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4009494e | 1 | \input texinfo @c -*-texinfo-*- |
db78a8cb | 2 | @setfilename ../../info/smtpmail |
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3 | @settitle Emacs SMTP Library |
4 | @syncodeindex vr fn | |
5 | @copying | |
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6 | Copyright @copyright{} 2003, 2004, 2005, 2006, 2007, 2008 |
7 | Free Software Foundation, Inc. | |
4009494e GM |
8 | |
9 | @quotation | |
10 | Permission is granted to copy, distribute and/or modify this document | |
11 | under the terms of the GNU Free Documentation License, Version 1.2 or | |
12 | any later version published by the Free Software Foundation; with no | |
13 | Invariant Sections, with the Front-Cover texts being ``A GNU Manual'', | |
14 | and with the Back-Cover Texts as in (a) below. A copy of the license | |
debf4439 | 15 | is included in the section entitled ``GNU Free Documentation License''. |
4009494e | 16 | |
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17 | (a) The FSF's Back-Cover Text is: ``You have the freedom to copy and |
18 | modify this GNU manual. Buying copies from the FSF supports it in | |
19 | developing GNU and promoting software freedom.'' | |
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20 | @end quotation |
21 | @end copying | |
22 | ||
23 | @dircategory Emacs | |
24 | @direntry | |
25 | * SMTP: (smtpmail). Emacs library for sending mail via SMTP. | |
26 | @end direntry | |
27 | ||
28 | @titlepage | |
29 | @title{Emacs SMTP Library} | |
30 | @subtitle{An Emacs package for sending mail via SMTP} | |
31 | @author{Simon Josefsson, Alex Schroeder} | |
32 | @page | |
33 | @vskip 0pt plus 1filll | |
34 | @insertcopying | |
35 | @end titlepage | |
36 | ||
37 | @contents | |
38 | ||
39 | @ifnottex | |
40 | @node Top | |
41 | @top Emacs SMTP Library | |
42 | ||
43 | @insertcopying | |
44 | @end ifnottex | |
45 | ||
46 | @menu | |
47 | * How Mail Works:: Brief introduction to mail concepts. | |
48 | * Emacs Speaks SMTP:: How to use the SMTP library in Emacs. | |
49 | * Authentication:: Authenticating yourself to the server. | |
50 | * Queued delivery:: Sending mail without an internet connection. | |
51 | * Server workarounds:: Mail servers with special requirements. | |
52 | * Debugging:: Tracking down problems. | |
53 | * GNU Free Documentation License:: The license for this documentation. | |
54 | ||
55 | Indices | |
56 | ||
57 | * Index:: Index over variables and functions. | |
58 | @end menu | |
59 | ||
60 | @node How Mail Works | |
61 | @chapter How Mail Works | |
62 | ||
63 | @cindex SMTP | |
64 | @cindex MTA | |
65 | On the internet, mail is sent from mail host to mail host using the | |
66 | simple mail transfer protocol (SMTP). To send and receive mail, you | |
67 | must get it from and send it to a mail host. Every mail host runs a | |
68 | mail transfer agent (MTA) such as Exim that accepts mails and passes | |
69 | them on. The communication between a mail host and other clients does | |
70 | not necessarily involve SMTP, however. Here is short overview of what | |
71 | is involved. | |
72 | ||
73 | @cindex MUA | |
74 | The mail program --- also called a mail user agent (MUA) --- | |
75 | usually sends outgoing mail to a mail host. When your computer is | |
76 | permanently connected to the internet, it might even be a mail host | |
77 | itself. In this case, the MUA will pipe mail to the | |
78 | @file{/usr/lib/sendmail} application. It will take care of your mail | |
79 | and pass it on to the next mail host. | |
80 | ||
81 | @cindex ISP | |
82 | When you are only connected to the internet from time to time, your | |
83 | internet service provider (ISP) has probably told you which mail host | |
84 | to use. You must configure your MUA to use that mail host. Since you | |
85 | are reading this manual, you probably want to configure Emacs to use | |
86 | SMTP to send mail to that mail host. More on that in the next | |
87 | section. | |
88 | ||
89 | @cindex MDA | |
90 | Things are different when reading mail. The mail host responsible | |
91 | for your mail keeps it in a file somewhere. The messages get into the | |
92 | file by way of a mail delivery agent (MDA) such as procmail. These | |
93 | delivery agents often allow you to filter and munge your mails before | |
94 | you get to see it. When your computer is that mail host, this file is | |
95 | called a spool, and sometimes located in the directory | |
96 | @file{/var/spool/mail/}. All your MUA has to do is read mail from the | |
97 | spool, then. | |
98 | ||
99 | @cindex POP3 | |
100 | @cindex IMAP | |
101 | When your computer is not always connected to the internet, you | |
102 | must get the mail from the remote mail host using a protocol such as | |
103 | POP3 or IMAP. POP3 essentially downloads all your mail from the mail | |
104 | host to your computer. The mail is stored in some file on your | |
105 | computer, and again, all your MUA has to do is read mail from the | |
106 | spool. | |
107 | ||
108 | When you read mail from various machines, downloading mail from the | |
109 | mail host to your current machine is not convenient. In that case, | |
110 | you will probably want to use the IMAP protocol. Your mail is kept on | |
111 | the mail host, and you can read it while you are connected via IMAP to | |
112 | the mail host. | |
113 | ||
114 | @cindex Webmail | |
115 | So how does reading mail via the web work, you ask. In that case, | |
116 | the web interface just allows you to remote-control a MUA on the web | |
117 | host. Whether the web host is also a mail host, and how all the | |
118 | pieces interact is completely irrelevant. You usually cannot use | |
119 | Emacs to read mail via the web, unless you use software that parses | |
120 | the ever-changing HTML of the web interface. | |
121 | ||
122 | @node Emacs Speaks SMTP | |
123 | @chapter Emacs Speaks SMTP | |
124 | ||
125 | Emacs includes a package for sending your mail to a SMTP server and | |
126 | have it take care of delivering it to the final destination, rather | |
127 | than letting the MTA on your local system take care of it. This can | |
128 | be useful if you don't have a MTA set up on your host, or if your | |
129 | machine is often disconnected from the internet. | |
130 | ||
131 | Sending mail via SMTP requires configuring your mail user agent | |
132 | (@pxref{Mail Methods,,,emacs}) to use the SMTP library. How to do | |
133 | this should be described for each mail user agent; for the default | |
134 | mail user agent the variable @code{send-mail-function} (@pxref{Mail | |
135 | Sending,,,emacs}) is used; for the Message and Gnus user agents the | |
136 | variable @code{message-send-mail-function} (@pxref{Mail | |
137 | Variables,,,message}) is used. | |
138 | ||
139 | @example | |
140 | ;; If you use the default mail user agent. | |
141 | (setq send-mail-function 'smtpmail-send-it) | |
142 | ;; If you use Message or Gnus. | |
143 | (setq message-send-mail-function 'smtpmail-send-it) | |
144 | @end example | |
145 | ||
146 | Before using SMTP you must find out the hostname of the SMTP server | |
147 | to use. Your system administrator should provide you with this | |
148 | information, but often it is the same as the server you receive mail | |
149 | from. | |
150 | ||
151 | @table @code | |
152 | @item smtpmail-smtp-server | |
153 | @vindex smtpmail-smtp-server | |
154 | @vindex SMTPSERVER | |
155 | The variable @code{smtpmail-smtp-server} controls the hostname of | |
156 | the server to use. It is a string with an IP address or hostname. It | |
157 | defaults to the contents of the @env{SMTPSERVER} environment | |
158 | variable, or, if empty, the contents of | |
159 | @code{smtpmail-default-smtp-server}. | |
160 | ||
161 | @item smtpmail-default-smtp-server | |
162 | @vindex smtpmail-default-smtp-server | |
163 | The variable @code{smtpmail-default-smtp-server} controls the | |
164 | default hostname of the server to use. It is a string with an IP | |
165 | address or hostname. It must be set before the SMTP library is | |
166 | loaded. It has no effect if set after the SMTP library has been | |
167 | loaded, or if @code{smtpmail-smtp-server} is defined. It is usually | |
168 | set by system administrators in a site wide initialization file. | |
169 | @end table | |
170 | ||
171 | The following example illustrates what you could put in | |
172 | @file{~/.emacs} to set the SMTP server name. | |
173 | ||
174 | @example | |
175 | ;; Send mail using SMTP via mail.example.org. | |
176 | (setq smtpmail-smtp-server "mail.example.org") | |
177 | @end example | |
178 | ||
179 | @cindex Mail Submission | |
180 | SMTP is normally used on the registered ``smtp'' TCP service port 25. | |
181 | Some environments use SMTP in ``Mail Submission'' mode, which uses | |
182 | port 587. Using other ports is not uncommon, either for security by | |
183 | obscurity purposes, port forwarding, or otherwise. | |
184 | ||
185 | @table @code | |
186 | @item smtpmail-smtp-service | |
187 | @vindex smtpmail-smtp-service | |
188 | The variable @code{smtpmail-smtp-service} controls the port on the | |
189 | server to contact. It is either a string, in which case it will be | |
190 | translated into an integer using system calls, or an integer. | |
191 | @end table | |
192 | ||
193 | The following example illustrates what you could put in | |
194 | @file{~/.emacs} to set the SMTP service port. | |
195 | ||
196 | @example | |
197 | ;; Send mail using SMTP on the mail submission port 587. | |
198 | (setq smtpmail-smtp-service 587) | |
199 | @end example | |
200 | ||
201 | @node Authentication | |
202 | @chapter Authentication | |
203 | ||
204 | @cindex SASL | |
205 | @cindex CRAM-MD5 | |
206 | @cindex LOGIN | |
207 | @cindex STARTTLS | |
208 | @cindex TLS | |
209 | @cindex SSL | |
210 | Many environments require SMTP clients to authenticate themselves | |
211 | before they are allowed to route mail via a server. The two following | |
212 | variables contains the authentication information needed for this. | |
213 | ||
214 | The first variable, @code{smtpmail-auth-credentials}, instructs the | |
215 | SMTP library to use a SASL authentication step, currently only the | |
216 | CRAM-MD5 and LOGIN mechanisms are supported and will be selected in | |
217 | that order if the server support both. | |
218 | ||
219 | The second variable, @code{smtpmail-starttls-credentials}, instructs | |
220 | the SMTP library to connect to the server using STARTTLS. This means | |
221 | the protocol exchange may be integrity protected and confidential by | |
222 | using the Transport Layer Security (TLS) protocol, and optionally also | |
223 | authentication of the client and server. | |
224 | ||
225 | TLS is a security protocol that is also known as SSL, although | |
226 | strictly speaking, SSL is an older variant of TLS. TLS is backwards | |
227 | compatible with SSL. In most mundane situations, the two terms are | |
228 | equivalent. | |
229 | ||
230 | The TLS feature uses the elisp package @file{starttls.el} (see it for | |
231 | more information on customization), which in turn require that at | |
232 | least one of the following external tools are installed: | |
233 | ||
234 | @enumerate | |
235 | @item | |
236 | The GNUTLS command line tool @samp{gnutls-cli}, you can get it from | |
237 | @url{http://www.gnu.org/software/gnutls/}. This is the recommended | |
238 | tool, mainly because it can verify the server certificates. | |
239 | ||
240 | @item | |
241 | The @samp{starttls} external program, you can get it from | |
242 | @file{starttls-*.tar.gz} from @uref{ftp://ftp.opaopa.org/pub/elisp/}. | |
243 | @end enumerate | |
244 | ||
245 | It is not uncommon to use both these mechanisms, e.g., to use STARTTLS | |
246 | to achieve integrity and confidentiality and then use SASL for client | |
247 | authentication. | |
248 | ||
249 | @table @code | |
250 | @item smtpmail-auth-credentials | |
251 | @vindex smtpmail-auth-credentials | |
252 | The variable @code{smtpmail-auth-credentials} contains a list of | |
253 | hostname, port, username and password tuples. When the SMTP library | |
254 | connects to a host on a certain port, this variable is searched to | |
255 | find a matching entry for that hostname and port. If an entry is | |
256 | found, the authentication process is invoked and the credentials are | |
257 | used. | |
258 | ||
259 | The hostname field follows the same format as | |
260 | @code{smtpmail-smtp-server} (i.e., a string) and the port field the | |
261 | same format as @code{smtpmail-smtp-service} (i.e., a string or an | |
262 | integer). The username and password fields, which either can be | |
263 | @code{nil} to indicate that the user is prompted for the value | |
264 | interactively, should be strings with the username and password, | |
265 | respectively, information that is normally provided by system | |
266 | administrators. | |
267 | ||
268 | @item smtpmail-starttls-credentials | |
269 | @vindex smtpmail-starttls-credentials | |
270 | The variable @code{smtpmail-starttls-credentials} contains a list of | |
271 | tuples with hostname, port, name of file containing client key, and | |
272 | name of file containing client certificate. The processing is similar | |
273 | to the previous variable. The client key and certificate may be | |
274 | @code{nil} if you do not wish to use client authentication. | |
275 | @end table | |
276 | ||
277 | The following example illustrates what you could put in | |
278 | @file{~/.emacs} to enable both SASL authentication and STARTTLS. The | |
279 | server name (@code{smtpmail-smtp-server}) is @var{hostname}, the | |
280 | server port (@code{smtpmail-smtp-service}) is @var{port}, and the | |
281 | username and password are @var{username} and @var{password} | |
282 | respectively. | |
283 | ||
284 | @example | |
285 | ;; Authenticate using this username and password against my server. | |
286 | (setq smtpmail-auth-credentials | |
287 | '(("@var{hostname}" "@var{port}" "@var{username}" "@var{password}"))) | |
288 | ||
289 | ;; Note that if @var{port} is an integer, you must not quote it as a | |
290 | ;; string. Normally @var{port} should be the integer 25, and the example | |
291 | ;; become: | |
292 | (setq smtpmail-auth-credentials | |
293 | '(("@var{hostname}" 25 "@var{username}" "@var{password}"))) | |
294 | ||
295 | ;; Use STARTTLS without authentication against the server. | |
296 | (setq smtpmail-starttls-credentials | |
297 | '(("@var{hostname}" "@var{port}" nil nil))) | |
298 | @end example | |
299 | ||
300 | @node Queued delivery | |
301 | @chapter Queued delivery | |
302 | ||
303 | @cindex Dialup connection | |
304 | If you connect to the internet via a dialup connection, or for some | |
305 | other reason don't have permanent internet connection, sending mail | |
306 | will fail when you are not connected. The SMTP library implements | |
307 | queued delivery, and the following variable control its behavior. | |
308 | ||
309 | @table @code | |
310 | @item smtpmail-queue-mail | |
311 | @vindex smtpmail-queue-mail | |
312 | The variable @code{smtpmail-queue-mail} controls whether a simple | |
313 | off line mail sender is active. This variable is a boolean, and | |
314 | defaults to @code{nil} (disabled). If this is non-@code{nil}, mail is | |
315 | not sent immediately but rather queued in the directory | |
316 | @code{smtpmail-queue-dir} and can be later sent manually by invoking | |
317 | @code{smtpmail-send-queued-mail} (typically when you connect to the | |
318 | internet). | |
319 | ||
320 | @item smtpmail-queue-dir | |
321 | @vindex smtpmail-queue-dir | |
322 | The variable @code{smtpmail-queue-dir} specifies the name of the | |
323 | directory to hold queued messages. It defaults to | |
324 | @file{~/Mail/queued-mail/}. | |
325 | @end table | |
326 | ||
327 | @findex smtpmail-send-queued-mail | |
328 | The function @code{smtpmail-send-queued-mail} can be used to send | |
329 | any queued mail when @code{smtpmail-queue-mail} is enabled. It is | |
330 | typically invoked interactively with @kbd{M-x | |
331 | smtpmail-send-queued-mail RET} when you are connected to the internet. | |
332 | ||
333 | @node Server workarounds | |
334 | @chapter Server workarounds | |
335 | ||
336 | Some SMTP servers have special requirements. The following variables | |
337 | implement support for common requirements. | |
338 | ||
339 | @table @code | |
340 | ||
341 | @item smtpmail-local-domain | |
342 | @vindex smtpmail-local-domain | |
343 | The variable @code{smtpmail-local-domain} controls the hostname sent | |
344 | in the first @code{EHLO} or @code{HELO} command sent to the server. | |
345 | It should only be set if the @code{system-name} function returns a | |
346 | name that isn't accepted by the server. Do not set this variable | |
347 | unless your server complains. | |
348 | ||
349 | @item smtpmail-sendto-domain | |
350 | @vindex smtpmail-sendto-domain | |
351 | The variable @code{smtpmail-sendto-domain} makes the SMTP library | |
352 | add @samp{@@} and the specified value to recipients specified in the | |
353 | message when they are sent using the @code{RCPT TO} command. Some | |
354 | configurations of sendmail requires this behavior. Don't bother to | |
355 | set this unless you have get an error like: | |
356 | ||
357 | @example | |
358 | Sending failed; SMTP protocol error | |
359 | @end example | |
360 | ||
361 | when sending mail, and the debug buffer (@pxref{Debugging})) contains | |
362 | an error such as: | |
363 | ||
364 | @example | |
365 | RCPT TO: @var{someone} | |
366 | 501 @var{someone}: recipient address must contain a domain | |
367 | @end example | |
368 | ||
369 | @end table | |
370 | ||
371 | ||
372 | @node Debugging | |
373 | @chapter Debugging | |
374 | ||
375 | Sometimes delivery fails, often with the generic error message | |
376 | @samp{Sending failed; SMTP protocol error}. Enabling one or both of | |
377 | the following variables and inspecting a trace buffer will often give | |
378 | clues to the reason for the error. | |
379 | ||
380 | @table @code | |
381 | ||
382 | @item smtpmail-debug-info | |
383 | @vindex smtpmail-debug-info | |
384 | The variable @code{smtpmail-debug-info} controls whether to print | |
385 | the SMTP protocol exchange in the minibuffer, and retain the entire | |
386 | exchange in a buffer @samp{*trace of SMTP session to @var{server}*}, | |
387 | where @var{server} is the name of the mail server to which you send | |
388 | mail. | |
389 | ||
390 | @item smtpmail-debug-verb | |
391 | @vindex smtpmail-debug-verb | |
392 | The variable @code{smtpmail-debug-verb} controls whether to send the | |
393 | @code{VERB} token to the server. The @code{VERB} server instructs the | |
394 | server to be more verbose, and often also to attempt final delivery | |
395 | while your SMTP session is still running. It is usually only useful | |
396 | together with @code{smtpmail-debug-info}. Note that this may cause | |
397 | mail delivery to take considerable time if the final destination | |
398 | cannot accept mail. | |
399 | ||
400 | @end table | |
401 | ||
402 | @node GNU Free Documentation License | |
403 | @chapter GNU Free Documentation License | |
404 | @include doclicense.texi | |
405 | ||
406 | @node Index | |
407 | @chapter Index | |
408 | ||
409 | @section Concept Index | |
410 | ||
411 | @printindex cp | |
412 | ||
413 | @section Function and Variable Index | |
414 | ||
415 | @printindex fn | |
416 | ||
417 | @contents | |
418 | @bye | |
419 | ||
420 | @ignore | |
421 | arch-tag: 6316abdf-b366-4562-87a2-f37e8f894b6f | |
422 | @end ignore |