1 . $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.8 2006/07/03 18:11:41 fanf2 Exp $
3 . /////////////////////////////////////////////////////////////////////////////
4 . This is the primary source of the Exim Manual. It is an xfpt document that is
5 . converted into DocBook XML for subsequent conversion into printing and online
6 . formats. The markup used herein is "standard" xfpt markup, with some extras.
7 . The markup is summarized in a file called Markup.txt.
8 . /////////////////////////////////////////////////////////////////////////////
15 . /////////////////////////////////////////////////////////////////////////////
16 . These definitions set some parameters and save some typing. Remember that
17 . the <bookinfo> element must also be updated for each new edition.
18 . /////////////////////////////////////////////////////////////////////////////
20 .set ACL "access control lists (ACLs)"
21 .set previousversion "4.61"
25 . /////////////////////////////////////////////////////////////////////////////
26 . Additional xfpt markup used by this document, over and above the default
27 . provided in the xfpt library.
28 . /////////////////////////////////////////////////////////////////////////////
30 . --- Override the &$ flag to automatically insert a $ with the variable name
32 .flag &$ $& "<varname>$" "</varname>"
34 . --- Short flags for daggers in option headings. They will always be inside
35 . --- an italic string, but we want the daggers to be roman.
37 .flag &!! "</emphasis>†<emphasis>"
38 .flag &!? "</emphasis>‡<emphasis>"
40 . --- A macro for an Exim option definition heading, generating a one-line
41 . --- table with four columns.
45 .itable all 0 0 4 8* left 5* center 5* center 6* right
46 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
50 . --- A macro for the common 2-column tables. The width of the first column
51 . --- is suitable for the many tables at the start of the main options chapter;
52 . --- the small number of other 2-column tables override it.
54 .macro table2 190pt 260pt
55 .itable none 0 0 2 $1 left $2 left
58 . --- Macros for the concept and option index entries. For a "range" style of
59 . --- entry, use .scindex for the start and .ecindex for the end. The first
60 . --- argument of .scindex and the only argument of .ecindex must be the ID
61 . --- that ties them together.
64 &<indexterm role="concept">&
65 &<primary>&$1&</primary>&
67 &<secondary>&$2&</secondary>&
73 &<indexterm role="concept" id="$1" class="startofrange">&
74 &<primary>&$2&</primary>&
76 &<secondary>&$3&</secondary>&
82 &<indexterm role="concept" startref="$1" class="endofrange"/>&
86 &<indexterm role="option">&
87 &<primary>&$1&</primary>&
89 &<secondary>&$2&</secondary>&
95 .echo "** Don't use .index; use .cindex or .oindex"
97 . ////////////////////////////////////////////////////////////////////////////
100 . ////////////////////////////////////////////////////////////////////////////
101 . The <bookinfo> element is removed from the XML before processing for Ascii
103 . ////////////////////////////////////////////////////////////////////////////
107 <title>Specification of the Exim Mail Transfer Agent</title>
108 <titleabbrev>The Exim MTA</titleabbrev>
109 <date>27 April 2006</date>
110 <author><firstname>Philip</firstname><surname>Hazel</surname></author>
111 <authorinitials>PH</authorinitials>
112 <affiliation><orgname>University of Cambridge Computing Service</orgname></affiliation>
113 <address>New Museums Site, Pembroke Street, Cambridge CB2 3QH, England</address>
114 <revhistory><revision>
115 <revnumber>4.62</revnumber>
116 <date>27 April 2006</date>
117 <authorinitials>PH</authorinitials>
118 </revision></revhistory>
119 <copyright><year>2006</year><holder>University of Cambridge</holder></copyright>
124 . /////////////////////////////////////////////////////////////////////////////
125 . This chunk of literal XML implements index entries of the form "x, see y" and
126 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
127 . at the top level, so we have to put the .chapter directive first.
128 . /////////////////////////////////////////////////////////////////////////////
130 .chapter "Introduction"
133 <indexterm role="concept">
134 <primary>$1, $2, etc.</primary>
135 <see><emphasis>numerical variables</emphasis></see>
137 <indexterm role="concept">
138 <primary>address</primary>
139 <secondary>rewriting</secondary>
140 <see><emphasis>rewriting</emphasis></see>
142 <indexterm role="concept">
143 <primary>Bounce Address Tag Validation</primary>
144 <see><emphasis>BATV</emphasis></see>
146 <indexterm role="concept">
147 <primary>Client SMTP Authorization</primary>
148 <see><emphasis>CSA</emphasis></see>
150 <indexterm role="concept">
151 <primary>CR character</primary>
152 <see><emphasis>carriage return</emphasis></see>
154 <indexterm role="concept">
155 <primary>CRL</primary>
156 <see><emphasis>certificate revocation list</emphasis></see>
158 <indexterm role="concept">
159 <primary>delivery</primary>
160 <secondary>failure report</secondary>
161 <see><emphasis>bounce message</emphasis></see>
163 <indexterm role="concept">
164 <primary>dialup</primary>
165 <see><emphasis>intermittently connected hosts</emphasis></see>
167 <indexterm role="concept">
168 <primary>exiscan</primary>
169 <see><emphasis>content scanning</emphasis></see>
171 <indexterm role="concept">
172 <primary>failover</primary>
173 <see><emphasis>fallback</emphasis></see>
175 <indexterm role="concept">
176 <primary>fallover</primary>
177 <see><emphasis>fallback</emphasis></see>
179 <indexterm role="concept">
180 <primary>filter</primary>
181 <secondary>Sieve</secondary>
182 <see><emphasis>Sieve filter</emphasis></see>
184 <indexterm role="concept">
185 <primary>ident</primary>
186 <see><emphasis>RFC 1413</emphasis></see>
188 <indexterm role="concept">
189 <primary>LF character</primary>
190 <see><emphasis>linefeed</emphasis></see>
192 <indexterm role="concept">
193 <primary>maximum</primary>
194 <see><emphasis>limit</emphasis></see>
196 <indexterm role="concept">
197 <primary>monitor</primary>
198 <see><emphasis>Exim monitor</emphasis></see>
200 <indexterm role="concept">
201 <primary>no_<emphasis>xxx</emphasis></primary>
202 <see>entry for xxx</see>
204 <indexterm role="concept">
205 <primary>NUL</primary>
206 <see><emphasis>binary zero</emphasis></see>
208 <indexterm role="concept">
209 <primary>passwd file</primary>
210 <see><emphasis>/etc/passwd</emphasis></see>
212 <indexterm role="concept">
213 <primary>process id</primary>
214 <see><emphasis>pid</emphasis></see>
216 <indexterm role="concept">
217 <primary>RBL</primary>
218 <see><emphasis>DNS list</emphasis></see>
220 <indexterm role="concept">
221 <primary>redirection</primary>
222 <see><emphasis>address redirection</emphasis></see>
224 <indexterm role="concept">
225 <primary>return path</primary>
226 <seealso><emphasis>envelope sender</emphasis></seealso>
228 <indexterm role="concept">
229 <primary>scanning</primary>
230 <see><emphasis>content scanning</emphasis></see>
232 <indexterm role="concept">
233 <primary>SSL</primary>
234 <see><emphasis>TLS</emphasis></see>
236 <indexterm role="concept">
237 <primary>string</primary>
238 <secondary>expansion</secondary>
239 <see><emphasis>expansion</emphasis></see>
241 <indexterm role="concept">
242 <primary>top bit</primary>
243 <see><emphasis>8-bit characters</emphasis></see>
245 <indexterm role="concept">
246 <primary>variables</primary>
247 <see><emphasis>expansion, variables</emphasis></see>
249 <indexterm role="concept">
250 <primary>zero, binary</primary>
251 <see><emphasis>binary zero</emphasis></see>
257 . /////////////////////////////////////////////////////////////////////////////
258 . This is the real start of the first chapter. See the comment above as to why
259 . we can't have the .chapter line here.
260 . chapter "Introduction"
261 . /////////////////////////////////////////////////////////////////////////////
263 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
264 Unix-like operating systems. It was designed on the assumption that it would be
265 run on hosts that are permanently connected to the Internet. However, it can be
266 used on intermittently connected hosts with suitable configuration adjustments.
268 Configuration files currently exist for the following operating systems: AIX,
269 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
270 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
271 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
272 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
273 Some of these operating systems are no longer current and cannot easily be
274 tested, so the configuration files may no longer work in practice.
276 There are also configuration files for compiling Exim in the Cygwin environment
277 that can be installed on systems running Windows. However, this document does
278 not contain any information about running Exim in the Cygwin environment.
280 The terms and conditions for the use and distribution of Exim are contained in
281 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
282 Public Licence, a copy of which may be found in the file &_LICENCE_&.
284 The use, supply or promotion of Exim for the purpose of sending bulk,
285 unsolicited electronic mail is incompatible with the basic aims of the program,
286 which revolve around the free provision of a service that enhances the quality
287 of personal communications. The author of Exim regards indiscriminate
288 mass-mailing as an antisocial, irresponsible abuse of the Internet.
290 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
291 experience of running and working on the Smail 3 code, I could never have
292 contemplated starting to write a new MTA. Many of the ideas and user interfaces
293 were originally taken from Smail 3, though the actual code of Exim is entirely
294 new, and has developed far beyond the initial concept.
296 Many people, both in Cambridge and around the world, have contributed to the
297 development and the testing of Exim, and to porting it to various operating
298 systems. I am grateful to them all. The distribution now contains a file called
299 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
303 .section "Exim documentation"
305 .cindex "documentation"
306 This edition of the Exim specification applies to version &version; of Exim.
307 Substantive changes from the &previousversion; edition are marked in some
308 renditions of the document; this paragraph is so marked if the rendition is
309 capable of showing a change indicator.
312 This document is very much a reference manual; it is not a tutorial. The reader
313 is expected to have some familiarity with the SMTP mail transfer protocol and
314 with general Unix system administration. Although there are some discussions
315 and examples in places, the information is mostly organized in a way that makes
316 it easy to look up, rather than in a natural order for sequential reading.
317 Furthermore, the manual aims to cover every aspect of Exim in detail, including
318 a number of rarely-used, special-purpose features that are unlikely to be of
321 .cindex "books about Exim"
322 An &"easier"& discussion of Exim which provides more in-depth explanatory,
323 introductory, and tutorial material can be found in a book entitled &'The Exim
324 SMTP Mail Server'&, published by UIT Cambridge
325 (&url(http://www.uit.co.uk/exim-book/)).
327 This book also contains a chapter that gives a general introduction to SMTP and
328 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
329 with the latest release of Exim. (Note that the earlier book about Exim,
330 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
332 .cindex "Debian" "information sources"
333 If you are using a Debian distribution of Exim, you will find information about
334 Debian-specific features in the file
336 &_/usr/share/doc/exim4-base/README.Debian_&
338 The command &(man update-exim.conf)& is another source of Debian-specific
341 .cindex "&_doc/NewStuff_&"
342 .cindex "&_doc/ChangeLog_&"
344 As the program develops, there may be features in newer versions that have not
345 yet made it into this document, which is updated only when the most significant
346 digit of the fractional part of the version number changes. Specifications of
347 new features that are not yet in this manual are placed in the file
348 &_doc/NewStuff_& in the Exim distribution.
350 Some features may be classified as &"experimental"&. These may change
351 incompatibly while they are developing, or even be withdrawn. For this reason,
352 they are not documented in this manual. Information about experimental features
353 can be found in the file &_doc/experimental.txt_&.
355 All changes to the program (whether new features, bug fixes, or other kinds of
356 change) are noted briefly in the file called &_doc/ChangeLog_&.
358 .cindex "&_doc/spec.txt_&"
359 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
360 that it can easily be searched with a text editor. Other files in the &_doc_&
364 .row &_OptionLists.txt_& "list of all options in alphabetical order"
365 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
366 .row &_exim.8_& "a man page of Exim's command line options"
367 .row &_experimental.txt_& "documentation of experimental features"
368 .row &_filter.txt_& "specification of the filter language"
369 .row &_pcrepattern.txt_& "specification of PCRE regular expressions"
370 .row &_pcretest.txt_& "specification of the PCRE testing program"
371 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
372 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
375 The main specification and the specification of the filtering language are also
376 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
377 &<<SECTavail>>& below tells you how to get hold of these.
381 .section "FTP and web sites"
384 The primary site for Exim source distributions is currently the University of
385 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
386 distribution'& below. In addition, there is a web site and an FTP site at
387 &%exim.org%&. These are now also hosted at the University of Cambridge. The
388 &%exim.org%& site was previously hosted for a number of years by Energis
389 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
393 As well as Exim distribution tar files, the Exim web site contains a number of
394 differently formatted versions of the documentation, including the FAQ in both
395 text and HTML formats. The HTML version comes with a keyword-in-context index.
396 A recent addition to the online information is the Exim wiki
397 (&url(http://www.exim.org/eximwiki/)). We hope that this will make it easier
398 for Exim users to contribute examples, tips, and know-how for the benefit of
403 .section "Mailing lists"
404 .cindex "mailing lists" "for Exim users"
405 The following are the three main Exim mailing lists:
408 .row &'exim-users@exim.org'& "general discussion list"
409 .row &'exim-dev@exim.org'& "discussion of bugs, enhancements, etc."
410 .row &'exim-announce@exim.org'& "moderated, low volume announcements list"
413 You can subscribe to these lists, change your existing subscriptions, and view
414 or search the archives via the mailing lists link on the Exim home page.
415 .cindex "Debian" "mailing list for"
416 If you are using a Debian distribution of Exim, you may wish to subscribe to
417 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&.
419 .section "Exim training"
420 .cindex "training courses"
421 From time to time (approximately annually at the time of writing), training
422 courses are run by the author of Exim in Cambridge, UK. Details of any
423 forthcoming courses can be found on the web site
424 &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
427 .section "Bug reports"
428 .cindex "bug reports"
429 .cindex "reporting bugs"
430 Reports of obvious bugs should be emailed to &'bugs@exim.org'&. However, if you
431 are unsure whether some behaviour is a bug or not, the best thing to do is to
432 post a message to the &'exim-dev'& mailing list and have it discussed.
436 .section "Where to find the Exim distribution" "SECTavail"
438 .cindex "distribution" "ftp site"
439 The master ftp site for the Exim distribution is
441 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
445 &*ftp://ftp.exim.org/pub/exim*&
447 The file references that follow are relative to the &_exim_& directories at
448 these sites. There are now quite a number of independent mirror sites around
449 the world. Those that I know about are listed in the file called &_Mirrors_&.
451 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
452 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
453 distributions), and &_Testing_& for testing versions. In the &_exim4_&
454 subdirectory, the current release can always be found in files called
457 &_exim-n.nn.tar.bz2_&
459 where &'n.nn'& is the highest such version number in the directory. The two
460 files contain identical data; the only difference is the type of compression.
461 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
463 .cindex "distribution" "signing details"
464 .cindex "distribution" "public key"
465 .cindex "public key for signed distribution"
466 The distributions are currently signed with Philip Hazel's GPG key. The
467 corresponding public key is available from a number of keyservers, and there is
468 also a copy in the file &_Public-Key_&. The signatures for the tar bundles are
471 &_exim-n.nn.tar.gz.sig_&
472 &_exim-n.nn.tar.bz2.sig_&
474 For each released version, the log of changes is made separately available in a
475 separate file in the directory &_ChangeLogs_& so that it is possible to
476 find out what has changed without having to download the entire distribution.
478 .cindex "documentation" "available formats"
479 The main distribution contains ASCII versions of this specification and other
480 documentation; other formats of the documents are available in separate files
481 inside the &_exim4_& directory of the FTP site:
483 &_exim-html-n.nn.tar.gz_&
484 &_exim-pdf-n.nn.tar.gz_&
485 &_exim-postscript-n.nn.tar.gz_&
486 &_exim-texinfo-n.nn.tar.gz_&
488 These tar files contain only the &_doc_& directory, not the complete
489 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
491 The FAQ is available for downloading in two different formats in these files:
494 &_exim4/FAQ.html.tar.gz_&
496 The first of these is a single ASCII file that can be searched with a text
497 editor. The second is a directory of HTML files, normally accessed by starting
498 at &_index.html_&. The HTML version of the FAQ (which is also included in the
499 HTML documentation tarbundle) includes a keyword-in-context index, which is
500 often the most convenient way of finding your way around.
505 A wish list is maintained, containing ideas for new features that have been
506 submitted. From time to time the file is exported to the ftp site into the file
507 &_exim4/WishList_&. Items are removed from the list if they get implemented.
511 .section "Contributed material"
512 .cindex "contributed material"
513 At the ftp site, there is a directory called &_Contrib_& that contains
514 miscellaneous files contributed to the Exim community by Exim users. There is
515 also a collection of contributed configuration examples in
516 &_exim4/config.samples.tar.gz_&. These samples are referenced from the FAQ.
520 .section "Limitations"
522 .cindex "limitations of Exim"
523 .cindex "bang paths" "not handled by Exim"
524 Exim is designed for use as an Internet MTA, and therefore handles addresses in
525 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
526 simple two-component bang paths can be converted by a straightforward rewriting
527 configuration. This restriction does not prevent Exim from being interfaced to
528 UUCP as a transport mechanism, provided that domain addresses are used.
530 .cindex "domainless addresses"
531 .cindex "address" "without domain"
532 Exim insists that every address it handles has a domain attached. For incoming
533 local messages, domainless addresses are automatically qualified with a
534 configured domain value. Configuration options specify from which remote
535 systems unqualified addresses are acceptable. These are then qualified on
538 .cindex "transport" "external"
539 .cindex "external transports"
540 The only external transport mechanisms that are currently implemented are SMTP
541 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
542 transport is available, and there are facilities for writing messages to files
543 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
544 to send messages to other transport mechanisms such as UUCP, provided they can
545 handle domain-style addresses. Batched SMTP input is also catered for.
547 Exim is not designed for storing mail for dial-in hosts. When the volumes of
548 such mail are large, it is better to get the messages &"delivered"& into files
549 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
552 Although Exim does have basic facilities for scanning incoming messages, these
553 are not comprehensive enough to do full virus or spam scanning. Such operations
554 are best carried out using additional specialized software packages. If you
555 compile Exim with the content-scanning extension, straightforward interfaces to
556 a number of common scanners are provided.
560 .section "Run time configuration"
561 Exim's run time configuration is held in a single text file that is divided
562 into a number of sections. The entries in this file consist of keywords and
563 values, in the style of Smail 3 configuration files. A default configuration
564 file which is suitable for simple online installations is provided in the
565 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
568 .section "Calling interface"
569 .cindex "Sendmail compatibility" "command line interface"
570 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
571 can be a straight replacement for &_/usr/lib/sendmail_& or
572 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
573 about Sendmail in order to run Exim. For actions other than sending messages,
574 Sendmail-compatible options also exist, but those that produce output (for
575 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
576 format. There are also some additional options that are compatible with Smail
577 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
578 documents all Exim's command line options. This information is automatically
579 made into the man page that forms part of the Exim distribution.
581 Control of messages on the queue can be done via certain privileged command
582 line options. There is also an optional monitor program called &'eximon'&,
583 which displays current information in an X window, and which contains a menu
584 interface to Exim's command line administration options.
588 .section "Terminology"
589 .cindex "terminology definitions"
590 .cindex "body of message" "definition of"
591 The &'body'& of a message is the actual data that the sender wants to transmit.
592 It is the last part of a message, and is separated from the &'header'& (see
593 below) by a blank line.
595 .cindex "bounce message" "definition of"
596 When a message cannot be delivered, it is normally returned to the sender in a
597 delivery failure message or a &"non-delivery report"& (NDR). The term
598 &'bounce'& is commonly used for this action, and the error reports are often
599 called &'bounce messages'&. This is a convenient shorthand for &"delivery
600 failure error report"&. Such messages have an empty sender address in the
601 message's &'envelope'& (see below) to ensure that they cannot themselves give
602 rise to further bounce messages.
604 The term &'default'& appears frequently in this manual. It is used to qualify a
605 value which is used in the absence of any setting in the configuration. It may
606 also qualify an action which is taken unless a configuration setting specifies
609 The term &'defer'& is used when the delivery of a message to a specific
610 destination cannot immediately take place for some reason (a remote host may be
611 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
614 The word &'domain'& is sometimes used to mean all but the first component of a
615 host's name. It is &'not'& used in that sense here, where it normally refers to
616 the part of an email address following the @ sign.
618 .cindex "envelope" "definition of"
619 .cindex "sender" "definition of"
620 A message in transit has an associated &'envelope'&, as well as a header and a
621 body. The envelope contains a sender address (to which bounce messages should
622 be delivered), and any number of recipient addresses. References to the
623 sender or the recipients of a message usually mean the addresses in the
624 envelope. An MTA uses these addresses for delivery, and for returning bounce
625 messages, not the addresses that appear in the header lines.
627 .cindex "message header" "definition of"
628 .cindex "header section" "definition of"
629 The &'header'& of a message is the first part of a message's text, consisting
630 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
631 &'Subject:'&, etc. Long header lines can be split over several text lines by
632 indenting the continuations. The header is separated from the body by a blank
635 .cindex "local part" "definition of"
636 .cindex "domain" "definition of"
637 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
638 part of an email address that precedes the @ sign. The part that follows the
639 @ sign is called the &'domain'& or &'mail domain'&.
641 .cindex "local delivery" "definition of"
642 .cindex "remote delivery" "definition of"
643 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
644 delivery to a file or a pipe on the local host from delivery by SMTP over
645 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
646 host it is running on are &'remote'&.
648 .cindex "return path" "definition of"
649 &'Return path'& is another name that is used for the sender address in a
652 .cindex "queue" "definition of"
653 The term &'queue'& is used to refer to the set of messages awaiting delivery,
654 because this term is in widespread use in the context of MTAs. However, in
655 Exim's case the reality is more like a pool than a queue, because there is
656 normally no ordering of waiting messages.
658 .cindex "queue runner" "definition of"
659 The term &'queue runner'& is used to describe a process that scans the queue
660 and attempts to deliver those messages whose retry times have come. This term
661 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
662 the waiting messages are normally processed in an unpredictable order.
664 .cindex "spool directory" "definition of"
665 The term &'spool directory'& is used for a directory in which Exim keeps the
666 messages on its queue &-- that is, those that it is in the process of
667 delivering. This should not be confused with the directory in which local
668 mailboxes are stored, which is called a &"spool directory"& by some people. In
669 the Exim documentation, &"spool"& is always used in the first sense.
676 . ////////////////////////////////////////////////////////////////////////////
677 . ////////////////////////////////////////////////////////////////////////////
679 .chapter "Incorporated code"
680 .cindex "incorporated code"
681 .cindex "regular expressions" "library"
683 A number of pieces of external code are included in the Exim distribution.
686 Regular expressions are supported in the main Exim program and in the Exim
687 monitor using the freely-distributable PCRE library, copyright ©
688 University of Cambridge. The source is distributed in the directory
689 &_src/pcre_&. However, this is a cut-down version of PCRE. If you want to use
690 the PCRE library in other programs, you should obtain and install the full
691 version from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
693 .cindex "cdb" "acknowledgement"
694 Support for the cdb (Constant DataBase) lookup method is provided by code
695 contributed by Nigel Metheringham of (at the time he contributed it) Planet
696 Online Ltd. The implementation is completely contained within the code of Exim.
697 It does not link against an external cdb library. The code contains the
698 following statements:
701 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
703 This program is free software; you can redistribute it and/or modify it under
704 the terms of the GNU General Public License as published by the Free Software
705 Foundation; either version 2 of the License, or (at your option) any later
708 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
709 the spec and sample code for cdb can be obtained from
710 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows some
711 code from Dan Bernstein's implementation (which has no license restrictions
715 .cindex "SPA authentication"
716 .cindex "Samba project"
717 .cindex "Microsoft Secure Password Authentication"
718 Client support for Microsoft's &'Secure Password Authentication'& is provided
719 by code contributed by Marc Prud'hommeaux. Server support was contributed by
720 Tom Kistner. This includes code taken from the Samba project, which is released
724 .cindex "&'pwcheck'& daemon"
725 .cindex "&'pwauthd'& daemon"
726 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
727 by code taken from the Cyrus-SASL library and adapted by Alexander S.
728 Sabourenkov. The permission notice appears below, in accordance with the
729 conditions expressed therein.
732 Copyright © 2001 Carnegie Mellon University. All rights reserved.
734 Redistribution and use in source and binary forms, with or without
735 modification, are permitted provided that the following conditions
739 Redistributions of source code must retain the above copyright
740 notice, this list of conditions and the following disclaimer.
742 Redistributions in binary form must reproduce the above copyright
743 notice, this list of conditions and the following disclaimer in
744 the documentation and/or other materials provided with the
747 The name &"Carnegie Mellon University"& must not be used to
748 endorse or promote products derived from this software without
749 prior written permission. For permission or any other legal
750 details, please contact
752 Office of Technology Transfer
753 Carnegie Mellon University
755 Pittsburgh, PA 15213-3890
756 (412) 268-4387, fax: (412) 268-7395
757 tech-transfer@andrew.cmu.edu
760 Redistributions of any form whatsoever must retain the following
763 &"This product includes software developed by Computing Services
764 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
766 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
767 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
768 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
769 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
770 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
771 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
772 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
777 .cindex "Exim monitor" "acknowledgement"
780 The Exim Monitor program, which is an X-Window application, includes
781 modified versions of the Athena StripChart and TextPop widgets.
782 This code is copyright by DEC and MIT, and their permission notice appears
783 below, in accordance with the conditions expressed therein.
786 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
787 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
791 Permission to use, copy, modify, and distribute this software and its
792 documentation for any purpose and without fee is hereby granted,
793 provided that the above copyright notice appear in all copies and that
794 both that copyright notice and this permission notice appear in
795 supporting documentation, and that the names of Digital or MIT not be
796 used in advertising or publicity pertaining to distribution of the
797 software without specific, written prior permission.
799 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
800 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
801 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
802 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
803 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
804 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
809 Many people have contributed code fragments, some large, some small, that were
810 not covered by any specific licence requirements. It is assumed that the
811 contributors are happy to see their code incoporated into Exim under the GPL.
818 . ////////////////////////////////////////////////////////////////////////////
819 . ////////////////////////////////////////////////////////////////////////////
821 .chapter "How Exim receives and delivers mail" "" &&&
822 "Receiving and delivering mail"
825 .section "Overall philosophy"
826 .cindex "design philosophy"
827 Exim is designed to work efficiently on systems that are permanently connected
828 to the Internet and are handling a general mix of mail. In such circumstances,
829 most messages can be delivered immediately. Consequently, Exim does not
830 maintain independent queues of messages for specific domains or hosts, though
831 it does try to send several messages in a single SMTP connection after a host
832 has been down, and it also maintains per-host retry information.
835 .section "Policy control"
836 .cindex "policy control" "overview"
837 Policy controls are now an important feature of MTAs that are connected to the
838 Internet. Perhaps their most important job is to stop MTAs being abused as
839 &"open relays"& by misguided individuals who send out vast amounts of
840 unsolicited junk, and want to disguise its source. Exim provides flexible
841 facilities for specifying policy controls on incoming mail:
844 .cindex "&ACL;" "introduction"
845 Exim 4 (unlike previous versions of Exim) implements policy controls on
846 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
847 series of statements that may either grant or deny access. ACLs can be used at
848 several places in the SMTP dialogue while receiving a message from a remote
849 host. However, the most common places are after each RCPT command, and at the
850 very end of the message. The sysadmin can specify conditions for accepting or
851 rejecting individual recipients or the entire message, respectively, at these
852 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
855 An ACL is also available for locally generated, non-SMTP messages. In this
856 case, the only available actions are to accept or deny the entire message.
858 When Exim is compiled with the content-scanning extension, facilities are
859 provided in the ACL mechanism for passing the message to external virus and/or
860 spam scanning software. The result of such a scan is passed back to the ACL,
861 which can then use it to decide what to do with the message.
863 When a message has been received, either from a remote host or from the local
864 host, but before the final acknowledgement has been sent, a locally supplied C
865 function called &[local_scan()]& can be run to inspect the message and decide
866 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
867 is accepted, the list of recipients can be modified by the function.
869 Using the &[local_scan()]& mechanism is another way of calling external scanner
870 software. The &%SA-Exim%& add-on package works this way. It does not require
871 Exim to be compiled with the content-scanning extension.
873 After a message has been accepted, a further checking mechanism is available in
874 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
875 runs at the start of every delivery process.
880 .section "User filters"
881 .cindex "filter" "introduction"
882 .cindex "Sieve filter"
883 In a conventional Exim configuration, users are able to run private filters by
884 setting up appropriate &_.forward_& files in their home directories. See
885 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
886 configuration needed to support this, and the separate document entitled
887 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
888 of filtering are available:
891 Sieve filters are written in the standard filtering language that is defined
894 Exim filters are written in a syntax that is unique to Exim, but which is more
895 powerful than Sieve, which it pre-dates.
898 User filters are run as part of the routing process, described below.
902 .section "Message identification" "SECTmessiden"
903 .cindex "message ids" "details of format"
904 .cindex "format" "of message id"
905 .cindex "id of message"
910 Every message handled by Exim is given a &'message id'& which is sixteen
911 characters long. It is divided into three parts, separated by hyphens, for
912 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
913 normally encoding numbers in base 62. However, in the Darwin operating
914 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
915 (avoiding the use of lower case letters) is used instead, because the message
916 id is used to construct file names, and the names of files in those systems are
917 not always case-sensitive.
919 .cindex "pid (process id)" "re-use of"
920 The detail of the contents of the message id have changed as Exim has evolved.
921 Earlier versions relied on the operating system not re-using a process id (pid)
922 within one second. On modern operating systems, this assumption can no longer
923 be made, so the algorithm had to be changed. To retain backward compatibility,
924 the format of the message id was retained, which is why the following rules are
928 The first six characters of the message id are the time at which the message
929 started to be received, to a granularity of one second. That is, this field
930 contains the number of seconds since the start of the epoch (the normal Unix
931 way of representing the date and time of day).
933 After the first hyphen, the next six characters are the id of the process that
934 received the message.
936 There are two different possibilities for the final two characters:
938 .cindex "&%localhost_number%&"
939 If &%localhost_number%& is not set, this value is the fractional part of the
940 time of reception, normally in units of 1/2000 of a second, but for systems
941 that must use base 36 instead of base 62 (because of case-insensitive file
942 systems), the units are 1/1000 of a second.
944 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
945 the fractional part of the time, which in this case is in units of 1/200
950 After a message has been received, Exim waits for the clock to tick at the
951 appropriate resolution before proceeding, so that if another message is
952 received by the same process, or by another process with the same (re-used)
953 pid, it is guaranteed that the time will be different. In most cases, the clock
954 will already have ticked while the message was being received.
957 .section "Receiving mail"
958 .cindex "receiving mail"
959 .cindex "message" "reception"
960 The only way Exim can receive mail from another host is using SMTP over
961 TCP/IP, in which case the sender and recipient addresses are transferred using
962 SMTP commands. However, from a locally running process (such as a user's MUA),
963 there are several possibilities:
966 If the process runs Exim with the &%-bm%& option, the message is read
967 non-interactively (usually via a pipe), with the recipients taken from the
968 command line, or from the body of the message if &%-t%& is also used.
970 If the process runs Exim with the &%-bS%& option, the message is also read
971 non-interactively, but in this case the recipients are listed at the start of
972 the message in a series of SMTP RCPT commands, terminated by a DATA
973 command. This is so-called &"batch SMTP"& format,
974 but it isn't really SMTP. The SMTP commands are just another way of passing
975 envelope addresses in a non-interactive submission.
977 If the process runs Exim with the &%-bs%& option, the message is read
978 interactively, using the SMTP protocol. A two-way pipe is normally used for
979 passing data between the local process and the Exim process.
980 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
981 example, the ACLs for SMTP commands are used for this form of submission.
983 A local process may also make a TCP/IP call to the host's loopback address
984 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
985 does not treat the loopback address specially. It treats all such connections
986 in the same way as connections from other hosts.
990 .cindex "message sender" "constructed by Exim"
991 .cindex "sender" "constructed by Exim"
992 In the three cases that do not involve TCP/IP, the sender address is
993 constructed from the login name of the user that called Exim and a default
994 qualification domain (which can be set by the &%qualify_domain%& configuration
995 option). For local or batch SMTP, a sender address that is passed using the
996 SMTP MAIL command is ignored. However, the system administrator may allow
997 certain users (&"trusted users"&) to specify a different sender address
998 unconditionally, or all users to specify certain forms of different sender
999 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1000 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1001 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1002 users to change sender addresses.
1004 Messages received by either of the non-interactive mechanisms are subject to
1005 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1006 (either over TCP/IP, or interacting with a local process) can be checked by a
1007 number of ACLs that operate at different times during the SMTP session. Either
1008 individual recipients, or the entire message, can be rejected if local policy
1009 requirements are not met. The &[local_scan()]& function (see chapter
1010 &<<CHAPlocalscan>>&) is run for all incoming messages.
1012 Exim can be configured not to start a delivery process when a message is
1013 received; this can be unconditional, or depend on the number of incoming SMTP
1014 connections or the system load. In these situations, new messages wait on the
1015 queue until a queue runner process picks them up. However, in standard
1016 configurations under normal conditions, delivery is started as soon as a
1017 message is received.
1023 .section "Handling an incoming message"
1024 .cindex "spool directory" "files that hold a message"
1025 .cindex "file" "how a message is held"
1026 When Exim accepts a message, it writes two files in its spool directory. The
1027 first contains the envelope information, the current status of the message, and
1028 the header lines, and the second contains the body of the message. The names of
1029 the two spool files consist of the message id, followed by &`-H`& for the
1030 file containing the envelope and header, and &`-D`& for the data file.
1032 .cindex "spool directory" "&_input_& sub-directory"
1033 By default all these message files are held in a single directory called
1034 &_input_& inside the general Exim spool directory. Some operating systems do
1035 not perform very well if the number of files in a directory gets large; to
1036 improve performance in such cases, the &%split_spool_directory%& option can be
1037 used. This causes Exim to split up the input files into 62 sub-directories
1038 whose names are single letters or digits. &new("When this is done, the queue is
1039 processed one sub-directory at a time instead of all at once, which can improve
1040 overall performance even when there are not enough files in each directory to
1041 affect file system performance.")
1043 The envelope information consists of the address of the message's sender and
1044 the addresses of the recipients. This information is entirely separate from
1045 any addresses contained in the header lines. The status of the message includes
1046 a list of recipients who have already received the message. The format of the
1047 first spool file is described in chapter &<<CHAPspool>>&.
1049 .cindex "rewriting" "addresses"
1050 Address rewriting that is specified in the rewrite section of the configuration
1051 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1052 both in the header lines and the envelope, at the time the message is accepted.
1053 If during the course of delivery additional addresses are generated (for
1054 example, via aliasing), these new addresses are rewritten as soon as they are
1055 generated. At the time a message is actually delivered (transported) further
1056 rewriting can take place; because this is a transport option, it can be
1057 different for different forms of delivery. It is also possible to specify the
1058 addition or removal of certain header lines at the time the message is
1059 delivered (see chapters &<<CHAProutergeneric>>& and
1060 &<<CHAPtransportgeneric>>&).
1064 .section "Life of a message"
1065 .cindex "message" "life of"
1066 .cindex "message" "frozen"
1067 A message remains in the spool directory until it is completely delivered to
1068 its recipients or to an error address, or until it is deleted by an
1069 administrator or by the user who originally created it. In cases when delivery
1070 cannot proceed &-- for example, when a message can neither be delivered to its
1071 recipients nor returned to its sender, the message is marked &"frozen"& on the
1072 spool, and no more deliveries are attempted.
1074 .cindex "frozen messages" "thawing"
1075 .cindex "message" "thawing frozen"
1076 An administrator can &"thaw"& such messages when the problem has been
1077 corrected, and can also freeze individual messages by hand if necessary. In
1078 addition, an administrator can force a delivery error, causing a bounce message
1081 .cindex "&%timeout_frozen_after%&"
1082 .cindex "&%ignore_bounce_errors_after%&"
1083 There are options called &%ignore_bounce_errors_after%& and
1084 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1085 The first applies only to frozen bounces, the second to any frozen messages.
1087 .cindex "message" "log file for"
1088 .cindex "log" "file for each message"
1089 While Exim is working on a message, it writes information about each delivery
1090 attempt to its main log file. This includes successful, unsuccessful, and
1091 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1092 lines are also written to a separate &'message log'& file for each message.
1093 These logs are solely for the benefit of the administrator, and are normally
1094 deleted along with the spool files when processing of a message is complete.
1095 The use of individual message logs can be disabled by setting
1096 &%no_message_logs%&; this might give an improvement in performance on very busy
1099 .cindex "journal file"
1100 .cindex "file" "journal"
1101 All the information Exim itself needs to set up a delivery is kept in the first
1102 spool file, along with the header lines. When a successful delivery occurs, the
1103 address is immediately written at the end of a journal file, whose name is the
1104 message id followed by &`-J`&. At the end of a delivery run, if there are some
1105 addresses left to be tried again later, the first spool file (the &`-H`& file)
1106 is updated to indicate which these are, and the journal file is then deleted.
1107 Updating the spool file is done by writing a new file and renaming it, to
1108 minimize the possibility of data loss.
1110 Should the system or the program crash after a successful delivery but before
1111 the spool file has been updated, the journal is left lying around. The next
1112 time Exim attempts to deliver the message, it reads the journal file and
1113 updates the spool file before proceeding. This minimizes the chances of double
1114 deliveries caused by crashes.
1118 .section "Processing an address for delivery" "SECTprocaddress"
1119 .cindex "drivers" "definition of"
1120 .cindex "router" "definition of"
1121 .cindex "transport" "definition of"
1122 The main delivery processing elements of Exim are called &'routers'& and
1123 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1124 number of them is provided in the source distribution, and compile-time options
1125 specify which ones are included in the binary. Run time options specify which
1126 ones are actually used for delivering messages.
1128 .cindex "drivers" "instance definition"
1129 Each driver that is specified in the run time configuration is an &'instance'&
1130 of that particular driver type. Multiple instances are allowed; for example,
1131 you can set up several different &(smtp)& transports, each with different
1132 option values that might specify different ports or different timeouts. Each
1133 instance has its own identifying name. In what follows we will normally use the
1134 instance name when discussing one particular instance (that is, one specific
1135 configuration of the driver), and the generic driver name when discussing
1136 the driver's features in general.
1138 A &'router'& is a driver that operates on an address, either determining how
1139 its delivery should happen, by assigning it to a specific transport, or
1140 converting the address into one or more new addresses (for example, via an
1141 alias file). A router may also explicitly choose to fail an address, causing it
1144 A &'transport'& is a driver that transmits a copy of the message from Exim's
1145 spool to some destination. There are two kinds of transport: for a &'local'&
1146 transport, the destination is a file or a pipe on the local host, whereas for a
1147 &'remote'& transport the destination is some other host. A message is passed
1148 to a specific transport as a result of successful routing. If a message has
1149 several recipients, it may be passed to a number of different transports.
1151 .cindex "preconditions" "definition of"
1152 An address is processed by passing it to each configured router instance in
1153 turn, subject to certain preconditions, until a router accepts the address or
1154 specifies that it should be bounced. We will describe this process in more
1155 detail shortly. First, as a simple example, we consider how each recipient
1156 address in a message is processed in a small configuration of three routers.
1158 To make this a more concrete example, it is described in terms of some actual
1159 routers, but remember, this is only an example. You can configure Exim's
1160 routers in many different ways, and there may be any number of routers in a
1163 The first router that is specified in a configuration is often one that handles
1164 addresses in domains that are not recognized specially by the local host. These
1165 are typically addresses for arbitrary domains on the Internet. A precondition
1166 is set up which looks for the special domains known to the host (for example,
1167 its own domain name), and the router is run for addresses that do &'not'&
1168 match. Typically, this is a router that looks up domains in the DNS in order to
1169 find the hosts to which this address routes. If it succeeds, the address is
1170 assigned to a suitable SMTP transport; if it does not succeed, the router is
1171 configured to fail the address.
1173 The second router is reached only when the domain is recognized as one that
1174 &"belongs"& to the local host. This router does redirection &-- also known as
1175 aliasing and forwarding. When it generates one or more new addresses from the
1176 original, each of them is routed independently from the start. Otherwise, the
1177 router may cause an address to fail, or it may simply decline to handle the
1178 address, in which case the address is passed to the next router.
1180 The final router in many configurations is one that checks to see if the
1181 address belongs to a local mailbox. The precondition may involve a check to
1182 see if the local part is the name of a login account, or it may look up the
1183 local part in a file or a database. If its preconditions are not met, or if
1184 the router declines, we have reached the end of the routers. When this happens,
1185 the address is bounced.
1189 .section "Processing an address for verification"
1190 .cindex "router" "for verification"
1191 .cindex "verifying address" "overview"
1192 As well as being used to decide how to deliver to an address, Exim's routers
1193 are also used for &'address verification'&. Verification can be requested as
1194 one of the checks to be performed in an ACL for incoming messages, on both
1195 sender and recipient addresses, and it can be tested using the &%-bv%& and
1196 &%-bvs%& command line options.
1198 When an address is being verified, the routers are run in &"verify mode"&. This
1199 does not affect the way the routers work, but it is a state that can be
1200 detected. By this means, a router can be skipped or made to behave differently
1201 when verifying. A common example is a configuration in which the first router
1202 sends all messages to a message-scanning program, unless they have been
1203 previously scanned. Thus, the first router accepts all addresses without any
1204 checking, making it useless for verifying. Normally, the &%no_verify%& option
1205 would be set for such a router, causing it to be skipped in verify mode.
1210 .section "Running an individual router" "SECTrunindrou"
1211 .cindex "router" "running details"
1212 .cindex "preconditions" "checking"
1213 .cindex "router" "result of running"
1214 As explained in the example above, a number of preconditions are checked before
1215 running a router. If any are not met, the router is skipped, and the address is
1216 passed to the next router. When all the preconditions on a router &'are'& met,
1217 the router is run. What happens next depends on the outcome, which is one of
1221 &'accept'&: The router accepts the address, and either assigns it to a
1222 transport, or generates one or more &"child"& addresses. Processing the
1223 original address ceases,
1224 .cindex "&%unseen%& option"
1225 unless the &%unseen%& option is set on the router. This option
1226 can be used to set up multiple deliveries with different routing (for example,
1227 for keeping archive copies of messages). When &%unseen%& is set, the address is
1228 passed to the next router. Normally, however, an &'accept'& return marks the
1231 Any child addresses generated by the router are processed independently,
1232 starting with the first router by default. It is possible to change this by
1233 setting the &%redirect_router%& option to specify which router to start at for
1234 child addresses. Unlike &%pass_router%& (see below) the router specified by
1235 &%redirect_router%& may be anywhere in the router configuration.
1237 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1238 requests that the address be passed to another router. By default the address
1239 is passed to the next router, but this can be changed by setting the
1240 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1241 must be below the current router (to avoid loops).
1243 &'decline'&: The router declines to accept the address because it does not
1244 recognize it at all. By default, the address is passed to the next router, but
1245 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1246 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1247 &'decline'& into &'fail'&.
1249 &'fail'&: The router determines that the address should fail, and queues it for
1250 the generation of a bounce message. There is no further processing of the
1251 original address unless &%unseen%& is set on the router.
1253 &'defer'&: The router cannot handle the address at the present time. (A
1254 database may be offline, or a DNS lookup may have timed out.) No further
1255 processing of the address happens in this delivery attempt. It is tried again
1256 next time the message is considered for delivery.
1258 &'error'&: There is some error in the router (for example, a syntax error in
1259 its configuration). The action is as for defer.
1262 If an address reaches the end of the routers without having been accepted by
1263 any of them, it is bounced as unrouteable. The default error message in this
1264 situation is &"unrouteable address"&, but you can set your own message by
1265 making use of the &%cannot_route_message%& option. This can be set for any
1266 router; the value from the last router that &"saw"& the address is used.
1268 Sometimes while routing you want to fail a delivery when some conditions are
1269 met but others are not, instead of passing the address on for further routing.
1270 You can do this by having a second router that explicitly fails the delivery
1271 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1272 facility for this purpose.
1275 .section "Duplicate addresses"
1276 .cindex "case of local parts"
1277 .cindex "address duplicate" "discarding"
1278 Once routing is complete, Exim scans the addresses that are assigned to local
1279 and remote transports, and discards any duplicates that it finds. During this
1280 check, local parts are treated as case-sensitive.
1283 .section "Router preconditions" "SECTrouprecon"
1284 .cindex "router preconditions" "order of processing"
1285 .cindex "preconditions" "order of processing"
1286 The preconditions that are tested for each router are listed below, in the
1287 order in which they are tested. The individual configuration options are
1288 described in more detail in chapter &<<CHAProutergeneric>>&.
1291 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1292 the local parts handled by the router may or must have certain prefixes and/or
1293 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1294 skipped. These conditions are tested first. When an affix is present, it is
1295 removed from the local part before further processing, including the evaluation
1296 of any other conditions.
1298 Routers can be designated for use only when not verifying an address, that is,
1299 only when routing it for delivery (or testing its delivery routing). If the
1300 &%verify%& option is set false, the router is skipped when Exim is verifying an
1302 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1303 &%verify_recipient%&, which independently control the use of the router for
1304 sender and recipient verification. You can set these options directly if
1305 you want a router to be used for only one type of verification.
1307 If the &%address_test%& option is set false, the router is skipped when Exim is
1308 run with the &%-bt%& option to test an address routing. This can be helpful
1309 when the first router sends all new messages to a scanner of some sort; it
1310 makes it possible to use &%-bt%& to test subsequent delivery routing without
1311 having to simulate the effect of the scanner.
1313 Routers can be designated for use only when verifying an address, as
1314 opposed to routing it for delivery. The &%verify_only%& option controls this.
1316 Individual routers can be explicitly skipped when running the routers to
1317 check an address given in the SMTP EXPN command (see the &%expn%& option).
1319 If the &%domains%& option is set, the domain of the address must be in the set
1320 of domains that it defines.
1322 .cindex "&$local_part_prefix$&"
1323 .cindex "&$local_part$&"
1324 .cindex "&$local_part_suffix$&"
1325 If the &%local_parts%& option is set, the local part of the address must be in
1326 the set of local parts that it defines. If &%local_part_prefix%& or
1327 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1328 part before this check. If you want to do precondition tests on local parts
1329 that include affixes, you can do so by using a &%condition%& option (see below)
1330 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1331 &$local_part_suffix$& as necessary.
1333 .cindex "&$local_user_uid$&"
1334 .cindex "&$local_user_gid$&"
1336 If the &%check_local_user%& option is set, the local part must be the name of
1337 an account on the local host. If this check succeeds, the uid and gid of the
1338 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1339 user's home directory is placed in &$home$&; these values can be used in the
1340 remaining preconditions.
1342 If the &%router_home_directory%& option is set, it is expanded at this point,
1343 because it overrides the value of &$home$&. If this expansion were left till
1344 later, the value of &$home$& as set by &%check_local_user%& would be used in
1345 subsequent tests. Having two different values of &$home$& in the same router
1346 could lead to confusion.
1348 If the &%senders%& option is set, the envelope sender address must be in the
1349 set of addresses that it defines.
1351 If the &%require_files%& option is set, the existence or non-existence of
1352 specified files is tested.
1354 .cindex "customizing" "precondition"
1355 If the &%condition%& option is set, it is evaluated and tested. This option
1356 uses an expanded string to allow you to set up your own custom preconditions.
1357 Expanded strings are described in chapter &<<CHAPexpand>>&.
1361 Note that &%require_files%& comes near the end of the list, so you cannot use
1362 it to check for the existence of a file in which to lookup up a domain, local
1363 part, or sender. However, as these options are all expanded, you can use the
1364 &%exists%& expansion condition to make such tests within each condition. The
1365 &%require_files%& option is intended for checking files that the router may be
1366 going to use internally, or which are needed by a specific transport (for
1367 example, &_.procmailrc_&).
1371 .section "Delivery in detail"
1372 .cindex "delivery" "in detail"
1373 When a message is to be delivered, the sequence of events is as follows:
1376 If a system-wide filter file is specified, the message is passed to it. The
1377 filter may add recipients to the message, replace the recipients, discard the
1378 message, cause a new message to be generated, or cause the message delivery to
1379 fail. The format of the system filter file is the same as for Exim user filter
1380 files, described in the separate document entitled &'Exim's interfaces to mail
1382 .cindex "Sieve filter" "not available for system filter"
1383 (&*Note*&: Sieve cannot be used for system filter files.)
1385 Some additional features are available in system filters &-- see chapter
1386 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1387 filter only once per delivery attempt, however many recipients it has. However,
1388 if there are several delivery attempts because one or more addresses could not
1389 be immediately delivered, the system filter is run each time. The filter
1390 condition &%first_delivery%& can be used to detect the first run of the system
1393 Each recipient address is offered to each configured router in turn, subject to
1394 its preconditions, until one is able to handle it. If no router can handle the
1395 address, that is, if they all decline, the address is failed. Because routers
1396 can be targeted at particular domains, several locally handled domains can be
1397 processed entirely independently of each other.
1399 .cindex "routing" "loops in"
1400 .cindex "loop" "while routing"
1401 A router that accepts an address may assign it to a local or a remote
1402 transport. However, the transport is not run at this time. Instead, the address
1403 is placed on a list for the particular transport, which will be run later.
1404 Alternatively, the router may generate one or more new addresses (typically
1405 from alias, forward, or filter files). New addresses are fed back into this
1406 process from the top, but in order to avoid loops, a router ignores any address
1407 which has an identically-named ancestor that was processed by itself.
1409 When all the routing has been done, addresses that have been successfully
1410 handled are passed to their assigned transports. When local transports are
1411 doing real local deliveries, they handle only one address at a time, but if a
1412 local transport is being used as a pseudo-remote transport (for example, to
1413 collect batched SMTP messages for transmission by some other means) multiple
1414 addresses can be handled. Remote transports can always handle more than one
1415 address at a time, but can be configured not to do so, or to restrict multiple
1416 addresses to the same domain.
1418 Each local delivery to a file or a pipe runs in a separate process under a
1419 non-privileged uid, and these deliveries are run one at a time. Remote
1420 deliveries also run in separate processes, normally under a uid that is private
1421 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1422 run in parallel. The maximum number of simultaneous remote deliveries for any
1423 one message is set by the &%remote_max_parallel%& option.
1424 The order in which deliveries are done is not defined, except that all local
1425 deliveries happen before any remote deliveries.
1427 .cindex "queue runner"
1428 When it encounters a local delivery during a queue run, Exim checks its retry
1429 database to see if there has been a previous temporary delivery failure for the
1430 address before running the local transport. If there was a previous failure,
1431 Exim does not attempt a new delivery until the retry time for the address is
1432 reached. However, this happens only for delivery attempts that are part of a
1433 queue run. Local deliveries are always attempted when delivery immediately
1434 follows message reception, even if retry times are set for them. This makes for
1435 better behaviour if one particular message is causing problems (for example,
1436 causing quota overflow, or provoking an error in a filter file).
1438 .cindex "delivery" "retry in remote transports"
1439 Remote transports do their own retry handling, since an address may be
1440 deliverable to one of a number of hosts, each of which may have a different
1441 retry time. If there have been previous temporary failures and no host has
1442 reached its retry time, no delivery is attempted, whether in a queue run or
1443 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1445 If there were any permanent errors, a bounce message is returned to an
1446 appropriate address (the sender in the common case), with details of the error
1447 for each failing address. Exim can be configured to send copies of bounce
1448 messages to other addresses.
1450 .cindex "delivery" "deferral"
1451 If one or more addresses suffered a temporary failure, the message is left on
1452 the queue, to be tried again later. Delivery of these addresses is said to be
1455 When all the recipient addresses have either been delivered or bounced,
1456 handling of the message is complete. The spool files and message log are
1457 deleted, though the message log can optionally be preserved if required.
1463 .section "Retry mechanism"
1464 .cindex "delivery" "retry mechanism"
1465 .cindex "retry" "description of mechanism"
1466 .cindex "queue runner"
1467 Exim's mechanism for retrying messages that fail to get delivered at the first
1468 attempt is the queue runner process. You must either run an Exim daemon that
1469 uses the &%-q%& option with a time interval to start queue runners at regular
1470 intervals, or use some other means (such as &'cron'&) to start them. If you do
1471 not arrange for queue runners to be run, messages that fail temporarily at the
1472 first attempt will remain on your queue for ever. A queue runner process works
1473 its way through the queue, one message at a time, trying each delivery that has
1474 passed its retry time.
1475 You can run several queue runners at once.
1477 Exim uses a set of configured rules to determine when next to retry the failing
1478 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1479 should give up trying to deliver to the address, at which point it generates a
1480 bounce message. If no retry rules are set for a particular host, address, and
1481 error combination, no retries are attempted, and temporary errors are treated
1486 .section "Temporary delivery failure"
1487 .cindex "delivery" "temporary failure"
1488 There are many reasons why a message may not be immediately deliverable to a
1489 particular address. Failure to connect to a remote machine (because it, or the
1490 connection to it, is down) is one of the most common. Temporary failures may be
1491 detected during routing as well as during the transport stage of delivery.
1492 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1493 is on a file system where the user is over quota. Exim can be configured to
1494 impose its own quotas on local mailboxes; where system quotas are set they will
1497 If a host is unreachable for a period of time, a number of messages may be
1498 waiting for it by the time it recovers, and sending them in a single SMTP
1499 connection is clearly beneficial. Whenever a delivery to a remote host is
1502 .cindex "hints database"
1503 Exim makes a note in its hints database, and whenever a successful
1504 SMTP delivery has happened, it looks to see if any other messages are waiting
1505 for the same host. If any are found, they are sent over the same SMTP
1506 connection, subject to a configuration limit as to the maximum number in any
1512 .section "Permanent delivery failure"
1513 .cindex "delivery" "permanent failure"
1514 .cindex "bounce message" "when generated"
1515 When a message cannot be delivered to some or all of its intended recipients, a
1516 bounce message is generated. Temporary delivery failures turn into permanent
1517 errors when their timeout expires. All the addresses that fail in a given
1518 delivery attempt are listed in a single message. If the original message has
1519 many recipients, it is possible for some addresses to fail in one delivery
1520 attempt and others to fail subsequently, giving rise to more than one bounce
1521 message. The wording of bounce messages can be customized by the administrator.
1522 See chapter &<<CHAPemsgcust>>& for details.
1524 .cindex "&'X-Failed-Recipients:'& header line"
1525 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1526 failed addresses, for the benefit of programs that try to analyse such messages
1529 .cindex "bounce message" "recipient of"
1530 A bounce message is normally sent to the sender of the original message, as
1531 obtained from the message's envelope. For incoming SMTP messages, this is the
1532 address given in the MAIL command. However, when an address is expanded via a
1533 forward or alias file, an alternative address can be specified for delivery
1534 failures of the generated addresses. For a mailing list expansion (see section
1535 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1540 .section "Failures to deliver bounce messages"
1541 .cindex "bounce message" "failure to deliver"
1542 If a bounce message (either locally generated or received from a remote host)
1543 itself suffers a permanent delivery failure, the message is left on the queue,
1544 but it is frozen, awaiting the attention of an administrator. There are options
1545 that can be used to make Exim discard such failed messages, or to keep them
1546 for only a short time (see &%timeout_frozen_after%& and
1547 &%ignore_bounce_errors_after%&).
1553 . ////////////////////////////////////////////////////////////////////////////
1554 . ////////////////////////////////////////////////////////////////////////////
1556 .chapter "Building and installing Exim"
1557 .scindex IIDbuex "building Exim"
1559 .section "Unpacking"
1560 Exim is distributed as a gzipped or bzipped tar file which, when upacked,
1561 creates a directory with the name of the current release (for example,
1562 &_exim-&version;_&) into which the following files are placed:
1565 .row &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1566 .row &_CHANGES_& "contains a reference to where changes are documented"
1567 .row &_LICENCE_& "the GNU General Public Licence"
1568 .row &_Makefile_& "top-level make file"
1569 .row &_NOTICE_& "conditions for the use of Exim"
1570 .row &_README_& "list of files, directories and simple build &&&
1574 Other files whose names begin with &_README_& may also be present. The
1575 following subdirectories are created:
1578 .row &_Local_& "an empty directory for local configuration files"
1579 .row &_OS_& "OS-specific files"
1580 .row &_doc_& "documentation files"
1581 .row &_exim_monitor_& "source files for the Exim monitor"
1582 .row &_scripts_& "scripts used in the build process"
1583 .row &_src_& "remaining source files"
1584 .row &_util_& "independent utilities"
1587 The main utility programs are contained in the &_src_& directory, and are built
1588 with the Exim binary. The &_util_& directory contains a few optional scripts
1589 that may be useful to some sites.
1592 .section "Multiple machine architectures and operating systems"
1593 .cindex "building Exim" "multiple OS/architectures"
1594 The building process for Exim is arranged to make it easy to build binaries for
1595 a number of different architectures and operating systems from the same set of
1596 source files. Compilation does not take place in the &_src_& directory.
1597 Instead, a &'build directory'& is created for each architecture and operating
1599 .cindex "symbolic link" "to build directory"
1600 Symbolic links to the sources are installed in this directory, which is where
1601 the actual building takes place. In most cases, Exim can discover the machine
1602 architecture and operating system for itself, but the defaults can be
1603 overridden if necessary.
1606 .section "DBM libraries" "SECTdb"
1607 .cindex "DBM libraries" "discussion of"
1608 .cindex "hints database" "DBM files used for"
1609 Even if you do not use any DBM files in your configuration, Exim still needs a
1610 DBM library in order to operate, because it uses indexed files for its hints
1611 databases. Unfortunately, there are a number of DBM libraries in existence, and
1612 different operating systems often have different ones installed.
1614 .cindex "Solaris" "DBM library for"
1615 .cindex "IRIX" "DBM library for"
1616 .cindex "BSD" "DBM library for"
1617 .cindex "Linux" "DBM library for"
1618 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1619 Linux distribution, the DBM configuration should happen automatically, and you
1620 may be able to ignore this section. Otherwise, you may have to learn more than
1621 you would like about DBM libraries from what follows.
1623 .cindex "&'ndbm'& DBM library"
1624 Licensed versions of Unix normally contain a library of DBM functions operating
1625 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1626 versions of Unix seem to vary in what they contain as standard. In particular,
1627 some early versions of Linux have no default DBM library, and different
1628 distributors have chosen to bundle different libraries with their packaged
1629 versions. However, the more recent releases seem to have standardised on the
1630 Berkeley DB library.
1632 Different DBM libraries have different conventions for naming the files they
1633 use. When a program opens a file called &_dbmfile_&, there are several
1637 A traditional &'ndbm'& implementation, such as that supplied as part of
1638 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1640 .cindex "&'gdbm'& DBM library"
1641 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1642 compatibility interface it makes two different hard links to it with names
1643 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1644 file name is used unmodified.
1646 .cindex "Berkeley DB library"
1647 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1648 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1649 programmer exactly the same as the traditional &'ndbm'& implementation.
1651 If the Berkeley package is used in its native mode, it operates on a single
1652 file called &_dbmfile_&; the programmer's interface is somewhat different to
1653 the traditional &'ndbm'& interface.
1655 To complicate things further, there are several very different versions of the
1656 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1657 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1658 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1659 versions of Berkeley DB can be obtained from
1660 &url(http://www.sleepycat.com/).
1662 .cindex "&'tdb'& DBM library"
1663 Yet another DBM library, called &'tdb'&, is available from
1664 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1665 operates on a single file.
1669 .cindex "DBM libraries" "configuration for building"
1670 Exim and its utilities can be compiled to use any of these interfaces. In order
1671 to use any version of the Berkeley DB package in native mode, you must set
1672 USE_DB in an appropriate configuration file (typically
1673 &_Local/Makefile_&). For example:
1677 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1678 error is diagnosed if you set more than one of these.
1680 At the lowest level, the build-time configuration sets none of these options,
1681 thereby assuming an interface of type (1). However, some operating system
1682 configuration files (for example, those for the BSD operating systems and
1683 Linux) assume type (4) by setting USE_DB as their default, and the
1684 configuration files for Cygwin set USE_GDBM. Anything you set in
1685 &_Local/Makefile_&, however, overrides these system defaults.
1687 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1688 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1689 in one of these lines:
1694 Settings like that will work if the DBM library is installed in the standard
1695 place. Sometimes it is not, and the library's header file may also not be in
1696 the default path. You may need to set INCLUDE to specify where the header
1697 file is, and to specify the path to the library more fully in DBMLIB, as in
1700 INCLUDE=-I/usr/local/include/db-4.1
1701 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1703 There is further detailed discussion about the various DBM libraries in the
1704 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1708 .section "Pre-building configuration"
1709 .cindex "building Exim" "pre-building configuration"
1710 .cindex "configuration for building Exim"
1711 .cindex "&_Local/Makefile_&"
1712 .cindex "&_src/EDITME_&"
1713 Before building Exim, a local configuration file that specifies options
1714 independent of any operating system has to be created with the name
1715 &_Local/Makefile_&. A template for this file is supplied as the file
1716 &_src/EDITME_&, and it contains full descriptions of all the option settings
1717 therein. These descriptions are therefore not repeated here. If you are
1718 building Exim for the first time, the simplest thing to do is to copy
1719 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1721 There are three settings that you must supply, because Exim will not build
1722 without them. They are the location of the run time configuration file
1723 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1724 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1725 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1726 a colon-separated list of file names; Exim uses the first of them that exists.
1728 There are a few other parameters that can be specified either at build time or
1729 at run time, to enable the same binary to be used on a number of different
1730 machines. However, if the locations of Exim's spool directory and log file
1731 directory (if not within the spool directory) are fixed, it is recommended that
1732 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1733 detected early in Exim's execution (such as a malformed configuration file) can
1736 .cindex "content scanning" "specifying at build time"
1737 Exim's interfaces for calling virus and spam scanning software directly from
1738 access control lists are not compiled by default. If you want to include these
1739 facilities, you need to set
1741 WITH_CONTENT_SCAN=yes
1743 in your &_Local/Makefile_&. For details of the facilities themselves, see
1744 chapter &<<CHAPexiscan>>&.
1747 .cindex "&_Local/eximon.conf_&"
1748 .cindex "_exim_monitor/EDITME_"
1749 If you are going to build the Exim monitor, a similar configuration process is
1750 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1751 your installation and saved under the name &_Local/eximon.conf_&. If you are
1752 happy with the default settings described in &_exim_monitor/EDITME_&,
1753 &_Local/eximon.conf_& can be empty, but it must exist.
1755 This is all the configuration that is needed in straightforward cases for known
1756 operating systems. However, the building process is set up so that it is easy
1757 to override options that are set by default or by operating-system-specific
1758 configuration files, for example to change the name of the C compiler, which
1759 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1764 .section "Support for iconv()"
1765 .cindex "&[iconv()]& support"
1767 The contents of header lines in messages may be encoded according to the rules
1768 described RFC 2047. This makes it possible to transmit characters that are not
1769 in the ASCII character set, and to label them as being in a particular
1770 character set. When Exim is inspecting header lines by means of the &%$h_%&
1771 mechanism, it decodes them, and translates them into a specified character set
1772 (default ISO-8859-1). The translation is possible only if the operating system
1773 supports the &[iconv()]& function.
1775 However, some of the operating systems that supply &[iconv()]& do not support
1776 very many conversions. The GNU &%libiconv%& library (available from
1777 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1778 systems to remedy this deficiency, as well as on systems that do not supply
1779 &[iconv()]& at all. After installing &%libiconv%&, you should add
1783 to your &_Local/Makefile_& and rebuild Exim.
1787 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1788 .cindex "TLS" "including support for TLS"
1789 .cindex "encryption" "including support for"
1790 .cindex "SUPPORT_TLS"
1791 .cindex "OpenSSL" "building Exim with"
1792 .cindex "GnuTLS" "building Exim with"
1793 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1794 command as per RFC 2487. It can also support legacy clients that expect to
1795 start a TLS session immediately on connection to a non-standard port (see the
1796 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1799 If you want to build Exim with TLS support, you must first install either the
1800 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1803 If OpenSSL is installed, you should set
1806 TLS_LIBS=-lssl -lcrypto
1808 in &_Local/Makefile_&. You may also need to specify the locations of the
1809 OpenSSL library and include files. For example:
1812 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1813 TLS_INCLUDE=-I/usr/local/openssl/include/
1815 .cindex "USE_GNUTLS"
1816 If GnuTLS is installed, you should set
1820 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1822 in &_Local/Makefile_&, and again you may need to specify the locations of the
1823 library and include files. For example:
1827 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1828 TLS_INCLUDE=-I/usr/gnu/include
1830 You do not need to set TLS_INCLUDE if the relevant directory is already
1831 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1832 given in chapter &<<CHAPTLS>>&.
1837 .section "Use of tcpwrappers"
1838 .cindex "tcpwrappers" "building Exim to support"
1839 .cindex "USE_TCP_WRAPPERS"
1840 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1841 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1842 alternative to Exim's own checking facilities for installations that are
1843 already making use of &'tcpwrappers'& for other purposes. To do this, you
1844 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1845 &_tcpd.h_& to be available at compile time, and also ensure that the library
1846 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1847 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1850 USE_TCP_WRAPPERS=yes
1851 CFLAGS=-O -I/usr/local/include
1852 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1854 in &_Local/Makefile_&. The name to use in the &'tcpwrappers'& control files is
1855 &"exim"&. For example, the line
1857 exim : LOCAL 192.168.1. .friendly.domain.example
1859 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1860 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1861 All other connections are denied. Consult the &'tcpwrappers'& documentation for
1866 .section "Including support for IPv6"
1867 .cindex "IPv6" "including support for"
1868 Exim contains code for use on systems that have IPv6 support. Setting
1869 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1870 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1871 where the IPv6 support is not fully integrated into the normal include and
1874 Two different types of DNS record for handling IPv6 addresses have been
1875 defined. AAAA records (analagous to A records for IPv4) are in use, and are
1876 currently seen as the mainstream. Another record type called A6 was proposed
1877 as better than AAAA because it had more flexibility. However, it was felt to be
1878 over-complex, and its status was reduced to &"experimental"&. It is not known
1879 if anyone is actually using A6 records. Exim has support for A6 records, but
1880 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1881 support has not been tested for some time.
1885 .section "The building process"
1886 .cindex "build directory"
1887 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
1888 created, run &'make'& at the top level. It determines the architecture and
1889 operating system types, and creates a build directory if one does not exist.
1890 For example, on a Sun system running Solaris 8, the directory
1891 &_build-SunOS5-5.8-sparc_& is created.
1892 .cindex "symbolic link" "to source files"
1893 Symbolic links to relevant source files are installed in the build directory.
1895 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
1896 building process fails if it is set.
1898 If this is the first time &'make'& has been run, it calls a script that builds
1899 a make file inside the build directory, using the configuration files from the
1900 &_Local_& directory. The new make file is then passed to another instance of
1901 &'make'&. This does the real work, building a number of utility scripts, and
1902 then compiling and linking the binaries for the Exim monitor (if configured), a
1903 number of utility programs, and finally Exim itself. The command &`make
1904 makefile`& can be used to force a rebuild of the make file in the build
1905 directory, should this ever be necessary.
1907 If you have problems building Exim, check for any comments there may be in the
1908 &_README_& file concerning your operating system, and also take a look at the
1909 FAQ, where some common problems are covered.
1913 .section 'Output from &"make"&'
1914 The output produced by the &'make'& process for compile lines is often very
1915 unreadable, because these lines can be very long. For this reason, the normal
1916 output is suppressed by default, and instead output similar to that which
1917 appears when compiling the 2.6 Linux kernel is generated: just a short line for
1918 each module that is being compiled or linked. However, it is still possible to
1919 get the full output, by calling &'make'& like this:
1923 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
1924 command reflection in &'make'&. When you ask for the full output, it is
1925 given in addition to the the short output.
1929 .section "Overriding build-time options for Exim" "SECToverride"
1930 .cindex "build-time options" "overriding"
1931 The main make file that is created at the beginning of the building process
1932 consists of the concatenation of a number of files which set configuration
1933 values, followed by a fixed set of &'make'& instructions. If a value is set
1934 more than once, the last setting overrides any previous ones. This provides a
1935 convenient way of overriding defaults. The files that are concatenated are, in
1938 &_OS/Makefile-Default_&
1939 &_OS/Makefile-_&<&'ostype'&>
1941 &_Local/Makefile-_&<&'ostype'&>
1942 &_Local/Makefile-_&<&'archtype'&>
1943 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
1944 &_OS/Makefile-Base_&
1946 .cindex "&_Local/Makefile_&"
1947 .cindex "building Exim" "operating system type"
1948 .cindex "building Exim" "architecture type"
1949 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
1950 architecture type. &_Local/Makefile_& is required to exist, and the building
1951 process fails if it is absent. The other three &_Local_& files are optional,
1952 and are often not needed.
1954 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
1955 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
1956 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
1957 values are used, thereby providing a means of forcing particular settings.
1958 Otherwise, the scripts try to get values from the &%uname%& command. If this
1959 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
1960 of &'ad hoc'& transformations are then applied, to produce the standard names
1961 that Exim expects. You can run these scripts directly from the shell in order
1962 to find out what values are being used on your system.
1965 &_OS/Makefile-Default_& contains comments about the variables that are set
1966 therein. Some (but not all) are mentioned below. If there is something that
1967 needs changing, review the contents of this file and the contents of the make
1968 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
1972 .cindex "building Exim" "overriding default settings"
1973 If you need to change any of the values that are set in &_OS/Makefile-Default_&
1974 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
1975 need to change the original files. Instead, you should make the changes by
1976 putting the new values in an appropriate &_Local_& file. For example,
1977 .cindex "Tru64-Unix build-time settings"
1978 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
1979 formerly DEC-OSF1) operating system, it is necessary to specify that the C
1980 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
1981 called with the option &%-std1%&, to make it recognize some of the features of
1982 Standard C that Exim uses. (Most other compilers recognize Standard C by
1983 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
1984 containing the lines
1989 If you are compiling for just one operating system, it may be easier to put
1990 these lines directly into &_Local/Makefile_&.
1992 Keeping all your local configuration settings separate from the distributed
1993 files makes it easy to transfer them to new versions of Exim simply by copying
1994 the contents of the &_Local_& directory.
1997 .cindex "NIS lookup type" "including support for"
1998 .cindex "NIS+ lookup type" "including support for"
1999 .cindex "LDAP" "including support for"
2000 .cindex "lookup" "inclusion in binary"
2001 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2002 lookup, but not all systems have these components installed, so the default is
2003 not to include the relevant code in the binary. All the different kinds of file
2004 and database lookup that Exim supports are implemented as separate code modules
2005 which are included only if the relevant compile-time options are set. In the
2006 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2012 and similar settings apply to the other lookup types. They are all listed in
2013 &_src/EDITME_&. In many cases the relevant include files and interface
2014 libraries need to be installed before compiling Exim.
2015 .cindex "cdb" "including support for"
2016 However, there are some optional lookup types (such as cdb) for which
2017 the code is entirely contained within Exim, and no external include
2018 files or libraries are required. When a lookup type is not included in the
2019 binary, attempts to configure Exim to use it cause run time configuration
2022 .cindex "Perl" "including support for"
2023 Exim can be linked with an embedded Perl interpreter, allowing Perl
2024 subroutines to be called during string expansion. To enable this facility,
2028 must be defined in &_Local/Makefile_&. Details of this facility are given in
2029 chapter &<<CHAPperl>>&.
2031 .cindex "X11 libraries" "location of"
2032 The location of the X11 libraries is something that varies a lot between
2033 operating systems, and there may be different versions of X11 to cope
2034 with. Exim itself makes no use of X11, but if you are compiling the Exim
2035 monitor, the X11 libraries must be available.
2036 The following three variables are set in &_OS/Makefile-Default_&:
2039 XINCLUDE=-I$(X11)/include
2040 XLFLAGS=-L$(X11)/lib
2042 These are overridden in some of the operating-system configuration files. For
2043 example, in &_OS/Makefile-SunOS5_& there is
2046 XINCLUDE=-I$(X11)/include
2047 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2049 If you need to override the default setting for your operating system, place a
2050 definition of all three of these variables into your
2051 &_Local/Makefile-<ostype>_& file.
2054 If you need to add any extra libraries to the link steps, these can be put in a
2055 variable called EXTRALIBS, which appears in all the link commands, but by
2056 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2057 command for linking the main Exim binary, and not for any associated utilities.
2059 .cindex "DBM libraries" "configuration for building"
2060 There is also DBMLIB, which appears in the link commands for binaries that
2061 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2062 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2063 binary, and which can be used, for example, to include additional X11
2066 .cindex "configuration file" "editing"
2067 The make file copes with rebuilding Exim correctly if any of the configuration
2068 files are edited. However, if an optional configuration file is deleted, it is
2069 necessary to touch the associated non-optional file (that is,
2070 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2073 .section "OS-specific header files"
2075 .cindex "building Exim" "OS-specific C header files"
2076 The &_OS_& directory contains a number of files with names of the form
2077 &_os.h-<ostype>_&. These are system-specific C header files that should not
2078 normally need to be changed. There is a list of macro settings that are
2079 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2080 are porting Exim to a new operating system.
2084 .section "Overriding build-time options for the monitor"
2085 .cindex "building Eximon" "overriding default options"
2086 A similar process is used for overriding things when building the Exim monitor,
2087 where the files that are involved are
2089 &_OS/eximon.conf-Default_&
2090 &_OS/eximon.conf-_&<&'ostype'&>
2091 &_Local/eximon.conf_&
2092 &_Local/eximon.conf-_&<&'ostype'&>
2093 &_Local/eximon.conf-_&<&'archtype'&>
2094 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2096 .cindex "&_Local/eximon.conf_&"
2097 As with Exim itself, the final three files need not exist, and in this case the
2098 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2099 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2100 variables of the same name, preceded by EXIMON_. For example, setting
2101 EXIMON_LOG_DEPTH in the environment overrides the value of
2102 LOG_DEPTH at run time.
2106 .section "Installing Exim binaries and scripts"
2107 .cindex "installing Exim"
2108 .cindex "BIN_DIRECTORY"
2109 The command &`make install`& runs the &(exim_install)& script with no
2110 arguments. The script copies binaries and utility scripts into the directory
2111 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2112 .cindex "setuid" "installing Exim with"
2113 The install script copies files only if they are newer than the files they are
2114 going to replace. The Exim binary is required to be owned by root and have the
2115 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2116 install`& as root so that it can set up the Exim binary in this way. However, in
2117 some special situations (for example, if a host is doing no local deliveries)
2118 it may be possible to run Exim without making the binary setuid root (see
2119 chapter &<<CHAPsecurity>>& for details).
2121 .cindex "CONFIGURE_FILE"
2122 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2123 in &_Local/Makefile_&. If this names a single file, and the file does not
2124 exist, the default configuration file &_src/configure.default_& is copied there
2125 by the installation script. If a run time configuration file already exists, it
2126 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2127 alternative files, no default is installed.
2129 .cindex "system aliases file"
2130 .cindex "&_/etc/aliases_&"
2131 One change is made to the default configuration file when it is installed: the
2132 default configuration contains a router that references a system aliases file.
2133 The path to this file is set to the value specified by
2134 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2135 If the system aliases file does not exist, the installation script creates it,
2136 and outputs a comment to the user.
2138 The created file contains no aliases, but it does contain comments about the
2139 aliases a site should normally have. Mail aliases have traditionally been
2140 kept in &_/etc/aliases_&. However, some operating systems are now using
2141 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2142 Exim's configuration if necessary.
2144 The default configuration uses the local host's name as the only local domain,
2145 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2146 running as the local user. System aliases and &_.forward_& files in users' home
2147 directories are supported, but no NIS or NIS+ support is configured. Domains
2148 other than the name of the local host are routed using the DNS, with delivery
2151 It is possible to install Exim for special purposes (such as building a binary
2152 distribution) in a private part of the file system. You can do this by a
2155 make DESTDIR=/some/directory/ install
2157 This has the effect of pre-pending the specified directory to all the file
2158 paths, except the name of the system aliases file that appears in the default
2159 configuration. (If a default alias file is created, its name &'is'& modified.)
2160 For backwards compatibility, ROOT is used if DESTDIR is not set,
2161 but this usage is deprecated.
2163 .cindex "installing Exim" "what is not installed"
2164 Running &'make install'& does not copy the Exim 4 conversion script
2165 &'convert4r4'&, or the &'pcretest'& test program. You will probably run the
2166 first of these only once (if you are upgrading from Exim 3), and the second
2167 isn't really part of Exim. None of the documentation files in the &_doc_&
2168 directory are copied, except for the info files when you have set
2169 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2171 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2172 to their names. The Exim binary itself, however, is handled differently. It is
2173 installed under a name that includes the version number and the compile number,
2174 for example &_exim-&version;-1_&. The script then arranges for a symbolic link
2175 called &_exim_& to point to the binary. If you are updating a previous version
2176 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2177 from the directory (as seen by other processes).
2179 .cindex "installing Exim" "testing the script"
2180 If you want to see what the &'make install'& will do before running it for
2181 real, you can pass the &%-n%& option to the installation script by this
2184 make INSTALL_ARG=-n install
2186 The contents of the variable INSTALL_ARG are passed to the installation
2187 script. You do not need to be root to run this test. Alternatively, you can run
2188 the installation script directly, but this must be from within the build
2189 directory. For example, from the top-level Exim directory you could use this
2192 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2194 .cindex "installing Exim" "install script options"
2195 There are two other options that can be supplied to the installation script.
2198 &%-no_chown%& bypasses the call to change the owner of the installed binary
2199 to root, and the call to make it a setuid binary.
2201 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2205 INSTALL_ARG can be used to pass these options to the script. For example:
2207 make INSTALL_ARG=-no_symlink install
2209 The installation script can also be given arguments specifying which files are
2210 to be copied. For example, to install just the Exim binary, and nothing else,
2211 without creating the symbolic link, you could use:
2213 make INSTALL_ARG='-no_symlink exim' install
2218 .section "Installing info documentation" "SECTinsinfdoc"
2219 .cindex "installing Exim" "&'info'& documentation"
2220 Not all systems use the GNU &'info'& system for documentation, and for this
2221 reason, the Texinfo source of Exim's documentation is not included in the main
2222 distribution. Instead it is available separately from the ftp site (see section
2225 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2226 source of the documentation is found in the source tree, running &`make
2227 install`& automatically builds the info files and installs them.
2231 .section "Setting up the spool directory"
2232 .cindex "spool directory" "creating"
2233 When it starts up, Exim tries to create its spool directory if it does not
2234 exist. The Exim uid and gid are used for the owner and group of the spool
2235 directory. Sub-directories are automatically created in the spool directory as
2242 .cindex "testing" "installation"
2243 Having installed Exim, you can check that the run time configuration file is
2244 syntactically valid by running the following command, which assumes that the
2245 Exim binary directory is within your PATH environment variable:
2249 If there are any errors in the configuration file, Exim outputs error messages.
2250 Otherwise it outputs the version number and build date,
2251 the DBM library that is being used, and information about which drivers and
2252 other optional code modules are included in the binary.
2253 Some simple routing tests can be done by using the address testing option. For
2256 &`exim -bt`& <&'local username'&>
2258 should verify that it recognizes a local mailbox, and
2260 &`exim -bt`& <&'remote address'&>
2262 a remote one. Then try getting it to deliver mail, both locally and remotely.
2263 This can be done by passing messages directly to Exim, without going through a
2264 user agent. For example:
2266 exim -v postmaster@your.domain.example
2267 From: user@your.domain.example
2268 To: postmaster@your.domain.example
2269 Subject: Testing Exim
2271 This is a test message.
2274 The &%-v%& option causes Exim to output some verification of what it is doing.
2275 In this case you should see copies of three log lines, one for the message's
2276 arrival, one for its delivery, and one containing &"Completed"&.
2278 .cindex "delivery" "problems with"
2279 If you encounter problems, look at Exim's log files (&'mainlog'& and
2280 &'paniclog'&) to see if there is any relevant information there. Another source
2281 of information is running Exim with debugging turned on, by specifying the
2282 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2283 with debugging turned on by a command of the form
2285 &`exim -d -M`& <&'exim-message-id'&>
2287 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2288 produces rather a lot of output, but you can cut this down to specific areas.
2289 For example, if you use &%-d-all+route%& only the debugging information
2290 relevant to routing is included. (See the &%-d%& option in chapter
2291 &<<CHAPcommandline>>& for more details.)
2293 .cindex '&"sticky"& bit'
2294 .cindex "lock files"
2295 One specific problem that has shown up on some sites is the inability to do
2296 local deliveries into a shared mailbox directory, because it does not have the
2297 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2298 writing to a mailbox file, and if it cannot create the lock file, the delivery
2299 is deferred. You can get round this either by setting the &"sticky bit"& on the
2300 directory, or by setting a specific group for local deliveries and allowing
2301 that group to create files in the directory (see the comments above the
2302 &(local_delivery)& transport in the default configuration file). Another
2303 approach is to configure Exim not to use lock files, but just to rely on
2304 &[fcntl()]& locking instead. However, you should do this only if all user
2305 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2306 see chapter &<<CHAPappendfile>>&.
2308 One thing that cannot be tested on a system that is already running an MTA is
2309 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2310 &%-oX%& option can be used to run an Exim daemon that listens on some other
2311 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2312 &'exim_checkaccess'& utility can be used to check out policy controls on
2315 Testing a new version on a system that is already running Exim can most easily
2316 be done by building a binary with a different CONFIGURE_FILE setting. From
2317 within the run time configuration, all other file and directory names
2318 that Exim uses can be altered, in order to keep it entirely clear of the
2322 .section "Replacing another MTA with Exim"
2323 .cindex "replacing another MTA"
2324 Building and installing Exim for the first time does not of itself put it in
2325 general use. The name by which the system's MTA is called by mail user agents
2326 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2327 operating system), and it is necessary to make this name point to the &'exim'&
2328 binary in order to get the user agents to pass messages to Exim. This is
2329 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2330 or &_/usr/lib/sendmail_&
2331 .cindex "symbolic link" "to &'exim'& binary"
2332 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2333 privilege and executable status from the old MTA. It is then necessary to stop
2334 and restart the mailer daemon, if one is running.
2336 .cindex "FreeBSD" "MTA indirection"
2337 .cindex "&_/etc/mail/mailer.conf_&"
2338 Some operating systems have introduced alternative ways of switching MTAs. For
2339 example, if you are running FreeBSD, you need to edit the file
2340 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2341 described. A typical example of the contents of this file for running Exim is
2344 sendmail /usr/exim/bin/exim
2345 send-mail /usr/exim/bin/exim
2346 mailq /usr/exim/bin/exim -bp
2347 newaliases /usr/bin/true
2349 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2350 your Exim installation is &"live"&. Check it by sending a message from your
2351 favourite user agent.
2353 You should consider what to tell your users about the change of MTA. Exim may
2354 have different capabilities to what was previously running, and there are
2355 various operational differences such as the text of messages produced by
2356 command line options and in bounce messages. If you allow your users to make
2357 use of Exim's filtering capabilities, you should make the document entitled
2358 &'Exim's interface to mail filtering'& available to them.
2362 .section "Upgrading Exim"
2363 .cindex "upgrading Exim"
2364 If you are already running Exim on your host, building and installing a new
2365 version automatically makes it available to MUAs, or any other programs that
2366 call the MTA directly. However, if you are running an Exim daemon, you do need
2367 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2368 new binary. You do not need to stop processing mail in order to install a new
2369 version of Exim. The install script does not modify an existing runtime
2375 .section "Stopping the Exim daemon on Solaris"
2376 .cindex "Solaris" "stopping Exim on"
2377 The standard command for stopping the mailer daemon on Solaris is
2379 /etc/init.d/sendmail stop
2381 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2382 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2383 for the text &"sendmail"&; this is not present because the actual program name
2384 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2385 solution is to replace the line that finds the process id with something like
2387 pid=`cat /var/spool/exim/exim-daemon.pid`
2389 to obtain the daemon's pid directly from the file that Exim saves it in.
2391 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2392 still be received from local processes, and if automatic delivery is configured
2393 (the normal case), deliveries will still occur.
2398 . ////////////////////////////////////////////////////////////////////////////
2399 . ////////////////////////////////////////////////////////////////////////////
2401 .chapter "The Exim command line" "CHAPcommandline"
2402 .scindex IIDclo1 "command line" "options"
2403 .scindex IIDclo2 "options" "command line"
2404 Exim's command line takes the standard Unix form of a sequence of options,
2405 each starting with a hyphen character, followed by a number of arguments. The
2406 options are compatible with the main options of Sendmail, and there are also
2407 some additional options, some of which are compatible with Smail 3. Certain
2408 combinations of options do not make sense, and provoke an error if used.
2409 The form of the arguments depends on which options are set.
2412 .section "Setting options by program name"
2414 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2415 were present before any other options.
2416 The &%-bp%& option requests a listing of the contents of the mail queue on the
2418 This feature is for compatibility with some systems that contain a command of
2419 that name in one of the standard libraries, symbolically linked to
2420 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2423 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2424 were present before any other options, for compatibility with Smail. The
2425 &%-bS%& option is used for reading in a number of messages in batched SMTP
2429 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2430 &%-oee%& options were present before any other options, for compatibility with
2431 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2434 .cindex "queue runner"
2435 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2436 were present before any other options, for compatibility with Smail. The &%-q%&
2437 option causes a single queue runner process to be started.
2439 .cindex "&'newaliases'&"
2440 .cindex "alias file" "building"
2441 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2442 If Exim is called under the name &'newaliases'& it behaves as if the option
2443 &%-bi%& were present before any other options, for compatibility with Sendmail.
2444 This option is used for rebuilding Sendmail's alias file. Exim does not have
2445 the concept of a single alias file, but can be configured to run a given
2446 command if called with the &%-bi%& option.
2449 .section "Trusted and admin users" "SECTtrustedadmin"
2450 Some Exim options are available only to &'trusted users'& and others are
2451 available only to &'admin users'&. In the description below, the phrases &"Exim
2452 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2453 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2454 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2457 .cindex "trusted user" "definition of"
2458 .cindex "user" "trusted definition of"
2459 The trusted users are root, the Exim user, any user listed in the
2460 &%trusted_users%& configuration option, and any user whose current group or any
2461 supplementary group is one of those listed in the &%trusted_groups%&
2462 configuration option. Note that the Exim group is not automatically trusted.
2464 .cindex '&"From"& line'
2465 .cindex "envelope sender"
2466 Trusted users are always permitted to use the &%-f%& option or a leading
2467 &"From&~"& line to specify the envelope sender of a message that is passed to
2468 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2469 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2470 users to set envelope senders.
2472 .cindex "&'From:'& header line"
2473 .cindex "&'Sender:'& header line"
2474 For a trusted user, there is never any check on the contents of the &'From:'&
2475 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2476 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2478 Trusted users may also specify a host name, host address, interface address,
2479 protocol name, ident value, and authentication data when submitting a message
2480 locally. Thus, they are able to insert messages into Exim's queue locally that
2481 have the characteristics of messages received from a remote host. Untrusted
2482 users may in some circumstances use &%-f%&, but can never set the other values
2483 that are available to trusted users.
2485 .cindex "user" "admin definition of"
2486 .cindex "admin user" "definition of"
2487 The admin users are root, the Exim user, and any user that is a member of the
2488 Exim group or of any group listed in the &%admin_groups%& configuration option.
2489 The current group does not have to be one of these groups.
2491 Admin users are permitted to list the queue, and to carry out certain
2492 operations on messages, for example, to force delivery failures. It is also
2493 necessary to be an admin user in order to see the full information provided by
2494 the Exim monitor, and full debugging output.
2496 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2497 Exim to attempt delivery of messages on its queue is restricted to admin users.
2498 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2499 option false (that is, specifying &%no_prod_requires_admin%&).
2501 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2502 is restricted to admin users unless &%queue_list_requires_admin%& is set
2507 &*Warning*&: If you configure your system so that admin users are able to
2508 edit Exim's configuration file, you are giving those users an easy way of
2509 getting root. There is further discussion of this issue at the start of chapter
2515 .section "Command line options"
2516 The command options are described in alphabetical order below.
2518 . ////////////////////////////////////////////////////////////////////////////
2519 . Insert a stylized XML comment here, to identify the start of the command line
2520 . options. This is for the benefit of the Perl script that automatically
2521 . creates a man page for the options.
2522 . ////////////////////////////////////////////////////////////////////////////
2525 <!-- === Start of command line options === -->
2532 .cindex "options" "command line; terminating"
2533 This is a pseudo-option whose only purpose is to terminate the options and
2534 therefore to cause subsequent command line items to be treated as arguments
2535 rather than options, even if they begin with hyphens.
2538 .oindex "&%--help%&"
2539 This option causes Exim to output a few sentences stating what it is.
2540 The same output is generated if the Exim binary is called with no options and
2543 .vitem &%-B%&<&'type'&>
2545 .cindex "8-bit characters"
2546 .cindex "Sendmail compatibility" "8-bit characters"
2547 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2548 clean; it ignores this option.
2553 .cindex "SMTP listener"
2554 .cindex "queue runner"
2555 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2556 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2557 that the daemon should also initiate periodic queue runs.
2559 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2560 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2561 disconnect from the controlling terminal. When running this way, it can be
2562 stopped by pressing ctrl-C.
2564 By default, Exim listens for incoming connections to the standard SMTP port on
2565 all the host's running interfaces. However, it is possible to listen on other
2566 ports, on multiple ports, and only on specific interfaces. Chapter
2567 &<<CHAPinterfaces>>& contains a description of the options that control this.
2569 When a listening daemon
2570 .cindex "daemon" "process id (pid)"
2571 .cindex "pid (process id)" "of daemon"
2572 is started without the use of &%-oX%& (that is, without overriding the normal
2573 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2574 in Exim's spool directory. This location can be overridden by setting
2575 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2578 When &%-oX%& is used on the command line to start a listening daemon, the
2579 process id is not written to the normal pid file path. However, &%-oP%& can be
2580 used to specify a path on the command line if a pid file is required.
2584 can be used to cause the daemon to re-exec itself. This should be done whenever
2585 Exim's configuration file, or any file that is incorporated into it by means of
2586 the &%.include%& facility, is changed, and also whenever a new version of Exim
2587 is installed. It is not necessary to do this when other files that are
2588 referenced from the configuration (for example, alias files) are changed,
2589 because these are reread each time they are used.
2593 This option has the same effect as &%-bd%& except that it never disconnects
2594 from the controlling terminal, even when no debugging is specified.
2598 .cindex "testing" "string expansion"
2599 .cindex "expansion" "testing"
2600 Run Exim in expansion testing mode. Exim discards its root privilege, to
2601 prevent ordinary users from using this mode to read otherwise inaccessible
2602 files. If no arguments are given, Exim runs interactively, prompting for lines
2603 of data. Otherwise, it processes each argument in turn.
2605 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2606 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2607 used without command line arguments. If successful, it uses the &[readline()]&
2608 function, which provides extensive line-editing facilities, for reading the
2609 test data. A line history is supported.
2611 Long expansion expressions can be split over several lines by using backslash
2612 continuations. As in Exim's run time configuration, white space at the start of
2613 continuation lines is ignored. Each argument or data line is passed through the
2614 string expansion mechanism, and the result is output. Variable values from the
2615 configuration file (for example, &$qualify_domain$&) are available, but no
2616 message-specific values (such as &$domain$&) are set, because no message is
2619 &*Note*&: If you use this mechanism to test lookups, and you change the data
2620 files or databases you are using, you must exit and restart Exim before trying
2621 the same lookup again. Otherwise, because each Exim process caches the results
2622 of lookups, you will just get the same result as before.
2624 .vitem &%-bF%&&~<&'filename'&>
2626 .cindex "system filter" "testing"
2627 .cindex "testing" "system filter"
2628 This option is the same as &%-bf%& except that it assumes that the filter being
2629 tested is a system filter. The additional commands that are available only in
2630 system filters are recognized.
2632 .vitem &%-bf%&&~<&'filename'&>
2634 .cindex "filter" "testing"
2635 .cindex "testing" "filter file"
2636 .cindex "forward file" "testing"
2637 .cindex "testing" "forward file"
2638 .cindex "Sieve filter" "testing"
2639 This option runs Exim in user filter testing mode; the file is the filter file
2640 to be tested, and a test message must be supplied on the standard input. If
2641 there are no message-dependent tests in the filter, an empty file can be
2644 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2645 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2646 filter and a user filter in the same run. For example:
2648 exim -bF /system/filter -bf /user/filter </test/message
2650 This is helpful when the system filter adds header lines or sets filter
2651 variables that are used by the user filter.
2653 If the test filter file does not begin with one of the special lines
2658 it is taken to be a normal &_.forward_& file, and is tested for validity under
2659 that interpretation. See sections &<<SECTitenonfilred>>& to
2660 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2663 The result of an Exim command that uses &%-bf%&, provided no errors are
2664 detected, is a list of the actions that Exim would try to take if presented
2665 with the message for real. More details of filter testing are given in the
2666 separate document entitled &'Exim's interfaces to mail filtering'&.
2668 When testing a filter file,
2669 .cindex "&""From""& line"
2670 .cindex "envelope sender"
2671 .cindex "&%-f%& option" "for filter testing"
2672 the envelope sender can be set by the &%-f%& option,
2673 or by a &"From&~"& line at the start of the test message. Various parameters
2674 that would normally be taken from the envelope recipient address of the message
2675 can be set by means of additional command line options (see the next four
2678 .vitem &%-bfd%&&~<&'domain'&>
2680 .cindex "&$qualify_domain$&"
2681 This sets the domain of the recipient address when a filter file is being
2682 tested by means of the &%-bf%& option. The default is the value of
2685 .vitem &%-bfl%&&~<&'local&~part'&>
2687 This sets the local part of the recipient address when a filter file is being
2688 tested by means of the &%-bf%& option. The default is the username of the
2689 process that calls Exim. A local part should be specified with any prefix or
2690 suffix stripped, because that is how it appears to the filter when a message is
2691 actually being delivered.
2693 .vitem &%-bfp%&&~<&'prefix'&>
2695 This sets the prefix of the local part of the recipient address when a filter
2696 file is being tested by means of the &%-bf%& option. The default is an empty
2699 .vitem &%-bfs%&&~<&'suffix'&>
2701 This sets the suffix of the local part of the recipient address when a filter
2702 file is being tested by means of the &%-bf%& option. The default is an empty
2705 .vitem &%-bh%&&~<&'IP&~address'&>
2707 .cindex "testing" "incoming SMTP"
2708 .cindex "SMTP" "testing incoming"
2709 .cindex "testing" "relay control"
2710 .cindex "relaying" "testing configuration"
2711 .cindex "policy control" "testing"
2712 .cindex "debugging" "&%-bh%& option"
2713 This option runs a fake SMTP session as if from the given IP address, using the
2714 standard input and output. The IP address may include a port number at the end,
2715 after a full stop. For example:
2717 exim -bh 10.9.8.7.1234
2718 exim -bh fe80::a00:20ff:fe86:a061.5678
2720 When an IPv6 address is given, it is converted into canonical form. In the case
2721 of the second example above, the value of &$sender_host_address$& after
2722 conversion to the canonical form is
2723 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2725 Comments as to what is going on are written to the standard error file. These
2726 include lines beginning with &"LOG"& for anything that would have been logged.
2727 This facility is provided for testing configuration options for incoming
2728 messages, to make sure they implement the required policy. For example, you can
2729 test your relay controls using &%-bh%&.
2733 You cannot test features of the configuration that rely on
2734 ident (RFC 1413) callouts. These cannot be done when testing using
2735 &%-bh%& because there is no incoming SMTP connection.
2737 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2738 are also skipped when testing using &%-bh%&. If you want these callouts to
2739 occur, use &%-bhc%& instead.
2741 Messages supplied during the testing session are discarded, and nothing is
2742 written to any of the real log files. There may be pauses when DNS (and other)
2743 lookups are taking place, and of course these may time out. The &%-oMi%& option
2744 can be used to specify a specific IP interface and port if this is important.
2746 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2747 output just states whether a given recipient address from a given host is
2748 acceptable or not. See section &<<SECTcheckaccess>>&.
2750 .vitem &%-bhc%&&~<&'IP&~address'&>
2752 This option operates in the same way as &%-bh%&, except that address
2753 verification callouts are performed if required. This includes consulting and
2754 updating the callout cache database.
2758 .cindex "alias file" "building"
2759 .cindex "building alias file"
2760 .cindex "Sendmail compatibility" "&%-bi%& option"
2761 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2762 Exim does not have the concept of a single alias file, and so it cannot mimic
2763 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2764 tend to appear in various scripts such as NIS make files, so the option must be
2767 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2768 configuration option is run, under the uid and gid of the caller of Exim. If
2769 the &%-oA%& option is used, its value is passed to the command as an argument.
2770 The command set by &%bi_command%& may not contain arguments. The command can
2771 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2772 if this is required. If the &%bi_command%& option is not set, calling Exim with
2777 .cindex "local message reception"
2778 This option runs an Exim receiving process that accepts an incoming,
2779 locally-generated message on the current input. The recipients are given as the
2780 command arguments (except when &%-t%& is also present &-- see below). Each
2781 argument can be a comma-separated list of RFC 2822 addresses. This is the
2782 default option for selecting the overall action of an Exim call; it is assumed
2783 if no other conflicting option is present.
2785 If any addresses in the message are unqualified (have no domain), they are
2786 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
2787 options, as appropriate. The &%-bnq%& option (see below) provides a way of
2788 suppressing this for special cases.
2790 Policy checks on the contents of local messages can be enforced by means of
2791 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
2793 .cindex "return code" "for &%-bm%&"
2794 The return code is zero if the message is successfully accepted. Otherwise, the
2795 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
2798 .cindex "message" "format"
2799 .cindex "format" "message"
2800 .cindex "&""From""& line"
2801 .cindex "UUCP" "&""From""& line"
2802 .cindex "Sendmail compatibility" "&""From""& line"
2803 of the message must be as defined in RFC 2822, except that, for
2804 compatibility with Sendmail and Smail, a line in one of the forms
2806 From sender Fri Jan 5 12:55 GMT 1997
2807 From sender Fri, 5 Jan 97 12:55:01
2809 (with the weekday optional, and possibly with additional text after the date)
2810 is permitted to appear at the start of the message. There appears to be no
2811 authoritative specification of the format of this line. Exim recognizes it by
2812 matching against the regular expression defined by the &%uucp_from_pattern%&
2813 option, which can be changed if necessary.
2816 .cindex "&%-f%& option" "overriding &""From""& line"
2817 specified sender is treated as if it were given as the argument to the
2818 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
2819 preference to the address taken from the message. The caller of Exim must be a
2820 trusted user for the sender of a message to be set in this way.
2824 .cindex "address qualification" "suppressing"
2825 By default, Exim automatically qualifies unqualified addresses (those
2826 without domains) that appear in messages that are submitted locally (that
2827 is, not over TCP/IP). This qualification applies both to addresses in
2828 envelopes, and addresses in header lines. Sender addresses are qualified using
2829 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
2830 defaults to the value of &%qualify_domain%&).
2832 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
2833 being used to re-submit messages that originally came from remote hosts after
2834 content scanning, you probably do not want to qualify unqualified addresses in
2835 header lines. (Such lines will be present only if you have not enabled a header
2836 syntax check in the appropriate ACL.)
2838 The &%-bnq%& option suppresses all qualification of unqualified addresses in
2839 messages that originate on the local host. When this is used, unqualified
2840 addresses in the envelope provoke errors (causing message rejection) and
2841 unqualified addresses in header lines are left alone.
2846 .cindex "configuration options" "extracting"
2847 .cindex "options" "configuration &-- extracting"
2848 If this option is given with no arguments, it causes the values of all Exim's
2849 main configuration options to be written to the standard output. The values
2850 of one or more specific options can be requested by giving their names as
2851 arguments, for example:
2853 exim -bP qualify_domain hold_domains
2855 However, any option setting that is preceded by the word &"hide"& in the
2856 configuration file is not shown in full, except to an admin user. For other
2857 users, the output is as in this example:
2859 mysql_servers = <value not displayable>
2861 If &%configure_file%& is given as an argument, the name of the run time
2862 configuration file is output.
2863 If a list of configuration files was supplied, the value that is output here
2864 is the name of the file that was actually used.
2866 .cindex "daemon" "process id (pid)"
2867 .cindex "pid (process id)" "of daemon"
2868 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
2869 directories where log files and daemon pid files are written are output,
2870 respectively. If these values are unset, log files are written in a
2871 sub-directory of the spool directory called &%log%&, and the pid file is
2872 written directly into the spool directory.
2874 If &%-bP%& is followed by a name preceded by &`+`&, for example,
2876 exim -bP +local_domains
2878 it searches for a matching named list of any type (domain, host, address, or
2879 local part) and outputs what it finds.
2881 .cindex "options" "router &-- extracting"
2882 .cindex "options" "transport &-- extracting"
2883 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
2884 followed by the name of an appropriate driver instance, the option settings for
2885 that driver are output. For example:
2887 exim -bP transport local_delivery
2889 The generic driver options are output first, followed by the driver's private
2890 options. A list of the names of drivers of a particular type can be obtained by
2891 using one of the words &%router_list%&, &%transport_list%&, or
2892 &%authenticator_list%&, and a complete list of all drivers with their option
2893 settings can be obtained by using &%routers%&, &%transports%&, or
2899 .cindex "queue" "listing messages on"
2900 .cindex "listing" "messages on the queue"
2901 This option requests a listing of the contents of the mail queue on the
2902 standard output. If the &%-bp%& option is followed by a list of message ids,
2903 just those messages are listed. By default, this option can be used only by an
2904 admin user. However, the &%queue_list_requires_admin%& option can be set false
2905 to allow any user to see the queue.
2907 Each message on the queue is displayed as in the following example:
2909 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
2910 red.king@looking-glass.fict.example
2913 .cindex "message" "size in queue listing"
2914 .cindex "size" "of message"
2915 The first line contains the length of time the message has been on the queue
2916 (in this case 25 minutes), the size of the message (2.9K), the unique local
2917 identifier for the message, and the message sender, as contained in the
2918 envelope. For bounce messages, the sender address is empty, and appears as
2919 &"<>"&. If the message was submitted locally by an untrusted user who overrode
2920 the default sender address, the user's login name is shown in parentheses
2921 before the sender address.
2923 .cindex "frozen messages" "in queue listing"
2924 If the message is frozen (attempts to deliver it are suspended) then the text
2925 &"*** frozen ***"& is displayed at the end of this line.
2927 The recipients of the message (taken from the envelope, not the headers) are
2928 displayed on subsequent lines. Those addresses to which the message has already
2929 been delivered are marked with the letter D. If an original address gets
2930 expanded into several addresses via an alias or forward file, the original is
2931 displayed with a D only when deliveries for all of its child addresses are
2937 This option operates like &%-bp%&, but in addition it shows delivered addresses
2938 that were generated from the original top level address(es) in each message by
2939 alias or forwarding operations. These addresses are flagged with &"+D"& instead
2945 .cindex "queue" "count of messages on"
2946 This option counts the number of messages on the queue, and writes the total
2947 to the standard output. It is restricted to admin users, unless
2948 &%queue_list_requires_admin%& is set false.
2953 This option operates like &%-bp%&, but the output is not sorted into
2954 chronological order of message arrival. This can speed it up when there are
2955 lots of messages on the queue, and is particularly useful if the output is
2956 going to be post-processed in a way that doesn't need the sorting.
2960 This option is a combination of &%-bpr%& and &%-bpa%&.
2964 This option is a combination of &%-bpr%& and &%-bpu%&.
2969 This option operates like &%-bp%& but shows only undelivered top-level
2970 addresses for each message displayed. Addresses generated by aliasing or
2971 forwarding are not shown, unless the message was deferred after processing by a
2972 router with the &%one_time%& option set.
2977 .cindex "testing" "retry configuration"
2978 .cindex "retry" "configuration testing"
2979 This option is for testing retry rules, and it must be followed by up to three
2980 arguments. It causes Exim to look for a retry rule that matches the values
2981 and to write it to the standard output. For example:
2983 exim -brt bach.comp.mus.example
2984 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
2986 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
2987 argument, which is required, can be a complete address in the form
2988 &'local_part@domain'&, or it can be just a domain name. If the second argument
2989 contains a dot, it is interpreted as an optional second domain name; if no
2990 retry rule is found for the first argument, the second is tried. This ties in
2991 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
2992 rule is found that matches the host, one that matches the mail domain is
2993 sought. Finally, an argument that is the name of a specific delivery error, as
2994 used in setting up retry rules, can be given. For example:
2996 exim -brt haydn.comp.mus.example quota_3d
2997 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3002 .cindex "testing" "rewriting"
3003 .cindex "rewriting" "testing"
3004 This option is for testing address rewriting rules, and it must be followed by
3005 a single argument, consisting of either a local part without a domain, or a
3006 complete address with a fully qualified domain. Exim outputs how this address
3007 would be rewritten for each possible place it might appear. See chapter
3008 &<<CHAPrewrite>>& for further details.
3012 .cindex "SMTP" "batched incoming"
3013 .cindex "batched SMTP input"
3014 This option is used for batched SMTP input, which is an alternative interface
3015 for non-interactive local message submission. A number of messages can be
3016 submitted in a single run. However, despite its name, this is not really SMTP
3017 input. Exim reads each message's envelope from SMTP commands on the standard
3018 input, but generates no responses. If the caller is trusted, or
3019 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3020 believed; otherwise the sender is always the caller of Exim.
3022 The message itself is read from the standard input, in SMTP format (leading
3023 dots doubled), terminated by a line containing just a single dot. An error is
3024 provoked if the terminating dot is missing. A further message may then follow.
3026 As for other local message submissions, the contents of incoming batch SMTP
3027 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3028 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3029 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3031 Some other SMTP commands are recognized in the input. HELO and EHLO act
3032 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3033 QUIT quits, ignoring the rest of the standard input.
3035 .cindex "return code" "for &%-bS%&"
3036 If any error is encountered, reports are written to the standard output and
3037 error streams, and Exim gives up immediately. The return code is 0 if no error
3038 was detected; it is 1 if one or more messages were accepted before the error
3039 was detected; otherwise it is 2.
3041 More details of input using batched SMTP are given in section
3042 &<<SECTincomingbatchedSMTP>>&.
3046 .cindex "SMTP" "local input"
3047 .cindex "local SMTP input"
3048 This option causes Exim to accept one or more messages by reading SMTP commands
3049 on the standard input, and producing SMTP replies on the standard output. SMTP
3050 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3051 Some user agents use this interface as a way of passing locally-generated
3052 messages to the MTA.
3055 .cindex "sender" "source of"
3056 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3057 set, the senders of messages are taken from the SMTP MAIL commands.
3058 Otherwise the content of these commands is ignored and the sender is set up as
3059 the calling user. Unqualified addresses are automatically qualified using
3060 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3061 &%-bnq%& option is used.
3065 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3066 using a listening daemon. Exim can distinguish the two cases by checking
3067 whether the standard input is a TCP/IP socket. When Exim is called from
3068 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3069 above concerning senders and qualification do not apply. In this situation,
3070 Exim behaves in exactly the same way as it does when receiving a message via
3071 the listening daemon.
3075 .cindex "testing" "addresses"
3076 .cindex "address" "testing"
3077 This option runs Exim in address testing mode, in which each argument is taken
3078 as an address to be tested for deliverability. The results are written to the
3079 standard output. If a test fails, and the caller is not an admin user, no
3080 details of the failure are output, because these might contain sensitive
3081 information such as usernames and passwords for database lookups.
3083 If no arguments are given, Exim runs in an interactive manner, prompting with a
3084 right angle bracket for addresses to be tested.
3086 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3087 &[readline()]& function, because it is running as &'root'& and there are
3090 Each address is handled as if it were the recipient address of a message
3091 (compare the &%-bv%& option). It is passed to the routers and the result is
3092 written to the standard output. However, any router that has
3093 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3094 genuine routing tests if your first router passes everything to a scanner
3098 .cindex "return code" "for &%-bt%&"
3099 return code is 2 if any address failed outright; it is 1 if no address
3100 failed outright but at least one could not be resolved for some reason. Return
3101 code 0 is given only when all addresses succeed.
3103 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3104 routers in the configuration makes any tests on the sender address of a
3106 .cindex "&%-f%& option" "for address testing"
3107 you can use the &%-f%& option to set an appropriate sender when running
3108 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3109 default qualifying domain. However, if you have set up (for example) routers
3110 whose behaviour depends on the contents of an incoming message, you cannot test
3111 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3116 .cindex "version number of Exim" "verifying"
3117 This option causes Exim to write the current version number, compilation
3118 number, and compilation date of the &'exim'& binary to the standard output.
3119 It also lists the DBM library this is being used, the optional modules (such as
3120 specific lookup types), the drivers that are included in the binary, and the
3121 name of the run time configuration file that is in use.
3123 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3124 configuration file. However, this is a static check only. It cannot check
3125 values that are to be expanded. For example, although a misspelt ACL verb is
3126 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3127 alone to discover (for example) all the typos in the configuration; some
3128 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3129 dynamic testing facilities.
3133 .cindex "verifying address" "using &%-bv%&"
3134 .cindex "address" "verification"
3135 This option runs Exim in address verification mode, in which each argument is
3136 taken as an address to be verified. During normal operation, verification
3137 happens mostly as a consequence processing a &%verify%& condition in an ACL
3138 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, see the &%-bh%&
3141 If verification fails, and the caller is not an admin user, no details of the
3142 failure are output, because these might contain sensitive information such as
3143 usernames and passwords for database lookups.
3145 If no arguments are given, Exim runs in an interactive manner, prompting with a
3146 right angle bracket for addresses to be verified.
3148 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3149 &[readline()]& function, because it is running as &'exim'& and there are
3152 Verification differs from address testing (the &%-bt%& option) in that routers
3153 that have &%no_verify%& set are skipped, and if the address is accepted by a
3154 router that has &%fail_verify%& set, verification fails. The address is
3155 verified as a recipient if &%-bv%& is used; to test verification for a sender
3156 address, &%-bvs%& should be used.
3158 If the &%-v%& option is not set, the output consists of a single line for each
3159 address, stating whether it was verified or not, and giving a reason in the
3160 latter case. Otherwise, more details are given of how the address has been
3161 handled, and in the case of address redirection, all the generated addresses
3162 are also considered. Without &%-v%&, generating more than one address by
3163 redirection causes verification to end successfully.
3166 .cindex "return code" "for &%-bv%&"
3167 return code is 2 if any address failed outright; it is 1 if no address
3168 failed outright but at least one could not be resolved for some reason. Return
3169 code 0 is given only when all addresses succeed.
3171 If any of the routers in the configuration makes any tests on the sender
3172 address of a message, you should use the &%-f%& option to set an appropriate
3173 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3174 calling user at the default qualifying domain.
3178 This option acts like &%-bv%&, but verifies the address as a sender rather
3179 than a recipient address. This affects any rewriting and qualification that
3182 .vitem &%-C%&&~<&'filelist'&>
3184 .cindex "configuration file" "alternate"
3185 .cindex "CONFIGURE_FILE"
3186 .cindex "alternate configuration file"
3187 This option causes Exim to find the run time configuration file from the given
3188 list instead of from the list specified by the CONFIGURE_FILE
3189 compile-time setting. Usually, the list will consist of just a single file
3190 name, but it can be a colon-separated list of names. In this case, the first
3191 file that exists is used. Failure to open an existing file stops Exim from
3192 proceeding any further along the list, and an error is generated.
3194 When this option is used by a caller other than root or the Exim user, and the
3195 list is different from the compiled-in list, Exim gives up its root privilege
3196 immediately, and runs with the real and effective uid and gid set to those of
3197 the caller. However, if ALT_CONFIG_ROOT_ONLY is defined in
3198 &_Local/Makefile_&, root privilege is retained for &%-C%& only if the caller of
3201 That is, the Exim user is no longer privileged in this regard. This build-time
3202 option is not set by default in the Exim source distribution tarbundle.
3203 However, if you are using a &"packaged"& version of Exim (source or binary),
3204 the packagers might have enabled it.
3206 Setting ALT_CONFIG_ROOT_ONLY locks out the possibility of testing a
3207 configuration using &%-C%& right through message reception and delivery, even
3208 if the caller is root. The reception works, but by that time, Exim is running
3209 as the Exim user, so when it re-executes to regain privilege for the delivery,
3210 the use of &%-C%& causes privilege to be lost. However, root can test reception
3211 and delivery using two separate commands (one to put a message on the queue,
3212 using &%-odq%&, and another to do the delivery, using &%-M%&).
3214 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3215 prefix string with which any file named in a &%-C%& command line option
3216 must start. In addition, the file name must not contain the sequence &`/../`&.
3217 However, if the value of the &%-C%& option is identical to the value of
3218 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3219 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3220 unset, any file name can be used with &%-C%&.
3222 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3223 to a directory to which only root has access. This prevents someone who has
3224 broken into the Exim account from running a privileged Exim with an arbitrary
3227 The &%-C%& facility is useful for ensuring that configuration files are
3228 syntactically correct, but cannot be used for test deliveries, unless the
3229 caller is privileged, or unless it is an exotic configuration that does not
3230 require privilege. No check is made on the owner or group of the files
3231 specified by this option.
3233 .vitem &%-D%&<&'macro'&>=<&'value'&>
3235 .cindex "macro" "setting on command line"
3236 This option can be used to override macro definitions in the configuration file
3237 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3238 unprivileged caller, it causes Exim to give up its root privilege.
3239 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3240 completely disabled, and its use causes an immediate error exit.
3242 The entire option (including equals sign if present) must all be within one
3243 command line item. &%-D%& can be used to set the value of a macro to the empty
3244 string, in which case the equals sign is optional. These two commands are
3250 To include spaces in a macro definition item, quotes must be used. If you use
3251 quotes, spaces are permitted around the macro name and the equals sign. For
3254 exim '-D ABC = something' ...
3256 &%-D%& may be repeated up to 10 times on a command line.
3258 .vitem &%-d%&<&'debug&~options'&>
3260 .cindex "debugging" "list of selectors"
3261 .cindex "debugging" "&%-d%& option"
3262 This option causes debugging information to be written to the standard
3263 error stream. It is restricted to admin users because debugging output may show
3264 database queries that contain password information. Also, the details of users'
3265 filter files should be protected. When &%-d%& is used, &%-v%& is assumed. If
3266 &%-d%& is given on its own, a lot of standard debugging data is output. This
3267 can be reduced, or increased to include some more rarely needed information, by
3268 directly following &%-d%& with a string made up of names preceded by plus or
3269 minus characters. These add or remove sets of debugging data, respectively. For
3270 example, &%-d+filter%& adds filter debugging, whereas &%-d-all+filter%& selects
3271 only filter debugging. Note that no spaces are allowed in the debug setting.
3272 The available debugging categories are:
3274 &`acl `& ACL interpretation
3275 &`auth `& authenticators
3276 &`deliver `& general delivery logic
3277 &`dns `& DNS lookups (see also resolver)
3278 &`dnsbl `& DNS black list (aka RBL) code
3279 &`exec `& arguments for &[execv()]& calls
3280 &`expand `& detailed debugging for string expansions
3281 &`filter `& filter handling
3282 &`hints_lookup `& hints data lookups
3283 &`host_lookup `& all types of name-to-IP address handling
3284 &`ident `& ident lookup
3285 &`interface `& lists of local interfaces
3286 &`lists `& matching things in lists
3287 &`load `& system load checks
3288 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3289 &<<CHAPlocalscan>>&)
3290 &`lookup `& general lookup code and all lookups
3291 &`memory `& memory handling
3292 &`pid `& add pid to debug output lines
3293 &`process_info `& setting info for the process log
3294 &`queue_run `& queue runs
3295 &`receive `& general message reception logic
3296 &`resolver `& turn on the DNS resolver's debugging output
3297 &`retry `& retry handling
3298 &`rewrite `& address rewriting
3299 &`route `& address routing
3300 &`timestamp `& add timestamp to debug output lines
3302 &`transport `& transports
3303 &`uid `& changes of uid/gid and looking up uid/gid
3304 &`verify `& address verification logic
3305 &`all `& almost all of the above (see below), and also &%-v%&
3307 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3308 for &`-all`&. The reason for this is that &`+all`& is something that people
3309 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3310 is included, an awful lot of output that is very rarely of interest is
3311 generated, so it now has to be explicitly requested. However, &`-all`& does
3312 turn everything off.
3314 .cindex "resolver" "debugging output"
3315 .cindex "DNS resolver" "debugging output"
3316 The &`resolver`& option produces output only if the DNS resolver was compiled
3317 with DEBUG enabled. This is not the case in some operating systems. Also,
3318 unfortunately, debugging output from the DNS resolver is written to stdout
3321 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3322 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3323 However, the &`pid`& selector is forced when debugging is turned on for a
3324 daemon, which then passes it on to any re-executed Exims. Exim also
3325 automatically adds the pid to debug lines when several remote deliveries are
3328 The &`timestamp`& selector causes the current time to be inserted at the start
3329 of all debug output lines. This can be useful when trying to track down delays
3332 If the &%debug_print%& option is set in any driver, it produces output whenever
3333 any debugging is selected, or if &%-v%& is used.
3335 .vitem &%-dd%&<&'debug&~options'&>
3337 This option behaves exactly like &%-d%& except when used on a command that
3338 starts a daemon process. In that case, debugging is turned off for the
3339 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3340 behaviour of the daemon without creating as much output as full debugging does.
3343 .oindex "&%-dropcr%&"
3344 This is an obsolete option that is now a no-op. It used to affect the way Exim
3345 handled CR and LF characters in incoming messages. What happens now is
3346 described in section &<<SECTlineendings>>&.
3350 .cindex "bounce message" "generating"
3351 This option specifies that an incoming message is a locally-generated delivery
3352 failure report. It is used internally by Exim when handling delivery failures
3353 and is not intended for external use. Its only effect is to stop Exim
3354 generating certain messages to the postmaster, as otherwise message cascades
3355 could occur in some situations. As part of the same option, a message id may
3356 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3357 new message contains the id, following &"R="&, as a cross-reference.
3360 .oindex "&%-e%&&'x'&"
3361 There are a number of Sendmail options starting with &%-oe%& which seem to be
3362 called by various programs without the leading &%o%& in the option. For
3363 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3364 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3366 .vitem &%-F%&&~<&'string'&>
3368 .cindex "sender" "name"
3369 .cindex "name" "of sender"
3370 This option sets the sender's full name for use when a locally-generated
3371 message is being accepted. In the absence of this option, the user's &'gecos'&
3372 entry from the password data is used. As users are generally permitted to alter
3373 their &'gecos'& entries, no security considerations are involved. White space
3374 between &%-F%& and the <&'string'&> is optional.
3376 .vitem &%-f%&&~<&'address'&>
3378 .cindex "sender" "address"
3379 .cindex "address" "sender"
3380 .cindex "trusted user"
3381 .cindex "envelope sender"
3382 .cindex "user" "trusted"
3383 This option sets the address of the envelope sender of a locally-generated
3384 message (also known as the return path). The option can normally be used only
3385 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3388 Processes running as root or the Exim user are always trusted. Other
3389 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3390 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3391 of a local message is set to the caller's login name at the default qualify
3394 There is one exception to the restriction on the use of &%-f%&: an empty sender
3395 can be specified by any user, trusted or not, to create a message that can
3396 never provoke a bounce. An empty sender can be specified either as an empty
3397 string, or as a pair of angle brackets with nothing between them, as in these
3398 examples of shell commands:
3400 exim -f '<>' user@domain
3401 exim -f "" user@domain
3403 In addition, the use of &%-f%& is not restricted when testing a filter file
3404 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3407 Allowing untrusted users to change the sender address does not of itself make
3408 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3409 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3410 though this can be overridden by setting &%no_local_from_check%&.
3413 .cindex "&""From""& line"
3414 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3415 given as two arguments or one combined argument). The sender of a
3416 locally-generated message can also be set (when permitted) by an initial
3417 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3418 if &%-f%& is also present, it overrides &"From&~"&.
3422 .cindex "Sendmail compatibility" "&%-G%& option ignored"
3423 This is a Sendmail option which is ignored by Exim.
3425 .vitem &%-h%&&~<&'number'&>
3427 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3428 This option is accepted for compatibility with Sendmail, but has no effect. (In
3429 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3434 .cindex "Solaris" "&'mail'& command"
3435 .cindex "dot in incoming" "non-SMTP message"
3436 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3437 line by itself should not terminate an incoming, non-SMTP message. I can find
3438 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3439 command in Solaris 2.4 uses it. See also &%-ti%&.
3441 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3443 .cindex "forcing delivery"
3444 .cindex "delivery" "forcing attempt"
3445 .cindex "frozen messages" "forcing delivery"
3446 This option requests Exim to run a delivery attempt on each message in turn. If
3447 any of the messages are frozen, they are automatically thawed before the
3448 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3449 and &%hold_domains%& are ignored.
3452 .cindex "hints database" "overriding retry hints"
3453 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3454 the normal retry time has not yet been reached. This option requires the caller
3455 to be an admin user. However, there is an option called &%prod_requires_admin%&
3456 which can be set false to relax this restriction (and also the same requirement
3457 for the &%-q%&, &%-R%&, and &%-S%& options).
3459 The deliveries happen synchronously, that is, the original Exim process does
3460 not terminate until all the delivery attempts have finished. No output is
3461 produced unless there is a serious error. If you want to see what is happening,
3462 use the &%-v%& option as well, or inspect Exim's main log.
3464 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3466 .cindex "message" "adding recipients"
3467 .cindex "recipient" "adding"
3468 This option requests Exim to add the addresses to the list of recipients of the
3469 message (&"ar"& for &"add recipients"&). The first argument must be a message
3470 id, and the remaining ones must be email addresses. However, if the message is
3471 active (in the middle of a delivery attempt), it is not altered. This option
3472 can be used only by an admin user.
3474 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3475 &~<&'message&~id'&>"
3477 .cindex "SMTP" "passed connection"
3478 .cindex "SMTP" "multiple deliveries"
3479 .cindex "multiple SMTP deliveries"
3480 This option is not intended for use by external callers. It is used internally
3481 by Exim to invoke another instance of itself to deliver a waiting message using
3482 an existing SMTP connection, which is passed as the standard input. Details are
3483 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3484 must be root or the Exim user in order to use it.
3488 This option is not intended for use by external callers. It is used internally
3489 by Exim in conjunction with the &%-MC%& option. It signifies that the
3490 connection to the remote host has been authenticated.
3494 This option is not intended for use by external callers. It is used internally
3495 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3496 which Exim is connected supports pipelining.
3498 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3500 This option is not intended for use by external callers. It is used internally
3501 by Exim in conjunction with the &%-MC%& option when the original delivery was
3502 started by a queue runner. It passes on the process id of the queue runner,
3503 together with the file descriptor number of an open pipe. Closure of the pipe
3504 signals the final completion of the sequence of processes that are passing
3505 messages through the same SMTP connection.
3509 This option is not intended for use by external callers. It is used internally
3510 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3511 SMTP SIZE option should be used on messages delivered down the existing
3516 This option is not intended for use by external callers. It is used internally
3517 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3518 host to which Exim is connected supports TLS encryption.
3520 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3522 .cindex "hints database" "not overridden by &%-Mc%&"
3523 .cindex "delivery" "manually started &-- not forced"
3524 This option requests Exim to run a delivery attempt on each message in turn,
3525 but unlike the &%-M%& option, it does check for retry hints, and respects any
3526 that are found. This option is not very useful to external callers. It is
3527 provided mainly for internal use by Exim when it needs to re-invoke itself in
3528 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3529 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3530 respects retry times and other options such as &%hold_domains%& that are
3531 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3532 If you want to run a specific delivery as if in a queue run, you should use
3533 &%-q%& with a message id argument. A distinction between queue run deliveries
3534 and other deliveries is made in one or two places.
3536 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3538 .cindex "message" "changing sender"
3539 .cindex "sender" "changing"
3540 This option requests Exim to change the sender address in the message to the
3541 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3542 &"edit sender"&). There must be exactly two arguments. The first argument must
3543 be a message id, and the second one an email address. However, if the message
3544 is active (in the middle of a delivery attempt), its status is not altered.
3545 This option can be used only by an admin user.
3547 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3549 .cindex "freezing messages"
3550 .cindex "message" "manually freezing"
3551 This option requests Exim to mark each listed message as &"frozen"&. This
3552 prevents any delivery attempts taking place until the message is &"thawed"&,
3553 either manually or as a result of the &%auto_thaw%& configuration option.
3554 However, if any of the messages are active (in the middle of a delivery
3555 attempt), their status is not altered. This option can be used only by an admin
3558 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3560 .cindex "giving up on messages"
3561 .cindex "message" "abandoning delivery attempts"
3562 .cindex "delivery" "abandoning further attempts"
3563 This option requests Exim to give up trying to deliver the listed messages,
3564 including any that are frozen. However, if any of the messages are active,
3565 their status is not altered. For non-bounce messages, a delivery error message
3566 is sent to the sender, containing the text &"cancelled by administrator"&.
3567 Bounce messages are just discarded. This option can be used only by an admin
3570 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3572 .cindex "delivery" "cancelling all"
3573 This option requests Exim to mark all the recipient addresses in the messages
3574 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3575 message is active (in the middle of a delivery attempt), its status is not
3576 altered. This option can be used only by an admin user.
3578 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3580 .cindex "delivery" "cancelling by address"
3581 .cindex "recipient" "removing"
3582 .cindex "removing recipients"
3583 This option requests Exim to mark the given addresses as already delivered
3584 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3585 the remaining ones must be email addresses. These are matched to recipient
3586 addresses in the message in a case-sensitive manner. If the message is active
3587 (in the middle of a delivery attempt), its status is not altered. This option
3588 can be used only by an admin user.
3590 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3592 .cindex "removing messages"
3593 .cindex "abandoning mail"
3594 .cindex "message" "manually discarding"
3595 This option requests Exim to remove the given messages from the queue. No
3596 bounce messages are sent; each message is simply forgotten. However, if any of
3597 the messages are active, their status is not altered. This option can be used
3598 only by an admin user or by the user who originally caused the message to be
3599 placed on the queue.
3601 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3603 .cindex "thawing messages"
3604 .cindex "unfreezing messages"
3605 .cindex "frozen messages" "thawing"
3606 .cindex "message" "thawing frozen"
3607 This option requests Exim to &"thaw"& any of the listed messages that are
3608 &"frozen"&, so that delivery attempts can resume. However, if any of the
3609 messages are active, their status is not altered. This option can be used only
3612 .vitem &%-Mvb%&&~<&'message&~id'&>
3614 .cindex "listing" "message body"
3615 .cindex "message" "listing body of"
3616 This option causes the contents of the message body (-D) spool file to be
3617 written to the standard output. This option can be used only by an admin user.
3619 .vitem &%-Mvh%&&~<&'message&~id'&>
3621 .cindex "listing" "message headers"
3622 .cindex "header lines" "listing"
3623 .cindex "message" "listing header lines"
3624 This option causes the contents of the message headers (-H) spool file to be
3625 written to the standard output. This option can be used only by an admin user.
3627 .vitem &%-Mvl%&&~<&'message&~id'&>
3629 .cindex "listing" "message log"
3630 .cindex "message" "listing message log"
3631 This option causes the contents of the message log spool file to be written to
3632 the standard output. This option can be used only by an admin user.
3636 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3637 treats it that way too.
3641 .cindex "debugging" "&%-N%& option"
3642 .cindex "debugging" "suppressing delivery"
3643 This is a debugging option that inhibits delivery of a message at the transport
3644 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3645 it just doesn't actually transport the message, but instead behaves as if it
3646 had successfully done so. However, it does not make any updates to the retry
3647 database, and the log entries for deliveries are flagged with &"*>"& rather
3650 Because &%-N%& discards any message to which it applies, only root or the Exim
3651 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3652 words, an ordinary user can use it only when supplying an incoming message to
3653 which it will apply. Although transportation never fails when &%-N%& is set, an
3654 address may be deferred because of a configuration problem on a transport, or a
3655 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3656 the message, and applies to any subsequent delivery attempts that may happen
3661 .cindex "Sendmail compatibility" "&%-n%& option ignored"
3662 This option is interpreted by Sendmail to mean &"no aliasing"&. It is ignored
3665 .vitem &%-O%&&~<&'data'&>
3667 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
3670 .vitem &%-oA%&&~<&'file&~name'&>
3672 .cindex "Sendmail compatibility" "&%-oA%& option"
3673 This option is used by Sendmail in conjunction with &%-bi%& to specify an
3674 alternative alias file name. Exim handles &%-bi%& differently; see the
3677 .vitem &%-oB%&&~<&'n'&>
3679 .cindex "SMTP" "passed connection"
3680 .cindex "SMTP" "multiple deliveries"
3681 .cindex "multiple SMTP deliveries"
3682 This is a debugging option which limits the maximum number of messages that can
3683 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
3684 transport. If <&'n'&> is omitted, the limit is set to 1.
3688 .cindex "background delivery"
3689 .cindex "delivery" "in the background"
3690 This option applies to all modes in which Exim accepts incoming messages,
3691 including the listening daemon. It requests &"background"& delivery of such
3692 messages, which means that the accepting process automatically starts a
3693 delivery process for each message received, but does not wait for the delivery
3694 processes to finish.
3696 When all the messages have been received, the reception process exits,
3697 leaving the delivery processes to finish in their own time. The standard output
3698 and error streams are closed at the start of each delivery process.
3699 This is the default action if none of the &%-od%& options are present.
3701 If one of the queueing options in the configuration file
3702 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
3703 overrides it if &%queue_only_override%& is set true, which is the default
3704 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
3708 .cindex "foreground delivery"
3709 .cindex "delivery" "in the foreground"
3710 This option requests &"foreground"& (synchronous) delivery when Exim has
3711 accepted a locally-generated message. (For the daemon it is exactly the same as
3712 &%-odb%&.) A delivery process is automatically started to deliver the message,
3713 and Exim waits for it to complete before proceeding.
3715 The original Exim reception process does not finish until the delivery
3716 process for the final message has ended. The standard error stream is left open
3719 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
3720 false and one of the queueing options in the configuration file is in effect.
3722 If there is a temporary delivery error during foreground delivery, the
3723 message is left on the queue for later delivery, and the original reception
3724 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
3725 restricted configuration that never queues messages.
3730 This option is synonymous with &%-odf%&. It is provided for compatibility with
3735 .cindex "non-immediate delivery"
3736 .cindex "delivery" "suppressing immediate"
3737 .cindex "queueing incoming messages"
3738 This option applies to all modes in which Exim accepts incoming messages,
3739 including the listening daemon. It specifies that the accepting process should
3740 not automatically start a delivery process for each message received. Messages
3741 are placed on the queue, and remain there until a subsequent queue runner
3742 process encounters them. There are several configuration options (such as
3743 &%queue_only%&) that can be used to queue incoming messages under certain
3744 conditions. This option overrides all of them and also &%-odqs%&. It always
3749 .cindex "SMTP" "delaying delivery"
3750 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
3751 However, like &%-odb%& and &%-odi%&, this option has no effect if
3752 &%queue_only_override%& is false and one of the queueing options in the
3753 configuration file is in effect.
3755 When &%-odqs%& does operate, a delivery process is started for each incoming
3756 message, in the background by default, but in the foreground if &%-odi%& is
3757 also present. The recipient addresses are routed, and local deliveries are done
3758 in the normal way. However, if any SMTP deliveries are required, they are not
3759 done at this time, so the message remains on the queue until a subsequent queue
3760 runner process encounters it. Because routing was done, Exim knows which
3761 messages are waiting for which hosts, and so a number of messages for the same
3762 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
3763 configuration option has the same effect for specific domains. See also the
3768 .cindex "error" "reporting"
3769 If an error is detected while a non-SMTP message is being received (for
3770 example, a malformed address), the error is reported to the sender in a mail
3773 .cindex "return code" "for &%-oee%&"
3775 this error message is successfully sent, the Exim receiving process
3776 exits with a return code of zero. If not, the return code is 2 if the problem
3777 is that the original message has no recipients, or 1 any other error. This is
3778 the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
3782 .cindex "error" "reporting"
3783 .cindex "return code" "for &%-oem%&"
3784 This is the same as &%-oee%&, except that Exim always exits with a non-zero
3785 return code, whether or not the error message was successfully sent.
3786 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
3790 .cindex "error" "reporting"
3791 If an error is detected while a non-SMTP message is being received, the
3792 error is reported by writing a message to the standard error file (stderr).
3793 .cindex "return code" "for &%-oep%&"
3794 The return code is 1 for all errors.
3798 .cindex "error" "reporting"
3799 This option is supported for compatibility with Sendmail, but has the same
3804 .cindex "error" "reporting"
3805 This option is supported for compatibility with Sendmail, but has the same
3810 .cindex "dot in incoming" "non-SMTP message"
3811 This option, which has the same effect as &%-i%&, specifies that a dot on a
3812 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
3813 single dot does terminate, though Exim does no special processing for other
3814 lines that start with a dot. This option is set by default if Exim is called as
3815 &'rmail'&. See also &%-ti%&.
3818 .oindex "&%-oitrue%&"
3819 This option is treated as synonymous with &%-oi%&.
3821 .vitem &%-oMa%&&~<&'host&~address'&>
3823 .cindex "sender host address" "specifying for local message"
3824 A number of options starting with &%-oM%& can be used to set values associated
3825 with remote hosts on locally-submitted messages (that is, messages not received
3826 over TCP/IP). These options can be used by any caller in conjunction with the
3827 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
3828 other circumstances, they are ignored unless the caller is trusted.
3830 The &%-oMa%& option sets the sender host address. This may include a port
3831 number at the end, after a full stop (period). For example:
3833 exim -bs -oMa 10.9.8.7.1234
3835 An alternative syntax is to enclose the IP address in square brackets,
3836 followed by a colon and the port number:
3838 exim -bs -oMa [10.9.8.7]:1234
3840 The IP address is placed in the &$sender_host_address$& variable, and the
3841 port, if present, in &$sender_host_port$&.
3843 .vitem &%-oMaa%&&~<&'name'&>
3845 .cindex "authentication name" "specifying for local message"
3846 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
3847 option sets the value of &$sender_host_authenticated$& (the authenticator
3848 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
3850 .vitem &%-oMai%&&~<&'string'&>
3852 .cindex "authentication id" "specifying for local message"
3853 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
3854 option sets the value of &$authenticated_id$& (the id that was authenticated).
3855 This overrides the default value (the caller's login id) for messages from
3856 local sources. See chapter &<<CHAPSMTPAUTH>>& for a discussion of authenticated
3859 .vitem &%-oMas%&&~<&'address'&>
3861 .cindex "authentication sender" "specifying for local message"
3862 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
3863 option sets the authenticated sender value in &$authenticated_sender$&. It
3864 overrides the sender address that is created from the caller's login id for
3865 messages from local sources. See chapter &<<CHAPSMTPAUTH>>& for a discussion of
3866 authenticated senders.
3868 .vitem &%-oMi%&&~<&'interface&~address'&>
3870 .cindex "interface address" "specifying for local message"
3871 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
3872 option sets the IP interface address value. A port number may be included,
3873 using the same syntax as for &%-oMa%&. The interface address is placed in
3874 &$interface_address$& and the port number, if present, in &$interface_port$&.
3876 .vitem &%-oMr%&&~<&'protocol&~name'&>
3878 .cindex "protocol" "incoming &-- specifying for local message"
3879 .cindex "&$received_protocol$&"
3880 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
3881 option sets the received protocol value that is stored in
3882 &$received_protocol$&. However, this applies only when &%-bs%& is not used. For
3883 interactive SMTP input (&%-bs%&), the protocol is always &"local-"& followed by
3884 one of the standard SMTP protocol names (see the description of
3885 &$received_protocol$& in section &<<SECTexpvar>>&). For &%-bS%& (batch SMTP)
3886 however, the protocol can be set by &%-oMr%&.
3888 .vitem &%-oMs%&&~<&'host&~name'&>
3890 .cindex "sender host name" "specifying for local message"
3891 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
3892 option sets the sender host name in &$sender_host_name$&. When this option is
3893 present, Exim does not attempt to look up a host name from an IP address; it
3894 uses the name it is given.
3896 .vitem &%-oMt%&&~<&'ident&~string'&>
3898 .cindex "sender ident string" "specifying for local message"
3899 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
3900 option sets the sender ident value in &$sender_ident$&. The default setting for
3901 local callers is the login id of the calling process.
3905 .cindex "Sendmail compatibility" "&%-om%& option ignored"
3906 In Sendmail, this option means &"me too"&, indicating that the sender of a
3907 message should receive a copy of the message if the sender appears in an alias
3908 expansion. Exim always does this, so the option does nothing.
3912 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
3913 This option is ignored. In Sendmail it specifies &"old style headers"&,
3914 whatever that means.
3916 .vitem &%-oP%&&~<&'path'&>
3918 .cindex "pid (process id)" "of daemon"
3919 .cindex "daemon" "process id (pid)"
3920 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
3921 value. The option specifies the file to which the process id of the daemon is
3922 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
3923 without &%-bd%&, this is the only way of causing Exim to write a pid file,
3924 because in those cases, the normal pid file is not used.
3926 .vitem &%-or%&&~<&'time'&>
3928 .cindex "timeout" "for non-SMTP input"
3929 This option sets a timeout value for incoming non-SMTP messages. If it is not
3930 set, Exim will wait forever for the standard input. The value can also be set
3931 by the &%receive_timeout%& option. The format used for specifying times is
3932 described in section &<<SECTtimeformat>>&.
3934 .vitem &%-os%&&~<&'time'&>
3936 .cindex "timeout" "for SMTP input"
3937 .cindex "SMTP timeout" "input"
3938 This option sets a timeout value for incoming SMTP messages. The timeout
3939 applies to each SMTP command and block of data. The value can also be set by
3940 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
3941 for specifying times is described in section &<<SECTtimeformat>>&.
3945 This option has exactly the same effect as &%-v%&.
3947 .vitem &%-oX%&&~<&'number&~or&~string'&>
3949 .cindex "TCP/IP" "setting listening ports"
3950 .cindex "TCP/IP" "setting listening interfaces"
3951 .cindex "port" "receiving TCP/IP"
3952 This option is relevant only when the &%-bd%& (start listening daemon) option
3953 is also given. It controls which ports and interfaces the daemon uses. Details
3954 of the syntax, and how it interacts with configuration file options, are given
3955 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
3956 file is written unless &%-oP%& is also present to specify a pid file name.
3960 .cindex "Perl" "starting the interpreter"
3961 This option applies when an embedded Perl interpreter is linked with Exim (see
3962 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
3963 option, forcing the starting of the interpreter to be delayed until it is
3968 .cindex "Perl" "starting the interpreter"
3969 This option applies when an embedded Perl interpreter is linked with Exim (see
3970 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
3971 option, forcing the starting of the interpreter to occur as soon as Exim is
3974 .vitem &%-p%&<&'rval'&>:<&'sval'&>
3976 For compatibility with Sendmail, this option is equivalent to
3978 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
3980 It sets the incoming protocol and host name (for trusted callers). The
3981 host name and its colon can be omitted when only the protocol is to be set.
3982 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
3983 to embedded Perl. It is therefore impossible to set a protocol value of &`p`&
3984 or &`s`& using this option (but that does not seem a real limitation).
3988 .cindex "queue runner" "starting manually"
3989 This option is normally restricted to admin users. However, there is a
3990 configuration option called &%prod_requires_admin%& which can be set false to
3991 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
3992 and &%-S%& options).
3994 .cindex "queue runner" "description of operation"
3995 The &%-q%& option starts one queue runner process. This scans the queue of
3996 waiting messages, and runs a delivery process for each one in turn. It waits
3997 for each delivery process to finish before starting the next one. A delivery
3998 process may not actually do any deliveries if the retry times for the addresses
3999 have not been reached. Use &%-qf%& (see below) if you want to override this.
4002 .cindex "SMTP" "passed connection"
4003 .cindex "SMTP" "multiple deliveries"
4004 .cindex "multiple SMTP deliveries"
4005 the delivery process spawns other processes to deliver other messages down
4006 passed SMTP connections, the queue runner waits for these to finish before
4009 When all the queued messages have been considered, the original queue runner
4010 process terminates. In other words, a single pass is made over the waiting
4011 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4012 this to be repeated periodically.
4014 Exim processes the waiting messages in an unpredictable order. It isn't very
4015 random, but it is likely to be different each time, which is all that matters.
4016 If one particular message screws up a remote MTA, other messages to the same
4017 MTA have a chance of getting through if they get tried first.
4019 It is possible to cause the messages to be processed in lexical message id
4020 order, which is essentially the order in which they arrived, by setting the
4021 &%queue_run_in_order%& option, but this is not recommended for normal use.
4023 .vitem &%-q%&<&'qflags'&>
4024 The &%-q%& option may be followed by one or more flag letters that change its
4025 behaviour. They are all optional, but if more than one is present, they must
4026 appear in the correct order. Each flag is described in a separate item below.
4030 .cindex "queue" "double scanning"
4031 .cindex "queue" "routing"
4032 .cindex "routing" "whole queue before delivery"
4033 An option starting with &%-qq%& requests a two-stage queue run. In the first
4034 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4035 every domain. Addresses are routed, local deliveries happen, but no remote
4038 .cindex "hints database" "remembering routing"
4039 The hints database that remembers which messages are waiting for specific hosts
4040 is updated, as if delivery to those hosts had been deferred. After this is
4041 complete, a second, normal queue scan happens, with routing and delivery taking
4042 place as normal. Messages that are routed to the same host should mostly be
4043 delivered down a single SMTP
4044 .cindex "SMTP" "passed connection"
4045 .cindex "SMTP" "multiple deliveries"
4046 .cindex "multiple SMTP deliveries"
4047 connection because of the hints that were set up during the first queue scan.
4048 This option may be useful for hosts that are connected to the Internet
4051 .vitem &%-q[q]i...%&
4053 .cindex "queue" "initial delivery"
4054 If the &'i'& flag is present, the queue runner runs delivery processes only for
4055 those messages that haven't previously been tried. (&'i'& stands for &"initial
4056 delivery"&.) This can be helpful if you are putting messages on the queue using
4057 &%-odq%& and want a queue runner just to process the new messages.
4059 .vitem &%-q[q][i]f...%&
4061 .cindex "queue" "forcing delivery"
4062 .cindex "delivery" "forcing in queue run"
4063 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4064 message, whereas without &'f'& only those non-frozen addresses that have passed
4065 their retry times are tried.
4067 .vitem &%-q[q][i]ff...%&
4069 .cindex "frozen messages" "forcing delivery"
4070 If &'ff'& is present, a delivery attempt is forced for every message, whether
4073 .vitem &%-q[q][i][f[f]]l%&
4075 .cindex "queue" "local deliveries only"
4076 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4077 be done. If a message requires any remote deliveries, it remains on the queue
4080 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4081 .cindex "queue" "delivering specific messages"
4082 When scanning the queue, Exim can be made to skip over messages whose ids are
4083 lexically less than a given value by following the &%-q%& option with a
4084 starting message id. For example:
4086 exim -q 0t5C6f-0000c8-00
4088 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4089 second message id is given, messages whose ids are lexically greater than it
4090 are also skipped. If the same id is given twice, for example,
4092 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4094 just one delivery process is started, for that message. This differs from
4095 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4096 that it counts as a delivery from a queue run. Note that the selection
4097 mechanism does not affect the order in which the messages are scanned. There
4098 are also other ways of selecting specific sets of messages for delivery in a
4099 queue run &-- see &%-R%& and &%-S%&.
4101 .vitem &%-q%&<&'qflags'&><&'time'&>
4102 .cindex "queue runner" "starting periodically"
4103 .cindex "periodic queue running"
4104 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4105 starting a queue runner process at intervals specified by the given time value
4106 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4107 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4108 single daemon process handles both functions. A common way of starting up a
4109 combined daemon at system boot time is to use a command such as
4111 /usr/exim/bin/exim -bd -q30m
4113 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4114 process every 30 minutes.
4116 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4117 pid file is written unless one is explicitly requested by the &%-oP%& option.
4119 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4121 This option is synonymous with &%-R%&. It is provided for Sendmail
4124 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4126 This option is synonymous with &%-S%&.
4128 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4130 .cindex "queue runner" "for specific recipients"
4131 .cindex "delivery" "to given domain"
4132 .cindex "domain" "delivery to"
4133 The <&'rsflags'&> may be empty, in which case the white space before the string
4134 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4135 which are the possible values for <&'rsflags'&>. White space is required if
4136 <&'rsflags'&> is not empty.
4138 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4139 perform a single queue run, except that, when scanning the messages on the
4140 queue, Exim processes only those that have at least one undelivered recipient
4141 address containing the given string, which is checked in a case-independent
4142 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4143 regular expression; otherwise it is a literal string.
4145 Once a message is selected, all its addresses are processed. For the first
4146 selected message, Exim overrides any retry information and forces a delivery
4147 attempt for each undelivered address. This means that if delivery of any
4148 address in the first message is successful, any existing retry information is
4149 deleted, and so delivery attempts for that address in subsequently selected
4150 messages (which are processed without forcing) will run. However, if delivery
4151 of any address does not succeed, the retry information is updated, and in
4152 subsequently selected messages, the failing address will be skipped.
4154 .cindex "frozen messages" "forcing delivery"
4155 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4156 all selected messages, not just the first; frozen messages are included when
4159 The &%-R%& option makes it straightforward to initiate delivery of all messages
4160 to a given domain after a host has been down for some time. When the SMTP
4161 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4162 effect is to run Exim with the &%-R%& option, but it can be configured to run
4163 an arbitrary command instead.
4167 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4169 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4171 .cindex "delivery" "from given sender"
4172 .cindex "queue runner" "for specific senders"
4173 This option acts like &%-R%& except that it checks the string against each
4174 message's sender instead of against the recipients. If &%-R%& is also set, both
4175 conditions must be met for a message to be selected. If either of the options
4176 has &'f'& or &'ff'& in its flags, the associated action is taken.
4178 .vitem &%-Tqt%&&~<&'times'&>
4180 This an option that is exclusively for use by the Exim testing suite. It is not
4181 recognized when Exim is run normally. It allows for the setting up of explicit
4182 &"queue times"& so that various warning/retry features can be tested.
4186 .cindex "recipient" "extracting from header lines"
4187 .cindex "&'Bcc:'& header line"
4188 .cindex "&'Cc:'& header line"
4189 .cindex "&'To:'& header line"
4190 When Exim is receiving a locally-generated, non-SMTP message on its standard
4191 input, the &%-t%& option causes the recipients of the message to be obtained
4192 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4193 from the command arguments. The addresses are extracted before any rewriting
4194 takes place and the &'Bcc:'& header line, if present, is then removed.
4196 .cindex "Sendmail compatibility" "&%-t%& option"
4197 If the command has any arguments, they specify addresses to which the message
4198 is &'not'& to be delivered. That is, the argument addresses are removed from
4199 the recipients list obtained from the headers. This is compatible with Smail 3
4200 and in accordance with the documented behaviour of several versions of
4201 Sendmail, as described in man pages on a number of operating systems (e.g.
4202 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4203 argument addresses to those obtained from the headers, and the O'Reilly
4204 Sendmail book documents it that way. Exim can be made to add argument addresses
4205 instead of subtracting them by setting the option
4206 &%extract_addresses_remove_arguments%& false.
4208 .cindex "&%Resent-%& header lines" "with &%-t%&"
4209 If there are any &%Resent-%& header lines in the message, Exim extracts
4210 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4211 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4212 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4213 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4215 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4216 message is resent several times). The RFC also specifies that they should be
4217 added at the front of the message, and separated by &'Received:'& lines. It is
4218 not at all clear how &%-t%& should operate in the present of multiple sets,
4219 nor indeed exactly what constitutes a &"set"&.
4220 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4221 are often added at the end of the header, and if a message is resent more than
4222 once, it is common for the original set of &%Resent-%& headers to be renamed as
4223 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4227 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4228 compatibility with Sendmail.
4230 .vitem &%-tls-on-connect%&
4231 .oindex "&%-tls-on-connect%&"
4232 .cindex "TLS" "use without STARTTLS"
4233 .cindex "TLS" "automatic start"
4234 This option is available when Exim is compiled with TLS support. It forces all
4235 incoming SMTP connections to behave as if the incoming port is listed in the
4236 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4237 &<<CHAPTLS>>& for further details.
4242 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4243 Sendmail uses this option for &"initial message submission"&, and its
4244 documentation states that in future releases, it may complain about
4245 syntactically invalid messages rather than fixing them when this flag is not
4246 set. Exim ignores this option.
4250 This option causes Exim to write information to the standard error stream,
4251 describing what it is doing. In particular, it shows the log lines for
4252 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4253 dialogue is shown. Some of the log lines shown may not actually be written to
4254 the log if the setting of &%log_selector%& discards them. Any relevant
4255 selectors are shown with each log line. If none are shown, the logging is
4260 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4261 National Language Support extended characters in the body of the mail item"&).
4262 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4270 . ////////////////////////////////////////////////////////////////////////////
4271 . Insert a stylized DocBook comment here, to identify the end of the command
4272 . line options. This is for the benefit of the Perl script that automatically
4273 . creates a man page for the options.
4274 . ////////////////////////////////////////////////////////////////////////////
4277 <!-- === End of command line options === -->
4284 . ////////////////////////////////////////////////////////////////////////////
4285 . ////////////////////////////////////////////////////////////////////////////
4288 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4289 "The runtime configuration file"
4291 .cindex "run time configuration"
4292 .cindex "configuration file" "general description"
4293 .cindex "CONFIGURE_FILE"
4294 .cindex "configuration file" "errors in"
4295 .cindex "error" "in configuration file"
4296 .cindex "return code" "for bad configuration"
4297 Exim uses a single run time configuration file that is read whenever an Exim
4298 binary is executed. Note that in normal operation, this happens frequently,
4299 because Exim is designed to operate in a distributed manner, without central
4302 If a syntax error is detected while reading the configuration file, Exim
4303 writes a message on the standard error, and exits with a non-zero return code.
4304 The message is also written to the panic log. &*Note*&: Only simple syntax
4305 errors can be detected at this time. The values of any expanded options are
4306 not checked until the expansion happens, even when the expansion does not
4307 actually alter the string.
4309 The name of the configuration file is compiled into the binary for security
4310 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4311 most configurations, this specifies a single file. However, it is permitted to
4312 give a colon-separated list of file names, in which case Exim uses the first
4313 existing file in the list.
4316 .cindex "EXIM_GROUP"
4317 .cindex "CONFIGURE_OWNER"
4318 .cindex "CONFIGURE_GROUP"
4319 .cindex "configuration file" "ownership"
4320 .cindex "ownership" "configuration file"
4321 The run time configuration file must be owned by root or by the user that is
4322 specified at compile time by the EXIM_USER option, or by the user that is
4323 specified at compile time by the CONFIGURE_OWNER option (if set). The
4324 configuration file must not be world-writeable or group-writeable, unless its
4325 group is the one specified at compile time by the EXIM_GROUP option or by the
4326 CONFIGURE_GROUP option.
4328 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4329 to root, anybody who is able to edit the run time configuration file has an
4330 easy way to run commands as root. If you make your mail administrators members
4331 of the Exim group, but do not trust them with root, make sure that the run time
4332 configuration is not group writeable.
4334 A default configuration file, which will work correctly in simple situations,
4335 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4336 defines just one file name, the installation process copies the default
4337 configuration to a new file of that name if it did not previously exist. If
4338 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4339 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4344 .section "Using a different configuration file"
4345 .cindex "configuration file" "alternate"
4346 A one-off alternate configuration can be specified by the &%-C%& command line
4347 option, which may specify a single file or a list of files. However, when
4348 &%-C%& is used, Exim gives up its root privilege, unless called by root or the
4349 Exim user (or unless the argument for &%-C%& is identical to the built-in value
4350 from CONFIGURE_FILE). &%-C%& is useful mainly for checking the syntax of
4351 configuration files before installing them. No owner or group checks are done
4352 on a configuration file specified by &%-C%&.
4354 The privileged use of &%-C%& by the Exim user can be locked out by setting
4355 ALT_CONFIG_ROOT_ONLY in &_Local/Makefile_& when building Exim. However,
4356 if you do this, you also lock out the possibility of testing a
4357 configuration using &%-C%& right through message reception and delivery, even
4358 if the caller is root. The reception works, but by that time, Exim is running
4359 as the Exim user, so when it re-execs to regain privilege for the delivery, the
4360 use of &%-C%& causes privilege to be lost. However, root can test reception and
4361 delivery using two separate commands (one to put a message on the queue, using
4362 &%-odq%&, and another to do the delivery, using &%-M%&).
4364 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4365 prefix string with which any file named in a &%-C%& command line option must
4366 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4367 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4368 name can be used with &%-C%&.
4370 One-off changes to a configuration can be specified by the &%-D%& command line
4371 option, which defines and overrides values for macros used inside the
4372 configuration file. However, like &%-C%&, the use of this option by a
4373 non-privileged user causes Exim to discard its root privilege.
4374 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4375 completely disabled, and its use causes an immediate error exit.
4377 Some sites may wish to use the same Exim binary on different machines that
4378 share a file system, but to use different configuration files on each machine.
4379 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4380 looks for a file whose name is the configuration file name followed by a dot
4381 and the machine's node name, as obtained from the &[uname()]& function. If this
4382 file does not exist, the standard name is tried. This processing occurs for
4383 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4385 In some esoteric situations different versions of Exim may be run under
4386 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4387 help with this. See the comments in &_src/EDITME_& for details.
4391 .section "Configuration file format" "SECTconffilfor"
4392 .cindex "configuration file" "format of"
4393 .cindex "format" "configuration file"
4394 Exim's configuration file is divided into a number of different parts. General
4395 option settings must always appear at the start of the file. The other parts
4396 are all optional, and may appear in any order. Each part other than the first
4397 is introduced by the word &"begin"& followed by the name of the part. The
4401 &'ACL'&: Access control lists for controlling incoming SMTP mail.
4403 .cindex "AUTH" "configuration"
4404 &'authenticators'&: Configuration settings for the authenticator drivers. These
4405 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4407 &'routers'&: Configuration settings for the router drivers. Routers process
4408 addresses and determine how the message is to be delivered.
4410 &'transports'&: Configuration settings for the transport drivers. Transports
4411 define mechanisms for copying messages to destinations.
4413 &'retry'&: Retry rules, for use when a message cannot be immediately delivered.
4415 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4416 when new addresses are generated during delivery.
4418 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4419 want to use this feature, you must set
4421 LOCAL_SCAN_HAS_OPTIONS=yes
4423 in &_Local/Makefile_& before building Exim. Full details of the
4424 &[local_scan()]& facility are given in chapter &<<CHAPlocalscan>>&.
4427 .cindex "configuration file" "leading white space in"
4428 .cindex "configuration file" "trailing white space in"
4429 .cindex "white space" "in configuration file"
4430 Leading and trailing white space in configuration lines is always ignored.
4432 Blank lines in the file, and lines starting with a # character (ignoring
4433 leading white space) are treated as comments and are ignored. &*Note*&: A
4434 # character other than at the beginning of a line is not treated specially,
4435 and does not introduce a comment.
4437 Any non-comment line can be continued by ending it with a backslash. Note that
4438 the general rule for white space means that trailing white space after the
4439 backslash and leading white space at the start of continuation
4440 lines is ignored. Comment lines beginning with # (but not empty lines) may
4441 appear in the middle of a sequence of continuation lines.
4443 A convenient way to create a configuration file is to start from the
4444 default, which is supplied in &_src/configure.default_&, and add, delete, or
4445 change settings as required.
4447 The ACLs, retry rules, and rewriting rules have their own syntax which is
4448 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4449 respectively. The other parts of the configuration file have some syntactic
4450 items in common, and these are described below, from section &<<SECTcos>>&
4451 onwards. Before that, the inclusion, macro, and conditional facilities are
4456 .section "File inclusions in the configuration file"
4457 .cindex "inclusions in configuration file"
4458 .cindex "configuration file" "including other files"
4459 .cindex ".include in configuration file"
4460 .cindex ".include_if_exists in configuration file"
4461 You can include other files inside Exim's run time configuration file by
4464 &`.include`& <&'file name'&>
4465 &`.include_if_exists`& <&'file name'&>
4467 on a line by itself. Double quotes round the file name are optional. If you use
4468 the first form, a configuration error occurs if the file does not exist; the
4469 second form does nothing for non-existent files. In all cases, an absolute file
4472 Includes may be nested to any depth, but remember that Exim reads its
4473 configuration file often, so it is a good idea to keep them to a minimum.
4474 If you change the contents of an included file, you must HUP the daemon,
4475 because an included file is read only when the configuration itself is read.
4477 The processing of inclusions happens early, at a physical line level, so, like
4478 comment lines, an inclusion can be used in the middle of an option setting,
4481 hosts_lookup = a.b.c \
4484 Include processing happens after macro processing (see below). Its effect is to
4485 process the lines of the included file as if they occurred inline where the
4490 .section "Macros in the configuration file" "SECTmacrodefs"
4491 .cindex "macro" "description of"
4492 .cindex "configuration file" "macros"
4493 If a line in the main part of the configuration (that is, before the first
4494 &"begin"& line) begins with an upper case letter, it is taken as a macro
4495 definition, and must be of the form
4497 <&'name'&> = <&'rest of line'&>
4499 The name must consist of letters, digits, and underscores, and need not all be
4500 in upper case, though that is recommended. The rest of the line, including any
4501 continuations, is the replacement text, and has leading and trailing white
4502 space removed. Quotes are not removed. The replacement text can never end with
4503 a backslash character, but this doesn't seem to be a serious limitation.
4505 Macros may also be defined between router, transport, authenticator, or ACL
4506 definitions. They may not, however, be defined within an individual driver or
4507 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4509 .section "Macro substitution"
4510 Once a macro is defined, all subsequent lines in the file (and any included
4511 files) are scanned for the macro name; if there are several macros, the line is
4512 scanned for each in turn, in the order in which the macros are defined. The
4513 replacement text is not re-scanned for the current macro, though it is scanned
4514 for subsequently defined macros. For this reason, a macro name may not contain
4515 the name of a previously defined macro as a substring. You could, for example,
4518 &`ABCD_XYZ = `&<&'something'&>
4519 &`ABCD = `&<&'something else'&>
4521 but putting the definitions in the opposite order would provoke a configuration
4522 error. Macro expansion is applied to individual physical lines from the file,
4523 before checking for line continuation or file inclusion (see above). If a line
4524 consists solely of a macro name, and the expansion of the macro is empty, the
4525 line is ignored. A macro at the start of a line may turn the line into a
4526 comment line or a &`.include`& line.
4529 .section "Redefining macros"
4530 Once defined, the value of a macro can be redefined later in the configuration
4531 (or in an included file). Redefinition is specified by using &'=='& instead of
4536 MAC == updated value
4538 Redefinition does not alter the order in which the macros are applied to the
4539 subsequent lines of the configuration file. It is still the same order in which
4540 the macros were originally defined. All that changes is the macro's value.
4541 Redefinition makes it possible to accumulate values. For example:
4545 MAC == MAC and something added
4547 This can be helpful in situations where the configuration file is built
4548 from a number of other files.
4550 .section "Overriding macro values"
4551 The values set for macros in the configuration file can be overridden by the
4552 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4553 used, unless called by root or the Exim user. A definition on the command line
4554 using the &%-D%& option causes all definitions and redefinitions within the
4559 .section "Example of macro usage"
4560 As an example of macro usage, consider a configuration where aliases are looked
4561 up in a MySQL database. It helps to keep the file less cluttered if long
4562 strings such as SQL statements are defined separately as macros, for example:
4564 ALIAS_QUERY = select mailbox from user where \
4565 login=${quote_mysql:$local_part};
4567 This can then be used in a &(redirect)& router setting like this:
4569 data = ${lookup mysql{ALIAS_QUERY}}
4571 In earlier versions of Exim macros were sometimes used for domain, host, or
4572 address lists. In Exim 4 these are handled better by named lists &-- see
4573 section &<<SECTnamedlists>>&.
4576 .section "Conditional skips in the configuration file"
4577 .cindex "configuration file" "conditional skips"
4579 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4580 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4581 portions of the configuration file. The processing happens whenever the file is
4582 read (that is, when an Exim binary starts to run).
4584 The implementation is very simple. Instances of the first four directives must
4585 be followed by text that includes the names of one or macros. The condition
4586 that is tested is whether or not any macro substitution has taken place in the
4590 message_size_limit = 50M
4592 message_size_limit = 100M
4595 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
4596 otherwise. If there is more than one macro named on the line, the condition
4597 is true if any of them are defined. That is, it is an &"or"& condition. To
4598 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
4600 Although you can use a macro expansion to generate one of these directives,
4601 it is not very useful, because the condition &"there was a macro substitution
4602 in this line"& will always be true.
4604 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
4605 to clarify complicated nestings.
4609 .section "Common option syntax" "SECTcos"
4610 .cindex "common option syntax"
4611 .cindex "syntax of common options"
4612 .cindex "configuration file" "common option syntax"
4613 For the main set of options, driver options, and &[local_scan()]& options,
4614 each setting is on a line by itself, and starts with a name consisting of
4615 lower-case letters and underscores. Many options require a data value, and in
4616 these cases the name must be followed by an equals sign (with optional white
4617 space) and then the value. For example:
4619 qualify_domain = mydomain.example.com
4621 Some option settings may contain sensitive data, for example, passwords for
4622 accessing databases. To stop non-admin users from using the &%-bP%& command
4623 line option to read these values, you can precede the option settings with the
4624 word &"hide"&. For example:
4626 hide mysql_servers = localhost/users/admin/secret-password
4628 For non-admin users, such options are displayed like this:
4630 mysql_servers = <value not displayable>
4632 If &"hide"& is used on a driver option, it hides the value of that option on
4633 all instances of the same driver.
4635 The following sections describe the syntax used for the different data types
4636 that are found in option settings.
4639 .section "Boolean options"
4640 .cindex "format" "boolean"
4641 .cindex "boolean configuration values"
4642 .oindex "&%no_%&&'xxx'&"
4643 .oindex "&%not_%&&'xxx'&"
4644 Options whose type is given as boolean are on/off switches. There are two
4645 different ways of specifying such options: with and without a data value. If
4646 the option name is specified on its own without data, the switch is turned on;
4647 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
4648 boolean options may be followed by an equals sign and one of the words
4649 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
4650 the following two settings have exactly the same effect:
4655 The following two lines also have the same (opposite) effect:
4660 You can use whichever syntax you prefer.
4665 .section "Integer values"
4666 .cindex "integer configuration values"
4667 .cindex "format" "integer"
4668 If an integer data item starts with the characters &"0x"&, the remainder of it
4669 is interpreted as a hexadecimal number. Otherwise, it is treated as octal if it
4670 starts with the digit 0, and decimal if not. If an integer value is followed by
4671 the letter K, it is multiplied by 1024; if it is followed by the letter M, it
4672 is multiplied by 1024x1024.
4674 When the values of integer option settings are output, values which are an
4675 exact multiple of 1024 or 1024x1024 are
4676 sometimes, but not always,
4677 printed using the letters K and M. The printing style is independent of the
4678 actual input format that was used.
4681 .section "Octal integer values"
4682 .cindex "integer format"
4683 .cindex "format" "octal integer"
4684 The value of an option specified as an octal integer is always interpreted in
4685 octal, whether or not it starts with the digit zero. Such options are always
4690 .section "Fixed point number values"
4691 .cindex "fixed point configuration values"
4692 .cindex "format" "fixed point"
4693 A fixed point number consists of a decimal integer, optionally followed by a
4694 decimal point and up to three further digits.
4698 .section "Time interval values" "SECTtimeformat"
4699 .cindex "time interval" "specifying in configuration"
4700 .cindex "format" "time interval"
4701 A time interval is specified as a sequence of numbers, each followed by one of
4702 the following letters, with no intervening white space:
4705 .row &~&%s%& seconds
4706 .row &~&%m%& minutes
4712 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
4713 intervals are output in the same format. Exim does not restrict the values; it
4714 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
4718 .section "String values" "SECTstrings"
4719 .cindex "string" "format of configuration values"
4720 .cindex "format" "string"
4721 If a string data item does not start with a double-quote character, it is taken
4722 as consisting of the remainder of the line plus any continuation lines,
4723 starting at the first character after any leading white space, with trailing
4724 white space removed, and with no interpretation of the characters in the
4725 string. Because Exim removes comment lines (those beginning with #) at an early
4726 stage, they can appear in the middle of a multi-line string. The following
4727 settings are therefore equivalent:
4729 trusted_users = uucp:mail
4731 trusted_users = uucp:\
4732 # This comment line is ignored
4735 .cindex "string" "quoted"
4736 .cindex "escape characters in quoted strings"
4737 If a string does start with a double-quote, it must end with a closing
4738 double-quote, and any backslash characters other than those used for line
4739 continuation are interpreted as escape characters, as follows:
4742 .row &~&`\\`& "single backslash"
4743 .row &~&`\n`& "newline"
4744 .row &~&`\r`& "carriage return"
4746 .row "&~&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
4747 .row "&~&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
4751 If a backslash is followed by some other character, including a double-quote
4752 character, that character replaces the pair.
4754 Quoting is necessary only if you want to make use of the backslash escapes to
4755 insert special characters, or if you need to specify a value with leading or
4756 trailing spaces. These cases are rare, so quoting is almost never needed in
4757 current versions of Exim. In versions of Exim before 3.14, quoting was required
4758 in order to continue lines, so you may come across older configuration files
4759 and examples that apparently quote unnecessarily.
4762 .section "Expanded strings"
4763 .cindex "string expansion" "definition of"
4764 .cindex "expansion" "definition of"
4765 Some strings in the configuration file are subjected to &'string expansion'&,
4766 by which means various parts of the string may be changed according to the
4767 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
4768 is as just described; in particular, the handling of backslashes in quoted
4769 strings is done as part of the input process, before expansion takes place.
4770 However, backslash is also an escape character for the expander, so any
4771 backslashes that are required for that reason must be doubled if they are
4772 within a quoted configuration string.
4775 .section "User and group names"
4776 .cindex "user name" "format of"
4777 .cindex "format" "user name"
4778 .cindex "group" "name format"
4779 .cindex "format" "group name"
4780 User and group names are specified as strings, using the syntax described
4781 above, but the strings are interpreted specially. A user or group name must
4782 either consist entirely of digits, or be a name that can be looked up using the
4783 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
4786 .section "List construction" "SECTlistconstruct"
4787 .cindex "list" "syntax of in configuration"
4788 .cindex "format" "list item in configuration"
4789 .cindex "string list" "definition"
4790 The data for some configuration options is a list of items, with colon as the
4791 default separator. Many of these options are shown with type &"string list"& in
4792 the descriptions later in this document. Others are listed as &"domain list"&,
4793 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
4794 are all the same; however, those other than &"string list"& are subject to
4795 particular kinds of interpretation, as described in chapter
4796 &<<CHAPdomhosaddlists>>&.
4798 In all these cases, the entire list is treated as a single string as far as the
4799 input syntax is concerned. The &%trusted_users%& setting in section
4800 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
4801 in a list, it must be entered as two colons. Leading and trailing white space
4802 on each item in a list is ignored. This makes it possible to include items that
4803 start with a colon, and in particular, certain forms of IPv6 address. For
4806 local_interfaces = 127.0.0.1 : ::::1
4808 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
4810 &*Note*&: Although leading and trailing white space is ignored in individual
4811 list items, it is not ignored when parsing the list. The space after the first
4812 colon in the example above is necessary. If it were not there, the list would
4813 be interpreted as the two items 127.0.0.1:: and 1.
4815 .cindex "list separator" "changing"
4816 .cindex "IPv6" "addresses in lists"
4817 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
4818 introduced to allow the separator character to be changed. If a list begins
4819 with a left angle bracket, followed by any punctuation character, that
4820 character is used instead of colon as the list separator. For example, the list
4821 above can be rewritten to use a semicolon separator like this:
4823 local_interfaces = <; 127.0.0.1 ; ::1
4825 This facility applies to all lists, with the exception of the list in
4826 &%log_file_path%&. It is recommended that the use of non-colon separators be
4827 confined to circumstances where they really are needed.
4831 .section "Empty items in lists" "SECTempitelis"
4832 .cindex "list" "empty item in"
4833 An empty item at the end of a list is always ignored. In other words, trailing
4834 separator characters are ignored. Thus, the list in
4836 senders = user@domain :
4838 contains only a single item. If you want to include an empty string as one item
4839 in a list, it must not be the last item. For example, this list contains three
4840 items, the second of which is empty:
4842 senders = user1@domain : : user2@domain
4844 &*Note*&: There must be white space between the two colons, as otherwise they
4845 are interpreted as representing a single colon data character (and the list
4846 would then contain just one item). If you want to specify a list that contains
4847 just one, empty item, you can do it as in this example:
4851 In this case, the first item is empty, and the second is discarded because it
4852 is at the end of the list.
4857 .section "Format of driver configurations" "SECTfordricon"
4858 .cindex "drivers" "configuration format"
4859 There are separate parts in the configuration for defining routers, transports,
4860 and authenticators. In each part, you are defining a number of driver
4861 instances, each with its own set of options. Each driver instance is defined by
4862 a sequence of lines like this:
4864 <&'instance name'&>:
4869 In the following example, the instance name is &(localuser)&, and it is
4870 followed by three options settings:
4875 transport = local_delivery
4877 For each driver instance, you specify which Exim code module it uses &-- by the
4878 setting of the &%driver%& option &-- and (optionally) some configuration
4879 settings. For example, in the case of transports, if you want a transport to
4880 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
4881 a local file you would use the &(appendfile)& driver. Each of the drivers is
4882 described in detail in its own separate chapter later in this manual.
4884 You can have several routers, transports, or authenticators that are based on
4885 the same underlying driver (each must have a different instance name).
4887 The order in which routers are defined is important, because addresses are
4888 passed to individual routers one by one, in order. The order in which
4889 transports are defined does not matter at all. The order in which
4890 authenticators are defined is used only when Exim, as a client, is searching
4891 them to find one that matches an authentication mechanism offered by the
4894 .cindex "generic options"
4895 .cindex "options" "generic &-- definition of"
4896 Within a driver instance definition, there are two kinds of option: &'generic'&
4897 and &'private'&. The generic options are those that apply to all drivers of the
4898 same type (that is, all routers, all transports or all authenticators). The
4899 &%driver%& option is a generic option that must appear in every definition.
4900 .cindex "private options"
4901 The private options are special for each driver, and none need appear, because
4902 they all have default values.
4904 The options may appear in any order, except that the &%driver%& option must
4905 precede any private options, since these depend on the particular driver. For
4906 this reason, it is recommended that &%driver%& always be the first option.
4908 Driver instance names, which are used for reference in log entries and
4909 elsewhere, can be any sequence of letters, digits, and underscores (starting
4910 with a letter) and must be unique among drivers of the same type. A router and
4911 a transport (for example) can each have the same name, but no two router
4912 instances can have the same name. The name of a driver instance should not be
4913 confused with the name of the underlying driver module. For example, the
4914 configuration lines:
4919 create an instance of the &(smtp)& transport driver whose name is
4920 &(remote_smtp)&. The same driver code can be used more than once, with
4921 different instance names and different option settings each time. A second
4922 instance of the &(smtp)& transport, with different options, might be defined
4928 command_timeout = 10s
4930 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
4931 these transport instances from routers, and these names would appear in log
4934 Comment lines may be present in the middle of driver specifications. The full
4935 list of option settings for any particular driver instance, including all the
4936 defaulted values, can be extracted by making use of the &%-bP%& command line
4944 . ////////////////////////////////////////////////////////////////////////////
4945 . ////////////////////////////////////////////////////////////////////////////
4947 .chapter "The default configuration file" "CHAPdefconfil"
4948 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
4949 .cindex "default" "configuration file &""walk through""&"
4950 The default configuration file supplied with Exim as &_src/configure.default_&
4951 is sufficient for a host with simple mail requirements. As an introduction to
4952 the way Exim is configured, this chapter &"walks through"& the default
4953 configuration, giving brief explanations of the settings. Detailed descriptions
4954 of the options are given in subsequent chapters. The default configuration file
4955 itself contains extensive comments about ways you might want to modify the
4956 initial settings. However, note that there are many options that are not
4957 mentioned at all in the default configuration.
4961 .section "Main configuration settings" "SECTdefconfmain"
4962 The main (global) configuration option settings must always come first in the
4963 file. The first thing you'll see in the file, after some initial comments, is
4966 # primary_hostname =
4968 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
4969 to know the official, fully qualified name of your host, and this is where you
4970 can specify it. However, in most cases you do not need to set this option. When
4971 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
4973 The first three non-comment configuration lines are as follows:
4975 domainlist local_domains = @
4976 domainlist relay_to_domains =
4977 hostlist relay_from_hosts = 127.0.0.1
4979 These are not, in fact, option settings. They are definitions of two named
4980 domain lists and one named host list. Exim allows you to give names to lists of
4981 domains, hosts, and email addresses, in order to make it easier to manage the
4982 configuration file (see section &<<SECTnamedlists>>&).
4984 The first line defines a domain list called &'local_domains'&; this is used
4985 later in the configuration to identify domains that are to be delivered
4988 .cindex "@ in a domain list"
4989 There is just one item in this list, the string &"@"&. This is a special form
4990 of entry which means &"the name of the local host"&. Thus, if the local host is
4991 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
4992 be delivered locally. Because the local host's name is referenced indirectly,
4993 the same configuration file can be used on different hosts.
4995 The second line defines a domain list called &'relay_to_domains'&, but the
4996 list itself is empty. Later in the configuration we will come to the part that
4997 controls mail relaying through the local host; it allows relaying to any
4998 domains in this list. By default, therefore, no relaying on the basis of a mail
4999 domain is permitted.
5001 The third line defines a host list called &'relay_from_hosts'&. This list is
5002 used later in the configuration to permit relaying from any host or IP address
5003 that matches the list. The default contains just the IP address of the IPv4
5004 loopback interface, which means that processes on the local host are able to
5005 submit mail for relaying by sending it over TCP/IP to that interface. No other
5006 hosts are permitted to submit messages for relaying.
5008 Just to be sure there's no misunderstanding: at this point in the configuration
5009 we aren't actually setting up any controls. We are just defining some domains
5010 and hosts that will be used in the controls that are specified later.
5012 The next two configuration lines are genuine option settings:
5014 acl_smtp_rcpt = acl_check_rcpt
5015 acl_smtp_data = acl_check_data
5017 These options specify &'Access Control Lists'& (ACLs) that are to be used
5018 during an incoming SMTP session for every recipient of a message (every RCPT
5019 command), and after the contents of the message have been received,
5020 respectively. The names of the lists are &'acl_check_rcpt'& and
5021 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5022 section of the configuration. The RCPT ACL controls which recipients are
5023 accepted for an incoming message &-- if a configuration does not provide an ACL
5024 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5025 contents of a message to be checked.
5027 Two commented-out option settings are next:
5029 # av_scanner = clamd:/tmp/clamd
5030 # spamd_address = 127.0.0.1 783
5032 These are example settings that can be used when Exim is compiled with the
5033 content-scanning extension. The first specifies the interface to the virus
5034 scanner, and the second specifies the interface to SpamAssassin. Further
5035 details are given in chapter &<<CHAPexiscan>>&.
5037 Three more commented-out option settings follow:
5039 # tls_advertise_hosts = *
5040 # tls_certificate = /etc/ssl/exim.crt
5041 # tls_privatekey = /etc/ssl/exim.pem
5043 These are example settings that can be used when Exim is compiled with
5044 support for TLS (aka SSL) as described in &<<SECTinctlsssl>>&. The
5045 first one specifies the list of clients that are allowed to use TLS
5046 when connecting to this server; in this case the wildcard means all
5047 clients. The other options specify where Exim should find its TLS
5048 certificate and private key, which together prove the server's
5049 identity to any clients that connect. More details are given in
5052 Another two commented-out option settings follow:
5054 # daemon_smtp_ports = 25 : 465 : 587
5055 # tls_on_connect_ports = 465
5057 These options provide better support for roaming users who wish to use
5058 this server for message submission. They are not much use unless you
5059 have turned on TLS (as described in the previous paragraph) and
5060 authentication (about which more in &<<SECTdefconfauth>>&). The usual
5061 SMTP port 25 is often blocked on end-user networks, so RFC 4409
5062 specifies that message submission should use port 587 instead. However
5063 some software (notably Microsoft Outlook) cannot be configured to use
5064 port 587 correctly, so these settings also enable the non-standard
5067 Two more commented-out options settings follow:
5070 # qualify_recipient =
5072 The first of these specifies a domain that Exim uses when it constructs a
5073 complete email address from a local login name. This is often needed when Exim
5074 receives a message from a local process. If you do not set &%qualify_domain%&,
5075 the value of &%primary_hostname%& is used. If you set both of these options,
5076 you can have different qualification domains for sender and recipient
5077 addresses. If you set only the first one, its value is used in both cases.
5079 .cindex "domain literal" "recognizing format"
5080 The following line must be uncommented if you want Exim to recognize
5081 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5082 (an IP address within square brackets) instead of a named domain.
5084 # allow_domain_literals
5086 The RFCs still require this form, but many people think that in the modern
5087 Internet it makes little sense to permit mail to be sent to specific hosts by
5088 quoting their IP addresses. This ancient format has been used by people who
5089 try to abuse hosts by using them for unwanted relaying. However, some
5090 people believe there are circumstances (for example, messages addressed to
5091 &'postmaster'&) where domain literals are still useful.
5093 The next configuration line is a kind of trigger guard:
5097 It specifies that no delivery must ever be run as the root user. The normal
5098 convention is to set up &'root'& as an alias for the system administrator. This
5099 setting is a guard against slips in the configuration.
5100 The list of users specified by &%never_users%& is not, however, the complete
5101 list; the build-time configuration in &_Local/Makefile_& has an option called
5102 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5103 contents of &%never_users%& are added to this list. By default
5104 FIXED_NEVER_USERS also specifies root.
5106 When a remote host connects to Exim in order to send mail, the only information
5107 Exim has about the host's identity is its IP address. The next configuration
5112 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5113 in order to get a host name. This improves the quality of the logging
5114 information, but if you feel it is too expensive, you can remove it entirely,
5115 or restrict the lookup to hosts on &"nearby"& networks.
5116 Note that it is not always possible to find a host name from an IP address,
5117 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5120 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5121 1413 (hence their names):
5125 rfc1413_query_timeout = 5s
5128 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5129 You can limit the hosts to which these calls are made, or change the timeout
5130 that is used. If you set the timeout to zero, all ident calls are disabled.
5131 Although they are cheap and can provide useful information for tracing problem
5132 messages, some hosts and firewalls have problems with ident calls. This can
5133 result in a timeout instead of an immediate refused connection, leading to
5134 delays on starting up an incoming SMTP session.
5136 When Exim receives messages over SMTP connections, it expects all addresses to
5137 be fully qualified with a domain, as required by the SMTP definition. However,
5138 if you are running a server to which simple clients submit messages, you may
5139 find that they send unqualified addresses. The two commented-out options:
5141 # sender_unqualified_hosts =
5142 # recipient_unqualified_hosts =
5144 show how you can specify hosts that are permitted to send unqualified sender
5145 and recipient addresses, respectively.
5147 The &%percent_hack_domains%& option is also commented out:
5149 # percent_hack_domains =
5151 It provides a list of domains for which the &"percent hack"& is to operate.
5152 This is an almost obsolete form of explicit email routing. If you do not know
5153 anything about it, you can safely ignore this topic.
5155 The last two settings in the main part of the default configuration are
5156 concerned with messages that have been &"frozen"& on Exim's queue. When a
5157 message is frozen, Exim no longer continues to try to deliver it. Freezing
5158 occurs when a bounce message encounters a permanent failure because the sender
5159 address of the original message that caused the bounce is invalid, so the
5160 bounce cannot be delivered. This is probably the most common case, but there
5161 are also other conditions that cause freezing, and frozen messages are not
5162 always bounce messages.
5164 ignore_bounce_errors_after = 2d
5165 timeout_frozen_after = 7d
5167 The first of these options specifies that failing bounce messages are to be
5168 discarded after 2 days on the queue. The second specifies that any frozen
5169 message (whether a bounce message or not) is to be timed out (and discarded)
5170 after a week. In this configuration, the first setting ensures that no failing
5171 bounce message ever lasts a week.
5175 .section "ACL configuration"
5176 .cindex "default" "ACLs"
5177 .cindex "&ACL;" "default configuration"
5178 In the default configuration, the ACL section follows the main configuration.
5179 It starts with the line
5183 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5184 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5185 and &%acl_smtp_data%& above.
5187 .cindex "RCPT" "ACL for"
5188 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5189 RCPT command specifies one of the message's recipients. The ACL statements
5190 are considered in order, until the recipient address is either accepted or
5191 rejected. The RCPT command is then accepted or rejected, according to the
5192 result of the ACL processing.
5196 This line, consisting of a name terminated by a colon, marks the start of the
5201 This ACL statement accepts the recipient if the sending host matches the list.
5202 But what does that strange list mean? It doesn't actually contain any host
5203 names or IP addresses. The presence of the colon puts an empty item in the
5204 list; Exim matches this only if the incoming message did not come from a remote
5205 host, because in that case, the remote hostname is empty. The colon is
5206 important. Without it, the list itself is empty, and can never match anything.
5208 What this statement is doing is to accept unconditionally all recipients in
5209 messages that are submitted by SMTP from local processes using the standard
5210 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5213 deny message = Restricted characters in address
5214 domains = +local_domains
5215 local_parts = ^[.] : ^.*[@%!/|]
5217 deny message = Restricted characters in address
5218 domains = !+local_domains
5219 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5221 These statements are concerned with local parts that contain any of the
5222 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5223 Although these characters are entirely legal in local parts (in the case of
5224 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5225 in Internet mail addresses.
5227 The first three have in the past been associated with explicitly routed
5228 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5229 option). Addresses containing these characters are regularly tried by spammers
5230 in an attempt to bypass relaying restrictions, and also by open relay testing
5231 programs. Unless you really need them it is safest to reject these characters
5232 at this early stage. This configuration is heavy-handed in rejecting these
5233 characters for all messages it accepts from remote hosts. This is a deliberate
5234 policy of being as safe as possible.
5236 The first rule above is stricter, and is applied to messages that are addressed
5237 to one of the local domains handled by this host. This is implemented by the
5238 first condition, which restricts it to domains that are listed in the
5239 &'local_domains'& domain list. The &"+"& character is used to indicate a
5240 reference to a named list. In this configuration, there is just one domain in
5241 &'local_domains'&, but in general there may be many.
5243 The second condition on the first statement uses two regular expressions to
5244 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5245 or &"|"&. If you have local accounts that include these characters, you will
5246 have to modify this rule.
5248 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5249 allows them because they have been encountered in practice. (Consider the
5250 common convention of local parts constructed as
5251 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5252 the author of Exim, who has no second initial.) However, a local part starting
5253 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5254 file name (for example, for a mailing list). This is also true for local parts
5255 that contain slashes. A pipe symbol can also be troublesome if the local part
5256 is incorporated unthinkingly into a shell command line.
5258 The second rule above applies to all other domains, and is less strict. This
5259 allows your own users to send outgoing messages to sites that use slashes
5260 and vertical bars in their local parts. It blocks local parts that begin
5261 with a dot, slash, or vertical bar, but allows these characters within the
5262 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5263 and &"!"& is blocked, as before. The motivation here is to prevent your users
5264 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5266 accept local_parts = postmaster
5267 domains = +local_domains
5269 This statement, which has two conditions, accepts an incoming address if the
5270 local part is &'postmaster'& and the domain is one of those listed in the
5271 &'local_domains'& domain list. The &"+"& character is used to indicate a
5272 reference to a named list. In this configuration, there is just one domain in
5273 &'local_domains'&, but in general there may be many.
5275 The presence of this statement means that mail to postmaster is never blocked
5276 by any of the subsequent tests. This can be helpful while sorting out problems
5277 in cases where the subsequent tests are incorrectly denying access.
5279 require verify = sender
5281 This statement requires the sender address to be verified before any subsequent
5282 ACL statement can be used. If verification fails, the incoming recipient
5283 address is refused. Verification consists of trying to route the address, to
5284 see if a bounce message could be delivered to it. In the case of remote
5285 addresses, basic verification checks only the domain, but &'callouts'& can be
5286 used for more verification if required. Section &<<SECTaddressverification>>&
5287 discusses the details of address verification.
5289 accept hosts = +relay_from_hosts
5290 control = submission
5292 This statement accepts the address if the message is coming from one of the
5293 hosts that are defined as being allowed to relay through this host. Recipient
5294 verification is omitted here, because in many cases the clients are dumb MUAs
5295 that do not cope well with SMTP error responses. For the same reason, the
5296 second line specifies &"submission mode"& for messages that are accepted. This
5297 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5298 messages that are deficient in some way, for example, because they lack a
5299 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5300 probably add recipient verification here, and disable submission mode.
5302 accept authenticated = *
5303 control = submission
5305 This statement accepts the address if the client host has authenticated itself.
5306 Submission mode is again specified, on the grounds that such messages are most
5307 likely to come from MUAs. The default configuration does not define any
5308 authenticators, though it does include some nearly complete commented-out
5309 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5310 fact authenticate until you complete the authenticator definitions.
5312 # deny message = rejected because $sender_host_address \
5313 # is in a black list at $dnslist_domain\n\
5315 # dnslists = black.list.example
5317 # warn message = X-Warning: $sender_host_address is \
5318 # in a black list at $dnslist_domain
5319 # log_message = found in $dnslist_domain
5320 # dnslists = black.list.example
5322 These commented-out lines are examples of how you could configure Exim to check
5323 sending hosts against a DNS black list. The first statement rejects messages
5324 from blacklisted hosts, whereas the second merely inserts a warning header
5327 accept domains = +local_domains
5331 This statement accepts the incoming recipient address if its domain is one of
5332 the local domains, but only if the address can be verified. Verification of
5333 local addresses normally checks both the local part and the domain. The
5334 &%endpass%& line needs some explanation: if the condition above &%endpass%&
5335 fails, that is, if the address is not in a local domain, control is passed to
5336 the next ACL statement. However, if the condition below &%endpass%& fails, that
5337 is, if a recipient in a local domain cannot be verified, access is denied and
5338 the recipient is rejected.
5340 accept domains = +relay_to_domains
5344 This statement accepts the incoming recipient address if its domain is one of
5345 the domains for which this host is a relay, but again, only if the address can
5348 deny message = relay not permitted
5350 The final statement denies access, giving a specific error message. Reaching
5351 the end of the ACL also causes access to be denied, but with the generic
5352 message &"administrative prohibition"&.
5356 This line marks the start of the second ACL, and names it. Most of the contents
5357 of this ACL are commented out:
5360 # message = This message contains a virus \
5363 These lines are examples of how to arrange for messages to be scanned for
5364 viruses when Exim has been compiled with the content-scanning extension, and a
5365 suitable virus scanner is installed. If the message is found to contain a
5366 virus, it is rejected with the given custom error message.
5368 # warn spam = nobody
5369 # message = X-Spam_score: $spam_score\n\
5370 # X-Spam_score_int: $spam_score_int\n\
5371 # X-Spam_bar: $spam_bar\n\
5372 # X-Spam_report: $spam_report
5374 These lines are an example of how to arrange for messages to be scanned by
5375 SpamAssassin when Exim has been compiled with the content-scanning extension,
5376 and SpamAssassin has been installed. The SpamAssassin check is run with
5377 &`nobody`& as its user parameter, and the results are added to the message as a
5378 series of extra header line. In this case, the message is not rejected,
5379 whatever the spam score.
5383 This final line in the DATA ACL accepts the message unconditionally.
5386 .section "Router configuration"
5387 .cindex "default" "routers"
5388 .cindex "routers" "default"
5389 The router configuration comes next in the default configuration, introduced
5394 Routers are the modules in Exim that make decisions about where to send
5395 messages. An address is passed to each router in turn, until it is either
5396 accepted, or failed. This means that the order in which you define the routers
5397 matters. Each router is fully described in its own chapter later in this
5398 manual. Here we give only brief overviews.
5401 # driver = ipliteral
5402 # domains = !+local_domains
5403 # transport = remote_smtp
5405 .cindex "domain literal" "default router"
5406 This router is commented out because the majority of sites do not want to
5407 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5408 you uncomment this router, you also need to uncomment the setting of
5409 &%allow_domain_literals%& in the main part of the configuration.
5413 domains = ! +local_domains
5414 transport = remote_smtp
5415 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5418 The first uncommented router handles addresses that do not involve any local
5419 domains. This is specified by the line
5421 domains = ! +local_domains
5423 The &%domains%& option lists the domains to which this router applies, but the
5424 exclamation mark is a negation sign, so the router is used only for domains
5425 that are not in the domain list called &'local_domains'& (which was defined at
5426 the start of the configuration). The plus sign before &'local_domains'&
5427 indicates that it is referring to a named list. Addresses in other domains are
5428 passed on to the following routers.
5430 The name of the router driver is &(dnslookup)&,
5431 and is specified by the &%driver%& option. Do not be confused by the fact that
5432 the name of this router instance is the same as the name of the driver. The
5433 instance name is arbitrary, but the name set in the &%driver%& option must be
5434 one of the driver modules that is in the Exim binary.
5436 The &(dnslookup)& router routes addresses by looking up their domains in the
5437 DNS in order to obtain a list of hosts to which the address is routed. If the
5438 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5439 specified by the &%transport%& option. If the router does not find the domain
5440 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5441 the address fails and is bounced.
5443 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5444 be entirely ignored. This option is present because a number of cases have been
5445 encountered where MX records in the DNS point to host names
5446 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5447 Completely ignoring these IP addresses causes Exim to fail to route the
5448 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5449 continue to try to deliver the message periodically until the address timed
5456 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5458 file_transport = address_file
5459 pipe_transport = address_pipe
5461 Control reaches this and subsequent routers only for addresses in the local
5462 domains. This router checks to see whether the local part is defined as an
5463 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5464 data that it looks up from that file. If no data is found for the local part,
5465 the value of the &%data%& option is empty, causing the address to be passed to
5468 &_/etc/aliases_& is a conventional name for the system aliases file that is
5469 often used. That is why it is referenced by from the default configuration
5470 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5471 &_Local/Makefile_& before building Exim.
5476 # local_part_suffix = +* : -*
5477 # local_part_suffix_optional
5478 file = $home/.forward
5483 file_transport = address_file
5484 pipe_transport = address_pipe
5485 reply_transport = address_reply
5487 This is the most complicated router in the default configuration. It is another
5488 redirection router, but this time it is looking for forwarding data set up by
5489 individual users. The &%check_local_user%& setting specifies a check that the
5490 local part of the address is the login name of a local user. If it is not, the
5491 router is skipped. The two commented options that follow &%check_local_user%&,
5494 # local_part_suffix = +* : -*
5495 # local_part_suffix_optional
5497 .cindex "&$local_part_suffix$&"
5498 show how you can specify the recognition of local part suffixes. If the first
5499 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5500 by any sequence of characters, is removed from the local part and placed in the
5501 variable &$local_part_suffix$&. The second suffix option specifies that the
5502 presence of a suffix in the local part is optional. When a suffix is present,
5503 the check for a local login uses the local part with the suffix removed.
5505 When a local user account is found, the file called &_.forward_& in the user's
5506 home directory is consulted. If it does not exist, or is empty, the router
5507 declines. Otherwise, the contents of &_.forward_& are interpreted as
5508 redirection data (see chapter &<<CHAPredirect>>& for more details).
5510 .cindex "Sieve filter" "enabling in default router"
5511 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5512 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5513 is commented out by default), the contents of the file are interpreted as a set
5514 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5515 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5516 separate document entitled &'Exim's interfaces to mail filtering'&.
5518 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5519 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5520 There are two reasons for doing this:
5523 Whether or not a local user has a &_.forward_& file is not really relevant when
5524 checking an address for validity; it makes sense not to waste resources doing
5527 More importantly, when Exim is verifying addresses or handling an EXPN
5528 command during an SMTP session, it is running as the Exim user, not as root.
5529 The group is the Exim group, and no additional groups are set up.
5530 It may therefore not be possible for Exim to read users' &_.forward_& files at
5534 The setting of &%check_ancestor%& prevents the router from generating a new
5535 address that is the same as any previous address that was redirected. (This
5536 works round a problem concerning a bad interaction between aliasing and
5537 forwarding &-- see section &<<SECTredlocmai>>&).
5539 The final three option settings specify the transports that are to be used when
5540 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5541 auto-reply, respectively. For example, if a &_.forward_& file contains
5543 a.nother@elsewhere.example, /home/spqr/archive
5545 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5551 # local_part_suffix = +* : -*
5552 # local_part_suffix_optional
5553 transport = local_delivery
5555 The final router sets up delivery into local mailboxes, provided that the local
5556 part is the name of a local login, by accepting the address and assigning it to
5557 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5558 routers, so the address is bounced. The commented suffix settings fulfil the
5559 same purpose as they do for the &(userforward)& router.
5562 .section "Transport configuration"
5563 .cindex "default" "transports"
5564 .cindex "transports" "default"
5565 Transports define mechanisms for actually delivering messages. They operate
5566 only when referenced from routers, so the order in which they are defined does
5567 not matter. The transports section of the configuration starts with
5571 One remote transport and four local transports are defined.
5576 This transport is used for delivering messages over SMTP connections. All its
5577 options are defaulted. The list of remote hosts comes from the router.
5581 file = /var/mail/$local_part
5588 This &(appendfile)& transport is used for local delivery to user mailboxes in
5589 traditional BSD mailbox format. By default it runs under the uid and gid of the
5590 local user, which requires the sticky bit to be set on the &_/var/mail_&
5591 directory. Some systems use the alternative approach of running mail deliveries
5592 under a particular group instead of using the sticky bit. The commented options
5593 show how this can be done.
5595 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
5596 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
5597 similarly-named options above.
5603 This transport is used for handling deliveries to pipes that are generated by
5604 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
5605 option specifies that any output generated by the pipe is to be returned to the
5614 This transport is used for handling deliveries to files that are generated by
5615 redirection. The name of the file is not specified in this instance of
5616 &(appendfile)&, because it comes from the &(redirect)& router.
5621 This transport is used for handling automatic replies generated by users'
5626 .section "Default retry rule"
5627 .cindex "retry" "default rule"
5628 .cindex "default" "retry rule"
5629 The retry section of the configuration file contains rules which affect the way
5630 Exim retries deliveries that cannot be completed at the first attempt. It is
5631 introduced by the line
5635 In the default configuration, there is just one rule, which applies to all
5638 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
5640 This causes any temporarily failing address to be retried every 15 minutes for
5641 2 hours, then at intervals starting at one hour and increasing by a factor of
5642 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
5643 is not delivered after 4 days of temporary failure, it is bounced.
5647 .section "Rewriting configuration"
5648 The rewriting section of the configuration, introduced by
5652 contains rules for rewriting addresses in messages as they arrive. There are no
5653 rewriting rules in the default configuration file.
5657 .section "Authenticators configuration" "SECTdefconfauth"
5658 .cindex "AUTH" "configuration"
5659 The authenticators section of the configuration, introduced by
5661 begin authenticators
5663 defines mechanisms for the use of the SMTP AUTH command. The default
5664 configuration file contains two commented-out example authenticators
5665 which support plaintext username/password authentication using the
5666 standard PLAIN mechanism and the traditional but non-standard LOGIN
5667 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
5668 to support most MUA software.
5670 The example PLAIN authenticator looks like this:
5673 # driver = plaintext
5674 # server_set_id = $auth2
5675 # server_prompts = :
5676 # server_condition = Authentication is not yet configured
5677 # server_advertise_condition = ${if def:tls_cipher }
5679 And the example LOGIN authenticator looks like this:
5682 # driver = plaintext
5683 # server_set_id = $auth1
5684 # server_prompts = <| Username: | Password:
5685 # server_condition = Authentication is not yet configured
5686 # server_advertise_condition = ${if def:tls_cipher }
5689 The &%server_set_id%& option makes Exim remember the authenticated username
5690 in &$authenticated_id$&, which can be used later in ACLs or routers. The
5691 &%server_prompts%& option configures the &(plaintext)& authenticator so
5692 that it implements the details of the specific authentication mechanism,
5693 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
5694 when Exim offers authentication to clients; in the examples, this is only
5695 when TLS or SSL has been started, so to enable the authenticators you also
5696 need to add support for TLS as described in &<<SECTdefconfmain>>&.
5698 The &%server_condition%& setting defines how to verify that the username and
5699 password are correct. In the examples it just produces an error message.
5700 To make the authenticators work, you can use a string expansion
5701 expression like one of the examples in &<<CHAPplaintext>>&.
5703 .ecindex IIDconfiwal
5707 . ////////////////////////////////////////////////////////////////////////////
5708 . ////////////////////////////////////////////////////////////////////////////
5710 .chapter "Regular expressions" "CHAPregexp"
5712 .cindex "regular expressions" "library"
5714 Exim supports the use of regular expressions in many of its options. It
5715 uses the PCRE regular expression library; this provides regular expression
5716 matching that is compatible with Perl 5. The syntax and semantics of
5717 regular expressions is discussed in many Perl reference books, and also in
5718 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
5719 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
5721 The documentation for the syntax and semantics of the regular expressions that
5722 are supported by PCRE is included in plain text in the file
5723 &_doc/pcrepattern.txt_& in the Exim distribution, and also in the HTML
5724 tarbundle of Exim documentation. It describes in detail the features of the
5725 regular expressions that PCRE supports, so no further description is included
5726 here. The PCRE functions are called from Exim using the default option settings
5727 (that is, with no PCRE options set), except that the PCRE_CASELESS option is
5728 set when the matching is required to be case-insensitive.
5730 In most cases, when a regular expression is required in an Exim configuration,
5731 it has to start with a circumflex, in order to distinguish it from plain text
5732 or an &"ends with"& wildcard. In this example of a configuration setting, the
5733 second item in the colon-separated list is a regular expression.
5735 domains = a.b.c : ^\\d{3} : *.y.z : ...
5737 The doubling of the backslash is required because of string expansion that
5738 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
5739 of this issue, and a way of avoiding the need for doubling backslashes. The
5740 regular expression that is eventually used in this example contains just one
5741 backslash. The circumflex is included in the regular expression, and has the
5742 normal effect of &"anchoring"& it to the start of the string that is being
5745 There are, however, two cases where a circumflex is not required for the
5746 recognition of a regular expression: these are the &%match%& condition in a
5747 string expansion, and the &%matches%& condition in an Exim filter file. In
5748 these cases, the relevant string is always treated as a regular expression; if
5749 it does not start with a circumflex, the expression is not anchored, and can
5750 match anywhere in the subject string.
5752 In all cases, if you want a regular expression to match at the end of a string,
5753 you must code the $ metacharacter to indicate this. For example:
5755 domains = ^\\d{3}\\.example
5757 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
5760 domains = ^\\d{3}\\.example\$
5762 if you want &'example'& to be the top-level domain. The backslash before the
5763 $ is needed because string expansion also interprets dollar characters.
5767 .section "Testing regular expressions"
5768 .cindex "testing" "regular expressions"
5769 .cindex "regular expressions" "testing"
5770 .cindex "&'pcretest'&"
5771 A program called &'pcretest'& forms part of the PCRE distribution and is built
5772 with PCRE during the process of building Exim. It is primarily intended for
5773 testing PCRE itself, but it can also be used for experimenting with regular
5774 expressions. After building Exim, the binary can be found in the build
5775 directory (it is not installed anywhere automatically). There is documentation
5776 of various options in &_doc/pcretest.txt_&, but for simple testing, none are
5777 needed. This is the output of a sample run of &'pcretest'&:
5779 &` re> `&&*&`/^([@]+)@.+\.(ac|edu)\.(?!kr)[a-z]{2}$/`&*&
5780 &`data> `&&*&`x@y.ac.uk`&*&
5784 &`data> `&&*&`x@y.ac.kr`&*&
5786 &`data> `&&*&`x@y.edu.com`&*&
5788 &`data> `&&*&`x@y.edu.co`&*&
5793 Input typed by the user is shown in bold face. After the &"re>"& prompt, a
5794 regular expression enclosed in delimiters is expected. If this compiles without
5795 error, &"data>"& prompts are given for strings against which the expression is
5796 matched. An empty data line causes a new regular expression to be read. If the
5797 match is successful, the captured substring values (that is, what would be in
5798 the variables &$0$&, &$1$&, &$2$&, etc.) are shown. The above example tests for
5799 an email address whose domain ends with either &"ac"& or &"edu"& followed by a
5800 two-character top-level domain that is not &"kr"&. The local part is captured
5801 in &$1$& and the &"ac"& or &"edu"& in &$2$&.
5808 . ////////////////////////////////////////////////////////////////////////////
5809 . ////////////////////////////////////////////////////////////////////////////
5811 .chapter "File and database lookups" "CHAPfdlookup"
5812 .scindex IIDfidalo1 "file" "lookups"
5813 .scindex IIDfidalo2 "database lookups"
5814 .cindex "lookup" "description of"
5815 Exim can be configured to look up data in files or databases as it processes
5816 messages. Two different kinds of syntax are used:
5819 A string that is to be expanded may contain explicit lookup requests. These
5820 cause parts of the string to be replaced by data that is obtained from the
5821 lookup. Lookups of this type are conditional expansion items. Different results
5822 can be defined for the cases of lookup success and failure. See chapter
5823 &<<CHAPexpand>>&, where string expansions are described in detail.
5825 Lists of domains, hosts, and email addresses can contain lookup requests as a
5826 way of avoiding excessively long linear lists. In this case, the data that is
5827 returned by the lookup is often (but not always) discarded; whether the lookup
5828 succeeds or fails is what really counts. These kinds of list are described in
5829 chapter &<<CHAPdomhosaddlists>>&.
5832 String expansions, lists, and lookups interact with each other in such a way
5833 that there is no order in which to describe any one of them that does not
5834 involve references to the others. Each of these three chapters makes more sense
5835 if you have read the other two first. If you are reading this for the first
5836 time, be aware that some of it will make a lot more sense after you have read
5837 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
5839 .section "Examples of different lookup syntax"
5840 It is easy to confuse the two different kinds of lookup, especially as the
5841 lists that may contain the second kind are always expanded before being
5842 processed as lists. Therefore, they may also contain lookups of the first kind.
5843 Be careful to distinguish between the following two examples:
5845 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
5846 domains = lsearch;/some/file
5848 The first uses a string expansion, the result of which must be a domain list.
5849 No strings have been specified for a successful or a failing lookup; the
5850 defaults in this case are the looked-up data and an empty string, respectively.
5851 The expansion takes place before the string is processed as a list, and the
5852 file that is searched could contain lines like this:
5854 192.168.3.4: domain1:domain2:...
5855 192.168.1.9: domain3:domain4:...
5857 When the lookup succeeds, the result of the expansion is a list of domains (and
5858 possibly other types of item that are allowed in domain lists).
5860 In the second example, the lookup is a single item in a domain list. It causes
5861 Exim to use a lookup to see if the domain that is being processed can be found
5862 in the file. The file could contains lines like this:
5867 Any data that follows the keys is not relevant when checking that the domain
5868 matches the list item.
5870 It is possible, though no doubt confusing, to use both kinds of lookup at once.
5871 Consider a file containing lines like this:
5873 192.168.5.6: lsearch;/another/file
5875 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
5876 first &%domains%& setting above generates the second setting, which therefore
5877 causes a second lookup to occur.
5879 The rest of this chapter describes the different lookup types that are
5880 available. Any of them can be used in any part of the configuration where a
5881 lookup is permitted.
5884 .section "Lookup types"
5885 .cindex "lookup" "types of"
5886 .cindex "single-key lookup" "definition of"
5887 Two different types of data lookup are implemented:
5890 The &'single-key'& type requires the specification of a file in which to look,
5891 and a single key to search for. The key must be a non-empty string for the
5892 lookup to succeed. The lookup type determines how the file is searched.
5894 .cindex "query-style lookup" "definition of"
5895 The &'query-style'& type accepts a generalized database query. No particular
5896 key value is assumed by Exim for query-style lookups. You can use whichever
5897 Exim variables you need to construct the database query.
5900 The code for each lookup type is in a separate source file that is included in
5901 the binary of Exim only if the corresponding compile-time option is set. The
5902 default settings in &_src/EDITME_& are:
5907 which means that only linear searching and DBM lookups are included by default.
5908 For some types of lookup (e.g. SQL databases), you need to install appropriate
5909 libraries and header files before building Exim.
5914 .section "Single-key lookup types" "SECTsinglekeylookups"
5915 .cindex "lookup" "single-key types"
5916 .cindex "single-key lookup" "list of types"
5917 The following single-key lookup types are implemented:
5920 .cindex "cdb" "description of"
5921 .cindex "lookup" "cdb"
5922 .cindex "binary zero" "in lookup key"
5923 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
5924 string without a terminating binary zero. The cdb format is designed for
5925 indexed files that are read frequently and never updated, except by total
5926 re-creation. As such, it is particulary suitable for large files containing
5927 aliases or other indexed data referenced by an MTA. Information about cdb can
5928 be found in several places:
5930 &url(http://www.pobox.com/~djb/cdb.html)
5931 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
5932 &url(http://packages.debian.org/stable/utils/freecdb.html)
5934 A cdb distribution is not needed in order to build Exim with cdb support,
5935 because the code for reading cdb files is included directly in Exim itself.
5936 However, no means of building or testing cdb files is provided with Exim, so
5937 you need to obtain a cdb distribution in order to do this.
5939 .cindex "DBM" "lookup type"
5940 .cindex "lookup" "dbm"
5941 .cindex "binary zero" "in lookup key"
5942 &(dbm)&: Calls to DBM library functions are used to extract data from the given
5943 DBM file by looking up the record with the given key. A terminating binary
5944 zero is included in the key that is passed to the DBM library. See section
5945 &<<SECTdb>>& for a discussion of DBM libraries.
5947 .cindex "Berkeley DB library" "file format"
5948 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
5949 when building DBM files using the &%exim_dbmbuild%& utility. However, when
5950 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
5951 the DB_UNKNOWN option. This enables it to handle any of the types of database
5952 that the library supports, and can be useful for accessing DBM files created by
5953 other applications. (For earlier DB versions, DB_HASH is always used.)
5955 .cindex "lookup" "dbmnz"
5956 .cindex "lookup" "dbm &-- terminating zero"
5957 .cindex "binary zero" "in lookup key"
5959 .cindex "&_/etc/userdbshadow.dat_&"
5960 .cindex "dmbnz lookup type"
5961 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
5962 is not included in the key that is passed to the DBM library. You may need this
5963 if you want to look up data in files that are created by or shared with some
5964 other application that does not use terminating zeros. For example, you need to
5965 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
5966 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
5967 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
5968 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
5970 .cindex "lookup" "dsearch"
5971 .cindex "dsearch lookup type"
5972 &(dsearch)&: The given file must be a directory; this is searched for a file
5973 whose name is the key. The key may not contain any forward slash characters.
5974 The result of a successful lookup is the name of the file. An example of how
5975 this lookup can be used to support virtual domains is given in section
5976 &<<SECTvirtualdomains>>&.
5978 .cindex "lookup" "iplsearch"
5979 .cindex "iplsearch lookup type"
5980 &(iplsearch)&: The given file is a text file containing keys and data. A key is
5981 terminated by a colon or white space or the end of the line. The keys in the
5982 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
5983 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
5984 being interpreted as a key terminator. For example:
5986 1.2.3.4: data for 1.2.3.4
5987 192.168.0.0/16 data for 192.168.0.0/16
5988 "abcd::cdab": data for abcd::cdab
5989 "abcd:abcd::/32" data for abcd:abcd::/32
5991 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
5992 file is searched linearly, using the CIDR masks where present, until a matching
5993 key is found. The first key that matches is used; there is no attempt to find a
5994 &"best"& match. Apart from the way the keys are matched, the processing for
5995 &(iplsearch)& is the same as for &(lsearch)&.
5997 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
5998 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
5999 lookup types support only literal keys.
6001 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6002 the implicit key is the host's IP address rather than its name (see section
6003 &<<SECThoslispatsikey>>&).
6006 .cindex "linear search"
6007 .cindex "lookup" "lsearch"
6008 .cindex "lsearch lookup type"
6009 &(lsearch)&: The given file is a text file that is searched linearly for a
6010 line beginning with the search key, terminated by a colon or white space or the
6011 end of the line. The first occurrence that is found in the file is used. White
6012 space between the key and the colon is permitted. The remainder of the line,
6013 with leading and trailing white space removed, is the data. This can be
6014 continued onto subsequent lines by starting them with any amount of white
6015 space, but only a single space character is included in the data at such a
6016 junction. If the data begins with a colon, the key must be terminated by a
6021 Empty lines and lines beginning with # are ignored, even if they occur in the
6022 middle of an item. This is the traditional textual format of alias files. Note
6023 that the keys in an &(lsearch)& file are literal strings. There is no
6024 wildcarding of any kind.
6026 .cindex "lookup" "lsearch &-- colons in keys"
6027 .cindex "white space" "in lsearch key"
6028 In most &(lsearch)& files, keys are not required to contain colons or #
6029 characters, or white space. However, if you need this feature, it is available.
6030 If a key begins with a doublequote character, it is terminated only by a
6031 matching quote (or end of line), and the normal escaping rules apply to its
6032 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6033 quoted keys (exactly as for unquoted keys). There is no special handling of
6034 quotes for the data part of an &(lsearch)& line.
6037 .cindex "NIS lookup type"
6038 .cindex "lookup" "NIS"
6039 .cindex "binary zero" "in lookup key"
6040 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6041 the given key, without a terminating binary zero. There is a variant called
6042 &(nis0)& which does include the terminating binary zero in the key. This is
6043 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6044 aliases; the full map names must be used.
6047 .cindex "wildlsearch lookup type"
6048 .cindex "lookup" "wildlsearch"
6049 .cindex "nwildlsearch lookup type"
6050 .cindex "lookup" "nwildlsearch"
6051 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6052 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6053 the file may be wildcarded. The difference between these two lookup types is
6054 that for &(wildlsearch)&, each key in the file is string-expanded before being
6055 used, whereas for &(nwildlsearch)&, no expansion takes place.
6057 Like &(lsearch)&, the testing is done case-insensitively. The following forms
6058 of wildcard are recognized:
6060 . ==== As this is a nested list, any displays it contains must be indented
6061 . ==== as otherwise they are too far to the left.
6064 The string may begin with an asterisk to mean &"ends with"&. For example:
6066 *.a.b.c data for anything.a.b.c
6067 *fish data for anythingfish
6070 The string may begin with a circumflex to indicate a regular expression. For
6071 example, for &(wildlsearch)&:
6073 ^\N\d+\.a\.b\N data for <digits>.a.b
6075 Note the use of &`\N`& to disable expansion of the contents of the regular
6076 expression. If you are using &(nwildlsearch)&, where the keys are not
6077 string-expanded, the equivalent entry is:
6079 ^\d+\.a\.b data for <digits>.a.b
6081 If the regular expression contains white space or colon characters, you must
6082 either quote it (see &(lsearch)& above), or represent these characters in other
6083 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6084 colon. This may be easier than quoting, because if you quote, you have to
6085 escape all the backslashes inside the quotes.
6087 &*Note*&: It is not possible to capture substrings in a regular expression
6088 match for later use, because the results of all lookups are cached. If a lookup
6089 is repeated, the result is taken from the cache, and no actual pattern matching
6090 takes place. The values of all the numeric variables are unset after a
6091 &((n)wildlsearch)& match.
6094 Although I cannot see it being of much use, the general matching function that
6095 is used to implement &((n)wildlsearch)& means that the string may begin with a
6096 lookup name terminated by a semicolon, and followed by lookup data. For
6099 cdb;/some/file data for keys that match the file
6101 The data that is obtained from the nested lookup is discarded.
6104 Keys that do not match any of these patterns are interpreted literally. The
6105 continuation rules for the data are the same as for &(lsearch)&, and keys may
6106 be followed by optional colons.
6108 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6109 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6110 lookup types support only literal keys.
6114 .section "Query-style lookup types"
6115 .cindex "lookup" "query-style types"
6116 .cindex "query-style lookup" "list of types"
6117 The supported query-style lookup types are listed below. Further details about
6118 many of them are given in later sections.
6121 .cindex "DNS" "as a lookup type"
6122 .cindex "lookup" "DNS"
6123 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6124 are given in the supplied query. The resulting data is the contents of the
6125 records. See section &<<SECTdnsdb>>&.
6127 .cindex "Interbase lookup type"
6128 .cindex "lookup" "Interbase"
6129 &(ibase)&: This does a lookup in an Interbase database.
6131 .cindex "LDAP" "lookup type"
6132 .cindex "lookup" "LDAP"
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 &<<SECTldap>>&.
6139 .cindex "MySQL" "lookup type"
6140 .cindex "lookup" "MySQL"
6141 &(mysql)&: The format of the query is an SQL statement that is passed to a
6142 MySQL database. See section &<<SECTsql>>&.
6144 .cindex "NIS+ lookup type"
6145 .cindex "lookup" "NIS+"
6146 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6147 the field to be returned. See section &<<SECTnisplus>>&.
6149 .cindex "Oracle" "lookup type"
6150 .cindex "lookup" "Oracle"
6151 &(oracle)&: The format of the query is an SQL statement that is passed to an
6152 Oracle database. See section &<<SECTsql>>&.
6154 .cindex "lookup" "passwd"
6155 .cindex "passwd lookup type"
6156 .cindex "&_/etc/passwd_&"
6157 &(passwd)& is a query-style lookup with queries that are just user names. The
6158 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6159 success, the result string is the same as you would get from an &(lsearch)&
6160 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6161 password value. For example:
6163 *:42:42:King Rat:/home/kr:/bin/bash
6166 .cindex "PostgreSQL lookup type"
6167 .cindex "lookup" "PostgreSQL"
6168 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6169 PostgreSQL database. See section &<<SECTsql>>&.
6172 .cindex "sqlite lookup type"
6173 .cindex "lookup" "sqlite"
6174 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6175 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6178 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6179 not likely to be useful in normal operation.
6181 .cindex "whoson lookup type"
6182 .cindex "lookup" "whoson"
6183 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a proposed
6184 Internet protocol that allows Internet server programs to check whether a
6185 particular (dynamically allocated) IP address is currently allocated to a known
6186 (trusted) user and, optionally, to obtain the identity of the said user. In
6187 Exim, this can be used to implement &"POP before SMTP"& checking using ACL
6190 require condition = \
6191 ${lookup whoson {$sender_host_address}{yes}{no}}
6193 The query consists of a single IP address. The value returned is the name of
6194 the authenticated user, which is stored in the variable &$value$&. However, in
6195 this example, the data in &$value$& is not used; the result of the lookup is
6196 one of the fixed strings &"yes"& or &"no"&.
6201 .section "Temporary errors in lookups"
6202 .cindex "lookup" "temporary error in"
6203 Lookup functions can return temporary error codes if the lookup cannot be
6204 completed. For example, an SQL or LDAP database might be unavailable. For this
6205 reason, it is not advisable to use a lookup that might do this for critical
6206 options such as a list of local domains.
6208 When a lookup cannot be completed in a router or transport, delivery
6209 of the message (to the relevant address) is deferred, as for any other
6210 temporary error. In other circumstances Exim may assume the lookup has failed,
6211 or may give up altogether.
6215 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6216 .cindex "wildcard lookups"
6217 .cindex "lookup" "default values"
6218 .cindex "lookup" "wildcard"
6219 .cindex "lookup" "* added to type"
6220 .cindex "default" "in single-key lookups"
6221 In this context, a &"default value"& is a value specified by the administrator
6222 that is to be used if a lookup fails.
6224 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6225 and the initial lookup fails, the key &"*"& is looked up in the file to
6226 provide a default value. See also the section on partial matching below.
6228 .cindex "*@ with single-key lookup"
6229 .cindex "lookup" "*@ added to type"
6230 .cindex "alias file" "per-domain default"
6231 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6232 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6233 character, a second lookup is done with everything before the last @ replaced
6234 by *. This makes it possible to provide per-domain defaults in alias files
6235 that include the domains in the keys. If the second lookup fails (or doesn't
6236 take place because there is no @ in the key), &"*"& is looked up.
6237 For example, a &(redirect)& router might contain:
6239 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6241 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6242 looks up these keys, in this order:
6248 The data is taken from whichever key it finds first. &*Note*&: In an
6249 &(lsearch)& file, this does not mean the first of these keys in the file. A
6250 complete scan is done for each key, and only if it is not found at all does
6251 Exim move on to try the next key.
6255 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6256 .cindex "partial matching"
6257 .cindex "wildcard lookups"
6258 .cindex "lookup" "partial matching"
6259 .cindex "lookup" "wildcard"
6260 .cindex "asterisk" "in search type"
6261 The normal operation of a single-key lookup is to search the file for an exact
6262 match with the given key. However, in a number of situations where domains are
6263 being looked up, it is useful to be able to do partial matching. In this case,
6264 information in the file that has a key starting with &"*."& is matched by any
6265 domain that ends with the components that follow the full stop. For example, if
6266 a key in a DBM file is
6268 *.dates.fict.example
6270 then when partial matching is enabled this is matched by (amongst others)
6271 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6272 by &'dates.fict.example'&, if that does not appear as a separate key in the
6275 &*Note*&: Partial matching is not available for query-style lookups. It is
6276 also not available for any lookup items in address lists (see section
6277 &<<SECTaddresslist>>&).
6279 Partial matching is implemented by doing a series of separate lookups using
6280 keys constructed by modifying the original subject key. This means that it can
6281 be used with any of the single-key lookup types, provided that
6282 partial matching keys
6283 beginning with a special prefix (default &"*."&) are included in the data file.
6284 Keys in the file that do not begin with the prefix are matched only by
6285 unmodified subject keys when partial matching is in use.
6287 Partial matching is requested by adding the string &"partial-"& to the front of
6288 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6289 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6290 is added at the start of the subject key, and it is looked up again. If that
6291 fails, further lookups are tried with dot-separated components removed from the
6292 start of the subject key, one-by-one, and &"*."& added on the front of what
6295 A minimum number of two non-* components are required. This can be adjusted
6296 by including a number before the hyphen in the search type. For example,
6297 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6298 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6299 subject key is &'2250.dates.fict.example'& then the following keys are looked
6300 up when the minimum number of non-* components is two:
6302 2250.dates.fict.example
6303 *.2250.dates.fict.example
6304 *.dates.fict.example
6307 As soon as one key in the sequence is successfully looked up, the lookup
6310 .cindex "lookup" "partial matching &-- changing prefix"
6311 .cindex "prefix" "for partial matching"
6312 The use of &"*."& as the partial matching prefix is a default that can be
6313 changed. The motivation for this feature is to allow Exim to operate with file
6314 formats that are used by other MTAs. A different prefix can be supplied in
6315 parentheses instead of the hyphen after &"partial"&. For example:
6317 domains = partial(.)lsearch;/some/file
6319 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6320 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6321 components is unchanged). The prefix may consist of any punctuation characters
6322 other than a closing parenthesis. It may be empty, for example:
6324 domains = partial1()cdb;/some/file
6326 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6327 &`a.b.c`&, &`b.c`&, and &`c`&.
6329 If &"partial0"& is specified, what happens at the end (when the lookup with
6330 just one non-wild component has failed, and the original key is shortened right
6331 down to the null string) depends on the prefix:
6334 If the prefix has zero length, the whole lookup fails.
6336 If the prefix has length 1, a lookup for just the prefix is done. For
6337 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6339 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6340 remainder is looked up. With the default prefix, therefore, the final lookup is
6341 for &"*"& on its own.
6343 Otherwise, the whole prefix is looked up.
6347 If the search type ends in &"*"& or &"*@"& (see section
6348 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6349 this implies happens after all partial lookups have failed. If &"partial0"& is
6350 specified, adding &"*"& to the search type has no effect with the default
6351 prefix, because the &"*"& key is already included in the sequence of partial
6352 lookups. However, there might be a use for lookup types such as
6353 &"partial0(.)lsearch*"&.
6355 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6356 in domain lists and the like. Partial matching works only in terms of
6357 dot-separated components; a key such as &`*fict.example`&
6358 in a database file is useless, because the asterisk in a partial matching
6359 subject key is always followed by a dot.
6364 .section "Lookup caching"
6365 .cindex "lookup" "caching"
6366 .cindex "caching" "lookup data"
6367 Exim caches all lookup results in order to avoid needless repetition of
6368 lookups. However, because (apart from the daemon) Exim operates as a collection
6369 of independent, short-lived processes, this caching applies only within a
6370 single Exim process. There is no inter-process lookup caching facility.
6372 For single-key lookups, Exim keeps the relevant files open in case there is
6373 another lookup that needs them. In some types of configuration this can lead to
6374 many files being kept open for messages with many recipients. To avoid hitting
6375 the operating system limit on the number of simultaneously open files, Exim
6376 closes the least recently used file when it needs to open more files than its
6377 own internal limit, which can be changed via the &%lookup_open_max%& option.
6379 The single-key lookup files are closed and the lookup caches are flushed at
6380 strategic points during delivery &-- for example, after all routing is
6386 .section "Quoting lookup data"
6387 .cindex "lookup" "quoting"
6388 .cindex "quoting" "in lookups"
6389 When data from an incoming message is included in a query-style lookup, there
6390 is the possibility of special characters in the data messing up the syntax of
6391 the query. For example, a NIS+ query that contains
6395 will be broken if the local part happens to contain a closing square bracket.
6396 For NIS+, data can be enclosed in double quotes like this:
6398 [name="$local_part"]
6400 but this still leaves the problem of a double quote in the data. The rule for
6401 NIS+ is that double quotes must be doubled. Other lookup types have different
6402 rules, and to cope with the differing requirements, an expansion operator
6403 of the following form is provided:
6405 ${quote_<lookup-type>:<string>}
6407 For example, the safest way to write the NIS+ query is
6409 [name="${quote_nisplus:$local_part}"]
6411 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6412 operator can be used for all lookup types, but has no effect for single-key
6413 lookups, since no quoting is ever needed in their key strings.
6418 .section "More about dnsdb" "SECTdnsdb"
6419 .cindex "dnsdb lookup"
6420 .cindex "lookup" "dnsdb"
6421 .cindex "DNS" "as a lookup type"
6422 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6423 of a record type and a domain name, separated by an equals sign. For example,
6424 an expansion string could contain:
6426 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6428 If the lookup succeeds, the result is placed in &$value$&, which in this case
6429 is used on its own as the result. If the lookup succeeds, the &`fail`& keyword
6430 causes a &'forced expansion failure'& &-- see section &<<SECTforexpfai>>& for
6431 an explanation of what this means.
6433 The supported DNS record types are A, CNAME, MX, NS, PTR, SRV, and TXT, and,
6434 when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6435 configured). If no type is given, TXT is assumed. When the type is PTR,
6436 the data can be an IP address, written as normal; inversion and the addition of
6437 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6439 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6441 If the data for a PTR record is not a syntactically valid IP address, it is not
6442 altered and nothing is added.
6444 .cindex "MX record" "in &(dnsdb)& lookup"
6445 .cindex "SRV record" "in &(dnsdb)& lookup"
6446 For an MX lookup, both the preference value and the host name are returned for
6447 each record, separated by a space. For an SRV lookup, the priority, weight,
6448 port, and host name are returned for each record, separated by spaces.
6450 For any record type, if multiple records are found (or, for A6 lookups, if a
6451 single record leads to multiple addresses), the data is returned as a
6452 concatenation, with newline as the default separator. The order, of course,
6453 depends on the DNS resolver. You can specify a different separator character
6454 between multiple records by putting a right angle-bracket followed immediately
6455 by the new separator at the start of the query. For example:
6457 ${lookup dnsdb{>: a=host1.example}}
6459 It is permitted to specify a space as the separator character. Further
6460 white space is ignored.
6462 .section "Pseudo dnsdb record types"
6463 .cindex "MX record" "in &(dnsdb)& lookup"
6464 By default, both the preference value and the host name are returned for
6465 each MX record, separated by a space. If you want only host names, you can use
6466 the pseudo-type MXH:
6468 ${lookup dnsdb{mxh=a.b.example}}
6470 In this case, the preference values are omitted, and just the host names are
6473 .cindex "name server" "for enclosing domain"
6474 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6475 records on the given domain, but if none are found, it removes the first
6476 component of the domain name, and tries again. This process continues until NS
6477 records are found or there are no more components left (or there is a DNS
6478 error). In other words, it may return the name servers for a top-level domain,
6479 but it never returns the root name servers. If there are no NS records for the
6480 top-level domain, the lookup fails. Consider these examples:
6482 ${lookup dnsdb{zns=xxx.quercite.com}}
6483 ${lookup dnsdb{zns=xxx.edu}}
6485 Assuming that in each case there are no NS records for the full domain name,
6486 the first returns the name servers for &%quercite.com%&, and the second returns
6487 the name servers for &%edu%&.
6489 You should be careful about how you use this lookup because, unless the
6490 top-level domain does not exist, the lookup always returns some host names. The
6491 sort of use to which this might be put is for seeing if the name servers for a
6492 given domain are on a blacklist. You can probably assume that the name servers
6493 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6496 .cindex "CSA" "in &(dnsdb)& lookup"
6497 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6498 records according to the CSA rules, which are described in section
6499 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6500 not sufficient because of the extra parent domain search behaviour of CSA. The
6501 result of a successful lookup such as:
6503 ${lookup dnsdb {csa=$sender_helo_name}}
6505 has two space-separated fields: an authorization code and a target host name.
6506 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6507 authorization required but absent, or &"?"& for unknown.
6510 .section "Multiple dnsdb lookups"
6511 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6512 However, you can specify a list of domains or IP addresses in a single
6513 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6514 the default separator, but with the ability to change this. For example:
6516 ${lookup dnsdb{one.domain.com:two.domain.com}}
6517 ${lookup dnsdb{a=one.host.com:two.host.com}}
6518 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6520 In order to retain backwards compatibility, there is one special case: if
6521 the lookup type is PTR and no change of separator is specified, Exim looks
6522 to see if the rest of the string is precisely one IPv6 address. In this
6523 case, it does not treat it as a list.
6525 The data from each lookup is concatenated, with newline separators by default,
6526 in the same way that multiple DNS records for a single item are handled. A
6527 different separator can be specified, as described above.
6529 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6530 temporary DNS error for any of them, the behaviour is controlled by
6531 an optional keyword followed by a comma that may appear before the record
6532 type. The possible keywords are &"defer_strict"&, &"defer_never"&, and
6533 &"defer_lax"&. With &"strict"& behaviour, any temporary DNS error causes the
6534 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6535 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6536 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6537 error causes the whole lookup to defer only if none of the other lookups
6538 succeed. The default is &"lax"&, so the following lookups are equivalent:
6540 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6541 ${lookup dnsdb{a=one.host.com:two.host.com}}
6543 Thus, in the default case, as long as at least one of the DNS lookups
6544 yields some data, the lookup succeeds.
6549 .section "More about LDAP" "SECTldap"
6550 .cindex "LDAP lookup"
6551 .cindex "lookup" "LDAP"
6552 .cindex "Solaris" "LDAP"
6553 The original LDAP implementation came from the University of Michigan; this has
6554 become &"Open LDAP"&, and there are now two different releases. Another
6555 implementation comes from Netscape, and Solaris 7 and subsequent releases
6556 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6557 the lookup function level, their error handling is different. For this reason
6558 it is necessary to set a compile-time variable when building Exim with LDAP, to
6559 indicate which LDAP library is in use. One of the following should appear in
6560 your &_Local/Makefile_&:
6562 LDAP_LIB_TYPE=UMICHIGAN
6563 LDAP_LIB_TYPE=OPENLDAP1
6564 LDAP_LIB_TYPE=OPENLDAP2
6565 LDAP_LIB_TYPE=NETSCAPE
6566 LDAP_LIB_TYPE=SOLARIS
6568 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
6569 same interface as the University of Michigan version.
6571 There are three LDAP lookup types in Exim. These behave slightly differently in
6572 the way they handle the results of a query:
6575 &(ldap)& requires the result to contain just one entry; if there are more, it
6578 &(ldapdn)& also requires the result to contain just one entry, but it is the
6579 Distinguished Name that is returned rather than any attribute values.
6581 &(ldapm)& permits the result to contain more than one entry; the attributes
6582 from all of them are returned.
6586 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
6587 Exim behaves as if the entry did not exist, and the lookup fails. The format of
6588 the data returned by a successful lookup is described in the next section.
6589 First we explain how LDAP queries are coded.
6592 .section "Format of LDAP queries" "SECTforldaque"
6593 .cindex "LDAP" "query format"
6594 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
6595 the configuration of a &(redirect)& router one might have this setting:
6597 data = ${lookup ldap \
6598 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
6599 c=UK?mailbox?base?}}
6601 .cindex "LDAP" "with TLS"
6602 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
6603 secure (encrypted) LDAP connections. The second of these ensures that an
6604 encrypted TLS connection is used.
6607 .section "LDAP quoting"
6608 .cindex "LDAP" "quoting"
6609 Two levels of quoting are required in LDAP queries, the first for LDAP itself
6610 and the second because the LDAP query is represented as a URL. Furthermore,
6611 within an LDAP query, two different kinds of quoting are required. For this
6612 reason, there are two different LDAP-specific quoting operators.
6614 The &%quote_ldap%& operator is designed for use on strings that are part of
6615 filter specifications. Conceptually, it first does the following conversions on
6623 in accordance with RFC 2254. The resulting string is then quoted according
6624 to the rules for URLs, that is, all non-alphanumeric characters except
6628 are converted to their hex values, preceded by a percent sign. For example:
6630 ${quote_ldap: a(bc)*, a<yz>; }
6634 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
6636 Removing the URL quoting, this is (with a leading and a trailing space):
6638 a\28bc\29\2A, a<yz>;
6640 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
6641 base DN specifications in queries. Conceptually, it first converts the string
6642 by inserting a backslash in front of any of the following characters:
6646 It also inserts a backslash before any leading spaces or # characters, and
6647 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
6648 is then quoted according to the rules for URLs. For example:
6650 ${quote_ldap_dn: a(bc)*, a<yz>; }
6654 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
6656 Removing the URL quoting, this is (with a trailing space):
6658 \ a(bc)*\, a\<yz\>\;\
6660 There are some further comments about quoting in the section on LDAP
6661 authentication below.
6664 .section "LDAP connections"
6665 .cindex "LDAP" "connections"
6666 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
6667 is in use, via a Unix domain socket. The example given above does not specify
6668 an LDAP server. A server that is reached by TCP/IP can be specified in a query
6671 ldap://<hostname>:<port>/...
6673 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
6674 used. When no server is specified in a query, a list of default servers is
6675 taken from the &%ldap_default_servers%& configuration option. This supplies a
6676 colon-separated list of servers which are tried in turn until one successfully
6677 handles a query, or there is a serious error. Successful handling either
6678 returns the requested data, or indicates that it does not exist. Serious errors
6679 are syntactical, or multiple values when only a single value is expected.
6680 Errors which cause the next server to be tried are connection failures, bind
6681 failures, and timeouts.
6683 For each server name in the list, a port number can be given. The standard way
6684 of specifing a host and port is to use a colon separator (RFC 1738). Because
6685 &%ldap_default_servers%& is a colon-separated list, such colons have to be
6686 doubled. For example
6688 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
6690 If &%ldap_default_servers%& is unset, a URL with no server name is passed
6691 to the LDAP library with no server name, and the library's default (normally
6692 the local host) is used.
6694 If you are using the OpenLDAP library, you can connect to an LDAP server using
6695 a Unix domain socket instead of a TCP/IP connection. This is specified by using
6696 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
6697 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
6700 For this type of connection, instead of a host name for the server, a pathname
6701 for the socket is required, and the port number is not relevant. The pathname
6702 can be specified either as an item in &%ldap_default_servers%&, or inline in
6703 the query. In the former case, you can have settings such as
6705 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
6707 When the pathname is given in the query, you have to escape the slashes as
6708 &`%2F`& to fit in with the LDAP URL syntax. For example:
6710 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
6712 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
6713 a pathname, it uses the Unix domain socket code, even if the query actually
6714 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
6715 socket connection. This behaviour means that you can use a setting of
6716 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
6717 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
6718 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
6721 If an explicit &`ldapi`& type is given in a query when a host name is
6722 specified, an error is diagnosed. However, if there are more items in
6723 &%ldap_default_servers%&, they are tried. In other words:
6726 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
6729 Using &`ldapi`& with a host name causes an error.
6733 Using &`ldapi`& with no host or path in the query, and no setting of
6734 &%ldap_default_servers%&, does whatever the library does by default.
6738 .section "LDAP authentication and control information"
6739 .cindex "LDAP" "authentication"
6740 The LDAP URL syntax provides no way of passing authentication and other control
6741 information to the server. To make this possible, the URL in an LDAP query may
6742 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
6743 spaces. If a value contains spaces it must be enclosed in double quotes, and
6744 when double quotes are used, backslash is interpreted in the usual way inside
6745 them. The following names are recognized:
6747 &`DEREFERENCE`& set the dereferencing parameter
6748 &`NETTIME `& set a timeout for a network operation
6749 &`USER `& set the DN, for authenticating the LDAP bind
6750 &`PASS `& set the password, likewise
6751 &`SIZE `& set the limit for the number of entries returned
6752 &`TIME `& set the maximum waiting time for a query
6754 The value of the DEREFERENCE parameter must be one of the words &"never"&,
6755 &"searching"&, &"finding"&, or &"always"&.
6757 The name CONNECT is an obsolete name for NETTIME, retained for
6758 backwards compatibility. This timeout (specified as a number of seconds) is
6759 enforced from the client end for operations that can be carried out over a
6760 network. Specifically, it applies to network connections and calls to the
6761 &'ldap_result()'& function. If the value is greater than zero, it is used if
6762 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
6763 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
6764 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
6765 Netscape SDK; for OpenLDAP no action is taken.
6767 The TIME parameter (also a number of seconds) is passed to the server to
6768 set a server-side limit on the time taken to complete a search.
6771 Here is an example of an LDAP query in an Exim lookup that uses some of these
6772 values. This is a single line, folded to fit on the page:
6775 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
6776 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
6779 The encoding of spaces as &`%20`& is a URL thing which should not be done for
6780 any of the auxiliary data. Exim configuration settings that include lookups
6781 which contain password information should be preceded by &"hide"& to prevent
6782 non-admin users from using the &%-bP%& option to see their values.
6784 The auxiliary data items may be given in any order. The default is no
6785 connection timeout (the system timeout is used), no user or password, no limit
6786 on the number of entries returned, and no time limit on queries.
6788 When a DN is quoted in the USER= setting for LDAP authentication, Exim
6789 removes any URL quoting that it may contain before passing it LDAP. Apparently
6790 some libraries do this for themselves, but some do not. Removing the URL
6791 quoting has two advantages:
6794 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
6795 DNs as with DNs inside actual queries.
6797 It permits spaces inside USER= DNs.
6800 For example, a setting such as
6802 USER=cn=${quote_ldap_dn:$1}
6804 should work even if &$1$& contains spaces.
6806 Expanded data for the PASS= value should be quoted using the &%quote%&
6807 expansion operator, rather than the LDAP quote operators. The only reason this
6808 field needs quoting is to ensure that it conforms to the Exim syntax, which
6809 does not allow unquoted spaces. For example:
6813 The LDAP authentication mechanism can be used to check passwords as part of
6814 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
6819 .section "Format of data returned by LDAP"
6820 .cindex "LDAP" "returned data formats"
6821 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
6822 as a sequence of values, for example
6824 cn=manager, o=University of Cambridge, c=UK
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
6828 the 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
6830 you know that whatever values are returned all came from a single entry in the
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.
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.
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:
6849 ldap:///o=base?attr1?sub?(uid=fred)
6852 ldap:///o=base?attr2?sub?(uid=fred)
6855 ldap:///o=base?attr1,attr2?sub?(uid=fred)
6856 attr1="value1.1, value1.2" attr2="value two"
6858 ldap:///o=base??sub?(uid=fred)
6859 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
6861 The &%extract%& operator in string expansions can be used to pick out
6862 individual fields from data that consists of &'key'&=&'value'& pairs. You can
6863 make use of Exim's &%-be%& option to run expansion tests and thereby check the
6864 results of LDAP lookups.
6869 .section "More about NIS+" "SECTnisplus"
6870 .cindex "NIS+ lookup type"
6871 .cindex "lookup" "NIS+"
6872 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
6873 and field name. If this is given, the result of a successful query is the
6874 contents of the named field; otherwise the result consists of a concatenation
6875 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
6876 values containing spaces are quoted. For example, the query
6878 [name=mg1456],passwd.org_dir
6880 might return the string
6882 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
6883 home=/home/mg1456 shell=/bin/bash shadow=""
6885 (split over two lines here to fit on the page), whereas
6887 [name=mg1456],passwd.org_dir:gcos
6893 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
6894 for the given indexed key. The effect of the &%quote_nisplus%& expansion
6895 operator is to double any quote characters within the text.
6899 .section "SQL lookups" "SECTsql"
6900 .cindex "SQL lookup types"
6901 Exim can support lookups in Interbase, MySQL, Oracle, PostgreSQL, and SQLite
6902 databases. Queries for these databases contain SQL statements, so an example
6905 ${lookup mysql{select mailbox from users where id='userx'}\
6908 If the result of the query contains more than one field, the data for each
6909 field in the row is returned, preceded by its name, so the result of
6911 ${lookup pgsql{select home,name from users where id='userx'}\
6916 home=/home/userx name="Mister X"
6918 Empty values and values containing spaces are double quoted, with embedded
6919 quotes escaped by a backslash. If the result of the query contains just one
6920 field, the value is passed back verbatim, without a field name, for example:
6924 If the result of the query yields more than one row, it is all concatenated,
6925 with a newline between the data for each row.
6928 .section "More about MySQL, PostgreSQL, Oracle, and Interbase"
6929 .cindex "MySQL" "lookup type"
6930 .cindex "PostgreSQL lookup type"
6931 .cindex "lookup" "MySQL"
6932 .cindex "lookup" "PostgreSQL"
6933 .cindex "Oracle" "lookup type"
6934 .cindex "lookup" "Oracle"
6935 .cindex "Interbase lookup type"
6936 .cindex "lookup" "Interbase"
6937 If any MySQL, PostgreSQL, Oracle, or Interbase lookups are used, the
6938 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
6939 option (as appropriate) must be set to a colon-separated list of server
6940 information. Each item in the list is a slash-separated list of four items:
6941 host name, database name, user name, and password. In the case of Oracle, the
6942 host name field is used for the &"service name"&, and the database name field
6943 is not used and should be empty. For example:
6945 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
6947 Because password data is sensitive, you should always precede the setting with
6948 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
6949 option. Here is an example where two MySQL servers are listed:
6951 hide mysql_servers = localhost/users/root/secret:\
6952 otherhost/users/root/othersecret
6954 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
6955 because this is a colon-separated list, the colon has to be doubled. For each
6956 query, these parameter groups are tried in order until a connection and a query
6959 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
6960 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
6961 respectively, and the characters single-quote, double-quote, and backslash
6962 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
6963 addition, escapes the percent and underscore characters. This cannot be done
6964 for MySQL because these escapes are not recognized in contexts where these
6965 characters are not special.
6968 .section "Special MySQL features"
6969 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
6970 causes a connection to the server on the local host by means of a Unix domain
6971 socket. An alternate socket can be specified in parentheses. The full syntax of
6972 each item in &%mysql_servers%& is:
6974 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
6975 <&'user'&>/<&'password'&>
6977 Any of the three sub-parts of the first field can be omitted. For normal use on
6978 the local host it can be left blank or set to just &"localhost"&.
6980 No database need be supplied &-- but if it is absent here, it must be given in
6983 If a MySQL query is issued that does not request any data (an insert, update,
6984 or delete command), the result of the lookup is the number of rows affected.
6986 &*Warning*&: This can be misleading. If an update does not actually change
6987 anything (for example, setting a field to the value it already has), the result
6988 is zero because no rows are affected.
6991 .section "Special PostgreSQL features"
6992 PostgreSQL lookups can also use Unix domain socket connections to the database.
6993 This is usually faster and costs less CPU time than a TCP/IP connection.
6994 However it can be used only if the mail server runs on the same machine as the
6995 database server. A configuration line for PostgreSQL via Unix domain sockets
6998 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7000 In other words, instead of supplying a host name, a path to the socket is
7001 given. The path name is enclosed in parentheses so that its slashes aren't
7002 visually confused with the delimiters for the other server parameters.
7004 If a PostgreSQL query is issued that does not request any data (an insert,
7005 update, or delete command), the result of the lookup is the number of rows
7008 .section "More about SQLite" "SECTsqlite"
7009 .cindex "lookup" "SQLite"
7010 .cindex "SQLite lookup type"
7011 SQLite is different to the other SQL lookups because a file name is required in
7012 addition to the SQL query. An SQLite database is a single file, and there is no
7013 daemon as in the other SQL databases. The interface to Exim requires the name
7014 of the file, as an absolute path, to be given at the start of the query. It is
7015 separated from the query by white space. This means that the path name cannot
7016 contain white space. Here is a lookup expansion example:
7018 ${lookup sqlite {/some/thing/sqlitedb \
7019 select name from aliases where id='userx';}}
7021 In a list, the syntax is similar. For example:
7023 domainlist relay_domains = sqlite;/some/thing/sqlitedb \
7024 select * from relays where ip='$sender_host_address';
7026 The only character affected by the &%quote_sqlite%& operator is a single
7027 quote, which it doubles.
7029 The SQLite library handles multiple simultaneous accesses to the database
7030 internally. Multiple readers are permitted, but only one process can
7031 update at once. Attempts to access the database while it is being updated
7032 are rejected after a timeout period, during which the SQLite library
7033 waits for the lock to be released. In Exim, the default timeout is set
7034 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7040 . ////////////////////////////////////////////////////////////////////////////
7041 . ////////////////////////////////////////////////////////////////////////////
7043 .chapter "Domain, host, address, and local part lists" &&&
7044 "CHAPdomhosaddlists" &&&
7045 "Domain, host, and address lists"
7046 .scindex IIDdohoadli "lists of domains; hosts; etc."
7047 A number of Exim configuration options contain lists of domains, hosts,
7048 email addresses, or local parts. For example, the &%hold_domains%& option
7049 contains a list of domains whose delivery is currently suspended. These lists
7050 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7051 arguments to expansion conditions such as &%match_domain%&.
7053 Each item in one of these lists is a pattern to be matched against a domain,
7054 host, email address, or local part, respectively. In the sections below, the
7055 different types of pattern for each case are described, but first we cover some
7056 general facilities that apply to all four kinds of list.
7060 .section "Expansion of lists"
7061 .cindex "expansion" "of lists"
7062 Each list is expanded as a single string before it is used. The result of
7063 expansion must be a list, possibly containing empty items, which is split up
7064 into separate items for matching. By default, colon is the separator character,
7065 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7066 &<<SECTempitelis>>& for details of the list syntax; the second of these
7067 discusses the way to specify empty list items.
7070 If the string expansion is forced to fail, Exim behaves as if the item it is
7071 testing (domain, host, address, or local part) is not in the list. Other
7072 expansion failures cause temporary errors.
7074 If an item in a list is a regular expression, backslashes, dollars and possibly
7075 other special characters in the expression must be protected against
7076 misinterpretation by the string expander. The easiest way to do this is to use
7077 the &`\N`& expansion feature to indicate that the contents of the regular
7078 expression should not be expanded. For example, in an ACL you might have:
7080 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7081 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7083 The first item is a regular expression that is protected from expansion by
7084 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7085 senders based on the receiving domain.
7090 .section "Negated items in lists"
7091 .cindex "list" "negation"
7092 .cindex "negation" "in lists"
7093 Items in a list may be positive or negative. Negative items are indicated by a
7094 leading exclamation mark, which may be followed by optional white space. A list
7095 defines a set of items (domains, etc). When Exim processes one of these lists,
7096 it is trying to find out whether a domain, host, address, or local part
7097 (respectively) is in the set that is defined by the list. It works like this:
7099 The list is scanned from left to right. If a positive item is matched, the
7100 subject that is being checked is in the set; if a negative item is matched, the
7101 subject is not in the set. If the end of the list is reached without the
7102 subject having matched any of the patterns, it is in the set if the last item
7103 was a negative one, but not if it was a positive one. For example, the list in
7105 domainlist relay_domains = !a.b.c : *.b.c
7107 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7108 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7109 list is positive. However, if the setting were
7111 domainlist relay_domains = !a.b.c
7113 then all domains other than &'a.b.c'& would match because the last item in the
7114 list is negative. In other words, a list that ends with a negative item behaves
7115 as if it had an extra item &`:*`& on the end.
7117 Another way of thinking about positive and negative items in lists is to read
7118 the connector as &"or"& after a positive item and as &"and"& after a negative
7123 .section "File names in lists" "SECTfilnamlis"
7124 .cindex "list" "file name in"
7125 If an item in a domain, host, address, or local part list is an absolute file
7126 name (beginning with a slash character), each line of the file is read and
7127 processed as if it were an independent item in the list, except that further
7128 file names are not allowed,
7129 and no expansion of the data from the file takes place.
7130 Empty lines in the file are ignored, and the file may also contain comment
7134 For domain and host lists, if a # character appears anywhere in a line of the
7135 file, it and all following characters are ignored.
7137 Because local parts may legitimately contain # characters, a comment in an
7138 address list or local part list file is recognized only if # is preceded by
7139 white space or the start of the line. For example:
7141 not#comment@x.y.z # but this is a comment
7145 Putting a file name in a list has the same effect as inserting each line of the
7146 file as an item in the list (blank lines and comments excepted). However, there
7147 is one important difference: the file is read each time the list is processed,
7148 so if its contents vary over time, Exim's behaviour changes.
7150 If a file name is preceded by an exclamation mark, the sense of any match
7151 within the file is inverted. For example, if
7153 hold_domains = !/etc/nohold-domains
7155 and the file contains the lines
7160 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7161 any domain matching &`*.b.c`& is not.
7165 .section "An lsearch file is not an out-of-line list"
7166 As will be described in the sections that follow, lookups can be used in lists
7167 to provide indexed methods of checking list membership. There has been some
7168 confusion about the way &(lsearch)& lookups work in lists. Because
7169 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7170 sometimes thought that it is allowed to contain wild cards and other kinds of
7171 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7172 always fixed strings, just as for any other single-key lookup type.
7174 If you want to use a file to contain wild-card patterns that form part of a
7175 list, just give the file name on its own, without a search type, as described
7176 in the previous section.
7181 .section "Named lists" "SECTnamedlists"
7182 .cindex "named lists"
7183 .cindex "list" "named"
7184 A list of domains, hosts, email addresses, or local parts can be given a name
7185 which is then used to refer to the list elsewhere in the configuration. This is
7186 particularly convenient if the same list is required in several different
7187 places. It also allows lists to be given meaningful names, which can improve
7188 the readability of the configuration. For example, it is conventional to define
7189 a domain list called &'local_domains'& for all the domains that are handled
7190 locally on a host, using a configuration line such as
7192 domainlist local_domains = localhost:my.dom.example
7194 Named lists are referenced by giving their name preceded by a plus sign, so,
7195 for example, a router that is intended to handle local domains would be
7196 configured with the line
7198 domains = +local_domains
7200 The first router in a configuration is often one that handles all domains
7201 except the local ones, using a configuration with a negated item like this:
7205 domains = ! +local_domains
7206 transport = remote_smtp
7209 The four kinds of named list are created by configuration lines starting with
7210 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7211 respectively. Then there follows the name that you are defining, followed by an
7212 equals sign and the list itself. For example:
7214 hostlist relay_hosts = 192.168.23.0/24 : my.friend.example
7215 addresslist bad_senders = cdb;/etc/badsenders
7217 A named list may refer to other named lists:
7219 domainlist dom1 = first.example : second.example
7220 domainlist dom2 = +dom1 : third.example
7221 domainlist dom3 = fourth.example : +dom2 : fifth.example
7223 &*Warning*&: If the last item in a referenced list is a negative one, the
7224 effect may not be what you intended, because the negation does not propagate
7225 out to the higher level. For example, consider:
7227 domainlist dom1 = !a.b
7228 domainlist dom2 = +dom1 : *.b
7230 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7231 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7232 means it matches the second list as well. The effect is not the same as
7234 domainlist dom2 = !a.b : *.b
7236 where &'x.y'& does not match. It's best to avoid negation altogether in
7237 referenced lists if you can.
7239 Named lists may have a performance advantage. When Exim is routing an
7240 address or checking an incoming message, it caches the result of tests on named
7241 lists. So, if you have a setting such as
7243 domains = +local_domains
7245 on several of your routers
7246 or in several ACL statements,
7247 the actual test is done only for the first one. However, the caching works only
7248 if there are no expansions within the list itself or any sublists that it
7249 references. In other words, caching happens only for lists that are known to be
7250 the same each time they are referenced.
7252 By default, there may be up to 16 named lists of each type. This limit can be
7253 extended by changing a compile-time variable. The use of domain and host lists
7254 is recommended for concepts such as local domains, relay domains, and relay
7255 hosts. The default configuration is set up like this.
7259 .section "Named lists compared with macros"
7260 .cindex "list" "named compared with macro"
7261 .cindex "macro" "compared with named list"
7262 At first sight, named lists might seem to be no different from macros in the
7263 configuration file. However, macros are just textual substitutions. If you
7266 ALIST = host1 : host2
7267 auth_advertise_hosts = !ALIST
7269 it probably won't do what you want, because that is exactly the same as
7271 auth_advertise_hosts = !host1 : host2
7273 Notice that the second host name is not negated. However, if you use a host
7276 hostlist alist = host1 : host2
7277 auth_advertise_hosts = ! +alist
7279 the negation applies to the whole list, and so that is equivalent to
7281 auth_advertise_hosts = !host1 : !host2
7285 .section "Named list caching"
7286 .cindex "list" "caching of named"
7287 .cindex "caching" "named lists"
7288 While processing a message, Exim caches the result of checking a named list if
7289 it is sure that the list is the same each time. In practice, this means that
7290 the cache operates only if the list contains no $ characters, which guarantees
7291 that it will not change when it is expanded. Sometimes, however, you may have
7292 an expanded list that you know will be the same each time within a given
7293 message. For example:
7295 domainlist special_domains = \
7296 ${lookup{$sender_host_address}cdb{/some/file}}
7298 This provides a list of domains that depends only on the sending host's IP
7299 address. If this domain list is referenced a number of times (for example,
7300 in several ACL lines, or in several routers) the result of the check is not
7301 cached by default, because Exim does not know that it is going to be the
7302 same list each time.
7304 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7305 cache the result anyway. For example:
7307 domainlist_cache special_domains = ${lookup{...
7309 If you do this, you should be absolutely sure that caching is going to do
7310 the right thing in all cases. When in doubt, leave it out.
7314 .section "Domain lists" "SECTdomainlist"
7315 .cindex "domain list" "patterns for"
7316 .cindex "list" "domain list"
7317 Domain lists contain patterns that are to be matched against a mail domain.
7318 The following types of item may appear in domain lists:
7321 .cindex "primary host name"
7322 .cindex "host name" "matched in domain list"
7323 .cindex "&%primary_hostname%&"
7324 .cindex "domain list" "matching primary host name"
7325 .cindex "@ in a domain list"
7326 If a pattern consists of a single @ character, it matches the local host name,
7327 as set by the &%primary_hostname%& option (or defaulted). This makes it
7328 possible to use the same configuration file on several different hosts that
7329 differ only in their names.
7331 .cindex "@[] in a domain list"
7332 .cindex "domain list" "matching local IP interfaces"
7333 .cindex "domain literal"
7334 If a pattern consists of the string &`@[]`& it matches any local IP interface
7335 address, enclosed in square brackets, as in an email address that contains a
7337 In today's Internet, the use of domain literals is controversial.
7340 .cindex "@mx_primary"
7341 .cindex "@mx_secondary"
7342 .cindex "domain list" "matching MX pointers to local host"
7343 If a pattern consists of the string &`@mx_any`& it matches any domain that
7344 has an MX record pointing to the local host or to any host that is listed in
7345 .cindex "&%hosts_treat_as_local%&"
7346 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7347 are similar, except that the first matches only when a primary MX target is the
7348 local host, and the second only when no primary MX target is the local host,
7349 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7350 preference value &-- there may of course be more than one of them.
7352 The MX lookup that takes place when matching a pattern of this type is
7353 performed with the resolver options for widening names turned off. Thus, for
7354 example, a single-component domain will &'not'& be expanded by adding the
7355 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7356 options of the &(dnslookup)& router for a discussion of domain widening.
7358 Sometimes you may want to ignore certain IP addresses when using one of these
7359 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7360 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7361 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7362 on a router). For example:
7364 domains = @mx_any/ignore=127.0.0.1
7366 This example matches any domain that has an MX record pointing to one of
7367 the local host's IP addresses other than 127.0.0.1.
7369 The list of IP addresses is in fact processed by the same code that processes
7370 host lists, so it may contain CIDR-coded network specifications and it may also
7371 contain negative items.
7373 Because the list of IP addresses is a sublist within a domain list, you have to
7374 be careful about delimiters if there is more than one address. Like any other
7375 list, the default delimiter can be changed. Thus, you might have:
7377 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7378 an.other.domain : ...
7380 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7381 involved, it is easiest to change the delimiter for the main list as well:
7383 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7384 an.other.domain ? ...
7387 .cindex "asterisk" "in domain list"
7388 .cindex "domain list" "asterisk in"
7389 .cindex "domain list" "matching &""ends with""&"
7390 If a pattern starts with an asterisk, the remaining characters of the pattern
7391 are compared with the terminating characters of the domain. The use of &"*"& in
7392 domain lists differs from its use in partial matching lookups. In a domain
7393 list, the character following the asterisk need not be a dot, whereas partial
7394 matching works only in terms of dot-separated components. For example, a domain
7395 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7399 .cindex "regular expressions" "in domain list"
7400 .cindex "domain list" "matching regular expression"
7401 If a pattern starts with a circumflex character, it is treated as a regular
7402 expression, and matched against the domain using a regular expression matching
7403 function. The circumflex is treated as part of the regular expression.
7404 References to descriptions of the syntax of regular expressions are given in
7405 chapter &<<CHAPregexp>>&.
7407 &*Warning*&: Because domain lists are expanded before being processed, you
7408 must escape any backslash and dollar characters in the regular expression, or
7409 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7410 it is not to be expanded (unless you really do want to build a regular
7411 expression by expansion, of course).
7413 .cindex "lookup" "in domain list"
7414 .cindex "domain list" "matching by lookup"
7415 If a pattern starts with the name of a single-key lookup type followed by a
7416 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7417 must be a file name in a suitable format for the lookup type. For example, for
7418 &"cdb;"& it must be an absolute path:
7420 domains = cdb;/etc/mail/local_domains.cdb
7422 The appropriate type of lookup is done on the file using the domain name as the
7423 key. In most cases, the data that is looked up is not used; Exim is interested
7424 only in whether or not the key is present in the file. However, when a lookup
7425 is used for the &%domains%& option on a router
7426 or a &%domains%& condition in an ACL statement, the data is preserved in the
7427 &$domain_data$& variable and can be referred to in other router options or
7428 other statements in the same ACL.
7431 Any of the single-key lookup type names may be preceded by
7432 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
7434 domains = partial-dbm;/partial/domains
7436 This causes partial matching logic to be invoked; a description of how this
7437 works is given in section &<<SECTpartiallookup>>&.
7440 .cindex "asterisk" "in lookup type"
7441 Any of the single-key lookup types may be followed by an asterisk. This causes
7442 a default lookup for a key consisting of a single asterisk to be done if the
7443 original lookup fails. This is not a useful feature when using a domain list to
7444 select particular domains (because any domain would match), but it might have
7445 value if the result of the lookup is being used via the &$domain_data$&
7448 If the pattern starts with the name of a query-style lookup type followed by a
7449 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
7450 pattern must be an appropriate query for the lookup type, as described in
7451 chapter &<<CHAPfdlookup>>&. For example:
7453 hold_domains = mysql;select domain from holdlist \
7454 where domain = '$domain';
7456 In most cases, the data that is looked up is not used (so for an SQL query, for
7457 example, it doesn't matter what field you select). Exim is interested only in
7458 whether or not the query succeeds. However, when a lookup is used for the
7459 &%domains%& option on a router, the data is preserved in the &$domain_data$&
7460 variable and can be referred to in other options.
7462 .cindex "domain list" "matching literal domain name"
7463 If none of the above cases apply, a caseless textual comparison is made
7464 between the pattern and the domain.
7467 Here is an example that uses several different kinds of pattern:
7469 domainlist funny_domains = \
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
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
7487 .section "Host lists" "SECThostlist"
7488 .cindex "host list" "patterns in"
7489 .cindex "list" "host list"
7490 Host lists are used to control what remote hosts are allowed to do. For
7491 example, some hosts may be allowed to use the local host as a relay, and some
7492 may be permitted to use the SMTP ETRN command. Hosts can be identified in
7493 two different ways, by name or by IP address. In a host list, some types of
7494 pattern are matched to a host name, and some are matched to an IP address.
7495 You need to be particularly careful with this when single-key lookups are
7496 involved, to ensure that the right value is being used as the key.
7499 .section "Special host list patterns"
7500 .cindex "empty item in hosts list"
7501 .cindex "host list" "empty string in"
7502 If a host list item is the empty string, it matches only when no remote host is
7503 involved. This is the case when a message is being received from a local
7504 process using SMTP on the standard input, that is, when a TCP/IP connection is
7507 .cindex "asterisk" "in host list"
7508 The special pattern &"*"& in a host list matches any host or no host. Neither
7509 the IP address nor the name is actually inspected.
7513 .section "Host list patterns that match by IP address" "SECThoslispatip"
7514 .cindex "host list" "matching IP addresses"
7515 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
7516 the incoming address actually appears in the IPv6 host as
7517 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
7518 list, it is converted into a traditional IPv4 address first. (Not all operating
7519 systems accept IPv4 calls on IPv6 sockets, as there have been some security
7522 The following types of pattern in a host list check the remote host by
7523 inspecting its IP address:
7526 If the pattern is a plain domain name (not a regular expression, not starting
7527 with *, not a lookup of any kind), Exim calls the operating system function
7528 to find the associated IP address(es). Exim uses the newer
7529 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
7530 This typically causes a forward DNS lookup of the name. The result is compared
7531 with the IP address of the subject host.
7533 If there is a temporary problem (such as a DNS timeout) with the host name
7534 lookup, a temporary error occurs. For example, if the list is being used in an
7535 ACL condition, the ACL gives a &"defer"& response, usually leading to a
7536 temporary SMTP error code. If no IP address can be found for the host name,
7537 what happens is described in section &<<SECTbehipnot>>& below.
7540 .cindex "@ in a host list"
7541 If the pattern is &"@"&, the primary host name is substituted and used as a
7542 domain name, as just described.
7545 If the pattern is an IP address, it is matched against the IP address of the
7546 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
7547 IPv6 addresses can be given in colon-separated format, but the colons have to
7548 be doubled so as not to be taken as item separators when the default list
7549 separator is used. IPv6 addresses are recognized even when Exim is compiled
7550 without IPv6 support. This means that if they appear in a host list on an
7551 IPv4-only host, Exim will not treat them as host names. They are just addresses
7552 that can never match a client host.
7555 .cindex "@[] in a host list"
7556 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
7557 the local host. For example, if the local host is an IPv4 host with one
7558 interface address 10.45.23.56, these two ACL statements have the same effect:
7560 accept hosts = 127.0.0.1 : 10.45.23.56
7564 .cindex "CIDR notation"
7565 If the pattern is an IP address followed by a slash and a mask length (for
7566 example 10.11.42.0/24), it is matched against the IP address of the subject
7567 host under the given mask. This allows, an entire network of hosts to be
7568 included (or excluded) by a single item. The mask uses CIDR notation; it
7569 specifies the number of address bits that must match, starting from the most
7570 significant end of the address.
7572 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
7573 of a range of addresses. It is the number of bits in the network portion of the
7574 address. The above example specifies a 24-bit netmask, so it matches all 256
7575 addresses in the 10.11.42.0 network. An item such as
7579 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
7580 32 for an IPv4 address is the same as no mask at all; just a single address
7583 Here is another example which shows an IPv4 and an IPv6 network:
7585 recipient_unqualified_hosts = 192.168.0.0/16: \
7586 3ffe::ffff::836f::::/48
7588 The doubling of list separator characters applies only when these items
7589 appear inline in a host list. It is not required when indirecting via a file.
7592 recipient_unqualified_hosts = /opt/exim/unqualnets
7594 could make use of a file containing
7599 to have exactly the same effect as the previous example. When listing IPv6
7600 addresses inline, it is usually more convenient to use the facility for
7601 changing separator characters. This list contains the same two networks:
7603 recipient_unqualified_hosts = <; 172.16.0.0/12; \
7606 The separator is changed to semicolon by the leading &"<;"& at the start of the
7612 .section "Host list patterns for single-key lookups by host address" &&&
7613 "SECThoslispatsikey"
7614 .cindex "host list" "lookup of IP address"
7615 When a host is to be identified by a single-key lookup of its complete IP
7616 address, the pattern takes this form:
7618 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7622 hosts_lookup = net-cdb;/hosts-by-ip.db
7624 The text form of the IP address of the subject host is used as the lookup key.
7625 IPv6 addresses are converted to an unabbreviated form, using lower case
7626 letters, with dots as separators because colon is the key terminator in
7627 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
7628 quoting the keys, but this is a facility that was added later.] The data
7629 returned by the lookup is not used.
7631 .cindex "IP address" "masking"
7632 .cindex "host list" "masked IP address"
7633 Single-key lookups can also be performed using masked IP addresses, using
7634 patterns of this form:
7636 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7640 net24-dbm;/networks.db
7642 The IP address of the subject host is masked using <&'number'&> as the mask
7643 length. A textual string is constructed from the masked value, followed by the
7644 mask, and this is used as the lookup key. For example, if the host's IP address
7645 is 192.168.34.6, the key that is looked up for the above example is
7646 &"192.168.34.0/24"&. IPv6 addresses are converted to a text value using lower
7647 case letters and dots as separators instead of the more usual colon, because
7648 colon is the key terminator in &(lsearch)& files. Full, unabbreviated IPv6
7649 addresses are always used.
7651 &*Warning*&: Specifing &%net32-%& (for an IPv4 address) or &%net128-%& (for an
7652 IPv6 address) is not the same as specifing just &%net-%& without a number. In
7653 the former case the key strings include the mask value, whereas in the latter
7654 case the IP address is used on its own.
7658 .section "Host list patterns that match by host name" "SECThoslispatnam"
7659 .cindex "host" "lookup failures"
7660 .cindex "unknown host name"
7661 .cindex "host list" "matching host name"
7662 There are several types of pattern that require Exim to know the name of the
7663 remote host. These are either wildcard patterns or lookups by name. (If a
7664 complete hostname is given without any wildcarding, it is used to find an IP
7665 address to match against, as described in the section &<<SECThoslispatip>>&
7668 If the remote host name is not already known when Exim encounters one of these
7669 patterns, it has to be found from the IP address.
7670 Although many sites on the Internet are conscientious about maintaining reverse
7671 DNS data for their hosts, there are also many that do not do this.
7672 Consequently, a name cannot always be found, and this may lead to unwanted
7673 effects. Take care when configuring host lists with wildcarded name patterns.
7674 Consider what will happen if a name cannot be found.
7676 Because of the problems of determining host names from IP addresses, matching
7677 against host names is not as common as matching against IP addresses.
7679 By default, in order to find a host name, Exim first does a reverse DNS lookup;
7680 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
7681 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
7682 are done can be changed by setting the &%host_lookup_order%& option.
7684 There are some options that control what happens if a host name cannot be
7685 found. These are described in section &<<SECTbehipnot>>& below.
7687 .cindex "host" "alias for"
7688 .cindex "alias for host"
7689 As a result of aliasing, hosts may have more than one name. When processing any
7690 of the following types of pattern, all the host's names are checked:
7693 .cindex "asterisk" "in host list"
7694 If a pattern starts with &"*"& the remainder of the item must match the end of
7695 the host name. For example, &`*.b.c`& matches all hosts whose names end in
7696 &'.b.c'&. This special simple form is provided because this is a very common
7697 requirement. Other kinds of wildcarding require the use of a regular
7700 .cindex "regular expressions" "in host list"
7701 .cindex "host list" "regular expression in"
7702 If the item starts with &"^"& it is taken to be a regular expression which is
7703 matched against the host name. For example,
7707 is a regular expression that matches either of the two hosts &'a.c.d'& or
7708 &'b.c.d'&. When a regular expression is used in a host list, you must take care
7709 that backslash and dollar characters are not misinterpreted as part of the
7710 string expansion. The simplest way to do this is to use &`\N`& to mark that
7711 part of the string as non-expandable. For example:
7713 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
7715 &*Warning*&: If you want to match a complete host name, you must include the
7716 &`$`& terminating metacharacter in the regular expression, as in the above
7717 example. Without it, a match at the start of the host name is all that is
7724 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
7725 .cindex "host" "lookup failures"
7726 While processing a host list, Exim may need to look up an IP address from a
7727 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
7728 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
7729 behaviour when it fails to find the information it is seeking is the same.
7731 .cindex "&`+include_unknown`&"
7732 .cindex "&`+ignore_unknown`&"
7733 By default, Exim behaves as if the host does not match the list. This may not
7734 always be what you want to happen. To change Exim's behaviour, the special
7735 items &`+include_unknown`& or &`+ignore_unknown`& may appear in the list (at
7736 top level &-- they are not recognized in an indirected file).
7739 If any item that follows &`+include_unknown`& requires information that
7740 cannot found, Exim behaves as if the host does match the list. For example,
7742 host_reject_connection = +include_unknown:*.enemy.ex
7744 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
7745 any hosts whose name it cannot find.
7748 If any item that follows &`+ignore_unknown`& requires information that cannot
7749 be found, Exim ignores that item and proceeds to the rest of the list. For
7752 accept hosts = +ignore_unknown : friend.example : \
7755 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
7756 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
7757 name can be found for 192.168.4.5, it is rejected.
7760 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
7761 list. The effect of each one lasts until the next, or until the end of the
7764 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
7765 apply to temporary DNS errors. They always cause a defer action (except when
7766 &%dns_again_means_nonexist%& converts them into permanent errors).
7770 .section "Host list patterns for single-key lookups by host name" &&&
7771 "SECThoslispatnamsk"
7772 .cindex "host" "lookup failures"
7773 .cindex "unknown host name"
7774 .cindex "host list" "matching host name"
7775 If a pattern is of the form
7777 <&'single-key-search-type'&>;<&'search-data'&>
7781 dbm;/host/accept/list
7783 a single-key lookup is performend, using the host name as its key. If the
7784 lookup succeeds, the host matches the item. The actual data that is looked up
7787 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
7788 keys in the file, not IP addresses. If you want to do lookups based on IP
7789 addresses, you must precede the search type with &"net-"& (see section
7790 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
7791 two items in the same list, one doing an address lookup and one doing a name
7792 lookup, both using the same file.
7796 .section "Host list patterns for query-style lookups"
7797 If a pattern is of the form
7799 <&'query-style-search-type'&>;<&'query'&>
7801 the query is obeyed, and if it succeeds, the host matches the item. The actual
7802 data that is looked up is not used. The variables &$sender_host_address$& and
7803 &$sender_host_name$& can be used in the query. For example:
7805 hosts_lookup = pgsql;\
7806 select ip from hostlist where ip='$sender_host_address'
7808 The value of &$sender_host_address$& for an IPv6 address contains colons. You
7809 can use the &%sg%& expansion item to change this if you need to. If you want to
7810 use masked IP addresses in database queries, you can use the &%mask%& expansion
7813 If the query contains a reference to &$sender_host_name$&, Exim automatically
7814 looks up the host name if has not already done so. (See section
7815 &<<SECThoslispatnam>>& for comments on finding host names.)
7817 Historical note: prior to release 4.30, Exim would always attempt to find a
7818 host name before running the query, unless the search type was preceded by
7819 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
7820 still recognized for query-style lookups, but its presence or absence has no
7821 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
7822 See section &<<SECThoslispatsikey>>&.)
7826 .section "Mixing wildcarded host names and addresses in host lists" &&&
7828 .cindex "host list" "mixing names and addresses in"
7829 If you have name lookups or wildcarded host names and IP addresses in the same
7830 host list, you should normally put the IP addresses first. For example, in an
7833 accept hosts = 10.9.8.7 : *.friend.example
7835 The reason for this lies in the left-to-right way that Exim processes lists.
7836 It can test IP addresses without doing any DNS lookups, but when it reaches an
7837 item that requires a host name, it fails if it cannot find a host name to
7838 compare with the pattern. If the above list is given in the opposite order, the
7839 &%accept%& statement fails for a host whose name cannot be found, even if its
7840 IP address is 10.9.8.7.
7842 If you really do want to do the name check first, and still recognize the IP
7843 address, you can rewrite the ACL like this:
7845 accept hosts = *.friend.example
7846 accept hosts = 10.9.8.7
7848 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
7849 &<<CHAPACL>>& for details of ACLs.
7855 .section "Address lists" "SECTaddresslist"
7856 .cindex "list" "address list"
7857 .cindex "address list" "empty item"
7858 .cindex "address list" "patterns"
7859 Address lists contain patterns that are matched against mail addresses. There
7860 is one special case to be considered: the sender address of a bounce message is
7861 always empty. You can test for this by providing an empty item in an address
7862 list. For example, you can set up a router to process bounce messages by
7863 using this option setting:
7867 The presence of the colon creates an empty item. If you do not provide any
7868 data, the list is empty and matches nothing. The empty sender can also be
7869 detected by a regular expression that matches an empty string,
7870 and by a query-style lookup that succeeds when &$sender_address$& is empty.
7872 Non-empty items in an address list can be straightforward email addresses. For
7875 senders = jbc@askone.example : hs@anacreon.example
7877 A certain amount of wildcarding is permitted. If a pattern contains an @
7878 character, but is not a regular expression and does not begin with a
7879 semicolon-terminated lookup type (described below), the local part of the
7880 subject address is compared with the local part of the pattern, which may start
7881 with an asterisk. If the local parts match, the domain is checked in exactly
7882 the same way as for a pattern in a domain list. For example, the domain can be
7883 wildcarded, refer to a named list, or be a lookup:
7885 deny senders = *@*.spamming.site:\
7886 *@+hostile_domains:\
7887 bozo@partial-lsearch;/list/of/dodgy/sites:\
7888 *@dbm;/bad/domains.db
7890 .cindex "local part" "starting with !"
7891 .cindex "address list" "local part starting with !"
7892 If a local part that begins with an exclamation mark is required, it has to be
7893 specified using a regular expression, because otherwise the exclamation mark is
7894 treated as a sign of negation, as is standard in lists.
7896 If a non-empty pattern that is not a regular expression or a lookup does not
7897 contain an @ character, it is matched against the domain part of the subject
7898 address. The only two formats that are recognized this way are a literal
7899 domain, or a domain pattern that starts with *. In both these cases, the effect
7900 is the same as if &`*@`& preceded the pattern. For example:
7902 deny senders = enemy.domain : *.enemy.domain
7905 The following kinds of more complicated address list pattern can match any
7906 address, including the empty address that is characteristic of bounce message
7910 .cindex "regular expressions" "in address list"
7911 .cindex "address list" "regular expression in"
7912 If (after expansion) a pattern starts with &"^"&, a regular expression match is
7913 done against the complete address, with the pattern as the regular expression.
7914 You must take care that backslash and dollar characters are not misinterpreted
7915 as part of the string expansion. The simplest way to do this is to use &`\N`&
7916 to mark that part of the string as non-expandable. For example:
7918 deny senders = \N^.*this.*@example\.com$\N : \
7919 \N^\d{8}.+@spamhaus.example$\N : ...
7921 The &`\N`& sequences are removed by the expansion, so these items do indeed
7922 start with &"^"& by the time they are being interpreted as address patterns.
7925 .cindex "address list" "lookup for complete address"
7926 Complete addresses can be looked up by using a pattern that starts with a
7927 lookup type terminated by a semicolon, followed by the data for the lookup. For
7930 deny senders = cdb;/etc/blocked.senders : \
7931 mysql;select address from blocked where \
7932 address='${quote_mysql:$sender_address}'
7934 Both query-style and single-key lookup types can be used. For a single-key
7935 lookup type, Exim uses the complete address as the key. However, empty keys are
7936 not supported for single-key lookups, so a match against the empty address
7937 always fails. This restriction does not apply to query-style lookups.
7939 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
7940 cannot be used, and is ignored if specified, with an entry being written to the
7942 .cindex "*@ with single-key lookup"
7943 However, you can configure lookup defaults, as described in section
7944 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
7945 default. For example, with this lookup:
7947 accept senders = lsearch*@;/some/file
7949 the file could contains lines like this:
7951 user1@domain1.example
7954 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
7957 nimrod@jaeger.example
7961 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
7962 would mean that every address matches, thus rendering the test useless.
7964 &*Warning 2*&: Do not confuse these two kinds of item:
7966 deny recipients = dbm*@;/some/file
7967 deny recipients = *@dbm;/some/file
7969 The first does a whole address lookup, with defaulting, as just described,
7970 because it starts with a lookup type. The second matches the local part and
7971 domain independently, as described in a bullet point below.
7975 The following kinds of address list pattern can match only non-empty addresses.
7976 If the subject address is empty, a match against any of these pattern types
7981 .cindex "@@ with single-key lookup"
7982 .cindex "address list" "@@ lookup type"
7983 .cindex "address list" "split local part and domain"
7984 If a pattern starts with &"@@"& followed by a single-key lookup item
7985 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
7986 split into a local part and a domain. The domain is looked up in the file. If
7987 it is not found, there is no match. If it is found, the data that is looked up
7988 from the file is treated as a colon-separated list of local part patterns, each
7989 of which is matched against the subject local part in turn.
7991 .cindex "asterisk" "in address list"
7992 The lookup may be a partial one, and/or one involving a search for a default
7993 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
7994 patterns that are looked up can be regular expressions or begin with &"*"&, or
7995 even be further lookups. They may also be independently negated. For example,
7998 deny senders = @@dbm;/etc/reject-by-domain
8000 the data from which the DBM file is built could contain lines like
8002 baddomain.com: !postmaster : *
8004 to reject all senders except &%postmaster%& from that domain.
8006 .cindex "local part" "starting with !"
8007 If a local part that actually begins with an exclamation mark is required, it
8008 has to be specified using a regular expression. In &(lsearch)& files, an entry
8009 may be split over several lines by indenting the second and subsequent lines,
8010 but the separating colon must still be included at line breaks. White space
8011 surrounding the colons is ignored. For example:
8013 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8016 As in all colon-separated lists in Exim, a colon can be included in an item by
8019 If the last item in the list starts with a right angle-bracket, the remainder
8020 of the item is taken as a new key to look up in order to obtain a continuation
8021 list of local parts. The new key can be any sequence of characters. Thus one
8022 might have entries like
8024 aol.com: spammer1 : spammer 2 : >*
8025 xyz.com: spammer3 : >*
8028 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8029 local parts for all domains, in addition to the specific local parts listed for
8030 each domain. Of course, using this feature costs another lookup each time a
8031 chain is followed, but the effort needed to maintain the data is reduced.
8033 .cindex "loop" "in lookups"
8034 It is possible to construct loops using this facility, and in order to catch
8035 them, the chains may be no more than fifty items long.
8038 The @@<&'lookup'&> style of item can also be used with a query-style
8039 lookup, but in this case, the chaining facility is not available. The lookup
8040 can only return a single list of local parts.
8043 &*Warning*&: There is an important difference between the address list items
8044 in these two examples:
8047 senders = *@+my_list
8049 In the first one, &`my_list`& is a named address list, whereas in the second
8050 example it is a named domain list.
8055 .section "Case of letters in address lists" "SECTcasletadd"
8056 .cindex "case of local parts"
8057 .cindex "address list" "case forcing"
8058 .cindex "case forcing in address lists"
8059 Domains in email addresses are always handled caselessly, but for local parts
8060 case may be significant on some systems (see &%caseful_local_part%& for how
8061 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8062 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8063 blocking lists should be done in a case-independent manner. Since most address
8064 lists in Exim are used for this kind of control, Exim attempts to do this by
8067 The domain portion of an address is always lowercased before matching it to an
8068 address list. The local part is lowercased by default, and any string
8069 comparisons that take place are done caselessly. This means that the data in
8070 the address list itself, in files included as plain file names, and in any file
8071 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8072 keys in files that are looked up by a search type other than &(lsearch)& (which
8073 works caselessly) must be in lower case, because these lookups are not
8076 .cindex "&`+caseful`&"
8077 To allow for the possibility of caseful address list matching, if an item in
8078 an address list is the string &"+caseful"&, the original case of the local
8079 part is restored for any comparisons that follow, and string comparisons are no
8080 longer case-independent. This does not affect the domain, which remains in
8081 lower case. However, although independent matches on the domain alone are still
8082 performed caselessly, regular expressions that match against an entire address
8083 become case-sensitive after &"+caseful"& has been seen.
8087 .section "Local part lists" "SECTlocparlis"
8088 .cindex "list" "local part list"
8089 .cindex "local part" "list"
8090 Case-sensitivity in local part lists is handled in the same way as for address
8091 lists, as just described. The &"+caseful"& item can be used if required. In a
8092 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8093 set false, the subject is lowercased and the matching is initially
8094 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8095 matching in the local part list, but not elsewhere in the router. If
8096 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8097 option is case-sensitive from the start.
8099 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8100 comments are handled in the same way as address lists &-- they are recognized
8101 only if the # is preceded by white space or the start of the line.
8102 Otherwise, local part lists are matched in the same way as domain lists, except
8103 that the special items that refer to the local host (&`@`&, &`@[]`&,
8104 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8105 Refer to section &<<SECTdomainlist>>& for details of the other available item
8107 .ecindex IIDdohoadli
8112 . ////////////////////////////////////////////////////////////////////////////
8113 . ////////////////////////////////////////////////////////////////////////////
8115 .chapter "String expansions" "CHAPexpand"
8116 .scindex IIDstrexp "expansion" "of strings"
8117 Many strings in Exim's run time configuration are expanded before use. Some of
8118 them are expanded every time they are used; others are expanded only once.
8120 When a string is being expanded it is copied verbatim from left to right except
8121 when a dollar or backslash character is encountered. A dollar specifies the
8122 start of a portion of the string that is interpreted and replaced as described
8123 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8124 escape character, as described in the following section.
8128 .section "Literal text in expanded strings" "SECTlittext"
8129 .cindex "expansion" "including literal text"
8130 An uninterpreted dollar can be included in an expanded string by putting a
8131 backslash in front of it. A backslash can be used to prevent any special
8132 character being treated specially in an expansion, including backslash itself.
8133 If the string appears in quotes in the configuration file, two backslashes are
8134 required because the quotes themselves cause interpretation of backslashes when
8135 the string is read in (see section &<<SECTstrings>>&).
8137 .cindex "expansion" "non-expandable substrings"
8138 A portion of the string can specified as non-expandable by placing it between
8139 two occurrences of &`\N`&. This is particularly useful for protecting regular
8140 expressions, which often contain backslashes and dollar signs. For example:
8142 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8144 On encountering the first &`\N`&, the expander copies subsequent characters
8145 without interpretation until it reaches the next &`\N`& or the end of the
8150 .section "Character escape sequences in expanded strings"
8151 .cindex "expansion" "escape sequences"
8152 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8153 expanded string is recognized as an escape sequence for the character newline,
8154 carriage return, or tab, respectively. A backslash followed by up to three
8155 octal digits is recognized as an octal encoding for a single character, and a
8156 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8159 These escape sequences are also recognized in quoted strings when they are read
8160 in. Their interpretation in expansions as well is useful for unquoted strings,
8161 and for other cases such as looked-up strings that are then expanded.
8164 .section "Testing string expansions"
8165 .cindex "expansion" "testing"
8166 .cindex "testing" "string expansion"
8167 .cindex "&%-be%& option"
8168 Many expansions can be tested by calling Exim with the &%-be%& option. This
8169 takes the command arguments, or lines from the standard input if there are no
8170 arguments, runs them through the string expansion code, and writes the results
8171 to the standard output. Variables based on configuration values are set up, but
8172 since no message is being processed, variables such as &$local_part$& have no
8173 value. Nevertheless the &%-be%& option can be useful for checking out file and
8174 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8177 Exim gives up its root privilege when it is called with the &%-be%& option, and
8178 instead runs under the uid and gid it was called with, to prevent users from
8179 using &%-be%& for reading files to which they do not have access.
8183 .section "Forced expansion failure" "SECTforexpfai"
8184 .cindex "expansion" "forced failure"
8185 A number of expansions that are described in the following section have
8186 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8187 (which are sometimes called &"curly brackets"&). Which of the two strings is
8188 used depends on some condition that is evaluated as part of the expansion. If,
8189 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8190 the entire string expansion fails in a way that can be detected by the code
8191 that requested the expansion. This is called &"forced expansion failure"&, and
8192 its consequences depend on the circumstances. In some cases it is no different
8193 from any other expansion failure, but in others a different action may be
8194 taken. Such variations are mentioned in the documentation of the option that is
8200 .section "Expansion items" "SECTexpansionitems"
8201 The following items are recognized in expanded strings. White space may be used
8202 between sub-items that are keywords or substrings enclosed in braces inside an
8203 outer set of braces, to improve readability. &*Warning*&: Within braces,
8204 white space is significant.
8207 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8208 .cindex "expansion" "variables"
8209 Substitute the contents of the named variable, for example:
8214 The second form can be used to separate the name from subsequent alphanumeric
8215 characters. This form (using braces) is available only for variables; it does
8216 &'not'& apply to message headers. The names of the variables are given in
8217 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8218 given, the expansion fails.
8220 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8221 .cindex "expansion" "operators"
8222 The string is first itself expanded, and then the operation specified by
8223 <&'op'&> is applied to it. For example:
8227 The string starts with the first character after the colon, which may be
8228 leading white space. A list of operators is given in section &<<SECTexpop>>&
8229 below. The operator notation is used for simple expansion items that have just
8230 one argument, because it reduces the number of braces and therefore makes the
8231 string easier to understand.
8233 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8234 {*&<&'arg'&>&*}...}*&"
8236 This expansion dynamically loads and then calls a locally-written C function.
8237 This functionality is available only if Exim is compiled with
8241 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8242 object so that it doesn't reload the same object file in the same Exim process
8243 (but of course Exim does start new processes frequently).
8245 There may be from zero to eight arguments to the function. When compiling
8246 a local function that is to be called in this way, &_local_scan.h_& should be
8247 included. The Exim variables and functions that are defined by that API
8248 are also available for dynamically loaded functions. The function itself
8249 must have the following type:
8251 int dlfunction(uschar **yield, int argc, uschar *argv[])
8253 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8254 function should return one of the following values:
8256 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8257 into the expanded string that is being built.
8259 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8260 from &'yield'&, if it is set.
8262 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8263 taken from &'yield'& if it is set.
8265 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8267 When compiling a function that is to be used in this way with gcc,
8268 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8269 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8271 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
8272 {*&<&'string3'&>&*}}*&"
8273 .cindex "expansion" "extracting substrings by key"
8274 .cindex "&%extract%&" "substrings by key"
8275 The key and <&'string1'&> are first expanded separately. Leading and trailing
8276 white space is removed from the key (but not from any of the strings). The key
8277 must not consist entirely of digits. The expanded <&'string1'&> must be of the
8280 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
8283 where the equals signs and spaces (but not both) are optional. If any of the
8284 values contain white space, they must be enclosed in double quotes, and any
8285 values that are enclosed in double quotes are subject to escape processing as
8286 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
8287 for the value that corresponds to the key. The search is case-insensitive. If
8288 the key is found, <&'string2'&> is expanded, and replaces the whole item;
8289 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8290 variable &$value$& contains the value that has been extracted. Afterwards, it
8291 is restored to any previous value it might have had.
8293 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8294 key is not found. If {<&'string2'&>} is also omitted, the value that was
8295 extracted is used. Thus, for example, these two expansions are identical, and
8298 ${extract{gid}{uid=1984 gid=2001}}
8299 ${extract{gid}{uid=1984 gid=2001}{$value}}
8301 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
8302 appear, for example:
8304 ${extract{Z}{A=... B=...}{$value} fail }
8306 This forces an expansion failure (see section &<<SECTforexpfai>>&);
8307 {<&'string2'&>} must be present for &"fail"& to be recognized.
8310 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
8311 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8312 .cindex "expansion" "extracting substrings by number"
8313 .cindex "&%extract%&" "substrings by number"
8314 The <&'number'&> argument must consist entirely of decimal digits,
8315 apart from leading and trailing white space, which is ignored.
8316 This is what distinguishes this form of &%extract%& from the previous kind. It
8317 behaves in the same way, except that, instead of extracting a named field, it
8318 extracts from <&'string1'&> the field whose number is given as the first
8319 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
8320 <&'string3'&> as before.
8322 The fields in the string are separated by any one of the characters in the
8323 separator string. These may include space or tab characters.
8324 The first field is numbered one. If the number is negative, the fields are
8325 counted from the end of the string, with the rightmost one numbered -1. If the
8326 number given is zero, the entire string is returned. If the modulus of the
8327 number is greater than the number of fields in the string, the result is the
8328 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
8329 provided. For example:
8331 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8335 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8337 yields &"99"&. Two successive separators mean that the field between them is
8338 empty (for example, the fifth field above).
8341 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8342 .cindex "hash function" "textual"
8343 .cindex "expansion" "textual hash"
8344 This is a textual hashing function, and was the first to be implemented in
8345 early versions of Exim. In current releases, there are other hashing functions
8346 (numeric, MD5, and SHA-1), which are described below.
8348 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
8349 <&'n'&>. If you are using fixed values for these numbers, that is, if
8350 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
8351 use the simpler operator notation that avoids some of the braces:
8353 ${hash_<n>_<m>:<string>}
8355 The second number is optional (in both notations). If <&'n'&> is greater than
8356 or equal to the length of the string, the expansion item returns the string.
8357 Otherwise it computes a new string of length <&'n'&> by applying a hashing
8358 function to the string. The new string consists of characters taken from the
8359 first <&'m'&> characters of the string
8361 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
8363 If <&'m'&> is not present the value 26 is used, so that only lower case
8364 letters appear. For example:
8366 &`$hash{3}{monty}} `& yields &`jmg`&
8367 &`$hash{5}{monty}} `& yields &`monty`&
8368 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
8371 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
8372 &*$h_*&<&'header&~name'&>&*:*&"
8373 See &*$rheader*& below.
8375 .vitem "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8376 &*$bh_*&<&'header&~name'&>&*:*&"
8377 See &*$rheader*& below.
8379 .vitem "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8380 &*$rh_*&<&'header&~name'&>&*:*&"
8381 .cindex "expansion" "header insertion"
8382 .cindex "&$header_$&"
8383 .cindex "&$bheader_$&"
8384 .cindex "&$rheader_$&"
8385 .cindex "header lines" "in expansion strings"
8386 .cindex "header lines" "character sets"
8387 .cindex "header lines" "decoding"
8388 Substitute the contents of the named message header line, for example
8392 The newline that terminates a header line is not included in the expansion, but
8393 internal newlines (caused by splitting the header line over several physical
8394 lines) may be present.
8396 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
8397 the data in the header line is interpreted.
8400 .cindex "white space" "in header lines"
8401 &%rheader%& gives the original &"raw"& content of the header line, with no
8402 processing at all, and without the removal of leading and trailing white space.
8405 .cindex "base64 encoding" "in header lines"
8406 &%bheader%& removes leading and trailing white space, and then decodes base64
8407 or quoted-printable MIME &"words"& within the header text, but does no
8408 character set translation. If decoding of what looks superficially like a MIME
8409 &"word"& fails, the raw string is returned. If decoding
8410 .cindex "binary zero" "in header line"
8411 produces a binary zero character, it is replaced by a question mark &-- this is
8412 what Exim does for binary zeros that are actually received in header lines.
8415 &%header%& tries to translate the string as decoded by &%bheader%& to a
8416 standard character set. This is an attempt to produce the same string as would
8417 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
8418 returned. Translation is attempted only on operating systems that support the
8419 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
8420 a system Makefile or in &_Local/Makefile_&.
8423 In a filter file, the target character set for &%header%& can be specified by a
8424 command of the following form:
8426 headers charset "UTF-8"
8428 This command affects all references to &$h_$& (or &$header_$&) expansions in
8429 subsequently obeyed filter commands. In the absence of this command, the target
8430 character set in a filter is taken from the setting of the &%headers_charset%&
8431 option in the runtime configuration. The value of this option defaults to the
8432 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
8435 Header names follow the syntax of RFC 2822, which states that they may contain
8436 any printing characters except space and colon. Consequently, curly brackets
8437 &'do not'& terminate header names, and should not be used to enclose them as
8438 if they were variables. Attempting to do so causes a syntax error.
8440 Only header lines that are common to all copies of a message are visible to
8441 this mechanism. These are the original header lines that are received with the
8442 message, and any that are added by an ACL &%warn%& statement or by a system
8443 filter. Header lines that are added to a particular copy of a message by a
8444 router or transport are not accessible.
8446 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
8447 before the DATA ACL, because the header structure is not set up until the
8448 message is received. Header lines that are added by &%warn%& statements in a
8449 RCPT ACL (for example) are saved until the message's incoming header lines
8450 are available, at which point they are added. When a DATA ACL is running,
8451 however, header lines added by earlier ACLs are visible.
8453 Upper case and lower case letters are synonymous in header names. If the
8454 following character is white space, the terminating colon may be omitted, but
8455 this is not recommended, because you may then forget it when it is needed. When
8456 white space terminates the header name, it is included in the expanded string.
8457 If the message does not contain the given header, the expansion item is
8458 replaced by an empty string. (See the &%def%& condition in section
8459 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
8461 If there is more than one header with the same name, they are all
8462 concatenated to form the substitution string, up to a maximum length of 64K. A
8463 newline character is inserted between each line. For the &%header%& expansion,
8464 for those headers that contain lists of addresses, a comma is also inserted at
8465 the junctions between lines. This does not happen for the &%rheader%&
8469 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
8470 .cindex "expansion" "hmac hashing"
8472 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
8473 shared secret and some text into a message authentication code, as specified in
8474 RFC 2104. This differs from &`${md5:secret_text...}`& or
8475 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
8476 cryptographic hash, allowing for authentication that is not possible with MD5
8477 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
8478 present. For example:
8480 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
8482 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
8485 dd97e3ba5d1a61b5006108f8c8252953
8487 As an example of how this might be used, you might put in the main part of
8488 an Exim configuration:
8490 SPAMSCAN_SECRET=cohgheeLei2thahw
8492 In a router or a transport you could then have:
8495 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
8496 ${hmac{md5}{SPAMSCAN_SECRET}\
8497 {${primary_hostname},${message_exim_id},$h_message-id:}}
8499 Then given a message, you can check where it was scanned by looking at the
8500 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
8501 this header line is authentic by recomputing the authentication code from the
8502 host name, message ID and the &'Message-id:'& header line. This can be done
8503 using Exim's &%-be%& option, or by other means, for example by using the
8504 &'hmac_md5_hex()'& function in Perl.
8507 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8508 .cindex "expansion" "conditional"
8509 .cindex "&%if%&, expansion item"
8510 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
8511 item; otherwise <&'string2'&> is used. The available conditions are described
8512 in section &<<SECTexpcond>>& below. For example:
8514 ${if eq {$local_part}{postmaster} {yes}{no} }
8516 The second string need not be present; if it is not and the condition is not
8517 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
8518 be present instead of the second string (without any curly brackets). In this
8519 case, the expansion is forced to fail if the condition is not true (see section
8520 &<<SECTforexpfai>>&).
8522 If both strings are omitted, the result is the string &`true`& if the condition
8523 is true, and the empty string if the condition is false. This makes it less
8524 cumbersome to write custom ACL and router conditions. For example, instead of
8526 condition = ${if >{$acl_m4}{3}{true}{false}}
8530 condition = ${if >{$acl_m4}{3}}
8533 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8534 .cindex "expansion" "string truncation"
8535 .cindex "&%length%&" "expansion item"
8536 The &%length%& item is used to extract the initial portion of a string. Both
8537 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
8538 you are using a fixed value for the number, that is, if <&'string1'&> does not
8539 change when expanded, you can use the simpler operator notation that avoids
8542 ${length_<n>:<string>}
8544 The result of this item is either the first <&'n'&> characters or the whole
8545 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
8546 &%strlen%&, which gives the length of a string.
8549 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
8550 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8551 This is the first of one of two different types of lookup item, which are both
8552 described in the next item.
8554 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
8555 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8556 .cindex "expansion" "lookup in"
8557 .cindex "file" "lookups"
8558 .cindex "lookup" "in expanded string"
8559 The two forms of lookup item specify data lookups in files and databases, as
8560 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
8561 lookups, and the second is used for query-style lookups. The <&'key'&>,
8562 <&'file'&>, and <&'query'&> strings are expanded before use.
8564 If there is any white space in a lookup item which is part of a filter command,
8565 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
8566 other place where white space is significant, the lookup item must be enclosed
8567 in double quotes. The use of data lookups in users' filter files may be locked
8568 out by the system administrator.
8571 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
8572 During its expansion, the variable &$value$& contains the data returned by the
8573 lookup. Afterwards it reverts to the value it had previously (at the outer
8574 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
8575 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
8576 string on failure. If <&'string2'&> is provided, it can itself be a nested
8577 lookup, thus providing a mechanism for looking up a default value when the
8578 original lookup fails.
8580 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
8581 data for the outer lookup while the parameters of the second lookup are
8582 expanded, and also while <&'string2'&> of the second lookup is expanded, should
8583 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
8584 appear, and in this case, if the lookup fails, the entire expansion is forced
8585 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
8586 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
8587 successful lookup, and nothing in the case of failure.
8589 For single-key lookups, the string &"partial"& is permitted to precede the
8590 search type in order to do partial matching, and * or *@ may follow a search
8591 type to request default lookups if the key does not match (see sections
8592 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
8594 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
8595 If a partial search is used, the variables &$1$& and &$2$& contain the wild
8596 and non-wild parts of the key during the expansion of the replacement text.
8597 They return to their previous values at the end of the lookup item.
8599 This example looks up the postmaster alias in the conventional alias file:
8601 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
8603 This example uses NIS+ to look up the full name of the user corresponding to
8604 the local part of an address, forcing the expansion to fail if it is not found:
8606 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
8610 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8611 .cindex "expansion" "numeric hash"
8612 .cindex "hash function" "numeric"
8613 The three strings are expanded; the first two must yield numbers. Call them
8614 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
8615 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
8616 can use the simpler operator notation that avoids some of the braces:
8618 ${nhash_<n>_<m>:<string>}
8620 The second number is optional (in both notations). If there is only one number,
8621 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
8622 processed by a div/mod hash function that returns two numbers, separated by a
8623 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
8626 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
8628 returns the string &"6/33"&.
8632 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
8633 .cindex "Perl" "use in expanded string"
8634 .cindex "expansion" "calling Perl from"
8635 This item is available only if Exim has been built to include an embedded Perl
8636 interpreter. The subroutine name and the arguments are first separately
8637 expanded, and then the Perl subroutine is called with those arguments. No
8638 additional arguments need be given; the maximum number permitted, including the
8639 name of the subroutine, is nine.
8641 The return value of the subroutine is inserted into the expanded string, unless
8642 the return value is &%undef%&. In that case, the expansion fails in the same
8643 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
8644 Whatever you return is evaluated in a scalar context. For example, if you
8645 return the name of a Perl vector, the return value is the size of the vector,
8648 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
8649 with the error message that was passed to &%die%&. More details of the embedded
8650 Perl facility are given in chapter &<<CHAPperl>>&.
8652 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
8653 out the use of this expansion item in filter files.
8656 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
8657 .cindex "prvs" "expansion item"
8658 The first argument is a complete email address and the second is secret
8659 keystring. The third argument, specifying a key number, is optional. If absent,
8660 it defaults to 0. The result of the expansion is a prvs-signed email address,
8661 to be typically used with the &%return_path%& option on an &(smtp)& transport
8662 as part of a bounce address tag validation (BATV) scheme. For more discussion
8663 and an example, see section &<<SECTverifyPRVS>>&.
8665 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
8666 {*&<&'string'&>&*}}*&"
8667 .cindex "prvscheck" "expansion item"
8668 This expansion item is the complement of the &%prvs%& item. It is used for
8669 checking prvs-signed addresses. If the expansion of the first argument does not
8670 yield a syntactically valid prvs-signed address, the whole item expands to the
8671 empty string. When the first argument does expand to a syntactically valid
8672 prvs-signed address, the second argument is expanded, with the prvs-decoded
8673 version of the address and the key number extracted from the address in the
8674 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
8676 These two variables can be used in the expansion of the second argument to
8677 retrieve the secret. The validity of the prvs-signed address is then checked
8678 against the secret. The result is stored in the variable &$prvscheck_result$&,
8679 which is empty for failure or &"1"& for success.
8681 The third argument is optional; if it is missing, it defaults to an empty
8682 string. This argument is now expanded. If the result is an empty string, the
8683 result of the expansion is the decoded version of the address. This is the case
8684 whether or not the signature was valid. Otherwise, the result of the expansion
8685 is the expansion of the third argument.
8687 All three variables can be used in the expansion of the third argument.
8688 However, once the expansion is complete, only &$prvscheck_result$& remains set.
8689 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
8691 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
8692 .cindex "expansion" "inserting an entire file"
8693 .cindex "file" "inserting into expansion"
8694 .cindex "&%readfile%& expansion item"
8695 The file name and end-of-line string are first expanded separately. The file is
8696 then read, and its contents replace the entire item. All newline characters in
8697 the file are replaced by the end-of-line string if it is present. Otherwise,
8698 newlines are left in the string.
8699 String expansion is not applied to the contents of the file. If you want this,
8700 you must wrap the item in an &%expand%& operator. If the file cannot be read,
8701 the string expansion fails.
8703 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
8704 locks out the use of this expansion item in filter files.
8708 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
8709 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
8710 .cindex "expansion" "inserting from a socket"
8711 .cindex "socket" "use of in expansion"
8712 .cindex "&%readsocket%& expansion item"
8714 This item inserts data from a Unix domain or Internet socket into the expanded
8715 string. The minimal way of using it uses just two arguments, as in these
8718 ${readsocket{/socket/name}{request string}}
8719 ${readsocket{inet:some.host:1234}{request string}}
8721 For a Unix domain socket, the first substring must be the path to the socket.
8722 For an Internet socket, the first substring must contain &`inet:`& followed by
8723 a host name or IP address, followed by a colon and a port, which can be a
8724 number or the name of a TCP port in &_/etc/services_&. An IP address may
8725 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
8728 ${readsocket{inet:[::1]:1234}{request string}}
8730 Only a single host name may be given, but if looking it up yields more than
8731 one IP address, they are each tried in turn until a connection is made. For
8732 both kinds of socket, Exim makes a connection, writes the request string
8733 (unless it is an empty string) and reads from the socket until an end-of-file
8734 is read. A timeout of 5 seconds is applied. Additional, optional arguments
8735 extend what can be done. Firstly, you can vary the timeout. For example:
8738 ${readsocket{/socket/name}{request-string}{3s}}
8740 A fourth argument allows you to change any newlines that are in the data
8741 that is read, in the same way as for &%readfile%& (see above). This example
8742 turns them into spaces:
8745 ${readsocket{inet:127.0.0.1:3294}{request-string}{3s}{ }}
8748 As with all expansions, the substrings are expanded before the processing
8749 happens. Errors in these sub-expansions cause the expansion to fail. In
8750 addition, the following errors can occur:
8753 Failure to create a socket file descriptor;
8755 Failure to connect the socket;
8757 Failure to write the request-string;
8759 Timeout on reading from the socket.
8762 By default, any of these errors causes the expansion to fail. However, if
8763 you supply a fifth substring, it is expanded and used when any of the above
8764 errors occurs. For example:
8766 ${readsocket{/socket/name}{request-string}{3s}{\n}\
8770 You can test for the existence of a Unix domain socket by wrapping this
8771 expansion in &`${if exists`&, but there is a race condition between that test
8772 and the actual opening of the socket, so it is safer to use the fifth argument
8773 if you want to be absolutely sure of avoiding an expansion error for a
8774 non-existent Unix domain socket, or a failure to connect to an Internet socket.
8777 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
8778 locks out the use of this expansion item in filter files.
8780 .vitem &*$rheader_*&<&'header&~name'&>&*:&~or&~$rh_*&<&'header&~name'&>&*:*&
8781 This item inserts &"raw"& header lines. It is described with the &%header%&
8782 expansion item above.
8784 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
8785 {*&<&'string2'&>&*}}*&"
8786 .cindex "expansion" "running a command"
8787 .cindex "&%run%& expansion item"
8788 The command and its arguments are first expanded separately, and then the
8789 command is run in a separate process, but under the same uid and gid. As in
8790 other command executions from Exim, a shell is not used by default. If you want
8791 a shell, you must explicitly code it.
8793 .cindex "return code" "from &%run%& expansion"
8795 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
8796 and replaces the entire item; during this expansion, the standard output from
8797 the command is in the variable &$value$&. If the command fails, <&'string2'&>,
8798 if present, is expanded and used. Once again, during the expansion, the
8799 standard output from the command is in the variable &$value$&. If <&'string2'&>
8800 is absent, the result is empty. Alternatively, <&'string2'&> can be the word
8801 &"fail"& (not in braces) to force expansion failure if the command does not
8802 succeed. If both strings are omitted, the result is contents of the standard
8803 output on success, and nothing on failure.
8806 The return code from the command is put in the variable &$runrc$&, and this
8807 remains set afterwards, so in a filter file you can do things like this:
8809 if "${run{x y z}{}}$runrc" is 1 then ...
8810 elif $runrc is 2 then ...
8814 If execution of the command fails (for example, the command does not exist),
8815 the return code is 127 &-- the same code that shells use for non-existent
8818 &*Warning*&: In a router or transport, you cannot assume the order in which
8819 option values are expanded, except for those preconditions whose order of
8820 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
8821 by the expansion of one option, and use it in another.
8823 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
8824 out the use of this expansion item in filter files.
8827 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
8828 .cindex "expansion" "string substitution"
8829 .cindex "&%sg%& expansion item"
8830 This item works like Perl's substitution operator (s) with the global (/g)
8831 option; hence its name. However, unlike the Perl equivalent, Exim does not
8832 modify the subject string; instead it returns the modified string for insertion
8833 into the overall expansion. The item takes three arguments: the subject string,
8834 a regular expression, and a substitution string. For example:
8836 ${sg{abcdefabcdef}{abc}{xyz}}
8838 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
8839 if any $ or \ characters are required in the regular expression or in the
8840 substitution string, they have to be escaped. For example:
8842 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
8844 yields &"defabc"&, and
8846 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
8848 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
8849 the regular expression from string expansion.
8853 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8854 .cindex "&%substr%&"
8855 .cindex "substring extraction"
8856 .cindex "expansion" "substring extraction"
8857 The three strings are expanded; the first two must yield numbers. Call them
8858 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
8859 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
8860 can use the simpler operator notation that avoids some of the braces:
8862 ${substr_<n>_<m>:<string>}
8864 The second number is optional (in both notations).
8865 If it is absent in the simpler format, the preceding underscore must also be
8868 The &%substr%& item can be used to extract more general substrings than
8869 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
8870 length required. For example
8872 ${substr{3}{2}{$local_part}}
8874 If the starting offset is greater than the string length the result is the
8875 null string; if the length plus starting offset is greater than the string
8876 length, the result is the right-hand part of the string, starting from the
8877 given offset. The first character in the string has offset zero.
8879 The &%substr%& expansion item can take negative offset values to count
8880 from the right-hand end of its operand. The last character is offset -1, the
8881 second-last is offset -2, and so on. Thus, for example,
8883 ${substr{-5}{2}{1234567}}
8885 yields &"34"&. If the absolute value of a negative offset is greater than the
8886 length of the string, the substring starts at the beginning of the string, and
8887 the length is reduced by the amount of overshoot. Thus, for example,
8889 ${substr{-5}{2}{12}}
8891 yields an empty string, but
8893 ${substr{-3}{2}{12}}
8897 When the second number is omitted from &%substr%&, the remainder of the string
8898 is taken if the offset is positive. If it is negative, all characters in the
8899 string preceding the offset point are taken. For example, an offset of -1 and
8900 no length, as in these semantically identical examples:
8903 ${substr{-1}{abcde}}
8905 yields all but the last character of the string, that is, &"abcd"&.
8909 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
8910 {*&<&'replacements'&>&*}}*&"
8911 .cindex "expansion" "character translation"
8912 .cindex "&%tr%& expansion item"
8913 This item does single-character translation on its subject string. The second
8914 argument is a list of characters to be translated in the subject string. Each
8915 matching character is replaced by the corresponding character from the
8916 replacement list. For example
8918 ${tr{abcdea}{ac}{13}}
8920 yields &`1b3de1`&. If there are duplicates in the second character string, the
8921 last occurrence is used. If the third string is shorter than the second, its
8922 last character is replicated. However, if it is empty, no translation takes
8928 .section "Expansion operators" "SECTexpop"
8929 .cindex "expansion" "operators"
8930 For expansion items that perform transformations on a single argument string,
8931 the &"operator"& notation is used because it is simpler and uses fewer braces.
8932 The substring is first expanded before the operation is applied to it. The
8933 following operations can be performed:
8936 .vitem &*${address:*&<&'string'&>&*}*&
8937 .cindex "expansion" "RFC 2822 address handling"
8938 .cindex "&%address%&" "expansion item"
8939 The string is interpreted as an RFC 2822 address, as it might appear in a
8940 header line, and the effective address is extracted from it. If the string does
8941 not parse successfully, the result is empty.
8944 .vitem &*${base62:*&<&'digits'&>&*}*&
8945 .cindex "&%base62%&"
8946 .cindex "expansion" "conversion to base 62"
8947 The string must consist entirely of decimal digits. The number is converted to
8948 base 62 and output as a string of six characters, including leading zeros. In
8949 the few operating environments where Exim uses base 36 instead of base 62 for
8950 its message identifiers (because those systems do not have case-sensitive file
8951 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
8952 be absolutely clear: this is &'not'& base64 encoding.
8954 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
8955 .cindex "&%base62d%&"
8956 .cindex "expansion" "conversion to base 62"
8957 The string must consist entirely of base-62 digits, or, in operating
8958 environments where Exim uses base 36 instead of base 62 for its message
8959 identifiers, base-36 digits. The number is converted to decimal and output as a
8962 .vitem &*${domain:*&<&'string'&>&*}*&
8963 .cindex "domain" "extraction"
8964 .cindex "expansion" "domain extraction"
8965 The string is interpreted as an RFC 2822 address and the domain is extracted
8966 from it. If the string does not parse successfully, the result is empty.
8969 .vitem &*${escape:*&<&'string'&>&*}*&
8970 .cindex "expansion" "escaping non-printing characters"
8971 .cindex "&%escape%&, expansion item"
8972 If the string contains any non-printing characters, they are converted to
8973 escape sequences starting with a backslash. Whether characters with the most
8974 significant bit set (so-called &"8-bit characters"&) count as printing or not
8975 is controlled by the &%print_topbitchars%& option.
8978 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
8979 .cindex "expansion" "expression evaluation"
8980 .cindex "expansion" "arithmetic expression"
8981 .cindex "&%eval%& expansion item"
8982 These items supports simple arithmetic in expansion strings. The string (after
8983 expansion) must be a conventional arithmetic expression, but it is limited to
8984 five basic operators (plus, minus, times, divide, remainder) and parentheses.
8985 All operations are carried out using integer arithmetic. Plus and minus have a
8986 lower priority than times, divide, and remainder; operators with the same
8987 priority are evaluated from left to right.
8989 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
8990 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
8991 decimal, even if they start with a leading zero. This can be useful when
8992 processing numbers extracted from dates or times, which often do have leading
8995 A number may be followed by &"K"& or &"M"& to multiply it by 1024 or 1024*1024,
8996 respectively. Negative numbers are supported. The result of the computation is
8997 a decimal representation of the answer (without &"K"& or &"M"&). For example:
9000 &`${eval:1+1} `& yields 2
9001 &`${eval:1+2*3} `& yields 7
9002 &`${eval:(1+2)*3} `& yields 9
9003 &`${eval:2+42%5} `& yields 4
9006 As a more realistic example, in an ACL you might have
9008 deny message = Too many bad recipients
9011 {>{$rcpt_count}{10}} \
9014 {$recipients_count} \
9015 {${eval:$rcpt_count/2}} \
9019 The condition is true if there have been more than 10 RCPT commands and
9020 fewer than half of them have resulted in a valid recipient.
9023 .vitem &*${expand:*&<&'string'&>&*}*&
9024 .cindex "expansion" "re-expansion of substring"
9025 The &%expand%& operator causes a string to be expanded for a second time. For
9028 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
9030 first looks up a string in a file while expanding the operand for &%expand%&,
9031 and then re-expands what it has found.
9034 .vitem &*${from_utf8:*&<&'string'&>&*}*&
9036 .cindex "UTF-8" "conversion from"
9037 .cindex "expansion" "UTF-8 conversion"
9038 .cindex "&%from_utf8%&"
9039 The world is slowly moving towards Unicode, although there are no standards for
9040 email yet. However, other applications (including some databases) are starting
9041 to store data in Unicode, using UTF-8 encoding. This operator converts from a
9042 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
9043 converted to underscores. The input must be a valid UTF-8 string. If it is not,
9044 the result is an undefined sequence of bytes.
9046 Unicode code points with values less than 256 are compatible with ASCII and
9047 ISO-8859-1 (also known as Latin-1).
9048 For example, character 169 is the copyright symbol in both cases, though the
9049 way it is encoded is different. In UTF-8, more than one byte is needed for
9050 characters with code values greater than 127, whereas ISO-8859-1 is a
9051 single-byte encoding (but thereby limited to 256 characters). This makes
9052 translation from UTF-8 to ISO-8859-1 straightforward.
9055 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9056 .cindex "hash function" "textual"
9057 .cindex "expansion" "textual hash"
9058 The &%hash%& operator is a simpler interface to the hashing function that can
9059 be used when the two parameters are fixed numbers (as opposed to strings that
9060 change when expanded). The effect is the same as
9062 ${hash{<n>}{<m>}{<string>}}
9064 See the description of the general &%hash%& item above for details. The
9065 abbreviation &%h%& can be used when &%hash%& is used as an operator.
9069 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
9070 .cindex "base64 encoding" "conversion from hex"
9071 .cindex "expansion" "hex to base64"
9072 .cindex "&%hex2b64%&"
9073 This operator converts a hex string into one that is base64 encoded. This can
9074 be useful for processing the output of the MD5 and SHA-1 hashing functions.
9077 .vitem &*${lc:*&<&'string'&>&*}*&
9078 .cindex "case forcing in strings"
9079 .cindex "string" "case forcing"
9080 .cindex "lower casing"
9081 .cindex "expansion" "case forcing"
9082 .cindex "&%lc%& expansion item"
9083 This forces the letters in the string into lower-case, for example:
9088 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
9089 .cindex "expansion" "string truncation"
9090 .cindex "&%length%&" "expansion item"
9091 The &%length%& operator is a simpler interface to the &%length%& function that
9092 can be used when the parameter is a fixed number (as opposed to a string that
9093 changes when expanded). The effect is the same as
9095 ${length{<number>}{<string>}}
9097 See the description of the general &%length%& item above for details. Note that
9098 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
9099 when &%length%& is used as an operator.
9102 .vitem &*${local_part:*&<&'string'&>&*}*&
9103 .cindex "expansion" "local part extraction"
9104 .cindex "&%local_part%& expansion item"
9105 The string is interpreted as an RFC 2822 address and the local part is
9106 extracted from it. If the string does not parse successfully, the result is
9110 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
9111 .cindex "masked IP address"
9112 .cindex "IP address" "masking"
9113 .cindex "CIDR notation"
9114 .cindex "expansion" "IP address masking"
9115 .cindex "&%mask%&, expansion item"
9116 If the form of the string to be operated on is not an IP address followed by a
9117 slash and an integer (that is, a network address in CIDR notation), the
9118 expansion fails. Otherwise, this operator converts the IP address to binary,
9119 masks off the least significant bits according to the bit count, and converts
9120 the result back to text, with mask appended. For example,
9122 ${mask:10.111.131.206/28}
9124 returns the string &"10.111.131.192/28"&. Since this operation is expected to
9125 be mostly used for looking up masked addresses in files, the result for an IPv6
9126 address uses dots to separate components instead of colons, because colon
9127 terminates a key string in lsearch files. So, for example,
9129 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
9133 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
9135 Letters in IPv6 addresses are always output in lower case.
9138 .vitem &*${md5:*&<&'string'&>&*}*&
9140 .cindex "expansion" "MD5 hash"
9141 .cindex "&%md5%& expansion item"
9142 The &%md5%& operator computes the MD5 hash value of the string, and returns it
9143 as a 32-digit hexadecimal number, in which any letters are in lower case.
9146 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9147 .cindex "expansion" "numeric hash"
9148 .cindex "hash function" "numeric"
9149 The &%nhash%& operator is a simpler interface to the numeric hashing function
9150 that can be used when the two parameters are fixed numbers (as opposed to
9151 strings that change when expanded). The effect is the same as
9153 ${nhash{<n>}{<m>}{<string>}}
9155 See the description of the general &%nhash%& item above for details.
9158 .vitem &*${quote:*&<&'string'&>&*}*&
9159 .cindex "quoting" "in string expansions"
9160 .cindex "expansion" "quoting"
9161 .cindex "&%quote%&, expansion item"
9162 The &%quote%& operator puts its argument into double quotes if it
9163 is an empty string or
9164 contains anything other than letters, digits, underscores, dots, and hyphens.
9165 Any occurrences of double quotes and backslashes are escaped with a backslash.
9166 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
9167 respectively For example,
9175 The place where this is useful is when the argument is a substitution from a
9176 variable or a message header.
9178 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
9179 .cindex "&%quote_local_part%& expansion item"
9180 This operator is like &%quote%&, except that it quotes the string only if
9181 required to do so by the rules of RFC 2822 for quoting local parts. For
9182 example, a plus sign would not cause quoting (but it would for &%quote%&).
9183 If you are creating a new email address from the contents of &$local_part$&
9184 (or any other unknown data), you should always use this operator.
9187 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
9188 .cindex "quoting" "lookup-specific"
9189 This operator applies lookup-specific quoting rules to the string. Each
9190 query-style lookup type has its own quoting rules which are described with
9191 the lookups in chapter &<<CHAPfdlookup>>&. For example,
9193 ${quote_ldap:two * two}
9199 For single-key lookup types, no quoting is ever necessary and this operator
9200 yields an unchanged string.
9203 .vitem &*${rxquote:*&<&'string'&>&*}*&
9204 .cindex "quoting" "in regular expressions"
9205 .cindex "regular expressions" "quoting"
9206 .cindex "&%rxquote%& expansion item"
9207 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
9208 characters in its argument. This is useful when substituting the values of
9209 variables or headers inside regular expressions.
9212 .vitem &*${rfc2047:*&<&'string'&>&*}*&
9213 .cindex "expansion" "RFC 2047"
9214 .cindex "RFC 2047" "expansion operator"
9215 .cindex "&%rfc2047%& expansion item"
9216 This operator encodes text according to the rules of RFC 2047. This is an
9217 encoding that is used in header lines to encode non-ASCII characters. It is
9218 assumed that the input string is in the encoding specified by the
9219 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
9220 contains only characters in the range 33&--126, and no instances of the
9223 ? = ( ) < > @ , ; : \ " . [ ] _
9225 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
9226 string, using as many &"encoded words"& as necessary to encode all the
9231 .vitem &*${sha1:*&<&'string'&>&*}*&
9232 .cindex "SHA-1 hash"
9233 .cindex "expansion" "SHA-1 hashing"
9234 .cindex "&%sha2%& expansion item"
9235 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
9236 it as a 40-digit hexadecimal number, in which any letters are in upper case.
9239 .vitem &*${stat:*&<&'string'&>&*}*&
9240 .cindex "expansion" "statting a file"
9241 .cindex "file" "extracting characteristics"
9242 .cindex "&%stat%& expansion item"
9243 The string, after expansion, must be a file path. A call to the &[stat()]&
9244 function is made for this path. If &[stat()]& fails, an error occurs and the
9245 expansion fails. If it succeeds, the data from the stat replaces the item, as a
9246 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
9247 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
9248 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
9249 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
9250 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
9251 can extract individual fields using the &%extract%& expansion item.
9253 The use of the &%stat%& expansion in users' filter files can be locked out by
9254 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
9255 systems for files larger than 2GB.
9257 .vitem &*${str2b64:*&<&'string'&>&*}*&
9258 .cindex "expansion" "base64 encoding"
9259 .cindex "base64 encoding" "in string expansion"
9260 .cindex "&%str2b64%& expansion item"
9261 This operator converts a string into one that is base64 encoded.
9265 .vitem &*${strlen:*&<&'string'&>&*}*&
9266 .cindex "expansion" "string length"
9267 .cindex "string" "length in expansion"
9268 .cindex "&%strlen%& expansion item"
9269 The item is replace by the length of the expanded string, expressed as a
9270 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
9273 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
9274 .cindex "&%substr%& expansion item"
9275 .cindex "substring extraction"
9276 .cindex "expansion" "substring expansion"
9277 The &%substr%& operator is a simpler interface to the &%substr%& function that
9278 can be used when the two parameters are fixed numbers (as opposed to strings
9279 that change when expanded). The effect is the same as
9281 ${substr{<start>}{<length>}{<string>}}
9283 See the description of the general &%substr%& item above for details. The
9284 abbreviation &%s%& can be used when &%substr%& is used as an operator.
9286 .vitem &*${time_eval:*&<&'string'&>&*}*&
9287 .cindex "&%time_eval%& expansion item"
9288 .cindex "time interval" "decoding"
9289 This item converts an Exim time interval such as &`2d4h5m`& into a number of
9292 .vitem &*${time_interval:*&<&'string'&>&*}*&
9293 .cindex "&%time_interval%& expansion item"
9294 .cindex "time interval" "formatting"
9295 The argument (after sub-expansion) must be a sequence of decimal digits that
9296 represents an interval of time as a number of seconds. It is converted into a
9297 number of larger units and output in Exim's normal time format, for example,
9300 .vitem &*${uc:*&<&'string'&>&*}*&
9301 .cindex "case forcing in strings"
9302 .cindex "string" "case forcing"
9303 .cindex "upper casing"
9304 .cindex "expansion" "case forcing"
9305 .cindex "&%uc%& expansion item"
9306 This forces the letters in the string into upper-case.
9314 .section "Expansion conditions" "SECTexpcond"
9315 .cindex "expansion" "conditions"
9316 The following conditions are available for testing by the &%${if%& construct
9317 while expanding strings:
9320 .vitem &*!*&<&'condition'&>
9321 .cindex "expansion" "negating a condition"
9322 .cindex "negation" "in expansion condition"
9323 Preceding any condition with an exclamation mark negates the result of the
9326 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9327 .cindex "numeric comparison"
9328 .cindex "expansion" "numeric comparison"
9329 There are a number of symbolic operators for doing numeric comparisons. They
9335 &`>= `& greater or equal
9337 &`<= `& less or equal
9341 ${if >{$message_size}{10M} ...
9343 Note that the general negation operator provides for inequality testing. The
9344 two strings must take the form of optionally signed decimal integers,
9345 optionally followed by one of the letters &"K"& or &"M"& (in either upper or
9346 lower case), signifying multiplication by 1024 or 1024*1024, respectively.
9348 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9349 .cindex "expansion" "encrypted comparison"
9350 .cindex "encrypted strings" "comparing"
9351 .cindex "&%crypteq%& expansion condition"
9352 This condition is included in the Exim binary if it is built to support any
9353 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
9354 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
9355 included in the binary.
9357 The &%crypteq%& condition has two arguments. The first is encrypted and
9358 compared against the second, which is already encrypted. The second string may
9359 be in the LDAP form for storing encrypted strings, which starts with the
9360 encryption type in curly brackets, followed by the data. If the second string
9361 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
9362 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
9363 Typically this will be a field from a password file. An example of an encrypted
9364 string in LDAP form is:
9366 {md5}CY9rzUYh03PK3k6DJie09g==
9368 If such a string appears directly in an expansion, the curly brackets have to
9369 be quoted, because they are part of the expansion syntax. For example:
9371 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
9373 The following encryption types (whose names are matched case-independently) are
9378 .cindex "base64 encoding" "in encrypted password"
9379 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
9380 printable characters to compare with the remainder of the second string. If the
9381 length of the comparison string is 24, Exim assumes that it is base64 encoded
9382 (as in the above example). If the length is 32, Exim assumes that it is a
9383 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
9387 .cindex "SHA-1 hash"
9388 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
9389 printable characters to compare with the remainder of the second string. If the
9390 length of the comparison string is 28, Exim assumes that it is base64 encoded.
9391 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
9392 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
9395 .cindex "&[crypt()]&"
9396 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
9397 only the first eight characters of the password. However, in modern operating
9398 systems this is no longer true, and in many cases the entire password is used,
9399 whatever its length.
9401 .cindex "&[crypt16()]&"
9402 &%{crypt16}%& calls the &[crypt16()]& function (also known as &[bigcrypt()]&),
9403 which was orginally created to use up to 16 characters of the password. Again,
9404 in modern operating systems, more characters may be used.
9407 Exim has its own version of &[crypt16()]& (which is just a double call to
9408 &[crypt()]&). For operating systems that have their own version, setting
9409 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
9410 operating system version instead of its own. This option is set by default in
9411 the OS-dependent &_Makefile_& for those operating systems that are known to
9412 support &[crypt16()]&.
9414 If you do not put any curly bracket encryption type in a &%crypteq%&
9415 comparison, the default is either &`{crypt}`& or &`{crypt16}`&, as determined
9416 by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default default is
9417 &`{crypt}`&. Whatever the default, you can always use either function by
9418 specifying it explicitly in curly brackets.
9420 Note that if a password is no longer than 8 characters, the results of
9421 encrypting it with &[crypt()]& and &[crypt16()]& are identical. That means that
9422 &[crypt16()]& is backwards compatible, as long as nobody feeds it a password
9423 longer than 8 characters.
9425 .vitem &*def:*&<&'variable&~name'&>
9426 .cindex "expansion" "checking for empty variable"
9427 .cindex "&%def%& expansion condition"
9428 The &%def%& condition must be followed by the name of one of the expansion
9429 variables defined in section &<<SECTexpvar>>&. The condition is true if the
9430 variable does not contain the empty string. For example:
9432 ${if def:sender_ident {from $sender_ident}}
9434 Note that the variable name is given without a leading &%$%& character. If the
9435 variable does not exist, the expansion fails.
9437 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
9438 &~&*def:h_*&<&'header&~name'&>&*:*&"
9439 .cindex "expansion" "checking header line existence"
9440 This condition is true if a message is being processed and the named header
9441 exists in the message. For example,
9443 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
9445 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
9446 the header name must be terminated by a colon if white space does not follow.
9448 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9449 .cindex "string" "comparison"
9450 .cindex "expansion" "string comparison"
9451 .cindex "&%eq%& expansion condition"
9452 The two substrings are first expanded. The condition is true if the two
9453 resulting strings are identical, including the case of letters.
9455 .vitem &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9456 .cindex "string" "comparison"
9457 .cindex "expansion" "string comparison"
9458 .cindex "&%eqi%& expansion condition"
9459 The two substrings are first expanded. The condition is true if the two
9460 resulting strings are identical when compared in a case-independent way.
9462 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
9463 .cindex "expansion" "file existence test"
9464 .cindex "file" "existence test"
9465 .cindex "&%exists%&, expansion condition"
9466 The substring is first expanded and then interpreted as an absolute path. The
9467 condition is true if the named file (or directory) exists. The existence test
9468 is done by calling the &[stat()]& function. The use of the &%exists%& test in
9469 users' filter files may be locked out by the system administrator.
9471 .vitem &*first_delivery*&
9472 .cindex "delivery" "first"
9473 .cindex "first delivery"
9474 .cindex "expansion" "first delivery test"
9475 .cindex "&%first_delivery%& expansion condition"
9476 This condition, which has no data, is true during a message's first delivery
9477 attempt. It is false during any subsequent delivery attempts.
9479 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9480 .cindex "&%ge%& expansion condition"
9483 .vitem &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9484 .cindex "string" "comparison"
9485 .cindex "expansion" "string comparison"
9486 .cindex "&%gei%& expansion condition"
9487 The two substrings are first expanded. The condition is true if the first
9488 string is lexically greater than or equal to the second string: for &%ge%& the
9489 comparison includes the case of letters, whereas for &%gei%& the comparison is
9492 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9493 .cindex "&%gt%& expansion condition"
9496 .vitem &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9497 .cindex "string" "comparison"
9498 .cindex "expansion" "string comparison"
9499 .cindex "&%gti%& expansion condition"
9500 The two substrings are first expanded. The condition is true if the first
9501 string is lexically greater than the second string: for &%gt%& the comparison
9502 includes the case of letters, whereas for &%gti%& the comparison is
9505 .vitem &*isip&~{*&<&'string'&>&*}*&
9506 .cindex "&%isip%& expansion condition"
9509 .vitem &*isip4&~{*&<&'string'&>&*}*&
9510 .cindex "&%isip4%& expansion condition"
9513 .vitem &*isip6&~{*&<&'string'&>&*}*&
9514 .cindex "IP address" "testing string format"
9515 .cindex "string" "testing for IP address"
9516 .cindex "&%isip6%& expansion condition"
9517 The substring is first expanded, and then tested to see if it has the form of
9518 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
9519 &%isip4%& and &%isip6%& test just for IPv4 or IPv6 addresses, respectively. For
9520 example, you could use
9522 ${if isip4{$sender_host_address}...
9524 to test which version of IP an incoming SMTP connection is using.
9527 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
9528 .cindex "LDAP" "use for authentication"
9529 .cindex "expansion" "LDAP authentication test"
9530 .cindex "&%ldapauth%& expansion condition"
9531 This condition supports user authentication using LDAP. See section
9532 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
9533 queries. For this use, the query must contain a user name and password. The
9534 query itself is not used, and can be empty. The condition is true if the
9535 password is not empty, and the user name and password are accepted by the LDAP
9536 server. An empty password is rejected without calling LDAP because LDAP binds
9537 with an empty password are considered anonymous regardless of the username, and
9538 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
9539 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
9543 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9544 .cindex "&%le%& expansion condition"
9547 .vitem &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9548 .cindex "string" "comparison"
9549 .cindex "expansion" "string comparison"
9550 .cindex "&%lei%& expansion condition"
9551 The two substrings are first expanded. The condition is true if the first
9552 string is lexically less than or equal to the second string: for &%le%& the
9553 comparison includes the case of letters, whereas for &%lei%& the comparison is
9556 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9557 .cindex "&%lt%& expansion condition"
9560 .vitem &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9561 .cindex "string" "comparison"
9562 .cindex "expansion" "string comparison"
9563 .cindex "&%lti%& expansion condition"
9564 The two substrings are first expanded. The condition is true if the first
9565 string is lexically less than the second string: for &%lt%& the comparison
9566 includes the case of letters, whereas for &%lti%& the comparison is
9570 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9571 .cindex "expansion" "regular expression comparison"
9572 .cindex "regular expressions" "match in expanded string"
9573 .cindex "&%match%&, expansion condition"
9574 The two substrings are first expanded. The second is then treated as a regular
9575 expression and applied to the first. Because of the pre-expansion, if the
9576 regular expression contains dollar, or backslash characters, they must be
9577 escaped. Care must also be taken if the regular expression contains braces
9578 (curly brackets). A closing brace must be escaped so that it is not taken as a
9579 premature termination of <&'string2'&>. The easiest approach is to use the
9580 &`\N`& feature to disable expansion of the regular expression.
9583 ${if match {$local_part}{\N^\d{3}\N} ...
9585 If the whole expansion string is in double quotes, further escaping of
9586 backslashes is also required.
9588 The condition is true if the regular expression match succeeds.
9589 The regular expression is not required to begin with a circumflex
9590 metacharacter, but if there is no circumflex, the expression is not anchored,
9591 and it may match anywhere in the subject, not just at the start. If you want
9592 the pattern to match at the end of the subject, you must include the &`$`&
9593 metacharacter at an appropriate point.
9595 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
9596 At the start of an &%if%& expansion the values of the numeric variable
9597 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
9598 succeeds causes them to be reset to the substrings of that condition and they
9599 will have these values during the expansion of the success string. At the end
9600 of the &%if%& expansion, the previous values are restored. After testing a
9601 combination of conditions using &%or%&, the subsequent values of the numeric
9602 variables are those of the condition that succeeded.
9604 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9605 .cindex "&%match_address%& expansion condition"
9606 See &*match_local_part*&.
9608 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9609 .cindex "&%match_domain%& expansion condition"
9610 See &*match_local_part*&.
9612 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9613 .cindex "&%match_ip%& expansion condition"
9614 This condition matches an IP address to a list of IP address patterns. It must
9615 be followed by two argument strings. The first (after expansion) must be an IP
9616 address or an empty string. The second (after expansion) is a restricted host
9617 list that can match only an IP address, not a host name. For example:
9619 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
9621 The specific types of host list item that are permitted in the list are:
9624 An IP address, optionally with a CIDR mask.
9626 A single asterisk, which matches any IP address.
9628 An empty item, which matches only if the IP address is empty. This could be
9629 useful for testing for a locally submitted message or one from specific hosts
9630 in a single test such as
9631 . ==== As this is a nested list, any displays it contains must be indented
9632 . ==== as otherwise they are too far to the left.
9634 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
9636 where the first item in the list is the empty string.
9638 The item @[] matches any of the local host's interface addresses.
9640 Lookups are assumed to be &"net-"& style lookups, even if &`net-`& is not
9641 specified. Thus, the following are equivalent:
9643 ${if match_ip{$sender_host_address}{lsearch;/some/file}...
9644 ${if match_ip{$sender_host_address}{net-lsearch;/some/file}...
9646 You do need to specify the &`net-`& prefix if you want to specify a
9647 specific address mask, for example, by using &`net24-`&.
9650 Consult section &<<SECThoslispatip>>& for further details of these patterns.
9652 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9653 .cindex "domain list" "in expansion condition"
9654 .cindex "address list" "in expansion condition"
9655 .cindex "local part list" "in expansion condition"
9656 .cindex "&%match_local_part%& expansion condition"
9657 This condition, together with &%match_address%& and &%match_domain%&, make it
9658 possible to test domain, address, and local part lists within expansions. Each
9659 condition requires two arguments: an item and a list to match. A trivial
9662 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
9664 In each case, the second argument may contain any of the allowable items for a
9665 list of the appropriate type. Also, because the second argument (after
9666 expansion) is a standard form of list, it is possible to refer to a named list.
9667 Thus, you can use conditions like this:
9669 ${if match_domain{$domain}{+local_domains}{...
9671 .cindex "&`+caseful`&"
9672 For address lists, the matching starts off caselessly, but the &`+caseful`&
9673 item can be used, as in all address lists, to cause subsequent items to
9674 have their local parts matched casefully. Domains are always matched
9677 &*Note*&: Host lists are &'not'& supported in this way. This is because
9678 hosts have two identities: a name and an IP address, and it is not clear
9679 how to specify cleanly how such a test would work. However, IP addresses can be
9680 matched using &%match_ip%&.
9682 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
9683 .cindex "PAM authentication"
9684 .cindex "AUTH" "with PAM"
9685 .cindex "Solaris" "PAM support"
9686 .cindex "expansion" "PAM authentication test"
9687 .cindex "&%pam%& expansion condition"
9688 &'Pluggable Authentication Modules'&
9689 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
9690 available in the latest releases of Solaris and in some GNU/Linux
9691 distributions. The Exim support, which is intended for use in conjunction with
9692 the SMTP AUTH command, is available only if Exim is compiled with
9696 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
9697 in some releases of GNU/Linux &%-ldl%& is also needed.
9699 The argument string is first expanded, and the result must be a
9700 colon-separated list of strings. Leading and trailing white space is ignored.
9701 The PAM module is initialized with the service name &"exim"& and the user name
9702 taken from the first item in the colon-separated data string (<&'string1'&>).
9703 The remaining items in the data string are passed over in response to requests
9704 from the authentication function. In the simple case there will only be one
9705 request, for a password, so the data consists of just two strings.
9707 There can be problems if any of the strings are permitted to contain colon
9708 characters. In the usual way, these have to be doubled to avoid being taken as
9709 separators. If the data is being inserted from a variable, the &%sg%& expansion
9710 item can be used to double any existing colons. For example, the configuration
9711 of a LOGIN authenticator might contain this setting:
9713 server_condition = ${if pam{$1:${sg{$2}{:}{::}}}{yes}{no}}
9715 For a PLAIN authenticator you could use:
9717 server_condition = ${if pam{$2:${sg{$3}{:}{::}}}{yes}{no}}
9719 In some operating systems, PAM authentication can be done only from a process
9720 running as root. Since Exim is running as the Exim user when receiving
9721 messages, this means that PAM cannot be used directly in those systems.
9722 A patched version of the &'pam_unix'& module that comes with the
9723 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
9724 The patched module allows one special uid/gid combination, in addition to root,
9725 to authenticate. If you build the patched module to allow the Exim user and
9726 group, PAM can then be used from an Exim authenticator.
9729 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
9730 .cindex "&'pwcheck'& daemon"
9732 .cindex "expansion" "&'pwcheck'& authentication test"
9733 .cindex "&%pwcheck%& expansion condition"
9734 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
9735 This is one way of making it possible for passwords to be checked by a process
9736 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
9737 deprecated. Its replacement is &'saslauthd'& (see below).
9739 The pwcheck support is not included in Exim by default. You need to specify
9740 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
9741 building Exim. For example:
9743 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
9745 You do not need to install the full Cyrus software suite in order to use
9746 the pwcheck daemon. You can compile and install just the daemon alone
9747 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
9748 access to the &_/var/pwcheck_& directory.
9750 The &%pwcheck%& condition takes one argument, which must be the user name and
9751 password, separated by a colon. For example, in a LOGIN authenticator
9752 configuration, you might have this:
9754 server_condition = ${if pwcheck{$1:$2}{1}{0}}
9756 .vitem &*queue_running*&
9757 .cindex "queue runner" "detecting when delivering from"
9758 .cindex "expansion" "queue runner test"
9759 .cindex "&%queue_runnint%& expansion condition"
9760 This condition, which has no data, is true during delivery attempts that are
9761 initiated by queue runner processes, and false otherwise.
9764 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
9766 .cindex "expansion" "Radius authentication"
9767 .cindex "&%radiu%& expansion condition"
9768 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
9769 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
9770 the Radius client configuration file in order to build Exim with Radius
9773 With just that one setting, Exim expects to be linked with the &%radiusclient%&
9774 library, using the original API. If you are using release 0.4.0 or later of
9775 this library, you need to set
9777 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
9779 in &_Local/Makefile_& when building Exim. You can also link Exim with the
9780 &%libradius%& library that comes with FreeBSD. To do this, set
9782 RADIUS_LIB_TYPE=RADLIB
9784 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
9785 You may also have to supply a suitable setting in EXTRALIBS so that the
9786 Radius library can be found when Exim is linked.
9788 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
9789 Radius client library, which calls the Radius server. The condition is true if
9790 the authentication is successful. For example:
9792 server_condition = ${if radius{<arguments>}{yes}{no}}
9796 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
9797 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
9798 .cindex "&'saslauthd'& daemon"
9800 .cindex "expansion" "&'saslauthd'& authentication test"
9801 .cindex "&%saslauthd%& expansion condition"
9802 This condition supports user authentication using the Cyrus &'saslauthd'&
9803 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
9804 Using this daemon is one way of making it possible for passwords to be checked
9805 by a process that is not running as root.
9807 The saslauthd support is not included in Exim by default. You need to specify
9808 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
9809 building Exim. For example:
9811 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
9813 You do not need to install the full Cyrus software suite in order to use
9814 the saslauthd daemon. You can compile and install just the daemon alone
9815 from the Cyrus SASL library.
9817 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
9818 two are mandatory. For example:
9820 server_condition = ${if saslauthd{{$1}{$2}}{1}{0}}
9822 The service and the realm are optional (which is why the arguments are enclosed
9823 in their own set of braces). For details of the meaning of the service and
9824 realm, and how to run the daemon, consult the Cyrus documentation.
9829 .section "Combining expansion conditions"
9830 .cindex "expansion" "combining conditions"
9831 Several conditions can be tested at once by combining them using the &%and%&
9832 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
9833 conditions on their own, and precede their lists of sub-conditions. Each
9834 sub-condition must be enclosed in braces within the overall braces that contain
9835 the list. No repetition of &%if%& is used.
9839 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
9840 .cindex "&""or""& expansion condition"
9841 .cindex "expansion" "&""or""& of conditions"
9842 The sub-conditions are evaluated from left to right. The condition is true if
9843 any one of the sub-conditions is true.
9846 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
9848 When a true sub-condition is found, the following ones are parsed but not
9849 evaluated. If there are several &"match"& sub-conditions the values of the
9850 numeric variables afterwards are taken from the first one that succeeds.
9852 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
9853 .cindex "&""and""& expansion condition"
9854 .cindex "expansion" "&""and""& of conditions"
9855 The sub-conditions are evaluated from left to right. The condition is true if
9856 all of the sub-conditions are true. If there are several &"match"&
9857 sub-conditions, the values of the numeric variables afterwards are taken from
9858 the last one. When a false sub-condition is found, the following ones are
9859 parsed but not evaluated.
9865 .section "Expansion variables" "SECTexpvar"
9866 .cindex "expansion variables" "list of"
9867 This section contains an alphabetical list of all the expansion variables. Some
9868 of them are available only when Exim is compiled with specific options such as
9869 support for TLS or the content scanning extension.
9872 .vitem "&$0$&, &$1$&, etc"
9873 .cindex "numerical variables (&$1$& &$2$& etc)"
9874 When a &%match%& expansion condition succeeds, these variables contain the
9875 captured substrings identified by the regular expression during subsequent
9876 processing of the success string of the containing &%if%& expansion item. They
9877 may also be set externally by some other matching process which precedes the
9878 expansion of the string. For example, the commands available in Exim filter
9879 files include an &%if%& command with its own regular expression matching
9882 .vitem "&$acl_c0$& &-- &$acl_c19$&"
9883 Values can be placed in these variables by the &%set%& modifier in an ACL. The
9884 values persist throughout the lifetime of an SMTP connection. They can be used
9885 to pass information between ACLs and different invocations of the same ACL.
9886 When a message is received, the values of these variables are saved with the
9887 message, and can be accessed by filters, routers, and transports during
9888 subsequent delivery.
9890 .vitem "&$acl_m0$& &-- &$acl_m19$&"
9891 Values can be placed in these variables by the &%set%& modifier in an ACL. They
9892 retain their values while a message is being received, but are reset
9893 afterwards. They are also reset by MAIL, RSET, EHLO, HELO, and after starting a
9894 TLS session. When a message is received, the values of these variables are
9895 saved with the message, and can be accessed by filters, routers, and transports
9896 during subsequent delivery.
9898 .vitem &$acl_verify_message$&
9899 .cindex "&$acl_verify_message$&"
9900 After an address verification has failed, this variable contains the failure
9901 message. It retains its value for use in subsequent modifiers. The message can
9902 be preserved by coding like this:
9904 warn !verify = sender
9905 set acl_m0 = $acl_verify_message
9907 You can use &$acl_verify_message$& during the expansion of the &%message%& or
9908 &%log_message%& modifiers, to include information about the verification
9911 .vitem &$address_data$&
9912 .cindex "&$address_data$&"
9913 This variable is set by means of the &%address_data%& option in routers. The
9914 value then remains with the address while it is processed by subsequent routers
9915 and eventually a transport. If the transport is handling multiple addresses,
9916 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
9917 for more details. &*Note*&: The contents of &$address_data$& are visible in
9920 If &$address_data$& is set when the routers are called from an ACL to verify
9921 a recipient address, the final value is still in the variable for subsequent
9922 conditions and modifiers of the ACL statement. If routing the address caused it
9923 to be redirected to just one address, the child address is also routed as part
9924 of the verification, and in this case the final value of &$address_data$& is
9925 from the child's routing.
9927 If &$address_data$& is set when the routers are called from an ACL to verify a
9928 sender address, the final value is also preserved, but this time in
9929 &$sender_address_data$&, to distinguish it from data from a recipient
9932 In both cases (recipient and sender verification), the value does not persist
9933 after the end of the current ACL statement. If you want to preserve
9934 these values for longer, you can save them in ACL variables.
9936 .vitem &$address_file$&
9937 .cindex "&$address_file$&"
9938 When, as a result of aliasing, forwarding, or filtering, a message is directed
9939 to a specific file, this variable holds the name of the file when the transport
9940 is running. At other times, the variable is empty. For example, using the
9941 default configuration, if user &%r2d2%& has a &_.forward_& file containing
9945 then when the &(address_file)& transport is running, &$address_file$&
9946 contains &"/home/r2d2/savemail"&.
9948 .cindex "Sieve filter" "value of &$address_file$&"
9949 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
9950 then up to the transport configuration to generate an appropriate absolute path
9951 to the relevant file.
9953 .vitem &$address_pipe$&
9954 .cindex "&$address_pipe$&"
9955 When, as a result of aliasing or forwarding, a message is directed to a pipe,
9956 this variable holds the pipe command when the transport is running.
9958 .vitem "&$auth1$& &-- &$auth3$&"
9959 .cindex "&$auth1$&, &$auth2$&, etc"
9960 These variables are used in SMTP authenticators (see chapters
9961 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
9963 .vitem &$authenticated_id$&
9964 .cindex "authentication" "id"
9965 .cindex "&$authenticated_id$&"
9966 When a server successfully authenticates a client it may be configured to
9967 preserve some of the authentication information in the variable
9968 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
9969 user/password authenticator configuration might preserve the user name for use
9970 in the routers. Note that this is not the same information that is saved in
9971 &$sender_host_authenticated$&. When a message is submitted locally (that is,
9972 not over a TCP connection) and if the submitter is not a trusted user,
9973 the value of &$authenticated_id$& is the login name of the calling process.
9975 .vitem &$authenticated_sender$&
9976 .cindex "sender" "authenticated"
9977 .cindex "authentication" "sender"
9978 .cindex "AUTH" "on MAIL command"
9979 .cindex "&$authenticated_sender$&"
9980 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
9981 SMTP MAIL command if it believes the sender is sufficiently trusted, as
9982 described in section &<<SECTauthparamail>>&. Unless the data is the string
9983 &"<>"&, it is set as the authenticated sender of the message, and the value is
9984 available during delivery in the &$authenticated_sender$& variable. If the
9985 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
9987 .cindex "&$qualify_domain$&"
9988 When a message is submitted locally (that is, not over a TCP connection), the
9989 value of &$authenticated_sender$& is an address constructed from the login
9990 name of the calling process and &$qualify_domain$&.
9993 .vitem &$authentication_failed$&
9994 .cindex "authentication" "failure"
9995 .cindex "&$authentication_failed$&"
9996 This variable is set to &"1"& in an Exim server if a client issues an AUTH
9997 command that does not succeed. Otherwise it is set to &"0"&. This makes it
9998 possible to distinguish between &"did not try to authenticate"&
9999 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
10000 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
10001 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
10002 negative response to an AUTH command, including (for example) an attempt to use
10003 an undefined mechanism.
10005 .vitem &$body_linecount$&
10006 .cindex "message body" "line count"
10007 .cindex "body of message" "line count"
10008 .cindex "&$body_linecount$&"
10009 When a message is being received or delivered, this variable contains the
10010 number of lines in the message's body. See also &$message_linecount$&.
10012 .vitem &$body_zerocount$&
10013 .cindex "message body" "binary zero count"
10014 .cindex "body of message" "binary zero count"
10015 .cindex "binary zero" "in message body"
10016 .cindex "&$body_zerocount$&"
10017 When a message is being received or delivered, this variable contains the
10018 number of binary zero bytes in the message's body.
10020 .vitem &$bounce_recipient$&
10021 .cindex "&$bounce_recipient$&"
10022 This is set to the recipient address of a bounce message while Exim is creating
10023 it. It is useful if a customized bounce message text file is in use (see
10024 chapter &<<CHAPemsgcust>>&).
10026 .vitem &$bounce_return_size_limit$&
10027 .cindex "&$bounce_return_size_limit$&"
10028 This contains the value set in the &%bounce_return_size_limit%& option, rounded
10029 up to a multiple of 1000. It is useful when a customized error message text
10030 file is in use (see chapter &<<CHAPemsgcust>>&).
10032 .vitem &$caller_gid$&
10033 .cindex "gid (group id)" "caller"
10034 .cindex "&$caller_gid$&"
10035 The real group id under which the process that called Exim was running. This is
10036 not the same as the group id of the originator of a message (see
10037 &$originator_gid$&). If Exim re-execs itself, this variable in the new
10038 incarnation normally contains the Exim gid.
10040 .vitem &$caller_uid$&
10041 .cindex "uid (user id)" "caller"
10042 .cindex "&$caller_uid$&"
10043 The real user id under which the process that called Exim was running. This is
10044 not the same as the user id of the originator of a message (see
10045 &$originator_uid$&). If Exim re-execs itself, this variable in the new
10046 incarnation normally contains the Exim uid.
10048 .vitem &$compile_date$&
10049 .cindex "&$compile_date$&"
10050 The date on which the Exim binary was compiled.
10052 .vitem &$compile_number$&
10053 .cindex "&$compile_number$&"
10054 The building process for Exim keeps a count of the number
10055 of times it has been compiled. This serves to distinguish different
10056 compilations of the same version of the program.
10058 .vitem &$demime_errorlevel$&
10059 .cindex "&$demime_errorlevel$&"
10060 This variable is available when Exim is compiled with
10061 the content-scanning extension and the obsolete &%demime%& condition. For
10062 details, see section &<<SECTdemimecond>>&.
10064 .vitem &$demime_reason$&
10065 .cindex "&$demime_reason$&"
10066 This variable is available when Exim is compiled with the
10067 content-scanning extension and the obsolete &%demime%& condition. For details,
10068 see section &<<SECTdemimecond>>&.
10071 .vitem &$dnslist_domain$&
10072 .cindex "black list (DNS)"
10073 .cindex "&$dnslist_domain$&"
10074 When a client host is found to be on a DNS (black) list,
10075 the list's domain name is put into this variable so that it can be included in
10076 the rejection message.
10078 .vitem &$dnslist_text$&
10079 .cindex "&$dnslist_text$&"
10080 When a client host is found to be on a DNS (black) list, the
10081 contents of any associated TXT record are placed in this variable.
10083 .vitem &$dnslist_value$&
10084 .cindex "&$dnslist_value$&"
10085 When a client host is found to be on a DNS (black) list,
10086 the IP address from the resource record is placed in this variable.
10087 If there are multiple records, all the addresses are included, comma-space
10091 .cindex "&$domain$&"
10092 When an address is being routed, or delivered on its own, this variable
10093 contains the domain. Global address rewriting happens when a message is
10094 received, so the value of &$domain$& during routing and delivery is the value
10095 after rewriting. &$domain$& is set during user filtering, but not during system
10096 filtering, because a message may have many recipients and the system filter is
10099 When more than one address is being delivered at once (for example, several
10100 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
10101 have the same domain. Transports can be restricted to handling only one domain
10102 at a time if the value of &$domain$& is required at transport time &-- this is
10103 the default for local transports. For further details of the environment in
10104 which local transports are run, see chapter &<<CHAPenvironment>>&.
10106 .cindex "&%delay_warning_condition%&"
10107 At the end of a delivery, if all deferred addresses have the same domain, it is
10108 set in &$domain$& during the expansion of &%delay_warning_condition%&.
10110 The &$domain$& variable is also used in some other circumstances:
10113 When an ACL is running for a RCPT command, &$domain$& contains the domain of
10114 the recipient address. The domain of the &'sender'& address is in
10115 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
10116 normally set during the running of the MAIL ACL. However, if the sender address
10117 is verified with a callout during the MAIL ACL, the sender domain is placed in
10118 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
10119 the &(smtp)& transport.
10122 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10123 &$domain$& contains the domain portion of the address that is being rewritten;
10124 it can be used in the expansion of the replacement address, for example, to
10125 rewrite domains by file lookup.
10128 With one important exception, whenever a domain list is being scanned,
10129 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
10130 a &%sender_domains%& condition in an ACL is being processed, the subject domain
10131 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
10132 that, in a RCPT ACL, the sender domain list can be dependent on the
10133 recipient domain (which is what is in &$domain$& at this time).
10136 .cindex "ETRN" "value of &$domain$&"
10137 .cindex "&%smtp_etrn_command%&"
10138 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
10139 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
10143 .vitem &$domain_data$&
10144 .cindex "&$domain_data$&"
10145 When the &%domains%& option on a router matches a domain by
10146 means of a lookup, the data read by the lookup is available during the running
10147 of the router as &$domain_data$&. In addition, if the driver routes the
10148 address to a transport, the value is available in that transport. If the
10149 transport is handling multiple addresses, the value from the first address is
10152 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
10153 domain by means of a lookup. The data read by the lookup is available during
10154 the rest of the ACL statement. In all other situations, this variable expands
10157 .vitem &$exim_gid$&
10158 .cindex "&$exim_gid$&"
10159 This variable contains the numerical value of the Exim group id.
10161 .vitem &$exim_path$&
10162 .cindex "&$exim_path$&"
10163 This variable contains the path to the Exim binary.
10165 .vitem &$exim_uid$&
10166 .cindex "&$exim_uid$&"
10167 This variable contains the numerical value of the Exim user id.
10169 .vitem &$found_extension$&
10170 .cindex "&$found_extension$&"
10171 This variable is available when Exim is compiled with the
10172 content-scanning extension and the obsolete &%demime%& condition. For details,
10173 see section &<<SECTdemimecond>>&.
10175 .vitem &$header_$&<&'name'&>
10176 This is not strictly an expansion variable. It is expansion syntax for
10177 inserting the message header line with the given name. Note that the name must
10178 be terminated by colon or white space, because it may contain a wide variety of
10179 characters. Note also that braces must &'not'& be used.
10183 When the &%check_local_user%& option is set for a router, the user's home
10184 directory is placed in &$home$& when the check succeeds. In particular, this
10185 means it is set during the running of users' filter files. A router may also
10186 explicitly set a home directory for use by a transport; this can be overridden
10187 by a setting on the transport itself.
10189 When running a filter test via the &%-bf%& option, &$home$& is set to the value
10190 of the environment variable HOME.
10194 When the &(smtp)& transport is expanding its options for encryption using TLS,
10195 &$host$& contains the name of the host to which it is connected. Likewise, when
10196 used in the client part of an authenticator configuration (see chapter
10197 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
10198 client is connected.
10200 .cindex "transport" "filter"
10201 .cindex "filter" "transport filter"
10202 When used in a transport filter (see chapter &<<CHAPtransportgeneric>>&)
10203 &$host$& refers to the host involved in the current connection. When a local
10204 transport is run as a result of a router that sets up a host list, &$host$&
10205 contains the name of the first host.
10207 .vitem &$host_address$&
10208 .cindex "&$host_address$&"
10209 This variable is set to the remote host's IP address whenever &$host$& is set
10210 for a remote connection. It is also set to the IP address that is being checked
10211 when the &%ignore_target_hosts%& option is being processed.
10213 .vitem &$host_data$&
10214 .cindex "&$host_data$&"
10215 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
10216 result of the lookup is made available in the &$host_data$& variable. This
10217 allows you, for example, to do things like this:
10219 deny hosts = net-lsearch;/some/file
10220 message = $host_data
10222 .vitem &$host_lookup_deferred$&
10223 .cindex "host name lookup" "failure of"
10224 .cindex "&$host_lookup_deferred$&"
10225 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
10226 message comes from a remote host and there is an attempt to look up the host's
10227 name from its IP address, and the attempt is not successful, one of these
10228 variables is set to &"1"&.
10231 If the lookup receives a definite negative response (for example, a DNS lookup
10232 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
10235 If there is any kind of problem during the lookup, such that Exim cannot
10236 tell whether or not the host name is defined (for example, a timeout for a DNS
10237 lookup), &$host_lookup_deferred$& is set to &"1"&.
10240 Looking up a host's name from its IP address consists of more than just a
10241 single reverse lookup. Exim checks that a forward lookup of at least one of the
10242 names it receives from a reverse lookup yields the original IP address. If this
10243 is not the case, Exim does not accept the looked up name(s), and
10244 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
10245 IP address (for example, the existence of a PTR record in the DNS) is not
10246 sufficient on its own for the success of a host name lookup. If the reverse
10247 lookup succeeds, but there is a lookup problem such as a timeout when checking
10248 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
10249 &"1"&. See also &$sender_host_name$&.
10251 .vitem &$host_lookup_failed$&
10252 .cindex "&$host_lookup_failed$&"
10253 See &$host_lookup_deferred$&.
10257 .cindex "&$inode$&"
10258 The only time this variable is set is while expanding the &%directory_file%&
10259 option in the &(appendfile)& transport. The variable contains the inode number
10260 of the temporary file which is about to be renamed. It can be used to construct
10261 a unique name for the file.
10263 .vitem &$interface_address$&
10264 .cindex "&$interface_address$&"
10265 As soon as a server starts processing a TCP/IP connection, this variable is set
10266 to the address of the local IP interface, and &$interface_port$& is set to the
10267 port number. These values are therefore available for use in the &"connect"&
10268 ACL. See also the &%-oMi%& command line option. As well as being used in ACLs,
10269 these variable could be used, for example, to make the file name for a TLS
10270 certificate depend on which interface and/or port is being used.
10272 .vitem &$interface_port$&
10273 .cindex "&$interface_port$&"
10274 See &$interface_address$&.
10277 .cindex "&$ldap_dn$&"
10278 This variable, which is available only when Exim is compiled with LDAP support,
10279 contains the DN from the last entry in the most recently successful LDAP
10282 .vitem &$load_average$&
10283 .cindex "&$load_average$&"
10284 This variable contains the system load average, multiplied by 1000 to that it
10285 is an integer. For example, if the load average is 0.21, the value of the
10286 variable is 210. The value is recomputed every time the variable is referenced.
10288 .vitem &$local_part$&
10289 .cindex "&$local_part$&"
10290 When an address is being routed, or delivered on its own, this
10291 variable contains the local part. When a number of addresses are being
10292 delivered together (for example, multiple RCPT commands in an SMTP
10293 session), &$local_part$& is not set.
10295 Global address rewriting happens when a message is received, so the value of
10296 &$local_part$& during routing and delivery is the value after rewriting.
10297 &$local_part$& is set during user filtering, but not during system filtering,
10298 because a message may have many recipients and the system filter is called just
10301 .cindex "&$local_part_prefix$&"
10302 .cindex "&$local_part_suffix$&"
10303 If a local part prefix or suffix has been recognized, it is not included in the
10304 value of &$local_part$& during routing and subsequent delivery. The values of
10305 any prefix or suffix are in &$local_part_prefix$& and
10306 &$local_part_suffix$&, respectively.
10308 When a message is being delivered to a file, pipe, or autoreply transport as a
10309 result of aliasing or forwarding, &$local_part$& is set to the local part of
10310 the parent address, not to the file name or command (see &$address_file$& and
10313 When an ACL is running for a RCPT command, &$local_part$& contains the
10314 local part of the recipient address.
10316 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10317 &$local_part$& contains the local part of the address that is being rewritten;
10318 it can be used in the expansion of the replacement address, for example.
10320 In all cases, all quoting is removed from the local part. For example, for both
10323 "abc:xyz"@test.example
10324 abc\:xyz@test.example
10326 the value of &$local_part$& is
10330 If you use &$local_part$& to create another address, you should always wrap it
10331 inside a quoting operator. For example, in a &(redirect)& router you could
10334 data = ${quote_local_part:$local_part}@new.domain.example
10336 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
10337 to process local parts in a case-dependent manner in a router, you can set the
10338 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
10340 .vitem &$local_part_data$&
10341 .cindex "&$local_part_data$&"
10342 When the &%local_parts%& option on a router matches a local part by means of a
10343 lookup, the data read by the lookup is available during the running of the
10344 router as &$local_part_data$&. In addition, if the driver routes the address
10345 to a transport, the value is available in that transport. If the transport is
10346 handling multiple addresses, the value from the first address is used.
10348 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
10349 matches a local part by means of a lookup. The data read by the lookup is
10350 available during the rest of the ACL statement. In all other situations, this
10351 variable expands to nothing.
10353 .vitem &$local_part_prefix$&
10354 .cindex "&$local_part_prefix$&"
10355 When an address is being routed or delivered, and a
10356 specific prefix for the local part was recognized, it is available in this
10357 variable, having been removed from &$local_part$&.
10359 .vitem &$local_part_suffix$&
10360 .cindex "&$local_part_suffix$&"
10361 When an address is being routed or delivered, and a
10362 specific suffix for the local part was recognized, it is available in this
10363 variable, having been removed from &$local_part$&.
10365 .vitem &$local_scan_data$&
10366 .cindex "&$local_scan_data$&"
10367 This variable contains the text returned by the &[local_scan()]& function when
10368 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
10370 .vitem &$local_user_gid$&
10371 .cindex "&$local_user_gid$&"
10372 See &$local_user_uid$&.
10374 .vitem &$local_user_uid$&
10375 .cindex "&$local_user_uid$&"
10376 This variable and &$local_user_gid$& are set to the uid and gid after the
10377 &%check_local_user%& router precondition succeeds. This means that their values
10378 are available for the remaining preconditions (&%senders%&, &%require_files%&,
10379 and &%condition%&), for the &%address_data%& expansion, and for any
10380 router-specific expansions. At all other times, the values in these variables
10381 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
10383 .vitem &$localhost_number$&
10384 .cindex "&$localhost_number$&"
10385 This contains the expanded value of the
10386 &%localhost_number%& option. The expansion happens after the main options have
10389 .vitem &$log_inodes$&
10390 .cindex "&$log_inodes$&"
10391 The number of free inodes in the disk partition where Exim's
10392 log files are being written. The value is recalculated whenever the variable is
10393 referenced. If the relevant file system does not have the concept of inodes,
10394 the value of is -1. See also the &%check_log_inodes%& option.
10396 .vitem &$log_space$&
10397 .cindex "&$log_space$&"
10398 The amount of free space (as a number of kilobytes) in the disk
10399 partition where Exim's log files are being written. The value is recalculated
10400 whenever the variable is referenced. If the operating system does not have the
10401 ability to find the amount of free space (only true for experimental systems),
10402 the space value is -1. See also the &%check_log_space%& option.
10405 .vitem &$mailstore_basename$&
10406 .cindex "&$mailstore_basename$&"
10407 This variable is set only when doing deliveries in &"mailstore"& format in the
10408 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
10409 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
10410 contains the basename of the files that are being written, that is, the name
10411 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
10414 .vitem &$malware_name$&
10415 .cindex "&$malware_name$&"
10416 This variable is available when Exim is compiled with the
10417 content-scanning extension. It is set to the name of the virus that was found
10418 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
10421 .vitem &$message_age$&
10422 .cindex "message" "age of"
10423 .cindex "&$message_age$&"
10424 This variable is set at the start of a delivery attempt to contain the number
10425 of seconds since the message was received. It does not change during a single
10428 .vitem &$message_body$&
10429 .cindex "body of message" "expansion variable"
10430 .cindex "message body" "in expansion"
10431 .cindex "binary zero" "in message body"
10432 .cindex "&$message_body$&"
10433 This variable contains the initial portion of a message's
10434 body while it is being delivered, and is intended mainly for use in filter
10435 files. The maximum number of characters of the body that are put into the
10436 variable is set by the &%message_body_visible%& configuration option; the
10437 default is 500. Newlines are converted into spaces to make it easier to search
10438 for phrases that might be split over a line break.
10439 Binary zeros are also converted into spaces.
10441 .vitem &$message_body_end$&
10442 .cindex "body of message" "expansion variable"
10443 .cindex "message body" "in expansion"
10444 .cindex "&$message_body_end$&"
10445 This variable contains the final portion of a message's
10446 body while it is being delivered. The format and maximum size are as for
10449 .vitem &$message_body_size$&
10450 .cindex "body of message" "size"
10451 .cindex "message body" "size"
10452 .cindex "&$message_body_size$&"
10453 When a message is being delivered, this variable contains the size of the body
10454 in bytes. The count starts from the character after the blank line that
10455 separates the body from the header. Newlines are included in the count. See
10456 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
10458 .vitem &$message_exim_id$&
10459 .cindex "&$message_exim_id$&"
10460 When a message is being received or delivered, this variable contains the
10461 unique message id that is generated and used by Exim to identify the message.
10462 An id is not created for a message until after its header has been successfully
10463 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
10464 line; it is the local id that Exim assigns to the message, for example:
10465 &`1BXTIK-0001yO-VA`&.
10467 .vitem &$message_headers$&
10468 This variable contains a concatenation of all the header lines when a message
10469 is being processed, except for lines added by routers or transports. The header
10470 lines are separated by newline characters.
10472 .vitem &$message_id$&
10473 This is an old name for &$message_exim_id$&, which is now deprecated.
10475 .vitem &$message_linecount$&
10476 .cindex "&$message_linecount$&"
10477 This variable contains the total number of lines in the header and body of the
10478 message. Compare &$body_linecount$&, which is the count for the body only.
10479 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
10480 number of lines received. Before delivery happens (that is, before filters,
10481 routers, and transports run) the count is increased to include the
10482 &'Received:'& header line that Exim standardly adds, and also any other header
10483 lines that are added by ACLs. The blank line that separates the message header
10484 from the body is not counted. Here is an example of the use of this variable in
10487 deny message = Too many lines in message header
10489 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
10491 In the MAIL and RCPT ACLs, the value is zero because at that stage the
10492 message has not yet been received.
10494 .vitem &$message_size$&
10495 .cindex "size" "of message"
10496 .cindex "message" "size"
10497 .cindex "&$message_size$&"
10498 When a message is being processed, this variable contains its size in bytes. In
10499 most cases, the size includes those headers that were received with the
10500 message, but not those (such as &'Envelope-to:'&) that are added to individual
10501 deliveries as they are written. However, there is one special case: during the
10502 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
10503 doing a delivery in maildir format, the value of &$message_size$& is the
10504 precise size of the file that has been written. See also
10505 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
10507 .cindex "RCPT" "value of &$message_size$&"
10508 While running an ACL at the time of an SMTP RCPT command, &$message_size$&
10509 contains the size supplied on the MAIL command, or -1 if no size was given. The
10510 value may not, of course, be truthful.
10512 .vitem &$mime_$&&'xxx'&
10513 A number of variables whose names start with &$mime$& are
10514 available when Exim is compiled with the content-scanning extension. For
10515 details, see section &<<SECTscanmimepart>>&.
10517 .vitem "&$n0$& &-- &$n9$&"
10518 These variables are counters that can be incremented by means
10519 of the &%add%& command in filter files.
10521 .vitem &$original_domain$&
10522 .cindex "&$domain$&"
10523 .cindex "&$original_domain$&"
10524 When a top-level address is being processed for delivery, this contains the
10525 same value as &$domain$&. However, if a &"child"& address (for example,
10526 generated by an alias, forward, or filter file) is being processed, this
10527 variable contains the domain of the original address. This differs from
10528 &$parent_domain$& only when there is more than one level of aliasing or
10529 forwarding. When more than one address is being delivered in a single transport
10530 run, &$original_domain$& is not set.
10532 If a new address is created by means of a &%deliver%& command in a system
10533 filter, it is set up with an artificial &"parent"& address. This has the local
10534 part &'system-filter'& and the default qualify domain.
10536 .vitem &$original_local_part$&
10537 .cindex "&$local_part$&"
10538 .cindex "&$original_local_part$&"
10539 When a top-level address is being processed for delivery, this contains the
10540 same value as &$local_part$&, unless a prefix or suffix was removed from the
10541 local part, because &$original_local_part$& always contains the full local
10542 part. When a &"child"& address (for example, generated by an alias, forward, or
10543 filter file) is being processed, this variable contains the full local part of
10544 the original address.
10546 If the router that did the redirection processed the local part
10547 case-insensitively, the value in &$original_local_part$& is in lower case.
10548 This variable differs from &$parent_local_part$& only when there is more than
10549 one level of aliasing or forwarding. When more than one address is being
10550 delivered in a single transport run, &$original_local_part$& is not set.
10552 If a new address is created by means of a &%deliver%& command in a system
10553 filter, it is set up with an artificial &"parent"& address. This has the local
10554 part &'system-filter'& and the default qualify domain.
10556 .vitem &$originator_gid$&
10557 .cindex "gid (group id)" "of originating user"
10558 .cindex "sender" "gid"
10559 .cindex "&$caller_gid$&"
10560 .cindex "&$originator_gid$&"
10561 This variable contains the value of &$caller_gid$& that was set when the
10562 message was received. For messages received via the command line, this is the
10563 gid of the sending user. For messages received by SMTP over TCP/IP, this is
10564 normally the gid of the Exim user.
10566 .vitem &$originator_uid$&
10567 .cindex "uid (user id)" "of originating user"
10568 .cindex "sender" "uid"
10569 .cindex "&$caller_uid$&"
10570 .cindex "&$originaltor_uid$&"
10571 The value of &$caller_uid$& that was set when the message was received. For
10572 messages received via the command line, this is the uid of the sending user.
10573 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
10576 .vitem &$parent_domain$&
10577 .cindex "&$parent_domain$&"
10578 This variable is similar to &$original_domain$& (see
10579 above), except that it refers to the immediately preceding parent address.
10581 .vitem &$parent_local_part$&
10582 .cindex "&$parent_local_part$&"
10583 This variable is similar to &$original_local_part$&
10584 (see above), except that it refers to the immediately preceding parent address.
10587 .cindex "pid (process id)" "of current process"
10589 This variable contains the current process id.
10591 .vitem &$pipe_addresses$&
10592 .cindex "filter" "transport filter"
10593 .cindex "transport" "filter"
10594 .cindex "&$pipe_addresses$&"
10595 This is not an expansion variable, but is mentioned here because the string
10596 &`$pipe_addresses`& is handled specially in the command specification for the
10597 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
10598 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
10599 It cannot be used in general expansion strings, and provokes an &"unknown
10600 variable"& error if encountered.
10602 .vitem &$primary_hostname$&
10603 .cindex "&$primary_hostname$&"
10604 This variable contains the value set by &%primary_hostname%& in the
10605 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
10606 a single-component name, Exim calls &[gethostbyname()]& (or
10607 &[getipnodebyname()]& where available) in an attempt to acquire a fully
10608 qualified host name. See also &$smtp_active_hostname$&.
10611 .vitem &$prvscheck_address$&
10612 This variable is used in conjunction with the &%prvscheck%& expansion item,
10613 which is described in sections &<<SECTexpansionitems>>& and
10614 &<<SECTverifyPRVS>>&.
10616 .vitem &$prvscheck_keynum$&
10617 This variable is used in conjunction with the &%prvscheck%& expansion item,
10618 which is described in sections &<<SECTexpansionitems>>& and
10619 &<<SECTverifyPRVS>>&.
10621 .vitem &$prvscheck_result$&
10622 This variable is used in conjunction with the &%prvscheck%& expansion item,
10623 which is described in sections &<<SECTexpansionitems>>& and
10624 &<<SECTverifyPRVS>>&.
10626 .vitem &$qualify_domain$&
10627 .cindex "&$qualify_domain$&"
10628 The value set for the &%qualify_domain%& option in the configuration file.
10630 .vitem &$qualify_recipient$&
10631 .cindex "&$qualify_recipient$&"
10632 The value set for the &%qualify_recipient%& option in the configuration file,
10633 or if not set, the value of &$qualify_domain$&.
10635 .vitem &$rcpt_count$&
10636 .cindex "&$rcpt_count$&"
10637 When a message is being received by SMTP, this variable contains the number of
10638 RCPT commands received for the current message. If this variable is used in a
10639 RCPT ACL, its value includes the current command.
10641 .vitem &$rcpt_defer_count$&
10642 .cindex "&$rcpt_defer_count$&"
10643 When a message is being received by SMTP, this variable contains the number of
10644 RCPT commands in the current message that have previously been rejected with a
10645 temporary (4&'xx'&) response.
10647 .vitem &$rcpt_fail_count$&
10648 .cindex "&$rcpt_fail_count$&"
10649 When a message is being received by SMTP, this variable contains the number of
10650 RCPT commands in the current message that have previously been rejected with a
10651 permanent (5&'xx'&) response.
10653 .vitem &$received_count$&
10654 .cindex "&$received_count$&"
10655 This variable contains the number of &'Received:'& header lines in the message,
10656 including the one added by Exim (so its value is always greater than zero). It
10657 is available in the DATA ACL, the non-SMTP ACL, and while routing and
10660 .vitem &$received_for$&
10661 .cindex "&$received_for$&"
10662 If there is only a single recipient address in an incoming message, this
10663 variable contains that address when the &'Received:'& header line is being
10664 built. The value is copied after recipient rewriting has happened, but before
10665 the &[local_scan()]& function is run.
10667 .vitem &$received_protocol$&
10668 .cindex "&$received_protocol$&"
10669 When a message is being processed, this variable contains the name of the
10670 protocol by which it was received. Most of the names used by Exim are defined
10671 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
10672 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
10673 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
10674 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
10675 connection and the client was successfully authenticated.
10677 Exim uses the protocol name &"smtps"& for the case when encryption is
10678 automatically set up on connection without the use of STARTTLS (see
10679 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
10680 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
10681 where the client initially uses EHLO, sets up an encrypted connection using
10682 STARTTLS, and then uses HELO afterwards.
10684 The &%-oMr%& option provides a way of specifying a custom protocol name for
10685 messages that are injected locally by trusted callers. This is commonly used to
10686 identify messages that are being re-injected after some kind of scanning.
10688 .vitem &$received_time$&
10689 .cindex "&$received_time$&"
10690 This variable contains the date and time when the current message was received,
10691 as a number of seconds since the start of the Unix epoch.
10693 .vitem &$recipient_data$&
10694 .cindex "&$recipient_data$&"
10695 This variable is set after an indexing lookup success in an ACL &%recipients%&
10696 condition. It contains the data from the lookup, and the value remains set
10697 until the next &%recipients%& test. Thus, you can do things like this:
10699 &`require recipients = cdb*@;/some/file`&
10700 &`deny `&&'some further test involving'& &`$recipient_data`&
10702 &*Warning*&: This variable is set only when a lookup is used as an indexing
10703 method in the address list, using the semicolon syntax as in the example above.
10704 The variable is not set for a lookup that is used as part of the string
10705 expansion that all such lists undergo before being interpreted.
10707 .vitem &$recipient_verify_failure$&
10708 .cindex "&$recipient_verify_failure$&"
10709 In an ACL, when a recipient verification fails, this variable contains
10710 information about the failure. It is set to one of the following words:
10713 &"qualify"&: The address was unqualified (no domain), and the message
10714 was neither local nor came from an exempted host.
10717 &"route"&: Routing failed.
10720 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
10721 or before the MAIL command (that is, on initial connection, HELO, or
10725 &"recipient"&: The RCPT command in a callout was rejected.
10728 &"postmaster"&: The postmaster check in a callout was rejected.
10731 The main use of this variable is expected to be to distinguish between
10732 rejections of MAIL and rejections of RCPT.
10734 .vitem &$recipients$&
10735 .cindex "&$recipients$&"
10736 This variable contains a list of envelope recipients for a
10737 message. A comma and a space separate the addresses in the replacement text.
10738 However, the variable is not generally available, to prevent exposure of Bcc
10739 recipients in unprivileged users' filter files. You can use &$recipients$& only
10740 in these two cases:
10743 In a system filter file.
10745 In the ACLs associated with the DATA command, that is, the ACLs defined by
10746 &%acl_smtp_predata%& and &%acl_smtp_data%&.
10750 .vitem &$recipients_count$&
10751 .cindex "&$recipients_count$&"
10752 When a message is being processed, this variable contains the number of
10753 envelope recipients that came with the message. Duplicates are not excluded
10754 from the count. While a message is being received over SMTP, the number
10755 increases for each accepted recipient. It can be referenced in an ACL.
10757 .vitem &$reply_address$&
10758 .cindex "&$reply_address$&"
10759 When a message is being processed, this variable contains the contents of the
10760 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
10761 contents of the &'From:'& header line. Apart from the removal of leading
10762 white space, the value is not processed in any way. In particular, no RFC 2047
10763 decoding or character code translation takes place.
10765 .vitem &$return_path$&
10766 .cindex "&$return_path$&"
10767 When a message is being delivered, this variable contains the return path &--
10768 the sender field that will be sent as part of the envelope. It is not enclosed
10769 in <> characters. At the start of routing an address, &$return_path$& has the
10770 same value as &$sender_address$&, but if, for example, an incoming message to a
10771 mailing list has been expanded by a router which specifies a different address
10772 for bounce messages, &$return_path$& subsequently contains the new bounce
10773 address, whereas &$sender_address$& always contains the original sender address
10774 that was received with the message. In other words, &$sender_address$& contains
10775 the incoming envelope sender, and &$return_path$& contains the outgoing
10778 .vitem &$return_size_limit$&
10779 .cindex "&$return_size_limit$&"
10780 This is an obsolete name for &$bounce_return_size_limit$&.
10783 .cindex "return code" "from &%run%& expansion"
10784 .cindex "&$runrc$&"
10785 This variable contains the return code from a command that is run by the
10786 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
10787 assume the order in which option values are expanded, except for those
10788 preconditions whose order of testing is documented. Therefore, you cannot
10789 reliably expect to set &$runrc$& by the expansion of one option, and use it in
10792 .vitem &$self_hostname$&
10793 .cindex "&%self%& option" "value of host name"
10794 .cindex "&$self_hostname$&"
10795 When an address is routed to a supposedly remote host that turns out to be the
10796 local host, what happens is controlled by the &%self%& generic router option.
10797 One of its values causes the address to be passed to another router. When this
10798 happens, &$self_hostname$& is set to the name of the local host that the
10799 original router encountered. In other circumstances its contents are null.
10801 .vitem &$sender_address$&
10802 .cindex "&$sender_address$&"
10803 When a message is being processed, this variable contains the sender's address
10804 that was received in the message's envelope. For bounce messages, the value of
10805 this variable is the empty string. See also &$return_path$&.
10807 .vitem &$sender_address_data$&
10808 .cindex "&$address_data$&"
10809 .cindex "&$sender_address_data$&"
10810 If &$address_data$& is set when the routers are called from an ACL to verify a
10811 sender address, the final value is preserved in &$sender_address_data$&, to
10812 distinguish it from data from a recipient address. The value does not persist
10813 after the end of the current ACL statement. If you want to preserve it for
10814 longer, you can save it in an ACL variable.
10816 .vitem &$sender_address_domain$&
10817 .cindex "&$sender_address_domain$&"
10818 The domain portion of &$sender_address$&.
10820 .vitem &$sender_address_local_part$&
10821 .cindex "&$sender_address_local_part$&"
10822 The local part portion of &$sender_address$&.
10824 .vitem &$sender_data$&
10825 .cindex "&$sender_data$&"
10826 This variable is set after a lookup success in an ACL &%senders%& condition or
10827 in a router &%senders%& option. It contains the data from the lookup, and the
10828 value remains set until the next &%senders%& test. Thus, you can do things like
10831 &`require senders = cdb*@;/some/file`&
10832 &`deny `&&'some further test involving'& &`$sender_data`&
10834 &*Warning*&: This variable is set only when a lookup is used as an indexing
10835 method in the address list, using the semicolon syntax as in the example above.
10836 The variable is not set for a lookup that is used as part of the string
10837 expansion that all such lists undergo before being interpreted.
10839 .vitem &$sender_fullhost$&
10840 .cindex "&$sender_fullhost$&"
10841 When a message is received from a remote host, this variable contains the host
10842 name and IP address in a single string. It ends with the IP address in square
10843 brackets, followed by a colon and a port number if the logging of ports is
10844 enabled. The format of the rest of the string depends on whether the host
10845 issued a HELO or EHLO SMTP command, and whether the host name was verified by
10846 looking up its IP address. (Looking up the IP address can be forced by the
10847 &%host_lookup%& option, independent of verification.) A plain host name at the
10848 start of the string is a verified host name; if this is not present,
10849 verification either failed or was not requested. A host name in parentheses is
10850 the argument of a HELO or EHLO command. This is omitted if it is identical to
10851 the verified host name or to the host's IP address in square brackets.
10853 .vitem &$sender_helo_name$&
10854 .cindex "&$sender_helo_name$&"
10855 When a message is received from a remote host that has issued a HELO or EHLO
10856 command, the argument of that command is placed in this variable. It is also
10857 set if HELO or EHLO is used when a message is received using SMTP locally via
10858 the &%-bs%& or &%-bS%& options.
10860 .vitem &$sender_host_address$&
10861 .cindex "&$sender_host_address$&"
10862 When a message is received from a remote host, this variable contains that
10863 host's IP address. For locally submitted messages, it is empty.
10865 .vitem &$sender_host_authenticated$&
10866 .cindex "&$sender_host_authenticated$&"
10867 This variable contains the name (not the public name) of the authenticator
10868 driver that successfully authenticated the client from which the message was
10869 received. It is empty if there was no successful authentication. See also
10870 &$authenticated_id$&.
10872 .vitem &$sender_host_name$&
10873 .cindex "&$sender_host_name$&"
10874 When a message is received from a remote host, this variable contains the
10875 host's name as obtained by looking up its IP address. For messages received by
10876 other means, this variable is empty.
10878 .cindex "&$host_lookup_failed$&"
10879 If the host name has not previously been looked up, a reference to
10880 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
10881 A looked up name is accepted only if it leads back to the original IP address
10882 via a forward lookup. If either the reverse or the forward lookup fails to find
10883 any data, or if the forward lookup does not yield the original IP address,
10884 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
10886 .cindex "&$host_lookup_deferred$&"
10887 However, if either of the lookups cannot be completed (for example, there is a
10888 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
10889 &$host_lookup_failed$& remains set to &"0"&.
10891 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
10892 host name again if there is a subsequent reference to &$sender_host_name$&
10893 in the same Exim process, but it does try again if &$sender_host_deferred$&
10896 Exim does not automatically look up every calling host's name. If you want
10897 maximum efficiency, you should arrange your configuration so that it avoids
10898 these lookups altogether. The lookup happens only if one or more of the
10899 following are true:
10902 A string containing &$sender_host_name$& is expanded.
10904 The calling host matches the list in &%host_lookup%&. In the default
10905 configuration, this option is set to *, so it must be changed if lookups are
10906 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
10908 Exim needs the host name in order to test an item in a host list. The items
10909 that require this are described in sections &<<SECThoslispatnam>>& and
10910 &<<SECThoslispatnamsk>>&.
10912 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
10913 In this case, the host name is required to compare with the name quoted in any
10914 EHLO or HELO commands that the client issues.
10916 The remote host issues a EHLO or HELO command that quotes one of the
10917 domains in &%helo_lookup_domains%&. The default value of this option is
10918 . ==== As this is a nested list, any displays it contains must be indented
10919 . ==== as otherwise they are too far to the left.
10921 helo_lookup_domains = @ : @[]
10923 which causes a lookup if a remote host (incorrectly) gives the server's name or
10924 IP address in an EHLO or HELO command.
10928 .vitem &$sender_host_port$&
10929 .cindex "&$sender_host_port$&"
10930 When a message is received from a remote host, this variable contains the port
10931 number that was used on the remote host.
10933 .vitem &$sender_ident$&
10934 .cindex "&$sender_ident$&"
10935 When a message is received from a remote host, this variable contains the
10936 identification received in response to an RFC 1413 request. When a message has
10937 been received locally, this variable contains the login name of the user that
10940 .vitem &$sender_rate_$&&'xxx'&
10941 A number of variables whose names begin &$sender_rate_$& are set as part of the
10942 &%ratelimit%& ACL condition. Details are given in section
10943 &<<SECTratelimiting>>&.
10945 .vitem &$sender_rcvhost$&
10946 .cindex "DNS" "reverse lookup"
10947 .cindex "reverse DNS lookup"
10948 .cindex "&$sender_rcvhost$&"
10949 This is provided specifically for use in &'Received:'& headers. It starts with
10950 either the verified host name (as obtained from a reverse DNS lookup) or, if
10951 there is no verified host name, the IP address in square brackets. After that
10952 there may be text in parentheses. When the first item is a verified host name,
10953 the first thing in the parentheses is the IP address in square brackets,
10954 followed by a colon and a port number if port logging is enabled. When the
10955 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
10958 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
10959 was used and its argument was not identical to the real host name or IP
10960 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
10961 all three items are present in the parentheses, a newline and tab are inserted
10962 into the string, to improve the formatting of the &'Received:'& header.
10964 .vitem &$sender_verify_failure$&
10965 .cindex "&$sender_verify_failure$&"
10966 In an ACL, when a sender verification fails, this variable contains information
10967 about the failure. The details are the same as for
10968 &$recipient_verify_failure$&.
10970 .vitem &$smtp_active_hostname$&
10971 .cindex "&$smtp_active_hostname$&"
10972 During an SMTP session, this variable contains the value of the active host
10973 name, as specified by the &%smtp_active_hostname%& option. The value of
10974 &$smtp_active_hostname$& is saved with any message that is received, so its
10975 value can be consulted during routing and delivery.
10977 .vitem &$smtp_command$&
10978 .cindex "&$smtp_command$&"
10979 During the processing of an incoming SMTP command, this variable contains the
10980 entire command. This makes it possible to distinguish between HELO and EHLO in
10981 the HELO ACL, and also to distinguish between commands such as these:
10986 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
10987 command, the address in &$smtp_command$& is the original address before any
10988 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
10989 the address after SMTP-time rewriting.
10991 .vitem &$smtp_command_argument$&
10992 .cindex "SMTP command" "argument for"
10993 .cindex "&$smtp_command_argument$&"
10994 While an ACL is running to check an SMTP command, this variable contains the
10995 argument, that is, the text that follows the command name, with leading white
10996 space removed. Following the introduction of &$smtp_command$&, this variable is
10997 somewhat redundant, but is retained for backwards compatibility.
10999 .vitem "&$sn0$& &-- &$sn9$&"
11000 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
11001 that were current at the end of the system filter file. This allows a system
11002 filter file to set values that can be tested in users' filter files. For
11003 example, a system filter could set a value indicating how likely it is that a
11004 message is junk mail.
11006 .vitem &$spam_$&&'xxx'&
11007 A number of variables whose names start with &$spam$& are available when Exim
11008 is compiled with the content-scanning extension. For details, see section
11009 &<<SECTscanspamass>>&.
11012 .vitem &$spool_directory$&
11013 .cindex "&$spool_directory$&"
11014 The name of Exim's spool directory.
11016 .vitem &$spool_inodes$&
11017 .cindex "&$spool_inodes$&"
11018 The number of free inodes in the disk partition where Exim's spool files are
11019 being written. The value is recalculated whenever the variable is referenced.
11020 If the relevant file system does not have the concept of inodes, the value of
11021 is -1. See also the &%check_spool_inodes%& option.
11023 .vitem &$spool_space$&
11024 .cindex "&$spool_space$&"
11025 The amount of free space (as a number of kilobytes) in the disk partition where
11026 Exim's spool files are being written. The value is recalculated whenever the
11027 variable is referenced. If the operating system does not have the ability to
11028 find the amount of free space (only true for experimental systems), the space
11029 value is -1. For example, to check in an ACL that there is at least 50
11030 megabytes free on the spool, you could write:
11032 condition = ${if > {$spool_space}{50000}}
11034 See also the &%check_spool_space%& option.
11037 .vitem &$thisaddress$&
11038 .cindex "&$thisaddress$&"
11039 This variable is set only during the processing of the &%foranyaddress%&
11040 command in a filter file. Its use is explained in the description of that
11041 command, which can be found in the separate document entitled &'Exim's
11042 interfaces to mail filtering'&.
11044 .vitem &$tls_certificate_verified$&
11045 .cindex "&$tls_certificate_verified$&"
11046 This variable is set to &"1"& if a TLS certificate was verified when the
11047 message was received, and &"0"& otherwise.
11049 .vitem &$tls_cipher$&
11050 .cindex "&$tls_cipher$&"
11051 When a message is received from a remote host over an encrypted SMTP
11052 connection, this variable is set to the cipher suite that was negotiated, for
11053 example DES-CBC3-SHA. In other circumstances, in particular, for message
11054 received over unencrypted connections, the variable is empty. See chapter
11055 &<<CHAPTLS>>& for details of TLS support.
11057 .vitem &$tls_peerdn$&
11058 .cindex "&$tls_peerdn$&"
11059 When a message is received from a remote host over an encrypted SMTP
11060 connection, and Exim is configured to request a certificate from the client,
11061 the value of the Distinguished Name of the certificate is made available in the
11062 &$tls_peerdn$& during subsequent processing.
11064 .vitem &$tod_bsdinbox$&
11065 .cindex "&$tod_bsdinbox$&"
11066 The time of day and the date, in the format required for BSD-style mailbox
11067 files, for example: Thu Oct 17 17:14:09 1995.
11069 .vitem &$tod_epoch$&
11070 .cindex "&$tod_epoch$&"
11071 The time and date as a number of seconds since the start of the Unix epoch.
11073 .vitem &$tod_full$&
11074 .cindex "&$tod_full$&"
11075 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
11076 +0100. The timezone is always given as a numerical offset from UTC, with
11077 positive values used for timezones that are ahead (east) of UTC, and negative
11078 values for those that are behind (west).
11081 .cindex "&$tod_log$&"
11082 The time and date in the format used for writing Exim's log files, for example:
11083 1995-10-12 15:32:29, but without a timezone.
11085 .vitem &$tod_logfile$&
11086 .cindex "&$tod_logfile$&"
11087 This variable contains the date in the format yyyymmdd. This is the format that
11088 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
11091 .vitem &$tod_zone$&
11092 .cindex "&$tod_zone$&"
11093 This variable contains the numerical value of the local timezone, for example:
11096 .vitem &$tod_zulu$&
11097 .cindex "&$tod_zulu$&"
11098 This variable contains the UTC date and time in &"Zulu"& format, as specified
11099 by ISO 8601, for example: 20030221154023Z.
11102 .cindex "&$value$&"
11103 This variable contains the result of an expansion lookup, extraction operation,
11104 or external command, as described above.
11106 .vitem &$version_number$&
11107 .cindex "&$version_number$&"
11108 The version number of Exim.
11110 .vitem &$warn_message_delay$&
11111 .cindex "&$warn_message_delay$&"
11112 This variable is set only during the creation of a message warning about a
11113 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11115 .vitem &$warn_message_recipients$&
11116 .cindex "&$warn_message_recipients$&"
11117 This variable is set only during the creation of a message warning about a
11118 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11124 . ////////////////////////////////////////////////////////////////////////////
11125 . ////////////////////////////////////////////////////////////////////////////
11127 .chapter "Embedded Perl" "CHAPperl"
11128 .scindex IIDperl "Perl" "calling from Exim"
11129 Exim can be built to include an embedded Perl interpreter. When this is done,
11130 Perl subroutines can be called as part of the string expansion process. To make
11131 use of the Perl support, you need version 5.004 or later of Perl installed on
11132 your system. To include the embedded interpreter in the Exim binary, include
11137 in your &_Local/Makefile_& and then build Exim in the normal way.
11140 .section "Setting up so Perl can be used"
11141 .cindex "&%perl_startup%&"
11142 Access to Perl subroutines is via a global configuration option called
11143 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
11144 no &%perl_startup%& option in the Exim configuration file then no Perl
11145 interpreter is started and there is almost no overhead for Exim (since none of
11146 the Perl library will be paged in unless used). If there is a &%perl_startup%&
11147 option then the associated value is taken to be Perl code which is executed in
11148 a newly created Perl interpreter.
11150 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
11151 need backslashes before any characters to escape special meanings. The option
11152 should usually be something like
11154 perl_startup = do '/etc/exim.pl'
11156 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
11157 use from Exim. Exim can be configured either to start up a Perl interpreter as
11158 soon as it is entered, or to wait until the first time it is needed. Starting
11159 the interpreter at the beginning ensures that it is done while Exim still has
11160 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
11161 fact used in a particular run. Also, note that this does not mean that Exim is
11162 necessarily running as root when Perl is called at a later time. By default,
11163 the interpreter is started only when it is needed, but this can be changed in
11167 .cindex "&%perl_at_start%&"
11168 Setting &%perl_at_start%& (a boolean option) in the configuration requests
11169 a startup when Exim is entered.
11171 The command line option &%-ps%& also requests a startup when Exim is entered,
11172 overriding the setting of &%perl_at_start%&.
11175 There is also a command line option &%-pd%& (for delay) which suppresses the
11176 initial startup, even if &%perl_at_start%& is set.
11179 .section "Calling Perl subroutines"
11180 When the configuration file includes a &%perl_startup%& option you can make use
11181 of the string expansion item to call the Perl subroutines that are defined
11182 by the &%perl_startup%& code. The operator is used in any of the following
11186 ${perl{foo}{argument}}
11187 ${perl{foo}{argument1}{argument2} ... }
11189 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
11190 arguments may be passed. Passing more than this results in an expansion failure
11191 with an error message of the form
11193 Too many arguments passed to Perl subroutine "foo" (max is 8)
11195 The return value of the Perl subroutine is evaluated in a scalar context before
11196 it is passed back to Exim to be inserted into the expanded string. If the
11197 return value is &'undef'&, the expansion is forced to fail in the same way as
11198 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
11199 by obeying Perl's &%die%& function, the expansion fails with the error message
11200 that was passed to &%die%&.
11203 .section "Calling Exim functions from Perl"
11204 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
11205 is available to call back into Exim's string expansion function. For example,
11208 my $lp = Exim::expand_string('$local_part');
11210 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
11211 Note those are single quotes and not double quotes to protect against
11212 &$local_part$& being interpolated as a Perl variable.
11214 If the string expansion is forced to fail by a &"fail"& item, the result of
11215 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
11216 expansion string, the Perl call from the original expansion string fails with
11217 an appropriate error message, in the same way as if &%die%& were used.
11219 .cindex "debugging" "from embedded Perl"
11220 .cindex "log" "writing from embedded Perl"
11221 Two other Exim functions are available for use from within Perl code.
11222 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
11223 debugging is enabled. If you want a newline at the end, you must supply it.
11224 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
11225 timestamp. In this case, you should not supply a terminating newline.
11228 .section "Use of standard output and error by Perl"
11229 .cindex "Perl" "standard output and error"
11230 You should not write to the standard error or output streams from within your
11231 Perl code, as it is not defined how these are set up. In versions of Exim
11232 before 4.50, it is possible for the standard output or error to refer to the
11233 SMTP connection during message reception via the daemon. Writing to this stream
11234 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
11235 error streams are connected to &_/dev/null_& in the daemon. The chaos is
11236 avoided, but the output is lost.
11238 .cindex "Perl" "use of &%warn%&"
11239 The Perl &%warn%& statement writes to the standard error stream by default.
11240 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
11241 you have no control. When Exim starts up the Perl interpreter, it arranges for
11242 output from the &%warn%& statement to be written to the Exim main log. You can
11243 change this by including appropriate Perl magic somewhere in your Perl code.
11244 For example, to discard &%warn%& output completely, you need this:
11246 $SIG{__WARN__} = sub { };
11248 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
11249 example, the code for the subroutine is empty, so it does nothing, but you can
11250 include any Perl code that you like. The text of the &%warn%& message is passed
11251 as the first subroutine argument.
11255 . ////////////////////////////////////////////////////////////////////////////
11256 . ////////////////////////////////////////////////////////////////////////////
11258 .chapter "Starting the daemon and the use of network interfaces" &&&
11259 "CHAPinterfaces" &&&
11260 "Starting the daemon"
11261 .cindex "daemon" "starting"
11262 .cindex "interface" "listening"
11263 .cindex "network interface"
11264 .cindex "interface" "network"
11265 .cindex "IP address" "for listening"
11266 .cindex "daemon" "listening IP addresses"
11267 .cindex "TCP/IP" "setting listening interfaces"
11268 .cindex "TCP/IP" "setting listening ports"
11269 A host that is connected to a TCP/IP network may have one or more physical
11270 hardware network interfaces. Each of these interfaces may be configured as one
11271 or more &"logical"& interfaces, which are the entities that a program actually
11272 works with. Each of these logical interfaces is associated with an IP address.
11273 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
11274 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
11275 knowledge about the host's interfaces for use in three different circumstances:
11278 When a listening daemon is started, Exim needs to know which interfaces
11279 and ports to listen on.
11281 When Exim is routing an address, it needs to know which IP addresses
11282 are associated with local interfaces. This is required for the correct
11283 processing of MX lists by removing the local host and others with the
11284 same or higher priority values. Also, Exim needs to detect cases
11285 when an address is routed to an IP address that in fact belongs to the
11286 local host. Unless the &%self%& router option or the &%allow_localhost%&
11287 option of the smtp transport is set (as appropriate), this is treated
11288 as an error situation.
11290 When Exim connects to a remote host, it may need to know which interface to use
11291 for the outgoing connection.
11295 Exim's default behaviour is likely to be appropriate in the vast majority
11296 of cases. If your host has only one interface, and you want all its IP
11297 addresses to be treated in the same way, and you are using only the
11298 standard SMTP port, you should not need to take any special action. The
11299 rest of this chapter does not apply to you.
11301 In a more complicated situation you may want to listen only on certain
11302 interfaces, or on different ports, and for this reason there are a number of
11303 options that can be used to influence Exim's behaviour. The rest of this
11304 chapter describes how they operate.
11306 When a message is received over TCP/IP, the interface and port that were
11307 actually used are set in &$interface_address$& and &$interface_port$&.
11311 .section "Starting a listening daemon"
11312 When a listening daemon is started (by means of the &%-bd%& command line
11313 option), the interfaces and ports on which it listens are controlled by the
11317 &%daemon_smtp_ports%& contains a list of default ports. (For backward
11318 compatibility, this option can also be specified in the singular.)
11320 &%local_interfaces%& contains list of interface IP addresses on which to
11321 listen. Each item may optionally also specify a port.
11324 The default list separator in both cases is a colon, but this can be changed as
11325 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
11326 it is usually best to change the separator to avoid having to double all the
11327 colons. For example:
11329 local_interfaces = <; 127.0.0.1 ; \
11332 3ffe:ffff:836f::fe86:a061
11334 There are two different formats for specifying a port along with an IP address
11335 in &%local_interfaces%&:
11338 The port is added onto the address with a dot separator. For example, to listen
11339 on port 1234 on two different IP addresses:
11341 local_interfaces = <; 192.168.23.65.1234 ; \
11342 3ffe:ffff:836f::fe86:a061.1234
11345 The IP address is enclosed in square brackets, and the port is added
11346 with a colon separator, for example:
11348 local_interfaces = <; [192.168.23.65]:1234 ; \
11349 [3ffe:ffff:836f::fe86:a061]:1234
11353 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
11354 default setting contains just one port:
11356 daemon_smtp_ports = smtp
11358 If more than one port is listed, each interface that does not have its own port
11359 specified listens on all of them. Ports that are listed in
11360 &%daemon_smtp_ports%& can be identified either by name (defined in
11361 &_/etc/services_&) or by number. However, when ports are given with individual
11362 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
11366 .section "Special IP listening addresses"
11367 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
11368 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
11369 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
11370 instead of setting up separate listening sockets for each interface. The
11371 default value of &%local_interfaces%& is
11373 local_interfaces = 0.0.0.0
11375 when Exim is built without IPv6 support; otherwise it is:
11377 local_interfaces = <; ::0 ; 0.0.0.0
11379 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
11383 .section "Overriding local_interfaces and daemon_smtp_ports"
11384 The &%-oX%& command line option can be used to override the values of
11385 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
11386 instance. Another way of doing this would be to use macros and the &%-D%&
11387 option. However, &%-oX%& can be used by any admin user, whereas modification of
11388 the runtime configuration by &%-D%& is allowed only when the caller is root or
11391 The value of &%-oX%& is a list of items. The default colon separator can be
11392 changed in the usual way if required. If there are any items that do not
11393 contain dots or colons (that is, are not IP addresses), the value of
11394 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
11395 items that do contain dots or colons, the value of &%local_interfaces%& is
11396 replaced by those items. Thus, for example,
11400 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
11403 -oX 192.168.34.5.1125
11405 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
11406 (However, since &%local_interfaces%& now contains no items without ports, the
11407 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
11411 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
11412 .cindex "ssmtp protocol"
11413 .cindex "smtps protocol"
11414 .cindex "SMTP" "ssmtp protocol"
11415 .cindex "SMTP" "smtps protocol"
11416 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
11417 before the STARTTLS command was standardized for SMTP. Some legacy clients
11418 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
11419 list of port numbers, connections to those ports must use SSMTP. The most
11420 common use of this option is expected to be
11422 tls_on_connect_ports = 465
11424 because 465 is the usual port number used by the legacy clients. There is also
11425 a command line option &%-tls-on-connect%&, which forces all ports to behave in
11426 this way when a daemon is started.
11428 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
11429 daemon to listen on those ports. You must still specify them in
11430 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
11431 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
11432 connections via the daemon.)
11437 .section "IPv6 address scopes"
11438 .cindex "IPv6" "address scopes"
11439 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
11440 can, in principle, have the same link-local IPv6 address on different
11441 interfaces. Thus, additional information is needed, over and above the IP
11442 address, to distinguish individual interfaces. A convention of using a
11443 percent sign followed by something (often the interface name) has been
11444 adopted in some cases, leading to addresses like this:
11446 fe80::202:b3ff:fe03:45c1%eth0
11448 To accommodate this usage, a percent sign followed by an arbitrary string is
11449 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
11450 to convert a textual IPv6 address for actual use. This function recognizes the
11451 percent convention in operating systems that support it, and it processes the
11452 address appropriately. Unfortunately, some older libraries have problems with
11453 &[getaddrinfo()]&. If
11455 IPV6_USE_INET_PTON=yes
11457 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
11458 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
11459 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
11460 function.) Of course, this means that the additional functionality of
11461 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
11463 .section "Disabling IPv6"
11464 .cindex "IPv6" "disabling"
11465 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
11466 run on a host whose kernel does not support IPv6. The binary will fall back to
11467 using IPv4, but it may waste resources looking up AAAA records, and trying to
11468 connect to IPv6 addresses, causing delays to mail delivery. If you set the
11469 .oindex "&%disable_ipv6%&"
11470 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
11471 activities take place. AAAA records are never looked up, and any IPv6 addresses
11472 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
11473 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
11474 to handle IPv6 literal addresses.
11476 On the other hand, when IPv6 is in use, there may be times when you want to
11477 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
11478 option to globally suppress the lookup of AAAA records for specified domains,
11479 and you can use the &%ignore_target_hosts%& generic router option to ignore
11480 IPv6 addresses in an individual router.
11484 .section "Examples of starting a listening daemon"
11485 The default case in an IPv6 environment is
11487 daemon_smtp_ports = smtp
11488 local_interfaces = <; ::0 ; 0.0.0.0
11490 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
11491 Either one or two sockets may be used, depending on the characteristics of
11492 the TCP/IP stack. (This is complicated and messy; for more information,
11493 read the comments in the &_daemon.c_& source file.)
11495 To specify listening on ports 25 and 26 on all interfaces:
11497 daemon_smtp_ports = 25 : 26
11499 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
11501 local_interfaces = <; ::0.25 ; ::0.26 \
11502 0.0.0.0.25 ; 0.0.0.0.26
11504 To listen on the default port on all IPv4 interfaces, and on port 26 on the
11505 IPv4 loopback address only:
11507 local_interfaces = 0.0.0.0 : 127.0.0.1.26
11509 To specify listening on the default port on specific interfaces only:
11511 local_interfaces = 192.168.34.67 : 192.168.34.67
11513 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
11517 .section "Recognising the local host" "SECTreclocipadd"
11518 The &%local_interfaces%& option is also used when Exim needs to determine
11519 whether or not an IP address refers to the local host. That is, the IP
11520 addresses of all the interfaces on which a daemon is listening are always
11523 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
11524 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
11525 available interfaces from the operating system, and extracts the relevant
11526 (that is, IPv4 or IPv6) addresses to use for checking.
11528 Some systems set up large numbers of virtual interfaces in order to provide
11529 many virtual web servers. In this situation, you may want to listen for
11530 email on only a few of the available interfaces, but nevertheless treat all
11531 interfaces as local when routing. You can do this by setting
11532 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
11533 &"all"& wildcard values. These addresses are recognized as local, but are not
11534 used for listening. Consider this example:
11536 local_interfaces = <; 127.0.0.1 ; ::1 ; \
11538 3ffe:2101:12:1:a00:20ff:fe86:a061
11540 extra_local_interfaces = <; ::0 ; 0.0.0.0
11542 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
11543 address, but all available interface addresses are treated as local when
11546 In some environments the local host name may be in an MX list, but with an IP
11547 address that is not assigned to any local interface. In other cases it may be
11548 desirable to treat other host names as if they referred to the local host. Both
11549 these cases can be handled by setting the &%hosts_treat_as_local%& option.
11550 This contains host names rather than IP addresses. When a host is referenced
11551 during routing, either via an MX record or directly, it is treated as the local
11552 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
11553 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
11557 .section "Delivering to a remote host"
11558 Delivery to a remote host is handled by the smtp transport. By default, it
11559 allows the system's TCP/IP functions to choose which interface to use (if
11560 there is more than one) when connecting to a remote host. However, the
11561 &%interface%& option can be set to specify which interface is used. See the
11562 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
11568 . ////////////////////////////////////////////////////////////////////////////
11569 . ////////////////////////////////////////////////////////////////////////////
11571 .chapter "Main configuration" "CHAPmainconfig"
11572 .scindex IIDconfima "configuration file" "main section"
11573 .scindex IIDmaiconf "main configuration"
11574 The first part of the run time configuration file contains three types of item:
11577 Macro definitions: These lines start with an upper case letter. See section
11578 &<<SECTmacrodefs>>& for details of macro processing.
11580 Named list definitions: These lines start with one of the words &"domainlist"&,
11581 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
11582 section &<<SECTnamedlists>>&.
11584 Main configuration settings: Each setting occupies one line of the file
11585 (with possible continuations). If any setting is preceded by the word
11586 &"hide"&, the &%-bP%& command line option displays its value to admin users
11587 only. See section &<<SECTcos>>& for a description of the syntax of these option
11591 This chapter specifies all the main configuration options, along with their
11592 types and default values. For ease of finding a particular option, they appear
11593 in alphabetical order in section &<<SECTalomo>>& below. However, because there
11594 are now so many options, they are first listed briefly in functional groups, as
11595 an aid to finding the name of the option you are looking for. Some options are
11596 listed in more than one group.
11598 .section "Miscellaneous"
11600 .row &%bi_command%& "to run for &%-bi%& command line option"
11601 .row &%disable_ipv6%& "do no IPv6 processing"
11602 .row &%keep_malformed%& "for broken files &-- should not happen"
11603 .row &%localhost_number%& "for unique message ids in clusters"
11604 .row &%message_body_visible%& "how much to show in &$message_body$&"
11605 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
11606 .row &%print_topbitchars%& "top-bit characters are printing"
11607 .row &%timezone%& "force time zone"
11611 .section "Exim parameters"
11613 .row &%exim_group%& "override compiled-in value"
11614 .row &%exim_path%& "override compiled-in value"
11615 .row &%exim_user%& "override compiled-in value"
11616 .row &%primary_hostname%& "default from &[uname()]&"
11617 .row &%split_spool_directory%& "use multiple directories"
11618 .row &%spool_directory%& "override compiled-in value"
11623 .section "Privilege controls"
11625 .row &%admin_groups%& "groups that are Exim admin users"
11626 .row &%deliver_drop_privilege%& "drop root for delivery processes"
11627 .row &%local_from_check%& "insert &'Sender:'& if necessary"
11628 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
11629 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
11630 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
11631 .row &%never_users%& "do not run deliveries as these"
11632 .row &%prod_requires_admin%& "forced delivery requires admin user"
11633 .row &%queue_list_requires_admin%& "queue listing requires admin user"
11634 .row &%trusted_groups%& "groups that are trusted"
11635 .row &%trusted_users%& "users that are trusted"
11642 .row &%hosts_connection_nolog%& "exemption from connect logging"
11643 .row &%log_file_path%& "override compiled-in value"
11644 .row &%log_selector%& "set/unset optional logging"
11645 .row &%log_timezone%& "add timezone to log lines"
11646 .row &%message_logs%& "create per-message logs"
11647 .row &%preserve_message_logs%& "after message completion"
11648 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
11649 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
11650 .row &%syslog_facility%& "set syslog &""facility""& field"
11651 .row &%syslog_processname%& "set syslog &""ident""& field"
11652 .row &%syslog_timestamp%& "timestamp syslog lines"
11653 .row &%write_rejectlog%& "control use of message log"
11658 .section "Frozen messages"
11660 .row &%auto_thaw%& "sets time for retrying frozen messages"
11661 .row &%freeze_tell%& "send message when freezing"
11662 .row &%move_frozen_messages%& "to another directory"
11663 .row &%timeout_frozen_after%& "keep frozen messages only so long"
11668 .section "Data lookups"
11670 .row &%ldap_default_servers%& "used if no server in query"
11671 .row &%ldap_version%& "set protocol version"
11672 .row &%lookup_open_max%& "lookup files held open"
11673 .row &%mysql_servers%& "as it says"
11674 .row &%oracle_servers%& "as it says"
11675 .row &%pgsql_servers%& "as it says"
11676 .row &%sqlite_lock_timeout%& "as it says"
11681 .section "Message ids"
11683 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
11684 .row &%message_id_header_text%& "ditto"
11689 .section "Embedded Perl Startup"
11691 .row &%perl_at_start%& "always start the interpreter"
11692 .row &%perl_startup%& "code to obey when starting Perl"
11699 .row &%daemon_smtp_ports%& "default ports"
11700 .row &%daemon_startup_retries%& "number of times to retry"
11701 .row &%daemon_startup_sleep%& "time to sleep between tries"
11702 .row &%extra_local_interfaces%& "not necessarily listened on"
11703 .row &%local_interfaces%& "on which to listen, with optional ports"
11704 .row &%pid_file_path%& "override compiled-in value"
11705 .row &%queue_run_max%& "maximum simultaneous queue runners"
11710 .section "Resource control"
11712 .row &%check_log_inodes%& "before accepting a message"
11713 .row &%check_log_space%& "before accepting a message"
11714 .row &%check_spool_inodes%& "before accepting a message"
11715 .row &%check_spool_space%& "before accepting a message"
11716 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
11717 .row &%queue_only_load%& "queue incoming if load high"
11718 .row &%queue_run_max%& "maximum simultaneous queue runners"
11719 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
11720 .row &%smtp_accept_max%& "simultaneous incoming connections"
11721 .row &%smtp_accept_max_nommail%& "non-mail commands"
11722 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
11723 .row &%smtp_accept_max_per_connection%& "messages per connection"
11724 .row &%smtp_accept_max_per_host%& "connections from one host"
11725 .row &%smtp_accept_queue%& "queue mail if more connections"
11726 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
11728 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
11729 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
11730 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
11731 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
11732 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
11737 .section "Policy controls"
11739 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
11740 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
11741 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
11742 .row &%acl_smtp_auth%& "ACL for AUTH"
11743 .row &%acl_smtp_connect%& "ACL for connection"
11744 .row &%acl_smtp_data%& "ACL for DATA"
11745 .row &%acl_smtp_etrn%& "ACL for ETRN"
11746 .row &%acl_smtp_expn%& "ACL for EXPN"
11747 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
11748 .row &%acl_smtp_mail%& "ACL for MAIL"
11749 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
11750 .row &%acl_smtp_mime%& "ACL for MIME parts"
11751 .row &%acl_smtp_predata%& "ACL for start of data"
11752 .row &%acl_smtp_quit%& "ACL for QUIT"
11753 .row &%acl_smtp_rcpt%& "ACL for RCPT"
11754 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
11755 .row &%acl_smtp_vrfy%& "ACL for VRFY"
11756 .row &%av_scanner%& "specify virus scanner"
11757 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
11759 .row &%dns_csa_search_limit%& "control CSA parent search depth"
11760 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
11761 .row &%header_maxsize%& "total size of message header"
11762 .row &%header_line_maxsize%& "individual header line limit"
11763 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
11764 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
11765 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
11766 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
11767 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
11768 .row &%host_lookup%& "host name looked up for these hosts"
11769 .row &%host_lookup_order%& "order of DNS and local name lookups"
11770 .row &%host_reject_connection%& "reject connection from these hosts"
11771 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
11772 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
11773 .row &%message_size_limit%& "for all messages"
11774 .row &%percent_hack_domains%& "recognize %-hack for these domains"
11775 .row &%spamd_address%& "set interface to SpamAssassin"
11780 .section "Callout cache"
11782 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
11784 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
11786 .row &%callout_negative_expire%& "timeout for negative address cache item"
11787 .row &%callout_positive_expire%& "timeout for positive address cache item"
11788 .row &%callout_random_local_part%& "string to use for &""random""& testing"
11795 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
11796 .row &%tls_certificate%& "location of server certificate"
11797 .row &%tls_crl%& "certificate revocation list"
11798 .row &%tls_dhparam%& "DH parameters for server"
11799 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
11800 .row &%tls_privatekey%& "location of server private key"
11801 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
11802 .row &%tls_require_ciphers%& "specify acceptable cipers"
11803 .row &%tls_try_verify_hosts%& "try to verify client certificate"
11804 .row &%tls_verify_certificates%& "expected client certificates"
11805 .row &%tls_verify_hosts%& "insist on client certificate verify"
11810 .section "Local user handling"
11812 .row &%finduser_retries%& "useful in NIS environments"
11813 .row &%gecos_name%& "used when creating &'Sender:'&"
11814 .row &%gecos_pattern%& "ditto"
11815 .row &%max_username_length%& "for systems that truncate"
11816 .row &%unknown_login%& "used when no login name found"
11817 .row &%unknown_username%& "ditto"
11818 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
11819 .row &%uucp_from_sender%& "ditto"
11824 .section "All incoming messages (SMTP and non-SMTP)"
11826 .row &%header_maxsize%& "total size of message header"
11827 .row &%header_line_maxsize%& "individual header line limit"
11828 .row &%message_size_limit%& "applies to all messages"
11829 .row &%percent_hack_domains%& "recognize %-hack for these domains"
11830 .row &%received_header_text%& "expanded to make &'Received:'&"
11831 .row &%received_headers_max%& "for mail loop detection"
11832 .row &%recipients_max%& "limit per message"
11833 .row &%recipients_max_reject%& "permanently reject excess"
11839 .section "Non-SMTP incoming messages"
11841 .row &%receive_timeout%& "for non-SMTP messages"
11848 .section "Incoming SMTP messages"
11849 See also the &'Policy controls'& section above.
11852 .row &%host_lookup%& "host name looked up for these hosts"
11853 .row &%host_lookup_order%& "order of DNS and local name lookups"
11854 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
11855 .row &%rfc1413_hosts%& "make ident calls to these hosts"
11856 .row &%rfc1413_query_timeout%& "zero disables ident calls"
11857 .row &%sender_unqualified_hosts%& "may send unqualified senders"
11858 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
11859 .row &%smtp_accept_max%& "simultaneous incoming connections"
11860 .row &%smtp_accept_max_nonmail%& "non-mail commands"
11861 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
11862 .row &%smtp_accept_max_per_connection%& "messages per connection"
11863 .row &%smtp_accept_max_per_host%& "connections from one host"
11864 .row &%smtp_accept_queue%& "queue mail if more connections"
11865 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
11867 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
11868 .row &%smtp_active_hostname%& "host name to use in messages"
11869 .row &%smtp_banner%& "text for welcome banner"
11870 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
11871 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
11872 .row &%smtp_enforce_sync%& "of SMTP command/responses"
11873 .row &%smtp_etrn_command%& "what to run for ETRN"
11874 .row &%smtp_etrn_serialize%& "only one at once"
11875 .row &%smtp_load_reserve%& "only reserve hosts if this load"
11876 .row &%smtp_max_unknown_commands%& "before dropping connection"
11877 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
11878 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
11879 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
11880 .row &%smtp_receive_timeout%& "per command or data line"
11881 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
11882 .row &%smtp_return_error_details%& "give detail on rejections"
11887 .section "SMTP extensions"
11889 .row &%accept_8bitmime%& "advertise 8BITMIME"
11890 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
11891 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
11892 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
11893 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
11894 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
11899 .section "Processing messages"
11901 .row &%allow_domain_literals%& "recognize domain literal syntax"
11902 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
11903 .row &%allow_utf8_domains%& "in addresses"
11904 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
11906 .row &%delivery_date_remove%& "from incoming messages"
11907 .row &%envelope_to_remote%& "from incoming messages"
11908 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
11909 .row &%headers_charset%& "default for translations"
11910 .row &%qualify_domain%& "default for senders"
11911 .row &%qualify_recipient%& "default for recipients"
11912 .row &%return_path_remove%& "from incoming messages"
11913 .row &%strip_excess_angle_brackets%& "in addresses"
11914 .row &%strip_trailing_dot%& "at end of addresses"
11915 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
11920 .section "System filter"
11922 .row &%system_filter%& "locate system filter"
11923 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
11925 .row &%system_filter_file_transport%& "transport for delivery to a file"
11926 .row &%system_filter_group%& "group for filter running"
11927 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
11928 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
11929 .row &%system_filter_user%& "user for filter running"
11934 .section "Routing and delivery"
11936 .row &%disable_ipv6%& "do no IPv6 processing"
11937 .row &%dns_again_means_nonexist%& "for broken domains"
11938 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
11939 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
11940 .row &%dns_retrans%& "parameter for resolver"
11941 .row &%dns_retry%& "parameter for resolver"
11942 .row &%hold_domains%& "hold delivery for these domains"
11943 .row &%local_interfaces%& "for routing checks"
11944 .row &%queue_domains%& "no immediate delivery for these"
11945 .row &%queue_only%& "no immediate delivery at all"
11946 .row &%queue_only_file%& "no immediate delivery if file exists"
11947 .row &%queue_only_load%& "no immediate delivery if load is high"
11948 .row &%queue_only_override%& "allow command line to override"
11949 .row &%queue_run_in_order%& "order of arrival"
11950 .row &%queue_run_max%& "of simultaneous queue runners"
11951 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
11952 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
11953 .row &%remote_sort_domains%& "order of remote deliveries"
11954 .row &%retry_data_expire%& "timeout for retry data"
11955 .row &%retry_interval_max%& "safety net for retry rules"
11960 .section "Bounce and warning messages"
11962 .row &%bounce_message_file%& "content of bounce"
11963 .row &%bounce_message_text%& "content of bounce"
11964 .row &%bounce_return_body%& "include body if returning message"
11965 .row &%bounce_return_message%& "include original message in bounce"
11966 .row &%bounce_return_size_limit%& "limit on returned message"
11967 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
11968 .row &%errors_copy%& "copy bounce messages"
11969 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
11970 .row &%delay_warning%& "time schedule"
11971 .row &%delay_warning_condition%& "condition for warning messages"
11972 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
11973 .row &%smtp_return_error_details%& "give detail on rejections"
11974 .row &%warn_message_file%& "content of warning message"
11979 .section "Alphabetical list of main options" "SECTalomo"
11980 Those options that undergo string expansion before use are marked with
11983 .option accept_8bitmime main boolean false
11985 .cindex "8-bit characters"
11986 This option causes Exim to send 8BITMIME in its response to an SMTP
11987 EHLO command, and to accept the BODY= parameter on MAIL commands.
11988 However, though Exim is 8-bit clean, it is not a protocol converter, and it
11989 takes no steps to do anything special with messages received by this route.
11990 Consequently, this option is turned off by default.
11992 .option acl_not_smtp main string&!! unset
11993 .cindex "&ACL;" "for non-SMTP messages"
11994 .cindex "non-SMTP messages" "ACLs for"
11995 This option defines the ACL that is run when a non-SMTP message has been
11996 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
11999 .option acl_not_smtp_mime main string&!! unset
12000 This option defines the ACL that is run for individual MIME parts of non-SMTP
12001 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
12004 .option acl_not_smtp_start main string&!! unset
12005 .cindex "&ACL;" "at start of non-SMTP message"
12006 .cindex "non-SMTP messages" "ACLs for"
12007 This option defines the ACL that is run before Exim starts reading a
12008 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
12010 .option acl_smtp_auth main string&!! unset
12011 .cindex "&ACL;" "setting up for SMTP commands"
12012 .cindex "AUTH" "ACL for"
12013 This option defines the ACL that is run when an SMTP AUTH command is
12014 received. See chapter &<<CHAPACL>>& for further details.
12016 .option acl_smtp_connect main string&!! unset
12017 .cindex "&ACL;" "on SMTP connection"
12018 This option defines the ACL that is run when an SMTP connection is received.
12019 See chapter &<<CHAPACL>>& for further details.
12021 .option acl_smtp_data main string&!! unset
12022 .cindex "DATA" "ACL for"
12023 This option defines the ACL that is run after an SMTP DATA command has been
12024 processed and the message itself has been received, but before the final
12025 acknowledgement is sent. See chapter &<<CHAPACL>>& for further details.
12027 .option acl_smtp_etrn main string&!! unset
12028 .cindex "ETRN" "ACL for"
12029 This option defines the ACL that is run when an SMTP ETRN command is
12030 received. See chapter &<<CHAPACL>>& for further details.
12032 .option acl_smtp_expn main string&!! unset
12033 .cindex "EXPN" "ACL for"
12034 This option defines the ACL that is run when an SMTP EXPN command is
12035 received. See chapter &<<CHAPACL>>& for further details.
12037 .option acl_smtp_helo main string&!! unset
12038 .cindex "EHLO" "ACL for"
12039 .cindex "HELO" "ACL for"
12040 This option defines the ACL that is run when an SMTP EHLO or HELO
12041 command is received. See chapter &<<CHAPACL>>& for further details.
12044 .option acl_smtp_mail main string&!! unset
12045 .cindex "MAIL" "ACL for"
12046 This option defines the ACL that is run when an SMTP MAIL command is
12047 received. See chapter &<<CHAPACL>>& for further details.
12049 .option acl_smtp_mailauth main string&!! unset
12050 .cindex "AUTH" "on MAIL command"
12051 This option defines the ACL that is run when there is an AUTH parameter on
12052 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
12053 &<<CHAPSMTPAUTH>>& for details of authentication.
12055 .option acl_smtp_mime main string&!! unset
12056 .cindex "MIME content scanning" "ACL for"
12057 This option is available when Exim is built with the content-scanning
12058 extension. It defines the ACL that is run for each MIME part in a message. See
12059 section &<<SECTscanmimepart>>& for details.
12061 .option acl_smtp_predata main string&!! unset
12062 This option defines the ACL that is run when an SMTP DATA command is
12063 received, before the message itself is received. See chapter &<<CHAPACL>>& for
12066 .option acl_smtp_quit main string&!! unset
12067 .cindex "QUIT" "ACL for"
12068 This option defines the ACL that is run when an SMTP QUIT command is
12069 received. See chapter &<<CHAPACL>>& for further details.
12071 .option acl_smtp_rcpt main string&!! unset
12072 .cindex "RCPT" "ACL for"
12073 This option defines the ACL that is run when an SMTP RCPT command is
12074 received. See chapter &<<CHAPACL>>& for further details.
12076 .option acl_smtp_starttls main string&!! unset
12077 .cindex "STARTTLS" "ACL for"
12078 This option defines the ACL that is run when an SMTP STARTTLS command is
12079 received. See chapter &<<CHAPACL>>& for further details.
12081 .option acl_smtp_vrfy main string&!! unset
12082 .cindex "VRFY" "ACL for"
12083 This option defines the ACL that is run when an SMTP VRFY command is
12084 received. See chapter &<<CHAPACL>>& for further details.
12086 .option admin_groups main "string list&!!" unset
12087 .cindex "admin user"
12088 This option is expanded just once, at the start of Exim's processing. If the
12089 current group or any of the supplementary groups of an Exim caller is in this
12090 colon-separated list, the caller has admin privileges. If all your system
12091 programmers are in a specific group, for example, you can give them all Exim
12092 admin privileges by putting that group in &%admin_groups%&. However, this does
12093 not permit them to read Exim's spool files (whose group owner is the Exim gid).
12094 To permit this, you have to add individuals to the Exim group.
12096 .option allow_domain_literals main boolean false
12097 .cindex "domain literal"
12098 If this option is set, the RFC 2822 domain literal format is permitted in
12099 email addresses. The option is not set by default, because the domain literal
12100 format is not normally required these days, and few people know about it. It
12101 has, however, been exploited by mail abusers.
12103 Unfortunately, it seems that some DNS black list maintainers are using this
12104 format to report black listing to postmasters. If you want to accept messages
12105 addressed to your hosts by IP address, you need to set
12106 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
12107 domains (defined in the named domain list &%local_domains%& in the default
12108 configuration). This &"magic string"& matches the domain literal form of all
12109 the local host's IP addresses.
12112 .option allow_mx_to_ip main boolean false
12113 .cindex "MX record" "pointing to IP address"
12114 It appears that more and more DNS zone administrators are breaking the rules
12115 and putting domain names that look like IP addresses on the right hand side of
12116 MX records. Exim follows the rules and rejects this, giving an error message
12117 that explains the mis-configuration. However, some other MTAs support this
12118 practice, so to avoid &"Why can't Exim do this?"& complaints,
12119 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
12120 recommended, except when you have no other choice.
12122 .option allow_utf8_domains main boolean false
12123 .cindex "domain" "UTF-8 characters in"
12124 .cindex "UTF-8" "in domain name"
12125 Lots of discussion is going on about internationalized domain names. One
12126 camp is strongly in favour of just using UTF-8 characters, and it seems
12127 that at least two other MTAs permit this. This option allows Exim users to
12128 experiment if they wish.
12130 If it is set true, Exim's domain parsing function allows valid
12131 UTF-8 multicharacters to appear in domain name components, in addition to
12132 letters, digits, and hyphens. However, just setting this option is not
12133 enough; if you want to look up these domain names in the DNS, you must also
12134 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
12135 suitable setting is:
12137 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
12138 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
12140 Alternatively, you can just disable this feature by setting
12142 dns_check_names_pattern =
12144 That is, set the option to an empty string so that no check is done.
12147 .option auth_advertise_hosts main "host list&!!" *
12148 .cindex "authentication" "advertising"
12149 .cindex "AUTH" "advertising"
12150 If any server authentication mechanisms are configured, Exim advertises them in
12151 response to an EHLO command only if the calling host matches this list.
12152 Otherwise, Exim does not advertise AUTH.
12153 Exim does not accept AUTH commands from clients to which it has not
12154 advertised the availability of AUTH. The advertising of individual
12155 authentication mechanisms can be controlled by the use of the
12156 &%server_advertise_condition%& generic authenticator option on the individual
12157 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
12159 Certain mail clients (for example, Netscape) require the user to provide a name
12160 and password for authentication if AUTH is advertised, even though it may
12161 not be needed (the host may accept messages from hosts on its local LAN without
12162 authentication, for example). The &%auth_advertise_hosts%& option can be used
12163 to make these clients more friendly by excluding them from the set of hosts to
12164 which Exim advertises AUTH.
12166 .cindex "AUTH" "advertising when encrypted"
12167 If you want to advertise the availability of AUTH only when the connection
12168 is encrypted using TLS, you can make use of the fact that the value of this
12169 option is expanded, with a setting like this:
12171 auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}
12173 .cindex "&$tls_cipher$&"
12174 If &$tls_cipher$& is empty, the session is not encrypted, and the result of
12175 the expansion is empty, thus matching no hosts. Otherwise, the result of the
12176 expansion is *, which matches all hosts.
12179 .option auto_thaw main time 0s
12180 .cindex "thawing messages"
12181 .cindex "unfreezing messages"
12182 If this option is set to a time greater than zero, a queue runner will try a
12183 new delivery attempt on any frozen message, other than a bounce message, if
12184 this much time has passed since it was frozen. This may result in the message
12185 being re-frozen if nothing has changed since the last attempt. It is a way of
12186 saying &"keep on trying, even though there are big problems"&.
12188 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
12189 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
12190 thought to be very useful any more, and its use should probably be avoided.
12192 .option av_scanner main string "see below"
12193 This option is available if Exim is built with the content-scanning extension.
12194 It specifies which anti-virus scanner to use. The default value is:
12196 sophie:/var/run/sophie
12198 If the value of &%av_scanner%& starts with dollar character, it is expanded
12199 before use. See section &<<SECTscanvirus>>& for further details.
12203 .option bi_command main string unset
12204 .cindex "&%-bi%& option"
12205 This option supplies the name of a command that is run when Exim is called with
12206 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
12207 just the command name, it is not a complete command line. If an argument is
12208 required, it must come from the &%-oA%& command line option.
12211 .option bounce_message_file main string unset
12212 .cindex "bounce message" "customizing"
12213 .cindex "customizing" "bounce message"
12214 This option defines a template file containing paragraphs of text to be used
12215 for constructing bounce messages. Details of the file's contents are given in
12216 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
12219 .option bounce_message_text main string unset
12220 When this option is set, its contents are included in the default bounce
12221 message immediately after &"This message was created automatically by mail
12222 delivery software."& It is not used if &%bounce_message_file%& is set.
12224 .option bounce_return_body main boolean true
12225 .cindex "bounce message" "including body"
12226 This option controls whether the body of an incoming message is included in a
12227 bounce message when &%bounce_return_message%& is true. The default setting
12228 causes the entire message, both header and body, to be returned (subject to the
12229 value of &%bounce_return_size_limit%&). If this option is false, only the
12230 message header is included. In the case of a non-SMTP message containing an
12231 error that is detected during reception, only those header lines preceding the
12232 point at which the error was detected are returned.
12233 .cindex "bounce message" "including original"
12235 .option bounce_return_message main boolean true
12236 If this option is set false, none of the original message is included in
12237 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
12238 &%bounce_return_body%&.
12241 .option bounce_return_size_limit main integer 100K
12242 .cindex "size limit" "of bounce"
12243 .cindex "bounce message" "size limit"
12244 .cindex "limit" "bounce message size"
12245 This option sets a limit in bytes on the size of messages that are returned to
12246 senders as part of bounce messages when &%bounce_return_message%& is true. The
12247 limit should be less than the value of the global &%message_size_limit%& and of
12248 any &%message_size_limit%& settings on transports, to allow for the bounce text
12249 that Exim generates. If this option is set to zero there is no limit.
12251 When the body of any message that is to be included in a bounce message is
12252 greater than the limit, it is truncated, and a comment pointing this out is
12253 added at the top. The actual cutoff may be greater than the value given, owing
12254 to the use of buffering for transferring the message in chunks (typically 8K in
12255 size). The idea is to save bandwidth on those undeliverable 15-megabyte
12258 .option bounce_sender_authentication main string unset
12259 .cindex "bounce message" "sender authentication"
12260 .cindex "authentication" "bounce message"
12261 .cindex "AUTH" "on bounce message"
12262 This option provides an authenticated sender address that is sent with any
12263 bounce messages generated by Exim that are sent over an authenticated SMTP
12264 connection. A typical setting might be:
12266 bounce_sender_authentication = mailer-daemon@my.domain.example
12268 which would cause bounce messages to be sent using the SMTP command:
12270 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
12272 The value of &%bounce_sender_authentication%& must always be a complete email
12275 .option callout_domain_negative_expire main time 3h
12276 .cindex "caching" "callout timeouts"
12277 .cindex "callout" "caching timeouts"
12278 This option specifies the expiry time for negative callout cache data for a
12279 domain. See section &<<SECTcallver>>& for details of callout verification, and
12280 section &<<SECTcallvercache>>& for details of the caching.
12283 .option callout_domain_positive_expire main time 7d
12284 This option specifies the expiry time for positive callout cache data for a
12285 domain. See section &<<SECTcallver>>& for details of callout verification, and
12286 section &<<SECTcallvercache>>& for details of the caching.
12289 .option callout_negative_expire main time 2h
12290 This option specifies the expiry time for negative callout cache data for an
12291 address. See section &<<SECTcallver>>& for details of callout verification, and
12292 section &<<SECTcallvercache>>& for details of the caching.
12295 .option callout_positive_expire main time 24h
12296 This option specifies the expiry time for positive callout cache data for an
12297 address. See section &<<SECTcallver>>& for details of callout verification, and
12298 section &<<SECTcallvercache>>& for details of the caching.
12301 .option callout_random_local_part main string&!! "see below"
12302 This option defines the &"random"& local part that can be used as part of
12303 callout verification. The default value is
12305 $primary_host_name-$tod_epoch-testing
12307 See section &<<CALLaddparcall>>& for details of how this value is used.
12310 .option check_log_inodes main integer 0
12311 See &%check_spool_space%& below.
12314 .option check_log_space main integer 0
12315 See &%check_spool_space%& below.
12317 .oindex "&%check_rfc2047_length%&"
12318 .cindex "RFC 2047" "disabling length check"
12319 .option check_rfc2047_length " User: main" boolean true
12320 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
12321 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
12322 word; strings to be encoded that exceed this length are supposed to use
12323 multiple encoded words. By default, Exim does not recognize encoded words that
12324 exceed the maximum length. However, it seems that some software, in violation
12325 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
12326 set false, Exim recognizes encoded words of any length.
12329 .option check_spool_inodes main integer 0
12330 See &%check_spool_space%& below.
12333 .option check_spool_space main integer 0
12334 .cindex "checking disk space"
12335 .cindex "disk space" "checking"
12336 .cindex "spool directory" "checking space"
12337 The four &%check_...%& options allow for checking of disk resources before a
12338 message is accepted.
12340 .cindex "&$log_inodes$&"
12341 .cindex "&$log_space$&"
12342 .cindex "&$spool_inodes$&"
12343 .cindex "&$spool_space$&"
12344 When any of these options are set, they apply to all incoming messages. If you
12345 want to apply different checks to different kinds of message, you can do so by
12346 testing the the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
12347 &$spool_space$& in an ACL with appropriate additional conditions.
12350 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
12351 either value is greater than zero, for example:
12353 check_spool_space = 10M
12354 check_spool_inodes = 100
12356 The spool partition is the one that contains the directory defined by
12357 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
12360 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
12361 files are written if either is greater than zero. These should be set only if
12362 &%log_file_path%& and &%spool_directory%& refer to different partitions.
12364 If there is less space or fewer inodes than requested, Exim refuses to accept
12365 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
12366 error response to the MAIL command. If ESMTP is in use and there was a
12367 SIZE parameter on the MAIL command, its value is added to the
12368 &%check_spool_space%& value, and the check is performed even if
12369 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
12371 The values for &%check_spool_space%& and &%check_log_space%& are held as a
12372 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
12374 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
12375 failure a message is written to stderr and Exim exits with a non-zero code, as
12376 it obviously cannot send an error message of any kind.
12378 .option daemon_smtp_ports main string &`smtp`&
12379 .cindex "port" "for daemon"
12380 .cindex "TCP/IP" "setting listening ports"
12381 This option specifies one or more default SMTP ports on which the Exim daemon
12382 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
12383 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
12385 .option daemon_startup_retries main integer 9
12386 .cindex "daemon startup" "retrying"
12387 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
12388 the daemon at startup when it cannot immediately bind a listening socket
12389 (typically because the socket is already in use): &%daemon_startup_retries%&
12390 defines the number of retries after the first failure, and
12391 &%daemon_startup_sleep%& defines the length of time to wait between retries.
12393 .option daemon_startup_sleep main time 30s
12394 See &%daemon_startup_retries%&.
12396 .option delay_warning main "time list" 24h
12397 .cindex "warning of delay"
12398 .cindex "delay warning" "specifying"
12399 When a message is delayed, Exim sends a warning message to the sender at
12400 intervals specified by this option. The data is a colon-separated list of times
12401 after which to send warning messages. If the value of the option is an empty
12402 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
12403 message has been on the queue for longer than the last time, the last interval
12404 between the times is used to compute subsequent warning times. For example,
12407 delay_warning = 4h:8h:24h
12409 the first message is sent after 4 hours, the second after 8 hours, and
12410 the third one after 24 hours. After that, messages are sent every 16 hours,
12411 because that is the interval between the last two times on the list. If you set
12412 just one time, it specifies the repeat interval. For example, with:
12416 messages are repeated every six hours. To stop warnings after a given time, set
12417 a very large time at the end of the list. For example:
12419 delay_warning = 2h:12h:99d
12422 .option delay_warning_condition main string&!! "see below"
12423 .cindex "&$domain$&"
12424 The string is expanded at the time a warning message might be sent. If all the
12425 deferred addresses have the same domain, it is set in &$domain$& during the
12426 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
12427 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
12428 &"false"& (the comparison being done caselessly) then the warning message is
12429 not sent. The default is
12431 delay_warning_condition = \
12432 ${if match{$h_precedence:}{(?i)bulk|list|junk}{no}{yes}}
12434 which suppresses the sending of warnings about messages that have &"bulk"&,
12435 &"list"& or &"junk"& in a &'Precedence:'& header.
12437 .option deliver_drop_privilege main boolean false
12438 .cindex "unprivileged delivery"
12439 .cindex "delivery" "unprivileged"
12440 If this option is set true, Exim drops its root privilege at the start of a
12441 delivery process, and runs as the Exim user throughout. This severely restricts
12442 the kinds of local delivery that are possible, but is viable in certain types
12443 of configuration. There is a discussion about the use of root privilege in
12444 chapter &<<CHAPsecurity>>&.
12446 .option deliver_queue_load_max main fixed-point unset
12447 .cindex "load average"
12448 .cindex "queue runner" "abandoning"
12449 When this option is set, a queue run is abandoned if the system load average
12450 becomes greater than the value of the option. The option has no effect on
12451 ancient operating systems on which Exim cannot determine the load average.
12452 See also &%queue_only_load%& and &%smtp_load_reserve%&.
12455 .option delivery_date_remove main boolean true
12456 .cindex "&'Delivery-date:'& header line"
12457 Exim's transports have an option for adding a &'Delivery-date:'& header to a
12458 message when it is delivered, in exactly the same way as &'Return-path:'& is
12459 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
12460 should not be present in incoming messages, and this option causes them to be
12461 removed at the time the message is received, to avoid any problems that might
12462 occur when a delivered message is subsequently sent on to some other recipient.
12465 .option disable_ipv6 main boolean false
12466 .cindex "IPv6" "disabling"
12467 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
12468 activities take place. AAAA records are never looked up, and any IPv6 addresses
12469 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
12470 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12471 to handle IPv6 literal addresses.
12474 .option dns_again_means_nonexist main "domain list&!!" unset
12475 .cindex "DNS" "&""try again""& response; overriding"
12476 DNS lookups give a &"try again"& response for the DNS errors
12477 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
12478 keep trying to deliver a message, or to give repeated temporary errors to
12479 incoming mail. Sometimes the effect is caused by a badly set up name server and
12480 may persist for a long time. If a domain which exhibits this problem matches
12481 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
12482 This option should be used with care. You can make it apply to reverse lookups
12483 by a setting such as this:
12485 dns_again_means_nonexist = *.in-addr.arpa
12487 This option applies to all DNS lookups that Exim does. It also applies when the
12488 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
12489 since these are most likely to be caused by DNS lookup problems. The
12490 &(dnslookup)& router has some options of its own for controlling what happens
12491 when lookups for MX or SRV records give temporary errors. These more specific
12492 options are applied after this global option.
12494 .option dns_check_names_pattern main string "see below"
12495 .cindex "DNS" "pre-check of name syntax"
12496 When this option is set to a non-empty string, it causes Exim to check domain
12497 names for characters that are not allowed in host names before handing them to
12498 the DNS resolver, because some resolvers give temporary errors for names that
12499 contain unusual characters. If a domain name contains any unwanted characters,
12500 a &"not found"& result is forced, and the resolver is not called. The check is
12501 done by matching the domain name against a regular expression, which is the
12502 value of this option. The default pattern is
12504 dns_check_names_pattern = \
12505 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
12507 which permits only letters, digits, slashes, and hyphens in components, but
12508 they must start and end with a letter or digit. Hyphens are not, in fact,
12509 permitted in host names, but they are found in certain NS records (which can be
12510 accessed in Exim by using a &%dnsdb%& lookup). If you set
12511 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
12514 .option dns_csa_search_limit main integer 5
12515 This option controls the depth of parental searching for CSA SRV records in the
12516 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
12518 .option dns_csa_use_reverse main boolean true
12519 This option controls whether or not an IP address, given as a CSA domain, is
12520 reversed and looked up in the reverse DNS, as described in more detail in
12521 section &<<SECTverifyCSA>>&.
12523 .option dns_ipv4_lookup main "domain list&!!" unset
12524 .cindex "IPv6" "DNS lookup for AAAA records"
12525 .cindex "DNS" "IPv6 lookup for AAAA records"
12526 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
12527 looks for IPv6 address records (AAAA records) as well as IPv4 address records
12528 (A records) when trying to find IP addresses for hosts, unless the host's
12529 domain matches this list.
12531 This is a fudge to help with name servers that give big delays or otherwise do
12532 not work for the AAAA record type. In due course, when the world's name
12533 servers have all been upgraded, there should be no need for this option.
12536 .option dns_retrans main time 0s
12537 .cindex "DNS" "resolver options"
12538 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
12539 retransmission and retry parameters for DNS lookups. Values of zero (the
12540 defaults) leave the system default settings unchanged. The first value is the
12541 time between retries, and the second is the number of retries. It isn't
12542 totally clear exactly how these settings affect the total time a DNS lookup may
12543 take. I haven't found any documentation about timeouts on DNS lookups; these
12544 parameter values are available in the external resolver interface structure,
12545 but nowhere does it seem to describe how they are used or what you might want
12549 .option dns_retry main integer 0
12550 See &%dns_retrans%& above.
12553 .option drop_cr main boolean false
12554 This is an obsolete option that is now a no-op. It used to affect the way Exim
12555 handled CR and LF characters in incoming messages. What happens now is
12556 described in section &<<SECTlineendings>>&.
12559 .option envelope_to_remove main boolean true
12560 .cindex "&'Envelope-to:'& header line"
12561 Exim's transports have an option for adding an &'Envelope-to:'& header to a
12562 message when it is delivered, in exactly the same way as &'Return-path:'& is
12563 handled. &'Envelope-to:'& records the original recipient address from the
12564 messages's envelope that caused the delivery to happen. Such headers should not
12565 be present in incoming messages, and this option causes them to be removed at
12566 the time the message is received, to avoid any problems that might occur when a
12567 delivered message is subsequently sent on to some other recipient.
12570 .option errors_copy main "string list&!!" unset
12571 .cindex "bounce message" "copy to other address"
12572 .cindex "copy of bounce message"
12573 Setting this option causes Exim to send bcc copies of bounce messages that it
12574 generates to other addresses. &*Note*&: This does not apply to bounce messages
12575 coming from elsewhere. The value of the option is a colon-separated list of
12576 items. Each item consists of a pattern, terminated by white space, followed by
12577 a comma-separated list of email addresses. If a pattern contains spaces, it
12578 must be enclosed in double quotes.
12580 Each pattern is processed in the same way as a single item in an address list
12581 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
12582 the bounce message, the message is copied to the addresses on the list. The
12583 items are scanned in order, and once a matching one is found, no further items
12584 are examined. For example:
12586 errors_copy = spqr@mydomain postmaster@mydomain.example :\
12587 rqps@mydomain hostmaster@mydomain.example,\
12588 postmaster@mydomain.example
12590 .cindex "&$domain$&"
12591 .cindex "&$local_part$&"
12592 The address list is expanded before use. The expansion variables &$local_part$&
12593 and &$domain$& are set from the original recipient of the error message, and if
12594 there was any wildcard matching in the pattern, the expansion
12595 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
12596 variables &$0$&, &$1$&, etc. are set in the normal way.
12599 .option errors_reply_to main string unset
12600 .cindex "bounce message" "&'Reply-to:'& in"
12601 By default, Exim's bounce and delivery warning messages contain the header line
12603 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
12605 .oindex &%quota_warn_message%&
12606 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
12607 A warning message that is generated by the &%quota_warn_message%& option in an
12608 &(appendfile)& transport may contain its own &'From:'& header line that
12609 overrides the default.
12611 Experience shows that people reply to bounce messages. If the
12612 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
12613 and warning messages. For example:
12615 errors_reply_to = postmaster@my.domain.example
12617 The value of the option is not expanded. It must specify a valid RFC 2822
12618 address. However, if a warning message that is generated by the
12619 &%quota_warn_message%& option in an &(appendfile)& transport contain its
12620 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
12624 .option exim_group main string "compile-time configured"
12625 .cindex "gid (group id)" "Exim's own"
12626 .cindex "Exim group"
12627 This option changes the gid under which Exim runs when it gives up root
12628 privilege. The default value is compiled into the binary. The value of this
12629 option is used only when &%exim_user%& is also set. Unless it consists entirely
12630 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
12631 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
12635 .option exim_path main string "see below"
12636 .cindex "Exim binary" "path name"
12637 This option specifies the path name of the Exim binary, which is used when Exim
12638 needs to re-exec itself. The default is set up to point to the file &'exim'& in
12639 the directory configured at compile time by the BIN_DIRECTORY setting. It
12640 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
12642 &*Warning*&: Do not use a macro to define the value of this option, because
12643 you will break those Exim utilities that scan the configuration file to find
12644 where the binary is. (They then use the &%-bP%& option to extract option
12645 settings such as the value of &%spool_directory%&.)
12648 .option exim_user main string "compile-time configured"
12649 .cindex "uid (user id)" "Exim's own"
12650 .cindex "Exim user"
12651 This option changes the uid under which Exim runs when it gives up root
12652 privilege. The default value is compiled into the binary. Ownership of the run
12653 time configuration file and the use of the &%-C%& and &%-D%& command line
12654 options is checked against the values in the binary, not what is set here.
12656 Unless it consists entirely of digits, the string is looked up using
12657 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
12658 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
12659 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
12662 .option extra_local_interfaces main "string list" unset
12663 This option defines network interfaces that are to be considered local when
12664 routing, but which are not used for listening by the daemon. See section
12665 &<<SECTreclocipadd>>& for details.
12668 .option "extract_addresses_remove_ &~arguments" main boolean true
12669 .cindex "&%-t%& option"
12670 .cindex "command line" "addresses with &%-t%&"
12671 .cindex "Sendmail compatibility" "&%-t%& option"
12672 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
12673 are present on the command line when the &%-t%& option is used to build an
12674 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
12675 line addresses are removed from the recipients list. This is also how Smail
12676 behaves. However, other Sendmail documentation (the O'Reilly book) states that
12677 command line addresses are added to those obtained from the header lines. When
12678 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
12679 argument headers. If it is set false, Exim adds rather than removes argument
12683 .option finduser_retries main integer 0
12684 .cindex "NIS" "looking up users; retrying"
12685 On systems running NIS or other schemes in which user and group information is
12686 distributed from a remote system, there can be times when &[getpwnam()]& and
12687 related functions fail, even when given valid data, because things time out.
12688 Unfortunately these failures cannot be distinguished from genuine &"not found"&
12689 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
12690 many extra times to find a user or a group, waiting for one second between
12693 .cindex "&_/etc/passwd_&" "multiple reading of"
12694 You should not set this option greater than zero if your user information is in
12695 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
12696 search the file multiple times for non-existent users, and also cause delay.
12700 .option freeze_tell main "string list, comma separated" unset
12701 .cindex "freezing messages" "sending a message when freezing"
12702 On encountering certain errors, or when configured to do so in a system filter,
12703 ACL, or special router, Exim freezes a message. This means that no further
12704 delivery attempts take place until an administrator thaws the message, or the
12705 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
12706 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
12707 warning message whenever it freezes something, unless the message it is
12708 freezing is a locally-generated bounce message. (Without this exception there
12709 is the possibility of looping.) The warning message is sent to the addresses
12710 supplied as the comma-separated value of this option. If several of the
12711 message's addresses cause freezing, only a single message is sent. If the
12712 freezing was automatic, the reason(s) for freezing can be found in the message
12713 log. If you configure freezing in a filter or ACL, you must arrange for any
12714 logging that you require.
12717 .option gecos_name main string&!! unset
12719 .cindex "&""gecos""& field" "parsing"
12720 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
12721 password file to hold other information in addition to users' real names. Exim
12722 looks up this field for use when it is creating &'Sender:'& or &'From:'&
12723 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
12724 of the field are used unchanged, except that, if an ampersand is encountered,
12725 it is replaced by the user's login name with the first character forced to
12726 upper case, since this is a convention that is observed on many systems.
12728 When these options are set, &%gecos_pattern%& is treated as a regular
12729 expression that is to be applied to the field (again with && replaced by the
12730 login name), and if it matches, &%gecos_name%& is expanded and used as the
12733 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
12734 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
12735 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
12736 name terminates at the first comma, the following can be used:
12738 gecos_pattern = ([^,]*)
12742 .option gecos_pattern main string unset
12743 See &%gecos_name%& above.
12746 .option headers_charset main string "see below"
12747 This option sets a default character set for translating from encoded MIME
12748 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
12749 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
12750 ultimate default is ISO-8859-1. For more details see the description of header
12751 insertions in section &<<SECTexpansionitems>>&.
12755 .option header_maxsize main integer "see below"
12756 .cindex "header section" "maximum size of"
12757 .cindex "limit" "size of message header section"
12758 This option controls the overall maximum size of a message's header
12759 section. The default is the value of HEADER_MAXSIZE in
12760 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
12761 sections are rejected.
12764 .option header_line_maxsize main integer 0
12765 .cindex "header lines" "maximum size of"
12766 .cindex "limit" "size of one header line"
12767 This option limits the length of any individual header line in a message, after
12768 all the continuations have been joined together. Messages with individual
12769 header lines that are longer than the limit are rejected. The default value of
12770 zero means &"no limit"&.
12775 .option helo_accept_junk_hosts main "host list&!!" unset
12776 .cindex "HELO" "accepting junk data"
12777 .cindex "EHLO" "accepting junk data"
12778 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
12779 mail, and gives an error response for invalid data. Unfortunately, there are
12780 some SMTP clients that send syntactic junk. They can be accommodated by setting
12781 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
12782 if you want to do semantic checking.
12783 See also &%helo_allow_chars%& for a way of extending the permitted character
12787 .option helo_allow_chars main string unset
12788 .cindex "HELO" "underscores in"
12789 .cindex "EHLO" "underscores in"
12790 .cindex "underscore in EHLO/HELO"
12791 This option can be set to a string of rogue characters that are permitted in
12792 all EHLO and HELO names in addition to the standard letters, digits,
12793 hyphens, and dots. If you really must allow underscores, you can set
12795 helo_allow_chars = _
12797 Note that the value is one string, not a list.
12800 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
12801 .cindex "HELO" "forcing reverse lookup"
12802 .cindex "EHLO" "forcing reverse lookup"
12803 If the domain given by a client in a HELO or EHLO command matches this
12804 list, a reverse lookup is done in order to establish the host's true name. The
12805 default forces a lookup if the client host gives the server's name or any of
12806 its IP addresses (in brackets), something that broken clients have been seen to
12810 .option helo_try_verify_hosts main "host list&!!" unset
12811 .cindex "HELO verifying" "optional"
12812 .cindex "EHLO verifying" "optional"
12813 By default, Exim just checks the syntax of HELO and EHLO commands (see
12814 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
12815 to do more extensive checking of the data supplied by these commands. The ACL
12816 condition &`verify`& &`=`& &`helo`& is provided to make this possible.
12817 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
12818 to force the check to occur. From release 4.53 onwards, this is no longer
12819 necessary. If the check has not been done before &`verify`& &`=`& &`helo`& is
12820 encountered, it is done at that time. Consequently, this option is obsolete.
12821 Its specification is retained here for backwards compatibility.
12823 When an EHLO or HELO command is received, if the calling host matches
12824 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
12825 EHLO command either:
12828 is an IP literal matching the calling address of the host, or
12830 .cindex "DNS" "reverse lookup"
12831 .cindex "reverse DNS lookup"
12832 matches the host name that Exim obtains by doing a reverse lookup of the
12833 calling host address, or
12835 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
12836 available) yields the calling host address.
12839 However, the EHLO or HELO command is not rejected if any of the checks
12840 fail. Processing continues, but the result of the check is remembered, and can
12841 be detected later in an ACL by the &`verify`& &`=`& &`helo`& condition.
12843 .option helo_verify_hosts main "host list&!!" unset
12844 .cindex "HELO verifying" "mandatory"
12845 .cindex "EHLO verifying" "mandatory"
12846 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
12847 backwards compatibility. For hosts that match this option, Exim checks the host
12848 name given in the HELO or EHLO in the same way as for
12849 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
12850 rejected with a 550 error, and entries are written to the main and reject logs.
12851 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
12854 .option hold_domains main "domain list&!!" unset
12855 .cindex "domain" "delaying delivery"
12856 .cindex "delivery" "delaying certain domains"
12857 This option allows mail for particular domains to be held on the queue
12858 manually. The option is overridden if a message delivery is forced with the
12859 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
12860 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
12861 item in &%hold_domains%&, no routing or delivery for that address is done, and
12862 it is deferred every time the message is looked at.
12864 This option is intended as a temporary operational measure for delaying the
12865 delivery of mail while some problem is being sorted out, or some new
12866 configuration tested. If you just want to delay the processing of some
12867 domains until a queue run occurs, you should use &%queue_domains%& or
12868 &%queue_smtp_domains%&, not &%hold_domains%&.
12870 A setting of &%hold_domains%& does not override Exim's code for removing
12871 messages from the queue if they have been there longer than the longest retry
12872 time in any retry rule. If you want to hold messages for longer than the normal
12873 retry times, insert a dummy retry rule with a long retry time.
12876 .option host_lookup main "host list&!!" unset
12877 .cindex "host name lookup" "forcing"
12878 Exim does not look up the name of a calling host from its IP address unless it
12879 is required to compare against some host list, or the host matches
12880 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
12881 option (which normally contains IP addresses rather than host names). The
12882 default configuration file contains
12886 which causes a lookup to happen for all hosts. If the expense of these lookups
12887 is felt to be too great, the setting can be changed or removed.
12889 After a successful reverse lookup, Exim does a forward lookup on the name it
12890 has obtained, to verify that it yields the IP address that it started with. If
12891 this check fails, Exim behaves as if the name lookup failed.
12893 .cindex "&$host_lookup_failed$&"
12894 .cindex "&$sender_host_name$&"
12895 After any kind of failure, the host name (in &$sender_host_name$&) remains
12896 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
12897 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and &`verify`& &`=`&
12898 &`reverse_host_lookup`& in ACLs.
12901 .option host_lookup_order main "string list" &`bydns:byaddr`&
12902 This option specifies the order of different lookup methods when Exim is trying
12903 to find a host name from an IP address. The default is to do a DNS lookup
12904 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
12905 if that fails. You can change the order of these lookups, or omit one entirely,
12908 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
12909 multiple PTR records in the DNS and the IP address is not listed in
12910 &_/etc/hosts_&. Different operating systems give different results in this
12911 case. That is why the default tries a DNS lookup first.
12915 .option host_reject_connection main "host list&!!" unset
12916 .cindex "host" "rejecting connections from"
12917 If this option is set, incoming SMTP calls from the hosts listed are rejected
12918 as soon as the connection is made.
12919 This option is obsolete, and retained only for backward compatibility, because
12920 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
12921 connections immediately.
12923 The ability to give an immediate rejection (either by this option or using an
12924 ACL) is provided for use in unusual cases. Many hosts will just try again,
12925 sometimes without much delay. Normally, it is better to use an ACL to reject
12926 incoming messages at a later stage, such as after RCPT commands. See
12927 chapter &<<CHAPACL>>&.
12930 .option hosts_connection_nolog main "host list&!!" unset
12931 .cindex "host" "not logging connections from"
12932 This option defines a list of hosts for which connection logging does not
12933 happen, even though the &%smtp_connection%& log selector is set. For example,
12934 you might want not to log SMTP connections from local processes, or from
12935 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
12936 the daemon; you should therefore strive to restrict its value to a short inline
12937 list of IP addresses and networks. To disable logging SMTP connections from
12938 local processes, you must create a host list with an empty item. For example:
12940 hosts_connection_nolog = :
12942 If the &%smtp_connection%& log selector is not set, this option has no effect.
12946 .option hosts_treat_as_local main "domain list&!!" unset
12947 .cindex "local host" "domains treated as"
12948 .cindex "host" "treated as local"
12949 If this option is set, any host names that match the domain list are treated as
12950 if they were the local host when Exim is scanning host lists obtained from MX
12952 or other sources. Note that the value of this option is a domain list, not a
12953 host list, because it is always used to check host names, not IP addresses.
12955 This option also applies when Exim is matching the special items
12956 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
12957 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
12958 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
12959 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
12960 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
12961 interfaces and recognising the local host.
12964 .option ignore_bounce_errors_after main time 10w
12965 .cindex "bounce message" "discarding"
12966 .cindex "discarding bounce message"
12967 This option affects the processing of bounce messages that cannot be delivered,
12968 that is, those that suffer a permanent delivery failure. (Bounce messages that
12969 suffer temporary delivery failures are of course retried in the usual way.)
12971 After a permanent delivery failure, bounce messages are frozen,
12972 because there is no sender to whom they can be returned. When a frozen bounce
12973 message has been on the queue for more than the given time, it is unfrozen at
12974 the next queue run, and a further delivery is attempted. If delivery fails
12975 again, the bounce message is discarded. This makes it possible to keep failed
12976 bounce messages around for a shorter time than the normal maximum retry time
12977 for frozen messages. For example,
12979 ignore_bounce_errors_after = 12h
12981 retries failed bounce message deliveries after 12 hours, discarding any further
12982 failures. If the value of this option is set to a zero time period, bounce
12983 failures are discarded immediately. Setting a very long time (as in the default
12984 value) has the effect of disabling this option. For ways of automatically
12985 dealing with other kinds of frozen message, see &%auto_thaw%& and
12986 &%timeout_frozen_after%&.
12989 .option ignore_fromline_hosts main "host list&!!" unset
12990 .cindex "&""From""& line"
12991 .cindex "UUCP" "&""From""& line"
12992 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
12993 the headers of a message. By default this is treated as the start of the
12994 message's body, which means that any following headers are not recognized as
12995 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
12996 match those hosts that insist on sending it. If the sender is actually a local
12997 process rather than a remote host, and is using &%-bs%& to inject the messages,
12998 &%ignore_fromline_local%& must be set to achieve this effect.
13001 .option ignore_fromline_local main boolean false
13002 See &%ignore_fromline_hosts%& above.
13005 .option keep_malformed main time 4d
13006 This option specifies the length of time to keep messages whose spool files
13007 have been corrupted in some way. This should, of course, never happen. At the
13008 next attempt to deliver such a message, it gets removed. The incident is
13012 .option ldap_default_servers main "string list" unset
13013 .cindex "LDAP" "default servers"
13014 This option provides a list of LDAP servers which are tried in turn when an
13015 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
13016 details of LDAP queries. This option is available only when Exim has been built
13020 .option ldap_version main integer unset
13021 .cindex "LDAP protocol version" "forcing"
13022 This option can be used to force Exim to set a specific protocol version for
13023 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
13024 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
13025 the LDAP headers; otherwise it is 2. This option is available only when Exim
13026 has been built with LDAP support.
13030 .option local_from_check main boolean true
13031 .cindex "&'Sender:'& header line" "disabling addition of"
13032 .cindex "&'From:'& header line" "disabling checking of"
13033 When a message is submitted locally (that is, not over a TCP/IP connection) by
13034 an untrusted user, Exim removes any existing &'Sender:'& header line, and
13035 checks that the &'From:'& header line matches the login of the calling user and
13036 the domain specified by &%qualify_domain%&.
13038 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
13039 locally submitted message is automatically qualified by Exim, unless the
13040 &%-bnq%& command line option is used.
13042 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
13043 on the local part. If the &'From:'& header line does not match, Exim adds a
13044 &'Sender:'& header with an address constructed from the calling user's login
13045 and the default qualify domain.
13047 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
13048 and no &'Sender:'& header is ever added. If, in addition, you want to retain
13049 &'Sender:'& header lines supplied by untrusted users, you must also set
13050 &%local_sender_retain%& to be true.
13052 .cindex "envelope sender"
13053 These options affect only the header lines in the message. The envelope sender
13054 is still forced to be the login id at the qualify domain unless
13055 &%untrusted_set_sender%& permits the user to supply an envelope sender.
13057 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
13058 request similar header line checking. See section &<<SECTthesenhea>>&, which
13059 has more details about &'Sender:'& processing.
13064 .option local_from_prefix main string unset
13065 When Exim checks the &'From:'& header line of locally submitted messages for
13066 matching the login id (see &%local_from_check%& above), it can be configured to
13067 ignore certain prefixes and suffixes in the local part of the address. This is
13068 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
13069 appropriate lists, in the same form as the &%local_part_prefix%& and
13070 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
13073 local_from_prefix = *-
13075 is set, a &'From:'& line containing
13077 From: anything-user@your.domain.example
13079 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
13080 matches the actual sender address that is constructed from the login name and
13084 .option local_from_suffix main string unset
13085 See &%local_from_prefix%& above.
13088 .option local_interfaces main "string list" "see below"
13089 This option controls which network interfaces are used by the daemon for
13090 listening; they are also used to identify the local host when routing. Chapter
13091 &<<CHAPinterfaces>>& contains a full description of this option and the related
13092 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
13093 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
13094 &%local_interfaces%& is
13096 local_interfaces = 0.0.0.0
13098 when Exim is built without IPv6 support; otherwise it is
13100 local_interfaces = <; ::0 ; 0.0.0.0
13103 .option local_scan_timeout main time 5m
13104 .cindex "timeout" "for &[local_scan()]& function"
13105 .cindex "&[local_scan()]& function" "timeout"
13106 This timeout applies to the &[local_scan()]& function (see chapter
13107 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
13108 the incoming message is rejected with a temporary error if it is an SMTP
13109 message. For a non-SMTP message, the message is dropped and Exim ends with a
13110 non-zero code. The incident is logged on the main and reject logs.
13114 .option local_sender_retain main boolean false
13115 .cindex "&'Sender:'& header line" "retaining from local submission"
13116 When a message is submitted locally (that is, not over a TCP/IP connection) by
13117 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
13118 do not want this to happen, you must set &%local_sender_retain%&, and you must
13119 also set &%local_from_check%& to be false (Exim will complain if you do not).
13120 See also the ACL modifier &`control = suppress_local_fixups`&. Section
13121 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
13126 .option localhost_number main string&!! unset
13127 .cindex "host" "locally unique number for"
13128 .cindex "message ids" "with multiple hosts"
13129 .cindex "&$localhost_number$&"
13130 Exim's message ids are normally unique only within the local host. If
13131 uniqueness among a set of hosts is required, each host must set a different
13132 value for the &%localhost_number%& option. The string is expanded immediately
13133 after reading the configuration file (so that a number can be computed from the
13134 host name, for example) and the result of the expansion must be a number in the
13135 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
13136 systems). This is available in subsequent string expansions via the variable
13137 &$localhost_number$&. When &%localhost_number is set%&, the final two
13138 characters of the message id, instead of just being a fractional part of the
13139 time, are computed from the time and the local host number as described in
13140 section &<<SECTmessiden>>&.
13144 .option log_file_path main "string list&!!" "set at compile time"
13145 .cindex "log" "file path for"
13146 This option sets the path which is used to determine the names of Exim's log
13147 files, or indicates that logging is to be to syslog, or both. It is expanded
13148 when Exim is entered, so it can, for example, contain a reference to the host
13149 name. If no specific path is set for the log files at compile or run time, they
13150 are written in a sub-directory called &_log_& in Exim's spool directory.
13151 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
13152 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
13153 used. If this string is fixed at your installation (contains no expansion
13154 variables) it is recommended that you do not set this option in the
13155 configuration file, but instead supply the path using LOG_FILE_PATH in
13156 &_Local/Makefile_& so that it is available to Exim for logging errors detected
13157 early on &-- in particular, failure to read the configuration file.
13160 .option log_selector main string unset
13161 .cindex "log" "selectors"
13162 This option can be used to reduce or increase the number of things that Exim
13163 writes to its log files. Its argument is made up of names preceded by plus or
13164 minus characters. For example:
13166 log_selector = +arguments -retry_defer
13168 A list of possible names and what they control is given in the chapter on
13169 logging, in section &<<SECTlogselector>>&.
13172 .option log_timezone main boolean false
13173 .cindex "log" "timezone for entries"
13174 .cindex "&$tod_log$&"
13175 .cindex "&$tod_zone$&"
13176 By default, the timestamps on log lines are in local time without the
13177 timezone. This means that if your timezone changes twice a year, the timestamps
13178 in log lines are ambiguous for an hour when the clocks go back. One way of
13179 avoiding this problem is to set the timezone to UTC. An alternative is to set
13180 &%log_timezone%& true. This turns on the addition of the timezone offset to
13181 timestamps in log lines. Turning on this option can add quite a lot to the size
13182 of log files because each line is extended by 6 characters. Note that the
13183 &$tod_log$& variable contains the log timestamp without the zone, but there is
13184 another variable called &$tod_zone$& that contains just the timezone offset.
13187 .option lookup_open_max main integer 25
13188 .cindex "too many open files"
13189 .cindex "open files" "too many"
13190 .cindex "file" "too many open"
13191 .cindex "lookup" "maximum open files"
13192 .cindex "limit" "open files for lookups"
13193 This option limits the number of simultaneously open files for single-key
13194 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
13195 Exim normally keeps these files open during routing, because often the same
13196 file is required several times. If the limit is reached, Exim closes the least
13197 recently used file. Note that if you are using the &'ndbm'& library, it
13198 actually opens two files for each logical DBM database, though it still counts
13199 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
13200 open files"& errors with NDBM, you need to reduce the value of
13201 &%lookup_open_max%&.
13204 .option max_username_length main integer 0
13205 .cindex "length" "of login name"
13206 .cindex "user name" "maximum length"
13207 .cindex "limit" "user name length"
13208 Some operating systems are broken in that they truncate long arguments to
13209 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
13210 this option is set greater than zero, any attempt to call &[getpwnam()]& with
13211 an argument that is longer behaves as if &[getpwnam()]& failed.
13215 .option message_body_visible main integer 500
13216 .cindex "body of message" "visible size"
13217 .cindex "message body" "visible size"
13218 .cindex "&$message_body$&"
13219 .cindex "&$message_body_end$&"
13220 This option specifies how much of a message's body is to be included in the
13221 &$message_body$& and &$message_body_end$& expansion variables.
13224 .option message_id_header_domain main string&!! unset
13225 .cindex "&'Message-ID:'& header line"
13226 If this option is set, the string is expanded and used as the right hand side
13227 (domain) of the &'Message-ID:'& header that Exim creates if a
13228 locally-originated incoming message does not have one. &"Locally-originated"&
13229 means &"not received over TCP/IP."&
13230 Otherwise, the primary host name is used.
13231 Only letters, digits, dot and hyphen are accepted; any other characters are
13232 replaced by hyphens. If the expansion is forced to fail, or if the result is an
13233 empty string, the option is ignored.
13236 .option message_id_header_text main string&!! unset
13237 If this variable is set, the string is expanded and used to augment the text of
13238 the &'Message-id:'& header that Exim creates if a locally-originated incoming
13239 message does not have one. The text of this header is required by RFC 2822 to
13240 take the form of an address. By default, Exim uses its internal message id as
13241 the local part, and the primary host name as the domain. If this option is set,
13242 it is expanded, and provided the expansion is not forced to fail, and does not
13243 yield an empty string, the result is inserted into the header immediately
13244 before the @, separated from the internal message id by a dot. Any characters
13245 that are illegal in an address are automatically converted into hyphens. This
13246 means that variables such as &$tod_log$& can be used, because the spaces and
13247 colons will become hyphens.
13250 .option message_logs main boolean true
13251 .cindex "message log" "disabling"
13252 .cindex "log" "message log; disabling"
13253 If this option is turned off, per-message log files are not created in the
13254 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
13255 Exim, by reducing the number of files involved in handling a message from a
13256 minimum of four (header spool file, body spool file, delivery journal, and
13257 per-message log) to three. The other major I/O activity is Exim's main log,
13258 which is not affected by this option.
13261 .option message_size_limit main string&!! 50M
13262 .cindex "message" "size limit"
13263 .cindex "limit" "message size"
13264 .cindex "size of message" "limit"
13265 This option limits the maximum size of message that Exim will process. The
13266 value is expanded for each incoming
13267 connection so, for example, it can be made to depend on the IP address of the
13268 remote host for messages arriving via TCP/IP. &*Note*&: This limit cannot be
13269 made to depend on a message's sender or any other properties of an individual
13270 message, because it has to be advertised in the server's response to EHLO.
13271 String expansion failure causes a temporary error. A value of zero means no
13272 limit, but its use is not recommended. See also &%bounce_return_size_limit%&.
13274 Incoming SMTP messages are failed with a 552 error if the limit is
13275 exceeded; locally-generated messages either get a stderr message or a delivery
13276 failure message to the sender, depending on the &%-oe%& setting. Rejection of
13277 an oversized message is logged in both the main and the reject logs. See also
13278 the generic transport option &%message_size_limit%&, which limits the size of
13279 message that an individual transport can process.
13282 .option move_frozen_messages main boolean false
13283 .cindex "frozen messages" "moving"
13284 This option, which is available only if Exim has been built with the setting
13286 SUPPORT_MOVE_FROZEN_MESSAGES=yes
13288 in &_Local/Makefile_&, causes frozen messages and their message logs to be
13289 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
13290 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
13291 standard utilities for handling such moved messages, and they do not show up in
13292 lists generated by &%-bp%& or by the Exim monitor.
13295 .option mua_wrapper main boolean false
13296 Setting this option true causes Exim to run in a very restrictive mode in which
13297 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
13298 contains a full description of this facility.
13302 .option mysql_servers main "string list" unset
13303 .cindex "MySQL" "server list"
13304 This option provides a list of MySQL servers and associated connection data, to
13305 be used in conjunction with &(mysql)& lookups (see section &<<SECTsql>>&). The
13306 option is available only if Exim has been built with MySQL support.
13309 .option never_users main "string list&!!" unset
13310 This option is expanded just once, at the start of Exim's processing. Local
13311 message deliveries are normally run in processes that are setuid to the
13312 recipient, and remote deliveries are normally run under Exim's own uid and gid.
13313 It is usually desirable to prevent any deliveries from running as root, as a
13316 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
13317 list of users that must not be used for local deliveries. This list is fixed in
13318 the binary and cannot be overridden by the configuration file. By default, it
13319 contains just the single user name &"root"&. The &%never_users%& runtime option
13320 can be used to add more users to the fixed list.
13322 If a message is to be delivered as one of the users on the fixed list or the
13323 &%never_users%& list, an error occurs, and delivery is deferred. A common
13326 never_users = root:daemon:bin
13328 Including root is redundant if it is also on the fixed list, but it does no
13329 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
13333 .option oracle_servers main "string list" unset
13334 .cindex "Oracle" "server list"
13335 This option provides a list of Oracle servers and associated connection data,
13336 to be used in conjunction with &(oracle)& lookups (see section &<<SECTsql>>&).
13337 The option is available only if Exim has been built with Oracle support.
13340 .option percent_hack_domains main "domain list&!!" unset
13341 .cindex "&""percent hack""&"
13342 .cindex "source routing" "in email address"
13343 .cindex "address" "source-routed"
13344 The &"percent hack"& is the convention whereby a local part containing a
13345 percent sign is re-interpreted as a new email address, with the percent
13346 replaced by @. This is sometimes called &"source routing"&, though that term is
13347 also applied to RFC 2822 addresses that begin with an @ character. If this
13348 option is set, Exim implements the percent facility for those domains listed,
13349 but no others. This happens before an incoming SMTP address is tested against
13352 &*Warning*&: The &"percent hack"& has often been abused by people who are
13353 trying to get round relaying restrictions. For this reason, it is best avoided
13354 if at all possible. Unfortunately, a number of less security-conscious MTAs
13355 implement it unconditionally. If you are running Exim on a gateway host, and
13356 routing mail through to internal MTAs without processing the local parts, it is
13357 a good idea to reject recipient addresses with percent characters in their
13358 local parts. Exim's default configuration does this.
13361 .option perl_at_start main boolean false
13362 This option is available only when Exim is built with an embedded Perl
13363 interpreter. See chapter &<<CHAPperl>>& for details of its use.
13366 .option perl_startup main string unset
13367 This option is available only when Exim is built with an embedded Perl
13368 interpreter. See chapter &<<CHAPperl>>& for details of its use.
13371 .option pgsql_servers main "string list" unset
13372 .cindex "PostgreSQL lookup type" "server list"
13373 This option provides a list of PostgreSQL servers and associated connection
13374 data, to be used in conjunction with &(pgsql)& lookups (see section
13375 &<<SECTsql>>&). The option is available only if Exim has been built with
13376 PostgreSQL support.
13379 .option pid_file_path main string&!! "set at compile time"
13380 .cindex "daemon" "pid file path"
13381 .cindex "pid file" "path for"
13382 This option sets the name of the file to which the Exim daemon writes its
13383 process id. The string is expanded, so it can contain, for example, references
13386 pid_file_path = /var/log/$primary_hostname/exim.pid
13388 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
13390 The value set by the option can be overridden by the &%-oP%& command line
13391 option. A pid file is not written if a &"non-standard"& daemon is run by means
13392 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
13395 .option pipelining_advertise_hosts main "host list&!!" *
13396 .cindex "PIPELINING advertising" "suppressing"
13397 This option can be used to suppress the advertisement of the SMTP
13398 PIPELINING extension to specific hosts. When PIPELINING is not
13399 advertised and &%smtp_enforce_sync%& is true, an Exim server enforces strict
13400 synchronization for each SMTP command and response.
13401 When PIPELINING is advertised, Exim assumes that clients will use it; &"out
13402 of order"& commands that are &"expected"& do not count as protocol errors (see
13403 &%smtp_max_synprot_errors%&).
13406 .option preserve_message_logs main boolean false
13407 .cindex "message logs" "preserving"
13408 If this option is set, message log files are not deleted when messages are
13409 completed. Instead, they are moved to a sub-directory of the spool directory
13410 called &_msglog.OLD_&, where they remain available for statistical or debugging
13411 purposes. This is a dangerous option to set on systems with any appreciable
13412 volume of mail. Use with care!
13415 .option primary_hostname main string "see below"
13416 .cindex "name" "of local host"
13417 .cindex "host" "name of local"
13418 .cindex "local host" "name of"
13419 .cindex "&$primary_hostname$&"
13420 This specifies the name of the current host. It is used in the default EHLO or
13421 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
13422 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
13423 The value is also used by default in some SMTP response messages from an Exim
13424 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
13426 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
13427 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
13428 contains only one component, Exim passes it to &[gethostbyname()]& (or
13429 &[getipnodebyname()]& when available) in order to obtain the fully qualified
13430 version. The variable &$primary_hostname$& contains the host name, whether set
13431 explicitly by this option, or defaulted.
13434 .option print_topbitchars main boolean false
13435 .cindex "printing characters"
13436 .cindex "8-bit characters"
13437 By default, Exim considers only those characters whose codes lie in the range
13438 32&--126 to be printing characters. In a number of circumstances (for example,
13439 when writing log entries) non-printing characters are converted into escape
13440 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
13441 is set, code values of 128 and above are also considered to be printing
13445 .option process_log_path main string unset
13446 .cindex "process log path"
13447 .cindex "log" "process log"
13448 .cindex "&'exiwhat'&"
13449 This option sets the name of the file to which an Exim process writes its
13450 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
13451 utility script. If this option is unset, the file called &_exim-process.info_&
13452 in Exim's spool directory is used. The ability to specify the name explicitly
13453 can be useful in environments where two different Exims are running, using
13454 different spool directories.
13457 .option prod_requires_admin main boolean true
13458 .cindex "&%-M%& option"
13459 .cindex "&%-R%& option"
13460 .cindex "&%-q%& option"
13461 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
13462 admin user unless &%prod_requires_admin%& is set false. See also
13463 &%queue_list_requires_admin%&.
13466 .option qualify_domain main string "see below"
13467 .cindex "domain" "for qualifying addresses"
13468 .cindex "address" "qualification"
13469 This option specifies the domain name that is added to any envelope sender
13470 addresses that do not have a domain qualification. It also applies to
13471 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
13472 are accepted by default only for locally-generated messages. Qualification is
13473 also applied to addresses in header lines such as &'From:'& and &'To:'& for
13474 locally-generated messages, unless the &%-bnq%& command line option is used.
13476 Messages from external sources must always contain fully qualified addresses,
13477 unless the sending host matches &%sender_unqualified_hosts%& or
13478 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
13479 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
13480 necessary. Internally, Exim always works with fully qualified envelope
13481 addresses. If &%qualify_domain%& is not set, it defaults to the
13482 &%primary_hostname%& value.
13485 .option qualify_recipient main string "see below"
13486 This option allows you to specify a different domain for qualifying recipient
13487 addresses to the one that is used for senders. See &%qualify_domain%& above.
13491 .option queue_domains main "domain list&!!" unset
13492 .cindex "domain" "specifying non-immediate delivery"
13493 .cindex "queueing incoming messages"
13494 .cindex "message" "queueing certain domains"
13495 This option lists domains for which immediate delivery is not required.
13496 A delivery process is started whenever a message is received, but only those
13497 domains that do not match are processed. All other deliveries wait until the
13498 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
13501 .option queue_list_requires_admin main boolean true
13502 .cindex "&%-bp%& option"
13503 The &%-bp%& command-line option, which lists the messages that are on the
13504 queue, requires the caller to be an admin user unless
13505 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
13508 .option queue_only main boolean false
13509 .cindex "queueing incoming messages"
13510 .cindex "message" "queueing unconditionally"
13511 If &%queue_only%& is set, a delivery process is not automatically started
13512 whenever a message is received. Instead, the message waits on the queue for the
13513 next queue run. Even if &%queue_only%& is false, incoming messages may not get
13514 delivered immediately when certain conditions (such as heavy load) occur.
13516 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
13517 and &%-odi%& command line options override &%queue_only%& unless
13518 &%queue_only_override%& is set false. See also &%queue_only_file%&,
13519 &%queue_only_load%&, and &%smtp_accept_queue%&.
13522 .option queue_only_file main string unset
13523 .cindex "queueing incoming messages"
13524 .cindex "message" "queueing by file existence"
13525 This option can be set to a colon-separated list of absolute path names, each
13526 one optionally preceded by &"smtp"&. When Exim is receiving a message,
13527 it tests for the existence of each listed path using a call to &[stat()]&. For
13528 each path that exists, the corresponding queuing option is set.
13529 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
13530 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
13532 queue_only_file = smtp/some/file
13534 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
13535 &_/some/file_& exists.
13538 .option queue_only_load main fixed-point unset
13539 .cindex "load average"
13540 .cindex "queueing incoming messages"
13541 .cindex "message" "queueing by load"
13542 If the system load average is higher than this value, incoming messages from
13543 all sources are queued, and no automatic deliveries are started. If this
13544 happens during local or remote SMTP input, all subsequent messages on the same
13545 connection are queued. Deliveries will subsequently be performed by queue
13546 runner processes. This option has no effect on ancient operating systems on
13547 which Exim cannot determine the load average. See also
13548 &%deliver_queue_load_max%& and &%smtp_load_reserve%&.
13551 .option queue_only_override main boolean true
13552 .cindex "queueing incoming messages"
13553 When this option is true, the &%-od%&&'x'& command line options override the
13554 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
13555 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
13556 to override; they are accepted, but ignored.
13559 .option queue_run_in_order main boolean false
13560 .cindex "queue runner" "processing messages in order"
13561 If this option is set, queue runs happen in order of message arrival instead of
13562 in an arbitrary order. For this to happen, a complete list of the entire queue
13563 must be set up before the deliveries start. When the queue is all held in a
13564 single directory (the default), a single list is created for both the ordered
13565 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
13566 single list is not created when &%queue_run_in_order%& is false. In this case,
13567 the sub-directories are processed one at a time (in a random order), and this
13568 avoids setting up one huge list for the whole queue. Thus, setting
13569 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
13570 when the queue is large, because of the extra work in setting up the single,
13571 large list. In most situations, &%queue_run_in_order%& should not be set.
13575 .option queue_run_max main integer 5
13576 .cindex "queue runner" "maximum number of"
13577 This controls the maximum number of queue runner processes that an Exim daemon
13578 can run simultaneously. This does not mean that it starts them all at once,
13579 but rather that if the maximum number are still running when the time comes to
13580 start another one, it refrains from starting another one. This can happen with
13581 very large queues and/or very sluggish deliveries. This option does not,
13582 however, interlock with other processes, so additional queue runners can be
13583 started by other means, or by killing and restarting the daemon.
13585 Setting this option to zero does not suppress queue runs; rather, it disables
13586 the limit, allowing any number of simultaneous queue runner processes to be
13587 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
13588 the daemon's command line.
13590 .option queue_smtp_domains main "domain list&!!" unset
13591 .cindex "queueing incoming messages"
13592 .cindex "message" "queueing remote deliveries"
13593 When this option is set, a delivery process is started whenever a message is
13594 received, routing is performed, and local deliveries take place.
13595 However, if any SMTP deliveries are required for domains that match
13596 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
13597 message waits on the queue for the next queue run. Since routing of the message
13598 has taken place, Exim knows to which remote hosts it must be delivered, and so
13599 when the queue run happens, multiple messages for the same host are delivered
13600 over a single SMTP connection. The &%-odqs%& command line option causes all
13601 SMTP deliveries to be queued in this way, and is equivalent to setting
13602 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
13606 .option receive_timeout main time 0s
13607 .cindex "timeout" "for non-SMTP input"
13608 This option sets the timeout for accepting a non-SMTP message, that is, the
13609 maximum time that Exim waits when reading a message on the standard input. If
13610 the value is zero, it will wait for ever. This setting is overridden by the
13611 &%-or%& command line option. The timeout for incoming SMTP messages is
13612 controlled by &%smtp_receive_timeout%&.
13614 .option received_header_text main string&!! "see below"
13615 .cindex "customizing" "&'Received:'& header"
13616 .cindex "&'Received:'& header line" "customizing"
13617 This string defines the contents of the &'Received:'& message header that is
13618 added to each message, except for the timestamp, which is automatically added
13619 on at the end (preceded by a semicolon). The string is expanded each time it is
13620 used. If the expansion yields an empty string, no &'Received:'& header line is
13621 added to the message. Otherwise, the string should start with the text
13622 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
13623 header lines. The default setting is:
13626 received_header_text = Received: \
13627 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
13628 {${if def:sender_ident \
13629 {from ${quote_local_part:$sender_ident} }}\
13630 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
13631 by $primary_hostname \
13632 ${if def:received_protocol {with $received_protocol}} \
13633 ${if def:tls_cipher {($tls_cipher)\n\t}}\
13634 (Exim $version_number)\n\t\
13635 ${if def:sender_address \
13636 {(envelope-from <$sender_address>)\n\t}}\
13637 id $message_exim_id\
13638 ${if def:received_for {\n\tfor $received_for}}
13641 The reference to the TLS cipher is omitted when Exim is built without TLS
13642 support. The use of conditional expansions ensures that this works for both
13643 locally generated messages and messages received from remote hosts, giving
13644 header lines such as the following:
13646 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
13647 by marley.carol.example with esmtp (Exim 4.00)
13648 (envelope-from <bob@carol.example>)
13649 id 16IOWa-00019l-00
13650 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
13651 Received: by scrooge.carol.example with local (Exim 4.00)
13652 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
13654 Until the body of the message has been received, the timestamp is the time when
13655 the message started to be received. Once the body has arrived, and all policy
13656 checks have taken place, the timestamp is updated to the time at which the
13657 message was accepted.
13660 .option received_headers_max main integer 30
13661 .cindex "loop" "prevention"
13662 .cindex "mail loop prevention"
13663 .cindex "&'Received:'& header line" "counting"
13664 When a message is to be delivered, the number of &'Received:'& headers is
13665 counted, and if it is greater than this parameter, a mail loop is assumed to
13666 have occurred, the delivery is abandoned, and an error message is generated.
13667 This applies to both local and remote deliveries.
13670 .option recipient_unqualified_hosts main "host list&!!" unset
13671 .cindex "unqualified addresses"
13672 .cindex "host" "unqualified addresses from"
13673 This option lists those hosts from which Exim is prepared to accept unqualified
13674 recipient addresses in message envelopes. The addresses are made fully
13675 qualified by the addition of the &%qualify_recipient%& value. This option also
13676 affects message header lines. Exim does not reject unqualified recipient
13677 addresses in headers, but it qualifies them only if the message came from a
13678 host that matches &%recipient_unqualified_hosts%&,
13679 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
13680 option was not set.
13683 .option recipients_max main integer 0
13684 .cindex "limit" "number of recipients"
13685 .cindex "recipient" "maximum number"
13686 If this option is set greater than zero, it specifies the maximum number of
13687 original recipients for any message. Additional recipients that are generated
13688 by aliasing or forwarding do not count. SMTP messages get a 452 response for
13689 all recipients over the limit; earlier recipients are delivered as normal.
13690 Non-SMTP messages with too many recipients are failed, and no deliveries are
13693 .cindex "RCPT" "maximum number of incoming"
13694 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
13695 RCPT commands in a single message.
13698 .option recipients_max_reject main boolean false
13699 If this option is set true, Exim rejects SMTP messages containing too many
13700 recipients by giving 552 errors to the surplus RCPT commands, and a 554
13701 error to the eventual DATA command. Otherwise (the default) it gives a 452
13702 error to the surplus RCPT commands and accepts the message on behalf of the
13703 initial set of recipients. The remote server should then re-send the message
13704 for the remaining recipients at a later time.
13707 .option remote_max_parallel main integer 2
13708 .cindex "delivery" "parallelism for remote"
13709 This option controls parallel delivery of one message to a number of remote
13710 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
13711 does all the remote deliveries for a message one by one. Otherwise, if a single
13712 message has to be delivered to more than one remote host, or if several copies
13713 have to be sent to the same remote host, up to &%remote_max_parallel%&
13714 deliveries are done simultaneously. If more than &%remote_max_parallel%&
13715 deliveries are required, the maximum number of processes are started, and as
13716 each one finishes, another is begun. The order of starting processes is the
13717 same as if sequential delivery were being done, and can be controlled by the
13718 &%remote_sort_domains%& option. If parallel delivery takes place while running
13719 with debugging turned on, the debugging output from each delivery process is
13720 tagged with its process id.
13722 This option controls only the maximum number of parallel deliveries for one
13723 message in one Exim delivery process. Because Exim has no central queue
13724 manager, there is no way of controlling the total number of simultaneous
13725 deliveries if the configuration allows a delivery attempt as soon as a message
13728 .cindex "number of deliveries"
13729 .cindex "delivery" "maximum number of"
13730 If you want to control the total number of deliveries on the system, you
13731 need to set the &%queue_only%& option. This ensures that all incoming messages
13732 are added to the queue without starting a delivery process. Then set up an Exim
13733 daemon to start queue runner processes at appropriate intervals (probably
13734 fairly often, for example, every minute), and limit the total number of queue
13735 runners by setting the &%queue_run_max%& parameter. Because each queue runner
13736 delivers only one message at a time, the maximum number of deliveries that can
13737 then take place at once is &%queue_run_max%& multiplied by
13738 &%remote_max_parallel%&.
13740 If it is purely remote deliveries you want to control, use
13741 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
13742 doing the SMTP routing before queuing, so that several messages for the same
13743 host will eventually get delivered down the same connection.
13746 .option remote_sort_domains main "domain list&!!" unset
13747 .cindex "sorting remote deliveries"
13748 .cindex "delivery" "sorting remote"
13749 When there are a number of remote deliveries for a message, they are sorted by
13750 domain into the order given by this list. For example,
13752 remote_sort_domains = *.cam.ac.uk:*.uk
13754 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
13755 then to those in the &%uk%& domain, then to any others.
13758 .option retry_data_expire main time 7d
13759 .cindex "hints database" "data expiry"
13760 This option sets a &"use before"& time on retry information in Exim's hints
13761 database. Any older retry data is ignored. This means that, for example, once a
13762 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
13766 .option retry_interval_max main time 24h
13767 .cindex "retry" "limit on interval"
13768 .cindex "limit" "on retry interval"
13769 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
13770 intervals between delivery attempts for messages that cannot be delivered
13771 straight away. This option sets an overall limit to the length of time between
13772 retries. It cannot be set greater than 24 hours; any attempt to do so forces
13776 .option return_path_remove main boolean true
13777 .cindex "&'Return-path:'& header line" "removing"
13778 RFC 2821, section 4.4, states that an SMTP server must insert a
13779 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
13780 The &'Return-path:'& header preserves the sender address as received in the
13781 MAIL command. This description implies that this header should not be present
13782 in an incoming message. If &%return_path_remove%& is true, any existing
13783 &'Return-path:'& headers are removed from messages at the time they are
13784 received. Exim's transports have options for adding &'Return-path:'& headers at
13785 the time of delivery. They are normally used only for final local deliveries.
13788 .option return_size_limit main integer 100K
13789 This option is an obsolete synonym for &%bounce_return_size_limit%&.
13792 .option rfc1413_hosts main "host list&!!" *
13794 .cindex "host" "for RFC 1413 calls"
13795 RFC 1413 identification calls are made to any client host which matches an item
13798 .option rfc1413_query_timeout main time 5s
13799 .cindex "RFC 1413" "query timeout"
13800 .cindex "timeout" "for RFC 1413 call"
13801 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
13802 no RFC 1413 calls are ever made.
13805 .option sender_unqualified_hosts main "host list&!!" unset
13806 .cindex "unqualified addresses"
13807 .cindex "host" "unqualified addresses from"
13808 This option lists those hosts from which Exim is prepared to accept unqualified
13809 sender addresses. The addresses are made fully qualified by the addition of
13810 &%qualify_domain%&. This option also affects message header lines. Exim does
13811 not reject unqualified addresses in headers that contain sender addresses, but
13812 it qualifies them only if the message came from a host that matches
13813 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
13814 using TCP/IP), and the &%-bnq%& option was not set.
13817 .option smtp_accept_keepalive main boolean true
13818 .cindex "keepalive" "on incoming connection"
13819 This option controls the setting of the SO_KEEPALIVE option on incoming
13820 TCP/IP socket connections. When set, it causes the kernel to probe idle
13821 connections periodically, by sending packets with &"old"& sequence numbers. The
13822 other end of the connection should send an acknowledgement if the connection is
13823 still okay or a reset if the connection has been aborted. The reason for doing
13824 this is that it has the beneficial effect of freeing up certain types of
13825 connection that can get stuck when the remote host is disconnected without
13826 tidying up the TCP/IP call properly. The keepalive mechanism takes several
13827 hours to detect unreachable hosts.
13831 .option smtp_accept_max main integer 20
13832 .cindex "limit" "incoming SMTP connections"
13833 .cindex "SMTP" "incoming connection count"
13835 This option specifies the maximum number of simultaneous incoming SMTP calls
13836 that Exim will accept. It applies only to the listening daemon; there is no
13837 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
13838 value is set to zero, no limit is applied. However, it is required to be
13839 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
13840 set. See also &%smtp_accept_reserve%&.
13844 .option smtp_accept_max_nonmail main integer 10
13845 .cindex "limit" "non-mail SMTP commands"
13846 .cindex "SMTP" "limiting non-mail commands"
13847 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
13848 the connection if there are too many. This option defines &"too many"&. The
13849 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
13850 client looping sending EHLO, for example. The check is applied only if the
13851 client host matches &%smtp_accept_max_nonmail_hosts%&.
13853 When a new message is expected, one occurrence of RSET is not counted. This
13854 allows a client to send one RSET between messages (this is not necessary,
13855 but some clients do it). Exim also allows one uncounted occurence of HELO
13856 or EHLO, and one occurrence of STARTTLS between messages. After
13857 starting up a TLS session, another EHLO is expected, and so it too is not
13858 counted. The first occurrence of AUTH in a connection, or immediately
13859 following STARTTLS is not counted. Otherwise, all commands other than
13860 MAIL, RCPT, DATA, and QUIT are counted.
13863 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
13864 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
13865 check by setting this option. The default value makes it apply to all hosts. By
13866 changing the value, you can exclude any badly-behaved hosts that you have to
13871 .option smtp_accept_max_per_connection main integer 1000
13872 .cindex "SMTP incoming message count" "limiting"
13873 .cindex "limit" "messages per SMTP connection"
13874 The value of this option limits the number of MAIL commands that Exim is
13875 prepared to accept over a single SMTP connection, whether or not each command
13876 results in the transfer of a message. After the limit is reached, a 421
13877 response is given to subsequent MAIL commands. This limit is a safety
13878 precaution against a client that goes mad (incidents of this type have been
13882 .option smtp_accept_max_per_host main string&!! unset
13883 .cindex "limit" "SMTP connections from one host"
13884 .cindex "host" "limiting SMTP connections from"
13885 This option restricts the number of simultaneous IP connections from a single
13886 host (strictly, from a single IP address) to the Exim daemon. The option is
13887 expanded, to enable different limits to be applied to different hosts by
13888 reference to &$sender_host_address$&. Once the limit is reached, additional
13889 connection attempts from the same host are rejected with error code 421. The
13890 default value of zero imposes no limit. If this option is set, it is required
13891 that &%smtp_accept_max%& be non-zero.
13893 &*Warning*&: When setting this option you should not use any expansion
13894 constructions that take an appreciable amount of time. The expansion and test
13895 happen in the main daemon loop, in order to reject additional connections
13896 without forking additional processes (otherwise a denial-of-service attack
13897 could cause a vast number or processes to be created). While the daemon is
13898 doing this processing, it cannot accept any other incoming connections.
13902 .option smtp_accept_queue main integer 0
13903 .cindex "SMTP" "incoming connection count"
13904 .cindex "queueing incoming messages"
13905 .cindex "message" "queueing by SMTP connection count"
13906 If the number of simultaneous incoming SMTP calls handled via the listening
13907 daemon exceeds this value, messages received by SMTP are just placed on the
13908 queue; no delivery processes are started automatically. A value of zero implies
13909 no limit, and clearly any non-zero value is useful only if it is less than the
13910 &%smtp_accept_max%& value (unless that is zero). See also &%queue_only%&,
13911 &%queue_only_load%&, &%queue_smtp_domains%&, and the various &%-od%&&'x'&
13912 command line options.
13915 .option smtp_accept_queue_per_connection main integer 10
13916 .cindex "queueing incoming messages"
13917 .cindex "message" "queueing by message count"
13918 This option limits the number of delivery processes that Exim starts
13919 automatically when receiving messages via SMTP, whether via the daemon or by
13920 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
13921 and the number of messages received in a single SMTP session exceeds this
13922 number, subsequent messages are placed on the queue, but no delivery processes
13923 are started. This helps to limit the number of Exim processes when a server
13924 restarts after downtime and there is a lot of mail waiting for it on other
13925 systems. On large systems, the default should probably be increased, and on
13926 dial-in client systems it should probably be set to zero (that is, disabled).
13929 .option smtp_accept_reserve main integer 0
13930 .cindex "SMTP" "incoming call count"
13931 .cindex "host" "reserved"
13932 When &%smtp_accept_max%& is set greater than zero, this option specifies a
13933 number of SMTP connections that are reserved for connections from the hosts
13934 that are specified in &%smtp_reserve_hosts%&. The value set in
13935 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
13936 restricted to this number of connections; the option specifies a minimum number
13937 of connection slots for them, not a maximum. It is a guarantee that that group
13938 of hosts can always get at least &%smtp_accept_reserve%& connections.
13940 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
13941 set to 5, once there are 45 active connections (from any hosts), new
13942 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&.
13943 See also &%smtp_accept_max_per_host%&.
13946 .option smtp_active_hostname main string&!! unset
13947 .cindex "host" "name in SMTP responses"
13948 .cindex "SMTP" "host name in responses"
13949 .cindex "&$primary_hostname$&"
13950 This option is provided for multi-homed servers that want to masquerade as
13951 several different hosts. At the start of an SMTP connection, its value is
13952 expanded and used instead of the value of &$primary_hostname$& in SMTP
13953 responses. For example, it is used as domain name in the response to an
13954 incoming HELO or EHLO command.
13956 .cindex "&$smtp_active_hostname$&"
13957 It is also used in HELO commands for callout verification. The active hostname
13958 is placed in the &$smtp_active_hostname$& variable, which is saved with any
13959 messages that are received. It is therefore available for use in routers and
13960 transports when the message is later delivered.
13962 If this option is unset, or if its expansion is forced to fail, or if the
13963 expansion results in an empty string, the value of &$primary_hostname$& is
13964 used. Other expansion failures cause a message to be written to the main and
13965 panic logs, and the SMTP command receives a temporary error. Typically, the
13966 value of &%smtp_active_hostname%& depends on the incoming interface address.
13969 smtp_active_hostname = ${if eq{$interface_address}{10.0.0.1}\
13970 {cox.mydomain}{box.mydomain}}
13973 .option smtp_banner main string&!! "see below"
13974 .cindex "SMTP" "welcome banner"
13975 .cindex "banner for SMTP"
13976 .cindex "welcome banner for SMTP"
13977 .cindex "customizing" "SMTP banner"
13978 This string, which is expanded every time it is used, is output as the initial
13979 positive response to an SMTP connection. The default setting is:
13981 smtp_banner = $smtp_active_hostname ESMTP Exim \
13982 $version_number $tod_full
13984 Failure to expand the string causes a panic error. If you want to create a
13985 multiline response to the initial SMTP connection, use &"\n"& in the string at
13986 appropriate points, but not at the end. Note that the 220 code is not included
13987 in this string. Exim adds it automatically (several times in the case of a
13988 multiline response).
13991 .option smtp_check_spool_space main boolean true
13992 .cindex "checking disk space"
13993 .cindex "disk space" "checking"
13994 .cindex "spool directory" "checking space"
13995 When this option is set, if an incoming SMTP session encounters the SIZE
13996 option on a MAIL command, it checks that there is enough space in the
13997 spool directory's partition to accept a message of that size, while still
13998 leaving free the amount specified by &%check_spool_space%& (even if that value
13999 is zero). If there isn't enough space, a temporary error code is returned.
14002 .option smtp_connect_backlog main integer 20
14003 .cindex "connection backlog"
14004 .cindex "SMTP" "connection backlog"
14005 .cindex "backlog of connections"
14006 This option specifies a maximum number of waiting SMTP connections. Exim passes
14007 this value to the TCP/IP system when it sets up its listener. Once this number
14008 of connections are waiting for the daemon's attention, subsequent connection
14009 attempts are refused at the TCP/IP level. At least, that is what the manuals
14010 say; in some circumstances such connection attempts have been observed to time
14011 out instead. For large systems it is probably a good idea to increase the
14012 value (to 50, say). It also gives some protection against denial-of-service
14013 attacks by SYN flooding.
14016 .option smtp_enforce_sync main boolean true
14017 .cindex "SMTP" "synchronization checking"
14018 .cindex "synchronization checking in SMTP"
14019 The SMTP protocol specification requires the client to wait for a response from
14020 the server at certain points in the dialogue. Without PIPELINING these
14021 synchronization points are after every command; with PIPELINING they are
14022 fewer, but they still exist.
14024 Some spamming sites send out a complete set of SMTP commands without waiting
14025 for any response. Exim protects against this by rejecting a message if the
14026 client has sent further input when it should not have. The error response &"554
14027 SMTP synchronization error"& is sent, and the connection is dropped. Testing
14028 for this error cannot be perfect because of transmission delays (unexpected
14029 input may be on its way but not yet received when Exim checks). However, it
14030 does detect many instances.
14032 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
14033 If you want to disable the check selectively (for example, only for certain
14034 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
14035 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
14039 .option smtp_etrn_command main string&!! unset
14040 .cindex "ETRN" "command to be run"
14041 .cindex "&$domain$&"
14042 If this option is set, the given command is run whenever an SMTP ETRN
14043 command is received from a host that is permitted to issue such commands (see
14044 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
14045 are independently expanded. The expansion variable &$domain$& is set to the
14046 argument of the ETRN command, and no syntax checking is done on it. For
14049 smtp_etrn_command = /etc/etrn_command $domain \
14050 $sender_host_address
14052 A new process is created to run the command, but Exim does not wait for it to
14053 complete. Consequently, its status cannot be checked. If the command cannot be
14054 run, a line is written to the panic log, but the ETRN caller still receives
14055 a 250 success response. Exim is normally running under its own uid when
14056 receiving SMTP, so it is not possible for it to change the uid before running
14060 .option smtp_etrn_serialize main boolean true
14061 .cindex "ETRN" "serializing"
14062 When this option is set, it prevents the simultaneous execution of more than
14063 one identical command as a result of ETRN in an SMTP connection. See
14064 section &<<SECTETRN>>& for details.
14067 .option smtp_load_reserve main fixed-point unset
14068 .cindex "load average"
14069 If the system load average ever gets higher than this, incoming SMTP calls are
14070 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
14071 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
14072 the load is over the limit. The option has no effect on ancient operating
14073 systems on which Exim cannot determine the load average. See also
14074 &%deliver_queue_load_max%& and &%queue_only_load%&.
14078 .option smtp_max_synprot_errors main integer 3
14079 .cindex "SMTP" "limiting syntax and protocol errors"
14080 .cindex "limit" "SMTP syntax and protocol errors"
14081 Exim rejects SMTP commands that contain syntax or protocol errors. In
14082 particular, a syntactically invalid email address, as in this command:
14084 RCPT TO:<abc xyz@a.b.c>
14086 causes immediate rejection of the command, before any other tests are done.
14087 (The ACL cannot be run if there is no valid address to set up for it.) An
14088 example of a protocol error is receiving RCPT before MAIL. If there are
14089 too many syntax or protocol errors in one SMTP session, the connection is
14090 dropped. The limit is set by this option.
14092 .cindex "PIPELINING" "expected errors"
14093 When the PIPELINING extension to SMTP is in use, some protocol errors are
14094 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
14095 Exim assumes that PIPELINING will be used if it advertises it (see
14096 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
14097 not count towards the limit.
14101 .option smtp_max_unknown_commands main integer 3
14102 .cindex "SMTP" "limiting unknown commands"
14103 .cindex "limit" "unknown SMTP commands"
14104 If there are too many unrecognized commands in an incoming SMTP session, an
14105 Exim server drops the connection. This is a defence against some kinds of abuse
14108 into making connections to SMTP ports; in these circumstances, a number of
14109 non-SMTP command lines are sent first.
14113 .option smtp_ratelimit_hosts main "host list&!!" unset
14114 .cindex "SMTP" "rate limiting"
14115 .cindex "limit" "rate of message arrival"
14116 .cindex "RCPT" "rate limiting"
14117 Some sites find it helpful to be able to limit the rate at which certain hosts
14118 can send them messages, and the rate at which an individual message can specify
14121 Exim has two rate-limiting facilities. This section describes the older
14122 facility, which can limit rates within a single connection. The newer
14123 &%ratelimit%& ACL condition can limit rates across all connections. See section
14124 &<<SECTratelimiting>>& for details of the newer facility.
14126 When a host matches &%smtp_ratelimit_hosts%&, the values of
14127 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
14128 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
14129 respectively. Each option, if set, must contain a set of four comma-separated
14133 A threshold, before which there is no rate limiting.
14135 An initial time delay. Unlike other times in Exim, numbers with decimal
14136 fractional parts are allowed here.
14138 A factor by which to increase the delay each time.
14140 A maximum value for the delay. This should normally be less than 5 minutes,
14141 because after that time, the client is liable to timeout the SMTP command.
14144 For example, these settings have been used successfully at the site which
14145 first suggested this feature, for controlling mail from their customers:
14147 smtp_ratelimit_mail = 2,0.5s,1.05,4m
14148 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
14150 The first setting specifies delays that are applied to MAIL commands after
14151 two have been received over a single connection. The initial delay is 0.5
14152 seconds, increasing by a factor of 1.05 each time. The second setting applies
14153 delays to RCPT commands when more than four occur in a single message.
14156 .option smtp_ratelimit_mail main string unset
14157 See &%smtp_ratelimit_hosts%& above.
14160 .option smtp_ratelimit_rcpt main string unset
14161 See &%smtp_ratelimit_hosts%& above.
14164 .option smtp_receive_timeout main time 5m
14165 .cindex "timeout" "for SMTP input"
14166 .cindex "SMTP timeout" "input"
14167 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
14168 input, including batch SMTP. If a line of input (either an SMTP command or a
14169 data line) is not received within this time, the SMTP connection is dropped and
14170 the message is abandoned.
14171 A line is written to the log containing one of the following messages:
14173 SMTP command timeout on connection from...
14174 SMTP data timeout on connection from...
14176 The former means that Exim was expecting to read an SMTP command; the latter
14177 means that it was in the DATA phase, reading the contents of a message.
14180 .cindex "&%-os%& option"
14181 The value set by this option can be overridden by the
14182 &%-os%& command-line option. A setting of zero time disables the timeout, but
14183 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
14184 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
14185 timeout is controlled by &%receive_timeout%& and &%-or%&.
14188 .option smtp_reserve_hosts main "host list&!!" unset
14189 This option defines hosts for which SMTP connections are reserved; see
14190 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
14193 .option smtp_return_error_details main boolean false
14194 .cindex "SMTP" "details policy failures"
14195 .cindex "policy control rejection" "returning details"
14196 In the default state, Exim uses bland messages such as
14197 &"Administrative prohibition"& when it rejects SMTP commands for policy
14198 reasons. Many sysadmins like this because it gives away little information
14199 to spammers. However, some other syadmins who are applying strict checking
14200 policies want to give out much fuller information about failures. Setting
14201 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
14202 example, instead of &"Administrative prohibition"&, it might give:
14204 550-Rejected after DATA: '>' missing at end of address:
14205 550 failing address in "From" header is: <user@dom.ain
14208 .option spamd_address main string "see below"
14209 This option is available when Exim is compiled with the content-scanning
14210 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
14211 The default value is
14215 See section &<<SECTscanspamass>>& for more details.
14219 .option split_spool_directory main boolean false
14220 .cindex "multiple spool directories"
14221 .cindex "spool directory" "split"
14222 .cindex "directories" "multiple"
14223 If this option is set, it causes Exim to split its input directory into 62
14224 subdirectories, each with a single alphanumeric character as its name. The
14225 sixth character of the message id is used to allocate messages to
14226 subdirectories; this is the least significant base-62 digit of the time of
14227 arrival of the message.
14229 Splitting up the spool in this way may provide better performance on systems
14230 where there are long mail queues, by reducing the number of files in any one
14231 directory. The msglog directory is also split up in a similar way to the input
14232 directory; however, if &%preserve_message_logs%& is set, all old msglog files
14233 are still placed in the single directory &_msglog.OLD_&.
14235 It is not necessary to take any special action for existing messages when
14236 changing &%split_spool_directory%&. Exim notices messages that are in the
14237 &"wrong"& place, and continues to process them. If the option is turned off
14238 after a period of being on, the subdirectories will eventually empty and be
14239 automatically deleted.
14241 When &%split_spool_directory%& is set, the behaviour of queue runner processes
14242 changes. Instead of creating a list of all messages in the queue, and then
14243 trying to deliver each one in turn, it constructs a list of those in one
14244 sub-directory and tries to deliver them, before moving on to the next
14245 sub-directory. The sub-directories are processed in a random order. This
14246 spreads out the scanning of the input directories, and uses less memory. It is
14247 particularly beneficial when there are lots of messages on the queue. However,
14248 if &%queue_run_in_order%& is set, none of this new processing happens. The
14249 entire queue has to be scanned and sorted before any deliveries can start.
14252 .option spool_directory main string&!! "set at compile time"
14253 .cindex "spool directory" "path to"
14254 This defines the directory in which Exim keeps its spool, that is, the messages
14255 it is waiting to deliver. The default value is taken from the compile-time
14256 configuration setting, if there is one. If not, this option must be set. The
14257 string is expanded, so it can contain, for example, a reference to
14258 &$primary_hostname$&.
14260 If the spool directory name is fixed on your installation, it is recommended
14261 that you set it at build time rather than from this option, particularly if the
14262 log files are being written to the spool directory (see &%log_file_path%&).
14263 Otherwise log files cannot be used for errors that are detected early on, such
14264 as failures in the configuration file.
14266 By using this option to override the compiled-in path, it is possible to run
14267 tests of Exim without using the standard spool.
14269 .option sqlite_lock_timeout main time 5s
14270 .cindex "sqlite" "lock timeout"
14271 This option controls the timeout that the &(sqlite)& lookup uses when trying to
14272 access an SQLite database. See section &<<SECTsqlite>>& for more details.
14274 .option strip_excess_angle_brackets main boolean false
14275 .cindex "angle brackets" "excess"
14276 If this option is set, redundant pairs of angle brackets round &"route-addr"&
14277 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
14278 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
14279 passed on to another MTA, the excess angle brackets are not passed on. If this
14280 option is not set, multiple pairs of angle brackets cause a syntax error.
14283 .option strip_trailing_dot main boolean false
14284 .cindex "trailing dot on domain"
14285 .cindex "dot" "trailing on domain"
14286 If this option is set, a trailing dot at the end of a domain in an address is
14287 ignored. If this is in the envelope and the message is passed on to another
14288 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
14289 domain causes a syntax error.
14290 However, addresses in header lines are checked only when an ACL requests header
14294 .option syslog_duplication main boolean true
14295 .cindex "syslog" "duplicate log lines; suppressing"
14296 When Exim is logging to syslog, it writes the log lines for its three
14297 separate logs at different syslog priorities so that they can in principle
14298 be separated on the logging hosts. Some installations do not require this
14299 separation, and in those cases, the duplication of certain log lines is a
14300 nuisance. If &%syslog_duplication%& is set false, only one copy of any
14301 particular log line is written to syslog. For lines that normally go to
14302 both the main log and the reject log, the reject log version (possibly
14303 containing message header lines) is written, at LOG_NOTICE priority.
14304 Lines that normally go to both the main and the panic log are written at
14305 the LOG_ALERT priority.
14308 .option syslog_facility main string unset
14309 .cindex "syslog" "facility; setting"
14310 This option sets the syslog &"facility"& name, used when Exim is logging to
14311 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
14312 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
14313 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
14314 details of Exim's logging.
14318 .option syslog_processname main string &`exim`&
14319 .cindex "syslog" "process name; setting"
14320 This option sets the syslog &"ident"& name, used when Exim is logging to
14321 syslog. The value must be no longer than 32 characters. See chapter
14322 &<<CHAPlog>>& for details of Exim's logging.
14326 .option syslog_timestamp main boolean true
14327 .cindex "syslog" "timestamps"
14328 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
14329 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
14330 details of Exim's logging.
14333 .option system_filter main string&!! unset
14334 .cindex "filter" "system filter"
14335 .cindex "system filter" "specifying"
14336 .cindex "Sieve filter" "not available for system filter"
14337 This option specifies an Exim filter file that is applied to all messages at
14338 the start of each delivery attempt, before any routing is done. System filters
14339 must be Exim filters; they cannot be Sieve filters. If the system filter
14340 generates any deliveries to files or pipes, or any new mail messages, the
14341 appropriate &%system_filter_..._transport%& option(s) must be set, to define
14342 which transports are to be used. Details of this facility are given in chapter
14343 &<<CHAPsystemfilter>>&.
14346 .option system_filter_directory_transport main string&!! unset
14347 .cindex "&$address_file$&"
14348 This sets the name of the transport driver that is to be used when the
14349 &%save%& command in a system message filter specifies a path ending in &"/"&,
14350 implying delivery of each message into a separate file in some directory.
14351 During the delivery, the variable &$address_file$& contains the path name.
14354 .option system_filter_file_transport main string&!! unset
14355 .cindex "file" "transport for system filter"
14356 This sets the name of the transport driver that is to be used when the &%save%&
14357 command in a system message filter specifies a path not ending in &"/"&. During
14358 the delivery, the variable &$address_file$& contains the path name.
14360 .option system_filter_group main string unset
14361 .cindex "gid (group id)" "system filter"
14362 This option is used only when &%system_filter_user%& is also set. It sets the
14363 gid under which the system filter is run, overriding any gid that is associated
14364 with the user. The value may be numerical or symbolic.
14366 .option system_filter_pipe_transport main string&!! unset
14367 .cindex "&(pipe)& transport" "for system filter"
14368 .cindex "&$address_pipe$&"
14369 This specifies the transport driver that is to be used when a &%pipe%& command
14370 is used in a system filter. During the delivery, the variable &$address_pipe$&
14371 contains the pipe command.
14374 .option system_filter_reply_transport main string&!! unset
14375 .cindex "&(autoreply)& transport" "for system filter"
14376 This specifies the transport driver that is to be used when a &%mail%& command
14377 is used in a system filter.
14379 .option system_filter_user main string unset
14380 .cindex "uid (user id)" "system filter"
14381 If this option is not set, the system filter is run in the main Exim delivery
14382 process, as root. When the option is set, the system filter runs in a separate
14383 process, as the given user. Unless the string consists entirely of digits, it
14384 is looked up in the password data. Failure to find the named user causes a
14385 configuration error. The gid is either taken from the password data, or
14386 specified by &%system_filter_group%&. When the uid is specified numerically,
14387 &%system_filter_group%& is required to be set.
14389 If the system filter generates any pipe, file, or reply deliveries, the uid
14390 under which the filter is run is used when transporting them, unless a
14391 transport option overrides. Normally you should set &%system_filter_user%& if
14392 your system filter generates these kinds of delivery.
14395 .option tcp_nodelay main boolean true
14396 .cindex "daemon" "TCP_NODELAY on sockets"
14397 .cindex "Nagle algorithm"
14398 .cindex "TCP_NODELAY on listening sockets"
14399 If this option is set false, it stops the Exim daemon setting the
14400 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
14401 turns off the &"Nagle algorithm"&, which is a way of improving network
14402 performance in interactive (character-by-character) situations. Turning it off
14403 should improve Exim's performance a bit, so that is what happens by default.
14404 However, it appears that some broken clients cannot cope, and time out. Hence
14405 this option. It affects only those sockets that are set up for listening by the
14406 daemon. Sockets created by the smtp transport for delivering mail always set
14410 .option timeout_frozen_after main time 0s
14411 .cindex "frozen messages" "timing out"
14412 .cindex "timeout" "frozen messages"
14413 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
14414 message of any kind that has been on the queue for longer than the given
14415 time is automatically cancelled at the next queue run. If it is a bounce
14416 message, it is just discarded; otherwise, a bounce is sent to the sender, in a
14417 similar manner to cancellation by the &%-Mg%& command line option. If you want
14418 to timeout frozen bounce messages earlier than other kinds of frozen message,
14419 see &%ignore_bounce_errors_after%&.
14422 .option timezone main string unset
14423 .cindex "timezone" "setting"
14424 The value of &%timezone%& is used to set the environment variable TZ while
14425 running Exim (if it is different on entry). This ensures that all timestamps
14426 created by Exim are in the required timezone. If you want all your timestamps
14427 to be in UTC (aka GMT) you should set
14431 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
14432 or, if that is not set, from the value of the TZ environment variable when Exim
14433 is built. If &%timezone%& is set to the empty string, either at build or run
14434 time, any existing TZ variable is removed from the environment when Exim
14435 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
14436 unfortunately not all, operating systems.
14439 .option tls_advertise_hosts main "host list&!!" unset
14440 .cindex "TLS" "advertising"
14441 .cindex "encryption" "on SMTP connection"
14442 .cindex "SMTP" "encrypted connection"
14443 When Exim is built with support for TLS encrypted connections, the availability
14444 of the STARTTLS command to set up an encrypted session is advertised in
14445 response to EHLO only to those client hosts that match this option. See
14446 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
14449 .option tls_certificate main string&!! unset
14450 .cindex "TLS" "server certificate; location of"
14451 .cindex "certificate for server" "location of"
14452 The value of this option is expanded, and must then be the absolute path to a
14453 file which contains the server's certificates. The server's private key is also
14454 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
14455 &<<CHAPTLS>>& for further details.
14457 &*Note*&: The certificates defined by this option are used only when Exim is
14458 receiving incoming messages as a server. If you want to supply certificates for
14459 use when sending messages as a client, you must set the &%tls_certificate%&
14460 option in the relevant &(smtp)& transport.
14463 .option tls_crl main string&!! unset
14464 .cindex "TLS" "server certificate revocation list"
14465 .cindex "certificate" "revocation list for server"
14466 This option specifies a certificate revocation list. The expanded value must
14467 be the name of a file that contains a CRL in PEM format.
14470 .option tls_dhparam main string&!! unset
14471 .cindex "TLS" "D-H parameters for server"
14472 The value of this option is expanded, and must then be the absolute path to
14473 a file which contains the server's DH parameter values.
14474 This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is
14475 ignored. See section &<<SECTopenvsgnu>>& for further details.
14478 .option tls_on_connect_ports main "string list" unset
14479 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
14480 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
14481 set up without waiting for the client to issue a STARTTLS command. For
14482 further details, see section &<<SECTsupobssmt>>&.
14486 .option tls_privatekey main string&!! unset
14487 .cindex "TLS" "server private key; location of"
14488 The value of this option is expanded, and must then be the absolute path to a
14489 file which contains the server's private key. If this option is unset, or if
14490 the expansion is forced to fail, or the result is an empty string, the private
14491 key is assumed to be in the same file as the server's certificates. See chapter
14492 &<<CHAPTLS>>& for further details.
14495 .option tls_remember_esmtp main boolean false
14496 .cindex "TLS" "esmtp state; remembering"
14497 .cindex "TLS" "broken clients"
14498 If this option is set true, Exim violates the RFCs by remembering that it is in
14499 &"esmtp"& state after successfully negotiating a TLS session. This provides
14500 support for broken clients that fail to send a new EHLO after starting a
14504 .option tls_require_ciphers main string&!! unset
14505 .cindex "TLS" "requiring specific ciphers"
14506 .cindex "cipher" "requiring specific"
14507 This option controls which ciphers can be used for incoming TLS connections.
14508 The &(smtp)& transport has an option of the same name for controlling outgoing
14509 connections. This option is expanded for each connection, so can be varied for
14510 different clients if required. The value of this option must be a list of
14511 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
14512 in somewhat different ways. If GnuTLS is being used, the client controls the
14513 preference order of the available ciphers. Details are given in sections
14514 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
14517 .option tls_try_verify_hosts main "host list&!!" unset
14518 .cindex "TLS" "client certificate verification"
14519 .cindex "certificate" "verification of client"
14520 See &%tls_verify_hosts%& below.
14523 .option tls_verify_certificates main string&!! unset
14524 .cindex "TLS" "client certificate verification"
14525 .cindex "certificate" "verification of client"
14526 The value of this option is expanded, and must then be the absolute path to
14527 a file containing permitted certificates for clients that
14528 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you
14529 are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a
14530 directory containing certificate files. This does not work with GnuTLS; the
14531 option must be set to the name of a single file if you are using GnuTLS.
14534 .option tls_verify_hosts main "host list&!!" unset
14535 .cindex "TLS" "client certificate verification"
14536 .cindex "certificate" "verification of client"
14537 This option, along with &%tls_try_verify_hosts%&, controls the checking of
14538 certificates from clients.
14539 The expected certificates are defined by &%tls_verify_certificates%&, which
14540 must be set. A configuration error occurs if either &%tls_verify_hosts%& or
14541 &%tls_try_verify_hosts%& is set and &%tls_verify_certificates%& is not set.
14543 Any client that matches &%tls_verify_hosts%& is constrained by
14544 &%tls_verify_certificates%&. The client must present one of the listed
14545 certificates. If it does not, the connection is aborted.
14547 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
14548 matches this option (but not &%tls_verify_hosts%&), Exim requests a
14549 certificate and checks it against &%tls_verify_certificates%&, but does not
14550 abort the connection if there is no certificate or if it does not match. This
14551 state can be detected in an ACL, which makes it possible to implement policies
14552 such as &"accept for relay only if a verified certificate has been received,
14553 but accept for local delivery if encrypted, even without a verified
14556 Client hosts that match neither of these lists are not asked to present
14560 .option trusted_groups main "string list&!!" unset
14561 .cindex "trusted group"
14562 .cindex "group" "trusted"
14563 This option is expanded just once, at the start of Exim's processing. If this
14564 option is set, any process that is running in one of the listed groups, or
14565 which has one of them as a supplementary group, is trusted. The groups can be
14566 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
14567 details of what trusted callers are permitted to do. If neither
14568 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
14571 .option trusted_users main "string list&!!" unset
14572 .cindex "trusted user"
14573 .cindex "user" "trusted"
14574 This option is expanded just once, at the start of Exim's processing. If this
14575 option is set, any process that is running as one of the listed users is
14576 trusted. The users can be specified numerically or by name. See section
14577 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
14578 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
14579 Exim user are trusted.
14581 .option unknown_login main string&!! unset
14582 .cindex "uid (user id)" "unknown caller"
14583 .cindex "&$caller_uid$&"
14584 This is a specialized feature for use in unusual configurations. By default, if
14585 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
14586 gives up. The &%unknown_login%& option can be used to set a login name to be
14587 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
14588 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
14589 is used for the user's real name (gecos field), unless this has been set by the
14592 .option unknown_username main string unset
14593 See &%unknown_login%&.
14595 .option untrusted_set_sender main "address list&!!" unset
14596 .cindex "trusted user"
14597 .cindex "sender" "setting by untrusted user"
14598 .cindex "untrusted user" "setting sender"
14599 .cindex "user" "untrusted setting sender"
14600 .cindex "envelope sender"
14601 When an untrusted user submits a message to Exim using the standard input, Exim
14602 normally creates an envelope sender address from the user's login and the
14603 default qualification domain. Data from the &%-f%& option (for setting envelope
14604 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
14605 is used) is ignored.
14607 However, untrusted users are permitted to set an empty envelope sender address,
14608 to declare that a message should never generate any bounces. For example:
14610 exim -f '<>' user@domain.example
14612 .cindex "&$sender_ident$&"
14613 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
14614 other envelope sender addresses in a controlled way. When it is set, untrusted
14615 users are allowed to set envelope sender addresses that match any of the
14616 patterns in the list. Like all address lists, the string is expanded. The
14617 identity of the user is in &$sender_ident$&, so you can, for example, restrict
14618 users to setting senders that start with their login ids
14619 followed by a hyphen
14620 by a setting like this:
14622 untrusted_set_sender = ^$sender_ident-
14624 If you want to allow untrusted users to set envelope sender addresses without
14625 restriction, you can use
14627 untrusted_set_sender = *
14629 The &%untrusted_set_sender%& option applies to all forms of local input, but
14630 only to the setting of the envelope sender. It does not permit untrusted users
14631 to use the other options which trusted user can use to override message
14632 parameters. Furthermore, it does not stop Exim from removing an existing
14633 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
14634 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
14635 overriding these actions. The handling of the &'Sender:'& header is also
14636 described in section &<<SECTthesenhea>>&.
14638 The log line for a message's arrival shows the envelope sender following
14639 &"<="&. For local messages, the user's login always follows, after &"U="&. In
14640 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
14641 envelope sender address, the user's login is shown in parentheses after the
14645 .option uucp_from_pattern main string "see below"
14646 .cindex "&""From""& line"
14647 .cindex "UUCP" "&""From""& line"
14648 Some applications that pass messages to an MTA via a command line interface use
14649 an initial line starting with &"From&~"& to pass the envelope sender. In
14650 particular, this is used by UUCP software. Exim recognizes such a line by means
14651 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
14652 matches, the sender address is constructed by expanding the contents of
14653 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
14654 default pattern recognizes lines in the following two forms:
14656 From ph10 Fri Jan 5 12:35 GMT 1996
14657 From ph10 Fri, 7 Jan 97 14:00:00 GMT
14659 The pattern can be seen by running
14661 exim -bP uucp_from_pattern
14663 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
14664 year in the second case. The first word after &"From&~"& is matched in the
14665 regular expression by a parenthesized subpattern. The default value for
14666 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
14667 (&"ph10"& in the example above) as the message's sender. See also
14668 &%ignore_fromline_hosts%&.
14671 .option uucp_from_sender main string&!! &`$1`&
14672 See &%uucp_from_pattern%& above.
14675 .option warn_message_file main string unset
14676 .cindex "warning of delay" "customizing the message"
14677 .cindex "customizing" "warning message"
14678 This option defines a template file containing paragraphs of text to be used
14679 for constructing the warning message which is sent by Exim when a message has
14680 been on the queue for a specified amount of time, as specified by
14681 &%delay_warning%&. Details of the file's contents are given in chapter
14682 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
14685 .option write_rejectlog main boolean true
14686 .cindex "reject log" "disabling"
14687 If this option is set false, Exim no longer writes anything to the reject log.
14688 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
14689 .ecindex IIDconfima
14690 .ecindex IIDmaiconf
14695 . ////////////////////////////////////////////////////////////////////////////
14696 . ////////////////////////////////////////////////////////////////////////////
14698 .chapter "Generic options for routers" "CHAProutergeneric"
14699 .scindex IIDgenoprou1 "options" "generic; for routers"
14700 .scindex IIDgenoprou2 "generic options" "router"
14701 This chapter describes the generic options that apply to all routers.
14702 Those that are preconditions are marked with ‡ in the &"use"& field.
14704 For a general description of how a router operates, see sections
14705 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
14706 which the preconditions are tested. The order of expansion of the options that
14707 provide data for a transport is: &%errors_to%&, &%headers_add%&,
14708 &%headers_remove%&, &%transport%&.
14712 .option address_data routers string&!! unset
14713 .cindex "router" "data attached to address"
14714 The string is expanded just before the router is run, that is, after all the
14715 precondition tests have succeeded. If the expansion is forced to fail, the
14716 router declines, the value of &%address_data%& remains unchanged, and the
14717 &%more%& option controls what happens next. Other expansion failures cause
14718 delivery of the address to be deferred.
14720 .cindex "&$address_data$&"
14721 When the expansion succeeds, the value is retained with the address, and can be
14722 accessed using the variable &$address_data$& in the current router, subsequent
14723 routers, and the eventual transport.
14725 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
14726 that runs a user's filter file, the contents of &$address_data$& are accessible
14727 in the filter. This is not normally a problem, because such data is usually
14728 either not confidential or it &"belongs"& to the current user, but if you do
14729 put confidential data into &$address_data$& you need to remember this point.
14731 Even if the router declines or passes, the value of &$address_data$& remains
14732 with the address, though it can be changed by another &%address_data%& setting
14733 on a subsequent router. If a router generates child addresses, the value of
14734 &$address_data$& propagates to them. This also applies to the special kind of
14735 &"child"& that is generated by a router with the &%unseen%& option.
14737 The idea of &%address_data%& is that you can use it to look up a lot of data
14738 for the address once, and then pick out parts of the data later. For example,
14739 you could use a single LDAP lookup to return a string of the form
14741 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
14743 In the transport you could pick out the mailbox by a setting such as
14745 file = ${extract{mailbox}{$address_data}}
14747 This makes the configuration file less messy, and also reduces the number of
14748 lookups (though Exim does cache lookups).
14750 The &%address_data%& facility is also useful as a means of passing information
14751 from one router to another, and from a router to a transport. In addition, if
14753 .cindex "&$sender_address_data$&"
14754 .cindex "&$address_data$&"
14755 When &$address_data$& is set by a router when verifying a recipient address
14756 from an ACL, it remains available for use in the rest of the ACL statement.
14757 After verifying a sender, the value is transferred to &$sender_address_data$&.
14762 .option address_test routers&!? boolean true
14763 .cindex "&%-bt%& option"
14764 .cindex "router" "skipping when address testing"
14765 If this option is set false, the router is skipped when routing is being tested
14766 by means of the &%-bt%& command line option. This can be a convenience when
14767 your first router sends messages to an external scanner, because it saves you
14768 having to set the &"already scanned"& indicator when testing real address
14773 .option cannot_route_message routers string&!! unset
14774 .cindex "router" "customizing &""cannot route""& message"
14775 .cindex "customizing" "&""cannot route""& message"
14776 This option specifies a text message that is used when an address cannot be
14777 routed because Exim has run out of routers. The default message is
14778 &"Unrouteable address"&. This option is useful only on routers that have
14779 &%more%& set false, or on the very last router in a configuration, because the
14780 value that is used is taken from the last router that is considered. This
14781 includes a router that is skipped because its preconditions are not met, as
14782 well as a router that declines. For example, using the default configuration,
14785 cannot_route_message = Remote domain not found in DNS
14787 on the first router, which is a &(dnslookup)& router with &%more%& set false,
14790 cannot_route_message = Unknown local user
14792 on the final router that checks for local users. If string expansion fails for
14793 this option, the default message is used. Unless the expansion failure was
14794 explicitly forced, a message about the failure is written to the main and panic
14795 logs, in addition to the normal message about the routing failure.
14798 .option caseful_local_part routers boolean false
14799 .cindex "case of local parts"
14800 .cindex "router" "case of local parts"
14801 By default, routers handle the local parts of addresses in a case-insensitive
14802 manner, though the actual case is preserved for transmission with the message.
14803 If you want the case of letters to be significant in a router, you must set
14804 this option true. For individual router options that contain address or local
14805 part lists (for example, &%local_parts%&), case-sensitive matching can be
14806 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
14809 .cindex "&$local_part$&"
14810 .cindex "&$original_local_part$&"
14811 .cindex "&$parent_local_part$&"
14812 The value of the &$local_part$& variable is forced to lower case while a
14813 router is running unless &%caseful_local_part%& is set. When a router assigns
14814 an address to a transport, the value of &$local_part$& when the transport runs
14815 is the same as it was in the router. Similarly, when a router generates child
14816 addresses by aliasing or forwarding, the values of &$original_local_part$&
14817 and &$parent_local_part$& are those that were used by the redirecting router.
14819 This option applies to the processing of an address by a router. When a
14820 recipient address is being processed in an ACL, there is a separate &%control%&
14821 modifier that can be used to specify case-sensitive processing within the ACL
14822 (see section &<<SECTcontrols>>&).
14826 .option check_local_user routers&!? boolean false
14827 .cindex "local user" "checking in router"
14828 .cindex "router" "checking for local user"
14829 .cindex "&_/etc/passwd_&"
14831 When this option is true, Exim checks that the local part of the recipient
14832 address (with affixes removed if relevant) is the name of an account on the
14833 local system. The check is done by calling the &[getpwnam()]& function rather
14834 than trying to read &_/etc/passwd_& directly. This means that other methods of
14835 holding password data (such as NIS) are supported. If the local part is a local
14836 user, &$home$& is set from the password data, and can be tested in other
14837 preconditions that are evaluated after this one (the order of evaluation is
14838 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
14839 overridden by &%router_home_directory%&. If the local part is not a local user,
14840 the router is skipped.
14842 If you want to check that the local part is either the name of a local user
14843 or matches something else, you cannot combine &%check_local_user%& with a
14844 setting of &%local_parts%&, because that specifies the logical &'and'& of the
14845 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
14846 setting to achieve this. For example:
14848 local_parts = passwd;$local_part : lsearch;/etc/other/users
14850 Note, however, that the side effects of &%check_local_user%& (such as setting
14851 up a home directory) do not occur when a &(passwd)& lookup is used in a
14852 &%local_parts%& (or any other) precondition.
14856 .option condition routers&!? string&!! unset
14857 .cindex "router" "customized precondition"
14858 This option specifies a general precondition test that has to succeed for the
14859 router to be called. The &%condition%& option is the last precondition to be
14860 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
14861 result is a forced failure, or an empty string, or one of the strings &"0"& or
14862 &"no"& or &"false"& (checked without regard to the case of the letters), the
14863 router is skipped, and the address is offered to the next one.
14865 If the result is any other value, the router is run (as this is the last
14866 precondition to be evaluated, all the other preconditions must be true).
14868 The &%condition%& option provides a means of applying custom conditions to the
14869 running of routers. Note that in the case of a simple conditional expansion,
14870 the default expansion values are exactly what is wanted. For example:
14872 condition = ${if >{$message_age}{600}}
14874 Because of the default behaviour of the string expansion, this is equivalent to
14876 condition = ${if >{$message_age}{600}{true}{}}
14878 If the expansion fails (other than forced failure) delivery is deferred. Some
14879 of the other precondition options are common special cases that could in fact
14880 be specified using &%condition%&.
14884 .option debug_print routers string&!! unset
14885 .cindex "testing" "variables in drivers"
14886 If this option is set and debugging is enabled (see the &%-d%& command line
14887 option), the string is expanded and included in the debugging output.
14888 If expansion of the string fails, the error message is written to the debugging
14889 output, and Exim carries on processing.
14890 This option is provided to help with checking out the values of variables and
14891 so on when debugging router configurations. For example, if a &%condition%&
14892 option appears not to be working, &%debug_print%& can be used to output the
14893 variables it references. The output happens after checks for &%domains%&,
14894 &%local_parts%&, and &%check_local_user%& but before any other preconditions
14895 are tested. A newline is added to the text if it does not end with one.
14899 .option disable_logging routers boolean false
14900 If this option is set true, nothing is logged for any routing errors
14901 or for any deliveries caused by this router. You should not set this option
14902 unless you really, really know what you are doing. See also the generic
14903 transport option of the same name.
14906 .option domains routers&!? "domain list&!!" unset
14907 .cindex "router" "restricting to specific domains"
14908 .cindex "&$domain_data$&"
14909 If this option is set, the router is skipped unless the current domain matches
14910 the list. If the match is achieved by means of a file lookup, the data that the
14911 lookup returned for the domain is placed in &$domain_data$& for use in string
14912 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
14913 a list of the order in which preconditions are evaluated.
14917 .option driver routers string unset
14918 This option must always be set. It specifies which of the available routers is
14923 .option errors_to routers string&!! unset
14924 .cindex "envelope sender"
14925 .cindex "router" "changing address for errors"
14926 If a router successfully handles an address, it may assign the address to a
14927 transport for delivery or it may generate child addresses. In both cases, if
14928 there is a delivery problem during later processing, the resulting bounce
14929 message is sent to the address that results from expanding this string,
14930 provided that the address verifies successfully. The &%errors_to%& option is
14931 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
14933 The &%errors_to%& setting associated with an address can be overridden if it
14934 subsequently passes through other routers that have their own &%errors_to%&
14935 settings, or if the message is delivered by a transport with a &%return_path%&
14938 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
14939 the expansion fails to verify, the errors address associated with the incoming
14940 address is used. At top level, this is the envelope sender. A non-forced
14941 expansion failure causes delivery to be deferred.
14943 If an address for which &%errors_to%& has been set ends up being delivered over
14944 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
14945 any bounces that are generated by other MTAs on the delivery route are also
14946 sent there. You can set &%errors_to%& to the empty string by either of these
14952 An expansion item that yields an empty string has the same effect. If you do
14953 this, a locally detected delivery error for addresses processed by this router
14954 no longer gives rise to a bounce message; the error is discarded. If the
14955 address is delivered to a remote host, the return path is set to &`<>`&, unless
14956 overridden by the &%return_path%& option on the transport.
14958 .cindex "&$address_data$&"
14959 If for some reason you want to discard local errors, but use a non-empty
14960 MAIL command for remote delivery, you can preserve the original return
14961 path in &$address_data$& in the router, and reinstate it in the transport by
14962 setting &%return_path%&.
14964 The most common use of &%errors_to%& is to direct mailing list bounces to the
14965 manager of the list, as described in section &<<SECTmailinglists>>&, or to
14966 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
14970 .option expn routers&!? boolean true
14971 .cindex "address" "testing"
14972 .cindex "testing" "addresses"
14973 .cindex "EXPN" "router skipping"
14974 .cindex "router" "skipping for EXPN"
14975 If this option is turned off, the router is skipped when testing an address
14976 as a result of processing an SMTP EXPN command. You might, for example,
14977 want to turn it off on a router for users' &_.forward_& files, while leaving it
14978 on for the system alias file.
14979 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
14982 The use of the SMTP EXPN command is controlled by an ACL (see chapter
14983 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
14984 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
14988 .option fail_verify routers boolean false
14989 .cindex "router" "forcing verification failure"
14990 Setting this option has the effect of setting both &%fail_verify_sender%& and
14991 &%fail_verify_recipient%& to the same value.
14995 .option fail_verify_recipient routers boolean false
14996 If this option is true and an address is accepted by this router when
14997 verifying a recipient, verification fails.
15001 .option fail_verify_sender routers boolean false
15002 If this option is true and an address is accepted by this router when
15003 verifying a sender, verification fails.
15007 .option fallback_hosts routers "string list" unset
15008 .cindex "router" "fallback hosts"
15009 .cindex "fallback" "hosts specified on router"
15010 String expansion is not applied to this option. The argument must be a
15011 colon-separated list of host names or IP addresses. The list separator can be
15012 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
15013 each name or address. In fact, the format of each item is exactly the same as
15014 defined for the list of hosts in a &(manualroute)& router (see section
15015 &<<SECTformatonehostitem>>&).
15017 If a router queues an address for a remote transport, this host list is
15018 associated with the address, and used instead of the transport's fallback host
15019 list. If &%hosts_randomize%& is set on the transport, the order of the list is
15020 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
15021 transport for further details.
15024 .option group routers string&!! "see below"
15025 .cindex "gid (group id)" "local delivery"
15026 .cindex "local transports" "uid and gid"
15027 .cindex "transport" "local"
15028 .cindex "router" "setting group"
15029 When a router queues an address for a transport, and the transport does not
15030 specify a group, the group given here is used when running the delivery
15032 The group may be specified numerically or by name. If expansion fails, the
15033 error is logged and delivery is deferred.
15034 The default is unset, unless &%check_local_user%& is set, when the default
15035 is taken from the password information. See also &%initgroups%& and &%user%&
15036 and the discussion in chapter &<<CHAPenvironment>>&.
15040 .option headers_add routers string&!! unset
15041 .cindex "header lines" "adding"
15042 .cindex "router" "adding header lines"
15043 This option specifies a string of text that is expanded at routing time, and
15044 associated with any addresses that are accepted by the router. However, this
15045 option has no effect when an address is just being verified. The way in which
15046 the text is used to add header lines at transport time is described in section
15047 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
15048 message is in the process of being transported. This means that references to
15049 header lines in string expansions in the transport's configuration do not
15050 &"see"& the added header lines.
15052 The &%headers_add%& option is expanded after &%errors_to%&, but before
15053 &%headers_remove%& and &%transport%&. If the expanded string is empty, or if
15054 the expansion is forced to fail, the option has no effect. Other expansion
15055 failures are treated as configuration errors.
15057 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
15058 router that has the &%one_time%& option set.
15060 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15061 additions are deleted when the address is passed on to subsequent routers.
15065 .option headers_remove routers string&!! unset
15066 .cindex "header lines" "removing"
15067 .cindex "router" "removing header lines"
15068 This option specifies a string of text that is expanded at routing time, and
15069 associated with any addresses that are accepted by the router. However, this
15070 option has no effect when an address is just being verified. The way in which
15071 the text is used to remove header lines at transport time is described in
15072 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
15073 the message is in the process of being transported. This means that references
15074 to header lines in string expansions in the transport's configuration still
15075 &"see"& the original header lines.
15077 The &%headers_remove%& option is expanded after &%errors_to%& and
15078 &%headers_add%&, but before &%transport%&. If the expansion is forced to fail,
15079 the option has no effect. Other expansion failures are treated as configuration
15082 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
15083 router that has the &%one_time%& option set.
15085 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15086 removal requests are deleted when the address is passed on to subsequent
15090 .option ignore_target_hosts routers "host list&!!" unset
15091 .cindex "IP address" "discarding"
15092 .cindex "router" "discarding IP addresses"
15093 Although this option is a host list, it should normally contain IP address
15094 entries rather than names. If any host that is looked up by the router has an
15095 IP address that matches an item in this list, Exim behaves as if that IP
15096 address did not exist. This option allows you to cope with rogue DNS entries
15099 remote.domain.example. A 127.0.0.1
15103 ignore_target_hosts = 127.0.0.1
15105 on the relevant router. If all the hosts found by a &(dnslookup)& router are
15106 discarded in this way, the router declines. In a conventional configuration, an
15107 attempt to mail to such a domain would normally provoke the &"unrouteable
15108 domain"& error, and an attempt to verify an address in the domain would fail.
15109 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
15110 router declines if presented with one of the listed addresses.
15112 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
15113 means of the first or the second of the following settings, respectively:
15115 ignore_target_hosts = 0.0.0.0/0
15116 ignore_target_hosts = <; 0::0/0
15118 The pattern in the first line matches all IPv4 addresses, whereas the pattern
15119 in the second line matches all IPv6 addresses.
15121 This option may also be useful for ignoring link-local and site-local IPv6
15122 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
15123 is expanded before use as a list, it is possible to make it dependent on the
15124 domain that is being routed.
15126 .cindex "&$host_address$&"
15127 During its expansion, &$host_address$& is set to the IP address that is being
15130 .option initgroups routers boolean false
15131 .cindex "additional groups"
15132 .cindex "groups" "additional"
15133 .cindex "local transports" "uid and gid"
15134 .cindex "transport" "local"
15135 If the router queues an address for a transport, and this option is true, and
15136 the uid supplied by the router is not overridden by the transport, the
15137 &[initgroups()]& function is called when running the transport to ensure that
15138 any additional groups associated with the uid are set up. See also &%group%&
15139 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
15143 .option local_part_prefix routers&!? "string list" unset
15144 .cindex "router" "prefix for local part"
15145 .cindex "prefix" "for local part; used in router"
15146 If this option is set, the router is skipped unless the local part starts with
15147 one of the given strings, or &%local_part_prefix_optional%& is true. See
15148 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
15151 The list is scanned from left to right, and the first prefix that matches is
15152 used. A limited form of wildcard is available; if the prefix begins with an
15153 asterisk, it matches the longest possible sequence of arbitrary characters at
15154 the start of the local part. An asterisk should therefore always be followed by
15155 some character that does not occur in normal local parts.
15156 .cindex "multiple mailboxes"
15157 .cindex "mailbox" "multiple"
15158 Wildcarding can be used to set up multiple user mailboxes, as described in
15159 section &<<SECTmulbox>>&.
15161 .cindex "&$local_part$&"
15162 .cindex "&$local_part_prefix$&"
15163 During the testing of the &%local_parts%& option, and while the router is
15164 running, the prefix is removed from the local part, and is available in the
15165 expansion variable &$local_part_prefix$&. When a message is being delivered, if
15166 the router accepts the address, this remains true during subsequent delivery by
15167 a transport. In particular, the local part that is transmitted in the RCPT
15168 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
15169 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
15170 the relevant transport.
15172 When an address is being verified, &%local_part_prefix%& affects only the
15173 behaviour of the router. If the callout feature of verification is in use, this
15174 means that the full address, including the prefix, will be used during the
15177 The prefix facility is commonly used to handle local parts of the form
15178 &%owner-something%&. Another common use is to support local parts of the form
15179 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
15180 to tell a user their forwarding is broken &-- by placing a router like this one
15181 immediately before the router that handles &_.forward_& files:
15185 local_part_prefix = real-
15187 transport = local_delivery
15189 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
15190 both conditions must be met if not optional. Care must be taken if wildcards
15191 are used in both a prefix and a suffix on the same router. Different
15192 separator characters must be used to avoid ambiguity.
15195 .option local_part_prefix_optional routers boolean false
15196 See &%local_part_prefix%& above.
15200 .option local_part_suffix routers&!? "string list" unset
15201 .cindex "router" "suffix for local part"
15202 .cindex "suffix for local part" "used in router"
15203 This option operates in the same way as &%local_part_prefix%&, except that the
15204 local part must end (rather than start) with the given string, the
15205 &%local_part_suffix_optional%& option determines whether the suffix is
15206 mandatory, and the wildcard * character, if present, must be the last
15207 character of the suffix. This option facility is commonly used to handle local
15208 parts of the form &%something-request%& and multiple user mailboxes of the form
15212 .option local_part_suffix_optional routers boolean false
15213 See &%local_part_suffix%& above.
15217 .option local_parts routers&!? "local part list&!!" unset
15218 .cindex "router" "restricting to specific local parts"
15219 .cindex "local part" "checking in router"
15220 The router is run only if the local part of the address matches the list.
15221 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15223 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
15224 string is expanded, it is possible to make it depend on the domain, for
15227 local_parts = dbm;/usr/local/specials/$domain
15229 .cindex "&$local_part_data$&"
15230 If the match is achieved by a lookup, the data that the lookup returned
15231 for the local part is placed in the variable &$local_part_data$& for use in
15232 expansions of the router's private options. You might use this option, for
15233 example, if you have a large number of local virtual domains, and you want to
15234 send all postmaster mail to the same place without having to set up an alias in
15235 each virtual domain:
15239 local_parts = postmaster
15240 data = postmaster@real.domain.example
15244 .option log_as_local routers boolean "see below"
15245 .cindex "log" "delivery line"
15246 .cindex "delivery" "log line format"
15247 Exim has two logging styles for delivery, the idea being to make local
15248 deliveries stand out more visibly from remote ones. In the &"local"& style, the
15249 recipient address is given just as the local part, without a domain. The use of
15250 this style is controlled by this option. It defaults to true for the &(accept)&
15251 router, and false for all the others. This option applies only when a
15252 router assigns an address to a transport. It has no effect on routers that
15253 redirect addresses.
15257 .option more routers boolean&!! true
15258 The result of string expansion for this option must be a valid boolean value,
15259 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
15260 result causes an error, and delivery is deferred. If the expansion is forced to
15261 fail, the default value for the option (true) is used. Other failures cause
15262 delivery to be deferred.
15264 If this option is set false, and the router declines to handle the address, no
15265 further routers are tried, routing fails, and the address is bounced.
15266 .cindex "&%self%& option"
15267 However, if the router explicitly passes an address to the following router by
15268 means of the setting
15272 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
15273 does not affect the behaviour if one of the precondition tests fails. In that
15274 case, the address is always passed to the next router.
15276 Note that &%address_data%& is not considered to be a precondition. If its
15277 expansion is forced to fail, the router declines, and the value of &%more%&
15278 controls what happens next.
15281 .option pass_on_timeout routers boolean false
15282 .cindex "timeout" "of router"
15283 .cindex "router" "timeout"
15284 If a router times out during a host lookup, it normally causes deferral of the
15285 address. If &%pass_on_timeout%& is set, the address is passed on to the next
15286 router, overriding &%no_more%&. This may be helpful for systems that are
15287 intermittently connected to the Internet, or those that want to pass to a smart
15288 host any messages that cannot immediately be delivered.
15290 There are occasional other temporary errors that can occur while doing DNS
15291 lookups. They are treated in the same way as a timeout, and this option
15292 applies to all of them.
15296 .option pass_router routers string unset
15297 .cindex "router" "go to after &""pass""&"
15298 When a router returns &"pass"&, the address is normally handed on to the next
15299 router in sequence. This can be changed by setting &%pass_router%& to the name
15300 of another router. However (unlike &%redirect_router%&) the named router must
15301 be below the current router, to avoid loops. Note that this option applies only
15302 to the special case of &"pass"&. It does not apply when a router returns
15307 .option redirect_router routers string unset
15308 .cindex "router" "start at after redirection"
15309 Sometimes an administrator knows that it is pointless to reprocess addresses
15310 generated from alias or forward files with the same router again. For
15311 example, if an alias file translates real names into login ids there is no
15312 point searching the alias file a second time, especially if it is a large file.
15314 The &%redirect_router%& option can be set to the name of any router instance.
15315 It causes the routing of any generated addresses to start at the named router
15316 instead of at the first router. This option has no effect if the router in
15317 which it is set does not generate new addresses.
15321 .option require_files routers&!? "string list&!!" unset
15322 .cindex "file" "requiring for router"
15323 .cindex "router" "requiring file existence"
15324 This option provides a general mechanism for predicating the running of a
15325 router on the existence or non-existence of certain files or directories.
15326 Before running a router, as one of its precondition tests, Exim works its way
15327 through the &%require_files%& list, expanding each item separately.
15329 Because the list is split before expansion, any colons in expansion items must
15330 be doubled, or the facility for using a different list separator must be used.
15331 If any expansion is forced to fail, the item is ignored. Other expansion
15332 failures cause routing of the address to be deferred.
15334 If any expanded string is empty, it is ignored. Otherwise, except as described
15335 below, each string must be a fully qualified file path, optionally preceded by
15336 &"!"&. The paths are passed to the &[stat()]& function to test for the
15337 existence of the files or directories. The router is skipped if any paths not
15338 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
15341 If &[stat()]& cannot determine whether a file exists or not, delivery of
15342 the message is deferred. This can happen when NFS-mounted filesystems are
15345 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
15346 options, so you cannot use it to check for the existence of a file in which to
15347 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
15348 full list of the order in which preconditions are evaluated.) However, as
15349 these options are all expanded, you can use the &%exists%& expansion condition
15350 to make such tests. The &%require_files%& option is intended for checking files
15351 that the router may be going to use internally, or which are needed by a
15352 transport (for example &_.procmailrc_&).
15354 During delivery, the &[stat()]& function is run as root, but there is a
15355 facility for some checking of the accessibility of a file by another user.
15356 This is not a proper permissions check, but just a &"rough"& check that
15357 operates as follows:
15359 If an item in a &%require_files%& list does not contain any forward slash
15360 characters, it is taken to be the user (and optional group, separated by a
15361 comma) to be checked for subsequent files in the list. If no group is specified
15362 but the user is specified symbolically, the gid associated with the uid is
15365 require_files = mail:/some/file
15366 require_files = $local_part:$home/.procmailrc
15368 If a user or group name in a &%require_files%& list does not exist, the
15369 &%require_files%& condition fails.
15371 Exim performs the check by scanning along the components of the file path, and
15372 checking the access for the given uid and gid. It checks for &"x"& access on
15373 directories, and &"r"& access on the final file. Note that this means that file
15374 access control lists, if the operating system has them, are ignored.
15376 &*Warning 1*&: When the router is being run to verify addresses for an
15377 incoming SMTP message, Exim is not running as root, but under its own uid. This
15378 may affect the result of a &%require_files%& check. In particular, &[stat()]&
15379 may yield the error EACCES (&"Permission denied"&). This means that the Exim
15380 user is not permitted to read one of the directories on the file's path.
15382 &*Warning 2*&: Even when Exim is running as root while delivering a message,
15383 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
15384 without root access. In this case, if a check for access by a particular user
15385 is requested, Exim creates a subprocess that runs as that user, and tries the
15386 check again in that process.
15388 The default action for handling an unresolved EACCES is to consider it to
15389 be caused by a configuration error, and routing is deferred because the
15390 existence or non-existence of the file cannot be determined. However, in some
15391 circumstances it may be desirable to treat this condition as if the file did
15392 not exist. If the file name (or the exclamation mark that precedes the file
15393 name for non-existence) is preceded by a plus sign, the EACCES error is treated
15394 as if the file did not exist. For example:
15396 require_files = +/some/file
15398 If the router is not an essential part of verification (for example, it
15399 handles users' &_.forward_& files), another solution is to set the &%verify%&
15400 option false so that the router is skipped when verifying.
15404 .option retry_use_local_part routers boolean "see below"
15405 .cindex "hints database" "retry keys"
15406 .cindex "local part" "in retry keys"
15407 When a delivery suffers a temporary routing failure, a retry record is created
15408 in Exim's hints database. For addresses whose routing depends only on the
15409 domain, the key for the retry record should not involve the local part, but for
15410 other addresses, both the domain and the local part should be included.
15411 Usually, remote routing is of the former kind, and local routing is of the
15414 This option controls whether the local part is used to form the key for retry
15415 hints for addresses that suffer temporary errors while being handled by this
15416 router. The default value is true for any router that has &%check_local_user%&
15417 set, and false otherwise. Note that this option does not apply to hints keys
15418 for transport delays; they are controlled by a generic transport option of the
15421 The setting of &%retry_use_local_part%& applies only to the router on which it
15422 appears. If the router generates child addresses, they are routed
15423 independently; this setting does not become attached to them.
15427 .option router_home_directory routers string&!! unset
15428 .cindex "router" "home directory for"
15429 .cindex "home directory" "for router"
15431 This option sets a home directory for use while the router is running. (Compare
15432 &%transport_home_directory%&, which sets a home directory for later
15433 transporting.) In particular, if used on a &(redirect)& router, this option
15434 sets a value for &$home$& while a filter is running. The value is expanded;
15435 forced expansion failure causes the option to be ignored &-- other failures
15436 cause the router to defer.
15438 Expansion of &%router_home_directory%& happens immediately after the
15439 &%check_local_user%& test (if configured), before any further expansions take
15441 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15443 While the router is running, &%router_home_directory%& overrides the value of
15444 &$home$& that came from &%check_local_user%&.
15446 When a router accepts an address and assigns it to a local transport (including
15447 the cases when a &(redirect)& router generates a pipe, file, or autoreply
15448 delivery), the home directory setting for the transport is taken from the first
15449 of these values that is set:
15452 The &%home_directory%& option on the transport;
15454 The &%transport_home_directory%& option on the router;
15456 The password data if &%check_local_user%& is set on the router;
15458 The &%router_home_directory%& option on the router.
15461 In other words, &%router_home_directory%& overrides the password data for the
15462 router, but not for the transport.
15466 .option self routers string freeze
15467 .cindex "MX record" "pointing to local host"
15468 .cindex "local host" "MX pointing to"
15469 This option applies to those routers that use a recipient address to find a
15470 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
15471 and &(manualroute)& routers.
15472 Certain configurations of the &(queryprogram)& router can also specify a list
15474 Usually such routers are configured to send the message to a remote host via an
15475 &(smtp)& transport. The &%self%& option specifies what happens when the first
15476 host on the list turns out to be the local host.
15477 The way in which Exim checks for the local host is described in section
15478 &<<SECTreclocipadd>>&.
15480 Normally this situation indicates either an error in Exim's configuration (for
15481 example, the router should be configured not to process this domain), or an
15482 error in the DNS (for example, the MX should not point to this host). For this
15483 reason, the default action is to log the incident, defer the address, and
15484 freeze the message. The following alternatives are provided for use in special
15489 Delivery of the message is tried again later, but the message is not frozen.
15491 .vitem "&%reroute%&: <&'domain'&>"
15492 The domain is changed to the given domain, and the address is passed back to
15493 be reprocessed by the routers. No rewriting of headers takes place. This
15494 behaviour is essentially a redirection.
15496 .vitem "&%reroute: rewrite:%& <&'domain'&>"
15497 The domain is changed to the given domain, and the address is passed back to be
15498 reprocessed by the routers. Any headers that contain the original domain are
15502 .cindex "&%more%& option"
15503 .cindex "&$self_hostname$&"
15504 The router passes the address to the next router, or to the router named in the
15505 &%pass_router%& option if it is set. This overrides &%no_more%&. During
15506 subsequent routing and delivery, the variable &$self_hostname$& contains the
15507 name of the local host that the router encountered. This can be used to
15508 distinguish between different cases for hosts with multiple names. The
15514 ensures that only those addresses that routed to the local host are passed on.
15515 Without &%no_more%&, addresses that were declined for other reasons would also
15516 be passed to the next router.
15519 Delivery fails and an error report is generated.
15522 .cindex "local host" "sending to"
15523 The anomaly is ignored and the address is queued for the transport. This
15524 setting should be used with extreme caution. For an &(smtp)& transport, it
15525 makes sense only in cases where the program that is listening on the SMTP port
15526 is not this version of Exim. That is, it must be some other MTA, or Exim with a
15527 different configuration file that handles the domain in another way.
15532 .option senders routers&!? "address list&!!" unset
15533 .cindex "router" "checking senders"
15534 If this option is set, the router is skipped unless the message's sender
15535 address matches something on the list.
15536 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15539 There are issues concerning verification when the running of routers is
15540 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
15541 setting, it sets the sender to the null string. When using the &%-bt%& option
15542 to check a configuration file, it is necessary also to use the &%-f%& option to
15543 set an appropriate sender. For incoming mail, the sender is unset when
15544 verifying the sender, but is available when verifying any recipients. If the
15545 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
15549 .option translate_ip_address routers string&!! unset
15550 .cindex "IP address" "translating"
15551 .cindex "packet radio"
15552 .cindex "router" "IP address translation"
15553 There exist some rare networking situations (for example, packet radio) where
15554 it is helpful to be able to translate IP addresses generated by normal routing
15555 mechanisms into other IP addresses, thus performing a kind of manual IP
15556 routing. This should be done only if the normal IP routing of the TCP/IP stack
15557 is inadequate or broken. Because this is an extremely uncommon requirement, the
15558 code to support this option is not included in the Exim binary unless
15559 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
15561 .cindex "&$host_address$&"
15562 The &%translate_ip_address%& string is expanded for every IP address generated
15563 by the router, with the generated address set in &$host_address$&. If the
15564 expansion is forced to fail, no action is taken.
15565 For any other expansion error, delivery of the message is deferred.
15566 If the result of the expansion is an IP address, that replaces the original
15567 address; otherwise the result is assumed to be a host name &-- this is looked
15568 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
15569 produce one or more replacement IP addresses. For example, to subvert all IP
15570 addresses in some specific networks, this could be added to a router:
15572 translate_ip_address = \
15573 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
15576 The file would contain lines like
15578 10.2.3.128/26 some.host
15579 10.8.4.34/26 10.44.8.15
15581 You should not make use of this facility unless you really understand what you
15586 .option transport routers string&!! unset
15587 This option specifies the transport to be used when a router accepts an address
15588 and sets it up for delivery. A transport is never needed if a router is used
15589 only for verification. The value of the option is expanded at routing time,
15590 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
15591 and result must be the name of one of the configured transports. If it is not,
15592 delivery is deferred.
15594 The &%transport%& option is not used by the &(redirect)& router, but it does
15595 have some private options that set up transports for pipe and file deliveries
15596 (see chapter &<<CHAPredirect>>&).
15600 .option transport_current_directory routers string&!! unset
15601 .cindex "current directory for local transport"
15602 This option associates a current directory with any address that is routed
15603 to a local transport. This can happen either because a transport is
15604 explicitly configured for the router, or because it generates a delivery to a
15605 file or a pipe. During the delivery process (that is, at transport time), this
15606 option string is expanded and is set as the current directory, unless
15607 overridden by a setting on the transport.
15608 If the expansion fails for any reason, including forced failure, an error is
15609 logged, and delivery is deferred.
15610 See chapter &<<CHAPenvironment>>& for details of the local delivery
15616 .option transport_home_directory routers string&!! "see below"
15617 .cindex "home directory" "for local transport"
15618 This option associates a home directory with any address that is routed to a
15619 local transport. This can happen either because a transport is explicitly
15620 configured for the router, or because it generates a delivery to a file or a
15621 pipe. During the delivery process (that is, at transport time), the option
15622 string is expanded and is set as the home directory, unless overridden by a
15623 setting of &%home_directory%& on the transport.
15624 If the expansion fails for any reason, including forced failure, an error is
15625 logged, and delivery is deferred.
15627 If the transport does not specify a home directory, and
15628 &%transport_home_directory%& is not set for the router, the home directory for
15629 the tranport is taken from the password data if &%check_local_user%& is set for
15630 the router. Otherwise it is taken from &%router_home_directory%& if that option
15631 is set; if not, no home directory is set for the transport.
15633 See chapter &<<CHAPenvironment>>& for further details of the local delivery
15639 .option unseen routers boolean&!! false
15640 .cindex "router" "carrying on after success"
15641 The result of string expansion for this option must be a valid boolean value,
15642 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
15643 result causes an error, and delivery is deferred. If the expansion is forced to
15644 fail, the default value for the option (false) is used. Other failures cause
15645 delivery to be deferred.
15647 When this option is set true, routing does not cease if the router accepts the
15648 address. Instead, a copy of the incoming address is passed to the next router,
15649 overriding a false setting of &%more%&. There is little point in setting
15650 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
15651 the value of &%unseen%& contains expansion items (and therefore, presumably, is
15652 sometimes true and sometimes false).
15654 .cindex "copy of message (&%unseen%& option)"
15655 The &%unseen%& option can be used to cause copies of messages to be delivered
15656 to some other destination, while also carrying out a normal delivery. In
15657 effect, the current address is made into a &"parent"& that has two children &--
15658 one that is delivered as specified by this router, and a clone that goes on to
15659 be routed further. For this reason, &%unseen%& may not be combined with the
15660 &%one_time%& option in a &(redirect)& router.
15662 &*Warning*&: Header lines added to the address (or specified for removal) by
15663 this router or by previous routers affect the &"unseen"& copy of the message
15664 only. The clone that continues to be processed by further routers starts with
15665 no added headers and none specified for removal. However, any data that was set
15666 by the &%address_data%& option in the current or previous routers is passed on.
15667 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
15668 qualifier in filter files.
15672 .option user routers string&!! "see below"
15673 .cindex "uid (user id)" "local delivery"
15674 .cindex "local transports" "uid and gid"
15675 .cindex "transport" "local"
15676 .cindex "router" "user for filter processing"
15677 .cindex "filter" "user for processing"
15678 When a router queues an address for a transport, and the transport does not
15679 specify a user, the user given here is used when running the delivery process.
15680 The user may be specified numerically or by name. If expansion fails, the
15681 error is logged and delivery is deferred.
15682 This user is also used by the &(redirect)& router when running a filter file.
15683 The default is unset, except when &%check_local_user%& is set. In this case,
15684 the default is taken from the password information. If the user is specified as
15685 a name, and &%group%& is not set, the group associated with the user is used.
15686 See also &%initgroups%& and &%group%& and the discussion in chapter
15687 &<<CHAPenvironment>>&.
15691 .option verify routers&!? boolean true
15692 Setting this option has the effect of setting &%verify_sender%& and
15693 &%verify_recipient%& to the same value.
15696 .option verify_only routers&!? boolean false
15697 .cindex "EXPN" "with &%verify_only%&"
15698 .cindex "&%-bv%& option"
15699 .cindex "router" "used only when verifying"
15700 If this option is set, the router is used only when verifying an address or
15701 testing with the &%-bv%& option, not when actually doing a delivery, testing
15702 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
15703 restricted to verifying only senders or recipients by means of
15704 &%verify_sender%& and &%verify_recipient%&.
15706 &*Warning*&: When the router is being run to verify addresses for an incoming
15707 SMTP message, Exim is not running as root, but under its own uid. If the router
15708 accesses any files, you need to make sure that they are accessible to the Exim
15712 .option verify_recipient routers&!? boolean true
15713 If this option is false, the router is skipped when verifying recipient
15715 or testing recipient verification using &%-bv%&.
15716 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15720 .option verify_sender routers&!? boolean true
15721 If this option is false, the router is skipped when verifying sender addresses
15722 or testing sender verification using &%-bvs%&.
15723 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15725 .ecindex IIDgenoprou1
15726 .ecindex IIDgenoprou2
15733 . ////////////////////////////////////////////////////////////////////////////
15734 . ////////////////////////////////////////////////////////////////////////////
15736 .chapter "The accept router"
15737 .cindex "&(accept)& router"
15738 .cindex "routers" "&(accept)&"
15739 The &(accept)& router has no private options of its own. Unless it is being
15740 used purely for verification (see &%verify_only%&) a transport is required to
15741 be defined by the generic &%transport%& option. If the preconditions that are
15742 specified by generic options are met, the router accepts the address and queues
15743 it for the given transport. The most common use of this router is for setting
15744 up deliveries to local mailboxes. For example:
15748 domains = mydomain.example
15750 transport = local_delivery
15752 The &%domains%& condition in this example checks the domain of the address, and
15753 &%check_local_user%& checks that the local part is the login of a local user.
15754 When both preconditions are met, the &(accept)& router runs, and queues the
15755 address for the &(local_delivery)& transport.
15762 . ////////////////////////////////////////////////////////////////////////////
15763 . ////////////////////////////////////////////////////////////////////////////
15765 .chapter "The dnslookup router" "CHAPdnslookup"
15766 .scindex IIDdnsrou1 "&(dnslookup)& router"
15767 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
15768 The &(dnslookup)& router looks up the hosts that handle mail for the
15769 recipient's domain in the DNS. A transport must always be set for this router,
15770 unless &%verify_only%& is set.
15772 If SRV support is configured (see &%check_srv%& below), Exim first searches for
15773 SRV records. If none are found, or if SRV support is not configured,
15774 MX records are looked up. If no MX records exist, address records are sought.
15775 However, &%mx_domains%& can be set to disable the direct use of address
15778 MX records of equal priority are sorted by Exim into a random order. Exim then
15779 looks for address records for the host names obtained from MX or SRV records.
15780 When a host has more than one IP address, they are sorted into a random order,
15781 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
15782 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
15783 generic option, the router declines.
15785 Unless they have the highest priority (lowest MX value), MX records that point
15786 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
15787 are discarded, together with any other MX records of equal or lower priority.
15789 .cindex "MX record" "pointing to local host"
15790 .cindex "local host" "MX pointing to"
15791 .cindex "&%self%& option" "in &(dnslookup)& router"
15792 If the host pointed to by the highest priority MX record, or looked up as an
15793 address record, is the local host, or matches &%hosts_treat_as_local%&, what
15794 happens is controlled by the generic &%self%& option.
15797 .section "Problems with DNS lookups" "SECTprowitdnsloo"
15798 There have been problems with DNS servers when SRV records are looked up.
15799 Some mis-behaving servers return a DNS error or timeout when a non-existent
15800 SRV record is sought. Similar problems have in the past been reported for
15801 MX records. The global &%dns_again_means_nonexist%& option can help with this
15802 problem, but it is heavy-handed because it is a global option.
15804 For this reason, there are two options, &%srv_fail_domains%& and
15805 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
15806 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
15807 an attempt to look up an SRV or MX record causes one of these results, and the
15808 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
15809 such record"&. In the case of an SRV lookup, this means that the router
15810 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
15811 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
15812 case routing fails.
15817 .section "Private options for dnslookup"
15818 .cindex "options" "&(dnslookup)& router"
15819 The private options for the &(dnslookup)& router are as follows:
15821 .option check_secondary_mx dnslookup boolean false
15822 .cindex "MX record" "checking for secondary"
15823 If this option is set, the router declines unless the local host is found in
15824 (and removed from) the list of hosts obtained by MX lookup. This can be used to
15825 process domains for which the local host is a secondary mail exchanger
15826 differently to other domains. The way in which Exim decides whether a host is
15827 the local host is described in section &<<SECTreclocipadd>>&.
15830 .option check_srv dnslookup string&!! unset
15831 .cindex "SRV record" "enabling use of"
15832 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
15833 addition to MX and address records. The support is disabled by default. To
15834 enable SRV support, set the &%check_srv%& option to the name of the service
15835 required. For example,
15839 looks for SRV records that refer to the normal smtp service. The option is
15840 expanded, so the service name can vary from message to message or address
15841 to address. This might be helpful if SRV records are being used for a
15842 submission service. If the expansion is forced to fail, the &%check_srv%&
15843 option is ignored, and the router proceeds to look for MX records in the
15846 When the expansion succeeds, the router searches first for SRV records for
15847 the given service (it assumes TCP protocol). A single SRV record with a
15848 host name that consists of just a single dot indicates &"no such service for
15849 this domain"&; if this is encountered, the router declines. If other kinds of
15850 SRV record are found, they are used to construct a host list for delivery
15851 according to the rules of RFC 2782. MX records are not sought in this case.
15853 When no SRV records are found, MX records (and address records) are sought in
15854 the traditional way. In other words, SRV records take precedence over MX
15855 records, just as MX records take precedence over address records. Note that
15856 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
15857 defined it. It is apparently believed that MX records are sufficient for email
15858 and that SRV records should not be used for this purpose. However, SRV records
15859 have an additional &"weight"& feature which some people might find useful when
15860 trying to split an SMTP load between hosts of different power.
15862 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
15863 when there is a DNS lookup error.
15867 .option mx_domains dnslookup "domain list&!!" unset
15868 .cindex "MX record" "required to exist"
15869 .cindex "SRV record" "required to exist"
15870 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
15871 record in order to be recognised. (The name of this option could be improved.)
15872 For example, if all the mail hosts in &'fict.example'& are known to have MX
15873 records, except for those in &'discworld.fict.example'&, you could use this
15876 mx_domains = ! *.discworld.fict.example : *.fict.example
15878 This specifies that messages addressed to a domain that matches the list but
15879 has no MX record should be bounced immediately instead of being routed using
15880 the address record.
15883 .option mx_fail_domains dnslookup "domain list&!!" unset
15884 If the DNS lookup for MX records for one of the domains in this list causes a
15885 DNS lookup error, Exim behaves as if no MX records were found. See section
15886 &<<SECTprowitdnsloo>>& for more discussion.
15891 .option qualify_single dnslookup boolean true
15892 .cindex "DNS" "resolver options"
15893 .cindex "DNS" "qualifying single-component names"
15894 When this option is true, the resolver option RES_DEFNAMES is set for DNS
15895 lookups. Typically, but not standardly, this causes the resolver to qualify
15896 single-component names with the default domain. For example, on a machine
15897 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
15898 &'thesaurus.ref.example'& inside the resolver. For details of what your
15899 resolver actually does, consult your man pages for &'resolver'& and
15904 .option rewrite_headers dnslookup boolean true
15905 .cindex "rewriting" "header lines"
15906 .cindex "header lines" "rewriting"
15907 If the domain name in the address that is being processed is not fully
15908 qualified, it may be expanded to its full form by a DNS lookup. For example, if
15909 an address is specified as &'dormouse@teaparty'&, the domain might be
15910 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
15911 occur as a result of setting the &%widen_domains%& option. If
15912 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
15913 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
15914 header lines of the message are rewritten with the full domain name.
15916 This option should be turned off only when it is known that no message is
15917 ever going to be sent outside an environment where the abbreviation makes
15920 When an MX record is looked up in the DNS and matches a wildcard record, name
15921 servers normally return a record containing the name that has been looked up,
15922 making it impossible to detect whether a wildcard was present or not. However,
15923 some name servers have recently been seen to return the wildcard entry. If the
15924 name returned by a DNS lookup begins with an asterisk, it is not used for
15928 .option same_domain_copy_routing dnslookup boolean false
15929 .cindex "address" "copying routing"
15930 Addresses with the same domain are normally routed by the &(dnslookup)& router
15931 to the same list of hosts. However, this cannot be presumed, because the router
15932 options and preconditions may refer to the local part of the address. By
15933 default, therefore, Exim routes each address in a message independently. DNS
15934 servers run caches, so repeated DNS lookups are not normally expensive, and in
15935 any case, personal messages rarely have more than a few recipients.
15937 If you are running mailing lists with large numbers of subscribers at the same
15938 domain, and you are using a &(dnslookup)& router which is independent of the
15939 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
15940 lookups for identical domains in one message. In this case, when &(dnslookup)&
15941 routes an address to a remote transport, any other unrouted addresses in the
15942 message that have the same domain are automatically given the same routing
15943 without processing them independently,
15944 provided the following conditions are met:
15947 No router that processed the address specified &%headers_add%& or
15948 &%headers_remove%&.
15950 The router did not change the address in any way, for example, by &"widening"&
15957 .option search_parents dnslookup boolean false
15958 .cindex "DNS" "resolver options"
15959 When this option is true, the resolver option RES_DNSRCH is set for DNS
15960 lookups. This is different from the &%qualify_single%& option in that it
15961 applies to domains containing dots. Typically, but not standardly, it causes
15962 the resolver to search for the name in the current domain and in parent
15963 domains. For example, on a machine in the &'fict.example'& domain, if looking
15964 up &'teaparty.wonderland'& failed, the resolver would try
15965 &'teaparty.wonderland.fict.example'&. For details of what your resolver
15966 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
15968 Setting this option true can cause problems in domains that have a wildcard MX
15969 record, because any domain that does not have its own MX record matches the
15974 .option srv_fail_domains dnslookup "domain list&!!" unset
15975 If the DNS lookup for SRV records for one of the domains in this list causes a
15976 DNS lookup error, Exim behaves as if no SRV records were found. See section
15977 &<<SECTprowitdnsloo>>& for more discussion.
15982 .option widen_domains dnslookup "string list" unset
15983 .cindex "domain" "partial; widening"
15984 If a DNS lookup fails and this option is set, each of its strings in turn is
15985 added onto the end of the domain, and the lookup is tried again. For example,
15988 widen_domains = fict.example:ref.example
15990 is set and a lookup of &'klingon.dictionary'& fails,
15991 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
15992 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
15993 and &%search_parents%& options can cause some widening to be undertaken inside
15994 the DNS resolver. &%widen_domains%& is not applied to sender addresses
15995 when verifying, unless &%rewrite_headers%& is false (not the default).
15998 .section "Effect of qualify_single and search_parents"
15999 When a domain from an envelope recipient is changed by the resolver as a result
16000 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
16001 corresponding address in the message's header lines unless &%rewrite_headers%&
16002 is set false. Exim then re-routes the address, using the full domain.
16004 These two options affect only the DNS lookup that takes place inside the router
16005 for the domain of the address that is being routed. They do not affect lookups
16006 such as that implied by
16010 that may happen while processing a router precondition before the router is
16011 entered. No widening ever takes place for these lookups.
16012 .ecindex IIDdnsrou1
16013 .ecindex IIDdnsrou2
16023 . ////////////////////////////////////////////////////////////////////////////
16024 . ////////////////////////////////////////////////////////////////////////////
16026 .chapter "The ipliteral router"
16027 .cindex "&(ipliteral)& router"
16028 .cindex "domain literal" "routing"
16029 .cindex "routers" "&(ipliteral)&"
16030 This router has no private options. Unless it is being used purely for
16031 verification (see &%verify_only%&) a transport is required to be defined by the
16032 generic &%transport%& option. The router accepts the address if its domain part
16033 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
16034 router handles the address
16038 by setting up delivery to the host with that IP address. IPv4 domain literals
16039 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
16040 are similar, but the address is preceded by &`ipv6:`&. For example:
16042 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
16044 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
16045 grounds that sooner or later somebody will try it.
16047 .cindex "&%self%& option" "in &(ipliteral)& router"
16048 If the IP address matches something in &%ignore_target_hosts%&, the router
16049 declines. If an IP literal turns out to refer to the local host, the generic
16050 &%self%& option determines what happens.
16052 The RFCs require support for domain literals; however, their use is
16053 controversial in today's Internet. If you want to use this router, you must
16054 also set the main configuration option &%allow_domain_literals%&. Otherwise,
16055 Exim will not recognize the domain literal syntax in addresses.
16059 . ////////////////////////////////////////////////////////////////////////////
16060 . ////////////////////////////////////////////////////////////////////////////
16062 .chapter "The iplookup router"
16063 .cindex "&(iplookup)& router"
16064 .cindex "routers" "&(iplookup)&"
16065 The &(iplookup)& router was written to fulfil a specific requirement in
16066 Cambridge University (which in fact no longer exists). For this reason, it is
16067 not included in the binary of Exim by default. If you want to include it, you
16070 ROUTER_IPLOOKUP=yes
16072 in your &_Local/Makefile_& configuration file.
16074 The &(iplookup)& router routes an address by sending it over a TCP or UDP
16075 connection to one or more specific hosts. The host can then return the same or
16076 a different address &-- in effect rewriting the recipient address in the
16077 message's envelope. The new address is then passed on to subsequent routers. If
16078 this process fails, the address can be passed on to other routers, or delivery
16079 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
16080 must not be specified for it.
16082 .cindex "options" "&(iplookup)& router"
16083 .option hosts iplookup string unset
16084 This option must be supplied. Its value is a colon-separated list of host
16085 names. The hosts are looked up using &[gethostbyname()]&
16086 (or &[getipnodebyname()]& when available)
16087 and are tried in order until one responds to the query. If none respond, what
16088 happens is controlled by &%optional%&.
16091 .option optional iplookup boolean false
16092 If &%optional%& is true, if no response is obtained from any host, the address
16093 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
16094 delivery to the address is deferred.
16097 .option port iplookup integer 0
16098 .cindex "port" "&(iplookup)& router"
16099 This option must be supplied. It specifies the port number for the TCP or UDP
16103 .option protocol iplookup string udp
16104 This option can be set to &"udp"& or &"tcp"& to specify which of the two
16105 protocols is to be used.
16108 .option query iplookup string&!! "&`$local_part@$domain $local_part@$domain`&"
16109 This defines the content of the query that is sent to the remote hosts. The
16110 repetition serves as a way of checking that a response is to the correct query
16111 in the default case (see &%response_pattern%& below).
16114 .option reroute iplookup string&!! unset
16115 If this option is not set, the rerouted address is precisely the byte string
16116 returned by the remote host, up to the first white space, if any. If set, the
16117 string is expanded to form the rerouted address. It can include parts matched
16118 in the response by &%response_pattern%& by means of numeric variables such as
16119 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
16120 whether or not a pattern is in use. In all cases, the rerouted address must end
16121 up in the form &'local_part@domain'&.
16124 .option response_pattern iplookup string unset
16125 This option can be set to a regular expression that is applied to the string
16126 returned from the remote host. If the pattern does not match the response, the
16127 router declines. If &%response_pattern%& is not set, no checking of the
16128 response is done, unless the query was defaulted, in which case there is a
16129 check that the text returned after the first white space is the original
16130 address. This checks that the answer that has been received is in response to
16131 the correct question. For example, if the response is just a new domain, the
16132 following could be used:
16134 response_pattern = ^([^@]+)$
16135 reroute = $local_part@$1
16138 .option timeout iplookup time 5s
16139 This specifies the amount of time to wait for a response from the remote
16140 machine. The same timeout is used for the &[connect()]& function for a TCP
16141 call. It does not apply to UDP.
16146 . ////////////////////////////////////////////////////////////////////////////
16147 . ////////////////////////////////////////////////////////////////////////////
16149 .chapter "The manualroute router"
16150 .scindex IIDmanrou1 "&(manualroute)& router"
16151 .scindex IIDmanrou2 "routers" "&(manualroute)&"
16152 .cindex "domain" "manually routing"
16153 The &(manualroute)& router is so-called because it provides a way of manually
16154 routing an address according to its domain. It is mainly used when you want to
16155 route addresses to remote hosts according to your own rules, bypassing the
16156 normal DNS routing that looks up MX records. However, &(manualroute)& can also
16157 route to local transports, a facility that may be useful if you want to save
16158 messages for dial-in hosts in local files.
16160 The &(manualroute)& router compares a list of domain patterns with the domain
16161 it is trying to route. If there is no match, the router declines. Each pattern
16162 has associated with it a list of hosts and some other optional data, which may
16163 include a transport. The combination of a pattern and its data is called a
16164 &"routing rule"&. For patterns that do not have an associated transport, the
16165 generic &%transport%& option must specify a transport, unless the router is
16166 being used purely for verification (see &%verify_only%&).
16169 In the case of verification, matching the domain pattern is sufficient for the
16170 router to accept the address. When actually routing an address for delivery,
16171 an address that matches a domain pattern is queued for the associated
16172 transport. If the transport is not a local one, a host list must be associated
16173 with the pattern; IP addresses are looked up for the hosts, and these are
16174 passed to the transport along with the mail address. For local transports, a
16175 host list is optional. If it is present, it is passed in &$host$& as a single
16178 The list of routing rules can be provided as an inline string in
16179 &%route_list%&, or the data can be obtained by looking up the domain in a file
16180 or database by setting &%route_data%&. Only one of these settings may appear in
16181 any one instance of &(manualroute)&. The format of routing rules is described
16182 below, following the list of private options.
16185 .section "Private options for manualroute" "SECTprioptman"
16187 .cindex "options" "&(manualroute)& router"
16188 The private options for the &(manualroute)& router are as follows:
16191 .option host_find_failed manualroute string freeze
16192 This option controls what happens when &(manualroute)& tries to find an IP
16193 address for a host, and the host does not exist. The option can be set to one
16202 The default assumes that this state is a serious configuration error. The
16203 difference between &"pass"& and &"decline"& is that the former forces the
16204 address to be passed to the next router (or the router defined by
16206 .cindex "&%more%& option"
16207 overriding &%no_more%&, whereas the latter passes the address to the next
16208 router only if &%more%& is true.
16210 This option applies only to a definite &"does not exist"& state; if a host
16211 lookup gets a temporary error, delivery is deferred unless the generic
16212 &%pass_on_timeout%& option is set.
16215 .option hosts_randomize manualroute boolean false
16216 .cindex "randomized host list"
16217 .cindex "host" "list of; randomized"
16218 If this option is set, the order of the items in a host list in a routing rule
16219 is randomized each time the list is used, unless an option in the routing rule
16220 overrides (see below). Randomizing the order of a host list can be used to do
16221 crude load sharing. However, if more than one mail address is routed by the
16222 same router to the same host list, the host lists are considered to be the same
16223 (even though they may be randomized into different orders) for the purpose of
16224 deciding whether to batch the deliveries into a single SMTP transaction.
16226 When &%hosts_randomize%& is true, a host list may be split
16227 into groups whose order is separately randomized. This makes it possible to
16228 set up MX-like behaviour. The boundaries between groups are indicated by an
16229 item that is just &`+`& in the host list. For example:
16231 route_list = * host1:host2:host3:+:host4:host5
16233 The order of the first three hosts and the order of the last two hosts is
16234 randomized for each use, but the first three always end up before the last two.
16235 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
16236 randomized host list is passed to an &(smtp)& transport that also has
16237 &%hosts_randomize set%&, the list is not re-randomized.
16240 .option route_data manualroute string&!! unset
16241 If this option is set, it must expand to yield the data part of a routing rule.
16242 Typically, the expansion string includes a lookup based on the domain. For
16245 route_data = ${lookup{$domain}dbm{/etc/routes}}
16247 If the expansion is forced to fail, or the result is an empty string, the
16248 router declines. Other kinds of expansion failure cause delivery to be
16252 .option route_list manualroute " "string list" " semicolon-separated""
16253 This string is a list of routing rules, in the form defined below. Note that,
16254 unlike most string lists, the items are separated by semicolons. This is so
16255 that they may contain colon-separated host lists.
16258 .option same_domain_copy_routing manualroute boolean false
16259 .cindex "address" "copying routing"
16260 Addresses with the same domain are normally routed by the &(manualroute)&
16261 router to the same list of hosts. However, this cannot be presumed, because the
16262 router options and preconditions may refer to the local part of the address. By
16263 default, therefore, Exim routes each address in a message independently. DNS
16264 servers run caches, so repeated DNS lookups are not normally expensive, and in
16265 any case, personal messages rarely have more than a few recipients.
16267 If you are running mailing lists with large numbers of subscribers at the same
16268 domain, and you are using a &(manualroute)& router which is independent of the
16269 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
16270 lookups for identical domains in one message. In this case, when
16271 &(manualroute)& routes an address to a remote transport, any other unrouted
16272 addresses in the message that have the same domain are automatically given the
16273 same routing without processing them independently. However, this is only done
16274 if &%headers_add%& and &%headers_remove%& are unset.
16279 .section "Routing rules in route_list"
16280 The value of &%route_list%& is a string consisting of a sequence of routing
16281 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
16282 entered as two semicolons. Alternatively, the list separator can be changed as
16283 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
16284 Empty rules are ignored. The format of each rule is
16286 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
16288 The following example contains two rules, each with a simple domain pattern and
16292 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
16293 thes.ref.example mail-3.ref.example:mail-4.ref.example
16295 The three parts of a rule are separated by white space. The pattern and the
16296 list of hosts can be enclosed in quotes if necessary, and if they are, the
16297 usual quoting rules apply. Each rule in a &%route_list%& must start with a
16298 single domain pattern, which is the only mandatory item in the rule. The
16299 pattern is in the same format as one item in a domain list (see section
16300 &<<SECTdomainlist>>&),
16301 except that it may not be the name of an interpolated file.
16302 That is, it may be wildcarded, or a regular expression, or a file or database
16303 lookup (with semicolons doubled, because of the use of semicolon as a separator
16304 in a &%route_list%&).
16306 The rules in &%route_list%& are searched in order until one of the patterns
16307 matches the domain that is being routed. The list of hosts and then options are
16308 then used as described below. If there is no match, the router declines. When
16309 &%route_list%& is set, &%route_data%& must not be set.
16313 .section "Routing rules in route_data"
16314 The use of &%route_list%& is convenient when there are only a small number of
16315 routing rules. For larger numbers, it is easier to use a file or database to
16316 hold the routing information, and use the &%route_data%& option instead.
16317 The value of &%route_data%& is a list of hosts, followed by (optional) options.
16318 Most commonly, &%route_data%& is set as a string that contains an
16319 expansion lookup. For example, suppose we place two routing rules in a file
16322 dict.ref.example: mail-1.ref.example:mail-2.ref.example
16323 thes.ref.example: mail-3.ref.example:mail-4.ref.example
16325 This data can be accessed by setting
16327 route_data = ${lookup{$domain}lsearch{/the/file/name}}
16329 Failure of the lookup results in an empty string, causing the router to
16330 decline. However, you do not have to use a lookup in &%route_data%&. The only
16331 requirement is that the result of expanding the string is a list of hosts,
16332 possibly followed by options, separated by white space. The list of hosts must
16333 be enclosed in quotes if it contains white space.
16338 .section "Format of the list of hosts"
16339 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
16340 always separately expanded before use. If the expansion fails, the router
16341 declines. The result of the expansion must be a colon-separated list of names
16342 and/or IP addresses, optionally also including ports. The format of each item
16343 in the list is described in the next section. The list separator can be changed
16344 as described in section &<<SECTlistconstruct>>&.
16346 If the list of hosts was obtained from a &%route_list%& item, the following
16347 variables are set during its expansion:
16350 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
16351 If the domain was matched against a regular expression, the numeric variables
16352 &$1$&, &$2$&, etc. may be set. For example:
16354 route_list = ^domain(\d+) host-$1.text.example
16357 &$0$& is always set to the entire domain.
16359 &$1$& is also set when partial matching is done in a file lookup.
16362 .cindex "&$value$&"
16363 If the pattern that matched the domain was a lookup item, the data that was
16364 looked up is available in the expansion variable &$value$&. For example:
16366 route_list = lsearch;;/some/file.routes $value
16370 Note the doubling of the semicolon in the pattern that is necessary because
16371 semicolon is the default route list separator.
16375 .section "Format of one host item" "SECTformatonehostitem"
16376 Each item in the list of hosts is either a host name or an IP address,
16377 optionally with an attached port number. When no port is given, an IP address
16378 is not enclosed in brackets. When a port is specified, it overrides the port
16379 specification on the transport. The port is separated from the name or address
16380 by a colon. This leads to some complications:
16383 Because colon is the default separator for the list of hosts, either
16384 the colon that specifies a port must be doubled, or the list separator must
16385 be changed. The following two examples have the same effect:
16387 route_list = * "host1.tld::1225 : host2.tld::1226"
16388 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
16391 When IPv6 addresses are involved, it gets worse, because they contain
16392 colons of their own. To make this case easier, it is permitted to
16393 enclose an IP address (either v4 or v6) in square brackets if a port
16394 number follows. For example:
16396 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
16400 .section "How the list of hosts is used" "SECThostshowused"
16401 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
16402 the hosts is tried, in the order specified, when carrying out the SMTP
16403 delivery. However, the order can be changed by setting the &%hosts_randomize%&
16404 option, either on the router (see section &<<SECTprioptman>>& above), or on the
16407 Hosts may be listed by name or by IP address. An unadorned name in the list of
16408 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
16409 interpreted as an indirection to a sublist of hosts obtained by looking up MX
16410 records in the DNS. For example:
16412 route_list = * x.y.z:p.q.r/MX:e.f.g
16414 If this feature is used with a port specifier, the port must come last. For
16417 route_list = * dom1.tld/mx::1225
16419 If the &%hosts_randomize%& option is set, the order of the items in the list is
16420 randomized before any lookups are done. Exim then scans the list; for any name
16421 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
16422 be an interface on the local host and the item is not the first in the list,
16423 Exim discards it and any subsequent items. If it is the first item, what
16424 happens is controlled by the
16425 .cindex "&%self%& option" "in &(manualroute)& router"
16426 &%self%& option of the router.
16428 A name on the list that is followed by &`/MX`& is replaced with the list of
16429 hosts obtained by looking up MX records for the name. This is always a DNS
16430 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
16431 below) are not relevant here. The order of these hosts is determined by the
16432 preference values in the MX records, according to the usual rules. Because
16433 randomizing happens before the MX lookup, it does not affect the order that is
16434 defined by MX preferences.
16436 If the local host is present in the sublist obtained from MX records, but is
16437 not the most preferred host in that list, it and any equally or less
16438 preferred hosts are removed before the sublist is inserted into the main list.
16440 If the local host is the most preferred host in the MX list, what happens
16441 depends on where in the original list of hosts the &`/MX`& item appears. If it
16442 is not the first item (that is, there are previous hosts in the main list),
16443 Exim discards this name and any subsequent items in the main list.
16445 If the MX item is first in the list of hosts, and the local host is the
16446 most preferred host, what happens is controlled by the &%self%& option of the
16449 DNS failures when lookup up the MX records are treated in the same way as DNS
16450 failures when looking up IP addresses: &%pass_on_timeout%& and
16451 &%host_find_failed%& are used when relevant.
16453 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
16454 whether obtained from an MX lookup or not.
16458 .section "How the options are used" "SECThowoptused"
16459 The options are a sequence of words; in practice no more than three are ever
16460 present. One of the words can be the name of a transport; this overrides the
16461 &%transport%& option on the router for this particular routing rule only. The
16462 other words (if present) control randomization of the list of hosts on a
16463 per-rule basis, and how the IP addresses of the hosts are to be found when
16464 routing to a remote transport. These options are as follows:
16467 &%randomize%&: randomize the order of the hosts in this list, overriding the
16468 setting of &%hosts_randomize%& for this routing rule only.
16470 &%no_randomize%&: do not randomize the order of the hosts in this list,
16471 overriding the setting of &%hosts_randomize%& for this routing rule only.
16473 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
16474 find IP addresses. This function may ultimately cause a DNS lookup, but it may
16475 also look in &_/etc/hosts_& or other sources of information.
16477 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
16478 no address records are found. If there is a temporary DNS error (such as a
16479 timeout), delivery is deferred.
16484 route_list = domain1 host1:host2:host3 randomize bydns;\
16485 domain2 host4:host5
16487 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
16488 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
16489 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
16490 or &[gethostbyname()]&, and the result of the lookup is the result of that
16493 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
16494 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
16495 instead of TRY_AGAIN. That is why the default action is to try a DNS
16496 lookup first. Only if that gives a definite &"no such host"& is the local
16501 If no IP address for a host can be found, what happens is controlled by the
16502 &%host_find_failed%& option.
16505 When an address is routed to a local transport, IP addresses are not looked up.
16506 The host list is passed to the transport in the &$host$& variable.
16510 .section "Manualroute examples"
16511 In some of the examples that follow, the presence of the &%remote_smtp%&
16512 transport, as defined in the default configuration file, is assumed:
16515 .cindex "smart host" "example router"
16516 The &(manualroute)& router can be used to forward all external mail to a
16517 &'smart host'&. If you have set up, in the main part of the configuration, a
16518 named domain list that contains your local domains, for example:
16520 domainlist local_domains = my.domain.example
16522 You can arrange for all other domains to be routed to a smart host by making
16523 your first router something like this:
16526 driver = manualroute
16527 domains = !+local_domains
16528 transport = remote_smtp
16529 route_list = * smarthost.ref.example
16531 This causes all non-local addresses to be sent to the single host
16532 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
16533 they are tried in order
16534 (but you can use &%hosts_randomize%& to vary the order each time).
16535 Another way of configuring the same thing is this:
16538 driver = manualroute
16539 transport = remote_smtp
16540 route_list = !+local_domains smarthost.ref.example
16542 There is no difference in behaviour between these two routers as they stand.
16543 However, they behave differently if &%no_more%& is added to them. In the first
16544 example, the router is skipped if the domain does not match the &%domains%&
16545 precondition; the following router is always tried. If the router runs, it
16546 always matches the domain and so can never decline. Therefore, &%no_more%&
16547 would have no effect. In the second case, the router is never skipped; it
16548 always runs. However, if it doesn't match the domain, it declines. In this case
16549 &%no_more%& would prevent subsequent routers from running.
16552 .cindex "mail hub example"
16553 A &'mail hub'& is a host which receives mail for a number of domains via MX
16554 records in the DNS and delivers it via its own private routing mechanism. Often
16555 the final destinations are behind a firewall, with the mail hub being the one
16556 machine that can connect to machines both inside and outside the firewall. The
16557 &(manualroute)& router is usually used on a mail hub to route incoming messages
16558 to the correct hosts. For a small number of domains, the routing can be inline,
16559 using the &%route_list%& option, but for a larger number a file or database
16560 lookup is easier to manage.
16562 If the domain names are in fact the names of the machines to which the mail is
16563 to be sent by the mail hub, the configuration can be quite simple. For
16567 driver = manualroute
16568 transport = remote_smtp
16569 route_list = *.rhodes.tvs.example $domain
16571 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
16572 whose names are the same as the mail domains. A similar approach can be taken
16573 if the host name can be obtained from the domain name by a string manipulation
16574 that the expansion facilities can handle. Otherwise, a lookup based on the
16575 domain can be used to find the host:
16578 driver = manualroute
16579 transport = remote_smtp
16580 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
16582 The result of the lookup must be the name or IP address of the host (or
16583 hosts) to which the address is to be routed. If the lookup fails, the route
16584 data is empty, causing the router to decline. The address then passes to the
16588 .cindex "batched SMTP output example"
16589 .cindex "SMTP" "batched outgoing; example"
16590 You can use &(manualroute)& to deliver messages to pipes or files in batched
16591 SMTP format for onward transportation by some other means. This is one way of
16592 storing mail for a dial-up host when it is not connected. The route list entry
16593 can be as simple as a single domain name in a configuration like this:
16596 driver = manualroute
16597 transport = batchsmtp_appendfile
16598 route_list = saved.domain.example
16600 though often a pattern is used to pick up more than one domain. If there are
16601 several domains or groups of domains with different transport requirements,
16602 different transports can be listed in the routing information:
16605 driver = manualroute
16607 *.saved.domain1.example $domain batch_appendfile; \
16608 *.saved.domain2.example \
16609 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
16612 .cindex "&$domain$&"
16614 The first of these just passes the domain in the &$host$& variable, which
16615 doesn't achieve much (since it is also in &$domain$&), but the second does a
16616 file lookup to find a value to pass, causing the router to decline to handle
16617 the address if the lookup fails.
16620 .cindex "UUCP" "example of router for"
16621 Routing mail directly to UUCP software is a specific case of the use of
16622 &(manualroute)& in a gateway to another mail environment. This is an example of
16623 one way it can be done:
16629 command = /usr/local/bin/uux -r - \
16630 ${substr_-5:$host}!rmail ${local_part}
16631 return_fail_output = true
16636 driver = manualroute
16638 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
16640 The file &_/usr/local/exim/uucphosts_& contains entries like
16642 darksite.ethereal.example: darksite.UUCP
16644 It can be set up more simply without adding and removing &".UUCP"& but this way
16645 makes clear the distinction between the domain name
16646 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
16648 .ecindex IIDmanrou1
16649 .ecindex IIDmanrou2
16658 . ////////////////////////////////////////////////////////////////////////////
16659 . ////////////////////////////////////////////////////////////////////////////
16661 .chapter "The queryprogram router" "CHAPdriverlast"
16662 .scindex IIDquerou1 "&(queryprogram)& router"
16663 .scindex IIDquerou2 "routers" "&(queryprogram)&"
16664 .cindex "routing" "by external program"
16665 The &(queryprogram)& router routes an address by running an external command
16666 and acting on its output. This is an expensive way to route, and is intended
16667 mainly for use in lightly-loaded systems, or for performing experiments.
16668 However, if it is possible to use the precondition options (&%domains%&,
16669 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
16670 be used in special cases, even on a busy host. There are the following private
16672 .cindex "options" "&(queryprogram)& router"
16674 .option command queryprogram string&!! unset
16675 This option must be set. It specifies the command that is to be run. The
16676 command is split up into a command name and arguments, and then each is
16677 expanded separately (exactly as for a &(pipe)& transport, described in chapter
16678 &<<CHAPpipetransport>>&).
16681 .option command_group queryprogram string unset
16682 .cindex "gid (group id)" "in &(queryprogram)& router"
16683 This option specifies a gid to be set when running the command while routing an
16684 address for deliver. It must be set if &%command_user%& specifies a numerical
16685 uid. If it begins with a digit, it is interpreted as the numerical value of the
16686 gid. Otherwise it is looked up using &[getgrnam()]&.
16689 .option command_user queryprogram string unset
16690 .cindex "uid (user id)" "for &(queryprogram)&"
16691 This option must be set. It specifies the uid which is set when running the
16692 command while routing an address for delivery. If the value begins with a digit,
16693 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
16694 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
16695 not set, a value for the gid also.
16697 &*Warning:*& Changing uid and gid is possible only when Exim is running as
16698 root, which it does during a normal delivery in a conventional configuration.
16699 However, when an address is being verified during message reception, Exim is
16700 usually running as the Exim user, not as root. If the &(queryprogram)& router
16701 is called from a non-root process, Exim cannot change uid or gid before running
16702 the command. In this circumstance the command runs under the current uid and
16706 .option current_directory queryprogram string /
16707 This option specifies an absolute path which is made the current directory
16708 before running the command.
16711 .option timeout queryprogram time 1h
16712 If the command does not complete within the timeout period, its process group
16713 is killed and the message is frozen. A value of zero time specifies no
16717 The standard output of the command is connected to a pipe, which is read when
16718 the command terminates. It should consist of a single line of output,
16719 containing up to five fields, separated by white space. The maximum length of
16720 the line is 1023 characters. Longer lines are silently truncated. The first
16721 field is one of the following words (case-insensitive):
16724 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
16727 &'Decline'&: the router declines; pass the address to the next router, unless
16728 &%no_more%& is set.
16730 &'Fail'&: routing failed; do not pass the address to any more routers. Any
16731 subsequent text on the line is an error message. If the router is run as part
16732 of address verification during an incoming SMTP message, the message is
16733 included in the SMTP response.
16735 &'Defer'&: routing could not be completed at this time; try again later. Any
16736 subsequent text on the line is an error message which is logged. It is not
16737 included in any SMTP response.
16739 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
16741 &'Pass'&: pass the address to the next router (or the router specified by
16742 &%pass_router%&), overriding &%no_more%&.
16744 &'Redirect'&: the message is redirected. The remainder of the line is a list of
16745 new addresses, which are routed independently, starting with the first router,
16746 or the router specified by &%redirect_router%&, if set.
16749 When the first word is &'accept'&, the remainder of the line consists of a
16750 number of keyed data values, as follows (split into two lines here, to fit on
16753 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
16754 LOOKUP=byname|bydns DATA=<text>
16756 The data items can be given in any order, and all are optional. If no transport
16757 is included, the transport specified by the generic &%transport%& option is
16758 used. The list of hosts and the lookup type are needed only if the transport is
16759 an &(smtp)& transport that does not itself supply a list of hosts.
16761 The format of the list of hosts is the same as for the &(manualroute)& router.
16762 As well as host names and IP addresses with optional port numbers, as described
16763 in section &<<SECTformatonehostitem>>&, it may contain names followed by
16764 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
16765 (see section &<<SECThostshowused>>&).
16767 If the lookup type is not specified, Exim behaves as follows when trying to
16768 find an IP address for each host: First, a DNS lookup is done. If this yields
16769 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
16770 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
16771 result of the lookup is the result of that call.
16773 .cindex "&$address_data$&"
16774 If the DATA field is set, its value is placed in the &$address_data$&
16775 variable. For example, this return line
16777 accept hosts=x1.y.example:x2.y.example data="rule1"
16779 routes the address to the default transport, passing a list of two hosts. When
16780 the transport runs, the string &"rule1"& is in &$address_data$&.
16781 .ecindex IIDquerou1
16782 .ecindex IIDquerou2
16787 . ////////////////////////////////////////////////////////////////////////////
16788 . ////////////////////////////////////////////////////////////////////////////
16790 .chapter "The redirect router" "CHAPredirect"
16791 .scindex IIDredrou1 "&(redirect)& router"
16792 .scindex IIDredrou2 "routers" "&(redirect)&"
16793 .cindex "alias file" "in a &(redirect)& router"
16794 .cindex "address redirection" "&(redirect)& router"
16795 The &(redirect)& router handles several kinds of address redirection. Its most
16796 common uses are for resolving local part aliases from a central alias file
16797 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
16798 files, but it has many other potential uses. The incoming address can be
16799 redirected in several different ways:
16802 It can be replaced by one or more new addresses which are themselves routed
16805 It can be routed to be delivered to a given file or directory.
16807 It can be routed to be delivered to a specified pipe command.
16809 It can cause an automatic reply to be generated.
16811 It can be forced to fail, with a custom error message.
16813 It can be temporarily deferred.
16815 It can be discarded.
16818 The generic &%transport%& option must not be set for &(redirect)& routers.
16819 However, there are some private options which define transports for delivery to
16820 files and pipes, and for generating autoreplies. See the &%file_transport%&,
16821 &%pipe_transport%& and &%reply_transport%& descriptions below.
16825 .section "Redirection data"
16826 The router operates by interpreting a text string which it obtains either by
16827 expanding the contents of the &%data%& option, or by reading the entire
16828 contents of a file whose name is given in the &%file%& option. These two
16829 options are mutually exclusive. The first is commonly used for handling system
16830 aliases, in a configuration like this:
16834 data = ${lookup{$local_part}lsearch{/etc/aliases}}
16836 If the lookup fails, the expanded string in this example is empty. When the
16837 expansion of &%data%& results in an empty string, the router declines. A forced
16838 expansion failure also causes the router to decline; other expansion failures
16839 cause delivery to be deferred.
16841 A configuration using &%file%& is commonly used for handling users'
16842 &_.forward_& files, like this:
16847 file = $home/.forward
16850 If the file does not exist, or causes no action to be taken (for example, it is
16851 empty or consists only of comments), the router declines. &*Warning*&: This
16852 is not the case when the file contains syntactically valid items that happen to
16853 yield empty addresses, for example, items containing only RFC 2822 address
16858 .section "Forward files and address verification"
16859 .cindex "address redirection" "while verifying"
16860 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
16861 &_.forward_& files, as in the example above. There are two reasons for this:
16864 When Exim is receiving an incoming SMTP message from a remote host, it is
16865 running under the Exim uid, not as root.
16866 Exim is unable to change uid to read the file as the user, and it may not be
16867 able to read it as the Exim user. So in practice the router may not be able to
16870 However, even when the router can operate, the existence of a &_.forward_& file
16871 is unimportant when verifying an address. What should be checked is whether the
16872 local part is a valid user name or not. Cutting out the redirection processing
16873 saves some resources.
16881 .section "Interpreting redirection data"
16882 .cindex "Sieve filter" "specifying in redirection data"
16883 .cindex "filter" "specifying in redirection data"
16884 The contents of the data string, whether obtained from &%data%& or &%file%&,
16885 can be interpreted in two different ways:
16888 If the &%allow_filter%& option is set true, and the data begins with the text
16889 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
16890 &'filtering'& instructions in the form of an Exim or Sieve filter file,
16891 respectively. Details of the syntax and semantics of filter files are described
16892 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
16893 document is intended for use by end users.
16895 Otherwise, the data must be a comma-separated list of redirection items, as
16896 described in the next section.
16899 When a message is redirected to a file (a &"mail folder"&), the file name given
16900 in a non-filter redirection list must always be an absolute path. A filter may
16901 generate a relative path &-- how this is handled depends on the transport's
16902 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
16903 for the &(appendfile)& transport.
16907 .section "Items in a non-filter redirection list" "SECTitenonfilred"
16908 .cindex "address redirection" "non-filter list items"
16909 When the redirection data is not an Exim or Sieve filter, for example, if it
16910 comes from a conventional alias or forward file, it consists of a list of
16911 addresses, file names, pipe commands, or certain special items (see section
16912 &<<SECTspecitredli>>& below). The special items can be individually enabled or
16913 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
16914 depending on their default values. The items in the list are separated by
16915 commas or newlines.
16916 If a comma is required in an item, the entire item must be enclosed in double
16919 Lines starting with a # character are comments, and are ignored, and # may
16920 also appear following a comma, in which case everything between the # and the
16921 next newline character is ignored.
16923 If an item is entirely enclosed in double quotes, these are removed. Otherwise
16924 double quotes are retained because some forms of mail address require their use
16925 (but never to enclose the entire address). In the following description,
16926 &"item"& refers to what remains after any surrounding double quotes have been
16929 .cindex "&$local_part$&"
16930 &*Warning*&: If you use an Exim expansion to construct a redirection address,
16931 and the expansion contains a reference to &$local_part$&, you should make use
16932 of the &%quote_local_part%& expansion operator, in case the local part contains
16933 special characters. For example, to redirect all mail for the domain
16934 &'obsolete.example'&, retaining the existing local part, you could use this
16937 data = ${quote_local_part:$local_part}@newdomain.example
16941 .section "Redirecting to a local mailbox" "SECTredlocmai"
16942 .cindex "routing" "loops in"
16943 .cindex "loop while routing" "avoidance of"
16944 .cindex "address redirection" "to local mailbox"
16945 A redirection item may safely be the same as the address currently under
16946 consideration. This does not cause a routing loop, because a router is
16947 automatically skipped if any ancestor of the address that is being processed
16948 is the same as the current address and was processed by the current router.
16949 Such an address is therefore passed to the following routers, so it is handled
16950 as if there were no redirection. When making this loop-avoidance test, the
16951 complete local part, including any prefix or suffix, is used.
16953 .cindex "address redirection" "local part without domain"
16954 Specifying the same local part without a domain is a common usage in personal
16955 filter files when the user wants to have messages delivered to the local
16956 mailbox and also forwarded elsewhere. For example, the user whose login is
16957 &'cleo'& might have a &_.forward_& file containing this:
16959 cleo, cleopatra@egypt.example
16961 .cindex "backslash in alias file"
16962 .cindex "alias file" "backslash in"
16963 For compatibility with other MTAs, such unqualified local parts may be
16964 preceeded by &"\"&, but this is not a requirement for loop prevention. However,
16965 it does make a difference if more than one domain is being handled
16968 If an item begins with &"\"& and the rest of the item parses as a valid RFC
16969 2822 address that does not include a domain, the item is qualified using the
16970 domain of the incoming address. In the absence of a leading &"\"&, unqualified
16971 addresses are qualified using the value in &%qualify_recipient%&, but you can
16972 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
16974 Care must be taken if there are alias names for local users.
16975 Consider an MTA handling a single local domain where the system alias file
16980 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
16981 messages in the local mailbox, and also forward copies elsewhere. He creates
16984 Sam.Reman, spqr@reme.elsewhere.example
16986 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
16987 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
16988 second time round, because it has previously routed it,
16989 and the following routers presumably cannot handle the alias. The forward file
16990 should really contain
16992 spqr, spqr@reme.elsewhere.example
16994 but because this is such a common error, the &%check_ancestor%& option (see
16995 below) exists to provide a way to get round it. This is normally set on a
16996 &(redirect)& router that is handling users' &_.forward_& files.
17000 .section "Special items in redirection lists" "SECTspecitredli"
17001 In addition to addresses, the following types of item may appear in redirection
17002 lists (that is, in non-filter redirection data):
17005 .cindex "pipe" "in redirection list"
17006 .cindex "address redirection" "to pipe"
17007 An item is treated as a pipe command if it begins with &"|"& and does not parse
17008 as a valid RFC 2822 address that includes a domain. A transport for running the
17009 command must be specified by the &%pipe_transport%& option.
17010 Normally, either the router or the transport specifies a user and a group under
17011 which to run the delivery. The default is to use the Exim user and group.
17013 Single or double quotes can be used for enclosing the individual arguments of
17014 the pipe command; no interpretation of escapes is done for single quotes. If
17015 the command contains a comma character, it is necessary to put the whole item
17016 in double quotes, for example:
17018 "|/some/command ready,steady,go"
17020 since items in redirection lists are terminated by commas. Do not, however,
17021 quote just the command. An item such as
17023 |"/some/command ready,steady,go"
17025 is interpreted as a pipe with a rather strange command name, and no arguments.
17028 .cindex "file" "in redirection list"
17029 .cindex "address redirection" "to file"
17030 An item is interpreted as a path name if it begins with &"/"& and does not
17031 parse as a valid RFC 2822 address that includes a domain. For example,
17033 /home/world/minbari
17035 is treated as a file name, but
17037 /s=molari/o=babylon/@x400gate.way
17039 is treated as an address. For a file name, a transport must be specified using
17040 the &%file_transport%& option. However, if the generated path name ends with a
17041 forward slash character, it is interpreted as a directory name rather than a
17042 file name, and &%directory_transport%& is used instead.
17044 Normally, either the router or the transport specifies a user and a group under
17045 which to run the delivery. The default is to use the Exim user and group.
17047 .cindex "&_/dev/null_&"
17048 However, if a redirection item is the path &_/dev/null_&, delivery to it is
17049 bypassed at a high level, and the log entry shows &"**bypassed**"&
17050 instead of a transport name. In this case the user and group are not used.
17053 .cindex "included address list"
17054 .cindex "address redirection" "included external list"
17055 If an item is of the form
17057 :include:<path name>
17059 a list of further items is taken from the given file and included at that
17060 point. &*Note*&: Such a file can not be a filter file; it is just an
17061 out-of-line addition to the list. The items in the included list are separated
17062 by commas or newlines and are not subject to expansion. If this is the first
17063 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
17064 the alias name. This example is incorrect:
17066 list1 :include:/opt/lists/list1
17068 It must be given as
17070 list1: :include:/opt/lists/list1
17073 .cindex "address redirection" "to black hole"
17074 Sometimes you want to throw away mail to a particular local part. Making the
17075 &%data%& option expand to an empty string does not work, because that causes
17076 the router to decline. Instead, the alias item
17077 .cindex "black hole"
17078 .cindex "abandoning mail"
17082 can be used. It does what its name implies. No delivery is done, and no error
17083 message is generated. This has the same effect as specifing &_/dev/null_&, but
17084 can be independently disabled.
17086 &*Warning*&: If &`:blackhole:`& appears anywhere in a redirection list, no
17087 delivery is done for the original local part, even if other redirection items
17088 are present. If you are generating a multi-item list (for example, by reading a
17089 database) and need the ability to provide a no-op item, you must use
17093 .cindex "delivery" "forcing failure"
17094 .cindex "delivery" "forcing deferral"
17095 .cindex "failing delivery" "forcing"
17096 .cindex "deferred delivery" "forcing"
17097 .cindex "customizing" "failure message"
17098 An attempt to deliver a particular address can be deferred or forced to fail by
17099 redirection items of the form
17104 respectively. When a redirection list contains such an item, it applies to the
17105 entire redirection; any other items in the list are ignored (&':blackhole:'& is
17106 different). Any text following &':fail:'& or &':defer:'& is placed in the error
17107 text associated with the failure. For example, an alias file might contain:
17109 X.Employee: :fail: Gone away, no forwarding address
17111 In the case of an address that is being verified from an ACL or as the subject
17113 .cindex "VRFY error text" "display of"
17114 VRFY command, the text is included in the SMTP error response by
17116 .cindex "EXPN error text" "display of"
17117 The text is not included in the response to an EXPN command.
17119 .cindex "&$acl_verify_message$&"
17120 In an ACL, an explicitly provided message overrides the default, but the
17121 default message is available in the variable &$acl_verify_message$& and can
17122 therefore be included in a custom message if this is desired. Exim sends a 451
17123 SMTP code for a &':defer:'&, and 550 for &':fail:'&. In non-SMTP cases the text
17124 is included in the error message that Exim generates.
17126 Normally the error text is the rest of the redirection list &-- a comma does
17127 not terminate it &-- but a newline does act as a terminator. Newlines are not
17128 normally present in alias expansions. In &(lsearch)& lookups they are removed
17129 as part of the continuation process, but they may exist in other kinds of
17130 lookup and in &':include:'& files.
17132 During routing for message delivery (as opposed to verification), a redirection
17133 containing &':fail:'& causes an immediate failure of the incoming address,
17134 whereas &':defer:'& causes the message to remain on the queue so that a
17135 subsequent delivery attempt can happen at a later time. If an address is
17136 deferred for too long, it will ultimately fail, because the normal retry
17140 .cindex "alias file" "exception to default"
17141 Sometimes it is useful to use a single-key search type with a default (see
17142 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
17143 for exceptions to the default. These can be handled by aliasing them to
17147 This differs from &':fail:'& in that it causes the &(redirect)& router to
17148 decline, whereas &':fail:'& forces routing to fail. A lookup which results in
17149 an empty redirection list has the same effect.
17153 .section "Duplicate addresses"
17154 .cindex "duplicate addresses"
17155 .cindex "address duplicate" "discarding"
17156 .cindex "pipe" "duplicated"
17157 Exim removes duplicate addresses from the list to which it is delivering, so as
17158 to deliver just one copy to each address. This does not apply to deliveries
17159 routed to pipes by different immediate parent addresses, but an indirect
17160 aliasing scheme of the type
17162 pipe: |/some/command $local_part
17166 does not work with a message that is addressed to both local parts, because
17167 when the second is aliased to the intermediate local part &"pipe"& it gets
17168 discarded as being the same as a previously handled address. However, a scheme
17171 localpart1: |/some/command $local_part
17172 localpart2: |/some/command $local_part
17174 does result in two different pipe deliveries, because the immediate parents of
17175 the pipes are distinct.
17179 .section "Repeated redirection expansion"
17180 .cindex "repeated redirection expansion"
17181 .cindex "address redirection" "repeated for each delivery attempt"
17182 When a message cannot be delivered to all of its recipients immediately,
17183 leading to two or more delivery attempts, redirection expansion is carried out
17184 afresh each time for those addresses whose children were not all previously
17185 delivered. If redirection is being used as a mailing list, this can lead to new
17186 members of the list receiving copies of old messages. The &%one_time%& option
17187 can be used to avoid this.
17190 .section "Errors in redirection lists"
17191 .cindex "address redirection" "errors"
17192 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
17193 error is skipped, and an entry is written to the main log. This may be useful
17194 for mailing lists that are automatically managed. Otherwise, if an error is
17195 detected while generating the list of new addresses, the original address is
17196 deferred. See also &%syntax_errors_to%&.
17200 .section "Private options for the redirect router"
17202 .cindex "options" "&(redirect)& router"
17203 The private options for the &(redirect)& router are as follows:
17206 .option allow_defer redirect boolean false
17207 Setting this option allows the use of &':defer:'& in non-filter redirection
17208 data, or the &%defer%& command in an Exim filter file.
17211 .option allow_fail redirect boolean false
17212 .cindex "failing delivery" "from filter"
17213 If this option is true, the &':fail:'& item can be used in a redirection list,
17214 and the &%fail%& command may be used in an Exim filter file.
17217 .option allow_filter redirect boolean false
17218 .cindex "filter" "enabling use of"
17219 .cindex "Sieve filter" "enabling use of"
17220 Setting this option allows Exim to interpret redirection data that starts with
17221 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
17222 are some features of Exim filter files that some administrators may wish to
17223 lock out; see the &%forbid_filter_%&&'xxx'& options below.
17225 It is also possible to lock out Exim filters or Sieve filters while allowing
17226 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
17229 The filter is run using the uid and gid set by the generic &%user%& and
17230 &%group%& options. These take their defaults from the password data if
17231 &%check_local_user%& is set, so in the normal case of users' personal filter
17232 files, the filter is run as the relevant user. When &%allow_filter%& is set
17233 true, Exim insists that either &%check_local_user%& or &%user%& is set.
17237 .option allow_freeze redirect boolean false
17238 .cindex "freezing messages" "allowing in filter"
17239 Setting this option allows the use of the &%freeze%& command in an Exim filter.
17240 This command is more normally encountered in system filters, and is disabled by
17241 default for redirection filters because it isn't something you usually want to
17242 let ordinary users do.
17246 .option check_ancestor redirect boolean false
17247 This option is concerned with handling generated addresses that are the same
17248 as some address in the list of redirection ancestors of the current address.
17249 Although it is turned off by default in the code, it is set in the default
17250 configuration file for handling users' &_.forward_& files. It is recommended
17251 for this use of the &(redirect)& router.
17253 When &%check_ancestor%& is set, if a generated address (including the domain)
17254 is the same as any ancestor of the current address, it is replaced by a copy of
17255 the current address. This helps in the case where local part A is aliased to B,
17256 and B has a &_.forward_& file pointing back to A. For example, within a single
17257 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
17258 &_&~jb/.forward_& contains:
17260 \Joe.Bloggs, <other item(s)>
17262 Without the &%check_ancestor%& setting, either local part (&"jb"& or
17263 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
17264 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
17265 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
17266 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
17267 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
17268 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
17269 original address. See also the &%repeat_use%& option below.
17272 .option check_group redirect boolean "see below"
17273 When the &%file%& option is used, the group owner of the file is checked only
17274 when this option is set. The permitted groups are those listed in the
17275 &%owngroups%& option, together with the user's default group if
17276 &%check_local_user%& is set. If the file has the wrong group, routing is
17277 deferred. The default setting for this option is true if &%check_local_user%&
17278 is set and the &%modemask%& option permits the group write bit, or if the
17279 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
17283 .option check_owner redirect boolean "see below"
17284 When the &%file%& option is used, the owner of the file is checked only when
17285 this option is set. If &%check_local_user%& is set, the local user is
17286 permitted; otherwise the owner must be one of those listed in the &%owners%&
17287 option. The default value for this option is true if &%check_local_user%& or
17288 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
17291 .option data redirect string&!! unset
17292 This option is mutually exclusive with &%file%&. One or other of them must be
17293 set, but not both. The contents of &%data%& are expanded, and then used as the
17294 list of forwarding items, or as a set of filtering instructions. If the
17295 expansion is forced to fail, or the result is an empty string or a string that
17296 has no effect (consists entirely of comments), the router declines.
17298 When filtering instructions are used, the string must begin with &"#Exim
17299 filter"&, and all comments in the string, including this initial one, must be
17300 terminated with newline characters. For example:
17302 data = #Exim filter\n\
17303 if $h_to: contains Exim then save $home/mail/exim endif
17305 If you are reading the data from a database where newlines cannot be included,
17306 you can use the &${sg}$& expansion item to turn the escape string of your
17307 choice into a newline.
17310 .option directory_transport redirect string&!! unset
17311 A &(redirect)& router sets up a direct delivery to a directory when a path name
17312 ending with a slash is specified as a new &"address"&. The transport used is
17313 specified by this option, which, after expansion, must be the name of a
17314 configured transport. This should normally be an &(appendfile)& transport.
17317 .option file redirect string&!! unset
17318 This option specifies the name of a file that contains the redirection data. It
17319 is mutually exclusive with the &%data%& option. The string is expanded before
17320 use; if the expansion is forced to fail, the router declines. Other expansion
17321 failures cause delivery to be deferred. The result of a successful expansion
17322 must be an absolute path. The entire file is read and used as the redirection
17323 data. If the data is an empty string or a string that has no effect (consists
17324 entirely of comments), the router declines.
17326 .cindex "NFS" "checking for file existence"
17327 If the attempt to open the file fails with a &"does not exist"& error, Exim
17328 runs a check on the containing directory,
17329 unless &%ignore_enotdir%& is true (see below).
17330 If the directory does not appear to exist, delivery is deferred. This can
17331 happen when users' &_.forward_& files are in NFS-mounted directories, and there
17332 is a mount problem. If the containing directory does exist, but the file does
17333 not, the router declines.
17336 .option file_transport redirect string&!! unset
17337 .cindex "&$address_file$&"
17338 A &(redirect)& router sets up a direct delivery to a file when a path name not
17339 ending in a slash is specified as a new &"address"&. The transport used is
17340 specified by this option, which, after expansion, must be the name of a
17341 configured transport. This should normally be an &(appendfile)& transport. When
17342 it is running, the file name is in &$address_file$&.
17345 .option forbid_blackhole redirect boolean false
17346 If this option is true, the &':blackhole:'& item may not appear in a
17350 .option forbid_exim_filter redirect boolean false
17351 If this option is set true, only Sieve filters are permitted when
17352 &%allow_filter%& is true.
17357 .option forbid_file redirect boolean false
17358 .cindex "delivery" "to file; forbidding"
17359 .cindex "Sieve filter" "forbidding delivery to a file"
17360 .cindex "Sieve filter" "&""keep""& facility; disabling"
17361 If this option is true, this router may not generate a new address that
17362 specifies delivery to a local file or directory, either from a filter or from a
17363 conventional forward file. This option is forced to be true if &%one_time%& is
17364 set. It applies to Sieve filters as well as to Exim filters, but if true, it
17365 locks out the Sieve's &"keep"& facility.
17368 .option forbid_filter_dlfunc redirect boolean false
17369 .cindex "filter" "locking out certain features"
17370 If this option is true, string expansions in Exim filters are not allowed to
17371 make use of the &%dlfunc%& expansion facility to run dynamically loaded
17374 .option forbid_filter_existstest redirect boolean false
17375 .cindex "expansion" "statting a file"
17376 If this option is true, string expansions in Exim filters are not allowed to
17377 make use of the &%exists%& condition or the &%stat%& expansion item.
17379 .option forbid_filter_logwrite redirect boolean false
17380 If this option is true, use of the logging facility in Exim filters is not
17381 permitted. Logging is in any case available only if the filter is being run
17382 under some unprivileged uid (which is normally the case for ordinary users'
17383 &_.forward_& files).
17386 .option forbid_filter_lookup redirect boolean false
17387 If this option is true, string expansions in Exim filter files are not allowed
17388 to make use of &%lookup%& items.
17391 .option forbid_filter_perl redirect boolean false
17392 This option has an effect only if Exim is built with embedded Perl support. If
17393 it is true, string expansions in Exim filter files are not allowed to make use
17394 of the embedded Perl support.
17397 .option forbid_filter_readfile redirect boolean false
17398 If this option is true, string expansions in Exim filter files are not allowed
17399 to make use of &%readfile%& items.
17402 .option forbid_filter_readsocket redirect boolean false
17403 If this option is true, string expansions in Exim filter files are not allowed
17404 to make use of &%readsocket%& items.
17407 .option forbid_filter_reply redirect boolean false
17408 If this option is true, this router may not generate an automatic reply
17409 message. Automatic replies can be generated only from Exim or Sieve filter
17410 files, not from traditional forward files. This option is forced to be true if
17411 &%one_time%& is set.
17414 .option forbid_filter_run redirect boolean false
17415 If this option is true, string expansions in Exim filter files are not allowed
17416 to make use of &%run%& items.
17419 .option forbid_include redirect boolean false
17420 If this option is true, items of the form
17422 :include:<path name>
17424 are not permitted in non-filter redirection lists.
17427 .option forbid_pipe redirect boolean false
17428 .cindex "delivery" "to pipe; forbidding"
17429 If this option is true, this router may not generate a new address which
17430 specifies delivery to a pipe, either from an Exim filter or from a conventional
17431 forward file. This option is forced to be true if &%one_time%& is set.
17434 .option forbid_sieve_filter redirect boolean false
17435 If this option is set true, only Exim filters are permitted when
17436 &%allow_filter%& is true.
17441 .option hide_child_in_errmsg redirect boolean false
17442 .cindex "bounce message" "redirection details; suppressing"
17443 If this option is true, it prevents Exim from quoting a child address if it
17444 generates a bounce or delay message for it. Instead it says &"an address
17445 generated from <&'the top level address'&>"&. Of course, this applies only to
17446 bounces generated locally. If a message is forwarded to another host, &'its'&
17447 bounce may well quote the generated address.
17450 .option ignore_eacces redirect boolean false
17452 If this option is set and an attempt to open a redirection file yields the
17453 EACCES error (permission denied), the &(redirect)& router behaves as if the
17454 file did not exist.
17457 .option ignore_enotdir redirect boolean false
17459 If this option is set and an attempt to open a redirection file yields the
17460 ENOTDIR error (something on the path is not a directory), the &(redirect)&
17461 router behaves as if the file did not exist.
17463 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
17464 router that has the &%file%& option set discovers that the file does not exist
17465 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
17466 against unmounted NFS directories. If the parent can not be statted, delivery
17467 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
17468 is set, because that option tells Exim to ignore &"something on the path is not
17469 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
17470 that some operating systems give ENOENT where others give ENOTDIR.
17474 .option include_directory redirect string unset
17475 If this option is set, the path names of any &':include:'& items in a
17476 redirection list must start with this directory.
17479 .option modemask redirect "octal integer" 022
17480 This specifies mode bits which must not be set for a file specified by the
17481 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
17484 .option one_time redirect boolean false
17485 .cindex "one-time aliasing/forwarding expansion"
17486 .cindex "alias file" "one-time expansion"
17487 .cindex "forward file" "one-time expansion"
17488 .cindex "mailing lists" "one-time expansion"
17489 .cindex "address redirection" "one-time expansion"
17490 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
17491 files each time it tries to deliver a message causes a problem when one or more
17492 of the generated addresses fails be delivered at the first attempt. The problem
17493 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
17494 but of what happens when the redirection list changes during the time that the
17495 message is on Exim's queue. This is particularly true in the case of mailing
17496 lists, where new subscribers might receive copies of messages that were posted
17497 before they subscribed.
17499 If &%one_time%& is set and any addresses generated by the router fail to
17500 deliver at the first attempt, the failing addresses are added to the message as
17501 &"top level"& addresses, and the parent address that generated them is marked
17502 &"delivered"&. Thus, redirection does not happen again at the next delivery
17505 &*Warning 1*&: Any header line addition or removal that is specified by this
17506 router would be lost if delivery did not succeed at the first attempt. For this
17507 reason, the &%headers_add%& and &%headers_remove%& generic options are not
17508 permitted when &%one_time%& is set.
17510 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
17511 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
17512 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
17514 &*Warning 3*&: The &%unseen%& generic router option may not be set with
17517 The original top-level address is remembered with each of the generated
17518 addresses, and is output in any log messages. However, any intermediate parent
17519 addresses are not recorded. This makes a difference to the log only if
17520 &%all_parents%& log selector is set. It is expected that &%one_time%& will
17521 typically be used for mailing lists, where there is normally just one level of
17525 .option owners redirect "string list" unset
17526 .cindex "ownership" "alias file"
17527 .cindex "ownership" "forward file"
17528 .cindex "alias file" "ownership"
17529 .cindex "forward file" "ownership"
17530 This specifies a list of permitted owners for the file specified by &%file%&.
17531 This list is in addition to the local user when &%check_local_user%& is set.
17532 See &%check_owner%& above.
17535 .option owngroups redirect "string list" unset
17536 This specifies a list of permitted groups for the file specified by &%file%&.
17537 The list is in addition to the local user's primary group when
17538 &%check_local_user%& is set. See &%check_group%& above.
17541 .option pipe_transport redirect string&!! unset
17542 .cindex "&$address_pipe$&"
17543 A &(redirect)& router sets up a direct delivery to a pipe when a string
17544 starting with a vertical bar character is specified as a new &"address"&. The
17545 transport used is specified by this option, which, after expansion, must be the
17546 name of a configured transport. This should normally be a &(pipe)& transport.
17547 When the transport is run, the pipe command is in &$address_pipe$&.
17550 .option qualify_domain redirect string&!! unset
17551 .cindex "&$qualify_recipient$&"
17552 If this option is set, and an unqualified address (one without a domain) is
17553 generated, and that address would normally be qualified by the global setting
17554 in &%qualify_recipient%&, it is instead qualified with the domain specified by
17555 expanding this string. If the expansion fails, the router declines. If you want
17556 to revert to the default, you can have the expansion generate
17557 &$qualify_recipient$&.
17559 This option applies to all unqualified addresses generated by Exim filters,
17560 but for traditional &_.forward_& files, it applies only to addresses that are
17561 not preceded by a backslash. Sieve filters cannot generate unqualified
17564 .option qualify_preserve_domain redirect boolean false
17565 .cindex "domain" "in redirection; preserving"
17566 .cindex "preserving domain in redirection"
17567 .cindex "address redirection" "domain; preserving"
17568 If this option is set, the router's local &%qualify_domain%& option must not be
17569 set (a configuration error occurs if it is). If an unqualified address (one
17570 without a domain) is generated, it is qualified with the domain of the parent
17571 address (the immediately preceding ancestor) instead of the global
17572 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
17573 this applies whether or not the address is preceded by a backslash.
17576 .option repeat_use redirect boolean true
17577 If this option is set false, the router is skipped for a child address that has
17578 any ancestor that was routed by this router. This test happens before any of
17579 the other preconditions are tested. Exim's default anti-looping rules skip
17580 only when the ancestor is the same as the current address. See also
17581 &%check_ancestor%& above and the generic &%redirect_router%& option.
17584 .option reply_transport redirect string&!! unset
17585 A &(redirect)& router sets up an automatic reply when a &%mail%& or
17586 &%vacation%& command is used in a filter file. The transport used is specified
17587 by this option, which, after expansion, must be the name of a configured
17588 transport. This should normally be an &(autoreply)& transport. Other transports
17589 are unlikely to do anything sensible or useful.
17592 .option rewrite redirect boolean true
17593 .cindex "address redirection" "disabling rewriting"
17594 If this option is set false, addresses generated by the router are not
17595 subject to address rewriting. Otherwise, they are treated like new addresses
17596 and are rewritten according to the global rewriting rules.
17599 .option sieve_subaddress redirect string&!! unset
17600 The value of this option is passed to a Sieve filter to specify the
17601 :subaddress part of an address.
17603 .option sieve_useraddress redirect string&!! unset
17604 The value of this option is passed to a Sieve filter to specify the :user part
17605 of an address. However, if it is unset, the entire original local part
17606 (including any prefix or suffix) is used for :user.
17609 .option sieve_vacation_directory redirect string&!! unset
17610 .cindex "Sieve filter" "vacation directory"
17611 To enable the &"vacation"& extension for Sieve filters, you must set
17612 &%sieve_vacation_directory%& to the directory where vacation databases are held
17613 (do not put anything else in that directory), and ensure that the
17614 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
17615 needs their own directory; Exim will create it if necessary.
17619 .option skip_syntax_errors redirect boolean false
17620 .cindex "forward file" "broken"
17621 .cindex "address redirection" "broken files"
17622 .cindex "alias file" "broken"
17623 .cindex "broken alias or forward files"
17624 .cindex "ignoring faulty addresses"
17625 .cindex "skipping faulty addresses"
17626 .cindex "error" "skipping bad syntax"
17627 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
17628 non-filter redirection data are skipped, and each failing address is logged. If
17629 &%syntax_errors_to%& is set, a message is sent to the address it defines,
17630 giving details of the failures. If &%syntax_errors_text%& is set, its contents
17631 are expanded and placed at the head of the error message generated by
17632 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
17633 be the same address as the generic &%errors_to%& option. The
17634 &%skip_syntax_errors%& option is often used when handling mailing lists.
17636 If all the addresses in a redirection list are skipped because of syntax
17637 errors, the router declines to handle the original address, and it is passed to
17638 the following routers.
17640 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
17641 error in the filter causes filtering to be abandoned without any action being
17642 taken. The incident is logged, and the router declines to handle the address,
17643 so it is passed to the following routers.
17645 .cindex "Sieve filter" "syntax errors in"
17646 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
17647 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
17648 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
17650 &%skip_syntax_errors%& can be used to specify that errors in users' forward
17651 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
17652 option, used with an address that does not get redirected, can be used to
17653 notify users of these errors, by means of a router like this:
17659 file = $home/.forward
17660 file_transport = address_file
17661 pipe_transport = address_pipe
17662 reply_transport = address_reply
17665 syntax_errors_to = real-$local_part@$domain
17666 syntax_errors_text = \
17667 This is an automatically generated message. An error has\n\
17668 been found in your .forward file. Details of the error are\n\
17669 reported below. While this error persists, you will receive\n\
17670 a copy of this message for every message that is addressed\n\
17671 to you. If your .forward file is a filter file, or if it is\n\
17672 a non-filter file containing no valid forwarding addresses,\n\
17673 a copy of each incoming message will be put in your normal\n\
17674 mailbox. If a non-filter file contains at least one valid\n\
17675 forwarding address, forwarding to the valid addresses will\n\
17676 happen, and those will be the only deliveries that occur.
17678 You also need a router to ensure that local addresses that are prefixed by
17679 &`real-`& are recognized, but not forwarded or filtered. For example, you could
17680 put this immediately before the &(userforward)& router:
17685 local_part_prefix = real-
17686 transport = local_delivery
17689 .option syntax_errors_text redirect string&!! unset
17690 See &%skip_syntax_errors%& above.
17693 .option syntax_errors_to redirect string unset
17694 See &%skip_syntax_errors%& above.
17695 .ecindex IIDredrou1
17696 .ecindex IIDredrou2
17703 . ////////////////////////////////////////////////////////////////////////////
17704 . ////////////////////////////////////////////////////////////////////////////
17706 .chapter "Environment for running local transports" "CHAPenvironment" &&&
17707 "Environment for local transports"
17708 .scindex IIDenvlotra1 "local transports" "environment for"
17709 .scindex IIDenvlotra2 "environment for local transports"
17710 .scindex IIDenvlotra3 "transport" "local; environment for"
17711 Local transports handle deliveries to files and pipes. (The &(autoreply)&
17712 transport can be thought of as similar to a pipe.) Exim always runs transports
17713 in subprocesses, under specified uids and gids. Typical deliveries to local
17714 mailboxes run under the uid and gid of the local user.
17716 Exim also sets a specific current directory while running the transport; for
17717 some transports a home directory setting is also relevant. The &(pipe)&
17718 transport is the only one that sets up environment variables; see section
17719 &<<SECTpipeenv>>& for details.
17721 The values used for the uid, gid, and the directories may come from several
17722 different places. In many cases, the router that handles the address associates
17723 settings with that address as a result of its &%check_local_user%&, &%group%&,
17724 or &%user%& options. However, values may also be given in the transport's own
17725 configuration, and these override anything that comes from the router.
17729 .section "Concurrent deliveries"
17730 .cindex "concurrent deliveries"
17731 .cindex "simultaneous deliveries"
17732 If two different messages for the same local recpient arrive more or less
17733 simultaneously, the two delivery processes are likely to run concurrently. When
17734 the &(appendfile)& transport is used to write to a file, Exim applies locking
17735 rules to stop concurrent processes from writing to the same file at the same
17738 However, when you use a &(pipe)& transport, it is up to you to arrange any
17739 locking that is needed. Here is a silly example:
17743 command = /bin/sh -c 'cat >>/some/file'
17745 This is supposed to write the message at the end of the file. However, if two
17746 messages arrive at the same time, the file will be scrambled. You can use the
17747 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
17748 file using the same algorithm that Exim itself uses.
17753 .section "Uids and gids" "SECTenvuidgid"
17754 .cindex "local transports" "uid and gid"
17755 .cindex "transport" "local; uid and gid"
17756 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
17757 overrides any group that the router set in the address, even if &%user%& is not
17758 set for the transport. This makes it possible, for example, to run local mail
17759 delivery under the uid of the recipient (set by the router), but in a special
17760 group (set by the transport). For example:
17763 # User/group are set by check_local_user in this router
17767 transport = group_delivery
17770 # This transport overrides the group
17772 driver = appendfile
17773 file = /var/spool/mail/$local_part
17776 If &%user%& is set for a transport, its value overrides what is set in the
17777 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
17778 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
17781 .cindex "&%initgroups%& option"
17782 When the uid is taken from the transport's configuration, the &[initgroups()]&
17783 function is called for the groups associated with that uid if the
17784 &%initgroups%& option is set for the transport. When the uid is not specified
17785 by the transport, but is associated with the address by a router, the option
17786 for calling &[initgroups()]& is taken from the router configuration.
17788 .cindex "&(pipe)& transport" "uid for"
17789 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
17790 is set and &%user%& is not set, the uid of the process that called Exim to
17791 receive the message is used, and if &%group%& is not set, the corresponding
17792 original gid is also used.
17794 This is the detailed preference order for obtaining a gid; the first of the
17795 following that is set is used:
17798 A &%group%& setting of the transport;
17800 A &%group%& setting of the router;
17802 A gid associated with a user setting of the router, either as a result of
17803 &%check_local_user%& or an explicit non-numeric &%user%& setting;
17805 The group associated with a non-numeric &%user%& setting of the transport;
17807 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
17808 the uid is the creator's uid;
17810 The Exim gid if the Exim uid is being used as a default.
17813 If, for example, the user is specified numerically on the router and there are
17814 no group settings, no gid is available. In this situation, an error occurs.
17815 This is different for the uid, for which there always is an ultimate default.
17816 The first of the following that is set is used:
17819 A &%user%& setting of the transport;
17821 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
17823 A &%user%& setting of the router;
17825 A &%check_local_user%& setting of the router;
17830 Of course, an error will still occur if the uid that is chosen is on the
17831 &%never_users%& list.
17837 .section "Current and home directories"
17838 .cindex "current directory for local transport"
17839 .cindex "home directory" "for local transport"
17840 .cindex "transport" "local; home directory for"
17841 .cindex "transport" "local; current directory for"
17842 Routers may set current and home directories for local transports by means of
17843 the &%transport_current_directory%& and &%transport_home_directory%& options.
17844 However, if the transport's &%current_directory%& or &%home_directory%& options
17845 are set, they override the router's values. In detail, the home directory
17846 for a local transport is taken from the first of these values that is set:
17849 The &%home_directory%& option on the transport;
17851 The &%transport_home_directory%& option on the router;
17853 The password data if &%check_local_user%& is set on the router;
17855 The &%router_home_directory%& option on the router.
17858 The current directory is taken from the first of these values that is set:
17861 The &%current_directory%& option on the transport;
17863 The &%transport_current_directory%& option on the router.
17867 If neither the router nor the transport sets a current directory, Exim uses the
17868 value of the home directory, if it is set. Otherwise it sets the current
17869 directory to &_/_& before running a local transport.
17873 .section "Expansion variables derived from the address"
17874 .cindex "&$domain$&"
17875 .cindex "&$local_part$&"
17876 .cindex "&$original_domain$&"
17877 Normally a local delivery is handling a single address, and in that case the
17878 variables such as &$domain$& and &$local_part$& are set during local
17879 deliveries. However, in some circumstances more than one address may be handled
17880 at once (for example, while writing batch SMTP for onward transmission by some
17881 other means). In this case, the variables associated with the local part are
17882 never set, &$domain$& is set only if all the addresses have the same domain,
17883 and &$original_domain$& is never set.
17884 .ecindex IIDenvlotra1
17885 .ecindex IIDenvlotra2
17886 .ecindex IIDenvlotra3
17894 . ////////////////////////////////////////////////////////////////////////////
17895 . ////////////////////////////////////////////////////////////////////////////
17897 .chapter "Generic options for transports" "CHAPtransportgeneric"
17898 .scindex IIDgenoptra1 "generic options" "transport"
17899 .scindex IIDgenoptra2 "options" "generic; for transports"
17900 .scindex IIDgenoptra3 "transport" "generic options for"
17901 The following generic options apply to all transports:
17904 .option body_only transports boolean false
17905 .cindex "transport" "body only"
17906 .cindex "message" "transporting body only"
17907 .cindex "body of message" "transporting"
17908 If this option is set, the message's headers are not transported. It is
17909 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
17910 or &(pipe)& transports, the settings of &%message_prefix%& and
17911 &%message_suffix%& should be checked, because this option does not
17912 automatically suppress them.
17915 .option current_directory transports string&!! unset
17916 .cindex "transport" "current directory for"
17917 This specifies the current directory that is to be set while running the
17918 transport, overriding any value that may have been set by the router.
17919 If the expansion fails for any reason, including forced failure, an error is
17920 logged, and delivery is deferred.
17923 .option disable_logging transports boolean false
17924 If this option is set true, nothing is logged for any
17925 deliveries by the transport or for any
17926 transport errors. You should not set this option unless you really, really know
17927 what you are doing.
17930 .option debug_print transports string&!! unset
17931 .cindex "testing" "variables in drivers"
17932 If this option is set and debugging is enabled (see the &%-d%& command line
17933 option), the string is expanded and included in the debugging output when the
17935 If expansion of the string fails, the error message is written to the debugging
17936 output, and Exim carries on processing.
17937 This facility is provided to help with checking out the values of variables and
17938 so on when debugging driver configurations. For example, if a &%headers_add%&
17939 option is not working properly, &%debug_print%& could be used to output the
17940 variables it references. A newline is added to the text if it does not end with
17944 .option delivery_date_add transports boolean false
17945 .cindex "&'Delivery-date:'& header line"
17946 If this option is true, a &'Delivery-date:'& header is added to the message.
17947 This gives the actual time the delivery was made. As this is not a standard
17948 header, Exim has a configuration option (&%delivery_date_remove%&) which
17949 requests its removal from incoming messages, so that delivered messages can
17950 safely be resent to other recipients.
17953 .option driver transports string unset
17954 This specifies which of the available transport drivers is to be used.
17955 There is no default, and this option must be set for every transport.
17958 .option envelope_to_add transports boolean false
17959 .cindex "&'Envelope-to:'& header line"
17960 If this option is true, an &'Envelope-to:'& header is added to the message.
17961 This gives the original address(es) in the incoming envelope that caused this
17962 delivery to happen. More than one address may be present if the transport is
17963 configured to handle several addresses at once, or if more than one original
17964 address was redirected to the same final address. As this is not a standard
17965 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
17966 its removal from incoming messages, so that delivered messages can safely be
17967 resent to other recipients.
17970 .option group transports string&!! "Exim group"
17971 .cindex "transport" "group; specifying"
17972 This option specifies a gid for running the transport process, overriding any
17973 value that the router supplies, and also overriding any value associated with
17974 &%user%& (see below).
17977 .option headers_add transports string&!! unset
17978 .cindex "header lines" "adding in transport"
17979 .cindex "transport" "header lines; adding"
17980 This option specifies a string of text that is expanded and added to the header
17981 portion of a message as it is transported, as described in section
17982 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
17983 routers. If the result of the expansion is an empty string, or if the expansion
17984 is forced to fail, no action is taken. Other expansion failures are treated as
17985 errors and cause the delivery to be deferred.
17989 .option headers_only transports boolean false
17990 .cindex "transport" "header lines only"
17991 .cindex "message" "transporting headers only"
17992 .cindex "header lines" "transporting"
17993 If this option is set, the message's body is not transported. It is mutually
17994 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
17995 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
17996 checked, since this option does not automatically suppress them.
17999 .option headers_remove transports string&!! unset
18000 .cindex "header lines" "removing"
18001 .cindex "transport" "header lines; removing"
18002 This option specifies a string that is expanded into a list of header names;
18003 these headers are omitted from the message as it is transported, as described
18004 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
18005 routers. If the result of the expansion is an empty string, or if the expansion
18006 is forced to fail, no action is taken. Other expansion failures are treated as
18007 errors and cause the delivery to be deferred.
18011 .option headers_rewrite transports string unset
18012 .cindex "transport" "header lines; rewriting"
18013 .cindex "rewriting" "at transport time"
18014 This option allows addresses in header lines to be rewritten at transport time,
18015 that is, as the message is being copied to its destination. The contents of the
18016 option are a colon-separated list of rewriting rules. Each rule is in exactly
18017 the same form as one of the general rewriting rules that are applied when a
18018 message is received. These are described in chapter &<<CHAPrewrite>>&. For
18021 headers_rewrite = a@b c@d f : \
18024 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
18025 &'w@z'& in all address-bearing header lines. The rules are applied to the
18026 header lines just before they are written out at transport time, so they affect
18027 only those copies of the message that pass through the transport. However, only
18028 the message's original header lines, and any that were added by a system
18029 filter, are rewritten. If a router or transport adds header lines, they are not
18030 affected by this option. These rewriting rules are &'not'& applied to the
18031 envelope. You can change the return path using &%return_path%&, but you cannot
18032 change envelope recipients at this time.
18035 .option home_directory transports string&!! unset
18036 .cindex "transport" "home directory for"
18038 This option specifies a home directory setting for a local transport,
18039 overriding any value that may be set by the router. The home directory is
18040 placed in &$home$& while expanding the transport's private options. It is also
18041 used as the current directory if no current directory is set by the
18042 &%current_directory%& option on the transport or the
18043 &%transport_current_directory%& option on the router. If the expansion fails
18044 for any reason, including forced failure, an error is logged, and delivery is
18048 .option initgroups transports boolean false
18049 .cindex "additional groups"
18050 .cindex "groups" "additional"
18051 .cindex "transport" "group; additional"
18052 If this option is true and the uid for the delivery process is provided by the
18053 transport, the &[initgroups()]& function is called when running the transport
18054 to ensure that any additional groups associated with the uid are set up.
18057 .option message_size_limit transports string&!! 0
18058 .cindex "limit" "message size per transport"
18059 .cindex "size of message" "limit"
18060 .cindex "transport" "message size; limiting"
18061 This option controls the size of messages passed through the transport. It is
18062 expanded before use; the result of the expansion must be a sequence of digits,
18063 optionally followed by K or M.
18064 If the expansion fails for any reason, including forced failure, or if the
18065 result is not of the required form, delivery is deferred.
18066 If the value is greater than zero and the size of a message exceeds this
18067 limit, the address is failed. If there is any chance that the resulting bounce
18068 message could be routed to the same transport, you should ensure that
18069 &%return_size_limit%& is less than the transport's &%message_size_limit%&, as
18070 otherwise the bounce message will fail to get delivered.
18074 .option rcpt_include_affixes transports boolean false
18075 .cindex "prefix" "for local part; including in envelope"
18076 .cindex "suffix" "for local part; including in envelope"
18077 .cindex "local part" "prefix"
18078 .cindex "local part" "suffix"
18079 When this option is false (the default), and an address that has had any
18080 affixes (prefixes or suffixes) removed from the local part is delivered by any
18081 form of SMTP or LMTP, the affixes are not included. For example, if a router
18084 local_part_prefix = *-
18086 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
18089 RCPT TO:<xyz@some.domain>
18091 This is also the case when an ACL-time callout is being used to verify a
18092 recipient address. However, if &%rcpt_include_affixes%& is set true, the
18093 whole local part is included in the RCPT command. This option applies to BSMTP
18094 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
18095 &(lmtp)& and &(smtp)& transports.
18098 .option retry_use_local_part transports boolean "see below"
18099 .cindex "hints database" "retry keys"
18100 When a delivery suffers a temporary failure, a retry record is created
18101 in Exim's hints database. For remote deliveries, the key for the retry record
18102 is based on the name and/or IP address of the failing remote host. For local
18103 deliveries, the key is normally the entire address, including both the local
18104 part and the domain. This is suitable for most common cases of local delivery
18105 temporary failure &-- for example, exceeding a mailbox quota should delay only
18106 deliveries to that mailbox, not to the whole domain.
18108 However, in some special cases you may want to treat a temporary local delivery
18109 as a failure associated with the domain, and not with a particular local part.
18110 (For example, if you are storing all mail for some domain in files.) You can do
18111 this by setting &%retry_use_local_part%& false.
18113 For all the local transports, its default value is true. For remote transports,
18114 the default value is false for tidiness, but changing the value has no effect
18115 on a remote transport in the current implementation.
18118 .option return_path transports string&!! unset
18119 .cindex "envelope sender"
18120 .cindex "transport" "return path; changing"
18121 .cindex "return path" "changing in transport"
18122 If this option is set, the string is expanded at transport time and replaces
18123 the existing return path (envelope sender) value in the copy of the message
18124 that is being delivered. An empty return path is permitted. This feature is
18125 designed for remote deliveries, where the value of this option is used in the
18126 SMTP MAIL command. If you set &%return_path%& for a local transport, the
18127 only effect is to change the address that is placed in the &'Return-path:'&
18128 header line, if one is added to the message (see the next option).
18130 .cindex "&$return_path$&"
18131 The expansion can refer to the existing value via &$return_path$&. This is
18132 either the message's envelope sender, or an address set by the
18133 &%errors_to%& option on a router. If the expansion is forced to fail, no
18134 replacement occurs; if it fails for another reason, delivery is deferred. This
18135 option can be used to support VERP (Variable Envelope Return Paths) &-- see
18136 section &<<SECTverp>>&.
18138 &*Note*&: If a delivery error is detected locally, including the case when a
18139 remote server rejects a message at SMTP time, the bounce message is not sent to
18140 the value of this option. It is sent to the previously set errors address.
18141 This defaults to the incoming sender address, but can be changed by setting
18142 &%errors_to%& in a router.
18146 .option return_path_add transports boolean false
18147 .cindex "&'Return-path:'& header line"
18148 If this option is true, a &'Return-path:'& header is added to the message.
18149 Although the return path is normally available in the prefix line of BSD
18150 mailboxes, this is commonly not displayed by MUAs, and so the user does not
18151 have easy access to it.
18153 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
18154 the delivery SMTP server makes the final delivery"&. This implies that this
18155 header should not be present in incoming messages. Exim has a configuration
18156 option, &%return_path_remove%&, which requests removal of this header from
18157 incoming messages, so that delivered messages can safely be resent to other
18161 .option shadow_condition transports string&!! unset
18162 See &%shadow_transport%& below.
18165 .option shadow_transport transports string unset
18166 .cindex "shadow transport"
18167 .cindex "transport" "shadow"
18168 A local transport may set the &%shadow_transport%& option to the name of
18169 another local transport. Shadow remote transports are not supported.
18171 Whenever a delivery to the main transport succeeds, and either
18172 &%shadow_condition%& is unset, or its expansion does not result in the empty
18173 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
18174 passed to the shadow transport, with the same delivery address or addresses. If
18175 expansion fails, no action is taken except that non-forced expansion failures
18176 cause a log line to be written.
18178 The result of the shadow transport is discarded and does not affect the
18179 subsequent processing of the message. Only a single level of shadowing is
18180 provided; the &%shadow_transport%& option is ignored on any transport when it
18181 is running as a shadow. Options concerned with output from pipes are also
18182 ignored. The log line for the successful delivery has an item added on the end,
18185 ST=<shadow transport name>
18187 If the shadow transport did not succeed, the error message is put in
18188 parentheses afterwards. Shadow transports can be used for a number of different
18189 purposes, including keeping more detailed log information than Exim normally
18190 provides, and implementing automatic acknowledgement policies based on message
18191 headers that some sites insist on.
18194 .option transport_filter transports string&!! unset
18195 .cindex "transport" "filter"
18196 .cindex "filter" "transport filter"
18197 This option sets up a filtering (in the Unix shell sense) process for messages
18198 at transport time. It should not be confused with mail filtering as set up by
18199 individual users or via a system filter.
18201 When the message is about to be written out, the command specified by
18202 &%transport_filter%& is started up in a separate, parallel process, and
18203 the entire message, including the header lines, is passed to it on its standard
18204 input (this in fact is done from a third process, to avoid deadlock). The
18205 command must be specified as an absolute path.
18207 The lines of the message that are written to the transport filter are
18208 terminated by newline (&"\n"&). The message is passed to the filter before any
18209 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
18210 lines beginning with a dot, and also before any processing implied by the
18211 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
18212 &(pipe)& transports.
18214 The standard error for the filter process is set to the same destination as its
18215 standard output; this is read and written to the message's ultimate
18216 destination. The process that writes the message to the filter, the
18217 filter itself, and the original process that reads the result and delivers it
18218 are all run in parallel, like a shell pipeline.
18220 The filter can perform any transformations it likes, but of course should take
18221 care not to break RFC 2822 syntax. A demonstration Perl script is provided in
18222 &_util/transport-filter.pl_&; this makes a few arbitrary modifications just to
18223 show the possibilities. Exim does not check the result, except to test for a
18224 final newline when SMTP is in use. All messages transmitted over SMTP must end
18225 with a newline, so Exim supplies one if it is missing.
18227 .cindex "content scanning" "per user"
18228 A transport filter can be used to provide content-scanning on a per-user basis
18229 at delivery time if the only required effect of the scan is to modify the
18230 message. For example, a content scan could insert a new header line containing
18231 a spam score. This could be interpreted by a filter in the user's MUA. It is
18232 not possible to discard a message at this stage.
18234 .cindex "SMTP" "SIZE"
18235 A problem might arise if the filter increases the size of a message that is
18236 being sent down an SMTP connection. If the receiving SMTP server has indicated
18237 support for the SIZE parameter, Exim will have sent the size of the message
18238 at the start of the SMTP session. If what is actually sent is substantially
18239 more, the server might reject the message. This can be worked round by setting
18240 the &%size_addition%& option on the &(smtp)& transport, either to allow for
18241 additions to the message, or to disable the use of SIZE altogether.
18243 .cindex "&$pipe_addresses$&"
18244 The value of the &%transport_filter%& option is the command string for starting
18245 the filter, which is run directly from Exim, not under a shell. The string is
18246 parsed by Exim in the same way as a command string for the &(pipe)& transport:
18247 Exim breaks it up into arguments and then expands each argument separately (see
18248 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
18249 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
18250 of arguments, one for each address that applies to this delivery. (This isn't
18251 an ideal name for this feature here, but as it was already implemented for the
18252 &(pipe)& transport, it seemed sensible not to change it.)
18255 .cindex "&$host_address$&"
18256 The expansion variables &$host$& and &$host_address$& are available when the
18257 transport is a remote one. They contain the name and IP address of the host to
18258 which the message is being sent. For example:
18260 transport_filter = /some/directory/transport-filter.pl \
18261 $host $host_address $sender_address $pipe_addresses
18264 Two problems arise if you want to use more complicated expansion items to
18265 generate transport filter commands, both of which due to the fact that the
18266 command is split up &'before'& expansion.
18268 If an expansion item contains white space, you must quote it, so that it is all
18269 part of the same command item. If the entire option setting is one such
18270 expansion item, you have to take care what kind of quoting you use. For
18273 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
18275 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
18276 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
18277 stripped by Exim when it read the option's value. When the value is used, if
18278 the single quotes were missing, the line would be split into two items,
18279 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
18280 Exim tried to expand the first one.
18282 Except for the special case of &$pipe_addresses$& that is mentioned above, an
18283 expansion cannot generate multiple arguments, or a command name followed by
18284 arguments. Consider this example:
18286 transport_filter = ${lookup{$host}lsearch{/some/file}\
18287 {$value}{/bin/cat}}
18289 The result of the lookup is interpreted as the name of the command, even
18290 if it contains white space. The simplest way round this is to use a shell:
18292 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/some/file}\
18293 {$value}{/bin/cat}}
18297 The filter process is run under the same uid and gid as the normal delivery.
18298 For remote deliveries this is the Exim uid/gid by default. The command should
18299 normally yield a zero return code. Transport filters are not supposed to fail.
18300 A non-zero code is taken to mean that the transport filter encountered some
18301 serious problem. Delivery of the message is deferred; the message remains on
18302 the queue and is tried again later. It is not possible to cause a message to be
18303 bounced from a transport filter.
18305 If a transport filter is set on an autoreply transport, the original message is
18306 passed through the filter as it is being copied into the newly generated
18307 message, which happens if the &%return_message%& option is set.
18310 .option transport_filter_timeout transports time 5m
18311 .cindex "transport filter" "timeout"
18312 When Exim is reading the output of a transport filter, it a applies a timeout
18313 that can be set by this option. Exceeding the timeout is normally treated as a
18314 temporary delivery failure. However, if a transport filter is used with a
18315 &(pipe)& transport, a timeout in the transport filter is treated in the same
18316 way as a timeout in the pipe command itself. By default, a timeout is a hard
18317 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
18318 becomes a temporary error.
18321 .option user transports string&!! "Exim user"
18322 .cindex "uid (user id)" "local delivery"
18323 .cindex "transport user" "specifying"
18324 This option specifies the user under whose uid the delivery process is to be
18325 run, overriding any uid that may have been set by the router. If the user is
18326 given as a name, the uid is looked up from the password data, and the
18327 associated group is taken as the value of the gid to be used if the &%group%&
18330 For deliveries that use local transports, a user and group are normally
18331 specified explicitly or implicitly (for example, as a result of
18332 &%check_local_user%&) by the router or transport.
18334 .cindex "hints database" "access by remote transport"
18335 For remote transports, you should leave this option unset unless you really are
18336 sure you know what you are doing. When a remote transport is running, it needs
18337 to be able to access Exim's hints databases, because each host may have its own
18339 .ecindex IIDgenoptra1
18340 .ecindex IIDgenoptra2
18341 .ecindex IIDgenoptra3
18348 . ////////////////////////////////////////////////////////////////////////////
18349 . ////////////////////////////////////////////////////////////////////////////
18351 .chapter "Address batching in local transports" "CHAPbatching" &&&
18353 .cindex "transport" "local; address batching in"
18354 The only remote transport (&(smtp)&) is normally configured to handle more than
18355 one address at a time, so that when several addresses are routed to the same
18356 remote host, just one copy of the message is sent. Local transports, however,
18357 normally handle one address at a time. That is, a separate instance of the
18358 transport is run for each address that is routed to the transport. A separate
18359 copy of the message is delivered each time.
18361 .cindex "batched local delivery"
18362 .cindex "&%batch_max%&"
18363 .cindex "&%batch_id%&"
18364 In special cases, it may be desirable to handle several addresses at once in a
18365 local transport, for example:
18368 In an &(appendfile)& transport, when storing messages in files for later
18369 delivery by some other means, a single copy of the message with multiple
18370 recipients saves space.
18372 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
18373 a single copy saves time, and is the normal way LMTP is expected to work.
18375 In a &(pipe)& transport, when passing the message
18376 to a scanner program or
18377 to some other delivery mechanism such as UUCP, multiple recipients may be
18382 These three local transports all have the same options for controlling multiple
18383 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
18384 repeating the information for each transport, these options are described here.
18386 The &%batch_max%& option specifies the maximum number of addresses that can be
18387 delivered together in a single run of the transport. Its default value is one
18388 (no batching). When more than one address is routed to a transport that has a
18389 &%batch_max%& value greater than one, the addresses are delivered in a batch
18390 (that is, in a single run of the transport with multiple recipients), subject
18391 to certain conditions:
18395 .cindex "&$local_part$&"
18396 If any of the transport's options contain a reference to &$local_part$&, no
18397 batching is possible.
18399 .cindex "&$domain$&"
18400 If any of the transport's options contain a reference to &$domain$&, only
18401 addresses with the same domain are batched.
18403 .cindex "customizing" "batching condition"
18404 If &%batch_id%& is set, it is expanded for each address, and only those
18405 addresses with the same expanded value are batched. This allows you to specify
18406 customized batching conditions. Failure of the expansion for any reason,
18407 including forced failure, disables batching, but it does not stop the delivery
18410 Batched addresses must also have the same errors address (where to send
18411 delivery errors), the same header additions and removals, the same user and
18412 group for the transport, and if a host list is present, the first host must
18417 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
18418 both when the file or pipe command is specified in the transport, and when it
18419 is specified by a &(redirect)& router, but all the batched addresses must of
18420 course be routed to the same file or pipe command. These two transports have an
18421 option called &%use_bsmtp%&, which causes them to deliver the message in
18422 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
18423 &%check_string%& and &%escape_string%& options are forced to the values
18426 escape_string = ".."
18428 when batched SMTP is in use. A full description of the batch SMTP mechanism is
18429 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
18430 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
18432 .cindex "&'Envelope-to:'& header line"
18433 If the generic &%envelope_to_add%& option is set for a batching transport, the
18434 &'Envelope-to:'& header that is added to the message contains all the addresses
18435 that are being processed together. If you are using a batching &(appendfile)&
18436 transport without &%use_bsmtp%&, the only way to preserve the recipient
18437 addresses is to set the &%envelope_to_add%& option.
18439 .cindex "&(pipe)& transport" "with multiple addresses"
18440 .cindex "&$pipe_addresses$&"
18441 If you are using a &(pipe)& transport without BSMTP, and setting the
18442 transport's &%command%& option, you can include &$pipe_addresses$& as part of
18443 the command. This is not a true variable; it is a bit of magic that causes each
18444 of the recipient addresses to be inserted into the command as a separate
18445 argument. This provides a way of accessing all the addresses that are being
18446 delivered in the batch. &*Note:*& This is not possible for pipe commands that
18447 are specififed by a &(redirect)& router.
18453 . ////////////////////////////////////////////////////////////////////////////
18454 . ////////////////////////////////////////////////////////////////////////////
18456 .chapter "The appendfile transport" "CHAPappendfile"
18457 .scindex IIDapptra1 "&(appendfile)& transport"
18458 .scindex IIDapptra2 "transports" "&(appendfile)&"
18459 .cindex "directory creation"
18460 .cindex "creating directories"
18461 The &(appendfile)& transport delivers a message by appending it to an existing
18462 file, or by creating an entirely new file in a specified directory. Single
18463 files to which messages are appended can be in the traditional Unix mailbox
18464 format, or optionally in the MBX format supported by the Pine MUA and
18465 University of Washington IMAP daemon, &'inter alia'&. When each message is
18466 being delivered as a separate file, &"maildir"& format can optionally be used
18467 to give added protection against failures that happen part-way through the
18468 delivery. A third form of separate-file delivery known as &"mailstore"& is also
18469 supported. For all file formats, Exim attempts to create as many levels of
18470 directory as necessary, provided that &%create_directory%& is set.
18472 The code for the optional formats is not included in the Exim binary by
18473 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
18474 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
18477 .cindex "quota" "system"
18478 Exim recognises system quota errors, and generates an appropriate message. Exim
18479 also supports its own quota control within the transport, for use when the
18480 system facility is unavailable or cannot be used for some reason.
18482 If there is an error while appending to a file (for example, quota exceeded or
18483 partition filled), Exim attempts to reset the file's length and last
18484 modification time back to what they were before. If there is an error while
18485 creating an entirely new file, the new file is removed.
18487 Before appending to a file, a number of security checks are made, and the
18488 file is locked. A detailed description is given below, after the list of
18491 The &(appendfile)& transport is most commonly used for local deliveries to
18492 users' mailboxes. However, it can also be used as a pseudo-remote transport for
18493 putting messages into files for remote delivery by some means other than Exim.
18494 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
18499 .section "The file and directory options" "SECTfildiropt"
18500 The &%file%& option specifies a single file, to which the message is appended;
18501 the &%directory%& option specifies a directory, in which a new file containing
18502 the message is created. Only one of these two options can be set, and for
18503 normal deliveries to mailboxes, one of them &'must'& be set.
18505 .cindex "&$address_file$&"
18506 .cindex "&$local_part$&"
18507 However, &(appendfile)& is also used for delivering messages to files or
18508 directories whose names (or parts of names) are obtained from alias,
18509 forwarding, or filtering operations (for example, a &%save%& command in a
18510 user's Exim filter). When such a transport is running, &$local_part$& contains
18511 the local part that was aliased or forwarded, and &$address_file$& contains the
18512 name (or partial name) of the file or directory generated by the redirection
18513 operation. There are two cases:
18516 If neither &%file%& nor &%directory%& is set, the redirection operation
18517 must specify an absolute path (one that begins with &`/`&). This is the most
18518 common case when users with local accounts use filtering to sort mail into
18519 different folders. See for example, the &(address_file)& transport in the
18520 default configuration. If the path ends with a slash, it is assumed to be the
18521 name of a directory. A delivery to a directory can also be forced by setting
18522 &%maildir_format%& or &%mailstore_format%&.
18524 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
18525 used to determine the file or directory name for the delivery. Normally, the
18526 contents of &$address_file$& are used in some way in the string expansion.
18530 .cindex "Sieve filter" "configuring &(appendfile)&"
18531 .cindex "Sieve filter" "relative mailbox path handling"
18532 As an example of the second case, consider an environment where users do not
18533 have home directories. They may be permitted to use Exim filter commands of the
18538 or Sieve filter commands of the form:
18540 require "fileinto";
18541 fileinto "folder23";
18543 In this situation, the expansion of &%file%& or &%directory%& in the transport
18544 must transform the relative path into an appropriate absolute file name. In the
18545 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
18546 is used as a result of a &"keep"& action in the filter. This example shows one
18547 way of handling this requirement:
18549 file = ${if eq{$address_file}{inbox} \
18550 {/var/mail/$local_part} \
18551 {${if eq{${substr_0_1:$address_file}}{/} \
18553 {$home/mail/$address_file} \
18557 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
18558 location, absolute paths are used without change, and other folders are in the
18559 &_mail_& directory within the home directory.
18561 &*Note 1*&: While processing an Exim filter, a relative path such as
18562 &_folder23_& is turned into an absolute path if a home directory is known to
18563 the router. In particular, this is the case if &%check_local_user%& is set. If
18564 you want to prevent this happening at routing time, you can set
18565 &%router_home_directory%& empty. This forces the router to pass the relative
18566 path to the transport.
18568 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
18569 the &%file%& or &%directory%& option is still used if it is set.
18574 .section "Private options for appendfile"
18575 .cindex "options" "&(appendfile)& transport"
18579 .option allow_fifo appendfile boolean false
18580 .cindex "fifo (named pipe)"
18581 .cindex "named pipe (fifo)"
18582 .cindex "pipe" "named (fifo)"
18583 Setting this option permits delivery to named pipes (FIFOs) as well as to
18584 regular files. If no process is reading the named pipe at delivery time, the
18585 delivery is deferred.
18588 .option allow_symlink appendfile boolean false
18589 .cindex "symbolic link" "to mailbox"
18590 .cindex "mailbox" "symbolic link"
18591 By default, &(appendfile)& will not deliver if the path name for the file is
18592 that of a symbolic link. Setting this option relaxes that constraint, but there
18593 are security issues involved in the use of symbolic links. Be sure you know
18594 what you are doing if you set this. Details of exactly what this option affects
18595 are included in the discussion which follows this list of options.
18598 .option batch_id appendfile string&!! unset
18599 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
18600 However, batching is automatically disabled for &(appendfile)& deliveries that
18601 happen as a result of forwarding or aliasing or other redirection directly to a
18605 .option batch_max appendfile integer 1
18606 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
18609 .option check_group appendfile boolean false
18610 When this option is set, the group owner of the file defined by the &%file%&
18611 option is checked to see that it is the same as the group under which the
18612 delivery process is running. The default setting is false because the default
18613 file mode is 0600, which means that the group is irrelevant.
18616 .option check_owner appendfile boolean true
18617 When this option is set, the owner of the file defined by the &%file%& option
18618 is checked to ensure that it is the same as the user under which the delivery
18619 process is running.
18622 .option check_string appendfile string "see below"
18623 .cindex "&""From""& line"
18624 As &(appendfile)& writes the message, the start of each line is tested for
18625 matching &%check_string%&, and if it does, the initial matching characters are
18626 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
18627 a literal string, not a regular expression, and the case of any letters it
18628 contains is significant.
18630 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
18631 are forced to &"."& and &".."& respectively, and any settings in the
18632 configuration are ignored. Otherwise, they default to &"From&~"& and
18633 &">From&~"& when the &%file%& option is set, and unset when any of the
18634 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
18636 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
18637 suitable for traditional &"BSD"& mailboxes, where a line beginning with
18638 &"From&~"& indicates the start of a new message. All four options need changing
18639 if another format is used. For example, to deliver to mailboxes in MMDF format:
18640 .cindex "MMDF format mailbox"
18641 .cindex "mailbox" "MMDF format"
18643 check_string = "\1\1\1\1\n"
18644 escape_string = "\1\1\1\1 \n"
18645 message_prefix = "\1\1\1\1\n"
18646 message_suffix = "\1\1\1\1\n"
18648 .option create_directory appendfile boolean true
18649 .cindex "directory creation"
18650 When this option is true, Exim attempts to create any missing superior
18651 directories for the file that it is about to write. A created directory's mode
18652 is given by the &%directory_mode%& option.
18654 The group ownership of a newly created directory is highly dependent on the
18655 operating system (and possibly the file system) that is being used. For
18656 example, in Solaris, if the parent directory has the setgid bit set, its group
18657 is propagated to the child; if not, the currently set group is used. However,
18658 in FreeBSD, the parent's group is always used.
18662 .option create_file appendfile string anywhere
18663 This option constrains the location of files and directories that are created
18664 by this transport. It applies to files defined by the &%file%& option and
18665 directories defined by the &%directory%& option. In the case of maildir
18666 delivery, it applies to the top level directory, not the maildir directories
18669 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
18670 &"belowhome"&. In the second and third cases, a home directory must have been
18671 set for the transport. This option is not useful when an explicit file name is
18672 given for normal mailbox deliveries. It is intended for the case when file
18673 names are generated from users' &_.forward_& files. These are usually handled
18674 by an &(appendfile)& transport called &%address_file%&. See also
18675 &%file_must_exist%&.
18678 .option directory appendfile string&!! unset
18679 This option is mutually exclusive with the &%file%& option, but one of &%file%&
18680 or &%directory%& must be set, unless the delivery is the direct result of a
18681 redirection (see section &<<SECTfildiropt>>&).
18683 When &%directory%& is set, the string is expanded, and the message is delivered
18684 into a new file or files in or below the given directory, instead of being
18685 appended to a single mailbox file. A number of different formats are provided
18686 (see &%maildir_format%& and &%mailstore_format%&), and see section
18687 &<<SECTopdir>>& for further details of this form of delivery.
18690 .option directory_file appendfile string&!! &`q${base62:$tod_epoch}-$inode`&
18692 .cindex "&$inode$&"
18693 When &%directory%& is set, but neither &%maildir_format%& nor
18694 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
18695 whose name is obtained by expanding this string. The default value generates a
18696 unique name from the current time, in base 62 form, and the inode of the file.
18697 The variable &$inode$& is available only when expanding this option.
18700 .option directory_mode appendfile "octal integer" 0700
18701 If &(appendfile)& creates any directories as a result of the
18702 &%create_directory%& option, their mode is specified by this option.
18705 .option escape_string appendfile string "see description"
18706 See &%check_string%& above.
18709 .option file appendfile string&!! unset
18710 This option is mutually exclusive with the &%directory%& option, but one of
18711 &%file%& or &%directory%& must be set, unless the delivery is the direct result
18712 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
18713 specifies a single file, to which the message is appended. One or more of
18714 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
18717 .cindex "NFS" "lock file"
18718 .cindex "locking files"
18719 .cindex "lock files"
18720 If you are using more than one host to deliver over NFS into the same
18721 mailboxes, you should always use lock files.
18723 The string value is expanded for each delivery, and must yield an absolute
18724 path. The most common settings of this option are variations on one of these
18727 file = /var/spool/mail/$local_part
18728 file = /home/$local_part/inbox
18731 .cindex "&""sticky""& bit"
18732 In the first example, all deliveries are done into the same directory. If Exim
18733 is configured to use lock files (see &%use_lockfile%& below) it must be able to
18734 create a file in the directory, so the &"sticky"& bit must be turned on for
18735 deliveries to be possible, or alternatively the &%group%& option can be used to
18736 run the delivery under a group id which has write access to the directory.
18740 .option file_format appendfile string unset
18741 .cindex "file" "mailbox; checking existing format"
18742 This option requests the transport to check the format of an existing file
18743 before adding to it. The check consists of matching a specific string at the
18744 start of the file. The value of the option consists of an even number of
18745 colon-separated strings. The first of each pair is the test string, and the
18746 second is the name of a transport. If the transport associated with a matched
18747 string is not the current transport, control is passed over to the other
18748 transport. For example, suppose the standard &(local_delivery)& transport has
18751 file_format = "From : local_delivery :\
18752 \1\1\1\1\n : local_mmdf_delivery"
18754 Mailboxes that begin with &"From"& are still handled by this transport, but if
18755 a mailbox begins with four binary ones followed by a newline, control is passed
18756 to a transport called &%local_mmdf_delivery%&, which presumably is configured
18757 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
18758 is assumed to match the current transport. If the start of a mailbox doesn't
18759 match any string, or if the transport named for a given string is not defined,
18760 delivery is deferred.
18763 .option file_must_exist appendfile boolean false
18764 If this option is true, the file specified by the &%file%& option must exist,
18765 and an error occurs if it does not. Otherwise, it is created if it does not
18769 .option lock_fcntl_timeout appendfile time 0s
18770 .cindex "timeout" "mailbox locking"
18771 .cindex "mailbox locking" "blocking and non-blocking"
18772 .cindex "locking files"
18773 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
18774 when locking an open mailbox file. If the call fails, the delivery process
18775 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
18776 Non-blocking calls are used so that the file is not kept open during the wait
18777 for the lock; the reason for this is to make it as safe as possible for
18778 deliveries over NFS in the case when processes might be accessing an NFS
18779 mailbox without using a lock file. This should not be done, but
18780 misunderstandings and hence misconfigurations are not unknown.
18782 On a busy system, however, the performance of a non-blocking lock approach is
18783 not as good as using a blocking lock with a timeout. In this case, the waiting
18784 is done inside the system call, and Exim's delivery process acquires the lock
18785 and can proceed as soon as the previous lock holder releases it.
18787 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
18788 timeout, are used. There may still be some retrying: the maximum number of
18791 (lock_retries * lock_interval) / lock_fcntl_timeout
18793 rounded up to the next whole number. In other words, the total time during
18794 which &(appendfile)& is trying to get a lock is roughly the same, unless
18795 &%lock_fcntl_timeout%& is set very large.
18797 You should consider setting this option if you are getting a lot of delayed
18798 local deliveries because of errors of the form
18800 failed to lock mailbox /some/file (fcntl)
18803 .option lock_flock_timeout appendfile time 0s
18804 This timeout applies to file locking when using &[flock()]& (see
18805 &%use_flock%&); the timeout operates in a similar manner to
18806 &%lock_fcntl_timeout%&.
18809 .option lock_interval appendfile time 3s
18810 This specifies the time to wait between attempts to lock the file. See below
18811 for details of locking.
18814 .option lock_retries appendfile integer 10
18815 This specifies the maximum number of attempts to lock the file. A value of zero
18816 is treated as 1. See below for details of locking.
18819 .option lockfile_mode appendfile "octal integer" 0600
18821 This specifies the mode of the created lock file, when a lock file is being
18822 used (see &%use_lockfile%& and &%use_mbx_lock%&).
18826 .option lockfile_timeout appendfile time 30m
18827 .cindex "timeout" "mailbox locking"
18828 When a lock file is being used (see &%use_lockfile%&), if a lock file already
18829 exists and is older than this value, it is assumed to have been left behind by
18830 accident, and Exim attempts to remove it.
18833 .option mailbox_filecount appendfile string&!! unset
18834 .cindex "mailbox" "specifying size of"
18835 .cindex "size" "of mailbox"
18836 If this option is set, it is expanded, and the result is taken as the current
18837 number of files in the mailbox. It must be a decimal number, optionally
18838 followed by K or M. This provides a way of obtaining this information from an
18839 external source that maintains the data.
18842 .option mailbox_size appendfile string&!! unset
18843 .cindex "mailbox" "specifying size of"
18844 .cindex "size" "of mailbox"
18845 If this option is set, it is expanded, and the result is taken as the current
18846 size the mailbox. It must be a decimal number, optionally followed by K or M.
18847 This provides a way of obtaining this information from an external source that
18848 maintains the data. This is likely to be helpful for maildir deliveries where
18849 it is computationally expensive to compute the size of a mailbox.
18853 .option maildir_format appendfile boolean false
18854 .cindex "maildir format" "specifying"
18855 If this option is set with the &%directory%& option, the delivery is into a new
18856 file, in the &"maildir"& format that is used by other mail software. When the
18857 transport is activated directly from a &(redirect)& router (for example, the
18858 &(address_file)& transport in the default configuration), setting
18859 &%maildir_format%& causes the path received from the router to be treated as a
18860 directory, whether or not it ends with &`/`&. This option is available only if
18861 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
18862 &<<SECTmaildirdelivery>>& below for further details.
18865 .option maildir_quota_directory_regex appendfile string "See below"
18866 .cindex "maildir format" "quota; directories included in"
18867 .cindex "quota" "maildir; directories included in"
18869 This option is relevant only when &%maildir_use_size_file%& is set. It defines
18870 a regular expression for specifying directories, relative to the quota
18871 directory (see &%quota_directory%&), that should be included in the quota
18872 calculation. The default value is:
18875 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
18877 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
18878 (directories whose names begin with a dot). If you want to exclude the
18880 folder from the count (as some sites do), you need to change this setting to
18882 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
18885 This uses a negative lookahead in the regular expression to exclude the
18886 directory whose name is &_.Trash_&. When a directory is excluded from quota
18887 calculations, quota processing is bypassed for any messages that are delivered
18888 directly into that directory.
18892 .option maildir_retries appendfile integer 10
18893 This option specifies the number of times to retry when writing a file in
18894 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
18897 .option maildir_tag appendfile string&!! unset
18898 This option applies only to deliveries in maildir format, and is described in
18899 section &<<SECTmaildirdelivery>>& below.
18902 .option maildir_use_size_file appendfile boolean false
18903 .cindex "maildir format" "&_maildirsize_& file"
18905 Setting this option true enables support for &_maildirsize_& files. Exim
18906 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
18907 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
18908 value is zero. See &%maildir_quota_directory_regex%& above and section
18909 &<<SECTmaildirdelivery>>& below for further details.
18913 .option maildirfolder_create_regex appendfile string unset
18914 .cindex "maildir format" "&_maildirfolder_& file"
18915 .cindex "&_maildirfolder_&, creating"
18916 The value of this option is a regular expression. If it is unset, it has no
18917 effect. Otherwise, before a maildir delivery takes place place, the pattern is
18918 matched against the name of the maildir directory, that is, the directory
18919 containing the &_new_& and &_tmp_& subdirectories that will be used for the
18920 delivery. If there is a match, Exim checks for the existence of a file called
18921 &_maildirfolder_& in the directory, and creates it if it does not exist.
18922 See section &<<SECTmaildirdelivery>>& for more details.
18926 .option mailstore_format appendfile boolean false
18927 .cindex "mailstore format" "specifying"
18928 If this option is set with the &%directory%& option, the delivery is into two
18929 new files in &"mailstore"& format. The option is available only if
18930 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
18931 below for further details.
18934 .option mailstore_prefix appendfile string&!! unset
18935 This option applies only to deliveries in mailstore format, and is described in
18936 section &<<SECTopdir>>& below.
18939 .option mailstore_suffix appendfile string&!! unset
18940 This option applies only to deliveries in mailstore format, and is described in
18941 section &<<SECTopdir>>& below.
18944 .option mbx_format appendfile boolean false
18945 .cindex "locking files"
18946 .cindex "file" "locking"
18947 .cindex "file" "MBX format"
18948 .cindex "MBX format" "specifying"
18949 This option is available only if Exim has been compiled with SUPPORT_MBX
18950 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
18951 the message is appended to the mailbox file in MBX format instead of
18952 traditional Unix format. This format is supported by Pine4 and its associated
18953 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
18955 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
18956 automatically changed by the use of &%mbx_format%&. They should normally be set
18957 empty when using MBX format, so this option almost always appears in this
18964 If none of the locking options are mentioned in the configuration,
18965 &%use_mbx_lock%& is assumed and the other locking options default to false. It
18966 is possible to specify the other kinds of locking with &%mbx_format%&, but
18967 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
18968 interworks with &'c-client'&, providing for shared access to the mailbox. It
18969 should not be used if any program that does not use this form of locking is
18970 going to access the mailbox, nor should it be used if the mailbox file is NFS
18971 mounted, because it works only when the mailbox is accessed from a single host.
18973 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
18974 the standard version of &'c-client'&, because as long as it has a mailbox open
18975 (this means for the whole of a Pine or IMAP session), Exim will not be able to
18976 append messages to it.
18979 .option message_prefix appendfile string&!! "see below"
18980 .cindex "&""From""& line"
18981 The string specified here is expanded and output at the start of every message.
18982 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
18983 in which case it is:
18985 message_prefix = "From ${if def:return_path{$return_path}\
18986 {MAILER-DAEMON}} $tod_bsdinbox\n"
18990 .option message_suffix appendfile string&!! "see below"
18991 The string specified here is expanded and output at the end of every message.
18992 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
18993 in which case it is a single newline character. The suffix can be suppressed by
18999 .option mode appendfile "octal integer" 0600
19000 If the output file is created, it is given this mode. If it already exists and
19001 has wider permissions, they are reduced to this mode. If it has narrower
19002 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
19003 if the delivery is the result of a &%save%& command in a filter file specifing
19004 a particular mode, the mode of the output file is always forced to take that
19005 value, and this option is ignored.
19008 .option mode_fail_narrower appendfile boolean true
19009 This option applies in the case when an existing mailbox file has a narrower
19010 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
19011 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
19012 continues with the delivery attempt, using the existing mode of the file.
19015 .option notify_comsat appendfile boolean false
19016 If this option is true, the &'comsat'& daemon is notified after every
19017 successful delivery to a user mailbox. This is the daemon that notifies logged
19018 on users about incoming mail.
19021 .option quota appendfile string&!! unset
19022 .cindex "quota" "imposed by Exim"
19023 This option imposes a limit on the size of the file to which Exim is appending,
19024 or to the total space used in the directory tree when the &%directory%& option
19025 is set. In the latter case, computation of the space used is expensive, because
19026 all the files in the directory (and any sub-directories) have to be
19027 individually inspected and their sizes summed. (See &%quota_size_regex%& and
19028 &%maildir_use_size_file%& for ways to avoid this in environments where users
19029 have no shell access to their mailboxes).
19031 As there is no interlock against two simultaneous deliveries into a
19032 multi-file mailbox, it is possible for the quota to be overrun in this case.
19033 For single-file mailboxes, of course, an interlock is a necessity.
19035 A file's size is taken as its &'used'& value. Because of blocking effects, this
19036 may be a lot less than the actual amount of disk space allocated to the file.
19037 If the sizes of a number of files are being added up, the rounding effect can
19038 become quite noticeable, especially on systems that have large block sizes.
19039 Nevertheless, it seems best to stick to the &'used'& figure, because this is
19040 the obvious value which users understand most easily.
19042 The value of the option is expanded, and must then be a numerical value
19043 (decimal point allowed), optionally followed by one of the letters K, M, or G,
19044 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
19045 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
19048 &*Note*&: A value of zero is interpreted as &"no quota"&.
19050 The expansion happens while Exim is running as root, before it changes uid for
19051 the delivery. This means that files that are inaccessible to the end user can
19052 be used to hold quota values that are looked up in the expansion. When delivery
19053 fails because this quota is exceeded, the handling of the error is as for
19054 system quota failures.
19056 By default, Exim's quota checking mimics system quotas, and restricts the
19057 mailbox to the specified maximum size, though the value is not accurate to the
19058 last byte, owing to separator lines and additional headers that may get added
19059 during message delivery. When a mailbox is nearly full, large messages may get
19060 refused even though small ones are accepted, because the size of the current
19061 message is added to the quota when the check is made. This behaviour can be
19062 changed by setting &%quota_is_inclusive%& false. When this is done, the check
19063 for exceeding the quota does not include the current message. Thus, deliveries
19064 continue until the quota has been exceeded; thereafter, no further messages are
19065 delivered. See also &%quota_warn_threshold%&.
19068 .option quota_directory appendfile string&!! unset
19069 This option defines the directory to check for quota purposes when delivering
19070 into individual files. The default is the delivery directory, or, if a file
19071 called &_maildirfolder_& exists in a maildir directory, the parent of the
19072 delivery directory.
19075 .option quota_filecount appendfile string&!! 0
19076 This option applies when the &%directory%& option is set. It limits the total
19077 number of files in the directory (compare the inode limit in system quotas). It
19078 can only be used if &%quota%& is also set. The value is expanded; an expansion
19079 failure causes delivery to be deferred. A value of zero is interpreted as
19083 .option quota_is_inclusive appendfile boolean true
19084 See &%quota%& above.
19087 .option quota_size_regex appendfile string unset
19088 This option applies when one of the delivery modes that writes a separate file
19089 for each message is being used. When Exim wants to find the size of one of
19090 these files in order to test the quota, it first checks &%quota_size_regex%&.
19091 If this is set to a regular expression that matches the file name, and it
19092 captures one string, that string is interpreted as a representation of the
19093 file's size. The value of &%quota_size_regex%& is not expanded.
19095 This feature is useful only when users have no shell access to their mailboxes
19096 &-- otherwise they could defeat the quota simply by renaming the files. This
19097 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
19098 the file length to the file name. For example:
19100 maildir_tag = ,S=$message_size
19101 quota_size_regex = ,S=(\d+)
19103 An alternative to &$message_size$& is &$message_linecount$&, which contains the
19104 number of lines in the message.
19106 The regular expression should not assume that the length is at the end of the
19107 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
19108 sometimes add other information onto the ends of message file names.
19112 .option quota_warn_message appendfile string&!! "see below"
19113 See below for the use of this option. If it is not set when
19114 &%quota_warn_threshold%& is set, it defaults to
19116 quota_warn_message = "\
19117 To: $local_part@$domain\n\
19118 Subject: Your mailbox\n\n\
19119 This message is automatically created \
19120 by mail delivery software.\n\n\
19121 The size of your mailbox has exceeded \
19122 a warning threshold that is\n\
19123 set by the system administrator.\n"
19127 .option quota_warn_threshold appendfile string&!! 0
19128 .cindex "quota" "warning threshold"
19129 .cindex "mailbox" "size warning"
19130 .cindex "size" "of mailbox"
19131 This option is expanded in the same way as &%quota%& (see above). If the
19132 resulting value is greater than zero, and delivery of the message causes the
19133 size of the file or total space in the directory tree to cross the given
19134 threshold, a warning message is sent. If &%quota%& is also set, the threshold
19135 may be specified as a percentage of it by following the value with a percent
19139 quota_warn_threshold = 75%
19141 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
19142 percent sign is ignored.
19144 The warning message itself is specified by the &%quota_warn_message%& option,
19145 and it must start with a &'To:'& header line containing the recipient(s) of the
19146 warning message. These do not necessarily have to include the recipient(s) of
19147 the original message. A &'Subject:'& line should also normally be supplied. You
19148 can include any other header lines that you want. If you do not include a
19149 &'From:'& line, the default is:
19151 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
19153 .oindex &%errors_reply_to%&
19154 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
19157 The &%quota%& option does not have to be set in order to use this option; they
19158 are independent of one another except when the threshold is specified as a
19162 .option use_bsmtp appendfile boolean false
19163 .cindex "envelope sender"
19164 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
19165 format, with the envelope sender and recipient(s) included as SMTP commands. If
19166 you want to include a leading HELO command with such messages, you can do
19167 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
19168 for details of batch SMTP.
19171 .option use_crlf appendfile boolean false
19172 .cindex "carriage return"
19174 This option causes lines to be terminated with the two-character CRLF sequence
19175 (carriage return, linefeed) instead of just a linefeed character. In the case
19176 of batched SMTP, the byte sequence written to the file is then an exact image
19177 of what would be sent down a real SMTP connection.
19179 The contents of the &%message_prefix%& and &%message_suffix%& options are
19180 written verbatim, so must contain their own carriage return characters if these
19181 are needed. In cases where these options have non-empty defaults, the values
19182 end with a single linefeed, so they must be changed to end with &`\r\n`& if
19183 &%use_crlf%& is set.
19186 .option use_fcntl_lock appendfile boolean "see below"
19187 This option controls the use of the &[fcntl()]& function to lock a file for
19188 exclusive use when a message is being appended. It is set by default unless
19189 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
19190 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
19191 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
19194 .option use_flock_lock appendfile boolean false
19195 This option is provided to support the use of &[flock()]& for file locking, for
19196 the few situations where it is needed. Most modern operating systems support
19197 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
19198 each other. Exim uses &[fcntl()]& locking by default.
19200 This option is required only if you are using an operating system where
19201 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
19202 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
19203 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
19205 .cindex "Solaris" "&[flock()]& support"
19206 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
19207 have it (and some, I think, provide a not quite right version built on top of
19208 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
19209 the ability to use it, and any attempt to do so will cause a configuration
19212 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
19213 is just being mapped onto &[fcntl()]& by the OS).
19216 .option use_lockfile appendfile boolean "see below"
19217 If this option is turned off, Exim does not attempt to create a lock file when
19218 appending to a mailbox file. In this situation, the only locking is by
19219 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
19220 sure that every MUA that is ever going to look at your users' mailboxes uses
19221 &[fcntl()]& rather than a lock file, and even then only when you are not
19222 delivering over NFS from more than one host.
19224 .cindex "NFS" "lock file"
19225 In order to append to an NFS file safely from more than one host, it is
19226 necessary to take out a lock &'before'& opening the file, and the lock file
19227 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
19230 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
19231 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
19232 except when &%mbx_format%& is set.
19235 .option use_mbx_lock appendfile boolean "see below"
19236 This option is available only if Exim has been compiled with SUPPORT_MBX
19237 set in &_Local/Makefile_&. Setting the option specifies that special MBX
19238 locking rules be used. It is set by default if &%mbx_format%& is set and none
19239 of the locking options are mentioned in the configuration. The locking rules
19240 are the same as are used by the &'c-client'& library that underlies Pine and
19241 the IMAP4 and POP daemons that come with it (see the discussion below). The
19242 rules allow for shared access to the mailbox. However, this kind of locking
19243 does not work when the mailbox is NFS mounted.
19245 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
19246 &%use_flock_lock%& to control what kind of locking is used in implementing the
19247 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
19248 without &%use_fcntl_lock%& or &%use_flock_lock%&.
19253 .section "Operational details for appending" "SECTopappend"
19254 .cindex "appending to a file"
19255 .cindex "file" "appending"
19256 Before appending to a file, the following preparations are made:
19259 If the name of the file is &_/dev/null_&, no action is taken, and a success
19263 .cindex "directory creation"
19264 If any directories on the file's path are missing, Exim creates them if the
19265 &%create_directory%& option is set. A created directory's mode is given by the
19266 &%directory_mode%& option.
19269 If &%file_format%& is set, the format of an existing file is checked. If this
19270 indicates that a different transport should be used, control is passed to that
19274 .cindex "file" "locking"
19275 .cindex "locking files"
19276 .cindex "NFS" "lock file"
19277 If &%use_lockfile%& is set, a lock file is built in a way that will work
19278 reliably over NFS, as follows:
19281 Create a &"hitching post"& file whose name is that of the lock file with the
19282 current time, primary host name, and process id added, by opening for writing
19283 as a new file. If this fails with an access error, delivery is deferred.
19285 Close the hitching post file, and hard link it to the lock file name.
19287 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
19288 Unlink the hitching post name.
19290 Otherwise, use &[stat()]& to get information about the hitching post file, and
19291 then unlink hitching post name. If the number of links is exactly two, creation
19292 of the lock file succeeded but something (for example, an NFS server crash and
19293 restart) caused this fact not to be communicated to the &[link()]& call.
19295 If creation of the lock file failed, wait for &%lock_interval%& and try again,
19296 up to &%lock_retries%& times. However, since any program that writes to a
19297 mailbox should complete its task very quickly, it is reasonable to time out old
19298 lock files that are normally the result of user agent and system crashes. If an
19299 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
19300 it before trying again.
19304 A call is made to &[lstat()]& to discover whether the main file exists, and if
19305 so, what its characteristics are. If &[lstat()]& fails for any reason other
19306 than non-existence, delivery is deferred.
19309 .cindex "symbolic link" "to mailbox"
19310 .cindex "mailbox" "symbolic link"
19311 If the file does exist and is a symbolic link, delivery is deferred, unless the
19312 &%allow_symlink%& option is set, in which case the ownership of the link is
19313 checked, and then &[stat()]& is called to find out about the real file, which
19314 is then subjected to the checks below. The check on the top-level link
19315 ownership prevents one user creating a link for another's mailbox in a sticky
19316 directory, though allowing symbolic links in this case is definitely not a good
19317 idea. If there is a chain of symbolic links, the intermediate ones are not
19321 If the file already exists but is not a regular file, or if the file's owner
19322 and group (if the group is being checked &-- see &%check_group%& above) are
19323 different from the user and group under which the delivery is running,
19324 delivery is deferred.
19327 If the file's permissions are more generous than specified, they are reduced.
19328 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
19329 is set false, in which case the delivery is tried using the existing
19333 The file's inode number is saved, and the file is then opened for appending.
19334 If this fails because the file has vanished, &(appendfile)& behaves as if it
19335 hadn't existed (see below). For any other failures, delivery is deferred.
19338 If the file is opened successfully, check that the inode number hasn't
19339 changed, that it is still a regular file, and that the owner and permissions
19340 have not changed. If anything is wrong, defer delivery and freeze the message.
19343 If the file did not exist originally, defer delivery if the &%file_must_exist%&
19344 option is set. Otherwise, check that the file is being created in a permitted
19345 directory if the &%create_file%& option is set (deferring on failure), and then
19346 open for writing as a new file, with the O_EXCL and O_CREAT options,
19347 except when dealing with a symbolic link (the &%allow_symlink%& option must be
19348 set). In this case, which can happen if the link points to a non-existent file,
19349 the file is opened for writing using O_CREAT but not O_EXCL, because
19350 that prevents link following.
19353 .cindex "loop" "while file testing"
19354 If opening fails because the file exists, obey the tests given above for
19355 existing files. However, to avoid looping in a situation where the file is
19356 being continuously created and destroyed, the exists/not-exists loop is broken
19357 after 10 repetitions, and the message is then frozen.
19360 If opening fails with any other error, defer delivery.
19363 .cindex "file" "locking"
19364 .cindex "locking files"
19365 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
19366 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
19367 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
19368 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
19369 file, and an exclusive lock on the file whose name is
19371 /tmp/.<device-number>.<inode-number>
19374 using the device and inode numbers of the open mailbox file, in accordance with
19375 the MBX locking rules. This file is created with a mode that is specified by
19376 the &%lockfile_mode%& option.
19379 If Exim fails to lock the file, there are two possible courses of action,
19380 depending on the value of the locking timeout. This is obtained from
19381 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
19383 If the timeout value is zero, the file is closed, Exim waits for
19384 &%lock_interval%&, and then goes back and re-opens the file as above and tries
19385 to lock it again. This happens up to &%lock_retries%& times, after which the
19386 delivery is deferred.
19388 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
19389 &[flock()]& are used (with the given timeout), so there has already been some
19390 waiting involved by the time locking fails. Nevertheless, Exim does not give up
19391 immediately. It retries up to
19393 (lock_retries * lock_interval) / <timeout>
19395 times (rounded up).
19398 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
19399 and/or &[flock()]& locks) and then deletes the lock file if one was created.
19402 .section "Operational details for delivery to a new file" "SECTopdir"
19403 .cindex "delivery" "to single file"
19404 .cindex "&""From""& line"
19405 When the &%directory%& option is set instead of &%file%&, each message is
19406 delivered into a newly-created file or set of files. When &(appendfile)& is
19407 activated directly from a &(redirect)& router, neither &%file%& nor
19408 &%directory%& is normally set, because the path for delivery is supplied by the
19409 router. (See for example, the &(address_file)& transport in the default
19410 configuration.) In this case, delivery is to a new file if either the path name
19411 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
19413 No locking is required while writing the message to a new file, so the various
19414 locking options of the transport are ignored. The &"From"& line that by default
19415 separates messages in a single file is not normally needed, nor is the escaping
19416 of message lines that start with &"From"&, and there is no need to ensure a
19417 newline at the end of each message. Consequently, the default values for
19418 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
19419 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
19421 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
19422 the files in the delivery directory by default. However, you can specify a
19423 different directory by setting &%quota_directory%&. Also, for maildir
19424 deliveries (see below) the &_maildirfolder_& convention is honoured.
19427 .cindex "maildir format"
19428 .cindex "mailstore format"
19429 There are three different ways in which delivery to individual files can be
19430 done, controlled by the settings of the &%maildir_format%& and
19431 &%mailstore_format%& options. Note that code to support maildir or mailstore
19432 formats is not included in the binary unless SUPPORT_MAILDIR or
19433 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
19435 .cindex "directory creation"
19436 In all three cases an attempt is made to create the directory and any necessary
19437 sub-directories if they do not exist, provided that the &%create_directory%&
19438 option is set (the default). The location of a created directory can be
19439 constrained by setting &%create_file%&. A created directory's mode is given by
19440 the &%directory_mode%& option. If creation fails, or if the
19441 &%create_directory%& option is not set when creation is required, delivery is
19446 .section "Maildir delivery" "SECTmaildirdelivery"
19447 .cindex "maildir format" "description of"
19449 If the &%maildir_format%& option is true, Exim delivers each message by writing
19450 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
19451 directory that is defined by the &%directory%& option (the &"delivery
19452 directory"&). If the delivery is successful, the file is renamed into the
19453 &_new_& subdirectory.
19456 In the file name, <&'stime'&> is the current time of day in seconds, and
19457 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
19458 Exim checks that the time-of-day clock has moved on by at least one microsecond
19459 before terminating the delivery process. This guarantees uniqueness for the
19460 file name. However, as a precaution, Exim calls &[stat()]& for the file before
19461 opening it. If any response other than ENOENT (does not exist) is given,
19462 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
19465 Before Exim carries out a maildir delivery, it ensures that subdirectories
19466 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
19467 do not exist, Exim tries to create them and any superior directories in their
19468 path, subject to the &%create_directory%& and &%create_file%& options. If the
19469 &%maildirfolder_create_regex%& option is set, and the regular expression it
19470 contains matches the delivery directory, Exim also ensures that a file called
19471 &_maildirfolder_& exists in the delivery directory. If a missing directory or
19472 &_maildirfolder_& file cannot be created, delivery is deferred.
19474 These features make it possible to use Exim to create all the necessary files
19475 and directories in a maildir mailbox, including subdirectories for maildir++
19476 folders. Consider this example:
19478 maildir_format = true
19479 directory = /var/mail/$local_part\
19480 ${if eq{$local_part_suffix}{}{}\
19481 {/.${substr_1:$local_part_suffix}}}
19482 maildirfolder_create_regex = /\.[^/]+$
19484 If &$local_part_suffix$& is empty (there was no suffix for the local part),
19485 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
19486 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
19487 not match this name, so Exim will not look for or create
19488 &_/var/mail/pimbo/maildirfolder_&, though it will create
19489 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
19491 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
19492 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
19493 does match &%maildirfolder_create_regex%&. In this case, Exim will create
19494 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
19495 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
19497 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
19498 not inadvertently match the toplevel maildir directory, because a
19499 &_maildirfolder_& file at top level would completely break quota calculations.
19502 .cindex "quota" "in maildir delivery"
19503 .cindex "maildir++"
19504 If Exim is required to check a &%quota%& setting before a maildir delivery, and
19505 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
19506 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
19507 Exim assumes the directory is a maildir++ folder directory, which is one level
19508 down from the user's top level mailbox directory. This causes it to start at
19509 the parent directory instead of the current directory when calculating the
19510 amount of space used.
19512 One problem with delivering into a multi-file mailbox is that it is
19513 computationally expensive to compute the size of the mailbox for quota
19514 checking. Various approaches have been taken to reduce the amount of work
19515 needed. The next two sections describe two of them. A third alternative is to
19516 use some external process for maintaining the size data, and use the expansion
19517 of the &%mailbox_size%& option as a way of importing it into Exim.
19522 .section "Using tags to record message sizes"
19523 If &%maildir_tag%& is set, the string is expanded for each delivery.
19524 When the maildir file is renamed into the &_new_& sub-directory, the
19525 tag is added to its name. However, if adding the tag takes the length of the
19526 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
19527 the tag is dropped and the maildir file is created with no tag.
19529 .cindex "&$message_size$&"
19530 Tags can be used to encode the size of files in their names; see
19531 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
19532 happens after the message has been written. The value of the &$message_size$&
19533 variable is set to the number of bytes actually written. If the expansion is
19534 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
19535 be deferred. The expanded tag may contain any printing characters except &"/"&.
19536 Non-printing characters in the string are ignored; if the resulting string is
19537 empty, it is ignored. If it starts with an alphanumeric character, a leading
19542 .section "Using a maildirsize file"
19543 .cindex "quota" "in maildir delivery"
19544 .cindex "maildir format" "&_maildirsize_& file"
19545 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
19546 storing quota and message size information in a file called &_maildirsize_&
19547 within the toplevel maildir directory. If this file does not exist, Exim
19548 creates it, setting the quota from the &%quota%& option of the transport. If
19549 the maildir directory itself does not exist, it is created before any attempt
19550 to write a &_maildirsize_& file.
19552 The &_maildirsize_& file is used to hold information about the sizes of
19553 messages in the maildir, thus speeding up quota calculations. The quota value
19554 in the file is just a cache; if the quota is changed in the transport, the new
19555 value overrides the cached value when the next message is delivered. The cache
19556 is maintained for the benefit of other programs that access the maildir and
19557 need to know the quota.
19559 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
19560 file is maintained (with a zero quota setting), but no quota is imposed.
19563 A regular expression is available for controlling which directories in the
19564 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
19565 See the description of the &%maildir_quota_directory_regex%& option above for
19570 .section "Mailstore delivery"
19571 .cindex "mailstore format" "description of"
19572 If the &%mailstore_format%& option is true, each message is written as two
19573 files in the given directory. A unique base name is constructed from the
19574 message id and the current delivery process, and the files that are written use
19575 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
19576 contains the message's envelope, and the &_.msg_& file contains the message
19577 itself. The base name is placed in the variable &$mailstore_basename$&.
19579 During delivery, the envelope is first written to a file with the suffix
19580 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
19581 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
19582 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
19583 file before accessing either of them. An alternative approach is to wait for
19584 the absence of a &_.tmp_& file.
19586 The envelope file starts with any text defined by the &%mailstore_prefix%&
19587 option, expanded and terminated by a newline if there isn't one. Then follows
19588 the sender address on one line, then all the recipient addresses, one per line.
19589 There can be more than one recipient only if the &%batch_max%& option is set
19590 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
19591 appended to the file, followed by a newline if it does not end with one.
19593 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
19594 failure, it is ignored. Other expansion errors are treated as serious
19595 configuration errors, and delivery is deferred. The variable
19596 &$mailstore_basename$& is available for use during these expansions.
19599 .section "Non-special new file delivery"
19600 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
19601 file is created directly in the named directory. For example, when delivering
19602 messages into files in batched SMTP format for later delivery to some host (see
19603 section &<<SECTbatchSMTP>>&), a setting such as
19605 directory = /var/bsmtp/$host
19607 might be used. A message is written to a file with a temporary name, which is
19608 then renamed when the delivery is complete. The final name is obtained by
19609 expanding the contents of the &%directory_file%& option.
19610 .ecindex IIDapptra1
19611 .ecindex IIDapptra2
19618 . ////////////////////////////////////////////////////////////////////////////
19619 . ////////////////////////////////////////////////////////////////////////////
19621 .chapter "The autoreply transport"
19622 .scindex IIDauttra1 "transports" "&(autoreply)&"
19623 .scindex IIDauttra2 "&(autoreply)& transport"
19624 The &(autoreply)& transport is not a true transport in that it does not cause
19625 the message to be transmitted. Instead, it generates a new mail message as an
19626 automatic reply to the incoming message. &'References:'& and
19627 &'Auto-Submitted:'& header lines are included. These are constructed according
19628 to the rules in RFCs 2822 and 3834, respectively.
19630 If the router that passes the message to this transport does not have the
19631 &%unseen%& option set, the original message (for the current recipient) is not
19632 delivered anywhere. However, when the &%unseen%& option is set on the router
19633 that passes the message to this transport, routing of the address continues, so
19634 another router can set up a normal message delivery.
19637 The &(autoreply)& transport is usually run as the result of mail filtering, a
19638 &"vacation"& message being the standard example. However, it can also be run
19639 directly from a router like any other transport. To reduce the possibility of
19640 message cascades, messages created by the &(autoreply)& transport always have
19641 empty envelope sender addresses, like bounce messages.
19643 The parameters of the message to be sent can be specified in the configuration
19644 by options described below. However, these are used only when the address
19645 passed to the transport does not contain its own reply information. When the
19646 transport is run as a consequence of a
19648 or &%vacation%& command in a filter file, the parameters of the message are
19649 supplied by the filter, and passed with the address. The transport's options
19650 that define the message are then ignored (so they are not usually set in this
19651 case). The message is specified entirely by the filter or by the transport; it
19652 is never built from a mixture of options. However, the &%file_optional%&,
19653 &%mode%&, and &%return_message%& options apply in all cases.
19655 &(Autoreply)& is implemented as a local transport. When used as a result of a
19656 command in a user's filter file, &(autoreply)& normally runs under the uid and
19657 gid of the user, and with appropriate current and home directories (see chapter
19658 &<<CHAPenvironment>>&).
19660 There is a subtle difference between routing a message to a &(pipe)& transport
19661 that generates some text to be returned to the sender, and routing it to an
19662 &(autoreply)& transport. This difference is noticeable only if more than one
19663 address from the same message is so handled. In the case of a pipe, the
19664 separate outputs from the different addresses are gathered up and returned to
19665 the sender in a single message, whereas if &(autoreply)& is used, a separate
19666 message is generated for each address that is passed to it.
19668 Non-printing characters are not permitted in the header lines generated for the
19669 message that &(autoreply)& creates, with the exception of newlines that are
19670 immediately followed by white space. If any non-printing characters are found,
19671 the transport defers.
19672 Whether characters with the top bit set count as printing characters or not is
19673 controlled by the &%print_topbitchars%& global option.
19675 If any of the generic options for manipulating headers (for example,
19676 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
19677 of the original message that is included in the generated message when
19678 &%return_message%& is set. They do not apply to the generated message itself.
19680 .cindex "&$sender_address$&"
19681 If the &(autoreply)& transport receives return code 2 from Exim when it submits
19682 the message, indicating that there were no recipients, it does not treat this
19683 as an error. This means that autoreplies sent to &$sender_address$& when this
19684 is empty (because the incoming message is a bounce message) do not cause
19685 problems. They are just discarded.
19689 .section "Private options for autoreply"
19690 .cindex "options" "&(autoreply)& transport"
19692 .option bcc autoreply string&!! unset
19693 This specifies the addresses that are to receive &"blind carbon copies"& of the
19694 message when the message is specified by the transport.
19697 .option cc autoreply string&!! unset
19698 This specifies recipients of the message and the contents of the &'Cc:'& header
19699 when the message is specified by the transport.
19702 .option file autoreply string&!! unset
19703 The contents of the file are sent as the body of the message when the message
19704 is specified by the transport. If both &%file%& and &%text%& are set, the text
19705 string comes first.
19708 .option file_expand autoreply boolean false
19709 If this is set, the contents of the file named by the &%file%& option are
19710 subjected to string expansion as they are added to the message.
19713 .option file_optional autoreply boolean false
19714 If this option is true, no error is generated if the file named by the &%file%&
19715 option or passed with the address does not exist or cannot be read.
19718 .option from autoreply string&!! unset
19719 This specifies the contents of the &'From:'& header when the message is
19720 specified by the transport.
19723 .option headers autoreply string&!! unset
19724 This specifies additional RFC 2822 headers that are to be added to the message
19725 when the message is specified by the transport. Several can be given by using
19726 &"\n"& to separate them. There is no check on the format.
19729 .option log autoreply string&!! unset
19730 This option names a file in which a record of every message sent is logged when
19731 the message is specified by the transport.
19734 .option mode autoreply "octal integer" 0600
19735 If either the log file or the &"once"& file has to be created, this mode is
19739 .option never_mail autoreply "address list&!!" unset
19741 If any run of the transport creates a message with a recipient that matches any
19742 item in the list, that recipient is quietly discarded. If all recipients are
19743 discarded, no message is created. This applies both when the recipients are
19744 generated by a filter and when they are specified in the transport.
19749 .option once autoreply string&!! unset
19750 This option names a file or DBM database in which a record of each &'To:'&
19751 recipient is kept when the message is specified by the transport. &*Note*&:
19752 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
19754 If &%once%& is unset, or is set to an empty string, the message is always sent.
19755 By default, if &%once%& is set to a non-empty file name, the message
19756 is not sent if a potential recipient is already listed in the database.
19757 However, if the &%once_repeat%& option specifies a time greater than zero, the
19758 message is sent if that much time has elapsed since a message was last sent to
19759 this recipient. A setting of zero time for &%once_repeat%& (the default)
19760 prevents a message from being sent a second time &-- in this case, zero means
19763 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
19764 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
19765 greater than zero, it changes the way Exim implements the &%once%& option.
19766 Instead of using a DBM file to record every recipient it sends to, it uses a
19767 regular file, whose size will never get larger than the given value.
19769 In the file, Exim keeps a linear list of recipient addresses and the times at
19770 which they were sent messages. If the file is full when a new address needs to
19771 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
19772 means that a given recipient may receive multiple messages, but at
19773 unpredictable intervals that depend on the rate of turnover of addresses in the
19774 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
19777 .option once_file_size autoreply integer 0
19778 See &%once%& above.
19781 .option once_repeat autoreply time&!! 0s
19782 See &%once%& above.
19783 After expansion, the value of this option must be a valid time value.
19786 .option reply_to autoreply string&!! unset
19787 This specifies the contents of the &'Reply-To:'& header when the message is
19788 specified by the transport.
19791 .option return_message autoreply boolean false
19792 If this is set, a copy of the original message is returned with the new
19793 message, subject to the maximum size set in the &%return_size_limit%& global
19794 configuration option.
19797 .option subject autoreply string&!! unset
19798 This specifies the contents of the &'Subject:'& header when the message is
19799 specified by the transport. It is tempting to quote the original subject in
19800 automatic responses. For example:
19802 subject = Re: $h_subject:
19804 There is a danger in doing this, however. It may allow a third party to
19805 subscribe your users to an opt-in mailing list, provided that the list accepts
19806 bounce messages as subscription confirmations. Well-managed lists require a
19807 non-bounce message to confirm a subscription, so the danger is relatively
19812 .option text autoreply string&!! unset
19813 This specifies a single string to be used as the body of the message when the
19814 message is specified by the transport. If both &%text%& and &%file%& are set,
19815 the text comes first.
19818 .option to autoreply string&!! unset
19819 This specifies recipients of the message and the contents of the &'To:'& header
19820 when the message is specified by the transport.
19821 .ecindex IIDauttra1
19822 .ecindex IIDauttra2
19827 . ////////////////////////////////////////////////////////////////////////////
19828 . ////////////////////////////////////////////////////////////////////////////
19830 .chapter "The lmtp transport" "CHAPLMTP"
19831 .cindex "transports" "&(lmtp)&"
19832 .cindex "&(lmtp)& transport"
19833 .cindex "LMTP" "over a pipe"
19834 .cindex "LMTP" "over a socket"
19835 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
19837 or by interacting with a Unix domain socket.
19838 This transport is something of a cross between the &(pipe)& and &(smtp)&
19839 transports. Exim also has support for using LMTP over TCP/IP; this is
19840 implemented as an option for the &(smtp)& transport. Because LMTP is expected
19841 to be of minority interest, the default build-time configure in &_src/EDITME_&
19842 has it commented out. You need to ensure that
19846 .cindex "options" "&(lmtp)& transport"
19847 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
19848 included in the Exim binary. The private options of the &(lmtp)& transport are
19851 .option batch_id lmtp string&!! unset
19852 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
19855 .option batch_max lmtp integer 1
19856 This limits the number of addresses that can be handled in a single delivery.
19857 Most LMTP servers can handle several addresses at once, so it is normally a
19858 good idea to increase this value. See the description of local delivery
19859 batching in chapter &<<CHAPbatching>>&.
19862 .option command lmtp string&!! unset
19863 This option must be set if &%socket%& is not set. The string is a command which
19864 is run in a separate process. It is split up into a command name and list of
19865 arguments, each of which is separately expanded (so expansion cannot change the
19866 number of arguments). The command is run directly, not via a shell. The message
19867 is passed to the new process using the standard input and output to operate the
19870 .option ignore_quota lmtp boolean false
19871 .cindex "LMTP" "ignoring quota errors"
19872 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
19873 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
19874 in its response to the LHLO command.
19876 .option socket lmtp string&!! unset
19877 This option must be set if &%command%& is not set. The result of expansion must
19878 be the name of a Unix domain socket. The transport connects to the socket and
19879 delivers the message to it using the LMTP protocol.
19882 .option timeout lmtp time 5m
19883 The transport is aborted if the created process
19884 or Unix domain socket
19885 does not respond to LMTP commands or message input within this timeout.
19888 Here is an example of a typical LMTP transport:
19892 command = /some/local/lmtp/delivery/program
19896 This delivers up to 20 addresses at a time, in a mixture of domains if
19897 necessary, running as the user &'exim'&.
19901 . ////////////////////////////////////////////////////////////////////////////
19902 . ////////////////////////////////////////////////////////////////////////////
19904 .chapter "The pipe transport" "CHAPpipetransport"
19905 .scindex IIDpiptra1 "transports" "&(pipe)&"
19906 .scindex IIDpiptra2 "&(pipe)& transport"
19907 The &(pipe)& transport is used to deliver messages via a pipe to a command
19908 running in another process. One example is the use of &(pipe)& as a
19909 pseudo-remote transport for passing messages to some other delivery mechanism
19910 (such as UUCP). Another is the use by individual users to automatically process
19911 their incoming messages. The &(pipe)& transport can be used in one of the
19915 .cindex "&$local_part$&"
19916 A router routes one address to a transport in the normal way, and the
19917 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
19918 contains the local part of the address (as usual), and the command that is run
19919 is specified by the &%command%& option on the transport.
19922 .cindex "&$pipe_addresses$&"
19923 If the &%batch_max%& option is set greater than 1 (the default is 1), the
19924 transport can handle more than one address in a single run. In this case, when
19925 more than one address is routed to the transport, &$local_part$& is not set
19926 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
19927 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
19928 that are routed to the transport.
19930 .cindex "&$address_pipe$&"
19931 A router redirects an address directly to a pipe command (for example, from an
19932 alias or forward file). In this case, &$address_pipe$& contains the text of the
19933 pipe command, and the &%command%& option on the transport is ignored. If only
19934 one address is being transported (&%batch_max%& is not greater than one, or
19935 only one address was redirected to this pipe command), &$local_part$& contains
19936 the local part that was redirected.
19941 The &(pipe)& transport is a non-interactive delivery method. Exim can also
19942 deliver messages over pipes using the LMTP interactive protocol. This is
19943 implemented by the &(lmtp)& transport.
19945 In the case when &(pipe)& is run as a consequence of an entry in a local user's
19946 &_.forward_& file, the command runs under the uid and gid of that user. In
19947 other cases, the uid and gid have to be specified explicitly, either on the
19948 transport or on the router that handles the address. Current and &"home"&
19949 directories are also controllable. See chapter &<<CHAPenvironment>>& for
19950 details of the local delivery environment &new("and chapter &<<CHAPbatching>>&
19951 for a discussion of local delivery batching.")
19954 .section "Concurrent delivery"
19955 If two messages arrive at almost the same time, and both are routed to a pipe
19956 delivery, the two pipe transports may be run concurrently. You must ensure that
19957 any pipe commands you set up are robust against this happening. If the commands
19958 write to a file, the &%exim_lock%& utility might be of use.
19963 .section "Returned status and data"
19964 .cindex "&(pipe)& transport" "returned data"
19965 If the command exits with a non-zero return code, the delivery is deemed to
19966 have failed, unless either the &%ignore_status%& option is set (in which case
19967 the return code is treated as zero), or the return code is one of those listed
19968 in the &%temp_errors%& option, which are interpreted as meaning &"try again
19969 later"&. In this case, delivery is deferred. Details of a permanent failure are
19970 logged, but are not included in the bounce message, which merely contains
19971 &"local delivery failed"&.
19973 If the return code is greater than 128 and the command being run is a shell
19974 script, it normally means that the script was terminated by a signal whose
19975 value is the return code minus 128.
19977 If Exim is unable to run the command (that is, if &[execve()]& fails), the
19978 return code is set to 127. This is the value that a shell returns if it is
19979 asked to run a non-existent command. The wording for the log line suggests that
19980 a non-existent command may be the problem.
19982 The &%return_output%& option can affect the result of a pipe delivery. If it is
19983 set and the command produces any output on its standard output or standard
19984 error streams, the command is considered to have failed, even if it gave a zero
19985 return code or if &%ignore_status%& is set. The output from the command is
19986 included as part of the bounce message. The &%return_fail_output%& option is
19987 similar, except that output is returned only when the command exits with a
19988 failure return code, that is, a value other than zero or a code that matches
19993 .section "How the command is run" "SECThowcommandrun"
19994 .cindex "&(pipe)& transport" "path for command"
19995 The command line is (by default) broken down into a command name and arguments
19996 by the &(pipe)& transport itself. The &%allow_commands%& and
19997 &%restrict_to_path%& options can be used to restrict the commands that may be
20000 .cindex "quoting" "in pipe command"
20001 Unquoted arguments are delimited by white space. If an argument appears in
20002 double quotes, backslash is interpreted as an escape character in the usual
20003 way. If an argument appears in single quotes, no escaping is done.
20005 String expansion is applied to the command line except when it comes from a
20006 traditional &_.forward_& file (commands from a filter file are expanded). The
20007 expansion is applied to each argument in turn rather than to the whole line.
20008 For this reason, any string expansion item that contains white space must be
20009 quoted so as to be contained within a single argument. A setting such as
20011 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
20013 will not work, because the expansion item gets split between several
20014 arguments. You have to write
20016 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
20018 to ensure that it is all in one argument. The expansion is done in this way,
20019 argument by argument, so that the number of arguments cannot be changed as a
20020 result of expansion, and quotes or backslashes in inserted variables do not
20021 interact with external quoting. However, this leads to problems if you want to
20022 generate multiple arguments (or the command name plus arguments) from a single
20023 expansion. In this situation, the simplest solution is to use a shell. For
20026 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
20029 .cindex "transport" "filter"
20030 .cindex "filter" "transport filter"
20031 .cindex "&$pipe_addresses$&"
20032 Special handling takes place when an argument consists of precisely the text
20033 &`$pipe_addresses`&. This is not a general expansion variable; the only
20034 place this string is recognized is when it appears as an argument for a pipe or
20035 transport filter command. It causes each address that is being handled to be
20036 inserted in the argument list at that point &'as a separate argument'&. This
20037 avoids any problems with spaces or shell metacharacters, and is of use when a
20038 &(pipe)& transport is handling groups of addresses in a batch.
20040 After splitting up into arguments and expansion, the resulting command is run
20041 in a subprocess directly from the transport, &'not'& under a shell. The
20042 message that is being delivered is supplied on the standard input, and the
20043 standard output and standard error are both connected to a single pipe that is
20044 read by Exim. The &%max_output%& option controls how much output the command
20045 may produce, and the &%return_output%& and &%return_fail_output%& options
20046 control what is done with it.
20048 Not running the command under a shell (by default) lessens the security risks
20049 in cases when a command from a user's filter file is built out of data that was
20050 taken from an incoming message. If a shell is required, it can of course be
20051 explicitly specified as the command to be run. However, there are circumstances
20052 where existing commands (for example, in &_.forward_& files) expect to be run
20053 under a shell and cannot easily be modified. To allow for these cases, there is
20054 an option called &%use_shell%&, which changes the way the &(pipe)& transport
20055 works. Instead of breaking up the command line as just described, it expands it
20056 as a single string and passes the result to &_/bin/sh_&. The
20057 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
20058 with &%use_shell%&, and the whole mechanism is inherently less secure.
20062 .section "Environment variables" "SECTpipeenv"
20063 .cindex "&(pipe)& transport" "environment for command"
20064 .cindex "environment for pipe transport"
20065 The environment variables listed below are set up when the command is invoked.
20066 This list is a compromise for maximum compatibility with other MTAs. Note that
20067 the &%environment%& option can be used to add additional variables to this
20070 &`DOMAIN `& the domain of the address
20071 &`HOME `& the home directory, if set
20072 &`HOST `& the host name when called from a router (see below)
20073 &`LOCAL_PART `& see below
20074 &`LOCAL_PART_PREFIX `& see below
20075 &`LOCAL_PART_SUFFIX `& see below
20076 &`LOGNAME `& see below
20077 &`MESSAGE_ID `& Exim's local ID for the message
20078 &`PATH `& as specified by the &%path%& option below
20079 &`QUALIFY_DOMAIN `& the sender qualification domain
20080 &`RECIPIENT `& the complete recipient address
20081 &`SENDER `& the sender of the message (empty if a bounce)
20082 &`SHELL `& &`/bin/sh`&
20083 &`TZ `& the value of the &%timezone%& option, if set
20084 &`USER `& see below
20086 When a &(pipe)& transport is called directly from (for example) an &(accept)&
20087 router, LOCAL_PART is set to the local part of the address. When it is
20088 called as a result of a forward or alias expansion, LOCAL_PART is set to
20089 the local part of the address that was expanded. In both cases, any affixes are
20090 removed from the local part, and made available in LOCAL_PART_PREFIX and
20091 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
20092 same value as LOCAL_PART for compatibility with other MTAs.
20095 HOST is set only when a &(pipe)& transport is called from a router that
20096 associates hosts with an address, typically when using &(pipe)& as a
20097 pseudo-remote transport. HOST is set to the first host name specified by
20101 If the transport's generic &%home_directory%& option is set, its value is used
20102 for the HOME environment variable. Otherwise, a home directory may be set
20103 by the router's &%transport_home_directory%& option, which defaults to the
20104 user's home directory if &%check_local_user%& is set.
20107 .section "Private options for pipe"
20108 .cindex "options" "&(pipe)& transport"
20112 .option allow_commands pipe "string list&!!" unset
20113 .cindex "&(pipe)& transport" "permitted commands"
20114 The string is expanded, and is then interpreted as a colon-separated list of
20115 permitted commands. If &%restrict_to_path%& is not set, the only commands
20116 permitted are those in the &%allow_commands%& list. They need not be absolute
20117 paths; the &%path%& option is still used for relative paths. If
20118 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
20119 in the &%allow_commands%& list, or a name without any slashes that is found on
20120 the path. In other words, if neither &%allow_commands%& nor
20121 &%restrict_to_path%& is set, there is no restriction on the command, but
20122 otherwise only commands that are permitted by one or the other are allowed. For
20125 allow_commands = /usr/bin/vacation
20127 and &%restrict_to_path%& is not set, the only permitted command is
20128 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
20129 &%use_shell%& is set.
20132 .option batch_id pipe string&!! unset
20133 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20136 .option batch_max pipe integer 1
20137 This limits the number of addresses that can be handled in a single delivery.
20138 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20141 .option check_string pipe string unset
20142 As &(pipe)& writes the message, the start of each line is tested for matching
20143 &%check_string%&, and if it does, the initial matching characters are replaced
20144 by the contents of &%escape_string%&, provided both are set. The value of
20145 &%check_string%& is a literal string, not a regular expression, and the case of
20146 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
20147 of &%check_string%& and &%escape_string%& are forced to values that implement
20148 the SMTP escaping protocol. Any settings made in the configuration file are
20152 .option command pipe string&!! unset
20153 This option need not be set when &(pipe)& is being used to deliver to pipes
20154 obtained directly from address redirections. In other cases, the option must be
20155 set, to provide a command to be run. It need not yield an absolute path (see
20156 the &%path%& option below). The command is split up into separate arguments by
20157 Exim, and each argument is separately expanded, as described in section
20158 &<<SECThowcommandrun>>& above.
20161 .option environment pipe string&!! unset
20162 .cindex "&(pipe)& transport" "environment for command"
20163 .cindex "environment for &(pipe)& transport"
20164 This option is used to add additional variables to the environment in which the
20165 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
20166 a string which is expanded, and then interpreted as a colon-separated list of
20167 environment settings of the form <&'name'&>=<&'value'&>.
20170 .option escape_string pipe string unset
20171 See &%check_string%& above.
20174 .option freeze_exec_fail pipe boolean false
20175 .cindex "exec failure"
20176 .cindex "failure of exec"
20177 .cindex "&(pipe)& transport" "failure of exec"
20178 Failure to exec the command in a pipe transport is by default treated like
20179 any other failure while running the command. However, if &%freeze_exec_fail%&
20180 is set, failure to exec is treated specially, and causes the message to be
20181 frozen, whatever the setting of &%ignore_status%&.
20184 .option ignore_status pipe boolean false
20185 If this option is true, the status returned by the subprocess that is set up to
20186 run the command is ignored, and Exim behaves as if zero had been returned.
20187 Otherwise, a non-zero status or termination by signal causes an error return
20188 from the transport unless the status value is one of those listed in
20189 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
20191 &*Note*&: This option does not apply to timeouts, which do not return a status.
20192 See the &%timeout_defer%& option for how timeouts are handled.
20194 .option log_defer_output pipe boolean false
20195 .cindex "&(pipe)& transport" "logging output"
20196 If this option is set, and the status returned by the command is
20197 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
20198 and any output was produced, the first line of it is written to the main log.
20201 .option log_fail_output pipe boolean false
20202 If this option is set, and the command returns any output, and also ends with a
20203 return code that is neither zero nor one of the return codes listed in
20204 &%temp_errors%& (that is, the delivery failed), the first line of output is
20205 written to the main log. This option and &%log_output%& are mutually exclusive.
20206 Only one of them may be set.
20210 .option log_output pipe boolean false
20211 If this option is set and the command returns any output, the first line of
20212 output is written to the main log, whatever the return code. This option and
20213 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
20217 .option max_output pipe integer 20K
20218 This specifies the maximum amount of output that the command may produce on its
20219 standard output and standard error file combined. If the limit is exceeded, the
20220 process running the command is killed. This is intended as a safety measure to
20221 catch runaway processes. The limit is applied independently of the settings of
20222 the options that control what is done with such output (for example,
20223 &%return_output%&). Because of buffering effects, the amount of output may
20224 exceed the limit by a small amount before Exim notices.
20227 .option message_prefix pipe string&!! "see below"
20228 The string specified here is expanded and output at the start of every message.
20229 The default is unset if &%use_bsmtp%& is set. Otherwise it is
20232 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
20236 .cindex "&%tmail%&"
20237 .cindex "&""From""& line"
20238 This is required by the commonly used &_/usr/bin/vacation_& program.
20239 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
20240 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
20246 .option message_suffix pipe string&!! "see below"
20247 The string specified here is expanded and output at the end of every message.
20248 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
20249 The suffix can be suppressed by setting
20254 .option path pipe string &`/bin:/usr/bin`&
20255 This option specifies the string that is set up in the PATH environment
20256 variable of the subprocess. If the &%command%& option does not yield an
20257 absolute path name, the command is sought in the PATH directories, in the usual
20258 way. &*Warning*&: This does not apply to a command specified as a transport
20262 .option pipe_as_creator pipe boolean false
20263 .cindex "uid (user id)" "local delivery"
20264 If the generic &%user%& option is not set and this option is true, the delivery
20265 process is run under the uid that was in force when Exim was originally called
20266 to accept the message. If the group id is not otherwise set (via the generic
20267 &%group%& option), the gid that was in force when Exim was originally called to
20268 accept the message is used.
20271 .option restrict_to_path pipe boolean false
20272 When this option is set, any command name not listed in &%allow_commands%& must
20273 contain no slashes. The command is searched for only in the directories listed
20274 in the &%path%& option. This option is intended for use in the case when a pipe
20275 command has been generated from a user's &_.forward_& file. This is usually
20276 handled by a &(pipe)& transport called &%address_pipe%&.
20279 .option return_fail_output pipe boolean false
20280 If this option is true, and the command produced any output and ended with a
20281 return code other than zero or one of the codes listed in &%temp_errors%& (that
20282 is, the delivery failed), the output is returned in the bounce message.
20283 However, if the message has a null sender (that is, it is itself a bounce
20284 message), output from the command is discarded. This option and
20285 &%return_output%& are mutually exclusive. Only one of them may be set.
20289 .option return_output pipe boolean false
20290 If this option is true, and the command produced any output, the delivery is
20291 deemed to have failed whatever the return code from the command, and the output
20292 is returned in the bounce message. Otherwise, the output is just discarded.
20293 However, if the message has a null sender (that is, it is a bounce message),
20294 output from the command is always discarded, whatever the setting of this
20295 option. This option and &%return_fail_output%& are mutually exclusive. Only one
20296 of them may be set.
20300 .option temp_errors pipe "string list" "see below"
20301 .cindex "&(pipe)& transport" "temporary failure"
20302 This option contains either a colon-separated list of numbers, or a single
20303 asterisk. If &%ignore_status%& is false
20304 and &%return_output%& is not set,
20305 and the command exits with a non-zero return code, the failure is treated as
20306 temporary and the delivery is deferred if the return code matches one of the
20307 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
20308 codes are treated as permanent errors. The default setting contains the codes
20309 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
20310 compiled on a system that does not define these macros, it assumes values of 75
20311 and 73, respectively.
20314 .option timeout pipe time 1h
20315 If the command fails to complete within this time, it is killed. This normally
20316 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
20317 specifies no timeout. In order to ensure that any subprocesses created by the
20318 command are also killed, Exim makes the initial process a process group leader,
20319 and kills the whole process group on a timeout. However, this can be defeated
20320 if one of the processes starts a new process group.
20322 .option timeout_defer pipe boolean false
20323 A timeout in a &(pipe)& transport, either in the command that the transport
20324 runs, or in a transport filter that is associated with it, is by default
20325 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
20326 is set true, both kinds of timeout become temporary errors, causing the
20327 delivery to be deferred.
20329 .option umask pipe "octal integer" 022
20330 This specifies the umask setting for the subprocess that runs the command.
20333 .option use_bsmtp pipe boolean false
20334 .cindex "envelope sender"
20335 If this option is set true, the &(pipe)& transport writes messages in &"batch
20336 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
20337 commands. If you want to include a leading HELO command with such messages,
20338 you can do so by setting the &%message_prefix%& option. See section
20339 &<<SECTbatchSMTP>>& for details of batch SMTP.
20341 .option use_classresources pipe boolean false
20342 .cindex "class resources (BSD)"
20343 This option is available only when Exim is running on FreeBSD, NetBSD, or
20344 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
20345 resource limits when a &(pipe)& transport is run to perform a delivery. The
20346 limits for the uid under which the pipe is to run are obtained from the login
20350 .option use_crlf pipe boolean false
20351 .cindex "carriage return"
20353 This option causes lines to be terminated with the two-character CRLF sequence
20354 (carriage return, linefeed) instead of just a linefeed character. In the case
20355 of batched SMTP, the byte sequence written to the pipe is then an exact image
20356 of what would be sent down a real SMTP connection.
20358 The contents of the &%message_prefix%& and &%message_suffix%& options are
20359 written verbatim, so must contain their own carriage return characters if these
20360 are needed. Since the default values for both &%message_prefix%& and
20361 &%message_suffix%& end with a single linefeed, their values must be changed to
20362 end with &`\r\n`& if &%use_crlf%& is set.
20365 .option use_shell pipe boolean false
20366 .cindex "&$pipe_addresses$&"
20367 If this option is set, it causes the command to be passed to &_/bin/sh_&
20368 instead of being run directly from the transport, as described in section
20369 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
20370 where the command is expected to be run under a shell and cannot easily be
20371 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
20372 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
20373 command is expanded as a single string, and handed to &_/bin/sh_& as data for
20378 .section "Using an external local delivery agent"
20379 .cindex "local delivery" "using an external agent"
20380 .cindex "&'procmail'&"
20381 .cindex "external local delivery"
20382 .cindex "delivery" "&'procmail'&"
20383 .cindex "delivery" "by external agent"
20384 The &(pipe)& transport can be used to pass all messages that require local
20385 delivery to a separate local delivery agent such as &%procmail%&. When doing
20386 this, care must be taken to ensure that the pipe is run under an appropriate
20387 uid and gid. In some configurations one wants this to be a uid that is trusted
20388 by the delivery agent to supply the correct sender of the message. It may be
20389 necessary to recompile or reconfigure the delivery agent so that it trusts an
20390 appropriate user. The following is an example transport and router
20391 configuration for &%procmail%&:
20396 command = /usr/local/bin/procmail -d $local_part
20400 check_string = "From "
20401 escape_string = ">From "
20409 transport = procmail_pipe
20411 In this example, the pipe is run as the local user, but with the group set to
20412 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
20413 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
20414 user to supply a correct sender address. If you do not specify either a
20415 &%group%& or a &%user%& option, the pipe command is run as the local user. The
20416 home directory is the user's home directory by default.
20418 &*Note*&: The command that the pipe transport runs does &'not'& begin with
20422 as shown in some &%procmail%& documentation, because Exim does not by default
20423 use a shell to run pipe commands.
20426 The next example shows a transport and a router for a system where local
20427 deliveries are handled by the Cyrus IMAP server.
20430 local_delivery_cyrus:
20432 command = /usr/cyrus/bin/deliver \
20433 -m ${substr_1:$local_part_suffix} -- $local_part
20445 local_part_suffix = .*
20446 transport = local_delivery_cyrus
20448 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
20449 &%return_output%& to cause any text written by Cyrus to be returned to the
20451 .ecindex IIDpiptra1
20452 .ecindex IIDpiptra2
20455 . ////////////////////////////////////////////////////////////////////////////
20456 . ////////////////////////////////////////////////////////////////////////////
20458 .chapter "The smtp transport" "CHAPsmtptrans"
20459 .scindex IIDsmttra1 "transports" "&(smtp)&"
20460 .scindex IIDsmttra2 "&(smtp)& transport"
20461 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
20462 or LMTP protocol. The list of hosts to try can either be taken from the address
20463 that is being processed (having been set up by the router), or specified
20464 explicitly for the transport. Timeout and retry processing (see chapter
20465 &<<CHAPretry>>&) is applied to each IP address independently.
20468 .section "Multiple messages on a single connection"
20469 The sending of multiple messages over a single TCP/IP connection can arise in
20473 If a message contains more than &%max_rcpt%& (see below) addresses that are
20474 routed to the same host, more than one copy of the message has to be sent to
20475 that host. In this situation, multiple copies may be sent in a single run of
20476 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
20477 does when it has too many addresses to send in one message also depends on the
20478 value of the global &%remote_max_parallel%& option. Details are given in
20479 section &<<SECToutSMTPTCP>>&.)
20481 .cindex "hints database" "remembering routing"
20482 When a message has been successfully delivered over a TCP/IP connection, Exim
20483 looks in its hints database to see if there are any other messages awaiting a
20484 connection to the same host. If there are, a new delivery process is started
20485 for one of them, and the current TCP/IP connection is passed on to it. The new
20486 process may in turn send multiple copies and possibly create yet another
20491 For each copy sent over the same TCP/IP connection, a sequence counter is
20492 incremented, and if it ever gets to the value of &%connection_max_messages%&,
20493 no further messages are sent over that connection.
20497 .section "Use of the $host variable"
20499 .cindex "&$host_address$&"
20500 At the start of a run of the &(smtp)& transport, the values of &$host$& and
20501 &$host_address$& are the name and IP address of the first host on the host list
20502 passed by the router. However, when the transport is about to connect to a
20503 specific host, and while it is connected to that host, &$host$& and
20504 &$host_address$& are set to the values for that host. These are the values
20505 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
20506 &%serialize_hosts%&, and the various TLS options are expanded.
20510 .section "Private options for smtp"
20511 .cindex "options" "&(smtp)& transport"
20512 The private options of the &(smtp)& transport are as follows:
20515 .option allow_localhost smtp boolean false
20516 .cindex "local host" "sending to"
20517 .cindex "fallback" "hosts specified on transport"
20518 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
20519 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
20520 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
20521 the delivery anyway. This should be used only in special cases when the
20522 configuration ensures that no looping will result (for example, a differently
20523 configured Exim is listening on the port to which the message is sent).
20526 .option authenticated_sender smtp string&!! unset
20528 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
20529 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
20530 overriding any existing authenticated sender value. If the string expansion is
20531 forced to fail, the option is ignored. Other expansion failures cause delivery
20532 to be deferred. If the result of expansion is an empty string, that is also
20535 If the SMTP session is not authenticated, the expansion of
20536 &%authenticated_sender%& still happens (and can cause the delivery to be
20537 deferred if it fails), but no AUTH= item is added to MAIL commands
20538 unless &%authenticated_sender_force%& is true.
20540 This option allows you to use the &(smtp)& transport in LMTP mode to
20541 deliver mail to Cyrus IMAP and provide the proper local part as the
20542 &"authenticated sender"&, via a setting such as:
20544 authenticated_sender = $local_part
20546 This removes the need for IMAP subfolders to be assigned special ACLs to
20547 allow direct delivery to those subfolders.
20549 Because of expected uses such as that just described for Cyrus (when no
20550 domain is involved), there is no checking on the syntax of the provided
20554 .option authenticated_sender_force smtp boolean false
20555 If this option is set true, the &%authenticated_sender%& option's value
20556 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
20557 authenticated as a client.
20560 .option command_timeout smtp time 5m
20561 This sets a timeout for receiving a response to an SMTP command that has been
20562 sent out. It is also used when waiting for the initial banner line from the
20563 remote host. Its value must not be zero.
20566 .option connect_timeout smtp time 5m
20567 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
20568 to a remote host. A setting of zero allows the system timeout (typically
20569 several minutes) to act. To have any effect, the value of this option must be
20570 less than the system timeout. However, it has been observed that on some
20571 systems there is no system timeout, which is why the default value for this
20572 option is 5 minutes, a value recommended by RFC 1123.
20575 .option connection_max_messages smtp integer 500
20576 .cindex "SMTP" "passed connection"
20577 .cindex "SMTP" "multiple deliveries"
20578 .cindex "multiple SMTP deliveries"
20579 This controls the maximum number of separate message deliveries that are sent
20580 over a single TCP/IP connection. If the value is zero, there is no limit.
20581 For testing purposes, this value can be overridden by the &%-oB%& command line
20585 .option data_timeout smtp time 5m
20586 This sets a timeout for the transmission of each block in the data portion of
20587 the message. As a result, the overall timeout for a message depends on the size
20588 of the message. Its value must not be zero. See also &%final_timeout%&.
20591 .option delay_after_cutoff smtp boolean true
20592 This option controls what happens when all remote IP addresses for a given
20593 domain have been inaccessible for so long that they have passed their retry
20596 In the default state, if the next retry time has not been reached for any of
20597 them, the address is bounced without trying any deliveries. In other words,
20598 Exim delays retrying an IP address after the final cutoff time until a new
20599 retry time is reached, and can therefore bounce an address without ever trying
20600 a delivery, when machines have been down for a long time. Some people are
20601 unhappy at this prospect, so...
20603 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
20604 addresses are past their final cutoff time, Exim tries to deliver to those
20605 IP addresses that have not been tried since the message arrived. If there are
20606 none, of if they all fail, the address is bounced. In other words, it does not
20607 delay when a new message arrives, but immediately tries those expired IP
20608 addresses that haven't been tried since the message arrived. If there is a
20609 continuous stream of messages for the dead hosts, unsetting
20610 &%delay_after_cutoff%& means that there will be many more attempts to deliver
20614 .option dns_qualify_single smtp boolean true
20615 If the &%hosts%& or &%fallback_hosts%& option is being used,
20616 and the &%gethostbyname%& option is false,
20617 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
20618 in chapter &<<CHAPdnslookup>>& for more details.
20621 .option dns_search_parents smtp boolean false
20622 .cindex "&%search_parents%&"
20623 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
20624 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
20625 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
20630 .option fallback_hosts smtp "string list" unset
20631 .cindex "fallback" "hosts specified on transport"
20632 String expansion is not applied to this option. The argument must be a
20633 colon-separated list of host names or IP addresses, optionally also including
20634 port numbers, though the separator can be changed, as described in section
20635 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
20636 item in a &%route_list%& setting for the &(manualroute)& router, as described
20637 in section &<<SECTformatonehostitem>>&.
20639 Fallback hosts can also be specified on routers, which associate them with the
20640 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
20641 &%fallback_hosts%& specified on the transport is used only if the address does
20642 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
20643 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
20644 However, &%hosts_randomize%& does apply to fallback host lists.
20646 If Exim is unable to deliver to any of the hosts for a particular address, and
20647 the errors are not permanent rejections, the address is put on a separate
20648 transport queue with its host list replaced by the fallback hosts, unless the
20649 address was routed via MX records and the current host was in the original MX
20650 list. In that situation, the fallback host list is not used.
20652 Once normal deliveries are complete, the fallback queue is delivered by
20653 re-running the same transports with the new host lists. If several failing
20654 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
20655 copy of the message is sent.
20657 The resolution of the host names on the fallback list is controlled by the
20658 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
20659 both to cases when the host list comes with the address and when it is taken
20660 from &%hosts%&. This option provides a &"use a smart host only if delivery
20664 .option final_timeout smtp time 10m
20665 This is the timeout that applies while waiting for the response to the final
20666 line containing just &"."& that terminates a message. Its value must not be
20670 .option gethostbyname smtp boolean false
20671 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
20672 being used, names are looked up using &[gethostbyname()]&
20673 (or &[getipnodebyname()]& when available)
20674 instead of using the DNS. Of course, that function may in fact use the DNS, but
20675 it may also consult other sources of information such as &_/etc/hosts_&.
20677 .option helo_data smtp string&!! &`$primary_hostname`&
20678 .cindex "HELO argument" "setting"
20679 .cindex "EHLO argument" "setting"
20680 .cindex "LHLO argument" "setting"
20682 The value of this option is expanded, and used as the argument for the EHLO,
20683 HELO, or LHLO command that starts the outgoing SMTP or LMTP session. The
20684 variables &$host$& and &$host_address$& are set to the identity of the remote
20685 host, and can be used to generate different values for different servers.
20688 .option hosts smtp "string list&!!" unset
20689 Hosts are associated with an address by a router such as &(dnslookup)&, which
20690 finds the hosts by looking up the address domain in the DNS, or by
20691 &(manualroute)&, which has lists of hosts in its configuration. However,
20692 email addresses can be passed to the &(smtp)& transport by any router, and not
20693 all of them can provide an associated list of hosts.
20695 The &%hosts%& option specifies a list of hosts to be used if the address being
20696 processed does not have any hosts associated with it. The hosts specified by
20697 &%hosts%& are also used, whether or not the address has its own hosts, if
20698 &%hosts_override%& is set.
20700 The string is first expanded, before being interpreted as a colon-separated
20701 list of host names or IP addresses, possibly including port numbers. The
20702 separator may be changed to something other than colon, as described in section
20703 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
20704 item in a &%route_list%& setting for the &(manualroute)& router, as described
20705 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
20706 of the &(manualroute)& router is not available here.
20708 If the expansion fails, delivery is deferred. Unless the failure was caused by
20709 the inability to complete a lookup, the error is logged to the panic log as
20710 well as the main log. Host names are looked up either by searching directly for
20711 address records in the DNS or by calling &[gethostbyname()]& (or
20712 &[getipnodebyname()]& when available), depending on the setting of the
20713 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
20714 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
20717 During delivery, the hosts are tried in order, subject to their retry status,
20718 unless &%hosts_randomize%& is set.
20721 .option hosts_avoid_esmtp smtp "host list&!!" unset
20722 .cindex "ESMTP" "avoiding use of"
20723 .cindex "HELO" "forcing use of"
20724 .cindex "EHLO" "avoiding use of"
20725 .cindex "PIPELINING" "avoiding the use of"
20726 This option is for use with broken hosts that announce ESMTP facilities (for
20727 example, PIPELINING) and then fail to implement them properly. When a host
20728 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
20729 start of the SMTP session. This means that it cannot use any of the ESMTP
20730 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
20733 .option hosts_avoid_tls smtp "host list&!!" unset
20734 .cindex "TLS" "avoiding for certain hosts"
20735 Exim will not try to start a TLS session when delivering to any host that
20736 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
20739 .option hosts_max_try smtp integer 5
20740 .cindex "host" "maximum number to try"
20741 .cindex "limit" "number of hosts tried"
20742 .cindex "limit" "number of MX tried"
20743 .cindex "MX record" "maximum tried"
20744 This option limits the number of IP addresses that are tried for any one
20745 delivery in cases where there are temporary delivery errors. Section
20746 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
20749 .option hosts_max_try_hardlimit smtp integer 50
20750 This is an additional check on the maximum number of IP addresses that Exim
20751 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
20756 .option hosts_nopass_tls smtp "host list&!!" unset
20757 .cindex "TLS" "passing connection"
20758 .cindex "multiple SMTP deliveries"
20759 .cindex "TLS" "multiple message deliveries"
20760 For any host that matches this list, a connection on which a TLS session has
20761 been started will not be passed to a new delivery process for sending another
20762 message on the same connection. See section &<<SECTmulmessam>>& for an
20763 explanation of when this might be needed.
20766 .option hosts_override smtp boolean false
20767 If this option is set and the &%hosts%& option is also set, any hosts that are
20768 attached to the address are ignored, and instead the hosts specified by the
20769 &%hosts%& option are always used. This option does not apply to
20770 &%fallback_hosts%&.
20773 .option hosts_randomize smtp boolean false
20774 .cindex "randomized host list"
20775 .cindex "host" "list of; randomized"
20776 .cindex "fallback" "randomized hosts"
20777 If this option is set, and either the list of hosts is taken from the
20778 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
20779 were not obtained from MX records (this includes fallback hosts from the
20780 router), and were not randomizied by the router, the order of trying the hosts
20781 is randomized each time the transport runs. Randomizing the order of a host
20782 list can be used to do crude load sharing.
20784 When &%hosts_randomize%& is true, a host list may be split into groups whose
20785 order is separately randomized. This makes it possible to set up MX-like
20786 behaviour. The boundaries between groups are indicated by an item that is just
20787 &`+`& in the host list. For example:
20789 hosts = host1:host2:host3:+:host4:host5
20791 The order of the first three hosts and the order of the last two hosts is
20792 randomized for each use, but the first three always end up before the last two.
20793 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
20795 .option hosts_require_auth smtp "host list&!!" unset
20796 .cindex "authentication" "required by client"
20797 This option provides a list of servers for which authentication must succeed
20798 before Exim will try to transfer a message. If authentication fails for
20799 servers which are not in this list, Exim tries to send unauthenticated. If
20800 authentication fails for one of these servers, delivery is deferred. This
20801 temporary error is detectable in the retry rules, so it can be turned into a
20802 hard failure if required. See also &%hosts_try_auth%&, and chapter
20803 &<<CHAPSMTPAUTH>>& for details of authentication.
20806 .option hosts_require_tls smtp "host list&!!" unset
20807 .cindex "TLS" "requiring for certain servers"
20808 Exim will insist on using a TLS session when delivering to any host that
20809 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
20810 &*Note*&: This option affects outgoing mail only. To insist on TLS for
20811 incoming messages, use an appropriate ACL.
20813 .option hosts_try_auth smtp "host list&!!" unset
20814 .cindex "authentication" "optional in client"
20815 This option provides a list of servers to which, provided they announce
20816 authentication support, Exim will attempt to authenticate as a client when it
20817 connects. If authentication fails, Exim will try to transfer the message
20818 unauthenticated. See also &%hosts_require_auth%&, and chapter
20819 &<<CHAPSMTPAUTH>>& for details of authentication.
20821 .option interface smtp "string list&!!" unset
20822 .cindex "bind IP address"
20823 .cindex "IP address" "binding"
20825 .cindex "&$host_address$&"
20826 This option specifies which interface to bind to when making an outgoing SMTP
20827 call. The variables &$host$& and &$host_address$& refer to the host to which a
20828 connection is about to be made during the expansion of the string. Forced
20829 expansion failure, or an empty string result causes the option to be ignored.
20830 Otherwise, after expansion,
20831 the string must be a list of IP addresses, colon-separated by default, but the
20832 separator can be changed in the usual way.
20835 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
20837 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
20838 connection. If none of them are the correct type, the option is ignored. If
20839 &%interface%& is not set, or is ignored, the system's IP functions choose which
20840 interface to use if the host has more than one.
20843 .option keepalive smtp boolean true
20844 .cindex "keepalive" "on outgoing connection"
20845 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
20846 connections. When set, it causes the kernel to probe idle connections
20847 periodically, by sending packets with &"old"& sequence numbers. The other end
20848 of the connection should send a acknowledgement if the connection is still okay
20849 or a reset if the connection has been aborted. The reason for doing this is
20850 that it has the beneficial effect of freeing up certain types of connection
20851 that can get stuck when the remote host is disconnected without tidying up the
20852 TCP/IP call properly. The keepalive mechanism takes several hours to detect
20856 .option lmtp_ignore_quota smtp boolean false
20857 .cindex "LMTP" "ignoring quota errors"
20858 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
20859 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
20860 has advertised support for IGNOREQUOTA in its response to the LHLO command.
20862 .option max_rcpt smtp integer 100
20863 .cindex "RCPT" "maximum number of outgoing"
20864 This option limits the number of RCPT commands that are sent in a single
20865 SMTP message transaction. Each set of addresses is treated independently, and
20866 so can cause parallel connections to the same host if &%remote_max_parallel%&
20870 .option multi_domain smtp boolean true
20871 .cindex "&$domain$&"
20872 When this option is set, the &(smtp)& transport can handle a number of
20873 addresses containing a mixture of different domains provided they all resolve
20874 to the same list of hosts. Turning the option off restricts the transport to
20875 handling only one domain at a time. This is useful if you want to use
20876 &$domain$& in an expansion for the transport, because it is set only when there
20877 is a single domain involved in a remote delivery.
20880 .option port smtp string&!! "see below"
20881 .cindex "port" "sending TCP/IP"
20882 .cindex "TCP/IP" "setting outgoing port"
20883 This option specifies the TCP/IP port on the server to which Exim connects. If
20884 it begins with a digit it is taken as a port number; otherwise it is looked up
20885 using &[getservbyname()]&. The default value is normally &"smtp"&, but if
20886 &%protocol%& is set to &"lmtp"&, the default is &"lmtp"&.
20887 If the expansion fails, or if a port number cannot be found, delivery is
20892 .option protocol smtp string smtp
20893 .cindex "LMTP" "over TCP/IP"
20894 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
20895 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
20896 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
20897 deliveries into closed message stores. Exim also has support for running LMTP
20898 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
20901 .option retry_include_ip_address smtp boolean true
20902 Exim normally includes both the host name and the IP address in the key it
20903 constructs for indexing retry data after a temporary delivery failure. This
20904 means that when one of several IP addresses for a host is failing, it gets
20905 tried periodically (controlled by the retry rules), but use of the other IP
20906 addresses is not affected.
20908 However, in some dialup environments hosts are assigned a different IP address
20909 each time they connect. In this situation the use of the IP address as part of
20910 the retry key leads to undesirable behaviour. Setting this option false causes
20911 Exim to use only the host name. This should normally be done on a separate
20912 instance of the &(smtp)& transport, set up specially to handle the dialup
20916 .option serialize_hosts smtp "host list&!!" unset
20917 .cindex "serializing connections"
20918 .cindex "host" "serializing connections"
20919 Because Exim operates in a distributed manner, if several messages for the same
20920 host arrive at around the same time, more than one simultaneous connection to
20921 the remote host can occur. This is not usually a problem except when there is a
20922 slow link between the hosts. In that situation it may be helpful to restrict
20923 Exim to one connection at a time. This can be done by setting
20924 &%serialize_hosts%& to match the relevant hosts.
20926 .cindex "hints database" "serializing deliveries to a host"
20927 Exim implements serialization by means of a hints database in which a record is
20928 written whenever a process connects to one of the restricted hosts. The record
20929 is deleted when the connection is completed. Obviously there is scope for
20930 records to get left lying around if there is a system or program crash. To
20931 guard against this, Exim ignores any records that are more than six hours old.
20933 If you set up this kind of serialization, you should also arrange to delete the
20934 relevant hints database whenever your system reboots. The names of the files
20935 start with &_misc_& and they are kept in the &_spool/db_& directory. There
20936 may be one or two files, depending on the type of DBM in use. The same files
20937 are used for ETRN serialization.
20940 .option size_addition smtp integer 1024
20941 .cindex "SMTP" "SIZE"
20942 .cindex "message" "size issue for transport filter"
20943 .cindex "size" "of message"
20944 .cindex "transport" "filter"
20945 .cindex "filter" "transport filter"
20946 If a remote SMTP server indicates that it supports the SIZE option of the
20947 MAIL command, Exim uses this to pass over the message size at the start of
20948 an SMTP transaction. It adds the value of &%size_addition%& to the value it
20949 sends, to allow for headers and other text that may be added during delivery by
20950 configuration options or in a transport filter. It may be necessary to increase
20951 this if a lot of text is added to messages.
20953 Alternatively, if the value of &%size_addition%& is set negative, it disables
20954 the use of the SIZE option altogether.
20957 .option tls_certificate smtp string&!! unset
20958 .cindex "TLS client certificate" "location of"
20959 .cindex "certificate for client" "location of"
20961 .cindex "&$host_address$&"
20962 The value of this option must be the absolute path to a file which contains the
20963 client's certificate, for possible use when sending a message over an encrypted
20964 connection. The values of &$host$& and &$host_address$& are set to the name and
20965 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
20968 &*Note*&: This option must be set if you want Exim to be able to use a TLS
20969 certificate when sending messages as a client. The global option of the same
20970 name specifies the certificate for Exim as a server; it is not automatically
20971 assumed that the same certificate should be used when Exim is operating as a
20975 .option tls_crl smtp string&!! unset
20976 .cindex "TLS" "client certificate revocation list"
20977 .cindex "certificate" "revocation list for client"
20978 This option specifies a certificate revocation list. The expanded value must
20979 be the name of a file that contains a CRL in PEM format.
20982 .option tls_privatekey smtp string&!! unset
20983 .cindex "TLS client private key" "location of"
20985 .cindex "&$host_address$&"
20986 The value of this option must be the absolute path to a file which contains the
20987 client's private key. This is used when sending a message over an encrypted
20988 connection using a client certificate. The values of &$host$& and
20989 &$host_address$& are set to the name and address of the server during the
20990 expansion. If this option is unset, or the expansion is forced to fail, or the
20991 result is an empty string, the private key is assumed to be in the same file as
20992 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
20995 .option tls_require_ciphers smtp string&!! unset
20996 .cindex "TLS" "requiring specific ciphers"
20997 .cindex "cipher" "requiring specific"
20999 .cindex "&$host_address$&"
21000 The value of this option must be a list of permitted cipher suites, for use
21001 when setting up an outgoing encrypted connection. (There is a global option of
21002 the same name for controlling incoming connections.) The values of &$host$& and
21003 &$host_address$& are set to the name and address of the server during the
21004 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
21005 is used in different ways by OpenSSL and GnuTLS (see sections
21006 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
21007 ciphers is a preference order.
21011 .option tls_tempfail_tryclear smtp boolean true
21012 When the server host is not in &%hosts_require_tls%&, and there is a problem in
21013 setting up a TLS session, this option determines whether or not Exim should try
21014 to deliver the message unencrypted. If it is set false, delivery to the
21015 current host is deferred; if there are other hosts, they are tried. If this
21016 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
21017 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
21018 TLS negotiation fails, Exim closes the current connection (because it is in an
21019 unknown state), opens a new one to the same host, and then tries the delivery
21023 .option tls_verify_certificates smtp string&!! unset
21024 .cindex "TLS" "server certificate verification"
21025 .cindex "certificate" "verification of server"
21027 .cindex "&$host_address$&"
21028 The value of this option must be the absolute path to a file containing
21029 permitted server certificates, for use when setting up an encrypted connection.
21030 Alternatively, if you are using OpenSSL, you can set
21031 &%tls_verify_certificates%& to the name of a directory containing certificate
21032 files. This does not work with GnuTLS; the option must be set to the name of a
21033 single file if you are using GnuTLS. The values of &$host$& and
21034 &$host_address$& are set to the name and address of the server during the
21035 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
21040 .section "How the limits for the number of hosts to try are used" &&&
21042 .cindex "host" "maximum number to try"
21043 .cindex "limit" "hosts; maximum number tried"
21044 There are two options that are concerned with the number of hosts that are
21045 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
21046 &%hosts_max_try_hardlimit%&.
21049 The &%hosts_max_try%& option limits the number of hosts that are tried
21050 for a single delivery. However, despite the term &"host"& in its name, the
21051 option actually applies to each IP address independently. In other words, a
21052 multihomed host is treated as several independent hosts, just as it is for
21055 Many of the larger ISPs have multiple MX records which often point to
21056 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
21057 created as a result of routing one of these domains.
21059 Trying every single IP address on such a long list does not seem sensible; if
21060 several at the top of the list fail, it is reasonable to assume there is some
21061 problem that is likely to affect all of them. Roughly speaking, the value of
21062 &%hosts_max_try%& is the maximum number that are tried before deferring the
21063 delivery. However, the logic cannot be quite that simple.
21065 Firstly, IP addresses that are skipped because their retry times have not
21066 arrived do not count, and in addition, addresses that are past their retry
21067 limits are also not counted, even when they are tried. This means that when
21068 some IP addresses are past their retry limits, more than the value of
21069 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
21070 that all IP addresses are considered before timing out an email address (but
21071 see below for an exception).
21073 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
21074 list to see if there is a subsequent host with a different (higher valued) MX.
21075 If there is, that host is considered next, and the current IP address is used
21076 but not counted. This behaviour helps in the case of a domain with a retry rule
21077 that hardly ever delays any hosts, as is now explained:
21079 Consider the case of a long list of hosts with one MX value, and a few with a
21080 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
21081 hosts at the top of the list are tried at first. With the default retry rule,
21082 which specifies increasing retry times, the higher MX hosts are eventually
21083 tried when those at the top of the list are skipped because they have not
21084 reached their retry times.
21086 However, it is common practice to put a fixed short retry time on domains for
21087 large ISPs, on the grounds that their servers are rarely down for very long.
21088 Unfortunately, these are exactly the domains that tend to resolve to long lists
21089 of hosts. The short retry time means that the lowest MX hosts are tried every
21090 time. The attempts may be in a different order because of random sorting, but
21091 without the special MX check, the higher MX hosts would never be tried until
21092 all the lower MX hosts had timed out (which might be several days), because
21093 there are always some lower MX hosts that have reached their retry times. With
21094 the special check, Exim considers at least one IP address from each MX value at
21095 every delivery attempt, even if the &%hosts_max_try%& limit has already been
21098 The above logic means that &%hosts_max_try%& is not a hard limit, and in
21099 particular, Exim normally eventually tries all the IP addresses before timing
21100 out an email address. When &%hosts_max_try%& was implemented, this seemed a
21101 reasonable thing to do. Recently, however, some lunatic DNS configurations have
21102 been set up with hundreds of IP addresses for some domains. It can
21103 take a very long time indeed for an address to time out in these cases.
21105 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
21106 Exim never tries more than this number of IP addresses; if it hits this limit
21107 and they are all timed out, the email address is bounced, even though not all
21108 possible IP addresses have been tried.
21109 .ecindex IIDsmttra1
21110 .ecindex IIDsmttra2
21116 . ////////////////////////////////////////////////////////////////////////////
21117 . ////////////////////////////////////////////////////////////////////////////
21119 .chapter "Address rewriting" "CHAPrewrite"
21120 .scindex IIDaddrew "rewriting" "addresses"
21121 There are some circumstances in which Exim automatically rewrites domains in
21122 addresses. The two most common are when an address is given without a domain
21123 (referred to as an &"unqualified address"&) or when an address contains an
21124 abbreviated domain that is expanded by DNS lookup.
21126 Unqualified envelope addresses are accepted only for locally submitted
21127 messages, or for messages that are received from hosts matching
21128 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
21129 appropriate. Unqualified addresses in header lines are qualified if they are in
21130 locally submitted messages, or messages from hosts that are permitted to send
21131 unqualified envelope addresses. Otherwise, unqualified addresses in header
21132 lines are neither qualified nor rewritten.
21134 One situation in which Exim does &'not'& automatically rewrite a domain is
21135 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
21136 such a domain should be rewritten using the &"canonical"& name, and some MTAs
21137 do this. The new RFCs do not contain this suggestion.
21140 .section "Explicitly configured address rewriting"
21141 This chapter describes the rewriting rules that can be used in the
21142 main rewrite section of the configuration file, and also in the generic
21143 &%headers_rewrite%& option that can be set on any transport.
21145 Some people believe that configured address rewriting is a Mortal Sin.
21146 Others believe that life is not possible without it. Exim provides the
21147 facility; you do not have to use it.
21149 The main rewriting rules that appear in the &"rewrite"& section of the
21150 configuration file are applied to addresses in incoming messages, both envelope
21151 addresses and addresses in header lines. Each rule specifies the types of
21152 address to which it applies.
21154 Rewriting of addresses in header lines applies only to those headers that
21155 were received with the message, and, in the case of transport rewriting, those
21156 that were added by a system filter. That is, it applies only to those headers
21157 that are common to all copies of the message. Header lines that are added by
21158 individual routers or transports (and which are therefore specific to
21159 individual recipient addresses) are not rewritten.
21161 In general, rewriting addresses from your own system or domain has some
21162 legitimacy. Rewriting other addresses should be done only with great care and
21163 in special circumstances. The author of Exim believes that rewriting should be
21164 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
21165 Although it can sometimes be used as a routing tool, this is very strongly
21168 There are two commonly encountered circumstances where rewriting is used, as
21169 illustrated by these examples:
21172 The company whose domain is &'hitch.fict.example'& has a number of hosts that
21173 exchange mail with each other behind a firewall, but there is only a single
21174 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
21175 &'hitch.fict.example'& when sending mail off-site.
21177 A host rewrites the local parts of its own users so that, for example,
21178 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
21183 .section "When does rewriting happen?"
21184 .cindex "rewriting" "timing of"
21185 .cindex "&ACL;" "rewriting addresses in"
21186 Configured address rewriting can take place at several different stages of a
21187 message's processing.
21189 .cindex "&$sender_address$&"
21190 At the start of an ACL for MAIL, the sender address may have been rewritten
21191 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
21192 ordinary rewrite rules have yet been applied. If, however, the sender address
21193 is verified in the ACL, it is rewritten before verification, and remains
21194 rewritten thereafter. The subsequent value of &$sender_address$& is the
21195 rewritten address. This also applies if sender verification happens in a
21196 RCPT ACL. Otherwise, when the sender address is not verified, it is
21197 rewritten as soon as a message's header lines have been received.
21199 .cindex "&$domain$&"
21200 .cindex "&$local_part$&"
21201 Similarly, at the start of an ACL for RCPT, the current recipient's address
21202 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
21203 rewrite rules have yet been applied to it. However, the behaviour is different
21204 from the sender address when a recipient is verified. The address is rewritten
21205 for the verification, but the rewriting is not remembered at this stage. The
21206 value of &$local_part$& and &$domain$& after verification are always the same
21207 as they were before (that is, they contain the unrewritten &-- except for
21208 SMTP-time rewriting &-- address).
21210 As soon as a message's header lines have been received, all the envelope
21211 recipient addresses are permanently rewritten, and rewriting is also applied to
21212 the addresses in the header lines (if configured). This happens before adding
21213 any header lines that were specified in MAIL or RCPT ACLs, and
21214 .cindex "&[local_scan()]& function" "address rewriting; timing of"
21215 before the DATA ACL and &[local_scan()]& functions are run.
21217 When an address is being routed, either for delivery or for verification,
21218 rewriting is applied immediately to child addresses that are generated by
21219 redirection, unless &%no_rewrite%& is set on the router.
21221 .cindex "envelope sender" "rewriting at transport time"
21222 .cindex "rewriting" "at transport time"
21223 .cindex "header lines" "rewriting at transport time"
21224 At transport time, additional rewriting of addresses in header lines can be
21225 specified by setting the generic &%headers_rewrite%& option on a transport.
21226 This option contains rules that are identical in form to those in the rewrite
21227 section of the configuration file. They are applied to the original message
21228 header lines and any that were added by ACLs or a system filter. They are not
21229 applied to header lines that are added by routers or the transport.
21231 The outgoing envelope sender can be rewritten by means of the &%return_path%&
21232 transport option. However, it is not possible to rewrite envelope recipients at
21238 .section "Testing the rewriting rules that apply on input"
21239 .cindex "rewriting" "testing"
21240 .cindex "testing" "rewriting"
21241 Exim's input rewriting configuration appears in a part of the run time
21242 configuration file headed by &"begin rewrite"&. It can be tested by the
21243 &%-brw%& command line option. This takes an address (which can be a full RFC
21244 2822 address) as its argument. The output is a list of how the address would be
21245 transformed by the rewriting rules for each of the different places it might
21246 appear in an incoming message, that is, for each different header and for the
21247 envelope sender and recipient fields. For example,
21249 exim -brw ph10@exim.workshop.example
21251 might produce the output
21253 sender: Philip.Hazel@exim.workshop.example
21254 from: Philip.Hazel@exim.workshop.example
21255 to: ph10@exim.workshop.example
21256 cc: ph10@exim.workshop.example
21257 bcc: ph10@exim.workshop.example
21258 reply-to: Philip.Hazel@exim.workshop.example
21259 env-from: Philip.Hazel@exim.workshop.example
21260 env-to: ph10@exim.workshop.example
21262 which shows that rewriting has been set up for that address when used in any of
21263 the source fields, but not when it appears as a recipient address. At the
21264 present time, there is no equivalent way of testing rewriting rules that are
21265 set for a particular transport.
21268 .section "Rewriting rules"
21269 .cindex "rewriting" "rules"
21270 The rewrite section of the configuration file consists of lines of rewriting
21273 <&'source pattern'&> <&'replacement'&> <&'flags'&>
21275 Rewriting rules that are specified for the &%headers_rewrite%& generic
21276 transport option are given as a colon-separated list. Each item in the list
21277 takes the same form as a line in the main rewriting configuration (except that
21278 any colons must be doubled, of course).
21280 The formats of source patterns and replacement strings are described below.
21281 Each is terminated by white space, unless enclosed in double quotes, in which
21282 case normal quoting conventions apply inside the quotes. The flags are single
21283 characters which may appear in any order. Spaces and tabs between them are
21286 For each address that could potentially be rewritten, the rules are scanned in
21287 order, and replacements for the address from earlier rules can themselves be
21288 replaced by later rules (but see the &"q"& and &"R"& flags).
21290 The order in which addresses are rewritten is undefined, may change between
21291 releases, and must not be relied on, with one exception: when a message is
21292 received, the envelope sender is always rewritten first, before any header
21293 lines are rewritten. For example, the replacement string for a rewrite of an
21294 address in &'To:'& must not assume that the message's address in &'From:'& has
21295 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
21296 that the envelope sender has already been rewritten.
21298 .cindex "&$domain$&"
21299 .cindex "&$local_part$&"
21300 The variables &$local_part$& and &$domain$& can be used in the replacement
21301 string to refer to the address that is being rewritten. Note that lookup-driven
21302 rewriting can be done by a rule of the form
21306 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
21307 refer to the address that is being rewritten.
21310 .section "Rewriting patterns"
21311 .cindex "rewriting" "patterns"
21312 .cindex "address list" "in a rewriting pattern"
21313 The source pattern in a rewriting rule is any item which may appear in an
21314 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
21315 single-item address list, which means that it is expanded before being tested
21316 against the address. As always, if you use a regular expression as a pattern,
21317 you must take care to escape dollar and backslash characters, or use the &`\N`&
21318 facility to suppress string expansion within the regular expression.
21320 Domains in patterns should be given in lower case. Local parts in patterns are
21321 case-sensitive. If you want to do case-insensitive matching of local parts, you
21322 can use a regular expression that starts with &`^(?i)`&.
21324 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
21325 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
21326 depending on the type of match which occurred. These can be used in the
21327 replacement string to insert portions of the incoming address. &$0$& always
21328 refers to the complete incoming address. When a regular expression is used, the
21329 numerical variables are set from its capturing subexpressions. For other types
21330 of pattern they are set as follows:
21333 If a local part or domain starts with an asterisk, the numerical variables
21334 refer to the character strings matched by asterisks, with &$1$& associated with
21335 the first asterisk, and &$2$& with the second, if present. For example, if the
21338 *queen@*.fict.example
21340 is matched against the address &'hearts-queen@wonderland.fict.example'& then
21342 $0 = hearts-queen@wonderland.fict.example
21346 Note that if the local part does not start with an asterisk, but the domain
21347 does, it is &$1$& that contains the wild part of the domain.
21350 If the domain part of the pattern is a partial lookup, the wild and fixed parts
21351 of the domain are placed in the next available numerical variables. Suppose,
21352 for example, that the address &'foo@bar.baz.example'& is processed by a
21353 rewriting rule of the form
21355 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
21357 and the key in the file that matches the domain is &`*.baz.example`&. Then
21363 If the address &'foo@baz.example'& is looked up, this matches the same
21364 wildcard file entry, and in this case &$2$& is set to the empty string, but
21365 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
21366 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
21367 whole domain. For non-partial domain lookups, no numerical variables are set.
21371 .section "Rewriting replacements"
21372 .cindex "rewriting" "replacements"
21373 If the replacement string for a rule is a single asterisk, addresses that
21374 match the pattern and the flags are &'not'& rewritten, and no subsequent
21375 rewriting rules are scanned. For example,
21377 hatta@lookingglass.fict.example * f
21379 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
21382 .cindex "&$domain$&"
21383 .cindex "&$local_part$&"
21384 If the replacement string is not a single asterisk, it is expanded, and must
21385 yield a fully qualified address. Within the expansion, the variables
21386 &$local_part$& and &$domain$& refer to the address that is being rewritten.
21387 Any letters they contain retain their original case &-- they are not lower
21388 cased. The numerical variables are set up according to the type of pattern that
21389 matched the address, as described above. If the expansion is forced to fail by
21390 the presence of &"fail"& in a conditional or lookup item, rewriting by the
21391 current rule is abandoned, but subsequent rules may take effect. Any other
21392 expansion failure causes the entire rewriting operation to be abandoned, and an
21393 entry written to the panic log.
21397 .section "Rewriting flags"
21398 There are three different kinds of flag that may appear on rewriting rules:
21401 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
21404 A flag that specifies rewriting at SMTP time: S.
21406 Flags that control the rewriting process: Q, q, R, w.
21409 For rules that are part of the &%headers_rewrite%& generic transport option,
21410 E, F, T, and S are not permitted.
21414 .section "Flags specifying which headers and envelope addresses to rewrite"
21415 .cindex "rewriting" "flags"
21416 If none of the following flag letters, nor the &"S"& flag (see section
21417 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
21418 and to both the sender and recipient fields of the envelope, whereas a
21419 transport-time rewriting rule just applies to all headers. Otherwise, the
21420 rewriting rule is skipped unless the relevant addresses are being processed.
21422 &`E`& rewrite all envelope fields
21423 &`F`& rewrite the envelope From field
21424 &`T`& rewrite the envelope To field
21425 &`b`& rewrite the &'Bcc:'& header
21426 &`c`& rewrite the &'Cc:'& header
21427 &`f`& rewrite the &'From:'& header
21428 &`h`& rewrite all headers
21429 &`r`& rewrite the &'Reply-To:'& header
21430 &`s`& rewrite the &'Sender:'& header
21431 &`t`& rewrite the &'To:'& header
21433 You should be particularly careful about rewriting &'Sender:'& headers, and
21434 restrict this to special known cases in your own domains.
21437 .section "The SMTP-time rewriting flag" "SECTrewriteS"
21438 .cindex "SMTP" "rewriting malformed addresses"
21439 .cindex "RCPT" "rewriting argument of"
21440 .cindex "MAIL" "rewriting argument of"
21441 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
21442 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
21443 before any other processing; even before syntax checking. The pattern is
21444 required to be a regular expression, and it is matched against the whole of the
21445 data for the command, including any surrounding angle brackets.
21447 .cindex "&$domain$&"
21448 .cindex "&$local_part$&"
21449 This form of rewrite rule allows for the handling of addresses that are not
21450 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
21451 input). Because the input is not required to be a syntactically valid address,
21452 the variables &$local_part$& and &$domain$& are not available during the
21453 expansion of the replacement string. The result of rewriting replaces the
21454 original address in the MAIL or RCPT command.
21457 .section "Flags controlling the rewriting process"
21458 There are four flags which control the way the rewriting process works. These
21459 take effect only when a rule is invoked, that is, when the address is of the
21460 correct type (matches the flags) and matches the pattern:
21463 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
21464 unqualified local part. It is qualified with &%qualify_recipient%&. In the
21465 absence of &"Q"& the rewritten address must always include a domain.
21467 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
21468 even if no rewriting actually takes place because of a &"fail"& in the
21469 expansion. The &"q"& flag is not effective if the address is of the wrong type
21470 (does not match the flags) or does not match the pattern.
21472 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
21473 address, up to ten times. It can be combined with the &"q"& flag, to stop
21474 rewriting once it fails to match (after at least one successful rewrite).
21476 .cindex "rewriting" "whole addresses"
21477 When an address in a header is rewritten, the rewriting normally applies only
21478 to the working part of the address, with any comments and RFC 2822 &"phrase"&
21479 left unchanged. For example, rewriting might change
21481 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
21485 From: Ford Prefect <prefectf@hitch.fict.example>
21488 Sometimes there is a need to replace the whole address item, and this can be
21489 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
21490 causes an address in a header line to be rewritten, the entire address is
21491 replaced, not just the working part. The replacement must be a complete RFC
21492 2822 address, including the angle brackets if necessary. If text outside angle
21493 brackets contains a character whose value is greater than 126 or less than 32
21494 (except for tab), the text is encoded according to RFC 2047. The character set
21495 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
21497 When the &"w"& flag is set on a rule that causes an envelope address to be
21498 rewritten, all but the working part of the replacement address is discarded.
21502 .section "Rewriting examples"
21503 Here is an example of the two common rewriting paradigms:
21505 *@*.hitch.fict.example $1@hitch.fict.example
21506 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
21507 {$value}fail}@hitch.fict.example bctfrF
21509 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
21510 the string expansion to fail if the lookup does not succeed. In this context it
21511 has the effect of leaving the original address unchanged, but Exim goes on to
21512 consider subsequent rewriting rules, if any, because the &"q"& flag is not
21513 present in that rule. An alternative to &"fail"& would be to supply &$1$&
21514 explicitly, which would cause the rewritten address to be the same as before,
21515 at the cost of a small bit of processing. Not supplying either of these is an
21516 error, since the rewritten address would then contain no local part.
21518 The first example above replaces the domain with a superior, more general
21519 domain. This may not be desirable for certain local parts. If the rule
21521 root@*.hitch.fict.example *
21523 were inserted before the first rule, rewriting would be suppressed for the
21524 local part &'root'& at any domain ending in &'hitch.fict.example'&.
21526 Rewriting can be made conditional on a number of tests, by making use of
21527 &${if$& in the expansion item. For example, to apply a rewriting rule only to
21528 messages that originate outside the local host:
21530 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
21531 {$1@hitch.fict.example}fail}"
21533 The replacement string is quoted in this example because it contains white
21536 .cindex "rewriting" "bang paths"
21537 .cindex "bang paths" "rewriting"
21538 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
21539 an address it treats it as an unqualified local part which it qualifies with
21540 the local qualification domain (if the source of the message is local or if the
21541 remote host is permitted to send unqualified addresses). Rewriting can
21542 sometimes be used to handle simple bang paths with a fixed number of
21543 components. For example, the rule
21545 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
21547 rewrites a two-component bang path &'host.name!user'& as the domain address
21548 &'user@host.name'&. However, there is a security implication in using this as
21549 a global rewriting rule for envelope addresses. It can provide a backdoor
21550 method for using your system as a relay, because the incoming addresses appear
21551 to be local. If the bang path addresses are received via SMTP, it is safer to
21552 use the &"S"& flag to rewrite them as they are received, so that relay checking
21553 can be done on the rewritten addresses.
21560 . ////////////////////////////////////////////////////////////////////////////
21561 . ////////////////////////////////////////////////////////////////////////////
21563 .chapter "Retry configuration" "CHAPretry"
21564 .scindex IIDretconf1 "retry configuration" "description of"
21565 .scindex IIDregconf2 "configuration file" "retry section"
21566 The &"retry"& section of the run time configuration file contains a list of
21567 retry rules that control how often Exim tries to deliver messages that cannot
21568 be delivered at the first attempt. If there are no retry rules, temporary
21569 errors are treated as permanent. The &%-brt%& command line option can be used
21570 to test which retry rule will be used for a given address, domain and error.
21572 The most common cause of retries is temporary failure to deliver to a remote
21573 host because the host is down, or inaccessible because of a network problem.
21574 Exim's retry processing in this case is applied on a per-host (strictly, per IP
21575 address) basis, not on a per-message basis. Thus, if one message has recently
21576 been delayed, delivery of a new message to the same host is not immediately
21577 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
21578 log selector is set, the message
21579 .cindex "retry" "time not reached"
21580 &"retry time not reached"& is written to the main log whenever a delivery is
21581 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
21582 the handling of errors during remote deliveries.
21584 Retry processing applies to routing as well as to delivering, except as covered
21585 in the next paragraph. The retry rules do not distinguish between these
21586 actions. It is not possible, for example, to specify different behaviour for
21587 failures to route the domain &'snark.fict.example'& and failures to deliver to
21588 the host &'snark.fict.example'&. I didn't think anyone would ever need this
21589 added complication, so did not implement it. However, although they share the
21590 same retry rule, the actual retry times for routing and transporting a given
21591 domain are maintained independently.
21593 When a delivery is not part of a queue run (typically an immediate delivery on
21594 receipt of a message), the routers are always run, and local deliveries are
21595 always attempted, even if retry times are set for them. This makes for better
21596 behaviour if one particular message is causing problems (for example, causing
21597 quota overflow, or provoking an error in a filter file). If such a delivery
21598 suffers a temporary failure, the retry data is updated as normal, and
21599 subsequent delivery attempts from queue runs occur only when the retry time for
21600 the local address is reached.
21604 .section "Retry rules"
21605 .cindex "retry" "rules"
21606 Each retry rule occupies one line and consists of three or four parts,
21607 separated by white space: a pattern, an error name, an optional list of sender
21608 addresses, and a list of retry parameters. The pattern and sender lists must be
21609 enclosed in double quotes if they contain white space. The rules are searched
21610 in order until one is found where the pattern, error name, and sender list (if
21611 present) match the failing host or address, the error that occurred, and the
21612 message's sender, respectively.
21615 The pattern is any single item that may appear in an address list (see section
21616 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
21617 which means that it is expanded before being tested against the address that
21618 has been delayed. Address list processing treats a plain domain name as if it
21619 were preceded by &"*@"&, which makes it possible for many retry rules to start
21620 with just a domain. For example,
21622 lookingglass.fict.example * F,24h,30m;
21624 provides a rule for any address in the &'lookingglass.fict.example'& domain,
21627 alice@lookingglass.fict.example * F,24h,30m;
21629 applies only to temporary failures involving the local part &%alice%&.
21630 In practice, almost all rules start with a domain name pattern without a local
21633 .cindex "regular expressions" "in retry rules"
21634 &*Warning*&: If you use a regular expression in a routing rule pattern, it
21635 must match a complete address, not just a domain, because that is how regular
21636 expressions work in address lists.
21638 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
21639 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
21643 .section "Choosing which retry rule to use for address errors"
21644 When Exim is looking for a retry rule after a routing attempt has failed (for
21645 example, after a DNS timeout), each line in the retry configuration is tested
21646 against the complete address only if &%retry_use_local_part%& is set for the
21647 router. Otherwise, only the domain is used, except when matching against a
21648 regular expression, when the local part of the address is replaced with &"*"&.
21649 A domain on its own can match a domain pattern, or a pattern that starts with
21650 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
21651 &%check_local_user%& is true, and false for other routers.
21653 Similarly, when Exim is looking for a retry rule after a local delivery has
21654 failed (for example, after a mailbox full error), each line in the retry
21655 configuration is tested against the complete address only if
21656 &%retry_use_local_part%& is set for the transport (it defaults true for all
21659 However, when Exim is looking for a retry rule after a remote delivery attempt
21660 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
21661 whole address is always used as the key when searching the retry rules. The
21662 rule that is found is used to create a retry time for the failing address.
21665 .section "Choosing which retry rule to use for host and message errors"
21666 For a temporary error that is not related to an individual address (for
21667 example, a connection timeout), each line in the retry configuration is checked
21668 twice. First, the name of the remote host is used as a domain name (preceded by
21669 &"*@"& when matching a regular expression). If this does not match the line,
21670 the domain from the email address is tried in a similar fashion. For example,
21671 suppose the MX records for &'a.b.c.example'& are
21673 a.b.c.example MX 5 x.y.z.example
21677 and the retry rules are
21679 p.q.r.example * F,24h,30m;
21680 a.b.c.example * F,4d,45m;
21682 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
21683 first rule matches neither the host nor the domain, so Exim looks at the second
21684 rule. This does not match the host, but it does match the domain, so it is used
21685 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
21686 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
21687 first retry rule is used, because it matches the host.
21689 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
21690 first rule to determine retry times, but for all the other hosts for the domain
21691 &'a.b.c.example'&, the second rule is used. The second rule is also used if
21692 routing to &'a.b.c.example'& suffers a temporary failure.
21694 &*Note*&: The host name is used when matching the patterns, not its IP address.
21695 However, if a message is routed directly to an IP address without the use of a
21696 host name, for example, if a &(manualroute)& router contains a setting such as:
21698 route_list = *.a.example 192.168.34.23
21700 then the &"host name"& that is used when searching for a retry rule is the
21701 textual form of the IP address.
21703 .section "Retry rules for specific errors"
21704 .cindex "retry" "specific errors; specifying"
21705 The second field in a retry rule is the name of a particular error, or an
21706 asterisk, which matches any error. The errors that can be tested for are:
21709 .vitem &%auth_failed%&
21710 Authentication failed when trying to send to a host in the
21711 &%hosts_require_auth%& list in an &(smtp)& transport.
21713 .vitem &%data_4xx%&
21714 A 4&'xx'& error was received for an outgoing DATA command, either immediately
21715 after the command, or after sending the message's data.
21717 .vitem &%mail_4xx%&
21718 A 4&'xx'& error was received for an outgoing MAIL command.
21720 .vitem &%rcpt_4xx%&
21721 A 4&'xx'& error was received for an outgoing RCPT command.
21724 For the three 4&'xx'& errors, either the first or both of the x's can be given
21725 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
21726 recognize 452 errors given to RCPT commands for addresses in a certain domain,
21727 and have retries every ten minutes with a one-hour timeout, you could set up a
21728 retry rule of this form:
21730 the.domain.name rcpt_452 F,1h,10m
21732 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
21733 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
21736 .vitem &%lost_connection%&
21737 A server unexpectedly closed the SMTP connection. There may, of course,
21738 legitimate reasons for this (host died, network died), but if it repeats a lot
21739 for the same host, it indicates something odd.
21741 .vitem &%refused_MX%&
21742 A connection to a host obtained from an MX record was refused.
21744 .vitem &%refused_A%&
21745 A connection to a host not obtained from an MX record was refused.
21748 A connection was refused.
21750 .vitem &%timeout_connect_MX%&
21751 A connection attempt to a host obtained from an MX record timed out.
21753 .vitem &%timeout_connect_A%&
21754 A connection attempt to a host not obtained from an MX record timed out.
21756 .vitem &%timeout_connect%&
21757 A connection attempt timed out.
21759 .vitem &%timeout_MX%&
21760 There was a timeout while connecting or during an SMTP session with a host
21761 obtained from an MX record.
21763 .vitem &%timeout_A%&
21764 There was a timeout while connecting or during an SMTP session with a host not
21765 obtained from an MX record.
21768 There was a timeout while connecting or during an SMTP session.
21770 .vitem &%tls_required%&
21771 The server was required to use TLS (it matched &%hosts_require_tls%& in the
21772 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
21773 to STARTTLS, or there was a problem setting up the TLS connection.
21776 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
21779 .vitem &%quota_%&<&'time'&>
21780 .cindex "quota" "error testing in retry rule"
21781 .cindex "retry" "quota error testing"
21782 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
21783 transport, and the mailbox has not been accessed for <&'time'&>. For example,
21784 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
21788 .cindex "mailbox" "time of last read"
21789 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
21790 timeouts when the mailbox is full and is not being read by its owner. Ideally,
21791 it should be based on the last time that the user accessed the mailbox.
21792 However, it is not always possible to determine this. Exim uses the following
21796 If the mailbox is a single file, the time of last access (the &"atime"&) is
21797 used. As no new messages are being delivered (because the mailbox is over
21798 quota), Exim does not access the file, so this is the time of last user access.
21800 .cindex "maildir format" "time of last read"
21801 For a maildir delivery, the time of last modification of the &_new_&
21802 subdirectory is used. As the mailbox is over quota, no new files are created in
21803 the &_new_& subdirectory, because no new messages are being delivered. Any
21804 change to the &_new_& subdirectory is therefore assumed to be the result of an
21805 MUA moving a new message to the &_cur_& directory when it is first read. The
21806 time that is used is therefore the last time that the user read a new message.
21808 For other kinds of multi-file mailbox, the time of last access cannot be
21809 obtained, so a retry rule that uses this type of error field is never matched.
21812 The quota errors apply both to system-enforced quotas and to Exim's own quota
21813 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
21814 when a local delivery is deferred because a partition is full (the ENOSPC
21819 .section "Retry rules for specified senders"
21820 .cindex "retry" "rules; sender-specific"
21821 You can specify retry rules that apply only when the failing message has a
21822 specific sender. In particular, this can be used to define retry rules that
21823 apply only to bounce messages. The third item in a retry rule can be of this
21826 &`senders=`&<&'address list'&>
21828 The retry timings themselves are then the fourth item. For example:
21830 * rcpt_4xx senders=: F,1h,30m
21832 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
21833 host. If the address list contains white space, it must be enclosed in quotes.
21836 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
21838 &*Warning*&: This facility can be unhelpful if it is used for host errors
21839 (which do not depend on the recipient). The reason is that the sender is used
21840 only to match the retry rule. Once the rule has been found for a host error,
21841 its contents are used to set a retry time for the host, and this will apply to
21842 all messages, not just those with specific senders.
21844 When testing retry rules using &%-brt%&, you can supply a sender using the
21845 &%-f%& command line option, like this:
21847 exim -f "" -brt user@dom.ain
21849 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
21850 list is never matched.
21856 .section "Retry parameters"
21857 .cindex "retry" "parameters in rules"
21858 The third (or fourth, if a senders list is present) field in a retry rule is a
21859 sequence of retry parameter sets, separated by semicolons. Each set consists of
21861 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
21863 The letter identifies the algorithm for computing a new retry time; the cutoff
21864 time is the time beyond which this algorithm no longer applies, and the
21865 arguments vary the algorithm's action. The cutoff time is measured from the
21866 time that the first failure for the domain (combined with the local part if
21867 relevant) was detected, not from the time the message was received.
21869 .cindex "retry" "algorithms"
21870 .cindex "retry" "fixed intervals"
21871 .cindex "retry" "increasing intervals"
21872 .cindex "retry" "random intervals"
21873 The available algorithms are:
21876 &'F'&: retry at fixed intervals. There is a single time parameter specifying
21879 &'G'&: retry at geometrically increasing intervals. The first argument
21880 specifies a starting value for the interval, and the second a multiplier, which
21881 is used to increase the size of the interval at each retry.
21883 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
21884 retry, the previous interval is multiplied by the factor in order to get a
21885 maximum for the next interval. The mininum interval is the first argument of
21886 the parameter, and an actual interval is chosen randomly between them. Such a
21887 rule has been found to be helpful in cluster configurations when all the
21888 members of the cluster restart at once, and may therefore synchronize their
21889 queue processing times.
21892 When computing the next retry time, the algorithm definitions are scanned in
21893 order until one whose cutoff time has not yet passed is reached. This is then
21894 used to compute a new retry time that is later than the current time. In the
21895 case of fixed interval retries, this simply means adding the interval to the
21896 current time. For geometrically increasing intervals, retry intervals are
21897 computed from the rule's parameters until one that is greater than the previous
21898 interval is found. The main configuration variable
21899 .cindex "limit" "retry interval"
21900 .cindex "retry interval" "maximum"
21901 .cindex "&%retry_interval_max%&"
21902 &%retry_interval_max%& limits the maximum interval between retries. It
21903 cannot be set greater than &`24h`&, which is its default value.
21905 A single remote domain may have a number of hosts associated with it, and each
21906 host may have more than one IP address. Retry algorithms are selected on the
21907 basis of the domain name, but are applied to each IP address independently. If,
21908 for example, a host has two IP addresses and one is unusable, Exim will
21909 generate retry times for it and will not try to use it until its next retry
21910 time comes. Thus the good IP address is likely to be tried first most of the
21913 .cindex "hints database" "use for retrying"
21914 Retry times are hints rather than promises. Exim does not make any attempt to
21915 run deliveries exactly at the computed times. Instead, a queue runner process
21916 starts delivery processes for delayed messages periodically, and these attempt
21917 new deliveries only for those addresses that have passed their next retry time.
21918 If a new message arrives for a deferred address, an immediate delivery attempt
21919 occurs only if the address has passed its retry time. In the absence of new
21920 messages, the minimum time between retries is the interval between queue runner
21921 processes. There is not much point in setting retry times of five minutes if
21922 your queue runners happen only once an hour, unless there are a significant
21923 number of incoming messages (which might be the case on a system that is
21924 sending everything to a smart host, for example).
21926 The data in the retry hints database can be inspected by using the
21927 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
21928 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
21929 &'exinext'& utility script can be used to find out what the next retry times
21930 are for the hosts associated with a particular mail domain, and also for local
21931 deliveries that have been deferred.
21934 .section "Retry rule examples"
21935 Here are some example retry rules:
21937 alice@wonderland.fict.example quota_5d F,7d,3h
21938 wonderland.fict.example quota_5d
21939 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
21940 lookingglass.fict.example * F,24h,30m;
21941 * refused_A F,2h,20m;
21942 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
21944 The first rule sets up special handling for mail to
21945 &'alice@wonderland.fict.example'& when there is an over-quota error and the
21946 mailbox has not been read for at least 5 days. Retries continue every three
21947 hours for 7 days. The second rule handles over-quota errors for all other local
21948 parts at &'wonderland.fict.example'&; the absence of a local part has the same
21949 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
21950 fail are bounced immediately if the mailbox has not been read for at least 5
21953 The third rule handles all other errors at &'wonderland.fict.example'&; retries
21954 happen every 15 minutes for an hour, then with geometrically increasing
21955 intervals until two days have passed since a delivery first failed. After the
21956 first hour there is a delay of one hour, then two hours, then four hours, and
21957 so on (this is a rather extreme example).
21959 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
21960 They happen every 30 minutes for 24 hours only. The remaining two rules handle
21961 all other domains, with special action for connection refusal from hosts that
21962 were not obtained from an MX record.
21964 The final rule in a retry configuration should always have asterisks in the
21965 first two fields so as to provide a general catch-all for any addresses that do
21966 not have their own special handling. This example tries every 15 minutes for 2
21967 hours, then with intervals starting at one hour and increasing by a factor of
21968 1.5 up to 16 hours, then every 8 hours up to 5 days.
21972 .section "Timeout of retry data"
21973 .cindex "timeout" "of retry data"
21974 .cindex "&%retry_data_expire%&"
21975 .cindex "hints database" "data expiry"
21976 .cindex "retry" "timeout of data"
21977 Exim timestamps the data that it writes to its retry hints database. When it
21978 consults the data during a delivery it ignores any that is older than the value
21979 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
21980 been tried for 7 days, Exim will try to deliver to it immediately a message
21981 arrives, and if that fails, it will calculate a retry time as if it were
21982 failing for the first time.
21984 This improves the behaviour for messages routed to rarely-used hosts such as MX
21985 backups. If such a host was down at one time, and happens to be down again when
21986 Exim tries a month later, using the old retry data would imply that it had been
21987 down all the time, which is not a justified assumption.
21989 If a host really is permanently dead, this behaviour causes a burst of retries
21990 every now and again, but only if messages routed to it are rare. It there is a
21991 message at least once every 7 days the retry data never expires.
21996 .section "Long-term failures"
21997 .cindex "delivery failure" "long-term"
21998 .cindex "retry" "after long-term failure"
21999 Special processing happens when an email address has been failing for so long
22000 that the cutoff time for the last algorithm is reached. For example, using the
22001 default retry rule:
22003 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
22005 the cutoff time is four days. Reaching the retry cutoff is independent of how
22006 long any specific message has been failing; it is the length of continuous
22007 failure for the recipient address that counts.
22009 When the cutoff time is reached for a local delivery, or for all the IP
22010 addresses associated with a remote delivery, a subsequent delivery failure
22011 causes Exim to give up on the address, and a bounce message is generated.
22012 In order to cater for new messages that use the failing address, a next retry
22013 time is still computed from the final algorithm, and is used as follows:
22015 For local deliveries, one delivery attempt is always made for any subsequent
22016 messages. If this delivery fails, the address fails immediately. The
22017 post-cutoff retry time is not used.
22019 If the delivery is remote, there are two possibilities, controlled by the
22020 .cindex "&%delay_after_cutoff%&"
22021 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
22022 default. Until the post-cutoff retry time for one of the IP addresses is
22023 reached, the failing email address is bounced immediately, without a delivery
22024 attempt taking place. After that time, one new delivery attempt is made to
22025 those IP addresses that are past their retry times, and if that still fails,
22026 the address is bounced and new retry times are computed.
22028 In other words, when all the hosts for a given email address have been failing
22029 for a long time, Exim bounces rather then defers until one of the hosts' retry
22030 times is reached. Then it tries once, and bounces if that attempt fails. This
22031 behaviour ensures that few resources are wasted in repeatedly trying to deliver
22032 to a broken destination, but if the host does recover, Exim will eventually
22035 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
22036 addresses are past their final cutoff time, Exim tries to deliver to those IP
22037 addresses that have not been tried since the message arrived. If there are
22038 no suitable IP addresses, or if they all fail, the address is bounced. In other
22039 words, it does not delay when a new message arrives, but tries the expired
22040 addresses immediately, unless they have been tried since the message arrived.
22041 If there is a continuous stream of messages for the failing domains, setting
22042 &%delay_after_cutoff%& false means that there will be many more attempts to
22043 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
22046 .section "Deliveries that work intermittently"
22047 .cindex "retry" "intermittently working deliveries"
22049 Some additional logic is needed to cope with cases where a host is
22050 intermittently available, or when a message has some attribute that prevents
22051 its delivery when others to the same address get through. In this situation,
22052 because some messages are successfully delivered, the &"retry clock"& for the
22053 host or address keeps getting reset by the successful deliveries, and so
22054 failing messages remain on the queue for ever because the cutoff time is never
22057 Two exceptional actions are applied to prevent this happening. The first
22058 applies to errors that are related to a message rather than a remote host.
22059 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
22060 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
22061 commands, and quota failures. For this type of error, if a message's arrival
22062 time is earlier than the &"first failed"& time for the error, the earlier time
22063 is used when scanning the retry rules to decide when to try next and when to
22064 time out the address.
22066 The exceptional second action applies in all cases. If a message has been on
22067 the queue for longer than the cutoff time of any applicable retry rule for a
22068 given address, a delivery is attempted for that address, even if it is not yet
22069 time, and if this delivery fails, the address is timed out. A new retry time is
22070 not computed in this case, so that other messages for the same address are
22071 considered immediately.
22073 .ecindex IIDretconf1
22074 .ecindex IIDregconf2
22081 . ////////////////////////////////////////////////////////////////////////////
22082 . ////////////////////////////////////////////////////////////////////////////
22084 .chapter "SMTP authentication" "CHAPSMTPAUTH"
22085 .scindex IIDauthconf1 "SMTP" "authentication configuration"
22086 .scindex IIDauthconf2 "authentication"
22087 The &"authenticators"& section of Exim's run time configuration is concerned
22088 with SMTP authentication. This facility is an extension to the SMTP protocol,
22089 described in RFC 2554, which allows a client SMTP host to authenticate itself
22090 to a server. This is a common way for a server to recognize clients that are
22091 permitted to use it as a relay. SMTP authentication is not of relevance to the
22092 transfer of mail between servers that have no managerial connection with each
22095 .cindex "AUTH" "description of"
22096 Very briefly, the way SMTP authentication works is as follows:
22099 The server advertises a number of authentication &'mechanisms'& in response to
22100 the client's EHLO command.
22102 The client issues an AUTH command, naming a specific mechanism. The command
22103 may, optionally, contain some authentication data.
22105 The server may issue one or more &'challenges'&, to which the client must send
22106 appropriate responses. In simple authentication mechanisms, the challenges are
22107 just prompts for user names and passwords. The server does not have to issue
22108 any challenges &-- in some mechanisms the relevant data may all be transmitted
22109 with the AUTH command.
22111 The server either accepts or denies authentication.
22113 If authentication succeeds, the client may optionally make use of the AUTH
22114 option on the MAIL command to pass an authenticated sender in subsequent
22115 mail transactions. Authentication lasts for the remainder of the SMTP
22118 If authentication fails, the client may give up, or it may try a different
22119 authentication mechanism, or it may try transferring mail over the
22120 unauthenticated connection.
22123 If you are setting up a client, and want to know which authentication
22124 mechanisms the server supports, you can use Telnet to connect to port 25 (the
22125 SMTP port) on the server, and issue an EHLO command. The response to this
22126 includes the list of supported mechanisms. For example:
22128 &`$ `&&*&`telnet server.example 25`&*&
22129 &`Trying 192.168.34.25...`&
22130 &`Connected to server.example.`&
22131 &`Escape character is '^]'.`&
22132 &`220 server.example ESMTP Exim 4.20 ...`&
22133 &*&`ehlo client.example`&*&
22134 &`250-server.example Hello client.example [10.8.4.5]`&
22135 &`250-SIZE 52428800`&
22140 The second-last line of this example output shows that the server supports
22141 authentication using the PLAIN mechanism. In Exim, the different authentication
22142 mechanisms are configured by specifying &'authenticator'& drivers. Like the
22143 routers and transports, which authenticators are included in the binary is
22144 controlled by build-time definitions. The following are currently available,
22145 included by setting
22148 AUTH_CYRUS_SASL=yes
22152 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
22153 authentication mechanism (RFC 2195), and the second provides an interface to
22154 the Cyrus SASL authentication library. The third can be configured to support
22155 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
22156 not formally documented, but used by several MUAs. The fourth authenticator
22157 supports Microsoft's &'Secure Password Authentication'& mechanism.
22159 The authenticators are configured using the same syntax as other drivers (see
22160 section &<<SECTfordricon>>&). If no authenticators are required, no
22161 authentication section need be present in the configuration file. Each
22162 authenticator can in principle have both server and client functions. When Exim
22163 is receiving SMTP mail, it is acting as a server; when it is sending out
22164 messages over SMTP, it is acting as a client. Authenticator configuration
22165 options are provided for use in both these circumstances.
22167 To make it clear which options apply to which situation, the prefixes
22168 &%server_%& and &%client_%& are used on option names that are specific to
22169 either the server or the client function, respectively. Server and client
22170 functions are disabled if none of their options are set. If an authenticator is
22171 to be used for both server and client functions, a single definition, using
22172 both sets of options, is required. For example:
22176 public_name = CRAM-MD5
22177 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
22179 client_secret = secret2
22181 The &%server_%& option is used when Exim is acting as a server, and the
22182 &%client_%& options when it is acting as a client.
22184 Descriptions of the individual authenticators are given in subsequent chapters.
22185 The remainder of this chapter covers the generic options for the
22186 authenticators, followed by general discussion of the way authentication works
22191 .section "Generic options for authenticators"
22192 .cindex "authentication" "generic options"
22193 .cindex "options" "generic; for authenticators"
22196 .option driver authenticators string unset
22197 This option must always be set. It specifies which of the available
22198 authenticators is to be used.
22201 .option public_name authenticators string unset
22202 This option specifies the name of the authentication mechanism that the driver
22203 implements, and by which it is known to the outside world. These names should
22204 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
22205 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
22206 defaults to the driver's instance name.
22209 .option server_advertise_condition authenticators string&!! unset
22210 When a server is about to advertise an authentication mechanism, the condition
22211 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
22212 mechanism is not advertised.
22213 If the expansion fails, the mechanism is not advertised. If the failure was not
22214 forced, and was not caused by a lookup defer, the incident is logged.
22215 See section &<<SECTauthexiser>>& below for further discussion.
22218 .option server_debug_print authenticators string&!! unset
22219 If this option is set and authentication debugging is enabled (see the &%-d%&
22220 command line option), the string is expanded and included in the debugging
22221 output when the authenticator is run as a server. This can help with checking
22222 out the values of variables.
22223 If expansion of the string fails, the error message is written to the debugging
22224 output, and Exim carries on processing.
22227 .option server_set_id authenticators string&!! unset
22228 .cindex "&$authenticated_id$&"
22229 When an Exim server successfully authenticates a client, this string is
22230 expanded using data from the authentication, and preserved for any incoming
22231 messages in the variable &$authenticated_id$&. It is also included in the log
22232 lines for incoming messages. For example, a user/password authenticator
22233 configuration might preserve the user name that was used to authenticate, and
22234 refer to it subsequently during delivery of the message.
22235 If expansion fails, the option is ignored.
22238 .option server_mail_auth_condition authenticators string&!! unset
22239 This option allows a server to discard authenticated sender addresses supplied
22240 as part of MAIL commands in SMTP connections that are authenticated by the
22241 driver on which &%server_mail_auth_condition%& is set. The option is not used
22242 as part of the authentication process; instead its (unexpanded) value is
22243 remembered for later use.
22244 How it is used is described in the following section.
22250 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
22251 .cindex "authentication" "sender; authenticated"
22252 .cindex "AUTH" "on MAIL command"
22253 When a client supplied an AUTH= item on a MAIL command, Exim applies
22254 the following checks before accepting it as the authenticated sender of the
22258 If the connection is not using extended SMTP (that is, HELO was used rather
22259 than EHLO), the use of AUTH= is a syntax error.
22261 If the value of the AUTH= parameter is &"<>"&, it is ignored.
22263 .cindex "&$authenticated_sender$&"
22264 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
22265 running, the value of &$authenticated_sender$& is set to the value obtained
22266 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
22267 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
22268 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
22269 given for the MAIL command.
22271 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
22272 is accepted and placed in &$authenticated_sender$& only if the client has
22275 If the AUTH= value was accepted by either of the two previous rules, and
22276 the client has authenticated, and the authenticator has a setting for the
22277 &%server_mail_auth_condition%&, the condition is checked at this point. The
22278 valued that was saved from the authenticator is expanded. If the expansion
22279 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
22280 &$authenticated_sender$& is deleted. If the expansion yields any other value,
22281 the value of &$authenticated_sender$& is retained and passed on with the
22286 When &$authenticated_sender$& is set for a message, it is passed on to other
22287 hosts to which Exim authenticates as a client. Do not confuse this value with
22288 &$authenticated_id$&, which is a string obtained from the authentication
22289 process, and which is not usually a complete email address.
22291 .cindex "&$sender_address$&"
22292 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
22293 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
22294 therefore make use of &$authenticated_sender$&. The converse is not true: the
22295 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
22300 .section "Authentication on an Exim server" "SECTauthexiser"
22301 .cindex "authentication" "on an Exim server"
22302 When Exim receives an EHLO command, it advertises the public names of those
22303 authenticators that are configured as servers, subject to the following
22307 The client host must match &%auth_advertise_hosts%& (default *).
22309 It the &%server_advertise_condition%& option is set, its expansion must not
22310 yield the empty string, &"0"&, &"no"&, or &"false"&.
22313 The order in which the authenticators are defined controls the order in which
22314 the mechanisms are advertised.
22316 Some mail clients (for example, some versions of Netscape) require the user to
22317 provide a name and password for authentication whenever AUTH is advertised,
22318 even though authentication may not in fact be needed (for example, Exim may be
22319 set up to allow unconditional relaying from the client by an IP address check).
22320 You can make such clients more friendly by not advertising AUTH to them.
22321 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
22322 that runs for RCPT) to relay without authentication, you should set
22324 auth_advertise_hosts = ! 10.9.8.0/24
22326 so that no authentication mechanisms are advertised to them.
22328 The &%server_advertise_condition%& controls the advertisement of individual
22329 authentication mechanisms. For example, it can be used to restrict the
22330 advertisement of a patricular mechanism to encrypted connections, by a setting
22333 server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}}
22335 .cindex "&$tls_cipher$&"
22336 If the session is encrypted, &$tls_cipher$& is not empty, and so the expansion
22337 yields &"yes"&, which allows the advertisement to happen.
22339 When an Exim server receives an AUTH command from a client, it rejects it
22340 immediately if AUTH was not advertised in response to an earlier EHLO
22341 command. This is the case if
22344 The client host does not match &%auth_advertise_hosts%&; or
22346 No authenticators are configured with server options; or
22348 Expansion of &%server_advertise_condition%& blocked the advertising of all the
22349 server authenticators.
22353 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
22354 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
22355 AUTH is accepted from any client host.
22357 If AUTH is not rejected by the ACL, Exim searches its configuration for a
22358 server authentication mechanism that was advertised in response to EHLO and
22359 that matches the one named in the AUTH command. If it finds one, it runs
22360 the appropriate authentication protocol, and authentication either succeeds or
22361 fails. If there is no matching advertised mechanism, the AUTH command is
22362 rejected with a 504 error.
22364 .cindex "&$received_protocol$&"
22365 .cindex "&$sender_host_authenticated$&"
22366 When a message is received from an authenticated host, the value of
22367 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
22368 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
22369 public name) of the authenticator driver that successfully authenticated the
22370 client from which the message was received. This variable is empty if there was
22371 no successful authentication.
22376 .section "Testing server authentication"
22377 .cindex "authentication" "testing a server"
22378 .cindex "AUTH" "testing a server"
22379 .cindex "base64 encoding" "creating authentication test data"
22380 Exim's &%-bh%& option can be useful for testing server authentication
22381 configurations. The data for the AUTH command has to be sent using base64
22382 encoding. A quick way to produce such data for testing is the following Perl
22386 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
22388 .cindex "binary zero" "in authentication data"
22389 This interprets its argument as a Perl string, and then encodes it. The
22390 interpretation as a Perl string allows binary zeros, which are required for
22391 some kinds of authentication, to be included in the data. For example, a
22392 command line to run this script on such data might be
22394 encode '\0user\0password'
22396 Note the use of single quotes to prevent the shell interpreting the
22397 backslashes, so that they can be interpreted by Perl to specify characters
22398 whose code value is zero.
22400 &*Warning 1*&: If either of the user or password strings starts with an octal
22401 digit, you must use three zeros instead of one after the leading backslash. If
22402 you do not, the octal digit that starts your string will be incorrectly
22403 interpreted as part of the code for the first character.
22405 &*Warning 2*&: If there are characters in the strings that Perl interprets
22406 specially, you must use a Perl escape to prevent them being misinterpreted. For
22407 example, a command such as
22409 encode '\0user@domain.com\0pas$$word'
22411 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
22413 If you have the &%mimencode%& command installed, another way to do produce
22414 base64-encoded strings is to run the command
22416 echo -e -n `\0user\0password' | mimencode
22418 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
22419 in the argument, and the &%-n%& option specifies no newline at the end of its
22420 output. However, not all versions of &%echo%& recognize these options, so you
22421 should check your version before relying on this suggestion.
22425 .section "Authentication by an Exim client"
22426 .cindex "authentication" "on an Exim client"
22427 The &(smtp)& transport has two options called &%hosts_require_auth%& and
22428 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
22429 announces support for authentication, and the host matches an entry in either
22430 of these options, Exim (as a client) tries to authenticate as follows:
22433 For each authenticator that is configured as a client, it searches the
22434 authentication mechanisms announced by the server for one whose name
22435 matches the public name of the authenticator.
22438 .cindex "&$host_address$&"
22439 When it finds one that matches, it runs the authenticator's client code.
22440 The variables &$host$& and &$host_address$& are available for any string
22441 expansions that the client might do. They are set to the server's name and
22442 IP address. If any expansion is forced to fail, the authentication attempt
22444 and Exim moves on to the next authenticator.
22445 Otherwise an expansion failure causes delivery to be
22448 If the result of the authentication attempt is a temporary error or a timeout,
22449 Exim abandons trying to send the message to the host for the moment. It will
22450 try again later. If there are any backup hosts available, they are tried in the
22453 If the response to authentication is a permanent error (5&'xx'& code), Exim
22454 carries on searching the list of authenticators and tries another one if
22455 possible. If all authentication attempts give permanent errors, or if there are
22456 no attempts because no mechanisms match (or option expansions force failure),
22457 what happens depends on whether the host matches &%hosts_require_auth%& or
22458 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
22459 delivery is deferred. The error can be detected in the retry rules, and thereby
22460 turned into a permanent error if you wish. In the second case, Exim tries to
22461 deliver the message unauthenticated.
22464 .cindex "AUTH" "on MAIL command"
22465 When Exim has authenticated itself to a remote server, it adds the AUTH
22466 parameter to the MAIL commands it sends, if it has an authenticated sender for
22467 the message. If the message came from a remote host, the authenticated sender
22468 is the one that was receiving on an incoming MAIL command, provided that the
22469 incoming connection was authenticated and the &%server_mail_auth%& condition
22470 allowed the authenticated sender to be retained. If a local process calls Exim
22471 to send a message, the sender address that is built from the login name and
22472 &%qualify_domain%& is treated as authenticated. However, if the
22473 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
22474 the authenticated sender that was received with the message.
22475 .ecindex IIDauthconf1
22476 .ecindex IIDauthconf2
22483 . ////////////////////////////////////////////////////////////////////////////
22484 . ////////////////////////////////////////////////////////////////////////////
22486 .chapter "The plaintext authenticator" "CHAPplaintext"
22487 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
22488 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
22489 The &(plaintext)& authenticator can be configured to support the PLAIN and
22490 LOGIN authentication mechanisms, both of which transfer authentication data as
22491 plain (unencrypted) text (though base64 encoded). The use of plain text is a
22492 security risk; you are strongly advised to insist on the use of SMTP encryption
22493 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
22494 use unencrypted plain text, you should not use the same passwords for SMTP
22495 connections as you do for login accounts.
22497 .section "Using plaintext in a server"
22498 .cindex "options" "&(plaintext)& authenticator (server)"
22499 When running as a server, &(plaintext)& performs the authentication test by
22500 expanding a string. It has the following options:
22502 .option server_prompts plaintext string&!! unset
22503 The contents of this option, after expansion, must be a colon-separated list of
22504 prompt strings. If expansion fails, a temporary authentication rejection is
22507 .option server_condition plaintext string&!! unset
22508 This option must be set in order to configure the driver as a server. Its use
22509 is described below.
22511 .cindex "AUTH" "in &(plaintext)& authenticator"
22512 .cindex "binary zero" "in &(plaintext)& authenticator"
22513 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
22514 "in &(plaintext)& authenticator"
22515 .cindex "&$auth1$&, &$auth2$&, etc"
22516 .cindex "base64 encoding" "in &(plaintext)& authenticator"
22517 The data sent by the client with the AUTH command, or in response to
22518 subsequent prompts, is base64 encoded, and so may contain any byte values
22519 when decoded. If any data is supplied with the command, it is treated as a
22520 list of strings, separated by NULs (binary zeros), the first three of which are
22521 placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$& (neither
22522 LOGIN nor PLAIN uses more than three strings).
22524 For compatibility with previous releases of Exim, the values are also placed in
22525 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
22526 variables for this purpose is now deprecated, as it can lead to confusion in
22527 string expansions that also use them for other things.
22529 If there are more strings in &%server_prompts%& than the number of strings
22530 supplied with the AUTH command, the remaining prompts are used to obtain more
22531 data. Each response from the client may be a list of NUL-separated strings.
22533 .cindex "&$authenticated_id$&"
22534 Once a sufficient number of data strings have been received,
22535 &%server_condition%& is expanded. If the expansion is forced to fail,
22536 authentication fails. Any other expansion failure causes a temporary error code
22537 to be returned. If the result of a successful expansion is an empty string,
22538 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
22539 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
22540 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
22541 For any other result, a temporary error code is returned, with the expanded
22542 string as the error text.
22544 &*Warning*&: If you use a lookup in the expansion to find the user's
22545 password, be sure to make the authentication fail if the user is unknown.
22546 There are good and bad examples at the end of the next section.
22550 .section "The PLAIN authentication mechanism"
22551 .cindex "PLAIN authentication mechanism"
22552 .cindex "authentication" "PLAIN mechanism"
22553 .cindex "binary zero" "in &(plaintext)& authenticator"
22554 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
22555 sent as one item of data (that is, one combined string containing two NUL
22556 separators). The data is sent either as part of the AUTH command, or
22557 subsequently in response to an empty prompt from the server.
22559 The second and third strings are a user name and a corresponding password.
22560 Using a single fixed user name and password as an example, this could be
22561 configured as follows:
22565 public_name = PLAIN
22567 server_condition = \
22568 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}\
22570 server_set_id = $auth2
22572 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
22573 the end of a string list are ignored). If all the data comes as part of the
22574 AUTH command, as is commonly the case, the prompt is not used. This
22575 authenticator is advertised in the response to EHLO as
22579 and a client host can authenticate itself by sending the command
22581 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
22583 As this contains three strings (more than the number of prompts), no further
22584 data is required from the client. Alternatively, the client may just send
22588 to initiate authentication, in which case the server replies with an empty
22589 prompt. The client must respond with the combined data string.
22591 The data string is base64 encoded, as required by the RFC. This example,
22592 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
22593 represents a zero byte. This is split up into three strings, the first of which
22594 is empty. The &%server_condition%& option in the authenticator checks that the
22595 second two are &`username`& and &`mysecret`& respectively.
22597 Having just one fixed user name and password, as in this example, is not very
22598 realistic, though for a small organization with only a handful of
22599 authenticating clients it could make sense.
22601 A more sophisticated instance of this authenticator could use the user name in
22602 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
22603 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
22604 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
22605 This is an incorrect example:
22607 server_condition = \
22608 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}{yes}{no}}
22610 The expansion uses the user name (&$auth2$&) as the key to look up a password,
22611 which it then compares to the supplied password (&$auth3$&). Why is this example
22612 incorrect? It works fine for existing users, but consider what happens if a
22613 non-existent user name is given. The lookup fails, but as no success/failure
22614 strings are given for the lookup, it yields an empty string. Thus, to defeat
22615 the authentication, all a client has to do is to supply a non-existent user
22616 name and an empty password. The correct way of writing this test is:
22618 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
22619 {${if eq{$value}{$auth3}{yes}{no}}}{no}}
22621 In this case, if the lookup succeeds, the result is checked; if the lookup
22622 fails, authentication fails. If &%crypteq%& is being used instead of &%eq%&,
22623 the first example is in fact safe, because &%crypteq%& always fails if its
22624 second argument is empty. However, the second way of writing the test makes the
22629 .section "The LOGIN authentication mechanism"
22630 .cindex "LOGIN authentication mechanism"
22631 .cindex "authentication" "LOGIN mechanism"
22632 The LOGIN authentication mechanism is not documented in any RFC, but is in use
22633 in a number of programs. No data is sent with the AUTH command. Instead, a
22634 user name and password are supplied separately, in response to prompts. The
22635 plaintext authenticator can be configured to support this as in this example:
22639 public_name = LOGIN
22640 server_prompts = User Name : Password
22641 server_condition = \
22642 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}\
22644 server_set_id = $auth1
22646 Because of the way plaintext operates, this authenticator accepts data supplied
22647 with the AUTH command (in contravention of the specification of LOGIN), but
22648 if the client does not supply it (as is the case for LOGIN clients), the prompt
22649 strings are used to obtain two data items.
22651 Some clients are very particular about the precise text of the prompts. For
22652 example, Outlook Express is reported to recognize only &"Username:"& and
22653 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
22654 strings. It uses the &%ldapauth%& expansion condition to check the user
22655 name and password by binding to an LDAP server:
22659 public_name = LOGIN
22660 server_prompts = Username:: : Password::
22661 server_condition = ${if ldapauth \
22662 {user="cn=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
22663 pass=${quote:$auth2} \
22664 ldap://ldap.example.org/}{yes}{no}}
22665 server_set_id = uid=$auth1,ou=people,o=example.org
22667 Note the use of the &%quote_ldap_dn%& operator to correctly quote the DN for
22668 authentication. However, the basic &%quote%& operator, rather than any of the
22669 LDAP quoting operators, is the correct one to use for the password, because
22670 quoting is needed only to make the password conform to the Exim syntax. At the
22671 LDAP level, the password is an uninterpreted string.
22675 .section "Support for different kinds of authentication"
22676 A number of string expansion features are provided for the purpose of
22677 interfacing to different ways of user authentication. These include checking
22678 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
22679 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
22685 .section "Using plaintext in a client"
22686 .cindex "options" "&(plaintext)& authenticator (client)"
22687 The &(plaintext)& authenticator has two client options:
22689 .option client_ignore_invalid_base64 plaintext boolean false
22690 If the client receives a server prompt that is not a valid base64 string,
22691 authentication is abandoned by default. However, if this option is set true,
22692 the error in the challenge is ignored and the client sends the response as
22695 .option client_send plaintext string&!! unset
22696 The string is a colon-separated list of authentication data strings. Each
22697 string is independently expanded before being sent to the server. The first
22698 string is sent with the AUTH command; any more strings are sent in response
22699 to prompts from the server. Before each string is expanded, the value of the
22700 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
22701 with &$auth1$& for the first prompt. Up to three prompts are stored in this
22702 way. Thus, the prompt that is received in response to sending the first string
22703 (with the AUTH command) can be used in the expansion of the second string, and
22704 so on. If an invalid base64 string is received when
22705 &%client_ignore_invalid_base64%& is set, an empty string is put in the
22706 &$auth$&<&'n'&> variable.
22708 &*Note*&: You cannot use expansion to create multiple strings, because
22709 splitting takes priority and happens first.
22711 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
22712 the data, further processing is applied to each string before it is sent. If
22713 there are any single circumflex characters in the string, they are converted to
22714 NULs. Should an actual circumflex be required as data, it must be doubled in
22717 This is an example of a client configuration that implements the PLAIN
22718 authentication mechanism with a fixed user name and password:
22722 public_name = PLAIN
22723 client_send = ^username^mysecret
22725 The lack of colons means that the entire text is sent with the AUTH
22726 command, with the circumflex characters converted to NULs. A similar example
22727 that uses the LOGIN mechanism is:
22731 public_name = LOGIN
22732 client_send = : username : mysecret
22734 The initial colon means that the first string is empty, so no data is sent with
22735 the AUTH command itself. The remaining strings are sent in response to
22737 .ecindex IIDplaiauth1
22738 .ecindex IIDplaiauth2
22743 . ////////////////////////////////////////////////////////////////////////////
22744 . ////////////////////////////////////////////////////////////////////////////
22746 .chapter "The cram_md5 authenticator"
22747 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
22748 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
22749 .cindex "CRAM-MD5 authentication mechanism"
22750 .cindex "authentication" "CRAM-MD5 mechanism"
22751 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
22752 sends a challenge string to the client, and the response consists of a user
22753 name and the CRAM-MD5 digest of the challenge string combined with a secret
22754 string (password) which is known to both server and client. Thus, the secret
22755 is not sent over the network as plain text, which makes this authenticator more
22756 secure than &(plaintext)&. However, the downside is that the secret has to be
22757 available in plain text at either end.
22760 .section "Using cram_md5 as a server"
22761 .cindex "options" "&(cram_md5)& authenticator (server)"
22762 This authenticator has one server option, which must be set to configure the
22763 authenticator as a server:
22765 .option server_secret cram_md5 string&!! unset
22766 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
22767 When the server receives the client's response, the user name is placed in
22768 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
22769 obtain the password for that user. The server then computes the CRAM-MD5 digest
22770 that the client should have sent, and checks that it received the correct
22771 string. If the expansion of &%server_secret%& is forced to fail, authentication
22772 fails. If the expansion fails for some other reason, a temporary error code is
22773 returned to the client.
22775 For compatibility with previous releases of Exim, the user name is also placed
22776 in &$1$&. However, the use of this variables for this purpose is now
22777 deprecated, as it can lead to confusion in string expansions that also use
22778 numeric variables for other things.
22780 For example, the following authenticator checks that the user name given by the
22781 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
22782 user name, authentication fails.
22786 public_name = CRAM-MD5
22787 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
22788 server_set_id = $auth1
22790 .cindex "&$authenticated_id$&"
22791 If authentication succeeds, the setting of &%server_set_id%& preserves the user
22792 name in &$authenticated_id$&. A more tyical configuration might look up the
22793 secret string in a file, using the user name as the key. For example:
22797 public_name = CRAM-MD5
22798 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}{$value}fail}
22799 server_set_id = $auth1
22801 Note that this expansion explicitly forces failure if the lookup fails
22802 because &$1$& contains an unknown user name.
22805 .section "Using cram_md5 as a client"
22806 .cindex "options" "&(cram_md5)& authenticator (client)"
22807 When used as a client, the &(cram_md5)& authenticator has two options:
22811 .option client_name cram_md5 string&!! "the primary host name"
22812 This string is expanded, and the result used as the user name data when
22813 computing the response to the server's challenge.
22816 .option client_secret cram_md5 string&!! unset
22817 This option must be set for the authenticator to work as a client. Its value is
22818 expanded and the result used as the secret string when computing the response.
22822 .cindex "&$host_address$&"
22823 Different user names and secrets can be used for different servers by referring
22824 to &$host$& or &$host_address$& in the options. Forced failure of either
22825 expansion string is treated as an indication that this authenticator is not
22826 prepared to handle this case. Exim moves on to the next configured client
22827 authenticator. Any other expansion failure causes Exim to give up trying to
22828 send the message to the current server.
22830 A simple example configuration of a &(cram_md5)& authenticator, using fixed
22835 public_name = CRAM-MD5
22837 client_secret = secret
22839 .ecindex IIDcramauth1
22840 .ecindex IIDcramauth2
22844 . ////////////////////////////////////////////////////////////////////////////
22845 . ////////////////////////////////////////////////////////////////////////////
22847 .chapter "The cyrus_sasl authenticator"
22848 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
22849 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
22850 .cindex "Cyrus" "SASL library"
22851 The code for this authenticator was provided by Matthew Byng-Maddick of A L
22852 Digital Ltd (&url(http://www.aldigital.co.uk)).
22854 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
22855 library implementation of the RFC 2222 (&"Simple Authentication and Security
22856 Layer"&). This library supports a number of authentication mechanisms,
22857 including PLAIN and LOGIN, but also several others that Exim does not support
22858 directly. In particular, there is support for Kerberos authentication.
22860 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
22861 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
22862 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
22863 name of the driver to determine which mechanism to support.
22865 Where access to some kind of secret file is required, for example in GSSAPI
22866 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
22867 user, and that the Cyrus SASL library has no way of escalating privileges
22868 by default. You may also find you need to set environment variables,
22869 depending on the driver you are using.
22872 .section "Using cyrus_sasl as a server"
22873 The &(cyrus_sasl)& authenticator has four private options. It puts the username
22874 (on a successful authentication) into &$auth1$&. For compatibility with
22875 previous releases of Exim, the username is also placed in &$1$&. However, the
22876 use of this variable for this purpose is now deprecated, as it can lead to
22877 confusion in string expansions that also use numeric variables for other
22881 .option server_hostname cyrus_sasl string&!! &`$primary_hostname`&
22882 This option selects the hostname that is used when communicating with
22883 the library. It is up to the underlying SASL plug-in what it does with
22887 .option server_mech cyrus_sasl string &`public_name`&
22888 This option selects the authentication mechanism this driver should
22889 use. It allows you to use a different underlying mechanism from the
22890 advertised name. For example:
22893 driver = cyrus_sasl
22894 public_name = X-ANYTHING
22895 server_mech = CRAM-MD5
22896 server_set_id = $auth1
22899 .option server_realm cyrus_sasl string unset
22900 This specifies the SASL realm that the server claims to be in.
22903 .option server_service cyrus_sasl string &`smtp`&
22904 This is the SASL service that the server claims to implement.
22907 For straightforward cases, you do not need to set any of the authenticator's
22908 private options. All you need to do is to specify an appropriate mechanism as
22909 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
22910 PLAIN, you could have two authenticators as follows:
22913 driver = cyrus_sasl
22914 public_name = CRAM-MD5
22915 server_set_id = $auth1
22918 driver = cyrus_sasl
22919 public_name = PLAIN
22920 server_set_id = $auth1
22922 Cyrus SASL does implement the LOGIN authentication method, even though it is
22923 not a standard method. It is disabled by default in the source distribution,
22924 but it is present in many binary distributions.
22925 .ecindex IIDcyrauth1
22926 .ecindex IIDcyrauth2
22931 . ////////////////////////////////////////////////////////////////////////////
22932 . ////////////////////////////////////////////////////////////////////////////
22934 .chapter "The spa authenticator" "CHAPspa"
22935 .scindex IIDspaauth1 "&(spa)& authenticator"
22936 .scindex IIDspaauth2 "authenticators" "&(spa)&"
22937 .cindex "authentication" "Microsoft Secure Password"
22938 .cindex "authentication" "NTLM"
22939 .cindex "Microsoft Secure Password Authentication"
22940 .cindex "NTLM authentication"
22941 The &(spa)& authenticator provides client support for Microsoft's &'Secure
22942 Password Authentication'& mechanism,
22943 which is also sometimes known as NTLM (NT LanMan). The code for client side of
22944 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
22945 taken from the Samba project (&url(http://www.samba.org)). The code for the
22946 server side was subsequently contributed by Tom Kistner. The mechanism works as
22950 After the AUTH command has been accepted, the client sends an SPA
22951 authentication request based on the user name and optional domain.
22953 The server sends back a challenge.
22955 The client builds a challenge response which makes use of the user's password
22956 and sends it to the server, which then accepts or rejects it.
22959 Encryption is used to protect the password in transit.
22963 .section "Using spa as a server"
22964 .cindex "options" "&(spa)& authenticator (server)"
22965 The &(spa)& authenticator has just one server option:
22967 .option server_password spa string&!! unset
22968 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
22969 This option is expanded, and the result must be the cleartext password for the
22970 authenticating user, whose name is at this point in &$auth1$&. For
22971 compatibility with previous releases of Exim, the user name is also placed in
22972 &$1$&. However, the use of this variable for this purpose is now deprecated, as
22973 it can lead to confusion in string expansions that also use numeric variables
22974 for other things. For example:
22979 server_password = \
22980 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
22982 If the expansion is forced to fail, authentication fails. Any other expansion
22983 failure causes a temporary error code to be returned.
22989 .section "Using spa as a client"
22990 .cindex "options" "&(spa)& authenticator (client)"
22991 The &(spa)& authenticator has the following client options:
22995 .option client_domain spa string&!! unset
22996 This option specifies an optional domain for the authentication.
22999 .option client_password spa string&!! unset
23000 This option specifies the user's password, and must be set.
23003 .option client_username spa string&!! unset
23004 This option specifies the user name, and must be set. Here is an example of a
23005 configuration of this authenticator for use with the mail servers at
23011 client_username = msn/msn_username
23012 client_password = msn_plaintext_password
23013 client_domain = DOMAIN_OR_UNSET
23015 .ecindex IIDspaauth1
23016 .ecindex IIDspaauth2
23022 . ////////////////////////////////////////////////////////////////////////////
23023 . ////////////////////////////////////////////////////////////////////////////
23025 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
23026 "Encrypted SMTP connections"
23027 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
23028 .scindex IIDencsmtp2 "SMTP" "encryption"
23029 .cindex "TLS" "on SMTP connection"
23032 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
23033 Sockets Layer), is implemented by making use of the OpenSSL library or the
23034 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
23035 cryptographic code in the Exim distribution itself for implementing TLS. In
23036 order to use this feature you must install OpenSSL or GnuTLS, and then build a
23037 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
23038 You also need to understand the basic concepts of encryption at a managerial
23039 level, and in particular, the way that public keys, private keys, and
23040 certificates are used.
23042 RFC 3207 defines how SMTP connections can make use of encryption. Once a
23043 connection is established, the client issues a STARTTLS command. If the
23044 server accepts this, the client and the server negotiate an encryption
23045 mechanism. If the negotiation succeeds, the data that subsequently passes
23046 between them is encrypted.
23048 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
23049 and if so, what cipher suite is in use, whether the client supplied a
23050 certificate, and whether or not that certificate was verified. This makes it
23051 possible for an Exim server to deny or accept certain commands based on the
23054 &*Warning*&: Certain types of firewall and certain anti-virus products can
23055 disrupt TLS connections. You need to turn off SMTP scanning for these products
23056 in order to get TLS to work.
23060 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol"
23061 .cindex "ssmtp protocol"
23062 .cindex "smtps protocol"
23063 .cindex "SMTP" "ssmtp protocol"
23064 .cindex "SMTP" "smtps protocol"
23065 Early implementations of encrypted SMTP used a different TCP port from normal
23066 SMTP, and expected an encryption negotiation to start immediately, instead of
23067 waiting for a STARTTLS command from the client using the standard SMTP
23068 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
23069 allocated for this purpose.
23071 This approach was abandoned when encrypted SMTP was standardised, but there are
23072 still some legacy clients that use it. Exim supports these clients by means of
23073 the &%tls_on_connect_ports%& global option. Its value must be a list of port
23074 numbers; the most common use is expected to be:
23076 tls_on_connect_ports = 465
23078 The port numbers specified by this option apply to all SMTP connections, both
23079 via the daemon and via &'inetd'&. You still need to specify all the ports that
23080 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
23081 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
23082 an extra port &-- rather, it specifies different behaviour on a port that is
23085 There is also a &%-tls-on-connect%& command line option. This overrides
23086 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
23093 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
23094 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
23095 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
23096 followed later, when the first versions of GnuTLS were released. To build Exim
23097 to use GnuTLS, you need to set
23101 in Local/Makefile, in addition to
23105 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
23106 include files and libraries for GnuTLS can be found.
23108 There are some differences in usage when using GnuTLS instead of OpenSSL:
23111 The &%tls_verify_certificates%& option must contain the name of a file, not the
23112 name of a directory (for OpenSSL it can be either).
23114 The &%tls_dhparam%& option is ignored, because early versions of GnuTLS had no
23115 facility for varying its Diffie-Hellman parameters. I understand that this has
23116 changed, but Exim has not been updated to provide this facility.
23118 .cindex "&$tls_peerdn$&"
23119 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
23120 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
23121 affects the value of the &$tls_peerdn$& variable.
23123 OpenSSL identifies cipher suites using hyphens as separators, for example:
23124 DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA_ARCFOUR_SHA. What is
23125 more, OpenSSL complains if underscores are present in a cipher list. To make
23126 life simpler, Exim changes underscores to hyhens for OpenSSL and hyphens to
23127 underscores for GnuTLS when processing lists of cipher suites in the
23128 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
23131 The &%tls_require_ciphers%& options operate differently, as described in the
23132 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
23136 .section "GnuTLS parameter computation"
23137 GnuTLS uses RSA and D-H parameters that take a substantial amount of time to
23138 compute. It is unreasonable to re-compute them for every TLS session.
23139 Therefore, Exim keeps this data in a file in its spool directory, called
23140 &_gnutls-params_&. The file is owned by the Exim user and is readable only by
23141 its owner. Every Exim process that start up GnuTLS reads the RSA and D-H
23142 parameters from this file. If the file does not exist, the first Exim process
23143 that needs it computes the data and writes it to a temporary file which is
23144 renamed once it is complete. It does not matter if several Exim processes do
23145 this simultaneously (apart from wasting a few resources). Once a file is in
23146 place, new Exim processes immediately start using it.
23148 For maximum security, the parameters that are stored in this file should be
23149 recalculated periodically, the frequency depending on your paranoia level.
23150 Arranging this is easy in principle; just delete the file when you want new
23151 values to be computed. However, there may be a problem. The calculation of new
23152 parameters needs random numbers, and these are obtained from &_/dev/random_&.
23153 If the system is not very active, &_/dev/random_& may delay returning data
23154 until enough randomness (entropy) is available. This may cause Exim to hang for
23155 a substantial amount of time, causing timeouts on incoming connections.
23157 The solution is to generate the parameters externally to Exim. They are stored
23158 in &_gnutls-params_& in PEM format, which means that they can be generated
23159 externally using the &(certtool)& command that is part of GnuTLS.
23161 To replace the parameters with new ones, instead of deleting the file
23162 and letting Exim re-create it, you can generate new parameters using
23163 &(certtool)& and, when this has been done, replace Exim's cache file by
23164 renaming. The relevant commands are something like this:
23168 # chown exim:exim new-params
23169 # chmod 0400 new-params
23170 # certtool --generate-privkey --bits 512 >new-params
23171 # echo "" >>new-params
23172 # certtool --generate-dh-params --bits 1024 >> new-params
23173 # mv new-params gnutls-params
23175 If Exim never has to generate the parameters itself, the possibility of
23176 stalling is removed.
23179 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
23180 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
23181 .cindex "&%tls_require_ciphers%&" "OpenSSL"
23182 There is a function in the OpenSSL library that can be passed a list of cipher
23183 suites before the cipher negotiation takes place. This specifies which ciphers
23184 are acceptable. The list is colon separated and may contain names like
23185 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
23186 directly to this function call. The following quotation from the OpenSSL
23187 documentation specifies what forms of item are allowed in the cipher string:
23190 It can consist of a single cipher suite such as RC4-SHA.
23192 It can represent a list of cipher suites containing a certain algorithm,
23193 or cipher suites of a certain type. For example SHA1 represents all
23194 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
23197 Lists of cipher suites can be combined in a single cipher string using
23198 the + character. This is used as a logical and operation. For example
23199 SHA1+DES represents all cipher suites containing the SHA1 and the DES
23203 Each cipher string can be optionally preceded by one of the characters &`!`&,
23206 If &`!`& is used, the ciphers are permanently deleted from the list. The
23207 ciphers deleted can never reappear in the list even if they are explicitly
23210 If &`-`& is used, the ciphers are deleted from the list, but some or all
23211 of the ciphers can be added again by later options.
23213 If &`+`& is used, the ciphers are moved to the end of the list. This
23214 option does not add any new ciphers; it just moves matching existing ones.
23217 If none of these characters is present, the string is interpreted as
23218 a list of ciphers to be appended to the current preference list. If the list
23219 includes any ciphers already present they will be ignored: that is, they will
23220 not be moved to the end of the list.
23226 .section "Requiring specific ciphers in GnuTLS" "SECTreqciphgnu"
23227 .cindex "TLS" "requiring specific ciphers (GnuTLS)"
23228 .cindex "&%tls_require_ciphers%&" "GnuTLS"
23229 The GnuTLS library does not have a combined function like OpenSSL. Instead,
23230 it allows the caller to specify separate lists of key-exchange methods,
23231 main cipher algorithms, and MAC algorithms. Unfortunately, these lists are
23232 numerical, and the library does not have a function for turning names into
23233 numbers. Consequently, the list of recognized names has to be built into
23236 At present, Exim permits only the list of main cipher algorithms to be
23237 changed. The &%tls_require_ciphers%& option is in the same format as for
23238 OpenSSL. Exim searches each item for the name of available algorithm. For
23239 example, if the list contains RSA_AES_SHA then AES is recognized.
23241 The cipher algorithms list starts out with a default set of algorithms. If
23242 the first item in &%tls_require_ciphers%& does &'not'& start with an
23243 exclamation mark, all the default items are deleted. Thus, only those specified
23244 can be used. If the first item in &%tls_require_ciphers%& &'does'& start with
23245 an exclamation mark, the defaults are left on the list.
23247 Then, any item that starts with an exclamation mark causes the relevant
23248 algorithms to be removed from the list, and any item that does not start
23249 with an exclamation mark causes the relevant algorithms to be added to the
23252 tls_require_ciphers = !RSA_ARCFOUR_SHA
23254 allows all the defaults except those that use ARCFOUR, whereas
23256 tls_require_ciphers = AES : 3DES
23258 allows only cipher suites that use AES and 3DES. The currently recognized
23259 algorithms are: AES_256, AES_128, AES (both of the preceding), 3DES, and
23260 ARCFOUR_128. Unrecognized algorithms are ignored. In a server, the order of the
23261 list is unimportant; the server will advertise the availability of all the
23262 relevant cipher suites. However, in a client, the order of the list specifies a
23263 preference order for the algorithms. The first one in the client's list that is
23264 also advertised by the server is tried first. The default order is as listed
23270 .section "Configuring an Exim server to use TLS"
23271 .cindex "TLS" "configuring an Exim server"
23272 When Exim has been built with TLS support, it advertises the availability of
23273 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
23274 but not to any others. The default value of this option is unset, which means
23275 that STARTTLS is not advertised at all. This default is chosen because you
23276 need to set some other options in order to make TLS avaliable, and also it is
23277 sensible for systems that want to use TLS only as a client.
23279 If a client issues a STARTTLS command and there is some configuration
23280 problem in the server, the command is rejected with a 454 error. If the client
23281 persists in trying to issue SMTP commands, all except QUIT are rejected
23284 554 Security failure
23286 If a STARTTLS command is issued within an existing TLS session, it is
23287 rejected with a 554 error code.
23289 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
23290 match some hosts. You can, of course, set it to * to match all hosts.
23291 However, this is not all you need to do. TLS sessions to a server won't work
23292 without some further configuration at the server end.
23294 It is rumoured that all existing clients that support TLS/SSL use RSA
23295 encryption. To make this work you need to set, in the server,
23297 tls_certificate = /some/file/name
23298 tls_privatekey = /some/file/name
23300 These options are, in fact, expanded strings, so you can make them depend on
23301 the identity of the client that is connected if you wish. The first file
23302 contains the server's X509 certificate, and the second contains the private key
23303 that goes with it. These files need to be readable by the Exim user, and must
23304 always be given as full path names. They can be the same file if both the
23305 certificate and the key are contained within it. If &%tls_privatekey%& is not
23306 set, or if its expansion is forced to fail or results in an empty string, this
23307 is assumed to be the case. The certificate file may also contain intermediate
23308 certificates that need to be sent to the client to enable it to authenticate
23309 the server's certificate.
23311 If you do not understand about certificates and keys, please try to find a
23312 source of this background information, which is not Exim-specific. (There are a
23313 few comments below in section &<<SECTcerandall>>&.)
23315 &*Note*&: These options do not apply when Exim is operating as a client &--
23316 they apply only in the case of a server. If you need to use a certificate in an
23317 Exim client, you must set the options of the same names in an &(smtp)&
23320 With just these options, an Exim server will be able to use TLS. It does not
23321 require the client to have a certificate (but see below for how to insist on
23322 this). There is one other option that may be needed in other situations. If
23324 tls_dhparam = /some/file/name
23326 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
23327 with the parameters contained in the file. This increases the set of cipher
23328 suites that the server supports. See the command
23332 for a way of generating this data. At present, &%tls_dhparam%& is used only
23333 when Exim is linked with OpenSSL. It is ignored if GnuTLS is being used.
23335 The strings supplied for these three options are expanded every time a client
23336 host connects. It is therefore possible to use different certificates and keys
23337 for different hosts, if you so wish, by making use of the client's IP address
23338 in &$sender_host_address$& to control the expansion. If a string expansion is
23339 forced to fail, Exim behaves as if the option is not set.
23341 .cindex "cipher" "logging"
23342 .cindex "log" "TLS cipher"
23343 .cindex "&$tls_cipher$&"
23344 The variable &$tls_cipher$& is set to the cipher suite that was negotiated for
23345 an incoming TLS connection. It is included in the &'Received:'& header of an
23346 incoming message (by default &-- you can, of course, change this), and it is
23347 also included in the log line that records a message's arrival, keyed by
23348 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
23349 condition can be used to test for specific cipher suites in ACLs.
23351 The ACLs that run for subsequent SMTP commands can check the name of the cipher
23352 suite and vary their actions accordingly. The cipher suite names are those used
23353 by OpenSSL. These may differ from the names used elsewhere. For example,
23354 OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other contexts
23355 is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL
23356 documentation for more details.
23360 .section "Requesting and verifying client certificates"
23361 .cindex "certificate" "verification of client"
23362 .cindex "TLS" "client certificate verification"
23363 If you want an Exim server to request a certificate when negotiating a TLS
23364 session with a client, you must set either &%tls_verify_hosts%& or
23365 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
23366 apply to all TLS connections. For any host that matches one of these options,
23367 Exim requests a certificate as part of the setup of the TLS session. The
23368 contents of the certificate are verified by comparing it with a list of
23369 expected certificates. These must be available in a file or,
23370 for OpenSSL only (not GnuTLS), a directory, identified by
23371 &%tls_verify_certificates%&.
23373 A file can contain multiple certificates, concatenated end to end. If a
23376 each certificate must be in a separate file, with a name (or a symbolic link)
23377 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
23378 certificate. You can compute the relevant hash by running the command
23380 openssl x509 -hash -noout -in /cert/file
23382 where &_/cert/file_& contains a single certificate.
23384 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
23385 what happens if the client does not supply a certificate, or if the certificate
23386 does not match any of the certificates in the collection named by
23387 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
23388 attempt to set up a TLS session is aborted, and the incoming connection is
23389 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
23390 session continues. ACLs that run for subsequent SMTP commands can detect the
23391 fact that no certificate was verified, and vary their actions accordingly. For
23392 example, you can insist on a certificate before accepting a message for
23393 relaying, but not when the message is destined for local delivery.
23395 .cindex "&$tls_peerdn$&"
23396 When a client supplies a certificate (whether it verifies or not), the value of
23397 the Distinguished Name of the certificate is made available in the variable
23398 &$tls_peerdn$& during subsequent processing of the message.
23400 .cindex "log" "distinguished name"
23401 Because it is often a long text string, it is not included in the log line or
23402 &'Received:'& header by default. You can arrange for it to be logged, keyed by
23403 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
23404 &%received_header_text%& to change the &'Received:'& header. When no
23405 certificate is supplied, &$tls_peerdn$& is empty.
23408 .section "Revoked certificates"
23409 .cindex "TLS" "revoked certificates"
23410 .cindex "revocation list"
23411 .cindex "certificate" "revocation list"
23412 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
23413 certificates are revoked. If you have such a list, you can pass it to an Exim
23414 server using the global option called &%tls_crl%& and to an Exim client using
23415 an identically named option for the &(smtp)& transport. In each case, the value
23416 of the option is expanded and must then be the name of a file that contains a
23420 .section "Configuring an Exim client to use TLS"
23421 .cindex "cipher" "logging"
23422 .cindex "log" "TLS cipher"
23423 .cindex "log" "distinguished name"
23424 .cindex "TLS" "configuring an Exim client"
23425 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
23426 deliveries as well as to incoming, the latter one causing logging of the
23427 server certificate's DN. The remaining client configuration for TLS is all
23428 within the &(smtp)& transport.
23430 It is not necessary to set any options to have TLS work in the &(smtp)&
23431 transport. If Exim is built with TLS support, and TLS is advertised by a
23432 server, the &(smtp)& transport always tries to start a TLS session. However,
23433 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
23434 transport) to a list of server hosts for which TLS should not be used.
23436 If you do not want Exim to attempt to send messages unencrypted when an attempt
23437 to set up an encrypted connection fails in any way, you can set
23438 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
23439 those hosts, delivery is always deferred if an encrypted connection cannot be
23440 set up. If there are any other hosts for the address, they are tried in the
23443 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
23444 the message unencrypted. It always does this if the response to STARTTLS is
23445 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
23446 session after a success response code, what happens is controlled by the
23447 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
23448 delivery to this host is deferred, and other hosts (if available) are tried. If
23449 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
23450 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
23451 negotiation fails, Exim closes the current connection (because it is in an
23452 unknown state), opens a new one to the same host, and then tries the delivery
23456 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
23457 transport provide the client with a certificate, which is passed to the server
23458 if it requests it. If the server is Exim, it will request a certificate only if
23459 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. &*Note*&:
23460 These options must be set in the &(smtp)& transport for Exim to use TLS when it
23461 is operating as a client. Exim does not assume that a server certificate (set
23462 by the global options of the same name) should also be used when operating as a
23465 If &%tls_verify_certificates%& is set, it must name a file or,
23466 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
23467 expected server certificates. The client verifies the server's certificate
23468 against this collection, taking into account any revoked certificates that are
23469 in the list defined by &%tls_crl%&.
23472 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
23473 list of permitted cipher suites. If either of these checks fails, delivery to
23474 the current host is abandoned, and the &(smtp)& transport tries to deliver to
23475 alternative hosts, if any.
23478 .cindex "&$host_address$&"
23479 All the TLS options in the &(smtp)& transport are expanded before use, with
23480 &$host$& and &$host_address$& containing the name and address of the server to
23481 which the client is connected. Forced failure of an expansion causes Exim to
23482 behave as if the relevant option were unset.
23486 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
23488 .cindex "multiple SMTP deliveries with TLS"
23489 .cindex "TLS" "multiple message deliveries"
23490 Exim sends multiple messages down the same TCP/IP connection by starting up
23491 an entirely new delivery process for each message, passing the socket from
23492 one process to the next. This implementation does not fit well with the use
23493 of TLS, because there is quite a lot of state information associated with a TLS
23494 connection, not just a socket identification. Passing all the state information
23495 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
23496 session before passing the socket to a new process. The new process may then
23497 try to start a new TLS session, and if successful, may try to re-authenticate
23498 if AUTH is in use, before sending the next message.
23500 The RFC is not clear as to whether or not an SMTP session continues in clear
23501 after TLS has been shut down, or whether TLS may be restarted again later, as
23502 just described. However, if the server is Exim, this shutdown and
23503 reinitialization works. It is not known which (if any) other servers operate
23504 successfully if the client closes a TLS session and continues with unencrypted
23505 SMTP, but there are certainly some that do not work. For such servers, Exim
23506 should not pass the socket to another process, because the failure of the
23507 subsequent attempt to use it would cause Exim to record a temporary host error,
23508 and delay other deliveries to that host.
23510 To test for this case, Exim sends an EHLO command to the server after
23511 closing down the TLS session. If this fails in any way, the connection is
23512 closed instead of being passed to a new delivery process, but no retry
23513 information is recorded.
23515 There is also a manual override; you can set &%hosts_nopass_tls%& on the
23516 &(smtp)& transport to match those hosts for which Exim should not pass
23517 connections to new processes if TLS has been used.
23522 .section "Certificates and all that" "SECTcerandall"
23523 .cindex "certificate" "references to discussion"
23524 In order to understand fully how TLS works, you need to know about
23525 certificates, certificate signing, and certificate authorities. This is not the
23526 place to give a tutorial, especially as I do not know very much about it
23527 myself. Some helpful introduction can be found in the FAQ for the SSL addition
23528 to Apache, currently at
23530 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
23532 Other parts of the &'modssl'& documentation are also helpful, and have
23533 links to further files.
23534 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
23535 0-201-61598-3), contains both introductory and more in-depth descriptions.
23536 Some sample programs taken from the book are available from
23538 &url(http://www.rtfm.com/openssl-examples/)
23542 .section "Certificate chains"
23543 The file named by &%tls_certificate%& may contain more than one
23544 certificate. This is useful in the case where the certificate that is being
23545 sent is validated by an intermediate certificate which the other end does
23546 not have. Multiple certificates must be in the correct order in the file.
23547 First the host's certificate itself, then the first intermediate
23548 certificate to validate the issuer of the host certificate, then the next
23549 intermediate certificate to validate the issuer of the first intermediate
23550 certificate, and so on, until finally (optionally) the root certificate.
23551 The root certificate must already be trusted by the recipient for
23552 validation to succeed, of course, but if it's not preinstalled, sending the
23553 root certificate along with the rest makes it available for the user to
23554 install if the receiving end is a client MUA that can interact with a user.
23557 .section "Self-signed certificates"
23558 .cindex "certificate" "self-signed"
23559 You can create a self-signed certificate using the &'req'& command provided
23560 with OpenSSL, like this:
23562 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
23565 &_file1_& and &_file2_& can be the same file; the key and the certificate are
23566 delimited and so can be identified independently. The &%-days%& option
23567 specifies a period for which the certificate is valid. The &%-nodes%& option is
23568 important: if you do not set it, the key is encrypted with a passphrase
23569 that you are prompted for, and any use that is made of the key causes more
23570 prompting for the passphrase. This is not helpful if you are going to use
23571 this certificate and key in an MTA, where prompting is not possible.
23573 A self-signed certificate made in this way is sufficient for testing, and
23574 may be adequate for all your requirements if you are mainly interested in
23575 encrypting transfers, and not in secure identification.
23577 However, many clients require that the certificate presented by the server be a
23578 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
23579 certificate. In this situation, the self-signed certificate described above
23580 must be installed on the client host as a trusted root &'certification
23581 authority'& (CA), and the certificate used by Exim must be a user certificate
23582 signed with that self-signed certificate.
23584 For information on creating self-signed CA certificates and using them to sign
23585 user certificates, see the &'General implementation overview'& chapter of the
23586 Open-source PKI book, available online at
23587 &url(http://ospkibook.sourceforge.net/).
23588 .ecindex IIDencsmtp1
23589 .ecindex IIDencsmtp2
23593 . ////////////////////////////////////////////////////////////////////////////
23594 . ////////////////////////////////////////////////////////////////////////////
23596 .chapter "Access control lists" "CHAPACL"
23597 .scindex IIDacl "&ACL;" "description"
23598 .cindex "control of incoming mail"
23599 .cindex "message" "controlling incoming"
23600 .cindex "policy control" "access control lists"
23601 Access Control Lists (ACLs) are defined in a separate section of the run time
23602 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
23603 name, terminated by a colon. Here is a complete ACL section that contains just
23604 one very small ACL:
23609 accept hosts = one.host.only
23611 You can have as many lists as you like in the ACL section, and the order in
23612 which they appear does not matter. The lists are self-terminating.
23614 The majority of ACLs are used to control Exim's behaviour when it receives
23615 certain SMTP commands. This applies both to incoming TCP/IP connections, and
23616 when a local process submits a message using SMTP by specifying the &%-bs%&
23617 option. The most common use is for controlling which recipients are accepted
23618 in incoming messages. In addition, you can define an ACL that is used to check
23619 local non-SMTP messages. The default configuration file contains an example of
23620 a realistic ACL for checking RCPT commands. This is discussed in chapter
23621 &<<CHAPdefconfil>>&.
23624 .section "Testing ACLs"
23625 The &%-bh%& command line option provides a way of testing your ACL
23626 configuration locally by running a fake SMTP session with which you interact.
23627 The host &'relay-test.mail-abuse.org'& provides a service for checking your
23628 relaying configuration (see section &<<SECTcheralcon>>& for more details).
23632 .section "Specifying when ACLs are used"
23633 .cindex "&ACL;" "options for specifying"
23634 In order to cause an ACL to be used, you have to name it in one of the relevant
23635 options in the main part of the configuration. These options are:
23636 .cindex "AUTH" "ACL for"
23637 .cindex "DATA" "ACLs for"
23638 .cindex "ETRN" "ACL for"
23639 .cindex "EXPN" "ACL for"
23640 .cindex "HELO" "ACL for"
23641 .cindex "EHLO" "ACL for"
23642 .cindex "MAIL" "ACL for"
23643 .cindex "QUIT" "ACL for"
23644 .cindex "RCPT" "ACL for"
23645 .cindex "STARTTLS" "ACL for"
23646 .cindex "VRFY" "ACL for"
23647 .cindex "SMTP connection" "ACL for"
23648 .cindex "non-smtp message" "ACL for"
23649 .cindex "MIME parts" "ACL for"
23652 .row &~&%acl_not_smtp%& "ACL for non-SMTP messages"
23653 .row &~&%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
23654 .row &~&%acl_not_smtp_start%& "ACL at start of non-SMTP message"
23655 .row &~&%acl_smtp_auth%& "ACL for AUTH"
23656 .row &~&%acl_smtp_connect%& "ACL for start of SMTP connection"
23657 .row &~&%acl_smtp_data%& "ACL after DATA is complete"
23658 .row &~&%acl_smtp_etrn%& "ACL for ETRN"
23659 .row &~&%acl_smtp_expn%& "ACL for EXPN"
23660 .row &~&%acl_smtp_helo%& "ACL for HELO or EHLO"
23661 .row &~&%acl_smtp_mail%& "ACL for MAIL"
23662 .row &~&%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
23663 .row &~&%acl_smtp_mime%& "ACL for content-scanning MIME parts"
23664 .row &~&%acl_smtp_predata%& "ACL at start of DATA command"
23665 .row &~&%acl_smtp_quit%& "ACL for QUIT"
23666 .row &~&%acl_smtp_rcpt%& "ACL for RCPT"
23667 .row &~&%acl_smtp_starttls%& "ACL for STARTTLS"
23668 .row &~&%acl_smtp_vrfy%& "ACL for VRFY"
23671 For example, if you set
23673 acl_smtp_rcpt = small_acl
23675 the little ACL defined above is used whenever Exim receives a RCPT command
23676 in an SMTP dialogue. The majority of policy tests on incoming messages can be
23677 done when RCPT commands arrive. A rejection of RCPT should cause the
23678 sending MTA to give up on the recipient address contained in the RCPT
23679 command, whereas rejection at other times may cause the client MTA to keep on
23680 trying to deliver the message. It is therefore recommended that you do as much
23681 testing as possible at RCPT time.
23684 .section "The non-SMTP ACL"
23685 .cindex "non-smtp message" "ACL for"
23686 The non-SMTP ACL applies to all non-interactive incoming messages, that is, it
23687 applies to batch SMTP as well as to non-SMTP messages. (Batch SMTP is not
23688 really SMTP.) This ACL is run just before the &[local_scan()]& function. Any
23689 kind of rejection is treated as permanent, because there is no way of sending a
23690 temporary error for these kinds of message. Many of the ACL conditions (for
23691 example, host tests, and tests on the state of the SMTP connection such as
23692 encryption and authentication) are not relevant and are forbidden in this ACL.
23695 .section "The connect ACL"
23696 .cindex "SMTP connection" "ACL for"
23697 The ACL test specified by &%acl_smtp_connect%& happens after the test specified
23698 by &%host_reject_connection%& (which is now an anomaly) and any TCP Wrappers
23699 testing (if configured).
23702 .section "The DATA ACLs"
23703 .cindex "DATA" "ACLs for"
23704 Two ACLs are associated with the DATA command, because it is two-stage
23705 command, with two responses being sent to the client.
23706 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
23707 is obeyed. This gives you control after all the RCPT commands, but before
23708 the message itself is received. It offers the opportunity to give a negative
23709 response to the DATA command before the data is transmitted. Header lines
23710 added by MAIL or RCPT ACLs are not visible at this time, but any that
23711 are defined here are visible when the &%acl_smtp_data%& ACL is run.
23713 You cannot test the contents of the message, for example, to verify addresses
23714 in the headers, at RCPT time or when the DATA command is received. Such
23715 tests have to appear in the ACL that is run after the message itself has been
23716 received, before the final response to the DATA command is sent. This is
23717 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
23718 associated with the DATA command.
23720 For both of these ACLs, it is not possible to reject individual recipients. An
23721 error response rejects the entire message. Unfortunately, it is known that some
23722 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
23723 before or after the data) correctly &-- they keep the message on their queues
23724 and try again later, but that is their problem, though it does waste some of
23728 .section "The MIME ACL"
23729 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
23730 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
23733 .section "The QUIT ACL" "SECTQUITACL"
23734 .cindex "QUIT" "ACL for"
23735 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
23736 does not affect the response code to QUIT, which is always 221. Thus, the ACL
23737 does not in fact control any access. For this reason, the only verbs that are
23738 permitted are &%accept%& and &%warn%&.
23740 This ACL can be used for tasks such as custom logging at the end of an SMTP
23741 session. For example, you can use ACL variables in other ACLs to count
23742 messages, recipients, etc., and log the totals at QUIT time using one or
23743 more &%logwrite%& modifiers on a &%warn%& verb.
23745 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
23746 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
23748 You do not need to have a final &%accept%&, but if you do, you can use a
23749 &%message%& modifier to specify custom text that is sent as part of the 221
23752 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
23753 failure (for example, failure to open a log file, or when Exim is bombing out
23754 because it has detected an unrecoverable error), all SMTP commands from the
23755 client are given temporary error responses until QUIT is received or the
23756 connection is closed. In these special cases, the QUIT ACL does not run.
23760 .section "Finding an ACL to use"
23761 .cindex "&ACL;" "finding which to use"
23762 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
23763 you can use different ACLs in different circumstances. For example,
23765 acl_smtp_rcpt = ${if ={25}{$interface_port} \
23766 {acl_check_rcpt} {acl_check_rcpt_submit} }
23768 In the default configuration file there are some example settings for
23769 providing an RFC 4409 message submission service on port 587 and a
23770 non-standard &"smtps"& service on port 465. You can use a string
23771 expansion like this to choose an ACL for MUAs on these ports which is
23772 more appropriate for this purpose than the default ACL on port 25.
23774 The expanded string does not have to be the name of an ACL in the
23775 configuration file; there are other possibilities. Having expanded the
23776 string, Exim searches for an ACL as follows:
23779 If the string begins with a slash, Exim uses it as a file name, and reads its
23780 contents as an ACL. The lines are processed in the same way as lines in the
23781 Exim configuration file. In particular, continuation lines are supported, blank
23782 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
23783 If the file does not exist or cannot be read, an error occurs (typically
23784 causing a temporary failure of whatever caused the ACL to be run). For example:
23786 acl_smtp_data = /etc/acls/\
23787 ${lookup{$sender_host_address}lsearch\
23788 {/etc/acllist}{$value}{default}}
23790 This looks up an ACL file to use on the basis of the host's IP address, falling
23791 back to a default if the lookup fails. If an ACL is successfully read from a
23792 file, it is retained in memory for the duration of the Exim process, so that it
23793 can be re-used without having to re-read the file.
23795 If the string does not start with a slash, and does not contain any spaces,
23796 Exim searches the ACL section of the configuration for an ACL whose name
23797 matches the string.
23799 If no named ACL is found, or if the string contains spaces, Exim parses
23800 the string as an inline ACL. This can save typing in cases where you just
23801 want to have something like
23803 acl_smtp_vrfy = accept
23805 in order to allow free use of the VRFY command. Such a string may contain
23806 newlines; it is processed in the same way as an ACL that is read from a file.
23812 .section "ACL return codes"
23813 .cindex "&ACL;" "return codes"
23814 Except for the QUIT ACL, which does not affect the SMTP return code (see
23815 section &<<SECTQUITACL>>& above), the result of running an ACL is either
23816 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
23817 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
23818 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
23819 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
23820 This also causes a 4&'xx'& return code.
23822 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
23823 &"deny"&, because there is no mechanism for passing temporary errors to the
23824 submitters of non-SMTP messages.
23827 ACLs that are relevant to message reception may also return &"discard"&. This
23828 has the effect of &"accept"&, but causes either the entire message or an
23829 individual recipient address to be discarded. In other words, it is a
23830 blackholing facility. Use it with care.
23832 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
23833 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
23834 RCPT ACL is to discard just the one recipient address. If there are no
23835 recipients left when the message's data is received, the DATA ACL is not
23836 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
23837 remaining recipients. The &"discard"& return is not permitted for the
23838 &%acl_smtp_predata%& ACL.
23841 .cindex "&[local_scan()]& function" "when all recipients discarded"
23842 The &[local_scan()]& function is always run, even if there are no remaining
23843 recipients; it may create new recipients.
23847 .section "Unset ACL options"
23848 .cindex "&ACL;" "unset options"
23849 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
23850 all the same. &*Note*&: These defaults apply only when the relevant ACL is
23851 not defined at all. For any defined ACL, the default action when control
23852 reaches the end of the ACL statements is &"deny"&.
23854 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
23855 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
23856 &%acl_smtp_mime%&, &%acl_smtp_predata%&, &%acl_smtp_quit%&, and
23857 &%acl_smtp_starttls%&, the action when the ACL is not defined is &"accept"&.
23859 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
23860 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
23861 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
23862 messages over an SMTP connection. For an example, see the ACL in the default
23863 configuration file.
23868 .section "Data for message ACLs"
23869 .cindex "&ACL;" "data for message ACL"
23871 .cindex &$local_part$&
23872 .cindex &$sender_address$&
23873 .cindex &$sender_host_address$&
23874 .cindex &$smtp_command$&
23875 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
23876 that contain information about the host and the message's sender (for example,
23877 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
23878 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
23879 &$local_part$& are set from the argument address. The entire SMTP command
23880 is available in &$smtp_command$&.
23882 When an ACL for the AUTH parameter of MAIL is running, the variables that
23883 contain information about the host are set, but &$sender_address$& is not yet
23884 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
23887 .cindex "&$message_size$&"
23888 The &$message_size$& variable is set to the value of the SIZE parameter on
23889 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
23890 that parameter is not given. The value is updated to the true message size by
23891 the time the final DATA ACL is run (after the message data has been
23894 .cindex "&$rcpt_count$&"
23895 .cindex "&$recipients_count$&"
23896 The &$rcpt_count$& variable increases by one for each RCPT command received.
23897 The &$recipients_count$& variable increases by one each time a RCPT command is
23898 accepted, so while an ACL for RCPT is being processed, it contains the number
23899 of previously accepted recipients. At DATA time (for both the DATA ACLs),
23900 &$rcpt_count$& contains the total number of RCPT commands, and
23901 &$recipients_count$& contains the total number of accepted recipients.
23907 .section "Data for non-message ACLs" "SECTdatfornon"
23908 .cindex "&ACL;" "data for non-message ACL"
23909 .cindex &$smtp_command_argument$&
23910 .cindex &$smtp_command$&
23911 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
23912 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
23913 and the entire SMTP command is available in &$smtp_command$&.
23914 These variables can be tested using a &%condition%& condition. For example,
23915 here is an ACL for use with AUTH, which insists that either the session is
23916 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
23917 does not permit authentication methods that use cleartext passwords on
23918 unencrypted connections.
23921 accept encrypted = *
23922 accept condition = ${if eq{${uc:$smtp_command_argument}}\
23924 deny message = TLS encryption or CRAM-MD5 required
23926 (Another way of applying this restriction is to arrange for the authenticators
23927 that use cleartext passwords not to be advertised when the connection is not
23928 encrypted. You can use the generic &%server_advertise_condition%& authenticator
23929 option to do this.)
23933 .section "Format of an ACL"
23934 .cindex "&ACL;" "format of"
23935 .cindex "&ACL;" "verbs; definition of"
23936 An individual ACL consists of a number of statements. Each statement starts
23937 with a verb, optionally followed by a number of conditions and &"modifiers"&.
23938 Modifiers can change the way the verb operates, define error and log messages,
23939 set variables, insert delays, and vary the processing of accepted messages.
23941 If all the conditions are met, the verb is obeyed. The same condition may be
23942 used (with different arguments) more than once in the same statement. This
23943 provides a means of specifying an &"and"& conjunction between conditions. For
23946 deny dnslists = list1.example
23947 dnslists = list2.example
23949 If there are no conditions, the verb is always obeyed. Exim stops evaluating
23950 the conditions and modifiers when it reaches a condition that fails. What
23951 happens then depends on the verb (and in one case, on a special modifier). Not
23952 all the conditions make sense at every testing point. For example, you cannot
23953 test a sender address in the ACL that is run for a VRFY command.
23956 .section "ACL verbs"
23957 The ACL verbs are as follows:
23960 .cindex "&%accept%&" "ACL verb"
23961 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
23962 of the conditions are not met, what happens depends on whether &%endpass%&
23963 appears among the conditions (for syntax see below). If the failing condition
23964 is before &%endpass%&, control is passed to the next ACL statement; if it is
23965 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
23966 check a RCPT command:
23968 accept domains = +local_domains
23972 If the recipient domain does not match the &%domains%& condition, control
23973 passes to the next statement. If it does match, the recipient is verified, and
23974 the command is accepted if verification succeeds. However, if verification
23975 fails, the ACL yields &"deny"&, because the failing condition is after
23979 .cindex "&%defer%&" "ACL verb"
23980 &%defer%&: If all the conditions are met, the ACL returns &"defer"& which, in
23981 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
23982 &%defer%& is the same as &%deny%&, because there is no way of sending a
23983 temporary error. For a RCPT command, &%defer%& is much the same as using a
23984 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
23985 be used in any ACL, and even for a recipient it might be a simpler approach.
23987 .cindex "&%deny%&" "ACL verb"
23988 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
23989 the conditions are not met, control is passed to the next ACL statement. For
23992 deny dnslists = blackholes.mail-abuse.org
23994 rejects commands from hosts that are on a DNS black list.
23997 .cindex "&%discard%&" "ACL verb"
23998 &%discard%&: This verb behaves like &%accept%&, except that it returns
23999 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
24000 that are concerned with receiving messages, and it causes recipients to be
24001 discarded. If the &%log_message%& modifier is set when &%discard%& operates,
24002 its contents are added to the line that is automatically written to the log.
24004 If &%discard%& is used in an ACL for RCPT, just the one recipient is
24005 discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
24006 message's recipients are discarded. Recipients that are discarded before
24007 DATA do not appear in the log line when the &%log_recipients%& log selector
24010 .cindex "&%drop%&" "ACL verb"
24011 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
24012 forcibly closed after the 5&'xx'& error message has been sent. For example:
24014 drop message = I don't take more than 20 RCPTs
24015 condition = ${if > {$rcpt_count}{20}}
24017 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
24018 The connection is always dropped after sending a 550 response.
24021 .cindex "&%require%&" "ACL verb"
24022 &%require%&: If all the conditions are met, control is passed to the next ACL
24023 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
24024 example, when checking a RCPT command,
24026 require verify = sender
24028 passes control to subsequent statements only if the message's sender can be
24029 verified. Otherwise, it rejects the command.
24032 .cindex "&%warn%&" "ACL verb"
24033 &%warn%&: If all the conditions are met, a header line is added to an incoming
24034 message and/or a line is written to Exim's main log. In all cases, control
24035 passes to the next ACL statement. The text of the added header line and the log
24036 line are specified by modifiers; if they are not present, a &%warn%& verb just
24037 checks its conditions and obeys any &"immediate"& modifiers such as &%set%& and
24038 &%logwrite%&. There is more about adding header lines in section
24039 &<<SECTaddheadacl>>&.
24041 If any condition on a &%warn%& statement cannot be completed (that is, there is
24042 some sort of defer), no header lines are added and the configured log line is
24043 not written. No further conditions or modifiers in the &%warn%& statement are
24044 processed. The incident is logged, but the ACL continues to be processed, from
24045 the next statement onwards.
24047 If a &%message%& modifier is present on a &%warn%& verb in an ACL that is not
24048 testing an incoming message, it is ignored, and the incident is logged.
24050 A &%warn%& statement may use the &%log_message%& modifier to cause a line to be
24051 written to the main log when the statement's conditions are true.
24052 If an identical log line is requested several times in the same message, only
24053 one copy is actually written to the log. If you want to force duplicates to be
24054 written, use the &%logwrite%& modifier instead.
24056 .cindex "&$acl_verify_message$&"
24057 When one of the &%warn%& conditions is an address verification that fails, the
24058 text of the verification failure message is in &$acl_verify_message$&. If you
24059 want this logged, you must set it up explicitly. For example:
24061 warn !verify = sender
24062 log_message = sender verify failed: $acl_verify_message
24066 At the end of each ACL there is an implicit unconditional &%deny%&.
24068 As you can see from the examples above, the conditions and modifiers are
24069 written one to a line, with the first one on the same line as the verb, and
24070 subsequent ones on following lines. If you have a very long condition, you can
24071 continue it onto several physical lines by the usual backslash continuation
24072 mechanism. It is conventional to align the conditions vertically.
24076 .section "ACL variables" "SECTaclvariables"
24077 .cindex "&ACL;" "variables"
24078 There are some special variables that can be set during ACL processing. They
24079 can be used to pass information between different ACLs, different invocations
24080 of the same ACL in the same SMTP connection, and between ACLs and the routers,
24081 transports, and filters that are used to deliver a message. There are two sets
24082 of these variables:
24085 The values of &$acl_c0$& to &$acl_c19$& persist throughout an SMTP
24086 connection. They are never reset. Thus, a value that is set while receiving one
24087 message is still available when receiving the next message on the same SMTP
24090 The values of &$acl_m0$& to &$acl_m19$& persist only while a message is
24091 being received. They are reset afterwards. They are also reset by MAIL, RSET,
24092 EHLO, HELO, and after starting up a TLS session.
24095 When a message is accepted, the current values of all the ACL variables are
24096 preserved with the message and are subsequently made available at delivery
24097 time. The ACL variables are set by modifier called &%set%&. For example:
24099 accept hosts = whatever
24100 set acl_m4 = some value
24102 &*Note*&: A leading dollar sign is not used when naming a variable that is to
24103 be set. If you want to set a variable without taking any action, you can use a
24104 &%warn%& verb without any other modifiers or conditions.
24108 .section "Condition and modifier processing"
24109 .cindex "&ACL;" "conditions; processing"
24110 .cindex "&ACL;" "modifiers; processing"
24111 An exclamation mark preceding a condition negates its result. For example:
24113 deny domains = *.dom.example
24114 !verify = recipient
24116 causes the ACL to return &"deny"& if the recipient domain ends in
24117 &'dom.example'& and the recipient address cannot be verified. Sometimes
24118 negation can be used on the right-hand side of a condition. For example, these
24119 two statements are equivalent:
24121 deny hosts = !192.168.3.4
24122 deny !hosts = 192.168.3.4
24124 However, for many conditions (&%verify%& being a good example), only left-hand
24125 side negation of the whole condition is possible.
24127 The arguments of conditions and modifiers are expanded. A forced failure
24128 of an expansion causes a condition to be ignored, that is, it behaves as if the
24129 condition is true. Consider these two statements:
24131 accept senders = ${lookup{$host_name}lsearch\
24132 {/some/file}{$value}fail}
24133 accept senders = ${lookup{$host_name}lsearch\
24134 {/some/file}{$value}{}}
24136 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
24137 the returned list is searched, but if the lookup fails the behaviour is
24138 different in the two cases. The &%fail%& in the first statement causes the
24139 condition to be ignored, leaving no further conditions. The &%accept%& verb
24140 therefore succeeds. The second statement, however, generates an empty list when
24141 the lookup fails. No sender can match an empty list, so the condition fails,
24142 and therefore the &%accept%& also fails.
24144 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
24145 specify actions that are taken as the conditions for a statement are checked;
24146 others specify text for messages that are used when access is denied or a
24147 warning is generated. The &%control%& modifier affects the way an incoming
24148 message is handled.
24150 The positioning of the modifiers in an ACL statement important, because the
24151 processing of a verb ceases as soon as its outcome is known. Only those
24152 modifiers that have already been encountered will take effect. For example,
24153 consider this use of the &%message%& modifier:
24155 require message = Can't verify sender
24157 message = Can't verify recipient
24159 message = This message cannot be used
24161 If sender verification fails, Exim knows that the result of the statement is
24162 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
24163 so its text is used as the error message. If sender verification succeeds, but
24164 recipient verification fails, the second message is used. If recipient
24165 verification succeeds, the third message becomes &"current"&, but is never used
24166 because there are no more conditions to cause failure.
24168 For the &%deny%& verb, on the other hand, it is always the last &%message%&
24169 modifier that is used, because all the conditions must be true for rejection to
24170 happen. Specifying more than one &%message%& modifier does not make sense, and
24171 the message can even be specified after all the conditions. For example:
24174 !senders = *@my.domain.example
24175 message = Invalid sender from client host
24177 The &"deny"& result does not happen until the end of the statement is reached,
24178 by which time Exim has set up the message.
24182 .section "ACL modifiers" "SECTACLmodi"
24183 .cindex "&ACL;" "modifiers; list of"
24184 The ACL modifiers are as follows:
24187 .vitem &*add_header*&&~=&~<&'text'&>
24188 This modifier specifies one of more header lines that are to be added to an
24189 incoming message, assuming, of course, that the message is ultimately
24190 accepted. For details, see section &<<SECTaddheadacl>>&.
24192 .vitem &*control*&&~=&~<&'text'&>
24193 .cindex "&%control%&" "ACL modifier"
24194 This modifier affects the subsequent processing of the SMTP connection or of an
24195 incoming message that is accepted. The effect of the first type of control
24196 lasts for the duration of the connection, whereas the effect of the second type
24197 lasts only until the current message has been received. The message-specific
24198 controls always apply to the whole message, not to individual recipients,
24199 even if the &%control%& modifier appears in a RCPT ACL.
24201 As there are now quite a few controls that can be applied, they are described
24202 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
24203 in several different ways. For example:
24205 . ==== As this is a nested list, any displays it contains must be indented
24206 . ==== as otherwise they are too far to the left.
24209 It can be at the end of an &%accept%& statement:
24211 accept ...some conditions
24212 control = queue_only
24214 In this case, the control is applied when this statement yields &"accept"&, in
24215 other words, when the conditions are all true.
24218 It can be in the middle of an &%accept%& statement:
24220 accept ...some conditions...
24221 control = queue_only
24222 ...some more conditions...
24224 If the first set of conditions are true, the control is applied, even if the
24225 statement does not accept because one of the second set of conditions is false.
24226 In this case, some subsequent statement must yield &"accept"& for the control
24230 It can be used with &%warn%& to apply the control, leaving the
24231 decision about accepting or denying to a subsequent verb. For
24234 warn ...some conditions...
24238 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
24239 &%logwrite%&, so it does not add anything to the message and does not write a
24243 If you want to apply a control unconditionally, you can use it with a
24244 &%require%& verb. For example:
24246 require control = no_multiline_response
24250 .vitem &*delay*&&~=&~<&'time'&>
24251 .cindex "&%delay%&" "ACL modifier"
24252 .cindex "&%-bh%& option"
24253 This modifier causes Exim to wait for the time interval before proceeding. The
24254 time is given in the usual Exim notation. This modifier may appear in any ACL.
24255 The delay happens as soon as the modifier is processed. However, when testing
24256 Exim using the &%-bh%& option, the delay is not actually imposed (an
24257 appropriate message is output instead).
24259 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
24262 deny ...some conditions...
24265 The delay happens if all the conditions are true, before the statement returns
24266 &"deny"&. Compare this with:
24269 ...some conditions...
24271 which waits for 30s before processing the conditions. The &%delay%& modifier
24272 can also be used with &%warn%& and together with &%control%&:
24274 warn ...some conditions...
24281 .cindex "&%endpass%&" "ACL modifier"
24282 This modifier, which has no argument, is recognized only in &%accept%&
24283 statements. It marks the boundary between the conditions whose failure causes
24284 control to pass to the next statement, and the conditions whose failure causes
24285 the ACL to return &"deny"&. See the description of &%accept%& above.
24287 .vitem &*log_message*&&~=&~<&'text'&>
24288 .cindex "&%log_message%&" "ACL modifier"
24289 This modifier sets up a message that is used as part of the log message if the
24290 ACL denies access or a &%warn%& statement's conditions are true. For example:
24292 require log_message = wrong cipher suite $tls_cipher
24293 encrypted = DES-CBC3-SHA
24295 &%log_message%& adds to any underlying error message that may exist because of
24296 the condition failure. For example, while verifying a recipient address, a
24297 &':fail:'& redirection might have already set up a message. Although the
24298 message is usually defined before the conditions to which it applies, the
24299 expansion does not happen until Exim decides that access is to be denied. This
24300 means that any variables that are set by the condition are available for
24301 inclusion in the message. For example, the &$dnslist_$&<&'xxx'&> variables are
24302 set after a DNS black list lookup succeeds. If the expansion of &%log_message%&
24303 fails, or if the result is an empty string, the modifier is ignored.
24305 .cindex "&$acl_verify_message$&"
24306 If you want to use a &%warn%& statement to log the result of an address
24307 verification, you can use &$acl_verify_message$& to include the verification
24310 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
24311 the start of the logged message. If the same warning log message is requested
24312 more than once while receiving a single email message, only one copy is
24313 actually logged. If you want to log multiple copies, use &%logwrite%& instead
24314 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
24315 is logged for a succesful &%warn%& statement.
24317 If &%log_message%& is not present and there is no underlying error message (for
24318 example, from the failure of address verification), but &%message%& is present,
24319 the &%message%& text is used for logging rejections. However, if any text for
24320 logging contains newlines, only the first line is logged. In the absence of
24321 both &%log_message%& and &%message%&, a default built-in message is used for
24322 logging rejections.
24324 .vitem &*logwrite*&&~=&~<&'text'&>
24325 .cindex "&%logwrite%&" "ACL modifier"
24326 .cindex "logging in ACL" "immediate"
24327 This modifier writes a message to a log file as soon as it is encountered when
24328 processing an ACL. (Compare &%log_message%&, which, except in the case of
24329 &%warn%&, is used only if the ACL statement denies access.) The &%logwrite%&
24330 modifier can be used to log special incidents in ACLs. For example:
24332 &`accept `&<&'some special conditions'&>
24333 &` control = freeze`&
24334 &` logwrite = froze message because ...`&
24336 By default, the message is written to the main log. However, it may begin
24337 with a colon, followed by a comma-separated list of log names, and then
24338 another colon, to specify exactly which logs are to be written. For
24341 logwrite = :main,reject: text for main and reject logs
24342 logwrite = :panic: text for panic log only
24345 .vitem &*message*&&~=&~<&'text'&>
24346 .cindex "&%message%&" "ACL modifier"
24347 This modifier sets up a text string that is expanded and used as an error
24348 message if the current statement causes the ACL to deny access. The expansion
24349 happens at the time Exim decides that access is to be denied, not at the time
24350 it processes &%message%&. If the expansion fails, or generates an empty string,
24351 the modifier is ignored. For ACLs that are triggered by SMTP commands, the
24352 message is returned as part of the SMTP error response.
24354 The text is literal; any quotes are taken as literals, but because the string
24355 is expanded, backslash escapes are processed anyway. If the message contains
24356 newlines, this gives rise to a multi-line SMTP response. Like &%log_message%&,
24357 the contents of &%message%& are not expanded until after a condition has
24360 .cindex "&$acl_verify_message$&"
24361 If &%message%& is used on a statement that verifies an address, the message
24362 specified overrides any message that is generated by the verification process.
24363 However, the original message is available in the variable
24364 &$acl_verify_message$&, so you can incorporate it into your message if you
24365 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
24366 routers to be passed back as part of the SMTP response, you should either not
24367 use a &%message%& modifier, or make use of &$acl_verify_message$&.
24369 For compatibility with previous releases of Exim, a &%message%& modifier that
24370 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
24371 modifier, but this usage is now deprecated. However, &%message%& acts only when
24372 all the conditions are true, wherever it appears in an ACL command, whereas
24373 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
24374 &%warn%& in an ACL that is not concerned with receiving a message, it has no
24377 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
24378 .cindex "&%set%&" "ACL modifier"
24379 This modifier puts a value into one of the ACL variables (see section
24380 &<<SECTaclvariables>>&).
24387 .section "Use of the control modifier" "SECTcontrols"
24388 .cindex "&%control%&" "ACL modifier"
24389 The &%control%& modifier supports the following settings:
24392 .vitem &*control&~=&~allow_auth_unadvertised*&
24393 This modifier allows a client host to use the SMTP AUTH command even when it
24394 has not been advertised in response to EHLO. Furthermore, because there are
24395 apparently some really broken clients that do this, Exim will accept AUTH after
24396 HELO (rather than EHLO) when this control is set. It should be used only if you
24397 really need it, and you should limit its use to those broken clients that do
24398 not work without it. For example:
24400 warn hosts = 192.168.34.25
24401 control = allow_auth_unadvertised
24403 Normally, when an Exim server receives an AUTH command, it checks the name of
24404 the authentication mechanism that is given in the command to ensure that it
24405 matches an advertised mechanism. When this control is set, the check that a
24406 mechanism has been advertised is bypassed. Any configured mechanism can be used
24407 by the client. This control is permitted only in the connection and HELO ACLs.
24410 .vitem &*control&~=&~caseful_local_part*&
24413 .vitem &*control&~=&~caselower_local_part*&
24414 .cindex "&ACL;" "case of local part in"
24415 .cindex "case of local parts"
24416 .cindex "&$local_part$&"
24417 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
24418 (that is, during RCPT processing). By default, the contents of &$local_part$&
24419 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
24420 any uppercase letters in the original local part are restored in &$local_part$&
24421 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
24424 These controls affect only the current recipient. Moreover, they apply only to
24425 local part handling that takes place directly in the ACL (for example, as a key
24426 in lookups). If a test to verify the recipient is obeyed, the case-related
24427 handling of the local part during the verification is controlled by the router
24428 configuration (see the &%caseful_local_part%& generic router option).
24430 This facility could be used, for example, to add a spam score to local parts
24431 containing upper case letters. For example, using &$acl_m4$& to accumulate the
24434 warn control = caseful_local_part
24435 set acl_m4 = ${eval:\
24437 ${if match{$local_part}{[A-Z]}{1}{0}}\
24439 control = caselower_local_part
24441 Notice that we put back the lower cased version afterwards, assuming that
24442 is what is wanted for subsequent tests.
24444 .vitem &*control&~=&~enforce_sync*&
24447 .vitem &*control&~=&~no_enforce_sync*&
24448 .cindex "SMTP" "synchronization checking"
24449 .cindex "synchronization checking in SMTP"
24450 These controls make it possible to be selective about when SMTP synchronization
24451 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
24452 state of the switch (it is true by default). See the description of this option
24453 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
24455 The effect of these two controls lasts for the remainder of the SMTP
24456 connection. They can appear in any ACL except the one for the non-SMTP
24457 messages. The most straightforward place to put them is in the ACL defined by
24458 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
24459 before the first synchronization check. The expected use is to turn off the
24460 synchronization checks for badly-behaved hosts that you nevertheless need to
24464 .vitem &*control&~=&~fakedefer/*&<&'message'&>
24465 .cindex "fake defer"
24466 .cindex "defer" "fake"
24467 This control works in exactly the same way as &%fakereject%& (described below)
24468 except that it causes an SMTP 450 response after the message data instead of a
24469 550 response. You must take care when using &%fakedefer%& because it causes the
24470 messages to be duplicated when the sender retries. Therefore, you should not
24471 use &%fakedefer%& if the message is to be delivered normally.
24473 .vitem &*control&~=&~fakereject/*&<&'message'&>
24474 .cindex "fake rejection"
24475 .cindex "rejection" "fake"
24476 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
24477 words, only when an SMTP message is being received. If Exim accepts the
24478 message, instead the final 250 response, a 550 rejection message is sent.
24479 However, Exim proceeds to deliver the message as normal. The control applies
24480 only to the current message, not to any subsequent ones that may be received in
24481 the same SMTP connection.
24483 The text for the 550 response is taken from the &%control%& modifier. If no
24484 message is supplied, the following is used:
24486 550-Your message has been rejected but is being
24487 550-kept for evaluation.
24488 550-If it was a legitimate message, it may still be
24489 550 delivered to the target recipient(s).
24491 This facilty should be used with extreme caution.
24493 .vitem &*control&~=&~freeze*&
24494 .cindex "frozen messages" "forcing in ACL"
24495 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
24496 other words, only when a message is being received. If the message is accepted,
24497 it is placed on Exim's queue and frozen. The control applies only to the
24498 current message, not to any subsequent ones that may be received in the same
24501 This modifier can optionally be followed by &`/no_tell`&. If the global option
24502 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
24503 is told about the freezing), provided all the &*control=freeze*& modifiers that
24504 are obeyed for the current message have the &`/no_tell`& option.
24507 .vitem &*control&~=&~no_mbox_unspool*&
24508 This control is available when Exim is compiled with the content scanning
24509 extension. Content scanning may require a copy of the current message, or parts
24510 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
24511 or spam scanner. Normally, such copies are deleted when they are no longer
24512 needed. If this control is set, the copies are not deleted. The control applies
24513 only to the current message, not to any subsequent ones that may be received in
24514 the same SMTP connection. It is provided for debugging purposes and is unlikely
24515 to be useful in production.
24517 .vitem &*control&~=&~no_multiline_response*&
24518 .cindex "multiline responses" "suppressing"
24519 This control is permitted for any ACL except the one for non-SMTP messages.
24520 It seems that there are broken clients in use that cannot handle multiline
24521 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
24523 If this control is set, multiline SMTP responses from ACL rejections are
24524 suppressed. One way of doing this would have been to put out these responses as
24525 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
24526 (&"use multiline responses for more"& it says &-- ha!), and some of the
24527 responses might get close to that. So this facility, which is after all only a
24528 sop to broken clients, is implemented by doing two very easy things:
24531 Extra information that is normally output as part of a rejection caused by
24532 sender verification failure is omitted. Only the final line (typically &"sender
24533 verification failed"&) is sent.
24535 If a &%message%& modifier supplies a multiline response, only the first
24539 The setting of the switch can, of course, be made conditional on the
24540 calling host. Its effect lasts until the end of the SMTP connection.
24542 .vitem &*control&~=&~queue_only*&
24543 .cindex "&%queue_only%&"
24544 .cindex "queueing incoming messages"
24545 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
24546 other words, only when a message is being received. If the message is accepted,
24547 it is placed on Exim's queue and left there for delivery by a subsequent queue
24548 runner. No immediate delivery process is started. In other words, it has the
24549 effect as the &%queue_only%& global option. However, the control applies only
24550 to the current message, not to any subsequent ones that may be received in the
24551 same SMTP connection.
24553 .vitem &*control&~=&~submission/*&<&'options'&>
24554 .cindex "message" "submission"
24555 .cindex "submission mode"
24556 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
24557 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
24558 the current message is a submission from a local MUA. In this case, Exim
24559 operates in &"submission mode"&, and applies certain fixups to the message if
24560 necessary. For example, it add a &'Date:'& header line if one is not present.
24561 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
24562 late (the message has already been created).
24564 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
24565 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
24566 submission mode; the available options for this control are described there.
24567 The control applies only to the current message, not to any subsequent ones
24568 that may be received in the same SMTP connection.
24570 .vitem &*control&~=&~suppress_local_fixups*&
24571 .cindex "submission fixups" "suppressing"
24572 This control applies to locally submitted (non TCP/IP) messages, and is the
24573 complement of &`control`& &`=`& &`submission`&. It disables the fixups that are
24574 normally applied to locally-submitted messages. Specifically:
24577 Any &'Sender:'& header line is left alone (in this respect, it is a
24578 dynamic version of &%local_sender_retain%&).
24580 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
24582 There is no check that &'From:'& corresponds to the actual sender.
24585 This feature may be useful when a remotely-originated message is accepted,
24586 passed to some scanning program, and then re-submitted for delivery.
24589 All four possibilities for message fixups can be specified:
24592 Locally submitted, fixups applied: the default.
24594 Locally submitted, no fixups applied: use &`control`& &`=`&
24595 &`suppress_local_fixups`&.
24597 Remotely submitted, no fixups applied: the default.
24599 Remotely submitted, fixups applied: use &`control`& &`=`& &`submission`&.
24604 .section "Adding header lines in ACLs" "SECTaddheadacl"
24605 .cindex "header lines" "adding in an ACL"
24606 .cindex "header lines" "position of added lines"
24607 .cindex "&%message%&" "ACL modifier"
24608 The &%add_header%& modifier can be used to add one or more extra header lines
24609 to an incoming message, as in this example:
24611 warn dnslists = sbl.spamhaus.org : \
24612 dialup.mail-abuse.org
24613 add_header = X-blacklisted-at: $dnslist_domain
24615 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
24616 MIME, and non-SMTP ACLs (in other words, those that are concerned with
24617 receiving a message). The message must ultimately be accepted for
24618 &%add_header%& to have any significant effect. You can use &%add_header%& with
24619 any ACL verb, including &%deny%& (though this is potentially useful only in a
24622 If the data for the &%add_header%& modifier contains one or more newlines that
24623 are not followed by a space or a tab, it is assumed to contain multiple header
24624 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
24625 front of any line that is not a valid header line.
24627 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
24628 They are added to the message before processing the DATA and MIME ACLs.
24629 However, if an identical header line is requested more than once, only one copy
24630 is actually added to the message. Further header lines may be accumulated
24631 during the DATA and MIME ACLs, after which they are added to the message, again
24632 with duplicates suppressed. Thus, it is possible to add two identical header
24633 lines to an SMTP message, but only if one is added before DATA and one after.
24634 In the case of non-SMTP messages, new headers are accumulated during the
24635 non-SMTP ACL, and added to the message at the end. If a message is rejected
24636 after DATA or by the non-SMTP ACL, all added header lines are included in the
24637 entry that is written to the reject log.
24639 .cindex "header lines" "added; visibility of"
24640 Header lines are not visible in string expansions until they are added to the
24641 message. It follows that header lines defined in the MAIL, RCPT, and predata
24642 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
24643 header lines that are added by the DATA or MIME ACLs are not visible in those
24644 ACLs. Because of this restriction, you cannot use header lines as a way of
24645 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
24646 this, you can use ACL variables, as described in section
24647 &<<SECTaclvariables>>&.
24649 The &%add_header%& modifier acts immediately it is encountered during the
24650 processing of an ACL. Notice the difference between these two cases:
24652 &`accept add_header = ADDED: some text`&
24653 &` `&<&'some condition'&>
24655 &`accept `&<&'some condition'&>
24656 &` add_header = ADDED: some text`&
24658 In the first case, the header line is always added, whether or not the
24659 condition is true. In the second case, the header line is added only if the
24660 condition is true. Multiple occurrences of &%add_header%& may occur in the same
24661 ACL statement. All those that are encountered before a condition fails are
24664 .cindex "&%warn%&" "ACL verb"
24665 For compatibility with previous versions of Exim, a &%message%& modifier for a
24666 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
24667 effect only if all the conditions are true, even if it appears before some of
24668 them. Furthermore, only the last occurrence of &%message%& is honoured. This
24669 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
24670 are present on a &%warn%& verb, both are processed according to their
24673 By default, new header lines are added to a message at the end of the existing
24674 header lines. However, you can specify that any particular header line should
24675 be added right at the start (before all the &'Received:'& lines), immediately
24676 after the first block of &'Received:'& lines, or immediately before any line
24677 that is not a &'Received:'& or &'Resent-something:'& header.
24679 This is done by specifying &":at_start:"&, &":after_received:"&, or
24680 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
24681 header line, respectively. (Header text cannot start with a colon, as there has
24682 to be a header name first.) For example:
24684 warn add_header = \
24685 :after_received:X-My-Header: something or other...
24687 If more than one header line is supplied in a single &%add_header%& modifier,
24688 each one is treated independently and can therefore be placed differently. If
24689 you add more than one line at the start, or after the Received: block, they end
24690 up in reverse order.
24692 &*Warning*&: This facility currently applies only to header lines that are
24693 added in an ACL. It does NOT work for header lines that are added in a
24694 system filter or in a router or transport.
24699 .section "ACL conditions" "SECTaclconditions"
24700 .cindex "&ACL;" "conditions; list of"
24701 Some of conditions listed in this section are available only when Exim is
24702 compiled with the content-scanning extension. They are included here briefly
24703 for completeness. More detailed descriptions can be found in the discussion on
24704 content scanning in chapter &<<CHAPexiscan>>&.
24706 Not all conditions are relevant in all circumstances. For example, testing
24707 senders and recipients does not make sense in an ACL that is being run as the
24708 result of the arrival of an ETRN command, and checks on message headers can be
24709 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
24710 can use the same condition (with different parameters) more than once in the
24711 same ACL statement. This provides a way of specifying an &"and"& conjunction.
24712 The conditions are as follows:
24716 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
24717 .cindex "&ACL;" "nested"
24718 .cindex "&ACL;" "indirect"
24719 .cindex "&%acl%&" "ACL condition"
24720 The possible values of the argument are the same as for the
24721 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
24722 &"accept"& the condition is true; if it returns &"deny"& the condition is
24723 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
24724 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
24725 condition false. This means that further processing of the &%warn%& verb
24726 ceases, but processing of the ACL continues.
24728 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
24729 the connection is dropped. If it returns &"discard"&, the verb must be
24730 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
24731 conditions are tested.
24733 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
24734 loops. This condition allows you to use different ACLs in different
24735 circumstances. For example, different ACLs can be used to handle RCPT commands
24736 for different local users or different local domains.
24738 .vitem &*authenticated&~=&~*&<&'string&~list'&>
24739 .cindex "&%authenticated%&" "ACL condition"
24740 .cindex "authentication" "ACL checking"
24741 .cindex "&ACL;" "testing for authentication"
24742 If the SMTP connection is not authenticated, the condition is false. Otherwise,
24743 the name of the authenticator is tested against the list. To test for
24744 authentication by any authenticator, you can set
24749 .vitem &*condition&~=&~*&<&'string'&>
24750 .cindex "&%condition%&" "ACL condition"
24751 .cindex "customizing" "ACL condition"
24752 .cindex "&ACL;" "customized test"
24753 .cindex "&ACL;" "testing; customized"
24754 This feature allows you to make up custom conditions. If the result of
24755 expanding the string is an empty string, the number zero, or one of the strings
24756 &"no"& or &"false"&, the condition is false. If the result is any non-zero
24757 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
24758 any other values, some error is assumed to have occurred, and the ACL returns
24761 .vitem &*decode&~=&~*&<&'location'&>
24762 .cindex "&%decode%&" "ACL condition"
24763 This condition is available only when Exim is compiled with the
24764 content-scanning extension, and it is allowed only the the ACL defined by
24765 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
24766 For details, see chapter &<<CHAPexiscan>>&.
24768 .vitem &*demime&~=&~*&<&'extension&~list'&>
24769 .cindex "&%demime%&" "ACL condition"
24770 This condition is available only when Exim is compiled with the
24771 content-scanning extension. Its use is described in section
24772 &<<SECTdemimecond>>&.
24774 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
24775 .cindex "&%dnslists%&" "ACL condition"
24776 .cindex "DNS list" "in ACL"
24777 .cindex "black list (DNS)"
24778 .cindex "&ACL;" "testing a DNS list"
24779 This condition checks for entries in DNS black lists. These are also known as
24780 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
24781 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
24782 different variants of this condition to describe briefly here. See sections
24783 &<<SECTmorednslists>>&--&<<SECTmorednslistslast>>& for details.
24785 .vitem &*domains&~=&~*&<&'domain&~list'&>
24786 .cindex "&%domains%&" "ACL condition"
24787 .cindex "domain" "ACL checking"
24788 .cindex "&ACL;" "testing a recipient domain"
24789 .cindex "&$domain_data$&"
24790 This condition is relevant only after a RCPT command. It checks that the domain
24791 of the recipient address is in the domain list. If percent-hack processing is
24792 enabled, it is done before this test is done. If the check succeeds with a
24793 lookup, the result of the lookup is placed in &$domain_data$& until the next
24796 .vitem &*encrypted&~=&~*&<&'string&~list'&>
24797 .cindex "&%encrypted%&" "ACL condition"
24798 .cindex "encryption" "checking in an ACL"
24799 .cindex "&ACL;" "testing for encryption"
24800 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
24801 name of the cipher suite in use is tested against the list. To test for
24802 encryption without testing for any specific cipher suite(s), set
24807 .vitem &*hosts&~=&~*&<&'&~host&~list'&>
24808 .cindex "&%hosts%&" "ACL condition"
24809 .cindex "host" "ACL checking"
24810 .cindex "&ACL;" "testing the client host"
24811 This condition tests that the calling host matches the host list. If you have
24812 name lookups or wildcarded host names and IP addresses in the same host list,
24813 you should normally put the IP addresses first. For example, you could have:
24815 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
24817 The reason for this lies in the left-to-right way that Exim processes lists.
24818 It can test IP addresses without doing any DNS lookups, but when it reaches an
24819 item that requires a host name, it fails if it cannot find a host name to
24820 compare with the pattern. If the above list is given in the opposite order, the
24821 &%accept%& statement fails for a host whose name cannot be found, even if its
24822 IP address is 10.9.8.7.
24824 If you really do want to do the name check first, and still recognize the IP
24825 address even if the name lookup fails, you can rewrite the ACL like this:
24827 accept hosts = dbm;/etc/friendly/hosts
24828 accept hosts = 10.9.8.7
24830 The default action on failing to find the host name is to assume that the host
24831 is not in the list, so the first &%accept%& statement fails. The second
24832 statement can then check the IP address.
24834 .cindex "&$host_data$&"
24835 If a &%hosts%& condition is satisfied by means of a lookup, the result
24836 of the lookup is made available in the &$host_data$& variable. This
24837 allows you, for example, to set up a statement like this:
24839 deny hosts = net-lsearch;/some/file
24840 message = $host_data
24842 which gives a custom error message for each denied host.
24844 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
24845 .cindex "&%local_parts%&" "ACL condition"
24846 .cindex "local part" "ACL checking"
24847 .cindex "&ACL;" "testing a local part"
24848 .cindex "&$local_part_data$&"
24849 This condition is relevant only after a RCPT command. It checks that the local
24850 part of the recipient address is in the list. If percent-hack processing is
24851 enabled, it is done before this test. If the check succeeds with a lookup, the
24852 result of the lookup is placed in &$local_part_data$&, which remains set until
24853 the next &%local_parts%& test.
24855 .vitem &*malware&~=&~*&<&'option'&>
24856 .cindex "&%malware%&" "ACL condition"
24857 .cindex "&ACL;" "virus scanning"
24858 .cindex "&ACL;" "scanning for viruses"
24859 This condition is available only when Exim is compiled with the
24860 content-scanning extension. It causes the incoming message to be scanned for
24861 viruses. For details, see chapter &<<CHAPexiscan>>&.
24863 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
24864 .cindex "&%mime_regex%&" "ACL condition"
24865 .cindex "&ACL;" "testing by regex matching"
24866 This condition is available only when Exim is compiled with the
24867 content-scanning extension, and it is allowed only the the ACL defined by
24868 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
24869 with any of the regular expressions. For details, see chapter
24872 .vitem &*ratelimit&~=&~*&<&'parameters'&>
24873 .cindex "rate limiting"
24874 This condition can be used to limit the rate at which a user or host submits
24875 messages. Details are given in section &<<SECTratelimiting>>&.
24877 .vitem &*recipients&~=&~*&<&'address&~list'&>
24878 .cindex "&%recipients%&" "ACL condition"
24879 .cindex "recipient" "ACL checking"
24880 .cindex "&ACL;" "testing a recipient"
24881 This condition is relevant only after a RCPT command. It checks the entire
24882 recipient address against a list of recipients.
24884 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
24885 .cindex "&%regex%&" "ACL condition"
24886 .cindex "&ACL;" "testing by regex matching"
24887 This condition is available only when Exim is compiled with the
24888 content-scanning extension, and is available only in the DATA, MIME, and
24889 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
24890 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
24892 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
24893 .cindex "&%sender_domains%&" "ACL condition"
24894 .cindex "sender" "ACL checking"
24895 .cindex "&ACL;" "testing a sender domain"
24896 .cindex "&$domain$&"
24897 .cindex "&$sender_address_domain$&"
24898 This condition tests the domain of the sender of the message against the given
24899 domain list. &*Note*&: The domain of the sender address is in
24900 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
24901 of this condition. This is an exception to the general rule for testing domain
24902 lists. It is done this way so that, if this condition is used in an ACL for a
24903 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
24904 influence the sender checking.
24906 &*Warning*&: It is a bad idea to use this condition on its own as a control on
24907 relaying, because sender addresses are easily, and commonly, forged.
24909 .vitem &*senders&~=&~*&<&'address&~list'&>
24910 .cindex "&%senders%&" "ACL condition"
24911 .cindex "sender" "ACL checking"
24912 .cindex "&ACL;" "testing a sender"
24913 This condition tests the sender of the message against the given list. To test
24914 for a bounce message, which has an empty sender, set
24918 &*Warning*&: It is a bad idea to use this condition on its own as a control on
24919 relaying, because sender addresses are easily, and commonly, forged.
24921 .vitem &*spam&~=&~*&<&'username'&>
24922 .cindex "&%spam%&" "ACL condition"
24923 .cindex "&ACL;" "scanning for spam"
24924 This condition is available only when Exim is compiled with the
24925 content-scanning extension. It causes the incoming message to be scanned by
24926 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
24928 .vitem &*verify&~=&~certificate*&
24929 .cindex "&%verify%&" "ACL condition"
24930 .cindex "TLS" "client certificate verification"
24931 .cindex "certificate" "verification of client"
24932 .cindex "&ACL;" "certificate verification"
24933 .cindex "&ACL;" "testing a TLS certificate"
24934 This condition is true in an SMTP session if the session is encrypted, and a
24935 certificate was received from the client, and the certificate was verified. The
24936 server requests a certificate only if the client matches &%tls_verify_hosts%&
24937 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
24939 .vitem &*verify&~=&~csa*&
24940 .cindex "CSA verification"
24941 This condition checks whether the sending host (the client) is authorized to
24942 send email. Details of how this works are given in section
24943 &<<SECTverifyCSA>>&.
24945 .vitem &*verify&~=&~header_sender/*&<&'options'&>
24946 .cindex "&%verify%&" "ACL condition"
24947 .cindex "&ACL;" "verifying sender in the header"
24948 .cindex "header lines" "verifying the sender in"
24949 .cindex "sender" "verifying in header"
24950 .cindex "verifying" "sender in header"
24951 This condition is relevant only in an ACL that is run after a message has been
24952 received, that is, in an ACL specified by &%acl_smtp_data%& or
24953 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
24954 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
24955 is loosely thought of as a &"sender"& address (hence the name of the test).
24956 However, an address that appears in one of these headers need not be an address
24957 that accepts bounce messages; only sender addresses in envelopes are required
24958 to accept bounces. Therefore, if you use the callout option on this check, you
24959 might want to arrange for a non-empty address in the MAIL command.
24961 Details of address verification and the options are given later, starting at
24962 section &<<SECTaddressverification>>& (callouts are described in section
24963 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
24964 condition to restrict it to bounce messages only:
24967 message = A valid sender header is required for bounces
24968 !verify = header_sender
24971 .vitem &*verify&~=&~header_syntax*&
24972 .cindex "&%verify%&" "ACL condition"
24973 .cindex "&ACL;" "verifying header syntax"
24974 .cindex "header lines" "verifying syntax"
24975 .cindex "verifying" "header syntax"
24976 This condition is relevant only in an ACL that is run after a message has been
24977 received, that is, in an ACL specified by &%acl_smtp_data%& or
24978 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
24979 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
24980 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
24981 permitted only in locally generated messages and from hosts that match
24982 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
24985 Note that this condition is a syntax check only. However, a common spamming
24986 ploy used to be to send syntactically invalid headers such as
24990 and this condition can be used to reject such messages, though they are not as
24991 common as they used to be.
24993 .vitem &*verify&~=&~helo*&
24994 .cindex "&%verify%&" "ACL condition"
24995 .cindex "&ACL;" "verifying HELO/EHLO"
24996 .cindex "HELO" "verifying"
24997 .cindex "EHLO" "verifying"
24998 .cindex "verifying" "EHLO"
24999 .cindex "verifying" "HELO"
25000 This condition is true if a HELO or EHLO command has been received from the
25001 client host, and its contents have been verified. It there has been no previous
25002 attempt to verify the the HELO/EHLO contents, it is carried out when this
25003 condition is encountered. See the description of the &%helo_verify_hosts%& and
25004 &%helo_try_verify_hosts%& options for details of how to request verification
25005 independently of this condition.
25007 .vitem &*verify&~=&~not_blind*&
25008 .cindex "verifying" "not blind"
25009 .cindex "bcc recipients" "verifying none"
25010 This condition checks that there are no blind (bcc) recipients in the message.
25011 Every envelope recipient must appear either in a &'To:'& header line or in a
25012 &'Cc:'& header line for this condition to be true. Local parts are checked
25013 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
25014 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
25015 used only in a DATA or non-SMTP ACL.
25017 There are, of course, many legitimate messages that make use of blind (bcc)
25018 recipients. This check should not be used on its own for blocking messages.
25021 .vitem &*verify&~=&~recipient/*&<&'options'&>
25022 .cindex "&%verify%&" "ACL condition"
25023 .cindex "&ACL;" "verifying recipient"
25024 .cindex "recipient" "verifying"
25025 .cindex "verifying" "recipient"
25026 .cindex "&$address_data$&"
25027 This condition is relevant only after a RCPT command. It verifies the current
25028 recipient. Details of address verification are given later, starting at section
25029 &<<SECTaddressverification>>&. After a recipient has been verified, the value
25030 of &$address_data$& is the last value that was set while routing the address.
25031 This applies even if the verification fails. When an address that is being
25032 verified is redirected to a single address, verification continues with the new
25033 address, and in that case, the subsequent value of &$address_data$& is the
25034 value for the child address.
25036 .vitem &*verify&~=&~reverse_host_lookup*&
25037 .cindex "&%verify%&" "ACL condition"
25038 .cindex "&ACL;" "verifying host reverse lookup"
25039 .cindex "host" "verifying reverse lookup"
25040 This condition ensures that a verified host name has been looked up from the IP
25041 address of the client host. (This may have happened already if the host name
25042 was needed for checking a host list, or if the host matched &%host_lookup%&.)
25043 Verification ensures that the host name obtained from a reverse DNS lookup, or
25044 one of its aliases, does, when it is itself looked up in the DNS, yield the
25045 original IP address.
25047 If this condition is used for a locally generated message (that is, when there
25048 is no client host involved), it always succeeds.
25050 .vitem &*verify&~=&~sender/*&<&'options'&>
25051 .cindex "&%verify%&" "ACL condition"
25052 .cindex "&ACL;" "verifying sender"
25053 .cindex "sender" "verifying"
25054 .cindex "verifying" "sender"
25055 This condition is relevant only after a MAIL or RCPT command, or after a
25056 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
25057 the message's sender is empty (that is, this is a bounce message), the
25058 condition is true. Otherwise, the sender address is verified.
25060 .cindex "&$address_data$&"
25061 .cindex "&$sender_address_data$&"
25062 If there is data in the &$address_data$& variable at the end of routing, its
25063 value is placed in &$sender_address_data$& at the end of verification. This
25064 value can be used in subsequent conditions and modifiers in the same ACL
25065 statement. It does not persist after the end of the current statement. If you
25066 want to preserve the value for longer, you can save it in an ACL variable.
25068 Details of verification are given later, starting at section
25069 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
25070 to avoid doing it more than once per message.
25072 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
25073 .cindex "&%verify%&" "ACL condition"
25074 This is a variation of the previous option, in which a modified address is
25075 verified as a sender.
25080 .section "Using DNS lists" "SECTmorednslists"
25081 .cindex "DNS list" "in ACL"
25082 .cindex "black list (DNS)"
25083 .cindex "&ACL;" "testing a DNS list"
25084 In its simplest form, the &%dnslists%& condition tests whether the calling host
25085 is on at least one of a number of DNS lists by looking up the inverted IP
25086 address in one or more DNS domains. For example, if the calling host's IP
25087 address is 192.168.62.43, and the ACL statement is
25089 deny dnslists = blackholes.mail-abuse.org : \
25090 dialups.mail-abuse.org
25092 the following records are looked up:
25094 43.62.168.192.blackholes.mail-abuse.org
25095 43.62.168.192.dialups.mail-abuse.org
25097 As soon as Exim finds an existing DNS record, processing of the list stops.
25098 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
25099 to test that a host is on more than one list (an &"and"& conjunction), you can
25100 use two separate conditions:
25102 deny dnslists = blackholes.mail-abuse.org
25103 dnslists = dialups.mail-abuse.org
25105 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
25106 behaves as if the host does not match the list item, that is, as if the DNS
25107 record does not exist. If there are further items in the DNS list, they are
25110 This is usually the required action when &%dnslists%& is used with &%deny%&
25111 (which is the most common usage), because it prevents a DNS failure from
25112 blocking mail. However, you can change this behaviour by putting one of the
25113 following special items in the list:
25115 &`+include_unknown `& behave as if the item is on the list
25116 &`+exclude_unknown `& behave as if the item is not on the list (default)
25117 &`+defer_unknown `& give a temporary error
25119 .cindex "&`+include_unknown`&"
25120 .cindex "&`+exclude_unknown`&"
25121 .cindex "&`+defer_unknown`&"
25122 Each of these applies to any subsequent items on the list. For example:
25124 deny dnslists = +defer_unknown : foo.bar.example
25126 Testing the list of domains stops as soon as a match is found. If you want to
25127 warn for one list and block for another, you can use two different statements:
25129 deny dnslists = blackholes.mail-abuse.org
25130 warn message = X-Warn: sending host is on dialups list
25131 dnslists = dialups.mail-abuse.org
25133 DNS list lookups are cached by Exim for the duration of the SMTP session,
25134 so a lookup based on the IP address is done at most once for any incoming
25135 connection. Exim does not share information between multiple incoming
25136 connections (but your local name server cache should be active).
25140 .section "Specifying the IP address for a DNS list lookup"
25141 .cindex "DNS list" "keyed by explicit IP address"
25142 By default, the IP address that is used in a DNS list lookup is the IP address
25143 of the calling host. However, you can specify another IP address by listing it
25144 after the domain name, introduced by a slash. For example:
25146 deny dnslists = black.list.tld/192.168.1.2
25148 This feature is not very helpful with explicit IP addresses; it is intended for
25149 use with IP addresses that are looked up, for example, the IP addresses of the
25150 MX hosts or nameservers of an email sender address. For an example, see section
25151 &<<SECTmulkeyfor>>& below.
25156 .section "DNS lists keyed on domain names"
25157 .cindex "DNS list" "keyed by domain name"
25158 There are some lists that are keyed on domain names rather than inverted IP
25159 addresses (see for example the &'domain based zones'& link at
25160 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
25161 with these lists. You can change the name that is looked up in a DNS list by
25162 listing it after the domain name, introduced by a slash. For example,
25164 deny message = Sender's domain is listed at $dnslist_domain
25165 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
25167 This particular example is useful only in ACLs that are obeyed after the
25168 RCPT or DATA commands, when a sender address is available. If (for
25169 example) the message's sender is &'user@tld.example'& the name that is looked
25170 up by this example is
25172 tld.example.dsn.rfc-ignorant.org
25174 A single &%dnslists%& condition can contain entries for both names and IP
25175 addresses. For example:
25177 deny dnslists = sbl.spamhaus.org : \
25178 dsn.rfc-ignorant.org/$sender_address_domain
25180 The first item checks the sending host's IP address; the second checks a domain
25181 name. The whole condition is true if either of the DNS lookups succeeds.
25186 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
25187 .cindex "DNS list" "multiple keys for"
25188 The syntax described above for looking up explicitly-defined values (either
25189 names or IP addresses) in a DNS blacklist is a simplification. After the domain
25190 name for the DNS list, what follows the slash can in fact be a list of items.
25191 As with all lists in Exim, the default separator is a colon. However, because
25192 this is a sublist within the list of DNS blacklist domains, it is necessary
25193 either to double the separators like this:
25195 dnslists = black.list.tld/name.1::name.2
25197 or to change the separator character, like this:
25199 dnslists = black.list.tld/<;name.1;name.2
25201 If an item in the list is an IP address, it is inverted before the DNS
25202 blacklist domain is appended. If it is not an IP address, no inversion
25203 occurs. Consider this condition:
25205 dnslists = black.list.tld/<;192.168.1.2;a.domain
25207 The DNS lookups that occur are:
25209 2.1.168.192.black.list.tld
25210 a.domain.black.list.tld
25212 Once a DNS record has been found (that matches a specific IP return
25213 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
25214 are done. If there is a temporary DNS error, the rest of the sublist of domains
25215 or IP addresses is tried. A temporary error for the whole dnslists item occurs
25216 only if no other DNS lookup in this sublist succeeds. In other words, a
25217 successful lookup for any of the items in the sublist overrides a temporary
25218 error for a previous item.
25220 The ability to supply a list of items after the slash is in some sense just a
25221 syntactic convenience. These two examples have the same effect:
25223 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
25224 dnslists = black.list.tld/a.domain::b.domain
25226 However, when the data for the list is obtained from a lookup, the second form
25227 is usually much more convenient. Consider this example:
25229 deny message = The mail servers for the domain \
25230 $sender_address_domain \
25231 are listed at $dnslist_domain ($dnslist_value); \
25233 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
25234 ${lookup dnsdb {>|mxh=\
25235 $sender_address_domain} }} }
25237 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
25238 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
25239 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
25240 of expanding the condition might be something like this:
25242 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
25244 Thus, this example checks whether or not the IP addresses of the sender
25245 domain's mail servers are on the Spamhaus black list.
25251 .section "Data returned by DNS lists"
25252 .cindex "DNS list" "data returned from"
25253 DNS lists are constructed using address records in the DNS. The original RBL
25254 just used the address 127.0.0.1 on the right hand side of each record, but the
25255 RBL+ list and some other lists use a number of values with different meanings.
25256 The values used on the RBL+ list are:
25260 127.1.0.3 DUL and RBL
25262 127.1.0.5 RSS and RBL
25263 127.1.0.6 RSS and DUL
25264 127.1.0.7 RSS and DUL and RBL
25266 Some DNS lists may return more than one address record.
25269 .section "Variables set from DNS lists"
25270 .cindex "DNS list" "variables set from"
25271 .cindex "&$dnslist_domain$&"
25272 .cindex "&$dnslist_text$&"
25273 .cindex "&$dnslist_value$&"
25274 When an entry is found in a DNS list, the variable &$dnslist_domain$&
25275 contains the name of the domain that matched, &$dnslist_value$& contains the
25276 data from the entry, and &$dnslist_text$& contains the contents of any
25277 associated TXT record. If more than one address record is returned by the DNS
25278 lookup, all the IP addresses are included in &$dnslist_value$&, separated by
25281 You can use these variables in &%message%& or &%log_message%& modifiers &--
25282 although these appear before the condition in the ACL, they are not expanded
25283 until after it has failed. For example:
25285 deny hosts = !+local_networks
25286 message = $sender_host_address is listed \
25288 dnslists = rbl-plus.mail-abuse.example
25293 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
25294 .cindex "DNS list" "matching specific returned data"
25295 You can add an equals sign and an IP address after a &%dnslists%& domain name
25296 in order to restrict its action to DNS records with a matching right hand side.
25299 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
25301 rejects only those hosts that yield 127.0.0.2. Without this additional data,
25302 any address record is considered to be a match. If more than one address record
25303 is found on the list, they are all checked for a matching right-hand side.
25305 More than one IP address may be given for checking, using a comma as a
25306 separator. These are alternatives &-- if any one of them matches, the
25307 &%dnslists%& condition is true. For example:
25309 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
25311 If you want to specify a constraining address list and also specify names or IP
25312 addresses to be looked up, the constraining address list must be specified
25313 first. For example:
25315 deny dnslists = dsn.rfc-ignorant.org\
25316 =127.0.0.2/$sender_address_domain
25319 If the character &`&&`& is used instead of &`=`&, the comparison for each
25320 listed IP address is done by a bitwise &"and"& instead of by an equality test.
25321 In other words, the listed addresses are used as bit masks. The comparison is
25322 true if all the bits in the mask are present in the address that is being
25323 tested. For example:
25325 dnslists = a.b.c&0.0.0.3
25327 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
25328 want to test whether one bit or another bit is present (as opposed to both
25329 being present), you must use multiple values. For example:
25331 dnslists = a.b.c&0.0.0.1,0.0.0.2
25333 matches if the final component of the address is an odd number or two times
25338 .section "Negated DNS matching conditions"
25339 You can supply a negative list of IP addresses as part of a &%dnslists%&
25342 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
25344 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
25345 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
25347 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
25349 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
25350 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
25351 words, the result of the test is inverted if an exclamation mark appears before
25352 the &`=`& (or the &`&&`&) sign.
25354 &*Note*&: This kind of negation is not the same as negation in a domain,
25355 host, or address list (which is why the syntax is different).
25357 If you are using just one list, the negation syntax does not gain you much. The
25358 previous example is precisely equivalent to
25360 deny dnslists = a.b.c
25361 !dnslists = a.b.c=127.0.0.2,127.0.0.3
25363 However, if you are using multiple lists, the negation syntax is clearer.
25364 Consider this example:
25366 deny dnslists = sbl.spamhaus.org : \
25368 dnsbl.njabl.org!=127.0.0.3 : \
25371 Using only positive lists, this would have to be:
25373 deny dnslists = sbl.spamhaus.org : \
25375 deny dnslists = dnsbl.njabl.org
25376 !dnslists = dnsbl.njabl.org=127.0.0.3
25377 deny dnslists = relays.ordb.org
25379 which is less clear, and harder to maintain.
25384 .section "DNS lists and IPv6" "SECTmorednslistslast"
25385 .cindex "IPv6" "DNS black lists"
25386 .cindex "DNS list" "IPv6 usage"
25387 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
25388 nibble by nibble. For example, if the calling host's IP address is
25389 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
25391 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
25392 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
25394 (split over two lines here to fit on the page). Unfortunately, some of the DNS
25395 lists contain wildcard records, intended for IPv4, that interact badly with
25396 IPv6. For example, the DNS entry
25398 *.3.some.list.example. A 127.0.0.1
25400 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
25401 Unfortunately, it also matches the entire 3::/4 IPv6 network.
25403 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
25404 &%condition%& condition, as in this example:
25406 deny condition = ${if isip4{$sender_host_address}}
25407 dnslists = some.list.example
25410 .section "Rate limiting senders" "SECTratelimiting"
25411 .cindex "rate limiting" "client sending"
25412 .cindex "limiting client sending rates"
25413 .oindex "&%smpt_ratelimit_*%&"
25414 The &%ratelimit%& ACL condition can be used to measure and control the rate at
25415 which clients can send email. This is more powerful than the
25416 &%smtp_ratelimit_*%& options, because those options control the rate of
25417 commands in a single SMTP session only, whereas the &%ratelimit%& condition
25418 works across all connections (concurrent and sequential) from the same client
25419 host. The syntax of the &%ratelimit%& condition is:
25421 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
25423 If the average client sending rate is less than &'m'& messages per time
25424 period &'p'& then the condition is false; otherwise it is true.
25426 As a side-effect, the &%ratelimit%& condition sets the expansion variable
25427 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
25428 configured value of &'m'&, and &$sender_rate_period$& to the configured value
25431 The parameter &'p'& is the smoothing time constant, in the form of an Exim
25432 time interval, for example, &`8h`& for eight hours. A larger time constant
25433 means that it takes Exim longer to forget a client's past behaviour. The
25434 parameter &'m'& is the maximum number of messages that a client is permitted to
25435 send in each time interval. It also specifies the number of messages permitted
25436 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
25437 constant, you can allow a client to send more messages in a burst without
25438 changing its overall sending rate limit. Conversely, if &'m'& and &'p'& are
25439 both small, messages must be sent at an even rate.
25441 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
25442 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
25443 when deploying the &%ratelimit%& ACL condition. The script prints usage
25444 instructions when it is run with no arguments.
25446 The key is used to look up the data for calculating the client's average
25447 sending rate. This data is stored in a database maintained by Exim in its spool
25448 directory, alongside the retry and other hints databases. The default key is
25449 &$sender_host_address$&, which applies the limit to each client host IP address.
25450 By changing the key you can change how Exim identifies clients for the purpose
25451 of ratelimiting. For example, to limit the sending rate of each authenticated
25452 user, independent of the computer they are sending from, set the key to
25453 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
25454 example, &$authenticated_id$& is only meaningful if the client has
25455 authenticated, and you can check with with the &%authenticated%& ACL condition.
25457 Internally, Exim includes the smoothing constant &'p'& and the options in the
25458 lookup key because they alter the meaning of the stored data. This is not true
25459 for the limit &'m'&, so you can alter the configured maximum rate and Exim will
25460 still remember clients' past behaviour, but if you alter the other ratelimit
25461 parameters Exim forgets past behaviour.
25463 Each &%ratelimit%& condition can have up to two options. The first option
25464 specifies what Exim measures the rate of, and the second specifies how Exim
25465 handles excessively fast clients. The options are separated by a slash, like
25466 the other parameters.
25468 The &%per_conn%& option limits the client's connection rate.
25470 The &%per_mail%& option limits the client's rate of sending messages. This is
25471 the default if none of the &%per_*%& options is specified.
25473 The &%per_byte%& option limits the sender's email bandwidth. Note that it is
25474 best to use this option in the DATA ACL; if it is used in an earlier ACL it
25475 relies on the SIZE parameter on the MAIL command, which may be inaccurate or
25476 completely missing. You can follow the limit &'m'& in the configuration with K,
25477 M, or G to specify limits in kilobytes, megabytes, or gigabytes, respectively.
25479 The &%per_cmd%& option causes Exim to recompute the rate every time the
25480 condition is processed. This can be used to limit the SMTP command rate. The
25481 alias &%per_rcpt%& is provided for use in the RCPT ACL instead of &%per_cmd%&
25482 to make it clear that the effect is to limit the rate at which recipients are
25483 accepted. Note that in this case the rate limiting engine will see a message
25484 with many recipients as a large high-speed burst.
25486 If a client's average rate is greater than the maximum, the rate limiting
25487 engine can react in two possible ways, depending on the presence of the
25488 &%strict%& or &%leaky%& options. This is independent of the other
25489 counter-measures (such as rejecting the message) that may be specified by the
25490 rest of the ACL. The default mode is leaky, which avoids a sender's
25491 over-aggressive retry rate preventing it from getting any email through.
25493 The &%strict%& option means that the client's recorded rate is always updated.
25494 The effect of this is that Exim measures the client's average rate of attempts
25495 to send email, which can be much higher than the maximum. If the client is over
25496 the limit it will be subjected to counter-measures until it slows down below
25497 the maximum rate. The smoothing period determines the time it takes for a high
25498 sending rate to decay exponentially to 37% of its peak value, which means that
25499 you can work out the time (the number of smoothing periods) that a client is
25500 subjected to counter-measures after an over-limit burst with this formula:
25502 ln(peakrate/maxrate)
25504 The &%leaky%& option means that the client's recorded rate is not updated if it
25505 is above the limit. The effect of this is that Exim measures the client's
25506 average rate of successfully sent email, which cannot be greater than the
25507 maximum. If the client is over the limit it will suffer some counter-measures,
25508 but it will still be able to send email at the configured maximum rate,
25509 whatever the rate of its attempts. This is generally the better choice if you
25510 have clients that retry automatically.
25512 Exim's other ACL facilities are used to define what counter-measures are taken
25513 when the rate limit is exceeded. This might be anything from logging a warning
25514 (for example, while measuring existing sending rates in order to define
25515 policy), through time delays to slow down fast senders, up to rejecting the
25516 message. For example:
25518 # Log all senders' rates
25520 ratelimit = 0 / 1h / strict
25521 log_message = Sender rate $sender_rate / $sender_rate_period
25523 # Slow down fast senders; note the need to truncate $sender_rate
25524 # at the decimal point.
25526 ratelimit = 100 / 1h / per_rcpt / strict
25527 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
25528 $sender_rate_limit }s
25530 # Keep authenticated users under control
25533 ratelimit = 100 / 1d / strict / $authenticated_id
25535 # System-wide rate limit
25537 message = Sorry, too busy. Try again later.
25538 ratelimit = 10 / 1s / $primary_hostname
25540 # Restrict incoming rate from each host, with a default
25541 # set using a macro and special cases looked up in a table.
25543 message = Sender rate exceeds $sender_rate_limit \
25544 messages per $sender_rate_period
25545 ratelimit = ${lookup {$sender_host_address} \
25546 cdb {DB/ratelimits.cdb} \
25547 {$value} {RATELIMIT} }
25549 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
25550 especially with the &%per_rcpt%& option, you may suffer from a performance
25551 bottleneck caused by locking on the ratelimit hints database. Apart from
25552 making your ACLs less complicated, you can reduce the problem by using a
25553 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
25554 this means that Exim will lose its hints data after a reboot (including retry
25555 hints, the callout cache, and ratelimit data).
25558 .section "Address verification" "SECTaddressverification"
25559 .cindex "verifying address" "options for"
25560 .cindex "policy control" "address verification"
25561 Several of the &%verify%& conditions described in section
25562 &<<SECTaclconditions>>& cause addresses to be verified. These conditions can be
25563 followed by options that modify the verification process. The options are
25564 separated from the keyword and from each other by slashes, and some of them
25565 contain parameters. For example:
25567 verify = sender/callout
25568 verify = recipient/defer_ok/callout=10s,defer_ok
25570 The first stage of address verification, which always happens, is to run the
25571 address through the routers, in &"verify mode"&. Routers can detect the
25572 difference between verification and routing for delivery, and their actions can
25573 be varied by a number of generic options such as &%verify%& and &%verify_only%&
25574 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
25575 The available options are as follows:
25578 If the &%callout%& option is specified, successful routing to one or more
25579 remote hosts is followed by a &"callout"& to those hosts as an additional
25580 check. Callouts and their sub-options are discussed in the next section.
25582 If there is a defer error while doing verification routing, the ACL
25583 normally returns &"defer"&. However, if you include &%defer_ok%& in the
25584 options, the condition is forced to be true instead. Note that this is a main
25585 verification option as well as a suboption for callouts.
25587 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
25588 discusses the reporting of sender address verification failures.
25590 The &%success_on_redirect%& option causes verification always to succeed
25591 immediately after a successful redirection. By default, if a redirection
25592 generates just one address, that address is also verified. See further
25593 discussion in section &<<SECTredirwhilveri>>&.
25596 .cindex "verifying address" "differentiating failures"
25597 .cindex "&$recipient_verify_failure$&"
25598 .cindex "&$sender_verify_failure$&"
25599 .cindex "&$acl_verify_message$&"
25600 After an address verification failure, &$acl_verify_message$& contains the
25601 error message that is associated with the failure. It can be preserved by
25604 warn !verify = sender
25605 set acl_m0 = $acl_verify_message
25607 If you are writing your own custom rejection message or log message when
25608 denying access, you can use this variable to include information about the
25609 verification failure.
25611 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
25612 appropriate) contains one of the following words:
25615 &%qualify%&: The address was unqualified (no domain), and the message
25616 was neither local nor came from an exempted host.
25618 &%route%&: Routing failed.
25620 &%mail%&: Routing succeeded, and a callout was attempted; rejection
25621 occurred at or before the MAIL command (that is, on initial
25622 connection, HELO, or MAIL).
25624 &%recipient%&: The RCPT command in a callout was rejected.
25626 &%postmaster%&: The postmaster check in a callout was rejected.
25629 The main use of these variables is expected to be to distinguish between
25630 rejections of MAIL and rejections of RCPT in callouts.
25635 .section "Callout verification" "SECTcallver"
25636 .cindex "verifying address" "by callout"
25637 .cindex "callout" "verification"
25638 .cindex "SMTP" "callout verification"
25639 For non-local addresses, routing verifies the domain, but is unable to do any
25640 checking of the local part. There are situations where some means of verifying
25641 the local part is desirable. One way this can be done is to make an SMTP
25642 &'callback'& to a delivery host for the sender address or a &'callforward'& to
25643 a subsequent host for a recipient address, to see if the host accepts the
25644 address. We use the term &'callout'& to cover both cases. Note that for a
25645 sender address, the callback is not to the client host that is trying to
25646 deliver the message, but to one of the hosts that accepts incoming mail for the
25649 Exim does not do callouts by default. If you want them to happen, you must
25650 request them by setting appropriate options on the &%verify%& condition, as
25651 described below. This facility should be used with care, because it can add a
25652 lot of resource usage to the cost of verifying an address. However, Exim does
25653 cache the results of callouts, which helps to reduce the cost. Details of
25654 caching are in section &<<SECTcallvercache>>&.
25656 Recipient callouts are usually used only between hosts that are controlled by
25657 the same administration. For example, a corporate gateway host could use
25658 callouts to check for valid recipients on an internal mailserver. A successful
25659 callout does not guarantee that a real delivery to the address would succeed;
25660 on the other hand, a failing callout does guarantee that a delivery would fail.
25662 If the &%callout%& option is present on a condition that verifies an address, a
25663 second stage of verification occurs if the address is successfully routed to
25664 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
25665 &(manualroute)& router, where the router specifies the hosts. However, if a
25666 router that does not set up hosts routes to an &(smtp)& transport with a
25667 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
25668 &%hosts_override%& set, its hosts are always used, whether or not the router
25669 supplies a host list.
25671 The port that is used is taken from the transport, if it is specified and is a
25672 remote transport. (For routers that do verification only, no transport need be
25673 specified.) Otherwise, the default SMTP port is used. If a remote transport
25674 specifies an outgoing interface, this is used; otherwise the interface is not
25677 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
25678 test whether a bounce message could be delivered to the sender address. The
25679 following SMTP commands are sent:
25681 &`HELO `&<&'smtp active host name'&>
25683 &`RCPT TO:`&<&'the address to be tested'&>
25686 LHLO is used instead of HELO if the transport's &%protocol%& option is
25689 A recipient callout check is similar. By default, it also uses an empty address
25690 for the sender. This default is chosen because most hosts do not make use of
25691 the sender address when verifying a recipient. Using the same address means
25692 that a single cache entry can be used for each recipient. Some sites, however,
25693 do make use of the sender address when verifying. These are catered for by the
25694 &%use_sender%& and &%use_postmaster%& options, described in the next section.
25696 If the response to the RCPT command is a 2&'xx'& code, the verification
25697 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
25698 Exim tries the next host, if any. If there is a problem with all the remote
25699 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
25700 &%callout%& option is given, in which case the condition is forced to succeed.
25706 .section "Additional parameters for callouts" "CALLaddparcall"
25707 .cindex "callout" "additional parameters for"
25708 The &%callout%& option can be followed by an equals sign and a number of
25709 optional parameters, separated by commas. For example:
25711 verify = recipient/callout=10s,defer_ok
25713 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
25714 separate verify options, is retained for backwards compatibility, but is now
25715 deprecated. The additional parameters for &%callout%& are as follows:
25719 .vitem <&'a&~time&~interval'&>
25720 .cindex "callout timeout" "specifying"
25721 This specifies the timeout that applies for the callout attempt to each host.
25724 verify = sender/callout=5s
25726 The default is 30 seconds. The timeout is used for each response from the
25727 remote host. It is also used for the intial connection, unless overridden by
25728 the &%connect%& parameter.
25731 .vitem &*connect&~=&~*&<&'time&~interval'&>
25732 .cindex "callout connection timeout" "specifying"
25733 This parameter makes it possible to set a different (usually smaller) timeout
25734 for making the SMTP connection. For example:
25736 verify = sender/callout=5s,connect=1s
25738 If not specified, this timeout defaults to the general timeout value.
25740 .vitem &*defer_ok*&
25741 .cindex "callout defer" "action on"
25742 When this parameter is present, failure to contact any host, or any other kind
25743 of temporary error, is treated as success by the ACL. However, the cache is not
25744 updated in this circumstance.
25746 .vitem &*fullpostmaster*&
25747 .cindex "callout" "full postmaster check"
25748 This operates like the &%postmaster%& option (see below), but if the check for
25749 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
25750 accordance with the specification in RFC 2821. The RFC states that the
25751 unqualified address &'postmaster'& should be accepted.
25754 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
25755 .cindex "callout" "sender when verifying header"
25756 When verifying addresses in header lines using the &%header_sender%&
25757 verification option, Exim behaves by default as if the addresses are envelope
25758 sender addresses from a message. Callout verification therefore tests to see
25759 whether a bounce message could be delivered, by using an empty address in the
25760 MAIL command. However, it is arguable that these addresses might never be used
25761 as envelope senders, and could therefore justifiably reject bounce messages
25762 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
25763 address to use in the MAIL command. For example:
25765 require verify = header_sender/callout=mailfrom=abcd@x.y.z
25767 This parameter is available only for the &%header_sender%& verification option.
25770 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
25771 .cindex "callout overall timeout" "specifying"
25772 This parameter sets an overall timeout for performing a callout verification.
25775 verify = sender/callout=5s,maxwait=30s
25777 This timeout defaults to four times the callout timeout for individual SMTP
25778 commands. The overall timeout applies when there is more than one host that can
25779 be tried. The timeout is checked before trying the next host. This prevents
25780 very long delays if there are a large number of hosts and all are timing out
25781 (for example, when network connections are timing out).
25784 .vitem &*no_cache*&
25785 .cindex "callout cache" "suppressing"
25786 .cindex "caching callout" "suppressing"
25787 When this parameter is given, the callout cache is neither read nor updated.
25789 .vitem &*postmaster*&
25790 .cindex "callout" "postmaster; checking"
25791 When this parameter is set, a sucessful callout check is followed by a similar
25792 check for the local part &'postmaster'& at the same domain. If this address is
25793 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
25794 the postmaster check is recorded in a cache record; if it is a failure, this is
25795 used to fail subsequent callouts for the domain without a connection being
25796 made, until the cache record expires.
25798 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
25799 The postmaster check uses an empty sender in the MAIL command by default.
25800 You can use this parameter to do a postmaster check using a different address.
25803 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
25805 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
25806 one overrides. The &%postmaster%& parameter is equivalent to this example:
25808 require verify = sender/callout=postmaster_mailfrom=
25810 &*Warning*&: The caching arrangements for postmaster checking do not take
25811 account of the sender address. It is assumed that either the empty address or
25812 a fixed non-empty address will be used. All that Exim remembers is that the
25813 postmaster check for the domain succeeded or failed.
25817 .cindex "callout" "&""random""& check"
25818 When this parameter is set, before doing the normal callout check, Exim does a
25819 check for a &"random"& local part at the same domain. The local part is not
25820 really random &-- it is defined by the expansion of the option
25821 &%callout_random_local_part%&, which defaults to
25823 $primary_host_name-$tod_epoch-testing
25825 The idea here is to try to determine whether the remote host accepts all local
25826 parts without checking. If it does, there is no point in doing callouts for
25827 specific local parts. If the &"random"& check succeeds, the result is saved in
25828 a cache record, and used to force the current and subsequent callout checks to
25829 succeed without a connection being made, until the cache record expires.
25831 .vitem &*use_postmaster*&
25832 .cindex "callout" "sender for recipient check"
25833 This parameter applies to recipient callouts only. For example:
25835 deny !verify = recipient/callout=use_postmaster
25837 .cindex "&$qualify_domain$&"
25838 It causes a non-empty postmaster address to be used in the MAIL command when
25839 performing the callout for the recipient, and also for a &"random"& check if
25840 that is configured. The local part of the address is &`postmaster`& and the
25841 domain is the contents of &$qualify_domain$&.
25843 .vitem &*use_sender*&
25844 This option applies to recipient callouts only. For example:
25846 require verify = recipient/callout=use_sender
25848 It causes the message's actual sender address to be used in the MAIL
25849 command when performing the callout, instead of an empty address. There is no
25850 need to use this option unless you know that the called hosts make use of the
25851 sender when checking recipients. If used indiscriminately, it reduces the
25852 usefulness of callout caching.
25855 If you use any of the parameters that set a non-empty sender for the MAIL
25856 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
25857 &%use_sender%&), you should think about possible loops. Recipient checking is
25858 usually done between two hosts that are under the same management, and the host
25859 that receives the callouts is not normally configured to do callouts itself.
25860 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
25861 these circumstances.
25863 However, if you use a non-empty sender address for a callout to an arbitrary
25864 host, there is the likelihood that the remote host will itself initiate a
25865 callout check back to your host. As it is checking what appears to be a message
25866 sender, it is likely to use an empty address in MAIL, thus avoiding a
25867 callout loop. However, to be on the safe side it would be best to set up your
25868 own ACLs so that they do not do sender verification checks when the recipient
25869 is the address you use for header sender or postmaster callout checking.
25871 Another issue to think about when using non-empty senders for callouts is
25872 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
25873 by the sender/recipient combination; thus, for any given recipient, many more
25874 actual callouts are performed than when an empty sender or postmaster is used.
25879 .section "Callout caching" "SECTcallvercache"
25880 .cindex "hints database" "callout cache"
25881 .cindex "callout" "caching"
25882 .cindex "caching" "callout"
25883 Exim caches the results of callouts in order to reduce the amount of resources
25884 used, unless you specify the &%no_cache%& parameter with the &%callout%&
25885 option. A hints database called &"callout"& is used for the cache. Two
25886 different record types are used: one records the result of a callout check for
25887 a specific address, and the other records information that applies to the
25888 entire domain (for example, that it accepts the local part &'postmaster'&).
25890 When an original callout fails, a detailed SMTP error message is given about
25891 the failure. However, for subsequent failures use the cache data, this message
25894 The expiry times for negative and positive address cache records are
25895 independent, and can be set by the global options &%callout_negative_expire%&
25896 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
25898 If a host gives a negative response to an SMTP connection, or rejects any
25899 commands up to and including
25903 (but not including the MAIL command with a non-empty address),
25904 any callout attempt is bound to fail. Exim remembers such failures in a
25905 domain cache record, which it uses to fail callouts for the domain without
25906 making new connections, until the domain record times out. There are two
25907 separate expiry times for domain cache records:
25908 &%callout_domain_negative_expire%& (default 3h) and
25909 &%callout_domain_positive_expire%& (default 7d).
25911 Domain records expire when the negative expiry time is reached if callouts
25912 cannot be made for the domain, or if the postmaster check failed.
25913 Otherwise, they expire when the positive expiry time is reached. This
25914 ensures that, for example, a host that stops accepting &"random"& local parts
25915 will eventually be noticed.
25917 The callout caching mechanism is based on the domain of the address that is
25918 being tested. If the domain routes to several hosts, it is assumed that their
25919 behaviour will be the same.
25923 .section "Sender address verification reporting" "SECTsenaddver"
25924 .cindex "verifying" "suppressing error details"
25925 When sender verification fails in an ACL, the details of the failure are
25926 given as additional output lines before the 550 response to the relevant
25927 SMTP command (RCPT or DATA). For example, if sender callout is in use,
25930 MAIL FROM:<xyz@abc.example>
25932 RCPT TO:<pqr@def.example>
25933 550-Verification failed for <xyz@abc.example>
25934 550-Called: 192.168.34.43
25935 550-Sent: RCPT TO:<xyz@abc.example>
25936 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
25937 550 Sender verification failed
25939 If more than one RCPT command fails in the same way, the details are given
25940 only for the first of them. However, some administrators do not want to send
25941 out this much information. You can suppress the details by adding
25942 &`/no_details`& to the ACL statement that requests sender verification. For
25945 verify = sender/no_details
25948 .section "Redirection while verifying" "SECTredirwhilveri"
25949 .cindex "verifying" "redirection while"
25950 .cindex "address redirection" "while verifying"
25951 A dilemma arises when a local address is redirected by aliasing or forwarding
25952 during verification: should the generated addresses themselves be verified,
25953 or should the successful expansion of the original address be enough to verify
25954 it? By default, Exim takes the following pragmatic approach:
25957 When an incoming address is redirected to just one child address, verification
25958 continues with the child address, and if that fails to verify, the original
25959 verification also fails.
25961 When an incoming address is redirected to more than one child address,
25962 verification does not continue. A success result is returned.
25965 This seems the most reasonable behaviour for the common use of aliasing as a
25966 way of redirecting different local parts to the same mailbox. It means, for
25967 example, that a pair of alias entries of the form
25970 aw123: :fail: Gone away, no forwarding address
25972 work as expected, with both local parts causing verification failure. When a
25973 redirection generates more than one address, the behaviour is more like a
25974 mailing list, where the existence of the alias itself is sufficient for
25975 verification to succeed.
25977 It is possible, however, to change the default behaviour so that all successful
25978 redirections count as successful verifications, however many new addresses are
25979 generated. This is specified by the &%success_on_redirect%& verification
25980 option. For example:
25982 require verify = recipient/success_on_redirect/callout=10s
25984 In this example, verification succeeds if a router generates a new address, and
25985 the callout does not occur, because no address was routed to a remote host.
25990 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
25991 .cindex "CSA" "verifying"
25992 Client SMTP Authorization is a system that allows a site to advertise
25993 which machines are and are not permitted to send email. This is done by placing
25994 special SRV records in the DNS; these are looked up using the client's HELO
25995 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
25996 Authorization checks in Exim are performed by the ACL condition:
26000 This fails if the client is not authorized. If there is a DNS problem, or if no
26001 valid CSA SRV record is found, or if the client is authorized, the condition
26002 succeeds. These three cases can be distinguished using the expansion variable
26003 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
26004 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
26005 be likely to cause problems for legitimate email.
26007 The error messages produced by the CSA code include slightly more
26008 detail. If &$csa_status$& is &"defer"&, this may be because of problems
26009 looking up the CSA SRV record, or problems looking up the CSA target
26010 address record. There are four reasons for &$csa_status$& being &"fail"&:
26013 The client's host name is explicitly not authorized.
26015 The client's IP address does not match any of the CSA target IP addresses.
26017 The client's host name is authorized but it has no valid target IP addresses
26018 (for example, the target's addresses are IPv6 and the client is using IPv4).
26020 The client's host name has no CSA SRV record but a parent domain has asserted
26021 that all subdomains must be explicitly authorized.
26024 The &%csa%& verification condition can take an argument which is the domain to
26025 use for the DNS query. The default is:
26027 verify = csa/$sender_helo_name
26029 This implementation includes an extension to CSA. If the query domain
26030 is an address literal such as [192.0.2.95], or if it is a bare IP
26031 address, Exim searches for CSA SRV records in the reverse DNS as if
26032 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
26035 verify = csa/$sender_host_address
26037 In fact, this is the check that Exim performs if the client does not say HELO.
26038 This extension can be turned off by setting the main configuration option
26039 &%dns_csa_use_reverse%& to be false.
26041 If a CSA SRV record is not found for the domain itself, a search
26042 is performed through its parent domains for a record which might be
26043 making assertions about subdomains. The maximum depth of this search is limited
26044 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
26045 default. Exim does not look for CSA SRV records in a top level domain, so the
26046 default settings handle HELO domains as long as seven
26047 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
26048 of legitimate HELO domains.
26050 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
26051 direct SRV lookups, this is not sufficient because of the extra parent domain
26052 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
26053 addresses into lookups in the reverse DNS space. The result of a successful
26056 ${lookup dnsdb {csa=$sender_helo_name}}
26058 has two space-separated fields: an authorization code and a target host name.
26059 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
26060 authorization required but absent, or &"?"& for unknown.
26065 .section "Bounce address tag validation" "SECTverifyPRVS"
26066 .cindex "BATV" "verifying"
26067 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
26068 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
26069 Genuine incoming bounce messages should therefore always be addressed to
26070 recipients that have a valid tag. This scheme is a way of detecting unwanted
26071 bounce messages caused by sender address forgeries (often called &"collateral
26072 spam"&), because the recipients of such messages do not include valid tags.
26074 There are two expansion items to help with the implementation of the BATV
26075 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
26076 the original envelope sender address by using a simple shared key to add a hash
26077 of the address and some time-based randomizing information. The &%prvs%&
26078 expansion item creates a signed address, and the &%prvscheck%& expansion item
26079 checks one. The syntax of these expansion items is described in section
26080 &<<SECTexpansionitems>>&.
26082 As an example, suppose the secret per-address keys are stored in an MySQL
26083 database. A query to look up the key for an address could be defined as a macro
26086 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
26087 WHERE sender='${quote_mysql:$prvscheck_address}'\
26090 Suppose also that the senders who make use of BATV are defined by an address
26091 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
26094 # Bounces: drop unsigned addresses for BATV senders
26095 deny message = This address does not send an unsigned reverse path.
26097 recipients = +batv_senders
26099 # Bounces: In case of prvs-signed address, check signature.
26100 deny message = Invalid reverse path signature.
26102 condition = ${prvscheck {$local_part@$domain}\
26103 {PRVSCHECK_SQL}{1}}
26104 !condition = $prvscheck_result
26106 The first statement rejects recipients for bounce messages that are addressed
26107 to plain BATV sender addresses, because it is known that BATV senders do not
26108 send out messages with plain sender addresses. The second statement rejects
26109 recipients that are prvs-signed, but with invalid signatures (either because
26110 the key is wrong, or the signature has timed out).
26112 A non-prvs-signed address is not rejected by the second statement, because the
26113 &%prvscheck%& expansion yields an empty string if its first argument is not a
26114 prvs-signed address, thus causing the &%condition%& condition to be false. If
26115 the first argument is a syntactically valid prvs-signed address, the yield is
26116 the third string (in this case &"1"&), whether or not the cryptographic and
26117 timeout checks succeed. The &$prvscheck_result$& variable contains the result
26118 of the checks (empty for failure, &"1"& for success).
26120 There are two more issues you must consider when implementing prvs-signing.
26121 Firstly, you need to ensure that prvs-signed addresses are not blocked by your
26122 ACLs. A prvs-signed address contains a slash character, but the default Exim
26123 configuration contains this statement in the RCPT ACL:
26125 deny message = Restricted characters in address
26126 domains = +local_domains
26127 local_parts = ^[.] : ^.*[@%!/|]
26129 This is a conservative rule that blocks local parts that contain slashes. You
26130 should remove the slash in the last line.
26132 Secondly, you have to ensure that the routers accept prvs-signed addresses and
26133 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
26134 router to remove the signature with a configuration along these lines:
26138 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
26140 This works because, if the third argument of &%prvscheck%& is empty, the result
26141 of the expansion of a prvs-signed address is the decoded value of the original
26142 address. This router should probably be the first of your routers that handles
26145 To create BATV-signed addresses in the first place, a transport of this form
26148 external_smtp_batv:
26150 return_path = ${prvs {$return_path} \
26151 {${lookup mysql{SELECT \
26152 secret FROM batv_prvs WHERE \
26153 sender='${quote_mysql:$sender_address}'} \
26156 If no key can be found for the existing return path, no signing takes place.
26160 .section "Using an ACL to control relaying" "SECTrelaycontrol"
26161 .cindex "&ACL;" "relay control"
26162 .cindex "relaying" "control by ACL"
26163 .cindex "policy control" "relay control"
26164 An MTA is said to &'relay'& a message if it receives it from some host and
26165 delivers it directly to another host as a result of a remote address contained
26166 within it. Redirecting a local address via an alias or forward file and then
26167 passing the message on to another host is not relaying,
26168 .cindex "&""percent hack""&"
26169 but a redirection as a result of the &"percent hack"& is.
26171 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
26172 A host which is acting as a gateway or an MX backup is concerned with incoming
26173 relaying from arbitrary hosts to a specific set of domains. On the other hand,
26174 a host which is acting as a smart host for a number of clients is concerned
26175 with outgoing relaying from those clients to the Internet at large. Often the
26176 same host is fulfilling both functions,
26178 . as illustrated in the diagram below,
26180 but in principle these two kinds of relaying are entirely independent. What is
26181 not wanted is the transmission of mail from arbitrary remote hosts through your
26182 system to arbitrary domains.
26185 You can implement relay control by means of suitable statements in the ACL that
26186 runs for each RCPT command. For convenience, it is often easiest to use
26187 Exim's named list facility to define the domains and hosts involved. For
26188 example, suppose you want to do the following:
26191 Deliver a number of domains to mailboxes on the local host (or process them
26192 locally in some other way). Let's say these are &'my.dom1.example'& and
26193 &'my.dom2.example'&.
26195 Relay mail for a number of other domains for which you are the secondary MX.
26196 These might be &'friend1.example'& and &'friend2.example'&.
26198 Relay mail from the hosts on your local LAN, to whatever domains are involved.
26199 Suppose your LAN is 192.168.45.0/24.
26203 In the main part of the configuration, you put the following definitions:
26205 domainlist local_domains = my.dom1.example : my.dom2.example
26206 domainlist relay_domains = friend1.example : friend2.example
26207 hostlist relay_hosts = 192.168.45.0/24
26209 Now you can use these definitions in the ACL that is run for every RCPT
26213 accept domains = +local_domains : +relay_domains
26214 accept hosts = +relay_hosts
26216 The first statement accepts any RCPT command that contains an address in
26217 the local or relay domains. For any other domain, control passes to the second
26218 statement, which accepts the command only if it comes from one of the relay
26219 hosts. In practice, you will probably want to make your ACL more sophisticated
26220 than this, for example, by including sender and recipient verification. The
26221 default configuration includes a more comprehensive example, which is described
26222 in chapter &<<CHAPdefconfil>>&.
26226 .section "Checking a relay configuration" "SECTcheralcon"
26227 .cindex "relaying" "checking control of"
26228 You can check the relay characteristics of your configuration in the same way
26229 that you can test any ACL behaviour for an incoming SMTP connection, by using
26230 the &%-bh%& option to run a fake SMTP session with which you interact.
26232 For specifically testing for unwanted relaying, the host
26233 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
26234 host from the host on which Exim is running, using the normal telnet port, you
26235 will see a normal telnet connection message and then quite a long delay. Be
26236 patient. The remote host is making an SMTP connection back to your host, and
26237 trying a number of common probes to test for open relay vulnerability. The
26238 results of the tests will eventually appear on your terminal.
26243 . ////////////////////////////////////////////////////////////////////////////
26244 . ////////////////////////////////////////////////////////////////////////////
26246 .chapter "Content scanning at ACL time" "CHAPexiscan"
26247 .scindex IIDcosca "content scanning" "at ACL time"
26248 The extension of Exim to include content scanning at ACL time, formerly known
26249 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
26250 was integrated into the main source for Exim release 4.50, and Tom continues to
26251 maintain it. Most of the wording of this chapter is taken from Tom's
26254 It is also possible to scan the content of messages at other times. The
26255 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
26256 scanning after all the ACLs have run. A transport filter can be used to scan
26257 messages at delivery time (see the &%transport_filter%& option, described in
26258 chapter &<<CHAPtransportgeneric>>&).
26260 If you want to include the ACL-time content-scanning features when you compile
26261 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
26262 &_Local/Makefile_&. When you do that, the Exim binary is built with:
26265 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
26266 for all MIME parts for SMTP and non-SMTP messages, respectively.
26268 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
26269 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
26270 run at the end of message reception (the &%acl_smtp_data%& ACL).
26272 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
26273 of messages, or parts of messages, for debugging purposes.
26275 Additional expansion variables that are set in the new ACL and by the new
26278 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
26281 There is another content-scanning configuration option for &_Local/Makefile_&,
26282 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
26283 condition is compiled, in addition to all the other content-scanning features.
26285 Content-scanning is continually evolving, and new features are still being
26286 added. While such features are still unstable and liable to incompatible
26287 changes, they are made available in Exim by setting options whose names begin
26288 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
26289 this manual. You can find out about them by reading the file called
26290 &_doc/experimental.txt_&.
26292 All the content-scanning facilites work on a MBOX copy of the message that is
26293 temporarily created in a file called:
26295 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
26297 The &_.eml_& extension is a friendly hint to virus scanners that they can
26298 expect an MBOX-like structure inside that file. The file is created when the
26299 first content scanning facility is called. Subsequent calls to content
26300 scanning conditions open the same file again. The directory is recursively
26301 removed when the &%acl_smtp_data%& ACL has finished running, unless
26303 control = no_mbox_unspool
26305 has been encountered. When the MIME ACL decodes files, they are put into the
26306 same directory by default.
26310 .section "Scanning for viruses" "SECTscanvirus"
26311 .cindex "virus scanning"
26312 .cindex "content scanning" "for viruses"
26313 .cindex "content scanning" "the &%malware%& condition"
26314 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
26315 It supports a &"generic"& interface to scanners called via the shell, and
26316 specialized interfaces for &"daemon"& type virus scanners, which are resident
26317 in memory and thus are much faster.
26319 .cindex "&%av_scanner%&"
26320 You can set the &%av_scanner%& option in first part of the Exim configuration
26321 file to specify which scanner to use, together with any additional options that
26322 are needed. The basic syntax is as follows:
26324 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
26326 If you do not set &%av_scanner%&, it defaults to
26328 av_scanner = sophie:/var/run/sophie
26330 If the value of &%av_scanner%& starts with dollar character, it is expanded
26331 before use. The following scanner types are supported in this release:
26334 .vitem &%aveserver%&
26335 .cindex "virus scanners" "Kaspersky"
26336 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
26337 at &url(http://www.kaspersky.com). This scanner type takes one option,
26338 which is the path to the daemon's UNIX socket. The default is shown in this
26341 av_scanner = aveserver:/var/run/aveserver
26345 .cindex "virus scanners" "clamd"
26346 This daemon-type scanner is GPL and free. You can get it at
26347 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
26348 unpack MIME containers, so it used to be recommended to unpack MIME attachments
26349 in the MIME ACL. This no longer believed to be necessary. One option is
26350 required: either the path and name of a UNIX socket file, or a hostname or IP
26351 number, and a port, separated by space, as in the second of these examples:
26353 av_scanner = clamd:/opt/clamd/socket
26354 av_scanner = clamd:192.168.2.100 1234
26356 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
26357 contributing the code for this scanner.
26360 .cindex "virus scanners" "command line interface"
26361 This is the keyword for the generic command line scanner interface. It can be
26362 used to attach virus scanners that are invoked from the shell. This scanner
26363 type takes 3 mandatory options:
26366 The full path and name of the scanner binary, with all command line options,
26367 and a placeholder (&`%s`&) for the directory to scan.
26370 A regular expression to match against the STDOUT and STDERR output of the
26371 virus scanner. If the expression matches, a virus was found. You must make
26372 absolutely sure that this expression matches on &"virus found"&. This is called
26373 the &"trigger"& expression.
26376 Another regular expression, containing exactly one pair of parentheses, to
26377 match the name of the virus found in the scanners output. This is called the
26378 &"name"& expression.
26381 For example, Sophos Sweep reports a virus on a line like this:
26383 Virus 'W32/Magistr-B' found in file ./those.bat
26385 For the trigger expression, we can just match the word &"found"&. For the name
26386 expression, we want to extract the W32/Magistr-B string, so we can match for
26387 the single quotes left and right of it. Altogether, this makes the
26388 configuration setting:
26390 av_scanner = cmdline:\
26391 /path/to/sweep -all -rec -archive %s:\
26395 .cindex "virus scanners" "DrWeb"
26396 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
26397 argument, either a full path to a UNIX socket, or an IP address and port
26398 separated by white space, as in these examples:
26400 av_scanner = drweb:/var/run/drwebd.sock
26401 av_scanner = drweb:192.168.2.20 31337
26403 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
26404 is used. Thanks to Alex Miller for contributing the code for this scanner.
26407 .cindex "virus scanners" "F-Secure"
26408 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
26409 argument which is the path to a UNIX socket. For example:
26411 av_scanner = fsecure:/path/to/.fsav
26413 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
26414 Thelmen for contributing the code for this scanner.
26416 .vitem &%kavdaemon%&
26417 .cindex "virus scanners" "Kaspersky"
26418 This is the scanner daemon of Kaspersky Version 4. This version of the
26419 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
26420 scanner type takes one option, which is the path to the daemon's UNIX socket.
26423 av_scanner = kavdaemon:/opt/AVP/AvpCtl
26425 The default path is &_/var/run/AvpCtl_&.
26428 .cindex "virus scanners" "mksd"
26429 This is a daemon type scanner that is aimed mainly at Polish users, though some
26430 parts of documentation are now available in English. You can get it at
26431 &url(http://linux.mks.com.pl/). The only option for this scanner type is
26432 the maximum number of processes used simultaneously to scan the attachments,
26433 provided that the demime facility is employed and also provided that mksd has
26434 been run with at least the same number of child processes. For example:
26436 av_scanner = mksd:2
26438 You can safely omit this option (the default value is 1).
26441 .cindex "virus scanners" "Sophos and Sophie"
26442 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
26443 You can get Sophie at &url(http://www.vanja.com/tools/sophie/). The only
26444 option for this scanner type is the path to the UNIX socket that Sophie uses
26445 for client communication. For example:
26447 av_scanner = sophie:/tmp/sophie
26449 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
26453 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
26454 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
26457 The &%av_scanner%& option is expanded each time &%malware%& is called. This
26458 makes it possible to use different scanners. See further below for an example.
26459 The &%malware%& condition caches its results, so when you use it multiple times
26460 for the same message, the actual scanning process is only carried out once.
26461 However, using expandable items in &%av_scanner%& disables this caching, in
26462 which case each use of the &%malware%& condition causes a new scan of the
26465 The &%malware%& condition takes a right-hand argument that is expanded before
26466 use. It can then be one of
26469 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
26470 The condition succeeds if a virus was found, and fail otherwise. This is the
26473 &"false"& or &"0"&, in which case no scanning is done and the condition fails
26476 A regular expression, in which case the message is scanned for viruses. The
26477 condition succeeds if a virus is found and its name matches the regular
26478 expression. This allows you to take special actions on certain types of virus.
26481 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
26482 even if there is a problem with the virus scanner.
26484 .cindex "&$malware_name$&"
26485 When a virus is found, the condition sets up an expansion variable called
26486 &$malware_name$& that contains the name of the virus. You can use it in a
26487 &%message%& modifier that specifies the error returned to the sender, and/or in
26490 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
26491 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
26492 &%malware%& condition.
26494 Here is a very simple scanning example:
26496 deny message = This message contains malware ($malware_name)
26500 The next example accepts messages when there is a problem with the scanner:
26502 deny message = This message contains malware ($malware_name)
26504 malware = */defer_ok
26506 The next example shows how to use an ACL variable to scan with both sophie and
26507 aveserver. It assumes you have set:
26509 av_scanner = $acl_m0
26511 in the main Exim configuration.
26513 deny message = This message contains malware ($malware_name)
26514 set acl_m0 = sophie
26517 deny message = This message contains malware ($malware_name)
26518 set acl_m0 = aveserver
26523 .section "Scanning with SpamAssassin" "SECTscanspamass"
26524 .cindex "content scanning" "for spam"
26525 .cindex "spam scanning"
26526 .cindex "SpamAssassin" "scanning with"
26527 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
26528 score and a report for the message. You can get SpamAssassin at
26529 &url(http://www.spamassassin.org), or, if you have a working Perl
26530 installation, you can use CPAN by running:
26532 perl -MCPAN -e 'install Mail::SpamAssassin'
26534 SpamAssassin has its own set of configuration files. Please review its
26535 documentation to see how you can tweak it. The default installation should work
26538 .cindex "&%spamd_address%&"
26539 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
26540 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
26541 port for &%spamd%&, you must set the &%spamd_address%& option in the global
26542 part of the Exim configuration as follows (example):
26544 spamd_address = 192.168.99.45 387
26546 You do not need to set this option if you use the default. As of version 2.60,
26547 &%spamd%& also supports communication over UNIX sockets. If you want to use
26548 these, supply &%spamd_address%& with an absolute file name instead of a
26551 spamd_address = /var/run/spamd_socket
26553 You can have multiple &%spamd%& servers to improve scalability. These can
26554 reside on other hardware reachable over the network. To specify multiple
26555 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
26556 option, separated with colons:
26558 spamd_address = 192.168.2.10 783 : \
26559 192.168.2.11 783 : \
26562 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
26563 fashion. When a server fails to respond to the connection attempt, all other
26564 servers are tried until one succeeds. If no server responds, the &%spam%&
26567 &*Warning*&: It is not possible to use the UNIX socket connection method with
26568 multiple &%spamd%& servers.
26571 .section "Calling SpamAssassin from an Exim ACL"
26572 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
26574 deny message = This message was classified as SPAM
26577 The right-hand side of the &%spam%& condition specifies the username that
26578 SpamAssassin should scan for. If you do not want to scan for a particular user,
26579 but rather use the SpamAssassin system-wide default profile, you can scan for
26580 an unknown user, or simply use &"nobody"&. However, you must put something on
26581 the right-hand side.
26583 The username allows you to use per-domain or per-user antispam profiles. The
26584 right-hand side is expanded before being used, so you can put lookups or
26585 conditions there. When the right-hand side evaluates to &"0"& or &"false"&, no
26586 scanning is done and the condition fails immediately.
26588 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
26589 large ones may cause significant performance degredation. As most spam messages
26590 are quite small, it is recommended that you do not scan the big ones. For
26593 deny message = This message was classified as SPAM
26594 condition = ${if < {$message_size}{10K}}
26598 The &%spam%& condition returns true if the threshold specified in the user's
26599 SpamAssassin profile has been matched or exceeded. If you want to use the
26600 &%spam%& condition for its side effects (see the variables below), you can make
26601 it always return &"true"& by appending &`:true`& to the username.
26603 .cindex "spam scanning" "returned variables"
26605 When the &%spam%& condition is run, it sets up a number of expansion
26606 variables. With the exception of &$spam_score_int$&, these are usable only
26607 within ACLs; their values are not retained with the message and so cannot be
26608 used at delivery time.
26612 .vitem &$spam_score$&
26613 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
26614 for inclusion in log or reject messages.
26616 .vitem &$spam_score_int$&
26617 The spam score of the message, multiplied by ten, as an integer value. For
26618 example &"34"& or &"305"&. This is useful for numeric comparisons in
26619 conditions. This variable is special; its value is saved with the message, and
26620 written to Exim's spool file. This means that it can be used during the whole
26621 life of the message on your Exim system, in particular, in routers or
26622 transports during the later delivery phase.
26624 .vitem &$spam_bar$&
26625 A string consisting of a number of &"+"& or &"-"& characters, representing the
26626 integer part of the spam score value. A spam score of 4.4 would have a
26627 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
26628 headers, since MUAs can match on such strings.
26630 .vitem &$spam_report$&
26631 A multiline text table, containing the full SpamAssassin report for the
26632 message. Useful for inclusion in headers or reject messages.
26635 The &%spam%& condition caches its results. If you call it again with the same
26636 user name, it does not scan again, but rather returns the same values as
26639 The &%spam%& condition returns DEFER if there is any error while running the
26640 message through SpamAssassin. If you want to treat DEFER as FAIL (to pass on to
26641 the next ACL statement block), append &`/defer_ok`& to the right-hand side of
26642 the spam condition, like this:
26644 deny message = This message was classified as SPAM
26645 spam = joe/defer_ok
26647 This causes messages to be accepted even if there is a problem with &%spamd%&.
26649 Here is a longer, commented example of the use of the &%spam%&
26652 # put headers in all messages (no matter if spam or not)
26653 warn message = X-Spam-Score: $spam_score ($spam_bar)
26655 warn message = X-Spam-Report: $spam_report
26658 # add second subject line with *SPAM* marker when message
26659 # is over threshold
26660 warn message = Subject: *SPAM* $h_Subject:
26663 # reject spam at high scores (> 12)
26664 deny message = This message scored $spam_score spam points.
26666 condition = ${if >{$spam_score_int}{120}{1}{0}}
26671 .section "Scanning MIME parts" "SECTscanmimepart"
26672 .cindex "content scanning" "MIME parts"
26673 .cindex "MIME content scanning"
26674 .cindex "&%acl_smtp_mime%&"
26675 .cindex "&%acl_not_smtp_mime%&"
26676 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
26677 each MIME part of an SMTP message, including multipart types, in the sequence
26678 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
26679 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
26680 options may both refer to the same ACL if you want the same processing in both
26683 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
26684 ACL in the case of an SMTP message, or just before a non-SMTP message is
26685 accepted. However, a MIME ACL is called only if the message contains a
26686 &'MIME-Version:'& header line. When a call to a MIME ACL does not yield
26687 &"accept"&, ACL processing is aborted and the appropriate result code is sent
26688 to the client. In the case of an SMTP message, the &%acl_smtp_data%& ACL is not
26689 called when this happens.
26691 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
26692 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
26693 condition to match against the raw MIME part. You can also use the
26694 &%mime_regex%& condition to match against the decoded MIME part (see section
26695 &<<SECTscanregex>>&).
26697 At the start of a MIME ACL, a number of variables are set from the header
26698 information for the relevant MIME part. These are described below. The contents
26699 of the MIME part are not by default decoded into a disk file except for MIME
26700 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
26701 part into a disk file, you can use the &%decode%& modifier. The general syntax
26704 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
26706 The right hand side is expanded before use. After expansion,
26710 &"0"& or &"false"&, in which case no decoding is done.
26712 The string &"default"&. In that case, the file is put in the temporary
26713 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
26714 a sequential file name consisting of the message id and a sequence number. The
26715 full path and name is available in &$mime_decoded_filename$& after decoding.
26717 A full path name starting with a slash. If the full name is an existing
26718 directory, it is used as a replacement for the default directory. The filename
26719 is then sequentially assigned. If the path does not exist, it is used as
26720 the full path and file name.
26722 If the string does not start with a slash, it is used as the
26723 filename, and the default path is then used.
26726 You can easily decode a file with its original, proposed filename using
26728 decode = $mime_filename
26730 However, you should keep in mind that &$mime_filename$& might contain
26731 anything. If you place files outside of the default path, they are not
26732 automatically unlinked.
26734 For RFC822 attachments (these are messages attached to messages, with a
26735 content-type of &"message/rfc822"&), the ACL is called again in the same manner
26736 as for the primary message, only that the &$mime_is_rfc822$& expansion
26737 variable is set (see below). Attached messages are always decoded to disk
26738 before being checked, and the files are unlinked once the check is done.
26740 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
26741 used to match regular expressions against raw and decoded MIME parts,
26742 respectively. They are described in section &<<SECTscanregex>>&.
26744 .cindex "MIME content scanning" "returned variables"
26745 The following list describes all expansion variables that are
26746 available in the MIME ACL:
26749 .vitem &$mime_boundary$&
26750 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
26751 have a boundary string, which is stored in this variable. If the current part
26752 has no boundary parameter in the &'Content-Type:'& header, this variable
26753 contains the empty string.
26755 .vitem &$mime_charset$&
26756 This variable contains the character set identifier, if one was found in the
26757 &'Content-Type:'& header. Examples for charset identifiers are:
26763 Please note that this value is not normalized, so you should do matches
26764 case-insensitively.
26766 .vitem &$mime_content_description$&
26767 This variable contains the normalized content of the &'Content-Description:'&
26768 header. It can contain a human-readable description of the parts content. Some
26769 implementations repeat the filename for attachments here, but they are usually
26770 only used for display purposes.
26772 .vitem &$mime_content_disposition$&
26773 This variable contains the normalized content of the &'Content-Disposition:'&
26774 header. You can expect strings like &"attachment"& or &"inline"& here.
26776 .vitem &$mime_content_id$&
26777 This variable contains the normalized content of the &'Content-ID:'& header.
26778 This is a unique ID that can be used to reference a part from another part.
26780 .vitem &$mime_content_size$&
26781 This variable is set only after the &%decode%& modifier (see above) has been
26782 successfully run. It contains the size of the decoded part in kilobytes. The
26783 size is always rounded up to full kilobytes, so only a completely empty part
26784 has a &$mime_content_size$& of zero.
26786 .vitem &$mime_content_transfer_encoding$&
26787 This variable contains the normalized content of the
26788 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
26789 type. Typical values are &"base64"& and &"quoted-printable"&.
26791 .vitem &$mime_content_type$&
26792 If the MIME part has a &'Content-Type:'& header, this variable contains its
26793 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
26794 are some examples of popular MIME types, as they may appear in this variable:
26798 application/octet-stream
26802 If the MIME part has no &'Content-Type:'& header, this variable contains the
26805 .vitem &$mime_decoded_filename$&
26806 This variable is set only after the &%decode%& modifier (see above) has been
26807 successfully run. It contains the full path and file name of the file
26808 containing the decoded data.
26813 .vitem &$mime_filename$&
26814 This is perhaps the most important of the MIME variables. It contains a
26815 proposed filename for an attachment, if one was found in either the
26816 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
26817 RFC2047 decoded, but no additional sanity checks are done. If no filename was
26818 found, this variable contains the empty string.
26820 .vitem &$mime_is_coverletter$&
26821 This variable attempts to differentiate the &"cover letter"& of an e-mail from
26822 attached data. It can be used to clamp down on flashy or unneccessarily encoded
26823 content in the cover letter, while not restricting attachments at all.
26825 The variable contains 1 (true) for a MIME part believed to be part of the
26826 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
26830 The outermost MIME part of a message is always a cover letter.
26833 If a multipart/alternative or multipart/related MIME part is a cover letter,
26834 so are all MIME subparts within that multipart.
26837 If any other multipart is a cover letter, the first subpart is a cover letter,
26838 and the rest are attachments.
26841 All parts contained within an attachment multipart are attachments.
26844 As an example, the following will ban &"HTML mail"& (including that sent with
26845 alternative plain text), while allowing HTML files to be attached. HTML
26846 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
26848 deny message = HTML mail is not accepted here
26849 !condition = $mime_is_rfc822
26850 condition = $mime_is_coverletter
26851 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
26853 .vitem &$mime_is_multipart$&
26854 This variable has the value 1 (true) when the current part has the main type
26855 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
26856 Since multipart entities only serve as containers for other parts, you may not
26857 want to carry out specific actions on them.
26859 .vitem &$mime_is_rfc822$&
26860 This variable has the value 1 (true) if the current part is not a part of the
26861 checked message itself, but part of an attached message. Attached message
26862 decoding is fully recursive.
26864 .vitem &$mime_part_count$&
26865 This variable is a counter that is raised for each processed MIME part. It
26866 starts at zero for the very first part (which is usually a multipart). The
26867 counter is per-message, so it is reset when processing RFC822 attachments (see
26868 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
26869 complete, so you can use it in the DATA ACL to determine the number of MIME
26870 parts of a message. For non-MIME messages, this variable contains the value -1.
26875 .section "Scanning with regular expressions" "SECTscanregex"
26876 .cindex "content scanning" "with regular expressions"
26877 .cindex "regular expressions" "content scanning with"
26878 You can specify your own custom regular expression matches on the full body of
26879 the message, or on individual MIME parts.
26881 The &%regex%& condition takes one or more regular expressions as arguments and
26882 matches them against the full message (when called in the DATA ACL) or a raw
26883 MIME part (when called in the MIME ACL). The &%regex%& condition matches
26884 linewise, with a maximum line length of 32K characters. That means you cannot
26885 have multiline matches with the &%regex%& condition.
26887 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
26888 to 32K of decoded content (the whole content at once, not linewise). If the
26889 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
26890 is decoded automatically when &%mime_regex%& is executed (using default path
26891 and filename values). If the decoded data is larger than 32K, only the first
26892 32K characters are checked.
26894 The regular expressions are passed as a colon-separated list. To include a
26895 literal colon, you must double it. Since the whole right-hand side string is
26896 expanded before being used, you must also escape dollar signs and backslashes
26897 with more backslashes, or use the &`\N`& facility to disable expansion.
26898 Here is a simple example that contains two regular expressions:
26900 deny message = contains blacklisted regex ($regex_match_string)
26901 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
26903 The conditions returns true if any one of the regular expressions matches. The
26904 &$regex_match_string$& expansion variable is then set up and contains the
26905 matching regular expression.
26907 &*Warning*&: With large messages, these conditions can be fairly
26913 .section "The demime condition" "SECTdemimecond"
26914 .cindex "content scanning" "MIME checking"
26915 .cindex "MIME content scanning"
26916 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
26917 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
26918 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
26919 ACL functionality, but provides no additional facilities. Please note that this
26920 condition is deprecated and kept only for backward compatibility. You must set
26921 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
26922 use the &%demime%& condition.
26924 The &%demime%& condition unpacks MIME containers in the message. It detects
26925 errors in MIME containers and can match file extensions found in the message
26926 against a list. Using this facility produces files containing the unpacked MIME
26927 parts of the message in the temporary scan directory. If you do antivirus
26928 scanning, it is recommened that you use the &%demime%& condition before the
26929 antivirus (&%malware%&) condition.
26931 On the right-hand side of the &%demime%& condition you can pass a
26932 colon-separated list of file extensions that it should match against. For
26935 deny message = Found blacklisted file attachment
26936 demime = vbs:com:bat:pif:prf:lnk
26938 If one of the file extensions is found, the condition is true, otherwise it is
26939 false. If there is a temporary error while demimeing (for example, &"disk
26940 full"&), the condition defers, and the message is temporarily rejected (unless
26941 the condition is on a &%warn%& verb).
26943 The right-hand side is expanded before being treated as a list, so you can have
26944 conditions and lookups there. If it expands to an empty string, &"false"&, or
26945 zero (&"0"&), no demimeing is done and the condition is false.
26947 The &%demime%& condition set the following variables:
26950 .vitem &$demime_errorlevel$&
26951 .cindex "&$demime_errorlevel$&"
26952 When an error is detected in a MIME container, this variable contains the
26953 severity of the error, as an integer number. The higher the value, the more
26954 severe the error (the current maximum value is 3). If this variable is unset or
26955 zero, no error occurred.
26957 .vitem &$demime_reason$&
26958 .cindex "&$demime_reason$&"
26959 When &$demime_errorlevel$& is greater than zero, this variable contains a
26960 human-readable text string describing the MIME error that occurred.
26964 .vitem &$found_extension$&
26965 .cindex "&$found_extension$&"
26966 When the &%demime%& condition is true, this variable contains the file
26967 extension it found.
26970 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
26971 the &%demime%& condition, and are not changed on subsequent calls.
26973 If you do not want to check for file extensions, but rather use the &%demime%&
26974 condition for unpacking or error checking purposes, pass &"*"& as the
26975 right-hand side value. Here is a more elaborate example of how to use this
26978 # Reject messages with serious MIME container errors
26979 deny message = Found MIME error ($demime_reason).
26981 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
26983 # Reject known virus spreading file extensions.
26984 # Accepting these is pretty much braindead.
26985 deny message = contains $found_extension file (blacklisted).
26986 demime = com:vbs:bat:pif:scr
26988 # Freeze .exe and .doc files. Postmaster can
26989 # examine them and eventually thaw them.
26990 deny log_message = Another $found_extension file.
26999 . ////////////////////////////////////////////////////////////////////////////
27000 . ////////////////////////////////////////////////////////////////////////////
27002 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
27003 "Local scan function"
27004 .scindex IIDlosca "&[local_scan()]& function" "description of"
27005 .cindex "customizing" "input scan using C function"
27006 .cindex "policy control" "by local scan function"
27007 In these days of email worms, viruses, and ever-increasing spam, some sites
27008 want to apply a lot of checking to messages before accepting them.
27010 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
27011 passing messages to external virus and spam scanning software. You can also do
27012 a certain amount in Exim itself through string expansions and the &%condition%&
27013 condition in the ACL that runs after the SMTP DATA command or the ACL for
27014 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
27016 To allow for further customization to a site's own requirements, there is the
27017 possibility of linking Exim with a private message scanning function, written
27018 in C. If you want to run code that is written in something other than C, you
27019 can of course use a little C stub to call it.
27021 The local scan function is run once for every incoming message, at the point
27022 when Exim is just about to accept the message.
27023 It can therefore be used to control non-SMTP messages from local processes as
27024 well as messages arriving via SMTP.
27026 Exim applies a timeout to calls of the local scan function, and there is an
27027 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
27028 Zero means &"no timeout"&.
27029 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
27030 before calling the local scan function, so that the most common types of crash
27031 are caught. If the timeout is exceeded or one of those signals is caught, the
27032 incoming message is rejected with a temporary error if it is an SMTP message.
27033 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
27034 code. The incident is logged on the main and reject logs.
27038 .section "Building Exim to use a local scan function"
27039 .cindex "&[local_scan()]& function" "building Exim to use"
27040 To make use of the local scan function feature, you must tell Exim where your
27041 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
27042 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
27043 directory, so you might set
27045 LOCAL_SCAN_SOURCE=Local/local_scan.c
27047 for example. The function must be called &[local_scan()]&. It is called by
27048 Exim after it has received a message, when the success return code is about to
27049 be sent. This is after all the ACLs have been run. The return code from your
27050 function controls whether the message is actually accepted or not. There is a
27051 commented template function (that just accepts the message) in the file
27052 _src/local_scan.c_.
27054 If you want to make use of Exim's run time configuration file to set options
27055 for your &[local_scan()]& function, you must also set
27057 LOCAL_SCAN_HAS_OPTIONS=yes
27059 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
27064 .section "API for local_scan()" "SECTapiforloc"
27065 .cindex "&[local_scan()]& function" "API description"
27066 You must include this line near the start of your code:
27068 #include "local_scan.h"
27070 This header file defines a number of variables and other values, and the
27071 prototype for the function itself. Exim is coded to use unsigned char values
27072 almost exclusively, and one of the things this header defines is a shorthand
27073 for &`unsigned char`& called &`uschar`&.
27074 It also contains the following macro definitions, to simplify casting character
27075 strings and pointers to character strings:
27077 #define CS (char *)
27078 #define CCS (const char *)
27079 #define CSS (char **)
27080 #define US (unsigned char *)
27081 #define CUS (const unsigned char *)
27082 #define USS (unsigned char **)
27084 The function prototype for &[local_scan()]& is:
27086 extern int local_scan(int fd, uschar **return_text);
27088 The arguments are as follows:
27091 &%fd%& is a file descriptor for the file that contains the body of the message
27092 (the -D file). The file is open for reading and writing, but updating it is not
27093 recommended. &*Warning*&: You must &'not'& close this file descriptor.
27095 The descriptor is positioned at character 19 of the file, which is the first
27096 character of the body itself, because the first 19 characters are the message
27097 id followed by &`-D`& and a newline. If you rewind the file, you should use the
27098 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
27099 case this changes in some future version.
27101 &%return_text%& is an address which you can use to return a pointer to a text
27102 string at the end of the function. The value it points to on entry is NULL.
27105 The function must return an &%int%& value which is one of the following macros:
27108 .vitem &`LOCAL_SCAN_ACCEPT`&
27109 .cindex "&$local_scan_data$&"
27110 The message is accepted. If you pass back a string of text, it is saved with
27111 the message, and made available in the variable &$local_scan_data$&. No
27112 newlines are permitted (if there are any, they are turned into spaces) and the
27113 maximum length of text is 1000 characters.
27115 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
27116 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
27117 queued without immediate delivery, and is frozen.
27119 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
27120 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
27121 queued without immediate delivery.
27123 .vitem &`LOCAL_SCAN_REJECT`&
27124 The message is rejected; the returned text is used as an error message which is
27125 passed back to the sender and which is also logged. Newlines are permitted &--
27126 they cause a multiline response for SMTP rejections, but are converted to
27127 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
27130 .vitem &`LOCAL_SCAN_TEMPREJECT`&
27131 The message is temporarily rejected; the returned text is used as an error
27132 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
27135 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
27136 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
27137 message is not written to the reject log. It has the effect of unsetting the
27138 &%rejected_header%& log selector for just this rejection. If
27139 &%rejected_header%& is already unset (see the discussion of the
27140 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
27141 same as LOCAL_SCAN_REJECT.
27143 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
27144 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
27145 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
27148 If the message is not being received by interactive SMTP, rejections are
27149 reported by writing to &%stderr%& or by sending an email, as configured by the
27150 &%-oe%& command line options.
27154 .section "Configuration options for local_scan()" "SECTconoptloc"
27155 .cindex "&[local_scan()]& function" "configuration options"
27156 It is possible to have option settings in the main configuration file
27157 that set values in static variables in the &[local_scan()]& module. If you
27158 want to do this, you must have the line
27160 LOCAL_SCAN_HAS_OPTIONS=yes
27162 in your &_Local/Makefile_& when you build Exim. (This line is in
27163 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
27164 file, you must define static variables to hold the option values, and a table
27167 The table must be a vector called &%local_scan_options%&, of type
27168 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
27169 and a pointer to the variable that holds the value. The entries must appear in
27170 alphabetical order. Following &%local_scan_options%& you must also define a
27171 variable called &%local_scan_options_count%& that contains the number of
27172 entries in the table. Here is a short example, showing two kinds of option:
27174 static int my_integer_option = 42;
27175 static uschar *my_string_option = US"a default string";
27177 optionlist local_scan_options[] = {
27178 { "my_integer", opt_int, &my_integer_option },
27179 { "my_string", opt_stringptr, &my_string_option }
27182 int local_scan_options_count =
27183 sizeof(local_scan_options)/sizeof(optionlist);
27185 The values of the variables can now be changed from Exim's runtime
27186 configuration file by including a local scan section as in this example:
27190 my_string = some string of text...
27192 The available types of option data are as follows:
27195 .vitem &*opt_bool*&
27196 This specifies a boolean (true/false) option. The address should point to a
27197 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
27198 that are defined as &"1"& and &"0"&, respectively. If you want to detect
27199 whether such a variable has been set at all, you can initialize it to
27200 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
27203 .vitem &*opt_fixed*&
27204 This specifies a fixed point number, such as is used for load averages.
27205 The address should point to a variable of type &`int`&. The value is stored
27206 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
27209 This specifies an integer; the address should point to a variable of type
27210 &`int`&. The value may be specified in any of the integer formats accepted by
27213 .vitem &*opt_mkint*&
27214 This is the same as &%opt_int%&, except that when such a value is output in a
27215 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
27216 printed with the suffix K or M.
27218 .vitem &*opt_octint*&
27219 This also specifies an integer, but the value is always interpeted as an
27220 octal integer, whether or not it starts with the digit zero, and it is
27221 always output in octal.
27223 .vitem &*opt_stringptr*&
27224 This specifies a string value; the address must be a pointer to a
27225 variable that points to a string (for example, of type &`uschar *`&).
27227 .vitem &*opt_time*&
27228 This specifies a time interval value. The address must point to a variable of
27229 type &`int`&. The value that is placed there is a number of seconds.
27232 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
27233 out the values of all the &[local_scan()]& options.
27237 .section "Available Exim variables"
27238 .cindex "&[local_scan()]& function" "available Exim variables"
27239 The header &_local_scan.h_& gives you access to a number of C variables. These
27240 are the only ones that are guaranteed to be maintained from release to release.
27241 Note, however, that you can obtain the value of any Exim variable by calling
27242 &'expand_string()'&. The exported variables are as follows:
27245 .vitem &*unsigned&~int&~debug_selector*&
27246 This variable is set to zero when no debugging is taking place. Otherwise, it
27247 is a bitmap of debugging selectors. Two bits are identified for use in
27248 &[local_scan()]&; they are defined as macros:
27251 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
27252 testing option that is not privileged &-- any caller may set it. All the
27253 other selector bits can be set only by admin users.
27256 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
27257 by the &`+local_scan`& debug selector. It is not included in the default set
27261 Thus, to write to the debugging output only when &`+local_scan`& has been
27262 selected, you should use code like this:
27264 if ((debug_selector & D_local_scan) != 0)
27265 debug_printf("xxx", ...);
27267 .vitem &*uschar&~*expand_string_message*&
27268 After a failing call to &'expand_string()'& (returned value NULL), the
27269 variable &%expand_string_message%& contains the error message, zero-terminated.
27271 .vitem &*header_line&~*header_list*&
27272 A pointer to a chain of header lines. The &%header_line%& structure is
27275 .vitem &*header_line&~*header_last*&
27276 A pointer to the last of the header lines.
27278 .vitem &*uschar&~*headers_charset*&
27279 The value of the &%headers_charset%& configuration option.
27281 .vitem &*BOOL&~host_checking*&
27282 This variable is TRUE during a host checking session that is initiated by the
27283 &%-bh%& command line option.
27285 .vitem &*uschar&~*interface_address*&
27286 The IP address of the interface that received the message, as a string. This
27287 is NULL for locally submitted messages.
27289 .vitem &*int&~interface_port*&
27290 The port on which this message was received.
27292 .vitem &*uschar&~*message_id*&
27293 This variable contains Exim's message id for the incoming message (the value of
27294 &$message_exim_id$&) as a zero-terminated string.
27296 .vitem &*uschar&~*received_protocol*&
27297 The name of the protocol by which the message was received.
27299 .vitem &*int&~recipients_count*&
27300 The number of accepted recipients.
27302 .vitem &*recipient_item&~*recipients_list*&
27303 .cindex "recipient" "adding in local scan"
27304 .cindex "recipient" "removing in local scan"
27305 The list of accepted recipients, held in a vector of length
27306 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
27307 can add additional recipients by calling &'receive_add_recipient()'& (see
27308 below). You can delete recipients by removing them from the vector and adusting
27309 the value in &%recipients_count%&. In particular, by setting
27310 &%recipients_count%& to zero you remove all recipients. If you then return the
27311 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
27312 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
27313 and then call &'receive_add_recipient()'& as often as needed.
27315 .vitem &*uschar&~*sender_address*&
27316 The envelope sender address. For bounce messages this is the empty string.
27318 .vitem &*uschar&~*sender_host_address*&
27319 The IP address of the sending host, as a string. This is NULL for
27320 locally-submitted messages.
27322 .vitem &*uschar&~*sender_host_authenticated*&
27323 The name of the authentication mechanism that was used, or NULL if the message
27324 was not received over an authenticated SMTP connection.
27326 .vitem &*uschar&~*sender_host_name*&
27327 The name of the sending host, if known.
27329 .vitem &*int&~sender_host_port*&
27330 The port on the sending host.
27332 .vitem &*BOOL&~smtp_input*&
27333 This variable is TRUE for all SMTP input, including BSMTP.
27335 .vitem &*BOOL&~smtp_batched_input*&
27336 This variable is TRUE for BSMTP input.
27338 .vitem &*int&~store_pool*&
27339 The contents of this variable control which pool of memory is used for new
27340 requests. See section &<<SECTmemhanloc>>& for details.
27344 .section "Structure of header lines"
27345 The &%header_line%& structure contains the members listed below.
27346 You can add additional header lines by calling the &'header_add()'& function
27347 (see below). You can cause header lines to be ignored (deleted) by setting
27352 .vitem &*struct&~header_line&~*next*&
27353 A pointer to the next header line, or NULL for the last line.
27355 .vitem &*int&~type*&
27356 A code identifying certain headers that Exim recognizes. The codes are printing
27357 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
27358 Notice in particular that any header line whose type is * is not transmitted
27359 with the message. This flagging is used for header lines that have been
27360 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
27361 lines.) Effectively, * means &"deleted"&.
27363 .vitem &*int&~slen*&
27364 The number of characters in the header line, including the terminating and any
27367 .vitem &*uschar&~*text*&
27368 A pointer to the text of the header. It always ends with a newline, followed by
27369 a zero byte. Internal newlines are preserved.
27374 .section "Structure of recipient items"
27375 The &%recipient_item%& structure contains these members:
27378 .vitem &*uschar&~*address*&
27379 This is a pointer to the recipient address as it was received.
27381 .vitem &*int&~pno*&
27382 This is used in later Exim processing when top level addresses are created by
27383 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
27384 and must always contain -1 at this stage.
27386 .vitem &*uschar&~*errors_to*&
27387 If this value is not NULL, bounce messages caused by failing to deliver to the
27388 recipient are sent to the address it contains. In other words, it overrides the
27389 envelope sender for this one recipient. (Compare the &%errors_to%& generic
27390 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
27391 an unqualified address, Exim qualifies it using the domain from
27392 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
27393 is NULL for all recipients.
27398 .section "Available Exim functions"
27399 .cindex "&[local_scan()]& function" "available Exim functions"
27400 The header &_local_scan.h_& gives you access to a number of Exim functions.
27401 These are the only ones that are guaranteed to be maintained from release to
27405 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
27406 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
27408 This function creates a child process that runs the command specified by
27409 &%argv%&. The environment for the process is specified by &%envp%&, which can
27410 be NULL if no environment variables are to be passed. A new umask is supplied
27411 for the process in &%newumask%&.
27413 Pipes to the standard input and output of the new process are set up
27414 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
27415 standard error is cloned to the standard output. If there are any file
27416 descriptors &"in the way"& in the new process, they are closed. If the final
27417 argument is TRUE, the new process is made into a process group leader.
27419 The function returns the pid of the new process, or -1 if things go wrong.
27421 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
27422 This function waits for a child process to terminate, or for a timeout (in
27423 seconds) to expire. A timeout value of zero means wait as long as it takes. The
27424 return value is as follows:
27429 The process terminated by a normal exit and the value is the process
27435 The process was terminated by a signal and the value is the negation of the
27441 The process timed out.
27445 The was some other error in wait(); &%errno%& is still set.
27448 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
27449 This function provide you with a means of submitting a new message to
27450 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
27451 want, but this packages it all up for you.) The function creates a pipe,
27452 forks a subprocess that is running
27454 exim -t -oem -oi -f <>
27456 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
27457 that is connected to the standard input. The yield of the function is the PID
27458 of the subprocess. You can then write a message to the file descriptor, with
27459 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
27461 When you have finished, call &'child_close()'& to wait for the process to
27462 finish and to collect its ending status. A timeout value of zero is usually
27463 fine in this circumstance. Unless you have made a mistake with the recipient
27464 addresses, you should get a return code of zero.
27467 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
27468 *sender_authentication)*&
27469 This function is a more sophisticated version of &'child_open()'&. The command
27472 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
27474 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
27477 .vitem &*void&~debug_printf(char&~*,&~...)*&
27478 This is Exim's debugging function, with arguments as for &'(printf()'&. The
27479 output is written to the standard error stream. If no debugging is selected,
27480 calls to &'debug_printf()'& have no effect. Normally, you should make calls
27481 conditional on the &`local_scan`& debug selector by coding like this:
27483 if ((debug_selector & D_local_scan) != 0)
27484 debug_printf("xxx", ...);
27487 .vitem &*uschar&~*expand_string(uschar&~*string)*&
27488 This is an interface to Exim's string expansion code. The return value is the
27489 expanded string, or NULL if there was an expansion failure.
27490 The C variable &%expand_string_message%& contains an error message after an
27491 expansion failure. If expansion does not change the string, the return value is
27492 the pointer to the input string. Otherwise, the return value points to a new
27493 block of memory that was obtained by a call to &'store_get()'&. See section
27494 &<<SECTmemhanloc>>& below for a discussion of memory handling.
27496 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
27497 This function allows you to an add additional header line at the end of the
27498 existing ones. The first argument is the type, and should normally be a space
27499 character. The second argument is a format string and any number of
27500 substitution arguments as for &[sprintf()]&. You may include internal newlines
27501 if you want, and you must ensure that the string ends with a newline.
27503 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
27504 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
27505 This function adds a new header line at a specified point in the header
27506 chain. The header itself is specified as for &'header_add()'&.
27508 If &%name%& is NULL, the new header is added at the end of the chain if
27509 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
27510 NULL, the header lines are searched for the first non-deleted header that
27511 matches the name. If one is found, the new header is added before it if
27512 &%after%& is false. If &%after%& is true, the new header is added after the
27513 found header and any adjacent subsequent ones with the same name (even if
27514 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
27515 option controls where the header is added. If it is true, addition is at the
27516 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
27517 headers, or at the top if there are no &'Received:'& headers, you could use
27519 header_add_at_position(TRUE, US"Received", TRUE,
27520 ' ', "X-xxx: ...");
27522 Normally, there is always at least one non-deleted &'Received:'& header, but
27523 there may not be if &%received_header_text%& expands to an empty string.
27526 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
27527 This function removes header lines. If &%occurrence%& is zero or negative, all
27528 occurrences of the header are removed. If occurrence is greater than zero, that
27529 particular instance of the header is removed. If no header(s) can be found that
27530 match the specification, the function does nothing.
27533 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
27534 int&~length,&~BOOL&~notdel)*&"
27535 This function tests whether the given header has the given name. It is not just
27536 a string comparison, because white space is permitted between the name and the
27537 colon. If the &%notdel%& argument is true, a false return is forced for all
27538 &"deleted"& headers; otherwise they are not treated specially. For example:
27540 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
27542 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
27543 .cindex "base64 encoding" "functions for &[local_scan()]& use"
27544 This function base64-encodes a string, which is passed by address and length.
27545 The text may contain bytes of any value, including zero. The result is passed
27546 back in dynamic memory that is obtained by calling &'store_get()'&. It is
27549 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
27550 This function decodes a base64-encoded string. Its arguments are a
27551 zero-terminated base64-encoded string and the address of a variable that is set
27552 to point to the result, which is in dynamic memory. The length of the decoded
27553 string is the yield of the function. If the input is invalid base64 data, the
27554 yield is -1. A zero byte is added to the end of the output string to make it
27555 easy to interpret as a C string (assuming it contains no zeros of its own). The
27556 added zero byte is not included in the returned count.
27558 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
27559 This function checks for a match in a domain list. Domains are always
27560 matched caselessly. The return value is one of the following:
27562 &`OK `& match succeeded
27563 &`FAIL `& match failed
27564 &`DEFER `& match deferred
27566 DEFER is usually caused by some kind of lookup defer, such as the
27567 inability to contact a database.
27569 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
27571 This function checks for a match in a local part list. The third argument
27572 controls case-sensitivity. The return values are as for
27573 &'lss_match_domain()'&.
27575 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
27577 This function checks for a match in an address list. The third argument
27578 controls the case-sensitivity of the local part match. The domain is always
27579 matched caselessly. The return values are as for &'lss_match_domain()'&.
27581 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
27583 This function checks for a match in a host list. The most common usage is
27586 lss_match_host(sender_host_name, sender_host_address, ...)
27588 .cindex "&$sender_host_address$&"
27589 An empty address field matches an empty item in the host list. If the host name
27590 is NULL, the name corresponding to &$sender_host_address$& is automatically
27591 looked up if a host name is required to match an item in the list. The return
27592 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
27593 returns ERROR in the case when it had to look up a host name, but the lookup
27596 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
27598 This function writes to Exim's log files. The first argument should be zero (it
27599 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
27600 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
27601 them. It specifies to which log or logs the message is written. The remaining
27602 arguments are a format and relevant insertion arguments. The string should not
27603 contain any newlines, not even at the end.
27606 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
27607 This function adds an additional recipient to the message. The first argument
27608 is the recipient address. If it is unqualified (has no domain), it is qualified
27609 with the &%qualify_recipient%& domain. The second argument must always be -1.
27611 This function does not allow you to specify a private &%errors_to%& address (as
27612 described with the structure of &%recipient_item%& above), because it pre-dates
27613 the addition of that field to the structure. However, it is easy to add such a
27614 value afterwards. For example:
27616 receive_add_recipient(US"monitor@mydom.example", -1);
27617 recipients_list[recipients_count-1].errors_to =
27618 US"postmaster@mydom.example";
27621 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
27622 This is a convenience function to remove a named recipient from the list of
27623 recipients. It returns true if a recipient was removed, and false if no
27624 matching recipient could be found. The argument must be a complete email
27631 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
27632 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
27633 This function decodes strings that are encoded according to RFC 2047. Typically
27634 these are the contents of header lines. First, each &"encoded word"& is decoded
27635 from the Q or B encoding into a byte-string. Then, if provided with the name of
27636 a charset encoding, and if the &[iconv()]& function is available, an attempt is
27637 made to translate the result to the named character set. If this fails, the
27638 binary string is returned with an error message.
27640 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
27641 maximum MIME word length is enforced. The third argument is the target
27642 encoding, or NULL if no translation is wanted.
27644 .cindex "binary zero" "in RFC 2047 decoding"
27645 .cindex "RFC 2047" "binary zero in"
27646 If a binary zero is encountered in the decoded string, it is replaced by the
27647 contents of the &%zeroval%& argument. For use with Exim headers, the value must
27648 not be 0 because header lines are handled as zero-terminated strings.
27650 The function returns the result of processing the string, zero-terminated; if
27651 &%lenptr%& is not NULL, the length of the result is set in the variable to
27652 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
27654 If an error is encountered, the function returns NULL and uses the &%error%&
27655 argument to return an error message. The variable pointed to by &%error%& is
27656 set to NULL if there is no error; it may be set non-NULL even when the function
27657 returns a non-NULL value if decoding was successful, but there was a problem
27661 .vitem &*int&~smtp_fflush(void)*&
27662 This function is used in conjunction with &'smtp_printf()'&, as described
27665 .vitem &*void&~smtp_printf(char&~*,&~...)*&
27666 The arguments of this function are like &[printf()]&; it writes to the SMTP
27667 output stream. You should use this function only when there is an SMTP output
27668 stream, that is, when the incoming message is being received via interactive
27669 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
27670 is FALSE. If you want to test for an incoming message from another host (as
27671 opposed to a local process that used the &%-bs%& command line option), you can
27672 test the value of &%sender_host_address%&, which is non-NULL when a remote host
27675 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
27676 output function, so it can be used for all forms of SMTP connection.
27678 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
27679 must start with an appropriate response code: 550 if you are going to return
27680 LOCAL_SCAN_REJECT, 451 if you are going to return
27681 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
27682 initial lines of a multi-line response, the code must be followed by a hyphen
27683 to indicate that the line is not the final response line. You must also ensure
27684 that the lines you write terminate with CRLF. For example:
27686 smtp_printf("550-this is some extra info\r\n");
27687 return LOCAL_SCAN_REJECT;
27689 Note that you can also create multi-line responses by including newlines in
27690 the data returned via the &%return_text%& argument. The added value of using
27691 &'smtp_printf()'& is that, for instance, you could introduce delays between
27692 multiple output lines.
27694 The &'smtp_printf()'& function does not return any error indication, because it
27695 does not automatically flush pending output, and therefore does not test
27696 the state of the stream. (In the main code of Exim, flushing and error
27697 detection is done when Exim is ready for the next SMTP input command.) If
27698 you want to flush the output and check for an error (for example, the
27699 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
27700 arguments. It flushes the output stream, and returns a non-zero value if there
27703 .vitem &*void&~*store_get(int)*&
27704 This function accesses Exim's internal store (memory) manager. It gets a new
27705 chunk of memory whose size is given by the argument. Exim bombs out if it ever
27706 runs out of memory. See the next section for a discussion of memory handling.
27708 .vitem &*void&~*store_get_perm(int)*&
27709 This function is like &'store_get()'&, but it always gets memory from the
27710 permanent pool. See the next section for a discussion of memory handling.
27712 .vitem &*uschar&~*string_copy(uschar&~*string)*&
27715 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
27718 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
27719 These three functions create strings using Exim's dynamic memory facilities.
27720 The first makes a copy of an entire string. The second copies up to a maximum
27721 number of characters, indicated by the second argument. The third uses a format
27722 and insertion arguments to create a new string. In each case, the result is a
27723 pointer to a new string in the current memory pool. See the next section for
27729 .section "More about Exim's memory handling" "SECTmemhanloc"
27730 .cindex "&[local_scan()]& function" "memory handling"
27731 No function is provided for freeing memory, because that is never needed.
27732 The dynamic memory that Exim uses when receiving a message is automatically
27733 recycled if another message is received by the same process (this applies only
27734 to incoming SMTP connections &-- other input methods can supply only one
27735 message at a time). After receiving the last message, a reception process
27738 Because it is recycled, the normal dynamic memory cannot be used for holding
27739 data that must be preserved over a number of incoming messages on the same SMTP
27740 connection. However, Exim in fact uses two pools of dynamic memory; the second
27741 one is not recycled, and can be used for this purpose.
27743 If you want to allocate memory that remains available for subsequent messages
27744 in the same SMTP connection, you should set
27746 store_pool = POOL_PERM
27748 before calling the function that does the allocation. There is no need to
27749 restore the value if you do not need to; however, if you do want to revert to
27750 the normal pool, you can either restore the previous value of &%store_pool%& or
27751 set it explicitly to POOL_MAIN.
27753 The pool setting applies to all functions that get dynamic memory, including
27754 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
27755 There is also a convenience function called &'store_get_perm()'& that gets a
27756 block of memory from the permanent pool while preserving the value of
27763 . ////////////////////////////////////////////////////////////////////////////
27764 . ////////////////////////////////////////////////////////////////////////////
27766 .chapter "System-wide message filtering" "CHAPsystemfilter"
27767 .scindex IIDsysfil1 "filter" "system filter"
27768 .scindex IIDsysfil2 "filtering all mail"
27769 .scindex IIDsysfil3 "system filter"
27770 The previous chapters (on ACLs and the local scan function) describe checks
27771 that can be applied to messages before they are accepted by a host. There is
27772 also a mechanism for checking messages once they have been received, but before
27773 they are delivered. This is called the &'system filter'&.
27775 The system filter operates in a similar manner to users' filter files, but it
27776 is run just once per message (however many recipients the message has).
27777 It should not normally be used as a substitute for routing, because &%deliver%&
27778 commands in a system router provide new envelope recipient addresses.
27779 The system filter must be an Exim filter. It cannot be a Sieve filter.
27781 The system filter is run at the start of a delivery attempt, before any routing
27782 is done. If a message fails to be completely delivered at the first attempt,
27783 the system filter is run again at the start of every retry.
27784 If you want your filter to do something only once per message, you can make use
27785 of the &%first_delivery%& condition in an &%if%& command in the filter to
27786 prevent it happening on retries.
27788 .cindex "&$domain$&"
27789 .cindex "&$local_part$&"
27790 &*Warning*&: Because the system filter runs just once, variables that are
27791 specific to individual recipient addresses, such as &$local_part$& and
27792 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
27793 you want to run a centrally-specified filter for each recipient address
27794 independently, you can do so by setting up a suitable &(redirect)& router, as
27795 described in section &<<SECTperaddfil>>& below.
27798 .section "Specifying a system filter"
27799 .cindex "uid (user id)" "system filter"
27800 .cindex "gid (group id)" "system filter"
27801 The name of the file that contains the system filter must be specified by
27802 setting &%system_filter%&. If you want the filter to run under a uid and gid
27803 other than root, you must also set &%system_filter_user%& and
27804 &%system_filter_group%& as appropriate. For example:
27806 system_filter = /etc/mail/exim.filter
27807 system_filter_user = exim
27809 If a system filter generates any deliveries directly to files or pipes (via the
27810 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
27811 specified by setting &%system_filter_file_transport%& and
27812 &%system_filter_pipe_transport%&, respectively. Similarly,
27813 &%system_filter_reply_transport%& must be set to handle any messages generated
27814 by the &%reply%& command.
27817 .section "Testing a system filter"
27818 You can run simple tests of a system filter in the same way as for a user
27819 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
27820 are permitted only in system filters are recognized.
27822 If you want to test the combined effect of a system filter and a user filter,
27823 you can use both &%-bF%& and &%-bf%& on the same command line.
27827 .section "Contents of a system filter"
27828 The language used to specify system filters is the same as for users' filter
27829 files. It is described in the separate end-user document &'Exim's interface to
27830 mail filtering'&. However, there are some additional features that are
27831 available only in system filters; these are described in subsequent sections.
27832 If they are encountered in a user's filter file or when testing with &%-bf%&,
27835 .cindex "frozen messages" "manual thaw; testing in filter"
27836 There are two special conditions which, though available in users' filter
27837 files, are designed for use in system filters. The condition &%first_delivery%&
27838 is true only for the first attempt at delivering a message, and
27839 &%manually_thawed%& is true only if the message has been frozen, and
27840 subsequently thawed by an admin user. An explicit forced delivery counts as a
27841 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
27843 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
27844 specify an &"unseen"& (non-significant) delivery, and that delivery does not
27845 succeed, it will not be tried again.
27846 If you want Exim to retry an unseen delivery until it succeeds, you should
27847 arrange to set it up every time the filter runs.
27849 When a system filter finishes running, the values of the variables &$n0$& &--
27850 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
27851 users' filter files. Thus a system filter can, for example, set up &"scores"&
27852 to which users' filter files can refer.
27856 .section "Additional variable for system filters"
27857 .cindex "&$recipients$&"
27858 The expansion variable &$recipients$&, containing a list of all the recipients
27859 of the message (separated by commas and white space), is available in system
27860 filters. It is not available in users' filters for privacy reasons.
27864 .section "Defer, freeze, and fail commands for system filters"
27865 .cindex "freezing messages"
27866 .cindex "message" "freezing"
27867 .cindex "message" "forced failure"
27868 .cindex "&%fail%&" "in system filter"
27869 .cindex "&%freeze%& in system filter"
27870 .cindex "&%defer%& in system filter"
27871 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
27872 always available in system filters, but are not normally enabled in users'
27873 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
27874 for the &(redirect)& router.) These commands can optionally be followed by the
27875 word &%text%& and a string containing an error message, for example:
27877 fail text "this message looks like spam to me"
27879 The keyword &%text%& is optional if the next character is a double quote.
27881 The &%defer%& command defers delivery of the original recipients of the
27882 message. The &%fail%& command causes all the original recipients to be failed,
27883 and a bounce message to be created. The &%freeze%& command suspends all
27884 delivery attempts for the original recipients. In all cases, any new deliveries
27885 that are specified by the filter are attempted as normal after the filter has
27888 The &%freeze%& command is ignored if the message has been manually unfrozen and
27889 not manually frozen since. This means that automatic freezing by a system
27890 filter can be used as a way of checking out suspicious messages. If a message
27891 is found to be all right, manually unfreezing it allows it to be delivered.
27893 .cindex "log" "&%fail%& command log line"
27894 .cindex "&%fail%&" "log line; reducing"
27895 The text given with a fail command is used as part of the bounce message as
27896 well as being written to the log. If the message is quite long, this can fill
27897 up a lot of log space when such failures are common. To reduce the size of the
27898 log message, Exim interprets the text in a special way if it starts with the
27899 two characters &`<<`& and contains &`>>`& later. The text between these two
27900 strings is written to the log, and the rest of the text is used in the bounce
27901 message. For example:
27903 fail "<<filter test 1>>Your message is rejected \
27904 because it contains attachments that we are \
27905 not prepared to receive."
27908 .cindex "loop" "caused by &%fail%&"
27909 Take great care with the &%fail%& command when basing the decision to fail on
27910 the contents of the message, because the bounce message will of course include
27911 the contents of the original message and will therefore trigger the &%fail%&
27912 command again (causing a mail loop) unless steps are taken to prevent this.
27913 Testing the &%error_message%& condition is one way to prevent this. You could
27916 if $message_body contains "this is spam" and not error_message
27917 then fail text "spam is not wanted here" endif
27919 though of course that might let through unwanted bounce messages. The
27920 alternative is clever checking of the body and/or headers to detect bounces
27921 generated by the filter.
27923 The interpretation of a system filter file ceases after a
27925 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
27926 set up earlier in the filter file are honoured, so you can use a sequence such
27932 to send a specified message when the system filter is freezing (or deferring or
27933 failing) a message. The normal deliveries for the message do not, of course,
27938 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
27939 .cindex "header lines" "adding; in system filter"
27940 .cindex "header lines" "removing; in system filter"
27941 .cindex "filter" "header lines; adding/removing"
27942 Two filter commands that are available only in system filters are:
27944 headers add <string>
27945 headers remove <string>
27947 The argument for the &%headers add%& is a string that is expanded and then
27948 added to the end of the message's headers. It is the responsibility of the
27949 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
27950 space is ignored, and if the string is otherwise empty, or if the expansion is
27951 forced to fail, the command has no effect.
27953 You can use &"\n"& within the string, followed by white space, to specify
27954 continued header lines. More than one header may be added in one command by
27955 including &"\n"& within the string without any following white space. For
27958 headers add "X-header-1: ....\n \
27959 continuation of X-header-1 ...\n\
27962 Note that the header line continuation white space after the first newline must
27963 be placed before the backslash that continues the input string, because white
27964 space after input continuations is ignored.
27966 The argument for &%headers remove%& is a colon-separated list of header names.
27967 This command applies only to those headers that are stored with the message;
27968 those that are added at delivery time (such as &'Envelope-To:'& and
27969 &'Return-Path:'&) cannot be removed by this means. If there is more than one
27970 header with the same name, they are all removed.
27972 The &%headers%& command in a system filter makes an immediate change to the set
27973 of header lines that was received with the message (with possible additions
27974 from ACL processing). Subsequent commands in the system filter operate on the
27975 modified set, which also forms the basis for subsequent message delivery.
27976 Unless further modified during routing or transporting, this set of headers is
27977 used for all recipients of the message.
27979 During routing and transporting, the variables that refer to the contents of
27980 header lines refer only to those lines that are in this set. Thus, header lines
27981 that are added by a system filter are visible to users' filter files and to all
27982 routers and transports. This contrasts with the manipulation of header lines by
27983 routers and transports, which is not immediate, but which instead is saved up
27984 until the message is actually being written (see section
27985 &<<SECTheadersaddrem>>&).
27987 If the message is not delivered at the first attempt, header lines that were
27988 added by the system filter are stored with the message, and so are still
27989 present at the next delivery attempt. Header lines that were removed are still
27990 present, but marked &"deleted"& so that they are not transported with the
27991 message. For this reason, it is usual to make the &%headers%& command
27992 conditional on &%first_delivery%& so that the set of header lines is not
27993 modified more than once.
27995 Because header modification in a system filter acts immediately, you have to
27996 use an indirect approach if you want to modify the contents of a header line.
27999 headers add "Old-Subject: $h_subject:"
28000 headers remove "Subject"
28001 headers add "Subject: new subject (was: $h_old-subject:)"
28002 headers remove "Old-Subject"
28007 .section "Setting an errors address in a system filter"
28008 .cindex "envelope sender"
28009 In a system filter, if a &%deliver%& command is followed by
28011 errors_to <some address>
28013 in order to change the envelope sender (and hence the error reporting) for that
28014 delivery, any address may be specified. (In a user filter, only the current
28015 user's address can be set.) For example, if some mail is being monitored, you
28018 unseen deliver monitor@spying.example errors_to root@local.example
28020 to take a copy which would not be sent back to the normal error reporting
28021 address if its delivery failed.
28025 .section "Per-address filtering" "SECTperaddfil"
28026 .cindex "&$domain$&"
28027 .cindex "&$local_part$&"
28028 In contrast to the system filter, which is run just once per message for each
28029 delivery attempt, it is also possible to set up a system-wide filtering
28030 operation that runs once for each recipient address. In this case, variables
28031 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
28032 filter file could be made dependent on them. This is an example of a router
28033 which implements such a filter:
28038 domains = +local_domains
28039 file = /central/filters/$local_part
28044 The filter is run in a separate process under its own uid. Therefore, either
28045 &%check_local_user%& must be set (as above), in which case the filter is run as
28046 the local user, or the &%user%& option must be used to specify which user to
28047 use. If both are set, &%user%& overrides.
28049 Care should be taken to ensure that none of the commands in the filter file
28050 specify a significant delivery if the message is to go on to be delivered to
28051 its intended recipient. The router will not then claim to have dealt with the
28052 address, so it will be passed on to subsequent routers to be delivered in the
28054 .ecindex IIDsysfil1
28055 .ecindex IIDsysfil2
28056 .ecindex IIDsysfil3
28063 . ////////////////////////////////////////////////////////////////////////////
28064 . ////////////////////////////////////////////////////////////////////////////
28066 .chapter "Message processing" "CHAPmsgproc"
28067 .scindex IIDmesproc "message" "general processing"
28068 Exim performs various transformations on the sender and recipient addresses of
28069 all messages that it handles, and also on the messages' header lines. Some of
28070 these are optional and configurable, while others always take place. All of
28071 this processing, except rewriting as a result of routing, and the addition or
28072 removal of header lines while delivering, happens when a message is received,
28073 before it is placed on Exim's queue.
28075 Some of the automatic processing takes place by default only for
28076 &"locally-originated"& messages. This adjective is used to describe messages
28077 that are not received over TCP/IP, but instead are passed to an Exim process on
28078 its standard input. This includes the interactive &"local SMTP"& case that is
28079 set up by the &%-bs%& command line option.
28081 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
28082 or ::1) are not considered to be locally-originated. Exim does not treat the
28083 loopback interface specially in any way.
28085 If you want the loopback interface to be treated specially, you must ensure
28086 that there are appropriate entries in your ACLs.
28091 .section "Submission mode for non-local messages" "SECTsubmodnon"
28092 .cindex "message" "submission"
28093 .cindex "submission mode"
28094 Processing that happens automatically for locally-originated messages (unless
28095 &%suppress_local_fixups%& is set) can also be requested for messages that are
28096 received over TCP/IP. The term &"submission mode"& is used to describe this
28097 state. Submisssion mode is set by the modifier
28099 control = submission
28101 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
28102 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
28103 a local submission, and is normally used when the source of the message is
28104 known to be an MUA running on a client host (as opposed to an MTA). For
28105 example, to set submission mode for messages originating on the IPv4 loopback
28106 interface, you could include the following in the MAIL ACL:
28108 warn hosts = 127.0.0.1
28109 control = submission
28111 .cindex "&%sender_retain%&"
28112 There are some options that can be used when setting submission mode. A slash
28113 is used to separate options. For example:
28115 control = submission/sender_retain
28117 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
28118 true and &%local_from_check%& false for the current incoming message. The first
28119 of these allows an existing &'Sender:'& header in the message to remain, and
28120 the second suppresses the check to ensure that &'From:'& matches the
28121 authenticated sender. With this setting, Exim still fixes up messages by adding
28122 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
28123 attempt to check sender authenticity in header lines.
28125 When &%sender_retain%& is not set, a submission mode setting may specify a
28126 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
28129 control = submission/domain=some.domain
28131 The domain may be empty. How this value is used is described in sections
28132 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
28133 that allows you to specify the user's full name for inclusion in a created
28134 &'Sender:'& or &'From:'& header line. For example:
28136 accept authenticated = *
28137 control = submission/domain=wonderland.example/\
28138 name=${lookup {$authenticated_id} \
28139 lsearch {/etc/exim/namelist}}
28141 Because the name may contain any characters, including slashes, the &%name%&
28142 option must be given last. The remainder of the string is used as the name. For
28143 the example above, if &_/etc/exim/namelist_& contains:
28145 bigegg: Humpty Dumpty
28147 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
28150 Sender: Humpty Dumpty <bigegg@wonderland.example>
28152 .cindex "return path" "in submission mode"
28153 By default, submission mode forces the return path to the same address as is
28154 used to create the &'Sender:'& header. However, if &%sender_retain%& is
28155 specified, the return path is also left unchanged.
28157 &*Note*&: The changes caused by submission mode take effect after the predata
28158 ACL. This means that any sender checks performed before the fix-ups use the
28159 untrusted sender address specified by the user, not the trusted sender address
28160 specified by submission mode. Although this might be slightly unexpected, it
28161 does mean that you can configure ACL checks to spot that a user is trying to
28162 spoof another's address.
28164 .section "Line endings" "SECTlineendings"
28165 .cindex "line endings"
28166 .cindex "carriage return"
28168 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
28169 linefeed) is the line ending for messages transmitted over the Internet using
28170 SMTP over TCP/IP. However, within individual operating systems, different
28171 conventions are used. For example, Unix-like systems use just LF, but others
28172 use CRLF or just CR.
28174 Exim was designed for Unix-like systems, and internally, it stores messages
28175 using the system's convention of a single LF as a line terminator. When
28176 receiving a message, all line endings are translated to this standard format.
28177 Originally, it was thought that programs that passed messages directly to an
28178 MTA within an operating system would use that system's convention. Experience
28179 has shown that this is not the case; for example, there are Unix applications
28180 that use CRLF in this circumstance. For this reason, and for compatibility with
28181 other MTAs, the way Exim handles line endings for all messages is now as
28185 LF not preceded by CR is treated as a line ending.
28187 CR is treated as a line ending; if it is immediately followed by LF, the LF
28190 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
28191 nor a local message in the state where a line containing only a dot is a
28194 If a bare CR is encountered within a header line, an extra space is added after
28195 the line terminator so as not to end the header line. The reasoning behind this
28196 is that bare CRs in header lines are most likely either to be mistakes, or
28197 people trying to play silly games.
28199 If the first header line received in a message ends with CRLF, a subsequent
28200 bare LF in a header line is treated in the same way as a bare CR in a header
28208 .section "Unqualified addresses"
28209 .cindex "unqualified addresses"
28210 .cindex "address" "qualification"
28211 By default, Exim expects every envelope address it receives from an external
28212 host to be fully qualified. Unqualified addresses cause negative responses to
28213 SMTP commands. However, because SMTP is used as a means of transporting
28214 messages from MUAs running on personal workstations, there is sometimes a
28215 requirement to accept unqualified addresses from specific hosts or IP networks.
28217 Exim has two options that separately control which hosts may send unqualified
28218 sender or receipient addresses in SMTP commands, namely
28219 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
28220 cases, if an unqualified address is accepted, it is qualified by adding the
28221 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
28223 .cindex "&%qualify_domain%&"
28224 .cindex "&%qualify_recipient%&"
28225 Unqualified addresses in header lines are automatically qualified for messages
28226 that are locally originated, unless the &%-bnq%& option is given on the command
28227 line. For messages received over SMTP, unqualified addresses in header lines
28228 are qualified only if unqualified addresses are permitted in SMTP commands. In
28229 other words, such qualification is also controlled by
28230 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
28235 .section "The UUCP From line"
28236 .cindex "&""From""& line"
28237 .cindex "UUCP" "&""From""& line"
28238 .cindex "sender" "address"
28239 .cindex "&%uucp_from_pattern%&"
28240 .cindex "&%uucp_from_sender%&"
28241 .cindex "envelope sender"
28242 .cindex "Sendmail compatibility" "&""From""& line"
28243 Messages that have come from UUCP (and some other applications) often begin
28244 with a line containing the envelope sender and a timestamp, following the word
28245 &"From"&. Examples of two common formats are:
28247 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
28248 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
28250 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
28251 Exim recognizes such lines at the start of messages that are submitted to it
28252 via the command line (that is, on the standard input). It does not recognize
28253 such lines in incoming SMTP messages, unless the sending host matches
28254 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
28255 and &%ignore_fromline_local%& is set. The recognition is controlled by a
28256 regular expression that is defined by the &%uucp_from_pattern%& option, whose
28257 default value matches the two common cases shown above and puts the address
28258 that follows &"From"& into &$1$&.
28260 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
28261 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
28262 a trusted user, the message's sender address is constructed by expanding the
28263 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
28264 then parsed as an RFC 2822 address. If there is no domain, the local part is
28265 qualified with &%qualify_domain%& unless it is the empty string. However, if
28266 the command line &%-f%& option is used, it overrides the &"From"& line.
28268 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
28269 sender address is not changed. This is also the case for incoming SMTP messages
28270 that are permitted to contain &"From"& lines.
28272 Only one &"From"& line is recognized. If there is more than one, the second is
28273 treated as a data line that starts the body of the message, as it is not valid
28274 as a header line. This also happens if a &"From"& line is present in an
28275 incoming SMTP message from a source that is not permitted to send them.
28279 .section "Resent- header lines"
28280 .cindex "&%Resent-%& header lines"
28281 RFC 2822 makes provision for sets of header lines starting with the string
28282 &`Resent-`& to be added to a message when it is resent by the original
28283 recipient to somebody else. These headers are &'Resent-Date:'&,
28284 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
28285 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
28288 &'Resent fields are strictly informational. They MUST NOT be used in the normal
28289 processing of replies or other such automatic actions on messages.'&
28292 This leaves things a bit vague as far as other processing actions such as
28293 address rewriting are concerned. Exim treats &%Resent-%& header lines as
28297 A &'Resent-From:'& line that just contains the login id of the submitting user
28298 is automatically rewritten in the same way as &'From:'& (see below).
28300 If there's a rewriting rule for a particular header line, it is also applied to
28301 &%Resent-%& header lines of the same type. For example, a rule that rewrites
28302 &'From:'& also rewrites &'Resent-From:'&.
28304 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
28307 For a locally-submitted message,
28308 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
28309 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
28310 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
28311 included in log lines in this case.
28313 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
28314 &%Resent-%& header lines are present.
28320 .section "The Auto-Submitted: header line"
28321 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
28322 includes the header line:
28324 Auto-Submitted: auto-replied
28327 .section "The Bcc: header line"
28328 .cindex "&'Bcc:'& header line"
28329 If Exim is called with the &%-t%& option, to take recipient addresses from a
28330 message's header, it removes any &'Bcc:'& header line that may exist (after
28331 extracting its addresses). If &%-t%& is not present on the command line, any
28332 existing &'Bcc:'& is not removed.
28335 .section "The Date: header line"
28336 .cindex "&'Date:'& header line"
28337 If a locally-generated or submission-mode message has no &'Date:'& header line,
28338 Exim adds one, using the current date and time, unless the
28339 &%suppress_local_fixups%& control has been specified.
28341 .section "The Delivery-date: header line"
28342 .cindex "&'Delivery-date:'& header line"
28343 .cindex "&%delivery_date_remove%&"
28344 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
28345 set. Exim can be configured to add them to the final delivery of messages. (See
28346 the generic &%delivery_date_add%& transport option.) They should not be present
28347 in messages in transit. If the &%delivery_date_remove%& configuration option is
28348 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
28352 .section "The Envelope-to: header line"
28353 .cindex "&'Envelope-to:'& header line"
28354 .cindex "&%envelope_to_remove%&"
28355 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
28356 Exim can be configured to add them to the final delivery of messages. (See the
28357 generic &%envelope_to_add%& transport option.) They should not be present in
28358 messages in transit. If the &%envelope_to_remove%& configuration option is set
28359 (the default), Exim removes &'Envelope-to:'& header lines from incoming
28363 .section "The From: header line" "SECTthefrohea"
28364 .cindex "&'From:'& header line"
28365 .cindex "Sendmail compatibility" "&""From""& line"
28366 .cindex "message" "submission"
28367 .cindex "submission mode"
28368 If a submission-mode message does not contain a &'From:'& header line, Exim
28369 adds one if either of the following conditions is true:
28372 The envelope sender address is not empty (that is, this is not a bounce
28373 message). The added header line copies the envelope sender address.
28375 .cindex "&$authenticated_id$&"
28376 The SMTP session is authenticated and &$authenticated_id$& is not empty.
28378 .cindex "&$qualify_domain$&"
28379 If no domain is specified by the submission control, the local part is
28380 &$authenticated_id$& and the domain is &$qualify_domain$&.
28382 If a non-empty domain is specified by the submission control, the local
28383 part is &$authenticated_id$&, and the the domain is the specified domain.
28385 If an empty domain is specified by the submission control,
28386 &$authenticated_id$& is assumed to be the complete address.
28390 A non-empty envelope sender takes precedence.
28392 If a locally-generated incoming message does not contain a &'From:'& header
28393 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
28394 containing the sender's address. The calling user's login name and full name
28395 are used to construct the address, as described in section &<<SECTconstr>>&.
28396 They are obtained from the password data by calling &[getpwuid()]& (but see the
28397 &%unknown_login%& configuration option). The address is qualified with
28398 &%qualify_domain%&.
28400 For compatibility with Sendmail, if an incoming, non-SMTP message has a
28401 &'From:'& header line containing just the unqualified login name of the calling
28402 user, this is replaced by an address containing the user's login name and full
28403 name as described in section &<<SECTconstr>>&.
28406 .section "The Message-ID: header line"
28407 .cindex "&'Message-ID:'& header line"
28408 .cindex "message" "submission"
28409 .cindex "&%message_id_header_text%&"
28410 If a locally-generated or submission-mode incoming message does not contain a
28411 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
28412 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
28413 to the message. If there are any &'Resent-:'& headers in the message, it
28414 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
28415 message id, preceded by the letter E to ensure it starts with a letter, and
28416 followed by @ and the primary host name. Additional information can be included
28417 in this header line by setting the &%message_id_header_text%& and/or
28418 &%message_id_header_domain%& options.
28421 .section "The Received: header line"
28422 .cindex "&'Received:'& header line"
28423 A &'Received:'& header line is added at the start of every message. The
28424 contents are defined by the &%received_header_text%& configuration option, and
28425 Exim automatically adds a semicolon and a timestamp to the configured string.
28427 The &'Received:'& header is generated as soon as the message's header lines
28428 have been received. At this stage, the timestamp in the &'Received:'& header
28429 line is the time that the message started to be received. This is the value
28430 that is seen by the DATA ACL and by the &[local_scan()]& function.
28432 Once a message is accepted, the timestamp in the &'Received:'& header line is
28433 changed to the time of acceptance, which is (apart from a small delay while the
28434 -H spool file is written) the earliest time at which delivery could start.
28437 .section "The References: header line"
28438 .cindex "&'References:'& header line"
28439 Messages created by the &(autoreply)& transport include a &'References:'&
28440 header line. This is constructed according to the rules that are described in
28441 section 3.64 of RFC 2822 (which states that replies should contain such a
28442 header line), and section 3.14 of RFC 3834 (which states that automatic
28443 responses are not different in this respect). However, because some mail
28444 processing software does not cope well with very long header lines, no more
28445 than 12 message IDs are copied from the &'References:'& header line in the
28446 incoming message. If there are more than 12, the first one and then the final
28447 11 are copied, before adding the message ID of the incoming message.
28451 .section "The Return-path: header line"
28452 .cindex "&'Return-path:'& header line"
28453 .cindex "&%return_path_remove%&"
28454 &'Return-path:'& header lines are defined as something an MTA may insert when
28455 it does the final delivery of messages. (See the generic &%return_path_add%&
28456 transport option.) Therefore, they should not be present in messages in
28457 transit. If the &%return_path_remove%& configuration option is set (the
28458 default), Exim removes &'Return-path:'& header lines from incoming messages.
28462 .section "The Sender: header line" "SECTthesenhea"
28463 .cindex "&'Sender:'& header line"
28464 .cindex "message" "submission"
28465 For a locally-originated message from an untrusted user, Exim may remove an
28466 existing &'Sender:'& header line, and it may add a new one. You can modify
28467 these actions by setting the &%local_sender_retain%& option true, the
28468 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
28471 When a local message is received from an untrusted user and
28472 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
28473 control has not been set, a check is made to see if the address given in the
28474 &'From:'& header line is the correct (local) sender of the message. The address
28475 that is expected has the login name as the local part and the value of
28476 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
28477 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
28478 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
28479 line is added to the message.
28481 If you set &%local_from_check%& false, this checking does not occur. However,
28482 the removal of an existing &'Sender:'& line still happens, unless you also set
28483 &%local_sender_retain%& to be true. It is not possible to set both of these
28484 options true at the same time.
28486 .cindex "submission mode"
28487 By default, no processing of &'Sender:'& header lines is done for messages
28488 received over TCP/IP or for messages submitted by trusted users. However, when
28489 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
28490 not specified on the submission control, the following processing takes place:
28492 .cindex "&$authenticated_id$&"
28493 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
28494 authenticated, and &$authenticated_id$& is not empty, a sender address is
28495 created as follows:
28498 .cindex "&$qualify_domain$&"
28499 If no domain is specified by the submission control, the local part is
28500 &$authenticated_id$& and the domain is &$qualify_domain$&.
28502 If a non-empty domain is specified by the submission control, the local part
28503 is &$authenticated_id$&, and the the domain is the specified domain.
28505 If an empty domain is specified by the submission control,
28506 &$authenticated_id$& is assumed to be the complete address.
28509 This address is compared with the address in the &'From:'& header line. If they
28510 are different, a &'Sender:'& header line containing the created address is
28511 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
28512 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
28514 .cindex "return path" "created from &'Sender:'&"
28515 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
28516 the message (the envelope sender address) is changed to be the same address,
28517 except in the case of submission mode when &%sender_retain%& is specified.
28521 .section "Adding and removing header lines in routers and transports" &&&
28522 "SECTheadersaddrem"
28523 .cindex "header lines" "adding; in router or transport"
28524 .cindex "header lines" "removing; in router or transport"
28525 When a message is delivered, the addition and removal of header lines can be
28526 specified in a system filter, or on any of the routers and transports that
28527 process the message. Section &<<SECTaddremheasys>>& contains details about
28528 modifying headers in a system filter. Header lines can also be added in an ACL
28529 as a message is received (see section &<<SECTaddheadacl>>&).
28531 In contrast to what happens in a system filter, header modifications that are
28532 specified on routers and transports apply only to the particular recipient
28533 addresses that are being processed by those routers and transports. These
28534 changes do not actually take place until a copy of the message is being
28535 transported. Therefore, they do not affect the basic set of header lines, and
28536 they do not affect the values of the variables that refer to header lines.
28538 &*Note*&: In particular, this means that any expansions in the configuration of
28539 the transport cannot refer to the modified header lines, because such
28540 expansions all occur before the message is actually transported.
28542 For both routers and transports, the result of expanding a &%headers_add%&
28543 option must be in the form of one or more RFC 2822 header lines, separated by
28544 newlines (coded as &"\n"&). For example:
28546 headers_add = X-added-header: added by $primary_hostname\n\
28547 X-added-second: another added header line
28549 Exim does not check the syntax of these added header lines.
28551 The result of expanding &%headers_remove%& must consist of a colon-separated
28552 list of header names. This is confusing, because header names themselves are
28553 often terminated by colons. In this case, the colons are the list separators,
28554 not part of the names. For example:
28556 headers_remove = return-receipt-to:acknowledge-to
28558 When &%headers_add%& or &%headers_remove%& is specified on a router, its value
28559 is expanded at routing time, and then associated with all addresses that are
28560 accepted by that router, and also with any new addresses that it generates. If
28561 an address passes through several routers as a result of aliasing or
28562 forwarding, the changes are cumulative.
28564 .cindex "&%unseen%& option"
28565 However, this does not apply to multiple routers that result from the use of
28566 the &%unseen%& option. Any header modifications that were specified by the
28567 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
28569 Addresses that end up with different &%headers_add%& or &%headers_remove%&
28570 settings cannot be delivered together in a batch, so a transport is always
28571 dealing with a set of addresses that have the same header-processing
28574 The transport starts by writing the original set of header lines that arrived
28575 with the message, possibly modified by the system filter. As it writes out
28576 these lines, it consults the list of header names that were attached to the
28577 recipient address(es) by &%headers_remove%& options in routers, and it also
28578 consults the transport's own &%headers_remove%& option. Header lines whose
28579 names are on either of these lists are not written out. If there are multiple
28580 instances of any listed header, they are all skipped.
28582 After the remaining original header lines have been written, new header
28583 lines that were specified by routers' &%headers_add%& options are written, in
28584 the order in which they were attached to the address. These are followed by any
28585 header lines specified by the transport's &%headers_add%& option.
28587 This way of handling header line modifications in routers and transports has
28588 the following consequences:
28591 The original set of header lines, possibly modified by the system filter,
28592 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
28593 to it, at all times.
28595 Header lines that are added by a router's
28596 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
28597 expansion syntax in subsequent routers or the transport.
28599 Conversely, header lines that are specified for removal by &%headers_remove%&
28600 in a router remain visible to subsequent routers and the transport.
28602 Headers added to an address by &%headers_add%& in a router cannot be removed by
28603 a later router or by a transport.
28605 An added header can refer to the contents of an original header that is to be
28606 removed, even it has the same name as the added header. For example:
28608 headers_remove = subject
28609 headers_add = Subject: new subject (was: $h_subject:)
28613 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
28614 for a &(redirect)& router that has the &%one_time%& option set.
28620 .section "Constructed addresses" "SECTconstr"
28621 .cindex "address" "constructed"
28622 .cindex "constructed address"
28623 When Exim constructs a sender address for a locally-generated message, it uses
28626 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
28630 Zaphod Beeblebrox <zaphod@end.univ.example>
28632 The user name is obtained from the &%-F%& command line option if set, or
28633 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
28634 &"gecos"& field from the password entry. If the &"gecos"& field contains an
28635 ampersand character, this is replaced by the login name with the first letter
28636 upper cased, as is conventional in a number of operating systems. See the
28637 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
28638 The &%unknown_username%& option can be used to specify user names in cases when
28639 there is no password file entry.
28642 In all cases, the user name is made to conform to RFC 2822 by quoting all or
28643 parts of it if necessary. In addition, if it contains any non-printing
28644 characters, it is encoded as described in RFC 2047, which defines a way of
28645 including non-ASCII characters in header lines. The value of the
28646 &%headers_charset%& option specifies the name of the encoding that is used (the
28647 characters are assumed to be in this encoding). The setting of
28648 &%print_topbitchars%& controls whether characters with the top bit set (that
28649 is, with codes greater than 127) count as printing characters or not.
28653 .section "Case of local parts"
28654 .cindex "case of local parts"
28655 .cindex "local part" "case of"
28656 RFC 2822 states that the case of letters in the local parts of addresses cannot
28657 be assumed to be non-significant. Exim preserves the case of local parts of
28658 addresses, but by default it uses a lower-cased form when it is routing,
28659 because on most Unix systems, usernames are in lower case and case-insensitive
28660 routing is required. However, any particular router can be made to use the
28661 original case for local parts by setting the &%caseful_local_part%& generic
28664 .cindex "mixed-case login names"
28665 If you must have mixed-case user names on your system, the best way to proceed,
28666 assuming you want case-independent handling of incoming email, is to set up
28667 your first router to convert incoming local parts in your domains to the
28668 correct case by means of a file lookup. For example:
28672 domains = +local_domains
28673 data = ${lookup{$local_part}cdb\
28674 {/etc/usercased.cdb}{$value}fail}\
28677 For this router, the local part is forced to lower case by the default action
28678 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
28679 up a new local part in the correct case. If you then set &%caseful_local_part%&
28680 on any subsequent routers which process your domains, they will operate on
28681 local parts with the correct case in a case-sensitive manner.
28685 .section "Dots in local parts"
28686 .cindex "dot" "in local part"
28687 .cindex "local part" "dots in"
28688 RFC 2822 forbids empty components in local parts. That is, an unquoted local
28689 part may not begin or end with a dot, nor have two consecutive dots in the
28690 middle. However, it seems that many MTAs do not enforce this, so Exim permits
28691 empty components for compatibility.
28695 .section "Rewriting addresses"
28696 .cindex "rewriting" "addresses"
28697 Rewriting of sender and recipient addresses, and addresses in headers, can
28698 happen automatically, or as the result of configuration options, as described
28699 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
28700 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
28702 Automatic rewriting includes qualification, as mentioned above. The other case
28703 in which it can happen is when an incomplete non-local domain is given. The
28704 routing process may cause this to be expanded into the full domain name. For
28705 example, a header such as
28709 might get rewritten as
28711 To: hare@teaparty.wonderland.fict.example
28713 Rewriting as a result of routing is the one kind of message processing that
28714 does not happen at input time, as it cannot be done until the address has
28717 Strictly, one should not do &'any'& deliveries of a message until all its
28718 addresses have been routed, in case any of the headers get changed as a
28719 result of routing. However, doing this in practice would hold up many
28720 deliveries for unreasonable amounts of time, just because one address could not
28721 immediately be routed. Exim therefore does not delay other deliveries when
28722 routing of one or more addresses is deferred.
28723 .ecindex IIDmesproc
28727 . ////////////////////////////////////////////////////////////////////////////
28728 . ////////////////////////////////////////////////////////////////////////////
28730 .chapter "SMTP processing" "CHAPSMTP"
28731 .scindex IIDsmtpproc1 "SMTP" "processing details"
28732 .scindex IIDsmtpproc2 "LMTP" "processing details"
28733 Exim supports a number of different ways of using the SMTP protocol, and its
28734 LMTP variant, which is an interactive protocol for transferring messages into a
28735 closed mail store application. This chapter contains details of how SMTP is
28736 processed. For incoming mail, the following are available:
28739 SMTP over TCP/IP (Exim daemon or &'inetd'&);
28741 SMTP over the standard input and output (the &%-bs%& option);
28743 Batched SMTP on the standard input (the &%-bS%& option).
28746 For mail delivery, the following are available:
28749 SMTP over TCP/IP (the &(smtp)& transport);
28751 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
28754 LMTP over a pipe to a process running in the local host (the &(lmtp)&
28757 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
28758 the &%use_bsmtp%& option set).
28761 &'Batched SMTP'& is the name for a process in which batches of messages are
28762 stored in or read from files (or pipes), in a format in which SMTP commands are
28763 used to contain the envelope information.
28767 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
28768 .cindex "SMTP" "outgoing over TCP/IP"
28769 .cindex "outgoing SMTP over TCP/IP"
28770 .cindex "LMTP" "over TCP/IP"
28771 .cindex "outgoing LMTP over TCP/IP"
28774 .cindex "SIZE option on MAIL command"
28775 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
28776 The &%protocol%& option selects which protocol is to be used, but the actual
28777 processing is the same in both cases.
28779 If, in response to its EHLO command, Exim is told that the SIZE
28780 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
28781 command. The value of <&'n'&> is the message size plus the value of the
28782 &%size_addition%& option (default 1024) to allow for additions to the message
28783 such as per-transport header lines, or changes made in a
28784 .cindex "transport" "filter"
28785 .cindex "filter" "transport filter"
28786 transport filter. If &%size_addition%& is set negative, the use of SIZE is
28789 If the remote server advertises support for PIPELINING, Exim uses the
28790 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
28791 required for the transaction.
28793 If the remote server advertises support for the STARTTLS command, and Exim
28794 was built to support TLS encryption, it tries to start a TLS session unless the
28795 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
28797 If the remote server advertises support for the AUTH command, Exim scans
28798 the authenticators configuration for any suitable client settings, as described
28799 in chapter &<<CHAPSMTPAUTH>>&.
28801 .cindex "carriage return"
28803 Responses from the remote host are supposed to be terminated by CR followed by
28804 LF. However, there are known to be hosts that do not send CR characters, so in
28805 order to be able to interwork with such hosts, Exim treats LF on its own as a
28808 If a message contains a number of different addresses, all those with the same
28809 characteristics (for example, the same envelope sender) that resolve to the
28810 same set of hosts, in the same order, are sent in a single SMTP transaction,
28811 even if they are for different domains, unless there are more than the setting
28812 of the &%max_rcpts%& option in the &(smtp)& transport allows, in which case
28813 they are split into groups containing no more than &%max_rcpts%& addresses
28814 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
28815 in parallel sessions. The order of hosts with identical MX values is not
28816 significant when checking whether addresses can be batched in this way.
28818 When the &(smtp)& transport suffers a temporary failure that is not
28819 message-related, Exim updates its transport-specific database, which contains
28820 records indexed by host name that remember which messages are waiting for each
28821 particular host. It also updates the retry database with new retry times.
28823 .cindex "hints database" "retry keys"
28824 Exim's retry hints are based on host name plus IP address, so if one address of
28825 a multi-homed host is broken, it will soon be skipped most of the time.
28826 See the next section for more detail about error handling.
28828 .cindex "SMTP" "passed connection"
28829 .cindex "SMTP" "batching over TCP/IP"
28830 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
28831 looks in the hints database for the transport to see if there are any queued
28832 messages waiting for the host to which it is connected. If it finds one, it
28833 creates a new Exim process using the &%-MC%& option (which can only be used by
28834 a process running as root or the Exim user) and passes the TCP/IP socket to it
28835 so that it can deliver another message using the same socket. The new process
28836 does only those deliveries that are routed to the connected host, and may in
28837 turn pass the socket on to a third process, and so on.
28839 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
28840 limit the number of messages sent down a single TCP/IP connection.
28842 .cindex "asterisk" "after IP address"
28843 The second and subsequent messages delivered down an existing connection are
28844 identified in the main log by the addition of an asterisk after the closing
28845 square bracket of the IP address.
28850 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
28851 .cindex "error" "in outgoing SMTP"
28852 .cindex "SMTP" "errors in outgoing"
28853 .cindex "host" "error"
28854 Three different kinds of error are recognized for outgoing SMTP: host errors,
28855 message errors, and recipient errors.
28858 .vitem "&*Host errors*&"
28859 A host error is not associated with a particular message or with a
28860 particular recipient of a message. The host errors are:
28863 Connection refused or timed out,
28865 Any error response code on connection,
28867 Any error response code to EHLO or HELO,
28869 Loss of connection at any time, except after &"."&,
28871 I/O errors at any time,
28873 Timeouts during the session, other than in response to MAIL, RCPT or
28874 the &"."& at the end of the data.
28877 For a host error, a permanent error response on connection, or in response to
28878 EHLO, causes all addresses routed to the host to be failed. Any other host
28879 error causes all addresses to be deferred, and retry data to be created for the
28880 host. It is not tried again, for any message, until its retry time arrives. If
28881 the current set of addresses are not all delivered in this run (to some
28882 alternative host), the message is added to the list of those waiting for this
28883 host, so if it is still undelivered when a subsequent successful delivery is
28884 made to the host, it will be sent down the same SMTP connection.
28886 .vitem "&*Message errors*&"
28887 .cindex "message" "error"
28888 A message error is associated with a particular message when sent to a
28889 particular host, but not with a particular recipient of the message. The
28890 message errors are:
28893 Any error response code to MAIL, DATA, or the &"."& that terminates
28896 Timeout after MAIL,
28898 Timeout or loss of connection after the &"."& that terminates the data. A
28899 timeout after the DATA command itself is treated as a host error, as is loss of
28900 connection at any other time.
28903 For a message error, a permanent error response (5&'xx'&) causes all addresses
28904 to be failed, and a delivery error report to be returned to the sender. A
28905 temporary error response (4&'xx'&), or one of the timeouts, causes all
28906 addresses to be deferred. Retry data is not created for the host, but instead,
28907 a retry record for the combination of host plus message id is created. The
28908 message is not added to the list of those waiting for this host. This ensures
28909 that the failing message will not be sent to this host again until the retry
28910 time arrives. However, other messages that are routed to the host are not
28911 affected, so if it is some property of the message that is causing the error,
28912 it will not stop the delivery of other mail.
28914 If the remote host specified support for the SIZE parameter in its response
28915 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
28916 over-large message will cause a message error because the error arrives as a
28919 .vitem "&*Recipient errors*&"
28920 .cindex "recipient" "error"
28921 A recipient error is associated with a particular recipient of a message. The
28922 recipient errors are:
28925 Any error response to RCPT,
28927 Timeout after RCPT.
28930 For a recipient error, a permanent error response (5&'xx'&) causes the
28931 recipient address to be failed, and a bounce message to be returned to the
28932 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
28933 address to be deferred, and routing retry data to be created for it. This is
28934 used to delay processing of the address in subsequent queue runs, until its
28935 routing retry time arrives. This applies to all messages, but because it
28936 operates only in queue runs, one attempt will be made to deliver a new message
28937 to the failing address before the delay starts to operate. This ensures that,
28938 if the failure is really related to the message rather than the recipient
28939 (&"message too big for this recipient"& is a possible example), other messages
28940 have a chance of getting delivered. If a delivery to the address does succeed,
28941 the retry information gets cleared, so all stuck messages get tried again, and
28942 the retry clock is reset.
28944 The message is not added to the list of those waiting for this host. Use of the
28945 host for other messages is unaffected, and except in the case of a timeout,
28946 other recipients are processed independently, and may be successfully delivered
28947 in the current SMTP session. After a timeout it is of course impossible to
28948 proceed with the session, so all addresses get deferred. However, those other
28949 than the one that failed do not suffer any subsequent retry delays. Therefore,
28950 if one recipient is causing trouble, the others have a chance of getting
28951 through when a subsequent delivery attempt occurs before the failing
28952 recipient's retry time.
28955 In all cases, if there are other hosts (or IP addresses) available for the
28956 current set of addresses (for example, from multiple MX records), they are
28957 tried in this run for any undelivered addresses, subject of course to their
28958 own retry data. In other words, recipient error retry data does not take effect
28959 until the next delivery attempt.
28961 Some hosts have been observed to give temporary error responses to every
28962 MAIL command at certain times (&"insufficient space"& has been seen). It
28963 would be nice if such circumstances could be recognized, and defer data for the
28964 host itself created, but this is not possible within the current Exim design.
28965 What actually happens is that retry data for every (host, message) combination
28968 The reason that timeouts after MAIL and RCPT are treated specially is that
28969 these can sometimes arise as a result of the remote host's verification
28970 procedures. Exim makes this assumption, and treats them as if a temporary error
28971 response had been received. A timeout after &"."& is treated specially because
28972 it is known that some broken implementations fail to recognize the end of the
28973 message if the last character of the last line is a binary zero. Thus, it is
28974 helpful to treat this case as a message error.
28976 Timeouts at other times are treated as host errors, assuming a problem with the
28977 host, or the connection to it. If a timeout after MAIL, RCPT,
28978 or &"."& is really a connection problem, the assumption is that at the next try
28979 the timeout is likely to occur at some other point in the dialogue, causing it
28980 then to be treated as a host error.
28982 There is experimental evidence that some MTAs drop the connection after the
28983 terminating &"."& if they do not like the contents of the message for some
28984 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
28985 should be given. That is why Exim treats this case as a message rather than a
28986 host error, in order not to delay other messages to the same host.
28991 .section "Incoming SMTP messages over TCP/IP"
28992 .cindex "SMTP" "incoming over TCP/IP"
28993 .cindex "incoming SMTP over TCP/IP"
28996 Incoming SMTP messages can be accepted in one of two ways: by running a
28997 listening daemon, or by using &'inetd'&. In the latter case, the entry in
28998 &_/etc/inetd.conf_& should be like this:
29000 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
29002 Exim distinguishes between this case and the case of a locally running user
29003 agent using the &%-bs%& option by checking whether or not the standard input is
29004 a socket. When it is, either the port must be privileged (less than 1024), or
29005 the caller must be root or the Exim user. If any other user passes a socket
29006 with an unprivileged port number, Exim prints a message on the standard error
29007 stream and exits with an error code.
29009 By default, Exim does not make a log entry when a remote host connects or
29010 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
29011 unexpected. It can be made to write such log entries by setting the
29012 &%smtp_connection%& log selector.
29014 .cindex "carriage return"
29016 Commands from the remote host are supposed to be terminated by CR followed by
29017 LF. However, there are known to be hosts that do not send CR characters. In
29018 order to be able to interwork with such hosts, Exim treats LF on its own as a
29020 Furthermore, because common code is used for receiving messages from all
29021 sources, a CR on its own is also interpreted as a line terminator. However, the
29022 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
29024 .cindex "EHLO" "invalid data"
29025 .cindex "HELO" "invalid data"
29026 One area that sometimes gives rise to problems concerns the EHLO or
29027 HELO commands. Some clients send syntactically invalid versions of these
29028 commands, which Exim rejects by default. (This is nothing to do with verifying
29029 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
29030 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
29031 match the broken hosts that send invalid commands.
29033 .cindex "SIZE option on MAIL command"
29034 .cindex "MAIL" "SIZE option"
29035 The amount of disk space available is checked whenever SIZE is received on
29036 a MAIL command, independently of whether &%message_size_limit%& or
29037 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
29038 false. A temporary error is given if there is not enough space. If
29039 &%check_spool_space%& is set, the check is for that amount of space plus the
29040 value given with SIZE, that is, it checks that the addition of the incoming
29041 message will not reduce the space below the threshold.
29043 When a message is successfully received, Exim includes the local message id in
29044 its response to the final &"."& that terminates the data. If the remote host
29045 logs this text it can help with tracing what has happened to a message.
29047 The Exim daemon can limit the number of simultaneous incoming connections it is
29048 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
29049 number of simultaneous incoming connections from a single remote host (see the
29050 &%smtp_accept_max_per_host%& option). Additional connection attempts are
29051 rejected using the SMTP temporary error code 421.
29053 The Exim daemon does not rely on the SIGCHLD signal to detect when a
29054 subprocess has finished, as this can get lost at busy times. Instead, it looks
29055 for completed subprocesses every time it wakes up. Provided there are other
29056 things happening (new incoming calls, starts of queue runs), completed
29057 processes will be noticed and tidied away. On very quiet systems you may
29058 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
29059 it will be noticed when the daemon next wakes up.
29061 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
29062 and can also be set up to reject SMTP calls from non-reserved hosts at times of
29063 high system load &-- for details see the &%smtp_accept_reserve%&,
29064 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
29065 applies in both the daemon and &'inetd'& cases.
29067 Exim normally starts a delivery process for each message received, though this
29068 can be varied by means of the &%-odq%& command line option and the
29069 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
29070 number of simultaneously running delivery processes started in this way from
29071 SMTP input can be limited by the &%smtp_accept_queue%& and
29072 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
29073 subsequently received messages are just put on the input queue without starting
29074 a delivery process.
29076 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
29077 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
29078 started up from the &'inetd'& daemon, because in that case each connection is
29079 handled by an entirely independent Exim process. Control by load average is,
29080 however, available with &'inetd'&.
29082 Exim can be configured to verify addresses in incoming SMTP commands as they
29083 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
29084 to rewrite addresses at this time &-- before any syntax checking is done. See
29085 section &<<SECTrewriteS>>&.
29087 Exim can also be configured to limit the rate at which a client host submits
29088 MAIL and RCPT commands in a single SMTP session. See the
29089 &%smtp_ratelimit_hosts%& option.
29093 .section "Unrecognized SMTP commands"
29094 .cindex "SMTP" "unrecognized commands"
29095 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
29096 commands during a single SMTP connection, it drops the connection after sending
29097 the error response to the last command. The default value for
29098 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
29099 abuse that subvert web servers into making connections to SMTP ports; in these
29100 circumstances, a number of non-SMTP lines are sent first.
29103 .section "Syntax and protocol errors in SMTP commands"
29104 .cindex "SMTP" "syntax errors"
29105 .cindex "SMTP" "protocol errors"
29106 A syntax error is detected if an SMTP command is recognized, but there is
29107 something syntactically wrong with its data, for example, a malformed email
29108 address in a RCPT command. Protocol errors include invalid command
29109 sequencing such as RCPT before MAIL. If Exim receives more than
29110 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
29111 drops the connection after sending the error response to the last command. The
29112 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
29113 broken clients that loop sending bad commands (yes, it has been seen).
29117 .section "Use of non-mail SMTP commands"
29118 .cindex "SMTP" "non-mail commands"
29119 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
29120 DATA. Exim counts such commands, and drops the connection if there are too
29121 many of them in a single SMTP session. This action catches some
29122 denial-of-service attempts and things like repeated failing AUTHs, or a mad
29123 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
29124 defines what &"too many"& means. Its default value is 10.
29126 When a new message is expected, one occurrence of RSET is not counted. This
29127 allows a client to send one RSET between messages (this is not necessary,
29128 but some clients do it). Exim also allows one uncounted occurence of HELO
29129 or EHLO, and one occurrence of STARTTLS between messages. After
29130 starting up a TLS session, another EHLO is expected, and so it too is not
29133 The first occurrence of AUTH in a connection, or immediately following
29134 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
29135 RCPT, DATA, and QUIT are counted.
29137 You can control which hosts are subject to the limit set by
29138 &%smtp_accept_max_nonmail%& by setting
29139 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
29140 the limit apply to all hosts. This option means that you can exclude any
29141 specific badly-behaved hosts that you have to live with.
29146 .section "The VRFY and EXPN commands"
29147 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
29148 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
29149 appropriate) in order to decide whether the command should be accepted or not.
29150 If no ACL is defined, the command is rejected.
29152 .cindex "VRFY" "processing"
29153 When VRFY is accepted, it runs exactly the same code as when Exim is
29154 called with the &%-bv%& option.
29156 .cindex "EXPN" "processing"
29157 When EXPN is accepted, a single-level expansion of the address is done.
29158 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
29159 than a verification (the &%-bv%& option). If an unqualified local part is given
29160 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
29161 of VRFY and EXPN commands are logged on the main and reject logs, and
29162 VRFY verification failures are logged on the main log for consistency with
29167 .section "The ETRN command" "SECTETRN"
29168 .cindex "ETRN" "processing"
29169 RFC 1985 describes an SMTP command called ETRN that is designed to
29170 overcome the security problems of the TURN command (which has fallen into
29171 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
29172 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
29173 should be accepted or not. If no ACL is defined, the command is rejected.
29175 The ETRN command is concerned with &"releasing"& messages that are awaiting
29176 delivery to certain hosts. As Exim does not organize its message queue by host,
29177 the only form of ETRN that is supported by default is the one where the
29178 text starts with the &"#"& prefix, in which case the remainder of the text is
29179 specific to the SMTP server. A valid ETRN command causes a run of Exim with
29180 the &%-R%& option to happen, with the remainder of the ETRN text as its
29181 argument. For example,
29189 which causes a delivery attempt on all messages with undelivered addresses
29190 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
29191 default), Exim prevents the simultaneous execution of more than one queue run
29192 for the same argument string as a result of an ETRN command. This stops
29193 a misbehaving client from starting more than one queue runner at once.
29195 .cindex "hints database" "ETRN serialization"
29196 Exim implements the serialization by means of a hints database in which a
29197 record is written whenever a process is started by ETRN, and deleted when
29198 the process completes. However, Exim does not keep the SMTP session waiting for
29199 the ETRN process to complete. Once ETRN is accepted, the client is sent
29200 a &"success"& return code. Obviously there is scope for hints records to get
29201 left lying around if there is a system or program crash. To guard against this,
29202 Exim ignores any records that are more than six hours old.
29204 .cindex "&%smtp_etrn_command%&"
29205 For more control over what ETRN does, the &%smtp_etrn_command%& option can
29206 used. This specifies a command that is run whenever ETRN is received,
29207 whatever the form of its argument. For
29210 smtp_etrn_command = /etc/etrn_command $domain \
29211 $sender_host_address
29213 .cindex "&$domain$&"
29214 The string is split up into arguments which are independently expanded. The
29215 expansion variable &$domain$& is set to the argument of the ETRN command,
29216 and no syntax checking is done on the contents of this argument. Exim does not
29217 wait for the command to complete, so its status code is not checked. Exim runs
29218 under its own uid and gid when receiving incoming SMTP, so it is not possible
29219 for it to change them before running the command.
29223 .section "Incoming local SMTP"
29224 .cindex "SMTP" "local incoming"
29225 Some user agents use SMTP to pass messages to their local MTA using the
29226 standard input and output, as opposed to passing the envelope on the command
29227 line and writing the message to the standard input. This is supported by the
29228 &%-bs%& option. This form of SMTP is handled in the same way as incoming
29229 messages over TCP/IP (including the use of ACLs), except that the envelope
29230 sender given in a MAIL command is ignored unless the caller is trusted. In
29231 an ACL you can detect this form of SMTP input by testing for an empty host
29232 identification. It is common to have this as the first line in the ACL that
29233 runs for RCPT commands:
29237 This accepts SMTP messages from local processes without doing any other tests.
29241 .section "Outgoing batched SMTP" "SECTbatchSMTP"
29242 .cindex "SMTP" "batched outgoing"
29243 .cindex "batched SMTP output"
29244 Both the &(appendfile)& and &(pipe)& transports can be used for handling
29245 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
29246 be output in BSMTP format. No SMTP responses are possible for this form of
29247 delivery. All it is doing is using SMTP commands as a way of transmitting the
29248 envelope along with the message.
29250 The message is written to the file or pipe preceded by the SMTP commands
29251 MAIL and RCPT, and followed by a line containing a single dot. Lines in
29252 the message that start with a dot have an extra dot added. The SMTP command
29253 HELO is not normally used. If it is required, the &%message_prefix%& option
29254 can be used to specify it.
29256 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
29257 one recipient address at a time by default. However, you can arrange for them
29258 to handle several addresses at once by setting the &%batch_max%& option. When
29259 this is done for BSMTP, messages may contain multiple RCPT commands. See
29260 chapter &<<CHAPbatching>>& for more details.
29263 When one or more addresses are routed to a BSMTP transport by a router that
29264 sets up a host list, the name of the first host on the list is available to the
29265 transport in the variable &$host$&. Here is an example of such a transport and
29270 driver = manualroute
29271 transport = smtp_appendfile
29272 route_list = domain.example batch.host.example
29276 driver = appendfile
29277 directory = /var/bsmtp/$host
29282 This causes messages addressed to &'domain.example'& to be written in BSMTP
29283 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
29284 message (unless there are more than 1000 recipients).
29288 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
29289 .cindex "SMTP" "batched incoming"
29290 .cindex "batched SMTP input"
29291 The &%-bS%& command line option causes Exim to accept one or more messages by
29292 reading SMTP on the standard input, but to generate no responses. If the caller
29293 is trusted, the senders in the MAIL commands are believed; otherwise the
29294 sender is always the caller of Exim. Unqualified senders and receivers are not
29295 rejected (there seems little point) but instead just get qualified. HELO
29296 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
29297 as NOOP; QUIT quits.
29299 No policy checking is done for BSMTP input. That is, no ACL is run at anytime.
29300 In this respect it is like non-SMTP local input.
29302 If an error is detected while reading a message, including a missing &"."& at
29303 the end, Exim gives up immediately. It writes details of the error to the
29304 standard output in a stylized way that the calling program should be able to
29305 make some use of automatically, for example:
29307 554 Unexpected end of file
29308 Transaction started in line 10
29309 Error detected in line 14
29311 It writes a more verbose version, for human consumption, to the standard error
29314 An error was detected while processing a file of BSMTP input.
29315 The error message was:
29317 501 '>' missing at end of address
29319 The SMTP transaction started in line 10.
29320 The error was detected in line 12.
29321 The SMTP command at fault was:
29323 rcpt to:<malformed@in.com.plete
29325 1 previous message was successfully processed.
29326 The rest of the batch was abandoned.
29328 The return code from Exim is zero only if there were no errors. It is 1 if some
29329 messages were accepted before an error was detected, and 2 if no messages were
29331 .ecindex IIDsmtpproc1
29332 .ecindex IIDsmtpproc2
29336 . ////////////////////////////////////////////////////////////////////////////
29337 . ////////////////////////////////////////////////////////////////////////////
29339 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
29340 "Customizing messages"
29341 When a message fails to be delivered, or remains on the queue for more than a
29342 configured amount of time, Exim sends a message to the original sender, or
29343 to an alternative configured address. The text of these messages is built into
29344 the code of Exim, but it is possible to change it, either by adding a single
29345 string, or by replacing each of the paragraphs by text supplied in a file.
29347 The &'From:'& and &'To:'& header lines are automatically generated; you can
29348 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
29349 option. Exim also adds the line
29351 Auto-Submitted: auto-generated
29353 to all warning and bounce messages,
29356 .section "Customizing bounce messages"
29357 .cindex "customizing" "bounce message"
29358 .cindex "bounce message" "customizing"
29359 If &%bounce_message_text%& is set, its contents are included in the default
29360 message immediately after &"This message was created automatically by mail
29361 delivery software."& The string is not expanded. It is not used if
29362 &%bounce_message_file%& is set.
29364 When &%bounce_message_file%& is set, it must point to a template file for
29365 constructing error messages. The file consists of a series of text items,
29366 separated by lines consisting of exactly four asterisks. If the file cannot be
29367 opened, default text is used and a message is written to the main and panic
29368 logs. If any text item in the file is empty, default text is used for that
29371 .cindex "&$bounce_recipient$&"
29372 .cindex "&$bounce_return_size_limit$&"
29373 Each item of text that is read from the file is expanded, and there are two
29374 expansion variables which can be of use here: &$bounce_recipient$& is set to
29375 the recipient of an error message while it is being created, and
29376 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
29377 option, rounded to a whole number.
29379 The items must appear in the file in the following order:
29382 The first item is included in the headers, and should include at least a
29383 &'Subject:'& header. Exim does not check the syntax of these headers.
29385 The second item forms the start of the error message. After it, Exim lists the
29386 failing addresses with their error messages.
29388 The third item is used to introduce any text from pipe transports that is to be
29389 returned to the sender. It is omitted if there is no such text.
29391 The fourth item is used to introduce the copy of the message that is returned
29392 as part of the error report.
29394 The fifth item is added after the fourth one if the returned message is
29395 truncated because it is bigger than &%return_size_limit%&.
29397 The sixth item is added after the copy of the original message.
29400 The default state (&%bounce_message_file%& unset) is equivalent to the
29401 following file, in which the sixth item is empty. The &'Subject:'& and some
29402 other lines have been split in order to fit them on the page:
29404 Subject: Mail delivery failed
29405 ${if eq{$sender_address}{$bounce_recipient}
29406 {: returning message to sender}}
29408 This message was created automatically by mail delivery software.
29410 A message ${if eq{$sender_address}{$bounce_recipient}
29411 {that you sent }{sent by
29415 }}could not be delivered to all of its recipients.
29416 The following address(es) failed:
29418 The following text was generated during the delivery attempt(s):
29420 ------ This is a copy of the message, including all the headers.
29423 ------ The body of the message is $message_size characters long;
29425 ------ $bounce_return_size_limit or so are included here.
29428 .section "Customizing warning messages" "SECTcustwarn"
29429 .cindex "customizing" "warning message"
29430 .cindex "warning of delay" "customizing the message"
29431 The option &%warn_message_file%& can be pointed at a template file for use when
29432 warnings about message delays are created. In this case there are only three
29436 The first item is included in the headers, and should include at least a
29437 &'Subject:'& header. Exim does not check the syntax of these headers.
29439 The second item forms the start of the warning message. After it, Exim lists
29440 the delayed addresses.
29442 The third item then ends the message.
29445 The default state is equivalent to the following file, except that some lines
29446 have been split here, in order to fit them on the page:
29448 Subject: Warning: message $message_exim_id delayed
29449 $warn_message_delay
29451 This message was created automatically by mail delivery software.
29453 A message ${if eq{$sender_address}{$warn_message_recipients}
29454 {that you sent }{sent by
29458 }}has not been delivered to all of its recipients after
29459 more than $warn_message_delay on the queue on $primary_hostname.
29461 The message identifier is: $message_exim_id
29462 The subject of the message is: $h_subject
29463 The date of the message is: $h_date
29465 The following address(es) have not yet been delivered:
29467 No action is required on your part. Delivery attempts will
29468 continue for some time, and this warning may be repeated at
29469 intervals if the message remains undelivered. Eventually the
29470 mail delivery software will give up, and when that happens,
29471 the message will be returned to you.
29473 .cindex "&$warn_message_delay$&"
29474 .cindex "&$warn_message_recipients$&"
29475 However, in the default state the subject and date lines are omitted if no
29476 appropriate headers exist. During the expansion of this file,
29477 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
29478 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
29479 of recipients for the warning message. There may be more than one if there are
29480 multiple addresses with different &%errors_to%& settings on the routers that
29486 . ////////////////////////////////////////////////////////////////////////////
29487 . ////////////////////////////////////////////////////////////////////////////
29489 .chapter "Some common configuration settings" "CHAPcomconreq"
29490 This chapter discusses some configuration settings that seem to be fairly
29491 common. More examples and discussion can be found in the Exim book.
29495 .section "Sending mail to a smart host"
29496 .cindex "smart host" "example router"
29497 If you want to send all mail for non-local domains to a &"smart host"&, you
29498 should replace the default &(dnslookup)& router with a router which does the
29499 routing explicitly:
29501 send_to_smart_host:
29502 driver = manualroute
29503 route_list = !+local_domains smart.host.name
29504 transport = remote_smtp
29506 You can use the smart host's IP address instead of the name if you wish.
29507 If you are using Exim only to submit messages to a smart host, and not for
29508 receiving incoming messages, you can arrange for it to do the submission
29509 synchronously by setting the &%mua_wrapper%& option (see chapter
29510 &<<CHAPnonqueueing>>&).
29515 .section "Using Exim to handle mailing lists" "SECTmailinglists"
29516 .cindex "mailing lists"
29517 Exim can be used to run simple mailing lists, but for large and/or complicated
29518 requirements, the use of additional specialized mailing list software such as
29519 Majordomo or Mailman is recommended.
29521 The &(redirect)& router can be used to handle mailing lists where each list
29522 is maintained in a separate file, which can therefore be managed by an
29523 independent manager. The &%domains%& router option can be used to run these
29524 lists in a separate domain from normal mail. For example:
29528 domains = lists.example
29529 file = /usr/lists/$local_part
29532 errors_to = $local_part-request@lists.example
29535 This router is skipped for domains other than &'lists.example'&. For addresses
29536 in that domain, it looks for a file that matches the local part. If there is no
29537 such file, the router declines, but because &%no_more%& is set, no subsequent
29538 routers are tried, and so the whole delivery fails.
29540 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
29541 expanded into a file name or a pipe delivery, which is usually inappropriate in
29544 .cindex "&%errors_to%&"
29545 The &%errors_to%& option specifies that any delivery errors caused by addresses
29546 taken from a mailing list are to be sent to the given address rather than the
29547 original sender of the message. However, before acting on this, Exim verifies
29548 the error address, and ignores it if verification fails.
29550 For example, using the configuration above, mail sent to
29551 &'dicts@lists.example'& is passed on to those addresses contained in
29552 &_/usr/lists/dicts_&, with error reports directed to
29553 &'dicts-request@lists.example'&, provided that this address can be verified.
29554 There could be a file called &_/usr/lists/dicts-request_& containing
29555 the address(es) of this particular list's manager(s), but other approaches,
29556 such as setting up an earlier router (possibly using the &%local_part_prefix%&
29557 or &%local_part_suffix%& options) to handle addresses of the form
29558 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
29562 .section "Syntax errors in mailing lists"
29563 .cindex "mailing lists" "syntax errors in"
29564 If an entry in redirection data contains a syntax error, Exim normally defers
29565 delivery of the original address. That means that a syntax error in a mailing
29566 list holds up all deliveries to the list. This may not be appropriate when a
29567 list is being maintained automatically from data supplied by users, and the
29568 addresses are not rigorously checked.
29570 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
29571 entries that fail to parse, noting the incident in the log. If in addition
29572 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
29573 whenever a broken address is skipped. It is usually appropriate to set
29574 &%syntax_errors_to%& to the same address as &%errors_to%&.
29578 .section "Re-expansion of mailing lists"
29579 .cindex "mailing lists" "re-expansion of"
29580 Exim remembers every individual address to which a message has been delivered,
29581 in order to avoid duplication, but it normally stores only the original
29582 recipient addresses with a message. If all the deliveries to a mailing list
29583 cannot be done at the first attempt, the mailing list is re-expanded when the
29584 delivery is next tried. This means that alterations to the list are taken into
29585 account at each delivery attempt, so addresses that have been added to
29586 the list since the message arrived will therefore receive a copy of the
29587 message, even though it pre-dates their subscription.
29589 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
29590 on the &(redirect)& router. If this is done, any addresses generated by the
29591 router that fail to deliver at the first attempt are added to the message as
29592 &"top level"& addresses, and the parent address that generated them is marked
29593 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
29594 subsequent delivery attempts. The disadvantage of this is that if any of the
29595 failing addresses are incorrect, correcting them in the file has no effect on
29596 pre-existing messages.
29598 The original top-level address is remembered with each of the generated
29599 addresses, and is output in any log messages. However, any intermediate parent
29600 addresses are not recorded. This makes a difference to the log only if the
29601 &%all_parents%& selector is set, but for mailing lists there is normally only
29602 one level of expansion anyway.
29606 .section "Closed mailing lists"
29607 .cindex "mailing lists" "closed"
29608 The examples so far have assumed open mailing lists, to which anybody may
29609 send mail. It is also possible to set up closed lists, where mail is accepted
29610 from specified senders only. This is done by making use of the generic
29611 &%senders%& option to restrict the router that handles the list.
29613 The following example uses the same file as a list of recipients and as a list
29614 of permitted senders. It requires three routers:
29618 domains = lists.example
29619 local_part_suffix = -request
29620 file = /usr/lists/$local_part$local_part_suffix
29625 domains = lists.example
29626 senders = ${if exists {/usr/lists/$local_part}\
29627 {lsearch;/usr/lists/$local_part}{*}}
29628 file = /usr/lists/$local_part
29631 errors_to = $local_part-request@lists.example
29636 domains = lists.example
29638 data = :fail: $local_part@lists.example is a closed mailing list
29640 All three routers have the same &%domains%& setting, so for any other domains,
29641 they are all skipped. The first router runs only if the local part ends in
29642 &%-request%&. It handles messages to the list manager(s) by means of an open
29645 The second router runs only if the &%senders%& precondition is satisfied. It
29646 checks for the existence of a list that corresponds to the local part, and then
29647 checks that the sender is on the list by means of a linear search. It is
29648 necessary to check for the existence of the file before trying to search it,
29649 because otherwise Exim thinks there is a configuration error. If the file does
29650 not exist, the expansion of &%senders%& is *, which matches all senders. This
29651 means that the router runs, but because there is no list, declines, and
29652 &%no_more%& ensures that no further routers are run. The address fails with an
29653 &"unrouteable address"& error.
29655 The third router runs only if the second router is skipped, which happens when
29656 a mailing list exists, but the sender is not on it. This router forcibly fails
29657 the address, giving a suitable error message.
29662 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
29664 .cindex "Variable Envelope Return Paths"
29665 .cindex "envelope sender"
29666 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
29667 are a way of helping mailing list administrators discover which subscription
29668 address is the cause of a particular delivery failure. The idea is to encode
29669 the original recipient address in the outgoing envelope sender address, so that
29670 if the message is forwarded by another host and then subsequently bounces, the
29671 original recipient can be extracted from the recipient address of the bounce.
29673 .oindex &%errors_to%&
29674 .oindex &%return_path%&
29675 Envelope sender addresses can be modified by Exim using two different
29676 facilities: the &%errors_to%& option on a router (as shown in previous mailing
29677 list examples), or the &%return_path%& option on a transport. The second of
29678 these is effective only if the message is successfully delivered to another
29679 host; it is not used for errors detected on the local host (see the description
29680 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
29681 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
29687 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
29688 {$1-request=$local_part%$domain@your.dom.example}fail}
29690 This has the effect of rewriting the return path (envelope sender) on outgoing
29691 SMTP messages, if the local part of the original return path ends in
29692 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
29693 local part and domain of the recipient into the return path. Suppose, for
29694 example, that a message whose return path has been set to
29695 &'somelist-request@your.dom.example'& is sent to
29696 &'subscriber@other.dom.example'&. In the transport, the return path is
29699 somelist-request=subscriber%other.dom.example@your.dom.example
29701 .cindex "&$local_part$&"
29702 For this to work, you must also arrange for outgoing messages that have
29703 &"-request"& in their return paths to have just a single recipient. That is
29704 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
29705 might be sent to several different recipients in the same domain, in which case
29706 &$local_part$& is not available in the transport, because it is not unique.
29708 Unless your host is doing nothing but mailing list deliveries, you should
29709 probably use a separate transport for the VERP deliveries, so as not to use
29710 extra resources for the others. This can easily be done by expanding the
29711 &%transport%& option in the router:
29715 domains = ! +local_domains
29717 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
29718 {verp_smtp}{remote_smtp}}
29721 If you want to change the return path using &%errors_to%& in a router instead
29722 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
29723 routers that handle mailing list addresses. This will ensure that all delivery
29724 errors, including those detected on the local host, are sent to the VERP
29727 On a host that does no local deliveries and has no manual routing, only the
29728 &(dnslookup)& router needs to be changed. A special transport is not needed for
29729 SMTP deliveries. Every mailing list recipient has its own return path value,
29730 and so Exim must hand them to the transport one at a time. Here is an example
29731 of a &(dnslookup)& router that implements VERP:
29735 domains = ! +local_domains
29736 transport = remote_smtp
29738 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
29739 {$1-request=$local_part%$domain@your.dom.example}fail}
29742 Before you start sending out messages with VERPed return paths, you must also
29743 configure Exim to accept the bounce messages that come back to those paths.
29744 Typically this is done by setting a &%local_part_suffix%& option for a
29745 router, and using this to route the messages to wherever you want to handle
29748 The overhead incurred in using VERP depends very much on the size of the
29749 message, the number of recipient addresses that resolve to the same remote
29750 host, and the speed of the connection over which the message is being sent. If
29751 a lot of addresses resolve to the same host and the connection is slow, sending
29752 a separate copy of the message for each address may take substantially longer
29753 than sending a single copy with many recipients (for which VERP cannot be
29761 .section "Virtual domains" "SECTvirtualdomains"
29762 .cindex "virtual domains"
29763 .cindex "domain" "virtual"
29764 The phrase &'virtual domain'& is unfortunately used with two rather different
29768 A domain for which there are no real mailboxes; all valid local parts are
29769 aliases for other email addresses. Common examples are organizational
29770 top-level domains and &"vanity"& domains.
29772 One of a number of independent domains that are all handled by the same host,
29773 with mailboxes on that host, but where the mailbox owners do not necessarily
29774 have login accounts on that host.
29777 The first usage is probably more common, and does seem more &"virtual"& than
29778 the second. This kind of domain can be handled in Exim with a straightforward
29779 aliasing router. One approach is to create a separate alias file for each
29780 virtual domain. Exim can test for the existence of the alias file to determine
29781 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
29782 to a router of this form:
29786 domains = dsearch;/etc/mail/virtual
29787 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
29790 The &%domains%& option specifies that the router is to be skipped, unless there
29791 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
29792 domain that is being processed. When the router runs, it looks up the local
29793 part in the file to find a new address (or list of addresses). The &%no_more%&
29794 setting ensures that if the lookup fails (leading to &%data%& being an empty
29795 string), Exim gives up on the address without trying any subsequent routers.
29797 This one router can handle all the virtual domains because the alias file names
29798 follow a fixed pattern. Permissions can be arranged so that appropriate people
29799 can edit the different alias files. A successful aliasing operation results in
29800 a new envelope recipient address, which is then routed from scratch.
29802 The other kind of &"virtual"& domain can also be handled in a straightforward
29803 way. One approach is to create a file for each domain containing a list of
29804 valid local parts, and use it in a router like this:
29808 domains = dsearch;/etc/mail/domains
29809 local_parts = lsearch;/etc/mail/domains/$domain
29810 transport = my_mailboxes
29812 The address is accepted if there is a file for the domain, and the local part
29813 can be found in the file. The &%domains%& option is used to check for the
29814 file's existence because &%domains%& is tested before the &%local_parts%&
29815 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
29816 because that option is tested after &%local_parts%&. The transport is as
29820 driver = appendfile
29821 file = /var/mail/$domain/$local_part
29824 This uses a directory of mailboxes for each domain. The &%user%& setting is
29825 required, to specify which uid is to be used for writing to the mailboxes.
29827 The configuration shown here is just one example of how you might support this
29828 requirement. There are many other ways this kind of configuration can be set
29829 up, for example, by using a database instead of separate files to hold all the
29830 information about the domains.
29834 .section "Multiple user mailboxes" "SECTmulbox"
29835 .cindex "multiple mailboxes"
29836 .cindex "mailbox" "multiple"
29837 .cindex "local part" "prefix"
29838 .cindex "local part" "suffix"
29839 Heavy email users often want to operate with multiple mailboxes, into which
29840 incoming mail is automatically sorted. A popular way of handling this is to
29841 allow users to use multiple sender addresses, so that replies can easily be
29842 identified. Users are permitted to add prefixes or suffixes to their local
29843 parts for this purpose. The wildcard facility of the generic router options
29844 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
29845 example, consider this router:
29850 file = $home/.forward
29851 local_part_suffix = -*
29852 local_part_suffix_optional
29855 .cindex "&$local_part_suffix$&"
29856 It runs a user's &_.forward_& file for all local parts of the form
29857 &'username-*'&. Within the filter file the user can distinguish different
29858 cases by testing the variable &$local_part_suffix$&. For example:
29860 if $local_part_suffix contains -special then
29861 save /home/$local_part/Mail/special
29864 If the filter file does not exist, or does not deal with such addresses, they
29865 fall through to subsequent routers, and, assuming no subsequent use of the
29866 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
29867 control over which suffixes are valid.
29869 Alternatively, a suffix can be used to trigger the use of a different
29870 &_.forward_& file &-- which is the way a similar facility is implemented in
29876 file = $home/.forward$local_part_suffix
29877 local_part_suffix = -*
29878 local_part_suffix_optional
29881 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
29882 example, &_.forward-special_& is used. Once again, if the appropriate file
29883 does not exist, or does not deal with the address, it is passed on to
29884 subsequent routers, which could, if required, look for an unqualified
29885 &_.forward_& file to use as a default.
29889 .section "Simplified vacation processing"
29890 .cindex "vacation processing"
29891 The traditional way of running the &'vacation'& program is for a user to set up
29892 a pipe command in a &_.forward_& file
29893 (see section &<<SECTspecitredli>>& for syntax details).
29894 This is prone to error by inexperienced users. There are two features of Exim
29895 that can be used to make this process simpler for users:
29898 A local part prefix such as &"vacation-"& can be specified on a router which
29899 can cause the message to be delivered directly to the &'vacation'& program, or
29900 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
29901 &_.forward_& file are then much simpler. For example:
29903 spqr, vacation-spqr
29906 The &%require_files%& generic router option can be used to trigger a
29907 vacation delivery by checking for the existence of a certain file in the
29908 user's home directory. The &%unseen%& generic option should also be used, to
29909 ensure that the original delivery also proceeds. In this case, all the user has
29910 to do is to create a file called, say, &_.vacation_&, containing a vacation
29914 Another advantage of both these methods is that they both work even when the
29915 use of arbitrary pipes by users is locked out.
29919 .section "Taking copies of mail"
29920 .cindex "message" "copying every"
29921 Some installations have policies that require archive copies of all messages to
29922 be made. A single copy of each message can easily be taken by an appropriate
29923 command in a system filter, which could, for example, use a different file for
29924 each day's messages.
29926 There is also a shadow transport mechanism that can be used to take copies of
29927 messages that are successfully delivered by local transports, one copy per
29928 delivery. This could be used, &'inter alia'&, to implement automatic
29929 notification of delivery by sites that insist on doing such things.
29933 .section "Intermittently connected hosts"
29934 .cindex "intermittently connected hosts"
29935 It has become quite common (because it is cheaper) for hosts to connect to the
29936 Internet periodically rather than remain connected all the time. The normal
29937 arrangement is that mail for such hosts accumulates on a system that is
29938 permanently connected.
29940 Exim was designed for use on permanently connected hosts, and so it is not
29941 particularly well-suited to use in an intermittently connected environment.
29942 Nevertheless there are some features that can be used.
29945 .section "Exim on the upstream server host"
29946 It is tempting to arrange for incoming mail for the intermittently connected
29947 host to remain on Exim's queue until the client connects. However, this
29948 approach does not scale very well. Two different kinds of waiting message are
29949 being mixed up in the same queue &-- those that cannot be delivered because of
29950 some temporary problem, and those that are waiting for their destination host
29951 to connect. This makes it hard to manage the queue, as well as wasting
29952 resources, because each queue runner scans the entire queue.
29954 A better approach is to separate off those messages that are waiting for an
29955 intermittently connected host. This can be done by delivering these messages
29956 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
29957 format, from where they are transmitted by other software when their
29958 destination connects. This makes it easy to collect all the mail for one host
29959 in a single directory, and to apply local timeout rules on a per-message basis
29962 On a very small scale, leaving the mail on Exim's queue can be made to work. If
29963 you are doing this, you should configure Exim with a long retry period for the
29964 intermittent host. For example:
29966 cheshire.wonderland.fict.example * F,5d,24h
29968 This stops a lot of failed delivery attempts from occurring, but Exim remembers
29969 which messages it has queued up for that host. Once the intermittent host comes
29970 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
29971 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
29972 causes all the queued up messages to be delivered, often down a single SMTP
29973 connection. While the host remains connected, any new messages get delivered
29976 If the connecting hosts do not have fixed IP addresses, that is, if a host is
29977 issued with a different IP address each time it connects, Exim's retry
29978 mechanisms on the holding host get confused, because the IP address is normally
29979 used as part of the key string for holding retry information. This can be
29980 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
29981 Since this has disadvantages for permanently connected hosts, it is best to
29982 arrange a separate transport for the intermittently connected ones.
29986 .section "Exim on the intermittently connected client host"
29987 The value of &%smtp_accept_queue_per_connection%& should probably be
29988 increased, or even set to zero (that is, disabled) on the intermittently
29989 connected host, so that all incoming messages down a single connection get
29990 delivered immediately.
29992 .cindex "SMTP" "passed connection"
29993 .cindex "SMTP" "multiple deliveries"
29994 .cindex "multiple SMTP deliveries"
29995 Mail waiting to be sent from an intermittently connected host will probably
29996 not have been routed, because without a connection DNS lookups are not
29997 possible. This means that if a normal queue run is done at connection time,
29998 each message is likely to be sent in a separate SMTP session. This can be
29999 avoided by starting the queue run with a command line option beginning with
30000 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
30001 first pass, routing is done but no deliveries take place. The second pass is a
30002 normal queue run; since all the messages have been previously routed, those
30003 destined for the same host are likely to get sent as multiple deliveries in a
30004 single SMTP connection.
30008 . ////////////////////////////////////////////////////////////////////////////
30009 . ////////////////////////////////////////////////////////////////////////////
30011 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
30012 "Exim as a non-queueing client"
30013 .cindex "client" "non-queueing"
30014 .cindex "smart host" "queueing; suppressing"
30015 On a personal computer, it is a common requirement for all
30016 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
30017 configured to operate that way, for all the popular operating systems.
30018 However, there are some MUAs for Unix-like systems that cannot be so
30019 configured: they submit messages using the command line interface of
30020 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
30023 If the personal computer runs continuously, there is no problem, because it can
30024 run a conventional MTA that handles delivery to the smart host, and deal with
30025 any delays via its queueing mechanism. However, if the computer does not run
30026 continuously or runs different operating systems at different times, queueing
30027 email is not desirable.
30029 There is therefore a requirement for something that can provide the
30030 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
30031 any queueing or retrying facilities. Furthermore, the delivery to the smart
30032 host should be synchronous, so that if it fails, the sending MUA is immediately
30033 informed. In other words, we want something that extends an MUA that submits
30034 to a local MTA via the command line so that it behaves like one that submits
30035 to a remote smart host using TCP/SMTP.
30037 There are a number of applications (for example, there is one called &'ssmtp'&)
30038 that do this job. However, people have found them to be lacking in various
30039 ways. For instance, you might want to allow aliasing and forwarding to be done
30040 before sending a message to the smart host.
30042 Exim already had the necessary infrastructure for doing this job. Just a few
30043 tweaks were needed to make it behave as required, though it is somewhat of an
30044 overkill to use a fully-featured MTA for this purpose.
30046 .cindex "&%mua_wrapper%&"
30047 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
30048 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
30049 assumes that it is being used to &"wrap"& a command-line MUA in the manner
30050 just described. As well as setting &%mua_wrapper%&, you also need to provide a
30051 compatible router and transport configuration. Typically there will be just one
30052 router and one transport, sending everything to a smart host.
30054 When run in MUA wrapping mode, the behaviour of Exim changes in the
30058 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
30059 In other words, the only way to submit messages is via the command line.
30061 Each message is synchonously delivered as soon as it is received (&%-odi%& is
30062 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
30063 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
30064 does not finish until the delivery attempt is complete. If the delivery is
30065 successful, a zero return code is given.
30067 Address redirection is permitted, but the final routing for all addresses must
30068 be to the same remote transport, and to the same list of hosts. Furthermore,
30069 the return address (envelope sender) must be the same for all recipients, as
30070 must any added or deleted header lines. In other words, it must be possible to
30071 deliver the message in a single SMTP transaction, however many recipients there
30074 If these conditions are not met, or if routing any address results in a
30075 failure or defer status, or if Exim is unable to deliver all the recipients
30076 successfully to one of the smart hosts, delivery of the entire message fails.
30078 Because no queueing is allowed, all failures are treated as permanent; there
30079 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
30080 smart host. Furthermore, because only a single yes/no response can be given to
30081 the caller, it is not possible to deliver to some recipients and not others. If
30082 there is an error (temporary or permanent) for any recipient, all are failed.
30084 If more than one smart host is listed, Exim will try another host after a
30085 connection failure or a timeout, in the normal way. However, if this kind of
30086 failure happens for all the hosts, the delivery fails.
30088 When delivery fails, an error message is written to the standard error stream
30089 (as well as to Exim's log), and Exim exits to the caller with a return code
30090 value 1. The message is expunged from Exim's spool files. No bounce messages
30091 are ever generated.
30093 No retry data is maintained, and any retry rules are ignored.
30095 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
30096 true, &%max_rcpt%& in the smtp transport is forced to &"unlimited"&,
30097 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
30100 The overall effect is that Exim makes a single synchronous attempt to deliver
30101 the message, failing if there is any kind of problem. Because no local
30102 deliveries are done and no daemon can be run, Exim does not need root
30103 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
30104 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
30105 the advantages and disadvantages of running without root privilege.
30110 . ////////////////////////////////////////////////////////////////////////////
30111 . ////////////////////////////////////////////////////////////////////////////
30113 .chapter "Log files" "CHAPlog"
30114 .scindex IIDloggen "log" "general description"
30115 .cindex "log" "types of"
30116 Exim writes three different logs, referred to as the main log, the reject log,
30121 The main log records the arrival of each message and each delivery in a single
30122 line in each case. The format is as compact as possible, in an attempt to keep
30123 down the size of log files. Two-character flag sequences make it easy to pick
30124 out these lines. A number of other events are recorded in the main log. Some of
30125 them are optional, in which case the &%log_selector%& option controls whether
30126 they are included or not. A Perl script called &'eximstats'&, which does simple
30127 analysis of main log files, is provided in the Exim distribution (see section
30128 &<<SECTmailstat>>&).
30130 .cindex "reject log"
30131 The reject log records information from messages that are rejected as a result
30132 of a configuration option (that is, for policy reasons).
30133 The first line of each rejection is a copy of the line that is also written to
30134 the main log. Then, if the message's header has been read at the time the log
30135 is written, its contents are written to this log. Only the original header
30136 lines are available; header lines added by ACLs are not logged. You can use the
30137 reject log to check that your policy controls are working correctly; on a busy
30138 host this may be easier than scanning the main log for rejection messages. You
30139 can suppress the writing of the reject log by setting &%write_rejectlog%&
30142 .cindex "panic log"
30143 .cindex "system log"
30144 When certain serious errors occur, Exim writes entries to its panic log. If the
30145 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
30146 are usually written to the main log as well, but can get lost amid the mass of
30147 other entries. The panic log should be empty under normal circumstances. It is
30148 therefore a good idea to check it (or to have a &'cron'& script check it)
30149 regularly, in order to become aware of any problems. When Exim cannot open its
30150 panic log, it tries as a last resort to write to the system log (syslog). This
30151 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
30152 message itself is written at priority LOG_CRIT.
30155 Every log line starts with a timestamp, in the format shown in the following
30156 example. Note that many of the examples shown in this chapter are line-wrapped.
30157 In the log file, this would be all on one line:
30159 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
30162 By default, the timestamps are in the local timezone. There are two
30163 ways of changing this:
30166 You can set the &%timezone%& option to a different time zone; in particular, if
30171 the timestamps will be in UTC (aka GMT).
30173 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
30176 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
30183 .section "Where the logs are written" "SECTwhelogwri"
30184 .cindex "log" "destination"
30185 .cindex "log" "to file"
30186 .cindex "log" "to syslog"
30188 The logs may be written to local files, or to syslog, or both. However, it
30189 should be noted that many syslog implementations use UDP as a transport, and
30190 are therefore unreliable in the sense that messages are not guaranteed to
30191 arrive at the loghost, nor is the ordering of messages necessarily maintained.
30192 It has also been reported that on large log files (tens of megabytes) you may
30193 need to tweak syslog to prevent it syncing the file with each write &-- on
30194 Linux this has been seen to make syslog take 90% plus of CPU time.
30196 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
30197 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
30198 configuration. This latter string is expanded, so it can contain, for example,
30199 references to the host name:
30201 log_file_path = /var/log/$primary_hostname/exim_%slog
30203 It is generally advisable, however, to set the string in &_Local/Makefile_&
30204 rather than at run time, because then the setting is available right from the
30205 start of Exim's execution. Otherwise, if there's something it wants to log
30206 before it has read the configuration file (for example, an error in the
30207 configuration file) it will not use the path you want, and may not be able to
30210 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
30211 list, currently limited to at most two items. This is one option where the
30212 facility for changing a list separator may not be used. The list must always be
30213 colon-separated. If an item in the list is &"syslog"& then syslog is used;
30214 otherwise the item must either be an absolute path, containing &`%s`& at the
30215 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
30216 implying the use of a default path.
30218 When Exim encounters an empty item in the list, it searches the list defined by
30219 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
30220 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
30221 mean &"use the path specified at build time"&. It no such item exists, log
30222 files are written in the &_log_& subdirectory of the spool directory. This is
30223 equivalent to the setting:
30225 log_file_path = $spool_directory/log/%slog
30227 If you do not specify anything at build time or run time, that is where the
30230 A log file path may also contain &`%D`& if datestamped log file names are in
30231 use &-- see section &<<SECTdatlogfil>>& below.
30233 Here are some examples of possible settings:
30235 &`LOG_FILE_PATH=syslog `& syslog only
30236 &`LOG_FILE_PATH=:syslog `& syslog and default path
30237 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
30238 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
30240 If there are more than two paths in the list, the first is used and a panic
30245 .section "Logging to local files that are periodically &""cycled""&"
30246 .cindex "log" "cycling local files"
30247 .cindex "cycling logs"
30248 .cindex "&'exicyclog'&"
30249 .cindex "log" "local files; writing to"
30250 Some operating systems provide centralized and standardised methods for cycling
30251 log files. For those that do not, a utility script called &'exicyclog'& is
30252 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
30253 main and reject logs each time it is called. The maximum number of old logs to
30254 keep can be set. It is suggested this script is run as a daily &'cron'& job.
30256 An Exim delivery process opens the main log when it first needs to write to it,
30257 and it keeps the file open in case subsequent entries are required &-- for
30258 example, if a number of different deliveries are being done for the same
30259 message. However, remote SMTP deliveries can take a long time, and this means
30260 that the file may be kept open long after it is renamed if &'exicyclog'& or
30261 something similar is being used to rename log files on a regular basis. To
30262 ensure that a switch of log files is noticed as soon as possible, Exim calls
30263 &[stat()]& on the main log's name before reusing an open file, and if the file
30264 does not exist, or its inode has changed, the old file is closed and Exim
30265 tries to open the main log from scratch. Thus, an old log file may remain open
30266 for quite some time, but no Exim processes should write to it once it has been
30271 .section "Datestamped log files" "SECTdatlogfil"
30272 .cindex "log" "datestamped files"
30273 Instead of cycling the main and reject log files by renaming them
30274 periodically, some sites like to use files whose names contain a datestamp,
30275 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_&.
30276 Exim has support for this way of working. It is enabled by setting the
30277 &%log_file_path%& option to a path that includes &`%D`& at the point where the
30278 datestamp is required. For example:
30280 log_file_path = /var/spool/exim/log/%slog-%D
30281 log_file_path = /var/log/exim-%s-%D.log
30282 log_file_path = /var/spool/exim/log/%D-%slog
30284 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
30285 examples of names generated by the above examples:
30287 /var/spool/exim/log/mainlog-20021225
30288 /var/log/exim-reject-20021225.log
30289 /var/spool/exim/log/20021225-mainlog
30291 When this form of log file is specified, Exim automatically switches to new
30292 files at midnight. It does not make any attempt to compress old logs; you
30293 will need to write your own script if you require this. You should not
30294 run &'exicyclog'& with this form of logging.
30296 The location of the panic log is also determined by &%log_file_path%&, but it
30297 is not datestamped, because rotation of the panic log does not make sense.
30298 When generating the name of the panic log, &`%D`& is removed from the string.
30299 In addition, if it immediately follows a slash, a following non-alphanumeric
30300 character is removed; otherwise a preceding non-alphanumeric character is
30301 removed. Thus, the three examples above would give these panic log names:
30303 /var/spool/exim/log/paniclog
30304 /var/log/exim-panic.log
30305 /var/spool/exim/log/paniclog
30309 .section "Logging to syslog"
30310 .cindex "log" "syslog; writing to"
30311 The use of syslog does not change what Exim logs or the format of its messages,
30312 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
30313 Exim's log lines are omitted when these lines are sent to syslog. Apart from
30314 that, the same strings are written to syslog as to log files. The syslog
30315 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
30316 by default, but you can change these by setting the &%syslog_facility%& and
30317 &%syslog_processname%& options, respectively. If Exim was compiled with
30318 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
30319 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
30320 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
30321 the time and host name to each line.
30322 The three log streams are mapped onto syslog priorities as follows:
30325 &'mainlog'& is mapped to LOG_INFO
30327 &'rejectlog'& is mapped to LOG_NOTICE
30329 &'paniclog'& is mapped to LOG_ALERT
30332 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
30333 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
30334 these are routed by syslog to the same place. You can suppress this duplication
30335 by setting &%syslog_duplication%& false.
30337 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
30338 entries contain multiple lines when headers are included. To cope with both
30339 these cases, entries written to syslog are split into separate &[syslog()]&
30340 calls at each internal newline, and also after a maximum of
30341 870 data characters. (This allows for a total syslog line length of 1024, when
30342 additions such as timestamps are added.) If you are running a syslog
30343 replacement that can handle lines longer than the 1024 characters allowed by
30344 RFC 3164, you should set
30346 SYSLOG_LONG_LINES=yes
30348 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
30349 lines, but it still splits at internal newlines in &'reject'& log entries.
30351 To make it easy to re-assemble split lines later, each component of a split
30352 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
30353 where <&'n'&> is the component number and <&'m'&> is the total number of
30354 components in the entry. The / delimiter is used when the line was split
30355 because it was too long; if it was split because of an internal newline, the \
30356 delimiter is used. For example, supposing the length limit to be 50 instead of
30357 870, the following would be the result of a typical rejection message to
30358 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
30359 name, and pid as added by syslog:
30361 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
30362 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
30363 [3/5] when scanning for sender: missing or malformed lo
30364 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
30367 The same error might cause the following lines to be written to &"rejectlog"&
30370 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
30371 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
30372 [3/18] er when scanning for sender: missing or malformed
30373 [4/18] local part in "<>" (envelope sender is <ph10@cam
30375 [6\18] Recipients: ph10@some.domain.cam.example
30376 [7\18] P Received: from [127.0.0.1] (ident=ph10)
30377 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
30378 [9\18] id 16RdAL-0006pc-00
30379 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
30380 [11\18] 09:43 +0100
30382 [13\18] Subject: this is a test header
30383 [18\18] X-something: this is another header
30384 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
30387 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
30389 Log lines that are neither too long nor contain newlines are written to syslog
30390 without modification.
30392 If only syslog is being used, the Exim monitor is unable to provide a log tail
30393 display, unless syslog is routing &'mainlog'& to a file on the local host and
30394 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
30399 .section "Log line flags"
30400 One line is written to the main log for each message received, and for each
30401 successful, unsuccessful, and delayed delivery. These lines can readily be
30402 picked out by the distinctive two-character flags that immediately follow the
30403 timestamp. The flags are:
30405 &`<=`& message arrival
30406 &`=>`& normal message delivery
30407 &`->`& additional address in same delivery
30408 &`*>`& delivery suppressed by &%-N%&
30409 &`**`& delivery failed; address bounced
30410 &`==`& delivery deferred; temporary problem
30414 .section "Logging message reception"
30415 .cindex "log" "reception line"
30416 The format of the single-line entry in the main log that is written for every
30417 message received is shown in the basic example below, which is split over
30418 several lines in order to fit it on the page:
30420 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
30421 H=mailer.fict.example [192.168.123.123] U=exim
30422 P=smtp S=5678 id=<incoming message id>
30424 The address immediately following &"<="& is the envelope sender address. A
30425 bounce message is shown with the sender address &"<>"&, and if it is locally
30426 generated, this is followed by an item of the form
30430 which is a reference to the message that caused the bounce to be sent.
30434 For messages from other hosts, the H and U fields identify the remote host and
30435 record the RFC 1413 identity of the user that sent the message, if one was
30436 received. The number given in square brackets is the IP address of the sending
30437 host. If there is a single, unparenthesized host name in the H field, as
30438 above, it has been verified to correspond to the IP address (see the
30439 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
30440 by the remote host in the SMTP HELO or EHLO command, and has not been
30441 verified. If verification yields a different name to that given for HELO or
30442 EHLO, the verified name appears first, followed by the HELO or EHLO
30443 name in parentheses.
30445 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
30446 without brackets, in the HELO or EHLO command, leading to entries in
30447 the log containing text like these examples:
30449 H=(10.21.32.43) [192.168.8.34]
30450 H=([10.21.32.43]) [192.168.8.34]
30452 This can be confusing. Only the final address in square brackets can be relied
30455 For locally generated messages (that is, messages not received over TCP/IP),
30456 the H field is omitted, and the U field contains the login name of the caller
30459 .cindex "authentication" "logging"
30460 .cindex "AUTH" "logging"
30461 For all messages, the P field specifies the protocol used to receive the
30462 message. This is the value that is stored in &$received_protocol$&. In the case
30463 of incoming SMTP messages, the value indicates whether or not any SMTP
30464 extensions (ESMTP), encryption, or authentication were used. If the SMTP
30465 session was encrypted, there is an additional X field that records the cipher
30466 suite that was used.
30468 The protocol is set to &"esmptsa"& or &"esmtpa"& for messages received from
30469 hosts that have authenticated themselves using the SMTP AUTH command. The first
30470 value is used when the SMTP connection was encrypted (&"secure"&). In this case
30471 there is an additional item A= followed by the name of the authenticator that
30472 was used. If an authenticated identification was set up by the authenticator's
30473 &%server_set_id%& option, this is logged too, separated by a colon from the
30474 authenticator name.
30476 .cindex "size" "of message"
30477 The id field records the existing message id, if present. The size of the
30478 received message is given by the S field. When the message is delivered,
30479 headers may be removed or added, so that the size of delivered copies of the
30480 message may not correspond with this value (and indeed may be different to each
30483 The &%log_selector%& option can be used to request the logging of additional
30484 data when a message is received. See section &<<SECTlogselector>>& below.
30488 .section "Logging deliveries"
30489 .cindex "log" "delivery line"
30490 The format of the single-line entry in the main log that is written for every
30491 delivery is shown in one of the examples below, for local and remote
30492 deliveries, respectively. Each example has been split into two lines in order
30493 to fit it on the page:
30495 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
30496 <marv@hitch.fict.example> R=localuser T=local_delivery
30497 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
30498 monk@holistic.fict.example R=dnslookup T=remote_smtp
30499 H=holistic.fict.example [192.168.234.234]
30501 For ordinary local deliveries, the original address is given in angle brackets
30502 after the final delivery address, which might be a pipe or a file. If
30503 intermediate address(es) exist between the original and the final address, the
30504 last of these is given in parentheses after the final address. The R and T
30505 fields record the router and transport that were used to process the address.
30507 If a shadow transport was run after a successful local delivery, the log line
30508 for the successful delivery has an item added on the end, of the form
30510 &`ST=<`&&'shadow transport name'&&`>`&
30512 If the shadow transport did not succeed, the error message is put in
30513 parentheses afterwards.
30515 .cindex "asterisk" "after IP address"
30516 When more than one address is included in a single delivery (for example, two
30517 SMTP RCPT commands in one transaction) the second and subsequent addresses are
30518 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
30519 down a single SMTP connection, an asterisk follows the IP address in the log
30520 lines for the second and subsequent messages.
30522 The generation of a reply message by a filter file gets logged as a
30523 &"delivery"& to the addressee, preceded by &">"&.
30525 The &%log_selector%& option can be used to request the logging of additional
30526 data when a message is delivered. See section &<<SECTlogselector>>& below.
30529 .section "Discarded deliveries"
30530 .cindex "discarded messages"
30531 .cindex "message" "discarded"
30532 .cindex "delivery" "discarded; logging"
30533 When a message is discarded as a result of the command &"seen finish"& being
30534 obeyed in a filter file which generates no deliveries, a log entry of the form
30536 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
30537 <low.club@bridge.example> R=userforward
30539 is written, to record why no deliveries are logged. When a message is discarded
30540 because it is aliased to &":blackhole:"& the log line is like this:
30542 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
30543 <hole@nowhere.example> R=blackhole_router
30547 .section "Deferred deliveries"
30548 When a delivery is deferred, a line of the following form is logged:
30550 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
30551 R=dnslookup T=smtp defer (146): Connection refused
30553 In the case of remote deliveries, the error is the one that was given for the
30554 last IP address that was tried. Details of individual SMTP failures are also
30555 written to the log, so the above line would be preceded by something like
30557 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
30558 mail1.endrest.example [192.168.239.239]: Connection refused
30560 When a deferred address is skipped because its retry time has not been reached,
30561 a message is written to the log, but this can be suppressed by setting an
30562 appropriate value in &%log_selector%&.
30566 .section "Delivery failures"
30567 .cindex "delivery" "failure; logging"
30568 If a delivery fails because an address cannot be routed, a line of the
30569 following form is logged:
30571 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
30572 <jim@trek99.example>: unknown mail domain
30574 If a delivery fails at transport time, the router and transport are shown, and
30575 the response from the remote host is included, as in this example:
30577 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
30578 R=dnslookup T=remote_smtp: SMTP error from remote mailer
30579 after pipelined RCPT TO:<ace400@pb.example>: host
30580 pbmail3.py.example [192.168.63.111]: 553 5.3.0
30581 <ace400@pb.example>...Addressee unknown
30583 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
30584 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
30585 disabling PIPELINING. The log lines for all forms of delivery failure are
30586 flagged with &`**`&.
30590 .section "Fake deliveries"
30591 .cindex "delivery" "fake; logging"
30592 If a delivery does not actually take place because the &%-N%& option has been
30593 used to suppress it, a normal delivery line is written to the log, except that
30594 &"=>"& is replaced by &"*>"&.
30598 .section "Completion"
30601 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
30603 is written to the main log when a message is about to be removed from the spool
30604 at the end of its processing.
30609 .section "Summary of Fields in Log Lines"
30610 .cindex "log" "summary of fields"
30611 A summary of the field identifiers that are used in log lines is shown in
30612 the following table:
30614 &`A `& authenticator name (and optional id)
30615 &`C `& SMTP confirmation on delivery
30616 &`CV `& certificate verification status
30617 &`DN `& distinguished name from peer certificate
30618 &`DT `& on &`=>`& lines: time taken for a delivery
30619 &`F `& sender address (on delivery lines)
30620 &`H `& host name and IP address
30621 &`I `& local interface used
30622 &`id `& message id for incoming message
30623 &`P `& on &`<=`& lines: protocol used
30624 &` `& on &`=>`& and &`**`& lines: return path
30625 &`QT `& on &`=>`& lines: time spent on queue so far
30626 &` `& on &"Completed"& lines: time spent on queue
30627 &`R `& on &`<=`& lines: reference for local bounce
30628 &` `& on &`=>`& &`**`& and &`==`& lines: router name
30629 &`S `& size of message
30630 &`ST `& shadow transport name
30631 &`T `& on &`<=`& lines: message subject (topic)
30632 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
30633 &`U `& local user or RFC 1413 identity
30634 &`X `& TLS cipher suite
30638 .section "Other log entries"
30639 Various other types of log entry are written from time to time. Most should be
30640 self-explanatory. Among the more common are:
30643 .cindex "retry" "time not reached"
30644 &'retry time not reached'&&~&~An address previously suffered a temporary error
30645 during routing or local delivery, and the time to retry has not yet arrived.
30646 This message is not written to an individual message log file unless it happens
30647 during the first delivery attempt.
30649 &'retry time not reached for any host'&&~&~An address previously suffered
30650 temporary errors during remote delivery, and the retry time has not yet arrived
30651 for any of the hosts to which it is routed.
30653 .cindex "spool directory" "file locked"
30654 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
30655 some other Exim process is already working on the message. This can be quite
30656 common if queue running processes are started at frequent intervals. The
30657 &'exiwhat'& utility script can be used to find out what Exim processes are
30660 .cindex "error" "ignored"
30661 &'error ignored'&&~&~There are several circumstances that give rise to this
30664 Exim failed to deliver a bounce message whose age was greater than
30665 &%ignore_bounce_errors_after%&. The bounce was discarded.
30667 A filter file set up a delivery using the &"noerror"& option, and the delivery
30668 failed. The delivery was discarded.
30670 A delivery set up by a router configured with
30671 . ==== As this is a nested list, any displays it contains must be indented
30672 . ==== as otherwise they are too far to the left.
30676 failed. The delivery was discarded.
30684 .section "Reducing or increasing what is logged" "SECTlogselector"
30685 .cindex "log" "selectors"
30686 By setting the &%log_selector%& global option, you can disable some of Exim's
30687 default logging, or you can request additional logging. The value of
30688 &%log_selector%& is made up of names preceded by plus or minus characters. For
30691 log_selector = +arguments -retry_defer
30693 The list of optional log items is in the following table, with the default
30694 selection marked by asterisks:
30696 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
30697 &` address_rewrite `& address rewriting
30698 &` all_parents `& all parents in => lines
30699 &` arguments `& command line arguments
30700 &`*connection_reject `& connection rejections
30701 &`*delay_delivery `& immediate delivery delayed
30702 &` deliver_time `& time taken to perform delivery
30703 &` delivery_size `& add &`S=`&&'nnn'& to => lines
30704 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
30705 &`*etrn `& ETRN commands
30706 &`*host_lookup_failed `& as it says
30707 &` ident_timeout `& timeout for ident connection
30708 &` incoming_interface `& incoming interface on <= lines
30709 &` incoming_port `& incoming port on <= lines
30710 &`*lost_incoming_connection `& as it says (includes timeouts)
30711 &` outgoing_port `& add remote port to => lines
30712 &`*queue_run `& start and end queue runs
30713 &` queue_time `& time on queue for one recipient
30714 &` queue_time_overall `& time on queue for whole message
30715 &` received_recipients `& recipients on <= lines
30716 &` received_sender `& sender on <= lines
30717 &`*rejected_header `& header contents on reject log
30718 &`*retry_defer `& &"retry time not reached"&
30719 &` return_path_on_delivery `& put return path on => and *\ lines
30720 &` sender_on_delivery `& add sender to => lines
30721 &`*sender_verify_fail `& sender verification failures
30722 &`*size_reject `& rejection because too big
30723 &`*skip_delivery `& delivery skipped in a queue run
30724 &` smtp_confirmation `& SMTP confirmation on => lines
30725 &` smtp_connection `& SMTP connections
30726 &` smtp_incomplete_transaction`& incomplete SMTP transactions
30727 &` smtp_protocol_error `& SMTP protocol errors
30728 &` smtp_syntax_error `& SMTP syntax errors
30729 &` subject `& contents of &'Subject:'& on <= lines
30730 &` tls_certificate_verified `& certificate verification status
30731 &`*tls_cipher `& TLS cipher suite on <= and => lines
30732 &` tls_peerdn `& TLS peer DN on <= and => lines
30733 &` unknown_in_list `& DNS lookup failed in list match
30735 &` all `& all of the above
30737 More details on each of these items follows:
30740 .cindex "&%warn%& statement" "log when skipping"
30741 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
30742 its conditions cannot be evaluated, a log line to this effect is written if
30743 this log selector is set.
30745 .cindex "log" "rewriting"
30746 .cindex "rewriting" "logging"
30747 &%address_rewrite%&: This applies both to global rewrites and per-transport
30748 rewrites, but not to rewrites in filters run as an unprivileged user (because
30749 such users cannot access the log).
30751 .cindex "log" "full parentage"
30752 &%all_parents%&: Normally only the original and final addresses are logged on
30753 delivery lines; with this selector, intermediate parents are given in
30754 parentheses between them.
30756 .cindex "log" "Exim arguments"
30757 .cindex "Exim arguments" "logging"
30758 &%arguments%&: This causes Exim to write the arguments with which it was called
30759 to the main log, preceded by the current working directory. This is a debugging
30760 feature, added to make it easier to find out how certain MUAs call
30761 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
30762 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
30763 that are empty or that contain white space are quoted. Non-printing characters
30764 are shown as escape sequences. This facility cannot log unrecognized arguments,
30765 because the arguments are checked before the configuration file is read. The
30766 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
30767 between the caller and Exim.
30769 .cindex "log" "connection rejections"
30770 &%connection_reject%&: A log entry is written whenever an incoming SMTP
30771 connection is rejected, for whatever reason.
30773 .cindex "log" "delayed delivery"
30774 .cindex "delayed delivery" "logging"
30775 &%delay_delivery%&: A log entry is written whenever a delivery process is not
30776 started for an incoming message because the load is too high or too many
30777 messages were received on one connection. Logging does not occur if no delivery
30778 process is started because &%queue_only%& is set or &%-odq%& was used.
30780 .cindex "log" "delivery duration"
30781 &%deliver_time%&: For each delivery, the amount of real time it has taken to
30782 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
30784 .cindex "log" "message size on delivery"
30785 .cindex "size" "of message"
30786 &%delivery_size%&: For each delivery, the size of message delivered is added to
30787 the &"=>"& line, tagged with S=.
30789 .cindex "log" "dnslist defer"
30790 .cindex "DNS list" "logging defer"
30791 .cindex "black list (DNS)"
30792 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
30793 DNS black list suffers a temporary error.
30795 .cindex "log" "ETRN commands"
30796 .cindex "ETRN" "logging"
30797 &%etrn%&: Every legal ETRN command that is received is logged, before the ACL
30798 is run to determine whether or not it is actually accepted. An invalid ETRN
30799 command, or one received within a message transaction is not logged by this
30800 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
30802 .cindex "log" "host lookup failure"
30803 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
30804 any addresses, or when a lookup of an IP address fails to find a host name, a
30805 log line is written. This logging does not apply to direct DNS lookups when
30806 routing email addresses, but it does apply to &"byname"& lookups.
30808 .cindex "log" "ident timeout"
30809 .cindex "RFC 1413" "logging timeout"
30810 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
30811 client's ident port times out.
30813 .cindex "log" "incoming interface"
30814 .cindex "interface" "logging"
30815 &%incoming_interface%&: The interface on which a message was received is added
30816 to the &"<="& line as an IP address in square brackets, tagged by I= and
30817 followed by a colon and the port number. The local interface and port are also
30818 added to other SMTP log lines, for example &"SMTP connection from"&, and to
30821 .cindex "log" "incoming remote port"
30822 .cindex "port" "logging remote"
30823 .cindex "TCP/IP" "logging incoming remote port"
30824 .cindex "&$sender_fullhost$&"
30825 .cindex "&$sender_rcvhost$&"
30826 &%incoming_port%&: The remote port number from which a message was received is
30827 added to log entries and &'Received:'& header lines, following the IP address
30828 in square brackets, and separated from it by a colon. This is implemented by
30829 changing the value that is put in the &$sender_fullhost$& and
30830 &$sender_rcvhost$& variables. Recording the remote port number has become more
30831 important with the widening use of NAT (see RFC 2505).
30833 .cindex "log" "dropped connection"
30834 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
30835 connection is unexpectedly dropped.
30837 .cindex "log" "outgoing remote port"
30838 .cindex "port" "logging outgoint remote"
30839 .cindex "TCP/IP" "logging ougtoing remote port"
30840 &%outgoing_port%&: The remote port number is added to delivery log lines (those
30841 containing => tags) following the IP address. This option is not included in
30842 the default setting, because for most ordinary configurations, the remote port
30843 number is always 25 (the SMTP port).
30845 .cindex "log" "queue run"
30846 .cindex "queue runner" "logging"
30847 &%queue_run%&: The start and end of every queue run are logged.
30849 .cindex "log" "queue time"
30850 &%queue_time%&: The amount of time the message has been in the queue on the
30851 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
30852 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
30853 includes reception time as well as the delivery time for the current address.
30854 This means that it may be longer than the difference between the arrival and
30855 delivery log line times, because the arrival log line is not written until the
30856 message has been successfully received.
30858 &%queue_time_overall%&: The amount of time the message has been in the queue on
30859 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
30860 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
30861 message, so it includes reception time as well as the total delivery time.
30863 .cindex "log" "recipients"
30864 &%received_recipients%&: The recipients of a message are listed in the main log
30865 as soon as the message is received. The list appears at the end of the log line
30866 that is written when a message is received, preceded by the word &"for"&. The
30867 addresses are listed after they have been qualified, but before any rewriting
30869 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
30872 .cindex "log" "sender reception"
30873 &%received_sender%&: The unrewritten original sender of a message is added to
30874 the end of the log line that records the message's arrival, after the word
30875 &"from"& (before the recipients if &%received_recipients%& is also set).
30877 .cindex "log" "header lines for rejection"
30878 &%rejected_header%&: If a message's header has been received at the time a
30879 rejection is written to the reject log, the complete header is added to the
30880 log. Header logging can be turned off individually for messages that are
30881 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
30883 .cindex "log" "retry defer"
30884 &%retry_defer%&: A log line is written if a delivery is deferred because a
30885 retry time has not yet been reached. However, this &"retry time not reached"&
30886 message is always omitted from individual message logs after the first delivery
30889 .cindex "log" "return path"
30890 &%return_path_on_delivery%&: The return path that is being transmitted with
30891 the message is included in delivery and bounce lines, using the tag P=.
30892 This is omitted if no delivery actually happens, for example, if routing fails,
30893 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
30895 .cindex "log" "sender on delivery"
30896 &%sender_on_delivery%&: The message's sender address is added to every delivery
30897 and bounce line, tagged by F= (for &"from"&).
30898 This is the original sender that was received with the message; it is not
30899 necessarily the same as the outgoing return path.
30901 .cindex "log" "sender verify failure"
30902 &%sender_verify_failure%&: If this selector is unset, the separate log line
30903 that gives details of a sender verification failure is not written. Log lines
30904 for the rejection of SMTP commands contain just &"sender verify failed"&, so
30905 some detail is lost.
30907 .cindex "log" "size rejection"
30908 &%size_reject%&: A log line is written whenever a message is rejected because
30911 .cindex "log" "frozen messages; skipped"
30912 .cindex "frozen messages" "logging skipping"
30913 &%skip_delivery%&: A log line is written whenever a message is skipped during a
30914 queue run because it is frozen or because another process is already delivering
30916 .cindex "&""spool file is locked""&"
30917 The message that is written is &"spool file is locked"&.
30919 .cindex "log" "smtp confirmation"
30920 .cindex "SMTP" "logging confirmation"
30921 &%smtp_confirmation%&: The response to the final &"."& in the SMTP dialogue for
30922 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
30923 A number of MTAs (including Exim) return an identifying string in this
30926 .cindex "log" "SMTP connections"
30927 .cindex "SMTP" "logging connections"
30928 &%smtp_connection%&: A log line is written whenever an SMTP connection is
30929 established or closed, unless the connection is from a host that matches
30930 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
30931 only when the closure is unexpected.) This applies to connections from local
30932 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
30933 dropped in the middle of a message, a log line is always written, whether or
30934 not this selector is set, but otherwise nothing is written at the start and end
30935 of connections unless this selector is enabled.
30937 For TCP/IP connections to an Exim daemon, the current number of connections is
30938 included in the log message for each new connection, but note that the count is
30939 reset if the daemon is restarted.
30940 Also, because connections are closed (and the closure is logged) in
30941 subprocesses, the count may not include connections that have been closed but
30942 whose termination the daemon has not yet noticed. Thus, while it is possible to
30943 match up the opening and closing of connections in the log, the value of the
30944 logged counts may not be entirely accurate.
30946 .cindex "log" "SMTP transaction; incomplete"
30947 .cindex "SMTP" "logging incomplete transactions"
30948 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
30949 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
30950 and the message sender plus any accepted recipients are included in the log
30951 line. This can provide evidence of dictionary attacks.
30953 .cindex "log" "SMTP protocol error"
30954 .cindex "SMTP" "logging protocol error"
30955 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
30956 encountered. Exim does not have perfect detection of all protocol errors
30957 because of transmission delays and the use of pipelining. If PIPELINING has
30958 been advertised to a client, an Exim server assumes that the client will use
30959 it, and therefore it does not count &"expected"& errors (for example, RCPT
30960 received after rejecting MAIL) as protocol errors.
30962 .cindex "SMTP" "logging syntax errors"
30963 .cindex "SMTP" "syntax errors; logging"
30964 .cindex "SMTP" "unknown command; logging"
30965 .cindex "log" "unknown SMTP command"
30966 .cindex "log" "SMTP syntax error"
30967 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
30968 encountered. An unrecognized command is treated as a syntax error. For an
30969 external connection, the host identity is given; for an internal connection
30970 using &%-bs%& the sender identification (normally the calling user) is given.
30972 .cindex "log" "subject"
30973 .cindex "subject" "logging"
30974 &%subject%&: The subject of the message is added to the arrival log line,
30975 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
30976 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
30977 specifies whether characters with values greater than 127 should be logged
30978 unchanged, or whether they should be rendered as escape sequences.
30980 .cindex "log" "certificate verification"
30981 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
30982 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
30983 verified, and &`CV=no`& if not.
30985 .cindex "log" "TLS cipher"
30986 .cindex "TLS" "logging cipher"
30987 &%tls_cipher%&: When a message is sent or received over an encrypted
30988 connection, the cipher suite used is added to the log line, preceded by X=.
30990 .cindex "log" "TLS peer DN"
30991 .cindex "TLS" "logging peer DN"
30992 &%tls_peerdn%&: When a message is sent or received over an encrypted
30993 connection, and a certificate is supplied by the remote host, the peer DN is
30994 added to the log line, preceded by DN=.
30996 .cindex "log" "DNS failure in list"
30997 &%unknown_in_list%&: This setting causes a log entry to be written when the
30998 result of a list match is failure because a DNS lookup failed.
31002 .section "Message log"
31003 .cindex "message" "log file for"
31004 .cindex "log" "message log; description of"
31005 .cindex "&_msglog_& directory"
31006 .cindex "&%preserve_message_logs%&"
31007 In addition to the general log files, Exim writes a log file for each message
31008 that it handles. The names of these per-message logs are the message ids, and
31009 they are kept in the &_msglog_& sub-directory of the spool directory. Each
31010 message log contains copies of the log lines that apply to the message. This
31011 makes it easier to inspect the status of an individual message without having
31012 to search the main log. A message log is deleted when processing of the message
31013 is complete, unless &%preserve_message_logs%& is set, but this should be used
31014 only with great care because they can fill up your disk very quickly.
31016 On a heavily loaded system, it may be desirable to disable the use of
31017 per-message logs, in order to reduce disk I/O. This can be done by setting the
31018 &%message_logs%& option false.
31022 . ////////////////////////////////////////////////////////////////////////////
31023 . ////////////////////////////////////////////////////////////////////////////
31025 .chapter "Exim utilities" "CHAPutils"
31026 .scindex IIDutils "utilities"
31027 A number of utility scripts and programs are supplied with Exim and are
31028 described in this chapter. There is also the Exim Monitor, which is covered in
31029 the next chapter. The utilities described here are:
31031 .itable none 0 0 4 2* left 8* left 30* left 40* left
31032 .row "" &<<SECTfinoutwha>>& &'exiwhat'& &&&
31033 "list what Exim processes are doing"
31034 .row "" &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
31035 .row "" &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
31036 .row "" &<<SECTextspeinf>>& &'exigrep'& "search the main log"
31037 .row "" &<<SECTexipick>>& &'exipick'& "select messages on &&&
31039 .row "" &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
31040 .row "" &<<SECTmailstat>>& &'eximstats'& &&&
31041 "extract statistics from the log"
31042 .row "" &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
31043 "check address acceptance from given IP"
31044 .row "" &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
31045 .row "" &<<SECTfinindret>>& &'exinext'& "extract retry information"
31046 .row "" &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
31047 .row "" &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
31048 .row "" &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
31049 .row "" &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
31052 Another utility that might be of use to sites with many MTAs is Tom Kistner's
31053 &'exilog'&. It provides log visualizations across multiple Exim servers. See
31054 &url(http://duncanthrax.net/exilog/) for details.
31059 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
31060 .cindex "&'exiwhat'&"
31061 .cindex "process" "querying"
31063 On operating systems that can restart a system call after receiving a signal
31064 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
31065 a line describing what it is doing to the file &_exim-process.info_& in the
31066 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
31067 processes it can find, having first emptied the file. It then waits for one
31068 second to allow the Exim processes to react before displaying the results. In
31069 order to run &'exiwhat'& successfully you have to have sufficient privilege to
31070 send the signal to the Exim processes, so it is normally run as root.
31072 &*Warning*&: This is not an efficient process. It is intended for occasional
31073 use by system administrators. It is not sensible, for example, to set up a
31074 script that sends SIGUSR1 signals to Exim processes at short intervals.
31077 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
31078 varies in different operating systems. Not only are different options used,
31079 but the format of the output is different. For this reason, there are some
31080 system configuration options that configure exactly how &'exiwhat'& works. If
31081 it doesn't seem to be working for you, check the following compile-time
31084 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
31085 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
31086 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
31087 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
31089 An example of typical output from &'exiwhat'& is
31091 164 daemon: -q1h, listening on port 25
31092 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
31093 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
31094 [10.19.42.42] (editor@ref.example)
31095 10592 handling incoming call from [192.168.243.242]
31096 10628 accepting a local non-SMTP message
31098 The first number in the output line is the process number. The third line has
31099 been split here, in order to fit it on the page.
31103 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
31104 .cindex "&'exiqgrep'&"
31105 .cindex "queue" "grepping"
31106 This utility is a Perl script contributed by Matt Hubbard. It runs
31110 to obtain a queue listing with undelivered recipients only, and then greps the
31111 output to select messages that match given criteria. The following selection
31112 options are available:
31115 .vitem &*-f*&&~<&'regex'&>
31116 Match the sender address. The field that is tested is enclosed in angle
31117 brackets, so you can test for bounce messages with
31121 .vitem &*-r*&&~<&'regex'&>
31122 Match a recipient address. The field that is tested is not enclosed in angle
31125 .vitem &*-s*&&~<&'regex'&>
31126 Match against the size field.
31128 .vitem &*-y*&&~<&'seconds'&>
31129 Match messages that are younger than the given time.
31131 .vitem &*-o*&&~<&'seconds'&>
31132 Match messages that are older than the given time.
31135 Match only frozen messages.
31138 Match only non-frozen messages.
31141 The following options control the format of the output:
31145 Display only the count of matching messages.
31148 Long format &-- display the full message information as output by Exim. This is
31152 Display message ids only.
31155 Brief format &-- one line per message.
31158 Display messages in reverse order.
31161 There is one more option, &%-h%&, which outputs a list of options.
31165 .section "Summarising the queue (exiqsumm)" "SECTsumtheque"
31166 .cindex "&'exiqsumm'&"
31167 .cindex "queue" "summary"
31168 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
31169 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
31170 running a command such as
31172 exim -bp | exiqsumm
31174 The output consists of one line for each domain that has messages waiting for
31175 it, as in the following example:
31177 3 2322 74m 66m msn.com.example
31179 Each line lists the number of
31180 pending deliveries for a domain, their total volume, and the length of time
31181 that the oldest and the newest messages have been waiting. Note that the number
31182 of pending deliveries is greater than the number of messages when messages
31183 have more than one recipient.
31185 A summary line is output at the end. By default the output is sorted on the
31186 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
31187 the output to be sorted by oldest message and by count of messages,
31190 The output of &'exim -bp'& contains the original addresses in the message, so
31191 this also applies to the output from &'exiqsumm'&. No domains from addresses
31192 generated by aliasing or forwarding are included (unless the &%one_time%&
31193 option of the &(redirect)& router has been used to convert them into &"top
31194 level"& addresses).
31199 .section "Extracting specific information from the log (exigrep)" &&&
31201 .cindex "&'exigrep'&"
31202 .cindex "log" "extracts; grepping for"
31203 The &'exigrep'& utility is a Perl script that searches one or more main log
31204 files for entries that match a given pattern. When it finds a match, it
31205 extracts all the log entries for the relevant message, not just those that
31206 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
31207 given message, or all mail for a given user, or for a given host, for example.
31208 The input files can be in Exim log format or syslog format.
31210 If a matching log line is not associated with a specific message, it is always
31211 included in &'exigrep'&'s output. The usage is:
31213 &`exigrep [-l] [-t<`&&'n'&&`>] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
31215 The &%-t%& argument specifies a number of seconds. It adds an additional
31216 condition for message selection. Messages that are complete are shown only if
31217 they spent more than <&'n'&> seconds on the queue.
31219 The &%-l%& flag means &"literal"&, that is, treat all characters in the
31220 pattern as standing for themselves. Otherwise the pattern must be a Perl
31221 regular expression. The pattern match is case-insensitive. If no file names are
31222 given on the command line, the standard input is read.
31224 If the location of a &'zcat'& command is known from the definition of
31225 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
31226 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
31229 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
31230 .cindex "&'exipick'&"
31231 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
31232 lists messages from the queue according to a variety of criteria. For details,
31239 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
31240 .cindex "log" "cycling local files"
31241 .cindex "cycling logs"
31242 .cindex "&'exicyclog'&"
31243 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
31244 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
31245 you are using log files with datestamps in their names (see section
31246 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
31247 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
31248 There are two command line options for &'exicyclog'&:
31250 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
31251 default that is set when Exim is built. The default default is 10.
31253 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
31254 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
31255 overriding the script's default, which is to find the setting from Exim's
31259 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
31260 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
31261 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
31262 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
31263 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
31264 logs are handled similarly.
31266 If the limit is greater than 99, the script uses 3-digit numbers such as
31267 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
31268 to one that is greater, or &'vice versa'&, you will have to fix the names of
31269 any existing log files.
31271 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
31272 the end are deleted. All files with numbers greater than 01 are compressed,
31273 using a compression command which is configured by the COMPRESS_COMMAND
31274 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
31275 root &%crontab%& entry of the form
31277 1 0 * * * su exim -c /usr/exim/bin/exicyclog
31279 assuming you have used the name &"exim"& for the Exim user. You can run
31280 &'exicyclog'& as root if you wish, but there is no need.
31284 .section "Mail statistics (eximstats)" "SECTmailstat"
31285 .cindex "statistics"
31286 .cindex "&'eximstats'&"
31287 A Perl script called &'eximstats'& is provided for extracting statistical
31288 information from log files. The output is either plain text, or HTML.
31289 Exim log files are also suported by the &'Lire'& system produced by the
31290 LogReport Foundation &url(http://www.logreport.org).
31292 The &'eximstats'& script has been hacked about quite a bit over time. The
31293 latest version is the result of some extensive revision by Steve Campbell. A
31294 lot of information is given by default, but there are options for suppressing
31295 various parts of it. Following any options, the arguments to the script are a
31296 list of files, which should be main log files. For example:
31298 eximstats -nr /var/spool/exim/log/mainlog.01
31300 By default, &'eximstats'& extracts information about the number and volume of
31301 messages received from or delivered to various hosts. The information is sorted
31302 both by message count and by volume, and the top fifty hosts in each category
31303 are listed on the standard output. Similar information, based on email
31304 addresses or domains instead of hosts can be requested by means of various
31305 options. For messages delivered and received locally, similar statistics are
31306 also produced per user.
31308 The output also includes total counts and statistics about delivery errors, and
31309 histograms showing the number of messages received and deliveries made in each
31310 hour of the day. A delivery with more than one address in its envelope (for
31311 example, an SMTP transaction with more than one RCPT command) is counted
31312 as a single delivery by &'eximstats'&.
31314 Though normally more deliveries than receipts are reported (as messages may
31315 have multiple recipients), it is possible for &'eximstats'& to report more
31316 messages received than delivered, even though the queue is empty at the start
31317 and end of the period in question. If an incoming message contains no valid
31318 recipients, no deliveries are recorded for it. A bounce message is handled as
31319 an entirely separate message.
31321 &'eximstats'& always outputs a grand total summary giving the volume and number
31322 of messages received and deliveries made, and the number of hosts involved in
31323 each case. It also outputs the number of messages that were delayed (that is,
31324 not completely delivered at the first attempt), and the number that had at
31325 least one address that failed.
31327 The remainder of the output is in sections that can be independently disabled
31328 or modified by various options. It consists of a summary of deliveries by
31329 transport, histograms of messages received and delivered per time interval
31330 (default per hour), information about the time messages spent on the queue,
31331 a list of relayed messages, lists of the top fifty sending hosts, local
31332 senders, destination hosts, and destination local users by count and by volume,
31333 and a list of delivery errors that occurred.
31335 The relay information lists messages that were actually relayed, that is, they
31336 came from a remote host and were directly delivered to some other remote host,
31337 without being processed (for example, for aliasing or forwarding) locally.
31339 There are quite a few options for &'eximstats'& to control exactly what it
31340 outputs. These are documented in the Perl script itself, and can be extracted
31341 by running the command &(perldoc)& on the script. For example:
31343 perldoc /usr/exim/bin/eximstats
31346 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
31347 .cindex "&'exim_checkaccess'&"
31348 .cindex "policy control" "checking access"
31349 .cindex "checking access"
31350 The &%-bh%& command line argument allows you to run a fake SMTP session with
31351 debugging output, in order to check what Exim is doing when it is applying
31352 policy controls to incoming SMTP mail. However, not everybody is sufficiently
31353 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
31354 sometimes you just want to answer the question &"Does this address have
31355 access?"& without bothering with any further details.
31357 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
31358 two arguments, an IP address and an email address:
31360 exim_checkaccess 10.9.8.7 A.User@a.domain.example
31362 The utility runs a call to Exim with the &%-bh%& option, to test whether the
31363 given email address would be accepted in a RCPT command in a TCP/IP
31364 connection from the host with the given IP address. The output of the utility
31365 is either the word &"accepted"&, or the SMTP error response, for example:
31368 550 Relay not permitted
31370 When running this test, the utility uses &`<>`& as the envelope sender address
31371 for the MAIL command, but you can change this by providing additional
31372 options. These are passed directly to the Exim command. For example, to specify
31373 that the test is to be run with the sender address &'himself@there.example'&
31376 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
31377 -f himself@there.example
31379 Note that these additional Exim command line items must be given after the two
31380 mandatory arguments.
31382 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
31383 while running its checks. You can run checks that include callouts by using
31384 &%-bhc%&, but this is not yet available in a &"packaged"& form.
31388 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
31389 .cindex "DBM" "building dbm files"
31390 .cindex "building DBM files"
31391 .cindex "&'exim_dbmbuild'&"
31392 .cindex "lower casing"
31393 .cindex "binary zero" "in lookup key"
31394 The &'exim_dbmbuild'& program reads an input file containing keys and data in
31395 the format used by the &(lsearch)& lookup (see section
31396 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
31397 names as keys and the remainder of the information as data. The lower-casing
31398 can be prevented by calling the program with the &%-nolc%& option.
31400 A terminating zero is included as part of the key string. This is expected by
31401 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
31402 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
31403 strings or the data strings. The &(dbmnz)& lookup type can be used with such
31406 The program requires two arguments: the name of the input file (which can be a
31407 single hyphen to indicate the standard input), and the name of the output file.
31408 It creates the output under a temporary name, and then renames it if all went
31412 If the native DB interface is in use (USE_DB is set in a compile-time
31413 configuration file &-- this is common in free versions of Unix) the two file
31414 names must be different, because in this mode the Berkeley DB functions create
31415 a single output file using exactly the name given. For example,
31417 exim_dbmbuild /etc/aliases /etc/aliases.db
31419 reads the system alias file and creates a DBM version of it in
31420 &_/etc/aliases.db_&.
31422 In systems that use the &'ndbm'& routines (mostly proprietary versions of
31423 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
31424 environment, the suffixes are added to the second argument of
31425 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
31426 when the Berkeley functions are used in compatibility mode (though this is not
31427 recommended), because in that case it adds a &_.db_& suffix to the file name.
31429 If a duplicate key is encountered, the program outputs a warning, and when it
31430 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
31431 option is used. By default, only the first of a set of duplicates is used &--
31432 this makes it compatible with &(lsearch)& lookups. There is an option
31433 &%-lastdup%& which causes it to use the data for the last duplicate instead.
31434 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
31435 &%stderr%&. For other errors, where it doesn't actually make a new file, the
31441 .section "Finding individual retry times (exinext)" "SECTfinindret"
31442 .cindex "retry" "times"
31443 .cindex "&'exinext'&"
31444 A utility called &'exinext'& (mostly a Perl script) provides the ability to
31445 fish specific information out of the retry database. Given a mail domain (or a
31446 complete address), it looks up the hosts for that domain, and outputs any retry
31447 information for the hosts or for the domain. At present, the retry information
31448 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
31449 output. For example:
31451 $ exinext piglet@milne.fict.example
31452 kanga.milne.example:192.168.8.1 error 146: Connection refused
31453 first failed: 21-Feb-1996 14:57:34
31454 last tried: 21-Feb-1996 14:57:34
31455 next try at: 21-Feb-1996 15:02:34
31456 roo.milne.example:192.168.8.3 error 146: Connection refused
31457 first failed: 20-Jan-1996 13:12:08
31458 last tried: 21-Feb-1996 11:42:03
31459 next try at: 21-Feb-1996 19:42:03
31460 past final cutoff time
31462 You can also give &'exinext'& a local part, without a domain, and it
31463 will give any retry information for that local part in your default domain.
31464 A message id can be used to obtain retry information pertaining to a specific
31465 message. This exists only when an attempt to deliver a message to a remote host
31466 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
31467 &'exinext'& is not particularly efficient, but then it is not expected to be
31470 The &'exinext'& utility calls Exim to find out information such as the location
31471 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
31472 passed on to the &'exim'& commands. The first specifies an alternate Exim
31473 configuration file, and the second sets macros for use within the configuration
31474 file. These features are mainly to help in testing, but might also be useful in
31475 environments where more than one configuration file is in use.
31479 .section "Hints database maintenance" "SECThindatmai"
31480 .cindex "hints database" "maintenance"
31481 .cindex "maintaining Exim's hints database"
31482 Three utility programs are provided for maintaining the DBM files that Exim
31483 uses to contain its delivery hint information. Each program requires two
31484 arguments. The first specifies the name of Exim's spool directory, and the
31485 second is the name of the database it is to operate on. These are as follows:
31488 &'retry'&: the database of retry information
31490 &'wait-'&<&'transport name'&>: databases of information about messages waiting
31493 &'callout'&: the callout cache
31495 &'ratelimit'&: the data for implementing the ratelimit ACL condition
31497 &'misc'&: other hints data
31500 The &'misc'& database is used for
31503 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
31505 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
31506 &(smtp)& transport)
31511 .section "exim_dumpdb"
31512 .cindex "&'exim_dumpdb'&"
31513 The entire contents of a database are written to the standard output by the
31514 &'exim_dumpdb'& program, which has no options or arguments other than the
31515 spool and database names. For example, to dump the retry database:
31517 exim_dumpdb /var/spool/exim retry
31519 Two lines of output are produced for each entry:
31521 T:mail.ref.example:192.168.242.242 146 77 Connection refused
31522 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
31524 The first item on the first line is the key of the record. It starts with one
31525 of the letters R, or T, depending on whether it refers to a routing or
31526 transport retry. For a local delivery, the next part is the local address; for
31527 a remote delivery it is the name of the remote host, followed by its failing IP
31528 address (unless &%no_retry_include_ip_address%& is set on the &(smtp)&
31529 transport). If the remote port is not the standard one (port 25), it is added
31530 to the IP address. Then there follows an error code, an additional error code,
31531 and a textual description of the error.
31533 The three times on the second line are the time of first failure, the time of
31534 the last delivery attempt, and the computed time for the next attempt. The line
31535 ends with an asterisk if the cutoff time for the last retry rule has been
31538 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
31539 consists of a host name followed by a list of ids for messages that are or were
31540 waiting to be delivered to that host. If there are a very large number for any
31541 one host, continuation records, with a sequence number added to the host name,
31542 may be seen. The data in these records is often out of date, because a message
31543 may be routed to several alternative hosts, and Exim makes no effort to keep
31548 .section "exim_tidydb"
31549 .cindex "&'exim_tidydb'&"
31550 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
31551 database. If run with no options, it removes all records that are more than 30
31552 days old. The age is calculated from the date and time that the record was last
31553 updated. Note that, in the case of the retry database, it is &'not'& the time
31554 since the first delivery failure. Information about a host that has been down
31555 for more than 30 days will remain in the database, provided that the record is
31556 updated sufficiently often.
31558 The cutoff date can be altered by means of the &%-t%& option, which must be
31559 followed by a time. For example, to remove all records older than a week from
31560 the retry database:
31562 exim_tidydb -t 7d /var/spool/exim retry
31564 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
31565 message ids. In the former these appear as data in records keyed by host &--
31566 they were messages that were waiting for that host &-- and in the latter they
31567 are the keys for retry information for messages that have suffered certain
31568 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
31569 message ids in database records are those of messages that are still on the
31570 queue. Message ids for messages that no longer exist are removed from
31571 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
31572 For the &'retry'& database, records whose keys are non-existent message ids are
31573 removed. The &'exim_tidydb'& utility outputs comments on the standard output
31574 whenever it removes information from the database.
31576 Certain records are automatically removed by Exim when they are no longer
31577 needed, but others are not. For example, if all the MX hosts for a domain are
31578 down, a retry record is created for each one. If the primary MX host comes back
31579 first, its record is removed when Exim successfully delivers to it, but the
31580 records for the others remain because Exim has not tried to use those hosts.
31582 It is important, therefore, to run &'exim_tidydb'& periodically on all the
31583 hints databases. You should do this at a quiet time of day, because it requires
31584 a database to be locked (and therefore inaccessible to Exim) while it does its
31585 work. Removing records from a DBM file does not normally make the file smaller,
31586 but all the common DBM libraries are able to re-use the space that is released.
31587 After an initial phase of increasing in size, the databases normally reach a
31588 point at which they no longer get any bigger, as long as they are regularly
31591 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
31592 databases is likely to keep on increasing.
31597 .section "exim_fixdb"
31598 .cindex "&'exim_fixdb'&"
31599 The &'exim_fixdb'& program is a utility for interactively modifying databases.
31600 Its main use is for testing Exim, but it might also be occasionally useful for
31601 getting round problems in a live system. It has no options, and its interface
31602 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
31603 key of a database record can then be entered, and the data for that record is
31606 If &"d"& is typed at the next prompt, the entire record is deleted. For all
31607 except the &'retry'& database, that is the only operation that can be carried
31608 out. For the &'retry'& database, each field is output preceded by a number, and
31609 data for individual fields can be changed by typing the field number followed
31610 by new data, for example:
31614 resets the time of the next delivery attempt. Time values are given as a
31615 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
31616 used as optional separators.
31621 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
31622 .cindex "mailbox" "maintenance"
31623 .cindex "&'exim_lock'&"
31624 .cindex "locking mailboxes"
31625 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
31626 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
31627 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
31628 a user agent while investigating a problem. The utility requires the name of
31629 the file as its first argument. If the locking is successful, the second
31630 argument is run as a command (using C's &[system()]& function); if there is no
31631 second argument, the value of the SHELL environment variable is used; if this
31632 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
31633 is unlocked and the utility ends. The following options are available:
31637 Use &[fcntl()]& locking on the open mailbox.
31640 Use &[flock()]& locking on the open mailbox, provided the operating system
31643 .vitem &%-interval%&
31644 This must be followed by a number, which is a number of seconds; it sets the
31645 interval to sleep between retries (default 3).
31647 .vitem &%-lockfile%&
31648 Create a lock file before opening the mailbox.
31651 Lock the mailbox using MBX rules.
31654 Suppress verification output.
31656 .vitem &%-retries%&
31657 This must be followed by a number; it sets the number of times to try to get
31658 the lock (default 10).
31660 .vitem &%-restore_time%&
31661 This option causes &%exim_lock%& to restore the modified and read times to the
31662 locked file before exiting. This allows you to access a locked mailbox (for
31663 example, to take a backup copy) without disturbing the times that the user
31666 .vitem &%-timeout%&
31667 This must be followed by a number, which is a number of seconds; it sets a
31668 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
31669 default), a non-blocking call is used.
31672 Generate verbose output.
31675 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
31676 default is to create a lock file and also to use &[fcntl()]& locking on the
31677 mailbox, which is the same as Exim's default. The use of &%-flock%& or
31678 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
31679 requires that the directory containing the file be writeable. Locking by lock
31680 file does not last for ever; Exim assumes that a lock file is expired if it is
31681 more than 30 minutes old.
31683 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
31684 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
31685 to be taken out on the open mailbox, and an exclusive lock on the file
31686 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
31687 number of the mailbox file. When the locking is released, if an exclusive lock
31688 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
31690 The default output contains verification of the locking that takes place. The
31691 &%-v%& option causes some additional information to be given. The &%-q%& option
31692 suppresses all output except error messages.
31696 exim_lock /var/spool/mail/spqr
31698 runs an interactive shell while the file is locked, whereas
31700 &`exim_lock -q /var/spool/mail/spqr <<End`&
31701 <&'some commands'&>
31704 runs a specific non-interactive sequence of commands while the file is locked,
31705 suppressing all verification output. A single command can be run by a command
31708 exim_lock -q /var/spool/mail/spqr \
31709 "cp /var/spool/mail/spqr /some/where"
31711 Note that if a command is supplied, it must be entirely contained within the
31712 second argument &-- hence the quotes.
31716 . ////////////////////////////////////////////////////////////////////////////
31717 . ////////////////////////////////////////////////////////////////////////////
31719 .chapter "The Exim monitor" "CHAPeximon"
31720 .scindex IIDeximon "Exim monitor" "description"
31721 .cindex "X-windows"
31722 .cindex "&'eximon'&"
31723 .cindex "Local/eximon.conf"
31724 .cindex "_exim_monitor/EDITME_"
31725 The Exim monitor is an application which displays in an X window information
31726 about the state of Exim's queue and what Exim is doing. An admin user can
31727 perform certain operations on messages from this GUI interface; however all
31728 such facilities are also available from the command line, and indeed, the
31729 monitor itself makes use of the command line to perform any actions requested.
31733 .section "Running the monitor"
31734 The monitor is started by running the script called &'eximon'&. This is a shell
31735 script that sets up a number of environment variables, and then runs the
31736 binary called &_eximon.bin_&. The default appearance of the monitor window can
31737 be changed by editing the &_Local/eximon.conf_& file created by editing
31738 &_exim_monitor/EDITME_&. Comments in that file describe what the various
31739 parameters are for.
31741 The parameters that get built into the &'eximon'& script can be overridden for
31742 a particular invocation by setting up environment variables of the same names,
31743 preceded by &`EXIMON_`&. For example, a shell command such as
31745 EXIMON_LOG_DEPTH=400 eximon
31747 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
31748 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
31749 overrides the Exim log file configuration. This makes it possible to have
31750 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
31751 syslog messages are routed to a file on the local host.
31753 X resources can be used to change the appearance of the window in the normal
31754 way. For example, a resource setting of the form
31756 Eximon*background: gray94
31758 changes the colour of the background to light grey rather than white. The
31759 stripcharts are drawn with both the data lines and the reference lines in
31760 black. This means that the reference lines are not visible when on top of the
31761 data. However, their colour can be changed by setting a resource called
31762 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
31763 For example, if your X server is running Unix, you could set up lighter
31764 reference lines in the stripcharts by obeying
31767 Eximon*highlight: gray
31770 .cindex "admin user"
31771 In order to see the contents of messages on the queue, and to operate on them,
31772 &'eximon'& must either be run as root or by an admin user.
31774 The monitor's window is divided into three parts. The first contains one or
31775 more stripcharts and two action buttons, the second contains a &"tail"& of the
31776 main log file, and the third is a display of the queue of messages awaiting
31777 delivery, with two more action buttons. The following sections describe these
31778 different parts of the display.
31783 .section "The stripcharts"
31784 .cindex "stripchart"
31785 The first stripchart is always a count of messages on the queue. Its name can
31786 be configured by setting QUEUE_STRIPCHART_NAME in the
31787 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
31788 configuration script by regular expression matches on log file entries, making
31789 it possible to display, for example, counts of messages delivered to certain
31790 hosts or using certain transports. The supplied defaults display counts of
31791 received and delivered messages, and of local and SMTP deliveries. The default
31792 period between stripchart updates is one minute; this can be adjusted by a
31793 parameter in the &_Local/eximon.conf_& file.
31795 The stripchart displays rescale themselves automatically as the value they are
31796 displaying changes. There are always 10 horizontal lines in each chart; the
31797 title string indicates the value of each division when it is greater than one.
31798 For example, &"x2"& means that each division represents a value of 2.
31800 It is also possible to have a stripchart which shows the percentage fullness of
31801 a particular disk partition, which is useful when local deliveries are confined
31802 to a single partition.
31804 .cindex "&%statvfs%& function"
31805 This relies on the availability of the &[statvfs()]& function or equivalent in
31806 the operating system. Most, but not all versions of Unix that support Exim have
31807 this. For this particular stripchart, the top of the chart always represents
31808 100%, and the scale is given as &"x10%"&. This chart is configured by setting
31809 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
31810 &_Local/eximon.conf_& file.
31815 .section "Main action buttons"
31816 .cindex "size" "of monitor window"
31817 .cindex "Exim monitor" "window size"
31818 .cindex "window size"
31819 Below the stripcharts there is an action button for quitting the monitor. Next
31820 to this is another button marked &"Size"&. They are placed here so that
31821 shrinking the window to its default minimum size leaves just the queue count
31822 stripchart and these two buttons visible. Pressing the &"Size"& button causes
31823 the window to expand to its maximum size, unless it is already at the maximum,
31824 in which case it is reduced to its minimum.
31826 When expanding to the maximum, if the window cannot be fully seen where it
31827 currently is, it is moved back to where it was the last time it was at full
31828 size. When it is expanding from its minimum size, the old position is
31829 remembered, and next time it is reduced to the minimum it is moved back there.
31831 The idea is that you can keep a reduced window just showing one or two
31832 stripcharts at a convenient place on your screen, easily expand it to show
31833 the full window when required, and just as easily put it back to what it was.
31834 The idea is copied from what the &'twm'& window manager does for its
31835 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
31836 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
31838 Normally, the monitor starts up with the window at its full size, but it can be
31839 built so that it starts up with the window at its smallest size, by setting
31840 START_SMALL=yes in &_Local/eximon.conf_&.
31844 .section "The log display"
31845 .cindex "log" "tail of; in monitor"
31846 The second section of the window is an area in which a display of the tail of
31847 the main log is maintained.
31848 To save space on the screen, the timestamp on each log line is shortened by
31849 removing the date and, if &%log_timezone%& is set, the timezone.
31850 The log tail is not available when the only destination for logging data is
31851 syslog, unless the syslog lines are routed to a local file whose name is passed
31852 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
31854 The log sub-window has a scroll bar at its lefthand side which can be used to
31855 move back to look at earlier text, and the up and down arrow keys also have a
31856 scrolling effect. The amount of log that is kept depends on the setting of
31857 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
31858 to use. When this is full, the earlier 50% of data is discarded &-- this is
31859 much more efficient than throwing it away line by line. The sub-window also has
31860 a horizontal scroll bar for accessing the ends of long log lines. This is the
31861 only means of horizontal scrolling; the right and left arrow keys are not
31862 available. Text can be cut from this part of the window using the mouse in the
31863 normal way. The size of this subwindow is controlled by parameters in the
31864 configuration file &_Local/eximon.conf_&.
31866 Searches of the text in the log window can be carried out by means of the ^R
31867 and ^S keystrokes, which default to a reverse and a forward search,
31868 respectively. The search covers only the text that is displayed in the window.
31869 It cannot go further back up the log.
31871 The point from which the search starts is indicated by a caret marker. This is
31872 normally at the end of the text in the window, but can be positioned explicitly
31873 by pointing and clicking with the left mouse button, and is moved automatically
31874 by a successful search. If new text arrives in the window when it is scrolled
31875 back, the caret remains where it is, but if the window is not scrolled back,
31876 the caret is moved to the end of the new text.
31878 Pressing ^R or ^S pops up a window into which the search text can be typed.
31879 There are buttons for selecting forward or reverse searching, for carrying out
31880 the search, and for cancelling. If the &"Search"& button is pressed, the search
31881 happens and the window remains so that further searches can be done. If the
31882 &"Return"& key is pressed, a single search is done and the window is closed. If
31883 ^C is typed the search is cancelled.
31885 The searching facility is implemented using the facilities of the Athena text
31886 widget. By default this pops up a window containing both &"search"& and
31887 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
31888 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
31889 However, the linkers in BSDI and HP-UX seem unable to handle an externally
31890 provided version of &%TextPop%& when the remaining parts of the text widget
31891 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
31892 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
31893 on these systems, at the expense of having unwanted items in the search popup
31898 .section "The queue display"
31899 .cindex "queue" "display in monitor"
31900 The bottom section of the monitor window contains a list of all messages that
31901 are on the queue, which includes those currently being received or delivered,
31902 as well as those awaiting delivery. The size of this subwindow is controlled by
31903 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
31904 at which it is updated is controlled by another parameter in the same file &--
31905 the default is 5 minutes, since queue scans can be quite expensive. However,
31906 there is an &"Update"& action button just above the display which can be used
31907 to force an update of the queue display at any time.
31909 When a host is down for some time, a lot of pending mail can build up for it,
31910 and this can make it hard to deal with other messages on the queue. To help
31911 with this situation there is a button next to &"Update"& called &"Hide"&. If
31912 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
31913 type anything in here and press &"Return"&, the text is added to a chain of
31914 such texts, and if every undelivered address in a message matches at least one
31915 of the texts, the message is not displayed.
31917 If there is an address that does not match any of the texts, all the addresses
31918 are displayed as normal. The matching happens on the ends of addresses so, for
31919 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
31920 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
31921 has been set up, a button called &"Unhide"& is displayed. If pressed, it
31922 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
31923 a hide request is automatically cancelled after one hour.
31925 While the dialogue box is displayed, you can't press any buttons or do anything
31926 else to the monitor window. For this reason, if you want to cut text from the
31927 queue display to use in the dialogue box, you have to do the cutting before
31928 pressing the &"Hide"& button.
31930 The queue display contains, for each unhidden queued message, the length of
31931 time it has been on the queue, the size of the message, the message id, the
31932 message sender, and the first undelivered recipient, all on one line. If it is
31933 a bounce message, the sender is shown as &"<>"&. If there is more than one
31934 recipient to which the message has not yet been delivered, subsequent ones are
31935 listed on additional lines, up to a maximum configured number, following which
31936 an ellipsis is displayed. Recipients that have already received the message are
31939 .cindex "frozen messages" "display"
31940 If a message is frozen, an asterisk is displayed at the left-hand side.
31942 The queue display has a vertical scroll bar, and can also be scrolled by means
31943 of the arrow keys. Text can be cut from it using the mouse in the normal way.
31944 The text searching facilities, as described above for the log window, are also
31945 available, but the caret is always moved to the end of the text when the queue
31946 display is updated.
31950 .section "The queue menu"
31951 .cindex "queue" "menu in monitor"
31952 If the &%shift%& key is held down and the left button is clicked when the mouse
31953 pointer is over the text for any message, an action menu pops up, and the first
31954 line of the queue display for the message is highlighted. This does not affect
31957 If you want to use some other event for popping up the menu, you can set the
31958 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
31959 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
31960 value set in this parameter is a standard X event description. For example, to
31961 run eximon using &%ctrl%& rather than &%shift%& you could use
31963 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
31965 The title of the menu is the message id, and it contains entries which act as
31969 &'message log'&: The contents of the message log for the message are displayed
31970 in a new text window.
31972 &'headers'&: Information from the spool file that contains the envelope
31973 information and headers is displayed in a new text window. See chapter
31974 &<<CHAPspool>>& for a description of the format of spool files.
31976 &'body'&: The contents of the spool file containing the body of the message are
31977 displayed in a new text window. There is a default limit of 20,000 bytes to the
31978 amount of data displayed. This can be changed by setting the BODY_MAX
31979 option at compile time, or the EXIMON_BODY_MAX option at run time.
31981 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
31982 delivery of the message. This causes an automatic thaw if the message is
31983 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
31984 a new text window. The delivery is run in a separate process, to avoid holding
31985 up the monitor while the delivery proceeds.
31987 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
31988 that the message be frozen.
31990 .cindex "thawing messages"
31991 .cindex "unfreezing messages"
31992 .cindex "frozen messages" "thawing"
31993 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
31994 that the message be thawed.
31996 .cindex "delivery" "forcing failure"
31997 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
31998 that Exim gives up trying to deliver the message. A bounce message is generated
31999 for any remaining undelivered addresses.
32001 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
32002 that the message be deleted from the system without generating a bounce
32005 &'add recipient'&: A dialog box is displayed into which a recipient address can
32006 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
32007 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
32008 Otherwise it must be entered as a fully qualified address. Pressing RETURN
32009 causes a call to Exim to be made using the &%-Mar%& option to request that an
32010 additional recipient be added to the message, unless the entry box is empty, in
32011 which case no action is taken.
32013 &'mark delivered'&: A dialog box is displayed into which a recipient address
32014 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
32015 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
32016 Otherwise it must be entered as a fully qualified address. Pressing RETURN
32017 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
32018 recipient address as already delivered, unless the entry box is empty, in which
32019 case no action is taken.
32021 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
32022 mark all recipient addresses as already delivered.
32024 &'edit sender'&: A dialog box is displayed initialized with the current
32025 sender's address. Pressing RETURN causes a call to Exim to be made using the
32026 &%-Mes%& option to replace the sender address, unless the entry box is empty,
32027 in which case no action is taken. If you want to set an empty sender (as in
32028 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
32029 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
32030 the address is qualified with that domain.
32033 When a delivery is forced, a window showing the &%-v%& output is displayed. In
32034 other cases when a call to Exim is made, if there is any output from Exim (in
32035 particular, if the command fails) a window containing the command and the
32036 output is displayed. Otherwise, the results of the action are normally apparent
32037 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
32038 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
32039 if no output is generated.
32041 The queue display is automatically updated for actions such as freezing and
32042 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
32043 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
32044 force an update of the display after one of these actions.
32046 In any text window that is displayed as result of a menu action, the normal
32047 cut-and-paste facility is available, and searching can be carried out using ^R
32048 and ^S, as described above for the log tail window.
32055 . ////////////////////////////////////////////////////////////////////////////
32056 . ////////////////////////////////////////////////////////////////////////////
32058 .chapter "Security considerations" "CHAPsecurity"
32059 .scindex IIDsecurcon "security" "discussion of"
32060 This chapter discusses a number of issues concerned with security, some of
32061 which are also covered in other parts of this manual.
32063 For reasons that this author does not understand, some people have promoted
32064 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
32065 existence of this chapter in the documentation. However, the intent of the
32066 chapter is simply to describe the way Exim works in relation to certain
32067 security concerns, not to make any specific claims about the effectiveness of
32068 its security as compared with other MTAs.
32070 What follows is a description of the way Exim is supposed to be. Best efforts
32071 have been made to try to ensure that the code agrees with the theory, but an
32072 absence of bugs can never be guaranteed. Any that are reported will get fixed
32073 as soon as possible.
32076 .section "Building a more &""hardened""& Exim"
32077 .cindex "security" "build-time features"
32078 There are a number of build-time options that can be set in &_Local/Makefile_&
32079 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
32080 Exim administrator who does not have the root password, or by someone who has
32081 penetrated the Exim (but not the root) account. These options are as follows:
32084 ALT_CONFIG_PREFIX can be set to a string that is required to match the
32085 start of any file names used with the &%-C%& option. When it is set, these file
32086 names are also not allowed to contain the sequence &"/../"&. (However, if the
32087 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
32088 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
32089 default setting for &%ALT_CONFIG_PREFIX%&.
32091 If the permitted configuration files are confined to a directory to
32092 which only root has access, this guards against someone who has broken
32093 into the Exim account from running a privileged Exim with an arbitrary
32094 configuration file, and using it to break into other accounts.
32096 If ALT_CONFIG_ROOT_ONLY is defined, root privilege is retained for &%-C%&
32097 and &%-D%& only if the caller of Exim is root. Without it, the Exim user may
32098 also use &%-C%& and &%-D%& and retain privilege. Setting this option locks out
32099 the possibility of testing a configuration using &%-C%& right through message
32100 reception and delivery, even if the caller is root. The reception works, but by
32101 that time, Exim is running as the Exim user, so when it re-execs to regain
32102 privilege for the delivery, the use of &%-C%& causes privilege to be lost.
32103 However, root can test reception and delivery using two separate commands.
32104 ALT_CONFIG_ROOT_ONLY is not set by default.
32106 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
32109 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
32110 never to be used for any deliveries. This is like the &%never_users%& runtime
32111 option, but it cannot be overridden; the runtime option adds additional users
32112 to the list. The default setting is &"root"&; this prevents a non-root user who
32113 is permitted to modify the runtime file from using Exim as a way to get root.
32119 .section "Root privilege"
32121 .cindex "root privilege"
32122 The Exim binary is normally setuid to root, which means that it gains root
32123 privilege (runs as root) when it starts execution. In some special cases (for
32124 example, when the daemon is not in use and there are no local deliveries), it
32125 may be possible to run Exim setuid to some user other than root. This is
32126 discussed in the next section. However, in most installations, root privilege
32127 is required for two things:
32130 To set up a socket connected to the standard SMTP port (25) when initialising
32131 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
32134 To be able to change uid and gid in order to read users' &_.forward_& files and
32135 perform local deliveries as the receiving user or as specified in the
32139 It is not necessary to be root to do any of the other things Exim does, such as
32140 receiving messages and delivering them externally over SMTP, and it is
32141 obviously more secure if Exim does not run as root except when necessary.
32142 For this reason, a user and group for Exim to use must be defined in
32143 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
32144 group"&. Their values can be changed by the run time configuration, though this
32145 is not recommended. Often a user called &'exim'& is used, but some sites use
32146 &'mail'& or another user name altogether.
32148 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
32149 abdication; the process cannot regain root afterwards. Prior to release 4.00,
32150 &[seteuid()]& was used in some circumstances, but this is no longer the case.
32152 After a new Exim process has interpreted its command line options, it changes
32153 uid and gid in the following cases:
32156 .cindex "&%-C%& option"
32157 .cindex "&%-D%& option"
32158 If the &%-C%& option is used to specify an alternate configuration file, or if
32159 the &%-D%& option is used to define macro values for the configuration, and the
32160 calling process is not running as root or the Exim user, the uid and gid are
32161 changed to those of the calling process.
32162 However, if ALT_CONFIG_ROOT_ONLY is defined in &_Local/Makefile_&, only
32163 root callers may use &%-C%& and &%-D%& without losing privilege, and if
32164 DISABLE_D_OPTION is set, the &%-D%& option may not be used at all.
32166 .cindex "&%-be%& option"
32167 .cindex "&%-bf%& option"
32168 .cindex "&%-bF%& option"
32169 If the expansion test option (&%-be%&) or one of the filter testing options
32170 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
32173 If the process is not a daemon process or a queue runner process or a delivery
32174 process or a process for testing address routing (started with &%-bt%&), the
32175 uid and gid are changed to the Exim user and group. This means that Exim always
32176 runs under its own uid and gid when receiving messages. This also applies when
32177 testing address verification
32178 .cindex "&%-bv%& option"
32179 .cindex "&%-bh%& option"
32180 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
32183 For a daemon, queue runner, delivery, or address testing process, the uid
32184 remains as root at this stage, but the gid is changed to the Exim group.
32187 The processes that initially retain root privilege behave as follows:
32190 A daemon process changes the gid to the Exim group and the uid to the Exim
32191 user after setting up one or more listening sockets. The &[initgroups()]&
32192 function is called, so that if the Exim user is in any additional groups, they
32193 will be used during message reception.
32195 A queue runner process retains root privilege throughout its execution. Its
32196 job is to fork a controlled sequence of delivery processes.
32198 A delivery process retains root privilege throughout most of its execution,
32199 but any actual deliveries (that is, the transports themselves) are run in
32200 subprocesses which always change to a non-root uid and gid. For local
32201 deliveries this is typically the uid and gid of the owner of the mailbox; for
32202 remote deliveries, the Exim uid and gid are used. Once all the delivery
32203 subprocesses have been run, a delivery process changes to the Exim uid and gid
32204 while doing post-delivery tidying up such as updating the retry database and
32205 generating bounce and warning messages.
32207 While the recipient addresses in a message are being routed, the delivery
32208 process runs as root. However, if a user's filter file has to be processed,
32209 this is done in a subprocess that runs under the individual user's uid and
32210 gid. A system filter is run as root unless &%system_filter_user%& is set.
32212 A process that is testing addresses (the &%-bt%& option) runs as root so that
32213 the routing is done in the same environment as a message delivery.
32219 .section "Running Exim without privilege" "SECTrunexiwitpri"
32220 .cindex "privilege" "running without"
32221 .cindex "unprivileged running"
32222 .cindex "root privilege" "running without"
32223 Some installations like to run Exim in an unprivileged state for more of its
32224 operation, for added security. Support for this mode of operation is provided
32225 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
32226 gid are changed to the Exim user and group at the start of a delivery process
32227 (and also queue runner and address testing processes). This means that address
32228 routing is no longer run as root, and the deliveries themselves cannot change
32231 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
32232 that the daemon can still be started in the usual way, and it can respond
32233 correctly to SIGHUP because the re-invocation regains root privilege.
32235 An alternative approach is to make Exim setuid to the Exim user and also setgid
32237 If you do this, the daemon must be started from a root process. (Calling
32238 Exim from a root process makes it behave in the way it does when it is setuid
32239 root.) However, the daemon cannot restart itself after a SIGHUP signal because
32240 it cannot regain privilege.
32242 It is still useful to set &%deliver_drop_privilege%& in this case, because it
32243 stops Exim from trying to re-invoke itself to do a delivery after a message has
32244 been received. Such a re-invocation is a waste of resources because it has no
32247 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
32248 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
32249 to the Exim user seems a clean approach, but there is one complication:
32251 In this style of operation, Exim is running with the real uid and gid set to
32252 those of the calling process, and the effective uid/gid set to Exim's values.
32253 Ideally, any association with the calling process' uid/gid should be dropped,
32254 that is, the real uid/gid should be reset to the effective values so as to
32255 discard any privileges that the caller may have. While some operating systems
32256 have a function that permits this action for a non-root effective uid, quite a
32257 number of them do not. Because of this lack of standardization, Exim does not
32258 address this problem at this time.
32260 For this reason, the recommended approach for &"mostly unprivileged"& running
32261 is to keep the Exim binary setuid to root, and to set
32262 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
32263 be used in the most straightforward way.
32265 If you configure Exim not to run delivery processes as root, there are a
32266 number of restrictions on what you can do:
32269 You can deliver only as the Exim user/group. You should explicitly use the
32270 &%user%& and &%group%& options to override routers or local transports that
32271 normally deliver as the recipient. This makes sure that configurations that
32272 work in this mode function the same way in normal mode. Any implicit or
32273 explicit specification of another user causes an error.
32275 Use of &_.forward_& files is severely restricted, such that it is usually
32276 not worthwhile to include them in the configuration.
32278 Users who wish to use &_.forward_& would have to make their home directory and
32279 the file itself accessible to the Exim user. Pipe and append-to-file entries,
32280 and their equivalents in Exim filters, cannot be used. While they could be
32281 enabled in the Exim user's name, that would be insecure and not very useful.
32283 Unless the local user mailboxes are all owned by the Exim user (possible in
32284 some POP3 or IMAP-only environments):
32287 They must be owned by the Exim group and be writable by that group. This
32288 implies you must set &%mode%& in the appendfile configuration, as well as the
32289 mode of the mailbox files themselves.
32291 You must set &%no_check_owner%&, since most or all of the files will not be
32292 owned by the Exim user.
32294 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
32295 on a newly created mailbox when unprivileged. This also implies that new
32296 mailboxes need to be created manually.
32301 These restrictions severely restrict what can be done in local deliveries.
32302 However, there are no restrictions on remote deliveries. If you are running a
32303 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
32304 gives more security at essentially no cost.
32306 If you are using the &%mua_wrapper%& facility (see chapter
32307 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
32312 .section "Delivering to local files"
32313 Full details of the checks applied by &(appendfile)& before it writes to a file
32314 are given in chapter &<<CHAPappendfile>>&.
32318 .section "IPv4 source routing"
32319 .cindex "source routing" "in IP packets"
32320 .cindex "IP source routing"
32321 Many operating systems suppress IP source-routed packets in the kernel, but
32322 some cannot be made to do this, so Exim does its own check. It logs incoming
32323 IPv4 source-routed TCP calls, and then drops them. Things are all different in
32324 IPv6. No special checking is currently done.
32328 .section "The VRFY, EXPN, and ETRN commands in SMTP"
32329 Support for these SMTP commands is disabled by default. If required, they can
32330 be enabled by defining suitable ACLs.
32335 .section "Privileged users"
32336 .cindex "trusted user"
32337 .cindex "admin user"
32338 .cindex "privileged user"
32339 .cindex "user" "trusted"
32340 .cindex "user" "admin"
32341 Exim recognises two sets of users with special privileges. Trusted users are
32342 able to submit new messages to Exim locally, but supply their own sender
32343 addresses and information about a sending host. For other users submitting
32344 local messages, Exim sets up the sender address from the uid, and doesn't
32345 permit a remote host to be specified.
32347 .cindex "&%-f%& option"
32348 However, an untrusted user is permitted to use the &%-f%& command line option
32349 in the special form &%-f <>%& to indicate that a delivery failure for the
32350 message should not cause an error report. This affects the message's envelope,
32351 but it does not affect the &'Sender:'& header. Untrusted users may also be
32352 permitted to use specific forms of address with the &%-f%& option by setting
32353 the &%untrusted_set_sender%& option.
32355 Trusted users are used to run processes that receive mail messages from some
32356 other mail domain and pass them on to Exim for delivery either locally, or over
32357 the Internet. Exim trusts a caller that is running as root, as the Exim user,
32358 as any user listed in the &%trusted_users%& configuration option, or under any
32359 group listed in the &%trusted_groups%& option.
32361 Admin users are permitted to do things to the messages on Exim's queue. They
32362 can freeze or thaw messages, cause them to be returned to their senders, remove
32363 them entirely, or modify them in various ways. In addition, admin users can run
32364 the Exim monitor and see all the information it is capable of providing, which
32365 includes the contents of files on the spool.
32367 .cindex "&%-M%& option"
32368 .cindex "&%-q%& option"
32369 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
32370 delivery of messages on its queue is restricted to admin users. This
32371 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
32372 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
32373 queue is also restricted to admin users. This restriction can be relaxed by
32374 setting &%no_queue_list_requires_admin%&.
32376 Exim recognises an admin user if the calling process is running as root or as
32377 the Exim user or if any of the groups associated with the calling process is
32378 the Exim group. It is not necessary actually to be running under the Exim
32379 group. However, if admin users who are not root or the Exim user are to access
32380 the contents of files on the spool via the Exim monitor (which runs
32381 unprivileged), Exim must be built to allow group read access to its spool
32386 .section "Spool files"
32387 .cindex "spool directory" "files"
32388 Exim's spool directory and everything it contains is owned by the Exim user and
32389 set to the Exim group. The mode for spool files is defined in the
32390 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
32391 any user who is a member of the Exim group can access these files.
32395 .section "Use of argv[0]"
32396 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
32397 of specific strings, Exim assumes certain options. For example, calling Exim
32398 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
32399 to calling it with the option &%-bS%&. There are no security implications in
32404 .section "Use of %f formatting"
32405 The only use made of &"%f"& by Exim is in formatting load average values. These
32406 are actually stored in integer variables as 1000 times the load average.
32407 Consequently, their range is limited and so therefore is the length of the
32412 .section "Embedded Exim path"
32413 Exim uses its own path name, which is embedded in the code, only when it needs
32414 to re-exec in order to regain root privilege. Therefore, it is not root when it
32415 does so. If some bug allowed the path to get overwritten, it would lead to an
32416 arbitrary program's being run as exim, not as root.
32420 .section "Use of sprintf()"
32421 .cindex "&[sprintf()]&"
32422 A large number of occurrences of &"sprintf"& in the code are actually calls to
32423 &'string_sprintf()'&, a function that returns the result in malloc'd store.
32424 The intermediate formatting is done into a large fixed buffer by a function
32425 that runs through the format string itself, and checks the length of each
32426 conversion before performing it, thus preventing buffer overruns.
32428 The remaining uses of &[sprintf()]& happen in controlled circumstances where
32429 the output buffer is known to be sufficiently long to contain the converted
32434 .section "Use of debug_printf() and log_write()"
32435 Arbitrary strings are passed to both these functions, but they do their
32436 formatting by calling the function &'string_vformat()'&, which runs through
32437 the format string itself, and checks the length of each conversion.
32441 .section "Use of strcat() and strcpy()"
32442 These are used only in cases where the output buffer is known to be large
32443 enough to hold the result.
32444 .ecindex IIDsecurcon
32449 . ////////////////////////////////////////////////////////////////////////////
32450 . ////////////////////////////////////////////////////////////////////////////
32452 .chapter "Format of spool files" "CHAPspool"
32453 .scindex IIDforspo1 "format" "spool files"
32454 .scindex IIDforspo2 "spool directory" "format of files"
32455 .scindex IIDforspo3 "spool files" "format of"
32456 .cindex "spool files" "editing"
32457 A message on Exim's queue consists of two files, whose names are the message id
32458 followed by -D and -H, respectively. The data portion of the message is kept in
32459 the -D file on its own. The message's envelope, status, and headers are all
32460 kept in the -H file, whose format is described in this chapter. Each of these
32461 two files contains the final component of its own name as its first line. This
32462 is insurance against disk crashes where the directory is lost but the files
32463 themselves are recoverable.
32465 Some people are tempted into editing -D files in order to modify messages. You
32466 need to be extremely careful if you do this; it is not recommended and you are
32467 on your own if you do it. Here are some of the pitfalls:
32470 You must ensure that Exim does not try to deliver the message while you are
32471 fiddling with it. The safest way is to take out a write lock on the -D file,
32472 which is what Exim itself does, using &[fcntl()]&. If you update the file in
32473 place, the lock will be retained. If you write a new file and rename it, the
32474 lock will be lost at the instant of rename.
32476 .cindex "&$body_linecount$&"
32477 If you change the number of lines in the file, the value of
32478 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
32479 present, this value is not used by Exim, but there is no guarantee that this
32480 will always be the case.
32482 If the message is in MIME format, you must take care not to break it.
32484 If the message is cryptographically signed, any change will invalidate the
32489 Files whose names end with -J may also be seen in the &_input_& directory (or
32490 its subdirectories when &%split_spool_directory%& is set). These are journal
32491 files, used to record addresses to which the message has been delivered during
32492 the course of a delivery run. At the end of the run, the -H file is updated,
32493 and the -J file is deleted.
32496 .section "Format of the -H file"
32497 .cindex "uid (user id)" "in spool file"
32498 .cindex "gid (group id)" "in spool file"
32499 The second line of the -H file contains the login name for the uid of the
32500 process that called Exim to read the message, followed by the numerical uid and
32501 gid. For a locally generated message, this is normally the user who sent the
32502 message. For a message received over TCP/IP, it is normally the Exim user.
32504 The third line of the file contains the address of the message's sender as
32505 transmitted in the envelope, contained in angle brackets. The sender address is
32506 empty for bounce messages. For incoming SMTP mail, the sender address is given
32507 in the MAIL command. For locally generated mail, the sender address is
32508 created by Exim from the login name of the current user and the configured
32509 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
32510 leading &"From&~"& line if the caller is trusted, or if the supplied address is
32511 &"<>"& or an address that matches &%untrusted_set_senders%&.
32513 The fourth line contains two numbers. The first is the time that the message
32514 was received, in the conventional Unix form &-- the number of seconds since the
32515 start of the epoch. The second number is a count of the number of messages
32516 warning of delayed delivery that have been sent to the sender.
32518 There follow a number of lines starting with a hyphen. These can appear in any
32519 order, and are omitted when not relevant:
32522 .vitem "&%-acl%& <&'number'&> <&'length'&>"
32523 This item is obsolete, and is not generated from Exim release 4.61 onwards;
32524 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
32525 recognized, to provide backward compatibility. In the old format, a line of
32526 this form is present for every ACL variable that is not empty. The number
32527 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
32528 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
32529 the data string for the variable. The string itself starts at the beginning of
32530 the next line, and is followed by a newline character. It may contain internal
32533 .vitem "&%-aclc%& <&'number'&> <&'length'&>"
32534 A line of this form is present for every ACL connection variable that is not
32535 empty. The number identifies the variable. The length is the length of the data
32536 string for the variable. The string itself starts at the beginning of the next
32537 line, and is followed by a newline character. It may contain internal newlines.
32539 .vitem "&%-aclm%& <&'number'&> <&'length'&>"
32540 A line of this form is present for every ACL message variable that is not
32541 empty. The number identifies the variable. The length is the length of the data
32542 string for the variable. The string itself starts at the beginning of the next
32543 line, and is followed by a newline character. It may contain internal newlines.
32545 .vitem "&%-active_hostname%& <&'hostname'&>"
32546 This is present if, when the message was received over SMTP, the value of
32547 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
32549 .vitem &%-allow_unqualified_recipient%&
32550 This is present if unqualified recipient addresses are permitted in header
32551 lines (to stop such addresses from being qualified if rewriting occurs at
32552 transport time). Local messages that were input using &%-bnq%& and remote
32553 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
32555 .vitem &%-allow_unqualified_sender%&
32556 This is present if unqualified sender addresses are permitted in header lines
32557 (to stop such addresses from being qualified if rewriting occurs at transport
32558 time). Local messages that were input using &%-bnq%& and remote messages from
32559 hosts that match &%sender_unqualified_hosts%& set this flag.
32561 .vitem "&%-auth_id%& <&'text'&>"
32562 The id information for a message received on an authenticated SMTP connection
32563 &-- the value of the &$authenticated_id$& variable.
32565 .vitem "&%-auth_sender%& <&'address'&>"
32566 The address of an authenticated sender &-- the value of the
32567 &$authenticated_sender$& variable.
32569 .vitem "&%-body_linecount%& <&'number'&>"
32570 This records the number of lines in the body of the message, and is always
32573 .vitem "&%-body_zerocount%& <&'number'&>"
32574 This records the number of binary zero bytes in the body of the message, and is
32575 present if the number is greater than zero.
32577 .vitem &%-deliver_firsttime%&
32578 This is written when a new message is first added to the spool. When the spool
32579 file is updated after a deferral, it is omitted.
32581 .vitem "&%-frozen%& <&'time'&>"
32582 .cindex "frozen messages" "spool data"
32583 The message is frozen, and the freezing happened at <&'time'&>.
32585 .vitem "&%-helo_name%& <&'text'&>"
32586 This records the host name as specified by a remote host in a HELO or EHLO
32589 .vitem "&%-host_address%& <&'address'&>.<&'port'&>"
32590 This records the IP address of the host from which the message was received and
32591 the remote port number that was used. It is omitted for locally generated
32594 .vitem "&%-host_auth%& <&'text'&>"
32595 If the message was received on an authenticated SMTP connection, this records
32596 the name of the authenticator &-- the value of the
32597 &$sender_host_authenticated$& variable.
32599 .vitem &%-host_lookup_failed%&
32600 This is present if an attempt to look up the sending host's name from its IP
32601 address failed. It corresponds to the &$host_lookup_failed$& variable.
32603 .vitem "&%-host_name%& <&'text'&>"
32604 .cindex "reverse DNS lookup"
32605 .cindex "DNS" "reverse lookup"
32606 This records the name of the remote host from which the message was received,
32607 if the host name was looked up from the IP address when the message was being
32608 received. It is not present if no reverse lookup was done.
32610 .vitem "&%-ident%& <&'text'&>"
32611 For locally submitted messages, this records the login of the originating user,
32612 unless it was a trusted user and the &%-oMt%& option was used to specify an
32613 ident value. For messages received over TCP/IP, this records the ident string
32614 supplied by the remote host, if any.
32616 .vitem "&%-interface_address%& <&'address'&>.<&'port'&>"
32617 This records the IP address of the local interface and the port number through
32618 which a message was received from a remote host. It is omitted for locally
32619 generated messages.
32622 The message is from a local sender.
32624 .vitem &%-localerror%&
32625 The message is a locally-generated bounce message.
32627 .vitem "&%-local_scan%& <&'string'&>"
32628 This records the data string that was returned by the &[local_scan()]& function
32629 when the message was received &-- the value of the &$local_scan_data$&
32630 variable. It is omitted if no data was returned.
32632 .vitem &%-manual_thaw%&
32633 The message was frozen but has been thawed manually, that is, by an explicit
32634 Exim command rather than via the auto-thaw process.
32637 A testing delivery process was started using the &%-N%& option to suppress any
32638 actual deliveries, but delivery was deferred. At any further delivery attempts,
32641 .vitem &%-received_protocol%&
32642 This records the value of the &$received_protocol$& variable, which contains
32643 the name of the protocol by which the message was received.
32645 .vitem &%-sender_set_untrusted%&
32646 The envelope sender of this message was set by an untrusted local caller (used
32647 to ensure that the caller is displayed in queue listings).
32649 .vitem "&%-spam_score_int%& <&'number'&>"
32650 If a message was scanned by SpamAssassin, this is present. It records the value
32651 of &$spam_score_int$&.
32653 .vitem &%-tls_certificate_verified%&
32654 A TLS certificate was received from the client that sent this message, and the
32655 certificate was verified by the server.
32657 .vitem "&%-tls_cipher%& <&'cipher name'&>"
32658 When the message was received over an encrypted connection, this records the
32659 name of the cipher suite that was used.
32661 .vitem "&%-tls_peerdn%& <&'peer DN'&>"
32662 When the message was received over an encrypted connection, and a certificate
32663 was received from the client, this records the Distinguished Name from that
32667 Following the options there is a list of those addresses to which the message
32668 is not to be delivered. This set of addresses is initialized from the command
32669 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
32670 is set; otherwise it starts out empty. Whenever a successful delivery is made,
32671 the address is added to this set. The addresses are kept internally as a
32672 balanced binary tree, and it is a representation of that tree which is written
32673 to the spool file. If an address is expanded via an alias or forward file, the
32674 original address is added to the tree when deliveries to all its child
32675 addresses are complete.
32677 If the tree is empty, there is a single line in the spool file containing just
32678 the text &"XX"&. Otherwise, each line consists of two letters, which are either
32679 Y or N, followed by an address. The address is the value for the node of the
32680 tree, and the letters indicate whether the node has a left branch and/or a
32681 right branch attached to it, respectively. If branches exist, they immediately
32682 follow. Here is an example of a three-node tree:
32684 YY darcy@austen.fict.example
32685 NN alice@wonderland.fict.example
32686 NN editor@thesaurus.ref.example
32688 After the non-recipients tree, there is a list of the message's recipients.
32689 This is a simple list, preceded by a count. It includes all the original
32690 recipients of the message, including those to whom the message has already been
32691 delivered. In the simplest case, the list contains one address per line. For
32695 editor@thesaurus.ref.example
32696 darcy@austen.fict.example
32698 alice@wonderland.fict.example
32700 However, when a child address has been added to the top-level addresses as a
32701 result of the use of the &%one_time%& option on a &(redirect)& router, each
32702 line is of the following form:
32704 <&'top-level address'&> <&'errors_to address'&> &&&
32705 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
32707 The 01 flag bit indicates the presence of the three other fields that follow
32708 the top-level address. Other bits may be used in future to support additional
32709 fields. The <&'parent number'&> is the offset in the recipients list of the
32710 original parent of the &"one time"& address. The first two fields are the
32711 envelope sender that is associated with this address and its length. If the
32712 length is zero, there is no special envelope sender (there are then two space
32713 characters in the line). A non-empty field can arise from a &(redirect)& router
32714 that has an &%errors_to%& setting.
32717 A blank line separates the envelope and status information from the headers
32718 which follow. A header may occupy several lines of the file, and to save effort
32719 when reading it in, each header is preceded by a number and an identifying
32720 character. The number is the number of characters in the header, including any
32721 embedded newlines and the terminating newline. The character is one of the
32725 .row <&'blank'&> "header in which Exim has no special interest"
32726 .row &`B`& "&'Bcc:'& header"
32727 .row &`C`& "&'Cc:'& header"
32728 .row &`F`& "&'From:'& header"
32729 .row &`I`& "&'Message-id:'& header"
32730 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
32731 .row &`R`& "&'Reply-To:'& header"
32732 .row &`S`& "&'Sender:'& header"
32733 .row &`T`& "&'To:'& header"
32734 .row &`*`& "replaced or deleted header"
32737 Deleted or replaced (rewritten) headers remain in the spool file for debugging
32738 purposes. They are not transmitted when the message is delivered. Here is a
32739 typical set of headers:
32741 111P Received: by hobbit.fict.example with local (Exim 4.00)
32742 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
32743 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
32744 038* X-rewrote-sender: bb@hobbit.fict.example
32745 042* From: Bilbo Baggins <bb@hobbit.fict.example>
32746 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
32747 099* To: alice@wonderland.fict.example, rdo@foundation,
32748 darcy@austen.fict.example, editor@thesaurus.ref.example
32749 104T To: alice@wonderland.fict.example, rdo@foundation.example,
32750 darcy@austen.fict.example, editor@thesaurus.ref.example
32751 038 Date: Fri, 11 May 2001 10:28:59 +0100
32753 The asterisked headers indicate that the envelope sender, &'From:'& header, and
32754 &'To:'& header have been rewritten, the last one because routing expanded the
32755 unqualified domain &'foundation'&.
32756 .ecindex IIDforspo1
32757 .ecindex IIDforspo2
32758 .ecindex IIDforspo3
32763 . ////////////////////////////////////////////////////////////////////////////
32764 . ////////////////////////////////////////////////////////////////////////////
32766 .chapter "Adding new drivers or lookup types" "" &&&
32767 "Adding drivers or lookups"
32768 .cindex "adding drivers"
32769 .cindex "new drivers" "adding"
32770 .cindex "drivers" "adding new"
32771 The following actions have to be taken in order to add a new router, transport,
32772 authenticator, or lookup type to Exim:
32775 Choose a name for the driver or lookup type that does not conflict with any
32776 existing name; I will use &"newdriver"& in what follows.
32778 Add to &_src/EDITME_& the line:
32780 <&'type'&>&`_NEWDRIVER=yes`&
32782 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
32783 code is not to be included in the binary by default, comment this line out. You
32784 should also add any relevant comments about the driver or lookup type.
32786 Add to &_src/config.h.defaults_& the line:
32788 #define <type>_NEWDRIVER
32791 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
32792 and create a table entry as is done for all the other drivers and lookup types.
32794 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
32795 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
32796 driver or lookup type and add it to the definition of OBJ.
32798 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
32801 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
32802 as for other drivers and lookups.
32805 Then all you need to do is write the code! A good way to start is to make a
32806 proforma by copying an existing module of the same type, globally changing all
32807 occurrences of the name, and cutting out most of the code. Note that any
32808 options you create must be listed in alphabetical order, because the tables are
32809 searched using a binary chop procedure.
32811 There is a &_README_& file in each of the sub-directories of &_src_& describing
32812 the interface that is expected.
32817 . ////////////////////////////////////////////////////////////////////////////
32818 . ////////////////////////////////////////////////////////////////////////////
32820 .makeindex "Option index" "option"
32822 .makeindex "Concept index" "concept"
32825 . /////////////////////////////////////////////////////////////////////////////
32826 . /////////////////////////////////////////////////////////////////////////////