1 . $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.87 2010/06/12 15:21:25 jetmore 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.
9 . WARNING: When you use the .new macro, make sure it appears *before* any
10 . adjacent index items; otherwise you get an empty "paragraph" which causes
11 . unwanted vertical space.
12 . /////////////////////////////////////////////////////////////////////////////
17 . /////////////////////////////////////////////////////////////////////////////
18 . This outputs the standard DocBook boilerplate.
19 . /////////////////////////////////////////////////////////////////////////////
23 . /////////////////////////////////////////////////////////////////////////////
24 . These lines are processing instructions for the Simple DocBook Processor that
25 . Philip Hazel has developed as a less cumbersome way of making PostScript and
26 . PDFs than using xmlto and fop. They will be ignored by all other XML
28 . /////////////////////////////////////////////////////////////////////////////
32 foot_right_recto="&chaptertitle; (&chapternumber;)"
33 foot_right_verso="&chaptertitle; (&chapternumber;)"
34 toc_chapter_blanks="yes,yes"
35 table_warn_overflow="overprint"
39 . /////////////////////////////////////////////////////////////////////////////
40 . This generate the outermost <book> element that wraps then entire document.
41 . /////////////////////////////////////////////////////////////////////////////
45 . /////////////////////////////////////////////////////////////////////////////
46 . These definitions set some parameters and save some typing. Remember that
47 . the <bookinfo> element must also be updated for each new edition.
48 . /////////////////////////////////////////////////////////////////////////////
50 .set previousversion "4.71"
53 .set ACL "access control lists (ACLs)"
54 .set I " "
57 . /////////////////////////////////////////////////////////////////////////////
58 . Additional xfpt markup used by this document, over and above the default
59 . provided in the xfpt library.
60 . /////////////////////////////////////////////////////////////////////////////
62 . --- Override the &$ flag to automatically insert a $ with the variable name
64 .flag &$ $& "<varname>$" "</varname>"
66 . --- Short flags for daggers in option headings. They will always be inside
67 . --- an italic string, but we want the daggers to be roman.
69 .flag &!! "</emphasis>†<emphasis>"
70 .flag &!? "</emphasis>‡<emphasis>"
72 . --- A macro for an Exim option definition heading, generating a one-line
73 . --- table with four columns. For cases when the option name is given with
74 . --- a space, so that it can be split, a fifth argument is used for the
84 .itable all 0 0 4 8* left 6* center 6* center 6* right
85 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
89 . --- A macro for the common 2-column tables. The width of the first column
90 . --- is suitable for the many tables at the start of the main options chapter;
91 . --- the small number of other 2-column tables override it.
93 .macro table2 196pt 254pt
94 .itable none 0 0 2 $1 left $2 left
97 . --- A macro that generates .row, but puts &I; at the start of the first
98 . --- argument, thus indenting it. Assume a minimum of two arguments, and
99 . --- allow up to four arguments, which is as many as we'll ever need.
103 .row "&I;$1" "$2" "$3" "$4"
107 .row "&I;$1" "$2" "$3"
115 . --- Macros for option, variable, and concept index entries. For a "range"
116 . --- style of entry, use .scindex for the start and .ecindex for the end. The
117 . --- first argument of .scindex and the only argument of .ecindex must be the
118 . --- ID that ties them together.
121 &<indexterm role="concept">&
122 &<primary>&$1&</primary>&
124 &<secondary>&$2&</secondary>&
130 &<indexterm role="concept" id="$1" class="startofrange">&
131 &<primary>&$2&</primary>&
133 &<secondary>&$3&</secondary>&
139 &<indexterm role="concept" startref="$1" class="endofrange"/>&
143 &<indexterm role="option">&
144 &<primary>&$1&</primary>&
146 &<secondary>&$2&</secondary>&
152 &<indexterm role="variable">&
153 &<primary>&$1&</primary>&
155 &<secondary>&$2&</secondary>&
161 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
163 . ////////////////////////////////////////////////////////////////////////////
166 . ////////////////////////////////////////////////////////////////////////////
167 . The <bookinfo> element is removed from the XML before processing for Ascii
169 . ////////////////////////////////////////////////////////////////////////////
173 <title>Specification of the Exim Mail Transfer Agent</title>
174 <titleabbrev>The Exim MTA</titleabbrev>
175 <date>29 May 2010</date>
176 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
177 <authorinitials>EM</authorinitials>
178 <revhistory><revision>
179 <revnumber>4.72</revnumber>
180 <date>29 May 2010</date>
181 <authorinitials>EM</authorinitials>
182 </revision></revhistory>
183 <copyright><year>2009</year><holder>University of Cambridge</holder></copyright>
188 . /////////////////////////////////////////////////////////////////////////////
189 . This chunk of literal XML implements index entries of the form "x, see y" and
190 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
191 . at the top level, so we have to put the .chapter directive first.
192 . /////////////////////////////////////////////////////////////////////////////
194 .chapter "Introduction" "CHID1"
197 <indexterm role="variable">
198 <primary>$1, $2, etc.</primary>
199 <see><emphasis>numerical variables</emphasis></see>
201 <indexterm role="concept">
202 <primary>address</primary>
203 <secondary>rewriting</secondary>
204 <see><emphasis>rewriting</emphasis></see>
206 <indexterm role="concept">
207 <primary>Bounce Address Tag Validation</primary>
208 <see><emphasis>BATV</emphasis></see>
210 <indexterm role="concept">
211 <primary>Client SMTP Authorization</primary>
212 <see><emphasis>CSA</emphasis></see>
214 <indexterm role="concept">
215 <primary>CR character</primary>
216 <see><emphasis>carriage return</emphasis></see>
218 <indexterm role="concept">
219 <primary>CRL</primary>
220 <see><emphasis>certificate revocation list</emphasis></see>
222 <indexterm role="concept">
223 <primary>delivery</primary>
224 <secondary>failure report</secondary>
225 <see><emphasis>bounce message</emphasis></see>
227 <indexterm role="concept">
228 <primary>dialup</primary>
229 <see><emphasis>intermittently connected hosts</emphasis></see>
231 <indexterm role="concept">
232 <primary>exiscan</primary>
233 <see><emphasis>content scanning</emphasis></see>
235 <indexterm role="concept">
236 <primary>failover</primary>
237 <see><emphasis>fallback</emphasis></see>
239 <indexterm role="concept">
240 <primary>fallover</primary>
241 <see><emphasis>fallback</emphasis></see>
243 <indexterm role="concept">
244 <primary>filter</primary>
245 <secondary>Sieve</secondary>
246 <see><emphasis>Sieve filter</emphasis></see>
248 <indexterm role="concept">
249 <primary>ident</primary>
250 <see><emphasis>RFC 1413</emphasis></see>
252 <indexterm role="concept">
253 <primary>LF character</primary>
254 <see><emphasis>linefeed</emphasis></see>
256 <indexterm role="concept">
257 <primary>maximum</primary>
258 <seealso><emphasis>limit</emphasis></seealso>
260 <indexterm role="concept">
261 <primary>monitor</primary>
262 <see><emphasis>Exim monitor</emphasis></see>
264 <indexterm role="concept">
265 <primary>no_<emphasis>xxx</emphasis></primary>
266 <see>entry for xxx</see>
268 <indexterm role="concept">
269 <primary>NUL</primary>
270 <see><emphasis>binary zero</emphasis></see>
272 <indexterm role="concept">
273 <primary>passwd file</primary>
274 <see><emphasis>/etc/passwd</emphasis></see>
276 <indexterm role="concept">
277 <primary>process id</primary>
278 <see><emphasis>pid</emphasis></see>
280 <indexterm role="concept">
281 <primary>RBL</primary>
282 <see><emphasis>DNS list</emphasis></see>
284 <indexterm role="concept">
285 <primary>redirection</primary>
286 <see><emphasis>address redirection</emphasis></see>
288 <indexterm role="concept">
289 <primary>return path</primary>
290 <seealso><emphasis>envelope sender</emphasis></seealso>
292 <indexterm role="concept">
293 <primary>scanning</primary>
294 <see><emphasis>content scanning</emphasis></see>
296 <indexterm role="concept">
297 <primary>SSL</primary>
298 <see><emphasis>TLS</emphasis></see>
300 <indexterm role="concept">
301 <primary>string</primary>
302 <secondary>expansion</secondary>
303 <see><emphasis>expansion</emphasis></see>
305 <indexterm role="concept">
306 <primary>top bit</primary>
307 <see><emphasis>8-bit characters</emphasis></see>
309 <indexterm role="concept">
310 <primary>variables</primary>
311 <see><emphasis>expansion, variables</emphasis></see>
313 <indexterm role="concept">
314 <primary>zero, binary</primary>
315 <see><emphasis>binary zero</emphasis></see>
321 . /////////////////////////////////////////////////////////////////////////////
322 . This is the real start of the first chapter. See the comment above as to why
323 . we can't have the .chapter line here.
324 . chapter "Introduction"
325 . /////////////////////////////////////////////////////////////////////////////
327 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
328 Unix-like operating systems. It was designed on the assumption that it would be
329 run on hosts that are permanently connected to the Internet. However, it can be
330 used on intermittently connected hosts with suitable configuration adjustments.
332 Configuration files currently exist for the following operating systems: AIX,
333 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
334 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
335 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
336 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
337 Some of these operating systems are no longer current and cannot easily be
338 tested, so the configuration files may no longer work in practice.
340 There are also configuration files for compiling Exim in the Cygwin environment
341 that can be installed on systems running Windows. However, this document does
342 not contain any information about running Exim in the Cygwin environment.
344 The terms and conditions for the use and distribution of Exim are contained in
345 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
346 Public Licence, a copy of which may be found in the file &_LICENCE_&.
348 The use, supply or promotion of Exim for the purpose of sending bulk,
349 unsolicited electronic mail is incompatible with the basic aims of the program,
350 which revolve around the free provision of a service that enhances the quality
351 of personal communications. The author of Exim regards indiscriminate
352 mass-mailing as an antisocial, irresponsible abuse of the Internet.
354 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
355 experience of running and working on the Smail 3 code, I could never have
356 contemplated starting to write a new MTA. Many of the ideas and user interfaces
357 were originally taken from Smail 3, though the actual code of Exim is entirely
358 new, and has developed far beyond the initial concept.
360 Many people, both in Cambridge and around the world, have contributed to the
361 development and the testing of Exim, and to porting it to various operating
362 systems. I am grateful to them all. The distribution now contains a file called
363 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
367 .section "Exim documentation" "SECID1"
368 . Keep this example change bar when updating the documentation!
370 .cindex "documentation"
371 This edition of the Exim specification applies to version &version; of Exim.
372 Substantive changes from the &previousversion; edition are marked in some
373 renditions of the document; this paragraph is so marked if the rendition is
374 capable of showing a change indicator.
377 This document is very much a reference manual; it is not a tutorial. The reader
378 is expected to have some familiarity with the SMTP mail transfer protocol and
379 with general Unix system administration. Although there are some discussions
380 and examples in places, the information is mostly organized in a way that makes
381 it easy to look up, rather than in a natural order for sequential reading.
382 Furthermore, the manual aims to cover every aspect of Exim in detail, including
383 a number of rarely-used, special-purpose features that are unlikely to be of
386 .cindex "books about Exim"
387 An &"easier"& discussion of Exim which provides more in-depth explanatory,
388 introductory, and tutorial material can be found in a book entitled &'The Exim
389 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
390 (&url(http://www.uit.co.uk/exim-book/)).
392 This book also contains a chapter that gives a general introduction to SMTP and
393 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
394 with the latest release of Exim. (Note that the earlier book about Exim,
395 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
397 .cindex "Debian" "information sources"
398 If you are using a Debian distribution of Exim, you will find information about
399 Debian-specific features in the file
400 &_/usr/share/doc/exim4-base/README.Debian_&.
401 The command &(man update-exim.conf)& is another source of Debian-specific
404 .cindex "&_doc/NewStuff_&"
405 .cindex "&_doc/ChangeLog_&"
407 As the program develops, there may be features in newer versions that have not
408 yet made it into this document, which is updated only when the most significant
409 digit of the fractional part of the version number changes. Specifications of
410 new features that are not yet in this manual are placed in the file
411 &_doc/NewStuff_& in the Exim distribution.
413 Some features may be classified as &"experimental"&. These may change
414 incompatibly while they are developing, or even be withdrawn. For this reason,
415 they are not documented in this manual. Information about experimental features
416 can be found in the file &_doc/experimental.txt_&.
418 All changes to the program (whether new features, bug fixes, or other kinds of
419 change) are noted briefly in the file called &_doc/ChangeLog_&.
421 .cindex "&_doc/spec.txt_&"
422 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
423 that it can easily be searched with a text editor. Other files in the &_doc_&
427 .row &_OptionLists.txt_& "list of all options in alphabetical order"
428 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
429 .row &_exim.8_& "a man page of Exim's command line options"
430 .row &_experimental.txt_& "documentation of experimental features"
431 .row &_filter.txt_& "specification of the filter language"
432 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
433 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
436 The main specification and the specification of the filtering language are also
437 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
438 &<<SECTavail>>& below tells you how to get hold of these.
442 .section "FTP and web sites" "SECID2"
445 The primary site for Exim source distributions is currently the University of
446 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
447 distribution'& below. In addition, there is a web site and an FTP site at
448 &%exim.org%&. These are now also hosted at the University of Cambridge. The
449 &%exim.org%& site was previously hosted for a number of years by Energis
450 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
454 As well as Exim distribution tar files, the Exim web site contains a number of
455 differently formatted versions of the documentation. A recent addition to the
456 online information is the Exim wiki (&url(http://wiki.exim.org)),
457 which contains what used to be a separate FAQ, as well as various other
458 examples, tips, and know-how that have been contributed by Exim users.
461 An Exim Bugzilla exists at &url(http://bugs.exim.org). You can use
462 this to report bugs, and also to add items to the wish list. Please search
463 first to check that you are not duplicating a previous entry.
467 .section "Mailing lists" "SECID3"
468 .cindex "mailing lists" "for Exim users"
469 The following Exim mailing lists exist:
472 .row &'exim-users@exim.org'& "General discussion list"
473 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
474 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
475 .row &'exim-future@exim.org'& "Discussion of long-term development"
478 You can subscribe to these lists, change your existing subscriptions, and view
479 or search the archives via the mailing lists link on the Exim home page.
480 .cindex "Debian" "mailing list for"
481 If you are using a Debian distribution of Exim, you may wish to subscribe to
482 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
485 &url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
487 Please ask Debian-specific questions on this list and not on the general Exim
490 .section "Exim training" "SECID4"
491 .cindex "training courses"
492 Training courses in Cambridge (UK) used to be run annually by the author of
493 Exim, before he retired. At the time of writing, there are no plans to run
494 further Exim courses in Cambridge. However, if that changes, relevant
495 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
497 .section "Bug reports" "SECID5"
498 .cindex "bug reports"
499 .cindex "reporting bugs"
500 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
501 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
502 whether some behaviour is a bug or not, the best thing to do is to post a
503 message to the &'exim-dev'& mailing list and have it discussed.
507 .section "Where to find the Exim distribution" "SECTavail"
509 .cindex "distribution" "ftp site"
510 The master ftp site for the Exim distribution is
512 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
516 &*ftp://ftp.exim.org/pub/exim*&
518 The file references that follow are relative to the &_exim_& directories at
519 these sites. There are now quite a number of independent mirror sites around
520 the world. Those that I know about are listed in the file called &_Mirrors_&.
522 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
523 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
524 distributions), and &_Testing_& for testing versions. In the &_exim4_&
525 subdirectory, the current release can always be found in files called
528 &_exim-n.nn.tar.bz2_&
530 where &'n.nn'& is the highest such version number in the directory. The two
531 files contain identical data; the only difference is the type of compression.
532 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
534 .cindex "distribution" "signing details"
535 .cindex "distribution" "public key"
536 .cindex "public key for signed distribution"
537 The distributions are currently signed with Nigel Metheringham's GPG key. The
538 corresponding public key is available from a number of keyservers, and there is
539 also a copy in the file &_nigel-pubkey.asc_&. The signatures for the tar bundles are
542 &_exim-n.nn.tar.gz.asc_&
543 &_exim-n.nn.tar.bz2.asc_&
545 For each released version, the log of changes is made separately available in a
546 separate file in the directory &_ChangeLogs_& so that it is possible to
547 find out what has changed without having to download the entire distribution.
549 .cindex "documentation" "available formats"
550 The main distribution contains ASCII versions of this specification and other
551 documentation; other formats of the documents are available in separate files
552 inside the &_exim4_& directory of the FTP site:
554 &_exim-html-n.nn.tar.gz_&
555 &_exim-pdf-n.nn.tar.gz_&
556 &_exim-postscript-n.nn.tar.gz_&
557 &_exim-texinfo-n.nn.tar.gz_&
559 These tar files contain only the &_doc_& directory, not the complete
560 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
563 .section "Limitations" "SECID6"
565 .cindex "limitations of Exim"
566 .cindex "bang paths" "not handled by Exim"
567 Exim is designed for use as an Internet MTA, and therefore handles addresses in
568 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
569 simple two-component bang paths can be converted by a straightforward rewriting
570 configuration. This restriction does not prevent Exim from being interfaced to
571 UUCP as a transport mechanism, provided that domain addresses are used.
573 .cindex "domainless addresses"
574 .cindex "address" "without domain"
575 Exim insists that every address it handles has a domain attached. For incoming
576 local messages, domainless addresses are automatically qualified with a
577 configured domain value. Configuration options specify from which remote
578 systems unqualified addresses are acceptable. These are then qualified on
581 .cindex "transport" "external"
582 .cindex "external transports"
583 The only external transport mechanisms that are currently implemented are SMTP
584 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
585 transport is available, and there are facilities for writing messages to files
586 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
587 to send messages to other transport mechanisms such as UUCP, provided they can
588 handle domain-style addresses. Batched SMTP input is also catered for.
590 Exim is not designed for storing mail for dial-in hosts. When the volumes of
591 such mail are large, it is better to get the messages &"delivered"& into files
592 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
595 Although Exim does have basic facilities for scanning incoming messages, these
596 are not comprehensive enough to do full virus or spam scanning. Such operations
597 are best carried out using additional specialized software packages. If you
598 compile Exim with the content-scanning extension, straightforward interfaces to
599 a number of common scanners are provided.
603 .section "Run time configuration" "SECID7"
604 Exim's run time configuration is held in a single text file that is divided
605 into a number of sections. The entries in this file consist of keywords and
606 values, in the style of Smail 3 configuration files. A default configuration
607 file which is suitable for simple online installations is provided in the
608 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
611 .section "Calling interface" "SECID8"
612 .cindex "Sendmail compatibility" "command line interface"
613 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
614 can be a straight replacement for &_/usr/lib/sendmail_& or
615 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
616 about Sendmail in order to run Exim. For actions other than sending messages,
617 Sendmail-compatible options also exist, but those that produce output (for
618 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
619 format. There are also some additional options that are compatible with Smail
620 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
621 documents all Exim's command line options. This information is automatically
622 made into the man page that forms part of the Exim distribution.
624 Control of messages on the queue can be done via certain privileged command
625 line options. There is also an optional monitor program called &'eximon'&,
626 which displays current information in an X window, and which contains a menu
627 interface to Exim's command line administration options.
631 .section "Terminology" "SECID9"
632 .cindex "terminology definitions"
633 .cindex "body of message" "definition of"
634 The &'body'& of a message is the actual data that the sender wants to transmit.
635 It is the last part of a message, and is separated from the &'header'& (see
636 below) by a blank line.
638 .cindex "bounce message" "definition of"
639 When a message cannot be delivered, it is normally returned to the sender in a
640 delivery failure message or a &"non-delivery report"& (NDR). The term
641 &'bounce'& is commonly used for this action, and the error reports are often
642 called &'bounce messages'&. This is a convenient shorthand for &"delivery
643 failure error report"&. Such messages have an empty sender address in the
644 message's &'envelope'& (see below) to ensure that they cannot themselves give
645 rise to further bounce messages.
647 The term &'default'& appears frequently in this manual. It is used to qualify a
648 value which is used in the absence of any setting in the configuration. It may
649 also qualify an action which is taken unless a configuration setting specifies
652 The term &'defer'& is used when the delivery of a message to a specific
653 destination cannot immediately take place for some reason (a remote host may be
654 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
657 The word &'domain'& is sometimes used to mean all but the first component of a
658 host's name. It is &'not'& used in that sense here, where it normally refers to
659 the part of an email address following the @ sign.
661 .cindex "envelope, definition of"
662 .cindex "sender" "definition of"
663 A message in transit has an associated &'envelope'&, as well as a header and a
664 body. The envelope contains a sender address (to which bounce messages should
665 be delivered), and any number of recipient addresses. References to the
666 sender or the recipients of a message usually mean the addresses in the
667 envelope. An MTA uses these addresses for delivery, and for returning bounce
668 messages, not the addresses that appear in the header lines.
670 .cindex "message" "header, definition of"
671 .cindex "header section" "definition of"
672 The &'header'& of a message is the first part of a message's text, consisting
673 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
674 &'Subject:'&, etc. Long header lines can be split over several text lines by
675 indenting the continuations. The header is separated from the body by a blank
678 .cindex "local part" "definition of"
679 .cindex "domain" "definition of"
680 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
681 part of an email address that precedes the @ sign. The part that follows the
682 @ sign is called the &'domain'& or &'mail domain'&.
684 .cindex "local delivery" "definition of"
685 .cindex "remote delivery, definition of"
686 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
687 delivery to a file or a pipe on the local host from delivery by SMTP over
688 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
689 host it is running on are &'remote'&.
691 .cindex "return path" "definition of"
692 &'Return path'& is another name that is used for the sender address in a
695 .cindex "queue" "definition of"
696 The term &'queue'& is used to refer to the set of messages awaiting delivery,
697 because this term is in widespread use in the context of MTAs. However, in
698 Exim's case the reality is more like a pool than a queue, because there is
699 normally no ordering of waiting messages.
701 .cindex "queue runner" "definition of"
702 The term &'queue runner'& is used to describe a process that scans the queue
703 and attempts to deliver those messages whose retry times have come. This term
704 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
705 the waiting messages are normally processed in an unpredictable order.
707 .cindex "spool directory" "definition of"
708 The term &'spool directory'& is used for a directory in which Exim keeps the
709 messages on its queue &-- that is, those that it is in the process of
710 delivering. This should not be confused with the directory in which local
711 mailboxes are stored, which is called a &"spool directory"& by some people. In
712 the Exim documentation, &"spool"& is always used in the first sense.
719 . ////////////////////////////////////////////////////////////////////////////
720 . ////////////////////////////////////////////////////////////////////////////
722 .chapter "Incorporated code" "CHID2"
723 .cindex "incorporated code"
724 .cindex "regular expressions" "library"
726 A number of pieces of external code are included in the Exim distribution.
729 Regular expressions are supported in the main Exim program and in the
730 Exim monitor using the freely-distributable PCRE library, copyright
731 © University of Cambridge. The source to PCRE is no longer shipped with
732 Exim, so you will need to use the version of PCRE shipped with your system,
733 or obtain and install the full version of the library from
734 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
736 .cindex "cdb" "acknowledgment"
737 Support for the cdb (Constant DataBase) lookup method is provided by code
738 contributed by Nigel Metheringham of (at the time he contributed it) Planet
739 Online Ltd. The implementation is completely contained within the code of Exim.
740 It does not link against an external cdb library. The code contains the
741 following statements:
744 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
746 This program is free software; you can redistribute it and/or modify it under
747 the terms of the GNU General Public License as published by the Free Software
748 Foundation; either version 2 of the License, or (at your option) any later
750 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
751 the spec and sample code for cdb can be obtained from
752 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
753 some code from Dan Bernstein's implementation (which has no license
754 restrictions applied to it).
757 .cindex "SPA authentication"
758 .cindex "Samba project"
759 .cindex "Microsoft Secure Password Authentication"
760 Client support for Microsoft's &'Secure Password Authentication'& is provided
761 by code contributed by Marc Prud'hommeaux. Server support was contributed by
762 Tom Kistner. This includes code taken from the Samba project, which is released
766 .cindex "&'pwcheck'& daemon"
767 .cindex "&'pwauthd'& daemon"
768 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
769 by code taken from the Cyrus-SASL library and adapted by Alexander S.
770 Sabourenkov. The permission notice appears below, in accordance with the
771 conditions expressed therein.
774 Copyright © 2001 Carnegie Mellon University. All rights reserved.
776 Redistribution and use in source and binary forms, with or without
777 modification, are permitted provided that the following conditions
781 Redistributions of source code must retain the above copyright
782 notice, this list of conditions and the following disclaimer.
784 Redistributions in binary form must reproduce the above copyright
785 notice, this list of conditions and the following disclaimer in
786 the documentation and/or other materials provided with the
789 The name &"Carnegie Mellon University"& must not be used to
790 endorse or promote products derived from this software without
791 prior written permission. For permission or any other legal
792 details, please contact
794 Office of Technology Transfer
795 Carnegie Mellon University
797 Pittsburgh, PA 15213-3890
798 (412) 268-4387, fax: (412) 268-7395
799 tech-transfer@andrew.cmu.edu
802 Redistributions of any form whatsoever must retain the following
805 &"This product includes software developed by Computing Services
806 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
808 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
809 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
810 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
811 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
812 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
813 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
814 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
819 .cindex "Exim monitor" "acknowledgment"
822 The Exim Monitor program, which is an X-Window application, includes
823 modified versions of the Athena StripChart and TextPop widgets.
824 This code is copyright by DEC and MIT, and their permission notice appears
825 below, in accordance with the conditions expressed therein.
828 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
829 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
833 Permission to use, copy, modify, and distribute this software and its
834 documentation for any purpose and without fee is hereby granted,
835 provided that the above copyright notice appear in all copies and that
836 both that copyright notice and this permission notice appear in
837 supporting documentation, and that the names of Digital or MIT not be
838 used in advertising or publicity pertaining to distribution of the
839 software without specific, written prior permission.
841 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
842 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
843 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
844 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
845 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
846 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
851 Many people have contributed code fragments, some large, some small, that were
852 not covered by any specific licence requirements. It is assumed that the
853 contributors are happy to see their code incorporated into Exim under the GPL.
860 . ////////////////////////////////////////////////////////////////////////////
861 . ////////////////////////////////////////////////////////////////////////////
863 .chapter "How Exim receives and delivers mail" "CHID11" &&&
864 "Receiving and delivering mail"
867 .section "Overall philosophy" "SECID10"
868 .cindex "design philosophy"
869 Exim is designed to work efficiently on systems that are permanently connected
870 to the Internet and are handling a general mix of mail. In such circumstances,
871 most messages can be delivered immediately. Consequently, Exim does not
872 maintain independent queues of messages for specific domains or hosts, though
873 it does try to send several messages in a single SMTP connection after a host
874 has been down, and it also maintains per-host retry information.
877 .section "Policy control" "SECID11"
878 .cindex "policy control" "overview"
879 Policy controls are now an important feature of MTAs that are connected to the
880 Internet. Perhaps their most important job is to stop MTAs being abused as
881 &"open relays"& by misguided individuals who send out vast amounts of
882 unsolicited junk, and want to disguise its source. Exim provides flexible
883 facilities for specifying policy controls on incoming mail:
886 .cindex "&ACL;" "introduction"
887 Exim 4 (unlike previous versions of Exim) implements policy controls on
888 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
889 series of statements that may either grant or deny access. ACLs can be used at
890 several places in the SMTP dialogue while receiving a message from a remote
891 host. However, the most common places are after each RCPT command, and at the
892 very end of the message. The sysadmin can specify conditions for accepting or
893 rejecting individual recipients or the entire message, respectively, at these
894 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
897 An ACL is also available for locally generated, non-SMTP messages. In this
898 case, the only available actions are to accept or deny the entire message.
900 When Exim is compiled with the content-scanning extension, facilities are
901 provided in the ACL mechanism for passing the message to external virus and/or
902 spam scanning software. The result of such a scan is passed back to the ACL,
903 which can then use it to decide what to do with the message.
905 When a message has been received, either from a remote host or from the local
906 host, but before the final acknowledgment has been sent, a locally supplied C
907 function called &[local_scan()]& can be run to inspect the message and decide
908 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
909 is accepted, the list of recipients can be modified by the function.
911 Using the &[local_scan()]& mechanism is another way of calling external scanner
912 software. The &%SA-Exim%& add-on package works this way. It does not require
913 Exim to be compiled with the content-scanning extension.
915 After a message has been accepted, a further checking mechanism is available in
916 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
917 runs at the start of every delivery process.
922 .section "User filters" "SECID12"
923 .cindex "filter" "introduction"
924 .cindex "Sieve filter"
925 In a conventional Exim configuration, users are able to run private filters by
926 setting up appropriate &_.forward_& files in their home directories. See
927 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
928 configuration needed to support this, and the separate document entitled
929 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
930 of filtering are available:
933 Sieve filters are written in the standard filtering language that is defined
936 Exim filters are written in a syntax that is unique to Exim, but which is more
937 powerful than Sieve, which it pre-dates.
940 User filters are run as part of the routing process, described below.
944 .section "Message identification" "SECTmessiden"
945 .cindex "message ids" "details of format"
946 .cindex "format" "of message id"
947 .cindex "id of message"
952 Every message handled by Exim is given a &'message id'& which is sixteen
953 characters long. It is divided into three parts, separated by hyphens, for
954 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
955 normally encoding numbers in base 62. However, in the Darwin operating
956 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
957 (avoiding the use of lower case letters) is used instead, because the message
958 id is used to construct file names, and the names of files in those systems are
959 not always case-sensitive.
961 .cindex "pid (process id)" "re-use of"
962 The detail of the contents of the message id have changed as Exim has evolved.
963 Earlier versions relied on the operating system not re-using a process id (pid)
964 within one second. On modern operating systems, this assumption can no longer
965 be made, so the algorithm had to be changed. To retain backward compatibility,
966 the format of the message id was retained, which is why the following rules are
970 The first six characters of the message id are the time at which the message
971 started to be received, to a granularity of one second. That is, this field
972 contains the number of seconds since the start of the epoch (the normal Unix
973 way of representing the date and time of day).
975 After the first hyphen, the next six characters are the id of the process that
976 received the message.
978 There are two different possibilities for the final two characters:
980 .oindex "&%localhost_number%&"
981 If &%localhost_number%& is not set, this value is the fractional part of the
982 time of reception, normally in units of 1/2000 of a second, but for systems
983 that must use base 36 instead of base 62 (because of case-insensitive file
984 systems), the units are 1/1000 of a second.
986 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
987 the fractional part of the time, which in this case is in units of 1/200
992 After a message has been received, Exim waits for the clock to tick at the
993 appropriate resolution before proceeding, so that if another message is
994 received by the same process, or by another process with the same (re-used)
995 pid, it is guaranteed that the time will be different. In most cases, the clock
996 will already have ticked while the message was being received.
999 .section "Receiving mail" "SECID13"
1000 .cindex "receiving mail"
1001 .cindex "message" "reception"
1002 The only way Exim can receive mail from another host is using SMTP over
1003 TCP/IP, in which case the sender and recipient addresses are transferred using
1004 SMTP commands. However, from a locally running process (such as a user's MUA),
1005 there are several possibilities:
1008 If the process runs Exim with the &%-bm%& option, the message is read
1009 non-interactively (usually via a pipe), with the recipients taken from the
1010 command line, or from the body of the message if &%-t%& is also used.
1012 If the process runs Exim with the &%-bS%& option, the message is also read
1013 non-interactively, but in this case the recipients are listed at the start of
1014 the message in a series of SMTP RCPT commands, terminated by a DATA
1015 command. This is so-called &"batch SMTP"& format,
1016 but it isn't really SMTP. The SMTP commands are just another way of passing
1017 envelope addresses in a non-interactive submission.
1019 If the process runs Exim with the &%-bs%& option, the message is read
1020 interactively, using the SMTP protocol. A two-way pipe is normally used for
1021 passing data between the local process and the Exim process.
1022 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1023 example, the ACLs for SMTP commands are used for this form of submission.
1025 A local process may also make a TCP/IP call to the host's loopback address
1026 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1027 does not treat the loopback address specially. It treats all such connections
1028 in the same way as connections from other hosts.
1032 .cindex "message sender, constructed by Exim"
1033 .cindex "sender" "constructed by Exim"
1034 In the three cases that do not involve TCP/IP, the sender address is
1035 constructed from the login name of the user that called Exim and a default
1036 qualification domain (which can be set by the &%qualify_domain%& configuration
1037 option). For local or batch SMTP, a sender address that is passed using the
1038 SMTP MAIL command is ignored. However, the system administrator may allow
1039 certain users (&"trusted users"&) to specify a different sender address
1040 unconditionally, or all users to specify certain forms of different sender
1041 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1042 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1043 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1044 users to change sender addresses.
1046 Messages received by either of the non-interactive mechanisms are subject to
1047 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1048 (either over TCP/IP, or interacting with a local process) can be checked by a
1049 number of ACLs that operate at different times during the SMTP session. Either
1050 individual recipients, or the entire message, can be rejected if local policy
1051 requirements are not met. The &[local_scan()]& function (see chapter
1052 &<<CHAPlocalscan>>&) is run for all incoming messages.
1054 Exim can be configured not to start a delivery process when a message is
1055 received; this can be unconditional, or depend on the number of incoming SMTP
1056 connections or the system load. In these situations, new messages wait on the
1057 queue until a queue runner process picks them up. However, in standard
1058 configurations under normal conditions, delivery is started as soon as a
1059 message is received.
1065 .section "Handling an incoming message" "SECID14"
1066 .cindex "spool directory" "files that hold a message"
1067 .cindex "file" "how a message is held"
1068 When Exim accepts a message, it writes two files in its spool directory. The
1069 first contains the envelope information, the current status of the message, and
1070 the header lines, and the second contains the body of the message. The names of
1071 the two spool files consist of the message id, followed by &`-H`& for the
1072 file containing the envelope and header, and &`-D`& for the data file.
1074 .cindex "spool directory" "&_input_& sub-directory"
1075 By default all these message files are held in a single directory called
1076 &_input_& inside the general Exim spool directory. Some operating systems do
1077 not perform very well if the number of files in a directory gets large; to
1078 improve performance in such cases, the &%split_spool_directory%& option can be
1079 used. This causes Exim to split up the input files into 62 sub-directories
1080 whose names are single letters or digits. When this is done, the queue is
1081 processed one sub-directory at a time instead of all at once, which can improve
1082 overall performance even when there are not enough files in each directory to
1083 affect file system performance.
1085 The envelope information consists of the address of the message's sender and
1086 the addresses of the recipients. This information is entirely separate from
1087 any addresses contained in the header lines. The status of the message includes
1088 a list of recipients who have already received the message. The format of the
1089 first spool file is described in chapter &<<CHAPspool>>&.
1091 .cindex "rewriting" "addresses"
1092 Address rewriting that is specified in the rewrite section of the configuration
1093 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1094 both in the header lines and the envelope, at the time the message is accepted.
1095 If during the course of delivery additional addresses are generated (for
1096 example, via aliasing), these new addresses are rewritten as soon as they are
1097 generated. At the time a message is actually delivered (transported) further
1098 rewriting can take place; because this is a transport option, it can be
1099 different for different forms of delivery. It is also possible to specify the
1100 addition or removal of certain header lines at the time the message is
1101 delivered (see chapters &<<CHAProutergeneric>>& and
1102 &<<CHAPtransportgeneric>>&).
1106 .section "Life of a message" "SECID15"
1107 .cindex "message" "life of"
1108 .cindex "message" "frozen"
1109 A message remains in the spool directory until it is completely delivered to
1110 its recipients or to an error address, or until it is deleted by an
1111 administrator or by the user who originally created it. In cases when delivery
1112 cannot proceed &-- for example, when a message can neither be delivered to its
1113 recipients nor returned to its sender, the message is marked &"frozen"& on the
1114 spool, and no more deliveries are attempted.
1116 .cindex "frozen messages" "thawing"
1117 .cindex "message" "thawing frozen"
1118 An administrator can &"thaw"& such messages when the problem has been
1119 corrected, and can also freeze individual messages by hand if necessary. In
1120 addition, an administrator can force a delivery error, causing a bounce message
1123 .oindex "&%timeout_frozen_after%&"
1124 .oindex "&%ignore_bounce_errors_after%&"
1125 There are options called &%ignore_bounce_errors_after%& and
1126 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1127 The first applies only to frozen bounces, the second to any frozen messages.
1129 .cindex "message" "log file for"
1130 .cindex "log" "file for each message"
1131 While Exim is working on a message, it writes information about each delivery
1132 attempt to its main log file. This includes successful, unsuccessful, and
1133 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1134 lines are also written to a separate &'message log'& file for each message.
1135 These logs are solely for the benefit of the administrator, and are normally
1136 deleted along with the spool files when processing of a message is complete.
1137 The use of individual message logs can be disabled by setting
1138 &%no_message_logs%&; this might give an improvement in performance on very busy
1141 .cindex "journal file"
1142 .cindex "file" "journal"
1143 All the information Exim itself needs to set up a delivery is kept in the first
1144 spool file, along with the header lines. When a successful delivery occurs, the
1145 address is immediately written at the end of a journal file, whose name is the
1146 message id followed by &`-J`&. At the end of a delivery run, if there are some
1147 addresses left to be tried again later, the first spool file (the &`-H`& file)
1148 is updated to indicate which these are, and the journal file is then deleted.
1149 Updating the spool file is done by writing a new file and renaming it, to
1150 minimize the possibility of data loss.
1152 Should the system or the program crash after a successful delivery but before
1153 the spool file has been updated, the journal is left lying around. The next
1154 time Exim attempts to deliver the message, it reads the journal file and
1155 updates the spool file before proceeding. This minimizes the chances of double
1156 deliveries caused by crashes.
1160 .section "Processing an address for delivery" "SECTprocaddress"
1161 .cindex "drivers" "definition of"
1162 .cindex "router" "definition of"
1163 .cindex "transport" "definition of"
1164 The main delivery processing elements of Exim are called &'routers'& and
1165 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1166 number of them is provided in the source distribution, and compile-time options
1167 specify which ones are included in the binary. Run time options specify which
1168 ones are actually used for delivering messages.
1170 .cindex "drivers" "instance definition"
1171 Each driver that is specified in the run time configuration is an &'instance'&
1172 of that particular driver type. Multiple instances are allowed; for example,
1173 you can set up several different &(smtp)& transports, each with different
1174 option values that might specify different ports or different timeouts. Each
1175 instance has its own identifying name. In what follows we will normally use the
1176 instance name when discussing one particular instance (that is, one specific
1177 configuration of the driver), and the generic driver name when discussing
1178 the driver's features in general.
1180 A &'router'& is a driver that operates on an address, either determining how
1181 its delivery should happen, by assigning it to a specific transport, or
1182 converting the address into one or more new addresses (for example, via an
1183 alias file). A router may also explicitly choose to fail an address, causing it
1186 A &'transport'& is a driver that transmits a copy of the message from Exim's
1187 spool to some destination. There are two kinds of transport: for a &'local'&
1188 transport, the destination is a file or a pipe on the local host, whereas for a
1189 &'remote'& transport the destination is some other host. A message is passed
1190 to a specific transport as a result of successful routing. If a message has
1191 several recipients, it may be passed to a number of different transports.
1193 .cindex "preconditions" "definition of"
1194 An address is processed by passing it to each configured router instance in
1195 turn, subject to certain preconditions, until a router accepts the address or
1196 specifies that it should be bounced. We will describe this process in more
1197 detail shortly. First, as a simple example, we consider how each recipient
1198 address in a message is processed in a small configuration of three routers.
1200 To make this a more concrete example, it is described in terms of some actual
1201 routers, but remember, this is only an example. You can configure Exim's
1202 routers in many different ways, and there may be any number of routers in a
1205 The first router that is specified in a configuration is often one that handles
1206 addresses in domains that are not recognized specially by the local host. These
1207 are typically addresses for arbitrary domains on the Internet. A precondition
1208 is set up which looks for the special domains known to the host (for example,
1209 its own domain name), and the router is run for addresses that do &'not'&
1210 match. Typically, this is a router that looks up domains in the DNS in order to
1211 find the hosts to which this address routes. If it succeeds, the address is
1212 assigned to a suitable SMTP transport; if it does not succeed, the router is
1213 configured to fail the address.
1215 The second router is reached only when the domain is recognized as one that
1216 &"belongs"& to the local host. This router does redirection &-- also known as
1217 aliasing and forwarding. When it generates one or more new addresses from the
1218 original, each of them is routed independently from the start. Otherwise, the
1219 router may cause an address to fail, or it may simply decline to handle the
1220 address, in which case the address is passed to the next router.
1222 The final router in many configurations is one that checks to see if the
1223 address belongs to a local mailbox. The precondition may involve a check to
1224 see if the local part is the name of a login account, or it may look up the
1225 local part in a file or a database. If its preconditions are not met, or if
1226 the router declines, we have reached the end of the routers. When this happens,
1227 the address is bounced.
1231 .section "Processing an address for verification" "SECID16"
1232 .cindex "router" "for verification"
1233 .cindex "verifying address" "overview"
1234 As well as being used to decide how to deliver to an address, Exim's routers
1235 are also used for &'address verification'&. Verification can be requested as
1236 one of the checks to be performed in an ACL for incoming messages, on both
1237 sender and recipient addresses, and it can be tested using the &%-bv%& and
1238 &%-bvs%& command line options.
1240 When an address is being verified, the routers are run in &"verify mode"&. This
1241 does not affect the way the routers work, but it is a state that can be
1242 detected. By this means, a router can be skipped or made to behave differently
1243 when verifying. A common example is a configuration in which the first router
1244 sends all messages to a message-scanning program, unless they have been
1245 previously scanned. Thus, the first router accepts all addresses without any
1246 checking, making it useless for verifying. Normally, the &%no_verify%& option
1247 would be set for such a router, causing it to be skipped in verify mode.
1252 .section "Running an individual router" "SECTrunindrou"
1253 .cindex "router" "running details"
1254 .cindex "preconditions" "checking"
1255 .cindex "router" "result of running"
1256 As explained in the example above, a number of preconditions are checked before
1257 running a router. If any are not met, the router is skipped, and the address is
1258 passed to the next router. When all the preconditions on a router &'are'& met,
1259 the router is run. What happens next depends on the outcome, which is one of
1263 &'accept'&: The router accepts the address, and either assigns it to a
1264 transport, or generates one or more &"child"& addresses. Processing the
1265 original address ceases,
1266 .oindex "&%unseen%&"
1267 unless the &%unseen%& option is set on the router. This option
1268 can be used to set up multiple deliveries with different routing (for example,
1269 for keeping archive copies of messages). When &%unseen%& is set, the address is
1270 passed to the next router. Normally, however, an &'accept'& return marks the
1273 Any child addresses generated by the router are processed independently,
1274 starting with the first router by default. It is possible to change this by
1275 setting the &%redirect_router%& option to specify which router to start at for
1276 child addresses. Unlike &%pass_router%& (see below) the router specified by
1277 &%redirect_router%& may be anywhere in the router configuration.
1279 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1280 requests that the address be passed to another router. By default the address
1281 is passed to the next router, but this can be changed by setting the
1282 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1283 must be below the current router (to avoid loops).
1285 &'decline'&: The router declines to accept the address because it does not
1286 recognize it at all. By default, the address is passed to the next router, but
1287 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1288 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1289 &'decline'& into &'fail'&.
1291 &'fail'&: The router determines that the address should fail, and queues it for
1292 the generation of a bounce message. There is no further processing of the
1293 original address unless &%unseen%& is set on the router.
1295 &'defer'&: The router cannot handle the address at the present time. (A
1296 database may be offline, or a DNS lookup may have timed out.) No further
1297 processing of the address happens in this delivery attempt. It is tried again
1298 next time the message is considered for delivery.
1300 &'error'&: There is some error in the router (for example, a syntax error in
1301 its configuration). The action is as for defer.
1304 If an address reaches the end of the routers without having been accepted by
1305 any of them, it is bounced as unrouteable. The default error message in this
1306 situation is &"unrouteable address"&, but you can set your own message by
1307 making use of the &%cannot_route_message%& option. This can be set for any
1308 router; the value from the last router that &"saw"& the address is used.
1310 Sometimes while routing you want to fail a delivery when some conditions are
1311 met but others are not, instead of passing the address on for further routing.
1312 You can do this by having a second router that explicitly fails the delivery
1313 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1314 facility for this purpose.
1317 .section "Duplicate addresses" "SECID17"
1318 .cindex "case of local parts"
1319 .cindex "address duplicate, discarding"
1320 .cindex "duplicate addresses"
1321 Once routing is complete, Exim scans the addresses that are assigned to local
1322 and remote transports, and discards any duplicates that it finds. During this
1323 check, local parts are treated as case-sensitive. This happens only when
1324 actually delivering a message; when testing routers with &%-bt%&, all the
1325 routed addresses are shown.
1329 .section "Router preconditions" "SECTrouprecon"
1330 .cindex "router" "preconditions, order of processing"
1331 .cindex "preconditions" "order of processing"
1332 The preconditions that are tested for each router are listed below, in the
1333 order in which they are tested. The individual configuration options are
1334 described in more detail in chapter &<<CHAProutergeneric>>&.
1337 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1338 the local parts handled by the router may or must have certain prefixes and/or
1339 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1340 skipped. These conditions are tested first. When an affix is present, it is
1341 removed from the local part before further processing, including the evaluation
1342 of any other conditions.
1344 Routers can be designated for use only when not verifying an address, that is,
1345 only when routing it for delivery (or testing its delivery routing). If the
1346 &%verify%& option is set false, the router is skipped when Exim is verifying an
1348 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1349 &%verify_recipient%&, which independently control the use of the router for
1350 sender and recipient verification. You can set these options directly if
1351 you want a router to be used for only one type of verification.
1353 If the &%address_test%& option is set false, the router is skipped when Exim is
1354 run with the &%-bt%& option to test an address routing. This can be helpful
1355 when the first router sends all new messages to a scanner of some sort; it
1356 makes it possible to use &%-bt%& to test subsequent delivery routing without
1357 having to simulate the effect of the scanner.
1359 Routers can be designated for use only when verifying an address, as
1360 opposed to routing it for delivery. The &%verify_only%& option controls this.
1362 Individual routers can be explicitly skipped when running the routers to
1363 check an address given in the SMTP EXPN command (see the &%expn%& option).
1365 If the &%domains%& option is set, the domain of the address must be in the set
1366 of domains that it defines.
1368 .vindex "&$local_part_prefix$&"
1369 .vindex "&$local_part$&"
1370 .vindex "&$local_part_suffix$&"
1371 If the &%local_parts%& option is set, the local part of the address must be in
1372 the set of local parts that it defines. If &%local_part_prefix%& or
1373 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1374 part before this check. If you want to do precondition tests on local parts
1375 that include affixes, you can do so by using a &%condition%& option (see below)
1376 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1377 &$local_part_suffix$& as necessary.
1379 .vindex "&$local_user_uid$&"
1380 .vindex "&$local_user_gid$&"
1382 If the &%check_local_user%& option is set, the local part must be the name of
1383 an account on the local host. If this check succeeds, the uid and gid of the
1384 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1385 user's home directory is placed in &$home$&; these values can be used in the
1386 remaining preconditions.
1388 If the &%router_home_directory%& option is set, it is expanded at this point,
1389 because it overrides the value of &$home$&. If this expansion were left till
1390 later, the value of &$home$& as set by &%check_local_user%& would be used in
1391 subsequent tests. Having two different values of &$home$& in the same router
1392 could lead to confusion.
1394 If the &%senders%& option is set, the envelope sender address must be in the
1395 set of addresses that it defines.
1397 If the &%require_files%& option is set, the existence or non-existence of
1398 specified files is tested.
1400 .cindex "customizing" "precondition"
1401 If the &%condition%& option is set, it is evaluated and tested. This option
1402 uses an expanded string to allow you to set up your own custom preconditions.
1403 Expanded strings are described in chapter &<<CHAPexpand>>&.
1407 Note that &%require_files%& comes near the end of the list, so you cannot use
1408 it to check for the existence of a file in which to lookup up a domain, local
1409 part, or sender. However, as these options are all expanded, you can use the
1410 &%exists%& expansion condition to make such tests within each condition. The
1411 &%require_files%& option is intended for checking files that the router may be
1412 going to use internally, or which are needed by a specific transport (for
1413 example, &_.procmailrc_&).
1417 .section "Delivery in detail" "SECID18"
1418 .cindex "delivery" "in detail"
1419 When a message is to be delivered, the sequence of events is as follows:
1422 If a system-wide filter file is specified, the message is passed to it. The
1423 filter may add recipients to the message, replace the recipients, discard the
1424 message, cause a new message to be generated, or cause the message delivery to
1425 fail. The format of the system filter file is the same as for Exim user filter
1426 files, described in the separate document entitled &'Exim's interfaces to mail
1428 .cindex "Sieve filter" "not available for system filter"
1429 (&*Note*&: Sieve cannot be used for system filter files.)
1431 Some additional features are available in system filters &-- see chapter
1432 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1433 filter only once per delivery attempt, however many recipients it has. However,
1434 if there are several delivery attempts because one or more addresses could not
1435 be immediately delivered, the system filter is run each time. The filter
1436 condition &%first_delivery%& can be used to detect the first run of the system
1439 Each recipient address is offered to each configured router in turn, subject to
1440 its preconditions, until one is able to handle it. If no router can handle the
1441 address, that is, if they all decline, the address is failed. Because routers
1442 can be targeted at particular domains, several locally handled domains can be
1443 processed entirely independently of each other.
1445 .cindex "routing" "loops in"
1446 .cindex "loop" "while routing"
1447 A router that accepts an address may assign it to a local or a remote
1448 transport. However, the transport is not run at this time. Instead, the address
1449 is placed on a list for the particular transport, which will be run later.
1450 Alternatively, the router may generate one or more new addresses (typically
1451 from alias, forward, or filter files). New addresses are fed back into this
1452 process from the top, but in order to avoid loops, a router ignores any address
1453 which has an identically-named ancestor that was processed by itself.
1455 When all the routing has been done, addresses that have been successfully
1456 handled are passed to their assigned transports. When local transports are
1457 doing real local deliveries, they handle only one address at a time, but if a
1458 local transport is being used as a pseudo-remote transport (for example, to
1459 collect batched SMTP messages for transmission by some other means) multiple
1460 addresses can be handled. Remote transports can always handle more than one
1461 address at a time, but can be configured not to do so, or to restrict multiple
1462 addresses to the same domain.
1464 Each local delivery to a file or a pipe runs in a separate process under a
1465 non-privileged uid, and these deliveries are run one at a time. Remote
1466 deliveries also run in separate processes, normally under a uid that is private
1467 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1468 run in parallel. The maximum number of simultaneous remote deliveries for any
1469 one message is set by the &%remote_max_parallel%& option.
1470 The order in which deliveries are done is not defined, except that all local
1471 deliveries happen before any remote deliveries.
1473 .cindex "queue runner"
1474 When it encounters a local delivery during a queue run, Exim checks its retry
1475 database to see if there has been a previous temporary delivery failure for the
1476 address before running the local transport. If there was a previous failure,
1477 Exim does not attempt a new delivery until the retry time for the address is
1478 reached. However, this happens only for delivery attempts that are part of a
1479 queue run. Local deliveries are always attempted when delivery immediately
1480 follows message reception, even if retry times are set for them. This makes for
1481 better behaviour if one particular message is causing problems (for example,
1482 causing quota overflow, or provoking an error in a filter file).
1484 .cindex "delivery" "retry in remote transports"
1485 Remote transports do their own retry handling, since an address may be
1486 deliverable to one of a number of hosts, each of which may have a different
1487 retry time. If there have been previous temporary failures and no host has
1488 reached its retry time, no delivery is attempted, whether in a queue run or
1489 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1491 If there were any permanent errors, a bounce message is returned to an
1492 appropriate address (the sender in the common case), with details of the error
1493 for each failing address. Exim can be configured to send copies of bounce
1494 messages to other addresses.
1496 .cindex "delivery" "deferral"
1497 If one or more addresses suffered a temporary failure, the message is left on
1498 the queue, to be tried again later. Delivery of these addresses is said to be
1501 When all the recipient addresses have either been delivered or bounced,
1502 handling of the message is complete. The spool files and message log are
1503 deleted, though the message log can optionally be preserved if required.
1509 .section "Retry mechanism" "SECID19"
1510 .cindex "delivery" "retry mechanism"
1511 .cindex "retry" "description of mechanism"
1512 .cindex "queue runner"
1513 Exim's mechanism for retrying messages that fail to get delivered at the first
1514 attempt is the queue runner process. You must either run an Exim daemon that
1515 uses the &%-q%& option with a time interval to start queue runners at regular
1516 intervals, or use some other means (such as &'cron'&) to start them. If you do
1517 not arrange for queue runners to be run, messages that fail temporarily at the
1518 first attempt will remain on your queue for ever. A queue runner process works
1519 its way through the queue, one message at a time, trying each delivery that has
1520 passed its retry time.
1521 You can run several queue runners at once.
1523 Exim uses a set of configured rules to determine when next to retry the failing
1524 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1525 should give up trying to deliver to the address, at which point it generates a
1526 bounce message. If no retry rules are set for a particular host, address, and
1527 error combination, no retries are attempted, and temporary errors are treated
1532 .section "Temporary delivery failure" "SECID20"
1533 .cindex "delivery" "temporary failure"
1534 There are many reasons why a message may not be immediately deliverable to a
1535 particular address. Failure to connect to a remote machine (because it, or the
1536 connection to it, is down) is one of the most common. Temporary failures may be
1537 detected during routing as well as during the transport stage of delivery.
1538 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1539 is on a file system where the user is over quota. Exim can be configured to
1540 impose its own quotas on local mailboxes; where system quotas are set they will
1543 If a host is unreachable for a period of time, a number of messages may be
1544 waiting for it by the time it recovers, and sending them in a single SMTP
1545 connection is clearly beneficial. Whenever a delivery to a remote host is
1548 .cindex "hints database"
1549 Exim makes a note in its hints database, and whenever a successful
1550 SMTP delivery has happened, it looks to see if any other messages are waiting
1551 for the same host. If any are found, they are sent over the same SMTP
1552 connection, subject to a configuration limit as to the maximum number in any
1558 .section "Permanent delivery failure" "SECID21"
1559 .cindex "delivery" "permanent failure"
1560 .cindex "bounce message" "when generated"
1561 When a message cannot be delivered to some or all of its intended recipients, a
1562 bounce message is generated. Temporary delivery failures turn into permanent
1563 errors when their timeout expires. All the addresses that fail in a given
1564 delivery attempt are listed in a single message. If the original message has
1565 many recipients, it is possible for some addresses to fail in one delivery
1566 attempt and others to fail subsequently, giving rise to more than one bounce
1567 message. The wording of bounce messages can be customized by the administrator.
1568 See chapter &<<CHAPemsgcust>>& for details.
1570 .cindex "&'X-Failed-Recipients:'& header line"
1571 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1572 failed addresses, for the benefit of programs that try to analyse such messages
1575 .cindex "bounce message" "recipient of"
1576 A bounce message is normally sent to the sender of the original message, as
1577 obtained from the message's envelope. For incoming SMTP messages, this is the
1578 address given in the MAIL command. However, when an address is expanded via a
1579 forward or alias file, an alternative address can be specified for delivery
1580 failures of the generated addresses. For a mailing list expansion (see section
1581 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1586 .section "Failures to deliver bounce messages" "SECID22"
1587 .cindex "bounce message" "failure to deliver"
1588 If a bounce message (either locally generated or received from a remote host)
1589 itself suffers a permanent delivery failure, the message is left on the queue,
1590 but it is frozen, awaiting the attention of an administrator. There are options
1591 that can be used to make Exim discard such failed messages, or to keep them
1592 for only a short time (see &%timeout_frozen_after%& and
1593 &%ignore_bounce_errors_after%&).
1599 . ////////////////////////////////////////////////////////////////////////////
1600 . ////////////////////////////////////////////////////////////////////////////
1602 .chapter "Building and installing Exim" "CHID3"
1603 .scindex IIDbuex "building Exim"
1605 .section "Unpacking" "SECID23"
1606 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1607 creates a directory with the name of the current release (for example,
1608 &_exim-&version;_&) into which the following files are placed:
1611 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1612 .irow &_CHANGES_& "contains a reference to where changes are &&&
1614 .irow &_LICENCE_& "the GNU General Public Licence"
1615 .irow &_Makefile_& "top-level make file"
1616 .irow &_NOTICE_& "conditions for the use of Exim"
1617 .irow &_README_& "list of files, directories and simple build &&&
1621 Other files whose names begin with &_README_& may also be present. The
1622 following subdirectories are created:
1625 .irow &_Local_& "an empty directory for local configuration files"
1626 .irow &_OS_& "OS-specific files"
1627 .irow &_doc_& "documentation files"
1628 .irow &_exim_monitor_& "source files for the Exim monitor"
1629 .irow &_scripts_& "scripts used in the build process"
1630 .irow &_src_& "remaining source files"
1631 .irow &_util_& "independent utilities"
1634 The main utility programs are contained in the &_src_& directory, and are built
1635 with the Exim binary. The &_util_& directory contains a few optional scripts
1636 that may be useful to some sites.
1639 .section "Multiple machine architectures and operating systems" "SECID24"
1640 .cindex "building Exim" "multiple OS/architectures"
1641 The building process for Exim is arranged to make it easy to build binaries for
1642 a number of different architectures and operating systems from the same set of
1643 source files. Compilation does not take place in the &_src_& directory.
1644 Instead, a &'build directory'& is created for each architecture and operating
1646 .cindex "symbolic link" "to build directory"
1647 Symbolic links to the sources are installed in this directory, which is where
1648 the actual building takes place. In most cases, Exim can discover the machine
1649 architecture and operating system for itself, but the defaults can be
1650 overridden if necessary.
1653 .section "PCRE library" "SECTpcre"
1654 .cindex "PCRE library"
1655 Exim no longer has an embedded PCRE library as the vast majority of
1656 modern systems include PCRE as a system library, although you may need
1657 to install the PCRE or PCRE development package for your operating
1658 system. If your system has a normal PCRE installation the Exim build
1659 process will need no further configuration. If the library or the
1660 headers are in an unusual location you will need to set the PCRE_LIBS
1661 and INCLUDE directives appropriately. If your operating system has no
1662 PCRE support then you will need to obtain and build the current PCRE
1663 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1665 .section "DBM libraries" "SECTdb"
1666 .cindex "DBM libraries" "discussion of"
1667 .cindex "hints database" "DBM files used for"
1668 Even if you do not use any DBM files in your configuration, Exim still needs a
1669 DBM library in order to operate, because it uses indexed files for its hints
1670 databases. Unfortunately, there are a number of DBM libraries in existence, and
1671 different operating systems often have different ones installed.
1673 .cindex "Solaris" "DBM library for"
1674 .cindex "IRIX, DBM library for"
1675 .cindex "BSD, DBM library for"
1676 .cindex "Linux, DBM library for"
1677 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1678 Linux distribution, the DBM configuration should happen automatically, and you
1679 may be able to ignore this section. Otherwise, you may have to learn more than
1680 you would like about DBM libraries from what follows.
1682 .cindex "&'ndbm'& DBM library"
1683 Licensed versions of Unix normally contain a library of DBM functions operating
1684 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1685 versions of Unix seem to vary in what they contain as standard. In particular,
1686 some early versions of Linux have no default DBM library, and different
1687 distributors have chosen to bundle different libraries with their packaged
1688 versions. However, the more recent releases seem to have standardized on the
1689 Berkeley DB library.
1691 Different DBM libraries have different conventions for naming the files they
1692 use. When a program opens a file called &_dbmfile_&, there are several
1696 A traditional &'ndbm'& implementation, such as that supplied as part of
1697 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1699 .cindex "&'gdbm'& DBM library"
1700 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1701 compatibility interface it makes two different hard links to it with names
1702 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1703 file name is used unmodified.
1705 .cindex "Berkeley DB library"
1706 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1707 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1708 programmer exactly the same as the traditional &'ndbm'& implementation.
1710 If the Berkeley package is used in its native mode, it operates on a single
1711 file called &_dbmfile_&; the programmer's interface is somewhat different to
1712 the traditional &'ndbm'& interface.
1714 To complicate things further, there are several very different versions of the
1715 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1716 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1717 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1718 versions of Berkeley DB can be obtained from
1719 &url(http://www.sleepycat.com/).
1721 .cindex "&'tdb'& DBM library"
1722 Yet another DBM library, called &'tdb'&, is available from
1723 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1724 operates on a single file.
1728 .cindex "DBM libraries" "configuration for building"
1729 Exim and its utilities can be compiled to use any of these interfaces. In order
1730 to use any version of the Berkeley DB package in native mode, you must set
1731 USE_DB in an appropriate configuration file (typically
1732 &_Local/Makefile_&). For example:
1736 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1737 error is diagnosed if you set more than one of these.
1739 At the lowest level, the build-time configuration sets none of these options,
1740 thereby assuming an interface of type (1). However, some operating system
1741 configuration files (for example, those for the BSD operating systems and
1742 Linux) assume type (4) by setting USE_DB as their default, and the
1743 configuration files for Cygwin set USE_GDBM. Anything you set in
1744 &_Local/Makefile_&, however, overrides these system defaults.
1746 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1747 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1748 in one of these lines:
1753 Settings like that will work if the DBM library is installed in the standard
1754 place. Sometimes it is not, and the library's header file may also not be in
1755 the default path. You may need to set INCLUDE to specify where the header
1756 file is, and to specify the path to the library more fully in DBMLIB, as in
1759 INCLUDE=-I/usr/local/include/db-4.1
1760 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1762 There is further detailed discussion about the various DBM libraries in the
1763 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1767 .section "Pre-building configuration" "SECID25"
1768 .cindex "building Exim" "pre-building configuration"
1769 .cindex "configuration for building Exim"
1770 .cindex "&_Local/Makefile_&"
1771 .cindex "&_src/EDITME_&"
1772 Before building Exim, a local configuration file that specifies options
1773 independent of any operating system has to be created with the name
1774 &_Local/Makefile_&. A template for this file is supplied as the file
1775 &_src/EDITME_&, and it contains full descriptions of all the option settings
1776 therein. These descriptions are therefore not repeated here. If you are
1777 building Exim for the first time, the simplest thing to do is to copy
1778 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1780 There are three settings that you must supply, because Exim will not build
1781 without them. They are the location of the run time configuration file
1782 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1783 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1784 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1785 a colon-separated list of file names; Exim uses the first of them that exists.
1787 There are a few other parameters that can be specified either at build time or
1788 at run time, to enable the same binary to be used on a number of different
1789 machines. However, if the locations of Exim's spool directory and log file
1790 directory (if not within the spool directory) are fixed, it is recommended that
1791 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1792 detected early in Exim's execution (such as a malformed configuration file) can
1795 .cindex "content scanning" "specifying at build time"
1796 Exim's interfaces for calling virus and spam scanning software directly from
1797 access control lists are not compiled by default. If you want to include these
1798 facilities, you need to set
1800 WITH_CONTENT_SCAN=yes
1802 in your &_Local/Makefile_&. For details of the facilities themselves, see
1803 chapter &<<CHAPexiscan>>&.
1806 .cindex "&_Local/eximon.conf_&"
1807 .cindex "&_exim_monitor/EDITME_&"
1808 If you are going to build the Exim monitor, a similar configuration process is
1809 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1810 your installation and saved under the name &_Local/eximon.conf_&. If you are
1811 happy with the default settings described in &_exim_monitor/EDITME_&,
1812 &_Local/eximon.conf_& can be empty, but it must exist.
1814 This is all the configuration that is needed in straightforward cases for known
1815 operating systems. However, the building process is set up so that it is easy
1816 to override options that are set by default or by operating-system-specific
1817 configuration files, for example to change the name of the C compiler, which
1818 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1823 .section "Support for iconv()" "SECID26"
1824 .cindex "&[iconv()]& support"
1826 The contents of header lines in messages may be encoded according to the rules
1827 described RFC 2047. This makes it possible to transmit characters that are not
1828 in the ASCII character set, and to label them as being in a particular
1829 character set. When Exim is inspecting header lines by means of the &%$h_%&
1830 mechanism, it decodes them, and translates them into a specified character set
1831 (default ISO-8859-1). The translation is possible only if the operating system
1832 supports the &[iconv()]& function.
1834 However, some of the operating systems that supply &[iconv()]& do not support
1835 very many conversions. The GNU &%libiconv%& library (available from
1836 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1837 systems to remedy this deficiency, as well as on systems that do not supply
1838 &[iconv()]& at all. After installing &%libiconv%&, you should add
1842 to your &_Local/Makefile_& and rebuild Exim.
1846 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1847 .cindex "TLS" "including support for TLS"
1848 .cindex "encryption" "including support for"
1849 .cindex "SUPPORT_TLS"
1850 .cindex "OpenSSL" "building Exim with"
1851 .cindex "GnuTLS" "building Exim with"
1852 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1853 command as per RFC 2487. It can also support legacy clients that expect to
1854 start a TLS session immediately on connection to a non-standard port (see the
1855 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1858 If you want to build Exim with TLS support, you must first install either the
1859 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1862 If OpenSSL is installed, you should set
1865 TLS_LIBS=-lssl -lcrypto
1867 in &_Local/Makefile_&. You may also need to specify the locations of the
1868 OpenSSL library and include files. For example:
1871 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1872 TLS_INCLUDE=-I/usr/local/openssl/include/
1874 .cindex "USE_GNUTLS"
1875 If GnuTLS is installed, you should set
1879 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1881 in &_Local/Makefile_&, and again you may need to specify the locations of the
1882 library and include files. For example:
1886 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1887 TLS_INCLUDE=-I/usr/gnu/include
1889 You do not need to set TLS_INCLUDE if the relevant directory is already
1890 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1891 given in chapter &<<CHAPTLS>>&.
1896 .section "Use of tcpwrappers" "SECID27"
1897 .cindex "tcpwrappers, building Exim to support"
1898 .cindex "USE_TCP_WRAPPERS"
1899 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1900 .cindex "tcp_wrappers_daemon_name"
1901 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1902 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1903 alternative to Exim's own checking facilities for installations that are
1904 already making use of &'tcpwrappers'& for other purposes. To do this, you
1905 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1906 &_tcpd.h_& to be available at compile time, and also ensure that the library
1907 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1908 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1911 USE_TCP_WRAPPERS=yes
1912 CFLAGS=-O -I/usr/local/include
1913 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1915 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1916 files is &"exim"&. For example, the line
1918 exim : LOCAL 192.168.1. .friendly.domain.example
1920 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1921 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1922 All other connections are denied. The daemon name used by &'tcpwrappers'&
1923 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1924 in &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1925 configure file. Consult the &'tcpwrappers'& documentation for
1930 .section "Including support for IPv6" "SECID28"
1931 .cindex "IPv6" "including support for"
1932 Exim contains code for use on systems that have IPv6 support. Setting
1933 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1934 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1935 where the IPv6 support is not fully integrated into the normal include and
1938 Two different types of DNS record for handling IPv6 addresses have been
1939 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1940 currently seen as the mainstream. Another record type called A6 was proposed
1941 as better than AAAA because it had more flexibility. However, it was felt to be
1942 over-complex, and its status was reduced to &"experimental"&. It is not known
1943 if anyone is actually using A6 records. Exim has support for A6 records, but
1944 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1945 support has not been tested for some time.
1949 .section "The building process" "SECID29"
1950 .cindex "build directory"
1951 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
1952 created, run &'make'& at the top level. It determines the architecture and
1953 operating system types, and creates a build directory if one does not exist.
1954 For example, on a Sun system running Solaris 8, the directory
1955 &_build-SunOS5-5.8-sparc_& is created.
1956 .cindex "symbolic link" "to source files"
1957 Symbolic links to relevant source files are installed in the build directory.
1959 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
1960 building process fails if it is set.
1962 If this is the first time &'make'& has been run, it calls a script that builds
1963 a make file inside the build directory, using the configuration files from the
1964 &_Local_& directory. The new make file is then passed to another instance of
1965 &'make'&. This does the real work, building a number of utility scripts, and
1966 then compiling and linking the binaries for the Exim monitor (if configured), a
1967 number of utility programs, and finally Exim itself. The command &`make
1968 makefile`& can be used to force a rebuild of the make file in the build
1969 directory, should this ever be necessary.
1971 If you have problems building Exim, check for any comments there may be in the
1972 &_README_& file concerning your operating system, and also take a look at the
1973 FAQ, where some common problems are covered.
1977 .section 'Output from &"make"&' "SECID283"
1978 The output produced by the &'make'& process for compile lines is often very
1979 unreadable, because these lines can be very long. For this reason, the normal
1980 output is suppressed by default, and instead output similar to that which
1981 appears when compiling the 2.6 Linux kernel is generated: just a short line for
1982 each module that is being compiled or linked. However, it is still possible to
1983 get the full output, by calling &'make'& like this:
1987 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
1988 command reflection in &'make'&. When you ask for the full output, it is
1989 given in addition to the short output.
1993 .section "Overriding build-time options for Exim" "SECToverride"
1994 .cindex "build-time options, overriding"
1995 The main make file that is created at the beginning of the building process
1996 consists of the concatenation of a number of files which set configuration
1997 values, followed by a fixed set of &'make'& instructions. If a value is set
1998 more than once, the last setting overrides any previous ones. This provides a
1999 convenient way of overriding defaults. The files that are concatenated are, in
2002 &_OS/Makefile-Default_&
2003 &_OS/Makefile-_&<&'ostype'&>
2005 &_Local/Makefile-_&<&'ostype'&>
2006 &_Local/Makefile-_&<&'archtype'&>
2007 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2008 &_OS/Makefile-Base_&
2010 .cindex "&_Local/Makefile_&"
2011 .cindex "building Exim" "operating system type"
2012 .cindex "building Exim" "architecture type"
2013 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2014 architecture type. &_Local/Makefile_& is required to exist, and the building
2015 process fails if it is absent. The other three &_Local_& files are optional,
2016 and are often not needed.
2018 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2019 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2020 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2021 values are used, thereby providing a means of forcing particular settings.
2022 Otherwise, the scripts try to get values from the &%uname%& command. If this
2023 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2024 of &'ad hoc'& transformations are then applied, to produce the standard names
2025 that Exim expects. You can run these scripts directly from the shell in order
2026 to find out what values are being used on your system.
2029 &_OS/Makefile-Default_& contains comments about the variables that are set
2030 therein. Some (but not all) are mentioned below. If there is something that
2031 needs changing, review the contents of this file and the contents of the make
2032 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2036 .cindex "building Exim" "overriding default settings"
2037 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2038 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2039 need to change the original files. Instead, you should make the changes by
2040 putting the new values in an appropriate &_Local_& file. For example,
2041 .cindex "Tru64-Unix build-time settings"
2042 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2043 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2044 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2045 called with the option &%-std1%&, to make it recognize some of the features of
2046 Standard C that Exim uses. (Most other compilers recognize Standard C by
2047 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2048 containing the lines
2053 If you are compiling for just one operating system, it may be easier to put
2054 these lines directly into &_Local/Makefile_&.
2056 Keeping all your local configuration settings separate from the distributed
2057 files makes it easy to transfer them to new versions of Exim simply by copying
2058 the contents of the &_Local_& directory.
2061 .cindex "NIS lookup type" "including support for"
2062 .cindex "NIS+ lookup type" "including support for"
2063 .cindex "LDAP" "including support for"
2064 .cindex "lookup" "inclusion in binary"
2065 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2066 lookup, but not all systems have these components installed, so the default is
2067 not to include the relevant code in the binary. All the different kinds of file
2068 and database lookup that Exim supports are implemented as separate code modules
2069 which are included only if the relevant compile-time options are set. In the
2070 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2076 and similar settings apply to the other lookup types. They are all listed in
2077 &_src/EDITME_&. In many cases the relevant include files and interface
2078 libraries need to be installed before compiling Exim.
2079 .cindex "cdb" "including support for"
2080 However, there are some optional lookup types (such as cdb) for which
2081 the code is entirely contained within Exim, and no external include
2082 files or libraries are required. When a lookup type is not included in the
2083 binary, attempts to configure Exim to use it cause run time configuration
2086 .cindex "Perl" "including support for"
2087 Exim can be linked with an embedded Perl interpreter, allowing Perl
2088 subroutines to be called during string expansion. To enable this facility,
2092 must be defined in &_Local/Makefile_&. Details of this facility are given in
2093 chapter &<<CHAPperl>>&.
2095 .cindex "X11 libraries, location of"
2096 The location of the X11 libraries is something that varies a lot between
2097 operating systems, and there may be different versions of X11 to cope
2098 with. Exim itself makes no use of X11, but if you are compiling the Exim
2099 monitor, the X11 libraries must be available.
2100 The following three variables are set in &_OS/Makefile-Default_&:
2103 XINCLUDE=-I$(X11)/include
2104 XLFLAGS=-L$(X11)/lib
2106 These are overridden in some of the operating-system configuration files. For
2107 example, in &_OS/Makefile-SunOS5_& there is
2110 XINCLUDE=-I$(X11)/include
2111 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2113 If you need to override the default setting for your operating system, place a
2114 definition of all three of these variables into your
2115 &_Local/Makefile-<ostype>_& file.
2118 If you need to add any extra libraries to the link steps, these can be put in a
2119 variable called EXTRALIBS, which appears in all the link commands, but by
2120 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2121 command for linking the main Exim binary, and not for any associated utilities.
2123 .cindex "DBM libraries" "configuration for building"
2124 There is also DBMLIB, which appears in the link commands for binaries that
2125 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2126 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2127 binary, and which can be used, for example, to include additional X11
2130 .cindex "configuration file" "editing"
2131 The make file copes with rebuilding Exim correctly if any of the configuration
2132 files are edited. However, if an optional configuration file is deleted, it is
2133 necessary to touch the associated non-optional file (that is,
2134 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2137 .section "OS-specific header files" "SECID30"
2139 .cindex "building Exim" "OS-specific C header files"
2140 The &_OS_& directory contains a number of files with names of the form
2141 &_os.h-<ostype>_&. These are system-specific C header files that should not
2142 normally need to be changed. There is a list of macro settings that are
2143 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2144 are porting Exim to a new operating system.
2148 .section "Overriding build-time options for the monitor" "SECID31"
2149 .cindex "building Eximon"
2150 A similar process is used for overriding things when building the Exim monitor,
2151 where the files that are involved are
2153 &_OS/eximon.conf-Default_&
2154 &_OS/eximon.conf-_&<&'ostype'&>
2155 &_Local/eximon.conf_&
2156 &_Local/eximon.conf-_&<&'ostype'&>
2157 &_Local/eximon.conf-_&<&'archtype'&>
2158 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2160 .cindex "&_Local/eximon.conf_&"
2161 As with Exim itself, the final three files need not exist, and in this case the
2162 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2163 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2164 variables of the same name, preceded by EXIMON_. For example, setting
2165 EXIMON_LOG_DEPTH in the environment overrides the value of
2166 LOG_DEPTH at run time.
2170 .section "Installing Exim binaries and scripts" "SECID32"
2171 .cindex "installing Exim"
2172 .cindex "BIN_DIRECTORY"
2173 The command &`make install`& runs the &(exim_install)& script with no
2174 arguments. The script copies binaries and utility scripts into the directory
2175 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2176 .cindex "setuid" "installing Exim with"
2177 The install script copies files only if they are newer than the files they are
2178 going to replace. The Exim binary is required to be owned by root and have the
2179 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2180 install`& as root so that it can set up the Exim binary in this way. However, in
2181 some special situations (for example, if a host is doing no local deliveries)
2182 it may be possible to run Exim without making the binary setuid root (see
2183 chapter &<<CHAPsecurity>>& for details).
2185 .cindex "CONFIGURE_FILE"
2186 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2187 in &_Local/Makefile_&. If this names a single file, and the file does not
2188 exist, the default configuration file &_src/configure.default_& is copied there
2189 by the installation script. If a run time configuration file already exists, it
2190 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2191 alternative files, no default is installed.
2193 .cindex "system aliases file"
2194 .cindex "&_/etc/aliases_&"
2195 One change is made to the default configuration file when it is installed: the
2196 default configuration contains a router that references a system aliases file.
2197 The path to this file is set to the value specified by
2198 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2199 If the system aliases file does not exist, the installation script creates it,
2200 and outputs a comment to the user.
2202 The created file contains no aliases, but it does contain comments about the
2203 aliases a site should normally have. Mail aliases have traditionally been
2204 kept in &_/etc/aliases_&. However, some operating systems are now using
2205 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2206 Exim's configuration if necessary.
2208 The default configuration uses the local host's name as the only local domain,
2209 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2210 running as the local user. System aliases and &_.forward_& files in users' home
2211 directories are supported, but no NIS or NIS+ support is configured. Domains
2212 other than the name of the local host are routed using the DNS, with delivery
2215 It is possible to install Exim for special purposes (such as building a binary
2216 distribution) in a private part of the file system. You can do this by a
2219 make DESTDIR=/some/directory/ install
2221 This has the effect of pre-pending the specified directory to all the file
2222 paths, except the name of the system aliases file that appears in the default
2223 configuration. (If a default alias file is created, its name &'is'& modified.)
2224 For backwards compatibility, ROOT is used if DESTDIR is not set,
2225 but this usage is deprecated.
2227 .cindex "installing Exim" "what is not installed"
2228 Running &'make install'& does not copy the Exim 4 conversion script
2229 &'convert4r4'&. You will probably run this only once if you are
2230 upgrading from Exim 3. None of the documentation files in the &_doc_&
2231 directory are copied, except for the info files when you have set
2232 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2234 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2235 to their names. The Exim binary itself, however, is handled differently. It is
2236 installed under a name that includes the version number and the compile number,
2237 for example &_exim-&version;-1_&. The script then arranges for a symbolic link
2238 called &_exim_& to point to the binary. If you are updating a previous version
2239 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2240 from the directory (as seen by other processes).
2242 .cindex "installing Exim" "testing the script"
2243 If you want to see what the &'make install'& will do before running it for
2244 real, you can pass the &%-n%& option to the installation script by this
2247 make INSTALL_ARG=-n install
2249 The contents of the variable INSTALL_ARG are passed to the installation
2250 script. You do not need to be root to run this test. Alternatively, you can run
2251 the installation script directly, but this must be from within the build
2252 directory. For example, from the top-level Exim directory you could use this
2255 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2257 .cindex "installing Exim" "install script options"
2258 There are two other options that can be supplied to the installation script.
2261 &%-no_chown%& bypasses the call to change the owner of the installed binary
2262 to root, and the call to make it a setuid binary.
2264 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2268 INSTALL_ARG can be used to pass these options to the script. For example:
2270 make INSTALL_ARG=-no_symlink install
2272 The installation script can also be given arguments specifying which files are
2273 to be copied. For example, to install just the Exim binary, and nothing else,
2274 without creating the symbolic link, you could use:
2276 make INSTALL_ARG='-no_symlink exim' install
2281 .section "Installing info documentation" "SECTinsinfdoc"
2282 .cindex "installing Exim" "&'info'& documentation"
2283 Not all systems use the GNU &'info'& system for documentation, and for this
2284 reason, the Texinfo source of Exim's documentation is not included in the main
2285 distribution. Instead it is available separately from the ftp site (see section
2288 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2289 source of the documentation is found in the source tree, running &`make
2290 install`& automatically builds the info files and installs them.
2294 .section "Setting up the spool directory" "SECID33"
2295 .cindex "spool directory" "creating"
2296 When it starts up, Exim tries to create its spool directory if it does not
2297 exist. The Exim uid and gid are used for the owner and group of the spool
2298 directory. Sub-directories are automatically created in the spool directory as
2304 .section "Testing" "SECID34"
2305 .cindex "testing" "installation"
2306 Having installed Exim, you can check that the run time configuration file is
2307 syntactically valid by running the following command, which assumes that the
2308 Exim binary directory is within your PATH environment variable:
2312 If there are any errors in the configuration file, Exim outputs error messages.
2313 Otherwise it outputs the version number and build date,
2314 the DBM library that is being used, and information about which drivers and
2315 other optional code modules are included in the binary.
2316 Some simple routing tests can be done by using the address testing option. For
2319 &`exim -bt`& <&'local username'&>
2321 should verify that it recognizes a local mailbox, and
2323 &`exim -bt`& <&'remote address'&>
2325 a remote one. Then try getting it to deliver mail, both locally and remotely.
2326 This can be done by passing messages directly to Exim, without going through a
2327 user agent. For example:
2329 exim -v postmaster@your.domain.example
2330 From: user@your.domain.example
2331 To: postmaster@your.domain.example
2332 Subject: Testing Exim
2334 This is a test message.
2337 The &%-v%& option causes Exim to output some verification of what it is doing.
2338 In this case you should see copies of three log lines, one for the message's
2339 arrival, one for its delivery, and one containing &"Completed"&.
2341 .cindex "delivery" "problems with"
2342 If you encounter problems, look at Exim's log files (&'mainlog'& and
2343 &'paniclog'&) to see if there is any relevant information there. Another source
2344 of information is running Exim with debugging turned on, by specifying the
2345 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2346 with debugging turned on by a command of the form
2348 &`exim -d -M`& <&'exim-message-id'&>
2350 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2351 produces rather a lot of output, but you can cut this down to specific areas.
2352 For example, if you use &%-d-all+route%& only the debugging information
2353 relevant to routing is included. (See the &%-d%& option in chapter
2354 &<<CHAPcommandline>>& for more details.)
2356 .cindex '&"sticky"& bit'
2357 .cindex "lock files"
2358 One specific problem that has shown up on some sites is the inability to do
2359 local deliveries into a shared mailbox directory, because it does not have the
2360 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2361 writing to a mailbox file, and if it cannot create the lock file, the delivery
2362 is deferred. You can get round this either by setting the &"sticky bit"& on the
2363 directory, or by setting a specific group for local deliveries and allowing
2364 that group to create files in the directory (see the comments above the
2365 &(local_delivery)& transport in the default configuration file). Another
2366 approach is to configure Exim not to use lock files, but just to rely on
2367 &[fcntl()]& locking instead. However, you should do this only if all user
2368 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2369 see chapter &<<CHAPappendfile>>&.
2371 One thing that cannot be tested on a system that is already running an MTA is
2372 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2373 &%-oX%& option can be used to run an Exim daemon that listens on some other
2374 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2375 &'exim_checkaccess'& utility can be used to check out policy controls on
2378 Testing a new version on a system that is already running Exim can most easily
2379 be done by building a binary with a different CONFIGURE_FILE setting. From
2380 within the run time configuration, all other file and directory names
2381 that Exim uses can be altered, in order to keep it entirely clear of the
2385 .section "Replacing another MTA with Exim" "SECID35"
2386 .cindex "replacing another MTA"
2387 Building and installing Exim for the first time does not of itself put it in
2388 general use. The name by which the system's MTA is called by mail user agents
2389 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2390 operating system), and it is necessary to make this name point to the &'exim'&
2391 binary in order to get the user agents to pass messages to Exim. This is
2392 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2393 or &_/usr/lib/sendmail_&
2394 .cindex "symbolic link" "to &'exim'& binary"
2395 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2396 privilege and executable status from the old MTA. It is then necessary to stop
2397 and restart the mailer daemon, if one is running.
2399 .cindex "FreeBSD, MTA indirection"
2400 .cindex "&_/etc/mail/mailer.conf_&"
2401 Some operating systems have introduced alternative ways of switching MTAs. For
2402 example, if you are running FreeBSD, you need to edit the file
2403 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2404 described. A typical example of the contents of this file for running Exim is
2407 sendmail /usr/exim/bin/exim
2408 send-mail /usr/exim/bin/exim
2409 mailq /usr/exim/bin/exim -bp
2410 newaliases /usr/bin/true
2412 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2413 your Exim installation is &"live"&. Check it by sending a message from your
2414 favourite user agent.
2416 You should consider what to tell your users about the change of MTA. Exim may
2417 have different capabilities to what was previously running, and there are
2418 various operational differences such as the text of messages produced by
2419 command line options and in bounce messages. If you allow your users to make
2420 use of Exim's filtering capabilities, you should make the document entitled
2421 &'Exim's interface to mail filtering'& available to them.
2425 .section "Upgrading Exim" "SECID36"
2426 .cindex "upgrading Exim"
2427 If you are already running Exim on your host, building and installing a new
2428 version automatically makes it available to MUAs, or any other programs that
2429 call the MTA directly. However, if you are running an Exim daemon, you do need
2430 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2431 new binary. You do not need to stop processing mail in order to install a new
2432 version of Exim. The install script does not modify an existing runtime
2438 .section "Stopping the Exim daemon on Solaris" "SECID37"
2439 .cindex "Solaris" "stopping Exim on"
2440 The standard command for stopping the mailer daemon on Solaris is
2442 /etc/init.d/sendmail stop
2444 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2445 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2446 for the text &"sendmail"&; this is not present because the actual program name
2447 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2448 solution is to replace the line that finds the process id with something like
2450 pid=`cat /var/spool/exim/exim-daemon.pid`
2452 to obtain the daemon's pid directly from the file that Exim saves it in.
2454 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2455 still be received from local processes, and if automatic delivery is configured
2456 (the normal case), deliveries will still occur.
2461 . ////////////////////////////////////////////////////////////////////////////
2462 . ////////////////////////////////////////////////////////////////////////////
2464 .chapter "The Exim command line" "CHAPcommandline"
2465 .scindex IIDclo1 "command line" "options"
2466 .scindex IIDclo2 "options" "command line"
2467 Exim's command line takes the standard Unix form of a sequence of options,
2468 each starting with a hyphen character, followed by a number of arguments. The
2469 options are compatible with the main options of Sendmail, and there are also
2470 some additional options, some of which are compatible with Smail 3. Certain
2471 combinations of options do not make sense, and provoke an error if used.
2472 The form of the arguments depends on which options are set.
2475 .section "Setting options by program name" "SECID38"
2477 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2478 were present before any other options.
2479 The &%-bp%& option requests a listing of the contents of the mail queue on the
2481 This feature is for compatibility with some systems that contain a command of
2482 that name in one of the standard libraries, symbolically linked to
2483 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2486 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2487 were present before any other options, for compatibility with Smail. The
2488 &%-bS%& option is used for reading in a number of messages in batched SMTP
2492 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2493 &%-oee%& options were present before any other options, for compatibility with
2494 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2497 .cindex "queue runner"
2498 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2499 were present before any other options, for compatibility with Smail. The &%-q%&
2500 option causes a single queue runner process to be started.
2502 .cindex "&'newaliases'&"
2503 .cindex "alias file" "building"
2504 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2505 If Exim is called under the name &'newaliases'& it behaves as if the option
2506 &%-bi%& were present before any other options, for compatibility with Sendmail.
2507 This option is used for rebuilding Sendmail's alias file. Exim does not have
2508 the concept of a single alias file, but can be configured to run a given
2509 command if called with the &%-bi%& option.
2512 .section "Trusted and admin users" "SECTtrustedadmin"
2513 Some Exim options are available only to &'trusted users'& and others are
2514 available only to &'admin users'&. In the description below, the phrases &"Exim
2515 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2516 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2517 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2520 .cindex "trusted users" "definition of"
2521 .cindex "user" "trusted definition of"
2522 The trusted users are root, the Exim user, any user listed in the
2523 &%trusted_users%& configuration option, and any user whose current group or any
2524 supplementary group is one of those listed in the &%trusted_groups%&
2525 configuration option. Note that the Exim group is not automatically trusted.
2527 .cindex '&"From"& line'
2528 .cindex "envelope sender"
2529 Trusted users are always permitted to use the &%-f%& option or a leading
2530 &"From&~"& line to specify the envelope sender of a message that is passed to
2531 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2532 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2533 users to set envelope senders.
2535 .cindex "&'From:'& header line"
2536 .cindex "&'Sender:'& header line"
2537 For a trusted user, there is never any check on the contents of the &'From:'&
2538 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2539 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2541 Trusted users may also specify a host name, host address, interface address,
2542 protocol name, ident value, and authentication data when submitting a message
2543 locally. Thus, they are able to insert messages into Exim's queue locally that
2544 have the characteristics of messages received from a remote host. Untrusted
2545 users may in some circumstances use &%-f%&, but can never set the other values
2546 that are available to trusted users.
2548 .cindex "user" "admin definition of"
2549 .cindex "admin user" "definition of"
2550 The admin users are root, the Exim user, and any user that is a member of the
2551 Exim group or of any group listed in the &%admin_groups%& configuration option.
2552 The current group does not have to be one of these groups.
2554 Admin users are permitted to list the queue, and to carry out certain
2555 operations on messages, for example, to force delivery failures. It is also
2556 necessary to be an admin user in order to see the full information provided by
2557 the Exim monitor, and full debugging output.
2559 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2560 Exim to attempt delivery of messages on its queue is restricted to admin users.
2561 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2562 option false (that is, specifying &%no_prod_requires_admin%&).
2564 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2565 is restricted to admin users unless &%queue_list_requires_admin%& is set
2570 &*Warning*&: If you configure your system so that admin users are able to
2571 edit Exim's configuration file, you are giving those users an easy way of
2572 getting root. There is further discussion of this issue at the start of chapter
2578 .section "Command line options" "SECID39"
2579 Exim's command line options are described in alphabetical order below. If none
2580 of the options that specifies a specific action (such as starting the daemon or
2581 a queue runner, or testing an address, or receiving a message in a specific
2582 format, or listing the queue) are present, and there is at least one argument
2583 on the command line, &%-bm%& (accept a local message on the standard input,
2584 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2585 outputs a brief message about itself and exits.
2587 . ////////////////////////////////////////////////////////////////////////////
2588 . Insert a stylized XML comment here, to identify the start of the command line
2589 . options. This is for the benefit of the Perl script that automatically
2590 . creates a man page for the options.
2591 . ////////////////////////////////////////////////////////////////////////////
2594 <!-- === Start of command line options === -->
2601 .cindex "options" "command line; terminating"
2602 This is a pseudo-option whose only purpose is to terminate the options and
2603 therefore to cause subsequent command line items to be treated as arguments
2604 rather than options, even if they begin with hyphens.
2607 .oindex "&%--help%&"
2608 This option causes Exim to output a few sentences stating what it is.
2609 The same output is generated if the Exim binary is called with no options and
2612 .vitem &%--version%&
2613 .oindex "&%--version%&"
2614 This option is an alias for &%-bV%& and causes version information to be
2617 .vitem &%-B%&<&'type'&>
2619 .cindex "8-bit characters"
2620 .cindex "Sendmail compatibility" "8-bit characters"
2621 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2622 clean; it ignores this option.
2627 .cindex "SMTP" "listener"
2628 .cindex "queue runner"
2629 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2630 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2631 that the daemon should also initiate periodic queue runs.
2633 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2634 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2635 disconnect from the controlling terminal. When running this way, it can be
2636 stopped by pressing ctrl-C.
2638 By default, Exim listens for incoming connections to the standard SMTP port on
2639 all the host's running interfaces. However, it is possible to listen on other
2640 ports, on multiple ports, and only on specific interfaces. Chapter
2641 &<<CHAPinterfaces>>& contains a description of the options that control this.
2643 When a listening daemon
2644 .cindex "daemon" "process id (pid)"
2645 .cindex "pid (process id)" "of daemon"
2646 is started without the use of &%-oX%& (that is, without overriding the normal
2647 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2648 in Exim's spool directory. This location can be overridden by setting
2649 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2652 When &%-oX%& is used on the command line to start a listening daemon, the
2653 process id is not written to the normal pid file path. However, &%-oP%& can be
2654 used to specify a path on the command line if a pid file is required.
2658 .cindex "daemon" "restarting"
2659 can be used to cause the daemon to re-execute itself. This should be done
2660 whenever Exim's configuration file, or any file that is incorporated into it by
2661 means of the &%.include%& facility, is changed, and also whenever a new version
2662 of Exim is installed. It is not necessary to do this when other files that are
2663 referenced from the configuration (for example, alias files) are changed,
2664 because these are reread each time they are used.
2668 This option has the same effect as &%-bd%& except that it never disconnects
2669 from the controlling terminal, even when no debugging is specified.
2673 .cindex "testing" "string expansion"
2674 .cindex "expansion" "testing"
2675 Run Exim in expansion testing mode. Exim discards its root privilege, to
2676 prevent ordinary users from using this mode to read otherwise inaccessible
2677 files. If no arguments are given, Exim runs interactively, prompting for lines
2678 of data. Otherwise, it processes each argument in turn.
2680 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2681 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2682 used without command line arguments. If successful, it uses the &[readline()]&
2683 function, which provides extensive line-editing facilities, for reading the
2684 test data. A line history is supported.
2686 Long expansion expressions can be split over several lines by using backslash
2687 continuations. As in Exim's run time configuration, white space at the start of
2688 continuation lines is ignored. Each argument or data line is passed through the
2689 string expansion mechanism, and the result is output. Variable values from the
2690 configuration file (for example, &$qualify_domain$&) are available, but no
2691 message-specific values (such as &$sender_domain$&) are set, because no message
2692 is being processed (but see &%-bem%& and &%-Mset%&).
2694 &*Note*&: If you use this mechanism to test lookups, and you change the data
2695 files or databases you are using, you must exit and restart Exim before trying
2696 the same lookup again. Otherwise, because each Exim process caches the results
2697 of lookups, you will just get the same result as before.
2699 .vitem &%-bem%&&~<&'filename'&>
2701 .cindex "testing" "string expansion"
2702 .cindex "expansion" "testing"
2703 This option operates like &%-be%& except that it must be followed by the name
2704 of a file. For example:
2706 exim -bem /tmp/testmessage
2708 The file is read as a message (as if receiving a locally-submitted non-SMTP
2709 message) before any of the test expansions are done. Thus, message-specific
2710 variables such as &$message_size$& and &$header_from:$& are available. However,
2711 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2712 recipients are read from the headers in the normal way, and are shown in the
2713 &$recipients$& variable. Note that recipients cannot be given on the command
2714 line, because further arguments are taken as strings to expand (just like
2717 .vitem &%-bF%&&~<&'filename'&>
2719 .cindex "system filter" "testing"
2720 .cindex "testing" "system filter"
2721 This option is the same as &%-bf%& except that it assumes that the filter being
2722 tested is a system filter. The additional commands that are available only in
2723 system filters are recognized.
2725 .vitem &%-bf%&&~<&'filename'&>
2727 .cindex "filter" "testing"
2728 .cindex "testing" "filter file"
2729 .cindex "forward file" "testing"
2730 .cindex "testing" "forward file"
2731 .cindex "Sieve filter" "testing"
2732 This option runs Exim in user filter testing mode; the file is the filter file
2733 to be tested, and a test message must be supplied on the standard input. If
2734 there are no message-dependent tests in the filter, an empty file can be
2737 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2738 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2739 filter and a user filter in the same run. For example:
2741 exim -bF /system/filter -bf /user/filter </test/message
2743 This is helpful when the system filter adds header lines or sets filter
2744 variables that are used by the user filter.
2746 If the test filter file does not begin with one of the special lines
2751 it is taken to be a normal &_.forward_& file, and is tested for validity under
2752 that interpretation. See sections &<<SECTitenonfilred>>& to
2753 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2756 The result of an Exim command that uses &%-bf%&, provided no errors are
2757 detected, is a list of the actions that Exim would try to take if presented
2758 with the message for real. More details of filter testing are given in the
2759 separate document entitled &'Exim's interfaces to mail filtering'&.
2761 When testing a filter file,
2762 .cindex "&""From""& line"
2763 .cindex "envelope sender"
2764 .oindex "&%-f%&" "for filter testing"
2765 the envelope sender can be set by the &%-f%& option,
2766 or by a &"From&~"& line at the start of the test message. Various parameters
2767 that would normally be taken from the envelope recipient address of the message
2768 can be set by means of additional command line options (see the next four
2771 .vitem &%-bfd%&&~<&'domain'&>
2773 .vindex "&$qualify_domain$&"
2774 This sets the domain of the recipient address when a filter file is being
2775 tested by means of the &%-bf%& option. The default is the value of
2778 .vitem &%-bfl%&&~<&'local&~part'&>
2780 This sets the local part of the recipient address when a filter file is being
2781 tested by means of the &%-bf%& option. The default is the username of the
2782 process that calls Exim. A local part should be specified with any prefix or
2783 suffix stripped, because that is how it appears to the filter when a message is
2784 actually being delivered.
2786 .vitem &%-bfp%&&~<&'prefix'&>
2788 This sets the prefix of the local part of the recipient address when a filter
2789 file is being tested by means of the &%-bf%& option. The default is an empty
2792 .vitem &%-bfs%&&~<&'suffix'&>
2794 This sets the suffix of the local part of the recipient address when a filter
2795 file is being tested by means of the &%-bf%& option. The default is an empty
2798 .vitem &%-bh%&&~<&'IP&~address'&>
2800 .cindex "testing" "incoming SMTP"
2801 .cindex "SMTP" "testing incoming"
2802 .cindex "testing" "relay control"
2803 .cindex "relaying" "testing configuration"
2804 .cindex "policy control" "testing"
2805 .cindex "debugging" "&%-bh%& option"
2806 This option runs a fake SMTP session as if from the given IP address, using the
2807 standard input and output. The IP address may include a port number at the end,
2808 after a full stop. For example:
2810 exim -bh 10.9.8.7.1234
2811 exim -bh fe80::a00:20ff:fe86:a061.5678
2813 When an IPv6 address is given, it is converted into canonical form. In the case
2814 of the second example above, the value of &$sender_host_address$& after
2815 conversion to the canonical form is
2816 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2818 Comments as to what is going on are written to the standard error file. These
2819 include lines beginning with &"LOG"& for anything that would have been logged.
2820 This facility is provided for testing configuration options for incoming
2821 messages, to make sure they implement the required policy. For example, you can
2822 test your relay controls using &%-bh%&.
2826 You can test features of the configuration that rely on ident (RFC 1413)
2827 information by using the &%-oMt%& option. However, Exim cannot actually perform
2828 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2831 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2832 are also skipped when testing using &%-bh%&. If you want these callouts to
2833 occur, use &%-bhc%& instead.
2835 Messages supplied during the testing session are discarded, and nothing is
2836 written to any of the real log files. There may be pauses when DNS (and other)
2837 lookups are taking place, and of course these may time out. The &%-oMi%& option
2838 can be used to specify a specific IP interface and port if this is important,
2839 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2840 session were authenticated.
2842 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2843 output just states whether a given recipient address from a given host is
2844 acceptable or not. See section &<<SECTcheckaccess>>&.
2846 Features such as authentication and encryption, where the client input is not
2847 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2848 specialized SMTP test program such as
2849 &url(http://jetmore.org/john/code/#swaks,swaks).
2851 .vitem &%-bhc%&&~<&'IP&~address'&>
2853 This option operates in the same way as &%-bh%&, except that address
2854 verification callouts are performed if required. This includes consulting and
2855 updating the callout cache database.
2859 .cindex "alias file" "building"
2860 .cindex "building alias file"
2861 .cindex "Sendmail compatibility" "&%-bi%& option"
2862 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2863 Exim does not have the concept of a single alias file, and so it cannot mimic
2864 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2865 tend to appear in various scripts such as NIS make files, so the option must be
2868 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2869 configuration option is run, under the uid and gid of the caller of Exim. If
2870 the &%-oA%& option is used, its value is passed to the command as an argument.
2871 The command set by &%bi_command%& may not contain arguments. The command can
2872 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2873 if this is required. If the &%bi_command%& option is not set, calling Exim with
2878 .cindex "local message reception"
2879 This option runs an Exim receiving process that accepts an incoming,
2880 locally-generated message on the current input. The recipients are given as the
2881 command arguments (except when &%-t%& is also present &-- see below). Each
2882 argument can be a comma-separated list of RFC 2822 addresses. This is the
2883 default option for selecting the overall action of an Exim call; it is assumed
2884 if no other conflicting option is present.
2886 If any addresses in the message are unqualified (have no domain), they are
2887 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
2888 options, as appropriate. The &%-bnq%& option (see below) provides a way of
2889 suppressing this for special cases.
2891 Policy checks on the contents of local messages can be enforced by means of
2892 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
2894 .cindex "return code" "for &%-bm%&"
2895 The return code is zero if the message is successfully accepted. Otherwise, the
2896 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
2899 .cindex "message" "format"
2900 .cindex "format" "message"
2901 .cindex "&""From""& line"
2902 .cindex "UUCP" "&""From""& line"
2903 .cindex "Sendmail compatibility" "&""From""& line"
2904 of the message must be as defined in RFC 2822, except that, for
2905 compatibility with Sendmail and Smail, a line in one of the forms
2907 From sender Fri Jan 5 12:55 GMT 1997
2908 From sender Fri, 5 Jan 97 12:55:01
2910 (with the weekday optional, and possibly with additional text after the date)
2911 is permitted to appear at the start of the message. There appears to be no
2912 authoritative specification of the format of this line. Exim recognizes it by
2913 matching against the regular expression defined by the &%uucp_from_pattern%&
2914 option, which can be changed if necessary.
2916 .oindex "&%-f%&" "overriding &""From""& line"
2917 The specified sender is treated as if it were given as the argument to the
2918 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
2919 preference to the address taken from the message. The caller of Exim must be a
2920 trusted user for the sender of a message to be set in this way.
2924 .cindex "address qualification, suppressing"
2925 By default, Exim automatically qualifies unqualified addresses (those
2926 without domains) that appear in messages that are submitted locally (that
2927 is, not over TCP/IP). This qualification applies both to addresses in
2928 envelopes, and addresses in header lines. Sender addresses are qualified using
2929 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
2930 defaults to the value of &%qualify_domain%&).
2932 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
2933 being used to re-submit messages that originally came from remote hosts after
2934 content scanning, you probably do not want to qualify unqualified addresses in
2935 header lines. (Such lines will be present only if you have not enabled a header
2936 syntax check in the appropriate ACL.)
2938 The &%-bnq%& option suppresses all qualification of unqualified addresses in
2939 messages that originate on the local host. When this is used, unqualified
2940 addresses in the envelope provoke errors (causing message rejection) and
2941 unqualified addresses in header lines are left alone.
2946 .cindex "configuration options" "extracting"
2947 .cindex "options" "configuration &-- extracting"
2948 If this option is given with no arguments, it causes the values of all Exim's
2949 main configuration options to be written to the standard output. The values
2950 of one or more specific options can be requested by giving their names as
2951 arguments, for example:
2953 exim -bP qualify_domain hold_domains
2955 .cindex "hiding configuration option values"
2956 .cindex "configuration options" "hiding value of"
2957 .cindex "options" "hiding value of"
2958 However, any option setting that is preceded by the word &"hide"& in the
2959 configuration file is not shown in full, except to an admin user. For other
2960 users, the output is as in this example:
2962 mysql_servers = <value not displayable>
2964 If &%configure_file%& is given as an argument, the name of the run time
2965 configuration file is output.
2966 If a list of configuration files was supplied, the value that is output here
2967 is the name of the file that was actually used.
2969 .cindex "daemon" "process id (pid)"
2970 .cindex "pid (process id)" "of daemon"
2971 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
2972 directories where log files and daemon pid files are written are output,
2973 respectively. If these values are unset, log files are written in a
2974 sub-directory of the spool directory called &%log%&, and the pid file is
2975 written directly into the spool directory.
2977 If &%-bP%& is followed by a name preceded by &`+`&, for example,
2979 exim -bP +local_domains
2981 it searches for a matching named list of any type (domain, host, address, or
2982 local part) and outputs what it finds.
2984 .cindex "options" "router &-- extracting"
2985 .cindex "options" "transport &-- extracting"
2986 .cindex "options" "authenticator &-- extracting"
2987 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
2988 followed by the name of an appropriate driver instance, the option settings for
2989 that driver are output. For example:
2991 exim -bP transport local_delivery
2993 The generic driver options are output first, followed by the driver's private
2994 options. A list of the names of drivers of a particular type can be obtained by
2995 using one of the words &%router_list%&, &%transport_list%&, or
2996 &%authenticator_list%&, and a complete list of all drivers with their option
2997 settings can be obtained by using &%routers%&, &%transports%&, or
3000 .cindex "options" "macro &-- extracting"
3001 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3002 are available, similarly to the drivers. Because macros are sometimes used
3003 for storing passwords, this option is restricted.
3004 The output format is one item per line.
3008 .cindex "queue" "listing messages on"
3009 .cindex "listing" "messages on the queue"
3010 This option requests a listing of the contents of the mail queue on the
3011 standard output. If the &%-bp%& option is followed by a list of message ids,
3012 just those messages are listed. By default, this option can be used only by an
3013 admin user. However, the &%queue_list_requires_admin%& option can be set false
3014 to allow any user to see the queue.
3016 Each message on the queue is displayed as in the following example:
3018 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3019 red.king@looking-glass.fict.example
3022 .cindex "message" "size in queue listing"
3023 .cindex "size" "of message"
3024 The first line contains the length of time the message has been on the queue
3025 (in this case 25 minutes), the size of the message (2.9K), the unique local
3026 identifier for the message, and the message sender, as contained in the
3027 envelope. For bounce messages, the sender address is empty, and appears as
3028 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3029 the default sender address, the user's login name is shown in parentheses
3030 before the sender address.
3032 .cindex "frozen messages" "in queue listing"
3033 If the message is frozen (attempts to deliver it are suspended) then the text
3034 &"*** frozen ***"& is displayed at the end of this line.
3036 The recipients of the message (taken from the envelope, not the headers) are
3037 displayed on subsequent lines. Those addresses to which the message has already
3038 been delivered are marked with the letter D. If an original address gets
3039 expanded into several addresses via an alias or forward file, the original is
3040 displayed with a D only when deliveries for all of its child addresses are
3046 This option operates like &%-bp%&, but in addition it shows delivered addresses
3047 that were generated from the original top level address(es) in each message by
3048 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3054 .cindex "queue" "count of messages on"
3055 This option counts the number of messages on the queue, and writes the total
3056 to the standard output. It is restricted to admin users, unless
3057 &%queue_list_requires_admin%& is set false.
3062 This option operates like &%-bp%&, but the output is not sorted into
3063 chronological order of message arrival. This can speed it up when there are
3064 lots of messages on the queue, and is particularly useful if the output is
3065 going to be post-processed in a way that doesn't need the sorting.
3069 This option is a combination of &%-bpr%& and &%-bpa%&.
3073 This option is a combination of &%-bpr%& and &%-bpu%&.
3078 This option operates like &%-bp%& but shows only undelivered top-level
3079 addresses for each message displayed. Addresses generated by aliasing or
3080 forwarding are not shown, unless the message was deferred after processing by a
3081 router with the &%one_time%& option set.
3086 .cindex "testing" "retry configuration"
3087 .cindex "retry" "configuration testing"
3088 This option is for testing retry rules, and it must be followed by up to three
3089 arguments. It causes Exim to look for a retry rule that matches the values
3090 and to write it to the standard output. For example:
3092 exim -brt bach.comp.mus.example
3093 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3095 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3096 argument, which is required, can be a complete address in the form
3097 &'local_part@domain'&, or it can be just a domain name. If the second argument
3098 contains a dot, it is interpreted as an optional second domain name; if no
3099 retry rule is found for the first argument, the second is tried. This ties in
3100 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3101 rule is found that matches the host, one that matches the mail domain is
3102 sought. Finally, an argument that is the name of a specific delivery error, as
3103 used in setting up retry rules, can be given. For example:
3105 exim -brt haydn.comp.mus.example quota_3d
3106 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3111 .cindex "testing" "rewriting"
3112 .cindex "rewriting" "testing"
3113 This option is for testing address rewriting rules, and it must be followed by
3114 a single argument, consisting of either a local part without a domain, or a
3115 complete address with a fully qualified domain. Exim outputs how this address
3116 would be rewritten for each possible place it might appear. See chapter
3117 &<<CHAPrewrite>>& for further details.
3121 .cindex "SMTP" "batched incoming"
3122 .cindex "batched SMTP input"
3123 This option is used for batched SMTP input, which is an alternative interface
3124 for non-interactive local message submission. A number of messages can be
3125 submitted in a single run. However, despite its name, this is not really SMTP
3126 input. Exim reads each message's envelope from SMTP commands on the standard
3127 input, but generates no responses. If the caller is trusted, or
3128 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3129 believed; otherwise the sender is always the caller of Exim.
3131 The message itself is read from the standard input, in SMTP format (leading
3132 dots doubled), terminated by a line containing just a single dot. An error is
3133 provoked if the terminating dot is missing. A further message may then follow.
3135 As for other local message submissions, the contents of incoming batch SMTP
3136 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3137 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3138 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3140 Some other SMTP commands are recognized in the input. HELO and EHLO act
3141 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3142 QUIT quits, ignoring the rest of the standard input.
3144 .cindex "return code" "for &%-bS%&"
3145 If any error is encountered, reports are written to the standard output and
3146 error streams, and Exim gives up immediately. The return code is 0 if no error
3147 was detected; it is 1 if one or more messages were accepted before the error
3148 was detected; otherwise it is 2.
3150 More details of input using batched SMTP are given in section
3151 &<<SECTincomingbatchedSMTP>>&.
3155 .cindex "SMTP" "local input"
3156 .cindex "local SMTP input"
3157 This option causes Exim to accept one or more messages by reading SMTP commands
3158 on the standard input, and producing SMTP replies on the standard output. SMTP
3159 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3160 Some user agents use this interface as a way of passing locally-generated
3161 messages to the MTA.
3164 .cindex "sender" "source of"
3165 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3166 set, the senders of messages are taken from the SMTP MAIL commands.
3167 Otherwise the content of these commands is ignored and the sender is set up as
3168 the calling user. Unqualified addresses are automatically qualified using
3169 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3170 &%-bnq%& option is used.
3174 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3175 using a listening daemon. Exim can distinguish the two cases by checking
3176 whether the standard input is a TCP/IP socket. When Exim is called from
3177 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3178 above concerning senders and qualification do not apply. In this situation,
3179 Exim behaves in exactly the same way as it does when receiving a message via
3180 the listening daemon.
3182 .vitem &%-bmalware%&&~<&'filename'&>
3183 .oindex "&%-bmalware%&"
3184 .cindex "testing", "malware"
3185 .cindex "malware scan test"
3186 This debugging option causes Exim to scan the given file,
3187 using the malware scanning framework. The option of av_scanner influences
3188 this option, so if av_scanner's value is dependent upon an expansion then
3189 the expansion should have defaults which apply to this invocation. Exim will
3190 have changed working directory before resolving the filename, so using fully
3191 qualified pathnames is advisable. Exim will be running as the Exim user
3192 when it tries to open the file, rather than as the invoking user.
3193 This option requires admin privileges.
3195 The &%-bmalware%& option will not be extended to be more generally useful,
3196 there are better tools for file-scanning. This option exists to help
3197 administrators verify their Exim and AV scanner configuration.
3201 .cindex "testing" "addresses"
3202 .cindex "address" "testing"
3203 This option runs Exim in address testing mode, in which each argument is taken
3204 as a recipient address to be tested for deliverability. The results are
3205 written to the standard output. If a test fails, and the caller is not an admin
3206 user, no details of the failure are output, because these might contain
3207 sensitive information such as usernames and passwords for database lookups.
3209 If no arguments are given, Exim runs in an interactive manner, prompting with a
3210 right angle bracket for addresses to be tested.
3212 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3213 &[readline()]& function, because it is running as &'root'& and there are
3216 Each address is handled as if it were the recipient address of a message
3217 (compare the &%-bv%& option). It is passed to the routers and the result is
3218 written to the standard output. However, any router that has
3219 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3220 genuine routing tests if your first router passes everything to a scanner
3223 .cindex "return code" "for &%-bt%&"
3224 The return code is 2 if any address failed outright; it is 1 if no address
3225 failed outright but at least one could not be resolved for some reason. Return
3226 code 0 is given only when all addresses succeed.
3228 .cindex "duplicate addresses"
3229 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3230 addresses after routing is complete, so that only one delivery takes place.
3231 This does not happen when testing with &%-bt%&; the full results of routing are
3234 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3235 routers in the configuration makes any tests on the sender address of a
3237 .oindex "&%-f%&" "for address testing"
3238 you can use the &%-f%& option to set an appropriate sender when running
3239 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3240 default qualifying domain. However, if you have set up (for example) routers
3241 whose behaviour depends on the contents of an incoming message, you cannot test
3242 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3247 .cindex "version number of Exim"
3248 This option causes Exim to write the current version number, compilation
3249 number, and compilation date of the &'exim'& binary to the standard output.
3250 It also lists the DBM library this is being used, the optional modules (such as
3251 specific lookup types), the drivers that are included in the binary, and the
3252 name of the run time configuration file that is in use.
3254 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3255 configuration file. However, this is a static check only. It cannot check
3256 values that are to be expanded. For example, although a misspelt ACL verb is
3257 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3258 alone to discover (for example) all the typos in the configuration; some
3259 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3260 dynamic testing facilities.
3264 .cindex "verifying address" "using &%-bv%&"
3265 .cindex "address" "verification"
3266 This option runs Exim in address verification mode, in which each argument is
3267 taken as a recipient address to be verified by the routers. (This does
3268 not involve any verification callouts). During normal operation, verification
3269 happens mostly as a consequence processing a &%verify%& condition in an ACL
3270 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3271 including callouts, see the &%-bh%& and &%-bhc%& options.
3273 If verification fails, and the caller is not an admin user, no details of the
3274 failure are output, because these might contain sensitive information such as
3275 usernames and passwords for database lookups.
3277 If no arguments are given, Exim runs in an interactive manner, prompting with a
3278 right angle bracket for addresses to be verified.
3280 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3281 &[readline()]& function, because it is running as &'exim'& and there are
3284 Verification differs from address testing (the &%-bt%& option) in that routers
3285 that have &%no_verify%& set are skipped, and if the address is accepted by a
3286 router that has &%fail_verify%& set, verification fails. The address is
3287 verified as a recipient if &%-bv%& is used; to test verification for a sender
3288 address, &%-bvs%& should be used.
3290 If the &%-v%& option is not set, the output consists of a single line for each
3291 address, stating whether it was verified or not, and giving a reason in the
3292 latter case. Without &%-v%&, generating more than one address by redirection
3293 causes verification to end successfully, without considering the generated
3294 addresses. However, if just one address is generated, processing continues,
3295 and the generated address must verify successfully for the overall verification
3298 When &%-v%& is set, more details are given of how the address has been handled,
3299 and in the case of address redirection, all the generated addresses are also
3300 considered. Verification may succeed for some and fail for others.
3303 .cindex "return code" "for &%-bv%&"
3304 return code is 2 if any address failed outright; it is 1 if no address
3305 failed outright but at least one could not be resolved for some reason. Return
3306 code 0 is given only when all addresses succeed.
3308 If any of the routers in the configuration makes any tests on the sender
3309 address of a message, you should use the &%-f%& option to set an appropriate
3310 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3311 calling user at the default qualifying domain.
3315 This option acts like &%-bv%&, but verifies the address as a sender rather
3316 than a recipient address. This affects any rewriting and qualification that
3319 .vitem &%-C%&&~<&'filelist'&>
3321 .cindex "configuration file" "alternate"
3322 .cindex "CONFIGURE_FILE"
3323 .cindex "alternate configuration file"
3324 This option causes Exim to find the run time configuration file from the given
3325 list instead of from the list specified by the CONFIGURE_FILE
3326 compile-time setting. Usually, the list will consist of just a single file
3327 name, but it can be a colon-separated list of names. In this case, the first
3328 file that exists is used. Failure to open an existing file stops Exim from
3329 proceeding any further along the list, and an error is generated.
3331 When this option is used by a caller other than root or the Exim user, and the
3332 list is different from the compiled-in list, Exim gives up its root privilege
3333 immediately, and runs with the real and effective uid and gid set to those of
3334 the caller. However, if ALT_CONFIG_ROOT_ONLY is defined in
3335 &_Local/Makefile_&, root privilege is retained for &%-C%& only if the caller of
3338 That is, the Exim user is no longer privileged in this regard. This build-time
3339 option is not set by default in the Exim source distribution tarbundle.
3340 However, if you are using a &"packaged"& version of Exim (source or binary),
3341 the packagers might have enabled it.
3343 Setting ALT_CONFIG_ROOT_ONLY locks out the possibility of testing a
3344 configuration using &%-C%& right through message reception and delivery, even
3345 if the caller is root. The reception works, but by that time, Exim is running
3346 as the Exim user, so when it re-executes to regain privilege for the delivery,
3347 the use of &%-C%& causes privilege to be lost. However, root can test reception
3348 and delivery using two separate commands (one to put a message on the queue,
3349 using &%-odq%&, and another to do the delivery, using &%-M%&).
3351 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3352 prefix string with which any file named in a &%-C%& command line option
3353 must start. In addition, the file name must not contain the sequence &`/../`&.
3354 However, if the value of the &%-C%& option is identical to the value of
3355 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3356 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3357 unset, any file name can be used with &%-C%&.
3359 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3360 to a directory to which only root has access. This prevents someone who has
3361 broken into the Exim account from running a privileged Exim with an arbitrary
3364 The &%-C%& facility is useful for ensuring that configuration files are
3365 syntactically correct, but cannot be used for test deliveries, unless the
3366 caller is privileged, or unless it is an exotic configuration that does not
3367 require privilege. No check is made on the owner or group of the files
3368 specified by this option.
3370 .vitem &%-D%&<&'macro'&>=<&'value'&>
3372 .cindex "macro" "setting on command line"
3373 This option can be used to override macro definitions in the configuration file
3374 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3375 unprivileged caller, it causes Exim to give up its root privilege.
3376 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3377 completely disabled, and its use causes an immediate error exit.
3379 The entire option (including equals sign if present) must all be within one
3380 command line item. &%-D%& can be used to set the value of a macro to the empty
3381 string, in which case the equals sign is optional. These two commands are
3387 To include spaces in a macro definition item, quotes must be used. If you use
3388 quotes, spaces are permitted around the macro name and the equals sign. For
3391 exim '-D ABC = something' ...
3393 &%-D%& may be repeated up to 10 times on a command line.
3395 .vitem &%-d%&<&'debug&~options'&>
3397 .cindex "debugging" "list of selectors"
3398 .cindex "debugging" "&%-d%& option"
3399 This option causes debugging information to be written to the standard
3400 error stream. It is restricted to admin users because debugging output may show
3401 database queries that contain password information. Also, the details of users'
3402 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3403 writes an error message to the standard error stream and exits with a non-zero
3406 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3407 standard debugging data is output. This can be reduced, or increased to include
3408 some more rarely needed information, by directly following &%-d%& with a string
3409 made up of names preceded by plus or minus characters. These add or remove sets
3410 of debugging data, respectively. For example, &%-d+filter%& adds filter
3411 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3412 no spaces are allowed in the debug setting. The available debugging categories
3415 &`acl `& ACL interpretation
3416 &`auth `& authenticators
3417 &`deliver `& general delivery logic
3418 &`dns `& DNS lookups (see also resolver)
3419 &`dnsbl `& DNS black list (aka RBL) code
3420 &`exec `& arguments for &[execv()]& calls
3421 &`expand `& detailed debugging for string expansions
3422 &`filter `& filter handling
3423 &`hints_lookup `& hints data lookups
3424 &`host_lookup `& all types of name-to-IP address handling
3425 &`ident `& ident lookup
3426 &`interface `& lists of local interfaces
3427 &`lists `& matching things in lists
3428 &`load `& system load checks
3429 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3430 &<<CHAPlocalscan>>&)
3431 &`lookup `& general lookup code and all lookups
3432 &`memory `& memory handling
3433 &`pid `& add pid to debug output lines
3434 &`process_info `& setting info for the process log
3435 &`queue_run `& queue runs
3436 &`receive `& general message reception logic
3437 &`resolver `& turn on the DNS resolver's debugging output
3438 &`retry `& retry handling
3439 &`rewrite `& address rewriting
3440 &`route `& address routing
3441 &`timestamp `& add timestamp to debug output lines
3443 &`transport `& transports
3444 &`uid `& changes of uid/gid and looking up uid/gid
3445 &`verify `& address verification logic
3446 &`all `& almost all of the above (see below), and also &%-v%&
3448 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3449 for &`-all`&. The reason for this is that &`+all`& is something that people
3450 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3451 is included, an awful lot of output that is very rarely of interest is
3452 generated, so it now has to be explicitly requested. However, &`-all`& does
3453 turn everything off.
3455 .cindex "resolver, debugging output"
3456 .cindex "DNS resolver, debugging output"
3457 The &`resolver`& option produces output only if the DNS resolver was compiled
3458 with DEBUG enabled. This is not the case in some operating systems. Also,
3459 unfortunately, debugging output from the DNS resolver is written to stdout
3462 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3463 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3464 However, the &`pid`& selector is forced when debugging is turned on for a
3465 daemon, which then passes it on to any re-executed Exims. Exim also
3466 automatically adds the pid to debug lines when several remote deliveries are
3469 The &`timestamp`& selector causes the current time to be inserted at the start
3470 of all debug output lines. This can be useful when trying to track down delays
3473 If the &%debug_print%& option is set in any driver, it produces output whenever
3474 any debugging is selected, or if &%-v%& is used.
3476 .vitem &%-dd%&<&'debug&~options'&>
3478 This option behaves exactly like &%-d%& except when used on a command that
3479 starts a daemon process. In that case, debugging is turned off for the
3480 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3481 behaviour of the daemon without creating as much output as full debugging does.
3484 .oindex "&%-dropcr%&"
3485 This is an obsolete option that is now a no-op. It used to affect the way Exim
3486 handled CR and LF characters in incoming messages. What happens now is
3487 described in section &<<SECTlineendings>>&.
3491 .cindex "bounce message" "generating"
3492 This option specifies that an incoming message is a locally-generated delivery
3493 failure report. It is used internally by Exim when handling delivery failures
3494 and is not intended for external use. Its only effect is to stop Exim
3495 generating certain messages to the postmaster, as otherwise message cascades
3496 could occur in some situations. As part of the same option, a message id may
3497 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3498 new message contains the id, following &"R="&, as a cross-reference.
3501 .oindex "&%-e%&&'x'&"
3502 There are a number of Sendmail options starting with &%-oe%& which seem to be
3503 called by various programs without the leading &%o%& in the option. For
3504 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3505 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3507 .vitem &%-F%&&~<&'string'&>
3509 .cindex "sender" "name"
3510 .cindex "name" "of sender"
3511 This option sets the sender's full name for use when a locally-generated
3512 message is being accepted. In the absence of this option, the user's &'gecos'&
3513 entry from the password data is used. As users are generally permitted to alter
3514 their &'gecos'& entries, no security considerations are involved. White space
3515 between &%-F%& and the <&'string'&> is optional.
3517 .vitem &%-f%&&~<&'address'&>
3519 .cindex "sender" "address"
3520 .cindex "address" "sender"
3521 .cindex "trusted users"
3522 .cindex "envelope sender"
3523 .cindex "user" "trusted"
3524 This option sets the address of the envelope sender of a locally-generated
3525 message (also known as the return path). The option can normally be used only
3526 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3529 Processes running as root or the Exim user are always trusted. Other
3530 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3531 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3532 of a local message is set to the caller's login name at the default qualify
3535 There is one exception to the restriction on the use of &%-f%&: an empty sender
3536 can be specified by any user, trusted or not, to create a message that can
3537 never provoke a bounce. An empty sender can be specified either as an empty
3538 string, or as a pair of angle brackets with nothing between them, as in these
3539 examples of shell commands:
3541 exim -f '<>' user@domain
3542 exim -f "" user@domain
3544 In addition, the use of &%-f%& is not restricted when testing a filter file
3545 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3548 Allowing untrusted users to change the sender address does not of itself make
3549 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3550 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3551 though this can be overridden by setting &%no_local_from_check%&.
3554 .cindex "&""From""& line"
3555 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3556 given as two arguments or one combined argument). The sender of a
3557 locally-generated message can also be set (when permitted) by an initial
3558 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3559 if &%-f%& is also present, it overrides &"From&~"&.
3563 .cindex "Sendmail compatibility" "&%-G%& option ignored"
3564 This is a Sendmail option which is ignored by Exim.
3566 .vitem &%-h%&&~<&'number'&>
3568 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3569 This option is accepted for compatibility with Sendmail, but has no effect. (In
3570 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3575 .cindex "Solaris" "&'mail'& command"
3576 .cindex "dot" "in incoming non-SMTP message"
3577 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3578 line by itself should not terminate an incoming, non-SMTP message. I can find
3579 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3580 command in Solaris 2.4 uses it. See also &%-ti%&.
3582 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3584 .cindex "forcing delivery"
3585 .cindex "delivery" "forcing attempt"
3586 .cindex "frozen messages" "forcing delivery"
3587 This option requests Exim to run a delivery attempt on each message in turn. If
3588 any of the messages are frozen, they are automatically thawed before the
3589 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3590 and &%hold_domains%& are ignored.
3593 .cindex "hints database" "overriding retry hints"
3594 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3595 the normal retry time has not yet been reached. This option requires the caller
3596 to be an admin user. However, there is an option called &%prod_requires_admin%&
3597 which can be set false to relax this restriction (and also the same requirement
3598 for the &%-q%&, &%-R%&, and &%-S%& options).
3600 The deliveries happen synchronously, that is, the original Exim process does
3601 not terminate until all the delivery attempts have finished. No output is
3602 produced unless there is a serious error. If you want to see what is happening,
3603 use the &%-v%& option as well, or inspect Exim's main log.
3605 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3607 .cindex "message" "adding recipients"
3608 .cindex "recipient" "adding"
3609 This option requests Exim to add the addresses to the list of recipients of the
3610 message (&"ar"& for &"add recipients"&). The first argument must be a message
3611 id, and the remaining ones must be email addresses. However, if the message is
3612 active (in the middle of a delivery attempt), it is not altered. This option
3613 can be used only by an admin user.
3615 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3616 &~<&'message&~id'&>"
3618 .cindex "SMTP" "passed connection"
3619 .cindex "SMTP" "multiple deliveries"
3620 .cindex "multiple SMTP deliveries"
3621 This option is not intended for use by external callers. It is used internally
3622 by Exim to invoke another instance of itself to deliver a waiting message using
3623 an existing SMTP connection, which is passed as the standard input. Details are
3624 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3625 must be root or the Exim user in order to use it.
3629 This option is not intended for use by external callers. It is used internally
3630 by Exim in conjunction with the &%-MC%& option. It signifies that the
3631 connection to the remote host has been authenticated.
3635 This option is not intended for use by external callers. It is used internally
3636 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3637 which Exim is connected supports pipelining.
3639 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3641 This option is not intended for use by external callers. It is used internally
3642 by Exim in conjunction with the &%-MC%& option when the original delivery was
3643 started by a queue runner. It passes on the process id of the queue runner,
3644 together with the file descriptor number of an open pipe. Closure of the pipe
3645 signals the final completion of the sequence of processes that are passing
3646 messages through the same SMTP connection.
3650 This option is not intended for use by external callers. It is used internally
3651 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3652 SMTP SIZE option should be used on messages delivered down the existing
3657 This option is not intended for use by external callers. It is used internally
3658 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3659 host to which Exim is connected supports TLS encryption.
3661 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3663 .cindex "hints database" "not overridden by &%-Mc%&"
3664 .cindex "delivery" "manually started &-- not forced"
3665 This option requests Exim to run a delivery attempt on each message in turn,
3666 but unlike the &%-M%& option, it does check for retry hints, and respects any
3667 that are found. This option is not very useful to external callers. It is
3668 provided mainly for internal use by Exim when it needs to re-invoke itself in
3669 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3670 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3671 respects retry times and other options such as &%hold_domains%& that are
3672 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3673 If you want to run a specific delivery as if in a queue run, you should use
3674 &%-q%& with a message id argument. A distinction between queue run deliveries
3675 and other deliveries is made in one or two places.
3677 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3679 .cindex "message" "changing sender"
3680 .cindex "sender" "changing"
3681 This option requests Exim to change the sender address in the message to the
3682 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3683 &"edit sender"&). There must be exactly two arguments. The first argument must
3684 be a message id, and the second one an email address. However, if the message
3685 is active (in the middle of a delivery attempt), its status is not altered.
3686 This option can be used only by an admin user.
3688 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3690 .cindex "freezing messages"
3691 .cindex "message" "manually freezing"
3692 This option requests Exim to mark each listed message as &"frozen"&. This
3693 prevents any delivery attempts taking place until the message is &"thawed"&,
3694 either manually or as a result of the &%auto_thaw%& configuration option.
3695 However, if any of the messages are active (in the middle of a delivery
3696 attempt), their status is not altered. This option can be used only by an admin
3699 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3701 .cindex "giving up on messages"
3702 .cindex "message" "abandoning delivery attempts"
3703 .cindex "delivery" "abandoning further attempts"
3704 This option requests Exim to give up trying to deliver the listed messages,
3705 including any that are frozen. However, if any of the messages are active,
3706 their status is not altered. For non-bounce messages, a delivery error message
3707 is sent to the sender, containing the text &"cancelled by administrator"&.
3708 Bounce messages are just discarded. This option can be used only by an admin
3711 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3713 .cindex "delivery" "cancelling all"
3714 This option requests Exim to mark all the recipient addresses in the messages
3715 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3716 message is active (in the middle of a delivery attempt), its status is not
3717 altered. This option can be used only by an admin user.
3719 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3721 .cindex "delivery" "cancelling by address"
3722 .cindex "recipient" "removing"
3723 .cindex "removing recipients"
3724 This option requests Exim to mark the given addresses as already delivered
3725 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3726 the remaining ones must be email addresses. These are matched to recipient
3727 addresses in the message in a case-sensitive manner. If the message is active
3728 (in the middle of a delivery attempt), its status is not altered. This option
3729 can be used only by an admin user.
3731 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3733 .cindex "removing messages"
3734 .cindex "abandoning mail"
3735 .cindex "message" "manually discarding"
3736 This option requests Exim to remove the given messages from the queue. No
3737 bounce messages are sent; each message is simply forgotten. However, if any of
3738 the messages are active, their status is not altered. This option can be used
3739 only by an admin user or by the user who originally caused the message to be
3740 placed on the queue.
3742 .vitem &%-Mset%&&~<&'message&~id'&>
3744 .cindex "testing" "string expansion"
3745 .cindex "expansion" "testing"
3746 This option is useful only in conjunction with &%-be%& (that is, when testing
3747 string expansions). Exim loads the given message from its spool before doing
3748 the test expansions, thus setting message-specific variables such as
3749 &$message_size$& and the header variables. The &$recipients$& variable is made
3750 available. This feature is provided to make it easier to test expansions that
3751 make use of these variables. However, this option can be used only by an admin
3752 user. See also &%-bem%&.
3754 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3756 .cindex "thawing messages"
3757 .cindex "unfreezing messages"
3758 .cindex "frozen messages" "thawing"
3759 .cindex "message" "thawing frozen"
3760 This option requests Exim to &"thaw"& any of the listed messages that are
3761 &"frozen"&, so that delivery attempts can resume. However, if any of the
3762 messages are active, their status is not altered. This option can be used only
3765 .vitem &%-Mvb%&&~<&'message&~id'&>
3767 .cindex "listing" "message body"
3768 .cindex "message" "listing body of"
3769 This option causes the contents of the message body (-D) spool file to be
3770 written to the standard output. This option can be used only by an admin user.
3772 .vitem &%-Mvc%&&~<&'message&~id'&>
3774 .cindex "message" "listing in RFC 2822 format"
3775 .cindex "listing" "message in RFC 2822 format"
3776 This option causes a copy of the complete message (header lines plus body) to
3777 be written to the standard output in RFC 2822 format. This option can be used
3778 only by an admin user.
3780 .vitem &%-Mvh%&&~<&'message&~id'&>
3782 .cindex "listing" "message headers"
3783 .cindex "header lines" "listing"
3784 .cindex "message" "listing header lines"
3785 This option causes the contents of the message headers (-H) spool file to be
3786 written to the standard output. This option can be used only by an admin user.
3788 .vitem &%-Mvl%&&~<&'message&~id'&>
3790 .cindex "listing" "message log"
3791 .cindex "message" "listing message log"
3792 This option causes the contents of the message log spool file to be written to
3793 the standard output. This option can be used only by an admin user.
3797 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3798 treats it that way too.
3802 .cindex "debugging" "&%-N%& option"
3803 .cindex "debugging" "suppressing delivery"
3804 This is a debugging option that inhibits delivery of a message at the transport
3805 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3806 it just doesn't actually transport the message, but instead behaves as if it
3807 had successfully done so. However, it does not make any updates to the retry
3808 database, and the log entries for deliveries are flagged with &"*>"& rather
3811 Because &%-N%& discards any message to which it applies, only root or the Exim
3812 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3813 words, an ordinary user can use it only when supplying an incoming message to
3814 which it will apply. Although transportation never fails when &%-N%& is set, an
3815 address may be deferred because of a configuration problem on a transport, or a
3816 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3817 the message, and applies to any subsequent delivery attempts that may happen
3822 .cindex "Sendmail compatibility" "&%-n%& option ignored"
3823 This option is interpreted by Sendmail to mean &"no aliasing"&. It is ignored
3826 .vitem &%-O%&&~<&'data'&>
3828 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
3831 .vitem &%-oA%&&~<&'file&~name'&>
3833 .cindex "Sendmail compatibility" "&%-oA%& option"
3834 This option is used by Sendmail in conjunction with &%-bi%& to specify an
3835 alternative alias file name. Exim handles &%-bi%& differently; see the
3838 .vitem &%-oB%&&~<&'n'&>
3840 .cindex "SMTP" "passed connection"
3841 .cindex "SMTP" "multiple deliveries"
3842 .cindex "multiple SMTP deliveries"
3843 This is a debugging option which limits the maximum number of messages that can
3844 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
3845 transport. If <&'n'&> is omitted, the limit is set to 1.
3849 .cindex "background delivery"
3850 .cindex "delivery" "in the background"
3851 This option applies to all modes in which Exim accepts incoming messages,
3852 including the listening daemon. It requests &"background"& delivery of such
3853 messages, which means that the accepting process automatically starts a
3854 delivery process for each message received, but does not wait for the delivery
3855 processes to finish.
3857 When all the messages have been received, the reception process exits,
3858 leaving the delivery processes to finish in their own time. The standard output
3859 and error streams are closed at the start of each delivery process.
3860 This is the default action if none of the &%-od%& options are present.
3862 If one of the queueing options in the configuration file
3863 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
3864 overrides it if &%queue_only_override%& is set true, which is the default
3865 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
3869 .cindex "foreground delivery"
3870 .cindex "delivery" "in the foreground"
3871 This option requests &"foreground"& (synchronous) delivery when Exim has
3872 accepted a locally-generated message. (For the daemon it is exactly the same as
3873 &%-odb%&.) A delivery process is automatically started to deliver the message,
3874 and Exim waits for it to complete before proceeding.
3876 The original Exim reception process does not finish until the delivery
3877 process for the final message has ended. The standard error stream is left open
3880 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
3881 false and one of the queueing options in the configuration file is in effect.
3883 If there is a temporary delivery error during foreground delivery, the
3884 message is left on the queue for later delivery, and the original reception
3885 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
3886 restricted configuration that never queues messages.
3891 This option is synonymous with &%-odf%&. It is provided for compatibility with
3896 .cindex "non-immediate delivery"
3897 .cindex "delivery" "suppressing immediate"
3898 .cindex "queueing incoming messages"
3899 This option applies to all modes in which Exim accepts incoming messages,
3900 including the listening daemon. It specifies that the accepting process should
3901 not automatically start a delivery process for each message received. Messages
3902 are placed on the queue, and remain there until a subsequent queue runner
3903 process encounters them. There are several configuration options (such as
3904 &%queue_only%&) that can be used to queue incoming messages under certain
3905 conditions. This option overrides all of them and also &%-odqs%&. It always
3910 .cindex "SMTP" "delaying delivery"
3911 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
3912 However, like &%-odb%& and &%-odi%&, this option has no effect if
3913 &%queue_only_override%& is false and one of the queueing options in the
3914 configuration file is in effect.
3916 When &%-odqs%& does operate, a delivery process is started for each incoming
3917 message, in the background by default, but in the foreground if &%-odi%& is
3918 also present. The recipient addresses are routed, and local deliveries are done
3919 in the normal way. However, if any SMTP deliveries are required, they are not
3920 done at this time, so the message remains on the queue until a subsequent queue
3921 runner process encounters it. Because routing was done, Exim knows which
3922 messages are waiting for which hosts, and so a number of messages for the same
3923 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
3924 configuration option has the same effect for specific domains. See also the
3929 .cindex "error" "reporting"
3930 If an error is detected while a non-SMTP message is being received (for
3931 example, a malformed address), the error is reported to the sender in a mail
3934 .cindex "return code" "for &%-oee%&"
3936 this error message is successfully sent, the Exim receiving process
3937 exits with a return code of zero. If not, the return code is 2 if the problem
3938 is that the original message has no recipients, or 1 any other error. This is
3939 the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
3943 .cindex "error" "reporting"
3944 .cindex "return code" "for &%-oem%&"
3945 This is the same as &%-oee%&, except that Exim always exits with a non-zero
3946 return code, whether or not the error message was successfully sent.
3947 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
3951 .cindex "error" "reporting"
3952 If an error is detected while a non-SMTP message is being received, the
3953 error is reported by writing a message to the standard error file (stderr).
3954 .cindex "return code" "for &%-oep%&"
3955 The return code is 1 for all errors.
3959 .cindex "error" "reporting"
3960 This option is supported for compatibility with Sendmail, but has the same
3965 .cindex "error" "reporting"
3966 This option is supported for compatibility with Sendmail, but has the same
3971 .cindex "dot" "in incoming non-SMTP message"
3972 This option, which has the same effect as &%-i%&, specifies that a dot on a
3973 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
3974 single dot does terminate, though Exim does no special processing for other
3975 lines that start with a dot. This option is set by default if Exim is called as
3976 &'rmail'&. See also &%-ti%&.
3979 .oindex "&%-oitrue%&"
3980 This option is treated as synonymous with &%-oi%&.
3982 .vitem &%-oMa%&&~<&'host&~address'&>
3984 .cindex "sender" "host address, specifying for local message"
3985 A number of options starting with &%-oM%& can be used to set values associated
3986 with remote hosts on locally-submitted messages (that is, messages not received
3987 over TCP/IP). These options can be used by any caller in conjunction with the
3988 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
3989 other circumstances, they are ignored unless the caller is trusted.
3991 The &%-oMa%& option sets the sender host address. This may include a port
3992 number at the end, after a full stop (period). For example:
3994 exim -bs -oMa 10.9.8.7.1234
3996 An alternative syntax is to enclose the IP address in square brackets,
3997 followed by a colon and the port number:
3999 exim -bs -oMa [10.9.8.7]:1234
4001 The IP address is placed in the &$sender_host_address$& variable, and the
4002 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4003 are present on the command line, the sender host IP address is taken from
4004 whichever one is last.
4006 .vitem &%-oMaa%&&~<&'name'&>
4008 .cindex "authentication" "name, specifying for local message"
4009 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4010 option sets the value of &$sender_host_authenticated$& (the authenticator
4011 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4012 This option can be used with &%-bh%& and &%-bs%& to set up an
4013 authenticated SMTP session without actually using the SMTP AUTH command.
4015 .vitem &%-oMai%&&~<&'string'&>
4017 .cindex "authentication" "id, specifying for local message"
4018 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4019 option sets the value of &$authenticated_id$& (the id that was authenticated).
4020 This overrides the default value (the caller's login id, except with &%-bh%&,
4021 where there is no default) for messages from local sources. See chapter
4022 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4024 .vitem &%-oMas%&&~<&'address'&>
4026 .cindex "authentication" "sender, specifying for local message"
4027 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4028 option sets the authenticated sender value in &$authenticated_sender$&. It
4029 overrides the sender address that is created from the caller's login id for
4030 messages from local sources, except when &%-bh%& is used, when there is no
4031 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4032 specified on a MAIL command overrides this value. See chapter
4033 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4035 .vitem &%-oMi%&&~<&'interface&~address'&>
4037 .cindex "interface" "address, specifying for local message"
4038 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4039 option sets the IP interface address value. A port number may be included,
4040 using the same syntax as for &%-oMa%&. The interface address is placed in
4041 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4043 .vitem &%-oMr%&&~<&'protocol&~name'&>
4045 .cindex "protocol, specifying for local message"
4046 .vindex "&$received_protocol$&"
4047 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4048 option sets the received protocol value that is stored in
4049 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4050 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4051 SMTP protocol names (see the description of &$received_protocol$& in section
4052 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4053 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4056 .vitem &%-oMs%&&~<&'host&~name'&>
4058 .cindex "sender" "host name, specifying for local message"
4059 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4060 option sets the sender host name in &$sender_host_name$&. When this option is
4061 present, Exim does not attempt to look up a host name from an IP address; it
4062 uses the name it is given.
4064 .vitem &%-oMt%&&~<&'ident&~string'&>
4066 .cindex "sender" "ident string, specifying for local message"
4067 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4068 option sets the sender ident value in &$sender_ident$&. The default setting for
4069 local callers is the login id of the calling process, except when &%-bh%& is
4070 used, when there is no default.
4074 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4075 In Sendmail, this option means &"me too"&, indicating that the sender of a
4076 message should receive a copy of the message if the sender appears in an alias
4077 expansion. Exim always does this, so the option does nothing.
4081 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4082 This option is ignored. In Sendmail it specifies &"old style headers"&,
4083 whatever that means.
4085 .vitem &%-oP%&&~<&'path'&>
4087 .cindex "pid (process id)" "of daemon"
4088 .cindex "daemon" "process id (pid)"
4089 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4090 value. The option specifies the file to which the process id of the daemon is
4091 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4092 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4093 because in those cases, the normal pid file is not used.
4095 .vitem &%-or%&&~<&'time'&>
4097 .cindex "timeout" "for non-SMTP input"
4098 This option sets a timeout value for incoming non-SMTP messages. If it is not
4099 set, Exim will wait forever for the standard input. The value can also be set
4100 by the &%receive_timeout%& option. The format used for specifying times is
4101 described in section &<<SECTtimeformat>>&.
4103 .vitem &%-os%&&~<&'time'&>
4105 .cindex "timeout" "for SMTP input"
4106 .cindex "SMTP" "input timeout"
4107 This option sets a timeout value for incoming SMTP messages. The timeout
4108 applies to each SMTP command and block of data. The value can also be set by
4109 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4110 for specifying times is described in section &<<SECTtimeformat>>&.
4114 This option has exactly the same effect as &%-v%&.
4116 .vitem &%-oX%&&~<&'number&~or&~string'&>
4118 .cindex "TCP/IP" "setting listening ports"
4119 .cindex "TCP/IP" "setting listening interfaces"
4120 .cindex "port" "receiving TCP/IP"
4121 This option is relevant only when the &%-bd%& (start listening daemon) option
4122 is also given. It controls which ports and interfaces the daemon uses. Details
4123 of the syntax, and how it interacts with configuration file options, are given
4124 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4125 file is written unless &%-oP%& is also present to specify a pid file name.
4129 .cindex "Perl" "starting the interpreter"
4130 This option applies when an embedded Perl interpreter is linked with Exim (see
4131 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4132 option, forcing the starting of the interpreter to be delayed until it is
4137 .cindex "Perl" "starting the interpreter"
4138 This option applies when an embedded Perl interpreter is linked with Exim (see
4139 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4140 option, forcing the starting of the interpreter to occur as soon as Exim is
4143 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4145 For compatibility with Sendmail, this option is equivalent to
4147 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4149 It sets the incoming protocol and host name (for trusted callers). The
4150 host name and its colon can be omitted when only the protocol is to be set.
4151 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4152 to embedded Perl. It is therefore impossible to set a protocol value of &`p`&
4153 or &`s`& using this option (but that does not seem a real limitation).
4157 .cindex "queue runner" "starting manually"
4158 This option is normally restricted to admin users. However, there is a
4159 configuration option called &%prod_requires_admin%& which can be set false to
4160 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4161 and &%-S%& options).
4163 .cindex "queue runner" "description of operation"
4164 The &%-q%& option starts one queue runner process. This scans the queue of
4165 waiting messages, and runs a delivery process for each one in turn. It waits
4166 for each delivery process to finish before starting the next one. A delivery
4167 process may not actually do any deliveries if the retry times for the addresses
4168 have not been reached. Use &%-qf%& (see below) if you want to override this.
4171 .cindex "SMTP" "passed connection"
4172 .cindex "SMTP" "multiple deliveries"
4173 .cindex "multiple SMTP deliveries"
4174 the delivery process spawns other processes to deliver other messages down
4175 passed SMTP connections, the queue runner waits for these to finish before
4178 When all the queued messages have been considered, the original queue runner
4179 process terminates. In other words, a single pass is made over the waiting
4180 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4181 this to be repeated periodically.
4183 Exim processes the waiting messages in an unpredictable order. It isn't very
4184 random, but it is likely to be different each time, which is all that matters.
4185 If one particular message screws up a remote MTA, other messages to the same
4186 MTA have a chance of getting through if they get tried first.
4188 It is possible to cause the messages to be processed in lexical message id
4189 order, which is essentially the order in which they arrived, by setting the
4190 &%queue_run_in_order%& option, but this is not recommended for normal use.
4192 .vitem &%-q%&<&'qflags'&>
4193 The &%-q%& option may be followed by one or more flag letters that change its
4194 behaviour. They are all optional, but if more than one is present, they must
4195 appear in the correct order. Each flag is described in a separate item below.
4199 .cindex "queue" "double scanning"
4200 .cindex "queue" "routing"
4201 .cindex "routing" "whole queue before delivery"
4202 An option starting with &%-qq%& requests a two-stage queue run. In the first
4203 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4204 every domain. Addresses are routed, local deliveries happen, but no remote
4207 .cindex "hints database" "remembering routing"
4208 The hints database that remembers which messages are waiting for specific hosts
4209 is updated, as if delivery to those hosts had been deferred. After this is
4210 complete, a second, normal queue scan happens, with routing and delivery taking
4211 place as normal. Messages that are routed to the same host should mostly be
4212 delivered down a single SMTP
4213 .cindex "SMTP" "passed connection"
4214 .cindex "SMTP" "multiple deliveries"
4215 .cindex "multiple SMTP deliveries"
4216 connection because of the hints that were set up during the first queue scan.
4217 This option may be useful for hosts that are connected to the Internet
4220 .vitem &%-q[q]i...%&
4222 .cindex "queue" "initial delivery"
4223 If the &'i'& flag is present, the queue runner runs delivery processes only for
4224 those messages that haven't previously been tried. (&'i'& stands for &"initial
4225 delivery"&.) This can be helpful if you are putting messages on the queue using
4226 &%-odq%& and want a queue runner just to process the new messages.
4228 .vitem &%-q[q][i]f...%&
4230 .cindex "queue" "forcing delivery"
4231 .cindex "delivery" "forcing in queue run"
4232 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4233 message, whereas without &'f'& only those non-frozen addresses that have passed
4234 their retry times are tried.
4236 .vitem &%-q[q][i]ff...%&
4238 .cindex "frozen messages" "forcing delivery"
4239 If &'ff'& is present, a delivery attempt is forced for every message, whether
4242 .vitem &%-q[q][i][f[f]]l%&
4244 .cindex "queue" "local deliveries only"
4245 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4246 be done. If a message requires any remote deliveries, it remains on the queue
4249 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4250 .cindex "queue" "delivering specific messages"
4251 When scanning the queue, Exim can be made to skip over messages whose ids are
4252 lexically less than a given value by following the &%-q%& option with a
4253 starting message id. For example:
4255 exim -q 0t5C6f-0000c8-00
4257 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4258 second message id is given, messages whose ids are lexically greater than it
4259 are also skipped. If the same id is given twice, for example,
4261 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4263 just one delivery process is started, for that message. This differs from
4264 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4265 that it counts as a delivery from a queue run. Note that the selection
4266 mechanism does not affect the order in which the messages are scanned. There
4267 are also other ways of selecting specific sets of messages for delivery in a
4268 queue run &-- see &%-R%& and &%-S%&.
4270 .vitem &%-q%&<&'qflags'&><&'time'&>
4271 .cindex "queue runner" "starting periodically"
4272 .cindex "periodic queue running"
4273 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4274 starting a queue runner process at intervals specified by the given time value
4275 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4276 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4277 single daemon process handles both functions. A common way of starting up a
4278 combined daemon at system boot time is to use a command such as
4280 /usr/exim/bin/exim -bd -q30m
4282 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4283 process every 30 minutes.
4285 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4286 pid file is written unless one is explicitly requested by the &%-oP%& option.
4288 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4290 This option is synonymous with &%-R%&. It is provided for Sendmail
4293 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4295 This option is synonymous with &%-S%&.
4297 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4299 .cindex "queue runner" "for specific recipients"
4300 .cindex "delivery" "to given domain"
4301 .cindex "domain" "delivery to"
4302 The <&'rsflags'&> may be empty, in which case the white space before the string
4303 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4304 which are the possible values for <&'rsflags'&>. White space is required if
4305 <&'rsflags'&> is not empty.
4307 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4308 perform a single queue run, except that, when scanning the messages on the
4309 queue, Exim processes only those that have at least one undelivered recipient
4310 address containing the given string, which is checked in a case-independent
4311 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4312 regular expression; otherwise it is a literal string.
4314 If you want to do periodic queue runs for messages with specific recipients,
4315 you can combine &%-R%& with &%-q%& and a time value. For example:
4317 exim -q25m -R @special.domain.example
4319 This example does a queue run for messages with recipients in the given domain
4320 every 25 minutes. Any additional flags that are specified with &%-q%& are
4321 applied to each queue run.
4323 Once a message is selected for delivery by this mechanism, all its addresses
4324 are processed. For the first selected message, Exim overrides any retry
4325 information and forces a delivery attempt for each undelivered address. This
4326 means that if delivery of any address in the first message is successful, any
4327 existing retry information is deleted, and so delivery attempts for that
4328 address in subsequently selected messages (which are processed without forcing)
4329 will run. However, if delivery of any address does not succeed, the retry
4330 information is updated, and in subsequently selected messages, the failing
4331 address will be skipped.
4333 .cindex "frozen messages" "forcing delivery"
4334 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4335 all selected messages, not just the first; frozen messages are included when
4338 The &%-R%& option makes it straightforward to initiate delivery of all messages
4339 to a given domain after a host has been down for some time. When the SMTP
4340 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4341 effect is to run Exim with the &%-R%& option, but it can be configured to run
4342 an arbitrary command instead.
4346 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4348 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4350 .cindex "delivery" "from given sender"
4351 .cindex "queue runner" "for specific senders"
4352 This option acts like &%-R%& except that it checks the string against each
4353 message's sender instead of against the recipients. If &%-R%& is also set, both
4354 conditions must be met for a message to be selected. If either of the options
4355 has &'f'& or &'ff'& in its flags, the associated action is taken.
4357 .vitem &%-Tqt%&&~<&'times'&>
4359 This an option that is exclusively for use by the Exim testing suite. It is not
4360 recognized when Exim is run normally. It allows for the setting up of explicit
4361 &"queue times"& so that various warning/retry features can be tested.
4365 .cindex "recipient" "extracting from header lines"
4366 .cindex "&'Bcc:'& header line"
4367 .cindex "&'Cc:'& header line"
4368 .cindex "&'To:'& header line"
4369 When Exim is receiving a locally-generated, non-SMTP message on its standard
4370 input, the &%-t%& option causes the recipients of the message to be obtained
4371 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4372 from the command arguments. The addresses are extracted before any rewriting
4373 takes place and the &'Bcc:'& header line, if present, is then removed.
4375 .cindex "Sendmail compatibility" "&%-t%& option"
4376 If the command has any arguments, they specify addresses to which the message
4377 is &'not'& to be delivered. That is, the argument addresses are removed from
4378 the recipients list obtained from the headers. This is compatible with Smail 3
4379 and in accordance with the documented behaviour of several versions of
4380 Sendmail, as described in man pages on a number of operating systems (e.g.
4381 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4382 argument addresses to those obtained from the headers, and the O'Reilly
4383 Sendmail book documents it that way. Exim can be made to add argument addresses
4384 instead of subtracting them by setting the option
4385 &%extract_addresses_remove_arguments%& false.
4387 .cindex "&%Resent-%& header lines" "with &%-t%&"
4388 If there are any &%Resent-%& header lines in the message, Exim extracts
4389 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4390 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4391 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4392 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4394 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4395 message is resent several times). The RFC also specifies that they should be
4396 added at the front of the message, and separated by &'Received:'& lines. It is
4397 not at all clear how &%-t%& should operate in the present of multiple sets,
4398 nor indeed exactly what constitutes a &"set"&.
4399 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4400 are often added at the end of the header, and if a message is resent more than
4401 once, it is common for the original set of &%Resent-%& headers to be renamed as
4402 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4406 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4407 compatibility with Sendmail.
4409 .vitem &%-tls-on-connect%&
4410 .oindex "&%-tls-on-connect%&"
4411 .cindex "TLS" "use without STARTTLS"
4412 .cindex "TLS" "automatic start"
4413 This option is available when Exim is compiled with TLS support. It forces all
4414 incoming SMTP connections to behave as if the incoming port is listed in the
4415 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4416 &<<CHAPTLS>>& for further details.
4421 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4422 Sendmail uses this option for &"initial message submission"&, and its
4423 documentation states that in future releases, it may complain about
4424 syntactically invalid messages rather than fixing them when this flag is not
4425 set. Exim ignores this option.
4429 This option causes Exim to write information to the standard error stream,
4430 describing what it is doing. In particular, it shows the log lines for
4431 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4432 dialogue is shown. Some of the log lines shown may not actually be written to
4433 the log if the setting of &%log_selector%& discards them. Any relevant
4434 selectors are shown with each log line. If none are shown, the logging is
4439 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4440 National Language Support extended characters in the body of the mail item"&).
4441 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4449 . ////////////////////////////////////////////////////////////////////////////
4450 . Insert a stylized DocBook comment here, to identify the end of the command
4451 . line options. This is for the benefit of the Perl script that automatically
4452 . creates a man page for the options.
4453 . ////////////////////////////////////////////////////////////////////////////
4456 <!-- === End of command line options === -->
4463 . ////////////////////////////////////////////////////////////////////////////
4464 . ////////////////////////////////////////////////////////////////////////////
4467 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4468 "The runtime configuration file"
4470 .cindex "run time configuration"
4471 .cindex "configuration file" "general description"
4472 .cindex "CONFIGURE_FILE"
4473 .cindex "configuration file" "errors in"
4474 .cindex "error" "in configuration file"
4475 .cindex "return code" "for bad configuration"
4476 Exim uses a single run time configuration file that is read whenever an Exim
4477 binary is executed. Note that in normal operation, this happens frequently,
4478 because Exim is designed to operate in a distributed manner, without central
4481 If a syntax error is detected while reading the configuration file, Exim
4482 writes a message on the standard error, and exits with a non-zero return code.
4483 The message is also written to the panic log. &*Note*&: Only simple syntax
4484 errors can be detected at this time. The values of any expanded options are
4485 not checked until the expansion happens, even when the expansion does not
4486 actually alter the string.
4488 The name of the configuration file is compiled into the binary for security
4489 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4490 most configurations, this specifies a single file. However, it is permitted to
4491 give a colon-separated list of file names, in which case Exim uses the first
4492 existing file in the list.
4495 .cindex "EXIM_GROUP"
4496 .cindex "CONFIGURE_OWNER"
4497 .cindex "CONFIGURE_GROUP"
4498 .cindex "configuration file" "ownership"
4499 .cindex "ownership" "configuration file"
4500 The run time configuration file must be owned by root or by the user that is
4501 specified at compile time by the EXIM_USER option, or by the user that is
4502 specified at compile time by the CONFIGURE_OWNER option (if set). The
4503 configuration file must not be world-writeable or group-writeable, unless its
4504 group is the one specified at compile time by the EXIM_GROUP option or by the
4505 CONFIGURE_GROUP option.
4507 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4508 to root, anybody who is able to edit the run time configuration file has an
4509 easy way to run commands as root. If you make your mail administrators members
4510 of the Exim group, but do not trust them with root, make sure that the run time
4511 configuration is not group writeable.
4513 A default configuration file, which will work correctly in simple situations,
4514 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4515 defines just one file name, the installation process copies the default
4516 configuration to a new file of that name if it did not previously exist. If
4517 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4518 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4523 .section "Using a different configuration file" "SECID40"
4524 .cindex "configuration file" "alternate"
4525 A one-off alternate configuration can be specified by the &%-C%& command line
4526 option, which may specify a single file or a list of files. However, when
4527 &%-C%& is used, Exim gives up its root privilege, unless called by root or the
4528 Exim user (or unless the argument for &%-C%& is identical to the built-in value
4529 from CONFIGURE_FILE). &%-C%& is useful mainly for checking the syntax of
4530 configuration files before installing them. No owner or group checks are done
4531 on a configuration file specified by &%-C%&.
4533 The privileged use of &%-C%& by the Exim user can be locked out by setting
4534 ALT_CONFIG_ROOT_ONLY in &_Local/Makefile_& when building Exim. However,
4535 if you do this, you also lock out the possibility of testing a
4536 configuration using &%-C%& right through message reception and delivery, even
4537 if the caller is root. The reception works, but by that time, Exim is running
4538 as the Exim user, so when it re-execs to regain privilege for the delivery, the
4539 use of &%-C%& causes privilege to be lost. However, root can test reception and
4540 delivery using two separate commands (one to put a message on the queue, using
4541 &%-odq%&, and another to do the delivery, using &%-M%&).
4543 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4544 prefix string with which any file named in a &%-C%& command line option must
4545 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4546 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4547 name can be used with &%-C%&.
4549 One-off changes to a configuration can be specified by the &%-D%& command line
4550 option, which defines and overrides values for macros used inside the
4551 configuration file. However, like &%-C%&, the use of this option by a
4552 non-privileged user causes Exim to discard its root privilege.
4553 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4554 completely disabled, and its use causes an immediate error exit.
4556 Some sites may wish to use the same Exim binary on different machines that
4557 share a file system, but to use different configuration files on each machine.
4558 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4559 looks for a file whose name is the configuration file name followed by a dot
4560 and the machine's node name, as obtained from the &[uname()]& function. If this
4561 file does not exist, the standard name is tried. This processing occurs for
4562 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4564 In some esoteric situations different versions of Exim may be run under
4565 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4566 help with this. See the comments in &_src/EDITME_& for details.
4570 .section "Configuration file format" "SECTconffilfor"
4571 .cindex "configuration file" "format of"
4572 .cindex "format" "configuration file"
4573 Exim's configuration file is divided into a number of different parts. General
4574 option settings must always appear at the start of the file. The other parts
4575 are all optional, and may appear in any order. Each part other than the first
4576 is introduced by the word &"begin"& followed by the name of the part. The
4580 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4583 .cindex "AUTH" "configuration"
4584 &'authenticators'&: Configuration settings for the authenticator drivers. These
4585 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4587 &'routers'&: Configuration settings for the router drivers. Routers process
4588 addresses and determine how the message is to be delivered (see chapters
4589 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4591 &'transports'&: Configuration settings for the transport drivers. Transports
4592 define mechanisms for copying messages to destinations (see chapters
4593 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4595 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4596 If there is no retry section, or if it is empty (that is, no retry rules are
4597 defined), Exim will not retry deliveries. In this situation, temporary errors
4598 are treated the same as permanent errors. Retry rules are discussed in chapter
4601 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4602 when new addresses are generated during delivery. Rewriting is discussed in
4603 chapter &<<CHAPrewrite>>&.
4605 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4606 want to use this feature, you must set
4608 LOCAL_SCAN_HAS_OPTIONS=yes
4610 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4611 facility are given in chapter &<<CHAPlocalscan>>&.
4614 .cindex "configuration file" "leading white space in"
4615 .cindex "configuration file" "trailing white space in"
4616 .cindex "white space" "in configuration file"
4617 Leading and trailing white space in configuration lines is always ignored.
4619 Blank lines in the file, and lines starting with a # character (ignoring
4620 leading white space) are treated as comments and are ignored. &*Note*&: A
4621 # character other than at the beginning of a line is not treated specially,
4622 and does not introduce a comment.
4624 Any non-comment line can be continued by ending it with a backslash. Note that
4625 the general rule for white space means that trailing white space after the
4626 backslash and leading white space at the start of continuation
4627 lines is ignored. Comment lines beginning with # (but not empty lines) may
4628 appear in the middle of a sequence of continuation lines.
4630 A convenient way to create a configuration file is to start from the
4631 default, which is supplied in &_src/configure.default_&, and add, delete, or
4632 change settings as required.
4634 The ACLs, retry rules, and rewriting rules have their own syntax which is
4635 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4636 respectively. The other parts of the configuration file have some syntactic
4637 items in common, and these are described below, from section &<<SECTcos>>&
4638 onwards. Before that, the inclusion, macro, and conditional facilities are
4643 .section "File inclusions in the configuration file" "SECID41"
4644 .cindex "inclusions in configuration file"
4645 .cindex "configuration file" "including other files"
4646 .cindex "&`.include`& in configuration file"
4647 .cindex "&`.include_if_exists`& in configuration file"
4648 You can include other files inside Exim's run time configuration file by
4651 &`.include`& <&'file name'&>
4652 &`.include_if_exists`& <&'file name'&>
4654 on a line by itself. Double quotes round the file name are optional. If you use
4655 the first form, a configuration error occurs if the file does not exist; the
4656 second form does nothing for non-existent files. In all cases, an absolute file
4659 Includes may be nested to any depth, but remember that Exim reads its
4660 configuration file often, so it is a good idea to keep them to a minimum.
4661 If you change the contents of an included file, you must HUP the daemon,
4662 because an included file is read only when the configuration itself is read.
4664 The processing of inclusions happens early, at a physical line level, so, like
4665 comment lines, an inclusion can be used in the middle of an option setting,
4668 hosts_lookup = a.b.c \
4671 Include processing happens after macro processing (see below). Its effect is to
4672 process the lines of the included file as if they occurred inline where the
4677 .section "Macros in the configuration file" "SECTmacrodefs"
4678 .cindex "macro" "description of"
4679 .cindex "configuration file" "macros"
4680 If a line in the main part of the configuration (that is, before the first
4681 &"begin"& line) begins with an upper case letter, it is taken as a macro
4682 definition, and must be of the form
4684 <&'name'&> = <&'rest of line'&>
4686 The name must consist of letters, digits, and underscores, and need not all be
4687 in upper case, though that is recommended. The rest of the line, including any
4688 continuations, is the replacement text, and has leading and trailing white
4689 space removed. Quotes are not removed. The replacement text can never end with
4690 a backslash character, but this doesn't seem to be a serious limitation.
4692 Macros may also be defined between router, transport, authenticator, or ACL
4693 definitions. They may not, however, be defined within an individual driver or
4694 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4696 .section "Macro substitution" "SECID42"
4697 Once a macro is defined, all subsequent lines in the file (and any included
4698 files) are scanned for the macro name; if there are several macros, the line is
4699 scanned for each in turn, in the order in which the macros are defined. The
4700 replacement text is not re-scanned for the current macro, though it is scanned
4701 for subsequently defined macros. For this reason, a macro name may not contain
4702 the name of a previously defined macro as a substring. You could, for example,
4705 &`ABCD_XYZ = `&<&'something'&>
4706 &`ABCD = `&<&'something else'&>
4708 but putting the definitions in the opposite order would provoke a configuration
4709 error. Macro expansion is applied to individual physical lines from the file,
4710 before checking for line continuation or file inclusion (see above). If a line
4711 consists solely of a macro name, and the expansion of the macro is empty, the
4712 line is ignored. A macro at the start of a line may turn the line into a
4713 comment line or a &`.include`& line.
4716 .section "Redefining macros" "SECID43"
4717 Once defined, the value of a macro can be redefined later in the configuration
4718 (or in an included file). Redefinition is specified by using &'=='& instead of
4723 MAC == updated value
4725 Redefinition does not alter the order in which the macros are applied to the
4726 subsequent lines of the configuration file. It is still the same order in which
4727 the macros were originally defined. All that changes is the macro's value.
4728 Redefinition makes it possible to accumulate values. For example:
4732 MAC == MAC and something added
4734 This can be helpful in situations where the configuration file is built
4735 from a number of other files.
4737 .section "Overriding macro values" "SECID44"
4738 The values set for macros in the configuration file can be overridden by the
4739 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4740 used, unless called by root or the Exim user. A definition on the command line
4741 using the &%-D%& option causes all definitions and redefinitions within the
4746 .section "Example of macro usage" "SECID45"
4747 As an example of macro usage, consider a configuration where aliases are looked
4748 up in a MySQL database. It helps to keep the file less cluttered if long
4749 strings such as SQL statements are defined separately as macros, for example:
4751 ALIAS_QUERY = select mailbox from user where \
4752 login='${quote_mysql:$local_part}';
4754 This can then be used in a &(redirect)& router setting like this:
4756 data = ${lookup mysql{ALIAS_QUERY}}
4758 In earlier versions of Exim macros were sometimes used for domain, host, or
4759 address lists. In Exim 4 these are handled better by named lists &-- see
4760 section &<<SECTnamedlists>>&.
4763 .section "Conditional skips in the configuration file" "SECID46"
4764 .cindex "configuration file" "conditional skips"
4765 .cindex "&`.ifdef`&"
4766 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4767 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4768 portions of the configuration file. The processing happens whenever the file is
4769 read (that is, when an Exim binary starts to run).
4771 The implementation is very simple. Instances of the first four directives must
4772 be followed by text that includes the names of one or macros. The condition
4773 that is tested is whether or not any macro substitution has taken place in the
4777 message_size_limit = 50M
4779 message_size_limit = 100M
4782 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
4783 otherwise. If there is more than one macro named on the line, the condition
4784 is true if any of them are defined. That is, it is an &"or"& condition. To
4785 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
4787 Although you can use a macro expansion to generate one of these directives,
4788 it is not very useful, because the condition &"there was a macro substitution
4789 in this line"& will always be true.
4791 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
4792 to clarify complicated nestings.
4796 .section "Common option syntax" "SECTcos"
4797 .cindex "common option syntax"
4798 .cindex "syntax of common options"
4799 .cindex "configuration file" "common option syntax"
4800 For the main set of options, driver options, and &[local_scan()]& options,
4801 each setting is on a line by itself, and starts with a name consisting of
4802 lower-case letters and underscores. Many options require a data value, and in
4803 these cases the name must be followed by an equals sign (with optional white
4804 space) and then the value. For example:
4806 qualify_domain = mydomain.example.com
4808 .cindex "hiding configuration option values"
4809 .cindex "configuration options" "hiding value of"
4810 .cindex "options" "hiding value of"
4811 Some option settings may contain sensitive data, for example, passwords for
4812 accessing databases. To stop non-admin users from using the &%-bP%& command
4813 line option to read these values, you can precede the option settings with the
4814 word &"hide"&. For example:
4816 hide mysql_servers = localhost/users/admin/secret-password
4818 For non-admin users, such options are displayed like this:
4820 mysql_servers = <value not displayable>
4822 If &"hide"& is used on a driver option, it hides the value of that option on
4823 all instances of the same driver.
4825 The following sections describe the syntax used for the different data types
4826 that are found in option settings.
4829 .section "Boolean options" "SECID47"
4830 .cindex "format" "boolean"
4831 .cindex "boolean configuration values"
4832 .oindex "&%no_%&&'xxx'&"
4833 .oindex "&%not_%&&'xxx'&"
4834 Options whose type is given as boolean are on/off switches. There are two
4835 different ways of specifying such options: with and without a data value. If
4836 the option name is specified on its own without data, the switch is turned on;
4837 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
4838 boolean options may be followed by an equals sign and one of the words
4839 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
4840 the following two settings have exactly the same effect:
4845 The following two lines also have the same (opposite) effect:
4850 You can use whichever syntax you prefer.
4855 .section "Integer values" "SECID48"
4856 .cindex "integer configuration values"
4857 .cindex "format" "integer"
4858 If an option's type is given as &"integer"&, the value can be given in decimal,
4859 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
4860 number is assumed. Otherwise, it is treated as an octal number unless it starts
4861 with the characters &"0x"&, in which case the remainder is interpreted as a
4864 If an integer value is followed by the letter K, it is multiplied by 1024; if
4865 it is followed by the letter M, it is multiplied by 1024x1024. When the values
4866 of integer option settings are output, values which are an exact multiple of
4867 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
4868 and M. The printing style is independent of the actual input format that was
4872 .section "Octal integer values" "SECID49"
4873 .cindex "integer format"
4874 .cindex "format" "octal integer"
4875 If an option's type is given as &"octal integer"&, its value is always
4876 interpreted as an octal number, whether or not it starts with the digit zero.
4877 Such options are always output in octal.
4880 .section "Fixed point numbers" "SECID50"
4881 .cindex "fixed point configuration values"
4882 .cindex "format" "fixed point"
4883 If an option's type is given as &"fixed-point"&, its value must be a decimal
4884 integer, optionally followed by a decimal point and up to three further digits.
4888 .section "Time intervals" "SECTtimeformat"
4889 .cindex "time interval" "specifying in configuration"
4890 .cindex "format" "time interval"
4891 A time interval is specified as a sequence of numbers, each followed by one of
4892 the following letters, with no intervening white space:
4902 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
4903 intervals are output in the same format. Exim does not restrict the values; it
4904 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
4908 .section "String values" "SECTstrings"
4909 .cindex "string" "format of configuration values"
4910 .cindex "format" "string"
4911 If an option's type is specified as &"string"&, the value can be specified with
4912 or without double-quotes. If it does not start with a double-quote, the value
4913 consists of the remainder of the line plus any continuation lines, starting at
4914 the first character after any leading white space, with trailing white space
4915 removed, and with no interpretation of the characters in the string. Because
4916 Exim removes comment lines (those beginning with #) at an early stage, they can
4917 appear in the middle of a multi-line string. The following two settings are
4918 therefore equivalent:
4920 trusted_users = uucp:mail
4921 trusted_users = uucp:\
4922 # This comment line is ignored
4925 .cindex "string" "quoted"
4926 .cindex "escape characters in quoted strings"
4927 If a string does start with a double-quote, it must end with a closing
4928 double-quote, and any backslash characters other than those used for line
4929 continuation are interpreted as escape characters, as follows:
4932 .irow &`\\`& "single backslash"
4933 .irow &`\n`& "newline"
4934 .irow &`\r`& "carriage return"
4936 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
4937 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
4941 If a backslash is followed by some other character, including a double-quote
4942 character, that character replaces the pair.
4944 Quoting is necessary only if you want to make use of the backslash escapes to
4945 insert special characters, or if you need to specify a value with leading or
4946 trailing spaces. These cases are rare, so quoting is almost never needed in
4947 current versions of Exim. In versions of Exim before 3.14, quoting was required
4948 in order to continue lines, so you may come across older configuration files
4949 and examples that apparently quote unnecessarily.
4952 .section "Expanded strings" "SECID51"
4953 .cindex "expansion" "definition of"
4954 Some strings in the configuration file are subjected to &'string expansion'&,
4955 by which means various parts of the string may be changed according to the
4956 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
4957 is as just described; in particular, the handling of backslashes in quoted
4958 strings is done as part of the input process, before expansion takes place.
4959 However, backslash is also an escape character for the expander, so any
4960 backslashes that are required for that reason must be doubled if they are
4961 within a quoted configuration string.
4964 .section "User and group names" "SECID52"
4965 .cindex "user name" "format of"
4966 .cindex "format" "user name"
4967 .cindex "groups" "name format"
4968 .cindex "format" "group name"
4969 User and group names are specified as strings, using the syntax described
4970 above, but the strings are interpreted specially. A user or group name must
4971 either consist entirely of digits, or be a name that can be looked up using the
4972 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
4975 .section "List construction" "SECTlistconstruct"
4976 .cindex "list" "syntax of in configuration"
4977 .cindex "format" "list item in configuration"
4978 .cindex "string" "list, definition of"
4979 The data for some configuration options is a list of items, with colon as the
4980 default separator. Many of these options are shown with type &"string list"& in
4981 the descriptions later in this document. Others are listed as &"domain list"&,
4982 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
4983 are all the same; however, those other than &"string list"& are subject to
4984 particular kinds of interpretation, as described in chapter
4985 &<<CHAPdomhosaddlists>>&.
4987 In all these cases, the entire list is treated as a single string as far as the
4988 input syntax is concerned. The &%trusted_users%& setting in section
4989 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
4990 in a list, it must be entered as two colons. Leading and trailing white space
4991 on each item in a list is ignored. This makes it possible to include items that
4992 start with a colon, and in particular, certain forms of IPv6 address. For
4995 local_interfaces = 127.0.0.1 : ::::1
4997 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
4999 &*Note*&: Although leading and trailing white space is ignored in individual
5000 list items, it is not ignored when parsing the list. The space after the first
5001 colon in the example above is necessary. If it were not there, the list would
5002 be interpreted as the two items 127.0.0.1:: and 1.
5004 .section "Changing list separators" "SECID53"
5005 .cindex "list separator" "changing"
5006 .cindex "IPv6" "addresses in lists"
5007 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5008 introduced to allow the separator character to be changed. If a list begins
5009 with a left angle bracket, followed by any punctuation character, that
5010 character is used instead of colon as the list separator. For example, the list
5011 above can be rewritten to use a semicolon separator like this:
5013 local_interfaces = <; 127.0.0.1 ; ::1
5015 This facility applies to all lists, with the exception of the list in
5016 &%log_file_path%&. It is recommended that the use of non-colon separators be
5017 confined to circumstances where they really are needed.
5019 .cindex "list separator" "newline as"
5020 .cindex "newline" "as list separator"
5021 It is also possible to use newline and other control characters (those with
5022 code values less than 32, plus DEL) as separators in lists. Such separators
5023 must be provided literally at the time the list is processed. For options that
5024 are string-expanded, you can write the separator using a normal escape
5025 sequence. This will be processed by the expander before the string is
5026 interpreted as a list. For example, if a newline-separated list of domains is
5027 generated by a lookup, you can process it directly by a line such as this:
5029 domains = <\n ${lookup mysql{.....}}
5031 This avoids having to change the list separator in such data. You are unlikely
5032 to want to use a control character as a separator in an option that is not
5033 expanded, because the value is literal text. However, it can be done by giving
5034 the value in quotes. For example:
5036 local_interfaces = "<\n 127.0.0.1 \n ::1"
5038 Unlike printing character separators, which can be included in list items by
5039 doubling, it is not possible to include a control character as data when it is
5040 set as the separator. Two such characters in succession are interpreted as
5041 enclosing an empty list item.
5045 .section "Empty items in lists" "SECTempitelis"
5046 .cindex "list" "empty item in"
5047 An empty item at the end of a list is always ignored. In other words, trailing
5048 separator characters are ignored. Thus, the list in
5050 senders = user@domain :
5052 contains only a single item. If you want to include an empty string as one item
5053 in a list, it must not be the last item. For example, this list contains three
5054 items, the second of which is empty:
5056 senders = user1@domain : : user2@domain
5058 &*Note*&: There must be white space between the two colons, as otherwise they
5059 are interpreted as representing a single colon data character (and the list
5060 would then contain just one item). If you want to specify a list that contains
5061 just one, empty item, you can do it as in this example:
5065 In this case, the first item is empty, and the second is discarded because it
5066 is at the end of the list.
5071 .section "Format of driver configurations" "SECTfordricon"
5072 .cindex "drivers" "configuration format"
5073 There are separate parts in the configuration for defining routers, transports,
5074 and authenticators. In each part, you are defining a number of driver
5075 instances, each with its own set of options. Each driver instance is defined by
5076 a sequence of lines like this:
5078 <&'instance name'&>:
5083 In the following example, the instance name is &(localuser)&, and it is
5084 followed by three options settings:
5089 transport = local_delivery
5091 For each driver instance, you specify which Exim code module it uses &-- by the
5092 setting of the &%driver%& option &-- and (optionally) some configuration
5093 settings. For example, in the case of transports, if you want a transport to
5094 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5095 a local file you would use the &(appendfile)& driver. Each of the drivers is
5096 described in detail in its own separate chapter later in this manual.
5098 You can have several routers, transports, or authenticators that are based on
5099 the same underlying driver (each must have a different instance name).
5101 The order in which routers are defined is important, because addresses are
5102 passed to individual routers one by one, in order. The order in which
5103 transports are defined does not matter at all. The order in which
5104 authenticators are defined is used only when Exim, as a client, is searching
5105 them to find one that matches an authentication mechanism offered by the
5108 .cindex "generic options"
5109 .cindex "options" "generic &-- definition of"
5110 Within a driver instance definition, there are two kinds of option: &'generic'&
5111 and &'private'&. The generic options are those that apply to all drivers of the
5112 same type (that is, all routers, all transports or all authenticators). The
5113 &%driver%& option is a generic option that must appear in every definition.
5114 .cindex "private options"
5115 The private options are special for each driver, and none need appear, because
5116 they all have default values.
5118 The options may appear in any order, except that the &%driver%& option must
5119 precede any private options, since these depend on the particular driver. For
5120 this reason, it is recommended that &%driver%& always be the first option.
5122 Driver instance names, which are used for reference in log entries and
5123 elsewhere, can be any sequence of letters, digits, and underscores (starting
5124 with a letter) and must be unique among drivers of the same type. A router and
5125 a transport (for example) can each have the same name, but no two router
5126 instances can have the same name. The name of a driver instance should not be
5127 confused with the name of the underlying driver module. For example, the
5128 configuration lines:
5133 create an instance of the &(smtp)& transport driver whose name is
5134 &(remote_smtp)&. The same driver code can be used more than once, with
5135 different instance names and different option settings each time. A second
5136 instance of the &(smtp)& transport, with different options, might be defined
5142 command_timeout = 10s
5144 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5145 these transport instances from routers, and these names would appear in log
5148 Comment lines may be present in the middle of driver specifications. The full
5149 list of option settings for any particular driver instance, including all the
5150 defaulted values, can be extracted by making use of the &%-bP%& command line
5158 . ////////////////////////////////////////////////////////////////////////////
5159 . ////////////////////////////////////////////////////////////////////////////
5161 .chapter "The default configuration file" "CHAPdefconfil"
5162 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5163 .cindex "default" "configuration file &""walk through""&"
5164 The default configuration file supplied with Exim as &_src/configure.default_&
5165 is sufficient for a host with simple mail requirements. As an introduction to
5166 the way Exim is configured, this chapter &"walks through"& the default
5167 configuration, giving brief explanations of the settings. Detailed descriptions
5168 of the options are given in subsequent chapters. The default configuration file
5169 itself contains extensive comments about ways you might want to modify the
5170 initial settings. However, note that there are many options that are not
5171 mentioned at all in the default configuration.
5175 .section "Main configuration settings" "SECTdefconfmain"
5176 The main (global) configuration option settings must always come first in the
5177 file. The first thing you'll see in the file, after some initial comments, is
5180 # primary_hostname =
5182 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5183 to know the official, fully qualified name of your host, and this is where you
5184 can specify it. However, in most cases you do not need to set this option. When
5185 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5187 The first three non-comment configuration lines are as follows:
5189 domainlist local_domains = @
5190 domainlist relay_to_domains =
5191 hostlist relay_from_hosts = 127.0.0.1
5193 These are not, in fact, option settings. They are definitions of two named
5194 domain lists and one named host list. Exim allows you to give names to lists of
5195 domains, hosts, and email addresses, in order to make it easier to manage the
5196 configuration file (see section &<<SECTnamedlists>>&).
5198 The first line defines a domain list called &'local_domains'&; this is used
5199 later in the configuration to identify domains that are to be delivered
5202 .cindex "@ in a domain list"
5203 There is just one item in this list, the string &"@"&. This is a special form
5204 of entry which means &"the name of the local host"&. Thus, if the local host is
5205 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5206 be delivered locally. Because the local host's name is referenced indirectly,
5207 the same configuration file can be used on different hosts.
5209 The second line defines a domain list called &'relay_to_domains'&, but the
5210 list itself is empty. Later in the configuration we will come to the part that
5211 controls mail relaying through the local host; it allows relaying to any
5212 domains in this list. By default, therefore, no relaying on the basis of a mail
5213 domain is permitted.
5215 The third line defines a host list called &'relay_from_hosts'&. This list is
5216 used later in the configuration to permit relaying from any host or IP address
5217 that matches the list. The default contains just the IP address of the IPv4
5218 loopback interface, which means that processes on the local host are able to
5219 submit mail for relaying by sending it over TCP/IP to that interface. No other
5220 hosts are permitted to submit messages for relaying.
5222 Just to be sure there's no misunderstanding: at this point in the configuration
5223 we aren't actually setting up any controls. We are just defining some domains
5224 and hosts that will be used in the controls that are specified later.
5226 The next two configuration lines are genuine option settings:
5228 acl_smtp_rcpt = acl_check_rcpt
5229 acl_smtp_data = acl_check_data
5231 These options specify &'Access Control Lists'& (ACLs) that are to be used
5232 during an incoming SMTP session for every recipient of a message (every RCPT
5233 command), and after the contents of the message have been received,
5234 respectively. The names of the lists are &'acl_check_rcpt'& and
5235 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5236 section of the configuration. The RCPT ACL controls which recipients are
5237 accepted for an incoming message &-- if a configuration does not provide an ACL
5238 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5239 contents of a message to be checked.
5241 Two commented-out option settings are next:
5243 # av_scanner = clamd:/tmp/clamd
5244 # spamd_address = 127.0.0.1 783
5246 These are example settings that can be used when Exim is compiled with the
5247 content-scanning extension. The first specifies the interface to the virus
5248 scanner, and the second specifies the interface to SpamAssassin. Further
5249 details are given in chapter &<<CHAPexiscan>>&.
5251 Three more commented-out option settings follow:
5253 # tls_advertise_hosts = *
5254 # tls_certificate = /etc/ssl/exim.crt
5255 # tls_privatekey = /etc/ssl/exim.pem
5257 These are example settings that can be used when Exim is compiled with
5258 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5259 first one specifies the list of clients that are allowed to use TLS when
5260 connecting to this server; in this case the wildcard means all clients. The
5261 other options specify where Exim should find its TLS certificate and private
5262 key, which together prove the server's identity to any clients that connect.
5263 More details are given in chapter &<<CHAPTLS>>&.
5265 Another two commented-out option settings follow:
5267 # daemon_smtp_ports = 25 : 465 : 587
5268 # tls_on_connect_ports = 465
5270 .cindex "port" "465 and 587"
5271 .cindex "port" "for message submission"
5272 .cindex "message" "submission, ports for"
5273 .cindex "ssmtp protocol"
5274 .cindex "smtps protocol"
5275 .cindex "SMTP" "ssmtp protocol"
5276 .cindex "SMTP" "smtps protocol"
5277 These options provide better support for roaming users who wish to use this
5278 server for message submission. They are not much use unless you have turned on
5279 TLS (as described in the previous paragraph) and authentication (about which
5280 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5281 on end-user networks, so RFC 4409 specifies that message submission should use
5282 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5283 configured to use port 587 correctly, so these settings also enable the
5284 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5285 &<<SECTsupobssmt>>&).
5287 Two more commented-out options settings follow:
5290 # qualify_recipient =
5292 The first of these specifies a domain that Exim uses when it constructs a
5293 complete email address from a local login name. This is often needed when Exim
5294 receives a message from a local process. If you do not set &%qualify_domain%&,
5295 the value of &%primary_hostname%& is used. If you set both of these options,
5296 you can have different qualification domains for sender and recipient
5297 addresses. If you set only the first one, its value is used in both cases.
5299 .cindex "domain literal" "recognizing format"
5300 The following line must be uncommented if you want Exim to recognize
5301 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5302 (an IP address within square brackets) instead of a named domain.
5304 # allow_domain_literals
5306 The RFCs still require this form, but many people think that in the modern
5307 Internet it makes little sense to permit mail to be sent to specific hosts by
5308 quoting their IP addresses. This ancient format has been used by people who
5309 try to abuse hosts by using them for unwanted relaying. However, some
5310 people believe there are circumstances (for example, messages addressed to
5311 &'postmaster'&) where domain literals are still useful.
5313 The next configuration line is a kind of trigger guard:
5317 It specifies that no delivery must ever be run as the root user. The normal
5318 convention is to set up &'root'& as an alias for the system administrator. This
5319 setting is a guard against slips in the configuration.
5320 The list of users specified by &%never_users%& is not, however, the complete
5321 list; the build-time configuration in &_Local/Makefile_& has an option called
5322 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5323 contents of &%never_users%& are added to this list. By default
5324 FIXED_NEVER_USERS also specifies root.
5326 When a remote host connects to Exim in order to send mail, the only information
5327 Exim has about the host's identity is its IP address. The next configuration
5332 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5333 in order to get a host name. This improves the quality of the logging
5334 information, but if you feel it is too expensive, you can remove it entirely,
5335 or restrict the lookup to hosts on &"nearby"& networks.
5336 Note that it is not always possible to find a host name from an IP address,
5337 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5340 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5341 1413 (hence their names):
5344 rfc1413_query_timeout = 5s
5346 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5347 You can limit the hosts to which these calls are made, or change the timeout
5348 that is used. If you set the timeout to zero, all ident calls are disabled.
5349 Although they are cheap and can provide useful information for tracing problem
5350 messages, some hosts and firewalls have problems with ident calls. This can
5351 result in a timeout instead of an immediate refused connection, leading to
5352 delays on starting up an incoming SMTP session.
5354 When Exim receives messages over SMTP connections, it expects all addresses to
5355 be fully qualified with a domain, as required by the SMTP definition. However,
5356 if you are running a server to which simple clients submit messages, you may
5357 find that they send unqualified addresses. The two commented-out options:
5359 # sender_unqualified_hosts =
5360 # recipient_unqualified_hosts =
5362 show how you can specify hosts that are permitted to send unqualified sender
5363 and recipient addresses, respectively.
5365 The &%percent_hack_domains%& option is also commented out:
5367 # percent_hack_domains =
5369 It provides a list of domains for which the &"percent hack"& is to operate.
5370 This is an almost obsolete form of explicit email routing. If you do not know
5371 anything about it, you can safely ignore this topic.
5373 The last two settings in the main part of the default configuration are
5374 concerned with messages that have been &"frozen"& on Exim's queue. When a
5375 message is frozen, Exim no longer continues to try to deliver it. Freezing
5376 occurs when a bounce message encounters a permanent failure because the sender
5377 address of the original message that caused the bounce is invalid, so the
5378 bounce cannot be delivered. This is probably the most common case, but there
5379 are also other conditions that cause freezing, and frozen messages are not
5380 always bounce messages.
5382 ignore_bounce_errors_after = 2d
5383 timeout_frozen_after = 7d
5385 The first of these options specifies that failing bounce messages are to be
5386 discarded after 2 days on the queue. The second specifies that any frozen
5387 message (whether a bounce message or not) is to be timed out (and discarded)
5388 after a week. In this configuration, the first setting ensures that no failing
5389 bounce message ever lasts a week.
5393 .section "ACL configuration" "SECID54"
5394 .cindex "default" "ACLs"
5395 .cindex "&ACL;" "default configuration"
5396 In the default configuration, the ACL section follows the main configuration.
5397 It starts with the line
5401 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5402 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5403 and &%acl_smtp_data%& above.
5405 .cindex "RCPT" "ACL for"
5406 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5407 RCPT command specifies one of the message's recipients. The ACL statements
5408 are considered in order, until the recipient address is either accepted or
5409 rejected. The RCPT command is then accepted or rejected, according to the
5410 result of the ACL processing.
5414 This line, consisting of a name terminated by a colon, marks the start of the
5419 This ACL statement accepts the recipient if the sending host matches the list.
5420 But what does that strange list mean? It doesn't actually contain any host
5421 names or IP addresses. The presence of the colon puts an empty item in the
5422 list; Exim matches this only if the incoming message did not come from a remote
5423 host, because in that case, the remote hostname is empty. The colon is
5424 important. Without it, the list itself is empty, and can never match anything.
5426 What this statement is doing is to accept unconditionally all recipients in
5427 messages that are submitted by SMTP from local processes using the standard
5428 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5431 deny message = Restricted characters in address
5432 domains = +local_domains
5433 local_parts = ^[.] : ^.*[@%!/|]
5435 deny message = Restricted characters in address
5436 domains = !+local_domains
5437 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5439 These statements are concerned with local parts that contain any of the
5440 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5441 Although these characters are entirely legal in local parts (in the case of
5442 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5443 in Internet mail addresses.
5445 The first three have in the past been associated with explicitly routed
5446 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5447 option). Addresses containing these characters are regularly tried by spammers
5448 in an attempt to bypass relaying restrictions, and also by open relay testing
5449 programs. Unless you really need them it is safest to reject these characters
5450 at this early stage. This configuration is heavy-handed in rejecting these
5451 characters for all messages it accepts from remote hosts. This is a deliberate
5452 policy of being as safe as possible.
5454 The first rule above is stricter, and is applied to messages that are addressed
5455 to one of the local domains handled by this host. This is implemented by the
5456 first condition, which restricts it to domains that are listed in the
5457 &'local_domains'& domain list. The &"+"& character is used to indicate a
5458 reference to a named list. In this configuration, there is just one domain in
5459 &'local_domains'&, but in general there may be many.
5461 The second condition on the first statement uses two regular expressions to
5462 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5463 or &"|"&. If you have local accounts that include these characters, you will
5464 have to modify this rule.
5466 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5467 allows them because they have been encountered in practice. (Consider the
5468 common convention of local parts constructed as
5469 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5470 the author of Exim, who has no second initial.) However, a local part starting
5471 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5472 file name (for example, for a mailing list). This is also true for local parts
5473 that contain slashes. A pipe symbol can also be troublesome if the local part
5474 is incorporated unthinkingly into a shell command line.
5476 The second rule above applies to all other domains, and is less strict. This
5477 allows your own users to send outgoing messages to sites that use slashes
5478 and vertical bars in their local parts. It blocks local parts that begin
5479 with a dot, slash, or vertical bar, but allows these characters within the
5480 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5481 and &"!"& is blocked, as before. The motivation here is to prevent your users
5482 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5484 accept local_parts = postmaster
5485 domains = +local_domains
5487 This statement, which has two conditions, accepts an incoming address if the
5488 local part is &'postmaster'& and the domain is one of those listed in the
5489 &'local_domains'& domain list. The &"+"& character is used to indicate a
5490 reference to a named list. In this configuration, there is just one domain in
5491 &'local_domains'&, but in general there may be many.
5493 The presence of this statement means that mail to postmaster is never blocked
5494 by any of the subsequent tests. This can be helpful while sorting out problems
5495 in cases where the subsequent tests are incorrectly denying access.
5497 require verify = sender
5499 This statement requires the sender address to be verified before any subsequent
5500 ACL statement can be used. If verification fails, the incoming recipient
5501 address is refused. Verification consists of trying to route the address, to
5502 see if a bounce message could be delivered to it. In the case of remote
5503 addresses, basic verification checks only the domain, but &'callouts'& can be
5504 used for more verification if required. Section &<<SECTaddressverification>>&
5505 discusses the details of address verification.
5507 accept hosts = +relay_from_hosts
5508 control = submission
5510 This statement accepts the address if the message is coming from one of the
5511 hosts that are defined as being allowed to relay through this host. Recipient
5512 verification is omitted here, because in many cases the clients are dumb MUAs
5513 that do not cope well with SMTP error responses. For the same reason, the
5514 second line specifies &"submission mode"& for messages that are accepted. This
5515 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5516 messages that are deficient in some way, for example, because they lack a
5517 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5518 probably add recipient verification here, and disable submission mode.
5520 accept authenticated = *
5521 control = submission
5523 This statement accepts the address if the client host has authenticated itself.
5524 Submission mode is again specified, on the grounds that such messages are most
5525 likely to come from MUAs. The default configuration does not define any
5526 authenticators, though it does include some nearly complete commented-out
5527 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5528 fact authenticate until you complete the authenticator definitions.
5530 require message = relay not permitted
5531 domains = +local_domains : +relay_domains
5533 This statement rejects the address if its domain is neither a local domain nor
5534 one of the domains for which this host is a relay.
5536 require verify = recipient
5538 This statement requires the recipient address to be verified; if verification
5539 fails, the address is rejected.
5541 # deny message = rejected because $sender_host_address \
5542 # is in a black list at $dnslist_domain\n\
5544 # dnslists = black.list.example
5546 # warn dnslists = black.list.example
5547 # add_header = X-Warning: $sender_host_address is in \
5548 # a black list at $dnslist_domain
5549 # log_message = found in $dnslist_domain
5551 These commented-out lines are examples of how you could configure Exim to check
5552 sending hosts against a DNS black list. The first statement rejects messages
5553 from blacklisted hosts, whereas the second just inserts a warning header
5556 # require verify = csa
5558 This commented-out line is an example of how you could turn on client SMTP
5559 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5564 The final statement in the first ACL unconditionally accepts any recipient
5565 address that has successfully passed all the previous tests.
5569 This line marks the start of the second ACL, and names it. Most of the contents
5570 of this ACL are commented out:
5573 # message = This message contains a virus \
5576 These lines are examples of how to arrange for messages to be scanned for
5577 viruses when Exim has been compiled with the content-scanning extension, and a
5578 suitable virus scanner is installed. If the message is found to contain a
5579 virus, it is rejected with the given custom error message.
5581 # warn spam = nobody
5582 # message = X-Spam_score: $spam_score\n\
5583 # X-Spam_score_int: $spam_score_int\n\
5584 # X-Spam_bar: $spam_bar\n\
5585 # X-Spam_report: $spam_report
5587 These lines are an example of how to arrange for messages to be scanned by
5588 SpamAssassin when Exim has been compiled with the content-scanning extension,
5589 and SpamAssassin has been installed. The SpamAssassin check is run with
5590 &`nobody`& as its user parameter, and the results are added to the message as a
5591 series of extra header line. In this case, the message is not rejected,
5592 whatever the spam score.
5596 This final line in the DATA ACL accepts the message unconditionally.
5599 .section "Router configuration" "SECID55"
5600 .cindex "default" "routers"
5601 .cindex "routers" "default"
5602 The router configuration comes next in the default configuration, introduced
5607 Routers are the modules in Exim that make decisions about where to send
5608 messages. An address is passed to each router in turn, until it is either
5609 accepted, or failed. This means that the order in which you define the routers
5610 matters. Each router is fully described in its own chapter later in this
5611 manual. Here we give only brief overviews.
5614 # driver = ipliteral
5615 # domains = !+local_domains
5616 # transport = remote_smtp
5618 .cindex "domain literal" "default router"
5619 This router is commented out because the majority of sites do not want to
5620 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5621 you uncomment this router, you also need to uncomment the setting of
5622 &%allow_domain_literals%& in the main part of the configuration.
5626 domains = ! +local_domains
5627 transport = remote_smtp
5628 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5631 The first uncommented router handles addresses that do not involve any local
5632 domains. This is specified by the line
5634 domains = ! +local_domains
5636 The &%domains%& option lists the domains to which this router applies, but the
5637 exclamation mark is a negation sign, so the router is used only for domains
5638 that are not in the domain list called &'local_domains'& (which was defined at
5639 the start of the configuration). The plus sign before &'local_domains'&
5640 indicates that it is referring to a named list. Addresses in other domains are
5641 passed on to the following routers.
5643 The name of the router driver is &(dnslookup)&,
5644 and is specified by the &%driver%& option. Do not be confused by the fact that
5645 the name of this router instance is the same as the name of the driver. The
5646 instance name is arbitrary, but the name set in the &%driver%& option must be
5647 one of the driver modules that is in the Exim binary.
5649 The &(dnslookup)& router routes addresses by looking up their domains in the
5650 DNS in order to obtain a list of hosts to which the address is routed. If the
5651 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5652 specified by the &%transport%& option. If the router does not find the domain
5653 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5654 the address fails and is bounced.
5656 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5657 be entirely ignored. This option is present because a number of cases have been
5658 encountered where MX records in the DNS point to host names
5659 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5660 Completely ignoring these IP addresses causes Exim to fail to route the
5661 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5662 continue to try to deliver the message periodically until the address timed
5669 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5671 file_transport = address_file
5672 pipe_transport = address_pipe
5674 Control reaches this and subsequent routers only for addresses in the local
5675 domains. This router checks to see whether the local part is defined as an
5676 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5677 data that it looks up from that file. If no data is found for the local part,
5678 the value of the &%data%& option is empty, causing the address to be passed to
5681 &_/etc/aliases_& is a conventional name for the system aliases file that is
5682 often used. That is why it is referenced by from the default configuration
5683 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5684 &_Local/Makefile_& before building Exim.
5689 # local_part_suffix = +* : -*
5690 # local_part_suffix_optional
5691 file = $home/.forward
5696 file_transport = address_file
5697 pipe_transport = address_pipe
5698 reply_transport = address_reply
5700 This is the most complicated router in the default configuration. It is another
5701 redirection router, but this time it is looking for forwarding data set up by
5702 individual users. The &%check_local_user%& setting specifies a check that the
5703 local part of the address is the login name of a local user. If it is not, the
5704 router is skipped. The two commented options that follow &%check_local_user%&,
5707 # local_part_suffix = +* : -*
5708 # local_part_suffix_optional
5710 .vindex "&$local_part_suffix$&"
5711 show how you can specify the recognition of local part suffixes. If the first
5712 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5713 by any sequence of characters, is removed from the local part and placed in the
5714 variable &$local_part_suffix$&. The second suffix option specifies that the
5715 presence of a suffix in the local part is optional. When a suffix is present,
5716 the check for a local login uses the local part with the suffix removed.
5718 When a local user account is found, the file called &_.forward_& in the user's
5719 home directory is consulted. If it does not exist, or is empty, the router
5720 declines. Otherwise, the contents of &_.forward_& are interpreted as
5721 redirection data (see chapter &<<CHAPredirect>>& for more details).
5723 .cindex "Sieve filter" "enabling in default router"
5724 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5725 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5726 is commented out by default), the contents of the file are interpreted as a set
5727 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5728 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5729 separate document entitled &'Exim's interfaces to mail filtering'&.
5731 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5732 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5733 There are two reasons for doing this:
5736 Whether or not a local user has a &_.forward_& file is not really relevant when
5737 checking an address for validity; it makes sense not to waste resources doing
5740 More importantly, when Exim is verifying addresses or handling an EXPN
5741 command during an SMTP session, it is running as the Exim user, not as root.
5742 The group is the Exim group, and no additional groups are set up.
5743 It may therefore not be possible for Exim to read users' &_.forward_& files at
5747 The setting of &%check_ancestor%& prevents the router from generating a new
5748 address that is the same as any previous address that was redirected. (This
5749 works round a problem concerning a bad interaction between aliasing and
5750 forwarding &-- see section &<<SECTredlocmai>>&).
5752 The final three option settings specify the transports that are to be used when
5753 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5754 auto-reply, respectively. For example, if a &_.forward_& file contains
5756 a.nother@elsewhere.example, /home/spqr/archive
5758 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5764 # local_part_suffix = +* : -*
5765 # local_part_suffix_optional
5766 transport = local_delivery
5768 The final router sets up delivery into local mailboxes, provided that the local
5769 part is the name of a local login, by accepting the address and assigning it to
5770 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5771 routers, so the address is bounced. The commented suffix settings fulfil the
5772 same purpose as they do for the &(userforward)& router.
5775 .section "Transport configuration" "SECID56"
5776 .cindex "default" "transports"
5777 .cindex "transports" "default"
5778 Transports define mechanisms for actually delivering messages. They operate
5779 only when referenced from routers, so the order in which they are defined does
5780 not matter. The transports section of the configuration starts with
5784 One remote transport and four local transports are defined.
5789 This transport is used for delivering messages over SMTP connections. All its
5790 options are defaulted. The list of remote hosts comes from the router.
5794 file = /var/mail/$local_part
5801 This &(appendfile)& transport is used for local delivery to user mailboxes in
5802 traditional BSD mailbox format. By default it runs under the uid and gid of the
5803 local user, which requires the sticky bit to be set on the &_/var/mail_&
5804 directory. Some systems use the alternative approach of running mail deliveries
5805 under a particular group instead of using the sticky bit. The commented options
5806 show how this can be done.
5808 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
5809 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
5810 similarly-named options above.
5816 This transport is used for handling deliveries to pipes that are generated by
5817 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
5818 option specifies that any output generated by the pipe is to be returned to the
5827 This transport is used for handling deliveries to files that are generated by
5828 redirection. The name of the file is not specified in this instance of
5829 &(appendfile)&, because it comes from the &(redirect)& router.
5834 This transport is used for handling automatic replies generated by users'
5839 .section "Default retry rule" "SECID57"
5840 .cindex "retry" "default rule"
5841 .cindex "default" "retry rule"
5842 The retry section of the configuration file contains rules which affect the way
5843 Exim retries deliveries that cannot be completed at the first attempt. It is
5844 introduced by the line
5848 In the default configuration, there is just one rule, which applies to all
5851 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
5853 This causes any temporarily failing address to be retried every 15 minutes for
5854 2 hours, then at intervals starting at one hour and increasing by a factor of
5855 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
5856 is not delivered after 4 days of temporary failure, it is bounced.
5858 If the retry section is removed from the configuration, or is empty (that is,
5859 if no retry rules are defined), Exim will not retry deliveries. This turns
5860 temporary errors into permanent errors.
5863 .section "Rewriting configuration" "SECID58"
5864 The rewriting section of the configuration, introduced by
5868 contains rules for rewriting addresses in messages as they arrive. There are no
5869 rewriting rules in the default configuration file.
5873 .section "Authenticators configuration" "SECTdefconfauth"
5874 .cindex "AUTH" "configuration"
5875 The authenticators section of the configuration, introduced by
5877 begin authenticators
5879 defines mechanisms for the use of the SMTP AUTH command. The default
5880 configuration file contains two commented-out example authenticators
5881 which support plaintext username/password authentication using the
5882 standard PLAIN mechanism and the traditional but non-standard LOGIN
5883 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
5884 to support most MUA software.
5886 The example PLAIN authenticator looks like this:
5889 # driver = plaintext
5890 # server_set_id = $auth2
5891 # server_prompts = :
5892 # server_condition = Authentication is not yet configured
5893 # server_advertise_condition = ${if def:tls_cipher }
5895 And the example LOGIN authenticator looks like this:
5898 # driver = plaintext
5899 # server_set_id = $auth1
5900 # server_prompts = <| Username: | Password:
5901 # server_condition = Authentication is not yet configured
5902 # server_advertise_condition = ${if def:tls_cipher }
5905 The &%server_set_id%& option makes Exim remember the authenticated username
5906 in &$authenticated_id$&, which can be used later in ACLs or routers. The
5907 &%server_prompts%& option configures the &(plaintext)& authenticator so
5908 that it implements the details of the specific authentication mechanism,
5909 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
5910 when Exim offers authentication to clients; in the examples, this is only
5911 when TLS or SSL has been started, so to enable the authenticators you also
5912 need to add support for TLS as described in &<<SECTdefconfmain>>&.
5914 The &%server_condition%& setting defines how to verify that the username and
5915 password are correct. In the examples it just produces an error message.
5916 To make the authenticators work, you can use a string expansion
5917 expression like one of the examples in &<<CHAPplaintext>>&.
5919 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
5920 usercode and password are in different positions. &<<CHAPplaintext>>&
5923 .ecindex IIDconfiwal
5927 . ////////////////////////////////////////////////////////////////////////////
5928 . ////////////////////////////////////////////////////////////////////////////
5930 .chapter "Regular expressions" "CHAPregexp"
5932 .cindex "regular expressions" "library"
5934 Exim supports the use of regular expressions in many of its options. It
5935 uses the PCRE regular expression library; this provides regular expression
5936 matching that is compatible with Perl 5. The syntax and semantics of
5937 regular expressions is discussed in many Perl reference books, and also in
5938 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
5939 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
5941 The documentation for the syntax and semantics of the regular expressions that
5942 are supported by PCRE is included in the PCRE distribution, and no further
5943 description is included here. The PCRE functions are called from Exim using
5944 the default option settings (that is, with no PCRE options set), except that
5945 the PCRE_CASELESS option is set when the matching is required to be
5948 In most cases, when a regular expression is required in an Exim configuration,
5949 it has to start with a circumflex, in order to distinguish it from plain text
5950 or an &"ends with"& wildcard. In this example of a configuration setting, the
5951 second item in the colon-separated list is a regular expression.
5953 domains = a.b.c : ^\\d{3} : *.y.z : ...
5955 The doubling of the backslash is required because of string expansion that
5956 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
5957 of this issue, and a way of avoiding the need for doubling backslashes. The
5958 regular expression that is eventually used in this example contains just one
5959 backslash. The circumflex is included in the regular expression, and has the
5960 normal effect of &"anchoring"& it to the start of the string that is being
5963 There are, however, two cases where a circumflex is not required for the
5964 recognition of a regular expression: these are the &%match%& condition in a
5965 string expansion, and the &%matches%& condition in an Exim filter file. In
5966 these cases, the relevant string is always treated as a regular expression; if
5967 it does not start with a circumflex, the expression is not anchored, and can
5968 match anywhere in the subject string.
5970 In all cases, if you want a regular expression to match at the end of a string,
5971 you must code the $ metacharacter to indicate this. For example:
5973 domains = ^\\d{3}\\.example
5975 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
5978 domains = ^\\d{3}\\.example\$
5980 if you want &'example'& to be the top-level domain. The backslash before the
5981 $ is needed because string expansion also interprets dollar characters.
5985 . ////////////////////////////////////////////////////////////////////////////
5986 . ////////////////////////////////////////////////////////////////////////////
5988 .chapter "File and database lookups" "CHAPfdlookup"
5989 .scindex IIDfidalo1 "file" "lookups"
5990 .scindex IIDfidalo2 "database" "lookups"
5991 .cindex "lookup" "description of"
5992 Exim can be configured to look up data in files or databases as it processes
5993 messages. Two different kinds of syntax are used:
5996 A string that is to be expanded may contain explicit lookup requests. These
5997 cause parts of the string to be replaced by data that is obtained from the
5998 lookup. Lookups of this type are conditional expansion items. Different results
5999 can be defined for the cases of lookup success and failure. See chapter
6000 &<<CHAPexpand>>&, where string expansions are described in detail.
6002 Lists of domains, hosts, and email addresses can contain lookup requests as a
6003 way of avoiding excessively long linear lists. In this case, the data that is
6004 returned by the lookup is often (but not always) discarded; whether the lookup
6005 succeeds or fails is what really counts. These kinds of list are described in
6006 chapter &<<CHAPdomhosaddlists>>&.
6009 String expansions, lists, and lookups interact with each other in such a way
6010 that there is no order in which to describe any one of them that does not
6011 involve references to the others. Each of these three chapters makes more sense
6012 if you have read the other two first. If you are reading this for the first
6013 time, be aware that some of it will make a lot more sense after you have read
6014 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6016 .section "Examples of different lookup syntax" "SECID60"
6017 It is easy to confuse the two different kinds of lookup, especially as the
6018 lists that may contain the second kind are always expanded before being
6019 processed as lists. Therefore, they may also contain lookups of the first kind.
6020 Be careful to distinguish between the following two examples:
6022 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6023 domains = lsearch;/some/file
6025 The first uses a string expansion, the result of which must be a domain list.
6026 No strings have been specified for a successful or a failing lookup; the
6027 defaults in this case are the looked-up data and an empty string, respectively.
6028 The expansion takes place before the string is processed as a list, and the
6029 file that is searched could contain lines like this:
6031 192.168.3.4: domain1:domain2:...
6032 192.168.1.9: domain3:domain4:...
6034 When the lookup succeeds, the result of the expansion is a list of domains (and
6035 possibly other types of item that are allowed in domain lists).
6037 In the second example, the lookup is a single item in a domain list. It causes
6038 Exim to use a lookup to see if the domain that is being processed can be found
6039 in the file. The file could contains lines like this:
6044 Any data that follows the keys is not relevant when checking that the domain
6045 matches the list item.
6047 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6048 Consider a file containing lines like this:
6050 192.168.5.6: lsearch;/another/file
6052 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6053 first &%domains%& setting above generates the second setting, which therefore
6054 causes a second lookup to occur.
6056 The rest of this chapter describes the different lookup types that are
6057 available. Any of them can be used in any part of the configuration where a
6058 lookup is permitted.
6061 .section "Lookup types" "SECID61"
6062 .cindex "lookup" "types of"
6063 .cindex "single-key lookup" "definition of"
6064 Two different types of data lookup are implemented:
6067 The &'single-key'& type requires the specification of a file in which to look,
6068 and a single key to search for. The key must be a non-empty string for the
6069 lookup to succeed. The lookup type determines how the file is searched.
6071 .cindex "query-style lookup" "definition of"
6072 The &'query-style'& type accepts a generalized database query. No particular
6073 key value is assumed by Exim for query-style lookups. You can use whichever
6074 Exim variables you need to construct the database query.
6077 The code for each lookup type is in a separate source file that is included in
6078 the binary of Exim only if the corresponding compile-time option is set. The
6079 default settings in &_src/EDITME_& are:
6084 which means that only linear searching and DBM lookups are included by default.
6085 For some types of lookup (e.g. SQL databases), you need to install appropriate
6086 libraries and header files before building Exim.
6091 .section "Single-key lookup types" "SECTsinglekeylookups"
6092 .cindex "lookup" "single-key types"
6093 .cindex "single-key lookup" "list of types"
6094 The following single-key lookup types are implemented:
6097 .cindex "cdb" "description of"
6098 .cindex "lookup" "cdb"
6099 .cindex "binary zero" "in lookup key"
6100 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6101 string without a terminating binary zero. The cdb format is designed for
6102 indexed files that are read frequently and never updated, except by total
6103 re-creation. As such, it is particularly suitable for large files containing
6104 aliases or other indexed data referenced by an MTA. Information about cdb can
6105 be found in several places:
6107 &url(http://www.pobox.com/~djb/cdb.html)
6108 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6109 &url(http://packages.debian.org/stable/utils/freecdb.html)
6111 A cdb distribution is not needed in order to build Exim with cdb support,
6112 because the code for reading cdb files is included directly in Exim itself.
6113 However, no means of building or testing cdb files is provided with Exim, so
6114 you need to obtain a cdb distribution in order to do this.
6116 .cindex "DBM" "lookup type"
6117 .cindex "lookup" "dbm"
6118 .cindex "binary zero" "in lookup key"
6119 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6120 DBM file by looking up the record with the given key. A terminating binary
6121 zero is included in the key that is passed to the DBM library. See section
6122 &<<SECTdb>>& for a discussion of DBM libraries.
6124 .cindex "Berkeley DB library" "file format"
6125 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6126 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6127 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6128 the DB_UNKNOWN option. This enables it to handle any of the types of database
6129 that the library supports, and can be useful for accessing DBM files created by
6130 other applications. (For earlier DB versions, DB_HASH is always used.)
6132 .cindex "lookup" "dbmnz"
6133 .cindex "lookup" "dbm &-- terminating zero"
6134 .cindex "binary zero" "in lookup key"
6136 .cindex "&_/etc/userdbshadow.dat_&"
6137 .cindex "dmbnz lookup type"
6138 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6139 is not included in the key that is passed to the DBM library. You may need this
6140 if you want to look up data in files that are created by or shared with some
6141 other application that does not use terminating zeros. For example, you need to
6142 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6143 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6144 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6145 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6147 .cindex "lookup" "dsearch"
6148 .cindex "dsearch lookup type"
6149 &(dsearch)&: The given file must be a directory; this is searched for an entry
6150 whose name is the key by calling the &[lstat()]& function. The key may not
6151 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6152 the lookup is the name of the entry, which may be a file, directory,
6153 symbolic link, or any other kind of directory entry. An example of how this
6154 lookup can be used to support virtual domains is given in section
6155 &<<SECTvirtualdomains>>&.
6157 .cindex "lookup" "iplsearch"
6158 .cindex "iplsearch lookup type"
6159 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6160 terminated by a colon or white space or the end of the line. The keys in the
6161 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6162 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6163 being interpreted as a key terminator. For example:
6165 1.2.3.4: data for 1.2.3.4
6166 192.168.0.0/16: data for 192.168.0.0/16
6167 "abcd::cdab": data for abcd::cdab
6168 "abcd:abcd::/32" data for abcd:abcd::/32
6170 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6171 file is searched linearly, using the CIDR masks where present, until a matching
6172 key is found. The first key that matches is used; there is no attempt to find a
6173 &"best"& match. Apart from the way the keys are matched, the processing for
6174 &(iplsearch)& is the same as for &(lsearch)&.
6176 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6177 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6178 lookup types support only literal keys.
6180 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6181 the implicit key is the host's IP address rather than its name (see section
6182 &<<SECThoslispatsikey>>&).
6184 .cindex "linear search"
6185 .cindex "lookup" "lsearch"
6186 .cindex "lsearch lookup type"
6187 .cindex "case sensitivity" "in lsearch lookup"
6188 &(lsearch)&: The given file is a text file that is searched linearly for a
6189 line beginning with the search key, terminated by a colon or white space or the
6190 end of the line. The search is case-insensitive; that is, upper and lower case
6191 letters are treated as the same. The first occurrence of the key that is found
6192 in the file is used.
6194 White space between the key and the colon is permitted. The remainder of the
6195 line, with leading and trailing white space removed, is the data. This can be
6196 continued onto subsequent lines by starting them with any amount of white
6197 space, but only a single space character is included in the data at such a
6198 junction. If the data begins with a colon, the key must be terminated by a
6203 Empty lines and lines beginning with # are ignored, even if they occur in the
6204 middle of an item. This is the traditional textual format of alias files. Note
6205 that the keys in an &(lsearch)& file are literal strings. There is no
6206 wildcarding of any kind.
6208 .cindex "lookup" "lsearch &-- colons in keys"
6209 .cindex "white space" "in lsearch key"
6210 In most &(lsearch)& files, keys are not required to contain colons or #
6211 characters, or white space. However, if you need this feature, it is available.
6212 If a key begins with a doublequote character, it is terminated only by a
6213 matching quote (or end of line), and the normal escaping rules apply to its
6214 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6215 quoted keys (exactly as for unquoted keys). There is no special handling of
6216 quotes for the data part of an &(lsearch)& line.
6219 .cindex "NIS lookup type"
6220 .cindex "lookup" "NIS"
6221 .cindex "binary zero" "in lookup key"
6222 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6223 the given key, without a terminating binary zero. There is a variant called
6224 &(nis0)& which does include the terminating binary zero in the key. This is
6225 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6226 aliases; the full map names must be used.
6229 .cindex "wildlsearch lookup type"
6230 .cindex "lookup" "wildlsearch"
6231 .cindex "nwildlsearch lookup type"
6232 .cindex "lookup" "nwildlsearch"
6233 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6234 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6235 the file may be wildcarded. The difference between these two lookup types is
6236 that for &(wildlsearch)&, each key in the file is string-expanded before being
6237 used, whereas for &(nwildlsearch)&, no expansion takes place.
6239 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6240 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6241 file that are regular expressions can be made case-sensitive by the use of
6242 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6244 . ==== As this is a nested list, any displays it contains must be indented
6245 . ==== as otherwise they are too far to the left.
6248 The string may begin with an asterisk to mean &"ends with"&. For example:
6250 *.a.b.c data for anything.a.b.c
6251 *fish data for anythingfish
6254 The string may begin with a circumflex to indicate a regular expression. For
6255 example, for &(wildlsearch)&:
6257 ^\N\d+\.a\.b\N data for <digits>.a.b
6259 Note the use of &`\N`& to disable expansion of the contents of the regular
6260 expression. If you are using &(nwildlsearch)&, where the keys are not
6261 string-expanded, the equivalent entry is:
6263 ^\d+\.a\.b data for <digits>.a.b
6265 The case-insensitive flag is set at the start of compiling the regular
6266 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6267 For example, to make the entire pattern case-sensitive:
6269 ^(?-i)\d+\.a\.b data for <digits>.a.b
6272 If the regular expression contains white space or colon characters, you must
6273 either quote it (see &(lsearch)& above), or represent these characters in other
6274 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6275 colon. This may be easier than quoting, because if you quote, you have to
6276 escape all the backslashes inside the quotes.
6278 &*Note*&: It is not possible to capture substrings in a regular expression
6279 match for later use, because the results of all lookups are cached. If a lookup
6280 is repeated, the result is taken from the cache, and no actual pattern matching
6281 takes place. The values of all the numeric variables are unset after a
6282 &((n)wildlsearch)& match.
6285 Although I cannot see it being of much use, the general matching function that
6286 is used to implement &((n)wildlsearch)& means that the string may begin with a
6287 lookup name terminated by a semicolon, and followed by lookup data. For
6290 cdb;/some/file data for keys that match the file
6292 The data that is obtained from the nested lookup is discarded.
6295 Keys that do not match any of these patterns are interpreted literally. The
6296 continuation rules for the data are the same as for &(lsearch)&, and keys may
6297 be followed by optional colons.
6299 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6300 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6301 lookup types support only literal keys.
6305 .section "Query-style lookup types" "SECID62"
6306 .cindex "lookup" "query-style types"
6307 .cindex "query-style lookup" "list of types"
6308 The supported query-style lookup types are listed below. Further details about
6309 many of them are given in later sections.
6312 .cindex "DNS" "as a lookup type"
6313 .cindex "lookup" "DNS"
6314 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6315 are given in the supplied query. The resulting data is the contents of the
6316 records. See section &<<SECTdnsdb>>&.
6318 .cindex "InterBase lookup type"
6319 .cindex "lookup" "InterBase"
6320 &(ibase)&: This does a lookup in an InterBase database.
6322 .cindex "LDAP" "lookup type"
6323 .cindex "lookup" "LDAP"
6324 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6325 returns attributes from a single entry. There is a variant called &(ldapm)&
6326 that permits values from multiple entries to be returned. A third variant
6327 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6328 any attribute values. See section &<<SECTldap>>&.
6330 .cindex "MySQL" "lookup type"
6331 .cindex "lookup" "MySQL"
6332 &(mysql)&: The format of the query is an SQL statement that is passed to a
6333 MySQL database. See section &<<SECTsql>>&.
6335 .cindex "NIS+ lookup type"
6336 .cindex "lookup" "NIS+"
6337 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6338 the field to be returned. See section &<<SECTnisplus>>&.
6340 .cindex "Oracle" "lookup type"
6341 .cindex "lookup" "Oracle"
6342 &(oracle)&: The format of the query is an SQL statement that is passed to an
6343 Oracle database. See section &<<SECTsql>>&.
6345 .cindex "lookup" "passwd"
6346 .cindex "passwd lookup type"
6347 .cindex "&_/etc/passwd_&"
6348 &(passwd)& is a query-style lookup with queries that are just user names. The
6349 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6350 success, the result string is the same as you would get from an &(lsearch)&
6351 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6352 password value. For example:
6354 *:42:42:King Rat:/home/kr:/bin/bash
6357 .cindex "PostgreSQL lookup type"
6358 .cindex "lookup" "PostgreSQL"
6359 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6360 PostgreSQL database. See section &<<SECTsql>>&.
6363 .cindex "sqlite lookup type"
6364 .cindex "lookup" "sqlite"
6365 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6366 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6369 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6370 not likely to be useful in normal operation.
6372 .cindex "whoson lookup type"
6373 .cindex "lookup" "whoson"
6374 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6375 allows a server to check whether a particular (dynamically allocated) IP
6376 address is currently allocated to a known (trusted) user and, optionally, to
6377 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6378 at one time for &"POP before SMTP"& authentication, but that approach has been
6379 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6380 &"POP before SMTP"& checking using ACL statements such as
6382 require condition = \
6383 ${lookup whoson {$sender_host_address}{yes}{no}}
6385 The query consists of a single IP address. The value returned is the name of
6386 the authenticated user, which is stored in the variable &$value$&. However, in
6387 this example, the data in &$value$& is not used; the result of the lookup is
6388 one of the fixed strings &"yes"& or &"no"&.
6393 .section "Temporary errors in lookups" "SECID63"
6394 .cindex "lookup" "temporary error in"
6395 Lookup functions can return temporary error codes if the lookup cannot be
6396 completed. For example, an SQL or LDAP database might be unavailable. For this
6397 reason, it is not advisable to use a lookup that might do this for critical
6398 options such as a list of local domains.
6400 When a lookup cannot be completed in a router or transport, delivery
6401 of the message (to the relevant address) is deferred, as for any other
6402 temporary error. In other circumstances Exim may assume the lookup has failed,
6403 or may give up altogether.
6407 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6408 .cindex "wildcard lookups"
6409 .cindex "lookup" "default values"
6410 .cindex "lookup" "wildcard"
6411 .cindex "lookup" "* added to type"
6412 .cindex "default" "in single-key lookups"
6413 In this context, a &"default value"& is a value specified by the administrator
6414 that is to be used if a lookup fails.
6416 &*Note:*& This section applies only to single-key lookups. For query-style
6417 lookups, the facilities of the query language must be used. An attempt to
6418 specify a default for a query-style lookup provokes an error.
6420 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6421 and the initial lookup fails, the key &"*"& is looked up in the file to
6422 provide a default value. See also the section on partial matching below.
6424 .cindex "*@ with single-key lookup"
6425 .cindex "lookup" "*@ added to type"
6426 .cindex "alias file" "per-domain default"
6427 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6428 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6429 character, a second lookup is done with everything before the last @ replaced
6430 by *. This makes it possible to provide per-domain defaults in alias files
6431 that include the domains in the keys. If the second lookup fails (or doesn't
6432 take place because there is no @ in the key), &"*"& is looked up.
6433 For example, a &(redirect)& router might contain:
6435 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6437 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6438 looks up these keys, in this order:
6444 The data is taken from whichever key it finds first. &*Note*&: In an
6445 &(lsearch)& file, this does not mean the first of these keys in the file. A
6446 complete scan is done for each key, and only if it is not found at all does
6447 Exim move on to try the next key.
6451 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6452 .cindex "partial matching"
6453 .cindex "wildcard lookups"
6454 .cindex "lookup" "partial matching"
6455 .cindex "lookup" "wildcard"
6456 .cindex "asterisk" "in search type"
6457 The normal operation of a single-key lookup is to search the file for an exact
6458 match with the given key. However, in a number of situations where domains are
6459 being looked up, it is useful to be able to do partial matching. In this case,
6460 information in the file that has a key starting with &"*."& is matched by any
6461 domain that ends with the components that follow the full stop. For example, if
6462 a key in a DBM file is
6464 *.dates.fict.example
6466 then when partial matching is enabled this is matched by (amongst others)
6467 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6468 by &'dates.fict.example'&, if that does not appear as a separate key in the
6471 &*Note*&: Partial matching is not available for query-style lookups. It is
6472 also not available for any lookup items in address lists (see section
6473 &<<SECTaddresslist>>&).
6475 Partial matching is implemented by doing a series of separate lookups using
6476 keys constructed by modifying the original subject key. This means that it can
6477 be used with any of the single-key lookup types, provided that
6478 partial matching keys
6479 beginning with a special prefix (default &"*."&) are included in the data file.
6480 Keys in the file that do not begin with the prefix are matched only by
6481 unmodified subject keys when partial matching is in use.
6483 Partial matching is requested by adding the string &"partial-"& to the front of
6484 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6485 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6486 is added at the start of the subject key, and it is looked up again. If that
6487 fails, further lookups are tried with dot-separated components removed from the
6488 start of the subject key, one-by-one, and &"*."& added on the front of what
6491 A minimum number of two non-* components are required. This can be adjusted
6492 by including a number before the hyphen in the search type. For example,
6493 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6494 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6495 subject key is &'2250.dates.fict.example'& then the following keys are looked
6496 up when the minimum number of non-* components is two:
6498 2250.dates.fict.example
6499 *.2250.dates.fict.example
6500 *.dates.fict.example
6503 As soon as one key in the sequence is successfully looked up, the lookup
6506 .cindex "lookup" "partial matching &-- changing prefix"
6507 .cindex "prefix" "for partial matching"
6508 The use of &"*."& as the partial matching prefix is a default that can be
6509 changed. The motivation for this feature is to allow Exim to operate with file
6510 formats that are used by other MTAs. A different prefix can be supplied in
6511 parentheses instead of the hyphen after &"partial"&. For example:
6513 domains = partial(.)lsearch;/some/file
6515 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6516 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6517 components is unchanged). The prefix may consist of any punctuation characters
6518 other than a closing parenthesis. It may be empty, for example:
6520 domains = partial1()cdb;/some/file
6522 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6523 &`a.b.c`&, &`b.c`&, and &`c`&.
6525 If &"partial0"& is specified, what happens at the end (when the lookup with
6526 just one non-wild component has failed, and the original key is shortened right
6527 down to the null string) depends on the prefix:
6530 If the prefix has zero length, the whole lookup fails.
6532 If the prefix has length 1, a lookup for just the prefix is done. For
6533 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6535 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6536 remainder is looked up. With the default prefix, therefore, the final lookup is
6537 for &"*"& on its own.
6539 Otherwise, the whole prefix is looked up.
6543 If the search type ends in &"*"& or &"*@"& (see section
6544 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6545 this implies happens after all partial lookups have failed. If &"partial0"& is
6546 specified, adding &"*"& to the search type has no effect with the default
6547 prefix, because the &"*"& key is already included in the sequence of partial
6548 lookups. However, there might be a use for lookup types such as
6549 &"partial0(.)lsearch*"&.
6551 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6552 in domain lists and the like. Partial matching works only in terms of
6553 dot-separated components; a key such as &`*fict.example`&
6554 in a database file is useless, because the asterisk in a partial matching
6555 subject key is always followed by a dot.
6560 .section "Lookup caching" "SECID64"
6561 .cindex "lookup" "caching"
6562 .cindex "caching" "lookup data"
6563 Exim caches all lookup results in order to avoid needless repetition of
6564 lookups. However, because (apart from the daemon) Exim operates as a collection
6565 of independent, short-lived processes, this caching applies only within a
6566 single Exim process. There is no inter-process lookup caching facility.
6568 For single-key lookups, Exim keeps the relevant files open in case there is
6569 another lookup that needs them. In some types of configuration this can lead to
6570 many files being kept open for messages with many recipients. To avoid hitting
6571 the operating system limit on the number of simultaneously open files, Exim
6572 closes the least recently used file when it needs to open more files than its
6573 own internal limit, which can be changed via the &%lookup_open_max%& option.
6575 The single-key lookup files are closed and the lookup caches are flushed at
6576 strategic points during delivery &-- for example, after all routing is
6582 .section "Quoting lookup data" "SECID65"
6583 .cindex "lookup" "quoting"
6584 .cindex "quoting" "in lookups"
6585 When data from an incoming message is included in a query-style lookup, there
6586 is the possibility of special characters in the data messing up the syntax of
6587 the query. For example, a NIS+ query that contains
6591 will be broken if the local part happens to contain a closing square bracket.
6592 For NIS+, data can be enclosed in double quotes like this:
6594 [name="$local_part"]
6596 but this still leaves the problem of a double quote in the data. The rule for
6597 NIS+ is that double quotes must be doubled. Other lookup types have different
6598 rules, and to cope with the differing requirements, an expansion operator
6599 of the following form is provided:
6601 ${quote_<lookup-type>:<string>}
6603 For example, the safest way to write the NIS+ query is
6605 [name="${quote_nisplus:$local_part}"]
6607 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6608 operator can be used for all lookup types, but has no effect for single-key
6609 lookups, since no quoting is ever needed in their key strings.
6614 .section "More about dnsdb" "SECTdnsdb"
6615 .cindex "dnsdb lookup"
6616 .cindex "lookup" "dnsdb"
6617 .cindex "DNS" "as a lookup type"
6618 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6619 of a record type and a domain name, separated by an equals sign. For example,
6620 an expansion string could contain:
6622 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6624 If the lookup succeeds, the result is placed in &$value$&, which in this case
6625 is used on its own as the result. If the lookup does not succeed, the
6626 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6627 &<<SECTforexpfai>>& for an explanation of what this means.
6629 The supported DNS record types are A, CNAME, MX, NS, PTR, SRV, and TXT, and,
6630 when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6631 configured). If no type is given, TXT is assumed. When the type is PTR,
6632 the data can be an IP address, written as normal; inversion and the addition of
6633 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6635 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6637 If the data for a PTR record is not a syntactically valid IP address, it is not
6638 altered and nothing is added.
6640 .cindex "MX record" "in &(dnsdb)& lookup"
6641 .cindex "SRV record" "in &(dnsdb)& lookup"
6642 For an MX lookup, both the preference value and the host name are returned for
6643 each record, separated by a space. For an SRV lookup, the priority, weight,
6644 port, and host name are returned for each record, separated by spaces.
6646 For any record type, if multiple records are found (or, for A6 lookups, if a
6647 single record leads to multiple addresses), the data is returned as a
6648 concatenation, with newline as the default separator. The order, of course,
6649 depends on the DNS resolver. You can specify a different separator character
6650 between multiple records by putting a right angle-bracket followed immediately
6651 by the new separator at the start of the query. For example:
6653 ${lookup dnsdb{>: a=host1.example}}
6655 It is permitted to specify a space as the separator character. Further
6656 white space is ignored.
6659 .cindex "TXT record" "in &(dnsdb)& lookup"
6660 For TXT records with multiple items of data, only the first item is returned,
6661 unless a separator for them is specified using a comma after the separator
6662 character followed immediately by the TXT record item separator. To concatenate
6663 items without a separator, use a semicolon instead.
6665 ${lookup dnsdb{>\n,: txt=a.b.example}}
6666 ${lookup dnsdb{>\n; txt=a.b.example}}
6668 It is permitted to specify a space as the separator character. Further
6669 white space is ignored.
6672 .section "Pseudo dnsdb record types" "SECID66"
6673 .cindex "MX record" "in &(dnsdb)& lookup"
6674 By default, both the preference value and the host name are returned for
6675 each MX record, separated by a space. If you want only host names, you can use
6676 the pseudo-type MXH:
6678 ${lookup dnsdb{mxh=a.b.example}}
6680 In this case, the preference values are omitted, and just the host names are
6683 .cindex "name server for enclosing domain"
6684 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6685 records on the given domain, but if none are found, it removes the first
6686 component of the domain name, and tries again. This process continues until NS
6687 records are found or there are no more components left (or there is a DNS
6688 error). In other words, it may return the name servers for a top-level domain,
6689 but it never returns the root name servers. If there are no NS records for the
6690 top-level domain, the lookup fails. Consider these examples:
6692 ${lookup dnsdb{zns=xxx.quercite.com}}
6693 ${lookup dnsdb{zns=xxx.edu}}
6695 Assuming that in each case there are no NS records for the full domain name,
6696 the first returns the name servers for &%quercite.com%&, and the second returns
6697 the name servers for &%edu%&.
6699 You should be careful about how you use this lookup because, unless the
6700 top-level domain does not exist, the lookup always returns some host names. The
6701 sort of use to which this might be put is for seeing if the name servers for a
6702 given domain are on a blacklist. You can probably assume that the name servers
6703 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6706 .cindex "CSA" "in &(dnsdb)& lookup"
6707 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6708 records according to the CSA rules, which are described in section
6709 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6710 not sufficient because of the extra parent domain search behaviour of CSA. The
6711 result of a successful lookup such as:
6713 ${lookup dnsdb {csa=$sender_helo_name}}
6715 has two space-separated fields: an authorization code and a target host name.
6716 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6717 authorization required but absent, or &"?"& for unknown.
6720 .section "Multiple dnsdb lookups" "SECID67"
6721 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6722 However, you can specify a list of domains or IP addresses in a single
6723 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6724 the default separator, but with the ability to change this. For example:
6726 ${lookup dnsdb{one.domain.com:two.domain.com}}
6727 ${lookup dnsdb{a=one.host.com:two.host.com}}
6728 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6730 In order to retain backwards compatibility, there is one special case: if
6731 the lookup type is PTR and no change of separator is specified, Exim looks
6732 to see if the rest of the string is precisely one IPv6 address. In this
6733 case, it does not treat it as a list.
6735 The data from each lookup is concatenated, with newline separators by default,
6736 in the same way that multiple DNS records for a single item are handled. A
6737 different separator can be specified, as described above.
6739 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6740 temporary DNS error for any of them, the behaviour is controlled by
6741 an optional keyword followed by a comma that may appear before the record
6742 type. The possible keywords are &"defer_strict"&, &"defer_never"&, and
6743 &"defer_lax"&. With &"strict"& behaviour, any temporary DNS error causes the
6744 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6745 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6746 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6747 error causes the whole lookup to defer only if none of the other lookups
6748 succeed. The default is &"lax"&, so the following lookups are equivalent:
6750 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6751 ${lookup dnsdb{a=one.host.com:two.host.com}}
6753 Thus, in the default case, as long as at least one of the DNS lookups
6754 yields some data, the lookup succeeds.
6759 .section "More about LDAP" "SECTldap"
6760 .cindex "LDAP" "lookup, more about"
6761 .cindex "lookup" "LDAP"
6762 .cindex "Solaris" "LDAP"
6763 The original LDAP implementation came from the University of Michigan; this has
6764 become &"Open LDAP"&, and there are now two different releases. Another
6765 implementation comes from Netscape, and Solaris 7 and subsequent releases
6766 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6767 the lookup function level, their error handling is different. For this reason
6768 it is necessary to set a compile-time variable when building Exim with LDAP, to
6769 indicate which LDAP library is in use. One of the following should appear in
6770 your &_Local/Makefile_&:
6772 LDAP_LIB_TYPE=UMICHIGAN
6773 LDAP_LIB_TYPE=OPENLDAP1
6774 LDAP_LIB_TYPE=OPENLDAP2
6775 LDAP_LIB_TYPE=NETSCAPE
6776 LDAP_LIB_TYPE=SOLARIS
6778 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
6779 same interface as the University of Michigan version.
6781 There are three LDAP lookup types in Exim. These behave slightly differently in
6782 the way they handle the results of a query:
6785 &(ldap)& requires the result to contain just one entry; if there are more, it
6788 &(ldapdn)& also requires the result to contain just one entry, but it is the
6789 Distinguished Name that is returned rather than any attribute values.
6791 &(ldapm)& permits the result to contain more than one entry; the attributes
6792 from all of them are returned.
6796 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
6797 Exim behaves as if the entry did not exist, and the lookup fails. The format of
6798 the data returned by a successful lookup is described in the next section.
6799 First we explain how LDAP queries are coded.
6802 .section "Format of LDAP queries" "SECTforldaque"
6803 .cindex "LDAP" "query format"
6804 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
6805 the configuration of a &(redirect)& router one might have this setting:
6807 data = ${lookup ldap \
6808 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
6809 c=UK?mailbox?base?}}
6811 .cindex "LDAP" "with TLS"
6812 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
6813 secure (encrypted) LDAP connections. The second of these ensures that an
6814 encrypted TLS connection is used.
6817 .section "LDAP quoting" "SECID68"
6818 .cindex "LDAP" "quoting"
6819 Two levels of quoting are required in LDAP queries, the first for LDAP itself
6820 and the second because the LDAP query is represented as a URL. Furthermore,
6821 within an LDAP query, two different kinds of quoting are required. For this
6822 reason, there are two different LDAP-specific quoting operators.
6824 The &%quote_ldap%& operator is designed for use on strings that are part of
6825 filter specifications. Conceptually, it first does the following conversions on
6833 in accordance with RFC 2254. The resulting string is then quoted according
6834 to the rules for URLs, that is, all non-alphanumeric characters except
6838 are converted to their hex values, preceded by a percent sign. For example:
6840 ${quote_ldap: a(bc)*, a<yz>; }
6844 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
6846 Removing the URL quoting, this is (with a leading and a trailing space):
6848 a\28bc\29\2A, a<yz>;
6850 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
6851 base DN specifications in queries. Conceptually, it first converts the string
6852 by inserting a backslash in front of any of the following characters:
6856 It also inserts a backslash before any leading spaces or # characters, and
6857 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
6858 is then quoted according to the rules for URLs. For example:
6860 ${quote_ldap_dn: a(bc)*, a<yz>; }
6864 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
6866 Removing the URL quoting, this is (with a trailing space):
6868 \ a(bc)*\, a\<yz\>\;\
6870 There are some further comments about quoting in the section on LDAP
6871 authentication below.
6874 .section "LDAP connections" "SECID69"
6875 .cindex "LDAP" "connections"
6876 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
6877 is in use, via a Unix domain socket. The example given above does not specify
6878 an LDAP server. A server that is reached by TCP/IP can be specified in a query
6881 ldap://<hostname>:<port>/...
6883 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
6884 used. When no server is specified in a query, a list of default servers is
6885 taken from the &%ldap_default_servers%& configuration option. This supplies a
6886 colon-separated list of servers which are tried in turn until one successfully
6887 handles a query, or there is a serious error. Successful handling either
6888 returns the requested data, or indicates that it does not exist. Serious errors
6889 are syntactical, or multiple values when only a single value is expected.
6890 Errors which cause the next server to be tried are connection failures, bind
6891 failures, and timeouts.
6893 For each server name in the list, a port number can be given. The standard way
6894 of specifying a host and port is to use a colon separator (RFC 1738). Because
6895 &%ldap_default_servers%& is a colon-separated list, such colons have to be
6896 doubled. For example
6898 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
6900 If &%ldap_default_servers%& is unset, a URL with no server name is passed
6901 to the LDAP library with no server name, and the library's default (normally
6902 the local host) is used.
6904 If you are using the OpenLDAP library, you can connect to an LDAP server using
6905 a Unix domain socket instead of a TCP/IP connection. This is specified by using
6906 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
6907 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
6910 For this type of connection, instead of a host name for the server, a pathname
6911 for the socket is required, and the port number is not relevant. The pathname
6912 can be specified either as an item in &%ldap_default_servers%&, or inline in
6913 the query. In the former case, you can have settings such as
6915 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
6917 When the pathname is given in the query, you have to escape the slashes as
6918 &`%2F`& to fit in with the LDAP URL syntax. For example:
6920 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
6922 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
6923 a pathname, it uses the Unix domain socket code, even if the query actually
6924 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
6925 socket connection. This behaviour means that you can use a setting of
6926 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
6927 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
6928 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
6931 If an explicit &`ldapi`& type is given in a query when a host name is
6932 specified, an error is diagnosed. However, if there are more items in
6933 &%ldap_default_servers%&, they are tried. In other words:
6936 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
6939 Using &`ldapi`& with a host name causes an error.
6943 Using &`ldapi`& with no host or path in the query, and no setting of
6944 &%ldap_default_servers%&, does whatever the library does by default.
6948 .section "LDAP authentication and control information" "SECID70"
6949 .cindex "LDAP" "authentication"
6950 The LDAP URL syntax provides no way of passing authentication and other control
6951 information to the server. To make this possible, the URL in an LDAP query may
6952 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
6953 spaces. If a value contains spaces it must be enclosed in double quotes, and
6954 when double quotes are used, backslash is interpreted in the usual way inside
6955 them. The following names are recognized:
6957 &`DEREFERENCE`& set the dereferencing parameter
6958 &`NETTIME `& set a timeout for a network operation
6959 &`USER `& set the DN, for authenticating the LDAP bind
6960 &`PASS `& set the password, likewise
6961 &`REFERRALS `& set the referrals parameter
6962 &`SIZE `& set the limit for the number of entries returned
6963 &`TIME `& set the maximum waiting time for a query
6965 The value of the DEREFERENCE parameter must be one of the words &"never"&,
6966 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
6967 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
6968 library from trying to follow referrals issued by the LDAP server.
6970 The name CONNECT is an obsolete name for NETTIME, retained for
6971 backwards compatibility. This timeout (specified as a number of seconds) is
6972 enforced from the client end for operations that can be carried out over a
6973 network. Specifically, it applies to network connections and calls to the
6974 &'ldap_result()'& function. If the value is greater than zero, it is used if
6975 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
6976 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
6977 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
6978 Netscape SDK; for OpenLDAP no action is taken.
6980 The TIME parameter (also a number of seconds) is passed to the server to
6981 set a server-side limit on the time taken to complete a search.
6984 Here is an example of an LDAP query in an Exim lookup that uses some of these
6985 values. This is a single line, folded to fit on the page:
6988 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
6989 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
6992 The encoding of spaces as &`%20`& is a URL thing which should not be done for
6993 any of the auxiliary data. Exim configuration settings that include lookups
6994 which contain password information should be preceded by &"hide"& to prevent
6995 non-admin users from using the &%-bP%& option to see their values.
6997 The auxiliary data items may be given in any order. The default is no
6998 connection timeout (the system timeout is used), no user or password, no limit
6999 on the number of entries returned, and no time limit on queries.
7001 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7002 removes any URL quoting that it may contain before passing it LDAP. Apparently
7003 some libraries do this for themselves, but some do not. Removing the URL
7004 quoting has two advantages:
7007 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7008 DNs as with DNs inside actual queries.
7010 It permits spaces inside USER= DNs.
7013 For example, a setting such as
7015 USER=cn=${quote_ldap_dn:$1}
7017 should work even if &$1$& contains spaces.
7019 Expanded data for the PASS= value should be quoted using the &%quote%&
7020 expansion operator, rather than the LDAP quote operators. The only reason this
7021 field needs quoting is to ensure that it conforms to the Exim syntax, which
7022 does not allow unquoted spaces. For example:
7026 The LDAP authentication mechanism can be used to check passwords as part of
7027 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7032 .section "Format of data returned by LDAP" "SECID71"
7033 .cindex "LDAP" "returned data formats"
7034 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7035 as a sequence of values, for example
7037 cn=manager, o=University of Cambridge, c=UK
7039 The &(ldap)& lookup type generates an error if more than one entry matches the
7040 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7041 the result between the data from different entries. It is possible for multiple
7042 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7043 you know that whatever values are returned all came from a single entry in the
7046 In the common case where you specify a single attribute in your LDAP query, the
7047 result is not quoted, and does not contain the attribute name. If the attribute
7048 has multiple values, they are separated by commas.
7050 If you specify multiple attributes, the result contains space-separated, quoted
7051 strings, each preceded by the attribute name and an equals sign. Within the
7052 quotes, the quote character, backslash, and newline are escaped with
7053 backslashes, and commas are used to separate multiple values for the attribute.
7054 Apart from the escaping, the string within quotes takes the same form as the
7055 output when a single attribute is requested. Specifying no attributes is the
7056 same as specifying all of an entry's attributes.
7058 Here are some examples of the output format. The first line of each pair is an
7059 LDAP query, and the second is the data that is returned. The attribute called
7060 &%attr1%& has two values, whereas &%attr2%& has only one value:
7062 ldap:///o=base?attr1?sub?(uid=fred)
7065 ldap:///o=base?attr2?sub?(uid=fred)
7068 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7069 attr1="value1.1, value1.2" attr2="value two"
7071 ldap:///o=base??sub?(uid=fred)
7072 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
7074 The &%extract%& operator in string expansions can be used to pick out
7075 individual fields from data that consists of &'key'&=&'value'& pairs. You can
7076 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7077 results of LDAP lookups.
7082 .section "More about NIS+" "SECTnisplus"
7083 .cindex "NIS+ lookup type"
7084 .cindex "lookup" "NIS+"
7085 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7086 and field name. If this is given, the result of a successful query is the
7087 contents of the named field; otherwise the result consists of a concatenation
7088 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7089 values containing spaces are quoted. For example, the query
7091 [name=mg1456],passwd.org_dir
7093 might return the string
7095 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7096 home=/home/mg1456 shell=/bin/bash shadow=""
7098 (split over two lines here to fit on the page), whereas
7100 [name=mg1456],passwd.org_dir:gcos
7106 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7107 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7108 operator is to double any quote characters within the text.
7112 .section "SQL lookups" "SECTsql"
7113 .cindex "SQL lookup types"
7114 .cindex "MySQL" "lookup type"
7115 .cindex "PostgreSQL lookup type"
7116 .cindex "lookup" "MySQL"
7117 .cindex "lookup" "PostgreSQL"
7118 .cindex "Oracle" "lookup type"
7119 .cindex "lookup" "Oracle"
7120 .cindex "InterBase lookup type"
7121 .cindex "lookup" "InterBase"
7122 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7123 databases. Queries for these databases contain SQL statements, so an example
7126 ${lookup mysql{select mailbox from users where id='userx'}\
7129 If the result of the query contains more than one field, the data for each
7130 field in the row is returned, preceded by its name, so the result of
7132 ${lookup pgsql{select home,name from users where id='userx'}\
7137 home=/home/userx name="Mister X"
7139 Empty values and values containing spaces are double quoted, with embedded
7140 quotes escaped by a backslash. If the result of the query contains just one
7141 field, the value is passed back verbatim, without a field name, for example:
7145 If the result of the query yields more than one row, it is all concatenated,
7146 with a newline between the data for each row.
7149 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7150 .cindex "MySQL" "lookup type"
7151 .cindex "PostgreSQL lookup type"
7152 .cindex "lookup" "MySQL"
7153 .cindex "lookup" "PostgreSQL"
7154 .cindex "Oracle" "lookup type"
7155 .cindex "lookup" "Oracle"
7156 .cindex "InterBase lookup type"
7157 .cindex "lookup" "InterBase"
7158 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7159 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7160 option (as appropriate) must be set to a colon-separated list of server
7162 (For MySQL and PostgreSQL only, the global option need not be set if all
7163 queries contain their own server information &-- see section
7164 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7165 items: host name, database name, user name, and password. In the case of
7166 Oracle, the host name field is used for the &"service name"&, and the database
7167 name field is not used and should be empty. For example:
7169 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7171 Because password data is sensitive, you should always precede the setting with
7172 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7173 option. Here is an example where two MySQL servers are listed:
7175 hide mysql_servers = localhost/users/root/secret:\
7176 otherhost/users/root/othersecret
7178 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7179 because this is a colon-separated list, the colon has to be doubled. For each
7180 query, these parameter groups are tried in order until a connection is made and
7181 a query is successfully processed. The result of a query may be that no data is
7182 found, but that is still a successful query. In other words, the list of
7183 servers provides a backup facility, not a list of different places to look.
7185 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7186 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7187 respectively, and the characters single-quote, double-quote, and backslash
7188 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
7189 addition, escapes the percent and underscore characters. This cannot be done
7190 for MySQL because these escapes are not recognized in contexts where these
7191 characters are not special.
7193 .section "Specifying the server in the query" "SECTspeserque"
7194 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7195 it is possible to specify a list of servers with an individual query. This is
7196 done by starting the query with
7198 &`servers=`&&'server1:server2:server3:...'&&`;`&
7200 Each item in the list may take one of two forms:
7202 If it contains no slashes it is assumed to be just a host name. The appropriate
7203 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7204 of the same name, and the remaining parameters (database, user, password) are
7207 If it contains any slashes, it is taken as a complete parameter set.
7209 The list of servers is used in exactly the same way as the global list.
7210 Once a connection to a server has happened and a query has been
7211 successfully executed, processing of the lookup ceases.
7213 This feature is intended for use in master/slave situations where updates
7214 are occurring and you want to update the master rather than a slave. If the
7215 master is in the list as a backup for reading, you might have a global setting
7218 mysql_servers = slave1/db/name/pw:\
7222 In an updating lookup, you could then write:
7224 ${lookup mysql{servers=master; UPDATE ...} }
7226 That query would then be sent only to the master server. If, on the other hand,
7227 the master is not to be used for reading, and so is not present in the global
7228 option, you can still update it by a query of this form:
7230 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7234 .section "Special MySQL features" "SECID73"
7235 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7236 causes a connection to the server on the local host by means of a Unix domain
7237 socket. An alternate socket can be specified in parentheses. The full syntax of
7238 each item in &%mysql_servers%& is:
7240 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
7241 <&'user'&>/<&'password'&>
7243 Any of the three sub-parts of the first field can be omitted. For normal use on
7244 the local host it can be left blank or set to just &"localhost"&.
7246 No database need be supplied &-- but if it is absent here, it must be given in
7249 If a MySQL query is issued that does not request any data (an insert, update,
7250 or delete command), the result of the lookup is the number of rows affected.
7252 &*Warning*&: This can be misleading. If an update does not actually change
7253 anything (for example, setting a field to the value it already has), the result
7254 is zero because no rows are affected.
7257 .section "Special PostgreSQL features" "SECID74"
7258 PostgreSQL lookups can also use Unix domain socket connections to the database.
7259 This is usually faster and costs less CPU time than a TCP/IP connection.
7260 However it can be used only if the mail server runs on the same machine as the
7261 database server. A configuration line for PostgreSQL via Unix domain sockets
7264 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7266 In other words, instead of supplying a host name, a path to the socket is
7267 given. The path name is enclosed in parentheses so that its slashes aren't
7268 visually confused with the delimiters for the other server parameters.
7270 If a PostgreSQL query is issued that does not request any data (an insert,
7271 update, or delete command), the result of the lookup is the number of rows
7274 .section "More about SQLite" "SECTsqlite"
7275 .cindex "lookup" "SQLite"
7276 .cindex "sqlite lookup type"
7277 SQLite is different to the other SQL lookups because a file name is required in
7278 addition to the SQL query. An SQLite database is a single file, and there is no
7279 daemon as in the other SQL databases. The interface to Exim requires the name
7280 of the file, as an absolute path, to be given at the start of the query. It is
7281 separated from the query by white space. This means that the path name cannot
7282 contain white space. Here is a lookup expansion example:
7284 ${lookup sqlite {/some/thing/sqlitedb \
7285 select name from aliases where id='userx';}}
7287 In a list, the syntax is similar. For example:
7289 domainlist relay_domains = sqlite;/some/thing/sqlitedb \
7290 select * from relays where ip='$sender_host_address';
7292 The only character affected by the &%quote_sqlite%& operator is a single
7293 quote, which it doubles.
7295 The SQLite library handles multiple simultaneous accesses to the database
7296 internally. Multiple readers are permitted, but only one process can
7297 update at once. Attempts to access the database while it is being updated
7298 are rejected after a timeout period, during which the SQLite library
7299 waits for the lock to be released. In Exim, the default timeout is set
7300 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7306 . ////////////////////////////////////////////////////////////////////////////
7307 . ////////////////////////////////////////////////////////////////////////////
7309 .chapter "Domain, host, address, and local part lists" &&&
7310 "CHAPdomhosaddlists" &&&
7311 "Domain, host, and address lists"
7312 .scindex IIDdohoadli "lists of domains; hosts; etc."
7313 A number of Exim configuration options contain lists of domains, hosts,
7314 email addresses, or local parts. For example, the &%hold_domains%& option
7315 contains a list of domains whose delivery is currently suspended. These lists
7316 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7317 arguments to expansion conditions such as &%match_domain%&.
7319 Each item in one of these lists is a pattern to be matched against a domain,
7320 host, email address, or local part, respectively. In the sections below, the
7321 different types of pattern for each case are described, but first we cover some
7322 general facilities that apply to all four kinds of list.
7326 .section "Expansion of lists" "SECID75"
7327 .cindex "expansion" "of lists"
7328 Each list is expanded as a single string before it is used. The result of
7329 expansion must be a list, possibly containing empty items, which is split up
7330 into separate items for matching. By default, colon is the separator character,
7331 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7332 &<<SECTempitelis>>& for details of the list syntax; the second of these
7333 discusses the way to specify empty list items.
7336 If the string expansion is forced to fail, Exim behaves as if the item it is
7337 testing (domain, host, address, or local part) is not in the list. Other
7338 expansion failures cause temporary errors.
7340 If an item in a list is a regular expression, backslashes, dollars and possibly
7341 other special characters in the expression must be protected against
7342 misinterpretation by the string expander. The easiest way to do this is to use
7343 the &`\N`& expansion feature to indicate that the contents of the regular
7344 expression should not be expanded. For example, in an ACL you might have:
7346 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7347 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7349 The first item is a regular expression that is protected from expansion by
7350 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7351 senders based on the receiving domain.
7356 .section "Negated items in lists" "SECID76"
7357 .cindex "list" "negation"
7358 .cindex "negation" "in lists"
7359 Items in a list may be positive or negative. Negative items are indicated by a
7360 leading exclamation mark, which may be followed by optional white space. A list
7361 defines a set of items (domains, etc). When Exim processes one of these lists,
7362 it is trying to find out whether a domain, host, address, or local part
7363 (respectively) is in the set that is defined by the list. It works like this:
7365 The list is scanned from left to right. If a positive item is matched, the
7366 subject that is being checked is in the set; if a negative item is matched, the
7367 subject is not in the set. If the end of the list is reached without the
7368 subject having matched any of the patterns, it is in the set if the last item
7369 was a negative one, but not if it was a positive one. For example, the list in
7371 domainlist relay_domains = !a.b.c : *.b.c
7373 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7374 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7375 list is positive. However, if the setting were
7377 domainlist relay_domains = !a.b.c
7379 then all domains other than &'a.b.c'& would match because the last item in the
7380 list is negative. In other words, a list that ends with a negative item behaves
7381 as if it had an extra item &`:*`& on the end.
7383 Another way of thinking about positive and negative items in lists is to read
7384 the connector as &"or"& after a positive item and as &"and"& after a negative
7389 .section "File names in lists" "SECTfilnamlis"
7390 .cindex "list" "file name in"
7391 If an item in a domain, host, address, or local part list is an absolute file
7392 name (beginning with a slash character), each line of the file is read and
7393 processed as if it were an independent item in the list, except that further
7394 file names are not allowed,
7395 and no expansion of the data from the file takes place.
7396 Empty lines in the file are ignored, and the file may also contain comment
7400 For domain and host lists, if a # character appears anywhere in a line of the
7401 file, it and all following characters are ignored.
7403 Because local parts may legitimately contain # characters, a comment in an
7404 address list or local part list file is recognized only if # is preceded by
7405 white space or the start of the line. For example:
7407 not#comment@x.y.z # but this is a comment
7411 Putting a file name in a list has the same effect as inserting each line of the
7412 file as an item in the list (blank lines and comments excepted). However, there
7413 is one important difference: the file is read each time the list is processed,
7414 so if its contents vary over time, Exim's behaviour changes.
7416 If a file name is preceded by an exclamation mark, the sense of any match
7417 within the file is inverted. For example, if
7419 hold_domains = !/etc/nohold-domains
7421 and the file contains the lines
7426 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7427 any domain matching &`*.b.c`& is not.
7431 .section "An lsearch file is not an out-of-line list" "SECID77"
7432 As will be described in the sections that follow, lookups can be used in lists
7433 to provide indexed methods of checking list membership. There has been some
7434 confusion about the way &(lsearch)& lookups work in lists. Because
7435 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7436 sometimes thought that it is allowed to contain wild cards and other kinds of
7437 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7438 always fixed strings, just as for any other single-key lookup type.
7440 If you want to use a file to contain wild-card patterns that form part of a
7441 list, just give the file name on its own, without a search type, as described
7442 in the previous section. You could also use the &(wildlsearch)& or
7443 &(nwildlsearch)&, but there is no advantage in doing this.
7448 .section "Named lists" "SECTnamedlists"
7449 .cindex "named lists"
7450 .cindex "list" "named"
7451 A list of domains, hosts, email addresses, or local parts can be given a name
7452 which is then used to refer to the list elsewhere in the configuration. This is
7453 particularly convenient if the same list is required in several different
7454 places. It also allows lists to be given meaningful names, which can improve
7455 the readability of the configuration. For example, it is conventional to define
7456 a domain list called &'local_domains'& for all the domains that are handled
7457 locally on a host, using a configuration line such as
7459 domainlist local_domains = localhost:my.dom.example
7461 Named lists are referenced by giving their name preceded by a plus sign, so,
7462 for example, a router that is intended to handle local domains would be
7463 configured with the line
7465 domains = +local_domains
7467 The first router in a configuration is often one that handles all domains
7468 except the local ones, using a configuration with a negated item like this:
7472 domains = ! +local_domains
7473 transport = remote_smtp
7476 The four kinds of named list are created by configuration lines starting with
7477 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7478 respectively. Then there follows the name that you are defining, followed by an
7479 equals sign and the list itself. For example:
7481 hostlist relay_hosts = 192.168.23.0/24 : my.friend.example
7482 addresslist bad_senders = cdb;/etc/badsenders
7484 A named list may refer to other named lists:
7486 domainlist dom1 = first.example : second.example
7487 domainlist dom2 = +dom1 : third.example
7488 domainlist dom3 = fourth.example : +dom2 : fifth.example
7490 &*Warning*&: If the last item in a referenced list is a negative one, the
7491 effect may not be what you intended, because the negation does not propagate
7492 out to the higher level. For example, consider:
7494 domainlist dom1 = !a.b
7495 domainlist dom2 = +dom1 : *.b
7497 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7498 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7499 means it matches the second list as well. The effect is not the same as
7501 domainlist dom2 = !a.b : *.b
7503 where &'x.y'& does not match. It's best to avoid negation altogether in
7504 referenced lists if you can.
7506 Named lists may have a performance advantage. When Exim is routing an
7507 address or checking an incoming message, it caches the result of tests on named
7508 lists. So, if you have a setting such as
7510 domains = +local_domains
7512 on several of your routers
7513 or in several ACL statements,
7514 the actual test is done only for the first one. However, the caching works only
7515 if there are no expansions within the list itself or any sublists that it
7516 references. In other words, caching happens only for lists that are known to be
7517 the same each time they are referenced.
7519 By default, there may be up to 16 named lists of each type. This limit can be
7520 extended by changing a compile-time variable. The use of domain and host lists
7521 is recommended for concepts such as local domains, relay domains, and relay
7522 hosts. The default configuration is set up like this.
7526 .section "Named lists compared with macros" "SECID78"
7527 .cindex "list" "named compared with macro"
7528 .cindex "macro" "compared with named list"
7529 At first sight, named lists might seem to be no different from macros in the
7530 configuration file. However, macros are just textual substitutions. If you
7533 ALIST = host1 : host2
7534 auth_advertise_hosts = !ALIST
7536 it probably won't do what you want, because that is exactly the same as
7538 auth_advertise_hosts = !host1 : host2
7540 Notice that the second host name is not negated. However, if you use a host
7543 hostlist alist = host1 : host2
7544 auth_advertise_hosts = ! +alist
7546 the negation applies to the whole list, and so that is equivalent to
7548 auth_advertise_hosts = !host1 : !host2
7552 .section "Named list caching" "SECID79"
7553 .cindex "list" "caching of named"
7554 .cindex "caching" "named lists"
7555 While processing a message, Exim caches the result of checking a named list if
7556 it is sure that the list is the same each time. In practice, this means that
7557 the cache operates only if the list contains no $ characters, which guarantees
7558 that it will not change when it is expanded. Sometimes, however, you may have
7559 an expanded list that you know will be the same each time within a given
7560 message. For example:
7562 domainlist special_domains = \
7563 ${lookup{$sender_host_address}cdb{/some/file}}
7565 This provides a list of domains that depends only on the sending host's IP
7566 address. If this domain list is referenced a number of times (for example,
7567 in several ACL lines, or in several routers) the result of the check is not
7568 cached by default, because Exim does not know that it is going to be the
7569 same list each time.
7571 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7572 cache the result anyway. For example:
7574 domainlist_cache special_domains = ${lookup{...
7576 If you do this, you should be absolutely sure that caching is going to do
7577 the right thing in all cases. When in doubt, leave it out.
7581 .section "Domain lists" "SECTdomainlist"
7582 .cindex "domain list" "patterns for"
7583 .cindex "list" "domain list"
7584 Domain lists contain patterns that are to be matched against a mail domain.
7585 The following types of item may appear in domain lists:
7588 .cindex "primary host name"
7589 .cindex "host name" "matched in domain list"
7590 .oindex "&%primary_hostname%&"
7591 .cindex "domain list" "matching primary host name"
7592 .cindex "@ in a domain list"
7593 If a pattern consists of a single @ character, it matches the local host name,
7594 as set by the &%primary_hostname%& option (or defaulted). This makes it
7595 possible to use the same configuration file on several different hosts that
7596 differ only in their names.
7598 .cindex "@[] in a domain list"
7599 .cindex "domain list" "matching local IP interfaces"
7600 .cindex "domain literal"
7601 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7602 in square brackets (as in an email address that contains a domain literal), but
7603 only if that IP address is recognized as local for email routing purposes. The
7604 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7605 control which of a host's several IP addresses are treated as local.
7606 In today's Internet, the use of domain literals is controversial.
7609 .cindex "@mx_primary"
7610 .cindex "@mx_secondary"
7611 .cindex "domain list" "matching MX pointers to local host"
7612 If a pattern consists of the string &`@mx_any`& it matches any domain that
7613 has an MX record pointing to the local host or to any host that is listed in
7614 .oindex "&%hosts_treat_as_local%&"
7615 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7616 are similar, except that the first matches only when a primary MX target is the
7617 local host, and the second only when no primary MX target is the local host,
7618 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7619 preference value &-- there may of course be more than one of them.
7621 The MX lookup that takes place when matching a pattern of this type is
7622 performed with the resolver options for widening names turned off. Thus, for
7623 example, a single-component domain will &'not'& be expanded by adding the
7624 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7625 options of the &(dnslookup)& router for a discussion of domain widening.
7627 Sometimes you may want to ignore certain IP addresses when using one of these
7628 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7629 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7630 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7631 on a router). For example:
7633 domains = @mx_any/ignore=127.0.0.1
7635 This example matches any domain that has an MX record pointing to one of
7636 the local host's IP addresses other than 127.0.0.1.
7638 The list of IP addresses is in fact processed by the same code that processes
7639 host lists, so it may contain CIDR-coded network specifications and it may also
7640 contain negative items.
7642 Because the list of IP addresses is a sublist within a domain list, you have to
7643 be careful about delimiters if there is more than one address. Like any other
7644 list, the default delimiter can be changed. Thus, you might have:
7646 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7647 an.other.domain : ...
7649 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7650 involved, it is easiest to change the delimiter for the main list as well:
7652 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7653 an.other.domain ? ...
7656 .cindex "asterisk" "in domain list"
7657 .cindex "domain list" "asterisk in"
7658 .cindex "domain list" "matching &""ends with""&"
7659 If a pattern starts with an asterisk, the remaining characters of the pattern
7660 are compared with the terminating characters of the domain. The use of &"*"& in
7661 domain lists differs from its use in partial matching lookups. In a domain
7662 list, the character following the asterisk need not be a dot, whereas partial
7663 matching works only in terms of dot-separated components. For example, a domain
7664 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7668 .cindex "regular expressions" "in domain list"
7669 .cindex "domain list" "matching regular expression"
7670 If a pattern starts with a circumflex character, it is treated as a regular
7671 expression, and matched against the domain using a regular expression matching
7672 function. The circumflex is treated as part of the regular expression.
7673 Email domains are case-independent, so this regular expression match is by
7674 default case-independent, but you can make it case-dependent by starting it
7675 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
7676 are given in chapter &<<CHAPregexp>>&.
7678 &*Warning*&: Because domain lists are expanded before being processed, you
7679 must escape any backslash and dollar characters in the regular expression, or
7680 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7681 it is not to be expanded (unless you really do want to build a regular
7682 expression by expansion, of course).
7684 .cindex "lookup" "in domain list"
7685 .cindex "domain list" "matching by lookup"
7686 If a pattern starts with the name of a single-key lookup type followed by a
7687 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7688 must be a file name in a suitable format for the lookup type. For example, for
7689 &"cdb;"& it must be an absolute path:
7691 domains = cdb;/etc/mail/local_domains.cdb
7693 The appropriate type of lookup is done on the file using the domain name as the
7694 key. In most cases, the data that is looked up is not used; Exim is interested
7695 only in whether or not the key is present in the file. However, when a lookup
7696 is used for the &%domains%& option on a router
7697 or a &%domains%& condition in an ACL statement, the data is preserved in the
7698 &$domain_data$& variable and can be referred to in other router options or
7699 other statements in the same ACL.
7702 Any of the single-key lookup type names may be preceded by
7703 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
7705 domains = partial-dbm;/partial/domains
7707 This causes partial matching logic to be invoked; a description of how this
7708 works is given in section &<<SECTpartiallookup>>&.
7711 .cindex "asterisk" "in lookup type"
7712 Any of the single-key lookup types may be followed by an asterisk. This causes
7713 a default lookup for a key consisting of a single asterisk to be done if the
7714 original lookup fails. This is not a useful feature when using a domain list to
7715 select particular domains (because any domain would match), but it might have
7716 value if the result of the lookup is being used via the &$domain_data$&
7719 If the pattern starts with the name of a query-style lookup type followed by a
7720 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
7721 pattern must be an appropriate query for the lookup type, as described in
7722 chapter &<<CHAPfdlookup>>&. For example:
7724 hold_domains = mysql;select domain from holdlist \
7725 where domain = '$domain';
7727 In most cases, the data that is looked up is not used (so for an SQL query, for
7728 example, it doesn't matter what field you select). Exim is interested only in
7729 whether or not the query succeeds. However, when a lookup is used for the
7730 &%domains%& option on a router, the data is preserved in the &$domain_data$&
7731 variable and can be referred to in other options.
7733 .cindex "domain list" "matching literal domain name"
7734 If none of the above cases apply, a caseless textual comparison is made
7735 between the pattern and the domain.
7738 Here is an example that uses several different kinds of pattern:
7740 domainlist funny_domains = \
7743 *.foundation.fict.example : \
7744 \N^[1-2]\d{3}\.fict\.example$\N : \
7745 partial-dbm;/opt/data/penguin/book : \
7746 nis;domains.byname : \
7747 nisplus;[name=$domain,status=local],domains.org_dir
7749 There are obvious processing trade-offs among the various matching modes. Using
7750 an asterisk is faster than a regular expression, and listing a few names
7751 explicitly probably is too. The use of a file or database lookup is expensive,
7752 but may be the only option if hundreds of names are required. Because the
7753 patterns are tested in order, it makes sense to put the most commonly matched
7758 .section "Host lists" "SECThostlist"
7759 .cindex "host list" "patterns in"
7760 .cindex "list" "host list"
7761 Host lists are used to control what remote hosts are allowed to do. For
7762 example, some hosts may be allowed to use the local host as a relay, and some
7763 may be permitted to use the SMTP ETRN command. Hosts can be identified in
7764 two different ways, by name or by IP address. In a host list, some types of
7765 pattern are matched to a host name, and some are matched to an IP address.
7766 You need to be particularly careful with this when single-key lookups are
7767 involved, to ensure that the right value is being used as the key.
7770 .section "Special host list patterns" "SECID80"
7771 .cindex "empty item in hosts list"
7772 .cindex "host list" "empty string in"
7773 If a host list item is the empty string, it matches only when no remote host is
7774 involved. This is the case when a message is being received from a local
7775 process using SMTP on the standard input, that is, when a TCP/IP connection is
7778 .cindex "asterisk" "in host list"
7779 The special pattern &"*"& in a host list matches any host or no host. Neither
7780 the IP address nor the name is actually inspected.
7784 .section "Host list patterns that match by IP address" "SECThoslispatip"
7785 .cindex "host list" "matching IP addresses"
7786 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
7787 the incoming address actually appears in the IPv6 host as
7788 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
7789 list, it is converted into a traditional IPv4 address first. (Not all operating
7790 systems accept IPv4 calls on IPv6 sockets, as there have been some security
7793 The following types of pattern in a host list check the remote host by
7794 inspecting its IP address:
7797 If the pattern is a plain domain name (not a regular expression, not starting
7798 with *, not a lookup of any kind), Exim calls the operating system function
7799 to find the associated IP address(es). Exim uses the newer
7800 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
7801 This typically causes a forward DNS lookup of the name. The result is compared
7802 with the IP address of the subject host.
7804 If there is a temporary problem (such as a DNS timeout) with the host name
7805 lookup, a temporary error occurs. For example, if the list is being used in an
7806 ACL condition, the ACL gives a &"defer"& response, usually leading to a
7807 temporary SMTP error code. If no IP address can be found for the host name,
7808 what happens is described in section &<<SECTbehipnot>>& below.
7811 .cindex "@ in a host list"
7812 If the pattern is &"@"&, the primary host name is substituted and used as a
7813 domain name, as just described.
7816 If the pattern is an IP address, it is matched against the IP address of the
7817 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
7818 IPv6 addresses can be given in colon-separated format, but the colons have to
7819 be doubled so as not to be taken as item separators when the default list
7820 separator is used. IPv6 addresses are recognized even when Exim is compiled
7821 without IPv6 support. This means that if they appear in a host list on an
7822 IPv4-only host, Exim will not treat them as host names. They are just addresses
7823 that can never match a client host.
7826 .cindex "@[] in a host list"
7827 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
7828 the local host. For example, if the local host is an IPv4 host with one
7829 interface address 10.45.23.56, these two ACL statements have the same effect:
7831 accept hosts = 127.0.0.1 : 10.45.23.56
7835 .cindex "CIDR notation"
7836 If the pattern is an IP address followed by a slash and a mask length (for
7837 example 10.11.42.0/24), it is matched against the IP address of the subject
7838 host under the given mask. This allows, an entire network of hosts to be
7839 included (or excluded) by a single item. The mask uses CIDR notation; it
7840 specifies the number of address bits that must match, starting from the most
7841 significant end of the address.
7843 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
7844 of a range of addresses. It is the number of bits in the network portion of the
7845 address. The above example specifies a 24-bit netmask, so it matches all 256
7846 addresses in the 10.11.42.0 network. An item such as
7850 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
7851 32 for an IPv4 address is the same as no mask at all; just a single address
7854 Here is another example which shows an IPv4 and an IPv6 network:
7856 recipient_unqualified_hosts = 192.168.0.0/16: \
7857 3ffe::ffff::836f::::/48
7859 The doubling of list separator characters applies only when these items
7860 appear inline in a host list. It is not required when indirecting via a file.
7863 recipient_unqualified_hosts = /opt/exim/unqualnets
7865 could make use of a file containing
7870 to have exactly the same effect as the previous example. When listing IPv6
7871 addresses inline, it is usually more convenient to use the facility for
7872 changing separator characters. This list contains the same two networks:
7874 recipient_unqualified_hosts = <; 172.16.0.0/12; \
7877 The separator is changed to semicolon by the leading &"<;"& at the start of the
7883 .section "Host list patterns for single-key lookups by host address" &&&
7884 "SECThoslispatsikey"
7885 .cindex "host list" "lookup of IP address"
7886 When a host is to be identified by a single-key lookup of its complete IP
7887 address, the pattern takes this form:
7889 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7893 hosts_lookup = net-cdb;/hosts-by-ip.db
7895 The text form of the IP address of the subject host is used as the lookup key.
7896 IPv6 addresses are converted to an unabbreviated form, using lower case
7897 letters, with dots as separators because colon is the key terminator in
7898 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
7899 quoting the keys, but this is a facility that was added later.] The data
7900 returned by the lookup is not used.
7902 .cindex "IP address" "masking"
7903 .cindex "host list" "masked IP address"
7904 Single-key lookups can also be performed using masked IP addresses, using
7905 patterns of this form:
7907 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7911 net24-dbm;/networks.db
7913 The IP address of the subject host is masked using <&'number'&> as the mask
7914 length. A textual string is constructed from the masked value, followed by the
7915 mask, and this is used as the lookup key. For example, if the host's IP address
7916 is 192.168.34.6, the key that is looked up for the above example is
7917 &"192.168.34.0/24"&.
7919 When an IPv6 address is converted to a string, dots are normally used instead
7920 of colons, so that keys in &(lsearch)& files need not contain colons (which
7921 terminate &(lsearch)& keys). This was implemented some time before the ability
7922 to quote keys was made available in &(lsearch)& files. However, the more
7923 recently implemented &(iplsearch)& files do require colons in IPv6 keys
7924 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
7925 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
7926 converted using colons and not dots. In all cases, full, unabbreviated IPv6
7927 addresses are always used.
7929 Ideally, it would be nice to tidy up this anomalous situation by changing to
7930 colons in all cases, given that quoting is now available for &(lsearch)&.
7931 However, this would be an incompatible change that might break some existing
7934 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
7935 IPv6 address) is not the same as specifying just &%net-%& without a number. In
7936 the former case the key strings include the mask value, whereas in the latter
7937 case the IP address is used on its own.
7941 .section "Host list patterns that match by host name" "SECThoslispatnam"
7942 .cindex "host" "lookup failures"
7943 .cindex "unknown host name"
7944 .cindex "host list" "matching host name"
7945 There are several types of pattern that require Exim to know the name of the
7946 remote host. These are either wildcard patterns or lookups by name. (If a
7947 complete hostname is given without any wildcarding, it is used to find an IP
7948 address to match against, as described in the section &<<SECThoslispatip>>&
7951 If the remote host name is not already known when Exim encounters one of these
7952 patterns, it has to be found from the IP address.
7953 Although many sites on the Internet are conscientious about maintaining reverse
7954 DNS data for their hosts, there are also many that do not do this.
7955 Consequently, a name cannot always be found, and this may lead to unwanted
7956 effects. Take care when configuring host lists with wildcarded name patterns.
7957 Consider what will happen if a name cannot be found.
7959 Because of the problems of determining host names from IP addresses, matching
7960 against host names is not as common as matching against IP addresses.
7962 By default, in order to find a host name, Exim first does a reverse DNS lookup;
7963 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
7964 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
7965 are done can be changed by setting the &%host_lookup_order%& option. For
7966 security, once Exim has found one or more names, it looks up the IP addresses
7967 for these names and compares them with the IP address that it started with.
7968 Only those names whose IP addresses match are accepted. Any other names are
7969 discarded. If no names are left, Exim behaves as if the host name cannot be
7970 found. In the most common case there is only one name and one IP address.
7972 There are some options that control what happens if a host name cannot be
7973 found. These are described in section &<<SECTbehipnot>>& below.
7975 .cindex "host" "alias for"
7976 .cindex "alias for host"
7977 As a result of aliasing, hosts may have more than one name. When processing any
7978 of the following types of pattern, all the host's names are checked:
7981 .cindex "asterisk" "in host list"
7982 If a pattern starts with &"*"& the remainder of the item must match the end of
7983 the host name. For example, &`*.b.c`& matches all hosts whose names end in
7984 &'.b.c'&. This special simple form is provided because this is a very common
7985 requirement. Other kinds of wildcarding require the use of a regular
7988 .cindex "regular expressions" "in host list"
7989 .cindex "host list" "regular expression in"
7990 If the item starts with &"^"& it is taken to be a regular expression which is
7991 matched against the host name. Host names are case-independent, so this regular
7992 expression match is by default case-independent, but you can make it
7993 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
7994 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
7999 is a regular expression that matches either of the two hosts &'a.c.d'& or
8000 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8001 that backslash and dollar characters are not misinterpreted as part of the
8002 string expansion. The simplest way to do this is to use &`\N`& to mark that
8003 part of the string as non-expandable. For example:
8005 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8007 &*Warning*&: If you want to match a complete host name, you must include the
8008 &`$`& terminating metacharacter in the regular expression, as in the above
8009 example. Without it, a match at the start of the host name is all that is
8016 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8017 .cindex "host" "lookup failures, permanent"
8018 While processing a host list, Exim may need to look up an IP address from a
8019 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8020 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8021 behaviour when it fails to find the information it is seeking is the same.
8023 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8024 apply to temporary DNS errors, whose handling is described in the next section.
8026 .cindex "&`+include_unknown`&"
8027 .cindex "&`+ignore_unknown`&"
8028 By default, Exim behaves as if the host does not match the list. This may not
8029 always be what you want to happen. To change Exim's behaviour, the special
8030 items &`+include_unknown`& or &`+ignore_unknown`& may appear in the list (at
8031 top level &-- they are not recognized in an indirected file).
8034 If any item that follows &`+include_unknown`& requires information that
8035 cannot found, Exim behaves as if the host does match the list. For example,
8037 host_reject_connection = +include_unknown:*.enemy.ex
8039 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8040 any hosts whose name it cannot find.
8043 If any item that follows &`+ignore_unknown`& requires information that cannot
8044 be found, Exim ignores that item and proceeds to the rest of the list. For
8047 accept hosts = +ignore_unknown : friend.example : \
8050 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8051 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8052 name can be found for 192.168.4.5, it is rejected.
8055 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8056 list. The effect of each one lasts until the next, or until the end of the
8060 .section "Temporary DNS errors when looking up host information" &&&
8062 .cindex "host" "lookup failures, temporary"
8063 .cindex "&`+include_defer`&"
8064 .cindex "&`+ignore_defer`&"
8065 A temporary DNS lookup failure normally causes a defer action (except when
8066 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8067 host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to
8068 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8069 section. These options should be used with care, probably only in non-critical
8070 host lists such as whitelists.
8074 .section "Host list patterns for single-key lookups by host name" &&&
8075 "SECThoslispatnamsk"
8076 .cindex "unknown host name"
8077 .cindex "host list" "matching host name"
8078 If a pattern is of the form
8080 <&'single-key-search-type'&>;<&'search-data'&>
8084 dbm;/host/accept/list
8086 a single-key lookup is performed, using the host name as its key. If the
8087 lookup succeeds, the host matches the item. The actual data that is looked up
8090 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8091 keys in the file, not IP addresses. If you want to do lookups based on IP
8092 addresses, you must precede the search type with &"net-"& (see section
8093 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8094 two items in the same list, one doing an address lookup and one doing a name
8095 lookup, both using the same file.
8099 .section "Host list patterns for query-style lookups" "SECID81"
8100 If a pattern is of the form
8102 <&'query-style-search-type'&>;<&'query'&>
8104 the query is obeyed, and if it succeeds, the host matches the item. The actual
8105 data that is looked up is not used. The variables &$sender_host_address$& and
8106 &$sender_host_name$& can be used in the query. For example:
8108 hosts_lookup = pgsql;\
8109 select ip from hostlist where ip='$sender_host_address'
8111 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8112 can use the &%sg%& expansion item to change this if you need to. If you want to
8113 use masked IP addresses in database queries, you can use the &%mask%& expansion
8116 If the query contains a reference to &$sender_host_name$&, Exim automatically
8117 looks up the host name if has not already done so. (See section
8118 &<<SECThoslispatnam>>& for comments on finding host names.)
8120 Historical note: prior to release 4.30, Exim would always attempt to find a
8121 host name before running the query, unless the search type was preceded by
8122 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8123 still recognized for query-style lookups, but its presence or absence has no
8124 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8125 See section &<<SECThoslispatsikey>>&.)
8129 .section "Mixing wildcarded host names and addresses in host lists" &&&
8131 .cindex "host list" "mixing names and addresses in"
8132 If you have name lookups or wildcarded host names and IP addresses in the same
8133 host list, you should normally put the IP addresses first. For example, in an
8136 accept hosts = 10.9.8.7 : *.friend.example
8138 The reason for this lies in the left-to-right way that Exim processes lists.
8139 It can test IP addresses without doing any DNS lookups, but when it reaches an
8140 item that requires a host name, it fails if it cannot find a host name to
8141 compare with the pattern. If the above list is given in the opposite order, the
8142 &%accept%& statement fails for a host whose name cannot be found, even if its
8143 IP address is 10.9.8.7.
8145 If you really do want to do the name check first, and still recognize the IP
8146 address, you can rewrite the ACL like this:
8148 accept hosts = *.friend.example
8149 accept hosts = 10.9.8.7
8151 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8152 &<<CHAPACL>>& for details of ACLs.
8158 .section "Address lists" "SECTaddresslist"
8159 .cindex "list" "address list"
8160 .cindex "address list" "empty item"
8161 .cindex "address list" "patterns"
8162 Address lists contain patterns that are matched against mail addresses. There
8163 is one special case to be considered: the sender address of a bounce message is
8164 always empty. You can test for this by providing an empty item in an address
8165 list. For example, you can set up a router to process bounce messages by
8166 using this option setting:
8170 The presence of the colon creates an empty item. If you do not provide any
8171 data, the list is empty and matches nothing. The empty sender can also be
8172 detected by a regular expression that matches an empty string,
8173 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8175 Non-empty items in an address list can be straightforward email addresses. For
8178 senders = jbc@askone.example : hs@anacreon.example
8180 A certain amount of wildcarding is permitted. If a pattern contains an @
8181 character, but is not a regular expression and does not begin with a
8182 semicolon-terminated lookup type (described below), the local part of the
8183 subject address is compared with the local part of the pattern, which may start
8184 with an asterisk. If the local parts match, the domain is checked in exactly
8185 the same way as for a pattern in a domain list. For example, the domain can be
8186 wildcarded, refer to a named list, or be a lookup:
8188 deny senders = *@*.spamming.site:\
8189 *@+hostile_domains:\
8190 bozo@partial-lsearch;/list/of/dodgy/sites:\
8191 *@dbm;/bad/domains.db
8193 .cindex "local part" "starting with !"
8194 .cindex "address list" "local part starting with !"
8195 If a local part that begins with an exclamation mark is required, it has to be
8196 specified using a regular expression, because otherwise the exclamation mark is
8197 treated as a sign of negation, as is standard in lists.
8199 If a non-empty pattern that is not a regular expression or a lookup does not
8200 contain an @ character, it is matched against the domain part of the subject
8201 address. The only two formats that are recognized this way are a literal
8202 domain, or a domain pattern that starts with *. In both these cases, the effect
8203 is the same as if &`*@`& preceded the pattern. For example:
8205 deny senders = enemy.domain : *.enemy.domain
8208 The following kinds of more complicated address list pattern can match any
8209 address, including the empty address that is characteristic of bounce message
8213 .cindex "regular expressions" "in address list"
8214 .cindex "address list" "regular expression in"
8215 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8216 done against the complete address, with the pattern as the regular expression.
8217 You must take care that backslash and dollar characters are not misinterpreted
8218 as part of the string expansion. The simplest way to do this is to use &`\N`&
8219 to mark that part of the string as non-expandable. For example:
8221 deny senders = \N^.*this.*@example\.com$\N : \
8222 \N^\d{8}.+@spamhaus.example$\N : ...
8224 The &`\N`& sequences are removed by the expansion, so these items do indeed
8225 start with &"^"& by the time they are being interpreted as address patterns.
8228 .cindex "address list" "lookup for complete address"
8229 Complete addresses can be looked up by using a pattern that starts with a
8230 lookup type terminated by a semicolon, followed by the data for the lookup. For
8233 deny senders = cdb;/etc/blocked.senders : \
8234 mysql;select address from blocked where \
8235 address='${quote_mysql:$sender_address}'
8237 Both query-style and single-key lookup types can be used. For a single-key
8238 lookup type, Exim uses the complete address as the key. However, empty keys are
8239 not supported for single-key lookups, so a match against the empty address
8240 always fails. This restriction does not apply to query-style lookups.
8242 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8243 cannot be used, and is ignored if specified, with an entry being written to the
8245 .cindex "*@ with single-key lookup"
8246 However, you can configure lookup defaults, as described in section
8247 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8248 default. For example, with this lookup:
8250 accept senders = lsearch*@;/some/file
8252 the file could contains lines like this:
8254 user1@domain1.example
8257 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8260 nimrod@jaeger.example
8264 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8265 would mean that every address matches, thus rendering the test useless.
8267 &*Warning 2*&: Do not confuse these two kinds of item:
8269 deny recipients = dbm*@;/some/file
8270 deny recipients = *@dbm;/some/file
8272 The first does a whole address lookup, with defaulting, as just described,
8273 because it starts with a lookup type. The second matches the local part and
8274 domain independently, as described in a bullet point below.
8278 The following kinds of address list pattern can match only non-empty addresses.
8279 If the subject address is empty, a match against any of these pattern types
8284 .cindex "@@ with single-key lookup"
8285 .cindex "address list" "@@ lookup type"
8286 .cindex "address list" "split local part and domain"
8287 If a pattern starts with &"@@"& followed by a single-key lookup item
8288 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8289 split into a local part and a domain. The domain is looked up in the file. If
8290 it is not found, there is no match. If it is found, the data that is looked up
8291 from the file is treated as a colon-separated list of local part patterns, each
8292 of which is matched against the subject local part in turn.
8294 .cindex "asterisk" "in address list"
8295 The lookup may be a partial one, and/or one involving a search for a default
8296 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8297 patterns that are looked up can be regular expressions or begin with &"*"&, or
8298 even be further lookups. They may also be independently negated. For example,
8301 deny senders = @@dbm;/etc/reject-by-domain
8303 the data from which the DBM file is built could contain lines like
8305 baddomain.com: !postmaster : *
8307 to reject all senders except &%postmaster%& from that domain.
8309 .cindex "local part" "starting with !"
8310 If a local part that actually begins with an exclamation mark is required, it
8311 has to be specified using a regular expression. In &(lsearch)& files, an entry
8312 may be split over several lines by indenting the second and subsequent lines,
8313 but the separating colon must still be included at line breaks. White space
8314 surrounding the colons is ignored. For example:
8316 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8319 As in all colon-separated lists in Exim, a colon can be included in an item by
8322 If the last item in the list starts with a right angle-bracket, the remainder
8323 of the item is taken as a new key to look up in order to obtain a continuation
8324 list of local parts. The new key can be any sequence of characters. Thus one
8325 might have entries like
8327 aol.com: spammer1 : spammer 2 : >*
8328 xyz.com: spammer3 : >*
8331 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8332 local parts for all domains, in addition to the specific local parts listed for
8333 each domain. Of course, using this feature costs another lookup each time a
8334 chain is followed, but the effort needed to maintain the data is reduced.
8336 .cindex "loop" "in lookups"
8337 It is possible to construct loops using this facility, and in order to catch
8338 them, the chains may be no more than fifty items long.
8341 The @@<&'lookup'&> style of item can also be used with a query-style
8342 lookup, but in this case, the chaining facility is not available. The lookup
8343 can only return a single list of local parts.
8346 &*Warning*&: There is an important difference between the address list items
8347 in these two examples:
8350 senders = *@+my_list
8352 In the first one, &`my_list`& is a named address list, whereas in the second
8353 example it is a named domain list.
8358 .section "Case of letters in address lists" "SECTcasletadd"
8359 .cindex "case of local parts"
8360 .cindex "address list" "case forcing"
8361 .cindex "case forcing in address lists"
8362 Domains in email addresses are always handled caselessly, but for local parts
8363 case may be significant on some systems (see &%caseful_local_part%& for how
8364 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8365 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8366 blocking lists should be done in a case-independent manner. Since most address
8367 lists in Exim are used for this kind of control, Exim attempts to do this by
8370 The domain portion of an address is always lowercased before matching it to an
8371 address list. The local part is lowercased by default, and any string
8372 comparisons that take place are done caselessly. This means that the data in
8373 the address list itself, in files included as plain file names, and in any file
8374 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8375 keys in files that are looked up by a search type other than &(lsearch)& (which
8376 works caselessly) must be in lower case, because these lookups are not
8379 .cindex "&`+caseful`&"
8380 To allow for the possibility of caseful address list matching, if an item in
8381 an address list is the string &"+caseful"&, the original case of the local
8382 part is restored for any comparisons that follow, and string comparisons are no
8383 longer case-independent. This does not affect the domain, which remains in
8384 lower case. However, although independent matches on the domain alone are still
8385 performed caselessly, regular expressions that match against an entire address
8386 become case-sensitive after &"+caseful"& has been seen.
8390 .section "Local part lists" "SECTlocparlis"
8391 .cindex "list" "local part list"
8392 .cindex "local part" "list"
8393 Case-sensitivity in local part lists is handled in the same way as for address
8394 lists, as just described. The &"+caseful"& item can be used if required. In a
8395 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8396 set false, the subject is lowercased and the matching is initially
8397 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8398 matching in the local part list, but not elsewhere in the router. If
8399 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8400 option is case-sensitive from the start.
8402 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8403 comments are handled in the same way as address lists &-- they are recognized
8404 only if the # is preceded by white space or the start of the line.
8405 Otherwise, local part lists are matched in the same way as domain lists, except
8406 that the special items that refer to the local host (&`@`&, &`@[]`&,
8407 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8408 Refer to section &<<SECTdomainlist>>& for details of the other available item
8410 .ecindex IIDdohoadli
8415 . ////////////////////////////////////////////////////////////////////////////
8416 . ////////////////////////////////////////////////////////////////////////////
8418 .chapter "String expansions" "CHAPexpand"
8419 .scindex IIDstrexp "expansion" "of strings"
8420 Many strings in Exim's run time configuration are expanded before use. Some of
8421 them are expanded every time they are used; others are expanded only once.
8423 When a string is being expanded it is copied verbatim from left to right except
8424 when a dollar or backslash character is encountered. A dollar specifies the
8425 start of a portion of the string that is interpreted and replaced as described
8426 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8427 escape character, as described in the following section.
8431 .section "Literal text in expanded strings" "SECTlittext"
8432 .cindex "expansion" "including literal text"
8433 An uninterpreted dollar can be included in an expanded string by putting a
8434 backslash in front of it. A backslash can be used to prevent any special
8435 character being treated specially in an expansion, including backslash itself.
8436 If the string appears in quotes in the configuration file, two backslashes are
8437 required because the quotes themselves cause interpretation of backslashes when
8438 the string is read in (see section &<<SECTstrings>>&).
8440 .cindex "expansion" "non-expandable substrings"
8441 A portion of the string can specified as non-expandable by placing it between
8442 two occurrences of &`\N`&. This is particularly useful for protecting regular
8443 expressions, which often contain backslashes and dollar signs. For example:
8445 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8447 On encountering the first &`\N`&, the expander copies subsequent characters
8448 without interpretation until it reaches the next &`\N`& or the end of the
8453 .section "Character escape sequences in expanded strings" "SECID82"
8454 .cindex "expansion" "escape sequences"
8455 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8456 expanded string is recognized as an escape sequence for the character newline,
8457 carriage return, or tab, respectively. A backslash followed by up to three
8458 octal digits is recognized as an octal encoding for a single character, and a
8459 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8462 These escape sequences are also recognized in quoted strings when they are read
8463 in. Their interpretation in expansions as well is useful for unquoted strings,
8464 and for other cases such as looked-up strings that are then expanded.
8467 .section "Testing string expansions" "SECID83"
8468 .cindex "expansion" "testing"
8469 .cindex "testing" "string expansion"
8471 Many expansions can be tested by calling Exim with the &%-be%& option. This
8472 takes the command arguments, or lines from the standard input if there are no
8473 arguments, runs them through the string expansion code, and writes the results
8474 to the standard output. Variables based on configuration values are set up, but
8475 since no message is being processed, variables such as &$local_part$& have no
8476 value. Nevertheless the &%-be%& option can be useful for checking out file and
8477 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8480 Exim gives up its root privilege when it is called with the &%-be%& option, and
8481 instead runs under the uid and gid it was called with, to prevent users from
8482 using &%-be%& for reading files to which they do not have access.
8485 If you want to test expansions that include variables whose values are taken
8486 from a message, there are two other options that can be used. The &%-bem%&
8487 option is like &%-be%& except that it is followed by a file name. The file is
8488 read as a message before doing the test expansions. For example:
8490 exim -bem /tmp/test.message '$h_subject:'
8492 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8493 Exim message identifier. For example:
8495 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8497 This loads the message from Exim's spool before doing the test expansions, and
8498 is therefore restricted to admin users.
8501 .section "Forced expansion failure" "SECTforexpfai"
8502 .cindex "expansion" "forced failure"
8503 A number of expansions that are described in the following section have
8504 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8505 (which are sometimes called &"curly brackets"&). Which of the two strings is
8506 used depends on some condition that is evaluated as part of the expansion. If,
8507 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8508 the entire string expansion fails in a way that can be detected by the code
8509 that requested the expansion. This is called &"forced expansion failure"&, and
8510 its consequences depend on the circumstances. In some cases it is no different
8511 from any other expansion failure, but in others a different action may be
8512 taken. Such variations are mentioned in the documentation of the option that is
8518 .section "Expansion items" "SECTexpansionitems"
8519 The following items are recognized in expanded strings. White space may be used
8520 between sub-items that are keywords or substrings enclosed in braces inside an
8521 outer set of braces, to improve readability. &*Warning*&: Within braces,
8522 white space is significant.
8525 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8526 .cindex "expansion" "variables"
8527 Substitute the contents of the named variable, for example:
8532 The second form can be used to separate the name from subsequent alphanumeric
8533 characters. This form (using braces) is available only for variables; it does
8534 &'not'& apply to message headers. The names of the variables are given in
8535 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8536 given, the expansion fails.
8538 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8539 .cindex "expansion" "operators"
8540 The string is first itself expanded, and then the operation specified by
8541 <&'op'&> is applied to it. For example:
8545 The string starts with the first character after the colon, which may be
8546 leading white space. A list of operators is given in section &<<SECTexpop>>&
8547 below. The operator notation is used for simple expansion items that have just
8548 one argument, because it reduces the number of braces and therefore makes the
8549 string easier to understand.
8551 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8552 This item inserts &"basic"& header lines. It is described with the &%header%&
8553 expansion item below.
8555 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8556 {*&<&'arg'&>&*}...}*&"
8558 This expansion dynamically loads and then calls a locally-written C function.
8559 This functionality is available only if Exim is compiled with
8563 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8564 object so that it doesn't reload the same object file in the same Exim process
8565 (but of course Exim does start new processes frequently).
8567 There may be from zero to eight arguments to the function. When compiling
8568 a local function that is to be called in this way, &_local_scan.h_& should be
8569 included. The Exim variables and functions that are defined by that API
8570 are also available for dynamically loaded functions. The function itself
8571 must have the following type:
8573 int dlfunction(uschar **yield, int argc, uschar *argv[])
8575 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8576 function should return one of the following values:
8578 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8579 into the expanded string that is being built.
8581 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8582 from &'yield'&, if it is set.
8584 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8585 taken from &'yield'& if it is set.
8587 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8589 When compiling a function that is to be used in this way with gcc,
8590 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8591 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8593 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
8594 {*&<&'string3'&>&*}}*&"
8595 .cindex "expansion" "extracting substrings by key"
8596 .cindex "&%extract%&" "substrings by key"
8597 The key and <&'string1'&> are first expanded separately. Leading and trailing
8598 white space is removed from the key (but not from any of the strings). The key
8599 must not consist entirely of digits. The expanded <&'string1'&> must be of the
8602 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
8605 where the equals signs and spaces (but not both) are optional. If any of the
8606 values contain white space, they must be enclosed in double quotes, and any
8607 values that are enclosed in double quotes are subject to escape processing as
8608 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
8609 for the value that corresponds to the key. The search is case-insensitive. If
8610 the key is found, <&'string2'&> is expanded, and replaces the whole item;
8611 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8612 variable &$value$& contains the value that has been extracted. Afterwards, it
8613 is restored to any previous value it might have had.
8615 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8616 key is not found. If {<&'string2'&>} is also omitted, the value that was
8617 extracted is used. Thus, for example, these two expansions are identical, and
8620 ${extract{gid}{uid=1984 gid=2001}}
8621 ${extract{gid}{uid=1984 gid=2001}{$value}}
8623 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
8624 appear, for example:
8626 ${extract{Z}{A=... B=...}{$value} fail }
8628 This forces an expansion failure (see section &<<SECTforexpfai>>&);
8629 {<&'string2'&>} must be present for &"fail"& to be recognized.
8632 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
8633 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8634 .cindex "expansion" "extracting substrings by number"
8635 .cindex "&%extract%&" "substrings by number"
8636 The <&'number'&> argument must consist entirely of decimal digits,
8637 apart from leading and trailing white space, which is ignored.
8638 This is what distinguishes this form of &%extract%& from the previous kind. It
8639 behaves in the same way, except that, instead of extracting a named field, it
8640 extracts from <&'string1'&> the field whose number is given as the first
8641 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
8642 <&'string3'&> as before.
8644 The fields in the string are separated by any one of the characters in the
8645 separator string. These may include space or tab characters.
8646 The first field is numbered one. If the number is negative, the fields are
8647 counted from the end of the string, with the rightmost one numbered -1. If the
8648 number given is zero, the entire string is returned. If the modulus of the
8649 number is greater than the number of fields in the string, the result is the
8650 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
8651 provided. For example:
8653 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8657 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8659 yields &"99"&. Two successive separators mean that the field between them is
8660 empty (for example, the fifth field above).
8663 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
8664 .cindex "list" "selecting by condition"
8665 .cindex "expansion" "selecting from list by condition"
8667 After expansion, <&'string'&> is interpreted as a list, colon-separated by
8668 default, but the separator can be changed in the usual way. For each item
8669 in this list, its value is place in &$item$&, and then the condition is
8670 evaluated. If the condition is true, &$item$& is added to the output as an
8671 item in a new list; if the condition is false, the item is discarded. The
8672 separator used for the output list is the same as the one used for the
8673 input, but a separator setting is not included in the output. For example:
8675 ${filter{a:b:c}{!eq{$item}{b}}
8677 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
8678 to what it was before. See also the &*map*& and &*reduce*& expansion items.
8681 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8682 .cindex "hash function" "textual"
8683 .cindex "expansion" "textual hash"
8684 This is a textual hashing function, and was the first to be implemented in
8685 early versions of Exim. In current releases, there are other hashing functions
8686 (numeric, MD5, and SHA-1), which are described below.
8688 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
8689 <&'n'&>. If you are using fixed values for these numbers, that is, if
8690 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
8691 use the simpler operator notation that avoids some of the braces:
8693 ${hash_<n>_<m>:<string>}
8695 The second number is optional (in both notations). If <&'n'&> is greater than
8696 or equal to the length of the string, the expansion item returns the string.
8697 Otherwise it computes a new string of length <&'n'&> by applying a hashing
8698 function to the string. The new string consists of characters taken from the
8699 first <&'m'&> characters of the string
8701 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
8703 If <&'m'&> is not present the value 26 is used, so that only lower case
8704 letters appear. For example:
8706 &`$hash{3}{monty}} `& yields &`jmg`&
8707 &`$hash{5}{monty}} `& yields &`monty`&
8708 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
8711 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
8712 &*$h_*&<&'header&~name'&>&*:*&" &&&
8713 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8714 &*$bh_*&<&'header&~name'&>&*:*&" &&&
8715 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8716 &*$rh_*&<&'header&~name'&>&*:*&"
8717 .cindex "expansion" "header insertion"
8718 .vindex "&$header_$&"
8719 .vindex "&$bheader_$&"
8720 .vindex "&$rheader_$&"
8721 .cindex "header lines" "in expansion strings"
8722 .cindex "header lines" "character sets"
8723 .cindex "header lines" "decoding"
8724 Substitute the contents of the named message header line, for example
8728 The newline that terminates a header line is not included in the expansion, but
8729 internal newlines (caused by splitting the header line over several physical
8730 lines) may be present.
8732 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
8733 the data in the header line is interpreted.
8736 .cindex "white space" "in header lines"
8737 &%rheader%& gives the original &"raw"& content of the header line, with no
8738 processing at all, and without the removal of leading and trailing white space.
8741 .cindex "base64 encoding" "in header lines"
8742 &%bheader%& removes leading and trailing white space, and then decodes base64
8743 or quoted-printable MIME &"words"& within the header text, but does no
8744 character set translation. If decoding of what looks superficially like a MIME
8745 &"word"& fails, the raw string is returned. If decoding
8746 .cindex "binary zero" "in header line"
8747 produces a binary zero character, it is replaced by a question mark &-- this is
8748 what Exim does for binary zeros that are actually received in header lines.
8751 &%header%& tries to translate the string as decoded by &%bheader%& to a
8752 standard character set. This is an attempt to produce the same string as would
8753 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
8754 returned. Translation is attempted only on operating systems that support the
8755 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
8756 a system Makefile or in &_Local/Makefile_&.
8759 In a filter file, the target character set for &%header%& can be specified by a
8760 command of the following form:
8762 headers charset "UTF-8"
8764 This command affects all references to &$h_$& (or &$header_$&) expansions in
8765 subsequently obeyed filter commands. In the absence of this command, the target
8766 character set in a filter is taken from the setting of the &%headers_charset%&
8767 option in the runtime configuration. The value of this option defaults to the
8768 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
8771 Header names follow the syntax of RFC 2822, which states that they may contain
8772 any printing characters except space and colon. Consequently, curly brackets
8773 &'do not'& terminate header names, and should not be used to enclose them as
8774 if they were variables. Attempting to do so causes a syntax error.
8776 Only header lines that are common to all copies of a message are visible to
8777 this mechanism. These are the original header lines that are received with the
8778 message, and any that are added by an ACL statement or by a system
8779 filter. Header lines that are added to a particular copy of a message by a
8780 router or transport are not accessible.
8782 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
8783 before the DATA ACL, because the header structure is not set up until the
8784 message is received. Header lines that are added in a RCPT ACL (for example)
8785 are saved until the message's incoming header lines are available, at which
8786 point they are added. When a DATA ACL is running, however, header lines added
8787 by earlier ACLs are visible.
8789 Upper case and lower case letters are synonymous in header names. If the
8790 following character is white space, the terminating colon may be omitted, but
8791 this is not recommended, because you may then forget it when it is needed. When
8792 white space terminates the header name, it is included in the expanded string.
8793 If the message does not contain the given header, the expansion item is
8794 replaced by an empty string. (See the &%def%& condition in section
8795 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
8797 If there is more than one header with the same name, they are all concatenated
8798 to form the substitution string, up to a maximum length of 64K. Unless
8799 &%rheader%& is being used, leading and trailing white space is removed from
8800 each header before concatenation, and a completely empty header is ignored. A
8801 newline character is then inserted between non-empty headers, but there is no
8802 newline at the very end. For the &%header%& and &%bheader%& expansion, for
8803 those headers that contain lists of addresses, a comma is also inserted at the
8804 junctions between headers. This does not happen for the &%rheader%& expansion.
8807 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
8808 .cindex "expansion" "hmac hashing"
8810 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
8811 shared secret and some text into a message authentication code, as specified in
8812 RFC 2104. This differs from &`${md5:secret_text...}`& or
8813 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
8814 cryptographic hash, allowing for authentication that is not possible with MD5
8815 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
8816 present. For example:
8818 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
8820 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
8823 dd97e3ba5d1a61b5006108f8c8252953
8825 As an example of how this might be used, you might put in the main part of
8826 an Exim configuration:
8828 SPAMSCAN_SECRET=cohgheeLei2thahw
8830 In a router or a transport you could then have:
8833 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
8834 ${hmac{md5}{SPAMSCAN_SECRET}\
8835 {${primary_hostname},${message_exim_id},$h_message-id:}}
8837 Then given a message, you can check where it was scanned by looking at the
8838 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
8839 this header line is authentic by recomputing the authentication code from the
8840 host name, message ID and the &'Message-id:'& header line. This can be done
8841 using Exim's &%-be%& option, or by other means, for example by using the
8842 &'hmac_md5_hex()'& function in Perl.
8845 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8846 .cindex "expansion" "conditional"
8847 .cindex "&%if%&, expansion item"
8848 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
8849 item; otherwise <&'string2'&> is used. The available conditions are described
8850 in section &<<SECTexpcond>>& below. For example:
8852 ${if eq {$local_part}{postmaster} {yes}{no} }
8854 The second string need not be present; if it is not and the condition is not
8855 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
8856 be present instead of the second string (without any curly brackets). In this
8857 case, the expansion is forced to fail if the condition is not true (see section
8858 &<<SECTforexpfai>>&).
8860 If both strings are omitted, the result is the string &`true`& if the condition
8861 is true, and the empty string if the condition is false. This makes it less
8862 cumbersome to write custom ACL and router conditions. For example, instead of
8864 condition = ${if >{$acl_m4}{3}{true}{false}}
8868 condition = ${if >{$acl_m4}{3}}
8871 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8872 .cindex "expansion" "string truncation"
8873 .cindex "&%length%& expansion item"
8874 The &%length%& item is used to extract the initial portion of a string. Both
8875 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
8876 you are using a fixed value for the number, that is, if <&'string1'&> does not
8877 change when expanded, you can use the simpler operator notation that avoids
8880 ${length_<n>:<string>}
8882 The result of this item is either the first <&'n'&> characters or the whole
8883 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
8884 &%strlen%&, which gives the length of a string.
8887 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
8888 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8889 This is the first of one of two different types of lookup item, which are both
8890 described in the next item.
8892 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
8893 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8894 .cindex "expansion" "lookup in"
8895 .cindex "file" "lookups"
8896 .cindex "lookup" "in expanded string"
8897 The two forms of lookup item specify data lookups in files and databases, as
8898 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
8899 lookups, and the second is used for query-style lookups. The <&'key'&>,
8900 <&'file'&>, and <&'query'&> strings are expanded before use.
8902 If there is any white space in a lookup item which is part of a filter command,
8903 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
8904 other place where white space is significant, the lookup item must be enclosed
8905 in double quotes. The use of data lookups in users' filter files may be locked
8906 out by the system administrator.
8909 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
8910 During its expansion, the variable &$value$& contains the data returned by the
8911 lookup. Afterwards it reverts to the value it had previously (at the outer
8912 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
8913 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
8914 string on failure. If <&'string2'&> is provided, it can itself be a nested
8915 lookup, thus providing a mechanism for looking up a default value when the
8916 original lookup fails.
8918 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
8919 data for the outer lookup while the parameters of the second lookup are
8920 expanded, and also while <&'string2'&> of the second lookup is expanded, should
8921 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
8922 appear, and in this case, if the lookup fails, the entire expansion is forced
8923 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
8924 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
8925 successful lookup, and nothing in the case of failure.
8927 For single-key lookups, the string &"partial"& is permitted to precede the
8928 search type in order to do partial matching, and * or *@ may follow a search
8929 type to request default lookups if the key does not match (see sections
8930 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
8932 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
8933 If a partial search is used, the variables &$1$& and &$2$& contain the wild
8934 and non-wild parts of the key during the expansion of the replacement text.
8935 They return to their previous values at the end of the lookup item.
8937 This example looks up the postmaster alias in the conventional alias file:
8939 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
8941 This example uses NIS+ to look up the full name of the user corresponding to
8942 the local part of an address, forcing the expansion to fail if it is not found:
8944 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
8949 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8950 .cindex "expansion" "list creation"
8952 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
8953 default, but the separator can be changed in the usual way. For each item
8954 in this list, its value is place in &$item$&, and then <&'string2'&> is
8955 expanded and added to the output as an item in a new list. The separator used
8956 for the output list is the same as the one used for the input, but a separator
8957 setting is not included in the output. For example:
8959 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
8961 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
8962 value of &$item$& is restored to what it was before. See also the &*filter*&
8963 and &*reduce*& expansion items.
8965 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8966 .cindex "expansion" "numeric hash"
8967 .cindex "hash function" "numeric"
8968 The three strings are expanded; the first two must yield numbers. Call them
8969 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
8970 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
8971 can use the simpler operator notation that avoids some of the braces:
8973 ${nhash_<n>_<m>:<string>}
8975 The second number is optional (in both notations). If there is only one number,
8976 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
8977 processed by a div/mod hash function that returns two numbers, separated by a
8978 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
8981 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
8983 returns the string &"6/33"&.
8987 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
8988 .cindex "Perl" "use in expanded string"
8989 .cindex "expansion" "calling Perl from"
8990 This item is available only if Exim has been built to include an embedded Perl
8991 interpreter. The subroutine name and the arguments are first separately
8992 expanded, and then the Perl subroutine is called with those arguments. No
8993 additional arguments need be given; the maximum number permitted, including the
8994 name of the subroutine, is nine.
8996 The return value of the subroutine is inserted into the expanded string, unless
8997 the return value is &%undef%&. In that case, the expansion fails in the same
8998 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
8999 Whatever you return is evaluated in a scalar context. For example, if you
9000 return the name of a Perl vector, the return value is the size of the vector,
9003 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9004 with the error message that was passed to &%die%&. More details of the embedded
9005 Perl facility are given in chapter &<<CHAPperl>>&.
9007 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9008 out the use of this expansion item in filter files.
9011 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9012 .cindex "&%prvs%& expansion item"
9013 The first argument is a complete email address and the second is secret
9014 keystring. The third argument, specifying a key number, is optional. If absent,
9015 it defaults to 0. The result of the expansion is a prvs-signed email address,
9016 to be typically used with the &%return_path%& option on an &(smtp)& transport
9017 as part of a bounce address tag validation (BATV) scheme. For more discussion
9018 and an example, see section &<<SECTverifyPRVS>>&.
9020 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9021 {*&<&'string'&>&*}}*&"
9022 .cindex "&%prvscheck%& expansion item"
9023 This expansion item is the complement of the &%prvs%& item. It is used for
9024 checking prvs-signed addresses. If the expansion of the first argument does not
9025 yield a syntactically valid prvs-signed address, the whole item expands to the
9026 empty string. When the first argument does expand to a syntactically valid
9027 prvs-signed address, the second argument is expanded, with the prvs-decoded
9028 version of the address and the key number extracted from the address in the
9029 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9031 These two variables can be used in the expansion of the second argument to
9032 retrieve the secret. The validity of the prvs-signed address is then checked
9033 against the secret. The result is stored in the variable &$prvscheck_result$&,
9034 which is empty for failure or &"1"& for success.
9036 The third argument is optional; if it is missing, it defaults to an empty
9037 string. This argument is now expanded. If the result is an empty string, the
9038 result of the expansion is the decoded version of the address. This is the case
9039 whether or not the signature was valid. Otherwise, the result of the expansion
9040 is the expansion of the third argument.
9042 All three variables can be used in the expansion of the third argument.
9043 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9044 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9046 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9047 .cindex "expansion" "inserting an entire file"
9048 .cindex "file" "inserting into expansion"
9049 .cindex "&%readfile%& expansion item"
9050 The file name and end-of-line string are first expanded separately. The file is
9051 then read, and its contents replace the entire item. All newline characters in
9052 the file are replaced by the end-of-line string if it is present. Otherwise,
9053 newlines are left in the string.
9054 String expansion is not applied to the contents of the file. If you want this,
9055 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9056 the string expansion fails.
9058 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9059 locks out the use of this expansion item in filter files.
9063 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9064 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9065 .cindex "expansion" "inserting from a socket"
9066 .cindex "socket, use of in expansion"
9067 .cindex "&%readsocket%& expansion item"
9068 This item inserts data from a Unix domain or Internet socket into the expanded
9069 string. The minimal way of using it uses just two arguments, as in these
9072 ${readsocket{/socket/name}{request string}}
9073 ${readsocket{inet:some.host:1234}{request string}}
9075 For a Unix domain socket, the first substring must be the path to the socket.
9076 For an Internet socket, the first substring must contain &`inet:`& followed by
9077 a host name or IP address, followed by a colon and a port, which can be a
9078 number or the name of a TCP port in &_/etc/services_&. An IP address may
9079 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9082 ${readsocket{inet:[::1]:1234}{request string}}
9084 Only a single host name may be given, but if looking it up yields more than
9085 one IP address, they are each tried in turn until a connection is made. For
9086 both kinds of socket, Exim makes a connection, writes the request string
9087 (unless it is an empty string) and reads from the socket until an end-of-file
9088 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9089 extend what can be done. Firstly, you can vary the timeout. For example:
9091 ${readsocket{/socket/name}{request string}{3s}}
9093 A fourth argument allows you to change any newlines that are in the data
9094 that is read, in the same way as for &%readfile%& (see above). This example
9095 turns them into spaces:
9097 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9099 As with all expansions, the substrings are expanded before the processing
9100 happens. Errors in these sub-expansions cause the expansion to fail. In
9101 addition, the following errors can occur:
9104 Failure to create a socket file descriptor;
9106 Failure to connect the socket;
9108 Failure to write the request string;
9110 Timeout on reading from the socket.
9113 By default, any of these errors causes the expansion to fail. However, if
9114 you supply a fifth substring, it is expanded and used when any of the above
9115 errors occurs. For example:
9117 ${readsocket{/socket/name}{request string}{3s}{\n}\
9120 You can test for the existence of a Unix domain socket by wrapping this
9121 expansion in &`${if exists`&, but there is a race condition between that test
9122 and the actual opening of the socket, so it is safer to use the fifth argument
9123 if you want to be absolutely sure of avoiding an expansion error for a
9124 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9126 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9127 locks out the use of this expansion item in filter files.
9130 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9131 .cindex "expansion" "reducing a list to a scalar"
9132 .cindex "list" "reducing to a scalar"
9135 This operation reduces a list to a single, scalar string. After expansion,
9136 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9137 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9138 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9139 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9140 them. The result of that expansion is assigned to &$value$& before the next
9141 iteration. When the end of the list is reached, the final value of &$value$& is
9142 added to the expansion output. The &*reduce*& expansion item can be used in a
9143 number of ways. For example, to add up a list of numbers:
9145 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9147 The result of that expansion would be &`6`&. The maximum of a list of numbers
9150 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9152 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9153 restored to what they were before. See also the &*filter*& and &*map*&
9156 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9157 This item inserts &"raw"& header lines. It is described with the &%header%&
9158 expansion item above.
9160 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9161 {*&<&'string2'&>&*}}*&"
9162 .cindex "expansion" "running a command"
9163 .cindex "&%run%& expansion item"
9164 The command and its arguments are first expanded separately, and then the
9165 command is run in a separate process, but under the same uid and gid. As in
9166 other command executions from Exim, a shell is not used by default. If you want
9167 a shell, you must explicitly code it.
9169 The standard input for the command exists, but is empty. The standard output
9170 and standard error are set to the same file descriptor.
9171 .cindex "return code" "from &%run%& expansion"
9173 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9174 and replaces the entire item; during this expansion, the standard output/error
9175 from the command is in the variable &$value$&. If the command fails,
9176 <&'string2'&>, if present, is expanded and used. Once again, during the
9177 expansion, the standard output/error from the command is in the variable
9180 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9181 can be the word &"fail"& (not in braces) to force expansion failure if the
9182 command does not succeed. If both strings are omitted, the result is contents
9183 of the standard output/error on success, and nothing on failure.
9186 The return code from the command is put in the variable &$runrc$&, and this
9187 remains set afterwards, so in a filter file you can do things like this:
9189 if "${run{x y z}{}}$runrc" is 1 then ...
9190 elif $runrc is 2 then ...
9194 If execution of the command fails (for example, the command does not exist),
9195 the return code is 127 &-- the same code that shells use for non-existent
9198 &*Warning*&: In a router or transport, you cannot assume the order in which
9199 option values are expanded, except for those preconditions whose order of
9200 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9201 by the expansion of one option, and use it in another.
9203 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9204 out the use of this expansion item in filter files.
9207 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9208 .cindex "expansion" "string substitution"
9209 .cindex "&%sg%& expansion item"
9210 This item works like Perl's substitution operator (s) with the global (/g)
9211 option; hence its name. However, unlike the Perl equivalent, Exim does not
9212 modify the subject string; instead it returns the modified string for insertion
9213 into the overall expansion. The item takes three arguments: the subject string,
9214 a regular expression, and a substitution string. For example:
9216 ${sg{abcdefabcdef}{abc}{xyz}}
9218 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9219 if any $ or \ characters are required in the regular expression or in the
9220 substitution string, they have to be escaped. For example:
9222 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9224 yields &"defabc"&, and
9226 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9228 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9229 the regular expression from string expansion.
9233 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9234 .cindex "&%substr%& expansion item"
9235 .cindex "substring extraction"
9236 .cindex "expansion" "substring extraction"
9237 The three strings are expanded; the first two must yield numbers. Call them
9238 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9239 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9240 can use the simpler operator notation that avoids some of the braces:
9242 ${substr_<n>_<m>:<string>}
9244 The second number is optional (in both notations).
9245 If it is absent in the simpler format, the preceding underscore must also be
9248 The &%substr%& item can be used to extract more general substrings than
9249 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9250 length required. For example
9252 ${substr{3}{2}{$local_part}}
9254 If the starting offset is greater than the string length the result is the
9255 null string; if the length plus starting offset is greater than the string
9256 length, the result is the right-hand part of the string, starting from the
9257 given offset. The first character in the string has offset zero.
9259 The &%substr%& expansion item can take negative offset values to count
9260 from the right-hand end of its operand. The last character is offset -1, the
9261 second-last is offset -2, and so on. Thus, for example,
9263 ${substr{-5}{2}{1234567}}
9265 yields &"34"&. If the absolute value of a negative offset is greater than the
9266 length of the string, the substring starts at the beginning of the string, and
9267 the length is reduced by the amount of overshoot. Thus, for example,
9269 ${substr{-5}{2}{12}}
9271 yields an empty string, but
9273 ${substr{-3}{2}{12}}
9277 When the second number is omitted from &%substr%&, the remainder of the string
9278 is taken if the offset is positive. If it is negative, all characters in the
9279 string preceding the offset point are taken. For example, an offset of -1 and
9280 no length, as in these semantically identical examples:
9283 ${substr{-1}{abcde}}
9285 yields all but the last character of the string, that is, &"abcd"&.
9289 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9290 {*&<&'replacements'&>&*}}*&"
9291 .cindex "expansion" "character translation"
9292 .cindex "&%tr%& expansion item"
9293 This item does single-character translation on its subject string. The second
9294 argument is a list of characters to be translated in the subject string. Each
9295 matching character is replaced by the corresponding character from the
9296 replacement list. For example
9298 ${tr{abcdea}{ac}{13}}
9300 yields &`1b3de1`&. If there are duplicates in the second character string, the
9301 last occurrence is used. If the third string is shorter than the second, its
9302 last character is replicated. However, if it is empty, no translation takes
9308 .section "Expansion operators" "SECTexpop"
9309 .cindex "expansion" "operators"
9310 For expansion items that perform transformations on a single argument string,
9311 the &"operator"& notation is used because it is simpler and uses fewer braces.
9312 The substring is first expanded before the operation is applied to it. The
9313 following operations can be performed:
9316 .vitem &*${address:*&<&'string'&>&*}*&
9317 .cindex "expansion" "RFC 2822 address handling"
9318 .cindex "&%address%& expansion item"
9319 The string is interpreted as an RFC 2822 address, as it might appear in a
9320 header line, and the effective address is extracted from it. If the string does
9321 not parse successfully, the result is empty.
9324 .vitem &*${addresses:*&<&'string'&>&*}*&
9325 .cindex "expansion" "RFC 2822 address handling"
9326 .cindex "&%addresses%& expansion item"
9327 The string (after expansion) is interpreted as a list of addresses in RFC
9328 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9329 operative address (&'local-part@domain'&) is extracted from each item, and the
9330 result of the expansion is a colon-separated list, with appropriate
9331 doubling of colons should any happen to be present in the email addresses.
9332 Syntactically invalid RFC2822 address items are omitted from the output.
9334 It is possible to specify a character other than colon for the output
9335 separator by starting the string with > followed by the new separator
9336 character. For example:
9338 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9340 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9341 expansion item, which extracts the working address from a single RFC2822
9342 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9346 .vitem &*${base62:*&<&'digits'&>&*}*&
9347 .cindex "&%base62%& expansion item"
9348 .cindex "expansion" "conversion to base 62"
9349 The string must consist entirely of decimal digits. The number is converted to
9350 base 62 and output as a string of six characters, including leading zeros. In
9351 the few operating environments where Exim uses base 36 instead of base 62 for
9352 its message identifiers (because those systems do not have case-sensitive file
9353 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9354 be absolutely clear: this is &'not'& base64 encoding.
9356 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9357 .cindex "&%base62d%& expansion item"
9358 .cindex "expansion" "conversion to base 62"
9359 The string must consist entirely of base-62 digits, or, in operating
9360 environments where Exim uses base 36 instead of base 62 for its message
9361 identifiers, base-36 digits. The number is converted to decimal and output as a
9364 .vitem &*${domain:*&<&'string'&>&*}*&
9365 .cindex "domain" "extraction"
9366 .cindex "expansion" "domain extraction"
9367 The string is interpreted as an RFC 2822 address and the domain is extracted
9368 from it. If the string does not parse successfully, the result is empty.
9371 .vitem &*${escape:*&<&'string'&>&*}*&
9372 .cindex "expansion" "escaping non-printing characters"
9373 .cindex "&%escape%& expansion item"
9374 If the string contains any non-printing characters, they are converted to
9375 escape sequences starting with a backslash. Whether characters with the most
9376 significant bit set (so-called &"8-bit characters"&) count as printing or not
9377 is controlled by the &%print_topbitchars%& option.
9380 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9381 .cindex "expansion" "expression evaluation"
9382 .cindex "expansion" "arithmetic expression"
9383 .cindex "&%eval%& expansion item"
9384 These items supports simple arithmetic and bitwise logical operations in
9385 expansion strings. The string (after expansion) must be a conventional
9386 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
9387 logical operators, and parentheses. All operations are carried out using
9388 integer arithmetic. The operator priorities are as follows (the same as in the
9389 C programming language):
9391 .irow &'highest:'& "not (~), negate (-)"
9392 .irow "" "multiply (*), divide (/), remainder (%)"
9393 .irow "" "plus (+), minus (-)"
9394 .irow "" "shift-left (<<), shift-right (>>)"
9397 .irow &'lowest:'& "or (|)"
9399 Binary operators with the same priority are evaluated from left to right. White
9400 space is permitted before or after operators.
9402 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
9403 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
9404 decimal, even if they start with a leading zero; hexadecimal numbers are not
9405 permitted. This can be useful when processing numbers extracted from dates or
9406 times, which often do have leading zeros.
9408 A number may be followed by &"K"& or &"M"& to multiply it by 1024 or 1024*1024,
9409 respectively. Negative numbers are supported. The result of the computation is
9410 a decimal representation of the answer (without &"K"& or &"M"&). For example:
9413 &`${eval:1+1} `& yields 2
9414 &`${eval:1+2*3} `& yields 7
9415 &`${eval:(1+2)*3} `& yields 9
9416 &`${eval:2+42%5} `& yields 4
9417 &`${eval:0xc&5} `& yields 4
9418 &`${eval:0xc|5} `& yields 13
9419 &`${eval:0xc^5} `& yields 9
9420 &`${eval:0xc>>1} `& yields 6
9421 &`${eval:0xc<<1} `& yields 24
9422 &`${eval:~255&0x1234} `& yields 4608
9423 &`${eval:-(~255&0x1234)} `& yields -4608
9426 As a more realistic example, in an ACL you might have
9428 deny message = Too many bad recipients
9431 {>{$rcpt_count}{10}} \
9434 {$recipients_count} \
9435 {${eval:$rcpt_count/2}} \
9439 The condition is true if there have been more than 10 RCPT commands and
9440 fewer than half of them have resulted in a valid recipient.
9443 .vitem &*${expand:*&<&'string'&>&*}*&
9444 .cindex "expansion" "re-expansion of substring"
9445 The &%expand%& operator causes a string to be expanded for a second time. For
9448 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
9450 first looks up a string in a file while expanding the operand for &%expand%&,
9451 and then re-expands what it has found.
9454 .vitem &*${from_utf8:*&<&'string'&>&*}*&
9456 .cindex "UTF-8" "conversion from"
9457 .cindex "expansion" "UTF-8 conversion"
9458 .cindex "&%from_utf8%& expansion item"
9459 The world is slowly moving towards Unicode, although there are no standards for
9460 email yet. However, other applications (including some databases) are starting
9461 to store data in Unicode, using UTF-8 encoding. This operator converts from a
9462 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
9463 converted to underscores. The input must be a valid UTF-8 string. If it is not,
9464 the result is an undefined sequence of bytes.
9466 Unicode code points with values less than 256 are compatible with ASCII and
9467 ISO-8859-1 (also known as Latin-1).
9468 For example, character 169 is the copyright symbol in both cases, though the
9469 way it is encoded is different. In UTF-8, more than one byte is needed for
9470 characters with code values greater than 127, whereas ISO-8859-1 is a
9471 single-byte encoding (but thereby limited to 256 characters). This makes
9472 translation from UTF-8 to ISO-8859-1 straightforward.
9475 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9476 .cindex "hash function" "textual"
9477 .cindex "expansion" "textual hash"
9478 The &%hash%& operator is a simpler interface to the hashing function that can
9479 be used when the two parameters are fixed numbers (as opposed to strings that
9480 change when expanded). The effect is the same as
9482 ${hash{<n>}{<m>}{<string>}}
9484 See the description of the general &%hash%& item above for details. The
9485 abbreviation &%h%& can be used when &%hash%& is used as an operator.
9489 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
9490 .cindex "base64 encoding" "conversion from hex"
9491 .cindex "expansion" "hex to base64"
9492 .cindex "&%hex2b64%& expansion item"
9493 This operator converts a hex string into one that is base64 encoded. This can
9494 be useful for processing the output of the MD5 and SHA-1 hashing functions.
9497 .vitem &*${lc:*&<&'string'&>&*}*&
9498 .cindex "case forcing in strings"
9499 .cindex "string" "case forcing"
9500 .cindex "lower casing"
9501 .cindex "expansion" "case forcing"
9502 .cindex "&%lc%& expansion item"
9503 This forces the letters in the string into lower-case, for example:
9508 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
9509 .cindex "expansion" "string truncation"
9510 .cindex "&%length%& expansion item"
9511 The &%length%& operator is a simpler interface to the &%length%& function that
9512 can be used when the parameter is a fixed number (as opposed to a string that
9513 changes when expanded). The effect is the same as
9515 ${length{<number>}{<string>}}
9517 See the description of the general &%length%& item above for details. Note that
9518 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
9519 when &%length%& is used as an operator.
9522 .vitem &*${local_part:*&<&'string'&>&*}*&
9523 .cindex "expansion" "local part extraction"
9524 .cindex "&%local_part%& expansion item"
9525 The string is interpreted as an RFC 2822 address and the local part is
9526 extracted from it. If the string does not parse successfully, the result is
9530 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
9531 .cindex "masked IP address"
9532 .cindex "IP address" "masking"
9533 .cindex "CIDR notation"
9534 .cindex "expansion" "IP address masking"
9535 .cindex "&%mask%& expansion item"
9536 If the form of the string to be operated on is not an IP address followed by a
9537 slash and an integer (that is, a network address in CIDR notation), the
9538 expansion fails. Otherwise, this operator converts the IP address to binary,
9539 masks off the least significant bits according to the bit count, and converts
9540 the result back to text, with mask appended. For example,
9542 ${mask:10.111.131.206/28}
9544 returns the string &"10.111.131.192/28"&. Since this operation is expected to
9545 be mostly used for looking up masked addresses in files, the result for an IPv6
9546 address uses dots to separate components instead of colons, because colon
9547 terminates a key string in lsearch files. So, for example,
9549 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
9553 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
9555 Letters in IPv6 addresses are always output in lower case.
9558 .vitem &*${md5:*&<&'string'&>&*}*&
9560 .cindex "expansion" "MD5 hash"
9561 .cindex "&%md5%& expansion item"
9562 The &%md5%& operator computes the MD5 hash value of the string, and returns it
9563 as a 32-digit hexadecimal number, in which any letters are in lower case.
9566 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9567 .cindex "expansion" "numeric hash"
9568 .cindex "hash function" "numeric"
9569 The &%nhash%& operator is a simpler interface to the numeric hashing function
9570 that can be used when the two parameters are fixed numbers (as opposed to
9571 strings that change when expanded). The effect is the same as
9573 ${nhash{<n>}{<m>}{<string>}}
9575 See the description of the general &%nhash%& item above for details.
9578 .vitem &*${quote:*&<&'string'&>&*}*&
9579 .cindex "quoting" "in string expansions"
9580 .cindex "expansion" "quoting"
9581 .cindex "&%quote%& expansion item"
9582 The &%quote%& operator puts its argument into double quotes if it
9583 is an empty string or
9584 contains anything other than letters, digits, underscores, dots, and hyphens.
9585 Any occurrences of double quotes and backslashes are escaped with a backslash.
9586 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
9587 respectively For example,
9595 The place where this is useful is when the argument is a substitution from a
9596 variable or a message header.
9598 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
9599 .cindex "&%quote_local_part%& expansion item"
9600 This operator is like &%quote%&, except that it quotes the string only if
9601 required to do so by the rules of RFC 2822 for quoting local parts. For
9602 example, a plus sign would not cause quoting (but it would for &%quote%&).
9603 If you are creating a new email address from the contents of &$local_part$&
9604 (or any other unknown data), you should always use this operator.
9607 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
9608 .cindex "quoting" "lookup-specific"
9609 This operator applies lookup-specific quoting rules to the string. Each
9610 query-style lookup type has its own quoting rules which are described with
9611 the lookups in chapter &<<CHAPfdlookup>>&. For example,
9613 ${quote_ldap:two * two}
9619 For single-key lookup types, no quoting is ever necessary and this operator
9620 yields an unchanged string.
9623 .vitem &*${randint:*&<&'n'&>&*}*&
9624 .cindex "random number"
9625 This operator returns a somewhat random number which is less than the
9626 supplied number and is at least 0. The quality of this randomness depends
9627 on how Exim was built; the values are not suitable for keying material.
9628 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
9629 Otherwise, the implementation may be arc4random(), random() seeded by
9630 srandomdev() or srandom(), or a custom implementation even weaker than
9634 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
9635 .cindex "expansion" "IP address"
9636 This operator reverses an IP address; for IPv4 addresses, the result is in
9637 dotted-quad decimal form, while for IPv6 addreses the result is in
9638 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
9639 for DNS. For example,
9641 ${reverse_ip:192.0.2.4} and ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.3}
9645 4.2.0.192 and 3.0.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
9649 .vitem &*${rfc2047:*&<&'string'&>&*}*&
9650 .cindex "expansion" "RFC 2047"
9651 .cindex "RFC 2047" "expansion operator"
9652 .cindex "&%rfc2047%& expansion item"
9653 This operator encodes text according to the rules of RFC 2047. This is an
9654 encoding that is used in header lines to encode non-ASCII characters. It is
9655 assumed that the input string is in the encoding specified by the
9656 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
9657 contains only characters in the range 33&--126, and no instances of the
9660 ? = ( ) < > @ , ; : \ " . [ ] _
9662 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
9663 string, using as many &"encoded words"& as necessary to encode all the
9667 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
9668 .cindex "expansion" "RFC 2047"
9669 .cindex "RFC 2047" "decoding"
9670 .cindex "&%rfc2047d%& expansion item"
9671 This operator decodes strings that are encoded as per RFC 2047. Binary zero
9672 bytes are replaced by question marks. Characters are converted into the
9673 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
9674 not recognized unless &%check_rfc2047_length%& is set false.
9676 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
9677 access a header line, RFC 2047 decoding is done automatically. You do not need
9678 to use this operator as well.
9682 .vitem &*${rxquote:*&<&'string'&>&*}*&
9683 .cindex "quoting" "in regular expressions"
9684 .cindex "regular expressions" "quoting"
9685 .cindex "&%rxquote%& expansion item"
9686 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
9687 characters in its argument. This is useful when substituting the values of
9688 variables or headers inside regular expressions.
9691 .vitem &*${sha1:*&<&'string'&>&*}*&
9692 .cindex "SHA-1 hash"
9693 .cindex "expansion" "SHA-1 hashing"
9694 .cindex "&%sha2%& expansion item"
9695 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
9696 it as a 40-digit hexadecimal number, in which any letters are in upper case.
9699 .vitem &*${stat:*&<&'string'&>&*}*&
9700 .cindex "expansion" "statting a file"
9701 .cindex "file" "extracting characteristics"
9702 .cindex "&%stat%& expansion item"
9703 The string, after expansion, must be a file path. A call to the &[stat()]&
9704 function is made for this path. If &[stat()]& fails, an error occurs and the
9705 expansion fails. If it succeeds, the data from the stat replaces the item, as a
9706 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
9707 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
9708 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
9709 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
9710 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
9711 can extract individual fields using the &%extract%& expansion item.
9713 The use of the &%stat%& expansion in users' filter files can be locked out by
9714 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
9715 systems for files larger than 2GB.
9717 .vitem &*${str2b64:*&<&'string'&>&*}*&
9718 .cindex "expansion" "base64 encoding"
9719 .cindex "base64 encoding" "in string expansion"
9720 .cindex "&%str2b64%& expansion item"
9721 This operator converts a string into one that is base64 encoded.
9725 .vitem &*${strlen:*&<&'string'&>&*}*&
9726 .cindex "expansion" "string length"
9727 .cindex "string" "length in expansion"
9728 .cindex "&%strlen%& expansion item"
9729 The item is replace by the length of the expanded string, expressed as a
9730 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
9733 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
9734 .cindex "&%substr%& expansion item"
9735 .cindex "substring extraction"
9736 .cindex "expansion" "substring expansion"
9737 The &%substr%& operator is a simpler interface to the &%substr%& function that
9738 can be used when the two parameters are fixed numbers (as opposed to strings
9739 that change when expanded). The effect is the same as
9741 ${substr{<start>}{<length>}{<string>}}
9743 See the description of the general &%substr%& item above for details. The
9744 abbreviation &%s%& can be used when &%substr%& is used as an operator.
9746 .vitem &*${time_eval:*&<&'string'&>&*}*&
9747 .cindex "&%time_eval%& expansion item"
9748 .cindex "time interval" "decoding"
9749 This item converts an Exim time interval such as &`2d4h5m`& into a number of
9752 .vitem &*${time_interval:*&<&'string'&>&*}*&
9753 .cindex "&%time_interval%& expansion item"
9754 .cindex "time interval" "formatting"
9755 The argument (after sub-expansion) must be a sequence of decimal digits that
9756 represents an interval of time as a number of seconds. It is converted into a
9757 number of larger units and output in Exim's normal time format, for example,
9760 .vitem &*${uc:*&<&'string'&>&*}*&
9761 .cindex "case forcing in strings"
9762 .cindex "string" "case forcing"
9763 .cindex "upper casing"
9764 .cindex "expansion" "case forcing"
9765 .cindex "&%uc%& expansion item"
9766 This forces the letters in the string into upper-case.
9774 .section "Expansion conditions" "SECTexpcond"
9775 .scindex IIDexpcond "expansion" "conditions"
9776 The following conditions are available for testing by the &%${if%& construct
9777 while expanding strings:
9780 .vitem &*!*&<&'condition'&>
9781 .cindex "expansion" "negating a condition"
9782 .cindex "negation" "in expansion condition"
9783 Preceding any condition with an exclamation mark negates the result of the
9786 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9787 .cindex "numeric comparison"
9788 .cindex "expansion" "numeric comparison"
9789 There are a number of symbolic operators for doing numeric comparisons. They
9795 &`>= `& greater or equal
9797 &`<= `& less or equal
9801 ${if >{$message_size}{10M} ...
9803 Note that the general negation operator provides for inequality testing. The
9804 two strings must take the form of optionally signed decimal integers,
9805 optionally followed by one of the letters &"K"& or &"M"& (in either upper or
9806 lower case), signifying multiplication by 1024 or 1024*1024, respectively.
9807 As a special case, the numerical value of an empty string is taken as
9810 .vitem &*bool&~{*&<&'string'&>&*}*&
9811 .cindex "expansion" "boolean parsing"
9812 .cindex "&%bool%& expansion condition"
9813 This condition turns a string holding a true or false representation into
9814 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
9815 (case-insensitively); also positive integer numbers map to true if non-zero,
9816 false if zero. Leading and trailing whitespace is ignored.
9817 All other string values will result in expansion failure.
9819 When combined with ACL variables, this expansion condition will let you
9820 make decisions in one place and act on those decisions in another place.
9823 ${if bool{$acl_m_privileged_sender} ...
9826 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
9827 .cindex "expansion" "boolean parsing"
9828 .cindex "&%bool_lax%& expansion condition"
9829 Like &%bool%&, this condition turns a string into a boolean state. But
9830 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
9831 loose definition that the Router &%condition%& option uses. The empty string
9832 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
9833 true. Leading and trailing whitespace is ignored.
9835 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
9837 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9838 .cindex "expansion" "encrypted comparison"
9839 .cindex "encrypted strings, comparing"
9840 .cindex "&%crypteq%& expansion condition"
9841 This condition is included in the Exim binary if it is built to support any
9842 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
9843 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
9844 included in the binary.
9846 The &%crypteq%& condition has two arguments. The first is encrypted and
9847 compared against the second, which is already encrypted. The second string may
9848 be in the LDAP form for storing encrypted strings, which starts with the
9849 encryption type in curly brackets, followed by the data. If the second string
9850 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
9851 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
9852 Typically this will be a field from a password file. An example of an encrypted
9853 string in LDAP form is:
9855 {md5}CY9rzUYh03PK3k6DJie09g==
9857 If such a string appears directly in an expansion, the curly brackets have to
9858 be quoted, because they are part of the expansion syntax. For example:
9860 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
9862 The following encryption types (whose names are matched case-independently) are
9867 .cindex "base64 encoding" "in encrypted password"
9868 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
9869 printable characters to compare with the remainder of the second string. If the
9870 length of the comparison string is 24, Exim assumes that it is base64 encoded
9871 (as in the above example). If the length is 32, Exim assumes that it is a
9872 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
9876 .cindex "SHA-1 hash"
9877 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
9878 printable characters to compare with the remainder of the second string. If the
9879 length of the comparison string is 28, Exim assumes that it is base64 encoded.
9880 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
9881 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
9884 .cindex "&[crypt()]&"
9885 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
9886 only the first eight characters of the password. However, in modern operating
9887 systems this is no longer true, and in many cases the entire password is used,
9888 whatever its length.
9891 .cindex "&[crypt16()]&"
9892 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
9893 use up to 16 characters of the password in some operating systems. Again, in
9894 modern operating systems, more characters may be used.
9896 Exim has its own version of &[crypt16()]&, which is just a double call to
9897 &[crypt()]&. For operating systems that have their own version, setting
9898 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
9899 operating system version instead of its own. This option is set by default in
9900 the OS-dependent &_Makefile_& for those operating systems that are known to
9901 support &[crypt16()]&.
9903 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
9904 it was not using the same algorithm as some operating systems' versions. It
9905 turns out that as well as &[crypt16()]& there is a function called
9906 &[bigcrypt()]& in some operating systems. This may or may not use the same
9907 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
9909 However, since there is now a move away from the traditional &[crypt()]&
9910 functions towards using SHA1 and other algorithms, tidying up this area of
9911 Exim is seen as very low priority.
9913 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
9914 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
9915 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
9916 default is &`{crypt}`&. Whatever the default, you can always use either
9917 function by specifying it explicitly in curly brackets.
9919 .vitem &*def:*&<&'variable&~name'&>
9920 .cindex "expansion" "checking for empty variable"
9921 .cindex "&%def%& expansion condition"
9922 The &%def%& condition must be followed by the name of one of the expansion
9923 variables defined in section &<<SECTexpvar>>&. The condition is true if the
9924 variable does not contain the empty string. For example:
9926 ${if def:sender_ident {from $sender_ident}}
9928 Note that the variable name is given without a leading &%$%& character. If the
9929 variable does not exist, the expansion fails.
9931 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
9932 &~&*def:h_*&<&'header&~name'&>&*:*&"
9933 .cindex "expansion" "checking header line existence"
9934 This condition is true if a message is being processed and the named header
9935 exists in the message. For example,
9937 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
9939 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
9940 the header name must be terminated by a colon if white space does not follow.
9942 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9943 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9944 .cindex "string" "comparison"
9945 .cindex "expansion" "string comparison"
9946 .cindex "&%eq%& expansion condition"
9947 .cindex "&%eqi%& expansion condition"
9948 The two substrings are first expanded. The condition is true if the two
9949 resulting strings are identical. For &%eq%& the comparison includes the case of
9950 letters, whereas for &%eqi%& the comparison is case-independent.
9952 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
9953 .cindex "expansion" "file existence test"
9954 .cindex "file" "existence test"
9955 .cindex "&%exists%&, expansion condition"
9956 The substring is first expanded and then interpreted as an absolute path. The
9957 condition is true if the named file (or directory) exists. The existence test
9958 is done by calling the &[stat()]& function. The use of the &%exists%& test in
9959 users' filter files may be locked out by the system administrator.
9961 .vitem &*first_delivery*&
9962 .cindex "delivery" "first"
9963 .cindex "first delivery"
9964 .cindex "expansion" "first delivery test"
9965 .cindex "&%first_delivery%& expansion condition"
9966 This condition, which has no data, is true during a message's first delivery
9967 attempt. It is false during any subsequent delivery attempts.
9970 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
9971 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
9972 .cindex "list" "iterative conditions"
9973 .cindex "expansion" "&*forall*& condition"
9974 .cindex "expansion" "&*forany*& condition"
9976 These conditions iterate over a list. The first argument is expanded to form
9977 the list. By default, the list separator is a colon, but it can be changed by
9978 the normal method. The second argument is interpreted as a condition that is to
9979 be applied to each item in the list in turn. During the interpretation of the
9980 condition, the current list item is placed in a variable called &$item$&.
9982 For &*forany*&, interpretation stops if the condition is true for any item, and
9983 the result of the whole condition is true. If the condition is false for all
9984 items in the list, the overall condition is false.
9986 For &*forall*&, interpretation stops if the condition is false for any item,
9987 and the result of the whole condition is false. If the condition is true for
9988 all items in the list, the overall condition is true.
9990 Note that negation of &*forany*& means that the condition must be false for all
9991 items for the overall condition to succeed, and negation of &*forall*& means
9992 that the condition must be false for at least one item. In this example, the
9993 list separator is changed to a comma:
9995 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
9997 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
9998 being processed, to enable these expansion items to be nested.
10001 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10002 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10003 .cindex "string" "comparison"
10004 .cindex "expansion" "string comparison"
10005 .cindex "&%ge%& expansion condition"
10006 .cindex "&%gei%& expansion condition"
10007 The two substrings are first expanded. The condition is true if the first
10008 string is lexically greater than or equal to the second string. For &%ge%& the
10009 comparison includes the case of letters, whereas for &%gei%& the comparison is
10012 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10013 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10014 .cindex "string" "comparison"
10015 .cindex "expansion" "string comparison"
10016 .cindex "&%gt%& expansion condition"
10017 .cindex "&%gti%& expansion condition"
10018 The two substrings are first expanded. The condition is true if the first
10019 string is lexically greater than the second string. For &%gt%& the comparison
10020 includes the case of letters, whereas for &%gti%& the comparison is
10023 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10024 &*isip4&~{*&<&'string'&>&*}*& &&&
10025 &*isip6&~{*&<&'string'&>&*}*&
10026 .cindex "IP address" "testing string format"
10027 .cindex "string" "testing for IP address"
10028 .cindex "&%isip%& expansion condition"
10029 .cindex "&%isip4%& expansion condition"
10030 .cindex "&%isip6%& expansion condition"
10031 The substring is first expanded, and then tested to see if it has the form of
10032 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10033 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10035 For an IPv4 address, the test is for four dot-separated components, each of
10036 which consists of from one to three digits. For an IPv6 address, up to eight
10037 colon-separated components are permitted, each containing from one to four
10038 hexadecimal digits. There may be fewer than eight components if an empty
10039 component (adjacent colons) is present. Only one empty component is permitted.
10041 &*Note*&: The checks are just on the form of the address; actual numerical
10042 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10043 check. The main use of these tests is to distinguish between IP addresses and
10044 host names, or between IPv4 and IPv6 addresses. For example, you could use
10046 ${if isip4{$sender_host_address}...
10048 to test which IP version an incoming SMTP connection is using.
10050 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10051 .cindex "LDAP" "use for authentication"
10052 .cindex "expansion" "LDAP authentication test"
10053 .cindex "&%ldapauth%& expansion condition"
10054 This condition supports user authentication using LDAP. See section
10055 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10056 queries. For this use, the query must contain a user name and password. The
10057 query itself is not used, and can be empty. The condition is true if the
10058 password is not empty, and the user name and password are accepted by the LDAP
10059 server. An empty password is rejected without calling LDAP because LDAP binds
10060 with an empty password are considered anonymous regardless of the username, and
10061 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10062 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10066 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10067 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10068 .cindex "string" "comparison"
10069 .cindex "expansion" "string comparison"
10070 .cindex "&%le%& expansion condition"
10071 .cindex "&%lei%& expansion condition"
10072 The two substrings are first expanded. The condition is true if the first
10073 string is lexically less than or equal to the second string. For &%le%& the
10074 comparison includes the case of letters, whereas for &%lei%& the comparison is
10077 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10078 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10079 .cindex "string" "comparison"
10080 .cindex "expansion" "string comparison"
10081 .cindex "&%lt%& expansion condition"
10082 .cindex "&%lti%& expansion condition"
10083 The two substrings are first expanded. The condition is true if the first
10084 string is lexically less than the second string. For &%lt%& the comparison
10085 includes the case of letters, whereas for &%lti%& the comparison is
10089 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10090 .cindex "expansion" "regular expression comparison"
10091 .cindex "regular expressions" "match in expanded string"
10092 .cindex "&%match%& expansion condition"
10093 The two substrings are first expanded. The second is then treated as a regular
10094 expression and applied to the first. Because of the pre-expansion, if the
10095 regular expression contains dollar, or backslash characters, they must be
10096 escaped. Care must also be taken if the regular expression contains braces
10097 (curly brackets). A closing brace must be escaped so that it is not taken as a
10098 premature termination of <&'string2'&>. The easiest approach is to use the
10099 &`\N`& feature to disable expansion of the regular expression.
10102 ${if match {$local_part}{\N^\d{3}\N} ...
10104 If the whole expansion string is in double quotes, further escaping of
10105 backslashes is also required.
10107 The condition is true if the regular expression match succeeds.
10108 The regular expression is not required to begin with a circumflex
10109 metacharacter, but if there is no circumflex, the expression is not anchored,
10110 and it may match anywhere in the subject, not just at the start. If you want
10111 the pattern to match at the end of the subject, you must include the &`$`&
10112 metacharacter at an appropriate point.
10114 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10115 At the start of an &%if%& expansion the values of the numeric variable
10116 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10117 succeeds causes them to be reset to the substrings of that condition and they
10118 will have these values during the expansion of the success string. At the end
10119 of the &%if%& expansion, the previous values are restored. After testing a
10120 combination of conditions using &%or%&, the subsequent values of the numeric
10121 variables are those of the condition that succeeded.
10123 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10124 .cindex "&%match_address%& expansion condition"
10125 See &*match_local_part*&.
10127 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10128 .cindex "&%match_domain%& expansion condition"
10129 See &*match_local_part*&.
10131 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10132 .cindex "&%match_ip%& expansion condition"
10133 This condition matches an IP address to a list of IP address patterns. It must
10134 be followed by two argument strings. The first (after expansion) must be an IP
10135 address or an empty string. The second (after expansion) is a restricted host
10136 list that can match only an IP address, not a host name. For example:
10138 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10140 The specific types of host list item that are permitted in the list are:
10143 An IP address, optionally with a CIDR mask.
10145 A single asterisk, which matches any IP address.
10147 An empty item, which matches only if the IP address is empty. This could be
10148 useful for testing for a locally submitted message or one from specific hosts
10149 in a single test such as
10150 . ==== As this is a nested list, any displays it contains must be indented
10151 . ==== as otherwise they are too far to the left. This comment applies to
10152 . ==== the use of xmlto plus fop. There's no problem when formatting with
10153 . ==== sdop, with or without the extra indent.
10155 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10157 where the first item in the list is the empty string.
10159 The item @[] matches any of the local host's interface addresses.
10161 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10162 even if &`net-`& is not specified. There is never any attempt to turn the IP
10163 address into a host name. The most common type of linear search for
10164 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10165 masks. For example:
10167 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10169 It is of course possible to use other kinds of lookup, and in such a case, you
10170 do need to specify the &`net-`& prefix if you want to specify a specific
10171 address mask, for example:
10173 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10175 However, unless you are combining a &%match_ip%& condition with others, it is
10176 just as easy to use the fact that a lookup is itself a condition, and write:
10178 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10182 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10184 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10185 .cindex "domain list" "in expansion condition"
10186 .cindex "address list" "in expansion condition"
10187 .cindex "local part" "list, in expansion condition"
10188 .cindex "&%match_local_part%& expansion condition"
10189 This condition, together with &%match_address%& and &%match_domain%&, make it
10190 possible to test domain, address, and local part lists within expansions. Each
10191 condition requires two arguments: an item and a list to match. A trivial
10194 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10196 In each case, the second argument may contain any of the allowable items for a
10197 list of the appropriate type. Also, because the second argument (after
10198 expansion) is a standard form of list, it is possible to refer to a named list.
10199 Thus, you can use conditions like this:
10201 ${if match_domain{$domain}{+local_domains}{...
10203 .cindex "&`+caseful`&"
10204 For address lists, the matching starts off caselessly, but the &`+caseful`&
10205 item can be used, as in all address lists, to cause subsequent items to
10206 have their local parts matched casefully. Domains are always matched
10209 &*Note*&: Host lists are &'not'& supported in this way. This is because
10210 hosts have two identities: a name and an IP address, and it is not clear
10211 how to specify cleanly how such a test would work. However, IP addresses can be
10212 matched using &%match_ip%&.
10214 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10215 .cindex "PAM authentication"
10216 .cindex "AUTH" "with PAM"
10217 .cindex "Solaris" "PAM support"
10218 .cindex "expansion" "PAM authentication test"
10219 .cindex "&%pam%& expansion condition"
10220 &'Pluggable Authentication Modules'&
10221 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10222 available in the latest releases of Solaris and in some GNU/Linux
10223 distributions. The Exim support, which is intended for use in conjunction with
10224 the SMTP AUTH command, is available only if Exim is compiled with
10228 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10229 in some releases of GNU/Linux &%-ldl%& is also needed.
10231 The argument string is first expanded, and the result must be a
10232 colon-separated list of strings. Leading and trailing white space is ignored.
10233 The PAM module is initialized with the service name &"exim"& and the user name
10234 taken from the first item in the colon-separated data string (<&'string1'&>).
10235 The remaining items in the data string are passed over in response to requests
10236 from the authentication function. In the simple case there will only be one
10237 request, for a password, so the data consists of just two strings.
10239 There can be problems if any of the strings are permitted to contain colon
10240 characters. In the usual way, these have to be doubled to avoid being taken as
10241 separators. If the data is being inserted from a variable, the &%sg%& expansion
10242 item can be used to double any existing colons. For example, the configuration
10243 of a LOGIN authenticator might contain this setting:
10245 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10247 For a PLAIN authenticator you could use:
10249 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10251 In some operating systems, PAM authentication can be done only from a process
10252 running as root. Since Exim is running as the Exim user when receiving
10253 messages, this means that PAM cannot be used directly in those systems.
10254 A patched version of the &'pam_unix'& module that comes with the
10255 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10256 The patched module allows one special uid/gid combination, in addition to root,
10257 to authenticate. If you build the patched module to allow the Exim user and
10258 group, PAM can then be used from an Exim authenticator.
10261 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10262 .cindex "&'pwcheck'& daemon"
10264 .cindex "expansion" "&'pwcheck'& authentication test"
10265 .cindex "&%pwcheck%& expansion condition"
10266 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
10267 This is one way of making it possible for passwords to be checked by a process
10268 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
10269 deprecated. Its replacement is &'saslauthd'& (see below).
10271 The pwcheck support is not included in Exim by default. You need to specify
10272 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
10273 building Exim. For example:
10275 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
10277 You do not need to install the full Cyrus software suite in order to use
10278 the pwcheck daemon. You can compile and install just the daemon alone
10279 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
10280 access to the &_/var/pwcheck_& directory.
10282 The &%pwcheck%& condition takes one argument, which must be the user name and
10283 password, separated by a colon. For example, in a LOGIN authenticator
10284 configuration, you might have this:
10286 server_condition = ${if pwcheck{$auth1:$auth2}}
10288 Again, for a PLAIN authenticator configuration, this would be:
10290 server_condition = ${if pwcheck{$auth2:$auth3}}
10292 .vitem &*queue_running*&
10293 .cindex "queue runner" "detecting when delivering from"
10294 .cindex "expansion" "queue runner test"
10295 .cindex "&%queue_running%& expansion condition"
10296 This condition, which has no data, is true during delivery attempts that are
10297 initiated by queue runner processes, and false otherwise.
10300 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
10302 .cindex "expansion" "Radius authentication"
10303 .cindex "&%radius%& expansion condition"
10304 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
10305 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
10306 the Radius client configuration file in order to build Exim with Radius
10309 With just that one setting, Exim expects to be linked with the &%radiusclient%&
10310 library, using the original API. If you are using release 0.4.0 or later of
10311 this library, you need to set
10313 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
10315 in &_Local/Makefile_& when building Exim. You can also link Exim with the
10316 &%libradius%& library that comes with FreeBSD. To do this, set
10318 RADIUS_LIB_TYPE=RADLIB
10320 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
10321 You may also have to supply a suitable setting in EXTRALIBS so that the
10322 Radius library can be found when Exim is linked.
10324 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
10325 Radius client library, which calls the Radius server. The condition is true if
10326 the authentication is successful. For example:
10328 server_condition = ${if radius{<arguments>}}
10332 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
10333 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
10334 .cindex "&'saslauthd'& daemon"
10336 .cindex "expansion" "&'saslauthd'& authentication test"
10337 .cindex "&%saslauthd%& expansion condition"
10338 This condition supports user authentication using the Cyrus &'saslauthd'&
10339 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
10340 Using this daemon is one way of making it possible for passwords to be checked
10341 by a process that is not running as root.
10343 The saslauthd support is not included in Exim by default. You need to specify
10344 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
10345 building Exim. For example:
10347 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
10349 You do not need to install the full Cyrus software suite in order to use
10350 the saslauthd daemon. You can compile and install just the daemon alone
10351 from the Cyrus SASL library.
10353 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
10354 two are mandatory. For example:
10356 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
10358 The service and the realm are optional (which is why the arguments are enclosed
10359 in their own set of braces). For details of the meaning of the service and
10360 realm, and how to run the daemon, consult the Cyrus documentation.
10365 .section "Combining expansion conditions" "SECID84"
10366 .cindex "expansion" "combining conditions"
10367 Several conditions can be tested at once by combining them using the &%and%&
10368 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
10369 conditions on their own, and precede their lists of sub-conditions. Each
10370 sub-condition must be enclosed in braces within the overall braces that contain
10371 the list. No repetition of &%if%& is used.
10375 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10376 .cindex "&""or""& expansion condition"
10377 .cindex "expansion" "&""or""& of conditions"
10378 The sub-conditions are evaluated from left to right. The condition is true if
10379 any one of the sub-conditions is true.
10382 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
10384 When a true sub-condition is found, the following ones are parsed but not
10385 evaluated. If there are several &"match"& sub-conditions the values of the
10386 numeric variables afterwards are taken from the first one that succeeds.
10388 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10389 .cindex "&""and""& expansion condition"
10390 .cindex "expansion" "&""and""& of conditions"
10391 The sub-conditions are evaluated from left to right. The condition is true if
10392 all of the sub-conditions are true. If there are several &"match"&
10393 sub-conditions, the values of the numeric variables afterwards are taken from
10394 the last one. When a false sub-condition is found, the following ones are
10395 parsed but not evaluated.
10397 .ecindex IIDexpcond
10402 .section "Expansion variables" "SECTexpvar"
10403 .cindex "expansion" "variables, list of"
10404 This section contains an alphabetical list of all the expansion variables. Some
10405 of them are available only when Exim is compiled with specific options such as
10406 support for TLS or the content scanning extension.
10409 .vitem "&$0$&, &$1$&, etc"
10410 .cindex "numerical variables (&$1$& &$2$& etc)"
10411 When a &%match%& expansion condition succeeds, these variables contain the
10412 captured substrings identified by the regular expression during subsequent
10413 processing of the success string of the containing &%if%& expansion item.
10414 However, they do not retain their values afterwards; in fact, their previous
10415 values are restored at the end of processing an &%if%& item. The numerical
10416 variables may also be set externally by some other matching process which
10417 precedes the expansion of the string. For example, the commands available in
10418 Exim filter files include an &%if%& command with its own regular expression
10419 matching condition.
10421 .vitem "&$acl_c...$&"
10422 Values can be placed in these variables by the &%set%& modifier in an ACL. They
10423 can be given any name that starts with &$acl_c$& and is at least six characters
10424 long, but the sixth character must be either a digit or an underscore. For
10425 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
10426 variables persist throughout the lifetime of an SMTP connection. They can be
10427 used to pass information between ACLs and between different invocations of the
10428 same ACL. When a message is received, the values of these variables are saved
10429 with the message, and can be accessed by filters, routers, and transports
10430 during subsequent delivery.
10432 .vitem "&$acl_m...$&"
10433 These variables are like the &$acl_c...$& variables, except that their values
10434 are reset after a message has been received. Thus, if several messages are
10435 received in one SMTP connection, &$acl_m...$& values are not passed on from one
10436 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
10437 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
10438 message is received, the values of these variables are saved with the message,
10439 and can be accessed by filters, routers, and transports during subsequent
10442 .vitem &$acl_verify_message$&
10443 .vindex "&$acl_verify_message$&"
10444 After an address verification has failed, this variable contains the failure
10445 message. It retains its value for use in subsequent modifiers. The message can
10446 be preserved by coding like this:
10448 warn !verify = sender
10449 set acl_m0 = $acl_verify_message
10451 You can use &$acl_verify_message$& during the expansion of the &%message%& or
10452 &%log_message%& modifiers, to include information about the verification
10455 .vitem &$address_data$&
10456 .vindex "&$address_data$&"
10457 This variable is set by means of the &%address_data%& option in routers. The
10458 value then remains with the address while it is processed by subsequent routers
10459 and eventually a transport. If the transport is handling multiple addresses,
10460 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
10461 for more details. &*Note*&: The contents of &$address_data$& are visible in
10464 If &$address_data$& is set when the routers are called from an ACL to verify
10465 a recipient address, the final value is still in the variable for subsequent
10466 conditions and modifiers of the ACL statement. If routing the address caused it
10467 to be redirected to just one address, the child address is also routed as part
10468 of the verification, and in this case the final value of &$address_data$& is
10469 from the child's routing.
10471 If &$address_data$& is set when the routers are called from an ACL to verify a
10472 sender address, the final value is also preserved, but this time in
10473 &$sender_address_data$&, to distinguish it from data from a recipient
10476 In both cases (recipient and sender verification), the value does not persist
10477 after the end of the current ACL statement. If you want to preserve
10478 these values for longer, you can save them in ACL variables.
10480 .vitem &$address_file$&
10481 .vindex "&$address_file$&"
10482 When, as a result of aliasing, forwarding, or filtering, a message is directed
10483 to a specific file, this variable holds the name of the file when the transport
10484 is running. At other times, the variable is empty. For example, using the
10485 default configuration, if user &%r2d2%& has a &_.forward_& file containing
10487 /home/r2d2/savemail
10489 then when the &(address_file)& transport is running, &$address_file$&
10490 contains the text string &`/home/r2d2/savemail`&.
10491 .cindex "Sieve filter" "value of &$address_file$&"
10492 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
10493 then up to the transport configuration to generate an appropriate absolute path
10494 to the relevant file.
10496 .vitem &$address_pipe$&
10497 .vindex "&$address_pipe$&"
10498 When, as a result of aliasing or forwarding, a message is directed to a pipe,
10499 this variable holds the pipe command when the transport is running.
10501 .vitem "&$auth1$& &-- &$auth3$&"
10502 .vindex "&$auth1$&, &$auth2$&, etc"
10503 These variables are used in SMTP authenticators (see chapters
10504 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
10506 .vitem &$authenticated_id$&
10507 .cindex "authentication" "id"
10508 .vindex "&$authenticated_id$&"
10509 When a server successfully authenticates a client it may be configured to
10510 preserve some of the authentication information in the variable
10511 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
10512 user/password authenticator configuration might preserve the user name for use
10513 in the routers. Note that this is not the same information that is saved in
10514 &$sender_host_authenticated$&.
10515 When a message is submitted locally (that is, not over a TCP connection)
10516 the value of &$authenticated_id$& is normally the login name of the calling
10517 process. However, a trusted user can override this by means of the &%-oMai%&
10518 command line option.
10523 .vitem &$authenticated_sender$&
10524 .cindex "sender" "authenticated"
10525 .cindex "authentication" "sender"
10526 .cindex "AUTH" "on MAIL command"
10527 .vindex "&$authenticated_sender$&"
10528 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
10529 SMTP MAIL command if it believes the sender is sufficiently trusted, as
10530 described in section &<<SECTauthparamail>>&. Unless the data is the string
10531 &"<>"&, it is set as the authenticated sender of the message, and the value is
10532 available during delivery in the &$authenticated_sender$& variable. If the
10533 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
10535 .vindex "&$qualify_domain$&"
10536 When a message is submitted locally (that is, not over a TCP connection), the
10537 value of &$authenticated_sender$& is an address constructed from the login
10538 name of the calling process and &$qualify_domain$&, except that a trusted user
10539 can override this by means of the &%-oMas%& command line option.
10542 .vitem &$authentication_failed$&
10543 .cindex "authentication" "failure"
10544 .vindex "&$authentication_failed$&"
10545 This variable is set to &"1"& in an Exim server if a client issues an AUTH
10546 command that does not succeed. Otherwise it is set to &"0"&. This makes it
10547 possible to distinguish between &"did not try to authenticate"&
10548 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
10549 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
10550 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
10551 negative response to an AUTH command, including (for example) an attempt to use
10552 an undefined mechanism.
10554 .vitem &$body_linecount$&
10555 .cindex "message body" "line count"
10556 .cindex "body of message" "line count"
10557 .vindex "&$body_linecount$&"
10558 When a message is being received or delivered, this variable contains the
10559 number of lines in the message's body. See also &$message_linecount$&.
10561 .vitem &$body_zerocount$&
10562 .cindex "message body" "binary zero count"
10563 .cindex "body of message" "binary zero count"
10564 .cindex "binary zero" "in message body"
10565 .vindex "&$body_zerocount$&"
10566 When a message is being received or delivered, this variable contains the
10567 number of binary zero bytes in the message's body.
10569 .vitem &$bounce_recipient$&
10570 .vindex "&$bounce_recipient$&"
10571 This is set to the recipient address of a bounce message while Exim is creating
10572 it. It is useful if a customized bounce message text file is in use (see
10573 chapter &<<CHAPemsgcust>>&).
10575 .vitem &$bounce_return_size_limit$&
10576 .vindex "&$bounce_return_size_limit$&"
10577 This contains the value set in the &%bounce_return_size_limit%& option, rounded
10578 up to a multiple of 1000. It is useful when a customized error message text
10579 file is in use (see chapter &<<CHAPemsgcust>>&).
10581 .vitem &$caller_gid$&
10582 .cindex "gid (group id)" "caller"
10583 .vindex "&$caller_gid$&"
10584 The real group id under which the process that called Exim was running. This is
10585 not the same as the group id of the originator of a message (see
10586 &$originator_gid$&). If Exim re-execs itself, this variable in the new
10587 incarnation normally contains the Exim gid.
10589 .vitem &$caller_uid$&
10590 .cindex "uid (user id)" "caller"
10591 .vindex "&$caller_uid$&"
10592 The real user id under which the process that called Exim was running. This is
10593 not the same as the user id of the originator of a message (see
10594 &$originator_uid$&). If Exim re-execs itself, this variable in the new
10595 incarnation normally contains the Exim uid.
10597 .vitem &$compile_date$&
10598 .vindex "&$compile_date$&"
10599 The date on which the Exim binary was compiled.
10601 .vitem &$compile_number$&
10602 .vindex "&$compile_number$&"
10603 The building process for Exim keeps a count of the number
10604 of times it has been compiled. This serves to distinguish different
10605 compilations of the same version of the program.
10607 .vitem &$demime_errorlevel$&
10608 .vindex "&$demime_errorlevel$&"
10609 This variable is available when Exim is compiled with
10610 the content-scanning extension and the obsolete &%demime%& condition. For
10611 details, see section &<<SECTdemimecond>>&.
10613 .vitem &$demime_reason$&
10614 .vindex "&$demime_reason$&"
10615 This variable is available when Exim is compiled with the
10616 content-scanning extension and the obsolete &%demime%& condition. For details,
10617 see section &<<SECTdemimecond>>&.
10619 .vitem &$dnslist_domain$& &&&
10620 &$dnslist_matched$& &&&
10621 &$dnslist_text$& &&&
10623 .vindex "&$dnslist_domain$&"
10624 .vindex "&$dnslist_matched$&"
10625 .vindex "&$dnslist_text$&"
10626 .vindex "&$dnslist_value$&"
10627 .cindex "black list (DNS)"
10628 When a DNS (black) list lookup succeeds, these variables are set to contain
10629 the following data from the lookup: the list's domain name, the key that was
10630 looked up, the contents of any associated TXT record, and the value from the
10631 main A record. See section &<<SECID204>>& for more details.
10634 .vindex "&$domain$&"
10635 When an address is being routed, or delivered on its own, this variable
10636 contains the domain. Uppercase letters in the domain are converted into lower
10637 case for &$domain$&.
10639 Global address rewriting happens when a message is received, so the value of
10640 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
10641 is set during user filtering, but not during system filtering, because a
10642 message may have many recipients and the system filter is called just once.
10644 When more than one address is being delivered at once (for example, several
10645 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
10646 have the same domain. Transports can be restricted to handling only one domain
10647 at a time if the value of &$domain$& is required at transport time &-- this is
10648 the default for local transports. For further details of the environment in
10649 which local transports are run, see chapter &<<CHAPenvironment>>&.
10651 .oindex "&%delay_warning_condition%&"
10652 At the end of a delivery, if all deferred addresses have the same domain, it is
10653 set in &$domain$& during the expansion of &%delay_warning_condition%&.
10655 The &$domain$& variable is also used in some other circumstances:
10658 When an ACL is running for a RCPT command, &$domain$& contains the domain of
10659 the recipient address. The domain of the &'sender'& address is in
10660 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
10661 normally set during the running of the MAIL ACL. However, if the sender address
10662 is verified with a callout during the MAIL ACL, the sender domain is placed in
10663 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
10664 the &(smtp)& transport.
10667 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10668 &$domain$& contains the domain portion of the address that is being rewritten;
10669 it can be used in the expansion of the replacement address, for example, to
10670 rewrite domains by file lookup.
10673 With one important exception, whenever a domain list is being scanned,
10674 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
10675 a &%sender_domains%& condition in an ACL is being processed, the subject domain
10676 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
10677 that, in a RCPT ACL, the sender domain list can be dependent on the
10678 recipient domain (which is what is in &$domain$& at this time).
10681 .cindex "ETRN" "value of &$domain$&"
10682 .oindex "&%smtp_etrn_command%&"
10683 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
10684 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
10688 .vitem &$domain_data$&
10689 .vindex "&$domain_data$&"
10690 When the &%domains%& option on a router matches a domain by
10691 means of a lookup, the data read by the lookup is available during the running
10692 of the router as &$domain_data$&. In addition, if the driver routes the
10693 address to a transport, the value is available in that transport. If the
10694 transport is handling multiple addresses, the value from the first address is
10697 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
10698 domain by means of a lookup. The data read by the lookup is available during
10699 the rest of the ACL statement. In all other situations, this variable expands
10702 .vitem &$exim_gid$&
10703 .vindex "&$exim_gid$&"
10704 This variable contains the numerical value of the Exim group id.
10706 .vitem &$exim_path$&
10707 .vindex "&$exim_path$&"
10708 This variable contains the path to the Exim binary.
10710 .vitem &$exim_uid$&
10711 .vindex "&$exim_uid$&"
10712 This variable contains the numerical value of the Exim user id.
10714 .vitem &$found_extension$&
10715 .vindex "&$found_extension$&"
10716 This variable is available when Exim is compiled with the
10717 content-scanning extension and the obsolete &%demime%& condition. For details,
10718 see section &<<SECTdemimecond>>&.
10720 .vitem &$header_$&<&'name'&>
10721 This is not strictly an expansion variable. It is expansion syntax for
10722 inserting the message header line with the given name. Note that the name must
10723 be terminated by colon or white space, because it may contain a wide variety of
10724 characters. Note also that braces must &'not'& be used.
10728 When the &%check_local_user%& option is set for a router, the user's home
10729 directory is placed in &$home$& when the check succeeds. In particular, this
10730 means it is set during the running of users' filter files. A router may also
10731 explicitly set a home directory for use by a transport; this can be overridden
10732 by a setting on the transport itself.
10734 When running a filter test via the &%-bf%& option, &$home$& is set to the value
10735 of the environment variable HOME.
10739 If a router assigns an address to a transport (any transport), and passes a
10740 list of hosts with the address, the value of &$host$& when the transport starts
10741 to run is the name of the first host on the list. Note that this applies both
10742 to local and remote transports.
10744 .cindex "transport" "filter"
10745 .cindex "filter" "transport filter"
10746 For the &(smtp)& transport, if there is more than one host, the value of
10747 &$host$& changes as the transport works its way through the list. In
10748 particular, when the &(smtp)& transport is expanding its options for encryption
10749 using TLS, or for specifying a transport filter (see chapter
10750 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
10753 When used in the client part of an authenticator configuration (see chapter
10754 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
10755 client is connected.
10758 .vitem &$host_address$&
10759 .vindex "&$host_address$&"
10760 This variable is set to the remote host's IP address whenever &$host$& is set
10761 for a remote connection. It is also set to the IP address that is being checked
10762 when the &%ignore_target_hosts%& option is being processed.
10764 .vitem &$host_data$&
10765 .vindex "&$host_data$&"
10766 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
10767 result of the lookup is made available in the &$host_data$& variable. This
10768 allows you, for example, to do things like this:
10770 deny hosts = net-lsearch;/some/file
10771 message = $host_data
10773 .vitem &$host_lookup_deferred$&
10774 .cindex "host name" "lookup, failure of"
10775 .vindex "&$host_lookup_deferred$&"
10776 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
10777 message comes from a remote host and there is an attempt to look up the host's
10778 name from its IP address, and the attempt is not successful, one of these
10779 variables is set to &"1"&.
10782 If the lookup receives a definite negative response (for example, a DNS lookup
10783 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
10786 If there is any kind of problem during the lookup, such that Exim cannot
10787 tell whether or not the host name is defined (for example, a timeout for a DNS
10788 lookup), &$host_lookup_deferred$& is set to &"1"&.
10791 Looking up a host's name from its IP address consists of more than just a
10792 single reverse lookup. Exim checks that a forward lookup of at least one of the
10793 names it receives from a reverse lookup yields the original IP address. If this
10794 is not the case, Exim does not accept the looked up name(s), and
10795 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
10796 IP address (for example, the existence of a PTR record in the DNS) is not
10797 sufficient on its own for the success of a host name lookup. If the reverse
10798 lookup succeeds, but there is a lookup problem such as a timeout when checking
10799 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
10800 &"1"&. See also &$sender_host_name$&.
10802 .vitem &$host_lookup_failed$&
10803 .vindex "&$host_lookup_failed$&"
10804 See &$host_lookup_deferred$&.
10808 .vindex "&$inode$&"
10809 The only time this variable is set is while expanding the &%directory_file%&
10810 option in the &(appendfile)& transport. The variable contains the inode number
10811 of the temporary file which is about to be renamed. It can be used to construct
10812 a unique name for the file.
10814 .vitem &$interface_address$&
10815 .vindex "&$interface_address$&"
10816 This is an obsolete name for &$received_ip_address$&.
10818 .vitem &$interface_port$&
10819 .vindex "&$interface_port$&"
10820 This is an obsolete name for &$received_port$&.
10824 This variable is used during the expansion of &*forall*& and &*forany*&
10825 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
10826 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
10830 .vindex "&$ldap_dn$&"
10831 This variable, which is available only when Exim is compiled with LDAP support,
10832 contains the DN from the last entry in the most recently successful LDAP
10835 .vitem &$load_average$&
10836 .vindex "&$load_average$&"
10837 This variable contains the system load average, multiplied by 1000 so that it
10838 is an integer. For example, if the load average is 0.21, the value of the
10839 variable is 210. The value is recomputed every time the variable is referenced.
10841 .vitem &$local_part$&
10842 .vindex "&$local_part$&"
10843 When an address is being routed, or delivered on its own, this
10844 variable contains the local part. When a number of addresses are being
10845 delivered together (for example, multiple RCPT commands in an SMTP
10846 session), &$local_part$& is not set.
10848 Global address rewriting happens when a message is received, so the value of
10849 &$local_part$& during routing and delivery is the value after rewriting.
10850 &$local_part$& is set during user filtering, but not during system filtering,
10851 because a message may have many recipients and the system filter is called just
10854 .vindex "&$local_part_prefix$&"
10855 .vindex "&$local_part_suffix$&"
10856 If a local part prefix or suffix has been recognized, it is not included in the
10857 value of &$local_part$& during routing and subsequent delivery. The values of
10858 any prefix or suffix are in &$local_part_prefix$& and
10859 &$local_part_suffix$&, respectively.
10861 When a message is being delivered to a file, pipe, or autoreply transport as a
10862 result of aliasing or forwarding, &$local_part$& is set to the local part of
10863 the parent address, not to the file name or command (see &$address_file$& and
10866 When an ACL is running for a RCPT command, &$local_part$& contains the
10867 local part of the recipient address.
10869 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10870 &$local_part$& contains the local part of the address that is being rewritten;
10871 it can be used in the expansion of the replacement address, for example.
10873 In all cases, all quoting is removed from the local part. For example, for both
10876 "abc:xyz"@test.example
10877 abc\:xyz@test.example
10879 the value of &$local_part$& is
10883 If you use &$local_part$& to create another address, you should always wrap it
10884 inside a quoting operator. For example, in a &(redirect)& router you could
10887 data = ${quote_local_part:$local_part}@new.domain.example
10889 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
10890 to process local parts in a case-dependent manner in a router, you can set the
10891 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
10893 .vitem &$local_part_data$&
10894 .vindex "&$local_part_data$&"
10895 When the &%local_parts%& option on a router matches a local part by means of a
10896 lookup, the data read by the lookup is available during the running of the
10897 router as &$local_part_data$&. In addition, if the driver routes the address
10898 to a transport, the value is available in that transport. If the transport is
10899 handling multiple addresses, the value from the first address is used.
10901 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
10902 matches a local part by means of a lookup. The data read by the lookup is
10903 available during the rest of the ACL statement. In all other situations, this
10904 variable expands to nothing.
10906 .vitem &$local_part_prefix$&
10907 .vindex "&$local_part_prefix$&"
10908 When an address is being routed or delivered, and a
10909 specific prefix for the local part was recognized, it is available in this
10910 variable, having been removed from &$local_part$&.
10912 .vitem &$local_part_suffix$&
10913 .vindex "&$local_part_suffix$&"
10914 When an address is being routed or delivered, and a
10915 specific suffix for the local part was recognized, it is available in this
10916 variable, having been removed from &$local_part$&.
10918 .vitem &$local_scan_data$&
10919 .vindex "&$local_scan_data$&"
10920 This variable contains the text returned by the &[local_scan()]& function when
10921 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
10923 .vitem &$local_user_gid$&
10924 .vindex "&$local_user_gid$&"
10925 See &$local_user_uid$&.
10927 .vitem &$local_user_uid$&
10928 .vindex "&$local_user_uid$&"
10929 This variable and &$local_user_gid$& are set to the uid and gid after the
10930 &%check_local_user%& router precondition succeeds. This means that their values
10931 are available for the remaining preconditions (&%senders%&, &%require_files%&,
10932 and &%condition%&), for the &%address_data%& expansion, and for any
10933 router-specific expansions. At all other times, the values in these variables
10934 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
10936 .vitem &$localhost_number$&
10937 .vindex "&$localhost_number$&"
10938 This contains the expanded value of the
10939 &%localhost_number%& option. The expansion happens after the main options have
10942 .vitem &$log_inodes$&
10943 .vindex "&$log_inodes$&"
10944 The number of free inodes in the disk partition where Exim's
10945 log files are being written. The value is recalculated whenever the variable is
10946 referenced. If the relevant file system does not have the concept of inodes,
10947 the value of is -1. See also the &%check_log_inodes%& option.
10949 .vitem &$log_space$&
10950 .vindex "&$log_space$&"
10951 The amount of free space (as a number of kilobytes) in the disk
10952 partition where Exim's log files are being written. The value is recalculated
10953 whenever the variable is referenced. If the operating system does not have the
10954 ability to find the amount of free space (only true for experimental systems),
10955 the space value is -1. See also the &%check_log_space%& option.
10958 .vitem &$mailstore_basename$&
10959 .vindex "&$mailstore_basename$&"
10960 This variable is set only when doing deliveries in &"mailstore"& format in the
10961 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
10962 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
10963 contains the basename of the files that are being written, that is, the name
10964 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
10967 .vitem &$malware_name$&
10968 .vindex "&$malware_name$&"
10969 This variable is available when Exim is compiled with the
10970 content-scanning extension. It is set to the name of the virus that was found
10971 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
10973 .vitem &$max_received_linelength$&
10974 .vindex "&$max_received_linelength$&"
10975 .cindex "maximum" "line length"
10976 .cindex "line length" "maximum"
10977 This variable contains the number of bytes in the longest line that was
10978 received as part of the message, not counting the line termination
10981 .vitem &$message_age$&
10982 .cindex "message" "age of"
10983 .vindex "&$message_age$&"
10984 This variable is set at the start of a delivery attempt to contain the number
10985 of seconds since the message was received. It does not change during a single
10988 .vitem &$message_body$&
10989 .cindex "body of message" "expansion variable"
10990 .cindex "message body" "in expansion"
10991 .cindex "binary zero" "in message body"
10992 .vindex "&$message_body$&"
10993 .oindex "&%message_body_visible%&"
10994 This variable contains the initial portion of a message's body while it is
10995 being delivered, and is intended mainly for use in filter files. The maximum
10996 number of characters of the body that are put into the variable is set by the
10997 &%message_body_visible%& configuration option; the default is 500.
10999 .oindex "&%message_body_newlines%&"
11000 By default, newlines are converted into spaces in &$message_body$&, to make it
11001 easier to search for phrases that might be split over a line break. However,
11002 this can be disabled by setting &%message_body_newlines%& to be true. Binary
11003 zeros are always converted into spaces.
11005 .vitem &$message_body_end$&
11006 .cindex "body of message" "expansion variable"
11007 .cindex "message body" "in expansion"
11008 .vindex "&$message_body_end$&"
11009 This variable contains the final portion of a message's
11010 body while it is being delivered. The format and maximum size are as for
11013 .vitem &$message_body_size$&
11014 .cindex "body of message" "size"
11015 .cindex "message body" "size"
11016 .vindex "&$message_body_size$&"
11017 When a message is being delivered, this variable contains the size of the body
11018 in bytes. The count starts from the character after the blank line that
11019 separates the body from the header. Newlines are included in the count. See
11020 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11022 .vitem &$message_exim_id$&
11023 .vindex "&$message_exim_id$&"
11024 When a message is being received or delivered, this variable contains the
11025 unique message id that is generated and used by Exim to identify the message.
11026 An id is not created for a message until after its header has been successfully
11027 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11028 line; it is the local id that Exim assigns to the message, for example:
11029 &`1BXTIK-0001yO-VA`&.
11031 .vitem &$message_headers$&
11032 .vindex &$message_headers$&
11033 This variable contains a concatenation of all the header lines when a message
11034 is being processed, except for lines added by routers or transports. The header
11035 lines are separated by newline characters. Their contents are decoded in the
11036 same way as a header line that is inserted by &%bheader%&.
11038 .vitem &$message_headers_raw$&
11039 .vindex &$message_headers_raw$&
11040 This variable is like &$message_headers$& except that no processing of the
11041 contents of header lines is done.
11043 .vitem &$message_id$&
11044 This is an old name for &$message_exim_id$&, which is now deprecated.
11046 .vitem &$message_linecount$&
11047 .vindex "&$message_linecount$&"
11048 This variable contains the total number of lines in the header and body of the
11049 message. Compare &$body_linecount$&, which is the count for the body only.
11050 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
11051 number of lines received. Before delivery happens (that is, before filters,
11052 routers, and transports run) the count is increased to include the
11053 &'Received:'& header line that Exim standardly adds, and also any other header
11054 lines that are added by ACLs. The blank line that separates the message header
11055 from the body is not counted. Here is an example of the use of this variable in
11058 deny message = Too many lines in message header
11060 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
11062 In the MAIL and RCPT ACLs, the value is zero because at that stage the
11063 message has not yet been received.
11065 .vitem &$message_size$&
11066 .cindex "size" "of message"
11067 .cindex "message" "size"
11068 .vindex "&$message_size$&"
11069 When a message is being processed, this variable contains its size in bytes. In
11070 most cases, the size includes those headers that were received with the
11071 message, but not those (such as &'Envelope-to:'&) that are added to individual
11072 deliveries as they are written. However, there is one special case: during the
11073 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11074 doing a delivery in maildir format, the value of &$message_size$& is the
11075 precise size of the file that has been written. See also
11076 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11078 .cindex "RCPT" "value of &$message_size$&"
11079 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11080 contains the size supplied on the MAIL command, or -1 if no size was given. The
11081 value may not, of course, be truthful.
11083 .vitem &$mime_$&&'xxx'&
11084 A number of variables whose names start with &$mime$& are
11085 available when Exim is compiled with the content-scanning extension. For
11086 details, see section &<<SECTscanmimepart>>&.
11088 .vitem "&$n0$& &-- &$n9$&"
11089 These variables are counters that can be incremented by means
11090 of the &%add%& command in filter files.
11092 .vitem &$original_domain$&
11093 .vindex "&$domain$&"
11094 .vindex "&$original_domain$&"
11095 When a top-level address is being processed for delivery, this contains the
11096 same value as &$domain$&. However, if a &"child"& address (for example,
11097 generated by an alias, forward, or filter file) is being processed, this
11098 variable contains the domain of the original address (lower cased). This
11099 differs from &$parent_domain$& only when there is more than one level of
11100 aliasing or forwarding. When more than one address is being delivered in a
11101 single transport run, &$original_domain$& is not set.
11103 If a new address is created by means of a &%deliver%& command in a system
11104 filter, it is set up with an artificial &"parent"& address. This has the local
11105 part &'system-filter'& and the default qualify domain.
11107 .vitem &$original_local_part$&
11108 .vindex "&$local_part$&"
11109 .vindex "&$original_local_part$&"
11110 When a top-level address is being processed for delivery, this contains the
11111 same value as &$local_part$&, unless a prefix or suffix was removed from the
11112 local part, because &$original_local_part$& always contains the full local
11113 part. When a &"child"& address (for example, generated by an alias, forward, or
11114 filter file) is being processed, this variable contains the full local part of
11115 the original address.
11117 If the router that did the redirection processed the local part
11118 case-insensitively, the value in &$original_local_part$& is in lower case.
11119 This variable differs from &$parent_local_part$& only when there is more than
11120 one level of aliasing or forwarding. When more than one address is being
11121 delivered in a single transport run, &$original_local_part$& is not set.
11123 If a new address is created by means of a &%deliver%& command in a system
11124 filter, it is set up with an artificial &"parent"& address. This has the local
11125 part &'system-filter'& and the default qualify domain.
11127 .vitem &$originator_gid$&
11128 .cindex "gid (group id)" "of originating user"
11129 .cindex "sender" "gid"
11130 .vindex "&$caller_gid$&"
11131 .vindex "&$originator_gid$&"
11132 This variable contains the value of &$caller_gid$& that was set when the
11133 message was received. For messages received via the command line, this is the
11134 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11135 normally the gid of the Exim user.
11137 .vitem &$originator_uid$&
11138 .cindex "uid (user id)" "of originating user"
11139 .cindex "sender" "uid"
11140 .vindex "&$caller_uid$&"
11141 .vindex "&$originaltor_uid$&"
11142 The value of &$caller_uid$& that was set when the message was received. For
11143 messages received via the command line, this is the uid of the sending user.
11144 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11147 .vitem &$parent_domain$&
11148 .vindex "&$parent_domain$&"
11149 This variable is similar to &$original_domain$& (see
11150 above), except that it refers to the immediately preceding parent address.
11152 .vitem &$parent_local_part$&
11153 .vindex "&$parent_local_part$&"
11154 This variable is similar to &$original_local_part$&
11155 (see above), except that it refers to the immediately preceding parent address.
11158 .cindex "pid (process id)" "of current process"
11160 This variable contains the current process id.
11162 .vitem &$pipe_addresses$&
11163 .cindex "filter" "transport filter"
11164 .cindex "transport" "filter"
11165 .vindex "&$pipe_addresses$&"
11166 This is not an expansion variable, but is mentioned here because the string
11167 &`$pipe_addresses`& is handled specially in the command specification for the
11168 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
11169 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
11170 It cannot be used in general expansion strings, and provokes an &"unknown
11171 variable"& error if encountered.
11173 .vitem &$primary_hostname$&
11174 .vindex "&$primary_hostname$&"
11175 This variable contains the value set by &%primary_hostname%& in the
11176 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
11177 a single-component name, Exim calls &[gethostbyname()]& (or
11178 &[getipnodebyname()]& where available) in an attempt to acquire a fully
11179 qualified host name. See also &$smtp_active_hostname$&.
11182 .vitem &$prvscheck_address$&
11183 This variable is used in conjunction with the &%prvscheck%& expansion item,
11184 which is described in sections &<<SECTexpansionitems>>& and
11185 &<<SECTverifyPRVS>>&.
11187 .vitem &$prvscheck_keynum$&
11188 This variable is used in conjunction with the &%prvscheck%& expansion item,
11189 which is described in sections &<<SECTexpansionitems>>& and
11190 &<<SECTverifyPRVS>>&.
11192 .vitem &$prvscheck_result$&
11193 This variable is used in conjunction with the &%prvscheck%& expansion item,
11194 which is described in sections &<<SECTexpansionitems>>& and
11195 &<<SECTverifyPRVS>>&.
11197 .vitem &$qualify_domain$&
11198 .vindex "&$qualify_domain$&"
11199 The value set for the &%qualify_domain%& option in the configuration file.
11201 .vitem &$qualify_recipient$&
11202 .vindex "&$qualify_recipient$&"
11203 The value set for the &%qualify_recipient%& option in the configuration file,
11204 or if not set, the value of &$qualify_domain$&.
11206 .vitem &$rcpt_count$&
11207 .vindex "&$rcpt_count$&"
11208 When a message is being received by SMTP, this variable contains the number of
11209 RCPT commands received for the current message. If this variable is used in a
11210 RCPT ACL, its value includes the current command.
11212 .vitem &$rcpt_defer_count$&
11213 .vindex "&$rcpt_defer_count$&"
11214 .cindex "4&'xx'& responses" "count of"
11215 When a message is being received by SMTP, this variable contains the number of
11216 RCPT commands in the current message that have previously been rejected with a
11217 temporary (4&'xx'&) response.
11219 .vitem &$rcpt_fail_count$&
11220 .vindex "&$rcpt_fail_count$&"
11221 When a message is being received by SMTP, this variable contains the number of
11222 RCPT commands in the current message that have previously been rejected with a
11223 permanent (5&'xx'&) response.
11225 .vitem &$received_count$&
11226 .vindex "&$received_count$&"
11227 This variable contains the number of &'Received:'& header lines in the message,
11228 including the one added by Exim (so its value is always greater than zero). It
11229 is available in the DATA ACL, the non-SMTP ACL, and while routing and
11232 .vitem &$received_for$&
11233 .vindex "&$received_for$&"
11234 If there is only a single recipient address in an incoming message, this
11235 variable contains that address when the &'Received:'& header line is being
11236 built. The value is copied after recipient rewriting has happened, but before
11237 the &[local_scan()]& function is run.
11239 .vitem &$received_ip_address$&
11240 .vindex "&$received_ip_address$&"
11241 As soon as an Exim server starts processing an incoming TCP/IP connection, this
11242 variable is set to the address of the local IP interface, and &$received_port$&
11243 is set to the local port number. (The remote IP address and port are in
11244 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
11245 the port value is -1 unless it has been set using the &%-oMi%& command line
11248 As well as being useful in ACLs (including the &"connect"& ACL), these variable
11249 could be used, for example, to make the file name for a TLS certificate depend
11250 on which interface and/or port is being used for the incoming connection. The
11251 values of &$received_ip_address$& and &$received_port$& are saved with any
11252 messages that are received, thus making these variables available at delivery
11255 &*Note:*& There are no equivalent variables for outgoing connections, because
11256 the values are unknown (unless they are explicitly set by options of the
11257 &(smtp)& transport).
11259 .vitem &$received_port$&
11260 .vindex "&$received_port$&"
11261 See &$received_ip_address$&.
11263 .vitem &$received_protocol$&
11264 .vindex "&$received_protocol$&"
11265 When a message is being processed, this variable contains the name of the
11266 protocol by which it was received. Most of the names used by Exim are defined
11267 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
11268 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
11269 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
11270 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
11271 connection and the client was successfully authenticated.
11273 Exim uses the protocol name &"smtps"& for the case when encryption is
11274 automatically set up on connection without the use of STARTTLS (see
11275 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
11276 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
11277 where the client initially uses EHLO, sets up an encrypted connection using
11278 STARTTLS, and then uses HELO afterwards.
11280 The &%-oMr%& option provides a way of specifying a custom protocol name for
11281 messages that are injected locally by trusted callers. This is commonly used to
11282 identify messages that are being re-injected after some kind of scanning.
11284 .vitem &$received_time$&
11285 .vindex "&$received_time$&"
11286 This variable contains the date and time when the current message was received,
11287 as a number of seconds since the start of the Unix epoch.
11289 .vitem &$recipient_data$&
11290 .vindex "&$recipient_data$&"
11291 This variable is set after an indexing lookup success in an ACL &%recipients%&
11292 condition. It contains the data from the lookup, and the value remains set
11293 until the next &%recipients%& test. Thus, you can do things like this:
11295 &`require recipients = cdb*@;/some/file`&
11296 &`deny `&&'some further test involving'& &`$recipient_data`&
11298 &*Warning*&: This variable is set only when a lookup is used as an indexing
11299 method in the address list, using the semicolon syntax as in the example above.
11300 The variable is not set for a lookup that is used as part of the string
11301 expansion that all such lists undergo before being interpreted.
11303 .vitem &$recipient_verify_failure$&
11304 .vindex "&$recipient_verify_failure$&"
11305 In an ACL, when a recipient verification fails, this variable contains
11306 information about the failure. It is set to one of the following words:
11309 &"qualify"&: The address was unqualified (no domain), and the message
11310 was neither local nor came from an exempted host.
11313 &"route"&: Routing failed.
11316 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
11317 or before the MAIL command (that is, on initial connection, HELO, or
11321 &"recipient"&: The RCPT command in a callout was rejected.
11324 &"postmaster"&: The postmaster check in a callout was rejected.
11327 The main use of this variable is expected to be to distinguish between
11328 rejections of MAIL and rejections of RCPT.
11330 .vitem &$recipients$&
11331 .vindex "&$recipients$&"
11332 This variable contains a list of envelope recipients for a message. A comma and
11333 a space separate the addresses in the replacement text. However, the variable
11334 is not generally available, to prevent exposure of Bcc recipients in
11335 unprivileged users' filter files. You can use &$recipients$& only in these
11339 In a system filter file.
11341 In the ACLs associated with the DATA command and with non-SMTP messages, that
11342 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
11343 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
11344 &%acl_not_smtp_mime%&.
11346 From within a &[local_scan()]& function.
11350 .vitem &$recipients_count$&
11351 .vindex "&$recipients_count$&"
11352 When a message is being processed, this variable contains the number of
11353 envelope recipients that came with the message. Duplicates are not excluded
11354 from the count. While a message is being received over SMTP, the number
11355 increases for each accepted recipient. It can be referenced in an ACL.
11358 .vitem &$regex_match_string$&
11359 .vindex "&$regex_match_string$&"
11360 This variable is set to contain the matching regular expression after a
11361 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
11364 .vitem &$reply_address$&
11365 .vindex "&$reply_address$&"
11366 When a message is being processed, this variable contains the contents of the
11367 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
11368 contents of the &'From:'& header line. Apart from the removal of leading
11369 white space, the value is not processed in any way. In particular, no RFC 2047
11370 decoding or character code translation takes place.
11372 .vitem &$return_path$&
11373 .vindex "&$return_path$&"
11374 When a message is being delivered, this variable contains the return path &--
11375 the sender field that will be sent as part of the envelope. It is not enclosed
11376 in <> characters. At the start of routing an address, &$return_path$& has the
11377 same value as &$sender_address$&, but if, for example, an incoming message to a
11378 mailing list has been expanded by a router which specifies a different address
11379 for bounce messages, &$return_path$& subsequently contains the new bounce
11380 address, whereas &$sender_address$& always contains the original sender address
11381 that was received with the message. In other words, &$sender_address$& contains
11382 the incoming envelope sender, and &$return_path$& contains the outgoing
11385 .vitem &$return_size_limit$&
11386 .vindex "&$return_size_limit$&"
11387 This is an obsolete name for &$bounce_return_size_limit$&.
11390 .cindex "return code" "from &%run%& expansion"
11391 .vindex "&$runrc$&"
11392 This variable contains the return code from a command that is run by the
11393 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
11394 assume the order in which option values are expanded, except for those
11395 preconditions whose order of testing is documented. Therefore, you cannot
11396 reliably expect to set &$runrc$& by the expansion of one option, and use it in
11399 .vitem &$self_hostname$&
11400 .oindex "&%self%&" "value of host name"
11401 .vindex "&$self_hostname$&"
11402 When an address is routed to a supposedly remote host that turns out to be the
11403 local host, what happens is controlled by the &%self%& generic router option.
11404 One of its values causes the address to be passed to another router. When this
11405 happens, &$self_hostname$& is set to the name of the local host that the
11406 original router encountered. In other circumstances its contents are null.
11408 .vitem &$sender_address$&
11409 .vindex "&$sender_address$&"
11410 When a message is being processed, this variable contains the sender's address
11411 that was received in the message's envelope. The case of letters in the address
11412 is retained, in both the local part and the domain. For bounce messages, the
11413 value of this variable is the empty string. See also &$return_path$&.
11415 .vitem &$sender_address_data$&
11416 .vindex "&$address_data$&"
11417 .vindex "&$sender_address_data$&"
11418 If &$address_data$& is set when the routers are called from an ACL to verify a
11419 sender address, the final value is preserved in &$sender_address_data$&, to
11420 distinguish it from data from a recipient address. The value does not persist
11421 after the end of the current ACL statement. If you want to preserve it for
11422 longer, you can save it in an ACL variable.
11424 .vitem &$sender_address_domain$&
11425 .vindex "&$sender_address_domain$&"
11426 The domain portion of &$sender_address$&.
11428 .vitem &$sender_address_local_part$&
11429 .vindex "&$sender_address_local_part$&"
11430 The local part portion of &$sender_address$&.
11432 .vitem &$sender_data$&
11433 .vindex "&$sender_data$&"
11434 This variable is set after a lookup success in an ACL &%senders%& condition or
11435 in a router &%senders%& option. It contains the data from the lookup, and the
11436 value remains set until the next &%senders%& test. Thus, you can do things like
11439 &`require senders = cdb*@;/some/file`&
11440 &`deny `&&'some further test involving'& &`$sender_data`&
11442 &*Warning*&: This variable is set only when a lookup is used as an indexing
11443 method in the address list, using the semicolon syntax as in the example above.
11444 The variable is not set for a lookup that is used as part of the string
11445 expansion that all such lists undergo before being interpreted.
11447 .vitem &$sender_fullhost$&
11448 .vindex "&$sender_fullhost$&"
11449 When a message is received from a remote host, this variable contains the host
11450 name and IP address in a single string. It ends with the IP address in square
11451 brackets, followed by a colon and a port number if the logging of ports is
11452 enabled. The format of the rest of the string depends on whether the host
11453 issued a HELO or EHLO SMTP command, and whether the host name was verified by
11454 looking up its IP address. (Looking up the IP address can be forced by the
11455 &%host_lookup%& option, independent of verification.) A plain host name at the
11456 start of the string is a verified host name; if this is not present,
11457 verification either failed or was not requested. A host name in parentheses is
11458 the argument of a HELO or EHLO command. This is omitted if it is identical to
11459 the verified host name or to the host's IP address in square brackets.
11461 .vitem &$sender_helo_name$&
11462 .vindex "&$sender_helo_name$&"
11463 When a message is received from a remote host that has issued a HELO or EHLO
11464 command, the argument of that command is placed in this variable. It is also
11465 set if HELO or EHLO is used when a message is received using SMTP locally via
11466 the &%-bs%& or &%-bS%& options.
11468 .vitem &$sender_host_address$&
11469 .vindex "&$sender_host_address$&"
11470 When a message is received from a remote host, this variable contains that
11471 host's IP address. For locally submitted messages, it is empty.
11473 .vitem &$sender_host_authenticated$&
11474 .vindex "&$sender_host_authenticated$&"
11475 This variable contains the name (not the public name) of the authenticator
11476 driver that successfully authenticated the client from which the message was
11477 received. It is empty if there was no successful authentication. See also
11478 &$authenticated_id$&.
11480 .vitem &$sender_host_name$&
11481 .vindex "&$sender_host_name$&"
11482 When a message is received from a remote host, this variable contains the
11483 host's name as obtained by looking up its IP address. For messages received by
11484 other means, this variable is empty.
11486 .vindex "&$host_lookup_failed$&"
11487 If the host name has not previously been looked up, a reference to
11488 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
11489 A looked up name is accepted only if it leads back to the original IP address
11490 via a forward lookup. If either the reverse or the forward lookup fails to find
11491 any data, or if the forward lookup does not yield the original IP address,
11492 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
11494 .vindex "&$host_lookup_deferred$&"
11495 However, if either of the lookups cannot be completed (for example, there is a
11496 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
11497 &$host_lookup_failed$& remains set to &"0"&.
11499 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
11500 host name again if there is a subsequent reference to &$sender_host_name$&
11501 in the same Exim process, but it does try again if &$host_lookup_deferred$&
11504 Exim does not automatically look up every calling host's name. If you want
11505 maximum efficiency, you should arrange your configuration so that it avoids
11506 these lookups altogether. The lookup happens only if one or more of the
11507 following are true:
11510 A string containing &$sender_host_name$& is expanded.
11512 The calling host matches the list in &%host_lookup%&. In the default
11513 configuration, this option is set to *, so it must be changed if lookups are
11514 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
11516 Exim needs the host name in order to test an item in a host list. The items
11517 that require this are described in sections &<<SECThoslispatnam>>& and
11518 &<<SECThoslispatnamsk>>&.
11520 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
11521 In this case, the host name is required to compare with the name quoted in any
11522 EHLO or HELO commands that the client issues.
11524 The remote host issues a EHLO or HELO command that quotes one of the
11525 domains in &%helo_lookup_domains%&. The default value of this option is
11526 . ==== As this is a nested list, any displays it contains must be indented
11527 . ==== as otherwise they are too far to the left.
11529 helo_lookup_domains = @ : @[]
11531 which causes a lookup if a remote host (incorrectly) gives the server's name or
11532 IP address in an EHLO or HELO command.
11536 .vitem &$sender_host_port$&
11537 .vindex "&$sender_host_port$&"
11538 When a message is received from a remote host, this variable contains the port
11539 number that was used on the remote host.
11541 .vitem &$sender_ident$&
11542 .vindex "&$sender_ident$&"
11543 When a message is received from a remote host, this variable contains the
11544 identification received in response to an RFC 1413 request. When a message has
11545 been received locally, this variable contains the login name of the user that
11548 .vitem &$sender_rate_$&&'xxx'&
11549 A number of variables whose names begin &$sender_rate_$& are set as part of the
11550 &%ratelimit%& ACL condition. Details are given in section
11551 &<<SECTratelimiting>>&.
11553 .vitem &$sender_rcvhost$&
11554 .cindex "DNS" "reverse lookup"
11555 .cindex "reverse DNS lookup"
11556 .vindex "&$sender_rcvhost$&"
11557 This is provided specifically for use in &'Received:'& headers. It starts with
11558 either the verified host name (as obtained from a reverse DNS lookup) or, if
11559 there is no verified host name, the IP address in square brackets. After that
11560 there may be text in parentheses. When the first item is a verified host name,
11561 the first thing in the parentheses is the IP address in square brackets,
11562 followed by a colon and a port number if port logging is enabled. When the
11563 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
11566 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
11567 was used and its argument was not identical to the real host name or IP
11568 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
11569 all three items are present in the parentheses, a newline and tab are inserted
11570 into the string, to improve the formatting of the &'Received:'& header.
11572 .vitem &$sender_verify_failure$&
11573 .vindex "&$sender_verify_failure$&"
11574 In an ACL, when a sender verification fails, this variable contains information
11575 about the failure. The details are the same as for
11576 &$recipient_verify_failure$&.
11578 .vitem &$sending_ip_address$&
11579 .vindex "&$sending_ip_address$&"
11580 This variable is set whenever an outgoing SMTP connection to another host has
11581 been set up. It contains the IP address of the local interface that is being
11582 used. This is useful if a host that has more than one IP address wants to take
11583 on different personalities depending on which one is being used. For incoming
11584 connections, see &$received_ip_address$&.
11586 .vitem &$sending_port$&
11587 .vindex "&$sending_port$&"
11588 This variable is set whenever an outgoing SMTP connection to another host has
11589 been set up. It contains the local port that is being used. For incoming
11590 connections, see &$received_port$&.
11592 .vitem &$smtp_active_hostname$&
11593 .vindex "&$smtp_active_hostname$&"
11594 During an incoming SMTP session, this variable contains the value of the active
11595 host name, as specified by the &%smtp_active_hostname%& option. The value of
11596 &$smtp_active_hostname$& is saved with any message that is received, so its
11597 value can be consulted during routing and delivery.
11599 .vitem &$smtp_command$&
11600 .vindex "&$smtp_command$&"
11601 During the processing of an incoming SMTP command, this variable contains the
11602 entire command. This makes it possible to distinguish between HELO and EHLO in
11603 the HELO ACL, and also to distinguish between commands such as these:
11608 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
11609 command, the address in &$smtp_command$& is the original address before any
11610 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
11611 the address after SMTP-time rewriting.
11613 .vitem &$smtp_command_argument$&
11614 .cindex "SMTP" "command, argument for"
11615 .vindex "&$smtp_command_argument$&"
11616 While an ACL is running to check an SMTP command, this variable contains the
11617 argument, that is, the text that follows the command name, with leading white
11618 space removed. Following the introduction of &$smtp_command$&, this variable is
11619 somewhat redundant, but is retained for backwards compatibility.
11621 .vitem &$smtp_count_at_connection_start$&
11622 .vindex "&$smtp_count_at_connection_start$&"
11623 This variable is set greater than zero only in processes spawned by the Exim
11624 daemon for handling incoming SMTP connections. The name is deliberately long,
11625 in order to emphasize what the contents are. When the daemon accepts a new
11626 connection, it increments this variable. A copy of the variable is passed to
11627 the child process that handles the connection, but its value is fixed, and
11628 never changes. It is only an approximation of how many incoming connections
11629 there actually are, because many other connections may come and go while a
11630 single connection is being processed. When a child process terminates, the
11631 daemon decrements its copy of the variable.
11633 .vitem "&$sn0$& &-- &$sn9$&"
11634 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
11635 that were current at the end of the system filter file. This allows a system
11636 filter file to set values that can be tested in users' filter files. For
11637 example, a system filter could set a value indicating how likely it is that a
11638 message is junk mail.
11640 .vitem &$spam_$&&'xxx'&
11641 A number of variables whose names start with &$spam$& are available when Exim
11642 is compiled with the content-scanning extension. For details, see section
11643 &<<SECTscanspamass>>&.
11646 .vitem &$spool_directory$&
11647 .vindex "&$spool_directory$&"
11648 The name of Exim's spool directory.
11650 .vitem &$spool_inodes$&
11651 .vindex "&$spool_inodes$&"
11652 The number of free inodes in the disk partition where Exim's spool files are
11653 being written. The value is recalculated whenever the variable is referenced.
11654 If the relevant file system does not have the concept of inodes, the value of
11655 is -1. See also the &%check_spool_inodes%& option.
11657 .vitem &$spool_space$&
11658 .vindex "&$spool_space$&"
11659 The amount of free space (as a number of kilobytes) in the disk partition where
11660 Exim's spool files are being written. The value is recalculated whenever the
11661 variable is referenced. If the operating system does not have the ability to
11662 find the amount of free space (only true for experimental systems), the space
11663 value is -1. For example, to check in an ACL that there is at least 50
11664 megabytes free on the spool, you could write:
11666 condition = ${if > {$spool_space}{50000}}
11668 See also the &%check_spool_space%& option.
11671 .vitem &$thisaddress$&
11672 .vindex "&$thisaddress$&"
11673 This variable is set only during the processing of the &%foranyaddress%&
11674 command in a filter file. Its use is explained in the description of that
11675 command, which can be found in the separate document entitled &'Exim's
11676 interfaces to mail filtering'&.
11678 .vitem &$tls_certificate_verified$&
11679 .vindex "&$tls_certificate_verified$&"
11680 This variable is set to &"1"& if a TLS certificate was verified when the
11681 message was received, and &"0"& otherwise.
11683 .vitem &$tls_cipher$&
11684 .vindex "&$tls_cipher$&"
11685 When a message is received from a remote host over an encrypted SMTP
11686 connection, this variable is set to the cipher suite that was negotiated, for
11687 example DES-CBC3-SHA. In other circumstances, in particular, for message
11688 received over unencrypted connections, the variable is empty. Testing
11689 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
11690 non-encrypted connections during ACL processing.
11692 The &$tls_cipher$& variable retains its value during message delivery, except
11693 when an outward SMTP delivery takes place via the &(smtp)& transport. In this
11694 case, &$tls_cipher$& is cleared before any outgoing SMTP connection is made,
11695 and then set to the outgoing cipher suite if one is negotiated. See chapter
11696 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
11697 details of the &(smtp)& transport.
11699 .vitem &$tls_peerdn$&
11700 .vindex "&$tls_peerdn$&"
11701 When a message is received from a remote host over an encrypted SMTP
11702 connection, and Exim is configured to request a certificate from the client,
11703 the value of the Distinguished Name of the certificate is made available in the
11704 &$tls_peerdn$& during subsequent processing. Like &$tls_cipher$&, the
11705 value is retained during message delivery, except during outbound SMTP
11708 .vitem &$tod_bsdinbox$&
11709 .vindex "&$tod_bsdinbox$&"
11710 The time of day and the date, in the format required for BSD-style mailbox
11711 files, for example: Thu Oct 17 17:14:09 1995.
11713 .vitem &$tod_epoch$&
11714 .vindex "&$tod_epoch$&"
11715 The time and date as a number of seconds since the start of the Unix epoch.
11717 .vitem &$tod_full$&
11718 .vindex "&$tod_full$&"
11719 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
11720 +0100. The timezone is always given as a numerical offset from UTC, with
11721 positive values used for timezones that are ahead (east) of UTC, and negative
11722 values for those that are behind (west).
11725 .vindex "&$tod_log$&"
11726 The time and date in the format used for writing Exim's log files, for example:
11727 1995-10-12 15:32:29, but without a timezone.
11729 .vitem &$tod_logfile$&
11730 .vindex "&$tod_logfile$&"
11731 This variable contains the date in the format yyyymmdd. This is the format that
11732 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
11735 .vitem &$tod_zone$&
11736 .vindex "&$tod_zone$&"
11737 This variable contains the numerical value of the local timezone, for example:
11740 .vitem &$tod_zulu$&
11741 .vindex "&$tod_zulu$&"
11742 This variable contains the UTC date and time in &"Zulu"& format, as specified
11743 by ISO 8601, for example: 20030221154023Z.
11746 .vindex "&$value$&"
11747 This variable contains the result of an expansion lookup, extraction operation,
11748 or external command, as described above. It is also used during a
11749 &*reduce*& expansion.
11751 .vitem &$version_number$&
11752 .vindex "&$version_number$&"
11753 The version number of Exim.
11755 .vitem &$warn_message_delay$&
11756 .vindex "&$warn_message_delay$&"
11757 This variable is set only during the creation of a message warning about a
11758 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11760 .vitem &$warn_message_recipients$&
11761 .vindex "&$warn_message_recipients$&"
11762 This variable is set only during the creation of a message warning about a
11763 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11769 . ////////////////////////////////////////////////////////////////////////////
11770 . ////////////////////////////////////////////////////////////////////////////
11772 .chapter "Embedded Perl" "CHAPperl"
11773 .scindex IIDperl "Perl" "calling from Exim"
11774 Exim can be built to include an embedded Perl interpreter. When this is done,
11775 Perl subroutines can be called as part of the string expansion process. To make
11776 use of the Perl support, you need version 5.004 or later of Perl installed on
11777 your system. To include the embedded interpreter in the Exim binary, include
11782 in your &_Local/Makefile_& and then build Exim in the normal way.
11785 .section "Setting up so Perl can be used" "SECID85"
11786 .oindex "&%perl_startup%&"
11787 Access to Perl subroutines is via a global configuration option called
11788 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
11789 no &%perl_startup%& option in the Exim configuration file then no Perl
11790 interpreter is started and there is almost no overhead for Exim (since none of
11791 the Perl library will be paged in unless used). If there is a &%perl_startup%&
11792 option then the associated value is taken to be Perl code which is executed in
11793 a newly created Perl interpreter.
11795 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
11796 need backslashes before any characters to escape special meanings. The option
11797 should usually be something like
11799 perl_startup = do '/etc/exim.pl'
11801 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
11802 use from Exim. Exim can be configured either to start up a Perl interpreter as
11803 soon as it is entered, or to wait until the first time it is needed. Starting
11804 the interpreter at the beginning ensures that it is done while Exim still has
11805 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
11806 fact used in a particular run. Also, note that this does not mean that Exim is
11807 necessarily running as root when Perl is called at a later time. By default,
11808 the interpreter is started only when it is needed, but this can be changed in
11812 .oindex "&%perl_at_start%&"
11813 Setting &%perl_at_start%& (a boolean option) in the configuration requests
11814 a startup when Exim is entered.
11816 The command line option &%-ps%& also requests a startup when Exim is entered,
11817 overriding the setting of &%perl_at_start%&.
11820 There is also a command line option &%-pd%& (for delay) which suppresses the
11821 initial startup, even if &%perl_at_start%& is set.
11824 .section "Calling Perl subroutines" "SECID86"
11825 When the configuration file includes a &%perl_startup%& option you can make use
11826 of the string expansion item to call the Perl subroutines that are defined
11827 by the &%perl_startup%& code. The operator is used in any of the following
11831 ${perl{foo}{argument}}
11832 ${perl{foo}{argument1}{argument2} ... }
11834 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
11835 arguments may be passed. Passing more than this results in an expansion failure
11836 with an error message of the form
11838 Too many arguments passed to Perl subroutine "foo" (max is 8)
11840 The return value of the Perl subroutine is evaluated in a scalar context before
11841 it is passed back to Exim to be inserted into the expanded string. If the
11842 return value is &'undef'&, the expansion is forced to fail in the same way as
11843 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
11844 by obeying Perl's &%die%& function, the expansion fails with the error message
11845 that was passed to &%die%&.
11848 .section "Calling Exim functions from Perl" "SECID87"
11849 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
11850 is available to call back into Exim's string expansion function. For example,
11853 my $lp = Exim::expand_string('$local_part');
11855 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
11856 Note those are single quotes and not double quotes to protect against
11857 &$local_part$& being interpolated as a Perl variable.
11859 If the string expansion is forced to fail by a &"fail"& item, the result of
11860 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
11861 expansion string, the Perl call from the original expansion string fails with
11862 an appropriate error message, in the same way as if &%die%& were used.
11864 .cindex "debugging" "from embedded Perl"
11865 .cindex "log" "writing from embedded Perl"
11866 Two other Exim functions are available for use from within Perl code.
11867 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
11868 debugging is enabled. If you want a newline at the end, you must supply it.
11869 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
11870 timestamp. In this case, you should not supply a terminating newline.
11873 .section "Use of standard output and error by Perl" "SECID88"
11874 .cindex "Perl" "standard output and error"
11875 You should not write to the standard error or output streams from within your
11876 Perl code, as it is not defined how these are set up. In versions of Exim
11877 before 4.50, it is possible for the standard output or error to refer to the
11878 SMTP connection during message reception via the daemon. Writing to this stream
11879 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
11880 error streams are connected to &_/dev/null_& in the daemon. The chaos is
11881 avoided, but the output is lost.
11883 .cindex "Perl" "use of &%warn%&"
11884 The Perl &%warn%& statement writes to the standard error stream by default.
11885 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
11886 you have no control. When Exim starts up the Perl interpreter, it arranges for
11887 output from the &%warn%& statement to be written to the Exim main log. You can
11888 change this by including appropriate Perl magic somewhere in your Perl code.
11889 For example, to discard &%warn%& output completely, you need this:
11891 $SIG{__WARN__} = sub { };
11893 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
11894 example, the code for the subroutine is empty, so it does nothing, but you can
11895 include any Perl code that you like. The text of the &%warn%& message is passed
11896 as the first subroutine argument.
11900 . ////////////////////////////////////////////////////////////////////////////
11901 . ////////////////////////////////////////////////////////////////////////////
11903 .chapter "Starting the daemon and the use of network interfaces" &&&
11904 "CHAPinterfaces" &&&
11905 "Starting the daemon"
11906 .cindex "daemon" "starting"
11907 .cindex "interface" "listening"
11908 .cindex "network interface"
11909 .cindex "interface" "network"
11910 .cindex "IP address" "for listening"
11911 .cindex "daemon" "listening IP addresses"
11912 .cindex "TCP/IP" "setting listening interfaces"
11913 .cindex "TCP/IP" "setting listening ports"
11914 A host that is connected to a TCP/IP network may have one or more physical
11915 hardware network interfaces. Each of these interfaces may be configured as one
11916 or more &"logical"& interfaces, which are the entities that a program actually
11917 works with. Each of these logical interfaces is associated with an IP address.
11918 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
11919 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
11920 knowledge about the host's interfaces for use in three different circumstances:
11923 When a listening daemon is started, Exim needs to know which interfaces
11924 and ports to listen on.
11926 When Exim is routing an address, it needs to know which IP addresses
11927 are associated with local interfaces. This is required for the correct
11928 processing of MX lists by removing the local host and others with the
11929 same or higher priority values. Also, Exim needs to detect cases
11930 when an address is routed to an IP address that in fact belongs to the
11931 local host. Unless the &%self%& router option or the &%allow_localhost%&
11932 option of the smtp transport is set (as appropriate), this is treated
11933 as an error situation.
11935 When Exim connects to a remote host, it may need to know which interface to use
11936 for the outgoing connection.
11940 Exim's default behaviour is likely to be appropriate in the vast majority
11941 of cases. If your host has only one interface, and you want all its IP
11942 addresses to be treated in the same way, and you are using only the
11943 standard SMTP port, you should not need to take any special action. The
11944 rest of this chapter does not apply to you.
11946 In a more complicated situation you may want to listen only on certain
11947 interfaces, or on different ports, and for this reason there are a number of
11948 options that can be used to influence Exim's behaviour. The rest of this
11949 chapter describes how they operate.
11951 When a message is received over TCP/IP, the interface and port that were
11952 actually used are set in &$received_ip_address$& and &$received_port$&.
11956 .section "Starting a listening daemon" "SECID89"
11957 When a listening daemon is started (by means of the &%-bd%& command line
11958 option), the interfaces and ports on which it listens are controlled by the
11962 &%daemon_smtp_ports%& contains a list of default ports. (For backward
11963 compatibility, this option can also be specified in the singular.)
11965 &%local_interfaces%& contains list of interface IP addresses on which to
11966 listen. Each item may optionally also specify a port.
11969 The default list separator in both cases is a colon, but this can be changed as
11970 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
11971 it is usually best to change the separator to avoid having to double all the
11972 colons. For example:
11974 local_interfaces = <; 127.0.0.1 ; \
11977 3ffe:ffff:836f::fe86:a061
11979 There are two different formats for specifying a port along with an IP address
11980 in &%local_interfaces%&:
11983 The port is added onto the address with a dot separator. For example, to listen
11984 on port 1234 on two different IP addresses:
11986 local_interfaces = <; 192.168.23.65.1234 ; \
11987 3ffe:ffff:836f::fe86:a061.1234
11990 The IP address is enclosed in square brackets, and the port is added
11991 with a colon separator, for example:
11993 local_interfaces = <; [192.168.23.65]:1234 ; \
11994 [3ffe:ffff:836f::fe86:a061]:1234
11998 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
11999 default setting contains just one port:
12001 daemon_smtp_ports = smtp
12003 If more than one port is listed, each interface that does not have its own port
12004 specified listens on all of them. Ports that are listed in
12005 &%daemon_smtp_ports%& can be identified either by name (defined in
12006 &_/etc/services_&) or by number. However, when ports are given with individual
12007 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
12011 .section "Special IP listening addresses" "SECID90"
12012 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
12013 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
12014 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
12015 instead of setting up separate listening sockets for each interface. The
12016 default value of &%local_interfaces%& is
12018 local_interfaces = 0.0.0.0
12020 when Exim is built without IPv6 support; otherwise it is:
12022 local_interfaces = <; ::0 ; 0.0.0.0
12024 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
12028 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
12029 The &%-oX%& command line option can be used to override the values of
12030 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
12031 instance. Another way of doing this would be to use macros and the &%-D%&
12032 option. However, &%-oX%& can be used by any admin user, whereas modification of
12033 the runtime configuration by &%-D%& is allowed only when the caller is root or
12036 The value of &%-oX%& is a list of items. The default colon separator can be
12037 changed in the usual way if required. If there are any items that do not
12038 contain dots or colons (that is, are not IP addresses), the value of
12039 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
12040 items that do contain dots or colons, the value of &%local_interfaces%& is
12041 replaced by those items. Thus, for example,
12045 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
12048 -oX 192.168.34.5.1125
12050 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
12051 (However, since &%local_interfaces%& now contains no items without ports, the
12052 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
12056 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
12057 .cindex "ssmtp protocol"
12058 .cindex "smtps protocol"
12059 .cindex "SMTP" "ssmtp protocol"
12060 .cindex "SMTP" "smtps protocol"
12061 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
12062 before the STARTTLS command was standardized for SMTP. Some legacy clients
12063 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
12064 list of port numbers, connections to those ports must use SSMTP. The most
12065 common use of this option is expected to be
12067 tls_on_connect_ports = 465
12069 because 465 is the usual port number used by the legacy clients. There is also
12070 a command line option &%-tls-on-connect%&, which forces all ports to behave in
12071 this way when a daemon is started.
12073 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
12074 daemon to listen on those ports. You must still specify them in
12075 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
12076 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
12077 connections via the daemon.)
12082 .section "IPv6 address scopes" "SECID92"
12083 .cindex "IPv6" "address scopes"
12084 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
12085 can, in principle, have the same link-local IPv6 address on different
12086 interfaces. Thus, additional information is needed, over and above the IP
12087 address, to distinguish individual interfaces. A convention of using a
12088 percent sign followed by something (often the interface name) has been
12089 adopted in some cases, leading to addresses like this:
12091 fe80::202:b3ff:fe03:45c1%eth0
12093 To accommodate this usage, a percent sign followed by an arbitrary string is
12094 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
12095 to convert a textual IPv6 address for actual use. This function recognizes the
12096 percent convention in operating systems that support it, and it processes the
12097 address appropriately. Unfortunately, some older libraries have problems with
12098 &[getaddrinfo()]&. If
12100 IPV6_USE_INET_PTON=yes
12102 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
12103 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
12104 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
12105 function.) Of course, this means that the additional functionality of
12106 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
12108 .section "Disabling IPv6" "SECID93"
12109 .cindex "IPv6" "disabling"
12110 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
12111 run on a host whose kernel does not support IPv6. The binary will fall back to
12112 using IPv4, but it may waste resources looking up AAAA records, and trying to
12113 connect to IPv6 addresses, causing delays to mail delivery. If you set the
12114 .oindex "&%disable_ipv6%&"
12115 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
12116 activities take place. AAAA records are never looked up, and any IPv6 addresses
12117 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
12118 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12119 to handle IPv6 literal addresses.
12121 On the other hand, when IPv6 is in use, there may be times when you want to
12122 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
12123 option to globally suppress the lookup of AAAA records for specified domains,
12124 and you can use the &%ignore_target_hosts%& generic router option to ignore
12125 IPv6 addresses in an individual router.
12129 .section "Examples of starting a listening daemon" "SECID94"
12130 The default case in an IPv6 environment is
12132 daemon_smtp_ports = smtp
12133 local_interfaces = <; ::0 ; 0.0.0.0
12135 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
12136 Either one or two sockets may be used, depending on the characteristics of
12137 the TCP/IP stack. (This is complicated and messy; for more information,
12138 read the comments in the &_daemon.c_& source file.)
12140 To specify listening on ports 25 and 26 on all interfaces:
12142 daemon_smtp_ports = 25 : 26
12144 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
12146 local_interfaces = <; ::0.25 ; ::0.26 \
12147 0.0.0.0.25 ; 0.0.0.0.26
12149 To listen on the default port on all IPv4 interfaces, and on port 26 on the
12150 IPv4 loopback address only:
12152 local_interfaces = 0.0.0.0 : 127.0.0.1.26
12154 To specify listening on the default port on specific interfaces only:
12156 local_interfaces = 192.168.34.67 : 192.168.34.67
12158 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
12162 .section "Recognizing the local host" "SECTreclocipadd"
12163 The &%local_interfaces%& option is also used when Exim needs to determine
12164 whether or not an IP address refers to the local host. That is, the IP
12165 addresses of all the interfaces on which a daemon is listening are always
12168 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
12169 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
12170 available interfaces from the operating system, and extracts the relevant
12171 (that is, IPv4 or IPv6) addresses to use for checking.
12173 Some systems set up large numbers of virtual interfaces in order to provide
12174 many virtual web servers. In this situation, you may want to listen for
12175 email on only a few of the available interfaces, but nevertheless treat all
12176 interfaces as local when routing. You can do this by setting
12177 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
12178 &"all"& wildcard values. These addresses are recognized as local, but are not
12179 used for listening. Consider this example:
12181 local_interfaces = <; 127.0.0.1 ; ::1 ; \
12183 3ffe:2101:12:1:a00:20ff:fe86:a061
12185 extra_local_interfaces = <; ::0 ; 0.0.0.0
12187 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
12188 address, but all available interface addresses are treated as local when
12191 In some environments the local host name may be in an MX list, but with an IP
12192 address that is not assigned to any local interface. In other cases it may be
12193 desirable to treat other host names as if they referred to the local host. Both
12194 these cases can be handled by setting the &%hosts_treat_as_local%& option.
12195 This contains host names rather than IP addresses. When a host is referenced
12196 during routing, either via an MX record or directly, it is treated as the local
12197 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
12198 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
12202 .section "Delivering to a remote host" "SECID95"
12203 Delivery to a remote host is handled by the smtp transport. By default, it
12204 allows the system's TCP/IP functions to choose which interface to use (if
12205 there is more than one) when connecting to a remote host. However, the
12206 &%interface%& option can be set to specify which interface is used. See the
12207 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
12213 . ////////////////////////////////////////////////////////////////////////////
12214 . ////////////////////////////////////////////////////////////////////////////
12216 .chapter "Main configuration" "CHAPmainconfig"
12217 .scindex IIDconfima "configuration file" "main section"
12218 .scindex IIDmaiconf "main configuration"
12219 The first part of the run time configuration file contains three types of item:
12222 Macro definitions: These lines start with an upper case letter. See section
12223 &<<SECTmacrodefs>>& for details of macro processing.
12225 Named list definitions: These lines start with one of the words &"domainlist"&,
12226 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
12227 section &<<SECTnamedlists>>&.
12229 Main configuration settings: Each setting occupies one line of the file
12230 (with possible continuations). If any setting is preceded by the word
12231 &"hide"&, the &%-bP%& command line option displays its value to admin users
12232 only. See section &<<SECTcos>>& for a description of the syntax of these option
12236 This chapter specifies all the main configuration options, along with their
12237 types and default values. For ease of finding a particular option, they appear
12238 in alphabetical order in section &<<SECTalomo>>& below. However, because there
12239 are now so many options, they are first listed briefly in functional groups, as
12240 an aid to finding the name of the option you are looking for. Some options are
12241 listed in more than one group.
12243 .section "Miscellaneous" "SECID96"
12245 .row &%bi_command%& "to run for &%-bi%& command line option"
12246 .row &%disable_ipv6%& "do no IPv6 processing"
12247 .row &%keep_malformed%& "for broken files &-- should not happen"
12248 .row &%localhost_number%& "for unique message ids in clusters"
12249 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
12250 .row &%message_body_visible%& "how much to show in &$message_body$&"
12251 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
12252 .row &%print_topbitchars%& "top-bit characters are printing"
12253 .row &%timezone%& "force time zone"
12257 .section "Exim parameters" "SECID97"
12259 .row &%exim_group%& "override compiled-in value"
12260 .row &%exim_path%& "override compiled-in value"
12261 .row &%exim_user%& "override compiled-in value"
12262 .row &%primary_hostname%& "default from &[uname()]&"
12263 .row &%split_spool_directory%& "use multiple directories"
12264 .row &%spool_directory%& "override compiled-in value"
12269 .section "Privilege controls" "SECID98"
12271 .row &%admin_groups%& "groups that are Exim admin users"
12272 .row &%deliver_drop_privilege%& "drop root for delivery processes"
12273 .row &%local_from_check%& "insert &'Sender:'& if necessary"
12274 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
12275 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
12276 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
12277 .row &%never_users%& "do not run deliveries as these"
12278 .row &%prod_requires_admin%& "forced delivery requires admin user"
12279 .row &%queue_list_requires_admin%& "queue listing requires admin user"
12280 .row &%trusted_groups%& "groups that are trusted"
12281 .row &%trusted_users%& "users that are trusted"
12286 .section "Logging" "SECID99"
12288 .row &%hosts_connection_nolog%& "exemption from connect logging"
12289 .row &%log_file_path%& "override compiled-in value"
12290 .row &%log_selector%& "set/unset optional logging"
12291 .row &%log_timezone%& "add timezone to log lines"
12292 .row &%message_logs%& "create per-message logs"
12293 .row &%preserve_message_logs%& "after message completion"
12294 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
12295 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
12296 .row &%syslog_facility%& "set syslog &""facility""& field"
12297 .row &%syslog_processname%& "set syslog &""ident""& field"
12298 .row &%syslog_timestamp%& "timestamp syslog lines"
12299 .row &%write_rejectlog%& "control use of message log"
12304 .section "Frozen messages" "SECID100"
12306 .row &%auto_thaw%& "sets time for retrying frozen messages"
12307 .row &%freeze_tell%& "send message when freezing"
12308 .row &%move_frozen_messages%& "to another directory"
12309 .row &%timeout_frozen_after%& "keep frozen messages only so long"
12314 .section "Data lookups" "SECID101"
12316 .row &%ibase_servers%& "InterBase servers"
12317 .row &%ldap_default_servers%& "used if no server in query"
12318 .row &%ldap_version%& "set protocol version"
12319 .row &%lookup_open_max%& "lookup files held open"
12320 .row &%mysql_servers%& "default MySQL servers"
12321 .row &%oracle_servers%& "Oracle servers"
12322 .row &%pgsql_servers%& "default PostgreSQL servers"
12323 .row &%sqlite_lock_timeout%& "as it says"
12328 .section "Message ids" "SECID102"
12330 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
12331 .row &%message_id_header_text%& "ditto"
12336 .section "Embedded Perl Startup" "SECID103"
12338 .row &%perl_at_start%& "always start the interpreter"
12339 .row &%perl_startup%& "code to obey when starting Perl"
12344 .section "Daemon" "SECID104"
12346 .row &%daemon_smtp_ports%& "default ports"
12347 .row &%daemon_startup_retries%& "number of times to retry"
12348 .row &%daemon_startup_sleep%& "time to sleep between tries"
12349 .row &%extra_local_interfaces%& "not necessarily listened on"
12350 .row &%local_interfaces%& "on which to listen, with optional ports"
12351 .row &%pid_file_path%& "override compiled-in value"
12352 .row &%queue_run_max%& "maximum simultaneous queue runners"
12357 .section "Resource control" "SECID105"
12359 .row &%check_log_inodes%& "before accepting a message"
12360 .row &%check_log_space%& "before accepting a message"
12361 .row &%check_spool_inodes%& "before accepting a message"
12362 .row &%check_spool_space%& "before accepting a message"
12363 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
12364 .row &%queue_only_load%& "queue incoming if load high"
12365 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12366 .row &%queue_run_max%& "maximum simultaneous queue runners"
12367 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12368 .row &%smtp_accept_max%& "simultaneous incoming connections"
12369 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12370 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12371 .row &%smtp_accept_max_per_connection%& "messages per connection"
12372 .row &%smtp_accept_max_per_host%& "connections from one host"
12373 .row &%smtp_accept_queue%& "queue mail if more connections"
12374 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12376 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12377 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12378 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12379 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
12380 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12385 .section "Policy controls" "SECID106"
12387 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
12388 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
12389 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
12390 .row &%acl_smtp_auth%& "ACL for AUTH"
12391 .row &%acl_smtp_connect%& "ACL for connection"
12392 .row &%acl_smtp_data%& "ACL for DATA"
12393 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
12394 .row &%acl_smtp_etrn%& "ACL for ETRN"
12395 .row &%acl_smtp_expn%& "ACL for EXPN"
12396 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
12397 .row &%acl_smtp_mail%& "ACL for MAIL"
12398 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
12399 .row &%acl_smtp_mime%& "ACL for MIME parts"
12400 .row &%acl_smtp_predata%& "ACL for start of data"
12401 .row &%acl_smtp_quit%& "ACL for QUIT"
12402 .row &%acl_smtp_rcpt%& "ACL for RCPT"
12403 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
12404 .row &%acl_smtp_vrfy%& "ACL for VRFY"
12405 .row &%av_scanner%& "specify virus scanner"
12406 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
12408 .row &%dns_csa_search_limit%& "control CSA parent search depth"
12409 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
12410 .row &%header_maxsize%& "total size of message header"
12411 .row &%header_line_maxsize%& "individual header line limit"
12412 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
12413 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
12414 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
12415 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
12416 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
12417 .row &%host_lookup%& "host name looked up for these hosts"
12418 .row &%host_lookup_order%& "order of DNS and local name lookups"
12419 .row &%host_reject_connection%& "reject connection from these hosts"
12420 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
12421 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
12422 .row &%message_size_limit%& "for all messages"
12423 .row &%percent_hack_domains%& "recognize %-hack for these domains"
12424 .row &%spamd_address%& "set interface to SpamAssassin"
12425 .row &%strict_acl_vars%& "object to unset ACL variables"
12430 .section "Callout cache" "SECID107"
12432 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
12434 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
12436 .row &%callout_negative_expire%& "timeout for negative address cache item"
12437 .row &%callout_positive_expire%& "timeout for positive address cache item"
12438 .row &%callout_random_local_part%& "string to use for &""random""& testing"
12443 .section "TLS" "SECID108"
12445 .row &%gnutls_require_kx%& "control GnuTLS key exchanges"
12446 .row &%gnutls_require_mac%& "control GnuTLS MAC algorithms"
12447 .row &%gnutls_require_protocols%& "control GnuTLS protocols"
12448 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
12449 .row &%openssl_options%& "adjust OpenSSL compatibility options"
12450 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
12451 .row &%tls_certificate%& "location of server certificate"
12452 .row &%tls_crl%& "certificate revocation list"
12453 .row &%tls_dhparam%& "DH parameters for server"
12454 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
12455 .row &%tls_privatekey%& "location of server private key"
12456 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
12457 .row &%tls_require_ciphers%& "specify acceptable ciphers"
12458 .row &%tls_try_verify_hosts%& "try to verify client certificate"
12459 .row &%tls_verify_certificates%& "expected client certificates"
12460 .row &%tls_verify_hosts%& "insist on client certificate verify"
12465 .section "Local user handling" "SECID109"
12467 .row &%finduser_retries%& "useful in NIS environments"
12468 .row &%gecos_name%& "used when creating &'Sender:'&"
12469 .row &%gecos_pattern%& "ditto"
12470 .row &%max_username_length%& "for systems that truncate"
12471 .row &%unknown_login%& "used when no login name found"
12472 .row &%unknown_username%& "ditto"
12473 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
12474 .row &%uucp_from_sender%& "ditto"
12479 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
12481 .row &%header_maxsize%& "total size of message header"
12482 .row &%header_line_maxsize%& "individual header line limit"
12483 .row &%message_size_limit%& "applies to all messages"
12484 .row &%percent_hack_domains%& "recognize %-hack for these domains"
12485 .row &%received_header_text%& "expanded to make &'Received:'&"
12486 .row &%received_headers_max%& "for mail loop detection"
12487 .row &%recipients_max%& "limit per message"
12488 .row &%recipients_max_reject%& "permanently reject excess recipients"
12494 .section "Non-SMTP incoming messages" "SECID111"
12496 .row &%receive_timeout%& "for non-SMTP messages"
12503 .section "Incoming SMTP messages" "SECID112"
12504 See also the &'Policy controls'& section above.
12507 .row &%host_lookup%& "host name looked up for these hosts"
12508 .row &%host_lookup_order%& "order of DNS and local name lookups"
12509 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
12510 .row &%rfc1413_hosts%& "make ident calls to these hosts"
12511 .row &%rfc1413_query_timeout%& "zero disables ident calls"
12512 .row &%sender_unqualified_hosts%& "may send unqualified senders"
12513 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
12514 .row &%smtp_accept_max%& "simultaneous incoming connections"
12515 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12516 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12517 .row &%smtp_accept_max_per_connection%& "messages per connection"
12518 .row &%smtp_accept_max_per_host%& "connections from one host"
12519 .row &%smtp_accept_queue%& "queue mail if more connections"
12520 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12522 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12523 .row &%smtp_active_hostname%& "host name to use in messages"
12524 .row &%smtp_banner%& "text for welcome banner"
12525 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12526 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12527 .row &%smtp_enforce_sync%& "of SMTP command/responses"
12528 .row &%smtp_etrn_command%& "what to run for ETRN"
12529 .row &%smtp_etrn_serialize%& "only one at once"
12530 .row &%smtp_load_reserve%& "only reserve hosts if this load"
12531 .row &%smtp_max_unknown_commands%& "before dropping connection"
12532 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
12533 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
12534 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
12535 .row &%smtp_receive_timeout%& "per command or data line"
12536 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12537 .row &%smtp_return_error_details%& "give detail on rejections"
12542 .section "SMTP extensions" "SECID113"
12544 .row &%accept_8bitmime%& "advertise 8BITMIME"
12545 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
12546 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
12547 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
12548 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
12549 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
12554 .section "Processing messages" "SECID114"
12556 .row &%allow_domain_literals%& "recognize domain literal syntax"
12557 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
12558 .row &%allow_utf8_domains%& "in addresses"
12559 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
12561 .row &%delivery_date_remove%& "from incoming messages"
12562 .row &%envelope_to_remove%& "from incoming messages"
12563 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
12564 .row &%headers_charset%& "default for translations"
12565 .row &%qualify_domain%& "default for senders"
12566 .row &%qualify_recipient%& "default for recipients"
12567 .row &%return_path_remove%& "from incoming messages"
12568 .row &%strip_excess_angle_brackets%& "in addresses"
12569 .row &%strip_trailing_dot%& "at end of addresses"
12570 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
12575 .section "System filter" "SECID115"
12577 .row &%system_filter%& "locate system filter"
12578 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
12580 .row &%system_filter_file_transport%& "transport for delivery to a file"
12581 .row &%system_filter_group%& "group for filter running"
12582 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
12583 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
12584 .row &%system_filter_user%& "user for filter running"
12589 .section "Routing and delivery" "SECID116"
12591 .row &%disable_ipv6%& "do no IPv6 processing"
12592 .row &%dns_again_means_nonexist%& "for broken domains"
12593 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
12594 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
12595 .row &%dns_retrans%& "parameter for resolver"
12596 .row &%dns_retry%& "parameter for resolver"
12597 .row &%hold_domains%& "hold delivery for these domains"
12598 .row &%local_interfaces%& "for routing checks"
12599 .row &%queue_domains%& "no immediate delivery for these"
12600 .row &%queue_only%& "no immediate delivery at all"
12601 .row &%queue_only_file%& "no immediate delivery if file exists"
12602 .row &%queue_only_load%& "no immediate delivery if load is high"
12603 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12604 .row &%queue_only_override%& "allow command line to override"
12605 .row &%queue_run_in_order%& "order of arrival"
12606 .row &%queue_run_max%& "of simultaneous queue runners"
12607 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
12608 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12609 .row &%remote_sort_domains%& "order of remote deliveries"
12610 .row &%retry_data_expire%& "timeout for retry data"
12611 .row &%retry_interval_max%& "safety net for retry rules"
12616 .section "Bounce and warning messages" "SECID117"
12618 .row &%bounce_message_file%& "content of bounce"
12619 .row &%bounce_message_text%& "content of bounce"
12620 .row &%bounce_return_body%& "include body if returning message"
12621 .row &%bounce_return_message%& "include original message in bounce"
12622 .row &%bounce_return_size_limit%& "limit on returned message"
12623 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
12624 .row &%dsn_from%& "set &'From:'& contents in bounces"
12625 .row &%errors_copy%& "copy bounce messages"
12626 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
12627 .row &%delay_warning%& "time schedule"
12628 .row &%delay_warning_condition%& "condition for warning messages"
12629 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
12630 .row &%smtp_return_error_details%& "give detail on rejections"
12631 .row &%warn_message_file%& "content of warning message"
12636 .section "Alphabetical list of main options" "SECTalomo"
12637 Those options that undergo string expansion before use are marked with
12640 .option accept_8bitmime main boolean false
12642 .cindex "8-bit characters"
12643 This option causes Exim to send 8BITMIME in its response to an SMTP
12644 EHLO command, and to accept the BODY= parameter on MAIL commands.
12645 However, though Exim is 8-bit clean, it is not a protocol converter, and it
12646 takes no steps to do anything special with messages received by this route.
12647 Consequently, this option is turned off by default.
12649 .option acl_not_smtp main string&!! unset
12650 .cindex "&ACL;" "for non-SMTP messages"
12651 .cindex "non-SMTP messages" "ACLs for"
12652 This option defines the ACL that is run when a non-SMTP message has been
12653 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
12656 .option acl_not_smtp_mime main string&!! unset
12657 This option defines the ACL that is run for individual MIME parts of non-SMTP
12658 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
12661 .option acl_not_smtp_start main string&!! unset
12662 .cindex "&ACL;" "at start of non-SMTP message"
12663 .cindex "non-SMTP messages" "ACLs for"
12664 This option defines the ACL that is run before Exim starts reading a
12665 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
12667 .option acl_smtp_auth main string&!! unset
12668 .cindex "&ACL;" "setting up for SMTP commands"
12669 .cindex "AUTH" "ACL for"
12670 This option defines the ACL that is run when an SMTP AUTH command is
12671 received. See chapter &<<CHAPACL>>& for further details.
12673 .option acl_smtp_connect main string&!! unset
12674 .cindex "&ACL;" "on SMTP connection"
12675 This option defines the ACL that is run when an SMTP connection is received.
12676 See chapter &<<CHAPACL>>& for further details.
12678 .option acl_smtp_data main string&!! unset
12679 .cindex "DATA" "ACL for"
12680 This option defines the ACL that is run after an SMTP DATA command has been
12681 processed and the message itself has been received, but before the final
12682 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
12684 .option acl_smtp_etrn main string&!! unset
12685 .cindex "ETRN" "ACL for"
12686 This option defines the ACL that is run when an SMTP ETRN command is
12687 received. See chapter &<<CHAPACL>>& for further details.
12689 .option acl_smtp_expn main string&!! unset
12690 .cindex "EXPN" "ACL for"
12691 This option defines the ACL that is run when an SMTP EXPN command is
12692 received. See chapter &<<CHAPACL>>& for further details.
12694 .option acl_smtp_helo main string&!! unset
12695 .cindex "EHLO" "ACL for"
12696 .cindex "HELO" "ACL for"
12697 This option defines the ACL that is run when an SMTP EHLO or HELO
12698 command is received. See chapter &<<CHAPACL>>& for further details.
12701 .option acl_smtp_mail main string&!! unset
12702 .cindex "MAIL" "ACL for"
12703 This option defines the ACL that is run when an SMTP MAIL command is
12704 received. See chapter &<<CHAPACL>>& for further details.
12706 .option acl_smtp_mailauth main string&!! unset
12707 .cindex "AUTH" "on MAIL command"
12708 This option defines the ACL that is run when there is an AUTH parameter on
12709 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
12710 &<<CHAPSMTPAUTH>>& for details of authentication.
12712 .option acl_smtp_mime main string&!! unset
12713 .cindex "MIME content scanning" "ACL for"
12714 This option is available when Exim is built with the content-scanning
12715 extension. It defines the ACL that is run for each MIME part in a message. See
12716 section &<<SECTscanmimepart>>& for details.
12718 .option acl_smtp_predata main string&!! unset
12719 This option defines the ACL that is run when an SMTP DATA command is
12720 received, before the message itself is received. See chapter &<<CHAPACL>>& for
12723 .option acl_smtp_quit main string&!! unset
12724 .cindex "QUIT, ACL for"
12725 This option defines the ACL that is run when an SMTP QUIT command is
12726 received. See chapter &<<CHAPACL>>& for further details.
12728 .option acl_smtp_rcpt main string&!! unset
12729 .cindex "RCPT" "ACL for"
12730 This option defines the ACL that is run when an SMTP RCPT command is
12731 received. See chapter &<<CHAPACL>>& for further details.
12733 .option acl_smtp_starttls main string&!! unset
12734 .cindex "STARTTLS, ACL for"
12735 This option defines the ACL that is run when an SMTP STARTTLS command is
12736 received. See chapter &<<CHAPACL>>& for further details.
12738 .option acl_smtp_vrfy main string&!! unset
12739 .cindex "VRFY" "ACL for"
12740 This option defines the ACL that is run when an SMTP VRFY command is
12741 received. See chapter &<<CHAPACL>>& for further details.
12743 .option admin_groups main "string list&!!" unset
12744 .cindex "admin user"
12745 This option is expanded just once, at the start of Exim's processing. If the
12746 current group or any of the supplementary groups of an Exim caller is in this
12747 colon-separated list, the caller has admin privileges. If all your system
12748 programmers are in a specific group, for example, you can give them all Exim
12749 admin privileges by putting that group in &%admin_groups%&. However, this does
12750 not permit them to read Exim's spool files (whose group owner is the Exim gid).
12751 To permit this, you have to add individuals to the Exim group.
12753 .option allow_domain_literals main boolean false
12754 .cindex "domain literal"
12755 If this option is set, the RFC 2822 domain literal format is permitted in
12756 email addresses. The option is not set by default, because the domain literal
12757 format is not normally required these days, and few people know about it. It
12758 has, however, been exploited by mail abusers.
12760 Unfortunately, it seems that some DNS black list maintainers are using this
12761 format to report black listing to postmasters. If you want to accept messages
12762 addressed to your hosts by IP address, you need to set
12763 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
12764 domains (defined in the named domain list &%local_domains%& in the default
12765 configuration). This &"magic string"& matches the domain literal form of all
12766 the local host's IP addresses.
12769 .option allow_mx_to_ip main boolean false
12770 .cindex "MX record" "pointing to IP address"
12771 It appears that more and more DNS zone administrators are breaking the rules
12772 and putting domain names that look like IP addresses on the right hand side of
12773 MX records. Exim follows the rules and rejects this, giving an error message
12774 that explains the mis-configuration. However, some other MTAs support this
12775 practice, so to avoid &"Why can't Exim do this?"& complaints,
12776 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
12777 recommended, except when you have no other choice.
12779 .option allow_utf8_domains main boolean false
12780 .cindex "domain" "UTF-8 characters in"
12781 .cindex "UTF-8" "in domain name"
12782 Lots of discussion is going on about internationalized domain names. One
12783 camp is strongly in favour of just using UTF-8 characters, and it seems
12784 that at least two other MTAs permit this. This option allows Exim users to
12785 experiment if they wish.
12787 If it is set true, Exim's domain parsing function allows valid
12788 UTF-8 multicharacters to appear in domain name components, in addition to
12789 letters, digits, and hyphens. However, just setting this option is not
12790 enough; if you want to look up these domain names in the DNS, you must also
12791 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
12792 suitable setting is:
12794 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
12795 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
12797 Alternatively, you can just disable this feature by setting
12799 dns_check_names_pattern =
12801 That is, set the option to an empty string so that no check is done.
12804 .option auth_advertise_hosts main "host list&!!" *
12805 .cindex "authentication" "advertising"
12806 .cindex "AUTH" "advertising"
12807 If any server authentication mechanisms are configured, Exim advertises them in
12808 response to an EHLO command only if the calling host matches this list.
12809 Otherwise, Exim does not advertise AUTH.
12810 Exim does not accept AUTH commands from clients to which it has not
12811 advertised the availability of AUTH. The advertising of individual
12812 authentication mechanisms can be controlled by the use of the
12813 &%server_advertise_condition%& generic authenticator option on the individual
12814 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
12816 Certain mail clients (for example, Netscape) require the user to provide a name
12817 and password for authentication if AUTH is advertised, even though it may
12818 not be needed (the host may accept messages from hosts on its local LAN without
12819 authentication, for example). The &%auth_advertise_hosts%& option can be used
12820 to make these clients more friendly by excluding them from the set of hosts to
12821 which Exim advertises AUTH.
12823 .cindex "AUTH" "advertising when encrypted"
12824 If you want to advertise the availability of AUTH only when the connection
12825 is encrypted using TLS, you can make use of the fact that the value of this
12826 option is expanded, with a setting like this:
12828 auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}
12830 .vindex "&$tls_cipher$&"
12831 If &$tls_cipher$& is empty, the session is not encrypted, and the result of
12832 the expansion is empty, thus matching no hosts. Otherwise, the result of the
12833 expansion is *, which matches all hosts.
12836 .option auto_thaw main time 0s
12837 .cindex "thawing messages"
12838 .cindex "unfreezing messages"
12839 If this option is set to a time greater than zero, a queue runner will try a
12840 new delivery attempt on any frozen message, other than a bounce message, if
12841 this much time has passed since it was frozen. This may result in the message
12842 being re-frozen if nothing has changed since the last attempt. It is a way of
12843 saying &"keep on trying, even though there are big problems"&.
12845 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
12846 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
12847 thought to be very useful any more, and its use should probably be avoided.
12849 .option av_scanner main string "see below"
12850 This option is available if Exim is built with the content-scanning extension.
12851 It specifies which anti-virus scanner to use. The default value is:
12853 sophie:/var/run/sophie
12855 If the value of &%av_scanner%& starts with a dollar character, it is expanded
12856 before use. See section &<<SECTscanvirus>>& for further details.
12860 .option bi_command main string unset
12862 This option supplies the name of a command that is run when Exim is called with
12863 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
12864 just the command name, it is not a complete command line. If an argument is
12865 required, it must come from the &%-oA%& command line option.
12868 .option bounce_message_file main string unset
12869 .cindex "bounce message" "customizing"
12870 .cindex "customizing" "bounce message"
12871 This option defines a template file containing paragraphs of text to be used
12872 for constructing bounce messages. Details of the file's contents are given in
12873 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
12876 .option bounce_message_text main string unset
12877 When this option is set, its contents are included in the default bounce
12878 message immediately after &"This message was created automatically by mail
12879 delivery software."& It is not used if &%bounce_message_file%& is set.
12881 .option bounce_return_body main boolean true
12882 .cindex "bounce message" "including body"
12883 This option controls whether the body of an incoming message is included in a
12884 bounce message when &%bounce_return_message%& is true. The default setting
12885 causes the entire message, both header and body, to be returned (subject to the
12886 value of &%bounce_return_size_limit%&). If this option is false, only the
12887 message header is included. In the case of a non-SMTP message containing an
12888 error that is detected during reception, only those header lines preceding the
12889 point at which the error was detected are returned.
12890 .cindex "bounce message" "including original"
12892 .option bounce_return_message main boolean true
12893 If this option is set false, none of the original message is included in
12894 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
12895 &%bounce_return_body%&.
12898 .option bounce_return_size_limit main integer 100K
12899 .cindex "size" "of bounce, limit"
12900 .cindex "bounce message" "size limit"
12901 .cindex "limit" "bounce message size"
12902 This option sets a limit in bytes on the size of messages that are returned to
12903 senders as part of bounce messages when &%bounce_return_message%& is true. The
12904 limit should be less than the value of the global &%message_size_limit%& and of
12905 any &%message_size_limit%& settings on transports, to allow for the bounce text
12906 that Exim generates. If this option is set to zero there is no limit.
12908 When the body of any message that is to be included in a bounce message is
12909 greater than the limit, it is truncated, and a comment pointing this out is
12910 added at the top. The actual cutoff may be greater than the value given, owing
12911 to the use of buffering for transferring the message in chunks (typically 8K in
12912 size). The idea is to save bandwidth on those undeliverable 15-megabyte
12915 .option bounce_sender_authentication main string unset
12916 .cindex "bounce message" "sender authentication"
12917 .cindex "authentication" "bounce message"
12918 .cindex "AUTH" "on bounce message"
12919 This option provides an authenticated sender address that is sent with any
12920 bounce messages generated by Exim that are sent over an authenticated SMTP
12921 connection. A typical setting might be:
12923 bounce_sender_authentication = mailer-daemon@my.domain.example
12925 which would cause bounce messages to be sent using the SMTP command:
12927 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
12929 The value of &%bounce_sender_authentication%& must always be a complete email
12932 .option callout_domain_negative_expire main time 3h
12933 .cindex "caching" "callout timeouts"
12934 .cindex "callout" "caching timeouts"
12935 This option specifies the expiry time for negative callout cache data for a
12936 domain. See section &<<SECTcallver>>& for details of callout verification, and
12937 section &<<SECTcallvercache>>& for details of the caching.
12940 .option callout_domain_positive_expire main time 7d
12941 This option specifies the expiry time for positive callout cache data for a
12942 domain. See section &<<SECTcallver>>& for details of callout verification, and
12943 section &<<SECTcallvercache>>& for details of the caching.
12946 .option callout_negative_expire main time 2h
12947 This option specifies the expiry time for negative callout cache data for an
12948 address. See section &<<SECTcallver>>& for details of callout verification, and
12949 section &<<SECTcallvercache>>& for details of the caching.
12952 .option callout_positive_expire main time 24h
12953 This option specifies the expiry time for positive callout cache data for an
12954 address. See section &<<SECTcallver>>& for details of callout verification, and
12955 section &<<SECTcallvercache>>& for details of the caching.
12958 .option callout_random_local_part main string&!! "see below"
12959 This option defines the &"random"& local part that can be used as part of
12960 callout verification. The default value is
12962 $primary_host_name-$tod_epoch-testing
12964 See section &<<CALLaddparcall>>& for details of how this value is used.
12967 .option check_log_inodes main integer 0
12968 See &%check_spool_space%& below.
12971 .option check_log_space main integer 0
12972 See &%check_spool_space%& below.
12974 .oindex "&%check_rfc2047_length%&"
12975 .cindex "RFC 2047" "disabling length check"
12976 .option check_rfc2047_length main boolean true
12977 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
12978 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
12979 word; strings to be encoded that exceed this length are supposed to use
12980 multiple encoded words. By default, Exim does not recognize encoded words that
12981 exceed the maximum length. However, it seems that some software, in violation
12982 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
12983 set false, Exim recognizes encoded words of any length.
12986 .option check_spool_inodes main integer 0
12987 See &%check_spool_space%& below.
12990 .option check_spool_space main integer 0
12991 .cindex "checking disk space"
12992 .cindex "disk space, checking"
12993 .cindex "spool directory" "checking space"
12994 The four &%check_...%& options allow for checking of disk resources before a
12995 message is accepted.
12997 .vindex "&$log_inodes$&"
12998 .vindex "&$log_space$&"
12999 .vindex "&$spool_inodes$&"
13000 .vindex "&$spool_space$&"
13001 When any of these options are set, they apply to all incoming messages. If you
13002 want to apply different checks to different kinds of message, you can do so by
13003 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
13004 &$spool_space$& in an ACL with appropriate additional conditions.
13007 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
13008 either value is greater than zero, for example:
13010 check_spool_space = 10M
13011 check_spool_inodes = 100
13013 The spool partition is the one that contains the directory defined by
13014 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
13017 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
13018 files are written if either is greater than zero. These should be set only if
13019 &%log_file_path%& and &%spool_directory%& refer to different partitions.
13021 If there is less space or fewer inodes than requested, Exim refuses to accept
13022 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
13023 error response to the MAIL command. If ESMTP is in use and there was a
13024 SIZE parameter on the MAIL command, its value is added to the
13025 &%check_spool_space%& value, and the check is performed even if
13026 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
13028 The values for &%check_spool_space%& and &%check_log_space%& are held as a
13029 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
13031 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
13032 failure a message is written to stderr and Exim exits with a non-zero code, as
13033 it obviously cannot send an error message of any kind.
13035 .option daemon_smtp_ports main string &`smtp`&
13036 .cindex "port" "for daemon"
13037 .cindex "TCP/IP" "setting listening ports"
13038 This option specifies one or more default SMTP ports on which the Exim daemon
13039 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
13040 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
13042 .option daemon_startup_retries main integer 9
13043 .cindex "daemon startup, retrying"
13044 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
13045 the daemon at startup when it cannot immediately bind a listening socket
13046 (typically because the socket is already in use): &%daemon_startup_retries%&
13047 defines the number of retries after the first failure, and
13048 &%daemon_startup_sleep%& defines the length of time to wait between retries.
13050 .option daemon_startup_sleep main time 30s
13051 See &%daemon_startup_retries%&.
13053 .option delay_warning main "time list" 24h
13054 .cindex "warning of delay"
13055 .cindex "delay warning, specifying"
13056 When a message is delayed, Exim sends a warning message to the sender at
13057 intervals specified by this option. The data is a colon-separated list of times
13058 after which to send warning messages. If the value of the option is an empty
13059 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
13060 message has been on the queue for longer than the last time, the last interval
13061 between the times is used to compute subsequent warning times. For example,
13064 delay_warning = 4h:8h:24h
13066 the first message is sent after 4 hours, the second after 8 hours, and
13067 the third one after 24 hours. After that, messages are sent every 16 hours,
13068 because that is the interval between the last two times on the list. If you set
13069 just one time, it specifies the repeat interval. For example, with:
13073 messages are repeated every six hours. To stop warnings after a given time, set
13074 a very large time at the end of the list. For example:
13076 delay_warning = 2h:12h:99d
13079 .option delay_warning_condition main string&!! "see below"
13080 .vindex "&$domain$&"
13081 The string is expanded at the time a warning message might be sent. If all the
13082 deferred addresses have the same domain, it is set in &$domain$& during the
13083 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
13084 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
13085 &"false"& (the comparison being done caselessly) then the warning message is
13086 not sent. The default is:
13088 delay_warning_condition = ${if or {\
13089 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
13090 { match{$h_precedence:}{(?i)bulk|list|junk} }\
13091 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
13094 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
13095 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
13096 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
13097 &"auto-replied"& in an &'Auto-Submitted:'& header.
13099 .option deliver_drop_privilege main boolean false
13100 .cindex "unprivileged delivery"
13101 .cindex "delivery" "unprivileged"
13102 If this option is set true, Exim drops its root privilege at the start of a
13103 delivery process, and runs as the Exim user throughout. This severely restricts
13104 the kinds of local delivery that are possible, but is viable in certain types
13105 of configuration. There is a discussion about the use of root privilege in
13106 chapter &<<CHAPsecurity>>&.
13108 .option deliver_queue_load_max main fixed-point unset
13109 .cindex "load average"
13110 .cindex "queue runner" "abandoning"
13111 When this option is set, a queue run is abandoned if the system load average
13112 becomes greater than the value of the option. The option has no effect on
13113 ancient operating systems on which Exim cannot determine the load average.
13114 See also &%queue_only_load%& and &%smtp_load_reserve%&.
13117 .option delivery_date_remove main boolean true
13118 .cindex "&'Delivery-date:'& header line"
13119 Exim's transports have an option for adding a &'Delivery-date:'& header to a
13120 message when it is delivered, in exactly the same way as &'Return-path:'& is
13121 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
13122 should not be present in incoming messages, and this option causes them to be
13123 removed at the time the message is received, to avoid any problems that might
13124 occur when a delivered message is subsequently sent on to some other recipient.
13126 .option disable_fsync main boolean false
13127 .cindex "&[fsync()]&, disabling"
13128 This option is available only if Exim was built with the compile-time option
13129 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
13130 a runtime configuration generates an &"unknown option"& error. You should not
13131 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
13132 really, really, really understand what you are doing. &'No pre-compiled
13133 distributions of Exim should ever make this option available.'&
13135 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
13136 updated files' data to be written to disc before continuing. Unexpected events
13137 such as crashes and power outages may cause data to be lost or scrambled.
13138 Here be Dragons. &*Beware.*&
13141 .option disable_ipv6 main boolean false
13142 .cindex "IPv6" "disabling"
13143 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
13144 activities take place. AAAA records are never looked up, and any IPv6 addresses
13145 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
13146 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13147 to handle IPv6 literal addresses.
13150 .option dns_again_means_nonexist main "domain list&!!" unset
13151 .cindex "DNS" "&""try again""& response; overriding"
13152 DNS lookups give a &"try again"& response for the DNS errors
13153 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
13154 keep trying to deliver a message, or to give repeated temporary errors to
13155 incoming mail. Sometimes the effect is caused by a badly set up name server and
13156 may persist for a long time. If a domain which exhibits this problem matches
13157 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
13158 This option should be used with care. You can make it apply to reverse lookups
13159 by a setting such as this:
13161 dns_again_means_nonexist = *.in-addr.arpa
13163 This option applies to all DNS lookups that Exim does. It also applies when the
13164 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
13165 since these are most likely to be caused by DNS lookup problems. The
13166 &(dnslookup)& router has some options of its own for controlling what happens
13167 when lookups for MX or SRV records give temporary errors. These more specific
13168 options are applied after this global option.
13170 .option dns_check_names_pattern main string "see below"
13171 .cindex "DNS" "pre-check of name syntax"
13172 When this option is set to a non-empty string, it causes Exim to check domain
13173 names for characters that are not allowed in host names before handing them to
13174 the DNS resolver, because some resolvers give temporary errors for names that
13175 contain unusual characters. If a domain name contains any unwanted characters,
13176 a &"not found"& result is forced, and the resolver is not called. The check is
13177 done by matching the domain name against a regular expression, which is the
13178 value of this option. The default pattern is
13180 dns_check_names_pattern = \
13181 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
13183 which permits only letters, digits, slashes, and hyphens in components, but
13184 they must start and end with a letter or digit. Slashes are not, in fact,
13185 permitted in host names, but they are found in certain NS records (which can be
13186 accessed in Exim by using a &%dnsdb%& lookup). If you set
13187 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
13190 .option dns_csa_search_limit main integer 5
13191 This option controls the depth of parental searching for CSA SRV records in the
13192 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
13194 .option dns_csa_use_reverse main boolean true
13195 This option controls whether or not an IP address, given as a CSA domain, is
13196 reversed and looked up in the reverse DNS, as described in more detail in
13197 section &<<SECTverifyCSA>>&.
13199 .option dns_ipv4_lookup main "domain list&!!" unset
13200 .cindex "IPv6" "DNS lookup for AAAA records"
13201 .cindex "DNS" "IPv6 lookup for AAAA records"
13202 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
13203 looks for IPv6 address records (AAAA records) as well as IPv4 address records
13204 (A records) when trying to find IP addresses for hosts, unless the host's
13205 domain matches this list.
13207 This is a fudge to help with name servers that give big delays or otherwise do
13208 not work for the AAAA record type. In due course, when the world's name
13209 servers have all been upgraded, there should be no need for this option.
13212 .option dns_retrans main time 0s
13213 .cindex "DNS" "resolver options"
13214 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
13215 retransmission and retry parameters for DNS lookups. Values of zero (the
13216 defaults) leave the system default settings unchanged. The first value is the
13217 time between retries, and the second is the number of retries. It isn't
13218 totally clear exactly how these settings affect the total time a DNS lookup may
13219 take. I haven't found any documentation about timeouts on DNS lookups; these
13220 parameter values are available in the external resolver interface structure,
13221 but nowhere does it seem to describe how they are used or what you might want
13225 .option dns_retry main integer 0
13226 See &%dns_retrans%& above.
13229 .option drop_cr main boolean false
13230 This is an obsolete option that is now a no-op. It used to affect the way Exim
13231 handled CR and LF characters in incoming messages. What happens now is
13232 described in section &<<SECTlineendings>>&.
13234 .option dsn_from main "string&!!" "see below"
13235 .cindex "&'From:'& header line" "in bounces"
13236 .cindex "bounce messages" "&'From:'& line, specifying"
13237 This option can be used to vary the contents of &'From:'& header lines in
13238 bounces and other automatically generated messages (&"Delivery Status
13239 Notifications"& &-- hence the name of the option). The default setting is:
13241 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
13243 The value is expanded every time it is needed. If the expansion fails, a
13244 panic is logged, and the default value is used.
13246 .option envelope_to_remove main boolean true
13247 .cindex "&'Envelope-to:'& header line"
13248 Exim's transports have an option for adding an &'Envelope-to:'& header to a
13249 message when it is delivered, in exactly the same way as &'Return-path:'& is
13250 handled. &'Envelope-to:'& records the original recipient address from the
13251 messages's envelope that caused the delivery to happen. Such headers should not
13252 be present in incoming messages, and this option causes them to be removed at
13253 the time the message is received, to avoid any problems that might occur when a
13254 delivered message is subsequently sent on to some other recipient.
13257 .option errors_copy main "string list&!!" unset
13258 .cindex "bounce message" "copy to other address"
13259 .cindex "copy of bounce message"
13260 Setting this option causes Exim to send bcc copies of bounce messages that it
13261 generates to other addresses. &*Note*&: This does not apply to bounce messages
13262 coming from elsewhere. The value of the option is a colon-separated list of
13263 items. Each item consists of a pattern, terminated by white space, followed by
13264 a comma-separated list of email addresses. If a pattern contains spaces, it
13265 must be enclosed in double quotes.
13267 Each pattern is processed in the same way as a single item in an address list
13268 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
13269 the bounce message, the message is copied to the addresses on the list. The
13270 items are scanned in order, and once a matching one is found, no further items
13271 are examined. For example:
13273 errors_copy = spqr@mydomain postmaster@mydomain.example :\
13274 rqps@mydomain hostmaster@mydomain.example,\
13275 postmaster@mydomain.example
13277 .vindex "&$domain$&"
13278 .vindex "&$local_part$&"
13279 The address list is expanded before use. The expansion variables &$local_part$&
13280 and &$domain$& are set from the original recipient of the error message, and if
13281 there was any wildcard matching in the pattern, the expansion
13282 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
13283 variables &$0$&, &$1$&, etc. are set in the normal way.
13286 .option errors_reply_to main string unset
13287 .cindex "bounce message" "&'Reply-to:'& in"
13288 By default, Exim's bounce and delivery warning messages contain the header line
13290 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
13292 .oindex &%quota_warn_message%&
13293 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
13294 A warning message that is generated by the &%quota_warn_message%& option in an
13295 &(appendfile)& transport may contain its own &'From:'& header line that
13296 overrides the default.
13298 Experience shows that people reply to bounce messages. If the
13299 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
13300 and warning messages. For example:
13302 errors_reply_to = postmaster@my.domain.example
13304 The value of the option is not expanded. It must specify a valid RFC 2822
13305 address. However, if a warning message that is generated by the
13306 &%quota_warn_message%& option in an &(appendfile)& transport contain its
13307 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
13311 .option exim_group main string "compile-time configured"
13312 .cindex "gid (group id)" "Exim's own"
13313 .cindex "Exim group"
13314 This option changes the gid under which Exim runs when it gives up root
13315 privilege. The default value is compiled into the binary. The value of this
13316 option is used only when &%exim_user%& is also set. Unless it consists entirely
13317 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
13318 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
13322 .option exim_path main string "see below"
13323 .cindex "Exim binary, path name"
13324 This option specifies the path name of the Exim binary, which is used when Exim
13325 needs to re-exec itself. The default is set up to point to the file &'exim'& in
13326 the directory configured at compile time by the BIN_DIRECTORY setting. It
13327 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
13329 &*Warning*&: Do not use a macro to define the value of this option, because
13330 you will break those Exim utilities that scan the configuration file to find
13331 where the binary is. (They then use the &%-bP%& option to extract option
13332 settings such as the value of &%spool_directory%&.)
13335 .option exim_user main string "compile-time configured"
13336 .cindex "uid (user id)" "Exim's own"
13337 .cindex "Exim user"
13338 This option changes the uid under which Exim runs when it gives up root
13339 privilege. The default value is compiled into the binary. Ownership of the run
13340 time configuration file and the use of the &%-C%& and &%-D%& command line
13341 options is checked against the values in the binary, not what is set here.
13343 Unless it consists entirely of digits, the string is looked up using
13344 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
13345 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
13346 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
13349 .option extra_local_interfaces main "string list" unset
13350 This option defines network interfaces that are to be considered local when
13351 routing, but which are not used for listening by the daemon. See section
13352 &<<SECTreclocipadd>>& for details.
13355 . Allow this long option name to split; give it unsplit as a fifth argument
13356 . for the automatic .oindex that is generated by .option.
13358 .option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
13359 extract_addresses_remove_arguments
13361 .cindex "command line" "addresses with &%-t%&"
13362 .cindex "Sendmail compatibility" "&%-t%& option"
13363 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
13364 are present on the command line when the &%-t%& option is used to build an
13365 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
13366 line addresses are removed from the recipients list. This is also how Smail
13367 behaves. However, other Sendmail documentation (the O'Reilly book) states that
13368 command line addresses are added to those obtained from the header lines. When
13369 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
13370 argument headers. If it is set false, Exim adds rather than removes argument
13374 .option finduser_retries main integer 0
13375 .cindex "NIS, retrying user lookups"
13376 On systems running NIS or other schemes in which user and group information is
13377 distributed from a remote system, there can be times when &[getpwnam()]& and
13378 related functions fail, even when given valid data, because things time out.
13379 Unfortunately these failures cannot be distinguished from genuine &"not found"&
13380 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
13381 many extra times to find a user or a group, waiting for one second between
13384 .cindex "&_/etc/passwd_&" "multiple reading of"
13385 You should not set this option greater than zero if your user information is in
13386 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
13387 search the file multiple times for non-existent users, and also cause delay.
13391 .option freeze_tell main "string list, comma separated" unset
13392 .cindex "freezing messages" "sending a message when freezing"
13393 On encountering certain errors, or when configured to do so in a system filter,
13394 ACL, or special router, Exim freezes a message. This means that no further
13395 delivery attempts take place until an administrator thaws the message, or the
13396 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
13397 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
13398 warning message whenever it freezes something, unless the message it is
13399 freezing is a locally-generated bounce message. (Without this exception there
13400 is the possibility of looping.) The warning message is sent to the addresses
13401 supplied as the comma-separated value of this option. If several of the
13402 message's addresses cause freezing, only a single message is sent. If the
13403 freezing was automatic, the reason(s) for freezing can be found in the message
13404 log. If you configure freezing in a filter or ACL, you must arrange for any
13405 logging that you require.
13408 .option gecos_name main string&!! unset
13410 .cindex "&""gecos""& field, parsing"
13411 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
13412 password file to hold other information in addition to users' real names. Exim
13413 looks up this field for use when it is creating &'Sender:'& or &'From:'&
13414 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
13415 of the field are used unchanged, except that, if an ampersand is encountered,
13416 it is replaced by the user's login name with the first character forced to
13417 upper case, since this is a convention that is observed on many systems.
13419 When these options are set, &%gecos_pattern%& is treated as a regular
13420 expression that is to be applied to the field (again with && replaced by the
13421 login name), and if it matches, &%gecos_name%& is expanded and used as the
13424 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
13425 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
13426 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
13427 name terminates at the first comma, the following can be used:
13429 gecos_pattern = ([^,]*)
13433 .option gecos_pattern main string unset
13434 See &%gecos_name%& above.
13437 .option gnutls_require_kx main string unset
13438 This option controls the key exchange mechanisms when GnuTLS is used in an Exim
13439 server. For details, see section &<<SECTreqciphgnu>>&.
13441 .option gnutls_require_mac main string unset
13442 This option controls the MAC algorithms when GnuTLS is used in an Exim
13443 server. For details, see section &<<SECTreqciphgnu>>&.
13445 .option gnutls_require_protocols main string unset
13446 This option controls the protocols when GnuTLS is used in an Exim
13447 server. For details, see section &<<SECTreqciphgnu>>&.
13449 .option gnutls_compat_mode main boolean unset
13450 This option controls whether GnuTLS is used in compatibility mode in an Exim
13451 server. This reduces security slightly, but improves interworking with older
13452 implementations of TLS.
13454 .option headers_charset main string "see below"
13455 This option sets a default character set for translating from encoded MIME
13456 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
13457 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
13458 ultimate default is ISO-8859-1. For more details see the description of header
13459 insertions in section &<<SECTexpansionitems>>&.
13463 .option header_maxsize main integer "see below"
13464 .cindex "header section" "maximum size of"
13465 .cindex "limit" "size of message header section"
13466 This option controls the overall maximum size of a message's header
13467 section. The default is the value of HEADER_MAXSIZE in
13468 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
13469 sections are rejected.
13472 .option header_line_maxsize main integer 0
13473 .cindex "header lines" "maximum size of"
13474 .cindex "limit" "size of one header line"
13475 This option limits the length of any individual header line in a message, after
13476 all the continuations have been joined together. Messages with individual
13477 header lines that are longer than the limit are rejected. The default value of
13478 zero means &"no limit"&.
13483 .option helo_accept_junk_hosts main "host list&!!" unset
13484 .cindex "HELO" "accepting junk data"
13485 .cindex "EHLO" "accepting junk data"
13486 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
13487 mail, and gives an error response for invalid data. Unfortunately, there are
13488 some SMTP clients that send syntactic junk. They can be accommodated by setting
13489 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
13490 if you want to do semantic checking.
13491 See also &%helo_allow_chars%& for a way of extending the permitted character
13495 .option helo_allow_chars main string unset
13496 .cindex "HELO" "underscores in"
13497 .cindex "EHLO" "underscores in"
13498 .cindex "underscore in EHLO/HELO"
13499 This option can be set to a string of rogue characters that are permitted in
13500 all EHLO and HELO names in addition to the standard letters, digits,
13501 hyphens, and dots. If you really must allow underscores, you can set
13503 helo_allow_chars = _
13505 Note that the value is one string, not a list.
13508 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
13509 .cindex "HELO" "forcing reverse lookup"
13510 .cindex "EHLO" "forcing reverse lookup"
13511 If the domain given by a client in a HELO or EHLO command matches this
13512 list, a reverse lookup is done in order to establish the host's true name. The
13513 default forces a lookup if the client host gives the server's name or any of
13514 its IP addresses (in brackets), something that broken clients have been seen to
13518 .option helo_try_verify_hosts main "host list&!!" unset
13519 .cindex "HELO verifying" "optional"
13520 .cindex "EHLO" "verifying, optional"
13521 By default, Exim just checks the syntax of HELO and EHLO commands (see
13522 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
13523 to do more extensive checking of the data supplied by these commands. The ACL
13524 condition &`verify = helo`& is provided to make this possible.
13525 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
13526 to force the check to occur. From release 4.53 onwards, this is no longer
13527 necessary. If the check has not been done before &`verify = helo`& is
13528 encountered, it is done at that time. Consequently, this option is obsolete.
13529 Its specification is retained here for backwards compatibility.
13531 When an EHLO or HELO command is received, if the calling host matches
13532 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
13533 EHLO command either:
13536 is an IP literal matching the calling address of the host, or
13538 .cindex "DNS" "reverse lookup"
13539 .cindex "reverse DNS lookup"
13540 matches the host name that Exim obtains by doing a reverse lookup of the
13541 calling host address, or
13543 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
13544 available) yields the calling host address.
13547 However, the EHLO or HELO command is not rejected if any of the checks
13548 fail. Processing continues, but the result of the check is remembered, and can
13549 be detected later in an ACL by the &`verify = helo`& condition.
13551 .option helo_verify_hosts main "host list&!!" unset
13552 .cindex "HELO verifying" "mandatory"
13553 .cindex "EHLO" "verifying, mandatory"
13554 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
13555 backwards compatibility. For hosts that match this option, Exim checks the host
13556 name given in the HELO or EHLO in the same way as for
13557 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
13558 rejected with a 550 error, and entries are written to the main and reject logs.
13559 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
13562 .option hold_domains main "domain list&!!" unset
13563 .cindex "domain" "delaying delivery"
13564 .cindex "delivery" "delaying certain domains"
13565 This option allows mail for particular domains to be held on the queue
13566 manually. The option is overridden if a message delivery is forced with the
13567 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
13568 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
13569 item in &%hold_domains%&, no routing or delivery for that address is done, and
13570 it is deferred every time the message is looked at.
13572 This option is intended as a temporary operational measure for delaying the
13573 delivery of mail while some problem is being sorted out, or some new
13574 configuration tested. If you just want to delay the processing of some
13575 domains until a queue run occurs, you should use &%queue_domains%& or
13576 &%queue_smtp_domains%&, not &%hold_domains%&.
13578 A setting of &%hold_domains%& does not override Exim's code for removing
13579 messages from the queue if they have been there longer than the longest retry
13580 time in any retry rule. If you want to hold messages for longer than the normal
13581 retry times, insert a dummy retry rule with a long retry time.
13584 .option host_lookup main "host list&!!" unset
13585 .cindex "host name" "lookup, forcing"
13586 Exim does not look up the name of a calling host from its IP address unless it
13587 is required to compare against some host list, or the host matches
13588 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
13589 option (which normally contains IP addresses rather than host names). The
13590 default configuration file contains
13594 which causes a lookup to happen for all hosts. If the expense of these lookups
13595 is felt to be too great, the setting can be changed or removed.
13597 After a successful reverse lookup, Exim does a forward lookup on the name it
13598 has obtained, to verify that it yields the IP address that it started with. If
13599 this check fails, Exim behaves as if the name lookup failed.
13601 .vindex "&$host_lookup_failed$&"
13602 .vindex "&$sender_host_name$&"
13603 After any kind of failure, the host name (in &$sender_host_name$&) remains
13604 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
13605 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
13606 &`verify = reverse_host_lookup`& in ACLs.
13609 .option host_lookup_order main "string list" &`bydns:byaddr`&
13610 This option specifies the order of different lookup methods when Exim is trying
13611 to find a host name from an IP address. The default is to do a DNS lookup
13612 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
13613 if that fails. You can change the order of these lookups, or omit one entirely,
13616 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
13617 multiple PTR records in the DNS and the IP address is not listed in
13618 &_/etc/hosts_&. Different operating systems give different results in this
13619 case. That is why the default tries a DNS lookup first.
13623 .option host_reject_connection main "host list&!!" unset
13624 .cindex "host" "rejecting connections from"
13625 If this option is set, incoming SMTP calls from the hosts listed are rejected
13626 as soon as the connection is made.
13627 This option is obsolete, and retained only for backward compatibility, because
13628 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
13629 connections immediately.
13631 The ability to give an immediate rejection (either by this option or using an
13632 ACL) is provided for use in unusual cases. Many hosts will just try again,
13633 sometimes without much delay. Normally, it is better to use an ACL to reject
13634 incoming messages at a later stage, such as after RCPT commands. See
13635 chapter &<<CHAPACL>>&.
13638 .option hosts_connection_nolog main "host list&!!" unset
13639 .cindex "host" "not logging connections from"
13640 This option defines a list of hosts for which connection logging does not
13641 happen, even though the &%smtp_connection%& log selector is set. For example,
13642 you might want not to log SMTP connections from local processes, or from
13643 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
13644 the daemon; you should therefore strive to restrict its value to a short inline
13645 list of IP addresses and networks. To disable logging SMTP connections from
13646 local processes, you must create a host list with an empty item. For example:
13648 hosts_connection_nolog = :
13650 If the &%smtp_connection%& log selector is not set, this option has no effect.
13654 .option hosts_treat_as_local main "domain list&!!" unset
13655 .cindex "local host" "domains treated as"
13656 .cindex "host" "treated as local"
13657 If this option is set, any host names that match the domain list are treated as
13658 if they were the local host when Exim is scanning host lists obtained from MX
13660 or other sources. Note that the value of this option is a domain list, not a
13661 host list, because it is always used to check host names, not IP addresses.
13663 This option also applies when Exim is matching the special items
13664 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
13665 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
13666 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
13667 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
13668 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
13669 interfaces and recognizing the local host.
13672 .option ibase_servers main "string list" unset
13673 .cindex "InterBase" "server list"
13674 This option provides a list of InterBase servers and associated connection data,
13675 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
13676 The option is available only if Exim has been built with InterBase support.
13680 .option ignore_bounce_errors_after main time 10w
13681 .cindex "bounce message" "discarding"
13682 .cindex "discarding bounce message"
13683 This option affects the processing of bounce messages that cannot be delivered,
13684 that is, those that suffer a permanent delivery failure. (Bounce messages that
13685 suffer temporary delivery failures are of course retried in the usual way.)
13687 After a permanent delivery failure, bounce messages are frozen,
13688 because there is no sender to whom they can be returned. When a frozen bounce
13689 message has been on the queue for more than the given time, it is unfrozen at
13690 the next queue run, and a further delivery is attempted. If delivery fails
13691 again, the bounce message is discarded. This makes it possible to keep failed
13692 bounce messages around for a shorter time than the normal maximum retry time
13693 for frozen messages. For example,
13695 ignore_bounce_errors_after = 12h
13697 retries failed bounce message deliveries after 12 hours, discarding any further
13698 failures. If the value of this option is set to a zero time period, bounce
13699 failures are discarded immediately. Setting a very long time (as in the default
13700 value) has the effect of disabling this option. For ways of automatically
13701 dealing with other kinds of frozen message, see &%auto_thaw%& and
13702 &%timeout_frozen_after%&.
13705 .option ignore_fromline_hosts main "host list&!!" unset
13706 .cindex "&""From""& line"
13707 .cindex "UUCP" "&""From""& line"
13708 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
13709 the headers of a message. By default this is treated as the start of the
13710 message's body, which means that any following headers are not recognized as
13711 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
13712 match those hosts that insist on sending it. If the sender is actually a local
13713 process rather than a remote host, and is using &%-bs%& to inject the messages,
13714 &%ignore_fromline_local%& must be set to achieve this effect.
13717 .option ignore_fromline_local main boolean false
13718 See &%ignore_fromline_hosts%& above.
13721 .option keep_malformed main time 4d
13722 This option specifies the length of time to keep messages whose spool files
13723 have been corrupted in some way. This should, of course, never happen. At the
13724 next attempt to deliver such a message, it gets removed. The incident is
13728 .option ldap_default_servers main "string list" unset
13729 .cindex "LDAP" "default servers"
13730 This option provides a list of LDAP servers which are tried in turn when an
13731 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
13732 details of LDAP queries. This option is available only when Exim has been built
13736 .option ldap_version main integer unset
13737 .cindex "LDAP" "protocol version, forcing"
13738 This option can be used to force Exim to set a specific protocol version for
13739 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
13740 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
13741 the LDAP headers; otherwise it is 2. This option is available only when Exim
13742 has been built with LDAP support.
13746 .option local_from_check main boolean true
13747 .cindex "&'Sender:'& header line" "disabling addition of"
13748 .cindex "&'From:'& header line" "disabling checking of"
13749 When a message is submitted locally (that is, not over a TCP/IP connection) by
13750 an untrusted user, Exim removes any existing &'Sender:'& header line, and
13751 checks that the &'From:'& header line matches the login of the calling user and
13752 the domain specified by &%qualify_domain%&.
13754 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
13755 locally submitted message is automatically qualified by Exim, unless the
13756 &%-bnq%& command line option is used.
13758 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
13759 on the local part. If the &'From:'& header line does not match, Exim adds a
13760 &'Sender:'& header with an address constructed from the calling user's login
13761 and the default qualify domain.
13763 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
13764 and no &'Sender:'& header is ever added. If, in addition, you want to retain
13765 &'Sender:'& header lines supplied by untrusted users, you must also set
13766 &%local_sender_retain%& to be true.
13768 .cindex "envelope sender"
13769 These options affect only the header lines in the message. The envelope sender
13770 is still forced to be the login id at the qualify domain unless
13771 &%untrusted_set_sender%& permits the user to supply an envelope sender.
13773 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
13774 request similar header line checking. See section &<<SECTthesenhea>>&, which
13775 has more details about &'Sender:'& processing.
13780 .option local_from_prefix main string unset
13781 When Exim checks the &'From:'& header line of locally submitted messages for
13782 matching the login id (see &%local_from_check%& above), it can be configured to
13783 ignore certain prefixes and suffixes in the local part of the address. This is
13784 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
13785 appropriate lists, in the same form as the &%local_part_prefix%& and
13786 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
13789 local_from_prefix = *-
13791 is set, a &'From:'& line containing
13793 From: anything-user@your.domain.example
13795 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
13796 matches the actual sender address that is constructed from the login name and
13800 .option local_from_suffix main string unset
13801 See &%local_from_prefix%& above.
13804 .option local_interfaces main "string list" "see below"
13805 This option controls which network interfaces are used by the daemon for
13806 listening; they are also used to identify the local host when routing. Chapter
13807 &<<CHAPinterfaces>>& contains a full description of this option and the related
13808 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
13809 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
13810 &%local_interfaces%& is
13812 local_interfaces = 0.0.0.0
13814 when Exim is built without IPv6 support; otherwise it is
13816 local_interfaces = <; ::0 ; 0.0.0.0
13819 .option local_scan_timeout main time 5m
13820 .cindex "timeout" "for &[local_scan()]& function"
13821 .cindex "&[local_scan()]& function" "timeout"
13822 This timeout applies to the &[local_scan()]& function (see chapter
13823 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
13824 the incoming message is rejected with a temporary error if it is an SMTP
13825 message. For a non-SMTP message, the message is dropped and Exim ends with a
13826 non-zero code. The incident is logged on the main and reject logs.
13830 .option local_sender_retain main boolean false
13831 .cindex "&'Sender:'& header line" "retaining from local submission"
13832 When a message is submitted locally (that is, not over a TCP/IP connection) by
13833 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
13834 do not want this to happen, you must set &%local_sender_retain%&, and you must
13835 also set &%local_from_check%& to be false (Exim will complain if you do not).
13836 See also the ACL modifier &`control = suppress_local_fixups`&. Section
13837 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
13842 .option localhost_number main string&!! unset
13843 .cindex "host" "locally unique number for"
13844 .cindex "message ids" "with multiple hosts"
13845 .vindex "&$localhost_number$&"
13846 Exim's message ids are normally unique only within the local host. If
13847 uniqueness among a set of hosts is required, each host must set a different
13848 value for the &%localhost_number%& option. The string is expanded immediately
13849 after reading the configuration file (so that a number can be computed from the
13850 host name, for example) and the result of the expansion must be a number in the
13851 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
13852 systems). This is available in subsequent string expansions via the variable
13853 &$localhost_number$&. When &%localhost_number is set%&, the final two
13854 characters of the message id, instead of just being a fractional part of the
13855 time, are computed from the time and the local host number as described in
13856 section &<<SECTmessiden>>&.
13860 .option log_file_path main "string list&!!" "set at compile time"
13861 .cindex "log" "file path for"
13862 This option sets the path which is used to determine the names of Exim's log
13863 files, or indicates that logging is to be to syslog, or both. It is expanded
13864 when Exim is entered, so it can, for example, contain a reference to the host
13865 name. If no specific path is set for the log files at compile or run time, they
13866 are written in a sub-directory called &_log_& in Exim's spool directory.
13867 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
13868 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
13869 used. If this string is fixed at your installation (contains no expansion
13870 variables) it is recommended that you do not set this option in the
13871 configuration file, but instead supply the path using LOG_FILE_PATH in
13872 &_Local/Makefile_& so that it is available to Exim for logging errors detected
13873 early on &-- in particular, failure to read the configuration file.
13876 .option log_selector main string unset
13877 .cindex "log" "selectors"
13878 This option can be used to reduce or increase the number of things that Exim
13879 writes to its log files. Its argument is made up of names preceded by plus or
13880 minus characters. For example:
13882 log_selector = +arguments -retry_defer
13884 A list of possible names and what they control is given in the chapter on
13885 logging, in section &<<SECTlogselector>>&.
13888 .option log_timezone main boolean false
13889 .cindex "log" "timezone for entries"
13890 .vindex "&$tod_log$&"
13891 .vindex "&$tod_zone$&"
13892 By default, the timestamps on log lines are in local time without the
13893 timezone. This means that if your timezone changes twice a year, the timestamps
13894 in log lines are ambiguous for an hour when the clocks go back. One way of
13895 avoiding this problem is to set the timezone to UTC. An alternative is to set
13896 &%log_timezone%& true. This turns on the addition of the timezone offset to
13897 timestamps in log lines. Turning on this option can add quite a lot to the size
13898 of log files because each line is extended by 6 characters. Note that the
13899 &$tod_log$& variable contains the log timestamp without the zone, but there is
13900 another variable called &$tod_zone$& that contains just the timezone offset.
13903 .option lookup_open_max main integer 25
13904 .cindex "too many open files"
13905 .cindex "open files, too many"
13906 .cindex "file" "too many open"
13907 .cindex "lookup" "maximum open files"
13908 .cindex "limit" "open files for lookups"
13909 This option limits the number of simultaneously open files for single-key
13910 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
13911 Exim normally keeps these files open during routing, because often the same
13912 file is required several times. If the limit is reached, Exim closes the least
13913 recently used file. Note that if you are using the &'ndbm'& library, it
13914 actually opens two files for each logical DBM database, though it still counts
13915 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
13916 open files"& errors with NDBM, you need to reduce the value of
13917 &%lookup_open_max%&.
13920 .option max_username_length main integer 0
13921 .cindex "length of login name"
13922 .cindex "user name" "maximum length"
13923 .cindex "limit" "user name length"
13924 Some operating systems are broken in that they truncate long arguments to
13925 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
13926 this option is set greater than zero, any attempt to call &[getpwnam()]& with
13927 an argument that is longer behaves as if &[getpwnam()]& failed.
13930 .option message_body_newlines main bool false
13931 .cindex "message body" "newlines in variables"
13932 .cindex "newline" "in message body variables"
13933 .vindex "&$message_body$&"
13934 .vindex "&$message_body_end$&"
13935 By default, newlines in the message body are replaced by spaces when setting
13936 the &$message_body$& and &$message_body_end$& expansion variables. If this
13937 option is set true, this no longer happens.
13940 .option message_body_visible main integer 500
13941 .cindex "body of message" "visible size"
13942 .cindex "message body" "visible size"
13943 .vindex "&$message_body$&"
13944 .vindex "&$message_body_end$&"
13945 This option specifies how much of a message's body is to be included in the
13946 &$message_body$& and &$message_body_end$& expansion variables.
13949 .option message_id_header_domain main string&!! unset
13950 .cindex "&'Message-ID:'& header line"
13951 If this option is set, the string is expanded and used as the right hand side
13952 (domain) of the &'Message-ID:'& header that Exim creates if a
13953 locally-originated incoming message does not have one. &"Locally-originated"&
13954 means &"not received over TCP/IP."&
13955 Otherwise, the primary host name is used.
13956 Only letters, digits, dot and hyphen are accepted; any other characters are
13957 replaced by hyphens. If the expansion is forced to fail, or if the result is an
13958 empty string, the option is ignored.
13961 .option message_id_header_text main string&!! unset
13962 If this variable is set, the string is expanded and used to augment the text of
13963 the &'Message-id:'& header that Exim creates if a locally-originated incoming
13964 message does not have one. The text of this header is required by RFC 2822 to
13965 take the form of an address. By default, Exim uses its internal message id as
13966 the local part, and the primary host name as the domain. If this option is set,
13967 it is expanded, and provided the expansion is not forced to fail, and does not
13968 yield an empty string, the result is inserted into the header immediately
13969 before the @, separated from the internal message id by a dot. Any characters
13970 that are illegal in an address are automatically converted into hyphens. This
13971 means that variables such as &$tod_log$& can be used, because the spaces and
13972 colons will become hyphens.
13975 .option message_logs main boolean true
13976 .cindex "message logs" "disabling"
13977 .cindex "log" "message log; disabling"
13978 If this option is turned off, per-message log files are not created in the
13979 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
13980 Exim, by reducing the number of files involved in handling a message from a
13981 minimum of four (header spool file, body spool file, delivery journal, and
13982 per-message log) to three. The other major I/O activity is Exim's main log,
13983 which is not affected by this option.
13986 .option message_size_limit main string&!! 50M
13987 .cindex "message" "size limit"
13988 .cindex "limit" "message size"
13989 .cindex "size" "of message, limit"
13990 This option limits the maximum size of message that Exim will process. The
13991 value is expanded for each incoming connection so, for example, it can be made
13992 to depend on the IP address of the remote host for messages arriving via
13993 TCP/IP. After expansion, the value must be a sequence of decimal digits,
13994 optionally followed by K or M.
13996 &*Note*&: This limit cannot be made to depend on a message's sender or any
13997 other properties of an individual message, because it has to be advertised in
13998 the server's response to EHLO. String expansion failure causes a temporary
13999 error. A value of zero means no limit, but its use is not recommended. See also
14000 &%bounce_return_size_limit%&.
14002 Incoming SMTP messages are failed with a 552 error if the limit is
14003 exceeded; locally-generated messages either get a stderr message or a delivery
14004 failure message to the sender, depending on the &%-oe%& setting. Rejection of
14005 an oversized message is logged in both the main and the reject logs. See also
14006 the generic transport option &%message_size_limit%&, which limits the size of
14007 message that an individual transport can process.
14009 If you use a virus-scanner and set this option to to a value larger than the
14010 maximum size that your virus-scanner is configured to support, you may get
14011 failures triggered by large mails. The right size to configure for the
14012 virus-scanner depends upon what data is passed and the options in use but it's
14013 probably safest to just set it to a little larger than this value. Eg, with a
14014 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
14015 some problems may result.
14018 .option move_frozen_messages main boolean false
14019 .cindex "frozen messages" "moving"
14020 This option, which is available only if Exim has been built with the setting
14022 SUPPORT_MOVE_FROZEN_MESSAGES=yes
14024 in &_Local/Makefile_&, causes frozen messages and their message logs to be
14025 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
14026 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
14027 standard utilities for handling such moved messages, and they do not show up in
14028 lists generated by &%-bp%& or by the Exim monitor.
14031 .option mua_wrapper main boolean false
14032 Setting this option true causes Exim to run in a very restrictive mode in which
14033 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
14034 contains a full description of this facility.
14038 .option mysql_servers main "string list" unset
14039 .cindex "MySQL" "server list"
14040 This option provides a list of MySQL servers and associated connection data, to
14041 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
14042 option is available only if Exim has been built with MySQL support.
14045 .option never_users main "string list&!!" unset
14046 This option is expanded just once, at the start of Exim's processing. Local
14047 message deliveries are normally run in processes that are setuid to the
14048 recipient, and remote deliveries are normally run under Exim's own uid and gid.
14049 It is usually desirable to prevent any deliveries from running as root, as a
14052 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
14053 list of users that must not be used for local deliveries. This list is fixed in
14054 the binary and cannot be overridden by the configuration file. By default, it
14055 contains just the single user name &"root"&. The &%never_users%& runtime option
14056 can be used to add more users to the fixed list.
14058 If a message is to be delivered as one of the users on the fixed list or the
14059 &%never_users%& list, an error occurs, and delivery is deferred. A common
14062 never_users = root:daemon:bin
14064 Including root is redundant if it is also on the fixed list, but it does no
14065 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
14069 .option openssl_options main "string list" +dont_insert_empty_fragments
14070 .cindex "OpenSSL "compatibility options"
14071 This option allows an administrator to adjust the SSL options applied
14072 by OpenSSL to connections. It is given as a space-separated list of items,
14073 each one to be +added or -subtracted from the current value. The default
14074 value is one option which happens to have been set historically. You can
14075 remove all options with:
14077 openssl_options = -all
14079 This option is only available if Exim is built against OpenSSL. The values
14080 available for this option vary according to the age of your OpenSSL install.
14081 The &"all"& value controls a subset of flags which are available, typically
14082 the bug workaround options. The &'SSL_CTX_set_options'& man page will
14083 list the values known on your system and Exim should support all the
14084 &"bug workaround"& options and many of the &"modifying"& options. The Exim
14085 names lose the leading &"SSL_OP_"& and are lower-cased.
14087 Note that adjusting the options can have severe impact upon the security of
14088 SSL as used by Exim. It is possible to disable safety checks and shoot
14089 yourself in the foot in various unpleasant ways. This option should not be
14090 adjusted lightly. An unrecognised item will be detected at by invoking Exim
14091 with the &%-bV%& flag.
14095 openssl_options = -all +microsoft_big_sslv3_buffer
14099 .option oracle_servers main "string list" unset
14100 .cindex "Oracle" "server list"
14101 This option provides a list of Oracle servers and associated connection data,
14102 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
14103 The option is available only if Exim has been built with Oracle support.
14106 .option percent_hack_domains main "domain list&!!" unset
14107 .cindex "&""percent hack""&"
14108 .cindex "source routing" "in email address"
14109 .cindex "address" "source-routed"
14110 The &"percent hack"& is the convention whereby a local part containing a
14111 percent sign is re-interpreted as a new email address, with the percent
14112 replaced by @. This is sometimes called &"source routing"&, though that term is
14113 also applied to RFC 2822 addresses that begin with an @ character. If this
14114 option is set, Exim implements the percent facility for those domains listed,
14115 but no others. This happens before an incoming SMTP address is tested against
14118 &*Warning*&: The &"percent hack"& has often been abused by people who are
14119 trying to get round relaying restrictions. For this reason, it is best avoided
14120 if at all possible. Unfortunately, a number of less security-conscious MTAs
14121 implement it unconditionally. If you are running Exim on a gateway host, and
14122 routing mail through to internal MTAs without processing the local parts, it is
14123 a good idea to reject recipient addresses with percent characters in their
14124 local parts. Exim's default configuration does this.
14127 .option perl_at_start main boolean false
14128 This option is available only when Exim is built with an embedded Perl
14129 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14132 .option perl_startup main string unset
14133 This option is available only when Exim is built with an embedded Perl
14134 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14137 .option pgsql_servers main "string list" unset
14138 .cindex "PostgreSQL lookup type" "server list"
14139 This option provides a list of PostgreSQL servers and associated connection
14140 data, to be used in conjunction with &(pgsql)& lookups (see section
14141 &<<SECID72>>&). The option is available only if Exim has been built with
14142 PostgreSQL support.
14145 .option pid_file_path main string&!! "set at compile time"
14146 .cindex "daemon" "pid file path"
14147 .cindex "pid file, path for"
14148 This option sets the name of the file to which the Exim daemon writes its
14149 process id. The string is expanded, so it can contain, for example, references
14152 pid_file_path = /var/log/$primary_hostname/exim.pid
14154 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
14156 The value set by the option can be overridden by the &%-oP%& command line
14157 option. A pid file is not written if a &"non-standard"& daemon is run by means
14158 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
14161 .option pipelining_advertise_hosts main "host list&!!" *
14162 .cindex "PIPELINING" "suppressing advertising"
14163 This option can be used to suppress the advertisement of the SMTP
14164 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
14165 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
14166 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
14167 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
14168 that clients will use it; &"out of order"& commands that are &"expected"& do
14169 not count as protocol errors (see &%smtp_max_synprot_errors%&).
14172 .option preserve_message_logs main boolean false
14173 .cindex "message logs" "preserving"
14174 If this option is set, message log files are not deleted when messages are
14175 completed. Instead, they are moved to a sub-directory of the spool directory
14176 called &_msglog.OLD_&, where they remain available for statistical or debugging
14177 purposes. This is a dangerous option to set on systems with any appreciable
14178 volume of mail. Use with care!
14181 .option primary_hostname main string "see below"
14182 .cindex "name" "of local host"
14183 .cindex "host" "name of local"
14184 .cindex "local host" "name of"
14185 .vindex "&$primary_hostname$&"
14186 This specifies the name of the current host. It is used in the default EHLO or
14187 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
14188 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
14189 The value is also used by default in some SMTP response messages from an Exim
14190 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
14192 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
14193 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
14194 contains only one component, Exim passes it to &[gethostbyname()]& (or
14195 &[getipnodebyname()]& when available) in order to obtain the fully qualified
14196 version. The variable &$primary_hostname$& contains the host name, whether set
14197 explicitly by this option, or defaulted.
14200 .option print_topbitchars main boolean false
14201 .cindex "printing characters"
14202 .cindex "8-bit characters"
14203 By default, Exim considers only those characters whose codes lie in the range
14204 32&--126 to be printing characters. In a number of circumstances (for example,
14205 when writing log entries) non-printing characters are converted into escape
14206 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
14207 is set, code values of 128 and above are also considered to be printing
14210 This option also affects the header syntax checks performed by the
14211 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
14212 the user's full name when constructing From: and Sender: addresses (as
14213 described in section &<<SECTconstr>>&). Setting this option can cause
14214 Exim to generate eight bit message headers that do not conform to the
14218 .option process_log_path main string unset
14219 .cindex "process log path"
14220 .cindex "log" "process log"
14221 .cindex "&'exiwhat'&"
14222 This option sets the name of the file to which an Exim process writes its
14223 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
14224 utility script. If this option is unset, the file called &_exim-process.info_&
14225 in Exim's spool directory is used. The ability to specify the name explicitly
14226 can be useful in environments where two different Exims are running, using
14227 different spool directories.
14230 .option prod_requires_admin main boolean true
14234 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
14235 admin user unless &%prod_requires_admin%& is set false. See also
14236 &%queue_list_requires_admin%&.
14239 .option qualify_domain main string "see below"
14240 .cindex "domain" "for qualifying addresses"
14241 .cindex "address" "qualification"
14242 This option specifies the domain name that is added to any envelope sender
14243 addresses that do not have a domain qualification. It also applies to
14244 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
14245 are accepted by default only for locally-generated messages. Qualification is
14246 also applied to addresses in header lines such as &'From:'& and &'To:'& for
14247 locally-generated messages, unless the &%-bnq%& command line option is used.
14249 Messages from external sources must always contain fully qualified addresses,
14250 unless the sending host matches &%sender_unqualified_hosts%& or
14251 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
14252 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
14253 necessary. Internally, Exim always works with fully qualified envelope
14254 addresses. If &%qualify_domain%& is not set, it defaults to the
14255 &%primary_hostname%& value.
14258 .option qualify_recipient main string "see below"
14259 This option allows you to specify a different domain for qualifying recipient
14260 addresses to the one that is used for senders. See &%qualify_domain%& above.
14264 .option queue_domains main "domain list&!!" unset
14265 .cindex "domain" "specifying non-immediate delivery"
14266 .cindex "queueing incoming messages"
14267 .cindex "message" "queueing certain domains"
14268 This option lists domains for which immediate delivery is not required.
14269 A delivery process is started whenever a message is received, but only those
14270 domains that do not match are processed. All other deliveries wait until the
14271 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
14274 .option queue_list_requires_admin main boolean true
14276 The &%-bp%& command-line option, which lists the messages that are on the
14277 queue, requires the caller to be an admin user unless
14278 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
14281 .option queue_only main boolean false
14282 .cindex "queueing incoming messages"
14283 .cindex "message" "queueing unconditionally"
14284 If &%queue_only%& is set, a delivery process is not automatically started
14285 whenever a message is received. Instead, the message waits on the queue for the
14286 next queue run. Even if &%queue_only%& is false, incoming messages may not get
14287 delivered immediately when certain conditions (such as heavy load) occur.
14289 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
14290 and &%-odi%& command line options override &%queue_only%& unless
14291 &%queue_only_override%& is set false. See also &%queue_only_file%&,
14292 &%queue_only_load%&, and &%smtp_accept_queue%&.
14295 .option queue_only_file main string unset
14296 .cindex "queueing incoming messages"
14297 .cindex "message" "queueing by file existence"
14298 This option can be set to a colon-separated list of absolute path names, each
14299 one optionally preceded by &"smtp"&. When Exim is receiving a message,
14300 it tests for the existence of each listed path using a call to &[stat()]&. For
14301 each path that exists, the corresponding queueing option is set.
14302 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
14303 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
14305 queue_only_file = smtp/some/file
14307 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
14308 &_/some/file_& exists.
14311 .option queue_only_load main fixed-point unset
14312 .cindex "load average"
14313 .cindex "queueing incoming messages"
14314 .cindex "message" "queueing by load"
14315 If the system load average is higher than this value, incoming messages from
14316 all sources are queued, and no automatic deliveries are started. If this
14317 happens during local or remote SMTP input, all subsequent messages received on
14318 the same SMTP connection are queued by default, whatever happens to the load in
14319 the meantime, but this can be changed by setting &%queue_only_load_latch%&
14322 Deliveries will subsequently be performed by queue runner processes. This
14323 option has no effect on ancient operating systems on which Exim cannot
14324 determine the load average. See also &%deliver_queue_load_max%& and
14325 &%smtp_load_reserve%&.
14328 .option queue_only_load_latch main boolean true
14329 .cindex "load average" "re-evaluating per message"
14330 When this option is true (the default), once one message has been queued
14331 because the load average is higher than the value set by &%queue_only_load%&,
14332 all subsequent messages received on the same SMTP connection are also queued.
14333 This is a deliberate choice; even though the load average may fall below the
14334 threshold, it doesn't seem right to deliver later messages on the same
14335 connection when not delivering earlier ones. However, there are special
14336 circumstances such as very long-lived connections from scanning appliances
14337 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
14338 should be set false. This causes the value of the load average to be
14339 re-evaluated for each message.
14342 .option queue_only_override main boolean true
14343 .cindex "queueing incoming messages"
14344 When this option is true, the &%-od%&&'x'& command line options override the
14345 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
14346 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
14347 to override; they are accepted, but ignored.
14350 .option queue_run_in_order main boolean false
14351 .cindex "queue runner" "processing messages in order"
14352 If this option is set, queue runs happen in order of message arrival instead of
14353 in an arbitrary order. For this to happen, a complete list of the entire queue
14354 must be set up before the deliveries start. When the queue is all held in a
14355 single directory (the default), a single list is created for both the ordered
14356 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
14357 single list is not created when &%queue_run_in_order%& is false. In this case,
14358 the sub-directories are processed one at a time (in a random order), and this
14359 avoids setting up one huge list for the whole queue. Thus, setting
14360 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
14361 when the queue is large, because of the extra work in setting up the single,
14362 large list. In most situations, &%queue_run_in_order%& should not be set.
14366 .option queue_run_max main integer 5
14367 .cindex "queue runner" "maximum number of"
14368 This controls the maximum number of queue runner processes that an Exim daemon
14369 can run simultaneously. This does not mean that it starts them all at once,
14370 but rather that if the maximum number are still running when the time comes to
14371 start another one, it refrains from starting another one. This can happen with
14372 very large queues and/or very sluggish deliveries. This option does not,
14373 however, interlock with other processes, so additional queue runners can be
14374 started by other means, or by killing and restarting the daemon.
14376 Setting this option to zero does not suppress queue runs; rather, it disables
14377 the limit, allowing any number of simultaneous queue runner processes to be
14378 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
14379 the daemon's command line.
14381 .option queue_smtp_domains main "domain list&!!" unset
14382 .cindex "queueing incoming messages"
14383 .cindex "message" "queueing remote deliveries"
14384 When this option is set, a delivery process is started whenever a message is
14385 received, routing is performed, and local deliveries take place.
14386 However, if any SMTP deliveries are required for domains that match
14387 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
14388 message waits on the queue for the next queue run. Since routing of the message
14389 has taken place, Exim knows to which remote hosts it must be delivered, and so
14390 when the queue run happens, multiple messages for the same host are delivered
14391 over a single SMTP connection. The &%-odqs%& command line option causes all
14392 SMTP deliveries to be queued in this way, and is equivalent to setting
14393 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
14397 .option receive_timeout main time 0s
14398 .cindex "timeout" "for non-SMTP input"
14399 This option sets the timeout for accepting a non-SMTP message, that is, the
14400 maximum time that Exim waits when reading a message on the standard input. If
14401 the value is zero, it will wait for ever. This setting is overridden by the
14402 &%-or%& command line option. The timeout for incoming SMTP messages is
14403 controlled by &%smtp_receive_timeout%&.
14405 .option received_header_text main string&!! "see below"
14406 .cindex "customizing" "&'Received:'& header"
14407 .cindex "&'Received:'& header line" "customizing"
14408 This string defines the contents of the &'Received:'& message header that is
14409 added to each message, except for the timestamp, which is automatically added
14410 on at the end (preceded by a semicolon). The string is expanded each time it is
14411 used. If the expansion yields an empty string, no &'Received:'& header line is
14412 added to the message. Otherwise, the string should start with the text
14413 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
14414 header lines. The default setting is:
14417 received_header_text = Received: \
14418 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
14419 {${if def:sender_ident \
14420 {from ${quote_local_part:$sender_ident} }}\
14421 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
14422 by $primary_hostname \
14423 ${if def:received_protocol {with $received_protocol}} \
14424 ${if def:tls_cipher {($tls_cipher)\n\t}}\
14425 (Exim $version_number)\n\t\
14426 ${if def:sender_address \
14427 {(envelope-from <$sender_address>)\n\t}}\
14428 id $message_exim_id\
14429 ${if def:received_for {\n\tfor $received_for}}
14432 The reference to the TLS cipher is omitted when Exim is built without TLS
14433 support. The use of conditional expansions ensures that this works for both
14434 locally generated messages and messages received from remote hosts, giving
14435 header lines such as the following:
14437 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
14438 by marley.carol.example with esmtp (Exim 4.00)
14439 (envelope-from <bob@carol.example>)
14440 id 16IOWa-00019l-00
14441 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
14442 Received: by scrooge.carol.example with local (Exim 4.00)
14443 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
14445 Until the body of the message has been received, the timestamp is the time when
14446 the message started to be received. Once the body has arrived, and all policy
14447 checks have taken place, the timestamp is updated to the time at which the
14448 message was accepted.
14451 .option received_headers_max main integer 30
14452 .cindex "loop" "prevention"
14453 .cindex "mail loop prevention"
14454 .cindex "&'Received:'& header line" "counting"
14455 When a message is to be delivered, the number of &'Received:'& headers is
14456 counted, and if it is greater than this parameter, a mail loop is assumed to
14457 have occurred, the delivery is abandoned, and an error message is generated.
14458 This applies to both local and remote deliveries.
14461 .option recipient_unqualified_hosts main "host list&!!" unset
14462 .cindex "unqualified addresses"
14463 .cindex "host" "unqualified addresses from"
14464 This option lists those hosts from which Exim is prepared to accept unqualified
14465 recipient addresses in message envelopes. The addresses are made fully
14466 qualified by the addition of the &%qualify_recipient%& value. This option also
14467 affects message header lines. Exim does not reject unqualified recipient
14468 addresses in headers, but it qualifies them only if the message came from a
14469 host that matches &%recipient_unqualified_hosts%&,
14470 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
14471 option was not set.
14474 .option recipients_max main integer 0
14475 .cindex "limit" "number of recipients"
14476 .cindex "recipient" "maximum number"
14477 If this option is set greater than zero, it specifies the maximum number of
14478 original recipients for any message. Additional recipients that are generated
14479 by aliasing or forwarding do not count. SMTP messages get a 452 response for
14480 all recipients over the limit; earlier recipients are delivered as normal.
14481 Non-SMTP messages with too many recipients are failed, and no deliveries are
14484 .cindex "RCPT" "maximum number of incoming"
14485 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
14486 RCPT commands in a single message.
14489 .option recipients_max_reject main boolean false
14490 If this option is set true, Exim rejects SMTP messages containing too many
14491 recipients by giving 552 errors to the surplus RCPT commands, and a 554
14492 error to the eventual DATA command. Otherwise (the default) it gives a 452
14493 error to the surplus RCPT commands and accepts the message on behalf of the
14494 initial set of recipients. The remote server should then re-send the message
14495 for the remaining recipients at a later time.
14498 .option remote_max_parallel main integer 2
14499 .cindex "delivery" "parallelism for remote"
14500 This option controls parallel delivery of one message to a number of remote
14501 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
14502 does all the remote deliveries for a message one by one. Otherwise, if a single
14503 message has to be delivered to more than one remote host, or if several copies
14504 have to be sent to the same remote host, up to &%remote_max_parallel%&
14505 deliveries are done simultaneously. If more than &%remote_max_parallel%&
14506 deliveries are required, the maximum number of processes are started, and as
14507 each one finishes, another is begun. The order of starting processes is the
14508 same as if sequential delivery were being done, and can be controlled by the
14509 &%remote_sort_domains%& option. If parallel delivery takes place while running
14510 with debugging turned on, the debugging output from each delivery process is
14511 tagged with its process id.
14513 This option controls only the maximum number of parallel deliveries for one
14514 message in one Exim delivery process. Because Exim has no central queue
14515 manager, there is no way of controlling the total number of simultaneous
14516 deliveries if the configuration allows a delivery attempt as soon as a message
14519 .cindex "number of deliveries"
14520 .cindex "delivery" "maximum number of"
14521 If you want to control the total number of deliveries on the system, you
14522 need to set the &%queue_only%& option. This ensures that all incoming messages
14523 are added to the queue without starting a delivery process. Then set up an Exim
14524 daemon to start queue runner processes at appropriate intervals (probably
14525 fairly often, for example, every minute), and limit the total number of queue
14526 runners by setting the &%queue_run_max%& parameter. Because each queue runner
14527 delivers only one message at a time, the maximum number of deliveries that can
14528 then take place at once is &%queue_run_max%& multiplied by
14529 &%remote_max_parallel%&.
14531 If it is purely remote deliveries you want to control, use
14532 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
14533 doing the SMTP routing before queueing, so that several messages for the same
14534 host will eventually get delivered down the same connection.
14537 .option remote_sort_domains main "domain list&!!" unset
14538 .cindex "sorting remote deliveries"
14539 .cindex "delivery" "sorting remote"
14540 When there are a number of remote deliveries for a message, they are sorted by
14541 domain into the order given by this list. For example,
14543 remote_sort_domains = *.cam.ac.uk:*.uk
14545 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
14546 then to those in the &%uk%& domain, then to any others.
14549 .option retry_data_expire main time 7d
14550 .cindex "hints database" "data expiry"
14551 This option sets a &"use before"& time on retry information in Exim's hints
14552 database. Any older retry data is ignored. This means that, for example, once a
14553 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
14557 .option retry_interval_max main time 24h
14558 .cindex "retry" "limit on interval"
14559 .cindex "limit" "on retry interval"
14560 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
14561 intervals between delivery attempts for messages that cannot be delivered
14562 straight away. This option sets an overall limit to the length of time between
14563 retries. It cannot be set greater than 24 hours; any attempt to do so forces
14567 .option return_path_remove main boolean true
14568 .cindex "&'Return-path:'& header line" "removing"
14569 RFC 2821, section 4.4, states that an SMTP server must insert a
14570 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
14571 The &'Return-path:'& header preserves the sender address as received in the
14572 MAIL command. This description implies that this header should not be present
14573 in an incoming message. If &%return_path_remove%& is true, any existing
14574 &'Return-path:'& headers are removed from messages at the time they are
14575 received. Exim's transports have options for adding &'Return-path:'& headers at
14576 the time of delivery. They are normally used only for final local deliveries.
14579 .option return_size_limit main integer 100K
14580 This option is an obsolete synonym for &%bounce_return_size_limit%&.
14583 .option rfc1413_hosts main "host list&!!" *
14585 .cindex "host" "for RFC 1413 calls"
14586 RFC 1413 identification calls are made to any client host which matches an item
14589 .option rfc1413_query_timeout main time 5s
14590 .cindex "RFC 1413" "query timeout"
14591 .cindex "timeout" "for RFC 1413 call"
14592 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
14593 no RFC 1413 calls are ever made.
14596 .option sender_unqualified_hosts main "host list&!!" unset
14597 .cindex "unqualified addresses"
14598 .cindex "host" "unqualified addresses from"
14599 This option lists those hosts from which Exim is prepared to accept unqualified
14600 sender addresses. The addresses are made fully qualified by the addition of
14601 &%qualify_domain%&. This option also affects message header lines. Exim does
14602 not reject unqualified addresses in headers that contain sender addresses, but
14603 it qualifies them only if the message came from a host that matches
14604 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
14605 using TCP/IP), and the &%-bnq%& option was not set.
14608 .option smtp_accept_keepalive main boolean true
14609 .cindex "keepalive" "on incoming connection"
14610 This option controls the setting of the SO_KEEPALIVE option on incoming
14611 TCP/IP socket connections. When set, it causes the kernel to probe idle
14612 connections periodically, by sending packets with &"old"& sequence numbers. The
14613 other end of the connection should send an acknowledgment if the connection is
14614 still okay or a reset if the connection has been aborted. The reason for doing
14615 this is that it has the beneficial effect of freeing up certain types of
14616 connection that can get stuck when the remote host is disconnected without
14617 tidying up the TCP/IP call properly. The keepalive mechanism takes several
14618 hours to detect unreachable hosts.
14622 .option smtp_accept_max main integer 20
14623 .cindex "limit" "incoming SMTP connections"
14624 .cindex "SMTP" "incoming connection count"
14626 This option specifies the maximum number of simultaneous incoming SMTP calls
14627 that Exim will accept. It applies only to the listening daemon; there is no
14628 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
14629 value is set to zero, no limit is applied. However, it is required to be
14630 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
14631 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
14633 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
14634 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
14635 that limit has not been reached for the client host, &%smtp_accept_reserve%&
14636 and &%smtp_load_reserve%& are then checked before accepting the connection.
14639 .option smtp_accept_max_nonmail main integer 10
14640 .cindex "limit" "non-mail SMTP commands"
14641 .cindex "SMTP" "limiting non-mail commands"
14642 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
14643 the connection if there are too many. This option defines &"too many"&. The
14644 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
14645 client looping sending EHLO, for example. The check is applied only if the
14646 client host matches &%smtp_accept_max_nonmail_hosts%&.
14648 When a new message is expected, one occurrence of RSET is not counted. This
14649 allows a client to send one RSET between messages (this is not necessary,
14650 but some clients do it). Exim also allows one uncounted occurrence of HELO
14651 or EHLO, and one occurrence of STARTTLS between messages. After
14652 starting up a TLS session, another EHLO is expected, and so it too is not
14653 counted. The first occurrence of AUTH in a connection, or immediately
14654 following STARTTLS is not counted. Otherwise, all commands other than
14655 MAIL, RCPT, DATA, and QUIT are counted.
14658 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
14659 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
14660 check by setting this option. The default value makes it apply to all hosts. By
14661 changing the value, you can exclude any badly-behaved hosts that you have to
14665 . Allow this long option name to split; give it unsplit as a fifth argument
14666 . for the automatic .oindex that is generated by .option.
14668 .option "smtp_accept_max_per_ &~&~connection" main integer 1000 &&&
14669 smtp_accept_max_per_connection
14670 .cindex "SMTP" "limiting incoming message count"
14671 .cindex "limit" "messages per SMTP connection"
14672 The value of this option limits the number of MAIL commands that Exim is
14673 prepared to accept over a single SMTP connection, whether or not each command
14674 results in the transfer of a message. After the limit is reached, a 421
14675 response is given to subsequent MAIL commands. This limit is a safety
14676 precaution against a client that goes mad (incidents of this type have been
14680 .option smtp_accept_max_per_host main string&!! unset
14681 .cindex "limit" "SMTP connections from one host"
14682 .cindex "host" "limiting SMTP connections from"
14683 This option restricts the number of simultaneous IP connections from a single
14684 host (strictly, from a single IP address) to the Exim daemon. The option is
14685 expanded, to enable different limits to be applied to different hosts by
14686 reference to &$sender_host_address$&. Once the limit is reached, additional
14687 connection attempts from the same host are rejected with error code 421. This
14688 is entirely independent of &%smtp_accept_reserve%&. The option's default value
14689 of zero imposes no limit. If this option is set greater than zero, it is
14690 required that &%smtp_accept_max%& be non-zero.
14692 &*Warning*&: When setting this option you should not use any expansion
14693 constructions that take an appreciable amount of time. The expansion and test
14694 happen in the main daemon loop, in order to reject additional connections
14695 without forking additional processes (otherwise a denial-of-service attack
14696 could cause a vast number or processes to be created). While the daemon is
14697 doing this processing, it cannot accept any other incoming connections.
14701 .option smtp_accept_queue main integer 0
14702 .cindex "SMTP" "incoming connection count"
14703 .cindex "queueing incoming messages"
14704 .cindex "message" "queueing by SMTP connection count"
14705 If the number of simultaneous incoming SMTP connections being handled via the
14706 listening daemon exceeds this value, messages received by SMTP are just placed
14707 on the queue; no delivery processes are started automatically. The count is
14708 fixed at the start of an SMTP connection. It cannot be updated in the
14709 subprocess that receives messages, and so the queueing or not queueing applies
14710 to all messages received in the same connection.
14712 A value of zero implies no limit, and clearly any non-zero value is useful only
14713 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
14714 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
14715 various &%-od%&&'x'& command line options.
14718 . Allow this long option name to split; give it unsplit as a fifth argument
14719 . for the automatic .oindex that is generated by .option.
14721 .option "smtp_accept_queue_per_ &~&~connection" main integer 10 &&&
14722 smtp_accept_queue_per_connection
14723 .cindex "queueing incoming messages"
14724 .cindex "message" "queueing by message count"
14725 This option limits the number of delivery processes that Exim starts
14726 automatically when receiving messages via SMTP, whether via the daemon or by
14727 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
14728 and the number of messages received in a single SMTP session exceeds this
14729 number, subsequent messages are placed on the queue, but no delivery processes
14730 are started. This helps to limit the number of Exim processes when a server
14731 restarts after downtime and there is a lot of mail waiting for it on other
14732 systems. On large systems, the default should probably be increased, and on
14733 dial-in client systems it should probably be set to zero (that is, disabled).
14736 .option smtp_accept_reserve main integer 0
14737 .cindex "SMTP" "incoming call count"
14738 .cindex "host" "reserved"
14739 When &%smtp_accept_max%& is set greater than zero, this option specifies a
14740 number of SMTP connections that are reserved for connections from the hosts
14741 that are specified in &%smtp_reserve_hosts%&. The value set in
14742 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
14743 restricted to this number of connections; the option specifies a minimum number
14744 of connection slots for them, not a maximum. It is a guarantee that this group
14745 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
14746 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
14749 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
14750 set to 5, once there are 45 active connections (from any hosts), new
14751 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
14752 provided the other criteria for acceptance are met.
14755 .option smtp_active_hostname main string&!! unset
14756 .cindex "host" "name in SMTP responses"
14757 .cindex "SMTP" "host name in responses"
14758 .vindex "&$primary_hostname$&"
14759 This option is provided for multi-homed servers that want to masquerade as
14760 several different hosts. At the start of an incoming SMTP connection, its value
14761 is expanded and used instead of the value of &$primary_hostname$& in SMTP
14762 responses. For example, it is used as domain name in the response to an
14763 incoming HELO or EHLO command.
14765 .vindex "&$smtp_active_hostname$&"
14766 The active hostname is placed in the &$smtp_active_hostname$& variable, which
14767 is saved with any messages that are received. It is therefore available for use
14768 in routers and transports when the message is later delivered.
14770 If this option is unset, or if its expansion is forced to fail, or if the
14771 expansion results in an empty string, the value of &$primary_hostname$& is
14772 used. Other expansion failures cause a message to be written to the main and
14773 panic logs, and the SMTP command receives a temporary error. Typically, the
14774 value of &%smtp_active_hostname%& depends on the incoming interface address.
14777 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
14778 {cox.mydomain}{box.mydomain}}
14781 Although &$smtp_active_hostname$& is primarily concerned with incoming
14782 messages, it is also used as the default for HELO commands in callout
14783 verification if there is no remote transport from which to obtain a
14784 &%helo_data%& value.
14786 .option smtp_banner main string&!! "see below"
14787 .cindex "SMTP" "welcome banner"
14788 .cindex "banner for SMTP"
14789 .cindex "welcome banner for SMTP"
14790 .cindex "customizing" "SMTP banner"
14791 This string, which is expanded every time it is used, is output as the initial
14792 positive response to an SMTP connection. The default setting is:
14794 smtp_banner = $smtp_active_hostname ESMTP Exim \
14795 $version_number $tod_full
14797 Failure to expand the string causes a panic error. If you want to create a
14798 multiline response to the initial SMTP connection, use &"\n"& in the string at
14799 appropriate points, but not at the end. Note that the 220 code is not included
14800 in this string. Exim adds it automatically (several times in the case of a
14801 multiline response).
14804 .option smtp_check_spool_space main boolean true
14805 .cindex "checking disk space"
14806 .cindex "disk space, checking"
14807 .cindex "spool directory" "checking space"
14808 When this option is set, if an incoming SMTP session encounters the SIZE
14809 option on a MAIL command, it checks that there is enough space in the
14810 spool directory's partition to accept a message of that size, while still
14811 leaving free the amount specified by &%check_spool_space%& (even if that value
14812 is zero). If there isn't enough space, a temporary error code is returned.
14815 .option smtp_connect_backlog main integer 20
14816 .cindex "connection backlog"
14817 .cindex "SMTP" "connection backlog"
14818 .cindex "backlog of connections"
14819 This option specifies a maximum number of waiting SMTP connections. Exim passes
14820 this value to the TCP/IP system when it sets up its listener. Once this number
14821 of connections are waiting for the daemon's attention, subsequent connection
14822 attempts are refused at the TCP/IP level. At least, that is what the manuals
14823 say; in some circumstances such connection attempts have been observed to time
14824 out instead. For large systems it is probably a good idea to increase the
14825 value (to 50, say). It also gives some protection against denial-of-service
14826 attacks by SYN flooding.
14829 .option smtp_enforce_sync main boolean true
14830 .cindex "SMTP" "synchronization checking"
14831 .cindex "synchronization checking in SMTP"
14832 The SMTP protocol specification requires the client to wait for a response from
14833 the server at certain points in the dialogue. Without PIPELINING these
14834 synchronization points are after every command; with PIPELINING they are
14835 fewer, but they still exist.
14837 Some spamming sites send out a complete set of SMTP commands without waiting
14838 for any response. Exim protects against this by rejecting a message if the
14839 client has sent further input when it should not have. The error response &"554
14840 SMTP synchronization error"& is sent, and the connection is dropped. Testing
14841 for this error cannot be perfect because of transmission delays (unexpected
14842 input may be on its way but not yet received when Exim checks). However, it
14843 does detect many instances.
14845 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
14846 If you want to disable the check selectively (for example, only for certain
14847 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
14848 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
14852 .option smtp_etrn_command main string&!! unset
14853 .cindex "ETRN" "command to be run"
14854 .vindex "&$domain$&"
14855 If this option is set, the given command is run whenever an SMTP ETRN
14856 command is received from a host that is permitted to issue such commands (see
14857 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
14858 are independently expanded. The expansion variable &$domain$& is set to the
14859 argument of the ETRN command, and no syntax checking is done on it. For
14862 smtp_etrn_command = /etc/etrn_command $domain \
14863 $sender_host_address
14865 A new process is created to run the command, but Exim does not wait for it to
14866 complete. Consequently, its status cannot be checked. If the command cannot be
14867 run, a line is written to the panic log, but the ETRN caller still receives
14868 a 250 success response. Exim is normally running under its own uid when
14869 receiving SMTP, so it is not possible for it to change the uid before running
14873 .option smtp_etrn_serialize main boolean true
14874 .cindex "ETRN" "serializing"
14875 When this option is set, it prevents the simultaneous execution of more than
14876 one identical command as a result of ETRN in an SMTP connection. See
14877 section &<<SECTETRN>>& for details.
14880 .option smtp_load_reserve main fixed-point unset
14881 .cindex "load average"
14882 If the system load average ever gets higher than this, incoming SMTP calls are
14883 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
14884 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
14885 the load is over the limit. The option has no effect on ancient operating
14886 systems on which Exim cannot determine the load average. See also
14887 &%deliver_queue_load_max%& and &%queue_only_load%&.
14891 .option smtp_max_synprot_errors main integer 3
14892 .cindex "SMTP" "limiting syntax and protocol errors"
14893 .cindex "limit" "SMTP syntax and protocol errors"
14894 Exim rejects SMTP commands that contain syntax or protocol errors. In
14895 particular, a syntactically invalid email address, as in this command:
14897 RCPT TO:<abc xyz@a.b.c>
14899 causes immediate rejection of the command, before any other tests are done.
14900 (The ACL cannot be run if there is no valid address to set up for it.) An
14901 example of a protocol error is receiving RCPT before MAIL. If there are
14902 too many syntax or protocol errors in one SMTP session, the connection is
14903 dropped. The limit is set by this option.
14905 .cindex "PIPELINING" "expected errors"
14906 When the PIPELINING extension to SMTP is in use, some protocol errors are
14907 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
14908 Exim assumes that PIPELINING will be used if it advertises it (see
14909 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
14910 not count towards the limit.
14914 .option smtp_max_unknown_commands main integer 3
14915 .cindex "SMTP" "limiting unknown commands"
14916 .cindex "limit" "unknown SMTP commands"
14917 If there are too many unrecognized commands in an incoming SMTP session, an
14918 Exim server drops the connection. This is a defence against some kinds of abuse
14921 into making connections to SMTP ports; in these circumstances, a number of
14922 non-SMTP command lines are sent first.
14926 .option smtp_ratelimit_hosts main "host list&!!" unset
14927 .cindex "SMTP" "rate limiting"
14928 .cindex "limit" "rate of message arrival"
14929 .cindex "RCPT" "rate limiting"
14930 Some sites find it helpful to be able to limit the rate at which certain hosts
14931 can send them messages, and the rate at which an individual message can specify
14934 Exim has two rate-limiting facilities. This section describes the older
14935 facility, which can limit rates within a single connection. The newer
14936 &%ratelimit%& ACL condition can limit rates across all connections. See section
14937 &<<SECTratelimiting>>& for details of the newer facility.
14939 When a host matches &%smtp_ratelimit_hosts%&, the values of
14940 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
14941 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
14942 respectively. Each option, if set, must contain a set of four comma-separated
14946 A threshold, before which there is no rate limiting.
14948 An initial time delay. Unlike other times in Exim, numbers with decimal
14949 fractional parts are allowed here.
14951 A factor by which to increase the delay each time.
14953 A maximum value for the delay. This should normally be less than 5 minutes,
14954 because after that time, the client is liable to timeout the SMTP command.
14957 For example, these settings have been used successfully at the site which
14958 first suggested this feature, for controlling mail from their customers:
14960 smtp_ratelimit_mail = 2,0.5s,1.05,4m
14961 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
14963 The first setting specifies delays that are applied to MAIL commands after
14964 two have been received over a single connection. The initial delay is 0.5
14965 seconds, increasing by a factor of 1.05 each time. The second setting applies
14966 delays to RCPT commands when more than four occur in a single message.
14969 .option smtp_ratelimit_mail main string unset
14970 See &%smtp_ratelimit_hosts%& above.
14973 .option smtp_ratelimit_rcpt main string unset
14974 See &%smtp_ratelimit_hosts%& above.
14977 .option smtp_receive_timeout main time 5m
14978 .cindex "timeout" "for SMTP input"
14979 .cindex "SMTP" "input timeout"
14980 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
14981 input, including batch SMTP. If a line of input (either an SMTP command or a
14982 data line) is not received within this time, the SMTP connection is dropped and
14983 the message is abandoned.
14984 A line is written to the log containing one of the following messages:
14986 SMTP command timeout on connection from...
14987 SMTP data timeout on connection from...
14989 The former means that Exim was expecting to read an SMTP command; the latter
14990 means that it was in the DATA phase, reading the contents of a message.
14994 The value set by this option can be overridden by the
14995 &%-os%& command-line option. A setting of zero time disables the timeout, but
14996 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
14997 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
14998 timeout is controlled by &%receive_timeout%& and &%-or%&.
15001 .option smtp_reserve_hosts main "host list&!!" unset
15002 This option defines hosts for which SMTP connections are reserved; see
15003 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
15006 .option smtp_return_error_details main boolean false
15007 .cindex "SMTP" "details policy failures"
15008 .cindex "policy control" "rejection, returning details"
15009 In the default state, Exim uses bland messages such as
15010 &"Administrative prohibition"& when it rejects SMTP commands for policy
15011 reasons. Many sysadmins like this because it gives away little information
15012 to spammers. However, some other sysadmins who are applying strict checking
15013 policies want to give out much fuller information about failures. Setting
15014 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
15015 example, instead of &"Administrative prohibition"&, it might give:
15017 550-Rejected after DATA: '>' missing at end of address:
15018 550 failing address in "From" header is: <user@dom.ain
15021 .option spamd_address main string "see below"
15022 This option is available when Exim is compiled with the content-scanning
15023 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
15024 The default value is
15028 See section &<<SECTscanspamass>>& for more details.
15032 .option split_spool_directory main boolean false
15033 .cindex "multiple spool directories"
15034 .cindex "spool directory" "split"
15035 .cindex "directories, multiple"
15036 If this option is set, it causes Exim to split its input directory into 62
15037 subdirectories, each with a single alphanumeric character as its name. The
15038 sixth character of the message id is used to allocate messages to
15039 subdirectories; this is the least significant base-62 digit of the time of
15040 arrival of the message.
15042 Splitting up the spool in this way may provide better performance on systems
15043 where there are long mail queues, by reducing the number of files in any one
15044 directory. The msglog directory is also split up in a similar way to the input
15045 directory; however, if &%preserve_message_logs%& is set, all old msglog files
15046 are still placed in the single directory &_msglog.OLD_&.
15048 It is not necessary to take any special action for existing messages when
15049 changing &%split_spool_directory%&. Exim notices messages that are in the
15050 &"wrong"& place, and continues to process them. If the option is turned off
15051 after a period of being on, the subdirectories will eventually empty and be
15052 automatically deleted.
15054 When &%split_spool_directory%& is set, the behaviour of queue runner processes
15055 changes. Instead of creating a list of all messages in the queue, and then
15056 trying to deliver each one in turn, it constructs a list of those in one
15057 sub-directory and tries to deliver them, before moving on to the next
15058 sub-directory. The sub-directories are processed in a random order. This
15059 spreads out the scanning of the input directories, and uses less memory. It is
15060 particularly beneficial when there are lots of messages on the queue. However,
15061 if &%queue_run_in_order%& is set, none of this new processing happens. The
15062 entire queue has to be scanned and sorted before any deliveries can start.
15065 .option spool_directory main string&!! "set at compile time"
15066 .cindex "spool directory" "path to"
15067 This defines the directory in which Exim keeps its spool, that is, the messages
15068 it is waiting to deliver. The default value is taken from the compile-time
15069 configuration setting, if there is one. If not, this option must be set. The
15070 string is expanded, so it can contain, for example, a reference to
15071 &$primary_hostname$&.
15073 If the spool directory name is fixed on your installation, it is recommended
15074 that you set it at build time rather than from this option, particularly if the
15075 log files are being written to the spool directory (see &%log_file_path%&).
15076 Otherwise log files cannot be used for errors that are detected early on, such
15077 as failures in the configuration file.
15079 By using this option to override the compiled-in path, it is possible to run
15080 tests of Exim without using the standard spool.
15082 .option sqlite_lock_timeout main time 5s
15083 .cindex "sqlite lookup type" "lock timeout"
15084 This option controls the timeout that the &(sqlite)& lookup uses when trying to
15085 access an SQLite database. See section &<<SECTsqlite>>& for more details.
15087 .option strict_acl_vars main boolean false
15088 .cindex "&ACL;" "variables, handling unset"
15089 This option controls what happens if a syntactically valid but undefined ACL
15090 variable is referenced. If it is false (the default), an empty string
15091 is substituted; if it is true, an error is generated. See section
15092 &<<SECTaclvariables>>& for details of ACL variables.
15094 .option strip_excess_angle_brackets main boolean false
15095 .cindex "angle brackets, excess"
15096 If this option is set, redundant pairs of angle brackets round &"route-addr"&
15097 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
15098 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
15099 passed on to another MTA, the excess angle brackets are not passed on. If this
15100 option is not set, multiple pairs of angle brackets cause a syntax error.
15103 .option strip_trailing_dot main boolean false
15104 .cindex "trailing dot on domain"
15105 .cindex "dot" "trailing on domain"
15106 If this option is set, a trailing dot at the end of a domain in an address is
15107 ignored. If this is in the envelope and the message is passed on to another
15108 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
15109 domain causes a syntax error.
15110 However, addresses in header lines are checked only when an ACL requests header
15114 .option syslog_duplication main boolean true
15115 .cindex "syslog" "duplicate log lines; suppressing"
15116 When Exim is logging to syslog, it writes the log lines for its three
15117 separate logs at different syslog priorities so that they can in principle
15118 be separated on the logging hosts. Some installations do not require this
15119 separation, and in those cases, the duplication of certain log lines is a
15120 nuisance. If &%syslog_duplication%& is set false, only one copy of any
15121 particular log line is written to syslog. For lines that normally go to
15122 both the main log and the reject log, the reject log version (possibly
15123 containing message header lines) is written, at LOG_NOTICE priority.
15124 Lines that normally go to both the main and the panic log are written at
15125 the LOG_ALERT priority.
15128 .option syslog_facility main string unset
15129 .cindex "syslog" "facility; setting"
15130 This option sets the syslog &"facility"& name, used when Exim is logging to
15131 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
15132 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
15133 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
15134 details of Exim's logging.
15138 .option syslog_processname main string &`exim`&
15139 .cindex "syslog" "process name; setting"
15140 This option sets the syslog &"ident"& name, used when Exim is logging to
15141 syslog. The value must be no longer than 32 characters. See chapter
15142 &<<CHAPlog>>& for details of Exim's logging.
15146 .option syslog_timestamp main boolean true
15147 .cindex "syslog" "timestamps"
15148 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
15149 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
15150 details of Exim's logging.
15153 .option system_filter main string&!! unset
15154 .cindex "filter" "system filter"
15155 .cindex "system filter" "specifying"
15156 .cindex "Sieve filter" "not available for system filter"
15157 This option specifies an Exim filter file that is applied to all messages at
15158 the start of each delivery attempt, before any routing is done. System filters
15159 must be Exim filters; they cannot be Sieve filters. If the system filter
15160 generates any deliveries to files or pipes, or any new mail messages, the
15161 appropriate &%system_filter_..._transport%& option(s) must be set, to define
15162 which transports are to be used. Details of this facility are given in chapter
15163 &<<CHAPsystemfilter>>&.
15166 .option system_filter_directory_transport main string&!! unset
15167 .vindex "&$address_file$&"
15168 This sets the name of the transport driver that is to be used when the
15169 &%save%& command in a system message filter specifies a path ending in &"/"&,
15170 implying delivery of each message into a separate file in some directory.
15171 During the delivery, the variable &$address_file$& contains the path name.
15174 .option system_filter_file_transport main string&!! unset
15175 .cindex "file" "transport for system filter"
15176 This sets the name of the transport driver that is to be used when the &%save%&
15177 command in a system message filter specifies a path not ending in &"/"&. During
15178 the delivery, the variable &$address_file$& contains the path name.
15180 .option system_filter_group main string unset
15181 .cindex "gid (group id)" "system filter"
15182 This option is used only when &%system_filter_user%& is also set. It sets the
15183 gid under which the system filter is run, overriding any gid that is associated
15184 with the user. The value may be numerical or symbolic.
15186 .option system_filter_pipe_transport main string&!! unset
15187 .cindex "&(pipe)& transport" "for system filter"
15188 .vindex "&$address_pipe$&"
15189 This specifies the transport driver that is to be used when a &%pipe%& command
15190 is used in a system filter. During the delivery, the variable &$address_pipe$&
15191 contains the pipe command.
15194 .option system_filter_reply_transport main string&!! unset
15195 .cindex "&(autoreply)& transport" "for system filter"
15196 This specifies the transport driver that is to be used when a &%mail%& command
15197 is used in a system filter.
15199 .option system_filter_user main string unset
15200 .cindex "uid (user id)" "system filter"
15201 If this option is not set, the system filter is run in the main Exim delivery
15202 process, as root. When the option is set, the system filter runs in a separate
15203 process, as the given user. Unless the string consists entirely of digits, it
15204 is looked up in the password data. Failure to find the named user causes a
15205 configuration error. The gid is either taken from the password data, or
15206 specified by &%system_filter_group%&. When the uid is specified numerically,
15207 &%system_filter_group%& is required to be set.
15209 If the system filter generates any pipe, file, or reply deliveries, the uid
15210 under which the filter is run is used when transporting them, unless a
15211 transport option overrides. Normally you should set &%system_filter_user%& if
15212 your system filter generates these kinds of delivery.
15215 .option tcp_nodelay main boolean true
15216 .cindex "daemon" "TCP_NODELAY on sockets"
15217 .cindex "Nagle algorithm"
15218 .cindex "TCP_NODELAY on listening sockets"
15219 If this option is set false, it stops the Exim daemon setting the
15220 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
15221 turns off the &"Nagle algorithm"&, which is a way of improving network
15222 performance in interactive (character-by-character) situations. Turning it off
15223 should improve Exim's performance a bit, so that is what happens by default.
15224 However, it appears that some broken clients cannot cope, and time out. Hence
15225 this option. It affects only those sockets that are set up for listening by the
15226 daemon. Sockets created by the smtp transport for delivering mail always set
15230 .option timeout_frozen_after main time 0s
15231 .cindex "frozen messages" "timing out"
15232 .cindex "timeout" "frozen messages"
15233 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
15234 message of any kind that has been on the queue for longer than the given time
15235 is automatically cancelled at the next queue run. If the frozen message is a
15236 bounce message, it is just discarded; otherwise, a bounce is sent to the
15237 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
15238 If you want to timeout frozen bounce messages earlier than other kinds of
15239 frozen message, see &%ignore_bounce_errors_after%&.
15241 &*Note:*& the default value of zero means no timeouts; with this setting,
15242 frozen messages remain on the queue forever (except for any frozen bounce
15243 messages that are released by &%ignore_bounce_errors_after%&).
15246 .option timezone main string unset
15247 .cindex "timezone, setting"
15248 The value of &%timezone%& is used to set the environment variable TZ while
15249 running Exim (if it is different on entry). This ensures that all timestamps
15250 created by Exim are in the required timezone. If you want all your timestamps
15251 to be in UTC (aka GMT) you should set
15255 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
15256 or, if that is not set, from the value of the TZ environment variable when Exim
15257 is built. If &%timezone%& is set to the empty string, either at build or run
15258 time, any existing TZ variable is removed from the environment when Exim
15259 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
15260 unfortunately not all, operating systems.
15263 .option tls_advertise_hosts main "host list&!!" unset
15264 .cindex "TLS" "advertising"
15265 .cindex "encryption" "on SMTP connection"
15266 .cindex "SMTP" "encrypted connection"
15267 When Exim is built with support for TLS encrypted connections, the availability
15268 of the STARTTLS command to set up an encrypted session is advertised in
15269 response to EHLO only to those client hosts that match this option. See
15270 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
15273 .option tls_certificate main string&!! unset
15274 .cindex "TLS" "server certificate; location of"
15275 .cindex "certificate" "server, location of"
15276 The value of this option is expanded, and must then be the absolute path to a
15277 file which contains the server's certificates. The server's private key is also
15278 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
15279 &<<CHAPTLS>>& for further details.
15281 &*Note*&: The certificates defined by this option are used only when Exim is
15282 receiving incoming messages as a server. If you want to supply certificates for
15283 use when sending messages as a client, you must set the &%tls_certificate%&
15284 option in the relevant &(smtp)& transport.
15287 .option tls_crl main string&!! unset
15288 .cindex "TLS" "server certificate revocation list"
15289 .cindex "certificate" "revocation list for server"
15290 This option specifies a certificate revocation list. The expanded value must
15291 be the name of a file that contains a CRL in PEM format.
15294 .option tls_dhparam main string&!! unset
15295 .cindex "TLS" "D-H parameters for server"
15296 The value of this option is expanded, and must then be the absolute path to
15297 a file which contains the server's DH parameter values.
15298 This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is
15299 ignored. See section &<<SECTopenvsgnu>>& for further details.
15302 .option tls_on_connect_ports main "string list" unset
15303 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
15304 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
15305 set up without waiting for the client to issue a STARTTLS command. For
15306 further details, see section &<<SECTsupobssmt>>&.
15310 .option tls_privatekey main string&!! unset
15311 .cindex "TLS" "server private key; location of"
15312 The value of this option is expanded, and must then be the absolute path to a
15313 file which contains the server's private key. If this option is unset, or if
15314 the expansion is forced to fail, or the result is an empty string, the private
15315 key is assumed to be in the same file as the server's certificates. See chapter
15316 &<<CHAPTLS>>& for further details.
15319 .option tls_remember_esmtp main boolean false
15320 .cindex "TLS" "esmtp state; remembering"
15321 .cindex "TLS" "broken clients"
15322 If this option is set true, Exim violates the RFCs by remembering that it is in
15323 &"esmtp"& state after successfully negotiating a TLS session. This provides
15324 support for broken clients that fail to send a new EHLO after starting a
15328 .option tls_require_ciphers main string&!! unset
15329 .cindex "TLS" "requiring specific ciphers"
15330 .cindex "cipher" "requiring specific"
15331 This option controls which ciphers can be used for incoming TLS connections.
15332 The &(smtp)& transport has an option of the same name for controlling outgoing
15333 connections. This option is expanded for each connection, so can be varied for
15334 different clients if required. The value of this option must be a list of
15335 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
15336 in somewhat different ways. If GnuTLS is being used, the client controls the
15337 preference order of the available ciphers. Details are given in sections
15338 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
15341 .option tls_try_verify_hosts main "host list&!!" unset
15342 .cindex "TLS" "client certificate verification"
15343 .cindex "certificate" "verification of client"
15344 See &%tls_verify_hosts%& below.
15347 .option tls_verify_certificates main string&!! unset
15348 .cindex "TLS" "client certificate verification"
15349 .cindex "certificate" "verification of client"
15350 The value of this option is expanded, and must then be the absolute path to
15351 a file containing permitted certificates for clients that
15352 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you
15353 are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a
15354 directory containing certificate files. This does not work with GnuTLS; the
15355 option must be set to the name of a single file if you are using GnuTLS.
15358 .option tls_verify_hosts main "host list&!!" unset
15359 .cindex "TLS" "client certificate verification"
15360 .cindex "certificate" "verification of client"
15361 This option, along with &%tls_try_verify_hosts%&, controls the checking of
15362 certificates from clients. The expected certificates are defined by
15363 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
15364 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
15365 &%tls_verify_certificates%& is not set.
15367 Any client that matches &%tls_verify_hosts%& is constrained by
15368 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
15369 present one of the listed certificates. If it does not, the connection is
15370 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
15371 the host to use TLS. It can still send SMTP commands through unencrypted
15372 connections. Forcing a client to use TLS has to be done separately using an
15373 ACL to reject inappropriate commands when the connection is not encrypted.
15375 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
15376 matches this option (but not &%tls_verify_hosts%&), Exim requests a
15377 certificate and checks it against &%tls_verify_certificates%&, but does not
15378 abort the connection if there is no certificate or if it does not match. This
15379 state can be detected in an ACL, which makes it possible to implement policies
15380 such as &"accept for relay only if a verified certificate has been received,
15381 but accept for local delivery if encrypted, even without a verified
15384 Client hosts that match neither of these lists are not asked to present
15388 .option trusted_groups main "string list&!!" unset
15389 .cindex "trusted groups"
15390 .cindex "groups" "trusted"
15391 This option is expanded just once, at the start of Exim's processing. If this
15392 option is set, any process that is running in one of the listed groups, or
15393 which has one of them as a supplementary group, is trusted. The groups can be
15394 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
15395 details of what trusted callers are permitted to do. If neither
15396 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
15399 .option trusted_users main "string list&!!" unset
15400 .cindex "trusted users"
15401 .cindex "user" "trusted"
15402 This option is expanded just once, at the start of Exim's processing. If this
15403 option is set, any process that is running as one of the listed users is
15404 trusted. The users can be specified numerically or by name. See section
15405 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
15406 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
15407 Exim user are trusted.
15409 .option unknown_login main string&!! unset
15410 .cindex "uid (user id)" "unknown caller"
15411 .vindex "&$caller_uid$&"
15412 This is a specialized feature for use in unusual configurations. By default, if
15413 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
15414 gives up. The &%unknown_login%& option can be used to set a login name to be
15415 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
15416 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
15417 is used for the user's real name (gecos field), unless this has been set by the
15420 .option unknown_username main string unset
15421 See &%unknown_login%&.
15423 .option untrusted_set_sender main "address list&!!" unset
15424 .cindex "trusted users"
15425 .cindex "sender" "setting by untrusted user"
15426 .cindex "untrusted user setting sender"
15427 .cindex "user" "untrusted setting sender"
15428 .cindex "envelope sender"
15429 When an untrusted user submits a message to Exim using the standard input, Exim
15430 normally creates an envelope sender address from the user's login and the
15431 default qualification domain. Data from the &%-f%& option (for setting envelope
15432 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
15433 is used) is ignored.
15435 However, untrusted users are permitted to set an empty envelope sender address,
15436 to declare that a message should never generate any bounces. For example:
15438 exim -f '<>' user@domain.example
15440 .vindex "&$sender_ident$&"
15441 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
15442 other envelope sender addresses in a controlled way. When it is set, untrusted
15443 users are allowed to set envelope sender addresses that match any of the
15444 patterns in the list. Like all address lists, the string is expanded. The
15445 identity of the user is in &$sender_ident$&, so you can, for example, restrict
15446 users to setting senders that start with their login ids
15447 followed by a hyphen
15448 by a setting like this:
15450 untrusted_set_sender = ^$sender_ident-
15452 If you want to allow untrusted users to set envelope sender addresses without
15453 restriction, you can use
15455 untrusted_set_sender = *
15457 The &%untrusted_set_sender%& option applies to all forms of local input, but
15458 only to the setting of the envelope sender. It does not permit untrusted users
15459 to use the other options which trusted user can use to override message
15460 parameters. Furthermore, it does not stop Exim from removing an existing
15461 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
15462 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
15463 overriding these actions. The handling of the &'Sender:'& header is also
15464 described in section &<<SECTthesenhea>>&.
15466 The log line for a message's arrival shows the envelope sender following
15467 &"<="&. For local messages, the user's login always follows, after &"U="&. In
15468 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
15469 envelope sender address, the user's login is shown in parentheses after the
15473 .option uucp_from_pattern main string "see below"
15474 .cindex "&""From""& line"
15475 .cindex "UUCP" "&""From""& line"
15476 Some applications that pass messages to an MTA via a command line interface use
15477 an initial line starting with &"From&~"& to pass the envelope sender. In
15478 particular, this is used by UUCP software. Exim recognizes such a line by means
15479 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
15480 matches, the sender address is constructed by expanding the contents of
15481 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
15482 default pattern recognizes lines in the following two forms:
15484 From ph10 Fri Jan 5 12:35 GMT 1996
15485 From ph10 Fri, 7 Jan 97 14:00:00 GMT
15487 The pattern can be seen by running
15489 exim -bP uucp_from_pattern
15491 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
15492 year in the second case. The first word after &"From&~"& is matched in the
15493 regular expression by a parenthesized subpattern. The default value for
15494 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
15495 (&"ph10"& in the example above) as the message's sender. See also
15496 &%ignore_fromline_hosts%&.
15499 .option uucp_from_sender main string&!! &`$1`&
15500 See &%uucp_from_pattern%& above.
15503 .option warn_message_file main string unset
15504 .cindex "warning of delay" "customizing the message"
15505 .cindex "customizing" "warning message"
15506 This option defines a template file containing paragraphs of text to be used
15507 for constructing the warning message which is sent by Exim when a message has
15508 been on the queue for a specified amount of time, as specified by
15509 &%delay_warning%&. Details of the file's contents are given in chapter
15510 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
15513 .option write_rejectlog main boolean true
15514 .cindex "reject log" "disabling"
15515 If this option is set false, Exim no longer writes anything to the reject log.
15516 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
15517 .ecindex IIDconfima
15518 .ecindex IIDmaiconf
15523 . ////////////////////////////////////////////////////////////////////////////
15524 . ////////////////////////////////////////////////////////////////////////////
15526 .chapter "Generic options for routers" "CHAProutergeneric"
15527 .scindex IIDgenoprou1 "options" "generic; for routers"
15528 .scindex IIDgenoprou2 "generic options" "router"
15529 This chapter describes the generic options that apply to all routers.
15530 Those that are preconditions are marked with ‡ in the &"use"& field.
15532 For a general description of how a router operates, see sections
15533 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
15534 which the preconditions are tested. The order of expansion of the options that
15535 provide data for a transport is: &%errors_to%&, &%headers_add%&,
15536 &%headers_remove%&, &%transport%&.
15540 .option address_data routers string&!! unset
15541 .cindex "router" "data attached to address"
15542 The string is expanded just before the router is run, that is, after all the
15543 precondition tests have succeeded. If the expansion is forced to fail, the
15544 router declines, the value of &%address_data%& remains unchanged, and the
15545 &%more%& option controls what happens next. Other expansion failures cause
15546 delivery of the address to be deferred.
15548 .vindex "&$address_data$&"
15549 When the expansion succeeds, the value is retained with the address, and can be
15550 accessed using the variable &$address_data$& in the current router, subsequent
15551 routers, and the eventual transport.
15553 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
15554 that runs a user's filter file, the contents of &$address_data$& are accessible
15555 in the filter. This is not normally a problem, because such data is usually
15556 either not confidential or it &"belongs"& to the current user, but if you do
15557 put confidential data into &$address_data$& you need to remember this point.
15559 Even if the router declines or passes, the value of &$address_data$& remains
15560 with the address, though it can be changed by another &%address_data%& setting
15561 on a subsequent router. If a router generates child addresses, the value of
15562 &$address_data$& propagates to them. This also applies to the special kind of
15563 &"child"& that is generated by a router with the &%unseen%& option.
15565 The idea of &%address_data%& is that you can use it to look up a lot of data
15566 for the address once, and then pick out parts of the data later. For example,
15567 you could use a single LDAP lookup to return a string of the form
15569 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
15571 In the transport you could pick out the mailbox by a setting such as
15573 file = ${extract{mailbox}{$address_data}}
15575 This makes the configuration file less messy, and also reduces the number of
15576 lookups (though Exim does cache lookups).
15578 .vindex "&$sender_address_data$&"
15579 .vindex "&$address_data$&"
15580 The &%address_data%& facility is also useful as a means of passing information
15581 from one router to another, and from a router to a transport. In addition, if
15582 &$address_data$& is set by a router when verifying a recipient address from an
15583 ACL, it remains available for use in the rest of the ACL statement. After
15584 verifying a sender, the value is transferred to &$sender_address_data$&.
15588 .option address_test routers&!? boolean true
15590 .cindex "router" "skipping when address testing"
15591 If this option is set false, the router is skipped when routing is being tested
15592 by means of the &%-bt%& command line option. This can be a convenience when
15593 your first router sends messages to an external scanner, because it saves you
15594 having to set the &"already scanned"& indicator when testing real address
15599 .option cannot_route_message routers string&!! unset
15600 .cindex "router" "customizing &""cannot route""& message"
15601 .cindex "customizing" "&""cannot route""& message"
15602 This option specifies a text message that is used when an address cannot be
15603 routed because Exim has run out of routers. The default message is
15604 &"Unrouteable address"&. This option is useful only on routers that have
15605 &%more%& set false, or on the very last router in a configuration, because the
15606 value that is used is taken from the last router that is considered. This
15607 includes a router that is skipped because its preconditions are not met, as
15608 well as a router that declines. For example, using the default configuration,
15611 cannot_route_message = Remote domain not found in DNS
15613 on the first router, which is a &(dnslookup)& router with &%more%& set false,
15616 cannot_route_message = Unknown local user
15618 on the final router that checks for local users. If string expansion fails for
15619 this option, the default message is used. Unless the expansion failure was
15620 explicitly forced, a message about the failure is written to the main and panic
15621 logs, in addition to the normal message about the routing failure.
15624 .option caseful_local_part routers boolean false
15625 .cindex "case of local parts"
15626 .cindex "router" "case of local parts"
15627 By default, routers handle the local parts of addresses in a case-insensitive
15628 manner, though the actual case is preserved for transmission with the message.
15629 If you want the case of letters to be significant in a router, you must set
15630 this option true. For individual router options that contain address or local
15631 part lists (for example, &%local_parts%&), case-sensitive matching can be
15632 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
15635 .vindex "&$local_part$&"
15636 .vindex "&$original_local_part$&"
15637 .vindex "&$parent_local_part$&"
15638 The value of the &$local_part$& variable is forced to lower case while a
15639 router is running unless &%caseful_local_part%& is set. When a router assigns
15640 an address to a transport, the value of &$local_part$& when the transport runs
15641 is the same as it was in the router. Similarly, when a router generates child
15642 addresses by aliasing or forwarding, the values of &$original_local_part$&
15643 and &$parent_local_part$& are those that were used by the redirecting router.
15645 This option applies to the processing of an address by a router. When a
15646 recipient address is being processed in an ACL, there is a separate &%control%&
15647 modifier that can be used to specify case-sensitive processing within the ACL
15648 (see section &<<SECTcontrols>>&).
15652 .option check_local_user routers&!? boolean false
15653 .cindex "local user, checking in router"
15654 .cindex "router" "checking for local user"
15655 .cindex "&_/etc/passwd_&"
15657 When this option is true, Exim checks that the local part of the recipient
15658 address (with affixes removed if relevant) is the name of an account on the
15659 local system. The check is done by calling the &[getpwnam()]& function rather
15660 than trying to read &_/etc/passwd_& directly. This means that other methods of
15661 holding password data (such as NIS) are supported. If the local part is a local
15662 user, &$home$& is set from the password data, and can be tested in other
15663 preconditions that are evaluated after this one (the order of evaluation is
15664 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
15665 overridden by &%router_home_directory%&. If the local part is not a local user,
15666 the router is skipped.
15668 If you want to check that the local part is either the name of a local user
15669 or matches something else, you cannot combine &%check_local_user%& with a
15670 setting of &%local_parts%&, because that specifies the logical &'and'& of the
15671 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
15672 setting to achieve this. For example:
15674 local_parts = passwd;$local_part : lsearch;/etc/other/users
15676 Note, however, that the side effects of &%check_local_user%& (such as setting
15677 up a home directory) do not occur when a &(passwd)& lookup is used in a
15678 &%local_parts%& (or any other) precondition.
15682 .option condition routers&!? string&!! unset
15683 .cindex "router" "customized precondition"
15684 This option specifies a general precondition test that has to succeed for the
15685 router to be called. The &%condition%& option is the last precondition to be
15686 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
15687 result is a forced failure, or an empty string, or one of the strings &"0"& or
15688 &"no"& or &"false"& (checked without regard to the case of the letters), the
15689 router is skipped, and the address is offered to the next one.
15691 If the result is any other value, the router is run (as this is the last
15692 precondition to be evaluated, all the other preconditions must be true).
15694 This option is unique in that multiple &%condition%& options may be present.
15695 All &%condition%& options must succeed.
15697 The &%condition%& option provides a means of applying custom conditions to the
15698 running of routers. Note that in the case of a simple conditional expansion,
15699 the default expansion values are exactly what is wanted. For example:
15701 condition = ${if >{$message_age}{600}}
15703 Because of the default behaviour of the string expansion, this is equivalent to
15705 condition = ${if >{$message_age}{600}{true}{}}
15707 A multiple condition example, which succeeds:
15709 condition = ${if >{$message_age}{600}}
15710 condition = ${if !eq{${lc:$local_part}}{postmaster}}
15713 If the expansion fails (other than forced failure) delivery is deferred. Some
15714 of the other precondition options are common special cases that could in fact
15715 be specified using &%condition%&.
15719 .option debug_print routers string&!! unset
15720 .cindex "testing" "variables in drivers"
15721 If this option is set and debugging is enabled (see the &%-d%& command line
15722 option), the string is expanded and included in the debugging output.
15723 If expansion of the string fails, the error message is written to the debugging
15724 output, and Exim carries on processing.
15725 This option is provided to help with checking out the values of variables and
15726 so on when debugging router configurations. For example, if a &%condition%&
15727 option appears not to be working, &%debug_print%& can be used to output the
15728 variables it references. The output happens after checks for &%domains%&,
15729 &%local_parts%&, and &%check_local_user%& but before any other preconditions
15730 are tested. A newline is added to the text if it does not end with one.
15734 .option disable_logging routers boolean false
15735 If this option is set true, nothing is logged for any routing errors
15736 or for any deliveries caused by this router. You should not set this option
15737 unless you really, really know what you are doing. See also the generic
15738 transport option of the same name.
15741 .option domains routers&!? "domain list&!!" unset
15742 .cindex "router" "restricting to specific domains"
15743 .vindex "&$domain_data$&"
15744 If this option is set, the router is skipped unless the current domain matches
15745 the list. If the match is achieved by means of a file lookup, the data that the
15746 lookup returned for the domain is placed in &$domain_data$& for use in string
15747 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
15748 a list of the order in which preconditions are evaluated.
15752 .option driver routers string unset
15753 This option must always be set. It specifies which of the available routers is
15758 .option errors_to routers string&!! unset
15759 .cindex "envelope sender"
15760 .cindex "router" "changing address for errors"
15761 If a router successfully handles an address, it may assign the address to a
15762 transport for delivery or it may generate child addresses. In both cases, if
15763 there is a delivery problem during later processing, the resulting bounce
15764 message is sent to the address that results from expanding this string,
15765 provided that the address verifies successfully. The &%errors_to%& option is
15766 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
15768 The &%errors_to%& setting associated with an address can be overridden if it
15769 subsequently passes through other routers that have their own &%errors_to%&
15770 settings, or if the message is delivered by a transport with a &%return_path%&
15773 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
15774 the expansion fails to verify, the errors address associated with the incoming
15775 address is used. At top level, this is the envelope sender. A non-forced
15776 expansion failure causes delivery to be deferred.
15778 If an address for which &%errors_to%& has been set ends up being delivered over
15779 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
15780 any bounces that are generated by other MTAs on the delivery route are also
15781 sent there. You can set &%errors_to%& to the empty string by either of these
15787 An expansion item that yields an empty string has the same effect. If you do
15788 this, a locally detected delivery error for addresses processed by this router
15789 no longer gives rise to a bounce message; the error is discarded. If the
15790 address is delivered to a remote host, the return path is set to &`<>`&, unless
15791 overridden by the &%return_path%& option on the transport.
15793 .vindex "&$address_data$&"
15794 If for some reason you want to discard local errors, but use a non-empty
15795 MAIL command for remote delivery, you can preserve the original return
15796 path in &$address_data$& in the router, and reinstate it in the transport by
15797 setting &%return_path%&.
15799 The most common use of &%errors_to%& is to direct mailing list bounces to the
15800 manager of the list, as described in section &<<SECTmailinglists>>&, or to
15801 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
15805 .option expn routers&!? boolean true
15806 .cindex "address" "testing"
15807 .cindex "testing" "addresses"
15808 .cindex "EXPN" "router skipping"
15809 .cindex "router" "skipping for EXPN"
15810 If this option is turned off, the router is skipped when testing an address
15811 as a result of processing an SMTP EXPN command. You might, for example,
15812 want to turn it off on a router for users' &_.forward_& files, while leaving it
15813 on for the system alias file.
15814 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15817 The use of the SMTP EXPN command is controlled by an ACL (see chapter
15818 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
15819 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
15823 .option fail_verify routers boolean false
15824 .cindex "router" "forcing verification failure"
15825 Setting this option has the effect of setting both &%fail_verify_sender%& and
15826 &%fail_verify_recipient%& to the same value.
15830 .option fail_verify_recipient routers boolean false
15831 If this option is true and an address is accepted by this router when
15832 verifying a recipient, verification fails.
15836 .option fail_verify_sender routers boolean false
15837 If this option is true and an address is accepted by this router when
15838 verifying a sender, verification fails.
15842 .option fallback_hosts routers "string list" unset
15843 .cindex "router" "fallback hosts"
15844 .cindex "fallback" "hosts specified on router"
15845 String expansion is not applied to this option. The argument must be a
15846 colon-separated list of host names or IP addresses. The list separator can be
15847 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
15848 each name or address. In fact, the format of each item is exactly the same as
15849 defined for the list of hosts in a &(manualroute)& router (see section
15850 &<<SECTformatonehostitem>>&).
15852 If a router queues an address for a remote transport, this host list is
15853 associated with the address, and used instead of the transport's fallback host
15854 list. If &%hosts_randomize%& is set on the transport, the order of the list is
15855 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
15856 transport for further details.
15859 .option group routers string&!! "see below"
15860 .cindex "gid (group id)" "local delivery"
15861 .cindex "local transports" "uid and gid"
15862 .cindex "transport" "local"
15863 .cindex "router" "setting group"
15864 When a router queues an address for a transport, and the transport does not
15865 specify a group, the group given here is used when running the delivery
15867 The group may be specified numerically or by name. If expansion fails, the
15868 error is logged and delivery is deferred.
15869 The default is unset, unless &%check_local_user%& is set, when the default
15870 is taken from the password information. See also &%initgroups%& and &%user%&
15871 and the discussion in chapter &<<CHAPenvironment>>&.
15875 .option headers_add routers string&!! unset
15876 .cindex "header lines" "adding"
15877 .cindex "router" "adding header lines"
15878 This option specifies a string of text that is expanded at routing time, and
15879 associated with any addresses that are accepted by the router. However, this
15880 option has no effect when an address is just being verified. The way in which
15881 the text is used to add header lines at transport time is described in section
15882 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
15883 message is in the process of being transported. This means that references to
15884 header lines in string expansions in the transport's configuration do not
15885 &"see"& the added header lines.
15887 The &%headers_add%& option is expanded after &%errors_to%&, but before
15888 &%headers_remove%& and &%transport%&. If the expanded string is empty, or if
15889 the expansion is forced to fail, the option has no effect. Other expansion
15890 failures are treated as configuration errors.
15892 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
15893 router that has the &%one_time%& option set.
15895 .cindex "duplicate addresses"
15896 .oindex "&%unseen%&"
15897 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15898 additions are deleted when the address is passed on to subsequent routers.
15899 For a &%redirect%& router, if a generated address is the same as the incoming
15900 address, this can lead to duplicate addresses with different header
15901 modifications. Exim does not do duplicate deliveries (except, in certain
15902 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
15903 which of the duplicates is discarded, so this ambiguous situation should be
15904 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
15908 .option headers_remove routers string&!! unset
15909 .cindex "header lines" "removing"
15910 .cindex "router" "removing header lines"
15911 This option specifies a string of text that is expanded at routing time, and
15912 associated with any addresses that are accepted by the router. However, this
15913 option has no effect when an address is just being verified. The way in which
15914 the text is used to remove header lines at transport time is described in
15915 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
15916 the message is in the process of being transported. This means that references
15917 to header lines in string expansions in the transport's configuration still
15918 &"see"& the original header lines.
15920 The &%headers_remove%& option is expanded after &%errors_to%& and
15921 &%headers_add%&, but before &%transport%&. If the expansion is forced to fail,
15922 the option has no effect. Other expansion failures are treated as configuration
15925 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
15926 router that has the &%one_time%& option set.
15928 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15929 removal requests are deleted when the address is passed on to subsequent
15930 routers, and this can lead to problems with duplicates -- see the similar
15931 warning for &%headers_add%& above.
15934 .option ignore_target_hosts routers "host list&!!" unset
15935 .cindex "IP address" "discarding"
15936 .cindex "router" "discarding IP addresses"
15937 Although this option is a host list, it should normally contain IP address
15938 entries rather than names. If any host that is looked up by the router has an
15939 IP address that matches an item in this list, Exim behaves as if that IP
15940 address did not exist. This option allows you to cope with rogue DNS entries
15943 remote.domain.example. A 127.0.0.1
15947 ignore_target_hosts = 127.0.0.1
15949 on the relevant router. If all the hosts found by a &(dnslookup)& router are
15950 discarded in this way, the router declines. In a conventional configuration, an
15951 attempt to mail to such a domain would normally provoke the &"unrouteable
15952 domain"& error, and an attempt to verify an address in the domain would fail.
15953 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
15954 router declines if presented with one of the listed addresses.
15956 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
15957 means of the first or the second of the following settings, respectively:
15959 ignore_target_hosts = 0.0.0.0/0
15960 ignore_target_hosts = <; 0::0/0
15962 The pattern in the first line matches all IPv4 addresses, whereas the pattern
15963 in the second line matches all IPv6 addresses.
15965 This option may also be useful for ignoring link-local and site-local IPv6
15966 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
15967 is expanded before use as a list, it is possible to make it dependent on the
15968 domain that is being routed.
15970 .vindex "&$host_address$&"
15971 During its expansion, &$host_address$& is set to the IP address that is being
15974 .option initgroups routers boolean false
15975 .cindex "additional groups"
15976 .cindex "groups" "additional"
15977 .cindex "local transports" "uid and gid"
15978 .cindex "transport" "local"
15979 If the router queues an address for a transport, and this option is true, and
15980 the uid supplied by the router is not overridden by the transport, the
15981 &[initgroups()]& function is called when running the transport to ensure that
15982 any additional groups associated with the uid are set up. See also &%group%&
15983 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
15987 .option local_part_prefix routers&!? "string list" unset
15988 .cindex "router" "prefix for local part"
15989 .cindex "prefix" "for local part, used in router"
15990 If this option is set, the router is skipped unless the local part starts with
15991 one of the given strings, or &%local_part_prefix_optional%& is true. See
15992 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
15995 The list is scanned from left to right, and the first prefix that matches is
15996 used. A limited form of wildcard is available; if the prefix begins with an
15997 asterisk, it matches the longest possible sequence of arbitrary characters at
15998 the start of the local part. An asterisk should therefore always be followed by
15999 some character that does not occur in normal local parts.
16000 .cindex "multiple mailboxes"
16001 .cindex "mailbox" "multiple"
16002 Wildcarding can be used to set up multiple user mailboxes, as described in
16003 section &<<SECTmulbox>>&.
16005 .vindex "&$local_part$&"
16006 .vindex "&$local_part_prefix$&"
16007 During the testing of the &%local_parts%& option, and while the router is
16008 running, the prefix is removed from the local part, and is available in the
16009 expansion variable &$local_part_prefix$&. When a message is being delivered, if
16010 the router accepts the address, this remains true during subsequent delivery by
16011 a transport. In particular, the local part that is transmitted in the RCPT
16012 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
16013 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
16014 the relevant transport.
16016 When an address is being verified, &%local_part_prefix%& affects only the
16017 behaviour of the router. If the callout feature of verification is in use, this
16018 means that the full address, including the prefix, will be used during the
16021 The prefix facility is commonly used to handle local parts of the form
16022 &%owner-something%&. Another common use is to support local parts of the form
16023 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
16024 to tell a user their forwarding is broken &-- by placing a router like this one
16025 immediately before the router that handles &_.forward_& files:
16029 local_part_prefix = real-
16031 transport = local_delivery
16033 For security, it would probably be a good idea to restrict the use of this
16034 router to locally-generated messages, using a condition such as this:
16036 condition = ${if match {$sender_host_address}\
16037 {\N^(|127\.0\.0\.1)$\N}}
16040 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
16041 both conditions must be met if not optional. Care must be taken if wildcards
16042 are used in both a prefix and a suffix on the same router. Different
16043 separator characters must be used to avoid ambiguity.
16046 .option local_part_prefix_optional routers boolean false
16047 See &%local_part_prefix%& above.
16051 .option local_part_suffix routers&!? "string list" unset
16052 .cindex "router" "suffix for local part"
16053 .cindex "suffix for local part" "used in router"
16054 This option operates in the same way as &%local_part_prefix%&, except that the
16055 local part must end (rather than start) with the given string, the
16056 &%local_part_suffix_optional%& option determines whether the suffix is
16057 mandatory, and the wildcard * character, if present, must be the last
16058 character of the suffix. This option facility is commonly used to handle local
16059 parts of the form &%something-request%& and multiple user mailboxes of the form
16063 .option local_part_suffix_optional routers boolean false
16064 See &%local_part_suffix%& above.
16068 .option local_parts routers&!? "local part list&!!" unset
16069 .cindex "router" "restricting to specific local parts"
16070 .cindex "local part" "checking in router"
16071 The router is run only if the local part of the address matches the list.
16072 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16074 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
16075 string is expanded, it is possible to make it depend on the domain, for
16078 local_parts = dbm;/usr/local/specials/$domain
16080 .vindex "&$local_part_data$&"
16081 If the match is achieved by a lookup, the data that the lookup returned
16082 for the local part is placed in the variable &$local_part_data$& for use in
16083 expansions of the router's private options. You might use this option, for
16084 example, if you have a large number of local virtual domains, and you want to
16085 send all postmaster mail to the same place without having to set up an alias in
16086 each virtual domain:
16090 local_parts = postmaster
16091 data = postmaster@real.domain.example
16095 .option log_as_local routers boolean "see below"
16096 .cindex "log" "delivery line"
16097 .cindex "delivery" "log line format"
16098 Exim has two logging styles for delivery, the idea being to make local
16099 deliveries stand out more visibly from remote ones. In the &"local"& style, the
16100 recipient address is given just as the local part, without a domain. The use of
16101 this style is controlled by this option. It defaults to true for the &(accept)&
16102 router, and false for all the others. This option applies only when a
16103 router assigns an address to a transport. It has no effect on routers that
16104 redirect addresses.
16108 .option more routers boolean&!! true
16109 The result of string expansion for this option must be a valid boolean value,
16110 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
16111 result causes an error, and delivery is deferred. If the expansion is forced to
16112 fail, the default value for the option (true) is used. Other failures cause
16113 delivery to be deferred.
16115 If this option is set false, and the router declines to handle the address, no
16116 further routers are tried, routing fails, and the address is bounced.
16118 However, if the router explicitly passes an address to the following router by
16119 means of the setting
16123 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
16124 does not affect the behaviour if one of the precondition tests fails. In that
16125 case, the address is always passed to the next router.
16127 Note that &%address_data%& is not considered to be a precondition. If its
16128 expansion is forced to fail, the router declines, and the value of &%more%&
16129 controls what happens next.
16132 .option pass_on_timeout routers boolean false
16133 .cindex "timeout" "of router"
16134 .cindex "router" "timeout"
16135 If a router times out during a host lookup, it normally causes deferral of the
16136 address. If &%pass_on_timeout%& is set, the address is passed on to the next
16137 router, overriding &%no_more%&. This may be helpful for systems that are
16138 intermittently connected to the Internet, or those that want to pass to a smart
16139 host any messages that cannot immediately be delivered.
16141 There are occasional other temporary errors that can occur while doing DNS
16142 lookups. They are treated in the same way as a timeout, and this option
16143 applies to all of them.
16147 .option pass_router routers string unset
16148 .cindex "router" "go to after &""pass""&"
16149 Routers that recognize the generic &%self%& option (&(dnslookup)&,
16150 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
16151 routing to continue, and overriding a false setting of &%more%&. When one of
16152 these routers returns &"pass"&, the address is normally handed on to the next
16153 router in sequence. This can be changed by setting &%pass_router%& to the name
16154 of another router. However (unlike &%redirect_router%&) the named router must
16155 be below the current router, to avoid loops. Note that this option applies only
16156 to the special case of &"pass"&. It does not apply when a router returns
16157 &"decline"& because it cannot handle an address.
16161 .option redirect_router routers string unset
16162 .cindex "router" "start at after redirection"
16163 Sometimes an administrator knows that it is pointless to reprocess addresses
16164 generated from alias or forward files with the same router again. For
16165 example, if an alias file translates real names into login ids there is no
16166 point searching the alias file a second time, especially if it is a large file.
16168 The &%redirect_router%& option can be set to the name of any router instance.
16169 It causes the routing of any generated addresses to start at the named router
16170 instead of at the first router. This option has no effect if the router in
16171 which it is set does not generate new addresses.
16175 .option require_files routers&!? "string list&!!" unset
16176 .cindex "file" "requiring for router"
16177 .cindex "router" "requiring file existence"
16178 This option provides a general mechanism for predicating the running of a
16179 router on the existence or non-existence of certain files or directories.
16180 Before running a router, as one of its precondition tests, Exim works its way
16181 through the &%require_files%& list, expanding each item separately.
16183 Because the list is split before expansion, any colons in expansion items must
16184 be doubled, or the facility for using a different list separator must be used.
16185 If any expansion is forced to fail, the item is ignored. Other expansion
16186 failures cause routing of the address to be deferred.
16188 If any expanded string is empty, it is ignored. Otherwise, except as described
16189 below, each string must be a fully qualified file path, optionally preceded by
16190 &"!"&. The paths are passed to the &[stat()]& function to test for the
16191 existence of the files or directories. The router is skipped if any paths not
16192 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
16195 If &[stat()]& cannot determine whether a file exists or not, delivery of
16196 the message is deferred. This can happen when NFS-mounted filesystems are
16199 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
16200 options, so you cannot use it to check for the existence of a file in which to
16201 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
16202 full list of the order in which preconditions are evaluated.) However, as
16203 these options are all expanded, you can use the &%exists%& expansion condition
16204 to make such tests. The &%require_files%& option is intended for checking files
16205 that the router may be going to use internally, or which are needed by a
16206 transport (for example &_.procmailrc_&).
16208 During delivery, the &[stat()]& function is run as root, but there is a
16209 facility for some checking of the accessibility of a file by another user.
16210 This is not a proper permissions check, but just a &"rough"& check that
16211 operates as follows:
16213 If an item in a &%require_files%& list does not contain any forward slash
16214 characters, it is taken to be the user (and optional group, separated by a
16215 comma) to be checked for subsequent files in the list. If no group is specified
16216 but the user is specified symbolically, the gid associated with the uid is
16219 require_files = mail:/some/file
16220 require_files = $local_part:$home/.procmailrc
16222 If a user or group name in a &%require_files%& list does not exist, the
16223 &%require_files%& condition fails.
16225 Exim performs the check by scanning along the components of the file path, and
16226 checking the access for the given uid and gid. It checks for &"x"& access on
16227 directories, and &"r"& access on the final file. Note that this means that file
16228 access control lists, if the operating system has them, are ignored.
16230 &*Warning 1*&: When the router is being run to verify addresses for an
16231 incoming SMTP message, Exim is not running as root, but under its own uid. This
16232 may affect the result of a &%require_files%& check. In particular, &[stat()]&
16233 may yield the error EACCES (&"Permission denied"&). This means that the Exim
16234 user is not permitted to read one of the directories on the file's path.
16236 &*Warning 2*&: Even when Exim is running as root while delivering a message,
16237 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
16238 without root access. In this case, if a check for access by a particular user
16239 is requested, Exim creates a subprocess that runs as that user, and tries the
16240 check again in that process.
16242 The default action for handling an unresolved EACCES is to consider it to
16243 be caused by a configuration error, and routing is deferred because the
16244 existence or non-existence of the file cannot be determined. However, in some
16245 circumstances it may be desirable to treat this condition as if the file did
16246 not exist. If the file name (or the exclamation mark that precedes the file
16247 name for non-existence) is preceded by a plus sign, the EACCES error is treated
16248 as if the file did not exist. For example:
16250 require_files = +/some/file
16252 If the router is not an essential part of verification (for example, it
16253 handles users' &_.forward_& files), another solution is to set the &%verify%&
16254 option false so that the router is skipped when verifying.
16258 .option retry_use_local_part routers boolean "see below"
16259 .cindex "hints database" "retry keys"
16260 .cindex "local part" "in retry keys"
16261 When a delivery suffers a temporary routing failure, a retry record is created
16262 in Exim's hints database. For addresses whose routing depends only on the
16263 domain, the key for the retry record should not involve the local part, but for
16264 other addresses, both the domain and the local part should be included.
16265 Usually, remote routing is of the former kind, and local routing is of the
16268 This option controls whether the local part is used to form the key for retry
16269 hints for addresses that suffer temporary errors while being handled by this
16270 router. The default value is true for any router that has &%check_local_user%&
16271 set, and false otherwise. Note that this option does not apply to hints keys
16272 for transport delays; they are controlled by a generic transport option of the
16275 The setting of &%retry_use_local_part%& applies only to the router on which it
16276 appears. If the router generates child addresses, they are routed
16277 independently; this setting does not become attached to them.
16281 .option router_home_directory routers string&!! unset
16282 .cindex "router" "home directory for"
16283 .cindex "home directory" "for router"
16285 This option sets a home directory for use while the router is running. (Compare
16286 &%transport_home_directory%&, which sets a home directory for later
16287 transporting.) In particular, if used on a &(redirect)& router, this option
16288 sets a value for &$home$& while a filter is running. The value is expanded;
16289 forced expansion failure causes the option to be ignored &-- other failures
16290 cause the router to defer.
16292 Expansion of &%router_home_directory%& happens immediately after the
16293 &%check_local_user%& test (if configured), before any further expansions take
16295 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16297 While the router is running, &%router_home_directory%& overrides the value of
16298 &$home$& that came from &%check_local_user%&.
16300 When a router accepts an address and assigns it to a local transport (including
16301 the cases when a &(redirect)& router generates a pipe, file, or autoreply
16302 delivery), the home directory setting for the transport is taken from the first
16303 of these values that is set:
16306 The &%home_directory%& option on the transport;
16308 The &%transport_home_directory%& option on the router;
16310 The password data if &%check_local_user%& is set on the router;
16312 The &%router_home_directory%& option on the router.
16315 In other words, &%router_home_directory%& overrides the password data for the
16316 router, but not for the transport.
16320 .option self routers string freeze
16321 .cindex "MX record" "pointing to local host"
16322 .cindex "local host" "MX pointing to"
16323 This option applies to those routers that use a recipient address to find a
16324 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
16325 and &(manualroute)& routers.
16326 Certain configurations of the &(queryprogram)& router can also specify a list
16328 Usually such routers are configured to send the message to a remote host via an
16329 &(smtp)& transport. The &%self%& option specifies what happens when the first
16330 host on the list turns out to be the local host.
16331 The way in which Exim checks for the local host is described in section
16332 &<<SECTreclocipadd>>&.
16334 Normally this situation indicates either an error in Exim's configuration (for
16335 example, the router should be configured not to process this domain), or an
16336 error in the DNS (for example, the MX should not point to this host). For this
16337 reason, the default action is to log the incident, defer the address, and
16338 freeze the message. The following alternatives are provided for use in special
16343 Delivery of the message is tried again later, but the message is not frozen.
16345 .vitem "&%reroute%&: <&'domain'&>"
16346 The domain is changed to the given domain, and the address is passed back to
16347 be reprocessed by the routers. No rewriting of headers takes place. This
16348 behaviour is essentially a redirection.
16350 .vitem "&%reroute: rewrite:%& <&'domain'&>"
16351 The domain is changed to the given domain, and the address is passed back to be
16352 reprocessed by the routers. Any headers that contain the original domain are
16357 .vindex "&$self_hostname$&"
16358 The router passes the address to the next router, or to the router named in the
16359 &%pass_router%& option if it is set. This overrides &%no_more%&. During
16360 subsequent routing and delivery, the variable &$self_hostname$& contains the
16361 name of the local host that the router encountered. This can be used to
16362 distinguish between different cases for hosts with multiple names. The
16368 ensures that only those addresses that routed to the local host are passed on.
16369 Without &%no_more%&, addresses that were declined for other reasons would also
16370 be passed to the next router.
16373 Delivery fails and an error report is generated.
16376 .cindex "local host" "sending to"
16377 The anomaly is ignored and the address is queued for the transport. This
16378 setting should be used with extreme caution. For an &(smtp)& transport, it
16379 makes sense only in cases where the program that is listening on the SMTP port
16380 is not this version of Exim. That is, it must be some other MTA, or Exim with a
16381 different configuration file that handles the domain in another way.
16386 .option senders routers&!? "address list&!!" unset
16387 .cindex "router" "checking senders"
16388 If this option is set, the router is skipped unless the message's sender
16389 address matches something on the list.
16390 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16393 There are issues concerning verification when the running of routers is
16394 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
16395 setting, it sets the sender to the null string. When using the &%-bt%& option
16396 to check a configuration file, it is necessary also to use the &%-f%& option to
16397 set an appropriate sender. For incoming mail, the sender is unset when
16398 verifying the sender, but is available when verifying any recipients. If the
16399 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
16403 .option translate_ip_address routers string&!! unset
16404 .cindex "IP address" "translating"
16405 .cindex "packet radio"
16406 .cindex "router" "IP address translation"
16407 There exist some rare networking situations (for example, packet radio) where
16408 it is helpful to be able to translate IP addresses generated by normal routing
16409 mechanisms into other IP addresses, thus performing a kind of manual IP
16410 routing. This should be done only if the normal IP routing of the TCP/IP stack
16411 is inadequate or broken. Because this is an extremely uncommon requirement, the
16412 code to support this option is not included in the Exim binary unless
16413 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
16415 .vindex "&$host_address$&"
16416 The &%translate_ip_address%& string is expanded for every IP address generated
16417 by the router, with the generated address set in &$host_address$&. If the
16418 expansion is forced to fail, no action is taken.
16419 For any other expansion error, delivery of the message is deferred.
16420 If the result of the expansion is an IP address, that replaces the original
16421 address; otherwise the result is assumed to be a host name &-- this is looked
16422 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
16423 produce one or more replacement IP addresses. For example, to subvert all IP
16424 addresses in some specific networks, this could be added to a router:
16426 translate_ip_address = \
16427 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
16430 The file would contain lines like
16432 10.2.3.128/26 some.host
16433 10.8.4.34/26 10.44.8.15
16435 You should not make use of this facility unless you really understand what you
16440 .option transport routers string&!! unset
16441 This option specifies the transport to be used when a router accepts an address
16442 and sets it up for delivery. A transport is never needed if a router is used
16443 only for verification. The value of the option is expanded at routing time,
16444 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
16445 and result must be the name of one of the configured transports. If it is not,
16446 delivery is deferred.
16448 The &%transport%& option is not used by the &(redirect)& router, but it does
16449 have some private options that set up transports for pipe and file deliveries
16450 (see chapter &<<CHAPredirect>>&).
16454 .option transport_current_directory routers string&!! unset
16455 .cindex "current directory for local transport"
16456 This option associates a current directory with any address that is routed
16457 to a local transport. This can happen either because a transport is
16458 explicitly configured for the router, or because it generates a delivery to a
16459 file or a pipe. During the delivery process (that is, at transport time), this
16460 option string is expanded and is set as the current directory, unless
16461 overridden by a setting on the transport.
16462 If the expansion fails for any reason, including forced failure, an error is
16463 logged, and delivery is deferred.
16464 See chapter &<<CHAPenvironment>>& for details of the local delivery
16470 .option transport_home_directory routers string&!! "see below"
16471 .cindex "home directory" "for local transport"
16472 This option associates a home directory with any address that is routed to a
16473 local transport. This can happen either because a transport is explicitly
16474 configured for the router, or because it generates a delivery to a file or a
16475 pipe. During the delivery process (that is, at transport time), the option
16476 string is expanded and is set as the home directory, unless overridden by a
16477 setting of &%home_directory%& on the transport.
16478 If the expansion fails for any reason, including forced failure, an error is
16479 logged, and delivery is deferred.
16481 If the transport does not specify a home directory, and
16482 &%transport_home_directory%& is not set for the router, the home directory for
16483 the transport is taken from the password data if &%check_local_user%& is set for
16484 the router. Otherwise it is taken from &%router_home_directory%& if that option
16485 is set; if not, no home directory is set for the transport.
16487 See chapter &<<CHAPenvironment>>& for further details of the local delivery
16493 .option unseen routers boolean&!! false
16494 .cindex "router" "carrying on after success"
16495 The result of string expansion for this option must be a valid boolean value,
16496 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
16497 result causes an error, and delivery is deferred. If the expansion is forced to
16498 fail, the default value for the option (false) is used. Other failures cause
16499 delivery to be deferred.
16501 When this option is set true, routing does not cease if the router accepts the
16502 address. Instead, a copy of the incoming address is passed to the next router,
16503 overriding a false setting of &%more%&. There is little point in setting
16504 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
16505 the value of &%unseen%& contains expansion items (and therefore, presumably, is
16506 sometimes true and sometimes false).
16508 .cindex "copy of message (&%unseen%& option)"
16509 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
16510 qualifier in filter files. It can be used to cause copies of messages to be
16511 delivered to some other destination, while also carrying out a normal delivery.
16512 In effect, the current address is made into a &"parent"& that has two children
16513 &-- one that is delivered as specified by this router, and a clone that goes on
16514 to be routed further. For this reason, &%unseen%& may not be combined with the
16515 &%one_time%& option in a &(redirect)& router.
16517 &*Warning*&: Header lines added to the address (or specified for removal) by
16518 this router or by previous routers affect the &"unseen"& copy of the message
16519 only. The clone that continues to be processed by further routers starts with
16520 no added headers and none specified for removal. For a &%redirect%& router, if
16521 a generated address is the same as the incoming address, this can lead to
16522 duplicate addresses with different header modifications. Exim does not do
16523 duplicate deliveries (except, in certain circumstances, to pipes -- see section
16524 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
16525 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
16526 &%redirect%& router may be of help.
16528 Unlike the handling of header modifications, any data that was set by the
16529 &%address_data%& option in the current or previous routers &'is'& passed on to
16530 subsequent routers.
16533 .option user routers string&!! "see below"
16534 .cindex "uid (user id)" "local delivery"
16535 .cindex "local transports" "uid and gid"
16536 .cindex "transport" "local"
16537 .cindex "router" "user for filter processing"
16538 .cindex "filter" "user for processing"
16539 When a router queues an address for a transport, and the transport does not
16540 specify a user, the user given here is used when running the delivery process.
16541 The user may be specified numerically or by name. If expansion fails, the
16542 error is logged and delivery is deferred.
16543 This user is also used by the &(redirect)& router when running a filter file.
16544 The default is unset, except when &%check_local_user%& is set. In this case,
16545 the default is taken from the password information. If the user is specified as
16546 a name, and &%group%& is not set, the group associated with the user is used.
16547 See also &%initgroups%& and &%group%& and the discussion in chapter
16548 &<<CHAPenvironment>>&.
16552 .option verify routers&!? boolean true
16553 Setting this option has the effect of setting &%verify_sender%& and
16554 &%verify_recipient%& to the same value.
16557 .option verify_only routers&!? boolean false
16558 .cindex "EXPN" "with &%verify_only%&"
16560 .cindex "router" "used only when verifying"
16561 If this option is set, the router is used only when verifying an address or
16562 testing with the &%-bv%& option, not when actually doing a delivery, testing
16563 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
16564 restricted to verifying only senders or recipients by means of
16565 &%verify_sender%& and &%verify_recipient%&.
16567 &*Warning*&: When the router is being run to verify addresses for an incoming
16568 SMTP message, Exim is not running as root, but under its own uid. If the router
16569 accesses any files, you need to make sure that they are accessible to the Exim
16573 .option verify_recipient routers&!? boolean true
16574 If this option is false, the router is skipped when verifying recipient
16576 or testing recipient verification using &%-bv%&.
16577 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16581 .option verify_sender routers&!? boolean true
16582 If this option is false, the router is skipped when verifying sender addresses
16583 or testing sender verification using &%-bvs%&.
16584 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16586 .ecindex IIDgenoprou1
16587 .ecindex IIDgenoprou2
16594 . ////////////////////////////////////////////////////////////////////////////
16595 . ////////////////////////////////////////////////////////////////////////////
16597 .chapter "The accept router" "CHID4"
16598 .cindex "&(accept)& router"
16599 .cindex "routers" "&(accept)&"
16600 The &(accept)& router has no private options of its own. Unless it is being
16601 used purely for verification (see &%verify_only%&) a transport is required to
16602 be defined by the generic &%transport%& option. If the preconditions that are
16603 specified by generic options are met, the router accepts the address and queues
16604 it for the given transport. The most common use of this router is for setting
16605 up deliveries to local mailboxes. For example:
16609 domains = mydomain.example
16611 transport = local_delivery
16613 The &%domains%& condition in this example checks the domain of the address, and
16614 &%check_local_user%& checks that the local part is the login of a local user.
16615 When both preconditions are met, the &(accept)& router runs, and queues the
16616 address for the &(local_delivery)& transport.
16623 . ////////////////////////////////////////////////////////////////////////////
16624 . ////////////////////////////////////////////////////////////////////////////
16626 .chapter "The dnslookup router" "CHAPdnslookup"
16627 .scindex IIDdnsrou1 "&(dnslookup)& router"
16628 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
16629 The &(dnslookup)& router looks up the hosts that handle mail for the
16630 recipient's domain in the DNS. A transport must always be set for this router,
16631 unless &%verify_only%& is set.
16633 If SRV support is configured (see &%check_srv%& below), Exim first searches for
16634 SRV records. If none are found, or if SRV support is not configured,
16635 MX records are looked up. If no MX records exist, address records are sought.
16636 However, &%mx_domains%& can be set to disable the direct use of address
16639 MX records of equal priority are sorted by Exim into a random order. Exim then
16640 looks for address records for the host names obtained from MX or SRV records.
16641 When a host has more than one IP address, they are sorted into a random order,
16642 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
16643 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
16644 generic option, the router declines.
16646 Unless they have the highest priority (lowest MX value), MX records that point
16647 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
16648 are discarded, together with any other MX records of equal or lower priority.
16650 .cindex "MX record" "pointing to local host"
16651 .cindex "local host" "MX pointing to"
16652 .oindex "&%self%&" "in &(dnslookup)& router"
16653 If the host pointed to by the highest priority MX record, or looked up as an
16654 address record, is the local host, or matches &%hosts_treat_as_local%&, what
16655 happens is controlled by the generic &%self%& option.
16658 .section "Problems with DNS lookups" "SECTprowitdnsloo"
16659 There have been problems with DNS servers when SRV records are looked up.
16660 Some mis-behaving servers return a DNS error or timeout when a non-existent
16661 SRV record is sought. Similar problems have in the past been reported for
16662 MX records. The global &%dns_again_means_nonexist%& option can help with this
16663 problem, but it is heavy-handed because it is a global option.
16665 For this reason, there are two options, &%srv_fail_domains%& and
16666 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
16667 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
16668 an attempt to look up an SRV or MX record causes one of these results, and the
16669 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
16670 such record"&. In the case of an SRV lookup, this means that the router
16671 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
16672 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
16673 case routing fails.
16678 .section "Private options for dnslookup" "SECID118"
16679 .cindex "options" "&(dnslookup)& router"
16680 The private options for the &(dnslookup)& router are as follows:
16682 .option check_secondary_mx dnslookup boolean false
16683 .cindex "MX record" "checking for secondary"
16684 If this option is set, the router declines unless the local host is found in
16685 (and removed from) the list of hosts obtained by MX lookup. This can be used to
16686 process domains for which the local host is a secondary mail exchanger
16687 differently to other domains. The way in which Exim decides whether a host is
16688 the local host is described in section &<<SECTreclocipadd>>&.
16691 .option check_srv dnslookup string&!! unset
16692 .cindex "SRV record" "enabling use of"
16693 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
16694 addition to MX and address records. The support is disabled by default. To
16695 enable SRV support, set the &%check_srv%& option to the name of the service
16696 required. For example,
16700 looks for SRV records that refer to the normal smtp service. The option is
16701 expanded, so the service name can vary from message to message or address
16702 to address. This might be helpful if SRV records are being used for a
16703 submission service. If the expansion is forced to fail, the &%check_srv%&
16704 option is ignored, and the router proceeds to look for MX records in the
16707 When the expansion succeeds, the router searches first for SRV records for
16708 the given service (it assumes TCP protocol). A single SRV record with a
16709 host name that consists of just a single dot indicates &"no such service for
16710 this domain"&; if this is encountered, the router declines. If other kinds of
16711 SRV record are found, they are used to construct a host list for delivery
16712 according to the rules of RFC 2782. MX records are not sought in this case.
16714 When no SRV records are found, MX records (and address records) are sought in
16715 the traditional way. In other words, SRV records take precedence over MX
16716 records, just as MX records take precedence over address records. Note that
16717 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
16718 defined it. It is apparently believed that MX records are sufficient for email
16719 and that SRV records should not be used for this purpose. However, SRV records
16720 have an additional &"weight"& feature which some people might find useful when
16721 trying to split an SMTP load between hosts of different power.
16723 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
16724 when there is a DNS lookup error.
16728 .option mx_domains dnslookup "domain list&!!" unset
16729 .cindex "MX record" "required to exist"
16730 .cindex "SRV record" "required to exist"
16731 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
16732 record in order to be recognized. (The name of this option could be improved.)
16733 For example, if all the mail hosts in &'fict.example'& are known to have MX
16734 records, except for those in &'discworld.fict.example'&, you could use this
16737 mx_domains = ! *.discworld.fict.example : *.fict.example
16739 This specifies that messages addressed to a domain that matches the list but
16740 has no MX record should be bounced immediately instead of being routed using
16741 the address record.
16744 .option mx_fail_domains dnslookup "domain list&!!" unset
16745 If the DNS lookup for MX records for one of the domains in this list causes a
16746 DNS lookup error, Exim behaves as if no MX records were found. See section
16747 &<<SECTprowitdnsloo>>& for more discussion.
16752 .option qualify_single dnslookup boolean true
16753 .cindex "DNS" "resolver options"
16754 .cindex "DNS" "qualifying single-component names"
16755 When this option is true, the resolver option RES_DEFNAMES is set for DNS
16756 lookups. Typically, but not standardly, this causes the resolver to qualify
16757 single-component names with the default domain. For example, on a machine
16758 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
16759 &'thesaurus.ref.example'& inside the resolver. For details of what your
16760 resolver actually does, consult your man pages for &'resolver'& and
16765 .option rewrite_headers dnslookup boolean true
16766 .cindex "rewriting" "header lines"
16767 .cindex "header lines" "rewriting"
16768 If the domain name in the address that is being processed is not fully
16769 qualified, it may be expanded to its full form by a DNS lookup. For example, if
16770 an address is specified as &'dormouse@teaparty'&, the domain might be
16771 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
16772 occur as a result of setting the &%widen_domains%& option. If
16773 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
16774 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
16775 header lines of the message are rewritten with the full domain name.
16777 This option should be turned off only when it is known that no message is
16778 ever going to be sent outside an environment where the abbreviation makes
16781 When an MX record is looked up in the DNS and matches a wildcard record, name
16782 servers normally return a record containing the name that has been looked up,
16783 making it impossible to detect whether a wildcard was present or not. However,
16784 some name servers have recently been seen to return the wildcard entry. If the
16785 name returned by a DNS lookup begins with an asterisk, it is not used for
16789 .option same_domain_copy_routing dnslookup boolean false
16790 .cindex "address" "copying routing"
16791 Addresses with the same domain are normally routed by the &(dnslookup)& router
16792 to the same list of hosts. However, this cannot be presumed, because the router
16793 options and preconditions may refer to the local part of the address. By
16794 default, therefore, Exim routes each address in a message independently. DNS
16795 servers run caches, so repeated DNS lookups are not normally expensive, and in
16796 any case, personal messages rarely have more than a few recipients.
16798 If you are running mailing lists with large numbers of subscribers at the same
16799 domain, and you are using a &(dnslookup)& router which is independent of the
16800 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
16801 lookups for identical domains in one message. In this case, when &(dnslookup)&
16802 routes an address to a remote transport, any other unrouted addresses in the
16803 message that have the same domain are automatically given the same routing
16804 without processing them independently,
16805 provided the following conditions are met:
16808 No router that processed the address specified &%headers_add%& or
16809 &%headers_remove%&.
16811 The router did not change the address in any way, for example, by &"widening"&
16818 .option search_parents dnslookup boolean false
16819 .cindex "DNS" "resolver options"
16820 When this option is true, the resolver option RES_DNSRCH is set for DNS
16821 lookups. This is different from the &%qualify_single%& option in that it
16822 applies to domains containing dots. Typically, but not standardly, it causes
16823 the resolver to search for the name in the current domain and in parent
16824 domains. For example, on a machine in the &'fict.example'& domain, if looking
16825 up &'teaparty.wonderland'& failed, the resolver would try
16826 &'teaparty.wonderland.fict.example'&. For details of what your resolver
16827 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
16829 Setting this option true can cause problems in domains that have a wildcard MX
16830 record, because any domain that does not have its own MX record matches the
16835 .option srv_fail_domains dnslookup "domain list&!!" unset
16836 If the DNS lookup for SRV records for one of the domains in this list causes a
16837 DNS lookup error, Exim behaves as if no SRV records were found. See section
16838 &<<SECTprowitdnsloo>>& for more discussion.
16843 .option widen_domains dnslookup "string list" unset
16844 .cindex "domain" "partial; widening"
16845 If a DNS lookup fails and this option is set, each of its strings in turn is
16846 added onto the end of the domain, and the lookup is tried again. For example,
16849 widen_domains = fict.example:ref.example
16851 is set and a lookup of &'klingon.dictionary'& fails,
16852 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
16853 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
16854 and &%search_parents%& options can cause some widening to be undertaken inside
16855 the DNS resolver. &%widen_domains%& is not applied to sender addresses
16856 when verifying, unless &%rewrite_headers%& is false (not the default).
16859 .section "Effect of qualify_single and search_parents" "SECID119"
16860 When a domain from an envelope recipient is changed by the resolver as a result
16861 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
16862 corresponding address in the message's header lines unless &%rewrite_headers%&
16863 is set false. Exim then re-routes the address, using the full domain.
16865 These two options affect only the DNS lookup that takes place inside the router
16866 for the domain of the address that is being routed. They do not affect lookups
16867 such as that implied by
16871 that may happen while processing a router precondition before the router is
16872 entered. No widening ever takes place for these lookups.
16873 .ecindex IIDdnsrou1
16874 .ecindex IIDdnsrou2
16884 . ////////////////////////////////////////////////////////////////////////////
16885 . ////////////////////////////////////////////////////////////////////////////
16887 .chapter "The ipliteral router" "CHID5"
16888 .cindex "&(ipliteral)& router"
16889 .cindex "domain literal" "routing"
16890 .cindex "routers" "&(ipliteral)&"
16891 This router has no private options. Unless it is being used purely for
16892 verification (see &%verify_only%&) a transport is required to be defined by the
16893 generic &%transport%& option. The router accepts the address if its domain part
16894 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
16895 router handles the address
16899 by setting up delivery to the host with that IP address. IPv4 domain literals
16900 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
16901 are similar, but the address is preceded by &`ipv6:`&. For example:
16903 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
16905 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
16906 grounds that sooner or later somebody will try it.
16908 .oindex "&%self%&" "in &(ipliteral)& router"
16909 If the IP address matches something in &%ignore_target_hosts%&, the router
16910 declines. If an IP literal turns out to refer to the local host, the generic
16911 &%self%& option determines what happens.
16913 The RFCs require support for domain literals; however, their use is
16914 controversial in today's Internet. If you want to use this router, you must
16915 also set the main configuration option &%allow_domain_literals%&. Otherwise,
16916 Exim will not recognize the domain literal syntax in addresses.
16920 . ////////////////////////////////////////////////////////////////////////////
16921 . ////////////////////////////////////////////////////////////////////////////
16923 .chapter "The iplookup router" "CHID6"
16924 .cindex "&(iplookup)& router"
16925 .cindex "routers" "&(iplookup)&"
16926 The &(iplookup)& router was written to fulfil a specific requirement in
16927 Cambridge University (which in fact no longer exists). For this reason, it is
16928 not included in the binary of Exim by default. If you want to include it, you
16931 ROUTER_IPLOOKUP=yes
16933 in your &_Local/Makefile_& configuration file.
16935 The &(iplookup)& router routes an address by sending it over a TCP or UDP
16936 connection to one or more specific hosts. The host can then return the same or
16937 a different address &-- in effect rewriting the recipient address in the
16938 message's envelope. The new address is then passed on to subsequent routers. If
16939 this process fails, the address can be passed on to other routers, or delivery
16940 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
16941 must not be specified for it.
16943 .cindex "options" "&(iplookup)& router"
16944 .option hosts iplookup string unset
16945 This option must be supplied. Its value is a colon-separated list of host
16946 names. The hosts are looked up using &[gethostbyname()]&
16947 (or &[getipnodebyname()]& when available)
16948 and are tried in order until one responds to the query. If none respond, what
16949 happens is controlled by &%optional%&.
16952 .option optional iplookup boolean false
16953 If &%optional%& is true, if no response is obtained from any host, the address
16954 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
16955 delivery to the address is deferred.
16958 .option port iplookup integer 0
16959 .cindex "port" "&(iplookup)& router"
16960 This option must be supplied. It specifies the port number for the TCP or UDP
16964 .option protocol iplookup string udp
16965 This option can be set to &"udp"& or &"tcp"& to specify which of the two
16966 protocols is to be used.
16969 .option query iplookup string&!! "see below"
16970 This defines the content of the query that is sent to the remote hosts. The
16973 $local_part@$domain $local_part@$domain
16975 The repetition serves as a way of checking that a response is to the correct
16976 query in the default case (see &%response_pattern%& below).
16979 .option reroute iplookup string&!! unset
16980 If this option is not set, the rerouted address is precisely the byte string
16981 returned by the remote host, up to the first white space, if any. If set, the
16982 string is expanded to form the rerouted address. It can include parts matched
16983 in the response by &%response_pattern%& by means of numeric variables such as
16984 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
16985 whether or not a pattern is in use. In all cases, the rerouted address must end
16986 up in the form &'local_part@domain'&.
16989 .option response_pattern iplookup string unset
16990 This option can be set to a regular expression that is applied to the string
16991 returned from the remote host. If the pattern does not match the response, the
16992 router declines. If &%response_pattern%& is not set, no checking of the
16993 response is done, unless the query was defaulted, in which case there is a
16994 check that the text returned after the first white space is the original
16995 address. This checks that the answer that has been received is in response to
16996 the correct question. For example, if the response is just a new domain, the
16997 following could be used:
16999 response_pattern = ^([^@]+)$
17000 reroute = $local_part@$1
17003 .option timeout iplookup time 5s
17004 This specifies the amount of time to wait for a response from the remote
17005 machine. The same timeout is used for the &[connect()]& function for a TCP
17006 call. It does not apply to UDP.
17011 . ////////////////////////////////////////////////////////////////////////////
17012 . ////////////////////////////////////////////////////////////////////////////
17014 .chapter "The manualroute router" "CHID7"
17015 .scindex IIDmanrou1 "&(manualroute)& router"
17016 .scindex IIDmanrou2 "routers" "&(manualroute)&"
17017 .cindex "domain" "manually routing"
17018 The &(manualroute)& router is so-called because it provides a way of manually
17019 routing an address according to its domain. It is mainly used when you want to
17020 route addresses to remote hosts according to your own rules, bypassing the
17021 normal DNS routing that looks up MX records. However, &(manualroute)& can also
17022 route to local transports, a facility that may be useful if you want to save
17023 messages for dial-in hosts in local files.
17025 The &(manualroute)& router compares a list of domain patterns with the domain
17026 it is trying to route. If there is no match, the router declines. Each pattern
17027 has associated with it a list of hosts and some other optional data, which may
17028 include a transport. The combination of a pattern and its data is called a
17029 &"routing rule"&. For patterns that do not have an associated transport, the
17030 generic &%transport%& option must specify a transport, unless the router is
17031 being used purely for verification (see &%verify_only%&).
17034 In the case of verification, matching the domain pattern is sufficient for the
17035 router to accept the address. When actually routing an address for delivery,
17036 an address that matches a domain pattern is queued for the associated
17037 transport. If the transport is not a local one, a host list must be associated
17038 with the pattern; IP addresses are looked up for the hosts, and these are
17039 passed to the transport along with the mail address. For local transports, a
17040 host list is optional. If it is present, it is passed in &$host$& as a single
17043 The list of routing rules can be provided as an inline string in
17044 &%route_list%&, or the data can be obtained by looking up the domain in a file
17045 or database by setting &%route_data%&. Only one of these settings may appear in
17046 any one instance of &(manualroute)&. The format of routing rules is described
17047 below, following the list of private options.
17050 .section "Private options for manualroute" "SECTprioptman"
17052 .cindex "options" "&(manualroute)& router"
17053 The private options for the &(manualroute)& router are as follows:
17055 .option host_all_ignored manualroute string defer
17056 See &%host_find_failed%&.
17058 .option host_find_failed manualroute string freeze
17059 This option controls what happens when &(manualroute)& tries to find an IP
17060 address for a host, and the host does not exist. The option can be set to one
17061 of the following values:
17070 The default (&"freeze"&) assumes that this state is a serious configuration
17071 error. The difference between &"pass"& and &"decline"& is that the former
17072 forces the address to be passed to the next router (or the router defined by
17075 overriding &%no_more%&, whereas the latter passes the address to the next
17076 router only if &%more%& is true.
17078 The value &"ignore"& causes Exim to completely ignore a host whose IP address
17079 cannot be found. If all the hosts in the list are ignored, the behaviour is
17080 controlled by the &%host_all_ignored%& option. This takes the same values
17081 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
17083 The &%host_find_failed%& option applies only to a definite &"does not exist"&
17084 state; if a host lookup gets a temporary error, delivery is deferred unless the
17085 generic &%pass_on_timeout%& option is set.
17088 .option hosts_randomize manualroute boolean false
17089 .cindex "randomized host list"
17090 .cindex "host" "list of; randomized"
17091 If this option is set, the order of the items in a host list in a routing rule
17092 is randomized each time the list is used, unless an option in the routing rule
17093 overrides (see below). Randomizing the order of a host list can be used to do
17094 crude load sharing. However, if more than one mail address is routed by the
17095 same router to the same host list, the host lists are considered to be the same
17096 (even though they may be randomized into different orders) for the purpose of
17097 deciding whether to batch the deliveries into a single SMTP transaction.
17099 When &%hosts_randomize%& is true, a host list may be split
17100 into groups whose order is separately randomized. This makes it possible to
17101 set up MX-like behaviour. The boundaries between groups are indicated by an
17102 item that is just &`+`& in the host list. For example:
17104 route_list = * host1:host2:host3:+:host4:host5
17106 The order of the first three hosts and the order of the last two hosts is
17107 randomized for each use, but the first three always end up before the last two.
17108 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
17109 randomized host list is passed to an &(smtp)& transport that also has
17110 &%hosts_randomize set%&, the list is not re-randomized.
17113 .option route_data manualroute string&!! unset
17114 If this option is set, it must expand to yield the data part of a routing rule.
17115 Typically, the expansion string includes a lookup based on the domain. For
17118 route_data = ${lookup{$domain}dbm{/etc/routes}}
17120 If the expansion is forced to fail, or the result is an empty string, the
17121 router declines. Other kinds of expansion failure cause delivery to be
17125 .option route_list manualroute "string list" unset
17126 This string is a list of routing rules, in the form defined below. Note that,
17127 unlike most string lists, the items are separated by semicolons. This is so
17128 that they may contain colon-separated host lists.
17131 .option same_domain_copy_routing manualroute boolean false
17132 .cindex "address" "copying routing"
17133 Addresses with the same domain are normally routed by the &(manualroute)&
17134 router to the same list of hosts. However, this cannot be presumed, because the
17135 router options and preconditions may refer to the local part of the address. By
17136 default, therefore, Exim routes each address in a message independently. DNS
17137 servers run caches, so repeated DNS lookups are not normally expensive, and in
17138 any case, personal messages rarely have more than a few recipients.
17140 If you are running mailing lists with large numbers of subscribers at the same
17141 domain, and you are using a &(manualroute)& router which is independent of the
17142 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
17143 lookups for identical domains in one message. In this case, when
17144 &(manualroute)& routes an address to a remote transport, any other unrouted
17145 addresses in the message that have the same domain are automatically given the
17146 same routing without processing them independently. However, this is only done
17147 if &%headers_add%& and &%headers_remove%& are unset.
17152 .section "Routing rules in route_list" "SECID120"
17153 The value of &%route_list%& is a string consisting of a sequence of routing
17154 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
17155 entered as two semicolons. Alternatively, the list separator can be changed as
17156 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
17157 Empty rules are ignored. The format of each rule is
17159 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
17161 The following example contains two rules, each with a simple domain pattern and
17165 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
17166 thes.ref.example mail-3.ref.example:mail-4.ref.example
17168 The three parts of a rule are separated by white space. The pattern and the
17169 list of hosts can be enclosed in quotes if necessary, and if they are, the
17170 usual quoting rules apply. Each rule in a &%route_list%& must start with a
17171 single domain pattern, which is the only mandatory item in the rule. The
17172 pattern is in the same format as one item in a domain list (see section
17173 &<<SECTdomainlist>>&),
17174 except that it may not be the name of an interpolated file.
17175 That is, it may be wildcarded, or a regular expression, or a file or database
17176 lookup (with semicolons doubled, because of the use of semicolon as a separator
17177 in a &%route_list%&).
17179 The rules in &%route_list%& are searched in order until one of the patterns
17180 matches the domain that is being routed. The list of hosts and then options are
17181 then used as described below. If there is no match, the router declines. When
17182 &%route_list%& is set, &%route_data%& must not be set.
17186 .section "Routing rules in route_data" "SECID121"
17187 The use of &%route_list%& is convenient when there are only a small number of
17188 routing rules. For larger numbers, it is easier to use a file or database to
17189 hold the routing information, and use the &%route_data%& option instead.
17190 The value of &%route_data%& is a list of hosts, followed by (optional) options.
17191 Most commonly, &%route_data%& is set as a string that contains an
17192 expansion lookup. For example, suppose we place two routing rules in a file
17195 dict.ref.example: mail-1.ref.example:mail-2.ref.example
17196 thes.ref.example: mail-3.ref.example:mail-4.ref.example
17198 This data can be accessed by setting
17200 route_data = ${lookup{$domain}lsearch{/the/file/name}}
17202 Failure of the lookup results in an empty string, causing the router to
17203 decline. However, you do not have to use a lookup in &%route_data%&. The only
17204 requirement is that the result of expanding the string is a list of hosts,
17205 possibly followed by options, separated by white space. The list of hosts must
17206 be enclosed in quotes if it contains white space.
17211 .section "Format of the list of hosts" "SECID122"
17212 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
17213 always separately expanded before use. If the expansion fails, the router
17214 declines. The result of the expansion must be a colon-separated list of names
17215 and/or IP addresses, optionally also including ports. The format of each item
17216 in the list is described in the next section. The list separator can be changed
17217 as described in section &<<SECTlistconstruct>>&.
17219 If the list of hosts was obtained from a &%route_list%& item, the following
17220 variables are set during its expansion:
17223 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
17224 If the domain was matched against a regular expression, the numeric variables
17225 &$1$&, &$2$&, etc. may be set. For example:
17227 route_list = ^domain(\d+) host-$1.text.example
17230 &$0$& is always set to the entire domain.
17232 &$1$& is also set when partial matching is done in a file lookup.
17235 .vindex "&$value$&"
17236 If the pattern that matched the domain was a lookup item, the data that was
17237 looked up is available in the expansion variable &$value$&. For example:
17239 route_list = lsearch;;/some/file.routes $value
17243 Note the doubling of the semicolon in the pattern that is necessary because
17244 semicolon is the default route list separator.
17248 .section "Format of one host item" "SECTformatonehostitem"
17249 Each item in the list of hosts is either a host name or an IP address,
17250 optionally with an attached port number. When no port is given, an IP address
17251 is not enclosed in brackets. When a port is specified, it overrides the port
17252 specification on the transport. The port is separated from the name or address
17253 by a colon. This leads to some complications:
17256 Because colon is the default separator for the list of hosts, either
17257 the colon that specifies a port must be doubled, or the list separator must
17258 be changed. The following two examples have the same effect:
17260 route_list = * "host1.tld::1225 : host2.tld::1226"
17261 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
17264 When IPv6 addresses are involved, it gets worse, because they contain
17265 colons of their own. To make this case easier, it is permitted to
17266 enclose an IP address (either v4 or v6) in square brackets if a port
17267 number follows. For example:
17269 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
17273 .section "How the list of hosts is used" "SECThostshowused"
17274 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
17275 the hosts is tried, in the order specified, when carrying out the SMTP
17276 delivery. However, the order can be changed by setting the &%hosts_randomize%&
17277 option, either on the router (see section &<<SECTprioptman>>& above), or on the
17280 Hosts may be listed by name or by IP address. An unadorned name in the list of
17281 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
17282 interpreted as an indirection to a sublist of hosts obtained by looking up MX
17283 records in the DNS. For example:
17285 route_list = * x.y.z:p.q.r/MX:e.f.g
17287 If this feature is used with a port specifier, the port must come last. For
17290 route_list = * dom1.tld/mx::1225
17292 If the &%hosts_randomize%& option is set, the order of the items in the list is
17293 randomized before any lookups are done. Exim then scans the list; for any name
17294 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
17295 be an interface on the local host and the item is not the first in the list,
17296 Exim discards it and any subsequent items. If it is the first item, what
17297 happens is controlled by the
17298 .oindex "&%self%&" "in &(manualroute)& router"
17299 &%self%& option of the router.
17301 A name on the list that is followed by &`/MX`& is replaced with the list of
17302 hosts obtained by looking up MX records for the name. This is always a DNS
17303 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
17304 below) are not relevant here. The order of these hosts is determined by the
17305 preference values in the MX records, according to the usual rules. Because
17306 randomizing happens before the MX lookup, it does not affect the order that is
17307 defined by MX preferences.
17309 If the local host is present in the sublist obtained from MX records, but is
17310 not the most preferred host in that list, it and any equally or less
17311 preferred hosts are removed before the sublist is inserted into the main list.
17313 If the local host is the most preferred host in the MX list, what happens
17314 depends on where in the original list of hosts the &`/MX`& item appears. If it
17315 is not the first item (that is, there are previous hosts in the main list),
17316 Exim discards this name and any subsequent items in the main list.
17318 If the MX item is first in the list of hosts, and the local host is the
17319 most preferred host, what happens is controlled by the &%self%& option of the
17322 DNS failures when lookup up the MX records are treated in the same way as DNS
17323 failures when looking up IP addresses: &%pass_on_timeout%& and
17324 &%host_find_failed%& are used when relevant.
17326 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
17327 whether obtained from an MX lookup or not.
17331 .section "How the options are used" "SECThowoptused"
17332 The options are a sequence of words; in practice no more than three are ever
17333 present. One of the words can be the name of a transport; this overrides the
17334 &%transport%& option on the router for this particular routing rule only. The
17335 other words (if present) control randomization of the list of hosts on a
17336 per-rule basis, and how the IP addresses of the hosts are to be found when
17337 routing to a remote transport. These options are as follows:
17340 &%randomize%&: randomize the order of the hosts in this list, overriding the
17341 setting of &%hosts_randomize%& for this routing rule only.
17343 &%no_randomize%&: do not randomize the order of the hosts in this list,
17344 overriding the setting of &%hosts_randomize%& for this routing rule only.
17346 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
17347 find IP addresses. This function may ultimately cause a DNS lookup, but it may
17348 also look in &_/etc/hosts_& or other sources of information.
17350 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
17351 no address records are found. If there is a temporary DNS error (such as a
17352 timeout), delivery is deferred.
17357 route_list = domain1 host1:host2:host3 randomize bydns;\
17358 domain2 host4:host5
17360 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
17361 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
17362 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
17363 or &[gethostbyname()]&, and the result of the lookup is the result of that
17366 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
17367 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
17368 instead of TRY_AGAIN. That is why the default action is to try a DNS
17369 lookup first. Only if that gives a definite &"no such host"& is the local
17374 If no IP address for a host can be found, what happens is controlled by the
17375 &%host_find_failed%& option.
17378 When an address is routed to a local transport, IP addresses are not looked up.
17379 The host list is passed to the transport in the &$host$& variable.
17383 .section "Manualroute examples" "SECID123"
17384 In some of the examples that follow, the presence of the &%remote_smtp%&
17385 transport, as defined in the default configuration file, is assumed:
17388 .cindex "smart host" "example router"
17389 The &(manualroute)& router can be used to forward all external mail to a
17390 &'smart host'&. If you have set up, in the main part of the configuration, a
17391 named domain list that contains your local domains, for example:
17393 domainlist local_domains = my.domain.example
17395 You can arrange for all other domains to be routed to a smart host by making
17396 your first router something like this:
17399 driver = manualroute
17400 domains = !+local_domains
17401 transport = remote_smtp
17402 route_list = * smarthost.ref.example
17404 This causes all non-local addresses to be sent to the single host
17405 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
17406 they are tried in order
17407 (but you can use &%hosts_randomize%& to vary the order each time).
17408 Another way of configuring the same thing is this:
17411 driver = manualroute
17412 transport = remote_smtp
17413 route_list = !+local_domains smarthost.ref.example
17415 There is no difference in behaviour between these two routers as they stand.
17416 However, they behave differently if &%no_more%& is added to them. In the first
17417 example, the router is skipped if the domain does not match the &%domains%&
17418 precondition; the following router is always tried. If the router runs, it
17419 always matches the domain and so can never decline. Therefore, &%no_more%&
17420 would have no effect. In the second case, the router is never skipped; it
17421 always runs. However, if it doesn't match the domain, it declines. In this case
17422 &%no_more%& would prevent subsequent routers from running.
17425 .cindex "mail hub example"
17426 A &'mail hub'& is a host which receives mail for a number of domains via MX
17427 records in the DNS and delivers it via its own private routing mechanism. Often
17428 the final destinations are behind a firewall, with the mail hub being the one
17429 machine that can connect to machines both inside and outside the firewall. The
17430 &(manualroute)& router is usually used on a mail hub to route incoming messages
17431 to the correct hosts. For a small number of domains, the routing can be inline,
17432 using the &%route_list%& option, but for a larger number a file or database
17433 lookup is easier to manage.
17435 If the domain names are in fact the names of the machines to which the mail is
17436 to be sent by the mail hub, the configuration can be quite simple. For
17440 driver = manualroute
17441 transport = remote_smtp
17442 route_list = *.rhodes.tvs.example $domain
17444 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
17445 whose names are the same as the mail domains. A similar approach can be taken
17446 if the host name can be obtained from the domain name by a string manipulation
17447 that the expansion facilities can handle. Otherwise, a lookup based on the
17448 domain can be used to find the host:
17451 driver = manualroute
17452 transport = remote_smtp
17453 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
17455 The result of the lookup must be the name or IP address of the host (or
17456 hosts) to which the address is to be routed. If the lookup fails, the route
17457 data is empty, causing the router to decline. The address then passes to the
17461 .cindex "batched SMTP output example"
17462 .cindex "SMTP" "batched outgoing; example"
17463 You can use &(manualroute)& to deliver messages to pipes or files in batched
17464 SMTP format for onward transportation by some other means. This is one way of
17465 storing mail for a dial-up host when it is not connected. The route list entry
17466 can be as simple as a single domain name in a configuration like this:
17469 driver = manualroute
17470 transport = batchsmtp_appendfile
17471 route_list = saved.domain.example
17473 though often a pattern is used to pick up more than one domain. If there are
17474 several domains or groups of domains with different transport requirements,
17475 different transports can be listed in the routing information:
17478 driver = manualroute
17480 *.saved.domain1.example $domain batch_appendfile; \
17481 *.saved.domain2.example \
17482 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
17485 .vindex "&$domain$&"
17487 The first of these just passes the domain in the &$host$& variable, which
17488 doesn't achieve much (since it is also in &$domain$&), but the second does a
17489 file lookup to find a value to pass, causing the router to decline to handle
17490 the address if the lookup fails.
17493 .cindex "UUCP" "example of router for"
17494 Routing mail directly to UUCP software is a specific case of the use of
17495 &(manualroute)& in a gateway to another mail environment. This is an example of
17496 one way it can be done:
17502 command = /usr/local/bin/uux -r - \
17503 ${substr_-5:$host}!rmail ${local_part}
17504 return_fail_output = true
17509 driver = manualroute
17511 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
17513 The file &_/usr/local/exim/uucphosts_& contains entries like
17515 darksite.ethereal.example: darksite.UUCP
17517 It can be set up more simply without adding and removing &".UUCP"& but this way
17518 makes clear the distinction between the domain name
17519 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
17521 .ecindex IIDmanrou1
17522 .ecindex IIDmanrou2
17531 . ////////////////////////////////////////////////////////////////////////////
17532 . ////////////////////////////////////////////////////////////////////////////
17534 .chapter "The queryprogram router" "CHAPdriverlast"
17535 .scindex IIDquerou1 "&(queryprogram)& router"
17536 .scindex IIDquerou2 "routers" "&(queryprogram)&"
17537 .cindex "routing" "by external program"
17538 The &(queryprogram)& router routes an address by running an external command
17539 and acting on its output. This is an expensive way to route, and is intended
17540 mainly for use in lightly-loaded systems, or for performing experiments.
17541 However, if it is possible to use the precondition options (&%domains%&,
17542 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
17543 be used in special cases, even on a busy host. There are the following private
17545 .cindex "options" "&(queryprogram)& router"
17547 .option command queryprogram string&!! unset
17548 This option must be set. It specifies the command that is to be run. The
17549 command is split up into a command name and arguments, and then each is
17550 expanded separately (exactly as for a &(pipe)& transport, described in chapter
17551 &<<CHAPpipetransport>>&).
17554 .option command_group queryprogram string unset
17555 .cindex "gid (group id)" "in &(queryprogram)& router"
17556 This option specifies a gid to be set when running the command while routing an
17557 address for deliver. It must be set if &%command_user%& specifies a numerical
17558 uid. If it begins with a digit, it is interpreted as the numerical value of the
17559 gid. Otherwise it is looked up using &[getgrnam()]&.
17562 .option command_user queryprogram string unset
17563 .cindex "uid (user id)" "for &(queryprogram)&"
17564 This option must be set. It specifies the uid which is set when running the
17565 command while routing an address for delivery. If the value begins with a digit,
17566 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
17567 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
17568 not set, a value for the gid also.
17570 &*Warning:*& Changing uid and gid is possible only when Exim is running as
17571 root, which it does during a normal delivery in a conventional configuration.
17572 However, when an address is being verified during message reception, Exim is
17573 usually running as the Exim user, not as root. If the &(queryprogram)& router
17574 is called from a non-root process, Exim cannot change uid or gid before running
17575 the command. In this circumstance the command runs under the current uid and
17579 .option current_directory queryprogram string /
17580 This option specifies an absolute path which is made the current directory
17581 before running the command.
17584 .option timeout queryprogram time 1h
17585 If the command does not complete within the timeout period, its process group
17586 is killed and the message is frozen. A value of zero time specifies no
17590 The standard output of the command is connected to a pipe, which is read when
17591 the command terminates. It should consist of a single line of output,
17592 containing up to five fields, separated by white space. The maximum length of
17593 the line is 1023 characters. Longer lines are silently truncated. The first
17594 field is one of the following words (case-insensitive):
17597 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
17600 &'Decline'&: the router declines; pass the address to the next router, unless
17601 &%no_more%& is set.
17603 &'Fail'&: routing failed; do not pass the address to any more routers. Any
17604 subsequent text on the line is an error message. If the router is run as part
17605 of address verification during an incoming SMTP message, the message is
17606 included in the SMTP response.
17608 &'Defer'&: routing could not be completed at this time; try again later. Any
17609 subsequent text on the line is an error message which is logged. It is not
17610 included in any SMTP response.
17612 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
17614 &'Pass'&: pass the address to the next router (or the router specified by
17615 &%pass_router%&), overriding &%no_more%&.
17617 &'Redirect'&: the message is redirected. The remainder of the line is a list of
17618 new addresses, which are routed independently, starting with the first router,
17619 or the router specified by &%redirect_router%&, if set.
17622 When the first word is &'accept'&, the remainder of the line consists of a
17623 number of keyed data values, as follows (split into two lines here, to fit on
17626 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
17627 LOOKUP=byname|bydns DATA=<text>
17629 The data items can be given in any order, and all are optional. If no transport
17630 is included, the transport specified by the generic &%transport%& option is
17631 used. The list of hosts and the lookup type are needed only if the transport is
17632 an &(smtp)& transport that does not itself supply a list of hosts.
17634 The format of the list of hosts is the same as for the &(manualroute)& router.
17635 As well as host names and IP addresses with optional port numbers, as described
17636 in section &<<SECTformatonehostitem>>&, it may contain names followed by
17637 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
17638 (see section &<<SECThostshowused>>&).
17640 If the lookup type is not specified, Exim behaves as follows when trying to
17641 find an IP address for each host: First, a DNS lookup is done. If this yields
17642 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
17643 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
17644 result of the lookup is the result of that call.
17646 .vindex "&$address_data$&"
17647 If the DATA field is set, its value is placed in the &$address_data$&
17648 variable. For example, this return line
17650 accept hosts=x1.y.example:x2.y.example data="rule1"
17652 routes the address to the default transport, passing a list of two hosts. When
17653 the transport runs, the string &"rule1"& is in &$address_data$&.
17654 .ecindex IIDquerou1
17655 .ecindex IIDquerou2
17660 . ////////////////////////////////////////////////////////////////////////////
17661 . ////////////////////////////////////////////////////////////////////////////
17663 .chapter "The redirect router" "CHAPredirect"
17664 .scindex IIDredrou1 "&(redirect)& router"
17665 .scindex IIDredrou2 "routers" "&(redirect)&"
17666 .cindex "alias file" "in a &(redirect)& router"
17667 .cindex "address redirection" "&(redirect)& router"
17668 The &(redirect)& router handles several kinds of address redirection. Its most
17669 common uses are for resolving local part aliases from a central alias file
17670 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
17671 files, but it has many other potential uses. The incoming address can be
17672 redirected in several different ways:
17675 It can be replaced by one or more new addresses which are themselves routed
17678 It can be routed to be delivered to a given file or directory.
17680 It can be routed to be delivered to a specified pipe command.
17682 It can cause an automatic reply to be generated.
17684 It can be forced to fail, optionally with a custom error message.
17686 It can be temporarily deferred, optionally with a custom message.
17688 It can be discarded.
17691 The generic &%transport%& option must not be set for &(redirect)& routers.
17692 However, there are some private options which define transports for delivery to
17693 files and pipes, and for generating autoreplies. See the &%file_transport%&,
17694 &%pipe_transport%& and &%reply_transport%& descriptions below.
17698 .section "Redirection data" "SECID124"
17699 The router operates by interpreting a text string which it obtains either by
17700 expanding the contents of the &%data%& option, or by reading the entire
17701 contents of a file whose name is given in the &%file%& option. These two
17702 options are mutually exclusive. The first is commonly used for handling system
17703 aliases, in a configuration like this:
17707 data = ${lookup{$local_part}lsearch{/etc/aliases}}
17709 If the lookup fails, the expanded string in this example is empty. When the
17710 expansion of &%data%& results in an empty string, the router declines. A forced
17711 expansion failure also causes the router to decline; other expansion failures
17712 cause delivery to be deferred.
17714 A configuration using &%file%& is commonly used for handling users'
17715 &_.forward_& files, like this:
17720 file = $home/.forward
17723 If the file does not exist, or causes no action to be taken (for example, it is
17724 empty or consists only of comments), the router declines. &*Warning*&: This
17725 is not the case when the file contains syntactically valid items that happen to
17726 yield empty addresses, for example, items containing only RFC 2822 address
17731 .section "Forward files and address verification" "SECID125"
17732 .cindex "address redirection" "while verifying"
17733 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
17734 &_.forward_& files, as in the example above. There are two reasons for this:
17737 When Exim is receiving an incoming SMTP message from a remote host, it is
17738 running under the Exim uid, not as root. Exim is unable to change uid to read
17739 the file as the user, and it may not be able to read it as the Exim user. So in
17740 practice the router may not be able to operate.
17742 However, even when the router can operate, the existence of a &_.forward_& file
17743 is unimportant when verifying an address. What should be checked is whether the
17744 local part is a valid user name or not. Cutting out the redirection processing
17745 saves some resources.
17753 .section "Interpreting redirection data" "SECID126"
17754 .cindex "Sieve filter" "specifying in redirection data"
17755 .cindex "filter" "specifying in redirection data"
17756 The contents of the data string, whether obtained from &%data%& or &%file%&,
17757 can be interpreted in two different ways:
17760 If the &%allow_filter%& option is set true, and the data begins with the text
17761 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
17762 &'filtering'& instructions in the form of an Exim or Sieve filter file,
17763 respectively. Details of the syntax and semantics of filter files are described
17764 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
17765 document is intended for use by end users.
17767 Otherwise, the data must be a comma-separated list of redirection items, as
17768 described in the next section.
17771 When a message is redirected to a file (a &"mail folder"&), the file name given
17772 in a non-filter redirection list must always be an absolute path. A filter may
17773 generate a relative path &-- how this is handled depends on the transport's
17774 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
17775 for the &(appendfile)& transport.
17779 .section "Items in a non-filter redirection list" "SECTitenonfilred"
17780 .cindex "address redirection" "non-filter list items"
17781 When the redirection data is not an Exim or Sieve filter, for example, if it
17782 comes from a conventional alias or forward file, it consists of a list of
17783 addresses, file names, pipe commands, or certain special items (see section
17784 &<<SECTspecitredli>>& below). The special items can be individually enabled or
17785 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
17786 depending on their default values. The items in the list are separated by
17787 commas or newlines.
17788 If a comma is required in an item, the entire item must be enclosed in double
17791 Lines starting with a # character are comments, and are ignored, and # may
17792 also appear following a comma, in which case everything between the # and the
17793 next newline character is ignored.
17795 If an item is entirely enclosed in double quotes, these are removed. Otherwise
17796 double quotes are retained because some forms of mail address require their use
17797 (but never to enclose the entire address). In the following description,
17798 &"item"& refers to what remains after any surrounding double quotes have been
17801 .vindex "&$local_part$&"
17802 &*Warning*&: If you use an Exim expansion to construct a redirection address,
17803 and the expansion contains a reference to &$local_part$&, you should make use
17804 of the &%quote_local_part%& expansion operator, in case the local part contains
17805 special characters. For example, to redirect all mail for the domain
17806 &'obsolete.example'&, retaining the existing local part, you could use this
17809 data = ${quote_local_part:$local_part}@newdomain.example
17813 .section "Redirecting to a local mailbox" "SECTredlocmai"
17814 .cindex "routing" "loops in"
17815 .cindex "loop" "while routing, avoidance of"
17816 .cindex "address redirection" "to local mailbox"
17817 A redirection item may safely be the same as the address currently under
17818 consideration. This does not cause a routing loop, because a router is
17819 automatically skipped if any ancestor of the address that is being processed
17820 is the same as the current address and was processed by the current router.
17821 Such an address is therefore passed to the following routers, so it is handled
17822 as if there were no redirection. When making this loop-avoidance test, the
17823 complete local part, including any prefix or suffix, is used.
17825 .cindex "address redirection" "local part without domain"
17826 Specifying the same local part without a domain is a common usage in personal
17827 filter files when the user wants to have messages delivered to the local
17828 mailbox and also forwarded elsewhere. For example, the user whose login is
17829 &'cleo'& might have a &_.forward_& file containing this:
17831 cleo, cleopatra@egypt.example
17833 .cindex "backslash in alias file"
17834 .cindex "alias file" "backslash in"
17835 For compatibility with other MTAs, such unqualified local parts may be
17836 preceded by &"\"&, but this is not a requirement for loop prevention. However,
17837 it does make a difference if more than one domain is being handled
17840 If an item begins with &"\"& and the rest of the item parses as a valid RFC
17841 2822 address that does not include a domain, the item is qualified using the
17842 domain of the incoming address. In the absence of a leading &"\"&, unqualified
17843 addresses are qualified using the value in &%qualify_recipient%&, but you can
17844 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
17846 Care must be taken if there are alias names for local users.
17847 Consider an MTA handling a single local domain where the system alias file
17852 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
17853 messages in the local mailbox, and also forward copies elsewhere. He creates
17856 Sam.Reman, spqr@reme.elsewhere.example
17858 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
17859 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
17860 second time round, because it has previously routed it,
17861 and the following routers presumably cannot handle the alias. The forward file
17862 should really contain
17864 spqr, spqr@reme.elsewhere.example
17866 but because this is such a common error, the &%check_ancestor%& option (see
17867 below) exists to provide a way to get round it. This is normally set on a
17868 &(redirect)& router that is handling users' &_.forward_& files.
17872 .section "Special items in redirection lists" "SECTspecitredli"
17873 In addition to addresses, the following types of item may appear in redirection
17874 lists (that is, in non-filter redirection data):
17877 .cindex "pipe" "in redirection list"
17878 .cindex "address redirection" "to pipe"
17879 An item is treated as a pipe command if it begins with &"|"& and does not parse
17880 as a valid RFC 2822 address that includes a domain. A transport for running the
17881 command must be specified by the &%pipe_transport%& option.
17882 Normally, either the router or the transport specifies a user and a group under
17883 which to run the delivery. The default is to use the Exim user and group.
17885 Single or double quotes can be used for enclosing the individual arguments of
17886 the pipe command; no interpretation of escapes is done for single quotes. If
17887 the command contains a comma character, it is necessary to put the whole item
17888 in double quotes, for example:
17890 "|/some/command ready,steady,go"
17892 since items in redirection lists are terminated by commas. Do not, however,
17893 quote just the command. An item such as
17895 |"/some/command ready,steady,go"
17897 is interpreted as a pipe with a rather strange command name, and no arguments.
17900 .cindex "file" "in redirection list"
17901 .cindex "address redirection" "to file"
17902 An item is interpreted as a path name if it begins with &"/"& and does not
17903 parse as a valid RFC 2822 address that includes a domain. For example,
17905 /home/world/minbari
17907 is treated as a file name, but
17909 /s=molari/o=babylon/@x400gate.way
17911 is treated as an address. For a file name, a transport must be specified using
17912 the &%file_transport%& option. However, if the generated path name ends with a
17913 forward slash character, it is interpreted as a directory name rather than a
17914 file name, and &%directory_transport%& is used instead.
17916 Normally, either the router or the transport specifies a user and a group under
17917 which to run the delivery. The default is to use the Exim user and group.
17919 .cindex "&_/dev/null_&"
17920 However, if a redirection item is the path &_/dev/null_&, delivery to it is
17921 bypassed at a high level, and the log entry shows &"**bypassed**"&
17922 instead of a transport name. In this case the user and group are not used.
17925 .cindex "included address list"
17926 .cindex "address redirection" "included external list"
17927 If an item is of the form
17929 :include:<path name>
17931 a list of further items is taken from the given file and included at that
17932 point. &*Note*&: Such a file can not be a filter file; it is just an
17933 out-of-line addition to the list. The items in the included list are separated
17934 by commas or newlines and are not subject to expansion. If this is the first
17935 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
17936 the alias name. This example is incorrect:
17938 list1 :include:/opt/lists/list1
17940 It must be given as
17942 list1: :include:/opt/lists/list1
17945 .cindex "address redirection" "to black hole"
17946 Sometimes you want to throw away mail to a particular local part. Making the
17947 &%data%& option expand to an empty string does not work, because that causes
17948 the router to decline. Instead, the alias item
17949 .cindex "black hole"
17950 .cindex "abandoning mail"
17951 &':blackhole:'& can be used. It does what its name implies. No delivery is
17952 done, and no error message is generated. This has the same effect as specifing
17953 &_/dev/null_& as a destination, but it can be independently disabled.
17955 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
17956 delivery is done for the original local part, even if other redirection items
17957 are present. If you are generating a multi-item list (for example, by reading a
17958 database) and need the ability to provide a no-op item, you must use
17962 .cindex "delivery" "forcing failure"
17963 .cindex "delivery" "forcing deferral"
17964 .cindex "failing delivery" "forcing"
17965 .cindex "deferred delivery, forcing"
17966 .cindex "customizing" "failure message"
17967 An attempt to deliver a particular address can be deferred or forced to fail by
17968 redirection items of the form
17973 respectively. When a redirection list contains such an item, it applies
17974 to the entire redirection; any other items in the list are ignored. Any
17975 text following &':fail:'& or &':defer:'& is placed in the error text
17976 associated with the failure. For example, an alias file might contain:
17978 X.Employee: :fail: Gone away, no forwarding address
17980 In the case of an address that is being verified from an ACL or as the subject
17982 .cindex "VRFY" "error text, display of"
17983 VRFY command, the text is included in the SMTP error response by
17985 .cindex "EXPN" "error text, display of"
17986 The text is not included in the response to an EXPN command. In non-SMTP cases
17987 the text is included in the error message that Exim generates.
17989 .cindex "SMTP" "error codes"
17990 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
17991 &':fail:'&. However, if the message starts with three digits followed by a
17992 space, optionally followed by an extended code of the form &'n.n.n'&, also
17993 followed by a space, and the very first digit is the same as the default error
17994 code, the code from the message is used instead. If the very first digit is
17995 incorrect, a panic error is logged, and the default code is used. You can
17996 suppress the use of the supplied code in a redirect router by setting the
17997 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
18000 .vindex "&$acl_verify_message$&"
18001 In an ACL, an explicitly provided message overrides the default, but the
18002 default message is available in the variable &$acl_verify_message$& and can
18003 therefore be included in a custom message if this is desired.
18005 Normally the error text is the rest of the redirection list &-- a comma does
18006 not terminate it &-- but a newline does act as a terminator. Newlines are not
18007 normally present in alias expansions. In &(lsearch)& lookups they are removed
18008 as part of the continuation process, but they may exist in other kinds of
18009 lookup and in &':include:'& files.
18011 During routing for message delivery (as opposed to verification), a redirection
18012 containing &':fail:'& causes an immediate failure of the incoming address,
18013 whereas &':defer:'& causes the message to remain on the queue so that a
18014 subsequent delivery attempt can happen at a later time. If an address is
18015 deferred for too long, it will ultimately fail, because the normal retry
18019 .cindex "alias file" "exception to default"
18020 Sometimes it is useful to use a single-key search type with a default (see
18021 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
18022 for exceptions to the default. These can be handled by aliasing them to
18023 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
18024 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
18025 results in an empty redirection list has the same effect.
18029 .section "Duplicate addresses" "SECTdupaddr"
18030 .cindex "duplicate addresses"
18031 .cindex "address duplicate, discarding"
18032 .cindex "pipe" "duplicated"
18033 Exim removes duplicate addresses from the list to which it is delivering, so as
18034 to deliver just one copy to each address. This does not apply to deliveries
18035 routed to pipes by different immediate parent addresses, but an indirect
18036 aliasing scheme of the type
18038 pipe: |/some/command $local_part
18042 does not work with a message that is addressed to both local parts, because
18043 when the second is aliased to the intermediate local part &"pipe"& it gets
18044 discarded as being the same as a previously handled address. However, a scheme
18047 localpart1: |/some/command $local_part
18048 localpart2: |/some/command $local_part
18050 does result in two different pipe deliveries, because the immediate parents of
18051 the pipes are distinct.
18055 .section "Repeated redirection expansion" "SECID128"
18056 .cindex "repeated redirection expansion"
18057 .cindex "address redirection" "repeated for each delivery attempt"
18058 When a message cannot be delivered to all of its recipients immediately,
18059 leading to two or more delivery attempts, redirection expansion is carried out
18060 afresh each time for those addresses whose children were not all previously
18061 delivered. If redirection is being used as a mailing list, this can lead to new
18062 members of the list receiving copies of old messages. The &%one_time%& option
18063 can be used to avoid this.
18066 .section "Errors in redirection lists" "SECID129"
18067 .cindex "address redirection" "errors"
18068 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
18069 error is skipped, and an entry is written to the main log. This may be useful
18070 for mailing lists that are automatically managed. Otherwise, if an error is
18071 detected while generating the list of new addresses, the original address is
18072 deferred. See also &%syntax_errors_to%&.
18076 .section "Private options for the redirect router" "SECID130"
18078 .cindex "options" "&(redirect)& router"
18079 The private options for the &(redirect)& router are as follows:
18082 .option allow_defer redirect boolean false
18083 Setting this option allows the use of &':defer:'& in non-filter redirection
18084 data, or the &%defer%& command in an Exim filter file.
18087 .option allow_fail redirect boolean false
18088 .cindex "failing delivery" "from filter"
18089 If this option is true, the &':fail:'& item can be used in a redirection list,
18090 and the &%fail%& command may be used in an Exim filter file.
18093 .option allow_filter redirect boolean false
18094 .cindex "filter" "enabling use of"
18095 .cindex "Sieve filter" "enabling use of"
18096 Setting this option allows Exim to interpret redirection data that starts with
18097 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
18098 are some features of Exim filter files that some administrators may wish to
18099 lock out; see the &%forbid_filter_%&&'xxx'& options below.
18101 It is also possible to lock out Exim filters or Sieve filters while allowing
18102 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
18105 The filter is run using the uid and gid set by the generic &%user%& and
18106 &%group%& options. These take their defaults from the password data if
18107 &%check_local_user%& is set, so in the normal case of users' personal filter
18108 files, the filter is run as the relevant user. When &%allow_filter%& is set
18109 true, Exim insists that either &%check_local_user%& or &%user%& is set.
18113 .option allow_freeze redirect boolean false
18114 .cindex "freezing messages" "allowing in filter"
18115 Setting this option allows the use of the &%freeze%& command in an Exim filter.
18116 This command is more normally encountered in system filters, and is disabled by
18117 default for redirection filters because it isn't something you usually want to
18118 let ordinary users do.
18122 .option check_ancestor redirect boolean false
18123 This option is concerned with handling generated addresses that are the same
18124 as some address in the list of redirection ancestors of the current address.
18125 Although it is turned off by default in the code, it is set in the default
18126 configuration file for handling users' &_.forward_& files. It is recommended
18127 for this use of the &(redirect)& router.
18129 When &%check_ancestor%& is set, if a generated address (including the domain)
18130 is the same as any ancestor of the current address, it is replaced by a copy of
18131 the current address. This helps in the case where local part A is aliased to B,
18132 and B has a &_.forward_& file pointing back to A. For example, within a single
18133 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
18134 &_&~jb/.forward_& contains:
18136 \Joe.Bloggs, <other item(s)>
18138 Without the &%check_ancestor%& setting, either local part (&"jb"& or
18139 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
18140 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
18141 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
18142 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
18143 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
18144 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
18145 original address. See also the &%repeat_use%& option below.
18148 .option check_group redirect boolean "see below"
18149 When the &%file%& option is used, the group owner of the file is checked only
18150 when this option is set. The permitted groups are those listed in the
18151 &%owngroups%& option, together with the user's default group if
18152 &%check_local_user%& is set. If the file has the wrong group, routing is
18153 deferred. The default setting for this option is true if &%check_local_user%&
18154 is set and the &%modemask%& option permits the group write bit, or if the
18155 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
18159 .option check_owner redirect boolean "see below"
18160 When the &%file%& option is used, the owner of the file is checked only when
18161 this option is set. If &%check_local_user%& is set, the local user is
18162 permitted; otherwise the owner must be one of those listed in the &%owners%&
18163 option. The default value for this option is true if &%check_local_user%& or
18164 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
18167 .option data redirect string&!! unset
18168 This option is mutually exclusive with &%file%&. One or other of them must be
18169 set, but not both. The contents of &%data%& are expanded, and then used as the
18170 list of forwarding items, or as a set of filtering instructions. If the
18171 expansion is forced to fail, or the result is an empty string or a string that
18172 has no effect (consists entirely of comments), the router declines.
18174 When filtering instructions are used, the string must begin with &"#Exim
18175 filter"&, and all comments in the string, including this initial one, must be
18176 terminated with newline characters. For example:
18178 data = #Exim filter\n\
18179 if $h_to: contains Exim then save $home/mail/exim endif
18181 If you are reading the data from a database where newlines cannot be included,
18182 you can use the &${sg}$& expansion item to turn the escape string of your
18183 choice into a newline.
18186 .option directory_transport redirect string&!! unset
18187 A &(redirect)& router sets up a direct delivery to a directory when a path name
18188 ending with a slash is specified as a new &"address"&. The transport used is
18189 specified by this option, which, after expansion, must be the name of a
18190 configured transport. This should normally be an &(appendfile)& transport.
18193 .option file redirect string&!! unset
18194 This option specifies the name of a file that contains the redirection data. It
18195 is mutually exclusive with the &%data%& option. The string is expanded before
18196 use; if the expansion is forced to fail, the router declines. Other expansion
18197 failures cause delivery to be deferred. The result of a successful expansion
18198 must be an absolute path. The entire file is read and used as the redirection
18199 data. If the data is an empty string or a string that has no effect (consists
18200 entirely of comments), the router declines.
18202 .cindex "NFS" "checking for file existence"
18203 If the attempt to open the file fails with a &"does not exist"& error, Exim
18204 runs a check on the containing directory,
18205 unless &%ignore_enotdir%& is true (see below).
18206 If the directory does not appear to exist, delivery is deferred. This can
18207 happen when users' &_.forward_& files are in NFS-mounted directories, and there
18208 is a mount problem. If the containing directory does exist, but the file does
18209 not, the router declines.
18212 .option file_transport redirect string&!! unset
18213 .vindex "&$address_file$&"
18214 A &(redirect)& router sets up a direct delivery to a file when a path name not
18215 ending in a slash is specified as a new &"address"&. The transport used is
18216 specified by this option, which, after expansion, must be the name of a
18217 configured transport. This should normally be an &(appendfile)& transport. When
18218 it is running, the file name is in &$address_file$&.
18221 .option filter_prepend_home redirect boolean true
18222 When this option is true, if a &(save)& command in an Exim filter specifies a
18223 relative path, and &$home$& is defined, it is automatically prepended to the
18224 relative path. If this option is set false, this action does not happen. The
18225 relative path is then passed to the transport unmodified.
18228 .option forbid_blackhole redirect boolean false
18229 If this option is true, the &':blackhole:'& item may not appear in a
18233 .option forbid_exim_filter redirect boolean false
18234 If this option is set true, only Sieve filters are permitted when
18235 &%allow_filter%& is true.
18240 .option forbid_file redirect boolean false
18241 .cindex "delivery" "to file; forbidding"
18242 .cindex "Sieve filter" "forbidding delivery to a file"
18243 .cindex "Sieve filter" "&""keep""& facility; disabling"
18244 If this option is true, this router may not generate a new address that
18245 specifies delivery to a local file or directory, either from a filter or from a
18246 conventional forward file. This option is forced to be true if &%one_time%& is
18247 set. It applies to Sieve filters as well as to Exim filters, but if true, it
18248 locks out the Sieve's &"keep"& facility.
18251 .option forbid_filter_dlfunc redirect boolean false
18252 .cindex "filter" "locking out certain features"
18253 If this option is true, string expansions in Exim filters are not allowed to
18254 make use of the &%dlfunc%& expansion facility to run dynamically loaded
18257 .option forbid_filter_existstest redirect boolean false
18258 .cindex "expansion" "statting a file"
18259 If this option is true, string expansions in Exim filters are not allowed to
18260 make use of the &%exists%& condition or the &%stat%& expansion item.
18262 .option forbid_filter_logwrite redirect boolean false
18263 If this option is true, use of the logging facility in Exim filters is not
18264 permitted. Logging is in any case available only if the filter is being run
18265 under some unprivileged uid (which is normally the case for ordinary users'
18266 &_.forward_& files).
18269 .option forbid_filter_lookup redirect boolean false
18270 If this option is true, string expansions in Exim filter files are not allowed
18271 to make use of &%lookup%& items.
18274 .option forbid_filter_perl redirect boolean false
18275 This option has an effect only if Exim is built with embedded Perl support. If
18276 it is true, string expansions in Exim filter files are not allowed to make use
18277 of the embedded Perl support.
18280 .option forbid_filter_readfile redirect boolean false
18281 If this option is true, string expansions in Exim filter files are not allowed
18282 to make use of &%readfile%& items.
18285 .option forbid_filter_readsocket redirect boolean false
18286 If this option is true, string expansions in Exim filter files are not allowed
18287 to make use of &%readsocket%& items.
18290 .option forbid_filter_reply redirect boolean false
18291 If this option is true, this router may not generate an automatic reply
18292 message. Automatic replies can be generated only from Exim or Sieve filter
18293 files, not from traditional forward files. This option is forced to be true if
18294 &%one_time%& is set.
18297 .option forbid_filter_run redirect boolean false
18298 If this option is true, string expansions in Exim filter files are not allowed
18299 to make use of &%run%& items.
18302 .option forbid_include redirect boolean false
18303 If this option is true, items of the form
18305 :include:<path name>
18307 are not permitted in non-filter redirection lists.
18310 .option forbid_pipe redirect boolean false
18311 .cindex "delivery" "to pipe; forbidding"
18312 If this option is true, this router may not generate a new address which
18313 specifies delivery to a pipe, either from an Exim filter or from a conventional
18314 forward file. This option is forced to be true if &%one_time%& is set.
18317 .option forbid_sieve_filter redirect boolean false
18318 If this option is set true, only Exim filters are permitted when
18319 &%allow_filter%& is true.
18322 .cindex "SMTP" "error codes"
18323 .option forbid_smtp_code redirect boolean false
18324 If this option is set true, any SMTP error codes that are present at the start
18325 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
18326 the default codes (451 and 550, respectively) are always used.
18331 .option hide_child_in_errmsg redirect boolean false
18332 .cindex "bounce message" "redirection details; suppressing"
18333 If this option is true, it prevents Exim from quoting a child address if it
18334 generates a bounce or delay message for it. Instead it says &"an address
18335 generated from <&'the top level address'&>"&. Of course, this applies only to
18336 bounces generated locally. If a message is forwarded to another host, &'its'&
18337 bounce may well quote the generated address.
18340 .option ignore_eacces redirect boolean false
18342 If this option is set and an attempt to open a redirection file yields the
18343 EACCES error (permission denied), the &(redirect)& router behaves as if the
18344 file did not exist.
18347 .option ignore_enotdir redirect boolean false
18349 If this option is set and an attempt to open a redirection file yields the
18350 ENOTDIR error (something on the path is not a directory), the &(redirect)&
18351 router behaves as if the file did not exist.
18353 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
18354 router that has the &%file%& option set discovers that the file does not exist
18355 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
18356 against unmounted NFS directories. If the parent can not be statted, delivery
18357 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
18358 is set, because that option tells Exim to ignore &"something on the path is not
18359 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
18360 that some operating systems give ENOENT where others give ENOTDIR.
18364 .option include_directory redirect string unset
18365 If this option is set, the path names of any &':include:'& items in a
18366 redirection list must start with this directory.
18369 .option modemask redirect "octal integer" 022
18370 This specifies mode bits which must not be set for a file specified by the
18371 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
18374 .option one_time redirect boolean false
18375 .cindex "one-time aliasing/forwarding expansion"
18376 .cindex "alias file" "one-time expansion"
18377 .cindex "forward file" "one-time expansion"
18378 .cindex "mailing lists" "one-time expansion"
18379 .cindex "address redirection" "one-time expansion"
18380 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
18381 files each time it tries to deliver a message causes a problem when one or more
18382 of the generated addresses fails be delivered at the first attempt. The problem
18383 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
18384 but of what happens when the redirection list changes during the time that the
18385 message is on Exim's queue. This is particularly true in the case of mailing
18386 lists, where new subscribers might receive copies of messages that were posted
18387 before they subscribed.
18389 If &%one_time%& is set and any addresses generated by the router fail to
18390 deliver at the first attempt, the failing addresses are added to the message as
18391 &"top level"& addresses, and the parent address that generated them is marked
18392 &"delivered"&. Thus, redirection does not happen again at the next delivery
18395 &*Warning 1*&: Any header line addition or removal that is specified by this
18396 router would be lost if delivery did not succeed at the first attempt. For this
18397 reason, the &%headers_add%& and &%headers_remove%& generic options are not
18398 permitted when &%one_time%& is set.
18400 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
18401 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
18402 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
18404 &*Warning 3*&: The &%unseen%& generic router option may not be set with
18407 The original top-level address is remembered with each of the generated
18408 addresses, and is output in any log messages. However, any intermediate parent
18409 addresses are not recorded. This makes a difference to the log only if
18410 &%all_parents%& log selector is set. It is expected that &%one_time%& will
18411 typically be used for mailing lists, where there is normally just one level of
18415 .option owners redirect "string list" unset
18416 .cindex "ownership" "alias file"
18417 .cindex "ownership" "forward file"
18418 .cindex "alias file" "ownership"
18419 .cindex "forward file" "ownership"
18420 This specifies a list of permitted owners for the file specified by &%file%&.
18421 This list is in addition to the local user when &%check_local_user%& is set.
18422 See &%check_owner%& above.
18425 .option owngroups redirect "string list" unset
18426 This specifies a list of permitted groups for the file specified by &%file%&.
18427 The list is in addition to the local user's primary group when
18428 &%check_local_user%& is set. See &%check_group%& above.
18431 .option pipe_transport redirect string&!! unset
18432 .vindex "&$address_pipe$&"
18433 A &(redirect)& router sets up a direct delivery to a pipe when a string
18434 starting with a vertical bar character is specified as a new &"address"&. The
18435 transport used is specified by this option, which, after expansion, must be the
18436 name of a configured transport. This should normally be a &(pipe)& transport.
18437 When the transport is run, the pipe command is in &$address_pipe$&.
18440 .option qualify_domain redirect string&!! unset
18441 .vindex "&$qualify_recipient$&"
18442 If this option is set, and an unqualified address (one without a domain) is
18443 generated, and that address would normally be qualified by the global setting
18444 in &%qualify_recipient%&, it is instead qualified with the domain specified by
18445 expanding this string. If the expansion fails, the router declines. If you want
18446 to revert to the default, you can have the expansion generate
18447 &$qualify_recipient$&.
18449 This option applies to all unqualified addresses generated by Exim filters,
18450 but for traditional &_.forward_& files, it applies only to addresses that are
18451 not preceded by a backslash. Sieve filters cannot generate unqualified
18454 .option qualify_preserve_domain redirect boolean false
18455 .cindex "domain" "in redirection; preserving"
18456 .cindex "preserving domain in redirection"
18457 .cindex "address redirection" "domain; preserving"
18458 If this option is set, the router's local &%qualify_domain%& option must not be
18459 set (a configuration error occurs if it is). If an unqualified address (one
18460 without a domain) is generated, it is qualified with the domain of the parent
18461 address (the immediately preceding ancestor) instead of the global
18462 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
18463 this applies whether or not the address is preceded by a backslash.
18466 .option repeat_use redirect boolean true
18467 If this option is set false, the router is skipped for a child address that has
18468 any ancestor that was routed by this router. This test happens before any of
18469 the other preconditions are tested. Exim's default anti-looping rules skip
18470 only when the ancestor is the same as the current address. See also
18471 &%check_ancestor%& above and the generic &%redirect_router%& option.
18474 .option reply_transport redirect string&!! unset
18475 A &(redirect)& router sets up an automatic reply when a &%mail%& or
18476 &%vacation%& command is used in a filter file. The transport used is specified
18477 by this option, which, after expansion, must be the name of a configured
18478 transport. This should normally be an &(autoreply)& transport. Other transports
18479 are unlikely to do anything sensible or useful.
18482 .option rewrite redirect boolean true
18483 .cindex "address redirection" "disabling rewriting"
18484 If this option is set false, addresses generated by the router are not
18485 subject to address rewriting. Otherwise, they are treated like new addresses
18486 and are rewritten according to the global rewriting rules.
18489 .option sieve_subaddress redirect string&!! unset
18490 The value of this option is passed to a Sieve filter to specify the
18491 :subaddress part of an address.
18493 .option sieve_useraddress redirect string&!! unset
18494 The value of this option is passed to a Sieve filter to specify the :user part
18495 of an address. However, if it is unset, the entire original local part
18496 (including any prefix or suffix) is used for :user.
18499 .option sieve_vacation_directory redirect string&!! unset
18500 .cindex "Sieve filter" "vacation directory"
18501 To enable the &"vacation"& extension for Sieve filters, you must set
18502 &%sieve_vacation_directory%& to the directory where vacation databases are held
18503 (do not put anything else in that directory), and ensure that the
18504 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
18505 needs their own directory; Exim will create it if necessary.
18509 .option skip_syntax_errors redirect boolean false
18510 .cindex "forward file" "broken"
18511 .cindex "address redirection" "broken files"
18512 .cindex "alias file" "broken"
18513 .cindex "broken alias or forward files"
18514 .cindex "ignoring faulty addresses"
18515 .cindex "skipping faulty addresses"
18516 .cindex "error" "skipping bad syntax"
18517 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
18518 non-filter redirection data are skipped, and each failing address is logged. If
18519 &%syntax_errors_to%& is set, a message is sent to the address it defines,
18520 giving details of the failures. If &%syntax_errors_text%& is set, its contents
18521 are expanded and placed at the head of the error message generated by
18522 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
18523 be the same address as the generic &%errors_to%& option. The
18524 &%skip_syntax_errors%& option is often used when handling mailing lists.
18526 If all the addresses in a redirection list are skipped because of syntax
18527 errors, the router declines to handle the original address, and it is passed to
18528 the following routers.
18530 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
18531 error in the filter causes filtering to be abandoned without any action being
18532 taken. The incident is logged, and the router declines to handle the address,
18533 so it is passed to the following routers.
18535 .cindex "Sieve filter" "syntax errors in"
18536 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
18537 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
18538 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
18540 &%skip_syntax_errors%& can be used to specify that errors in users' forward
18541 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
18542 option, used with an address that does not get redirected, can be used to
18543 notify users of these errors, by means of a router like this:
18549 file = $home/.forward
18550 file_transport = address_file
18551 pipe_transport = address_pipe
18552 reply_transport = address_reply
18555 syntax_errors_to = real-$local_part@$domain
18556 syntax_errors_text = \
18557 This is an automatically generated message. An error has\n\
18558 been found in your .forward file. Details of the error are\n\
18559 reported below. While this error persists, you will receive\n\
18560 a copy of this message for every message that is addressed\n\
18561 to you. If your .forward file is a filter file, or if it is\n\
18562 a non-filter file containing no valid forwarding addresses,\n\
18563 a copy of each incoming message will be put in your normal\n\
18564 mailbox. If a non-filter file contains at least one valid\n\
18565 forwarding address, forwarding to the valid addresses will\n\
18566 happen, and those will be the only deliveries that occur.
18568 You also need a router to ensure that local addresses that are prefixed by
18569 &`real-`& are recognized, but not forwarded or filtered. For example, you could
18570 put this immediately before the &(userforward)& router:
18575 local_part_prefix = real-
18576 transport = local_delivery
18578 For security, it would probably be a good idea to restrict the use of this
18579 router to locally-generated messages, using a condition such as this:
18581 condition = ${if match {$sender_host_address}\
18582 {\N^(|127\.0\.0\.1)$\N}}
18586 .option syntax_errors_text redirect string&!! unset
18587 See &%skip_syntax_errors%& above.
18590 .option syntax_errors_to redirect string unset
18591 See &%skip_syntax_errors%& above.
18592 .ecindex IIDredrou1
18593 .ecindex IIDredrou2
18600 . ////////////////////////////////////////////////////////////////////////////
18601 . ////////////////////////////////////////////////////////////////////////////
18603 .chapter "Environment for running local transports" "CHAPenvironment" &&&
18604 "Environment for local transports"
18605 .scindex IIDenvlotra1 "local transports" "environment for"
18606 .scindex IIDenvlotra2 "environment for local transports"
18607 .scindex IIDenvlotra3 "transport" "local; environment for"
18608 Local transports handle deliveries to files and pipes. (The &(autoreply)&
18609 transport can be thought of as similar to a pipe.) Exim always runs transports
18610 in subprocesses, under specified uids and gids. Typical deliveries to local
18611 mailboxes run under the uid and gid of the local user.
18613 Exim also sets a specific current directory while running the transport; for
18614 some transports a home directory setting is also relevant. The &(pipe)&
18615 transport is the only one that sets up environment variables; see section
18616 &<<SECTpipeenv>>& for details.
18618 The values used for the uid, gid, and the directories may come from several
18619 different places. In many cases, the router that handles the address associates
18620 settings with that address as a result of its &%check_local_user%&, &%group%&,
18621 or &%user%& options. However, values may also be given in the transport's own
18622 configuration, and these override anything that comes from the router.
18626 .section "Concurrent deliveries" "SECID131"
18627 .cindex "concurrent deliveries"
18628 .cindex "simultaneous deliveries"
18629 If two different messages for the same local recipient arrive more or less
18630 simultaneously, the two delivery processes are likely to run concurrently. When
18631 the &(appendfile)& transport is used to write to a file, Exim applies locking
18632 rules to stop concurrent processes from writing to the same file at the same
18635 However, when you use a &(pipe)& transport, it is up to you to arrange any
18636 locking that is needed. Here is a silly example:
18640 command = /bin/sh -c 'cat >>/some/file'
18642 This is supposed to write the message at the end of the file. However, if two
18643 messages arrive at the same time, the file will be scrambled. You can use the
18644 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
18645 file using the same algorithm that Exim itself uses.
18650 .section "Uids and gids" "SECTenvuidgid"
18651 .cindex "local transports" "uid and gid"
18652 .cindex "transport" "local; uid and gid"
18653 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
18654 overrides any group that the router set in the address, even if &%user%& is not
18655 set for the transport. This makes it possible, for example, to run local mail
18656 delivery under the uid of the recipient (set by the router), but in a special
18657 group (set by the transport). For example:
18660 # User/group are set by check_local_user in this router
18664 transport = group_delivery
18667 # This transport overrides the group
18669 driver = appendfile
18670 file = /var/spool/mail/$local_part
18673 If &%user%& is set for a transport, its value overrides what is set in the
18674 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
18675 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
18678 .oindex "&%initgroups%&"
18679 When the uid is taken from the transport's configuration, the &[initgroups()]&
18680 function is called for the groups associated with that uid if the
18681 &%initgroups%& option is set for the transport. When the uid is not specified
18682 by the transport, but is associated with the address by a router, the option
18683 for calling &[initgroups()]& is taken from the router configuration.
18685 .cindex "&(pipe)& transport" "uid for"
18686 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
18687 is set and &%user%& is not set, the uid of the process that called Exim to
18688 receive the message is used, and if &%group%& is not set, the corresponding
18689 original gid is also used.
18691 This is the detailed preference order for obtaining a gid; the first of the
18692 following that is set is used:
18695 A &%group%& setting of the transport;
18697 A &%group%& setting of the router;
18699 A gid associated with a user setting of the router, either as a result of
18700 &%check_local_user%& or an explicit non-numeric &%user%& setting;
18702 The group associated with a non-numeric &%user%& setting of the transport;
18704 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
18705 the uid is the creator's uid;
18707 The Exim gid if the Exim uid is being used as a default.
18710 If, for example, the user is specified numerically on the router and there are
18711 no group settings, no gid is available. In this situation, an error occurs.
18712 This is different for the uid, for which there always is an ultimate default.
18713 The first of the following that is set is used:
18716 A &%user%& setting of the transport;
18718 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
18720 A &%user%& setting of the router;
18722 A &%check_local_user%& setting of the router;
18727 Of course, an error will still occur if the uid that is chosen is on the
18728 &%never_users%& list.
18734 .section "Current and home directories" "SECID132"
18735 .cindex "current directory for local transport"
18736 .cindex "home directory" "for local transport"
18737 .cindex "transport" "local; home directory for"
18738 .cindex "transport" "local; current directory for"
18739 Routers may set current and home directories for local transports by means of
18740 the &%transport_current_directory%& and &%transport_home_directory%& options.
18741 However, if the transport's &%current_directory%& or &%home_directory%& options
18742 are set, they override the router's values. In detail, the home directory
18743 for a local transport is taken from the first of these values that is set:
18746 The &%home_directory%& option on the transport;
18748 The &%transport_home_directory%& option on the router;
18750 The password data if &%check_local_user%& is set on the router;
18752 The &%router_home_directory%& option on the router.
18755 The current directory is taken from the first of these values that is set:
18758 The &%current_directory%& option on the transport;
18760 The &%transport_current_directory%& option on the router.
18764 If neither the router nor the transport sets a current directory, Exim uses the
18765 value of the home directory, if it is set. Otherwise it sets the current
18766 directory to &_/_& before running a local transport.
18770 .section "Expansion variables derived from the address" "SECID133"
18771 .vindex "&$domain$&"
18772 .vindex "&$local_part$&"
18773 .vindex "&$original_domain$&"
18774 Normally a local delivery is handling a single address, and in that case the
18775 variables such as &$domain$& and &$local_part$& are set during local
18776 deliveries. However, in some circumstances more than one address may be handled
18777 at once (for example, while writing batch SMTP for onward transmission by some
18778 other means). In this case, the variables associated with the local part are
18779 never set, &$domain$& is set only if all the addresses have the same domain,
18780 and &$original_domain$& is never set.
18781 .ecindex IIDenvlotra1
18782 .ecindex IIDenvlotra2
18783 .ecindex IIDenvlotra3
18791 . ////////////////////////////////////////////////////////////////////////////
18792 . ////////////////////////////////////////////////////////////////////////////
18794 .chapter "Generic options for transports" "CHAPtransportgeneric"
18795 .scindex IIDgenoptra1 "generic options" "transport"
18796 .scindex IIDgenoptra2 "options" "generic; for transports"
18797 .scindex IIDgenoptra3 "transport" "generic options for"
18798 The following generic options apply to all transports:
18801 .option body_only transports boolean false
18802 .cindex "transport" "body only"
18803 .cindex "message" "transporting body only"
18804 .cindex "body of message" "transporting"
18805 If this option is set, the message's headers are not transported. It is
18806 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
18807 or &(pipe)& transports, the settings of &%message_prefix%& and
18808 &%message_suffix%& should be checked, because this option does not
18809 automatically suppress them.
18812 .option current_directory transports string&!! unset
18813 .cindex "transport" "current directory for"
18814 This specifies the current directory that is to be set while running the
18815 transport, overriding any value that may have been set by the router.
18816 If the expansion fails for any reason, including forced failure, an error is
18817 logged, and delivery is deferred.
18820 .option disable_logging transports boolean false
18821 If this option is set true, nothing is logged for any
18822 deliveries by the transport or for any
18823 transport errors. You should not set this option unless you really, really know
18824 what you are doing.
18827 .option debug_print transports string&!! unset
18828 .cindex "testing" "variables in drivers"
18829 If this option is set and debugging is enabled (see the &%-d%& command line
18830 option), the string is expanded and included in the debugging output when the
18832 If expansion of the string fails, the error message is written to the debugging
18833 output, and Exim carries on processing.
18834 This facility is provided to help with checking out the values of variables and
18835 so on when debugging driver configurations. For example, if a &%headers_add%&
18836 option is not working properly, &%debug_print%& could be used to output the
18837 variables it references. A newline is added to the text if it does not end with
18841 .option delivery_date_add transports boolean false
18842 .cindex "&'Delivery-date:'& header line"
18843 If this option is true, a &'Delivery-date:'& header is added to the message.
18844 This gives the actual time the delivery was made. As this is not a standard
18845 header, Exim has a configuration option (&%delivery_date_remove%&) which
18846 requests its removal from incoming messages, so that delivered messages can
18847 safely be resent to other recipients.
18850 .option driver transports string unset
18851 This specifies which of the available transport drivers is to be used.
18852 There is no default, and this option must be set for every transport.
18855 .option envelope_to_add transports boolean false
18856 .cindex "&'Envelope-to:'& header line"
18857 If this option is true, an &'Envelope-to:'& header is added to the message.
18858 This gives the original address(es) in the incoming envelope that caused this
18859 delivery to happen. More than one address may be present if the transport is
18860 configured to handle several addresses at once, or if more than one original
18861 address was redirected to the same final address. As this is not a standard
18862 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
18863 its removal from incoming messages, so that delivered messages can safely be
18864 resent to other recipients.
18867 .option group transports string&!! "Exim group"
18868 .cindex "transport" "group; specifying"
18869 This option specifies a gid for running the transport process, overriding any
18870 value that the router supplies, and also overriding any value associated with
18871 &%user%& (see below).
18874 .option headers_add transports string&!! unset
18875 .cindex "header lines" "adding in transport"
18876 .cindex "transport" "header lines; adding"
18877 This option specifies a string of text that is expanded and added to the header
18878 portion of a message as it is transported, as described in section
18879 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
18880 routers. If the result of the expansion is an empty string, or if the expansion
18881 is forced to fail, no action is taken. Other expansion failures are treated as
18882 errors and cause the delivery to be deferred.
18886 .option headers_only transports boolean false
18887 .cindex "transport" "header lines only"
18888 .cindex "message" "transporting headers only"
18889 .cindex "header lines" "transporting"
18890 If this option is set, the message's body is not transported. It is mutually
18891 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
18892 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
18893 checked, since this option does not automatically suppress them.
18896 .option headers_remove transports string&!! unset
18897 .cindex "header lines" "removing"
18898 .cindex "transport" "header lines; removing"
18899 This option specifies a string that is expanded into a list of header names;
18900 these headers are omitted from the message as it is transported, as described
18901 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
18902 routers. If the result of the expansion is an empty string, or if the expansion
18903 is forced to fail, no action is taken. Other expansion failures are treated as
18904 errors and cause the delivery to be deferred.
18908 .option headers_rewrite transports string unset
18909 .cindex "transport" "header lines; rewriting"
18910 .cindex "rewriting" "at transport time"
18911 This option allows addresses in header lines to be rewritten at transport time,
18912 that is, as the message is being copied to its destination. The contents of the
18913 option are a colon-separated list of rewriting rules. Each rule is in exactly
18914 the same form as one of the general rewriting rules that are applied when a
18915 message is received. These are described in chapter &<<CHAPrewrite>>&. For
18918 headers_rewrite = a@b c@d f : \
18921 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
18922 &'w@z'& in all address-bearing header lines. The rules are applied to the
18923 header lines just before they are written out at transport time, so they affect
18924 only those copies of the message that pass through the transport. However, only
18925 the message's original header lines, and any that were added by a system
18926 filter, are rewritten. If a router or transport adds header lines, they are not
18927 affected by this option. These rewriting rules are &'not'& applied to the
18928 envelope. You can change the return path using &%return_path%&, but you cannot
18929 change envelope recipients at this time.
18932 .option home_directory transports string&!! unset
18933 .cindex "transport" "home directory for"
18935 This option specifies a home directory setting for a local transport,
18936 overriding any value that may be set by the router. The home directory is
18937 placed in &$home$& while expanding the transport's private options. It is also
18938 used as the current directory if no current directory is set by the
18939 &%current_directory%& option on the transport or the
18940 &%transport_current_directory%& option on the router. If the expansion fails
18941 for any reason, including forced failure, an error is logged, and delivery is
18945 .option initgroups transports boolean false
18946 .cindex "additional groups"
18947 .cindex "groups" "additional"
18948 .cindex "transport" "group; additional"
18949 If this option is true and the uid for the delivery process is provided by the
18950 transport, the &[initgroups()]& function is called when running the transport
18951 to ensure that any additional groups associated with the uid are set up.
18954 .option message_size_limit transports string&!! 0
18955 .cindex "limit" "message size per transport"
18956 .cindex "size" "of message, limit"
18957 .cindex "transport" "message size; limiting"
18958 This option controls the size of messages passed through the transport. It is
18959 expanded before use; the result of the expansion must be a sequence of decimal
18960 digits, optionally followed by K or M. If the expansion fails for any reason,
18961 including forced failure, or if the result is not of the required form,
18962 delivery is deferred. If the value is greater than zero and the size of a
18963 message exceeds this limit, the address is failed. If there is any chance that
18964 the resulting bounce message could be routed to the same transport, you should
18965 ensure that &%return_size_limit%& is less than the transport's
18966 &%message_size_limit%&, as otherwise the bounce message will fail to get
18971 .option rcpt_include_affixes transports boolean false
18972 .cindex "prefix" "for local part, including in envelope"
18973 .cindex "suffix for local part" "including in envelope"
18974 .cindex "local part" "prefix"
18975 .cindex "local part" "suffix"
18976 When this option is false (the default), and an address that has had any
18977 affixes (prefixes or suffixes) removed from the local part is delivered by any
18978 form of SMTP or LMTP, the affixes are not included. For example, if a router
18981 local_part_prefix = *-
18983 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
18986 RCPT TO:<xyz@some.domain>
18988 This is also the case when an ACL-time callout is being used to verify a
18989 recipient address. However, if &%rcpt_include_affixes%& is set true, the
18990 whole local part is included in the RCPT command. This option applies to BSMTP
18991 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
18992 &(lmtp)& and &(smtp)& transports.
18995 .option retry_use_local_part transports boolean "see below"
18996 .cindex "hints database" "retry keys"
18997 When a delivery suffers a temporary failure, a retry record is created
18998 in Exim's hints database. For remote deliveries, the key for the retry record
18999 is based on the name and/or IP address of the failing remote host. For local
19000 deliveries, the key is normally the entire address, including both the local
19001 part and the domain. This is suitable for most common cases of local delivery
19002 temporary failure &-- for example, exceeding a mailbox quota should delay only
19003 deliveries to that mailbox, not to the whole domain.
19005 However, in some special cases you may want to treat a temporary local delivery
19006 as a failure associated with the domain, and not with a particular local part.
19007 (For example, if you are storing all mail for some domain in files.) You can do
19008 this by setting &%retry_use_local_part%& false.
19010 For all the local transports, its default value is true. For remote transports,
19011 the default value is false for tidiness, but changing the value has no effect
19012 on a remote transport in the current implementation.
19015 .option return_path transports string&!! unset
19016 .cindex "envelope sender"
19017 .cindex "transport" "return path; changing"
19018 .cindex "return path" "changing in transport"
19019 If this option is set, the string is expanded at transport time and replaces
19020 the existing return path (envelope sender) value in the copy of the message
19021 that is being delivered. An empty return path is permitted. This feature is
19022 designed for remote deliveries, where the value of this option is used in the
19023 SMTP MAIL command. If you set &%return_path%& for a local transport, the
19024 only effect is to change the address that is placed in the &'Return-path:'&
19025 header line, if one is added to the message (see the next option).
19027 &*Note:*& A changed return path is not logged unless you add
19028 &%return_path_on_delivery%& to the log selector.
19030 .vindex "&$return_path$&"
19031 The expansion can refer to the existing value via &$return_path$&. This is
19032 either the message's envelope sender, or an address set by the
19033 &%errors_to%& option on a router. If the expansion is forced to fail, no
19034 replacement occurs; if it fails for another reason, delivery is deferred. This
19035 option can be used to support VERP (Variable Envelope Return Paths) &-- see
19036 section &<<SECTverp>>&.
19038 &*Note*&: If a delivery error is detected locally, including the case when a
19039 remote server rejects a message at SMTP time, the bounce message is not sent to
19040 the value of this option. It is sent to the previously set errors address.
19041 This defaults to the incoming sender address, but can be changed by setting
19042 &%errors_to%& in a router.
19046 .option return_path_add transports boolean false
19047 .cindex "&'Return-path:'& header line"
19048 If this option is true, a &'Return-path:'& header is added to the message.
19049 Although the return path is normally available in the prefix line of BSD
19050 mailboxes, this is commonly not displayed by MUAs, and so the user does not
19051 have easy access to it.
19053 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
19054 the delivery SMTP server makes the final delivery"&. This implies that this
19055 header should not be present in incoming messages. Exim has a configuration
19056 option, &%return_path_remove%&, which requests removal of this header from
19057 incoming messages, so that delivered messages can safely be resent to other
19061 .option shadow_condition transports string&!! unset
19062 See &%shadow_transport%& below.
19065 .option shadow_transport transports string unset
19066 .cindex "shadow transport"
19067 .cindex "transport" "shadow"
19068 A local transport may set the &%shadow_transport%& option to the name of
19069 another local transport. Shadow remote transports are not supported.
19071 Whenever a delivery to the main transport succeeds, and either
19072 &%shadow_condition%& is unset, or its expansion does not result in the empty
19073 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
19074 passed to the shadow transport, with the same delivery address or addresses. If
19075 expansion fails, no action is taken except that non-forced expansion failures
19076 cause a log line to be written.
19078 The result of the shadow transport is discarded and does not affect the
19079 subsequent processing of the message. Only a single level of shadowing is
19080 provided; the &%shadow_transport%& option is ignored on any transport when it
19081 is running as a shadow. Options concerned with output from pipes are also
19082 ignored. The log line for the successful delivery has an item added on the end,
19085 ST=<shadow transport name>
19087 If the shadow transport did not succeed, the error message is put in
19088 parentheses afterwards. Shadow transports can be used for a number of different
19089 purposes, including keeping more detailed log information than Exim normally
19090 provides, and implementing automatic acknowledgment policies based on message
19091 headers that some sites insist on.
19094 .option transport_filter transports string&!! unset
19095 .cindex "transport" "filter"
19096 .cindex "filter" "transport filter"
19097 This option sets up a filtering (in the Unix shell sense) process for messages
19098 at transport time. It should not be confused with mail filtering as set up by
19099 individual users or via a system filter.
19101 When the message is about to be written out, the command specified by
19102 &%transport_filter%& is started up in a separate, parallel process, and
19103 the entire message, including the header lines, is passed to it on its standard
19104 input (this in fact is done from a third process, to avoid deadlock). The
19105 command must be specified as an absolute path.
19107 The lines of the message that are written to the transport filter are
19108 terminated by newline (&"\n"&). The message is passed to the filter before any
19109 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
19110 lines beginning with a dot, and also before any processing implied by the
19111 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
19112 &(pipe)& transports.
19114 The standard error for the filter process is set to the same destination as its
19115 standard output; this is read and written to the message's ultimate
19116 destination. The process that writes the message to the filter, the
19117 filter itself, and the original process that reads the result and delivers it
19118 are all run in parallel, like a shell pipeline.
19120 The filter can perform any transformations it likes, but of course should take
19121 care not to break RFC 2822 syntax. Exim does not check the result, except to
19122 test for a final newline when SMTP is in use. All messages transmitted over
19123 SMTP must end with a newline, so Exim supplies one if it is missing.
19125 .cindex "content scanning" "per user"
19126 A transport filter can be used to provide content-scanning on a per-user basis
19127 at delivery time if the only required effect of the scan is to modify the
19128 message. For example, a content scan could insert a new header line containing
19129 a spam score. This could be interpreted by a filter in the user's MUA. It is
19130 not possible to discard a message at this stage.
19132 .cindex "SMTP" "SIZE"
19133 A problem might arise if the filter increases the size of a message that is
19134 being sent down an SMTP connection. If the receiving SMTP server has indicated
19135 support for the SIZE parameter, Exim will have sent the size of the message
19136 at the start of the SMTP session. If what is actually sent is substantially
19137 more, the server might reject the message. This can be worked round by setting
19138 the &%size_addition%& option on the &(smtp)& transport, either to allow for
19139 additions to the message, or to disable the use of SIZE altogether.
19141 .vindex "&$pipe_addresses$&"
19142 The value of the &%transport_filter%& option is the command string for starting
19143 the filter, which is run directly from Exim, not under a shell. The string is
19144 parsed by Exim in the same way as a command string for the &(pipe)& transport:
19145 Exim breaks it up into arguments and then expands each argument separately (see
19146 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
19147 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
19148 of arguments, one for each address that applies to this delivery. (This isn't
19149 an ideal name for this feature here, but as it was already implemented for the
19150 &(pipe)& transport, it seemed sensible not to change it.)
19153 .vindex "&$host_address$&"
19154 The expansion variables &$host$& and &$host_address$& are available when the
19155 transport is a remote one. They contain the name and IP address of the host to
19156 which the message is being sent. For example:
19158 transport_filter = /some/directory/transport-filter.pl \
19159 $host $host_address $sender_address $pipe_addresses
19162 Two problems arise if you want to use more complicated expansion items to
19163 generate transport filter commands, both of which due to the fact that the
19164 command is split up &'before'& expansion.
19166 If an expansion item contains white space, you must quote it, so that it is all
19167 part of the same command item. If the entire option setting is one such
19168 expansion item, you have to take care what kind of quoting you use. For
19171 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
19173 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
19174 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
19175 stripped by Exim when it read the option's value. When the value is used, if
19176 the single quotes were missing, the line would be split into two items,
19177 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
19178 Exim tried to expand the first one.
19180 Except for the special case of &$pipe_addresses$& that is mentioned above, an
19181 expansion cannot generate multiple arguments, or a command name followed by
19182 arguments. Consider this example:
19184 transport_filter = ${lookup{$host}lsearch{/a/file}\
19185 {$value}{/bin/cat}}
19187 The result of the lookup is interpreted as the name of the command, even
19188 if it contains white space. The simplest way round this is to use a shell:
19190 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
19191 {$value}{/bin/cat}}
19195 The filter process is run under the same uid and gid as the normal delivery.
19196 For remote deliveries this is the Exim uid/gid by default. The command should
19197 normally yield a zero return code. Transport filters are not supposed to fail.
19198 A non-zero code is taken to mean that the transport filter encountered some
19199 serious problem. Delivery of the message is deferred; the message remains on
19200 the queue and is tried again later. It is not possible to cause a message to be
19201 bounced from a transport filter.
19203 If a transport filter is set on an autoreply transport, the original message is
19204 passed through the filter as it is being copied into the newly generated
19205 message, which happens if the &%return_message%& option is set.
19208 .option transport_filter_timeout transports time 5m
19209 .cindex "transport" "filter, timeout"
19210 When Exim is reading the output of a transport filter, it a applies a timeout
19211 that can be set by this option. Exceeding the timeout is normally treated as a
19212 temporary delivery failure. However, if a transport filter is used with a
19213 &(pipe)& transport, a timeout in the transport filter is treated in the same
19214 way as a timeout in the pipe command itself. By default, a timeout is a hard
19215 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
19216 becomes a temporary error.
19219 .option user transports string&!! "Exim user"
19220 .cindex "uid (user id)" "local delivery"
19221 .cindex "transport" "user, specifying"
19222 This option specifies the user under whose uid the delivery process is to be
19223 run, overriding any uid that may have been set by the router. If the user is
19224 given as a name, the uid is looked up from the password data, and the
19225 associated group is taken as the value of the gid to be used if the &%group%&
19228 For deliveries that use local transports, a user and group are normally
19229 specified explicitly or implicitly (for example, as a result of
19230 &%check_local_user%&) by the router or transport.
19232 .cindex "hints database" "access by remote transport"
19233 For remote transports, you should leave this option unset unless you really are
19234 sure you know what you are doing. When a remote transport is running, it needs
19235 to be able to access Exim's hints databases, because each host may have its own
19237 .ecindex IIDgenoptra1
19238 .ecindex IIDgenoptra2
19239 .ecindex IIDgenoptra3
19246 . ////////////////////////////////////////////////////////////////////////////
19247 . ////////////////////////////////////////////////////////////////////////////
19249 .chapter "Address batching in local transports" "CHAPbatching" &&&
19251 .cindex "transport" "local; address batching in"
19252 The only remote transport (&(smtp)&) is normally configured to handle more than
19253 one address at a time, so that when several addresses are routed to the same
19254 remote host, just one copy of the message is sent. Local transports, however,
19255 normally handle one address at a time. That is, a separate instance of the
19256 transport is run for each address that is routed to the transport. A separate
19257 copy of the message is delivered each time.
19259 .cindex "batched local delivery"
19260 .oindex "&%batch_max%&"
19261 .oindex "&%batch_id%&"
19262 In special cases, it may be desirable to handle several addresses at once in a
19263 local transport, for example:
19266 In an &(appendfile)& transport, when storing messages in files for later
19267 delivery by some other means, a single copy of the message with multiple
19268 recipients saves space.
19270 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
19271 a single copy saves time, and is the normal way LMTP is expected to work.
19273 In a &(pipe)& transport, when passing the message
19274 to a scanner program or
19275 to some other delivery mechanism such as UUCP, multiple recipients may be
19279 These three local transports all have the same options for controlling multiple
19280 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
19281 repeating the information for each transport, these options are described here.
19283 The &%batch_max%& option specifies the maximum number of addresses that can be
19284 delivered together in a single run of the transport. Its default value is one
19285 (no batching). When more than one address is routed to a transport that has a
19286 &%batch_max%& value greater than one, the addresses are delivered in a batch
19287 (that is, in a single run of the transport with multiple recipients), subject
19288 to certain conditions:
19291 .vindex "&$local_part$&"
19292 If any of the transport's options contain a reference to &$local_part$&, no
19293 batching is possible.
19295 .vindex "&$domain$&"
19296 If any of the transport's options contain a reference to &$domain$&, only
19297 addresses with the same domain are batched.
19299 .cindex "customizing" "batching condition"
19300 If &%batch_id%& is set, it is expanded for each address, and only those
19301 addresses with the same expanded value are batched. This allows you to specify
19302 customized batching conditions. Failure of the expansion for any reason,
19303 including forced failure, disables batching, but it does not stop the delivery
19306 Batched addresses must also have the same errors address (where to send
19307 delivery errors), the same header additions and removals, the same user and
19308 group for the transport, and if a host list is present, the first host must
19312 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
19313 both when the file or pipe command is specified in the transport, and when it
19314 is specified by a &(redirect)& router, but all the batched addresses must of
19315 course be routed to the same file or pipe command. These two transports have an
19316 option called &%use_bsmtp%&, which causes them to deliver the message in
19317 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
19318 &%check_string%& and &%escape_string%& options are forced to the values
19321 escape_string = ".."
19323 when batched SMTP is in use. A full description of the batch SMTP mechanism is
19324 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
19325 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
19327 .cindex "&'Envelope-to:'& header line"
19328 If the generic &%envelope_to_add%& option is set for a batching transport, the
19329 &'Envelope-to:'& header that is added to the message contains all the addresses
19330 that are being processed together. If you are using a batching &(appendfile)&
19331 transport without &%use_bsmtp%&, the only way to preserve the recipient
19332 addresses is to set the &%envelope_to_add%& option.
19334 .cindex "&(pipe)& transport" "with multiple addresses"
19335 .vindex "&$pipe_addresses$&"
19336 If you are using a &(pipe)& transport without BSMTP, and setting the
19337 transport's &%command%& option, you can include &$pipe_addresses$& as part of
19338 the command. This is not a true variable; it is a bit of magic that causes each
19339 of the recipient addresses to be inserted into the command as a separate
19340 argument. This provides a way of accessing all the addresses that are being
19341 delivered in the batch. &*Note:*& This is not possible for pipe commands that
19342 are specified by a &(redirect)& router.
19347 . ////////////////////////////////////////////////////////////////////////////
19348 . ////////////////////////////////////////////////////////////////////////////
19350 .chapter "The appendfile transport" "CHAPappendfile"
19351 .scindex IIDapptra1 "&(appendfile)& transport"
19352 .scindex IIDapptra2 "transports" "&(appendfile)&"
19353 .cindex "directory creation"
19354 .cindex "creating directories"
19355 The &(appendfile)& transport delivers a message by appending it to an existing
19356 file, or by creating an entirely new file in a specified directory. Single
19357 files to which messages are appended can be in the traditional Unix mailbox
19358 format, or optionally in the MBX format supported by the Pine MUA and
19359 University of Washington IMAP daemon, &'inter alia'&. When each message is
19360 being delivered as a separate file, &"maildir"& format can optionally be used
19361 to give added protection against failures that happen part-way through the
19362 delivery. A third form of separate-file delivery known as &"mailstore"& is also
19363 supported. For all file formats, Exim attempts to create as many levels of
19364 directory as necessary, provided that &%create_directory%& is set.
19366 The code for the optional formats is not included in the Exim binary by
19367 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
19368 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
19371 .cindex "quota" "system"
19372 Exim recognizes system quota errors, and generates an appropriate message. Exim
19373 also supports its own quota control within the transport, for use when the
19374 system facility is unavailable or cannot be used for some reason.
19376 If there is an error while appending to a file (for example, quota exceeded or
19377 partition filled), Exim attempts to reset the file's length and last
19378 modification time back to what they were before. If there is an error while
19379 creating an entirely new file, the new file is removed.
19381 Before appending to a file, a number of security checks are made, and the
19382 file is locked. A detailed description is given below, after the list of
19385 The &(appendfile)& transport is most commonly used for local deliveries to
19386 users' mailboxes. However, it can also be used as a pseudo-remote transport for
19387 putting messages into files for remote delivery by some means other than Exim.
19388 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
19393 .section "The file and directory options" "SECTfildiropt"
19394 The &%file%& option specifies a single file, to which the message is appended;
19395 the &%directory%& option specifies a directory, in which a new file containing
19396 the message is created. Only one of these two options can be set, and for
19397 normal deliveries to mailboxes, one of them &'must'& be set.
19399 .vindex "&$address_file$&"
19400 .vindex "&$local_part$&"
19401 However, &(appendfile)& is also used for delivering messages to files or
19402 directories whose names (or parts of names) are obtained from alias,
19403 forwarding, or filtering operations (for example, a &%save%& command in a
19404 user's Exim filter). When such a transport is running, &$local_part$& contains
19405 the local part that was aliased or forwarded, and &$address_file$& contains the
19406 name (or partial name) of the file or directory generated by the redirection
19407 operation. There are two cases:
19410 If neither &%file%& nor &%directory%& is set, the redirection operation
19411 must specify an absolute path (one that begins with &`/`&). This is the most
19412 common case when users with local accounts use filtering to sort mail into
19413 different folders. See for example, the &(address_file)& transport in the
19414 default configuration. If the path ends with a slash, it is assumed to be the
19415 name of a directory. A delivery to a directory can also be forced by setting
19416 &%maildir_format%& or &%mailstore_format%&.
19418 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
19419 used to determine the file or directory name for the delivery. Normally, the
19420 contents of &$address_file$& are used in some way in the string expansion.
19424 .cindex "Sieve filter" "configuring &(appendfile)&"
19425 .cindex "Sieve filter" "relative mailbox path handling"
19426 As an example of the second case, consider an environment where users do not
19427 have home directories. They may be permitted to use Exim filter commands of the
19432 or Sieve filter commands of the form:
19434 require "fileinto";
19435 fileinto "folder23";
19437 In this situation, the expansion of &%file%& or &%directory%& in the transport
19438 must transform the relative path into an appropriate absolute file name. In the
19439 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
19440 is used as a result of a &"keep"& action in the filter. This example shows one
19441 way of handling this requirement:
19443 file = ${if eq{$address_file}{inbox} \
19444 {/var/mail/$local_part} \
19445 {${if eq{${substr_0_1:$address_file}}{/} \
19447 {$home/mail/$address_file} \
19451 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
19452 location, absolute paths are used without change, and other folders are in the
19453 &_mail_& directory within the home directory.
19455 &*Note 1*&: While processing an Exim filter, a relative path such as
19456 &_folder23_& is turned into an absolute path if a home directory is known to
19457 the router. In particular, this is the case if &%check_local_user%& is set. If
19458 you want to prevent this happening at routing time, you can set
19459 &%router_home_directory%& empty. This forces the router to pass the relative
19460 path to the transport.
19462 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
19463 the &%file%& or &%directory%& option is still used if it is set.
19468 .section "Private options for appendfile" "SECID134"
19469 .cindex "options" "&(appendfile)& transport"
19473 .option allow_fifo appendfile boolean false
19474 .cindex "fifo (named pipe)"
19475 .cindex "named pipe (fifo)"
19476 .cindex "pipe" "named (fifo)"
19477 Setting this option permits delivery to named pipes (FIFOs) as well as to
19478 regular files. If no process is reading the named pipe at delivery time, the
19479 delivery is deferred.
19482 .option allow_symlink appendfile boolean false
19483 .cindex "symbolic link" "to mailbox"
19484 .cindex "mailbox" "symbolic link"
19485 By default, &(appendfile)& will not deliver if the path name for the file is
19486 that of a symbolic link. Setting this option relaxes that constraint, but there
19487 are security issues involved in the use of symbolic links. Be sure you know
19488 what you are doing if you set this. Details of exactly what this option affects
19489 are included in the discussion which follows this list of options.
19492 .option batch_id appendfile string&!! unset
19493 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
19494 However, batching is automatically disabled for &(appendfile)& deliveries that
19495 happen as a result of forwarding or aliasing or other redirection directly to a
19499 .option batch_max appendfile integer 1
19500 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
19503 .option check_group appendfile boolean false
19504 When this option is set, the group owner of the file defined by the &%file%&
19505 option is checked to see that it is the same as the group under which the
19506 delivery process is running. The default setting is false because the default
19507 file mode is 0600, which means that the group is irrelevant.
19510 .option check_owner appendfile boolean true
19511 When this option is set, the owner of the file defined by the &%file%& option
19512 is checked to ensure that it is the same as the user under which the delivery
19513 process is running.
19516 .option check_string appendfile string "see below"
19517 .cindex "&""From""& line"
19518 As &(appendfile)& writes the message, the start of each line is tested for
19519 matching &%check_string%&, and if it does, the initial matching characters are
19520 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
19521 a literal string, not a regular expression, and the case of any letters it
19522 contains is significant.
19524 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
19525 are forced to &"."& and &".."& respectively, and any settings in the
19526 configuration are ignored. Otherwise, they default to &"From&~"& and
19527 &">From&~"& when the &%file%& option is set, and unset when any of the
19528 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
19530 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
19531 suitable for traditional &"BSD"& mailboxes, where a line beginning with
19532 &"From&~"& indicates the start of a new message. All four options need changing
19533 if another format is used. For example, to deliver to mailboxes in MMDF format:
19534 .cindex "MMDF format mailbox"
19535 .cindex "mailbox" "MMDF format"
19537 check_string = "\1\1\1\1\n"
19538 escape_string = "\1\1\1\1 \n"
19539 message_prefix = "\1\1\1\1\n"
19540 message_suffix = "\1\1\1\1\n"
19542 .option create_directory appendfile boolean true
19543 .cindex "directory creation"
19544 When this option is true, Exim attempts to create any missing superior
19545 directories for the file that it is about to write. A created directory's mode
19546 is given by the &%directory_mode%& option.
19548 The group ownership of a newly created directory is highly dependent on the
19549 operating system (and possibly the file system) that is being used. For
19550 example, in Solaris, if the parent directory has the setgid bit set, its group
19551 is propagated to the child; if not, the currently set group is used. However,
19552 in FreeBSD, the parent's group is always used.
19556 .option create_file appendfile string anywhere
19557 This option constrains the location of files and directories that are created
19558 by this transport. It applies to files defined by the &%file%& option and
19559 directories defined by the &%directory%& option. In the case of maildir
19560 delivery, it applies to the top level directory, not the maildir directories
19563 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
19564 &"belowhome"&. In the second and third cases, a home directory must have been
19565 set for the transport. This option is not useful when an explicit file name is
19566 given for normal mailbox deliveries. It is intended for the case when file
19567 names are generated from users' &_.forward_& files. These are usually handled
19568 by an &(appendfile)& transport called &%address_file%&. See also
19569 &%file_must_exist%&.
19572 .option directory appendfile string&!! unset
19573 This option is mutually exclusive with the &%file%& option, but one of &%file%&
19574 or &%directory%& must be set, unless the delivery is the direct result of a
19575 redirection (see section &<<SECTfildiropt>>&).
19577 When &%directory%& is set, the string is expanded, and the message is delivered
19578 into a new file or files in or below the given directory, instead of being
19579 appended to a single mailbox file. A number of different formats are provided
19580 (see &%maildir_format%& and &%mailstore_format%&), and see section
19581 &<<SECTopdir>>& for further details of this form of delivery.
19584 .option directory_file appendfile string&!! "see below"
19586 .vindex "&$inode$&"
19587 When &%directory%& is set, but neither &%maildir_format%& nor
19588 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
19589 whose name is obtained by expanding this string. The default value is:
19591 q${base62:$tod_epoch}-$inode
19593 This generates a unique name from the current time, in base 62 form, and the
19594 inode of the file. The variable &$inode$& is available only when expanding this
19598 .option directory_mode appendfile "octal integer" 0700
19599 If &(appendfile)& creates any directories as a result of the
19600 &%create_directory%& option, their mode is specified by this option.
19603 .option escape_string appendfile string "see description"
19604 See &%check_string%& above.
19607 .option file appendfile string&!! unset
19608 This option is mutually exclusive with the &%directory%& option, but one of
19609 &%file%& or &%directory%& must be set, unless the delivery is the direct result
19610 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
19611 specifies a single file, to which the message is appended. One or more of
19612 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
19615 .cindex "NFS" "lock file"
19616 .cindex "locking files"
19617 .cindex "lock files"
19618 If you are using more than one host to deliver over NFS into the same
19619 mailboxes, you should always use lock files.
19621 The string value is expanded for each delivery, and must yield an absolute
19622 path. The most common settings of this option are variations on one of these
19625 file = /var/spool/mail/$local_part
19626 file = /home/$local_part/inbox
19629 .cindex "&""sticky""& bit"
19630 In the first example, all deliveries are done into the same directory. If Exim
19631 is configured to use lock files (see &%use_lockfile%& below) it must be able to
19632 create a file in the directory, so the &"sticky"& bit must be turned on for
19633 deliveries to be possible, or alternatively the &%group%& option can be used to
19634 run the delivery under a group id which has write access to the directory.
19638 .option file_format appendfile string unset
19639 .cindex "file" "mailbox; checking existing format"
19640 This option requests the transport to check the format of an existing file
19641 before adding to it. The check consists of matching a specific string at the
19642 start of the file. The value of the option consists of an even number of
19643 colon-separated strings. The first of each pair is the test string, and the
19644 second is the name of a transport. If the transport associated with a matched
19645 string is not the current transport, control is passed over to the other
19646 transport. For example, suppose the standard &(local_delivery)& transport has
19649 file_format = "From : local_delivery :\
19650 \1\1\1\1\n : local_mmdf_delivery"
19652 Mailboxes that begin with &"From"& are still handled by this transport, but if
19653 a mailbox begins with four binary ones followed by a newline, control is passed
19654 to a transport called &%local_mmdf_delivery%&, which presumably is configured
19655 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
19656 is assumed to match the current transport. If the start of a mailbox doesn't
19657 match any string, or if the transport named for a given string is not defined,
19658 delivery is deferred.
19661 .option file_must_exist appendfile boolean false
19662 If this option is true, the file specified by the &%file%& option must exist.
19663 A temporary error occurs if it does not, causing delivery to be deferred.
19664 If this option is false, the file is created if it does not exist.
19667 .option lock_fcntl_timeout appendfile time 0s
19668 .cindex "timeout" "mailbox locking"
19669 .cindex "mailbox" "locking, blocking and non-blocking"
19670 .cindex "locking files"
19671 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
19672 when locking an open mailbox file. If the call fails, the delivery process
19673 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
19674 Non-blocking calls are used so that the file is not kept open during the wait
19675 for the lock; the reason for this is to make it as safe as possible for
19676 deliveries over NFS in the case when processes might be accessing an NFS
19677 mailbox without using a lock file. This should not be done, but
19678 misunderstandings and hence misconfigurations are not unknown.
19680 On a busy system, however, the performance of a non-blocking lock approach is
19681 not as good as using a blocking lock with a timeout. In this case, the waiting
19682 is done inside the system call, and Exim's delivery process acquires the lock
19683 and can proceed as soon as the previous lock holder releases it.
19685 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
19686 timeout, are used. There may still be some retrying: the maximum number of
19689 (lock_retries * lock_interval) / lock_fcntl_timeout
19691 rounded up to the next whole number. In other words, the total time during
19692 which &(appendfile)& is trying to get a lock is roughly the same, unless
19693 &%lock_fcntl_timeout%& is set very large.
19695 You should consider setting this option if you are getting a lot of delayed
19696 local deliveries because of errors of the form
19698 failed to lock mailbox /some/file (fcntl)
19701 .option lock_flock_timeout appendfile time 0s
19702 This timeout applies to file locking when using &[flock()]& (see
19703 &%use_flock%&); the timeout operates in a similar manner to
19704 &%lock_fcntl_timeout%&.
19707 .option lock_interval appendfile time 3s
19708 This specifies the time to wait between attempts to lock the file. See below
19709 for details of locking.
19712 .option lock_retries appendfile integer 10
19713 This specifies the maximum number of attempts to lock the file. A value of zero
19714 is treated as 1. See below for details of locking.
19717 .option lockfile_mode appendfile "octal integer" 0600
19718 This specifies the mode of the created lock file, when a lock file is being
19719 used (see &%use_lockfile%& and &%use_mbx_lock%&).
19722 .option lockfile_timeout appendfile time 30m
19723 .cindex "timeout" "mailbox locking"
19724 When a lock file is being used (see &%use_lockfile%&), if a lock file already
19725 exists and is older than this value, it is assumed to have been left behind by
19726 accident, and Exim attempts to remove it.
19729 .option mailbox_filecount appendfile string&!! unset
19730 .cindex "mailbox" "specifying size of"
19731 .cindex "size" "of mailbox"
19732 If this option is set, it is expanded, and the result is taken as the current
19733 number of files in the mailbox. It must be a decimal number, optionally
19734 followed by K or M. This provides a way of obtaining this information from an
19735 external source that maintains the data.
19738 .option mailbox_size appendfile string&!! unset
19739 .cindex "mailbox" "specifying size of"
19740 .cindex "size" "of mailbox"
19741 If this option is set, it is expanded, and the result is taken as the current
19742 size the mailbox. It must be a decimal number, optionally followed by K or M.
19743 This provides a way of obtaining this information from an external source that
19744 maintains the data. This is likely to be helpful for maildir deliveries where
19745 it is computationally expensive to compute the size of a mailbox.
19749 .option maildir_format appendfile boolean false
19750 .cindex "maildir format" "specifying"
19751 If this option is set with the &%directory%& option, the delivery is into a new
19752 file, in the &"maildir"& format that is used by other mail software. When the
19753 transport is activated directly from a &(redirect)& router (for example, the
19754 &(address_file)& transport in the default configuration), setting
19755 &%maildir_format%& causes the path received from the router to be treated as a
19756 directory, whether or not it ends with &`/`&. This option is available only if
19757 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
19758 &<<SECTmaildirdelivery>>& below for further details.
19761 .option maildir_quota_directory_regex appendfile string "See below"
19762 .cindex "maildir format" "quota; directories included in"
19763 .cindex "quota" "maildir; directories included in"
19764 This option is relevant only when &%maildir_use_size_file%& is set. It defines
19765 a regular expression for specifying directories, relative to the quota
19766 directory (see &%quota_directory%&), that should be included in the quota
19767 calculation. The default value is:
19769 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
19771 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
19772 (directories whose names begin with a dot). If you want to exclude the
19774 folder from the count (as some sites do), you need to change this setting to
19776 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
19778 This uses a negative lookahead in the regular expression to exclude the
19779 directory whose name is &_.Trash_&. When a directory is excluded from quota
19780 calculations, quota processing is bypassed for any messages that are delivered
19781 directly into that directory.
19784 .option maildir_retries appendfile integer 10
19785 This option specifies the number of times to retry when writing a file in
19786 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
19789 .option maildir_tag appendfile string&!! unset
19790 This option applies only to deliveries in maildir format, and is described in
19791 section &<<SECTmaildirdelivery>>& below.
19794 .option maildir_use_size_file appendfile boolean false
19795 .cindex "maildir format" "&_maildirsize_& file"
19796 Setting this option true enables support for &_maildirsize_& files. Exim
19797 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
19798 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
19799 value is zero. See &%maildir_quota_directory_regex%& above and section
19800 &<<SECTmaildirdelivery>>& below for further details.
19802 .option maildirfolder_create_regex appendfile string unset
19803 .cindex "maildir format" "&_maildirfolder_& file"
19804 .cindex "&_maildirfolder_&, creating"
19805 The value of this option is a regular expression. If it is unset, it has no
19806 effect. Otherwise, before a maildir delivery takes place, the pattern is
19807 matched against the name of the maildir directory, that is, the directory
19808 containing the &_new_& and &_tmp_& subdirectories that will be used for the
19809 delivery. If there is a match, Exim checks for the existence of a file called
19810 &_maildirfolder_& in the directory, and creates it if it does not exist.
19811 See section &<<SECTmaildirdelivery>>& for more details.
19814 .option mailstore_format appendfile boolean false
19815 .cindex "mailstore format" "specifying"
19816 If this option is set with the &%directory%& option, the delivery is into two
19817 new files in &"mailstore"& format. The option is available only if
19818 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
19819 below for further details.
19822 .option mailstore_prefix appendfile string&!! unset
19823 This option applies only to deliveries in mailstore format, and is described in
19824 section &<<SECTopdir>>& below.
19827 .option mailstore_suffix appendfile string&!! unset
19828 This option applies only to deliveries in mailstore format, and is described in
19829 section &<<SECTopdir>>& below.
19832 .option mbx_format appendfile boolean false
19833 .cindex "locking files"
19834 .cindex "file" "locking"
19835 .cindex "file" "MBX format"
19836 .cindex "MBX format, specifying"
19837 This option is available only if Exim has been compiled with SUPPORT_MBX
19838 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
19839 the message is appended to the mailbox file in MBX format instead of
19840 traditional Unix format. This format is supported by Pine4 and its associated
19841 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
19843 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
19844 automatically changed by the use of &%mbx_format%&. They should normally be set
19845 empty when using MBX format, so this option almost always appears in this
19852 If none of the locking options are mentioned in the configuration,
19853 &%use_mbx_lock%& is assumed and the other locking options default to false. It
19854 is possible to specify the other kinds of locking with &%mbx_format%&, but
19855 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
19856 interworks with &'c-client'&, providing for shared access to the mailbox. It
19857 should not be used if any program that does not use this form of locking is
19858 going to access the mailbox, nor should it be used if the mailbox file is NFS
19859 mounted, because it works only when the mailbox is accessed from a single host.
19861 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
19862 the standard version of &'c-client'&, because as long as it has a mailbox open
19863 (this means for the whole of a Pine or IMAP session), Exim will not be able to
19864 append messages to it.
19867 .option message_prefix appendfile string&!! "see below"
19868 .cindex "&""From""& line"
19869 The string specified here is expanded and output at the start of every message.
19870 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
19871 in which case it is:
19873 message_prefix = "From ${if def:return_path{$return_path}\
19874 {MAILER-DAEMON}} $tod_bsdinbox\n"
19876 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
19877 &`\n`& to &`\r\n`& in &%message_prefix%&.
19879 .option message_suffix appendfile string&!! "see below"
19880 The string specified here is expanded and output at the end of every message.
19881 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
19882 in which case it is a single newline character. The suffix can be suppressed by
19887 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
19888 &`\n`& to &`\r\n`& in &%message_suffix%&.
19890 .option mode appendfile "octal integer" 0600
19891 If the output file is created, it is given this mode. If it already exists and
19892 has wider permissions, they are reduced to this mode. If it has narrower
19893 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
19894 if the delivery is the result of a &%save%& command in a filter file specifying
19895 a particular mode, the mode of the output file is always forced to take that
19896 value, and this option is ignored.
19899 .option mode_fail_narrower appendfile boolean true
19900 This option applies in the case when an existing mailbox file has a narrower
19901 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
19902 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
19903 continues with the delivery attempt, using the existing mode of the file.
19906 .option notify_comsat appendfile boolean false
19907 If this option is true, the &'comsat'& daemon is notified after every
19908 successful delivery to a user mailbox. This is the daemon that notifies logged
19909 on users about incoming mail.
19912 .option quota appendfile string&!! unset
19913 .cindex "quota" "imposed by Exim"
19914 This option imposes a limit on the size of the file to which Exim is appending,
19915 or to the total space used in the directory tree when the &%directory%& option
19916 is set. In the latter case, computation of the space used is expensive, because
19917 all the files in the directory (and any sub-directories) have to be
19918 individually inspected and their sizes summed. (See &%quota_size_regex%& and
19919 &%maildir_use_size_file%& for ways to avoid this in environments where users
19920 have no shell access to their mailboxes).
19922 As there is no interlock against two simultaneous deliveries into a
19923 multi-file mailbox, it is possible for the quota to be overrun in this case.
19924 For single-file mailboxes, of course, an interlock is a necessity.
19926 A file's size is taken as its &'used'& value. Because of blocking effects, this
19927 may be a lot less than the actual amount of disk space allocated to the file.
19928 If the sizes of a number of files are being added up, the rounding effect can
19929 become quite noticeable, especially on systems that have large block sizes.
19930 Nevertheless, it seems best to stick to the &'used'& figure, because this is
19931 the obvious value which users understand most easily.
19933 The value of the option is expanded, and must then be a numerical value
19934 (decimal point allowed), optionally followed by one of the letters K, M, or G,
19935 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
19936 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
19939 &*Note*&: A value of zero is interpreted as &"no quota"&.
19941 The expansion happens while Exim is running as root, before it changes uid for
19942 the delivery. This means that files that are inaccessible to the end user can
19943 be used to hold quota values that are looked up in the expansion. When delivery
19944 fails because this quota is exceeded, the handling of the error is as for
19945 system quota failures.
19947 By default, Exim's quota checking mimics system quotas, and restricts the
19948 mailbox to the specified maximum size, though the value is not accurate to the
19949 last byte, owing to separator lines and additional headers that may get added
19950 during message delivery. When a mailbox is nearly full, large messages may get
19951 refused even though small ones are accepted, because the size of the current
19952 message is added to the quota when the check is made. This behaviour can be
19953 changed by setting &%quota_is_inclusive%& false. When this is done, the check
19954 for exceeding the quota does not include the current message. Thus, deliveries
19955 continue until the quota has been exceeded; thereafter, no further messages are
19956 delivered. See also &%quota_warn_threshold%&.
19959 .option quota_directory appendfile string&!! unset
19960 This option defines the directory to check for quota purposes when delivering
19961 into individual files. The default is the delivery directory, or, if a file
19962 called &_maildirfolder_& exists in a maildir directory, the parent of the
19963 delivery directory.
19966 .option quota_filecount appendfile string&!! 0
19967 This option applies when the &%directory%& option is set. It limits the total
19968 number of files in the directory (compare the inode limit in system quotas). It
19969 can only be used if &%quota%& is also set. The value is expanded; an expansion
19970 failure causes delivery to be deferred. A value of zero is interpreted as
19974 .option quota_is_inclusive appendfile boolean true
19975 See &%quota%& above.
19978 .option quota_size_regex appendfile string unset
19979 This option applies when one of the delivery modes that writes a separate file
19980 for each message is being used. When Exim wants to find the size of one of
19981 these files in order to test the quota, it first checks &%quota_size_regex%&.
19982 If this is set to a regular expression that matches the file name, and it
19983 captures one string, that string is interpreted as a representation of the
19984 file's size. The value of &%quota_size_regex%& is not expanded.
19986 This feature is useful only when users have no shell access to their mailboxes
19987 &-- otherwise they could defeat the quota simply by renaming the files. This
19988 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
19989 the file length to the file name. For example:
19991 maildir_tag = ,S=$message_size
19992 quota_size_regex = ,S=(\d+)
19994 An alternative to &$message_size$& is &$message_linecount$&, which contains the
19995 number of lines in the message.
19997 The regular expression should not assume that the length is at the end of the
19998 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
19999 sometimes add other information onto the ends of message file names.
20003 .option quota_warn_message appendfile string&!! "see below"
20004 See below for the use of this option. If it is not set when
20005 &%quota_warn_threshold%& is set, it defaults to
20007 quota_warn_message = "\
20008 To: $local_part@$domain\n\
20009 Subject: Your mailbox\n\n\
20010 This message is automatically created \
20011 by mail delivery software.\n\n\
20012 The size of your mailbox has exceeded \
20013 a warning threshold that is\n\
20014 set by the system administrator.\n"
20018 .option quota_warn_threshold appendfile string&!! 0
20019 .cindex "quota" "warning threshold"
20020 .cindex "mailbox" "size warning"
20021 .cindex "size" "of mailbox"
20022 This option is expanded in the same way as &%quota%& (see above). If the
20023 resulting value is greater than zero, and delivery of the message causes the
20024 size of the file or total space in the directory tree to cross the given
20025 threshold, a warning message is sent. If &%quota%& is also set, the threshold
20026 may be specified as a percentage of it by following the value with a percent
20030 quota_warn_threshold = 75%
20032 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
20033 percent sign is ignored.
20035 The warning message itself is specified by the &%quota_warn_message%& option,
20036 and it must start with a &'To:'& header line containing the recipient(s) of the
20037 warning message. These do not necessarily have to include the recipient(s) of
20038 the original message. A &'Subject:'& line should also normally be supplied. You
20039 can include any other header lines that you want. If you do not include a
20040 &'From:'& line, the default is:
20042 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
20044 .oindex &%errors_reply_to%&
20045 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
20048 The &%quota%& option does not have to be set in order to use this option; they
20049 are independent of one another except when the threshold is specified as a
20053 .option use_bsmtp appendfile boolean false
20054 .cindex "envelope sender"
20055 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
20056 format, with the envelope sender and recipient(s) included as SMTP commands. If
20057 you want to include a leading HELO command with such messages, you can do
20058 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
20059 for details of batch SMTP.
20062 .option use_crlf appendfile boolean false
20063 .cindex "carriage return"
20065 This option causes lines to be terminated with the two-character CRLF sequence
20066 (carriage return, linefeed) instead of just a linefeed character. In the case
20067 of batched SMTP, the byte sequence written to the file is then an exact image
20068 of what would be sent down a real SMTP connection.
20070 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
20071 (which are used to supply the traditional &"From&~"& and blank line separators
20072 in Berkeley-style mailboxes) are written verbatim, so must contain their own
20073 carriage return characters if these are needed. In cases where these options
20074 have non-empty defaults, the values end with a single linefeed, so they must be
20075 changed to end with &`\r\n`& if &%use_crlf%& is set.
20078 .option use_fcntl_lock appendfile boolean "see below"
20079 This option controls the use of the &[fcntl()]& function to lock a file for
20080 exclusive use when a message is being appended. It is set by default unless
20081 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
20082 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
20083 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
20086 .option use_flock_lock appendfile boolean false
20087 This option is provided to support the use of &[flock()]& for file locking, for
20088 the few situations where it is needed. Most modern operating systems support
20089 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
20090 each other. Exim uses &[fcntl()]& locking by default.
20092 This option is required only if you are using an operating system where
20093 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
20094 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
20095 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
20097 .cindex "Solaris" "&[flock()]& support"
20098 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
20099 have it (and some, I think, provide a not quite right version built on top of
20100 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
20101 the ability to use it, and any attempt to do so will cause a configuration
20104 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
20105 is just being mapped onto &[fcntl()]& by the OS).
20108 .option use_lockfile appendfile boolean "see below"
20109 If this option is turned off, Exim does not attempt to create a lock file when
20110 appending to a mailbox file. In this situation, the only locking is by
20111 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
20112 sure that every MUA that is ever going to look at your users' mailboxes uses
20113 &[fcntl()]& rather than a lock file, and even then only when you are not
20114 delivering over NFS from more than one host.
20116 .cindex "NFS" "lock file"
20117 In order to append to an NFS file safely from more than one host, it is
20118 necessary to take out a lock &'before'& opening the file, and the lock file
20119 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
20122 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
20123 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
20124 except when &%mbx_format%& is set.
20127 .option use_mbx_lock appendfile boolean "see below"
20128 This option is available only if Exim has been compiled with SUPPORT_MBX
20129 set in &_Local/Makefile_&. Setting the option specifies that special MBX
20130 locking rules be used. It is set by default if &%mbx_format%& is set and none
20131 of the locking options are mentioned in the configuration. The locking rules
20132 are the same as are used by the &'c-client'& library that underlies Pine and
20133 the IMAP4 and POP daemons that come with it (see the discussion below). The
20134 rules allow for shared access to the mailbox. However, this kind of locking
20135 does not work when the mailbox is NFS mounted.
20137 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
20138 &%use_flock_lock%& to control what kind of locking is used in implementing the
20139 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
20140 without &%use_fcntl_lock%& or &%use_flock_lock%&.
20145 .section "Operational details for appending" "SECTopappend"
20146 .cindex "appending to a file"
20147 .cindex "file" "appending"
20148 Before appending to a file, the following preparations are made:
20151 If the name of the file is &_/dev/null_&, no action is taken, and a success
20155 .cindex "directory creation"
20156 If any directories on the file's path are missing, Exim creates them if the
20157 &%create_directory%& option is set. A created directory's mode is given by the
20158 &%directory_mode%& option.
20161 If &%file_format%& is set, the format of an existing file is checked. If this
20162 indicates that a different transport should be used, control is passed to that
20166 .cindex "file" "locking"
20167 .cindex "locking files"
20168 .cindex "NFS" "lock file"
20169 If &%use_lockfile%& is set, a lock file is built in a way that will work
20170 reliably over NFS, as follows:
20173 Create a &"hitching post"& file whose name is that of the lock file with the
20174 current time, primary host name, and process id added, by opening for writing
20175 as a new file. If this fails with an access error, delivery is deferred.
20177 Close the hitching post file, and hard link it to the lock file name.
20179 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
20180 Unlink the hitching post name.
20182 Otherwise, use &[stat()]& to get information about the hitching post file, and
20183 then unlink hitching post name. If the number of links is exactly two, creation
20184 of the lock file succeeded but something (for example, an NFS server crash and
20185 restart) caused this fact not to be communicated to the &[link()]& call.
20187 If creation of the lock file failed, wait for &%lock_interval%& and try again,
20188 up to &%lock_retries%& times. However, since any program that writes to a
20189 mailbox should complete its task very quickly, it is reasonable to time out old
20190 lock files that are normally the result of user agent and system crashes. If an
20191 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
20192 it before trying again.
20196 A call is made to &[lstat()]& to discover whether the main file exists, and if
20197 so, what its characteristics are. If &[lstat()]& fails for any reason other
20198 than non-existence, delivery is deferred.
20201 .cindex "symbolic link" "to mailbox"
20202 .cindex "mailbox" "symbolic link"
20203 If the file does exist and is a symbolic link, delivery is deferred, unless the
20204 &%allow_symlink%& option is set, in which case the ownership of the link is
20205 checked, and then &[stat()]& is called to find out about the real file, which
20206 is then subjected to the checks below. The check on the top-level link
20207 ownership prevents one user creating a link for another's mailbox in a sticky
20208 directory, though allowing symbolic links in this case is definitely not a good
20209 idea. If there is a chain of symbolic links, the intermediate ones are not
20213 If the file already exists but is not a regular file, or if the file's owner
20214 and group (if the group is being checked &-- see &%check_group%& above) are
20215 different from the user and group under which the delivery is running,
20216 delivery is deferred.
20219 If the file's permissions are more generous than specified, they are reduced.
20220 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
20221 is set false, in which case the delivery is tried using the existing
20225 The file's inode number is saved, and the file is then opened for appending.
20226 If this fails because the file has vanished, &(appendfile)& behaves as if it
20227 hadn't existed (see below). For any other failures, delivery is deferred.
20230 If the file is opened successfully, check that the inode number hasn't
20231 changed, that it is still a regular file, and that the owner and permissions
20232 have not changed. If anything is wrong, defer delivery and freeze the message.
20235 If the file did not exist originally, defer delivery if the &%file_must_exist%&
20236 option is set. Otherwise, check that the file is being created in a permitted
20237 directory if the &%create_file%& option is set (deferring on failure), and then
20238 open for writing as a new file, with the O_EXCL and O_CREAT options,
20239 except when dealing with a symbolic link (the &%allow_symlink%& option must be
20240 set). In this case, which can happen if the link points to a non-existent file,
20241 the file is opened for writing using O_CREAT but not O_EXCL, because
20242 that prevents link following.
20245 .cindex "loop" "while file testing"
20246 If opening fails because the file exists, obey the tests given above for
20247 existing files. However, to avoid looping in a situation where the file is
20248 being continuously created and destroyed, the exists/not-exists loop is broken
20249 after 10 repetitions, and the message is then frozen.
20252 If opening fails with any other error, defer delivery.
20255 .cindex "file" "locking"
20256 .cindex "locking files"
20257 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
20258 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
20259 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
20260 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
20261 file, and an exclusive lock on the file whose name is
20263 /tmp/.<device-number>.<inode-number>
20265 using the device and inode numbers of the open mailbox file, in accordance with
20266 the MBX locking rules. This file is created with a mode that is specified by
20267 the &%lockfile_mode%& option.
20269 If Exim fails to lock the file, there are two possible courses of action,
20270 depending on the value of the locking timeout. This is obtained from
20271 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
20273 If the timeout value is zero, the file is closed, Exim waits for
20274 &%lock_interval%&, and then goes back and re-opens the file as above and tries
20275 to lock it again. This happens up to &%lock_retries%& times, after which the
20276 delivery is deferred.
20278 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
20279 &[flock()]& are used (with the given timeout), so there has already been some
20280 waiting involved by the time locking fails. Nevertheless, Exim does not give up
20281 immediately. It retries up to
20283 (lock_retries * lock_interval) / <timeout>
20285 times (rounded up).
20288 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
20289 and/or &[flock()]& locks) and then deletes the lock file if one was created.
20292 .section "Operational details for delivery to a new file" "SECTopdir"
20293 .cindex "delivery" "to single file"
20294 .cindex "&""From""& line"
20295 When the &%directory%& option is set instead of &%file%&, each message is
20296 delivered into a newly-created file or set of files. When &(appendfile)& is
20297 activated directly from a &(redirect)& router, neither &%file%& nor
20298 &%directory%& is normally set, because the path for delivery is supplied by the
20299 router. (See for example, the &(address_file)& transport in the default
20300 configuration.) In this case, delivery is to a new file if either the path name
20301 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
20303 No locking is required while writing the message to a new file, so the various
20304 locking options of the transport are ignored. The &"From"& line that by default
20305 separates messages in a single file is not normally needed, nor is the escaping
20306 of message lines that start with &"From"&, and there is no need to ensure a
20307 newline at the end of each message. Consequently, the default values for
20308 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
20309 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
20311 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
20312 the files in the delivery directory by default. However, you can specify a
20313 different directory by setting &%quota_directory%&. Also, for maildir
20314 deliveries (see below) the &_maildirfolder_& convention is honoured.
20317 .cindex "maildir format"
20318 .cindex "mailstore format"
20319 There are three different ways in which delivery to individual files can be
20320 done, controlled by the settings of the &%maildir_format%& and
20321 &%mailstore_format%& options. Note that code to support maildir or mailstore
20322 formats is not included in the binary unless SUPPORT_MAILDIR or
20323 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
20325 .cindex "directory creation"
20326 In all three cases an attempt is made to create the directory and any necessary
20327 sub-directories if they do not exist, provided that the &%create_directory%&
20328 option is set (the default). The location of a created directory can be
20329 constrained by setting &%create_file%&. A created directory's mode is given by
20330 the &%directory_mode%& option. If creation fails, or if the
20331 &%create_directory%& option is not set when creation is required, delivery is
20336 .section "Maildir delivery" "SECTmaildirdelivery"
20337 .cindex "maildir format" "description of"
20338 If the &%maildir_format%& option is true, Exim delivers each message by writing
20339 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
20340 directory that is defined by the &%directory%& option (the &"delivery
20341 directory"&). If the delivery is successful, the file is renamed into the
20342 &_new_& subdirectory.
20344 In the file name, <&'stime'&> is the current time of day in seconds, and
20345 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
20346 Exim checks that the time-of-day clock has moved on by at least one microsecond
20347 before terminating the delivery process. This guarantees uniqueness for the
20348 file name. However, as a precaution, Exim calls &[stat()]& for the file before
20349 opening it. If any response other than ENOENT (does not exist) is given,
20350 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
20352 Before Exim carries out a maildir delivery, it ensures that subdirectories
20353 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
20354 do not exist, Exim tries to create them and any superior directories in their
20355 path, subject to the &%create_directory%& and &%create_file%& options. If the
20356 &%maildirfolder_create_regex%& option is set, and the regular expression it
20357 contains matches the delivery directory, Exim also ensures that a file called
20358 &_maildirfolder_& exists in the delivery directory. If a missing directory or
20359 &_maildirfolder_& file cannot be created, delivery is deferred.
20361 These features make it possible to use Exim to create all the necessary files
20362 and directories in a maildir mailbox, including subdirectories for maildir++
20363 folders. Consider this example:
20365 maildir_format = true
20366 directory = /var/mail/$local_part\
20367 ${if eq{$local_part_suffix}{}{}\
20368 {/.${substr_1:$local_part_suffix}}}
20369 maildirfolder_create_regex = /\.[^/]+$
20371 If &$local_part_suffix$& is empty (there was no suffix for the local part),
20372 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
20373 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
20374 not match this name, so Exim will not look for or create the file
20375 &_/var/mail/pimbo/maildirfolder_&, though it will create
20376 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
20378 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
20379 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
20380 does match &%maildirfolder_create_regex%&. In this case, Exim will create
20381 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
20382 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
20384 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
20385 not inadvertently match the toplevel maildir directory, because a
20386 &_maildirfolder_& file at top level would completely break quota calculations.
20388 .cindex "quota" "in maildir delivery"
20389 .cindex "maildir++"
20390 If Exim is required to check a &%quota%& setting before a maildir delivery, and
20391 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
20392 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
20393 Exim assumes the directory is a maildir++ folder directory, which is one level
20394 down from the user's top level mailbox directory. This causes it to start at
20395 the parent directory instead of the current directory when calculating the
20396 amount of space used.
20398 One problem with delivering into a multi-file mailbox is that it is
20399 computationally expensive to compute the size of the mailbox for quota
20400 checking. Various approaches have been taken to reduce the amount of work
20401 needed. The next two sections describe two of them. A third alternative is to
20402 use some external process for maintaining the size data, and use the expansion
20403 of the &%mailbox_size%& option as a way of importing it into Exim.
20408 .section "Using tags to record message sizes" "SECID135"
20409 If &%maildir_tag%& is set, the string is expanded for each delivery.
20410 When the maildir file is renamed into the &_new_& sub-directory, the
20411 tag is added to its name. However, if adding the tag takes the length of the
20412 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
20413 the tag is dropped and the maildir file is created with no tag.
20415 .vindex "&$message_size$&"
20416 Tags can be used to encode the size of files in their names; see
20417 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
20418 happens after the message has been written. The value of the &$message_size$&
20419 variable is set to the number of bytes actually written. If the expansion is
20420 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
20421 be deferred. The expanded tag may contain any printing characters except &"/"&.
20422 Non-printing characters in the string are ignored; if the resulting string is
20423 empty, it is ignored. If it starts with an alphanumeric character, a leading
20428 .section "Using a maildirsize file" "SECID136"
20429 .cindex "quota" "in maildir delivery"
20430 .cindex "maildir format" "&_maildirsize_& file"
20431 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
20432 storing quota and message size information in a file called &_maildirsize_&
20433 within the toplevel maildir directory. If this file does not exist, Exim
20434 creates it, setting the quota from the &%quota%& option of the transport. If
20435 the maildir directory itself does not exist, it is created before any attempt
20436 to write a &_maildirsize_& file.
20438 The &_maildirsize_& file is used to hold information about the sizes of
20439 messages in the maildir, thus speeding up quota calculations. The quota value
20440 in the file is just a cache; if the quota is changed in the transport, the new
20441 value overrides the cached value when the next message is delivered. The cache
20442 is maintained for the benefit of other programs that access the maildir and
20443 need to know the quota.
20445 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
20446 file is maintained (with a zero quota setting), but no quota is imposed.
20448 A regular expression is available for controlling which directories in the
20449 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
20450 See the description of the &%maildir_quota_directory_regex%& option above for
20454 .section "Mailstore delivery" "SECID137"
20455 .cindex "mailstore format" "description of"
20456 If the &%mailstore_format%& option is true, each message is written as two
20457 files in the given directory. A unique base name is constructed from the
20458 message id and the current delivery process, and the files that are written use
20459 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
20460 contains the message's envelope, and the &_.msg_& file contains the message
20461 itself. The base name is placed in the variable &$mailstore_basename$&.
20463 During delivery, the envelope is first written to a file with the suffix
20464 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
20465 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
20466 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
20467 file before accessing either of them. An alternative approach is to wait for
20468 the absence of a &_.tmp_& file.
20470 The envelope file starts with any text defined by the &%mailstore_prefix%&
20471 option, expanded and terminated by a newline if there isn't one. Then follows
20472 the sender address on one line, then all the recipient addresses, one per line.
20473 There can be more than one recipient only if the &%batch_max%& option is set
20474 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
20475 appended to the file, followed by a newline if it does not end with one.
20477 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
20478 failure, it is ignored. Other expansion errors are treated as serious
20479 configuration errors, and delivery is deferred. The variable
20480 &$mailstore_basename$& is available for use during these expansions.
20483 .section "Non-special new file delivery" "SECID138"
20484 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
20485 file is created directly in the named directory. For example, when delivering
20486 messages into files in batched SMTP format for later delivery to some host (see
20487 section &<<SECTbatchSMTP>>&), a setting such as
20489 directory = /var/bsmtp/$host
20491 might be used. A message is written to a file with a temporary name, which is
20492 then renamed when the delivery is complete. The final name is obtained by
20493 expanding the contents of the &%directory_file%& option.
20494 .ecindex IIDapptra1
20495 .ecindex IIDapptra2
20502 . ////////////////////////////////////////////////////////////////////////////
20503 . ////////////////////////////////////////////////////////////////////////////
20505 .chapter "The autoreply transport" "CHID8"
20506 .scindex IIDauttra1 "transports" "&(autoreply)&"
20507 .scindex IIDauttra2 "&(autoreply)& transport"
20508 The &(autoreply)& transport is not a true transport in that it does not cause
20509 the message to be transmitted. Instead, it generates a new mail message as an
20510 automatic reply to the incoming message. &'References:'& and
20511 &'Auto-Submitted:'& header lines are included. These are constructed according
20512 to the rules in RFCs 2822 and 3834, respectively.
20514 If the router that passes the message to this transport does not have the
20515 &%unseen%& option set, the original message (for the current recipient) is not
20516 delivered anywhere. However, when the &%unseen%& option is set on the router
20517 that passes the message to this transport, routing of the address continues, so
20518 another router can set up a normal message delivery.
20521 The &(autoreply)& transport is usually run as the result of mail filtering, a
20522 &"vacation"& message being the standard example. However, it can also be run
20523 directly from a router like any other transport. To reduce the possibility of
20524 message cascades, messages created by the &(autoreply)& transport always have
20525 empty envelope sender addresses, like bounce messages.
20527 The parameters of the message to be sent can be specified in the configuration
20528 by options described below. However, these are used only when the address
20529 passed to the transport does not contain its own reply information. When the
20530 transport is run as a consequence of a
20532 or &%vacation%& command in a filter file, the parameters of the message are
20533 supplied by the filter, and passed with the address. The transport's options
20534 that define the message are then ignored (so they are not usually set in this
20535 case). The message is specified entirely by the filter or by the transport; it
20536 is never built from a mixture of options. However, the &%file_optional%&,
20537 &%mode%&, and &%return_message%& options apply in all cases.
20539 &(Autoreply)& is implemented as a local transport. When used as a result of a
20540 command in a user's filter file, &(autoreply)& normally runs under the uid and
20541 gid of the user, and with appropriate current and home directories (see chapter
20542 &<<CHAPenvironment>>&).
20544 There is a subtle difference between routing a message to a &(pipe)& transport
20545 that generates some text to be returned to the sender, and routing it to an
20546 &(autoreply)& transport. This difference is noticeable only if more than one
20547 address from the same message is so handled. In the case of a pipe, the
20548 separate outputs from the different addresses are gathered up and returned to
20549 the sender in a single message, whereas if &(autoreply)& is used, a separate
20550 message is generated for each address that is passed to it.
20552 Non-printing characters are not permitted in the header lines generated for the
20553 message that &(autoreply)& creates, with the exception of newlines that are
20554 immediately followed by white space. If any non-printing characters are found,
20555 the transport defers.
20556 Whether characters with the top bit set count as printing characters or not is
20557 controlled by the &%print_topbitchars%& global option.
20559 If any of the generic options for manipulating headers (for example,
20560 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
20561 of the original message that is included in the generated message when
20562 &%return_message%& is set. They do not apply to the generated message itself.
20564 .vindex "&$sender_address$&"
20565 If the &(autoreply)& transport receives return code 2 from Exim when it submits
20566 the message, indicating that there were no recipients, it does not treat this
20567 as an error. This means that autoreplies sent to &$sender_address$& when this
20568 is empty (because the incoming message is a bounce message) do not cause
20569 problems. They are just discarded.
20573 .section "Private options for autoreply" "SECID139"
20574 .cindex "options" "&(autoreply)& transport"
20576 .option bcc autoreply string&!! unset
20577 This specifies the addresses that are to receive &"blind carbon copies"& of the
20578 message when the message is specified by the transport.
20581 .option cc autoreply string&!! unset
20582 This specifies recipients of the message and the contents of the &'Cc:'& header
20583 when the message is specified by the transport.
20586 .option file autoreply string&!! unset
20587 The contents of the file are sent as the body of the message when the message
20588 is specified by the transport. If both &%file%& and &%text%& are set, the text
20589 string comes first.
20592 .option file_expand autoreply boolean false
20593 If this is set, the contents of the file named by the &%file%& option are
20594 subjected to string expansion as they are added to the message.
20597 .option file_optional autoreply boolean false
20598 If this option is true, no error is generated if the file named by the &%file%&
20599 option or passed with the address does not exist or cannot be read.
20602 .option from autoreply string&!! unset
20603 This specifies the contents of the &'From:'& header when the message is
20604 specified by the transport.
20607 .option headers autoreply string&!! unset
20608 This specifies additional RFC 2822 headers that are to be added to the message
20609 when the message is specified by the transport. Several can be given by using
20610 &"\n"& to separate them. There is no check on the format.
20613 .option log autoreply string&!! unset
20614 This option names a file in which a record of every message sent is logged when
20615 the message is specified by the transport.
20618 .option mode autoreply "octal integer" 0600
20619 If either the log file or the &"once"& file has to be created, this mode is
20623 .option never_mail autoreply "address list&!!" unset
20624 If any run of the transport creates a message with a recipient that matches any
20625 item in the list, that recipient is quietly discarded. If all recipients are
20626 discarded, no message is created. This applies both when the recipients are
20627 generated by a filter and when they are specified in the transport.
20631 .option once autoreply string&!! unset
20632 This option names a file or DBM database in which a record of each &'To:'&
20633 recipient is kept when the message is specified by the transport. &*Note*&:
20634 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
20636 If &%once%& is unset, or is set to an empty string, the message is always sent.
20637 By default, if &%once%& is set to a non-empty file name, the message
20638 is not sent if a potential recipient is already listed in the database.
20639 However, if the &%once_repeat%& option specifies a time greater than zero, the
20640 message is sent if that much time has elapsed since a message was last sent to
20641 this recipient. A setting of zero time for &%once_repeat%& (the default)
20642 prevents a message from being sent a second time &-- in this case, zero means
20645 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
20646 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
20647 greater than zero, it changes the way Exim implements the &%once%& option.
20648 Instead of using a DBM file to record every recipient it sends to, it uses a
20649 regular file, whose size will never get larger than the given value.
20651 In the file, Exim keeps a linear list of recipient addresses and the times at
20652 which they were sent messages. If the file is full when a new address needs to
20653 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
20654 means that a given recipient may receive multiple messages, but at
20655 unpredictable intervals that depend on the rate of turnover of addresses in the
20656 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
20659 .option once_file_size autoreply integer 0
20660 See &%once%& above.
20663 .option once_repeat autoreply time&!! 0s
20664 See &%once%& above.
20665 After expansion, the value of this option must be a valid time value.
20668 .option reply_to autoreply string&!! unset
20669 This specifies the contents of the &'Reply-To:'& header when the message is
20670 specified by the transport.
20673 .option return_message autoreply boolean false
20674 If this is set, a copy of the original message is returned with the new
20675 message, subject to the maximum size set in the &%return_size_limit%& global
20676 configuration option.
20679 .option subject autoreply string&!! unset
20680 This specifies the contents of the &'Subject:'& header when the message is
20681 specified by the transport. It is tempting to quote the original subject in
20682 automatic responses. For example:
20684 subject = Re: $h_subject:
20686 There is a danger in doing this, however. It may allow a third party to
20687 subscribe your users to an opt-in mailing list, provided that the list accepts
20688 bounce messages as subscription confirmations. Well-managed lists require a
20689 non-bounce message to confirm a subscription, so the danger is relatively
20694 .option text autoreply string&!! unset
20695 This specifies a single string to be used as the body of the message when the
20696 message is specified by the transport. If both &%text%& and &%file%& are set,
20697 the text comes first.
20700 .option to autoreply string&!! unset
20701 This specifies recipients of the message and the contents of the &'To:'& header
20702 when the message is specified by the transport.
20703 .ecindex IIDauttra1
20704 .ecindex IIDauttra2
20709 . ////////////////////////////////////////////////////////////////////////////
20710 . ////////////////////////////////////////////////////////////////////////////
20712 .chapter "The lmtp transport" "CHAPLMTP"
20713 .cindex "transports" "&(lmtp)&"
20714 .cindex "&(lmtp)& transport"
20715 .cindex "LMTP" "over a pipe"
20716 .cindex "LMTP" "over a socket"
20717 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
20719 or by interacting with a Unix domain socket.
20720 This transport is something of a cross between the &(pipe)& and &(smtp)&
20721 transports. Exim also has support for using LMTP over TCP/IP; this is
20722 implemented as an option for the &(smtp)& transport. Because LMTP is expected
20723 to be of minority interest, the default build-time configure in &_src/EDITME_&
20724 has it commented out. You need to ensure that
20728 .cindex "options" "&(lmtp)& transport"
20729 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
20730 included in the Exim binary. The private options of the &(lmtp)& transport are
20733 .option batch_id lmtp string&!! unset
20734 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20737 .option batch_max lmtp integer 1
20738 This limits the number of addresses that can be handled in a single delivery.
20739 Most LMTP servers can handle several addresses at once, so it is normally a
20740 good idea to increase this value. See the description of local delivery
20741 batching in chapter &<<CHAPbatching>>&.
20744 .option command lmtp string&!! unset
20745 This option must be set if &%socket%& is not set. The string is a command which
20746 is run in a separate process. It is split up into a command name and list of
20747 arguments, each of which is separately expanded (so expansion cannot change the
20748 number of arguments). The command is run directly, not via a shell. The message
20749 is passed to the new process using the standard input and output to operate the
20752 .option ignore_quota lmtp boolean false
20753 .cindex "LMTP" "ignoring quota errors"
20754 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
20755 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
20756 in its response to the LHLO command.
20758 .option socket lmtp string&!! unset
20759 This option must be set if &%command%& is not set. The result of expansion must
20760 be the name of a Unix domain socket. The transport connects to the socket and
20761 delivers the message to it using the LMTP protocol.
20764 .option timeout lmtp time 5m
20765 The transport is aborted if the created process or Unix domain socket does not
20766 respond to LMTP commands or message input within this timeout. Delivery
20767 is deferred, and will be tried again later. Here is an example of a typical
20772 command = /some/local/lmtp/delivery/program
20776 This delivers up to 20 addresses at a time, in a mixture of domains if
20777 necessary, running as the user &'exim'&.
20781 . ////////////////////////////////////////////////////////////////////////////
20782 . ////////////////////////////////////////////////////////////////////////////
20784 .chapter "The pipe transport" "CHAPpipetransport"
20785 .scindex IIDpiptra1 "transports" "&(pipe)&"
20786 .scindex IIDpiptra2 "&(pipe)& transport"
20787 The &(pipe)& transport is used to deliver messages via a pipe to a command
20788 running in another process. One example is the use of &(pipe)& as a
20789 pseudo-remote transport for passing messages to some other delivery mechanism
20790 (such as UUCP). Another is the use by individual users to automatically process
20791 their incoming messages. The &(pipe)& transport can be used in one of the
20795 .vindex "&$local_part$&"
20796 A router routes one address to a transport in the normal way, and the
20797 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
20798 contains the local part of the address (as usual), and the command that is run
20799 is specified by the &%command%& option on the transport.
20801 .vindex "&$pipe_addresses$&"
20802 If the &%batch_max%& option is set greater than 1 (the default is 1), the
20803 transport can handle more than one address in a single run. In this case, when
20804 more than one address is routed to the transport, &$local_part$& is not set
20805 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
20806 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
20807 that are routed to the transport.
20809 .vindex "&$address_pipe$&"
20810 A router redirects an address directly to a pipe command (for example, from an
20811 alias or forward file). In this case, &$address_pipe$& contains the text of the
20812 pipe command, and the &%command%& option on the transport is ignored. If only
20813 one address is being transported (&%batch_max%& is not greater than one, or
20814 only one address was redirected to this pipe command), &$local_part$& contains
20815 the local part that was redirected.
20819 The &(pipe)& transport is a non-interactive delivery method. Exim can also
20820 deliver messages over pipes using the LMTP interactive protocol. This is
20821 implemented by the &(lmtp)& transport.
20823 In the case when &(pipe)& is run as a consequence of an entry in a local user's
20824 &_.forward_& file, the command runs under the uid and gid of that user. In
20825 other cases, the uid and gid have to be specified explicitly, either on the
20826 transport or on the router that handles the address. Current and &"home"&
20827 directories are also controllable. See chapter &<<CHAPenvironment>>& for
20828 details of the local delivery environment and chapter &<<CHAPbatching>>&
20829 for a discussion of local delivery batching.
20832 .section "Concurrent delivery" "SECID140"
20833 If two messages arrive at almost the same time, and both are routed to a pipe
20834 delivery, the two pipe transports may be run concurrently. You must ensure that
20835 any pipe commands you set up are robust against this happening. If the commands
20836 write to a file, the &%exim_lock%& utility might be of use.
20841 .section "Returned status and data" "SECID141"
20842 .cindex "&(pipe)& transport" "returned data"
20843 If the command exits with a non-zero return code, the delivery is deemed to
20844 have failed, unless either the &%ignore_status%& option is set (in which case
20845 the return code is treated as zero), or the return code is one of those listed
20846 in the &%temp_errors%& option, which are interpreted as meaning &"try again
20847 later"&. In this case, delivery is deferred. Details of a permanent failure are
20848 logged, but are not included in the bounce message, which merely contains
20849 &"local delivery failed"&.
20851 If the return code is greater than 128 and the command being run is a shell
20852 script, it normally means that the script was terminated by a signal whose
20853 value is the return code minus 128.
20855 If Exim is unable to run the command (that is, if &[execve()]& fails), the
20856 return code is set to 127. This is the value that a shell returns if it is
20857 asked to run a non-existent command. The wording for the log line suggests that
20858 a non-existent command may be the problem.
20860 The &%return_output%& option can affect the result of a pipe delivery. If it is
20861 set and the command produces any output on its standard output or standard
20862 error streams, the command is considered to have failed, even if it gave a zero
20863 return code or if &%ignore_status%& is set. The output from the command is
20864 included as part of the bounce message. The &%return_fail_output%& option is
20865 similar, except that output is returned only when the command exits with a
20866 failure return code, that is, a value other than zero or a code that matches
20871 .section "How the command is run" "SECThowcommandrun"
20872 .cindex "&(pipe)& transport" "path for command"
20873 The command line is (by default) broken down into a command name and arguments
20874 by the &(pipe)& transport itself. The &%allow_commands%& and
20875 &%restrict_to_path%& options can be used to restrict the commands that may be
20878 .cindex "quoting" "in pipe command"
20879 Unquoted arguments are delimited by white space. If an argument appears in
20880 double quotes, backslash is interpreted as an escape character in the usual
20881 way. If an argument appears in single quotes, no escaping is done.
20883 String expansion is applied to the command line except when it comes from a
20884 traditional &_.forward_& file (commands from a filter file are expanded). The
20885 expansion is applied to each argument in turn rather than to the whole line.
20886 For this reason, any string expansion item that contains white space must be
20887 quoted so as to be contained within a single argument. A setting such as
20889 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
20891 will not work, because the expansion item gets split between several
20892 arguments. You have to write
20894 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
20896 to ensure that it is all in one argument. The expansion is done in this way,
20897 argument by argument, so that the number of arguments cannot be changed as a
20898 result of expansion, and quotes or backslashes in inserted variables do not
20899 interact with external quoting. However, this leads to problems if you want to
20900 generate multiple arguments (or the command name plus arguments) from a single
20901 expansion. In this situation, the simplest solution is to use a shell. For
20904 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
20907 .cindex "transport" "filter"
20908 .cindex "filter" "transport filter"
20909 .vindex "&$pipe_addresses$&"
20910 Special handling takes place when an argument consists of precisely the text
20911 &`$pipe_addresses`&. This is not a general expansion variable; the only
20912 place this string is recognized is when it appears as an argument for a pipe or
20913 transport filter command. It causes each address that is being handled to be
20914 inserted in the argument list at that point &'as a separate argument'&. This
20915 avoids any problems with spaces or shell metacharacters, and is of use when a
20916 &(pipe)& transport is handling groups of addresses in a batch.
20918 After splitting up into arguments and expansion, the resulting command is run
20919 in a subprocess directly from the transport, &'not'& under a shell. The
20920 message that is being delivered is supplied on the standard input, and the
20921 standard output and standard error are both connected to a single pipe that is
20922 read by Exim. The &%max_output%& option controls how much output the command
20923 may produce, and the &%return_output%& and &%return_fail_output%& options
20924 control what is done with it.
20926 Not running the command under a shell (by default) lessens the security risks
20927 in cases when a command from a user's filter file is built out of data that was
20928 taken from an incoming message. If a shell is required, it can of course be
20929 explicitly specified as the command to be run. However, there are circumstances
20930 where existing commands (for example, in &_.forward_& files) expect to be run
20931 under a shell and cannot easily be modified. To allow for these cases, there is
20932 an option called &%use_shell%&, which changes the way the &(pipe)& transport
20933 works. Instead of breaking up the command line as just described, it expands it
20934 as a single string and passes the result to &_/bin/sh_&. The
20935 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
20936 with &%use_shell%&, and the whole mechanism is inherently less secure.
20940 .section "Environment variables" "SECTpipeenv"
20941 .cindex "&(pipe)& transport" "environment for command"
20942 .cindex "environment for pipe transport"
20943 The environment variables listed below are set up when the command is invoked.
20944 This list is a compromise for maximum compatibility with other MTAs. Note that
20945 the &%environment%& option can be used to add additional variables to this
20948 &`DOMAIN `& the domain of the address
20949 &`HOME `& the home directory, if set
20950 &`HOST `& the host name when called from a router (see below)
20951 &`LOCAL_PART `& see below
20952 &`LOCAL_PART_PREFIX `& see below
20953 &`LOCAL_PART_SUFFIX `& see below
20954 &`LOGNAME `& see below
20955 &`MESSAGE_ID `& Exim's local ID for the message
20956 &`PATH `& as specified by the &%path%& option below
20957 &`QUALIFY_DOMAIN `& the sender qualification domain
20958 &`RECIPIENT `& the complete recipient address
20959 &`SENDER `& the sender of the message (empty if a bounce)
20960 &`SHELL `& &`/bin/sh`&
20961 &`TZ `& the value of the &%timezone%& option, if set
20962 &`USER `& see below
20964 When a &(pipe)& transport is called directly from (for example) an &(accept)&
20965 router, LOCAL_PART is set to the local part of the address. When it is
20966 called as a result of a forward or alias expansion, LOCAL_PART is set to
20967 the local part of the address that was expanded. In both cases, any affixes are
20968 removed from the local part, and made available in LOCAL_PART_PREFIX and
20969 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
20970 same value as LOCAL_PART for compatibility with other MTAs.
20973 HOST is set only when a &(pipe)& transport is called from a router that
20974 associates hosts with an address, typically when using &(pipe)& as a
20975 pseudo-remote transport. HOST is set to the first host name specified by
20979 If the transport's generic &%home_directory%& option is set, its value is used
20980 for the HOME environment variable. Otherwise, a home directory may be set
20981 by the router's &%transport_home_directory%& option, which defaults to the
20982 user's home directory if &%check_local_user%& is set.
20985 .section "Private options for pipe" "SECID142"
20986 .cindex "options" "&(pipe)& transport"
20990 .option allow_commands pipe "string list&!!" unset
20991 .cindex "&(pipe)& transport" "permitted commands"
20992 The string is expanded, and is then interpreted as a colon-separated list of
20993 permitted commands. If &%restrict_to_path%& is not set, the only commands
20994 permitted are those in the &%allow_commands%& list. They need not be absolute
20995 paths; the &%path%& option is still used for relative paths. If
20996 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
20997 in the &%allow_commands%& list, or a name without any slashes that is found on
20998 the path. In other words, if neither &%allow_commands%& nor
20999 &%restrict_to_path%& is set, there is no restriction on the command, but
21000 otherwise only commands that are permitted by one or the other are allowed. For
21003 allow_commands = /usr/bin/vacation
21005 and &%restrict_to_path%& is not set, the only permitted command is
21006 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
21007 &%use_shell%& is set.
21010 .option batch_id pipe string&!! unset
21011 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21014 .option batch_max pipe integer 1
21015 This limits the number of addresses that can be handled in a single delivery.
21016 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21019 .option check_string pipe string unset
21020 As &(pipe)& writes the message, the start of each line is tested for matching
21021 &%check_string%&, and if it does, the initial matching characters are replaced
21022 by the contents of &%escape_string%&, provided both are set. The value of
21023 &%check_string%& is a literal string, not a regular expression, and the case of
21024 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
21025 of &%check_string%& and &%escape_string%& are forced to values that implement
21026 the SMTP escaping protocol. Any settings made in the configuration file are
21030 .option command pipe string&!! unset
21031 This option need not be set when &(pipe)& is being used to deliver to pipes
21032 obtained directly from address redirections. In other cases, the option must be
21033 set, to provide a command to be run. It need not yield an absolute path (see
21034 the &%path%& option below). The command is split up into separate arguments by
21035 Exim, and each argument is separately expanded, as described in section
21036 &<<SECThowcommandrun>>& above.
21039 .option environment pipe string&!! unset
21040 .cindex "&(pipe)& transport" "environment for command"
21041 .cindex "environment for &(pipe)& transport"
21042 This option is used to add additional variables to the environment in which the
21043 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
21044 a string which is expanded, and then interpreted as a colon-separated list of
21045 environment settings of the form <&'name'&>=<&'value'&>.
21048 .option escape_string pipe string unset
21049 See &%check_string%& above.
21052 .option freeze_exec_fail pipe boolean false
21053 .cindex "exec failure"
21054 .cindex "failure of exec"
21055 .cindex "&(pipe)& transport" "failure of exec"
21056 Failure to exec the command in a pipe transport is by default treated like
21057 any other failure while running the command. However, if &%freeze_exec_fail%&
21058 is set, failure to exec is treated specially, and causes the message to be
21059 frozen, whatever the setting of &%ignore_status%&.
21062 .option ignore_status pipe boolean false
21063 If this option is true, the status returned by the subprocess that is set up to
21064 run the command is ignored, and Exim behaves as if zero had been returned.
21065 Otherwise, a non-zero status or termination by signal causes an error return
21066 from the transport unless the status value is one of those listed in
21067 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
21069 &*Note*&: This option does not apply to timeouts, which do not return a status.
21070 See the &%timeout_defer%& option for how timeouts are handled.
21072 .option log_defer_output pipe boolean false
21073 .cindex "&(pipe)& transport" "logging output"
21074 If this option is set, and the status returned by the command is
21075 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
21076 and any output was produced, the first line of it is written to the main log.
21079 .option log_fail_output pipe boolean false
21080 If this option is set, and the command returns any output, and also ends with a
21081 return code that is neither zero nor one of the return codes listed in
21082 &%temp_errors%& (that is, the delivery failed), the first line of output is
21083 written to the main log. This option and &%log_output%& are mutually exclusive.
21084 Only one of them may be set.
21088 .option log_output pipe boolean false
21089 If this option is set and the command returns any output, the first line of
21090 output is written to the main log, whatever the return code. This option and
21091 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
21095 .option max_output pipe integer 20K
21096 This specifies the maximum amount of output that the command may produce on its
21097 standard output and standard error file combined. If the limit is exceeded, the
21098 process running the command is killed. This is intended as a safety measure to
21099 catch runaway processes. The limit is applied independently of the settings of
21100 the options that control what is done with such output (for example,
21101 &%return_output%&). Because of buffering effects, the amount of output may
21102 exceed the limit by a small amount before Exim notices.
21105 .option message_prefix pipe string&!! "see below"
21106 The string specified here is expanded and output at the start of every message.
21107 The default is unset if &%use_bsmtp%& is set. Otherwise it is
21110 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
21114 .cindex "&%tmail%&"
21115 .cindex "&""From""& line"
21116 This is required by the commonly used &_/usr/bin/vacation_& program.
21117 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
21118 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
21123 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21124 &`\n`& to &`\r\n`& in &%message_prefix%&.
21127 .option message_suffix pipe string&!! "see below"
21128 The string specified here is expanded and output at the end of every message.
21129 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
21130 The suffix can be suppressed by setting
21134 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21135 &`\n`& to &`\r\n`& in &%message_suffix%&.
21138 .option path pipe string "see below"
21139 This option specifies the string that is set up in the PATH environment
21140 variable of the subprocess. The default is:
21144 If the &%command%& option does not yield an absolute path name, the command is
21145 sought in the PATH directories, in the usual way. &*Warning*&: This does not
21146 apply to a command specified as a transport filter.
21149 .option permit_coredump pipe boolean false
21150 Normally Exim inhibits core-dumps during delivery. If you have a need to get
21151 a core-dump of a pipe command, enable this command. This enables core-dumps
21152 during delivery and affects both the Exim binary and the pipe command run.
21153 It is recommended that this option remain off unless and until you have a need
21154 for it and that this only be enabled when needed, as the risk of excessive
21155 resource consumption can be quite high. Note also that Exim is typically
21156 installed as a setuid binary and most operating systems will inhibit coredumps
21157 of these by default, so further OS-specific action may be required.
21160 .option pipe_as_creator pipe boolean false
21161 .cindex "uid (user id)" "local delivery"
21162 If the generic &%user%& option is not set and this option is true, the delivery
21163 process is run under the uid that was in force when Exim was originally called
21164 to accept the message. If the group id is not otherwise set (via the generic
21165 &%group%& option), the gid that was in force when Exim was originally called to
21166 accept the message is used.
21169 .option restrict_to_path pipe boolean false
21170 When this option is set, any command name not listed in &%allow_commands%& must
21171 contain no slashes. The command is searched for only in the directories listed
21172 in the &%path%& option. This option is intended for use in the case when a pipe
21173 command has been generated from a user's &_.forward_& file. This is usually
21174 handled by a &(pipe)& transport called &%address_pipe%&.
21177 .option return_fail_output pipe boolean false
21178 If this option is true, and the command produced any output and ended with a
21179 return code other than zero or one of the codes listed in &%temp_errors%& (that
21180 is, the delivery failed), the output is returned in the bounce message.
21181 However, if the message has a null sender (that is, it is itself a bounce
21182 message), output from the command is discarded. This option and
21183 &%return_output%& are mutually exclusive. Only one of them may be set.
21187 .option return_output pipe boolean false
21188 If this option is true, and the command produced any output, the delivery is
21189 deemed to have failed whatever the return code from the command, and the output
21190 is returned in the bounce message. Otherwise, the output is just discarded.
21191 However, if the message has a null sender (that is, it is a bounce message),
21192 output from the command is always discarded, whatever the setting of this
21193 option. This option and &%return_fail_output%& are mutually exclusive. Only one
21194 of them may be set.
21198 .option temp_errors pipe "string list" "see below"
21199 .cindex "&(pipe)& transport" "temporary failure"
21200 This option contains either a colon-separated list of numbers, or a single
21201 asterisk. If &%ignore_status%& is false
21202 and &%return_output%& is not set,
21203 and the command exits with a non-zero return code, the failure is treated as
21204 temporary and the delivery is deferred if the return code matches one of the
21205 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
21206 codes are treated as permanent errors. The default setting contains the codes
21207 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
21208 compiled on a system that does not define these macros, it assumes values of 75
21209 and 73, respectively.
21212 .option timeout pipe time 1h
21213 If the command fails to complete within this time, it is killed. This normally
21214 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
21215 specifies no timeout. In order to ensure that any subprocesses created by the
21216 command are also killed, Exim makes the initial process a process group leader,
21217 and kills the whole process group on a timeout. However, this can be defeated
21218 if one of the processes starts a new process group.
21220 .option timeout_defer pipe boolean false
21221 A timeout in a &(pipe)& transport, either in the command that the transport
21222 runs, or in a transport filter that is associated with it, is by default
21223 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
21224 is set true, both kinds of timeout become temporary errors, causing the
21225 delivery to be deferred.
21227 .option umask pipe "octal integer" 022
21228 This specifies the umask setting for the subprocess that runs the command.
21231 .option use_bsmtp pipe boolean false
21232 .cindex "envelope sender"
21233 If this option is set true, the &(pipe)& transport writes messages in &"batch
21234 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
21235 commands. If you want to include a leading HELO command with such messages,
21236 you can do so by setting the &%message_prefix%& option. See section
21237 &<<SECTbatchSMTP>>& for details of batch SMTP.
21239 .option use_classresources pipe boolean false
21240 .cindex "class resources (BSD)"
21241 This option is available only when Exim is running on FreeBSD, NetBSD, or
21242 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
21243 resource limits when a &(pipe)& transport is run to perform a delivery. The
21244 limits for the uid under which the pipe is to run are obtained from the login
21248 .option use_crlf pipe boolean false
21249 .cindex "carriage return"
21251 This option causes lines to be terminated with the two-character CRLF sequence
21252 (carriage return, linefeed) instead of just a linefeed character. In the case
21253 of batched SMTP, the byte sequence written to the pipe is then an exact image
21254 of what would be sent down a real SMTP connection.
21256 The contents of the &%message_prefix%& and &%message_suffix%& options are
21257 written verbatim, so must contain their own carriage return characters if these
21258 are needed. When &%use_bsmtp%& is not set, the default values for both
21259 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
21260 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
21263 .option use_shell pipe boolean false
21264 .vindex "&$pipe_addresses$&"
21265 If this option is set, it causes the command to be passed to &_/bin/sh_&
21266 instead of being run directly from the transport, as described in section
21267 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
21268 where the command is expected to be run under a shell and cannot easily be
21269 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
21270 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
21271 command is expanded as a single string, and handed to &_/bin/sh_& as data for
21276 .section "Using an external local delivery agent" "SECID143"
21277 .cindex "local delivery" "using an external agent"
21278 .cindex "&'procmail'&"
21279 .cindex "external local delivery"
21280 .cindex "delivery" "&'procmail'&"
21281 .cindex "delivery" "by external agent"
21282 The &(pipe)& transport can be used to pass all messages that require local
21283 delivery to a separate local delivery agent such as &%procmail%&. When doing
21284 this, care must be taken to ensure that the pipe is run under an appropriate
21285 uid and gid. In some configurations one wants this to be a uid that is trusted
21286 by the delivery agent to supply the correct sender of the message. It may be
21287 necessary to recompile or reconfigure the delivery agent so that it trusts an
21288 appropriate user. The following is an example transport and router
21289 configuration for &%procmail%&:
21294 command = /usr/local/bin/procmail -d $local_part
21298 check_string = "From "
21299 escape_string = ">From "
21308 transport = procmail_pipe
21310 In this example, the pipe is run as the local user, but with the group set to
21311 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
21312 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
21313 user to supply a correct sender address. If you do not specify either a
21314 &%group%& or a &%user%& option, the pipe command is run as the local user. The
21315 home directory is the user's home directory by default.
21317 &*Note*&: The command that the pipe transport runs does &'not'& begin with
21321 as shown in some &%procmail%& documentation, because Exim does not by default
21322 use a shell to run pipe commands.
21325 The next example shows a transport and a router for a system where local
21326 deliveries are handled by the Cyrus IMAP server.
21329 local_delivery_cyrus:
21331 command = /usr/cyrus/bin/deliver \
21332 -m ${substr_1:$local_part_suffix} -- $local_part
21344 local_part_suffix = .*
21345 transport = local_delivery_cyrus
21347 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
21348 &%return_output%& to cause any text written by Cyrus to be returned to the
21350 .ecindex IIDpiptra1
21351 .ecindex IIDpiptra2
21354 . ////////////////////////////////////////////////////////////////////////////
21355 . ////////////////////////////////////////////////////////////////////////////
21357 .chapter "The smtp transport" "CHAPsmtptrans"
21358 .scindex IIDsmttra1 "transports" "&(smtp)&"
21359 .scindex IIDsmttra2 "&(smtp)& transport"
21360 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
21361 or LMTP protocol. The list of hosts to try can either be taken from the address
21362 that is being processed (having been set up by the router), or specified
21363 explicitly for the transport. Timeout and retry processing (see chapter
21364 &<<CHAPretry>>&) is applied to each IP address independently.
21367 .section "Multiple messages on a single connection" "SECID144"
21368 The sending of multiple messages over a single TCP/IP connection can arise in
21372 If a message contains more than &%max_rcpt%& (see below) addresses that are
21373 routed to the same host, more than one copy of the message has to be sent to
21374 that host. In this situation, multiple copies may be sent in a single run of
21375 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
21376 does when it has too many addresses to send in one message also depends on the
21377 value of the global &%remote_max_parallel%& option. Details are given in
21378 section &<<SECToutSMTPTCP>>&.)
21380 .cindex "hints database" "remembering routing"
21381 When a message has been successfully delivered over a TCP/IP connection, Exim
21382 looks in its hints database to see if there are any other messages awaiting a
21383 connection to the same host. If there are, a new delivery process is started
21384 for one of them, and the current TCP/IP connection is passed on to it. The new
21385 process may in turn send multiple copies and possibly create yet another
21390 For each copy sent over the same TCP/IP connection, a sequence counter is
21391 incremented, and if it ever gets to the value of &%connection_max_messages%&,
21392 no further messages are sent over that connection.
21396 .section "Use of the $host and $host_address variables" "SECID145"
21398 .vindex "&$host_address$&"
21399 At the start of a run of the &(smtp)& transport, the values of &$host$& and
21400 &$host_address$& are the name and IP address of the first host on the host list
21401 passed by the router. However, when the transport is about to connect to a
21402 specific host, and while it is connected to that host, &$host$& and
21403 &$host_address$& are set to the values for that host. These are the values
21404 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
21405 &%serialize_hosts%&, and the various TLS options are expanded.
21408 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
21409 .vindex &$tls_cipher$&
21410 .vindex &$tls_peerdn$&
21411 At the start of a run of the &(smtp)& transport, the values of &$tls_cipher$&
21412 and &$tls_peerdn$& are the values that were set when the message was received.
21413 These are the values that are used for options that are expanded before any
21414 SMTP connections are made. Just before each connection is made, these two
21415 variables are emptied. If TLS is subsequently started, they are set to the
21416 appropriate values for the outgoing connection, and these are the values that
21417 are in force when any authenticators are run and when the
21418 &%authenticated_sender%& option is expanded.
21421 .section "Private options for smtp" "SECID146"
21422 .cindex "options" "&(smtp)& transport"
21423 The private options of the &(smtp)& transport are as follows:
21426 .option address_retry_include_sender smtp boolean true
21427 .cindex "4&'xx'& responses" "retrying after"
21428 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
21429 is the combination of sender and recipient that is delayed in subsequent queue
21430 runs until the retry time is reached. You can delay the recipient without
21431 reference to the sender (which is what earlier versions of Exim did), by
21432 setting &%address_retry_include_sender%& false. However, this can lead to
21433 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
21435 .option allow_localhost smtp boolean false
21436 .cindex "local host" "sending to"
21437 .cindex "fallback" "hosts specified on transport"
21438 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
21439 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
21440 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
21441 the delivery anyway. This should be used only in special cases when the
21442 configuration ensures that no looping will result (for example, a differently
21443 configured Exim is listening on the port to which the message is sent).
21446 .option authenticated_sender smtp string&!! unset
21448 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
21449 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
21450 overriding any existing authenticated sender value. If the string expansion is
21451 forced to fail, the option is ignored. Other expansion failures cause delivery
21452 to be deferred. If the result of expansion is an empty string, that is also
21455 The expansion happens after the outgoing connection has been made and TLS
21456 started, if required. This means that the &$host$&, &$host_address$&,
21457 &$tls_cipher$&, and &$tls_peerdn$& variables are set according to the
21458 particular connection.
21460 If the SMTP session is not authenticated, the expansion of
21461 &%authenticated_sender%& still happens (and can cause the delivery to be
21462 deferred if it fails), but no AUTH= item is added to MAIL commands
21463 unless &%authenticated_sender_force%& is true.
21465 This option allows you to use the &(smtp)& transport in LMTP mode to
21466 deliver mail to Cyrus IMAP and provide the proper local part as the
21467 &"authenticated sender"&, via a setting such as:
21469 authenticated_sender = $local_part
21471 This removes the need for IMAP subfolders to be assigned special ACLs to
21472 allow direct delivery to those subfolders.
21474 Because of expected uses such as that just described for Cyrus (when no
21475 domain is involved), there is no checking on the syntax of the provided
21479 .option authenticated_sender_force smtp boolean false
21480 If this option is set true, the &%authenticated_sender%& option's value
21481 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
21482 authenticated as a client.
21485 .option command_timeout smtp time 5m
21486 This sets a timeout for receiving a response to an SMTP command that has been
21487 sent out. It is also used when waiting for the initial banner line from the
21488 remote host. Its value must not be zero.
21491 .option connect_timeout smtp time 5m
21492 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
21493 to a remote host. A setting of zero allows the system timeout (typically
21494 several minutes) to act. To have any effect, the value of this option must be
21495 less than the system timeout. However, it has been observed that on some
21496 systems there is no system timeout, which is why the default value for this
21497 option is 5 minutes, a value recommended by RFC 1123.
21500 .option connection_max_messages smtp integer 500
21501 .cindex "SMTP" "passed connection"
21502 .cindex "SMTP" "multiple deliveries"
21503 .cindex "multiple SMTP deliveries"
21504 This controls the maximum number of separate message deliveries that are sent
21505 over a single TCP/IP connection. If the value is zero, there is no limit.
21506 For testing purposes, this value can be overridden by the &%-oB%& command line
21510 .option data_timeout smtp time 5m
21511 This sets a timeout for the transmission of each block in the data portion of
21512 the message. As a result, the overall timeout for a message depends on the size
21513 of the message. Its value must not be zero. See also &%final_timeout%&.
21516 .option delay_after_cutoff smtp boolean true
21517 This option controls what happens when all remote IP addresses for a given
21518 domain have been inaccessible for so long that they have passed their retry
21521 In the default state, if the next retry time has not been reached for any of
21522 them, the address is bounced without trying any deliveries. In other words,
21523 Exim delays retrying an IP address after the final cutoff time until a new
21524 retry time is reached, and can therefore bounce an address without ever trying
21525 a delivery, when machines have been down for a long time. Some people are
21526 unhappy at this prospect, so...
21528 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
21529 addresses are past their final cutoff time, Exim tries to deliver to those
21530 IP addresses that have not been tried since the message arrived. If there are
21531 none, of if they all fail, the address is bounced. In other words, it does not
21532 delay when a new message arrives, but immediately tries those expired IP
21533 addresses that haven't been tried since the message arrived. If there is a
21534 continuous stream of messages for the dead hosts, unsetting
21535 &%delay_after_cutoff%& means that there will be many more attempts to deliver
21539 .option dns_qualify_single smtp boolean true
21540 If the &%hosts%& or &%fallback_hosts%& option is being used,
21541 and the &%gethostbyname%& option is false,
21542 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
21543 in chapter &<<CHAPdnslookup>>& for more details.
21546 .option dns_search_parents smtp boolean false
21547 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
21548 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
21549 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
21554 .option fallback_hosts smtp "string list" unset
21555 .cindex "fallback" "hosts specified on transport"
21556 String expansion is not applied to this option. The argument must be a
21557 colon-separated list of host names or IP addresses, optionally also including
21558 port numbers, though the separator can be changed, as described in section
21559 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
21560 item in a &%route_list%& setting for the &(manualroute)& router, as described
21561 in section &<<SECTformatonehostitem>>&.
21563 Fallback hosts can also be specified on routers, which associate them with the
21564 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
21565 &%fallback_hosts%& specified on the transport is used only if the address does
21566 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
21567 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
21568 However, &%hosts_randomize%& does apply to fallback host lists.
21570 If Exim is unable to deliver to any of the hosts for a particular address, and
21571 the errors are not permanent rejections, the address is put on a separate
21572 transport queue with its host list replaced by the fallback hosts, unless the
21573 address was routed via MX records and the current host was in the original MX
21574 list. In that situation, the fallback host list is not used.
21576 Once normal deliveries are complete, the fallback queue is delivered by
21577 re-running the same transports with the new host lists. If several failing
21578 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
21579 copy of the message is sent.
21581 The resolution of the host names on the fallback list is controlled by the
21582 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
21583 both to cases when the host list comes with the address and when it is taken
21584 from &%hosts%&. This option provides a &"use a smart host only if delivery
21588 .option final_timeout smtp time 10m
21589 This is the timeout that applies while waiting for the response to the final
21590 line containing just &"."& that terminates a message. Its value must not be
21593 .option gethostbyname smtp boolean false
21594 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
21595 being used, names are looked up using &[gethostbyname()]&
21596 (or &[getipnodebyname()]& when available)
21597 instead of using the DNS. Of course, that function may in fact use the DNS, but
21598 it may also consult other sources of information such as &_/etc/hosts_&.
21600 .option gnutls_require_kx smtp string unset
21601 This option controls the key exchange mechanisms when GnuTLS is used in an Exim
21602 client. For details, see section &<<SECTreqciphgnu>>&.
21604 .option gnutls_require_mac smtp string unset
21605 This option controls the MAC algorithms when GnuTLS is used in an Exim
21606 client. For details, see section &<<SECTreqciphgnu>>&.
21608 .option gnutls_require_protocols smtp string unset
21609 This option controls the protocols when GnuTLS is used in an Exim
21610 client. For details, see section &<<SECTreqciphgnu>>&.
21612 .option gnutls_compat_mode smtp boolean unset
21613 This option controls whether GnuTLS is used in compatibility mode in an Exim
21614 server. This reduces security slightly, but improves interworking with older
21615 implementations of TLS.
21617 .option helo_data smtp string&!! "see below"
21618 .cindex "HELO" "argument, setting"
21619 .cindex "EHLO" "argument, setting"
21620 .cindex "LHLO argument setting"
21621 The value of this option is expanded after a connection to a another host has
21622 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
21623 command that starts the outgoing SMTP or LMTP session. The default value of the
21628 During the expansion, the variables &$host$& and &$host_address$& are set to
21629 the identity of the remote host, and the variables &$sending_ip_address$& and
21630 &$sending_port$& are set to the local IP address and port number that are being
21631 used. These variables can be used to generate different values for different
21632 servers or different local IP addresses. For example, if you want the string
21633 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
21634 interface address, you could use this:
21636 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
21637 {$primary_hostname}}
21639 The use of &%helo_data%& applies both to sending messages and when doing
21642 .option hosts smtp "string list&!!" unset
21643 Hosts are associated with an address by a router such as &(dnslookup)&, which
21644 finds the hosts by looking up the address domain in the DNS, or by
21645 &(manualroute)&, which has lists of hosts in its configuration. However,
21646 email addresses can be passed to the &(smtp)& transport by any router, and not
21647 all of them can provide an associated list of hosts.
21649 The &%hosts%& option specifies a list of hosts to be used if the address being
21650 processed does not have any hosts associated with it. The hosts specified by
21651 &%hosts%& are also used, whether or not the address has its own hosts, if
21652 &%hosts_override%& is set.
21654 The string is first expanded, before being interpreted as a colon-separated
21655 list of host names or IP addresses, possibly including port numbers. The
21656 separator may be changed to something other than colon, as described in section
21657 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
21658 item in a &%route_list%& setting for the &(manualroute)& router, as described
21659 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
21660 of the &(manualroute)& router is not available here.
21662 If the expansion fails, delivery is deferred. Unless the failure was caused by
21663 the inability to complete a lookup, the error is logged to the panic log as
21664 well as the main log. Host names are looked up either by searching directly for
21665 address records in the DNS or by calling &[gethostbyname()]& (or
21666 &[getipnodebyname()]& when available), depending on the setting of the
21667 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
21668 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
21671 During delivery, the hosts are tried in order, subject to their retry status,
21672 unless &%hosts_randomize%& is set.
21675 .option hosts_avoid_esmtp smtp "host list&!!" unset
21676 .cindex "ESMTP, avoiding use of"
21677 .cindex "HELO" "forcing use of"
21678 .cindex "EHLO" "avoiding use of"
21679 .cindex "PIPELINING" "avoiding the use of"
21680 This option is for use with broken hosts that announce ESMTP facilities (for
21681 example, PIPELINING) and then fail to implement them properly. When a host
21682 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
21683 start of the SMTP session. This means that it cannot use any of the ESMTP
21684 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
21687 .option hosts_avoid_pipelining smtp "host list&!!" unset
21688 .cindex "PIPELINING" "avoiding the use of"
21689 Exim will not use the SMTP PIPELINING extension when delivering to any host
21690 that matches this list, even if the server host advertises PIPELINING support.
21693 .option hosts_avoid_tls smtp "host list&!!" unset
21694 .cindex "TLS" "avoiding for certain hosts"
21695 Exim will not try to start a TLS session when delivering to any host that
21696 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
21699 .option hosts_max_try smtp integer 5
21700 .cindex "host" "maximum number to try"
21701 .cindex "limit" "number of hosts tried"
21702 .cindex "limit" "number of MX tried"
21703 .cindex "MX record" "maximum tried"
21704 This option limits the number of IP addresses that are tried for any one
21705 delivery in cases where there are temporary delivery errors. Section
21706 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
21709 .option hosts_max_try_hardlimit smtp integer 50
21710 This is an additional check on the maximum number of IP addresses that Exim
21711 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
21716 .option hosts_nopass_tls smtp "host list&!!" unset
21717 .cindex "TLS" "passing connection"
21718 .cindex "multiple SMTP deliveries"
21719 .cindex "TLS" "multiple message deliveries"
21720 For any host that matches this list, a connection on which a TLS session has
21721 been started will not be passed to a new delivery process for sending another
21722 message on the same connection. See section &<<SECTmulmessam>>& for an
21723 explanation of when this might be needed.
21726 .option hosts_override smtp boolean false
21727 If this option is set and the &%hosts%& option is also set, any hosts that are
21728 attached to the address are ignored, and instead the hosts specified by the
21729 &%hosts%& option are always used. This option does not apply to
21730 &%fallback_hosts%&.
21733 .option hosts_randomize smtp boolean false
21734 .cindex "randomized host list"
21735 .cindex "host" "list of; randomized"
21736 .cindex "fallback" "randomized hosts"
21737 If this option is set, and either the list of hosts is taken from the
21738 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
21739 were not obtained from MX records (this includes fallback hosts from the
21740 router), and were not randomized by the router, the order of trying the hosts
21741 is randomized each time the transport runs. Randomizing the order of a host
21742 list can be used to do crude load sharing.
21744 When &%hosts_randomize%& is true, a host list may be split into groups whose
21745 order is separately randomized. This makes it possible to set up MX-like
21746 behaviour. The boundaries between groups are indicated by an item that is just
21747 &`+`& in the host list. For example:
21749 hosts = host1:host2:host3:+:host4:host5
21751 The order of the first three hosts and the order of the last two hosts is
21752 randomized for each use, but the first three always end up before the last two.
21753 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
21755 .option hosts_require_auth smtp "host list&!!" unset
21756 .cindex "authentication" "required by client"
21757 This option provides a list of servers for which authentication must succeed
21758 before Exim will try to transfer a message. If authentication fails for
21759 servers which are not in this list, Exim tries to send unauthenticated. If
21760 authentication fails for one of these servers, delivery is deferred. This
21761 temporary error is detectable in the retry rules, so it can be turned into a
21762 hard failure if required. See also &%hosts_try_auth%&, and chapter
21763 &<<CHAPSMTPAUTH>>& for details of authentication.
21766 .option hosts_require_tls smtp "host list&!!" unset
21767 .cindex "TLS" "requiring for certain servers"
21768 Exim will insist on using a TLS session when delivering to any host that
21769 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
21770 &*Note*&: This option affects outgoing mail only. To insist on TLS for
21771 incoming messages, use an appropriate ACL.
21773 .option hosts_try_auth smtp "host list&!!" unset
21774 .cindex "authentication" "optional in client"
21775 This option provides a list of servers to which, provided they announce
21776 authentication support, Exim will attempt to authenticate as a client when it
21777 connects. If authentication fails, Exim will try to transfer the message
21778 unauthenticated. See also &%hosts_require_auth%&, and chapter
21779 &<<CHAPSMTPAUTH>>& for details of authentication.
21781 .option interface smtp "string list&!!" unset
21782 .cindex "bind IP address"
21783 .cindex "IP address" "binding"
21785 .vindex "&$host_address$&"
21786 This option specifies which interface to bind to when making an outgoing SMTP
21787 call. The value is an IP address, not an interface name such as
21788 &`eth0`&. Do not confuse this with the interface address that was used when a
21789 message was received, which is in &$received_ip_address$&, formerly known as
21790 &$interface_address$&. The name was changed to minimize confusion with the
21791 outgoing interface address. There is no variable that contains an outgoing
21792 interface address because, unless it is set by this option, its value is
21795 During the expansion of the &%interface%& option the variables &$host$& and
21796 &$host_address$& refer to the host to which a connection is about to be made
21797 during the expansion of the string. Forced expansion failure, or an empty
21798 string result causes the option to be ignored. Otherwise, after expansion, the
21799 string must be a list of IP addresses, colon-separated by default, but the
21800 separator can be changed in the usual way. For example:
21802 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
21804 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
21805 connection. If none of them are the correct type, the option is ignored. If
21806 &%interface%& is not set, or is ignored, the system's IP functions choose which
21807 interface to use if the host has more than one.
21810 .option keepalive smtp boolean true
21811 .cindex "keepalive" "on outgoing connection"
21812 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
21813 connections. When set, it causes the kernel to probe idle connections
21814 periodically, by sending packets with &"old"& sequence numbers. The other end
21815 of the connection should send a acknowledgment if the connection is still okay
21816 or a reset if the connection has been aborted. The reason for doing this is
21817 that it has the beneficial effect of freeing up certain types of connection
21818 that can get stuck when the remote host is disconnected without tidying up the
21819 TCP/IP call properly. The keepalive mechanism takes several hours to detect
21823 .option lmtp_ignore_quota smtp boolean false
21824 .cindex "LMTP" "ignoring quota errors"
21825 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
21826 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
21827 has advertised support for IGNOREQUOTA in its response to the LHLO command.
21829 .option max_rcpt smtp integer 100
21830 .cindex "RCPT" "maximum number of outgoing"
21831 This option limits the number of RCPT commands that are sent in a single
21832 SMTP message transaction. Each set of addresses is treated independently, and
21833 so can cause parallel connections to the same host if &%remote_max_parallel%&
21837 .option multi_domain smtp boolean true
21838 .vindex "&$domain$&"
21839 When this option is set, the &(smtp)& transport can handle a number of
21840 addresses containing a mixture of different domains provided they all resolve
21841 to the same list of hosts. Turning the option off restricts the transport to
21842 handling only one domain at a time. This is useful if you want to use
21843 &$domain$& in an expansion for the transport, because it is set only when there
21844 is a single domain involved in a remote delivery.
21847 .option port smtp string&!! "see below"
21848 .cindex "port" "sending TCP/IP"
21849 .cindex "TCP/IP" "setting outgoing port"
21850 This option specifies the TCP/IP port on the server to which Exim connects.
21851 &*Note:*& Do not confuse this with the port that was used when a message was
21852 received, which is in &$received_port$&, formerly known as &$interface_port$&.
21853 The name was changed to minimize confusion with the outgoing port. There is no
21854 variable that contains an outgoing port.
21856 If the value of this option begins with a digit it is taken as a port number;
21857 otherwise it is looked up using &[getservbyname()]&. The default value is
21858 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
21859 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
21864 .option protocol smtp string smtp
21865 .cindex "LMTP" "over TCP/IP"
21866 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
21867 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
21868 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
21869 deliveries into closed message stores. Exim also has support for running LMTP
21870 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
21873 .option retry_include_ip_address smtp boolean true
21874 Exim normally includes both the host name and the IP address in the key it
21875 constructs for indexing retry data after a temporary delivery failure. This
21876 means that when one of several IP addresses for a host is failing, it gets
21877 tried periodically (controlled by the retry rules), but use of the other IP
21878 addresses is not affected.
21880 However, in some dialup environments hosts are assigned a different IP address
21881 each time they connect. In this situation the use of the IP address as part of
21882 the retry key leads to undesirable behaviour. Setting this option false causes
21883 Exim to use only the host name. This should normally be done on a separate
21884 instance of the &(smtp)& transport, set up specially to handle the dialup
21888 .option serialize_hosts smtp "host list&!!" unset
21889 .cindex "serializing connections"
21890 .cindex "host" "serializing connections"
21891 Because Exim operates in a distributed manner, if several messages for the same
21892 host arrive at around the same time, more than one simultaneous connection to
21893 the remote host can occur. This is not usually a problem except when there is a
21894 slow link between the hosts. In that situation it may be helpful to restrict
21895 Exim to one connection at a time. This can be done by setting
21896 &%serialize_hosts%& to match the relevant hosts.
21898 .cindex "hints database" "serializing deliveries to a host"
21899 Exim implements serialization by means of a hints database in which a record is
21900 written whenever a process connects to one of the restricted hosts. The record
21901 is deleted when the connection is completed. Obviously there is scope for
21902 records to get left lying around if there is a system or program crash. To
21903 guard against this, Exim ignores any records that are more than six hours old.
21905 If you set up this kind of serialization, you should also arrange to delete the
21906 relevant hints database whenever your system reboots. The names of the files
21907 start with &_misc_& and they are kept in the &_spool/db_& directory. There
21908 may be one or two files, depending on the type of DBM in use. The same files
21909 are used for ETRN serialization.
21912 .option size_addition smtp integer 1024
21913 .cindex "SMTP" "SIZE"
21914 .cindex "message" "size issue for transport filter"
21915 .cindex "size" "of message"
21916 .cindex "transport" "filter"
21917 .cindex "filter" "transport filter"
21918 If a remote SMTP server indicates that it supports the SIZE option of the
21919 MAIL command, Exim uses this to pass over the message size at the start of
21920 an SMTP transaction. It adds the value of &%size_addition%& to the value it
21921 sends, to allow for headers and other text that may be added during delivery by
21922 configuration options or in a transport filter. It may be necessary to increase
21923 this if a lot of text is added to messages.
21925 Alternatively, if the value of &%size_addition%& is set negative, it disables
21926 the use of the SIZE option altogether.
21929 .option tls_certificate smtp string&!! unset
21930 .cindex "TLS" "client certificate, location of"
21931 .cindex "certificate" "client, location of"
21933 .vindex "&$host_address$&"
21934 The value of this option must be the absolute path to a file which contains the
21935 client's certificate, for possible use when sending a message over an encrypted
21936 connection. The values of &$host$& and &$host_address$& are set to the name and
21937 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
21940 &*Note*&: This option must be set if you want Exim to be able to use a TLS
21941 certificate when sending messages as a client. The global option of the same
21942 name specifies the certificate for Exim as a server; it is not automatically
21943 assumed that the same certificate should be used when Exim is operating as a
21947 .option tls_crl smtp string&!! unset
21948 .cindex "TLS" "client certificate revocation list"
21949 .cindex "certificate" "revocation list for client"
21950 This option specifies a certificate revocation list. The expanded value must
21951 be the name of a file that contains a CRL in PEM format.
21954 .option tls_privatekey smtp string&!! unset
21955 .cindex "TLS" "client private key, location of"
21957 .vindex "&$host_address$&"
21958 The value of this option must be the absolute path to a file which contains the
21959 client's private key. This is used when sending a message over an encrypted
21960 connection using a client certificate. The values of &$host$& and
21961 &$host_address$& are set to the name and address of the server during the
21962 expansion. If this option is unset, or the expansion is forced to fail, or the
21963 result is an empty string, the private key is assumed to be in the same file as
21964 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
21967 .option tls_require_ciphers smtp string&!! unset
21968 .cindex "TLS" "requiring specific ciphers"
21969 .cindex "cipher" "requiring specific"
21971 .vindex "&$host_address$&"
21972 The value of this option must be a list of permitted cipher suites, for use
21973 when setting up an outgoing encrypted connection. (There is a global option of
21974 the same name for controlling incoming connections.) The values of &$host$& and
21975 &$host_address$& are set to the name and address of the server during the
21976 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
21977 is used in different ways by OpenSSL and GnuTLS (see sections
21978 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
21979 ciphers is a preference order.
21983 .option tls_tempfail_tryclear smtp boolean true
21984 .cindex "4&'xx'& responses" "to STARTTLS"
21985 When the server host is not in &%hosts_require_tls%&, and there is a problem in
21986 setting up a TLS session, this option determines whether or not Exim should try
21987 to deliver the message unencrypted. If it is set false, delivery to the
21988 current host is deferred; if there are other hosts, they are tried. If this
21989 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
21990 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
21991 TLS negotiation fails, Exim closes the current connection (because it is in an
21992 unknown state), opens a new one to the same host, and then tries the delivery
21996 .option tls_verify_certificates smtp string&!! unset
21997 .cindex "TLS" "server certificate verification"
21998 .cindex "certificate" "verification of server"
22000 .vindex "&$host_address$&"
22001 The value of this option must be the absolute path to a file containing
22002 permitted server certificates, for use when setting up an encrypted connection.
22003 Alternatively, if you are using OpenSSL, you can set
22004 &%tls_verify_certificates%& to the name of a directory containing certificate
22005 files. This does not work with GnuTLS; the option must be set to the name of a
22006 single file if you are using GnuTLS. The values of &$host$& and
22007 &$host_address$& are set to the name and address of the server during the
22008 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
22013 .section "How the limits for the number of hosts to try are used" &&&
22015 .cindex "host" "maximum number to try"
22016 .cindex "limit" "hosts; maximum number tried"
22017 There are two options that are concerned with the number of hosts that are
22018 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
22019 &%hosts_max_try_hardlimit%&.
22022 The &%hosts_max_try%& option limits the number of hosts that are tried
22023 for a single delivery. However, despite the term &"host"& in its name, the
22024 option actually applies to each IP address independently. In other words, a
22025 multihomed host is treated as several independent hosts, just as it is for
22028 Many of the larger ISPs have multiple MX records which often point to
22029 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
22030 created as a result of routing one of these domains.
22032 Trying every single IP address on such a long list does not seem sensible; if
22033 several at the top of the list fail, it is reasonable to assume there is some
22034 problem that is likely to affect all of them. Roughly speaking, the value of
22035 &%hosts_max_try%& is the maximum number that are tried before deferring the
22036 delivery. However, the logic cannot be quite that simple.
22038 Firstly, IP addresses that are skipped because their retry times have not
22039 arrived do not count, and in addition, addresses that are past their retry
22040 limits are also not counted, even when they are tried. This means that when
22041 some IP addresses are past their retry limits, more than the value of
22042 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
22043 that all IP addresses are considered before timing out an email address (but
22044 see below for an exception).
22046 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
22047 list to see if there is a subsequent host with a different (higher valued) MX.
22048 If there is, that host is considered next, and the current IP address is used
22049 but not counted. This behaviour helps in the case of a domain with a retry rule
22050 that hardly ever delays any hosts, as is now explained:
22052 Consider the case of a long list of hosts with one MX value, and a few with a
22053 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
22054 hosts at the top of the list are tried at first. With the default retry rule,
22055 which specifies increasing retry times, the higher MX hosts are eventually
22056 tried when those at the top of the list are skipped because they have not
22057 reached their retry times.
22059 However, it is common practice to put a fixed short retry time on domains for
22060 large ISPs, on the grounds that their servers are rarely down for very long.
22061 Unfortunately, these are exactly the domains that tend to resolve to long lists
22062 of hosts. The short retry time means that the lowest MX hosts are tried every
22063 time. The attempts may be in a different order because of random sorting, but
22064 without the special MX check, the higher MX hosts would never be tried until
22065 all the lower MX hosts had timed out (which might be several days), because
22066 there are always some lower MX hosts that have reached their retry times. With
22067 the special check, Exim considers at least one IP address from each MX value at
22068 every delivery attempt, even if the &%hosts_max_try%& limit has already been
22071 The above logic means that &%hosts_max_try%& is not a hard limit, and in
22072 particular, Exim normally eventually tries all the IP addresses before timing
22073 out an email address. When &%hosts_max_try%& was implemented, this seemed a
22074 reasonable thing to do. Recently, however, some lunatic DNS configurations have
22075 been set up with hundreds of IP addresses for some domains. It can
22076 take a very long time indeed for an address to time out in these cases.
22078 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
22079 Exim never tries more than this number of IP addresses; if it hits this limit
22080 and they are all timed out, the email address is bounced, even though not all
22081 possible IP addresses have been tried.
22082 .ecindex IIDsmttra1
22083 .ecindex IIDsmttra2
22089 . ////////////////////////////////////////////////////////////////////////////
22090 . ////////////////////////////////////////////////////////////////////////////
22092 .chapter "Address rewriting" "CHAPrewrite"
22093 .scindex IIDaddrew "rewriting" "addresses"
22094 There are some circumstances in which Exim automatically rewrites domains in
22095 addresses. The two most common are when an address is given without a domain
22096 (referred to as an &"unqualified address"&) or when an address contains an
22097 abbreviated domain that is expanded by DNS lookup.
22099 Unqualified envelope addresses are accepted only for locally submitted
22100 messages, or for messages that are received from hosts matching
22101 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
22102 appropriate. Unqualified addresses in header lines are qualified if they are in
22103 locally submitted messages, or messages from hosts that are permitted to send
22104 unqualified envelope addresses. Otherwise, unqualified addresses in header
22105 lines are neither qualified nor rewritten.
22107 One situation in which Exim does &'not'& automatically rewrite a domain is
22108 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
22109 such a domain should be rewritten using the &"canonical"& name, and some MTAs
22110 do this. The new RFCs do not contain this suggestion.
22113 .section "Explicitly configured address rewriting" "SECID147"
22114 This chapter describes the rewriting rules that can be used in the
22115 main rewrite section of the configuration file, and also in the generic
22116 &%headers_rewrite%& option that can be set on any transport.
22118 Some people believe that configured address rewriting is a Mortal Sin.
22119 Others believe that life is not possible without it. Exim provides the
22120 facility; you do not have to use it.
22122 The main rewriting rules that appear in the &"rewrite"& section of the
22123 configuration file are applied to addresses in incoming messages, both envelope
22124 addresses and addresses in header lines. Each rule specifies the types of
22125 address to which it applies.
22127 Whether or not addresses in header lines are rewritten depends on the origin of
22128 the headers and the type of rewriting. Global rewriting, that is, rewriting
22129 rules from the rewrite section of the configuration file, is applied only to
22130 those headers that were received with the message. Header lines that are added
22131 by ACLs or by a system filter or by individual routers or transports (which
22132 are specific to individual recipient addresses) are not rewritten by the global
22135 Rewriting at transport time, by means of the &%headers_rewrite%& option,
22136 applies all headers except those added by routers and transports. That is, as
22137 well as the headers that were received with the message, it also applies to
22138 headers that were added by an ACL or a system filter.
22141 In general, rewriting addresses from your own system or domain has some
22142 legitimacy. Rewriting other addresses should be done only with great care and
22143 in special circumstances. The author of Exim believes that rewriting should be
22144 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
22145 Although it can sometimes be used as a routing tool, this is very strongly
22148 There are two commonly encountered circumstances where rewriting is used, as
22149 illustrated by these examples:
22152 The company whose domain is &'hitch.fict.example'& has a number of hosts that
22153 exchange mail with each other behind a firewall, but there is only a single
22154 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
22155 &'hitch.fict.example'& when sending mail off-site.
22157 A host rewrites the local parts of its own users so that, for example,
22158 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
22163 .section "When does rewriting happen?" "SECID148"
22164 .cindex "rewriting" "timing of"
22165 .cindex "&ACL;" "rewriting addresses in"
22166 Configured address rewriting can take place at several different stages of a
22167 message's processing.
22169 .vindex "&$sender_address$&"
22170 At the start of an ACL for MAIL, the sender address may have been rewritten
22171 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
22172 ordinary rewrite rules have yet been applied. If, however, the sender address
22173 is verified in the ACL, it is rewritten before verification, and remains
22174 rewritten thereafter. The subsequent value of &$sender_address$& is the
22175 rewritten address. This also applies if sender verification happens in a
22176 RCPT ACL. Otherwise, when the sender address is not verified, it is
22177 rewritten as soon as a message's header lines have been received.
22179 .vindex "&$domain$&"
22180 .vindex "&$local_part$&"
22181 Similarly, at the start of an ACL for RCPT, the current recipient's address
22182 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
22183 rewrite rules have yet been applied to it. However, the behaviour is different
22184 from the sender address when a recipient is verified. The address is rewritten
22185 for the verification, but the rewriting is not remembered at this stage. The
22186 value of &$local_part$& and &$domain$& after verification are always the same
22187 as they were before (that is, they contain the unrewritten &-- except for
22188 SMTP-time rewriting &-- address).
22190 As soon as a message's header lines have been received, all the envelope
22191 recipient addresses are permanently rewritten, and rewriting is also applied to
22192 the addresses in the header lines (if configured). This happens before adding
22193 any header lines that were specified in MAIL or RCPT ACLs, and
22194 .cindex "&[local_scan()]& function" "address rewriting; timing of"
22195 before the DATA ACL and &[local_scan()]& functions are run.
22197 When an address is being routed, either for delivery or for verification,
22198 rewriting is applied immediately to child addresses that are generated by
22199 redirection, unless &%no_rewrite%& is set on the router.
22201 .cindex "envelope sender" "rewriting at transport time"
22202 .cindex "rewriting" "at transport time"
22203 .cindex "header lines" "rewriting at transport time"
22204 At transport time, additional rewriting of addresses in header lines can be
22205 specified by setting the generic &%headers_rewrite%& option on a transport.
22206 This option contains rules that are identical in form to those in the rewrite
22207 section of the configuration file. They are applied to the original message
22208 header lines and any that were added by ACLs or a system filter. They are not
22209 applied to header lines that are added by routers or the transport.
22211 The outgoing envelope sender can be rewritten by means of the &%return_path%&
22212 transport option. However, it is not possible to rewrite envelope recipients at
22218 .section "Testing the rewriting rules that apply on input" "SECID149"
22219 .cindex "rewriting" "testing"
22220 .cindex "testing" "rewriting"
22221 Exim's input rewriting configuration appears in a part of the run time
22222 configuration file headed by &"begin rewrite"&. It can be tested by the
22223 &%-brw%& command line option. This takes an address (which can be a full RFC
22224 2822 address) as its argument. The output is a list of how the address would be
22225 transformed by the rewriting rules for each of the different places it might
22226 appear in an incoming message, that is, for each different header and for the
22227 envelope sender and recipient fields. For example,
22229 exim -brw ph10@exim.workshop.example
22231 might produce the output
22233 sender: Philip.Hazel@exim.workshop.example
22234 from: Philip.Hazel@exim.workshop.example
22235 to: ph10@exim.workshop.example
22236 cc: ph10@exim.workshop.example
22237 bcc: ph10@exim.workshop.example
22238 reply-to: Philip.Hazel@exim.workshop.example
22239 env-from: Philip.Hazel@exim.workshop.example
22240 env-to: ph10@exim.workshop.example
22242 which shows that rewriting has been set up for that address when used in any of
22243 the source fields, but not when it appears as a recipient address. At the
22244 present time, there is no equivalent way of testing rewriting rules that are
22245 set for a particular transport.
22248 .section "Rewriting rules" "SECID150"
22249 .cindex "rewriting" "rules"
22250 The rewrite section of the configuration file consists of lines of rewriting
22253 <&'source pattern'&> <&'replacement'&> <&'flags'&>
22255 Rewriting rules that are specified for the &%headers_rewrite%& generic
22256 transport option are given as a colon-separated list. Each item in the list
22257 takes the same form as a line in the main rewriting configuration (except that
22258 any colons must be doubled, of course).
22260 The formats of source patterns and replacement strings are described below.
22261 Each is terminated by white space, unless enclosed in double quotes, in which
22262 case normal quoting conventions apply inside the quotes. The flags are single
22263 characters which may appear in any order. Spaces and tabs between them are
22266 For each address that could potentially be rewritten, the rules are scanned in
22267 order, and replacements for the address from earlier rules can themselves be
22268 replaced by later rules (but see the &"q"& and &"R"& flags).
22270 The order in which addresses are rewritten is undefined, may change between
22271 releases, and must not be relied on, with one exception: when a message is
22272 received, the envelope sender is always rewritten first, before any header
22273 lines are rewritten. For example, the replacement string for a rewrite of an
22274 address in &'To:'& must not assume that the message's address in &'From:'& has
22275 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
22276 that the envelope sender has already been rewritten.
22278 .vindex "&$domain$&"
22279 .vindex "&$local_part$&"
22280 The variables &$local_part$& and &$domain$& can be used in the replacement
22281 string to refer to the address that is being rewritten. Note that lookup-driven
22282 rewriting can be done by a rule of the form
22286 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
22287 refer to the address that is being rewritten.
22290 .section "Rewriting patterns" "SECID151"
22291 .cindex "rewriting" "patterns"
22292 .cindex "address list" "in a rewriting pattern"
22293 The source pattern in a rewriting rule is any item which may appear in an
22294 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
22295 single-item address list, which means that it is expanded before being tested
22296 against the address. As always, if you use a regular expression as a pattern,
22297 you must take care to escape dollar and backslash characters, or use the &`\N`&
22298 facility to suppress string expansion within the regular expression.
22300 Domains in patterns should be given in lower case. Local parts in patterns are
22301 case-sensitive. If you want to do case-insensitive matching of local parts, you
22302 can use a regular expression that starts with &`^(?i)`&.
22304 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
22305 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
22306 depending on the type of match which occurred. These can be used in the
22307 replacement string to insert portions of the incoming address. &$0$& always
22308 refers to the complete incoming address. When a regular expression is used, the
22309 numerical variables are set from its capturing subexpressions. For other types
22310 of pattern they are set as follows:
22313 If a local part or domain starts with an asterisk, the numerical variables
22314 refer to the character strings matched by asterisks, with &$1$& associated with
22315 the first asterisk, and &$2$& with the second, if present. For example, if the
22318 *queen@*.fict.example
22320 is matched against the address &'hearts-queen@wonderland.fict.example'& then
22322 $0 = hearts-queen@wonderland.fict.example
22326 Note that if the local part does not start with an asterisk, but the domain
22327 does, it is &$1$& that contains the wild part of the domain.
22330 If the domain part of the pattern is a partial lookup, the wild and fixed parts
22331 of the domain are placed in the next available numerical variables. Suppose,
22332 for example, that the address &'foo@bar.baz.example'& is processed by a
22333 rewriting rule of the form
22335 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
22337 and the key in the file that matches the domain is &`*.baz.example`&. Then
22343 If the address &'foo@baz.example'& is looked up, this matches the same
22344 wildcard file entry, and in this case &$2$& is set to the empty string, but
22345 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
22346 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
22347 whole domain. For non-partial domain lookups, no numerical variables are set.
22351 .section "Rewriting replacements" "SECID152"
22352 .cindex "rewriting" "replacements"
22353 If the replacement string for a rule is a single asterisk, addresses that
22354 match the pattern and the flags are &'not'& rewritten, and no subsequent
22355 rewriting rules are scanned. For example,
22357 hatta@lookingglass.fict.example * f
22359 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
22362 .vindex "&$domain$&"
22363 .vindex "&$local_part$&"
22364 If the replacement string is not a single asterisk, it is expanded, and must
22365 yield a fully qualified address. Within the expansion, the variables
22366 &$local_part$& and &$domain$& refer to the address that is being rewritten.
22367 Any letters they contain retain their original case &-- they are not lower
22368 cased. The numerical variables are set up according to the type of pattern that
22369 matched the address, as described above. If the expansion is forced to fail by
22370 the presence of &"fail"& in a conditional or lookup item, rewriting by the
22371 current rule is abandoned, but subsequent rules may take effect. Any other
22372 expansion failure causes the entire rewriting operation to be abandoned, and an
22373 entry written to the panic log.
22377 .section "Rewriting flags" "SECID153"
22378 There are three different kinds of flag that may appear on rewriting rules:
22381 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
22384 A flag that specifies rewriting at SMTP time: S.
22386 Flags that control the rewriting process: Q, q, R, w.
22389 For rules that are part of the &%headers_rewrite%& generic transport option,
22390 E, F, T, and S are not permitted.
22394 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
22396 .cindex "rewriting" "flags"
22397 If none of the following flag letters, nor the &"S"& flag (see section
22398 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
22399 and to both the sender and recipient fields of the envelope, whereas a
22400 transport-time rewriting rule just applies to all headers. Otherwise, the
22401 rewriting rule is skipped unless the relevant addresses are being processed.
22403 &`E`& rewrite all envelope fields
22404 &`F`& rewrite the envelope From field
22405 &`T`& rewrite the envelope To field
22406 &`b`& rewrite the &'Bcc:'& header
22407 &`c`& rewrite the &'Cc:'& header
22408 &`f`& rewrite the &'From:'& header
22409 &`h`& rewrite all headers
22410 &`r`& rewrite the &'Reply-To:'& header
22411 &`s`& rewrite the &'Sender:'& header
22412 &`t`& rewrite the &'To:'& header
22414 "All headers" means all of the headers listed above that can be selected
22415 individually, plus their &'Resent-'& versions. It does not include
22416 other headers such as &'Subject:'& etc.
22418 You should be particularly careful about rewriting &'Sender:'& headers, and
22419 restrict this to special known cases in your own domains.
22422 .section "The SMTP-time rewriting flag" "SECTrewriteS"
22423 .cindex "SMTP" "rewriting malformed addresses"
22424 .cindex "RCPT" "rewriting argument of"
22425 .cindex "MAIL" "rewriting argument of"
22426 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
22427 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
22428 before any other processing; even before syntax checking. The pattern is
22429 required to be a regular expression, and it is matched against the whole of the
22430 data for the command, including any surrounding angle brackets.
22432 .vindex "&$domain$&"
22433 .vindex "&$local_part$&"
22434 This form of rewrite rule allows for the handling of addresses that are not
22435 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
22436 input). Because the input is not required to be a syntactically valid address,
22437 the variables &$local_part$& and &$domain$& are not available during the
22438 expansion of the replacement string. The result of rewriting replaces the
22439 original address in the MAIL or RCPT command.
22442 .section "Flags controlling the rewriting process" "SECID155"
22443 There are four flags which control the way the rewriting process works. These
22444 take effect only when a rule is invoked, that is, when the address is of the
22445 correct type (matches the flags) and matches the pattern:
22448 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
22449 unqualified local part. It is qualified with &%qualify_recipient%&. In the
22450 absence of &"Q"& the rewritten address must always include a domain.
22452 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
22453 even if no rewriting actually takes place because of a &"fail"& in the
22454 expansion. The &"q"& flag is not effective if the address is of the wrong type
22455 (does not match the flags) or does not match the pattern.
22457 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
22458 address, up to ten times. It can be combined with the &"q"& flag, to stop
22459 rewriting once it fails to match (after at least one successful rewrite).
22461 .cindex "rewriting" "whole addresses"
22462 When an address in a header is rewritten, the rewriting normally applies only
22463 to the working part of the address, with any comments and RFC 2822 &"phrase"&
22464 left unchanged. For example, rewriting might change
22466 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
22470 From: Ford Prefect <prefectf@hitch.fict.example>
22473 Sometimes there is a need to replace the whole address item, and this can be
22474 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
22475 causes an address in a header line to be rewritten, the entire address is
22476 replaced, not just the working part. The replacement must be a complete RFC
22477 2822 address, including the angle brackets if necessary. If text outside angle
22478 brackets contains a character whose value is greater than 126 or less than 32
22479 (except for tab), the text is encoded according to RFC 2047. The character set
22480 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
22482 When the &"w"& flag is set on a rule that causes an envelope address to be
22483 rewritten, all but the working part of the replacement address is discarded.
22487 .section "Rewriting examples" "SECID156"
22488 Here is an example of the two common rewriting paradigms:
22490 *@*.hitch.fict.example $1@hitch.fict.example
22491 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
22492 {$value}fail}@hitch.fict.example bctfrF
22494 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
22495 the string expansion to fail if the lookup does not succeed. In this context it
22496 has the effect of leaving the original address unchanged, but Exim goes on to
22497 consider subsequent rewriting rules, if any, because the &"q"& flag is not
22498 present in that rule. An alternative to &"fail"& would be to supply &$1$&
22499 explicitly, which would cause the rewritten address to be the same as before,
22500 at the cost of a small bit of processing. Not supplying either of these is an
22501 error, since the rewritten address would then contain no local part.
22503 The first example above replaces the domain with a superior, more general
22504 domain. This may not be desirable for certain local parts. If the rule
22506 root@*.hitch.fict.example *
22508 were inserted before the first rule, rewriting would be suppressed for the
22509 local part &'root'& at any domain ending in &'hitch.fict.example'&.
22511 Rewriting can be made conditional on a number of tests, by making use of
22512 &${if$& in the expansion item. For example, to apply a rewriting rule only to
22513 messages that originate outside the local host:
22515 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
22516 {$1@hitch.fict.example}fail}"
22518 The replacement string is quoted in this example because it contains white
22521 .cindex "rewriting" "bang paths"
22522 .cindex "bang paths" "rewriting"
22523 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
22524 an address it treats it as an unqualified local part which it qualifies with
22525 the local qualification domain (if the source of the message is local or if the
22526 remote host is permitted to send unqualified addresses). Rewriting can
22527 sometimes be used to handle simple bang paths with a fixed number of
22528 components. For example, the rule
22530 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
22532 rewrites a two-component bang path &'host.name!user'& as the domain address
22533 &'user@host.name'&. However, there is a security implication in using this as
22534 a global rewriting rule for envelope addresses. It can provide a backdoor
22535 method for using your system as a relay, because the incoming addresses appear
22536 to be local. If the bang path addresses are received via SMTP, it is safer to
22537 use the &"S"& flag to rewrite them as they are received, so that relay checking
22538 can be done on the rewritten addresses.
22545 . ////////////////////////////////////////////////////////////////////////////
22546 . ////////////////////////////////////////////////////////////////////////////
22548 .chapter "Retry configuration" "CHAPretry"
22549 .scindex IIDretconf1 "retry" "configuration, description of"
22550 .scindex IIDregconf2 "configuration file" "retry section"
22551 The &"retry"& section of the runtime configuration file contains a list of
22552 retry rules that control how often Exim tries to deliver messages that cannot
22553 be delivered at the first attempt. If there are no retry rules (the section is
22554 empty or not present), there are no retries. In this situation, temporary
22555 errors are treated as permanent. The default configuration contains a single,
22556 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
22557 line option can be used to test which retry rule will be used for a given
22558 address, domain and error.
22560 The most common cause of retries is temporary failure to deliver to a remote
22561 host because the host is down, or inaccessible because of a network problem.
22562 Exim's retry processing in this case is applied on a per-host (strictly, per IP
22563 address) basis, not on a per-message basis. Thus, if one message has recently
22564 been delayed, delivery of a new message to the same host is not immediately
22565 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
22566 log selector is set, the message
22567 .cindex "retry" "time not reached"
22568 &"retry time not reached"& is written to the main log whenever a delivery is
22569 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
22570 the handling of errors during remote deliveries.
22572 Retry processing applies to routing as well as to delivering, except as covered
22573 in the next paragraph. The retry rules do not distinguish between these
22574 actions. It is not possible, for example, to specify different behaviour for
22575 failures to route the domain &'snark.fict.example'& and failures to deliver to
22576 the host &'snark.fict.example'&. I didn't think anyone would ever need this
22577 added complication, so did not implement it. However, although they share the
22578 same retry rule, the actual retry times for routing and transporting a given
22579 domain are maintained independently.
22581 When a delivery is not part of a queue run (typically an immediate delivery on
22582 receipt of a message), the routers are always run, and local deliveries are
22583 always attempted, even if retry times are set for them. This makes for better
22584 behaviour if one particular message is causing problems (for example, causing
22585 quota overflow, or provoking an error in a filter file). If such a delivery
22586 suffers a temporary failure, the retry data is updated as normal, and
22587 subsequent delivery attempts from queue runs occur only when the retry time for
22588 the local address is reached.
22590 .section "Changing retry rules" "SECID157"
22591 If you change the retry rules in your configuration, you should consider
22592 whether or not to delete the retry data that is stored in Exim's spool area in
22593 files with names like &_db/retry_&. Deleting any of Exim's hints files is
22594 always safe; that is why they are called &"hints"&.
22596 The hints retry data contains suggested retry times based on the previous
22597 rules. In the case of a long-running problem with a remote host, it might
22598 record the fact that the host has timed out. If your new rules increase the
22599 timeout time for such a host, you should definitely remove the old retry data
22600 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
22601 messages that it should now be retaining.
22605 .section "Format of retry rules" "SECID158"
22606 .cindex "retry" "rules"
22607 Each retry rule occupies one line and consists of three or four parts,
22608 separated by white space: a pattern, an error name, an optional list of sender
22609 addresses, and a list of retry parameters. The pattern and sender lists must be
22610 enclosed in double quotes if they contain white space. The rules are searched
22611 in order until one is found where the pattern, error name, and sender list (if
22612 present) match the failing host or address, the error that occurred, and the
22613 message's sender, respectively.
22616 The pattern is any single item that may appear in an address list (see section
22617 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
22618 which means that it is expanded before being tested against the address that
22619 has been delayed. A negated address list item is permitted. Address
22620 list processing treats a plain domain name as if it were preceded by &"*@"&,
22621 which makes it possible for many retry rules to start with just a domain. For
22624 lookingglass.fict.example * F,24h,30m;
22626 provides a rule for any address in the &'lookingglass.fict.example'& domain,
22629 alice@lookingglass.fict.example * F,24h,30m;
22631 applies only to temporary failures involving the local part &%alice%&.
22632 In practice, almost all rules start with a domain name pattern without a local
22635 .cindex "regular expressions" "in retry rules"
22636 &*Warning*&: If you use a regular expression in a routing rule pattern, it
22637 must match a complete address, not just a domain, because that is how regular
22638 expressions work in address lists.
22640 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
22641 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
22645 .section "Choosing which retry rule to use for address errors" "SECID159"
22646 When Exim is looking for a retry rule after a routing attempt has failed (for
22647 example, after a DNS timeout), each line in the retry configuration is tested
22648 against the complete address only if &%retry_use_local_part%& is set for the
22649 router. Otherwise, only the domain is used, except when matching against a
22650 regular expression, when the local part of the address is replaced with &"*"&.
22651 A domain on its own can match a domain pattern, or a pattern that starts with
22652 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
22653 &%check_local_user%& is true, and false for other routers.
22655 Similarly, when Exim is looking for a retry rule after a local delivery has
22656 failed (for example, after a mailbox full error), each line in the retry
22657 configuration is tested against the complete address only if
22658 &%retry_use_local_part%& is set for the transport (it defaults true for all
22661 .cindex "4&'xx'& responses" "retry rules for"
22662 However, when Exim is looking for a retry rule after a remote delivery attempt
22663 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
22664 whole address is always used as the key when searching the retry rules. The
22665 rule that is found is used to create a retry time for the combination of the
22666 failing address and the message's sender. It is the combination of sender and
22667 recipient that is delayed in subsequent queue runs until its retry time is
22668 reached. You can delay the recipient without regard to the sender by setting
22669 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
22670 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
22675 .section "Choosing which retry rule to use for host and message errors" &&&
22677 For a temporary error that is not related to an individual address (for
22678 example, a connection timeout), each line in the retry configuration is checked
22679 twice. First, the name of the remote host is used as a domain name (preceded by
22680 &"*@"& when matching a regular expression). If this does not match the line,
22681 the domain from the email address is tried in a similar fashion. For example,
22682 suppose the MX records for &'a.b.c.example'& are
22684 a.b.c.example MX 5 x.y.z.example
22688 and the retry rules are
22690 p.q.r.example * F,24h,30m;
22691 a.b.c.example * F,4d,45m;
22693 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
22694 first rule matches neither the host nor the domain, so Exim looks at the second
22695 rule. This does not match the host, but it does match the domain, so it is used
22696 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
22697 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
22698 first retry rule is used, because it matches the host.
22700 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
22701 first rule to determine retry times, but for all the other hosts for the domain
22702 &'a.b.c.example'&, the second rule is used. The second rule is also used if
22703 routing to &'a.b.c.example'& suffers a temporary failure.
22705 &*Note*&: The host name is used when matching the patterns, not its IP address.
22706 However, if a message is routed directly to an IP address without the use of a
22707 host name, for example, if a &(manualroute)& router contains a setting such as:
22709 route_list = *.a.example 192.168.34.23
22711 then the &"host name"& that is used when searching for a retry rule is the
22712 textual form of the IP address.
22714 .section "Retry rules for specific errors" "SECID161"
22715 .cindex "retry" "specific errors; specifying"
22716 The second field in a retry rule is the name of a particular error, or an
22717 asterisk, which matches any error. The errors that can be tested for are:
22720 .vitem &%auth_failed%&
22721 Authentication failed when trying to send to a host in the
22722 &%hosts_require_auth%& list in an &(smtp)& transport.
22724 .vitem &%data_4xx%&
22725 A 4&'xx'& error was received for an outgoing DATA command, either immediately
22726 after the command, or after sending the message's data.
22728 .vitem &%mail_4xx%&
22729 A 4&'xx'& error was received for an outgoing MAIL command.
22731 .vitem &%rcpt_4xx%&
22732 A 4&'xx'& error was received for an outgoing RCPT command.
22735 For the three 4&'xx'& errors, either the first or both of the x's can be given
22736 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
22737 recognize 452 errors given to RCPT commands for addresses in a certain domain,
22738 and have retries every ten minutes with a one-hour timeout, you could set up a
22739 retry rule of this form:
22741 the.domain.name rcpt_452 F,1h,10m
22743 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
22744 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
22747 .vitem &%lost_connection%&
22748 A server unexpectedly closed the SMTP connection. There may, of course,
22749 legitimate reasons for this (host died, network died), but if it repeats a lot
22750 for the same host, it indicates something odd.
22752 .vitem &%refused_MX%&
22753 A connection to a host obtained from an MX record was refused.
22755 .vitem &%refused_A%&
22756 A connection to a host not obtained from an MX record was refused.
22759 A connection was refused.
22761 .vitem &%timeout_connect_MX%&
22762 A connection attempt to a host obtained from an MX record timed out.
22764 .vitem &%timeout_connect_A%&
22765 A connection attempt to a host not obtained from an MX record timed out.
22767 .vitem &%timeout_connect%&
22768 A connection attempt timed out.
22770 .vitem &%timeout_MX%&
22771 There was a timeout while connecting or during an SMTP session with a host
22772 obtained from an MX record.
22774 .vitem &%timeout_A%&
22775 There was a timeout while connecting or during an SMTP session with a host not
22776 obtained from an MX record.
22779 There was a timeout while connecting or during an SMTP session.
22781 .vitem &%tls_required%&
22782 The server was required to use TLS (it matched &%hosts_require_tls%& in the
22783 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
22784 to STARTTLS, or there was a problem setting up the TLS connection.
22787 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
22790 .vitem &%quota_%&<&'time'&>
22791 .cindex "quota" "error testing in retry rule"
22792 .cindex "retry" "quota error testing"
22793 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
22794 transport, and the mailbox has not been accessed for <&'time'&>. For example,
22795 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
22799 .cindex "mailbox" "time of last read"
22800 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
22801 timeouts when the mailbox is full and is not being read by its owner. Ideally,
22802 it should be based on the last time that the user accessed the mailbox.
22803 However, it is not always possible to determine this. Exim uses the following
22807 If the mailbox is a single file, the time of last access (the &"atime"&) is
22808 used. As no new messages are being delivered (because the mailbox is over
22809 quota), Exim does not access the file, so this is the time of last user access.
22811 .cindex "maildir format" "time of last read"
22812 For a maildir delivery, the time of last modification of the &_new_&
22813 subdirectory is used. As the mailbox is over quota, no new files are created in
22814 the &_new_& subdirectory, because no new messages are being delivered. Any
22815 change to the &_new_& subdirectory is therefore assumed to be the result of an
22816 MUA moving a new message to the &_cur_& directory when it is first read. The
22817 time that is used is therefore the last time that the user read a new message.
22819 For other kinds of multi-file mailbox, the time of last access cannot be
22820 obtained, so a retry rule that uses this type of error field is never matched.
22823 The quota errors apply both to system-enforced quotas and to Exim's own quota
22824 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
22825 when a local delivery is deferred because a partition is full (the ENOSPC
22830 .section "Retry rules for specified senders" "SECID162"
22831 .cindex "retry" "rules; sender-specific"
22832 You can specify retry rules that apply only when the failing message has a
22833 specific sender. In particular, this can be used to define retry rules that
22834 apply only to bounce messages. The third item in a retry rule can be of this
22837 &`senders=`&<&'address list'&>
22839 The retry timings themselves are then the fourth item. For example:
22841 * rcpt_4xx senders=: F,1h,30m
22843 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
22844 host. If the address list contains white space, it must be enclosed in quotes.
22847 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
22849 &*Warning*&: This facility can be unhelpful if it is used for host errors
22850 (which do not depend on the recipient). The reason is that the sender is used
22851 only to match the retry rule. Once the rule has been found for a host error,
22852 its contents are used to set a retry time for the host, and this will apply to
22853 all messages, not just those with specific senders.
22855 When testing retry rules using &%-brt%&, you can supply a sender using the
22856 &%-f%& command line option, like this:
22858 exim -f "" -brt user@dom.ain
22860 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
22861 list is never matched.
22867 .section "Retry parameters" "SECID163"
22868 .cindex "retry" "parameters in rules"
22869 The third (or fourth, if a senders list is present) field in a retry rule is a
22870 sequence of retry parameter sets, separated by semicolons. Each set consists of
22872 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
22874 The letter identifies the algorithm for computing a new retry time; the cutoff
22875 time is the time beyond which this algorithm no longer applies, and the
22876 arguments vary the algorithm's action. The cutoff time is measured from the
22877 time that the first failure for the domain (combined with the local part if
22878 relevant) was detected, not from the time the message was received.
22880 .cindex "retry" "algorithms"
22881 .cindex "retry" "fixed intervals"
22882 .cindex "retry" "increasing intervals"
22883 .cindex "retry" "random intervals"
22884 The available algorithms are:
22887 &'F'&: retry at fixed intervals. There is a single time parameter specifying
22890 &'G'&: retry at geometrically increasing intervals. The first argument
22891 specifies a starting value for the interval, and the second a multiplier, which
22892 is used to increase the size of the interval at each retry.
22894 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
22895 retry, the previous interval is multiplied by the factor in order to get a
22896 maximum for the next interval. The minimum interval is the first argument of
22897 the parameter, and an actual interval is chosen randomly between them. Such a
22898 rule has been found to be helpful in cluster configurations when all the
22899 members of the cluster restart at once, and may therefore synchronize their
22900 queue processing times.
22903 When computing the next retry time, the algorithm definitions are scanned in
22904 order until one whose cutoff time has not yet passed is reached. This is then
22905 used to compute a new retry time that is later than the current time. In the
22906 case of fixed interval retries, this simply means adding the interval to the
22907 current time. For geometrically increasing intervals, retry intervals are
22908 computed from the rule's parameters until one that is greater than the previous
22909 interval is found. The main configuration variable
22910 .cindex "limit" "retry interval"
22911 .cindex "retry" "interval, maximum"
22912 .oindex "&%retry_interval_max%&"
22913 &%retry_interval_max%& limits the maximum interval between retries. It
22914 cannot be set greater than &`24h`&, which is its default value.
22916 A single remote domain may have a number of hosts associated with it, and each
22917 host may have more than one IP address. Retry algorithms are selected on the
22918 basis of the domain name, but are applied to each IP address independently. If,
22919 for example, a host has two IP addresses and one is unusable, Exim will
22920 generate retry times for it and will not try to use it until its next retry
22921 time comes. Thus the good IP address is likely to be tried first most of the
22924 .cindex "hints database" "use for retrying"
22925 Retry times are hints rather than promises. Exim does not make any attempt to
22926 run deliveries exactly at the computed times. Instead, a queue runner process
22927 starts delivery processes for delayed messages periodically, and these attempt
22928 new deliveries only for those addresses that have passed their next retry time.
22929 If a new message arrives for a deferred address, an immediate delivery attempt
22930 occurs only if the address has passed its retry time. In the absence of new
22931 messages, the minimum time between retries is the interval between queue runner
22932 processes. There is not much point in setting retry times of five minutes if
22933 your queue runners happen only once an hour, unless there are a significant
22934 number of incoming messages (which might be the case on a system that is
22935 sending everything to a smart host, for example).
22937 The data in the retry hints database can be inspected by using the
22938 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
22939 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
22940 &'exinext'& utility script can be used to find out what the next retry times
22941 are for the hosts associated with a particular mail domain, and also for local
22942 deliveries that have been deferred.
22945 .section "Retry rule examples" "SECID164"
22946 Here are some example retry rules:
22948 alice@wonderland.fict.example quota_5d F,7d,3h
22949 wonderland.fict.example quota_5d
22950 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
22951 lookingglass.fict.example * F,24h,30m;
22952 * refused_A F,2h,20m;
22953 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
22955 The first rule sets up special handling for mail to
22956 &'alice@wonderland.fict.example'& when there is an over-quota error and the
22957 mailbox has not been read for at least 5 days. Retries continue every three
22958 hours for 7 days. The second rule handles over-quota errors for all other local
22959 parts at &'wonderland.fict.example'&; the absence of a local part has the same
22960 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
22961 fail are bounced immediately if the mailbox has not been read for at least 5
22964 The third rule handles all other errors at &'wonderland.fict.example'&; retries
22965 happen every 15 minutes for an hour, then with geometrically increasing
22966 intervals until two days have passed since a delivery first failed. After the
22967 first hour there is a delay of one hour, then two hours, then four hours, and
22968 so on (this is a rather extreme example).
22970 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
22971 They happen every 30 minutes for 24 hours only. The remaining two rules handle
22972 all other domains, with special action for connection refusal from hosts that
22973 were not obtained from an MX record.
22975 The final rule in a retry configuration should always have asterisks in the
22976 first two fields so as to provide a general catch-all for any addresses that do
22977 not have their own special handling. This example tries every 15 minutes for 2
22978 hours, then with intervals starting at one hour and increasing by a factor of
22979 1.5 up to 16 hours, then every 8 hours up to 5 days.
22983 .section "Timeout of retry data" "SECID165"
22984 .cindex "timeout" "of retry data"
22985 .oindex "&%retry_data_expire%&"
22986 .cindex "hints database" "data expiry"
22987 .cindex "retry" "timeout of data"
22988 Exim timestamps the data that it writes to its retry hints database. When it
22989 consults the data during a delivery it ignores any that is older than the value
22990 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
22991 been tried for 7 days, Exim will try to deliver to it immediately a message
22992 arrives, and if that fails, it will calculate a retry time as if it were
22993 failing for the first time.
22995 This improves the behaviour for messages routed to rarely-used hosts such as MX
22996 backups. If such a host was down at one time, and happens to be down again when
22997 Exim tries a month later, using the old retry data would imply that it had been
22998 down all the time, which is not a justified assumption.
23000 If a host really is permanently dead, this behaviour causes a burst of retries
23001 every now and again, but only if messages routed to it are rare. If there is a
23002 message at least once every 7 days the retry data never expires.
23007 .section "Long-term failures" "SECID166"
23008 .cindex "delivery failure, long-term"
23009 .cindex "retry" "after long-term failure"
23010 Special processing happens when an email address has been failing for so long
23011 that the cutoff time for the last algorithm is reached. For example, using the
23012 default retry rule:
23014 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
23016 the cutoff time is four days. Reaching the retry cutoff is independent of how
23017 long any specific message has been failing; it is the length of continuous
23018 failure for the recipient address that counts.
23020 When the cutoff time is reached for a local delivery, or for all the IP
23021 addresses associated with a remote delivery, a subsequent delivery failure
23022 causes Exim to give up on the address, and a bounce message is generated.
23023 In order to cater for new messages that use the failing address, a next retry
23024 time is still computed from the final algorithm, and is used as follows:
23026 For local deliveries, one delivery attempt is always made for any subsequent
23027 messages. If this delivery fails, the address fails immediately. The
23028 post-cutoff retry time is not used.
23030 If the delivery is remote, there are two possibilities, controlled by the
23031 .oindex "&%delay_after_cutoff%&"
23032 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
23033 default. Until the post-cutoff retry time for one of the IP addresses is
23034 reached, the failing email address is bounced immediately, without a delivery
23035 attempt taking place. After that time, one new delivery attempt is made to
23036 those IP addresses that are past their retry times, and if that still fails,
23037 the address is bounced and new retry times are computed.
23039 In other words, when all the hosts for a given email address have been failing
23040 for a long time, Exim bounces rather then defers until one of the hosts' retry
23041 times is reached. Then it tries once, and bounces if that attempt fails. This
23042 behaviour ensures that few resources are wasted in repeatedly trying to deliver
23043 to a broken destination, but if the host does recover, Exim will eventually
23046 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
23047 addresses are past their final cutoff time, Exim tries to deliver to those IP
23048 addresses that have not been tried since the message arrived. If there are
23049 no suitable IP addresses, or if they all fail, the address is bounced. In other
23050 words, it does not delay when a new message arrives, but tries the expired
23051 addresses immediately, unless they have been tried since the message arrived.
23052 If there is a continuous stream of messages for the failing domains, setting
23053 &%delay_after_cutoff%& false means that there will be many more attempts to
23054 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
23057 .section "Deliveries that work intermittently" "SECID167"
23058 .cindex "retry" "intermittently working deliveries"
23059 Some additional logic is needed to cope with cases where a host is
23060 intermittently available, or when a message has some attribute that prevents
23061 its delivery when others to the same address get through. In this situation,
23062 because some messages are successfully delivered, the &"retry clock"& for the
23063 host or address keeps getting reset by the successful deliveries, and so
23064 failing messages remain on the queue for ever because the cutoff time is never
23067 Two exceptional actions are applied to prevent this happening. The first
23068 applies to errors that are related to a message rather than a remote host.
23069 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
23070 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
23071 commands, and quota failures. For this type of error, if a message's arrival
23072 time is earlier than the &"first failed"& time for the error, the earlier time
23073 is used when scanning the retry rules to decide when to try next and when to
23074 time out the address.
23076 The exceptional second action applies in all cases. If a message has been on
23077 the queue for longer than the cutoff time of any applicable retry rule for a
23078 given address, a delivery is attempted for that address, even if it is not yet
23079 time, and if this delivery fails, the address is timed out. A new retry time is
23080 not computed in this case, so that other messages for the same address are
23081 considered immediately.
23082 .ecindex IIDretconf1
23083 .ecindex IIDregconf2
23090 . ////////////////////////////////////////////////////////////////////////////
23091 . ////////////////////////////////////////////////////////////////////////////
23093 .chapter "SMTP authentication" "CHAPSMTPAUTH"
23094 .scindex IIDauthconf1 "SMTP" "authentication configuration"
23095 .scindex IIDauthconf2 "authentication"
23096 The &"authenticators"& section of Exim's run time configuration is concerned
23097 with SMTP authentication. This facility is an extension to the SMTP protocol,
23098 described in RFC 2554, which allows a client SMTP host to authenticate itself
23099 to a server. This is a common way for a server to recognize clients that are
23100 permitted to use it as a relay. SMTP authentication is not of relevance to the
23101 transfer of mail between servers that have no managerial connection with each
23104 .cindex "AUTH" "description of"
23105 Very briefly, the way SMTP authentication works is as follows:
23108 The server advertises a number of authentication &'mechanisms'& in response to
23109 the client's EHLO command.
23111 The client issues an AUTH command, naming a specific mechanism. The command
23112 may, optionally, contain some authentication data.
23114 The server may issue one or more &'challenges'&, to which the client must send
23115 appropriate responses. In simple authentication mechanisms, the challenges are
23116 just prompts for user names and passwords. The server does not have to issue
23117 any challenges &-- in some mechanisms the relevant data may all be transmitted
23118 with the AUTH command.
23120 The server either accepts or denies authentication.
23122 If authentication succeeds, the client may optionally make use of the AUTH
23123 option on the MAIL command to pass an authenticated sender in subsequent
23124 mail transactions. Authentication lasts for the remainder of the SMTP
23127 If authentication fails, the client may give up, or it may try a different
23128 authentication mechanism, or it may try transferring mail over the
23129 unauthenticated connection.
23132 If you are setting up a client, and want to know which authentication
23133 mechanisms the server supports, you can use Telnet to connect to port 25 (the
23134 SMTP port) on the server, and issue an EHLO command. The response to this
23135 includes the list of supported mechanisms. For example:
23137 &`$ `&&*&`telnet server.example 25`&*&
23138 &`Trying 192.168.34.25...`&
23139 &`Connected to server.example.`&
23140 &`Escape character is '^]'.`&
23141 &`220 server.example ESMTP Exim 4.20 ...`&
23142 &*&`ehlo client.example`&*&
23143 &`250-server.example Hello client.example [10.8.4.5]`&
23144 &`250-SIZE 52428800`&
23149 The second-last line of this example output shows that the server supports
23150 authentication using the PLAIN mechanism. In Exim, the different authentication
23151 mechanisms are configured by specifying &'authenticator'& drivers. Like the
23152 routers and transports, which authenticators are included in the binary is
23153 controlled by build-time definitions. The following are currently available,
23154 included by setting
23157 AUTH_CYRUS_SASL=yes
23161 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
23162 authentication mechanism (RFC 2195), and the second provides an interface to
23163 the Cyrus SASL authentication library. The third can be configured to support
23164 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
23165 not formally documented, but used by several MUAs. The fourth authenticator
23166 supports Microsoft's &'Secure Password Authentication'& mechanism.
23168 The authenticators are configured using the same syntax as other drivers (see
23169 section &<<SECTfordricon>>&). If no authenticators are required, no
23170 authentication section need be present in the configuration file. Each
23171 authenticator can in principle have both server and client functions. When Exim
23172 is receiving SMTP mail, it is acting as a server; when it is sending out
23173 messages over SMTP, it is acting as a client. Authenticator configuration
23174 options are provided for use in both these circumstances.
23176 To make it clear which options apply to which situation, the prefixes
23177 &%server_%& and &%client_%& are used on option names that are specific to
23178 either the server or the client function, respectively. Server and client
23179 functions are disabled if none of their options are set. If an authenticator is
23180 to be used for both server and client functions, a single definition, using
23181 both sets of options, is required. For example:
23185 public_name = CRAM-MD5
23186 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
23188 client_secret = secret2
23190 The &%server_%& option is used when Exim is acting as a server, and the
23191 &%client_%& options when it is acting as a client.
23193 Descriptions of the individual authenticators are given in subsequent chapters.
23194 The remainder of this chapter covers the generic options for the
23195 authenticators, followed by general discussion of the way authentication works
23200 .section "Generic options for authenticators" "SECID168"
23201 .cindex "authentication" "generic options"
23202 .cindex "options" "generic; for authenticators"
23204 .option client_condition authenticators string&!! unset
23205 When Exim is authenticating as a client, it skips any authenticator whose
23206 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
23207 used, for example, to skip plain text authenticators when the connection is not
23208 encrypted by a setting such as:
23210 client_condition = ${if !eq{$tls_cipher}{}}
23212 (Older documentation incorrectly states that &$tls_cipher$& contains the cipher
23213 used for incoming messages. In fact, during SMTP delivery, it contains the
23214 cipher used for the delivery.)
23217 .option driver authenticators string unset
23218 This option must always be set. It specifies which of the available
23219 authenticators is to be used.
23222 .option public_name authenticators string unset
23223 This option specifies the name of the authentication mechanism that the driver
23224 implements, and by which it is known to the outside world. These names should
23225 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
23226 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
23227 defaults to the driver's instance name.
23230 .option server_advertise_condition authenticators string&!! unset
23231 When a server is about to advertise an authentication mechanism, the condition
23232 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
23233 mechanism is not advertised.
23234 If the expansion fails, the mechanism is not advertised. If the failure was not
23235 forced, and was not caused by a lookup defer, the incident is logged.
23236 See section &<<SECTauthexiser>>& below for further discussion.
23239 .option server_condition authenticators string&!! unset
23240 This option must be set for a &%plaintext%& server authenticator, where it
23241 is used directly to control authentication. See section &<<SECTplainserver>>&
23244 For the other authenticators, &%server_condition%& can be used as an additional
23245 authentication or authorization mechanism that is applied after the other
23246 authenticator conditions succeed. If it is set, it is expanded when the
23247 authenticator would otherwise return a success code. If the expansion is forced
23248 to fail, authentication fails. Any other expansion failure causes a temporary
23249 error code to be returned. If the result of a successful expansion is an empty
23250 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
23251 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
23252 other result, a temporary error code is returned, with the expanded string as
23256 .option server_debug_print authenticators string&!! unset
23257 If this option is set and authentication debugging is enabled (see the &%-d%&
23258 command line option), the string is expanded and included in the debugging
23259 output when the authenticator is run as a server. This can help with checking
23260 out the values of variables.
23261 If expansion of the string fails, the error message is written to the debugging
23262 output, and Exim carries on processing.
23265 .option server_set_id authenticators string&!! unset
23266 .vindex "&$authenticated_id$&"
23267 When an Exim server successfully authenticates a client, this string is
23268 expanded using data from the authentication, and preserved for any incoming
23269 messages in the variable &$authenticated_id$&. It is also included in the log
23270 lines for incoming messages. For example, a user/password authenticator
23271 configuration might preserve the user name that was used to authenticate, and
23272 refer to it subsequently during delivery of the message.
23273 If expansion fails, the option is ignored.
23276 .option server_mail_auth_condition authenticators string&!! unset
23277 This option allows a server to discard authenticated sender addresses supplied
23278 as part of MAIL commands in SMTP connections that are authenticated by the
23279 driver on which &%server_mail_auth_condition%& is set. The option is not used
23280 as part of the authentication process; instead its (unexpanded) value is
23281 remembered for later use.
23282 How it is used is described in the following section.
23288 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
23289 .cindex "authentication" "sender; authenticated"
23290 .cindex "AUTH" "on MAIL command"
23291 When a client supplied an AUTH= item on a MAIL command, Exim applies
23292 the following checks before accepting it as the authenticated sender of the
23296 If the connection is not using extended SMTP (that is, HELO was used rather
23297 than EHLO), the use of AUTH= is a syntax error.
23299 If the value of the AUTH= parameter is &"<>"&, it is ignored.
23301 .vindex "&$authenticated_sender$&"
23302 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
23303 running, the value of &$authenticated_sender$& is set to the value obtained
23304 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
23305 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
23306 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
23307 given for the MAIL command.
23309 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
23310 is accepted and placed in &$authenticated_sender$& only if the client has
23313 If the AUTH= value was accepted by either of the two previous rules, and
23314 the client has authenticated, and the authenticator has a setting for the
23315 &%server_mail_auth_condition%&, the condition is checked at this point. The
23316 valued that was saved from the authenticator is expanded. If the expansion
23317 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
23318 &$authenticated_sender$& is deleted. If the expansion yields any other value,
23319 the value of &$authenticated_sender$& is retained and passed on with the
23324 When &$authenticated_sender$& is set for a message, it is passed on to other
23325 hosts to which Exim authenticates as a client. Do not confuse this value with
23326 &$authenticated_id$&, which is a string obtained from the authentication
23327 process, and which is not usually a complete email address.
23329 .vindex "&$sender_address$&"
23330 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
23331 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
23332 therefore make use of &$authenticated_sender$&. The converse is not true: the
23333 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
23338 .section "Authentication on an Exim server" "SECTauthexiser"
23339 .cindex "authentication" "on an Exim server"
23340 When Exim receives an EHLO command, it advertises the public names of those
23341 authenticators that are configured as servers, subject to the following
23345 The client host must match &%auth_advertise_hosts%& (default *).
23347 It the &%server_advertise_condition%& option is set, its expansion must not
23348 yield the empty string, &"0"&, &"no"&, or &"false"&.
23351 The order in which the authenticators are defined controls the order in which
23352 the mechanisms are advertised.
23354 Some mail clients (for example, some versions of Netscape) require the user to
23355 provide a name and password for authentication whenever AUTH is advertised,
23356 even though authentication may not in fact be needed (for example, Exim may be
23357 set up to allow unconditional relaying from the client by an IP address check).
23358 You can make such clients more friendly by not advertising AUTH to them.
23359 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
23360 that runs for RCPT) to relay without authentication, you should set
23362 auth_advertise_hosts = ! 10.9.8.0/24
23364 so that no authentication mechanisms are advertised to them.
23366 The &%server_advertise_condition%& controls the advertisement of individual
23367 authentication mechanisms. For example, it can be used to restrict the
23368 advertisement of a particular mechanism to encrypted connections, by a setting
23371 server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}}
23373 .vindex "&$tls_cipher$&"
23374 If the session is encrypted, &$tls_cipher$& is not empty, and so the expansion
23375 yields &"yes"&, which allows the advertisement to happen.
23377 When an Exim server receives an AUTH command from a client, it rejects it
23378 immediately if AUTH was not advertised in response to an earlier EHLO
23379 command. This is the case if
23382 The client host does not match &%auth_advertise_hosts%&; or
23384 No authenticators are configured with server options; or
23386 Expansion of &%server_advertise_condition%& blocked the advertising of all the
23387 server authenticators.
23391 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
23392 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
23393 AUTH is accepted from any client host.
23395 If AUTH is not rejected by the ACL, Exim searches its configuration for a
23396 server authentication mechanism that was advertised in response to EHLO and
23397 that matches the one named in the AUTH command. If it finds one, it runs
23398 the appropriate authentication protocol, and authentication either succeeds or
23399 fails. If there is no matching advertised mechanism, the AUTH command is
23400 rejected with a 504 error.
23402 .vindex "&$received_protocol$&"
23403 .vindex "&$sender_host_authenticated$&"
23404 When a message is received from an authenticated host, the value of
23405 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
23406 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
23407 public name) of the authenticator driver that successfully authenticated the
23408 client from which the message was received. This variable is empty if there was
23409 no successful authentication.
23414 .section "Testing server authentication" "SECID169"
23415 .cindex "authentication" "testing a server"
23416 .cindex "AUTH" "testing a server"
23417 .cindex "base64 encoding" "creating authentication test data"
23418 Exim's &%-bh%& option can be useful for testing server authentication
23419 configurations. The data for the AUTH command has to be sent using base64
23420 encoding. A quick way to produce such data for testing is the following Perl
23424 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
23426 .cindex "binary zero" "in authentication data"
23427 This interprets its argument as a Perl string, and then encodes it. The
23428 interpretation as a Perl string allows binary zeros, which are required for
23429 some kinds of authentication, to be included in the data. For example, a
23430 command line to run this script on such data might be
23432 encode '\0user\0password'
23434 Note the use of single quotes to prevent the shell interpreting the
23435 backslashes, so that they can be interpreted by Perl to specify characters
23436 whose code value is zero.
23438 &*Warning 1*&: If either of the user or password strings starts with an octal
23439 digit, you must use three zeros instead of one after the leading backslash. If
23440 you do not, the octal digit that starts your string will be incorrectly
23441 interpreted as part of the code for the first character.
23443 &*Warning 2*&: If there are characters in the strings that Perl interprets
23444 specially, you must use a Perl escape to prevent them being misinterpreted. For
23445 example, a command such as
23447 encode '\0user@domain.com\0pas$$word'
23449 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
23451 If you have the &%mimencode%& command installed, another way to do produce
23452 base64-encoded strings is to run the command
23454 echo -e -n `\0user\0password' | mimencode
23456 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
23457 in the argument, and the &%-n%& option specifies no newline at the end of its
23458 output. However, not all versions of &%echo%& recognize these options, so you
23459 should check your version before relying on this suggestion.
23463 .section "Authentication by an Exim client" "SECID170"
23464 .cindex "authentication" "on an Exim client"
23465 The &(smtp)& transport has two options called &%hosts_require_auth%& and
23466 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
23467 announces support for authentication, and the host matches an entry in either
23468 of these options, Exim (as a client) tries to authenticate as follows:
23471 For each authenticator that is configured as a client, in the order in which
23472 they are defined in the configuration, it searches the authentication
23473 mechanisms announced by the server for one whose name matches the public name
23474 of the authenticator.
23477 .vindex "&$host_address$&"
23478 When it finds one that matches, it runs the authenticator's client code. The
23479 variables &$host$& and &$host_address$& are available for any string expansions
23480 that the client might do. They are set to the server's name and IP address. If
23481 any expansion is forced to fail, the authentication attempt is abandoned, and
23482 Exim moves on to the next authenticator. Otherwise an expansion failure causes
23483 delivery to be deferred.
23485 If the result of the authentication attempt is a temporary error or a timeout,
23486 Exim abandons trying to send the message to the host for the moment. It will
23487 try again later. If there are any backup hosts available, they are tried in the
23490 If the response to authentication is a permanent error (5&'xx'& code), Exim
23491 carries on searching the list of authenticators and tries another one if
23492 possible. If all authentication attempts give permanent errors, or if there are
23493 no attempts because no mechanisms match (or option expansions force failure),
23494 what happens depends on whether the host matches &%hosts_require_auth%& or
23495 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
23496 delivery is deferred. The error can be detected in the retry rules, and thereby
23497 turned into a permanent error if you wish. In the second case, Exim tries to
23498 deliver the message unauthenticated.
23501 .cindex "AUTH" "on MAIL command"
23502 When Exim has authenticated itself to a remote server, it adds the AUTH
23503 parameter to the MAIL commands it sends, if it has an authenticated sender for
23504 the message. If the message came from a remote host, the authenticated sender
23505 is the one that was receiving on an incoming MAIL command, provided that the
23506 incoming connection was authenticated and the &%server_mail_auth%& condition
23507 allowed the authenticated sender to be retained. If a local process calls Exim
23508 to send a message, the sender address that is built from the login name and
23509 &%qualify_domain%& is treated as authenticated. However, if the
23510 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
23511 the authenticated sender that was received with the message.
23512 .ecindex IIDauthconf1
23513 .ecindex IIDauthconf2
23520 . ////////////////////////////////////////////////////////////////////////////
23521 . ////////////////////////////////////////////////////////////////////////////
23523 .chapter "The plaintext authenticator" "CHAPplaintext"
23524 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
23525 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
23526 The &(plaintext)& authenticator can be configured to support the PLAIN and
23527 LOGIN authentication mechanisms, both of which transfer authentication data as
23528 plain (unencrypted) text (though base64 encoded). The use of plain text is a
23529 security risk; you are strongly advised to insist on the use of SMTP encryption
23530 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
23531 use unencrypted plain text, you should not use the same passwords for SMTP
23532 connections as you do for login accounts.
23534 .section "Plaintext options" "SECID171"
23535 .cindex "options" "&(plaintext)& authenticator (server)"
23536 When configured as a server, &(plaintext)& uses the following options:
23538 .option server_condition authenticators string&!! unset
23539 This is actually a global authentication option, but it must be set in order to
23540 configure the &(plaintext)& driver as a server. Its use is described below.
23542 .option server_prompts plaintext string&!! unset
23543 The contents of this option, after expansion, must be a colon-separated list of
23544 prompt strings. If expansion fails, a temporary authentication rejection is
23547 .section "Using plaintext in a server" "SECTplainserver"
23548 .cindex "AUTH" "in &(plaintext)& authenticator"
23549 .cindex "binary zero" "in &(plaintext)& authenticator"
23550 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
23551 "in &(plaintext)& authenticator"
23552 .vindex "&$auth1$&, &$auth2$&, etc"
23553 .cindex "base64 encoding" "in &(plaintext)& authenticator"
23555 When running as a server, &(plaintext)& performs the authentication test by
23556 expanding a string. The data sent by the client with the AUTH command, or in
23557 response to subsequent prompts, is base64 encoded, and so may contain any byte
23558 values when decoded. If any data is supplied with the command, it is treated as
23559 a list of strings, separated by NULs (binary zeros), the first three of which
23560 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
23561 (neither LOGIN nor PLAIN uses more than three strings).
23563 For compatibility with previous releases of Exim, the values are also placed in
23564 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
23565 variables for this purpose is now deprecated, as it can lead to confusion in
23566 string expansions that also use them for other things.
23568 If there are more strings in &%server_prompts%& than the number of strings
23569 supplied with the AUTH command, the remaining prompts are used to obtain more
23570 data. Each response from the client may be a list of NUL-separated strings.
23572 .vindex "&$authenticated_id$&"
23573 Once a sufficient number of data strings have been received,
23574 &%server_condition%& is expanded. If the expansion is forced to fail,
23575 authentication fails. Any other expansion failure causes a temporary error code
23576 to be returned. If the result of a successful expansion is an empty string,
23577 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
23578 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
23579 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
23580 For any other result, a temporary error code is returned, with the expanded
23581 string as the error text.
23583 &*Warning*&: If you use a lookup in the expansion to find the user's
23584 password, be sure to make the authentication fail if the user is unknown.
23585 There are good and bad examples at the end of the next section.
23589 .section "The PLAIN authentication mechanism" "SECID172"
23590 .cindex "PLAIN authentication mechanism"
23591 .cindex "authentication" "PLAIN mechanism"
23592 .cindex "binary zero" "in &(plaintext)& authenticator"
23593 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
23594 sent as one item of data (that is, one combined string containing two NUL
23595 separators). The data is sent either as part of the AUTH command, or
23596 subsequently in response to an empty prompt from the server.
23598 The second and third strings are a user name and a corresponding password.
23599 Using a single fixed user name and password as an example, this could be
23600 configured as follows:
23604 public_name = PLAIN
23606 server_condition = \
23607 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
23608 server_set_id = $auth2
23610 Note that the default result strings from &%if%& (&"true"& or an empty string)
23611 are exactly what we want here, so they need not be specified. Obviously, if the
23612 password contains expansion-significant characters such as dollar, backslash,
23613 or closing brace, they have to be escaped.
23615 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
23616 the end of a string list are ignored). If all the data comes as part of the
23617 AUTH command, as is commonly the case, the prompt is not used. This
23618 authenticator is advertised in the response to EHLO as
23622 and a client host can authenticate itself by sending the command
23624 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
23626 As this contains three strings (more than the number of prompts), no further
23627 data is required from the client. Alternatively, the client may just send
23631 to initiate authentication, in which case the server replies with an empty
23632 prompt. The client must respond with the combined data string.
23634 The data string is base64 encoded, as required by the RFC. This example,
23635 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
23636 represents a zero byte. This is split up into three strings, the first of which
23637 is empty. The &%server_condition%& option in the authenticator checks that the
23638 second two are &`username`& and &`mysecret`& respectively.
23640 Having just one fixed user name and password, as in this example, is not very
23641 realistic, though for a small organization with only a handful of
23642 authenticating clients it could make sense.
23644 A more sophisticated instance of this authenticator could use the user name in
23645 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
23646 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
23647 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
23648 This is an incorrect example:
23650 server_condition = \
23651 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
23653 The expansion uses the user name (&$auth2$&) as the key to look up a password,
23654 which it then compares to the supplied password (&$auth3$&). Why is this example
23655 incorrect? It works fine for existing users, but consider what happens if a
23656 non-existent user name is given. The lookup fails, but as no success/failure
23657 strings are given for the lookup, it yields an empty string. Thus, to defeat
23658 the authentication, all a client has to do is to supply a non-existent user
23659 name and an empty password. The correct way of writing this test is:
23661 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
23662 {${if eq{$value}{$auth3}}} {false}}
23664 In this case, if the lookup succeeds, the result is checked; if the lookup
23665 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
23666 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
23667 always fails if its second argument is empty. However, the second way of
23668 writing the test makes the logic clearer.
23671 .section "The LOGIN authentication mechanism" "SECID173"
23672 .cindex "LOGIN authentication mechanism"
23673 .cindex "authentication" "LOGIN mechanism"
23674 The LOGIN authentication mechanism is not documented in any RFC, but is in use
23675 in a number of programs. No data is sent with the AUTH command. Instead, a
23676 user name and password are supplied separately, in response to prompts. The
23677 plaintext authenticator can be configured to support this as in this example:
23681 public_name = LOGIN
23682 server_prompts = User Name : Password
23683 server_condition = \
23684 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
23685 server_set_id = $auth1
23687 Because of the way plaintext operates, this authenticator accepts data supplied
23688 with the AUTH command (in contravention of the specification of LOGIN), but
23689 if the client does not supply it (as is the case for LOGIN clients), the prompt
23690 strings are used to obtain two data items.
23692 Some clients are very particular about the precise text of the prompts. For
23693 example, Outlook Express is reported to recognize only &"Username:"& and
23694 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
23695 strings. It uses the &%ldapauth%& expansion condition to check the user
23696 name and password by binding to an LDAP server:
23700 public_name = LOGIN
23701 server_prompts = Username:: : Password::
23702 server_condition = ${if and{{
23704 ldapauth{user="cn=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
23705 pass=${quote:$auth2} \
23706 ldap://ldap.example.org/} }} }
23707 server_set_id = uid=$auth1,ou=people,o=example.org
23709 We have to check that the username is not empty before using it, because LDAP
23710 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
23711 operator to correctly quote the DN for authentication. However, the basic
23712 &%quote%& operator, rather than any of the LDAP quoting operators, is the
23713 correct one to use for the password, because quoting is needed only to make
23714 the password conform to the Exim syntax. At the LDAP level, the password is an
23715 uninterpreted string.
23718 .section "Support for different kinds of authentication" "SECID174"
23719 A number of string expansion features are provided for the purpose of
23720 interfacing to different ways of user authentication. These include checking
23721 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
23722 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
23728 .section "Using plaintext in a client" "SECID175"
23729 .cindex "options" "&(plaintext)& authenticator (client)"
23730 The &(plaintext)& authenticator has two client options:
23732 .option client_ignore_invalid_base64 plaintext boolean false
23733 If the client receives a server prompt that is not a valid base64 string,
23734 authentication is abandoned by default. However, if this option is set true,
23735 the error in the challenge is ignored and the client sends the response as
23738 .option client_send plaintext string&!! unset
23739 The string is a colon-separated list of authentication data strings. Each
23740 string is independently expanded before being sent to the server. The first
23741 string is sent with the AUTH command; any more strings are sent in response
23742 to prompts from the server. Before each string is expanded, the value of the
23743 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
23744 with &$auth1$& for the first prompt. Up to three prompts are stored in this
23745 way. Thus, the prompt that is received in response to sending the first string
23746 (with the AUTH command) can be used in the expansion of the second string, and
23747 so on. If an invalid base64 string is received when
23748 &%client_ignore_invalid_base64%& is set, an empty string is put in the
23749 &$auth$&<&'n'&> variable.
23751 &*Note*&: You cannot use expansion to create multiple strings, because
23752 splitting takes priority and happens first.
23754 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
23755 the data, further processing is applied to each string before it is sent. If
23756 there are any single circumflex characters in the string, they are converted to
23757 NULs. Should an actual circumflex be required as data, it must be doubled in
23760 This is an example of a client configuration that implements the PLAIN
23761 authentication mechanism with a fixed user name and password:
23765 public_name = PLAIN
23766 client_send = ^username^mysecret
23768 The lack of colons means that the entire text is sent with the AUTH
23769 command, with the circumflex characters converted to NULs. A similar example
23770 that uses the LOGIN mechanism is:
23774 public_name = LOGIN
23775 client_send = : username : mysecret
23777 The initial colon means that the first string is empty, so no data is sent with
23778 the AUTH command itself. The remaining strings are sent in response to
23780 .ecindex IIDplaiauth1
23781 .ecindex IIDplaiauth2
23786 . ////////////////////////////////////////////////////////////////////////////
23787 . ////////////////////////////////////////////////////////////////////////////
23789 .chapter "The cram_md5 authenticator" "CHID9"
23790 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
23791 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
23792 .cindex "CRAM-MD5 authentication mechanism"
23793 .cindex "authentication" "CRAM-MD5 mechanism"
23794 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
23795 sends a challenge string to the client, and the response consists of a user
23796 name and the CRAM-MD5 digest of the challenge string combined with a secret
23797 string (password) which is known to both server and client. Thus, the secret
23798 is not sent over the network as plain text, which makes this authenticator more
23799 secure than &(plaintext)&. However, the downside is that the secret has to be
23800 available in plain text at either end.
23803 .section "Using cram_md5 as a server" "SECID176"
23804 .cindex "options" "&(cram_md5)& authenticator (server)"
23805 This authenticator has one server option, which must be set to configure the
23806 authenticator as a server:
23808 .option server_secret cram_md5 string&!! unset
23809 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
23810 When the server receives the client's response, the user name is placed in
23811 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
23812 obtain the password for that user. The server then computes the CRAM-MD5 digest
23813 that the client should have sent, and checks that it received the correct
23814 string. If the expansion of &%server_secret%& is forced to fail, authentication
23815 fails. If the expansion fails for some other reason, a temporary error code is
23816 returned to the client.
23818 For compatibility with previous releases of Exim, the user name is also placed
23819 in &$1$&. However, the use of this variables for this purpose is now
23820 deprecated, as it can lead to confusion in string expansions that also use
23821 numeric variables for other things.
23823 For example, the following authenticator checks that the user name given by the
23824 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
23825 user name, authentication fails.
23829 public_name = CRAM-MD5
23830 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
23831 server_set_id = $auth1
23833 .vindex "&$authenticated_id$&"
23834 If authentication succeeds, the setting of &%server_set_id%& preserves the user
23835 name in &$authenticated_id$&. A more typical configuration might look up the
23836 secret string in a file, using the user name as the key. For example:
23840 public_name = CRAM-MD5
23841 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
23843 server_set_id = $auth1
23845 Note that this expansion explicitly forces failure if the lookup fails
23846 because &$auth1$& contains an unknown user name.
23849 .section "Using cram_md5 as a client" "SECID177"
23850 .cindex "options" "&(cram_md5)& authenticator (client)"
23851 When used as a client, the &(cram_md5)& authenticator has two options:
23855 .option client_name cram_md5 string&!! "the primary host name"
23856 This string is expanded, and the result used as the user name data when
23857 computing the response to the server's challenge.
23860 .option client_secret cram_md5 string&!! unset
23861 This option must be set for the authenticator to work as a client. Its value is
23862 expanded and the result used as the secret string when computing the response.
23866 .vindex "&$host_address$&"
23867 Different user names and secrets can be used for different servers by referring
23868 to &$host$& or &$host_address$& in the options. Forced failure of either
23869 expansion string is treated as an indication that this authenticator is not
23870 prepared to handle this case. Exim moves on to the next configured client
23871 authenticator. Any other expansion failure causes Exim to give up trying to
23872 send the message to the current server.
23874 A simple example configuration of a &(cram_md5)& authenticator, using fixed
23879 public_name = CRAM-MD5
23881 client_secret = secret
23883 .ecindex IIDcramauth1
23884 .ecindex IIDcramauth2
23888 . ////////////////////////////////////////////////////////////////////////////
23889 . ////////////////////////////////////////////////////////////////////////////
23891 .chapter "The cyrus_sasl authenticator" "CHID10"
23892 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
23893 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
23894 .cindex "Cyrus" "SASL library"
23896 The code for this authenticator was provided by Matthew Byng-Maddick of A L
23897 Digital Ltd (&url(http://www.aldigital.co.uk)).
23899 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
23900 library implementation of the RFC 2222 (&"Simple Authentication and Security
23901 Layer"&). This library supports a number of authentication mechanisms,
23902 including PLAIN and LOGIN, but also several others that Exim does not support
23903 directly. In particular, there is support for Kerberos authentication.
23905 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
23906 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
23907 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
23908 name of the driver to determine which mechanism to support.
23910 Where access to some kind of secret file is required, for example in GSSAPI
23911 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
23912 user, and that the Cyrus SASL library has no way of escalating privileges
23913 by default. You may also find you need to set environment variables,
23914 depending on the driver you are using.
23916 The application name provided by Exim is &"exim"&, so various SASL options may
23917 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
23918 Kerberos, note that because of limitations in the GSSAPI interface,
23919 changing the server keytab might need to be communicated down to the Kerberos
23920 layer independently. The mechanism for doing so is dependent upon the Kerberos
23921 implementation. For example, for Heimdal, the environment variable KRB5_KTNAME
23922 may be set to point to an alternative keytab file. Exim will pass this
23923 variable through from its own inherited environment when started as root or the
23924 Exim user. The keytab file needs to be readable by the Exim user.
23927 .section "Using cyrus_sasl as a server" "SECID178"
23928 The &(cyrus_sasl)& authenticator has four private options. It puts the username
23929 (on a successful authentication) into &$auth1$&. For compatibility with
23930 previous releases of Exim, the username is also placed in &$1$&. However, the
23931 use of this variable for this purpose is now deprecated, as it can lead to
23932 confusion in string expansions that also use numeric variables for other
23936 .option server_hostname cyrus_sasl string&!! "see below"
23937 This option selects the hostname that is used when communicating with the
23938 library. The default value is &`$primary_hostname`&. It is up to the underlying
23939 SASL plug-in what it does with this data.
23942 .option server_mech cyrus_sasl string "see below"
23943 This option selects the authentication mechanism this driver should use. The
23944 default is the value of the generic &%public_name%& option. This option allows
23945 you to use a different underlying mechanism from the advertised name. For
23949 driver = cyrus_sasl
23950 public_name = X-ANYTHING
23951 server_mech = CRAM-MD5
23952 server_set_id = $auth1
23955 .option server_realm cyrus_sasl string unset
23956 This specifies the SASL realm that the server claims to be in.
23959 .option server_service cyrus_sasl string &`smtp`&
23960 This is the SASL service that the server claims to implement.
23963 For straightforward cases, you do not need to set any of the authenticator's
23964 private options. All you need to do is to specify an appropriate mechanism as
23965 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
23966 PLAIN, you could have two authenticators as follows:
23969 driver = cyrus_sasl
23970 public_name = CRAM-MD5
23971 server_set_id = $auth1
23974 driver = cyrus_sasl
23975 public_name = PLAIN
23976 server_set_id = $auth2
23978 Cyrus SASL does implement the LOGIN authentication method, even though it is
23979 not a standard method. It is disabled by default in the source distribution,
23980 but it is present in many binary distributions.
23981 .ecindex IIDcyrauth1
23982 .ecindex IIDcyrauth2
23987 . ////////////////////////////////////////////////////////////////////////////
23988 . ////////////////////////////////////////////////////////////////////////////
23989 .chapter "The dovecot authenticator" "CHAPdovecot"
23990 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
23991 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
23992 This authenticator is an interface to the authentication facility of the
23993 Dovecot POP/IMAP server, which can support a number of authentication methods.
23994 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
23995 to use the same mechanisms for SMTP authentication. This is a server
23996 authenticator only. There is only one option:
23998 .option server_socket dovecot string unset
24000 This option must specify the socket that is the interface to Dovecot
24001 authentication. The &%public_name%& option must specify an authentication
24002 mechanism that Dovecot is configured to support. You can have several
24003 authenticators for different mechanisms. For example:
24007 public_name = PLAIN
24008 server_socket = /var/run/dovecot/auth-client
24009 server_set_id = $auth2
24014 server_socket = /var/run/dovecot/auth-client
24015 server_set_id = $auth1
24017 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
24018 &$received_ip_address$& (that is, the connection is local), the &"secured"&
24019 option is passed in the Dovecot authentication command. If, for a TLS
24020 connection, a client certificate has been verified, the &"valid-client-cert"&
24021 option is passed. When authentication succeeds, the identity of the user
24022 who authenticated is placed in &$auth1$&.
24023 .ecindex IIDdcotauth1
24024 .ecindex IIDdcotauth2
24027 . ////////////////////////////////////////////////////////////////////////////
24028 . ////////////////////////////////////////////////////////////////////////////
24030 .chapter "The spa authenticator" "CHAPspa"
24031 .scindex IIDspaauth1 "&(spa)& authenticator"
24032 .scindex IIDspaauth2 "authenticators" "&(spa)&"
24033 .cindex "authentication" "Microsoft Secure Password"
24034 .cindex "authentication" "NTLM"
24035 .cindex "Microsoft Secure Password Authentication"
24036 .cindex "NTLM authentication"
24037 The &(spa)& authenticator provides client support for Microsoft's &'Secure
24038 Password Authentication'& mechanism,
24039 which is also sometimes known as NTLM (NT LanMan). The code for client side of
24040 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
24041 taken from the Samba project (&url(http://www.samba.org)). The code for the
24042 server side was subsequently contributed by Tom Kistner. The mechanism works as
24046 After the AUTH command has been accepted, the client sends an SPA
24047 authentication request based on the user name and optional domain.
24049 The server sends back a challenge.
24051 The client builds a challenge response which makes use of the user's password
24052 and sends it to the server, which then accepts or rejects it.
24055 Encryption is used to protect the password in transit.
24059 .section "Using spa as a server" "SECID179"
24060 .cindex "options" "&(spa)& authenticator (server)"
24061 The &(spa)& authenticator has just one server option:
24063 .option server_password spa string&!! unset
24064 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
24065 This option is expanded, and the result must be the cleartext password for the
24066 authenticating user, whose name is at this point in &$auth1$&. For
24067 compatibility with previous releases of Exim, the user name is also placed in
24068 &$1$&. However, the use of this variable for this purpose is now deprecated, as
24069 it can lead to confusion in string expansions that also use numeric variables
24070 for other things. For example:
24075 server_password = \
24076 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
24078 If the expansion is forced to fail, authentication fails. Any other expansion
24079 failure causes a temporary error code to be returned.
24085 .section "Using spa as a client" "SECID180"
24086 .cindex "options" "&(spa)& authenticator (client)"
24087 The &(spa)& authenticator has the following client options:
24091 .option client_domain spa string&!! unset
24092 This option specifies an optional domain for the authentication.
24095 .option client_password spa string&!! unset
24096 This option specifies the user's password, and must be set.
24099 .option client_username spa string&!! unset
24100 This option specifies the user name, and must be set. Here is an example of a
24101 configuration of this authenticator for use with the mail servers at
24107 client_username = msn/msn_username
24108 client_password = msn_plaintext_password
24109 client_domain = DOMAIN_OR_UNSET
24111 .ecindex IIDspaauth1
24112 .ecindex IIDspaauth2
24118 . ////////////////////////////////////////////////////////////////////////////
24119 . ////////////////////////////////////////////////////////////////////////////
24121 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
24122 "Encrypted SMTP connections"
24123 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
24124 .scindex IIDencsmtp2 "SMTP" "encryption"
24125 .cindex "TLS" "on SMTP connection"
24128 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
24129 Sockets Layer), is implemented by making use of the OpenSSL library or the
24130 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
24131 cryptographic code in the Exim distribution itself for implementing TLS. In
24132 order to use this feature you must install OpenSSL or GnuTLS, and then build a
24133 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
24134 You also need to understand the basic concepts of encryption at a managerial
24135 level, and in particular, the way that public keys, private keys, and
24136 certificates are used.
24138 RFC 3207 defines how SMTP connections can make use of encryption. Once a
24139 connection is established, the client issues a STARTTLS command. If the
24140 server accepts this, the client and the server negotiate an encryption
24141 mechanism. If the negotiation succeeds, the data that subsequently passes
24142 between them is encrypted.
24144 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
24145 and if so, what cipher suite is in use, whether the client supplied a
24146 certificate, and whether or not that certificate was verified. This makes it
24147 possible for an Exim server to deny or accept certain commands based on the
24150 &*Warning*&: Certain types of firewall and certain anti-virus products can
24151 disrupt TLS connections. You need to turn off SMTP scanning for these products
24152 in order to get TLS to work.
24156 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
24158 .cindex "ssmtp protocol"
24159 .cindex "smtps protocol"
24160 .cindex "SMTP" "ssmtp protocol"
24161 .cindex "SMTP" "smtps protocol"
24162 Early implementations of encrypted SMTP used a different TCP port from normal
24163 SMTP, and expected an encryption negotiation to start immediately, instead of
24164 waiting for a STARTTLS command from the client using the standard SMTP
24165 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
24166 allocated for this purpose.
24168 This approach was abandoned when encrypted SMTP was standardized, but there are
24169 still some legacy clients that use it. Exim supports these clients by means of
24170 the &%tls_on_connect_ports%& global option. Its value must be a list of port
24171 numbers; the most common use is expected to be:
24173 tls_on_connect_ports = 465
24175 The port numbers specified by this option apply to all SMTP connections, both
24176 via the daemon and via &'inetd'&. You still need to specify all the ports that
24177 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
24178 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
24179 an extra port &-- rather, it specifies different behaviour on a port that is
24182 There is also a &%-tls-on-connect%& command line option. This overrides
24183 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
24190 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
24191 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
24192 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
24193 followed later, when the first versions of GnuTLS were released. To build Exim
24194 to use GnuTLS, you need to set
24198 in Local/Makefile, in addition to
24202 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
24203 include files and libraries for GnuTLS can be found.
24205 There are some differences in usage when using GnuTLS instead of OpenSSL:
24208 The &%tls_verify_certificates%& option must contain the name of a file, not the
24209 name of a directory (for OpenSSL it can be either).
24211 The &%tls_dhparam%& option is ignored, because early versions of GnuTLS had no
24212 facility for varying its Diffie-Hellman parameters. I understand that this has
24213 changed, but Exim has not been updated to provide this facility.
24215 .vindex "&$tls_peerdn$&"
24216 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
24217 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
24218 affects the value of the &$tls_peerdn$& variable.
24220 OpenSSL identifies cipher suites using hyphens as separators, for example:
24221 DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA_ARCFOUR_SHA. What is
24222 more, OpenSSL complains if underscores are present in a cipher list. To make
24223 life simpler, Exim changes underscores to hyphens for OpenSSL and hyphens to
24224 underscores for GnuTLS when processing lists of cipher suites in the
24225 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
24228 The &%tls_require_ciphers%& options operate differently, as described in the
24229 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
24233 .section "GnuTLS parameter computation" "SECID181"
24234 GnuTLS uses D-H parameters that may take a substantial amount of time
24235 to compute. It is unreasonable to re-compute them for every TLS session.
24236 Therefore, Exim keeps this data in a file in its spool directory, called
24237 &_gnutls-params_&. The file is owned by the Exim user and is readable only by
24238 its owner. Every Exim process that start up GnuTLS reads the D-H
24239 parameters from this file. If the file does not exist, the first Exim process
24240 that needs it computes the data and writes it to a temporary file which is
24241 renamed once it is complete. It does not matter if several Exim processes do
24242 this simultaneously (apart from wasting a few resources). Once a file is in
24243 place, new Exim processes immediately start using it.
24245 For maximum security, the parameters that are stored in this file should be
24246 recalculated periodically, the frequency depending on your paranoia level.
24247 Arranging this is easy in principle; just delete the file when you want new
24248 values to be computed. However, there may be a problem. The calculation of new
24249 parameters needs random numbers, and these are obtained from &_/dev/random_&.
24250 If the system is not very active, &_/dev/random_& may delay returning data
24251 until enough randomness (entropy) is available. This may cause Exim to hang for
24252 a substantial amount of time, causing timeouts on incoming connections.
24254 The solution is to generate the parameters externally to Exim. They are stored
24255 in &_gnutls-params_& in PEM format, which means that they can be generated
24256 externally using the &(certtool)& command that is part of GnuTLS.
24258 To replace the parameters with new ones, instead of deleting the file
24259 and letting Exim re-create it, you can generate new parameters using
24260 &(certtool)& and, when this has been done, replace Exim's cache file by
24261 renaming. The relevant commands are something like this:
24265 # chown exim:exim new-params
24266 # chmod 0400 new-params
24267 # certtool --generate-privkey --bits 512 >new-params
24268 # echo "" >>new-params
24269 # certtool --generate-dh-params --bits 1024 >> new-params
24270 # mv new-params gnutls-params
24272 If Exim never has to generate the parameters itself, the possibility of
24273 stalling is removed.
24276 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
24277 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
24278 .oindex "&%tls_require_ciphers%&" "OpenSSL"
24279 There is a function in the OpenSSL library that can be passed a list of cipher
24280 suites before the cipher negotiation takes place. This specifies which ciphers
24281 are acceptable. The list is colon separated and may contain names like
24282 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
24283 directly to this function call. The following quotation from the OpenSSL
24284 documentation specifies what forms of item are allowed in the cipher string:
24287 It can consist of a single cipher suite such as RC4-SHA.
24289 It can represent a list of cipher suites containing a certain algorithm,
24290 or cipher suites of a certain type. For example SHA1 represents all
24291 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
24294 Lists of cipher suites can be combined in a single cipher string using
24295 the + character. This is used as a logical and operation. For example
24296 SHA1+DES represents all cipher suites containing the SHA1 and the DES
24300 Each cipher string can be optionally preceded by one of the characters &`!`&,
24303 If &`!`& is used, the ciphers are permanently deleted from the list. The
24304 ciphers deleted can never reappear in the list even if they are explicitly
24307 If &`-`& is used, the ciphers are deleted from the list, but some or all
24308 of the ciphers can be added again by later options.
24310 If &`+`& is used, the ciphers are moved to the end of the list. This
24311 option does not add any new ciphers; it just moves matching existing ones.
24314 If none of these characters is present, the string is interpreted as
24315 a list of ciphers to be appended to the current preference list. If the list
24316 includes any ciphers already present they will be ignored: that is, they will
24317 not be moved to the end of the list.
24322 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
24324 .cindex "GnuTLS" "specifying parameters for"
24325 .cindex "TLS" "specifying ciphers (GnuTLS)"
24326 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
24327 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
24328 .cindex "TLS" "specifying protocols (GnuTLS)"
24329 .oindex "&%tls_require_ciphers%&" "GnuTLS"
24330 The GnuTLS library allows the caller to specify separate lists of permitted key
24331 exchange methods, main cipher algorithms, MAC algorithms, and protocols.
24332 Unfortunately, these lists are numerical, and the library does not have a
24333 function for turning names into numbers. Consequently, lists of recognized
24334 names have to be built into the application. The permitted key exchange
24335 methods, ciphers, and MAC algorithms may be used in any combination to form a
24336 cipher suite. This is unlike OpenSSL, where complete cipher suite names are
24337 passed to its control function.
24339 For compatibility with OpenSSL, the &%tls_require_ciphers%& option can be set
24340 to complete cipher suite names such as RSA_ARCFOUR_SHA, but for GnuTLS this
24341 option controls only the cipher algorithms. Exim searches each item in the
24342 list for the name of an available algorithm. For example, if the list
24343 contains RSA_AES_SHA, then AES is recognized, and the behaviour is exactly
24344 the same as if just AES were given.
24346 .oindex "&%gnutls_require_kx%&"
24347 .oindex "&%gnutls_require_mac%&"
24348 .oindex "&%gnutls_require_protocols%&"
24349 There are additional options called &%gnutls_require_kx%&,
24350 &%gnutls_require_mac%&, and &%gnutls_require_protocols%& that can be used to
24351 restrict the key exchange methods, MAC algorithms, and protocols, respectively.
24352 These options are ignored if OpenSSL is in use.
24354 All four options are available as global options, controlling how Exim
24355 behaves as a server, and also as options of the &(smtp)& transport, controlling
24356 how Exim behaves as a client. All the values are string expanded. After
24357 expansion, the values must be colon-separated lists, though the separator
24358 can be changed in the usual way.
24360 Each of the four lists starts out with a default set of algorithms. If the
24361 first item in a list does &'not'& start with an exclamation mark, all the
24362 default items are deleted. In this case, only those that are explicitly
24363 specified can be used. If the first item in a list &'does'& start with an
24364 exclamation mark, the defaults are left on the list.
24366 Then, any item that starts with an exclamation mark causes the relevant
24367 entry to be removed from the list, and any item that does not start with an
24368 exclamation mark causes a new entry to be added to the list. Unrecognized
24369 items in the list are ignored. Thus:
24371 tls_require_ciphers = !ARCFOUR
24373 allows all the defaults except ARCFOUR, whereas
24375 tls_require_ciphers = AES : 3DES
24377 allows only cipher suites that use AES or 3DES.
24379 For &%tls_require_ciphers%& the recognized names are AES_256, AES_128, AES
24380 (both of the preceding), 3DES, ARCFOUR_128, ARCFOUR_40, and ARCFOUR (both of
24381 the preceding). The default list does not contain all of these; it just has
24382 AES_256, AES_128, 3DES, and ARCFOUR_128.
24384 For &%gnutls_require_kx%&, the recognized names are DHE_RSA, RSA (which
24385 includes DHE_RSA), DHE_DSS, and DHE (which includes both DHE_RSA and
24386 DHE_DSS). The default list contains RSA, DHE_DSS, DHE_RSA.
24388 For &%gnutls_require_mac%&, the recognized names are SHA (synonym SHA1), and
24389 MD5. The default list contains SHA, MD5.
24391 For &%gnutls_require_protocols%&, the recognized names are TLS1 and SSL3.
24392 The default list contains TLS1, SSL3.
24394 In a server, the order of items in these lists is unimportant. The server
24395 advertises the availability of all the relevant cipher suites. However, in a
24396 client, the order in the &%tls_require_ciphers%& list specifies a preference
24397 order for the cipher algorithms. The first one in the client's list that is
24398 also advertised by the server is tried first. The default order is as listed
24403 .section "Configuring an Exim server to use TLS" "SECID182"
24404 .cindex "TLS" "configuring an Exim server"
24405 When Exim has been built with TLS support, it advertises the availability of
24406 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
24407 but not to any others. The default value of this option is unset, which means
24408 that STARTTLS is not advertised at all. This default is chosen because you
24409 need to set some other options in order to make TLS available, and also it is
24410 sensible for systems that want to use TLS only as a client.
24412 If a client issues a STARTTLS command and there is some configuration
24413 problem in the server, the command is rejected with a 454 error. If the client
24414 persists in trying to issue SMTP commands, all except QUIT are rejected
24417 554 Security failure
24419 If a STARTTLS command is issued within an existing TLS session, it is
24420 rejected with a 554 error code.
24422 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
24423 match some hosts. You can, of course, set it to * to match all hosts.
24424 However, this is not all you need to do. TLS sessions to a server won't work
24425 without some further configuration at the server end.
24427 It is rumoured that all existing clients that support TLS/SSL use RSA
24428 encryption. To make this work you need to set, in the server,
24430 tls_certificate = /some/file/name
24431 tls_privatekey = /some/file/name
24433 These options are, in fact, expanded strings, so you can make them depend on
24434 the identity of the client that is connected if you wish. The first file
24435 contains the server's X509 certificate, and the second contains the private key
24436 that goes with it. These files need to be readable by the Exim user, and must
24437 always be given as full path names. They can be the same file if both the
24438 certificate and the key are contained within it. If &%tls_privatekey%& is not
24439 set, or if its expansion is forced to fail or results in an empty string, this
24440 is assumed to be the case. The certificate file may also contain intermediate
24441 certificates that need to be sent to the client to enable it to authenticate
24442 the server's certificate.
24444 If you do not understand about certificates and keys, please try to find a
24445 source of this background information, which is not Exim-specific. (There are a
24446 few comments below in section &<<SECTcerandall>>&.)
24448 &*Note*&: These options do not apply when Exim is operating as a client &--
24449 they apply only in the case of a server. If you need to use a certificate in an
24450 Exim client, you must set the options of the same names in an &(smtp)&
24453 With just these options, an Exim server will be able to use TLS. It does not
24454 require the client to have a certificate (but see below for how to insist on
24455 this). There is one other option that may be needed in other situations. If
24457 tls_dhparam = /some/file/name
24459 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
24460 with the parameters contained in the file. This increases the set of cipher
24461 suites that the server supports. See the command
24465 for a way of generating this data. At present, &%tls_dhparam%& is used only
24466 when Exim is linked with OpenSSL. It is ignored if GnuTLS is being used.
24468 The strings supplied for these three options are expanded every time a client
24469 host connects. It is therefore possible to use different certificates and keys
24470 for different hosts, if you so wish, by making use of the client's IP address
24471 in &$sender_host_address$& to control the expansion. If a string expansion is
24472 forced to fail, Exim behaves as if the option is not set.
24474 .cindex "cipher" "logging"
24475 .cindex "log" "TLS cipher"
24476 .vindex "&$tls_cipher$&"
24477 The variable &$tls_cipher$& is set to the cipher suite that was negotiated for
24478 an incoming TLS connection. It is included in the &'Received:'& header of an
24479 incoming message (by default &-- you can, of course, change this), and it is
24480 also included in the log line that records a message's arrival, keyed by
24481 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
24482 condition can be used to test for specific cipher suites in ACLs.
24483 (For outgoing SMTP deliveries, &$tls_cipher$& is reset &-- see section
24486 Once TLS has been established, the ACLs that run for subsequent SMTP commands
24487 can check the name of the cipher suite and vary their actions accordingly. The
24488 cipher suite names vary, depending on which TLS library is being used. For
24489 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
24490 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
24491 documentation for more details.
24494 .section "Requesting and verifying client certificates" "SECID183"
24495 .cindex "certificate" "verification of client"
24496 .cindex "TLS" "client certificate verification"
24497 If you want an Exim server to request a certificate when negotiating a TLS
24498 session with a client, you must set either &%tls_verify_hosts%& or
24499 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
24500 apply to all TLS connections. For any host that matches one of these options,
24501 Exim requests a certificate as part of the setup of the TLS session. The
24502 contents of the certificate are verified by comparing it with a list of
24503 expected certificates. These must be available in a file or,
24504 for OpenSSL only (not GnuTLS), a directory, identified by
24505 &%tls_verify_certificates%&.
24507 A file can contain multiple certificates, concatenated end to end. If a
24510 each certificate must be in a separate file, with a name (or a symbolic link)
24511 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
24512 certificate. You can compute the relevant hash by running the command
24514 openssl x509 -hash -noout -in /cert/file
24516 where &_/cert/file_& contains a single certificate.
24518 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
24519 what happens if the client does not supply a certificate, or if the certificate
24520 does not match any of the certificates in the collection named by
24521 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
24522 attempt to set up a TLS session is aborted, and the incoming connection is
24523 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
24524 session continues. ACLs that run for subsequent SMTP commands can detect the
24525 fact that no certificate was verified, and vary their actions accordingly. For
24526 example, you can insist on a certificate before accepting a message for
24527 relaying, but not when the message is destined for local delivery.
24529 .vindex "&$tls_peerdn$&"
24530 When a client supplies a certificate (whether it verifies or not), the value of
24531 the Distinguished Name of the certificate is made available in the variable
24532 &$tls_peerdn$& during subsequent processing of the message.
24534 .cindex "log" "distinguished name"
24535 Because it is often a long text string, it is not included in the log line or
24536 &'Received:'& header by default. You can arrange for it to be logged, keyed by
24537 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
24538 &%received_header_text%& to change the &'Received:'& header. When no
24539 certificate is supplied, &$tls_peerdn$& is empty.
24542 .section "Revoked certificates" "SECID184"
24543 .cindex "TLS" "revoked certificates"
24544 .cindex "revocation list"
24545 .cindex "certificate" "revocation list"
24546 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
24547 certificates are revoked. If you have such a list, you can pass it to an Exim
24548 server using the global option called &%tls_crl%& and to an Exim client using
24549 an identically named option for the &(smtp)& transport. In each case, the value
24550 of the option is expanded and must then be the name of a file that contains a
24554 .section "Configuring an Exim client to use TLS" "SECID185"
24555 .cindex "cipher" "logging"
24556 .cindex "log" "TLS cipher"
24557 .cindex "log" "distinguished name"
24558 .cindex "TLS" "configuring an Exim client"
24559 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
24560 deliveries as well as to incoming, the latter one causing logging of the
24561 server certificate's DN. The remaining client configuration for TLS is all
24562 within the &(smtp)& transport.
24564 It is not necessary to set any options to have TLS work in the &(smtp)&
24565 transport. If Exim is built with TLS support, and TLS is advertised by a
24566 server, the &(smtp)& transport always tries to start a TLS session. However,
24567 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
24568 transport) to a list of server hosts for which TLS should not be used.
24570 If you do not want Exim to attempt to send messages unencrypted when an attempt
24571 to set up an encrypted connection fails in any way, you can set
24572 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
24573 those hosts, delivery is always deferred if an encrypted connection cannot be
24574 set up. If there are any other hosts for the address, they are tried in the
24577 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
24578 the message unencrypted. It always does this if the response to STARTTLS is
24579 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
24580 session after a success response code, what happens is controlled by the
24581 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
24582 delivery to this host is deferred, and other hosts (if available) are tried. If
24583 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
24584 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
24585 negotiation fails, Exim closes the current connection (because it is in an
24586 unknown state), opens a new one to the same host, and then tries the delivery
24589 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
24590 transport provide the client with a certificate, which is passed to the server
24591 if it requests it. If the server is Exim, it will request a certificate only if
24592 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
24594 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
24595 must name a file or,
24596 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
24597 expected server certificates. The client verifies the server's certificate
24598 against this collection, taking into account any revoked certificates that are
24599 in the list defined by &%tls_crl%&.
24602 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
24603 list of permitted cipher suites. If either of these checks fails, delivery to
24604 the current host is abandoned, and the &(smtp)& transport tries to deliver to
24605 alternative hosts, if any.
24608 These options must be set in the &(smtp)& transport for Exim to use TLS when it
24609 is operating as a client. Exim does not assume that a server certificate (set
24610 by the global options of the same name) should also be used when operating as a
24614 .vindex "&$host_address$&"
24615 All the TLS options in the &(smtp)& transport are expanded before use, with
24616 &$host$& and &$host_address$& containing the name and address of the server to
24617 which the client is connected. Forced failure of an expansion causes Exim to
24618 behave as if the relevant option were unset.
24620 .vindex &$tls_cipher$&
24621 .vindex &$tls_peerdn$&
24622 Before an SMTP connection is established, the &$tls_cipher$& and &$tls_peerdn$&
24623 variables are emptied. (Until the first connection, they contain the values
24624 that were set when the message was received.) If STARTTLS is subsequently
24625 successfully obeyed, these variables are set to the relevant values for the
24626 outgoing connection.
24630 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
24632 .cindex "multiple SMTP deliveries with TLS"
24633 .cindex "TLS" "multiple message deliveries"
24634 Exim sends multiple messages down the same TCP/IP connection by starting up
24635 an entirely new delivery process for each message, passing the socket from
24636 one process to the next. This implementation does not fit well with the use
24637 of TLS, because there is quite a lot of state information associated with a TLS
24638 connection, not just a socket identification. Passing all the state information
24639 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
24640 session before passing the socket to a new process. The new process may then
24641 try to start a new TLS session, and if successful, may try to re-authenticate
24642 if AUTH is in use, before sending the next message.
24644 The RFC is not clear as to whether or not an SMTP session continues in clear
24645 after TLS has been shut down, or whether TLS may be restarted again later, as
24646 just described. However, if the server is Exim, this shutdown and
24647 reinitialization works. It is not known which (if any) other servers operate
24648 successfully if the client closes a TLS session and continues with unencrypted
24649 SMTP, but there are certainly some that do not work. For such servers, Exim
24650 should not pass the socket to another process, because the failure of the
24651 subsequent attempt to use it would cause Exim to record a temporary host error,
24652 and delay other deliveries to that host.
24654 To test for this case, Exim sends an EHLO command to the server after
24655 closing down the TLS session. If this fails in any way, the connection is
24656 closed instead of being passed to a new delivery process, but no retry
24657 information is recorded.
24659 There is also a manual override; you can set &%hosts_nopass_tls%& on the
24660 &(smtp)& transport to match those hosts for which Exim should not pass
24661 connections to new processes if TLS has been used.
24666 .section "Certificates and all that" "SECTcerandall"
24667 .cindex "certificate" "references to discussion"
24668 In order to understand fully how TLS works, you need to know about
24669 certificates, certificate signing, and certificate authorities. This is not the
24670 place to give a tutorial, especially as I do not know very much about it
24671 myself. Some helpful introduction can be found in the FAQ for the SSL addition
24672 to Apache, currently at
24674 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
24676 Other parts of the &'modssl'& documentation are also helpful, and have
24677 links to further files.
24678 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
24679 0-201-61598-3), contains both introductory and more in-depth descriptions.
24680 Some sample programs taken from the book are available from
24682 &url(http://www.rtfm.com/openssl-examples/)
24686 .section "Certificate chains" "SECID186"
24687 The file named by &%tls_certificate%& may contain more than one
24688 certificate. This is useful in the case where the certificate that is being
24689 sent is validated by an intermediate certificate which the other end does
24690 not have. Multiple certificates must be in the correct order in the file.
24691 First the host's certificate itself, then the first intermediate
24692 certificate to validate the issuer of the host certificate, then the next
24693 intermediate certificate to validate the issuer of the first intermediate
24694 certificate, and so on, until finally (optionally) the root certificate.
24695 The root certificate must already be trusted by the recipient for
24696 validation to succeed, of course, but if it's not preinstalled, sending the
24697 root certificate along with the rest makes it available for the user to
24698 install if the receiving end is a client MUA that can interact with a user.
24701 .section "Self-signed certificates" "SECID187"
24702 .cindex "certificate" "self-signed"
24703 You can create a self-signed certificate using the &'req'& command provided
24704 with OpenSSL, like this:
24706 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
24709 &_file1_& and &_file2_& can be the same file; the key and the certificate are
24710 delimited and so can be identified independently. The &%-days%& option
24711 specifies a period for which the certificate is valid. The &%-nodes%& option is
24712 important: if you do not set it, the key is encrypted with a passphrase
24713 that you are prompted for, and any use that is made of the key causes more
24714 prompting for the passphrase. This is not helpful if you are going to use
24715 this certificate and key in an MTA, where prompting is not possible.
24717 A self-signed certificate made in this way is sufficient for testing, and
24718 may be adequate for all your requirements if you are mainly interested in
24719 encrypting transfers, and not in secure identification.
24721 However, many clients require that the certificate presented by the server be a
24722 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
24723 certificate. In this situation, the self-signed certificate described above
24724 must be installed on the client host as a trusted root &'certification
24725 authority'& (CA), and the certificate used by Exim must be a user certificate
24726 signed with that self-signed certificate.
24728 For information on creating self-signed CA certificates and using them to sign
24729 user certificates, see the &'General implementation overview'& chapter of the
24730 Open-source PKI book, available online at
24731 &url(http://ospkibook.sourceforge.net/).
24732 .ecindex IIDencsmtp1
24733 .ecindex IIDencsmtp2
24737 . ////////////////////////////////////////////////////////////////////////////
24738 . ////////////////////////////////////////////////////////////////////////////
24740 .chapter "Access control lists" "CHAPACL"
24741 .scindex IIDacl "&ACL;" "description"
24742 .cindex "control of incoming mail"
24743 .cindex "message" "controlling incoming"
24744 .cindex "policy control" "access control lists"
24745 Access Control Lists (ACLs) are defined in a separate section of the run time
24746 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
24747 name, terminated by a colon. Here is a complete ACL section that contains just
24748 one very small ACL:
24752 accept hosts = one.host.only
24754 You can have as many lists as you like in the ACL section, and the order in
24755 which they appear does not matter. The lists are self-terminating.
24757 The majority of ACLs are used to control Exim's behaviour when it receives
24758 certain SMTP commands. This applies both to incoming TCP/IP connections, and
24759 when a local process submits a message using SMTP by specifying the &%-bs%&
24760 option. The most common use is for controlling which recipients are accepted
24761 in incoming messages. In addition, you can define an ACL that is used to check
24762 local non-SMTP messages. The default configuration file contains an example of
24763 a realistic ACL for checking RCPT commands. This is discussed in chapter
24764 &<<CHAPdefconfil>>&.
24767 .section "Testing ACLs" "SECID188"
24768 The &%-bh%& command line option provides a way of testing your ACL
24769 configuration locally by running a fake SMTP session with which you interact.
24770 The host &'relay-test.mail-abuse.org'& provides a service for checking your
24771 relaying configuration (see section &<<SECTcheralcon>>& for more details).
24775 .section "Specifying when ACLs are used" "SECID189"
24776 .cindex "&ACL;" "options for specifying"
24777 In order to cause an ACL to be used, you have to name it in one of the relevant
24778 options in the main part of the configuration. These options are:
24779 .cindex "AUTH" "ACL for"
24780 .cindex "DATA" "ACLs for"
24781 .cindex "ETRN" "ACL for"
24782 .cindex "EXPN" "ACL for"
24783 .cindex "HELO" "ACL for"
24784 .cindex "EHLO" "ACL for"
24785 .cindex "MAIL" "ACL for"
24786 .cindex "QUIT, ACL for"
24787 .cindex "RCPT" "ACL for"
24788 .cindex "STARTTLS, ACL for"
24789 .cindex "VRFY" "ACL for"
24790 .cindex "SMTP" "connection, ACL for"
24791 .cindex "non-SMTP messages" "ACLs for"
24792 .cindex "MIME content scanning" "ACL for"
24795 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
24796 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
24797 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
24798 .irow &%acl_smtp_auth%& "ACL for AUTH"
24799 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
24800 .irow &%acl_smtp_data%& "ACL after DATA is complete"
24801 .irow &%acl_smtp_etrn%& "ACL for ETRN"
24802 .irow &%acl_smtp_expn%& "ACL for EXPN"
24803 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
24804 .irow &%acl_smtp_mail%& "ACL for MAIL"
24805 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
24806 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
24807 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
24808 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
24809 .irow &%acl_smtp_quit%& "ACL for QUIT"
24810 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
24811 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
24812 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
24815 For example, if you set
24817 acl_smtp_rcpt = small_acl
24819 the little ACL defined above is used whenever Exim receives a RCPT command
24820 in an SMTP dialogue. The majority of policy tests on incoming messages can be
24821 done when RCPT commands arrive. A rejection of RCPT should cause the
24822 sending MTA to give up on the recipient address contained in the RCPT
24823 command, whereas rejection at other times may cause the client MTA to keep on
24824 trying to deliver the message. It is therefore recommended that you do as much
24825 testing as possible at RCPT time.
24828 .section "The non-SMTP ACLs" "SECID190"
24829 .cindex "non-SMTP messages" "ACLs for"
24830 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
24831 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
24832 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
24833 the state of the SMTP connection such as encryption and authentication) are not
24834 relevant and are forbidden in these ACLs. However, the sender and recipients
24835 are known, so the &%senders%& and &%sender_domains%& conditions and the
24836 &$sender_address$& and &$recipients$& variables can be used. Variables such as
24837 &$authenticated_sender$& are also available. You can specify added header lines
24838 in any of these ACLs.
24840 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
24841 non-SMTP message, before any of the message has been read. (This is the
24842 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
24843 batched SMTP input, it runs after the DATA command has been reached. The
24844 result of this ACL is ignored; it cannot be used to reject a message. If you
24845 really need to, you could set a value in an ACL variable here and reject based
24846 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
24847 controls, and in particular, it can be used to set
24849 control = suppress_local_fixups
24851 This cannot be used in the other non-SMTP ACLs because by the time they are
24852 run, it is too late.
24854 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
24855 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
24857 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
24858 kind of rejection is treated as permanent, because there is no way of sending a
24859 temporary error for these kinds of message.
24862 .section "The SMTP connect ACL" "SECID191"
24863 .cindex "SMTP" "connection, ACL for"
24864 .oindex &%smtp_banner%&
24865 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
24866 session, after the test specified by &%host_reject_connection%& (which is now
24867 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
24868 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
24869 the message override the banner message that is otherwise specified by the
24870 &%smtp_banner%& option.
24873 .section "The EHLO/HELO ACL" "SECID192"
24874 .cindex "EHLO" "ACL for"
24875 .cindex "HELO" "ACL for"
24876 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
24877 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
24878 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
24879 Note that a client may issue more than one EHLO or HELO command in an SMTP
24880 session, and indeed is required to issue a new EHLO or HELO after successfully
24881 setting up encryption following a STARTTLS command.
24883 If the command is accepted by an &%accept%& verb that has a &%message%&
24884 modifier, the message may not contain more than one line (it will be truncated
24885 at the first newline and a panic logged if it does). Such a message cannot
24886 affect the EHLO options that are listed on the second and subsequent lines of
24890 .section "The DATA ACLs" "SECID193"
24891 .cindex "DATA" "ACLs for"
24892 Two ACLs are associated with the DATA command, because it is two-stage
24893 command, with two responses being sent to the client.
24894 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
24895 is obeyed. This gives you control after all the RCPT commands, but before
24896 the message itself is received. It offers the opportunity to give a negative
24897 response to the DATA command before the data is transmitted. Header lines
24898 added by MAIL or RCPT ACLs are not visible at this time, but any that
24899 are defined here are visible when the &%acl_smtp_data%& ACL is run.
24901 You cannot test the contents of the message, for example, to verify addresses
24902 in the headers, at RCPT time or when the DATA command is received. Such
24903 tests have to appear in the ACL that is run after the message itself has been
24904 received, before the final response to the DATA command is sent. This is
24905 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
24906 associated with the DATA command.
24908 For both of these ACLs, it is not possible to reject individual recipients. An
24909 error response rejects the entire message. Unfortunately, it is known that some
24910 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
24911 before or after the data) correctly &-- they keep the message on their queues
24912 and try again later, but that is their problem, though it does waste some of
24916 .section "The SMTP MIME ACL" "SECID194"
24917 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
24918 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
24921 .section "The QUIT ACL" "SECTQUITACL"
24922 .cindex "QUIT, ACL for"
24923 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
24924 does not affect the response code to QUIT, which is always 221. Thus, the ACL
24925 does not in fact control any access. For this reason, the only verbs that are
24926 permitted are &%accept%& and &%warn%&.
24928 This ACL can be used for tasks such as custom logging at the end of an SMTP
24929 session. For example, you can use ACL variables in other ACLs to count
24930 messages, recipients, etc., and log the totals at QUIT time using one or
24931 more &%logwrite%& modifiers on a &%warn%& verb.
24933 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
24934 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
24936 You do not need to have a final &%accept%&, but if you do, you can use a
24937 &%message%& modifier to specify custom text that is sent as part of the 221
24940 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
24941 failure (for example, failure to open a log file, or when Exim is bombing out
24942 because it has detected an unrecoverable error), all SMTP commands from the
24943 client are given temporary error responses until QUIT is received or the
24944 connection is closed. In these special cases, the QUIT ACL does not run.
24947 .section "The not-QUIT ACL" "SECTNOTQUITACL"
24948 .vindex &$acl_smtp_notquit$&
24949 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
24950 an SMTP session ends without sending QUIT. However, when Exim itself is is bad
24951 trouble, such as being unable to write to its log files, this ACL is not run,
24952 because it might try to do things (such as write to log files) that make the
24953 situation even worse.
24955 Like the QUIT ACL, this ACL is provided to make it possible to do customized
24956 logging or to gather statistics, and its outcome is ignored. The &%delay%&
24957 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
24960 .vindex &$smtp_notquit_reason$&
24961 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
24962 to a string that indicates the reason for the termination of the SMTP
24963 connection. The possible values are:
24965 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
24966 .irow &`bad-commands`& "Too many unknown or non-mail commands"
24967 .irow &`command-timeout`& "Timeout while reading SMTP commands"
24968 .irow &`connection-lost`& "The SMTP connection has been lost"
24969 .irow &`data-timeout`& "Timeout while reading message data"
24970 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
24971 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
24972 .irow &`signal-exit`& "SIGTERM or SIGINT"
24973 .irow &`synchronization-error`& "SMTP synchronization error"
24974 .irow &`tls-failed`& "TLS failed to start"
24976 In most cases when an SMTP connection is closed without having received QUIT,
24977 Exim sends an SMTP response message before actually closing the connection.
24978 With the exception of the &`acl-drop`& case, the default message can be
24979 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
24980 &%drop%& verb in another ACL, it is the message from the other ACL that is
24984 .section "Finding an ACL to use" "SECID195"
24985 .cindex "&ACL;" "finding which to use"
24986 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
24987 you can use different ACLs in different circumstances. For example,
24989 acl_smtp_rcpt = ${if ={25}{$interface_port} \
24990 {acl_check_rcpt} {acl_check_rcpt_submit} }
24992 In the default configuration file there are some example settings for
24993 providing an RFC 4409 message submission service on port 587 and a
24994 non-standard &"smtps"& service on port 465. You can use a string
24995 expansion like this to choose an ACL for MUAs on these ports which is
24996 more appropriate for this purpose than the default ACL on port 25.
24998 The expanded string does not have to be the name of an ACL in the
24999 configuration file; there are other possibilities. Having expanded the
25000 string, Exim searches for an ACL as follows:
25003 If the string begins with a slash, Exim uses it as a file name, and reads its
25004 contents as an ACL. The lines are processed in the same way as lines in the
25005 Exim configuration file. In particular, continuation lines are supported, blank
25006 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
25007 If the file does not exist or cannot be read, an error occurs (typically
25008 causing a temporary failure of whatever caused the ACL to be run). For example:
25010 acl_smtp_data = /etc/acls/\
25011 ${lookup{$sender_host_address}lsearch\
25012 {/etc/acllist}{$value}{default}}
25014 This looks up an ACL file to use on the basis of the host's IP address, falling
25015 back to a default if the lookup fails. If an ACL is successfully read from a
25016 file, it is retained in memory for the duration of the Exim process, so that it
25017 can be re-used without having to re-read the file.
25019 If the string does not start with a slash, and does not contain any spaces,
25020 Exim searches the ACL section of the configuration for an ACL whose name
25021 matches the string.
25023 If no named ACL is found, or if the string contains spaces, Exim parses
25024 the string as an inline ACL. This can save typing in cases where you just
25025 want to have something like
25027 acl_smtp_vrfy = accept
25029 in order to allow free use of the VRFY command. Such a string may contain
25030 newlines; it is processed in the same way as an ACL that is read from a file.
25036 .section "ACL return codes" "SECID196"
25037 .cindex "&ACL;" "return codes"
25038 Except for the QUIT ACL, which does not affect the SMTP return code (see
25039 section &<<SECTQUITACL>>& above), the result of running an ACL is either
25040 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
25041 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
25042 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
25043 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
25044 This also causes a 4&'xx'& return code.
25046 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
25047 &"deny"&, because there is no mechanism for passing temporary errors to the
25048 submitters of non-SMTP messages.
25051 ACLs that are relevant to message reception may also return &"discard"&. This
25052 has the effect of &"accept"&, but causes either the entire message or an
25053 individual recipient address to be discarded. In other words, it is a
25054 blackholing facility. Use it with care.
25056 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
25057 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
25058 RCPT ACL is to discard just the one recipient address. If there are no
25059 recipients left when the message's data is received, the DATA ACL is not
25060 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
25061 remaining recipients. The &"discard"& return is not permitted for the
25062 &%acl_smtp_predata%& ACL.
25065 .cindex "&[local_scan()]& function" "when all recipients discarded"
25066 The &[local_scan()]& function is always run, even if there are no remaining
25067 recipients; it may create new recipients.
25071 .section "Unset ACL options" "SECID197"
25072 .cindex "&ACL;" "unset options"
25073 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
25074 all the same. &*Note*&: These defaults apply only when the relevant ACL is
25075 not defined at all. For any defined ACL, the default action when control
25076 reaches the end of the ACL statements is &"deny"&.
25078 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
25079 these two are ACLs that are used only for their side effects. They cannot be
25080 used to accept or reject anything.
25082 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
25083 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
25084 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
25085 when the ACL is not defined is &"accept"&.
25087 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
25088 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
25089 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
25090 messages over an SMTP connection. For an example, see the ACL in the default
25091 configuration file.
25096 .section "Data for message ACLs" "SECID198"
25097 .cindex "&ACL;" "data for message ACL"
25099 .vindex &$local_part$&
25100 .vindex &$sender_address$&
25101 .vindex &$sender_host_address$&
25102 .vindex &$smtp_command$&
25103 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
25104 that contain information about the host and the message's sender (for example,
25105 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
25106 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
25107 &$local_part$& are set from the argument address. The entire SMTP command
25108 is available in &$smtp_command$&.
25110 When an ACL for the AUTH parameter of MAIL is running, the variables that
25111 contain information about the host are set, but &$sender_address$& is not yet
25112 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
25115 .vindex "&$message_size$&"
25116 The &$message_size$& variable is set to the value of the SIZE parameter on
25117 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
25118 that parameter is not given. The value is updated to the true message size by
25119 the time the final DATA ACL is run (after the message data has been
25122 .vindex "&$rcpt_count$&"
25123 .vindex "&$recipients_count$&"
25124 The &$rcpt_count$& variable increases by one for each RCPT command received.
25125 The &$recipients_count$& variable increases by one each time a RCPT command is
25126 accepted, so while an ACL for RCPT is being processed, it contains the number
25127 of previously accepted recipients. At DATA time (for both the DATA ACLs),
25128 &$rcpt_count$& contains the total number of RCPT commands, and
25129 &$recipients_count$& contains the total number of accepted recipients.
25135 .section "Data for non-message ACLs" "SECTdatfornon"
25136 .cindex "&ACL;" "data for non-message ACL"
25137 .vindex &$smtp_command_argument$&
25138 .vindex &$smtp_command$&
25139 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
25140 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
25141 and the entire SMTP command is available in &$smtp_command$&.
25142 These variables can be tested using a &%condition%& condition. For example,
25143 here is an ACL for use with AUTH, which insists that either the session is
25144 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
25145 does not permit authentication methods that use cleartext passwords on
25146 unencrypted connections.
25149 accept encrypted = *
25150 accept condition = ${if eq{${uc:$smtp_command_argument}}\
25152 deny message = TLS encryption or CRAM-MD5 required
25154 (Another way of applying this restriction is to arrange for the authenticators
25155 that use cleartext passwords not to be advertised when the connection is not
25156 encrypted. You can use the generic &%server_advertise_condition%& authenticator
25157 option to do this.)
25161 .section "Format of an ACL" "SECID199"
25162 .cindex "&ACL;" "format of"
25163 .cindex "&ACL;" "verbs, definition of"
25164 An individual ACL consists of a number of statements. Each statement starts
25165 with a verb, optionally followed by a number of conditions and &"modifiers"&.
25166 Modifiers can change the way the verb operates, define error and log messages,
25167 set variables, insert delays, and vary the processing of accepted messages.
25169 If all the conditions are met, the verb is obeyed. The same condition may be
25170 used (with different arguments) more than once in the same statement. This
25171 provides a means of specifying an &"and"& conjunction between conditions. For
25174 deny dnslists = list1.example
25175 dnslists = list2.example
25177 If there are no conditions, the verb is always obeyed. Exim stops evaluating
25178 the conditions and modifiers when it reaches a condition that fails. What
25179 happens then depends on the verb (and in one case, on a special modifier). Not
25180 all the conditions make sense at every testing point. For example, you cannot
25181 test a sender address in the ACL that is run for a VRFY command.
25184 .section "ACL verbs" "SECID200"
25185 The ACL verbs are as follows:
25188 .cindex "&%accept%& ACL verb"
25189 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
25190 of the conditions are not met, what happens depends on whether &%endpass%&
25191 appears among the conditions (for syntax see below). If the failing condition
25192 is before &%endpass%&, control is passed to the next ACL statement; if it is
25193 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
25194 check a RCPT command:
25196 accept domains = +local_domains
25200 If the recipient domain does not match the &%domains%& condition, control
25201 passes to the next statement. If it does match, the recipient is verified, and
25202 the command is accepted if verification succeeds. However, if verification
25203 fails, the ACL yields &"deny"&, because the failing condition is after
25206 The &%endpass%& feature has turned out to be confusing to many people, so its
25207 use is not recommended nowadays. It is always possible to rewrite an ACL so
25208 that &%endpass%& is not needed, and it is no longer used in the default
25211 .cindex "&%message%& ACL modifier" "with &%accept%&"
25212 If a &%message%& modifier appears on an &%accept%& statement, its action
25213 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
25214 (when an &%accept%& verb either accepts or passes control to the next
25215 statement), &%message%& can be used to vary the message that is sent when an
25216 SMTP command is accepted. For example, in a RCPT ACL you could have:
25218 &`accept `&<&'some conditions'&>
25219 &` message = OK, I will allow you through today`&
25221 You can specify an SMTP response code, optionally followed by an &"extended
25222 response code"& at the start of the message, but the first digit must be the
25223 same as would be sent by default, which is 2 for an &%accept%& verb.
25225 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
25226 an error message that is used when access is denied. This behaviour is retained
25227 for backward compatibility, but current &"best practice"& is to avoid the use
25232 .cindex "&%defer%& ACL verb"
25233 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
25234 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
25235 &%defer%& is the same as &%deny%&, because there is no way of sending a
25236 temporary error. For a RCPT command, &%defer%& is much the same as using a
25237 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
25238 be used in any ACL, and even for a recipient it might be a simpler approach.
25242 .cindex "&%deny%& ACL verb"
25243 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
25244 the conditions are not met, control is passed to the next ACL statement. For
25247 deny dnslists = blackholes.mail-abuse.org
25249 rejects commands from hosts that are on a DNS black list.
25253 .cindex "&%discard%& ACL verb"
25254 &%discard%&: This verb behaves like &%accept%&, except that it returns
25255 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
25256 that are concerned with receiving messages. When all the conditions are true,
25257 the sending entity receives a &"success"& response. However, &%discard%& causes
25258 recipients to be discarded. If it is used in an ACL for RCPT, just the one
25259 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
25260 message's recipients are discarded. Recipients that are discarded before DATA
25261 do not appear in the log line when the &%received_recipients%& log selector is set.
25263 If the &%log_message%& modifier is set when &%discard%& operates,
25264 its contents are added to the line that is automatically written to the log.
25265 The &%message%& modifier operates exactly as it does for &%accept%&.
25269 .cindex "&%drop%& ACL verb"
25270 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
25271 forcibly closed after the 5&'xx'& error message has been sent. For example:
25273 drop message = I don't take more than 20 RCPTs
25274 condition = ${if > {$rcpt_count}{20}}
25276 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
25277 The connection is always dropped after sending a 550 response.
25280 .cindex "&%require%& ACL verb"
25281 &%require%&: If all the conditions are met, control is passed to the next ACL
25282 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
25283 example, when checking a RCPT command,
25285 require message = Sender did not verify
25288 passes control to subsequent statements only if the message's sender can be
25289 verified. Otherwise, it rejects the command. Note the positioning of the
25290 &%message%& modifier, before the &%verify%& condition. The reason for this is
25291 discussed in section &<<SECTcondmodproc>>&.
25294 .cindex "&%warn%& ACL verb"
25295 &%warn%&: If all the conditions are true, a line specified by the
25296 &%log_message%& modifier is written to Exim's main log. Control always passes
25297 to the next ACL statement. If any condition is false, the log line is not
25298 written. If an identical log line is requested several times in the same
25299 message, only one copy is actually written to the log. If you want to force
25300 duplicates to be written, use the &%logwrite%& modifier instead.
25302 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
25303 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
25304 &%logwrite%&, and &%add_header%&) that appear before the first failing
25305 condition. There is more about adding header lines in section
25306 &<<SECTaddheadacl>>&.
25308 If any condition on a &%warn%& statement cannot be completed (that is, there is
25309 some sort of defer), the log line specified by &%log_message%& is not written.
25310 This does not include the case of a forced failure from a lookup, which
25311 is considered to be a successful completion. After a defer, no further
25312 conditions or modifiers in the &%warn%& statement are processed. The incident
25313 is logged, and the ACL continues to be processed, from the next statement
25317 .vindex "&$acl_verify_message$&"
25318 When one of the &%warn%& conditions is an address verification that fails, the
25319 text of the verification failure message is in &$acl_verify_message$&. If you
25320 want this logged, you must set it up explicitly. For example:
25322 warn !verify = sender
25323 log_message = sender verify failed: $acl_verify_message
25327 At the end of each ACL there is an implicit unconditional &%deny%&.
25329 As you can see from the examples above, the conditions and modifiers are
25330 written one to a line, with the first one on the same line as the verb, and
25331 subsequent ones on following lines. If you have a very long condition, you can
25332 continue it onto several physical lines by the usual backslash continuation
25333 mechanism. It is conventional to align the conditions vertically.
25337 .section "ACL variables" "SECTaclvariables"
25338 .cindex "&ACL;" "variables"
25339 There are some special variables that can be set during ACL processing. They
25340 can be used to pass information between different ACLs, different invocations
25341 of the same ACL in the same SMTP connection, and between ACLs and the routers,
25342 transports, and filters that are used to deliver a message. The names of these
25343 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
25344 an underscore, but the remainder of the name can be any sequence of
25345 alphanumeric characters and underscores that you choose. There is no limit on
25346 the number of ACL variables. The two sets act as follows:
25348 The values of those variables whose names begin with &$acl_c$& persist
25349 throughout an SMTP connection. They are never reset. Thus, a value that is set
25350 while receiving one message is still available when receiving the next message
25351 on the same SMTP connection.
25353 The values of those variables whose names begin with &$acl_m$& persist only
25354 while a message is being received. They are reset afterwards. They are also
25355 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
25358 When a message is accepted, the current values of all the ACL variables are
25359 preserved with the message and are subsequently made available at delivery
25360 time. The ACL variables are set by a modifier called &%set%&. For example:
25362 accept hosts = whatever
25363 set acl_m4 = some value
25364 accept authenticated = *
25365 set acl_c_auth = yes
25367 &*Note*&: A leading dollar sign is not used when naming a variable that is to
25368 be set. If you want to set a variable without taking any action, you can use a
25369 &%warn%& verb without any other modifiers or conditions.
25371 .oindex &%strict_acl_vars%&
25372 What happens if a syntactically valid but undefined ACL variable is
25373 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
25374 false (the default), an empty string is substituted; if it is true, an
25375 error is generated.
25377 Versions of Exim before 4.64 have a limited set of numbered variables, but
25378 their names are compatible, so there is no problem with upgrading.
25381 .section "Condition and modifier processing" "SECTcondmodproc"
25382 .cindex "&ACL;" "conditions; processing"
25383 .cindex "&ACL;" "modifiers; processing"
25384 An exclamation mark preceding a condition negates its result. For example:
25386 deny domains = *.dom.example
25387 !verify = recipient
25389 causes the ACL to return &"deny"& if the recipient domain ends in
25390 &'dom.example'& and the recipient address cannot be verified. Sometimes
25391 negation can be used on the right-hand side of a condition. For example, these
25392 two statements are equivalent:
25394 deny hosts = !192.168.3.4
25395 deny !hosts = 192.168.3.4
25397 However, for many conditions (&%verify%& being a good example), only left-hand
25398 side negation of the whole condition is possible.
25400 The arguments of conditions and modifiers are expanded. A forced failure
25401 of an expansion causes a condition to be ignored, that is, it behaves as if the
25402 condition is true. Consider these two statements:
25404 accept senders = ${lookup{$host_name}lsearch\
25405 {/some/file}{$value}fail}
25406 accept senders = ${lookup{$host_name}lsearch\
25407 {/some/file}{$value}{}}
25409 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
25410 the returned list is searched, but if the lookup fails the behaviour is
25411 different in the two cases. The &%fail%& in the first statement causes the
25412 condition to be ignored, leaving no further conditions. The &%accept%& verb
25413 therefore succeeds. The second statement, however, generates an empty list when
25414 the lookup fails. No sender can match an empty list, so the condition fails,
25415 and therefore the &%accept%& also fails.
25417 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
25418 specify actions that are taken as the conditions for a statement are checked;
25419 others specify text for messages that are used when access is denied or a
25420 warning is generated. The &%control%& modifier affects the way an incoming
25421 message is handled.
25423 The positioning of the modifiers in an ACL statement important, because the
25424 processing of a verb ceases as soon as its outcome is known. Only those
25425 modifiers that have already been encountered will take effect. For example,
25426 consider this use of the &%message%& modifier:
25428 require message = Can't verify sender
25430 message = Can't verify recipient
25432 message = This message cannot be used
25434 If sender verification fails, Exim knows that the result of the statement is
25435 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
25436 so its text is used as the error message. If sender verification succeeds, but
25437 recipient verification fails, the second message is used. If recipient
25438 verification succeeds, the third message becomes &"current"&, but is never used
25439 because there are no more conditions to cause failure.
25441 For the &%deny%& verb, on the other hand, it is always the last &%message%&
25442 modifier that is used, because all the conditions must be true for rejection to
25443 happen. Specifying more than one &%message%& modifier does not make sense, and
25444 the message can even be specified after all the conditions. For example:
25447 !senders = *@my.domain.example
25448 message = Invalid sender from client host
25450 The &"deny"& result does not happen until the end of the statement is reached,
25451 by which time Exim has set up the message.
25455 .section "ACL modifiers" "SECTACLmodi"
25456 .cindex "&ACL;" "modifiers; list of"
25457 The ACL modifiers are as follows:
25460 .vitem &*add_header*&&~=&~<&'text'&>
25461 This modifier specifies one or more header lines that are to be added to an
25462 incoming message, assuming, of course, that the message is ultimately
25463 accepted. For details, see section &<<SECTaddheadacl>>&.
25465 .vitem &*continue*&&~=&~<&'text'&>
25466 .cindex "&%continue%& ACL modifier"
25467 .cindex "database" "updating in ACL"
25468 This modifier does nothing of itself, and processing of the ACL always
25469 continues with the next condition or modifier. The value of &%continue%& is in
25470 the side effects of expanding its argument. Typically this could be used to
25471 update a database. It is really just a syntactic tidiness, to avoid having to
25472 write rather ugly lines like this:
25474 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
25476 Instead, all you need is
25478 &`continue = `&<&'some expansion'&>
25481 .vitem &*control*&&~=&~<&'text'&>
25482 .cindex "&%control%& ACL modifier"
25483 This modifier affects the subsequent processing of the SMTP connection or of an
25484 incoming message that is accepted. The effect of the first type of control
25485 lasts for the duration of the connection, whereas the effect of the second type
25486 lasts only until the current message has been received. The message-specific
25487 controls always apply to the whole message, not to individual recipients,
25488 even if the &%control%& modifier appears in a RCPT ACL.
25490 As there are now quite a few controls that can be applied, they are described
25491 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
25492 in several different ways. For example:
25494 . ==== As this is a nested list, any displays it contains must be indented
25495 . ==== as otherwise they are too far to the left. That comment applies only
25496 . ==== when xmlto and fop are used; formatting with sdop gets it right either
25500 It can be at the end of an &%accept%& statement:
25502 accept ...some conditions
25503 control = queue_only
25505 In this case, the control is applied when this statement yields &"accept"&, in
25506 other words, when the conditions are all true.
25509 It can be in the middle of an &%accept%& statement:
25511 accept ...some conditions...
25512 control = queue_only
25513 ...some more conditions...
25515 If the first set of conditions are true, the control is applied, even if the
25516 statement does not accept because one of the second set of conditions is false.
25517 In this case, some subsequent statement must yield &"accept"& for the control
25521 It can be used with &%warn%& to apply the control, leaving the
25522 decision about accepting or denying to a subsequent verb. For
25525 warn ...some conditions...
25529 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
25530 &%logwrite%&, so it does not add anything to the message and does not write a
25534 If you want to apply a control unconditionally, you can use it with a
25535 &%require%& verb. For example:
25537 require control = no_multiline_responses
25541 .vitem &*delay*&&~=&~<&'time'&>
25542 .cindex "&%delay%& ACL modifier"
25544 This modifier may appear in any ACL. It causes Exim to wait for the time
25545 interval before proceeding. However, when testing Exim using the &%-bh%&
25546 option, the delay is not actually imposed (an appropriate message is output
25547 instead). The time is given in the usual Exim notation, and the delay happens
25548 as soon as the modifier is processed. In an SMTP session, pending output is
25549 flushed before the delay is imposed.
25551 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
25554 deny ...some conditions...
25557 The delay happens if all the conditions are true, before the statement returns
25558 &"deny"&. Compare this with:
25561 ...some conditions...
25563 which waits for 30s before processing the conditions. The &%delay%& modifier
25564 can also be used with &%warn%& and together with &%control%&:
25566 warn ...some conditions...
25572 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
25573 responses to several commands are no longer buffered and sent in one packet (as
25574 they would normally be) because all output is flushed before imposing the
25575 delay. This optimization is disabled so that a number of small delays do not
25576 appear to the client as one large aggregated delay that might provoke an
25577 unwanted timeout. You can, however, disable output flushing for &%delay%& by
25578 using a &%control%& modifier to set &%no_delay_flush%&.
25582 .cindex "&%endpass%& ACL modifier"
25583 This modifier, which has no argument, is recognized only in &%accept%& and
25584 &%discard%& statements. It marks the boundary between the conditions whose
25585 failure causes control to pass to the next statement, and the conditions whose
25586 failure causes the ACL to return &"deny"&. This concept has proved to be
25587 confusing to some people, so the use of &%endpass%& is no longer recommended as
25588 &"best practice"&. See the description of &%accept%& above for more details.
25591 .vitem &*log_message*&&~=&~<&'text'&>
25592 .cindex "&%log_message%& ACL modifier"
25593 This modifier sets up a message that is used as part of the log message if the
25594 ACL denies access or a &%warn%& statement's conditions are true. For example:
25596 require log_message = wrong cipher suite $tls_cipher
25597 encrypted = DES-CBC3-SHA
25599 &%log_message%& is also used when recipients are discarded by &%discard%&. For
25602 &`discard `&<&'some conditions'&>
25603 &` log_message = Discarded $local_part@$domain because...`&
25605 When access is denied, &%log_message%& adds to any underlying error message
25606 that may exist because of a condition failure. For example, while verifying a
25607 recipient address, a &':fail:'& redirection might have already set up a
25610 The message may be defined before the conditions to which it applies, because
25611 the string expansion does not happen until Exim decides that access is to be
25612 denied. This means that any variables that are set by the condition are
25613 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
25614 variables are set after a DNS black list lookup succeeds. If the expansion of
25615 &%log_message%& fails, or if the result is an empty string, the modifier is
25618 .vindex "&$acl_verify_message$&"
25619 If you want to use a &%warn%& statement to log the result of an address
25620 verification, you can use &$acl_verify_message$& to include the verification
25623 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
25624 the start of the logged message. If the same warning log message is requested
25625 more than once while receiving a single email message, only one copy is
25626 actually logged. If you want to log multiple copies, use &%logwrite%& instead
25627 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
25628 is logged for a successful &%warn%& statement.
25630 If &%log_message%& is not present and there is no underlying error message (for
25631 example, from the failure of address verification), but &%message%& is present,
25632 the &%message%& text is used for logging rejections. However, if any text for
25633 logging contains newlines, only the first line is logged. In the absence of
25634 both &%log_message%& and &%message%&, a default built-in message is used for
25635 logging rejections.
25638 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
25639 .cindex "&%log_reject_target%& ACL modifier"
25640 .cindex "logging in ACL" "specifying which log"
25641 This modifier makes it possible to specify which logs are used for messages
25642 about ACL rejections. Its argument is a colon-separated list of words that can
25643 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
25644 may be empty, in which case a rejection is not logged at all. For example, this
25645 ACL fragment writes no logging information when access is denied:
25647 &`deny `&<&'some conditions'&>
25648 &` log_reject_target =`&
25650 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
25651 permanent and temporary rejections. Its effect lasts for the rest of the
25655 .vitem &*logwrite*&&~=&~<&'text'&>
25656 .cindex "&%logwrite%& ACL modifier"
25657 .cindex "logging in ACL" "immediate"
25658 This modifier writes a message to a log file as soon as it is encountered when
25659 processing an ACL. (Compare &%log_message%&, which, except in the case of
25660 &%warn%& and &%discard%&, is used only if the ACL statement denies
25661 access.) The &%logwrite%& modifier can be used to log special incidents in
25664 &`accept `&<&'some special conditions'&>
25665 &` control = freeze`&
25666 &` logwrite = froze message because ...`&
25668 By default, the message is written to the main log. However, it may begin
25669 with a colon, followed by a comma-separated list of log names, and then
25670 another colon, to specify exactly which logs are to be written. For
25673 logwrite = :main,reject: text for main and reject logs
25674 logwrite = :panic: text for panic log only
25678 .vitem &*message*&&~=&~<&'text'&>
25679 .cindex "&%message%& ACL modifier"
25680 This modifier sets up a text string that is expanded and used as a response
25681 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
25682 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
25683 there is some complication if &%endpass%& is involved; see the description of
25684 &%accept%& for details.)
25686 The expansion of the message happens at the time Exim decides that the ACL is
25687 to end, not at the time it processes &%message%&. If the expansion fails, or
25688 generates an empty string, the modifier is ignored. Here is an example where
25689 &%message%& must be specified first, because the ACL ends with a rejection if
25690 the &%hosts%& condition fails:
25692 require message = Host not recognized
25695 (Once a condition has failed, no further conditions or modifiers are
25698 .cindex "SMTP" "error codes"
25699 .oindex "&%smtp_banner%&
25700 For ACLs that are triggered by SMTP commands, the message is returned as part
25701 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
25702 is meaningful only for SMTP, as no message is returned when a non-SMTP message
25703 is accepted. In the case of the connect ACL, accepting with a message modifier
25704 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
25705 accept message may not contain more than one line (otherwise it will be
25706 truncated at the first newline and a panic logged), and it cannot affect the
25709 When SMTP is involved, the message may begin with an overriding response code,
25710 consisting of three digits optionally followed by an &"extended response code"&
25711 of the form &'n.n.n'&, each code being followed by a space. For example:
25713 deny message = 599 1.2.3 Host not welcome
25714 hosts = 192.168.34.0/24
25716 The first digit of the supplied response code must be the same as would be sent
25717 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
25718 access, but for the predata ACL, note that the default success code is 354, not
25721 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
25722 the message modifier cannot override the 221 response code.
25724 The text in a &%message%& modifier is literal; any quotes are taken as
25725 literals, but because the string is expanded, backslash escapes are processed
25726 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
25729 .vindex "&$acl_verify_message$&"
25730 If &%message%& is used on a statement that verifies an address, the message
25731 specified overrides any message that is generated by the verification process.
25732 However, the original message is available in the variable
25733 &$acl_verify_message$&, so you can incorporate it into your message if you
25734 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
25735 routers to be passed back as part of the SMTP response, you should either not
25736 use a &%message%& modifier, or make use of &$acl_verify_message$&.
25738 For compatibility with previous releases of Exim, a &%message%& modifier that
25739 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
25740 modifier, but this usage is now deprecated. However, &%message%& acts only when
25741 all the conditions are true, wherever it appears in an ACL command, whereas
25742 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
25743 &%warn%& in an ACL that is not concerned with receiving a message, it has no
25747 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
25748 .cindex "&%set%& ACL modifier"
25749 This modifier puts a value into one of the ACL variables (see section
25750 &<<SECTaclvariables>>&).
25757 .section "Use of the control modifier" "SECTcontrols"
25758 .cindex "&%control%& ACL modifier"
25759 The &%control%& modifier supports the following settings:
25762 .vitem &*control&~=&~allow_auth_unadvertised*&
25763 This modifier allows a client host to use the SMTP AUTH command even when it
25764 has not been advertised in response to EHLO. Furthermore, because there are
25765 apparently some really broken clients that do this, Exim will accept AUTH after
25766 HELO (rather than EHLO) when this control is set. It should be used only if you
25767 really need it, and you should limit its use to those broken clients that do
25768 not work without it. For example:
25770 warn hosts = 192.168.34.25
25771 control = allow_auth_unadvertised
25773 Normally, when an Exim server receives an AUTH command, it checks the name of
25774 the authentication mechanism that is given in the command to ensure that it
25775 matches an advertised mechanism. When this control is set, the check that a
25776 mechanism has been advertised is bypassed. Any configured mechanism can be used
25777 by the client. This control is permitted only in the connection and HELO ACLs.
25780 .vitem &*control&~=&~caseful_local_part*& &&&
25781 &*control&~=&~caselower_local_part*&
25782 .cindex "&ACL;" "case of local part in"
25783 .cindex "case of local parts"
25784 .vindex "&$local_part$&"
25785 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
25786 (that is, during RCPT processing). By default, the contents of &$local_part$&
25787 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
25788 any uppercase letters in the original local part are restored in &$local_part$&
25789 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
25792 These controls affect only the current recipient. Moreover, they apply only to
25793 local part handling that takes place directly in the ACL (for example, as a key
25794 in lookups). If a test to verify the recipient is obeyed, the case-related
25795 handling of the local part during the verification is controlled by the router
25796 configuration (see the &%caseful_local_part%& generic router option).
25798 This facility could be used, for example, to add a spam score to local parts
25799 containing upper case letters. For example, using &$acl_m4$& to accumulate the
25802 warn control = caseful_local_part
25803 set acl_m4 = ${eval:\
25805 ${if match{$local_part}{[A-Z]}{1}{0}}\
25807 control = caselower_local_part
25809 Notice that we put back the lower cased version afterwards, assuming that
25810 is what is wanted for subsequent tests.
25812 .vitem &*control&~=&~debug/*&<&'options'&>
25813 .cindex "&ACL;" "enabling debug logging"
25814 .cindex "debugging" "enabling from an ACL"
25815 This control turns on debug logging, almost as though Exim had been invoked
25816 with &`-d`&, with the output going to a new logfile, by default called
25817 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
25818 may access any variables already defined. The logging may be adjusted with
25819 the &'opts'& option, which takes the same values as the &`-d`& command-line
25820 option. Some examples (which depend on variables that don't exist in all
25824 control = debug/tag=.$sender_host_address
25825 control = debug/opts=+expand+acl
25826 control = debug/tag=.$message_exim_id/opts=+expand
25829 .vitem &*control&~=&~enforce_sync*& &&&
25830 &*control&~=&~no_enforce_sync*&
25831 .cindex "SMTP" "synchronization checking"
25832 .cindex "synchronization checking in SMTP"
25833 These controls make it possible to be selective about when SMTP synchronization
25834 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
25835 state of the switch (it is true by default). See the description of this option
25836 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
25838 The effect of these two controls lasts for the remainder of the SMTP
25839 connection. They can appear in any ACL except the one for the non-SMTP
25840 messages. The most straightforward place to put them is in the ACL defined by
25841 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
25842 before the first synchronization check. The expected use is to turn off the
25843 synchronization checks for badly-behaved hosts that you nevertheless need to
25847 .vitem &*control&~=&~fakedefer/*&<&'message'&>
25848 .cindex "fake defer"
25849 .cindex "defer, fake"
25850 This control works in exactly the same way as &%fakereject%& (described below)
25851 except that it causes an SMTP 450 response after the message data instead of a
25852 550 response. You must take care when using &%fakedefer%& because it causes the
25853 messages to be duplicated when the sender retries. Therefore, you should not
25854 use &%fakedefer%& if the message is to be delivered normally.
25856 .vitem &*control&~=&~fakereject/*&<&'message'&>
25857 .cindex "fake rejection"
25858 .cindex "rejection, fake"
25859 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
25860 words, only when an SMTP message is being received. If Exim accepts the
25861 message, instead the final 250 response, a 550 rejection message is sent.
25862 However, Exim proceeds to deliver the message as normal. The control applies
25863 only to the current message, not to any subsequent ones that may be received in
25864 the same SMTP connection.
25866 The text for the 550 response is taken from the &%control%& modifier. If no
25867 message is supplied, the following is used:
25869 550-Your message has been rejected but is being
25870 550-kept for evaluation.
25871 550-If it was a legitimate message, it may still be
25872 550 delivered to the target recipient(s).
25874 This facility should be used with extreme caution.
25876 .vitem &*control&~=&~freeze*&
25877 .cindex "frozen messages" "forcing in ACL"
25878 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
25879 other words, only when a message is being received. If the message is accepted,
25880 it is placed on Exim's queue and frozen. The control applies only to the
25881 current message, not to any subsequent ones that may be received in the same
25884 This modifier can optionally be followed by &`/no_tell`&. If the global option
25885 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
25886 is told about the freezing), provided all the &*control=freeze*& modifiers that
25887 are obeyed for the current message have the &`/no_tell`& option.
25889 .vitem &*control&~=&~no_delay_flush*&
25890 .cindex "SMTP" "output flushing, disabling for delay"
25891 Exim normally flushes SMTP output before implementing a delay in an ACL, to
25892 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
25893 use. This control, as long as it is encountered before the &%delay%& modifier,
25894 disables such output flushing.
25896 .vitem &*control&~=&~no_callout_flush*&
25897 .cindex "SMTP" "output flushing, disabling for callout"
25898 Exim normally flushes SMTP output before performing a callout in an ACL, to
25899 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
25900 use. This control, as long as it is encountered before the &%verify%& condition
25901 that causes the callout, disables such output flushing.
25903 .vitem &*control&~=&~no_mbox_unspool*&
25904 This control is available when Exim is compiled with the content scanning
25905 extension. Content scanning may require a copy of the current message, or parts
25906 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
25907 or spam scanner. Normally, such copies are deleted when they are no longer
25908 needed. If this control is set, the copies are not deleted. The control applies
25909 only to the current message, not to any subsequent ones that may be received in
25910 the same SMTP connection. It is provided for debugging purposes and is unlikely
25911 to be useful in production.
25913 .vitem &*control&~=&~no_multiline_responses*&
25914 .cindex "multiline responses, suppressing"
25915 This control is permitted for any ACL except the one for non-SMTP messages.
25916 It seems that there are broken clients in use that cannot handle multiline
25917 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
25919 If this control is set, multiline SMTP responses from ACL rejections are
25920 suppressed. One way of doing this would have been to put out these responses as
25921 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
25922 (&"use multiline responses for more"& it says &-- ha!), and some of the
25923 responses might get close to that. So this facility, which is after all only a
25924 sop to broken clients, is implemented by doing two very easy things:
25927 Extra information that is normally output as part of a rejection caused by
25928 sender verification failure is omitted. Only the final line (typically &"sender
25929 verification failed"&) is sent.
25931 If a &%message%& modifier supplies a multiline response, only the first
25935 The setting of the switch can, of course, be made conditional on the
25936 calling host. Its effect lasts until the end of the SMTP connection.
25938 .vitem &*control&~=&~no_pipelining*&
25939 .cindex "PIPELINING" "suppressing advertising"
25940 This control turns off the advertising of the PIPELINING extension to SMTP in
25941 the current session. To be useful, it must be obeyed before Exim sends its
25942 response to an EHLO command. Therefore, it should normally appear in an ACL
25943 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
25944 &%pipelining_advertise_hosts%&.
25946 .vitem &*control&~=&~queue_only*&
25947 .oindex "&%queue_only%&"
25948 .cindex "queueing incoming messages"
25949 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
25950 other words, only when a message is being received. If the message is accepted,
25951 it is placed on Exim's queue and left there for delivery by a subsequent queue
25952 runner. No immediate delivery process is started. In other words, it has the
25953 effect as the &%queue_only%& global option. However, the control applies only
25954 to the current message, not to any subsequent ones that may be received in the
25955 same SMTP connection.
25957 .vitem &*control&~=&~submission/*&<&'options'&>
25958 .cindex "message" "submission"
25959 .cindex "submission mode"
25960 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
25961 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
25962 the current message is a submission from a local MUA. In this case, Exim
25963 operates in &"submission mode"&, and applies certain fixups to the message if
25964 necessary. For example, it adds a &'Date:'& header line if one is not present.
25965 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
25966 late (the message has already been created).
25968 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
25969 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
25970 submission mode; the available options for this control are described there.
25971 The control applies only to the current message, not to any subsequent ones
25972 that may be received in the same SMTP connection.
25974 .vitem &*control&~=&~suppress_local_fixups*&
25975 .cindex "submission fixups, suppressing"
25976 This control applies to locally submitted (non TCP/IP) messages, and is the
25977 complement of &`control = submission`&. It disables the fixups that are
25978 normally applied to locally-submitted messages. Specifically:
25981 Any &'Sender:'& header line is left alone (in this respect, it is a
25982 dynamic version of &%local_sender_retain%&).
25984 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
25986 There is no check that &'From:'& corresponds to the actual sender.
25989 This control may be useful when a remotely-originated message is accepted,
25990 passed to some scanning program, and then re-submitted for delivery. It can be
25991 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
25992 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
25995 &*Note:*& This control applies only to the current message, not to any others
25996 that are being submitted at the same time using &%-bs%& or &%-bS%&.
26000 .section "Summary of message fixup control" "SECTsummesfix"
26001 All four possibilities for message fixups can be specified:
26004 Locally submitted, fixups applied: the default.
26006 Locally submitted, no fixups applied: use
26007 &`control = suppress_local_fixups`&.
26009 Remotely submitted, no fixups applied: the default.
26011 Remotely submitted, fixups applied: use &`control = submission`&.
26016 .section "Adding header lines in ACLs" "SECTaddheadacl"
26017 .cindex "header lines" "adding in an ACL"
26018 .cindex "header lines" "position of added lines"
26019 .cindex "&%message%& ACL modifier"
26020 The &%add_header%& modifier can be used to add one or more extra header lines
26021 to an incoming message, as in this example:
26023 warn dnslists = sbl.spamhaus.org : \
26024 dialup.mail-abuse.org
26025 add_header = X-blacklisted-at: $dnslist_domain
26027 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
26028 MIME, and non-SMTP ACLs (in other words, those that are concerned with
26029 receiving a message). The message must ultimately be accepted for
26030 &%add_header%& to have any significant effect. You can use &%add_header%& with
26031 any ACL verb, including &%deny%& (though this is potentially useful only in a
26034 If the data for the &%add_header%& modifier contains one or more newlines that
26035 are not followed by a space or a tab, it is assumed to contain multiple header
26036 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
26037 front of any line that is not a valid header line.
26039 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
26040 They are added to the message before processing the DATA and MIME ACLs.
26041 However, if an identical header line is requested more than once, only one copy
26042 is actually added to the message. Further header lines may be accumulated
26043 during the DATA and MIME ACLs, after which they are added to the message, again
26044 with duplicates suppressed. Thus, it is possible to add two identical header
26045 lines to an SMTP message, but only if one is added before DATA and one after.
26046 In the case of non-SMTP messages, new headers are accumulated during the
26047 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
26048 message is rejected after DATA or by the non-SMTP ACL, all added header lines
26049 are included in the entry that is written to the reject log.
26051 .cindex "header lines" "added; visibility of"
26052 Header lines are not visible in string expansions until they are added to the
26053 message. It follows that header lines defined in the MAIL, RCPT, and predata
26054 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
26055 header lines that are added by the DATA or MIME ACLs are not visible in those
26056 ACLs. Because of this restriction, you cannot use header lines as a way of
26057 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
26058 this, you can use ACL variables, as described in section
26059 &<<SECTaclvariables>>&.
26061 The &%add_header%& modifier acts immediately it is encountered during the
26062 processing of an ACL. Notice the difference between these two cases:
26064 &`accept add_header = ADDED: some text`&
26065 &` `&<&'some condition'&>
26067 &`accept `&<&'some condition'&>
26068 &` add_header = ADDED: some text`&
26070 In the first case, the header line is always added, whether or not the
26071 condition is true. In the second case, the header line is added only if the
26072 condition is true. Multiple occurrences of &%add_header%& may occur in the same
26073 ACL statement. All those that are encountered before a condition fails are
26076 .cindex "&%warn%& ACL verb"
26077 For compatibility with previous versions of Exim, a &%message%& modifier for a
26078 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
26079 effect only if all the conditions are true, even if it appears before some of
26080 them. Furthermore, only the last occurrence of &%message%& is honoured. This
26081 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
26082 are present on a &%warn%& verb, both are processed according to their
26085 By default, new header lines are added to a message at the end of the existing
26086 header lines. However, you can specify that any particular header line should
26087 be added right at the start (before all the &'Received:'& lines), immediately
26088 after the first block of &'Received:'& lines, or immediately before any line
26089 that is not a &'Received:'& or &'Resent-something:'& header.
26091 This is done by specifying &":at_start:"&, &":after_received:"&, or
26092 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
26093 header line, respectively. (Header text cannot start with a colon, as there has
26094 to be a header name first.) For example:
26096 warn add_header = \
26097 :after_received:X-My-Header: something or other...
26099 If more than one header line is supplied in a single &%add_header%& modifier,
26100 each one is treated independently and can therefore be placed differently. If
26101 you add more than one line at the start, or after the Received: block, they end
26102 up in reverse order.
26104 &*Warning*&: This facility currently applies only to header lines that are
26105 added in an ACL. It does NOT work for header lines that are added in a
26106 system filter or in a router or transport.
26111 .section "ACL conditions" "SECTaclconditions"
26112 .cindex "&ACL;" "conditions; list of"
26113 Some of conditions listed in this section are available only when Exim is
26114 compiled with the content-scanning extension. They are included here briefly
26115 for completeness. More detailed descriptions can be found in the discussion on
26116 content scanning in chapter &<<CHAPexiscan>>&.
26118 Not all conditions are relevant in all circumstances. For example, testing
26119 senders and recipients does not make sense in an ACL that is being run as the
26120 result of the arrival of an ETRN command, and checks on message headers can be
26121 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
26122 can use the same condition (with different parameters) more than once in the
26123 same ACL statement. This provides a way of specifying an &"and"& conjunction.
26124 The conditions are as follows:
26128 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
26129 .cindex "&ACL;" "nested"
26130 .cindex "&ACL;" "indirect"
26131 .cindex "&%acl%& ACL condition"
26132 The possible values of the argument are the same as for the
26133 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
26134 &"accept"& the condition is true; if it returns &"deny"& the condition is
26135 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
26136 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
26137 condition false. This means that further processing of the &%warn%& verb
26138 ceases, but processing of the ACL continues.
26140 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
26141 the connection is dropped. If it returns &"discard"&, the verb must be
26142 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
26143 conditions are tested.
26145 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
26146 loops. This condition allows you to use different ACLs in different
26147 circumstances. For example, different ACLs can be used to handle RCPT commands
26148 for different local users or different local domains.
26150 .vitem &*authenticated&~=&~*&<&'string&~list'&>
26151 .cindex "&%authenticated%& ACL condition"
26152 .cindex "authentication" "ACL checking"
26153 .cindex "&ACL;" "testing for authentication"
26154 If the SMTP connection is not authenticated, the condition is false. Otherwise,
26155 the name of the authenticator is tested against the list. To test for
26156 authentication by any authenticator, you can set
26161 .vitem &*condition&~=&~*&<&'string'&>
26162 .cindex "&%condition%& ACL condition"
26163 .cindex "customizing" "ACL condition"
26164 .cindex "&ACL;" "customized test"
26165 .cindex "&ACL;" "testing, customized"
26166 This feature allows you to make up custom conditions. If the result of
26167 expanding the string is an empty string, the number zero, or one of the strings
26168 &"no"& or &"false"&, the condition is false. If the result is any non-zero
26169 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
26170 any other value, some error is assumed to have occurred, and the ACL returns
26171 &"defer"&. However, if the expansion is forced to fail, the condition is
26172 ignored. The effect is to treat it as true, whether it is positive or
26175 .vitem &*decode&~=&~*&<&'location'&>
26176 .cindex "&%decode%& ACL condition"
26177 This condition is available only when Exim is compiled with the
26178 content-scanning extension, and it is allowed only in the ACL defined by
26179 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
26180 If all goes well, the condition is true. It is false only if there are
26181 problems such as a syntax error or a memory shortage. For more details, see
26182 chapter &<<CHAPexiscan>>&.
26184 .vitem &*demime&~=&~*&<&'extension&~list'&>
26185 .cindex "&%demime%& ACL condition"
26186 This condition is available only when Exim is compiled with the
26187 content-scanning extension. Its use is described in section
26188 &<<SECTdemimecond>>&.
26190 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
26191 .cindex "&%dnslists%& ACL condition"
26192 .cindex "DNS list" "in ACL"
26193 .cindex "black list (DNS)"
26194 .cindex "&ACL;" "testing a DNS list"
26195 This condition checks for entries in DNS black lists. These are also known as
26196 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
26197 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
26198 different variants of this condition to describe briefly here. See sections
26199 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
26201 .vitem &*domains&~=&~*&<&'domain&~list'&>
26202 .cindex "&%domains%& ACL condition"
26203 .cindex "domain" "ACL checking"
26204 .cindex "&ACL;" "testing a recipient domain"
26205 .vindex "&$domain_data$&"
26206 This condition is relevant only after a RCPT command. It checks that the domain
26207 of the recipient address is in the domain list. If percent-hack processing is
26208 enabled, it is done before this test is done. If the check succeeds with a
26209 lookup, the result of the lookup is placed in &$domain_data$& until the next
26212 &*Note carefully*& (because many people seem to fall foul of this): you cannot
26213 use &%domains%& in a DATA ACL.
26216 .vitem &*encrypted&~=&~*&<&'string&~list'&>
26217 .cindex "&%encrypted%& ACL condition"
26218 .cindex "encryption" "checking in an ACL"
26219 .cindex "&ACL;" "testing for encryption"
26220 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
26221 name of the cipher suite in use is tested against the list. To test for
26222 encryption without testing for any specific cipher suite(s), set
26228 .vitem &*hosts&~=&~*&<&'&~host&~list'&>
26229 .cindex "&%hosts%& ACL condition"
26230 .cindex "host" "ACL checking"
26231 .cindex "&ACL;" "testing the client host"
26232 This condition tests that the calling host matches the host list. If you have
26233 name lookups or wildcarded host names and IP addresses in the same host list,
26234 you should normally put the IP addresses first. For example, you could have:
26236 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
26238 The lookup in this example uses the host name for its key. This is implied by
26239 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
26240 and it wouldn't matter which way round you had these two items.)
26242 The reason for the problem with host names lies in the left-to-right way that
26243 Exim processes lists. It can test IP addresses without doing any DNS lookups,
26244 but when it reaches an item that requires a host name, it fails if it cannot
26245 find a host name to compare with the pattern. If the above list is given in the
26246 opposite order, the &%accept%& statement fails for a host whose name cannot be
26247 found, even if its IP address is 10.9.8.7.
26249 If you really do want to do the name check first, and still recognize the IP
26250 address even if the name lookup fails, you can rewrite the ACL like this:
26252 accept hosts = dbm;/etc/friendly/hosts
26253 accept hosts = 10.9.8.7
26255 The default action on failing to find the host name is to assume that the host
26256 is not in the list, so the first &%accept%& statement fails. The second
26257 statement can then check the IP address.
26259 .vindex "&$host_data$&"
26260 If a &%hosts%& condition is satisfied by means of a lookup, the result
26261 of the lookup is made available in the &$host_data$& variable. This
26262 allows you, for example, to set up a statement like this:
26264 deny hosts = net-lsearch;/some/file
26265 message = $host_data
26267 which gives a custom error message for each denied host.
26269 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
26270 .cindex "&%local_parts%& ACL condition"
26271 .cindex "local part" "ACL checking"
26272 .cindex "&ACL;" "testing a local part"
26273 .vindex "&$local_part_data$&"
26274 This condition is relevant only after a RCPT command. It checks that the local
26275 part of the recipient address is in the list. If percent-hack processing is
26276 enabled, it is done before this test. If the check succeeds with a lookup, the
26277 result of the lookup is placed in &$local_part_data$&, which remains set until
26278 the next &%local_parts%& test.
26280 .vitem &*malware&~=&~*&<&'option'&>
26281 .cindex "&%malware%& ACL condition"
26282 .cindex "&ACL;" "virus scanning"
26283 .cindex "&ACL;" "scanning for viruses"
26284 This condition is available only when Exim is compiled with the
26285 content-scanning extension. It causes the incoming message to be scanned for
26286 viruses. For details, see chapter &<<CHAPexiscan>>&.
26288 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
26289 .cindex "&%mime_regex%& ACL condition"
26290 .cindex "&ACL;" "testing by regex matching"
26291 This condition is available only when Exim is compiled with the
26292 content-scanning extension, and it is allowed only in the ACL defined by
26293 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
26294 with any of the regular expressions. For details, see chapter
26297 .vitem &*ratelimit&~=&~*&<&'parameters'&>
26298 .cindex "rate limiting"
26299 This condition can be used to limit the rate at which a user or host submits
26300 messages. Details are given in section &<<SECTratelimiting>>&.
26302 .vitem &*recipients&~=&~*&<&'address&~list'&>
26303 .cindex "&%recipients%& ACL condition"
26304 .cindex "recipient" "ACL checking"
26305 .cindex "&ACL;" "testing a recipient"
26306 This condition is relevant only after a RCPT command. It checks the entire
26307 recipient address against a list of recipients.
26309 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
26310 .cindex "&%regex%& ACL condition"
26311 .cindex "&ACL;" "testing by regex matching"
26312 This condition is available only when Exim is compiled with the
26313 content-scanning extension, and is available only in the DATA, MIME, and
26314 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
26315 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
26317 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
26318 .cindex "&%sender_domains%& ACL condition"
26319 .cindex "sender" "ACL checking"
26320 .cindex "&ACL;" "testing a sender domain"
26321 .vindex "&$domain$&"
26322 .vindex "&$sender_address_domain$&"
26323 This condition tests the domain of the sender of the message against the given
26324 domain list. &*Note*&: The domain of the sender address is in
26325 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
26326 of this condition. This is an exception to the general rule for testing domain
26327 lists. It is done this way so that, if this condition is used in an ACL for a
26328 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
26329 influence the sender checking.
26331 &*Warning*&: It is a bad idea to use this condition on its own as a control on
26332 relaying, because sender addresses are easily, and commonly, forged.
26334 .vitem &*senders&~=&~*&<&'address&~list'&>
26335 .cindex "&%senders%& ACL condition"
26336 .cindex "sender" "ACL checking"
26337 .cindex "&ACL;" "testing a sender"
26338 This condition tests the sender of the message against the given list. To test
26339 for a bounce message, which has an empty sender, set
26343 &*Warning*&: It is a bad idea to use this condition on its own as a control on
26344 relaying, because sender addresses are easily, and commonly, forged.
26346 .vitem &*spam&~=&~*&<&'username'&>
26347 .cindex "&%spam%& ACL condition"
26348 .cindex "&ACL;" "scanning for spam"
26349 This condition is available only when Exim is compiled with the
26350 content-scanning extension. It causes the incoming message to be scanned by
26351 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
26353 .vitem &*verify&~=&~certificate*&
26354 .cindex "&%verify%& ACL condition"
26355 .cindex "TLS" "client certificate verification"
26356 .cindex "certificate" "verification of client"
26357 .cindex "&ACL;" "certificate verification"
26358 .cindex "&ACL;" "testing a TLS certificate"
26359 This condition is true in an SMTP session if the session is encrypted, and a
26360 certificate was received from the client, and the certificate was verified. The
26361 server requests a certificate only if the client matches &%tls_verify_hosts%&
26362 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
26364 .vitem &*verify&~=&~csa*&
26365 .cindex "CSA verification"
26366 This condition checks whether the sending host (the client) is authorized to
26367 send email. Details of how this works are given in section
26368 &<<SECTverifyCSA>>&.
26370 .vitem &*verify&~=&~header_sender/*&<&'options'&>
26371 .cindex "&%verify%& ACL condition"
26372 .cindex "&ACL;" "verifying sender in the header"
26373 .cindex "header lines" "verifying the sender in"
26374 .cindex "sender" "verifying in header"
26375 .cindex "verifying" "sender in header"
26376 This condition is relevant only in an ACL that is run after a message has been
26377 received, that is, in an ACL specified by &%acl_smtp_data%& or
26378 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
26379 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
26380 is loosely thought of as a &"sender"& address (hence the name of the test).
26381 However, an address that appears in one of these headers need not be an address
26382 that accepts bounce messages; only sender addresses in envelopes are required
26383 to accept bounces. Therefore, if you use the callout option on this check, you
26384 might want to arrange for a non-empty address in the MAIL command.
26386 Details of address verification and the options are given later, starting at
26387 section &<<SECTaddressverification>>& (callouts are described in section
26388 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
26389 condition to restrict it to bounce messages only:
26392 message = A valid sender header is required for bounces
26393 !verify = header_sender
26396 .vitem &*verify&~=&~header_syntax*&
26397 .cindex "&%verify%& ACL condition"
26398 .cindex "&ACL;" "verifying header syntax"
26399 .cindex "header lines" "verifying syntax"
26400 .cindex "verifying" "header syntax"
26401 This condition is relevant only in an ACL that is run after a message has been
26402 received, that is, in an ACL specified by &%acl_smtp_data%& or
26403 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
26404 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
26405 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
26406 permitted only in locally generated messages and from hosts that match
26407 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26410 Note that this condition is a syntax check only. However, a common spamming
26411 ploy used to be to send syntactically invalid headers such as
26415 and this condition can be used to reject such messages, though they are not as
26416 common as they used to be.
26418 .vitem &*verify&~=&~helo*&
26419 .cindex "&%verify%& ACL condition"
26420 .cindex "&ACL;" "verifying HELO/EHLO"
26421 .cindex "HELO" "verifying"
26422 .cindex "EHLO" "verifying"
26423 .cindex "verifying" "EHLO"
26424 .cindex "verifying" "HELO"
26425 This condition is true if a HELO or EHLO command has been received from the
26426 client host, and its contents have been verified. If there has been no previous
26427 attempt to verify the HELO/EHLO contents, it is carried out when this
26428 condition is encountered. See the description of the &%helo_verify_hosts%& and
26429 &%helo_try_verify_hosts%& options for details of how to request verification
26430 independently of this condition.
26432 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
26433 option), this condition is always true.
26436 .vitem &*verify&~=&~not_blind*&
26437 .cindex "verifying" "not blind"
26438 .cindex "bcc recipients, verifying none"
26439 This condition checks that there are no blind (bcc) recipients in the message.
26440 Every envelope recipient must appear either in a &'To:'& header line or in a
26441 &'Cc:'& header line for this condition to be true. Local parts are checked
26442 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
26443 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
26444 used only in a DATA or non-SMTP ACL.
26446 There are, of course, many legitimate messages that make use of blind (bcc)
26447 recipients. This check should not be used on its own for blocking messages.
26450 .vitem &*verify&~=&~recipient/*&<&'options'&>
26451 .cindex "&%verify%& ACL condition"
26452 .cindex "&ACL;" "verifying recipient"
26453 .cindex "recipient" "verifying"
26454 .cindex "verifying" "recipient"
26455 .vindex "&$address_data$&"
26456 This condition is relevant only after a RCPT command. It verifies the current
26457 recipient. Details of address verification are given later, starting at section
26458 &<<SECTaddressverification>>&. After a recipient has been verified, the value
26459 of &$address_data$& is the last value that was set while routing the address.
26460 This applies even if the verification fails. When an address that is being
26461 verified is redirected to a single address, verification continues with the new
26462 address, and in that case, the subsequent value of &$address_data$& is the
26463 value for the child address.
26465 .vitem &*verify&~=&~reverse_host_lookup*&
26466 .cindex "&%verify%& ACL condition"
26467 .cindex "&ACL;" "verifying host reverse lookup"
26468 .cindex "host" "verifying reverse lookup"
26469 This condition ensures that a verified host name has been looked up from the IP
26470 address of the client host. (This may have happened already if the host name
26471 was needed for checking a host list, or if the host matched &%host_lookup%&.)
26472 Verification ensures that the host name obtained from a reverse DNS lookup, or
26473 one of its aliases, does, when it is itself looked up in the DNS, yield the
26474 original IP address.
26476 If this condition is used for a locally generated message (that is, when there
26477 is no client host involved), it always succeeds.
26479 .vitem &*verify&~=&~sender/*&<&'options'&>
26480 .cindex "&%verify%& ACL condition"
26481 .cindex "&ACL;" "verifying sender"
26482 .cindex "sender" "verifying"
26483 .cindex "verifying" "sender"
26484 This condition is relevant only after a MAIL or RCPT command, or after a
26485 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
26486 the message's sender is empty (that is, this is a bounce message), the
26487 condition is true. Otherwise, the sender address is verified.
26489 .vindex "&$address_data$&"
26490 .vindex "&$sender_address_data$&"
26491 If there is data in the &$address_data$& variable at the end of routing, its
26492 value is placed in &$sender_address_data$& at the end of verification. This
26493 value can be used in subsequent conditions and modifiers in the same ACL
26494 statement. It does not persist after the end of the current statement. If you
26495 want to preserve the value for longer, you can save it in an ACL variable.
26497 Details of verification are given later, starting at section
26498 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
26499 to avoid doing it more than once per message.
26501 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
26502 .cindex "&%verify%& ACL condition"
26503 This is a variation of the previous option, in which a modified address is
26504 verified as a sender.
26509 .section "Using DNS lists" "SECTmorednslists"
26510 .cindex "DNS list" "in ACL"
26511 .cindex "black list (DNS)"
26512 .cindex "&ACL;" "testing a DNS list"
26513 In its simplest form, the &%dnslists%& condition tests whether the calling host
26514 is on at least one of a number of DNS lists by looking up the inverted IP
26515 address in one or more DNS domains. (Note that DNS list domains are not mail
26516 domains, so the &`+`& syntax for named lists doesn't work - it is used for
26517 special options instead.) For example, if the calling host's IP
26518 address is 192.168.62.43, and the ACL statement is
26520 deny dnslists = blackholes.mail-abuse.org : \
26521 dialups.mail-abuse.org
26523 the following records are looked up:
26525 43.62.168.192.blackholes.mail-abuse.org
26526 43.62.168.192.dialups.mail-abuse.org
26528 As soon as Exim finds an existing DNS record, processing of the list stops.
26529 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
26530 to test that a host is on more than one list (an &"and"& conjunction), you can
26531 use two separate conditions:
26533 deny dnslists = blackholes.mail-abuse.org
26534 dnslists = dialups.mail-abuse.org
26536 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
26537 behaves as if the host does not match the list item, that is, as if the DNS
26538 record does not exist. If there are further items in the DNS list, they are
26541 This is usually the required action when &%dnslists%& is used with &%deny%&
26542 (which is the most common usage), because it prevents a DNS failure from
26543 blocking mail. However, you can change this behaviour by putting one of the
26544 following special items in the list:
26546 &`+include_unknown `& behave as if the item is on the list
26547 &`+exclude_unknown `& behave as if the item is not on the list (default)
26548 &`+defer_unknown `& give a temporary error
26550 .cindex "&`+include_unknown`&"
26551 .cindex "&`+exclude_unknown`&"
26552 .cindex "&`+defer_unknown`&"
26553 Each of these applies to any subsequent items on the list. For example:
26555 deny dnslists = +defer_unknown : foo.bar.example
26557 Testing the list of domains stops as soon as a match is found. If you want to
26558 warn for one list and block for another, you can use two different statements:
26560 deny dnslists = blackholes.mail-abuse.org
26561 warn message = X-Warn: sending host is on dialups list
26562 dnslists = dialups.mail-abuse.org
26564 DNS list lookups are cached by Exim for the duration of the SMTP session,
26565 so a lookup based on the IP address is done at most once for any incoming
26566 connection. Exim does not share information between multiple incoming
26567 connections (but your local name server cache should be active).
26571 .section "Specifying the IP address for a DNS list lookup" "SECID201"
26572 .cindex "DNS list" "keyed by explicit IP address"
26573 By default, the IP address that is used in a DNS list lookup is the IP address
26574 of the calling host. However, you can specify another IP address by listing it
26575 after the domain name, introduced by a slash. For example:
26577 deny dnslists = black.list.tld/192.168.1.2
26579 This feature is not very helpful with explicit IP addresses; it is intended for
26580 use with IP addresses that are looked up, for example, the IP addresses of the
26581 MX hosts or nameservers of an email sender address. For an example, see section
26582 &<<SECTmulkeyfor>>& below.
26587 .section "DNS lists keyed on domain names" "SECID202"
26588 .cindex "DNS list" "keyed by domain name"
26589 There are some lists that are keyed on domain names rather than inverted IP
26590 addresses (see for example the &'domain based zones'& link at
26591 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
26592 with these lists. You can change the name that is looked up in a DNS list by
26593 listing it after the domain name, introduced by a slash. For example,
26595 deny message = Sender's domain is listed at $dnslist_domain
26596 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
26598 This particular example is useful only in ACLs that are obeyed after the
26599 RCPT or DATA commands, when a sender address is available. If (for
26600 example) the message's sender is &'user@tld.example'& the name that is looked
26601 up by this example is
26603 tld.example.dsn.rfc-ignorant.org
26605 A single &%dnslists%& condition can contain entries for both names and IP
26606 addresses. For example:
26608 deny dnslists = sbl.spamhaus.org : \
26609 dsn.rfc-ignorant.org/$sender_address_domain
26611 The first item checks the sending host's IP address; the second checks a domain
26612 name. The whole condition is true if either of the DNS lookups succeeds.
26617 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
26618 .cindex "DNS list" "multiple keys for"
26619 The syntax described above for looking up explicitly-defined values (either
26620 names or IP addresses) in a DNS blacklist is a simplification. After the domain
26621 name for the DNS list, what follows the slash can in fact be a list of items.
26622 As with all lists in Exim, the default separator is a colon. However, because
26623 this is a sublist within the list of DNS blacklist domains, it is necessary
26624 either to double the separators like this:
26626 dnslists = black.list.tld/name.1::name.2
26628 or to change the separator character, like this:
26630 dnslists = black.list.tld/<;name.1;name.2
26632 If an item in the list is an IP address, it is inverted before the DNS
26633 blacklist domain is appended. If it is not an IP address, no inversion
26634 occurs. Consider this condition:
26636 dnslists = black.list.tld/<;192.168.1.2;a.domain
26638 The DNS lookups that occur are:
26640 2.1.168.192.black.list.tld
26641 a.domain.black.list.tld
26643 Once a DNS record has been found (that matches a specific IP return
26644 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
26645 are done. If there is a temporary DNS error, the rest of the sublist of domains
26646 or IP addresses is tried. A temporary error for the whole dnslists item occurs
26647 only if no other DNS lookup in this sublist succeeds. In other words, a
26648 successful lookup for any of the items in the sublist overrides a temporary
26649 error for a previous item.
26651 The ability to supply a list of items after the slash is in some sense just a
26652 syntactic convenience. These two examples have the same effect:
26654 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
26655 dnslists = black.list.tld/a.domain::b.domain
26657 However, when the data for the list is obtained from a lookup, the second form
26658 is usually much more convenient. Consider this example:
26660 deny message = The mail servers for the domain \
26661 $sender_address_domain \
26662 are listed at $dnslist_domain ($dnslist_value); \
26664 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
26665 ${lookup dnsdb {>|mxh=\
26666 $sender_address_domain} }} }
26668 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
26669 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
26670 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
26671 of expanding the condition might be something like this:
26673 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
26675 Thus, this example checks whether or not the IP addresses of the sender
26676 domain's mail servers are on the Spamhaus black list.
26678 The key that was used for a successful DNS list lookup is put into the variable
26679 &$dnslist_matched$& (see section &<<SECID204>>&).
26684 .section "Data returned by DNS lists" "SECID203"
26685 .cindex "DNS list" "data returned from"
26686 DNS lists are constructed using address records in the DNS. The original RBL
26687 just used the address 127.0.0.1 on the right hand side of each record, but the
26688 RBL+ list and some other lists use a number of values with different meanings.
26689 The values used on the RBL+ list are:
26693 127.1.0.3 DUL and RBL
26695 127.1.0.5 RSS and RBL
26696 127.1.0.6 RSS and DUL
26697 127.1.0.7 RSS and DUL and RBL
26699 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
26700 different values. Some DNS lists may return more than one address record;
26701 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
26704 .section "Variables set from DNS lists" "SECID204"
26705 .cindex "expansion" "variables, set from DNS list"
26706 .cindex "DNS list" "variables set from"
26707 .vindex "&$dnslist_domain$&"
26708 .vindex "&$dnslist_matched$&"
26709 .vindex "&$dnslist_text$&"
26710 .vindex "&$dnslist_value$&"
26711 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
26712 the name of the overall domain that matched (for example,
26713 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
26714 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
26715 the DNS record. When the key is an IP address, it is not reversed in
26716 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
26717 cases, for example:
26719 deny dnslists = spamhaus.example
26721 the key is also available in another variable (in this case,
26722 &$sender_host_address$&). In more complicated cases, however, this is not true.
26723 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
26724 might generate a dnslists lookup like this:
26726 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
26728 If this condition succeeds, the value in &$dnslist_matched$& might be
26729 &`192.168.6.7`& (for example).
26731 If more than one address record is returned by the DNS lookup, all the IP
26732 addresses are included in &$dnslist_value$&, separated by commas and spaces.
26733 The variable &$dnslist_text$& contains the contents of any associated TXT
26734 record. For lists such as RBL+ the TXT record for a merged entry is often not
26735 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
26738 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
26739 &-- although these appear before the condition in the ACL, they are not
26740 expanded until after it has failed. For example:
26742 deny hosts = !+local_networks
26743 message = $sender_host_address is listed \
26745 dnslists = rbl-plus.mail-abuse.example
26750 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
26751 .cindex "DNS list" "matching specific returned data"
26752 You can add an equals sign and an IP address after a &%dnslists%& domain name
26753 in order to restrict its action to DNS records with a matching right hand side.
26756 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
26758 rejects only those hosts that yield 127.0.0.2. Without this additional data,
26759 any address record is considered to be a match. For the moment, we assume
26760 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
26761 describes how multiple records are handled.
26763 More than one IP address may be given for checking, using a comma as a
26764 separator. These are alternatives &-- if any one of them matches, the
26765 &%dnslists%& condition is true. For example:
26767 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
26769 If you want to specify a constraining address list and also specify names or IP
26770 addresses to be looked up, the constraining address list must be specified
26771 first. For example:
26773 deny dnslists = dsn.rfc-ignorant.org\
26774 =127.0.0.2/$sender_address_domain
26777 If the character &`&&`& is used instead of &`=`&, the comparison for each
26778 listed IP address is done by a bitwise &"and"& instead of by an equality test.
26779 In other words, the listed addresses are used as bit masks. The comparison is
26780 true if all the bits in the mask are present in the address that is being
26781 tested. For example:
26783 dnslists = a.b.c&0.0.0.3
26785 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
26786 want to test whether one bit or another bit is present (as opposed to both
26787 being present), you must use multiple values. For example:
26789 dnslists = a.b.c&0.0.0.1,0.0.0.2
26791 matches if the final component of the address is an odd number or two times
26796 .section "Negated DNS matching conditions" "SECID205"
26797 You can supply a negative list of IP addresses as part of a &%dnslists%&
26800 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
26802 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
26803 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
26805 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
26807 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
26808 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
26809 words, the result of the test is inverted if an exclamation mark appears before
26810 the &`=`& (or the &`&&`&) sign.
26812 &*Note*&: This kind of negation is not the same as negation in a domain,
26813 host, or address list (which is why the syntax is different).
26815 If you are using just one list, the negation syntax does not gain you much. The
26816 previous example is precisely equivalent to
26818 deny dnslists = a.b.c
26819 !dnslists = a.b.c=127.0.0.2,127.0.0.3
26821 However, if you are using multiple lists, the negation syntax is clearer.
26822 Consider this example:
26824 deny dnslists = sbl.spamhaus.org : \
26826 dnsbl.njabl.org!=127.0.0.3 : \
26829 Using only positive lists, this would have to be:
26831 deny dnslists = sbl.spamhaus.org : \
26833 deny dnslists = dnsbl.njabl.org
26834 !dnslists = dnsbl.njabl.org=127.0.0.3
26835 deny dnslists = relays.ordb.org
26837 which is less clear, and harder to maintain.
26842 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
26843 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
26844 thereby providing more than one IP address. When an item in a &%dnslists%& list
26845 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
26846 the match to specific results from the DNS lookup, there are two ways in which
26847 the checking can be handled. For example, consider the condition:
26849 dnslists = a.b.c=127.0.0.1
26851 What happens if the DNS lookup for the incoming IP address yields both
26852 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
26853 condition true because at least one given value was found, or is it false
26854 because at least one of the found values was not listed? And how does this
26855 affect negated conditions? Both possibilities are provided for with the help of
26856 additional separators &`==`& and &`=&&`&.
26859 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
26860 IP addresses matches one of the listed addresses. For the example above, the
26861 condition is true because 127.0.0.1 matches.
26863 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
26864 looked up IP addresses matches one of the listed addresses. If the condition is
26867 dnslists = a.b.c==127.0.0.1
26869 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26870 false because 127.0.0.2 is not listed. You would need to have:
26872 dnslists = a.b.c==127.0.0.1,127.0.0.2
26874 for the condition to be true.
26877 When &`!`& is used to negate IP address matching, it inverts the result, giving
26878 the precise opposite of the behaviour above. Thus:
26880 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
26881 addresses matches one of the listed addresses. Consider:
26883 dnslists = a.b.c!&0.0.0.1
26885 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26886 false because 127.0.0.1 matches.
26888 If &`!==`& or &`!=&&`& is used, the condition is true there is at least one
26889 looked up IP address that does not match. Consider:
26891 dnslists = a.b.c!=&0.0.0.1
26893 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26894 true, because 127.0.0.2 does not match. You would need to have:
26896 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
26898 for the condition to be false.
26900 When the DNS lookup yields only a single IP address, there is no difference
26901 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
26906 .section "Detailed information from merged DNS lists" "SECTmordetinf"
26907 .cindex "DNS list" "information from merged"
26908 When the facility for restricting the matching IP values in a DNS list is used,
26909 the text from the TXT record that is set in &$dnslist_text$& may not reflect
26910 the true reason for rejection. This happens when lists are merged and the IP
26911 address in the A record is used to distinguish them; unfortunately there is
26912 only one TXT record. One way round this is not to use merged lists, but that
26913 can be inefficient because it requires multiple DNS lookups where one would do
26914 in the vast majority of cases when the host of interest is not on any of the
26917 A less inefficient way of solving this problem is available. If
26918 two domain names, comma-separated, are given, the second is used first to
26919 do an initial check, making use of any IP value restrictions that are set.
26920 If there is a match, the first domain is used, without any IP value
26921 restrictions, to get the TXT record. As a byproduct of this, there is also
26922 a check that the IP being tested is indeed on the first list. The first
26923 domain is the one that is put in &$dnslist_domain$&. For example:
26926 rejected because $sender_host_address is blacklisted \
26927 at $dnslist_domain\n$dnslist_text
26929 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
26930 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
26932 For the first blacklist item, this starts by doing a lookup in
26933 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
26934 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
26935 value, and as long as something is found, it looks for the corresponding TXT
26936 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
26937 The second blacklist item is processed similarly.
26939 If you are interested in more than one merged list, the same list must be
26940 given several times, but because the results of the DNS lookups are cached,
26941 the DNS calls themselves are not repeated. For example:
26943 reject dnslists = \
26944 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
26945 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
26946 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
26947 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
26949 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
26950 values matches (or if no record is found), this is the only lookup that is
26951 done. Only if there is a match is one of the more specific lists consulted.
26955 .section "DNS lists and IPv6" "SECTmorednslistslast"
26956 .cindex "IPv6" "DNS black lists"
26957 .cindex "DNS list" "IPv6 usage"
26958 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
26959 nibble by nibble. For example, if the calling host's IP address is
26960 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
26962 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
26963 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
26965 (split over two lines here to fit on the page). Unfortunately, some of the DNS
26966 lists contain wildcard records, intended for IPv4, that interact badly with
26967 IPv6. For example, the DNS entry
26969 *.3.some.list.example. A 127.0.0.1
26971 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
26972 Unfortunately, it also matches the entire 3::/4 IPv6 network.
26974 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
26975 &%condition%& condition, as in this example:
26977 deny condition = ${if isip4{$sender_host_address}}
26978 dnslists = some.list.example
26981 .section "Rate limiting incoming messages" "SECTratelimiting"
26982 .cindex "rate limiting" "client sending"
26983 .cindex "limiting client sending rates"
26984 .oindex "&%smtp_ratelimit_*%&"
26985 The &%ratelimit%& ACL condition can be used to measure and control the rate at
26986 which clients can send email. This is more powerful than the
26987 &%smtp_ratelimit_*%& options, because those options control the rate of
26988 commands in a single SMTP session only, whereas the &%ratelimit%& condition
26989 works across all connections (concurrent and sequential) from the same client
26990 host. The syntax of the &%ratelimit%& condition is:
26992 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
26994 If the average client sending rate is less than &'m'& messages per time
26995 period &'p'& then the condition is false; otherwise it is true.
26997 As a side-effect, the &%ratelimit%& condition sets the expansion variable
26998 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
26999 configured value of &'m'&, and &$sender_rate_period$& to the configured value
27002 The parameter &'p'& is the smoothing time constant, in the form of an Exim
27003 time interval, for example, &`8h`& for eight hours. A larger time constant
27004 means that it takes Exim longer to forget a client's past behaviour. The
27005 parameter &'m'& is the maximum number of messages that a client is permitted to
27006 send in each time interval. It also specifies the number of messages permitted
27007 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
27008 constant, you can allow a client to send more messages in a burst without
27009 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
27010 both small, messages must be sent at an even rate.
27012 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
27013 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
27014 when deploying the &%ratelimit%& ACL condition. The script prints usage
27015 instructions when it is run with no arguments.
27017 The key is used to look up the data for calculating the client's average
27018 sending rate. This data is stored in Exim's spool directory, alongside the
27019 retry and other hints databases. The default key is &$sender_host_address$&,
27020 which means Exim computes the sending rate of each client host IP address.
27021 By changing the key you can change how Exim identifies clients for the purpose
27022 of ratelimiting. For example, to limit the sending rate of each authenticated
27023 user, independent of the computer they are sending from, set the key to
27024 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
27025 example, &$authenticated_id$& is only meaningful if the client has
27026 authenticated (which you can check with the &%authenticated%& ACL condition).
27028 The lookup key does not have to identify clients: If you want to limit the
27029 rate at which a recipient receives messages, you can use the key
27030 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
27033 Internally, Exim appends the smoothing constant &'p'& and the options onto the
27034 lookup key because they alter the meaning of the stored data. This is not true
27035 for the limit &'m'&, so you can alter the configured maximum rate and Exim will
27036 still remember clients' past behaviour, but if you alter the other ratelimit
27037 parameters Exim forgets past behaviour.
27039 Each &%ratelimit%& condition can have up to three options. One option
27040 specifies what Exim measures the rate of, and the second specifies how Exim
27041 handles excessively fast clients. The third option can be &`noupdate`&, to
27042 disable updating of the ratelimiting database (see section &<<rearatdat>>&).
27043 The options are separated by a slash, like the other parameters. They may
27044 appear in any order.
27046 .section "Ratelimit options for what is being measured" "ratoptmea"
27047 The &%per_conn%& option limits the client's connection rate.
27049 The &%per_mail%& option limits the client's rate of sending messages. This is
27050 the default if none of the &%per_*%& options is specified.
27052 The &%per_byte%& option limits the sender's email bandwidth. Note that it is
27053 best to use this option in the DATA ACL; if it is used in an earlier ACL it
27054 relies on the SIZE parameter specified by the client in its MAIL command,
27055 which may be inaccurate or completely missing. You can follow the limit &'m'&
27056 in the configuration with K, M, or G to specify limits in kilobytes,
27057 megabytes, or gigabytes, respectively.
27059 The &%per_rcpt%& option causes Exim to limit the rate at which
27060 recipients are accepted. To be effective, it would need to be used in
27061 either the &%acl_smtp_rcpt%& or the &%acl_not_smtp%& ACL. In the
27062 &%acl_smtp_rcpt%& ACL, the number of recipients is incremented by one.
27063 In the case of a locally submitted message in the &%acl_not_smtp%& ACL,
27064 the number of recipients is incremented by the &%$recipients_count%&
27065 for the entire message. Note that in either case the rate limiting
27066 engine will see a message with many recipients as a large high-speed
27069 The &%per_cmd%& option causes Exim to recompute the rate every time the
27070 condition is processed. This can be used to limit the SMTP command rate.
27071 This command is essentially an alias of &%per_rcpt%& to make it clear
27072 that the effect is to limit the rate at which individual commands,
27073 rather than recipients, are accepted.
27075 .section "Ratelimit options for handling fast clients" "ratophanfas"
27076 If a client's average rate is greater than the maximum, the rate limiting
27077 engine can react in two possible ways, depending on the presence of the
27078 &%strict%& or &%leaky%& options. This is independent of the other
27079 counter-measures (such as rejecting the message) that may be specified by the
27080 rest of the ACL. The default mode is leaky, which avoids a sender's
27081 over-aggressive retry rate preventing it from getting any email through.
27083 The &%strict%& option means that the client's recorded rate is always
27084 updated. The effect of this is that Exim measures the client's average rate
27085 of attempts to send email, which can be much higher than the maximum it is
27086 actually allowed. If the client is over the limit it may be subjected to
27087 counter-measures by the ACL until it slows down below the maximum rate. If
27088 the client stops attempting to send email for the time specified in the &'p'&
27089 parameter then its computed rate will decay exponentially to 37% of its peak
27090 value. You can work out the time (the number of smoothing periods) that a
27091 client is subjected to counter-measures after an over-limit burst with this
27094 ln(peakrate/maxrate)
27096 The &%leaky%& (default) option means that the client's recorded rate is not
27097 updated if it is above the limit. The effect of this is that Exim measures the
27098 client's average rate of successfully sent email, which cannot be greater than
27099 the maximum allowed. If the client is over the limit it may suffer some
27100 counter-measures (as specified in the ACL), but it will still be able to send
27101 email at the configured maximum rate, whatever the rate of its attempts. This
27102 is generally the better choice if you have clients that retry automatically.
27104 .section "Using rate limiting" "useratlim"
27105 Exim's other ACL facilities are used to define what counter-measures are taken
27106 when the rate limit is exceeded. This might be anything from logging a warning
27107 (for example, while measuring existing sending rates in order to define
27108 policy), through time delays to slow down fast senders, up to rejecting the
27109 message. For example:
27111 # Log all senders' rates
27112 warn ratelimit = 0 / 1h / strict
27113 log_message = Sender rate $sender_rate / $sender_rate_period
27115 # Slow down fast senders; note the need to truncate $sender_rate
27116 # at the decimal point.
27117 warn ratelimit = 100 / 1h / per_rcpt / strict
27118 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
27119 $sender_rate_limit }s
27121 # Keep authenticated users under control
27122 deny authenticated = *
27123 ratelimit = 100 / 1d / strict / $authenticated_id
27125 # System-wide rate limit
27126 defer message = Sorry, too busy. Try again later.
27127 ratelimit = 10 / 1s / $primary_hostname
27129 # Restrict incoming rate from each host, with a default
27130 # set using a macro and special cases looked up in a table.
27131 defer message = Sender rate exceeds $sender_rate_limit \
27132 messages per $sender_rate_period
27133 ratelimit = ${lookup {$sender_host_address} \
27134 cdb {DB/ratelimits.cdb} \
27135 {$value} {RATELIMIT} }
27137 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
27138 especially with the &%per_rcpt%& option, you may suffer from a performance
27139 bottleneck caused by locking on the ratelimit hints database. Apart from
27140 making your ACLs less complicated, you can reduce the problem by using a
27141 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
27142 this means that Exim will lose its hints data after a reboot (including retry
27143 hints, the callout cache, and ratelimit data).
27146 .section "Reading ratelimit data without updating" "rearatdat"
27147 .cindex "rate limitint" "reading data without updating"
27148 If the &%noupdate%& option is present on a &%ratelimit%& ACL condition, Exim
27149 computes the rate and checks the limit as normal, but it does not update the
27150 saved data. This means that, in relevant ACLs, it is possible to lookup the
27151 existence of a specified (or auto-generated) ratelimit key without incrementing
27152 the ratelimit counter for that key. In order for this to be useful, another ACL
27153 entry must set the rate for the same key (otherwise it will always be zero).
27157 deny ratelimit = 100 / 5m / strict / per_cmd / noupdate
27158 log_message = RATE: $sender_rate/$sender_rate_period \
27159 (max $sender_rate_limit)
27162 &'... some other logic and tests...'&
27166 warn ratelimit = 100 / 5m / strict / per_cmd
27167 condition = ${if le{$sender_rate}{$sender_rate_limit}}
27168 logwrite = RATE UPDATE: $sender_rate/$sender_rate_period \
27169 (max $sender_rate_limit)
27171 In this example, the rate is tested and used to deny access (when it is too
27172 high) in the connect ACL, but the actual computation of the remembered rate
27173 happens later, on a per-command basis, in another ACL.
27177 .section "Address verification" "SECTaddressverification"
27178 .cindex "verifying address" "options for"
27179 .cindex "policy control" "address verification"
27180 Several of the &%verify%& conditions described in section
27181 &<<SECTaclconditions>>& cause addresses to be verified. Section
27182 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
27183 The verification conditions can be followed by options that modify the
27184 verification process. The options are separated from the keyword and from each
27185 other by slashes, and some of them contain parameters. For example:
27187 verify = sender/callout
27188 verify = recipient/defer_ok/callout=10s,defer_ok
27190 The first stage of address verification, which always happens, is to run the
27191 address through the routers, in &"verify mode"&. Routers can detect the
27192 difference between verification and routing for delivery, and their actions can
27193 be varied by a number of generic options such as &%verify%& and &%verify_only%&
27194 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
27195 The available options are as follows:
27198 If the &%callout%& option is specified, successful routing to one or more
27199 remote hosts is followed by a &"callout"& to those hosts as an additional
27200 check. Callouts and their sub-options are discussed in the next section.
27202 If there is a defer error while doing verification routing, the ACL
27203 normally returns &"defer"&. However, if you include &%defer_ok%& in the
27204 options, the condition is forced to be true instead. Note that this is a main
27205 verification option as well as a suboption for callouts.
27207 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
27208 discusses the reporting of sender address verification failures.
27210 The &%success_on_redirect%& option causes verification always to succeed
27211 immediately after a successful redirection. By default, if a redirection
27212 generates just one address, that address is also verified. See further
27213 discussion in section &<<SECTredirwhilveri>>&.
27216 .cindex "verifying address" "differentiating failures"
27217 .vindex "&$recipient_verify_failure$&"
27218 .vindex "&$sender_verify_failure$&"
27219 .vindex "&$acl_verify_message$&"
27220 After an address verification failure, &$acl_verify_message$& contains the
27221 error message that is associated with the failure. It can be preserved by
27224 warn !verify = sender
27225 set acl_m0 = $acl_verify_message
27227 If you are writing your own custom rejection message or log message when
27228 denying access, you can use this variable to include information about the
27229 verification failure.
27231 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
27232 appropriate) contains one of the following words:
27235 &%qualify%&: The address was unqualified (no domain), and the message
27236 was neither local nor came from an exempted host.
27238 &%route%&: Routing failed.
27240 &%mail%&: Routing succeeded, and a callout was attempted; rejection
27241 occurred at or before the MAIL command (that is, on initial
27242 connection, HELO, or MAIL).
27244 &%recipient%&: The RCPT command in a callout was rejected.
27246 &%postmaster%&: The postmaster check in a callout was rejected.
27249 The main use of these variables is expected to be to distinguish between
27250 rejections of MAIL and rejections of RCPT in callouts.
27255 .section "Callout verification" "SECTcallver"
27256 .cindex "verifying address" "by callout"
27257 .cindex "callout" "verification"
27258 .cindex "SMTP" "callout verification"
27259 For non-local addresses, routing verifies the domain, but is unable to do any
27260 checking of the local part. There are situations where some means of verifying
27261 the local part is desirable. One way this can be done is to make an SMTP
27262 &'callback'& to a delivery host for the sender address or a &'callforward'& to
27263 a subsequent host for a recipient address, to see if the host accepts the
27264 address. We use the term &'callout'& to cover both cases. Note that for a
27265 sender address, the callback is not to the client host that is trying to
27266 deliver the message, but to one of the hosts that accepts incoming mail for the
27269 Exim does not do callouts by default. If you want them to happen, you must
27270 request them by setting appropriate options on the &%verify%& condition, as
27271 described below. This facility should be used with care, because it can add a
27272 lot of resource usage to the cost of verifying an address. However, Exim does
27273 cache the results of callouts, which helps to reduce the cost. Details of
27274 caching are in section &<<SECTcallvercache>>&.
27276 Recipient callouts are usually used only between hosts that are controlled by
27277 the same administration. For example, a corporate gateway host could use
27278 callouts to check for valid recipients on an internal mailserver. A successful
27279 callout does not guarantee that a real delivery to the address would succeed;
27280 on the other hand, a failing callout does guarantee that a delivery would fail.
27282 If the &%callout%& option is present on a condition that verifies an address, a
27283 second stage of verification occurs if the address is successfully routed to
27284 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
27285 &(manualroute)& router, where the router specifies the hosts. However, if a
27286 router that does not set up hosts routes to an &(smtp)& transport with a
27287 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
27288 &%hosts_override%& set, its hosts are always used, whether or not the router
27289 supplies a host list.
27291 The port that is used is taken from the transport, if it is specified and is a
27292 remote transport. (For routers that do verification only, no transport need be
27293 specified.) Otherwise, the default SMTP port is used. If a remote transport
27294 specifies an outgoing interface, this is used; otherwise the interface is not
27295 specified. Likewise, the text that is used for the HELO command is taken from
27296 the transport's &%helo_data%& option; if there is no transport, the value of
27297 &$smtp_active_hostname$& is used.
27299 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
27300 test whether a bounce message could be delivered to the sender address. The
27301 following SMTP commands are sent:
27303 &`HELO `&<&'local host name'&>
27305 &`RCPT TO:`&<&'the address to be tested'&>
27308 LHLO is used instead of HELO if the transport's &%protocol%& option is
27311 A recipient callout check is similar. By default, it also uses an empty address
27312 for the sender. This default is chosen because most hosts do not make use of
27313 the sender address when verifying a recipient. Using the same address means
27314 that a single cache entry can be used for each recipient. Some sites, however,
27315 do make use of the sender address when verifying. These are catered for by the
27316 &%use_sender%& and &%use_postmaster%& options, described in the next section.
27318 If the response to the RCPT command is a 2&'xx'& code, the verification
27319 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
27320 Exim tries the next host, if any. If there is a problem with all the remote
27321 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
27322 &%callout%& option is given, in which case the condition is forced to succeed.
27324 .cindex "SMTP" "output flushing, disabling for callout"
27325 A callout may take a little time. For this reason, Exim normally flushes SMTP
27326 output before performing a callout in an ACL, to avoid unexpected timeouts in
27327 clients when the SMTP PIPELINING extension is in use. The flushing can be
27328 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
27333 .section "Additional parameters for callouts" "CALLaddparcall"
27334 .cindex "callout" "additional parameters for"
27335 The &%callout%& option can be followed by an equals sign and a number of
27336 optional parameters, separated by commas. For example:
27338 verify = recipient/callout=10s,defer_ok
27340 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
27341 separate verify options, is retained for backwards compatibility, but is now
27342 deprecated. The additional parameters for &%callout%& are as follows:
27346 .vitem <&'a&~time&~interval'&>
27347 .cindex "callout" "timeout, specifying"
27348 This specifies the timeout that applies for the callout attempt to each host.
27351 verify = sender/callout=5s
27353 The default is 30 seconds. The timeout is used for each response from the
27354 remote host. It is also used for the initial connection, unless overridden by
27355 the &%connect%& parameter.
27358 .vitem &*connect&~=&~*&<&'time&~interval'&>
27359 .cindex "callout" "connection timeout, specifying"
27360 This parameter makes it possible to set a different (usually smaller) timeout
27361 for making the SMTP connection. For example:
27363 verify = sender/callout=5s,connect=1s
27365 If not specified, this timeout defaults to the general timeout value.
27367 .vitem &*defer_ok*&
27368 .cindex "callout" "defer, action on"
27369 When this parameter is present, failure to contact any host, or any other kind
27370 of temporary error, is treated as success by the ACL. However, the cache is not
27371 updated in this circumstance.
27373 .vitem &*fullpostmaster*&
27374 .cindex "callout" "full postmaster check"
27375 This operates like the &%postmaster%& option (see below), but if the check for
27376 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
27377 accordance with the specification in RFC 2821. The RFC states that the
27378 unqualified address &'postmaster'& should be accepted.
27381 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
27382 .cindex "callout" "sender when verifying header"
27383 When verifying addresses in header lines using the &%header_sender%&
27384 verification option, Exim behaves by default as if the addresses are envelope
27385 sender addresses from a message. Callout verification therefore tests to see
27386 whether a bounce message could be delivered, by using an empty address in the
27387 MAIL command. However, it is arguable that these addresses might never be used
27388 as envelope senders, and could therefore justifiably reject bounce messages
27389 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
27390 address to use in the MAIL command. For example:
27392 require verify = header_sender/callout=mailfrom=abcd@x.y.z
27394 This parameter is available only for the &%header_sender%& verification option.
27397 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
27398 .cindex "callout" "overall timeout, specifying"
27399 This parameter sets an overall timeout for performing a callout verification.
27402 verify = sender/callout=5s,maxwait=30s
27404 This timeout defaults to four times the callout timeout for individual SMTP
27405 commands. The overall timeout applies when there is more than one host that can
27406 be tried. The timeout is checked before trying the next host. This prevents
27407 very long delays if there are a large number of hosts and all are timing out
27408 (for example, when network connections are timing out).
27411 .vitem &*no_cache*&
27412 .cindex "callout" "cache, suppressing"
27413 .cindex "caching callout, suppressing"
27414 When this parameter is given, the callout cache is neither read nor updated.
27416 .vitem &*postmaster*&
27417 .cindex "callout" "postmaster; checking"
27418 When this parameter is set, a successful callout check is followed by a similar
27419 check for the local part &'postmaster'& at the same domain. If this address is
27420 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
27421 the postmaster check is recorded in a cache record; if it is a failure, this is
27422 used to fail subsequent callouts for the domain without a connection being
27423 made, until the cache record expires.
27425 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
27426 The postmaster check uses an empty sender in the MAIL command by default.
27427 You can use this parameter to do a postmaster check using a different address.
27430 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
27432 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
27433 one overrides. The &%postmaster%& parameter is equivalent to this example:
27435 require verify = sender/callout=postmaster_mailfrom=
27437 &*Warning*&: The caching arrangements for postmaster checking do not take
27438 account of the sender address. It is assumed that either the empty address or
27439 a fixed non-empty address will be used. All that Exim remembers is that the
27440 postmaster check for the domain succeeded or failed.
27444 .cindex "callout" "&""random""& check"
27445 When this parameter is set, before doing the normal callout check, Exim does a
27446 check for a &"random"& local part at the same domain. The local part is not
27447 really random &-- it is defined by the expansion of the option
27448 &%callout_random_local_part%&, which defaults to
27450 $primary_host_name-$tod_epoch-testing
27452 The idea here is to try to determine whether the remote host accepts all local
27453 parts without checking. If it does, there is no point in doing callouts for
27454 specific local parts. If the &"random"& check succeeds, the result is saved in
27455 a cache record, and used to force the current and subsequent callout checks to
27456 succeed without a connection being made, until the cache record expires.
27458 .vitem &*use_postmaster*&
27459 .cindex "callout" "sender for recipient check"
27460 This parameter applies to recipient callouts only. For example:
27462 deny !verify = recipient/callout=use_postmaster
27464 .vindex "&$qualify_domain$&"
27465 It causes a non-empty postmaster address to be used in the MAIL command when
27466 performing the callout for the recipient, and also for a &"random"& check if
27467 that is configured. The local part of the address is &`postmaster`& and the
27468 domain is the contents of &$qualify_domain$&.
27470 .vitem &*use_sender*&
27471 This option applies to recipient callouts only. For example:
27473 require verify = recipient/callout=use_sender
27475 It causes the message's actual sender address to be used in the MAIL
27476 command when performing the callout, instead of an empty address. There is no
27477 need to use this option unless you know that the called hosts make use of the
27478 sender when checking recipients. If used indiscriminately, it reduces the
27479 usefulness of callout caching.
27482 If you use any of the parameters that set a non-empty sender for the MAIL
27483 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
27484 &%use_sender%&), you should think about possible loops. Recipient checking is
27485 usually done between two hosts that are under the same management, and the host
27486 that receives the callouts is not normally configured to do callouts itself.
27487 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
27488 these circumstances.
27490 However, if you use a non-empty sender address for a callout to an arbitrary
27491 host, there is the likelihood that the remote host will itself initiate a
27492 callout check back to your host. As it is checking what appears to be a message
27493 sender, it is likely to use an empty address in MAIL, thus avoiding a
27494 callout loop. However, to be on the safe side it would be best to set up your
27495 own ACLs so that they do not do sender verification checks when the recipient
27496 is the address you use for header sender or postmaster callout checking.
27498 Another issue to think about when using non-empty senders for callouts is
27499 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
27500 by the sender/recipient combination; thus, for any given recipient, many more
27501 actual callouts are performed than when an empty sender or postmaster is used.
27506 .section "Callout caching" "SECTcallvercache"
27507 .cindex "hints database" "callout cache"
27508 .cindex "callout" "cache, description of"
27509 .cindex "caching" "callout"
27510 Exim caches the results of callouts in order to reduce the amount of resources
27511 used, unless you specify the &%no_cache%& parameter with the &%callout%&
27512 option. A hints database called &"callout"& is used for the cache. Two
27513 different record types are used: one records the result of a callout check for
27514 a specific address, and the other records information that applies to the
27515 entire domain (for example, that it accepts the local part &'postmaster'&).
27517 When an original callout fails, a detailed SMTP error message is given about
27518 the failure. However, for subsequent failures use the cache data, this message
27521 The expiry times for negative and positive address cache records are
27522 independent, and can be set by the global options &%callout_negative_expire%&
27523 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
27525 If a host gives a negative response to an SMTP connection, or rejects any
27526 commands up to and including
27530 (but not including the MAIL command with a non-empty address),
27531 any callout attempt is bound to fail. Exim remembers such failures in a
27532 domain cache record, which it uses to fail callouts for the domain without
27533 making new connections, until the domain record times out. There are two
27534 separate expiry times for domain cache records:
27535 &%callout_domain_negative_expire%& (default 3h) and
27536 &%callout_domain_positive_expire%& (default 7d).
27538 Domain records expire when the negative expiry time is reached if callouts
27539 cannot be made for the domain, or if the postmaster check failed.
27540 Otherwise, they expire when the positive expiry time is reached. This
27541 ensures that, for example, a host that stops accepting &"random"& local parts
27542 will eventually be noticed.
27544 The callout caching mechanism is based on the domain of the address that is
27545 being tested. If the domain routes to several hosts, it is assumed that their
27546 behaviour will be the same.
27550 .section "Sender address verification reporting" "SECTsenaddver"
27551 .cindex "verifying" "suppressing error details"
27552 See section &<<SECTaddressverification>>& for a general discussion of
27553 verification. When sender verification fails in an ACL, the details of the
27554 failure are given as additional output lines before the 550 response to the
27555 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
27558 MAIL FROM:<xyz@abc.example>
27560 RCPT TO:<pqr@def.example>
27561 550-Verification failed for <xyz@abc.example>
27562 550-Called: 192.168.34.43
27563 550-Sent: RCPT TO:<xyz@abc.example>
27564 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
27565 550 Sender verification failed
27567 If more than one RCPT command fails in the same way, the details are given
27568 only for the first of them. However, some administrators do not want to send
27569 out this much information. You can suppress the details by adding
27570 &`/no_details`& to the ACL statement that requests sender verification. For
27573 verify = sender/no_details
27576 .section "Redirection while verifying" "SECTredirwhilveri"
27577 .cindex "verifying" "redirection while"
27578 .cindex "address redirection" "while verifying"
27579 A dilemma arises when a local address is redirected by aliasing or forwarding
27580 during verification: should the generated addresses themselves be verified,
27581 or should the successful expansion of the original address be enough to verify
27582 it? By default, Exim takes the following pragmatic approach:
27585 When an incoming address is redirected to just one child address, verification
27586 continues with the child address, and if that fails to verify, the original
27587 verification also fails.
27589 When an incoming address is redirected to more than one child address,
27590 verification does not continue. A success result is returned.
27593 This seems the most reasonable behaviour for the common use of aliasing as a
27594 way of redirecting different local parts to the same mailbox. It means, for
27595 example, that a pair of alias entries of the form
27598 aw123: :fail: Gone away, no forwarding address
27600 work as expected, with both local parts causing verification failure. When a
27601 redirection generates more than one address, the behaviour is more like a
27602 mailing list, where the existence of the alias itself is sufficient for
27603 verification to succeed.
27605 It is possible, however, to change the default behaviour so that all successful
27606 redirections count as successful verifications, however many new addresses are
27607 generated. This is specified by the &%success_on_redirect%& verification
27608 option. For example:
27610 require verify = recipient/success_on_redirect/callout=10s
27612 In this example, verification succeeds if a router generates a new address, and
27613 the callout does not occur, because no address was routed to a remote host.
27615 When verification is being tested via the &%-bv%& option, the treatment of
27616 redirections is as just described, unless the &%-v%& or any debugging option is
27617 also specified. In that case, full verification is done for every generated
27618 address and a report is output for each of them.
27622 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
27623 .cindex "CSA" "verifying"
27624 Client SMTP Authorization is a system that allows a site to advertise
27625 which machines are and are not permitted to send email. This is done by placing
27626 special SRV records in the DNS; these are looked up using the client's HELO
27627 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
27628 Authorization checks in Exim are performed by the ACL condition:
27632 This fails if the client is not authorized. If there is a DNS problem, or if no
27633 valid CSA SRV record is found, or if the client is authorized, the condition
27634 succeeds. These three cases can be distinguished using the expansion variable
27635 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
27636 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
27637 be likely to cause problems for legitimate email.
27639 The error messages produced by the CSA code include slightly more
27640 detail. If &$csa_status$& is &"defer"&, this may be because of problems
27641 looking up the CSA SRV record, or problems looking up the CSA target
27642 address record. There are four reasons for &$csa_status$& being &"fail"&:
27645 The client's host name is explicitly not authorized.
27647 The client's IP address does not match any of the CSA target IP addresses.
27649 The client's host name is authorized but it has no valid target IP addresses
27650 (for example, the target's addresses are IPv6 and the client is using IPv4).
27652 The client's host name has no CSA SRV record but a parent domain has asserted
27653 that all subdomains must be explicitly authorized.
27656 The &%csa%& verification condition can take an argument which is the domain to
27657 use for the DNS query. The default is:
27659 verify = csa/$sender_helo_name
27661 This implementation includes an extension to CSA. If the query domain
27662 is an address literal such as [192.0.2.95], or if it is a bare IP
27663 address, Exim searches for CSA SRV records in the reverse DNS as if
27664 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
27667 verify = csa/$sender_host_address
27669 In fact, this is the check that Exim performs if the client does not say HELO.
27670 This extension can be turned off by setting the main configuration option
27671 &%dns_csa_use_reverse%& to be false.
27673 If a CSA SRV record is not found for the domain itself, a search
27674 is performed through its parent domains for a record which might be
27675 making assertions about subdomains. The maximum depth of this search is limited
27676 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
27677 default. Exim does not look for CSA SRV records in a top level domain, so the
27678 default settings handle HELO domains as long as seven
27679 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
27680 of legitimate HELO domains.
27682 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
27683 direct SRV lookups, this is not sufficient because of the extra parent domain
27684 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
27685 addresses into lookups in the reverse DNS space. The result of a successful
27688 ${lookup dnsdb {csa=$sender_helo_name}}
27690 has two space-separated fields: an authorization code and a target host name.
27691 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
27692 authorization required but absent, or &"?"& for unknown.
27697 .section "Bounce address tag validation" "SECTverifyPRVS"
27698 .cindex "BATV, verifying"
27699 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
27700 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
27701 Genuine incoming bounce messages should therefore always be addressed to
27702 recipients that have a valid tag. This scheme is a way of detecting unwanted
27703 bounce messages caused by sender address forgeries (often called &"collateral
27704 spam"&), because the recipients of such messages do not include valid tags.
27706 There are two expansion items to help with the implementation of the BATV
27707 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
27708 the original envelope sender address by using a simple key to add a hash of the
27709 address and some time-based randomizing information. The &%prvs%& expansion
27710 item creates a signed address, and the &%prvscheck%& expansion item checks one.
27711 The syntax of these expansion items is described in section
27712 &<<SECTexpansionitems>>&.
27714 As an example, suppose the secret per-address keys are stored in an MySQL
27715 database. A query to look up the key for an address could be defined as a macro
27718 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
27719 WHERE sender='${quote_mysql:$prvscheck_address}'\
27722 Suppose also that the senders who make use of BATV are defined by an address
27723 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
27726 # Bounces: drop unsigned addresses for BATV senders
27727 deny message = This address does not send an unsigned reverse path
27729 recipients = +batv_senders
27731 # Bounces: In case of prvs-signed address, check signature.
27732 deny message = Invalid reverse path signature.
27734 condition = ${prvscheck {$local_part@$domain}\
27735 {PRVSCHECK_SQL}{1}}
27736 !condition = $prvscheck_result
27738 The first statement rejects recipients for bounce messages that are addressed
27739 to plain BATV sender addresses, because it is known that BATV senders do not
27740 send out messages with plain sender addresses. The second statement rejects
27741 recipients that are prvs-signed, but with invalid signatures (either because
27742 the key is wrong, or the signature has timed out).
27744 A non-prvs-signed address is not rejected by the second statement, because the
27745 &%prvscheck%& expansion yields an empty string if its first argument is not a
27746 prvs-signed address, thus causing the &%condition%& condition to be false. If
27747 the first argument is a syntactically valid prvs-signed address, the yield is
27748 the third string (in this case &"1"&), whether or not the cryptographic and
27749 timeout checks succeed. The &$prvscheck_result$& variable contains the result
27750 of the checks (empty for failure, &"1"& for success).
27752 There is one more issue you must consider when implementing prvs-signing:
27753 you have to ensure that the routers accept prvs-signed addresses and
27754 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
27755 router to remove the signature with a configuration along these lines:
27759 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
27761 This works because, if the third argument of &%prvscheck%& is empty, the result
27762 of the expansion of a prvs-signed address is the decoded value of the original
27763 address. This router should probably be the first of your routers that handles
27766 To create BATV-signed addresses in the first place, a transport of this form
27769 external_smtp_batv:
27771 return_path = ${prvs {$return_path} \
27772 {${lookup mysql{SELECT \
27773 secret FROM batv_prvs WHERE \
27774 sender='${quote_mysql:$sender_address}'} \
27777 If no key can be found for the existing return path, no signing takes place.
27781 .section "Using an ACL to control relaying" "SECTrelaycontrol"
27782 .cindex "&ACL;" "relay control"
27783 .cindex "relaying" "control by ACL"
27784 .cindex "policy control" "relay control"
27785 An MTA is said to &'relay'& a message if it receives it from some host and
27786 delivers it directly to another host as a result of a remote address contained
27787 within it. Redirecting a local address via an alias or forward file and then
27788 passing the message on to another host is not relaying,
27789 .cindex "&""percent hack""&"
27790 but a redirection as a result of the &"percent hack"& is.
27792 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
27793 A host which is acting as a gateway or an MX backup is concerned with incoming
27794 relaying from arbitrary hosts to a specific set of domains. On the other hand,
27795 a host which is acting as a smart host for a number of clients is concerned
27796 with outgoing relaying from those clients to the Internet at large. Often the
27797 same host is fulfilling both functions,
27799 . as illustrated in the diagram below,
27801 but in principle these two kinds of relaying are entirely independent. What is
27802 not wanted is the transmission of mail from arbitrary remote hosts through your
27803 system to arbitrary domains.
27806 You can implement relay control by means of suitable statements in the ACL that
27807 runs for each RCPT command. For convenience, it is often easiest to use
27808 Exim's named list facility to define the domains and hosts involved. For
27809 example, suppose you want to do the following:
27812 Deliver a number of domains to mailboxes on the local host (or process them
27813 locally in some other way). Let's say these are &'my.dom1.example'& and
27814 &'my.dom2.example'&.
27816 Relay mail for a number of other domains for which you are the secondary MX.
27817 These might be &'friend1.example'& and &'friend2.example'&.
27819 Relay mail from the hosts on your local LAN, to whatever domains are involved.
27820 Suppose your LAN is 192.168.45.0/24.
27824 In the main part of the configuration, you put the following definitions:
27826 domainlist local_domains = my.dom1.example : my.dom2.example
27827 domainlist relay_domains = friend1.example : friend2.example
27828 hostlist relay_hosts = 192.168.45.0/24
27830 Now you can use these definitions in the ACL that is run for every RCPT
27834 accept domains = +local_domains : +relay_domains
27835 accept hosts = +relay_hosts
27837 The first statement accepts any RCPT command that contains an address in
27838 the local or relay domains. For any other domain, control passes to the second
27839 statement, which accepts the command only if it comes from one of the relay
27840 hosts. In practice, you will probably want to make your ACL more sophisticated
27841 than this, for example, by including sender and recipient verification. The
27842 default configuration includes a more comprehensive example, which is described
27843 in chapter &<<CHAPdefconfil>>&.
27847 .section "Checking a relay configuration" "SECTcheralcon"
27848 .cindex "relaying" "checking control of"
27849 You can check the relay characteristics of your configuration in the same way
27850 that you can test any ACL behaviour for an incoming SMTP connection, by using
27851 the &%-bh%& option to run a fake SMTP session with which you interact.
27853 For specifically testing for unwanted relaying, the host
27854 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
27855 host from the host on which Exim is running, using the normal telnet port, you
27856 will see a normal telnet connection message and then quite a long delay. Be
27857 patient. The remote host is making an SMTP connection back to your host, and
27858 trying a number of common probes to test for open relay vulnerability. The
27859 results of the tests will eventually appear on your terminal.
27864 . ////////////////////////////////////////////////////////////////////////////
27865 . ////////////////////////////////////////////////////////////////////////////
27867 .chapter "Content scanning at ACL time" "CHAPexiscan"
27868 .scindex IIDcosca "content scanning" "at ACL time"
27869 The extension of Exim to include content scanning at ACL time, formerly known
27870 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
27871 was integrated into the main source for Exim release 4.50, and Tom continues to
27872 maintain it. Most of the wording of this chapter is taken from Tom's
27875 It is also possible to scan the content of messages at other times. The
27876 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
27877 scanning after all the ACLs have run. A transport filter can be used to scan
27878 messages at delivery time (see the &%transport_filter%& option, described in
27879 chapter &<<CHAPtransportgeneric>>&).
27881 If you want to include the ACL-time content-scanning features when you compile
27882 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
27883 &_Local/Makefile_&. When you do that, the Exim binary is built with:
27886 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
27887 for all MIME parts for SMTP and non-SMTP messages, respectively.
27889 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
27890 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
27891 run at the end of message reception (the &%acl_smtp_data%& ACL).
27893 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
27894 of messages, or parts of messages, for debugging purposes.
27896 Additional expansion variables that are set in the new ACL and by the new
27899 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
27902 There is another content-scanning configuration option for &_Local/Makefile_&,
27903 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
27904 condition is compiled, in addition to all the other content-scanning features.
27906 Content-scanning is continually evolving, and new features are still being
27907 added. While such features are still unstable and liable to incompatible
27908 changes, they are made available in Exim by setting options whose names begin
27909 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
27910 this manual. You can find out about them by reading the file called
27911 &_doc/experimental.txt_&.
27913 All the content-scanning facilities work on a MBOX copy of the message that is
27914 temporarily created in a file called:
27916 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
27918 The &_.eml_& extension is a friendly hint to virus scanners that they can
27919 expect an MBOX-like structure inside that file. The file is created when the
27920 first content scanning facility is called. Subsequent calls to content
27921 scanning conditions open the same file again. The directory is recursively
27922 removed when the &%acl_smtp_data%& ACL has finished running, unless
27924 control = no_mbox_unspool
27926 has been encountered. When the MIME ACL decodes files, they are put into the
27927 same directory by default.
27931 .section "Scanning for viruses" "SECTscanvirus"
27932 .cindex "virus scanning"
27933 .cindex "content scanning" "for viruses"
27934 .cindex "content scanning" "the &%malware%& condition"
27935 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
27936 It supports a &"generic"& interface to scanners called via the shell, and
27937 specialized interfaces for &"daemon"& type virus scanners, which are resident
27938 in memory and thus are much faster.
27940 .oindex "&%av_scanner%&"
27941 You can set the &%av_scanner%& option in first part of the Exim configuration
27942 file to specify which scanner to use, together with any additional options that
27943 are needed. The basic syntax is as follows:
27945 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
27947 If you do not set &%av_scanner%&, it defaults to
27949 av_scanner = sophie:/var/run/sophie
27951 If the value of &%av_scanner%& starts with a dollar character, it is expanded
27952 before use. The following scanner types are supported in this release:
27955 .vitem &%aveserver%&
27956 .cindex "virus scanners" "Kaspersky"
27957 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
27958 at &url(http://www.kaspersky.com). This scanner type takes one option,
27959 which is the path to the daemon's UNIX socket. The default is shown in this
27962 av_scanner = aveserver:/var/run/aveserver
27966 .cindex "virus scanners" "clamd"
27967 This daemon-type scanner is GPL and free. You can get it at
27968 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
27969 unpack MIME containers, so it used to be recommended to unpack MIME attachments
27970 in the MIME ACL. This no longer believed to be necessary. One option is
27971 required: either the path and name of a UNIX socket file, or a hostname or IP
27972 number, and a port, separated by space, as in the second of these examples:
27974 av_scanner = clamd:/opt/clamd/socket
27975 av_scanner = clamd:192.0.2.3 1234
27976 av_scanner = clamd:192.0.2.3 1234:local
27978 If the value of av_scanner points to a UNIX socket file or contains the local
27979 keyword, then the ClamAV interface will pass a filename containing the data
27980 to be scanned, which will should normally result in less I/O happening and be
27981 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
27982 Exim does not assume that there is a common filesystem with the remote host.
27983 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
27984 you be running a version of ClamAV prior to 0.95.
27985 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
27986 contributing the code for this scanner.
27989 .cindex "virus scanners" "command line interface"
27990 This is the keyword for the generic command line scanner interface. It can be
27991 used to attach virus scanners that are invoked from the shell. This scanner
27992 type takes 3 mandatory options:
27995 The full path and name of the scanner binary, with all command line options,
27996 and a placeholder (&`%s`&) for the directory to scan.
27999 A regular expression to match against the STDOUT and STDERR output of the
28000 virus scanner. If the expression matches, a virus was found. You must make
28001 absolutely sure that this expression matches on &"virus found"&. This is called
28002 the &"trigger"& expression.
28005 Another regular expression, containing exactly one pair of parentheses, to
28006 match the name of the virus found in the scanners output. This is called the
28007 &"name"& expression.
28010 For example, Sophos Sweep reports a virus on a line like this:
28012 Virus 'W32/Magistr-B' found in file ./those.bat
28014 For the trigger expression, we can match the phrase &"found in file"&. For the
28015 name expression, we want to extract the W32/Magistr-B string, so we can match
28016 for the single quotes left and right of it. Altogether, this makes the
28017 configuration setting:
28019 av_scanner = cmdline:\
28020 /path/to/sweep -ss -all -rec -archive %s:\
28021 found in file:'(.+)'
28024 .cindex "virus scanners" "DrWeb"
28025 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
28026 argument, either a full path to a UNIX socket, or an IP address and port
28027 separated by white space, as in these examples:
28029 av_scanner = drweb:/var/run/drwebd.sock
28030 av_scanner = drweb:192.168.2.20 31337
28032 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
28033 is used. Thanks to Alex Miller for contributing the code for this scanner.
28036 .cindex "virus scanners" "F-Secure"
28037 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
28038 argument which is the path to a UNIX socket. For example:
28040 av_scanner = fsecure:/path/to/.fsav
28042 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
28043 Thelmen for contributing the code for this scanner.
28045 .vitem &%kavdaemon%&
28046 .cindex "virus scanners" "Kaspersky"
28047 This is the scanner daemon of Kaspersky Version 4. This version of the
28048 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
28049 scanner type takes one option, which is the path to the daemon's UNIX socket.
28052 av_scanner = kavdaemon:/opt/AVP/AvpCtl
28054 The default path is &_/var/run/AvpCtl_&.
28057 .cindex "virus scanners" "mksd"
28058 This is a daemon type scanner that is aimed mainly at Polish users, though some
28059 parts of documentation are now available in English. You can get it at
28060 &url(http://linux.mks.com.pl/). The only option for this scanner type is
28061 the maximum number of processes used simultaneously to scan the attachments,
28062 provided that the demime facility is employed and also provided that mksd has
28063 been run with at least the same number of child processes. For example:
28065 av_scanner = mksd:2
28067 You can safely omit this option (the default value is 1).
28070 .cindex "virus scanners" "Sophos and Sophie"
28071 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
28072 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
28073 for this scanner type is the path to the UNIX socket that Sophie uses for
28074 client communication. For example:
28076 av_scanner = sophie:/tmp/sophie
28078 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
28082 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
28083 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
28086 The &%av_scanner%& option is expanded each time &%malware%& is called. This
28087 makes it possible to use different scanners. See further below for an example.
28088 The &%malware%& condition caches its results, so when you use it multiple times
28089 for the same message, the actual scanning process is only carried out once.
28090 However, using expandable items in &%av_scanner%& disables this caching, in
28091 which case each use of the &%malware%& condition causes a new scan of the
28094 The &%malware%& condition takes a right-hand argument that is expanded before
28095 use. It can then be one of
28098 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
28099 The condition succeeds if a virus was found, and fail otherwise. This is the
28102 &"false"& or &"0"& or an empty string, in which case no scanning is done and
28103 the condition fails immediately.
28105 A regular expression, in which case the message is scanned for viruses. The
28106 condition succeeds if a virus is found and its name matches the regular
28107 expression. This allows you to take special actions on certain types of virus.
28110 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
28111 even if there is a problem with the virus scanner. Otherwise, such a problem
28112 causes the ACL to defer.
28114 .vindex "&$malware_name$&"
28115 When a virus is found, the condition sets up an expansion variable called
28116 &$malware_name$& that contains the name of the virus. You can use it in a
28117 &%message%& modifier that specifies the error returned to the sender, and/or in
28120 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
28121 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
28122 &%malware%& condition.
28124 Beware the interaction of Exim's &%message_size_limit%& with any size limits
28125 imposed by your anti-virus scanner.
28127 Here is a very simple scanning example:
28129 deny message = This message contains malware ($malware_name)
28133 The next example accepts messages when there is a problem with the scanner:
28135 deny message = This message contains malware ($malware_name)
28137 malware = */defer_ok
28139 The next example shows how to use an ACL variable to scan with both sophie and
28140 aveserver. It assumes you have set:
28142 av_scanner = $acl_m0
28144 in the main Exim configuration.
28146 deny message = This message contains malware ($malware_name)
28147 set acl_m0 = sophie
28150 deny message = This message contains malware ($malware_name)
28151 set acl_m0 = aveserver
28156 .section "Scanning with SpamAssassin" "SECTscanspamass"
28157 .cindex "content scanning" "for spam"
28158 .cindex "spam scanning"
28159 .cindex "SpamAssassin"
28160 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
28161 score and a report for the message. You can get SpamAssassin at
28162 &url(http://www.spamassassin.org), or, if you have a working Perl
28163 installation, you can use CPAN by running:
28165 perl -MCPAN -e 'install Mail::SpamAssassin'
28167 SpamAssassin has its own set of configuration files. Please review its
28168 documentation to see how you can tweak it. The default installation should work
28171 .oindex "&%spamd_address%&"
28172 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
28173 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
28174 port for &%spamd%&, you must set the &%spamd_address%& option in the global
28175 part of the Exim configuration as follows (example):
28177 spamd_address = 192.168.99.45 387
28179 You do not need to set this option if you use the default. As of version 2.60,
28180 &%spamd%& also supports communication over UNIX sockets. If you want to use
28181 these, supply &%spamd_address%& with an absolute file name instead of a
28184 spamd_address = /var/run/spamd_socket
28186 You can have multiple &%spamd%& servers to improve scalability. These can
28187 reside on other hardware reachable over the network. To specify multiple
28188 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
28189 option, separated with colons:
28191 spamd_address = 192.168.2.10 783 : \
28192 192.168.2.11 783 : \
28195 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
28196 fashion. When a server fails to respond to the connection attempt, all other
28197 servers are tried until one succeeds. If no server responds, the &%spam%&
28200 &*Warning*&: It is not possible to use the UNIX socket connection method with
28201 multiple &%spamd%& servers.
28203 The &%spamd_address%& variable is expanded before use if it starts with
28204 a dollar sign. In this case, the expansion may return a string that is
28205 used as the list so that multiple spamd servers can be the result of an
28208 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
28209 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
28211 deny message = This message was classified as SPAM
28214 The right-hand side of the &%spam%& condition specifies a name. This is
28215 relevant if you have set up multiple SpamAssassin profiles. If you do not want
28216 to scan using a specific profile, but rather use the SpamAssassin system-wide
28217 default profile, you can scan for an unknown name, or simply use &"nobody"&.
28218 However, you must put something on the right-hand side.
28220 The name allows you to use per-domain or per-user antispam profiles in
28221 principle, but this is not straightforward in practice, because a message may
28222 have multiple recipients, not necessarily all in the same domain. Because the
28223 &%spam%& condition has to be called from a DATA ACL in order to be able to
28224 read the contents of the message, the variables &$local_part$& and &$domain$&
28227 The right-hand side of the &%spam%& condition is expanded before being used, so
28228 you can put lookups or conditions there. When the right-hand side evaluates to
28229 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
28232 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
28233 large ones may cause significant performance degradation. As most spam messages
28234 are quite small, it is recommended that you do not scan the big ones. For
28237 deny message = This message was classified as SPAM
28238 condition = ${if < {$message_size}{10K}}
28242 The &%spam%& condition returns true if the threshold specified in the user's
28243 SpamAssassin profile has been matched or exceeded. If you want to use the
28244 &%spam%& condition for its side effects (see the variables below), you can make
28245 it always return &"true"& by appending &`:true`& to the username.
28247 .cindex "spam scanning" "returned variables"
28248 When the &%spam%& condition is run, it sets up a number of expansion
28249 variables. These variables are saved with the received message, thus they are
28250 available for use at delivery time.
28253 .vitem &$spam_score$&
28254 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
28255 for inclusion in log or reject messages.
28257 .vitem &$spam_score_int$&
28258 The spam score of the message, multiplied by ten, as an integer value. For
28259 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
28260 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
28261 The integer value is useful for numeric comparisons in conditions.
28264 .vitem &$spam_bar$&
28265 A string consisting of a number of &"+"& or &"-"& characters, representing the
28266 integer part of the spam score value. A spam score of 4.4 would have a
28267 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
28268 headers, since MUAs can match on such strings.
28270 .vitem &$spam_report$&
28271 A multiline text table, containing the full SpamAssassin report for the
28272 message. Useful for inclusion in headers or reject messages.
28275 The &%spam%& condition caches its results unless expansion in
28276 spamd_address was used. If you call it again with the same user name, it
28277 does not scan again, but rather returns the same values as before.
28279 The &%spam%& condition returns DEFER if there is any error while running
28280 the message through SpamAssassin or if the expansion of spamd_address
28281 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
28282 statement block), append &`/defer_ok`& to the right-hand side of the
28283 spam condition, like this:
28285 deny message = This message was classified as SPAM
28286 spam = joe/defer_ok
28288 This causes messages to be accepted even if there is a problem with &%spamd%&.
28290 Here is a longer, commented example of the use of the &%spam%&
28293 # put headers in all messages (no matter if spam or not)
28294 warn spam = nobody:true
28295 add_header = X-Spam-Score: $spam_score ($spam_bar)
28296 add_header = X-Spam-Report: $spam_report
28298 # add second subject line with *SPAM* marker when message
28299 # is over threshold
28301 add_header = Subject: *SPAM* $h_Subject:
28303 # reject spam at high scores (> 12)
28304 deny message = This message scored $spam_score spam points.
28306 condition = ${if >{$spam_score_int}{120}{1}{0}}
28311 .section "Scanning MIME parts" "SECTscanmimepart"
28312 .cindex "content scanning" "MIME parts"
28313 .cindex "MIME content scanning"
28314 .oindex "&%acl_smtp_mime%&"
28315 .oindex "&%acl_not_smtp_mime%&"
28316 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
28317 each MIME part of an SMTP message, including multipart types, in the sequence
28318 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
28319 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
28320 options may both refer to the same ACL if you want the same processing in both
28323 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
28324 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
28325 the case of a non-SMTP message. However, a MIME ACL is called only if the
28326 message contains a &'Content-Type:'& header line. When a call to a MIME
28327 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
28328 result code is sent to the client. In the case of an SMTP message, the
28329 &%acl_smtp_data%& ACL is not called when this happens.
28331 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
28332 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
28333 condition to match against the raw MIME part. You can also use the
28334 &%mime_regex%& condition to match against the decoded MIME part (see section
28335 &<<SECTscanregex>>&).
28337 At the start of a MIME ACL, a number of variables are set from the header
28338 information for the relevant MIME part. These are described below. The contents
28339 of the MIME part are not by default decoded into a disk file except for MIME
28340 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
28341 part into a disk file, you can use the &%decode%& condition. The general
28344 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
28346 The right hand side is expanded before use. After expansion,
28350 &"0"& or &"false"&, in which case no decoding is done.
28352 The string &"default"&. In that case, the file is put in the temporary
28353 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
28354 a sequential file name consisting of the message id and a sequence number. The
28355 full path and name is available in &$mime_decoded_filename$& after decoding.
28357 A full path name starting with a slash. If the full name is an existing
28358 directory, it is used as a replacement for the default directory. The filename
28359 is then sequentially assigned. If the path does not exist, it is used as
28360 the full path and file name.
28362 If the string does not start with a slash, it is used as the
28363 filename, and the default path is then used.
28365 The &%decode%& condition normally succeeds. It is only false for syntax
28366 errors or unusual circumstances such as memory shortages. You can easily decode
28367 a file with its original, proposed filename using
28369 decode = $mime_filename
28371 However, you should keep in mind that &$mime_filename$& might contain
28372 anything. If you place files outside of the default path, they are not
28373 automatically unlinked.
28375 For RFC822 attachments (these are messages attached to messages, with a
28376 content-type of &"message/rfc822"&), the ACL is called again in the same manner
28377 as for the primary message, only that the &$mime_is_rfc822$& expansion
28378 variable is set (see below). Attached messages are always decoded to disk
28379 before being checked, and the files are unlinked once the check is done.
28381 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
28382 used to match regular expressions against raw and decoded MIME parts,
28383 respectively. They are described in section &<<SECTscanregex>>&.
28385 .cindex "MIME content scanning" "returned variables"
28386 The following list describes all expansion variables that are
28387 available in the MIME ACL:
28390 .vitem &$mime_boundary$&
28391 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
28392 have a boundary string, which is stored in this variable. If the current part
28393 has no boundary parameter in the &'Content-Type:'& header, this variable
28394 contains the empty string.
28396 .vitem &$mime_charset$&
28397 This variable contains the character set identifier, if one was found in the
28398 &'Content-Type:'& header. Examples for charset identifiers are:
28404 Please note that this value is not normalized, so you should do matches
28405 case-insensitively.
28407 .vitem &$mime_content_description$&
28408 This variable contains the normalized content of the &'Content-Description:'&
28409 header. It can contain a human-readable description of the parts content. Some
28410 implementations repeat the filename for attachments here, but they are usually
28411 only used for display purposes.
28413 .vitem &$mime_content_disposition$&
28414 This variable contains the normalized content of the &'Content-Disposition:'&
28415 header. You can expect strings like &"attachment"& or &"inline"& here.
28417 .vitem &$mime_content_id$&
28418 This variable contains the normalized content of the &'Content-ID:'& header.
28419 This is a unique ID that can be used to reference a part from another part.
28421 .vitem &$mime_content_size$&
28422 This variable is set only after the &%decode%& modifier (see above) has been
28423 successfully run. It contains the size of the decoded part in kilobytes. The
28424 size is always rounded up to full kilobytes, so only a completely empty part
28425 has a &$mime_content_size$& of zero.
28427 .vitem &$mime_content_transfer_encoding$&
28428 This variable contains the normalized content of the
28429 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
28430 type. Typical values are &"base64"& and &"quoted-printable"&.
28432 .vitem &$mime_content_type$&
28433 If the MIME part has a &'Content-Type:'& header, this variable contains its
28434 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
28435 are some examples of popular MIME types, as they may appear in this variable:
28439 application/octet-stream
28443 If the MIME part has no &'Content-Type:'& header, this variable contains the
28446 .vitem &$mime_decoded_filename$&
28447 This variable is set only after the &%decode%& modifier (see above) has been
28448 successfully run. It contains the full path and file name of the file
28449 containing the decoded data.
28454 .vitem &$mime_filename$&
28455 This is perhaps the most important of the MIME variables. It contains a
28456 proposed filename for an attachment, if one was found in either the
28457 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
28458 RFC2047 decoded, but no additional sanity checks are done. If no filename was
28459 found, this variable contains the empty string.
28461 .vitem &$mime_is_coverletter$&
28462 This variable attempts to differentiate the &"cover letter"& of an e-mail from
28463 attached data. It can be used to clamp down on flashy or unnecessarily encoded
28464 content in the cover letter, while not restricting attachments at all.
28466 The variable contains 1 (true) for a MIME part believed to be part of the
28467 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
28471 The outermost MIME part of a message is always a cover letter.
28474 If a multipart/alternative or multipart/related MIME part is a cover letter,
28475 so are all MIME subparts within that multipart.
28478 If any other multipart is a cover letter, the first subpart is a cover letter,
28479 and the rest are attachments.
28482 All parts contained within an attachment multipart are attachments.
28485 As an example, the following will ban &"HTML mail"& (including that sent with
28486 alternative plain text), while allowing HTML files to be attached. HTML
28487 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
28489 deny message = HTML mail is not accepted here
28490 !condition = $mime_is_rfc822
28491 condition = $mime_is_coverletter
28492 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
28494 .vitem &$mime_is_multipart$&
28495 This variable has the value 1 (true) when the current part has the main type
28496 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
28497 Since multipart entities only serve as containers for other parts, you may not
28498 want to carry out specific actions on them.
28500 .vitem &$mime_is_rfc822$&
28501 This variable has the value 1 (true) if the current part is not a part of the
28502 checked message itself, but part of an attached message. Attached message
28503 decoding is fully recursive.
28505 .vitem &$mime_part_count$&
28506 This variable is a counter that is raised for each processed MIME part. It
28507 starts at zero for the very first part (which is usually a multipart). The
28508 counter is per-message, so it is reset when processing RFC822 attachments (see
28509 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
28510 complete, so you can use it in the DATA ACL to determine the number of MIME
28511 parts of a message. For non-MIME messages, this variable contains the value -1.
28516 .section "Scanning with regular expressions" "SECTscanregex"
28517 .cindex "content scanning" "with regular expressions"
28518 .cindex "regular expressions" "content scanning with"
28519 You can specify your own custom regular expression matches on the full body of
28520 the message, or on individual MIME parts.
28522 The &%regex%& condition takes one or more regular expressions as arguments and
28523 matches them against the full message (when called in the DATA ACL) or a raw
28524 MIME part (when called in the MIME ACL). The &%regex%& condition matches
28525 linewise, with a maximum line length of 32K characters. That means you cannot
28526 have multiline matches with the &%regex%& condition.
28528 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
28529 to 32K of decoded content (the whole content at once, not linewise). If the
28530 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
28531 is decoded automatically when &%mime_regex%& is executed (using default path
28532 and filename values). If the decoded data is larger than 32K, only the first
28533 32K characters are checked.
28535 The regular expressions are passed as a colon-separated list. To include a
28536 literal colon, you must double it. Since the whole right-hand side string is
28537 expanded before being used, you must also escape dollar signs and backslashes
28538 with more backslashes, or use the &`\N`& facility to disable expansion.
28539 Here is a simple example that contains two regular expressions:
28541 deny message = contains blacklisted regex ($regex_match_string)
28542 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
28544 The conditions returns true if any one of the regular expressions matches. The
28545 &$regex_match_string$& expansion variable is then set up and contains the
28546 matching regular expression.
28548 &*Warning*&: With large messages, these conditions can be fairly
28554 .section "The demime condition" "SECTdemimecond"
28555 .cindex "content scanning" "MIME checking"
28556 .cindex "MIME content scanning"
28557 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
28558 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
28559 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
28560 ACL functionality, but provides no additional facilities. Please note that this
28561 condition is deprecated and kept only for backward compatibility. You must set
28562 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
28563 use the &%demime%& condition.
28565 The &%demime%& condition unpacks MIME containers in the message. It detects
28566 errors in MIME containers and can match file extensions found in the message
28567 against a list. Using this facility produces files containing the unpacked MIME
28568 parts of the message in the temporary scan directory. If you do antivirus
28569 scanning, it is recommended that you use the &%demime%& condition before the
28570 antivirus (&%malware%&) condition.
28572 On the right-hand side of the &%demime%& condition you can pass a
28573 colon-separated list of file extensions that it should match against. For
28576 deny message = Found blacklisted file attachment
28577 demime = vbs:com:bat:pif:prf:lnk
28579 If one of the file extensions is found, the condition is true, otherwise it is
28580 false. If there is a temporary error while demimeing (for example, &"disk
28581 full"&), the condition defers, and the message is temporarily rejected (unless
28582 the condition is on a &%warn%& verb).
28584 The right-hand side is expanded before being treated as a list, so you can have
28585 conditions and lookups there. If it expands to an empty string, &"false"&, or
28586 zero (&"0"&), no demimeing is done and the condition is false.
28588 The &%demime%& condition set the following variables:
28591 .vitem &$demime_errorlevel$&
28592 .vindex "&$demime_errorlevel$&"
28593 When an error is detected in a MIME container, this variable contains the
28594 severity of the error, as an integer number. The higher the value, the more
28595 severe the error (the current maximum value is 3). If this variable is unset or
28596 zero, no error occurred.
28598 .vitem &$demime_reason$&
28599 .vindex "&$demime_reason$&"
28600 When &$demime_errorlevel$& is greater than zero, this variable contains a
28601 human-readable text string describing the MIME error that occurred.
28605 .vitem &$found_extension$&
28606 .vindex "&$found_extension$&"
28607 When the &%demime%& condition is true, this variable contains the file
28608 extension it found.
28611 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
28612 the &%demime%& condition, and are not changed on subsequent calls.
28614 If you do not want to check for file extensions, but rather use the &%demime%&
28615 condition for unpacking or error checking purposes, pass &"*"& as the
28616 right-hand side value. Here is a more elaborate example of how to use this
28619 # Reject messages with serious MIME container errors
28620 deny message = Found MIME error ($demime_reason).
28622 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
28624 # Reject known virus spreading file extensions.
28625 # Accepting these is pretty much braindead.
28626 deny message = contains $found_extension file (blacklisted).
28627 demime = com:vbs:bat:pif:scr
28629 # Freeze .exe and .doc files. Postmaster can
28630 # examine them and eventually thaw them.
28631 deny log_message = Another $found_extension file.
28640 . ////////////////////////////////////////////////////////////////////////////
28641 . ////////////////////////////////////////////////////////////////////////////
28643 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
28644 "Local scan function"
28645 .scindex IIDlosca "&[local_scan()]& function" "description of"
28646 .cindex "customizing" "input scan using C function"
28647 .cindex "policy control" "by local scan function"
28648 In these days of email worms, viruses, and ever-increasing spam, some sites
28649 want to apply a lot of checking to messages before accepting them.
28651 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
28652 passing messages to external virus and spam scanning software. You can also do
28653 a certain amount in Exim itself through string expansions and the &%condition%&
28654 condition in the ACL that runs after the SMTP DATA command or the ACL for
28655 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
28657 To allow for further customization to a site's own requirements, there is the
28658 possibility of linking Exim with a private message scanning function, written
28659 in C. If you want to run code that is written in something other than C, you
28660 can of course use a little C stub to call it.
28662 The local scan function is run once for every incoming message, at the point
28663 when Exim is just about to accept the message.
28664 It can therefore be used to control non-SMTP messages from local processes as
28665 well as messages arriving via SMTP.
28667 Exim applies a timeout to calls of the local scan function, and there is an
28668 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
28669 Zero means &"no timeout"&.
28670 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
28671 before calling the local scan function, so that the most common types of crash
28672 are caught. If the timeout is exceeded or one of those signals is caught, the
28673 incoming message is rejected with a temporary error if it is an SMTP message.
28674 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
28675 code. The incident is logged on the main and reject logs.
28679 .section "Building Exim to use a local scan function" "SECID207"
28680 .cindex "&[local_scan()]& function" "building Exim to use"
28681 To make use of the local scan function feature, you must tell Exim where your
28682 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
28683 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
28684 directory, so you might set
28686 LOCAL_SCAN_SOURCE=Local/local_scan.c
28688 for example. The function must be called &[local_scan()]&. It is called by
28689 Exim after it has received a message, when the success return code is about to
28690 be sent. This is after all the ACLs have been run. The return code from your
28691 function controls whether the message is actually accepted or not. There is a
28692 commented template function (that just accepts the message) in the file
28693 _src/local_scan.c_.
28695 If you want to make use of Exim's run time configuration file to set options
28696 for your &[local_scan()]& function, you must also set
28698 LOCAL_SCAN_HAS_OPTIONS=yes
28700 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
28705 .section "API for local_scan()" "SECTapiforloc"
28706 .cindex "&[local_scan()]& function" "API description"
28707 You must include this line near the start of your code:
28709 #include "local_scan.h"
28711 This header file defines a number of variables and other values, and the
28712 prototype for the function itself. Exim is coded to use unsigned char values
28713 almost exclusively, and one of the things this header defines is a shorthand
28714 for &`unsigned char`& called &`uschar`&.
28715 It also contains the following macro definitions, to simplify casting character
28716 strings and pointers to character strings:
28718 #define CS (char *)
28719 #define CCS (const char *)
28720 #define CSS (char **)
28721 #define US (unsigned char *)
28722 #define CUS (const unsigned char *)
28723 #define USS (unsigned char **)
28725 The function prototype for &[local_scan()]& is:
28727 extern int local_scan(int fd, uschar **return_text);
28729 The arguments are as follows:
28732 &%fd%& is a file descriptor for the file that contains the body of the message
28733 (the -D file). The file is open for reading and writing, but updating it is not
28734 recommended. &*Warning*&: You must &'not'& close this file descriptor.
28736 The descriptor is positioned at character 19 of the file, which is the first
28737 character of the body itself, because the first 19 characters are the message
28738 id followed by &`-D`& and a newline. If you rewind the file, you should use the
28739 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
28740 case this changes in some future version.
28742 &%return_text%& is an address which you can use to return a pointer to a text
28743 string at the end of the function. The value it points to on entry is NULL.
28746 The function must return an &%int%& value which is one of the following macros:
28749 .vitem &`LOCAL_SCAN_ACCEPT`&
28750 .vindex "&$local_scan_data$&"
28751 The message is accepted. If you pass back a string of text, it is saved with
28752 the message, and made available in the variable &$local_scan_data$&. No
28753 newlines are permitted (if there are any, they are turned into spaces) and the
28754 maximum length of text is 1000 characters.
28756 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
28757 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
28758 queued without immediate delivery, and is frozen.
28760 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
28761 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
28762 queued without immediate delivery.
28764 .vitem &`LOCAL_SCAN_REJECT`&
28765 The message is rejected; the returned text is used as an error message which is
28766 passed back to the sender and which is also logged. Newlines are permitted &--
28767 they cause a multiline response for SMTP rejections, but are converted to
28768 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
28771 .vitem &`LOCAL_SCAN_TEMPREJECT`&
28772 The message is temporarily rejected; the returned text is used as an error
28773 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
28776 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
28777 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
28778 message is not written to the reject log. It has the effect of unsetting the
28779 &%rejected_header%& log selector for just this rejection. If
28780 &%rejected_header%& is already unset (see the discussion of the
28781 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
28782 same as LOCAL_SCAN_REJECT.
28784 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
28785 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
28786 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
28789 If the message is not being received by interactive SMTP, rejections are
28790 reported by writing to &%stderr%& or by sending an email, as configured by the
28791 &%-oe%& command line options.
28795 .section "Configuration options for local_scan()" "SECTconoptloc"
28796 .cindex "&[local_scan()]& function" "configuration options"
28797 It is possible to have option settings in the main configuration file
28798 that set values in static variables in the &[local_scan()]& module. If you
28799 want to do this, you must have the line
28801 LOCAL_SCAN_HAS_OPTIONS=yes
28803 in your &_Local/Makefile_& when you build Exim. (This line is in
28804 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
28805 file, you must define static variables to hold the option values, and a table
28808 The table must be a vector called &%local_scan_options%&, of type
28809 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
28810 and a pointer to the variable that holds the value. The entries must appear in
28811 alphabetical order. Following &%local_scan_options%& you must also define a
28812 variable called &%local_scan_options_count%& that contains the number of
28813 entries in the table. Here is a short example, showing two kinds of option:
28815 static int my_integer_option = 42;
28816 static uschar *my_string_option = US"a default string";
28818 optionlist local_scan_options[] = {
28819 { "my_integer", opt_int, &my_integer_option },
28820 { "my_string", opt_stringptr, &my_string_option }
28823 int local_scan_options_count =
28824 sizeof(local_scan_options)/sizeof(optionlist);
28826 The values of the variables can now be changed from Exim's runtime
28827 configuration file by including a local scan section as in this example:
28831 my_string = some string of text...
28833 The available types of option data are as follows:
28836 .vitem &*opt_bool*&
28837 This specifies a boolean (true/false) option. The address should point to a
28838 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
28839 that are defined as &"1"& and &"0"&, respectively. If you want to detect
28840 whether such a variable has been set at all, you can initialize it to
28841 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
28844 .vitem &*opt_fixed*&
28845 This specifies a fixed point number, such as is used for load averages.
28846 The address should point to a variable of type &`int`&. The value is stored
28847 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
28850 This specifies an integer; the address should point to a variable of type
28851 &`int`&. The value may be specified in any of the integer formats accepted by
28854 .vitem &*opt_mkint*&
28855 This is the same as &%opt_int%&, except that when such a value is output in a
28856 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
28857 printed with the suffix K or M.
28859 .vitem &*opt_octint*&
28860 This also specifies an integer, but the value is always interpreted as an
28861 octal integer, whether or not it starts with the digit zero, and it is
28862 always output in octal.
28864 .vitem &*opt_stringptr*&
28865 This specifies a string value; the address must be a pointer to a
28866 variable that points to a string (for example, of type &`uschar *`&).
28868 .vitem &*opt_time*&
28869 This specifies a time interval value. The address must point to a variable of
28870 type &`int`&. The value that is placed there is a number of seconds.
28873 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
28874 out the values of all the &[local_scan()]& options.
28878 .section "Available Exim variables" "SECID208"
28879 .cindex "&[local_scan()]& function" "available Exim variables"
28880 The header &_local_scan.h_& gives you access to a number of C variables. These
28881 are the only ones that are guaranteed to be maintained from release to release.
28882 Note, however, that you can obtain the value of any Exim expansion variable,
28883 including &$recipients$&, by calling &'expand_string()'&. The exported
28884 C variables are as follows:
28887 .vitem &*int&~body_linecount*&
28888 This variable contains the number of lines in the message's body.
28890 .vitem &*int&~body_zerocount*&
28891 This variable contains the number of binary zero bytes in the message's body.
28893 .vitem &*unsigned&~int&~debug_selector*&
28894 This variable is set to zero when no debugging is taking place. Otherwise, it
28895 is a bitmap of debugging selectors. Two bits are identified for use in
28896 &[local_scan()]&; they are defined as macros:
28899 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
28900 testing option that is not privileged &-- any caller may set it. All the
28901 other selector bits can be set only by admin users.
28904 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
28905 by the &`+local_scan`& debug selector. It is not included in the default set
28909 Thus, to write to the debugging output only when &`+local_scan`& has been
28910 selected, you should use code like this:
28912 if ((debug_selector & D_local_scan) != 0)
28913 debug_printf("xxx", ...);
28915 .vitem &*uschar&~*expand_string_message*&
28916 After a failing call to &'expand_string()'& (returned value NULL), the
28917 variable &%expand_string_message%& contains the error message, zero-terminated.
28919 .vitem &*header_line&~*header_list*&
28920 A pointer to a chain of header lines. The &%header_line%& structure is
28923 .vitem &*header_line&~*header_last*&
28924 A pointer to the last of the header lines.
28926 .vitem &*uschar&~*headers_charset*&
28927 The value of the &%headers_charset%& configuration option.
28929 .vitem &*BOOL&~host_checking*&
28930 This variable is TRUE during a host checking session that is initiated by the
28931 &%-bh%& command line option.
28933 .vitem &*uschar&~*interface_address*&
28934 The IP address of the interface that received the message, as a string. This
28935 is NULL for locally submitted messages.
28937 .vitem &*int&~interface_port*&
28938 The port on which this message was received. When testing with the &%-bh%&
28939 command line option, the value of this variable is -1 unless a port has been
28940 specified via the &%-oMi%& option.
28942 .vitem &*uschar&~*message_id*&
28943 This variable contains Exim's message id for the incoming message (the value of
28944 &$message_exim_id$&) as a zero-terminated string.
28946 .vitem &*uschar&~*received_protocol*&
28947 The name of the protocol by which the message was received.
28949 .vitem &*int&~recipients_count*&
28950 The number of accepted recipients.
28952 .vitem &*recipient_item&~*recipients_list*&
28953 .cindex "recipient" "adding in local scan"
28954 .cindex "recipient" "removing in local scan"
28955 The list of accepted recipients, held in a vector of length
28956 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
28957 can add additional recipients by calling &'receive_add_recipient()'& (see
28958 below). You can delete recipients by removing them from the vector and
28959 adjusting the value in &%recipients_count%&. In particular, by setting
28960 &%recipients_count%& to zero you remove all recipients. If you then return the
28961 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
28962 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
28963 and then call &'receive_add_recipient()'& as often as needed.
28965 .vitem &*uschar&~*sender_address*&
28966 The envelope sender address. For bounce messages this is the empty string.
28968 .vitem &*uschar&~*sender_host_address*&
28969 The IP address of the sending host, as a string. This is NULL for
28970 locally-submitted messages.
28972 .vitem &*uschar&~*sender_host_authenticated*&
28973 The name of the authentication mechanism that was used, or NULL if the message
28974 was not received over an authenticated SMTP connection.
28976 .vitem &*uschar&~*sender_host_name*&
28977 The name of the sending host, if known.
28979 .vitem &*int&~sender_host_port*&
28980 The port on the sending host.
28982 .vitem &*BOOL&~smtp_input*&
28983 This variable is TRUE for all SMTP input, including BSMTP.
28985 .vitem &*BOOL&~smtp_batched_input*&
28986 This variable is TRUE for BSMTP input.
28988 .vitem &*int&~store_pool*&
28989 The contents of this variable control which pool of memory is used for new
28990 requests. See section &<<SECTmemhanloc>>& for details.
28994 .section "Structure of header lines" "SECID209"
28995 The &%header_line%& structure contains the members listed below.
28996 You can add additional header lines by calling the &'header_add()'& function
28997 (see below). You can cause header lines to be ignored (deleted) by setting
29002 .vitem &*struct&~header_line&~*next*&
29003 A pointer to the next header line, or NULL for the last line.
29005 .vitem &*int&~type*&
29006 A code identifying certain headers that Exim recognizes. The codes are printing
29007 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
29008 Notice in particular that any header line whose type is * is not transmitted
29009 with the message. This flagging is used for header lines that have been
29010 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
29011 lines.) Effectively, * means &"deleted"&.
29013 .vitem &*int&~slen*&
29014 The number of characters in the header line, including the terminating and any
29017 .vitem &*uschar&~*text*&
29018 A pointer to the text of the header. It always ends with a newline, followed by
29019 a zero byte. Internal newlines are preserved.
29024 .section "Structure of recipient items" "SECID210"
29025 The &%recipient_item%& structure contains these members:
29028 .vitem &*uschar&~*address*&
29029 This is a pointer to the recipient address as it was received.
29031 .vitem &*int&~pno*&
29032 This is used in later Exim processing when top level addresses are created by
29033 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
29034 and must always contain -1 at this stage.
29036 .vitem &*uschar&~*errors_to*&
29037 If this value is not NULL, bounce messages caused by failing to deliver to the
29038 recipient are sent to the address it contains. In other words, it overrides the
29039 envelope sender for this one recipient. (Compare the &%errors_to%& generic
29040 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
29041 an unqualified address, Exim qualifies it using the domain from
29042 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
29043 is NULL for all recipients.
29048 .section "Available Exim functions" "SECID211"
29049 .cindex "&[local_scan()]& function" "available Exim functions"
29050 The header &_local_scan.h_& gives you access to a number of Exim functions.
29051 These are the only ones that are guaranteed to be maintained from release to
29055 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
29056 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
29058 This function creates a child process that runs the command specified by
29059 &%argv%&. The environment for the process is specified by &%envp%&, which can
29060 be NULL if no environment variables are to be passed. A new umask is supplied
29061 for the process in &%newumask%&.
29063 Pipes to the standard input and output of the new process are set up
29064 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
29065 standard error is cloned to the standard output. If there are any file
29066 descriptors &"in the way"& in the new process, they are closed. If the final
29067 argument is TRUE, the new process is made into a process group leader.
29069 The function returns the pid of the new process, or -1 if things go wrong.
29071 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
29072 This function waits for a child process to terminate, or for a timeout (in
29073 seconds) to expire. A timeout value of zero means wait as long as it takes. The
29074 return value is as follows:
29079 The process terminated by a normal exit and the value is the process
29085 The process was terminated by a signal and the value is the negation of the
29091 The process timed out.
29095 The was some other error in wait(); &%errno%& is still set.
29098 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
29099 This function provide you with a means of submitting a new message to
29100 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
29101 want, but this packages it all up for you.) The function creates a pipe,
29102 forks a subprocess that is running
29104 exim -t -oem -oi -f <>
29106 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
29107 that is connected to the standard input. The yield of the function is the PID
29108 of the subprocess. You can then write a message to the file descriptor, with
29109 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
29111 When you have finished, call &'child_close()'& to wait for the process to
29112 finish and to collect its ending status. A timeout value of zero is usually
29113 fine in this circumstance. Unless you have made a mistake with the recipient
29114 addresses, you should get a return code of zero.
29117 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
29118 *sender_authentication)*&
29119 This function is a more sophisticated version of &'child_open()'&. The command
29122 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
29124 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
29127 .vitem &*void&~debug_printf(char&~*,&~...)*&
29128 This is Exim's debugging function, with arguments as for &'(printf()'&. The
29129 output is written to the standard error stream. If no debugging is selected,
29130 calls to &'debug_printf()'& have no effect. Normally, you should make calls
29131 conditional on the &`local_scan`& debug selector by coding like this:
29133 if ((debug_selector & D_local_scan) != 0)
29134 debug_printf("xxx", ...);
29137 .vitem &*uschar&~*expand_string(uschar&~*string)*&
29138 This is an interface to Exim's string expansion code. The return value is the
29139 expanded string, or NULL if there was an expansion failure.
29140 The C variable &%expand_string_message%& contains an error message after an
29141 expansion failure. If expansion does not change the string, the return value is
29142 the pointer to the input string. Otherwise, the return value points to a new
29143 block of memory that was obtained by a call to &'store_get()'&. See section
29144 &<<SECTmemhanloc>>& below for a discussion of memory handling.
29146 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
29147 This function allows you to an add additional header line at the end of the
29148 existing ones. The first argument is the type, and should normally be a space
29149 character. The second argument is a format string and any number of
29150 substitution arguments as for &[sprintf()]&. You may include internal newlines
29151 if you want, and you must ensure that the string ends with a newline.
29153 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
29154 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
29155 This function adds a new header line at a specified point in the header
29156 chain. The header itself is specified as for &'header_add()'&.
29158 If &%name%& is NULL, the new header is added at the end of the chain if
29159 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
29160 NULL, the header lines are searched for the first non-deleted header that
29161 matches the name. If one is found, the new header is added before it if
29162 &%after%& is false. If &%after%& is true, the new header is added after the
29163 found header and any adjacent subsequent ones with the same name (even if
29164 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
29165 option controls where the header is added. If it is true, addition is at the
29166 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
29167 headers, or at the top if there are no &'Received:'& headers, you could use
29169 header_add_at_position(TRUE, US"Received", TRUE,
29170 ' ', "X-xxx: ...");
29172 Normally, there is always at least one non-deleted &'Received:'& header, but
29173 there may not be if &%received_header_text%& expands to an empty string.
29176 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
29177 This function removes header lines. If &%occurrence%& is zero or negative, all
29178 occurrences of the header are removed. If occurrence is greater than zero, that
29179 particular instance of the header is removed. If no header(s) can be found that
29180 match the specification, the function does nothing.
29183 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
29184 int&~length,&~BOOL&~notdel)*&"
29185 This function tests whether the given header has the given name. It is not just
29186 a string comparison, because white space is permitted between the name and the
29187 colon. If the &%notdel%& argument is true, a false return is forced for all
29188 &"deleted"& headers; otherwise they are not treated specially. For example:
29190 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
29192 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
29193 .cindex "base64 encoding" "functions for &[local_scan()]& use"
29194 This function base64-encodes a string, which is passed by address and length.
29195 The text may contain bytes of any value, including zero. The result is passed
29196 back in dynamic memory that is obtained by calling &'store_get()'&. It is
29199 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
29200 This function decodes a base64-encoded string. Its arguments are a
29201 zero-terminated base64-encoded string and the address of a variable that is set
29202 to point to the result, which is in dynamic memory. The length of the decoded
29203 string is the yield of the function. If the input is invalid base64 data, the
29204 yield is -1. A zero byte is added to the end of the output string to make it
29205 easy to interpret as a C string (assuming it contains no zeros of its own). The
29206 added zero byte is not included in the returned count.
29208 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
29209 This function checks for a match in a domain list. Domains are always
29210 matched caselessly. The return value is one of the following:
29212 &`OK `& match succeeded
29213 &`FAIL `& match failed
29214 &`DEFER `& match deferred
29216 DEFER is usually caused by some kind of lookup defer, such as the
29217 inability to contact a database.
29219 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
29221 This function checks for a match in a local part list. The third argument
29222 controls case-sensitivity. The return values are as for
29223 &'lss_match_domain()'&.
29225 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
29227 This function checks for a match in an address list. The third argument
29228 controls the case-sensitivity of the local part match. The domain is always
29229 matched caselessly. The return values are as for &'lss_match_domain()'&.
29231 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
29233 This function checks for a match in a host list. The most common usage is
29236 lss_match_host(sender_host_name, sender_host_address, ...)
29238 .vindex "&$sender_host_address$&"
29239 An empty address field matches an empty item in the host list. If the host name
29240 is NULL, the name corresponding to &$sender_host_address$& is automatically
29241 looked up if a host name is required to match an item in the list. The return
29242 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
29243 returns ERROR in the case when it had to look up a host name, but the lookup
29246 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
29248 This function writes to Exim's log files. The first argument should be zero (it
29249 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
29250 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
29251 them. It specifies to which log or logs the message is written. The remaining
29252 arguments are a format and relevant insertion arguments. The string should not
29253 contain any newlines, not even at the end.
29256 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
29257 This function adds an additional recipient to the message. The first argument
29258 is the recipient address. If it is unqualified (has no domain), it is qualified
29259 with the &%qualify_recipient%& domain. The second argument must always be -1.
29261 This function does not allow you to specify a private &%errors_to%& address (as
29262 described with the structure of &%recipient_item%& above), because it pre-dates
29263 the addition of that field to the structure. However, it is easy to add such a
29264 value afterwards. For example:
29266 receive_add_recipient(US"monitor@mydom.example", -1);
29267 recipients_list[recipients_count-1].errors_to =
29268 US"postmaster@mydom.example";
29271 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
29272 This is a convenience function to remove a named recipient from the list of
29273 recipients. It returns true if a recipient was removed, and false if no
29274 matching recipient could be found. The argument must be a complete email
29281 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
29282 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
29283 This function decodes strings that are encoded according to RFC 2047. Typically
29284 these are the contents of header lines. First, each &"encoded word"& is decoded
29285 from the Q or B encoding into a byte-string. Then, if provided with the name of
29286 a charset encoding, and if the &[iconv()]& function is available, an attempt is
29287 made to translate the result to the named character set. If this fails, the
29288 binary string is returned with an error message.
29290 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
29291 maximum MIME word length is enforced. The third argument is the target
29292 encoding, or NULL if no translation is wanted.
29294 .cindex "binary zero" "in RFC 2047 decoding"
29295 .cindex "RFC 2047" "binary zero in"
29296 If a binary zero is encountered in the decoded string, it is replaced by the
29297 contents of the &%zeroval%& argument. For use with Exim headers, the value must
29298 not be 0 because header lines are handled as zero-terminated strings.
29300 The function returns the result of processing the string, zero-terminated; if
29301 &%lenptr%& is not NULL, the length of the result is set in the variable to
29302 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
29304 If an error is encountered, the function returns NULL and uses the &%error%&
29305 argument to return an error message. The variable pointed to by &%error%& is
29306 set to NULL if there is no error; it may be set non-NULL even when the function
29307 returns a non-NULL value if decoding was successful, but there was a problem
29311 .vitem &*int&~smtp_fflush(void)*&
29312 This function is used in conjunction with &'smtp_printf()'&, as described
29315 .vitem &*void&~smtp_printf(char&~*,&~...)*&
29316 The arguments of this function are like &[printf()]&; it writes to the SMTP
29317 output stream. You should use this function only when there is an SMTP output
29318 stream, that is, when the incoming message is being received via interactive
29319 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
29320 is FALSE. If you want to test for an incoming message from another host (as
29321 opposed to a local process that used the &%-bs%& command line option), you can
29322 test the value of &%sender_host_address%&, which is non-NULL when a remote host
29325 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
29326 output function, so it can be used for all forms of SMTP connection.
29328 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
29329 must start with an appropriate response code: 550 if you are going to return
29330 LOCAL_SCAN_REJECT, 451 if you are going to return
29331 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
29332 initial lines of a multi-line response, the code must be followed by a hyphen
29333 to indicate that the line is not the final response line. You must also ensure
29334 that the lines you write terminate with CRLF. For example:
29336 smtp_printf("550-this is some extra info\r\n");
29337 return LOCAL_SCAN_REJECT;
29339 Note that you can also create multi-line responses by including newlines in
29340 the data returned via the &%return_text%& argument. The added value of using
29341 &'smtp_printf()'& is that, for instance, you could introduce delays between
29342 multiple output lines.
29344 The &'smtp_printf()'& function does not return any error indication, because it
29345 does not automatically flush pending output, and therefore does not test
29346 the state of the stream. (In the main code of Exim, flushing and error
29347 detection is done when Exim is ready for the next SMTP input command.) If
29348 you want to flush the output and check for an error (for example, the
29349 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
29350 arguments. It flushes the output stream, and returns a non-zero value if there
29353 .vitem &*void&~*store_get(int)*&
29354 This function accesses Exim's internal store (memory) manager. It gets a new
29355 chunk of memory whose size is given by the argument. Exim bombs out if it ever
29356 runs out of memory. See the next section for a discussion of memory handling.
29358 .vitem &*void&~*store_get_perm(int)*&
29359 This function is like &'store_get()'&, but it always gets memory from the
29360 permanent pool. See the next section for a discussion of memory handling.
29362 .vitem &*uschar&~*string_copy(uschar&~*string)*&
29365 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
29368 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
29369 These three functions create strings using Exim's dynamic memory facilities.
29370 The first makes a copy of an entire string. The second copies up to a maximum
29371 number of characters, indicated by the second argument. The third uses a format
29372 and insertion arguments to create a new string. In each case, the result is a
29373 pointer to a new string in the current memory pool. See the next section for
29379 .section "More about Exim's memory handling" "SECTmemhanloc"
29380 .cindex "&[local_scan()]& function" "memory handling"
29381 No function is provided for freeing memory, because that is never needed.
29382 The dynamic memory that Exim uses when receiving a message is automatically
29383 recycled if another message is received by the same process (this applies only
29384 to incoming SMTP connections &-- other input methods can supply only one
29385 message at a time). After receiving the last message, a reception process
29388 Because it is recycled, the normal dynamic memory cannot be used for holding
29389 data that must be preserved over a number of incoming messages on the same SMTP
29390 connection. However, Exim in fact uses two pools of dynamic memory; the second
29391 one is not recycled, and can be used for this purpose.
29393 If you want to allocate memory that remains available for subsequent messages
29394 in the same SMTP connection, you should set
29396 store_pool = POOL_PERM
29398 before calling the function that does the allocation. There is no need to
29399 restore the value if you do not need to; however, if you do want to revert to
29400 the normal pool, you can either restore the previous value of &%store_pool%& or
29401 set it explicitly to POOL_MAIN.
29403 The pool setting applies to all functions that get dynamic memory, including
29404 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
29405 There is also a convenience function called &'store_get_perm()'& that gets a
29406 block of memory from the permanent pool while preserving the value of
29413 . ////////////////////////////////////////////////////////////////////////////
29414 . ////////////////////////////////////////////////////////////////////////////
29416 .chapter "System-wide message filtering" "CHAPsystemfilter"
29417 .scindex IIDsysfil1 "filter" "system filter"
29418 .scindex IIDsysfil2 "filtering all mail"
29419 .scindex IIDsysfil3 "system filter"
29420 The previous chapters (on ACLs and the local scan function) describe checks
29421 that can be applied to messages before they are accepted by a host. There is
29422 also a mechanism for checking messages once they have been received, but before
29423 they are delivered. This is called the &'system filter'&.
29425 The system filter operates in a similar manner to users' filter files, but it
29426 is run just once per message (however many recipients the message has).
29427 It should not normally be used as a substitute for routing, because &%deliver%&
29428 commands in a system router provide new envelope recipient addresses.
29429 The system filter must be an Exim filter. It cannot be a Sieve filter.
29431 The system filter is run at the start of a delivery attempt, before any routing
29432 is done. If a message fails to be completely delivered at the first attempt,
29433 the system filter is run again at the start of every retry.
29434 If you want your filter to do something only once per message, you can make use
29435 of the &%first_delivery%& condition in an &%if%& command in the filter to
29436 prevent it happening on retries.
29438 .vindex "&$domain$&"
29439 .vindex "&$local_part$&"
29440 &*Warning*&: Because the system filter runs just once, variables that are
29441 specific to individual recipient addresses, such as &$local_part$& and
29442 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
29443 you want to run a centrally-specified filter for each recipient address
29444 independently, you can do so by setting up a suitable &(redirect)& router, as
29445 described in section &<<SECTperaddfil>>& below.
29448 .section "Specifying a system filter" "SECID212"
29449 .cindex "uid (user id)" "system filter"
29450 .cindex "gid (group id)" "system filter"
29451 The name of the file that contains the system filter must be specified by
29452 setting &%system_filter%&. If you want the filter to run under a uid and gid
29453 other than root, you must also set &%system_filter_user%& and
29454 &%system_filter_group%& as appropriate. For example:
29456 system_filter = /etc/mail/exim.filter
29457 system_filter_user = exim
29459 If a system filter generates any deliveries directly to files or pipes (via the
29460 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
29461 specified by setting &%system_filter_file_transport%& and
29462 &%system_filter_pipe_transport%&, respectively. Similarly,
29463 &%system_filter_reply_transport%& must be set to handle any messages generated
29464 by the &%reply%& command.
29467 .section "Testing a system filter" "SECID213"
29468 You can run simple tests of a system filter in the same way as for a user
29469 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
29470 are permitted only in system filters are recognized.
29472 If you want to test the combined effect of a system filter and a user filter,
29473 you can use both &%-bF%& and &%-bf%& on the same command line.
29477 .section "Contents of a system filter" "SECID214"
29478 The language used to specify system filters is the same as for users' filter
29479 files. It is described in the separate end-user document &'Exim's interface to
29480 mail filtering'&. However, there are some additional features that are
29481 available only in system filters; these are described in subsequent sections.
29482 If they are encountered in a user's filter file or when testing with &%-bf%&,
29485 .cindex "frozen messages" "manual thaw; testing in filter"
29486 There are two special conditions which, though available in users' filter
29487 files, are designed for use in system filters. The condition &%first_delivery%&
29488 is true only for the first attempt at delivering a message, and
29489 &%manually_thawed%& is true only if the message has been frozen, and
29490 subsequently thawed by an admin user. An explicit forced delivery counts as a
29491 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
29493 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
29494 specify an &"unseen"& (non-significant) delivery, and that delivery does not
29495 succeed, it will not be tried again.
29496 If you want Exim to retry an unseen delivery until it succeeds, you should
29497 arrange to set it up every time the filter runs.
29499 When a system filter finishes running, the values of the variables &$n0$& &--
29500 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
29501 users' filter files. Thus a system filter can, for example, set up &"scores"&
29502 to which users' filter files can refer.
29506 .section "Additional variable for system filters" "SECID215"
29507 .vindex "&$recipients$&"
29508 The expansion variable &$recipients$&, containing a list of all the recipients
29509 of the message (separated by commas and white space), is available in system
29510 filters. It is not available in users' filters for privacy reasons.
29514 .section "Defer, freeze, and fail commands for system filters" "SECID216"
29515 .cindex "freezing messages"
29516 .cindex "message" "freezing"
29517 .cindex "message" "forced failure"
29518 .cindex "&%fail%&" "in system filter"
29519 .cindex "&%freeze%& in system filter"
29520 .cindex "&%defer%& in system filter"
29521 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
29522 always available in system filters, but are not normally enabled in users'
29523 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
29524 for the &(redirect)& router.) These commands can optionally be followed by the
29525 word &%text%& and a string containing an error message, for example:
29527 fail text "this message looks like spam to me"
29529 The keyword &%text%& is optional if the next character is a double quote.
29531 The &%defer%& command defers delivery of the original recipients of the
29532 message. The &%fail%& command causes all the original recipients to be failed,
29533 and a bounce message to be created. The &%freeze%& command suspends all
29534 delivery attempts for the original recipients. In all cases, any new deliveries
29535 that are specified by the filter are attempted as normal after the filter has
29538 The &%freeze%& command is ignored if the message has been manually unfrozen and
29539 not manually frozen since. This means that automatic freezing by a system
29540 filter can be used as a way of checking out suspicious messages. If a message
29541 is found to be all right, manually unfreezing it allows it to be delivered.
29543 .cindex "log" "&%fail%& command log line"
29544 .cindex "&%fail%&" "log line; reducing"
29545 The text given with a fail command is used as part of the bounce message as
29546 well as being written to the log. If the message is quite long, this can fill
29547 up a lot of log space when such failures are common. To reduce the size of the
29548 log message, Exim interprets the text in a special way if it starts with the
29549 two characters &`<<`& and contains &`>>`& later. The text between these two
29550 strings is written to the log, and the rest of the text is used in the bounce
29551 message. For example:
29553 fail "<<filter test 1>>Your message is rejected \
29554 because it contains attachments that we are \
29555 not prepared to receive."
29558 .cindex "loop" "caused by &%fail%&"
29559 Take great care with the &%fail%& command when basing the decision to fail on
29560 the contents of the message, because the bounce message will of course include
29561 the contents of the original message and will therefore trigger the &%fail%&
29562 command again (causing a mail loop) unless steps are taken to prevent this.
29563 Testing the &%error_message%& condition is one way to prevent this. You could
29566 if $message_body contains "this is spam" and not error_message
29567 then fail text "spam is not wanted here" endif
29569 though of course that might let through unwanted bounce messages. The
29570 alternative is clever checking of the body and/or headers to detect bounces
29571 generated by the filter.
29573 The interpretation of a system filter file ceases after a
29575 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
29576 set up earlier in the filter file are honoured, so you can use a sequence such
29582 to send a specified message when the system filter is freezing (or deferring or
29583 failing) a message. The normal deliveries for the message do not, of course,
29588 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
29589 .cindex "header lines" "adding; in system filter"
29590 .cindex "header lines" "removing; in system filter"
29591 .cindex "filter" "header lines; adding/removing"
29592 Two filter commands that are available only in system filters are:
29594 headers add <string>
29595 headers remove <string>
29597 The argument for the &%headers add%& is a string that is expanded and then
29598 added to the end of the message's headers. It is the responsibility of the
29599 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
29600 space is ignored, and if the string is otherwise empty, or if the expansion is
29601 forced to fail, the command has no effect.
29603 You can use &"\n"& within the string, followed by white space, to specify
29604 continued header lines. More than one header may be added in one command by
29605 including &"\n"& within the string without any following white space. For
29608 headers add "X-header-1: ....\n \
29609 continuation of X-header-1 ...\n\
29612 Note that the header line continuation white space after the first newline must
29613 be placed before the backslash that continues the input string, because white
29614 space after input continuations is ignored.
29616 The argument for &%headers remove%& is a colon-separated list of header names.
29617 This command applies only to those headers that are stored with the message;
29618 those that are added at delivery time (such as &'Envelope-To:'& and
29619 &'Return-Path:'&) cannot be removed by this means. If there is more than one
29620 header with the same name, they are all removed.
29622 The &%headers%& command in a system filter makes an immediate change to the set
29623 of header lines that was received with the message (with possible additions
29624 from ACL processing). Subsequent commands in the system filter operate on the
29625 modified set, which also forms the basis for subsequent message delivery.
29626 Unless further modified during routing or transporting, this set of headers is
29627 used for all recipients of the message.
29629 During routing and transporting, the variables that refer to the contents of
29630 header lines refer only to those lines that are in this set. Thus, header lines
29631 that are added by a system filter are visible to users' filter files and to all
29632 routers and transports. This contrasts with the manipulation of header lines by
29633 routers and transports, which is not immediate, but which instead is saved up
29634 until the message is actually being written (see section
29635 &<<SECTheadersaddrem>>&).
29637 If the message is not delivered at the first attempt, header lines that were
29638 added by the system filter are stored with the message, and so are still
29639 present at the next delivery attempt. Header lines that were removed are still
29640 present, but marked &"deleted"& so that they are not transported with the
29641 message. For this reason, it is usual to make the &%headers%& command
29642 conditional on &%first_delivery%& so that the set of header lines is not
29643 modified more than once.
29645 Because header modification in a system filter acts immediately, you have to
29646 use an indirect approach if you want to modify the contents of a header line.
29649 headers add "Old-Subject: $h_subject:"
29650 headers remove "Subject"
29651 headers add "Subject: new subject (was: $h_old-subject:)"
29652 headers remove "Old-Subject"
29657 .section "Setting an errors address in a system filter" "SECID217"
29658 .cindex "envelope sender"
29659 In a system filter, if a &%deliver%& command is followed by
29661 errors_to <some address>
29663 in order to change the envelope sender (and hence the error reporting) for that
29664 delivery, any address may be specified. (In a user filter, only the current
29665 user's address can be set.) For example, if some mail is being monitored, you
29668 unseen deliver monitor@spying.example errors_to root@local.example
29670 to take a copy which would not be sent back to the normal error reporting
29671 address if its delivery failed.
29675 .section "Per-address filtering" "SECTperaddfil"
29676 .vindex "&$domain$&"
29677 .vindex "&$local_part$&"
29678 In contrast to the system filter, which is run just once per message for each
29679 delivery attempt, it is also possible to set up a system-wide filtering
29680 operation that runs once for each recipient address. In this case, variables
29681 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
29682 filter file could be made dependent on them. This is an example of a router
29683 which implements such a filter:
29688 domains = +local_domains
29689 file = /central/filters/$local_part
29694 The filter is run in a separate process under its own uid. Therefore, either
29695 &%check_local_user%& must be set (as above), in which case the filter is run as
29696 the local user, or the &%user%& option must be used to specify which user to
29697 use. If both are set, &%user%& overrides.
29699 Care should be taken to ensure that none of the commands in the filter file
29700 specify a significant delivery if the message is to go on to be delivered to
29701 its intended recipient. The router will not then claim to have dealt with the
29702 address, so it will be passed on to subsequent routers to be delivered in the
29704 .ecindex IIDsysfil1
29705 .ecindex IIDsysfil2
29706 .ecindex IIDsysfil3
29713 . ////////////////////////////////////////////////////////////////////////////
29714 . ////////////////////////////////////////////////////////////////////////////
29716 .chapter "Message processing" "CHAPmsgproc"
29717 .scindex IIDmesproc "message" "general processing"
29718 Exim performs various transformations on the sender and recipient addresses of
29719 all messages that it handles, and also on the messages' header lines. Some of
29720 these are optional and configurable, while others always take place. All of
29721 this processing, except rewriting as a result of routing, and the addition or
29722 removal of header lines while delivering, happens when a message is received,
29723 before it is placed on Exim's queue.
29725 Some of the automatic processing takes place by default only for
29726 &"locally-originated"& messages. This adjective is used to describe messages
29727 that are not received over TCP/IP, but instead are passed to an Exim process on
29728 its standard input. This includes the interactive &"local SMTP"& case that is
29729 set up by the &%-bs%& command line option.
29731 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
29732 or ::1) are not considered to be locally-originated. Exim does not treat the
29733 loopback interface specially in any way.
29735 If you want the loopback interface to be treated specially, you must ensure
29736 that there are appropriate entries in your ACLs.
29741 .section "Submission mode for non-local messages" "SECTsubmodnon"
29742 .cindex "message" "submission"
29743 .cindex "submission mode"
29744 Processing that happens automatically for locally-originated messages (unless
29745 &%suppress_local_fixups%& is set) can also be requested for messages that are
29746 received over TCP/IP. The term &"submission mode"& is used to describe this
29747 state. Submission mode is set by the modifier
29749 control = submission
29751 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
29752 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
29753 a local submission, and is normally used when the source of the message is
29754 known to be an MUA running on a client host (as opposed to an MTA). For
29755 example, to set submission mode for messages originating on the IPv4 loopback
29756 interface, you could include the following in the MAIL ACL:
29758 warn hosts = 127.0.0.1
29759 control = submission
29761 .cindex "&%sender_retain%& submission option"
29762 There are some options that can be used when setting submission mode. A slash
29763 is used to separate options. For example:
29765 control = submission/sender_retain
29767 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
29768 true and &%local_from_check%& false for the current incoming message. The first
29769 of these allows an existing &'Sender:'& header in the message to remain, and
29770 the second suppresses the check to ensure that &'From:'& matches the
29771 authenticated sender. With this setting, Exim still fixes up messages by adding
29772 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
29773 attempt to check sender authenticity in header lines.
29775 When &%sender_retain%& is not set, a submission mode setting may specify a
29776 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
29779 control = submission/domain=some.domain
29781 The domain may be empty. How this value is used is described in sections
29782 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
29783 that allows you to specify the user's full name for inclusion in a created
29784 &'Sender:'& or &'From:'& header line. For example:
29786 accept authenticated = *
29787 control = submission/domain=wonderland.example/\
29788 name=${lookup {$authenticated_id} \
29789 lsearch {/etc/exim/namelist}}
29791 Because the name may contain any characters, including slashes, the &%name%&
29792 option must be given last. The remainder of the string is used as the name. For
29793 the example above, if &_/etc/exim/namelist_& contains:
29795 bigegg: Humpty Dumpty
29797 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
29800 Sender: Humpty Dumpty <bigegg@wonderland.example>
29802 .cindex "return path" "in submission mode"
29803 By default, submission mode forces the return path to the same address as is
29804 used to create the &'Sender:'& header. However, if &%sender_retain%& is
29805 specified, the return path is also left unchanged.
29807 &*Note*&: The changes caused by submission mode take effect after the predata
29808 ACL. This means that any sender checks performed before the fix-ups use the
29809 untrusted sender address specified by the user, not the trusted sender address
29810 specified by submission mode. Although this might be slightly unexpected, it
29811 does mean that you can configure ACL checks to spot that a user is trying to
29812 spoof another's address.
29814 .section "Line endings" "SECTlineendings"
29815 .cindex "line endings"
29816 .cindex "carriage return"
29818 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
29819 linefeed) is the line ending for messages transmitted over the Internet using
29820 SMTP over TCP/IP. However, within individual operating systems, different
29821 conventions are used. For example, Unix-like systems use just LF, but others
29822 use CRLF or just CR.
29824 Exim was designed for Unix-like systems, and internally, it stores messages
29825 using the system's convention of a single LF as a line terminator. When
29826 receiving a message, all line endings are translated to this standard format.
29827 Originally, it was thought that programs that passed messages directly to an
29828 MTA within an operating system would use that system's convention. Experience
29829 has shown that this is not the case; for example, there are Unix applications
29830 that use CRLF in this circumstance. For this reason, and for compatibility with
29831 other MTAs, the way Exim handles line endings for all messages is now as
29835 LF not preceded by CR is treated as a line ending.
29837 CR is treated as a line ending; if it is immediately followed by LF, the LF
29840 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
29841 nor a local message in the state where a line containing only a dot is a
29844 If a bare CR is encountered within a header line, an extra space is added after
29845 the line terminator so as not to end the header line. The reasoning behind this
29846 is that bare CRs in header lines are most likely either to be mistakes, or
29847 people trying to play silly games.
29849 If the first header line received in a message ends with CRLF, a subsequent
29850 bare LF in a header line is treated in the same way as a bare CR in a header
29858 .section "Unqualified addresses" "SECID218"
29859 .cindex "unqualified addresses"
29860 .cindex "address" "qualification"
29861 By default, Exim expects every envelope address it receives from an external
29862 host to be fully qualified. Unqualified addresses cause negative responses to
29863 SMTP commands. However, because SMTP is used as a means of transporting
29864 messages from MUAs running on personal workstations, there is sometimes a
29865 requirement to accept unqualified addresses from specific hosts or IP networks.
29867 Exim has two options that separately control which hosts may send unqualified
29868 sender or recipient addresses in SMTP commands, namely
29869 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
29870 cases, if an unqualified address is accepted, it is qualified by adding the
29871 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
29873 .oindex "&%qualify_domain%&"
29874 .oindex "&%qualify_recipient%&"
29875 Unqualified addresses in header lines are automatically qualified for messages
29876 that are locally originated, unless the &%-bnq%& option is given on the command
29877 line. For messages received over SMTP, unqualified addresses in header lines
29878 are qualified only if unqualified addresses are permitted in SMTP commands. In
29879 other words, such qualification is also controlled by
29880 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
29885 .section "The UUCP From line" "SECID219"
29886 .cindex "&""From""& line"
29887 .cindex "UUCP" "&""From""& line"
29888 .cindex "sender" "address"
29889 .oindex "&%uucp_from_pattern%&"
29890 .oindex "&%uucp_from_sender%&"
29891 .cindex "envelope sender"
29892 .cindex "Sendmail compatibility" "&""From""& line"
29893 Messages that have come from UUCP (and some other applications) often begin
29894 with a line containing the envelope sender and a timestamp, following the word
29895 &"From"&. Examples of two common formats are:
29897 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
29898 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
29900 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
29901 Exim recognizes such lines at the start of messages that are submitted to it
29902 via the command line (that is, on the standard input). It does not recognize
29903 such lines in incoming SMTP messages, unless the sending host matches
29904 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
29905 and &%ignore_fromline_local%& is set. The recognition is controlled by a
29906 regular expression that is defined by the &%uucp_from_pattern%& option, whose
29907 default value matches the two common cases shown above and puts the address
29908 that follows &"From"& into &$1$&.
29910 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
29911 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
29912 a trusted user, the message's sender address is constructed by expanding the
29913 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
29914 then parsed as an RFC 2822 address. If there is no domain, the local part is
29915 qualified with &%qualify_domain%& unless it is the empty string. However, if
29916 the command line &%-f%& option is used, it overrides the &"From"& line.
29918 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
29919 sender address is not changed. This is also the case for incoming SMTP messages
29920 that are permitted to contain &"From"& lines.
29922 Only one &"From"& line is recognized. If there is more than one, the second is
29923 treated as a data line that starts the body of the message, as it is not valid
29924 as a header line. This also happens if a &"From"& line is present in an
29925 incoming SMTP message from a source that is not permitted to send them.
29929 .section "Resent- header lines" "SECID220"
29930 .cindex "&%Resent-%& header lines"
29931 RFC 2822 makes provision for sets of header lines starting with the string
29932 &`Resent-`& to be added to a message when it is resent by the original
29933 recipient to somebody else. These headers are &'Resent-Date:'&,
29934 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
29935 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
29938 &'Resent fields are strictly informational. They MUST NOT be used in the normal
29939 processing of replies or other such automatic actions on messages.'&
29942 This leaves things a bit vague as far as other processing actions such as
29943 address rewriting are concerned. Exim treats &%Resent-%& header lines as
29947 A &'Resent-From:'& line that just contains the login id of the submitting user
29948 is automatically rewritten in the same way as &'From:'& (see below).
29950 If there's a rewriting rule for a particular header line, it is also applied to
29951 &%Resent-%& header lines of the same type. For example, a rule that rewrites
29952 &'From:'& also rewrites &'Resent-From:'&.
29954 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
29957 For a locally-submitted message,
29958 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
29959 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
29960 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
29961 included in log lines in this case.
29963 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
29964 &%Resent-%& header lines are present.
29970 .section "The Auto-Submitted: header line" "SECID221"
29971 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
29972 includes the header line:
29974 Auto-Submitted: auto-replied
29977 .section "The Bcc: header line" "SECID222"
29978 .cindex "&'Bcc:'& header line"
29979 If Exim is called with the &%-t%& option, to take recipient addresses from a
29980 message's header, it removes any &'Bcc:'& header line that may exist (after
29981 extracting its addresses). If &%-t%& is not present on the command line, any
29982 existing &'Bcc:'& is not removed.
29985 .section "The Date: header line" "SECID223"
29986 .cindex "&'Date:'& header line"
29987 If a locally-generated or submission-mode message has no &'Date:'& header line,
29988 Exim adds one, using the current date and time, unless the
29989 &%suppress_local_fixups%& control has been specified.
29991 .section "The Delivery-date: header line" "SECID224"
29992 .cindex "&'Delivery-date:'& header line"
29993 .oindex "&%delivery_date_remove%&"
29994 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
29995 set. Exim can be configured to add them to the final delivery of messages. (See
29996 the generic &%delivery_date_add%& transport option.) They should not be present
29997 in messages in transit. If the &%delivery_date_remove%& configuration option is
29998 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
30002 .section "The Envelope-to: header line" "SECID225"
30003 .cindex "&'Envelope-to:'& header line"
30004 .oindex "&%envelope_to_remove%&"
30005 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
30006 Exim can be configured to add them to the final delivery of messages. (See the
30007 generic &%envelope_to_add%& transport option.) They should not be present in
30008 messages in transit. If the &%envelope_to_remove%& configuration option is set
30009 (the default), Exim removes &'Envelope-to:'& header lines from incoming
30013 .section "The From: header line" "SECTthefrohea"
30014 .cindex "&'From:'& header line"
30015 .cindex "Sendmail compatibility" "&""From""& line"
30016 .cindex "message" "submission"
30017 .cindex "submission mode"
30018 If a submission-mode message does not contain a &'From:'& header line, Exim
30019 adds one if either of the following conditions is true:
30022 The envelope sender address is not empty (that is, this is not a bounce
30023 message). The added header line copies the envelope sender address.
30025 .vindex "&$authenticated_id$&"
30026 The SMTP session is authenticated and &$authenticated_id$& is not empty.
30028 .vindex "&$qualify_domain$&"
30029 If no domain is specified by the submission control, the local part is
30030 &$authenticated_id$& and the domain is &$qualify_domain$&.
30032 If a non-empty domain is specified by the submission control, the local
30033 part is &$authenticated_id$&, and the domain is the specified domain.
30035 If an empty domain is specified by the submission control,
30036 &$authenticated_id$& is assumed to be the complete address.
30040 A non-empty envelope sender takes precedence.
30042 If a locally-generated incoming message does not contain a &'From:'& header
30043 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
30044 containing the sender's address. The calling user's login name and full name
30045 are used to construct the address, as described in section &<<SECTconstr>>&.
30046 They are obtained from the password data by calling &[getpwuid()]& (but see the
30047 &%unknown_login%& configuration option). The address is qualified with
30048 &%qualify_domain%&.
30050 For compatibility with Sendmail, if an incoming, non-SMTP message has a
30051 &'From:'& header line containing just the unqualified login name of the calling
30052 user, this is replaced by an address containing the user's login name and full
30053 name as described in section &<<SECTconstr>>&.
30056 .section "The Message-ID: header line" "SECID226"
30057 .cindex "&'Message-ID:'& header line"
30058 .cindex "message" "submission"
30059 .oindex "&%message_id_header_text%&"
30060 If a locally-generated or submission-mode incoming message does not contain a
30061 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
30062 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
30063 to the message. If there are any &'Resent-:'& headers in the message, it
30064 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
30065 message id, preceded by the letter E to ensure it starts with a letter, and
30066 followed by @ and the primary host name. Additional information can be included
30067 in this header line by setting the &%message_id_header_text%& and/or
30068 &%message_id_header_domain%& options.
30071 .section "The Received: header line" "SECID227"
30072 .cindex "&'Received:'& header line"
30073 A &'Received:'& header line is added at the start of every message. The
30074 contents are defined by the &%received_header_text%& configuration option, and
30075 Exim automatically adds a semicolon and a timestamp to the configured string.
30077 The &'Received:'& header is generated as soon as the message's header lines
30078 have been received. At this stage, the timestamp in the &'Received:'& header
30079 line is the time that the message started to be received. This is the value
30080 that is seen by the DATA ACL and by the &[local_scan()]& function.
30082 Once a message is accepted, the timestamp in the &'Received:'& header line is
30083 changed to the time of acceptance, which is (apart from a small delay while the
30084 -H spool file is written) the earliest time at which delivery could start.
30087 .section "The References: header line" "SECID228"
30088 .cindex "&'References:'& header line"
30089 Messages created by the &(autoreply)& transport include a &'References:'&
30090 header line. This is constructed according to the rules that are described in
30091 section 3.64 of RFC 2822 (which states that replies should contain such a
30092 header line), and section 3.14 of RFC 3834 (which states that automatic
30093 responses are not different in this respect). However, because some mail
30094 processing software does not cope well with very long header lines, no more
30095 than 12 message IDs are copied from the &'References:'& header line in the
30096 incoming message. If there are more than 12, the first one and then the final
30097 11 are copied, before adding the message ID of the incoming message.
30101 .section "The Return-path: header line" "SECID229"
30102 .cindex "&'Return-path:'& header line"
30103 .oindex "&%return_path_remove%&"
30104 &'Return-path:'& header lines are defined as something an MTA may insert when
30105 it does the final delivery of messages. (See the generic &%return_path_add%&
30106 transport option.) Therefore, they should not be present in messages in
30107 transit. If the &%return_path_remove%& configuration option is set (the
30108 default), Exim removes &'Return-path:'& header lines from incoming messages.
30112 .section "The Sender: header line" "SECTthesenhea"
30113 .cindex "&'Sender:'& header line"
30114 .cindex "message" "submission"
30115 For a locally-originated message from an untrusted user, Exim may remove an
30116 existing &'Sender:'& header line, and it may add a new one. You can modify
30117 these actions by setting the &%local_sender_retain%& option true, the
30118 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
30121 When a local message is received from an untrusted user and
30122 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
30123 control has not been set, a check is made to see if the address given in the
30124 &'From:'& header line is the correct (local) sender of the message. The address
30125 that is expected has the login name as the local part and the value of
30126 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
30127 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
30128 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
30129 line is added to the message.
30131 If you set &%local_from_check%& false, this checking does not occur. However,
30132 the removal of an existing &'Sender:'& line still happens, unless you also set
30133 &%local_sender_retain%& to be true. It is not possible to set both of these
30134 options true at the same time.
30136 .cindex "submission mode"
30137 By default, no processing of &'Sender:'& header lines is done for messages
30138 received over TCP/IP or for messages submitted by trusted users. However, when
30139 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
30140 not specified on the submission control, the following processing takes place:
30142 .vindex "&$authenticated_id$&"
30143 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
30144 authenticated, and &$authenticated_id$& is not empty, a sender address is
30145 created as follows:
30148 .vindex "&$qualify_domain$&"
30149 If no domain is specified by the submission control, the local part is
30150 &$authenticated_id$& and the domain is &$qualify_domain$&.
30152 If a non-empty domain is specified by the submission control, the local part
30153 is &$authenticated_id$&, and the domain is the specified domain.
30155 If an empty domain is specified by the submission control,
30156 &$authenticated_id$& is assumed to be the complete address.
30159 This address is compared with the address in the &'From:'& header line. If they
30160 are different, a &'Sender:'& header line containing the created address is
30161 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
30162 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
30164 .cindex "return path" "created from &'Sender:'&"
30165 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
30166 the message (the envelope sender address) is changed to be the same address,
30167 except in the case of submission mode when &%sender_retain%& is specified.
30171 .section "Adding and removing header lines in routers and transports" &&&
30172 "SECTheadersaddrem"
30173 .cindex "header lines" "adding; in router or transport"
30174 .cindex "header lines" "removing; in router or transport"
30175 When a message is delivered, the addition and removal of header lines can be
30176 specified in a system filter, or on any of the routers and transports that
30177 process the message. Section &<<SECTaddremheasys>>& contains details about
30178 modifying headers in a system filter. Header lines can also be added in an ACL
30179 as a message is received (see section &<<SECTaddheadacl>>&).
30181 In contrast to what happens in a system filter, header modifications that are
30182 specified on routers and transports apply only to the particular recipient
30183 addresses that are being processed by those routers and transports. These
30184 changes do not actually take place until a copy of the message is being
30185 transported. Therefore, they do not affect the basic set of header lines, and
30186 they do not affect the values of the variables that refer to header lines.
30188 &*Note*&: In particular, this means that any expansions in the configuration of
30189 the transport cannot refer to the modified header lines, because such
30190 expansions all occur before the message is actually transported.
30192 For both routers and transports, the result of expanding a &%headers_add%&
30193 option must be in the form of one or more RFC 2822 header lines, separated by
30194 newlines (coded as &"\n"&). For example:
30196 headers_add = X-added-header: added by $primary_hostname\n\
30197 X-added-second: another added header line
30199 Exim does not check the syntax of these added header lines.
30201 The result of expanding &%headers_remove%& must consist of a colon-separated
30202 list of header names. This is confusing, because header names themselves are
30203 often terminated by colons. In this case, the colons are the list separators,
30204 not part of the names. For example:
30206 headers_remove = return-receipt-to:acknowledge-to
30208 When &%headers_add%& or &%headers_remove%& is specified on a router, its value
30209 is expanded at routing time, and then associated with all addresses that are
30210 accepted by that router, and also with any new addresses that it generates. If
30211 an address passes through several routers as a result of aliasing or
30212 forwarding, the changes are cumulative.
30214 .oindex "&%unseen%&"
30215 However, this does not apply to multiple routers that result from the use of
30216 the &%unseen%& option. Any header modifications that were specified by the
30217 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
30219 Addresses that end up with different &%headers_add%& or &%headers_remove%&
30220 settings cannot be delivered together in a batch, so a transport is always
30221 dealing with a set of addresses that have the same header-processing
30224 The transport starts by writing the original set of header lines that arrived
30225 with the message, possibly modified by the system filter. As it writes out
30226 these lines, it consults the list of header names that were attached to the
30227 recipient address(es) by &%headers_remove%& options in routers, and it also
30228 consults the transport's own &%headers_remove%& option. Header lines whose
30229 names are on either of these lists are not written out. If there are multiple
30230 instances of any listed header, they are all skipped.
30232 After the remaining original header lines have been written, new header
30233 lines that were specified by routers' &%headers_add%& options are written, in
30234 the order in which they were attached to the address. These are followed by any
30235 header lines specified by the transport's &%headers_add%& option.
30237 This way of handling header line modifications in routers and transports has
30238 the following consequences:
30241 The original set of header lines, possibly modified by the system filter,
30242 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
30243 to it, at all times.
30245 Header lines that are added by a router's
30246 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
30247 expansion syntax in subsequent routers or the transport.
30249 Conversely, header lines that are specified for removal by &%headers_remove%&
30250 in a router remain visible to subsequent routers and the transport.
30252 Headers added to an address by &%headers_add%& in a router cannot be removed by
30253 a later router or by a transport.
30255 An added header can refer to the contents of an original header that is to be
30256 removed, even it has the same name as the added header. For example:
30258 headers_remove = subject
30259 headers_add = Subject: new subject (was: $h_subject:)
30263 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
30264 for a &(redirect)& router that has the &%one_time%& option set.
30270 .section "Constructed addresses" "SECTconstr"
30271 .cindex "address" "constructed"
30272 .cindex "constructed address"
30273 When Exim constructs a sender address for a locally-generated message, it uses
30276 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
30280 Zaphod Beeblebrox <zaphod@end.univ.example>
30282 The user name is obtained from the &%-F%& command line option if set, or
30283 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
30284 &"gecos"& field from the password entry. If the &"gecos"& field contains an
30285 ampersand character, this is replaced by the login name with the first letter
30286 upper cased, as is conventional in a number of operating systems. See the
30287 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
30288 The &%unknown_username%& option can be used to specify user names in cases when
30289 there is no password file entry.
30292 In all cases, the user name is made to conform to RFC 2822 by quoting all or
30293 parts of it if necessary. In addition, if it contains any non-printing
30294 characters, it is encoded as described in RFC 2047, which defines a way of
30295 including non-ASCII characters in header lines. The value of the
30296 &%headers_charset%& option specifies the name of the encoding that is used (the
30297 characters are assumed to be in this encoding). The setting of
30298 &%print_topbitchars%& controls whether characters with the top bit set (that
30299 is, with codes greater than 127) count as printing characters or not.
30303 .section "Case of local parts" "SECID230"
30304 .cindex "case of local parts"
30305 .cindex "local part" "case of"
30306 RFC 2822 states that the case of letters in the local parts of addresses cannot
30307 be assumed to be non-significant. Exim preserves the case of local parts of
30308 addresses, but by default it uses a lower-cased form when it is routing,
30309 because on most Unix systems, usernames are in lower case and case-insensitive
30310 routing is required. However, any particular router can be made to use the
30311 original case for local parts by setting the &%caseful_local_part%& generic
30314 .cindex "mixed-case login names"
30315 If you must have mixed-case user names on your system, the best way to proceed,
30316 assuming you want case-independent handling of incoming email, is to set up
30317 your first router to convert incoming local parts in your domains to the
30318 correct case by means of a file lookup. For example:
30322 domains = +local_domains
30323 data = ${lookup{$local_part}cdb\
30324 {/etc/usercased.cdb}{$value}fail}\
30327 For this router, the local part is forced to lower case by the default action
30328 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
30329 up a new local part in the correct case. If you then set &%caseful_local_part%&
30330 on any subsequent routers which process your domains, they will operate on
30331 local parts with the correct case in a case-sensitive manner.
30335 .section "Dots in local parts" "SECID231"
30336 .cindex "dot" "in local part"
30337 .cindex "local part" "dots in"
30338 RFC 2822 forbids empty components in local parts. That is, an unquoted local
30339 part may not begin or end with a dot, nor have two consecutive dots in the
30340 middle. However, it seems that many MTAs do not enforce this, so Exim permits
30341 empty components for compatibility.
30345 .section "Rewriting addresses" "SECID232"
30346 .cindex "rewriting" "addresses"
30347 Rewriting of sender and recipient addresses, and addresses in headers, can
30348 happen automatically, or as the result of configuration options, as described
30349 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
30350 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
30352 Automatic rewriting includes qualification, as mentioned above. The other case
30353 in which it can happen is when an incomplete non-local domain is given. The
30354 routing process may cause this to be expanded into the full domain name. For
30355 example, a header such as
30359 might get rewritten as
30361 To: hare@teaparty.wonderland.fict.example
30363 Rewriting as a result of routing is the one kind of message processing that
30364 does not happen at input time, as it cannot be done until the address has
30367 Strictly, one should not do &'any'& deliveries of a message until all its
30368 addresses have been routed, in case any of the headers get changed as a
30369 result of routing. However, doing this in practice would hold up many
30370 deliveries for unreasonable amounts of time, just because one address could not
30371 immediately be routed. Exim therefore does not delay other deliveries when
30372 routing of one or more addresses is deferred.
30373 .ecindex IIDmesproc
30377 . ////////////////////////////////////////////////////////////////////////////
30378 . ////////////////////////////////////////////////////////////////////////////
30380 .chapter "SMTP processing" "CHAPSMTP"
30381 .scindex IIDsmtpproc1 "SMTP" "processing details"
30382 .scindex IIDsmtpproc2 "LMTP" "processing details"
30383 Exim supports a number of different ways of using the SMTP protocol, and its
30384 LMTP variant, which is an interactive protocol for transferring messages into a
30385 closed mail store application. This chapter contains details of how SMTP is
30386 processed. For incoming mail, the following are available:
30389 SMTP over TCP/IP (Exim daemon or &'inetd'&);
30391 SMTP over the standard input and output (the &%-bs%& option);
30393 Batched SMTP on the standard input (the &%-bS%& option).
30396 For mail delivery, the following are available:
30399 SMTP over TCP/IP (the &(smtp)& transport);
30401 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
30404 LMTP over a pipe to a process running in the local host (the &(lmtp)&
30407 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
30408 the &%use_bsmtp%& option set).
30411 &'Batched SMTP'& is the name for a process in which batches of messages are
30412 stored in or read from files (or pipes), in a format in which SMTP commands are
30413 used to contain the envelope information.
30417 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
30418 .cindex "SMTP" "outgoing over TCP/IP"
30419 .cindex "outgoing SMTP over TCP/IP"
30420 .cindex "LMTP" "over TCP/IP"
30421 .cindex "outgoing LMTP over TCP/IP"
30424 .cindex "SIZE option on MAIL command"
30425 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
30426 The &%protocol%& option selects which protocol is to be used, but the actual
30427 processing is the same in both cases.
30429 If, in response to its EHLO command, Exim is told that the SIZE
30430 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
30431 command. The value of <&'n'&> is the message size plus the value of the
30432 &%size_addition%& option (default 1024) to allow for additions to the message
30433 such as per-transport header lines, or changes made in a
30434 .cindex "transport" "filter"
30435 .cindex "filter" "transport filter"
30436 transport filter. If &%size_addition%& is set negative, the use of SIZE is
30439 If the remote server advertises support for PIPELINING, Exim uses the
30440 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
30441 required for the transaction.
30443 If the remote server advertises support for the STARTTLS command, and Exim
30444 was built to support TLS encryption, it tries to start a TLS session unless the
30445 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
30447 If the remote server advertises support for the AUTH command, Exim scans
30448 the authenticators configuration for any suitable client settings, as described
30449 in chapter &<<CHAPSMTPAUTH>>&.
30451 .cindex "carriage return"
30453 Responses from the remote host are supposed to be terminated by CR followed by
30454 LF. However, there are known to be hosts that do not send CR characters, so in
30455 order to be able to interwork with such hosts, Exim treats LF on its own as a
30458 If a message contains a number of different addresses, all those with the same
30459 characteristics (for example, the same envelope sender) that resolve to the
30460 same set of hosts, in the same order, are sent in a single SMTP transaction,
30461 even if they are for different domains, unless there are more than the setting
30462 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
30463 they are split into groups containing no more than &%max_rcpt%&s addresses
30464 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
30465 in parallel sessions. The order of hosts with identical MX values is not
30466 significant when checking whether addresses can be batched in this way.
30468 When the &(smtp)& transport suffers a temporary failure that is not
30469 message-related, Exim updates its transport-specific database, which contains
30470 records indexed by host name that remember which messages are waiting for each
30471 particular host. It also updates the retry database with new retry times.
30473 .cindex "hints database" "retry keys"
30474 Exim's retry hints are based on host name plus IP address, so if one address of
30475 a multi-homed host is broken, it will soon be skipped most of the time.
30476 See the next section for more detail about error handling.
30478 .cindex "SMTP" "passed connection"
30479 .cindex "SMTP" "batching over TCP/IP"
30480 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
30481 looks in the hints database for the transport to see if there are any queued
30482 messages waiting for the host to which it is connected. If it finds one, it
30483 creates a new Exim process using the &%-MC%& option (which can only be used by
30484 a process running as root or the Exim user) and passes the TCP/IP socket to it
30485 so that it can deliver another message using the same socket. The new process
30486 does only those deliveries that are routed to the connected host, and may in
30487 turn pass the socket on to a third process, and so on.
30489 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
30490 limit the number of messages sent down a single TCP/IP connection.
30492 .cindex "asterisk" "after IP address"
30493 The second and subsequent messages delivered down an existing connection are
30494 identified in the main log by the addition of an asterisk after the closing
30495 square bracket of the IP address.
30500 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
30501 .cindex "error" "in outgoing SMTP"
30502 .cindex "SMTP" "errors in outgoing"
30503 .cindex "host" "error"
30504 Three different kinds of error are recognized for outgoing SMTP: host errors,
30505 message errors, and recipient errors.
30508 .vitem "&*Host errors*&"
30509 A host error is not associated with a particular message or with a
30510 particular recipient of a message. The host errors are:
30513 Connection refused or timed out,
30515 Any error response code on connection,
30517 Any error response code to EHLO or HELO,
30519 Loss of connection at any time, except after &"."&,
30521 I/O errors at any time,
30523 Timeouts during the session, other than in response to MAIL, RCPT or
30524 the &"."& at the end of the data.
30527 For a host error, a permanent error response on connection, or in response to
30528 EHLO, causes all addresses routed to the host to be failed. Any other host
30529 error causes all addresses to be deferred, and retry data to be created for the
30530 host. It is not tried again, for any message, until its retry time arrives. If
30531 the current set of addresses are not all delivered in this run (to some
30532 alternative host), the message is added to the list of those waiting for this
30533 host, so if it is still undelivered when a subsequent successful delivery is
30534 made to the host, it will be sent down the same SMTP connection.
30536 .vitem "&*Message errors*&"
30537 .cindex "message" "error"
30538 A message error is associated with a particular message when sent to a
30539 particular host, but not with a particular recipient of the message. The
30540 message errors are:
30543 Any error response code to MAIL, DATA, or the &"."& that terminates
30546 Timeout after MAIL,
30548 Timeout or loss of connection after the &"."& that terminates the data. A
30549 timeout after the DATA command itself is treated as a host error, as is loss of
30550 connection at any other time.
30553 For a message error, a permanent error response (5&'xx'&) causes all addresses
30554 to be failed, and a delivery error report to be returned to the sender. A
30555 temporary error response (4&'xx'&), or one of the timeouts, causes all
30556 addresses to be deferred. Retry data is not created for the host, but instead,
30557 a retry record for the combination of host plus message id is created. The
30558 message is not added to the list of those waiting for this host. This ensures
30559 that the failing message will not be sent to this host again until the retry
30560 time arrives. However, other messages that are routed to the host are not
30561 affected, so if it is some property of the message that is causing the error,
30562 it will not stop the delivery of other mail.
30564 If the remote host specified support for the SIZE parameter in its response
30565 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
30566 over-large message will cause a message error because the error arrives as a
30569 .vitem "&*Recipient errors*&"
30570 .cindex "recipient" "error"
30571 A recipient error is associated with a particular recipient of a message. The
30572 recipient errors are:
30575 Any error response to RCPT,
30577 Timeout after RCPT.
30580 For a recipient error, a permanent error response (5&'xx'&) causes the
30581 recipient address to be failed, and a bounce message to be returned to the
30582 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
30583 address to be deferred, and routing retry data to be created for it. This is
30584 used to delay processing of the address in subsequent queue runs, until its
30585 routing retry time arrives. This applies to all messages, but because it
30586 operates only in queue runs, one attempt will be made to deliver a new message
30587 to the failing address before the delay starts to operate. This ensures that,
30588 if the failure is really related to the message rather than the recipient
30589 (&"message too big for this recipient"& is a possible example), other messages
30590 have a chance of getting delivered. If a delivery to the address does succeed,
30591 the retry information gets cleared, so all stuck messages get tried again, and
30592 the retry clock is reset.
30594 The message is not added to the list of those waiting for this host. Use of the
30595 host for other messages is unaffected, and except in the case of a timeout,
30596 other recipients are processed independently, and may be successfully delivered
30597 in the current SMTP session. After a timeout it is of course impossible to
30598 proceed with the session, so all addresses get deferred. However, those other
30599 than the one that failed do not suffer any subsequent retry delays. Therefore,
30600 if one recipient is causing trouble, the others have a chance of getting
30601 through when a subsequent delivery attempt occurs before the failing
30602 recipient's retry time.
30605 In all cases, if there are other hosts (or IP addresses) available for the
30606 current set of addresses (for example, from multiple MX records), they are
30607 tried in this run for any undelivered addresses, subject of course to their
30608 own retry data. In other words, recipient error retry data does not take effect
30609 until the next delivery attempt.
30611 Some hosts have been observed to give temporary error responses to every
30612 MAIL command at certain times (&"insufficient space"& has been seen). It
30613 would be nice if such circumstances could be recognized, and defer data for the
30614 host itself created, but this is not possible within the current Exim design.
30615 What actually happens is that retry data for every (host, message) combination
30618 The reason that timeouts after MAIL and RCPT are treated specially is that
30619 these can sometimes arise as a result of the remote host's verification
30620 procedures. Exim makes this assumption, and treats them as if a temporary error
30621 response had been received. A timeout after &"."& is treated specially because
30622 it is known that some broken implementations fail to recognize the end of the
30623 message if the last character of the last line is a binary zero. Thus, it is
30624 helpful to treat this case as a message error.
30626 Timeouts at other times are treated as host errors, assuming a problem with the
30627 host, or the connection to it. If a timeout after MAIL, RCPT,
30628 or &"."& is really a connection problem, the assumption is that at the next try
30629 the timeout is likely to occur at some other point in the dialogue, causing it
30630 then to be treated as a host error.
30632 There is experimental evidence that some MTAs drop the connection after the
30633 terminating &"."& if they do not like the contents of the message for some
30634 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
30635 should be given. That is why Exim treats this case as a message rather than a
30636 host error, in order not to delay other messages to the same host.
30641 .section "Incoming SMTP messages over TCP/IP" "SECID233"
30642 .cindex "SMTP" "incoming over TCP/IP"
30643 .cindex "incoming SMTP over TCP/IP"
30646 Incoming SMTP messages can be accepted in one of two ways: by running a
30647 listening daemon, or by using &'inetd'&. In the latter case, the entry in
30648 &_/etc/inetd.conf_& should be like this:
30650 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
30652 Exim distinguishes between this case and the case of a locally running user
30653 agent using the &%-bs%& option by checking whether or not the standard input is
30654 a socket. When it is, either the port must be privileged (less than 1024), or
30655 the caller must be root or the Exim user. If any other user passes a socket
30656 with an unprivileged port number, Exim prints a message on the standard error
30657 stream and exits with an error code.
30659 By default, Exim does not make a log entry when a remote host connects or
30660 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
30661 unexpected. It can be made to write such log entries by setting the
30662 &%smtp_connection%& log selector.
30664 .cindex "carriage return"
30666 Commands from the remote host are supposed to be terminated by CR followed by
30667 LF. However, there are known to be hosts that do not send CR characters. In
30668 order to be able to interwork with such hosts, Exim treats LF on its own as a
30670 Furthermore, because common code is used for receiving messages from all
30671 sources, a CR on its own is also interpreted as a line terminator. However, the
30672 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
30674 .cindex "EHLO" "invalid data"
30675 .cindex "HELO" "invalid data"
30676 One area that sometimes gives rise to problems concerns the EHLO or
30677 HELO commands. Some clients send syntactically invalid versions of these
30678 commands, which Exim rejects by default. (This is nothing to do with verifying
30679 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
30680 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
30681 match the broken hosts that send invalid commands.
30683 .cindex "SIZE option on MAIL command"
30684 .cindex "MAIL" "SIZE option"
30685 The amount of disk space available is checked whenever SIZE is received on
30686 a MAIL command, independently of whether &%message_size_limit%& or
30687 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
30688 false. A temporary error is given if there is not enough space. If
30689 &%check_spool_space%& is set, the check is for that amount of space plus the
30690 value given with SIZE, that is, it checks that the addition of the incoming
30691 message will not reduce the space below the threshold.
30693 When a message is successfully received, Exim includes the local message id in
30694 its response to the final &"."& that terminates the data. If the remote host
30695 logs this text it can help with tracing what has happened to a message.
30697 The Exim daemon can limit the number of simultaneous incoming connections it is
30698 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
30699 number of simultaneous incoming connections from a single remote host (see the
30700 &%smtp_accept_max_per_host%& option). Additional connection attempts are
30701 rejected using the SMTP temporary error code 421.
30703 The Exim daemon does not rely on the SIGCHLD signal to detect when a
30704 subprocess has finished, as this can get lost at busy times. Instead, it looks
30705 for completed subprocesses every time it wakes up. Provided there are other
30706 things happening (new incoming calls, starts of queue runs), completed
30707 processes will be noticed and tidied away. On very quiet systems you may
30708 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
30709 it will be noticed when the daemon next wakes up.
30711 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
30712 and can also be set up to reject SMTP calls from non-reserved hosts at times of
30713 high system load &-- for details see the &%smtp_accept_reserve%&,
30714 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
30715 applies in both the daemon and &'inetd'& cases.
30717 Exim normally starts a delivery process for each message received, though this
30718 can be varied by means of the &%-odq%& command line option and the
30719 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
30720 number of simultaneously running delivery processes started in this way from
30721 SMTP input can be limited by the &%smtp_accept_queue%& and
30722 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
30723 subsequently received messages are just put on the input queue without starting
30724 a delivery process.
30726 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
30727 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
30728 started up from the &'inetd'& daemon, because in that case each connection is
30729 handled by an entirely independent Exim process. Control by load average is,
30730 however, available with &'inetd'&.
30732 Exim can be configured to verify addresses in incoming SMTP commands as they
30733 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
30734 to rewrite addresses at this time &-- before any syntax checking is done. See
30735 section &<<SECTrewriteS>>&.
30737 Exim can also be configured to limit the rate at which a client host submits
30738 MAIL and RCPT commands in a single SMTP session. See the
30739 &%smtp_ratelimit_hosts%& option.
30743 .section "Unrecognized SMTP commands" "SECID234"
30744 .cindex "SMTP" "unrecognized commands"
30745 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
30746 commands during a single SMTP connection, it drops the connection after sending
30747 the error response to the last command. The default value for
30748 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
30749 abuse that subvert web servers into making connections to SMTP ports; in these
30750 circumstances, a number of non-SMTP lines are sent first.
30753 .section "Syntax and protocol errors in SMTP commands" "SECID235"
30754 .cindex "SMTP" "syntax errors"
30755 .cindex "SMTP" "protocol errors"
30756 A syntax error is detected if an SMTP command is recognized, but there is
30757 something syntactically wrong with its data, for example, a malformed email
30758 address in a RCPT command. Protocol errors include invalid command
30759 sequencing such as RCPT before MAIL. If Exim receives more than
30760 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
30761 drops the connection after sending the error response to the last command. The
30762 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
30763 broken clients that loop sending bad commands (yes, it has been seen).
30767 .section "Use of non-mail SMTP commands" "SECID236"
30768 .cindex "SMTP" "non-mail commands"
30769 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
30770 DATA. Exim counts such commands, and drops the connection if there are too
30771 many of them in a single SMTP session. This action catches some
30772 denial-of-service attempts and things like repeated failing AUTHs, or a mad
30773 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
30774 defines what &"too many"& means. Its default value is 10.
30776 When a new message is expected, one occurrence of RSET is not counted. This
30777 allows a client to send one RSET between messages (this is not necessary,
30778 but some clients do it). Exim also allows one uncounted occurrence of HELO
30779 or EHLO, and one occurrence of STARTTLS between messages. After
30780 starting up a TLS session, another EHLO is expected, and so it too is not
30783 The first occurrence of AUTH in a connection, or immediately following
30784 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
30785 RCPT, DATA, and QUIT are counted.
30787 You can control which hosts are subject to the limit set by
30788 &%smtp_accept_max_nonmail%& by setting
30789 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
30790 the limit apply to all hosts. This option means that you can exclude any
30791 specific badly-behaved hosts that you have to live with.
30796 .section "The VRFY and EXPN commands" "SECID237"
30797 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
30798 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
30799 appropriate) in order to decide whether the command should be accepted or not.
30800 If no ACL is defined, the command is rejected.
30802 .cindex "VRFY" "processing"
30803 When VRFY is accepted, it runs exactly the same code as when Exim is
30804 called with the &%-bv%& option.
30806 .cindex "EXPN" "processing"
30807 When EXPN is accepted, a single-level expansion of the address is done.
30808 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
30809 than a verification (the &%-bv%& option). If an unqualified local part is given
30810 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
30811 of VRFY and EXPN commands are logged on the main and reject logs, and
30812 VRFY verification failures are logged on the main log for consistency with
30817 .section "The ETRN command" "SECTETRN"
30818 .cindex "ETRN" "processing"
30819 RFC 1985 describes an SMTP command called ETRN that is designed to
30820 overcome the security problems of the TURN command (which has fallen into
30821 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
30822 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
30823 should be accepted or not. If no ACL is defined, the command is rejected.
30825 The ETRN command is concerned with &"releasing"& messages that are awaiting
30826 delivery to certain hosts. As Exim does not organize its message queue by host,
30827 the only form of ETRN that is supported by default is the one where the
30828 text starts with the &"#"& prefix, in which case the remainder of the text is
30829 specific to the SMTP server. A valid ETRN command causes a run of Exim with
30830 the &%-R%& option to happen, with the remainder of the ETRN text as its
30831 argument. For example,
30839 which causes a delivery attempt on all messages with undelivered addresses
30840 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
30841 default), Exim prevents the simultaneous execution of more than one queue run
30842 for the same argument string as a result of an ETRN command. This stops
30843 a misbehaving client from starting more than one queue runner at once.
30845 .cindex "hints database" "ETRN serialization"
30846 Exim implements the serialization by means of a hints database in which a
30847 record is written whenever a process is started by ETRN, and deleted when
30848 the process completes. However, Exim does not keep the SMTP session waiting for
30849 the ETRN process to complete. Once ETRN is accepted, the client is sent
30850 a &"success"& return code. Obviously there is scope for hints records to get
30851 left lying around if there is a system or program crash. To guard against this,
30852 Exim ignores any records that are more than six hours old.
30854 .oindex "&%smtp_etrn_command%&"
30855 For more control over what ETRN does, the &%smtp_etrn_command%& option can
30856 used. This specifies a command that is run whenever ETRN is received,
30857 whatever the form of its argument. For
30860 smtp_etrn_command = /etc/etrn_command $domain \
30861 $sender_host_address
30863 .vindex "&$domain$&"
30864 The string is split up into arguments which are independently expanded. The
30865 expansion variable &$domain$& is set to the argument of the ETRN command,
30866 and no syntax checking is done on the contents of this argument. Exim does not
30867 wait for the command to complete, so its status code is not checked. Exim runs
30868 under its own uid and gid when receiving incoming SMTP, so it is not possible
30869 for it to change them before running the command.
30873 .section "Incoming local SMTP" "SECID238"
30874 .cindex "SMTP" "local incoming"
30875 Some user agents use SMTP to pass messages to their local MTA using the
30876 standard input and output, as opposed to passing the envelope on the command
30877 line and writing the message to the standard input. This is supported by the
30878 &%-bs%& option. This form of SMTP is handled in the same way as incoming
30879 messages over TCP/IP (including the use of ACLs), except that the envelope
30880 sender given in a MAIL command is ignored unless the caller is trusted. In
30881 an ACL you can detect this form of SMTP input by testing for an empty host
30882 identification. It is common to have this as the first line in the ACL that
30883 runs for RCPT commands:
30887 This accepts SMTP messages from local processes without doing any other tests.
30891 .section "Outgoing batched SMTP" "SECTbatchSMTP"
30892 .cindex "SMTP" "batched outgoing"
30893 .cindex "batched SMTP output"
30894 Both the &(appendfile)& and &(pipe)& transports can be used for handling
30895 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
30896 be output in BSMTP format. No SMTP responses are possible for this form of
30897 delivery. All it is doing is using SMTP commands as a way of transmitting the
30898 envelope along with the message.
30900 The message is written to the file or pipe preceded by the SMTP commands
30901 MAIL and RCPT, and followed by a line containing a single dot. Lines in
30902 the message that start with a dot have an extra dot added. The SMTP command
30903 HELO is not normally used. If it is required, the &%message_prefix%& option
30904 can be used to specify it.
30906 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
30907 one recipient address at a time by default. However, you can arrange for them
30908 to handle several addresses at once by setting the &%batch_max%& option. When
30909 this is done for BSMTP, messages may contain multiple RCPT commands. See
30910 chapter &<<CHAPbatching>>& for more details.
30913 When one or more addresses are routed to a BSMTP transport by a router that
30914 sets up a host list, the name of the first host on the list is available to the
30915 transport in the variable &$host$&. Here is an example of such a transport and
30920 driver = manualroute
30921 transport = smtp_appendfile
30922 route_list = domain.example batch.host.example
30926 driver = appendfile
30927 directory = /var/bsmtp/$host
30932 This causes messages addressed to &'domain.example'& to be written in BSMTP
30933 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
30934 message (unless there are more than 1000 recipients).
30938 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
30939 .cindex "SMTP" "batched incoming"
30940 .cindex "batched SMTP input"
30941 The &%-bS%& command line option causes Exim to accept one or more messages by
30942 reading SMTP on the standard input, but to generate no responses. If the caller
30943 is trusted, the senders in the MAIL commands are believed; otherwise the
30944 sender is always the caller of Exim. Unqualified senders and receivers are not
30945 rejected (there seems little point) but instead just get qualified. HELO
30946 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
30947 as NOOP; QUIT quits.
30949 No policy checking is done for BSMTP input. That is, no ACL is run at anytime.
30950 In this respect it is like non-SMTP local input.
30952 If an error is detected while reading a message, including a missing &"."& at
30953 the end, Exim gives up immediately. It writes details of the error to the
30954 standard output in a stylized way that the calling program should be able to
30955 make some use of automatically, for example:
30957 554 Unexpected end of file
30958 Transaction started in line 10
30959 Error detected in line 14
30961 It writes a more verbose version, for human consumption, to the standard error
30964 An error was detected while processing a file of BSMTP input.
30965 The error message was:
30967 501 '>' missing at end of address
30969 The SMTP transaction started in line 10.
30970 The error was detected in line 12.
30971 The SMTP command at fault was:
30973 rcpt to:<malformed@in.com.plete
30975 1 previous message was successfully processed.
30976 The rest of the batch was abandoned.
30978 The return code from Exim is zero only if there were no errors. It is 1 if some
30979 messages were accepted before an error was detected, and 2 if no messages were
30981 .ecindex IIDsmtpproc1
30982 .ecindex IIDsmtpproc2
30986 . ////////////////////////////////////////////////////////////////////////////
30987 . ////////////////////////////////////////////////////////////////////////////
30989 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
30990 "Customizing messages"
30991 When a message fails to be delivered, or remains on the queue for more than a
30992 configured amount of time, Exim sends a message to the original sender, or
30993 to an alternative configured address. The text of these messages is built into
30994 the code of Exim, but it is possible to change it, either by adding a single
30995 string, or by replacing each of the paragraphs by text supplied in a file.
30997 The &'From:'& and &'To:'& header lines are automatically generated; you can
30998 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
30999 option. Exim also adds the line
31001 Auto-Submitted: auto-generated
31003 to all warning and bounce messages,
31006 .section "Customizing bounce messages" "SECID239"
31007 .cindex "customizing" "bounce message"
31008 .cindex "bounce message" "customizing"
31009 If &%bounce_message_text%& is set, its contents are included in the default
31010 message immediately after &"This message was created automatically by mail
31011 delivery software."& The string is not expanded. It is not used if
31012 &%bounce_message_file%& is set.
31014 When &%bounce_message_file%& is set, it must point to a template file for
31015 constructing error messages. The file consists of a series of text items,
31016 separated by lines consisting of exactly four asterisks. If the file cannot be
31017 opened, default text is used and a message is written to the main and panic
31018 logs. If any text item in the file is empty, default text is used for that
31021 .vindex "&$bounce_recipient$&"
31022 .vindex "&$bounce_return_size_limit$&"
31023 Each item of text that is read from the file is expanded, and there are two
31024 expansion variables which can be of use here: &$bounce_recipient$& is set to
31025 the recipient of an error message while it is being created, and
31026 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
31027 option, rounded to a whole number.
31029 The items must appear in the file in the following order:
31032 The first item is included in the headers, and should include at least a
31033 &'Subject:'& header. Exim does not check the syntax of these headers.
31035 The second item forms the start of the error message. After it, Exim lists the
31036 failing addresses with their error messages.
31038 The third item is used to introduce any text from pipe transports that is to be
31039 returned to the sender. It is omitted if there is no such text.
31041 The fourth item is used to introduce the copy of the message that is returned
31042 as part of the error report.
31044 The fifth item is added after the fourth one if the returned message is
31045 truncated because it is bigger than &%return_size_limit%&.
31047 The sixth item is added after the copy of the original message.
31050 The default state (&%bounce_message_file%& unset) is equivalent to the
31051 following file, in which the sixth item is empty. The &'Subject:'& and some
31052 other lines have been split in order to fit them on the page:
31054 Subject: Mail delivery failed
31055 ${if eq{$sender_address}{$bounce_recipient}
31056 {: returning message to sender}}
31058 This message was created automatically by mail delivery software.
31060 A message ${if eq{$sender_address}{$bounce_recipient}
31061 {that you sent }{sent by
31065 }}could not be delivered to all of its recipients.
31066 This is a permanent error. The following address(es) failed:
31068 The following text was generated during the delivery attempt(s):
31070 ------ This is a copy of the message, including all the headers.
31073 ------ The body of the message is $message_size characters long;
31075 ------ $bounce_return_size_limit or so are included here.
31078 .section "Customizing warning messages" "SECTcustwarn"
31079 .cindex "customizing" "warning message"
31080 .cindex "warning of delay" "customizing the message"
31081 The option &%warn_message_file%& can be pointed at a template file for use when
31082 warnings about message delays are created. In this case there are only three
31086 The first item is included in the headers, and should include at least a
31087 &'Subject:'& header. Exim does not check the syntax of these headers.
31089 The second item forms the start of the warning message. After it, Exim lists
31090 the delayed addresses.
31092 The third item then ends the message.
31095 The default state is equivalent to the following file, except that some lines
31096 have been split here, in order to fit them on the page:
31098 Subject: Warning: message $message_exim_id delayed
31099 $warn_message_delay
31101 This message was created automatically by mail delivery software.
31103 A message ${if eq{$sender_address}{$warn_message_recipients}
31104 {that you sent }{sent by
31108 }}has not been delivered to all of its recipients after
31109 more than $warn_message_delay on the queue on $primary_hostname.
31111 The message identifier is: $message_exim_id
31112 The subject of the message is: $h_subject
31113 The date of the message is: $h_date
31115 The following address(es) have not yet been delivered:
31117 No action is required on your part. Delivery attempts will
31118 continue for some time, and this warning may be repeated at
31119 intervals if the message remains undelivered. Eventually the
31120 mail delivery software will give up, and when that happens,
31121 the message will be returned to you.
31123 .vindex "&$warn_message_delay$&"
31124 .vindex "&$warn_message_recipients$&"
31125 However, in the default state the subject and date lines are omitted if no
31126 appropriate headers exist. During the expansion of this file,
31127 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
31128 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
31129 of recipients for the warning message. There may be more than one if there are
31130 multiple addresses with different &%errors_to%& settings on the routers that
31136 . ////////////////////////////////////////////////////////////////////////////
31137 . ////////////////////////////////////////////////////////////////////////////
31139 .chapter "Some common configuration settings" "CHAPcomconreq"
31140 This chapter discusses some configuration settings that seem to be fairly
31141 common. More examples and discussion can be found in the Exim book.
31145 .section "Sending mail to a smart host" "SECID240"
31146 .cindex "smart host" "example router"
31147 If you want to send all mail for non-local domains to a &"smart host"&, you
31148 should replace the default &(dnslookup)& router with a router which does the
31149 routing explicitly:
31151 send_to_smart_host:
31152 driver = manualroute
31153 route_list = !+local_domains smart.host.name
31154 transport = remote_smtp
31156 You can use the smart host's IP address instead of the name if you wish.
31157 If you are using Exim only to submit messages to a smart host, and not for
31158 receiving incoming messages, you can arrange for it to do the submission
31159 synchronously by setting the &%mua_wrapper%& option (see chapter
31160 &<<CHAPnonqueueing>>&).
31165 .section "Using Exim to handle mailing lists" "SECTmailinglists"
31166 .cindex "mailing lists"
31167 Exim can be used to run simple mailing lists, but for large and/or complicated
31168 requirements, the use of additional specialized mailing list software such as
31169 Majordomo or Mailman is recommended.
31171 The &(redirect)& router can be used to handle mailing lists where each list
31172 is maintained in a separate file, which can therefore be managed by an
31173 independent manager. The &%domains%& router option can be used to run these
31174 lists in a separate domain from normal mail. For example:
31178 domains = lists.example
31179 file = /usr/lists/$local_part
31182 errors_to = $local_part-request@lists.example
31185 This router is skipped for domains other than &'lists.example'&. For addresses
31186 in that domain, it looks for a file that matches the local part. If there is no
31187 such file, the router declines, but because &%no_more%& is set, no subsequent
31188 routers are tried, and so the whole delivery fails.
31190 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
31191 expanded into a file name or a pipe delivery, which is usually inappropriate in
31194 .oindex "&%errors_to%&"
31195 The &%errors_to%& option specifies that any delivery errors caused by addresses
31196 taken from a mailing list are to be sent to the given address rather than the
31197 original sender of the message. However, before acting on this, Exim verifies
31198 the error address, and ignores it if verification fails.
31200 For example, using the configuration above, mail sent to
31201 &'dicts@lists.example'& is passed on to those addresses contained in
31202 &_/usr/lists/dicts_&, with error reports directed to
31203 &'dicts-request@lists.example'&, provided that this address can be verified.
31204 There could be a file called &_/usr/lists/dicts-request_& containing
31205 the address(es) of this particular list's manager(s), but other approaches,
31206 such as setting up an earlier router (possibly using the &%local_part_prefix%&
31207 or &%local_part_suffix%& options) to handle addresses of the form
31208 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
31212 .section "Syntax errors in mailing lists" "SECID241"
31213 .cindex "mailing lists" "syntax errors in"
31214 If an entry in redirection data contains a syntax error, Exim normally defers
31215 delivery of the original address. That means that a syntax error in a mailing
31216 list holds up all deliveries to the list. This may not be appropriate when a
31217 list is being maintained automatically from data supplied by users, and the
31218 addresses are not rigorously checked.
31220 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
31221 entries that fail to parse, noting the incident in the log. If in addition
31222 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
31223 whenever a broken address is skipped. It is usually appropriate to set
31224 &%syntax_errors_to%& to the same address as &%errors_to%&.
31228 .section "Re-expansion of mailing lists" "SECID242"
31229 .cindex "mailing lists" "re-expansion of"
31230 Exim remembers every individual address to which a message has been delivered,
31231 in order to avoid duplication, but it normally stores only the original
31232 recipient addresses with a message. If all the deliveries to a mailing list
31233 cannot be done at the first attempt, the mailing list is re-expanded when the
31234 delivery is next tried. This means that alterations to the list are taken into
31235 account at each delivery attempt, so addresses that have been added to
31236 the list since the message arrived will therefore receive a copy of the
31237 message, even though it pre-dates their subscription.
31239 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
31240 on the &(redirect)& router. If this is done, any addresses generated by the
31241 router that fail to deliver at the first attempt are added to the message as
31242 &"top level"& addresses, and the parent address that generated them is marked
31243 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
31244 subsequent delivery attempts. The disadvantage of this is that if any of the
31245 failing addresses are incorrect, correcting them in the file has no effect on
31246 pre-existing messages.
31248 The original top-level address is remembered with each of the generated
31249 addresses, and is output in any log messages. However, any intermediate parent
31250 addresses are not recorded. This makes a difference to the log only if the
31251 &%all_parents%& selector is set, but for mailing lists there is normally only
31252 one level of expansion anyway.
31256 .section "Closed mailing lists" "SECID243"
31257 .cindex "mailing lists" "closed"
31258 The examples so far have assumed open mailing lists, to which anybody may
31259 send mail. It is also possible to set up closed lists, where mail is accepted
31260 from specified senders only. This is done by making use of the generic
31261 &%senders%& option to restrict the router that handles the list.
31263 The following example uses the same file as a list of recipients and as a list
31264 of permitted senders. It requires three routers:
31268 domains = lists.example
31269 local_part_suffix = -request
31270 file = /usr/lists/$local_part$local_part_suffix
31275 domains = lists.example
31276 senders = ${if exists {/usr/lists/$local_part}\
31277 {lsearch;/usr/lists/$local_part}{*}}
31278 file = /usr/lists/$local_part
31281 errors_to = $local_part-request@lists.example
31286 domains = lists.example
31288 data = :fail: $local_part@lists.example is a closed mailing list
31290 All three routers have the same &%domains%& setting, so for any other domains,
31291 they are all skipped. The first router runs only if the local part ends in
31292 &%-request%&. It handles messages to the list manager(s) by means of an open
31295 The second router runs only if the &%senders%& precondition is satisfied. It
31296 checks for the existence of a list that corresponds to the local part, and then
31297 checks that the sender is on the list by means of a linear search. It is
31298 necessary to check for the existence of the file before trying to search it,
31299 because otherwise Exim thinks there is a configuration error. If the file does
31300 not exist, the expansion of &%senders%& is *, which matches all senders. This
31301 means that the router runs, but because there is no list, declines, and
31302 &%no_more%& ensures that no further routers are run. The address fails with an
31303 &"unrouteable address"& error.
31305 The third router runs only if the second router is skipped, which happens when
31306 a mailing list exists, but the sender is not on it. This router forcibly fails
31307 the address, giving a suitable error message.
31312 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
31314 .cindex "Variable Envelope Return Paths"
31315 .cindex "envelope sender"
31316 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
31317 are a way of helping mailing list administrators discover which subscription
31318 address is the cause of a particular delivery failure. The idea is to encode
31319 the original recipient address in the outgoing envelope sender address, so that
31320 if the message is forwarded by another host and then subsequently bounces, the
31321 original recipient can be extracted from the recipient address of the bounce.
31323 .oindex &%errors_to%&
31324 .oindex &%return_path%&
31325 Envelope sender addresses can be modified by Exim using two different
31326 facilities: the &%errors_to%& option on a router (as shown in previous mailing
31327 list examples), or the &%return_path%& option on a transport. The second of
31328 these is effective only if the message is successfully delivered to another
31329 host; it is not used for errors detected on the local host (see the description
31330 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
31331 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
31337 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
31338 {$1-request+$local_part=$domain@your.dom.example}fail}
31340 This has the effect of rewriting the return path (envelope sender) on outgoing
31341 SMTP messages, if the local part of the original return path ends in
31342 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
31343 local part and domain of the recipient into the return path. Suppose, for
31344 example, that a message whose return path has been set to
31345 &'somelist-request@your.dom.example'& is sent to
31346 &'subscriber@other.dom.example'&. In the transport, the return path is
31349 somelist-request+subscriber=other.dom.example@your.dom.example
31351 .vindex "&$local_part$&"
31352 For this to work, you must tell Exim to send multiple copies of messages that
31353 have more than one recipient, so that each copy has just one recipient. This is
31354 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
31355 might be sent to several different recipients in the same domain, in which case
31356 &$local_part$& is not available in the transport, because it is not unique.
31358 Unless your host is doing nothing but mailing list deliveries, you should
31359 probably use a separate transport for the VERP deliveries, so as not to use
31360 extra resources in making one-per-recipient copies for other deliveries. This
31361 can easily be done by expanding the &%transport%& option in the router:
31365 domains = ! +local_domains
31367 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
31368 {verp_smtp}{remote_smtp}}
31371 If you want to change the return path using &%errors_to%& in a router instead
31372 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
31373 routers that handle mailing list addresses. This will ensure that all delivery
31374 errors, including those detected on the local host, are sent to the VERP
31377 On a host that does no local deliveries and has no manual routing, only the
31378 &(dnslookup)& router needs to be changed. A special transport is not needed for
31379 SMTP deliveries. Every mailing list recipient has its own return path value,
31380 and so Exim must hand them to the transport one at a time. Here is an example
31381 of a &(dnslookup)& router that implements VERP:
31385 domains = ! +local_domains
31386 transport = remote_smtp
31388 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
31389 {$1-request+$local_part=$domain@your.dom.example}fail}
31392 Before you start sending out messages with VERPed return paths, you must also
31393 configure Exim to accept the bounce messages that come back to those paths.
31394 Typically this is done by setting a &%local_part_suffix%& option for a
31395 router, and using this to route the messages to wherever you want to handle
31398 The overhead incurred in using VERP depends very much on the size of the
31399 message, the number of recipient addresses that resolve to the same remote
31400 host, and the speed of the connection over which the message is being sent. If
31401 a lot of addresses resolve to the same host and the connection is slow, sending
31402 a separate copy of the message for each address may take substantially longer
31403 than sending a single copy with many recipients (for which VERP cannot be
31411 .section "Virtual domains" "SECTvirtualdomains"
31412 .cindex "virtual domains"
31413 .cindex "domain" "virtual"
31414 The phrase &'virtual domain'& is unfortunately used with two rather different
31418 A domain for which there are no real mailboxes; all valid local parts are
31419 aliases for other email addresses. Common examples are organizational
31420 top-level domains and &"vanity"& domains.
31422 One of a number of independent domains that are all handled by the same host,
31423 with mailboxes on that host, but where the mailbox owners do not necessarily
31424 have login accounts on that host.
31427 The first usage is probably more common, and does seem more &"virtual"& than
31428 the second. This kind of domain can be handled in Exim with a straightforward
31429 aliasing router. One approach is to create a separate alias file for each
31430 virtual domain. Exim can test for the existence of the alias file to determine
31431 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
31432 to a router of this form:
31436 domains = dsearch;/etc/mail/virtual
31437 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
31440 The &%domains%& option specifies that the router is to be skipped, unless there
31441 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
31442 domain that is being processed. When the router runs, it looks up the local
31443 part in the file to find a new address (or list of addresses). The &%no_more%&
31444 setting ensures that if the lookup fails (leading to &%data%& being an empty
31445 string), Exim gives up on the address without trying any subsequent routers.
31447 This one router can handle all the virtual domains because the alias file names
31448 follow a fixed pattern. Permissions can be arranged so that appropriate people
31449 can edit the different alias files. A successful aliasing operation results in
31450 a new envelope recipient address, which is then routed from scratch.
31452 The other kind of &"virtual"& domain can also be handled in a straightforward
31453 way. One approach is to create a file for each domain containing a list of
31454 valid local parts, and use it in a router like this:
31458 domains = dsearch;/etc/mail/domains
31459 local_parts = lsearch;/etc/mail/domains/$domain
31460 transport = my_mailboxes
31462 The address is accepted if there is a file for the domain, and the local part
31463 can be found in the file. The &%domains%& option is used to check for the
31464 file's existence because &%domains%& is tested before the &%local_parts%&
31465 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
31466 because that option is tested after &%local_parts%&. The transport is as
31470 driver = appendfile
31471 file = /var/mail/$domain/$local_part
31474 This uses a directory of mailboxes for each domain. The &%user%& setting is
31475 required, to specify which uid is to be used for writing to the mailboxes.
31477 The configuration shown here is just one example of how you might support this
31478 requirement. There are many other ways this kind of configuration can be set
31479 up, for example, by using a database instead of separate files to hold all the
31480 information about the domains.
31484 .section "Multiple user mailboxes" "SECTmulbox"
31485 .cindex "multiple mailboxes"
31486 .cindex "mailbox" "multiple"
31487 .cindex "local part" "prefix"
31488 .cindex "local part" "suffix"
31489 Heavy email users often want to operate with multiple mailboxes, into which
31490 incoming mail is automatically sorted. A popular way of handling this is to
31491 allow users to use multiple sender addresses, so that replies can easily be
31492 identified. Users are permitted to add prefixes or suffixes to their local
31493 parts for this purpose. The wildcard facility of the generic router options
31494 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
31495 example, consider this router:
31500 file = $home/.forward
31501 local_part_suffix = -*
31502 local_part_suffix_optional
31505 .vindex "&$local_part_suffix$&"
31506 It runs a user's &_.forward_& file for all local parts of the form
31507 &'username-*'&. Within the filter file the user can distinguish different
31508 cases by testing the variable &$local_part_suffix$&. For example:
31510 if $local_part_suffix contains -special then
31511 save /home/$local_part/Mail/special
31514 If the filter file does not exist, or does not deal with such addresses, they
31515 fall through to subsequent routers, and, assuming no subsequent use of the
31516 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
31517 control over which suffixes are valid.
31519 Alternatively, a suffix can be used to trigger the use of a different
31520 &_.forward_& file &-- which is the way a similar facility is implemented in
31526 file = $home/.forward$local_part_suffix
31527 local_part_suffix = -*
31528 local_part_suffix_optional
31531 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
31532 example, &_.forward-special_& is used. Once again, if the appropriate file
31533 does not exist, or does not deal with the address, it is passed on to
31534 subsequent routers, which could, if required, look for an unqualified
31535 &_.forward_& file to use as a default.
31539 .section "Simplified vacation processing" "SECID244"
31540 .cindex "vacation processing"
31541 The traditional way of running the &'vacation'& program is for a user to set up
31542 a pipe command in a &_.forward_& file
31543 (see section &<<SECTspecitredli>>& for syntax details).
31544 This is prone to error by inexperienced users. There are two features of Exim
31545 that can be used to make this process simpler for users:
31548 A local part prefix such as &"vacation-"& can be specified on a router which
31549 can cause the message to be delivered directly to the &'vacation'& program, or
31550 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
31551 &_.forward_& file are then much simpler. For example:
31553 spqr, vacation-spqr
31556 The &%require_files%& generic router option can be used to trigger a
31557 vacation delivery by checking for the existence of a certain file in the
31558 user's home directory. The &%unseen%& generic option should also be used, to
31559 ensure that the original delivery also proceeds. In this case, all the user has
31560 to do is to create a file called, say, &_.vacation_&, containing a vacation
31564 Another advantage of both these methods is that they both work even when the
31565 use of arbitrary pipes by users is locked out.
31569 .section "Taking copies of mail" "SECID245"
31570 .cindex "message" "copying every"
31571 Some installations have policies that require archive copies of all messages to
31572 be made. A single copy of each message can easily be taken by an appropriate
31573 command in a system filter, which could, for example, use a different file for
31574 each day's messages.
31576 There is also a shadow transport mechanism that can be used to take copies of
31577 messages that are successfully delivered by local transports, one copy per
31578 delivery. This could be used, &'inter alia'&, to implement automatic
31579 notification of delivery by sites that insist on doing such things.
31583 .section "Intermittently connected hosts" "SECID246"
31584 .cindex "intermittently connected hosts"
31585 It has become quite common (because it is cheaper) for hosts to connect to the
31586 Internet periodically rather than remain connected all the time. The normal
31587 arrangement is that mail for such hosts accumulates on a system that is
31588 permanently connected.
31590 Exim was designed for use on permanently connected hosts, and so it is not
31591 particularly well-suited to use in an intermittently connected environment.
31592 Nevertheless there are some features that can be used.
31595 .section "Exim on the upstream server host" "SECID247"
31596 It is tempting to arrange for incoming mail for the intermittently connected
31597 host to remain on Exim's queue until the client connects. However, this
31598 approach does not scale very well. Two different kinds of waiting message are
31599 being mixed up in the same queue &-- those that cannot be delivered because of
31600 some temporary problem, and those that are waiting for their destination host
31601 to connect. This makes it hard to manage the queue, as well as wasting
31602 resources, because each queue runner scans the entire queue.
31604 A better approach is to separate off those messages that are waiting for an
31605 intermittently connected host. This can be done by delivering these messages
31606 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
31607 format, from where they are transmitted by other software when their
31608 destination connects. This makes it easy to collect all the mail for one host
31609 in a single directory, and to apply local timeout rules on a per-message basis
31612 On a very small scale, leaving the mail on Exim's queue can be made to work. If
31613 you are doing this, you should configure Exim with a long retry period for the
31614 intermittent host. For example:
31616 cheshire.wonderland.fict.example * F,5d,24h
31618 This stops a lot of failed delivery attempts from occurring, but Exim remembers
31619 which messages it has queued up for that host. Once the intermittent host comes
31620 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
31621 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
31622 causes all the queued up messages to be delivered, often down a single SMTP
31623 connection. While the host remains connected, any new messages get delivered
31626 If the connecting hosts do not have fixed IP addresses, that is, if a host is
31627 issued with a different IP address each time it connects, Exim's retry
31628 mechanisms on the holding host get confused, because the IP address is normally
31629 used as part of the key string for holding retry information. This can be
31630 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
31631 Since this has disadvantages for permanently connected hosts, it is best to
31632 arrange a separate transport for the intermittently connected ones.
31636 .section "Exim on the intermittently connected client host" "SECID248"
31637 The value of &%smtp_accept_queue_per_connection%& should probably be
31638 increased, or even set to zero (that is, disabled) on the intermittently
31639 connected host, so that all incoming messages down a single connection get
31640 delivered immediately.
31642 .cindex "SMTP" "passed connection"
31643 .cindex "SMTP" "multiple deliveries"
31644 .cindex "multiple SMTP deliveries"
31645 Mail waiting to be sent from an intermittently connected host will probably
31646 not have been routed, because without a connection DNS lookups are not
31647 possible. This means that if a normal queue run is done at connection time,
31648 each message is likely to be sent in a separate SMTP session. This can be
31649 avoided by starting the queue run with a command line option beginning with
31650 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
31651 first pass, routing is done but no deliveries take place. The second pass is a
31652 normal queue run; since all the messages have been previously routed, those
31653 destined for the same host are likely to get sent as multiple deliveries in a
31654 single SMTP connection.
31658 . ////////////////////////////////////////////////////////////////////////////
31659 . ////////////////////////////////////////////////////////////////////////////
31661 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
31662 "Exim as a non-queueing client"
31663 .cindex "client, non-queueing"
31664 .cindex "smart host" "suppressing queueing"
31665 On a personal computer, it is a common requirement for all
31666 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
31667 configured to operate that way, for all the popular operating systems.
31668 However, there are some MUAs for Unix-like systems that cannot be so
31669 configured: they submit messages using the command line interface of
31670 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
31673 If the personal computer runs continuously, there is no problem, because it can
31674 run a conventional MTA that handles delivery to the smart host, and deal with
31675 any delays via its queueing mechanism. However, if the computer does not run
31676 continuously or runs different operating systems at different times, queueing
31677 email is not desirable.
31679 There is therefore a requirement for something that can provide the
31680 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
31681 any queueing or retrying facilities. Furthermore, the delivery to the smart
31682 host should be synchronous, so that if it fails, the sending MUA is immediately
31683 informed. In other words, we want something that extends an MUA that submits
31684 to a local MTA via the command line so that it behaves like one that submits
31685 to a remote smart host using TCP/SMTP.
31687 There are a number of applications (for example, there is one called &'ssmtp'&)
31688 that do this job. However, people have found them to be lacking in various
31689 ways. For instance, you might want to allow aliasing and forwarding to be done
31690 before sending a message to the smart host.
31692 Exim already had the necessary infrastructure for doing this job. Just a few
31693 tweaks were needed to make it behave as required, though it is somewhat of an
31694 overkill to use a fully-featured MTA for this purpose.
31696 .oindex "&%mua_wrapper%&"
31697 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
31698 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
31699 assumes that it is being used to &"wrap"& a command-line MUA in the manner
31700 just described. As well as setting &%mua_wrapper%&, you also need to provide a
31701 compatible router and transport configuration. Typically there will be just one
31702 router and one transport, sending everything to a smart host.
31704 When run in MUA wrapping mode, the behaviour of Exim changes in the
31708 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
31709 In other words, the only way to submit messages is via the command line.
31711 Each message is synchronously delivered as soon as it is received (&%-odi%& is
31712 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
31713 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
31714 does not finish until the delivery attempt is complete. If the delivery is
31715 successful, a zero return code is given.
31717 Address redirection is permitted, but the final routing for all addresses must
31718 be to the same remote transport, and to the same list of hosts. Furthermore,
31719 the return address (envelope sender) must be the same for all recipients, as
31720 must any added or deleted header lines. In other words, it must be possible to
31721 deliver the message in a single SMTP transaction, however many recipients there
31724 If these conditions are not met, or if routing any address results in a
31725 failure or defer status, or if Exim is unable to deliver all the recipients
31726 successfully to one of the smart hosts, delivery of the entire message fails.
31728 Because no queueing is allowed, all failures are treated as permanent; there
31729 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
31730 smart host. Furthermore, because only a single yes/no response can be given to
31731 the caller, it is not possible to deliver to some recipients and not others. If
31732 there is an error (temporary or permanent) for any recipient, all are failed.
31734 If more than one smart host is listed, Exim will try another host after a
31735 connection failure or a timeout, in the normal way. However, if this kind of
31736 failure happens for all the hosts, the delivery fails.
31738 When delivery fails, an error message is written to the standard error stream
31739 (as well as to Exim's log), and Exim exits to the caller with a return code
31740 value 1. The message is expunged from Exim's spool files. No bounce messages
31741 are ever generated.
31743 No retry data is maintained, and any retry rules are ignored.
31745 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
31746 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
31747 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
31750 The overall effect is that Exim makes a single synchronous attempt to deliver
31751 the message, failing if there is any kind of problem. Because no local
31752 deliveries are done and no daemon can be run, Exim does not need root
31753 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
31754 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
31755 the advantages and disadvantages of running without root privilege.
31760 . ////////////////////////////////////////////////////////////////////////////
31761 . ////////////////////////////////////////////////////////////////////////////
31763 .chapter "Log files" "CHAPlog"
31764 .scindex IIDloggen "log" "general description"
31765 .cindex "log" "types of"
31766 Exim writes three different logs, referred to as the main log, the reject log,
31771 The main log records the arrival of each message and each delivery in a single
31772 line in each case. The format is as compact as possible, in an attempt to keep
31773 down the size of log files. Two-character flag sequences make it easy to pick
31774 out these lines. A number of other events are recorded in the main log. Some of
31775 them are optional, in which case the &%log_selector%& option controls whether
31776 they are included or not. A Perl script called &'eximstats'&, which does simple
31777 analysis of main log files, is provided in the Exim distribution (see section
31778 &<<SECTmailstat>>&).
31780 .cindex "reject log"
31781 The reject log records information from messages that are rejected as a result
31782 of a configuration option (that is, for policy reasons).
31783 The first line of each rejection is a copy of the line that is also written to
31784 the main log. Then, if the message's header has been read at the time the log
31785 is written, its contents are written to this log. Only the original header
31786 lines are available; header lines added by ACLs are not logged. You can use the
31787 reject log to check that your policy controls are working correctly; on a busy
31788 host this may be easier than scanning the main log for rejection messages. You
31789 can suppress the writing of the reject log by setting &%write_rejectlog%&
31792 .cindex "panic log"
31793 .cindex "system log"
31794 When certain serious errors occur, Exim writes entries to its panic log. If the
31795 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
31796 are usually written to the main log as well, but can get lost amid the mass of
31797 other entries. The panic log should be empty under normal circumstances. It is
31798 therefore a good idea to check it (or to have a &'cron'& script check it)
31799 regularly, in order to become aware of any problems. When Exim cannot open its
31800 panic log, it tries as a last resort to write to the system log (syslog). This
31801 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
31802 message itself is written at priority LOG_CRIT.
31805 Every log line starts with a timestamp, in the format shown in the following
31806 example. Note that many of the examples shown in this chapter are line-wrapped.
31807 In the log file, this would be all on one line:
31809 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
31812 By default, the timestamps are in the local timezone. There are two
31813 ways of changing this:
31816 You can set the &%timezone%& option to a different time zone; in particular, if
31821 the timestamps will be in UTC (aka GMT).
31823 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
31826 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
31830 .cindex "log" "process ids in"
31831 .cindex "pid (process id)" "in log lines"
31832 Exim does not include its process id in log lines by default, but you can
31833 request that it does so by specifying the &`pid`& log selector (see section
31834 &<<SECTlogselector>>&). When this is set, the process id is output, in square
31835 brackets, immediately after the time and date.
31840 .section "Where the logs are written" "SECTwhelogwri"
31841 .cindex "log" "destination"
31842 .cindex "log" "to file"
31843 .cindex "log" "to syslog"
31845 The logs may be written to local files, or to syslog, or both. However, it
31846 should be noted that many syslog implementations use UDP as a transport, and
31847 are therefore unreliable in the sense that messages are not guaranteed to
31848 arrive at the loghost, nor is the ordering of messages necessarily maintained.
31849 It has also been reported that on large log files (tens of megabytes) you may
31850 need to tweak syslog to prevent it syncing the file with each write &-- on
31851 Linux this has been seen to make syslog take 90% plus of CPU time.
31853 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
31854 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
31855 configuration. This latter string is expanded, so it can contain, for example,
31856 references to the host name:
31858 log_file_path = /var/log/$primary_hostname/exim_%slog
31860 It is generally advisable, however, to set the string in &_Local/Makefile_&
31861 rather than at run time, because then the setting is available right from the
31862 start of Exim's execution. Otherwise, if there's something it wants to log
31863 before it has read the configuration file (for example, an error in the
31864 configuration file) it will not use the path you want, and may not be able to
31867 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
31868 list, currently limited to at most two items. This is one option where the
31869 facility for changing a list separator may not be used. The list must always be
31870 colon-separated. If an item in the list is &"syslog"& then syslog is used;
31871 otherwise the item must either be an absolute path, containing &`%s`& at the
31872 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
31873 implying the use of a default path.
31875 When Exim encounters an empty item in the list, it searches the list defined by
31876 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
31877 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
31878 mean &"use the path specified at build time"&. It no such item exists, log
31879 files are written in the &_log_& subdirectory of the spool directory. This is
31880 equivalent to the setting:
31882 log_file_path = $spool_directory/log/%slog
31884 If you do not specify anything at build time or run time, that is where the
31887 A log file path may also contain &`%D`& if datestamped log file names are in
31888 use &-- see section &<<SECTdatlogfil>>& below.
31890 Here are some examples of possible settings:
31892 &`LOG_FILE_PATH=syslog `& syslog only
31893 &`LOG_FILE_PATH=:syslog `& syslog and default path
31894 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
31895 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
31897 If there are more than two paths in the list, the first is used and a panic
31902 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
31903 .cindex "log" "cycling local files"
31904 .cindex "cycling logs"
31905 .cindex "&'exicyclog'&"
31906 .cindex "log" "local files; writing to"
31907 Some operating systems provide centralized and standardized methods for cycling
31908 log files. For those that do not, a utility script called &'exicyclog'& is
31909 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
31910 main and reject logs each time it is called. The maximum number of old logs to
31911 keep can be set. It is suggested this script is run as a daily &'cron'& job.
31913 An Exim delivery process opens the main log when it first needs to write to it,
31914 and it keeps the file open in case subsequent entries are required &-- for
31915 example, if a number of different deliveries are being done for the same
31916 message. However, remote SMTP deliveries can take a long time, and this means
31917 that the file may be kept open long after it is renamed if &'exicyclog'& or
31918 something similar is being used to rename log files on a regular basis. To
31919 ensure that a switch of log files is noticed as soon as possible, Exim calls
31920 &[stat()]& on the main log's name before reusing an open file, and if the file
31921 does not exist, or its inode has changed, the old file is closed and Exim
31922 tries to open the main log from scratch. Thus, an old log file may remain open
31923 for quite some time, but no Exim processes should write to it once it has been
31928 .section "Datestamped log files" "SECTdatlogfil"
31929 .cindex "log" "datestamped files"
31930 Instead of cycling the main and reject log files by renaming them
31931 periodically, some sites like to use files whose names contain a datestamp,
31932 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_&.
31933 Exim has support for this way of working. It is enabled by setting the
31934 &%log_file_path%& option to a path that includes &`%D`& at the point where the
31935 datestamp is required. For example:
31937 log_file_path = /var/spool/exim/log/%slog-%D
31938 log_file_path = /var/log/exim-%s-%D.log
31939 log_file_path = /var/spool/exim/log/%D-%slog
31941 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
31942 examples of names generated by the above examples:
31944 /var/spool/exim/log/mainlog-20021225
31945 /var/log/exim-reject-20021225.log
31946 /var/spool/exim/log/20021225-mainlog
31948 When this form of log file is specified, Exim automatically switches to new
31949 files at midnight. It does not make any attempt to compress old logs; you
31950 will need to write your own script if you require this. You should not
31951 run &'exicyclog'& with this form of logging.
31953 The location of the panic log is also determined by &%log_file_path%&, but it
31954 is not datestamped, because rotation of the panic log does not make sense.
31955 When generating the name of the panic log, &`%D`& is removed from the string.
31956 In addition, if it immediately follows a slash, a following non-alphanumeric
31957 character is removed; otherwise a preceding non-alphanumeric character is
31958 removed. Thus, the three examples above would give these panic log names:
31960 /var/spool/exim/log/paniclog
31961 /var/log/exim-panic.log
31962 /var/spool/exim/log/paniclog
31966 .section "Logging to syslog" "SECID249"
31967 .cindex "log" "syslog; writing to"
31968 The use of syslog does not change what Exim logs or the format of its messages,
31969 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
31970 Exim's log lines are omitted when these lines are sent to syslog. Apart from
31971 that, the same strings are written to syslog as to log files. The syslog
31972 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
31973 by default, but you can change these by setting the &%syslog_facility%& and
31974 &%syslog_processname%& options, respectively. If Exim was compiled with
31975 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
31976 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
31977 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
31978 the time and host name to each line.
31979 The three log streams are mapped onto syslog priorities as follows:
31982 &'mainlog'& is mapped to LOG_INFO
31984 &'rejectlog'& is mapped to LOG_NOTICE
31986 &'paniclog'& is mapped to LOG_ALERT
31989 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
31990 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
31991 these are routed by syslog to the same place. You can suppress this duplication
31992 by setting &%syslog_duplication%& false.
31994 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
31995 entries contain multiple lines when headers are included. To cope with both
31996 these cases, entries written to syslog are split into separate &[syslog()]&
31997 calls at each internal newline, and also after a maximum of
31998 870 data characters. (This allows for a total syslog line length of 1024, when
31999 additions such as timestamps are added.) If you are running a syslog
32000 replacement that can handle lines longer than the 1024 characters allowed by
32001 RFC 3164, you should set
32003 SYSLOG_LONG_LINES=yes
32005 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
32006 lines, but it still splits at internal newlines in &'reject'& log entries.
32008 To make it easy to re-assemble split lines later, each component of a split
32009 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
32010 where <&'n'&> is the component number and <&'m'&> is the total number of
32011 components in the entry. The / delimiter is used when the line was split
32012 because it was too long; if it was split because of an internal newline, the \
32013 delimiter is used. For example, supposing the length limit to be 50 instead of
32014 870, the following would be the result of a typical rejection message to
32015 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
32016 name, and pid as added by syslog:
32018 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
32019 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
32020 [3/5] when scanning for sender: missing or malformed lo
32021 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
32024 The same error might cause the following lines to be written to &"rejectlog"&
32027 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
32028 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
32029 [3/18] er when scanning for sender: missing or malformed
32030 [4/18] local part in "<>" (envelope sender is <ph10@cam
32032 [6\18] Recipients: ph10@some.domain.cam.example
32033 [7\18] P Received: from [127.0.0.1] (ident=ph10)
32034 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
32035 [9\18] id 16RdAL-0006pc-00
32036 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
32037 [11\18] 09:43 +0100
32039 [13\18] Subject: this is a test header
32040 [18\18] X-something: this is another header
32041 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
32044 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
32046 Log lines that are neither too long nor contain newlines are written to syslog
32047 without modification.
32049 If only syslog is being used, the Exim monitor is unable to provide a log tail
32050 display, unless syslog is routing &'mainlog'& to a file on the local host and
32051 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
32056 .section "Log line flags" "SECID250"
32057 One line is written to the main log for each message received, and for each
32058 successful, unsuccessful, and delayed delivery. These lines can readily be
32059 picked out by the distinctive two-character flags that immediately follow the
32060 timestamp. The flags are:
32062 &`<=`& message arrival
32063 &`=>`& normal message delivery
32064 &`->`& additional address in same delivery
32065 &`*>`& delivery suppressed by &%-N%&
32066 &`**`& delivery failed; address bounced
32067 &`==`& delivery deferred; temporary problem
32071 .section "Logging message reception" "SECID251"
32072 .cindex "log" "reception line"
32073 The format of the single-line entry in the main log that is written for every
32074 message received is shown in the basic example below, which is split over
32075 several lines in order to fit it on the page:
32077 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
32078 H=mailer.fict.example [192.168.123.123] U=exim
32079 P=smtp S=5678 id=<incoming message id>
32081 The address immediately following &"<="& is the envelope sender address. A
32082 bounce message is shown with the sender address &"<>"&, and if it is locally
32083 generated, this is followed by an item of the form
32087 which is a reference to the message that caused the bounce to be sent.
32091 For messages from other hosts, the H and U fields identify the remote host and
32092 record the RFC 1413 identity of the user that sent the message, if one was
32093 received. The number given in square brackets is the IP address of the sending
32094 host. If there is a single, unparenthesized host name in the H field, as
32095 above, it has been verified to correspond to the IP address (see the
32096 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
32097 by the remote host in the SMTP HELO or EHLO command, and has not been
32098 verified. If verification yields a different name to that given for HELO or
32099 EHLO, the verified name appears first, followed by the HELO or EHLO
32100 name in parentheses.
32102 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
32103 without brackets, in the HELO or EHLO command, leading to entries in
32104 the log containing text like these examples:
32106 H=(10.21.32.43) [192.168.8.34]
32107 H=([10.21.32.43]) [192.168.8.34]
32109 This can be confusing. Only the final address in square brackets can be relied
32112 For locally generated messages (that is, messages not received over TCP/IP),
32113 the H field is omitted, and the U field contains the login name of the caller
32116 .cindex "authentication" "logging"
32117 .cindex "AUTH" "logging"
32118 For all messages, the P field specifies the protocol used to receive the
32119 message. This is the value that is stored in &$received_protocol$&. In the case
32120 of incoming SMTP messages, the value indicates whether or not any SMTP
32121 extensions (ESMTP), encryption, or authentication were used. If the SMTP
32122 session was encrypted, there is an additional X field that records the cipher
32123 suite that was used.
32125 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
32126 hosts that have authenticated themselves using the SMTP AUTH command. The first
32127 value is used when the SMTP connection was encrypted (&"secure"&). In this case
32128 there is an additional item A= followed by the name of the authenticator that
32129 was used. If an authenticated identification was set up by the authenticator's
32130 &%server_set_id%& option, this is logged too, separated by a colon from the
32131 authenticator name.
32133 .cindex "size" "of message"
32134 The id field records the existing message id, if present. The size of the
32135 received message is given by the S field. When the message is delivered,
32136 headers may be removed or added, so that the size of delivered copies of the
32137 message may not correspond with this value (and indeed may be different to each
32140 The &%log_selector%& option can be used to request the logging of additional
32141 data when a message is received. See section &<<SECTlogselector>>& below.
32145 .section "Logging deliveries" "SECID252"
32146 .cindex "log" "delivery line"
32147 The format of the single-line entry in the main log that is written for every
32148 delivery is shown in one of the examples below, for local and remote
32149 deliveries, respectively. Each example has been split into two lines in order
32150 to fit it on the page:
32152 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
32153 <marv@hitch.fict.example> R=localuser T=local_delivery
32154 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
32155 monk@holistic.fict.example R=dnslookup T=remote_smtp
32156 H=holistic.fict.example [192.168.234.234]
32158 For ordinary local deliveries, the original address is given in angle brackets
32159 after the final delivery address, which might be a pipe or a file. If
32160 intermediate address(es) exist between the original and the final address, the
32161 last of these is given in parentheses after the final address. The R and T
32162 fields record the router and transport that were used to process the address.
32164 If a shadow transport was run after a successful local delivery, the log line
32165 for the successful delivery has an item added on the end, of the form
32167 &`ST=<`&&'shadow transport name'&&`>`&
32169 If the shadow transport did not succeed, the error message is put in
32170 parentheses afterwards.
32172 .cindex "asterisk" "after IP address"
32173 When more than one address is included in a single delivery (for example, two
32174 SMTP RCPT commands in one transaction) the second and subsequent addresses are
32175 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
32176 down a single SMTP connection, an asterisk follows the IP address in the log
32177 lines for the second and subsequent messages.
32179 The generation of a reply message by a filter file gets logged as a
32180 &"delivery"& to the addressee, preceded by &">"&.
32182 The &%log_selector%& option can be used to request the logging of additional
32183 data when a message is delivered. See section &<<SECTlogselector>>& below.
32186 .section "Discarded deliveries" "SECID253"
32187 .cindex "discarded messages"
32188 .cindex "message" "discarded"
32189 .cindex "delivery" "discarded; logging"
32190 When a message is discarded as a result of the command &"seen finish"& being
32191 obeyed in a filter file which generates no deliveries, a log entry of the form
32193 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
32194 <low.club@bridge.example> R=userforward
32196 is written, to record why no deliveries are logged. When a message is discarded
32197 because it is aliased to &":blackhole:"& the log line is like this:
32199 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
32200 <hole@nowhere.example> R=blackhole_router
32204 .section "Deferred deliveries" "SECID254"
32205 When a delivery is deferred, a line of the following form is logged:
32207 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
32208 R=dnslookup T=smtp defer (146): Connection refused
32210 In the case of remote deliveries, the error is the one that was given for the
32211 last IP address that was tried. Details of individual SMTP failures are also
32212 written to the log, so the above line would be preceded by something like
32214 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
32215 mail1.endrest.example [192.168.239.239]: Connection refused
32217 When a deferred address is skipped because its retry time has not been reached,
32218 a message is written to the log, but this can be suppressed by setting an
32219 appropriate value in &%log_selector%&.
32223 .section "Delivery failures" "SECID255"
32224 .cindex "delivery" "failure; logging"
32225 If a delivery fails because an address cannot be routed, a line of the
32226 following form is logged:
32228 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
32229 <jim@trek99.example>: unknown mail domain
32231 If a delivery fails at transport time, the router and transport are shown, and
32232 the response from the remote host is included, as in this example:
32234 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
32235 R=dnslookup T=remote_smtp: SMTP error from remote mailer
32236 after pipelined RCPT TO:<ace400@pb.example>: host
32237 pbmail3.py.example [192.168.63.111]: 553 5.3.0
32238 <ace400@pb.example>...Addressee unknown
32240 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
32241 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
32242 disabling PIPELINING. The log lines for all forms of delivery failure are
32243 flagged with &`**`&.
32247 .section "Fake deliveries" "SECID256"
32248 .cindex "delivery" "fake; logging"
32249 If a delivery does not actually take place because the &%-N%& option has been
32250 used to suppress it, a normal delivery line is written to the log, except that
32251 &"=>"& is replaced by &"*>"&.
32255 .section "Completion" "SECID257"
32258 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
32260 is written to the main log when a message is about to be removed from the spool
32261 at the end of its processing.
32266 .section "Summary of Fields in Log Lines" "SECID258"
32267 .cindex "log" "summary of fields"
32268 A summary of the field identifiers that are used in log lines is shown in
32269 the following table:
32271 &`A `& authenticator name (and optional id)
32272 &`C `& SMTP confirmation on delivery
32273 &` `& command list for &"no mail in SMTP session"&
32274 &`CV `& certificate verification status
32275 &`D `& duration of &"no mail in SMTP session"&
32276 &`DN `& distinguished name from peer certificate
32277 &`DT `& on &`=>`& lines: time taken for a delivery
32278 &`F `& sender address (on delivery lines)
32279 &`H `& host name and IP address
32280 &`I `& local interface used
32281 &`id `& message id for incoming message
32282 &`P `& on &`<=`& lines: protocol used
32283 &` `& on &`=>`& and &`**`& lines: return path
32284 &`QT `& on &`=>`& lines: time spent on queue so far
32285 &` `& on &"Completed"& lines: time spent on queue
32286 &`R `& on &`<=`& lines: reference for local bounce
32287 &` `& on &`=>`& &`**`& and &`==`& lines: router name
32288 &`S `& size of message
32289 &`ST `& shadow transport name
32290 &`T `& on &`<=`& lines: message subject (topic)
32291 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
32292 &`U `& local user or RFC 1413 identity
32293 &`X `& TLS cipher suite
32297 .section "Other log entries" "SECID259"
32298 Various other types of log entry are written from time to time. Most should be
32299 self-explanatory. Among the more common are:
32302 .cindex "retry" "time not reached"
32303 &'retry time not reached'&&~&~An address previously suffered a temporary error
32304 during routing or local delivery, and the time to retry has not yet arrived.
32305 This message is not written to an individual message log file unless it happens
32306 during the first delivery attempt.
32308 &'retry time not reached for any host'&&~&~An address previously suffered
32309 temporary errors during remote delivery, and the retry time has not yet arrived
32310 for any of the hosts to which it is routed.
32312 .cindex "spool directory" "file locked"
32313 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
32314 some other Exim process is already working on the message. This can be quite
32315 common if queue running processes are started at frequent intervals. The
32316 &'exiwhat'& utility script can be used to find out what Exim processes are
32319 .cindex "error" "ignored"
32320 &'error ignored'&&~&~There are several circumstances that give rise to this
32323 Exim failed to deliver a bounce message whose age was greater than
32324 &%ignore_bounce_errors_after%&. The bounce was discarded.
32326 A filter file set up a delivery using the &"noerror"& option, and the delivery
32327 failed. The delivery was discarded.
32329 A delivery set up by a router configured with
32330 . ==== As this is a nested list, any displays it contains must be indented
32331 . ==== as otherwise they are too far to the left.
32335 failed. The delivery was discarded.
32343 .section "Reducing or increasing what is logged" "SECTlogselector"
32344 .cindex "log" "selectors"
32345 By setting the &%log_selector%& global option, you can disable some of Exim's
32346 default logging, or you can request additional logging. The value of
32347 &%log_selector%& is made up of names preceded by plus or minus characters. For
32350 log_selector = +arguments -retry_defer
32352 The list of optional log items is in the following table, with the default
32353 selection marked by asterisks:
32355 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
32356 &` address_rewrite `& address rewriting
32357 &` all_parents `& all parents in => lines
32358 &` arguments `& command line arguments
32359 &`*connection_reject `& connection rejections
32360 &`*delay_delivery `& immediate delivery delayed
32361 &` deliver_time `& time taken to perform delivery
32362 &` delivery_size `& add &`S=`&&'nnn'& to => lines
32363 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
32364 &`*etrn `& ETRN commands
32365 &`*host_lookup_failed `& as it says
32366 &` ident_timeout `& timeout for ident connection
32367 &` incoming_interface `& incoming interface on <= lines
32368 &` incoming_port `& incoming port on <= lines
32369 &`*lost_incoming_connection `& as it says (includes timeouts)
32370 &` outgoing_port `& add remote port to => lines
32371 &`*queue_run `& start and end queue runs
32372 &` queue_time `& time on queue for one recipient
32373 &` queue_time_overall `& time on queue for whole message
32374 &` pid `& Exim process id
32375 &` received_recipients `& recipients on <= lines
32376 &` received_sender `& sender on <= lines
32377 &`*rejected_header `& header contents on reject log
32378 &`*retry_defer `& &"retry time not reached"&
32379 &` return_path_on_delivery `& put return path on => and ** lines
32380 &` sender_on_delivery `& add sender to => lines
32381 &`*sender_verify_fail `& sender verification failures
32382 &`*size_reject `& rejection because too big
32383 &`*skip_delivery `& delivery skipped in a queue run
32384 &` smtp_confirmation `& SMTP confirmation on => lines
32385 &` smtp_connection `& SMTP connections
32386 &` smtp_incomplete_transaction`& incomplete SMTP transactions
32387 &` smtp_no_mail `& session with no MAIL commands
32388 &` smtp_protocol_error `& SMTP protocol errors
32389 &` smtp_syntax_error `& SMTP syntax errors
32390 &` subject `& contents of &'Subject:'& on <= lines
32391 &` tls_certificate_verified `& certificate verification status
32392 &`*tls_cipher `& TLS cipher suite on <= and => lines
32393 &` tls_peerdn `& TLS peer DN on <= and => lines
32394 &` unknown_in_list `& DNS lookup failed in list match
32396 &` all `& all of the above
32398 More details on each of these items follows:
32401 .cindex "&%warn%& ACL verb" "log when skipping"
32402 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
32403 its conditions cannot be evaluated, a log line to this effect is written if
32404 this log selector is set.
32406 .cindex "log" "rewriting"
32407 .cindex "rewriting" "logging"
32408 &%address_rewrite%&: This applies both to global rewrites and per-transport
32409 rewrites, but not to rewrites in filters run as an unprivileged user (because
32410 such users cannot access the log).
32412 .cindex "log" "full parentage"
32413 &%all_parents%&: Normally only the original and final addresses are logged on
32414 delivery lines; with this selector, intermediate parents are given in
32415 parentheses between them.
32417 .cindex "log" "Exim arguments"
32418 .cindex "Exim arguments, logging"
32419 &%arguments%&: This causes Exim to write the arguments with which it was called
32420 to the main log, preceded by the current working directory. This is a debugging
32421 feature, added to make it easier to find out how certain MUAs call
32422 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
32423 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
32424 that are empty or that contain white space are quoted. Non-printing characters
32425 are shown as escape sequences. This facility cannot log unrecognized arguments,
32426 because the arguments are checked before the configuration file is read. The
32427 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
32428 between the caller and Exim.
32430 .cindex "log" "connection rejections"
32431 &%connection_reject%&: A log entry is written whenever an incoming SMTP
32432 connection is rejected, for whatever reason.
32434 .cindex "log" "delayed delivery"
32435 .cindex "delayed delivery, logging"
32436 &%delay_delivery%&: A log entry is written whenever a delivery process is not
32437 started for an incoming message because the load is too high or too many
32438 messages were received on one connection. Logging does not occur if no delivery
32439 process is started because &%queue_only%& is set or &%-odq%& was used.
32441 .cindex "log" "delivery duration"
32442 &%deliver_time%&: For each delivery, the amount of real time it has taken to
32443 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
32445 .cindex "log" "message size on delivery"
32446 .cindex "size" "of message"
32447 &%delivery_size%&: For each delivery, the size of message delivered is added to
32448 the &"=>"& line, tagged with S=.
32450 .cindex "log" "dnslist defer"
32451 .cindex "DNS list" "logging defer"
32452 .cindex "black list (DNS)"
32453 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
32454 DNS black list suffers a temporary error.
32456 .cindex "log" "ETRN commands"
32457 .cindex "ETRN" "logging"
32458 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
32459 is run to determine whether or not it is actually accepted. An invalid ETRN
32460 command, or one received within a message transaction is not logged by this
32461 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
32463 .cindex "log" "host lookup failure"
32464 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
32465 any addresses, or when a lookup of an IP address fails to find a host name, a
32466 log line is written. This logging does not apply to direct DNS lookups when
32467 routing email addresses, but it does apply to &"byname"& lookups.
32469 .cindex "log" "ident timeout"
32470 .cindex "RFC 1413" "logging timeout"
32471 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
32472 client's ident port times out.
32474 .cindex "log" "incoming interface"
32475 .cindex "interface" "logging"
32476 &%incoming_interface%&: The interface on which a message was received is added
32477 to the &"<="& line as an IP address in square brackets, tagged by I= and
32478 followed by a colon and the port number. The local interface and port are also
32479 added to other SMTP log lines, for example &"SMTP connection from"&, and to
32482 .cindex "log" "incoming remote port"
32483 .cindex "port" "logging remote"
32484 .cindex "TCP/IP" "logging incoming remote port"
32485 .vindex "&$sender_fullhost$&"
32486 .vindex "&$sender_rcvhost$&"
32487 &%incoming_port%&: The remote port number from which a message was received is
32488 added to log entries and &'Received:'& header lines, following the IP address
32489 in square brackets, and separated from it by a colon. This is implemented by
32490 changing the value that is put in the &$sender_fullhost$& and
32491 &$sender_rcvhost$& variables. Recording the remote port number has become more
32492 important with the widening use of NAT (see RFC 2505).
32494 .cindex "log" "dropped connection"
32495 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
32496 connection is unexpectedly dropped.
32498 .cindex "log" "outgoing remote port"
32499 .cindex "port" "logging outgoint remote"
32500 .cindex "TCP/IP" "logging ougtoing remote port"
32501 &%outgoing_port%&: The remote port number is added to delivery log lines (those
32502 containing => tags) following the IP address. This option is not included in
32503 the default setting, because for most ordinary configurations, the remote port
32504 number is always 25 (the SMTP port).
32506 .cindex "log" "process ids in"
32507 .cindex "pid (process id)" "in log lines"
32508 &%pid%&: The current process id is added to every log line, in square brackets,
32509 immediately after the time and date.
32511 .cindex "log" "queue run"
32512 .cindex "queue runner" "logging"
32513 &%queue_run%&: The start and end of every queue run are logged.
32515 .cindex "log" "queue time"
32516 &%queue_time%&: The amount of time the message has been in the queue on the
32517 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
32518 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
32519 includes reception time as well as the delivery time for the current address.
32520 This means that it may be longer than the difference between the arrival and
32521 delivery log line times, because the arrival log line is not written until the
32522 message has been successfully received.
32524 &%queue_time_overall%&: The amount of time the message has been in the queue on
32525 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
32526 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
32527 message, so it includes reception time as well as the total delivery time.
32529 .cindex "log" "recipients"
32530 &%received_recipients%&: The recipients of a message are listed in the main log
32531 as soon as the message is received. The list appears at the end of the log line
32532 that is written when a message is received, preceded by the word &"for"&. The
32533 addresses are listed after they have been qualified, but before any rewriting
32535 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
32538 .cindex "log" "sender reception"
32539 &%received_sender%&: The unrewritten original sender of a message is added to
32540 the end of the log line that records the message's arrival, after the word
32541 &"from"& (before the recipients if &%received_recipients%& is also set).
32543 .cindex "log" "header lines for rejection"
32544 &%rejected_header%&: If a message's header has been received at the time a
32545 rejection is written to the reject log, the complete header is added to the
32546 log. Header logging can be turned off individually for messages that are
32547 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
32549 .cindex "log" "retry defer"
32550 &%retry_defer%&: A log line is written if a delivery is deferred because a
32551 retry time has not yet been reached. However, this &"retry time not reached"&
32552 message is always omitted from individual message logs after the first delivery
32555 .cindex "log" "return path"
32556 &%return_path_on_delivery%&: The return path that is being transmitted with
32557 the message is included in delivery and bounce lines, using the tag P=.
32558 This is omitted if no delivery actually happens, for example, if routing fails,
32559 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
32561 .cindex "log" "sender on delivery"
32562 &%sender_on_delivery%&: The message's sender address is added to every delivery
32563 and bounce line, tagged by F= (for &"from"&).
32564 This is the original sender that was received with the message; it is not
32565 necessarily the same as the outgoing return path.
32567 .cindex "log" "sender verify failure"
32568 &%sender_verify_fail%&: If this selector is unset, the separate log line that
32569 gives details of a sender verification failure is not written. Log lines for
32570 the rejection of SMTP commands contain just &"sender verify failed"&, so some
32573 .cindex "log" "size rejection"
32574 &%size_reject%&: A log line is written whenever a message is rejected because
32577 .cindex "log" "frozen messages; skipped"
32578 .cindex "frozen messages" "logging skipping"
32579 &%skip_delivery%&: A log line is written whenever a message is skipped during a
32580 queue run because it is frozen or because another process is already delivering
32582 .cindex "&""spool file is locked""&"
32583 The message that is written is &"spool file is locked"&.
32585 .cindex "log" "smtp confirmation"
32586 .cindex "SMTP" "logging confirmation"
32587 &%smtp_confirmation%&: The response to the final &"."& in the SMTP dialogue for
32588 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
32589 A number of MTAs (including Exim) return an identifying string in this
32592 .cindex "log" "SMTP connections"
32593 .cindex "SMTP" "logging connections"
32594 &%smtp_connection%&: A log line is written whenever an SMTP connection is
32595 established or closed, unless the connection is from a host that matches
32596 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
32597 only when the closure is unexpected.) This applies to connections from local
32598 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
32599 dropped in the middle of a message, a log line is always written, whether or
32600 not this selector is set, but otherwise nothing is written at the start and end
32601 of connections unless this selector is enabled.
32603 For TCP/IP connections to an Exim daemon, the current number of connections is
32604 included in the log message for each new connection, but note that the count is
32605 reset if the daemon is restarted.
32606 Also, because connections are closed (and the closure is logged) in
32607 subprocesses, the count may not include connections that have been closed but
32608 whose termination the daemon has not yet noticed. Thus, while it is possible to
32609 match up the opening and closing of connections in the log, the value of the
32610 logged counts may not be entirely accurate.
32612 .cindex "log" "SMTP transaction; incomplete"
32613 .cindex "SMTP" "logging incomplete transactions"
32614 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
32615 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
32616 and the message sender plus any accepted recipients are included in the log
32617 line. This can provide evidence of dictionary attacks.
32619 .cindex "log" "non-MAIL SMTP sessions"
32620 .cindex "MAIL" "logging session without"
32621 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
32622 connection terminates without having issued a MAIL command. This includes both
32623 the case when the connection is dropped, and the case when QUIT is used. It
32624 does not include cases where the connection is rejected right at the start (by
32625 an ACL, or because there are too many connections, or whatever). These cases
32626 already have their own log lines.
32628 The log line that is written contains the identity of the client in the usual
32629 way, followed by D= and a time, which records the duration of the connection.
32630 If the connection was authenticated, this fact is logged exactly as it is for
32631 an incoming message, with an A= item. If the connection was encrypted, CV=,
32632 DN=, and X= items may appear as they do for an incoming message, controlled by
32633 the same logging options.
32635 Finally, if any SMTP commands were issued during the connection, a C= item
32636 is added to the line, listing the commands that were used. For example,
32640 shows that the client issued QUIT straight after EHLO. If there were fewer
32641 than 20 commands, they are all listed. If there were more than 20 commands,
32642 the last 20 are listed, preceded by &"..."&. However, with the default
32643 setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case
32644 have been aborted before 20 non-mail commands are processed.
32646 .cindex "log" "SMTP protocol error"
32647 .cindex "SMTP" "logging protocol error"
32648 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
32649 encountered. Exim does not have perfect detection of all protocol errors
32650 because of transmission delays and the use of pipelining. If PIPELINING has
32651 been advertised to a client, an Exim server assumes that the client will use
32652 it, and therefore it does not count &"expected"& errors (for example, RCPT
32653 received after rejecting MAIL) as protocol errors.
32655 .cindex "SMTP" "logging syntax errors"
32656 .cindex "SMTP" "syntax errors; logging"
32657 .cindex "SMTP" "unknown command; logging"
32658 .cindex "log" "unknown SMTP command"
32659 .cindex "log" "SMTP syntax error"
32660 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
32661 encountered. An unrecognized command is treated as a syntax error. For an
32662 external connection, the host identity is given; for an internal connection
32663 using &%-bs%& the sender identification (normally the calling user) is given.
32665 .cindex "log" "subject"
32666 .cindex "subject, logging"
32667 &%subject%&: The subject of the message is added to the arrival log line,
32668 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
32669 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
32670 specifies whether characters with values greater than 127 should be logged
32671 unchanged, or whether they should be rendered as escape sequences.
32673 .cindex "log" "certificate verification"
32674 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
32675 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
32676 verified, and &`CV=no`& if not.
32678 .cindex "log" "TLS cipher"
32679 .cindex "TLS" "logging cipher"
32680 &%tls_cipher%&: When a message is sent or received over an encrypted
32681 connection, the cipher suite used is added to the log line, preceded by X=.
32683 .cindex "log" "TLS peer DN"
32684 .cindex "TLS" "logging peer DN"
32685 &%tls_peerdn%&: When a message is sent or received over an encrypted
32686 connection, and a certificate is supplied by the remote host, the peer DN is
32687 added to the log line, preceded by DN=.
32689 .cindex "log" "DNS failure in list"
32690 &%unknown_in_list%&: This setting causes a log entry to be written when the
32691 result of a list match is failure because a DNS lookup failed.
32695 .section "Message log" "SECID260"
32696 .cindex "message" "log file for"
32697 .cindex "log" "message log; description of"
32698 .cindex "&_msglog_& directory"
32699 .oindex "&%preserve_message_logs%&"
32700 In addition to the general log files, Exim writes a log file for each message
32701 that it handles. The names of these per-message logs are the message ids, and
32702 they are kept in the &_msglog_& sub-directory of the spool directory. Each
32703 message log contains copies of the log lines that apply to the message. This
32704 makes it easier to inspect the status of an individual message without having
32705 to search the main log. A message log is deleted when processing of the message
32706 is complete, unless &%preserve_message_logs%& is set, but this should be used
32707 only with great care because they can fill up your disk very quickly.
32709 On a heavily loaded system, it may be desirable to disable the use of
32710 per-message logs, in order to reduce disk I/O. This can be done by setting the
32711 &%message_logs%& option false.
32717 . ////////////////////////////////////////////////////////////////////////////
32718 . ////////////////////////////////////////////////////////////////////////////
32720 .chapter "Exim utilities" "CHAPutils"
32721 .scindex IIDutils "utilities"
32722 A number of utility scripts and programs are supplied with Exim and are
32723 described in this chapter. There is also the Exim Monitor, which is covered in
32724 the next chapter. The utilities described here are:
32726 .itable none 0 0 3 7* left 15* left 40* left
32727 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
32728 "list what Exim processes are doing"
32729 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
32730 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
32731 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
32732 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
32734 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
32735 .irow &<<SECTmailstat>>& &'eximstats'& &&&
32736 "extract statistics from the log"
32737 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
32738 "check address acceptance from given IP"
32739 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
32740 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
32741 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
32742 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
32743 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
32744 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
32747 Another utility that might be of use to sites with many MTAs is Tom Kistner's
32748 &'exilog'&. It provides log visualizations across multiple Exim servers. See
32749 &url(http://duncanthrax.net/exilog/) for details.
32754 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
32755 .cindex "&'exiwhat'&"
32756 .cindex "process, querying"
32758 On operating systems that can restart a system call after receiving a signal
32759 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
32760 a line describing what it is doing to the file &_exim-process.info_& in the
32761 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
32762 processes it can find, having first emptied the file. It then waits for one
32763 second to allow the Exim processes to react before displaying the results. In
32764 order to run &'exiwhat'& successfully you have to have sufficient privilege to
32765 send the signal to the Exim processes, so it is normally run as root.
32767 &*Warning*&: This is not an efficient process. It is intended for occasional
32768 use by system administrators. It is not sensible, for example, to set up a
32769 script that sends SIGUSR1 signals to Exim processes at short intervals.
32772 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
32773 varies in different operating systems. Not only are different options used,
32774 but the format of the output is different. For this reason, there are some
32775 system configuration options that configure exactly how &'exiwhat'& works. If
32776 it doesn't seem to be working for you, check the following compile-time
32779 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
32780 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
32781 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
32782 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
32784 An example of typical output from &'exiwhat'& is
32786 164 daemon: -q1h, listening on port 25
32787 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
32788 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
32789 [10.19.42.42] (editor@ref.example)
32790 10592 handling incoming call from [192.168.243.242]
32791 10628 accepting a local non-SMTP message
32793 The first number in the output line is the process number. The third line has
32794 been split here, in order to fit it on the page.
32798 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
32799 .cindex "&'exiqgrep'&"
32800 .cindex "queue" "grepping"
32801 This utility is a Perl script contributed by Matt Hubbard. It runs
32805 to obtain a queue listing with undelivered recipients only, and then greps the
32806 output to select messages that match given criteria. The following selection
32807 options are available:
32810 .vitem &*-f*&&~<&'regex'&>
32811 Match the sender address. The field that is tested is enclosed in angle
32812 brackets, so you can test for bounce messages with
32816 .vitem &*-r*&&~<&'regex'&>
32817 Match a recipient address. The field that is tested is not enclosed in angle
32820 .vitem &*-s*&&~<&'regex'&>
32821 Match against the size field.
32823 .vitem &*-y*&&~<&'seconds'&>
32824 Match messages that are younger than the given time.
32826 .vitem &*-o*&&~<&'seconds'&>
32827 Match messages that are older than the given time.
32830 Match only frozen messages.
32833 Match only non-frozen messages.
32836 The following options control the format of the output:
32840 Display only the count of matching messages.
32843 Long format &-- display the full message information as output by Exim. This is
32847 Display message ids only.
32850 Brief format &-- one line per message.
32853 Display messages in reverse order.
32856 There is one more option, &%-h%&, which outputs a list of options.
32860 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
32861 .cindex "&'exiqsumm'&"
32862 .cindex "queue" "summary"
32863 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
32864 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
32865 running a command such as
32867 exim -bp | exiqsumm
32869 The output consists of one line for each domain that has messages waiting for
32870 it, as in the following example:
32872 3 2322 74m 66m msn.com.example
32874 Each line lists the number of pending deliveries for a domain, their total
32875 volume, and the length of time that the oldest and the newest messages have
32876 been waiting. Note that the number of pending deliveries is greater than the
32877 number of messages when messages have more than one recipient.
32879 A summary line is output at the end. By default the output is sorted on the
32880 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
32881 the output to be sorted by oldest message and by count of messages,
32882 respectively. There are also three options that split the messages for each
32883 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
32884 separates frozen messages, and &%-s%& separates messages according to their
32887 The output of &'exim -bp'& contains the original addresses in the message, so
32888 this also applies to the output from &'exiqsumm'&. No domains from addresses
32889 generated by aliasing or forwarding are included (unless the &%one_time%&
32890 option of the &(redirect)& router has been used to convert them into &"top
32891 level"& addresses).
32896 .section "Extracting specific information from the log (exigrep)" &&&
32898 .cindex "&'exigrep'&"
32899 .cindex "log" "extracts; grepping for"
32900 The &'exigrep'& utility is a Perl script that searches one or more main log
32901 files for entries that match a given pattern. When it finds a match, it
32902 extracts all the log entries for the relevant message, not just those that
32903 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
32904 given message, or all mail for a given user, or for a given host, for example.
32905 The input files can be in Exim log format or syslog format.
32906 If a matching log line is not associated with a specific message, it is
32907 included in &'exigrep'&'s output without any additional lines. The usage is:
32909 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
32911 If no log file names are given on the command line, the standard input is read.
32913 The &%-t%& argument specifies a number of seconds. It adds an additional
32914 condition for message selection. Messages that are complete are shown only if
32915 they spent more than <&'n'&> seconds on the queue.
32917 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
32918 makes it case-sensitive. This may give a performance improvement when searching
32919 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
32920 option; with &%-I%& they do not. In both cases it is possible to change the
32921 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
32923 The &%-l%& option means &"literal"&, that is, treat all characters in the
32924 pattern as standing for themselves. Otherwise the pattern must be a Perl
32925 regular expression.
32927 The &%-v%& option inverts the matching condition. That is, a line is selected
32928 if it does &'not'& match the pattern.
32930 If the location of a &'zcat'& command is known from the definition of
32931 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
32932 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
32935 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
32936 .cindex "&'exipick'&"
32937 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
32938 lists messages from the queue according to a variety of criteria. For details
32939 of &'exipick'&'s facilities, visit the web page at
32940 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
32941 the &%--help%& option.
32944 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
32945 .cindex "log" "cycling local files"
32946 .cindex "cycling logs"
32947 .cindex "&'exicyclog'&"
32948 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
32949 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
32950 you are using log files with datestamps in their names (see section
32951 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
32952 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
32953 There are two command line options for &'exicyclog'&:
32955 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
32956 default that is set when Exim is built. The default default is 10.
32958 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
32959 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
32960 overriding the script's default, which is to find the setting from Exim's
32964 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
32965 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
32966 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
32967 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
32968 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
32969 logs are handled similarly.
32971 If the limit is greater than 99, the script uses 3-digit numbers such as
32972 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
32973 to one that is greater, or &'vice versa'&, you will have to fix the names of
32974 any existing log files.
32976 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
32977 the end are deleted. All files with numbers greater than 01 are compressed,
32978 using a compression command which is configured by the COMPRESS_COMMAND
32979 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
32980 root &%crontab%& entry of the form
32982 1 0 * * * su exim -c /usr/exim/bin/exicyclog
32984 assuming you have used the name &"exim"& for the Exim user. You can run
32985 &'exicyclog'& as root if you wish, but there is no need.
32989 .section "Mail statistics (eximstats)" "SECTmailstat"
32990 .cindex "statistics"
32991 .cindex "&'eximstats'&"
32992 A Perl script called &'eximstats'& is provided for extracting statistical
32993 information from log files. The output is either plain text, or HTML.
32994 Exim log files are also supported by the &'Lire'& system produced by the
32995 LogReport Foundation &url(http://www.logreport.org).
32997 The &'eximstats'& script has been hacked about quite a bit over time. The
32998 latest version is the result of some extensive revision by Steve Campbell. A
32999 lot of information is given by default, but there are options for suppressing
33000 various parts of it. Following any options, the arguments to the script are a
33001 list of files, which should be main log files. For example:
33003 eximstats -nr /var/spool/exim/log/mainlog.01
33005 By default, &'eximstats'& extracts information about the number and volume of
33006 messages received from or delivered to various hosts. The information is sorted
33007 both by message count and by volume, and the top fifty hosts in each category
33008 are listed on the standard output. Similar information, based on email
33009 addresses or domains instead of hosts can be requested by means of various
33010 options. For messages delivered and received locally, similar statistics are
33011 also produced per user.
33013 The output also includes total counts and statistics about delivery errors, and
33014 histograms showing the number of messages received and deliveries made in each
33015 hour of the day. A delivery with more than one address in its envelope (for
33016 example, an SMTP transaction with more than one RCPT command) is counted
33017 as a single delivery by &'eximstats'&.
33019 Though normally more deliveries than receipts are reported (as messages may
33020 have multiple recipients), it is possible for &'eximstats'& to report more
33021 messages received than delivered, even though the queue is empty at the start
33022 and end of the period in question. If an incoming message contains no valid
33023 recipients, no deliveries are recorded for it. A bounce message is handled as
33024 an entirely separate message.
33026 &'eximstats'& always outputs a grand total summary giving the volume and number
33027 of messages received and deliveries made, and the number of hosts involved in
33028 each case. It also outputs the number of messages that were delayed (that is,
33029 not completely delivered at the first attempt), and the number that had at
33030 least one address that failed.
33032 The remainder of the output is in sections that can be independently disabled
33033 or modified by various options. It consists of a summary of deliveries by
33034 transport, histograms of messages received and delivered per time interval
33035 (default per hour), information about the time messages spent on the queue,
33036 a list of relayed messages, lists of the top fifty sending hosts, local
33037 senders, destination hosts, and destination local users by count and by volume,
33038 and a list of delivery errors that occurred.
33040 The relay information lists messages that were actually relayed, that is, they
33041 came from a remote host and were directly delivered to some other remote host,
33042 without being processed (for example, for aliasing or forwarding) locally.
33044 There are quite a few options for &'eximstats'& to control exactly what it
33045 outputs. These are documented in the Perl script itself, and can be extracted
33046 by running the command &(perldoc)& on the script. For example:
33048 perldoc /usr/exim/bin/eximstats
33051 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
33052 .cindex "&'exim_checkaccess'&"
33053 .cindex "policy control" "checking access"
33054 .cindex "checking access"
33055 The &%-bh%& command line argument allows you to run a fake SMTP session with
33056 debugging output, in order to check what Exim is doing when it is applying
33057 policy controls to incoming SMTP mail. However, not everybody is sufficiently
33058 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
33059 sometimes you just want to answer the question &"Does this address have
33060 access?"& without bothering with any further details.
33062 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
33063 two arguments, an IP address and an email address:
33065 exim_checkaccess 10.9.8.7 A.User@a.domain.example
33067 The utility runs a call to Exim with the &%-bh%& option, to test whether the
33068 given email address would be accepted in a RCPT command in a TCP/IP
33069 connection from the host with the given IP address. The output of the utility
33070 is either the word &"accepted"&, or the SMTP error response, for example:
33073 550 Relay not permitted
33075 When running this test, the utility uses &`<>`& as the envelope sender address
33076 for the MAIL command, but you can change this by providing additional
33077 options. These are passed directly to the Exim command. For example, to specify
33078 that the test is to be run with the sender address &'himself@there.example'&
33081 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
33082 -f himself@there.example
33084 Note that these additional Exim command line items must be given after the two
33085 mandatory arguments.
33087 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
33088 while running its checks. You can run checks that include callouts by using
33089 &%-bhc%&, but this is not yet available in a &"packaged"& form.
33093 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
33094 .cindex "DBM" "building dbm files"
33095 .cindex "building DBM files"
33096 .cindex "&'exim_dbmbuild'&"
33097 .cindex "lower casing"
33098 .cindex "binary zero" "in lookup key"
33099 The &'exim_dbmbuild'& program reads an input file containing keys and data in
33100 the format used by the &(lsearch)& lookup (see section
33101 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
33102 names as keys and the remainder of the information as data. The lower-casing
33103 can be prevented by calling the program with the &%-nolc%& option.
33105 A terminating zero is included as part of the key string. This is expected by
33106 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
33107 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
33108 strings or the data strings. The &(dbmnz)& lookup type can be used with such
33111 The program requires two arguments: the name of the input file (which can be a
33112 single hyphen to indicate the standard input), and the name of the output file.
33113 It creates the output under a temporary name, and then renames it if all went
33117 If the native DB interface is in use (USE_DB is set in a compile-time
33118 configuration file &-- this is common in free versions of Unix) the two file
33119 names must be different, because in this mode the Berkeley DB functions create
33120 a single output file using exactly the name given. For example,
33122 exim_dbmbuild /etc/aliases /etc/aliases.db
33124 reads the system alias file and creates a DBM version of it in
33125 &_/etc/aliases.db_&.
33127 In systems that use the &'ndbm'& routines (mostly proprietary versions of
33128 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
33129 environment, the suffixes are added to the second argument of
33130 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
33131 when the Berkeley functions are used in compatibility mode (though this is not
33132 recommended), because in that case it adds a &_.db_& suffix to the file name.
33134 If a duplicate key is encountered, the program outputs a warning, and when it
33135 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
33136 option is used. By default, only the first of a set of duplicates is used &--
33137 this makes it compatible with &(lsearch)& lookups. There is an option
33138 &%-lastdup%& which causes it to use the data for the last duplicate instead.
33139 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
33140 &%stderr%&. For other errors, where it doesn't actually make a new file, the
33146 .section "Finding individual retry times (exinext)" "SECTfinindret"
33147 .cindex "retry" "times"
33148 .cindex "&'exinext'&"
33149 A utility called &'exinext'& (mostly a Perl script) provides the ability to
33150 fish specific information out of the retry database. Given a mail domain (or a
33151 complete address), it looks up the hosts for that domain, and outputs any retry
33152 information for the hosts or for the domain. At present, the retry information
33153 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
33154 output. For example:
33156 $ exinext piglet@milne.fict.example
33157 kanga.milne.example:192.168.8.1 error 146: Connection refused
33158 first failed: 21-Feb-1996 14:57:34
33159 last tried: 21-Feb-1996 14:57:34
33160 next try at: 21-Feb-1996 15:02:34
33161 roo.milne.example:192.168.8.3 error 146: Connection refused
33162 first failed: 20-Jan-1996 13:12:08
33163 last tried: 21-Feb-1996 11:42:03
33164 next try at: 21-Feb-1996 19:42:03
33165 past final cutoff time
33167 You can also give &'exinext'& a local part, without a domain, and it
33168 will give any retry information for that local part in your default domain.
33169 A message id can be used to obtain retry information pertaining to a specific
33170 message. This exists only when an attempt to deliver a message to a remote host
33171 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
33172 &'exinext'& is not particularly efficient, but then it is not expected to be
33175 The &'exinext'& utility calls Exim to find out information such as the location
33176 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
33177 passed on to the &'exim'& commands. The first specifies an alternate Exim
33178 configuration file, and the second sets macros for use within the configuration
33179 file. These features are mainly to help in testing, but might also be useful in
33180 environments where more than one configuration file is in use.
33184 .section "Hints database maintenance" "SECThindatmai"
33185 .cindex "hints database" "maintenance"
33186 .cindex "maintaining Exim's hints database"
33187 Three utility programs are provided for maintaining the DBM files that Exim
33188 uses to contain its delivery hint information. Each program requires two
33189 arguments. The first specifies the name of Exim's spool directory, and the
33190 second is the name of the database it is to operate on. These are as follows:
33193 &'retry'&: the database of retry information
33195 &'wait-'&<&'transport name'&>: databases of information about messages waiting
33198 &'callout'&: the callout cache
33200 &'ratelimit'&: the data for implementing the ratelimit ACL condition
33202 &'misc'&: other hints data
33205 The &'misc'& database is used for
33208 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
33210 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
33211 &(smtp)& transport)
33216 .section "exim_dumpdb" "SECID261"
33217 .cindex "&'exim_dumpdb'&"
33218 The entire contents of a database are written to the standard output by the
33219 &'exim_dumpdb'& program, which has no options or arguments other than the
33220 spool and database names. For example, to dump the retry database:
33222 exim_dumpdb /var/spool/exim retry
33224 Two lines of output are produced for each entry:
33226 T:mail.ref.example:192.168.242.242 146 77 Connection refused
33227 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
33229 The first item on the first line is the key of the record. It starts with one
33230 of the letters R, or T, depending on whether it refers to a routing or
33231 transport retry. For a local delivery, the next part is the local address; for
33232 a remote delivery it is the name of the remote host, followed by its failing IP
33233 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
33234 transport). If the remote port is not the standard one (port 25), it is added
33235 to the IP address. Then there follows an error code, an additional error code,
33236 and a textual description of the error.
33238 The three times on the second line are the time of first failure, the time of
33239 the last delivery attempt, and the computed time for the next attempt. The line
33240 ends with an asterisk if the cutoff time for the last retry rule has been
33243 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
33244 consists of a host name followed by a list of ids for messages that are or were
33245 waiting to be delivered to that host. If there are a very large number for any
33246 one host, continuation records, with a sequence number added to the host name,
33247 may be seen. The data in these records is often out of date, because a message
33248 may be routed to several alternative hosts, and Exim makes no effort to keep
33253 .section "exim_tidydb" "SECID262"
33254 .cindex "&'exim_tidydb'&"
33255 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
33256 database. If run with no options, it removes all records that are more than 30
33257 days old. The age is calculated from the date and time that the record was last
33258 updated. Note that, in the case of the retry database, it is &'not'& the time
33259 since the first delivery failure. Information about a host that has been down
33260 for more than 30 days will remain in the database, provided that the record is
33261 updated sufficiently often.
33263 The cutoff date can be altered by means of the &%-t%& option, which must be
33264 followed by a time. For example, to remove all records older than a week from
33265 the retry database:
33267 exim_tidydb -t 7d /var/spool/exim retry
33269 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
33270 message ids. In the former these appear as data in records keyed by host &--
33271 they were messages that were waiting for that host &-- and in the latter they
33272 are the keys for retry information for messages that have suffered certain
33273 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
33274 message ids in database records are those of messages that are still on the
33275 queue. Message ids for messages that no longer exist are removed from
33276 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
33277 For the &'retry'& database, records whose keys are non-existent message ids are
33278 removed. The &'exim_tidydb'& utility outputs comments on the standard output
33279 whenever it removes information from the database.
33281 Certain records are automatically removed by Exim when they are no longer
33282 needed, but others are not. For example, if all the MX hosts for a domain are
33283 down, a retry record is created for each one. If the primary MX host comes back
33284 first, its record is removed when Exim successfully delivers to it, but the
33285 records for the others remain because Exim has not tried to use those hosts.
33287 It is important, therefore, to run &'exim_tidydb'& periodically on all the
33288 hints databases. You should do this at a quiet time of day, because it requires
33289 a database to be locked (and therefore inaccessible to Exim) while it does its
33290 work. Removing records from a DBM file does not normally make the file smaller,
33291 but all the common DBM libraries are able to re-use the space that is released.
33292 After an initial phase of increasing in size, the databases normally reach a
33293 point at which they no longer get any bigger, as long as they are regularly
33296 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
33297 databases is likely to keep on increasing.
33302 .section "exim_fixdb" "SECID263"
33303 .cindex "&'exim_fixdb'&"
33304 The &'exim_fixdb'& program is a utility for interactively modifying databases.
33305 Its main use is for testing Exim, but it might also be occasionally useful for
33306 getting round problems in a live system. It has no options, and its interface
33307 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
33308 key of a database record can then be entered, and the data for that record is
33311 If &"d"& is typed at the next prompt, the entire record is deleted. For all
33312 except the &'retry'& database, that is the only operation that can be carried
33313 out. For the &'retry'& database, each field is output preceded by a number, and
33314 data for individual fields can be changed by typing the field number followed
33315 by new data, for example:
33319 resets the time of the next delivery attempt. Time values are given as a
33320 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
33321 used as optional separators.
33326 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
33327 .cindex "mailbox" "maintenance"
33328 .cindex "&'exim_lock'&"
33329 .cindex "locking mailboxes"
33330 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
33331 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
33332 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
33333 a user agent while investigating a problem. The utility requires the name of
33334 the file as its first argument. If the locking is successful, the second
33335 argument is run as a command (using C's &[system()]& function); if there is no
33336 second argument, the value of the SHELL environment variable is used; if this
33337 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
33338 is unlocked and the utility ends. The following options are available:
33342 Use &[fcntl()]& locking on the open mailbox.
33345 Use &[flock()]& locking on the open mailbox, provided the operating system
33348 .vitem &%-interval%&
33349 This must be followed by a number, which is a number of seconds; it sets the
33350 interval to sleep between retries (default 3).
33352 .vitem &%-lockfile%&
33353 Create a lock file before opening the mailbox.
33356 Lock the mailbox using MBX rules.
33359 Suppress verification output.
33361 .vitem &%-retries%&
33362 This must be followed by a number; it sets the number of times to try to get
33363 the lock (default 10).
33365 .vitem &%-restore_time%&
33366 This option causes &%exim_lock%& to restore the modified and read times to the
33367 locked file before exiting. This allows you to access a locked mailbox (for
33368 example, to take a backup copy) without disturbing the times that the user
33371 .vitem &%-timeout%&
33372 This must be followed by a number, which is a number of seconds; it sets a
33373 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
33374 default), a non-blocking call is used.
33377 Generate verbose output.
33380 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
33381 default is to create a lock file and also to use &[fcntl()]& locking on the
33382 mailbox, which is the same as Exim's default. The use of &%-flock%& or
33383 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
33384 requires that the directory containing the file be writeable. Locking by lock
33385 file does not last for ever; Exim assumes that a lock file is expired if it is
33386 more than 30 minutes old.
33388 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
33389 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
33390 to be taken out on the open mailbox, and an exclusive lock on the file
33391 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
33392 number of the mailbox file. When the locking is released, if an exclusive lock
33393 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
33395 The default output contains verification of the locking that takes place. The
33396 &%-v%& option causes some additional information to be given. The &%-q%& option
33397 suppresses all output except error messages.
33401 exim_lock /var/spool/mail/spqr
33403 runs an interactive shell while the file is locked, whereas
33405 &`exim_lock -q /var/spool/mail/spqr <<End`&
33406 <&'some commands'&>
33409 runs a specific non-interactive sequence of commands while the file is locked,
33410 suppressing all verification output. A single command can be run by a command
33413 exim_lock -q /var/spool/mail/spqr \
33414 "cp /var/spool/mail/spqr /some/where"
33416 Note that if a command is supplied, it must be entirely contained within the
33417 second argument &-- hence the quotes.
33421 . ////////////////////////////////////////////////////////////////////////////
33422 . ////////////////////////////////////////////////////////////////////////////
33424 .chapter "The Exim monitor" "CHAPeximon"
33425 .scindex IIDeximon "Exim monitor" "description"
33426 .cindex "X-windows"
33427 .cindex "&'eximon'&"
33428 .cindex "Local/eximon.conf"
33429 .cindex "&_exim_monitor/EDITME_&"
33430 The Exim monitor is an application which displays in an X window information
33431 about the state of Exim's queue and what Exim is doing. An admin user can
33432 perform certain operations on messages from this GUI interface; however all
33433 such facilities are also available from the command line, and indeed, the
33434 monitor itself makes use of the command line to perform any actions requested.
33438 .section "Running the monitor" "SECID264"
33439 The monitor is started by running the script called &'eximon'&. This is a shell
33440 script that sets up a number of environment variables, and then runs the
33441 binary called &_eximon.bin_&. The default appearance of the monitor window can
33442 be changed by editing the &_Local/eximon.conf_& file created by editing
33443 &_exim_monitor/EDITME_&. Comments in that file describe what the various
33444 parameters are for.
33446 The parameters that get built into the &'eximon'& script can be overridden for
33447 a particular invocation by setting up environment variables of the same names,
33448 preceded by &`EXIMON_`&. For example, a shell command such as
33450 EXIMON_LOG_DEPTH=400 eximon
33452 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
33453 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
33454 overrides the Exim log file configuration. This makes it possible to have
33455 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
33456 syslog messages are routed to a file on the local host.
33458 X resources can be used to change the appearance of the window in the normal
33459 way. For example, a resource setting of the form
33461 Eximon*background: gray94
33463 changes the colour of the background to light grey rather than white. The
33464 stripcharts are drawn with both the data lines and the reference lines in
33465 black. This means that the reference lines are not visible when on top of the
33466 data. However, their colour can be changed by setting a resource called
33467 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
33468 For example, if your X server is running Unix, you could set up lighter
33469 reference lines in the stripcharts by obeying
33472 Eximon*highlight: gray
33475 .cindex "admin user"
33476 In order to see the contents of messages on the queue, and to operate on them,
33477 &'eximon'& must either be run as root or by an admin user.
33479 The monitor's window is divided into three parts. The first contains one or
33480 more stripcharts and two action buttons, the second contains a &"tail"& of the
33481 main log file, and the third is a display of the queue of messages awaiting
33482 delivery, with two more action buttons. The following sections describe these
33483 different parts of the display.
33488 .section "The stripcharts" "SECID265"
33489 .cindex "stripchart"
33490 The first stripchart is always a count of messages on the queue. Its name can
33491 be configured by setting QUEUE_STRIPCHART_NAME in the
33492 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
33493 configuration script by regular expression matches on log file entries, making
33494 it possible to display, for example, counts of messages delivered to certain
33495 hosts or using certain transports. The supplied defaults display counts of
33496 received and delivered messages, and of local and SMTP deliveries. The default
33497 period between stripchart updates is one minute; this can be adjusted by a
33498 parameter in the &_Local/eximon.conf_& file.
33500 The stripchart displays rescale themselves automatically as the value they are
33501 displaying changes. There are always 10 horizontal lines in each chart; the
33502 title string indicates the value of each division when it is greater than one.
33503 For example, &"x2"& means that each division represents a value of 2.
33505 It is also possible to have a stripchart which shows the percentage fullness of
33506 a particular disk partition, which is useful when local deliveries are confined
33507 to a single partition.
33509 .cindex "&%statvfs%& function"
33510 This relies on the availability of the &[statvfs()]& function or equivalent in
33511 the operating system. Most, but not all versions of Unix that support Exim have
33512 this. For this particular stripchart, the top of the chart always represents
33513 100%, and the scale is given as &"x10%"&. This chart is configured by setting
33514 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
33515 &_Local/eximon.conf_& file.
33520 .section "Main action buttons" "SECID266"
33521 .cindex "size" "of monitor window"
33522 .cindex "Exim monitor" "window size"
33523 .cindex "window size"
33524 Below the stripcharts there is an action button for quitting the monitor. Next
33525 to this is another button marked &"Size"&. They are placed here so that
33526 shrinking the window to its default minimum size leaves just the queue count
33527 stripchart and these two buttons visible. Pressing the &"Size"& button causes
33528 the window to expand to its maximum size, unless it is already at the maximum,
33529 in which case it is reduced to its minimum.
33531 When expanding to the maximum, if the window cannot be fully seen where it
33532 currently is, it is moved back to where it was the last time it was at full
33533 size. When it is expanding from its minimum size, the old position is
33534 remembered, and next time it is reduced to the minimum it is moved back there.
33536 The idea is that you can keep a reduced window just showing one or two
33537 stripcharts at a convenient place on your screen, easily expand it to show
33538 the full window when required, and just as easily put it back to what it was.
33539 The idea is copied from what the &'twm'& window manager does for its
33540 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
33541 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
33543 Normally, the monitor starts up with the window at its full size, but it can be
33544 built so that it starts up with the window at its smallest size, by setting
33545 START_SMALL=yes in &_Local/eximon.conf_&.
33549 .section "The log display" "SECID267"
33550 .cindex "log" "tail of; in monitor"
33551 The second section of the window is an area in which a display of the tail of
33552 the main log is maintained.
33553 To save space on the screen, the timestamp on each log line is shortened by
33554 removing the date and, if &%log_timezone%& is set, the timezone.
33555 The log tail is not available when the only destination for logging data is
33556 syslog, unless the syslog lines are routed to a local file whose name is passed
33557 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
33559 The log sub-window has a scroll bar at its lefthand side which can be used to
33560 move back to look at earlier text, and the up and down arrow keys also have a
33561 scrolling effect. The amount of log that is kept depends on the setting of
33562 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
33563 to use. When this is full, the earlier 50% of data is discarded &-- this is
33564 much more efficient than throwing it away line by line. The sub-window also has
33565 a horizontal scroll bar for accessing the ends of long log lines. This is the
33566 only means of horizontal scrolling; the right and left arrow keys are not
33567 available. Text can be cut from this part of the window using the mouse in the
33568 normal way. The size of this subwindow is controlled by parameters in the
33569 configuration file &_Local/eximon.conf_&.
33571 Searches of the text in the log window can be carried out by means of the ^R
33572 and ^S keystrokes, which default to a reverse and a forward search,
33573 respectively. The search covers only the text that is displayed in the window.
33574 It cannot go further back up the log.
33576 The point from which the search starts is indicated by a caret marker. This is
33577 normally at the end of the text in the window, but can be positioned explicitly
33578 by pointing and clicking with the left mouse button, and is moved automatically
33579 by a successful search. If new text arrives in the window when it is scrolled
33580 back, the caret remains where it is, but if the window is not scrolled back,
33581 the caret is moved to the end of the new text.
33583 Pressing ^R or ^S pops up a window into which the search text can be typed.
33584 There are buttons for selecting forward or reverse searching, for carrying out
33585 the search, and for cancelling. If the &"Search"& button is pressed, the search
33586 happens and the window remains so that further searches can be done. If the
33587 &"Return"& key is pressed, a single search is done and the window is closed. If
33588 ^C is typed the search is cancelled.
33590 The searching facility is implemented using the facilities of the Athena text
33591 widget. By default this pops up a window containing both &"search"& and
33592 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
33593 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
33594 However, the linkers in BSDI and HP-UX seem unable to handle an externally
33595 provided version of &%TextPop%& when the remaining parts of the text widget
33596 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
33597 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
33598 on these systems, at the expense of having unwanted items in the search popup
33603 .section "The queue display" "SECID268"
33604 .cindex "queue" "display in monitor"
33605 The bottom section of the monitor window contains a list of all messages that
33606 are on the queue, which includes those currently being received or delivered,
33607 as well as those awaiting delivery. The size of this subwindow is controlled by
33608 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
33609 at which it is updated is controlled by another parameter in the same file &--
33610 the default is 5 minutes, since queue scans can be quite expensive. However,
33611 there is an &"Update"& action button just above the display which can be used
33612 to force an update of the queue display at any time.
33614 When a host is down for some time, a lot of pending mail can build up for it,
33615 and this can make it hard to deal with other messages on the queue. To help
33616 with this situation there is a button next to &"Update"& called &"Hide"&. If
33617 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
33618 type anything in here and press &"Return"&, the text is added to a chain of
33619 such texts, and if every undelivered address in a message matches at least one
33620 of the texts, the message is not displayed.
33622 If there is an address that does not match any of the texts, all the addresses
33623 are displayed as normal. The matching happens on the ends of addresses so, for
33624 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
33625 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
33626 has been set up, a button called &"Unhide"& is displayed. If pressed, it
33627 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
33628 a hide request is automatically cancelled after one hour.
33630 While the dialogue box is displayed, you can't press any buttons or do anything
33631 else to the monitor window. For this reason, if you want to cut text from the
33632 queue display to use in the dialogue box, you have to do the cutting before
33633 pressing the &"Hide"& button.
33635 The queue display contains, for each unhidden queued message, the length of
33636 time it has been on the queue, the size of the message, the message id, the
33637 message sender, and the first undelivered recipient, all on one line. If it is
33638 a bounce message, the sender is shown as &"<>"&. If there is more than one
33639 recipient to which the message has not yet been delivered, subsequent ones are
33640 listed on additional lines, up to a maximum configured number, following which
33641 an ellipsis is displayed. Recipients that have already received the message are
33644 .cindex "frozen messages" "display"
33645 If a message is frozen, an asterisk is displayed at the left-hand side.
33647 The queue display has a vertical scroll bar, and can also be scrolled by means
33648 of the arrow keys. Text can be cut from it using the mouse in the normal way.
33649 The text searching facilities, as described above for the log window, are also
33650 available, but the caret is always moved to the end of the text when the queue
33651 display is updated.
33655 .section "The queue menu" "SECID269"
33656 .cindex "queue" "menu in monitor"
33657 If the &%shift%& key is held down and the left button is clicked when the mouse
33658 pointer is over the text for any message, an action menu pops up, and the first
33659 line of the queue display for the message is highlighted. This does not affect
33662 If you want to use some other event for popping up the menu, you can set the
33663 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
33664 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
33665 value set in this parameter is a standard X event description. For example, to
33666 run eximon using &%ctrl%& rather than &%shift%& you could use
33668 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
33670 The title of the menu is the message id, and it contains entries which act as
33674 &'message log'&: The contents of the message log for the message are displayed
33675 in a new text window.
33677 &'headers'&: Information from the spool file that contains the envelope
33678 information and headers is displayed in a new text window. See chapter
33679 &<<CHAPspool>>& for a description of the format of spool files.
33681 &'body'&: The contents of the spool file containing the body of the message are
33682 displayed in a new text window. There is a default limit of 20,000 bytes to the
33683 amount of data displayed. This can be changed by setting the BODY_MAX
33684 option at compile time, or the EXIMON_BODY_MAX option at run time.
33686 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
33687 delivery of the message. This causes an automatic thaw if the message is
33688 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
33689 a new text window. The delivery is run in a separate process, to avoid holding
33690 up the monitor while the delivery proceeds.
33692 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
33693 that the message be frozen.
33695 .cindex "thawing messages"
33696 .cindex "unfreezing messages"
33697 .cindex "frozen messages" "thawing"
33698 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
33699 that the message be thawed.
33701 .cindex "delivery" "forcing failure"
33702 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
33703 that Exim gives up trying to deliver the message. A bounce message is generated
33704 for any remaining undelivered addresses.
33706 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
33707 that the message be deleted from the system without generating a bounce
33710 &'add recipient'&: A dialog box is displayed into which a recipient address can
33711 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
33712 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
33713 Otherwise it must be entered as a fully qualified address. Pressing RETURN
33714 causes a call to Exim to be made using the &%-Mar%& option to request that an
33715 additional recipient be added to the message, unless the entry box is empty, in
33716 which case no action is taken.
33718 &'mark delivered'&: A dialog box is displayed into which a recipient address
33719 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
33720 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
33721 Otherwise it must be entered as a fully qualified address. Pressing RETURN
33722 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
33723 recipient address as already delivered, unless the entry box is empty, in which
33724 case no action is taken.
33726 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
33727 mark all recipient addresses as already delivered.
33729 &'edit sender'&: A dialog box is displayed initialized with the current
33730 sender's address. Pressing RETURN causes a call to Exim to be made using the
33731 &%-Mes%& option to replace the sender address, unless the entry box is empty,
33732 in which case no action is taken. If you want to set an empty sender (as in
33733 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
33734 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
33735 the address is qualified with that domain.
33738 When a delivery is forced, a window showing the &%-v%& output is displayed. In
33739 other cases when a call to Exim is made, if there is any output from Exim (in
33740 particular, if the command fails) a window containing the command and the
33741 output is displayed. Otherwise, the results of the action are normally apparent
33742 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
33743 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
33744 if no output is generated.
33746 The queue display is automatically updated for actions such as freezing and
33747 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
33748 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
33749 force an update of the display after one of these actions.
33751 In any text window that is displayed as result of a menu action, the normal
33752 cut-and-paste facility is available, and searching can be carried out using ^R
33753 and ^S, as described above for the log tail window.
33760 . ////////////////////////////////////////////////////////////////////////////
33761 . ////////////////////////////////////////////////////////////////////////////
33763 .chapter "Security considerations" "CHAPsecurity"
33764 .scindex IIDsecurcon "security" "discussion of"
33765 This chapter discusses a number of issues concerned with security, some of
33766 which are also covered in other parts of this manual.
33768 For reasons that this author does not understand, some people have promoted
33769 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
33770 existence of this chapter in the documentation. However, the intent of the
33771 chapter is simply to describe the way Exim works in relation to certain
33772 security concerns, not to make any specific claims about the effectiveness of
33773 its security as compared with other MTAs.
33775 What follows is a description of the way Exim is supposed to be. Best efforts
33776 have been made to try to ensure that the code agrees with the theory, but an
33777 absence of bugs can never be guaranteed. Any that are reported will get fixed
33778 as soon as possible.
33781 .section "Building a more &""hardened""& Exim" "SECID286"
33782 .cindex "security" "build-time features"
33783 There are a number of build-time options that can be set in &_Local/Makefile_&
33784 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
33785 Exim administrator who does not have the root password, or by someone who has
33786 penetrated the Exim (but not the root) account. These options are as follows:
33789 ALT_CONFIG_PREFIX can be set to a string that is required to match the
33790 start of any file names used with the &%-C%& option. When it is set, these file
33791 names are also not allowed to contain the sequence &"/../"&. (However, if the
33792 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
33793 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
33794 default setting for &%ALT_CONFIG_PREFIX%&.
33796 If the permitted configuration files are confined to a directory to
33797 which only root has access, this guards against someone who has broken
33798 into the Exim account from running a privileged Exim with an arbitrary
33799 configuration file, and using it to break into other accounts.
33801 If ALT_CONFIG_ROOT_ONLY is defined, root privilege is retained for &%-C%&
33802 and &%-D%& only if the caller of Exim is root. Without it, the Exim user may
33803 also use &%-C%& and &%-D%& and retain privilege. Setting this option locks out
33804 the possibility of testing a configuration using &%-C%& right through message
33805 reception and delivery, even if the caller is root. The reception works, but by
33806 that time, Exim is running as the Exim user, so when it re-execs to regain
33807 privilege for the delivery, the use of &%-C%& causes privilege to be lost.
33808 However, root can test reception and delivery using two separate commands.
33809 ALT_CONFIG_ROOT_ONLY is not set by default.
33811 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
33814 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
33815 never to be used for any deliveries. This is like the &%never_users%& runtime
33816 option, but it cannot be overridden; the runtime option adds additional users
33817 to the list. The default setting is &"root"&; this prevents a non-root user who
33818 is permitted to modify the runtime file from using Exim as a way to get root.
33824 .section "Root privilege" "SECID270"
33826 .cindex "root privilege"
33827 The Exim binary is normally setuid to root, which means that it gains root
33828 privilege (runs as root) when it starts execution. In some special cases (for
33829 example, when the daemon is not in use and there are no local deliveries), it
33830 may be possible to run Exim setuid to some user other than root. This is
33831 discussed in the next section. However, in most installations, root privilege
33832 is required for two things:
33835 To set up a socket connected to the standard SMTP port (25) when initialising
33836 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
33839 To be able to change uid and gid in order to read users' &_.forward_& files and
33840 perform local deliveries as the receiving user or as specified in the
33844 It is not necessary to be root to do any of the other things Exim does, such as
33845 receiving messages and delivering them externally over SMTP, and it is
33846 obviously more secure if Exim does not run as root except when necessary.
33847 For this reason, a user and group for Exim to use must be defined in
33848 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
33849 group"&. Their values can be changed by the run time configuration, though this
33850 is not recommended. Often a user called &'exim'& is used, but some sites use
33851 &'mail'& or another user name altogether.
33853 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
33854 abdication; the process cannot regain root afterwards. Prior to release 4.00,
33855 &[seteuid()]& was used in some circumstances, but this is no longer the case.
33857 After a new Exim process has interpreted its command line options, it changes
33858 uid and gid in the following cases:
33863 If the &%-C%& option is used to specify an alternate configuration file, or if
33864 the &%-D%& option is used to define macro values for the configuration, and the
33865 calling process is not running as root or the Exim user, the uid and gid are
33866 changed to those of the calling process.
33867 However, if ALT_CONFIG_ROOT_ONLY is defined in &_Local/Makefile_&, only
33868 root callers may use &%-C%& and &%-D%& without losing privilege, and if
33869 DISABLE_D_OPTION is set, the &%-D%& option may not be used at all.
33874 If the expansion test option (&%-be%&) or one of the filter testing options
33875 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
33878 If the process is not a daemon process or a queue runner process or a delivery
33879 process or a process for testing address routing (started with &%-bt%&), the
33880 uid and gid are changed to the Exim user and group. This means that Exim always
33881 runs under its own uid and gid when receiving messages. This also applies when
33882 testing address verification
33885 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
33888 For a daemon, queue runner, delivery, or address testing process, the uid
33889 remains as root at this stage, but the gid is changed to the Exim group.
33892 The processes that initially retain root privilege behave as follows:
33895 A daemon process changes the gid to the Exim group and the uid to the Exim
33896 user after setting up one or more listening sockets. The &[initgroups()]&
33897 function is called, so that if the Exim user is in any additional groups, they
33898 will be used during message reception.
33900 A queue runner process retains root privilege throughout its execution. Its
33901 job is to fork a controlled sequence of delivery processes.
33903 A delivery process retains root privilege throughout most of its execution,
33904 but any actual deliveries (that is, the transports themselves) are run in
33905 subprocesses which always change to a non-root uid and gid. For local
33906 deliveries this is typically the uid and gid of the owner of the mailbox; for
33907 remote deliveries, the Exim uid and gid are used. Once all the delivery
33908 subprocesses have been run, a delivery process changes to the Exim uid and gid
33909 while doing post-delivery tidying up such as updating the retry database and
33910 generating bounce and warning messages.
33912 While the recipient addresses in a message are being routed, the delivery
33913 process runs as root. However, if a user's filter file has to be processed,
33914 this is done in a subprocess that runs under the individual user's uid and
33915 gid. A system filter is run as root unless &%system_filter_user%& is set.
33917 A process that is testing addresses (the &%-bt%& option) runs as root so that
33918 the routing is done in the same environment as a message delivery.
33924 .section "Running Exim without privilege" "SECTrunexiwitpri"
33925 .cindex "privilege, running without"
33926 .cindex "unprivileged running"
33927 .cindex "root privilege" "running without"
33928 Some installations like to run Exim in an unprivileged state for more of its
33929 operation, for added security. Support for this mode of operation is provided
33930 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
33931 gid are changed to the Exim user and group at the start of a delivery process
33932 (and also queue runner and address testing processes). This means that address
33933 routing is no longer run as root, and the deliveries themselves cannot change
33937 .cindex "daemon" "restarting"
33938 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
33939 that the daemon can still be started in the usual way, and it can respond
33940 correctly to SIGHUP because the re-invocation regains root privilege.
33942 An alternative approach is to make Exim setuid to the Exim user and also setgid
33943 to the Exim group. If you do this, the daemon must be started from a root
33944 process. (Calling Exim from a root process makes it behave in the way it does
33945 when it is setuid root.) However, the daemon cannot restart itself after a
33946 SIGHUP signal because it cannot regain privilege.
33948 It is still useful to set &%deliver_drop_privilege%& in this case, because it
33949 stops Exim from trying to re-invoke itself to do a delivery after a message has
33950 been received. Such a re-invocation is a waste of resources because it has no
33953 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
33954 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
33955 to the Exim user seems a clean approach, but there is one complication:
33957 In this style of operation, Exim is running with the real uid and gid set to
33958 those of the calling process, and the effective uid/gid set to Exim's values.
33959 Ideally, any association with the calling process' uid/gid should be dropped,
33960 that is, the real uid/gid should be reset to the effective values so as to
33961 discard any privileges that the caller may have. While some operating systems
33962 have a function that permits this action for a non-root effective uid, quite a
33963 number of them do not. Because of this lack of standardization, Exim does not
33964 address this problem at this time.
33966 For this reason, the recommended approach for &"mostly unprivileged"& running
33967 is to keep the Exim binary setuid to root, and to set
33968 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
33969 be used in the most straightforward way.
33971 If you configure Exim not to run delivery processes as root, there are a
33972 number of restrictions on what you can do:
33975 You can deliver only as the Exim user/group. You should explicitly use the
33976 &%user%& and &%group%& options to override routers or local transports that
33977 normally deliver as the recipient. This makes sure that configurations that
33978 work in this mode function the same way in normal mode. Any implicit or
33979 explicit specification of another user causes an error.
33981 Use of &_.forward_& files is severely restricted, such that it is usually
33982 not worthwhile to include them in the configuration.
33984 Users who wish to use &_.forward_& would have to make their home directory and
33985 the file itself accessible to the Exim user. Pipe and append-to-file entries,
33986 and their equivalents in Exim filters, cannot be used. While they could be
33987 enabled in the Exim user's name, that would be insecure and not very useful.
33989 Unless the local user mailboxes are all owned by the Exim user (possible in
33990 some POP3 or IMAP-only environments):
33993 They must be owned by the Exim group and be writeable by that group. This
33994 implies you must set &%mode%& in the appendfile configuration, as well as the
33995 mode of the mailbox files themselves.
33997 You must set &%no_check_owner%&, since most or all of the files will not be
33998 owned by the Exim user.
34000 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
34001 on a newly created mailbox when unprivileged. This also implies that new
34002 mailboxes need to be created manually.
34007 These restrictions severely restrict what can be done in local deliveries.
34008 However, there are no restrictions on remote deliveries. If you are running a
34009 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
34010 gives more security at essentially no cost.
34012 If you are using the &%mua_wrapper%& facility (see chapter
34013 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
34018 .section "Delivering to local files" "SECID271"
34019 Full details of the checks applied by &(appendfile)& before it writes to a file
34020 are given in chapter &<<CHAPappendfile>>&.
34024 .section "IPv4 source routing" "SECID272"
34025 .cindex "source routing" "in IP packets"
34026 .cindex "IP source routing"
34027 Many operating systems suppress IP source-routed packets in the kernel, but
34028 some cannot be made to do this, so Exim does its own check. It logs incoming
34029 IPv4 source-routed TCP calls, and then drops them. Things are all different in
34030 IPv6. No special checking is currently done.
34034 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
34035 Support for these SMTP commands is disabled by default. If required, they can
34036 be enabled by defining suitable ACLs.
34041 .section "Privileged users" "SECID274"
34042 .cindex "trusted users"
34043 .cindex "admin user"
34044 .cindex "privileged user"
34045 .cindex "user" "trusted"
34046 .cindex "user" "admin"
34047 Exim recognizes two sets of users with special privileges. Trusted users are
34048 able to submit new messages to Exim locally, but supply their own sender
34049 addresses and information about a sending host. For other users submitting
34050 local messages, Exim sets up the sender address from the uid, and doesn't
34051 permit a remote host to be specified.
34054 However, an untrusted user is permitted to use the &%-f%& command line option
34055 in the special form &%-f <>%& to indicate that a delivery failure for the
34056 message should not cause an error report. This affects the message's envelope,
34057 but it does not affect the &'Sender:'& header. Untrusted users may also be
34058 permitted to use specific forms of address with the &%-f%& option by setting
34059 the &%untrusted_set_sender%& option.
34061 Trusted users are used to run processes that receive mail messages from some
34062 other mail domain and pass them on to Exim for delivery either locally, or over
34063 the Internet. Exim trusts a caller that is running as root, as the Exim user,
34064 as any user listed in the &%trusted_users%& configuration option, or under any
34065 group listed in the &%trusted_groups%& option.
34067 Admin users are permitted to do things to the messages on Exim's queue. They
34068 can freeze or thaw messages, cause them to be returned to their senders, remove
34069 them entirely, or modify them in various ways. In addition, admin users can run
34070 the Exim monitor and see all the information it is capable of providing, which
34071 includes the contents of files on the spool.
34075 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
34076 delivery of messages on its queue is restricted to admin users. This
34077 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
34078 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
34079 queue is also restricted to admin users. This restriction can be relaxed by
34080 setting &%no_queue_list_requires_admin%&.
34082 Exim recognizes an admin user if the calling process is running as root or as
34083 the Exim user or if any of the groups associated with the calling process is
34084 the Exim group. It is not necessary actually to be running under the Exim
34085 group. However, if admin users who are not root or the Exim user are to access
34086 the contents of files on the spool via the Exim monitor (which runs
34087 unprivileged), Exim must be built to allow group read access to its spool
34092 .section "Spool files" "SECID275"
34093 .cindex "spool directory" "files"
34094 Exim's spool directory and everything it contains is owned by the Exim user and
34095 set to the Exim group. The mode for spool files is defined in the
34096 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
34097 any user who is a member of the Exim group can access these files.
34101 .section "Use of argv[0]" "SECID276"
34102 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
34103 of specific strings, Exim assumes certain options. For example, calling Exim
34104 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
34105 to calling it with the option &%-bS%&. There are no security implications in
34110 .section "Use of %f formatting" "SECID277"
34111 The only use made of &"%f"& by Exim is in formatting load average values. These
34112 are actually stored in integer variables as 1000 times the load average.
34113 Consequently, their range is limited and so therefore is the length of the
34118 .section "Embedded Exim path" "SECID278"
34119 Exim uses its own path name, which is embedded in the code, only when it needs
34120 to re-exec in order to regain root privilege. Therefore, it is not root when it
34121 does so. If some bug allowed the path to get overwritten, it would lead to an
34122 arbitrary program's being run as exim, not as root.
34126 .section "Use of sprintf()" "SECID279"
34127 .cindex "&[sprintf()]&"
34128 A large number of occurrences of &"sprintf"& in the code are actually calls to
34129 &'string_sprintf()'&, a function that returns the result in malloc'd store.
34130 The intermediate formatting is done into a large fixed buffer by a function
34131 that runs through the format string itself, and checks the length of each
34132 conversion before performing it, thus preventing buffer overruns.
34134 The remaining uses of &[sprintf()]& happen in controlled circumstances where
34135 the output buffer is known to be sufficiently long to contain the converted
34140 .section "Use of debug_printf() and log_write()" "SECID280"
34141 Arbitrary strings are passed to both these functions, but they do their
34142 formatting by calling the function &'string_vformat()'&, which runs through
34143 the format string itself, and checks the length of each conversion.
34147 .section "Use of strcat() and strcpy()" "SECID281"
34148 These are used only in cases where the output buffer is known to be large
34149 enough to hold the result.
34150 .ecindex IIDsecurcon
34155 . ////////////////////////////////////////////////////////////////////////////
34156 . ////////////////////////////////////////////////////////////////////////////
34158 .chapter "Format of spool files" "CHAPspool"
34159 .scindex IIDforspo1 "format" "spool files"
34160 .scindex IIDforspo2 "spool directory" "format of files"
34161 .scindex IIDforspo3 "spool files" "format of"
34162 .cindex "spool files" "editing"
34163 A message on Exim's queue consists of two files, whose names are the message id
34164 followed by -D and -H, respectively. The data portion of the message is kept in
34165 the -D file on its own. The message's envelope, status, and headers are all
34166 kept in the -H file, whose format is described in this chapter. Each of these
34167 two files contains the final component of its own name as its first line. This
34168 is insurance against disk crashes where the directory is lost but the files
34169 themselves are recoverable.
34171 Some people are tempted into editing -D files in order to modify messages. You
34172 need to be extremely careful if you do this; it is not recommended and you are
34173 on your own if you do it. Here are some of the pitfalls:
34176 You must ensure that Exim does not try to deliver the message while you are
34177 fiddling with it. The safest way is to take out a write lock on the -D file,
34178 which is what Exim itself does, using &[fcntl()]&. If you update the file in
34179 place, the lock will be retained. If you write a new file and rename it, the
34180 lock will be lost at the instant of rename.
34182 .vindex "&$body_linecount$&"
34183 If you change the number of lines in the file, the value of
34184 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
34185 present, this value is not used by Exim, but there is no guarantee that this
34186 will always be the case.
34188 If the message is in MIME format, you must take care not to break it.
34190 If the message is cryptographically signed, any change will invalidate the
34193 All in all, modifying -D files is fraught with danger.
34195 Files whose names end with -J may also be seen in the &_input_& directory (or
34196 its subdirectories when &%split_spool_directory%& is set). These are journal
34197 files, used to record addresses to which the message has been delivered during
34198 the course of a delivery attempt. If there are still undelivered recipients at
34199 the end, the -H file is updated, and the -J file is deleted. If, however, there
34200 is some kind of crash (for example, a power outage) before this happens, the -J
34201 file remains in existence. When Exim next processes the message, it notices the
34202 -J file and uses it to update the -H file before starting the next delivery
34205 .section "Format of the -H file" "SECID282"
34206 .cindex "uid (user id)" "in spool file"
34207 .cindex "gid (group id)" "in spool file"
34208 The second line of the -H file contains the login name for the uid of the
34209 process that called Exim to read the message, followed by the numerical uid and
34210 gid. For a locally generated message, this is normally the user who sent the
34211 message. For a message received over TCP/IP via the daemon, it is
34212 normally the Exim user.
34214 The third line of the file contains the address of the message's sender as
34215 transmitted in the envelope, contained in angle brackets. The sender address is
34216 empty for bounce messages. For incoming SMTP mail, the sender address is given
34217 in the MAIL command. For locally generated mail, the sender address is
34218 created by Exim from the login name of the current user and the configured
34219 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
34220 leading &"From&~"& line if the caller is trusted, or if the supplied address is
34221 &"<>"& or an address that matches &%untrusted_set_senders%&.
34223 The fourth line contains two numbers. The first is the time that the message
34224 was received, in the conventional Unix form &-- the number of seconds since the
34225 start of the epoch. The second number is a count of the number of messages
34226 warning of delayed delivery that have been sent to the sender.
34228 There follow a number of lines starting with a hyphen. These can appear in any
34229 order, and are omitted when not relevant:
34232 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
34233 This item is obsolete, and is not generated from Exim release 4.61 onwards;
34234 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
34235 recognized, to provide backward compatibility. In the old format, a line of
34236 this form is present for every ACL variable that is not empty. The number
34237 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
34238 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
34239 the data string for the variable. The string itself starts at the beginning of
34240 the next line, and is followed by a newline character. It may contain internal
34243 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
34244 A line of this form is present for every ACL connection variable that is
34245 defined. Note that there is a space between &%-aclc%& and the rest of the name.
34246 The length is the length of the data string for the variable. The string itself
34247 starts at the beginning of the next line, and is followed by a newline
34248 character. It may contain internal newlines.
34250 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
34251 A line of this form is present for every ACL message variable that is defined.
34252 Note that there is a space between &%-aclm%& and the rest of the name. The
34253 length is the length of the data string for the variable. The string itself
34254 starts at the beginning of the next line, and is followed by a newline
34255 character. It may contain internal newlines.
34257 .vitem "&%-active_hostname%&&~<&'hostname'&>"
34258 This is present if, when the message was received over SMTP, the value of
34259 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
34261 .vitem &%-allow_unqualified_recipient%&
34262 This is present if unqualified recipient addresses are permitted in header
34263 lines (to stop such addresses from being qualified if rewriting occurs at
34264 transport time). Local messages that were input using &%-bnq%& and remote
34265 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
34267 .vitem &%-allow_unqualified_sender%&
34268 This is present if unqualified sender addresses are permitted in header lines
34269 (to stop such addresses from being qualified if rewriting occurs at transport
34270 time). Local messages that were input using &%-bnq%& and remote messages from
34271 hosts that match &%sender_unqualified_hosts%& set this flag.
34273 .vitem "&%-auth_id%&&~<&'text'&>"
34274 The id information for a message received on an authenticated SMTP connection
34275 &-- the value of the &$authenticated_id$& variable.
34277 .vitem "&%-auth_sender%&&~<&'address'&>"
34278 The address of an authenticated sender &-- the value of the
34279 &$authenticated_sender$& variable.
34281 .vitem "&%-body_linecount%&&~<&'number'&>"
34282 This records the number of lines in the body of the message, and is always
34285 .vitem "&%-body_zerocount%&&~<&'number'&>"
34286 This records the number of binary zero bytes in the body of the message, and is
34287 present if the number is greater than zero.
34289 .vitem &%-deliver_firsttime%&
34290 This is written when a new message is first added to the spool. When the spool
34291 file is updated after a deferral, it is omitted.
34293 .vitem "&%-frozen%&&~<&'time'&>"
34294 .cindex "frozen messages" "spool data"
34295 The message is frozen, and the freezing happened at <&'time'&>.
34297 .vitem "&%-helo_name%&&~<&'text'&>"
34298 This records the host name as specified by a remote host in a HELO or EHLO
34301 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
34302 This records the IP address of the host from which the message was received and
34303 the remote port number that was used. It is omitted for locally generated
34306 .vitem "&%-host_auth%&&~<&'text'&>"
34307 If the message was received on an authenticated SMTP connection, this records
34308 the name of the authenticator &-- the value of the
34309 &$sender_host_authenticated$& variable.
34311 .vitem &%-host_lookup_failed%&
34312 This is present if an attempt to look up the sending host's name from its IP
34313 address failed. It corresponds to the &$host_lookup_failed$& variable.
34315 .vitem "&%-host_name%&&~<&'text'&>"
34316 .cindex "reverse DNS lookup"
34317 .cindex "DNS" "reverse lookup"
34318 This records the name of the remote host from which the message was received,
34319 if the host name was looked up from the IP address when the message was being
34320 received. It is not present if no reverse lookup was done.
34322 .vitem "&%-ident%&&~<&'text'&>"
34323 For locally submitted messages, this records the login of the originating user,
34324 unless it was a trusted user and the &%-oMt%& option was used to specify an
34325 ident value. For messages received over TCP/IP, this records the ident string
34326 supplied by the remote host, if any.
34328 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
34329 This records the IP address of the local interface and the port number through
34330 which a message was received from a remote host. It is omitted for locally
34331 generated messages.
34334 The message is from a local sender.
34336 .vitem &%-localerror%&
34337 The message is a locally-generated bounce message.
34339 .vitem "&%-local_scan%&&~<&'string'&>"
34340 This records the data string that was returned by the &[local_scan()]& function
34341 when the message was received &-- the value of the &$local_scan_data$&
34342 variable. It is omitted if no data was returned.
34344 .vitem &%-manual_thaw%&
34345 The message was frozen but has been thawed manually, that is, by an explicit
34346 Exim command rather than via the auto-thaw process.
34349 A testing delivery process was started using the &%-N%& option to suppress any
34350 actual deliveries, but delivery was deferred. At any further delivery attempts,
34353 .vitem &%-received_protocol%&
34354 This records the value of the &$received_protocol$& variable, which contains
34355 the name of the protocol by which the message was received.
34357 .vitem &%-sender_set_untrusted%&
34358 The envelope sender of this message was set by an untrusted local caller (used
34359 to ensure that the caller is displayed in queue listings).
34361 .vitem "&%-spam_score_int%&&~<&'number'&>"
34362 If a message was scanned by SpamAssassin, this is present. It records the value
34363 of &$spam_score_int$&.
34365 .vitem &%-tls_certificate_verified%&
34366 A TLS certificate was received from the client that sent this message, and the
34367 certificate was verified by the server.
34369 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
34370 When the message was received over an encrypted connection, this records the
34371 name of the cipher suite that was used.
34373 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
34374 When the message was received over an encrypted connection, and a certificate
34375 was received from the client, this records the Distinguished Name from that
34379 Following the options there is a list of those addresses to which the message
34380 is not to be delivered. This set of addresses is initialized from the command
34381 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
34382 is set; otherwise it starts out empty. Whenever a successful delivery is made,
34383 the address is added to this set. The addresses are kept internally as a
34384 balanced binary tree, and it is a representation of that tree which is written
34385 to the spool file. If an address is expanded via an alias or forward file, the
34386 original address is added to the tree when deliveries to all its child
34387 addresses are complete.
34389 If the tree is empty, there is a single line in the spool file containing just
34390 the text &"XX"&. Otherwise, each line consists of two letters, which are either
34391 Y or N, followed by an address. The address is the value for the node of the
34392 tree, and the letters indicate whether the node has a left branch and/or a
34393 right branch attached to it, respectively. If branches exist, they immediately
34394 follow. Here is an example of a three-node tree:
34396 YY darcy@austen.fict.example
34397 NN alice@wonderland.fict.example
34398 NN editor@thesaurus.ref.example
34400 After the non-recipients tree, there is a list of the message's recipients.
34401 This is a simple list, preceded by a count. It includes all the original
34402 recipients of the message, including those to whom the message has already been
34403 delivered. In the simplest case, the list contains one address per line. For
34407 editor@thesaurus.ref.example
34408 darcy@austen.fict.example
34410 alice@wonderland.fict.example
34412 However, when a child address has been added to the top-level addresses as a
34413 result of the use of the &%one_time%& option on a &(redirect)& router, each
34414 line is of the following form:
34416 <&'top-level address'&> <&'errors_to address'&> &&&
34417 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
34419 The 01 flag bit indicates the presence of the three other fields that follow
34420 the top-level address. Other bits may be used in future to support additional
34421 fields. The <&'parent number'&> is the offset in the recipients list of the
34422 original parent of the &"one time"& address. The first two fields are the
34423 envelope sender that is associated with this address and its length. If the
34424 length is zero, there is no special envelope sender (there are then two space
34425 characters in the line). A non-empty field can arise from a &(redirect)& router
34426 that has an &%errors_to%& setting.
34429 A blank line separates the envelope and status information from the headers
34430 which follow. A header may occupy several lines of the file, and to save effort
34431 when reading it in, each header is preceded by a number and an identifying
34432 character. The number is the number of characters in the header, including any
34433 embedded newlines and the terminating newline. The character is one of the
34437 .row <&'blank'&> "header in which Exim has no special interest"
34438 .row &`B`& "&'Bcc:'& header"
34439 .row &`C`& "&'Cc:'& header"
34440 .row &`F`& "&'From:'& header"
34441 .row &`I`& "&'Message-id:'& header"
34442 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
34443 .row &`R`& "&'Reply-To:'& header"
34444 .row &`S`& "&'Sender:'& header"
34445 .row &`T`& "&'To:'& header"
34446 .row &`*`& "replaced or deleted header"
34449 Deleted or replaced (rewritten) headers remain in the spool file for debugging
34450 purposes. They are not transmitted when the message is delivered. Here is a
34451 typical set of headers:
34453 111P Received: by hobbit.fict.example with local (Exim 4.00)
34454 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
34455 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
34456 038* X-rewrote-sender: bb@hobbit.fict.example
34457 042* From: Bilbo Baggins <bb@hobbit.fict.example>
34458 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
34459 099* To: alice@wonderland.fict.example, rdo@foundation,
34460 darcy@austen.fict.example, editor@thesaurus.ref.example
34461 104T To: alice@wonderland.fict.example, rdo@foundation.example,
34462 darcy@austen.fict.example, editor@thesaurus.ref.example
34463 038 Date: Fri, 11 May 2001 10:28:59 +0100
34465 The asterisked headers indicate that the envelope sender, &'From:'& header, and
34466 &'To:'& header have been rewritten, the last one because routing expanded the
34467 unqualified domain &'foundation'&.
34468 .ecindex IIDforspo1
34469 .ecindex IIDforspo2
34470 .ecindex IIDforspo3
34472 . ////////////////////////////////////////////////////////////////////////////
34473 . ////////////////////////////////////////////////////////////////////////////
34475 .chapter "Support for DKIM (DomainKeys Identified Mail) - RFC4871" "CHID12" &&&
34479 Since version 4.70, DKIM support is compiled into Exim by default. It can be
34480 disabled by setting DISABLE_DKIM=yes in Local/Makefile.
34482 Exim's DKIM implementation allows to
34484 Sign outgoing messages: This function is implemented in the SMTP transport.
34485 It can co-exist with all other Exim features, including transport filters.
34487 Verify signatures in incoming messages: This is implemented by an additional
34488 ACL (acl_smtp_dkim), which can be called several times per message, with
34489 different signature contexts.
34492 In typical Exim style, the verification implementation does not include any
34493 default "policy". Instead it enables you to build your own policy using
34494 Exim's standard controls.
34496 Please note that verification of DKIM signatures in incoming mail is turned
34497 on by default for logging purposes. For each signature in incoming email,
34498 exim will log a line displaying the most important signature details, and the
34499 signature status. Here is an example:
34501 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM: d=facebookmail.com s=q1-2009b c=relaxed/relaxed a=rsa-sha1 i=@facebookmail.com t=1252484542 [verification succeeded]
34503 You might want to turn off DKIM verification processing entirely for internal
34504 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
34505 control modifier. This should typically be done in the RCPT ACL, at points
34506 where you accept mail from relay sources (internal hosts or authenticated
34510 .section "Signing outgoing messages" "SECID513"
34511 .cindex "DKIM" "signing"
34513 Signing is implemented by setting private options on the SMTP transport.
34514 These options take (expandable) strings as arguments.
34516 .option dkim_domain smtp string&!! unset
34518 The domain you want to sign with. The result of this expanded
34519 option is put into the &%$dkim_domain%& expansion variable.
34521 .option dkim_selector smtp string&!! unset
34523 This sets the key selector string. You can use the &%$dkim_domain%& expansion
34524 variable to look up a matching selector. The result is put in the expansion
34525 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
34526 option along with &%$dkim_domain%&.
34528 .option dkim_private_key smtp string&!! unset
34530 This sets the private key to use. You can use the &%$dkim_domain%& and
34531 &%$dkim_selector%& expansion variables to determine the private key to use.
34532 The result can either
34534 be a valid RSA private key in ASCII armor, including line breaks.
34536 start with a slash, in which case it is treated as a file that contains
34539 be "0", "false" or the empty string, in which case the message will not
34540 be signed. This case will not result in an error, even if &%dkim_strict%&
34544 .option dkim_canon smtp string&!! unset
34546 This option sets the canonicalization method used when signing a message.
34547 The DKIM RFC currently supports two methods: "simple" and "relaxed".
34548 The option defaults to "relaxed" when unset. Note: the current implementation
34549 only supports using the same canonicalization method for both headers and body.
34551 .option dkim_strict smtp string&!! unset
34553 This option defines how Exim behaves when signing a message that
34554 should be signed fails for some reason. When the expansion evaluates to
34555 either "1" or "true", Exim will defer. Otherwise Exim will send the message
34556 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
34559 .option dkim_sign_headers smtp string&!! unset
34561 When set, this option must expand to (or be specified as) a colon-separated
34562 list of header names. Headers with these names will be included in the message
34563 signature. When unspecified, the header names recommended in RFC4871 will be
34567 .section "Verifying DKIM signatures in incoming mail" "SECID514"
34568 .cindex "DKIM" "verification"
34570 Verification of DKIM signatures in incoming email is implemented via the
34571 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
34572 syntactically(!) correct signature in the incoming message.
34574 To evaluate the signature in the ACL a large number of expansion variables
34575 containing the signature status and its details are set up during the
34576 runtime of the ACL.
34578 Calling the ACL only for existing signatures is not sufficient to build
34579 more advanced policies. For that reason, the global option
34580 &%dkim_verify_signers%&, and a global expansion variable
34581 &%$dkim_signers%& exist.
34583 The global option &%dkim_verify_signers%& can be set to a colon-separated
34584 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
34585 called. It is expanded when the message has been received. At this point,
34586 the expansion variable &%$dkim_signers%& already contains a colon-separated
34587 list of signer domains and identities for the message. When
34588 &%dkim_verify_signers%& is not specified in the main configuration,
34591 dkim_verify_signers = $dkim_signers
34593 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
34594 DKIM signature in the message. Current DKIM verifiers may want to explicitly
34595 call the ACL for known domains or identities. This would be achieved as follows:
34597 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
34599 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
34600 and "ebay.com", plus all domains and identities that have signatures in the message.
34601 You can also be more creative in constructing your policy. For example:
34603 dkim_verify_signers = $sender_address_domain:$dkim_signers
34606 If a domain or identity is listed several times in the (expanded) value of
34607 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
34610 Inside the &%acl_smtp_dkim%&, the following expansion variables are
34611 available (from most to least important):
34614 .vitem &%$dkim_cur_signer%&
34615 The signer that is being evaluated in this ACL run. This can be a domain or
34616 an identity. This is one of the list items from the expanded main option
34617 &%dkim_verify_signers%& (see above).
34618 .vitem &%$dkim_verify_status%&
34619 A string describing the general status of the signature. One of
34621 &%none%&: There is no signature in the message for the current domain or
34622 identity (as reflected by &%$dkim_cur_signer%&).
34624 &%invalid%&: The signature could not be verified due to a processing error.
34625 More detail is available in &%$dkim_verify_reason%&.
34627 &%fail%&: Verification of the signature failed. More detail is
34628 available in &%$dkim_verify_reason%&.
34630 &%pass%&: The signature passed verification. It is valid.
34632 .vitem &%$dkim_verify_reason%&
34633 A string giving a litte bit more detail when &%$dkim_verify_status%& is either
34634 "fail" or "invalid". One of
34636 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
34637 key for the domain could not be retrieved. This may be a temporary problem.
34639 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
34640 record for the domain is syntactically invalid.
34642 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
34643 body hash does not match the one specified in the signature header. This
34644 means that the message body was modified in transit.
34646 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
34647 could not be verified. This may mean that headers were modified,
34648 re-written or otherwise changed in a way which is incompatible with
34649 DKIM verification. It may of course also mean that the signature is forged.
34651 .vitem &%$dkim_domain%&
34652 The signing domain. IMPORTANT: This variable is only populated if there is
34653 an actual signature in the message for the current domain or identity (as
34654 reflected by &%$dkim_cur_signer%&).
34655 .vitem &%$dkim_identity%&
34656 The signing identity, if present. IMPORTANT: This variable is only populated
34657 if there is an actual signature in the message for the current domain or
34658 identity (as reflected by &%$dkim_cur_signer%&).
34659 .vitem &%$dkim_selector%&
34660 The key record selector string.
34661 .vitem &%$dkim_algo%&
34662 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
34663 .vitem &%$dkim_canon_body%&
34664 The body canonicalization method. One of 'relaxed' or 'simple'.
34665 .vitem &%dkim_canon_headers%&
34666 The header canonicalization method. One of 'relaxed' or 'simple'.
34667 .vitem &%$dkim_copiedheaders%&
34668 A transcript of headers and their values which are included in the signature
34669 (copied from the 'z=' tag of the signature).
34670 .vitem &%$dkim_bodylength%&
34671 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
34672 limit was set by the signer, "9999999999999" is returned. This makes sure
34673 that this variable always expands to an integer value.
34674 .vitem &%$dkim_created%&
34675 UNIX timestamp reflecting the date and time when the signature was created.
34676 When this was not specified by the signer, "0" is returned.
34677 .vitem &%$dkim_expires%&
34678 UNIX timestamp reflecting the date and time when the signer wants the
34679 signature to be treated as "expired". When this was not specified by the
34680 signer, "9999999999999" is returned. This makes it possible to do useful
34681 integer size comparisons against this value.
34682 .vitem &%$dkim_headernames%&
34683 A colon-separated list of names of headers included in the signature.
34684 .vitem &%$dkim_key_testing%&
34685 "1" if the key record has the "testing" flag set, "0" if not.
34686 .vitem &%$dkim_key_nosubdomaining%&
34687 "1" if the key record forbids subdomaining, "0" otherwise.
34688 .vitem &%$dkim_key_srvtype%&
34689 Service type (tag s=) from the key record. Defaults to "*" if not specified
34691 .vitem &%$dkim_key_granularity%&
34692 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
34694 .vitem &%$dkim_key_notes%&
34695 Notes from the key record (tag n=).
34698 In addition, two ACL conditions are provided:
34701 .vitem &%dkim_signers%&
34702 ACL condition that checks a colon-separated list of domains or identities
34703 for a match against the domain or identity that the ACL is currently verifying
34704 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
34705 verb to a group of domains or identities. For example:
34708 # Warn when message apparently from GMail has no signature at all
34709 warn log_message = GMail sender without DKIM signature
34710 sender_domains = gmail.com
34711 dkim_signers = gmail.com
34715 .vitem &%dkim_status%&
34716 ACL condition that checks a colon-separated list of possible DKIM verification
34717 results agains the actual result of verification. This is typically used
34718 to restrict an ACL verb to a list of verification outcomes, like:
34721 deny message = Message from Paypal with invalid or missing signature
34722 sender_domains = paypal.com:paypal.de
34723 dkim_signers = paypal.com:paypal.de
34724 dkim_status = none:invalid:fail
34727 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
34728 see the documentation of the &%$dkim_verify_status%& expansion variable above
34729 for more information of what they mean.
34732 . ////////////////////////////////////////////////////////////////////////////
34733 . ////////////////////////////////////////////////////////////////////////////
34735 .chapter "Adding new drivers or lookup types" "CHID13" &&&
34736 "Adding drivers or lookups"
34737 .cindex "adding drivers"
34738 .cindex "new drivers, adding"
34739 .cindex "drivers" "adding new"
34740 The following actions have to be taken in order to add a new router, transport,
34741 authenticator, or lookup type to Exim:
34744 Choose a name for the driver or lookup type that does not conflict with any
34745 existing name; I will use &"newdriver"& in what follows.
34747 Add to &_src/EDITME_& the line:
34749 <&'type'&>&`_NEWDRIVER=yes`&
34751 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
34752 code is not to be included in the binary by default, comment this line out. You
34753 should also add any relevant comments about the driver or lookup type.
34755 Add to &_src/config.h.defaults_& the line:
34757 #define <type>_NEWDRIVER
34760 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
34761 and create a table entry as is done for all the other drivers and lookup types.
34763 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
34764 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
34765 driver or lookup type and add it to the definition of OBJ.
34767 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
34770 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
34771 as for other drivers and lookups.
34774 Then all you need to do is write the code! A good way to start is to make a
34775 proforma by copying an existing module of the same type, globally changing all
34776 occurrences of the name, and cutting out most of the code. Note that any
34777 options you create must be listed in alphabetical order, because the tables are
34778 searched using a binary chop procedure.
34780 There is a &_README_& file in each of the sub-directories of &_src_& describing
34781 the interface that is expected.
34786 . ////////////////////////////////////////////////////////////////////////////
34787 . ////////////////////////////////////////////////////////////////////////////
34789 . /////////////////////////////////////////////////////////////////////////////
34790 . These lines are processing instructions for the Simple DocBook Processor that
34791 . Philip Hazel has developed as a less cumbersome way of making PostScript and
34792 . PDFs than using xmlto and fop. They will be ignored by all other XML
34794 . /////////////////////////////////////////////////////////////////////////////
34799 foot_right_recto="&chaptertitle;"
34800 foot_right_verso="&chaptertitle;"
34804 .makeindex "Options index" "option"
34805 .makeindex "Variables index" "variable"
34806 .makeindex "Concept index" "concept"
34809 . /////////////////////////////////////////////////////////////////////////////
34810 . /////////////////////////////////////////////////////////////////////////////