${lookup {$authenticated_id} \ | |
30121 | lsearch {/etc/exim/namelist}} | |
30122 | ||
30123 | Because the name may contain any characters, including slashes, the name option | |
30124 | must be given last. The remainder of the string is used as the name. For the | |
30125 | example above, if /etc/exim/namelist contains: | |
30126 | ||
30127 | bigegg: Humpty Dumpty | |
30128 | ||
30129 | then when the sender has authenticated as bigegg, the generated Sender: line | |
30130 | would be: | |
30131 | ||
30132 | Sender: Humpty Dumpty <bigegg@wonderland.example> | |
30133 | ||
30134 | By default, submission mode forces the return path to the same address as is | |
30135 | used to create the Sender: header. However, if sender_retain is specified, the | |
30136 | return path is also left unchanged. | |
30137 | ||
30138 | Note: The changes caused by submission mode take effect after the predata ACL. | |
30139 | This means that any sender checks performed before the fix-ups use the | |
30140 | untrusted sender address specified by the user, not the trusted sender address | |
30141 | specified by submission mode. Although this might be slightly unexpected, it | |
30142 | does mean that you can configure ACL checks to spot that a user is trying to | |
30143 | spoof another's address. | |
30144 | ||
30145 | ||
30146 | 46.2 Line endings | |
30147 | ----------------- | |
30148 | ||
30149 | RFC 2821 specifies that CRLF (two characters: carriage-return, followed by | |
30150 | linefeed) is the line ending for messages transmitted over the Internet using | |
30151 | SMTP over TCP/IP. However, within individual operating systems, different | |
30152 | conventions are used. For example, Unix-like systems use just LF, but others | |
30153 | use CRLF or just CR. | |
30154 | ||
30155 | Exim was designed for Unix-like systems, and internally, it stores messages | |
30156 | using the system's convention of a single LF as a line terminator. When | |
30157 | receiving a message, all line endings are translated to this standard format. | |
30158 | Originally, it was thought that programs that passed messages directly to an | |
30159 | MTA within an operating system would use that system's convention. Experience | |
30160 | has shown that this is not the case; for example, there are Unix applications | |
30161 | that use CRLF in this circumstance. For this reason, and for compatibility with | |
30162 | other MTAs, the way Exim handles line endings for all messages is now as | |
30163 | follows: | |
30164 | ||
30165 | * LF not preceded by CR is treated as a line ending. | |
30166 | ||
30167 | * CR is treated as a line ending; if it is immediately followed by LF, the LF | |
30168 | is ignored. | |
30169 | ||
30170 | * The sequence "CR, dot, CR" does not terminate an incoming SMTP message, nor | |
30171 | a local message in the state where a line containing only a dot is a | |
30172 | terminator. | |
30173 | ||
30174 | * If a bare CR is encountered within a header line, an extra space is added | |
30175 | after the line terminator so as not to end the header line. The reasoning | |
30176 | behind this is that bare CRs in header lines are most likely either to be | |
30177 | mistakes, or people trying to play silly games. | |
30178 | ||
30179 | * If the first header line received in a message ends with CRLF, a subsequent | |
30180 | bare LF in a header line is treated in the same way as a bare CR in a | |
30181 | header line. | |
30182 | ||
30183 | ||
30184 | 46.3 Unqualified addresses | |
30185 | -------------------------- | |
30186 | ||
30187 | By default, Exim expects every envelope address it receives from an external | |
30188 | host to be fully qualified. Unqualified addresses cause negative responses to | |
30189 | SMTP commands. However, because SMTP is used as a means of transporting | |
30190 | messages from MUAs running on personal workstations, there is sometimes a | |
30191 | requirement to accept unqualified addresses from specific hosts or IP networks. | |
30192 | ||
30193 | Exim has two options that separately control which hosts may send unqualified | |
30194 | sender or recipient addresses in SMTP commands, namely sender_unqualified_hosts | |
30195 | and recipient_unqualified_hosts. In both cases, if an unqualified address is | |
30196 | accepted, it is qualified by adding the value of qualify_domain or | |
30197 | qualify_recipient, as appropriate. | |
30198 | ||
30199 | Unqualified addresses in header lines are automatically qualified for messages | |
30200 | that are locally originated, unless the -bnq option is given on the command | |
30201 | line. For messages received over SMTP, unqualified addresses in header lines | |
30202 | are qualified only if unqualified addresses are permitted in SMTP commands. In | |
30203 | other words, such qualification is also controlled by sender_unqualified_hosts | |
30204 | and recipient_unqualified_hosts, | |
30205 | ||
30206 | ||
30207 | 46.4 The UUCP From line | |
30208 | ----------------------- | |
30209 | ||
30210 | Messages that have come from UUCP (and some other applications) often begin | |
30211 | with a line containing the envelope sender and a timestamp, following the word | |
30212 | "From". Examples of two common formats are: | |
30213 | ||
30214 | From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996 | |
30215 | From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT | |
30216 | ||
30217 | This line precedes the RFC 2822 header lines. For compatibility with Sendmail, | |
30218 | Exim recognizes such lines at the start of messages that are submitted to it | |
30219 | via the command line (that is, on the standard input). It does not recognize | |
30220 | such lines in incoming SMTP messages, unless the sending host matches | |
30221 | ignore_fromline_hosts or the -bs option was used for a local message and | |
30222 | ignore_fromline_local is set. The recognition is controlled by a regular | |
30223 | expression that is defined by the uucp_from_pattern option, whose default value | |
30224 | matches the two common cases shown above and puts the address that follows | |
30225 | "From" into $1. | |
30226 | ||
30227 | When the caller of Exim for a non-SMTP message that contains a "From" line is a | |
30228 | trusted user, the message's sender address is constructed by expanding the | |
30229 | contents of uucp_sender_address, whose default value is "$1". This is then | |
30230 | parsed as an RFC 2822 address. If there is no domain, the local part is | |
30231 | qualified with qualify_domain unless it is the empty string. However, if the | |
30232 | command line -f option is used, it overrides the "From" line. | |
30233 | ||
30234 | If the caller of Exim is not trusted, the "From" line is recognized, but the | |
30235 | sender address is not changed. This is also the case for incoming SMTP messages | |
30236 | that are permitted to contain "From" lines. | |
30237 | ||
30238 | Only one "From" line is recognized. If there is more than one, the second is | |
30239 | treated as a data line that starts the body of the message, as it is not valid | |
30240 | as a header line. This also happens if a "From" line is present in an incoming | |
30241 | SMTP message from a source that is not permitted to send them. | |
30242 | ||
30243 | ||
30244 | 46.5 Resent- header lines | |
30245 | ------------------------- | |
30246 | ||
30247 | RFC 2822 makes provision for sets of header lines starting with the string | |
30248 | "Resent-" to be added to a message when it is resent by the original recipient | |
30249 | to somebody else. These headers are Resent-Date:, Resent-From:, Resent-Sender:, | |
30250 | Resent-To:, Resent-Cc:, Resent-Bcc: and Resent-Message-ID:. The RFC says: | |
30251 | ||
30252 | Resent fields are strictly informational. They MUST NOT be used in the | |
30253 | normal processing of replies or other such automatic actions on messages. | |
30254 | ||
30255 | This leaves things a bit vague as far as other processing actions such as | |
30256 | address rewriting are concerned. Exim treats Resent- header lines as follows: | |
30257 | ||
30258 | * A Resent-From: line that just contains the login id of the submitting user | |
30259 | is automatically rewritten in the same way as From: (see below). | |
30260 | ||
30261 | * If there's a rewriting rule for a particular header line, it is also | |
30262 | applied to Resent- header lines of the same type. For example, a rule that | |
30263 | rewrites From: also rewrites Resent-From:. | |
30264 | ||
30265 | * For local messages, if Sender: is removed on input, Resent-Sender: is also | |
30266 | removed. | |
30267 | ||
30268 | * For a locally-submitted message, if there are any Resent- header lines but | |
30269 | no Resent-Date:, Resent-From:, or Resent-Message-Id:, they are added as | |
30270 | necessary. It is the contents of Resent-Message-Id: (rather than | |
30271 | Message-Id:) which are included in log lines in this case. | |
30272 | ||
30273 | * The logic for adding Sender: is duplicated for Resent-Sender: when any | |
30274 | Resent- header lines are present. | |
30275 | ||
30276 | ||
30277 | 46.6 The Auto-Submitted: header line | |
30278 | ------------------------------------ | |
30279 | ||
30280 | Whenever Exim generates an autoreply, a bounce, or a delay warning message, it | |
30281 | includes the header line: | |
30282 | ||
30283 | Auto-Submitted: auto-replied | |
30284 | ||
30285 | ||
30286 | 46.7 The Bcc: header line | |
30287 | ------------------------- | |
30288 | ||
30289 | If Exim is called with the -t option, to take recipient addresses from a | |
30290 | message's header, it removes any Bcc: header line that may exist (after | |
30291 | extracting its addresses). If -t is not present on the command line, any | |
30292 | existing Bcc: is not removed. | |
30293 | ||
30294 | ||
30295 | 46.8 The Date: header line | |
30296 | -------------------------- | |
30297 | ||
30298 | If a locally-generated or submission-mode message has no Date: header line, | |
30299 | Exim adds one, using the current date and time, unless the | |
30300 | suppress_local_fixups control has been specified. | |
30301 | ||
30302 | ||
30303 | 46.9 The Delivery-date: header line | |
30304 | ----------------------------------- | |
30305 | ||
30306 | Delivery-date: header lines are not part of the standard RFC 2822 header set. | |
30307 | Exim can be configured to add them to the final delivery of messages. (See the | |
30308 | generic delivery_date_add transport option.) They should not be present in | |
30309 | messages in transit. If the delivery_date_remove configuration option is set | |
30310 | (the default), Exim removes Delivery-date: header lines from incoming messages. | |
30311 | ||
30312 | ||
30313 | 46.10 The Envelope-to: header line | |
30314 | ---------------------------------- | |
30315 | ||
30316 | Envelope-to: header lines are not part of the standard RFC 2822 header set. | |
30317 | Exim can be configured to add them to the final delivery of messages. (See the | |
30318 | generic envelope_to_add transport option.) They should not be present in | |
30319 | messages in transit. If the envelope_to_remove configuration option is set (the | |
30320 | default), Exim removes Envelope-to: header lines from incoming messages. | |
30321 | ||
30322 | ||
30323 | 46.11 The From: header line | |
30324 | --------------------------- | |
30325 | ||
30326 | If a submission-mode message does not contain a From: header line, Exim adds | |
30327 | one if either of the following conditions is true: | |
30328 | ||
30329 | * The envelope sender address is not empty (that is, this is not a bounce | |
30330 | message). The added header line copies the envelope sender address. | |
30331 | ||
30332 | * The SMTP session is authenticated and $authenticated_id is not empty. | |
30333 | ||
30334 | 1. If no domain is specified by the submission control, the local part is | |
30335 | $authenticated_id and the domain is $qualify_domain. | |
30336 | ||
30337 | 2. If a non-empty domain is specified by the submission control, the local | |
30338 | part is $authenticated_id, and the domain is the specified domain. | |
30339 | ||
30340 | 3. If an empty domain is specified by the submission control, | |
30341 | $authenticated_id is assumed to be the complete address. | |
30342 | ||
30343 | A non-empty envelope sender takes precedence. | |
30344 | ||
30345 | If a locally-generated incoming message does not contain a From: header line, | |
30346 | and the suppress_local_fixups control is not set, Exim adds one containing the | |
30347 | sender's address. The calling user's login name and full name are used to | |
30348 | construct the address, as described in section 46.18. They are obtained from | |
30349 | the password data by calling getpwuid() (but see the unknown_login | |
30350 | configuration option). The address is qualified with qualify_domain. | |
30351 | ||
30352 | For compatibility with Sendmail, if an incoming, non-SMTP message has a From: | |
30353 | header line containing just the unqualified login name of the calling user, | |
30354 | this is replaced by an address containing the user's login name and full name | |
30355 | as described in section 46.18. | |
30356 | ||
30357 | ||
30358 | 46.12 The Message-ID: header line | |
30359 | --------------------------------- | |
30360 | ||
30361 | If a locally-generated or submission-mode incoming message does not contain a | |
30362 | Message-ID: or Resent-Message-ID: header line, and the suppress_local_fixups | |
30363 | control is not set, Exim adds a suitable header line to the message. If there | |
30364 | are any Resent-: headers in the message, it creates Resent-Message-ID:. The id | |
30365 | is constructed from Exim's internal message id, preceded by the letter E to | |
30366 | ensure it starts with a letter, and followed by @ and the primary host name. | |
30367 | Additional information can be included in this header line by setting the | |
30368 | message_id_header_text and/or message_id_header_domain options. | |
30369 | ||
30370 | ||
30371 | 46.13 The Received: header line | |
30372 | ------------------------------- | |
30373 | ||
30374 | A Received: header line is added at the start of every message. The contents | |
30375 | are defined by the received_header_text configuration option, and Exim | |
30376 | automatically adds a semicolon and a timestamp to the configured string. | |
30377 | ||
30378 | The Received: header is generated as soon as the message's header lines have | |
30379 | been received. At this stage, the timestamp in the Received: header line is the | |
30380 | time that the message started to be received. This is the value that is seen by | |
30381 | the DATA ACL and by the local_scan() function. | |
30382 | ||
30383 | Once a message is accepted, the timestamp in the Received: header line is | |
30384 | changed to the time of acceptance, which is (apart from a small delay while the | |
30385 | -H spool file is written) the earliest time at which delivery could start. | |
30386 | ||
30387 | ||
30388 | 46.14 The References: header line | |
30389 | --------------------------------- | |
30390 | ||
30391 | Messages created by the autoreply transport include a References: header line. | |
30392 | This is constructed according to the rules that are described in section 3.64 | |
30393 | of RFC 2822 (which states that replies should contain such a header line), and | |
30394 | section 3.14 of RFC 3834 (which states that automatic responses are not | |
30395 | different in this respect). However, because some mail processing software does | |
30396 | not cope well with very long header lines, no more than 12 message IDs are | |
30397 | copied from the References: header line in the incoming message. If there are | |
30398 | more than 12, the first one and then the final 11 are copied, before adding the | |
30399 | message ID of the incoming message. | |
30400 | ||
30401 | ||
30402 | 46.15 The Return-path: header line | |
30403 | ---------------------------------- | |
30404 | ||
30405 | Return-path: header lines are defined as something an MTA may insert when it | |
30406 | does the final delivery of messages. (See the generic return_path_add transport | |
30407 | option.) Therefore, they should not be present in messages in transit. If the | |
30408 | return_path_remove configuration option is set (the default), Exim removes | |
30409 | Return-path: header lines from incoming messages. | |
30410 | ||
30411 | ||
30412 | 46.16 The Sender: header line | |
30413 | ----------------------------- | |
30414 | ||
30415 | For a locally-originated message from an untrusted user, Exim may remove an | |
30416 | existing Sender: header line, and it may add a new one. You can modify these | |
30417 | actions by setting the local_sender_retain option true, the local_from_check | |
30418 | option false, or by using the suppress_local_fixups control setting. | |
30419 | ||
30420 | When a local message is received from an untrusted user and local_from_check is | |
30421 | true (the default), and the suppress_local_fixups control has not been set, a | |
30422 | check is made to see if the address given in the From: header line is the | |
30423 | correct (local) sender of the message. The address that is expected has the | |
30424 | login name as the local part and the value of qualify_domain as the domain. | |
30425 | Prefixes and suffixes for the local part can be permitted by setting | |
30426 | local_from_prefix and local_from_suffix appropriately. If From: does not | |
30427 | contain the correct sender, a Sender: line is added to the message. | |
30428 | ||
30429 | If you set local_from_check false, this checking does not occur. However, the | |
30430 | removal of an existing Sender: line still happens, unless you also set | |
30431 | local_sender_retain to be true. It is not possible to set both of these options | |
30432 | true at the same time. | |
30433 | ||
30434 | By default, no processing of Sender: header lines is done for messages received | |
30435 | over TCP/IP or for messages submitted by trusted users. However, when a message | |
30436 | is received over TCP/IP in submission mode, and sender_retain is not specified | |
30437 | on the submission control, the following processing takes place: | |
30438 | ||
30439 | First, any existing Sender: lines are removed. Then, if the SMTP session is | |
30440 | authenticated, and $authenticated_id is not empty, a sender address is created | |
30441 | as follows: | |
30442 | ||
30443 | * If no domain is specified by the submission control, the local part is | |
30444 | $authenticated_id and the domain is $qualify_domain. | |
30445 | ||
30446 | * If a non-empty domain is specified by the submission control, the local | |
30447 | part is $authenticated_id, and the domain is the specified domain. | |
30448 | ||
30449 | * If an empty domain is specified by the submission control, | |
30450 | $authenticated_id is assumed to be the complete address. | |
30451 | ||
30452 | This address is compared with the address in the From: header line. If they are | |
30453 | different, a Sender: header line containing the created address is added. | |
30454 | Prefixes and suffixes for the local part in From: can be permitted by setting | |
30455 | local_from_prefix and local_from_suffix appropriately. | |
30456 | ||
30457 | Note: Whenever a Sender: header line is created, the return path for the | |
30458 | message (the envelope sender address) is changed to be the same address, except | |
30459 | in the case of submission mode when sender_retain is specified. | |
30460 | ||
30461 | ||
30462 | 46.17 Adding and removing header lines in routers and transports | |
30463 | ---------------------------------------------------------------- | |
30464 | ||
30465 | When a message is delivered, the addition and removal of header lines can be | |
30466 | specified in a system filter, or on any of the routers and transports that | |
30467 | process the message. Section 45.6 contains details about modifying headers in a | |
30468 | system filter. Header lines can also be added in an ACL as a message is | |
30469 | received (see section 42.24). | |
30470 | ||
30471 | In contrast to what happens in a system filter, header modifications that are | |
30472 | specified on routers and transports apply only to the particular recipient | |
30473 | addresses that are being processed by those routers and transports. These | |
30474 | changes do not actually take place until a copy of the message is being | |
30475 | transported. Therefore, they do not affect the basic set of header lines, and | |
30476 | they do not affect the values of the variables that refer to header lines. | |
30477 | ||
30478 | Note: In particular, this means that any expansions in the configuration of the | |
30479 | transport cannot refer to the modified header lines, because such expansions | |
30480 | all occur before the message is actually transported. | |
30481 | ||
30482 | For both routers and transports, the argument of a headers_add option must be | |
30483 | in the form of one or more RFC 2822 header lines, separated by newlines (coded | |
30484 | as "\n"). For example: | |
30485 | ||
30486 | headers_add = X-added-header: added by $primary_hostname\n\ | |
30487 | X-added-second: another added header line | |
30488 | ||
30489 | Exim does not check the syntax of these added header lines. | |
30490 | ||
30491 | Multiple headers_add options for a single router or transport can be specified; | |
30492 | the values will append to a single list of header lines. Each header-line is | |
30493 | separately expanded. | |
30494 | ||
30495 | The argument of a headers_remove option must consist of a colon-separated list | |
30496 | of header names. This is confusing, because header names themselves are often | |
30497 | terminated by colons. In this case, the colons are the list separators, not | |
30498 | part of the names. For example: | |
30499 | ||
30500 | headers_remove = return-receipt-to:acknowledge-to | |
30501 | ||
30502 | Multiple headers_remove options for a single router or transport can be | |
30503 | specified; the arguments will append to a single header-names list. Each item | |
30504 | is separately expanded. | |
30505 | ||
30506 | When headers_add or headers_remove is specified on a router, items are expanded | |
30507 | at routing time, and then associated with all addresses that are accepted by | |
30508 | that router, and also with any new addresses that it generates. If an address | |
30509 | passes through several routers as a result of aliasing or forwarding, the | |
30510 | changes are cumulative. | |
30511 | ||
30512 | However, this does not apply to multiple routers that result from the use of | |
30513 | the unseen option. Any header modifications that were specified by the "unseen" | |
30514 | router or its predecessors apply only to the "unseen" delivery. | |
30515 | ||
30516 | Addresses that end up with different headers_add or headers_remove settings | |
30517 | cannot be delivered together in a batch, so a transport is always dealing with | |
30518 | a set of addresses that have the same header-processing requirements. | |
30519 | ||
30520 | The transport starts by writing the original set of header lines that arrived | |
30521 | with the message, possibly modified by the system filter. As it writes out | |
30522 | these lines, it consults the list of header names that were attached to the | |
30523 | recipient address(es) by headers_remove options in routers, and it also | |
30524 | consults the transport's own headers_remove option. Header lines whose names | |
30525 | are on either of these lists are not written out. If there are multiple | |
30526 | instances of any listed header, they are all skipped. | |
30527 | ||
30528 | After the remaining original header lines have been written, new header lines | |
30529 | that were specified by routers' headers_add options are written, in the order | |
30530 | in which they were attached to the address. These are followed by any header | |
30531 | lines specified by the transport's headers_add option. | |
30532 | ||
30533 | This way of handling header line modifications in routers and transports has | |
30534 | the following consequences: | |
30535 | ||
30536 | * The original set of header lines, possibly modified by the system filter, | |
30537 | remains "visible", in the sense that the $header_xxx variables refer to it, | |
30538 | at all times. | |
30539 | ||
30540 | * Header lines that are added by a router's headers_add option are not | |
30541 | accessible by means of the $header_xxx expansion syntax in subsequent | |
30542 | routers or the transport. | |
30543 | ||
30544 | * Conversely, header lines that are specified for removal by headers_remove | |
30545 | in a router remain visible to subsequent routers and the transport. | |
30546 | ||
30547 | * Headers added to an address by headers_add in a router cannot be removed by | |
30548 | a later router or by a transport. | |
30549 | ||
30550 | * An added header can refer to the contents of an original header that is to | |
30551 | be removed, even it has the same name as the added header. For example: | |
30552 | ||
30553 | headers_remove = subject | |
30554 | headers_add = Subject: new subject (was: $h_subject:) | |
30555 | ||
30556 | Warning: The headers_add and headers_remove options cannot be used for a | |
30557 | redirect router that has the one_time option set. | |
30558 | ||
30559 | ||
30560 | 46.18 Constructed addresses | |
30561 | --------------------------- | |
30562 | ||
30563 | When Exim constructs a sender address for a locally-generated message, it uses | |
30564 | the form | |
30565 | ||
30566 | <user name> <login@qualify_domain> | |
30567 | ||
30568 | For example: | |
30569 | ||
30570 | Zaphod Beeblebrox <zaphod@end.univ.example> | |
30571 | ||
30572 | The user name is obtained from the -F command line option if set, or otherwise | |
30573 | by looking up the calling user by getpwuid() and extracting the "gecos" field | |
30574 | from the password entry. If the "gecos" field contains an ampersand character, | |
30575 | this is replaced by the login name with the first letter upper cased, as is | |
30576 | conventional in a number of operating systems. See the gecos_name option for a | |
30577 | way to tailor the handling of the "gecos" field. The unknown_username option | |
30578 | can be used to specify user names in cases when there is no password file | |
30579 | entry. | |
30580 | ||
30581 | In all cases, the user name is made to conform to RFC 2822 by quoting all or | |
30582 | parts of it if necessary. In addition, if it contains any non-printing | |
30583 | characters, it is encoded as described in RFC 2047, which defines a way of | |
30584 | including non-ASCII characters in header lines. The value of the | |
30585 | headers_charset option specifies the name of the encoding that is used (the | |
30586 | characters are assumed to be in this encoding). The setting of | |
30587 | print_topbitchars controls whether characters with the top bit set (that is, | |
30588 | with codes greater than 127) count as printing characters or not. | |
30589 | ||
30590 | ||
30591 | 46.19 Case of local parts | |
30592 | ------------------------- | |
30593 | ||
30594 | RFC 2822 states that the case of letters in the local parts of addresses cannot | |
30595 | be assumed to be non-significant. Exim preserves the case of local parts of | |
30596 | addresses, but by default it uses a lower-cased form when it is routing, | |
30597 | because on most Unix systems, usernames are in lower case and case-insensitive | |
30598 | routing is required. However, any particular router can be made to use the | |
30599 | original case for local parts by setting the caseful_local_part generic router | |
30600 | option. | |
30601 | ||
30602 | If you must have mixed-case user names on your system, the best way to proceed, | |
30603 | assuming you want case-independent handling of incoming email, is to set up | |
30604 | your first router to convert incoming local parts in your domains to the | |
30605 | correct case by means of a file lookup. For example: | |
30606 | ||
30607 | correct_case: | |
30608 | driver = redirect | |
30609 | domains = +local_domains | |
30610 | data = ${lookup{$local_part}cdb\ | |
30611 | {/etc/usercased.cdb}{$value}fail}\ | |
30612 | @$domain | |
30613 | ||
30614 | For this router, the local part is forced to lower case by the default action ( | |
30615 | caseful_local_part is not set). The lower-cased local part is used to look up a | |
30616 | new local part in the correct case. If you then set caseful_local_part on any | |
30617 | subsequent routers which process your domains, they will operate on local parts | |
30618 | with the correct case in a case-sensitive manner. | |
30619 | ||
30620 | ||
30621 | 46.20 Dots in local parts | |
30622 | ------------------------- | |
30623 | ||
30624 | RFC 2822 forbids empty components in local parts. That is, an unquoted local | |
30625 | part may not begin or end with a dot, nor have two consecutive dots in the | |
30626 | middle. However, it seems that many MTAs do not enforce this, so Exim permits | |
30627 | empty components for compatibility. | |
30628 | ||
30629 | ||
30630 | 46.21 Rewriting addresses | |
30631 | ------------------------- | |
30632 | ||
30633 | Rewriting of sender and recipient addresses, and addresses in headers, can | |
30634 | happen automatically, or as the result of configuration options, as described | |
30635 | in chapter 31. The headers that may be affected by this are Bcc:, Cc:, From:, | |
30636 | Reply-To:, Sender:, and To:. | |
30637 | ||
30638 | Automatic rewriting includes qualification, as mentioned above. The other case | |
30639 | in which it can happen is when an incomplete non-local domain is given. The | |
30640 | routing process may cause this to be expanded into the full domain name. For | |
30641 | example, a header such as | |
30642 | ||
30643 | To: hare@teaparty | |
30644 | ||
30645 | might get rewritten as | |
30646 | ||
30647 | To: hare@teaparty.wonderland.fict.example | |
30648 | ||
30649 | Rewriting as a result of routing is the one kind of message processing that | |
30650 | does not happen at input time, as it cannot be done until the address has been | |
30651 | routed. | |
30652 | ||
30653 | Strictly, one should not do any deliveries of a message until all its addresses | |
30654 | have been routed, in case any of the headers get changed as a result of | |
30655 | routing. However, doing this in practice would hold up many deliveries for | |
30656 | unreasonable amounts of time, just because one address could not immediately be | |
30657 | routed. Exim therefore does not delay other deliveries when routing of one or | |
30658 | more addresses is deferred. | |
30659 | ||
30660 | ||
30661 | ||
30662 | =============================================================================== | |
30663 | 47. SMTP PROCESSING | |
30664 | ||
30665 | Exim supports a number of different ways of using the SMTP protocol, and its | |
30666 | LMTP variant, which is an interactive protocol for transferring messages into a | |
30667 | closed mail store application. This chapter contains details of how SMTP is | |
30668 | processed. For incoming mail, the following are available: | |
30669 | ||
30670 | * SMTP over TCP/IP (Exim daemon or inetd); | |
30671 | ||
30672 | * SMTP over the standard input and output (the -bs option); | |
30673 | ||
30674 | * Batched SMTP on the standard input (the -bS option). | |
30675 | ||
30676 | For mail delivery, the following are available: | |
30677 | ||
30678 | * SMTP over TCP/IP (the smtp transport); | |
30679 | ||
30680 | * LMTP over TCP/IP (the smtp transport with the protocol option set to | |
30681 | "lmtp"); | |
30682 | ||
30683 | * LMTP over a pipe to a process running in the local host (the lmtp | |
30684 | transport); | |
30685 | ||
30686 | * Batched SMTP to a file or pipe (the appendfile and pipe transports with the | |
30687 | use_bsmtp option set). | |
30688 | ||
30689 | Batched SMTP is the name for a process in which batches of messages are stored | |
30690 | in or read from files (or pipes), in a format in which SMTP commands are used | |
30691 | to contain the envelope information. | |
30692 | ||
30693 | ||
30694 | 47.1 Outgoing SMTP and LMTP over TCP/IP | |
30695 | --------------------------------------- | |
30696 | ||
30697 | Outgoing SMTP and LMTP over TCP/IP is implemented by the smtp transport. The | |
30698 | protocol option selects which protocol is to be used, but the actual processing | |
30699 | is the same in both cases. | |
30700 | ||
30701 | If, in response to its EHLO command, Exim is told that the SIZE parameter is | |
30702 | supported, it adds SIZE=<n> to each subsequent MAIL command. The value of <n> | |
30703 | is the message size plus the value of the size_addition option (default 1024) | |
30704 | to allow for additions to the message such as per-transport header lines, or | |
30705 | changes made in a transport filter. If size_addition is set negative, the use | |
30706 | of SIZE is suppressed. | |
30707 | ||
30708 | If the remote server advertises support for PIPELINING, Exim uses the | |
30709 | pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets | |
30710 | required for the transaction. | |
30711 | ||
30712 | If the remote server advertises support for the STARTTLS command, and Exim was | |
30713 | built to support TLS encryption, it tries to start a TLS session unless the | |
30714 | server matches hosts_avoid_tls. See chapter 41 for more details. Either a match | |
30715 | in that or hosts_verify_avoid_tls apply when the transport is called for | |
30716 | verification. | |
30717 | ||
30718 | If the remote server advertises support for the AUTH command, Exim scans the | |
30719 | authenticators configuration for any suitable client settings, as described in | |
30720 | chapter 33. | |
30721 | ||
30722 | Responses from the remote host are supposed to be terminated by CR followed by | |
30723 | LF. However, there are known to be hosts that do not send CR characters, so in | |
30724 | order to be able to interwork with such hosts, Exim treats LF on its own as a | |
30725 | line terminator. | |
30726 | ||
30727 | If a message contains a number of different addresses, all those with the same | |
30728 | characteristics (for example, the same envelope sender) that resolve to the | |
30729 | same set of hosts, in the same order, are sent in a single SMTP transaction, | |
30730 | even if they are for different domains, unless there are more than the setting | |
30731 | of the max_rcpts option in the smtp transport allows, in which case they are | |
30732 | split into groups containing no more than max_rcpts addresses each. If | |
30733 | remote_max_parallel is greater than one, such groups may be sent in parallel | |
30734 | sessions. The order of hosts with identical MX values is not significant when | |
30735 | checking whether addresses can be batched in this way. | |
30736 | ||
30737 | When the smtp transport suffers a temporary failure that is not | |
30738 | message-related, Exim updates its transport-specific database, which contains | |
30739 | records indexed by host name that remember which messages are waiting for each | |
30740 | particular host. It also updates the retry database with new retry times. | |
30741 | ||
30742 | Exim's retry hints are based on host name plus IP address, so if one address of | |
30743 | a multi-homed host is broken, it will soon be skipped most of the time. See the | |
30744 | next section for more detail about error handling. | |
30745 | ||
30746 | When a message is successfully delivered over a TCP/IP SMTP connection, Exim | |
30747 | looks in the hints database for the transport to see if there are any queued | |
30748 | messages waiting for the host to which it is connected. If it finds one, it | |
30749 | creates a new Exim process using the -MC option (which can only be used by a | |
30750 | process running as root or the Exim user) and passes the TCP/IP socket to it so | |
30751 | that it can deliver another message using the same socket. The new process does | |
30752 | only those deliveries that are routed to the connected host, and may in turn | |
30753 | pass the socket on to a third process, and so on. | |
30754 | ||
30755 | The connection_max_messages option of the smtp transport can be used to limit | |
30756 | the number of messages sent down a single TCP/IP connection. | |
30757 | ||
30758 | The second and subsequent messages delivered down an existing connection are | |
30759 | identified in the main log by the addition of an asterisk after the closing | |
30760 | square bracket of the IP address. | |
30761 | ||
30762 | ||
30763 | 47.2 Errors in outgoing SMTP | |
30764 | ---------------------------- | |
30765 | ||
30766 | Three different kinds of error are recognized for outgoing SMTP: host errors, | |
30767 | message errors, and recipient errors. | |
30768 | ||
30769 | Host errors | |
30770 | ||
30771 | A host error is not associated with a particular message or with a | |
30772 | particular recipient of a message. The host errors are: | |
30773 | ||
30774 | * Connection refused or timed out, | |
30775 | ||
30776 | * Any error response code on connection, | |
30777 | ||
30778 | * Any error response code to EHLO or HELO, | |
30779 | ||
30780 | * Loss of connection at any time, except after ".", | |
30781 | ||
30782 | * I/O errors at any time, | |
30783 | ||
30784 | * Timeouts during the session, other than in response to MAIL, RCPT or | |
30785 | the "." at the end of the data. | |
30786 | ||
30787 | For a host error, a permanent error response on connection, or in response | |
30788 | to EHLO, causes all addresses routed to the host to be failed. Any other | |
30789 | host error causes all addresses to be deferred, and retry data to be | |
30790 | created for the host. It is not tried again, for any message, until its | |
30791 | retry time arrives. If the current set of addresses are not all delivered | |
30792 | in this run (to some alternative host), the message is added to the list of | |
30793 | those waiting for this host, so if it is still undelivered when a | |
30794 | subsequent successful delivery is made to the host, it will be sent down | |
30795 | the same SMTP connection. | |
30796 | ||
30797 | Message errors | |
30798 | ||
30799 | A message error is associated with a particular message when sent to a | |
30800 | particular host, but not with a particular recipient of the message. The | |
30801 | message errors are: | |
30802 | ||
30803 | * Any error response code to MAIL, DATA, or the "." that terminates the | |
30804 | data, | |
30805 | ||
30806 | * Timeout after MAIL, | |
30807 | ||
30808 | * Timeout or loss of connection after the "." that terminates the data. A | |
30809 | timeout after the DATA command itself is treated as a host error, as is | |
30810 | loss of connection at any other time. | |
30811 | ||
30812 | For a message error, a permanent error response (5xx) causes all addresses | |
30813 | to be failed, and a delivery error report to be returned to the sender. A | |
30814 | temporary error response (4xx), or one of the timeouts, causes all | |
30815 | addresses to be deferred. Retry data is not created for the host, but | |
30816 | instead, a retry record for the combination of host plus message id is | |
30817 | created. The message is not added to the list of those waiting for this | |
30818 | host. This ensures that the failing message will not be sent to this host | |
30819 | again until the retry time arrives. However, other messages that are routed | |
30820 | to the host are not affected, so if it is some property of the message that | |
30821 | is causing the error, it will not stop the delivery of other mail. | |
30822 | ||
30823 | If the remote host specified support for the SIZE parameter in its response | |
30824 | to EHLO, Exim adds SIZE=nnn to the MAIL command, so an over-large message | |
30825 | will cause a message error because the error arrives as a response to MAIL. | |
30826 | ||
30827 | Recipient errors | |
30828 | ||
30829 | A recipient error is associated with a particular recipient of a message. | |
30830 | The recipient errors are: | |
30831 | ||
30832 | * Any error response to RCPT, | |
30833 | ||
30834 | * Timeout after RCPT. | |
30835 | ||
30836 | For a recipient error, a permanent error response (5xx) causes the | |
30837 | recipient address to be failed, and a bounce message to be returned to the | |
30838 | sender. A temporary error response (4xx) or a timeout causes the failing | |
30839 | address to be deferred, and routing retry data to be created for it. This | |
30840 | is used to delay processing of the address in subsequent queue runs, until | |
30841 | its routing retry time arrives. This applies to all messages, but because | |
30842 | it operates only in queue runs, one attempt will be made to deliver a new | |
30843 | message to the failing address before the delay starts to operate. This | |
30844 | ensures that, if the failure is really related to the message rather than | |
30845 | the recipient ("message too big for this recipient" is a possible example), | |
30846 | other messages have a chance of getting delivered. If a delivery to the | |
30847 | address does succeed, the retry information gets cleared, so all stuck | |
30848 | messages get tried again, and the retry clock is reset. | |
30849 | ||
30850 | The message is not added to the list of those waiting for this host. Use of | |
30851 | the host for other messages is unaffected, and except in the case of a | |
30852 | timeout, other recipients are processed independently, and may be | |
30853 | successfully delivered in the current SMTP session. After a timeout it is | |
30854 | of course impossible to proceed with the session, so all addresses get | |
30855 | deferred. However, those other than the one that failed do not suffer any | |
30856 | subsequent retry delays. Therefore, if one recipient is causing trouble, | |
30857 | the others have a chance of getting through when a subsequent delivery | |
30858 | attempt occurs before the failing recipient's retry time. | |
30859 | ||
30860 | In all cases, if there are other hosts (or IP addresses) available for the | |
30861 | current set of addresses (for example, from multiple MX records), they are | |
30862 | tried in this run for any undelivered addresses, subject of course to their own | |
30863 | retry data. In other words, recipient error retry data does not take effect | |
30864 | until the next delivery attempt. | |
30865 | ||
30866 | Some hosts have been observed to give temporary error responses to every MAIL | |
30867 | command at certain times ("insufficient space" has been seen). It would be nice | |
30868 | if such circumstances could be recognized, and defer data for the host itself | |
30869 | created, but this is not possible within the current Exim design. What actually | |
30870 | happens is that retry data for every (host, message) combination is created. | |
30871 | ||
30872 | The reason that timeouts after MAIL and RCPT are treated specially is that | |
30873 | these can sometimes arise as a result of the remote host's verification | |
30874 | procedures. Exim makes this assumption, and treats them as if a temporary error | |
30875 | response had been received. A timeout after "." is treated specially because it | |
30876 | is known that some broken implementations fail to recognize the end of the | |
30877 | message if the last character of the last line is a binary zero. Thus, it is | |
30878 | helpful to treat this case as a message error. | |
30879 | ||
30880 | Timeouts at other times are treated as host errors, assuming a problem with the | |
30881 | host, or the connection to it. If a timeout after MAIL, RCPT, or "." is really | |
30882 | a connection problem, the assumption is that at the next try the timeout is | |
30883 | likely to occur at some other point in the dialogue, causing it then to be | |
30884 | treated as a host error. | |
30885 | ||
30886 | There is experimental evidence that some MTAs drop the connection after the | |
30887 | terminating "." if they do not like the contents of the message for some | |
30888 | reason, in contravention of the RFC, which indicates that a 5xx response should | |
30889 | be given. That is why Exim treats this case as a message rather than a host | |
30890 | error, in order not to delay other messages to the same host. | |
30891 | ||
30892 | ||
30893 | 47.3 Incoming SMTP messages over TCP/IP | |
30894 | --------------------------------------- | |
30895 | ||
30896 | Incoming SMTP messages can be accepted in one of two ways: by running a | |
30897 | listening daemon, or by using inetd. In the latter case, the entry in /etc/ | |
30898 | inetd.conf should be like this: | |
30899 | ||
30900 | smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs | |
30901 | ||
30902 | Exim distinguishes between this case and the case of a locally running user | |
30903 | agent using the -bs option by checking whether or not the standard input is a | |
30904 | socket. When it is, either the port must be privileged (less than 1024), or the | |
30905 | caller must be root or the Exim user. If any other user passes a socket with an | |
30906 | unprivileged port number, Exim prints a message on the standard error stream | |
30907 | and exits with an error code. | |
30908 | ||
30909 | By default, Exim does not make a log entry when a remote host connects or | |
30910 | disconnects (either via the daemon or inetd), unless the disconnection is | |
30911 | unexpected. It can be made to write such log entries by setting the | |
30912 | smtp_connection log selector. | |
30913 | ||
30914 | Commands from the remote host are supposed to be terminated by CR followed by | |
30915 | LF. However, there are known to be hosts that do not send CR characters. In | |
30916 | order to be able to interwork with such hosts, Exim treats LF on its own as a | |
30917 | line terminator. Furthermore, because common code is used for receiving | |
30918 | messages from all sources, a CR on its own is also interpreted as a line | |
30919 | terminator. However, the sequence "CR, dot, CR" does not terminate incoming | |
30920 | SMTP data. | |
30921 | ||
30922 | One area that sometimes gives rise to problems concerns the EHLO or HELO | |
30923 | commands. Some clients send syntactically invalid versions of these commands, | |
30924 | which Exim rejects by default. (This is nothing to do with verifying the data | |
30925 | that is sent, so helo_verify_hosts is not relevant.) You can tell Exim not to | |
30926 | apply a syntax check by setting helo_accept_junk_hosts to match the broken | |
30927 | hosts that send invalid commands. | |
30928 | ||
30929 | The amount of disk space available is checked whenever SIZE is received on a | |
30930 | MAIL command, independently of whether message_size_limit or check_spool_space | |
30931 | is configured, unless smtp_check_spool_space is set false. A temporary error is | |
30932 | given if there is not enough space. If check_spool_space is set, the check is | |
30933 | for that amount of space plus the value given with SIZE, that is, it checks | |
30934 | that the addition of the incoming message will not reduce the space below the | |
30935 | threshold. | |
30936 | ||
30937 | When a message is successfully received, Exim includes the local message id in | |
30938 | its response to the final "." that terminates the data. If the remote host logs | |
30939 | this text it can help with tracing what has happened to a message. | |
30940 | ||
30941 | The Exim daemon can limit the number of simultaneous incoming connections it is | |
30942 | prepared to handle (see the smtp_accept_max option). It can also limit the | |
30943 | number of simultaneous incoming connections from a single remote host (see the | |
30944 | smtp_accept_max_per_host option). Additional connection attempts are rejected | |
30945 | using the SMTP temporary error code 421. | |
30946 | ||
30947 | The Exim daemon does not rely on the SIGCHLD signal to detect when a subprocess | |
30948 | has finished, as this can get lost at busy times. Instead, it looks for | |
30949 | completed subprocesses every time it wakes up. Provided there are other things | |
30950 | happening (new incoming calls, starts of queue runs), completed processes will | |
30951 | be noticed and tidied away. On very quiet systems you may sometimes see a | |
30952 | "defunct" Exim process hanging about. This is not a problem; it will be noticed | |
30953 | when the daemon next wakes up. | |
30954 | ||
30955 | When running as a daemon, Exim can reserve some SMTP slots for specific hosts, | |
30956 | and can also be set up to reject SMTP calls from non-reserved hosts at times of | |
30957 | high system load - for details see the smtp_accept_reserve, smtp_load_reserve, | |
30958 | and smtp_reserve_hosts options. The load check applies in both the daemon and | |
30959 | inetd cases. | |
30960 | ||
30961 | Exim normally starts a delivery process for each message received, though this | |
30962 | can be varied by means of the -odq command line option and the queue_only, | |
30963 | queue_only_file, and queue_only_load options. The number of simultaneously | |
30964 | running delivery processes started in this way from SMTP input can be limited | |
30965 | by the smtp_accept_queue and smtp_accept_queue_per_connection options. When | |
30966 | either limit is reached, subsequently received messages are just put on the | |
30967 | input queue without starting a delivery process. | |
30968 | ||
30969 | The controls that involve counts of incoming SMTP calls (smtp_accept_max, | |
30970 | smtp_accept_queue, smtp_accept_reserve) are not available when Exim is started | |
30971 | up from the inetd daemon, because in that case each connection is handled by an | |
30972 | entirely independent Exim process. Control by load average is, however, | |
30973 | available with inetd. | |
30974 | ||
30975 | Exim can be configured to verify addresses in incoming SMTP commands as they | |
30976 | are received. See chapter 42 for details. It can also be configured to rewrite | |
30977 | addresses at this time - before any syntax checking is done. See section 31.9. | |
30978 | ||
30979 | Exim can also be configured to limit the rate at which a client host submits | |
30980 | MAIL and RCPT commands in a single SMTP session. See the smtp_ratelimit_hosts | |
30981 | option. | |
30982 | ||
30983 | ||
30984 | 47.4 Unrecognized SMTP commands | |
30985 | ------------------------------- | |
30986 | ||
30987 | If Exim receives more than smtp_max_unknown_commands unrecognized SMTP commands | |
30988 | during a single SMTP connection, it drops the connection after sending the | |
30989 | error response to the last command. The default value for | |
30990 | smtp_max_unknown_commands is 3. This is a defence against some kinds of abuse | |
30991 | that subvert web servers into making connections to SMTP ports; in these | |
30992 | circumstances, a number of non-SMTP lines are sent first. | |
30993 | ||
30994 | ||
30995 | 47.5 Syntax and protocol errors in SMTP commands | |
30996 | ------------------------------------------------ | |
30997 | ||
30998 | A syntax error is detected if an SMTP command is recognized, but there is | |
30999 | something syntactically wrong with its data, for example, a malformed email | |
31000 | address in a RCPT command. Protocol errors include invalid command sequencing | |
31001 | such as RCPT before MAIL. If Exim receives more than smtp_max_synprot_errors | |
31002 | such commands during a single SMTP connection, it drops the connection after | |
31003 | sending the error response to the last command. The default value for | |
31004 | smtp_max_synprot_errors is 3. This is a defence against broken clients that | |
31005 | loop sending bad commands (yes, it has been seen). | |
31006 | ||
31007 | ||
31008 | 47.6 Use of non-mail SMTP commands | |
31009 | ---------------------------------- | |
31010 | ||
31011 | The "non-mail" SMTP commands are those other than MAIL, RCPT, and DATA. Exim | |
31012 | counts such commands, and drops the connection if there are too many of them in | |
31013 | a single SMTP session. This action catches some denial-of-service attempts and | |
31014 | things like repeated failing AUTHs, or a mad client looping sending EHLO. The | |
31015 | global option smtp_accept_max_nonmail defines what "too many" means. Its | |
31016 | default value is 10. | |
31017 | ||
31018 | When a new message is expected, one occurrence of RSET is not counted. This | |
31019 | allows a client to send one RSET between messages (this is not necessary, but | |
31020 | some clients do it). Exim also allows one uncounted occurrence of HELO or EHLO, | |
31021 | and one occurrence of STARTTLS between messages. After starting up a TLS | |
31022 | session, another EHLO is expected, and so it too is not counted. | |
31023 | ||
31024 | The first occurrence of AUTH in a connection, or immediately following STARTTLS | |
31025 | is also not counted. Otherwise, all commands other than MAIL, RCPT, DATA, and | |
31026 | QUIT are counted. | |
31027 | ||
31028 | You can control which hosts are subject to the limit set by | |
31029 | smtp_accept_max_nonmail by setting smtp_accept_max_nonmail_hosts. The default | |
31030 | value is "*", which makes the limit apply to all hosts. This option means that | |
31031 | you can exclude any specific badly-behaved hosts that you have to live with. | |
31032 | ||
31033 | ||
31034 | 47.7 The VRFY and EXPN commands | |
31035 | ------------------------------- | |
31036 | ||
31037 | When Exim receives a VRFY or EXPN command on a TCP/IP connection, it runs the | |
31038 | ACL specified by acl_smtp_vrfy or acl_smtp_expn (as appropriate) in order to | |
31039 | decide whether the command should be accepted or not. If no ACL is defined, the | |
31040 | command is rejected. | |
31041 | ||
31042 | When VRFY is accepted, it runs exactly the same code as when Exim is called | |
31043 | with the -bv option. | |
31044 | ||
31045 | When EXPN is accepted, a single-level expansion of the address is done. EXPN is | |
31046 | treated as an "address test" (similar to the -bt option) rather than a | |
31047 | verification (the -bv option). If an unqualified local part is given as the | |
31048 | argument to EXPN, it is qualified with qualify_domain. Rejections of VRFY and | |
31049 | EXPN commands are logged on the main and reject logs, and VRFY verification | |
31050 | failures are logged on the main log for consistency with RCPT failures. | |
31051 | ||
31052 | ||
31053 | 47.8 The ETRN command | |
31054 | --------------------- | |
31055 | ||
31056 | RFC 1985 describes an SMTP command called ETRN that is designed to overcome the | |
31057 | security problems of the TURN command (which has fallen into disuse). When Exim | |
31058 | receives an ETRN command on a TCP/IP connection, it runs the ACL specified by | |
31059 | acl_smtp_etrn in order to decide whether the command should be accepted or not. | |
31060 | If no ACL is defined, the command is rejected. | |
31061 | ||
31062 | The ETRN command is concerned with "releasing" messages that are awaiting | |
31063 | delivery to certain hosts. As Exim does not organize its message queue by host, | |
31064 | the only form of ETRN that is supported by default is the one where the text | |
31065 | starts with the "#" prefix, in which case the remainder of the text is specific | |
31066 | to the SMTP server. A valid ETRN command causes a run of Exim with the -R | |
31067 | option to happen, with the remainder of the ETRN text as its argument. For | |
31068 | example, | |
31069 | ||
31070 | ETRN #brigadoon | |
31071 | ||
31072 | runs the command | |
31073 | ||
31074 | exim -R brigadoon | |
31075 | ||
31076 | which causes a delivery attempt on all messages with undelivered addresses | |
31077 | containing the text "brigadoon". When smtp_etrn_serialize is set (the default), | |
31078 | Exim prevents the simultaneous execution of more than one queue run for the | |
31079 | same argument string as a result of an ETRN command. This stops a misbehaving | |
31080 | client from starting more than one queue runner at once. | |
31081 | ||
31082 | Exim implements the serialization by means of a hints database in which a | |
31083 | record is written whenever a process is started by ETRN, and deleted when the | |
31084 | process completes. However, Exim does not keep the SMTP session waiting for the | |
31085 | ETRN process to complete. Once ETRN is accepted, the client is sent a "success" | |
31086 | return code. Obviously there is scope for hints records to get left lying | |
31087 | around if there is a system or program crash. To guard against this, Exim | |
31088 | ignores any records that are more than six hours old. | |
31089 | ||
31090 | For more control over what ETRN does, the smtp_etrn_command option can used. | |
31091 | This specifies a command that is run whenever ETRN is received, whatever the | |
31092 | form of its argument. For example: | |
31093 | ||
31094 | smtp_etrn_command = /etc/etrn_command $domain \ | |
31095 | $sender_host_address | |
31096 | ||
31097 | The string is split up into arguments which are independently expanded. The | |
31098 | expansion variable $domain is set to the argument of the ETRN command, and no | |
31099 | syntax checking is done on the contents of this argument. Exim does not wait | |
31100 | for the command to complete, so its status code is not checked. Exim runs under | |
31101 | its own uid and gid when receiving incoming SMTP, so it is not possible for it | |
31102 | to change them before running the command. | |
31103 | ||
31104 | ||
31105 | 47.9 Incoming local SMTP | |
31106 | ------------------------ | |
31107 | ||
31108 | Some user agents use SMTP to pass messages to their local MTA using the | |
31109 | standard input and output, as opposed to passing the envelope on the command | |
31110 | line and writing the message to the standard input. This is supported by the | |
31111 | -bs option. This form of SMTP is handled in the same way as incoming messages | |
31112 | over TCP/IP (including the use of ACLs), except that the envelope sender given | |
31113 | in a MAIL command is ignored unless the caller is trusted. In an ACL you can | |
31114 | detect this form of SMTP input by testing for an empty host identification. It | |
31115 | is common to have this as the first line in the ACL that runs for RCPT | |
31116 | commands: | |
31117 | ||
31118 | accept hosts = : | |
31119 | ||
31120 | This accepts SMTP messages from local processes without doing any other tests. | |
31121 | ||
31122 | ||
31123 | 47.10 Outgoing batched SMTP | |
31124 | --------------------------- | |
31125 | ||
31126 | Both the appendfile and pipe transports can be used for handling batched SMTP. | |
31127 | Each has an option called use_bsmtp which causes messages to be output in BSMTP | |
31128 | format. No SMTP responses are possible for this form of delivery. All it is | |
31129 | doing is using SMTP commands as a way of transmitting the envelope along with | |
31130 | the message. | |
31131 | ||
31132 | The message is written to the file or pipe preceded by the SMTP commands MAIL | |
31133 | and RCPT, and followed by a line containing a single dot. Lines in the message | |
31134 | that start with a dot have an extra dot added. The SMTP command HELO is not | |
31135 | normally used. If it is required, the message_prefix option can be used to | |
31136 | specify it. | |
31137 | ||
31138 | Because appendfile and pipe are both local transports, they accept only one | |
31139 | recipient address at a time by default. However, you can arrange for them to | |
31140 | handle several addresses at once by setting the batch_max option. When this is | |
31141 | done for BSMTP, messages may contain multiple RCPT commands. See chapter 25 for | |
31142 | more details. | |
31143 | ||
31144 | When one or more addresses are routed to a BSMTP transport by a router that | |
31145 | sets up a host list, the name of the first host on the list is available to the | |
31146 | transport in the variable $host. Here is an example of such a transport and | |
31147 | router: | |
31148 | ||
31149 | begin routers | |
31150 | route_append: | |
31151 | driver = manualroute | |
31152 | transport = smtp_appendfile | |
31153 | route_list = domain.example batch.host.example | |
31154 | ||
31155 | begin transports | |
31156 | smtp_appendfile: | |
31157 | driver = appendfile | |
31158 | directory = /var/bsmtp/$host | |
31159 | batch_max = 1000 | |
31160 | use_bsmtp | |
31161 | user = exim | |
31162 | ||
31163 | This causes messages addressed to domain.example to be written in BSMTP format | |
31164 | to /var/bsmtp/batch.host.example, with only a single copy of each message | |
31165 | (unless there are more than 1000 recipients). | |
31166 | ||
31167 | ||
31168 | 47.11 Incoming batched SMTP | |
31169 | --------------------------- | |
31170 | ||
31171 | The -bS command line option causes Exim to accept one or more messages by | |
31172 | reading SMTP on the standard input, but to generate no responses. If the caller | |
31173 | is trusted, the senders in the MAIL commands are believed; otherwise the sender | |
31174 | is always the caller of Exim. Unqualified senders and receivers are not | |
31175 | rejected (there seems little point) but instead just get qualified. HELO and | |
31176 | EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act as NOOP; QUIT quits. | |
31177 | ||
31178 | Minimal policy checking is done for BSMTP input. Only the non-SMTP ACL is run | |
31179 | in the same way as for non-SMTP local input. | |
31180 | ||
31181 | If an error is detected while reading a message, including a missing "." at the | |
31182 | end, Exim gives up immediately. It writes details of the error to the standard | |
31183 | output in a stylized way that the calling program should be able to make some | |
31184 | use of automatically, for example: | |
31185 | ||
31186 | 554 Unexpected end of file | |
31187 | Transaction started in line 10 | |
31188 | Error detected in line 14 | |
31189 | ||
31190 | It writes a more verbose version, for human consumption, to the standard error | |
31191 | file, for example: | |
31192 | ||
31193 | An error was detected while processing a file of BSMTP input. | |
31194 | The error message was: | |
31195 | ||
31196 | 501 '>' missing at end of address | |
31197 | ||
31198 | The SMTP transaction started in line 10. | |
31199 | The error was detected in line 12. | |
31200 | The SMTP command at fault was: | |
31201 | ||
31202 | rcpt to:<malformed@in.com.plete | |
31203 | ||
31204 | 1 previous message was successfully processed. | |
31205 | The rest of the batch was abandoned. | |
31206 | ||
31207 | The return code from Exim is zero only if there were no errors. It is 1 if some | |
31208 | messages were accepted before an error was detected, and 2 if no messages were | |
31209 | accepted. | |
31210 | ||
31211 | ||
31212 | ||
31213 | =============================================================================== | |
31214 | 48. CUSTOMIZING BOUNCE AND WARNING MESSAGES | |
31215 | ||
31216 | When a message fails to be delivered, or remains on the queue for more than a | |
31217 | configured amount of time, Exim sends a message to the original sender, or to | |
31218 | an alternative configured address. The text of these messages is built into the | |
31219 | code of Exim, but it is possible to change it, either by adding a single | |
31220 | string, or by replacing each of the paragraphs by text supplied in a file. | |
31221 | ||
31222 | The From: and To: header lines are automatically generated; you can cause a | |
31223 | Reply-To: line to be added by setting the errors_reply_to option. Exim also | |
31224 | adds the line | |
31225 | ||
31226 | Auto-Submitted: auto-generated | |
31227 | ||
31228 | to all warning and bounce messages, | |
31229 | ||
31230 | ||
31231 | 48.1 Customizing bounce messages | |
31232 | -------------------------------- | |
31233 | ||
31234 | If bounce_message_text is set, its contents are included in the default message | |
31235 | immediately after "This message was created automatically by mail delivery | |
31236 | software." The string is not expanded. It is not used if bounce_message_file is | |
31237 | set. | |
31238 | ||
31239 | When bounce_message_file is set, it must point to a template file for | |
31240 | constructing error messages. The file consists of a series of text items, | |
31241 | separated by lines consisting of exactly four asterisks. If the file cannot be | |
31242 | opened, default text is used and a message is written to the main and panic | |
31243 | logs. If any text item in the file is empty, default text is used for that | |
31244 | item. | |
31245 | ||
31246 | Each item of text that is read from the file is expanded, and there are two | |
31247 | expansion variables which can be of use here: $bounce_recipient is set to the | |
31248 | recipient of an error message while it is being created, and | |
31249 | $bounce_return_size_limit contains the value of the return_size_limit option, | |
31250 | rounded to a whole number. | |
31251 | ||
31252 | The items must appear in the file in the following order: | |
31253 | ||
31254 | * The first item is included in the headers, and should include at least a | |
31255 | Subject: header. Exim does not check the syntax of these headers. | |
31256 | ||
31257 | * The second item forms the start of the error message. After it, Exim lists | |
31258 | the failing addresses with their error messages. | |
31259 | ||
31260 | * The third item is used to introduce any text from pipe transports that is | |
31261 | to be returned to the sender. It is omitted if there is no such text. | |
31262 | ||
31263 | * The fourth item is used to introduce the copy of the message that is | |
31264 | returned as part of the error report. | |
31265 | ||
31266 | * The fifth item is added after the fourth one if the returned message is | |
31267 | truncated because it is bigger than return_size_limit. | |
31268 | ||
31269 | * The sixth item is added after the copy of the original message. | |
31270 | ||
31271 | The default state (bounce_message_file unset) is equivalent to the following | |
31272 | file, in which the sixth item is empty. The Subject: and some other lines have | |
31273 | been split in order to fit them on the page: | |
31274 | ||
31275 | Subject: Mail delivery failed | |
31276 | ${if eq{$sender_address}{$bounce_recipient} | |
31277 | {: returning message to sender}} | |
31278 | **** | |
31279 | This message was created automatically by mail delivery software. | |
31280 | ||
31281 | A message ${if eq{$sender_address}{$bounce_recipient} | |
31282 | {that you sent }{sent by | |
31283 | ||
31284 | <$sender_address> | |
31285 | ||
31286 | }}could not be delivered to all of its recipients. | |
31287 | This is a permanent error. The following address(es) failed: | |
31288 | **** | |
31289 | The following text was generated during the delivery attempt(s): | |
31290 | **** | |
31291 | ------ This is a copy of the message, including all the headers. | |
31292 | ------ | |
31293 | **** | |
31294 | ------ The body of the message is $message_size characters long; | |
31295 | only the first | |
31296 | ------ $bounce_return_size_limit or so are included here. | |
31297 | **** | |
31298 | ||
31299 | ||
31300 | 48.2 Customizing warning messages | |
31301 | --------------------------------- | |
31302 | ||
31303 | The option warn_message_file can be pointed at a template file for use when | |
31304 | warnings about message delays are created. In this case there are only three | |
31305 | text sections: | |
31306 | ||
31307 | * The first item is included in the headers, and should include at least a | |
31308 | Subject: header. Exim does not check the syntax of these headers. | |
31309 | ||
31310 | * The second item forms the start of the warning message. After it, Exim | |
31311 | lists the delayed addresses. | |
31312 | ||
31313 | * The third item then ends the message. | |
31314 | ||
31315 | The default state is equivalent to the following file, except that some lines | |
31316 | have been split here, in order to fit them on the page: | |
31317 | ||
31318 | Subject: Warning: message $message_exim_id delayed | |
31319 | $warn_message_delay | |
31320 | **** | |
31321 | This message was created automatically by mail delivery software. | |
31322 | ||
31323 | A message ${if eq{$sender_address}{$warn_message_recipients} | |
31324 | {that you sent }{sent by | |
31325 | ||
31326 | <$sender_address> | |
31327 | ||
31328 | }}has not been delivered to all of its recipients after | |
31329 | more than $warn_message_delay on the queue on $primary_hostname. | |
31330 | ||
31331 | The message identifier is: $message_exim_id | |
31332 | The subject of the message is: $h_subject | |
31333 | The date of the message is: $h_date | |
31334 | ||
31335 | The following address(es) have not yet been delivered: | |
31336 | **** | |
31337 | No action is required on your part. Delivery attempts will | |
31338 | continue for some time, and this warning may be repeated at | |
31339 | intervals if the message remains undelivered. Eventually the | |
31340 | mail delivery software will give up, and when that happens, | |
31341 | the message will be returned to you. | |
31342 | ||
31343 | However, in the default state the subject and date lines are omitted if no | |
31344 | appropriate headers exist. During the expansion of this file, | |
31345 | $warn_message_delay is set to the delay time in one of the forms "<n> minutes" | |
31346 | or "<n> hours", and $warn_message_recipients contains a list of recipients for | |
31347 | the warning message. There may be more than one if there are multiple addresses | |
31348 | with different errors_to settings on the routers that handled them. | |
31349 | ||
31350 | ||
31351 | ||
31352 | =============================================================================== | |
31353 | 49. SOME COMMON CONFIGURATION SETTINGS | |
31354 | ||
31355 | This chapter discusses some configuration settings that seem to be fairly | |
31356 | common. More examples and discussion can be found in the Exim book. | |
31357 | ||
31358 | ||
31359 | 49.1 Sending mail to a smart host | |
31360 | --------------------------------- | |
31361 | ||
31362 | If you want to send all mail for non-local domains to a "smart host", you | |
31363 | should replace the default dnslookup router with a router which does the | |
31364 | routing explicitly: | |
31365 | ||
31366 | send_to_smart_host: | |
31367 | driver = manualroute | |
31368 | route_list = !+local_domains smart.host.name | |
31369 | transport = remote_smtp | |
31370 | ||
31371 | You can use the smart host's IP address instead of the name if you wish. If you | |
31372 | are using Exim only to submit messages to a smart host, and not for receiving | |
31373 | incoming messages, you can arrange for it to do the submission synchronously by | |
31374 | setting the mua_wrapper option (see chapter 50). | |
31375 | ||
31376 | ||
31377 | 49.2 Using Exim to handle mailing lists | |
31378 | --------------------------------------- | |
31379 | ||
31380 | Exim can be used to run simple mailing lists, but for large and/or complicated | |
31381 | requirements, the use of additional specialized mailing list software such as | |
31382 | Majordomo or Mailman is recommended. | |
31383 | ||
31384 | The redirect router can be used to handle mailing lists where each list is | |
31385 | maintained in a separate file, which can therefore be managed by an independent | |
31386 | manager. The domains router option can be used to run these lists in a separate | |
31387 | domain from normal mail. For example: | |
31388 | ||
31389 | lists: | |
31390 | driver = redirect | |
31391 | domains = lists.example | |
31392 | file = /usr/lists/$local_part | |
31393 | forbid_pipe | |
31394 | forbid_file | |
31395 | errors_to = $local_part-request@lists.example | |
31396 | no_more | |
31397 | ||
31398 | This router is skipped for domains other than lists.example. For addresses in | |
31399 | that domain, it looks for a file that matches the local part. If there is no | |
31400 | such file, the router declines, but because no_more is set, no subsequent | |
31401 | routers are tried, and so the whole delivery fails. | |
31402 | ||
31403 | The forbid_pipe and forbid_file options prevent a local part from being | |
31404 | expanded into a file name or a pipe delivery, which is usually inappropriate in | |
31405 | a mailing list. | |
31406 | ||
31407 | The errors_to option specifies that any delivery errors caused by addresses | |
31408 | taken from a mailing list are to be sent to the given address rather than the | |
31409 | original sender of the message. However, before acting on this, Exim verifies | |
31410 | the error address, and ignores it if verification fails. | |
31411 | ||
31412 | For example, using the configuration above, mail sent to dicts@lists.example is | |
31413 | passed on to those addresses contained in /usr/lists/dicts, with error reports | |
31414 | directed to dicts-request@lists.example, provided that this address can be | |
31415 | verified. There could be a file called /usr/lists/dicts-request containing the | |
31416 | address(es) of this particular list's manager(s), but other approaches, such as | |
31417 | setting up an earlier router (possibly using the local_part_prefix or | |
31418 | local_part_suffix options) to handle addresses of the form owner-xxx or xxx- | |
31419 | request, are also possible. | |
31420 | ||
31421 | ||
31422 | 49.3 Syntax errors in mailing lists | |
31423 | ----------------------------------- | |
31424 | ||
31425 | If an entry in redirection data contains a syntax error, Exim normally defers | |
31426 | delivery of the original address. That means that a syntax error in a mailing | |
31427 | list holds up all deliveries to the list. This may not be appropriate when a | |
31428 | list is being maintained automatically from data supplied by users, and the | |
31429 | addresses are not rigorously checked. | |
31430 | ||
31431 | If the skip_syntax_errors option is set, the redirect router just skips entries | |
31432 | that fail to parse, noting the incident in the log. If in addition | |
31433 | syntax_errors_to is set to a verifiable address, a message is sent to it | |
31434 | whenever a broken address is skipped. It is usually appropriate to set | |
31435 | syntax_errors_to to the same address as errors_to. | |
31436 | ||
31437 | ||
31438 | 49.4 Re-expansion of mailing lists | |
31439 | ---------------------------------- | |
31440 | ||
31441 | Exim remembers every individual address to which a message has been delivered, | |
31442 | in order to avoid duplication, but it normally stores only the original | |
31443 | recipient addresses with a message. If all the deliveries to a mailing list | |
31444 | cannot be done at the first attempt, the mailing list is re-expanded when the | |
31445 | delivery is next tried. This means that alterations to the list are taken into | |
31446 | account at each delivery attempt, so addresses that have been added to the list | |
31447 | since the message arrived will therefore receive a copy of the message, even | |
31448 | though it pre-dates their subscription. | |
31449 | ||
31450 | If this behaviour is felt to be undesirable, the one_time option can be set on | |
31451 | the redirect router. If this is done, any addresses generated by the router | |
31452 | that fail to deliver at the first attempt are added to the message as "top | |
31453 | level" addresses, and the parent address that generated them is marked | |
31454 | "delivered". Thus, expansion of the mailing list does not happen again at the | |
31455 | subsequent delivery attempts. The disadvantage of this is that if any of the | |
31456 | failing addresses are incorrect, correcting them in the file has no effect on | |
31457 | pre-existing messages. | |
31458 | ||
31459 | The original top-level address is remembered with each of the generated | |
31460 | addresses, and is output in any log messages. However, any intermediate parent | |
31461 | addresses are not recorded. This makes a difference to the log only if the | |
31462 | all_parents selector is set, but for mailing lists there is normally only one | |
31463 | level of expansion anyway. | |
31464 | ||
31465 | ||
31466 | 49.5 Closed mailing lists | |
31467 | ------------------------- | |
31468 | ||
31469 | The examples so far have assumed open mailing lists, to which anybody may send | |
31470 | mail. It is also possible to set up closed lists, where mail is accepted from | |
31471 | specified senders only. This is done by making use of the generic senders | |
31472 | option to restrict the router that handles the list. | |
31473 | ||
31474 | The following example uses the same file as a list of recipients and as a list | |
31475 | of permitted senders. It requires three routers: | |
31476 | ||
31477 | lists_request: | |
31478 | driver = redirect | |
31479 | domains = lists.example | |
31480 | local_part_suffix = -request | |
31481 | file = /usr/lists/$local_part$local_part_suffix | |
31482 | no_more | |
31483 | ||
31484 | lists_post: | |
31485 | driver = redirect | |
31486 | domains = lists.example | |
31487 | senders = ${if exists {/usr/lists/$local_part}\ | |
31488 | {lsearch;/usr/lists/$local_part}{*}} | |
31489 | file = /usr/lists/$local_part | |
31490 | forbid_pipe | |
31491 | forbid_file | |
31492 | errors_to = $local_part-request@lists.example | |
31493 | no_more | |
31494 | ||
31495 | lists_closed: | |
31496 | driver = redirect | |
31497 | domains = lists.example | |
31498 | allow_fail | |
31499 | data = :fail: $local_part@lists.example is a closed mailing list | |
31500 | ||
31501 | All three routers have the same domains setting, so for any other domains, they | |
31502 | are all skipped. The first router runs only if the local part ends in -request. | |
31503 | It handles messages to the list manager(s) by means of an open mailing list. | |
31504 | ||
31505 | The second router runs only if the senders precondition is satisfied. It checks | |
31506 | for the existence of a list that corresponds to the local part, and then checks | |
31507 | that the sender is on the list by means of a linear search. It is necessary to | |
31508 | check for the existence of the file before trying to search it, because | |
31509 | otherwise Exim thinks there is a configuration error. If the file does not | |
31510 | exist, the expansion of senders is *, which matches all senders. This means | |
31511 | that the router runs, but because there is no list, declines, and no_more | |
31512 | ensures that no further routers are run. The address fails with an "unrouteable | |
31513 | address" error. | |
31514 | ||
31515 | The third router runs only if the second router is skipped, which happens when | |
31516 | a mailing list exists, but the sender is not on it. This router forcibly fails | |
31517 | the address, giving a suitable error message. | |
31518 | ||
31519 | ||
31520 | 49.6 Variable Envelope Return Paths (VERP) | |
31521 | ------------------------------------------ | |
31522 | ||
31523 | Variable Envelope Return Paths - see http://cr.yp.to/proto/verp.txt - are a way | |
31524 | of helping mailing list administrators discover which subscription address is | |
31525 | the cause of a particular delivery failure. The idea is to encode the original | |
31526 | recipient address in the outgoing envelope sender address, so that if the | |
31527 | message is forwarded by another host and then subsequently bounces, the | |
31528 | original recipient can be extracted from the recipient address of the bounce. | |
31529 | ||
31530 | Envelope sender addresses can be modified by Exim using two different | |
31531 | facilities: the errors_to option on a router (as shown in previous mailing list | |
31532 | examples), or the return_path option on a transport. The second of these is | |
31533 | effective only if the message is successfully delivered to another host; it is | |
31534 | not used for errors detected on the local host (see the description of | |
31535 | return_path in chapter 24). Here is an example of the use of return_path to | |
31536 | implement VERP on an smtp transport: | |
31537 | ||
31538 | verp_smtp: | |
31539 | driver = smtp | |
31540 | max_rcpt = 1 | |
31541 | return_path = \ | |
31542 | ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\ | |
31543 | {$1-request+$local_part=$domain@your.dom.example}fail} | |
31544 | ||
31545 | This has the effect of rewriting the return path (envelope sender) on outgoing | |
31546 | SMTP messages, if the local part of the original return path ends in | |
31547 | "-request", and the domain is your.dom.example. The rewriting inserts the local | |
31548 | part and domain of the recipient into the return path. Suppose, for example, | |
31549 | that a message whose return path has been set to | |
31550 | somelist-request@your.dom.example is sent to subscriber@other.dom.example. In | |
31551 | the transport, the return path is rewritten as | |
31552 | ||
31553 | somelist-request+subscriber=other.dom.example@your.dom.example | |
31554 | ||
31555 | For this to work, you must tell Exim to send multiple copies of messages that | |
31556 | have more than one recipient, so that each copy has just one recipient. This is | |
31557 | achieved by setting max_rcpt to 1. Without this, a single copy of a message | |
31558 | might be sent to several different recipients in the same domain, in which case | |
31559 | $local_part is not available in the transport, because it is not unique. | |
31560 | ||
31561 | Unless your host is doing nothing but mailing list deliveries, you should | |
31562 | probably use a separate transport for the VERP deliveries, so as not to use | |
31563 | extra resources in making one-per-recipient copies for other deliveries. This | |
31564 | can easily be done by expanding the transport option in the router: | |
31565 | ||
31566 | dnslookup: | |
31567 | driver = dnslookup | |
31568 | domains = ! +local_domains | |
31569 | transport = \ | |
31570 | ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\ | |
31571 | {verp_smtp}{remote_smtp}} | |
31572 | no_more | |
31573 | ||
31574 | If you want to change the return path using errors_to in a router instead of | |
31575 | using return_path in the transport, you need to set errors_to on all routers | |
31576 | that handle mailing list addresses. This will ensure that all delivery errors, | |
31577 | including those detected on the local host, are sent to the VERP address. | |
31578 | ||
31579 | On a host that does no local deliveries and has no manual routing, only the | |
31580 | dnslookup router needs to be changed. A special transport is not needed for | |
31581 | SMTP deliveries. Every mailing list recipient has its own return path value, | |
31582 | and so Exim must hand them to the transport one at a time. Here is an example | |
31583 | of a dnslookup router that implements VERP: | |
31584 | ||
31585 | verp_dnslookup: | |
31586 | driver = dnslookup | |
31587 | domains = ! +local_domains | |
31588 | transport = remote_smtp | |
31589 | errors_to = \ | |
31590 | ${if match {$return_path}{^(.+?)-request@your.dom.example\$}} | |
31591 | {$1-request+$local_part=$domain@your.dom.example}fail} | |
31592 | no_more | |
31593 | ||
31594 | Before you start sending out messages with VERPed return paths, you must also | |
31595 | configure Exim to accept the bounce messages that come back to those paths. | |
31596 | Typically this is done by setting a local_part_suffix option for a router, and | |
31597 | using this to route the messages to wherever you want to handle them. | |
31598 | ||
31599 | The overhead incurred in using VERP depends very much on the size of the | |
31600 | message, the number of recipient addresses that resolve to the same remote | |
31601 | host, and the speed of the connection over which the message is being sent. If | |
31602 | a lot of addresses resolve to the same host and the connection is slow, sending | |
31603 | a separate copy of the message for each address may take substantially longer | |
31604 | than sending a single copy with many recipients (for which VERP cannot be | |
31605 | used). | |
31606 | ||
31607 | ||
31608 | 49.7 Virtual domains | |
31609 | -------------------- | |
31610 | ||
31611 | The phrase virtual domain is unfortunately used with two rather different | |
31612 | meanings: | |
31613 | ||
31614 | * A domain for which there are no real mailboxes; all valid local parts are | |
31615 | aliases for other email addresses. Common examples are organizational | |
31616 | top-level domains and "vanity" domains. | |
31617 | ||
31618 | * One of a number of independent domains that are all handled by the same | |
31619 | host, with mailboxes on that host, but where the mailbox owners do not | |
31620 | necessarily have login accounts on that host. | |
31621 | ||
31622 | The first usage is probably more common, and does seem more "virtual" than the | |
31623 | second. This kind of domain can be handled in Exim with a straightforward | |
31624 | aliasing router. One approach is to create a separate alias file for each | |
31625 | virtual domain. Exim can test for the existence of the alias file to determine | |
31626 | whether the domain exists. The dsearch lookup type is useful here, leading to a | |
31627 | router of this form: | |
31628 | ||
31629 | virtual: | |
31630 | driver = redirect | |
31631 | domains = dsearch;/etc/mail/virtual | |
31632 | data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}} | |
31633 | no_more | |
31634 | ||
31635 | The domains option specifies that the router is to be skipped, unless there is | |
31636 | a file in the /etc/mail/virtual directory whose name is the same as the domain | |
31637 | that is being processed. When the router runs, it looks up the local part in | |
31638 | the file to find a new address (or list of addresses). The no_more setting | |
31639 | ensures that if the lookup fails (leading to data being an empty string), Exim | |
31640 | gives up on the address without trying any subsequent routers. | |
31641 | ||
31642 | This one router can handle all the virtual domains because the alias file names | |
31643 | follow a fixed pattern. Permissions can be arranged so that appropriate people | |
31644 | can edit the different alias files. A successful aliasing operation results in | |
31645 | a new envelope recipient address, which is then routed from scratch. | |
31646 | ||
31647 | The other kind of "virtual" domain can also be handled in a straightforward | |
31648 | way. One approach is to create a file for each domain containing a list of | |
31649 | valid local parts, and use it in a router like this: | |
31650 | ||
31651 | my_domains: | |
31652 | driver = accept | |
31653 | domains = dsearch;/etc/mail/domains | |
31654 | local_parts = lsearch;/etc/mail/domains/$domain | |
31655 | transport = my_mailboxes | |
31656 | ||
31657 | The address is accepted if there is a file for the domain, and the local part | |
31658 | can be found in the file. The domains option is used to check for the file's | |
31659 | existence because domains is tested before the local_parts option (see section | |
31660 | 3.12). You cannot use require_files, because that option is tested after | |
31661 | local_parts. The transport is as follows: | |
31662 | ||
31663 | my_mailboxes: | |
31664 | driver = appendfile | |
31665 | file = /var/mail/$domain/$local_part | |
31666 | user = mail | |
31667 | ||
31668 | This uses a directory of mailboxes for each domain. The user setting is | |
31669 | required, to specify which uid is to be used for writing to the mailboxes. | |
31670 | ||
31671 | The configuration shown here is just one example of how you might support this | |
31672 | requirement. There are many other ways this kind of configuration can be set | |
31673 | up, for example, by using a database instead of separate files to hold all the | |
31674 | information about the domains. | |
31675 | ||
31676 | ||
31677 | 49.8 Multiple user mailboxes | |
31678 | ---------------------------- | |
31679 | ||
31680 | Heavy email users often want to operate with multiple mailboxes, into which | |
31681 | incoming mail is automatically sorted. A popular way of handling this is to | |
31682 | allow users to use multiple sender addresses, so that replies can easily be | |
31683 | identified. Users are permitted to add prefixes or suffixes to their local | |
31684 | parts for this purpose. The wildcard facility of the generic router options | |
31685 | local_part_prefix and local_part_suffix can be used for this. For example, | |
31686 | consider this router: | |
31687 | ||
31688 | userforward: | |
31689 | driver = redirect | |
31690 | check_local_user | |
31691 | file = $home/.forward | |
31692 | local_part_suffix = -* | |
31693 | local_part_suffix_optional | |
31694 | allow_filter | |
31695 | ||
31696 | It runs a user's .forward file for all local parts of the form username-*. | |
31697 | Within the filter file the user can distinguish different cases by testing the | |
31698 | variable $local_part_suffix. For example: | |
31699 | ||
31700 | if $local_part_suffix contains -special then | |
31701 | save /home/$local_part/Mail/special | |
31702 | endif | |
31703 | ||
31704 | If the filter file does not exist, or does not deal with such addresses, they | |
31705 | fall through to subsequent routers, and, assuming no subsequent use of the | |
31706 | local_part_suffix option is made, they presumably fail. Thus, users have | |
31707 | control over which suffixes are valid. | |
31708 | ||
31709 | Alternatively, a suffix can be used to trigger the use of a different .forward | |
31710 | file - which is the way a similar facility is implemented in another MTA: | |
31711 | ||
31712 | userforward: | |
31713 | driver = redirect | |
31714 | check_local_user | |
31715 | file = $home/.forward$local_part_suffix | |
31716 | local_part_suffix = -* | |
31717 | local_part_suffix_optional | |
31718 | allow_filter | |
31719 | ||
31720 | If there is no suffix, .forward is used; if the suffix is -special, for | |
31721 | example, .forward-special is used. Once again, if the appropriate file does not | |
31722 | exist, or does not deal with the address, it is passed on to subsequent | |
31723 | routers, which could, if required, look for an unqualified .forward file to use | |
31724 | as a default. | |
31725 | ||
31726 | ||
31727 | 49.9 Simplified vacation processing | |
31728 | ----------------------------------- | |
31729 | ||
31730 | The traditional way of running the vacation program is for a user to set up a | |
31731 | pipe command in a .forward file (see section 22.6 for syntax details). This is | |
31732 | prone to error by inexperienced users. There are two features of Exim that can | |
31733 | be used to make this process simpler for users: | |
31734 | ||
31735 | * A local part prefix such as "vacation-" can be specified on a router which | |
31736 | can cause the message to be delivered directly to the vacation program, or | |
31737 | alternatively can use Exim's autoreply transport. The contents of a user's | |
31738 | .forward file are then much simpler. For example: | |
31739 | ||
31740 | spqr, vacation-spqr | |
31741 | ||
31742 | * The require_files generic router option can be used to trigger a vacation | |
31743 | delivery by checking for the existence of a certain file in the user's home | |
31744 | directory. The unseen generic option should also be used, to ensure that | |
31745 | the original delivery also proceeds. In this case, all the user has to do | |
31746 | is to create a file called, say, .vacation, containing a vacation message. | |
31747 | ||
31748 | Another advantage of both these methods is that they both work even when the | |
31749 | use of arbitrary pipes by users is locked out. | |
31750 | ||
31751 | ||
31752 | 49.10 Taking copies of mail | |
31753 | --------------------------- | |
31754 | ||
31755 | Some installations have policies that require archive copies of all messages to | |
31756 | be made. A single copy of each message can easily be taken by an appropriate | |
31757 | command in a system filter, which could, for example, use a different file for | |
31758 | each day's messages. | |
31759 | ||
31760 | There is also a shadow transport mechanism that can be used to take copies of | |
31761 | messages that are successfully delivered by local transports, one copy per | |
31762 | delivery. This could be used, inter alia, to implement automatic notification | |
31763 | of delivery by sites that insist on doing such things. | |
31764 | ||
31765 | ||
31766 | 49.11 Intermittently connected hosts | |
31767 | ------------------------------------ | |
31768 | ||
31769 | It has become quite common (because it is cheaper) for hosts to connect to the | |
31770 | Internet periodically rather than remain connected all the time. The normal | |
31771 | arrangement is that mail for such hosts accumulates on a system that is | |
31772 | permanently connected. | |
31773 | ||
31774 | Exim was designed for use on permanently connected hosts, and so it is not | |
31775 | particularly well-suited to use in an intermittently connected environment. | |
31776 | Nevertheless there are some features that can be used. | |
31777 | ||
31778 | ||
31779 | 49.12 Exim on the upstream server host | |
31780 | -------------------------------------- | |
31781 | ||
31782 | It is tempting to arrange for incoming mail for the intermittently connected | |
31783 | host to remain on Exim's queue until the client connects. However, this | |
31784 | approach does not scale very well. Two different kinds of waiting message are | |
31785 | being mixed up in the same queue - those that cannot be delivered because of | |
31786 | some temporary problem, and those that are waiting for their destination host | |
31787 | to connect. This makes it hard to manage the queue, as well as wasting | |
31788 | resources, because each queue runner scans the entire queue. | |
31789 | ||
31790 | A better approach is to separate off those messages that are waiting for an | |
31791 | intermittently connected host. This can be done by delivering these messages | |
31792 | into local files in batch SMTP, "mailstore", or other envelope-preserving | |
31793 | format, from where they are transmitted by other software when their | |
31794 | destination connects. This makes it easy to collect all the mail for one host | |
31795 | in a single directory, and to apply local timeout rules on a per-message basis | |
31796 | if required. | |
31797 | ||
31798 | On a very small scale, leaving the mail on Exim's queue can be made to work. If | |
31799 | you are doing this, you should configure Exim with a long retry period for the | |
31800 | intermittent host. For example: | |
31801 | ||
31802 | cheshire.wonderland.fict.example * F,5d,24h | |
31803 | ||
31804 | This stops a lot of failed delivery attempts from occurring, but Exim remembers | |
31805 | which messages it has queued up for that host. Once the intermittent host comes | |
31806 | online, forcing delivery of one message (either by using the -M or -R options, | |
31807 | or by using the ETRN SMTP command (see section 47.8) causes all the queued up | |
31808 | messages to be delivered, often down a single SMTP connection. While the host | |
31809 | remains connected, any new messages get delivered immediately. | |
31810 | ||
31811 | If the connecting hosts do not have fixed IP addresses, that is, if a host is | |
31812 | issued with a different IP address each time it connects, Exim's retry | |
31813 | mechanisms on the holding host get confused, because the IP address is normally | |
31814 | used as part of the key string for holding retry information. This can be | |
31815 | avoided by unsetting retry_include_ip_address on the smtp transport. Since this | |
31816 | has disadvantages for permanently connected hosts, it is best to arrange a | |
31817 | separate transport for the intermittently connected ones. | |
31818 | ||
31819 | ||
31820 | 49.13 Exim on the intermittently connected client host | |
31821 | ------------------------------------------------------ | |
31822 | ||
31823 | The value of smtp_accept_queue_per_connection should probably be increased, or | |
31824 | even set to zero (that is, disabled) on the intermittently connected host, so | |
31825 | that all incoming messages down a single connection get delivered immediately. | |
31826 | ||
31827 | Mail waiting to be sent from an intermittently connected host will probably not | |
31828 | have been routed, because without a connection DNS lookups are not possible. | |
31829 | This means that if a normal queue run is done at connection time, each message | |
31830 | is likely to be sent in a separate SMTP session. This can be avoided by | |
31831 | starting the queue run with a command line option beginning with -qq instead of | |
31832 | -q. In this case, the queue is scanned twice. In the first pass, routing is | |
31833 | done but no deliveries take place. The second pass is a normal queue run; since | |
31834 | all the messages have been previously routed, those destined for the same host | |
31835 | are likely to get sent as multiple deliveries in a single SMTP connection. | |
31836 | ||
31837 | ||
31838 | ||
31839 | =============================================================================== | |
31840 | 50. USING EXIM AS A NON-QUEUEING CLIENT | |
31841 | ||
31842 | On a personal computer, it is a common requirement for all email to be sent to | |
31843 | a "smart host". There are plenty of MUAs that can be configured to operate that | |
31844 | way, for all the popular operating systems. However, there are some MUAs for | |
31845 | Unix-like systems that cannot be so configured: they submit messages using the | |
31846 | command line interface of /usr/sbin/sendmail. Furthermore, utility programs | |
31847 | such as cron submit messages this way. | |
31848 | ||
31849 | If the personal computer runs continuously, there is no problem, because it can | |
31850 | run a conventional MTA that handles delivery to the smart host, and deal with | |
31851 | any delays via its queueing mechanism. However, if the computer does not run | |
31852 | continuously or runs different operating systems at different times, queueing | |
31853 | email is not desirable. | |
31854 | ||
31855 | There is therefore a requirement for something that can provide the /usr/sbin/ | |
31856 | sendmail interface but deliver messages to a smart host without any queueing or | |
31857 | retrying facilities. Furthermore, the delivery to the smart host should be | |
31858 | synchronous, so that if it fails, the sending MUA is immediately informed. In | |
31859 | other words, we want something that extends an MUA that submits to a local MTA | |
31860 | via the command line so that it behaves like one that submits to a remote smart | |
31861 | host using TCP/SMTP. | |
31862 | ||
31863 | There are a number of applications (for example, there is one called ssmtp) | |
31864 | that do this job. However, people have found them to be lacking in various | |
31865 | ways. For instance, you might want to allow aliasing and forwarding to be done | |
31866 | before sending a message to the smart host. | |
31867 | ||
31868 | Exim already had the necessary infrastructure for doing this job. Just a few | |
31869 | tweaks were needed to make it behave as required, though it is somewhat of an | |
31870 | overkill to use a fully-featured MTA for this purpose. | |
31871 | ||
31872 | There is a Boolean global option called mua_wrapper, defaulting false. Setting | |
31873 | mua_wrapper true causes Exim to run in a special mode where it assumes that it | |
31874 | is being used to "wrap" a command-line MUA in the manner just described. As | |
31875 | well as setting mua_wrapper, you also need to provide a compatible router and | |
31876 | transport configuration. Typically there will be just one router and one | |
31877 | transport, sending everything to a smart host. | |
31878 | ||
31879 | When run in MUA wrapping mode, the behaviour of Exim changes in the following | |
31880 | ways: | |
31881 | ||
31882 | * A daemon cannot be run, nor will Exim accept incoming messages from inetd. | |
31883 | In other words, the only way to submit messages is via the command line. | |
31884 | ||
31885 | * Each message is synchronously delivered as soon as it is received (-odi is | |
31886 | assumed). All queueing options (queue_only, queue_smtp_domains, control in | |
31887 | an ACL, etc.) are quietly ignored. The Exim reception process does not | |
31888 | finish until the delivery attempt is complete. If the delivery is | |
31889 | successful, a zero return code is given. | |
31890 | ||
31891 | * Address redirection is permitted, but the final routing for all addresses | |
31892 | must be to the same remote transport, and to the same list of hosts. | |
31893 | Furthermore, the return address (envelope sender) must be the same for all | |
31894 | recipients, as must any added or deleted header lines. In other words, it | |
31895 | must be possible to deliver the message in a single SMTP transaction, | |
31896 | however many recipients there are. | |
31897 | ||
31898 | * If these conditions are not met, or if routing any address results in a | |
31899 | failure or defer status, or if Exim is unable to deliver all the recipients | |
31900 | successfully to one of the smart hosts, delivery of the entire message | |
31901 | fails. | |
31902 | ||
31903 | * Because no queueing is allowed, all failures are treated as permanent; | |
31904 | there is no distinction between 4xx and 5xx SMTP response codes from the | |
31905 | smart host. Furthermore, because only a single yes/no response can be given | |
31906 | to the caller, it is not possible to deliver to some recipients and not | |
31907 | others. If there is an error (temporary or permanent) for any recipient, | |
31908 | all are failed. | |
31909 | ||
31910 | * If more than one smart host is listed, Exim will try another host after a | |
31911 | connection failure or a timeout, in the normal way. However, if this kind | |
31912 | of failure happens for all the hosts, the delivery fails. | |
31913 | ||
31914 | * When delivery fails, an error message is written to the standard error | |
31915 | stream (as well as to Exim's log), and Exim exits to the caller with a | |
31916 | return code value 1. The message is expunged from Exim's spool files. No | |
31917 | bounce messages are ever generated. | |
31918 | ||
31919 | * No retry data is maintained, and any retry rules are ignored. | |
31920 | ||
31921 | * A number of Exim options are overridden: deliver_drop_privilege is forced | |
31922 | true, max_rcpt in the smtp transport is forced to "unlimited", | |
31923 | remote_max_parallel is forced to one, and fallback hosts are ignored. | |
31924 | ||
31925 | The overall effect is that Exim makes a single synchronous attempt to deliver | |
31926 | the message, failing if there is any kind of problem. Because no local | |
31927 | deliveries are done and no daemon can be run, Exim does not need root | |
31928 | privilege. It should be possible to run it setuid to exim instead of setuid to | |
31929 | root. See section 54.3 for a general discussion about the advantages and | |
31930 | disadvantages of running without root privilege. | |
31931 | ||
31932 | ||
31933 | ||
31934 | =============================================================================== | |
31935 | 51. LOG FILES | |
31936 | ||
31937 | Exim writes three different logs, referred to as the main log, the reject log, | |
31938 | and the panic log: | |
31939 | ||
31940 | * The main log records the arrival of each message and each delivery in a | |
31941 | single line in each case. The format is as compact as possible, in an | |
31942 | attempt to keep down the size of log files. Two-character flag sequences | |
31943 | make it easy to pick out these lines. A number of other events are recorded | |
31944 | in the main log. Some of them are optional, in which case the log_selector | |
31945 | option controls whether they are included or not. A Perl script called | |
31946 | eximstats, which does simple analysis of main log files, is provided in the | |
31947 | Exim distribution (see section 52.7). | |
31948 | ||
31949 | * The reject log records information from messages that are rejected as a | |
31950 | result of a configuration option (that is, for policy reasons). The first | |
31951 | line of each rejection is a copy of the line that is also written to the | |
31952 | main log. Then, if the message's header has been read at the time the log | |
31953 | is written, its contents are written to this log. Only the original header | |
31954 | lines are available; header lines added by ACLs are not logged. You can use | |
31955 | the reject log to check that your policy controls are working correctly; on | |
31956 | a busy host this may be easier than scanning the main log for rejection | |
31957 | messages. You can suppress the writing of the reject log by setting | |
31958 | write_rejectlog false. | |
31959 | ||
31960 | * When certain serious errors occur, Exim writes entries to its panic log. If | |
31961 | the error is sufficiently disastrous, Exim bombs out afterwards. Panic log | |
31962 | entries are usually written to the main log as well, but can get lost amid | |
31963 | the mass of other entries. The panic log should be empty under normal | |
31964 | circumstances. It is therefore a good idea to check it (or to have a cron | |
31965 | script check it) regularly, in order to become aware of any problems. When | |
31966 | Exim cannot open its panic log, it tries as a last resort to write to the | |
31967 | system log (syslog). This is opened with LOG_PID+LOG_CONS and the facility | |
31968 | code of LOG_MAIL. The message itself is written at priority LOG_CRIT. | |
31969 | ||
31970 | Every log line starts with a timestamp, in the format shown in the following | |
31971 | example. Note that many of the examples shown in this chapter are line-wrapped. | |
31972 | In the log file, this would be all on one line: | |
31973 | ||
31974 | 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed | |
31975 | by QUIT | |
31976 | ||
31977 | By default, the timestamps are in the local timezone. There are two ways of | |
31978 | changing this: | |
31979 | ||
31980 | * You can set the timezone option to a different time zone; in particular, if | |
31981 | you set | |
31982 | ||
31983 | timezone = UTC | |
31984 | ||
31985 | the timestamps will be in UTC (aka GMT). | |
31986 | ||
31987 | * If you set log_timezone true, the time zone is added to the timestamp, for | |
31988 | example: | |
31989 | ||
31990 | 2003-04-25 11:17:07 +0100 Start queue run: pid=12762 | |
31991 | ||
31992 | Exim does not include its process id in log lines by default, but you can | |
31993 | request that it does so by specifying the "pid" log selector (see section 51.15 | |
31994 | ). When this is set, the process id is output, in square brackets, immediately | |
31995 | after the time and date. | |
31996 | ||
31997 | ||
31998 | 51.1 Where the logs are written | |
31999 | ------------------------------- | |
32000 | ||
32001 | The logs may be written to local files, or to syslog, or both. However, it | |
32002 | should be noted that many syslog implementations use UDP as a transport, and | |
32003 | are therefore unreliable in the sense that messages are not guaranteed to | |
32004 | arrive at the loghost, nor is the ordering of messages necessarily maintained. | |
32005 | It has also been reported that on large log files (tens of megabytes) you may | |
32006 | need to tweak syslog to prevent it syncing the file with each write - on Linux | |
32007 | this has been seen to make syslog take 90% plus of CPU time. | |
32008 | ||
32009 | The destination for Exim's logs is configured by setting LOG_FILE_PATH in Local | |
32010 | /Makefile or by setting log_file_path in the run time configuration. This | |
32011 | latter string is expanded, so it can contain, for example, references to the | |
32012 | host name: | |
32013 | ||
32014 | log_file_path = /var/log/$primary_hostname/exim_%slog | |
32015 | ||
32016 | It is generally advisable, however, to set the string in Local/Makefile rather | |
32017 | than at run time, because then the setting is available right from the start of | |
32018 | Exim's execution. Otherwise, if there's something it wants to log before it has | |
32019 | read the configuration file (for example, an error in the configuration file) | |
32020 | it will not use the path you want, and may not be able to log at all. | |
32021 | ||
32022 | The value of LOG_FILE_PATH or log_file_path is a colon-separated list, | |
32023 | currently limited to at most two items. This is one option where the facility | |
32024 | for changing a list separator may not be used. The list must always be | |
32025 | colon-separated. If an item in the list is "syslog" then syslog is used; | |
32026 | otherwise the item must either be an absolute path, containing "%s" at the | |
32027 | point where "main", "reject", or "panic" is to be inserted, or be empty, | |
32028 | implying the use of a default path. | |
32029 | ||
32030 | When Exim encounters an empty item in the list, it searches the list defined by | |
32031 | LOG_FILE_PATH, and uses the first item it finds that is neither empty nor | |
32032 | "syslog". This means that an empty item in log_file_path can be used to mean | |
32033 | "use the path specified at build time". It no such item exists, log files are | |
32034 | written in the log subdirectory of the spool directory. This is equivalent to | |
32035 | the setting: | |
32036 | ||
32037 | log_file_path = $spool_directory/log/%slog | |
32038 | ||
32039 | If you do not specify anything at build time or run time, that is where the | |
32040 | logs are written. | |
32041 | ||
32042 | A log file path may also contain "%D" or "%M" if datestamped log file names are | |
32043 | in use - see section 51.3 below. | |
32044 | ||
32045 | Here are some examples of possible settings: | |
32046 | ||
32047 | LOG_FILE_PATH=syslog syslog only | |
32048 | LOG_FILE_PATH=:syslog syslog and default path | |
32049 | LOG_FILE_PATH=syslog : /usr/log/exim_%s syslog and specified path | |
32050 | LOG_FILE_PATH=/usr/log/exim_%s specified path only | |
32051 | ||
32052 | If there are more than two paths in the list, the first is used and a panic | |
32053 | error is logged. | |
32054 | ||
32055 | ||
32056 | 51.2 Logging to local files that are periodically "cycled" | |
32057 | ---------------------------------------------------------- | |
32058 | ||
32059 | Some operating systems provide centralized and standardized methods for cycling | |
32060 | log files. For those that do not, a utility script called exicyclog is provided | |
32061 | (see section 52.6). This renames and compresses the main and reject logs each | |
32062 | time it is called. The maximum number of old logs to keep can be set. It is | |
32063 | suggested this script is run as a daily cron job. | |
32064 | ||
32065 | An Exim delivery process opens the main log when it first needs to write to it, | |
32066 | and it keeps the file open in case subsequent entries are required - for | |
32067 | example, if a number of different deliveries are being done for the same | |
32068 | message. However, remote SMTP deliveries can take a long time, and this means | |
32069 | that the file may be kept open long after it is renamed if exicyclog or | |
32070 | something similar is being used to rename log files on a regular basis. To | |
32071 | ensure that a switch of log files is noticed as soon as possible, Exim calls | |
32072 | stat() on the main log's name before reusing an open file, and if the file does | |
32073 | not exist, or its inode has changed, the old file is closed and Exim tries to | |
32074 | open the main log from scratch. Thus, an old log file may remain open for quite | |
32075 | some time, but no Exim processes should write to it once it has been renamed. | |
32076 | ||
32077 | ||
32078 | 51.3 Datestamped log files | |
32079 | -------------------------- | |
32080 | ||
32081 | Instead of cycling the main and reject log files by renaming them periodically, | |
32082 | some sites like to use files whose names contain a datestamp, for example, | |
32083 | mainlog-20031225. The datestamp is in the form yyyymmdd or yyyymm. Exim has | |
32084 | support for this way of working. It is enabled by setting the log_file_path | |
32085 | option to a path that includes "%D" or "%M" at the point where the datestamp is | |
32086 | required. For example: | |
32087 | ||
32088 | log_file_path = /var/spool/exim/log/%slog-%D | |
32089 | log_file_path = /var/log/exim-%s-%D.log | |
32090 | log_file_path = /var/spool/exim/log/%D-%slog | |
32091 | log_file_path = /var/log/exim/%s.%M | |
32092 | ||
32093 | As before, "%s" is replaced by "main" or "reject"; the following are examples | |
32094 | of names generated by the above examples: | |
32095 | ||
32096 | /var/spool/exim/log/mainlog-20021225 | |
32097 | /var/log/exim-reject-20021225.log | |
32098 | /var/spool/exim/log/20021225-mainlog | |
32099 | /var/log/exim/main.200212 | |
32100 | ||
32101 | When this form of log file is specified, Exim automatically switches to new | |
32102 | files at midnight. It does not make any attempt to compress old logs; you will | |
32103 | need to write your own script if you require this. You should not run exicyclog | |
32104 | with this form of logging. | |
32105 | ||
32106 | The location of the panic log is also determined by log_file_path, but it is | |
32107 | not datestamped, because rotation of the panic log does not make sense. When | |
32108 | generating the name of the panic log, "%D" or "%M" are removed from the string. | |
32109 | In addition, if it immediately follows a slash, a following non-alphanumeric | |
32110 | character is removed; otherwise a preceding non-alphanumeric character is | |
32111 | removed. Thus, the four examples above would give these panic log names: | |
32112 | ||
32113 | /var/spool/exim/log/paniclog | |
32114 | /var/log/exim-panic.log | |
32115 | /var/spool/exim/log/paniclog | |
32116 | /var/log/exim/panic | |
32117 | ||
32118 | ||
32119 | 51.4 Logging to syslog | |
32120 | ---------------------- | |
32121 | ||
32122 | The use of syslog does not change what Exim logs or the format of its messages, | |
32123 | except in one respect. If syslog_timestamp is set false, the timestamps on | |
32124 | Exim's log lines are omitted when these lines are sent to syslog. Apart from | |
32125 | that, the same strings are written to syslog as to log files. The syslog | |
32126 | "facility" is set to LOG_MAIL, and the program name to "exim" by default, but | |
32127 | you can change these by setting the syslog_facility and syslog_processname | |
32128 | options, respectively. If Exim was compiled with SYSLOG_LOG_PID set in Local/ | |
32129 | Makefile (this is the default in src/EDITME), then, on systems that permit it | |
32130 | (all except ULTRIX), the LOG_PID flag is set so that the syslog() call adds the | |
32131 | pid as well as the time and host name to each line. The three log streams are | |
32132 | mapped onto syslog priorities as follows: | |
32133 | ||
32134 | * mainlog is mapped to LOG_INFO | |
32135 | ||
32136 | * rejectlog is mapped to LOG_NOTICE | |
32137 | ||
32138 | * paniclog is mapped to LOG_ALERT | |
32139 | ||
32140 | Many log lines are written to both mainlog and rejectlog, and some are written | |
32141 | to both mainlog and paniclog, so there will be duplicates if these are routed | |
32142 | by syslog to the same place. You can suppress this duplication by setting | |
32143 | syslog_duplication false. | |
32144 | ||
32145 | Exim's log lines can sometimes be very long, and some of its rejectlog entries | |
32146 | contain multiple lines when headers are included. To cope with both these | |
32147 | cases, entries written to syslog are split into separate syslog() calls at each | |
32148 | internal newline, and also after a maximum of 870 data characters. (This allows | |
32149 | for a total syslog line length of 1024, when additions such as timestamps are | |
32150 | added.) If you are running a syslog replacement that can handle lines longer | |
32151 | than the 1024 characters allowed by RFC 3164, you should set | |
32152 | ||
32153 | SYSLOG_LONG_LINES=yes | |
32154 | ||
32155 | in Local/Makefile before building Exim. That stops Exim from splitting long | |
32156 | lines, but it still splits at internal newlines in reject log entries. | |
32157 | ||
32158 | To make it easy to re-assemble split lines later, each component of a split | |
32159 | entry starts with a string of the form [<n>/<m>] or [<n>\<m>] where <n> is the | |
32160 | component number and <m> is the total number of components in the entry. The / | |
32161 | delimiter is used when the line was split because it was too long; if it was | |
32162 | split because of an internal newline, the \ delimiter is used. For example, | |
32163 | supposing the length limit to be 50 instead of 870, the following would be the | |
32164 | result of a typical rejection message to mainlog (LOG_INFO), each line in | |
32165 | addition being preceded by the time, host name, and pid as added by syslog: | |
32166 | ||
32167 | [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from | |
32168 | [2/5] [127.0.0.1] (ph10): syntax error in 'From' header | |
32169 | [3/5] when scanning for sender: missing or malformed lo | |
32170 | [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa | |
32171 | [5/5] mple>) | |
32172 | ||
32173 | The same error might cause the following lines to be written to "rejectlog" | |
32174 | (LOG_NOTICE): | |
32175 | ||
32176 | [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro | |
32177 | [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head | |
32178 | [3/18] er when scanning for sender: missing or malformed | |
32179 | [4/18] local part in "<>" (envelope sender is <ph10@cam | |
32180 | [5\18] .example>) | |
32181 | [6\18] Recipients: ph10@some.domain.cam.example | |
32182 | [7\18] P Received: from [127.0.0.1] (ident=ph10) | |
32183 | [8\18] by xxxxx.cam.example with smtp (Exim 4.00) | |
32184 | [9\18] id 16RdAL-0006pc-00 | |
32185 | [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16: | |
32186 | [11\18] 09:43 +0100 | |
32187 | [12\18] F From: <> | |
32188 | [13\18] Subject: this is a test header | |
32189 | [18\18] X-something: this is another header | |
32190 | [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp | |
32191 | [16\18] le> | |
32192 | [17\18] B Bcc: | |
32193 | [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100 | |
32194 | ||
32195 | Log lines that are neither too long nor contain newlines are written to syslog | |
32196 | without modification. | |
32197 | ||
32198 | If only syslog is being used, the Exim monitor is unable to provide a log tail | |
32199 | display, unless syslog is routing mainlog to a file on the local host and the | |
32200 | environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor where it | |
32201 | is. | |
32202 | ||
32203 | ||
32204 | 51.5 Log line flags | |
32205 | ------------------- | |
32206 | ||
32207 | One line is written to the main log for each message received, and for each | |
32208 | successful, unsuccessful, and delayed delivery. These lines can readily be | |
32209 | picked out by the distinctive two-character flags that immediately follow the | |
32210 | timestamp. The flags are: | |
32211 | ||
32212 | <= message arrival | |
32213 | => normal message delivery | |
32214 | -> additional address in same delivery | |
32215 | >> cutthrough message delivery | |
32216 | *> delivery suppressed by -N | |
32217 | ** delivery failed; address bounced | |
32218 | == delivery deferred; temporary problem | |
32219 | ||
32220 | ||
32221 | 51.6 Logging message reception | |
32222 | ------------------------------ | |
32223 | ||
32224 | The format of the single-line entry in the main log that is written for every | |
32225 | message received is shown in the basic example below, which is split over | |
32226 | several lines in order to fit it on the page: | |
32227 | ||
32228 | 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example | |
32229 | H=mailer.fict.example [192.168.123.123] U=exim | |
32230 | P=smtp S=5678 id=<incoming message id> | |
32231 | ||
32232 | The address immediately following "<=" is the envelope sender address. A bounce | |
32233 | message is shown with the sender address "<>", and if it is locally generated, | |
32234 | this is followed by an item of the form | |
32235 | ||
32236 | R=<message id> | |
32237 | ||
32238 | which is a reference to the message that caused the bounce to be sent. | |
32239 | ||
32240 | For messages from other hosts, the H and U fields identify the remote host and | |
32241 | record the RFC 1413 identity of the user that sent the message, if one was | |
32242 | received. The number given in square brackets is the IP address of the sending | |
32243 | host. If there is a single, unparenthesized host name in the H field, as above, | |
32244 | it has been verified to correspond to the IP address (see the host_lookup | |
32245 | option). If the name is in parentheses, it was the name quoted by the remote | |
32246 | host in the SMTP HELO or EHLO command, and has not been verified. If | |
32247 | verification yields a different name to that given for HELO or EHLO, the | |
32248 | verified name appears first, followed by the HELO or EHLO name in parentheses. | |
32249 | ||
32250 | Misconfigured hosts (and mail forgers) sometimes put an IP address, with or | |
32251 | without brackets, in the HELO or EHLO command, leading to entries in the log | |
32252 | containing text like these examples: | |
32253 | ||
32254 | H=(10.21.32.43) [192.168.8.34] | |
32255 | H=([10.21.32.43]) [192.168.8.34] | |
32256 | ||
32257 | This can be confusing. Only the final address in square brackets can be relied | |
32258 | on. | |
32259 | ||
32260 | For locally generated messages (that is, messages not received over TCP/IP), | |
32261 | the H field is omitted, and the U field contains the login name of the caller | |
32262 | of Exim. | |
32263 | ||
32264 | For all messages, the P field specifies the protocol used to receive the | |
32265 | message. This is the value that is stored in $received_protocol. In the case of | |
32266 | incoming SMTP messages, the value indicates whether or not any SMTP extensions | |
32267 | (ESMTP), encryption, or authentication were used. If the SMTP session was | |
32268 | encrypted, there is an additional X field that records the cipher suite that | |
32269 | was used. | |
32270 | ||
32271 | The protocol is set to "esmtpsa" or "esmtpa" for messages received from hosts | |
32272 | that have authenticated themselves using the SMTP AUTH command. The first value | |
32273 | is used when the SMTP connection was encrypted ("secure"). In this case there | |
32274 | is an additional item A= followed by the name of the authenticator that was | |
32275 | used. If an authenticated identification was set up by the authenticator's | |
32276 | server_set_id option, this is logged too, separated by a colon from the | |
32277 | authenticator name. | |
32278 | ||
32279 | The id field records the existing message id, if present. The size of the | |
32280 | received message is given by the S field. When the message is delivered, | |
32281 | headers may be removed or added, so that the size of delivered copies of the | |
32282 | message may not correspond with this value (and indeed may be different to each | |
32283 | other). | |
32284 | ||
32285 | The log_selector option can be used to request the logging of additional data | |
32286 | when a message is received. See section 51.15 below. | |
32287 | ||
32288 | ||
32289 | 51.7 Logging deliveries | |
32290 | ----------------------- | |
32291 | ||
32292 | The format of the single-line entry in the main log that is written for every | |
32293 | delivery is shown in one of the examples below, for local and remote | |
32294 | deliveries, respectively. Each example has been split into two lines in order | |
32295 | to fit it on the page: | |
32296 | ||
32297 | 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv | |
32298 | <marv@hitch.fict.example> R=localuser T=local_delivery | |
32299 | 2002-10-31 09:00:10 16ZCW1-0005MB-00 => | |
32300 | monk@holistic.fict.example R=dnslookup T=remote_smtp | |
32301 | H=holistic.fict.example [192.168.234.234] | |
32302 | ||
32303 | For ordinary local deliveries, the original address is given in angle brackets | |
32304 | after the final delivery address, which might be a pipe or a file. If | |
32305 | intermediate address(es) exist between the original and the final address, the | |
32306 | last of these is given in parentheses after the final address. The R and T | |
32307 | fields record the router and transport that were used to process the address. | |
32308 | ||
32309 | If SMTP AUTH was used for the delivery there is an additional item A= followed | |
32310 | by the name of the authenticator that was used. If an authenticated | |
32311 | identification was set up by the authenticator's client_set_id option, this is | |
32312 | logged too, separated by a colon from the authenticator name. | |
32313 | ||
32314 | If a shadow transport was run after a successful local delivery, the log line | |
32315 | for the successful delivery has an item added on the end, of the form | |
32316 | ||
32317 | ST=<shadow transport name> | |
32318 | ||
32319 | If the shadow transport did not succeed, the error message is put in | |
32320 | parentheses afterwards. | |
32321 | ||
32322 | When more than one address is included in a single delivery (for example, two | |
32323 | SMTP RCPT commands in one transaction) the second and subsequent addresses are | |
32324 | flagged with "->" instead of "=>". When two or more messages are delivered down | |
32325 | a single SMTP connection, an asterisk follows the IP address in the log lines | |
32326 | for the second and subsequent messages. | |
32327 | ||
32328 | When delivery is done in cutthrough mode it is flagged with ">>" and the log | |
32329 | line precedes the reception line, since cutthrough waits for a possible | |
32330 | rejection from the destination in case it can reject the sourced item. | |
32331 | ||
32332 | The generation of a reply message by a filter file gets logged as a "delivery" | |
32333 | to the addressee, preceded by ">". | |
32334 | ||
32335 | The log_selector option can be used to request the logging of additional data | |
32336 | when a message is delivered. See section 51.15 below. | |
32337 | ||
32338 | ||
32339 | 51.8 Discarded deliveries | |
32340 | ------------------------- | |
32341 | ||
32342 | When a message is discarded as a result of the command "seen finish" being | |
32343 | obeyed in a filter file which generates no deliveries, a log entry of the form | |
32344 | ||
32345 | 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded | |
32346 | <low.club@bridge.example> R=userforward | |
32347 | ||
32348 | is written, to record why no deliveries are logged. When a message is discarded | |
32349 | because it is aliased to ":blackhole:" the log line is like this: | |
32350 | ||
32351 | 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole: | |
32352 | <hole@nowhere.example> R=blackhole_router | |
32353 | ||
32354 | ||
32355 | 51.9 Deferred deliveries | |
32356 | ------------------------ | |
32357 | ||
32358 | When a delivery is deferred, a line of the following form is logged: | |
32359 | ||
32360 | 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example | |
32361 | R=dnslookup T=smtp defer (146): Connection refused | |
32362 | ||
32363 | In the case of remote deliveries, the error is the one that was given for the | |
32364 | last IP address that was tried. Details of individual SMTP failures are also | |
32365 | written to the log, so the above line would be preceded by something like | |
32366 | ||
32367 | 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to | |
32368 | mail1.endrest.example [192.168.239.239]: Connection refused | |
32369 | ||
32370 | When a deferred address is skipped because its retry time has not been reached, | |
32371 | a message is written to the log, but this can be suppressed by setting an | |
32372 | appropriate value in log_selector. | |
32373 | ||
32374 | ||
32375 | 51.10 Delivery failures | |
32376 | ----------------------- | |
32377 | ||
32378 | If a delivery fails because an address cannot be routed, a line of the | |
32379 | following form is logged: | |
32380 | ||
32381 | 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example | |
32382 | <jim@trek99.example>: unknown mail domain | |
32383 | ||
32384 | If a delivery fails at transport time, the router and transport are shown, and | |
32385 | the response from the remote host is included, as in this example: | |
32386 | ||
32387 | 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example | |
32388 | R=dnslookup T=remote_smtp: SMTP error from remote mailer | |
32389 | after pipelined RCPT TO:<ace400@pb.example>: host | |
32390 | pbmail3.py.example [192.168.63.111]: 553 5.3.0 | |
32391 | <ace400@pb.example>...Addressee unknown | |
32392 | ||
32393 | The word "pipelined" indicates that the SMTP PIPELINING extension was being | |
32394 | used. See hosts_avoid_esmtp in the smtp transport for a way of disabling | |
32395 | PIPELINING. The log lines for all forms of delivery failure are flagged with | |
32396 | "**". | |
32397 | ||
32398 | ||
32399 | 51.11 Fake deliveries | |
32400 | --------------------- | |
32401 | ||
32402 | If a delivery does not actually take place because the -N option has been used | |
32403 | to suppress it, a normal delivery line is written to the log, except that "=>" | |
32404 | is replaced by "*>". | |
32405 | ||
32406 | ||
32407 | 51.12 Completion | |
32408 | ---------------- | |
32409 | ||
32410 | A line of the form | |
32411 | ||
32412 | 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed | |
32413 | ||
32414 | is written to the main log when a message is about to be removed from the spool | |
32415 | at the end of its processing. | |
32416 | ||
32417 | ||
32418 | 51.13 Summary of Fields in Log Lines | |
32419 | ------------------------------------ | |
32420 | ||
32421 | A summary of the field identifiers that are used in log lines is shown in the | |
32422 | following table: | |
32423 | ||
32424 | A authenticator name (and optional id and sender) | |
32425 | C SMTP confirmation on delivery | |
32426 | command list for "no mail in SMTP session" | |
32427 | CV certificate verification status | |
32428 | D duration of "no mail in SMTP session" | |
32429 | DN distinguished name from peer certificate | |
32430 | DT on => lines: time taken for a delivery | |
32431 | F sender address (on delivery lines) | |
32432 | H host name and IP address | |
32433 | I local interface used | |
32434 | id message id for incoming message | |
32435 | P on <= lines: protocol used | |
32436 | on => and ** lines: return path | |
32437 | QT on => lines: time spent on queue so far | |
32438 | on "Completed" lines: time spent on queue | |
32439 | R on <= lines: reference for local bounce | |
32440 | on => ** and == lines: router name | |
32441 | S size of message | |
32442 | SNI server name indication from TLS client hello | |
32443 | ST shadow transport name | |
32444 | T on <= lines: message subject (topic) | |
32445 | on => ** and == lines: transport name | |
32446 | U local user or RFC 1413 identity | |
32447 | X TLS cipher suite | |
32448 | ||
32449 | ||
32450 | 51.14 Other log entries | |
32451 | ----------------------- | |
32452 | ||
32453 | Various other types of log entry are written from time to time. Most should be | |
32454 | self-explanatory. Among the more common are: | |
32455 | ||
32456 | * retry time not reached An address previously suffered a temporary error | |
32457 | during routing or local delivery, and the time to retry has not yet | |
32458 | arrived. This message is not written to an individual message log file | |
32459 | unless it happens during the first delivery attempt. | |
32460 | ||
32461 | * retry time not reached for any host An address previously suffered | |
32462 | temporary errors during remote delivery, and the retry time has not yet | |
32463 | arrived for any of the hosts to which it is routed. | |
32464 | ||
32465 | * spool file locked An attempt to deliver a message cannot proceed because | |
32466 | some other Exim process is already working on the message. This can be | |
32467 | quite common if queue running processes are started at frequent intervals. | |
32468 | The exiwhat utility script can be used to find out what Exim processes are | |
32469 | doing. | |
32470 | ||
32471 | * error ignored There are several circumstances that give rise to this | |
32472 | message: | |
32473 | ||
32474 | 1. Exim failed to deliver a bounce message whose age was greater than | |
32475 | ignore_bounce_errors_after. The bounce was discarded. | |
32476 | ||
32477 | 2. A filter file set up a delivery using the "noerror" option, and the | |
32478 | delivery failed. The delivery was discarded. | |
32479 | ||
32480 | 3. A delivery set up by a router configured with | |
32481 | ||
32482 | errors_to = <> | |
32483 | ||
32484 | failed. The delivery was discarded. | |
32485 | ||
32486 | ||
32487 | 51.15 Reducing or increasing what is logged | |
32488 | ------------------------------------------- | |
32489 | ||
32490 | By setting the log_selector global option, you can disable some of Exim's | |
32491 | default logging, or you can request additional logging. The value of | |
32492 | log_selector is made up of names preceded by plus or minus characters. For | |
32493 | example: | |
32494 | ||
32495 | log_selector = +arguments -retry_defer | |
32496 | ||
32497 | The list of optional log items is in the following table, with the default | |
32498 | selection marked by asterisks: | |
32499 | ||
32500 | 8bitmime received 8BITMIME status | |
32501 | *acl_warn_skipped skipped warn statement in ACL | |
32502 | address_rewrite address rewriting | |
32503 | all_parents all parents in => lines | |
32504 | arguments command line arguments | |
32505 | *connection_reject connection rejections | |
32506 | *delay_delivery immediate delivery delayed | |
32507 | deliver_time time taken to perform delivery | |
32508 | delivery_size add S=nnn to => lines | |
32509 | *dnslist_defer defers of DNS list (aka RBL) lookups | |
32510 | *etrn ETRN commands | |
32511 | *host_lookup_failed as it says | |
32512 | ident_timeout timeout for ident connection | |
32513 | incoming_interface incoming interface on <= lines | |
32514 | incoming_port incoming port on <= lines | |
32515 | *lost_incoming_connection as it says (includes timeouts) | |
32516 | outgoing_port add remote port to => lines | |
32517 | *queue_run start and end queue runs | |
32518 | queue_time time on queue for one recipient | |
32519 | queue_time_overall time on queue for whole message | |
32520 | pid Exim process id | |
32521 | received_recipients recipients on <= lines | |
32522 | received_sender sender on <= lines | |
32523 | *rejected_header header contents on reject log | |
32524 | *retry_defer "retry time not reached" | |
32525 | return_path_on_delivery put return path on => and ** lines | |
32526 | sender_on_delivery add sender to => lines | |
32527 | *sender_verify_fail sender verification failures | |
32528 | *size_reject rejection because too big | |
32529 | *skip_delivery delivery skipped in a queue run | |
32530 | *smtp_confirmation SMTP confirmation on => lines | |
32531 | smtp_connection SMTP connections | |
32532 | smtp_incomplete_transaction incomplete SMTP transactions | |
32533 | smtp_mailauth AUTH argument to MAIL commands | |
32534 | smtp_no_mail session with no MAIL commands | |
32535 | smtp_protocol_error SMTP protocol errors | |
32536 | smtp_syntax_error SMTP syntax errors | |
32537 | subject contents of Subject: on <= lines | |
32538 | tls_certificate_verified certificate verification status | |
32539 | *tls_cipher TLS cipher suite on <= and => lines | |
32540 | tls_peerdn TLS peer DN on <= and => lines | |
32541 | tls_sni TLS SNI on <= lines | |
32542 | unknown_in_list DNS lookup failed in list match | |
32543 | ||
32544 | all all of the above | |
32545 | ||
32546 | More details on each of these items follows: | |
32547 | ||
32548 | * 8bitmime: This causes Exim to log any 8BITMIME status of received messages, | |
32549 | which may help in tracking down interoperability issues with ancient MTAs | |
32550 | that are not 8bit clean. This is added to the "<=" line, tagged with "M8S=" | |
32551 | and a value of "0", "7" or "8", corresponding to "not given", "7BIT" and | |
32552 | "8BITMIME" respectively. | |
32553 | ||
32554 | * acl_warn_skipped: When an ACL warn statement is skipped because one of its | |
32555 | conditions cannot be evaluated, a log line to this effect is written if | |
32556 | this log selector is set. | |
32557 | ||
32558 | * address_rewrite: This applies both to global rewrites and per-transport | |
32559 | rewrites, but not to rewrites in filters run as an unprivileged user | |
32560 | (because such users cannot access the log). | |
32561 | ||
32562 | * all_parents: Normally only the original and final addresses are logged on | |
32563 | delivery lines; with this selector, intermediate parents are given in | |
32564 | parentheses between them. | |
32565 | ||
32566 | * arguments: This causes Exim to write the arguments with which it was called | |
32567 | to the main log, preceded by the current working directory. This is a | |
32568 | debugging feature, added to make it easier to find out how certain MUAs | |
32569 | call /usr/sbin/sendmail. The logging does not happen if Exim has given up | |
32570 | root privilege because it was called with the -C or -D options. Arguments | |
32571 | that are empty or that contain white space are quoted. Non-printing | |
32572 | characters are shown as escape sequences. This facility cannot log | |
32573 | unrecognized arguments, because the arguments are checked before the | |
32574 | configuration file is read. The only way to log such cases is to interpose | |
32575 | a script such as util/logargs.sh between the caller and Exim. | |
32576 | ||
32577 | * connection_reject: A log entry is written whenever an incoming SMTP | |
32578 | connection is rejected, for whatever reason. | |
32579 | ||
32580 | * delay_delivery: A log entry is written whenever a delivery process is not | |
32581 | started for an incoming message because the load is too high or too many | |
32582 | messages were received on one connection. Logging does not occur if no | |
32583 | delivery process is started because queue_only is set or -odq was used. | |
32584 | ||
32585 | * deliver_time: For each delivery, the amount of real time it has taken to | |
32586 | perform the actual delivery is logged as DT=<time>, for example, "DT=1s". | |
32587 | ||
32588 | * delivery_size: For each delivery, the size of message delivered is added to | |
32589 | the "=>" line, tagged with S=. | |
32590 | ||
32591 | * dnslist_defer: A log entry is written if an attempt to look up a host in a | |
32592 | DNS black list suffers a temporary error. | |
32593 | ||
32594 | * etrn: Every valid ETRN command that is received is logged, before the ACL | |
32595 | is run to determine whether or not it is actually accepted. An invalid ETRN | |
32596 | command, or one received within a message transaction is not logged by this | |
32597 | selector (see smtp_syntax_error and smtp_protocol_error). | |
32598 | ||
32599 | * host_lookup_failed: When a lookup of a host's IP addresses fails to find | |
32600 | any addresses, or when a lookup of an IP address fails to find a host name, | |
32601 | a log line is written. This logging does not apply to direct DNS lookups | |
32602 | when routing email addresses, but it does apply to "byname" lookups. | |
32603 | ||
32604 | * ident_timeout: A log line is written whenever an attempt to connect to a | |
32605 | client's ident port times out. | |
32606 | ||
32607 | * incoming_interface: The interface on which a message was received is added | |
32608 | to the "<=" line as an IP address in square brackets, tagged by I= and | |
32609 | followed by a colon and the port number. The local interface and port are | |
32610 | also added to other SMTP log lines, for example "SMTP connection from", and | |
32611 | to rejection lines. | |
32612 | ||
32613 | * incoming_port: The remote port number from which a message was received is | |
32614 | added to log entries and Received: header lines, following the IP address | |
32615 | in square brackets, and separated from it by a colon. This is implemented | |
32616 | by changing the value that is put in the $sender_fullhost and | |
32617 | $sender_rcvhost variables. Recording the remote port number has become more | |
32618 | important with the widening use of NAT (see RFC 2505). | |
32619 | ||
32620 | * lost_incoming_connection: A log line is written when an incoming SMTP | |
32621 | connection is unexpectedly dropped. | |
32622 | ||
32623 | * outgoing_port: The remote port number is added to delivery log lines (those | |
32624 | containing => tags) following the IP address. This option is not included | |
32625 | in the default setting, because for most ordinary configurations, the | |
32626 | remote port number is always 25 (the SMTP port). | |
32627 | ||
32628 | * pid: The current process id is added to every log line, in square brackets, | |
32629 | immediately after the time and date. | |
32630 | ||
32631 | * queue_run: The start and end of every queue run are logged. | |
32632 | ||
32633 | * queue_time: The amount of time the message has been in the queue on the | |
32634 | local host is logged as QT=<time> on delivery ("=>") lines, for example, | |
32635 | "QT=3m45s". The clock starts when Exim starts to receive the message, so it | |
32636 | includes reception time as well as the delivery time for the current | |
32637 | address. This means that it may be longer than the difference between the | |
32638 | arrival and delivery log line times, because the arrival log line is not | |
32639 | written until the message has been successfully received. | |
32640 | ||
32641 | * queue_time_overall: The amount of time the message has been in the queue on | |
32642 | the local host is logged as QT=<time> on "Completed" lines, for example, | |
32643 | "QT=3m45s". The clock starts when Exim starts to receive the message, so it | |
32644 | includes reception time as well as the total delivery time. | |
32645 | ||
32646 | * received_recipients: The recipients of a message are listed in the main log | |
32647 | as soon as the message is received. The list appears at the end of the log | |
32648 | line that is written when a message is received, preceded by the word | |
32649 | "for". The addresses are listed after they have been qualified, but before | |
32650 | any rewriting has taken place. Recipients that were discarded by an ACL for | |
32651 | MAIL or RCPT do not appear in the list. | |
32652 | ||
32653 | * received_sender: The unrewritten original sender of a message is added to | |
32654 | the end of the log line that records the message's arrival, after the word | |
32655 | "from" (before the recipients if received_recipients is also set). | |
32656 | ||
32657 | * rejected_header: If a message's header has been received at the time a | |
32658 | rejection is written to the reject log, the complete header is added to the | |
32659 | log. Header logging can be turned off individually for messages that are | |
32660 | rejected by the local_scan() function (see section 44.2). | |
32661 | ||
32662 | * retry_defer: A log line is written if a delivery is deferred because a | |
32663 | retry time has not yet been reached. However, this "retry time not reached" | |
32664 | message is always omitted from individual message logs after the first | |
32665 | delivery attempt. | |
32666 | ||
32667 | * return_path_on_delivery: The return path that is being transmitted with the | |
32668 | message is included in delivery and bounce lines, using the tag P=. This is | |
32669 | omitted if no delivery actually happens, for example, if routing fails, or | |
32670 | if delivery is to /dev/null or to ":blackhole:". | |
32671 | ||
32672 | * sender_on_delivery: The message's sender address is added to every delivery | |
32673 | and bounce line, tagged by F= (for "from"). This is the original sender | |
32674 | that was received with the message; it is not necessarily the same as the | |
32675 | outgoing return path. | |
32676 | ||
32677 | * sender_verify_fail: If this selector is unset, the separate log line that | |
32678 | gives details of a sender verification failure is not written. Log lines | |
32679 | for the rejection of SMTP commands contain just "sender verify failed", so | |
32680 | some detail is lost. | |
32681 | ||
32682 | * size_reject: A log line is written whenever a message is rejected because | |
32683 | it is too big. | |
32684 | ||
32685 | * skip_delivery: A log line is written whenever a message is skipped during a | |
32686 | queue run because it is frozen or because another process is already | |
32687 | delivering it. The message that is written is "spool file is locked". | |
32688 | ||
32689 | * smtp_confirmation: The response to the final "." in the SMTP or LMTP | |
32690 | dialogue for outgoing messages is added to delivery log lines in the form | |
32691 | "C="<text>. A number of MTAs (including Exim) return an identifying string | |
32692 | in this response. | |
32693 | ||
32694 | * smtp_connection: A log line is written whenever an SMTP connection is | |
32695 | established or closed, unless the connection is from a host that matches | |
32696 | hosts_connection_nolog. (In contrast, lost_incoming_connection applies only | |
32697 | when the closure is unexpected.) This applies to connections from local | |
32698 | processes that use -bs as well as to TCP/IP connections. If a connection is | |
32699 | dropped in the middle of a message, a log line is always written, whether | |
32700 | or not this selector is set, but otherwise nothing is written at the start | |
32701 | and end of connections unless this selector is enabled. | |
32702 | ||
32703 | For TCP/IP connections to an Exim daemon, the current number of connections | |
32704 | is included in the log message for each new connection, but note that the | |
32705 | count is reset if the daemon is restarted. Also, because connections are | |
32706 | closed (and the closure is logged) in subprocesses, the count may not | |
32707 | include connections that have been closed but whose termination the daemon | |
32708 | has not yet noticed. Thus, while it is possible to match up the opening and | |
32709 | closing of connections in the log, the value of the logged counts may not | |
32710 | be entirely accurate. | |
32711 | ||
32712 | * smtp_incomplete_transaction: When a mail transaction is aborted by RSET, | |
32713 | QUIT, loss of connection, or otherwise, the incident is logged, and the | |
32714 | message sender plus any accepted recipients are included in the log line. | |
32715 | This can provide evidence of dictionary attacks. | |
32716 | ||
32717 | * smtp_no_mail: A line is written to the main log whenever an accepted SMTP | |
32718 | connection terminates without having issued a MAIL command. This includes | |
32719 | both the case when the connection is dropped, and the case when QUIT is | |
32720 | used. It does not include cases where the connection is rejected right at | |
32721 | the start (by an ACL, or because there are too many connections, or | |
32722 | whatever). These cases already have their own log lines. | |
32723 | ||
32724 | The log line that is written contains the identity of the client in the | |
32725 | usual way, followed by D= and a time, which records the duration of the | |
32726 | connection. If the connection was authenticated, this fact is logged | |
32727 | exactly as it is for an incoming message, with an A= item. If the | |
32728 | connection was encrypted, CV=, DN=, and X= items may appear as they do for | |
32729 | an incoming message, controlled by the same logging options. | |
32730 | ||
32731 | Finally, if any SMTP commands were issued during the connection, a C= item | |
32732 | is added to the line, listing the commands that were used. For example, | |
32733 | ||
32734 | C=EHLO,QUIT | |
32735 | ||
32736 | shows that the client issued QUIT straight after EHLO. If there were fewer | |
32737 | than 20 commands, they are all listed. If there were more than 20 commands, | |
32738 | the last 20 are listed, preceded by "...". However, with the default | |
32739 | setting of 10 for smtp_accep_max_nonmail, the connection will in any case | |
32740 | have been aborted before 20 non-mail commands are processed. | |
32741 | ||
32742 | * smtp_mailauth: A third subfield with the authenticated sender, | |
32743 | colon-separated, is appended to the A= item for a message arrival or | |
32744 | delivery log line, if an AUTH argument to the SMTP MAIL command (see 33.2) | |
32745 | was accepted or used. | |
32746 | ||
32747 | * smtp_protocol_error: A log line is written for every SMTP protocol error | |
32748 | encountered. Exim does not have perfect detection of all protocol errors | |
32749 | because of transmission delays and the use of pipelining. If PIPELINING has | |
32750 | been advertised to a client, an Exim server assumes that the client will | |
32751 | use it, and therefore it does not count "expected" errors (for example, | |
32752 | RCPT received after rejecting MAIL) as protocol errors. | |
32753 | ||
32754 | * smtp_syntax_error: A log line is written for every SMTP syntax error | |
32755 | encountered. An unrecognized command is treated as a syntax error. For an | |
32756 | external connection, the host identity is given; for an internal connection | |
32757 | using -bs the sender identification (normally the calling user) is given. | |
32758 | ||
32759 | * subject: The subject of the message is added to the arrival log line, | |
32760 | preceded by "T=" (T for "topic", since S is already used for "size"). Any | |
32761 | MIME "words" in the subject are decoded. The print_topbitchars option | |
32762 | specifies whether characters with values greater than 127 should be logged | |
32763 | unchanged, or whether they should be rendered as escape sequences. | |
32764 | ||
32765 | * tls_certificate_verified: An extra item is added to <= and => log lines | |
32766 | when TLS is in use. The item is "CV=yes" if the peer's certificate was | |
32767 | verified, and "CV=no" if not. | |
32768 | ||
32769 | * tls_cipher: When a message is sent or received over an encrypted | |
32770 | connection, the cipher suite used is added to the log line, preceded by X=. | |
32771 | ||
32772 | * tls_peerdn: When a message is sent or received over an encrypted | |
32773 | connection, and a certificate is supplied by the remote host, the peer DN | |
32774 | is added to the log line, preceded by DN=. | |
32775 | ||
32776 | * tls_sni: When a message is received over an encrypted connection, and the | |
32777 | remote host provided the Server Name Indication extension, the SNI is added | |
32778 | to the log line, preceded by SNI=. | |
32779 | ||
32780 | * unknown_in_list: This setting causes a log entry to be written when the | |
32781 | result of a list match is failure because a DNS lookup failed. | |
32782 | ||
32783 | ||
32784 | 51.16 Message log | |
32785 | ----------------- | |
32786 | ||
32787 | In addition to the general log files, Exim writes a log file for each message | |
32788 | that it handles. The names of these per-message logs are the message ids, and | |
32789 | they are kept in the msglog sub-directory of the spool directory. Each message | |
32790 | log contains copies of the log lines that apply to the message. This makes it | |
32791 | easier to inspect the status of an individual message without having to search | |
32792 | the main log. A message log is deleted when processing of the message is | |
32793 | complete, unless preserve_message_logs is set, but this should be used only | |
32794 | with great care because they can fill up your disk very quickly. | |
32795 | ||
32796 | On a heavily loaded system, it may be desirable to disable the use of | |
32797 | per-message logs, in order to reduce disk I/O. This can be done by setting the | |
32798 | message_logs option false. | |
32799 | ||
32800 | ||
32801 | ||
32802 | =============================================================================== | |
32803 | 52. EXIM UTILITIES | |
32804 | ||
32805 | A number of utility scripts and programs are supplied with Exim and are | |
32806 | described in this chapter. There is also the Exim Monitor, which is covered in | |
32807 | the next chapter. The utilities described here are: | |
32808 | ||
32809 | 52.1 exiwhat list what Exim processes are doing | |
32810 | 52.2 exiqgrep grep the queue | |
32811 | 52.3 exiqsumm summarize the queue | |
32812 | 52.4 exigrep search the main log | |
32813 | 52.5 exipick select messages on various criteria | |
32814 | 52.6 exicyclog cycle (rotate) log files | |
32815 | 52.7 eximstats extract statistics from the log | |
32816 | 52.8 exim_checkaccess check address acceptance from given IP | |
32817 | 52.9 exim_dbmbuild build a DBM file | |
32818 | 52.10 exinext extract retry information | |
32819 | 52.11 exim_dumpdb dump a hints database | |
32820 | 52.11 exim_tidydb clean up a hints database | |
32821 | 52.11 exim_fixdb patch a hints database | |
32822 | 52.15 exim_lock lock a mailbox file | |
32823 | ||
32824 | Another utility that might be of use to sites with many MTAs is Tom Kistner's | |
32825 | exilog. It provides log visualizations across multiple Exim servers. See http:/ | |
32826 | /duncanthrax.net/exilog/ for details. | |
32827 | ||
32828 | ||
32829 | 52.1 Finding out what Exim processes are doing (exiwhat) | |
32830 | -------------------------------------------------------- | |
32831 | ||
32832 | On operating systems that can restart a system call after receiving a signal | |
32833 | (most modern OS), an Exim process responds to the SIGUSR1 signal by writing a | |
32834 | line describing what it is doing to the file exim-process.info in the Exim | |
32835 | spool directory. The exiwhat script sends the signal to all Exim processes it | |
32836 | can find, having first emptied the file. It then waits for one second to allow | |
32837 | the Exim processes to react before displaying the results. In order to run | |
32838 | exiwhat successfully you have to have sufficient privilege to send the signal | |
32839 | to the Exim processes, so it is normally run as root. | |
32840 | ||
32841 | Warning: This is not an efficient process. It is intended for occasional use by | |
32842 | system administrators. It is not sensible, for example, to set up a script that | |
32843 | sends SIGUSR1 signals to Exim processes at short intervals. | |
32844 | ||
32845 | Unfortunately, the ps command that exiwhat uses to find Exim processes varies | |
32846 | in different operating systems. Not only are different options used, but the | |
32847 | format of the output is different. For this reason, there are some system | |
32848 | configuration options that configure exactly how exiwhat works. If it doesn't | |
32849 | seem to be working for you, check the following compile-time options: | |
32850 | ||
32851 | EXIWHAT_PS_CMD the command for running ps | |
32852 | EXIWHAT_PS_ARG the argument for ps | |
32853 | EXIWHAT_EGREP_ARG the argument for egrep to select from ps output | |
32854 | EXIWHAT_KILL_ARG the argument for the kill command | |
32855 | ||
32856 | An example of typical output from exiwhat is | |
32857 | ||
32858 | 164 daemon: -q1h, listening on port 25 | |
32859 | 10483 running queue: waiting for 0tAycK-0002ij-00 (10492) | |
32860 | 10492 delivering 0tAycK-0002ij-00 to mail.ref.example | |
32861 | [10.19.42.42] (editor@ref.example) | |
32862 | 10592 handling incoming call from [192.168.243.242] | |
32863 | 10628 accepting a local non-SMTP message | |
32864 | ||
32865 | The first number in the output line is the process number. The third line has | |
32866 | been split here, in order to fit it on the page. | |
32867 | ||
32868 | ||
32869 | 52.2 Selective queue listing (exiqgrep) | |
32870 | --------------------------------------- | |
32871 | ||
32872 | This utility is a Perl script contributed by Matt Hubbard. It runs | |
32873 | ||
32874 | exim -bpu | |
32875 | ||
32876 | or (in case -a switch is specified) | |
32877 | ||
32878 | exim -bp | |
32879 | ||
32880 | The -C option is used to specify an alternate exim.conf which might contain | |
32881 | alternate exim configuration the queue management might be using. | |
32882 | ||
32883 | to obtain a queue listing, and then greps the output to select messages that | |
32884 | match given criteria. The following selection options are available: | |
32885 | ||
32886 | -f <regex> | |
32887 | ||
32888 | Match the sender address using a case-insensitive search. The field that is | |
32889 | tested is enclosed in angle brackets, so you can test for bounce messages | |
32890 | with | |
32891 | ||
32892 | exiqgrep -f '^<>$' | |
32893 | ||
32894 | -r <regex> | |
32895 | ||
32896 | Match a recipient address using a case-insensitve search. The field that is | |
32897 | tested is not enclosed in angle brackets. | |
32898 | ||
32899 | -s <regex> | |
32900 | ||
32901 | Match against the size field. | |
32902 | ||
32903 | -y <seconds> | |
32904 | ||
32905 | Match messages that are younger than the given time. | |
32906 | ||
32907 | -o <seconds> | |
32908 | ||
32909 | Match messages that are older than the given time. | |
32910 | ||
32911 | -z | |
32912 | ||
32913 | Match only frozen messages. | |
32914 | ||
32915 | -x | |
32916 | ||
32917 | Match only non-frozen messages. | |
32918 | ||
32919 | The following options control the format of the output: | |
32920 | ||
32921 | -c | |
32922 | ||
32923 | Display only the count of matching messages. | |
32924 | ||
32925 | -l | |
32926 | ||
32927 | Long format - display the full message information as output by Exim. This | |
32928 | is the default. | |
32929 | ||
32930 | -i | |
32931 | ||
32932 | Display message ids only. | |
32933 | ||
32934 | -b | |
32935 | ||
32936 | Brief format - one line per message. | |
32937 | ||
32938 | -R | |
32939 | ||
32940 | Display messages in reverse order. | |
32941 | ||
32942 | -a | |
32943 | ||
32944 | Include delivered recipients in queue listing. | |
32945 | ||
32946 | There is one more option, -h, which outputs a list of options. | |
32947 | ||
32948 | ||
32949 | 52.3 Summarizing the queue (exiqsumm) | |
32950 | ------------------------------------- | |
32951 | ||
32952 | The exiqsumm utility is a Perl script which reads the output of "exim -bp" and | |
32953 | produces a summary of the messages on the queue. Thus, you use it by running a | |
32954 | command such as | |
32955 | ||
32956 | exim -bp | exiqsumm | |
32957 | ||
32958 | The output consists of one line for each domain that has messages waiting for | |
32959 | it, as in the following example: | |
32960 | ||
32961 | 3 2322 74m 66m msn.com.example | |
32962 | ||
32963 | Each line lists the number of pending deliveries for a domain, their total | |
32964 | volume, and the length of time that the oldest and the newest messages have | |
32965 | been waiting. Note that the number of pending deliveries is greater than the | |
32966 | number of messages when messages have more than one recipient. | |
32967 | ||
32968 | A summary line is output at the end. By default the output is sorted on the | |
32969 | domain name, but exiqsumm has the options -a and -c, which cause the output to | |
32970 | be sorted by oldest message and by count of messages, respectively. There are | |
32971 | also three options that split the messages for each domain into two or more | |
32972 | subcounts: -b separates bounce messages, -f separates frozen messages, and -s | |
32973 | separates messages according to their sender. | |
32974 | ||
32975 | The output of exim -bp contains the original addresses in the message, so this | |
32976 | also applies to the output from exiqsumm. No domains from addresses generated | |
32977 | by aliasing or forwarding are included (unless the one_time option of the | |
32978 | redirect router has been used to convert them into "top level" addresses). | |
32979 | ||
32980 | ||
32981 | 52.4 Extracting specific information from the log (exigrep) | |
32982 | ----------------------------------------------------------- | |
32983 | ||
32984 | The exigrep utility is a Perl script that searches one or more main log files | |
32985 | for entries that match a given pattern. When it finds a match, it extracts all | |
32986 | the log entries for the relevant message, not just those that match the | |
32987 | pattern. Thus, exigrep can extract complete log entries for a given message, or | |
32988 | all mail for a given user, or for a given host, for example. The input files | |
32989 | can be in Exim log format or syslog format. If a matching log line is not | |
32990 | associated with a specific message, it is included in exigrep's output without | |
32991 | any additional lines. The usage is: | |
32992 | ||
32993 | exigrep [-t<n>] [-I] [-l] [-v] <pattern> [<log file>] ... | |
32994 | ||
32995 | If no log file names are given on the command line, the standard input is read. | |
32996 | ||
32997 | The -t argument specifies a number of seconds. It adds an additional condition | |
32998 | for message selection. Messages that are complete are shown only if they spent | |
32999 | more than <n> seconds on the queue. | |
33000 | ||
33001 | By default, exigrep does case-insensitive matching. The -I option makes it | |
33002 | case-sensitive. This may give a performance improvement when searching large | |
33003 | log files. Without -I, the Perl pattern matches use Perl's "/i" option; with -I | |
33004 | they do not. In both cases it is possible to change the case sensitivity within | |
33005 | the pattern by using "(?i)" or "(?-i)". | |
33006 | ||
33007 | The -l option means "literal", that is, treat all characters in the pattern as | |
33008 | standing for themselves. Otherwise the pattern must be a Perl regular | |
33009 | expression. | |
33010 | ||
33011 | The -v option inverts the matching condition. That is, a line is selected if it | |
33012 | does not match the pattern. | |
33013 | ||
33014 | If the location of a zcat command is known from the definition of ZCAT_COMMAND | |
33015 | in Local/Makefile, exigrep automatically passes any file whose name ends in | |
33016 | COMPRESS_SUFFIX through zcat as it searches it. | |
33017 | ||
33018 | ||
33019 | 52.5 Selecting messages by various criteria (exipick) | |
33020 | ----------------------------------------------------- | |
33021 | ||
33022 | John Jetmore's exipick utility is included in the Exim distribution. It lists | |
33023 | messages from the queue according to a variety of criteria. For details of | |
33024 | exipick's facilities, visit the web page at http://www.exim.org/eximwiki/ | |
33025 | ToolExipickManPage or run exipick with the --help option. | |
33026 | ||
33027 | ||
33028 | 52.6 Cycling log files (exicyclog) | |
33029 | ---------------------------------- | |
33030 | ||
33031 | The exicyclog script can be used to cycle (rotate) mainlog and rejectlog files. | |
33032 | This is not necessary if only syslog is being used, or if you are using log | |
33033 | files with datestamps in their names (see section 51.3). Some operating systems | |
33034 | have their own standard mechanisms for log cycling, and these can be used | |
33035 | instead of exicyclog if preferred. There are two command line options for | |
33036 | exicyclog: | |
33037 | ||
33038 | * -k <count> specifies the number of log files to keep, overriding the | |
33039 | default that is set when Exim is built. The default default is 10. | |
33040 | ||
33041 | * -l <path> specifies the log file path, in the same format as Exim's | |
33042 | log_file_path option (for example, "/var/log/exim_%slog"), again overriding | |
33043 | the script's default, which is to find the setting from Exim's | |
33044 | configuration. | |
33045 | ||
33046 | Each time exicyclog is run the file names get "shuffled down" by one. If the | |
33047 | main log file name is mainlog (the default) then when exicyclog is run mainlog | |
33048 | becomes mainlog.01, the previous mainlog.01 becomes mainlog.02 and so on, up to | |
33049 | the limit that is set in the script or by the -k option. Log files whose | |
33050 | numbers exceed the limit are discarded. Reject logs are handled similarly. | |
33051 | ||
33052 | If the limit is greater than 99, the script uses 3-digit numbers such as | |
33053 | mainlog.001, mainlog.002, etc. If you change from a number less than 99 to one | |
33054 | that is greater, or vice versa, you will have to fix the names of any existing | |
33055 | log files. | |
33056 | ||
33057 | If no mainlog file exists, the script does nothing. Files that "drop off" the | |
33058 | end are deleted. All files with numbers greater than 01 are compressed, using a | |
33059 | compression command which is configured by the COMPRESS_COMMAND setting in | |
33060 | Local/Makefile. It is usual to run exicyclog daily from a root crontab entry of | |
33061 | the form | |
33062 | ||
33063 | 1 0 * * * su exim -c /usr/exim/bin/exicyclog | |
33064 | ||
33065 | assuming you have used the name "exim" for the Exim user. You can run exicyclog | |
33066 | as root if you wish, but there is no need. | |
33067 | ||
33068 | ||
33069 | 52.7 Mail statistics (eximstats) | |
33070 | -------------------------------- | |
33071 | ||
33072 | A Perl script called eximstats is provided for extracting statistical | |
33073 | information from log files. The output is either plain text, or HTML. Exim log | |
33074 | files are also supported by the Lire system produced by the LogReport | |
33075 | Foundation http://www.logreport.org. | |
33076 | ||
33077 | The eximstats script has been hacked about quite a bit over time. The latest | |
33078 | version is the result of some extensive revision by Steve Campbell. A lot of | |
33079 | information is given by default, but there are options for suppressing various | |
33080 | parts of it. Following any options, the arguments to the script are a list of | |
33081 | files, which should be main log files. For example: | |
33082 | ||
33083 | eximstats -nr /var/spool/exim/log/mainlog.01 | |
33084 | ||
33085 | By default, eximstats extracts information about the number and volume of | |
33086 | messages received from or delivered to various hosts. The information is sorted | |
33087 | both by message count and by volume, and the top fifty hosts in each category | |
33088 | are listed on the standard output. Similar information, based on email | |
33089 | addresses or domains instead of hosts can be requested by means of various | |
33090 | options. For messages delivered and received locally, similar statistics are | |
33091 | also produced per user. | |
33092 | ||
33093 | The output also includes total counts and statistics about delivery errors, and | |
33094 | histograms showing the number of messages received and deliveries made in each | |
33095 | hour of the day. A delivery with more than one address in its envelope (for | |
33096 | example, an SMTP transaction with more than one RCPT command) is counted as a | |
33097 | single delivery by eximstats. | |
33098 | ||
33099 | Though normally more deliveries than receipts are reported (as messages may | |
33100 | have multiple recipients), it is possible for eximstats to report more messages | |
33101 | received than delivered, even though the queue is empty at the start and end of | |
33102 | the period in question. If an incoming message contains no valid recipients, no | |
33103 | deliveries are recorded for it. A bounce message is handled as an entirely | |
33104 | separate message. | |
33105 | ||
33106 | eximstats always outputs a grand total summary giving the volume and number of | |
33107 | messages received and deliveries made, and the number of hosts involved in each | |
33108 | case. It also outputs the number of messages that were delayed (that is, not | |
33109 | completely delivered at the first attempt), and the number that had at least | |
33110 | one address that failed. | |
33111 | ||
33112 | The remainder of the output is in sections that can be independently disabled | |
33113 | or modified by various options. It consists of a summary of deliveries by | |
33114 | transport, histograms of messages received and delivered per time interval | |
33115 | (default per hour), information about the time messages spent on the queue, a | |
33116 | list of relayed messages, lists of the top fifty sending hosts, local senders, | |
33117 | destination hosts, and destination local users by count and by volume, and a | |
33118 | list of delivery errors that occurred. | |
33119 | ||
33120 | The relay information lists messages that were actually relayed, that is, they | |
33121 | came from a remote host and were directly delivered to some other remote host, | |
33122 | without being processed (for example, for aliasing or forwarding) locally. | |
33123 | ||
33124 | There are quite a few options for eximstats to control exactly what it outputs. | |
33125 | These are documented in the Perl script itself, and can be extracted by running | |
33126 | the command perldoc on the script. For example: | |
33127 | ||
33128 | perldoc /usr/exim/bin/eximstats | |
33129 | ||
33130 | ||
33131 | 52.8 Checking access policy (exim_checkaccess) | |
33132 | ---------------------------------------------- | |
33133 | ||
33134 | The -bh command line argument allows you to run a fake SMTP session with | |
33135 | debugging output, in order to check what Exim is doing when it is applying | |
33136 | policy controls to incoming SMTP mail. However, not everybody is sufficiently | |
33137 | familiar with the SMTP protocol to be able to make full use of -bh, and | |
33138 | sometimes you just want to answer the question "Does this address have access?" | |
33139 | without bothering with any further details. | |
33140 | ||
33141 | The exim_checkaccess utility is a "packaged" version of -bh. It takes two | |
33142 | arguments, an IP address and an email address: | |
33143 | ||
33144 | exim_checkaccess 10.9.8.7 A.User@a.domain.example | |
33145 | ||
33146 | The utility runs a call to Exim with the -bh option, to test whether the given | |
33147 | email address would be accepted in a RCPT command in a TCP/IP connection from | |
33148 | the host with the given IP address. The output of the utility is either the | |
33149 | word "accepted", or the SMTP error response, for example: | |
33150 | ||
33151 | Rejected: | |
33152 | 550 Relay not permitted | |
33153 | ||
33154 | When running this test, the utility uses "<>" as the envelope sender address | |
33155 | for the MAIL command, but you can change this by providing additional options. | |
33156 | These are passed directly to the Exim command. For example, to specify that the | |
33157 | test is to be run with the sender address himself@there.example you can use: | |
33158 | ||
33159 | exim_checkaccess 10.9.8.7 A.User@a.domain.example \ | |
33160 | -f himself@there.example | |
33161 | ||
33162 | Note that these additional Exim command line items must be given after the two | |
33163 | mandatory arguments. | |
33164 | ||
33165 | Because the exim_checkaccess uses -bh, it does not perform callouts while | |
33166 | running its checks. You can run checks that include callouts by using -bhc, but | |
33167 | this is not yet available in a "packaged" form. | |
33168 | ||
33169 | ||
33170 | 52.9 Making DBM files (exim_dbmbuild) | |
33171 | ------------------------------------- | |
33172 | ||
33173 | The exim_dbmbuild program reads an input file containing keys and data in the | |
33174 | format used by the lsearch lookup (see section 9.3). It writes a DBM file using | |
33175 | the lower-cased alias names as keys and the remainder of the information as | |
33176 | data. The lower-casing can be prevented by calling the program with the -nolc | |
33177 | option. | |
33178 | ||
33179 | A terminating zero is included as part of the key string. This is expected by | |
33180 | the dbm lookup type. However, if the option -nozero is given, exim_dbmbuild | |
33181 | creates files without terminating zeroes in either the key strings or the data | |
33182 | strings. The dbmnz lookup type can be used with such files. | |
33183 | ||
33184 | The program requires two arguments: the name of the input file (which can be a | |
33185 | single hyphen to indicate the standard input), and the name of the output file. | |
33186 | It creates the output under a temporary name, and then renames it if all went | |
33187 | well. | |
33188 | ||
33189 | If the native DB interface is in use (USE_DB is set in a compile-time | |
33190 | configuration file - this is common in free versions of Unix) the two file | |
33191 | names must be different, because in this mode the Berkeley DB functions create | |
33192 | a single output file using exactly the name given. For example, | |
33193 | ||
33194 | exim_dbmbuild /etc/aliases /etc/aliases.db | |
33195 | ||
33196 | reads the system alias file and creates a DBM version of it in /etc/aliases.db. | |
33197 | ||
33198 | In systems that use the ndbm routines (mostly proprietary versions of Unix), | |
33199 | two files are used, with the suffixes .dir and .pag. In this environment, the | |
33200 | suffixes are added to the second argument of exim_dbmbuild, so it can be the | |
33201 | same as the first. This is also the case when the Berkeley functions are used | |
33202 | in compatibility mode (though this is not recommended), because in that case it | |
33203 | adds a .db suffix to the file name. | |
33204 | ||
33205 | If a duplicate key is encountered, the program outputs a warning, and when it | |
33206 | finishes, its return code is 1 rather than zero, unless the -noduperr option is | |
33207 | used. By default, only the first of a set of duplicates is used - this makes it | |
33208 | compatible with lsearch lookups. There is an option -lastdup which causes it to | |
33209 | use the data for the last duplicate instead. There is also an option -nowarn, | |
33210 | which stops it listing duplicate keys to stderr. For other errors, where it | |
33211 | doesn't actually make a new file, the return code is 2. | |
33212 | ||
33213 | ||
33214 | 52.10 Finding individual retry times (exinext) | |
33215 | ---------------------------------------------- | |
33216 | ||
33217 | A utility called exinext (mostly a Perl script) provides the ability to fish | |
33218 | specific information out of the retry database. Given a mail domain (or a | |
33219 | complete address), it looks up the hosts for that domain, and outputs any retry | |
33220 | information for the hosts or for the domain. At present, the retry information | |
33221 | is obtained by running exim_dumpdb (see below) and post-processing the output. | |
33222 | For example: | |
33223 | ||
33224 | $ exinext piglet@milne.fict.example | |
33225 | kanga.milne.example:192.168.8.1 error 146: Connection refused | |
33226 | first failed: 21-Feb-1996 14:57:34 | |
33227 | last tried: 21-Feb-1996 14:57:34 | |
33228 | next try at: 21-Feb-1996 15:02:34 | |
33229 | roo.milne.example:192.168.8.3 error 146: Connection refused | |
33230 | first failed: 20-Jan-1996 13:12:08 | |
33231 | last tried: 21-Feb-1996 11:42:03 | |
33232 | next try at: 21-Feb-1996 19:42:03 | |
33233 | past final cutoff time | |
33234 | ||
33235 | You can also give exinext a local part, without a domain, and it will give any | |
33236 | retry information for that local part in your default domain. A message id can | |
33237 | be used to obtain retry information pertaining to a specific message. This | |
33238 | exists only when an attempt to deliver a message to a remote host suffers a | |
33239 | message-specific error (see section 47.2). exinext is not particularly | |
33240 | efficient, but then it is not expected to be run very often. | |
33241 | ||
33242 | The exinext utility calls Exim to find out information such as the location of | |
33243 | the spool directory. The utility has -C and -D options, which are passed on to | |
33244 | the exim commands. The first specifies an alternate Exim configuration file, | |
33245 | and the second sets macros for use within the configuration file. These | |
33246 | features are mainly to help in testing, but might also be useful in | |
33247 | environments where more than one configuration file is in use. | |
33248 | ||
33249 | ||
33250 | 52.11 Hints database maintenance | |
33251 | -------------------------------- | |
33252 | ||
33253 | Three utility programs are provided for maintaining the DBM files that Exim | |
33254 | uses to contain its delivery hint information. Each program requires two | |
33255 | arguments. The first specifies the name of Exim's spool directory, and the | |
33256 | second is the name of the database it is to operate on. These are as follows: | |
33257 | ||
33258 | * retry: the database of retry information | |
33259 | ||
33260 | * wait-<transport name>: databases of information about messages waiting for | |
33261 | remote hosts | |
33262 | ||
33263 | * callout: the callout cache | |
33264 | ||
33265 | * ratelimit: the data for implementing the ratelimit ACL condition | |
33266 | ||
33267 | * misc: other hints data | |
33268 | ||
33269 | The misc database is used for | |
33270 | ||
33271 | * Serializing ETRN runs (when smtp_etrn_serialize is set) | |
33272 | ||
33273 | * Serializing delivery to a specific host (when serialize_hosts is set in an | |
33274 | smtp transport) | |
33275 | ||
33276 | ||
33277 | 52.12 exim_dumpdb | |
33278 | ----------------- | |
33279 | ||
33280 | The entire contents of a database are written to the standard output by the | |
33281 | exim_dumpdb program, which has no options or arguments other than the spool and | |
33282 | database names. For example, to dump the retry database: | |
33283 | ||
33284 | exim_dumpdb /var/spool/exim retry | |
33285 | ||
33286 | Two lines of output are produced for each entry: | |
33287 | ||
33288 | T:mail.ref.example:192.168.242.242 146 77 Connection refused | |
33289 | 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 * | |
33290 | ||
33291 | The first item on the first line is the key of the record. It starts with one | |
33292 | of the letters R, or T, depending on whether it refers to a routing or | |
33293 | transport retry. For a local delivery, the next part is the local address; for | |
33294 | a remote delivery it is the name of the remote host, followed by its failing IP | |
33295 | address (unless retry_include_ip_address is set false on the smtp transport). | |
33296 | If the remote port is not the standard one (port 25), it is added to the IP | |
33297 | address. Then there follows an error code, an additional error code, and a | |
33298 | textual description of the error. | |
33299 | ||
33300 | The three times on the second line are the time of first failure, the time of | |
33301 | the last delivery attempt, and the computed time for the next attempt. The line | |
33302 | ends with an asterisk if the cutoff time for the last retry rule has been | |
33303 | exceeded. | |
33304 | ||
33305 | Each output line from exim_dumpdb for the wait-xxx databases consists of a host | |
33306 | name followed by a list of ids for messages that are or were waiting to be | |
33307 | delivered to that host. If there are a very large number for any one host, | |
33308 | continuation records, with a sequence number added to the host name, may be | |
33309 | seen. The data in these records is often out of date, because a message may be | |
33310 | routed to several alternative hosts, and Exim makes no effort to keep | |
33311 | cross-references. | |
33312 | ||
33313 | ||
33314 | 52.13 exim_tidydb | |
33315 | ----------------- | |
33316 | ||
33317 | The exim_tidydb utility program is used to tidy up the contents of a hints | |
33318 | database. If run with no options, it removes all records that are more than 30 | |
33319 | days old. The age is calculated from the date and time that the record was last | |
33320 | updated. Note that, in the case of the retry database, it is not the time since | |
33321 | the first delivery failure. Information about a host that has been down for | |
33322 | more than 30 days will remain in the database, provided that the record is | |
33323 | updated sufficiently often. | |
33324 | ||
33325 | The cutoff date can be altered by means of the -t option, which must be | |
33326 | followed by a time. For example, to remove all records older than a week from | |
33327 | the retry database: | |
33328 | ||
33329 | exim_tidydb -t 7d /var/spool/exim retry | |
33330 | ||
33331 | Both the wait-xxx and retry databases contain items that involve message ids. | |
33332 | In the former these appear as data in records keyed by host - they were | |
33333 | messages that were waiting for that host - and in the latter they are the keys | |
33334 | for retry information for messages that have suffered certain types of error. | |
33335 | When exim_tidydb is run, a check is made to ensure that message ids in database | |
33336 | records are those of messages that are still on the queue. Message ids for | |
33337 | messages that no longer exist are removed from wait-xxx records, and if this | |
33338 | leaves any records empty, they are deleted. For the retry database, records | |
33339 | whose keys are non-existent message ids are removed. The exim_tidydb utility | |
33340 | outputs comments on the standard output whenever it removes information from | |
33341 | the database. | |
33342 | ||
33343 | Certain records are automatically removed by Exim when they are no longer | |
33344 | needed, but others are not. For example, if all the MX hosts for a domain are | |
33345 | down, a retry record is created for each one. If the primary MX host comes back | |
33346 | first, its record is removed when Exim successfully delivers to it, but the | |
33347 | records for the others remain because Exim has not tried to use those hosts. | |
33348 | ||
33349 | It is important, therefore, to run exim_tidydb periodically on all the hints | |
33350 | databases. You should do this at a quiet time of day, because it requires a | |
33351 | database to be locked (and therefore inaccessible to Exim) while it does its | |
33352 | work. Removing records from a DBM file does not normally make the file smaller, | |
33353 | but all the common DBM libraries are able to re-use the space that is released. | |
33354 | After an initial phase of increasing in size, the databases normally reach a | |
33355 | point at which they no longer get any bigger, as long as they are regularly | |
33356 | tidied. | |
33357 | ||
33358 | Warning: If you never run exim_tidydb, the space used by the hints databases is | |
33359 | likely to keep on increasing. | |
33360 | ||
33361 | ||
33362 | 52.14 exim_fixdb | |
33363 | ---------------- | |
33364 | ||
33365 | The exim_fixdb program is a utility for interactively modifying databases. Its | |
33366 | main use is for testing Exim, but it might also be occasionally useful for | |
33367 | getting round problems in a live system. It has no options, and its interface | |
33368 | is somewhat crude. On entry, it prompts for input with a right angle-bracket. A | |
33369 | key of a database record can then be entered, and the data for that record is | |
33370 | displayed. | |
33371 | ||
33372 | If "d" is typed at the next prompt, the entire record is deleted. For all | |
33373 | except the retry database, that is the only operation that can be carried out. | |
33374 | For the retry database, each field is output preceded by a number, and data for | |
33375 | individual fields can be changed by typing the field number followed by new | |
33376 | data, for example: | |
33377 | ||
33378 | > 4 951102:1000 | |
33379 | ||
33380 | resets the time of the next delivery attempt. Time values are given as a | |
33381 | sequence of digit pairs for year, month, day, hour, and minute. Colons can be | |
33382 | used as optional separators. | |
33383 | ||
33384 | ||
33385 | 52.15 Mailbox maintenance (exim_lock) | |
33386 | ------------------------------------- | |
33387 | ||
33388 | The exim_lock utility locks a mailbox file using the same algorithm as Exim. | |
33389 | For a discussion of locking issues, see section 26.3. Exim_lock can be used to | |
33390 | prevent any modification of a mailbox by Exim or a user agent while | |
33391 | investigating a problem. The utility requires the name of the file as its first | |
33392 | argument. If the locking is successful, the second argument is run as a command | |
33393 | (using C's system() function); if there is no second argument, the value of the | |
33394 | SHELL environment variable is used; if this is unset or empty, /bin/sh is run. | |
33395 | When the command finishes, the mailbox is unlocked and the utility ends. The | |
33396 | following options are available: | |
33397 | ||
33398 | -fcntl | |
33399 | ||
33400 | Use fcntl() locking on the open mailbox. | |
33401 | ||
33402 | -flock | |
33403 | ||
33404 | Use flock() locking on the open mailbox, provided the operating system | |
33405 | supports it. | |
33406 | ||
33407 | -interval | |
33408 | ||
33409 | This must be followed by a number, which is a number of seconds; it sets | |
33410 | the interval to sleep between retries (default 3). | |
33411 | ||
33412 | -lockfile | |
33413 | ||
33414 | Create a lock file before opening the mailbox. | |
33415 | ||
33416 | -mbx | |
33417 | ||
33418 | Lock the mailbox using MBX rules. | |
33419 | ||
33420 | -q | |
33421 | ||
33422 | Suppress verification output. | |
33423 | ||
33424 | -retries | |
33425 | ||
33426 | This must be followed by a number; it sets the number of times to try to | |
33427 | get the lock (default 10). | |
33428 | ||
33429 | -restore_time | |
33430 | ||
33431 | This option causes exim_lock to restore the modified and read times to the | |
33432 | locked file before exiting. This allows you to access a locked mailbox (for | |
33433 | example, to take a backup copy) without disturbing the times that the user | |
33434 | subsequently sees. | |
33435 | ||
33436 | -timeout | |
33437 | ||
33438 | This must be followed by a number, which is a number of seconds; it sets a | |
33439 | timeout to be used with a blocking fcntl() lock. If it is not set (the | |
33440 | default), a non-blocking call is used. | |
33441 | ||
33442 | -v | |
33443 | ||
33444 | Generate verbose output. | |
33445 | ||
33446 | If none of -fcntl, -flock, -lockfile or -mbx are given, the default is to | |
33447 | create a lock file and also to use fcntl() locking on the mailbox, which is the | |
33448 | same as Exim's default. The use of -flock or -fcntl requires that the file be | |
33449 | writeable; the use of -lockfile requires that the directory containing the file | |
33450 | be writeable. Locking by lock file does not last for ever; Exim assumes that a | |
33451 | lock file is expired if it is more than 30 minutes old. | |
33452 | ||
33453 | The -mbx option can be used with either or both of -fcntl or -flock. It assumes | |
33454 | -fcntl by default. MBX locking causes a shared lock to be taken out on the open | |
33455 | mailbox, and an exclusive lock on the file /tmp/.n.m where n and m are the | |
33456 | device number and inode number of the mailbox file. When the locking is | |
33457 | released, if an exclusive lock can be obtained for the mailbox, the file in / | |
33458 | tmp is deleted. | |
33459 | ||
33460 | The default output contains verification of the locking that takes place. The | |
33461 | -v option causes some additional information to be given. The -q option | |
33462 | suppresses all output except error messages. | |
33463 | ||
33464 | A command such as | |
33465 | ||
33466 | exim_lock /var/spool/mail/spqr | |
33467 | ||
33468 | runs an interactive shell while the file is locked, whereas | |
33469 | ||
33470 | exim_lock -q /var/spool/mail/spqr <<End | |
33471 | <some commands> | |
33472 | End | |
33473 | ||
33474 | runs a specific non-interactive sequence of commands while the file is locked, | |
33475 | suppressing all verification output. A single command can be run by a command | |
33476 | such as | |
33477 | ||
33478 | exim_lock -q /var/spool/mail/spqr \ | |
33479 | "cp /var/spool/mail/spqr /some/where" | |
33480 | ||
33481 | Note that if a command is supplied, it must be entirely contained within the | |
33482 | second argument - hence the quotes. | |
33483 | ||
33484 | ||
33485 | ||
33486 | =============================================================================== | |
33487 | 53. THE EXIM MONITOR | |
33488 | ||
33489 | The Exim monitor is an application which displays in an X window information | |
33490 | about the state of Exim's queue and what Exim is doing. An admin user can | |
33491 | perform certain operations on messages from this GUI interface; however all | |
33492 | such facilities are also available from the command line, and indeed, the | |
33493 | monitor itself makes use of the command line to perform any actions requested. | |
33494 | ||
33495 | ||
33496 | 53.1 Running the monitor | |
33497 | ------------------------ | |
33498 | ||
33499 | The monitor is started by running the script called eximon. This is a shell | |
33500 | script that sets up a number of environment variables, and then runs the binary | |
33501 | called eximon.bin. The default appearance of the monitor window can be changed | |
33502 | by editing the Local/eximon.conf file created by editing exim_monitor/EDITME. | |
33503 | Comments in that file describe what the various parameters are for. | |
33504 | ||
33505 | The parameters that get built into the eximon script can be overridden for a | |
33506 | particular invocation by setting up environment variables of the same names, | |
33507 | preceded by "EXIMON_". For example, a shell command such as | |
33508 | ||
33509 | EXIMON_LOG_DEPTH=400 eximon | |
33510 | ||
33511 | (in a Bourne-compatible shell) runs eximon with an overriding setting of the | |
33512 | LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it | |
33513 | overrides the Exim log file configuration. This makes it possible to have | |
33514 | eximon tailing log data that is written to syslog, provided that MAIL.INFO | |
33515 | syslog messages are routed to a file on the local host. | |
33516 | ||
33517 | X resources can be used to change the appearance of the window in the normal | |
33518 | way. For example, a resource setting of the form | |
33519 | ||
33520 | Eximon*background: gray94 | |
33521 | ||
33522 | changes the colour of the background to light grey rather than white. The | |
33523 | stripcharts are drawn with both the data lines and the reference lines in | |
33524 | black. This means that the reference lines are not visible when on top of the | |
33525 | data. However, their colour can be changed by setting a resource called | |
33526 | "highlight" (an odd name, but that's what the Athena stripchart widget uses). | |
33527 | For example, if your X server is running Unix, you could set up lighter | |
33528 | reference lines in the stripcharts by obeying | |
33529 | ||
33530 | xrdb -merge <<End | |
33531 | Eximon*highlight: gray | |
33532 | End | |
33533 | ||
33534 | In order to see the contents of messages on the queue, and to operate on them, | |
33535 | eximon must either be run as root or by an admin user. | |
33536 | ||
33537 | The command-line parameters of eximon are passed to eximon.bin and may contain | |
33538 | X11 resource parameters interpreted by the X11 library. In addition, if the | |
33539 | first parameter starts with the string "gdb" then it is removed and the binary | |
33540 | is invoked under gdb (the parameter is used as the gdb command-name, so | |
33541 | versioned variants of gdb can be invoked). | |
33542 | ||
33543 | The monitor's window is divided into three parts. The first contains one or | |
33544 | more stripcharts and two action buttons, the second contains a "tail" of the | |
33545 | main log file, and the third is a display of the queue of messages awaiting | |
33546 | delivery, with two more action buttons. The following sections describe these | |
33547 | different parts of the display. | |
33548 | ||
33549 | ||
33550 | 53.2 The stripcharts | |
33551 | -------------------- | |
33552 | ||
33553 | The first stripchart is always a count of messages on the queue. Its name can | |
33554 | be configured by setting QUEUE_STRIPCHART_NAME in the Local/eximon.conf file. | |
33555 | The remaining stripcharts are defined in the configuration script by regular | |
33556 | expression matches on log file entries, making it possible to display, for | |
33557 | example, counts of messages delivered to certain hosts or using certain | |
33558 | transports. The supplied defaults display counts of received and delivered | |
33559 | messages, and of local and SMTP deliveries. The default period between | |
33560 | stripchart updates is one minute; this can be adjusted by a parameter in the | |
33561 | Local/eximon.conf file. | |
33562 | ||
33563 | The stripchart displays rescale themselves automatically as the value they are | |
33564 | displaying changes. There are always 10 horizontal lines in each chart; the | |
33565 | title string indicates the value of each division when it is greater than one. | |
33566 | For example, "x2" means that each division represents a value of 2. | |
33567 | ||
33568 | It is also possible to have a stripchart which shows the percentage fullness of | |
33569 | a particular disk partition, which is useful when local deliveries are confined | |
33570 | to a single partition. | |
33571 | ||
33572 | This relies on the availability of the statvfs() function or equivalent in the | |
33573 | operating system. Most, but not all versions of Unix that support Exim have | |
33574 | this. For this particular stripchart, the top of the chart always represents | |
33575 | 100%, and the scale is given as "x10%". This chart is configured by setting | |
33576 | SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the Local/eximon.conf | |
33577 | file. | |
33578 | ||
33579 | ||
33580 | 53.3 Main action buttons | |
33581 | ------------------------ | |
33582 | ||
33583 | Below the stripcharts there is an action button for quitting the monitor. Next | |
33584 | to this is another button marked "Size". They are placed here so that shrinking | |
33585 | the window to its default minimum size leaves just the queue count stripchart | |
33586 | and these two buttons visible. Pressing the "Size" button causes the window to | |
33587 | expand to its maximum size, unless it is already at the maximum, in which case | |
33588 | it is reduced to its minimum. | |
33589 | ||
33590 | When expanding to the maximum, if the window cannot be fully seen where it | |
33591 | currently is, it is moved back to where it was the last time it was at full | |
33592 | size. When it is expanding from its minimum size, the old position is | |
33593 | remembered, and next time it is reduced to the minimum it is moved back there. | |
33594 | ||
33595 | The idea is that you can keep a reduced window just showing one or two | |
33596 | stripcharts at a convenient place on your screen, easily expand it to show the | |
33597 | full window when required, and just as easily put it back to what it was. The | |
33598 | idea is copied from what the twm window manager does for its f.fullzoom action. | |
33599 | The minimum size of the window can be changed by setting the MIN_HEIGHT and | |
33600 | MIN_WIDTH values in Local/eximon.conf. | |
33601 | ||
33602 | Normally, the monitor starts up with the window at its full size, but it can be | |
33603 | built so that it starts up with the window at its smallest size, by setting | |
33604 | START_SMALL=yes in Local/eximon.conf. | |
33605 | ||
33606 | ||
33607 | 53.4 The log display | |
33608 | -------------------- | |
33609 | ||
33610 | The second section of the window is an area in which a display of the tail of | |
33611 | the main log is maintained. To save space on the screen, the timestamp on each | |
33612 | log line is shortened by removing the date and, if log_timezone is set, the | |
33613 | timezone. The log tail is not available when the only destination for logging | |
33614 | data is syslog, unless the syslog lines are routed to a local file whose name | |
33615 | is passed to eximon via the EXIMON_LOG_FILE_PATH environment variable. | |
33616 | ||
33617 | The log sub-window has a scroll bar at its lefthand side which can be used to | |
33618 | move back to look at earlier text, and the up and down arrow keys also have a | |
33619 | scrolling effect. The amount of log that is kept depends on the setting of | |
33620 | LOG_BUFFER in Local/eximon.conf, which specifies the amount of memory to use. | |
33621 | When this is full, the earlier 50% of data is discarded - this is much more | |
33622 | efficient than throwing it away line by line. The sub-window also has a | |
33623 | horizontal scroll bar for accessing the ends of long log lines. This is the | |
33624 | only means of horizontal scrolling; the right and left arrow keys are not | |
33625 | available. Text can be cut from this part of the window using the mouse in the | |
33626 | normal way. The size of this subwindow is controlled by parameters in the | |
33627 | configuration file Local/eximon.conf. | |
33628 | ||
33629 | Searches of the text in the log window can be carried out by means of the ^R | |
33630 | and ^S keystrokes, which default to a reverse and a forward search, | |
33631 | respectively. The search covers only the text that is displayed in the window. | |
33632 | It cannot go further back up the log. | |
33633 | ||
33634 | The point from which the search starts is indicated by a caret marker. This is | |
33635 | normally at the end of the text in the window, but can be positioned explicitly | |
33636 | by pointing and clicking with the left mouse button, and is moved automatically | |
33637 | by a successful search. If new text arrives in the window when it is scrolled | |
33638 | back, the caret remains where it is, but if the window is not scrolled back, | |
33639 | the caret is moved to the end of the new text. | |
33640 | ||
33641 | Pressing ^R or ^S pops up a window into which the search text can be typed. | |
33642 | There are buttons for selecting forward or reverse searching, for carrying out | |
33643 | the search, and for cancelling. If the "Search" button is pressed, the search | |
33644 | happens and the window remains so that further searches can be done. If the | |
33645 | "Return" key is pressed, a single search is done and the window is closed. If ^ | |
33646 | C is typed the search is cancelled. | |
33647 | ||
33648 | The searching facility is implemented using the facilities of the Athena text | |
33649 | widget. By default this pops up a window containing both "search" and "replace" | |
33650 | options. In order to suppress the unwanted "replace" portion for eximon, a | |
33651 | modified version of the TextPop widget is distributed with Exim. However, the | |
33652 | linkers in BSDI and HP-UX seem unable to handle an externally provided version | |
33653 | of TextPop when the remaining parts of the text widget come from the standard | |
33654 | libraries. The compile-time option EXIMON_TEXTPOP can be unset to cut out the | |
33655 | modified TextPop, making it possible to build Eximon on these systems, at the | |
33656 | expense of having unwanted items in the search popup window. | |
33657 | ||
33658 | ||
33659 | 53.5 The queue display | |
33660 | ---------------------- | |
33661 | ||
33662 | The bottom section of the monitor window contains a list of all messages that | |
33663 | are on the queue, which includes those currently being received or delivered, | |
33664 | as well as those awaiting delivery. The size of this subwindow is controlled by | |
33665 | parameters in the configuration file Local/eximon.conf, and the frequency at | |
33666 | which it is updated is controlled by another parameter in the same file - the | |
33667 | default is 5 minutes, since queue scans can be quite expensive. However, there | |
33668 | is an "Update" action button just above the display which can be used to force | |
33669 | an update of the queue display at any time. | |
33670 | ||
33671 | When a host is down for some time, a lot of pending mail can build up for it, | |
33672 | and this can make it hard to deal with other messages on the queue. To help | |
33673 | with this situation there is a button next to "Update" called "Hide". If | |
33674 | pressed, a dialogue box called "Hide addresses ending with" is put up. If you | |
33675 | type anything in here and press "Return", the text is added to a chain of such | |
33676 | texts, and if every undelivered address in a message matches at least one of | |
33677 | the texts, the message is not displayed. | |
33678 | ||
33679 | If there is an address that does not match any of the texts, all the addresses | |
33680 | are displayed as normal. The matching happens on the ends of addresses so, for | |
33681 | example, cam.ac.uk specifies all addresses in Cambridge, while | |
33682 | xxx@foo.com.example specifies just one specific address. When any hiding has | |
33683 | been set up, a button called "Unhide" is displayed. If pressed, it cancels all | |
33684 | hiding. Also, to ensure that hidden messages do not get forgotten, a hide | |
33685 | request is automatically cancelled after one hour. | |
33686 | ||
33687 | While the dialogue box is displayed, you can't press any buttons or do anything | |
33688 | else to the monitor window. For this reason, if you want to cut text from the | |
33689 | queue display to use in the dialogue box, you have to do the cutting before | |
33690 | pressing the "Hide" button. | |
33691 | ||
33692 | The queue display contains, for each unhidden queued message, the length of | |
33693 | time it has been on the queue, the size of the message, the message id, the | |
33694 | message sender, and the first undelivered recipient, all on one line. If it is | |
33695 | a bounce message, the sender is shown as "<>". If there is more than one | |
33696 | recipient to which the message has not yet been delivered, subsequent ones are | |
33697 | listed on additional lines, up to a maximum configured number, following which | |
33698 | an ellipsis is displayed. Recipients that have already received the message are | |
33699 | not shown. | |
33700 | ||
33701 | If a message is frozen, an asterisk is displayed at the left-hand side. | |
33702 | ||
33703 | The queue display has a vertical scroll bar, and can also be scrolled by means | |
33704 | of the arrow keys. Text can be cut from it using the mouse in the normal way. | |
33705 | The text searching facilities, as described above for the log window, are also | |
33706 | available, but the caret is always moved to the end of the text when the queue | |
33707 | display is updated. | |
33708 | ||
33709 | ||
33710 | 53.6 The queue menu | |
33711 | ------------------- | |
33712 | ||
33713 | If the shift key is held down and the left button is clicked when the mouse | |
33714 | pointer is over the text for any message, an action menu pops up, and the first | |
33715 | line of the queue display for the message is highlighted. This does not affect | |
33716 | any selected text. | |
33717 | ||
33718 | If you want to use some other event for popping up the menu, you can set the | |
33719 | MENU_EVENT parameter in Local/eximon.conf to change the default, or set | |
33720 | EXIMON_MENU_EVENT in the environment before starting the monitor. The value set | |
33721 | in this parameter is a standard X event description. For example, to run eximon | |
33722 | using ctrl rather than shift you could use | |
33723 | ||
33724 | EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon | |
33725 | ||
33726 | The title of the menu is the message id, and it contains entries which act as | |
33727 | follows: | |
33728 | ||
33729 | * message log: The contents of the message log for the message are displayed | |
33730 | in a new text window. | |
33731 | ||
33732 | * headers: Information from the spool file that contains the envelope | |
33733 | information and headers is displayed in a new text window. See chapter 55 | |
33734 | for a description of the format of spool files. | |
33735 | ||
33736 | * body: The contents of the spool file containing the body of the message are | |
33737 | displayed in a new text window. There is a default limit of 20,000 bytes to | |
33738 | the amount of data displayed. This can be changed by setting the BODY_MAX | |
33739 | option at compile time, or the EXIMON_BODY_MAX option at run time. | |
33740 | ||
33741 | * deliver message: A call to Exim is made using the -M option to request | |
33742 | delivery of the message. This causes an automatic thaw if the message is | |
33743 | frozen. The -v option is also set, and the output from Exim is displayed in | |
33744 | a new text window. The delivery is run in a separate process, to avoid | |
33745 | holding up the monitor while the delivery proceeds. | |
33746 | ||
33747 | * freeze message: A call to Exim is made using the -Mf option to request that | |
33748 | the message be frozen. | |
33749 | ||
33750 | * thaw message: A call to Exim is made using the -Mt option to request that | |
33751 | the message be thawed. | |
33752 | ||
33753 | * give up on msg: A call to Exim is made using the -Mg option to request that | |
33754 | Exim gives up trying to deliver the message. A bounce message is generated | |
33755 | for any remaining undelivered addresses. | |
33756 | ||
33757 | * remove message: A call to Exim is made using the -Mrm option to request | |
33758 | that the message be deleted from the system without generating a bounce | |
33759 | message. | |
33760 | ||
33761 | * add recipient: A dialog box is displayed into which a recipient address can | |
33762 | be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter | |
33763 | is set in Local/eximon.conf, the address is qualified with that domain. | |
33764 | Otherwise it must be entered as a fully qualified address. Pressing RETURN | |
33765 | causes a call to Exim to be made using the -Mar option to request that an | |
33766 | additional recipient be added to the message, unless the entry box is | |
33767 | empty, in which case no action is taken. | |
33768 | ||
33769 | * mark delivered: A dialog box is displayed into which a recipient address | |
33770 | can be typed. If the address is not qualified and the QUALIFY_DOMAIN | |
33771 | parameter is set in Local/eximon.conf, the address is qualified with that | |
33772 | domain. Otherwise it must be entered as a fully qualified address. Pressing | |
33773 | RETURN causes a call to Exim to be made using the -Mmd option to mark the | |
33774 | given recipient address as already delivered, unless the entry box is | |
33775 | empty, in which case no action is taken. | |
33776 | ||
33777 | * mark all delivered: A call to Exim is made using the -Mmad option to mark | |
33778 | all recipient addresses as already delivered. | |
33779 | ||
33780 | * edit sender: A dialog box is displayed initialized with the current | |
33781 | sender's address. Pressing RETURN causes a call to Exim to be made using | |
33782 | the -Mes option to replace the sender address, unless the entry box is | |
33783 | empty, in which case no action is taken. If you want to set an empty sender | |
33784 | (as in bounce messages), you must specify it as "<>". Otherwise, if the | |
33785 | address is not qualified and the QUALIFY_DOMAIN parameter is set in Local/ | |
33786 | eximon.conf, the address is qualified with that domain. | |
33787 | ||
33788 | When a delivery is forced, a window showing the -v output is displayed. In | |
33789 | other cases when a call to Exim is made, if there is any output from Exim (in | |
33790 | particular, if the command fails) a window containing the command and the | |
33791 | output is displayed. Otherwise, the results of the action are normally apparent | |
33792 | from the log and queue displays. However, if you set ACTION_OUTPUT=yes in Local | |
33793 | /eximon.conf, a window showing the Exim command is always opened, even if no | |
33794 | output is generated. | |
33795 | ||
33796 | The queue display is automatically updated for actions such as freezing and | |
33797 | thawing, unless ACTION_QUEUE_UPDATE=no has been set in Local/eximon.conf. In | |
33798 | this case the "Update" button has to be used to force an update of the display | |
33799 | after one of these actions. | |
33800 | ||
33801 | In any text window that is displayed as result of a menu action, the normal | |
33802 | cut-and-paste facility is available, and searching can be carried out using ^R | |
33803 | and ^S, as described above for the log tail window. | |
33804 | ||
33805 | ||
33806 | ||
33807 | =============================================================================== | |
33808 | 54. SECURITY CONSIDERATIONS | |
33809 | ||
33810 | This chapter discusses a number of issues concerned with security, some of | |
33811 | which are also covered in other parts of this manual. | |
33812 | ||
33813 | For reasons that this author does not understand, some people have promoted | |
33814 | Exim as a "particularly secure" mailer. Perhaps it is because of the existence | |
33815 | of this chapter in the documentation. However, the intent of the chapter is | |
33816 | simply to describe the way Exim works in relation to certain security concerns, | |
33817 | not to make any specific claims about the effectiveness of its security as | |
33818 | compared with other MTAs. | |
33819 | ||
33820 | What follows is a description of the way Exim is supposed to be. Best efforts | |
33821 | have been made to try to ensure that the code agrees with the theory, but an | |
33822 | absence of bugs can never be guaranteed. Any that are reported will get fixed | |
33823 | as soon as possible. | |
33824 | ||
33825 | ||
33826 | 54.1 Building a more "hardened" Exim | |
33827 | ------------------------------------ | |
33828 | ||
33829 | There are a number of build-time options that can be set in Local/Makefile to | |
33830 | create Exim binaries that are "harder" to attack, in particular by a rogue Exim | |
33831 | administrator who does not have the root password, or by someone who has | |
33832 | penetrated the Exim (but not the root) account. These options are as follows: | |
33833 | ||
33834 | * ALT_CONFIG_PREFIX can be set to a string that is required to match the | |
33835 | start of any file names used with the -C option. When it is set, these file | |
33836 | names are also not allowed to contain the sequence "/../". (However, if the | |
33837 | value of the -C option is identical to the value of CONFIGURE_FILE in Local | |
33838 | /Makefile, Exim ignores -C and proceeds as usual.) There is no default | |
33839 | setting for ALT_CONFIG_PREFIX. | |
33840 | ||
33841 | If the permitted configuration files are confined to a directory to which | |
33842 | only root has access, this guards against someone who has broken into the | |
33843 | Exim account from running a privileged Exim with an arbitrary configuration | |
33844 | file, and using it to break into other accounts. | |
33845 | ||
33846 | * If a non-trusted configuration file (i.e. not the default configuration | |
33847 | file or one which is trusted by virtue of being listed in the | |
33848 | TRUSTED_CONFIG_LIST file) is specified with -C, or if macros are given with | |
33849 | -D (but see the next item), then root privilege is retained only if the | |
33850 | caller of Exim is root. This locks out the possibility of testing a | |
33851 | configuration using -C right through message reception and delivery, even | |
33852 | if the caller is root. The reception works, but by that time, Exim is | |
33853 | running as the Exim user, so when it re-execs to regain privilege for the | |
33854 | delivery, the use of -C causes privilege to be lost. However, root can test | |
33855 | reception and delivery using two separate commands. | |
33856 | ||
33857 | * The WHITELIST_D_MACROS build option declares some macros to be safe to | |
33858 | override with -D if the real uid is one of root, the Exim run-time user or | |
33859 | the CONFIGURE_OWNER, if defined. The potential impact of this option is | |
33860 | limited by requiring the run-time value supplied to -D to match a regex | |
33861 | that errs on the restrictive side. Requiring build-time selection of safe | |
33862 | macros is onerous but this option is intended solely as a transition | |
33863 | mechanism to permit previously-working configurations to continue to work | |
33864 | after release 4.73. | |
33865 | ||
33866 | * If DISABLE_D_OPTION is defined, the use of the -D command line option is | |
33867 | disabled. | |
33868 | ||
33869 | * FIXED_NEVER_USERS can be set to a colon-separated list of users that are | |
33870 | never to be used for any deliveries. This is like the never_users runtime | |
33871 | option, but it cannot be overridden; the runtime option adds additional | |
33872 | users to the list. The default setting is "root"; this prevents a non-root | |
33873 | user who is permitted to modify the runtime file from using Exim as a way | |
33874 | to get root. | |
33875 | ||
33876 | ||
33877 | 54.2 Root privilege | |
33878 | ------------------- | |
33879 | ||
33880 | The Exim binary is normally setuid to root, which means that it gains root | |
33881 | privilege (runs as root) when it starts execution. In some special cases (for | |
33882 | example, when the daemon is not in use and there are no local deliveries), it | |
33883 | may be possible to run Exim setuid to some user other than root. This is | |
33884 | discussed in the next section. However, in most installations, root privilege | |
33885 | is required for two things: | |
33886 | ||
33887 | * To set up a socket connected to the standard SMTP port (25) when | |
33888 | initialising the listening daemon. If Exim is run from inetd, this | |
33889 | privileged action is not required. | |
33890 | ||
33891 | * To be able to change uid and gid in order to read users' .forward files and | |
33892 | perform local deliveries as the receiving user or as specified in the | |
33893 | configuration. | |
33894 | ||
33895 | It is not necessary to be root to do any of the other things Exim does, such as | |
33896 | receiving messages and delivering them externally over SMTP, and it is | |
33897 | obviously more secure if Exim does not run as root except when necessary. For | |
33898 | this reason, a user and group for Exim to use must be defined in Local/Makefile | |
33899 | . These are known as "the Exim user" and "the Exim group". Their values can be | |
33900 | changed by the run time configuration, though this is not recommended. Often a | |
33901 | user called exim is used, but some sites use mail or another user name | |
33902 | altogether. | |
33903 | ||
33904 | Exim uses setuid() whenever it gives up root privilege. This is a permanent | |
33905 | abdication; the process cannot regain root afterwards. Prior to release 4.00, | |
33906 | seteuid() was used in some circumstances, but this is no longer the case. | |
33907 | ||
33908 | After a new Exim process has interpreted its command line options, it changes | |
33909 | uid and gid in the following cases: | |
33910 | ||
33911 | * If the -C option is used to specify an alternate configuration file, or if | |
33912 | the -D option is used to define macro values for the configuration, and the | |
33913 | calling process is not running as root, the uid and gid are changed to | |
33914 | those of the calling process. However, if DISABLE_D_OPTION is defined in | |
33915 | Local/Makefile, the -D option may not be used at all. If WHITELIST_D_MACROS | |
33916 | is defined in Local/Makefile, then some macro values can be supplied if the | |
33917 | calling process is running as root, the Exim run-time user or | |
33918 | CONFIGURE_OWNER, if defined. | |
33919 | ||
33920 | * If the expansion test option (-be) or one of the filter testing options ( | |
33921 | -bf or -bF) are used, the uid and gid are changed to those of the calling | |
33922 | process. | |
33923 | ||
33924 | * If the process is not a daemon process or a queue runner process or a | |
33925 | delivery process or a process for testing address routing (started with -bt | |
33926 | ), the uid and gid are changed to the Exim user and group. This means that | |
33927 | Exim always runs under its own uid and gid when receiving messages. This | |
33928 | also applies when testing address verification (the -bv option) and testing | |
33929 | incoming message policy controls (the -bh option). | |
33930 | ||
33931 | * For a daemon, queue runner, delivery, or address testing process, the uid | |
33932 | remains as root at this stage, but the gid is changed to the Exim group. | |
33933 | ||
33934 | The processes that initially retain root privilege behave as follows: | |
33935 | ||
33936 | * A daemon process changes the gid to the Exim group and the uid to the Exim | |
33937 | user after setting up one or more listening sockets. The initgroups() | |
33938 | function is called, so that if the Exim user is in any additional groups, | |
33939 | they will be used during message reception. | |
33940 | ||
33941 | * A queue runner process retains root privilege throughout its execution. Its | |
33942 | job is to fork a controlled sequence of delivery processes. | |
33943 | ||
33944 | * A delivery process retains root privilege throughout most of its execution, | |
33945 | but any actual deliveries (that is, the transports themselves) are run in | |
33946 | subprocesses which always change to a non-root uid and gid. For local | |
33947 | deliveries this is typically the uid and gid of the owner of the mailbox; | |
33948 | for remote deliveries, the Exim uid and gid are used. Once all the delivery | |
33949 | subprocesses have been run, a delivery process changes to the Exim uid and | |
33950 | gid while doing post-delivery tidying up such as updating the retry | |
33951 | database and generating bounce and warning messages. | |
33952 | ||
33953 | While the recipient addresses in a message are being routed, the delivery | |
33954 | process runs as root. However, if a user's filter file has to be processed, | |
33955 | this is done in a subprocess that runs under the individual user's uid and | |
33956 | gid. A system filter is run as root unless system_filter_user is set. | |
33957 | ||
33958 | * A process that is testing addresses (the -bt option) runs as root so that | |
33959 | the routing is done in the same environment as a message delivery. | |
33960 | ||
33961 | ||
33962 | 54.3 Running Exim without privilege | |
33963 | ----------------------------------- | |
33964 | ||
33965 | Some installations like to run Exim in an unprivileged state for more of its | |
33966 | operation, for added security. Support for this mode of operation is provided | |
33967 | by the global option deliver_drop_privilege. When this is set, the uid and gid | |
33968 | are changed to the Exim user and group at the start of a delivery process (and | |
33969 | also queue runner and address testing processes). This means that address | |
33970 | routing is no longer run as root, and the deliveries themselves cannot change | |
33971 | to any other uid. | |
33972 | ||
33973 | Leaving the binary setuid to root, but setting deliver_drop_privilege means | |
33974 | that the daemon can still be started in the usual way, and it can respond | |
33975 | correctly to SIGHUP because the re-invocation regains root privilege. | |
33976 | ||
33977 | An alternative approach is to make Exim setuid to the Exim user and also setgid | |
33978 | to the Exim group. If you do this, the daemon must be started from a root | |
33979 | process. (Calling Exim from a root process makes it behave in the way it does | |
33980 | when it is setuid root.) However, the daemon cannot restart itself after a | |
33981 | SIGHUP signal because it cannot regain privilege. | |
33982 | ||
33983 | It is still useful to set deliver_drop_privilege in this case, because it stops | |
33984 | Exim from trying to re-invoke itself to do a delivery after a message has been | |
33985 | received. Such a re-invocation is a waste of resources because it has no | |
33986 | effect. | |
33987 | ||
33988 | If restarting the daemon is not an issue (for example, if mua_wrapper is set, | |
33989 | or inetd is being used instead of a daemon), having the binary setuid to the | |
33990 | Exim user seems a clean approach, but there is one complication: | |
33991 | ||
33992 | In this style of operation, Exim is running with the real uid and gid set to | |
33993 | those of the calling process, and the effective uid/gid set to Exim's values. | |
33994 | Ideally, any association with the calling process' uid/gid should be dropped, | |
33995 | that is, the real uid/gid should be reset to the effective values so as to | |
33996 | discard any privileges that the caller may have. While some operating systems | |
33997 | have a function that permits this action for a non-root effective uid, quite a | |
33998 | number of them do not. Because of this lack of standardization, Exim does not | |
33999 | address this problem at this time. | |
34000 | ||
34001 | For this reason, the recommended approach for "mostly unprivileged" running is | |
34002 | to keep the Exim binary setuid to root, and to set deliver_drop_privilege. This | |
34003 | also has the advantage of allowing a daemon to be used in the most | |
34004 | straightforward way. | |
34005 | ||
34006 | If you configure Exim not to run delivery processes as root, there are a number | |
34007 | of restrictions on what you can do: | |
34008 | ||
34009 | * You can deliver only as the Exim user/group. You should explicitly use the | |
34010 | user and group options to override routers or local transports that | |
34011 | normally deliver as the recipient. This makes sure that configurations that | |
34012 | work in this mode function the same way in normal mode. Any implicit or | |
34013 | explicit specification of another user causes an error. | |
34014 | ||
34015 | * Use of .forward files is severely restricted, such that it is usually not | |
34016 | worthwhile to include them in the configuration. | |
34017 | ||
34018 | * Users who wish to use .forward would have to make their home directory and | |
34019 | the file itself accessible to the Exim user. Pipe and append-to-file | |
34020 | entries, and their equivalents in Exim filters, cannot be used. While they | |
34021 | could be enabled in the Exim user's name, that would be insecure and not | |
34022 | very useful. | |
34023 | ||
34024 | * Unless the local user mailboxes are all owned by the Exim user (possible in | |
34025 | some POP3 or IMAP-only environments): | |
34026 | ||
34027 | 1. They must be owned by the Exim group and be writeable by that group. | |
34028 | This implies you must set mode in the appendfile configuration, as well | |
34029 | as the mode of the mailbox files themselves. | |
34030 | ||
34031 | 2. You must set no_check_owner, since most or all of the files will not be | |
34032 | owned by the Exim user. | |
34033 | ||
34034 | 3. You must set file_must_exist, because Exim cannot set the owner | |
34035 | correctly on a newly created mailbox when unprivileged. This also | |
34036 | implies that new mailboxes need to be created manually. | |
34037 | ||
34038 | These restrictions severely restrict what can be done in local deliveries. | |
34039 | However, there are no restrictions on remote deliveries. If you are running a | |
34040 | gateway host that does no local deliveries, setting deliver_drop_privilege | |
34041 | gives more security at essentially no cost. | |
34042 | ||
34043 | If you are using the mua_wrapper facility (see chapter 50), | |
34044 | deliver_drop_privilege is forced to be true. | |
34045 | ||
34046 | ||
34047 | 54.4 Delivering to local files | |
34048 | ------------------------------ | |
34049 | ||
34050 | Full details of the checks applied by appendfile before it writes to a file are | |
34051 | given in chapter 26. | |
34052 | ||
34053 | ||
34054 | 54.5 Running local commands | |
34055 | --------------------------- | |
34056 | ||
34057 | There are a number of ways in which an administrator can configure Exim to run | |
34058 | commands based upon received, untrustworthy, data. Further, in some | |
34059 | configurations a user who can control a .forward file can also arrange to run | |
34060 | commands. Configuration to check includes, but is not limited to: | |
34061 | ||
34062 | * Use of use_shell in the pipe transport: various forms of shell command | |
34063 | injection may be possible with this option present. It is dangerous and | |
34064 | should be used only with considerable caution. Consider constraints which | |
34065 | whitelist allowed characters in a variable which is to be used in a pipe | |
34066 | transport that has use_shell enabled. | |
34067 | ||
34068 | * A number of options such as forbid_filter_run, forbid_filter_perl, | |
34069 | forbid_filter_dlfunc and so forth which restrict facilities available to | |
34070 | .forward files in a redirect router. If Exim is running on a central mail | |
34071 | hub to which ordinary users do not have shell access, but home directories | |
34072 | are NFS mounted (for instance) then administrators should review the list | |
34073 | of these forbid options available, and should bear in mind that the options | |
34074 | that may need forbidding can change as new features are added between | |
34075 | releases. | |
34076 | ||
34077 | * The ${run...} expansion item does not use a shell by default, but | |
34078 | administrators can configure use of /bin/sh as part of the command. Such | |
34079 | invocations should be viewed with prejudicial suspicion. | |
34080 | ||
34081 | * Administrators who use embedded Perl are advised to explore how Perl's | |
34082 | taint checking might apply to their usage. | |
34083 | ||
34084 | * Use of ${expand...} is somewhat analagous to shell's eval builtin and | |
34085 | administrators are well advised to view its use with suspicion, in case | |
34086 | (for instance) it allows a local-part to contain embedded Exim directives. | |
34087 | ||
34088 | * Use of ${match_local_part...} and friends becomes more dangerous if Exim | |
34089 | was built with EXPAND_LISTMATCH_RHS defined: the second string in each can | |
34090 | reference arbitrary lists and files, rather than just being a list of | |
34091 | opaque strings. The EXPAND_LISTMATCH_RHS option was added and set false by | |
34092 | default because of real-world security vulnerabilities caused by its use | |
34093 | with untrustworthy data injected in, for SQL injection attacks. Consider | |
34094 | the use of the inlisti expansion condition instead. | |
34095 | ||
34096 | ||
34097 | 54.6 Trust in configuration data | |
34098 | -------------------------------- | |
34099 | ||
34100 | If configuration data for Exim can come from untrustworthy sources, there are | |
34101 | some issues to be aware of: | |
34102 | ||
34103 | * Use of ${expand...} may provide a path for shell injection attacks. | |
34104 | ||
34105 | * Letting untrusted data provide a regular expression is unwise. | |
34106 | ||
34107 | * Using ${match...} to apply a fixed regular expression against untrusted | |
34108 | data may result in pathological behaviour within PCRE. Be aware of what | |
34109 | "backtracking" means and consider options for being more strict with a | |
34110 | regular expression. Avenues to explore include limiting what can match | |
34111 | (avoiding "." when "[a-z0-9]" or other character class will do), use of | |
34112 | atomic grouping and possessive quantifiers or just not using regular | |
34113 | expressions against untrusted data. | |
34114 | ||
34115 | * It can be important to correctly use ${quote:...}, ${quote_local_part:...} | |
34116 | and ${quote_<lookup-type>:...} expansion items to ensure that data is | |
34117 | correctly constructed. | |
34118 | ||
34119 | * Some lookups might return multiple results, even though normal usage is | |
34120 | only expected to yield one result. | |
34121 | ||
34122 | ||
34123 | 54.7 IPv4 source routing | |
34124 | ------------------------ | |
34125 | ||
34126 | Many operating systems suppress IP source-routed packets in the kernel, but | |
34127 | some cannot be made to do this, so Exim does its own check. It logs incoming | |
34128 | IPv4 source-routed TCP calls, and then drops them. Things are all different in | |
34129 | IPv6. No special checking is currently done. | |
34130 | ||
34131 | ||
34132 | 54.8 The VRFY, EXPN, and ETRN commands in SMTP | |
34133 | ---------------------------------------------- | |
34134 | ||
34135 | Support for these SMTP commands is disabled by default. If required, they can | |
34136 | be enabled by defining suitable ACLs. | |
34137 | ||
34138 | ||
34139 | 54.9 Privileged users | |
34140 | --------------------- | |
34141 | ||
34142 | Exim recognizes two sets of users with special privileges. Trusted users are | |
34143 | able to submit new messages to Exim locally, but supply their own sender | |
34144 | addresses and information about a sending host. For other users submitting | |
34145 | local messages, Exim sets up the sender address from the uid, and doesn't | |
34146 | permit a remote host to be specified. | |
34147 | ||
34148 | However, an untrusted user is permitted to use the -f command line option in | |
34149 | the special form -f <> to indicate that a delivery failure for the message | |
34150 | should not cause an error report. This affects the message's envelope, but it | |
34151 | does not affect the Sender: header. Untrusted users may also be permitted to | |
34152 | use specific forms of address with the -f option by setting the | |
34153 | untrusted_set_sender option. | |
34154 | ||
34155 | Trusted users are used to run processes that receive mail messages from some | |
34156 | other mail domain and pass them on to Exim for delivery either locally, or over | |
34157 | the Internet. Exim trusts a caller that is running as root, as the Exim user, | |
34158 | as any user listed in the trusted_users configuration option, or under any | |
34159 | group listed in the trusted_groups option. | |
34160 | ||
34161 | Admin users are permitted to do things to the messages on Exim's queue. They | |
34162 | can freeze or thaw messages, cause them to be returned to their senders, remove | |
34163 | them entirely, or modify them in various ways. In addition, admin users can run | |
34164 | the Exim monitor and see all the information it is capable of providing, which | |
34165 | includes the contents of files on the spool. | |
34166 | ||
34167 | By default, the use of the -M and -q options to cause Exim to attempt delivery | |
34168 | of messages on its queue is restricted to admin users. This restriction can be | |
34169 | relaxed by setting the no_prod_requires_admin option. Similarly, the use of -bp | |
34170 | (and its variants) to list the contents of the queue is also restricted to | |
34171 | admin users. This restriction can be relaxed by setting | |
34172 | no_queue_list_requires_admin. | |
34173 | ||
34174 | Exim recognizes an admin user if the calling process is running as root or as | |
34175 | the Exim user or if any of the groups associated with the calling process is | |
34176 | the Exim group. It is not necessary actually to be running under the Exim | |
34177 | group. However, if admin users who are not root or the Exim user are to access | |
34178 | the contents of files on the spool via the Exim monitor (which runs | |
34179 | unprivileged), Exim must be built to allow group read access to its spool | |
34180 | files. | |
34181 | ||
34182 | ||
34183 | 54.10 Spool files | |
34184 | ----------------- | |
34185 | ||
34186 | Exim's spool directory and everything it contains is owned by the Exim user and | |
34187 | set to the Exim group. The mode for spool files is defined in the Local/ | |
34188 | Makefile configuration file, and defaults to 0640. This means that any user who | |
34189 | is a member of the Exim group can access these files. | |
34190 | ||
34191 | ||
34192 | 54.11 Use of argv[0] | |
34193 | -------------------- | |
34194 | ||
34195 | Exim examines the last component of argv[0], and if it matches one of a set of | |
34196 | specific strings, Exim assumes certain options. For example, calling Exim with | |
34197 | the last component of argv[0] set to "rsmtp" is exactly equivalent to calling | |
34198 | it with the option -bS. There are no security implications in this. | |
34199 | ||
34200 | ||
34201 | 54.12 Use of %f formatting | |
34202 | -------------------------- | |
34203 | ||
34204 | The only use made of "%f" by Exim is in formatting load average values. These | |
34205 | are actually stored in integer variables as 1000 times the load average. | |
34206 | Consequently, their range is limited and so therefore is the length of the | |
34207 | converted output. | |
34208 | ||
34209 | ||
34210 | 54.13 Embedded Exim path | |
34211 | ------------------------ | |
34212 | ||
34213 | Exim uses its own path name, which is embedded in the code, only when it needs | |
34214 | to re-exec in order to regain root privilege. Therefore, it is not root when it | |
34215 | does so. If some bug allowed the path to get overwritten, it would lead to an | |
34216 | arbitrary program's being run as exim, not as root. | |
34217 | ||
34218 | ||
34219 | 54.14 Dynamic module directory | |
34220 | ------------------------------ | |
34221 | ||
34222 | Any dynamically loadable modules must be installed into the directory defined | |
34223 | in "LOOKUP_MODULE_DIR" in Local/Makefile for Exim to permit loading it. | |
34224 | ||
34225 | ||
34226 | 54.15 Use of sprintf() | |
34227 | ---------------------- | |
34228 | ||
34229 | A large number of occurrences of "sprintf" in the code are actually calls to | |
34230 | string_sprintf(), a function that returns the result in malloc'd store. The | |
34231 | intermediate formatting is done into a large fixed buffer by a function that | |
34232 | runs through the format string itself, and checks the length of each conversion | |
34233 | before performing it, thus preventing buffer overruns. | |
34234 | ||
34235 | The remaining uses of sprintf() happen in controlled circumstances where the | |
34236 | output buffer is known to be sufficiently long to contain the converted string. | |
34237 | ||
34238 | ||
34239 | 54.16 Use of debug_printf() and log_write() | |
34240 | ------------------------------------------- | |
34241 | ||
34242 | Arbitrary strings are passed to both these functions, but they do their | |
34243 | formatting by calling the function string_vformat(), which runs through the | |
34244 | format string itself, and checks the length of each conversion. | |
34245 | ||
34246 | ||
34247 | 54.17 Use of strcat() and strcpy() | |
34248 | ---------------------------------- | |
34249 | ||
34250 | These are used only in cases where the output buffer is known to be large | |
34251 | enough to hold the result. | |
34252 | ||
34253 | ||
34254 | ||
34255 | =============================================================================== | |
34256 | 55. FORMAT OF SPOOL FILES | |
34257 | ||
34258 | A message on Exim's queue consists of two files, whose names are the message id | |
34259 | followed by -D and -H, respectively. The data portion of the message is kept in | |
34260 | the -D file on its own. The message's envelope, status, and headers are all | |
34261 | kept in the -H file, whose format is described in this chapter. Each of these | |
34262 | two files contains the final component of its own name as its first line. This | |
34263 | is insurance against disk crashes where the directory is lost but the files | |
34264 | themselves are recoverable. | |
34265 | ||
34266 | Some people are tempted into editing -D files in order to modify messages. You | |
34267 | need to be extremely careful if you do this; it is not recommended and you are | |
34268 | on your own if you do it. Here are some of the pitfalls: | |
34269 | ||
34270 | * You must ensure that Exim does not try to deliver the message while you are | |
34271 | fiddling with it. The safest way is to take out a write lock on the -D | |
34272 | file, which is what Exim itself does, using fcntl(). If you update the file | |
34273 | in place, the lock will be retained. If you write a new file and rename it, | |
34274 | the lock will be lost at the instant of rename. | |
34275 | ||
34276 | * If you change the number of lines in the file, the value of $body_linecount | |
34277 | , which is stored in the -H file, will be incorrect. At present, this value | |
34278 | is not used by Exim, but there is no guarantee that this will always be the | |
34279 | case. | |
34280 | ||
34281 | * If the message is in MIME format, you must take care not to break it. | |
34282 | ||
34283 | * If the message is cryptographically signed, any change will invalidate the | |
34284 | signature. | |
34285 | ||
34286 | All in all, modifying -D files is fraught with danger. | |
34287 | ||
34288 | Files whose names end with -J may also be seen in the input directory (or its | |
34289 | subdirectories when split_spool_directory is set). These are journal files, | |
34290 | used to record addresses to which the message has been delivered during the | |
34291 | course of a delivery attempt. If there are still undelivered recipients at the | |
34292 | end, the -H file is updated, and the -J file is deleted. If, however, there is | |
34293 | some kind of crash (for example, a power outage) before this happens, the -J | |
34294 | file remains in existence. When Exim next processes the message, it notices the | |
34295 | -J file and uses it to update the -H file before starting the next delivery | |
34296 | attempt. | |
34297 | ||
34298 | ||
34299 | 55.1 Format of the -H file | |
34300 | -------------------------- | |
34301 | ||
34302 | The second line of the -H file contains the login name for the uid of the | |
34303 | process that called Exim to read the message, followed by the numerical uid and | |
34304 | gid. For a locally generated message, this is normally the user who sent the | |
34305 | message. For a message received over TCP/IP via the daemon, it is normally the | |
34306 | Exim user. | |
34307 | ||
34308 | The third line of the file contains the address of the message's sender as | |
34309 | transmitted in the envelope, contained in angle brackets. The sender address is | |
34310 | empty for bounce messages. For incoming SMTP mail, the sender address is given | |
34311 | in the MAIL command. For locally generated mail, the sender address is created | |
34312 | by Exim from the login name of the current user and the configured | |
34313 | qualify_domain. However, this can be overridden by the -f option or a leading | |
34314 | "From " line if the caller is trusted, or if the supplied address is "<>" or an | |
34315 | address that matches untrusted_set_senders. | |
34316 | ||
34317 | The fourth line contains two numbers. The first is the time that the message | |
34318 | was received, in the conventional Unix form - the number of seconds since the | |
34319 | start of the epoch. The second number is a count of the number of messages | |
34320 | warning of delayed delivery that have been sent to the sender. | |
34321 | ||
34322 | There follow a number of lines starting with a hyphen. These can appear in any | |
34323 | order, and are omitted when not relevant: | |
34324 | ||
34325 | -acl <number> <length> | |
34326 | ||
34327 | This item is obsolete, and is not generated from Exim release 4.61 onwards; | |
34328 | -aclc and -aclm are used instead. However, -acl is still recognized, to | |
34329 | provide backward compatibility. In the old format, a line of this form is | |
34330 | present for every ACL variable that is not empty. The number identifies the | |
34331 | variable; the acl_cx variables are numbered 0-9 and the acl_mx variables | |
34332 | are numbered 10-19. The length is the length of the data string for the | |
34333 | variable. The string itself starts at the beginning of the next line, and | |
34334 | is followed by a newline character. It may contain internal newlines. | |
34335 | ||
34336 | -aclc <rest-of-name> <length> | |
34337 | ||
34338 | A line of this form is present for every ACL connection variable that is | |
34339 | defined. Note that there is a space between -aclc and the rest of the name. | |
34340 | The length is the length of the data string for the variable. The string | |
34341 | itself starts at the beginning of the next line, and is followed by a | |
34342 | newline character. It may contain internal newlines. | |
34343 | ||
34344 | -aclm <rest-of-name> <length> | |
34345 | ||
34346 | A line of this form is present for every ACL message variable that is | |
34347 | defined. Note that there is a space between -aclm and the rest of the name. | |
34348 | The length is the length of the data string for the variable. The string | |
34349 | itself starts at the beginning of the next line, and is followed by a | |
34350 | newline character. It may contain internal newlines. | |
34351 | ||
34352 | -active_hostname <hostname> | |
34353 | ||
34354 | This is present if, when the message was received over SMTP, the value of | |
34355 | $smtp_active_hostname was different to the value of $primary_hostname. | |
34356 | ||
34357 | -allow_unqualified_recipient | |
34358 | ||
34359 | This is present if unqualified recipient addresses are permitted in header | |
34360 | lines (to stop such addresses from being qualified if rewriting occurs at | |
34361 | transport time). Local messages that were input using -bnq and remote | |
34362 | messages from hosts that match recipient_unqualified_hosts set this flag. | |
34363 | ||
34364 | -allow_unqualified_sender | |
34365 | ||
34366 | This is present if unqualified sender addresses are permitted in header | |
34367 | lines (to stop such addresses from being qualified if rewriting occurs at | |
34368 | transport time). Local messages that were input using -bnq and remote | |
34369 | messages from hosts that match sender_unqualified_hosts set this flag. | |
34370 | ||
34371 | -auth_id <text> | |
34372 | ||
34373 | The id information for a message received on an authenticated SMTP | |
34374 | connection - the value of the $authenticated_id variable. | |
34375 | ||
34376 | -auth_sender <address> | |
34377 | ||
34378 | The address of an authenticated sender - the value of the | |
34379 | $authenticated_sender variable. | |
34380 | ||
34381 | -body_linecount <number> | |
34382 | ||
34383 | This records the number of lines in the body of the message, and is always | |
34384 | present. | |
34385 | ||
34386 | -body_zerocount <number> | |
34387 | ||
34388 | This records the number of binary zero bytes in the body of the message, | |
34389 | and is present if the number is greater than zero. | |
34390 | ||
34391 | -deliver_firsttime | |
34392 | ||
34393 | This is written when a new message is first added to the spool. When the | |
34394 | spool file is updated after a deferral, it is omitted. | |
34395 | ||
34396 | -frozen <time> | |
34397 | ||
34398 | The message is frozen, and the freezing happened at <time>. | |
34399 | ||
34400 | -helo_name <text> | |
34401 | ||
34402 | This records the host name as specified by a remote host in a HELO or EHLO | |
34403 | command. | |
34404 | ||
34405 | -host_address <address>.<port> | |
34406 | ||
34407 | This records the IP address of the host from which the message was received | |
34408 | and the remote port number that was used. It is omitted for locally | |
34409 | generated messages. | |
34410 | ||
34411 | -host_auth <text> | |
34412 | ||
34413 | If the message was received on an authenticated SMTP connection, this | |
34414 | records the name of the authenticator - the value of the | |
34415 | $sender_host_authenticated variable. | |
34416 | ||
34417 | -host_lookup_failed | |
34418 | ||
34419 | This is present if an attempt to look up the sending host's name from its | |
34420 | IP address failed. It corresponds to the $host_lookup_failed variable. | |
34421 | ||
34422 | -host_name <text> | |
34423 | ||
34424 | This records the name of the remote host from which the message was | |
34425 | received, if the host name was looked up from the IP address when the | |
34426 | message was being received. It is not present if no reverse lookup was | |
34427 | done. | |
34428 | ||
34429 | -ident <text> | |
34430 | ||
34431 | For locally submitted messages, this records the login of the originating | |
34432 | user, unless it was a trusted user and the -oMt option was used to specify | |
34433 | an ident value. For messages received over TCP/IP, this records the ident | |
34434 | string supplied by the remote host, if any. | |
34435 | ||
34436 | -interface_address <address>.<port> | |
34437 | ||
34438 | This records the IP address of the local interface and the port number | |
34439 | through which a message was received from a remote host. It is omitted for | |
34440 | locally generated messages. | |
34441 | ||
34442 | -local | |
34443 | ||
34444 | The message is from a local sender. | |
34445 | ||
34446 | -localerror | |
34447 | ||
34448 | The message is a locally-generated bounce message. | |
34449 | ||
34450 | -local_scan <string> | |
34451 | ||
34452 | This records the data string that was returned by the local_scan() function | |
34453 | when the message was received - the value of the $local_scan_data variable. | |
34454 | It is omitted if no data was returned. | |
34455 | ||
34456 | -manual_thaw | |
34457 | ||
34458 | The message was frozen but has been thawed manually, that is, by an | |
34459 | explicit Exim command rather than via the auto-thaw process. | |
34460 | ||
34461 | -N | |
34462 | ||
34463 | A testing delivery process was started using the -N option to suppress any | |
34464 | actual deliveries, but delivery was deferred. At any further delivery | |
34465 | attempts, -N is assumed. | |
34466 | ||
34467 | -received_protocol | |
34468 | ||
34469 | This records the value of the $received_protocol variable, which contains | |
34470 | the name of the protocol by which the message was received. | |
34471 | ||
34472 | -sender_set_untrusted | |
34473 | ||
34474 | The envelope sender of this message was set by an untrusted local caller | |
34475 | (used to ensure that the caller is displayed in queue listings). | |
34476 | ||
34477 | -spam_score_int <number> | |
34478 | ||
34479 | If a message was scanned by SpamAssassin, this is present. It records the | |
34480 | value of $spam_score_int. | |
34481 | ||
34482 | -tls_certificate_verified | |
34483 | ||
34484 | A TLS certificate was received from the client that sent this message, and | |
34485 | the certificate was verified by the server. | |
34486 | ||
34487 | -tls_cipher <cipher name> | |
34488 | ||
34489 | When the message was received over an encrypted connection, this records | |
34490 | the name of the cipher suite that was used. | |
34491 | ||
34492 | -tls_peerdn <peer DN> | |
34493 | ||
34494 | When the message was received over an encrypted connection, and a | |
34495 | certificate was received from the client, this records the Distinguished | |
34496 | Name from that certificate. | |
34497 | ||
34498 | Following the options there is a list of those addresses to which the message | |
34499 | is not to be delivered. This set of addresses is initialized from the command | |
34500 | line when the -t option is used and extract_addresses_remove_arguments is set; | |
34501 | otherwise it starts out empty. Whenever a successful delivery is made, the | |
34502 | address is added to this set. The addresses are kept internally as a balanced | |
34503 | binary tree, and it is a representation of that tree which is written to the | |
34504 | spool file. If an address is expanded via an alias or forward file, the | |
34505 | original address is added to the tree when deliveries to all its child | |
34506 | addresses are complete. | |
34507 | ||
34508 | If the tree is empty, there is a single line in the spool file containing just | |
34509 | the text "XX". Otherwise, each line consists of two letters, which are either Y | |
34510 | or N, followed by an address. The address is the value for the node of the | |
34511 | tree, and the letters indicate whether the node has a left branch and/or a | |
34512 | right branch attached to it, respectively. If branches exist, they immediately | |
34513 | follow. Here is an example of a three-node tree: | |
34514 | ||
34515 | YY darcy@austen.fict.example | |
34516 | NN alice@wonderland.fict.example | |
34517 | NN editor@thesaurus.ref.example | |
34518 | ||
34519 | After the non-recipients tree, there is a list of the message's recipients. | |
34520 | This is a simple list, preceded by a count. It includes all the original | |
34521 | recipients of the message, including those to whom the message has already been | |
34522 | delivered. In the simplest case, the list contains one address per line. For | |
34523 | example: | |
34524 | ||
34525 | 4 | |
34526 | editor@thesaurus.ref.example | |
34527 | darcy@austen.fict.example | |
34528 | rdo@foundation | |
34529 | alice@wonderland.fict.example | |
34530 | ||
34531 | However, when a child address has been added to the top-level addresses as a | |
34532 | result of the use of the one_time option on a redirect router, each line is of | |
34533 | the following form: | |
34534 | ||
34535 | <top-level address> <errors_to address> <length>,<parent number>#<flag bits> | |
34536 | ||
34537 | The 01 flag bit indicates the presence of the three other fields that follow | |
34538 | the top-level address. Other bits may be used in future to support additional | |
34539 | fields. The <parent number> is the offset in the recipients list of the | |
34540 | original parent of the "one time" address. The first two fields are the | |
34541 | envelope sender that is associated with this address and its length. If the | |
34542 | length is zero, there is no special envelope sender (there are then two space | |
34543 | characters in the line). A non-empty field can arise from a redirect router | |
34544 | that has an errors_to setting. | |
34545 | ||
34546 | A blank line separates the envelope and status information from the headers | |
34547 | which follow. A header may occupy several lines of the file, and to save effort | |
34548 | when reading it in, each header is preceded by a number and an identifying | |
34549 | character. The number is the number of characters in the header, including any | |
34550 | embedded newlines and the terminating newline. The character is one of the | |
34551 | following: | |
34552 | ||
34553 | <blank> header in which Exim has no special interest | |
34554 | "B" Bcc: header | |
34555 | "C" Cc: header | |
34556 | "F" From: header | |
34557 | "I" Message-id: header | |
34558 | "P" Received: header - P for "postmark" | |
34559 | "R" Reply-To: header | |
34560 | "S" Sender: header | |
34561 | "T" To: header | |
34562 | "*" replaced or deleted header | |
34563 | ||
34564 | Deleted or replaced (rewritten) headers remain in the spool file for debugging | |
34565 | purposes. They are not transmitted when the message is delivered. Here is a | |
34566 | typical set of headers: | |
34567 | ||
34568 | 111P Received: by hobbit.fict.example with local (Exim 4.00) | |
34569 | id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100 | |
34570 | 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example> | |
34571 | 038* X-rewrote-sender: bb@hobbit.fict.example | |
34572 | 042* From: Bilbo Baggins <bb@hobbit.fict.example> | |
34573 | 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example> | |
34574 | 099* To: alice@wonderland.fict.example, rdo@foundation, | |
34575 | darcy@austen.fict.example, editor@thesaurus.ref.example | |
34576 | 104T To: alice@wonderland.fict.example, rdo@foundation.example, | |
34577 | darcy@austen.fict.example, editor@thesaurus.ref.example | |
34578 | 038 Date: Fri, 11 May 2001 10:28:59 +0100 | |
34579 | ||
34580 | The asterisked headers indicate that the envelope sender, From: header, and To: | |
34581 | header have been rewritten, the last one because routing expanded the | |
34582 | unqualified domain foundation. | |
34583 | ||
34584 | ||
34585 | ||
34586 | =============================================================================== | |
34587 | 56. SUPPORT FOR DKIM (DOMAINKEYS IDENTIFIED MAIL) | |
34588 | ||
34589 | DKIM is a mechanism by which messages sent by some entity can be provably | |
34590 | linked to a domain which that entity controls. It permits reputation to be | |
34591 | tracked on a per-domain basis, rather than merely upon source IP address. DKIM | |
34592 | is documented in RFC 4871. | |
34593 | ||
34594 | Since version 4.70, DKIM support is compiled into Exim by default. It can be | |
34595 | disabled by setting DISABLE_DKIM=yes in Local/Makefile. | |
34596 | ||
34597 | Exim's DKIM implementation allows to | |
34598 | ||
34599 | 1. Sign outgoing messages: This function is implemented in the SMTP transport. | |
34600 | It can co-exist with all other Exim features (including transport filters) | |
34601 | except cutthrough delivery. | |
34602 | ||
34603 | 2. Verify signatures in incoming messages: This is implemented by an | |
34604 | additional ACL (acl_smtp_dkim), which can be called several times per | |
34605 | message, with different signature contexts. | |
34606 | ||
34607 | In typical Exim style, the verification implementation does not include any | |
34608 | default "policy". Instead it enables you to build your own policy using Exim's | |
34609 | standard controls. | |
34610 | ||
34611 | Please note that verification of DKIM signatures in incoming mail is turned on | |
34612 | by default for logging purposes. For each signature in incoming email, exim | |
34613 | will log a line displaying the most important signature details, and the | |
34614 | signature status. Here is an example (with line-breaks added for clarity): | |
34615 | ||
34616 | 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM: | |
34617 | d=facebookmail.com s=q1-2009b | |
34618 | c=relaxed/relaxed a=rsa-sha1 | |
34619 | i=@facebookmail.com t=1252484542 [verification succeeded] | |
34620 | ||
34621 | You might want to turn off DKIM verification processing entirely for internal | |
34622 | or relay mail sources. To do that, set the dkim_disable_verify ACL control | |
34623 | modifier. This should typically be done in the RCPT ACL, at points where you | |
34624 | accept mail from relay sources (internal hosts or authenticated senders). | |
34625 | ||
34626 | ||
34627 | 56.1 Signing outgoing messages | |
34628 | ------------------------------ | |
34629 | ||
34630 | Signing is implemented by setting private options on the SMTP transport. These | |
34631 | options take (expandable) strings as arguments. | |
34632 | ||
34633 | +-----------+---------+-------------+--------------+ | |
34634 | |dkim_domain|Use: smtp|Type: string*|Default: unset| | |
34635 | +-----------+---------+-------------+--------------+ | |
34636 | ||
34637 | MANDATORY: The domain you want to sign with. The result of this expanded option | |
34638 | is put into the $dkim_domain expansion variable. | |
34639 | ||
34640 | +-------------+---------+-------------+--------------+ | |
34641 | |dkim_selector|Use: smtp|Type: string*|Default: unset| | |
34642 | +-------------+---------+-------------+--------------+ | |
34643 | ||
34644 | MANDATORY: This sets the key selector string. You can use the $dkim_domain | |
34645 | expansion variable to look up a matching selector. The result is put in the | |
34646 | expansion variable $dkim_selector which should be used in the dkim_private_key | |
34647 | option along with $dkim_domain. | |
34648 | ||
34649 | +----------------+---------+-------------+--------------+ | |
34650 | |dkim_private_key|Use: smtp|Type: string*|Default: unset| | |
34651 | +----------------+---------+-------------+--------------+ | |
34652 | ||
34653 | MANDATORY: This sets the private key to use. You can use the $dkim_domain and | |
34654 | $dkim_selector expansion variables to determine the private key to use. The | |
34655 | result can either | |
34656 | ||
34657 | * be a valid RSA private key in ASCII armor, including line breaks. | |
34658 | ||
34659 | * start with a slash, in which case it is treated as a file that contains the | |
34660 | private key. | |
34661 | ||
34662 | * be "0", "false" or the empty string, in which case the message will not be | |
34663 | signed. This case will not result in an error, even if dkim_strict is set. | |
34664 | ||
34665 | +----------+---------+-------------+--------------+ | |
34666 | |dkim_canon|Use: smtp|Type: string*|Default: unset| | |
34667 | +----------+---------+-------------+--------------+ | |
34668 | ||
34669 | OPTIONAL: This option sets the canonicalization method used when signing a | |
34670 | message. The DKIM RFC currently supports two methods: "simple" and "relaxed". | |
34671 | The option defaults to "relaxed" when unset. Note: the current implementation | |
34672 | only supports using the same canonicalization method for both headers and body. | |
34673 | ||
34674 | +-----------+---------+-------------+--------------+ | |
34675 | |dkim_strict|Use: smtp|Type: string*|Default: unset| | |
34676 | +-----------+---------+-------------+--------------+ | |
34677 | ||
34678 | OPTIONAL: This option defines how Exim behaves when signing a message that | |
34679 | should be signed fails for some reason. When the expansion evaluates to either | |
34680 | "1" or "true", Exim will defer. Otherwise Exim will send the message unsigned. | |
34681 | You can use the $dkim_domain and $dkim_selector expansion variables here. | |
34682 | ||
34683 | +-----------------+---------+-------------+--------------+ | |
34684 | |dkim_sign_headers|Use: smtp|Type: string*|Default: unset| | |
34685 | +-----------------+---------+-------------+--------------+ | |
34686 | ||
34687 | OPTIONAL: When set, this option must expand to (or be specified as) a | |
34688 | colon-separated list of header names. Headers with these names will be included | |
34689 | in the message signature. When unspecified, the header names recommended in | |
34690 | RFC4871 will be used. | |
34691 | ||
34692 | ||
34693 | 56.2 Verifying DKIM signatures in incoming mail | |
34694 | ----------------------------------------------- | |
34695 | ||
34696 | Verification of DKIM signatures in incoming email is implemented via the | |
34697 | acl_smtp_dkim ACL. By default, this ACL is called once for each syntactically | |
34698 | (!) correct signature in the incoming message. A missing ACL definition | |
34699 | defaults to accept. If any ACL call does not acccept, the message is not | |
34700 | accepted. If a cutthrough delivery was in progress for the message it is | |
34701 | summarily dropped (having wasted the transmission effort). | |
34702 | ||
34703 | To evaluate the signature in the ACL a large number of expansion variables | |
34704 | containing the signature status and its details are set up during the runtime | |
34705 | of the ACL. | |
34706 | ||
34707 | Calling the ACL only for existing signatures is not sufficient to build more | |
34708 | advanced policies. For that reason, the global option dkim_verify_signers, and | |
34709 | a global expansion variable $dkim_signers exist. | |
34710 | ||
34711 | The global option dkim_verify_signers can be set to a colon-separated list of | |
34712 | DKIM domains or identities for which the ACL acl_smtp_dkim is called. It is | |
34713 | expanded when the message has been received. At this point, the expansion | |
34714 | variable $dkim_signers already contains a colon-separated list of signer | |
34715 | domains and identities for the message. When dkim_verify_signers is not | |
34716 | specified in the main configuration, it defaults as: | |
34717 | ||
34718 | dkim_verify_signers = $dkim_signers | |
34719 | ||
34720 | This leads to the default behaviour of calling acl_smtp_dkim for each DKIM | |
34721 | signature in the message. Current DKIM verifiers may want to explicitly call | |
34722 | the ACL for known domains or identities. This would be achieved as follows: | |
34723 | ||
34724 | dkim_verify_signers = paypal.com:ebay.com:$dkim_signers | |
34725 | ||
34726 | This would result in acl_smtp_dkim always being called for "paypal.com" and | |
34727 | "ebay.com", plus all domains and identities that have signatures in the | |
34728 | message. You can also be more creative in constructing your policy. For | |
34729 | example: | |
34730 | ||
34731 | dkim_verify_signers = $sender_address_domain:$dkim_signers | |
34732 | ||
34733 | If a domain or identity is listed several times in the (expanded) value of | |
34734 | dkim_verify_signers, the ACL is only called once for that domain or identity. | |
34735 | ||
34736 | Inside the acl_smtp_dkim, the following expansion variables are available (from | |
34737 | most to least important): | |
34738 | ||
34739 | $dkim_cur_signer | |
34740 | ||
34741 | The signer that is being evaluated in this ACL run. This can be a domain or | |
34742 | an identity. This is one of the list items from the expanded main option | |
34743 | dkim_verify_signers (see above). | |
34744 | ||
34745 | $dkim_verify_status | |
34746 | ||
34747 | A string describing the general status of the signature. One of | |
34748 | ||
34749 | * none: There is no signature in the message for the current domain or | |
34750 | identity (as reflected by $dkim_cur_signer). | |
34751 | ||
34752 | * invalid: The signature could not be verified due to a processing error. | |
34753 | More detail is available in $dkim_verify_reason. | |
34754 | ||
34755 | * fail: Verification of the signature failed. More detail is available in | |
34756 | $dkim_verify_reason. | |
34757 | ||
34758 | * pass: The signature passed verification. It is valid. | |
34759 | ||
34760 | $dkim_verify_reason | |
34761 | ||
34762 | A string giving a litte bit more detail when $dkim_verify_status is either | |
34763 | "fail" or "invalid". One of | |
34764 | ||
34765 | * pubkey_unavailable (when $dkim_verify_status="invalid"): The public key | |
34766 | for the domain could not be retrieved. This may be a temporary problem. | |
34767 | ||
34768 | * pubkey_syntax (when $dkim_verify_status="invalid"): The public key | |
34769 | record for the domain is syntactically invalid. | |
34770 | ||
34771 | * bodyhash_mismatch (when $dkim_verify_status="fail"): The calculated | |
34772 | body hash does not match the one specified in the signature header. | |
34773 | This means that the message body was modified in transit. | |
34774 | ||
34775 | * signature_incorrect (when $dkim_verify_status="fail"): The signature | |
34776 | could not be verified. This may mean that headers were modified, | |
34777 | re-written or otherwise changed in a way which is incompatible with | |
34778 | DKIM verification. It may of course also mean that the signature is | |
34779 | forged. | |
34780 | ||
34781 | $dkim_domain | |
34782 | ||
34783 | The signing domain. IMPORTANT: This variable is only populated if there is | |
34784 | an actual signature in the message for the current domain or identity (as | |
34785 | reflected by $dkim_cur_signer). | |
34786 | ||
34787 | $dkim_identity | |
34788 | ||
34789 | The signing identity, if present. IMPORTANT: This variable is only | |
34790 | populated if there is an actual signature in the message for the current | |
34791 | domain or identity (as reflected by $dkim_cur_signer). | |
34792 | ||
34793 | $dkim_selector | |
34794 | ||
34795 | The key record selector string. | |
34796 | ||
34797 | $dkim_algo | |
34798 | ||
34799 | The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'. | |
34800 | ||
34801 | $dkim_canon_body | |
34802 | ||
34803 | The body canonicalization method. One of 'relaxed' or 'simple'. | |
34804 | ||
34805 | dkim_canon_headers | |
34806 | ||
34807 | The header canonicalization method. One of 'relaxed' or 'simple'. | |
34808 | ||
34809 | $dkim_copiedheaders | |
34810 | ||
34811 | A transcript of headers and their values which are included in the | |
34812 | signature (copied from the 'z=' tag of the signature). | |
34813 | ||
34814 | $dkim_bodylength | |
34815 | ||
34816 | The number of signed body bytes. If zero ("0"), the body is unsigned. If no | |
34817 | limit was set by the signer, "9999999999999" is returned. This makes sure | |
34818 | that this variable always expands to an integer value. | |
34819 | ||
34820 | $dkim_created | |
34821 | ||
34822 | UNIX timestamp reflecting the date and time when the signature was created. | |
34823 | When this was not specified by the signer, "0" is returned. | |
34824 | ||
34825 | $dkim_expires | |
34826 | ||
34827 | UNIX timestamp reflecting the date and time when the signer wants the | |
34828 | signature to be treated as "expired". When this was not specified by the | |
34829 | signer, "9999999999999" is returned. This makes it possible to do useful | |
34830 | integer size comparisons against this value. | |
34831 | ||
34832 | $dkim_headernames | |
34833 | ||
34834 | A colon-separated list of names of headers included in the signature. | |
34835 | ||
34836 | $dkim_key_testing | |
34837 | ||
34838 | "1" if the key record has the "testing" flag set, "0" if not. | |
34839 | ||
34840 | $dkim_key_nosubdomains | |
34841 | ||
34842 | "1" if the key record forbids subdomaining, "0" otherwise. | |
34843 | ||
34844 | $dkim_key_srvtype | |
34845 | ||
34846 | Service type (tag s=) from the key record. Defaults to "*" if not specified | |
34847 | in the key record. | |
34848 | ||
34849 | $dkim_key_granularity | |
34850 | ||
34851 | Key granularity (tag g=) from the key record. Defaults to "*" if not | |
34852 | specified in the key record. | |
34853 | ||
34854 | $dkim_key_notes | |
34855 | ||
34856 | Notes from the key record (tag n=). | |
34857 | ||
34858 | In addition, two ACL conditions are provided: | |
34859 | ||
34860 | dkim_signers | |
34861 | ||
34862 | ACL condition that checks a colon-separated list of domains or identities | |
34863 | for a match against the domain or identity that the ACL is currently | |
34864 | verifying (reflected by $dkim_cur_signer). This is typically used to | |
34865 | restrict an ACL verb to a group of domains or identities. For example: | |
34866 | ||
34867 | # Warn when Mail purportedly from GMail has no signature at all | |
34868 | warn log_message = GMail sender without DKIM signature | |
34869 | sender_domains = gmail.com | |
34870 | dkim_signers = gmail.com | |
34871 | dkim_status = none | |
34872 | ||
34873 | dkim_status | |
34874 | ||
34875 | ACL condition that checks a colon-separated list of possible DKIM | |
34876 | verification results against the actual result of verification. This is | |
34877 | typically used to restrict an ACL verb to a list of verification outcomes, | |
34878 | for example: | |
34879 | ||
34880 | deny message = Mail from Paypal with invalid/missing signature | |
34881 | sender_domains = paypal.com:paypal.de | |
34882 | dkim_signers = paypal.com:paypal.de | |
34883 | dkim_status = none:invalid:fail | |
34884 | ||
34885 | The possible status keywords are: 'none','invalid','fail' and 'pass'. | |
34886 | Please see the documentation of the $dkim_verify_status expansion variable | |
34887 | above for more information of what they mean. | |
34888 | ||
34889 | ||
34890 | ||
34891 | =============================================================================== | |
34892 | 57. ADDING NEW DRIVERS OR LOOKUP TYPES | |
34893 | ||
34894 | The following actions have to be taken in order to add a new router, transport, | |
34895 | authenticator, or lookup type to Exim: | |
34896 | ||
34897 | 1. Choose a name for the driver or lookup type that does not conflict with any | |
34898 | existing name; I will use "newdriver" in what follows. | |
34899 | ||
34900 | 2. Add to src/EDITME the line: | |
34901 | ||
34902 | <type>_NEWDRIVER=yes | |
34903 | ||
34904 | where <type> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the code is not to | |
34905 | be included in the binary by default, comment this line out. You should | |
34906 | also add any relevant comments about the driver or lookup type. | |
34907 | ||
34908 | 3. Add to src/config.h.defaults the line: | |
34909 | ||
34910 | #define <type>_NEWDRIVER | |
34911 | ||
34912 | 4. Edit src/drtables.c, adding conditional code to pull in the private header | |
34913 | and create a table entry as is done for all the other drivers and lookup | |
34914 | types. | |
34915 | ||
34916 | 5. Edit scripts/lookups-Makefile if this is a new lookup; there is a for-loop | |
34917 | near the bottom, ranging the "name_mod" variable over a list of all | |
34918 | lookups. Add your "NEWDRIVER" to that list. As long as the dynamic module | |
34919 | would be named newdriver.so, you can use the simple form that most lookups | |
34920 | have. | |
34921 | ||
34922 | 6. Edit Makefile in the appropriate sub-directory (src/routers, src/transports | |
34923 | , src/auths, or src/lookups); add a line for the new driver or lookup type | |
34924 | and add it to the definition of OBJ. | |
34925 | ||
34926 | 7. Create newdriver.h and newdriver.c in the appropriate sub-directory of src. | |
34927 | ||
34928 | 8. Edit scripts/MakeLinks and add commands to link the .h and .c files as for | |
34929 | other drivers and lookups. | |
34930 | ||
34931 | Then all you need to do is write the code! A good way to start is to make a | |
34932 | proforma by copying an existing module of the same type, globally changing all | |
34933 | occurrences of the name, and cutting out most of the code. Note that any | |
34934 | options you create must be listed in alphabetical order, because the tables are | |
34935 | searched using a binary chop procedure. | |
34936 | ||
34937 | There is a README file in each of the sub-directories of src describing the | |
34938 | interface that is expected. | |
34939 |