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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 | |
acaf905b | 6 | Copyright @copyright{} 2003-2012 |
3f548a7c | 7 | Free Software Foundation, Inc. |
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8 | |
9 | @quotation | |
10 | Permission is granted to copy, distribute and/or modify this document | |
6a2c4aec | 11 | under the terms of the GNU Free Documentation License, Version 1.3 or |
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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 | |
6f093307 GM |
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 | ||
0c973505 | 23 | @dircategory Emacs lisp libraries |
4009494e | 24 | @direntry |
62e034c2 | 25 | * SMTP: (smtpmail). Emacs library for sending mail via SMTP. |
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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 | |
9360256a | 47 | * How Mail Works:: Brief introduction to mail concepts. |
4009494e | 48 | * Emacs Speaks SMTP:: How to use the SMTP library in Emacs. |
9360256a | 49 | * Authentication:: Authenticating yourself to the server. |
9f26dc24 | 50 | * Encryption:: Protecting your connection to the server. |
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51 | * Queued delivery:: Sending mail without an internet connection. |
52 | * Server workarounds:: Mail servers with special requirements. | |
53 | * Debugging:: Tracking down problems. | |
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54 | * GNU Free Documentation License:: The license for this documentation. |
55 | ||
56 | Indices | |
57 | ||
9360256a | 58 | * Index:: Index over variables and functions. |
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59 | @end menu |
60 | ||
61 | @node How Mail Works | |
62 | @chapter How Mail Works | |
63 | ||
64 | @cindex SMTP | |
65 | @cindex MTA | |
66 | On the internet, mail is sent from mail host to mail host using the | |
67 | simple mail transfer protocol (SMTP). To send and receive mail, you | |
68 | must get it from and send it to a mail host. Every mail host runs a | |
69 | mail transfer agent (MTA) such as Exim that accepts mails and passes | |
70 | them on. The communication between a mail host and other clients does | |
71 | not necessarily involve SMTP, however. Here is short overview of what | |
72 | is involved. | |
73 | ||
74 | @cindex MUA | |
75 | The mail program --- also called a mail user agent (MUA) --- | |
76 | usually sends outgoing mail to a mail host. When your computer is | |
77 | permanently connected to the internet, it might even be a mail host | |
78 | itself. In this case, the MUA will pipe mail to the | |
79 | @file{/usr/lib/sendmail} application. It will take care of your mail | |
80 | and pass it on to the next mail host. | |
81 | ||
82 | @cindex ISP | |
83 | When you are only connected to the internet from time to time, your | |
84 | internet service provider (ISP) has probably told you which mail host | |
85 | to use. You must configure your MUA to use that mail host. Since you | |
86 | are reading this manual, you probably want to configure Emacs to use | |
87 | SMTP to send mail to that mail host. More on that in the next | |
88 | section. | |
89 | ||
90 | @cindex MDA | |
91 | Things are different when reading mail. The mail host responsible | |
92 | for your mail keeps it in a file somewhere. The messages get into the | |
93 | file by way of a mail delivery agent (MDA) such as procmail. These | |
94 | delivery agents often allow you to filter and munge your mails before | |
95 | you get to see it. When your computer is that mail host, this file is | |
96 | called a spool, and sometimes located in the directory | |
97 | @file{/var/spool/mail/}. All your MUA has to do is read mail from the | |
98 | spool, then. | |
99 | ||
100 | @cindex POP3 | |
101 | @cindex IMAP | |
102 | When your computer is not always connected to the internet, you | |
103 | must get the mail from the remote mail host using a protocol such as | |
1df7defd | 104 | POP3 or IMAP@. POP3 essentially downloads all your mail from the mail |
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105 | host to your computer. The mail is stored in some file on your |
106 | computer, and again, all your MUA has to do is read mail from the | |
107 | spool. | |
108 | ||
109 | When you read mail from various machines, downloading mail from the | |
110 | mail host to your current machine is not convenient. In that case, | |
111 | you will probably want to use the IMAP protocol. Your mail is kept on | |
112 | the mail host, and you can read it while you are connected via IMAP to | |
113 | the mail host. | |
114 | ||
115 | @cindex Webmail | |
116 | So how does reading mail via the web work, you ask. In that case, | |
117 | the web interface just allows you to remote-control a MUA on the web | |
118 | host. Whether the web host is also a mail host, and how all the | |
119 | pieces interact is completely irrelevant. You usually cannot use | |
120 | Emacs to read mail via the web, unless you use software that parses | |
121 | the ever-changing HTML of the web interface. | |
122 | ||
123 | @node Emacs Speaks SMTP | |
124 | @chapter Emacs Speaks SMTP | |
125 | ||
126 | Emacs includes a package for sending your mail to a SMTP server and | |
127 | have it take care of delivering it to the final destination, rather | |
128 | than letting the MTA on your local system take care of it. This can | |
129 | be useful if you don't have a MTA set up on your host, or if your | |
130 | machine is often disconnected from the internet. | |
131 | ||
132 | Sending mail via SMTP requires configuring your mail user agent | |
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133 | (@pxref{Mail Methods,,,emacs}) to use the SMTP library. If you |
134 | have not configured anything, then in Emacs 24.1 and later the first | |
135 | time you try to send a mail Emacs will ask how you want to send | |
136 | mail. To use this library, answer @samp{smtp} when prompted. Emacs | |
137 | then asks for the name of the SMTP server. | |
138 | ||
139 | If you prefer, or if you are using a non-standard mail user agent, | |
140 | you can configure this yourself. The normal way to do this is to set | |
141 | the variable @code{send-mail-function} (@pxref{Mail | |
142 | Sending,,,emacs}) to the value you want to use. To use this library: | |
143 | ||
144 | @smallexample | |
4009494e | 145 | (setq send-mail-function 'smtpmail-send-it) |
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146 | @end smallexample |
147 | ||
148 | @noindent | |
149 | The default value for this variable is @code{sendmail-query-once}, | |
150 | which interactively asks how you want to send mail. | |
151 | ||
152 | Your mail user agent might use a different variable for this purpose. | |
153 | It should inherit from @code{send-mail-function}, but if it does not, | |
154 | or if you prefer, you can set that variable directly. Consult your | |
155 | mail user agent's documentation for more details. For example, | |
156 | (@pxref{Mail Variables,,,message}). | |
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157 | |
158 | Before using SMTP you must find out the hostname of the SMTP server | |
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159 | to use. Your system administrator or mail service provider should |
160 | supply this information. Often it is some variant of the server you | |
161 | receive mail from. If your email address is | |
162 | @samp{yourname@@example.com}, then the name of the SMTP server is | |
163 | may be something like @samp{smtp.example.com}. | |
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164 | |
165 | @table @code | |
166 | @item smtpmail-smtp-server | |
167 | @vindex smtpmail-smtp-server | |
168 | @vindex SMTPSERVER | |
169 | The variable @code{smtpmail-smtp-server} controls the hostname of | |
170 | the server to use. It is a string with an IP address or hostname. It | |
171 | defaults to the contents of the @env{SMTPSERVER} environment | |
172 | variable, or, if empty, the contents of | |
173 | @code{smtpmail-default-smtp-server}. | |
174 | ||
175 | @item smtpmail-default-smtp-server | |
176 | @vindex smtpmail-default-smtp-server | |
177 | The variable @code{smtpmail-default-smtp-server} controls the | |
178 | default hostname of the server to use. It is a string with an IP | |
179 | address or hostname. It must be set before the SMTP library is | |
180 | loaded. It has no effect if set after the SMTP library has been | |
181 | loaded, or if @code{smtpmail-smtp-server} is defined. It is usually | |
182 | set by system administrators in a site wide initialization file. | |
183 | @end table | |
184 | ||
185 | The following example illustrates what you could put in | |
186 | @file{~/.emacs} to set the SMTP server name. | |
187 | ||
188 | @example | |
189 | ;; Send mail using SMTP via mail.example.org. | |
190 | (setq smtpmail-smtp-server "mail.example.org") | |
191 | @end example | |
192 | ||
193 | @cindex Mail Submission | |
194 | SMTP is normally used on the registered ``smtp'' TCP service port 25. | |
195 | Some environments use SMTP in ``Mail Submission'' mode, which uses | |
196 | port 587. Using other ports is not uncommon, either for security by | |
197 | obscurity purposes, port forwarding, or otherwise. | |
198 | ||
199 | @table @code | |
200 | @item smtpmail-smtp-service | |
201 | @vindex smtpmail-smtp-service | |
202 | The variable @code{smtpmail-smtp-service} controls the port on the | |
203 | server to contact. It is either a string, in which case it will be | |
204 | translated into an integer using system calls, or an integer. | |
205 | @end table | |
206 | ||
207 | The following example illustrates what you could put in | |
208 | @file{~/.emacs} to set the SMTP service port. | |
209 | ||
210 | @example | |
211 | ;; Send mail using SMTP on the mail submission port 587. | |
212 | (setq smtpmail-smtp-service 587) | |
213 | @end example | |
214 | ||
215 | @node Authentication | |
216 | @chapter Authentication | |
217 | ||
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218 | @cindex password |
219 | @cindex user name | |
220 | Most SMTP servers require clients to authenticate themselves before | |
221 | they are allowed to send mail. Authentication usually involves | |
1df7defd | 222 | supplying a user name and password. |
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223 | |
224 | If you have not configured anything, then the first time you try to | |
225 | send mail via a server, Emacs (version 24.1 and later) prompts you | |
226 | for the user name and password to use, and then offers to save the | |
227 | information. By default, Emacs stores authentication information in | |
228 | a file @file{~/.authinfo}. | |
229 | ||
230 | @cindex authinfo | |
231 | The basic format of the @file{~/.authinfo} file is one line for each | |
232 | set of credentials. Each line consists of pairs of variables and | |
233 | values. A simple example would be: | |
234 | ||
235 | @smallexample | |
236 | machine mail.example.org port 25 login myuser password mypassword | |
237 | @end smallexample | |
238 | ||
239 | @noindent | |
240 | This specifies that when using the SMTP server called @samp{mail.example.org} | |
241 | on port 25, Emacs should send the user name @samp{myuser} and the | |
242 | password @samp{mypassword}. Either or both of the login and password | |
243 | fields may be absent, in which case Emacs prompts for the information | |
244 | when you try to send mail. (This replaces the old | |
245 | @code{smtpmail-auth-credentials} variable used prior to Emacs 24.1.) | |
246 | ||
247 | @vindex smtpmail-smtp-user | |
248 | When the SMTP library connects to a host on a certain port, it | |
249 | searches the @file{~/.authinfo} file for a matching entry. If an | |
250 | entry is found, the authentication process is invoked and the | |
251 | credentials are used. If the variable @code{smtpmail-smtp-user} is | |
252 | set to a non-@code{nil} value, then only entries for that user are | |
253 | considered. For more information on the @file{~/.authinfo} | |
254 | file, @pxref{Top,,auth-source, auth, Emacs auth-source Library}. | |
255 | ||
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256 | @cindex SASL |
257 | @cindex CRAM-MD5 | |
9f26dc24 | 258 | @cindex PLAIN |
4009494e | 259 | @cindex LOGIN |
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260 | The process by which the SMTP library authenticates you to the server |
261 | is known as ``Simple Authentication and Security Layer'' (SASL). | |
262 | There are various SASL mechanisms, and this library supports three of | |
1df7defd | 263 | them: CRAM-MD5, PLAIN, and LOGIN@. It tries each of them, in that order, |
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264 | until one succeeds. The first uses a form of encryption to obscure |
265 | your password, while the other two do not. | |
266 | ||
267 | ||
268 | @node Encryption | |
269 | @chapter Encryption | |
270 | ||
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271 | @cindex STARTTLS |
272 | @cindex TLS | |
273 | @cindex SSL | |
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274 | For greater security, you can encrypt your connection to the SMTP |
275 | server. If this is to work, both Emacs and the server must support it. | |
276 | ||
277 | The SMTP library supports the ``Transport Layer Security'' (TLS), and | |
278 | the older ``Secure Sockets Layer'' (SSL) encryption mechanisms. | |
279 | It also supports STARTTLS, which is a variant of TLS in which the | |
280 | initial connection to the server is made in plain text, requesting a | |
281 | switch to an encrypted channel for the rest of the process. | |
282 | ||
283 | @vindex smtpmail-stream-type | |
284 | The variable @code{smtpmail-stream-type} controls what form of | |
285 | connection the SMTP library uses. The default value is @code{nil}, | |
286 | which means to use a plain connection, but try to switch to a STARTTLS | |
287 | encrypted connection if the server supports it. Other possible values | |
288 | are: @code{starttls} - insist on STARTTLS; @code{ssl} - use TLS/SSL; | |
289 | and @code{plain} - no encryption. | |
290 | ||
291 | Use of any form of TLS/SSL requires support in Emacs. You can either | |
292 | use the built-in support (in Emacs 24.1 and later), or the | |
293 | @file{starttls.el} Lisp library. The built-in support uses the GnuTLS | |
294 | @footnote{@url{http://www.gnu.org/software/gnutls/}} library. | |
295 | If your Emacs has GnuTLS support built-in, the function | |
296 | @code{gnutls-available-p} is defined and returns non-@code{nil}. | |
297 | Otherwise, you must use the @file{starttls.el} library (see that file for | |
298 | more information on customization options, etc.). The Lisp library | |
299 | requires one of the following external tools to be installed: | |
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300 | |
301 | @enumerate | |
302 | @item | |
9f26dc24 | 303 | The GnuTLS command line tool @samp{gnutls-cli}, which you can get from |
4009494e | 304 | @url{http://www.gnu.org/software/gnutls/}. This is the recommended |
9f26dc24 | 305 | tool, mainly because it can verify server certificates. |
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306 | |
307 | @item | |
9f26dc24 | 308 | The @samp{starttls} external program, which you can get from |
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309 | @file{starttls-*.tar.gz} from @uref{ftp://ftp.opaopa.org/pub/elisp/}. |
310 | @end enumerate | |
311 | ||
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312 | @cindex certificates |
313 | @cindex keys | |
314 | The SMTP server may also request that you verify your identity by | |
315 | sending a certificate and the associated encryption key to the server. | |
316 | If you need to do this, you can use an @file{~/.authinfo} entry like this: | |
4009494e | 317 | |
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318 | @smallexample |
319 | machine mail.example.org port 25 key "~/.my_smtp_tls.key" cert "~/.my_smtp_tls.cert" | |
320 | @end smallexample | |
4009494e | 321 | |
9f26dc24 GM |
322 | @noindent |
323 | (This replaces the old @code{smtpmail-starttls-credentials} variable used | |
324 | prior to Emacs 24.1.) | |
4009494e | 325 | |
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326 | |
327 | @node Queued delivery | |
328 | @chapter Queued delivery | |
329 | ||
330 | @cindex Dialup connection | |
331 | If you connect to the internet via a dialup connection, or for some | |
332 | other reason don't have permanent internet connection, sending mail | |
333 | will fail when you are not connected. The SMTP library implements | |
334 | queued delivery, and the following variable control its behavior. | |
335 | ||
336 | @table @code | |
337 | @item smtpmail-queue-mail | |
338 | @vindex smtpmail-queue-mail | |
339 | The variable @code{smtpmail-queue-mail} controls whether a simple | |
340 | off line mail sender is active. This variable is a boolean, and | |
341 | defaults to @code{nil} (disabled). If this is non-@code{nil}, mail is | |
342 | not sent immediately but rather queued in the directory | |
343 | @code{smtpmail-queue-dir} and can be later sent manually by invoking | |
344 | @code{smtpmail-send-queued-mail} (typically when you connect to the | |
345 | internet). | |
346 | ||
347 | @item smtpmail-queue-dir | |
348 | @vindex smtpmail-queue-dir | |
349 | The variable @code{smtpmail-queue-dir} specifies the name of the | |
350 | directory to hold queued messages. It defaults to | |
351 | @file{~/Mail/queued-mail/}. | |
352 | @end table | |
353 | ||
354 | @findex smtpmail-send-queued-mail | |
355 | The function @code{smtpmail-send-queued-mail} can be used to send | |
356 | any queued mail when @code{smtpmail-queue-mail} is enabled. It is | |
357 | typically invoked interactively with @kbd{M-x | |
358 | smtpmail-send-queued-mail RET} when you are connected to the internet. | |
359 | ||
360 | @node Server workarounds | |
361 | @chapter Server workarounds | |
362 | ||
363 | Some SMTP servers have special requirements. The following variables | |
364 | implement support for common requirements. | |
365 | ||
366 | @table @code | |
367 | ||
368 | @item smtpmail-local-domain | |
369 | @vindex smtpmail-local-domain | |
370 | The variable @code{smtpmail-local-domain} controls the hostname sent | |
371 | in the first @code{EHLO} or @code{HELO} command sent to the server. | |
372 | It should only be set if the @code{system-name} function returns a | |
373 | name that isn't accepted by the server. Do not set this variable | |
374 | unless your server complains. | |
375 | ||
376 | @item smtpmail-sendto-domain | |
377 | @vindex smtpmail-sendto-domain | |
378 | The variable @code{smtpmail-sendto-domain} makes the SMTP library | |
379 | add @samp{@@} and the specified value to recipients specified in the | |
380 | message when they are sent using the @code{RCPT TO} command. Some | |
381 | configurations of sendmail requires this behavior. Don't bother to | |
382 | set this unless you have get an error like: | |
383 | ||
384 | @example | |
b1fbbb32 | 385 | Sending failed; SMTP protocol error |
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386 | @end example |
387 | ||
388 | when sending mail, and the debug buffer (@pxref{Debugging})) contains | |
389 | an error such as: | |
390 | ||
391 | @example | |
b1fbbb32 GM |
392 | RCPT TO: @var{someone} |
393 | 501 @var{someone}: recipient address must contain a domain | |
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394 | @end example |
395 | ||
396 | @end table | |
397 | ||
398 | ||
399 | @node Debugging | |
400 | @chapter Debugging | |
401 | ||
402 | Sometimes delivery fails, often with the generic error message | |
403 | @samp{Sending failed; SMTP protocol error}. Enabling one or both of | |
404 | the following variables and inspecting a trace buffer will often give | |
405 | clues to the reason for the error. | |
406 | ||
407 | @table @code | |
408 | ||
409 | @item smtpmail-debug-info | |
410 | @vindex smtpmail-debug-info | |
411 | The variable @code{smtpmail-debug-info} controls whether to print | |
412 | the SMTP protocol exchange in the minibuffer, and retain the entire | |
413 | exchange in a buffer @samp{*trace of SMTP session to @var{server}*}, | |
414 | where @var{server} is the name of the mail server to which you send | |
415 | mail. | |
416 | ||
417 | @item smtpmail-debug-verb | |
418 | @vindex smtpmail-debug-verb | |
419 | The variable @code{smtpmail-debug-verb} controls whether to send the | |
420 | @code{VERB} token to the server. The @code{VERB} server instructs the | |
421 | server to be more verbose, and often also to attempt final delivery | |
422 | while your SMTP session is still running. It is usually only useful | |
423 | together with @code{smtpmail-debug-info}. Note that this may cause | |
424 | mail delivery to take considerable time if the final destination | |
425 | cannot accept mail. | |
426 | ||
427 | @end table | |
428 | ||
429 | @node GNU Free Documentation License | |
430 | @chapter GNU Free Documentation License | |
431 | @include doclicense.texi | |
432 | ||
433 | @node Index | |
434 | @chapter Index | |
435 | ||
436 | @section Concept Index | |
437 | ||
438 | @printindex cp | |
439 | ||
440 | @section Function and Variable Index | |
441 | ||
442 | @printindex fn | |
443 | ||
4009494e | 444 | @bye |