1 . /////////////////////////////////////////////////////////////////////////////
2 . This is the primary source of the Exim Manual. It is an xfpt document that is
3 . converted into DocBook XML for subsequent conversion into printing and online
4 . formats. The markup used herein is "standard" xfpt markup, with some extras.
5 . The markup is summarized in a file called Markup.txt.
7 . WARNING: When you use the .new macro, make sure it appears *before* any
8 . adjacent index items; otherwise you get an empty "paragraph" which causes
9 . unwanted vertical space.
10 . /////////////////////////////////////////////////////////////////////////////
15 . /////////////////////////////////////////////////////////////////////////////
16 . This outputs the standard DocBook boilerplate.
17 . /////////////////////////////////////////////////////////////////////////////
21 . /////////////////////////////////////////////////////////////////////////////
22 . These lines are processing instructions for the Simple DocBook Processor that
23 . Philip Hazel has developed as a less cumbersome way of making PostScript and
24 . PDFs than using xmlto and fop. They will be ignored by all other XML
26 . /////////////////////////////////////////////////////////////////////////////
30 foot_right_recto="&chaptertitle; (&chapternumber;)"
31 foot_right_verso="&chaptertitle; (&chapternumber;)"
32 toc_chapter_blanks="yes,yes"
33 table_warn_overflow="overprint"
37 . /////////////////////////////////////////////////////////////////////////////
38 . This generate the outermost <book> element that wraps then entire document.
39 . /////////////////////////////////////////////////////////////////////////////
43 . /////////////////////////////////////////////////////////////////////////////
44 . These definitions set some parameters and save some typing.
45 . Update the Copyright year (only) when changing content.
46 . /////////////////////////////////////////////////////////////////////////////
48 .set previousversion "4.87"
49 .include ./local_params
51 .set ACL "access control lists (ACLs)"
52 .set I " "
58 . /////////////////////////////////////////////////////////////////////////////
59 . Additional xfpt markup used by this document, over and above the default
60 . provided in the xfpt library.
61 . /////////////////////////////////////////////////////////////////////////////
63 . --- Override the &$ flag to automatically insert a $ with the variable name
65 .flag &$ $& "<varname>$" "</varname>"
67 . --- Short flags for daggers in option headings. They will always be inside
68 . --- an italic string, but we want the daggers to be roman.
70 .flag &!! "</emphasis>†<emphasis>"
71 .flag &!? "</emphasis>‡<emphasis>"
73 . --- A macro for an Exim option definition heading, generating a one-line
74 . --- table with four columns. For cases when the option name is given with
75 . --- a space, so that it can be split, a fifth argument is used for the
85 .itable all 0 0 4 8* left 6* center 6* center 6* right
86 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
90 . --- A macro for the common 2-column tables. The width of the first column
91 . --- is suitable for the many tables at the start of the main options chapter;
92 . --- the small number of other 2-column tables override it.
94 .macro table2 196pt 254pt
95 .itable none 0 0 2 $1 left $2 left
98 . --- A macro that generates .row, but puts &I; at the start of the first
99 . --- argument, thus indenting it. Assume a minimum of two arguments, and
100 . --- allow up to four arguments, which is as many as we'll ever need.
104 .row "&I;$1" "$2" "$3" "$4"
108 .row "&I;$1" "$2" "$3"
116 . --- Macros for option, variable, and concept index entries. For a "range"
117 . --- style of entry, use .scindex for the start and .ecindex for the end. The
118 . --- first argument of .scindex and the only argument of .ecindex must be the
119 . --- ID that ties them together.
122 &<indexterm role="concept">&
123 &<primary>&$1&</primary>&
125 &<secondary>&$2&</secondary>&
131 &<indexterm role="concept" id="$1" class="startofrange">&
132 &<primary>&$2&</primary>&
134 &<secondary>&$3&</secondary>&
140 &<indexterm role="concept" startref="$1" class="endofrange"/>&
144 &<indexterm role="option">&
145 &<primary>&$1&</primary>&
147 &<secondary>&$2&</secondary>&
153 &<indexterm role="variable">&
154 &<primary>&$1&</primary>&
156 &<secondary>&$2&</secondary>&
162 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
164 . ////////////////////////////////////////////////////////////////////////////
167 . ////////////////////////////////////////////////////////////////////////////
168 . The <bookinfo> element is removed from the XML before processing for Ascii
170 . ////////////////////////////////////////////////////////////////////////////
174 <title>Specification of the Exim Mail Transfer Agent</title>
175 <titleabbrev>The Exim MTA</titleabbrev>
179 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
180 <authorinitials>EM</authorinitials>
181 <revhistory><revision>
183 <authorinitials>EM</authorinitials>
184 </revision></revhistory>
187 </year><holder>University of Cambridge</holder></copyright>
192 . /////////////////////////////////////////////////////////////////////////////
193 . This chunk of literal XML implements index entries of the form "x, see y" and
194 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
195 . at the top level, so we have to put the .chapter directive first.
196 . /////////////////////////////////////////////////////////////////////////////
198 .chapter "Introduction" "CHID1"
201 <indexterm role="variable">
202 <primary>$1, $2, etc.</primary>
203 <see><emphasis>numerical variables</emphasis></see>
205 <indexterm role="concept">
206 <primary>address</primary>
207 <secondary>rewriting</secondary>
208 <see><emphasis>rewriting</emphasis></see>
210 <indexterm role="concept">
211 <primary>Bounce Address Tag Validation</primary>
212 <see><emphasis>BATV</emphasis></see>
214 <indexterm role="concept">
215 <primary>Client SMTP Authorization</primary>
216 <see><emphasis>CSA</emphasis></see>
218 <indexterm role="concept">
219 <primary>CR character</primary>
220 <see><emphasis>carriage return</emphasis></see>
222 <indexterm role="concept">
223 <primary>CRL</primary>
224 <see><emphasis>certificate revocation list</emphasis></see>
226 <indexterm role="concept">
227 <primary>delivery</primary>
228 <secondary>failure report</secondary>
229 <see><emphasis>bounce message</emphasis></see>
231 <indexterm role="concept">
232 <primary>dialup</primary>
233 <see><emphasis>intermittently connected hosts</emphasis></see>
235 <indexterm role="concept">
236 <primary>exiscan</primary>
237 <see><emphasis>content scanning</emphasis></see>
239 <indexterm role="concept">
240 <primary>failover</primary>
241 <see><emphasis>fallback</emphasis></see>
243 <indexterm role="concept">
244 <primary>fallover</primary>
245 <see><emphasis>fallback</emphasis></see>
247 <indexterm role="concept">
248 <primary>filter</primary>
249 <secondary>Sieve</secondary>
250 <see><emphasis>Sieve filter</emphasis></see>
252 <indexterm role="concept">
253 <primary>ident</primary>
254 <see><emphasis>RFC 1413</emphasis></see>
256 <indexterm role="concept">
257 <primary>LF character</primary>
258 <see><emphasis>linefeed</emphasis></see>
260 <indexterm role="concept">
261 <primary>maximum</primary>
262 <seealso><emphasis>limit</emphasis></seealso>
264 <indexterm role="concept">
265 <primary>monitor</primary>
266 <see><emphasis>Exim monitor</emphasis></see>
268 <indexterm role="concept">
269 <primary>no_<emphasis>xxx</emphasis></primary>
270 <see>entry for xxx</see>
272 <indexterm role="concept">
273 <primary>NUL</primary>
274 <see><emphasis>binary zero</emphasis></see>
276 <indexterm role="concept">
277 <primary>passwd file</primary>
278 <see><emphasis>/etc/passwd</emphasis></see>
280 <indexterm role="concept">
281 <primary>process id</primary>
282 <see><emphasis>pid</emphasis></see>
284 <indexterm role="concept">
285 <primary>RBL</primary>
286 <see><emphasis>DNS list</emphasis></see>
288 <indexterm role="concept">
289 <primary>redirection</primary>
290 <see><emphasis>address redirection</emphasis></see>
292 <indexterm role="concept">
293 <primary>return path</primary>
294 <seealso><emphasis>envelope sender</emphasis></seealso>
296 <indexterm role="concept">
297 <primary>scanning</primary>
298 <see><emphasis>content scanning</emphasis></see>
300 <indexterm role="concept">
301 <primary>SSL</primary>
302 <see><emphasis>TLS</emphasis></see>
304 <indexterm role="concept">
305 <primary>string</primary>
306 <secondary>expansion</secondary>
307 <see><emphasis>expansion</emphasis></see>
309 <indexterm role="concept">
310 <primary>top bit</primary>
311 <see><emphasis>8-bit characters</emphasis></see>
313 <indexterm role="concept">
314 <primary>variables</primary>
315 <see><emphasis>expansion, variables</emphasis></see>
317 <indexterm role="concept">
318 <primary>zero, binary</primary>
319 <see><emphasis>binary zero</emphasis></see>
325 . /////////////////////////////////////////////////////////////////////////////
326 . This is the real start of the first chapter. See the comment above as to why
327 . we can't have the .chapter line here.
328 . chapter "Introduction"
329 . /////////////////////////////////////////////////////////////////////////////
331 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
332 Unix-like operating systems. It was designed on the assumption that it would be
333 run on hosts that are permanently connected to the Internet. However, it can be
334 used on intermittently connected hosts with suitable configuration adjustments.
336 Configuration files currently exist for the following operating systems: AIX,
337 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
338 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
339 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
340 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
341 Some of these operating systems are no longer current and cannot easily be
342 tested, so the configuration files may no longer work in practice.
344 There are also configuration files for compiling Exim in the Cygwin environment
345 that can be installed on systems running Windows. However, this document does
346 not contain any information about running Exim in the Cygwin environment.
348 The terms and conditions for the use and distribution of Exim are contained in
349 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
350 Public Licence, a copy of which may be found in the file &_LICENCE_&.
352 The use, supply or promotion of Exim for the purpose of sending bulk,
353 unsolicited electronic mail is incompatible with the basic aims of the program,
354 which revolve around the free provision of a service that enhances the quality
355 of personal communications. The author of Exim regards indiscriminate
356 mass-mailing as an antisocial, irresponsible abuse of the Internet.
358 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
359 experience of running and working on the Smail 3 code, I could never have
360 contemplated starting to write a new MTA. Many of the ideas and user interfaces
361 were originally taken from Smail 3, though the actual code of Exim is entirely
362 new, and has developed far beyond the initial concept.
364 Many people, both in Cambridge and around the world, have contributed to the
365 development and the testing of Exim, and to porting it to various operating
366 systems. I am grateful to them all. The distribution now contains a file called
367 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
371 .section "Exim documentation" "SECID1"
372 . Keep this example change bar when updating the documentation!
375 .cindex "documentation"
376 This edition of the Exim specification applies to version &version() of Exim.
377 Substantive changes from the &previousversion; edition are marked in some
378 renditions of the document; this paragraph is so marked if the rendition is
379 capable of showing a change indicator.
382 This document is very much a reference manual; it is not a tutorial. The reader
383 is expected to have some familiarity with the SMTP mail transfer protocol and
384 with general Unix system administration. Although there are some discussions
385 and examples in places, the information is mostly organized in a way that makes
386 it easy to look up, rather than in a natural order for sequential reading.
387 Furthermore, the manual aims to cover every aspect of Exim in detail, including
388 a number of rarely-used, special-purpose features that are unlikely to be of
391 .cindex "books about Exim"
392 An &"easier"& discussion of Exim which provides more in-depth explanatory,
393 introductory, and tutorial material can be found in a book entitled &'The Exim
394 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
395 (&url(http://www.uit.co.uk/exim-book/)).
397 This book also contains a chapter that gives a general introduction to SMTP and
398 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
399 with the latest release of Exim. (Note that the earlier book about Exim,
400 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
402 .cindex "Debian" "information sources"
403 If you are using a Debian distribution of Exim, you will find information about
404 Debian-specific features in the file
405 &_/usr/share/doc/exim4-base/README.Debian_&.
406 The command &(man update-exim.conf)& is another source of Debian-specific
409 .cindex "&_doc/NewStuff_&"
410 .cindex "&_doc/ChangeLog_&"
412 As the program develops, there may be features in newer versions that have not
413 yet made it into this document, which is updated only when the most significant
414 digit of the fractional part of the version number changes. Specifications of
415 new features that are not yet in this manual are placed in the file
416 &_doc/NewStuff_& in the Exim distribution.
418 Some features may be classified as &"experimental"&. These may change
419 incompatibly while they are developing, or even be withdrawn. For this reason,
420 they are not documented in this manual. Information about experimental features
421 can be found in the file &_doc/experimental.txt_&.
423 All changes to the program (whether new features, bug fixes, or other kinds of
424 change) are noted briefly in the file called &_doc/ChangeLog_&.
426 .cindex "&_doc/spec.txt_&"
427 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
428 that it can easily be searched with a text editor. Other files in the &_doc_&
432 .row &_OptionLists.txt_& "list of all options in alphabetical order"
433 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
434 .row &_exim.8_& "a man page of Exim's command line options"
435 .row &_experimental.txt_& "documentation of experimental features"
436 .row &_filter.txt_& "specification of the filter language"
437 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
438 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
441 The main specification and the specification of the filtering language are also
442 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
443 &<<SECTavail>>& below tells you how to get hold of these.
447 .section "FTP and web sites" "SECID2"
450 The primary site for Exim source distributions is currently the University of
451 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
452 distribution'& below. In addition, there is a web site and an FTP site at
453 &%exim.org%&. These are now also hosted at the University of Cambridge. The
454 &%exim.org%& site was previously hosted for a number of years by Energis
455 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
459 As well as Exim distribution tar files, the Exim web site contains a number of
460 differently formatted versions of the documentation. A recent addition to the
461 online information is the Exim wiki (&url(http://wiki.exim.org)),
462 which contains what used to be a separate FAQ, as well as various other
463 examples, tips, and know-how that have been contributed by Exim users.
466 An Exim Bugzilla exists at &url(http://bugs.exim.org). You can use
467 this to report bugs, and also to add items to the wish list. Please search
468 first to check that you are not duplicating a previous entry.
472 .section "Mailing lists" "SECID3"
473 .cindex "mailing lists" "for Exim users"
474 The following Exim mailing lists exist:
477 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
478 .row &'exim-users@exim.org'& "General discussion list"
479 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
480 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
483 You can subscribe to these lists, change your existing subscriptions, and view
484 or search the archives via the mailing lists link on the Exim home page.
485 .cindex "Debian" "mailing list for"
486 If you are using a Debian distribution of Exim, you may wish to subscribe to
487 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
490 &url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
492 Please ask Debian-specific questions on this list and not on the general Exim
495 .section "Exim training" "SECID4"
496 .cindex "training courses"
497 Training courses in Cambridge (UK) used to be run annually by the author of
498 Exim, before he retired. At the time of writing, there are no plans to run
499 further Exim courses in Cambridge. However, if that changes, relevant
500 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
502 .section "Bug reports" "SECID5"
503 .cindex "bug reports"
504 .cindex "reporting bugs"
505 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
506 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
507 whether some behaviour is a bug or not, the best thing to do is to post a
508 message to the &'exim-dev'& mailing list and have it discussed.
512 .section "Where to find the Exim distribution" "SECTavail"
514 .cindex "distribution" "ftp site"
515 The master ftp site for the Exim distribution is
517 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
521 &*ftp://ftp.exim.org/pub/exim*&
523 The file references that follow are relative to the &_exim_& directories at
524 these sites. There are now quite a number of independent mirror sites around
525 the world. Those that I know about are listed in the file called &_Mirrors_&.
527 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
528 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
529 distributions), and &_Testing_& for testing versions. In the &_exim4_&
530 subdirectory, the current release can always be found in files called
533 &_exim-n.nn.tar.bz2_&
535 where &'n.nn'& is the highest such version number in the directory. The two
536 files contain identical data; the only difference is the type of compression.
537 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
539 .cindex "distribution" "signing details"
540 .cindex "distribution" "public key"
541 .cindex "public key for signed distribution"
542 The distributions will be PGP signed by an individual key of the Release
543 Coordinator. This key will have a uid containing an email address in the
544 &'exim.org'& domain and will have signatures from other people, including
545 other Exim maintainers. We expect that the key will be in the "strong set" of
546 PGP keys. There should be a trust path to that key from Nigel Metheringham's
547 PGP key, a version of which can be found in the release directory in the file
548 &_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools,
549 such as &'pool.sks-keyservers.net'&.
551 At time of last update, releases were being made by Phil Pennock and signed with
552 key &'0x403043153903637F'&, although that key is expected to be replaced in 2013.
553 A trust path from Nigel's key to Phil's can be observed at
554 &url(https://www.security.spodhuis.org/exim-trustpath).
556 Releases have also been authorized to be performed by Todd Lyons who signs with
557 key &'0xC4F4F94804D29EBA'&. A direct trust path exists between previous RE Phil
558 Pennock and Todd Lyons through a common associate.
560 The signatures for the tar bundles are in:
562 &_exim-n.nn.tar.gz.asc_&
563 &_exim-n.nn.tar.bz2.asc_&
565 For each released version, the log of changes is made separately available in a
566 separate file in the directory &_ChangeLogs_& so that it is possible to
567 find out what has changed without having to download the entire distribution.
569 .cindex "documentation" "available formats"
570 The main distribution contains ASCII versions of this specification and other
571 documentation; other formats of the documents are available in separate files
572 inside the &_exim4_& directory of the FTP site:
574 &_exim-html-n.nn.tar.gz_&
575 &_exim-pdf-n.nn.tar.gz_&
576 &_exim-postscript-n.nn.tar.gz_&
577 &_exim-texinfo-n.nn.tar.gz_&
579 These tar files contain only the &_doc_& directory, not the complete
580 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
583 .section "Limitations" "SECID6"
585 .cindex "limitations of Exim"
586 .cindex "bang paths" "not handled by Exim"
587 Exim is designed for use as an Internet MTA, and therefore handles addresses in
588 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
589 simple two-component bang paths can be converted by a straightforward rewriting
590 configuration. This restriction does not prevent Exim from being interfaced to
591 UUCP as a transport mechanism, provided that domain addresses are used.
593 .cindex "domainless addresses"
594 .cindex "address" "without domain"
595 Exim insists that every address it handles has a domain attached. For incoming
596 local messages, domainless addresses are automatically qualified with a
597 configured domain value. Configuration options specify from which remote
598 systems unqualified addresses are acceptable. These are then qualified on
601 .cindex "transport" "external"
602 .cindex "external transports"
603 The only external transport mechanisms that are currently implemented are SMTP
604 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
605 transport is available, and there are facilities for writing messages to files
606 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
607 to send messages to other transport mechanisms such as UUCP, provided they can
608 handle domain-style addresses. Batched SMTP input is also catered for.
610 Exim is not designed for storing mail for dial-in hosts. When the volumes of
611 such mail are large, it is better to get the messages &"delivered"& into files
612 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
615 Although Exim does have basic facilities for scanning incoming messages, these
616 are not comprehensive enough to do full virus or spam scanning. Such operations
617 are best carried out using additional specialized software packages. If you
618 compile Exim with the content-scanning extension, straightforward interfaces to
619 a number of common scanners are provided.
623 .section "Run time configuration" "SECID7"
624 Exim's run time configuration is held in a single text file that is divided
625 into a number of sections. The entries in this file consist of keywords and
626 values, in the style of Smail 3 configuration files. A default configuration
627 file which is suitable for simple online installations is provided in the
628 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
631 .section "Calling interface" "SECID8"
632 .cindex "Sendmail compatibility" "command line interface"
633 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
634 can be a straight replacement for &_/usr/lib/sendmail_& or
635 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
636 about Sendmail in order to run Exim. For actions other than sending messages,
637 Sendmail-compatible options also exist, but those that produce output (for
638 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
639 format. There are also some additional options that are compatible with Smail
640 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
641 documents all Exim's command line options. This information is automatically
642 made into the man page that forms part of the Exim distribution.
644 Control of messages on the queue can be done via certain privileged command
645 line options. There is also an optional monitor program called &'eximon'&,
646 which displays current information in an X window, and which contains a menu
647 interface to Exim's command line administration options.
651 .section "Terminology" "SECID9"
652 .cindex "terminology definitions"
653 .cindex "body of message" "definition of"
654 The &'body'& of a message is the actual data that the sender wants to transmit.
655 It is the last part of a message, and is separated from the &'header'& (see
656 below) by a blank line.
658 .cindex "bounce message" "definition of"
659 When a message cannot be delivered, it is normally returned to the sender in a
660 delivery failure message or a &"non-delivery report"& (NDR). The term
661 &'bounce'& is commonly used for this action, and the error reports are often
662 called &'bounce messages'&. This is a convenient shorthand for &"delivery
663 failure error report"&. Such messages have an empty sender address in the
664 message's &'envelope'& (see below) to ensure that they cannot themselves give
665 rise to further bounce messages.
667 The term &'default'& appears frequently in this manual. It is used to qualify a
668 value which is used in the absence of any setting in the configuration. It may
669 also qualify an action which is taken unless a configuration setting specifies
672 The term &'defer'& is used when the delivery of a message to a specific
673 destination cannot immediately take place for some reason (a remote host may be
674 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
677 The word &'domain'& is sometimes used to mean all but the first component of a
678 host's name. It is &'not'& used in that sense here, where it normally refers to
679 the part of an email address following the @ sign.
681 .cindex "envelope, definition of"
682 .cindex "sender" "definition of"
683 A message in transit has an associated &'envelope'&, as well as a header and a
684 body. The envelope contains a sender address (to which bounce messages should
685 be delivered), and any number of recipient addresses. References to the
686 sender or the recipients of a message usually mean the addresses in the
687 envelope. An MTA uses these addresses for delivery, and for returning bounce
688 messages, not the addresses that appear in the header lines.
690 .cindex "message" "header, definition of"
691 .cindex "header section" "definition of"
692 The &'header'& of a message is the first part of a message's text, consisting
693 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
694 &'Subject:'&, etc. Long header lines can be split over several text lines by
695 indenting the continuations. The header is separated from the body by a blank
698 .cindex "local part" "definition of"
699 .cindex "domain" "definition of"
700 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
701 part of an email address that precedes the @ sign. The part that follows the
702 @ sign is called the &'domain'& or &'mail domain'&.
704 .cindex "local delivery" "definition of"
705 .cindex "remote delivery, definition of"
706 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
707 delivery to a file or a pipe on the local host from delivery by SMTP over
708 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
709 host it is running on are &'remote'&.
711 .cindex "return path" "definition of"
712 &'Return path'& is another name that is used for the sender address in a
715 .cindex "queue" "definition of"
716 The term &'queue'& is used to refer to the set of messages awaiting delivery,
717 because this term is in widespread use in the context of MTAs. However, in
718 Exim's case the reality is more like a pool than a queue, because there is
719 normally no ordering of waiting messages.
721 .cindex "queue runner" "definition of"
722 The term &'queue runner'& is used to describe a process that scans the queue
723 and attempts to deliver those messages whose retry times have come. This term
724 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
725 the waiting messages are normally processed in an unpredictable order.
727 .cindex "spool directory" "definition of"
728 The term &'spool directory'& is used for a directory in which Exim keeps the
729 messages on its queue &-- that is, those that it is in the process of
730 delivering. This should not be confused with the directory in which local
731 mailboxes are stored, which is called a &"spool directory"& by some people. In
732 the Exim documentation, &"spool"& is always used in the first sense.
739 . ////////////////////////////////////////////////////////////////////////////
740 . ////////////////////////////////////////////////////////////////////////////
742 .chapter "Incorporated code" "CHID2"
743 .cindex "incorporated code"
744 .cindex "regular expressions" "library"
747 A number of pieces of external code are included in the Exim distribution.
750 Regular expressions are supported in the main Exim program and in the
751 Exim monitor using the freely-distributable PCRE library, copyright
752 © University of Cambridge. The source to PCRE is no longer shipped with
753 Exim, so you will need to use the version of PCRE shipped with your system,
754 or obtain and install the full version of the library from
755 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
757 .cindex "cdb" "acknowledgment"
758 Support for the cdb (Constant DataBase) lookup method is provided by code
759 contributed by Nigel Metheringham of (at the time he contributed it) Planet
760 Online Ltd. The implementation is completely contained within the code of Exim.
761 It does not link against an external cdb library. The code contains the
762 following statements:
765 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
767 This program is free software; you can redistribute it and/or modify it under
768 the terms of the GNU General Public License as published by the Free Software
769 Foundation; either version 2 of the License, or (at your option) any later
771 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
772 the spec and sample code for cdb can be obtained from
773 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
774 some code from Dan Bernstein's implementation (which has no license
775 restrictions applied to it).
778 .cindex "SPA authentication"
779 .cindex "Samba project"
780 .cindex "Microsoft Secure Password Authentication"
781 Client support for Microsoft's &'Secure Password Authentication'& is provided
782 by code contributed by Marc Prud'hommeaux. Server support was contributed by
783 Tom Kistner. This includes code taken from the Samba project, which is released
787 .cindex "&'pwcheck'& daemon"
788 .cindex "&'pwauthd'& daemon"
789 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
790 by code taken from the Cyrus-SASL library and adapted by Alexander S.
791 Sabourenkov. The permission notice appears below, in accordance with the
792 conditions expressed therein.
795 Copyright © 2001 Carnegie Mellon University. All rights reserved.
797 Redistribution and use in source and binary forms, with or without
798 modification, are permitted provided that the following conditions
802 Redistributions of source code must retain the above copyright
803 notice, this list of conditions and the following disclaimer.
805 Redistributions in binary form must reproduce the above copyright
806 notice, this list of conditions and the following disclaimer in
807 the documentation and/or other materials provided with the
810 The name &"Carnegie Mellon University"& must not be used to
811 endorse or promote products derived from this software without
812 prior written permission. For permission or any other legal
813 details, please contact
815 Office of Technology Transfer
816 Carnegie Mellon University
818 Pittsburgh, PA 15213-3890
819 (412) 268-4387, fax: (412) 268-7395
820 tech-transfer@andrew.cmu.edu
823 Redistributions of any form whatsoever must retain the following
826 &"This product includes software developed by Computing Services
827 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
829 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
830 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
831 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
832 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
833 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
834 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
835 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
840 .cindex "Exim monitor" "acknowledgment"
843 The Exim Monitor program, which is an X-Window application, includes
844 modified versions of the Athena StripChart and TextPop widgets.
845 This code is copyright by DEC and MIT, and their permission notice appears
846 below, in accordance with the conditions expressed therein.
849 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
850 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
854 Permission to use, copy, modify, and distribute this software and its
855 documentation for any purpose and without fee is hereby granted,
856 provided that the above copyright notice appear in all copies and that
857 both that copyright notice and this permission notice appear in
858 supporting documentation, and that the names of Digital or MIT not be
859 used in advertising or publicity pertaining to distribution of the
860 software without specific, written prior permission.
862 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
863 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
864 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
865 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
866 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
867 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
872 .cindex "opendmarc" "acknowledgment"
873 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
874 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
875 derived code are indicated in the respective source files. The full OpenDMARC
876 license is provided in the LICENSE.opendmarc file contained in the distributed
880 Many people have contributed code fragments, some large, some small, that were
881 not covered by any specific licence requirements. It is assumed that the
882 contributors are happy to see their code incorporated into Exim under the GPL.
889 . ////////////////////////////////////////////////////////////////////////////
890 . ////////////////////////////////////////////////////////////////////////////
892 .chapter "How Exim receives and delivers mail" "CHID11" &&&
893 "Receiving and delivering mail"
896 .section "Overall philosophy" "SECID10"
897 .cindex "design philosophy"
898 Exim is designed to work efficiently on systems that are permanently connected
899 to the Internet and are handling a general mix of mail. In such circumstances,
900 most messages can be delivered immediately. Consequently, Exim does not
901 maintain independent queues of messages for specific domains or hosts, though
902 it does try to send several messages in a single SMTP connection after a host
903 has been down, and it also maintains per-host retry information.
906 .section "Policy control" "SECID11"
907 .cindex "policy control" "overview"
908 Policy controls are now an important feature of MTAs that are connected to the
909 Internet. Perhaps their most important job is to stop MTAs being abused as
910 &"open relays"& by misguided individuals who send out vast amounts of
911 unsolicited junk, and want to disguise its source. Exim provides flexible
912 facilities for specifying policy controls on incoming mail:
915 .cindex "&ACL;" "introduction"
916 Exim 4 (unlike previous versions of Exim) implements policy controls on
917 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
918 series of statements that may either grant or deny access. ACLs can be used at
919 several places in the SMTP dialogue while receiving a message from a remote
920 host. However, the most common places are after each RCPT command, and at the
921 very end of the message. The sysadmin can specify conditions for accepting or
922 rejecting individual recipients or the entire message, respectively, at these
923 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
926 An ACL is also available for locally generated, non-SMTP messages. In this
927 case, the only available actions are to accept or deny the entire message.
929 When Exim is compiled with the content-scanning extension, facilities are
930 provided in the ACL mechanism for passing the message to external virus and/or
931 spam scanning software. The result of such a scan is passed back to the ACL,
932 which can then use it to decide what to do with the message.
934 When a message has been received, either from a remote host or from the local
935 host, but before the final acknowledgment has been sent, a locally supplied C
936 function called &[local_scan()]& can be run to inspect the message and decide
937 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
938 is accepted, the list of recipients can be modified by the function.
940 Using the &[local_scan()]& mechanism is another way of calling external scanner
941 software. The &%SA-Exim%& add-on package works this way. It does not require
942 Exim to be compiled with the content-scanning extension.
944 After a message has been accepted, a further checking mechanism is available in
945 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
946 runs at the start of every delivery process.
951 .section "User filters" "SECID12"
952 .cindex "filter" "introduction"
953 .cindex "Sieve filter"
954 In a conventional Exim configuration, users are able to run private filters by
955 setting up appropriate &_.forward_& files in their home directories. See
956 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
957 configuration needed to support this, and the separate document entitled
958 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
959 of filtering are available:
962 Sieve filters are written in the standard filtering language that is defined
965 Exim filters are written in a syntax that is unique to Exim, but which is more
966 powerful than Sieve, which it pre-dates.
969 User filters are run as part of the routing process, described below.
973 .section "Message identification" "SECTmessiden"
974 .cindex "message ids" "details of format"
975 .cindex "format" "of message id"
976 .cindex "id of message"
981 Every message handled by Exim is given a &'message id'& which is sixteen
982 characters long. It is divided into three parts, separated by hyphens, for
983 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
984 normally encoding numbers in base 62. However, in the Darwin operating
985 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
986 (avoiding the use of lower case letters) is used instead, because the message
987 id is used to construct file names, and the names of files in those systems are
988 not always case-sensitive.
990 .cindex "pid (process id)" "re-use of"
991 The detail of the contents of the message id have changed as Exim has evolved.
992 Earlier versions relied on the operating system not re-using a process id (pid)
993 within one second. On modern operating systems, this assumption can no longer
994 be made, so the algorithm had to be changed. To retain backward compatibility,
995 the format of the message id was retained, which is why the following rules are
999 The first six characters of the message id are the time at which the message
1000 started to be received, to a granularity of one second. That is, this field
1001 contains the number of seconds since the start of the epoch (the normal Unix
1002 way of representing the date and time of day).
1004 After the first hyphen, the next six characters are the id of the process that
1005 received the message.
1007 There are two different possibilities for the final two characters:
1009 .oindex "&%localhost_number%&"
1010 If &%localhost_number%& is not set, this value is the fractional part of the
1011 time of reception, normally in units of 1/2000 of a second, but for systems
1012 that must use base 36 instead of base 62 (because of case-insensitive file
1013 systems), the units are 1/1000 of a second.
1015 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1016 the fractional part of the time, which in this case is in units of 1/200
1017 (1/100) of a second.
1021 After a message has been received, Exim waits for the clock to tick at the
1022 appropriate resolution before proceeding, so that if another message is
1023 received by the same process, or by another process with the same (re-used)
1024 pid, it is guaranteed that the time will be different. In most cases, the clock
1025 will already have ticked while the message was being received.
1028 .section "Receiving mail" "SECID13"
1029 .cindex "receiving mail"
1030 .cindex "message" "reception"
1031 The only way Exim can receive mail from another host is using SMTP over
1032 TCP/IP, in which case the sender and recipient addresses are transferred using
1033 SMTP commands. However, from a locally running process (such as a user's MUA),
1034 there are several possibilities:
1037 If the process runs Exim with the &%-bm%& option, the message is read
1038 non-interactively (usually via a pipe), with the recipients taken from the
1039 command line, or from the body of the message if &%-t%& is also used.
1041 If the process runs Exim with the &%-bS%& option, the message is also read
1042 non-interactively, but in this case the recipients are listed at the start of
1043 the message in a series of SMTP RCPT commands, terminated by a DATA
1044 command. This is so-called &"batch SMTP"& format,
1045 but it isn't really SMTP. The SMTP commands are just another way of passing
1046 envelope addresses in a non-interactive submission.
1048 If the process runs Exim with the &%-bs%& option, the message is read
1049 interactively, using the SMTP protocol. A two-way pipe is normally used for
1050 passing data between the local process and the Exim process.
1051 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1052 example, the ACLs for SMTP commands are used for this form of submission.
1054 A local process may also make a TCP/IP call to the host's loopback address
1055 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1056 does not treat the loopback address specially. It treats all such connections
1057 in the same way as connections from other hosts.
1061 .cindex "message sender, constructed by Exim"
1062 .cindex "sender" "constructed by Exim"
1063 In the three cases that do not involve TCP/IP, the sender address is
1064 constructed from the login name of the user that called Exim and a default
1065 qualification domain (which can be set by the &%qualify_domain%& configuration
1066 option). For local or batch SMTP, a sender address that is passed using the
1067 SMTP MAIL command is ignored. However, the system administrator may allow
1068 certain users (&"trusted users"&) to specify a different sender address
1069 unconditionally, or all users to specify certain forms of different sender
1070 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1071 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1072 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1073 users to change sender addresses.
1075 Messages received by either of the non-interactive mechanisms are subject to
1076 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1077 (either over TCP/IP, or interacting with a local process) can be checked by a
1078 number of ACLs that operate at different times during the SMTP session. Either
1079 individual recipients, or the entire message, can be rejected if local policy
1080 requirements are not met. The &[local_scan()]& function (see chapter
1081 &<<CHAPlocalscan>>&) is run for all incoming messages.
1083 Exim can be configured not to start a delivery process when a message is
1084 received; this can be unconditional, or depend on the number of incoming SMTP
1085 connections or the system load. In these situations, new messages wait on the
1086 queue until a queue runner process picks them up. However, in standard
1087 configurations under normal conditions, delivery is started as soon as a
1088 message is received.
1094 .section "Handling an incoming message" "SECID14"
1095 .cindex "spool directory" "files that hold a message"
1096 .cindex "file" "how a message is held"
1097 When Exim accepts a message, it writes two files in its spool directory. The
1098 first contains the envelope information, the current status of the message, and
1099 the header lines, and the second contains the body of the message. The names of
1100 the two spool files consist of the message id, followed by &`-H`& for the
1101 file containing the envelope and header, and &`-D`& for the data file.
1103 .cindex "spool directory" "&_input_& sub-directory"
1104 By default all these message files are held in a single directory called
1105 &_input_& inside the general Exim spool directory. Some operating systems do
1106 not perform very well if the number of files in a directory gets large; to
1107 improve performance in such cases, the &%split_spool_directory%& option can be
1108 used. This causes Exim to split up the input files into 62 sub-directories
1109 whose names are single letters or digits. When this is done, the queue is
1110 processed one sub-directory at a time instead of all at once, which can improve
1111 overall performance even when there are not enough files in each directory to
1112 affect file system performance.
1114 The envelope information consists of the address of the message's sender and
1115 the addresses of the recipients. This information is entirely separate from
1116 any addresses contained in the header lines. The status of the message includes
1117 a list of recipients who have already received the message. The format of the
1118 first spool file is described in chapter &<<CHAPspool>>&.
1120 .cindex "rewriting" "addresses"
1121 Address rewriting that is specified in the rewrite section of the configuration
1122 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1123 both in the header lines and the envelope, at the time the message is accepted.
1124 If during the course of delivery additional addresses are generated (for
1125 example, via aliasing), these new addresses are rewritten as soon as they are
1126 generated. At the time a message is actually delivered (transported) further
1127 rewriting can take place; because this is a transport option, it can be
1128 different for different forms of delivery. It is also possible to specify the
1129 addition or removal of certain header lines at the time the message is
1130 delivered (see chapters &<<CHAProutergeneric>>& and
1131 &<<CHAPtransportgeneric>>&).
1135 .section "Life of a message" "SECID15"
1136 .cindex "message" "life of"
1137 .cindex "message" "frozen"
1138 A message remains in the spool directory until it is completely delivered to
1139 its recipients or to an error address, or until it is deleted by an
1140 administrator or by the user who originally created it. In cases when delivery
1141 cannot proceed &-- for example, when a message can neither be delivered to its
1142 recipients nor returned to its sender, the message is marked &"frozen"& on the
1143 spool, and no more deliveries are attempted.
1145 .cindex "frozen messages" "thawing"
1146 .cindex "message" "thawing frozen"
1147 An administrator can &"thaw"& such messages when the problem has been
1148 corrected, and can also freeze individual messages by hand if necessary. In
1149 addition, an administrator can force a delivery error, causing a bounce message
1152 .oindex "&%timeout_frozen_after%&"
1153 .oindex "&%ignore_bounce_errors_after%&"
1154 There are options called &%ignore_bounce_errors_after%& and
1155 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1156 The first applies only to frozen bounces, the second to any frozen messages.
1158 .cindex "message" "log file for"
1159 .cindex "log" "file for each message"
1160 While Exim is working on a message, it writes information about each delivery
1161 attempt to its main log file. This includes successful, unsuccessful, and
1162 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1163 lines are also written to a separate &'message log'& file for each message.
1164 These logs are solely for the benefit of the administrator, and are normally
1165 deleted along with the spool files when processing of a message is complete.
1166 The use of individual message logs can be disabled by setting
1167 &%no_message_logs%&; this might give an improvement in performance on very busy
1170 .cindex "journal file"
1171 .cindex "file" "journal"
1172 All the information Exim itself needs to set up a delivery is kept in the first
1173 spool file, along with the header lines. When a successful delivery occurs, the
1174 address is immediately written at the end of a journal file, whose name is the
1175 message id followed by &`-J`&. At the end of a delivery run, if there are some
1176 addresses left to be tried again later, the first spool file (the &`-H`& file)
1177 is updated to indicate which these are, and the journal file is then deleted.
1178 Updating the spool file is done by writing a new file and renaming it, to
1179 minimize the possibility of data loss.
1181 Should the system or the program crash after a successful delivery but before
1182 the spool file has been updated, the journal is left lying around. The next
1183 time Exim attempts to deliver the message, it reads the journal file and
1184 updates the spool file before proceeding. This minimizes the chances of double
1185 deliveries caused by crashes.
1189 .section "Processing an address for delivery" "SECTprocaddress"
1190 .cindex "drivers" "definition of"
1191 .cindex "router" "definition of"
1192 .cindex "transport" "definition of"
1193 The main delivery processing elements of Exim are called &'routers'& and
1194 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1195 number of them is provided in the source distribution, and compile-time options
1196 specify which ones are included in the binary. Run time options specify which
1197 ones are actually used for delivering messages.
1199 .cindex "drivers" "instance definition"
1200 Each driver that is specified in the run time configuration is an &'instance'&
1201 of that particular driver type. Multiple instances are allowed; for example,
1202 you can set up several different &(smtp)& transports, each with different
1203 option values that might specify different ports or different timeouts. Each
1204 instance has its own identifying name. In what follows we will normally use the
1205 instance name when discussing one particular instance (that is, one specific
1206 configuration of the driver), and the generic driver name when discussing
1207 the driver's features in general.
1209 A &'router'& is a driver that operates on an address, either determining how
1210 its delivery should happen, by assigning it to a specific transport, or
1211 converting the address into one or more new addresses (for example, via an
1212 alias file). A router may also explicitly choose to fail an address, causing it
1215 A &'transport'& is a driver that transmits a copy of the message from Exim's
1216 spool to some destination. There are two kinds of transport: for a &'local'&
1217 transport, the destination is a file or a pipe on the local host, whereas for a
1218 &'remote'& transport the destination is some other host. A message is passed
1219 to a specific transport as a result of successful routing. If a message has
1220 several recipients, it may be passed to a number of different transports.
1222 .cindex "preconditions" "definition of"
1223 An address is processed by passing it to each configured router instance in
1224 turn, subject to certain preconditions, until a router accepts the address or
1225 specifies that it should be bounced. We will describe this process in more
1226 detail shortly. First, as a simple example, we consider how each recipient
1227 address in a message is processed in a small configuration of three routers.
1229 To make this a more concrete example, it is described in terms of some actual
1230 routers, but remember, this is only an example. You can configure Exim's
1231 routers in many different ways, and there may be any number of routers in a
1234 The first router that is specified in a configuration is often one that handles
1235 addresses in domains that are not recognized specially by the local host. These
1236 are typically addresses for arbitrary domains on the Internet. A precondition
1237 is set up which looks for the special domains known to the host (for example,
1238 its own domain name), and the router is run for addresses that do &'not'&
1239 match. Typically, this is a router that looks up domains in the DNS in order to
1240 find the hosts to which this address routes. If it succeeds, the address is
1241 assigned to a suitable SMTP transport; if it does not succeed, the router is
1242 configured to fail the address.
1244 The second router is reached only when the domain is recognized as one that
1245 &"belongs"& to the local host. This router does redirection &-- also known as
1246 aliasing and forwarding. When it generates one or more new addresses from the
1247 original, each of them is routed independently from the start. Otherwise, the
1248 router may cause an address to fail, or it may simply decline to handle the
1249 address, in which case the address is passed to the next router.
1251 The final router in many configurations is one that checks to see if the
1252 address belongs to a local mailbox. The precondition may involve a check to
1253 see if the local part is the name of a login account, or it may look up the
1254 local part in a file or a database. If its preconditions are not met, or if
1255 the router declines, we have reached the end of the routers. When this happens,
1256 the address is bounced.
1260 .section "Processing an address for verification" "SECID16"
1261 .cindex "router" "for verification"
1262 .cindex "verifying address" "overview"
1263 As well as being used to decide how to deliver to an address, Exim's routers
1264 are also used for &'address verification'&. Verification can be requested as
1265 one of the checks to be performed in an ACL for incoming messages, on both
1266 sender and recipient addresses, and it can be tested using the &%-bv%& and
1267 &%-bvs%& command line options.
1269 When an address is being verified, the routers are run in &"verify mode"&. This
1270 does not affect the way the routers work, but it is a state that can be
1271 detected. By this means, a router can be skipped or made to behave differently
1272 when verifying. A common example is a configuration in which the first router
1273 sends all messages to a message-scanning program, unless they have been
1274 previously scanned. Thus, the first router accepts all addresses without any
1275 checking, making it useless for verifying. Normally, the &%no_verify%& option
1276 would be set for such a router, causing it to be skipped in verify mode.
1281 .section "Running an individual router" "SECTrunindrou"
1282 .cindex "router" "running details"
1283 .cindex "preconditions" "checking"
1284 .cindex "router" "result of running"
1285 As explained in the example above, a number of preconditions are checked before
1286 running a router. If any are not met, the router is skipped, and the address is
1287 passed to the next router. When all the preconditions on a router &'are'& met,
1288 the router is run. What happens next depends on the outcome, which is one of
1292 &'accept'&: The router accepts the address, and either assigns it to a
1293 transport, or generates one or more &"child"& addresses. Processing the
1294 original address ceases,
1295 .oindex "&%unseen%&"
1296 unless the &%unseen%& option is set on the router. This option
1297 can be used to set up multiple deliveries with different routing (for example,
1298 for keeping archive copies of messages). When &%unseen%& is set, the address is
1299 passed to the next router. Normally, however, an &'accept'& return marks the
1302 Any child addresses generated by the router are processed independently,
1303 starting with the first router by default. It is possible to change this by
1304 setting the &%redirect_router%& option to specify which router to start at for
1305 child addresses. Unlike &%pass_router%& (see below) the router specified by
1306 &%redirect_router%& may be anywhere in the router configuration.
1308 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1309 requests that the address be passed to another router. By default the address
1310 is passed to the next router, but this can be changed by setting the
1311 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1312 must be below the current router (to avoid loops).
1314 &'decline'&: The router declines to accept the address because it does not
1315 recognize it at all. By default, the address is passed to the next router, but
1316 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1317 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1318 &'decline'& into &'fail'&.
1320 &'fail'&: The router determines that the address should fail, and queues it for
1321 the generation of a bounce message. There is no further processing of the
1322 original address unless &%unseen%& is set on the router.
1324 &'defer'&: The router cannot handle the address at the present time. (A
1325 database may be offline, or a DNS lookup may have timed out.) No further
1326 processing of the address happens in this delivery attempt. It is tried again
1327 next time the message is considered for delivery.
1329 &'error'&: There is some error in the router (for example, a syntax error in
1330 its configuration). The action is as for defer.
1333 If an address reaches the end of the routers without having been accepted by
1334 any of them, it is bounced as unrouteable. The default error message in this
1335 situation is &"unrouteable address"&, but you can set your own message by
1336 making use of the &%cannot_route_message%& option. This can be set for any
1337 router; the value from the last router that &"saw"& the address is used.
1339 Sometimes while routing you want to fail a delivery when some conditions are
1340 met but others are not, instead of passing the address on for further routing.
1341 You can do this by having a second router that explicitly fails the delivery
1342 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1343 facility for this purpose.
1346 .section "Duplicate addresses" "SECID17"
1347 .cindex "case of local parts"
1348 .cindex "address duplicate, discarding"
1349 .cindex "duplicate addresses"
1350 Once routing is complete, Exim scans the addresses that are assigned to local
1351 and remote transports, and discards any duplicates that it finds. During this
1352 check, local parts are treated as case-sensitive. This happens only when
1353 actually delivering a message; when testing routers with &%-bt%&, all the
1354 routed addresses are shown.
1358 .section "Router preconditions" "SECTrouprecon"
1359 .cindex "router" "preconditions, order of processing"
1360 .cindex "preconditions" "order of processing"
1361 The preconditions that are tested for each router are listed below, in the
1362 order in which they are tested. The individual configuration options are
1363 described in more detail in chapter &<<CHAProutergeneric>>&.
1366 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1367 the local parts handled by the router may or must have certain prefixes and/or
1368 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1369 skipped. These conditions are tested first. When an affix is present, it is
1370 removed from the local part before further processing, including the evaluation
1371 of any other conditions.
1373 Routers can be designated for use only when not verifying an address, that is,
1374 only when routing it for delivery (or testing its delivery routing). If the
1375 &%verify%& option is set false, the router is skipped when Exim is verifying an
1377 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1378 &%verify_recipient%&, which independently control the use of the router for
1379 sender and recipient verification. You can set these options directly if
1380 you want a router to be used for only one type of verification.
1381 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1383 If the &%address_test%& option is set false, the router is skipped when Exim is
1384 run with the &%-bt%& option to test an address routing. This can be helpful
1385 when the first router sends all new messages to a scanner of some sort; it
1386 makes it possible to use &%-bt%& to test subsequent delivery routing without
1387 having to simulate the effect of the scanner.
1389 Routers can be designated for use only when verifying an address, as
1390 opposed to routing it for delivery. The &%verify_only%& option controls this.
1391 Again, cutthrough delivery counts as a verification.
1393 Individual routers can be explicitly skipped when running the routers to
1394 check an address given in the SMTP EXPN command (see the &%expn%& option).
1396 If the &%domains%& option is set, the domain of the address must be in the set
1397 of domains that it defines.
1399 .vindex "&$local_part_prefix$&"
1400 .vindex "&$local_part$&"
1401 .vindex "&$local_part_suffix$&"
1402 If the &%local_parts%& option is set, the local part of the address must be in
1403 the set of local parts that it defines. If &%local_part_prefix%& or
1404 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1405 part before this check. If you want to do precondition tests on local parts
1406 that include affixes, you can do so by using a &%condition%& option (see below)
1407 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1408 &$local_part_suffix$& as necessary.
1410 .vindex "&$local_user_uid$&"
1411 .vindex "&$local_user_gid$&"
1413 If the &%check_local_user%& option is set, the local part must be the name of
1414 an account on the local host. If this check succeeds, the uid and gid of the
1415 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1416 user's home directory is placed in &$home$&; these values can be used in the
1417 remaining preconditions.
1419 If the &%router_home_directory%& option is set, it is expanded at this point,
1420 because it overrides the value of &$home$&. If this expansion were left till
1421 later, the value of &$home$& as set by &%check_local_user%& would be used in
1422 subsequent tests. Having two different values of &$home$& in the same router
1423 could lead to confusion.
1425 If the &%senders%& option is set, the envelope sender address must be in the
1426 set of addresses that it defines.
1428 If the &%require_files%& option is set, the existence or non-existence of
1429 specified files is tested.
1431 .cindex "customizing" "precondition"
1432 If the &%condition%& option is set, it is evaluated and tested. This option
1433 uses an expanded string to allow you to set up your own custom preconditions.
1434 Expanded strings are described in chapter &<<CHAPexpand>>&.
1438 Note that &%require_files%& comes near the end of the list, so you cannot use
1439 it to check for the existence of a file in which to lookup up a domain, local
1440 part, or sender. However, as these options are all expanded, you can use the
1441 &%exists%& expansion condition to make such tests within each condition. The
1442 &%require_files%& option is intended for checking files that the router may be
1443 going to use internally, or which are needed by a specific transport (for
1444 example, &_.procmailrc_&).
1448 .section "Delivery in detail" "SECID18"
1449 .cindex "delivery" "in detail"
1450 When a message is to be delivered, the sequence of events is as follows:
1453 If a system-wide filter file is specified, the message is passed to it. The
1454 filter may add recipients to the message, replace the recipients, discard the
1455 message, cause a new message to be generated, or cause the message delivery to
1456 fail. The format of the system filter file is the same as for Exim user filter
1457 files, described in the separate document entitled &'Exim's interfaces to mail
1459 .cindex "Sieve filter" "not available for system filter"
1460 (&*Note*&: Sieve cannot be used for system filter files.)
1462 Some additional features are available in system filters &-- see chapter
1463 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1464 filter only once per delivery attempt, however many recipients it has. However,
1465 if there are several delivery attempts because one or more addresses could not
1466 be immediately delivered, the system filter is run each time. The filter
1467 condition &%first_delivery%& can be used to detect the first run of the system
1470 Each recipient address is offered to each configured router in turn, subject to
1471 its preconditions, until one is able to handle it. If no router can handle the
1472 address, that is, if they all decline, the address is failed. Because routers
1473 can be targeted at particular domains, several locally handled domains can be
1474 processed entirely independently of each other.
1476 .cindex "routing" "loops in"
1477 .cindex "loop" "while routing"
1478 A router that accepts an address may assign it to a local or a remote
1479 transport. However, the transport is not run at this time. Instead, the address
1480 is placed on a list for the particular transport, which will be run later.
1481 Alternatively, the router may generate one or more new addresses (typically
1482 from alias, forward, or filter files). New addresses are fed back into this
1483 process from the top, but in order to avoid loops, a router ignores any address
1484 which has an identically-named ancestor that was processed by itself.
1486 When all the routing has been done, addresses that have been successfully
1487 handled are passed to their assigned transports. When local transports are
1488 doing real local deliveries, they handle only one address at a time, but if a
1489 local transport is being used as a pseudo-remote transport (for example, to
1490 collect batched SMTP messages for transmission by some other means) multiple
1491 addresses can be handled. Remote transports can always handle more than one
1492 address at a time, but can be configured not to do so, or to restrict multiple
1493 addresses to the same domain.
1495 Each local delivery to a file or a pipe runs in a separate process under a
1496 non-privileged uid, and these deliveries are run one at a time. Remote
1497 deliveries also run in separate processes, normally under a uid that is private
1498 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1499 run in parallel. The maximum number of simultaneous remote deliveries for any
1500 one message is set by the &%remote_max_parallel%& option.
1501 The order in which deliveries are done is not defined, except that all local
1502 deliveries happen before any remote deliveries.
1504 .cindex "queue runner"
1505 When it encounters a local delivery during a queue run, Exim checks its retry
1506 database to see if there has been a previous temporary delivery failure for the
1507 address before running the local transport. If there was a previous failure,
1508 Exim does not attempt a new delivery until the retry time for the address is
1509 reached. However, this happens only for delivery attempts that are part of a
1510 queue run. Local deliveries are always attempted when delivery immediately
1511 follows message reception, even if retry times are set for them. This makes for
1512 better behaviour if one particular message is causing problems (for example,
1513 causing quota overflow, or provoking an error in a filter file).
1515 .cindex "delivery" "retry in remote transports"
1516 Remote transports do their own retry handling, since an address may be
1517 deliverable to one of a number of hosts, each of which may have a different
1518 retry time. If there have been previous temporary failures and no host has
1519 reached its retry time, no delivery is attempted, whether in a queue run or
1520 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1522 If there were any permanent errors, a bounce message is returned to an
1523 appropriate address (the sender in the common case), with details of the error
1524 for each failing address. Exim can be configured to send copies of bounce
1525 messages to other addresses.
1527 .cindex "delivery" "deferral"
1528 If one or more addresses suffered a temporary failure, the message is left on
1529 the queue, to be tried again later. Delivery of these addresses is said to be
1532 When all the recipient addresses have either been delivered or bounced,
1533 handling of the message is complete. The spool files and message log are
1534 deleted, though the message log can optionally be preserved if required.
1540 .section "Retry mechanism" "SECID19"
1541 .cindex "delivery" "retry mechanism"
1542 .cindex "retry" "description of mechanism"
1543 .cindex "queue runner"
1544 Exim's mechanism for retrying messages that fail to get delivered at the first
1545 attempt is the queue runner process. You must either run an Exim daemon that
1546 uses the &%-q%& option with a time interval to start queue runners at regular
1547 intervals, or use some other means (such as &'cron'&) to start them. If you do
1548 not arrange for queue runners to be run, messages that fail temporarily at the
1549 first attempt will remain on your queue for ever. A queue runner process works
1550 its way through the queue, one message at a time, trying each delivery that has
1551 passed its retry time.
1552 You can run several queue runners at once.
1554 Exim uses a set of configured rules to determine when next to retry the failing
1555 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1556 should give up trying to deliver to the address, at which point it generates a
1557 bounce message. If no retry rules are set for a particular host, address, and
1558 error combination, no retries are attempted, and temporary errors are treated
1563 .section "Temporary delivery failure" "SECID20"
1564 .cindex "delivery" "temporary failure"
1565 There are many reasons why a message may not be immediately deliverable to a
1566 particular address. Failure to connect to a remote machine (because it, or the
1567 connection to it, is down) is one of the most common. Temporary failures may be
1568 detected during routing as well as during the transport stage of delivery.
1569 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1570 is on a file system where the user is over quota. Exim can be configured to
1571 impose its own quotas on local mailboxes; where system quotas are set they will
1574 If a host is unreachable for a period of time, a number of messages may be
1575 waiting for it by the time it recovers, and sending them in a single SMTP
1576 connection is clearly beneficial. Whenever a delivery to a remote host is
1578 .cindex "hints database" "deferred deliveries"
1579 Exim makes a note in its hints database, and whenever a successful
1580 SMTP delivery has happened, it looks to see if any other messages are waiting
1581 for the same host. If any are found, they are sent over the same SMTP
1582 connection, subject to a configuration limit as to the maximum number in any
1587 .section "Permanent delivery failure" "SECID21"
1588 .cindex "delivery" "permanent failure"
1589 .cindex "bounce message" "when generated"
1590 When a message cannot be delivered to some or all of its intended recipients, a
1591 bounce message is generated. Temporary delivery failures turn into permanent
1592 errors when their timeout expires. All the addresses that fail in a given
1593 delivery attempt are listed in a single message. If the original message has
1594 many recipients, it is possible for some addresses to fail in one delivery
1595 attempt and others to fail subsequently, giving rise to more than one bounce
1596 message. The wording of bounce messages can be customized by the administrator.
1597 See chapter &<<CHAPemsgcust>>& for details.
1599 .cindex "&'X-Failed-Recipients:'& header line"
1600 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1601 failed addresses, for the benefit of programs that try to analyse such messages
1604 .cindex "bounce message" "recipient of"
1605 A bounce message is normally sent to the sender of the original message, as
1606 obtained from the message's envelope. For incoming SMTP messages, this is the
1607 address given in the MAIL command. However, when an address is expanded via a
1608 forward or alias file, an alternative address can be specified for delivery
1609 failures of the generated addresses. For a mailing list expansion (see section
1610 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1615 .section "Failures to deliver bounce messages" "SECID22"
1616 .cindex "bounce message" "failure to deliver"
1617 If a bounce message (either locally generated or received from a remote host)
1618 itself suffers a permanent delivery failure, the message is left on the queue,
1619 but it is frozen, awaiting the attention of an administrator. There are options
1620 that can be used to make Exim discard such failed messages, or to keep them
1621 for only a short time (see &%timeout_frozen_after%& and
1622 &%ignore_bounce_errors_after%&).
1628 . ////////////////////////////////////////////////////////////////////////////
1629 . ////////////////////////////////////////////////////////////////////////////
1631 .chapter "Building and installing Exim" "CHID3"
1632 .scindex IIDbuex "building Exim"
1634 .section "Unpacking" "SECID23"
1635 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1636 creates a directory with the name of the current release (for example,
1637 &_exim-&version()_&) into which the following files are placed:
1640 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1641 .irow &_CHANGES_& "contains a reference to where changes are &&&
1643 .irow &_LICENCE_& "the GNU General Public Licence"
1644 .irow &_Makefile_& "top-level make file"
1645 .irow &_NOTICE_& "conditions for the use of Exim"
1646 .irow &_README_& "list of files, directories and simple build &&&
1650 Other files whose names begin with &_README_& may also be present. The
1651 following subdirectories are created:
1654 .irow &_Local_& "an empty directory for local configuration files"
1655 .irow &_OS_& "OS-specific files"
1656 .irow &_doc_& "documentation files"
1657 .irow &_exim_monitor_& "source files for the Exim monitor"
1658 .irow &_scripts_& "scripts used in the build process"
1659 .irow &_src_& "remaining source files"
1660 .irow &_util_& "independent utilities"
1663 The main utility programs are contained in the &_src_& directory, and are built
1664 with the Exim binary. The &_util_& directory contains a few optional scripts
1665 that may be useful to some sites.
1668 .section "Multiple machine architectures and operating systems" "SECID24"
1669 .cindex "building Exim" "multiple OS/architectures"
1670 The building process for Exim is arranged to make it easy to build binaries for
1671 a number of different architectures and operating systems from the same set of
1672 source files. Compilation does not take place in the &_src_& directory.
1673 Instead, a &'build directory'& is created for each architecture and operating
1675 .cindex "symbolic link" "to build directory"
1676 Symbolic links to the sources are installed in this directory, which is where
1677 the actual building takes place. In most cases, Exim can discover the machine
1678 architecture and operating system for itself, but the defaults can be
1679 overridden if necessary.
1682 .section "PCRE library" "SECTpcre"
1683 .cindex "PCRE library"
1684 Exim no longer has an embedded PCRE library as the vast majority of
1685 modern systems include PCRE as a system library, although you may need
1686 to install the PCRE or PCRE development package for your operating
1687 system. If your system has a normal PCRE installation the Exim build
1688 process will need no further configuration. If the library or the
1689 headers are in an unusual location you will need to either set the PCRE_LIBS
1690 and INCLUDE directives appropriately,
1691 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1692 If your operating system has no
1693 PCRE support then you will need to obtain and build the current PCRE
1694 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1695 More information on PCRE is available at &url(http://www.pcre.org/).
1697 .section "DBM libraries" "SECTdb"
1698 .cindex "DBM libraries" "discussion of"
1699 .cindex "hints database" "DBM files used for"
1700 Even if you do not use any DBM files in your configuration, Exim still needs a
1701 DBM library in order to operate, because it uses indexed files for its hints
1702 databases. Unfortunately, there are a number of DBM libraries in existence, and
1703 different operating systems often have different ones installed.
1705 .cindex "Solaris" "DBM library for"
1706 .cindex "IRIX, DBM library for"
1707 .cindex "BSD, DBM library for"
1708 .cindex "Linux, DBM library for"
1709 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1710 Linux distribution, the DBM configuration should happen automatically, and you
1711 may be able to ignore this section. Otherwise, you may have to learn more than
1712 you would like about DBM libraries from what follows.
1714 .cindex "&'ndbm'& DBM library"
1715 Licensed versions of Unix normally contain a library of DBM functions operating
1716 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1717 versions of Unix seem to vary in what they contain as standard. In particular,
1718 some early versions of Linux have no default DBM library, and different
1719 distributors have chosen to bundle different libraries with their packaged
1720 versions. However, the more recent releases seem to have standardized on the
1721 Berkeley DB library.
1723 Different DBM libraries have different conventions for naming the files they
1724 use. When a program opens a file called &_dbmfile_&, there are several
1728 A traditional &'ndbm'& implementation, such as that supplied as part of
1729 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1731 .cindex "&'gdbm'& DBM library"
1732 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1733 compatibility interface it makes two different hard links to it with names
1734 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1735 file name is used unmodified.
1737 .cindex "Berkeley DB library"
1738 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1739 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1740 programmer exactly the same as the traditional &'ndbm'& implementation.
1742 If the Berkeley package is used in its native mode, it operates on a single
1743 file called &_dbmfile_&; the programmer's interface is somewhat different to
1744 the traditional &'ndbm'& interface.
1746 To complicate things further, there are several very different versions of the
1747 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1748 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1749 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1750 versions of Berkeley DB can be obtained from
1751 &url(http://www.sleepycat.com/).
1753 .cindex "&'tdb'& DBM library"
1754 Yet another DBM library, called &'tdb'&, is available from
1755 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1756 operates on a single file.
1760 .cindex "DBM libraries" "configuration for building"
1761 Exim and its utilities can be compiled to use any of these interfaces. In order
1762 to use any version of the Berkeley DB package in native mode, you must set
1763 USE_DB in an appropriate configuration file (typically
1764 &_Local/Makefile_&). For example:
1768 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1769 error is diagnosed if you set more than one of these.
1771 At the lowest level, the build-time configuration sets none of these options,
1772 thereby assuming an interface of type (1). However, some operating system
1773 configuration files (for example, those for the BSD operating systems and
1774 Linux) assume type (4) by setting USE_DB as their default, and the
1775 configuration files for Cygwin set USE_GDBM. Anything you set in
1776 &_Local/Makefile_&, however, overrides these system defaults.
1778 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1779 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1780 in one of these lines:
1785 Settings like that will work if the DBM library is installed in the standard
1786 place. Sometimes it is not, and the library's header file may also not be in
1787 the default path. You may need to set INCLUDE to specify where the header
1788 file is, and to specify the path to the library more fully in DBMLIB, as in
1791 INCLUDE=-I/usr/local/include/db-4.1
1792 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1794 There is further detailed discussion about the various DBM libraries in the
1795 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1799 .section "Pre-building configuration" "SECID25"
1800 .cindex "building Exim" "pre-building configuration"
1801 .cindex "configuration for building Exim"
1802 .cindex "&_Local/Makefile_&"
1803 .cindex "&_src/EDITME_&"
1804 Before building Exim, a local configuration file that specifies options
1805 independent of any operating system has to be created with the name
1806 &_Local/Makefile_&. A template for this file is supplied as the file
1807 &_src/EDITME_&, and it contains full descriptions of all the option settings
1808 therein. These descriptions are therefore not repeated here. If you are
1809 building Exim for the first time, the simplest thing to do is to copy
1810 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1812 There are three settings that you must supply, because Exim will not build
1813 without them. They are the location of the run time configuration file
1814 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1815 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1816 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1817 a colon-separated list of file names; Exim uses the first of them that exists.
1819 There are a few other parameters that can be specified either at build time or
1820 at run time, to enable the same binary to be used on a number of different
1821 machines. However, if the locations of Exim's spool directory and log file
1822 directory (if not within the spool directory) are fixed, it is recommended that
1823 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1824 detected early in Exim's execution (such as a malformed configuration file) can
1827 .cindex "content scanning" "specifying at build time"
1828 Exim's interfaces for calling virus and spam scanning software directly from
1829 access control lists are not compiled by default. If you want to include these
1830 facilities, you need to set
1832 WITH_CONTENT_SCAN=yes
1834 in your &_Local/Makefile_&. For details of the facilities themselves, see
1835 chapter &<<CHAPexiscan>>&.
1838 .cindex "&_Local/eximon.conf_&"
1839 .cindex "&_exim_monitor/EDITME_&"
1840 If you are going to build the Exim monitor, a similar configuration process is
1841 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1842 your installation and saved under the name &_Local/eximon.conf_&. If you are
1843 happy with the default settings described in &_exim_monitor/EDITME_&,
1844 &_Local/eximon.conf_& can be empty, but it must exist.
1846 This is all the configuration that is needed in straightforward cases for known
1847 operating systems. However, the building process is set up so that it is easy
1848 to override options that are set by default or by operating-system-specific
1849 configuration files, for example to change the name of the C compiler, which
1850 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1855 .section "Support for iconv()" "SECID26"
1856 .cindex "&[iconv()]& support"
1858 The contents of header lines in messages may be encoded according to the rules
1859 described RFC 2047. This makes it possible to transmit characters that are not
1860 in the ASCII character set, and to label them as being in a particular
1861 character set. When Exim is inspecting header lines by means of the &%$h_%&
1862 mechanism, it decodes them, and translates them into a specified character set
1863 (default is set at build time). The translation is possible only if the operating system
1864 supports the &[iconv()]& function.
1866 However, some of the operating systems that supply &[iconv()]& do not support
1867 very many conversions. The GNU &%libiconv%& library (available from
1868 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1869 systems to remedy this deficiency, as well as on systems that do not supply
1870 &[iconv()]& at all. After installing &%libiconv%&, you should add
1874 to your &_Local/Makefile_& and rebuild Exim.
1878 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1879 .cindex "TLS" "including support for TLS"
1880 .cindex "encryption" "including support for"
1881 .cindex "SUPPORT_TLS"
1882 .cindex "OpenSSL" "building Exim with"
1883 .cindex "GnuTLS" "building Exim with"
1884 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1885 command as per RFC 2487. It can also support legacy clients that expect to
1886 start a TLS session immediately on connection to a non-standard port (see the
1887 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1890 If you want to build Exim with TLS support, you must first install either the
1891 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1894 If OpenSSL is installed, you should set
1897 TLS_LIBS=-lssl -lcrypto
1899 in &_Local/Makefile_&. You may also need to specify the locations of the
1900 OpenSSL library and include files. For example:
1903 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1904 TLS_INCLUDE=-I/usr/local/openssl/include/
1906 .cindex "pkg-config" "OpenSSL"
1907 If you have &'pkg-config'& available, then instead you can just use:
1910 USE_OPENSSL_PC=openssl
1912 .cindex "USE_GNUTLS"
1913 If GnuTLS is installed, you should set
1917 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1919 in &_Local/Makefile_&, and again you may need to specify the locations of the
1920 library and include files. For example:
1924 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1925 TLS_INCLUDE=-I/usr/gnu/include
1927 .cindex "pkg-config" "GnuTLS"
1928 If you have &'pkg-config'& available, then instead you can just use:
1932 USE_GNUTLS_PC=gnutls
1935 You do not need to set TLS_INCLUDE if the relevant directory is already
1936 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1937 given in chapter &<<CHAPTLS>>&.
1942 .section "Use of tcpwrappers" "SECID27"
1944 .cindex "tcpwrappers, building Exim to support"
1945 .cindex "USE_TCP_WRAPPERS"
1946 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1947 .cindex "tcp_wrappers_daemon_name"
1948 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1949 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1950 alternative to Exim's own checking facilities for installations that are
1951 already making use of &'tcpwrappers'& for other purposes. To do this, you
1952 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1953 &_tcpd.h_& to be available at compile time, and also ensure that the library
1954 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1955 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1958 USE_TCP_WRAPPERS=yes
1959 CFLAGS=-O -I/usr/local/include
1960 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1962 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1963 files is &"exim"&. For example, the line
1965 exim : LOCAL 192.168.1. .friendly.domain.example
1967 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1968 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1969 All other connections are denied. The daemon name used by &'tcpwrappers'&
1970 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1971 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1972 configure file. Consult the &'tcpwrappers'& documentation for
1976 .section "Including support for IPv6" "SECID28"
1977 .cindex "IPv6" "including support for"
1978 Exim contains code for use on systems that have IPv6 support. Setting
1979 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1980 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1981 where the IPv6 support is not fully integrated into the normal include and
1984 Two different types of DNS record for handling IPv6 addresses have been
1985 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1986 currently seen as the mainstream. Another record type called A6 was proposed
1987 as better than AAAA because it had more flexibility. However, it was felt to be
1988 over-complex, and its status was reduced to &"experimental"&.
1990 have a compile option for including A6 record support but this has now been
1995 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
1996 .cindex "lookup modules"
1997 .cindex "dynamic modules"
1998 .cindex ".so building"
1999 On some platforms, Exim supports not compiling all lookup types directly into
2000 the main binary, instead putting some into external modules which can be loaded
2002 This permits packagers to build Exim with support for lookups with extensive
2003 library dependencies without requiring all users to install all of those
2005 Most, but not all, lookup types can be built this way.
2007 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2008 installed; Exim will only load modules from that directory, as a security
2009 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2010 for your OS; see &_OS/Makefile-Linux_& for an example.
2011 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2012 see &_src/EDITME_& for details.
2014 Then, for each module to be loaded dynamically, define the relevant
2015 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2016 For example, this will build in lsearch but load sqlite and mysql support
2025 .section "The building process" "SECID29"
2026 .cindex "build directory"
2027 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2028 created, run &'make'& at the top level. It determines the architecture and
2029 operating system types, and creates a build directory if one does not exist.
2030 For example, on a Sun system running Solaris 8, the directory
2031 &_build-SunOS5-5.8-sparc_& is created.
2032 .cindex "symbolic link" "to source files"
2033 Symbolic links to relevant source files are installed in the build directory.
2035 If this is the first time &'make'& has been run, it calls a script that builds
2036 a make file inside the build directory, using the configuration files from the
2037 &_Local_& directory. The new make file is then passed to another instance of
2038 &'make'&. This does the real work, building a number of utility scripts, and
2039 then compiling and linking the binaries for the Exim monitor (if configured), a
2040 number of utility programs, and finally Exim itself. The command &`make
2041 makefile`& can be used to force a rebuild of the make file in the build
2042 directory, should this ever be necessary.
2044 If you have problems building Exim, check for any comments there may be in the
2045 &_README_& file concerning your operating system, and also take a look at the
2046 FAQ, where some common problems are covered.
2050 .section 'Output from &"make"&' "SECID283"
2051 The output produced by the &'make'& process for compile lines is often very
2052 unreadable, because these lines can be very long. For this reason, the normal
2053 output is suppressed by default, and instead output similar to that which
2054 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2055 each module that is being compiled or linked. However, it is still possible to
2056 get the full output, by calling &'make'& like this:
2060 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2061 command reflection in &'make'&. When you ask for the full output, it is
2062 given in addition to the short output.
2066 .section "Overriding build-time options for Exim" "SECToverride"
2067 .cindex "build-time options, overriding"
2068 The main make file that is created at the beginning of the building process
2069 consists of the concatenation of a number of files which set configuration
2070 values, followed by a fixed set of &'make'& instructions. If a value is set
2071 more than once, the last setting overrides any previous ones. This provides a
2072 convenient way of overriding defaults. The files that are concatenated are, in
2075 &_OS/Makefile-Default_&
2076 &_OS/Makefile-_&<&'ostype'&>
2078 &_Local/Makefile-_&<&'ostype'&>
2079 &_Local/Makefile-_&<&'archtype'&>
2080 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2081 &_OS/Makefile-Base_&
2083 .cindex "&_Local/Makefile_&"
2084 .cindex "building Exim" "operating system type"
2085 .cindex "building Exim" "architecture type"
2086 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2087 architecture type. &_Local/Makefile_& is required to exist, and the building
2088 process fails if it is absent. The other three &_Local_& files are optional,
2089 and are often not needed.
2091 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2092 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2093 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2094 values are used, thereby providing a means of forcing particular settings.
2095 Otherwise, the scripts try to get values from the &%uname%& command. If this
2096 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2097 of &'ad hoc'& transformations are then applied, to produce the standard names
2098 that Exim expects. You can run these scripts directly from the shell in order
2099 to find out what values are being used on your system.
2102 &_OS/Makefile-Default_& contains comments about the variables that are set
2103 therein. Some (but not all) are mentioned below. If there is something that
2104 needs changing, review the contents of this file and the contents of the make
2105 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2109 .cindex "building Exim" "overriding default settings"
2110 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2111 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2112 need to change the original files. Instead, you should make the changes by
2113 putting the new values in an appropriate &_Local_& file. For example,
2114 .cindex "Tru64-Unix build-time settings"
2115 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2116 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2117 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2118 called with the option &%-std1%&, to make it recognize some of the features of
2119 Standard C that Exim uses. (Most other compilers recognize Standard C by
2120 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2121 containing the lines
2126 If you are compiling for just one operating system, it may be easier to put
2127 these lines directly into &_Local/Makefile_&.
2129 Keeping all your local configuration settings separate from the distributed
2130 files makes it easy to transfer them to new versions of Exim simply by copying
2131 the contents of the &_Local_& directory.
2134 .cindex "NIS lookup type" "including support for"
2135 .cindex "NIS+ lookup type" "including support for"
2136 .cindex "LDAP" "including support for"
2137 .cindex "lookup" "inclusion in binary"
2138 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2139 lookup, but not all systems have these components installed, so the default is
2140 not to include the relevant code in the binary. All the different kinds of file
2141 and database lookup that Exim supports are implemented as separate code modules
2142 which are included only if the relevant compile-time options are set. In the
2143 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2149 and similar settings apply to the other lookup types. They are all listed in
2150 &_src/EDITME_&. In many cases the relevant include files and interface
2151 libraries need to be installed before compiling Exim.
2152 .cindex "cdb" "including support for"
2153 However, there are some optional lookup types (such as cdb) for which
2154 the code is entirely contained within Exim, and no external include
2155 files or libraries are required. When a lookup type is not included in the
2156 binary, attempts to configure Exim to use it cause run time configuration
2159 .cindex "pkg-config" "lookups"
2160 .cindex "pkg-config" "authenticators"
2161 Many systems now use a tool called &'pkg-config'& to encapsulate information
2162 about how to compile against a library; Exim has some initial support for
2163 being able to use pkg-config for lookups and authenticators. For any given
2164 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2165 variable with the &`_PC`& suffix in the name and assign as the value the
2166 name of the package to be queried. The results of querying via the
2167 &'pkg-config'& command will be added to the appropriate Makefile variables
2168 with &`+=`& directives, so your version of &'make'& will need to support that
2169 syntax. For instance:
2172 LOOKUP_SQLITE_PC=sqlite3
2174 AUTH_GSASL_PC=libgsasl
2175 AUTH_HEIMDAL_GSSAPI=yes
2176 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2179 .cindex "Perl" "including support for"
2180 Exim can be linked with an embedded Perl interpreter, allowing Perl
2181 subroutines to be called during string expansion. To enable this facility,
2185 must be defined in &_Local/Makefile_&. Details of this facility are given in
2186 chapter &<<CHAPperl>>&.
2188 .cindex "X11 libraries, location of"
2189 The location of the X11 libraries is something that varies a lot between
2190 operating systems, and there may be different versions of X11 to cope
2191 with. Exim itself makes no use of X11, but if you are compiling the Exim
2192 monitor, the X11 libraries must be available.
2193 The following three variables are set in &_OS/Makefile-Default_&:
2196 XINCLUDE=-I$(X11)/include
2197 XLFLAGS=-L$(X11)/lib
2199 These are overridden in some of the operating-system configuration files. For
2200 example, in &_OS/Makefile-SunOS5_& there is
2203 XINCLUDE=-I$(X11)/include
2204 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2206 If you need to override the default setting for your operating system, place a
2207 definition of all three of these variables into your
2208 &_Local/Makefile-<ostype>_& file.
2211 If you need to add any extra libraries to the link steps, these can be put in a
2212 variable called EXTRALIBS, which appears in all the link commands, but by
2213 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2214 command for linking the main Exim binary, and not for any associated utilities.
2216 .cindex "DBM libraries" "configuration for building"
2217 There is also DBMLIB, which appears in the link commands for binaries that
2218 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2219 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2220 binary, and which can be used, for example, to include additional X11
2223 .cindex "configuration file" "editing"
2224 The make file copes with rebuilding Exim correctly if any of the configuration
2225 files are edited. However, if an optional configuration file is deleted, it is
2226 necessary to touch the associated non-optional file (that is,
2227 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2230 .section "OS-specific header files" "SECID30"
2232 .cindex "building Exim" "OS-specific C header files"
2233 The &_OS_& directory contains a number of files with names of the form
2234 &_os.h-<ostype>_&. These are system-specific C header files that should not
2235 normally need to be changed. There is a list of macro settings that are
2236 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2237 are porting Exim to a new operating system.
2241 .section "Overriding build-time options for the monitor" "SECID31"
2242 .cindex "building Eximon"
2243 A similar process is used for overriding things when building the Exim monitor,
2244 where the files that are involved are
2246 &_OS/eximon.conf-Default_&
2247 &_OS/eximon.conf-_&<&'ostype'&>
2248 &_Local/eximon.conf_&
2249 &_Local/eximon.conf-_&<&'ostype'&>
2250 &_Local/eximon.conf-_&<&'archtype'&>
2251 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2253 .cindex "&_Local/eximon.conf_&"
2254 As with Exim itself, the final three files need not exist, and in this case the
2255 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2256 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2257 variables of the same name, preceded by EXIMON_. For example, setting
2258 EXIMON_LOG_DEPTH in the environment overrides the value of
2259 LOG_DEPTH at run time.
2263 .section "Installing Exim binaries and scripts" "SECID32"
2264 .cindex "installing Exim"
2265 .cindex "BIN_DIRECTORY"
2266 The command &`make install`& runs the &(exim_install)& script with no
2267 arguments. The script copies binaries and utility scripts into the directory
2268 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2269 .cindex "setuid" "installing Exim with"
2270 The install script copies files only if they are newer than the files they are
2271 going to replace. The Exim binary is required to be owned by root and have the
2272 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2273 install`& as root so that it can set up the Exim binary in this way. However, in
2274 some special situations (for example, if a host is doing no local deliveries)
2275 it may be possible to run Exim without making the binary setuid root (see
2276 chapter &<<CHAPsecurity>>& for details).
2278 .cindex "CONFIGURE_FILE"
2279 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2280 in &_Local/Makefile_&. If this names a single file, and the file does not
2281 exist, the default configuration file &_src/configure.default_& is copied there
2282 by the installation script. If a run time configuration file already exists, it
2283 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2284 alternative files, no default is installed.
2286 .cindex "system aliases file"
2287 .cindex "&_/etc/aliases_&"
2288 One change is made to the default configuration file when it is installed: the
2289 default configuration contains a router that references a system aliases file.
2290 The path to this file is set to the value specified by
2291 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2292 If the system aliases file does not exist, the installation script creates it,
2293 and outputs a comment to the user.
2295 The created file contains no aliases, but it does contain comments about the
2296 aliases a site should normally have. Mail aliases have traditionally been
2297 kept in &_/etc/aliases_&. However, some operating systems are now using
2298 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2299 Exim's configuration if necessary.
2301 The default configuration uses the local host's name as the only local domain,
2302 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2303 running as the local user. System aliases and &_.forward_& files in users' home
2304 directories are supported, but no NIS or NIS+ support is configured. Domains
2305 other than the name of the local host are routed using the DNS, with delivery
2308 It is possible to install Exim for special purposes (such as building a binary
2309 distribution) in a private part of the file system. You can do this by a
2312 make DESTDIR=/some/directory/ install
2314 This has the effect of pre-pending the specified directory to all the file
2315 paths, except the name of the system aliases file that appears in the default
2316 configuration. (If a default alias file is created, its name &'is'& modified.)
2317 For backwards compatibility, ROOT is used if DESTDIR is not set,
2318 but this usage is deprecated.
2320 .cindex "installing Exim" "what is not installed"
2321 Running &'make install'& does not copy the Exim 4 conversion script
2322 &'convert4r4'&. You will probably run this only once if you are
2323 upgrading from Exim 3. None of the documentation files in the &_doc_&
2324 directory are copied, except for the info files when you have set
2325 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2327 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2328 to their names. The Exim binary itself, however, is handled differently. It is
2329 installed under a name that includes the version number and the compile number,
2330 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2331 called &_exim_& to point to the binary. If you are updating a previous version
2332 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2333 from the directory (as seen by other processes).
2335 .cindex "installing Exim" "testing the script"
2336 If you want to see what the &'make install'& will do before running it for
2337 real, you can pass the &%-n%& option to the installation script by this
2340 make INSTALL_ARG=-n install
2342 The contents of the variable INSTALL_ARG are passed to the installation
2343 script. You do not need to be root to run this test. Alternatively, you can run
2344 the installation script directly, but this must be from within the build
2345 directory. For example, from the top-level Exim directory you could use this
2348 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2350 .cindex "installing Exim" "install script options"
2351 There are two other options that can be supplied to the installation script.
2354 &%-no_chown%& bypasses the call to change the owner of the installed binary
2355 to root, and the call to make it a setuid binary.
2357 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2361 INSTALL_ARG can be used to pass these options to the script. For example:
2363 make INSTALL_ARG=-no_symlink install
2365 The installation script can also be given arguments specifying which files are
2366 to be copied. For example, to install just the Exim binary, and nothing else,
2367 without creating the symbolic link, you could use:
2369 make INSTALL_ARG='-no_symlink exim' install
2374 .section "Installing info documentation" "SECTinsinfdoc"
2375 .cindex "installing Exim" "&'info'& documentation"
2376 Not all systems use the GNU &'info'& system for documentation, and for this
2377 reason, the Texinfo source of Exim's documentation is not included in the main
2378 distribution. Instead it is available separately from the ftp site (see section
2381 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2382 source of the documentation is found in the source tree, running &`make
2383 install`& automatically builds the info files and installs them.
2387 .section "Setting up the spool directory" "SECID33"
2388 .cindex "spool directory" "creating"
2389 When it starts up, Exim tries to create its spool directory if it does not
2390 exist. The Exim uid and gid are used for the owner and group of the spool
2391 directory. Sub-directories are automatically created in the spool directory as
2397 .section "Testing" "SECID34"
2398 .cindex "testing" "installation"
2399 Having installed Exim, you can check that the run time configuration file is
2400 syntactically valid by running the following command, which assumes that the
2401 Exim binary directory is within your PATH environment variable:
2405 If there are any errors in the configuration file, Exim outputs error messages.
2406 Otherwise it outputs the version number and build date,
2407 the DBM library that is being used, and information about which drivers and
2408 other optional code modules are included in the binary.
2409 Some simple routing tests can be done by using the address testing option. For
2412 &`exim -bt`& <&'local username'&>
2414 should verify that it recognizes a local mailbox, and
2416 &`exim -bt`& <&'remote address'&>
2418 a remote one. Then try getting it to deliver mail, both locally and remotely.
2419 This can be done by passing messages directly to Exim, without going through a
2420 user agent. For example:
2422 exim -v postmaster@your.domain.example
2423 From: user@your.domain.example
2424 To: postmaster@your.domain.example
2425 Subject: Testing Exim
2427 This is a test message.
2430 The &%-v%& option causes Exim to output some verification of what it is doing.
2431 In this case you should see copies of three log lines, one for the message's
2432 arrival, one for its delivery, and one containing &"Completed"&.
2434 .cindex "delivery" "problems with"
2435 If you encounter problems, look at Exim's log files (&'mainlog'& and
2436 &'paniclog'&) to see if there is any relevant information there. Another source
2437 of information is running Exim with debugging turned on, by specifying the
2438 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2439 with debugging turned on by a command of the form
2441 &`exim -d -M`& <&'exim-message-id'&>
2443 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2444 produces rather a lot of output, but you can cut this down to specific areas.
2445 For example, if you use &%-d-all+route%& only the debugging information
2446 relevant to routing is included. (See the &%-d%& option in chapter
2447 &<<CHAPcommandline>>& for more details.)
2449 .cindex '&"sticky"& bit'
2450 .cindex "lock files"
2451 One specific problem that has shown up on some sites is the inability to do
2452 local deliveries into a shared mailbox directory, because it does not have the
2453 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2454 writing to a mailbox file, and if it cannot create the lock file, the delivery
2455 is deferred. You can get round this either by setting the &"sticky bit"& on the
2456 directory, or by setting a specific group for local deliveries and allowing
2457 that group to create files in the directory (see the comments above the
2458 &(local_delivery)& transport in the default configuration file). Another
2459 approach is to configure Exim not to use lock files, but just to rely on
2460 &[fcntl()]& locking instead. However, you should do this only if all user
2461 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2462 see chapter &<<CHAPappendfile>>&.
2464 One thing that cannot be tested on a system that is already running an MTA is
2465 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2466 &%-oX%& option can be used to run an Exim daemon that listens on some other
2467 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2468 &'exim_checkaccess'& utility can be used to check out policy controls on
2471 Testing a new version on a system that is already running Exim can most easily
2472 be done by building a binary with a different CONFIGURE_FILE setting. From
2473 within the run time configuration, all other file and directory names
2474 that Exim uses can be altered, in order to keep it entirely clear of the
2478 .section "Replacing another MTA with Exim" "SECID35"
2479 .cindex "replacing another MTA"
2480 Building and installing Exim for the first time does not of itself put it in
2481 general use. The name by which the system's MTA is called by mail user agents
2482 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2483 operating system), and it is necessary to make this name point to the &'exim'&
2484 binary in order to get the user agents to pass messages to Exim. This is
2485 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2486 or &_/usr/lib/sendmail_&
2487 .cindex "symbolic link" "to &'exim'& binary"
2488 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2489 privilege and executable status from the old MTA. It is then necessary to stop
2490 and restart the mailer daemon, if one is running.
2492 .cindex "FreeBSD, MTA indirection"
2493 .cindex "&_/etc/mail/mailer.conf_&"
2494 Some operating systems have introduced alternative ways of switching MTAs. For
2495 example, if you are running FreeBSD, you need to edit the file
2496 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2497 described. A typical example of the contents of this file for running Exim is
2500 sendmail /usr/exim/bin/exim
2501 send-mail /usr/exim/bin/exim
2502 mailq /usr/exim/bin/exim -bp
2503 newaliases /usr/bin/true
2505 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2506 your Exim installation is &"live"&. Check it by sending a message from your
2507 favourite user agent.
2509 You should consider what to tell your users about the change of MTA. Exim may
2510 have different capabilities to what was previously running, and there are
2511 various operational differences such as the text of messages produced by
2512 command line options and in bounce messages. If you allow your users to make
2513 use of Exim's filtering capabilities, you should make the document entitled
2514 &'Exim's interface to mail filtering'& available to them.
2518 .section "Upgrading Exim" "SECID36"
2519 .cindex "upgrading Exim"
2520 If you are already running Exim on your host, building and installing a new
2521 version automatically makes it available to MUAs, or any other programs that
2522 call the MTA directly. However, if you are running an Exim daemon, you do need
2523 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2524 new binary. You do not need to stop processing mail in order to install a new
2525 version of Exim. The install script does not modify an existing runtime
2531 .section "Stopping the Exim daemon on Solaris" "SECID37"
2532 .cindex "Solaris" "stopping Exim on"
2533 The standard command for stopping the mailer daemon on Solaris is
2535 /etc/init.d/sendmail stop
2537 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2538 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2539 for the text &"sendmail"&; this is not present because the actual program name
2540 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2541 solution is to replace the line that finds the process id with something like
2543 pid=`cat /var/spool/exim/exim-daemon.pid`
2545 to obtain the daemon's pid directly from the file that Exim saves it in.
2547 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2548 still be received from local processes, and if automatic delivery is configured
2549 (the normal case), deliveries will still occur.
2554 . ////////////////////////////////////////////////////////////////////////////
2555 . ////////////////////////////////////////////////////////////////////////////
2557 .chapter "The Exim command line" "CHAPcommandline"
2558 .scindex IIDclo1 "command line" "options"
2559 .scindex IIDclo2 "options" "command line"
2560 Exim's command line takes the standard Unix form of a sequence of options,
2561 each starting with a hyphen character, followed by a number of arguments. The
2562 options are compatible with the main options of Sendmail, and there are also
2563 some additional options, some of which are compatible with Smail 3. Certain
2564 combinations of options do not make sense, and provoke an error if used.
2565 The form of the arguments depends on which options are set.
2568 .section "Setting options by program name" "SECID38"
2570 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2571 were present before any other options.
2572 The &%-bp%& option requests a listing of the contents of the mail queue on the
2574 This feature is for compatibility with some systems that contain a command of
2575 that name in one of the standard libraries, symbolically linked to
2576 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2579 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2580 were present before any other options, for compatibility with Smail. The
2581 &%-bS%& option is used for reading in a number of messages in batched SMTP
2585 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2586 &%-oee%& options were present before any other options, for compatibility with
2587 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2590 .cindex "queue runner"
2591 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2592 were present before any other options, for compatibility with Smail. The &%-q%&
2593 option causes a single queue runner process to be started.
2595 .cindex "&'newaliases'&"
2596 .cindex "alias file" "building"
2597 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2598 If Exim is called under the name &'newaliases'& it behaves as if the option
2599 &%-bi%& were present before any other options, for compatibility with Sendmail.
2600 This option is used for rebuilding Sendmail's alias file. Exim does not have
2601 the concept of a single alias file, but can be configured to run a given
2602 command if called with the &%-bi%& option.
2605 .section "Trusted and admin users" "SECTtrustedadmin"
2606 Some Exim options are available only to &'trusted users'& and others are
2607 available only to &'admin users'&. In the description below, the phrases &"Exim
2608 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2609 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2610 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2613 .cindex "trusted users" "definition of"
2614 .cindex "user" "trusted definition of"
2615 The trusted users are root, the Exim user, any user listed in the
2616 &%trusted_users%& configuration option, and any user whose current group or any
2617 supplementary group is one of those listed in the &%trusted_groups%&
2618 configuration option. Note that the Exim group is not automatically trusted.
2620 .cindex '&"From"& line'
2621 .cindex "envelope sender"
2622 Trusted users are always permitted to use the &%-f%& option or a leading
2623 &"From&~"& line to specify the envelope sender of a message that is passed to
2624 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2625 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2626 users to set envelope senders.
2628 .cindex "&'From:'& header line"
2629 .cindex "&'Sender:'& header line"
2630 For a trusted user, there is never any check on the contents of the &'From:'&
2631 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2632 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2634 Trusted users may also specify a host name, host address, interface address,
2635 protocol name, ident value, and authentication data when submitting a message
2636 locally. Thus, they are able to insert messages into Exim's queue locally that
2637 have the characteristics of messages received from a remote host. Untrusted
2638 users may in some circumstances use &%-f%&, but can never set the other values
2639 that are available to trusted users.
2641 .cindex "user" "admin definition of"
2642 .cindex "admin user" "definition of"
2643 The admin users are root, the Exim user, and any user that is a member of the
2644 Exim group or of any group listed in the &%admin_groups%& configuration option.
2645 The current group does not have to be one of these groups.
2647 Admin users are permitted to list the queue, and to carry out certain
2648 operations on messages, for example, to force delivery failures. It is also
2649 necessary to be an admin user in order to see the full information provided by
2650 the Exim monitor, and full debugging output.
2652 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2653 Exim to attempt delivery of messages on its queue is restricted to admin users.
2654 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2655 option false (that is, specifying &%no_prod_requires_admin%&).
2657 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2658 is restricted to admin users unless &%queue_list_requires_admin%& is set
2663 &*Warning*&: If you configure your system so that admin users are able to
2664 edit Exim's configuration file, you are giving those users an easy way of
2665 getting root. There is further discussion of this issue at the start of chapter
2671 .section "Command line options" "SECID39"
2672 Exim's command line options are described in alphabetical order below. If none
2673 of the options that specifies a specific action (such as starting the daemon or
2674 a queue runner, or testing an address, or receiving a message in a specific
2675 format, or listing the queue) are present, and there is at least one argument
2676 on the command line, &%-bm%& (accept a local message on the standard input,
2677 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2678 outputs a brief message about itself and exits.
2680 . ////////////////////////////////////////////////////////////////////////////
2681 . Insert a stylized XML comment here, to identify the start of the command line
2682 . options. This is for the benefit of the Perl script that automatically
2683 . creates a man page for the options.
2684 . ////////////////////////////////////////////////////////////////////////////
2687 <!-- === Start of command line options === -->
2694 .cindex "options" "command line; terminating"
2695 This is a pseudo-option whose only purpose is to terminate the options and
2696 therefore to cause subsequent command line items to be treated as arguments
2697 rather than options, even if they begin with hyphens.
2700 .oindex "&%--help%&"
2701 This option causes Exim to output a few sentences stating what it is.
2702 The same output is generated if the Exim binary is called with no options and
2705 .vitem &%--version%&
2706 .oindex "&%--version%&"
2707 This option is an alias for &%-bV%& and causes version information to be
2714 These options are used by Sendmail for selecting configuration files and are
2717 .vitem &%-B%&<&'type'&>
2719 .cindex "8-bit characters"
2720 .cindex "Sendmail compatibility" "8-bit characters"
2721 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2722 clean; it ignores this option.
2727 .cindex "SMTP" "listener"
2728 .cindex "queue runner"
2729 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2730 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2731 that the daemon should also initiate periodic queue runs.
2733 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2734 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2735 disconnect from the controlling terminal. When running this way, it can be
2736 stopped by pressing ctrl-C.
2738 By default, Exim listens for incoming connections to the standard SMTP port on
2739 all the host's running interfaces. However, it is possible to listen on other
2740 ports, on multiple ports, and only on specific interfaces. Chapter
2741 &<<CHAPinterfaces>>& contains a description of the options that control this.
2743 When a listening daemon
2744 .cindex "daemon" "process id (pid)"
2745 .cindex "pid (process id)" "of daemon"
2746 is started without the use of &%-oX%& (that is, without overriding the normal
2747 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2748 in Exim's spool directory. This location can be overridden by setting
2749 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2752 When &%-oX%& is used on the command line to start a listening daemon, the
2753 process id is not written to the normal pid file path. However, &%-oP%& can be
2754 used to specify a path on the command line if a pid file is required.
2758 .cindex "daemon" "restarting"
2759 can be used to cause the daemon to re-execute itself. This should be done
2760 whenever Exim's configuration file, or any file that is incorporated into it by
2761 means of the &%.include%& facility, is changed, and also whenever a new version
2762 of Exim is installed. It is not necessary to do this when other files that are
2763 referenced from the configuration (for example, alias files) are changed,
2764 because these are reread each time they are used.
2768 This option has the same effect as &%-bd%& except that it never disconnects
2769 from the controlling terminal, even when no debugging is specified.
2773 .cindex "testing" "string expansion"
2774 .cindex "expansion" "testing"
2775 Run Exim in expansion testing mode. Exim discards its root privilege, to
2776 prevent ordinary users from using this mode to read otherwise inaccessible
2777 files. If no arguments are given, Exim runs interactively, prompting for lines
2778 of data. Otherwise, it processes each argument in turn.
2780 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2781 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2782 used without command line arguments. If successful, it uses the &[readline()]&
2783 function, which provides extensive line-editing facilities, for reading the
2784 test data. A line history is supported.
2786 Long expansion expressions can be split over several lines by using backslash
2787 continuations. As in Exim's run time configuration, white space at the start of
2788 continuation lines is ignored. Each argument or data line is passed through the
2789 string expansion mechanism, and the result is output. Variable values from the
2790 configuration file (for example, &$qualify_domain$&) are available, but no
2791 message-specific values (such as &$message_exim_id$&) are set, because no message
2792 is being processed (but see &%-bem%& and &%-Mset%&).
2794 &*Note*&: If you use this mechanism to test lookups, and you change the data
2795 files or databases you are using, you must exit and restart Exim before trying
2796 the same lookup again. Otherwise, because each Exim process caches the results
2797 of lookups, you will just get the same result as before.
2799 .vitem &%-bem%&&~<&'filename'&>
2801 .cindex "testing" "string expansion"
2802 .cindex "expansion" "testing"
2803 This option operates like &%-be%& except that it must be followed by the name
2804 of a file. For example:
2806 exim -bem /tmp/testmessage
2808 The file is read as a message (as if receiving a locally-submitted non-SMTP
2809 message) before any of the test expansions are done. Thus, message-specific
2810 variables such as &$message_size$& and &$header_from:$& are available. However,
2811 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2812 recipients are read from the headers in the normal way, and are shown in the
2813 &$recipients$& variable. Note that recipients cannot be given on the command
2814 line, because further arguments are taken as strings to expand (just like
2817 .vitem &%-bF%&&~<&'filename'&>
2819 .cindex "system filter" "testing"
2820 .cindex "testing" "system filter"
2821 This option is the same as &%-bf%& except that it assumes that the filter being
2822 tested is a system filter. The additional commands that are available only in
2823 system filters are recognized.
2825 .vitem &%-bf%&&~<&'filename'&>
2827 .cindex "filter" "testing"
2828 .cindex "testing" "filter file"
2829 .cindex "forward file" "testing"
2830 .cindex "testing" "forward file"
2831 .cindex "Sieve filter" "testing"
2832 This option runs Exim in user filter testing mode; the file is the filter file
2833 to be tested, and a test message must be supplied on the standard input. If
2834 there are no message-dependent tests in the filter, an empty file can be
2837 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2838 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2839 filter and a user filter in the same run. For example:
2841 exim -bF /system/filter -bf /user/filter </test/message
2843 This is helpful when the system filter adds header lines or sets filter
2844 variables that are used by the user filter.
2846 If the test filter file does not begin with one of the special lines
2851 it is taken to be a normal &_.forward_& file, and is tested for validity under
2852 that interpretation. See sections &<<SECTitenonfilred>>& to
2853 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2856 The result of an Exim command that uses &%-bf%&, provided no errors are
2857 detected, is a list of the actions that Exim would try to take if presented
2858 with the message for real. More details of filter testing are given in the
2859 separate document entitled &'Exim's interfaces to mail filtering'&.
2861 When testing a filter file,
2862 .cindex "&""From""& line"
2863 .cindex "envelope sender"
2864 .oindex "&%-f%&" "for filter testing"
2865 the envelope sender can be set by the &%-f%& option,
2866 or by a &"From&~"& line at the start of the test message. Various parameters
2867 that would normally be taken from the envelope recipient address of the message
2868 can be set by means of additional command line options (see the next four
2871 .vitem &%-bfd%&&~<&'domain'&>
2873 .vindex "&$qualify_domain$&"
2874 This sets the domain of the recipient address when a filter file is being
2875 tested by means of the &%-bf%& option. The default is the value of
2878 .vitem &%-bfl%&&~<&'local&~part'&>
2880 This sets the local part of the recipient address when a filter file is being
2881 tested by means of the &%-bf%& option. The default is the username of the
2882 process that calls Exim. A local part should be specified with any prefix or
2883 suffix stripped, because that is how it appears to the filter when a message is
2884 actually being delivered.
2886 .vitem &%-bfp%&&~<&'prefix'&>
2888 This sets the prefix of the local part of the recipient address when a filter
2889 file is being tested by means of the &%-bf%& option. The default is an empty
2892 .vitem &%-bfs%&&~<&'suffix'&>
2894 This sets the suffix of the local part of the recipient address when a filter
2895 file is being tested by means of the &%-bf%& option. The default is an empty
2898 .vitem &%-bh%&&~<&'IP&~address'&>
2900 .cindex "testing" "incoming SMTP"
2901 .cindex "SMTP" "testing incoming"
2902 .cindex "testing" "relay control"
2903 .cindex "relaying" "testing configuration"
2904 .cindex "policy control" "testing"
2905 .cindex "debugging" "&%-bh%& option"
2906 This option runs a fake SMTP session as if from the given IP address, using the
2907 standard input and output. The IP address may include a port number at the end,
2908 after a full stop. For example:
2910 exim -bh 10.9.8.7.1234
2911 exim -bh fe80::a00:20ff:fe86:a061.5678
2913 When an IPv6 address is given, it is converted into canonical form. In the case
2914 of the second example above, the value of &$sender_host_address$& after
2915 conversion to the canonical form is
2916 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2918 Comments as to what is going on are written to the standard error file. These
2919 include lines beginning with &"LOG"& for anything that would have been logged.
2920 This facility is provided for testing configuration options for incoming
2921 messages, to make sure they implement the required policy. For example, you can
2922 test your relay controls using &%-bh%&.
2926 You can test features of the configuration that rely on ident (RFC 1413)
2927 information by using the &%-oMt%& option. However, Exim cannot actually perform
2928 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2931 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2932 are also skipped when testing using &%-bh%&. If you want these callouts to
2933 occur, use &%-bhc%& instead.
2935 Messages supplied during the testing session are discarded, and nothing is
2936 written to any of the real log files. There may be pauses when DNS (and other)
2937 lookups are taking place, and of course these may time out. The &%-oMi%& option
2938 can be used to specify a specific IP interface and port if this is important,
2939 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2940 session were authenticated.
2942 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2943 output just states whether a given recipient address from a given host is
2944 acceptable or not. See section &<<SECTcheckaccess>>&.
2946 Features such as authentication and encryption, where the client input is not
2947 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2948 specialized SMTP test program such as
2949 &url(http://jetmore.org/john/code/#swaks,swaks).
2951 .vitem &%-bhc%&&~<&'IP&~address'&>
2953 This option operates in the same way as &%-bh%&, except that address
2954 verification callouts are performed if required. This includes consulting and
2955 updating the callout cache database.
2959 .cindex "alias file" "building"
2960 .cindex "building alias file"
2961 .cindex "Sendmail compatibility" "&%-bi%& option"
2962 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2963 Exim does not have the concept of a single alias file, and so it cannot mimic
2964 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2965 tend to appear in various scripts such as NIS make files, so the option must be
2968 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2969 configuration option is run, under the uid and gid of the caller of Exim. If
2970 the &%-oA%& option is used, its value is passed to the command as an argument.
2971 The command set by &%bi_command%& may not contain arguments. The command can
2972 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2973 if this is required. If the &%bi_command%& option is not set, calling Exim with
2976 . // Keep :help first, then the rest in alphabetical order
2978 .oindex "&%-bI:help%&"
2979 .cindex "querying exim information"
2980 We shall provide various options starting &`-bI:`& for querying Exim for
2981 information. The output of many of these will be intended for machine
2982 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2983 synopsis of supported options beginning &`-bI:`&. Use of any of these
2984 options shall cause Exim to exit after producing the requested output.
2987 .oindex "&%-bI:dscp%&"
2988 .cindex "DSCP" "values"
2989 This option causes Exim to emit an alphabetically sorted list of all
2990 recognised DSCP names.
2992 .vitem &%-bI:sieve%&
2993 .oindex "&%-bI:sieve%&"
2994 .cindex "Sieve filter" "capabilities"
2995 This option causes Exim to emit an alphabetically sorted list of all supported
2996 Sieve protocol extensions on stdout, one per line. This is anticipated to be
2997 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
2998 &`SIEVE`& capability response line. As the precise list may depend upon
2999 compile-time build options, which this option will adapt to, this is the only
3000 way to guarantee a correct response.
3004 .cindex "local message reception"
3005 This option runs an Exim receiving process that accepts an incoming,
3006 locally-generated message on the standard input. The recipients are given as the
3007 command arguments (except when &%-t%& is also present &-- see below). Each
3008 argument can be a comma-separated list of RFC 2822 addresses. This is the
3009 default option for selecting the overall action of an Exim call; it is assumed
3010 if no other conflicting option is present.
3012 If any addresses in the message are unqualified (have no domain), they are
3013 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3014 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3015 suppressing this for special cases.
3017 Policy checks on the contents of local messages can be enforced by means of
3018 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3020 .cindex "return code" "for &%-bm%&"
3021 The return code is zero if the message is successfully accepted. Otherwise, the
3022 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3025 .cindex "message" "format"
3026 .cindex "format" "message"
3027 .cindex "&""From""& line"
3028 .cindex "UUCP" "&""From""& line"
3029 .cindex "Sendmail compatibility" "&""From""& line"
3030 of the message must be as defined in RFC 2822, except that, for
3031 compatibility with Sendmail and Smail, a line in one of the forms
3033 From sender Fri Jan 5 12:55 GMT 1997
3034 From sender Fri, 5 Jan 97 12:55:01
3036 (with the weekday optional, and possibly with additional text after the date)
3037 is permitted to appear at the start of the message. There appears to be no
3038 authoritative specification of the format of this line. Exim recognizes it by
3039 matching against the regular expression defined by the &%uucp_from_pattern%&
3040 option, which can be changed if necessary.
3042 .oindex "&%-f%&" "overriding &""From""& line"
3043 The specified sender is treated as if it were given as the argument to the
3044 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3045 preference to the address taken from the message. The caller of Exim must be a
3046 trusted user for the sender of a message to be set in this way.
3048 .vitem &%-bmalware%&&~<&'filename'&>
3049 .oindex "&%-bmalware%&"
3050 .cindex "testing", "malware"
3051 .cindex "malware scan test"
3052 This debugging option causes Exim to scan the given file or directory
3053 (depending on the used scanner interface),
3054 using the malware scanning framework. The option of &%av_scanner%& influences
3055 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3056 the expansion should have defaults which apply to this invocation. ACLs are
3057 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3058 will never be populated and &%-bmalware%& will fail.
3060 Exim will have changed working directory before resolving the filename, so
3061 using fully qualified pathnames is advisable. Exim will be running as the Exim
3062 user when it tries to open the file, rather than as the invoking user.
3063 This option requires admin privileges.
3065 The &%-bmalware%& option will not be extended to be more generally useful,
3066 there are better tools for file-scanning. This option exists to help
3067 administrators verify their Exim and AV scanner configuration.
3071 .cindex "address qualification, suppressing"
3072 By default, Exim automatically qualifies unqualified addresses (those
3073 without domains) that appear in messages that are submitted locally (that
3074 is, not over TCP/IP). This qualification applies both to addresses in
3075 envelopes, and addresses in header lines. Sender addresses are qualified using
3076 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3077 defaults to the value of &%qualify_domain%&).
3079 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3080 being used to re-submit messages that originally came from remote hosts after
3081 content scanning, you probably do not want to qualify unqualified addresses in
3082 header lines. (Such lines will be present only if you have not enabled a header
3083 syntax check in the appropriate ACL.)
3085 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3086 messages that originate on the local host. When this is used, unqualified
3087 addresses in the envelope provoke errors (causing message rejection) and
3088 unqualified addresses in header lines are left alone.
3093 .cindex "configuration options" "extracting"
3094 .cindex "options" "configuration &-- extracting"
3095 If this option is given with no arguments, it causes the values of all Exim's
3096 main configuration options to be written to the standard output. The values
3097 of one or more specific options can be requested by giving their names as
3098 arguments, for example:
3100 exim -bP qualify_domain hold_domains
3102 .cindex "hiding configuration option values"
3103 .cindex "configuration options" "hiding value of"
3104 .cindex "options" "hiding value of"
3105 However, any option setting that is preceded by the word &"hide"& in the
3106 configuration file is not shown in full, except to an admin user. For other
3107 users, the output is as in this example:
3109 mysql_servers = <value not displayable>
3111 If &%config%& is given as an argument, the config is
3112 output, as it was parsed, any include file resolved, any comment removed.
3114 If &%config_file%& is given as an argument, the name of the run time
3115 configuration file is output. (&%configure_file%& works too, for
3116 backward compatibility.)
3117 If a list of configuration files was supplied, the value that is output here
3118 is the name of the file that was actually used.
3120 .cindex "options" "hiding name of"
3121 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3122 name will not be output.
3124 .cindex "daemon" "process id (pid)"
3125 .cindex "pid (process id)" "of daemon"
3126 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3127 directories where log files and daemon pid files are written are output,
3128 respectively. If these values are unset, log files are written in a
3129 sub-directory of the spool directory called &%log%&, and the pid file is
3130 written directly into the spool directory.
3132 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3134 exim -bP +local_domains
3136 it searches for a matching named list of any type (domain, host, address, or
3137 local part) and outputs what it finds.
3139 .cindex "options" "router &-- extracting"
3140 .cindex "options" "transport &-- extracting"
3141 .cindex "options" "authenticator &-- extracting"
3142 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3143 followed by the name of an appropriate driver instance, the option settings for
3144 that driver are output. For example:
3146 exim -bP transport local_delivery
3148 The generic driver options are output first, followed by the driver's private
3149 options. A list of the names of drivers of a particular type can be obtained by
3150 using one of the words &%router_list%&, &%transport_list%&, or
3151 &%authenticator_list%&, and a complete list of all drivers with their option
3152 settings can be obtained by using &%routers%&, &%transports%&, or
3155 .cindex "environment"
3156 If &%environment%& is given as an argument, the set of environment
3157 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3160 .cindex "options" "macro &-- extracting"
3161 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3162 are available, similarly to the drivers. Because macros are sometimes used
3163 for storing passwords, this option is restricted.
3164 The output format is one item per line.
3168 .cindex "queue" "listing messages on"
3169 .cindex "listing" "messages on the queue"
3170 This option requests a listing of the contents of the mail queue on the
3171 standard output. If the &%-bp%& option is followed by a list of message ids,
3172 just those messages are listed. By default, this option can be used only by an
3173 admin user. However, the &%queue_list_requires_admin%& option can be set false
3174 to allow any user to see the queue.
3176 Each message on the queue is displayed as in the following example:
3178 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3179 red.king@looking-glass.fict.example
3182 .cindex "message" "size in queue listing"
3183 .cindex "size" "of message"
3184 The first line contains the length of time the message has been on the queue
3185 (in this case 25 minutes), the size of the message (2.9K), the unique local
3186 identifier for the message, and the message sender, as contained in the
3187 envelope. For bounce messages, the sender address is empty, and appears as
3188 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3189 the default sender address, the user's login name is shown in parentheses
3190 before the sender address.
3192 .cindex "frozen messages" "in queue listing"
3193 If the message is frozen (attempts to deliver it are suspended) then the text
3194 &"*** frozen ***"& is displayed at the end of this line.
3196 The recipients of the message (taken from the envelope, not the headers) are
3197 displayed on subsequent lines. Those addresses to which the message has already
3198 been delivered are marked with the letter D. If an original address gets
3199 expanded into several addresses via an alias or forward file, the original is
3200 displayed with a D only when deliveries for all of its child addresses are
3206 This option operates like &%-bp%&, but in addition it shows delivered addresses
3207 that were generated from the original top level address(es) in each message by
3208 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3214 .cindex "queue" "count of messages on"
3215 This option counts the number of messages on the queue, and writes the total
3216 to the standard output. It is restricted to admin users, unless
3217 &%queue_list_requires_admin%& is set false.
3222 This option operates like &%-bp%&, but the output is not sorted into
3223 chronological order of message arrival. This can speed it up when there are
3224 lots of messages on the queue, and is particularly useful if the output is
3225 going to be post-processed in a way that doesn't need the sorting.
3229 This option is a combination of &%-bpr%& and &%-bpa%&.
3233 This option is a combination of &%-bpr%& and &%-bpu%&.
3238 This option operates like &%-bp%& but shows only undelivered top-level
3239 addresses for each message displayed. Addresses generated by aliasing or
3240 forwarding are not shown, unless the message was deferred after processing by a
3241 router with the &%one_time%& option set.
3246 .cindex "testing" "retry configuration"
3247 .cindex "retry" "configuration testing"
3248 This option is for testing retry rules, and it must be followed by up to three
3249 arguments. It causes Exim to look for a retry rule that matches the values
3250 and to write it to the standard output. For example:
3252 exim -brt bach.comp.mus.example
3253 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3255 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3256 argument, which is required, can be a complete address in the form
3257 &'local_part@domain'&, or it can be just a domain name. If the second argument
3258 contains a dot, it is interpreted as an optional second domain name; if no
3259 retry rule is found for the first argument, the second is tried. This ties in
3260 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3261 rule is found that matches the host, one that matches the mail domain is
3262 sought. Finally, an argument that is the name of a specific delivery error, as
3263 used in setting up retry rules, can be given. For example:
3265 exim -brt haydn.comp.mus.example quota_3d
3266 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3271 .cindex "testing" "rewriting"
3272 .cindex "rewriting" "testing"
3273 This option is for testing address rewriting rules, and it must be followed by
3274 a single argument, consisting of either a local part without a domain, or a
3275 complete address with a fully qualified domain. Exim outputs how this address
3276 would be rewritten for each possible place it might appear. See chapter
3277 &<<CHAPrewrite>>& for further details.
3281 .cindex "SMTP" "batched incoming"
3282 .cindex "batched SMTP input"
3283 This option is used for batched SMTP input, which is an alternative interface
3284 for non-interactive local message submission. A number of messages can be
3285 submitted in a single run. However, despite its name, this is not really SMTP
3286 input. Exim reads each message's envelope from SMTP commands on the standard
3287 input, but generates no responses. If the caller is trusted, or
3288 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3289 believed; otherwise the sender is always the caller of Exim.
3291 The message itself is read from the standard input, in SMTP format (leading
3292 dots doubled), terminated by a line containing just a single dot. An error is
3293 provoked if the terminating dot is missing. A further message may then follow.
3295 As for other local message submissions, the contents of incoming batch SMTP
3296 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3297 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3298 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3300 Some other SMTP commands are recognized in the input. HELO and EHLO act
3301 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3302 QUIT quits, ignoring the rest of the standard input.
3304 .cindex "return code" "for &%-bS%&"
3305 If any error is encountered, reports are written to the standard output and
3306 error streams, and Exim gives up immediately. The return code is 0 if no error
3307 was detected; it is 1 if one or more messages were accepted before the error
3308 was detected; otherwise it is 2.
3310 More details of input using batched SMTP are given in section
3311 &<<SECTincomingbatchedSMTP>>&.
3315 .cindex "SMTP" "local input"
3316 .cindex "local SMTP input"
3317 This option causes Exim to accept one or more messages by reading SMTP commands
3318 on the standard input, and producing SMTP replies on the standard output. SMTP
3319 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3320 Some user agents use this interface as a way of passing locally-generated
3321 messages to the MTA.
3324 .cindex "sender" "source of"
3325 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3326 set, the senders of messages are taken from the SMTP MAIL commands.
3327 Otherwise the content of these commands is ignored and the sender is set up as
3328 the calling user. Unqualified addresses are automatically qualified using
3329 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3330 &%-bnq%& option is used.
3334 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3335 using a listening daemon. Exim can distinguish the two cases by checking
3336 whether the standard input is a TCP/IP socket. When Exim is called from
3337 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3338 above concerning senders and qualification do not apply. In this situation,
3339 Exim behaves in exactly the same way as it does when receiving a message via
3340 the listening daemon.
3344 .cindex "testing" "addresses"
3345 .cindex "address" "testing"
3346 This option runs Exim in address testing mode, in which each argument is taken
3347 as a recipient address to be tested for deliverability. The results are
3348 written to the standard output. If a test fails, and the caller is not an admin
3349 user, no details of the failure are output, because these might contain
3350 sensitive information such as usernames and passwords for database lookups.
3352 If no arguments are given, Exim runs in an interactive manner, prompting with a
3353 right angle bracket for addresses to be tested.
3355 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3356 &[readline()]& function, because it is running as &'root'& and there are
3359 Each address is handled as if it were the recipient address of a message
3360 (compare the &%-bv%& option). It is passed to the routers and the result is
3361 written to the standard output. However, any router that has
3362 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3363 genuine routing tests if your first router passes everything to a scanner
3366 .cindex "return code" "for &%-bt%&"
3367 The return code is 2 if any address failed outright; it is 1 if no address
3368 failed outright but at least one could not be resolved for some reason. Return
3369 code 0 is given only when all addresses succeed.
3371 .cindex "duplicate addresses"
3372 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3373 addresses after routing is complete, so that only one delivery takes place.
3374 This does not happen when testing with &%-bt%&; the full results of routing are
3377 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3378 routers in the configuration makes any tests on the sender address of a
3380 .oindex "&%-f%&" "for address testing"
3381 you can use the &%-f%& option to set an appropriate sender when running
3382 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3383 default qualifying domain. However, if you have set up (for example) routers
3384 whose behaviour depends on the contents of an incoming message, you cannot test
3385 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3390 .cindex "version number of Exim"
3391 This option causes Exim to write the current version number, compilation
3392 number, and compilation date of the &'exim'& binary to the standard output.
3393 It also lists the DBM library that is being used, the optional modules (such as
3394 specific lookup types), the drivers that are included in the binary, and the
3395 name of the run time configuration file that is in use.
3397 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3398 configuration file. However, this is a static check only. It cannot check
3399 values that are to be expanded. For example, although a misspelt ACL verb is
3400 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3401 alone to discover (for example) all the typos in the configuration; some
3402 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3403 dynamic testing facilities.
3407 .cindex "verifying address" "using &%-bv%&"
3408 .cindex "address" "verification"
3409 This option runs Exim in address verification mode, in which each argument is
3410 taken as a recipient address to be verified by the routers. (This does
3411 not involve any verification callouts). During normal operation, verification
3412 happens mostly as a consequence processing a &%verify%& condition in an ACL
3413 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3414 including callouts, see the &%-bh%& and &%-bhc%& options.
3416 If verification fails, and the caller is not an admin user, no details of the
3417 failure are output, because these might contain sensitive information such as
3418 usernames and passwords for database lookups.
3420 If no arguments are given, Exim runs in an interactive manner, prompting with a
3421 right angle bracket for addresses to be verified.
3423 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3424 &[readline()]& function, because it is running as &'exim'& and there are
3427 Verification differs from address testing (the &%-bt%& option) in that routers
3428 that have &%no_verify%& set are skipped, and if the address is accepted by a
3429 router that has &%fail_verify%& set, verification fails. The address is
3430 verified as a recipient if &%-bv%& is used; to test verification for a sender
3431 address, &%-bvs%& should be used.
3433 If the &%-v%& option is not set, the output consists of a single line for each
3434 address, stating whether it was verified or not, and giving a reason in the
3435 latter case. Without &%-v%&, generating more than one address by redirection
3436 causes verification to end successfully, without considering the generated
3437 addresses. However, if just one address is generated, processing continues,
3438 and the generated address must verify successfully for the overall verification
3441 When &%-v%& is set, more details are given of how the address has been handled,
3442 and in the case of address redirection, all the generated addresses are also
3443 considered. Verification may succeed for some and fail for others.
3446 .cindex "return code" "for &%-bv%&"
3447 return code is 2 if any address failed outright; it is 1 if no address
3448 failed outright but at least one could not be resolved for some reason. Return
3449 code 0 is given only when all addresses succeed.
3451 If any of the routers in the configuration makes any tests on the sender
3452 address of a message, you should use the &%-f%& option to set an appropriate
3453 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3454 calling user at the default qualifying domain.
3458 This option acts like &%-bv%&, but verifies the address as a sender rather
3459 than a recipient address. This affects any rewriting and qualification that
3466 .cindex "inetd" "wait mode"
3467 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3468 similarly to the &%-bd%& option. All port specifications on the command-line
3469 and in the configuration file are ignored. Queue-running may not be specified.
3471 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3472 listening for connections. This permits the system to start up and have
3473 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3474 each port only when the first connection is received.
3476 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3477 which the daemon will exit, which should cause inetd to listen once more.
3479 .vitem &%-C%&&~<&'filelist'&>
3481 .cindex "configuration file" "alternate"
3482 .cindex "CONFIGURE_FILE"
3483 .cindex "alternate configuration file"
3484 This option causes Exim to find the run time configuration file from the given
3485 list instead of from the list specified by the CONFIGURE_FILE
3486 compile-time setting. Usually, the list will consist of just a single file
3487 name, but it can be a colon-separated list of names. In this case, the first
3488 file that exists is used. Failure to open an existing file stops Exim from
3489 proceeding any further along the list, and an error is generated.
3491 When this option is used by a caller other than root, and the list is different
3492 from the compiled-in list, Exim gives up its root privilege immediately, and
3493 runs with the real and effective uid and gid set to those of the caller.
3494 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3495 file contains a list of full pathnames, one per line, for configuration files
3496 which are trusted. Root privilege is retained for any configuration file so
3497 listed, as long as the caller is the Exim user (or the user specified in the
3498 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3499 not writeable by inappropriate users or groups.
3501 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3502 configuration using &%-C%& right through message reception and delivery,
3503 even if the caller is root. The reception works, but by that time, Exim is
3504 running as the Exim user, so when it re-executes to regain privilege for the
3505 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3506 test reception and delivery using two separate commands (one to put a message
3507 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3509 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3510 prefix string with which any file named in a &%-C%& command line option
3511 must start. In addition, the file name must not contain the sequence &`/../`&.
3512 However, if the value of the &%-C%& option is identical to the value of
3513 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3514 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3515 unset, any file name can be used with &%-C%&.
3517 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3518 to a directory to which only root has access. This prevents someone who has
3519 broken into the Exim account from running a privileged Exim with an arbitrary
3522 The &%-C%& facility is useful for ensuring that configuration files are
3523 syntactically correct, but cannot be used for test deliveries, unless the
3524 caller is privileged, or unless it is an exotic configuration that does not
3525 require privilege. No check is made on the owner or group of the files
3526 specified by this option.
3529 .vitem &%-D%&<&'macro'&>=<&'value'&>
3531 .cindex "macro" "setting on command line"
3532 This option can be used to override macro definitions in the configuration file
3533 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3534 unprivileged caller, it causes Exim to give up its root privilege.
3535 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3536 completely disabled, and its use causes an immediate error exit.
3538 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3539 colon-separated list of macros which are considered safe and, if &%-D%& only
3540 supplies macros from this list, and the values are acceptable, then Exim will
3541 not give up root privilege if the caller is root, the Exim run-time user, or
3542 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3543 to be removed in the future. Acceptable values for the macros satisfy the
3544 regexp: &`^[A-Za-z0-9_/.-]*$`&
3546 The entire option (including equals sign if present) must all be within one
3547 command line item. &%-D%& can be used to set the value of a macro to the empty
3548 string, in which case the equals sign is optional. These two commands are
3554 To include spaces in a macro definition item, quotes must be used. If you use
3555 quotes, spaces are permitted around the macro name and the equals sign. For
3558 exim '-D ABC = something' ...
3560 &%-D%& may be repeated up to 10 times on a command line.
3561 Only macro names up to 22 letters long can be set.
3564 .vitem &%-d%&<&'debug&~options'&>
3566 .cindex "debugging" "list of selectors"
3567 .cindex "debugging" "&%-d%& option"
3568 This option causes debugging information to be written to the standard
3569 error stream. It is restricted to admin users because debugging output may show
3570 database queries that contain password information. Also, the details of users'
3571 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3572 writes an error message to the standard error stream and exits with a non-zero
3575 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3576 standard debugging data is output. This can be reduced, or increased to include
3577 some more rarely needed information, by directly following &%-d%& with a string
3578 made up of names preceded by plus or minus characters. These add or remove sets
3579 of debugging data, respectively. For example, &%-d+filter%& adds filter
3580 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3581 no spaces are allowed in the debug setting. The available debugging categories
3584 &`acl `& ACL interpretation
3585 &`auth `& authenticators
3586 &`deliver `& general delivery logic
3587 &`dns `& DNS lookups (see also resolver)
3588 &`dnsbl `& DNS black list (aka RBL) code
3589 &`exec `& arguments for &[execv()]& calls
3590 &`expand `& detailed debugging for string expansions
3591 &`filter `& filter handling
3592 &`hints_lookup `& hints data lookups
3593 &`host_lookup `& all types of name-to-IP address handling
3594 &`ident `& ident lookup
3595 &`interface `& lists of local interfaces
3596 &`lists `& matching things in lists
3597 &`load `& system load checks
3598 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3599 &<<CHAPlocalscan>>&)
3600 &`lookup `& general lookup code and all lookups
3601 &`memory `& memory handling
3602 &`pid `& add pid to debug output lines
3603 &`process_info `& setting info for the process log
3604 &`queue_run `& queue runs
3605 &`receive `& general message reception logic
3606 &`resolver `& turn on the DNS resolver's debugging output
3607 &`retry `& retry handling
3608 &`rewrite `& address rewriting
3609 &`route `& address routing
3610 &`timestamp `& add timestamp to debug output lines
3612 &`transport `& transports
3613 &`uid `& changes of uid/gid and looking up uid/gid
3614 &`verify `& address verification logic
3615 &`all `& almost all of the above (see below), and also &%-v%&
3617 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3618 for &`-all`&. The reason for this is that &`+all`& is something that people
3619 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3620 is included, an awful lot of output that is very rarely of interest is
3621 generated, so it now has to be explicitly requested. However, &`-all`& does
3622 turn everything off.
3624 .cindex "resolver, debugging output"
3625 .cindex "DNS resolver, debugging output"
3626 The &`resolver`& option produces output only if the DNS resolver was compiled
3627 with DEBUG enabled. This is not the case in some operating systems. Also,
3628 unfortunately, debugging output from the DNS resolver is written to stdout
3631 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3632 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3633 However, the &`pid`& selector is forced when debugging is turned on for a
3634 daemon, which then passes it on to any re-executed Exims. Exim also
3635 automatically adds the pid to debug lines when several remote deliveries are
3638 The &`timestamp`& selector causes the current time to be inserted at the start
3639 of all debug output lines. This can be useful when trying to track down delays
3642 If the &%debug_print%& option is set in any driver, it produces output whenever
3643 any debugging is selected, or if &%-v%& is used.
3645 .vitem &%-dd%&<&'debug&~options'&>
3647 This option behaves exactly like &%-d%& except when used on a command that
3648 starts a daemon process. In that case, debugging is turned off for the
3649 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3650 behaviour of the daemon without creating as much output as full debugging does.
3653 .oindex "&%-dropcr%&"
3654 This is an obsolete option that is now a no-op. It used to affect the way Exim
3655 handled CR and LF characters in incoming messages. What happens now is
3656 described in section &<<SECTlineendings>>&.
3660 .cindex "bounce message" "generating"
3661 This option specifies that an incoming message is a locally-generated delivery
3662 failure report. It is used internally by Exim when handling delivery failures
3663 and is not intended for external use. Its only effect is to stop Exim
3664 generating certain messages to the postmaster, as otherwise message cascades
3665 could occur in some situations. As part of the same option, a message id may
3666 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3667 new message contains the id, following &"R="&, as a cross-reference.
3670 .oindex "&%-e%&&'x'&"
3671 There are a number of Sendmail options starting with &%-oe%& which seem to be
3672 called by various programs without the leading &%o%& in the option. For
3673 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3674 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3676 .vitem &%-F%&&~<&'string'&>
3678 .cindex "sender" "name"
3679 .cindex "name" "of sender"
3680 This option sets the sender's full name for use when a locally-generated
3681 message is being accepted. In the absence of this option, the user's &'gecos'&
3682 entry from the password data is used. As users are generally permitted to alter
3683 their &'gecos'& entries, no security considerations are involved. White space
3684 between &%-F%& and the <&'string'&> is optional.
3686 .vitem &%-f%&&~<&'address'&>
3688 .cindex "sender" "address"
3689 .cindex "address" "sender"
3690 .cindex "trusted users"
3691 .cindex "envelope sender"
3692 .cindex "user" "trusted"
3693 This option sets the address of the envelope sender of a locally-generated
3694 message (also known as the return path). The option can normally be used only
3695 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3698 Processes running as root or the Exim user are always trusted. Other
3699 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3700 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3701 of a local message is set to the caller's login name at the default qualify
3704 There is one exception to the restriction on the use of &%-f%&: an empty sender
3705 can be specified by any user, trusted or not, to create a message that can
3706 never provoke a bounce. An empty sender can be specified either as an empty
3707 string, or as a pair of angle brackets with nothing between them, as in these
3708 examples of shell commands:
3710 exim -f '<>' user@domain
3711 exim -f "" user@domain
3713 In addition, the use of &%-f%& is not restricted when testing a filter file
3714 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3717 Allowing untrusted users to change the sender address does not of itself make
3718 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3719 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3720 though this can be overridden by setting &%no_local_from_check%&.
3723 .cindex "&""From""& line"
3724 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3725 given as two arguments or one combined argument). The sender of a
3726 locally-generated message can also be set (when permitted) by an initial
3727 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3728 if &%-f%& is also present, it overrides &"From&~"&.
3732 .cindex "submission fixups, suppressing (command-line)"
3733 This option is equivalent to an ACL applying:
3735 control = suppress_local_fixups
3737 for every message received. Note that Sendmail will complain about such
3738 bad formatting, where Exim silently just does not fix it up. This may change
3741 As this affects audit information, the caller must be a trusted user to use
3744 .vitem &%-h%&&~<&'number'&>
3746 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3747 This option is accepted for compatibility with Sendmail, but has no effect. (In
3748 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3753 .cindex "Solaris" "&'mail'& command"
3754 .cindex "dot" "in incoming non-SMTP message"
3755 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3756 line by itself should not terminate an incoming, non-SMTP message. I can find
3757 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3758 command in Solaris 2.4 uses it. See also &%-ti%&.
3760 .vitem &%-L%&&~<&'tag'&>
3762 .cindex "syslog" "process name; set with flag"
3763 This option is equivalent to setting &%syslog_processname%& in the config
3764 file and setting &%log_file_path%& to &`syslog`&.
3765 Its use is restricted to administrators. The configuration file has to be
3766 read and parsed, to determine access rights, before this is set and takes
3767 effect, so early configuration file errors will not honour this flag.
3769 The tag should not be longer than 32 characters.
3771 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3773 .cindex "forcing delivery"
3774 .cindex "delivery" "forcing attempt"
3775 .cindex "frozen messages" "forcing delivery"
3776 This option requests Exim to run a delivery attempt on each message in turn. If
3777 any of the messages are frozen, they are automatically thawed before the
3778 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3779 and &%hold_domains%& are ignored.
3782 .cindex "hints database" "overriding retry hints"
3783 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3784 the normal retry time has not yet been reached. This option requires the caller
3785 to be an admin user. However, there is an option called &%prod_requires_admin%&
3786 which can be set false to relax this restriction (and also the same requirement
3787 for the &%-q%&, &%-R%&, and &%-S%& options).
3789 The deliveries happen synchronously, that is, the original Exim process does
3790 not terminate until all the delivery attempts have finished. No output is
3791 produced unless there is a serious error. If you want to see what is happening,
3792 use the &%-v%& option as well, or inspect Exim's main log.
3794 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3796 .cindex "message" "adding recipients"
3797 .cindex "recipient" "adding"
3798 This option requests Exim to add the addresses to the list of recipients of the
3799 message (&"ar"& for &"add recipients"&). The first argument must be a message
3800 id, and the remaining ones must be email addresses. However, if the message is
3801 active (in the middle of a delivery attempt), it is not altered. This option
3802 can be used only by an admin user.
3804 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3805 &~<&'message&~id'&>"
3807 .cindex "SMTP" "passed connection"
3808 .cindex "SMTP" "multiple deliveries"
3809 .cindex "multiple SMTP deliveries"
3810 This option is not intended for use by external callers. It is used internally
3811 by Exim to invoke another instance of itself to deliver a waiting message using
3812 an existing SMTP connection, which is passed as the standard input. Details are
3813 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3814 must be root or the Exim user in order to use it.
3818 This option is not intended for use by external callers. It is used internally
3819 by Exim in conjunction with the &%-MC%& option. It signifies that the
3820 connection to the remote host has been authenticated.
3824 This option is not intended for use by external callers. It is used internally
3825 by Exim in conjunction with the &%-MC%& option. It signifies that the
3826 remote host supports the ESMTP &_DSN_& extension.
3831 This option is not intended for use by external callers. It is used internally
3832 by Exim in conjunction with the &%-MC%& option. It signifies that an
3833 alternate queue is used, named by the following option.
3838 This option is not intended for use by external callers. It is used internally
3839 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3840 which Exim is connected supports pipelining.
3842 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3844 This option is not intended for use by external callers. It is used internally
3845 by Exim in conjunction with the &%-MC%& option when the original delivery was
3846 started by a queue runner. It passes on the process id of the queue runner,
3847 together with the file descriptor number of an open pipe. Closure of the pipe
3848 signals the final completion of the sequence of processes that are passing
3849 messages through the same SMTP connection.
3853 This option is not intended for use by external callers. It is used internally
3854 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3855 SMTP SIZE option should be used on messages delivered down the existing
3860 This option is not intended for use by external callers. It is used internally
3861 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3862 host to which Exim is connected supports TLS encryption.
3864 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3866 .cindex "hints database" "not overridden by &%-Mc%&"
3867 .cindex "delivery" "manually started &-- not forced"
3868 This option requests Exim to run a delivery attempt on each message in turn,
3869 but unlike the &%-M%& option, it does check for retry hints, and respects any
3870 that are found. This option is not very useful to external callers. It is
3871 provided mainly for internal use by Exim when it needs to re-invoke itself in
3872 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3873 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3874 respects retry times and other options such as &%hold_domains%& that are
3875 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3876 If you want to run a specific delivery as if in a queue run, you should use
3877 &%-q%& with a message id argument. A distinction between queue run deliveries
3878 and other deliveries is made in one or two places.
3880 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3882 .cindex "message" "changing sender"
3883 .cindex "sender" "changing"
3884 This option requests Exim to change the sender address in the message to the
3885 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3886 &"edit sender"&). There must be exactly two arguments. The first argument must
3887 be a message id, and the second one an email address. However, if the message
3888 is active (in the middle of a delivery attempt), its status is not altered.
3889 This option can be used only by an admin user.
3891 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3893 .cindex "freezing messages"
3894 .cindex "message" "manually freezing"
3895 This option requests Exim to mark each listed message as &"frozen"&. This
3896 prevents any delivery attempts taking place until the message is &"thawed"&,
3897 either manually or as a result of the &%auto_thaw%& configuration option.
3898 However, if any of the messages are active (in the middle of a delivery
3899 attempt), their status is not altered. This option can be used only by an admin
3902 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3904 .cindex "giving up on messages"
3905 .cindex "message" "abandoning delivery attempts"
3906 .cindex "delivery" "abandoning further attempts"
3907 This option requests Exim to give up trying to deliver the listed messages,
3908 including any that are frozen. However, if any of the messages are active,
3909 their status is not altered. For non-bounce messages, a delivery error message
3910 is sent to the sender, containing the text &"cancelled by administrator"&.
3911 Bounce messages are just discarded. This option can be used only by an admin
3914 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3916 .cindex "delivery" "cancelling all"
3917 This option requests Exim to mark all the recipient addresses in the messages
3918 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3919 message is active (in the middle of a delivery attempt), its status is not
3920 altered. This option can be used only by an admin user.
3922 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3924 .cindex "delivery" "cancelling by address"
3925 .cindex "recipient" "removing"
3926 .cindex "removing recipients"
3927 This option requests Exim to mark the given addresses as already delivered
3928 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3929 the remaining ones must be email addresses. These are matched to recipient
3930 addresses in the message in a case-sensitive manner. If the message is active
3931 (in the middle of a delivery attempt), its status is not altered. This option
3932 can be used only by an admin user.
3934 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3936 .cindex "removing messages"
3937 .cindex "abandoning mail"
3938 .cindex "message" "manually discarding"
3939 This option requests Exim to remove the given messages from the queue. No
3940 bounce messages are sent; each message is simply forgotten. However, if any of
3941 the messages are active, their status is not altered. This option can be used
3942 only by an admin user or by the user who originally caused the message to be
3943 placed on the queue.
3945 .vitem &%-Mset%&&~<&'message&~id'&>
3947 .cindex "testing" "string expansion"
3948 .cindex "expansion" "testing"
3949 This option is useful only in conjunction with &%-be%& (that is, when testing
3950 string expansions). Exim loads the given message from its spool before doing
3951 the test expansions, thus setting message-specific variables such as
3952 &$message_size$& and the header variables. The &$recipients$& variable is made
3953 available. This feature is provided to make it easier to test expansions that
3954 make use of these variables. However, this option can be used only by an admin
3955 user. See also &%-bem%&.
3957 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3959 .cindex "thawing messages"
3960 .cindex "unfreezing messages"
3961 .cindex "frozen messages" "thawing"
3962 .cindex "message" "thawing frozen"
3963 This option requests Exim to &"thaw"& any of the listed messages that are
3964 &"frozen"&, so that delivery attempts can resume. However, if any of the
3965 messages are active, their status is not altered. This option can be used only
3968 .vitem &%-Mvb%&&~<&'message&~id'&>
3970 .cindex "listing" "message body"
3971 .cindex "message" "listing body of"
3972 This option causes the contents of the message body (-D) spool file to be
3973 written to the standard output. This option can be used only by an admin user.
3975 .vitem &%-Mvc%&&~<&'message&~id'&>
3977 .cindex "message" "listing in RFC 2822 format"
3978 .cindex "listing" "message in RFC 2822 format"
3979 This option causes a copy of the complete message (header lines plus body) to
3980 be written to the standard output in RFC 2822 format. This option can be used
3981 only by an admin user.
3983 .vitem &%-Mvh%&&~<&'message&~id'&>
3985 .cindex "listing" "message headers"
3986 .cindex "header lines" "listing"
3987 .cindex "message" "listing header lines"
3988 This option causes the contents of the message headers (-H) spool file to be
3989 written to the standard output. This option can be used only by an admin user.
3991 .vitem &%-Mvl%&&~<&'message&~id'&>
3993 .cindex "listing" "message log"
3994 .cindex "message" "listing message log"
3995 This option causes the contents of the message log spool file to be written to
3996 the standard output. This option can be used only by an admin user.
4000 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4001 treats it that way too.
4005 .cindex "debugging" "&%-N%& option"
4006 .cindex "debugging" "suppressing delivery"
4007 This is a debugging option that inhibits delivery of a message at the transport
4008 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4009 it just doesn't actually transport the message, but instead behaves as if it
4010 had successfully done so. However, it does not make any updates to the retry
4011 database, and the log entries for deliveries are flagged with &"*>"& rather
4014 Because &%-N%& discards any message to which it applies, only root or the Exim
4015 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4016 words, an ordinary user can use it only when supplying an incoming message to
4017 which it will apply. Although transportation never fails when &%-N%& is set, an
4018 address may be deferred because of a configuration problem on a transport, or a
4019 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4020 the message, and applies to any subsequent delivery attempts that may happen
4025 This option is interpreted by Sendmail to mean &"no aliasing"&.
4026 For normal modes of operation, it is ignored by Exim.
4027 When combined with &%-bP%& it makes the output more terse (suppresses
4028 option names, environment values and config pretty printing).
4030 .vitem &%-O%&&~<&'data'&>
4032 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4035 .vitem &%-oA%&&~<&'file&~name'&>
4037 .cindex "Sendmail compatibility" "&%-oA%& option"
4038 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4039 alternative alias file name. Exim handles &%-bi%& differently; see the
4042 .vitem &%-oB%&&~<&'n'&>
4044 .cindex "SMTP" "passed connection"
4045 .cindex "SMTP" "multiple deliveries"
4046 .cindex "multiple SMTP deliveries"
4047 This is a debugging option which limits the maximum number of messages that can
4048 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4049 transport. If <&'n'&> is omitted, the limit is set to 1.
4053 .cindex "background delivery"
4054 .cindex "delivery" "in the background"
4055 This option applies to all modes in which Exim accepts incoming messages,
4056 including the listening daemon. It requests &"background"& delivery of such
4057 messages, which means that the accepting process automatically starts a
4058 delivery process for each message received, but does not wait for the delivery
4059 processes to finish.
4061 When all the messages have been received, the reception process exits,
4062 leaving the delivery processes to finish in their own time. The standard output
4063 and error streams are closed at the start of each delivery process.
4064 This is the default action if none of the &%-od%& options are present.
4066 If one of the queueing options in the configuration file
4067 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4068 overrides it if &%queue_only_override%& is set true, which is the default
4069 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4073 .cindex "foreground delivery"
4074 .cindex "delivery" "in the foreground"
4075 This option requests &"foreground"& (synchronous) delivery when Exim has
4076 accepted a locally-generated message. (For the daemon it is exactly the same as
4077 &%-odb%&.) A delivery process is automatically started to deliver the message,
4078 and Exim waits for it to complete before proceeding.
4080 The original Exim reception process does not finish until the delivery
4081 process for the final message has ended. The standard error stream is left open
4084 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4085 false and one of the queueing options in the configuration file is in effect.
4087 If there is a temporary delivery error during foreground delivery, the
4088 message is left on the queue for later delivery, and the original reception
4089 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4090 restricted configuration that never queues messages.
4095 This option is synonymous with &%-odf%&. It is provided for compatibility with
4100 .cindex "non-immediate delivery"
4101 .cindex "delivery" "suppressing immediate"
4102 .cindex "queueing incoming messages"
4103 This option applies to all modes in which Exim accepts incoming messages,
4104 including the listening daemon. It specifies that the accepting process should
4105 not automatically start a delivery process for each message received. Messages
4106 are placed on the queue, and remain there until a subsequent queue runner
4107 process encounters them. There are several configuration options (such as
4108 &%queue_only%&) that can be used to queue incoming messages under certain
4109 conditions. This option overrides all of them and also &%-odqs%&. It always
4114 .cindex "SMTP" "delaying delivery"
4115 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4116 However, like &%-odb%& and &%-odi%&, this option has no effect if
4117 &%queue_only_override%& is false and one of the queueing options in the
4118 configuration file is in effect.
4120 When &%-odqs%& does operate, a delivery process is started for each incoming
4121 message, in the background by default, but in the foreground if &%-odi%& is
4122 also present. The recipient addresses are routed, and local deliveries are done
4123 in the normal way. However, if any SMTP deliveries are required, they are not
4124 done at this time, so the message remains on the queue until a subsequent queue
4125 runner process encounters it. Because routing was done, Exim knows which
4126 messages are waiting for which hosts, and so a number of messages for the same
4127 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4128 configuration option has the same effect for specific domains. See also the
4133 .cindex "error" "reporting"
4134 If an error is detected while a non-SMTP message is being received (for
4135 example, a malformed address), the error is reported to the sender in a mail
4138 .cindex "return code" "for &%-oee%&"
4140 this error message is successfully sent, the Exim receiving process
4141 exits with a return code of zero. If not, the return code is 2 if the problem
4142 is that the original message has no recipients, or 1 for any other error.
4143 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4147 .cindex "error" "reporting"
4148 .cindex "return code" "for &%-oem%&"
4149 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4150 return code, whether or not the error message was successfully sent.
4151 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4155 .cindex "error" "reporting"
4156 If an error is detected while a non-SMTP message is being received, the
4157 error is reported by writing a message to the standard error file (stderr).
4158 .cindex "return code" "for &%-oep%&"
4159 The return code is 1 for all errors.
4163 .cindex "error" "reporting"
4164 This option is supported for compatibility with Sendmail, but has the same
4169 .cindex "error" "reporting"
4170 This option is supported for compatibility with Sendmail, but has the same
4175 .cindex "dot" "in incoming non-SMTP message"
4176 This option, which has the same effect as &%-i%&, specifies that a dot on a
4177 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4178 single dot does terminate, though Exim does no special processing for other
4179 lines that start with a dot. This option is set by default if Exim is called as
4180 &'rmail'&. See also &%-ti%&.
4183 .oindex "&%-oitrue%&"
4184 This option is treated as synonymous with &%-oi%&.
4186 .vitem &%-oMa%&&~<&'host&~address'&>
4188 .cindex "sender" "host address, specifying for local message"
4189 A number of options starting with &%-oM%& can be used to set values associated
4190 with remote hosts on locally-submitted messages (that is, messages not received
4191 over TCP/IP). These options can be used by any caller in conjunction with the
4192 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4193 other circumstances, they are ignored unless the caller is trusted.
4195 The &%-oMa%& option sets the sender host address. This may include a port
4196 number at the end, after a full stop (period). For example:
4198 exim -bs -oMa 10.9.8.7.1234
4200 An alternative syntax is to enclose the IP address in square brackets,
4201 followed by a colon and the port number:
4203 exim -bs -oMa [10.9.8.7]:1234
4205 The IP address is placed in the &$sender_host_address$& variable, and the
4206 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4207 are present on the command line, the sender host IP address is taken from
4208 whichever one is last.
4210 .vitem &%-oMaa%&&~<&'name'&>
4212 .cindex "authentication" "name, specifying for local message"
4213 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4214 option sets the value of &$sender_host_authenticated$& (the authenticator
4215 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4216 This option can be used with &%-bh%& and &%-bs%& to set up an
4217 authenticated SMTP session without actually using the SMTP AUTH command.
4219 .vitem &%-oMai%&&~<&'string'&>
4221 .cindex "authentication" "id, specifying for local message"
4222 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4223 option sets the value of &$authenticated_id$& (the id that was authenticated).
4224 This overrides the default value (the caller's login id, except with &%-bh%&,
4225 where there is no default) for messages from local sources. See chapter
4226 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4228 .vitem &%-oMas%&&~<&'address'&>
4230 .cindex "authentication" "sender, specifying for local message"
4231 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4232 option sets the authenticated sender value in &$authenticated_sender$&. It
4233 overrides the sender address that is created from the caller's login id for
4234 messages from local sources, except when &%-bh%& is used, when there is no
4235 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4236 specified on a MAIL command overrides this value. See chapter
4237 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4239 .vitem &%-oMi%&&~<&'interface&~address'&>
4241 .cindex "interface" "address, specifying for local message"
4242 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4243 option sets the IP interface address value. A port number may be included,
4244 using the same syntax as for &%-oMa%&. The interface address is placed in
4245 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4247 .vitem &%-oMm%&&~<&'message&~reference'&>
4249 .cindex "message reference" "message reference, specifying for local message"
4250 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4251 option sets the message reference, e.g. message-id, and is logged during
4252 delivery. This is useful when some kind of audit trail is required to tie
4253 messages together. The format of the message reference is checked and will
4254 abort if the format is invalid. The option will only be accepted if exim is
4255 running in trusted mode, not as any regular user.
4257 The best example of a message reference is when Exim sends a bounce message.
4258 The message reference is the message-id of the original message for which Exim
4259 is sending the bounce.
4261 .vitem &%-oMr%&&~<&'protocol&~name'&>
4263 .cindex "protocol, specifying for local message"
4264 .vindex "&$received_protocol$&"
4265 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4266 option sets the received protocol value that is stored in
4267 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4268 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4269 SMTP protocol names (see the description of &$received_protocol$& in section
4270 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4271 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4274 .vitem &%-oMs%&&~<&'host&~name'&>
4276 .cindex "sender" "host name, specifying for local message"
4277 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4278 option sets the sender host name in &$sender_host_name$&. When this option is
4279 present, Exim does not attempt to look up a host name from an IP address; it
4280 uses the name it is given.
4282 .vitem &%-oMt%&&~<&'ident&~string'&>
4284 .cindex "sender" "ident string, specifying for local message"
4285 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4286 option sets the sender ident value in &$sender_ident$&. The default setting for
4287 local callers is the login id of the calling process, except when &%-bh%& is
4288 used, when there is no default.
4292 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4293 In Sendmail, this option means &"me too"&, indicating that the sender of a
4294 message should receive a copy of the message if the sender appears in an alias
4295 expansion. Exim always does this, so the option does nothing.
4299 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4300 This option is ignored. In Sendmail it specifies &"old style headers"&,
4301 whatever that means.
4303 .vitem &%-oP%&&~<&'path'&>
4305 .cindex "pid (process id)" "of daemon"
4306 .cindex "daemon" "process id (pid)"
4307 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4308 value. The option specifies the file to which the process id of the daemon is
4309 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4310 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4311 because in those cases, the normal pid file is not used.
4313 .vitem &%-or%&&~<&'time'&>
4315 .cindex "timeout" "for non-SMTP input"
4316 This option sets a timeout value for incoming non-SMTP messages. If it is not
4317 set, Exim will wait forever for the standard input. The value can also be set
4318 by the &%receive_timeout%& option. The format used for specifying times is
4319 described in section &<<SECTtimeformat>>&.
4321 .vitem &%-os%&&~<&'time'&>
4323 .cindex "timeout" "for SMTP input"
4324 .cindex "SMTP" "input timeout"
4325 This option sets a timeout value for incoming SMTP messages. The timeout
4326 applies to each SMTP command and block of data. The value can also be set by
4327 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4328 for specifying times is described in section &<<SECTtimeformat>>&.
4332 This option has exactly the same effect as &%-v%&.
4334 .vitem &%-oX%&&~<&'number&~or&~string'&>
4336 .cindex "TCP/IP" "setting listening ports"
4337 .cindex "TCP/IP" "setting listening interfaces"
4338 .cindex "port" "receiving TCP/IP"
4339 This option is relevant only when the &%-bd%& (start listening daemon) option
4340 is also given. It controls which ports and interfaces the daemon uses. Details
4341 of the syntax, and how it interacts with configuration file options, are given
4342 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4343 file is written unless &%-oP%& is also present to specify a pid file name.
4347 .cindex "Perl" "starting the interpreter"
4348 This option applies when an embedded Perl interpreter is linked with Exim (see
4349 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4350 option, forcing the starting of the interpreter to be delayed until it is
4355 .cindex "Perl" "starting the interpreter"
4356 This option applies when an embedded Perl interpreter is linked with Exim (see
4357 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4358 option, forcing the starting of the interpreter to occur as soon as Exim is
4361 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4363 For compatibility with Sendmail, this option is equivalent to
4365 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4367 It sets the incoming protocol and host name (for trusted callers). The
4368 host name and its colon can be omitted when only the protocol is to be set.
4369 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4370 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4371 or &`s`& using this option (but that does not seem a real limitation).
4375 .cindex "queue runner" "starting manually"
4376 This option is normally restricted to admin users. However, there is a
4377 configuration option called &%prod_requires_admin%& which can be set false to
4378 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4379 and &%-S%& options).
4381 .cindex "queue runner" "description of operation"
4383 If other commandline options do not specify an action,
4385 the &%-q%& option starts one queue runner process. This scans the queue of
4386 waiting messages, and runs a delivery process for each one in turn. It waits
4387 for each delivery process to finish before starting the next one. A delivery
4388 process may not actually do any deliveries if the retry times for the addresses
4389 have not been reached. Use &%-qf%& (see below) if you want to override this.
4392 .cindex "SMTP" "passed connection"
4393 .cindex "SMTP" "multiple deliveries"
4394 .cindex "multiple SMTP deliveries"
4395 the delivery process spawns other processes to deliver other messages down
4396 passed SMTP connections, the queue runner waits for these to finish before
4399 When all the queued messages have been considered, the original queue runner
4400 process terminates. In other words, a single pass is made over the waiting
4401 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4402 this to be repeated periodically.
4404 Exim processes the waiting messages in an unpredictable order. It isn't very
4405 random, but it is likely to be different each time, which is all that matters.
4406 If one particular message screws up a remote MTA, other messages to the same
4407 MTA have a chance of getting through if they get tried first.
4409 It is possible to cause the messages to be processed in lexical message id
4410 order, which is essentially the order in which they arrived, by setting the
4411 &%queue_run_in_order%& option, but this is not recommended for normal use.
4413 .vitem &%-q%&<&'qflags'&>
4414 The &%-q%& option may be followed by one or more flag letters that change its
4415 behaviour. They are all optional, but if more than one is present, they must
4416 appear in the correct order. Each flag is described in a separate item below.
4420 .cindex "queue" "double scanning"
4421 .cindex "queue" "routing"
4422 .cindex "routing" "whole queue before delivery"
4423 An option starting with &%-qq%& requests a two-stage queue run. In the first
4424 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4425 every domain. Addresses are routed, local deliveries happen, but no remote
4428 .cindex "hints database" "remembering routing"
4429 The hints database that remembers which messages are waiting for specific hosts
4430 is updated, as if delivery to those hosts had been deferred. After this is
4431 complete, a second, normal queue scan happens, with routing and delivery taking
4432 place as normal. Messages that are routed to the same host should mostly be
4433 delivered down a single SMTP
4434 .cindex "SMTP" "passed connection"
4435 .cindex "SMTP" "multiple deliveries"
4436 .cindex "multiple SMTP deliveries"
4437 connection because of the hints that were set up during the first queue scan.
4438 This option may be useful for hosts that are connected to the Internet
4441 .vitem &%-q[q]i...%&
4443 .cindex "queue" "initial delivery"
4444 If the &'i'& flag is present, the queue runner runs delivery processes only for
4445 those messages that haven't previously been tried. (&'i'& stands for &"initial
4446 delivery"&.) This can be helpful if you are putting messages on the queue using
4447 &%-odq%& and want a queue runner just to process the new messages.
4449 .vitem &%-q[q][i]f...%&
4451 .cindex "queue" "forcing delivery"
4452 .cindex "delivery" "forcing in queue run"
4453 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4454 message, whereas without &'f'& only those non-frozen addresses that have passed
4455 their retry times are tried.
4457 .vitem &%-q[q][i]ff...%&
4459 .cindex "frozen messages" "forcing delivery"
4460 If &'ff'& is present, a delivery attempt is forced for every message, whether
4463 .vitem &%-q[q][i][f[f]]l%&
4465 .cindex "queue" "local deliveries only"
4466 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4467 be done. If a message requires any remote deliveries, it remains on the queue
4471 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4474 .cindex "named queues"
4475 .cindex "queue" "delivering specific messages"
4476 If the &'G'& flag and a name is present, the queue runner operates on the
4477 queue with the given name rather than the default queue.
4478 The name should not contain a &'/'& character.
4479 For a periodic queue run (see below)
4480 append to the name a slash and a time value.
4482 If other commandline options speicify an action, a &'-qG<name>'& option
4483 will specify a queue to operate on.
4486 exim -bp -qGquarantine
4488 exim -qGoffpeak -Rf @special.domain.example
4492 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4493 When scanning the queue, Exim can be made to skip over messages whose ids are
4494 lexically less than a given value by following the &%-q%& option with a
4495 starting message id. For example:
4497 exim -q 0t5C6f-0000c8-00
4499 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4500 second message id is given, messages whose ids are lexically greater than it
4501 are also skipped. If the same id is given twice, for example,
4503 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4505 just one delivery process is started, for that message. This differs from
4506 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4507 that it counts as a delivery from a queue run. Note that the selection
4508 mechanism does not affect the order in which the messages are scanned. There
4509 are also other ways of selecting specific sets of messages for delivery in a
4510 queue run &-- see &%-R%& and &%-S%&.
4512 .vitem &%-q%&<&'qflags'&><&'time'&>
4513 .cindex "queue runner" "starting periodically"
4514 .cindex "periodic queue running"
4515 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4516 starting a queue runner process at intervals specified by the given time value
4517 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4518 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4519 single daemon process handles both functions. A common way of starting up a
4520 combined daemon at system boot time is to use a command such as
4522 /usr/exim/bin/exim -bd -q30m
4524 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4525 process every 30 minutes.
4527 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4528 pid file is written unless one is explicitly requested by the &%-oP%& option.
4530 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4532 This option is synonymous with &%-R%&. It is provided for Sendmail
4535 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4537 This option is synonymous with &%-S%&.
4539 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4541 .cindex "queue runner" "for specific recipients"
4542 .cindex "delivery" "to given domain"
4543 .cindex "domain" "delivery to"
4544 The <&'rsflags'&> may be empty, in which case the white space before the string
4545 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4546 which are the possible values for <&'rsflags'&>. White space is required if
4547 <&'rsflags'&> is not empty.
4549 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4550 perform a single queue run, except that, when scanning the messages on the
4551 queue, Exim processes only those that have at least one undelivered recipient
4552 address containing the given string, which is checked in a case-independent
4553 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4554 regular expression; otherwise it is a literal string.
4556 If you want to do periodic queue runs for messages with specific recipients,
4557 you can combine &%-R%& with &%-q%& and a time value. For example:
4559 exim -q25m -R @special.domain.example
4561 This example does a queue run for messages with recipients in the given domain
4562 every 25 minutes. Any additional flags that are specified with &%-q%& are
4563 applied to each queue run.
4565 Once a message is selected for delivery by this mechanism, all its addresses
4566 are processed. For the first selected message, Exim overrides any retry
4567 information and forces a delivery attempt for each undelivered address. This
4568 means that if delivery of any address in the first message is successful, any
4569 existing retry information is deleted, and so delivery attempts for that
4570 address in subsequently selected messages (which are processed without forcing)
4571 will run. However, if delivery of any address does not succeed, the retry
4572 information is updated, and in subsequently selected messages, the failing
4573 address will be skipped.
4575 .cindex "frozen messages" "forcing delivery"
4576 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4577 all selected messages, not just the first; frozen messages are included when
4580 The &%-R%& option makes it straightforward to initiate delivery of all messages
4581 to a given domain after a host has been down for some time. When the SMTP
4582 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4583 effect is to run Exim with the &%-R%& option, but it can be configured to run
4584 an arbitrary command instead.
4588 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4590 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4592 .cindex "delivery" "from given sender"
4593 .cindex "queue runner" "for specific senders"
4594 This option acts like &%-R%& except that it checks the string against each
4595 message's sender instead of against the recipients. If &%-R%& is also set, both
4596 conditions must be met for a message to be selected. If either of the options
4597 has &'f'& or &'ff'& in its flags, the associated action is taken.
4599 .vitem &%-Tqt%&&~<&'times'&>
4601 This is an option that is exclusively for use by the Exim testing suite. It is not
4602 recognized when Exim is run normally. It allows for the setting up of explicit
4603 &"queue times"& so that various warning/retry features can be tested.
4607 .cindex "recipient" "extracting from header lines"
4608 .cindex "&'Bcc:'& header line"
4609 .cindex "&'Cc:'& header line"
4610 .cindex "&'To:'& header line"
4611 When Exim is receiving a locally-generated, non-SMTP message on its standard
4612 input, the &%-t%& option causes the recipients of the message to be obtained
4613 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4614 from the command arguments. The addresses are extracted before any rewriting
4615 takes place and the &'Bcc:'& header line, if present, is then removed.
4617 .cindex "Sendmail compatibility" "&%-t%& option"
4618 If the command has any arguments, they specify addresses to which the message
4619 is &'not'& to be delivered. That is, the argument addresses are removed from
4620 the recipients list obtained from the headers. This is compatible with Smail 3
4621 and in accordance with the documented behaviour of several versions of
4622 Sendmail, as described in man pages on a number of operating systems (e.g.
4623 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4624 argument addresses to those obtained from the headers, and the O'Reilly
4625 Sendmail book documents it that way. Exim can be made to add argument addresses
4626 instead of subtracting them by setting the option
4627 &%extract_addresses_remove_arguments%& false.
4629 .cindex "&%Resent-%& header lines" "with &%-t%&"
4630 If there are any &%Resent-%& header lines in the message, Exim extracts
4631 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4632 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4633 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4634 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4636 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4637 message is resent several times). The RFC also specifies that they should be
4638 added at the front of the message, and separated by &'Received:'& lines. It is
4639 not at all clear how &%-t%& should operate in the present of multiple sets,
4640 nor indeed exactly what constitutes a &"set"&.
4641 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4642 are often added at the end of the header, and if a message is resent more than
4643 once, it is common for the original set of &%Resent-%& headers to be renamed as
4644 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4648 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4649 compatibility with Sendmail.
4651 .vitem &%-tls-on-connect%&
4652 .oindex "&%-tls-on-connect%&"
4653 .cindex "TLS" "use without STARTTLS"
4654 .cindex "TLS" "automatic start"
4655 This option is available when Exim is compiled with TLS support. It forces all
4656 incoming SMTP connections to behave as if the incoming port is listed in the
4657 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4658 &<<CHAPTLS>>& for further details.
4663 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4664 Sendmail uses this option for &"initial message submission"&, and its
4665 documentation states that in future releases, it may complain about
4666 syntactically invalid messages rather than fixing them when this flag is not
4667 set. Exim ignores this option.
4671 This option causes Exim to write information to the standard error stream,
4672 describing what it is doing. In particular, it shows the log lines for
4673 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4674 dialogue is shown. Some of the log lines shown may not actually be written to
4675 the log if the setting of &%log_selector%& discards them. Any relevant
4676 selectors are shown with each log line. If none are shown, the logging is
4681 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4682 National Language Support extended characters in the body of the mail item"&).
4683 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4686 .vitem &%-X%&&~<&'logfile'&>
4688 This option is interpreted by Sendmail to cause debug information to be sent
4689 to the named file. It is ignored by Exim.
4691 .vitem &%-z%&&~<&'log-line'&>
4693 This option writes its argument to Exim's logfile.
4694 Use is restricted to administrators; the intent is for operational notes.
4695 Quotes should be used to maintain a multi-word item as a single argument,
4703 . ////////////////////////////////////////////////////////////////////////////
4704 . Insert a stylized DocBook comment here, to identify the end of the command
4705 . line options. This is for the benefit of the Perl script that automatically
4706 . creates a man page for the options.
4707 . ////////////////////////////////////////////////////////////////////////////
4710 <!-- === End of command line options === -->
4717 . ////////////////////////////////////////////////////////////////////////////
4718 . ////////////////////////////////////////////////////////////////////////////
4721 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4722 "The runtime configuration file"
4724 .cindex "run time configuration"
4725 .cindex "configuration file" "general description"
4726 .cindex "CONFIGURE_FILE"
4727 .cindex "configuration file" "errors in"
4728 .cindex "error" "in configuration file"
4729 .cindex "return code" "for bad configuration"
4730 Exim uses a single run time configuration file that is read whenever an Exim
4731 binary is executed. Note that in normal operation, this happens frequently,
4732 because Exim is designed to operate in a distributed manner, without central
4735 If a syntax error is detected while reading the configuration file, Exim
4736 writes a message on the standard error, and exits with a non-zero return code.
4737 The message is also written to the panic log. &*Note*&: Only simple syntax
4738 errors can be detected at this time. The values of any expanded options are
4739 not checked until the expansion happens, even when the expansion does not
4740 actually alter the string.
4742 The name of the configuration file is compiled into the binary for security
4743 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4744 most configurations, this specifies a single file. However, it is permitted to
4745 give a colon-separated list of file names, in which case Exim uses the first
4746 existing file in the list.
4749 .cindex "EXIM_GROUP"
4750 .cindex "CONFIGURE_OWNER"
4751 .cindex "CONFIGURE_GROUP"
4752 .cindex "configuration file" "ownership"
4753 .cindex "ownership" "configuration file"
4754 The run time configuration file must be owned by root or by the user that is
4755 specified at compile time by the CONFIGURE_OWNER option (if set). The
4756 configuration file must not be world-writeable, or group-writeable unless its
4757 group is the root group or the one specified at compile time by the
4758 CONFIGURE_GROUP option.
4760 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4761 to root, anybody who is able to edit the run time configuration file has an
4762 easy way to run commands as root. If you specify a user or group in the
4763 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4764 who are members of that group will trivially be able to obtain root privileges.
4766 Up to Exim version 4.72, the run time configuration file was also permitted to
4767 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4768 since it offered a simple privilege escalation for any attacker who managed to
4769 compromise the Exim user account.
4771 A default configuration file, which will work correctly in simple situations,
4772 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4773 defines just one file name, the installation process copies the default
4774 configuration to a new file of that name if it did not previously exist. If
4775 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4776 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4781 .section "Using a different configuration file" "SECID40"
4782 .cindex "configuration file" "alternate"
4783 A one-off alternate configuration can be specified by the &%-C%& command line
4784 option, which may specify a single file or a list of files. However, when
4785 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4786 unless the argument for &%-C%& is identical to the built-in value from
4787 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4788 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4789 is useful mainly for checking the syntax of configuration files before
4790 installing them. No owner or group checks are done on a configuration file
4791 specified by &%-C%&, if root privilege has been dropped.
4793 Even the Exim user is not trusted to specify an arbitrary configuration file
4794 with the &%-C%& option to be used with root privileges, unless that file is
4795 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4796 testing a configuration using &%-C%& right through message reception and
4797 delivery, even if the caller is root. The reception works, but by that time,
4798 Exim is running as the Exim user, so when it re-execs to regain privilege for
4799 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4800 can test reception and delivery using two separate commands (one to put a
4801 message on the queue, using &%-odq%&, and another to do the delivery, using
4804 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4805 prefix string with which any file named in a &%-C%& command line option must
4806 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4807 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4808 name can be used with &%-C%&.
4810 One-off changes to a configuration can be specified by the &%-D%& command line
4811 option, which defines and overrides values for macros used inside the
4812 configuration file. However, like &%-C%&, the use of this option by a
4813 non-privileged user causes Exim to discard its root privilege.
4814 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4815 completely disabled, and its use causes an immediate error exit.
4817 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4818 to declare certain macro names trusted, such that root privilege will not
4819 necessarily be discarded.
4820 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4821 considered safe and, if &%-D%& only supplies macros from this list, and the
4822 values are acceptable, then Exim will not give up root privilege if the caller
4823 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4824 transition mechanism and is expected to be removed in the future. Acceptable
4825 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4827 Some sites may wish to use the same Exim binary on different machines that
4828 share a file system, but to use different configuration files on each machine.
4829 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4830 looks for a file whose name is the configuration file name followed by a dot
4831 and the machine's node name, as obtained from the &[uname()]& function. If this
4832 file does not exist, the standard name is tried. This processing occurs for
4833 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4835 In some esoteric situations different versions of Exim may be run under
4836 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4837 help with this. See the comments in &_src/EDITME_& for details.
4841 .section "Configuration file format" "SECTconffilfor"
4842 .cindex "configuration file" "format of"
4843 .cindex "format" "configuration file"
4844 Exim's configuration file is divided into a number of different parts. General
4845 option settings must always appear at the start of the file. The other parts
4846 are all optional, and may appear in any order. Each part other than the first
4847 is introduced by the word &"begin"& followed by at least one literal
4848 space, and the name of the part. The optional parts are:
4851 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4854 .cindex "AUTH" "configuration"
4855 &'authenticators'&: Configuration settings for the authenticator drivers. These
4856 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4858 &'routers'&: Configuration settings for the router drivers. Routers process
4859 addresses and determine how the message is to be delivered (see chapters
4860 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4862 &'transports'&: Configuration settings for the transport drivers. Transports
4863 define mechanisms for copying messages to destinations (see chapters
4864 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4866 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4867 If there is no retry section, or if it is empty (that is, no retry rules are
4868 defined), Exim will not retry deliveries. In this situation, temporary errors
4869 are treated the same as permanent errors. Retry rules are discussed in chapter
4872 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4873 when new addresses are generated during delivery. Rewriting is discussed in
4874 chapter &<<CHAPrewrite>>&.
4876 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4877 want to use this feature, you must set
4879 LOCAL_SCAN_HAS_OPTIONS=yes
4881 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4882 facility are given in chapter &<<CHAPlocalscan>>&.
4885 .cindex "configuration file" "leading white space in"
4886 .cindex "configuration file" "trailing white space in"
4887 .cindex "white space" "in configuration file"
4888 Leading and trailing white space in configuration lines is always ignored.
4890 Blank lines in the file, and lines starting with a # character (ignoring
4891 leading white space) are treated as comments and are ignored. &*Note*&: A
4892 # character other than at the beginning of a line is not treated specially,
4893 and does not introduce a comment.
4895 Any non-comment line can be continued by ending it with a backslash. Note that
4896 the general rule for white space means that trailing white space after the
4897 backslash and leading white space at the start of continuation
4898 lines is ignored. Comment lines beginning with # (but not empty lines) may
4899 appear in the middle of a sequence of continuation lines.
4901 A convenient way to create a configuration file is to start from the
4902 default, which is supplied in &_src/configure.default_&, and add, delete, or
4903 change settings as required.
4905 The ACLs, retry rules, and rewriting rules have their own syntax which is
4906 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4907 respectively. The other parts of the configuration file have some syntactic
4908 items in common, and these are described below, from section &<<SECTcos>>&
4909 onwards. Before that, the inclusion, macro, and conditional facilities are
4914 .section "File inclusions in the configuration file" "SECID41"
4915 .cindex "inclusions in configuration file"
4916 .cindex "configuration file" "including other files"
4917 .cindex "&`.include`& in configuration file"
4918 .cindex "&`.include_if_exists`& in configuration file"
4919 You can include other files inside Exim's run time configuration file by
4922 &`.include`& <&'file name'&>
4923 &`.include_if_exists`& <&'file name'&>
4925 on a line by itself. Double quotes round the file name are optional. If you use
4926 the first form, a configuration error occurs if the file does not exist; the
4927 second form does nothing for non-existent files. In all cases, an absolute file
4930 Includes may be nested to any depth, but remember that Exim reads its
4931 configuration file often, so it is a good idea to keep them to a minimum.
4932 If you change the contents of an included file, you must HUP the daemon,
4933 because an included file is read only when the configuration itself is read.
4935 The processing of inclusions happens early, at a physical line level, so, like
4936 comment lines, an inclusion can be used in the middle of an option setting,
4939 hosts_lookup = a.b.c \
4942 Include processing happens after macro processing (see below). Its effect is to
4943 process the lines of the included file as if they occurred inline where the
4948 .section "Macros in the configuration file" "SECTmacrodefs"
4949 .cindex "macro" "description of"
4950 .cindex "configuration file" "macros"
4951 If a line in the main part of the configuration (that is, before the first
4952 &"begin"& line) begins with an upper case letter, it is taken as a macro
4953 definition, and must be of the form
4955 <&'name'&> = <&'rest of line'&>
4957 The name must consist of letters, digits, and underscores, and need not all be
4958 in upper case, though that is recommended. The rest of the line, including any
4959 continuations, is the replacement text, and has leading and trailing white
4960 space removed. Quotes are not removed. The replacement text can never end with
4961 a backslash character, but this doesn't seem to be a serious limitation.
4963 Macros may also be defined between router, transport, authenticator, or ACL
4964 definitions. They may not, however, be defined within an individual driver or
4965 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4967 .section "Macro substitution" "SECID42"
4968 Once a macro is defined, all subsequent lines in the file (and any included
4969 files) are scanned for the macro name; if there are several macros, the line is
4970 scanned for each in turn, in the order in which the macros are defined. The
4971 replacement text is not re-scanned for the current macro, though it is scanned
4972 for subsequently defined macros. For this reason, a macro name may not contain
4973 the name of a previously defined macro as a substring. You could, for example,
4976 &`ABCD_XYZ = `&<&'something'&>
4977 &`ABCD = `&<&'something else'&>
4979 but putting the definitions in the opposite order would provoke a configuration
4980 error. Macro expansion is applied to individual physical lines from the file,
4981 before checking for line continuation or file inclusion (see above). If a line
4982 consists solely of a macro name, and the expansion of the macro is empty, the
4983 line is ignored. A macro at the start of a line may turn the line into a
4984 comment line or a &`.include`& line.
4987 .section "Redefining macros" "SECID43"
4988 Once defined, the value of a macro can be redefined later in the configuration
4989 (or in an included file). Redefinition is specified by using &'=='& instead of
4994 MAC == updated value
4996 Redefinition does not alter the order in which the macros are applied to the
4997 subsequent lines of the configuration file. It is still the same order in which
4998 the macros were originally defined. All that changes is the macro's value.
4999 Redefinition makes it possible to accumulate values. For example:
5003 MAC == MAC and something added
5005 This can be helpful in situations where the configuration file is built
5006 from a number of other files.
5008 .section "Overriding macro values" "SECID44"
5009 The values set for macros in the configuration file can be overridden by the
5010 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5011 used, unless called by root or the Exim user. A definition on the command line
5012 using the &%-D%& option causes all definitions and redefinitions within the
5017 .section "Example of macro usage" "SECID45"
5018 As an example of macro usage, consider a configuration where aliases are looked
5019 up in a MySQL database. It helps to keep the file less cluttered if long
5020 strings such as SQL statements are defined separately as macros, for example:
5022 ALIAS_QUERY = select mailbox from user where \
5023 login='${quote_mysql:$local_part}';
5025 This can then be used in a &(redirect)& router setting like this:
5027 data = ${lookup mysql{ALIAS_QUERY}}
5029 In earlier versions of Exim macros were sometimes used for domain, host, or
5030 address lists. In Exim 4 these are handled better by named lists &-- see
5031 section &<<SECTnamedlists>>&.
5034 .section "Conditional skips in the configuration file" "SECID46"
5035 .cindex "configuration file" "conditional skips"
5036 .cindex "&`.ifdef`&"
5037 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5038 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5039 portions of the configuration file. The processing happens whenever the file is
5040 read (that is, when an Exim binary starts to run).
5042 The implementation is very simple. Instances of the first four directives must
5043 be followed by text that includes the names of one or macros. The condition
5044 that is tested is whether or not any macro substitution has taken place in the
5048 message_size_limit = 50M
5050 message_size_limit = 100M
5053 sets a message size limit of 50M if the macro &`AAA`& is defined
5054 (or &`A`& or &`AA`&), and 100M
5055 otherwise. If there is more than one macro named on the line, the condition
5056 is true if any of them are defined. That is, it is an &"or"& condition. To
5057 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5059 Although you can use a macro expansion to generate one of these directives,
5060 it is not very useful, because the condition &"there was a macro substitution
5061 in this line"& will always be true.
5063 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5064 to clarify complicated nestings.
5068 .section "Common option syntax" "SECTcos"
5069 .cindex "common option syntax"
5070 .cindex "syntax of common options"
5071 .cindex "configuration file" "common option syntax"
5072 For the main set of options, driver options, and &[local_scan()]& options,
5073 each setting is on a line by itself, and starts with a name consisting of
5074 lower-case letters and underscores. Many options require a data value, and in
5075 these cases the name must be followed by an equals sign (with optional white
5076 space) and then the value. For example:
5078 qualify_domain = mydomain.example.com
5080 .cindex "hiding configuration option values"
5081 .cindex "configuration options" "hiding value of"
5082 .cindex "options" "hiding value of"
5083 Some option settings may contain sensitive data, for example, passwords for
5084 accessing databases. To stop non-admin users from using the &%-bP%& command
5085 line option to read these values, you can precede the option settings with the
5086 word &"hide"&. For example:
5088 hide mysql_servers = localhost/users/admin/secret-password
5090 For non-admin users, such options are displayed like this:
5092 mysql_servers = <value not displayable>
5094 If &"hide"& is used on a driver option, it hides the value of that option on
5095 all instances of the same driver.
5097 The following sections describe the syntax used for the different data types
5098 that are found in option settings.
5101 .section "Boolean options" "SECID47"
5102 .cindex "format" "boolean"
5103 .cindex "boolean configuration values"
5104 .oindex "&%no_%&&'xxx'&"
5105 .oindex "&%not_%&&'xxx'&"
5106 Options whose type is given as boolean are on/off switches. There are two
5107 different ways of specifying such options: with and without a data value. If
5108 the option name is specified on its own without data, the switch is turned on;
5109 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5110 boolean options may be followed by an equals sign and one of the words
5111 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5112 the following two settings have exactly the same effect:
5117 The following two lines also have the same (opposite) effect:
5122 You can use whichever syntax you prefer.
5127 .section "Integer values" "SECID48"
5128 .cindex "integer configuration values"
5129 .cindex "format" "integer"
5130 If an option's type is given as &"integer"&, the value can be given in decimal,
5131 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5132 number is assumed. Otherwise, it is treated as an octal number unless it starts
5133 with the characters &"0x"&, in which case the remainder is interpreted as a
5136 If an integer value is followed by the letter K, it is multiplied by 1024; if
5137 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5138 of integer option settings are output, values which are an exact multiple of
5139 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5140 and M. The printing style is independent of the actual input format that was
5144 .section "Octal integer values" "SECID49"
5145 .cindex "integer format"
5146 .cindex "format" "octal integer"
5147 If an option's type is given as &"octal integer"&, its value is always
5148 interpreted as an octal number, whether or not it starts with the digit zero.
5149 Such options are always output in octal.
5152 .section "Fixed point numbers" "SECID50"
5153 .cindex "fixed point configuration values"
5154 .cindex "format" "fixed point"
5155 If an option's type is given as &"fixed-point"&, its value must be a decimal
5156 integer, optionally followed by a decimal point and up to three further digits.
5160 .section "Time intervals" "SECTtimeformat"
5161 .cindex "time interval" "specifying in configuration"
5162 .cindex "format" "time interval"
5163 A time interval is specified as a sequence of numbers, each followed by one of
5164 the following letters, with no intervening white space:
5174 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5175 intervals are output in the same format. Exim does not restrict the values; it
5176 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5180 .section "String values" "SECTstrings"
5181 .cindex "string" "format of configuration values"
5182 .cindex "format" "string"
5183 If an option's type is specified as &"string"&, the value can be specified with
5184 or without double-quotes. If it does not start with a double-quote, the value
5185 consists of the remainder of the line plus any continuation lines, starting at
5186 the first character after any leading white space, with trailing white space
5187 removed, and with no interpretation of the characters in the string. Because
5188 Exim removes comment lines (those beginning with #) at an early stage, they can
5189 appear in the middle of a multi-line string. The following two settings are
5190 therefore equivalent:
5192 trusted_users = uucp:mail
5193 trusted_users = uucp:\
5194 # This comment line is ignored
5197 .cindex "string" "quoted"
5198 .cindex "escape characters in quoted strings"
5199 If a string does start with a double-quote, it must end with a closing
5200 double-quote, and any backslash characters other than those used for line
5201 continuation are interpreted as escape characters, as follows:
5204 .irow &`\\`& "single backslash"
5205 .irow &`\n`& "newline"
5206 .irow &`\r`& "carriage return"
5208 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5209 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5213 If a backslash is followed by some other character, including a double-quote
5214 character, that character replaces the pair.
5216 Quoting is necessary only if you want to make use of the backslash escapes to
5217 insert special characters, or if you need to specify a value with leading or
5218 trailing spaces. These cases are rare, so quoting is almost never needed in
5219 current versions of Exim. In versions of Exim before 3.14, quoting was required
5220 in order to continue lines, so you may come across older configuration files
5221 and examples that apparently quote unnecessarily.
5224 .section "Expanded strings" "SECID51"
5225 .cindex "expansion" "definition of"
5226 Some strings in the configuration file are subjected to &'string expansion'&,
5227 by which means various parts of the string may be changed according to the
5228 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5229 is as just described; in particular, the handling of backslashes in quoted
5230 strings is done as part of the input process, before expansion takes place.
5231 However, backslash is also an escape character for the expander, so any
5232 backslashes that are required for that reason must be doubled if they are
5233 within a quoted configuration string.
5236 .section "User and group names" "SECID52"
5237 .cindex "user name" "format of"
5238 .cindex "format" "user name"
5239 .cindex "groups" "name format"
5240 .cindex "format" "group name"
5241 User and group names are specified as strings, using the syntax described
5242 above, but the strings are interpreted specially. A user or group name must
5243 either consist entirely of digits, or be a name that can be looked up using the
5244 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5247 .section "List construction" "SECTlistconstruct"
5248 .cindex "list" "syntax of in configuration"
5249 .cindex "format" "list item in configuration"
5250 .cindex "string" "list, definition of"
5251 The data for some configuration options is a list of items, with colon as the
5252 default separator. Many of these options are shown with type &"string list"& in
5253 the descriptions later in this document. Others are listed as &"domain list"&,
5254 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5255 are all the same; however, those other than &"string list"& are subject to
5256 particular kinds of interpretation, as described in chapter
5257 &<<CHAPdomhosaddlists>>&.
5259 In all these cases, the entire list is treated as a single string as far as the
5260 input syntax is concerned. The &%trusted_users%& setting in section
5261 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5262 in a list, it must be entered as two colons. Leading and trailing white space
5263 on each item in a list is ignored. This makes it possible to include items that
5264 start with a colon, and in particular, certain forms of IPv6 address. For
5267 local_interfaces = 127.0.0.1 : ::::1
5269 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5271 &*Note*&: Although leading and trailing white space is ignored in individual
5272 list items, it is not ignored when parsing the list. The space after the first
5273 colon in the example above is necessary. If it were not there, the list would
5274 be interpreted as the two items 127.0.0.1:: and 1.
5276 .section "Changing list separators" "SECTlistsepchange"
5277 .cindex "list separator" "changing"
5278 .cindex "IPv6" "addresses in lists"
5279 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5280 introduced to allow the separator character to be changed. If a list begins
5281 with a left angle bracket, followed by any punctuation character, that
5282 character is used instead of colon as the list separator. For example, the list
5283 above can be rewritten to use a semicolon separator like this:
5285 local_interfaces = <; 127.0.0.1 ; ::1
5287 This facility applies to all lists, with the exception of the list in
5288 &%log_file_path%&. It is recommended that the use of non-colon separators be
5289 confined to circumstances where they really are needed.
5291 .cindex "list separator" "newline as"
5292 .cindex "newline" "as list separator"
5293 It is also possible to use newline and other control characters (those with
5294 code values less than 32, plus DEL) as separators in lists. Such separators
5295 must be provided literally at the time the list is processed. For options that
5296 are string-expanded, you can write the separator using a normal escape
5297 sequence. This will be processed by the expander before the string is
5298 interpreted as a list. For example, if a newline-separated list of domains is
5299 generated by a lookup, you can process it directly by a line such as this:
5301 domains = <\n ${lookup mysql{.....}}
5303 This avoids having to change the list separator in such data. You are unlikely
5304 to want to use a control character as a separator in an option that is not
5305 expanded, because the value is literal text. However, it can be done by giving
5306 the value in quotes. For example:
5308 local_interfaces = "<\n 127.0.0.1 \n ::1"
5310 Unlike printing character separators, which can be included in list items by
5311 doubling, it is not possible to include a control character as data when it is
5312 set as the separator. Two such characters in succession are interpreted as
5313 enclosing an empty list item.
5317 .section "Empty items in lists" "SECTempitelis"
5318 .cindex "list" "empty item in"
5319 An empty item at the end of a list is always ignored. In other words, trailing
5320 separator characters are ignored. Thus, the list in
5322 senders = user@domain :
5324 contains only a single item. If you want to include an empty string as one item
5325 in a list, it must not be the last item. For example, this list contains three
5326 items, the second of which is empty:
5328 senders = user1@domain : : user2@domain
5330 &*Note*&: There must be white space between the two colons, as otherwise they
5331 are interpreted as representing a single colon data character (and the list
5332 would then contain just one item). If you want to specify a list that contains
5333 just one, empty item, you can do it as in this example:
5337 In this case, the first item is empty, and the second is discarded because it
5338 is at the end of the list.
5343 .section "Format of driver configurations" "SECTfordricon"
5344 .cindex "drivers" "configuration format"
5345 There are separate parts in the configuration for defining routers, transports,
5346 and authenticators. In each part, you are defining a number of driver
5347 instances, each with its own set of options. Each driver instance is defined by
5348 a sequence of lines like this:
5350 <&'instance name'&>:
5355 In the following example, the instance name is &(localuser)&, and it is
5356 followed by three options settings:
5361 transport = local_delivery
5363 For each driver instance, you specify which Exim code module it uses &-- by the
5364 setting of the &%driver%& option &-- and (optionally) some configuration
5365 settings. For example, in the case of transports, if you want a transport to
5366 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5367 a local file you would use the &(appendfile)& driver. Each of the drivers is
5368 described in detail in its own separate chapter later in this manual.
5370 You can have several routers, transports, or authenticators that are based on
5371 the same underlying driver (each must have a different instance name).
5373 The order in which routers are defined is important, because addresses are
5374 passed to individual routers one by one, in order. The order in which
5375 transports are defined does not matter at all. The order in which
5376 authenticators are defined is used only when Exim, as a client, is searching
5377 them to find one that matches an authentication mechanism offered by the
5380 .cindex "generic options"
5381 .cindex "options" "generic &-- definition of"
5382 Within a driver instance definition, there are two kinds of option: &'generic'&
5383 and &'private'&. The generic options are those that apply to all drivers of the
5384 same type (that is, all routers, all transports or all authenticators). The
5385 &%driver%& option is a generic option that must appear in every definition.
5386 .cindex "private options"
5387 The private options are special for each driver, and none need appear, because
5388 they all have default values.
5390 The options may appear in any order, except that the &%driver%& option must
5391 precede any private options, since these depend on the particular driver. For
5392 this reason, it is recommended that &%driver%& always be the first option.
5394 Driver instance names, which are used for reference in log entries and
5395 elsewhere, can be any sequence of letters, digits, and underscores (starting
5396 with a letter) and must be unique among drivers of the same type. A router and
5397 a transport (for example) can each have the same name, but no two router
5398 instances can have the same name. The name of a driver instance should not be
5399 confused with the name of the underlying driver module. For example, the
5400 configuration lines:
5405 create an instance of the &(smtp)& transport driver whose name is
5406 &(remote_smtp)&. The same driver code can be used more than once, with
5407 different instance names and different option settings each time. A second
5408 instance of the &(smtp)& transport, with different options, might be defined
5414 command_timeout = 10s
5416 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5417 these transport instances from routers, and these names would appear in log
5420 Comment lines may be present in the middle of driver specifications. The full
5421 list of option settings for any particular driver instance, including all the
5422 defaulted values, can be extracted by making use of the &%-bP%& command line
5430 . ////////////////////////////////////////////////////////////////////////////
5431 . ////////////////////////////////////////////////////////////////////////////
5433 .chapter "The default configuration file" "CHAPdefconfil"
5434 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5435 .cindex "default" "configuration file &""walk through""&"
5436 The default configuration file supplied with Exim as &_src/configure.default_&
5437 is sufficient for a host with simple mail requirements. As an introduction to
5438 the way Exim is configured, this chapter &"walks through"& the default
5439 configuration, giving brief explanations of the settings. Detailed descriptions
5440 of the options are given in subsequent chapters. The default configuration file
5441 itself contains extensive comments about ways you might want to modify the
5442 initial settings. However, note that there are many options that are not
5443 mentioned at all in the default configuration.
5447 .section "Main configuration settings" "SECTdefconfmain"
5448 The main (global) configuration option settings must always come first in the
5449 file. The first thing you'll see in the file, after some initial comments, is
5452 # primary_hostname =
5454 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5455 to know the official, fully qualified name of your host, and this is where you
5456 can specify it. However, in most cases you do not need to set this option. When
5457 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5459 The first three non-comment configuration lines are as follows:
5461 domainlist local_domains = @
5462 domainlist relay_to_domains =
5463 hostlist relay_from_hosts = 127.0.0.1
5465 These are not, in fact, option settings. They are definitions of two named
5466 domain lists and one named host list. Exim allows you to give names to lists of
5467 domains, hosts, and email addresses, in order to make it easier to manage the
5468 configuration file (see section &<<SECTnamedlists>>&).
5470 The first line defines a domain list called &'local_domains'&; this is used
5471 later in the configuration to identify domains that are to be delivered
5474 .cindex "@ in a domain list"
5475 There is just one item in this list, the string &"@"&. This is a special form
5476 of entry which means &"the name of the local host"&. Thus, if the local host is
5477 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5478 be delivered locally. Because the local host's name is referenced indirectly,
5479 the same configuration file can be used on different hosts.
5481 The second line defines a domain list called &'relay_to_domains'&, but the
5482 list itself is empty. Later in the configuration we will come to the part that
5483 controls mail relaying through the local host; it allows relaying to any
5484 domains in this list. By default, therefore, no relaying on the basis of a mail
5485 domain is permitted.
5487 The third line defines a host list called &'relay_from_hosts'&. This list is
5488 used later in the configuration to permit relaying from any host or IP address
5489 that matches the list. The default contains just the IP address of the IPv4
5490 loopback interface, which means that processes on the local host are able to
5491 submit mail for relaying by sending it over TCP/IP to that interface. No other
5492 hosts are permitted to submit messages for relaying.
5494 Just to be sure there's no misunderstanding: at this point in the configuration
5495 we aren't actually setting up any controls. We are just defining some domains
5496 and hosts that will be used in the controls that are specified later.
5498 The next two configuration lines are genuine option settings:
5500 acl_smtp_rcpt = acl_check_rcpt
5501 acl_smtp_data = acl_check_data
5503 These options specify &'Access Control Lists'& (ACLs) that are to be used
5504 during an incoming SMTP session for every recipient of a message (every RCPT
5505 command), and after the contents of the message have been received,
5506 respectively. The names of the lists are &'acl_check_rcpt'& and
5507 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5508 section of the configuration. The RCPT ACL controls which recipients are
5509 accepted for an incoming message &-- if a configuration does not provide an ACL
5510 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5511 contents of a message to be checked.
5513 Two commented-out option settings are next:
5515 # av_scanner = clamd:/tmp/clamd
5516 # spamd_address = 127.0.0.1 783
5518 These are example settings that can be used when Exim is compiled with the
5519 content-scanning extension. The first specifies the interface to the virus
5520 scanner, and the second specifies the interface to SpamAssassin. Further
5521 details are given in chapter &<<CHAPexiscan>>&.
5523 Three more commented-out option settings follow:
5525 # tls_advertise_hosts = *
5526 # tls_certificate = /etc/ssl/exim.crt
5527 # tls_privatekey = /etc/ssl/exim.pem
5529 These are example settings that can be used when Exim is compiled with
5530 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5531 first one specifies the list of clients that are allowed to use TLS when
5532 connecting to this server; in this case the wildcard means all clients. The
5533 other options specify where Exim should find its TLS certificate and private
5534 key, which together prove the server's identity to any clients that connect.
5535 More details are given in chapter &<<CHAPTLS>>&.
5537 Another two commented-out option settings follow:
5539 # daemon_smtp_ports = 25 : 465 : 587
5540 # tls_on_connect_ports = 465
5542 .cindex "port" "465 and 587"
5543 .cindex "port" "for message submission"
5544 .cindex "message" "submission, ports for"
5545 .cindex "ssmtp protocol"
5546 .cindex "smtps protocol"
5547 .cindex "SMTP" "ssmtp protocol"
5548 .cindex "SMTP" "smtps protocol"
5549 These options provide better support for roaming users who wish to use this
5550 server for message submission. They are not much use unless you have turned on
5551 TLS (as described in the previous paragraph) and authentication (about which
5552 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5553 on end-user networks, so RFC 4409 specifies that message submission should use
5554 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5555 configured to use port 587 correctly, so these settings also enable the
5556 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5557 &<<SECTsupobssmt>>&).
5559 Two more commented-out options settings follow:
5562 # qualify_recipient =
5564 The first of these specifies a domain that Exim uses when it constructs a
5565 complete email address from a local login name. This is often needed when Exim
5566 receives a message from a local process. If you do not set &%qualify_domain%&,
5567 the value of &%primary_hostname%& is used. If you set both of these options,
5568 you can have different qualification domains for sender and recipient
5569 addresses. If you set only the first one, its value is used in both cases.
5571 .cindex "domain literal" "recognizing format"
5572 The following line must be uncommented if you want Exim to recognize
5573 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5574 (an IP address within square brackets) instead of a named domain.
5576 # allow_domain_literals
5578 The RFCs still require this form, but many people think that in the modern
5579 Internet it makes little sense to permit mail to be sent to specific hosts by
5580 quoting their IP addresses. This ancient format has been used by people who
5581 try to abuse hosts by using them for unwanted relaying. However, some
5582 people believe there are circumstances (for example, messages addressed to
5583 &'postmaster'&) where domain literals are still useful.
5585 The next configuration line is a kind of trigger guard:
5589 It specifies that no delivery must ever be run as the root user. The normal
5590 convention is to set up &'root'& as an alias for the system administrator. This
5591 setting is a guard against slips in the configuration.
5592 The list of users specified by &%never_users%& is not, however, the complete
5593 list; the build-time configuration in &_Local/Makefile_& has an option called
5594 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5595 contents of &%never_users%& are added to this list. By default
5596 FIXED_NEVER_USERS also specifies root.
5598 When a remote host connects to Exim in order to send mail, the only information
5599 Exim has about the host's identity is its IP address. The next configuration
5604 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5605 in order to get a host name. This improves the quality of the logging
5606 information, but if you feel it is too expensive, you can remove it entirely,
5607 or restrict the lookup to hosts on &"nearby"& networks.
5608 Note that it is not always possible to find a host name from an IP address,
5609 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5612 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5613 1413 (hence their names):
5616 rfc1413_query_timeout = 0s
5618 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5619 Few hosts offer RFC1413 service these days; calls have to be
5620 terminated by a timeout and this needlessly delays the startup
5621 of an incoming SMTP connection.
5622 If you have hosts for which you trust RFC1413 and need this
5623 information, you can change this.
5625 This line enables an efficiency SMTP option. It is negotiated by clients
5626 and not expected to cause problems but can be disabled if needed.
5631 When Exim receives messages over SMTP connections, it expects all addresses to
5632 be fully qualified with a domain, as required by the SMTP definition. However,
5633 if you are running a server to which simple clients submit messages, you may
5634 find that they send unqualified addresses. The two commented-out options:
5636 # sender_unqualified_hosts =
5637 # recipient_unqualified_hosts =
5639 show how you can specify hosts that are permitted to send unqualified sender
5640 and recipient addresses, respectively.
5642 The &%log_selector%& option is used to increase the detail of logging
5645 log_selector = +smtp_protocol_error +smtp_syntax_error \
5646 +tls_certificate_verified
5649 The &%percent_hack_domains%& option is also commented out:
5651 # percent_hack_domains =
5653 It provides a list of domains for which the &"percent hack"& is to operate.
5654 This is an almost obsolete form of explicit email routing. If you do not know
5655 anything about it, you can safely ignore this topic.
5657 The next two settings in the main part of the default configuration are
5658 concerned with messages that have been &"frozen"& on Exim's queue. When a
5659 message is frozen, Exim no longer continues to try to deliver it. Freezing
5660 occurs when a bounce message encounters a permanent failure because the sender
5661 address of the original message that caused the bounce is invalid, so the
5662 bounce cannot be delivered. This is probably the most common case, but there
5663 are also other conditions that cause freezing, and frozen messages are not
5664 always bounce messages.
5666 ignore_bounce_errors_after = 2d
5667 timeout_frozen_after = 7d
5669 The first of these options specifies that failing bounce messages are to be
5670 discarded after 2 days on the queue. The second specifies that any frozen
5671 message (whether a bounce message or not) is to be timed out (and discarded)
5672 after a week. In this configuration, the first setting ensures that no failing
5673 bounce message ever lasts a week.
5675 Exim queues it's messages in a spool directory. If you expect to have
5676 large queues, you may consider using this option. It splits the spool
5677 directory into subdirectories to avoid file system degradation from
5678 many files in a single directory, resulting in better performance.
5679 Manual manipulation of queued messages becomes more complex (though fortunately
5682 # split_spool_directory = true
5685 In an ideal world everybody follows the standards. For non-ASCII
5686 messages RFC 2047 is a standard, allowing a maximum line length of 76
5687 characters. Exim adheres that standard and won't process messages which
5688 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5689 In particular, the Exim maintainers have had multiple reports of
5690 problems from Russian administrators of issues until they disable this
5691 check, because of some popular, yet buggy, mail composition software.
5693 # check_rfc2047_length = false
5696 If you need to be strictly RFC compliant you may wish to disable the
5697 8BITMIME advertisement. Use this, if you exchange mails with systems
5698 that are not 8-bit clean.
5700 # accept_8bitmime = false
5703 Libraries you use may depend on specific environment settings. This
5704 imposes a security risk (e.g. PATH). There are two lists:
5705 &%keep_environment%& for the variables to import as they are, and
5706 &%add_environment%& for variables we want to set to a fixed value.
5707 Note that TZ is handled separately, by the $%timezone%$ runtime
5708 option and by the TIMEZONE_DEFAULT buildtime option.
5710 # keep_environment = ^LDAP
5711 # add_environment = PATH=/usr/bin::/bin
5715 .section "ACL configuration" "SECID54"
5716 .cindex "default" "ACLs"
5717 .cindex "&ACL;" "default configuration"
5718 In the default configuration, the ACL section follows the main configuration.
5719 It starts with the line
5723 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5724 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5725 and &%acl_smtp_data%& above.
5727 .cindex "RCPT" "ACL for"
5728 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5729 RCPT command specifies one of the message's recipients. The ACL statements
5730 are considered in order, until the recipient address is either accepted or
5731 rejected. The RCPT command is then accepted or rejected, according to the
5732 result of the ACL processing.
5736 This line, consisting of a name terminated by a colon, marks the start of the
5741 This ACL statement accepts the recipient if the sending host matches the list.
5742 But what does that strange list mean? It doesn't actually contain any host
5743 names or IP addresses. The presence of the colon puts an empty item in the
5744 list; Exim matches this only if the incoming message did not come from a remote
5745 host, because in that case, the remote hostname is empty. The colon is
5746 important. Without it, the list itself is empty, and can never match anything.
5748 What this statement is doing is to accept unconditionally all recipients in
5749 messages that are submitted by SMTP from local processes using the standard
5750 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5753 deny message = Restricted characters in address
5754 domains = +local_domains
5755 local_parts = ^[.] : ^.*[@%!/|]
5757 deny message = Restricted characters in address
5758 domains = !+local_domains
5759 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5761 These statements are concerned with local parts that contain any of the
5762 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5763 Although these characters are entirely legal in local parts (in the case of
5764 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5765 in Internet mail addresses.
5767 The first three have in the past been associated with explicitly routed
5768 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5769 option). Addresses containing these characters are regularly tried by spammers
5770 in an attempt to bypass relaying restrictions, and also by open relay testing
5771 programs. Unless you really need them it is safest to reject these characters
5772 at this early stage. This configuration is heavy-handed in rejecting these
5773 characters for all messages it accepts from remote hosts. This is a deliberate
5774 policy of being as safe as possible.
5776 The first rule above is stricter, and is applied to messages that are addressed
5777 to one of the local domains handled by this host. This is implemented by the
5778 first condition, which restricts it to domains that are listed in the
5779 &'local_domains'& domain list. The &"+"& character is used to indicate a
5780 reference to a named list. In this configuration, there is just one domain in
5781 &'local_domains'&, but in general there may be many.
5783 The second condition on the first statement uses two regular expressions to
5784 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5785 or &"|"&. If you have local accounts that include these characters, you will
5786 have to modify this rule.
5788 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5789 allows them because they have been encountered in practice. (Consider the
5790 common convention of local parts constructed as
5791 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5792 the author of Exim, who has no second initial.) However, a local part starting
5793 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5794 file name (for example, for a mailing list). This is also true for local parts
5795 that contain slashes. A pipe symbol can also be troublesome if the local part
5796 is incorporated unthinkingly into a shell command line.
5798 The second rule above applies to all other domains, and is less strict. This
5799 allows your own users to send outgoing messages to sites that use slashes
5800 and vertical bars in their local parts. It blocks local parts that begin
5801 with a dot, slash, or vertical bar, but allows these characters within the
5802 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5803 and &"!"& is blocked, as before. The motivation here is to prevent your users
5804 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5806 accept local_parts = postmaster
5807 domains = +local_domains
5809 This statement, which has two conditions, accepts an incoming address if the
5810 local part is &'postmaster'& and the domain is one of those listed in the
5811 &'local_domains'& domain list. The &"+"& character is used to indicate a
5812 reference to a named list. In this configuration, there is just one domain in
5813 &'local_domains'&, but in general there may be many.
5815 The presence of this statement means that mail to postmaster is never blocked
5816 by any of the subsequent tests. This can be helpful while sorting out problems
5817 in cases where the subsequent tests are incorrectly denying access.
5819 require verify = sender
5821 This statement requires the sender address to be verified before any subsequent
5822 ACL statement can be used. If verification fails, the incoming recipient
5823 address is refused. Verification consists of trying to route the address, to
5824 see if a bounce message could be delivered to it. In the case of remote
5825 addresses, basic verification checks only the domain, but &'callouts'& can be
5826 used for more verification if required. Section &<<SECTaddressverification>>&
5827 discusses the details of address verification.
5829 accept hosts = +relay_from_hosts
5830 control = submission
5832 This statement accepts the address if the message is coming from one of the
5833 hosts that are defined as being allowed to relay through this host. Recipient
5834 verification is omitted here, because in many cases the clients are dumb MUAs
5835 that do not cope well with SMTP error responses. For the same reason, the
5836 second line specifies &"submission mode"& for messages that are accepted. This
5837 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5838 messages that are deficient in some way, for example, because they lack a
5839 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5840 probably add recipient verification here, and disable submission mode.
5842 accept authenticated = *
5843 control = submission
5845 This statement accepts the address if the client host has authenticated itself.
5846 Submission mode is again specified, on the grounds that such messages are most
5847 likely to come from MUAs. The default configuration does not define any
5848 authenticators, though it does include some nearly complete commented-out
5849 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5850 fact authenticate until you complete the authenticator definitions.
5852 require message = relay not permitted
5853 domains = +local_domains : +relay_to_domains
5855 This statement rejects the address if its domain is neither a local domain nor
5856 one of the domains for which this host is a relay.
5858 require verify = recipient
5860 This statement requires the recipient address to be verified; if verification
5861 fails, the address is rejected.
5863 # deny message = rejected because $sender_host_address \
5864 # is in a black list at $dnslist_domain\n\
5866 # dnslists = black.list.example
5868 # warn dnslists = black.list.example
5869 # add_header = X-Warning: $sender_host_address is in \
5870 # a black list at $dnslist_domain
5871 # log_message = found in $dnslist_domain
5873 These commented-out lines are examples of how you could configure Exim to check
5874 sending hosts against a DNS black list. The first statement rejects messages
5875 from blacklisted hosts, whereas the second just inserts a warning header
5878 # require verify = csa
5880 This commented-out line is an example of how you could turn on client SMTP
5881 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5886 The final statement in the first ACL unconditionally accepts any recipient
5887 address that has successfully passed all the previous tests.
5891 This line marks the start of the second ACL, and names it. Most of the contents
5892 of this ACL are commented out:
5895 # message = This message contains a virus \
5898 These lines are examples of how to arrange for messages to be scanned for
5899 viruses when Exim has been compiled with the content-scanning extension, and a
5900 suitable virus scanner is installed. If the message is found to contain a
5901 virus, it is rejected with the given custom error message.
5903 # warn spam = nobody
5904 # message = X-Spam_score: $spam_score\n\
5905 # X-Spam_score_int: $spam_score_int\n\
5906 # X-Spam_bar: $spam_bar\n\
5907 # X-Spam_report: $spam_report
5909 These lines are an example of how to arrange for messages to be scanned by
5910 SpamAssassin when Exim has been compiled with the content-scanning extension,
5911 and SpamAssassin has been installed. The SpamAssassin check is run with
5912 &`nobody`& as its user parameter, and the results are added to the message as a
5913 series of extra header line. In this case, the message is not rejected,
5914 whatever the spam score.
5918 This final line in the DATA ACL accepts the message unconditionally.
5921 .section "Router configuration" "SECID55"
5922 .cindex "default" "routers"
5923 .cindex "routers" "default"
5924 The router configuration comes next in the default configuration, introduced
5929 Routers are the modules in Exim that make decisions about where to send
5930 messages. An address is passed to each router in turn, until it is either
5931 accepted, or failed. This means that the order in which you define the routers
5932 matters. Each router is fully described in its own chapter later in this
5933 manual. Here we give only brief overviews.
5936 # driver = ipliteral
5937 # domains = !+local_domains
5938 # transport = remote_smtp
5940 .cindex "domain literal" "default router"
5941 This router is commented out because the majority of sites do not want to
5942 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5943 you uncomment this router, you also need to uncomment the setting of
5944 &%allow_domain_literals%& in the main part of the configuration.
5948 domains = ! +local_domains
5949 transport = remote_smtp
5950 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5953 The first uncommented router handles addresses that do not involve any local
5954 domains. This is specified by the line
5956 domains = ! +local_domains
5958 The &%domains%& option lists the domains to which this router applies, but the
5959 exclamation mark is a negation sign, so the router is used only for domains
5960 that are not in the domain list called &'local_domains'& (which was defined at
5961 the start of the configuration). The plus sign before &'local_domains'&
5962 indicates that it is referring to a named list. Addresses in other domains are
5963 passed on to the following routers.
5965 The name of the router driver is &(dnslookup)&,
5966 and is specified by the &%driver%& option. Do not be confused by the fact that
5967 the name of this router instance is the same as the name of the driver. The
5968 instance name is arbitrary, but the name set in the &%driver%& option must be
5969 one of the driver modules that is in the Exim binary.
5971 The &(dnslookup)& router routes addresses by looking up their domains in the
5972 DNS in order to obtain a list of hosts to which the address is routed. If the
5973 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5974 specified by the &%transport%& option. If the router does not find the domain
5975 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5976 the address fails and is bounced.
5978 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5979 be entirely ignored. This option is present because a number of cases have been
5980 encountered where MX records in the DNS point to host names
5981 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5982 Completely ignoring these IP addresses causes Exim to fail to route the
5983 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5984 continue to try to deliver the message periodically until the address timed
5991 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5993 file_transport = address_file
5994 pipe_transport = address_pipe
5996 Control reaches this and subsequent routers only for addresses in the local
5997 domains. This router checks to see whether the local part is defined as an
5998 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5999 data that it looks up from that file. If no data is found for the local part,
6000 the value of the &%data%& option is empty, causing the address to be passed to
6003 &_/etc/aliases_& is a conventional name for the system aliases file that is
6004 often used. That is why it is referenced by from the default configuration
6005 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6006 &_Local/Makefile_& before building Exim.
6011 # local_part_suffix = +* : -*
6012 # local_part_suffix_optional
6013 file = $home/.forward
6018 file_transport = address_file
6019 pipe_transport = address_pipe
6020 reply_transport = address_reply
6022 This is the most complicated router in the default configuration. It is another
6023 redirection router, but this time it is looking for forwarding data set up by
6024 individual users. The &%check_local_user%& setting specifies a check that the
6025 local part of the address is the login name of a local user. If it is not, the
6026 router is skipped. The two commented options that follow &%check_local_user%&,
6029 # local_part_suffix = +* : -*
6030 # local_part_suffix_optional
6032 .vindex "&$local_part_suffix$&"
6033 show how you can specify the recognition of local part suffixes. If the first
6034 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6035 by any sequence of characters, is removed from the local part and placed in the
6036 variable &$local_part_suffix$&. The second suffix option specifies that the
6037 presence of a suffix in the local part is optional. When a suffix is present,
6038 the check for a local login uses the local part with the suffix removed.
6040 When a local user account is found, the file called &_.forward_& in the user's
6041 home directory is consulted. If it does not exist, or is empty, the router
6042 declines. Otherwise, the contents of &_.forward_& are interpreted as
6043 redirection data (see chapter &<<CHAPredirect>>& for more details).
6045 .cindex "Sieve filter" "enabling in default router"
6046 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6047 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6048 is commented out by default), the contents of the file are interpreted as a set
6049 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6050 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6051 separate document entitled &'Exim's interfaces to mail filtering'&.
6053 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6054 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6055 There are two reasons for doing this:
6058 Whether or not a local user has a &_.forward_& file is not really relevant when
6059 checking an address for validity; it makes sense not to waste resources doing
6062 More importantly, when Exim is verifying addresses or handling an EXPN
6063 command during an SMTP session, it is running as the Exim user, not as root.
6064 The group is the Exim group, and no additional groups are set up.
6065 It may therefore not be possible for Exim to read users' &_.forward_& files at
6069 The setting of &%check_ancestor%& prevents the router from generating a new
6070 address that is the same as any previous address that was redirected. (This
6071 works round a problem concerning a bad interaction between aliasing and
6072 forwarding &-- see section &<<SECTredlocmai>>&).
6074 The final three option settings specify the transports that are to be used when
6075 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6076 auto-reply, respectively. For example, if a &_.forward_& file contains
6078 a.nother@elsewhere.example, /home/spqr/archive
6080 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6086 # local_part_suffix = +* : -*
6087 # local_part_suffix_optional
6088 transport = local_delivery
6090 The final router sets up delivery into local mailboxes, provided that the local
6091 part is the name of a local login, by accepting the address and assigning it to
6092 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6093 routers, so the address is bounced. The commented suffix settings fulfil the
6094 same purpose as they do for the &(userforward)& router.
6097 .section "Transport configuration" "SECID56"
6098 .cindex "default" "transports"
6099 .cindex "transports" "default"
6100 Transports define mechanisms for actually delivering messages. They operate
6101 only when referenced from routers, so the order in which they are defined does
6102 not matter. The transports section of the configuration starts with
6106 One remote transport and four local transports are defined.
6112 This transport is used for delivering messages over SMTP connections.
6113 The list of remote hosts comes from the router.
6114 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6115 It is negotiated between client and server
6116 and not expected to cause problems but can be disabled if needed.
6117 All other options are defaulted.
6121 file = /var/mail/$local_part
6128 This &(appendfile)& transport is used for local delivery to user mailboxes in
6129 traditional BSD mailbox format. By default it runs under the uid and gid of the
6130 local user, which requires the sticky bit to be set on the &_/var/mail_&
6131 directory. Some systems use the alternative approach of running mail deliveries
6132 under a particular group instead of using the sticky bit. The commented options
6133 show how this can be done.
6135 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6136 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6137 similarly-named options above.
6143 This transport is used for handling deliveries to pipes that are generated by
6144 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6145 option specifies that any output on stdout or stderr generated by the pipe is to
6146 be returned to the sender.
6154 This transport is used for handling deliveries to files that are generated by
6155 redirection. The name of the file is not specified in this instance of
6156 &(appendfile)&, because it comes from the &(redirect)& router.
6161 This transport is used for handling automatic replies generated by users'
6166 .section "Default retry rule" "SECID57"
6167 .cindex "retry" "default rule"
6168 .cindex "default" "retry rule"
6169 The retry section of the configuration file contains rules which affect the way
6170 Exim retries deliveries that cannot be completed at the first attempt. It is
6171 introduced by the line
6175 In the default configuration, there is just one rule, which applies to all
6178 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6180 This causes any temporarily failing address to be retried every 15 minutes for
6181 2 hours, then at intervals starting at one hour and increasing by a factor of
6182 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6183 is not delivered after 4 days of temporary failure, it is bounced. The time is
6184 measured from first failure, not from the time the message was received.
6186 If the retry section is removed from the configuration, or is empty (that is,
6187 if no retry rules are defined), Exim will not retry deliveries. This turns
6188 temporary errors into permanent errors.
6191 .section "Rewriting configuration" "SECID58"
6192 The rewriting section of the configuration, introduced by
6196 contains rules for rewriting addresses in messages as they arrive. There are no
6197 rewriting rules in the default configuration file.
6201 .section "Authenticators configuration" "SECTdefconfauth"
6202 .cindex "AUTH" "configuration"
6203 The authenticators section of the configuration, introduced by
6205 begin authenticators
6207 defines mechanisms for the use of the SMTP AUTH command. The default
6208 configuration file contains two commented-out example authenticators
6209 which support plaintext username/password authentication using the
6210 standard PLAIN mechanism and the traditional but non-standard LOGIN
6211 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6212 to support most MUA software.
6214 The example PLAIN authenticator looks like this:
6217 # driver = plaintext
6218 # server_set_id = $auth2
6219 # server_prompts = :
6220 # server_condition = Authentication is not yet configured
6221 # server_advertise_condition = ${if def:tls_in_cipher }
6223 And the example LOGIN authenticator looks like this:
6226 # driver = plaintext
6227 # server_set_id = $auth1
6228 # server_prompts = <| Username: | Password:
6229 # server_condition = Authentication is not yet configured
6230 # server_advertise_condition = ${if def:tls_in_cipher }
6233 The &%server_set_id%& option makes Exim remember the authenticated username
6234 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6235 &%server_prompts%& option configures the &(plaintext)& authenticator so
6236 that it implements the details of the specific authentication mechanism,
6237 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6238 when Exim offers authentication to clients; in the examples, this is only
6239 when TLS or SSL has been started, so to enable the authenticators you also
6240 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6242 The &%server_condition%& setting defines how to verify that the username and
6243 password are correct. In the examples it just produces an error message.
6244 To make the authenticators work, you can use a string expansion
6245 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6247 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6248 usercode and password are in different positions.
6249 Chapter &<<CHAPplaintext>>& covers both.
6251 .ecindex IIDconfiwal
6255 . ////////////////////////////////////////////////////////////////////////////
6256 . ////////////////////////////////////////////////////////////////////////////
6258 .chapter "Regular expressions" "CHAPregexp"
6260 .cindex "regular expressions" "library"
6262 Exim supports the use of regular expressions in many of its options. It
6263 uses the PCRE regular expression library; this provides regular expression
6264 matching that is compatible with Perl 5. The syntax and semantics of
6265 regular expressions is discussed in many Perl reference books, and also in
6266 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6267 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6269 The documentation for the syntax and semantics of the regular expressions that
6270 are supported by PCRE is included in the PCRE distribution, and no further
6271 description is included here. The PCRE functions are called from Exim using
6272 the default option settings (that is, with no PCRE options set), except that
6273 the PCRE_CASELESS option is set when the matching is required to be
6276 In most cases, when a regular expression is required in an Exim configuration,
6277 it has to start with a circumflex, in order to distinguish it from plain text
6278 or an &"ends with"& wildcard. In this example of a configuration setting, the
6279 second item in the colon-separated list is a regular expression.
6281 domains = a.b.c : ^\\d{3} : *.y.z : ...
6283 The doubling of the backslash is required because of string expansion that
6284 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6285 of this issue, and a way of avoiding the need for doubling backslashes. The
6286 regular expression that is eventually used in this example contains just one
6287 backslash. The circumflex is included in the regular expression, and has the
6288 normal effect of &"anchoring"& it to the start of the string that is being
6291 There are, however, two cases where a circumflex is not required for the
6292 recognition of a regular expression: these are the &%match%& condition in a
6293 string expansion, and the &%matches%& condition in an Exim filter file. In
6294 these cases, the relevant string is always treated as a regular expression; if
6295 it does not start with a circumflex, the expression is not anchored, and can
6296 match anywhere in the subject string.
6298 In all cases, if you want a regular expression to match at the end of a string,
6299 you must code the $ metacharacter to indicate this. For example:
6301 domains = ^\\d{3}\\.example
6303 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6306 domains = ^\\d{3}\\.example\$
6308 if you want &'example'& to be the top-level domain. The backslash before the
6309 $ is needed because string expansion also interprets dollar characters.
6313 . ////////////////////////////////////////////////////////////////////////////
6314 . ////////////////////////////////////////////////////////////////////////////
6316 .chapter "File and database lookups" "CHAPfdlookup"
6317 .scindex IIDfidalo1 "file" "lookups"
6318 .scindex IIDfidalo2 "database" "lookups"
6319 .cindex "lookup" "description of"
6320 Exim can be configured to look up data in files or databases as it processes
6321 messages. Two different kinds of syntax are used:
6324 A string that is to be expanded may contain explicit lookup requests. These
6325 cause parts of the string to be replaced by data that is obtained from the
6326 lookup. Lookups of this type are conditional expansion items. Different results
6327 can be defined for the cases of lookup success and failure. See chapter
6328 &<<CHAPexpand>>&, where string expansions are described in detail.
6329 The key for the lookup is specified as part of the string expansion.
6331 Lists of domains, hosts, and email addresses can contain lookup requests as a
6332 way of avoiding excessively long linear lists. In this case, the data that is
6333 returned by the lookup is often (but not always) discarded; whether the lookup
6334 succeeds or fails is what really counts. These kinds of list are described in
6335 chapter &<<CHAPdomhosaddlists>>&.
6336 The key for the lookup is given by the context in which the list is expanded.
6339 String expansions, lists, and lookups interact with each other in such a way
6340 that there is no order in which to describe any one of them that does not
6341 involve references to the others. Each of these three chapters makes more sense
6342 if you have read the other two first. If you are reading this for the first
6343 time, be aware that some of it will make a lot more sense after you have read
6344 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6346 .section "Examples of different lookup syntax" "SECID60"
6347 It is easy to confuse the two different kinds of lookup, especially as the
6348 lists that may contain the second kind are always expanded before being
6349 processed as lists. Therefore, they may also contain lookups of the first kind.
6350 Be careful to distinguish between the following two examples:
6352 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6353 domains = lsearch;/some/file
6355 The first uses a string expansion, the result of which must be a domain list.
6356 No strings have been specified for a successful or a failing lookup; the
6357 defaults in this case are the looked-up data and an empty string, respectively.
6358 The expansion takes place before the string is processed as a list, and the
6359 file that is searched could contain lines like this:
6361 192.168.3.4: domain1:domain2:...
6362 192.168.1.9: domain3:domain4:...
6364 When the lookup succeeds, the result of the expansion is a list of domains (and
6365 possibly other types of item that are allowed in domain lists).
6367 In the second example, the lookup is a single item in a domain list. It causes
6368 Exim to use a lookup to see if the domain that is being processed can be found
6369 in the file. The file could contains lines like this:
6374 Any data that follows the keys is not relevant when checking that the domain
6375 matches the list item.
6377 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6378 Consider a file containing lines like this:
6380 192.168.5.6: lsearch;/another/file
6382 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6383 first &%domains%& setting above generates the second setting, which therefore
6384 causes a second lookup to occur.
6386 The rest of this chapter describes the different lookup types that are
6387 available. Any of them can be used in any part of the configuration where a
6388 lookup is permitted.
6391 .section "Lookup types" "SECID61"
6392 .cindex "lookup" "types of"
6393 .cindex "single-key lookup" "definition of"
6394 Two different types of data lookup are implemented:
6397 The &'single-key'& type requires the specification of a file in which to look,
6398 and a single key to search for. The key must be a non-empty string for the
6399 lookup to succeed. The lookup type determines how the file is searched.
6401 .cindex "query-style lookup" "definition of"
6402 The &'query-style'& type accepts a generalized database query. No particular
6403 key value is assumed by Exim for query-style lookups. You can use whichever
6404 Exim variables you need to construct the database query.
6407 The code for each lookup type is in a separate source file that is included in
6408 the binary of Exim only if the corresponding compile-time option is set. The
6409 default settings in &_src/EDITME_& are:
6414 which means that only linear searching and DBM lookups are included by default.
6415 For some types of lookup (e.g. SQL databases), you need to install appropriate
6416 libraries and header files before building Exim.
6421 .section "Single-key lookup types" "SECTsinglekeylookups"
6422 .cindex "lookup" "single-key types"
6423 .cindex "single-key lookup" "list of types"
6424 The following single-key lookup types are implemented:
6427 .cindex "cdb" "description of"
6428 .cindex "lookup" "cdb"
6429 .cindex "binary zero" "in lookup key"
6430 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6431 string without a terminating binary zero. The cdb format is designed for
6432 indexed files that are read frequently and never updated, except by total
6433 re-creation. As such, it is particularly suitable for large files containing
6434 aliases or other indexed data referenced by an MTA. Information about cdb can
6435 be found in several places:
6437 &url(http://www.pobox.com/~djb/cdb.html)
6438 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6439 &url(http://packages.debian.org/stable/utils/freecdb.html)
6441 A cdb distribution is not needed in order to build Exim with cdb support,
6442 because the code for reading cdb files is included directly in Exim itself.
6443 However, no means of building or testing cdb files is provided with Exim, so
6444 you need to obtain a cdb distribution in order to do this.
6446 .cindex "DBM" "lookup type"
6447 .cindex "lookup" "dbm"
6448 .cindex "binary zero" "in lookup key"
6449 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6450 DBM file by looking up the record with the given key. A terminating binary
6451 zero is included in the key that is passed to the DBM library. See section
6452 &<<SECTdb>>& for a discussion of DBM libraries.
6454 .cindex "Berkeley DB library" "file format"
6455 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6456 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6457 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6458 the DB_UNKNOWN option. This enables it to handle any of the types of database
6459 that the library supports, and can be useful for accessing DBM files created by
6460 other applications. (For earlier DB versions, DB_HASH is always used.)
6462 .cindex "lookup" "dbmjz"
6463 .cindex "lookup" "dbm &-- embedded NULs"
6465 .cindex "dbmjz lookup type"
6466 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6467 interpreted as an Exim list; the elements of the list are joined together with
6468 ASCII NUL characters to form the lookup key. An example usage would be to
6469 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6470 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6471 &(cram_md5)& authenticator.
6473 .cindex "lookup" "dbmnz"
6474 .cindex "lookup" "dbm &-- terminating zero"
6475 .cindex "binary zero" "in lookup key"
6477 .cindex "&_/etc/userdbshadow.dat_&"
6478 .cindex "dbmnz lookup type"
6479 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6480 is not included in the key that is passed to the DBM library. You may need this
6481 if you want to look up data in files that are created by or shared with some
6482 other application that does not use terminating zeros. For example, you need to
6483 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6484 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6485 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6486 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6488 .cindex "lookup" "dsearch"
6489 .cindex "dsearch lookup type"
6490 &(dsearch)&: The given file must be a directory; this is searched for an entry
6491 whose name is the key by calling the &[lstat()]& function. The key may not
6492 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6493 the lookup is the name of the entry, which may be a file, directory,
6494 symbolic link, or any other kind of directory entry. An example of how this
6495 lookup can be used to support virtual domains is given in section
6496 &<<SECTvirtualdomains>>&.
6498 .cindex "lookup" "iplsearch"
6499 .cindex "iplsearch lookup type"
6500 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6501 terminated by a colon or white space or the end of the line. The keys in the
6502 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6503 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6504 being interpreted as a key terminator. For example:
6506 1.2.3.4: data for 1.2.3.4
6507 192.168.0.0/16: data for 192.168.0.0/16
6508 "abcd::cdab": data for abcd::cdab
6509 "abcd:abcd::/32" data for abcd:abcd::/32
6511 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6512 file is searched linearly, using the CIDR masks where present, until a matching
6513 key is found. The first key that matches is used; there is no attempt to find a
6514 &"best"& match. Apart from the way the keys are matched, the processing for
6515 &(iplsearch)& is the same as for &(lsearch)&.
6517 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6518 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6519 lookup types support only literal keys.
6521 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6522 the implicit key is the host's IP address rather than its name (see section
6523 &<<SECThoslispatsikey>>&).
6525 .cindex "linear search"
6526 .cindex "lookup" "lsearch"
6527 .cindex "lsearch lookup type"
6528 .cindex "case sensitivity" "in lsearch lookup"
6529 &(lsearch)&: The given file is a text file that is searched linearly for a
6530 line beginning with the search key, terminated by a colon or white space or the
6531 end of the line. The search is case-insensitive; that is, upper and lower case
6532 letters are treated as the same. The first occurrence of the key that is found
6533 in the file is used.
6535 White space between the key and the colon is permitted. The remainder of the
6536 line, with leading and trailing white space removed, is the data. This can be
6537 continued onto subsequent lines by starting them with any amount of white
6538 space, but only a single space character is included in the data at such a
6539 junction. If the data begins with a colon, the key must be terminated by a
6544 Empty lines and lines beginning with # are ignored, even if they occur in the
6545 middle of an item. This is the traditional textual format of alias files. Note
6546 that the keys in an &(lsearch)& file are literal strings. There is no
6547 wildcarding of any kind.
6549 .cindex "lookup" "lsearch &-- colons in keys"
6550 .cindex "white space" "in lsearch key"
6551 In most &(lsearch)& files, keys are not required to contain colons or #
6552 characters, or white space. However, if you need this feature, it is available.
6553 If a key begins with a doublequote character, it is terminated only by a
6554 matching quote (or end of line), and the normal escaping rules apply to its
6555 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6556 quoted keys (exactly as for unquoted keys). There is no special handling of
6557 quotes for the data part of an &(lsearch)& line.
6560 .cindex "NIS lookup type"
6561 .cindex "lookup" "NIS"
6562 .cindex "binary zero" "in lookup key"
6563 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6564 the given key, without a terminating binary zero. There is a variant called
6565 &(nis0)& which does include the terminating binary zero in the key. This is
6566 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6567 aliases; the full map names must be used.
6570 .cindex "wildlsearch lookup type"
6571 .cindex "lookup" "wildlsearch"
6572 .cindex "nwildlsearch lookup type"
6573 .cindex "lookup" "nwildlsearch"
6574 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6575 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6576 the file may be wildcarded. The difference between these two lookup types is
6577 that for &(wildlsearch)&, each key in the file is string-expanded before being
6578 used, whereas for &(nwildlsearch)&, no expansion takes place.
6580 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6581 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6582 file that are regular expressions can be made case-sensitive by the use of
6583 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6585 . ==== As this is a nested list, any displays it contains must be indented
6586 . ==== as otherwise they are too far to the left.
6589 The string may begin with an asterisk to mean &"ends with"&. For example:
6591 *.a.b.c data for anything.a.b.c
6592 *fish data for anythingfish
6595 The string may begin with a circumflex to indicate a regular expression. For
6596 example, for &(wildlsearch)&:
6598 ^\N\d+\.a\.b\N data for <digits>.a.b
6600 Note the use of &`\N`& to disable expansion of the contents of the regular
6601 expression. If you are using &(nwildlsearch)&, where the keys are not
6602 string-expanded, the equivalent entry is:
6604 ^\d+\.a\.b data for <digits>.a.b
6606 The case-insensitive flag is set at the start of compiling the regular
6607 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6608 For example, to make the entire pattern case-sensitive:
6610 ^(?-i)\d+\.a\.b data for <digits>.a.b
6613 If the regular expression contains white space or colon characters, you must
6614 either quote it (see &(lsearch)& above), or represent these characters in other
6615 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6616 colon. This may be easier than quoting, because if you quote, you have to
6617 escape all the backslashes inside the quotes.
6619 &*Note*&: It is not possible to capture substrings in a regular expression
6620 match for later use, because the results of all lookups are cached. If a lookup
6621 is repeated, the result is taken from the cache, and no actual pattern matching
6622 takes place. The values of all the numeric variables are unset after a
6623 &((n)wildlsearch)& match.
6626 Although I cannot see it being of much use, the general matching function that
6627 is used to implement &((n)wildlsearch)& means that the string may begin with a
6628 lookup name terminated by a semicolon, and followed by lookup data. For
6631 cdb;/some/file data for keys that match the file
6633 The data that is obtained from the nested lookup is discarded.
6636 Keys that do not match any of these patterns are interpreted literally. The
6637 continuation rules for the data are the same as for &(lsearch)&, and keys may
6638 be followed by optional colons.
6640 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6641 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6642 lookup types support only literal keys.
6646 .section "Query-style lookup types" "SECTquerystylelookups"
6647 .cindex "lookup" "query-style types"
6648 .cindex "query-style lookup" "list of types"
6649 The supported query-style lookup types are listed below. Further details about
6650 many of them are given in later sections.
6653 .cindex "DNS" "as a lookup type"
6654 .cindex "lookup" "DNS"
6655 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6656 are given in the supplied query. The resulting data is the contents of the
6657 records. See section &<<SECTdnsdb>>&.
6659 .cindex "InterBase lookup type"
6660 .cindex "lookup" "InterBase"
6661 &(ibase)&: This does a lookup in an InterBase database.
6663 .cindex "LDAP" "lookup type"
6664 .cindex "lookup" "LDAP"
6665 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6666 returns attributes from a single entry. There is a variant called &(ldapm)&
6667 that permits values from multiple entries to be returned. A third variant
6668 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6669 any attribute values. See section &<<SECTldap>>&.
6671 .cindex "MySQL" "lookup type"
6672 .cindex "lookup" "MySQL"
6673 &(mysql)&: The format of the query is an SQL statement that is passed to a
6674 MySQL database. See section &<<SECTsql>>&.
6676 .cindex "NIS+ lookup type"
6677 .cindex "lookup" "NIS+"
6678 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6679 the field to be returned. See section &<<SECTnisplus>>&.
6681 .cindex "Oracle" "lookup type"
6682 .cindex "lookup" "Oracle"
6683 &(oracle)&: The format of the query is an SQL statement that is passed to an
6684 Oracle database. See section &<<SECTsql>>&.
6686 .cindex "lookup" "passwd"
6687 .cindex "passwd lookup type"
6688 .cindex "&_/etc/passwd_&"
6689 &(passwd)& is a query-style lookup with queries that are just user names. The
6690 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6691 success, the result string is the same as you would get from an &(lsearch)&
6692 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6693 password value. For example:
6695 *:42:42:King Rat:/home/kr:/bin/bash
6698 .cindex "PostgreSQL lookup type"
6699 .cindex "lookup" "PostgreSQL"
6700 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6701 PostgreSQL database. See section &<<SECTsql>>&.
6704 .cindex "Redis lookup type"
6705 .cindex lookup Redis
6706 &(redis)&: The format of the query is an SQL statement that is passed to a
6707 Redis database. See section &<<SECTsql>>&.
6710 .cindex "sqlite lookup type"
6711 .cindex "lookup" "sqlite"
6712 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6713 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6716 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6717 not likely to be useful in normal operation.
6719 .cindex "whoson lookup type"
6720 .cindex "lookup" "whoson"
6721 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6722 allows a server to check whether a particular (dynamically allocated) IP
6723 address is currently allocated to a known (trusted) user and, optionally, to
6724 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6725 at one time for &"POP before SMTP"& authentication, but that approach has been
6726 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6727 &"POP before SMTP"& checking using ACL statements such as
6729 require condition = \
6730 ${lookup whoson {$sender_host_address}{yes}{no}}
6732 The query consists of a single IP address. The value returned is the name of
6733 the authenticated user, which is stored in the variable &$value$&. However, in
6734 this example, the data in &$value$& is not used; the result of the lookup is
6735 one of the fixed strings &"yes"& or &"no"&.
6740 .section "Temporary errors in lookups" "SECID63"
6741 .cindex "lookup" "temporary error in"
6742 Lookup functions can return temporary error codes if the lookup cannot be
6743 completed. For example, an SQL or LDAP database might be unavailable. For this
6744 reason, it is not advisable to use a lookup that might do this for critical
6745 options such as a list of local domains.
6747 When a lookup cannot be completed in a router or transport, delivery
6748 of the message (to the relevant address) is deferred, as for any other
6749 temporary error. In other circumstances Exim may assume the lookup has failed,
6750 or may give up altogether.
6754 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6755 .cindex "wildcard lookups"
6756 .cindex "lookup" "default values"
6757 .cindex "lookup" "wildcard"
6758 .cindex "lookup" "* added to type"
6759 .cindex "default" "in single-key lookups"
6760 In this context, a &"default value"& is a value specified by the administrator
6761 that is to be used if a lookup fails.
6763 &*Note:*& This section applies only to single-key lookups. For query-style
6764 lookups, the facilities of the query language must be used. An attempt to
6765 specify a default for a query-style lookup provokes an error.
6767 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6768 and the initial lookup fails, the key &"*"& is looked up in the file to
6769 provide a default value. See also the section on partial matching below.
6771 .cindex "*@ with single-key lookup"
6772 .cindex "lookup" "*@ added to type"
6773 .cindex "alias file" "per-domain default"
6774 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6775 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6776 character, a second lookup is done with everything before the last @ replaced
6777 by *. This makes it possible to provide per-domain defaults in alias files
6778 that include the domains in the keys. If the second lookup fails (or doesn't
6779 take place because there is no @ in the key), &"*"& is looked up.
6780 For example, a &(redirect)& router might contain:
6782 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6784 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6785 looks up these keys, in this order:
6791 The data is taken from whichever key it finds first. &*Note*&: In an
6792 &(lsearch)& file, this does not mean the first of these keys in the file. A
6793 complete scan is done for each key, and only if it is not found at all does
6794 Exim move on to try the next key.
6798 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6799 .cindex "partial matching"
6800 .cindex "wildcard lookups"
6801 .cindex "lookup" "partial matching"
6802 .cindex "lookup" "wildcard"
6803 .cindex "asterisk" "in search type"
6804 The normal operation of a single-key lookup is to search the file for an exact
6805 match with the given key. However, in a number of situations where domains are
6806 being looked up, it is useful to be able to do partial matching. In this case,
6807 information in the file that has a key starting with &"*."& is matched by any
6808 domain that ends with the components that follow the full stop. For example, if
6809 a key in a DBM file is
6811 *.dates.fict.example
6813 then when partial matching is enabled this is matched by (amongst others)
6814 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6815 by &'dates.fict.example'&, if that does not appear as a separate key in the
6818 &*Note*&: Partial matching is not available for query-style lookups. It is
6819 also not available for any lookup items in address lists (see section
6820 &<<SECTaddresslist>>&).
6822 Partial matching is implemented by doing a series of separate lookups using
6823 keys constructed by modifying the original subject key. This means that it can
6824 be used with any of the single-key lookup types, provided that
6825 partial matching keys
6826 beginning with a special prefix (default &"*."&) are included in the data file.
6827 Keys in the file that do not begin with the prefix are matched only by
6828 unmodified subject keys when partial matching is in use.
6830 Partial matching is requested by adding the string &"partial-"& to the front of
6831 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6832 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6833 is added at the start of the subject key, and it is looked up again. If that
6834 fails, further lookups are tried with dot-separated components removed from the
6835 start of the subject key, one-by-one, and &"*."& added on the front of what
6838 A minimum number of two non-* components are required. This can be adjusted
6839 by including a number before the hyphen in the search type. For example,
6840 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6841 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6842 subject key is &'2250.dates.fict.example'& then the following keys are looked
6843 up when the minimum number of non-* components is two:
6845 2250.dates.fict.example
6846 *.2250.dates.fict.example
6847 *.dates.fict.example
6850 As soon as one key in the sequence is successfully looked up, the lookup
6853 .cindex "lookup" "partial matching &-- changing prefix"
6854 .cindex "prefix" "for partial matching"
6855 The use of &"*."& as the partial matching prefix is a default that can be
6856 changed. The motivation for this feature is to allow Exim to operate with file
6857 formats that are used by other MTAs. A different prefix can be supplied in
6858 parentheses instead of the hyphen after &"partial"&. For example:
6860 domains = partial(.)lsearch;/some/file
6862 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6863 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6864 components is unchanged). The prefix may consist of any punctuation characters
6865 other than a closing parenthesis. It may be empty, for example:
6867 domains = partial1()cdb;/some/file
6869 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6870 &`a.b.c`&, &`b.c`&, and &`c`&.
6872 If &"partial0"& is specified, what happens at the end (when the lookup with
6873 just one non-wild component has failed, and the original key is shortened right
6874 down to the null string) depends on the prefix:
6877 If the prefix has zero length, the whole lookup fails.
6879 If the prefix has length 1, a lookup for just the prefix is done. For
6880 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6882 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6883 remainder is looked up. With the default prefix, therefore, the final lookup is
6884 for &"*"& on its own.
6886 Otherwise, the whole prefix is looked up.
6890 If the search type ends in &"*"& or &"*@"& (see section
6891 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6892 this implies happens after all partial lookups have failed. If &"partial0"& is
6893 specified, adding &"*"& to the search type has no effect with the default
6894 prefix, because the &"*"& key is already included in the sequence of partial
6895 lookups. However, there might be a use for lookup types such as
6896 &"partial0(.)lsearch*"&.
6898 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6899 in domain lists and the like. Partial matching works only in terms of
6900 dot-separated components; a key such as &`*fict.example`&
6901 in a database file is useless, because the asterisk in a partial matching
6902 subject key is always followed by a dot.
6907 .section "Lookup caching" "SECID64"
6908 .cindex "lookup" "caching"
6909 .cindex "caching" "lookup data"
6910 Exim caches all lookup results in order to avoid needless repetition of
6911 lookups. However, because (apart from the daemon) Exim operates as a collection
6912 of independent, short-lived processes, this caching applies only within a
6913 single Exim process. There is no inter-process lookup caching facility.
6915 For single-key lookups, Exim keeps the relevant files open in case there is
6916 another lookup that needs them. In some types of configuration this can lead to
6917 many files being kept open for messages with many recipients. To avoid hitting
6918 the operating system limit on the number of simultaneously open files, Exim
6919 closes the least recently used file when it needs to open more files than its
6920 own internal limit, which can be changed via the &%lookup_open_max%& option.
6922 The single-key lookup files are closed and the lookup caches are flushed at
6923 strategic points during delivery &-- for example, after all routing is
6929 .section "Quoting lookup data" "SECID65"
6930 .cindex "lookup" "quoting"
6931 .cindex "quoting" "in lookups"
6932 When data from an incoming message is included in a query-style lookup, there
6933 is the possibility of special characters in the data messing up the syntax of
6934 the query. For example, a NIS+ query that contains
6938 will be broken if the local part happens to contain a closing square bracket.
6939 For NIS+, data can be enclosed in double quotes like this:
6941 [name="$local_part"]
6943 but this still leaves the problem of a double quote in the data. The rule for
6944 NIS+ is that double quotes must be doubled. Other lookup types have different
6945 rules, and to cope with the differing requirements, an expansion operator
6946 of the following form is provided:
6948 ${quote_<lookup-type>:<string>}
6950 For example, the safest way to write the NIS+ query is
6952 [name="${quote_nisplus:$local_part}"]
6954 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6955 operator can be used for all lookup types, but has no effect for single-key
6956 lookups, since no quoting is ever needed in their key strings.
6961 .section "More about dnsdb" "SECTdnsdb"
6962 .cindex "dnsdb lookup"
6963 .cindex "lookup" "dnsdb"
6964 .cindex "DNS" "as a lookup type"
6965 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6966 of a record type and a domain name, separated by an equals sign. For example,
6967 an expansion string could contain:
6969 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6971 If the lookup succeeds, the result is placed in &$value$&, which in this case
6972 is used on its own as the result. If the lookup does not succeed, the
6973 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6974 &<<SECTforexpfai>>& for an explanation of what this means.
6976 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
6977 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
6978 If no type is given, TXT is assumed.
6980 For any record type, if multiple records are found, the data is returned as a
6981 concatenation, with newline as the default separator. The order, of course,
6982 depends on the DNS resolver. You can specify a different separator character
6983 between multiple records by putting a right angle-bracket followed immediately
6984 by the new separator at the start of the query. For example:
6986 ${lookup dnsdb{>: a=host1.example}}
6988 It is permitted to specify a space as the separator character. Further
6989 white space is ignored.
6990 For lookup types that return multiple fields per record,
6991 an alternate field separator can be specified using a comma after the main
6992 separator character, followed immediately by the field separator.
6994 .cindex "PTR record" "in &(dnsdb)& lookup"
6995 When the type is PTR,
6996 the data can be an IP address, written as normal; inversion and the addition of
6997 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6999 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7001 If the data for a PTR record is not a syntactically valid IP address, it is not
7002 altered and nothing is added.
7004 .cindex "MX record" "in &(dnsdb)& lookup"
7005 .cindex "SRV record" "in &(dnsdb)& lookup"
7006 For an MX lookup, both the preference value and the host name are returned for
7007 each record, separated by a space. For an SRV lookup, the priority, weight,
7008 port, and host name are returned for each record, separated by spaces.
7009 The field separator can be modified as above.
7011 .cindex "TXT record" "in &(dnsdb)& lookup"
7012 .cindex "SPF record" "in &(dnsdb)& lookup"
7013 For TXT records with multiple items of data, only the first item is returned,
7014 unless a field separator is specified.
7015 To concatenate items without a separator, use a semicolon instead.
7017 default behaviour is to concatenate multiple items without using a separator.
7019 ${lookup dnsdb{>\n,: txt=a.b.example}}
7020 ${lookup dnsdb{>\n; txt=a.b.example}}
7021 ${lookup dnsdb{spf=example.org}}
7023 It is permitted to specify a space as the separator character. Further
7024 white space is ignored.
7026 .cindex "SOA record" "in &(dnsdb)& lookup"
7027 For an SOA lookup, while no result is obtained the lookup is redone with
7028 successively more leading components dropped from the given domain.
7029 Only the primary-nameserver field is returned unless a field separator is
7032 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7035 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7036 .cindex "dnsdb modifiers"
7037 .cindex "modifiers" "dnsdb"
7038 .cindex "options" "dnsdb"
7039 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7040 each followed by a comma,
7041 that may appear before the record type.
7043 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7044 temporary DNS error for any of them, the behaviour is controlled by
7045 a defer-option modifier.
7046 The possible keywords are
7047 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7048 With &"strict"& behaviour, any temporary DNS error causes the
7049 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7050 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7051 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7052 error causes the whole lookup to defer only if none of the other lookups
7053 succeed. The default is &"lax"&, so the following lookups are equivalent:
7055 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7056 ${lookup dnsdb{a=one.host.com:two.host.com}}
7058 Thus, in the default case, as long as at least one of the DNS lookups
7059 yields some data, the lookup succeeds.
7061 .cindex "DNSSEC" "dns lookup"
7062 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7063 The possible keywords are
7064 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7065 With &"strict"& or &"lax"& DNSSEC information is requested
7067 With &"strict"& a response from the DNS resolver that
7068 is not labelled as authenticated data
7069 is treated as equivalent to a temporary DNS error.
7070 The default is &"never"&.
7072 See also the &$lookup_dnssec_authenticated$& variable.
7074 .cindex timeout "dns lookup"
7075 .cindex "DNS" timeout
7076 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7077 The form is &"retrans_VAL"& where VAL is an Exim time specification
7079 The default value is set by the main configuration option &%dns_retrans%&.
7081 Retries for the dnsdb lookup can be controlled by a retry modifier.
7082 The form if &"retry_VAL"& where VAL is an integer.
7083 The default count is set by the main configuration option &%dns_retry%&.
7085 .cindex cacheing "of dns lookup"
7086 .cindex TTL "of dns lookup"
7088 Dnsdb lookup results are cached within a single process (and its children).
7089 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7090 value of the set of returned DNS records.
7093 .section "Pseudo dnsdb record types" "SECID66"
7094 .cindex "MX record" "in &(dnsdb)& lookup"
7095 By default, both the preference value and the host name are returned for
7096 each MX record, separated by a space. If you want only host names, you can use
7097 the pseudo-type MXH:
7099 ${lookup dnsdb{mxh=a.b.example}}
7101 In this case, the preference values are omitted, and just the host names are
7104 .cindex "name server for enclosing domain"
7105 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7106 records on the given domain, but if none are found, it removes the first
7107 component of the domain name, and tries again. This process continues until NS
7108 records are found or there are no more components left (or there is a DNS
7109 error). In other words, it may return the name servers for a top-level domain,
7110 but it never returns the root name servers. If there are no NS records for the
7111 top-level domain, the lookup fails. Consider these examples:
7113 ${lookup dnsdb{zns=xxx.quercite.com}}
7114 ${lookup dnsdb{zns=xxx.edu}}
7116 Assuming that in each case there are no NS records for the full domain name,
7117 the first returns the name servers for &%quercite.com%&, and the second returns
7118 the name servers for &%edu%&.
7120 You should be careful about how you use this lookup because, unless the
7121 top-level domain does not exist, the lookup always returns some host names. The
7122 sort of use to which this might be put is for seeing if the name servers for a
7123 given domain are on a blacklist. You can probably assume that the name servers
7124 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7127 .cindex "CSA" "in &(dnsdb)& lookup"
7128 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7129 records according to the CSA rules, which are described in section
7130 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7131 not sufficient because of the extra parent domain search behaviour of CSA. The
7132 result of a successful lookup such as:
7134 ${lookup dnsdb {csa=$sender_helo_name}}
7136 has two space-separated fields: an authorization code and a target host name.
7137 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7138 authorization required but absent, or &"?"& for unknown.
7140 .cindex "A+" "in &(dnsdb)& lookup"
7141 The pseudo-type A+ performs an AAAA
7142 and then an A lookup. All results are returned; defer processing
7143 (see below) is handled separately for each lookup. Example:
7145 ${lookup dnsdb {>; a+=$sender_helo_name}}
7149 .section "Multiple dnsdb lookups" "SECID67"
7150 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7151 However, you can specify a list of domains or IP addresses in a single
7152 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7153 the default separator, but with the ability to change this. For example:
7155 ${lookup dnsdb{one.domain.com:two.domain.com}}
7156 ${lookup dnsdb{a=one.host.com:two.host.com}}
7157 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7159 In order to retain backwards compatibility, there is one special case: if
7160 the lookup type is PTR and no change of separator is specified, Exim looks
7161 to see if the rest of the string is precisely one IPv6 address. In this
7162 case, it does not treat it as a list.
7164 The data from each lookup is concatenated, with newline separators by default,
7165 in the same way that multiple DNS records for a single item are handled. A
7166 different separator can be specified, as described above.
7171 .section "More about LDAP" "SECTldap"
7172 .cindex "LDAP" "lookup, more about"
7173 .cindex "lookup" "LDAP"
7174 .cindex "Solaris" "LDAP"
7175 The original LDAP implementation came from the University of Michigan; this has
7176 become &"Open LDAP"&, and there are now two different releases. Another
7177 implementation comes from Netscape, and Solaris 7 and subsequent releases
7178 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7179 the lookup function level, their error handling is different. For this reason
7180 it is necessary to set a compile-time variable when building Exim with LDAP, to
7181 indicate which LDAP library is in use. One of the following should appear in
7182 your &_Local/Makefile_&:
7184 LDAP_LIB_TYPE=UMICHIGAN
7185 LDAP_LIB_TYPE=OPENLDAP1
7186 LDAP_LIB_TYPE=OPENLDAP2
7187 LDAP_LIB_TYPE=NETSCAPE
7188 LDAP_LIB_TYPE=SOLARIS
7190 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7191 same interface as the University of Michigan version.
7193 There are three LDAP lookup types in Exim. These behave slightly differently in
7194 the way they handle the results of a query:
7197 &(ldap)& requires the result to contain just one entry; if there are more, it
7200 &(ldapdn)& also requires the result to contain just one entry, but it is the
7201 Distinguished Name that is returned rather than any attribute values.
7203 &(ldapm)& permits the result to contain more than one entry; the attributes
7204 from all of them are returned.
7208 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7209 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7210 the data returned by a successful lookup is described in the next section.
7211 First we explain how LDAP queries are coded.
7214 .section "Format of LDAP queries" "SECTforldaque"
7215 .cindex "LDAP" "query format"
7216 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7217 the configuration of a &(redirect)& router one might have this setting:
7219 data = ${lookup ldap \
7220 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7221 c=UK?mailbox?base?}}
7223 .cindex "LDAP" "with TLS"
7224 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7225 secure (encrypted) LDAP connections. The second of these ensures that an
7226 encrypted TLS connection is used.
7228 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7229 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7230 See the &%ldap_start_tls%& option.
7232 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7233 controlled. Every part of the TLS configuration can be configured by settings in
7234 &_exim.conf_&. Depending on the version of the client libraries installed on
7235 your system, some of the initialization may have required setting options in
7236 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7237 certificates. This revealed a nuance where the current UID that exim was
7238 running as could affect which config files it read. With Exim 4.83, these
7239 methods become optional, only taking effect if not specifically set in
7243 .section "LDAP quoting" "SECID68"
7244 .cindex "LDAP" "quoting"
7245 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7246 and the second because the LDAP query is represented as a URL. Furthermore,
7247 within an LDAP query, two different kinds of quoting are required. For this
7248 reason, there are two different LDAP-specific quoting operators.
7250 The &%quote_ldap%& operator is designed for use on strings that are part of
7251 filter specifications. Conceptually, it first does the following conversions on
7259 in accordance with RFC 2254. The resulting string is then quoted according
7260 to the rules for URLs, that is, all non-alphanumeric characters except
7264 are converted to their hex values, preceded by a percent sign. For example:
7266 ${quote_ldap: a(bc)*, a<yz>; }
7270 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7272 Removing the URL quoting, this is (with a leading and a trailing space):
7274 a\28bc\29\2A, a<yz>;
7276 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7277 base DN specifications in queries. Conceptually, it first converts the string
7278 by inserting a backslash in front of any of the following characters:
7282 It also inserts a backslash before any leading spaces or # characters, and
7283 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7284 is then quoted according to the rules for URLs. For example:
7286 ${quote_ldap_dn: a(bc)*, a<yz>; }
7290 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7292 Removing the URL quoting, this is (with a trailing space):
7294 \ a(bc)*\, a\<yz\>\;\
7296 There are some further comments about quoting in the section on LDAP
7297 authentication below.
7300 .section "LDAP connections" "SECID69"
7301 .cindex "LDAP" "connections"
7302 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7303 is in use, via a Unix domain socket. The example given above does not specify
7304 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7307 ldap://<hostname>:<port>/...
7309 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7310 used. When no server is specified in a query, a list of default servers is
7311 taken from the &%ldap_default_servers%& configuration option. This supplies a
7312 colon-separated list of servers which are tried in turn until one successfully
7313 handles a query, or there is a serious error. Successful handling either
7314 returns the requested data, or indicates that it does not exist. Serious errors
7315 are syntactical, or multiple values when only a single value is expected.
7316 Errors which cause the next server to be tried are connection failures, bind
7317 failures, and timeouts.
7319 For each server name in the list, a port number can be given. The standard way
7320 of specifying a host and port is to use a colon separator (RFC 1738). Because
7321 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7322 doubled. For example
7324 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7326 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7327 to the LDAP library with no server name, and the library's default (normally
7328 the local host) is used.
7330 If you are using the OpenLDAP library, you can connect to an LDAP server using
7331 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7332 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7333 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7336 For this type of connection, instead of a host name for the server, a pathname
7337 for the socket is required, and the port number is not relevant. The pathname
7338 can be specified either as an item in &%ldap_default_servers%&, or inline in
7339 the query. In the former case, you can have settings such as
7341 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7343 When the pathname is given in the query, you have to escape the slashes as
7344 &`%2F`& to fit in with the LDAP URL syntax. For example:
7346 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7348 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7349 a pathname, it uses the Unix domain socket code, even if the query actually
7350 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7351 socket connection. This behaviour means that you can use a setting of
7352 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7353 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7354 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7357 If an explicit &`ldapi`& type is given in a query when a host name is
7358 specified, an error is diagnosed. However, if there are more items in
7359 &%ldap_default_servers%&, they are tried. In other words:
7362 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7365 Using &`ldapi`& with a host name causes an error.
7369 Using &`ldapi`& with no host or path in the query, and no setting of
7370 &%ldap_default_servers%&, does whatever the library does by default.
7374 .section "LDAP authentication and control information" "SECID70"
7375 .cindex "LDAP" "authentication"
7376 The LDAP URL syntax provides no way of passing authentication and other control
7377 information to the server. To make this possible, the URL in an LDAP query may
7378 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7379 spaces. If a value contains spaces it must be enclosed in double quotes, and
7380 when double quotes are used, backslash is interpreted in the usual way inside
7381 them. The following names are recognized:
7383 &`DEREFERENCE`& set the dereferencing parameter
7384 &`NETTIME `& set a timeout for a network operation
7385 &`USER `& set the DN, for authenticating the LDAP bind
7386 &`PASS `& set the password, likewise
7387 &`REFERRALS `& set the referrals parameter
7388 &`SERVERS `& set alternate server list for this query only
7389 &`SIZE `& set the limit for the number of entries returned
7390 &`TIME `& set the maximum waiting time for a query
7392 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7393 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7394 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7395 library from trying to follow referrals issued by the LDAP server.
7397 .cindex LDAP timeout
7398 .cindex timeout "LDAP lookup"
7399 The name CONNECT is an obsolete name for NETTIME, retained for
7400 backwards compatibility. This timeout (specified as a number of seconds) is
7401 enforced from the client end for operations that can be carried out over a
7402 network. Specifically, it applies to network connections and calls to the
7403 &'ldap_result()'& function. If the value is greater than zero, it is used if
7404 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7405 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7406 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7407 Netscape SDK; for OpenLDAP no action is taken.
7409 The TIME parameter (also a number of seconds) is passed to the server to
7410 set a server-side limit on the time taken to complete a search.
7412 The SERVERS parameter allows you to specify an alternate list of ldap servers
7413 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7414 default list of ldap servers, and a single lookup can specify a single ldap
7415 server to use. But when you need to do a lookup with a list of servers that is
7416 different than the default list (maybe different order, maybe a completely
7417 different set of servers), the SERVERS parameter allows you to specify this
7418 alternate list (colon-separated).
7420 Here is an example of an LDAP query in an Exim lookup that uses some of these
7421 values. This is a single line, folded to fit on the page:
7424 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7425 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7428 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7429 any of the auxiliary data. Exim configuration settings that include lookups
7430 which contain password information should be preceded by &"hide"& to prevent
7431 non-admin users from using the &%-bP%& option to see their values.
7433 The auxiliary data items may be given in any order. The default is no
7434 connection timeout (the system timeout is used), no user or password, no limit
7435 on the number of entries returned, and no time limit on queries.
7437 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7438 removes any URL quoting that it may contain before passing it LDAP. Apparently
7439 some libraries do this for themselves, but some do not. Removing the URL
7440 quoting has two advantages:
7443 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7444 DNs as with DNs inside actual queries.
7446 It permits spaces inside USER= DNs.
7449 For example, a setting such as
7451 USER=cn=${quote_ldap_dn:$1}
7453 should work even if &$1$& contains spaces.
7455 Expanded data for the PASS= value should be quoted using the &%quote%&
7456 expansion operator, rather than the LDAP quote operators. The only reason this
7457 field needs quoting is to ensure that it conforms to the Exim syntax, which
7458 does not allow unquoted spaces. For example:
7462 The LDAP authentication mechanism can be used to check passwords as part of
7463 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7468 .section "Format of data returned by LDAP" "SECID71"
7469 .cindex "LDAP" "returned data formats"
7470 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7471 as a sequence of values, for example
7473 cn=manager,o=University of Cambridge,c=UK
7475 The &(ldap)& lookup type generates an error if more than one entry matches the
7476 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7477 the result between the data from different entries. It is possible for multiple
7478 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7479 you know that whatever values are returned all came from a single entry in the
7482 In the common case where you specify a single attribute in your LDAP query, the
7483 result is not quoted, and does not contain the attribute name. If the attribute
7484 has multiple values, they are separated by commas. Any comma that is
7485 part of an attribute's value is doubled.
7487 If you specify multiple attributes, the result contains space-separated, quoted
7488 strings, each preceded by the attribute name and an equals sign. Within the
7489 quotes, the quote character, backslash, and newline are escaped with
7490 backslashes, and commas are used to separate multiple values for the attribute.
7491 Any commas in attribute values are doubled
7492 (permitting treatment of the values as a comma-separated list).
7493 Apart from the escaping, the string within quotes takes the same form as the
7494 output when a single attribute is requested. Specifying no attributes is the
7495 same as specifying all of an entry's attributes.
7497 Here are some examples of the output format. The first line of each pair is an
7498 LDAP query, and the second is the data that is returned. The attribute called
7499 &%attr1%& has two values, one of them with an embedded comma, whereas
7500 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7501 (they have SUP &%attr%& in their schema definitions).
7504 ldap:///o=base?attr1?sub?(uid=fred)
7507 ldap:///o=base?attr2?sub?(uid=fred)
7510 ldap:///o=base?attr?sub?(uid=fred)
7511 value1.1,value1,,2,value two
7513 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7514 attr1="value1.1,value1,,2" attr2="value two"
7516 ldap:///o=base??sub?(uid=fred)
7517 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7520 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7521 results of LDAP lookups.
7522 The &%extract%& operator in string expansions can be used to pick out
7523 individual fields from data that consists of &'key'&=&'value'& pairs.
7524 The &%listextract%& operator should be used to pick out individual values
7525 of attributes, even when only a single value is expected.
7526 The doubling of embedded commas allows you to use the returned data as a
7527 comma separated list (using the "<," syntax for changing the input list separator).
7532 .section "More about NIS+" "SECTnisplus"
7533 .cindex "NIS+ lookup type"
7534 .cindex "lookup" "NIS+"
7535 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7536 and field name. If this is given, the result of a successful query is the
7537 contents of the named field; otherwise the result consists of a concatenation
7538 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7539 values containing spaces are quoted. For example, the query
7541 [name=mg1456],passwd.org_dir
7543 might return the string
7545 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7546 home=/home/mg1456 shell=/bin/bash shadow=""
7548 (split over two lines here to fit on the page), whereas
7550 [name=mg1456],passwd.org_dir:gcos
7556 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7557 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7558 operator is to double any quote characters within the text.
7562 .section "SQL lookups" "SECTsql"
7563 .cindex "SQL lookup types"
7564 .cindex "MySQL" "lookup type"
7565 .cindex "PostgreSQL lookup type"
7566 .cindex "lookup" "MySQL"
7567 .cindex "lookup" "PostgreSQL"
7568 .cindex "Oracle" "lookup type"
7569 .cindex "lookup" "Oracle"
7570 .cindex "InterBase lookup type"
7571 .cindex "lookup" "InterBase"
7572 .cindex "Redis lookup type"
7573 .cindex lookup Redis
7574 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7576 databases. Queries for these databases contain SQL statements, so an example
7579 ${lookup mysql{select mailbox from users where id='userx'}\
7582 If the result of the query contains more than one field, the data for each
7583 field in the row is returned, preceded by its name, so the result of
7585 ${lookup pgsql{select home,name from users where id='userx'}\
7590 home=/home/userx name="Mister X"
7592 Empty values and values containing spaces are double quoted, with embedded
7593 quotes escaped by a backslash. If the result of the query contains just one
7594 field, the value is passed back verbatim, without a field name, for example:
7598 If the result of the query yields more than one row, it is all concatenated,
7599 with a newline between the data for each row.
7602 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
7603 .cindex "MySQL" "lookup type"
7604 .cindex "PostgreSQL lookup type"
7605 .cindex "lookup" "MySQL"
7606 .cindex "lookup" "PostgreSQL"
7607 .cindex "Oracle" "lookup type"
7608 .cindex "lookup" "Oracle"
7609 .cindex "InterBase lookup type"
7610 .cindex "lookup" "InterBase"
7611 .cindex "Redis lookup type"
7612 .cindex lookup Redis
7613 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
7614 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
7615 or &%redis_servers%&
7616 option (as appropriate) must be set to a colon-separated list of server
7618 (For MySQL and PostgreSQL, the global option need not be set if all
7619 queries contain their own server information &-- see section
7620 &<<SECTspeserque>>&.)
7622 each item in the list is a slash-separated list of four
7623 items: host name, database name, user name, and password. In the case of
7624 Oracle, the host name field is used for the &"service name"&, and the database
7625 name field is not used and should be empty. For example:
7627 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7629 Because password data is sensitive, you should always precede the setting with
7630 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7631 option. Here is an example where two MySQL servers are listed:
7633 hide mysql_servers = localhost/users/root/secret:\
7634 otherhost/users/root/othersecret
7636 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7637 because this is a colon-separated list, the colon has to be doubled. For each
7638 query, these parameter groups are tried in order until a connection is made and
7639 a query is successfully processed. The result of a query may be that no data is
7640 found, but that is still a successful query. In other words, the list of
7641 servers provides a backup facility, not a list of different places to look.
7643 For Redis the global option need not be specified if all queries contain their
7644 own server information &-- see section &<<SECTspeserque>>&.
7645 If specified, the option must be set to a colon-separated list of server
7647 Each item in the list is a slash-separated list of three items:
7648 host, database number, and password.
7650 The host is required and may be either an IPv4 address and optional
7651 port number (separated by a colon, which needs doubling due to the
7652 higher-level list), or a Unix socket pathname enclosed in parentheses
7654 The database number is optional; if present that number is selected in the backend
7656 The password is optional; if present it is used to authenticate to the backend
7659 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7660 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7661 respectively, and the characters single-quote, double-quote, and backslash
7662 itself are escaped with backslashes.
7664 The &%quote_redis%& expansion operator
7665 escapes whitespace and backslash characters with a backslash.
7667 .section "Specifying the server in the query" "SECTspeserque"
7668 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
7669 it is possible to specify a list of servers with an individual query. This is
7670 done by starting the query with
7672 &`servers=`&&'server1:server2:server3:...'&&`;`&
7674 Each item in the list may take one of two forms:
7676 If it contains no slashes it is assumed to be just a host name. The appropriate
7677 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7678 of the same name, and the remaining parameters (database, user, password) are
7681 If it contains any slashes, it is taken as a complete parameter set.
7683 The list of servers is used in exactly the same way as the global list.
7684 Once a connection to a server has happened and a query has been
7685 successfully executed, processing of the lookup ceases.
7687 This feature is intended for use in master/slave situations where updates
7688 are occurring and you want to update the master rather than a slave. If the
7689 master is in the list as a backup for reading, you might have a global setting
7692 mysql_servers = slave1/db/name/pw:\
7696 In an updating lookup, you could then write:
7698 ${lookup mysql{servers=master; UPDATE ...} }
7700 That query would then be sent only to the master server. If, on the other hand,
7701 the master is not to be used for reading, and so is not present in the global
7702 option, you can still update it by a query of this form:
7704 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7708 .section "Special MySQL features" "SECID73"
7709 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7710 causes a connection to the server on the local host by means of a Unix domain
7711 socket. An alternate socket can be specified in parentheses.
7712 An option group name for MySQL option files can be specified in square brackets;
7713 the default value is &"exim"&.
7714 The full syntax of each item in &%mysql_servers%& is:
7716 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
7717 <&'database'&>/<&'user'&>/<&'password'&>
7719 Any of the four sub-parts of the first field can be omitted. For normal use on
7720 the local host it can be left blank or set to just &"localhost"&.
7722 No database need be supplied &-- but if it is absent here, it must be given in
7725 If a MySQL query is issued that does not request any data (an insert, update,
7726 or delete command), the result of the lookup is the number of rows affected.
7728 &*Warning*&: This can be misleading. If an update does not actually change
7729 anything (for example, setting a field to the value it already has), the result
7730 is zero because no rows are affected.
7733 .section "Special PostgreSQL features" "SECID74"
7734 PostgreSQL lookups can also use Unix domain socket connections to the database.
7735 This is usually faster and costs less CPU time than a TCP/IP connection.
7736 However it can be used only if the mail server runs on the same machine as the
7737 database server. A configuration line for PostgreSQL via Unix domain sockets
7740 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7742 In other words, instead of supplying a host name, a path to the socket is
7743 given. The path name is enclosed in parentheses so that its slashes aren't
7744 visually confused with the delimiters for the other server parameters.
7746 If a PostgreSQL query is issued that does not request any data (an insert,
7747 update, or delete command), the result of the lookup is the number of rows
7750 .section "More about SQLite" "SECTsqlite"
7751 .cindex "lookup" "SQLite"
7752 .cindex "sqlite lookup type"
7753 SQLite is different to the other SQL lookups because a file name is required in
7754 addition to the SQL query. An SQLite database is a single file, and there is no
7755 daemon as in the other SQL databases. The interface to Exim requires the name
7756 of the file, as an absolute path, to be given at the start of the query. It is
7757 separated from the query by white space. This means that the path name cannot
7758 contain white space. Here is a lookup expansion example:
7760 ${lookup sqlite {/some/thing/sqlitedb \
7761 select name from aliases where id='userx';}}
7763 In a list, the syntax is similar. For example:
7765 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7766 select * from relays where ip='$sender_host_address';
7768 The only character affected by the &%quote_sqlite%& operator is a single
7769 quote, which it doubles.
7771 .cindex timeout SQLite
7772 .cindex sqlite "lookup timeout"
7773 The SQLite library handles multiple simultaneous accesses to the database
7774 internally. Multiple readers are permitted, but only one process can
7775 update at once. Attempts to access the database while it is being updated
7776 are rejected after a timeout period, during which the SQLite library
7777 waits for the lock to be released. In Exim, the default timeout is set
7778 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7784 . ////////////////////////////////////////////////////////////////////////////
7785 . ////////////////////////////////////////////////////////////////////////////
7787 .chapter "Domain, host, address, and local part lists" &&&
7788 "CHAPdomhosaddlists" &&&
7789 "Domain, host, and address lists"
7790 .scindex IIDdohoadli "lists of domains; hosts; etc."
7791 A number of Exim configuration options contain lists of domains, hosts,
7792 email addresses, or local parts. For example, the &%hold_domains%& option
7793 contains a list of domains whose delivery is currently suspended. These lists
7794 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7795 arguments to expansion conditions such as &%match_domain%&.
7797 Each item in one of these lists is a pattern to be matched against a domain,
7798 host, email address, or local part, respectively. In the sections below, the
7799 different types of pattern for each case are described, but first we cover some
7800 general facilities that apply to all four kinds of list.
7802 Note that other parts of Exim use a &'string list'& which does not
7803 support all the complexity available in
7804 domain, host, address and local part lists.
7808 .section "Expansion of lists" "SECTlistexpand"
7809 .cindex "expansion" "of lists"
7810 Each list is expanded as a single string before it is used.
7813 &'Exception: the router headers_remove option, where list-item
7814 splitting is done before string-expansion.'&
7818 expansion must be a list, possibly containing empty items, which is split up
7819 into separate items for matching. By default, colon is the separator character,
7820 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7821 &<<SECTempitelis>>& for details of the list syntax; the second of these
7822 discusses the way to specify empty list items.
7825 If the string expansion is forced to fail, Exim behaves as if the item it is
7826 testing (domain, host, address, or local part) is not in the list. Other
7827 expansion failures cause temporary errors.
7829 If an item in a list is a regular expression, backslashes, dollars and possibly
7830 other special characters in the expression must be protected against
7831 misinterpretation by the string expander. The easiest way to do this is to use
7832 the &`\N`& expansion feature to indicate that the contents of the regular
7833 expression should not be expanded. For example, in an ACL you might have:
7835 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7836 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7838 The first item is a regular expression that is protected from expansion by
7839 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7840 senders based on the receiving domain.
7845 .section "Negated items in lists" "SECID76"
7846 .cindex "list" "negation"
7847 .cindex "negation" "in lists"
7848 Items in a list may be positive or negative. Negative items are indicated by a
7849 leading exclamation mark, which may be followed by optional white space. A list
7850 defines a set of items (domains, etc). When Exim processes one of these lists,
7851 it is trying to find out whether a domain, host, address, or local part
7852 (respectively) is in the set that is defined by the list. It works like this:
7854 The list is scanned from left to right. If a positive item is matched, the
7855 subject that is being checked is in the set; if a negative item is matched, the
7856 subject is not in the set. If the end of the list is reached without the
7857 subject having matched any of the patterns, it is in the set if the last item
7858 was a negative one, but not if it was a positive one. For example, the list in
7860 domainlist relay_to_domains = !a.b.c : *.b.c
7862 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7863 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7864 list is positive. However, if the setting were
7866 domainlist relay_to_domains = !a.b.c
7868 then all domains other than &'a.b.c'& would match because the last item in the
7869 list is negative. In other words, a list that ends with a negative item behaves
7870 as if it had an extra item &`:*`& on the end.
7872 Another way of thinking about positive and negative items in lists is to read
7873 the connector as &"or"& after a positive item and as &"and"& after a negative
7878 .section "File names in lists" "SECTfilnamlis"
7879 .cindex "list" "file name in"
7880 If an item in a domain, host, address, or local part list is an absolute file
7881 name (beginning with a slash character), each line of the file is read and
7882 processed as if it were an independent item in the list, except that further
7883 file names are not allowed,
7884 and no expansion of the data from the file takes place.
7885 Empty lines in the file are ignored, and the file may also contain comment
7889 For domain and host lists, if a # character appears anywhere in a line of the
7890 file, it and all following characters are ignored.
7892 Because local parts may legitimately contain # characters, a comment in an
7893 address list or local part list file is recognized only if # is preceded by
7894 white space or the start of the line. For example:
7896 not#comment@x.y.z # but this is a comment
7900 Putting a file name in a list has the same effect as inserting each line of the
7901 file as an item in the list (blank lines and comments excepted). However, there
7902 is one important difference: the file is read each time the list is processed,
7903 so if its contents vary over time, Exim's behaviour changes.
7905 If a file name is preceded by an exclamation mark, the sense of any match
7906 within the file is inverted. For example, if
7908 hold_domains = !/etc/nohold-domains
7910 and the file contains the lines
7915 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7916 any domain matching &`*.b.c`& is not.
7920 .section "An lsearch file is not an out-of-line list" "SECID77"
7921 As will be described in the sections that follow, lookups can be used in lists
7922 to provide indexed methods of checking list membership. There has been some
7923 confusion about the way &(lsearch)& lookups work in lists. Because
7924 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7925 sometimes thought that it is allowed to contain wild cards and other kinds of
7926 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7927 always fixed strings, just as for any other single-key lookup type.
7929 If you want to use a file to contain wild-card patterns that form part of a
7930 list, just give the file name on its own, without a search type, as described
7931 in the previous section. You could also use the &(wildlsearch)& or
7932 &(nwildlsearch)&, but there is no advantage in doing this.
7937 .section "Named lists" "SECTnamedlists"
7938 .cindex "named lists"
7939 .cindex "list" "named"
7940 A list of domains, hosts, email addresses, or local parts can be given a name
7941 which is then used to refer to the list elsewhere in the configuration. This is
7942 particularly convenient if the same list is required in several different
7943 places. It also allows lists to be given meaningful names, which can improve
7944 the readability of the configuration. For example, it is conventional to define
7945 a domain list called &'local_domains'& for all the domains that are handled
7946 locally on a host, using a configuration line such as
7948 domainlist local_domains = localhost:my.dom.example
7950 Named lists are referenced by giving their name preceded by a plus sign, so,
7951 for example, a router that is intended to handle local domains would be
7952 configured with the line
7954 domains = +local_domains
7956 The first router in a configuration is often one that handles all domains
7957 except the local ones, using a configuration with a negated item like this:
7961 domains = ! +local_domains
7962 transport = remote_smtp
7965 The four kinds of named list are created by configuration lines starting with
7966 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7967 respectively. Then there follows the name that you are defining, followed by an
7968 equals sign and the list itself. For example:
7970 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
7971 addresslist bad_senders = cdb;/etc/badsenders
7973 A named list may refer to other named lists:
7975 domainlist dom1 = first.example : second.example
7976 domainlist dom2 = +dom1 : third.example
7977 domainlist dom3 = fourth.example : +dom2 : fifth.example
7979 &*Warning*&: If the last item in a referenced list is a negative one, the
7980 effect may not be what you intended, because the negation does not propagate
7981 out to the higher level. For example, consider:
7983 domainlist dom1 = !a.b
7984 domainlist dom2 = +dom1 : *.b
7986 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7987 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7988 means it matches the second list as well. The effect is not the same as
7990 domainlist dom2 = !a.b : *.b
7992 where &'x.y'& does not match. It's best to avoid negation altogether in
7993 referenced lists if you can.
7995 Named lists may have a performance advantage. When Exim is routing an
7996 address or checking an incoming message, it caches the result of tests on named
7997 lists. So, if you have a setting such as
7999 domains = +local_domains
8001 on several of your routers
8002 or in several ACL statements,
8003 the actual test is done only for the first one. However, the caching works only
8004 if there are no expansions within the list itself or any sublists that it
8005 references. In other words, caching happens only for lists that are known to be
8006 the same each time they are referenced.
8008 By default, there may be up to 16 named lists of each type. This limit can be
8009 extended by changing a compile-time variable. The use of domain and host lists
8010 is recommended for concepts such as local domains, relay domains, and relay
8011 hosts. The default configuration is set up like this.
8015 .section "Named lists compared with macros" "SECID78"
8016 .cindex "list" "named compared with macro"
8017 .cindex "macro" "compared with named list"
8018 At first sight, named lists might seem to be no different from macros in the
8019 configuration file. However, macros are just textual substitutions. If you
8022 ALIST = host1 : host2
8023 auth_advertise_hosts = !ALIST
8025 it probably won't do what you want, because that is exactly the same as
8027 auth_advertise_hosts = !host1 : host2
8029 Notice that the second host name is not negated. However, if you use a host
8032 hostlist alist = host1 : host2
8033 auth_advertise_hosts = ! +alist
8035 the negation applies to the whole list, and so that is equivalent to
8037 auth_advertise_hosts = !host1 : !host2
8041 .section "Named list caching" "SECID79"
8042 .cindex "list" "caching of named"
8043 .cindex "caching" "named lists"
8044 While processing a message, Exim caches the result of checking a named list if
8045 it is sure that the list is the same each time. In practice, this means that
8046 the cache operates only if the list contains no $ characters, which guarantees
8047 that it will not change when it is expanded. Sometimes, however, you may have
8048 an expanded list that you know will be the same each time within a given
8049 message. For example:
8051 domainlist special_domains = \
8052 ${lookup{$sender_host_address}cdb{/some/file}}
8054 This provides a list of domains that depends only on the sending host's IP
8055 address. If this domain list is referenced a number of times (for example,
8056 in several ACL lines, or in several routers) the result of the check is not
8057 cached by default, because Exim does not know that it is going to be the
8058 same list each time.
8060 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8061 cache the result anyway. For example:
8063 domainlist_cache special_domains = ${lookup{...
8065 If you do this, you should be absolutely sure that caching is going to do
8066 the right thing in all cases. When in doubt, leave it out.
8070 .section "Domain lists" "SECTdomainlist"
8071 .cindex "domain list" "patterns for"
8072 .cindex "list" "domain list"
8073 Domain lists contain patterns that are to be matched against a mail domain.
8074 The following types of item may appear in domain lists:
8077 .cindex "primary host name"
8078 .cindex "host name" "matched in domain list"
8079 .oindex "&%primary_hostname%&"
8080 .cindex "domain list" "matching primary host name"
8081 .cindex "@ in a domain list"
8082 If a pattern consists of a single @ character, it matches the local host name,
8083 as set by the &%primary_hostname%& option (or defaulted). This makes it
8084 possible to use the same configuration file on several different hosts that
8085 differ only in their names.
8087 .cindex "@[] in a domain list"
8088 .cindex "domain list" "matching local IP interfaces"
8089 .cindex "domain literal"
8090 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8091 in square brackets (as in an email address that contains a domain literal), but
8092 only if that IP address is recognized as local for email routing purposes. The
8093 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8094 control which of a host's several IP addresses are treated as local.
8095 In today's Internet, the use of domain literals is controversial.
8098 .cindex "@mx_primary"
8099 .cindex "@mx_secondary"
8100 .cindex "domain list" "matching MX pointers to local host"
8101 If a pattern consists of the string &`@mx_any`& it matches any domain that
8102 has an MX record pointing to the local host or to any host that is listed in
8103 .oindex "&%hosts_treat_as_local%&"
8104 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8105 are similar, except that the first matches only when a primary MX target is the
8106 local host, and the second only when no primary MX target is the local host,
8107 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8108 preference value &-- there may of course be more than one of them.
8110 The MX lookup that takes place when matching a pattern of this type is
8111 performed with the resolver options for widening names turned off. Thus, for
8112 example, a single-component domain will &'not'& be expanded by adding the
8113 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8114 options of the &(dnslookup)& router for a discussion of domain widening.
8116 Sometimes you may want to ignore certain IP addresses when using one of these
8117 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8118 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8119 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8120 on a router). For example:
8122 domains = @mx_any/ignore=127.0.0.1
8124 This example matches any domain that has an MX record pointing to one of
8125 the local host's IP addresses other than 127.0.0.1.
8127 The list of IP addresses is in fact processed by the same code that processes
8128 host lists, so it may contain CIDR-coded network specifications and it may also
8129 contain negative items.
8131 Because the list of IP addresses is a sublist within a domain list, you have to
8132 be careful about delimiters if there is more than one address. Like any other
8133 list, the default delimiter can be changed. Thus, you might have:
8135 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8136 an.other.domain : ...
8138 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8139 involved, it is easiest to change the delimiter for the main list as well:
8141 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8142 an.other.domain ? ...
8145 .cindex "asterisk" "in domain list"
8146 .cindex "domain list" "asterisk in"
8147 .cindex "domain list" "matching &""ends with""&"
8148 If a pattern starts with an asterisk, the remaining characters of the pattern
8149 are compared with the terminating characters of the domain. The use of &"*"& in
8150 domain lists differs from its use in partial matching lookups. In a domain
8151 list, the character following the asterisk need not be a dot, whereas partial
8152 matching works only in terms of dot-separated components. For example, a domain
8153 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8157 .cindex "regular expressions" "in domain list"
8158 .cindex "domain list" "matching regular expression"
8159 If a pattern starts with a circumflex character, it is treated as a regular
8160 expression, and matched against the domain using a regular expression matching
8161 function. The circumflex is treated as part of the regular expression.
8162 Email domains are case-independent, so this regular expression match is by
8163 default case-independent, but you can make it case-dependent by starting it
8164 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8165 are given in chapter &<<CHAPregexp>>&.
8167 &*Warning*&: Because domain lists are expanded before being processed, you
8168 must escape any backslash and dollar characters in the regular expression, or
8169 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8170 it is not to be expanded (unless you really do want to build a regular
8171 expression by expansion, of course).
8173 .cindex "lookup" "in domain list"
8174 .cindex "domain list" "matching by lookup"
8175 If a pattern starts with the name of a single-key lookup type followed by a
8176 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8177 must be a file name in a suitable format for the lookup type. For example, for
8178 &"cdb;"& it must be an absolute path:
8180 domains = cdb;/etc/mail/local_domains.cdb
8182 The appropriate type of lookup is done on the file using the domain name as the
8183 key. In most cases, the data that is looked up is not used; Exim is interested
8184 only in whether or not the key is present in the file. However, when a lookup
8185 is used for the &%domains%& option on a router
8186 or a &%domains%& condition in an ACL statement, the data is preserved in the
8187 &$domain_data$& variable and can be referred to in other router options or
8188 other statements in the same ACL.
8191 Any of the single-key lookup type names may be preceded by
8192 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8194 domains = partial-dbm;/partial/domains
8196 This causes partial matching logic to be invoked; a description of how this
8197 works is given in section &<<SECTpartiallookup>>&.
8200 .cindex "asterisk" "in lookup type"
8201 Any of the single-key lookup types may be followed by an asterisk. This causes
8202 a default lookup for a key consisting of a single asterisk to be done if the
8203 original lookup fails. This is not a useful feature when using a domain list to
8204 select particular domains (because any domain would match), but it might have
8205 value if the result of the lookup is being used via the &$domain_data$&
8208 If the pattern starts with the name of a query-style lookup type followed by a
8209 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8210 pattern must be an appropriate query for the lookup type, as described in
8211 chapter &<<CHAPfdlookup>>&. For example:
8213 hold_domains = mysql;select domain from holdlist \
8214 where domain = '${quote_mysql:$domain}';
8216 In most cases, the data that is looked up is not used (so for an SQL query, for
8217 example, it doesn't matter what field you select). Exim is interested only in
8218 whether or not the query succeeds. However, when a lookup is used for the
8219 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8220 variable and can be referred to in other options.
8222 .cindex "domain list" "matching literal domain name"
8223 If none of the above cases apply, a caseless textual comparison is made
8224 between the pattern and the domain.
8227 Here is an example that uses several different kinds of pattern:
8229 domainlist funny_domains = \
8232 *.foundation.fict.example : \
8233 \N^[1-2]\d{3}\.fict\.example$\N : \
8234 partial-dbm;/opt/data/penguin/book : \
8235 nis;domains.byname : \
8236 nisplus;[name=$domain,status=local],domains.org_dir
8238 There are obvious processing trade-offs among the various matching modes. Using
8239 an asterisk is faster than a regular expression, and listing a few names
8240 explicitly probably is too. The use of a file or database lookup is expensive,
8241 but may be the only option if hundreds of names are required. Because the
8242 patterns are tested in order, it makes sense to put the most commonly matched
8247 .section "Host lists" "SECThostlist"
8248 .cindex "host list" "patterns in"
8249 .cindex "list" "host list"
8250 Host lists are used to control what remote hosts are allowed to do. For
8251 example, some hosts may be allowed to use the local host as a relay, and some
8252 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8253 two different ways, by name or by IP address. In a host list, some types of
8254 pattern are matched to a host name, and some are matched to an IP address.
8255 You need to be particularly careful with this when single-key lookups are
8256 involved, to ensure that the right value is being used as the key.
8259 .section "Special host list patterns" "SECID80"
8260 .cindex "empty item in hosts list"
8261 .cindex "host list" "empty string in"
8262 If a host list item is the empty string, it matches only when no remote host is
8263 involved. This is the case when a message is being received from a local
8264 process using SMTP on the standard input, that is, when a TCP/IP connection is
8267 .cindex "asterisk" "in host list"
8268 The special pattern &"*"& in a host list matches any host or no host. Neither
8269 the IP address nor the name is actually inspected.
8273 .section "Host list patterns that match by IP address" "SECThoslispatip"
8274 .cindex "host list" "matching IP addresses"
8275 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8276 the incoming address actually appears in the IPv6 host as
8277 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8278 list, it is converted into a traditional IPv4 address first. (Not all operating
8279 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8282 The following types of pattern in a host list check the remote host by
8283 inspecting its IP address:
8286 If the pattern is a plain domain name (not a regular expression, not starting
8287 with *, not a lookup of any kind), Exim calls the operating system function
8288 to find the associated IP address(es). Exim uses the newer
8289 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8290 This typically causes a forward DNS lookup of the name. The result is compared
8291 with the IP address of the subject host.
8293 If there is a temporary problem (such as a DNS timeout) with the host name
8294 lookup, a temporary error occurs. For example, if the list is being used in an
8295 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8296 temporary SMTP error code. If no IP address can be found for the host name,
8297 what happens is described in section &<<SECTbehipnot>>& below.
8300 .cindex "@ in a host list"
8301 If the pattern is &"@"&, the primary host name is substituted and used as a
8302 domain name, as just described.
8305 If the pattern is an IP address, it is matched against the IP address of the
8306 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8307 IPv6 addresses can be given in colon-separated format, but the colons have to
8308 be doubled so as not to be taken as item separators when the default list
8309 separator is used. IPv6 addresses are recognized even when Exim is compiled
8310 without IPv6 support. This means that if they appear in a host list on an
8311 IPv4-only host, Exim will not treat them as host names. They are just addresses
8312 that can never match a client host.
8315 .cindex "@[] in a host list"
8316 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8317 the local host. For example, if the local host is an IPv4 host with one
8318 interface address 10.45.23.56, these two ACL statements have the same effect:
8320 accept hosts = 127.0.0.1 : 10.45.23.56
8324 .cindex "CIDR notation"
8325 If the pattern is an IP address followed by a slash and a mask length (for
8326 example 10.11.42.0/24), it is matched against the IP address of the subject
8327 host under the given mask. This allows, an entire network of hosts to be
8328 included (or excluded) by a single item. The mask uses CIDR notation; it
8329 specifies the number of address bits that must match, starting from the most
8330 significant end of the address.
8332 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8333 of a range of addresses. It is the number of bits in the network portion of the
8334 address. The above example specifies a 24-bit netmask, so it matches all 256
8335 addresses in the 10.11.42.0 network. An item such as
8339 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8340 32 for an IPv4 address is the same as no mask at all; just a single address
8343 Here is another example which shows an IPv4 and an IPv6 network:
8345 recipient_unqualified_hosts = 192.168.0.0/16: \
8346 3ffe::ffff::836f::::/48
8348 The doubling of list separator characters applies only when these items
8349 appear inline in a host list. It is not required when indirecting via a file.
8352 recipient_unqualified_hosts = /opt/exim/unqualnets
8354 could make use of a file containing
8359 to have exactly the same effect as the previous example. When listing IPv6
8360 addresses inline, it is usually more convenient to use the facility for
8361 changing separator characters. This list contains the same two networks:
8363 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8366 The separator is changed to semicolon by the leading &"<;"& at the start of the
8372 .section "Host list patterns for single-key lookups by host address" &&&
8373 "SECThoslispatsikey"
8374 .cindex "host list" "lookup of IP address"
8375 When a host is to be identified by a single-key lookup of its complete IP
8376 address, the pattern takes this form:
8378 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8382 hosts_lookup = net-cdb;/hosts-by-ip.db
8384 The text form of the IP address of the subject host is used as the lookup key.
8385 IPv6 addresses are converted to an unabbreviated form, using lower case
8386 letters, with dots as separators because colon is the key terminator in
8387 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8388 quoting the keys, but this is a facility that was added later.] The data
8389 returned by the lookup is not used.
8391 .cindex "IP address" "masking"
8392 .cindex "host list" "masked IP address"
8393 Single-key lookups can also be performed using masked IP addresses, using
8394 patterns of this form:
8396 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8400 net24-dbm;/networks.db
8402 The IP address of the subject host is masked using <&'number'&> as the mask
8403 length. A textual string is constructed from the masked value, followed by the
8404 mask, and this is used as the lookup key. For example, if the host's IP address
8405 is 192.168.34.6, the key that is looked up for the above example is
8406 &"192.168.34.0/24"&.
8408 When an IPv6 address is converted to a string, dots are normally used instead
8409 of colons, so that keys in &(lsearch)& files need not contain colons (which
8410 terminate &(lsearch)& keys). This was implemented some time before the ability
8411 to quote keys was made available in &(lsearch)& files. However, the more
8412 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8413 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8414 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8415 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8416 addresses are always used.
8418 Ideally, it would be nice to tidy up this anomalous situation by changing to
8419 colons in all cases, given that quoting is now available for &(lsearch)&.
8420 However, this would be an incompatible change that might break some existing
8423 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8424 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8425 the former case the key strings include the mask value, whereas in the latter
8426 case the IP address is used on its own.
8430 .section "Host list patterns that match by host name" "SECThoslispatnam"
8431 .cindex "host" "lookup failures"
8432 .cindex "unknown host name"
8433 .cindex "host list" "matching host name"
8434 There are several types of pattern that require Exim to know the name of the
8435 remote host. These are either wildcard patterns or lookups by name. (If a
8436 complete hostname is given without any wildcarding, it is used to find an IP
8437 address to match against, as described in section &<<SECThoslispatip>>&
8440 If the remote host name is not already known when Exim encounters one of these
8441 patterns, it has to be found from the IP address.
8442 Although many sites on the Internet are conscientious about maintaining reverse
8443 DNS data for their hosts, there are also many that do not do this.
8444 Consequently, a name cannot always be found, and this may lead to unwanted
8445 effects. Take care when configuring host lists with wildcarded name patterns.
8446 Consider what will happen if a name cannot be found.
8448 Because of the problems of determining host names from IP addresses, matching
8449 against host names is not as common as matching against IP addresses.
8451 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8452 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8453 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8454 are done can be changed by setting the &%host_lookup_order%& option. For
8455 security, once Exim has found one or more names, it looks up the IP addresses
8456 for these names and compares them with the IP address that it started with.
8457 Only those names whose IP addresses match are accepted. Any other names are
8458 discarded. If no names are left, Exim behaves as if the host name cannot be
8459 found. In the most common case there is only one name and one IP address.
8461 There are some options that control what happens if a host name cannot be
8462 found. These are described in section &<<SECTbehipnot>>& below.
8464 .cindex "host" "alias for"
8465 .cindex "alias for host"
8466 As a result of aliasing, hosts may have more than one name. When processing any
8467 of the following types of pattern, all the host's names are checked:
8470 .cindex "asterisk" "in host list"
8471 If a pattern starts with &"*"& the remainder of the item must match the end of
8472 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8473 &'.b.c'&. This special simple form is provided because this is a very common
8474 requirement. Other kinds of wildcarding require the use of a regular
8477 .cindex "regular expressions" "in host list"
8478 .cindex "host list" "regular expression in"
8479 If the item starts with &"^"& it is taken to be a regular expression which is
8480 matched against the host name. Host names are case-independent, so this regular
8481 expression match is by default case-independent, but you can make it
8482 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8483 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8488 is a regular expression that matches either of the two hosts &'a.c.d'& or
8489 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8490 that backslash and dollar characters are not misinterpreted as part of the
8491 string expansion. The simplest way to do this is to use &`\N`& to mark that
8492 part of the string as non-expandable. For example:
8494 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8496 &*Warning*&: If you want to match a complete host name, you must include the
8497 &`$`& terminating metacharacter in the regular expression, as in the above
8498 example. Without it, a match at the start of the host name is all that is
8505 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8506 .cindex "host" "lookup failures, permanent"
8507 While processing a host list, Exim may need to look up an IP address from a
8508 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8509 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8510 behaviour when it fails to find the information it is seeking is the same.
8512 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8513 apply to temporary DNS errors, whose handling is described in the next section.
8515 .cindex "&`+include_unknown`&"
8516 .cindex "&`+ignore_unknown`&"
8517 Exim parses a host list from left to right. If it encounters a permanent
8518 lookup failure in any item in the host list before it has found a match,
8519 Exim treats it as a failure and the default behavior is as if the host
8520 does not match the list. This may not always be what you want to happen.
8521 To change Exim's behaviour, the special items &`+include_unknown`& or
8522 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8523 not recognized in an indirected file).
8526 If any item that follows &`+include_unknown`& requires information that
8527 cannot found, Exim behaves as if the host does match the list. For example,
8529 host_reject_connection = +include_unknown:*.enemy.ex
8531 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8532 any hosts whose name it cannot find.
8535 If any item that follows &`+ignore_unknown`& requires information that cannot
8536 be found, Exim ignores that item and proceeds to the rest of the list. For
8539 accept hosts = +ignore_unknown : friend.example : \
8542 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8543 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8544 name can be found for 192.168.4.5, it is rejected.
8547 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8548 list. The effect of each one lasts until the next, or until the end of the
8551 .section "Mixing wildcarded host names and addresses in host lists" &&&
8553 .cindex "host list" "mixing names and addresses in"
8555 This section explains the host/ip processing logic with the same concepts
8556 as the previous section, but specifically addresses what happens when a
8557 wildcarded hostname is one of the items in the hostlist.
8560 If you have name lookups or wildcarded host names and
8561 IP addresses in the same host list, you should normally put the IP
8562 addresses first. For example, in an ACL you could have:
8564 accept hosts = 10.9.8.7 : *.friend.example
8566 The reason you normally would order it this way lies in the
8567 left-to-right way that Exim processes lists. It can test IP addresses
8568 without doing any DNS lookups, but when it reaches an item that requires
8569 a host name, it fails if it cannot find a host name to compare with the
8570 pattern. If the above list is given in the opposite order, the
8571 &%accept%& statement fails for a host whose name cannot be found, even
8572 if its IP address is 10.9.8.7.
8575 If you really do want to do the name check first, and still recognize the IP
8576 address, you can rewrite the ACL like this:
8578 accept hosts = *.friend.example
8579 accept hosts = 10.9.8.7
8581 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8582 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8583 &`+ignore_unknown`&, which was discussed in depth in the first example in
8588 .section "Temporary DNS errors when looking up host information" &&&
8590 .cindex "host" "lookup failures, temporary"
8591 .cindex "&`+include_defer`&"
8592 .cindex "&`+ignore_defer`&"
8593 A temporary DNS lookup failure normally causes a defer action (except when
8594 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8595 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8596 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8597 section. These options should be used with care, probably only in non-critical
8598 host lists such as whitelists.
8602 .section "Host list patterns for single-key lookups by host name" &&&
8603 "SECThoslispatnamsk"
8604 .cindex "unknown host name"
8605 .cindex "host list" "matching host name"
8606 If a pattern is of the form
8608 <&'single-key-search-type'&>;<&'search-data'&>
8612 dbm;/host/accept/list
8614 a single-key lookup is performed, using the host name as its key. If the
8615 lookup succeeds, the host matches the item. The actual data that is looked up
8618 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8619 keys in the file, not IP addresses. If you want to do lookups based on IP
8620 addresses, you must precede the search type with &"net-"& (see section
8621 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8622 two items in the same list, one doing an address lookup and one doing a name
8623 lookup, both using the same file.
8627 .section "Host list patterns for query-style lookups" "SECID81"
8628 If a pattern is of the form
8630 <&'query-style-search-type'&>;<&'query'&>
8632 the query is obeyed, and if it succeeds, the host matches the item. The actual
8633 data that is looked up is not used. The variables &$sender_host_address$& and
8634 &$sender_host_name$& can be used in the query. For example:
8636 hosts_lookup = pgsql;\
8637 select ip from hostlist where ip='$sender_host_address'
8639 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8640 can use the &%sg%& expansion item to change this if you need to. If you want to
8641 use masked IP addresses in database queries, you can use the &%mask%& expansion
8644 If the query contains a reference to &$sender_host_name$&, Exim automatically
8645 looks up the host name if it has not already done so. (See section
8646 &<<SECThoslispatnam>>& for comments on finding host names.)
8648 Historical note: prior to release 4.30, Exim would always attempt to find a
8649 host name before running the query, unless the search type was preceded by
8650 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8651 still recognized for query-style lookups, but its presence or absence has no
8652 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8653 See section &<<SECThoslispatsikey>>&.)
8659 .section "Address lists" "SECTaddresslist"
8660 .cindex "list" "address list"
8661 .cindex "address list" "empty item"
8662 .cindex "address list" "patterns"
8663 Address lists contain patterns that are matched against mail addresses. There
8664 is one special case to be considered: the sender address of a bounce message is
8665 always empty. You can test for this by providing an empty item in an address
8666 list. For example, you can set up a router to process bounce messages by
8667 using this option setting:
8671 The presence of the colon creates an empty item. If you do not provide any
8672 data, the list is empty and matches nothing. The empty sender can also be
8673 detected by a regular expression that matches an empty string,
8674 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8676 Non-empty items in an address list can be straightforward email addresses. For
8679 senders = jbc@askone.example : hs@anacreon.example
8681 A certain amount of wildcarding is permitted. If a pattern contains an @
8682 character, but is not a regular expression and does not begin with a
8683 semicolon-terminated lookup type (described below), the local part of the
8684 subject address is compared with the local part of the pattern, which may start
8685 with an asterisk. If the local parts match, the domain is checked in exactly
8686 the same way as for a pattern in a domain list. For example, the domain can be
8687 wildcarded, refer to a named list, or be a lookup:
8689 deny senders = *@*.spamming.site:\
8690 *@+hostile_domains:\
8691 bozo@partial-lsearch;/list/of/dodgy/sites:\
8692 *@dbm;/bad/domains.db
8694 .cindex "local part" "starting with !"
8695 .cindex "address list" "local part starting with !"
8696 If a local part that begins with an exclamation mark is required, it has to be
8697 specified using a regular expression, because otherwise the exclamation mark is
8698 treated as a sign of negation, as is standard in lists.
8700 If a non-empty pattern that is not a regular expression or a lookup does not
8701 contain an @ character, it is matched against the domain part of the subject
8702 address. The only two formats that are recognized this way are a literal
8703 domain, or a domain pattern that starts with *. In both these cases, the effect
8704 is the same as if &`*@`& preceded the pattern. For example:
8706 deny senders = enemy.domain : *.enemy.domain
8709 The following kinds of more complicated address list pattern can match any
8710 address, including the empty address that is characteristic of bounce message
8714 .cindex "regular expressions" "in address list"
8715 .cindex "address list" "regular expression in"
8716 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8717 done against the complete address, with the pattern as the regular expression.
8718 You must take care that backslash and dollar characters are not misinterpreted
8719 as part of the string expansion. The simplest way to do this is to use &`\N`&
8720 to mark that part of the string as non-expandable. For example:
8722 deny senders = \N^.*this.*@example\.com$\N : \
8723 \N^\d{8}.+@spamhaus.example$\N : ...
8725 The &`\N`& sequences are removed by the expansion, so these items do indeed
8726 start with &"^"& by the time they are being interpreted as address patterns.
8729 .cindex "address list" "lookup for complete address"
8730 Complete addresses can be looked up by using a pattern that starts with a
8731 lookup type terminated by a semicolon, followed by the data for the lookup. For
8734 deny senders = cdb;/etc/blocked.senders : \
8735 mysql;select address from blocked where \
8736 address='${quote_mysql:$sender_address}'
8738 Both query-style and single-key lookup types can be used. For a single-key
8739 lookup type, Exim uses the complete address as the key. However, empty keys are
8740 not supported for single-key lookups, so a match against the empty address
8741 always fails. This restriction does not apply to query-style lookups.
8743 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8744 cannot be used, and is ignored if specified, with an entry being written to the
8746 .cindex "*@ with single-key lookup"
8747 However, you can configure lookup defaults, as described in section
8748 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8749 default. For example, with this lookup:
8751 accept senders = lsearch*@;/some/file
8753 the file could contains lines like this:
8755 user1@domain1.example
8758 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8761 nimrod@jaeger.example
8765 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8766 would mean that every address matches, thus rendering the test useless.
8768 &*Warning 2*&: Do not confuse these two kinds of item:
8770 deny recipients = dbm*@;/some/file
8771 deny recipients = *@dbm;/some/file
8773 The first does a whole address lookup, with defaulting, as just described,
8774 because it starts with a lookup type. The second matches the local part and
8775 domain independently, as described in a bullet point below.
8779 The following kinds of address list pattern can match only non-empty addresses.
8780 If the subject address is empty, a match against any of these pattern types
8785 .cindex "@@ with single-key lookup"
8786 .cindex "address list" "@@ lookup type"
8787 .cindex "address list" "split local part and domain"
8788 If a pattern starts with &"@@"& followed by a single-key lookup item
8789 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8790 split into a local part and a domain. The domain is looked up in the file. If
8791 it is not found, there is no match. If it is found, the data that is looked up
8792 from the file is treated as a colon-separated list of local part patterns, each
8793 of which is matched against the subject local part in turn.
8795 .cindex "asterisk" "in address list"
8796 The lookup may be a partial one, and/or one involving a search for a default
8797 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8798 patterns that are looked up can be regular expressions or begin with &"*"&, or
8799 even be further lookups. They may also be independently negated. For example,
8802 deny senders = @@dbm;/etc/reject-by-domain
8804 the data from which the DBM file is built could contain lines like
8806 baddomain.com: !postmaster : *
8808 to reject all senders except &%postmaster%& from that domain.
8810 .cindex "local part" "starting with !"
8811 If a local part that actually begins with an exclamation mark is required, it
8812 has to be specified using a regular expression. In &(lsearch)& files, an entry
8813 may be split over several lines by indenting the second and subsequent lines,
8814 but the separating colon must still be included at line breaks. White space
8815 surrounding the colons is ignored. For example:
8817 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8820 As in all colon-separated lists in Exim, a colon can be included in an item by
8823 If the last item in the list starts with a right angle-bracket, the remainder
8824 of the item is taken as a new key to look up in order to obtain a continuation
8825 list of local parts. The new key can be any sequence of characters. Thus one
8826 might have entries like
8828 aol.com: spammer1 : spammer 2 : >*
8829 xyz.com: spammer3 : >*
8832 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8833 local parts for all domains, in addition to the specific local parts listed for
8834 each domain. Of course, using this feature costs another lookup each time a
8835 chain is followed, but the effort needed to maintain the data is reduced.
8837 .cindex "loop" "in lookups"
8838 It is possible to construct loops using this facility, and in order to catch
8839 them, the chains may be no more than fifty items long.
8842 The @@<&'lookup'&> style of item can also be used with a query-style
8843 lookup, but in this case, the chaining facility is not available. The lookup
8844 can only return a single list of local parts.
8847 &*Warning*&: There is an important difference between the address list items
8848 in these two examples:
8851 senders = *@+my_list
8853 In the first one, &`my_list`& is a named address list, whereas in the second
8854 example it is a named domain list.
8859 .section "Case of letters in address lists" "SECTcasletadd"
8860 .cindex "case of local parts"
8861 .cindex "address list" "case forcing"
8862 .cindex "case forcing in address lists"
8863 Domains in email addresses are always handled caselessly, but for local parts
8864 case may be significant on some systems (see &%caseful_local_part%& for how
8865 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8866 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8867 blocking lists should be done in a case-independent manner. Since most address
8868 lists in Exim are used for this kind of control, Exim attempts to do this by
8871 The domain portion of an address is always lowercased before matching it to an
8872 address list. The local part is lowercased by default, and any string
8873 comparisons that take place are done caselessly. This means that the data in
8874 the address list itself, in files included as plain file names, and in any file
8875 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8876 keys in files that are looked up by a search type other than &(lsearch)& (which
8877 works caselessly) must be in lower case, because these lookups are not
8880 .cindex "&`+caseful`&"
8881 To allow for the possibility of caseful address list matching, if an item in
8882 an address list is the string &"+caseful"&, the original case of the local
8883 part is restored for any comparisons that follow, and string comparisons are no
8884 longer case-independent. This does not affect the domain, which remains in
8885 lower case. However, although independent matches on the domain alone are still
8886 performed caselessly, regular expressions that match against an entire address
8887 become case-sensitive after &"+caseful"& has been seen.
8891 .section "Local part lists" "SECTlocparlis"
8892 .cindex "list" "local part list"
8893 .cindex "local part" "list"
8894 Case-sensitivity in local part lists is handled in the same way as for address
8895 lists, as just described. The &"+caseful"& item can be used if required. In a
8896 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8897 set false, the subject is lowercased and the matching is initially
8898 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8899 matching in the local part list, but not elsewhere in the router. If
8900 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8901 option is case-sensitive from the start.
8903 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8904 comments are handled in the same way as address lists &-- they are recognized
8905 only if the # is preceded by white space or the start of the line.
8906 Otherwise, local part lists are matched in the same way as domain lists, except
8907 that the special items that refer to the local host (&`@`&, &`@[]`&,
8908 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8909 Refer to section &<<SECTdomainlist>>& for details of the other available item
8911 .ecindex IIDdohoadli
8916 . ////////////////////////////////////////////////////////////////////////////
8917 . ////////////////////////////////////////////////////////////////////////////
8919 .chapter "String expansions" "CHAPexpand"
8920 .scindex IIDstrexp "expansion" "of strings"
8921 Many strings in Exim's run time configuration are expanded before use. Some of
8922 them are expanded every time they are used; others are expanded only once.
8924 When a string is being expanded it is copied verbatim from left to right except
8925 when a dollar or backslash character is encountered. A dollar specifies the
8926 start of a portion of the string that is interpreted and replaced as described
8927 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8928 escape character, as described in the following section.
8930 Whether a string is expanded depends upon the context. Usually this is solely
8931 dependent upon the option for which a value is sought; in this documentation,
8932 options for which string expansion is performed are marked with † after
8933 the data type. ACL rules always expand strings. A couple of expansion
8934 conditions do not expand some of the brace-delimited branches, for security
8939 .section "Literal text in expanded strings" "SECTlittext"
8940 .cindex "expansion" "including literal text"
8941 An uninterpreted dollar can be included in an expanded string by putting a
8942 backslash in front of it. A backslash can be used to prevent any special
8943 character being treated specially in an expansion, including backslash itself.
8944 If the string appears in quotes in the configuration file, two backslashes are
8945 required because the quotes themselves cause interpretation of backslashes when
8946 the string is read in (see section &<<SECTstrings>>&).
8948 .cindex "expansion" "non-expandable substrings"
8949 A portion of the string can specified as non-expandable by placing it between
8950 two occurrences of &`\N`&. This is particularly useful for protecting regular
8951 expressions, which often contain backslashes and dollar signs. For example:
8953 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8955 On encountering the first &`\N`&, the expander copies subsequent characters
8956 without interpretation until it reaches the next &`\N`& or the end of the
8961 .section "Character escape sequences in expanded strings" "SECID82"
8962 .cindex "expansion" "escape sequences"
8963 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8964 expanded string is recognized as an escape sequence for the character newline,
8965 carriage return, or tab, respectively. A backslash followed by up to three
8966 octal digits is recognized as an octal encoding for a single character, and a
8967 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8970 These escape sequences are also recognized in quoted strings when they are read
8971 in. Their interpretation in expansions as well is useful for unquoted strings,
8972 and for other cases such as looked-up strings that are then expanded.
8975 .section "Testing string expansions" "SECID83"
8976 .cindex "expansion" "testing"
8977 .cindex "testing" "string expansion"
8979 Many expansions can be tested by calling Exim with the &%-be%& option. This
8980 takes the command arguments, or lines from the standard input if there are no
8981 arguments, runs them through the string expansion code, and writes the results
8982 to the standard output. Variables based on configuration values are set up, but
8983 since no message is being processed, variables such as &$local_part$& have no
8984 value. Nevertheless the &%-be%& option can be useful for checking out file and
8985 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8988 Exim gives up its root privilege when it is called with the &%-be%& option, and
8989 instead runs under the uid and gid it was called with, to prevent users from
8990 using &%-be%& for reading files to which they do not have access.
8993 If you want to test expansions that include variables whose values are taken
8994 from a message, there are two other options that can be used. The &%-bem%&
8995 option is like &%-be%& except that it is followed by a file name. The file is
8996 read as a message before doing the test expansions. For example:
8998 exim -bem /tmp/test.message '$h_subject:'
9000 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9001 Exim message identifier. For example:
9003 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9005 This loads the message from Exim's spool before doing the test expansions, and
9006 is therefore restricted to admin users.
9009 .section "Forced expansion failure" "SECTforexpfai"
9010 .cindex "expansion" "forced failure"
9011 A number of expansions that are described in the following section have
9012 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9013 (which are sometimes called &"curly brackets"&). Which of the two strings is
9014 used depends on some condition that is evaluated as part of the expansion. If,
9015 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9016 the entire string expansion fails in a way that can be detected by the code
9017 that requested the expansion. This is called &"forced expansion failure"&, and
9018 its consequences depend on the circumstances. In some cases it is no different
9019 from any other expansion failure, but in others a different action may be
9020 taken. Such variations are mentioned in the documentation of the option that is
9026 .section "Expansion items" "SECTexpansionitems"
9027 The following items are recognized in expanded strings. White space may be used
9028 between sub-items that are keywords or substrings enclosed in braces inside an
9029 outer set of braces, to improve readability. &*Warning*&: Within braces,
9030 white space is significant.
9033 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9034 .cindex "expansion" "variables"
9035 Substitute the contents of the named variable, for example:
9040 The second form can be used to separate the name from subsequent alphanumeric
9041 characters. This form (using braces) is available only for variables; it does
9042 &'not'& apply to message headers. The names of the variables are given in
9043 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9044 given, the expansion fails.
9046 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9047 .cindex "expansion" "operators"
9048 The string is first itself expanded, and then the operation specified by
9049 <&'op'&> is applied to it. For example:
9053 The string starts with the first character after the colon, which may be
9054 leading white space. A list of operators is given in section &<<SECTexpop>>&
9055 below. The operator notation is used for simple expansion items that have just
9056 one argument, because it reduces the number of braces and therefore makes the
9057 string easier to understand.
9059 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9060 This item inserts &"basic"& header lines. It is described with the &%header%&
9061 expansion item below.
9064 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9065 .cindex "expansion" "calling an acl"
9066 .cindex "&%acl%&" "call from expansion"
9067 The name and zero to nine argument strings are first expanded separately. The expanded
9068 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9069 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9070 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9071 and may use the variables; if another acl expansion is used the values
9072 are restored after it returns. If the ACL sets
9073 a value using a "message =" modifier and returns accept or deny, the value becomes
9074 the result of the expansion.
9075 If no message is set and the ACL returns accept or deny
9076 the expansion result is an empty string.
9077 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9080 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9081 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9082 .cindex "expansion" "extracting cerificate fields"
9083 .cindex "&%certextract%&" "certificate fields"
9084 .cindex "certificate" "extracting fields"
9085 The <&'certificate'&> must be a variable of type certificate.
9086 The field name is expanded and used to retrieve the relevant field from
9087 the certificate. Supported fields are:
9091 &`subject `& RFC4514 DN
9092 &`issuer `& RFC4514 DN
9097 &`subj_altname `& tagged list
9101 If the field is found,
9102 <&'string2'&> is expanded, and replaces the whole item;
9103 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9104 variable &$value$& contains the value that has been extracted. Afterwards, it
9105 is restored to any previous value it might have had.
9107 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9108 key is not found. If {<&'string2'&>} is also omitted, the value that was
9111 Some field names take optional modifiers, appended and separated by commas.
9113 The field selectors marked as "RFC4514" above
9114 output a Distinguished Name string which is
9116 parseable by Exim as a comma-separated tagged list
9117 (the exceptions being elements containing commas).
9118 RDN elements of a single type may be selected by
9119 a modifier of the type label; if so the expansion
9120 result is a list (newline-separated by default).
9121 The separator may be changed by another modifier of
9122 a right angle-bracket followed immediately by the new separator.
9123 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9125 The field selectors marked as "time" above
9126 take an optional modifier of "int"
9127 for which the result is the number of seconds since epoch.
9128 Otherwise the result is a human-readable string
9129 in the timezone selected by the main "timezone" option.
9131 The field selectors marked as "list" above return a list,
9132 newline-separated by default,
9133 (embedded separator characters in elements are doubled).
9134 The separator may be changed by a modifier of
9135 a right angle-bracket followed immediately by the new separator.
9137 The field selectors marked as "tagged" above
9138 prefix each list element with a type string and an equals sign.
9139 Elements of only one type may be selected by a modifier
9140 which is one of "dns", "uri" or "mail";
9141 if so the element tags are omitted.
9143 If not otherwise noted field values are presented in human-readable form.
9145 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9146 {*&<&'arg'&>&*}...}*&"
9148 This expansion dynamically loads and then calls a locally-written C function.
9149 This functionality is available only if Exim is compiled with
9153 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9154 object so that it doesn't reload the same object file in the same Exim process
9155 (but of course Exim does start new processes frequently).
9157 There may be from zero to eight arguments to the function. When compiling
9158 a local function that is to be called in this way, &_local_scan.h_& should be
9159 included. The Exim variables and functions that are defined by that API
9160 are also available for dynamically loaded functions. The function itself
9161 must have the following type:
9163 int dlfunction(uschar **yield, int argc, uschar *argv[])
9165 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9166 function should return one of the following values:
9168 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9169 into the expanded string that is being built.
9171 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9172 from &'yield'&, if it is set.
9174 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9175 taken from &'yield'& if it is set.
9177 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9179 When compiling a function that is to be used in this way with gcc,
9180 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9181 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9184 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9185 .cindex "expansion" "extracting value from environment"
9186 .cindex "environment" "values from"
9187 The key is first expanded separately, and leading and trailing white space
9189 This is then searched for as a name in the environment.
9190 If a variable is found then its value is placed in &$value$&
9191 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9193 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9194 appear, for example:
9196 ${env{USER}{$value} fail }
9198 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9199 {<&'string1'&>} must be present for &"fail"& to be recognized.
9201 If {<&'string2'&>} is omitted an empty string is substituted on
9203 If {<&'string1'&>} is omitted the search result is substituted on
9206 The environment is adjusted by the &%keep_environment%& and
9207 &%add_environment%& main section options.
9210 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9211 {*&<&'string3'&>&*}}*&"
9212 .cindex "expansion" "extracting substrings by key"
9213 .cindex "&%extract%&" "substrings by key"
9214 The key and <&'string1'&> are first expanded separately. Leading and trailing
9215 white space is removed from the key (but not from any of the strings). The key
9216 must not be empty and must not consist entirely of digits.
9217 The expanded <&'string1'&> must be of the form:
9219 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9222 where the equals signs and spaces (but not both) are optional. If any of the
9223 values contain white space, they must be enclosed in double quotes, and any
9224 values that are enclosed in double quotes are subject to escape processing as
9225 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9226 for the value that corresponds to the key. The search is case-insensitive. If
9227 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9228 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9229 variable &$value$& contains the value that has been extracted. Afterwards, it
9230 is restored to any previous value it might have had.
9232 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9233 key is not found. If {<&'string2'&>} is also omitted, the value that was
9234 extracted is used. Thus, for example, these two expansions are identical, and
9237 ${extract{gid}{uid=1984 gid=2001}}
9238 ${extract{gid}{uid=1984 gid=2001}{$value}}
9240 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9241 appear, for example:
9243 ${extract{Z}{A=... B=...}{$value} fail }
9245 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9246 {<&'string2'&>} must be present for &"fail"& to be recognized.
9249 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9250 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9251 .cindex "expansion" "extracting substrings by number"
9252 .cindex "&%extract%&" "substrings by number"
9253 The <&'number'&> argument must consist entirely of decimal digits,
9254 apart from leading and trailing white space, which is ignored.
9255 This is what distinguishes this form of &%extract%& from the previous kind. It
9256 behaves in the same way, except that, instead of extracting a named field, it
9257 extracts from <&'string1'&> the field whose number is given as the first
9258 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9259 <&'string3'&> as before.
9261 The fields in the string are separated by any one of the characters in the
9262 separator string. These may include space or tab characters.
9263 The first field is numbered one. If the number is negative, the fields are
9264 counted from the end of the string, with the rightmost one numbered -1. If the
9265 number given is zero, the entire string is returned. If the modulus of the
9266 number is greater than the number of fields in the string, the result is the
9267 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9268 provided. For example:
9270 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9274 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9276 yields &"99"&. Two successive separators mean that the field between them is
9277 empty (for example, the fifth field above).
9280 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9281 .cindex "list" "selecting by condition"
9282 .cindex "expansion" "selecting from list by condition"
9284 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9285 default, but the separator can be changed in the usual way. For each item
9286 in this list, its value is place in &$item$&, and then the condition is
9287 evaluated. If the condition is true, &$item$& is added to the output as an
9288 item in a new list; if the condition is false, the item is discarded. The
9289 separator used for the output list is the same as the one used for the
9290 input, but a separator setting is not included in the output. For example:
9292 ${filter{a:b:c}{!eq{$item}{b}}
9294 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9295 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9298 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9299 .cindex "hash function" "textual"
9300 .cindex "expansion" "textual hash"
9301 This is a textual hashing function, and was the first to be implemented in
9302 early versions of Exim. In current releases, there are other hashing functions
9303 (numeric, MD5, and SHA-1), which are described below.
9305 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9306 <&'n'&>. If you are using fixed values for these numbers, that is, if
9307 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9308 use the simpler operator notation that avoids some of the braces:
9310 ${hash_<n>_<m>:<string>}
9312 The second number is optional (in both notations). If <&'n'&> is greater than
9313 or equal to the length of the string, the expansion item returns the string.
9314 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9315 function to the string. The new string consists of characters taken from the
9316 first <&'m'&> characters of the string
9318 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9320 If <&'m'&> is not present the value 26 is used, so that only lower case
9321 letters appear. For example:
9323 &`$hash{3}{monty}} `& yields &`jmg`&
9324 &`$hash{5}{monty}} `& yields &`monty`&
9325 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9328 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9329 &*$h_*&<&'header&~name'&>&*:*&" &&&
9330 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9331 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9332 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9333 &*$rh_*&<&'header&~name'&>&*:*&"
9334 .cindex "expansion" "header insertion"
9335 .vindex "&$header_$&"
9336 .vindex "&$bheader_$&"
9337 .vindex "&$rheader_$&"
9338 .cindex "header lines" "in expansion strings"
9339 .cindex "header lines" "character sets"
9340 .cindex "header lines" "decoding"
9341 Substitute the contents of the named message header line, for example
9345 The newline that terminates a header line is not included in the expansion, but
9346 internal newlines (caused by splitting the header line over several physical
9347 lines) may be present.
9349 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9350 the data in the header line is interpreted.
9353 .cindex "white space" "in header lines"
9354 &%rheader%& gives the original &"raw"& content of the header line, with no
9355 processing at all, and without the removal of leading and trailing white space.
9358 .cindex "base64 encoding" "in header lines"
9359 &%bheader%& removes leading and trailing white space, and then decodes base64
9360 or quoted-printable MIME &"words"& within the header text, but does no
9361 character set translation. If decoding of what looks superficially like a MIME
9362 &"word"& fails, the raw string is returned. If decoding
9363 .cindex "binary zero" "in header line"
9364 produces a binary zero character, it is replaced by a question mark &-- this is
9365 what Exim does for binary zeros that are actually received in header lines.
9368 &%header%& tries to translate the string as decoded by &%bheader%& to a
9369 standard character set. This is an attempt to produce the same string as would
9370 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9371 returned. Translation is attempted only on operating systems that support the
9372 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9373 a system Makefile or in &_Local/Makefile_&.
9376 In a filter file, the target character set for &%header%& can be specified by a
9377 command of the following form:
9379 headers charset "UTF-8"
9381 This command affects all references to &$h_$& (or &$header_$&) expansions in
9382 subsequently obeyed filter commands. In the absence of this command, the target
9383 character set in a filter is taken from the setting of the &%headers_charset%&
9384 option in the runtime configuration. The value of this option defaults to the
9385 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9388 Header names follow the syntax of RFC 2822, which states that they may contain
9389 any printing characters except space and colon. Consequently, curly brackets
9390 &'do not'& terminate header names, and should not be used to enclose them as
9391 if they were variables. Attempting to do so causes a syntax error.
9393 Only header lines that are common to all copies of a message are visible to
9394 this mechanism. These are the original header lines that are received with the
9395 message, and any that are added by an ACL statement or by a system
9396 filter. Header lines that are added to a particular copy of a message by a
9397 router or transport are not accessible.
9399 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
9400 before the DATA ACL, because the header structure is not set up until the
9401 message is received. Header lines that are added in a RCPT ACL (for example)
9402 are saved until the message's incoming header lines are available, at which
9403 point they are added. When a DATA ACL is running, however, header lines added
9404 by earlier ACLs are visible.
9406 Upper case and lower case letters are synonymous in header names. If the
9407 following character is white space, the terminating colon may be omitted, but
9408 this is not recommended, because you may then forget it when it is needed. When
9409 white space terminates the header name, this white space is included in the
9410 expanded string. If the message does not contain the given header, the
9411 expansion item is replaced by an empty string. (See the &%def%& condition in
9412 section &<<SECTexpcond>>& for a means of testing for the existence of a
9415 If there is more than one header with the same name, they are all concatenated
9416 to form the substitution string, up to a maximum length of 64K. Unless
9417 &%rheader%& is being used, leading and trailing white space is removed from
9418 each header before concatenation, and a completely empty header is ignored. A
9419 newline character is then inserted between non-empty headers, but there is no
9420 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9421 those headers that contain lists of addresses, a comma is also inserted at the
9422 junctions between headers. This does not happen for the &%rheader%& expansion.
9425 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9426 .cindex "expansion" "hmac hashing"
9428 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9429 shared secret and some text into a message authentication code, as specified in
9430 RFC 2104. This differs from &`${md5:secret_text...}`& or
9431 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9432 cryptographic hash, allowing for authentication that is not possible with MD5
9433 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9434 present. For example:
9436 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9438 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9441 dd97e3ba5d1a61b5006108f8c8252953
9443 As an example of how this might be used, you might put in the main part of
9444 an Exim configuration:
9446 SPAMSCAN_SECRET=cohgheeLei2thahw
9448 In a router or a transport you could then have:
9451 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9452 ${hmac{md5}{SPAMSCAN_SECRET}\
9453 {${primary_hostname},${message_exim_id},$h_message-id:}}
9455 Then given a message, you can check where it was scanned by looking at the
9456 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9457 this header line is authentic by recomputing the authentication code from the
9458 host name, message ID and the &'Message-id:'& header line. This can be done
9459 using Exim's &%-be%& option, or by other means, for example by using the
9460 &'hmac_md5_hex()'& function in Perl.
9463 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9464 .cindex "expansion" "conditional"
9465 .cindex "&%if%&, expansion item"
9466 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9467 item; otherwise <&'string2'&> is used. The available conditions are described
9468 in section &<<SECTexpcond>>& below. For example:
9470 ${if eq {$local_part}{postmaster} {yes}{no} }
9472 The second string need not be present; if it is not and the condition is not
9473 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9474 be present instead of the second string (without any curly brackets). In this
9475 case, the expansion is forced to fail if the condition is not true (see section
9476 &<<SECTforexpfai>>&).
9478 If both strings are omitted, the result is the string &`true`& if the condition
9479 is true, and the empty string if the condition is false. This makes it less
9480 cumbersome to write custom ACL and router conditions. For example, instead of
9482 condition = ${if >{$acl_m4}{3}{true}{false}}
9486 condition = ${if >{$acl_m4}{3}}
9491 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
9492 .cindex expansion "imap folder"
9493 .cindex "&%imapfolder%& expansion item"
9494 This item converts a (possibly multilevel, or with non-ASCII characters)
9495 folder specification to a Maildir name for filesystem use.
9496 For information on internationalisation support see &<<SECTi18nMDA>>&.
9500 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9501 .cindex "expansion" "string truncation"
9502 .cindex "&%length%& expansion item"
9503 The &%length%& item is used to extract the initial portion of a string. Both
9504 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9505 you are using a fixed value for the number, that is, if <&'string1'&> does not
9506 change when expanded, you can use the simpler operator notation that avoids
9509 ${length_<n>:<string>}
9511 The result of this item is either the first <&'n'&> characters or the whole
9512 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9513 &%strlen%&, which gives the length of a string.
9516 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9517 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9518 .cindex "expansion" "extracting list elements by number"
9519 .cindex "&%listextract%&" "extract list elements by number"
9520 .cindex "list" "extracting elements by number"
9521 The <&'number'&> argument must consist entirely of decimal digits,
9522 apart from an optional leading minus,
9523 and leading and trailing white space (which is ignored).
9525 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9526 default, but the separator can be changed in the usual way.
9528 The first field of the list is numbered one.
9529 If the number is negative, the fields are
9530 counted from the end of the list, with the rightmost one numbered -1.
9531 The numbered element of the list is extracted and placed in &$value$&,
9532 then <&'string2'&> is expanded as the result.
9534 If the modulus of the
9535 number is zero or greater than the number of fields in the string,
9536 the result is the expansion of <&'string3'&>.
9540 ${listextract{2}{x:42:99}}
9544 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9546 yields &"result: 42"&.
9548 If {<&'string3'&>} is omitted, an empty string is used for string3.
9549 If {<&'string2'&>} is also omitted, the value that was
9551 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9554 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9555 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9556 This is the first of one of two different types of lookup item, which are both
9557 described in the next item.
9559 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9560 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9561 .cindex "expansion" "lookup in"
9562 .cindex "file" "lookups"
9563 .cindex "lookup" "in expanded string"
9564 The two forms of lookup item specify data lookups in files and databases, as
9565 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9566 lookups, and the second is used for query-style lookups. The <&'key'&>,
9567 <&'file'&>, and <&'query'&> strings are expanded before use.
9569 If there is any white space in a lookup item which is part of a filter command,
9570 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9571 other place where white space is significant, the lookup item must be enclosed
9572 in double quotes. The use of data lookups in users' filter files may be locked
9573 out by the system administrator.
9576 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9577 During its expansion, the variable &$value$& contains the data returned by the
9578 lookup. Afterwards it reverts to the value it had previously (at the outer
9579 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9580 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9581 string on failure. If <&'string2'&> is provided, it can itself be a nested
9582 lookup, thus providing a mechanism for looking up a default value when the
9583 original lookup fails.
9585 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9586 data for the outer lookup while the parameters of the second lookup are
9587 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9588 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9589 appear, and in this case, if the lookup fails, the entire expansion is forced
9590 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9591 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9592 successful lookup, and nothing in the case of failure.
9594 For single-key lookups, the string &"partial"& is permitted to precede the
9595 search type in order to do partial matching, and * or *@ may follow a search
9596 type to request default lookups if the key does not match (see sections
9597 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9599 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9600 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9601 and non-wild parts of the key during the expansion of the replacement text.
9602 They return to their previous values at the end of the lookup item.
9604 This example looks up the postmaster alias in the conventional alias file:
9606 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9608 This example uses NIS+ to look up the full name of the user corresponding to
9609 the local part of an address, forcing the expansion to fail if it is not found:
9611 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9616 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9617 .cindex "expansion" "list creation"
9619 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9620 default, but the separator can be changed in the usual way. For each item
9621 in this list, its value is place in &$item$&, and then <&'string2'&> is
9622 expanded and added to the output as an item in a new list. The separator used
9623 for the output list is the same as the one used for the input, but a separator
9624 setting is not included in the output. For example:
9626 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9628 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9629 value of &$item$& is restored to what it was before. See also the &*filter*&
9630 and &*reduce*& expansion items.
9632 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9633 .cindex "expansion" "numeric hash"
9634 .cindex "hash function" "numeric"
9635 The three strings are expanded; the first two must yield numbers. Call them
9636 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9637 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9638 can use the simpler operator notation that avoids some of the braces:
9640 ${nhash_<n>_<m>:<string>}
9642 The second number is optional (in both notations). If there is only one number,
9643 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9644 processed by a div/mod hash function that returns two numbers, separated by a
9645 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9648 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9650 returns the string &"6/33"&.
9654 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9655 .cindex "Perl" "use in expanded string"
9656 .cindex "expansion" "calling Perl from"
9657 This item is available only if Exim has been built to include an embedded Perl
9658 interpreter. The subroutine name and the arguments are first separately
9659 expanded, and then the Perl subroutine is called with those arguments. No
9660 additional arguments need be given; the maximum number permitted, including the
9661 name of the subroutine, is nine.
9663 The return value of the subroutine is inserted into the expanded string, unless
9664 the return value is &%undef%&. In that case, the expansion fails in the same
9665 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9666 Whatever you return is evaluated in a scalar context. For example, if you
9667 return the name of a Perl vector, the return value is the size of the vector,
9670 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9671 with the error message that was passed to &%die%&. More details of the embedded
9672 Perl facility are given in chapter &<<CHAPperl>>&.
9674 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9675 out the use of this expansion item in filter files.
9678 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9679 .cindex "&%prvs%& expansion item"
9680 The first argument is a complete email address and the second is secret
9681 keystring. The third argument, specifying a key number, is optional. If absent,
9682 it defaults to 0. The result of the expansion is a prvs-signed email address,
9683 to be typically used with the &%return_path%& option on an &(smtp)& transport
9684 as part of a bounce address tag validation (BATV) scheme. For more discussion
9685 and an example, see section &<<SECTverifyPRVS>>&.
9687 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9688 {*&<&'string'&>&*}}*&"
9689 .cindex "&%prvscheck%& expansion item"
9690 This expansion item is the complement of the &%prvs%& item. It is used for
9691 checking prvs-signed addresses. If the expansion of the first argument does not
9692 yield a syntactically valid prvs-signed address, the whole item expands to the
9693 empty string. When the first argument does expand to a syntactically valid
9694 prvs-signed address, the second argument is expanded, with the prvs-decoded
9695 version of the address and the key number extracted from the address in the
9696 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9698 These two variables can be used in the expansion of the second argument to
9699 retrieve the secret. The validity of the prvs-signed address is then checked
9700 against the secret. The result is stored in the variable &$prvscheck_result$&,
9701 which is empty for failure or &"1"& for success.
9703 The third argument is optional; if it is missing, it defaults to an empty
9704 string. This argument is now expanded. If the result is an empty string, the
9705 result of the expansion is the decoded version of the address. This is the case
9706 whether or not the signature was valid. Otherwise, the result of the expansion
9707 is the expansion of the third argument.
9709 All three variables can be used in the expansion of the third argument.
9710 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9711 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9713 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9714 .cindex "expansion" "inserting an entire file"
9715 .cindex "file" "inserting into expansion"
9716 .cindex "&%readfile%& expansion item"
9717 The file name and end-of-line string are first expanded separately. The file is
9718 then read, and its contents replace the entire item. All newline characters in
9719 the file are replaced by the end-of-line string if it is present. Otherwise,
9720 newlines are left in the string.
9721 String expansion is not applied to the contents of the file. If you want this,
9722 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9723 the string expansion fails.
9725 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9726 locks out the use of this expansion item in filter files.
9730 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9731 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9732 .cindex "expansion" "inserting from a socket"
9733 .cindex "socket, use of in expansion"
9734 .cindex "&%readsocket%& expansion item"
9735 This item inserts data from a Unix domain or TCP socket into the expanded
9736 string. The minimal way of using it uses just two arguments, as in these
9739 ${readsocket{/socket/name}{request string}}
9740 ${readsocket{inet:some.host:1234}{request string}}
9742 For a Unix domain socket, the first substring must be the path to the socket.
9743 For an Internet socket, the first substring must contain &`inet:`& followed by
9744 a host name or IP address, followed by a colon and a port, which can be a
9745 number or the name of a TCP port in &_/etc/services_&. An IP address may
9746 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9749 ${readsocket{inet:[::1]:1234}{request string}}
9751 Only a single host name may be given, but if looking it up yields more than
9752 one IP address, they are each tried in turn until a connection is made. For
9753 both kinds of socket, Exim makes a connection, writes the request string
9754 unless it is an empty string; and no terminating NUL is ever sent)
9755 and reads from the socket until an end-of-file
9756 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9757 extend what can be done. Firstly, you can vary the timeout. For example:
9759 ${readsocket{/socket/name}{request string}{3s}}
9761 A fourth argument allows you to change any newlines that are in the data
9762 that is read, in the same way as for &%readfile%& (see above). This example
9763 turns them into spaces:
9765 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9767 As with all expansions, the substrings are expanded before the processing
9768 happens. Errors in these sub-expansions cause the expansion to fail. In
9769 addition, the following errors can occur:
9772 Failure to create a socket file descriptor;
9774 Failure to connect the socket;
9776 Failure to write the request string;
9778 Timeout on reading from the socket.
9781 By default, any of these errors causes the expansion to fail. However, if
9782 you supply a fifth substring, it is expanded and used when any of the above
9783 errors occurs. For example:
9785 ${readsocket{/socket/name}{request string}{3s}{\n}\
9788 You can test for the existence of a Unix domain socket by wrapping this
9789 expansion in &`${if exists`&, but there is a race condition between that test
9790 and the actual opening of the socket, so it is safer to use the fifth argument
9791 if you want to be absolutely sure of avoiding an expansion error for a
9792 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9794 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9795 locks out the use of this expansion item in filter files.
9798 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9799 .cindex "expansion" "reducing a list to a scalar"
9800 .cindex "list" "reducing to a scalar"
9803 This operation reduces a list to a single, scalar string. After expansion,
9804 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9805 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9806 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9807 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9808 them. The result of that expansion is assigned to &$value$& before the next
9809 iteration. When the end of the list is reached, the final value of &$value$& is
9810 added to the expansion output. The &*reduce*& expansion item can be used in a
9811 number of ways. For example, to add up a list of numbers:
9813 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9815 The result of that expansion would be &`6`&. The maximum of a list of numbers
9818 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9820 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9821 restored to what they were before. See also the &*filter*& and &*map*&
9824 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9825 This item inserts &"raw"& header lines. It is described with the &%header%&
9826 expansion item above.
9828 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9829 {*&<&'string2'&>&*}}*&"
9830 .cindex "expansion" "running a command"
9831 .cindex "&%run%& expansion item"
9832 The command and its arguments are first expanded as one string. The string is
9833 split apart into individual arguments by spaces, and then the command is run
9834 in a separate process, but under the same uid and gid. As in other command
9835 executions from Exim, a shell is not used by default. If the command requires
9836 a shell, you must explicitly code it.
9838 Since the arguments are split by spaces, when there is a variable expansion
9839 which has an empty result, it will cause the situation that the argument will
9840 simply be omitted when the program is actually executed by Exim. If the
9841 script/program requires a specific number of arguments and the expanded
9842 variable could possibly result in this empty expansion, the variable must be
9843 quoted. This is more difficult if the expanded variable itself could result
9844 in a string containing quotes, because it would interfere with the quotes
9845 around the command arguments. A possible guard against this is to wrap the
9846 variable in the &%sg%& operator to change any quote marks to some other
9849 The standard input for the command exists, but is empty. The standard output
9850 and standard error are set to the same file descriptor.
9851 .cindex "return code" "from &%run%& expansion"
9853 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9854 and replaces the entire item; during this expansion, the standard output/error
9855 from the command is in the variable &$value$&. If the command fails,
9856 <&'string2'&>, if present, is expanded and used. Once again, during the
9857 expansion, the standard output/error from the command is in the variable
9860 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9861 can be the word &"fail"& (not in braces) to force expansion failure if the
9862 command does not succeed. If both strings are omitted, the result is contents
9863 of the standard output/error on success, and nothing on failure.
9865 .vindex "&$run_in_acl$&"
9866 The standard output/error of the command is put in the variable &$value$&.
9867 In this ACL example, the output of a command is logged for the admin to
9870 warn condition = ${run{/usr/bin/id}{yes}{no}}
9871 log_message = Output of id: $value
9873 If the command requires shell idioms, such as the > redirect operator, the
9874 shell must be invoked directly, such as with:
9876 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9880 The return code from the command is put in the variable &$runrc$&, and this
9881 remains set afterwards, so in a filter file you can do things like this:
9883 if "${run{x y z}{}}$runrc" is 1 then ...
9884 elif $runrc is 2 then ...
9888 If execution of the command fails (for example, the command does not exist),
9889 the return code is 127 &-- the same code that shells use for non-existent
9892 &*Warning*&: In a router or transport, you cannot assume the order in which
9893 option values are expanded, except for those preconditions whose order of
9894 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9895 by the expansion of one option, and use it in another.
9897 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9898 out the use of this expansion item in filter files.
9901 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9902 .cindex "expansion" "string substitution"
9903 .cindex "&%sg%& expansion item"
9904 This item works like Perl's substitution operator (s) with the global (/g)
9905 option; hence its name. However, unlike the Perl equivalent, Exim does not
9906 modify the subject string; instead it returns the modified string for insertion
9907 into the overall expansion. The item takes three arguments: the subject string,
9908 a regular expression, and a substitution string. For example:
9910 ${sg{abcdefabcdef}{abc}{xyz}}
9912 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9913 if any $ or \ characters are required in the regular expression or in the
9914 substitution string, they have to be escaped. For example:
9916 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9918 yields &"defabc"&, and
9920 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9922 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9923 the regular expression from string expansion.
9927 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
9928 .cindex sorting "a list"
9929 .cindex list sorting
9930 .cindex expansion "list sorting"
9931 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9932 default, but the separator can be changed in the usual way.
9933 The <&'comparator'&> argument is interpreted as the operator
9934 of a two-argument expansion condition.
9935 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
9936 The comparison should return true when applied to two values
9937 if the first value should sort before the second value.
9938 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
9939 the element being placed in &$item$&,
9940 to give values for comparison.
9942 The item result is a sorted list,
9943 with the original list separator,
9944 of the list elements (in full) of the original.
9948 ${sort{3:2:1:4}{<}{$item}}
9950 sorts a list of numbers, and
9952 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
9954 will sort an MX lookup into priority order.
9957 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9958 .cindex "&%substr%& expansion item"
9959 .cindex "substring extraction"
9960 .cindex "expansion" "substring extraction"
9961 The three strings are expanded; the first two must yield numbers. Call them
9962 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9963 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9964 can use the simpler operator notation that avoids some of the braces:
9966 ${substr_<n>_<m>:<string>}
9968 The second number is optional (in both notations).
9969 If it is absent in the simpler format, the preceding underscore must also be
9972 The &%substr%& item can be used to extract more general substrings than
9973 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9974 length required. For example
9976 ${substr{3}{2}{$local_part}}
9978 If the starting offset is greater than the string length the result is the
9979 null string; if the length plus starting offset is greater than the string
9980 length, the result is the right-hand part of the string, starting from the
9981 given offset. The first character in the string has offset zero.
9983 The &%substr%& expansion item can take negative offset values to count
9984 from the right-hand end of its operand. The last character is offset -1, the
9985 second-last is offset -2, and so on. Thus, for example,
9987 ${substr{-5}{2}{1234567}}
9989 yields &"34"&. If the absolute value of a negative offset is greater than the
9990 length of the string, the substring starts at the beginning of the string, and
9991 the length is reduced by the amount of overshoot. Thus, for example,
9993 ${substr{-5}{2}{12}}
9995 yields an empty string, but
9997 ${substr{-3}{2}{12}}
10001 When the second number is omitted from &%substr%&, the remainder of the string
10002 is taken if the offset is positive. If it is negative, all characters in the
10003 string preceding the offset point are taken. For example, an offset of -1 and
10004 no length, as in these semantically identical examples:
10007 ${substr{-1}{abcde}}
10009 yields all but the last character of the string, that is, &"abcd"&.
10013 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10014 {*&<&'replacements'&>&*}}*&"
10015 .cindex "expansion" "character translation"
10016 .cindex "&%tr%& expansion item"
10017 This item does single-character translation on its subject string. The second
10018 argument is a list of characters to be translated in the subject string. Each
10019 matching character is replaced by the corresponding character from the
10020 replacement list. For example
10022 ${tr{abcdea}{ac}{13}}
10024 yields &`1b3de1`&. If there are duplicates in the second character string, the
10025 last occurrence is used. If the third string is shorter than the second, its
10026 last character is replicated. However, if it is empty, no translation takes
10032 .section "Expansion operators" "SECTexpop"
10033 .cindex "expansion" "operators"
10034 For expansion items that perform transformations on a single argument string,
10035 the &"operator"& notation is used because it is simpler and uses fewer braces.
10036 The substring is first expanded before the operation is applied to it. The
10037 following operations can be performed:
10040 .vitem &*${address:*&<&'string'&>&*}*&
10041 .cindex "expansion" "RFC 2822 address handling"
10042 .cindex "&%address%& expansion item"
10043 The string is interpreted as an RFC 2822 address, as it might appear in a
10044 header line, and the effective address is extracted from it. If the string does
10045 not parse successfully, the result is empty.
10048 .vitem &*${addresses:*&<&'string'&>&*}*&
10049 .cindex "expansion" "RFC 2822 address handling"
10050 .cindex "&%addresses%& expansion item"
10051 The string (after expansion) is interpreted as a list of addresses in RFC
10052 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10053 operative address (&'local-part@domain'&) is extracted from each item, and the
10054 result of the expansion is a colon-separated list, with appropriate
10055 doubling of colons should any happen to be present in the email addresses.
10056 Syntactically invalid RFC2822 address items are omitted from the output.
10058 It is possible to specify a character other than colon for the output
10059 separator by starting the string with > followed by the new separator
10060 character. For example:
10062 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10064 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
10065 expansion item, which extracts the working address from a single RFC2822
10066 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
10069 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10070 a strict interpretation of header line formatting. Exim parses the bare,
10071 unquoted portion of an email address and if it finds a comma, treats it as an
10072 email address separator. For the example header line:
10074 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10076 The first example below demonstrates that Q-encoded email addresses are parsed
10077 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10078 It does not see the comma because it's still encoded as "=2C". The second
10079 example below is passed the contents of &`$header_from:`&, meaning it gets
10080 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10081 The third example shows that the presence of a comma is skipped when it is
10084 # exim -be '${addresses:From: \
10085 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10087 # exim -be '${addresses:From: Last, First <user@example.com>}'
10088 Last:user@example.com
10089 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10094 .vitem &*${base32:*&<&'digits'&>&*}*&
10095 .cindex "&%base32%& expansion item"
10096 .cindex "expansion" "conversion to base 32"
10097 The string must consist entirely of decimal digits. The number is converted to
10098 base 32 and output as a (empty, for zero) string of characters.
10099 Only lowercase letters are used.
10101 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10102 .cindex "&%base32d%& expansion item"
10103 .cindex "expansion" "conversion to base 32"
10104 The string must consist entirely of base-32 digits.
10105 The number is converted to decimal and output as a string.
10108 .vitem &*${base62:*&<&'digits'&>&*}*&
10109 .cindex "&%base62%& expansion item"
10110 .cindex "expansion" "conversion to base 62"
10111 The string must consist entirely of decimal digits. The number is converted to
10112 base 62 and output as a string of six characters, including leading zeros. In
10113 the few operating environments where Exim uses base 36 instead of base 62 for
10114 its message identifiers (because those systems do not have case-sensitive file
10115 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
10116 be absolutely clear: this is &'not'& base64 encoding.
10118 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10119 .cindex "&%base62d%& expansion item"
10120 .cindex "expansion" "conversion to base 62"
10121 The string must consist entirely of base-62 digits, or, in operating
10122 environments where Exim uses base 36 instead of base 62 for its message
10123 identifiers, base-36 digits. The number is converted to decimal and output as a
10126 .vitem &*${base64:*&<&'string'&>&*}*&
10127 .cindex "expansion" "base64 encoding"
10128 .cindex "base64 encoding" "in string expansion"
10129 .cindex "&%base64%& expansion item"
10130 .cindex certificate "base64 of DER"
10131 This operator converts a string into one that is base64 encoded.
10133 If the string is a single variable of type certificate,
10134 returns the base64 encoding of the DER form of the certificate.
10137 .vitem &*${base64d:*&<&'string'&>&*}*&
10138 .cindex "expansion" "base64 decoding"
10139 .cindex "base64 decoding" "in string expansion"
10140 .cindex "&%base64d%& expansion item"
10141 This operator converts a base64-encoded string into the un-coded form.
10144 .vitem &*${domain:*&<&'string'&>&*}*&
10145 .cindex "domain" "extraction"
10146 .cindex "expansion" "domain extraction"
10147 The string is interpreted as an RFC 2822 address and the domain is extracted
10148 from it. If the string does not parse successfully, the result is empty.
10151 .vitem &*${escape:*&<&'string'&>&*}*&
10152 .cindex "expansion" "escaping non-printing characters"
10153 .cindex "&%escape%& expansion item"
10154 If the string contains any non-printing characters, they are converted to
10155 escape sequences starting with a backslash. Whether characters with the most
10156 significant bit set (so-called &"8-bit characters"&) count as printing or not
10157 is controlled by the &%print_topbitchars%& option.
10160 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10161 .cindex "expansion" "expression evaluation"
10162 .cindex "expansion" "arithmetic expression"
10163 .cindex "&%eval%& expansion item"
10164 These items supports simple arithmetic and bitwise logical operations in
10165 expansion strings. The string (after expansion) must be a conventional
10166 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10167 logical operators, and parentheses. All operations are carried out using
10168 integer arithmetic. The operator priorities are as follows (the same as in the
10169 C programming language):
10171 .irow &'highest:'& "not (~), negate (-)"
10172 .irow "" "multiply (*), divide (/), remainder (%)"
10173 .irow "" "plus (+), minus (-)"
10174 .irow "" "shift-left (<<), shift-right (>>)"
10175 .irow "" "and (&&)"
10177 .irow &'lowest:'& "or (|)"
10179 Binary operators with the same priority are evaluated from left to right. White
10180 space is permitted before or after operators.
10182 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10183 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10184 decimal, even if they start with a leading zero; hexadecimal numbers are not
10185 permitted. This can be useful when processing numbers extracted from dates or
10186 times, which often do have leading zeros.
10188 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10190 respectively. Negative numbers are supported. The result of the computation is
10191 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10194 &`${eval:1+1} `& yields 2
10195 &`${eval:1+2*3} `& yields 7
10196 &`${eval:(1+2)*3} `& yields 9
10197 &`${eval:2+42%5} `& yields 4
10198 &`${eval:0xc&5} `& yields 4
10199 &`${eval:0xc|5} `& yields 13
10200 &`${eval:0xc^5} `& yields 9
10201 &`${eval:0xc>>1} `& yields 6
10202 &`${eval:0xc<<1} `& yields 24
10203 &`${eval:~255&0x1234} `& yields 4608
10204 &`${eval:-(~255&0x1234)} `& yields -4608
10207 As a more realistic example, in an ACL you might have
10209 deny message = Too many bad recipients
10212 {>{$rcpt_count}{10}} \
10215 {$recipients_count} \
10216 {${eval:$rcpt_count/2}} \
10220 The condition is true if there have been more than 10 RCPT commands and
10221 fewer than half of them have resulted in a valid recipient.
10224 .vitem &*${expand:*&<&'string'&>&*}*&
10225 .cindex "expansion" "re-expansion of substring"
10226 The &%expand%& operator causes a string to be expanded for a second time. For
10229 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10231 first looks up a string in a file while expanding the operand for &%expand%&,
10232 and then re-expands what it has found.
10235 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10237 .cindex "UTF-8" "conversion from"
10238 .cindex "expansion" "UTF-8 conversion"
10239 .cindex "&%from_utf8%& expansion item"
10240 The world is slowly moving towards Unicode, although there are no standards for
10241 email yet. However, other applications (including some databases) are starting
10242 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10243 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10244 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10245 the result is an undefined sequence of bytes.
10247 Unicode code points with values less than 256 are compatible with ASCII and
10248 ISO-8859-1 (also known as Latin-1).
10249 For example, character 169 is the copyright symbol in both cases, though the
10250 way it is encoded is different. In UTF-8, more than one byte is needed for
10251 characters with code values greater than 127, whereas ISO-8859-1 is a
10252 single-byte encoding (but thereby limited to 256 characters). This makes
10253 translation from UTF-8 to ISO-8859-1 straightforward.
10256 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10257 .cindex "hash function" "textual"
10258 .cindex "expansion" "textual hash"
10259 The &%hash%& operator is a simpler interface to the hashing function that can
10260 be used when the two parameters are fixed numbers (as opposed to strings that
10261 change when expanded). The effect is the same as
10263 ${hash{<n>}{<m>}{<string>}}
10265 See the description of the general &%hash%& item above for details. The
10266 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10270 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10271 .cindex "base64 encoding" "conversion from hex"
10272 .cindex "expansion" "hex to base64"
10273 .cindex "&%hex2b64%& expansion item"
10274 This operator converts a hex string into one that is base64 encoded. This can
10275 be useful for processing the output of the MD5 and SHA-1 hashing functions.
10279 .vitem &*${hexquote:*&<&'string'&>&*}*&
10280 .cindex "quoting" "hex-encoded unprintable characters"
10281 .cindex "&%hexquote%& expansion item"
10282 This operator converts non-printable characters in a string into a hex
10283 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10284 as is, and other byte values are converted to &`\xNN`&, for example a
10285 byte value 127 is converted to &`\x7f`&.
10288 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
10289 .cindex "&%ipv6denorm%& expansion item"
10290 .cindex "IP address" normalisation
10291 This expands an IPv6 address to a full eight-element colon-separated set
10292 of hex digits including leading zeroes.
10293 A trailing ipv4-style dotted-decimal set is converted to hex.
10294 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10296 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
10297 .cindex "&%ipv6norm%& expansion item"
10298 .cindex "IP address" normalisation
10299 .cindex "IP address" "canonical form"
10300 This converts an IPv6 address to canonical form.
10301 Leading zeroes of groups are omitted, and the longest
10302 set of zero-valued groups is replaced with a double colon.
10303 A trailing ipv4-style dotted-decimal set is converted to hex.
10304 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10307 .vitem &*${lc:*&<&'string'&>&*}*&
10308 .cindex "case forcing in strings"
10309 .cindex "string" "case forcing"
10310 .cindex "lower casing"
10311 .cindex "expansion" "case forcing"
10312 .cindex "&%lc%& expansion item"
10313 This forces the letters in the string into lower-case, for example:
10318 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10319 .cindex "expansion" "string truncation"
10320 .cindex "&%length%& expansion item"
10321 The &%length%& operator is a simpler interface to the &%length%& function that
10322 can be used when the parameter is a fixed number (as opposed to a string that
10323 changes when expanded). The effect is the same as
10325 ${length{<number>}{<string>}}
10327 See the description of the general &%length%& item above for details. Note that
10328 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10329 when &%length%& is used as an operator.
10332 .vitem &*${listcount:*&<&'string'&>&*}*&
10333 .cindex "expansion" "list item count"
10334 .cindex "list" "item count"
10335 .cindex "list" "count of items"
10336 .cindex "&%listcount%& expansion item"
10337 The string is interpreted as a list and the number of items is returned.
10340 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10341 .cindex "expansion" "named list"
10342 .cindex "&%listnamed%& expansion item"
10343 The name is interpreted as a named list and the content of the list is returned,
10344 expanding any referenced lists, re-quoting as needed for colon-separation.
10345 If the optional type is given it must be one of "a", "d", "h" or "l"
10346 and selects address-, domain-, host- or localpart- lists to search among respectively.
10347 Otherwise all types are searched in an undefined order and the first
10348 matching list is returned.
10351 .vitem &*${local_part:*&<&'string'&>&*}*&
10352 .cindex "expansion" "local part extraction"
10353 .cindex "&%local_part%& expansion item"
10354 The string is interpreted as an RFC 2822 address and the local part is
10355 extracted from it. If the string does not parse successfully, the result is
10359 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10360 .cindex "masked IP address"
10361 .cindex "IP address" "masking"
10362 .cindex "CIDR notation"
10363 .cindex "expansion" "IP address masking"
10364 .cindex "&%mask%& expansion item"
10365 If the form of the string to be operated on is not an IP address followed by a
10366 slash and an integer (that is, a network address in CIDR notation), the
10367 expansion fails. Otherwise, this operator converts the IP address to binary,
10368 masks off the least significant bits according to the bit count, and converts
10369 the result back to text, with mask appended. For example,
10371 ${mask:10.111.131.206/28}
10373 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10374 be mostly used for looking up masked addresses in files, the result for an IPv6
10375 address uses dots to separate components instead of colons, because colon
10376 terminates a key string in lsearch files. So, for example,
10378 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10382 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10384 Letters in IPv6 addresses are always output in lower case.
10387 .vitem &*${md5:*&<&'string'&>&*}*&
10389 .cindex "expansion" "MD5 hash"
10390 .cindex certificate fingerprint
10391 .cindex "&%md5%& expansion item"
10392 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10393 as a 32-digit hexadecimal number, in which any letters are in lower case.
10395 If the string is a single variable of type certificate,
10396 returns the MD5 hash fingerprint of the certificate.
10399 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10400 .cindex "expansion" "numeric hash"
10401 .cindex "hash function" "numeric"
10402 The &%nhash%& operator is a simpler interface to the numeric hashing function
10403 that can be used when the two parameters are fixed numbers (as opposed to
10404 strings that change when expanded). The effect is the same as
10406 ${nhash{<n>}{<m>}{<string>}}
10408 See the description of the general &%nhash%& item above for details.
10411 .vitem &*${quote:*&<&'string'&>&*}*&
10412 .cindex "quoting" "in string expansions"
10413 .cindex "expansion" "quoting"
10414 .cindex "&%quote%& expansion item"
10415 The &%quote%& operator puts its argument into double quotes if it
10416 is an empty string or
10417 contains anything other than letters, digits, underscores, dots, and hyphens.
10418 Any occurrences of double quotes and backslashes are escaped with a backslash.
10419 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10420 respectively For example,
10428 The place where this is useful is when the argument is a substitution from a
10429 variable or a message header.
10431 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10432 .cindex "&%quote_local_part%& expansion item"
10433 This operator is like &%quote%&, except that it quotes the string only if
10434 required to do so by the rules of RFC 2822 for quoting local parts. For
10435 example, a plus sign would not cause quoting (but it would for &%quote%&).
10436 If you are creating a new email address from the contents of &$local_part$&
10437 (or any other unknown data), you should always use this operator.
10440 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10441 .cindex "quoting" "lookup-specific"
10442 This operator applies lookup-specific quoting rules to the string. Each
10443 query-style lookup type has its own quoting rules which are described with
10444 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10446 ${quote_ldap:two * two}
10452 For single-key lookup types, no quoting is ever necessary and this operator
10453 yields an unchanged string.
10456 .vitem &*${randint:*&<&'n'&>&*}*&
10457 .cindex "random number"
10458 This operator returns a somewhat random number which is less than the
10459 supplied number and is at least 0. The quality of this randomness depends
10460 on how Exim was built; the values are not suitable for keying material.
10461 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10462 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10463 for versions of GnuTLS with that function.
10464 Otherwise, the implementation may be arc4random(), random() seeded by
10465 srandomdev() or srandom(), or a custom implementation even weaker than
10469 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10470 .cindex "expansion" "IP address"
10471 This operator reverses an IP address; for IPv4 addresses, the result is in
10472 dotted-quad decimal form, while for IPv6 addresses the result is in
10473 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10474 for DNS. For example,
10476 ${reverse_ip:192.0.2.4}
10477 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10482 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10486 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10487 .cindex "expansion" "RFC 2047"
10488 .cindex "RFC 2047" "expansion operator"
10489 .cindex "&%rfc2047%& expansion item"
10490 This operator encodes text according to the rules of RFC 2047. This is an
10491 encoding that is used in header lines to encode non-ASCII characters. It is
10492 assumed that the input string is in the encoding specified by the
10493 &%headers_charset%& option, which gets its default at build time. If the string
10494 contains only characters in the range 33&--126, and no instances of the
10497 ? = ( ) < > @ , ; : \ " . [ ] _
10499 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10500 string, using as many &"encoded words"& as necessary to encode all the
10504 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10505 .cindex "expansion" "RFC 2047"
10506 .cindex "RFC 2047" "decoding"
10507 .cindex "&%rfc2047d%& expansion item"
10508 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10509 bytes are replaced by question marks. Characters are converted into the
10510 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10511 not recognized unless &%check_rfc2047_length%& is set false.
10513 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10514 access a header line, RFC 2047 decoding is done automatically. You do not need
10515 to use this operator as well.
10519 .vitem &*${rxquote:*&<&'string'&>&*}*&
10520 .cindex "quoting" "in regular expressions"
10521 .cindex "regular expressions" "quoting"
10522 .cindex "&%rxquote%& expansion item"
10523 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10524 characters in its argument. This is useful when substituting the values of
10525 variables or headers inside regular expressions.
10528 .vitem &*${sha1:*&<&'string'&>&*}*&
10529 .cindex "SHA-1 hash"
10530 .cindex "expansion" "SHA-1 hashing"
10531 .cindex certificate fingerprint
10532 .cindex "&%sha1%& expansion item"
10533 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10534 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10536 If the string is a single variable of type certificate,
10537 returns the SHA-1 hash fingerprint of the certificate.
10540 .vitem &*${sha256:*&<&'string'&>&*}*&
10541 .cindex "SHA-256 hash"
10542 .cindex certificate fingerprint
10543 .cindex "expansion" "SHA-256 hashing"
10544 .cindex "&%sha256%& expansion item"
10546 The &%sha256%& operator computes the SHA-256 hash value of the string
10548 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10551 If the string is a single variable of type certificate,
10552 returns the SHA-256 hash fingerprint of the certificate.
10556 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
10557 &*${sha3_<n>:*&<&'string'&>&*}*&
10558 .cindex "SHA3 hash"
10559 .cindex "expansion" "SHA3 hashing"
10560 .cindex "&%sha3%& expansion item"
10561 The &%sha3%& operator computes the SHA3-256 hash value of the string
10563 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10565 If a number is appended, separated by an underbar, it specifies
10566 the output length. Values of 224, 256, 384 and 512 are accepted;
10567 with 256 being the default.
10569 The &%sha3%& expansion item is only supported if Exim has been
10570 compiled with GnuTLS 3.5.0 or later.
10574 .vitem &*${stat:*&<&'string'&>&*}*&
10575 .cindex "expansion" "statting a file"
10576 .cindex "file" "extracting characteristics"
10577 .cindex "&%stat%& expansion item"
10578 The string, after expansion, must be a file path. A call to the &[stat()]&
10579 function is made for this path. If &[stat()]& fails, an error occurs and the
10580 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10581 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10582 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10583 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10584 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10585 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10586 can extract individual fields using the &%extract%& expansion item.
10588 The use of the &%stat%& expansion in users' filter files can be locked out by
10589 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10590 systems for files larger than 2GB.
10592 .vitem &*${str2b64:*&<&'string'&>&*}*&
10593 .cindex "&%str2b64%& expansion item"
10594 Now deprecated, a synonym for the &%base64%& expansion operator.
10598 .vitem &*${strlen:*&<&'string'&>&*}*&
10599 .cindex "expansion" "string length"
10600 .cindex "string" "length in expansion"
10601 .cindex "&%strlen%& expansion item"
10602 The item is replace by the length of the expanded string, expressed as a
10603 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10606 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10607 .cindex "&%substr%& expansion item"
10608 .cindex "substring extraction"
10609 .cindex "expansion" "substring expansion"
10610 The &%substr%& operator is a simpler interface to the &%substr%& function that
10611 can be used when the two parameters are fixed numbers (as opposed to strings
10612 that change when expanded). The effect is the same as
10614 ${substr{<start>}{<length>}{<string>}}
10616 See the description of the general &%substr%& item above for details. The
10617 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10619 .vitem &*${time_eval:*&<&'string'&>&*}*&
10620 .cindex "&%time_eval%& expansion item"
10621 .cindex "time interval" "decoding"
10622 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10625 .vitem &*${time_interval:*&<&'string'&>&*}*&
10626 .cindex "&%time_interval%& expansion item"
10627 .cindex "time interval" "formatting"
10628 The argument (after sub-expansion) must be a sequence of decimal digits that
10629 represents an interval of time as a number of seconds. It is converted into a
10630 number of larger units and output in Exim's normal time format, for example,
10633 .vitem &*${uc:*&<&'string'&>&*}*&
10634 .cindex "case forcing in strings"
10635 .cindex "string" "case forcing"
10636 .cindex "upper casing"
10637 .cindex "expansion" "case forcing"
10638 .cindex "&%uc%& expansion item"
10639 This forces the letters in the string into upper-case.
10641 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10642 .cindex "correction of invalid utf-8 sequences in strings"
10643 .cindex "utf-8" "utf-8 sequences"
10644 .cindex "incorrect utf-8"
10645 .cindex "expansion" "utf-8 forcing"
10646 .cindex "&%utf8clean%& expansion item"
10647 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10649 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
10650 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
10651 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
10652 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
10653 .cindex expansion UTF-8
10654 .cindex UTF-8 expansion
10656 .cindex internationalisation
10657 .cindex "&%utf8_domain_to_alabel%& expansion item"
10658 .cindex "&%utf8_domain_from_alabel%& expansion item"
10659 .cindex "&%utf8_localpart_to_alabel%& expansion item"
10660 .cindex "&%utf8_localpart_from_alabel%& expansion item"
10661 These convert EAI mail name components between UTF-8 and a-label forms.
10662 For information on internationalisation support see &<<SECTi18nMTA>>&.
10670 .section "Expansion conditions" "SECTexpcond"
10671 .scindex IIDexpcond "expansion" "conditions"
10672 The following conditions are available for testing by the &%${if%& construct
10673 while expanding strings:
10676 .vitem &*!*&<&'condition'&>
10677 .cindex "expansion" "negating a condition"
10678 .cindex "negation" "in expansion condition"
10679 Preceding any condition with an exclamation mark negates the result of the
10682 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10683 .cindex "numeric comparison"
10684 .cindex "expansion" "numeric comparison"
10685 There are a number of symbolic operators for doing numeric comparisons. They
10691 &`>= `& greater or equal
10693 &`<= `& less or equal
10697 ${if >{$message_size}{10M} ...
10699 Note that the general negation operator provides for inequality testing. The
10700 two strings must take the form of optionally signed decimal integers,
10701 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10702 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10703 As a special case, the numerical value of an empty string is taken as
10706 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10707 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10708 10M, not if 10M is larger than &$message_size$&.
10711 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10712 {*&<&'arg2'&>&*}...}*&
10713 .cindex "expansion" "calling an acl"
10714 .cindex "&%acl%&" "expansion condition"
10715 The name and zero to nine argument strings are first expanded separately. The expanded
10716 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10717 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10718 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10719 and may use the variables; if another acl expansion is used the values
10720 are restored after it returns. If the ACL sets
10721 a value using a "message =" modifier the variable $value becomes
10722 the result of the expansion, otherwise it is empty.
10723 If the ACL returns accept the condition is true; if deny, false.
10724 If the ACL returns defer the result is a forced-fail.
10726 .vitem &*bool&~{*&<&'string'&>&*}*&
10727 .cindex "expansion" "boolean parsing"
10728 .cindex "&%bool%& expansion condition"
10729 This condition turns a string holding a true or false representation into
10730 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10731 (case-insensitively); also integer numbers map to true if non-zero,
10733 An empty string is treated as false.
10734 Leading and trailing whitespace is ignored;
10735 thus a string consisting only of whitespace is false.
10736 All other string values will result in expansion failure.
10738 When combined with ACL variables, this expansion condition will let you
10739 make decisions in one place and act on those decisions in another place.
10742 ${if bool{$acl_m_privileged_sender} ...
10746 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10747 .cindex "expansion" "boolean parsing"
10748 .cindex "&%bool_lax%& expansion condition"
10749 Like &%bool%&, this condition turns a string into a boolean state. But
10750 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10751 loose definition that the Router &%condition%& option uses. The empty string
10752 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10753 true. Leading and trailing whitespace is ignored.
10755 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10757 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10758 .cindex "expansion" "encrypted comparison"
10759 .cindex "encrypted strings, comparing"
10760 .cindex "&%crypteq%& expansion condition"
10761 This condition is included in the Exim binary if it is built to support any
10762 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10763 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10764 included in the binary.
10766 The &%crypteq%& condition has two arguments. The first is encrypted and
10767 compared against the second, which is already encrypted. The second string may
10768 be in the LDAP form for storing encrypted strings, which starts with the
10769 encryption type in curly brackets, followed by the data. If the second string
10770 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10771 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10772 Typically this will be a field from a password file. An example of an encrypted
10773 string in LDAP form is:
10775 {md5}CY9rzUYh03PK3k6DJie09g==
10777 If such a string appears directly in an expansion, the curly brackets have to
10778 be quoted, because they are part of the expansion syntax. For example:
10780 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10782 The following encryption types (whose names are matched case-independently) are
10787 .cindex "base64 encoding" "in encrypted password"
10788 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10789 printable characters to compare with the remainder of the second string. If the
10790 length of the comparison string is 24, Exim assumes that it is base64 encoded
10791 (as in the above example). If the length is 32, Exim assumes that it is a
10792 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10796 .cindex "SHA-1 hash"
10797 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10798 printable characters to compare with the remainder of the second string. If the
10799 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10800 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10801 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10804 .cindex "&[crypt()]&"
10805 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10806 only the first eight characters of the password. However, in modern operating
10807 systems this is no longer true, and in many cases the entire password is used,
10808 whatever its length.
10811 .cindex "&[crypt16()]&"
10812 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10813 use up to 16 characters of the password in some operating systems. Again, in
10814 modern operating systems, more characters may be used.
10816 Exim has its own version of &[crypt16()]&, which is just a double call to
10817 &[crypt()]&. For operating systems that have their own version, setting
10818 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10819 operating system version instead of its own. This option is set by default in
10820 the OS-dependent &_Makefile_& for those operating systems that are known to
10821 support &[crypt16()]&.
10823 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10824 it was not using the same algorithm as some operating systems' versions. It
10825 turns out that as well as &[crypt16()]& there is a function called
10826 &[bigcrypt()]& in some operating systems. This may or may not use the same
10827 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10829 However, since there is now a move away from the traditional &[crypt()]&
10830 functions towards using SHA1 and other algorithms, tidying up this area of
10831 Exim is seen as very low priority.
10833 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10834 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10835 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10836 default is &`{crypt}`&. Whatever the default, you can always use either
10837 function by specifying it explicitly in curly brackets.
10839 .vitem &*def:*&<&'variable&~name'&>
10840 .cindex "expansion" "checking for empty variable"
10841 .cindex "&%def%& expansion condition"
10842 The &%def%& condition must be followed by the name of one of the expansion
10843 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10844 variable does not contain the empty string. For example:
10846 ${if def:sender_ident {from $sender_ident}}
10848 Note that the variable name is given without a leading &%$%& character. If the
10849 variable does not exist, the expansion fails.
10851 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10852 &~&*def:h_*&<&'header&~name'&>&*:*&"
10853 .cindex "expansion" "checking header line existence"
10854 This condition is true if a message is being processed and the named header
10855 exists in the message. For example,
10857 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10859 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10860 the header name must be terminated by a colon if white space does not follow.
10862 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10863 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10864 .cindex "string" "comparison"
10865 .cindex "expansion" "string comparison"
10866 .cindex "&%eq%& expansion condition"
10867 .cindex "&%eqi%& expansion condition"
10868 The two substrings are first expanded. The condition is true if the two
10869 resulting strings are identical. For &%eq%& the comparison includes the case of
10870 letters, whereas for &%eqi%& the comparison is case-independent.
10872 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10873 .cindex "expansion" "file existence test"
10874 .cindex "file" "existence test"
10875 .cindex "&%exists%&, expansion condition"
10876 The substring is first expanded and then interpreted as an absolute path. The
10877 condition is true if the named file (or directory) exists. The existence test
10878 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10879 users' filter files may be locked out by the system administrator.
10881 .vitem &*first_delivery*&
10882 .cindex "delivery" "first"
10883 .cindex "first delivery"
10884 .cindex "expansion" "first delivery test"
10885 .cindex "&%first_delivery%& expansion condition"
10886 This condition, which has no data, is true during a message's first delivery
10887 attempt. It is false during any subsequent delivery attempts.
10890 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10891 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10892 .cindex "list" "iterative conditions"
10893 .cindex "expansion" "&*forall*& condition"
10894 .cindex "expansion" "&*forany*& condition"
10896 These conditions iterate over a list. The first argument is expanded to form
10897 the list. By default, the list separator is a colon, but it can be changed by
10898 the normal method. The second argument is interpreted as a condition that is to
10899 be applied to each item in the list in turn. During the interpretation of the
10900 condition, the current list item is placed in a variable called &$item$&.
10902 For &*forany*&, interpretation stops if the condition is true for any item, and
10903 the result of the whole condition is true. If the condition is false for all
10904 items in the list, the overall condition is false.
10906 For &*forall*&, interpretation stops if the condition is false for any item,
10907 and the result of the whole condition is false. If the condition is true for
10908 all items in the list, the overall condition is true.
10910 Note that negation of &*forany*& means that the condition must be false for all
10911 items for the overall condition to succeed, and negation of &*forall*& means
10912 that the condition must be false for at least one item. In this example, the
10913 list separator is changed to a comma:
10915 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10917 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10918 being processed, to enable these expansion items to be nested.
10920 To scan a named list, expand it with the &*listnamed*& operator.
10923 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10924 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10925 .cindex "string" "comparison"
10926 .cindex "expansion" "string comparison"
10927 .cindex "&%ge%& expansion condition"
10928 .cindex "&%gei%& expansion condition"
10929 The two substrings are first expanded. The condition is true if the first
10930 string is lexically greater than or equal to the second string. For &%ge%& the
10931 comparison includes the case of letters, whereas for &%gei%& the comparison is
10934 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10935 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10936 .cindex "string" "comparison"
10937 .cindex "expansion" "string comparison"
10938 .cindex "&%gt%& expansion condition"
10939 .cindex "&%gti%& expansion condition"
10940 The two substrings are first expanded. The condition is true if the first
10941 string is lexically greater than the second string. For &%gt%& the comparison
10942 includes the case of letters, whereas for &%gti%& the comparison is
10945 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10946 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10947 .cindex "string" "comparison"
10948 .cindex "list" "iterative conditions"
10949 Both strings are expanded; the second string is treated as a list of simple
10950 strings; if the first string is a member of the second, then the condition
10953 These are simpler to use versions of the more powerful &*forany*& condition.
10954 Examples, and the &*forany*& equivalents:
10956 ${if inlist{needle}{foo:needle:bar}}
10957 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10958 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10959 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10962 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10963 &*isip4&~{*&<&'string'&>&*}*& &&&
10964 &*isip6&~{*&<&'string'&>&*}*&
10965 .cindex "IP address" "testing string format"
10966 .cindex "string" "testing for IP address"
10967 .cindex "&%isip%& expansion condition"
10968 .cindex "&%isip4%& expansion condition"
10969 .cindex "&%isip6%& expansion condition"
10970 The substring is first expanded, and then tested to see if it has the form of
10971 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10972 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10974 For an IPv4 address, the test is for four dot-separated components, each of
10975 which consists of from one to three digits. For an IPv6 address, up to eight
10976 colon-separated components are permitted, each containing from one to four
10977 hexadecimal digits. There may be fewer than eight components if an empty
10978 component (adjacent colons) is present. Only one empty component is permitted.
10980 &*Note*&: The checks are just on the form of the address; actual numerical
10981 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10982 check. The main use of these tests is to distinguish between IP addresses and
10983 host names, or between IPv4 and IPv6 addresses. For example, you could use
10985 ${if isip4{$sender_host_address}...
10987 to test which IP version an incoming SMTP connection is using.
10989 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10990 .cindex "LDAP" "use for authentication"
10991 .cindex "expansion" "LDAP authentication test"
10992 .cindex "&%ldapauth%& expansion condition"
10993 This condition supports user authentication using LDAP. See section
10994 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10995 queries. For this use, the query must contain a user name and password. The
10996 query itself is not used, and can be empty. The condition is true if the
10997 password is not empty, and the user name and password are accepted by the LDAP
10998 server. An empty password is rejected without calling LDAP because LDAP binds
10999 with an empty password are considered anonymous regardless of the username, and
11000 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11001 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11005 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11006 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11007 .cindex "string" "comparison"
11008 .cindex "expansion" "string comparison"
11009 .cindex "&%le%& expansion condition"
11010 .cindex "&%lei%& expansion condition"
11011 The two substrings are first expanded. The condition is true if the first
11012 string is lexically less than or equal to the second string. For &%le%& the
11013 comparison includes the case of letters, whereas for &%lei%& the comparison is
11016 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11017 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11018 .cindex "string" "comparison"
11019 .cindex "expansion" "string comparison"
11020 .cindex "&%lt%& expansion condition"
11021 .cindex "&%lti%& expansion condition"
11022 The two substrings are first expanded. The condition is true if the first
11023 string is lexically less than the second string. For &%lt%& the comparison
11024 includes the case of letters, whereas for &%lti%& the comparison is
11028 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11029 .cindex "expansion" "regular expression comparison"
11030 .cindex "regular expressions" "match in expanded string"
11031 .cindex "&%match%& expansion condition"
11032 The two substrings are first expanded. The second is then treated as a regular
11033 expression and applied to the first. Because of the pre-expansion, if the
11034 regular expression contains dollar, or backslash characters, they must be
11035 escaped. Care must also be taken if the regular expression contains braces
11036 (curly brackets). A closing brace must be escaped so that it is not taken as a
11037 premature termination of <&'string2'&>. The easiest approach is to use the
11038 &`\N`& feature to disable expansion of the regular expression.
11041 ${if match {$local_part}{\N^\d{3}\N} ...
11043 If the whole expansion string is in double quotes, further escaping of
11044 backslashes is also required.
11046 The condition is true if the regular expression match succeeds.
11047 The regular expression is not required to begin with a circumflex
11048 metacharacter, but if there is no circumflex, the expression is not anchored,
11049 and it may match anywhere in the subject, not just at the start. If you want
11050 the pattern to match at the end of the subject, you must include the &`$`&
11051 metacharacter at an appropriate point.
11053 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11054 At the start of an &%if%& expansion the values of the numeric variable
11055 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11056 succeeds causes them to be reset to the substrings of that condition and they
11057 will have these values during the expansion of the success string. At the end
11058 of the &%if%& expansion, the previous values are restored. After testing a
11059 combination of conditions using &%or%&, the subsequent values of the numeric
11060 variables are those of the condition that succeeded.
11062 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11063 .cindex "&%match_address%& expansion condition"
11064 See &*match_local_part*&.
11066 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11067 .cindex "&%match_domain%& expansion condition"
11068 See &*match_local_part*&.
11070 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11071 .cindex "&%match_ip%& expansion condition"
11072 This condition matches an IP address to a list of IP address patterns. It must
11073 be followed by two argument strings. The first (after expansion) must be an IP
11074 address or an empty string. The second (not expanded) is a restricted host
11075 list that can match only an IP address, not a host name. For example:
11077 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11079 The specific types of host list item that are permitted in the list are:
11082 An IP address, optionally with a CIDR mask.
11084 A single asterisk, which matches any IP address.
11086 An empty item, which matches only if the IP address is empty. This could be
11087 useful for testing for a locally submitted message or one from specific hosts
11088 in a single test such as
11089 . ==== As this is a nested list, any displays it contains must be indented
11090 . ==== as otherwise they are too far to the left. This comment applies to
11091 . ==== the use of xmlto plus fop. There's no problem when formatting with
11092 . ==== sdop, with or without the extra indent.
11094 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11096 where the first item in the list is the empty string.
11098 The item @[] matches any of the local host's interface addresses.
11100 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11101 even if &`net-`& is not specified. There is never any attempt to turn the IP
11102 address into a host name. The most common type of linear search for
11103 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11104 masks. For example:
11106 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11108 It is of course possible to use other kinds of lookup, and in such a case, you
11109 do need to specify the &`net-`& prefix if you want to specify a specific
11110 address mask, for example:
11112 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11114 However, unless you are combining a &%match_ip%& condition with others, it is
11115 just as easy to use the fact that a lookup is itself a condition, and write:
11117 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11121 Note that <&'string2'&> is not itself subject to string expansion, unless
11122 Exim was built with the EXPAND_LISTMATCH_RHS option.
11124 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11126 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11127 .cindex "domain list" "in expansion condition"
11128 .cindex "address list" "in expansion condition"
11129 .cindex "local part" "list, in expansion condition"
11130 .cindex "&%match_local_part%& expansion condition"
11131 This condition, together with &%match_address%& and &%match_domain%&, make it
11132 possible to test domain, address, and local part lists within expansions. Each
11133 condition requires two arguments: an item and a list to match. A trivial
11136 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11138 In each case, the second argument may contain any of the allowable items for a
11139 list of the appropriate type. Also, because the second argument (after
11140 expansion) is a standard form of list, it is possible to refer to a named list.
11141 Thus, you can use conditions like this:
11143 ${if match_domain{$domain}{+local_domains}{...
11145 .cindex "&`+caseful`&"
11146 For address lists, the matching starts off caselessly, but the &`+caseful`&
11147 item can be used, as in all address lists, to cause subsequent items to
11148 have their local parts matched casefully. Domains are always matched
11151 Note that <&'string2'&> is not itself subject to string expansion, unless
11152 Exim was built with the EXPAND_LISTMATCH_RHS option.
11154 &*Note*&: Host lists are &'not'& supported in this way. This is because
11155 hosts have two identities: a name and an IP address, and it is not clear
11156 how to specify cleanly how such a test would work. However, IP addresses can be
11157 matched using &%match_ip%&.
11159 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11160 .cindex "PAM authentication"
11161 .cindex "AUTH" "with PAM"
11162 .cindex "Solaris" "PAM support"
11163 .cindex "expansion" "PAM authentication test"
11164 .cindex "&%pam%& expansion condition"
11165 &'Pluggable Authentication Modules'&
11166 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
11167 available in the latest releases of Solaris and in some GNU/Linux
11168 distributions. The Exim support, which is intended for use in conjunction with
11169 the SMTP AUTH command, is available only if Exim is compiled with
11173 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11174 in some releases of GNU/Linux &%-ldl%& is also needed.
11176 The argument string is first expanded, and the result must be a
11177 colon-separated list of strings. Leading and trailing white space is ignored.
11178 The PAM module is initialized with the service name &"exim"& and the user name
11179 taken from the first item in the colon-separated data string (<&'string1'&>).
11180 The remaining items in the data string are passed over in response to requests
11181 from the authentication function. In the simple case there will only be one
11182 request, for a password, so the data consists of just two strings.
11184 There can be problems if any of the strings are permitted to contain colon
11185 characters. In the usual way, these have to be doubled to avoid being taken as
11186 separators. If the data is being inserted from a variable, the &%sg%& expansion
11187 item can be used to double any existing colons. For example, the configuration
11188 of a LOGIN authenticator might contain this setting:
11190 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
11192 For a PLAIN authenticator you could use:
11194 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
11196 In some operating systems, PAM authentication can be done only from a process
11197 running as root. Since Exim is running as the Exim user when receiving
11198 messages, this means that PAM cannot be used directly in those systems.
11199 A patched version of the &'pam_unix'& module that comes with the
11200 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
11201 The patched module allows one special uid/gid combination, in addition to root,
11202 to authenticate. If you build the patched module to allow the Exim user and
11203 group, PAM can then be used from an Exim authenticator.
11206 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11207 .cindex "&'pwcheck'& daemon"
11209 .cindex "expansion" "&'pwcheck'& authentication test"
11210 .cindex "&%pwcheck%& expansion condition"
11211 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11212 This is one way of making it possible for passwords to be checked by a process
11213 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11214 deprecated. Its replacement is &'saslauthd'& (see below).
11216 The pwcheck support is not included in Exim by default. You need to specify
11217 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11218 building Exim. For example:
11220 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
11222 You do not need to install the full Cyrus software suite in order to use
11223 the pwcheck daemon. You can compile and install just the daemon alone
11224 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11225 access to the &_/var/pwcheck_& directory.
11227 The &%pwcheck%& condition takes one argument, which must be the user name and
11228 password, separated by a colon. For example, in a LOGIN authenticator
11229 configuration, you might have this:
11231 server_condition = ${if pwcheck{$auth1:$auth2}}
11233 Again, for a PLAIN authenticator configuration, this would be:
11235 server_condition = ${if pwcheck{$auth2:$auth3}}
11237 .vitem &*queue_running*&
11238 .cindex "queue runner" "detecting when delivering from"
11239 .cindex "expansion" "queue runner test"
11240 .cindex "&%queue_running%& expansion condition"
11241 This condition, which has no data, is true during delivery attempts that are
11242 initiated by queue runner processes, and false otherwise.
11245 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11247 .cindex "expansion" "Radius authentication"
11248 .cindex "&%radius%& expansion condition"
11249 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11250 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11251 the Radius client configuration file in order to build Exim with Radius
11254 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11255 library, using the original API. If you are using release 0.4.0 or later of
11256 this library, you need to set
11258 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11260 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11261 &%libradius%& library that comes with FreeBSD. To do this, set
11263 RADIUS_LIB_TYPE=RADLIB
11265 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11266 You may also have to supply a suitable setting in EXTRALIBS so that the
11267 Radius library can be found when Exim is linked.
11269 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11270 Radius client library, which calls the Radius server. The condition is true if
11271 the authentication is successful. For example:
11273 server_condition = ${if radius{<arguments>}}
11277 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11278 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11279 .cindex "&'saslauthd'& daemon"
11281 .cindex "expansion" "&'saslauthd'& authentication test"
11282 .cindex "&%saslauthd%& expansion condition"
11283 This condition supports user authentication using the Cyrus &'saslauthd'&
11284 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11285 Using this daemon is one way of making it possible for passwords to be checked
11286 by a process that is not running as root.
11288 The saslauthd support is not included in Exim by default. You need to specify
11289 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11290 building Exim. For example:
11292 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11294 You do not need to install the full Cyrus software suite in order to use
11295 the saslauthd daemon. You can compile and install just the daemon alone
11296 from the Cyrus SASL library.
11298 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11299 two are mandatory. For example:
11301 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11303 The service and the realm are optional (which is why the arguments are enclosed
11304 in their own set of braces). For details of the meaning of the service and
11305 realm, and how to run the daemon, consult the Cyrus documentation.
11310 .section "Combining expansion conditions" "SECID84"
11311 .cindex "expansion" "combining conditions"
11312 Several conditions can be tested at once by combining them using the &%and%&
11313 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11314 conditions on their own, and precede their lists of sub-conditions. Each
11315 sub-condition must be enclosed in braces within the overall braces that contain
11316 the list. No repetition of &%if%& is used.
11320 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11321 .cindex "&""or""& expansion condition"
11322 .cindex "expansion" "&""or""& of conditions"
11323 The sub-conditions are evaluated from left to right. The condition is true if
11324 any one of the sub-conditions is true.
11327 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11329 When a true sub-condition is found, the following ones are parsed but not
11330 evaluated. If there are several &"match"& sub-conditions the values of the
11331 numeric variables afterwards are taken from the first one that succeeds.
11333 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11334 .cindex "&""and""& expansion condition"
11335 .cindex "expansion" "&""and""& of conditions"
11336 The sub-conditions are evaluated from left to right. The condition is true if
11337 all of the sub-conditions are true. If there are several &"match"&
11338 sub-conditions, the values of the numeric variables afterwards are taken from
11339 the last one. When a false sub-condition is found, the following ones are
11340 parsed but not evaluated.
11342 .ecindex IIDexpcond
11347 .section "Expansion variables" "SECTexpvar"
11348 .cindex "expansion" "variables, list of"
11349 This section contains an alphabetical list of all the expansion variables. Some
11350 of them are available only when Exim is compiled with specific options such as
11351 support for TLS or the content scanning extension.
11354 .vitem "&$0$&, &$1$&, etc"
11355 .cindex "numerical variables (&$1$& &$2$& etc)"
11356 When a &%match%& expansion condition succeeds, these variables contain the
11357 captured substrings identified by the regular expression during subsequent
11358 processing of the success string of the containing &%if%& expansion item.
11359 In the expansion condition case
11360 they do not retain their values afterwards; in fact, their previous
11361 values are restored at the end of processing an &%if%& item. The numerical
11362 variables may also be set externally by some other matching process which
11363 precedes the expansion of the string. For example, the commands available in
11364 Exim filter files include an &%if%& command with its own regular expression
11365 matching condition.
11367 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11368 Within an acl condition, expansion condition or expansion item
11369 any arguments are copied to these variables,
11370 any unused variables being made empty.
11372 .vitem "&$acl_c...$&"
11373 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11374 can be given any name that starts with &$acl_c$& and is at least six characters
11375 long, but the sixth character must be either a digit or an underscore. For
11376 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11377 variables persist throughout the lifetime of an SMTP connection. They can be
11378 used to pass information between ACLs and between different invocations of the
11379 same ACL. When a message is received, the values of these variables are saved
11380 with the message, and can be accessed by filters, routers, and transports
11381 during subsequent delivery.
11383 .vitem "&$acl_m...$&"
11384 These variables are like the &$acl_c...$& variables, except that their values
11385 are reset after a message has been received. Thus, if several messages are
11386 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11387 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11388 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11389 message is received, the values of these variables are saved with the message,
11390 and can be accessed by filters, routers, and transports during subsequent
11393 .vitem &$acl_narg$&
11394 Within an acl condition, expansion condition or expansion item
11395 this variable has the number of arguments.
11397 .vitem &$acl_verify_message$&
11398 .vindex "&$acl_verify_message$&"
11399 After an address verification has failed, this variable contains the failure
11400 message. It retains its value for use in subsequent modifiers. The message can
11401 be preserved by coding like this:
11403 warn !verify = sender
11404 set acl_m0 = $acl_verify_message
11406 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11407 &%log_message%& modifiers, to include information about the verification
11410 .vitem &$address_data$&
11411 .vindex "&$address_data$&"
11412 This variable is set by means of the &%address_data%& option in routers. The
11413 value then remains with the address while it is processed by subsequent routers
11414 and eventually a transport. If the transport is handling multiple addresses,
11415 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11416 for more details. &*Note*&: The contents of &$address_data$& are visible in
11419 If &$address_data$& is set when the routers are called from an ACL to verify
11420 a recipient address, the final value is still in the variable for subsequent
11421 conditions and modifiers of the ACL statement. If routing the address caused it
11422 to be redirected to just one address, the child address is also routed as part
11423 of the verification, and in this case the final value of &$address_data$& is
11424 from the child's routing.
11426 If &$address_data$& is set when the routers are called from an ACL to verify a
11427 sender address, the final value is also preserved, but this time in
11428 &$sender_address_data$&, to distinguish it from data from a recipient
11431 In both cases (recipient and sender verification), the value does not persist
11432 after the end of the current ACL statement. If you want to preserve
11433 these values for longer, you can save them in ACL variables.
11435 .vitem &$address_file$&
11436 .vindex "&$address_file$&"
11437 When, as a result of aliasing, forwarding, or filtering, a message is directed
11438 to a specific file, this variable holds the name of the file when the transport
11439 is running. At other times, the variable is empty. For example, using the
11440 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11442 /home/r2d2/savemail
11444 then when the &(address_file)& transport is running, &$address_file$&
11445 contains the text string &`/home/r2d2/savemail`&.
11446 .cindex "Sieve filter" "value of &$address_file$&"
11447 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11448 then up to the transport configuration to generate an appropriate absolute path
11449 to the relevant file.
11451 .vitem &$address_pipe$&
11452 .vindex "&$address_pipe$&"
11453 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11454 this variable holds the pipe command when the transport is running.
11456 .vitem "&$auth1$& &-- &$auth3$&"
11457 .vindex "&$auth1$&, &$auth2$&, etc"
11458 These variables are used in SMTP authenticators (see chapters
11459 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
11461 .vitem &$authenticated_id$&
11462 .cindex "authentication" "id"
11463 .vindex "&$authenticated_id$&"
11464 When a server successfully authenticates a client it may be configured to
11465 preserve some of the authentication information in the variable
11466 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11467 user/password authenticator configuration might preserve the user name for use
11468 in the routers. Note that this is not the same information that is saved in
11469 &$sender_host_authenticated$&.
11470 When a message is submitted locally (that is, not over a TCP connection)
11471 the value of &$authenticated_id$& is normally the login name of the calling
11472 process. However, a trusted user can override this by means of the &%-oMai%&
11473 command line option.
11475 .vitem &$authenticated_fail_id$&
11476 .cindex "authentication" "fail" "id"
11477 .vindex "&$authenticated_fail_id$&"
11478 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11479 will contain the failed authentication id. If more than one authentication
11480 id is attempted, it will contain only the last one. The variable is
11481 available for processing in the ACL's, generally the quit or notquit ACL.
11482 A message to a local recipient could still be accepted without requiring
11483 authentication, which means this variable could also be visible in all of
11487 .vitem &$authenticated_sender$&
11488 .cindex "sender" "authenticated"
11489 .cindex "authentication" "sender"
11490 .cindex "AUTH" "on MAIL command"
11491 .vindex "&$authenticated_sender$&"
11492 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11493 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11494 described in section &<<SECTauthparamail>>&. Unless the data is the string
11495 &"<>"&, it is set as the authenticated sender of the message, and the value is
11496 available during delivery in the &$authenticated_sender$& variable. If the
11497 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11499 .vindex "&$qualify_domain$&"
11500 When a message is submitted locally (that is, not over a TCP connection), the
11501 value of &$authenticated_sender$& is an address constructed from the login
11502 name of the calling process and &$qualify_domain$&, except that a trusted user
11503 can override this by means of the &%-oMas%& command line option.
11506 .vitem &$authentication_failed$&
11507 .cindex "authentication" "failure"
11508 .vindex "&$authentication_failed$&"
11509 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11510 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11511 possible to distinguish between &"did not try to authenticate"&
11512 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11513 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11514 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11515 negative response to an AUTH command, including (for example) an attempt to use
11516 an undefined mechanism.
11518 .vitem &$av_failed$&
11519 .cindex "content scanning" "AV scanner failure"
11520 This variable is available when Exim is compiled with the content-scanning
11521 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11522 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11523 the ACL malware condition.
11525 .vitem &$body_linecount$&
11526 .cindex "message body" "line count"
11527 .cindex "body of message" "line count"
11528 .vindex "&$body_linecount$&"
11529 When a message is being received or delivered, this variable contains the
11530 number of lines in the message's body. See also &$message_linecount$&.
11532 .vitem &$body_zerocount$&
11533 .cindex "message body" "binary zero count"
11534 .cindex "body of message" "binary zero count"
11535 .cindex "binary zero" "in message body"
11536 .vindex "&$body_zerocount$&"
11537 When a message is being received or delivered, this variable contains the
11538 number of binary zero bytes (ASCII NULs) in the message's body.
11540 .vitem &$bounce_recipient$&
11541 .vindex "&$bounce_recipient$&"
11542 This is set to the recipient address of a bounce message while Exim is creating
11543 it. It is useful if a customized bounce message text file is in use (see
11544 chapter &<<CHAPemsgcust>>&).
11546 .vitem &$bounce_return_size_limit$&
11547 .vindex "&$bounce_return_size_limit$&"
11548 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11549 up to a multiple of 1000. It is useful when a customized error message text
11550 file is in use (see chapter &<<CHAPemsgcust>>&).
11552 .vitem &$caller_gid$&
11553 .cindex "gid (group id)" "caller"
11554 .vindex "&$caller_gid$&"
11555 The real group id under which the process that called Exim was running. This is
11556 not the same as the group id of the originator of a message (see
11557 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11558 incarnation normally contains the Exim gid.
11560 .vitem &$caller_uid$&
11561 .cindex "uid (user id)" "caller"
11562 .vindex "&$caller_uid$&"
11563 The real user id under which the process that called Exim was running. This is
11564 not the same as the user id of the originator of a message (see
11565 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11566 incarnation normally contains the Exim uid.
11568 .vitem &$callout_address$&
11569 .vindex "&$callout_address$&"
11570 After a callout for verification, spamd or malware daemon service, the
11571 address that was connected to.
11573 .vitem &$compile_number$&
11574 .vindex "&$compile_number$&"
11575 The building process for Exim keeps a count of the number
11576 of times it has been compiled. This serves to distinguish different
11577 compilations of the same version of the program.
11579 .vitem &$config_dir$&
11580 .vindex "&$config_dir$&"
11581 The directory name of the main configuration file. That is, the content of
11582 &$config_file$& with the last component stripped. The value does not
11583 contain the trailing slash. If &$config_file$& does not contain a slash,
11584 &$config_dir$& is ".".
11586 .vitem &$config_file$&
11587 .vindex "&$config_file$&"
11588 The name of the main configuration file Exim is using.
11590 .vitem &$dkim_cur_signer$& &&&
11591 &$dkim_verify_status$& &&&
11592 &$dkim_verify_reason$& &&&
11593 &$dkim_domain$& &&&
11594 &$dkim_identity$& &&&
11595 &$dkim_selector$& &&&
11597 &$dkim_canon_body$& &&&
11598 &$dkim_canon_headers$& &&&
11599 &$dkim_copiedheaders$& &&&
11600 &$dkim_bodylength$& &&&
11601 &$dkim_created$& &&&
11602 &$dkim_expires$& &&&
11603 &$dkim_headernames$& &&&
11604 &$dkim_key_testing$& &&&
11605 &$dkim_key_nosubdomains$& &&&
11606 &$dkim_key_srvtype$& &&&
11607 &$dkim_key_granularity$& &&&
11608 &$dkim_key_notes$& &&&
11609 &$dkim_key_length$&
11610 These variables are only available within the DKIM ACL.
11611 For details see chapter &<<CHAPdkim>>&.
11613 .vitem &$dkim_signers$&
11614 .vindex &$dkim_signers$&
11615 When a message has been received this variable contains
11616 a colon-separated list of signer domains and identities for the message.
11617 For details see chapter &<<CHAPdkim>>&.
11619 .vitem &$dnslist_domain$& &&&
11620 &$dnslist_matched$& &&&
11621 &$dnslist_text$& &&&
11623 .vindex "&$dnslist_domain$&"
11624 .vindex "&$dnslist_matched$&"
11625 .vindex "&$dnslist_text$&"
11626 .vindex "&$dnslist_value$&"
11627 .cindex "black list (DNS)"
11628 When a DNS (black) list lookup succeeds, these variables are set to contain
11629 the following data from the lookup: the list's domain name, the key that was
11630 looked up, the contents of any associated TXT record, and the value from the
11631 main A record. See section &<<SECID204>>& for more details.
11634 .vindex "&$domain$&"
11635 When an address is being routed, or delivered on its own, this variable
11636 contains the domain. Uppercase letters in the domain are converted into lower
11637 case for &$domain$&.
11639 Global address rewriting happens when a message is received, so the value of
11640 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11641 is set during user filtering, but not during system filtering, because a
11642 message may have many recipients and the system filter is called just once.
11644 When more than one address is being delivered at once (for example, several
11645 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11646 have the same domain. Transports can be restricted to handling only one domain
11647 at a time if the value of &$domain$& is required at transport time &-- this is
11648 the default for local transports. For further details of the environment in
11649 which local transports are run, see chapter &<<CHAPenvironment>>&.
11651 .oindex "&%delay_warning_condition%&"
11652 At the end of a delivery, if all deferred addresses have the same domain, it is
11653 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11655 The &$domain$& variable is also used in some other circumstances:
11658 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11659 the recipient address. The domain of the &'sender'& address is in
11660 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11661 normally set during the running of the MAIL ACL. However, if the sender address
11662 is verified with a callout during the MAIL ACL, the sender domain is placed in
11663 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11664 the &(smtp)& transport.
11667 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11668 &$domain$& contains the domain portion of the address that is being rewritten;
11669 it can be used in the expansion of the replacement address, for example, to
11670 rewrite domains by file lookup.
11673 With one important exception, whenever a domain list is being scanned,
11674 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11675 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11676 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11677 that, in a RCPT ACL, the sender domain list can be dependent on the
11678 recipient domain (which is what is in &$domain$& at this time).
11681 .cindex "ETRN" "value of &$domain$&"
11682 .oindex "&%smtp_etrn_command%&"
11683 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11684 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11688 .vitem &$domain_data$&
11689 .vindex "&$domain_data$&"
11690 When the &%domains%& option on a router matches a domain by
11691 means of a lookup, the data read by the lookup is available during the running
11692 of the router as &$domain_data$&. In addition, if the driver routes the
11693 address to a transport, the value is available in that transport. If the
11694 transport is handling multiple addresses, the value from the first address is
11697 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11698 domain by means of a lookup. The data read by the lookup is available during
11699 the rest of the ACL statement. In all other situations, this variable expands
11702 .vitem &$exim_gid$&
11703 .vindex "&$exim_gid$&"
11704 This variable contains the numerical value of the Exim group id.
11706 .vitem &$exim_path$&
11707 .vindex "&$exim_path$&"
11708 This variable contains the path to the Exim binary.
11710 .vitem &$exim_uid$&
11711 .vindex "&$exim_uid$&"
11712 This variable contains the numerical value of the Exim user id.
11714 .vitem &$exim_version$&
11715 .vindex "&$exim_version$&"
11716 This variable contains the version string of the Exim build.
11717 The first character is a major version number, currently 4.
11718 Then after a dot, the next group of digits is a minor version number.
11719 There may be other characters following the minor version.
11721 .vitem &$header_$&<&'name'&>
11722 This is not strictly an expansion variable. It is expansion syntax for
11723 inserting the message header line with the given name. Note that the name must
11724 be terminated by colon or white space, because it may contain a wide variety of
11725 characters. Note also that braces must &'not'& be used.
11727 .vitem &$headers_added$&
11728 .vindex "&$headers_added$&"
11729 Within an ACL this variable contains the headers added so far by
11730 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11731 The headers are a newline-separated list.
11735 When the &%check_local_user%& option is set for a router, the user's home
11736 directory is placed in &$home$& when the check succeeds. In particular, this
11737 means it is set during the running of users' filter files. A router may also
11738 explicitly set a home directory for use by a transport; this can be overridden
11739 by a setting on the transport itself.
11741 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11742 of the environment variable HOME, which is subject to the
11743 &%keep_environment%& and &%add_environment%& main config options.
11747 If a router assigns an address to a transport (any transport), and passes a
11748 list of hosts with the address, the value of &$host$& when the transport starts
11749 to run is the name of the first host on the list. Note that this applies both
11750 to local and remote transports.
11752 .cindex "transport" "filter"
11753 .cindex "filter" "transport filter"
11754 For the &(smtp)& transport, if there is more than one host, the value of
11755 &$host$& changes as the transport works its way through the list. In
11756 particular, when the &(smtp)& transport is expanding its options for encryption
11757 using TLS, or for specifying a transport filter (see chapter
11758 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11761 When used in the client part of an authenticator configuration (see chapter
11762 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11763 client is connected.
11766 .vitem &$host_address$&
11767 .vindex "&$host_address$&"
11768 This variable is set to the remote host's IP address whenever &$host$& is set
11769 for a remote connection. It is also set to the IP address that is being checked
11770 when the &%ignore_target_hosts%& option is being processed.
11772 .vitem &$host_data$&
11773 .vindex "&$host_data$&"
11774 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11775 result of the lookup is made available in the &$host_data$& variable. This
11776 allows you, for example, to do things like this:
11778 deny hosts = net-lsearch;/some/file
11779 message = $host_data
11781 .vitem &$host_lookup_deferred$&
11782 .cindex "host name" "lookup, failure of"
11783 .vindex "&$host_lookup_deferred$&"
11784 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11785 message comes from a remote host and there is an attempt to look up the host's
11786 name from its IP address, and the attempt is not successful, one of these
11787 variables is set to &"1"&.
11790 If the lookup receives a definite negative response (for example, a DNS lookup
11791 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11794 If there is any kind of problem during the lookup, such that Exim cannot
11795 tell whether or not the host name is defined (for example, a timeout for a DNS
11796 lookup), &$host_lookup_deferred$& is set to &"1"&.
11799 Looking up a host's name from its IP address consists of more than just a
11800 single reverse lookup. Exim checks that a forward lookup of at least one of the
11801 names it receives from a reverse lookup yields the original IP address. If this
11802 is not the case, Exim does not accept the looked up name(s), and
11803 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11804 IP address (for example, the existence of a PTR record in the DNS) is not
11805 sufficient on its own for the success of a host name lookup. If the reverse
11806 lookup succeeds, but there is a lookup problem such as a timeout when checking
11807 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11808 &"1"&. See also &$sender_host_name$&.
11810 .vitem &$host_lookup_failed$&
11811 .vindex "&$host_lookup_failed$&"
11812 See &$host_lookup_deferred$&.
11814 .vitem &$host_port$&
11815 .vindex "&$host_port$&"
11816 This variable is set to the remote host's TCP port whenever &$host$& is set
11817 for an outbound connection.
11819 .vitem &$initial_cwd$&
11820 .vindex "&$initial_cwd$&
11821 This variable contains the full path name of the initial working
11822 directory of the current Exim process. This may differ from the current
11823 working directory, as Exim changes this to "/" during early startup, and
11824 to &$spool_directory$& later.
11827 .vindex "&$inode$&"
11828 The only time this variable is set is while expanding the &%directory_file%&
11829 option in the &(appendfile)& transport. The variable contains the inode number
11830 of the temporary file which is about to be renamed. It can be used to construct
11831 a unique name for the file.
11833 .vitem &$interface_address$&
11834 .vindex "&$interface_address$&"
11835 This is an obsolete name for &$received_ip_address$&.
11837 .vitem &$interface_port$&
11838 .vindex "&$interface_port$&"
11839 This is an obsolete name for &$received_port$&.
11843 This variable is used during the expansion of &*forall*& and &*forany*&
11844 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11845 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11849 .vindex "&$ldap_dn$&"
11850 This variable, which is available only when Exim is compiled with LDAP support,
11851 contains the DN from the last entry in the most recently successful LDAP
11854 .vitem &$load_average$&
11855 .vindex "&$load_average$&"
11856 This variable contains the system load average, multiplied by 1000 so that it
11857 is an integer. For example, if the load average is 0.21, the value of the
11858 variable is 210. The value is recomputed every time the variable is referenced.
11860 .vitem &$local_part$&
11861 .vindex "&$local_part$&"
11862 When an address is being routed, or delivered on its own, this
11863 variable contains the local part. When a number of addresses are being
11864 delivered together (for example, multiple RCPT commands in an SMTP
11865 session), &$local_part$& is not set.
11867 Global address rewriting happens when a message is received, so the value of
11868 &$local_part$& during routing and delivery is the value after rewriting.
11869 &$local_part$& is set during user filtering, but not during system filtering,
11870 because a message may have many recipients and the system filter is called just
11873 .vindex "&$local_part_prefix$&"
11874 .vindex "&$local_part_suffix$&"
11875 If a local part prefix or suffix has been recognized, it is not included in the
11876 value of &$local_part$& during routing and subsequent delivery. The values of
11877 any prefix or suffix are in &$local_part_prefix$& and
11878 &$local_part_suffix$&, respectively.
11880 When a message is being delivered to a file, pipe, or autoreply transport as a
11881 result of aliasing or forwarding, &$local_part$& is set to the local part of
11882 the parent address, not to the file name or command (see &$address_file$& and
11885 When an ACL is running for a RCPT command, &$local_part$& contains the
11886 local part of the recipient address.
11888 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11889 &$local_part$& contains the local part of the address that is being rewritten;
11890 it can be used in the expansion of the replacement address, for example.
11892 In all cases, all quoting is removed from the local part. For example, for both
11895 "abc:xyz"@test.example
11896 abc\:xyz@test.example
11898 the value of &$local_part$& is
11902 If you use &$local_part$& to create another address, you should always wrap it
11903 inside a quoting operator. For example, in a &(redirect)& router you could
11906 data = ${quote_local_part:$local_part}@new.domain.example
11908 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11909 to process local parts in a case-dependent manner in a router, you can set the
11910 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11912 .vitem &$local_part_data$&
11913 .vindex "&$local_part_data$&"
11914 When the &%local_parts%& option on a router matches a local part by means of a
11915 lookup, the data read by the lookup is available during the running of the
11916 router as &$local_part_data$&. In addition, if the driver routes the address
11917 to a transport, the value is available in that transport. If the transport is
11918 handling multiple addresses, the value from the first address is used.
11920 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11921 matches a local part by means of a lookup. The data read by the lookup is
11922 available during the rest of the ACL statement. In all other situations, this
11923 variable expands to nothing.
11925 .vitem &$local_part_prefix$&
11926 .vindex "&$local_part_prefix$&"
11927 When an address is being routed or delivered, and a
11928 specific prefix for the local part was recognized, it is available in this
11929 variable, having been removed from &$local_part$&.
11931 .vitem &$local_part_suffix$&
11932 .vindex "&$local_part_suffix$&"
11933 When an address is being routed or delivered, and a
11934 specific suffix for the local part was recognized, it is available in this
11935 variable, having been removed from &$local_part$&.
11937 .vitem &$local_scan_data$&
11938 .vindex "&$local_scan_data$&"
11939 This variable contains the text returned by the &[local_scan()]& function when
11940 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11942 .vitem &$local_user_gid$&
11943 .vindex "&$local_user_gid$&"
11944 See &$local_user_uid$&.
11946 .vitem &$local_user_uid$&
11947 .vindex "&$local_user_uid$&"
11948 This variable and &$local_user_gid$& are set to the uid and gid after the
11949 &%check_local_user%& router precondition succeeds. This means that their values
11950 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11951 and &%condition%&), for the &%address_data%& expansion, and for any
11952 router-specific expansions. At all other times, the values in these variables
11953 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11955 .vitem &$localhost_number$&
11956 .vindex "&$localhost_number$&"
11957 This contains the expanded value of the
11958 &%localhost_number%& option. The expansion happens after the main options have
11961 .vitem &$log_inodes$&
11962 .vindex "&$log_inodes$&"
11963 The number of free inodes in the disk partition where Exim's
11964 log files are being written. The value is recalculated whenever the variable is
11965 referenced. If the relevant file system does not have the concept of inodes,
11966 the value of is -1. See also the &%check_log_inodes%& option.
11968 .vitem &$log_space$&
11969 .vindex "&$log_space$&"
11970 The amount of free space (as a number of kilobytes) in the disk
11971 partition where Exim's log files are being written. The value is recalculated
11972 whenever the variable is referenced. If the operating system does not have the
11973 ability to find the amount of free space (only true for experimental systems),
11974 the space value is -1. See also the &%check_log_space%& option.
11977 .vitem &$lookup_dnssec_authenticated$&
11978 .vindex "&$lookup_dnssec_authenticated$&"
11979 This variable is set after a DNS lookup done by
11980 a dnsdb lookup expansion, dnslookup router or smtp transport.
11981 .cindex "DNS" "DNSSEC"
11982 It will be empty if &(DNSSEC)& was not requested,
11983 &"no"& if the result was not labelled as authenticated data
11984 and &"yes"& if it was.
11985 Results that are labelled as authoritative answer that match
11986 the &%dns_trust_aa%& configuration variable count also
11987 as authenticated data.
11989 .vitem &$mailstore_basename$&
11990 .vindex "&$mailstore_basename$&"
11991 This variable is set only when doing deliveries in &"mailstore"& format in the
11992 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11993 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11994 contains the basename of the files that are being written, that is, the name
11995 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11998 .vitem &$malware_name$&
11999 .vindex "&$malware_name$&"
12000 This variable is available when Exim is compiled with the
12001 content-scanning extension. It is set to the name of the virus that was found
12002 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12004 .vitem &$max_received_linelength$&
12005 .vindex "&$max_received_linelength$&"
12006 .cindex "maximum" "line length"
12007 .cindex "line length" "maximum"
12008 This variable contains the number of bytes in the longest line that was
12009 received as part of the message, not counting the line termination
12012 .vitem &$message_age$&
12013 .cindex "message" "age of"
12014 .vindex "&$message_age$&"
12015 This variable is set at the start of a delivery attempt to contain the number
12016 of seconds since the message was received. It does not change during a single
12019 .vitem &$message_body$&
12020 .cindex "body of message" "expansion variable"
12021 .cindex "message body" "in expansion"
12022 .cindex "binary zero" "in message body"
12023 .vindex "&$message_body$&"
12024 .oindex "&%message_body_visible%&"
12025 This variable contains the initial portion of a message's body while it is
12026 being delivered, and is intended mainly for use in filter files. The maximum
12027 number of characters of the body that are put into the variable is set by the
12028 &%message_body_visible%& configuration option; the default is 500.
12030 .oindex "&%message_body_newlines%&"
12031 By default, newlines are converted into spaces in &$message_body$&, to make it
12032 easier to search for phrases that might be split over a line break. However,
12033 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12034 zeros are always converted into spaces.
12036 .vitem &$message_body_end$&
12037 .cindex "body of message" "expansion variable"
12038 .cindex "message body" "in expansion"
12039 .vindex "&$message_body_end$&"
12040 This variable contains the final portion of a message's
12041 body while it is being delivered. The format and maximum size are as for
12044 .vitem &$message_body_size$&
12045 .cindex "body of message" "size"
12046 .cindex "message body" "size"
12047 .vindex "&$message_body_size$&"
12048 When a message is being delivered, this variable contains the size of the body
12049 in bytes. The count starts from the character after the blank line that
12050 separates the body from the header. Newlines are included in the count. See
12051 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12053 .vitem &$message_exim_id$&
12054 .vindex "&$message_exim_id$&"
12055 When a message is being received or delivered, this variable contains the
12056 unique message id that is generated and used by Exim to identify the message.
12057 An id is not created for a message until after its header has been successfully
12058 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12059 line; it is the local id that Exim assigns to the message, for example:
12060 &`1BXTIK-0001yO-VA`&.
12062 .vitem &$message_headers$&
12063 .vindex &$message_headers$&
12064 This variable contains a concatenation of all the header lines when a message
12065 is being processed, except for lines added by routers or transports. The header
12066 lines are separated by newline characters. Their contents are decoded in the
12067 same way as a header line that is inserted by &%bheader%&.
12069 .vitem &$message_headers_raw$&
12070 .vindex &$message_headers_raw$&
12071 This variable is like &$message_headers$& except that no processing of the
12072 contents of header lines is done.
12074 .vitem &$message_id$&
12075 This is an old name for &$message_exim_id$&. It is now deprecated.
12077 .vitem &$message_linecount$&
12078 .vindex "&$message_linecount$&"
12079 This variable contains the total number of lines in the header and body of the
12080 message. Compare &$body_linecount$&, which is the count for the body only.
12081 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12082 number of lines received. Before delivery happens (that is, before filters,
12083 routers, and transports run) the count is increased to include the
12084 &'Received:'& header line that Exim standardly adds, and also any other header
12085 lines that are added by ACLs. The blank line that separates the message header
12086 from the body is not counted.
12088 As with the special case of &$message_size$&, during the expansion of the
12089 appendfile transport's maildir_tag option in maildir format, the value of
12090 &$message_linecount$& is the precise size of the number of newlines in the
12091 file that has been written (minus one for the blank line between the
12092 header and the body).
12094 Here is an example of the use of this variable in a DATA ACL:
12096 deny message = Too many lines in message header
12098 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12100 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12101 message has not yet been received.
12103 .vitem &$message_size$&
12104 .cindex "size" "of message"
12105 .cindex "message" "size"
12106 .vindex "&$message_size$&"
12107 When a message is being processed, this variable contains its size in bytes. In
12108 most cases, the size includes those headers that were received with the
12109 message, but not those (such as &'Envelope-to:'&) that are added to individual
12110 deliveries as they are written. However, there is one special case: during the
12111 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12112 doing a delivery in maildir format, the value of &$message_size$& is the
12113 precise size of the file that has been written. See also
12114 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12116 .cindex "RCPT" "value of &$message_size$&"
12117 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12118 contains the size supplied on the MAIL command, or -1 if no size was given. The
12119 value may not, of course, be truthful.
12121 .vitem &$mime_$&&'xxx'&
12122 A number of variables whose names start with &$mime$& are
12123 available when Exim is compiled with the content-scanning extension. For
12124 details, see section &<<SECTscanmimepart>>&.
12126 .vitem "&$n0$& &-- &$n9$&"
12127 These variables are counters that can be incremented by means
12128 of the &%add%& command in filter files.
12130 .vitem &$original_domain$&
12131 .vindex "&$domain$&"
12132 .vindex "&$original_domain$&"
12133 When a top-level address is being processed for delivery, this contains the
12134 same value as &$domain$&. However, if a &"child"& address (for example,
12135 generated by an alias, forward, or filter file) is being processed, this
12136 variable contains the domain of the original address (lower cased). This
12137 differs from &$parent_domain$& only when there is more than one level of
12138 aliasing or forwarding. When more than one address is being delivered in a
12139 single transport run, &$original_domain$& is not set.
12141 If a new address is created by means of a &%deliver%& command in a system
12142 filter, it is set up with an artificial &"parent"& address. This has the local
12143 part &'system-filter'& and the default qualify domain.
12145 .vitem &$original_local_part$&
12146 .vindex "&$local_part$&"
12147 .vindex "&$original_local_part$&"
12148 When a top-level address is being processed for delivery, this contains the
12149 same value as &$local_part$&, unless a prefix or suffix was removed from the
12150 local part, because &$original_local_part$& always contains the full local
12151 part. When a &"child"& address (for example, generated by an alias, forward, or
12152 filter file) is being processed, this variable contains the full local part of
12153 the original address.
12155 If the router that did the redirection processed the local part
12156 case-insensitively, the value in &$original_local_part$& is in lower case.
12157 This variable differs from &$parent_local_part$& only when there is more than
12158 one level of aliasing or forwarding. When more than one address is being
12159 delivered in a single transport run, &$original_local_part$& is not set.
12161 If a new address is created by means of a &%deliver%& command in a system
12162 filter, it is set up with an artificial &"parent"& address. This has the local
12163 part &'system-filter'& and the default qualify domain.
12165 .vitem &$originator_gid$&
12166 .cindex "gid (group id)" "of originating user"
12167 .cindex "sender" "gid"
12168 .vindex "&$caller_gid$&"
12169 .vindex "&$originator_gid$&"
12170 This variable contains the value of &$caller_gid$& that was set when the
12171 message was received. For messages received via the command line, this is the
12172 gid of the sending user. For messages received by SMTP over TCP/IP, this is
12173 normally the gid of the Exim user.
12175 .vitem &$originator_uid$&
12176 .cindex "uid (user id)" "of originating user"
12177 .cindex "sender" "uid"
12178 .vindex "&$caller_uid$&"
12179 .vindex "&$originaltor_uid$&"
12180 The value of &$caller_uid$& that was set when the message was received. For
12181 messages received via the command line, this is the uid of the sending user.
12182 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
12185 .vitem &$parent_domain$&
12186 .vindex "&$parent_domain$&"
12187 This variable is similar to &$original_domain$& (see
12188 above), except that it refers to the immediately preceding parent address.
12190 .vitem &$parent_local_part$&
12191 .vindex "&$parent_local_part$&"
12192 This variable is similar to &$original_local_part$&
12193 (see above), except that it refers to the immediately preceding parent address.
12196 .cindex "pid (process id)" "of current process"
12198 This variable contains the current process id.
12200 .vitem &$pipe_addresses$&
12201 .cindex "filter" "transport filter"
12202 .cindex "transport" "filter"
12203 .vindex "&$pipe_addresses$&"
12204 This is not an expansion variable, but is mentioned here because the string
12205 &`$pipe_addresses`& is handled specially in the command specification for the
12206 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
12207 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12208 It cannot be used in general expansion strings, and provokes an &"unknown
12209 variable"& error if encountered.
12211 .vitem &$primary_hostname$&
12212 .vindex "&$primary_hostname$&"
12213 This variable contains the value set by &%primary_hostname%& in the
12214 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12215 a single-component name, Exim calls &[gethostbyname()]& (or
12216 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12217 qualified host name. See also &$smtp_active_hostname$&.
12221 .vitem &$proxy_external_address$& &&&
12222 &$proxy_external_port$& &&&
12223 &$proxy_local_address$& &&&
12224 &$proxy_local_port$& &&&
12226 These variables are only available when built with Proxy Protocol
12228 For details see chapter &<<SECTproxyInbound>>&.
12231 .vitem &$prdr_requested$&
12232 .cindex "PRDR" "variable for"
12233 This variable is set to &"yes"& if PRDR was requested by the client for the
12234 current message, otherwise &"no"&.
12236 .vitem &$prvscheck_address$&
12237 This variable is used in conjunction with the &%prvscheck%& expansion item,
12238 which is described in sections &<<SECTexpansionitems>>& and
12239 &<<SECTverifyPRVS>>&.
12241 .vitem &$prvscheck_keynum$&
12242 This variable is used in conjunction with the &%prvscheck%& expansion item,
12243 which is described in sections &<<SECTexpansionitems>>& and
12244 &<<SECTverifyPRVS>>&.
12246 .vitem &$prvscheck_result$&
12247 This variable is used in conjunction with the &%prvscheck%& expansion item,
12248 which is described in sections &<<SECTexpansionitems>>& and
12249 &<<SECTverifyPRVS>>&.
12251 .vitem &$qualify_domain$&
12252 .vindex "&$qualify_domain$&"
12253 The value set for the &%qualify_domain%& option in the configuration file.
12255 .vitem &$qualify_recipient$&
12256 .vindex "&$qualify_recipient$&"
12257 The value set for the &%qualify_recipient%& option in the configuration file,
12258 or if not set, the value of &$qualify_domain$&.
12261 .vitem &$queue_name$&
12262 .vindex &$queue_name$&
12263 .cindex "named queues"
12264 .cindex queues named
12265 The name of the spool queue in use; empty for the default queue.
12268 .vitem &$rcpt_count$&
12269 .vindex "&$rcpt_count$&"
12270 When a message is being received by SMTP, this variable contains the number of
12271 RCPT commands received for the current message. If this variable is used in a
12272 RCPT ACL, its value includes the current command.
12274 .vitem &$rcpt_defer_count$&
12275 .vindex "&$rcpt_defer_count$&"
12276 .cindex "4&'xx'& responses" "count of"
12277 When a message is being received by SMTP, this variable contains the number of
12278 RCPT commands in the current message that have previously been rejected with a
12279 temporary (4&'xx'&) response.
12281 .vitem &$rcpt_fail_count$&
12282 .vindex "&$rcpt_fail_count$&"
12283 When a message is being received by SMTP, this variable contains the number of
12284 RCPT commands in the current message that have previously been rejected with a
12285 permanent (5&'xx'&) response.
12287 .vitem &$received_count$&
12288 .vindex "&$received_count$&"
12289 This variable contains the number of &'Received:'& header lines in the message,
12290 including the one added by Exim (so its value is always greater than zero). It
12291 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12294 .vitem &$received_for$&
12295 .vindex "&$received_for$&"
12296 If there is only a single recipient address in an incoming message, this
12297 variable contains that address when the &'Received:'& header line is being
12298 built. The value is copied after recipient rewriting has happened, but before
12299 the &[local_scan()]& function is run.
12301 .vitem &$received_ip_address$&
12302 .vindex "&$received_ip_address$&"
12303 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12304 variable is set to the address of the local IP interface, and &$received_port$&
12305 is set to the local port number. (The remote IP address and port are in
12306 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12307 the port value is -1 unless it has been set using the &%-oMi%& command line
12310 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12311 could be used, for example, to make the file name for a TLS certificate depend
12312 on which interface and/or port is being used for the incoming connection. The
12313 values of &$received_ip_address$& and &$received_port$& are saved with any
12314 messages that are received, thus making these variables available at delivery
12316 For outbound connections see &$sending_ip_address$&.
12318 .vitem &$received_port$&
12319 .vindex "&$received_port$&"
12320 See &$received_ip_address$&.
12322 .vitem &$received_protocol$&
12323 .vindex "&$received_protocol$&"
12324 When a message is being processed, this variable contains the name of the
12325 protocol by which it was received. Most of the names used by Exim are defined
12326 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12327 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12328 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12329 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12330 connection and the client was successfully authenticated.
12332 Exim uses the protocol name &"smtps"& for the case when encryption is
12333 automatically set up on connection without the use of STARTTLS (see
12334 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12335 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12336 where the client initially uses EHLO, sets up an encrypted connection using
12337 STARTTLS, and then uses HELO afterwards.
12339 The &%-oMr%& option provides a way of specifying a custom protocol name for
12340 messages that are injected locally by trusted callers. This is commonly used to
12341 identify messages that are being re-injected after some kind of scanning.
12343 .vitem &$received_time$&
12344 .vindex "&$received_time$&"
12345 This variable contains the date and time when the current message was received,
12346 as a number of seconds since the start of the Unix epoch.
12348 .vitem &$recipient_data$&
12349 .vindex "&$recipient_data$&"
12350 This variable is set after an indexing lookup success in an ACL &%recipients%&
12351 condition. It contains the data from the lookup, and the value remains set
12352 until the next &%recipients%& test. Thus, you can do things like this:
12354 &`require recipients = cdb*@;/some/file`&
12355 &`deny `&&'some further test involving'& &`$recipient_data`&
12357 &*Warning*&: This variable is set only when a lookup is used as an indexing
12358 method in the address list, using the semicolon syntax as in the example above.
12359 The variable is not set for a lookup that is used as part of the string
12360 expansion that all such lists undergo before being interpreted.
12362 .vitem &$recipient_verify_failure$&
12363 .vindex "&$recipient_verify_failure$&"
12364 In an ACL, when a recipient verification fails, this variable contains
12365 information about the failure. It is set to one of the following words:
12368 &"qualify"&: The address was unqualified (no domain), and the message
12369 was neither local nor came from an exempted host.
12372 &"route"&: Routing failed.
12375 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12376 or before the MAIL command (that is, on initial connection, HELO, or
12380 &"recipient"&: The RCPT command in a callout was rejected.
12383 &"postmaster"&: The postmaster check in a callout was rejected.
12386 The main use of this variable is expected to be to distinguish between
12387 rejections of MAIL and rejections of RCPT.
12389 .vitem &$recipients$&
12390 .vindex "&$recipients$&"
12391 This variable contains a list of envelope recipients for a message. A comma and
12392 a space separate the addresses in the replacement text. However, the variable
12393 is not generally available, to prevent exposure of Bcc recipients in
12394 unprivileged users' filter files. You can use &$recipients$& only in these
12398 In a system filter file.
12400 In the ACLs associated with the DATA command and with non-SMTP messages, that
12401 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12402 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12403 &%acl_not_smtp_mime%&.
12405 From within a &[local_scan()]& function.
12409 .vitem &$recipients_count$&
12410 .vindex "&$recipients_count$&"
12411 When a message is being processed, this variable contains the number of
12412 envelope recipients that came with the message. Duplicates are not excluded
12413 from the count. While a message is being received over SMTP, the number
12414 increases for each accepted recipient. It can be referenced in an ACL.
12417 .vitem &$regex_match_string$&
12418 .vindex "&$regex_match_string$&"
12419 This variable is set to contain the matching regular expression after a
12420 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12422 .vitem "&$regex1$&, &$regex2$&, etc"
12423 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
12424 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
12425 these variables contain the
12426 captured substrings identified by the regular expression.
12429 .vitem &$reply_address$&
12430 .vindex "&$reply_address$&"
12431 When a message is being processed, this variable contains the contents of the
12432 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12433 contents of the &'From:'& header line. Apart from the removal of leading
12434 white space, the value is not processed in any way. In particular, no RFC 2047
12435 decoding or character code translation takes place.
12437 .vitem &$return_path$&
12438 .vindex "&$return_path$&"
12439 When a message is being delivered, this variable contains the return path &--
12440 the sender field that will be sent as part of the envelope. It is not enclosed
12441 in <> characters. At the start of routing an address, &$return_path$& has the
12442 same value as &$sender_address$&, but if, for example, an incoming message to a
12443 mailing list has been expanded by a router which specifies a different address
12444 for bounce messages, &$return_path$& subsequently contains the new bounce
12445 address, whereas &$sender_address$& always contains the original sender address
12446 that was received with the message. In other words, &$sender_address$& contains
12447 the incoming envelope sender, and &$return_path$& contains the outgoing
12450 .vitem &$return_size_limit$&
12451 .vindex "&$return_size_limit$&"
12452 This is an obsolete name for &$bounce_return_size_limit$&.
12454 .vitem &$router_name$&
12455 .cindex "router" "name"
12456 .cindex "name" "of router"
12457 .vindex "&$router_name$&"
12458 During the running of a router this variable contains its name.
12461 .cindex "return code" "from &%run%& expansion"
12462 .vindex "&$runrc$&"
12463 This variable contains the return code from a command that is run by the
12464 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12465 assume the order in which option values are expanded, except for those
12466 preconditions whose order of testing is documented. Therefore, you cannot
12467 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12470 .vitem &$self_hostname$&
12471 .oindex "&%self%&" "value of host name"
12472 .vindex "&$self_hostname$&"
12473 When an address is routed to a supposedly remote host that turns out to be the
12474 local host, what happens is controlled by the &%self%& generic router option.
12475 One of its values causes the address to be passed to another router. When this
12476 happens, &$self_hostname$& is set to the name of the local host that the
12477 original router encountered. In other circumstances its contents are null.
12479 .vitem &$sender_address$&
12480 .vindex "&$sender_address$&"
12481 When a message is being processed, this variable contains the sender's address
12482 that was received in the message's envelope. The case of letters in the address
12483 is retained, in both the local part and the domain. For bounce messages, the
12484 value of this variable is the empty string. See also &$return_path$&.
12486 .vitem &$sender_address_data$&
12487 .vindex "&$address_data$&"
12488 .vindex "&$sender_address_data$&"
12489 If &$address_data$& is set when the routers are called from an ACL to verify a
12490 sender address, the final value is preserved in &$sender_address_data$&, to
12491 distinguish it from data from a recipient address. The value does not persist
12492 after the end of the current ACL statement. If you want to preserve it for
12493 longer, you can save it in an ACL variable.
12495 .vitem &$sender_address_domain$&
12496 .vindex "&$sender_address_domain$&"
12497 The domain portion of &$sender_address$&.
12499 .vitem &$sender_address_local_part$&
12500 .vindex "&$sender_address_local_part$&"
12501 The local part portion of &$sender_address$&.
12503 .vitem &$sender_data$&
12504 .vindex "&$sender_data$&"
12505 This variable is set after a lookup success in an ACL &%senders%& condition or
12506 in a router &%senders%& option. It contains the data from the lookup, and the
12507 value remains set until the next &%senders%& test. Thus, you can do things like
12510 &`require senders = cdb*@;/some/file`&
12511 &`deny `&&'some further test involving'& &`$sender_data`&
12513 &*Warning*&: This variable is set only when a lookup is used as an indexing
12514 method in the address list, using the semicolon syntax as in the example above.
12515 The variable is not set for a lookup that is used as part of the string
12516 expansion that all such lists undergo before being interpreted.
12518 .vitem &$sender_fullhost$&
12519 .vindex "&$sender_fullhost$&"
12520 When a message is received from a remote host, this variable contains the host
12521 name and IP address in a single string. It ends with the IP address in square
12522 brackets, followed by a colon and a port number if the logging of ports is
12523 enabled. The format of the rest of the string depends on whether the host
12524 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12525 looking up its IP address. (Looking up the IP address can be forced by the
12526 &%host_lookup%& option, independent of verification.) A plain host name at the
12527 start of the string is a verified host name; if this is not present,
12528 verification either failed or was not requested. A host name in parentheses is
12529 the argument of a HELO or EHLO command. This is omitted if it is identical to
12530 the verified host name or to the host's IP address in square brackets.
12532 .vitem &$sender_helo_dnssec$&
12533 .vindex "&$sender_helo_dnssec$&"
12534 This boolean variable is true if a successful HELO verification was
12535 .cindex "DNS" "DNSSEC"
12536 done using DNS information the resolver library stated was authenticated data.
12538 .vitem &$sender_helo_name$&
12539 .vindex "&$sender_helo_name$&"
12540 When a message is received from a remote host that has issued a HELO or EHLO
12541 command, the argument of that command is placed in this variable. It is also
12542 set if HELO or EHLO is used when a message is received using SMTP locally via
12543 the &%-bs%& or &%-bS%& options.
12545 .vitem &$sender_host_address$&
12546 .vindex "&$sender_host_address$&"
12547 When a message is received from a remote host using SMTP,
12548 this variable contains that
12549 host's IP address. For locally non-SMTP submitted messages, it is empty.
12551 .vitem &$sender_host_authenticated$&
12552 .vindex "&$sender_host_authenticated$&"
12553 This variable contains the name (not the public name) of the authenticator
12554 driver that successfully authenticated the client from which the message was
12555 received. It is empty if there was no successful authentication. See also
12556 &$authenticated_id$&.
12558 .vitem &$sender_host_dnssec$&
12559 .vindex "&$sender_host_dnssec$&"
12560 If an attempt to populate &$sender_host_name$& has been made
12561 (by reference, &%hosts_lookup%& or
12562 otherwise) then this boolean will have been set true if, and only if, the
12563 resolver library states that both
12564 the reverse and forward DNS were authenticated data. At all
12565 other times, this variable is false.
12567 .cindex "DNS" "DNSSEC"
12568 It is likely that you will need to coerce DNSSEC support on in the resolver
12569 library, by setting:
12574 Exim does not perform DNSSEC validation itself, instead leaving that to a
12575 validating resolver (e.g. unbound, or bind with suitable configuration).
12577 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12578 mechanism in the list, then this variable will be false.
12581 .vitem &$sender_host_name$&
12582 .vindex "&$sender_host_name$&"
12583 When a message is received from a remote host, this variable contains the
12584 host's name as obtained by looking up its IP address. For messages received by
12585 other means, this variable is empty.
12587 .vindex "&$host_lookup_failed$&"
12588 If the host name has not previously been looked up, a reference to
12589 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12590 A looked up name is accepted only if it leads back to the original IP address
12591 via a forward lookup. If either the reverse or the forward lookup fails to find
12592 any data, or if the forward lookup does not yield the original IP address,
12593 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12595 .vindex "&$host_lookup_deferred$&"
12596 However, if either of the lookups cannot be completed (for example, there is a
12597 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12598 &$host_lookup_failed$& remains set to &"0"&.
12600 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12601 host name again if there is a subsequent reference to &$sender_host_name$&
12602 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12605 Exim does not automatically look up every calling host's name. If you want
12606 maximum efficiency, you should arrange your configuration so that it avoids
12607 these lookups altogether. The lookup happens only if one or more of the
12608 following are true:
12611 A string containing &$sender_host_name$& is expanded.
12613 The calling host matches the list in &%host_lookup%&. In the default
12614 configuration, this option is set to *, so it must be changed if lookups are
12615 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12617 Exim needs the host name in order to test an item in a host list. The items
12618 that require this are described in sections &<<SECThoslispatnam>>& and
12619 &<<SECThoslispatnamsk>>&.
12621 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12622 In this case, the host name is required to compare with the name quoted in any
12623 EHLO or HELO commands that the client issues.
12625 The remote host issues a EHLO or HELO command that quotes one of the
12626 domains in &%helo_lookup_domains%&. The default value of this option is
12627 . ==== As this is a nested list, any displays it contains must be indented
12628 . ==== as otherwise they are too far to the left.
12630 helo_lookup_domains = @ : @[]
12632 which causes a lookup if a remote host (incorrectly) gives the server's name or
12633 IP address in an EHLO or HELO command.
12637 .vitem &$sender_host_port$&
12638 .vindex "&$sender_host_port$&"
12639 When a message is received from a remote host, this variable contains the port
12640 number that was used on the remote host.
12642 .vitem &$sender_ident$&
12643 .vindex "&$sender_ident$&"
12644 When a message is received from a remote host, this variable contains the
12645 identification received in response to an RFC 1413 request. When a message has
12646 been received locally, this variable contains the login name of the user that
12649 .vitem &$sender_rate_$&&'xxx'&
12650 A number of variables whose names begin &$sender_rate_$& are set as part of the
12651 &%ratelimit%& ACL condition. Details are given in section
12652 &<<SECTratelimiting>>&.
12654 .vitem &$sender_rcvhost$&
12655 .cindex "DNS" "reverse lookup"
12656 .cindex "reverse DNS lookup"
12657 .vindex "&$sender_rcvhost$&"
12658 This is provided specifically for use in &'Received:'& headers. It starts with
12659 either the verified host name (as obtained from a reverse DNS lookup) or, if
12660 there is no verified host name, the IP address in square brackets. After that
12661 there may be text in parentheses. When the first item is a verified host name,
12662 the first thing in the parentheses is the IP address in square brackets,
12663 followed by a colon and a port number if port logging is enabled. When the
12664 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12667 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12668 was used and its argument was not identical to the real host name or IP
12669 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12670 all three items are present in the parentheses, a newline and tab are inserted
12671 into the string, to improve the formatting of the &'Received:'& header.
12673 .vitem &$sender_verify_failure$&
12674 .vindex "&$sender_verify_failure$&"
12675 In an ACL, when a sender verification fails, this variable contains information
12676 about the failure. The details are the same as for
12677 &$recipient_verify_failure$&.
12679 .vitem &$sending_ip_address$&
12680 .vindex "&$sending_ip_address$&"
12681 This variable is set whenever an outgoing SMTP connection to another host has
12682 been set up. It contains the IP address of the local interface that is being
12683 used. This is useful if a host that has more than one IP address wants to take
12684 on different personalities depending on which one is being used. For incoming
12685 connections, see &$received_ip_address$&.
12687 .vitem &$sending_port$&
12688 .vindex "&$sending_port$&"
12689 This variable is set whenever an outgoing SMTP connection to another host has
12690 been set up. It contains the local port that is being used. For incoming
12691 connections, see &$received_port$&.
12693 .vitem &$smtp_active_hostname$&
12694 .vindex "&$smtp_active_hostname$&"
12695 During an incoming SMTP session, this variable contains the value of the active
12696 host name, as specified by the &%smtp_active_hostname%& option. The value of
12697 &$smtp_active_hostname$& is saved with any message that is received, so its
12698 value can be consulted during routing and delivery.
12700 .vitem &$smtp_command$&
12701 .vindex "&$smtp_command$&"
12702 During the processing of an incoming SMTP command, this variable contains the
12703 entire command. This makes it possible to distinguish between HELO and EHLO in
12704 the HELO ACL, and also to distinguish between commands such as these:
12709 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12710 command, the address in &$smtp_command$& is the original address before any
12711 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12712 the address after SMTP-time rewriting.
12714 .vitem &$smtp_command_argument$&
12715 .cindex "SMTP" "command, argument for"
12716 .vindex "&$smtp_command_argument$&"
12717 While an ACL is running to check an SMTP command, this variable contains the
12718 argument, that is, the text that follows the command name, with leading white
12719 space removed. Following the introduction of &$smtp_command$&, this variable is
12720 somewhat redundant, but is retained for backwards compatibility.
12722 .vitem &$smtp_count_at_connection_start$&
12723 .vindex "&$smtp_count_at_connection_start$&"
12724 This variable is set greater than zero only in processes spawned by the Exim
12725 daemon for handling incoming SMTP connections. The name is deliberately long,
12726 in order to emphasize what the contents are. When the daemon accepts a new
12727 connection, it increments this variable. A copy of the variable is passed to
12728 the child process that handles the connection, but its value is fixed, and
12729 never changes. It is only an approximation of how many incoming connections
12730 there actually are, because many other connections may come and go while a
12731 single connection is being processed. When a child process terminates, the
12732 daemon decrements its copy of the variable.
12734 .vitem "&$sn0$& &-- &$sn9$&"
12735 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12736 that were current at the end of the system filter file. This allows a system
12737 filter file to set values that can be tested in users' filter files. For
12738 example, a system filter could set a value indicating how likely it is that a
12739 message is junk mail.
12741 .vitem &$spam_$&&'xxx'&
12742 A number of variables whose names start with &$spam$& are available when Exim
12743 is compiled with the content-scanning extension. For details, see section
12744 &<<SECTscanspamass>>&.
12747 .vitem &$spool_directory$&
12748 .vindex "&$spool_directory$&"
12749 The name of Exim's spool directory.
12751 .vitem &$spool_inodes$&
12752 .vindex "&$spool_inodes$&"
12753 The number of free inodes in the disk partition where Exim's spool files are
12754 being written. The value is recalculated whenever the variable is referenced.
12755 If the relevant file system does not have the concept of inodes, the value of
12756 is -1. See also the &%check_spool_inodes%& option.
12758 .vitem &$spool_space$&
12759 .vindex "&$spool_space$&"
12760 The amount of free space (as a number of kilobytes) in the disk partition where
12761 Exim's spool files are being written. The value is recalculated whenever the
12762 variable is referenced. If the operating system does not have the ability to
12763 find the amount of free space (only true for experimental systems), the space
12764 value is -1. For example, to check in an ACL that there is at least 50
12765 megabytes free on the spool, you could write:
12767 condition = ${if > {$spool_space}{50000}}
12769 See also the &%check_spool_space%& option.
12772 .vitem &$thisaddress$&
12773 .vindex "&$thisaddress$&"
12774 This variable is set only during the processing of the &%foranyaddress%&
12775 command in a filter file. Its use is explained in the description of that
12776 command, which can be found in the separate document entitled &'Exim's
12777 interfaces to mail filtering'&.
12779 .vitem &$tls_in_bits$&
12780 .vindex "&$tls_in_bits$&"
12781 Contains an approximation of the TLS cipher's bit-strength
12782 on the inbound connection; the meaning of
12783 this depends upon the TLS implementation used.
12784 If TLS has not been negotiated, the value will be 0.
12785 The value of this is automatically fed into the Cyrus SASL authenticator
12786 when acting as a server, to specify the "external SSF" (a SASL term).
12788 The deprecated &$tls_bits$& variable refers to the inbound side
12789 except when used in the context of an outbound SMTP delivery, when it refers to
12792 .vitem &$tls_out_bits$&
12793 .vindex "&$tls_out_bits$&"
12794 Contains an approximation of the TLS cipher's bit-strength
12795 on an outbound SMTP connection; the meaning of
12796 this depends upon the TLS implementation used.
12797 If TLS has not been negotiated, the value will be 0.
12799 .vitem &$tls_in_ourcert$&
12800 .vindex "&$tls_in_ourcert$&"
12801 .cindex certificate veriables
12802 This variable refers to the certificate presented to the peer of an
12803 inbound connection when the message was received.
12804 It is only useful as the argument of a
12805 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12806 or a &%def%& condition.
12808 .vitem &$tls_in_peercert$&
12809 .vindex "&$tls_in_peercert$&"
12810 This variable refers to the certificate presented by the peer of an
12811 inbound connection when the message was received.
12812 It is only useful as the argument of a
12813 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12814 or a &%def%& condition.
12815 If certificate verification fails it may refer to a failing chain element
12816 which is not the leaf.
12818 .vitem &$tls_out_ourcert$&
12819 .vindex "&$tls_out_ourcert$&"
12820 This variable refers to the certificate presented to the peer of an
12821 outbound connection. It is only useful as the argument of a
12822 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12823 or a &%def%& condition.
12825 .vitem &$tls_out_peercert$&
12826 .vindex "&$tls_out_peercert$&"
12827 This variable refers to the certificate presented by the peer of an
12828 outbound connection. It is only useful as the argument of a
12829 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12830 or a &%def%& condition.
12831 If certificate verification fails it may refer to a failing chain element
12832 which is not the leaf.
12834 .vitem &$tls_in_certificate_verified$&
12835 .vindex "&$tls_in_certificate_verified$&"
12836 This variable is set to &"1"& if a TLS certificate was verified when the
12837 message was received, and &"0"& otherwise.
12839 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
12840 except when used in the context of an outbound SMTP delivery, when it refers to
12843 .vitem &$tls_out_certificate_verified$&
12844 .vindex "&$tls_out_certificate_verified$&"
12845 This variable is set to &"1"& if a TLS certificate was verified when an
12846 outbound SMTP connection was made,
12847 and &"0"& otherwise.
12849 .vitem &$tls_in_cipher$&
12850 .vindex "&$tls_in_cipher$&"
12851 .vindex "&$tls_cipher$&"
12852 When a message is received from a remote host over an encrypted SMTP
12853 connection, this variable is set to the cipher suite that was negotiated, for
12854 example DES-CBC3-SHA. In other circumstances, in particular, for message
12855 received over unencrypted connections, the variable is empty. Testing
12856 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
12857 non-encrypted connections during ACL processing.
12859 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12860 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12861 becomes the same as &$tls_out_cipher$&.
12863 .vitem &$tls_out_cipher$&
12864 .vindex "&$tls_out_cipher$&"
12866 cleared before any outgoing SMTP connection is made,
12867 and then set to the outgoing cipher suite if one is negotiated. See chapter
12868 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12869 details of the &(smtp)& transport.
12871 .vitem &$tls_in_ocsp$&
12872 .vindex "&$tls_in_ocsp$&"
12873 When a message is received from a remote client connection
12874 the result of any OCSP request from the client is encoded in this variable:
12876 0 OCSP proof was not requested (default value)
12877 1 No response to request
12878 2 Response not verified
12879 3 Verification failed
12880 4 Verification succeeded
12883 .vitem &$tls_out_ocsp$&
12884 .vindex "&$tls_out_ocsp$&"
12885 When a message is sent to a remote host connection
12886 the result of any OCSP request made is encoded in this variable.
12887 See &$tls_in_ocsp$& for values.
12889 .vitem &$tls_in_peerdn$&
12890 .vindex "&$tls_in_peerdn$&"
12891 .vindex "&$tls_peerdn$&"
12892 .cindex certificate "extracting fields"
12893 When a message is received from a remote host over an encrypted SMTP
12894 connection, and Exim is configured to request a certificate from the client,
12895 the value of the Distinguished Name of the certificate is made available in the
12896 &$tls_in_peerdn$& during subsequent processing.
12897 If certificate verification fails it may refer to a failing chain element
12898 which is not the leaf.
12900 The deprecated &$tls_peerdn$& variable refers to the inbound side
12901 except when used in the context of an outbound SMTP delivery, when it refers to
12904 .vitem &$tls_out_peerdn$&
12905 .vindex "&$tls_out_peerdn$&"
12906 When a message is being delivered to a remote host over an encrypted SMTP
12907 connection, and Exim is configured to request a certificate from the server,
12908 the value of the Distinguished Name of the certificate is made available in the
12909 &$tls_out_peerdn$& during subsequent processing.
12910 If certificate verification fails it may refer to a failing chain element
12911 which is not the leaf.
12913 .vitem &$tls_in_sni$&
12914 .vindex "&$tls_in_sni$&"
12915 .vindex "&$tls_sni$&"
12916 .cindex "TLS" "Server Name Indication"
12917 When a TLS session is being established, if the client sends the Server
12918 Name Indication extension, the value will be placed in this variable.
12919 If the variable appears in &%tls_certificate%& then this option and
12920 some others, described in &<<SECTtlssni>>&,
12921 will be re-expanded early in the TLS session, to permit
12922 a different certificate to be presented (and optionally a different key to be
12923 used) to the client, based upon the value of the SNI extension.
12925 The deprecated &$tls_sni$& variable refers to the inbound side
12926 except when used in the context of an outbound SMTP delivery, when it refers to
12929 .vitem &$tls_out_sni$&
12930 .vindex "&$tls_out_sni$&"
12931 .cindex "TLS" "Server Name Indication"
12933 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12936 .vitem &$tod_bsdinbox$&
12937 .vindex "&$tod_bsdinbox$&"
12938 The time of day and the date, in the format required for BSD-style mailbox
12939 files, for example: Thu Oct 17 17:14:09 1995.
12941 .vitem &$tod_epoch$&
12942 .vindex "&$tod_epoch$&"
12943 The time and date as a number of seconds since the start of the Unix epoch.
12945 .vitem &$tod_epoch_l$&
12946 .vindex "&$tod_epoch_l$&"
12947 The time and date as a number of microseconds since the start of the Unix epoch.
12949 .vitem &$tod_full$&
12950 .vindex "&$tod_full$&"
12951 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12952 +0100. The timezone is always given as a numerical offset from UTC, with
12953 positive values used for timezones that are ahead (east) of UTC, and negative
12954 values for those that are behind (west).
12957 .vindex "&$tod_log$&"
12958 The time and date in the format used for writing Exim's log files, for example:
12959 1995-10-12 15:32:29, but without a timezone.
12961 .vitem &$tod_logfile$&
12962 .vindex "&$tod_logfile$&"
12963 This variable contains the date in the format yyyymmdd. This is the format that
12964 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12967 .vitem &$tod_zone$&
12968 .vindex "&$tod_zone$&"
12969 This variable contains the numerical value of the local timezone, for example:
12972 .vitem &$tod_zulu$&
12973 .vindex "&$tod_zulu$&"
12974 This variable contains the UTC date and time in &"Zulu"& format, as specified
12975 by ISO 8601, for example: 20030221154023Z.
12977 .vitem &$transport_name$&
12978 .cindex "transport" "name"
12979 .cindex "name" "of transport"
12980 .vindex "&$transport_name$&"
12981 During the running of a transport, this variable contains its name.
12984 .vindex "&$value$&"
12985 This variable contains the result of an expansion lookup, extraction operation,
12986 or external command, as described above. It is also used during a
12987 &*reduce*& expansion.
12989 .vitem &$verify_mode$&
12990 .vindex "&$verify_mode$&"
12991 While a router or transport is being run in verify mode
12992 or for cutthrough delivery,
12993 contains "S" for sender-verification or "R" for recipient-verification.
12996 .vitem &$version_number$&
12997 .vindex "&$version_number$&"
12998 The version number of Exim.
13000 .vitem &$warn_message_delay$&
13001 .vindex "&$warn_message_delay$&"
13002 This variable is set only during the creation of a message warning about a
13003 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13005 .vitem &$warn_message_recipients$&
13006 .vindex "&$warn_message_recipients$&"
13007 This variable is set only during the creation of a message warning about a
13008 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13014 . ////////////////////////////////////////////////////////////////////////////
13015 . ////////////////////////////////////////////////////////////////////////////
13017 .chapter "Embedded Perl" "CHAPperl"
13018 .scindex IIDperl "Perl" "calling from Exim"
13019 Exim can be built to include an embedded Perl interpreter. When this is done,
13020 Perl subroutines can be called as part of the string expansion process. To make
13021 use of the Perl support, you need version 5.004 or later of Perl installed on
13022 your system. To include the embedded interpreter in the Exim binary, include
13027 in your &_Local/Makefile_& and then build Exim in the normal way.
13030 .section "Setting up so Perl can be used" "SECID85"
13031 .oindex "&%perl_startup%&"
13032 Access to Perl subroutines is via a global configuration option called
13033 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
13034 no &%perl_startup%& option in the Exim configuration file then no Perl
13035 interpreter is started and there is almost no overhead for Exim (since none of
13036 the Perl library will be paged in unless used). If there is a &%perl_startup%&
13037 option then the associated value is taken to be Perl code which is executed in
13038 a newly created Perl interpreter.
13040 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
13041 need backslashes before any characters to escape special meanings. The option
13042 should usually be something like
13044 perl_startup = do '/etc/exim.pl'
13046 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
13047 use from Exim. Exim can be configured either to start up a Perl interpreter as
13048 soon as it is entered, or to wait until the first time it is needed. Starting
13049 the interpreter at the beginning ensures that it is done while Exim still has
13050 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
13051 fact used in a particular run. Also, note that this does not mean that Exim is
13052 necessarily running as root when Perl is called at a later time. By default,
13053 the interpreter is started only when it is needed, but this can be changed in
13057 .oindex "&%perl_at_start%&"
13058 Setting &%perl_at_start%& (a boolean option) in the configuration requests
13059 a startup when Exim is entered.
13061 The command line option &%-ps%& also requests a startup when Exim is entered,
13062 overriding the setting of &%perl_at_start%&.
13065 There is also a command line option &%-pd%& (for delay) which suppresses the
13066 initial startup, even if &%perl_at_start%& is set.
13070 .oindex "&%perl_taintmode%&"
13071 .cindex "Perl" "taintmode"
13072 To provide more security executing Perl code via the embedded Perl
13073 interpeter, the &%perl_taintmode%& option can be set. This enables the
13074 taint mode of the Perl interpreter. You are encouraged to set this
13075 option to a true value. To avoid breaking existing installations, it
13080 .section "Calling Perl subroutines" "SECID86"
13081 When the configuration file includes a &%perl_startup%& option you can make use
13082 of the string expansion item to call the Perl subroutines that are defined
13083 by the &%perl_startup%& code. The operator is used in any of the following
13087 ${perl{foo}{argument}}
13088 ${perl{foo}{argument1}{argument2} ... }
13090 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
13091 arguments may be passed. Passing more than this results in an expansion failure
13092 with an error message of the form
13094 Too many arguments passed to Perl subroutine "foo" (max is 8)
13096 The return value of the Perl subroutine is evaluated in a scalar context before
13097 it is passed back to Exim to be inserted into the expanded string. If the
13098 return value is &'undef'&, the expansion is forced to fail in the same way as
13099 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
13100 by obeying Perl's &%die%& function, the expansion fails with the error message
13101 that was passed to &%die%&.
13104 .section "Calling Exim functions from Perl" "SECID87"
13105 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
13106 is available to call back into Exim's string expansion function. For example,
13109 my $lp = Exim::expand_string('$local_part');
13111 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
13112 Note those are single quotes and not double quotes to protect against
13113 &$local_part$& being interpolated as a Perl variable.
13115 If the string expansion is forced to fail by a &"fail"& item, the result of
13116 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
13117 expansion string, the Perl call from the original expansion string fails with
13118 an appropriate error message, in the same way as if &%die%& were used.
13120 .cindex "debugging" "from embedded Perl"
13121 .cindex "log" "writing from embedded Perl"
13122 Two other Exim functions are available for use from within Perl code.
13123 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
13124 debugging is enabled. If you want a newline at the end, you must supply it.
13125 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
13126 timestamp. In this case, you should not supply a terminating newline.
13129 .section "Use of standard output and error by Perl" "SECID88"
13130 .cindex "Perl" "standard output and error"
13131 You should not write to the standard error or output streams from within your
13132 Perl code, as it is not defined how these are set up. In versions of Exim
13133 before 4.50, it is possible for the standard output or error to refer to the
13134 SMTP connection during message reception via the daemon. Writing to this stream
13135 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
13136 error streams are connected to &_/dev/null_& in the daemon. The chaos is
13137 avoided, but the output is lost.
13139 .cindex "Perl" "use of &%warn%&"
13140 The Perl &%warn%& statement writes to the standard error stream by default.
13141 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
13142 you have no control. When Exim starts up the Perl interpreter, it arranges for
13143 output from the &%warn%& statement to be written to the Exim main log. You can
13144 change this by including appropriate Perl magic somewhere in your Perl code.
13145 For example, to discard &%warn%& output completely, you need this:
13147 $SIG{__WARN__} = sub { };
13149 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
13150 example, the code for the subroutine is empty, so it does nothing, but you can
13151 include any Perl code that you like. The text of the &%warn%& message is passed
13152 as the first subroutine argument.
13156 . ////////////////////////////////////////////////////////////////////////////
13157 . ////////////////////////////////////////////////////////////////////////////
13159 .chapter "Starting the daemon and the use of network interfaces" &&&
13160 "CHAPinterfaces" &&&
13161 "Starting the daemon"
13162 .cindex "daemon" "starting"
13163 .cindex "interface" "listening"
13164 .cindex "network interface"
13165 .cindex "interface" "network"
13166 .cindex "IP address" "for listening"
13167 .cindex "daemon" "listening IP addresses"
13168 .cindex "TCP/IP" "setting listening interfaces"
13169 .cindex "TCP/IP" "setting listening ports"
13170 A host that is connected to a TCP/IP network may have one or more physical
13171 hardware network interfaces. Each of these interfaces may be configured as one
13172 or more &"logical"& interfaces, which are the entities that a program actually
13173 works with. Each of these logical interfaces is associated with an IP address.
13174 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
13175 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
13176 knowledge about the host's interfaces for use in three different circumstances:
13179 When a listening daemon is started, Exim needs to know which interfaces
13180 and ports to listen on.
13182 When Exim is routing an address, it needs to know which IP addresses
13183 are associated with local interfaces. This is required for the correct
13184 processing of MX lists by removing the local host and others with the
13185 same or higher priority values. Also, Exim needs to detect cases
13186 when an address is routed to an IP address that in fact belongs to the
13187 local host. Unless the &%self%& router option or the &%allow_localhost%&
13188 option of the smtp transport is set (as appropriate), this is treated
13189 as an error situation.
13191 When Exim connects to a remote host, it may need to know which interface to use
13192 for the outgoing connection.
13196 Exim's default behaviour is likely to be appropriate in the vast majority
13197 of cases. If your host has only one interface, and you want all its IP
13198 addresses to be treated in the same way, and you are using only the
13199 standard SMTP port, you should not need to take any special action. The
13200 rest of this chapter does not apply to you.
13202 In a more complicated situation you may want to listen only on certain
13203 interfaces, or on different ports, and for this reason there are a number of
13204 options that can be used to influence Exim's behaviour. The rest of this
13205 chapter describes how they operate.
13207 When a message is received over TCP/IP, the interface and port that were
13208 actually used are set in &$received_ip_address$& and &$received_port$&.
13212 .section "Starting a listening daemon" "SECID89"
13213 When a listening daemon is started (by means of the &%-bd%& command line
13214 option), the interfaces and ports on which it listens are controlled by the
13218 &%daemon_smtp_ports%& contains a list of default ports
13220 (For backward compatibility, this option can also be specified in the singular.)
13222 &%local_interfaces%& contains list of interface IP addresses on which to
13223 listen. Each item may optionally also specify a port.
13226 The default list separator in both cases is a colon, but this can be changed as
13227 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
13228 it is usually best to change the separator to avoid having to double all the
13229 colons. For example:
13231 local_interfaces = <; 127.0.0.1 ; \
13234 3ffe:ffff:836f::fe86:a061
13236 There are two different formats for specifying a port along with an IP address
13237 in &%local_interfaces%&:
13240 The port is added onto the address with a dot separator. For example, to listen
13241 on port 1234 on two different IP addresses:
13243 local_interfaces = <; 192.168.23.65.1234 ; \
13244 3ffe:ffff:836f::fe86:a061.1234
13247 The IP address is enclosed in square brackets, and the port is added
13248 with a colon separator, for example:
13250 local_interfaces = <; [192.168.23.65]:1234 ; \
13251 [3ffe:ffff:836f::fe86:a061]:1234
13255 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13256 default setting contains just one port:
13258 daemon_smtp_ports = smtp
13260 If more than one port is listed, each interface that does not have its own port
13261 specified listens on all of them. Ports that are listed in
13262 &%daemon_smtp_ports%& can be identified either by name (defined in
13263 &_/etc/services_&) or by number. However, when ports are given with individual
13264 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13268 .section "Special IP listening addresses" "SECID90"
13269 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13270 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13271 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13272 instead of setting up separate listening sockets for each interface. The
13273 default value of &%local_interfaces%& is
13275 local_interfaces = 0.0.0.0
13277 when Exim is built without IPv6 support; otherwise it is:
13279 local_interfaces = <; ::0 ; 0.0.0.0
13281 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13285 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13286 The &%-oX%& command line option can be used to override the values of
13287 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13288 instance. Another way of doing this would be to use macros and the &%-D%&
13289 option. However, &%-oX%& can be used by any admin user, whereas modification of
13290 the runtime configuration by &%-D%& is allowed only when the caller is root or
13293 The value of &%-oX%& is a list of items. The default colon separator can be
13294 changed in the usual way if required. If there are any items that do not
13295 contain dots or colons (that is, are not IP addresses), the value of
13296 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13297 items that do contain dots or colons, the value of &%local_interfaces%& is
13298 replaced by those items. Thus, for example,
13302 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13305 -oX 192.168.34.5.1125
13307 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13308 (However, since &%local_interfaces%& now contains no items without ports, the
13309 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13313 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
13314 .cindex "ssmtp protocol"
13315 .cindex "smtps protocol"
13316 .cindex "SMTP" "ssmtp protocol"
13317 .cindex "SMTP" "smtps protocol"
13318 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
13319 before the STARTTLS command was standardized for SMTP. Some legacy clients
13320 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
13321 list of port numbers or service names,
13322 connections to those ports must use SSMTP. The most
13323 common use of this option is expected to be
13325 tls_on_connect_ports = 465
13327 because 465 is the usual port number used by the legacy clients. There is also
13328 a command line option &%-tls-on-connect%&, which forces all ports to behave in
13329 this way when a daemon is started.
13331 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13332 daemon to listen on those ports. You must still specify them in
13333 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13334 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13335 connections via the daemon.)
13340 .section "IPv6 address scopes" "SECID92"
13341 .cindex "IPv6" "address scopes"
13342 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13343 can, in principle, have the same link-local IPv6 address on different
13344 interfaces. Thus, additional information is needed, over and above the IP
13345 address, to distinguish individual interfaces. A convention of using a
13346 percent sign followed by something (often the interface name) has been
13347 adopted in some cases, leading to addresses like this:
13349 fe80::202:b3ff:fe03:45c1%eth0
13351 To accommodate this usage, a percent sign followed by an arbitrary string is
13352 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13353 to convert a textual IPv6 address for actual use. This function recognizes the
13354 percent convention in operating systems that support it, and it processes the
13355 address appropriately. Unfortunately, some older libraries have problems with
13356 &[getaddrinfo()]&. If
13358 IPV6_USE_INET_PTON=yes
13360 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13361 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13362 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13363 function.) Of course, this means that the additional functionality of
13364 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13366 .section "Disabling IPv6" "SECID93"
13367 .cindex "IPv6" "disabling"
13368 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13369 run on a host whose kernel does not support IPv6. The binary will fall back to
13370 using IPv4, but it may waste resources looking up AAAA records, and trying to
13371 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13372 .oindex "&%disable_ipv6%&"
13373 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13374 activities take place. AAAA records are never looked up, and any IPv6 addresses
13375 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13376 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13377 to handle IPv6 literal addresses.
13379 On the other hand, when IPv6 is in use, there may be times when you want to
13380 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13381 option to globally suppress the lookup of AAAA records for specified domains,
13382 and you can use the &%ignore_target_hosts%& generic router option to ignore
13383 IPv6 addresses in an individual router.
13387 .section "Examples of starting a listening daemon" "SECID94"
13388 The default case in an IPv6 environment is
13390 daemon_smtp_ports = smtp
13391 local_interfaces = <; ::0 ; 0.0.0.0
13393 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13394 Either one or two sockets may be used, depending on the characteristics of
13395 the TCP/IP stack. (This is complicated and messy; for more information,
13396 read the comments in the &_daemon.c_& source file.)
13398 To specify listening on ports 25 and 26 on all interfaces:
13400 daemon_smtp_ports = 25 : 26
13402 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13404 local_interfaces = <; ::0.25 ; ::0.26 \
13405 0.0.0.0.25 ; 0.0.0.0.26
13407 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13408 IPv4 loopback address only:
13410 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13412 To specify listening on the default port on specific interfaces only:
13414 local_interfaces = 10.0.0.67 : 192.168.34.67
13416 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13420 .section "Recognizing the local host" "SECTreclocipadd"
13421 The &%local_interfaces%& option is also used when Exim needs to determine
13422 whether or not an IP address refers to the local host. That is, the IP
13423 addresses of all the interfaces on which a daemon is listening are always
13426 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13427 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13428 available interfaces from the operating system, and extracts the relevant
13429 (that is, IPv4 or IPv6) addresses to use for checking.
13431 Some systems set up large numbers of virtual interfaces in order to provide
13432 many virtual web servers. In this situation, you may want to listen for
13433 email on only a few of the available interfaces, but nevertheless treat all
13434 interfaces as local when routing. You can do this by setting
13435 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13436 &"all"& wildcard values. These addresses are recognized as local, but are not
13437 used for listening. Consider this example:
13439 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13441 3ffe:2101:12:1:a00:20ff:fe86:a061
13443 extra_local_interfaces = <; ::0 ; 0.0.0.0
13445 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13446 address, but all available interface addresses are treated as local when
13449 In some environments the local host name may be in an MX list, but with an IP
13450 address that is not assigned to any local interface. In other cases it may be
13451 desirable to treat other host names as if they referred to the local host. Both
13452 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13453 This contains host names rather than IP addresses. When a host is referenced
13454 during routing, either via an MX record or directly, it is treated as the local
13455 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13456 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13460 .section "Delivering to a remote host" "SECID95"
13461 Delivery to a remote host is handled by the smtp transport. By default, it
13462 allows the system's TCP/IP functions to choose which interface to use (if
13463 there is more than one) when connecting to a remote host. However, the
13464 &%interface%& option can be set to specify which interface is used. See the
13465 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13471 . ////////////////////////////////////////////////////////////////////////////
13472 . ////////////////////////////////////////////////////////////////////////////
13474 .chapter "Main configuration" "CHAPmainconfig"
13475 .scindex IIDconfima "configuration file" "main section"
13476 .scindex IIDmaiconf "main configuration"
13477 The first part of the run time configuration file contains three types of item:
13480 Macro definitions: These lines start with an upper case letter. See section
13481 &<<SECTmacrodefs>>& for details of macro processing.
13483 Named list definitions: These lines start with one of the words &"domainlist"&,
13484 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13485 section &<<SECTnamedlists>>&.
13487 Main configuration settings: Each setting occupies one line of the file
13488 (with possible continuations). If any setting is preceded by the word
13489 &"hide"&, the &%-bP%& command line option displays its value to admin users
13490 only. See section &<<SECTcos>>& for a description of the syntax of these option
13494 This chapter specifies all the main configuration options, along with their
13495 types and default values. For ease of finding a particular option, they appear
13496 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13497 are now so many options, they are first listed briefly in functional groups, as
13498 an aid to finding the name of the option you are looking for. Some options are
13499 listed in more than one group.
13501 .section "Miscellaneous" "SECID96"
13503 .row &%bi_command%& "to run for &%-bi%& command line option"
13504 .row &%disable_ipv6%& "do no IPv6 processing"
13505 .row &%keep_malformed%& "for broken files &-- should not happen"
13506 .row &%localhost_number%& "for unique message ids in clusters"
13507 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13508 .row &%message_body_visible%& "how much to show in &$message_body$&"
13509 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13510 .row &%print_topbitchars%& "top-bit characters are printing"
13511 .row &%timezone%& "force time zone"
13515 .section "Exim parameters" "SECID97"
13517 .row &%exim_group%& "override compiled-in value"
13518 .row &%exim_path%& "override compiled-in value"
13519 .row &%exim_user%& "override compiled-in value"
13520 .row &%primary_hostname%& "default from &[uname()]&"
13521 .row &%split_spool_directory%& "use multiple directories"
13522 .row &%spool_directory%& "override compiled-in value"
13527 .section "Privilege controls" "SECID98"
13529 .row &%admin_groups%& "groups that are Exim admin users"
13530 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13531 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13532 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13533 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13534 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13535 .row &%never_users%& "do not run deliveries as these"
13536 .row &%prod_requires_admin%& "forced delivery requires admin user"
13537 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13538 .row &%trusted_groups%& "groups that are trusted"
13539 .row &%trusted_users%& "users that are trusted"
13544 .section "Logging" "SECID99"
13546 .row &%event_action%& "custom logging"
13547 .row &%hosts_connection_nolog%& "exemption from connect logging"
13548 .row &%log_file_path%& "override compiled-in value"
13549 .row &%log_selector%& "set/unset optional logging"
13550 .row &%log_timezone%& "add timezone to log lines"
13551 .row &%message_logs%& "create per-message logs"
13552 .row &%preserve_message_logs%& "after message completion"
13553 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13554 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
13555 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13556 .row &%syslog_facility%& "set syslog &""facility""& field"
13557 .row &%syslog_processname%& "set syslog &""ident""& field"
13558 .row &%syslog_timestamp%& "timestamp syslog lines"
13559 .row &%write_rejectlog%& "control use of message log"
13564 .section "Frozen messages" "SECID100"
13566 .row &%auto_thaw%& "sets time for retrying frozen messages"
13567 .row &%freeze_tell%& "send message when freezing"
13568 .row &%move_frozen_messages%& "to another directory"
13569 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13574 .section "Data lookups" "SECID101"
13576 .row &%ibase_servers%& "InterBase servers"
13577 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13578 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13579 .row &%ldap_cert_file%& "client cert file for LDAP"
13580 .row &%ldap_cert_key%& "client key file for LDAP"
13581 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13582 .row &%ldap_default_servers%& "used if no server in query"
13583 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13584 .row &%ldap_start_tls%& "require TLS within LDAP"
13585 .row &%ldap_version%& "set protocol version"
13586 .row &%lookup_open_max%& "lookup files held open"
13587 .row &%mysql_servers%& "default MySQL servers"
13588 .row &%oracle_servers%& "Oracle servers"
13589 .row &%pgsql_servers%& "default PostgreSQL servers"
13590 .row &%sqlite_lock_timeout%& "as it says"
13595 .section "Message ids" "SECID102"
13597 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13598 .row &%message_id_header_text%& "ditto"
13603 .section "Embedded Perl Startup" "SECID103"
13605 .row &%perl_at_start%& "always start the interpreter"
13606 .row &%perl_startup%& "code to obey when starting Perl"
13607 .row &%perl_taintmode%& "enable taint mode in Perl"
13612 .section "Daemon" "SECID104"
13614 .row &%daemon_smtp_ports%& "default ports"
13615 .row &%daemon_startup_retries%& "number of times to retry"
13616 .row &%daemon_startup_sleep%& "time to sleep between tries"
13617 .row &%extra_local_interfaces%& "not necessarily listened on"
13618 .row &%local_interfaces%& "on which to listen, with optional ports"
13619 .row &%pid_file_path%& "override compiled-in value"
13620 .row &%queue_run_max%& "maximum simultaneous queue runners"
13625 .section "Resource control" "SECID105"
13627 .row &%check_log_inodes%& "before accepting a message"
13628 .row &%check_log_space%& "before accepting a message"
13629 .row &%check_spool_inodes%& "before accepting a message"
13630 .row &%check_spool_space%& "before accepting a message"
13631 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13632 .row &%queue_only_load%& "queue incoming if load high"
13633 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13634 .row &%queue_run_max%& "maximum simultaneous queue runners"
13635 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13636 .row &%smtp_accept_max%& "simultaneous incoming connections"
13637 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13638 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13639 .row &%smtp_accept_max_per_connection%& "messages per connection"
13640 .row &%smtp_accept_max_per_host%& "connections from one host"
13641 .row &%smtp_accept_queue%& "queue mail if more connections"
13642 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13644 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13645 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13646 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13647 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13648 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13653 .section "Policy controls" "SECID106"
13655 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13656 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13657 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13658 .row &%acl_smtp_auth%& "ACL for AUTH"
13659 .row &%acl_smtp_connect%& "ACL for connection"
13660 .row &%acl_smtp_data%& "ACL for DATA"
13661 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13662 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13663 .row &%acl_smtp_etrn%& "ACL for ETRN"
13664 .row &%acl_smtp_expn%& "ACL for EXPN"
13665 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13666 .row &%acl_smtp_mail%& "ACL for MAIL"
13667 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13668 .row &%acl_smtp_mime%& "ACL for MIME parts"
13669 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
13670 .row &%acl_smtp_predata%& "ACL for start of data"
13671 .row &%acl_smtp_quit%& "ACL for QUIT"
13672 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13673 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13674 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13675 .row &%av_scanner%& "specify virus scanner"
13676 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13678 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13679 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13680 .row &%header_maxsize%& "total size of message header"
13681 .row &%header_line_maxsize%& "individual header line limit"
13682 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13683 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13684 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13685 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13686 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13687 .row &%host_lookup%& "host name looked up for these hosts"
13688 .row &%host_lookup_order%& "order of DNS and local name lookups"
13689 .row &%hosts_proxy%& "use proxy protocol for these hosts"
13690 .row &%host_reject_connection%& "reject connection from these hosts"
13691 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13692 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13693 .row &%message_size_limit%& "for all messages"
13694 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13695 .row &%spamd_address%& "set interface to SpamAssassin"
13696 .row &%strict_acl_vars%& "object to unset ACL variables"
13701 .section "Callout cache" "SECID107"
13703 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13705 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13707 .row &%callout_negative_expire%& "timeout for negative address cache item"
13708 .row &%callout_positive_expire%& "timeout for positive address cache item"
13709 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13714 .section "TLS" "SECID108"
13716 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13717 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13718 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13719 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13720 .row &%tls_certificate%& "location of server certificate"
13721 .row &%tls_crl%& "certificate revocation list"
13722 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13723 .row &%tls_dhparam%& "DH parameters for server"
13724 .row &%tls_eccurve%& "EC curve selection for server"
13725 .row &%tls_ocsp_file%& "location of server certificate status proof"
13726 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13727 .row &%tls_privatekey%& "location of server private key"
13728 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13729 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13730 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13731 .row &%tls_verify_certificates%& "expected client certificates"
13732 .row &%tls_verify_hosts%& "insist on client certificate verify"
13737 .section "Local user handling" "SECID109"
13739 .row &%finduser_retries%& "useful in NIS environments"
13740 .row &%gecos_name%& "used when creating &'Sender:'&"
13741 .row &%gecos_pattern%& "ditto"
13742 .row &%max_username_length%& "for systems that truncate"
13743 .row &%unknown_login%& "used when no login name found"
13744 .row &%unknown_username%& "ditto"
13745 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13746 .row &%uucp_from_sender%& "ditto"
13751 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13753 .row &%header_maxsize%& "total size of message header"
13754 .row &%header_line_maxsize%& "individual header line limit"
13755 .row &%message_size_limit%& "applies to all messages"
13756 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13757 .row &%received_header_text%& "expanded to make &'Received:'&"
13758 .row &%received_headers_max%& "for mail loop detection"
13759 .row &%recipients_max%& "limit per message"
13760 .row &%recipients_max_reject%& "permanently reject excess recipients"
13766 .section "Non-SMTP incoming messages" "SECID111"
13768 .row &%receive_timeout%& "for non-SMTP messages"
13775 .section "Incoming SMTP messages" "SECID112"
13776 See also the &'Policy controls'& section above.
13779 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
13780 .row &%host_lookup%& "host name looked up for these hosts"
13781 .row &%host_lookup_order%& "order of DNS and local name lookups"
13782 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13783 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13784 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13785 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13786 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13787 .row &%smtp_accept_max%& "simultaneous incoming connections"
13788 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13789 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13790 .row &%smtp_accept_max_per_connection%& "messages per connection"
13791 .row &%smtp_accept_max_per_host%& "connections from one host"
13792 .row &%smtp_accept_queue%& "queue mail if more connections"
13793 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13795 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13796 .row &%smtp_active_hostname%& "host name to use in messages"
13797 .row &%smtp_banner%& "text for welcome banner"
13798 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13799 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13800 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13801 .row &%smtp_etrn_command%& "what to run for ETRN"
13802 .row &%smtp_etrn_serialize%& "only one at once"
13803 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13804 .row &%smtp_max_unknown_commands%& "before dropping connection"
13805 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13806 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13807 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13808 .row &%smtp_receive_timeout%& "per command or data line"
13809 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13810 .row &%smtp_return_error_details%& "give detail on rejections"
13815 .section "SMTP extensions" "SECID113"
13817 .row &%accept_8bitmime%& "advertise 8BITMIME"
13818 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13819 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
13820 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
13821 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13822 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13823 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13824 .row &%prdr_enable%& "advertise PRDR to all hosts"
13825 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
13826 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13831 .section "Processing messages" "SECID114"
13833 .row &%allow_domain_literals%& "recognize domain literal syntax"
13834 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13835 .row &%allow_utf8_domains%& "in addresses"
13836 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13838 .row &%delivery_date_remove%& "from incoming messages"
13839 .row &%envelope_to_remove%& "from incoming messages"
13840 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13841 .row &%headers_charset%& "default for translations"
13842 .row &%qualify_domain%& "default for senders"
13843 .row &%qualify_recipient%& "default for recipients"
13844 .row &%return_path_remove%& "from incoming messages"
13845 .row &%strip_excess_angle_brackets%& "in addresses"
13846 .row &%strip_trailing_dot%& "at end of addresses"
13847 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13852 .section "System filter" "SECID115"
13854 .row &%system_filter%& "locate system filter"
13855 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13857 .row &%system_filter_file_transport%& "transport for delivery to a file"
13858 .row &%system_filter_group%& "group for filter running"
13859 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13860 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13861 .row &%system_filter_user%& "user for filter running"
13866 .section "Routing and delivery" "SECID116"
13868 .row &%disable_ipv6%& "do no IPv6 processing"
13869 .row &%dns_again_means_nonexist%& "for broken domains"
13870 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13871 .row &%dns_dnssec_ok%& "parameter for resolver"
13872 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13873 .row &%dns_retrans%& "parameter for resolver"
13874 .row &%dns_retry%& "parameter for resolver"
13875 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
13876 .row &%dns_use_edns0%& "parameter for resolver"
13877 .row &%hold_domains%& "hold delivery for these domains"
13878 .row &%local_interfaces%& "for routing checks"
13879 .row &%queue_domains%& "no immediate delivery for these"
13880 .row &%queue_only%& "no immediate delivery at all"
13881 .row &%queue_only_file%& "no immediate delivery if file exists"
13882 .row &%queue_only_load%& "no immediate delivery if load is high"
13883 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13884 .row &%queue_only_override%& "allow command line to override"
13885 .row &%queue_run_in_order%& "order of arrival"
13886 .row &%queue_run_max%& "of simultaneous queue runners"
13887 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13888 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13889 .row &%remote_sort_domains%& "order of remote deliveries"
13890 .row &%retry_data_expire%& "timeout for retry data"
13891 .row &%retry_interval_max%& "safety net for retry rules"
13896 .section "Bounce and warning messages" "SECID117"
13898 .row &%bounce_message_file%& "content of bounce"
13899 .row &%bounce_message_text%& "content of bounce"
13900 .row &%bounce_return_body%& "include body if returning message"
13901 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
13902 .row &%bounce_return_message%& "include original message in bounce"
13903 .row &%bounce_return_size_limit%& "limit on returned message"
13904 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13905 .row &%dsn_from%& "set &'From:'& contents in bounces"
13906 .row &%errors_copy%& "copy bounce messages"
13907 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13908 .row &%delay_warning%& "time schedule"
13909 .row &%delay_warning_condition%& "condition for warning messages"
13910 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13911 .row &%smtp_return_error_details%& "give detail on rejections"
13912 .row &%warn_message_file%& "content of warning message"
13917 .section "Alphabetical list of main options" "SECTalomo"
13918 Those options that undergo string expansion before use are marked with
13921 .option accept_8bitmime main boolean true
13923 .cindex "8-bit characters"
13924 .cindex "log" "selectors"
13925 .cindex "log" "8BITMIME"
13926 This option causes Exim to send 8BITMIME in its response to an SMTP
13927 EHLO command, and to accept the BODY= parameter on MAIL commands.
13928 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13929 takes no steps to do anything special with messages received by this route.
13931 Historically Exim kept this option off by default, but the maintainers
13932 feel that in today's Internet, this causes more problems than it solves.
13933 It now defaults to true.
13934 A more detailed analysis of the issues is provided by Dan Bernstein:
13936 &url(http://cr.yp.to/smtp/8bitmime.html)
13939 To log received 8BITMIME status use
13941 log_selector = +8bitmime
13944 .option acl_not_smtp main string&!! unset
13945 .cindex "&ACL;" "for non-SMTP messages"
13946 .cindex "non-SMTP messages" "ACLs for"
13947 This option defines the ACL that is run when a non-SMTP message has been
13948 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
13951 .option acl_not_smtp_mime main string&!! unset
13952 This option defines the ACL that is run for individual MIME parts of non-SMTP
13953 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
13956 .option acl_not_smtp_start main string&!! unset
13957 .cindex "&ACL;" "at start of non-SMTP message"
13958 .cindex "non-SMTP messages" "ACLs for"
13959 This option defines the ACL that is run before Exim starts reading a
13960 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
13962 .option acl_smtp_auth main string&!! unset
13963 .cindex "&ACL;" "setting up for SMTP commands"
13964 .cindex "AUTH" "ACL for"
13965 This option defines the ACL that is run when an SMTP AUTH command is
13966 received. See chapter &<<CHAPACL>>& for further details.
13968 .option acl_smtp_connect main string&!! unset
13969 .cindex "&ACL;" "on SMTP connection"
13970 This option defines the ACL that is run when an SMTP connection is received.
13971 See chapter &<<CHAPACL>>& for further details.
13973 .option acl_smtp_data main string&!! unset
13974 .cindex "DATA" "ACL for"
13975 This option defines the ACL that is run after an SMTP DATA command has been
13976 processed and the message itself has been received, but before the final
13977 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13979 .option acl_smtp_data_prdr main string&!! accept
13980 .cindex "PRDR" "ACL for"
13981 .cindex "DATA" "PRDR ACL for"
13982 .cindex "&ACL;" "PRDR-related"
13983 .cindex "&ACL;" "per-user data processing"
13984 This option defines the ACL that,
13985 if the PRDR feature has been negotiated,
13986 is run for each recipient after an SMTP DATA command has been
13987 processed and the message itself has been received, but before the
13988 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13990 .option acl_smtp_dkim main string&!! unset
13991 .cindex DKIM "ACL for"
13992 This option defines the ACL that is run for each DKIM signature
13993 of a received message.
13994 See chapter &<<CHAPdkim>>& for further details.
13996 .option acl_smtp_etrn main string&!! unset
13997 .cindex "ETRN" "ACL for"
13998 This option defines the ACL that is run when an SMTP ETRN command is
13999 received. See chapter &<<CHAPACL>>& for further details.
14001 .option acl_smtp_expn main string&!! unset
14002 .cindex "EXPN" "ACL for"
14003 This option defines the ACL that is run when an SMTP EXPN command is
14004 received. See chapter &<<CHAPACL>>& for further details.
14006 .option acl_smtp_helo main string&!! unset
14007 .cindex "EHLO" "ACL for"
14008 .cindex "HELO" "ACL for"
14009 This option defines the ACL that is run when an SMTP EHLO or HELO
14010 command is received. See chapter &<<CHAPACL>>& for further details.
14013 .option acl_smtp_mail main string&!! unset
14014 .cindex "MAIL" "ACL for"
14015 This option defines the ACL that is run when an SMTP MAIL command is
14016 received. See chapter &<<CHAPACL>>& for further details.
14018 .option acl_smtp_mailauth main string&!! unset
14019 .cindex "AUTH" "on MAIL command"
14020 This option defines the ACL that is run when there is an AUTH parameter on
14021 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
14022 &<<CHAPSMTPAUTH>>& for details of authentication.
14024 .option acl_smtp_mime main string&!! unset
14025 .cindex "MIME content scanning" "ACL for"
14026 This option is available when Exim is built with the content-scanning
14027 extension. It defines the ACL that is run for each MIME part in a message. See
14028 section &<<SECTscanmimepart>>& for details.
14030 .option acl_smtp_notquit main string&!! unset
14031 .cindex "not-QUIT, ACL for"
14032 This option defines the ACL that is run when an SMTP session
14033 ends without a QUIT command being received.
14034 See chapter &<<CHAPACL>>& for further details.
14036 .option acl_smtp_predata main string&!! unset
14037 This option defines the ACL that is run when an SMTP DATA command is
14038 received, before the message itself is received. See chapter &<<CHAPACL>>& for
14041 .option acl_smtp_quit main string&!! unset
14042 .cindex "QUIT, ACL for"
14043 This option defines the ACL that is run when an SMTP QUIT command is
14044 received. See chapter &<<CHAPACL>>& for further details.
14046 .option acl_smtp_rcpt main string&!! unset
14047 .cindex "RCPT" "ACL for"
14048 This option defines the ACL that is run when an SMTP RCPT command is
14049 received. See chapter &<<CHAPACL>>& for further details.
14051 .option acl_smtp_starttls main string&!! unset
14052 .cindex "STARTTLS, ACL for"
14053 This option defines the ACL that is run when an SMTP STARTTLS command is
14054 received. See chapter &<<CHAPACL>>& for further details.
14056 .option acl_smtp_vrfy main string&!! unset
14057 .cindex "VRFY" "ACL for"
14058 This option defines the ACL that is run when an SMTP VRFY command is
14059 received. See chapter &<<CHAPACL>>& for further details.
14061 .option add_environment main "string list" empty
14062 .cindex "environment" "set values"
14063 This option allows to set individual environment variables that the
14064 currently linked libraries and programs in child processes use.
14065 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
14067 .option admin_groups main "string list&!!" unset
14068 .cindex "admin user"
14069 This option is expanded just once, at the start of Exim's processing. If the
14070 current group or any of the supplementary groups of an Exim caller is in this
14071 colon-separated list, the caller has admin privileges. If all your system
14072 programmers are in a specific group, for example, you can give them all Exim
14073 admin privileges by putting that group in &%admin_groups%&. However, this does
14074 not permit them to read Exim's spool files (whose group owner is the Exim gid).
14075 To permit this, you have to add individuals to the Exim group.
14077 .option allow_domain_literals main boolean false
14078 .cindex "domain literal"
14079 If this option is set, the RFC 2822 domain literal format is permitted in
14080 email addresses. The option is not set by default, because the domain literal
14081 format is not normally required these days, and few people know about it. It
14082 has, however, been exploited by mail abusers.
14084 Unfortunately, it seems that some DNS black list maintainers are using this
14085 format to report black listing to postmasters. If you want to accept messages
14086 addressed to your hosts by IP address, you need to set
14087 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
14088 domains (defined in the named domain list &%local_domains%& in the default
14089 configuration). This &"magic string"& matches the domain literal form of all
14090 the local host's IP addresses.
14093 .option allow_mx_to_ip main boolean false
14094 .cindex "MX record" "pointing to IP address"
14095 It appears that more and more DNS zone administrators are breaking the rules
14096 and putting domain names that look like IP addresses on the right hand side of
14097 MX records. Exim follows the rules and rejects this, giving an error message
14098 that explains the misconfiguration. However, some other MTAs support this
14099 practice, so to avoid &"Why can't Exim do this?"& complaints,
14100 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
14101 recommended, except when you have no other choice.
14103 .option allow_utf8_domains main boolean false
14104 .cindex "domain" "UTF-8 characters in"
14105 .cindex "UTF-8" "in domain name"
14106 Lots of discussion is going on about internationalized domain names. One
14107 camp is strongly in favour of just using UTF-8 characters, and it seems
14108 that at least two other MTAs permit this. This option allows Exim users to
14109 experiment if they wish.
14111 If it is set true, Exim's domain parsing function allows valid
14112 UTF-8 multicharacters to appear in domain name components, in addition to
14113 letters, digits, and hyphens. However, just setting this option is not
14114 enough; if you want to look up these domain names in the DNS, you must also
14115 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
14116 suitable setting is:
14118 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
14119 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
14121 Alternatively, you can just disable this feature by setting
14123 dns_check_names_pattern =
14125 That is, set the option to an empty string so that no check is done.
14128 .option auth_advertise_hosts main "host list&!!" *
14129 .cindex "authentication" "advertising"
14130 .cindex "AUTH" "advertising"
14131 If any server authentication mechanisms are configured, Exim advertises them in
14132 response to an EHLO command only if the calling host matches this list.
14133 Otherwise, Exim does not advertise AUTH.
14134 Exim does not accept AUTH commands from clients to which it has not
14135 advertised the availability of AUTH. The advertising of individual
14136 authentication mechanisms can be controlled by the use of the
14137 &%server_advertise_condition%& generic authenticator option on the individual
14138 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
14140 Certain mail clients (for example, Netscape) require the user to provide a name
14141 and password for authentication if AUTH is advertised, even though it may
14142 not be needed (the host may accept messages from hosts on its local LAN without
14143 authentication, for example). The &%auth_advertise_hosts%& option can be used
14144 to make these clients more friendly by excluding them from the set of hosts to
14145 which Exim advertises AUTH.
14147 .cindex "AUTH" "advertising when encrypted"
14148 If you want to advertise the availability of AUTH only when the connection
14149 is encrypted using TLS, you can make use of the fact that the value of this
14150 option is expanded, with a setting like this:
14152 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
14154 .vindex "&$tls_in_cipher$&"
14155 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
14156 the expansion is empty, thus matching no hosts. Otherwise, the result of the
14157 expansion is *, which matches all hosts.
14160 .option auto_thaw main time 0s
14161 .cindex "thawing messages"
14162 .cindex "unfreezing messages"
14163 If this option is set to a time greater than zero, a queue runner will try a
14164 new delivery attempt on any frozen message, other than a bounce message, if
14165 this much time has passed since it was frozen. This may result in the message
14166 being re-frozen if nothing has changed since the last attempt. It is a way of
14167 saying &"keep on trying, even though there are big problems"&.
14169 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
14170 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
14171 thought to be very useful any more, and its use should probably be avoided.
14174 .option av_scanner main string "see below"
14175 This option is available if Exim is built with the content-scanning extension.
14176 It specifies which anti-virus scanner to use. The default value is:
14178 sophie:/var/run/sophie
14180 If the value of &%av_scanner%& starts with a dollar character, it is expanded
14181 before use. See section &<<SECTscanvirus>>& for further details.
14184 .option bi_command main string unset
14186 This option supplies the name of a command that is run when Exim is called with
14187 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
14188 just the command name, it is not a complete command line. If an argument is
14189 required, it must come from the &%-oA%& command line option.
14192 .option bounce_message_file main string unset
14193 .cindex "bounce message" "customizing"
14194 .cindex "customizing" "bounce message"
14195 This option defines a template file containing paragraphs of text to be used
14196 for constructing bounce messages. Details of the file's contents are given in
14197 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
14200 .option bounce_message_text main string unset
14201 When this option is set, its contents are included in the default bounce
14202 message immediately after &"This message was created automatically by mail
14203 delivery software."& It is not used if &%bounce_message_file%& is set.
14205 .option bounce_return_body main boolean true
14206 .cindex "bounce message" "including body"
14207 This option controls whether the body of an incoming message is included in a
14208 bounce message when &%bounce_return_message%& is true. The default setting
14209 causes the entire message, both header and body, to be returned (subject to the
14210 value of &%bounce_return_size_limit%&). If this option is false, only the
14211 message header is included. In the case of a non-SMTP message containing an
14212 error that is detected during reception, only those header lines preceding the
14213 point at which the error was detected are returned.
14214 .cindex "bounce message" "including original"
14216 .option bounce_return_linesize_limit main integer 998
14217 .cindex "size" "of bounce lines, limit"
14218 .cindex "bounce message" "line length limit"
14219 .cindex "limit" "bounce message line length"
14220 This option sets a limit in bytes on the line length of messages
14221 that are returned to senders due to delivery problems,
14222 when &%bounce_return_message%& is true.
14223 The default value corresponds to RFC limits.
14224 If the message being returned has lines longer than this value it is
14225 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
14227 The option also applies to bounces returned when an error is detected
14228 during reception of a message.
14229 In this case lines from the original are truncated.
14231 The option does not apply to messages generated by an &(autoreply)& transport.
14234 .option bounce_return_message main boolean true
14235 If this option is set false, none of the original message is included in
14236 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
14237 &%bounce_return_body%&.
14240 .option bounce_return_size_limit main integer 100K
14241 .cindex "size" "of bounce, limit"
14242 .cindex "bounce message" "size limit"
14243 .cindex "limit" "bounce message size"
14244 This option sets a limit in bytes on the size of messages that are returned to
14245 senders as part of bounce messages when &%bounce_return_message%& is true. The
14246 limit should be less than the value of the global &%message_size_limit%& and of
14247 any &%message_size_limit%& settings on transports, to allow for the bounce text
14248 that Exim generates. If this option is set to zero there is no limit.
14250 When the body of any message that is to be included in a bounce message is
14251 greater than the limit, it is truncated, and a comment pointing this out is
14252 added at the top. The actual cutoff may be greater than the value given, owing
14253 to the use of buffering for transferring the message in chunks (typically 8K in
14254 size). The idea is to save bandwidth on those undeliverable 15-megabyte
14257 .option bounce_sender_authentication main string unset
14258 .cindex "bounce message" "sender authentication"
14259 .cindex "authentication" "bounce message"
14260 .cindex "AUTH" "on bounce message"
14261 This option provides an authenticated sender address that is sent with any
14262 bounce messages generated by Exim that are sent over an authenticated SMTP
14263 connection. A typical setting might be:
14265 bounce_sender_authentication = mailer-daemon@my.domain.example
14267 which would cause bounce messages to be sent using the SMTP command:
14269 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14271 The value of &%bounce_sender_authentication%& must always be a complete email
14274 .option callout_domain_negative_expire main time 3h
14275 .cindex "caching" "callout timeouts"
14276 .cindex "callout" "caching timeouts"
14277 This option specifies the expiry time for negative callout cache data for a
14278 domain. See section &<<SECTcallver>>& for details of callout verification, and
14279 section &<<SECTcallvercache>>& for details of the caching.
14282 .option callout_domain_positive_expire main time 7d
14283 This option specifies the expiry time for positive callout cache data for a
14284 domain. See section &<<SECTcallver>>& for details of callout verification, and
14285 section &<<SECTcallvercache>>& for details of the caching.
14288 .option callout_negative_expire main time 2h
14289 This option specifies the expiry time for negative callout cache data for an
14290 address. See section &<<SECTcallver>>& for details of callout verification, and
14291 section &<<SECTcallvercache>>& for details of the caching.
14294 .option callout_positive_expire main time 24h
14295 This option specifies the expiry time for positive callout cache data for an
14296 address. See section &<<SECTcallver>>& for details of callout verification, and
14297 section &<<SECTcallvercache>>& for details of the caching.
14300 .option callout_random_local_part main string&!! "see below"
14301 This option defines the &"random"& local part that can be used as part of
14302 callout verification. The default value is
14304 $primary_hostname-$tod_epoch-testing
14306 See section &<<CALLaddparcall>>& for details of how this value is used.
14309 .option check_log_inodes main integer 0
14310 See &%check_spool_space%& below.
14313 .option check_log_space main integer 0
14314 See &%check_spool_space%& below.
14316 .oindex "&%check_rfc2047_length%&"
14317 .cindex "RFC 2047" "disabling length check"
14318 .option check_rfc2047_length main boolean true
14319 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14320 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14321 word; strings to be encoded that exceed this length are supposed to use
14322 multiple encoded words. By default, Exim does not recognize encoded words that
14323 exceed the maximum length. However, it seems that some software, in violation
14324 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14325 set false, Exim recognizes encoded words of any length.
14328 .option check_spool_inodes main integer 0
14329 See &%check_spool_space%& below.
14332 .option check_spool_space main integer 0
14333 .cindex "checking disk space"
14334 .cindex "disk space, checking"
14335 .cindex "spool directory" "checking space"
14336 The four &%check_...%& options allow for checking of disk resources before a
14337 message is accepted.
14339 .vindex "&$log_inodes$&"
14340 .vindex "&$log_space$&"
14341 .vindex "&$spool_inodes$&"
14342 .vindex "&$spool_space$&"
14343 When any of these options are set, they apply to all incoming messages. If you
14344 want to apply different checks to different kinds of message, you can do so by
14345 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14346 &$spool_space$& in an ACL with appropriate additional conditions.
14349 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14350 either value is greater than zero, for example:
14352 check_spool_space = 10M
14353 check_spool_inodes = 100
14355 The spool partition is the one that contains the directory defined by
14356 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14359 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14360 files are written if either is greater than zero. These should be set only if
14361 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14363 If there is less space or fewer inodes than requested, Exim refuses to accept
14364 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14365 error response to the MAIL command. If ESMTP is in use and there was a
14366 SIZE parameter on the MAIL command, its value is added to the
14367 &%check_spool_space%& value, and the check is performed even if
14368 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14370 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14371 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
14373 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14374 failure a message is written to stderr and Exim exits with a non-zero code, as
14375 it obviously cannot send an error message of any kind.
14378 .option chunking_advertise_hosts main "host list&!!" *
14379 .cindex CHUNKING advertisement
14380 .cindex "RFC 3030" "CHUNKING"
14381 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
14383 Hosts may use the BDAT command as an alternate to DATA.
14386 .option daemon_smtp_ports main string &`smtp`&
14387 .cindex "port" "for daemon"
14388 .cindex "TCP/IP" "setting listening ports"
14389 This option specifies one or more default SMTP ports on which the Exim daemon
14390 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14391 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14393 .option daemon_startup_retries main integer 9
14394 .cindex "daemon startup, retrying"
14395 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14396 the daemon at startup when it cannot immediately bind a listening socket
14397 (typically because the socket is already in use): &%daemon_startup_retries%&
14398 defines the number of retries after the first failure, and
14399 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14401 .option daemon_startup_sleep main time 30s
14402 See &%daemon_startup_retries%&.
14404 .option delay_warning main "time list" 24h
14405 .cindex "warning of delay"
14406 .cindex "delay warning, specifying"
14407 When a message is delayed, Exim sends a warning message to the sender at
14408 intervals specified by this option. The data is a colon-separated list of times
14409 after which to send warning messages. If the value of the option is an empty
14410 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14411 message has been on the queue for longer than the last time, the last interval
14412 between the times is used to compute subsequent warning times. For example,
14415 delay_warning = 4h:8h:24h
14417 the first message is sent after 4 hours, the second after 8 hours, and
14418 the third one after 24 hours. After that, messages are sent every 16 hours,
14419 because that is the interval between the last two times on the list. If you set
14420 just one time, it specifies the repeat interval. For example, with:
14424 messages are repeated every six hours. To stop warnings after a given time, set
14425 a very large time at the end of the list. For example:
14427 delay_warning = 2h:12h:99d
14429 Note that the option is only evaluated at the time a delivery attempt fails,
14430 which depends on retry and queue-runner configuration.
14431 Typically retries will be configured more frequently than warning messages.
14433 .option delay_warning_condition main string&!! "see below"
14434 .vindex "&$domain$&"
14435 The string is expanded at the time a warning message might be sent. If all the
14436 deferred addresses have the same domain, it is set in &$domain$& during the
14437 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14438 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14439 &"false"& (the comparison being done caselessly) then the warning message is
14440 not sent. The default is:
14442 delay_warning_condition = ${if or {\
14443 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14444 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14445 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14448 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14449 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14450 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14451 &"auto-replied"& in an &'Auto-Submitted:'& header.
14453 .option deliver_drop_privilege main boolean false
14454 .cindex "unprivileged delivery"
14455 .cindex "delivery" "unprivileged"
14456 If this option is set true, Exim drops its root privilege at the start of a
14457 delivery process, and runs as the Exim user throughout. This severely restricts
14458 the kinds of local delivery that are possible, but is viable in certain types
14459 of configuration. There is a discussion about the use of root privilege in
14460 chapter &<<CHAPsecurity>>&.
14462 .option deliver_queue_load_max main fixed-point unset
14463 .cindex "load average"
14464 .cindex "queue runner" "abandoning"
14465 When this option is set, a queue run is abandoned if the system load average
14466 becomes greater than the value of the option. The option has no effect on
14467 ancient operating systems on which Exim cannot determine the load average.
14468 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14471 .option delivery_date_remove main boolean true
14472 .cindex "&'Delivery-date:'& header line"
14473 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14474 message when it is delivered, in exactly the same way as &'Return-path:'& is
14475 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14476 should not be present in incoming messages, and this option causes them to be
14477 removed at the time the message is received, to avoid any problems that might
14478 occur when a delivered message is subsequently sent on to some other recipient.
14480 .option disable_fsync main boolean false
14481 .cindex "&[fsync()]&, disabling"
14482 This option is available only if Exim was built with the compile-time option
14483 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14484 a runtime configuration generates an &"unknown option"& error. You should not
14485 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14486 really, really, really understand what you are doing. &'No pre-compiled
14487 distributions of Exim should ever make this option available.'&
14489 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14490 updated files' data to be written to disc before continuing. Unexpected events
14491 such as crashes and power outages may cause data to be lost or scrambled.
14492 Here be Dragons. &*Beware.*&
14495 .option disable_ipv6 main boolean false
14496 .cindex "IPv6" "disabling"
14497 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14498 activities take place. AAAA records are never looked up, and any IPv6 addresses
14499 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14500 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14501 to handle IPv6 literal addresses.
14504 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14505 .cindex DKIM "controlling calls to the ACL"
14506 This option gives a list of DKIM domains for which the DKIM ACL is run.
14507 It is expanded after the message is received; by default it runs
14508 the ACL once for each signature in the message.
14509 See chapter &<<CHAPdkim>>&.
14512 .option dns_again_means_nonexist main "domain list&!!" unset
14513 .cindex "DNS" "&""try again""& response; overriding"
14514 DNS lookups give a &"try again"& response for the DNS errors
14515 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14516 keep trying to deliver a message, or to give repeated temporary errors to
14517 incoming mail. Sometimes the effect is caused by a badly set up name server and
14518 may persist for a long time. If a domain which exhibits this problem matches
14519 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14520 This option should be used with care. You can make it apply to reverse lookups
14521 by a setting such as this:
14523 dns_again_means_nonexist = *.in-addr.arpa
14525 This option applies to all DNS lookups that Exim does. It also applies when the
14526 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14527 since these are most likely to be caused by DNS lookup problems. The
14528 &(dnslookup)& router has some options of its own for controlling what happens
14529 when lookups for MX or SRV records give temporary errors. These more specific
14530 options are applied after this global option.
14532 .option dns_check_names_pattern main string "see below"
14533 .cindex "DNS" "pre-check of name syntax"
14534 When this option is set to a non-empty string, it causes Exim to check domain
14535 names for characters that are not allowed in host names before handing them to
14536 the DNS resolver, because some resolvers give temporary errors for names that
14537 contain unusual characters. If a domain name contains any unwanted characters,
14538 a &"not found"& result is forced, and the resolver is not called. The check is
14539 done by matching the domain name against a regular expression, which is the
14540 value of this option. The default pattern is
14542 dns_check_names_pattern = \
14543 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
14545 which permits only letters, digits, slashes, and hyphens in components, but
14546 they must start and end with a letter or digit. Slashes are not, in fact,
14547 permitted in host names, but they are found in certain NS records (which can be
14548 accessed in Exim by using a &%dnsdb%& lookup). If you set
14549 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
14552 .option dns_csa_search_limit main integer 5
14553 This option controls the depth of parental searching for CSA SRV records in the
14554 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
14556 .option dns_csa_use_reverse main boolean true
14557 This option controls whether or not an IP address, given as a CSA domain, is
14558 reversed and looked up in the reverse DNS, as described in more detail in
14559 section &<<SECTverifyCSA>>&.
14562 .option dns_dnssec_ok main integer -1
14563 .cindex "DNS" "resolver options"
14564 .cindex "DNS" "DNSSEC"
14565 If this option is set to a non-negative number then Exim will initialise the
14566 DNS resolver library to either use or not use DNSSEC, overriding the system
14567 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14569 If the resolver library does not support DNSSEC then this option has no effect.
14572 .option dns_ipv4_lookup main "domain list&!!" unset
14573 .cindex "IPv6" "DNS lookup for AAAA records"
14574 .cindex "DNS" "IPv6 lookup for AAAA records"
14575 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14576 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14577 (A records) when trying to find IP addresses for hosts, unless the host's
14578 domain matches this list.
14580 This is a fudge to help with name servers that give big delays or otherwise do
14581 not work for the AAAA record type. In due course, when the world's name
14582 servers have all been upgraded, there should be no need for this option.
14585 .option dns_retrans main time 0s
14586 .cindex "DNS" "resolver options"
14587 .cindex timeout "dns lookup"
14588 .cindex "DNS" timeout
14589 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14590 retransmission and retry parameters for DNS lookups. Values of zero (the
14591 defaults) leave the system default settings unchanged. The first value is the
14592 time between retries, and the second is the number of retries. It isn't
14593 totally clear exactly how these settings affect the total time a DNS lookup may
14594 take. I haven't found any documentation about timeouts on DNS lookups; these
14595 parameter values are available in the external resolver interface structure,
14596 but nowhere does it seem to describe how they are used or what you might want
14598 See also the &%slow_lookup_log%& option.
14601 .option dns_retry main integer 0
14602 See &%dns_retrans%& above.
14605 .option dns_trust_aa main "domain list&!!" unset
14606 .cindex "DNS" "resolver options"
14607 .cindex "DNS" "DNSSEC"
14608 If this option is set then lookup results marked with the AA bit
14609 (Authoritative Answer) are trusted the same way as if they were
14610 DNSSEC-verified. The authority section's name of the answer must
14611 match with this expanded domain list.
14613 Use this option only if you talk directly to a resolver that is
14614 authoritative for some zones and does not set the AD (Authentic Data)
14615 bit in the answer. Some DNS servers may have an configuration option to
14616 mark the answers from their own zones as verified (they set the AD bit).
14617 Others do not have this option. It is considered as poor practice using
14618 a resolver that is an authoritative server for some zones.
14620 Use this option only if you really have to (e.g. if you want
14621 to use DANE for remote delivery to a server that is listed in the DNS
14622 zones that your resolver is authoritative for).
14624 If the DNS answer packet has the AA bit set and contains resource record
14625 in the answer section, the name of the first NS record appearing in the
14626 authority section is compared against the list. If the answer packet is
14627 authoritative but the answer section is empty, the name of the first SOA
14628 record in the authoritative section is used instead.
14630 .cindex "DNS" "resolver options"
14631 .option dns_use_edns0 main integer -1
14632 .cindex "DNS" "resolver options"
14633 .cindex "DNS" "EDNS0"
14634 If this option is set to a non-negative number then Exim will initialise the
14635 DNS resolver library to either use or not use EDNS0 extensions, overriding
14636 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14639 If the resolver library does not support EDNS0 then this option has no effect.
14642 .option drop_cr main boolean false
14643 This is an obsolete option that is now a no-op. It used to affect the way Exim
14644 handled CR and LF characters in incoming messages. What happens now is
14645 described in section &<<SECTlineendings>>&.
14647 .option dsn_advertise_hosts main "host list&!!" unset
14648 .cindex "bounce messages" "success"
14649 .cindex "DSN" "success"
14650 .cindex "Delivery Status Notification" "success"
14651 DSN extensions (RFC3461) will be advertised in the EHLO message to,
14652 and accepted from, these hosts.
14653 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
14654 and RET and ORCPT options on MAIL FROM commands.
14655 A NOTIFY=SUCCESS option requests success-DSN messages.
14656 A NOTIFY= option with no argument requests that no delay or failure DSNs
14659 .option dsn_from main "string&!!" "see below"
14660 .cindex "&'From:'& header line" "in bounces"
14661 .cindex "bounce messages" "&'From:'& line, specifying"
14662 This option can be used to vary the contents of &'From:'& header lines in
14663 bounces and other automatically generated messages (&"Delivery Status
14664 Notifications"& &-- hence the name of the option). The default setting is:
14666 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14668 The value is expanded every time it is needed. If the expansion fails, a
14669 panic is logged, and the default value is used.
14671 .option envelope_to_remove main boolean true
14672 .cindex "&'Envelope-to:'& header line"
14673 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14674 message when it is delivered, in exactly the same way as &'Return-path:'& is
14675 handled. &'Envelope-to:'& records the original recipient address from the
14676 message's envelope that caused the delivery to happen. Such headers should not
14677 be present in incoming messages, and this option causes them to be removed at
14678 the time the message is received, to avoid any problems that might occur when a
14679 delivered message is subsequently sent on to some other recipient.
14682 .option errors_copy main "string list&!!" unset
14683 .cindex "bounce message" "copy to other address"
14684 .cindex "copy of bounce message"
14685 Setting this option causes Exim to send bcc copies of bounce messages that it
14686 generates to other addresses. &*Note*&: This does not apply to bounce messages
14687 coming from elsewhere. The value of the option is a colon-separated list of
14688 items. Each item consists of a pattern, terminated by white space, followed by
14689 a comma-separated list of email addresses. If a pattern contains spaces, it
14690 must be enclosed in double quotes.
14692 Each pattern is processed in the same way as a single item in an address list
14693 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14694 the bounce message, the message is copied to the addresses on the list. The
14695 items are scanned in order, and once a matching one is found, no further items
14696 are examined. For example:
14698 errors_copy = spqr@mydomain postmaster@mydomain.example :\
14699 rqps@mydomain hostmaster@mydomain.example,\
14700 postmaster@mydomain.example
14702 .vindex "&$domain$&"
14703 .vindex "&$local_part$&"
14704 The address list is expanded before use. The expansion variables &$local_part$&
14705 and &$domain$& are set from the original recipient of the error message, and if
14706 there was any wildcard matching in the pattern, the expansion
14707 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
14708 variables &$0$&, &$1$&, etc. are set in the normal way.
14711 .option errors_reply_to main string unset
14712 .cindex "bounce message" "&'Reply-to:'& in"
14713 By default, Exim's bounce and delivery warning messages contain the header line
14715 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
14717 .oindex &%quota_warn_message%&
14718 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
14719 A warning message that is generated by the &%quota_warn_message%& option in an
14720 &(appendfile)& transport may contain its own &'From:'& header line that
14721 overrides the default.
14723 Experience shows that people reply to bounce messages. If the
14724 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
14725 and warning messages. For example:
14727 errors_reply_to = postmaster@my.domain.example
14729 The value of the option is not expanded. It must specify a valid RFC 2822
14730 address. However, if a warning message that is generated by the
14731 &%quota_warn_message%& option in an &(appendfile)& transport contain its
14732 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
14736 .option event_action main string&!! unset
14738 This option declares a string to be expanded for Exim's events mechanism.
14739 For details see &<<CHAPevents>>&.
14742 .option exim_group main string "compile-time configured"
14743 .cindex "gid (group id)" "Exim's own"
14744 .cindex "Exim group"
14745 This option changes the gid under which Exim runs when it gives up root
14746 privilege. The default value is compiled into the binary. The value of this
14747 option is used only when &%exim_user%& is also set. Unless it consists entirely
14748 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14749 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
14753 .option exim_path main string "see below"
14754 .cindex "Exim binary, path name"
14755 This option specifies the path name of the Exim binary, which is used when Exim
14756 needs to re-exec itself. The default is set up to point to the file &'exim'& in
14757 the directory configured at compile time by the BIN_DIRECTORY setting. It
14758 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
14760 &*Warning*&: Do not use a macro to define the value of this option, because
14761 you will break those Exim utilities that scan the configuration file to find
14762 where the binary is. (They then use the &%-bP%& option to extract option
14763 settings such as the value of &%spool_directory%&.)
14766 .option exim_user main string "compile-time configured"
14767 .cindex "uid (user id)" "Exim's own"
14768 .cindex "Exim user"
14769 This option changes the uid under which Exim runs when it gives up root
14770 privilege. The default value is compiled into the binary. Ownership of the run
14771 time configuration file and the use of the &%-C%& and &%-D%& command line
14772 options is checked against the values in the binary, not what is set here.
14774 Unless it consists entirely of digits, the string is looked up using
14775 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
14776 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
14777 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
14780 .option extra_local_interfaces main "string list" unset
14781 This option defines network interfaces that are to be considered local when
14782 routing, but which are not used for listening by the daemon. See section
14783 &<<SECTreclocipadd>>& for details.
14786 . Allow this long option name to split; give it unsplit as a fifth argument
14787 . for the automatic .oindex that is generated by .option.
14789 .option "extract_addresses_remove_arguments" main boolean true &&&
14790 extract_addresses_remove_arguments
14792 .cindex "command line" "addresses with &%-t%&"
14793 .cindex "Sendmail compatibility" "&%-t%& option"
14794 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14795 are present on the command line when the &%-t%& option is used to build an
14796 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14797 line addresses are removed from the recipients list. This is also how Smail
14798 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14799 command line addresses are added to those obtained from the header lines. When
14800 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14801 argument headers. If it is set false, Exim adds rather than removes argument
14805 .option finduser_retries main integer 0
14806 .cindex "NIS, retrying user lookups"
14807 On systems running NIS or other schemes in which user and group information is
14808 distributed from a remote system, there can be times when &[getpwnam()]& and
14809 related functions fail, even when given valid data, because things time out.
14810 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14811 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14812 many extra times to find a user or a group, waiting for one second between
14815 .cindex "&_/etc/passwd_&" "multiple reading of"
14816 You should not set this option greater than zero if your user information is in
14817 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14818 search the file multiple times for non-existent users, and also cause delay.
14822 .option freeze_tell main "string list, comma separated" unset
14823 .cindex "freezing messages" "sending a message when freezing"
14824 On encountering certain errors, or when configured to do so in a system filter,
14825 ACL, or special router, Exim freezes a message. This means that no further
14826 delivery attempts take place until an administrator thaws the message, or the
14827 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14828 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14829 warning message whenever it freezes something, unless the message it is
14830 freezing is a locally-generated bounce message. (Without this exception there
14831 is the possibility of looping.) The warning message is sent to the addresses
14832 supplied as the comma-separated value of this option. If several of the
14833 message's addresses cause freezing, only a single message is sent. If the
14834 freezing was automatic, the reason(s) for freezing can be found in the message
14835 log. If you configure freezing in a filter or ACL, you must arrange for any
14836 logging that you require.
14839 .option gecos_name main string&!! unset
14841 .cindex "&""gecos""& field, parsing"
14842 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14843 password file to hold other information in addition to users' real names. Exim
14844 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14845 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14846 of the field are used unchanged, except that, if an ampersand is encountered,
14847 it is replaced by the user's login name with the first character forced to
14848 upper case, since this is a convention that is observed on many systems.
14850 When these options are set, &%gecos_pattern%& is treated as a regular
14851 expression that is to be applied to the field (again with && replaced by the
14852 login name), and if it matches, &%gecos_name%& is expanded and used as the
14855 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14856 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14857 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14858 name terminates at the first comma, the following can be used:
14860 gecos_pattern = ([^,]*)
14864 .option gecos_pattern main string unset
14865 See &%gecos_name%& above.
14868 .option gnutls_compat_mode main boolean unset
14869 This option controls whether GnuTLS is used in compatibility mode in an Exim
14870 server. This reduces security slightly, but improves interworking with older
14871 implementations of TLS.
14874 option gnutls_allow_auto_pkcs11 main boolean unset
14875 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14876 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14879 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14884 .option headers_charset main string "see below"
14885 This option sets a default character set for translating from encoded MIME
14886 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14887 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14888 ultimate default is ISO-8859-1. For more details see the description of header
14889 insertions in section &<<SECTexpansionitems>>&.
14893 .option header_maxsize main integer "see below"
14894 .cindex "header section" "maximum size of"
14895 .cindex "limit" "size of message header section"
14896 This option controls the overall maximum size of a message's header
14897 section. The default is the value of HEADER_MAXSIZE in
14898 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14899 sections are rejected.
14902 .option header_line_maxsize main integer 0
14903 .cindex "header lines" "maximum size of"
14904 .cindex "limit" "size of one header line"
14905 This option limits the length of any individual header line in a message, after
14906 all the continuations have been joined together. Messages with individual
14907 header lines that are longer than the limit are rejected. The default value of
14908 zero means &"no limit"&.
14913 .option helo_accept_junk_hosts main "host list&!!" unset
14914 .cindex "HELO" "accepting junk data"
14915 .cindex "EHLO" "accepting junk data"
14916 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14917 mail, and gives an error response for invalid data. Unfortunately, there are
14918 some SMTP clients that send syntactic junk. They can be accommodated by setting
14919 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14920 if you want to do semantic checking.
14921 See also &%helo_allow_chars%& for a way of extending the permitted character
14925 .option helo_allow_chars main string unset
14926 .cindex "HELO" "underscores in"
14927 .cindex "EHLO" "underscores in"
14928 .cindex "underscore in EHLO/HELO"
14929 This option can be set to a string of rogue characters that are permitted in
14930 all EHLO and HELO names in addition to the standard letters, digits,
14931 hyphens, and dots. If you really must allow underscores, you can set
14933 helo_allow_chars = _
14935 Note that the value is one string, not a list.
14938 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
14939 .cindex "HELO" "forcing reverse lookup"
14940 .cindex "EHLO" "forcing reverse lookup"
14941 If the domain given by a client in a HELO or EHLO command matches this
14942 list, a reverse lookup is done in order to establish the host's true name. The
14943 default forces a lookup if the client host gives the server's name or any of
14944 its IP addresses (in brackets), something that broken clients have been seen to
14948 .option helo_try_verify_hosts main "host list&!!" unset
14949 .cindex "HELO verifying" "optional"
14950 .cindex "EHLO" "verifying, optional"
14951 By default, Exim just checks the syntax of HELO and EHLO commands (see
14952 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
14953 to do more extensive checking of the data supplied by these commands. The ACL
14954 condition &`verify = helo`& is provided to make this possible.
14955 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
14956 to force the check to occur. From release 4.53 onwards, this is no longer
14957 necessary. If the check has not been done before &`verify = helo`& is
14958 encountered, it is done at that time. Consequently, this option is obsolete.
14959 Its specification is retained here for backwards compatibility.
14961 When an EHLO or HELO command is received, if the calling host matches
14962 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
14963 EHLO command either:
14966 is an IP literal matching the calling address of the host, or
14968 .cindex "DNS" "reverse lookup"
14969 .cindex "reverse DNS lookup"
14970 matches the host name that Exim obtains by doing a reverse lookup of the
14971 calling host address, or
14973 when looked up in DNS yields the calling host address.
14976 However, the EHLO or HELO command is not rejected if any of the checks
14977 fail. Processing continues, but the result of the check is remembered, and can
14978 be detected later in an ACL by the &`verify = helo`& condition.
14980 If DNS was used for successful verification, the variable
14981 .cindex "DNS" "DNSSEC"
14982 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
14984 .option helo_verify_hosts main "host list&!!" unset
14985 .cindex "HELO verifying" "mandatory"
14986 .cindex "EHLO" "verifying, mandatory"
14987 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
14988 backwards compatibility. For hosts that match this option, Exim checks the host
14989 name given in the HELO or EHLO in the same way as for
14990 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
14991 rejected with a 550 error, and entries are written to the main and reject logs.
14992 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
14995 .option hold_domains main "domain list&!!" unset
14996 .cindex "domain" "delaying delivery"
14997 .cindex "delivery" "delaying certain domains"
14998 This option allows mail for particular domains to be held on the queue
14999 manually. The option is overridden if a message delivery is forced with the
15000 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
15001 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
15002 item in &%hold_domains%&, no routing or delivery for that address is done, and
15003 it is deferred every time the message is looked at.
15005 This option is intended as a temporary operational measure for delaying the
15006 delivery of mail while some problem is being sorted out, or some new
15007 configuration tested. If you just want to delay the processing of some
15008 domains until a queue run occurs, you should use &%queue_domains%& or
15009 &%queue_smtp_domains%&, not &%hold_domains%&.
15011 A setting of &%hold_domains%& does not override Exim's code for removing
15012 messages from the queue if they have been there longer than the longest retry
15013 time in any retry rule. If you want to hold messages for longer than the normal
15014 retry times, insert a dummy retry rule with a long retry time.
15017 .option host_lookup main "host list&!!" unset
15018 .cindex "host name" "lookup, forcing"
15019 Exim does not look up the name of a calling host from its IP address unless it
15020 is required to compare against some host list, or the host matches
15021 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
15022 option (which normally contains IP addresses rather than host names). The
15023 default configuration file contains
15027 which causes a lookup to happen for all hosts. If the expense of these lookups
15028 is felt to be too great, the setting can be changed or removed.
15030 After a successful reverse lookup, Exim does a forward lookup on the name it
15031 has obtained, to verify that it yields the IP address that it started with. If
15032 this check fails, Exim behaves as if the name lookup failed.
15034 .vindex "&$host_lookup_failed$&"
15035 .vindex "&$sender_host_name$&"
15036 After any kind of failure, the host name (in &$sender_host_name$&) remains
15037 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
15038 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
15039 &`verify = reverse_host_lookup`& in ACLs.
15042 .option host_lookup_order main "string list" &`bydns:byaddr`&
15043 This option specifies the order of different lookup methods when Exim is trying
15044 to find a host name from an IP address. The default is to do a DNS lookup
15045 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
15046 if that fails. You can change the order of these lookups, or omit one entirely,
15049 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
15050 multiple PTR records in the DNS and the IP address is not listed in
15051 &_/etc/hosts_&. Different operating systems give different results in this
15052 case. That is why the default tries a DNS lookup first.
15056 .option host_reject_connection main "host list&!!" unset
15057 .cindex "host" "rejecting connections from"
15058 If this option is set, incoming SMTP calls from the hosts listed are rejected
15059 as soon as the connection is made.
15060 This option is obsolete, and retained only for backward compatibility, because
15061 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
15062 connections immediately.
15064 The ability to give an immediate rejection (either by this option or using an
15065 ACL) is provided for use in unusual cases. Many hosts will just try again,
15066 sometimes without much delay. Normally, it is better to use an ACL to reject
15067 incoming messages at a later stage, such as after RCPT commands. See
15068 chapter &<<CHAPACL>>&.
15071 .option hosts_connection_nolog main "host list&!!" unset
15072 .cindex "host" "not logging connections from"
15073 This option defines a list of hosts for which connection logging does not
15074 happen, even though the &%smtp_connection%& log selector is set. For example,
15075 you might want not to log SMTP connections from local processes, or from
15076 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
15077 the daemon; you should therefore strive to restrict its value to a short inline
15078 list of IP addresses and networks. To disable logging SMTP connections from
15079 local processes, you must create a host list with an empty item. For example:
15081 hosts_connection_nolog = :
15083 If the &%smtp_connection%& log selector is not set, this option has no effect.
15087 .option hosts_proxy main "host list&!!" unset
15088 .cindex proxy "proxy protocol"
15089 This option enables use of Proxy Protocol proxies for incoming
15090 connections. For details see &<<SECTproxyInbound>>&.
15093 .option hosts_treat_as_local main "domain list&!!" unset
15094 .cindex "local host" "domains treated as"
15095 .cindex "host" "treated as local"
15096 If this option is set, any host names that match the domain list are treated as
15097 if they were the local host when Exim is scanning host lists obtained from MX
15099 or other sources. Note that the value of this option is a domain list, not a
15100 host list, because it is always used to check host names, not IP addresses.
15102 This option also applies when Exim is matching the special items
15103 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
15104 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
15105 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
15106 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
15107 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
15108 interfaces and recognizing the local host.
15111 .option ibase_servers main "string list" unset
15112 .cindex "InterBase" "server list"
15113 This option provides a list of InterBase servers and associated connection data,
15114 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
15115 The option is available only if Exim has been built with InterBase support.
15119 .option ignore_bounce_errors_after main time 10w
15120 .cindex "bounce message" "discarding"
15121 .cindex "discarding bounce message"
15122 This option affects the processing of bounce messages that cannot be delivered,
15123 that is, those that suffer a permanent delivery failure. (Bounce messages that
15124 suffer temporary delivery failures are of course retried in the usual way.)
15126 After a permanent delivery failure, bounce messages are frozen,
15127 because there is no sender to whom they can be returned. When a frozen bounce
15128 message has been on the queue for more than the given time, it is unfrozen at
15129 the next queue run, and a further delivery is attempted. If delivery fails
15130 again, the bounce message is discarded. This makes it possible to keep failed
15131 bounce messages around for a shorter time than the normal maximum retry time
15132 for frozen messages. For example,
15134 ignore_bounce_errors_after = 12h
15136 retries failed bounce message deliveries after 12 hours, discarding any further
15137 failures. If the value of this option is set to a zero time period, bounce
15138 failures are discarded immediately. Setting a very long time (as in the default
15139 value) has the effect of disabling this option. For ways of automatically
15140 dealing with other kinds of frozen message, see &%auto_thaw%& and
15141 &%timeout_frozen_after%&.
15144 .option ignore_fromline_hosts main "host list&!!" unset
15145 .cindex "&""From""& line"
15146 .cindex "UUCP" "&""From""& line"
15147 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
15148 the headers of a message. By default this is treated as the start of the
15149 message's body, which means that any following headers are not recognized as
15150 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
15151 match those hosts that insist on sending it. If the sender is actually a local
15152 process rather than a remote host, and is using &%-bs%& to inject the messages,
15153 &%ignore_fromline_local%& must be set to achieve this effect.
15156 .option ignore_fromline_local main boolean false
15157 See &%ignore_fromline_hosts%& above.
15159 .option keep_environment main "string list" unset
15160 .cindex "environment" "values from"
15161 This option contains a string list of environment variables to keep.
15162 You have to trust these variables or you have to be sure that
15163 these variables do not impose any security risk. Keep in mind that
15164 during the startup phase Exim is running with an effective UID 0 in most
15165 installations. As the default value is an empty list, the default
15166 environment for using libraries, running embedded Perl code, or running
15167 external binaries is empty, and does not not even contain PATH or HOME.
15169 Actually the list is interpreted as a list of patterns
15170 (&<<SECTlistexpand>>&), except that it is not expanded first.
15172 WARNING: Macro substitution is still done first, so having a macro
15173 FOO and having FOO_HOME in your &%keep_environment%& option may have
15174 unexpected results. You may work around this using a regular expression
15175 that does not match the macro name: ^[F]OO_HOME$.
15177 Current versions of Exim issue a warning during startup if you do not mention
15178 &%keep_environment%& in your runtime configuration file and if your
15179 current environment is not empty. Future versions may not issue that warning
15182 See the &%add_environment%& main config option for a way to set
15183 environment variables to a fixed value. The environment for &(pipe)&
15184 transports is handled separately, see section &<<SECTpipeenv>>& for
15188 .option keep_malformed main time 4d
15189 This option specifies the length of time to keep messages whose spool files
15190 have been corrupted in some way. This should, of course, never happen. At the
15191 next attempt to deliver such a message, it gets removed. The incident is
15195 .option ldap_ca_cert_dir main string unset
15196 .cindex "LDAP", "TLS CA certificate directory"
15197 .cindex certificate "directory for LDAP"
15198 This option indicates which directory contains CA certificates for verifying
15199 a TLS certificate presented by an LDAP server.
15200 While Exim does not provide a default value, your SSL library may.
15201 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15202 and constrained to be a directory.
15205 .option ldap_ca_cert_file main string unset
15206 .cindex "LDAP", "TLS CA certificate file"
15207 .cindex certificate "file for LDAP"
15208 This option indicates which file contains CA certificates for verifying
15209 a TLS certificate presented by an LDAP server.
15210 While Exim does not provide a default value, your SSL library may.
15211 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15212 and constrained to be a file.
15215 .option ldap_cert_file main string unset
15216 .cindex "LDAP" "TLS client certificate file"
15217 .cindex certificate "file for LDAP"
15218 This option indicates which file contains an TLS client certificate which
15219 Exim should present to the LDAP server during TLS negotiation.
15220 Should be used together with &%ldap_cert_key%&.
15223 .option ldap_cert_key main string unset
15224 .cindex "LDAP" "TLS client key file"
15225 .cindex certificate "key for LDAP"
15226 This option indicates which file contains the secret/private key to use
15227 to prove identity to the LDAP server during TLS negotiation.
15228 Should be used together with &%ldap_cert_file%&, which contains the
15229 identity to be proven.
15232 .option ldap_cipher_suite main string unset
15233 .cindex "LDAP" "TLS cipher suite"
15234 This controls the TLS cipher-suite negotiation during TLS negotiation with
15235 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
15236 cipher-suite options with OpenSSL (as used by LDAP client libraries).
15239 .option ldap_default_servers main "string list" unset
15240 .cindex "LDAP" "default servers"
15241 This option provides a list of LDAP servers which are tried in turn when an
15242 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
15243 details of LDAP queries. This option is available only when Exim has been built
15247 .option ldap_require_cert main string unset.
15248 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
15249 This should be one of the values "hard", "demand", "allow", "try" or "never".
15250 A value other than one of these is interpreted as "never".
15251 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
15252 Although Exim does not set a default, the LDAP library probably defaults
15256 .option ldap_start_tls main boolean false
15257 .cindex "LDAP" "whether or not to negotiate TLS"
15258 If set, Exim will attempt to negotiate TLS with the LDAP server when
15259 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
15260 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
15262 In the event of failure to negotiate TLS, the action taken is controlled
15263 by &%ldap_require_cert%&.
15266 .option ldap_version main integer unset
15267 .cindex "LDAP" "protocol version, forcing"
15268 This option can be used to force Exim to set a specific protocol version for
15269 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
15270 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
15271 the LDAP headers; otherwise it is 2. This option is available only when Exim
15272 has been built with LDAP support.
15276 .option local_from_check main boolean true
15277 .cindex "&'Sender:'& header line" "disabling addition of"
15278 .cindex "&'From:'& header line" "disabling checking of"
15279 When a message is submitted locally (that is, not over a TCP/IP connection) by
15280 an untrusted user, Exim removes any existing &'Sender:'& header line, and
15281 checks that the &'From:'& header line matches the login of the calling user and
15282 the domain specified by &%qualify_domain%&.
15284 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
15285 locally submitted message is automatically qualified by Exim, unless the
15286 &%-bnq%& command line option is used.
15288 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
15289 on the local part. If the &'From:'& header line does not match, Exim adds a
15290 &'Sender:'& header with an address constructed from the calling user's login
15291 and the default qualify domain.
15293 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
15294 and no &'Sender:'& header is ever added. If, in addition, you want to retain
15295 &'Sender:'& header lines supplied by untrusted users, you must also set
15296 &%local_sender_retain%& to be true.
15298 .cindex "envelope sender"
15299 These options affect only the header lines in the message. The envelope sender
15300 is still forced to be the login id at the qualify domain unless
15301 &%untrusted_set_sender%& permits the user to supply an envelope sender.
15303 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
15304 request similar header line checking. See section &<<SECTthesenhea>>&, which
15305 has more details about &'Sender:'& processing.
15310 .option local_from_prefix main string unset
15311 When Exim checks the &'From:'& header line of locally submitted messages for
15312 matching the login id (see &%local_from_check%& above), it can be configured to
15313 ignore certain prefixes and suffixes in the local part of the address. This is
15314 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15315 appropriate lists, in the same form as the &%local_part_prefix%& and
15316 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15319 local_from_prefix = *-
15321 is set, a &'From:'& line containing
15323 From: anything-user@your.domain.example
15325 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15326 matches the actual sender address that is constructed from the login name and
15330 .option local_from_suffix main string unset
15331 See &%local_from_prefix%& above.
15334 .option local_interfaces main "string list" "see below"
15335 This option controls which network interfaces are used by the daemon for
15336 listening; they are also used to identify the local host when routing. Chapter
15337 &<<CHAPinterfaces>>& contains a full description of this option and the related
15338 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15339 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15340 &%local_interfaces%& is
15342 local_interfaces = 0.0.0.0
15344 when Exim is built without IPv6 support; otherwise it is
15346 local_interfaces = <; ::0 ; 0.0.0.0
15349 .option local_scan_timeout main time 5m
15350 .cindex "timeout" "for &[local_scan()]& function"
15351 .cindex "&[local_scan()]& function" "timeout"
15352 This timeout applies to the &[local_scan()]& function (see chapter
15353 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15354 the incoming message is rejected with a temporary error if it is an SMTP
15355 message. For a non-SMTP message, the message is dropped and Exim ends with a
15356 non-zero code. The incident is logged on the main and reject logs.
15360 .option local_sender_retain main boolean false
15361 .cindex "&'Sender:'& header line" "retaining from local submission"
15362 When a message is submitted locally (that is, not over a TCP/IP connection) by
15363 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15364 do not want this to happen, you must set &%local_sender_retain%&, and you must
15365 also set &%local_from_check%& to be false (Exim will complain if you do not).
15366 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15367 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15372 .option localhost_number main string&!! unset
15373 .cindex "host" "locally unique number for"
15374 .cindex "message ids" "with multiple hosts"
15375 .vindex "&$localhost_number$&"
15376 Exim's message ids are normally unique only within the local host. If
15377 uniqueness among a set of hosts is required, each host must set a different
15378 value for the &%localhost_number%& option. The string is expanded immediately
15379 after reading the configuration file (so that a number can be computed from the
15380 host name, for example) and the result of the expansion must be a number in the
15381 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15382 systems). This is available in subsequent string expansions via the variable
15383 &$localhost_number$&. When &%localhost_number is set%&, the final two
15384 characters of the message id, instead of just being a fractional part of the
15385 time, are computed from the time and the local host number as described in
15386 section &<<SECTmessiden>>&.
15390 .option log_file_path main "string list&!!" "set at compile time"
15391 .cindex "log" "file path for"
15392 This option sets the path which is used to determine the names of Exim's log
15393 files, or indicates that logging is to be to syslog, or both. It is expanded
15394 when Exim is entered, so it can, for example, contain a reference to the host
15395 name. If no specific path is set for the log files at compile or run time,
15396 or if the option is unset at run time (i.e. &`log_file_path = `&)
15397 they are written in a sub-directory called &_log_& in Exim's spool directory.
15398 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15399 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15400 used. If this string is fixed at your installation (contains no expansion
15401 variables) it is recommended that you do not set this option in the
15402 configuration file, but instead supply the path using LOG_FILE_PATH in
15403 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15404 early on &-- in particular, failure to read the configuration file.
15407 .option log_selector main string unset
15408 .cindex "log" "selectors"
15409 This option can be used to reduce or increase the number of things that Exim
15410 writes to its log files. Its argument is made up of names preceded by plus or
15411 minus characters. For example:
15413 log_selector = +arguments -retry_defer
15415 A list of possible names and what they control is given in the chapter on
15416 logging, in section &<<SECTlogselector>>&.
15419 .option log_timezone main boolean false
15420 .cindex "log" "timezone for entries"
15421 .vindex "&$tod_log$&"
15422 .vindex "&$tod_zone$&"
15423 By default, the timestamps on log lines are in local time without the
15424 timezone. This means that if your timezone changes twice a year, the timestamps
15425 in log lines are ambiguous for an hour when the clocks go back. One way of
15426 avoiding this problem is to set the timezone to UTC. An alternative is to set
15427 &%log_timezone%& true. This turns on the addition of the timezone offset to
15428 timestamps in log lines. Turning on this option can add quite a lot to the size
15429 of log files because each line is extended by 6 characters. Note that the
15430 &$tod_log$& variable contains the log timestamp without the zone, but there is
15431 another variable called &$tod_zone$& that contains just the timezone offset.
15434 .option lookup_open_max main integer 25
15435 .cindex "too many open files"
15436 .cindex "open files, too many"
15437 .cindex "file" "too many open"
15438 .cindex "lookup" "maximum open files"
15439 .cindex "limit" "open files for lookups"
15440 This option limits the number of simultaneously open files for single-key
15441 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15442 Exim normally keeps these files open during routing, because often the same
15443 file is required several times. If the limit is reached, Exim closes the least
15444 recently used file. Note that if you are using the &'ndbm'& library, it
15445 actually opens two files for each logical DBM database, though it still counts
15446 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15447 open files"& errors with NDBM, you need to reduce the value of
15448 &%lookup_open_max%&.
15451 .option max_username_length main integer 0
15452 .cindex "length of login name"
15453 .cindex "user name" "maximum length"
15454 .cindex "limit" "user name length"
15455 Some operating systems are broken in that they truncate long arguments to
15456 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15457 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15458 an argument that is longer behaves as if &[getpwnam()]& failed.
15461 .option message_body_newlines main bool false
15462 .cindex "message body" "newlines in variables"
15463 .cindex "newline" "in message body variables"
15464 .vindex "&$message_body$&"
15465 .vindex "&$message_body_end$&"
15466 By default, newlines in the message body are replaced by spaces when setting
15467 the &$message_body$& and &$message_body_end$& expansion variables. If this
15468 option is set true, this no longer happens.
15471 .option message_body_visible main integer 500
15472 .cindex "body of message" "visible size"
15473 .cindex "message body" "visible size"
15474 .vindex "&$message_body$&"
15475 .vindex "&$message_body_end$&"
15476 This option specifies how much of a message's body is to be included in the
15477 &$message_body$& and &$message_body_end$& expansion variables.
15480 .option message_id_header_domain main string&!! unset
15481 .cindex "&'Message-ID:'& header line"
15482 If this option is set, the string is expanded and used as the right hand side
15483 (domain) of the &'Message-ID:'& header that Exim creates if a
15484 locally-originated incoming message does not have one. &"Locally-originated"&
15485 means &"not received over TCP/IP."&
15486 Otherwise, the primary host name is used.
15487 Only letters, digits, dot and hyphen are accepted; any other characters are
15488 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15489 empty string, the option is ignored.
15492 .option message_id_header_text main string&!! unset
15493 If this variable is set, the string is expanded and used to augment the text of
15494 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15495 message does not have one. The text of this header is required by RFC 2822 to
15496 take the form of an address. By default, Exim uses its internal message id as
15497 the local part, and the primary host name as the domain. If this option is set,
15498 it is expanded, and provided the expansion is not forced to fail, and does not
15499 yield an empty string, the result is inserted into the header immediately
15500 before the @, separated from the internal message id by a dot. Any characters
15501 that are illegal in an address are automatically converted into hyphens. This
15502 means that variables such as &$tod_log$& can be used, because the spaces and
15503 colons will become hyphens.
15506 .option message_logs main boolean true
15507 .cindex "message logs" "disabling"
15508 .cindex "log" "message log; disabling"
15509 If this option is turned off, per-message log files are not created in the
15510 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
15511 Exim, by reducing the number of files involved in handling a message from a
15512 minimum of four (header spool file, body spool file, delivery journal, and
15513 per-message log) to three. The other major I/O activity is Exim's main log,
15514 which is not affected by this option.
15517 .option message_size_limit main string&!! 50M
15518 .cindex "message" "size limit"
15519 .cindex "limit" "message size"
15520 .cindex "size" "of message, limit"
15521 This option limits the maximum size of message that Exim will process. The
15522 value is expanded for each incoming connection so, for example, it can be made
15523 to depend on the IP address of the remote host for messages arriving via
15524 TCP/IP. After expansion, the value must be a sequence of decimal digits,
15525 optionally followed by K or M.
15527 &*Note*&: This limit cannot be made to depend on a message's sender or any
15528 other properties of an individual message, because it has to be advertised in
15529 the server's response to EHLO. String expansion failure causes a temporary
15530 error. A value of zero means no limit, but its use is not recommended. See also
15531 &%bounce_return_size_limit%&.
15533 Incoming SMTP messages are failed with a 552 error if the limit is
15534 exceeded; locally-generated messages either get a stderr message or a delivery
15535 failure message to the sender, depending on the &%-oe%& setting. Rejection of
15536 an oversized message is logged in both the main and the reject logs. See also
15537 the generic transport option &%message_size_limit%&, which limits the size of
15538 message that an individual transport can process.
15540 If you use a virus-scanner and set this option to to a value larger than the
15541 maximum size that your virus-scanner is configured to support, you may get
15542 failures triggered by large mails. The right size to configure for the
15543 virus-scanner depends upon what data is passed and the options in use but it's
15544 probably safest to just set it to a little larger than this value. E.g., with a
15545 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
15546 some problems may result.
15548 A value of 0 will disable size limit checking; Exim will still advertise the
15549 SIZE extension in an EHLO response, but without a limit, so as to permit
15550 SMTP clients to still indicate the message size along with the MAIL verb.
15553 .option move_frozen_messages main boolean false
15554 .cindex "frozen messages" "moving"
15555 This option, which is available only if Exim has been built with the setting
15557 SUPPORT_MOVE_FROZEN_MESSAGES=yes
15559 in &_Local/Makefile_&, causes frozen messages and their message logs to be
15560 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
15561 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
15562 standard utilities for handling such moved messages, and they do not show up in
15563 lists generated by &%-bp%& or by the Exim monitor.
15566 .option mua_wrapper main boolean false
15567 Setting this option true causes Exim to run in a very restrictive mode in which
15568 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
15569 contains a full description of this facility.
15573 .option mysql_servers main "string list" unset
15574 .cindex "MySQL" "server list"
15575 This option provides a list of MySQL servers and associated connection data, to
15576 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
15577 option is available only if Exim has been built with MySQL support.
15580 .option never_users main "string list&!!" unset
15581 This option is expanded just once, at the start of Exim's processing. Local
15582 message deliveries are normally run in processes that are setuid to the
15583 recipient, and remote deliveries are normally run under Exim's own uid and gid.
15584 It is usually desirable to prevent any deliveries from running as root, as a
15587 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
15588 list of users that must not be used for local deliveries. This list is fixed in
15589 the binary and cannot be overridden by the configuration file. By default, it
15590 contains just the single user name &"root"&. The &%never_users%& runtime option
15591 can be used to add more users to the fixed list.
15593 If a message is to be delivered as one of the users on the fixed list or the
15594 &%never_users%& list, an error occurs, and delivery is deferred. A common
15597 never_users = root:daemon:bin
15599 Including root is redundant if it is also on the fixed list, but it does no
15600 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
15604 .option openssl_options main "string list" "+no_sslv2 +single_dh_use"
15605 .cindex "OpenSSL "compatibility options"
15606 This option allows an administrator to adjust the SSL options applied
15607 by OpenSSL to connections. It is given as a space-separated list of items,
15608 each one to be +added or -subtracted from the current value.
15610 This option is only available if Exim is built against OpenSSL. The values
15611 available for this option vary according to the age of your OpenSSL install.
15612 The &"all"& value controls a subset of flags which are available, typically
15613 the bug workaround options. The &'SSL_CTX_set_options'& man page will
15614 list the values known on your system and Exim should support all the
15615 &"bug workaround"& options and many of the &"modifying"& options. The Exim
15616 names lose the leading &"SSL_OP_"& and are lower-cased.
15618 Note that adjusting the options can have severe impact upon the security of
15619 SSL as used by Exim. It is possible to disable safety checks and shoot
15620 yourself in the foot in various unpleasant ways. This option should not be
15621 adjusted lightly. An unrecognised item will be detected at startup, by
15622 invoking Exim with the &%-bV%& flag.
15624 The option affects Exim operating both as a server and as a client.
15626 Historical note: prior to release 4.80, Exim defaulted this value to
15627 "+dont_insert_empty_fragments", which may still be needed for compatibility
15628 with some clients, but which lowers security by increasing exposure to
15629 some now infamous attacks.
15633 # Make both old MS and old Eudora happy:
15634 openssl_options = -all +microsoft_big_sslv3_buffer \
15635 +dont_insert_empty_fragments
15637 # Disable older protocol versions:
15638 openssl_options = +no_sslv2 +no_sslv3
15641 Possible options may include:
15645 &`allow_unsafe_legacy_renegotiation`&
15647 &`cipher_server_preference`&
15649 &`dont_insert_empty_fragments`&
15653 &`legacy_server_connect`&
15655 &`microsoft_big_sslv3_buffer`&
15657 &`microsoft_sess_id_bug`&
15659 &`msie_sslv2_rsa_padding`&
15661 &`netscape_challenge_bug`&
15663 &`netscape_reuse_cipher_change_bug`&
15667 &`no_session_resumption_on_renegotiation`&
15681 &`safari_ecdhe_ecdsa_bug`&
15685 &`single_ecdh_use`&
15687 &`ssleay_080_client_dh_bug`&
15689 &`sslref2_reuse_cert_type_bug`&
15691 &`tls_block_padding_bug`&
15695 &`tls_rollback_bug`&
15698 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
15699 all clients connecting using the MacOS SecureTransport TLS facility prior
15700 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
15701 to negotiate TLS then this option value might help, provided that your OpenSSL
15702 release is new enough to contain this work-around. This may be a situation
15703 where you have to upgrade OpenSSL to get buggy clients working.
15706 .option oracle_servers main "string list" unset
15707 .cindex "Oracle" "server list"
15708 This option provides a list of Oracle servers and associated connection data,
15709 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
15710 The option is available only if Exim has been built with Oracle support.
15713 .option percent_hack_domains main "domain list&!!" unset
15714 .cindex "&""percent hack""&"
15715 .cindex "source routing" "in email address"
15716 .cindex "address" "source-routed"
15717 The &"percent hack"& is the convention whereby a local part containing a
15718 percent sign is re-interpreted as a new email address, with the percent
15719 replaced by @. This is sometimes called &"source routing"&, though that term is
15720 also applied to RFC 2822 addresses that begin with an @ character. If this
15721 option is set, Exim implements the percent facility for those domains listed,
15722 but no others. This happens before an incoming SMTP address is tested against
15725 &*Warning*&: The &"percent hack"& has often been abused by people who are
15726 trying to get round relaying restrictions. For this reason, it is best avoided
15727 if at all possible. Unfortunately, a number of less security-conscious MTAs
15728 implement it unconditionally. If you are running Exim on a gateway host, and
15729 routing mail through to internal MTAs without processing the local parts, it is
15730 a good idea to reject recipient addresses with percent characters in their
15731 local parts. Exim's default configuration does this.
15734 .option perl_at_start main boolean false
15736 This option is available only when Exim is built with an embedded Perl
15737 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15740 .option perl_startup main string unset
15742 This option is available only when Exim is built with an embedded Perl
15743 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15745 .option perl_startup main boolean false
15747 This Option enables the taint mode of the embedded Perl interpreter.
15750 .option pgsql_servers main "string list" unset
15751 .cindex "PostgreSQL lookup type" "server list"
15752 This option provides a list of PostgreSQL servers and associated connection
15753 data, to be used in conjunction with &(pgsql)& lookups (see section
15754 &<<SECID72>>&). The option is available only if Exim has been built with
15755 PostgreSQL support.
15758 .option pid_file_path main string&!! "set at compile time"
15759 .cindex "daemon" "pid file path"
15760 .cindex "pid file, path for"
15761 This option sets the name of the file to which the Exim daemon writes its
15762 process id. The string is expanded, so it can contain, for example, references
15765 pid_file_path = /var/log/$primary_hostname/exim.pid
15767 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
15769 The value set by the option can be overridden by the &%-oP%& command line
15770 option. A pid file is not written if a &"non-standard"& daemon is run by means
15771 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
15774 .option pipelining_advertise_hosts main "host list&!!" *
15775 .cindex "PIPELINING" "suppressing advertising"
15776 This option can be used to suppress the advertisement of the SMTP
15777 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
15778 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
15779 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
15780 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
15781 that clients will use it; &"out of order"& commands that are &"expected"& do
15782 not count as protocol errors (see &%smtp_max_synprot_errors%&).
15785 .option prdr_enable main boolean false
15786 .cindex "PRDR" "enabling on server"
15787 This option can be used to enable the Per-Recipient Data Response extension
15788 to SMTP, defined by Eric Hall.
15789 If the option is set, PRDR is advertised by Exim when operating as a server.
15790 If the client requests PRDR, and more than one recipient, for a message
15791 an additional ACL is called for each recipient after the message content
15792 is received. See section &<<SECTPRDRACL>>&.
15794 .option preserve_message_logs main boolean false
15795 .cindex "message logs" "preserving"
15796 If this option is set, message log files are not deleted when messages are
15797 completed. Instead, they are moved to a sub-directory of the spool directory
15798 called &_msglog.OLD_&, where they remain available for statistical or debugging
15799 purposes. This is a dangerous option to set on systems with any appreciable
15800 volume of mail. Use with care!
15803 .option primary_hostname main string "see below"
15804 .cindex "name" "of local host"
15805 .cindex "host" "name of local"
15806 .cindex "local host" "name of"
15807 .vindex "&$primary_hostname$&"
15808 This specifies the name of the current host. It is used in the default EHLO or
15809 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
15810 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
15811 The value is also used by default in some SMTP response messages from an Exim
15812 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
15814 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
15815 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
15816 contains only one component, Exim passes it to &[gethostbyname()]& (or
15817 &[getipnodebyname()]& when available) in order to obtain the fully qualified
15818 version. The variable &$primary_hostname$& contains the host name, whether set
15819 explicitly by this option, or defaulted.
15822 .option print_topbitchars main boolean false
15823 .cindex "printing characters"
15824 .cindex "8-bit characters"
15825 By default, Exim considers only those characters whose codes lie in the range
15826 32&--126 to be printing characters. In a number of circumstances (for example,
15827 when writing log entries) non-printing characters are converted into escape
15828 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
15829 is set, code values of 128 and above are also considered to be printing
15832 This option also affects the header syntax checks performed by the
15833 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
15834 the user's full name when constructing From: and Sender: addresses (as
15835 described in section &<<SECTconstr>>&). Setting this option can cause
15836 Exim to generate eight bit message headers that do not conform to the
15840 .option process_log_path main string unset
15841 .cindex "process log path"
15842 .cindex "log" "process log"
15843 .cindex "&'exiwhat'&"
15844 This option sets the name of the file to which an Exim process writes its
15845 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15846 utility script. If this option is unset, the file called &_exim-process.info_&
15847 in Exim's spool directory is used. The ability to specify the name explicitly
15848 can be useful in environments where two different Exims are running, using
15849 different spool directories.
15852 .option prod_requires_admin main boolean true
15856 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15857 admin user unless &%prod_requires_admin%& is set false. See also
15858 &%queue_list_requires_admin%&.
15861 .option qualify_domain main string "see below"
15862 .cindex "domain" "for qualifying addresses"
15863 .cindex "address" "qualification"
15864 This option specifies the domain name that is added to any envelope sender
15865 addresses that do not have a domain qualification. It also applies to
15866 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15867 are accepted by default only for locally-generated messages. Qualification is
15868 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15869 locally-generated messages, unless the &%-bnq%& command line option is used.
15871 Messages from external sources must always contain fully qualified addresses,
15872 unless the sending host matches &%sender_unqualified_hosts%& or
15873 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15874 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15875 necessary. Internally, Exim always works with fully qualified envelope
15876 addresses. If &%qualify_domain%& is not set, it defaults to the
15877 &%primary_hostname%& value.
15880 .option qualify_recipient main string "see below"
15881 This option allows you to specify a different domain for qualifying recipient
15882 addresses to the one that is used for senders. See &%qualify_domain%& above.
15886 .option queue_domains main "domain list&!!" unset
15887 .cindex "domain" "specifying non-immediate delivery"
15888 .cindex "queueing incoming messages"
15889 .cindex "message" "queueing certain domains"
15890 This option lists domains for which immediate delivery is not required.
15891 A delivery process is started whenever a message is received, but only those
15892 domains that do not match are processed. All other deliveries wait until the
15893 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15896 .option queue_list_requires_admin main boolean true
15898 The &%-bp%& command-line option, which lists the messages that are on the
15899 queue, requires the caller to be an admin user unless
15900 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15903 .option queue_only main boolean false
15904 .cindex "queueing incoming messages"
15905 .cindex "message" "queueing unconditionally"
15906 If &%queue_only%& is set, a delivery process is not automatically started
15907 whenever a message is received. Instead, the message waits on the queue for the
15908 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15909 delivered immediately when certain conditions (such as heavy load) occur.
15911 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15912 and &%-odi%& command line options override &%queue_only%& unless
15913 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15914 &%queue_only_load%&, and &%smtp_accept_queue%&.
15917 .option queue_only_file main string unset
15918 .cindex "queueing incoming messages"
15919 .cindex "message" "queueing by file existence"
15920 This option can be set to a colon-separated list of absolute path names, each
15921 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15922 it tests for the existence of each listed path using a call to &[stat()]&. For
15923 each path that exists, the corresponding queueing option is set.
15924 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
15925 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
15927 queue_only_file = smtp/some/file
15929 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
15930 &_/some/file_& exists.
15933 .option queue_only_load main fixed-point unset
15934 .cindex "load average"
15935 .cindex "queueing incoming messages"
15936 .cindex "message" "queueing by load"
15937 If the system load average is higher than this value, incoming messages from
15938 all sources are queued, and no automatic deliveries are started. If this
15939 happens during local or remote SMTP input, all subsequent messages received on
15940 the same SMTP connection are queued by default, whatever happens to the load in
15941 the meantime, but this can be changed by setting &%queue_only_load_latch%&
15944 Deliveries will subsequently be performed by queue runner processes. This
15945 option has no effect on ancient operating systems on which Exim cannot
15946 determine the load average. See also &%deliver_queue_load_max%& and
15947 &%smtp_load_reserve%&.
15950 .option queue_only_load_latch main boolean true
15951 .cindex "load average" "re-evaluating per message"
15952 When this option is true (the default), once one message has been queued
15953 because the load average is higher than the value set by &%queue_only_load%&,
15954 all subsequent messages received on the same SMTP connection are also queued.
15955 This is a deliberate choice; even though the load average may fall below the
15956 threshold, it doesn't seem right to deliver later messages on the same
15957 connection when not delivering earlier ones. However, there are special
15958 circumstances such as very long-lived connections from scanning appliances
15959 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
15960 should be set false. This causes the value of the load average to be
15961 re-evaluated for each message.
15964 .option queue_only_override main boolean true
15965 .cindex "queueing incoming messages"
15966 When this option is true, the &%-od%&&'x'& command line options override the
15967 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
15968 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
15969 to override; they are accepted, but ignored.
15972 .option queue_run_in_order main boolean false
15973 .cindex "queue runner" "processing messages in order"
15974 If this option is set, queue runs happen in order of message arrival instead of
15975 in an arbitrary order. For this to happen, a complete list of the entire queue
15976 must be set up before the deliveries start. When the queue is all held in a
15977 single directory (the default), a single list is created for both the ordered
15978 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
15979 single list is not created when &%queue_run_in_order%& is false. In this case,
15980 the sub-directories are processed one at a time (in a random order), and this
15981 avoids setting up one huge list for the whole queue. Thus, setting
15982 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
15983 when the queue is large, because of the extra work in setting up the single,
15984 large list. In most situations, &%queue_run_in_order%& should not be set.
15988 .option queue_run_max main integer&!! 5
15989 .cindex "queue runner" "maximum number of"
15990 This controls the maximum number of queue runner processes that an Exim daemon
15991 can run simultaneously. This does not mean that it starts them all at once,
15992 but rather that if the maximum number are still running when the time comes to
15993 start another one, it refrains from starting another one. This can happen with
15994 very large queues and/or very sluggish deliveries. This option does not,
15995 however, interlock with other processes, so additional queue runners can be
15996 started by other means, or by killing and restarting the daemon.
15998 Setting this option to zero does not suppress queue runs; rather, it disables
15999 the limit, allowing any number of simultaneous queue runner processes to be
16000 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
16001 the daemon's command line.
16004 .cindex queues named
16005 .cindex "named queues"
16006 To set limits for different named queues use
16007 an expansion depending on the &$queue_name$& variable.
16010 .option queue_smtp_domains main "domain list&!!" unset
16011 .cindex "queueing incoming messages"
16012 .cindex "message" "queueing remote deliveries"
16013 When this option is set, a delivery process is started whenever a message is
16014 received, routing is performed, and local deliveries take place.
16015 However, if any SMTP deliveries are required for domains that match
16016 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
16017 message waits on the queue for the next queue run. Since routing of the message
16018 has taken place, Exim knows to which remote hosts it must be delivered, and so
16019 when the queue run happens, multiple messages for the same host are delivered
16020 over a single SMTP connection. The &%-odqs%& command line option causes all
16021 SMTP deliveries to be queued in this way, and is equivalent to setting
16022 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
16026 .option receive_timeout main time 0s
16027 .cindex "timeout" "for non-SMTP input"
16028 This option sets the timeout for accepting a non-SMTP message, that is, the
16029 maximum time that Exim waits when reading a message on the standard input. If
16030 the value is zero, it will wait for ever. This setting is overridden by the
16031 &%-or%& command line option. The timeout for incoming SMTP messages is
16032 controlled by &%smtp_receive_timeout%&.
16034 .option received_header_text main string&!! "see below"
16035 .cindex "customizing" "&'Received:'& header"
16036 .cindex "&'Received:'& header line" "customizing"
16037 This string defines the contents of the &'Received:'& message header that is
16038 added to each message, except for the timestamp, which is automatically added
16039 on at the end (preceded by a semicolon). The string is expanded each time it is
16040 used. If the expansion yields an empty string, no &'Received:'& header line is
16041 added to the message. Otherwise, the string should start with the text
16042 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
16043 header lines. The default setting is:
16046 received_header_text = Received: \
16047 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
16048 {${if def:sender_ident \
16049 {from ${quote_local_part:$sender_ident} }}\
16050 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
16051 by $primary_hostname \
16052 ${if def:received_protocol {with $received_protocol}} \
16053 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
16054 (Exim $version_number)\n\t\
16055 ${if def:sender_address \
16056 {(envelope-from <$sender_address>)\n\t}}\
16057 id $message_exim_id\
16058 ${if def:received_for {\n\tfor $received_for}}
16061 The reference to the TLS cipher is omitted when Exim is built without TLS
16062 support. The use of conditional expansions ensures that this works for both
16063 locally generated messages and messages received from remote hosts, giving
16064 header lines such as the following:
16066 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
16067 by marley.carol.example with esmtp (Exim 4.00)
16068 (envelope-from <bob@carol.example>)
16069 id 16IOWa-00019l-00
16070 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
16071 Received: by scrooge.carol.example with local (Exim 4.00)
16072 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
16074 Until the body of the message has been received, the timestamp is the time when
16075 the message started to be received. Once the body has arrived, and all policy
16076 checks have taken place, the timestamp is updated to the time at which the
16077 message was accepted.
16080 .option received_headers_max main integer 30
16081 .cindex "loop" "prevention"
16082 .cindex "mail loop prevention"
16083 .cindex "&'Received:'& header line" "counting"
16084 When a message is to be delivered, the number of &'Received:'& headers is
16085 counted, and if it is greater than this parameter, a mail loop is assumed to
16086 have occurred, the delivery is abandoned, and an error message is generated.
16087 This applies to both local and remote deliveries.
16090 .option recipient_unqualified_hosts main "host list&!!" unset
16091 .cindex "unqualified addresses"
16092 .cindex "host" "unqualified addresses from"
16093 This option lists those hosts from which Exim is prepared to accept unqualified
16094 recipient addresses in message envelopes. The addresses are made fully
16095 qualified by the addition of the &%qualify_recipient%& value. This option also
16096 affects message header lines. Exim does not reject unqualified recipient
16097 addresses in headers, but it qualifies them only if the message came from a
16098 host that matches &%recipient_unqualified_hosts%&,
16099 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
16100 option was not set.
16103 .option recipients_max main integer 0
16104 .cindex "limit" "number of recipients"
16105 .cindex "recipient" "maximum number"
16106 If this option is set greater than zero, it specifies the maximum number of
16107 original recipients for any message. Additional recipients that are generated
16108 by aliasing or forwarding do not count. SMTP messages get a 452 response for
16109 all recipients over the limit; earlier recipients are delivered as normal.
16110 Non-SMTP messages with too many recipients are failed, and no deliveries are
16113 .cindex "RCPT" "maximum number of incoming"
16114 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
16115 RCPT commands in a single message.
16118 .option recipients_max_reject main boolean false
16119 If this option is set true, Exim rejects SMTP messages containing too many
16120 recipients by giving 552 errors to the surplus RCPT commands, and a 554
16121 error to the eventual DATA command. Otherwise (the default) it gives a 452
16122 error to the surplus RCPT commands and accepts the message on behalf of the
16123 initial set of recipients. The remote server should then re-send the message
16124 for the remaining recipients at a later time.
16127 .option remote_max_parallel main integer 2
16128 .cindex "delivery" "parallelism for remote"
16129 This option controls parallel delivery of one message to a number of remote
16130 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
16131 does all the remote deliveries for a message one by one. Otherwise, if a single
16132 message has to be delivered to more than one remote host, or if several copies
16133 have to be sent to the same remote host, up to &%remote_max_parallel%&
16134 deliveries are done simultaneously. If more than &%remote_max_parallel%&
16135 deliveries are required, the maximum number of processes are started, and as
16136 each one finishes, another is begun. The order of starting processes is the
16137 same as if sequential delivery were being done, and can be controlled by the
16138 &%remote_sort_domains%& option. If parallel delivery takes place while running
16139 with debugging turned on, the debugging output from each delivery process is
16140 tagged with its process id.
16142 This option controls only the maximum number of parallel deliveries for one
16143 message in one Exim delivery process. Because Exim has no central queue
16144 manager, there is no way of controlling the total number of simultaneous
16145 deliveries if the configuration allows a delivery attempt as soon as a message
16148 .cindex "number of deliveries"
16149 .cindex "delivery" "maximum number of"
16150 If you want to control the total number of deliveries on the system, you
16151 need to set the &%queue_only%& option. This ensures that all incoming messages
16152 are added to the queue without starting a delivery process. Then set up an Exim
16153 daemon to start queue runner processes at appropriate intervals (probably
16154 fairly often, for example, every minute), and limit the total number of queue
16155 runners by setting the &%queue_run_max%& parameter. Because each queue runner
16156 delivers only one message at a time, the maximum number of deliveries that can
16157 then take place at once is &%queue_run_max%& multiplied by
16158 &%remote_max_parallel%&.
16160 If it is purely remote deliveries you want to control, use
16161 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
16162 doing the SMTP routing before queueing, so that several messages for the same
16163 host will eventually get delivered down the same connection.
16166 .option remote_sort_domains main "domain list&!!" unset
16167 .cindex "sorting remote deliveries"
16168 .cindex "delivery" "sorting remote"
16169 When there are a number of remote deliveries for a message, they are sorted by
16170 domain into the order given by this list. For example,
16172 remote_sort_domains = *.cam.ac.uk:*.uk
16174 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
16175 then to those in the &%uk%& domain, then to any others.
16178 .option retry_data_expire main time 7d
16179 .cindex "hints database" "data expiry"
16180 This option sets a &"use before"& time on retry information in Exim's hints
16181 database. Any older retry data is ignored. This means that, for example, once a
16182 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
16186 .option retry_interval_max main time 24h
16187 .cindex "retry" "limit on interval"
16188 .cindex "limit" "on retry interval"
16189 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
16190 intervals between delivery attempts for messages that cannot be delivered
16191 straight away. This option sets an overall limit to the length of time between
16192 retries. It cannot be set greater than 24 hours; any attempt to do so forces
16196 .option return_path_remove main boolean true
16197 .cindex "&'Return-path:'& header line" "removing"
16198 RFC 2821, section 4.4, states that an SMTP server must insert a
16199 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
16200 The &'Return-path:'& header preserves the sender address as received in the
16201 MAIL command. This description implies that this header should not be present
16202 in an incoming message. If &%return_path_remove%& is true, any existing
16203 &'Return-path:'& headers are removed from messages at the time they are
16204 received. Exim's transports have options for adding &'Return-path:'& headers at
16205 the time of delivery. They are normally used only for final local deliveries.
16208 .option return_size_limit main integer 100K
16209 This option is an obsolete synonym for &%bounce_return_size_limit%&.
16212 .option rfc1413_hosts main "host list&!!" @[]
16214 .cindex "host" "for RFC 1413 calls"
16215 RFC 1413 identification calls are made to any client host which matches
16216 an item in the list.
16217 The default value specifies just this host, being any local interface
16220 .option rfc1413_query_timeout main time 0s
16221 .cindex "RFC 1413" "query timeout"
16222 .cindex "timeout" "for RFC 1413 call"
16223 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
16224 no RFC 1413 calls are ever made.
16227 .option sender_unqualified_hosts main "host list&!!" unset
16228 .cindex "unqualified addresses"
16229 .cindex "host" "unqualified addresses from"
16230 This option lists those hosts from which Exim is prepared to accept unqualified
16231 sender addresses. The addresses are made fully qualified by the addition of
16232 &%qualify_domain%&. This option also affects message header lines. Exim does
16233 not reject unqualified addresses in headers that contain sender addresses, but
16234 it qualifies them only if the message came from a host that matches
16235 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
16236 using TCP/IP), and the &%-bnq%& option was not set.
16238 .option set_environment main "string list" empty
16239 .cindex "environment"
16240 This option allows to set individual environment variables that the
16241 currently linked libraries and programs in child processes use. The
16242 default list is empty,
16245 .option slow_lookup_log main integer 0
16246 .cindex "logging" "slow lookups"
16247 .cindex "dns" "logging slow lookups"
16248 This option controls logging of slow lookups.
16249 If the value is nonzero it is taken as a number of milliseconds
16250 and lookups taking longer than this are logged.
16251 Currently this applies only to DNS lookups.
16255 .option smtp_accept_keepalive main boolean true
16256 .cindex "keepalive" "on incoming connection"
16257 This option controls the setting of the SO_KEEPALIVE option on incoming
16258 TCP/IP socket connections. When set, it causes the kernel to probe idle
16259 connections periodically, by sending packets with &"old"& sequence numbers. The
16260 other end of the connection should send an acknowledgment if the connection is
16261 still okay or a reset if the connection has been aborted. The reason for doing
16262 this is that it has the beneficial effect of freeing up certain types of
16263 connection that can get stuck when the remote host is disconnected without
16264 tidying up the TCP/IP call properly. The keepalive mechanism takes several
16265 hours to detect unreachable hosts.
16269 .option smtp_accept_max main integer 20
16270 .cindex "limit" "incoming SMTP connections"
16271 .cindex "SMTP" "incoming connection count"
16273 This option specifies the maximum number of simultaneous incoming SMTP calls
16274 that Exim will accept. It applies only to the listening daemon; there is no
16275 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
16276 value is set to zero, no limit is applied. However, it is required to be
16277 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
16278 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
16280 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
16281 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
16282 that limit has not been reached for the client host, &%smtp_accept_reserve%&
16283 and &%smtp_load_reserve%& are then checked before accepting the connection.
16286 .option smtp_accept_max_nonmail main integer 10
16287 .cindex "limit" "non-mail SMTP commands"
16288 .cindex "SMTP" "limiting non-mail commands"
16289 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
16290 the connection if there are too many. This option defines &"too many"&. The
16291 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
16292 client looping sending EHLO, for example. The check is applied only if the
16293 client host matches &%smtp_accept_max_nonmail_hosts%&.
16295 When a new message is expected, one occurrence of RSET is not counted. This
16296 allows a client to send one RSET between messages (this is not necessary,
16297 but some clients do it). Exim also allows one uncounted occurrence of HELO
16298 or EHLO, and one occurrence of STARTTLS between messages. After
16299 starting up a TLS session, another EHLO is expected, and so it too is not
16300 counted. The first occurrence of AUTH in a connection, or immediately
16301 following STARTTLS is not counted. Otherwise, all commands other than
16302 MAIL, RCPT, DATA, and QUIT are counted.
16305 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
16306 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
16307 check by setting this option. The default value makes it apply to all hosts. By
16308 changing the value, you can exclude any badly-behaved hosts that you have to
16312 . Allow this long option name to split; give it unsplit as a fifth argument
16313 . for the automatic .oindex that is generated by .option.
16314 . We insert " &~&~" which is both pretty nasty visually and results in
16315 . non-searchable text. HowItWorks.txt mentions an option for inserting
16316 . zero-width-space, which would be nicer visually and results in (at least)
16317 . html that Firefox will split on when it's forced to reflow (rather than
16318 . inserting a horizontal scrollbar). However, the text is still not
16319 . searchable. NM changed this occurrence for bug 1197 to no longer allow
16320 . the option name to split.
16322 .option "smtp_accept_max_per_connection" main integer 1000 &&&
16323 smtp_accept_max_per_connection
16324 .cindex "SMTP" "limiting incoming message count"
16325 .cindex "limit" "messages per SMTP connection"
16326 The value of this option limits the number of MAIL commands that Exim is
16327 prepared to accept over a single SMTP connection, whether or not each command
16328 results in the transfer of a message. After the limit is reached, a 421
16329 response is given to subsequent MAIL commands. This limit is a safety
16330 precaution against a client that goes mad (incidents of this type have been
16334 .option smtp_accept_max_per_host main string&!! unset
16335 .cindex "limit" "SMTP connections from one host"
16336 .cindex "host" "limiting SMTP connections from"
16337 This option restricts the number of simultaneous IP connections from a single
16338 host (strictly, from a single IP address) to the Exim daemon. The option is
16339 expanded, to enable different limits to be applied to different hosts by
16340 reference to &$sender_host_address$&. Once the limit is reached, additional
16341 connection attempts from the same host are rejected with error code 421. This
16342 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16343 of zero imposes no limit. If this option is set greater than zero, it is
16344 required that &%smtp_accept_max%& be non-zero.
16346 &*Warning*&: When setting this option you should not use any expansion
16347 constructions that take an appreciable amount of time. The expansion and test
16348 happen in the main daemon loop, in order to reject additional connections
16349 without forking additional processes (otherwise a denial-of-service attack
16350 could cause a vast number or processes to be created). While the daemon is
16351 doing this processing, it cannot accept any other incoming connections.
16355 .option smtp_accept_queue main integer 0
16356 .cindex "SMTP" "incoming connection count"
16357 .cindex "queueing incoming messages"
16358 .cindex "message" "queueing by SMTP connection count"
16359 If the number of simultaneous incoming SMTP connections being handled via the
16360 listening daemon exceeds this value, messages received by SMTP are just placed
16361 on the queue; no delivery processes are started automatically. The count is
16362 fixed at the start of an SMTP connection. It cannot be updated in the
16363 subprocess that receives messages, and so the queueing or not queueing applies
16364 to all messages received in the same connection.
16366 A value of zero implies no limit, and clearly any non-zero value is useful only
16367 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16368 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16369 various &%-od%&&'x'& command line options.
16372 . See the comment on smtp_accept_max_per_connection
16374 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16375 smtp_accept_queue_per_connection
16376 .cindex "queueing incoming messages"
16377 .cindex "message" "queueing by message count"
16378 This option limits the number of delivery processes that Exim starts
16379 automatically when receiving messages via SMTP, whether via the daemon or by
16380 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16381 and the number of messages received in a single SMTP session exceeds this
16382 number, subsequent messages are placed on the queue, but no delivery processes
16383 are started. This helps to limit the number of Exim processes when a server
16384 restarts after downtime and there is a lot of mail waiting for it on other
16385 systems. On large systems, the default should probably be increased, and on
16386 dial-in client systems it should probably be set to zero (that is, disabled).
16389 .option smtp_accept_reserve main integer 0
16390 .cindex "SMTP" "incoming call count"
16391 .cindex "host" "reserved"
16392 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16393 number of SMTP connections that are reserved for connections from the hosts
16394 that are specified in &%smtp_reserve_hosts%&. The value set in
16395 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16396 restricted to this number of connections; the option specifies a minimum number
16397 of connection slots for them, not a maximum. It is a guarantee that this group
16398 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16399 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16402 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16403 set to 5, once there are 45 active connections (from any hosts), new
16404 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16405 provided the other criteria for acceptance are met.
16408 .option smtp_active_hostname main string&!! unset
16409 .cindex "host" "name in SMTP responses"
16410 .cindex "SMTP" "host name in responses"
16411 .vindex "&$primary_hostname$&"
16412 This option is provided for multi-homed servers that want to masquerade as
16413 several different hosts. At the start of an incoming SMTP connection, its value
16414 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16415 responses. For example, it is used as domain name in the response to an
16416 incoming HELO or EHLO command.
16418 .vindex "&$smtp_active_hostname$&"
16419 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16420 is saved with any messages that are received. It is therefore available for use
16421 in routers and transports when the message is later delivered.
16423 If this option is unset, or if its expansion is forced to fail, or if the
16424 expansion results in an empty string, the value of &$primary_hostname$& is
16425 used. Other expansion failures cause a message to be written to the main and
16426 panic logs, and the SMTP command receives a temporary error. Typically, the
16427 value of &%smtp_active_hostname%& depends on the incoming interface address.
16430 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16431 {cox.mydomain}{box.mydomain}}
16434 Although &$smtp_active_hostname$& is primarily concerned with incoming
16435 messages, it is also used as the default for HELO commands in callout
16436 verification if there is no remote transport from which to obtain a
16437 &%helo_data%& value.
16439 .option smtp_banner main string&!! "see below"
16440 .cindex "SMTP" "welcome banner"
16441 .cindex "banner for SMTP"
16442 .cindex "welcome banner for SMTP"
16443 .cindex "customizing" "SMTP banner"
16444 This string, which is expanded every time it is used, is output as the initial
16445 positive response to an SMTP connection. The default setting is:
16447 smtp_banner = $smtp_active_hostname ESMTP Exim \
16448 $version_number $tod_full
16450 Failure to expand the string causes a panic error. If you want to create a
16451 multiline response to the initial SMTP connection, use &"\n"& in the string at
16452 appropriate points, but not at the end. Note that the 220 code is not included
16453 in this string. Exim adds it automatically (several times in the case of a
16454 multiline response).
16457 .option smtp_check_spool_space main boolean true
16458 .cindex "checking disk space"
16459 .cindex "disk space, checking"
16460 .cindex "spool directory" "checking space"
16461 When this option is set, if an incoming SMTP session encounters the SIZE
16462 option on a MAIL command, it checks that there is enough space in the
16463 spool directory's partition to accept a message of that size, while still
16464 leaving free the amount specified by &%check_spool_space%& (even if that value
16465 is zero). If there isn't enough space, a temporary error code is returned.
16468 .option smtp_connect_backlog main integer 20
16469 .cindex "connection backlog"
16470 .cindex "SMTP" "connection backlog"
16471 .cindex "backlog of connections"
16472 This option specifies a maximum number of waiting SMTP connections. Exim passes
16473 this value to the TCP/IP system when it sets up its listener. Once this number
16474 of connections are waiting for the daemon's attention, subsequent connection
16475 attempts are refused at the TCP/IP level. At least, that is what the manuals
16476 say; in some circumstances such connection attempts have been observed to time
16477 out instead. For large systems it is probably a good idea to increase the
16478 value (to 50, say). It also gives some protection against denial-of-service
16479 attacks by SYN flooding.
16482 .option smtp_enforce_sync main boolean true
16483 .cindex "SMTP" "synchronization checking"
16484 .cindex "synchronization checking in SMTP"
16485 The SMTP protocol specification requires the client to wait for a response from
16486 the server at certain points in the dialogue. Without PIPELINING these
16487 synchronization points are after every command; with PIPELINING they are
16488 fewer, but they still exist.
16490 Some spamming sites send out a complete set of SMTP commands without waiting
16491 for any response. Exim protects against this by rejecting a message if the
16492 client has sent further input when it should not have. The error response &"554
16493 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16494 for this error cannot be perfect because of transmission delays (unexpected
16495 input may be on its way but not yet received when Exim checks). However, it
16496 does detect many instances.
16498 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
16499 If you want to disable the check selectively (for example, only for certain
16500 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
16501 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
16505 .option smtp_etrn_command main string&!! unset
16506 .cindex "ETRN" "command to be run"
16507 .vindex "&$domain$&"
16508 If this option is set, the given command is run whenever an SMTP ETRN
16509 command is received from a host that is permitted to issue such commands (see
16510 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
16511 are independently expanded. The expansion variable &$domain$& is set to the
16512 argument of the ETRN command, and no syntax checking is done on it. For
16515 smtp_etrn_command = /etc/etrn_command $domain \
16516 $sender_host_address
16518 A new process is created to run the command, but Exim does not wait for it to
16519 complete. Consequently, its status cannot be checked. If the command cannot be
16520 run, a line is written to the panic log, but the ETRN caller still receives
16521 a 250 success response. Exim is normally running under its own uid when
16522 receiving SMTP, so it is not possible for it to change the uid before running
16526 .option smtp_etrn_serialize main boolean true
16527 .cindex "ETRN" "serializing"
16528 When this option is set, it prevents the simultaneous execution of more than
16529 one identical command as a result of ETRN in an SMTP connection. See
16530 section &<<SECTETRN>>& for details.
16533 .option smtp_load_reserve main fixed-point unset
16534 .cindex "load average"
16535 If the system load average ever gets higher than this, incoming SMTP calls are
16536 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
16537 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
16538 the load is over the limit. The option has no effect on ancient operating
16539 systems on which Exim cannot determine the load average. See also
16540 &%deliver_queue_load_max%& and &%queue_only_load%&.
16544 .option smtp_max_synprot_errors main integer 3
16545 .cindex "SMTP" "limiting syntax and protocol errors"
16546 .cindex "limit" "SMTP syntax and protocol errors"
16547 Exim rejects SMTP commands that contain syntax or protocol errors. In
16548 particular, a syntactically invalid email address, as in this command:
16550 RCPT TO:<abc xyz@a.b.c>
16552 causes immediate rejection of the command, before any other tests are done.
16553 (The ACL cannot be run if there is no valid address to set up for it.) An
16554 example of a protocol error is receiving RCPT before MAIL. If there are
16555 too many syntax or protocol errors in one SMTP session, the connection is
16556 dropped. The limit is set by this option.
16558 .cindex "PIPELINING" "expected errors"
16559 When the PIPELINING extension to SMTP is in use, some protocol errors are
16560 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
16561 Exim assumes that PIPELINING will be used if it advertises it (see
16562 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
16563 not count towards the limit.
16567 .option smtp_max_unknown_commands main integer 3
16568 .cindex "SMTP" "limiting unknown commands"
16569 .cindex "limit" "unknown SMTP commands"
16570 If there are too many unrecognized commands in an incoming SMTP session, an
16571 Exim server drops the connection. This is a defence against some kinds of abuse
16574 into making connections to SMTP ports; in these circumstances, a number of
16575 non-SMTP command lines are sent first.
16579 .option smtp_ratelimit_hosts main "host list&!!" unset
16580 .cindex "SMTP" "rate limiting"
16581 .cindex "limit" "rate of message arrival"
16582 .cindex "RCPT" "rate limiting"
16583 Some sites find it helpful to be able to limit the rate at which certain hosts
16584 can send them messages, and the rate at which an individual message can specify
16587 Exim has two rate-limiting facilities. This section describes the older
16588 facility, which can limit rates within a single connection. The newer
16589 &%ratelimit%& ACL condition can limit rates across all connections. See section
16590 &<<SECTratelimiting>>& for details of the newer facility.
16592 When a host matches &%smtp_ratelimit_hosts%&, the values of
16593 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
16594 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
16595 respectively. Each option, if set, must contain a set of four comma-separated
16599 A threshold, before which there is no rate limiting.
16601 An initial time delay. Unlike other times in Exim, numbers with decimal
16602 fractional parts are allowed here.
16604 A factor by which to increase the delay each time.
16606 A maximum value for the delay. This should normally be less than 5 minutes,
16607 because after that time, the client is liable to timeout the SMTP command.
16610 For example, these settings have been used successfully at the site which
16611 first suggested this feature, for controlling mail from their customers:
16613 smtp_ratelimit_mail = 2,0.5s,1.05,4m
16614 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
16616 The first setting specifies delays that are applied to MAIL commands after
16617 two have been received over a single connection. The initial delay is 0.5
16618 seconds, increasing by a factor of 1.05 each time. The second setting applies
16619 delays to RCPT commands when more than four occur in a single message.
16622 .option smtp_ratelimit_mail main string unset
16623 See &%smtp_ratelimit_hosts%& above.
16626 .option smtp_ratelimit_rcpt main string unset
16627 See &%smtp_ratelimit_hosts%& above.
16630 .option smtp_receive_timeout main time&!! 5m
16631 .cindex "timeout" "for SMTP input"
16632 .cindex "SMTP" "input timeout"
16633 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
16634 input, including batch SMTP. If a line of input (either an SMTP command or a
16635 data line) is not received within this time, the SMTP connection is dropped and
16636 the message is abandoned.
16637 A line is written to the log containing one of the following messages:
16639 SMTP command timeout on connection from...
16640 SMTP data timeout on connection from...
16642 The former means that Exim was expecting to read an SMTP command; the latter
16643 means that it was in the DATA phase, reading the contents of a message.
16645 If the first character of the option is a &"$"& the option is
16646 expanded before use and may depend on
16647 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
16651 The value set by this option can be overridden by the
16652 &%-os%& command-line option. A setting of zero time disables the timeout, but
16653 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
16654 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
16655 timeout is controlled by &%receive_timeout%& and &%-or%&.
16658 .option smtp_reserve_hosts main "host list&!!" unset
16659 This option defines hosts for which SMTP connections are reserved; see
16660 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
16663 .option smtp_return_error_details main boolean false
16664 .cindex "SMTP" "details policy failures"
16665 .cindex "policy control" "rejection, returning details"
16666 In the default state, Exim uses bland messages such as
16667 &"Administrative prohibition"& when it rejects SMTP commands for policy
16668 reasons. Many sysadmins like this because it gives away little information
16669 to spammers. However, some other sysadmins who are applying strict checking
16670 policies want to give out much fuller information about failures. Setting
16671 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
16672 example, instead of &"Administrative prohibition"&, it might give:
16674 550-Rejected after DATA: '>' missing at end of address:
16675 550 failing address in "From" header is: <user@dom.ain
16679 .option smtputf8_advertise_hosts main "host list&!!" *
16680 .cindex "SMTPUTF8" "advertising"
16681 When Exim is built with support for internationalised mail names,
16682 the availability therof is advertised in
16683 response to EHLO only to those client hosts that match this option. See
16684 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
16687 .option spamd_address main string "see below"
16688 This option is available when Exim is compiled with the content-scanning
16689 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
16690 The default value is
16694 See section &<<SECTscanspamass>>& for more details.
16698 .option split_spool_directory main boolean false
16699 .cindex "multiple spool directories"
16700 .cindex "spool directory" "split"
16701 .cindex "directories, multiple"
16702 If this option is set, it causes Exim to split its input directory into 62
16703 subdirectories, each with a single alphanumeric character as its name. The
16704 sixth character of the message id is used to allocate messages to
16705 subdirectories; this is the least significant base-62 digit of the time of
16706 arrival of the message.
16708 Splitting up the spool in this way may provide better performance on systems
16709 where there are long mail queues, by reducing the number of files in any one
16710 directory. The msglog directory is also split up in a similar way to the input
16711 directory; however, if &%preserve_message_logs%& is set, all old msglog files
16712 are still placed in the single directory &_msglog.OLD_&.
16714 It is not necessary to take any special action for existing messages when
16715 changing &%split_spool_directory%&. Exim notices messages that are in the
16716 &"wrong"& place, and continues to process them. If the option is turned off
16717 after a period of being on, the subdirectories will eventually empty and be
16718 automatically deleted.
16720 When &%split_spool_directory%& is set, the behaviour of queue runner processes
16721 changes. Instead of creating a list of all messages in the queue, and then
16722 trying to deliver each one in turn, it constructs a list of those in one
16723 sub-directory and tries to deliver them, before moving on to the next
16724 sub-directory. The sub-directories are processed in a random order. This
16725 spreads out the scanning of the input directories, and uses less memory. It is
16726 particularly beneficial when there are lots of messages on the queue. However,
16727 if &%queue_run_in_order%& is set, none of this new processing happens. The
16728 entire queue has to be scanned and sorted before any deliveries can start.
16731 .option spool_directory main string&!! "set at compile time"
16732 .cindex "spool directory" "path to"
16733 This defines the directory in which Exim keeps its spool, that is, the messages
16734 it is waiting to deliver. The default value is taken from the compile-time
16735 configuration setting, if there is one. If not, this option must be set. The
16736 string is expanded, so it can contain, for example, a reference to
16737 &$primary_hostname$&.
16739 If the spool directory name is fixed on your installation, it is recommended
16740 that you set it at build time rather than from this option, particularly if the
16741 log files are being written to the spool directory (see &%log_file_path%&).
16742 Otherwise log files cannot be used for errors that are detected early on, such
16743 as failures in the configuration file.
16745 By using this option to override the compiled-in path, it is possible to run
16746 tests of Exim without using the standard spool.
16748 .option sqlite_lock_timeout main time 5s
16749 .cindex "sqlite lookup type" "lock timeout"
16750 This option controls the timeout that the &(sqlite)& lookup uses when trying to
16751 access an SQLite database. See section &<<SECTsqlite>>& for more details.
16753 .option strict_acl_vars main boolean false
16754 .cindex "&ACL;" "variables, handling unset"
16755 This option controls what happens if a syntactically valid but undefined ACL
16756 variable is referenced. If it is false (the default), an empty string
16757 is substituted; if it is true, an error is generated. See section
16758 &<<SECTaclvariables>>& for details of ACL variables.
16760 .option strip_excess_angle_brackets main boolean false
16761 .cindex "angle brackets, excess"
16762 If this option is set, redundant pairs of angle brackets round &"route-addr"&
16763 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
16764 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
16765 passed on to another MTA, the excess angle brackets are not passed on. If this
16766 option is not set, multiple pairs of angle brackets cause a syntax error.
16769 .option strip_trailing_dot main boolean false
16770 .cindex "trailing dot on domain"
16771 .cindex "dot" "trailing on domain"
16772 If this option is set, a trailing dot at the end of a domain in an address is
16773 ignored. If this is in the envelope and the message is passed on to another
16774 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
16775 domain causes a syntax error.
16776 However, addresses in header lines are checked only when an ACL requests header
16780 .option syslog_duplication main boolean true
16781 .cindex "syslog" "duplicate log lines; suppressing"
16782 When Exim is logging to syslog, it writes the log lines for its three
16783 separate logs at different syslog priorities so that they can in principle
16784 be separated on the logging hosts. Some installations do not require this
16785 separation, and in those cases, the duplication of certain log lines is a
16786 nuisance. If &%syslog_duplication%& is set false, only one copy of any
16787 particular log line is written to syslog. For lines that normally go to
16788 both the main log and the reject log, the reject log version (possibly
16789 containing message header lines) is written, at LOG_NOTICE priority.
16790 Lines that normally go to both the main and the panic log are written at
16791 the LOG_ALERT priority.
16794 .option syslog_facility main string unset
16795 .cindex "syslog" "facility; setting"
16796 This option sets the syslog &"facility"& name, used when Exim is logging to
16797 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
16798 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
16799 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
16800 details of Exim's logging.
16804 .option syslog_processname main string &`exim`&
16805 .cindex "syslog" "process name; setting"
16806 This option sets the syslog &"ident"& name, used when Exim is logging to
16807 syslog. The value must be no longer than 32 characters. See chapter
16808 &<<CHAPlog>>& for details of Exim's logging.
16812 .option syslog_timestamp main boolean true
16813 .cindex "syslog" "timestamps"
16814 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
16815 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
16816 details of Exim's logging.
16819 .option system_filter main string&!! unset
16820 .cindex "filter" "system filter"
16821 .cindex "system filter" "specifying"
16822 .cindex "Sieve filter" "not available for system filter"
16823 This option specifies an Exim filter file that is applied to all messages at
16824 the start of each delivery attempt, before any routing is done. System filters
16825 must be Exim filters; they cannot be Sieve filters. If the system filter
16826 generates any deliveries to files or pipes, or any new mail messages, the
16827 appropriate &%system_filter_..._transport%& option(s) must be set, to define
16828 which transports are to be used. Details of this facility are given in chapter
16829 &<<CHAPsystemfilter>>&.
16832 .option system_filter_directory_transport main string&!! unset
16833 .vindex "&$address_file$&"
16834 This sets the name of the transport driver that is to be used when the
16835 &%save%& command in a system message filter specifies a path ending in &"/"&,
16836 implying delivery of each message into a separate file in some directory.
16837 During the delivery, the variable &$address_file$& contains the path name.
16840 .option system_filter_file_transport main string&!! unset
16841 .cindex "file" "transport for system filter"
16842 This sets the name of the transport driver that is to be used when the &%save%&
16843 command in a system message filter specifies a path not ending in &"/"&. During
16844 the delivery, the variable &$address_file$& contains the path name.
16846 .option system_filter_group main string unset
16847 .cindex "gid (group id)" "system filter"
16848 This option is used only when &%system_filter_user%& is also set. It sets the
16849 gid under which the system filter is run, overriding any gid that is associated
16850 with the user. The value may be numerical or symbolic.
16852 .option system_filter_pipe_transport main string&!! unset
16853 .cindex "&(pipe)& transport" "for system filter"
16854 .vindex "&$address_pipe$&"
16855 This specifies the transport driver that is to be used when a &%pipe%& command
16856 is used in a system filter. During the delivery, the variable &$address_pipe$&
16857 contains the pipe command.
16860 .option system_filter_reply_transport main string&!! unset
16861 .cindex "&(autoreply)& transport" "for system filter"
16862 This specifies the transport driver that is to be used when a &%mail%& command
16863 is used in a system filter.
16866 .option system_filter_user main string unset
16867 .cindex "uid (user id)" "system filter"
16868 If this option is set to root, the system filter is run in the main Exim
16869 delivery process, as root. Otherwise, the system filter runs in a separate
16870 process, as the given user, defaulting to the Exim run-time user.
16871 Unless the string consists entirely of digits, it
16872 is looked up in the password data. Failure to find the named user causes a
16873 configuration error. The gid is either taken from the password data, or
16874 specified by &%system_filter_group%&. When the uid is specified numerically,
16875 &%system_filter_group%& is required to be set.
16877 If the system filter generates any pipe, file, or reply deliveries, the uid
16878 under which the filter is run is used when transporting them, unless a
16879 transport option overrides.
16882 .option tcp_nodelay main boolean true
16883 .cindex "daemon" "TCP_NODELAY on sockets"
16884 .cindex "Nagle algorithm"
16885 .cindex "TCP_NODELAY on listening sockets"
16886 If this option is set false, it stops the Exim daemon setting the
16887 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16888 turns off the &"Nagle algorithm"&, which is a way of improving network
16889 performance in interactive (character-by-character) situations. Turning it off
16890 should improve Exim's performance a bit, so that is what happens by default.
16891 However, it appears that some broken clients cannot cope, and time out. Hence
16892 this option. It affects only those sockets that are set up for listening by the
16893 daemon. Sockets created by the smtp transport for delivering mail always set
16897 .option timeout_frozen_after main time 0s
16898 .cindex "frozen messages" "timing out"
16899 .cindex "timeout" "frozen messages"
16900 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16901 message of any kind that has been on the queue for longer than the given time
16902 is automatically cancelled at the next queue run. If the frozen message is a
16903 bounce message, it is just discarded; otherwise, a bounce is sent to the
16904 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16905 If you want to timeout frozen bounce messages earlier than other kinds of
16906 frozen message, see &%ignore_bounce_errors_after%&.
16908 &*Note:*& the default value of zero means no timeouts; with this setting,
16909 frozen messages remain on the queue forever (except for any frozen bounce
16910 messages that are released by &%ignore_bounce_errors_after%&).
16913 .option timezone main string unset
16914 .cindex "timezone, setting"
16915 .cindex "environment" "values from"
16916 The value of &%timezone%& is used to set the environment variable TZ while
16917 running Exim (if it is different on entry). This ensures that all timestamps
16918 created by Exim are in the required timezone. If you want all your timestamps
16919 to be in UTC (aka GMT) you should set
16923 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
16924 or, if that is not set, from the value of the TZ environment variable when Exim
16925 is built. If &%timezone%& is set to the empty string, either at build or run
16926 time, any existing TZ variable is removed from the environment when Exim
16927 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
16928 unfortunately not all, operating systems.
16931 .option tls_advertise_hosts main "host list&!!" *
16932 .cindex "TLS" "advertising"
16933 .cindex "encryption" "on SMTP connection"
16934 .cindex "SMTP" "encrypted connection"
16935 When Exim is built with support for TLS encrypted connections, the availability
16936 of the STARTTLS command to set up an encrypted session is advertised in
16937 response to EHLO only to those client hosts that match this option. See
16938 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
16939 Note that the default value requires that a certificate be supplied
16940 using the &%tls_certificate%& option. If TLS support for incoming connections
16941 is not required the &%tls_advertise_hosts%& option should be set empty.
16944 .option tls_certificate main string&!! unset
16945 .cindex "TLS" "server certificate; location of"
16946 .cindex "certificate" "server, location of"
16947 The value of this option is expanded, and must then be the absolute path to a
16948 file which contains the server's certificates. The server's private key is also
16949 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
16950 &<<CHAPTLS>>& for further details.
16952 &*Note*&: The certificates defined by this option are used only when Exim is
16953 receiving incoming messages as a server. If you want to supply certificates for
16954 use when sending messages as a client, you must set the &%tls_certificate%&
16955 option in the relevant &(smtp)& transport.
16957 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
16958 if the OpenSSL build supports TLS extensions and the TLS client sends the
16959 Server Name Indication extension, then this option and others documented in
16960 &<<SECTtlssni>>& will be re-expanded.
16963 If this option is unset or empty a fresh self-signed certificate will be
16964 generated for every connection.
16967 .option tls_crl main string&!! unset
16968 .cindex "TLS" "server certificate revocation list"
16969 .cindex "certificate" "revocation list for server"
16970 This option specifies a certificate revocation list. The expanded value must
16971 be the name of a file that contains a CRL in PEM format.
16973 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16976 .option tls_dh_max_bits main integer 2236
16977 .cindex "TLS" "D-H bit count"
16978 The number of bits used for Diffie-Hellman key-exchange may be suggested by
16979 the chosen TLS library. That value might prove to be too high for
16980 interoperability. This option provides a maximum clamp on the value
16981 suggested, trading off security for interoperability.
16983 The value must be at least 1024.
16985 The value 2236 was chosen because, at time of adding the option, it was the
16986 hard-coded maximum value supported by the NSS cryptographic library, as used
16987 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
16989 If you prefer more security and are willing to break some clients, raise this
16992 Note that the value passed to GnuTLS for *generating* a new prime may be a
16993 little less than this figure, because GnuTLS is inexact and may produce a
16994 larger prime than requested.
16997 .option tls_dhparam main string&!! unset
16998 .cindex "TLS" "D-H parameters for server"
16999 The value of this option is expanded and indicates the source of DH parameters
17000 to be used by Exim.
17002 If it is a filename starting with a &`/`&, then it names a file from which DH
17003 parameters should be loaded. If the file exists, it should hold a PEM-encoded
17004 PKCS#3 representation of the DH prime. If the file does not exist, for
17005 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
17006 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
17007 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
17008 and treated as though the &%tls_dhparam%& were set to "none".
17010 If this option expands to the string "none", then no DH parameters will be
17013 If this option expands to the string "historic" and Exim is using GnuTLS, then
17014 Exim will attempt to load a file from inside the spool directory. If the file
17015 does not exist, Exim will attempt to create it.
17016 See section &<<SECTgnutlsparam>>& for further details.
17018 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
17019 a default DH prime; the default is the 2048 bit prime described in section
17020 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
17021 in IKE is assigned number 23.
17023 Otherwise, the option must expand to the name used by Exim for any of a number
17024 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
17025 "ike" followed by the number used by IKE, or "default" which corresponds to
17028 The available primes are:
17029 &`ike1`&, &`ike2`&, &`ike5`&,
17030 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
17031 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
17033 Some of these will be too small to be accepted by clients.
17034 Some may be too large to be accepted by clients.
17036 The TLS protocol does not negotiate an acceptable size for this; clients tend
17037 to hard-drop connections if what is offered by the server is unacceptable,
17038 whether too large or too small, and there's no provision for the client to
17039 tell the server what these constraints are. Thus, as a server operator, you
17040 need to make an educated guess as to what is most likely to work for your
17043 Some known size constraints suggest that a bit-size in the range 2048 to 2236
17044 is most likely to maximise interoperability. The upper bound comes from
17045 applications using the Mozilla Network Security Services (NSS) library, which
17046 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
17047 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
17048 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
17049 acceptable bound from 1024 to 2048.
17052 .option tls_eccurve main string&!! prime256v1
17053 .cindex TLS "EC cryptography"
17054 If built with a recent-enough version of OpenSSL,
17055 this option selects a EC curve for use by Exim.
17057 Curve names of the form &'prime256v1'& are accepted.
17058 For even more-recent library versions, names of the form &'P-512'&
17059 are also accepted, plus the special value &'auto'&
17060 which tells the library to choose.
17062 If the option is set to an empty string, no EC curves will be enabled.
17065 .option tls_ocsp_file main string&!! unset
17066 .cindex TLS "certificate status"
17067 .cindex TLS "OCSP proof file"
17069 must if set expand to the absolute path to a file which contains a current
17070 status proof for the server's certificate, as obtained from the
17071 Certificate Authority.
17073 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
17076 .option tls_on_connect_ports main "string list" unset
17079 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
17080 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
17081 set up without waiting for the client to issue a STARTTLS command. For
17082 further details, see section &<<SECTsupobssmt>>&.
17086 .option tls_privatekey main string&!! unset
17087 .cindex "TLS" "server private key; location of"
17088 The value of this option is expanded, and must then be the absolute path to a
17089 file which contains the server's private key. If this option is unset, or if
17090 the expansion is forced to fail, or the result is an empty string, the private
17091 key is assumed to be in the same file as the server's certificates. See chapter
17092 &<<CHAPTLS>>& for further details.
17094 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17097 .option tls_remember_esmtp main boolean false
17098 .cindex "TLS" "esmtp state; remembering"
17099 .cindex "TLS" "broken clients"
17100 If this option is set true, Exim violates the RFCs by remembering that it is in
17101 &"esmtp"& state after successfully negotiating a TLS session. This provides
17102 support for broken clients that fail to send a new EHLO after starting a
17106 .option tls_require_ciphers main string&!! unset
17107 .cindex "TLS" "requiring specific ciphers"
17108 .cindex "cipher" "requiring specific"
17109 This option controls which ciphers can be used for incoming TLS connections.
17110 The &(smtp)& transport has an option of the same name for controlling outgoing
17111 connections. This option is expanded for each connection, so can be varied for
17112 different clients if required. The value of this option must be a list of
17113 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
17114 in somewhat different ways. If GnuTLS is being used, the client controls the
17115 preference order of the available ciphers. Details are given in sections
17116 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
17119 .option tls_try_verify_hosts main "host list&!!" unset
17120 .cindex "TLS" "client certificate verification"
17121 .cindex "certificate" "verification of client"
17122 See &%tls_verify_hosts%& below.
17125 .option tls_verify_certificates main string&!! system
17126 .cindex "TLS" "client certificate verification"
17127 .cindex "certificate" "verification of client"
17128 The value of this option is expanded, and must then be either the
17130 or the absolute path to
17131 a file or directory containing permitted certificates for clients that
17132 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
17134 The "system" value for the option will use a
17135 system default location compiled into the SSL library.
17136 This is not available for GnuTLS versions preceding 3.0.20,
17137 and will be taken as empty; an explicit location
17140 The use of a directory for the option value is not available for GnuTLS versions
17141 preceding 3.3.6 and a single file must be used.
17143 With OpenSSL the certificates specified
17145 either by file or directory
17146 are added to those given by the system default location.
17148 These certificates should be for the certificate authorities trusted, rather
17149 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
17150 the value is a file then the certificates are sent by Exim as a server to
17151 connecting clients, defining the list of accepted certificate authorities.
17152 Thus the values defined should be considered public data. To avoid this,
17153 use the explicit directory version.
17155 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17157 A forced expansion failure or setting to an empty string is equivalent to
17161 .option tls_verify_hosts main "host list&!!" unset
17162 .cindex "TLS" "client certificate verification"
17163 .cindex "certificate" "verification of client"
17164 This option, along with &%tls_try_verify_hosts%&, controls the checking of
17165 certificates from clients. The expected certificates are defined by
17166 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
17167 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
17168 &%tls_verify_certificates%& is not set.
17170 Any client that matches &%tls_verify_hosts%& is constrained by
17171 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
17172 present one of the listed certificates. If it does not, the connection is
17173 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
17174 the host to use TLS. It can still send SMTP commands through unencrypted
17175 connections. Forcing a client to use TLS has to be done separately using an
17176 ACL to reject inappropriate commands when the connection is not encrypted.
17178 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
17179 matches this option (but not &%tls_verify_hosts%&), Exim requests a
17180 certificate and checks it against &%tls_verify_certificates%&, but does not
17181 abort the connection if there is no certificate or if it does not match. This
17182 state can be detected in an ACL, which makes it possible to implement policies
17183 such as &"accept for relay only if a verified certificate has been received,
17184 but accept for local delivery if encrypted, even without a verified
17187 Client hosts that match neither of these lists are not asked to present
17191 .option trusted_groups main "string list&!!" unset
17192 .cindex "trusted groups"
17193 .cindex "groups" "trusted"
17194 This option is expanded just once, at the start of Exim's processing. If this
17195 option is set, any process that is running in one of the listed groups, or
17196 which has one of them as a supplementary group, is trusted. The groups can be
17197 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
17198 details of what trusted callers are permitted to do. If neither
17199 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
17202 .option trusted_users main "string list&!!" unset
17203 .cindex "trusted users"
17204 .cindex "user" "trusted"
17205 This option is expanded just once, at the start of Exim's processing. If this
17206 option is set, any process that is running as one of the listed users is
17207 trusted. The users can be specified numerically or by name. See section
17208 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
17209 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
17210 Exim user are trusted.
17212 .option unknown_login main string&!! unset
17213 .cindex "uid (user id)" "unknown caller"
17214 .vindex "&$caller_uid$&"
17215 This is a specialized feature for use in unusual configurations. By default, if
17216 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
17217 gives up. The &%unknown_login%& option can be used to set a login name to be
17218 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
17219 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
17220 is used for the user's real name (gecos field), unless this has been set by the
17223 .option unknown_username main string unset
17224 See &%unknown_login%&.
17226 .option untrusted_set_sender main "address list&!!" unset
17227 .cindex "trusted users"
17228 .cindex "sender" "setting by untrusted user"
17229 .cindex "untrusted user setting sender"
17230 .cindex "user" "untrusted setting sender"
17231 .cindex "envelope sender"
17232 When an untrusted user submits a message to Exim using the standard input, Exim
17233 normally creates an envelope sender address from the user's login and the
17234 default qualification domain. Data from the &%-f%& option (for setting envelope
17235 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
17236 is used) is ignored.
17238 However, untrusted users are permitted to set an empty envelope sender address,
17239 to declare that a message should never generate any bounces. For example:
17241 exim -f '<>' user@domain.example
17243 .vindex "&$sender_ident$&"
17244 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
17245 other envelope sender addresses in a controlled way. When it is set, untrusted
17246 users are allowed to set envelope sender addresses that match any of the
17247 patterns in the list. Like all address lists, the string is expanded. The
17248 identity of the user is in &$sender_ident$&, so you can, for example, restrict
17249 users to setting senders that start with their login ids
17250 followed by a hyphen
17251 by a setting like this:
17253 untrusted_set_sender = ^$sender_ident-
17255 If you want to allow untrusted users to set envelope sender addresses without
17256 restriction, you can use
17258 untrusted_set_sender = *
17260 The &%untrusted_set_sender%& option applies to all forms of local input, but
17261 only to the setting of the envelope sender. It does not permit untrusted users
17262 to use the other options which trusted user can use to override message
17263 parameters. Furthermore, it does not stop Exim from removing an existing
17264 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
17265 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
17266 overriding these actions. The handling of the &'Sender:'& header is also
17267 described in section &<<SECTthesenhea>>&.
17269 The log line for a message's arrival shows the envelope sender following
17270 &"<="&. For local messages, the user's login always follows, after &"U="&. In
17271 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
17272 envelope sender address, the user's login is shown in parentheses after the
17276 .option uucp_from_pattern main string "see below"
17277 .cindex "&""From""& line"
17278 .cindex "UUCP" "&""From""& line"
17279 Some applications that pass messages to an MTA via a command line interface use
17280 an initial line starting with &"From&~"& to pass the envelope sender. In
17281 particular, this is used by UUCP software. Exim recognizes such a line by means
17282 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
17283 matches, the sender address is constructed by expanding the contents of
17284 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
17285 default pattern recognizes lines in the following two forms:
17287 From ph10 Fri Jan 5 12:35 GMT 1996
17288 From ph10 Fri, 7 Jan 97 14:00:00 GMT
17290 The pattern can be seen by running
17292 exim -bP uucp_from_pattern
17294 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
17295 year in the second case. The first word after &"From&~"& is matched in the
17296 regular expression by a parenthesized subpattern. The default value for
17297 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
17298 (&"ph10"& in the example above) as the message's sender. See also
17299 &%ignore_fromline_hosts%&.
17302 .option uucp_from_sender main string&!! &`$1`&
17303 See &%uucp_from_pattern%& above.
17306 .option warn_message_file main string unset
17307 .cindex "warning of delay" "customizing the message"
17308 .cindex "customizing" "warning message"
17309 This option defines a template file containing paragraphs of text to be used
17310 for constructing the warning message which is sent by Exim when a message has
17311 been on the queue for a specified amount of time, as specified by
17312 &%delay_warning%&. Details of the file's contents are given in chapter
17313 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
17316 .option write_rejectlog main boolean true
17317 .cindex "reject log" "disabling"
17318 If this option is set false, Exim no longer writes anything to the reject log.
17319 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
17320 .ecindex IIDconfima
17321 .ecindex IIDmaiconf
17326 . ////////////////////////////////////////////////////////////////////////////
17327 . ////////////////////////////////////////////////////////////////////////////
17329 .chapter "Generic options for routers" "CHAProutergeneric"
17330 .scindex IIDgenoprou1 "options" "generic; for routers"
17331 .scindex IIDgenoprou2 "generic options" "router"
17332 This chapter describes the generic options that apply to all routers.
17333 Those that are preconditions are marked with ‡ in the &"use"& field.
17335 For a general description of how a router operates, see sections
17336 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
17337 which the preconditions are tested. The order of expansion of the options that
17338 provide data for a transport is: &%errors_to%&, &%headers_add%&,
17339 &%headers_remove%&, &%transport%&.
17343 .option address_data routers string&!! unset
17344 .cindex "router" "data attached to address"
17345 The string is expanded just before the router is run, that is, after all the
17346 precondition tests have succeeded. If the expansion is forced to fail, the
17347 router declines, the value of &%address_data%& remains unchanged, and the
17348 &%more%& option controls what happens next. Other expansion failures cause
17349 delivery of the address to be deferred.
17351 .vindex "&$address_data$&"
17352 When the expansion succeeds, the value is retained with the address, and can be
17353 accessed using the variable &$address_data$& in the current router, subsequent
17354 routers, and the eventual transport.
17356 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17357 that runs a user's filter file, the contents of &$address_data$& are accessible
17358 in the filter. This is not normally a problem, because such data is usually
17359 either not confidential or it &"belongs"& to the current user, but if you do
17360 put confidential data into &$address_data$& you need to remember this point.
17362 Even if the router declines or passes, the value of &$address_data$& remains
17363 with the address, though it can be changed by another &%address_data%& setting
17364 on a subsequent router. If a router generates child addresses, the value of
17365 &$address_data$& propagates to them. This also applies to the special kind of
17366 &"child"& that is generated by a router with the &%unseen%& option.
17368 The idea of &%address_data%& is that you can use it to look up a lot of data
17369 for the address once, and then pick out parts of the data later. For example,
17370 you could use a single LDAP lookup to return a string of the form
17372 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17374 In the transport you could pick out the mailbox by a setting such as
17376 file = ${extract{mailbox}{$address_data}}
17378 This makes the configuration file less messy, and also reduces the number of
17379 lookups (though Exim does cache lookups).
17381 .vindex "&$sender_address_data$&"
17382 .vindex "&$address_data$&"
17383 The &%address_data%& facility is also useful as a means of passing information
17384 from one router to another, and from a router to a transport. In addition, if
17385 &$address_data$& is set by a router when verifying a recipient address from an
17386 ACL, it remains available for use in the rest of the ACL statement. After
17387 verifying a sender, the value is transferred to &$sender_address_data$&.
17391 .option address_test routers&!? boolean true
17393 .cindex "router" "skipping when address testing"
17394 If this option is set false, the router is skipped when routing is being tested
17395 by means of the &%-bt%& command line option. This can be a convenience when
17396 your first router sends messages to an external scanner, because it saves you
17397 having to set the &"already scanned"& indicator when testing real address
17402 .option cannot_route_message routers string&!! unset
17403 .cindex "router" "customizing &""cannot route""& message"
17404 .cindex "customizing" "&""cannot route""& message"
17405 This option specifies a text message that is used when an address cannot be
17406 routed because Exim has run out of routers. The default message is
17407 &"Unrouteable address"&. This option is useful only on routers that have
17408 &%more%& set false, or on the very last router in a configuration, because the
17409 value that is used is taken from the last router that is considered. This
17410 includes a router that is skipped because its preconditions are not met, as
17411 well as a router that declines. For example, using the default configuration,
17414 cannot_route_message = Remote domain not found in DNS
17416 on the first router, which is a &(dnslookup)& router with &%more%& set false,
17419 cannot_route_message = Unknown local user
17421 on the final router that checks for local users. If string expansion fails for
17422 this option, the default message is used. Unless the expansion failure was
17423 explicitly forced, a message about the failure is written to the main and panic
17424 logs, in addition to the normal message about the routing failure.
17427 .option caseful_local_part routers boolean false
17428 .cindex "case of local parts"
17429 .cindex "router" "case of local parts"
17430 By default, routers handle the local parts of addresses in a case-insensitive
17431 manner, though the actual case is preserved for transmission with the message.
17432 If you want the case of letters to be significant in a router, you must set
17433 this option true. For individual router options that contain address or local
17434 part lists (for example, &%local_parts%&), case-sensitive matching can be
17435 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
17438 .vindex "&$local_part$&"
17439 .vindex "&$original_local_part$&"
17440 .vindex "&$parent_local_part$&"
17441 The value of the &$local_part$& variable is forced to lower case while a
17442 router is running unless &%caseful_local_part%& is set. When a router assigns
17443 an address to a transport, the value of &$local_part$& when the transport runs
17444 is the same as it was in the router. Similarly, when a router generates child
17445 addresses by aliasing or forwarding, the values of &$original_local_part$&
17446 and &$parent_local_part$& are those that were used by the redirecting router.
17448 This option applies to the processing of an address by a router. When a
17449 recipient address is being processed in an ACL, there is a separate &%control%&
17450 modifier that can be used to specify case-sensitive processing within the ACL
17451 (see section &<<SECTcontrols>>&).
17455 .option check_local_user routers&!? boolean false
17456 .cindex "local user, checking in router"
17457 .cindex "router" "checking for local user"
17458 .cindex "&_/etc/passwd_&"
17460 When this option is true, Exim checks that the local part of the recipient
17461 address (with affixes removed if relevant) is the name of an account on the
17462 local system. The check is done by calling the &[getpwnam()]& function rather
17463 than trying to read &_/etc/passwd_& directly. This means that other methods of
17464 holding password data (such as NIS) are supported. If the local part is a local
17465 user, &$home$& is set from the password data, and can be tested in other
17466 preconditions that are evaluated after this one (the order of evaluation is
17467 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
17468 overridden by &%router_home_directory%&. If the local part is not a local user,
17469 the router is skipped.
17471 If you want to check that the local part is either the name of a local user
17472 or matches something else, you cannot combine &%check_local_user%& with a
17473 setting of &%local_parts%&, because that specifies the logical &'and'& of the
17474 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
17475 setting to achieve this. For example:
17477 local_parts = passwd;$local_part : lsearch;/etc/other/users
17479 Note, however, that the side effects of &%check_local_user%& (such as setting
17480 up a home directory) do not occur when a &(passwd)& lookup is used in a
17481 &%local_parts%& (or any other) precondition.
17485 .option condition routers&!? string&!! unset
17486 .cindex "router" "customized precondition"
17487 This option specifies a general precondition test that has to succeed for the
17488 router to be called. The &%condition%& option is the last precondition to be
17489 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
17490 result is a forced failure, or an empty string, or one of the strings &"0"& or
17491 &"no"& or &"false"& (checked without regard to the case of the letters), the
17492 router is skipped, and the address is offered to the next one.
17494 If the result is any other value, the router is run (as this is the last
17495 precondition to be evaluated, all the other preconditions must be true).
17497 This option is unusual in that multiple &%condition%& options may be present.
17498 All &%condition%& options must succeed.
17500 The &%condition%& option provides a means of applying custom conditions to the
17501 running of routers. Note that in the case of a simple conditional expansion,
17502 the default expansion values are exactly what is wanted. For example:
17504 condition = ${if >{$message_age}{600}}
17506 Because of the default behaviour of the string expansion, this is equivalent to
17508 condition = ${if >{$message_age}{600}{true}{}}
17511 A multiple condition example, which succeeds:
17513 condition = ${if >{$message_age}{600}}
17514 condition = ${if !eq{${lc:$local_part}}{postmaster}}
17518 If the expansion fails (other than forced failure) delivery is deferred. Some
17519 of the other precondition options are common special cases that could in fact
17520 be specified using &%condition%&.
17522 Historical note: We have &%condition%& on ACLs and on Routers. Routers
17523 are far older, and use one set of semantics. ACLs are newer and when
17524 they were created, the ACL &%condition%& process was given far stricter
17525 parse semantics. The &%bool{}%& expansion condition uses the same rules as
17526 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
17527 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
17528 Router rules processing behavior.
17530 This is best illustrated in an example:
17532 # If used in an ACL condition will fail with a syntax error, but
17533 # in a router condition any extra characters are treated as a string
17535 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
17538 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
17541 In each example above, the &%if%& statement actually ends after
17542 &"{google.com}}"&. Since no true or false braces were defined, the
17543 default &%if%& behavior is to return a boolean true or a null answer
17544 (which evaluates to false). The rest of the line is then treated as a
17545 string. So the first example resulted in the boolean answer &"true"&
17546 with the string &" {yes} {no}}"& appended to it. The second example
17547 resulted in the null output (indicating false) with the string
17548 &" {yes} {no}}"& appended to it.
17550 In fact you can put excess forward braces in too. In the router
17551 &%condition%&, Exim's parser only looks for &"{"& symbols when they
17552 mean something, like after a &"$"& or when required as part of a
17553 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
17556 Thus, in a Router, the above expansion strings will both always evaluate
17557 true, as the result of expansion is a non-empty string which doesn't
17558 match an explicit false value. This can be tricky to debug. By
17559 contrast, in an ACL either of those strings will always result in an
17560 expansion error because the result doesn't look sufficiently boolean.
17563 .option debug_print routers string&!! unset
17564 .cindex "testing" "variables in drivers"
17565 If this option is set and debugging is enabled (see the &%-d%& command line
17566 option) or in address-testing mode (see the &%-bt%& command line option),
17567 the string is expanded and included in the debugging output.
17568 If expansion of the string fails, the error message is written to the debugging
17569 output, and Exim carries on processing.
17570 This option is provided to help with checking out the values of variables and
17571 so on when debugging router configurations. For example, if a &%condition%&
17572 option appears not to be working, &%debug_print%& can be used to output the
17573 variables it references. The output happens after checks for &%domains%&,
17574 &%local_parts%&, and &%check_local_user%& but before any other preconditions
17575 are tested. A newline is added to the text if it does not end with one.
17576 The variable &$router_name$& contains the name of the router.
17580 .option disable_logging routers boolean false
17581 If this option is set true, nothing is logged for any routing errors
17582 or for any deliveries caused by this router. You should not set this option
17583 unless you really, really know what you are doing. See also the generic
17584 transport option of the same name.
17586 .option dnssec_request_domains routers "domain list&!!" unset
17587 .cindex "MX record" "security"
17588 .cindex "DNSSEC" "MX lookup"
17589 .cindex "security" "MX lookup"
17590 .cindex "DNS" "DNSSEC"
17591 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17592 the dnssec request bit set.
17593 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17595 .option dnssec_require_domains routers "domain list&!!" unset
17596 .cindex "MX record" "security"
17597 .cindex "DNSSEC" "MX lookup"
17598 .cindex "security" "MX lookup"
17599 .cindex "DNS" "DNSSEC"
17600 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
17601 the dnssec request bit set. Any returns not having the Authenticated Data bit
17602 (AD bit) set will be ignored and logged as a host-lookup failure.
17603 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17606 .option domains routers&!? "domain list&!!" unset
17607 .cindex "router" "restricting to specific domains"
17608 .vindex "&$domain_data$&"
17609 If this option is set, the router is skipped unless the current domain matches
17610 the list. If the match is achieved by means of a file lookup, the data that the
17611 lookup returned for the domain is placed in &$domain_data$& for use in string
17612 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
17613 a list of the order in which preconditions are evaluated.
17617 .option driver routers string unset
17618 This option must always be set. It specifies which of the available routers is
17622 .option dsn_lasthop routers boolean false
17623 .cindex "DSN" "success"
17624 .cindex "Delivery Status Notification" "success"
17625 If this option is set true, and extended DSN (RFC3461) processing is in effect,
17626 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
17627 instead send a success DSN as if the next hop does not support DSN.
17628 Not effective on redirect routers.
17632 .option errors_to routers string&!! unset
17633 .cindex "envelope sender"
17634 .cindex "router" "changing address for errors"
17635 If a router successfully handles an address, it may assign the address to a
17636 transport for delivery or it may generate child addresses. In both cases, if
17637 there is a delivery problem during later processing, the resulting bounce
17638 message is sent to the address that results from expanding this string,
17639 provided that the address verifies successfully. The &%errors_to%& option is
17640 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
17642 The &%errors_to%& setting associated with an address can be overridden if it
17643 subsequently passes through other routers that have their own &%errors_to%&
17644 settings, or if the message is delivered by a transport with a &%return_path%&
17647 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
17648 the expansion fails to verify, the errors address associated with the incoming
17649 address is used. At top level, this is the envelope sender. A non-forced
17650 expansion failure causes delivery to be deferred.
17652 If an address for which &%errors_to%& has been set ends up being delivered over
17653 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
17654 any bounces that are generated by other MTAs on the delivery route are also
17655 sent there. You can set &%errors_to%& to the empty string by either of these
17661 An expansion item that yields an empty string has the same effect. If you do
17662 this, a locally detected delivery error for addresses processed by this router
17663 no longer gives rise to a bounce message; the error is discarded. If the
17664 address is delivered to a remote host, the return path is set to &`<>`&, unless
17665 overridden by the &%return_path%& option on the transport.
17667 .vindex "&$address_data$&"
17668 If for some reason you want to discard local errors, but use a non-empty
17669 MAIL command for remote delivery, you can preserve the original return
17670 path in &$address_data$& in the router, and reinstate it in the transport by
17671 setting &%return_path%&.
17673 The most common use of &%errors_to%& is to direct mailing list bounces to the
17674 manager of the list, as described in section &<<SECTmailinglists>>&, or to
17675 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
17679 .option expn routers&!? boolean true
17680 .cindex "address" "testing"
17681 .cindex "testing" "addresses"
17682 .cindex "EXPN" "router skipping"
17683 .cindex "router" "skipping for EXPN"
17684 If this option is turned off, the router is skipped when testing an address
17685 as a result of processing an SMTP EXPN command. You might, for example,
17686 want to turn it off on a router for users' &_.forward_& files, while leaving it
17687 on for the system alias file.
17688 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17691 The use of the SMTP EXPN command is controlled by an ACL (see chapter
17692 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
17693 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
17697 .option fail_verify routers boolean false
17698 .cindex "router" "forcing verification failure"
17699 Setting this option has the effect of setting both &%fail_verify_sender%& and
17700 &%fail_verify_recipient%& to the same value.
17704 .option fail_verify_recipient routers boolean false
17705 If this option is true and an address is accepted by this router when
17706 verifying a recipient, verification fails.
17710 .option fail_verify_sender routers boolean false
17711 If this option is true and an address is accepted by this router when
17712 verifying a sender, verification fails.
17716 .option fallback_hosts routers "string list" unset
17717 .cindex "router" "fallback hosts"
17718 .cindex "fallback" "hosts specified on router"
17719 String expansion is not applied to this option. The argument must be a
17720 colon-separated list of host names or IP addresses. The list separator can be
17721 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
17722 each name or address. In fact, the format of each item is exactly the same as
17723 defined for the list of hosts in a &(manualroute)& router (see section
17724 &<<SECTformatonehostitem>>&).
17726 If a router queues an address for a remote transport, this host list is
17727 associated with the address, and used instead of the transport's fallback host
17728 list. If &%hosts_randomize%& is set on the transport, the order of the list is
17729 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
17730 transport for further details.
17733 .option group routers string&!! "see below"
17734 .cindex "gid (group id)" "local delivery"
17735 .cindex "local transports" "uid and gid"
17736 .cindex "transport" "local"
17737 .cindex "router" "setting group"
17738 When a router queues an address for a transport, and the transport does not
17739 specify a group, the group given here is used when running the delivery
17741 The group may be specified numerically or by name. If expansion fails, the
17742 error is logged and delivery is deferred.
17743 The default is unset, unless &%check_local_user%& is set, when the default
17744 is taken from the password information. See also &%initgroups%& and &%user%&
17745 and the discussion in chapter &<<CHAPenvironment>>&.
17749 .option headers_add routers list&!! unset
17750 .cindex "header lines" "adding"
17751 .cindex "router" "adding header lines"
17752 This option specifies a list of text headers,
17753 newline-separated (by default, changeable in the usual way),
17754 that is associated with any addresses that are accepted by the router.
17755 Each item is separately expanded, at routing time. However, this
17756 option has no effect when an address is just being verified. The way in which
17757 the text is used to add header lines at transport time is described in section
17758 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
17759 message is in the process of being transported. This means that references to
17760 header lines in string expansions in the transport's configuration do not
17761 &"see"& the added header lines.
17763 The &%headers_add%& option is expanded after &%errors_to%&, but before
17764 &%headers_remove%& and &%transport%&. If an item is empty, or if
17765 an item expansion is forced to fail, the item has no effect. Other expansion
17766 failures are treated as configuration errors.
17768 Unlike most options, &%headers_add%& can be specified multiple times
17769 for a router; all listed headers are added.
17771 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
17772 router that has the &%one_time%& option set.
17774 .cindex "duplicate addresses"
17775 .oindex "&%unseen%&"
17776 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17777 additions are deleted when the address is passed on to subsequent routers.
17778 For a &%redirect%& router, if a generated address is the same as the incoming
17779 address, this can lead to duplicate addresses with different header
17780 modifications. Exim does not do duplicate deliveries (except, in certain
17781 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
17782 which of the duplicates is discarded, so this ambiguous situation should be
17783 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
17787 .option headers_remove routers list&!! unset
17788 .cindex "header lines" "removing"
17789 .cindex "router" "removing header lines"
17790 This option specifies a list of text headers,
17791 colon-separated (by default, changeable in the usual way),
17792 that is associated with any addresses that are accepted by the router.
17793 Each item is separately expanded, at routing time. However, this
17794 option has no effect when an address is just being verified. The way in which
17795 the text is used to remove header lines at transport time is described in
17796 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
17797 the message is in the process of being transported. This means that references
17798 to header lines in string expansions in the transport's configuration still
17799 &"see"& the original header lines.
17801 The &%headers_remove%& option is expanded after &%errors_to%& and
17802 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
17803 the item has no effect. Other expansion failures are treated as configuration
17806 Unlike most options, &%headers_remove%& can be specified multiple times
17807 for a router; all listed headers are removed.
17809 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
17810 router that has the &%one_time%& option set.
17812 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17813 removal requests are deleted when the address is passed on to subsequent
17814 routers, and this can lead to problems with duplicates -- see the similar
17815 warning for &%headers_add%& above.
17817 &*Warning 3*&: Because of the separate expansion of the list items,
17818 items that contain a list separator must have it doubled.
17819 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
17823 .option ignore_target_hosts routers "host list&!!" unset
17824 .cindex "IP address" "discarding"
17825 .cindex "router" "discarding IP addresses"
17826 Although this option is a host list, it should normally contain IP address
17827 entries rather than names. If any host that is looked up by the router has an
17828 IP address that matches an item in this list, Exim behaves as if that IP
17829 address did not exist. This option allows you to cope with rogue DNS entries
17832 remote.domain.example. A 127.0.0.1
17836 ignore_target_hosts = 127.0.0.1
17838 on the relevant router. If all the hosts found by a &(dnslookup)& router are
17839 discarded in this way, the router declines. In a conventional configuration, an
17840 attempt to mail to such a domain would normally provoke the &"unrouteable
17841 domain"& error, and an attempt to verify an address in the domain would fail.
17842 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
17843 router declines if presented with one of the listed addresses.
17845 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
17846 means of the first or the second of the following settings, respectively:
17848 ignore_target_hosts = 0.0.0.0/0
17849 ignore_target_hosts = <; 0::0/0
17851 The pattern in the first line matches all IPv4 addresses, whereas the pattern
17852 in the second line matches all IPv6 addresses.
17854 This option may also be useful for ignoring link-local and site-local IPv6
17855 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
17856 is expanded before use as a list, it is possible to make it dependent on the
17857 domain that is being routed.
17859 .vindex "&$host_address$&"
17860 During its expansion, &$host_address$& is set to the IP address that is being
17863 .option initgroups routers boolean false
17864 .cindex "additional groups"
17865 .cindex "groups" "additional"
17866 .cindex "local transports" "uid and gid"
17867 .cindex "transport" "local"
17868 If the router queues an address for a transport, and this option is true, and
17869 the uid supplied by the router is not overridden by the transport, the
17870 &[initgroups()]& function is called when running the transport to ensure that
17871 any additional groups associated with the uid are set up. See also &%group%&
17872 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
17876 .option local_part_prefix routers&!? "string list" unset
17877 .cindex "router" "prefix for local part"
17878 .cindex "prefix" "for local part, used in router"
17879 If this option is set, the router is skipped unless the local part starts with
17880 one of the given strings, or &%local_part_prefix_optional%& is true. See
17881 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
17884 The list is scanned from left to right, and the first prefix that matches is
17885 used. A limited form of wildcard is available; if the prefix begins with an
17886 asterisk, it matches the longest possible sequence of arbitrary characters at
17887 the start of the local part. An asterisk should therefore always be followed by
17888 some character that does not occur in normal local parts.
17889 .cindex "multiple mailboxes"
17890 .cindex "mailbox" "multiple"
17891 Wildcarding can be used to set up multiple user mailboxes, as described in
17892 section &<<SECTmulbox>>&.
17894 .vindex "&$local_part$&"
17895 .vindex "&$local_part_prefix$&"
17896 During the testing of the &%local_parts%& option, and while the router is
17897 running, the prefix is removed from the local part, and is available in the
17898 expansion variable &$local_part_prefix$&. When a message is being delivered, if
17899 the router accepts the address, this remains true during subsequent delivery by
17900 a transport. In particular, the local part that is transmitted in the RCPT
17901 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
17902 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
17903 the relevant transport.
17905 When an address is being verified, &%local_part_prefix%& affects only the
17906 behaviour of the router. If the callout feature of verification is in use, this
17907 means that the full address, including the prefix, will be used during the
17910 The prefix facility is commonly used to handle local parts of the form
17911 &%owner-something%&. Another common use is to support local parts of the form
17912 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
17913 to tell a user their forwarding is broken &-- by placing a router like this one
17914 immediately before the router that handles &_.forward_& files:
17918 local_part_prefix = real-
17920 transport = local_delivery
17922 For security, it would probably be a good idea to restrict the use of this
17923 router to locally-generated messages, using a condition such as this:
17925 condition = ${if match {$sender_host_address}\
17926 {\N^(|127\.0\.0\.1)$\N}}
17929 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
17930 both conditions must be met if not optional. Care must be taken if wildcards
17931 are used in both a prefix and a suffix on the same router. Different
17932 separator characters must be used to avoid ambiguity.
17935 .option local_part_prefix_optional routers boolean false
17936 See &%local_part_prefix%& above.
17940 .option local_part_suffix routers&!? "string list" unset
17941 .cindex "router" "suffix for local part"
17942 .cindex "suffix for local part" "used in router"
17943 This option operates in the same way as &%local_part_prefix%&, except that the
17944 local part must end (rather than start) with the given string, the
17945 &%local_part_suffix_optional%& option determines whether the suffix is
17946 mandatory, and the wildcard * character, if present, must be the last
17947 character of the suffix. This option facility is commonly used to handle local
17948 parts of the form &%something-request%& and multiple user mailboxes of the form
17952 .option local_part_suffix_optional routers boolean false
17953 See &%local_part_suffix%& above.
17957 .option local_parts routers&!? "local part list&!!" unset
17958 .cindex "router" "restricting to specific local parts"
17959 .cindex "local part" "checking in router"
17960 The router is run only if the local part of the address matches the list.
17961 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17963 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
17964 string is expanded, it is possible to make it depend on the domain, for
17967 local_parts = dbm;/usr/local/specials/$domain
17969 .vindex "&$local_part_data$&"
17970 If the match is achieved by a lookup, the data that the lookup returned
17971 for the local part is placed in the variable &$local_part_data$& for use in
17972 expansions of the router's private options. You might use this option, for
17973 example, if you have a large number of local virtual domains, and you want to
17974 send all postmaster mail to the same place without having to set up an alias in
17975 each virtual domain:
17979 local_parts = postmaster
17980 data = postmaster@real.domain.example
17984 .option log_as_local routers boolean "see below"
17985 .cindex "log" "delivery line"
17986 .cindex "delivery" "log line format"
17987 Exim has two logging styles for delivery, the idea being to make local
17988 deliveries stand out more visibly from remote ones. In the &"local"& style, the
17989 recipient address is given just as the local part, without a domain. The use of
17990 this style is controlled by this option. It defaults to true for the &(accept)&
17991 router, and false for all the others. This option applies only when a
17992 router assigns an address to a transport. It has no effect on routers that
17993 redirect addresses.
17997 .option more routers boolean&!! true
17998 The result of string expansion for this option must be a valid boolean value,
17999 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18000 result causes an error, and delivery is deferred. If the expansion is forced to
18001 fail, the default value for the option (true) is used. Other failures cause
18002 delivery to be deferred.
18004 If this option is set false, and the router declines to handle the address, no
18005 further routers are tried, routing fails, and the address is bounced.
18007 However, if the router explicitly passes an address to the following router by
18008 means of the setting
18012 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
18013 does not affect the behaviour if one of the precondition tests fails. In that
18014 case, the address is always passed to the next router.
18016 Note that &%address_data%& is not considered to be a precondition. If its
18017 expansion is forced to fail, the router declines, and the value of &%more%&
18018 controls what happens next.
18021 .option pass_on_timeout routers boolean false
18022 .cindex "timeout" "of router"
18023 .cindex "router" "timeout"
18024 If a router times out during a host lookup, it normally causes deferral of the
18025 address. If &%pass_on_timeout%& is set, the address is passed on to the next
18026 router, overriding &%no_more%&. This may be helpful for systems that are
18027 intermittently connected to the Internet, or those that want to pass to a smart
18028 host any messages that cannot immediately be delivered.
18030 There are occasional other temporary errors that can occur while doing DNS
18031 lookups. They are treated in the same way as a timeout, and this option
18032 applies to all of them.
18036 .option pass_router routers string unset
18037 .cindex "router" "go to after &""pass""&"
18038 Routers that recognize the generic &%self%& option (&(dnslookup)&,
18039 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
18040 routing to continue, and overriding a false setting of &%more%&. When one of
18041 these routers returns &"pass"&, the address is normally handed on to the next
18042 router in sequence. This can be changed by setting &%pass_router%& to the name
18043 of another router. However (unlike &%redirect_router%&) the named router must
18044 be below the current router, to avoid loops. Note that this option applies only
18045 to the special case of &"pass"&. It does not apply when a router returns
18046 &"decline"& because it cannot handle an address.
18050 .option redirect_router routers string unset
18051 .cindex "router" "start at after redirection"
18052 Sometimes an administrator knows that it is pointless to reprocess addresses
18053 generated from alias or forward files with the same router again. For
18054 example, if an alias file translates real names into login ids there is no
18055 point searching the alias file a second time, especially if it is a large file.
18057 The &%redirect_router%& option can be set to the name of any router instance.
18058 It causes the routing of any generated addresses to start at the named router
18059 instead of at the first router. This option has no effect if the router in
18060 which it is set does not generate new addresses.
18064 .option require_files routers&!? "string list&!!" unset
18065 .cindex "file" "requiring for router"
18066 .cindex "router" "requiring file existence"
18067 This option provides a general mechanism for predicating the running of a
18068 router on the existence or non-existence of certain files or directories.
18069 Before running a router, as one of its precondition tests, Exim works its way
18070 through the &%require_files%& list, expanding each item separately.
18072 Because the list is split before expansion, any colons in expansion items must
18073 be doubled, or the facility for using a different list separator must be used.
18074 If any expansion is forced to fail, the item is ignored. Other expansion
18075 failures cause routing of the address to be deferred.
18077 If any expanded string is empty, it is ignored. Otherwise, except as described
18078 below, each string must be a fully qualified file path, optionally preceded by
18079 &"!"&. The paths are passed to the &[stat()]& function to test for the
18080 existence of the files or directories. The router is skipped if any paths not
18081 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
18084 If &[stat()]& cannot determine whether a file exists or not, delivery of
18085 the message is deferred. This can happen when NFS-mounted filesystems are
18088 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
18089 options, so you cannot use it to check for the existence of a file in which to
18090 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
18091 full list of the order in which preconditions are evaluated.) However, as
18092 these options are all expanded, you can use the &%exists%& expansion condition
18093 to make such tests. The &%require_files%& option is intended for checking files
18094 that the router may be going to use internally, or which are needed by a
18095 transport (for example &_.procmailrc_&).
18097 During delivery, the &[stat()]& function is run as root, but there is a
18098 facility for some checking of the accessibility of a file by another user.
18099 This is not a proper permissions check, but just a &"rough"& check that
18100 operates as follows:
18102 If an item in a &%require_files%& list does not contain any forward slash
18103 characters, it is taken to be the user (and optional group, separated by a
18104 comma) to be checked for subsequent files in the list. If no group is specified
18105 but the user is specified symbolically, the gid associated with the uid is
18108 require_files = mail:/some/file
18109 require_files = $local_part:$home/.procmailrc
18111 If a user or group name in a &%require_files%& list does not exist, the
18112 &%require_files%& condition fails.
18114 Exim performs the check by scanning along the components of the file path, and
18115 checking the access for the given uid and gid. It checks for &"x"& access on
18116 directories, and &"r"& access on the final file. Note that this means that file
18117 access control lists, if the operating system has them, are ignored.
18119 &*Warning 1*&: When the router is being run to verify addresses for an
18120 incoming SMTP message, Exim is not running as root, but under its own uid. This
18121 may affect the result of a &%require_files%& check. In particular, &[stat()]&
18122 may yield the error EACCES (&"Permission denied"&). This means that the Exim
18123 user is not permitted to read one of the directories on the file's path.
18125 &*Warning 2*&: Even when Exim is running as root while delivering a message,
18126 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
18127 without root access. In this case, if a check for access by a particular user
18128 is requested, Exim creates a subprocess that runs as that user, and tries the
18129 check again in that process.
18131 The default action for handling an unresolved EACCES is to consider it to
18132 be caused by a configuration error, and routing is deferred because the
18133 existence or non-existence of the file cannot be determined. However, in some
18134 circumstances it may be desirable to treat this condition as if the file did
18135 not exist. If the file name (or the exclamation mark that precedes the file
18136 name for non-existence) is preceded by a plus sign, the EACCES error is treated
18137 as if the file did not exist. For example:
18139 require_files = +/some/file
18141 If the router is not an essential part of verification (for example, it
18142 handles users' &_.forward_& files), another solution is to set the &%verify%&
18143 option false so that the router is skipped when verifying.
18147 .option retry_use_local_part routers boolean "see below"
18148 .cindex "hints database" "retry keys"
18149 .cindex "local part" "in retry keys"
18150 When a delivery suffers a temporary routing failure, a retry record is created
18151 in Exim's hints database. For addresses whose routing depends only on the
18152 domain, the key for the retry record should not involve the local part, but for
18153 other addresses, both the domain and the local part should be included.
18154 Usually, remote routing is of the former kind, and local routing is of the
18157 This option controls whether the local part is used to form the key for retry
18158 hints for addresses that suffer temporary errors while being handled by this
18159 router. The default value is true for any router that has &%check_local_user%&
18160 set, and false otherwise. Note that this option does not apply to hints keys
18161 for transport delays; they are controlled by a generic transport option of the
18164 The setting of &%retry_use_local_part%& applies only to the router on which it
18165 appears. If the router generates child addresses, they are routed
18166 independently; this setting does not become attached to them.
18170 .option router_home_directory routers string&!! unset
18171 .cindex "router" "home directory for"
18172 .cindex "home directory" "for router"
18174 This option sets a home directory for use while the router is running. (Compare
18175 &%transport_home_directory%&, which sets a home directory for later
18176 transporting.) In particular, if used on a &(redirect)& router, this option
18177 sets a value for &$home$& while a filter is running. The value is expanded;
18178 forced expansion failure causes the option to be ignored &-- other failures
18179 cause the router to defer.
18181 Expansion of &%router_home_directory%& happens immediately after the
18182 &%check_local_user%& test (if configured), before any further expansions take
18184 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18186 While the router is running, &%router_home_directory%& overrides the value of
18187 &$home$& that came from &%check_local_user%&.
18189 When a router accepts an address and assigns it to a local transport (including
18190 the cases when a &(redirect)& router generates a pipe, file, or autoreply
18191 delivery), the home directory setting for the transport is taken from the first
18192 of these values that is set:
18195 The &%home_directory%& option on the transport;
18197 The &%transport_home_directory%& option on the router;
18199 The password data if &%check_local_user%& is set on the router;
18201 The &%router_home_directory%& option on the router.
18204 In other words, &%router_home_directory%& overrides the password data for the
18205 router, but not for the transport.
18209 .option self routers string freeze
18210 .cindex "MX record" "pointing to local host"
18211 .cindex "local host" "MX pointing to"
18212 This option applies to those routers that use a recipient address to find a
18213 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
18214 and &(manualroute)& routers.
18215 Certain configurations of the &(queryprogram)& router can also specify a list
18217 Usually such routers are configured to send the message to a remote host via an
18218 &(smtp)& transport. The &%self%& option specifies what happens when the first
18219 host on the list turns out to be the local host.
18220 The way in which Exim checks for the local host is described in section
18221 &<<SECTreclocipadd>>&.
18223 Normally this situation indicates either an error in Exim's configuration (for
18224 example, the router should be configured not to process this domain), or an
18225 error in the DNS (for example, the MX should not point to this host). For this
18226 reason, the default action is to log the incident, defer the address, and
18227 freeze the message. The following alternatives are provided for use in special
18232 Delivery of the message is tried again later, but the message is not frozen.
18234 .vitem "&%reroute%&: <&'domain'&>"
18235 The domain is changed to the given domain, and the address is passed back to
18236 be reprocessed by the routers. No rewriting of headers takes place. This
18237 behaviour is essentially a redirection.
18239 .vitem "&%reroute: rewrite:%& <&'domain'&>"
18240 The domain is changed to the given domain, and the address is passed back to be
18241 reprocessed by the routers. Any headers that contain the original domain are
18246 .vindex "&$self_hostname$&"
18247 The router passes the address to the next router, or to the router named in the
18248 &%pass_router%& option if it is set. This overrides &%no_more%&. During
18249 subsequent routing and delivery, the variable &$self_hostname$& contains the
18250 name of the local host that the router encountered. This can be used to
18251 distinguish between different cases for hosts with multiple names. The
18257 ensures that only those addresses that routed to the local host are passed on.
18258 Without &%no_more%&, addresses that were declined for other reasons would also
18259 be passed to the next router.
18262 Delivery fails and an error report is generated.
18265 .cindex "local host" "sending to"
18266 The anomaly is ignored and the address is queued for the transport. This
18267 setting should be used with extreme caution. For an &(smtp)& transport, it
18268 makes sense only in cases where the program that is listening on the SMTP port
18269 is not this version of Exim. That is, it must be some other MTA, or Exim with a
18270 different configuration file that handles the domain in another way.
18275 .option senders routers&!? "address list&!!" unset
18276 .cindex "router" "checking senders"
18277 If this option is set, the router is skipped unless the message's sender
18278 address matches something on the list.
18279 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18282 There are issues concerning verification when the running of routers is
18283 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
18284 setting, it sets the sender to the null string. When using the &%-bt%& option
18285 to check a configuration file, it is necessary also to use the &%-f%& option to
18286 set an appropriate sender. For incoming mail, the sender is unset when
18287 verifying the sender, but is available when verifying any recipients. If the
18288 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
18292 .option translate_ip_address routers string&!! unset
18293 .cindex "IP address" "translating"
18294 .cindex "packet radio"
18295 .cindex "router" "IP address translation"
18296 There exist some rare networking situations (for example, packet radio) where
18297 it is helpful to be able to translate IP addresses generated by normal routing
18298 mechanisms into other IP addresses, thus performing a kind of manual IP
18299 routing. This should be done only if the normal IP routing of the TCP/IP stack
18300 is inadequate or broken. Because this is an extremely uncommon requirement, the
18301 code to support this option is not included in the Exim binary unless
18302 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
18304 .vindex "&$host_address$&"
18305 The &%translate_ip_address%& string is expanded for every IP address generated
18306 by the router, with the generated address set in &$host_address$&. If the
18307 expansion is forced to fail, no action is taken.
18308 For any other expansion error, delivery of the message is deferred.
18309 If the result of the expansion is an IP address, that replaces the original
18310 address; otherwise the result is assumed to be a host name &-- this is looked
18311 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
18312 produce one or more replacement IP addresses. For example, to subvert all IP
18313 addresses in some specific networks, this could be added to a router:
18315 translate_ip_address = \
18316 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
18319 The file would contain lines like
18321 10.2.3.128/26 some.host
18322 10.8.4.34/26 10.44.8.15
18324 You should not make use of this facility unless you really understand what you
18329 .option transport routers string&!! unset
18330 This option specifies the transport to be used when a router accepts an address
18331 and sets it up for delivery. A transport is never needed if a router is used
18332 only for verification. The value of the option is expanded at routing time,
18333 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
18334 and result must be the name of one of the configured transports. If it is not,
18335 delivery is deferred.
18337 The &%transport%& option is not used by the &(redirect)& router, but it does
18338 have some private options that set up transports for pipe and file deliveries
18339 (see chapter &<<CHAPredirect>>&).
18343 .option transport_current_directory routers string&!! unset
18344 .cindex "current directory for local transport"
18345 This option associates a current directory with any address that is routed
18346 to a local transport. This can happen either because a transport is
18347 explicitly configured for the router, or because it generates a delivery to a
18348 file or a pipe. During the delivery process (that is, at transport time), this
18349 option string is expanded and is set as the current directory, unless
18350 overridden by a setting on the transport.
18351 If the expansion fails for any reason, including forced failure, an error is
18352 logged, and delivery is deferred.
18353 See chapter &<<CHAPenvironment>>& for details of the local delivery
18359 .option transport_home_directory routers string&!! "see below"
18360 .cindex "home directory" "for local transport"
18361 This option associates a home directory with any address that is routed to a
18362 local transport. This can happen either because a transport is explicitly
18363 configured for the router, or because it generates a delivery to a file or a
18364 pipe. During the delivery process (that is, at transport time), the option
18365 string is expanded and is set as the home directory, unless overridden by a
18366 setting of &%home_directory%& on the transport.
18367 If the expansion fails for any reason, including forced failure, an error is
18368 logged, and delivery is deferred.
18370 If the transport does not specify a home directory, and
18371 &%transport_home_directory%& is not set for the router, the home directory for
18372 the transport is taken from the password data if &%check_local_user%& is set for
18373 the router. Otherwise it is taken from &%router_home_directory%& if that option
18374 is set; if not, no home directory is set for the transport.
18376 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18382 .option unseen routers boolean&!! false
18383 .cindex "router" "carrying on after success"
18384 The result of string expansion for this option must be a valid boolean value,
18385 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18386 result causes an error, and delivery is deferred. If the expansion is forced to
18387 fail, the default value for the option (false) is used. Other failures cause
18388 delivery to be deferred.
18390 When this option is set true, routing does not cease if the router accepts the
18391 address. Instead, a copy of the incoming address is passed to the next router,
18392 overriding a false setting of &%more%&. There is little point in setting
18393 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18394 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18395 sometimes true and sometimes false).
18397 .cindex "copy of message (&%unseen%& option)"
18398 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18399 qualifier in filter files. It can be used to cause copies of messages to be
18400 delivered to some other destination, while also carrying out a normal delivery.
18401 In effect, the current address is made into a &"parent"& that has two children
18402 &-- one that is delivered as specified by this router, and a clone that goes on
18403 to be routed further. For this reason, &%unseen%& may not be combined with the
18404 &%one_time%& option in a &(redirect)& router.
18406 &*Warning*&: Header lines added to the address (or specified for removal) by
18407 this router or by previous routers affect the &"unseen"& copy of the message
18408 only. The clone that continues to be processed by further routers starts with
18409 no added headers and none specified for removal. For a &%redirect%& router, if
18410 a generated address is the same as the incoming address, this can lead to
18411 duplicate addresses with different header modifications. Exim does not do
18412 duplicate deliveries (except, in certain circumstances, to pipes -- see section
18413 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
18414 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
18415 &%redirect%& router may be of help.
18417 Unlike the handling of header modifications, any data that was set by the
18418 &%address_data%& option in the current or previous routers &'is'& passed on to
18419 subsequent routers.
18422 .option user routers string&!! "see below"
18423 .cindex "uid (user id)" "local delivery"
18424 .cindex "local transports" "uid and gid"
18425 .cindex "transport" "local"
18426 .cindex "router" "user for filter processing"
18427 .cindex "filter" "user for processing"
18428 When a router queues an address for a transport, and the transport does not
18429 specify a user, the user given here is used when running the delivery process.
18430 The user may be specified numerically or by name. If expansion fails, the
18431 error is logged and delivery is deferred.
18432 This user is also used by the &(redirect)& router when running a filter file.
18433 The default is unset, except when &%check_local_user%& is set. In this case,
18434 the default is taken from the password information. If the user is specified as
18435 a name, and &%group%& is not set, the group associated with the user is used.
18436 See also &%initgroups%& and &%group%& and the discussion in chapter
18437 &<<CHAPenvironment>>&.
18441 .option verify routers&!? boolean true
18442 Setting this option has the effect of setting &%verify_sender%& and
18443 &%verify_recipient%& to the same value.
18446 .option verify_only routers&!? boolean false
18447 .cindex "EXPN" "with &%verify_only%&"
18449 .cindex "router" "used only when verifying"
18450 If this option is set, the router is used only when verifying an address,
18451 delivering in cutthrough mode or
18452 testing with the &%-bv%& option, not when actually doing a delivery, testing
18453 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
18454 restricted to verifying only senders or recipients by means of
18455 &%verify_sender%& and &%verify_recipient%&.
18457 &*Warning*&: When the router is being run to verify addresses for an incoming
18458 SMTP message, Exim is not running as root, but under its own uid. If the router
18459 accesses any files, you need to make sure that they are accessible to the Exim
18463 .option verify_recipient routers&!? boolean true
18464 If this option is false, the router is skipped when verifying recipient
18466 delivering in cutthrough mode
18467 or testing recipient verification using &%-bv%&.
18468 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18470 See also the &$verify_mode$& variable.
18473 .option verify_sender routers&!? boolean true
18474 If this option is false, the router is skipped when verifying sender addresses
18475 or testing sender verification using &%-bvs%&.
18476 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18478 See also the &$verify_mode$& variable.
18479 .ecindex IIDgenoprou1
18480 .ecindex IIDgenoprou2
18487 . ////////////////////////////////////////////////////////////////////////////
18488 . ////////////////////////////////////////////////////////////////////////////
18490 .chapter "The accept router" "CHID4"
18491 .cindex "&(accept)& router"
18492 .cindex "routers" "&(accept)&"
18493 The &(accept)& router has no private options of its own. Unless it is being
18494 used purely for verification (see &%verify_only%&) a transport is required to
18495 be defined by the generic &%transport%& option. If the preconditions that are
18496 specified by generic options are met, the router accepts the address and queues
18497 it for the given transport. The most common use of this router is for setting
18498 up deliveries to local mailboxes. For example:
18502 domains = mydomain.example
18504 transport = local_delivery
18506 The &%domains%& condition in this example checks the domain of the address, and
18507 &%check_local_user%& checks that the local part is the login of a local user.
18508 When both preconditions are met, the &(accept)& router runs, and queues the
18509 address for the &(local_delivery)& transport.
18516 . ////////////////////////////////////////////////////////////////////////////
18517 . ////////////////////////////////////////////////////////////////////////////
18519 .chapter "The dnslookup router" "CHAPdnslookup"
18520 .scindex IIDdnsrou1 "&(dnslookup)& router"
18521 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
18522 The &(dnslookup)& router looks up the hosts that handle mail for the
18523 recipient's domain in the DNS. A transport must always be set for this router,
18524 unless &%verify_only%& is set.
18526 If SRV support is configured (see &%check_srv%& below), Exim first searches for
18527 SRV records. If none are found, or if SRV support is not configured,
18528 MX records are looked up. If no MX records exist, address records are sought.
18529 However, &%mx_domains%& can be set to disable the direct use of address
18532 MX records of equal priority are sorted by Exim into a random order. Exim then
18533 looks for address records for the host names obtained from MX or SRV records.
18534 When a host has more than one IP address, they are sorted into a random order,
18535 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
18536 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
18537 generic option, the router declines.
18539 Unless they have the highest priority (lowest MX value), MX records that point
18540 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
18541 are discarded, together with any other MX records of equal or lower priority.
18543 .cindex "MX record" "pointing to local host"
18544 .cindex "local host" "MX pointing to"
18545 .oindex "&%self%&" "in &(dnslookup)& router"
18546 If the host pointed to by the highest priority MX record, or looked up as an
18547 address record, is the local host, or matches &%hosts_treat_as_local%&, what
18548 happens is controlled by the generic &%self%& option.
18551 .section "Problems with DNS lookups" "SECTprowitdnsloo"
18552 There have been problems with DNS servers when SRV records are looked up.
18553 Some misbehaving servers return a DNS error or timeout when a non-existent
18554 SRV record is sought. Similar problems have in the past been reported for
18555 MX records. The global &%dns_again_means_nonexist%& option can help with this
18556 problem, but it is heavy-handed because it is a global option.
18558 For this reason, there are two options, &%srv_fail_domains%& and
18559 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
18560 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
18561 an attempt to look up an SRV or MX record causes one of these results, and the
18562 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
18563 such record"&. In the case of an SRV lookup, this means that the router
18564 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
18565 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
18566 case routing fails.
18569 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
18570 .cindex "&(dnslookup)& router" "declines"
18571 There are a few cases where a &(dnslookup)& router will decline to accept
18572 an address; if such a router is expected to handle "all remaining non-local
18573 domains", then it is important to set &%no_more%&.
18575 The router will defer rather than decline if the domain
18576 is found in the &%fail_defer_domains%& router option.
18578 Reasons for a &(dnslookup)& router to decline currently include:
18580 The domain does not exist in DNS
18582 The domain exists but the MX record's host part is just "."; this is a common
18583 convention (borrowed from SRV) used to indicate that there is no such service
18584 for this domain and to not fall back to trying A/AAAA records.
18586 Ditto, but for SRV records, when &%check_srv%& is set on this router.
18588 MX record points to a non-existent host.
18590 MX record points to an IP address and the main section option
18591 &%allow_mx_to_ip%& is not set.
18593 MX records exist and point to valid hosts, but all hosts resolve only to
18594 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
18596 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
18597 &%dns_check_names_pattern%& for handling one variant of this)
18599 &%check_secondary_mx%& is set on this router but the local host can
18600 not be found in the MX records (see below)
18606 .section "Private options for dnslookup" "SECID118"
18607 .cindex "options" "&(dnslookup)& router"
18608 The private options for the &(dnslookup)& router are as follows:
18610 .option check_secondary_mx dnslookup boolean false
18611 .cindex "MX record" "checking for secondary"
18612 If this option is set, the router declines unless the local host is found in
18613 (and removed from) the list of hosts obtained by MX lookup. This can be used to
18614 process domains for which the local host is a secondary mail exchanger
18615 differently to other domains. The way in which Exim decides whether a host is
18616 the local host is described in section &<<SECTreclocipadd>>&.
18619 .option check_srv dnslookup string&!! unset
18620 .cindex "SRV record" "enabling use of"
18621 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
18622 addition to MX and address records. The support is disabled by default. To
18623 enable SRV support, set the &%check_srv%& option to the name of the service
18624 required. For example,
18628 looks for SRV records that refer to the normal smtp service. The option is
18629 expanded, so the service name can vary from message to message or address
18630 to address. This might be helpful if SRV records are being used for a
18631 submission service. If the expansion is forced to fail, the &%check_srv%&
18632 option is ignored, and the router proceeds to look for MX records in the
18635 When the expansion succeeds, the router searches first for SRV records for
18636 the given service (it assumes TCP protocol). A single SRV record with a
18637 host name that consists of just a single dot indicates &"no such service for
18638 this domain"&; if this is encountered, the router declines. If other kinds of
18639 SRV record are found, they are used to construct a host list for delivery
18640 according to the rules of RFC 2782. MX records are not sought in this case.
18642 When no SRV records are found, MX records (and address records) are sought in
18643 the traditional way. In other words, SRV records take precedence over MX
18644 records, just as MX records take precedence over address records. Note that
18645 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
18646 defined it. It is apparently believed that MX records are sufficient for email
18647 and that SRV records should not be used for this purpose. However, SRV records
18648 have an additional &"weight"& feature which some people might find useful when
18649 trying to split an SMTP load between hosts of different power.
18651 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
18652 when there is a DNS lookup error.
18657 .option fail_defer_domains dnslookup "domain list&!!" unset
18658 .cindex "MX record" "not found"
18659 DNS lookups for domains matching &%fail_defer_domains%&
18660 which find no matching record will cause the router to defer
18661 rather than the default behaviour of decline.
18662 This maybe be useful for queueing messages for a newly created
18663 domain while the DNS configuration is not ready.
18664 However, it will result in any message with mistyped domains
18668 .option mx_domains dnslookup "domain list&!!" unset
18669 .cindex "MX record" "required to exist"
18670 .cindex "SRV record" "required to exist"
18671 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
18672 record in order to be recognized. (The name of this option could be improved.)
18673 For example, if all the mail hosts in &'fict.example'& are known to have MX
18674 records, except for those in &'discworld.fict.example'&, you could use this
18677 mx_domains = ! *.discworld.fict.example : *.fict.example
18679 This specifies that messages addressed to a domain that matches the list but
18680 has no MX record should be bounced immediately instead of being routed using
18681 the address record.
18684 .option mx_fail_domains dnslookup "domain list&!!" unset
18685 If the DNS lookup for MX records for one of the domains in this list causes a
18686 DNS lookup error, Exim behaves as if no MX records were found. See section
18687 &<<SECTprowitdnsloo>>& for more discussion.
18692 .option qualify_single dnslookup boolean true
18693 .cindex "DNS" "resolver options"
18694 .cindex "DNS" "qualifying single-component names"
18695 When this option is true, the resolver option RES_DEFNAMES is set for DNS
18696 lookups. Typically, but not standardly, this causes the resolver to qualify
18697 single-component names with the default domain. For example, on a machine
18698 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
18699 &'thesaurus.ref.example'& inside the resolver. For details of what your
18700 resolver actually does, consult your man pages for &'resolver'& and
18705 .option rewrite_headers dnslookup boolean true
18706 .cindex "rewriting" "header lines"
18707 .cindex "header lines" "rewriting"
18708 If the domain name in the address that is being processed is not fully
18709 qualified, it may be expanded to its full form by a DNS lookup. For example, if
18710 an address is specified as &'dormouse@teaparty'&, the domain might be
18711 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
18712 occur as a result of setting the &%widen_domains%& option. If
18713 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
18714 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
18715 header lines of the message are rewritten with the full domain name.
18717 This option should be turned off only when it is known that no message is
18718 ever going to be sent outside an environment where the abbreviation makes
18721 When an MX record is looked up in the DNS and matches a wildcard record, name
18722 servers normally return a record containing the name that has been looked up,
18723 making it impossible to detect whether a wildcard was present or not. However,
18724 some name servers have recently been seen to return the wildcard entry. If the
18725 name returned by a DNS lookup begins with an asterisk, it is not used for
18729 .option same_domain_copy_routing dnslookup boolean false
18730 .cindex "address" "copying routing"
18731 Addresses with the same domain are normally routed by the &(dnslookup)& router
18732 to the same list of hosts. However, this cannot be presumed, because the router
18733 options and preconditions may refer to the local part of the address. By
18734 default, therefore, Exim routes each address in a message independently. DNS
18735 servers run caches, so repeated DNS lookups are not normally expensive, and in
18736 any case, personal messages rarely have more than a few recipients.
18738 If you are running mailing lists with large numbers of subscribers at the same
18739 domain, and you are using a &(dnslookup)& router which is independent of the
18740 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18741 lookups for identical domains in one message. In this case, when &(dnslookup)&
18742 routes an address to a remote transport, any other unrouted addresses in the
18743 message that have the same domain are automatically given the same routing
18744 without processing them independently,
18745 provided the following conditions are met:
18748 No router that processed the address specified &%headers_add%& or
18749 &%headers_remove%&.
18751 The router did not change the address in any way, for example, by &"widening"&
18758 .option search_parents dnslookup boolean false
18759 .cindex "DNS" "resolver options"
18760 When this option is true, the resolver option RES_DNSRCH is set for DNS
18761 lookups. This is different from the &%qualify_single%& option in that it
18762 applies to domains containing dots. Typically, but not standardly, it causes
18763 the resolver to search for the name in the current domain and in parent
18764 domains. For example, on a machine in the &'fict.example'& domain, if looking
18765 up &'teaparty.wonderland'& failed, the resolver would try
18766 &'teaparty.wonderland.fict.example'&. For details of what your resolver
18767 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
18769 Setting this option true can cause problems in domains that have a wildcard MX
18770 record, because any domain that does not have its own MX record matches the
18775 .option srv_fail_domains dnslookup "domain list&!!" unset
18776 If the DNS lookup for SRV records for one of the domains in this list causes a
18777 DNS lookup error, Exim behaves as if no SRV records were found. See section
18778 &<<SECTprowitdnsloo>>& for more discussion.
18783 .option widen_domains dnslookup "string list" unset
18784 .cindex "domain" "partial; widening"
18785 If a DNS lookup fails and this option is set, each of its strings in turn is
18786 added onto the end of the domain, and the lookup is tried again. For example,
18789 widen_domains = fict.example:ref.example
18791 is set and a lookup of &'klingon.dictionary'& fails,
18792 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
18793 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
18794 and &%search_parents%& options can cause some widening to be undertaken inside
18795 the DNS resolver. &%widen_domains%& is not applied to sender addresses
18796 when verifying, unless &%rewrite_headers%& is false (not the default).
18799 .section "Effect of qualify_single and search_parents" "SECID119"
18800 When a domain from an envelope recipient is changed by the resolver as a result
18801 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
18802 corresponding address in the message's header lines unless &%rewrite_headers%&
18803 is set false. Exim then re-routes the address, using the full domain.
18805 These two options affect only the DNS lookup that takes place inside the router
18806 for the domain of the address that is being routed. They do not affect lookups
18807 such as that implied by
18811 that may happen while processing a router precondition before the router is
18812 entered. No widening ever takes place for these lookups.
18813 .ecindex IIDdnsrou1
18814 .ecindex IIDdnsrou2
18824 . ////////////////////////////////////////////////////////////////////////////
18825 . ////////////////////////////////////////////////////////////////////////////
18827 .chapter "The ipliteral router" "CHID5"
18828 .cindex "&(ipliteral)& router"
18829 .cindex "domain literal" "routing"
18830 .cindex "routers" "&(ipliteral)&"
18831 This router has no private options. Unless it is being used purely for
18832 verification (see &%verify_only%&) a transport is required to be defined by the
18833 generic &%transport%& option. The router accepts the address if its domain part
18834 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
18835 router handles the address
18839 by setting up delivery to the host with that IP address. IPv4 domain literals
18840 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
18841 are similar, but the address is preceded by &`ipv6:`&. For example:
18843 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
18845 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
18846 grounds that sooner or later somebody will try it.
18848 .oindex "&%self%&" "in &(ipliteral)& router"
18849 If the IP address matches something in &%ignore_target_hosts%&, the router
18850 declines. If an IP literal turns out to refer to the local host, the generic
18851 &%self%& option determines what happens.
18853 The RFCs require support for domain literals; however, their use is
18854 controversial in today's Internet. If you want to use this router, you must
18855 also set the main configuration option &%allow_domain_literals%&. Otherwise,
18856 Exim will not recognize the domain literal syntax in addresses.
18860 . ////////////////////////////////////////////////////////////////////////////
18861 . ////////////////////////////////////////////////////////////////////////////
18863 .chapter "The iplookup router" "CHID6"
18864 .cindex "&(iplookup)& router"
18865 .cindex "routers" "&(iplookup)&"
18866 The &(iplookup)& router was written to fulfil a specific requirement in
18867 Cambridge University (which in fact no longer exists). For this reason, it is
18868 not included in the binary of Exim by default. If you want to include it, you
18871 ROUTER_IPLOOKUP=yes
18873 in your &_Local/Makefile_& configuration file.
18875 The &(iplookup)& router routes an address by sending it over a TCP or UDP
18876 connection to one or more specific hosts. The host can then return the same or
18877 a different address &-- in effect rewriting the recipient address in the
18878 message's envelope. The new address is then passed on to subsequent routers. If
18879 this process fails, the address can be passed on to other routers, or delivery
18880 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
18881 must not be specified for it.
18883 .cindex "options" "&(iplookup)& router"
18884 .option hosts iplookup string unset
18885 This option must be supplied. Its value is a colon-separated list of host
18886 names. The hosts are looked up using &[gethostbyname()]&
18887 (or &[getipnodebyname()]& when available)
18888 and are tried in order until one responds to the query. If none respond, what
18889 happens is controlled by &%optional%&.
18892 .option optional iplookup boolean false
18893 If &%optional%& is true, if no response is obtained from any host, the address
18894 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
18895 delivery to the address is deferred.
18898 .option port iplookup integer 0
18899 .cindex "port" "&(iplookup)& router"
18900 This option must be supplied. It specifies the port number for the TCP or UDP
18904 .option protocol iplookup string udp
18905 This option can be set to &"udp"& or &"tcp"& to specify which of the two
18906 protocols is to be used.
18909 .option query iplookup string&!! "see below"
18910 This defines the content of the query that is sent to the remote hosts. The
18913 $local_part@$domain $local_part@$domain
18915 The repetition serves as a way of checking that a response is to the correct
18916 query in the default case (see &%response_pattern%& below).
18919 .option reroute iplookup string&!! unset
18920 If this option is not set, the rerouted address is precisely the byte string
18921 returned by the remote host, up to the first white space, if any. If set, the
18922 string is expanded to form the rerouted address. It can include parts matched
18923 in the response by &%response_pattern%& by means of numeric variables such as
18924 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
18925 whether or not a pattern is in use. In all cases, the rerouted address must end
18926 up in the form &'local_part@domain'&.
18929 .option response_pattern iplookup string unset
18930 This option can be set to a regular expression that is applied to the string
18931 returned from the remote host. If the pattern does not match the response, the
18932 router declines. If &%response_pattern%& is not set, no checking of the
18933 response is done, unless the query was defaulted, in which case there is a
18934 check that the text returned after the first white space is the original
18935 address. This checks that the answer that has been received is in response to
18936 the correct question. For example, if the response is just a new domain, the
18937 following could be used:
18939 response_pattern = ^([^@]+)$
18940 reroute = $local_part@$1
18943 .option timeout iplookup time 5s
18944 This specifies the amount of time to wait for a response from the remote
18945 machine. The same timeout is used for the &[connect()]& function for a TCP
18946 call. It does not apply to UDP.
18951 . ////////////////////////////////////////////////////////////////////////////
18952 . ////////////////////////////////////////////////////////////////////////////
18954 .chapter "The manualroute router" "CHID7"
18955 .scindex IIDmanrou1 "&(manualroute)& router"
18956 .scindex IIDmanrou2 "routers" "&(manualroute)&"
18957 .cindex "domain" "manually routing"
18958 The &(manualroute)& router is so-called because it provides a way of manually
18959 routing an address according to its domain. It is mainly used when you want to
18960 route addresses to remote hosts according to your own rules, bypassing the
18961 normal DNS routing that looks up MX records. However, &(manualroute)& can also
18962 route to local transports, a facility that may be useful if you want to save
18963 messages for dial-in hosts in local files.
18965 The &(manualroute)& router compares a list of domain patterns with the domain
18966 it is trying to route. If there is no match, the router declines. Each pattern
18967 has associated with it a list of hosts and some other optional data, which may
18968 include a transport. The combination of a pattern and its data is called a
18969 &"routing rule"&. For patterns that do not have an associated transport, the
18970 generic &%transport%& option must specify a transport, unless the router is
18971 being used purely for verification (see &%verify_only%&).
18974 In the case of verification, matching the domain pattern is sufficient for the
18975 router to accept the address. When actually routing an address for delivery,
18976 an address that matches a domain pattern is queued for the associated
18977 transport. If the transport is not a local one, a host list must be associated
18978 with the pattern; IP addresses are looked up for the hosts, and these are
18979 passed to the transport along with the mail address. For local transports, a
18980 host list is optional. If it is present, it is passed in &$host$& as a single
18983 The list of routing rules can be provided as an inline string in
18984 &%route_list%&, or the data can be obtained by looking up the domain in a file
18985 or database by setting &%route_data%&. Only one of these settings may appear in
18986 any one instance of &(manualroute)&. The format of routing rules is described
18987 below, following the list of private options.
18990 .section "Private options for manualroute" "SECTprioptman"
18992 .cindex "options" "&(manualroute)& router"
18993 The private options for the &(manualroute)& router are as follows:
18995 .option host_all_ignored manualroute string defer
18996 See &%host_find_failed%&.
18998 .option host_find_failed manualroute string freeze
18999 This option controls what happens when &(manualroute)& tries to find an IP
19000 address for a host, and the host does not exist. The option can be set to one
19001 of the following values:
19010 The default (&"freeze"&) assumes that this state is a serious configuration
19011 error. The difference between &"pass"& and &"decline"& is that the former
19012 forces the address to be passed to the next router (or the router defined by
19015 overriding &%no_more%&, whereas the latter passes the address to the next
19016 router only if &%more%& is true.
19018 The value &"ignore"& causes Exim to completely ignore a host whose IP address
19019 cannot be found. If all the hosts in the list are ignored, the behaviour is
19020 controlled by the &%host_all_ignored%& option. This takes the same values
19021 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
19023 The &%host_find_failed%& option applies only to a definite &"does not exist"&
19024 state; if a host lookup gets a temporary error, delivery is deferred unless the
19025 generic &%pass_on_timeout%& option is set.
19028 .option hosts_randomize manualroute boolean false
19029 .cindex "randomized host list"
19030 .cindex "host" "list of; randomized"
19031 If this option is set, the order of the items in a host list in a routing rule
19032 is randomized each time the list is used, unless an option in the routing rule
19033 overrides (see below). Randomizing the order of a host list can be used to do
19034 crude load sharing. However, if more than one mail address is routed by the
19035 same router to the same host list, the host lists are considered to be the same
19036 (even though they may be randomized into different orders) for the purpose of
19037 deciding whether to batch the deliveries into a single SMTP transaction.
19039 When &%hosts_randomize%& is true, a host list may be split
19040 into groups whose order is separately randomized. This makes it possible to
19041 set up MX-like behaviour. The boundaries between groups are indicated by an
19042 item that is just &`+`& in the host list. For example:
19044 route_list = * host1:host2:host3:+:host4:host5
19046 The order of the first three hosts and the order of the last two hosts is
19047 randomized for each use, but the first three always end up before the last two.
19048 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
19049 randomized host list is passed to an &(smtp)& transport that also has
19050 &%hosts_randomize set%&, the list is not re-randomized.
19053 .option route_data manualroute string&!! unset
19054 If this option is set, it must expand to yield the data part of a routing rule.
19055 Typically, the expansion string includes a lookup based on the domain. For
19058 route_data = ${lookup{$domain}dbm{/etc/routes}}
19060 If the expansion is forced to fail, or the result is an empty string, the
19061 router declines. Other kinds of expansion failure cause delivery to be
19065 .option route_list manualroute "string list" unset
19066 This string is a list of routing rules, in the form defined below. Note that,
19067 unlike most string lists, the items are separated by semicolons. This is so
19068 that they may contain colon-separated host lists.
19071 .option same_domain_copy_routing manualroute boolean false
19072 .cindex "address" "copying routing"
19073 Addresses with the same domain are normally routed by the &(manualroute)&
19074 router to the same list of hosts. However, this cannot be presumed, because the
19075 router options and preconditions may refer to the local part of the address. By
19076 default, therefore, Exim routes each address in a message independently. DNS
19077 servers run caches, so repeated DNS lookups are not normally expensive, and in
19078 any case, personal messages rarely have more than a few recipients.
19080 If you are running mailing lists with large numbers of subscribers at the same
19081 domain, and you are using a &(manualroute)& router which is independent of the
19082 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19083 lookups for identical domains in one message. In this case, when
19084 &(manualroute)& routes an address to a remote transport, any other unrouted
19085 addresses in the message that have the same domain are automatically given the
19086 same routing without processing them independently. However, this is only done
19087 if &%headers_add%& and &%headers_remove%& are unset.
19092 .section "Routing rules in route_list" "SECID120"
19093 The value of &%route_list%& is a string consisting of a sequence of routing
19094 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
19095 entered as two semicolons. Alternatively, the list separator can be changed as
19096 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
19097 Empty rules are ignored. The format of each rule is
19099 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
19101 The following example contains two rules, each with a simple domain pattern and
19105 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
19106 thes.ref.example mail-3.ref.example:mail-4.ref.example
19108 The three parts of a rule are separated by white space. The pattern and the
19109 list of hosts can be enclosed in quotes if necessary, and if they are, the
19110 usual quoting rules apply. Each rule in a &%route_list%& must start with a
19111 single domain pattern, which is the only mandatory item in the rule. The
19112 pattern is in the same format as one item in a domain list (see section
19113 &<<SECTdomainlist>>&),
19114 except that it may not be the name of an interpolated file.
19115 That is, it may be wildcarded, or a regular expression, or a file or database
19116 lookup (with semicolons doubled, because of the use of semicolon as a separator
19117 in a &%route_list%&).
19119 The rules in &%route_list%& are searched in order until one of the patterns
19120 matches the domain that is being routed. The list of hosts and then options are
19121 then used as described below. If there is no match, the router declines. When
19122 &%route_list%& is set, &%route_data%& must not be set.
19126 .section "Routing rules in route_data" "SECID121"
19127 The use of &%route_list%& is convenient when there are only a small number of
19128 routing rules. For larger numbers, it is easier to use a file or database to
19129 hold the routing information, and use the &%route_data%& option instead.
19130 The value of &%route_data%& is a list of hosts, followed by (optional) options.
19131 Most commonly, &%route_data%& is set as a string that contains an
19132 expansion lookup. For example, suppose we place two routing rules in a file
19135 dict.ref.example: mail-1.ref.example:mail-2.ref.example
19136 thes.ref.example: mail-3.ref.example:mail-4.ref.example
19138 This data can be accessed by setting
19140 route_data = ${lookup{$domain}lsearch{/the/file/name}}
19142 Failure of the lookup results in an empty string, causing the router to
19143 decline. However, you do not have to use a lookup in &%route_data%&. The only
19144 requirement is that the result of expanding the string is a list of hosts,
19145 possibly followed by options, separated by white space. The list of hosts must
19146 be enclosed in quotes if it contains white space.
19151 .section "Format of the list of hosts" "SECID122"
19152 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
19153 always separately expanded before use. If the expansion fails, the router
19154 declines. The result of the expansion must be a colon-separated list of names
19155 and/or IP addresses, optionally also including ports. The format of each item
19156 in the list is described in the next section. The list separator can be changed
19157 as described in section &<<SECTlistconstruct>>&.
19159 If the list of hosts was obtained from a &%route_list%& item, the following
19160 variables are set during its expansion:
19163 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
19164 If the domain was matched against a regular expression, the numeric variables
19165 &$1$&, &$2$&, etc. may be set. For example:
19167 route_list = ^domain(\d+) host-$1.text.example
19170 &$0$& is always set to the entire domain.
19172 &$1$& is also set when partial matching is done in a file lookup.
19175 .vindex "&$value$&"
19176 If the pattern that matched the domain was a lookup item, the data that was
19177 looked up is available in the expansion variable &$value$&. For example:
19179 route_list = lsearch;;/some/file.routes $value
19183 Note the doubling of the semicolon in the pattern that is necessary because
19184 semicolon is the default route list separator.
19188 .section "Format of one host item" "SECTformatonehostitem"
19189 Each item in the list of hosts is either a host name or an IP address,
19190 optionally with an attached port number. When no port is given, an IP address
19191 is not enclosed in brackets. When a port is specified, it overrides the port
19192 specification on the transport. The port is separated from the name or address
19193 by a colon. This leads to some complications:
19196 Because colon is the default separator for the list of hosts, either
19197 the colon that specifies a port must be doubled, or the list separator must
19198 be changed. The following two examples have the same effect:
19200 route_list = * "host1.tld::1225 : host2.tld::1226"
19201 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
19204 When IPv6 addresses are involved, it gets worse, because they contain
19205 colons of their own. To make this case easier, it is permitted to
19206 enclose an IP address (either v4 or v6) in square brackets if a port
19207 number follows. For example:
19209 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
19213 .section "How the list of hosts is used" "SECThostshowused"
19214 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
19215 the hosts is tried, in the order specified, when carrying out the SMTP
19216 delivery. However, the order can be changed by setting the &%hosts_randomize%&
19217 option, either on the router (see section &<<SECTprioptman>>& above), or on the
19220 Hosts may be listed by name or by IP address. An unadorned name in the list of
19221 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
19222 interpreted as an indirection to a sublist of hosts obtained by looking up MX
19223 records in the DNS. For example:
19225 route_list = * x.y.z:p.q.r/MX:e.f.g
19227 If this feature is used with a port specifier, the port must come last. For
19230 route_list = * dom1.tld/mx::1225
19232 If the &%hosts_randomize%& option is set, the order of the items in the list is
19233 randomized before any lookups are done. Exim then scans the list; for any name
19234 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
19235 be an interface on the local host and the item is not the first in the list,
19236 Exim discards it and any subsequent items. If it is the first item, what
19237 happens is controlled by the
19238 .oindex "&%self%&" "in &(manualroute)& router"
19239 &%self%& option of the router.
19241 A name on the list that is followed by &`/MX`& is replaced with the list of
19242 hosts obtained by looking up MX records for the name. This is always a DNS
19243 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
19244 below) are not relevant here. The order of these hosts is determined by the
19245 preference values in the MX records, according to the usual rules. Because
19246 randomizing happens before the MX lookup, it does not affect the order that is
19247 defined by MX preferences.
19249 If the local host is present in the sublist obtained from MX records, but is
19250 not the most preferred host in that list, it and any equally or less
19251 preferred hosts are removed before the sublist is inserted into the main list.
19253 If the local host is the most preferred host in the MX list, what happens
19254 depends on where in the original list of hosts the &`/MX`& item appears. If it
19255 is not the first item (that is, there are previous hosts in the main list),
19256 Exim discards this name and any subsequent items in the main list.
19258 If the MX item is first in the list of hosts, and the local host is the
19259 most preferred host, what happens is controlled by the &%self%& option of the
19262 DNS failures when lookup up the MX records are treated in the same way as DNS
19263 failures when looking up IP addresses: &%pass_on_timeout%& and
19264 &%host_find_failed%& are used when relevant.
19266 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
19267 whether obtained from an MX lookup or not.
19271 .section "How the options are used" "SECThowoptused"
19272 The options are a sequence of words; in practice no more than three are ever
19273 present. One of the words can be the name of a transport; this overrides the
19274 &%transport%& option on the router for this particular routing rule only. The
19275 other words (if present) control randomization of the list of hosts on a
19276 per-rule basis, and how the IP addresses of the hosts are to be found when
19277 routing to a remote transport. These options are as follows:
19280 &%randomize%&: randomize the order of the hosts in this list, overriding the
19281 setting of &%hosts_randomize%& for this routing rule only.
19283 &%no_randomize%&: do not randomize the order of the hosts in this list,
19284 overriding the setting of &%hosts_randomize%& for this routing rule only.
19286 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
19287 find IP addresses. This function may ultimately cause a DNS lookup, but it may
19288 also look in &_/etc/hosts_& or other sources of information.
19290 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
19291 no address records are found. If there is a temporary DNS error (such as a
19292 timeout), delivery is deferred.
19297 route_list = domain1 host1:host2:host3 randomize bydns;\
19298 domain2 host4:host5
19300 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
19301 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
19302 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
19303 or &[gethostbyname()]&, and the result of the lookup is the result of that
19306 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
19307 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
19308 instead of TRY_AGAIN. That is why the default action is to try a DNS
19309 lookup first. Only if that gives a definite &"no such host"& is the local
19314 If no IP address for a host can be found, what happens is controlled by the
19315 &%host_find_failed%& option.
19318 When an address is routed to a local transport, IP addresses are not looked up.
19319 The host list is passed to the transport in the &$host$& variable.
19323 .section "Manualroute examples" "SECID123"
19324 In some of the examples that follow, the presence of the &%remote_smtp%&
19325 transport, as defined in the default configuration file, is assumed:
19328 .cindex "smart host" "example router"
19329 The &(manualroute)& router can be used to forward all external mail to a
19330 &'smart host'&. If you have set up, in the main part of the configuration, a
19331 named domain list that contains your local domains, for example:
19333 domainlist local_domains = my.domain.example
19335 You can arrange for all other domains to be routed to a smart host by making
19336 your first router something like this:
19339 driver = manualroute
19340 domains = !+local_domains
19341 transport = remote_smtp
19342 route_list = * smarthost.ref.example
19344 This causes all non-local addresses to be sent to the single host
19345 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19346 they are tried in order
19347 (but you can use &%hosts_randomize%& to vary the order each time).
19348 Another way of configuring the same thing is this:
19351 driver = manualroute
19352 transport = remote_smtp
19353 route_list = !+local_domains smarthost.ref.example
19355 There is no difference in behaviour between these two routers as they stand.
19356 However, they behave differently if &%no_more%& is added to them. In the first
19357 example, the router is skipped if the domain does not match the &%domains%&
19358 precondition; the following router is always tried. If the router runs, it
19359 always matches the domain and so can never decline. Therefore, &%no_more%&
19360 would have no effect. In the second case, the router is never skipped; it
19361 always runs. However, if it doesn't match the domain, it declines. In this case
19362 &%no_more%& would prevent subsequent routers from running.
19365 .cindex "mail hub example"
19366 A &'mail hub'& is a host which receives mail for a number of domains via MX
19367 records in the DNS and delivers it via its own private routing mechanism. Often
19368 the final destinations are behind a firewall, with the mail hub being the one
19369 machine that can connect to machines both inside and outside the firewall. The
19370 &(manualroute)& router is usually used on a mail hub to route incoming messages
19371 to the correct hosts. For a small number of domains, the routing can be inline,
19372 using the &%route_list%& option, but for a larger number a file or database
19373 lookup is easier to manage.
19375 If the domain names are in fact the names of the machines to which the mail is
19376 to be sent by the mail hub, the configuration can be quite simple. For
19380 driver = manualroute
19381 transport = remote_smtp
19382 route_list = *.rhodes.tvs.example $domain
19384 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
19385 whose names are the same as the mail domains. A similar approach can be taken
19386 if the host name can be obtained from the domain name by a string manipulation
19387 that the expansion facilities can handle. Otherwise, a lookup based on the
19388 domain can be used to find the host:
19391 driver = manualroute
19392 transport = remote_smtp
19393 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
19395 The result of the lookup must be the name or IP address of the host (or
19396 hosts) to which the address is to be routed. If the lookup fails, the route
19397 data is empty, causing the router to decline. The address then passes to the
19401 .cindex "batched SMTP output example"
19402 .cindex "SMTP" "batched outgoing; example"
19403 You can use &(manualroute)& to deliver messages to pipes or files in batched
19404 SMTP format for onward transportation by some other means. This is one way of
19405 storing mail for a dial-up host when it is not connected. The route list entry
19406 can be as simple as a single domain name in a configuration like this:
19409 driver = manualroute
19410 transport = batchsmtp_appendfile
19411 route_list = saved.domain.example
19413 though often a pattern is used to pick up more than one domain. If there are
19414 several domains or groups of domains with different transport requirements,
19415 different transports can be listed in the routing information:
19418 driver = manualroute
19420 *.saved.domain1.example $domain batch_appendfile; \
19421 *.saved.domain2.example \
19422 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
19425 .vindex "&$domain$&"
19427 The first of these just passes the domain in the &$host$& variable, which
19428 doesn't achieve much (since it is also in &$domain$&), but the second does a
19429 file lookup to find a value to pass, causing the router to decline to handle
19430 the address if the lookup fails.
19433 .cindex "UUCP" "example of router for"
19434 Routing mail directly to UUCP software is a specific case of the use of
19435 &(manualroute)& in a gateway to another mail environment. This is an example of
19436 one way it can be done:
19442 command = /usr/local/bin/uux -r - \
19443 ${substr_-5:$host}!rmail ${local_part}
19444 return_fail_output = true
19449 driver = manualroute
19451 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
19453 The file &_/usr/local/exim/uucphosts_& contains entries like
19455 darksite.ethereal.example: darksite.UUCP
19457 It can be set up more simply without adding and removing &".UUCP"& but this way
19458 makes clear the distinction between the domain name
19459 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
19461 .ecindex IIDmanrou1
19462 .ecindex IIDmanrou2
19471 . ////////////////////////////////////////////////////////////////////////////
19472 . ////////////////////////////////////////////////////////////////////////////
19474 .chapter "The queryprogram router" "CHAPdriverlast"
19475 .scindex IIDquerou1 "&(queryprogram)& router"
19476 .scindex IIDquerou2 "routers" "&(queryprogram)&"
19477 .cindex "routing" "by external program"
19478 The &(queryprogram)& router routes an address by running an external command
19479 and acting on its output. This is an expensive way to route, and is intended
19480 mainly for use in lightly-loaded systems, or for performing experiments.
19481 However, if it is possible to use the precondition options (&%domains%&,
19482 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
19483 be used in special cases, even on a busy host. There are the following private
19485 .cindex "options" "&(queryprogram)& router"
19487 .option command queryprogram string&!! unset
19488 This option must be set. It specifies the command that is to be run. The
19489 command is split up into a command name and arguments, and then each is
19490 expanded separately (exactly as for a &(pipe)& transport, described in chapter
19491 &<<CHAPpipetransport>>&).
19494 .option command_group queryprogram string unset
19495 .cindex "gid (group id)" "in &(queryprogram)& router"
19496 This option specifies a gid to be set when running the command while routing an
19497 address for deliver. It must be set if &%command_user%& specifies a numerical
19498 uid. If it begins with a digit, it is interpreted as the numerical value of the
19499 gid. Otherwise it is looked up using &[getgrnam()]&.
19502 .option command_user queryprogram string unset
19503 .cindex "uid (user id)" "for &(queryprogram)&"
19504 This option must be set. It specifies the uid which is set when running the
19505 command while routing an address for delivery. If the value begins with a digit,
19506 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
19507 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
19508 not set, a value for the gid also.
19510 &*Warning:*& Changing uid and gid is possible only when Exim is running as
19511 root, which it does during a normal delivery in a conventional configuration.
19512 However, when an address is being verified during message reception, Exim is
19513 usually running as the Exim user, not as root. If the &(queryprogram)& router
19514 is called from a non-root process, Exim cannot change uid or gid before running
19515 the command. In this circumstance the command runs under the current uid and
19519 .option current_directory queryprogram string /
19520 This option specifies an absolute path which is made the current directory
19521 before running the command.
19524 .option timeout queryprogram time 1h
19525 If the command does not complete within the timeout period, its process group
19526 is killed and the message is frozen. A value of zero time specifies no
19530 The standard output of the command is connected to a pipe, which is read when
19531 the command terminates. It should consist of a single line of output,
19532 containing up to five fields, separated by white space. The maximum length of
19533 the line is 1023 characters. Longer lines are silently truncated. The first
19534 field is one of the following words (case-insensitive):
19537 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
19540 &'Decline'&: the router declines; pass the address to the next router, unless
19541 &%no_more%& is set.
19543 &'Fail'&: routing failed; do not pass the address to any more routers. Any
19544 subsequent text on the line is an error message. If the router is run as part
19545 of address verification during an incoming SMTP message, the message is
19546 included in the SMTP response.
19548 &'Defer'&: routing could not be completed at this time; try again later. Any
19549 subsequent text on the line is an error message which is logged. It is not
19550 included in any SMTP response.
19552 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
19554 &'Pass'&: pass the address to the next router (or the router specified by
19555 &%pass_router%&), overriding &%no_more%&.
19557 &'Redirect'&: the message is redirected. The remainder of the line is a list of
19558 new addresses, which are routed independently, starting with the first router,
19559 or the router specified by &%redirect_router%&, if set.
19562 When the first word is &'accept'&, the remainder of the line consists of a
19563 number of keyed data values, as follows (split into two lines here, to fit on
19566 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
19567 LOOKUP=byname|bydns DATA=<text>
19569 The data items can be given in any order, and all are optional. If no transport
19570 is included, the transport specified by the generic &%transport%& option is
19571 used. The list of hosts and the lookup type are needed only if the transport is
19572 an &(smtp)& transport that does not itself supply a list of hosts.
19574 The format of the list of hosts is the same as for the &(manualroute)& router.
19575 As well as host names and IP addresses with optional port numbers, as described
19576 in section &<<SECTformatonehostitem>>&, it may contain names followed by
19577 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
19578 (see section &<<SECThostshowused>>&).
19580 If the lookup type is not specified, Exim behaves as follows when trying to
19581 find an IP address for each host: First, a DNS lookup is done. If this yields
19582 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
19583 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
19584 result of the lookup is the result of that call.
19586 .vindex "&$address_data$&"
19587 If the DATA field is set, its value is placed in the &$address_data$&
19588 variable. For example, this return line
19590 accept hosts=x1.y.example:x2.y.example data="rule1"
19592 routes the address to the default transport, passing a list of two hosts. When
19593 the transport runs, the string &"rule1"& is in &$address_data$&.
19594 .ecindex IIDquerou1
19595 .ecindex IIDquerou2
19600 . ////////////////////////////////////////////////////////////////////////////
19601 . ////////////////////////////////////////////////////////////////////////////
19603 .chapter "The redirect router" "CHAPredirect"
19604 .scindex IIDredrou1 "&(redirect)& router"
19605 .scindex IIDredrou2 "routers" "&(redirect)&"
19606 .cindex "alias file" "in a &(redirect)& router"
19607 .cindex "address redirection" "&(redirect)& router"
19608 The &(redirect)& router handles several kinds of address redirection. Its most
19609 common uses are for resolving local part aliases from a central alias file
19610 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
19611 files, but it has many other potential uses. The incoming address can be
19612 redirected in several different ways:
19615 It can be replaced by one or more new addresses which are themselves routed
19618 It can be routed to be delivered to a given file or directory.
19620 It can be routed to be delivered to a specified pipe command.
19622 It can cause an automatic reply to be generated.
19624 It can be forced to fail, optionally with a custom error message.
19626 It can be temporarily deferred, optionally with a custom message.
19628 It can be discarded.
19631 The generic &%transport%& option must not be set for &(redirect)& routers.
19632 However, there are some private options which define transports for delivery to
19633 files and pipes, and for generating autoreplies. See the &%file_transport%&,
19634 &%pipe_transport%& and &%reply_transport%& descriptions below.
19636 If success DSNs have been requested
19637 .cindex "DSN" "success"
19638 .cindex "Delivery Status Notification" "success"
19639 redirection triggers one and the DSN options are not passed any further.
19643 .section "Redirection data" "SECID124"
19644 The router operates by interpreting a text string which it obtains either by
19645 expanding the contents of the &%data%& option, or by reading the entire
19646 contents of a file whose name is given in the &%file%& option. These two
19647 options are mutually exclusive. The first is commonly used for handling system
19648 aliases, in a configuration like this:
19652 data = ${lookup{$local_part}lsearch{/etc/aliases}}
19654 If the lookup fails, the expanded string in this example is empty. When the
19655 expansion of &%data%& results in an empty string, the router declines. A forced
19656 expansion failure also causes the router to decline; other expansion failures
19657 cause delivery to be deferred.
19659 A configuration using &%file%& is commonly used for handling users'
19660 &_.forward_& files, like this:
19665 file = $home/.forward
19668 If the file does not exist, or causes no action to be taken (for example, it is
19669 empty or consists only of comments), the router declines. &*Warning*&: This
19670 is not the case when the file contains syntactically valid items that happen to
19671 yield empty addresses, for example, items containing only RFC 2822 address
19676 .section "Forward files and address verification" "SECID125"
19677 .cindex "address redirection" "while verifying"
19678 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
19679 &_.forward_& files, as in the example above. There are two reasons for this:
19682 When Exim is receiving an incoming SMTP message from a remote host, it is
19683 running under the Exim uid, not as root. Exim is unable to change uid to read
19684 the file as the user, and it may not be able to read it as the Exim user. So in
19685 practice the router may not be able to operate.
19687 However, even when the router can operate, the existence of a &_.forward_& file
19688 is unimportant when verifying an address. What should be checked is whether the
19689 local part is a valid user name or not. Cutting out the redirection processing
19690 saves some resources.
19698 .section "Interpreting redirection data" "SECID126"
19699 .cindex "Sieve filter" "specifying in redirection data"
19700 .cindex "filter" "specifying in redirection data"
19701 The contents of the data string, whether obtained from &%data%& or &%file%&,
19702 can be interpreted in two different ways:
19705 If the &%allow_filter%& option is set true, and the data begins with the text
19706 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
19707 &'filtering'& instructions in the form of an Exim or Sieve filter file,
19708 respectively. Details of the syntax and semantics of filter files are described
19709 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
19710 document is intended for use by end users.
19712 Otherwise, the data must be a comma-separated list of redirection items, as
19713 described in the next section.
19716 When a message is redirected to a file (a &"mail folder"&), the file name given
19717 in a non-filter redirection list must always be an absolute path. A filter may
19718 generate a relative path &-- how this is handled depends on the transport's
19719 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
19720 for the &(appendfile)& transport.
19724 .section "Items in a non-filter redirection list" "SECTitenonfilred"
19725 .cindex "address redirection" "non-filter list items"
19726 When the redirection data is not an Exim or Sieve filter, for example, if it
19727 comes from a conventional alias or forward file, it consists of a list of
19728 addresses, file names, pipe commands, or certain special items (see section
19729 &<<SECTspecitredli>>& below). The special items can be individually enabled or
19730 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
19731 depending on their default values. The items in the list are separated by
19732 commas or newlines.
19733 If a comma is required in an item, the entire item must be enclosed in double
19736 Lines starting with a # character are comments, and are ignored, and # may
19737 also appear following a comma, in which case everything between the # and the
19738 next newline character is ignored.
19740 If an item is entirely enclosed in double quotes, these are removed. Otherwise
19741 double quotes are retained because some forms of mail address require their use
19742 (but never to enclose the entire address). In the following description,
19743 &"item"& refers to what remains after any surrounding double quotes have been
19746 .vindex "&$local_part$&"
19747 &*Warning*&: If you use an Exim expansion to construct a redirection address,
19748 and the expansion contains a reference to &$local_part$&, you should make use
19749 of the &%quote_local_part%& expansion operator, in case the local part contains
19750 special characters. For example, to redirect all mail for the domain
19751 &'obsolete.example'&, retaining the existing local part, you could use this
19754 data = ${quote_local_part:$local_part}@newdomain.example
19758 .section "Redirecting to a local mailbox" "SECTredlocmai"
19759 .cindex "routing" "loops in"
19760 .cindex "loop" "while routing, avoidance of"
19761 .cindex "address redirection" "to local mailbox"
19762 A redirection item may safely be the same as the address currently under
19763 consideration. This does not cause a routing loop, because a router is
19764 automatically skipped if any ancestor of the address that is being processed
19765 is the same as the current address and was processed by the current router.
19766 Such an address is therefore passed to the following routers, so it is handled
19767 as if there were no redirection. When making this loop-avoidance test, the
19768 complete local part, including any prefix or suffix, is used.
19770 .cindex "address redirection" "local part without domain"
19771 Specifying the same local part without a domain is a common usage in personal
19772 filter files when the user wants to have messages delivered to the local
19773 mailbox and also forwarded elsewhere. For example, the user whose login is
19774 &'cleo'& might have a &_.forward_& file containing this:
19776 cleo, cleopatra@egypt.example
19778 .cindex "backslash in alias file"
19779 .cindex "alias file" "backslash in"
19780 For compatibility with other MTAs, such unqualified local parts may be
19781 preceded by &"\"&, but this is not a requirement for loop prevention. However,
19782 it does make a difference if more than one domain is being handled
19785 If an item begins with &"\"& and the rest of the item parses as a valid RFC
19786 2822 address that does not include a domain, the item is qualified using the
19787 domain of the incoming address. In the absence of a leading &"\"&, unqualified
19788 addresses are qualified using the value in &%qualify_recipient%&, but you can
19789 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
19791 Care must be taken if there are alias names for local users.
19792 Consider an MTA handling a single local domain where the system alias file
19797 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
19798 messages in the local mailbox, and also forward copies elsewhere. He creates
19801 Sam.Reman, spqr@reme.elsewhere.example
19803 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
19804 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
19805 second time round, because it has previously routed it,
19806 and the following routers presumably cannot handle the alias. The forward file
19807 should really contain
19809 spqr, spqr@reme.elsewhere.example
19811 but because this is such a common error, the &%check_ancestor%& option (see
19812 below) exists to provide a way to get round it. This is normally set on a
19813 &(redirect)& router that is handling users' &_.forward_& files.
19817 .section "Special items in redirection lists" "SECTspecitredli"
19818 In addition to addresses, the following types of item may appear in redirection
19819 lists (that is, in non-filter redirection data):
19822 .cindex "pipe" "in redirection list"
19823 .cindex "address redirection" "to pipe"
19824 An item is treated as a pipe command if it begins with &"|"& and does not parse
19825 as a valid RFC 2822 address that includes a domain. A transport for running the
19826 command must be specified by the &%pipe_transport%& option.
19827 Normally, either the router or the transport specifies a user and a group under
19828 which to run the delivery. The default is to use the Exim user and group.
19830 Single or double quotes can be used for enclosing the individual arguments of
19831 the pipe command; no interpretation of escapes is done for single quotes. If
19832 the command contains a comma character, it is necessary to put the whole item
19833 in double quotes, for example:
19835 "|/some/command ready,steady,go"
19837 since items in redirection lists are terminated by commas. Do not, however,
19838 quote just the command. An item such as
19840 |"/some/command ready,steady,go"
19842 is interpreted as a pipe with a rather strange command name, and no arguments.
19844 Note that the above example assumes that the text comes from a lookup source
19845 of some sort, so that the quotes are part of the data. If composing a
19846 redirect router with a &%data%& option directly specifying this command, the
19847 quotes will be used by the configuration parser to define the extent of one
19848 string, but will not be passed down into the redirect router itself. There
19849 are two main approaches to get around this: escape quotes to be part of the
19850 data itself, or avoid using this mechanism and instead create a custom
19851 transport with the &%command%& option set and reference that transport from
19852 an &%accept%& router.
19855 .cindex "file" "in redirection list"
19856 .cindex "address redirection" "to file"
19857 An item is interpreted as a path name if it begins with &"/"& and does not
19858 parse as a valid RFC 2822 address that includes a domain. For example,
19860 /home/world/minbari
19862 is treated as a file name, but
19864 /s=molari/o=babylon/@x400gate.way
19866 is treated as an address. For a file name, a transport must be specified using
19867 the &%file_transport%& option. However, if the generated path name ends with a
19868 forward slash character, it is interpreted as a directory name rather than a
19869 file name, and &%directory_transport%& is used instead.
19871 Normally, either the router or the transport specifies a user and a group under
19872 which to run the delivery. The default is to use the Exim user and group.
19874 .cindex "&_/dev/null_&"
19875 However, if a redirection item is the path &_/dev/null_&, delivery to it is
19876 bypassed at a high level, and the log entry shows &"**bypassed**"&
19877 instead of a transport name. In this case the user and group are not used.
19880 .cindex "included address list"
19881 .cindex "address redirection" "included external list"
19882 If an item is of the form
19884 :include:<path name>
19886 a list of further items is taken from the given file and included at that
19887 point. &*Note*&: Such a file can not be a filter file; it is just an
19888 out-of-line addition to the list. The items in the included list are separated
19889 by commas or newlines and are not subject to expansion. If this is the first
19890 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
19891 the alias name. This example is incorrect:
19893 list1 :include:/opt/lists/list1
19895 It must be given as
19897 list1: :include:/opt/lists/list1
19900 .cindex "address redirection" "to black hole"
19901 .cindex "delivery" "discard"
19902 .cindex "delivery" "blackhole"
19903 .cindex "black hole"
19904 .cindex "abandoning mail"
19905 Sometimes you want to throw away mail to a particular local part. Making the
19906 &%data%& option expand to an empty string does not work, because that causes
19907 the router to decline. Instead, the alias item
19911 can be used. It does what its name implies. No delivery is
19912 done, and no error message is generated. This has the same effect as specifying
19913 &_/dev/null_& as a destination, but it can be independently disabled.
19915 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
19916 delivery is done for the original local part, even if other redirection items
19917 are present. If you are generating a multi-item list (for example, by reading a
19918 database) and need the ability to provide a no-op item, you must use
19922 .cindex "delivery" "forcing failure"
19923 .cindex "delivery" "forcing deferral"
19924 .cindex "failing delivery" "forcing"
19925 .cindex "deferred delivery, forcing"
19926 .cindex "customizing" "failure message"
19927 An attempt to deliver a particular address can be deferred or forced to fail by
19928 redirection items of the form
19933 respectively. When a redirection list contains such an item, it applies
19934 to the entire redirection; any other items in the list are ignored. Any
19935 text following &':fail:'& or &':defer:'& is placed in the error text
19936 associated with the failure. For example, an alias file might contain:
19938 X.Employee: :fail: Gone away, no forwarding address
19940 In the case of an address that is being verified from an ACL or as the subject
19942 .cindex "VRFY" "error text, display of"
19943 VRFY command, the text is included in the SMTP error response by
19945 .cindex "EXPN" "error text, display of"
19946 The text is not included in the response to an EXPN command. In non-SMTP cases
19947 the text is included in the error message that Exim generates.
19949 .cindex "SMTP" "error codes"
19950 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
19951 &':fail:'&. However, if the message starts with three digits followed by a
19952 space, optionally followed by an extended code of the form &'n.n.n'&, also
19953 followed by a space, and the very first digit is the same as the default error
19954 code, the code from the message is used instead. If the very first digit is
19955 incorrect, a panic error is logged, and the default code is used. You can
19956 suppress the use of the supplied code in a redirect router by setting the
19957 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
19960 .vindex "&$acl_verify_message$&"
19961 In an ACL, an explicitly provided message overrides the default, but the
19962 default message is available in the variable &$acl_verify_message$& and can
19963 therefore be included in a custom message if this is desired.
19965 Normally the error text is the rest of the redirection list &-- a comma does
19966 not terminate it &-- but a newline does act as a terminator. Newlines are not
19967 normally present in alias expansions. In &(lsearch)& lookups they are removed
19968 as part of the continuation process, but they may exist in other kinds of
19969 lookup and in &':include:'& files.
19971 During routing for message delivery (as opposed to verification), a redirection
19972 containing &':fail:'& causes an immediate failure of the incoming address,
19973 whereas &':defer:'& causes the message to remain on the queue so that a
19974 subsequent delivery attempt can happen at a later time. If an address is
19975 deferred for too long, it will ultimately fail, because the normal retry
19979 .cindex "alias file" "exception to default"
19980 Sometimes it is useful to use a single-key search type with a default (see
19981 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
19982 for exceptions to the default. These can be handled by aliasing them to
19983 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
19984 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
19985 results in an empty redirection list has the same effect.
19989 .section "Duplicate addresses" "SECTdupaddr"
19990 .cindex "duplicate addresses"
19991 .cindex "address duplicate, discarding"
19992 .cindex "pipe" "duplicated"
19993 Exim removes duplicate addresses from the list to which it is delivering, so as
19994 to deliver just one copy to each address. This does not apply to deliveries
19995 routed to pipes by different immediate parent addresses, but an indirect
19996 aliasing scheme of the type
19998 pipe: |/some/command $local_part
20002 does not work with a message that is addressed to both local parts, because
20003 when the second is aliased to the intermediate local part &"pipe"& it gets
20004 discarded as being the same as a previously handled address. However, a scheme
20007 localpart1: |/some/command $local_part
20008 localpart2: |/some/command $local_part
20010 does result in two different pipe deliveries, because the immediate parents of
20011 the pipes are distinct.
20015 .section "Repeated redirection expansion" "SECID128"
20016 .cindex "repeated redirection expansion"
20017 .cindex "address redirection" "repeated for each delivery attempt"
20018 When a message cannot be delivered to all of its recipients immediately,
20019 leading to two or more delivery attempts, redirection expansion is carried out
20020 afresh each time for those addresses whose children were not all previously
20021 delivered. If redirection is being used as a mailing list, this can lead to new
20022 members of the list receiving copies of old messages. The &%one_time%& option
20023 can be used to avoid this.
20026 .section "Errors in redirection lists" "SECID129"
20027 .cindex "address redirection" "errors"
20028 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
20029 error is skipped, and an entry is written to the main log. This may be useful
20030 for mailing lists that are automatically managed. Otherwise, if an error is
20031 detected while generating the list of new addresses, the original address is
20032 deferred. See also &%syntax_errors_to%&.
20036 .section "Private options for the redirect router" "SECID130"
20038 .cindex "options" "&(redirect)& router"
20039 The private options for the &(redirect)& router are as follows:
20042 .option allow_defer redirect boolean false
20043 Setting this option allows the use of &':defer:'& in non-filter redirection
20044 data, or the &%defer%& command in an Exim filter file.
20047 .option allow_fail redirect boolean false
20048 .cindex "failing delivery" "from filter"
20049 If this option is true, the &':fail:'& item can be used in a redirection list,
20050 and the &%fail%& command may be used in an Exim filter file.
20053 .option allow_filter redirect boolean false
20054 .cindex "filter" "enabling use of"
20055 .cindex "Sieve filter" "enabling use of"
20056 Setting this option allows Exim to interpret redirection data that starts with
20057 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
20058 are some features of Exim filter files that some administrators may wish to
20059 lock out; see the &%forbid_filter_%&&'xxx'& options below.
20061 It is also possible to lock out Exim filters or Sieve filters while allowing
20062 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
20065 The filter is run using the uid and gid set by the generic &%user%& and
20066 &%group%& options. These take their defaults from the password data if
20067 &%check_local_user%& is set, so in the normal case of users' personal filter
20068 files, the filter is run as the relevant user. When &%allow_filter%& is set
20069 true, Exim insists that either &%check_local_user%& or &%user%& is set.
20073 .option allow_freeze redirect boolean false
20074 .cindex "freezing messages" "allowing in filter"
20075 Setting this option allows the use of the &%freeze%& command in an Exim filter.
20076 This command is more normally encountered in system filters, and is disabled by
20077 default for redirection filters because it isn't something you usually want to
20078 let ordinary users do.
20082 .option check_ancestor redirect boolean false
20083 This option is concerned with handling generated addresses that are the same
20084 as some address in the list of redirection ancestors of the current address.
20085 Although it is turned off by default in the code, it is set in the default
20086 configuration file for handling users' &_.forward_& files. It is recommended
20087 for this use of the &(redirect)& router.
20089 When &%check_ancestor%& is set, if a generated address (including the domain)
20090 is the same as any ancestor of the current address, it is replaced by a copy of
20091 the current address. This helps in the case where local part A is aliased to B,
20092 and B has a &_.forward_& file pointing back to A. For example, within a single
20093 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
20094 &_&~jb/.forward_& contains:
20096 \Joe.Bloggs, <other item(s)>
20098 Without the &%check_ancestor%& setting, either local part (&"jb"& or
20099 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
20100 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
20101 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
20102 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
20103 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
20104 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
20105 original address. See also the &%repeat_use%& option below.
20108 .option check_group redirect boolean "see below"
20109 When the &%file%& option is used, the group owner of the file is checked only
20110 when this option is set. The permitted groups are those listed in the
20111 &%owngroups%& option, together with the user's default group if
20112 &%check_local_user%& is set. If the file has the wrong group, routing is
20113 deferred. The default setting for this option is true if &%check_local_user%&
20114 is set and the &%modemask%& option permits the group write bit, or if the
20115 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
20119 .option check_owner redirect boolean "see below"
20120 When the &%file%& option is used, the owner of the file is checked only when
20121 this option is set. If &%check_local_user%& is set, the local user is
20122 permitted; otherwise the owner must be one of those listed in the &%owners%&
20123 option. The default value for this option is true if &%check_local_user%& or
20124 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
20127 .option data redirect string&!! unset
20128 This option is mutually exclusive with &%file%&. One or other of them must be
20129 set, but not both. The contents of &%data%& are expanded, and then used as the
20130 list of forwarding items, or as a set of filtering instructions. If the
20131 expansion is forced to fail, or the result is an empty string or a string that
20132 has no effect (consists entirely of comments), the router declines.
20134 When filtering instructions are used, the string must begin with &"#Exim
20135 filter"&, and all comments in the string, including this initial one, must be
20136 terminated with newline characters. For example:
20138 data = #Exim filter\n\
20139 if $h_to: contains Exim then save $home/mail/exim endif
20141 If you are reading the data from a database where newlines cannot be included,
20142 you can use the &${sg}$& expansion item to turn the escape string of your
20143 choice into a newline.
20146 .option directory_transport redirect string&!! unset
20147 A &(redirect)& router sets up a direct delivery to a directory when a path name
20148 ending with a slash is specified as a new &"address"&. The transport used is
20149 specified by this option, which, after expansion, must be the name of a
20150 configured transport. This should normally be an &(appendfile)& transport.
20153 .option file redirect string&!! unset
20154 This option specifies the name of a file that contains the redirection data. It
20155 is mutually exclusive with the &%data%& option. The string is expanded before
20156 use; if the expansion is forced to fail, the router declines. Other expansion
20157 failures cause delivery to be deferred. The result of a successful expansion
20158 must be an absolute path. The entire file is read and used as the redirection
20159 data. If the data is an empty string or a string that has no effect (consists
20160 entirely of comments), the router declines.
20162 .cindex "NFS" "checking for file existence"
20163 If the attempt to open the file fails with a &"does not exist"& error, Exim
20164 runs a check on the containing directory,
20165 unless &%ignore_enotdir%& is true (see below).
20166 If the directory does not appear to exist, delivery is deferred. This can
20167 happen when users' &_.forward_& files are in NFS-mounted directories, and there
20168 is a mount problem. If the containing directory does exist, but the file does
20169 not, the router declines.
20172 .option file_transport redirect string&!! unset
20173 .vindex "&$address_file$&"
20174 A &(redirect)& router sets up a direct delivery to a file when a path name not
20175 ending in a slash is specified as a new &"address"&. The transport used is
20176 specified by this option, which, after expansion, must be the name of a
20177 configured transport. This should normally be an &(appendfile)& transport. When
20178 it is running, the file name is in &$address_file$&.
20181 .option filter_prepend_home redirect boolean true
20182 When this option is true, if a &(save)& command in an Exim filter specifies a
20183 relative path, and &$home$& is defined, it is automatically prepended to the
20184 relative path. If this option is set false, this action does not happen. The
20185 relative path is then passed to the transport unmodified.
20188 .option forbid_blackhole redirect boolean false
20189 If this option is true, the &':blackhole:'& item may not appear in a
20193 .option forbid_exim_filter redirect boolean false
20194 If this option is set true, only Sieve filters are permitted when
20195 &%allow_filter%& is true.
20200 .option forbid_file redirect boolean false
20201 .cindex "delivery" "to file; forbidding"
20202 .cindex "Sieve filter" "forbidding delivery to a file"
20203 .cindex "Sieve filter" "&""keep""& facility; disabling"
20204 If this option is true, this router may not generate a new address that
20205 specifies delivery to a local file or directory, either from a filter or from a
20206 conventional forward file. This option is forced to be true if &%one_time%& is
20207 set. It applies to Sieve filters as well as to Exim filters, but if true, it
20208 locks out the Sieve's &"keep"& facility.
20211 .option forbid_filter_dlfunc redirect boolean false
20212 .cindex "filter" "locking out certain features"
20213 If this option is true, string expansions in Exim filters are not allowed to
20214 make use of the &%dlfunc%& expansion facility to run dynamically loaded
20217 .option forbid_filter_existstest redirect boolean false
20218 .cindex "expansion" "statting a file"
20219 If this option is true, string expansions in Exim filters are not allowed to
20220 make use of the &%exists%& condition or the &%stat%& expansion item.
20222 .option forbid_filter_logwrite redirect boolean false
20223 If this option is true, use of the logging facility in Exim filters is not
20224 permitted. Logging is in any case available only if the filter is being run
20225 under some unprivileged uid (which is normally the case for ordinary users'
20226 &_.forward_& files).
20229 .option forbid_filter_lookup redirect boolean false
20230 If this option is true, string expansions in Exim filter files are not allowed
20231 to make use of &%lookup%& items.
20234 .option forbid_filter_perl redirect boolean false
20235 This option has an effect only if Exim is built with embedded Perl support. If
20236 it is true, string expansions in Exim filter files are not allowed to make use
20237 of the embedded Perl support.
20240 .option forbid_filter_readfile redirect boolean false
20241 If this option is true, string expansions in Exim filter files are not allowed
20242 to make use of &%readfile%& items.
20245 .option forbid_filter_readsocket redirect boolean false
20246 If this option is true, string expansions in Exim filter files are not allowed
20247 to make use of &%readsocket%& items.
20250 .option forbid_filter_reply redirect boolean false
20251 If this option is true, this router may not generate an automatic reply
20252 message. Automatic replies can be generated only from Exim or Sieve filter
20253 files, not from traditional forward files. This option is forced to be true if
20254 &%one_time%& is set.
20257 .option forbid_filter_run redirect boolean false
20258 If this option is true, string expansions in Exim filter files are not allowed
20259 to make use of &%run%& items.
20262 .option forbid_include redirect boolean false
20263 If this option is true, items of the form
20265 :include:<path name>
20267 are not permitted in non-filter redirection lists.
20270 .option forbid_pipe redirect boolean false
20271 .cindex "delivery" "to pipe; forbidding"
20272 If this option is true, this router may not generate a new address which
20273 specifies delivery to a pipe, either from an Exim filter or from a conventional
20274 forward file. This option is forced to be true if &%one_time%& is set.
20277 .option forbid_sieve_filter redirect boolean false
20278 If this option is set true, only Exim filters are permitted when
20279 &%allow_filter%& is true.
20282 .cindex "SMTP" "error codes"
20283 .option forbid_smtp_code redirect boolean false
20284 If this option is set true, any SMTP error codes that are present at the start
20285 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
20286 the default codes (451 and 550, respectively) are always used.
20291 .option hide_child_in_errmsg redirect boolean false
20292 .cindex "bounce message" "redirection details; suppressing"
20293 If this option is true, it prevents Exim from quoting a child address if it
20294 generates a bounce or delay message for it. Instead it says &"an address
20295 generated from <&'the top level address'&>"&. Of course, this applies only to
20296 bounces generated locally. If a message is forwarded to another host, &'its'&
20297 bounce may well quote the generated address.
20300 .option ignore_eacces redirect boolean false
20302 If this option is set and an attempt to open a redirection file yields the
20303 EACCES error (permission denied), the &(redirect)& router behaves as if the
20304 file did not exist.
20307 .option ignore_enotdir redirect boolean false
20309 If this option is set and an attempt to open a redirection file yields the
20310 ENOTDIR error (something on the path is not a directory), the &(redirect)&
20311 router behaves as if the file did not exist.
20313 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
20314 router that has the &%file%& option set discovers that the file does not exist
20315 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
20316 against unmounted NFS directories. If the parent can not be statted, delivery
20317 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
20318 is set, because that option tells Exim to ignore &"something on the path is not
20319 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
20320 that some operating systems give ENOENT where others give ENOTDIR.
20324 .option include_directory redirect string unset
20325 If this option is set, the path names of any &':include:'& items in a
20326 redirection list must start with this directory.
20329 .option modemask redirect "octal integer" 022
20330 This specifies mode bits which must not be set for a file specified by the
20331 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
20334 .option one_time redirect boolean false
20335 .cindex "one-time aliasing/forwarding expansion"
20336 .cindex "alias file" "one-time expansion"
20337 .cindex "forward file" "one-time expansion"
20338 .cindex "mailing lists" "one-time expansion"
20339 .cindex "address redirection" "one-time expansion"
20340 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
20341 files each time it tries to deliver a message causes a problem when one or more
20342 of the generated addresses fails be delivered at the first attempt. The problem
20343 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
20344 but of what happens when the redirection list changes during the time that the
20345 message is on Exim's queue. This is particularly true in the case of mailing
20346 lists, where new subscribers might receive copies of messages that were posted
20347 before they subscribed.
20349 If &%one_time%& is set and any addresses generated by the router fail to
20350 deliver at the first attempt, the failing addresses are added to the message as
20351 &"top level"& addresses, and the parent address that generated them is marked
20352 &"delivered"&. Thus, redirection does not happen again at the next delivery
20355 &*Warning 1*&: Any header line addition or removal that is specified by this
20356 router would be lost if delivery did not succeed at the first attempt. For this
20357 reason, the &%headers_add%& and &%headers_remove%& generic options are not
20358 permitted when &%one_time%& is set.
20360 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
20361 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
20362 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
20364 &*Warning 3*&: The &%unseen%& generic router option may not be set with
20367 The original top-level address is remembered with each of the generated
20368 addresses, and is output in any log messages. However, any intermediate parent
20369 addresses are not recorded. This makes a difference to the log only if
20370 &%all_parents%& log selector is set. It is expected that &%one_time%& will
20371 typically be used for mailing lists, where there is normally just one level of
20375 .option owners redirect "string list" unset
20376 .cindex "ownership" "alias file"
20377 .cindex "ownership" "forward file"
20378 .cindex "alias file" "ownership"
20379 .cindex "forward file" "ownership"
20380 This specifies a list of permitted owners for the file specified by &%file%&.
20381 This list is in addition to the local user when &%check_local_user%& is set.
20382 See &%check_owner%& above.
20385 .option owngroups redirect "string list" unset
20386 This specifies a list of permitted groups for the file specified by &%file%&.
20387 The list is in addition to the local user's primary group when
20388 &%check_local_user%& is set. See &%check_group%& above.
20391 .option pipe_transport redirect string&!! unset
20392 .vindex "&$address_pipe$&"
20393 A &(redirect)& router sets up a direct delivery to a pipe when a string
20394 starting with a vertical bar character is specified as a new &"address"&. The
20395 transport used is specified by this option, which, after expansion, must be the
20396 name of a configured transport. This should normally be a &(pipe)& transport.
20397 When the transport is run, the pipe command is in &$address_pipe$&.
20400 .option qualify_domain redirect string&!! unset
20401 .vindex "&$qualify_recipient$&"
20402 If this option is set, and an unqualified address (one without a domain) is
20403 generated, and that address would normally be qualified by the global setting
20404 in &%qualify_recipient%&, it is instead qualified with the domain specified by
20405 expanding this string. If the expansion fails, the router declines. If you want
20406 to revert to the default, you can have the expansion generate
20407 &$qualify_recipient$&.
20409 This option applies to all unqualified addresses generated by Exim filters,
20410 but for traditional &_.forward_& files, it applies only to addresses that are
20411 not preceded by a backslash. Sieve filters cannot generate unqualified
20414 .option qualify_preserve_domain redirect boolean false
20415 .cindex "domain" "in redirection; preserving"
20416 .cindex "preserving domain in redirection"
20417 .cindex "address redirection" "domain; preserving"
20418 If this option is set, the router's local &%qualify_domain%& option must not be
20419 set (a configuration error occurs if it is). If an unqualified address (one
20420 without a domain) is generated, it is qualified with the domain of the parent
20421 address (the immediately preceding ancestor) instead of the global
20422 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
20423 this applies whether or not the address is preceded by a backslash.
20426 .option repeat_use redirect boolean true
20427 If this option is set false, the router is skipped for a child address that has
20428 any ancestor that was routed by this router. This test happens before any of
20429 the other preconditions are tested. Exim's default anti-looping rules skip
20430 only when the ancestor is the same as the current address. See also
20431 &%check_ancestor%& above and the generic &%redirect_router%& option.
20434 .option reply_transport redirect string&!! unset
20435 A &(redirect)& router sets up an automatic reply when a &%mail%& or
20436 &%vacation%& command is used in a filter file. The transport used is specified
20437 by this option, which, after expansion, must be the name of a configured
20438 transport. This should normally be an &(autoreply)& transport. Other transports
20439 are unlikely to do anything sensible or useful.
20442 .option rewrite redirect boolean true
20443 .cindex "address redirection" "disabling rewriting"
20444 If this option is set false, addresses generated by the router are not
20445 subject to address rewriting. Otherwise, they are treated like new addresses
20446 and are rewritten according to the global rewriting rules.
20449 .option sieve_subaddress redirect string&!! unset
20450 The value of this option is passed to a Sieve filter to specify the
20451 :subaddress part of an address.
20453 .option sieve_useraddress redirect string&!! unset
20454 The value of this option is passed to a Sieve filter to specify the :user part
20455 of an address. However, if it is unset, the entire original local part
20456 (including any prefix or suffix) is used for :user.
20459 .option sieve_vacation_directory redirect string&!! unset
20460 .cindex "Sieve filter" "vacation directory"
20461 To enable the &"vacation"& extension for Sieve filters, you must set
20462 &%sieve_vacation_directory%& to the directory where vacation databases are held
20463 (do not put anything else in that directory), and ensure that the
20464 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
20465 needs their own directory; Exim will create it if necessary.
20469 .option skip_syntax_errors redirect boolean false
20470 .cindex "forward file" "broken"
20471 .cindex "address redirection" "broken files"
20472 .cindex "alias file" "broken"
20473 .cindex "broken alias or forward files"
20474 .cindex "ignoring faulty addresses"
20475 .cindex "skipping faulty addresses"
20476 .cindex "error" "skipping bad syntax"
20477 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
20478 non-filter redirection data are skipped, and each failing address is logged. If
20479 &%syntax_errors_to%& is set, a message is sent to the address it defines,
20480 giving details of the failures. If &%syntax_errors_text%& is set, its contents
20481 are expanded and placed at the head of the error message generated by
20482 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
20483 be the same address as the generic &%errors_to%& option. The
20484 &%skip_syntax_errors%& option is often used when handling mailing lists.
20486 If all the addresses in a redirection list are skipped because of syntax
20487 errors, the router declines to handle the original address, and it is passed to
20488 the following routers.
20490 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
20491 error in the filter causes filtering to be abandoned without any action being
20492 taken. The incident is logged, and the router declines to handle the address,
20493 so it is passed to the following routers.
20495 .cindex "Sieve filter" "syntax errors in"
20496 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
20497 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
20498 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
20500 &%skip_syntax_errors%& can be used to specify that errors in users' forward
20501 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
20502 option, used with an address that does not get redirected, can be used to
20503 notify users of these errors, by means of a router like this:
20509 file = $home/.forward
20510 file_transport = address_file
20511 pipe_transport = address_pipe
20512 reply_transport = address_reply
20515 syntax_errors_to = real-$local_part@$domain
20516 syntax_errors_text = \
20517 This is an automatically generated message. An error has\n\
20518 been found in your .forward file. Details of the error are\n\
20519 reported below. While this error persists, you will receive\n\
20520 a copy of this message for every message that is addressed\n\
20521 to you. If your .forward file is a filter file, or if it is\n\
20522 a non-filter file containing no valid forwarding addresses,\n\
20523 a copy of each incoming message will be put in your normal\n\
20524 mailbox. If a non-filter file contains at least one valid\n\
20525 forwarding address, forwarding to the valid addresses will\n\
20526 happen, and those will be the only deliveries that occur.
20528 You also need a router to ensure that local addresses that are prefixed by
20529 &`real-`& are recognized, but not forwarded or filtered. For example, you could
20530 put this immediately before the &(userforward)& router:
20535 local_part_prefix = real-
20536 transport = local_delivery
20538 For security, it would probably be a good idea to restrict the use of this
20539 router to locally-generated messages, using a condition such as this:
20541 condition = ${if match {$sender_host_address}\
20542 {\N^(|127\.0\.0\.1)$\N}}
20546 .option syntax_errors_text redirect string&!! unset
20547 See &%skip_syntax_errors%& above.
20550 .option syntax_errors_to redirect string unset
20551 See &%skip_syntax_errors%& above.
20552 .ecindex IIDredrou1
20553 .ecindex IIDredrou2
20560 . ////////////////////////////////////////////////////////////////////////////
20561 . ////////////////////////////////////////////////////////////////////////////
20563 .chapter "Environment for running local transports" "CHAPenvironment" &&&
20564 "Environment for local transports"
20565 .scindex IIDenvlotra1 "local transports" "environment for"
20566 .scindex IIDenvlotra2 "environment" "local transports"
20567 .scindex IIDenvlotra3 "transport" "local; environment for"
20568 Local transports handle deliveries to files and pipes. (The &(autoreply)&
20569 transport can be thought of as similar to a pipe.) Exim always runs transports
20570 in subprocesses, under specified uids and gids. Typical deliveries to local
20571 mailboxes run under the uid and gid of the local user.
20573 Exim also sets a specific current directory while running the transport; for
20574 some transports a home directory setting is also relevant. The &(pipe)&
20575 transport is the only one that sets up environment variables; see section
20576 &<<SECTpipeenv>>& for details.
20578 The values used for the uid, gid, and the directories may come from several
20579 different places. In many cases, the router that handles the address associates
20580 settings with that address as a result of its &%check_local_user%&, &%group%&,
20581 or &%user%& options. However, values may also be given in the transport's own
20582 configuration, and these override anything that comes from the router.
20586 .section "Concurrent deliveries" "SECID131"
20587 .cindex "concurrent deliveries"
20588 .cindex "simultaneous deliveries"
20589 If two different messages for the same local recipient arrive more or less
20590 simultaneously, the two delivery processes are likely to run concurrently. When
20591 the &(appendfile)& transport is used to write to a file, Exim applies locking
20592 rules to stop concurrent processes from writing to the same file at the same
20595 However, when you use a &(pipe)& transport, it is up to you to arrange any
20596 locking that is needed. Here is a silly example:
20600 command = /bin/sh -c 'cat >>/some/file'
20602 This is supposed to write the message at the end of the file. However, if two
20603 messages arrive at the same time, the file will be scrambled. You can use the
20604 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
20605 file using the same algorithm that Exim itself uses.
20610 .section "Uids and gids" "SECTenvuidgid"
20611 .cindex "local transports" "uid and gid"
20612 .cindex "transport" "local; uid and gid"
20613 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
20614 overrides any group that the router set in the address, even if &%user%& is not
20615 set for the transport. This makes it possible, for example, to run local mail
20616 delivery under the uid of the recipient (set by the router), but in a special
20617 group (set by the transport). For example:
20620 # User/group are set by check_local_user in this router
20624 transport = group_delivery
20627 # This transport overrides the group
20629 driver = appendfile
20630 file = /var/spool/mail/$local_part
20633 If &%user%& is set for a transport, its value overrides what is set in the
20634 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
20635 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
20638 .oindex "&%initgroups%&"
20639 When the uid is taken from the transport's configuration, the &[initgroups()]&
20640 function is called for the groups associated with that uid if the
20641 &%initgroups%& option is set for the transport. When the uid is not specified
20642 by the transport, but is associated with the address by a router, the option
20643 for calling &[initgroups()]& is taken from the router configuration.
20645 .cindex "&(pipe)& transport" "uid for"
20646 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
20647 is set and &%user%& is not set, the uid of the process that called Exim to
20648 receive the message is used, and if &%group%& is not set, the corresponding
20649 original gid is also used.
20651 This is the detailed preference order for obtaining a gid; the first of the
20652 following that is set is used:
20655 A &%group%& setting of the transport;
20657 A &%group%& setting of the router;
20659 A gid associated with a user setting of the router, either as a result of
20660 &%check_local_user%& or an explicit non-numeric &%user%& setting;
20662 The group associated with a non-numeric &%user%& setting of the transport;
20664 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
20665 the uid is the creator's uid;
20667 The Exim gid if the Exim uid is being used as a default.
20670 If, for example, the user is specified numerically on the router and there are
20671 no group settings, no gid is available. In this situation, an error occurs.
20672 This is different for the uid, for which there always is an ultimate default.
20673 The first of the following that is set is used:
20676 A &%user%& setting of the transport;
20678 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
20680 A &%user%& setting of the router;
20682 A &%check_local_user%& setting of the router;
20687 Of course, an error will still occur if the uid that is chosen is on the
20688 &%never_users%& list.
20694 .section "Current and home directories" "SECID132"
20695 .cindex "current directory for local transport"
20696 .cindex "home directory" "for local transport"
20697 .cindex "transport" "local; home directory for"
20698 .cindex "transport" "local; current directory for"
20699 Routers may set current and home directories for local transports by means of
20700 the &%transport_current_directory%& and &%transport_home_directory%& options.
20701 However, if the transport's &%current_directory%& or &%home_directory%& options
20702 are set, they override the router's values. In detail, the home directory
20703 for a local transport is taken from the first of these values that is set:
20706 The &%home_directory%& option on the transport;
20708 The &%transport_home_directory%& option on the router;
20710 The password data if &%check_local_user%& is set on the router;
20712 The &%router_home_directory%& option on the router.
20715 The current directory is taken from the first of these values that is set:
20718 The &%current_directory%& option on the transport;
20720 The &%transport_current_directory%& option on the router.
20724 If neither the router nor the transport sets a current directory, Exim uses the
20725 value of the home directory, if it is set. Otherwise it sets the current
20726 directory to &_/_& before running a local transport.
20730 .section "Expansion variables derived from the address" "SECID133"
20731 .vindex "&$domain$&"
20732 .vindex "&$local_part$&"
20733 .vindex "&$original_domain$&"
20734 Normally a local delivery is handling a single address, and in that case the
20735 variables such as &$domain$& and &$local_part$& are set during local
20736 deliveries. However, in some circumstances more than one address may be handled
20737 at once (for example, while writing batch SMTP for onward transmission by some
20738 other means). In this case, the variables associated with the local part are
20739 never set, &$domain$& is set only if all the addresses have the same domain,
20740 and &$original_domain$& is never set.
20741 .ecindex IIDenvlotra1
20742 .ecindex IIDenvlotra2
20743 .ecindex IIDenvlotra3
20751 . ////////////////////////////////////////////////////////////////////////////
20752 . ////////////////////////////////////////////////////////////////////////////
20754 .chapter "Generic options for transports" "CHAPtransportgeneric"
20755 .scindex IIDgenoptra1 "generic options" "transport"
20756 .scindex IIDgenoptra2 "options" "generic; for transports"
20757 .scindex IIDgenoptra3 "transport" "generic options for"
20758 The following generic options apply to all transports:
20761 .option body_only transports boolean false
20762 .cindex "transport" "body only"
20763 .cindex "message" "transporting body only"
20764 .cindex "body of message" "transporting"
20765 If this option is set, the message's headers are not transported. It is
20766 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
20767 or &(pipe)& transports, the settings of &%message_prefix%& and
20768 &%message_suffix%& should be checked, because this option does not
20769 automatically suppress them.
20772 .option current_directory transports string&!! unset
20773 .cindex "transport" "current directory for"
20774 This specifies the current directory that is to be set while running the
20775 transport, overriding any value that may have been set by the router.
20776 If the expansion fails for any reason, including forced failure, an error is
20777 logged, and delivery is deferred.
20780 .option disable_logging transports boolean false
20781 If this option is set true, nothing is logged for any
20782 deliveries by the transport or for any
20783 transport errors. You should not set this option unless you really, really know
20784 what you are doing.
20787 .option debug_print transports string&!! unset
20788 .cindex "testing" "variables in drivers"
20789 If this option is set and debugging is enabled (see the &%-d%& command line
20790 option), the string is expanded and included in the debugging output when the
20792 If expansion of the string fails, the error message is written to the debugging
20793 output, and Exim carries on processing.
20794 This facility is provided to help with checking out the values of variables and
20795 so on when debugging driver configurations. For example, if a &%headers_add%&
20796 option is not working properly, &%debug_print%& could be used to output the
20797 variables it references. A newline is added to the text if it does not end with
20799 The variables &$transport_name$& and &$router_name$& contain the name of the
20800 transport and the router that called it.
20802 .option delivery_date_add transports boolean false
20803 .cindex "&'Delivery-date:'& header line"
20804 If this option is true, a &'Delivery-date:'& header is added to the message.
20805 This gives the actual time the delivery was made. As this is not a standard
20806 header, Exim has a configuration option (&%delivery_date_remove%&) which
20807 requests its removal from incoming messages, so that delivered messages can
20808 safely be resent to other recipients.
20811 .option driver transports string unset
20812 This specifies which of the available transport drivers is to be used.
20813 There is no default, and this option must be set for every transport.
20816 .option envelope_to_add transports boolean false
20817 .cindex "&'Envelope-to:'& header line"
20818 If this option is true, an &'Envelope-to:'& header is added to the message.
20819 This gives the original address(es) in the incoming envelope that caused this
20820 delivery to happen. More than one address may be present if the transport is
20821 configured to handle several addresses at once, or if more than one original
20822 address was redirected to the same final address. As this is not a standard
20823 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
20824 its removal from incoming messages, so that delivered messages can safely be
20825 resent to other recipients.
20828 .option event_action transports string&!! unset
20830 This option declares a string to be expanded for Exim's events mechanism.
20831 For details see &<<CHAPevents>>&.
20834 .option group transports string&!! "Exim group"
20835 .cindex "transport" "group; specifying"
20836 This option specifies a gid for running the transport process, overriding any
20837 value that the router supplies, and also overriding any value associated with
20838 &%user%& (see below).
20841 .option headers_add transports list&!! unset
20842 .cindex "header lines" "adding in transport"
20843 .cindex "transport" "header lines; adding"
20844 This option specifies a list of text headers,
20845 newline-separated (by default, changeable in the usual way),
20846 which are (separately) expanded and added to the header
20847 portion of a message as it is transported, as described in section
20848 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
20849 routers. If the result of the expansion is an empty string, or if the expansion
20850 is forced to fail, no action is taken. Other expansion failures are treated as
20851 errors and cause the delivery to be deferred.
20853 Unlike most options, &%headers_add%& can be specified multiple times
20854 for a transport; all listed headers are added.
20857 .option headers_only transports boolean false
20858 .cindex "transport" "header lines only"
20859 .cindex "message" "transporting headers only"
20860 .cindex "header lines" "transporting"
20861 If this option is set, the message's body is not transported. It is mutually
20862 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
20863 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
20864 checked, since this option does not automatically suppress them.
20867 .option headers_remove transports list&!! unset
20868 .cindex "header lines" "removing"
20869 .cindex "transport" "header lines; removing"
20870 This option specifies a list of header names,
20871 colon-separated (by default, changeable in the usual way);
20872 these headers are omitted from the message as it is transported, as described
20873 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
20875 Each list item is separately expanded.
20876 If the result of the expansion is an empty string, or if the expansion
20877 is forced to fail, no action is taken. Other expansion failures are treated as
20878 errors and cause the delivery to be deferred.
20880 Unlike most options, &%headers_remove%& can be specified multiple times
20881 for a transport; all listed headers are removed.
20883 &*Warning*&: Because of the separate expansion of the list items,
20884 items that contain a list separator must have it doubled.
20885 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
20889 .option headers_rewrite transports string unset
20890 .cindex "transport" "header lines; rewriting"
20891 .cindex "rewriting" "at transport time"
20892 This option allows addresses in header lines to be rewritten at transport time,
20893 that is, as the message is being copied to its destination. The contents of the
20894 option are a colon-separated list of rewriting rules. Each rule is in exactly
20895 the same form as one of the general rewriting rules that are applied when a
20896 message is received. These are described in chapter &<<CHAPrewrite>>&. For
20899 headers_rewrite = a@b c@d f : \
20902 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
20903 &'w@z'& in all address-bearing header lines. The rules are applied to the
20904 header lines just before they are written out at transport time, so they affect
20905 only those copies of the message that pass through the transport. However, only
20906 the message's original header lines, and any that were added by a system
20907 filter, are rewritten. If a router or transport adds header lines, they are not
20908 affected by this option. These rewriting rules are &'not'& applied to the
20909 envelope. You can change the return path using &%return_path%&, but you cannot
20910 change envelope recipients at this time.
20913 .option home_directory transports string&!! unset
20914 .cindex "transport" "home directory for"
20916 This option specifies a home directory setting for a local transport,
20917 overriding any value that may be set by the router. The home directory is
20918 placed in &$home$& while expanding the transport's private options. It is also
20919 used as the current directory if no current directory is set by the
20920 &%current_directory%& option on the transport or the
20921 &%transport_current_directory%& option on the router. If the expansion fails
20922 for any reason, including forced failure, an error is logged, and delivery is
20926 .option initgroups transports boolean false
20927 .cindex "additional groups"
20928 .cindex "groups" "additional"
20929 .cindex "transport" "group; additional"
20930 If this option is true and the uid for the delivery process is provided by the
20931 transport, the &[initgroups()]& function is called when running the transport
20932 to ensure that any additional groups associated with the uid are set up.
20935 .option max_parallel transports integer&!! unset
20936 .cindex limit "transport parallelism"
20937 .cindex transport "parallel processes"
20938 .cindex transport "concurrency limit"
20939 .cindex "delivery" "parallelism for transport"
20940 If this option is set and expands to an integer greater than zero
20941 it limits the number of concurrent runs of the transport.
20942 The control does not apply to shadow transports.
20944 .cindex "hints database" "transport concurrency control"
20945 Exim implements this control by means of a hints database in which a record is
20946 incremented whenever a transport process is beaing created. The record
20947 is decremented and possibly removed when the process terminates.
20948 Obviously there is scope for
20949 records to get left lying around if there is a system or program crash. To
20950 guard against this, Exim ignores any records that are more than six hours old.
20952 If you use this option, you should also arrange to delete the
20953 relevant hints database whenever your system reboots. The names of the files
20954 start with &_misc_& and they are kept in the &_spool/db_& directory. There
20955 may be one or two files, depending on the type of DBM in use. The same files
20956 are used for ETRN and smtp transport serialization.
20959 .option message_size_limit transports string&!! 0
20960 .cindex "limit" "message size per transport"
20961 .cindex "size" "of message, limit"
20962 .cindex "transport" "message size; limiting"
20963 This option controls the size of messages passed through the transport. It is
20964 expanded before use; the result of the expansion must be a sequence of decimal
20965 digits, optionally followed by K or M. If the expansion fails for any reason,
20966 including forced failure, or if the result is not of the required form,
20967 delivery is deferred. If the value is greater than zero and the size of a
20968 message exceeds this limit, the address is failed. If there is any chance that
20969 the resulting bounce message could be routed to the same transport, you should
20970 ensure that &%return_size_limit%& is less than the transport's
20971 &%message_size_limit%&, as otherwise the bounce message will fail to get
20976 .option rcpt_include_affixes transports boolean false
20977 .cindex "prefix" "for local part, including in envelope"
20978 .cindex "suffix for local part" "including in envelope"
20979 .cindex "local part" "prefix"
20980 .cindex "local part" "suffix"
20981 When this option is false (the default), and an address that has had any
20982 affixes (prefixes or suffixes) removed from the local part is delivered by any
20983 form of SMTP or LMTP, the affixes are not included. For example, if a router
20986 local_part_prefix = *-
20988 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
20991 RCPT TO:<xyz@some.domain>
20993 This is also the case when an ACL-time callout is being used to verify a
20994 recipient address. However, if &%rcpt_include_affixes%& is set true, the
20995 whole local part is included in the RCPT command. This option applies to BSMTP
20996 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
20997 &(lmtp)& and &(smtp)& transports.
21000 .option retry_use_local_part transports boolean "see below"
21001 .cindex "hints database" "retry keys"
21002 When a delivery suffers a temporary failure, a retry record is created
21003 in Exim's hints database. For remote deliveries, the key for the retry record
21004 is based on the name and/or IP address of the failing remote host. For local
21005 deliveries, the key is normally the entire address, including both the local
21006 part and the domain. This is suitable for most common cases of local delivery
21007 temporary failure &-- for example, exceeding a mailbox quota should delay only
21008 deliveries to that mailbox, not to the whole domain.
21010 However, in some special cases you may want to treat a temporary local delivery
21011 as a failure associated with the domain, and not with a particular local part.
21012 (For example, if you are storing all mail for some domain in files.) You can do
21013 this by setting &%retry_use_local_part%& false.
21015 For all the local transports, its default value is true. For remote transports,
21016 the default value is false for tidiness, but changing the value has no effect
21017 on a remote transport in the current implementation.
21020 .option return_path transports string&!! unset
21021 .cindex "envelope sender"
21022 .cindex "transport" "return path; changing"
21023 .cindex "return path" "changing in transport"
21024 If this option is set, the string is expanded at transport time and replaces
21025 the existing return path (envelope sender) value in the copy of the message
21026 that is being delivered. An empty return path is permitted. This feature is
21027 designed for remote deliveries, where the value of this option is used in the
21028 SMTP MAIL command. If you set &%return_path%& for a local transport, the
21029 only effect is to change the address that is placed in the &'Return-path:'&
21030 header line, if one is added to the message (see the next option).
21032 &*Note:*& A changed return path is not logged unless you add
21033 &%return_path_on_delivery%& to the log selector.
21035 .vindex "&$return_path$&"
21036 The expansion can refer to the existing value via &$return_path$&. This is
21037 either the message's envelope sender, or an address set by the
21038 &%errors_to%& option on a router. If the expansion is forced to fail, no
21039 replacement occurs; if it fails for another reason, delivery is deferred. This
21040 option can be used to support VERP (Variable Envelope Return Paths) &-- see
21041 section &<<SECTverp>>&.
21043 &*Note*&: If a delivery error is detected locally, including the case when a
21044 remote server rejects a message at SMTP time, the bounce message is not sent to
21045 the value of this option. It is sent to the previously set errors address.
21046 This defaults to the incoming sender address, but can be changed by setting
21047 &%errors_to%& in a router.
21051 .option return_path_add transports boolean false
21052 .cindex "&'Return-path:'& header line"
21053 If this option is true, a &'Return-path:'& header is added to the message.
21054 Although the return path is normally available in the prefix line of BSD
21055 mailboxes, this is commonly not displayed by MUAs, and so the user does not
21056 have easy access to it.
21058 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
21059 the delivery SMTP server makes the final delivery"&. This implies that this
21060 header should not be present in incoming messages. Exim has a configuration
21061 option, &%return_path_remove%&, which requests removal of this header from
21062 incoming messages, so that delivered messages can safely be resent to other
21066 .option shadow_condition transports string&!! unset
21067 See &%shadow_transport%& below.
21070 .option shadow_transport transports string unset
21071 .cindex "shadow transport"
21072 .cindex "transport" "shadow"
21073 A local transport may set the &%shadow_transport%& option to the name of
21074 another local transport. Shadow remote transports are not supported.
21076 Whenever a delivery to the main transport succeeds, and either
21077 &%shadow_condition%& is unset, or its expansion does not result in the empty
21078 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
21079 passed to the shadow transport, with the same delivery address or addresses. If
21080 expansion fails, no action is taken except that non-forced expansion failures
21081 cause a log line to be written.
21083 The result of the shadow transport is discarded and does not affect the
21084 subsequent processing of the message. Only a single level of shadowing is
21085 provided; the &%shadow_transport%& option is ignored on any transport when it
21086 is running as a shadow. Options concerned with output from pipes are also
21087 ignored. The log line for the successful delivery has an item added on the end,
21090 ST=<shadow transport name>
21092 If the shadow transport did not succeed, the error message is put in
21093 parentheses afterwards. Shadow transports can be used for a number of different
21094 purposes, including keeping more detailed log information than Exim normally
21095 provides, and implementing automatic acknowledgment policies based on message
21096 headers that some sites insist on.
21099 .option transport_filter transports string&!! unset
21100 .cindex "transport" "filter"
21101 .cindex "filter" "transport filter"
21102 This option sets up a filtering (in the Unix shell sense) process for messages
21103 at transport time. It should not be confused with mail filtering as set up by
21104 individual users or via a system filter.
21105 If unset, or expanding to an empty string, no filtering is done.
21107 When the message is about to be written out, the command specified by
21108 &%transport_filter%& is started up in a separate, parallel process, and
21109 the entire message, including the header lines, is passed to it on its standard
21110 input (this in fact is done from a third process, to avoid deadlock). The
21111 command must be specified as an absolute path.
21113 The lines of the message that are written to the transport filter are
21114 terminated by newline (&"\n"&). The message is passed to the filter before any
21115 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
21116 lines beginning with a dot, and also before any processing implied by the
21117 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
21118 &(pipe)& transports.
21120 The standard error for the filter process is set to the same destination as its
21121 standard output; this is read and written to the message's ultimate
21122 destination. The process that writes the message to the filter, the
21123 filter itself, and the original process that reads the result and delivers it
21124 are all run in parallel, like a shell pipeline.
21126 The filter can perform any transformations it likes, but of course should take
21127 care not to break RFC 2822 syntax. Exim does not check the result, except to
21128 test for a final newline when SMTP is in use. All messages transmitted over
21129 SMTP must end with a newline, so Exim supplies one if it is missing.
21131 .cindex "content scanning" "per user"
21132 A transport filter can be used to provide content-scanning on a per-user basis
21133 at delivery time if the only required effect of the scan is to modify the
21134 message. For example, a content scan could insert a new header line containing
21135 a spam score. This could be interpreted by a filter in the user's MUA. It is
21136 not possible to discard a message at this stage.
21138 .cindex "SMTP" "SIZE"
21139 A problem might arise if the filter increases the size of a message that is
21140 being sent down an SMTP connection. If the receiving SMTP server has indicated
21141 support for the SIZE parameter, Exim will have sent the size of the message
21142 at the start of the SMTP session. If what is actually sent is substantially
21143 more, the server might reject the message. This can be worked round by setting
21144 the &%size_addition%& option on the &(smtp)& transport, either to allow for
21145 additions to the message, or to disable the use of SIZE altogether.
21147 .vindex "&$pipe_addresses$&"
21148 The value of the &%transport_filter%& option is the command string for starting
21149 the filter, which is run directly from Exim, not under a shell. The string is
21150 parsed by Exim in the same way as a command string for the &(pipe)& transport:
21151 Exim breaks it up into arguments and then expands each argument separately (see
21152 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
21153 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
21154 of arguments, one for each address that applies to this delivery. (This isn't
21155 an ideal name for this feature here, but as it was already implemented for the
21156 &(pipe)& transport, it seemed sensible not to change it.)
21159 .vindex "&$host_address$&"
21160 The expansion variables &$host$& and &$host_address$& are available when the
21161 transport is a remote one. They contain the name and IP address of the host to
21162 which the message is being sent. For example:
21164 transport_filter = /some/directory/transport-filter.pl \
21165 $host $host_address $sender_address $pipe_addresses
21168 Two problems arise if you want to use more complicated expansion items to
21169 generate transport filter commands, both of which due to the fact that the
21170 command is split up &'before'& expansion.
21172 If an expansion item contains white space, you must quote it, so that it is all
21173 part of the same command item. If the entire option setting is one such
21174 expansion item, you have to take care what kind of quoting you use. For
21177 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
21179 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
21180 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
21181 stripped by Exim when it read the option's value. When the value is used, if
21182 the single quotes were missing, the line would be split into two items,
21183 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
21184 Exim tried to expand the first one.
21186 Except for the special case of &$pipe_addresses$& that is mentioned above, an
21187 expansion cannot generate multiple arguments, or a command name followed by
21188 arguments. Consider this example:
21190 transport_filter = ${lookup{$host}lsearch{/a/file}\
21191 {$value}{/bin/cat}}
21193 The result of the lookup is interpreted as the name of the command, even
21194 if it contains white space. The simplest way round this is to use a shell:
21196 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
21197 {$value}{/bin/cat}}
21201 The filter process is run under the same uid and gid as the normal delivery.
21202 For remote deliveries this is the Exim uid/gid by default. The command should
21203 normally yield a zero return code. Transport filters are not supposed to fail.
21204 A non-zero code is taken to mean that the transport filter encountered some
21205 serious problem. Delivery of the message is deferred; the message remains on
21206 the queue and is tried again later. It is not possible to cause a message to be
21207 bounced from a transport filter.
21209 If a transport filter is set on an autoreply transport, the original message is
21210 passed through the filter as it is being copied into the newly generated
21211 message, which happens if the &%return_message%& option is set.
21214 .option transport_filter_timeout transports time 5m
21215 .cindex "transport" "filter, timeout"
21216 When Exim is reading the output of a transport filter, it applies a timeout
21217 that can be set by this option. Exceeding the timeout is normally treated as a
21218 temporary delivery failure. However, if a transport filter is used with a
21219 &(pipe)& transport, a timeout in the transport filter is treated in the same
21220 way as a timeout in the pipe command itself. By default, a timeout is a hard
21221 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
21222 becomes a temporary error.
21225 .option user transports string&!! "Exim user"
21226 .cindex "uid (user id)" "local delivery"
21227 .cindex "transport" "user, specifying"
21228 This option specifies the user under whose uid the delivery process is to be
21229 run, overriding any uid that may have been set by the router. If the user is
21230 given as a name, the uid is looked up from the password data, and the
21231 associated group is taken as the value of the gid to be used if the &%group%&
21234 For deliveries that use local transports, a user and group are normally
21235 specified explicitly or implicitly (for example, as a result of
21236 &%check_local_user%&) by the router or transport.
21238 .cindex "hints database" "access by remote transport"
21239 For remote transports, you should leave this option unset unless you really are
21240 sure you know what you are doing. When a remote transport is running, it needs
21241 to be able to access Exim's hints databases, because each host may have its own
21243 .ecindex IIDgenoptra1
21244 .ecindex IIDgenoptra2
21245 .ecindex IIDgenoptra3
21252 . ////////////////////////////////////////////////////////////////////////////
21253 . ////////////////////////////////////////////////////////////////////////////
21255 .chapter "Address batching in local transports" "CHAPbatching" &&&
21257 .cindex "transport" "local; address batching in"
21258 The only remote transport (&(smtp)&) is normally configured to handle more than
21259 one address at a time, so that when several addresses are routed to the same
21260 remote host, just one copy of the message is sent. Local transports, however,
21261 normally handle one address at a time. That is, a separate instance of the
21262 transport is run for each address that is routed to the transport. A separate
21263 copy of the message is delivered each time.
21265 .cindex "batched local delivery"
21266 .oindex "&%batch_max%&"
21267 .oindex "&%batch_id%&"
21268 In special cases, it may be desirable to handle several addresses at once in a
21269 local transport, for example:
21272 In an &(appendfile)& transport, when storing messages in files for later
21273 delivery by some other means, a single copy of the message with multiple
21274 recipients saves space.
21276 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
21277 a single copy saves time, and is the normal way LMTP is expected to work.
21279 In a &(pipe)& transport, when passing the message
21280 to a scanner program or
21281 to some other delivery mechanism such as UUCP, multiple recipients may be
21285 These three local transports all have the same options for controlling multiple
21286 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
21287 repeating the information for each transport, these options are described here.
21289 The &%batch_max%& option specifies the maximum number of addresses that can be
21290 delivered together in a single run of the transport. Its default value is one
21291 (no batching). When more than one address is routed to a transport that has a
21292 &%batch_max%& value greater than one, the addresses are delivered in a batch
21293 (that is, in a single run of the transport with multiple recipients), subject
21294 to certain conditions:
21297 .vindex "&$local_part$&"
21298 If any of the transport's options contain a reference to &$local_part$&, no
21299 batching is possible.
21301 .vindex "&$domain$&"
21302 If any of the transport's options contain a reference to &$domain$&, only
21303 addresses with the same domain are batched.
21305 .cindex "customizing" "batching condition"
21306 If &%batch_id%& is set, it is expanded for each address, and only those
21307 addresses with the same expanded value are batched. This allows you to specify
21308 customized batching conditions. Failure of the expansion for any reason,
21309 including forced failure, disables batching, but it does not stop the delivery
21312 Batched addresses must also have the same errors address (where to send
21313 delivery errors), the same header additions and removals, the same user and
21314 group for the transport, and if a host list is present, the first host must
21318 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
21319 both when the file or pipe command is specified in the transport, and when it
21320 is specified by a &(redirect)& router, but all the batched addresses must of
21321 course be routed to the same file or pipe command. These two transports have an
21322 option called &%use_bsmtp%&, which causes them to deliver the message in
21323 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
21324 &%check_string%& and &%escape_string%& options are forced to the values
21327 escape_string = ".."
21329 when batched SMTP is in use. A full description of the batch SMTP mechanism is
21330 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
21331 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
21333 .cindex "&'Envelope-to:'& header line"
21334 If the generic &%envelope_to_add%& option is set for a batching transport, the
21335 &'Envelope-to:'& header that is added to the message contains all the addresses
21336 that are being processed together. If you are using a batching &(appendfile)&
21337 transport without &%use_bsmtp%&, the only way to preserve the recipient
21338 addresses is to set the &%envelope_to_add%& option.
21340 .cindex "&(pipe)& transport" "with multiple addresses"
21341 .vindex "&$pipe_addresses$&"
21342 If you are using a &(pipe)& transport without BSMTP, and setting the
21343 transport's &%command%& option, you can include &$pipe_addresses$& as part of
21344 the command. This is not a true variable; it is a bit of magic that causes each
21345 of the recipient addresses to be inserted into the command as a separate
21346 argument. This provides a way of accessing all the addresses that are being
21347 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21348 are specified by a &(redirect)& router.
21353 . ////////////////////////////////////////////////////////////////////////////
21354 . ////////////////////////////////////////////////////////////////////////////
21356 .chapter "The appendfile transport" "CHAPappendfile"
21357 .scindex IIDapptra1 "&(appendfile)& transport"
21358 .scindex IIDapptra2 "transports" "&(appendfile)&"
21359 .cindex "directory creation"
21360 .cindex "creating directories"
21361 The &(appendfile)& transport delivers a message by appending it to an existing
21362 file, or by creating an entirely new file in a specified directory. Single
21363 files to which messages are appended can be in the traditional Unix mailbox
21364 format, or optionally in the MBX format supported by the Pine MUA and
21365 University of Washington IMAP daemon, &'inter alia'&. When each message is
21366 being delivered as a separate file, &"maildir"& format can optionally be used
21367 to give added protection against failures that happen part-way through the
21368 delivery. A third form of separate-file delivery known as &"mailstore"& is also
21369 supported. For all file formats, Exim attempts to create as many levels of
21370 directory as necessary, provided that &%create_directory%& is set.
21372 The code for the optional formats is not included in the Exim binary by
21373 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
21374 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
21377 .cindex "quota" "system"
21378 Exim recognizes system quota errors, and generates an appropriate message. Exim
21379 also supports its own quota control within the transport, for use when the
21380 system facility is unavailable or cannot be used for some reason.
21382 If there is an error while appending to a file (for example, quota exceeded or
21383 partition filled), Exim attempts to reset the file's length and last
21384 modification time back to what they were before. If there is an error while
21385 creating an entirely new file, the new file is removed.
21387 Before appending to a file, a number of security checks are made, and the
21388 file is locked. A detailed description is given below, after the list of
21391 The &(appendfile)& transport is most commonly used for local deliveries to
21392 users' mailboxes. However, it can also be used as a pseudo-remote transport for
21393 putting messages into files for remote delivery by some means other than Exim.
21394 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
21399 .section "The file and directory options" "SECTfildiropt"
21400 The &%file%& option specifies a single file, to which the message is appended;
21401 the &%directory%& option specifies a directory, in which a new file containing
21402 the message is created. Only one of these two options can be set, and for
21403 normal deliveries to mailboxes, one of them &'must'& be set.
21405 .vindex "&$address_file$&"
21406 .vindex "&$local_part$&"
21407 However, &(appendfile)& is also used for delivering messages to files or
21408 directories whose names (or parts of names) are obtained from alias,
21409 forwarding, or filtering operations (for example, a &%save%& command in a
21410 user's Exim filter). When such a transport is running, &$local_part$& contains
21411 the local part that was aliased or forwarded, and &$address_file$& contains the
21412 name (or partial name) of the file or directory generated by the redirection
21413 operation. There are two cases:
21416 If neither &%file%& nor &%directory%& is set, the redirection operation
21417 must specify an absolute path (one that begins with &`/`&). This is the most
21418 common case when users with local accounts use filtering to sort mail into
21419 different folders. See for example, the &(address_file)& transport in the
21420 default configuration. If the path ends with a slash, it is assumed to be the
21421 name of a directory. A delivery to a directory can also be forced by setting
21422 &%maildir_format%& or &%mailstore_format%&.
21424 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
21425 used to determine the file or directory name for the delivery. Normally, the
21426 contents of &$address_file$& are used in some way in the string expansion.
21430 .cindex "Sieve filter" "configuring &(appendfile)&"
21431 .cindex "Sieve filter" "relative mailbox path handling"
21432 As an example of the second case, consider an environment where users do not
21433 have home directories. They may be permitted to use Exim filter commands of the
21438 or Sieve filter commands of the form:
21440 require "fileinto";
21441 fileinto "folder23";
21443 In this situation, the expansion of &%file%& or &%directory%& in the transport
21444 must transform the relative path into an appropriate absolute file name. In the
21445 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
21446 is used as a result of a &"keep"& action in the filter. This example shows one
21447 way of handling this requirement:
21449 file = ${if eq{$address_file}{inbox} \
21450 {/var/mail/$local_part} \
21451 {${if eq{${substr_0_1:$address_file}}{/} \
21453 {$home/mail/$address_file} \
21457 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
21458 location, absolute paths are used without change, and other folders are in the
21459 &_mail_& directory within the home directory.
21461 &*Note 1*&: While processing an Exim filter, a relative path such as
21462 &_folder23_& is turned into an absolute path if a home directory is known to
21463 the router. In particular, this is the case if &%check_local_user%& is set. If
21464 you want to prevent this happening at routing time, you can set
21465 &%router_home_directory%& empty. This forces the router to pass the relative
21466 path to the transport.
21468 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
21469 the &%file%& or &%directory%& option is still used if it is set.
21474 .section "Private options for appendfile" "SECID134"
21475 .cindex "options" "&(appendfile)& transport"
21479 .option allow_fifo appendfile boolean false
21480 .cindex "fifo (named pipe)"
21481 .cindex "named pipe (fifo)"
21482 .cindex "pipe" "named (fifo)"
21483 Setting this option permits delivery to named pipes (FIFOs) as well as to
21484 regular files. If no process is reading the named pipe at delivery time, the
21485 delivery is deferred.
21488 .option allow_symlink appendfile boolean false
21489 .cindex "symbolic link" "to mailbox"
21490 .cindex "mailbox" "symbolic link"
21491 By default, &(appendfile)& will not deliver if the path name for the file is
21492 that of a symbolic link. Setting this option relaxes that constraint, but there
21493 are security issues involved in the use of symbolic links. Be sure you know
21494 what you are doing if you set this. Details of exactly what this option affects
21495 are included in the discussion which follows this list of options.
21498 .option batch_id appendfile string&!! unset
21499 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21500 However, batching is automatically disabled for &(appendfile)& deliveries that
21501 happen as a result of forwarding or aliasing or other redirection directly to a
21505 .option batch_max appendfile integer 1
21506 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21509 .option check_group appendfile boolean false
21510 When this option is set, the group owner of the file defined by the &%file%&
21511 option is checked to see that it is the same as the group under which the
21512 delivery process is running. The default setting is false because the default
21513 file mode is 0600, which means that the group is irrelevant.
21516 .option check_owner appendfile boolean true
21517 When this option is set, the owner of the file defined by the &%file%& option
21518 is checked to ensure that it is the same as the user under which the delivery
21519 process is running.
21522 .option check_string appendfile string "see below"
21523 .cindex "&""From""& line"
21524 As &(appendfile)& writes the message, the start of each line is tested for
21525 matching &%check_string%&, and if it does, the initial matching characters are
21526 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
21527 a literal string, not a regular expression, and the case of any letters it
21528 contains is significant.
21530 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
21531 are forced to &"."& and &".."& respectively, and any settings in the
21532 configuration are ignored. Otherwise, they default to &"From&~"& and
21533 &">From&~"& when the &%file%& option is set, and unset when any of the
21534 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
21536 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
21537 suitable for traditional &"BSD"& mailboxes, where a line beginning with
21538 &"From&~"& indicates the start of a new message. All four options need changing
21539 if another format is used. For example, to deliver to mailboxes in MMDF format:
21540 .cindex "MMDF format mailbox"
21541 .cindex "mailbox" "MMDF format"
21543 check_string = "\1\1\1\1\n"
21544 escape_string = "\1\1\1\1 \n"
21545 message_prefix = "\1\1\1\1\n"
21546 message_suffix = "\1\1\1\1\n"
21548 .option create_directory appendfile boolean true
21549 .cindex "directory creation"
21550 When this option is true, Exim attempts to create any missing superior
21551 directories for the file that it is about to write. A created directory's mode
21552 is given by the &%directory_mode%& option.
21554 The group ownership of a newly created directory is highly dependent on the
21555 operating system (and possibly the file system) that is being used. For
21556 example, in Solaris, if the parent directory has the setgid bit set, its group
21557 is propagated to the child; if not, the currently set group is used. However,
21558 in FreeBSD, the parent's group is always used.
21562 .option create_file appendfile string anywhere
21563 This option constrains the location of files and directories that are created
21564 by this transport. It applies to files defined by the &%file%& option and
21565 directories defined by the &%directory%& option. In the case of maildir
21566 delivery, it applies to the top level directory, not the maildir directories
21569 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
21570 &"belowhome"&. In the second and third cases, a home directory must have been
21571 set for the transport. This option is not useful when an explicit file name is
21572 given for normal mailbox deliveries. It is intended for the case when file
21573 names are generated from users' &_.forward_& files. These are usually handled
21574 by an &(appendfile)& transport called &%address_file%&. See also
21575 &%file_must_exist%&.
21578 .option directory appendfile string&!! unset
21579 This option is mutually exclusive with the &%file%& option, but one of &%file%&
21580 or &%directory%& must be set, unless the delivery is the direct result of a
21581 redirection (see section &<<SECTfildiropt>>&).
21583 When &%directory%& is set, the string is expanded, and the message is delivered
21584 into a new file or files in or below the given directory, instead of being
21585 appended to a single mailbox file. A number of different formats are provided
21586 (see &%maildir_format%& and &%mailstore_format%&), and see section
21587 &<<SECTopdir>>& for further details of this form of delivery.
21590 .option directory_file appendfile string&!! "see below"
21592 .vindex "&$inode$&"
21593 When &%directory%& is set, but neither &%maildir_format%& nor
21594 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
21595 whose name is obtained by expanding this string. The default value is:
21597 q${base62:$tod_epoch}-$inode
21599 This generates a unique name from the current time, in base 62 form, and the
21600 inode of the file. The variable &$inode$& is available only when expanding this
21604 .option directory_mode appendfile "octal integer" 0700
21605 If &(appendfile)& creates any directories as a result of the
21606 &%create_directory%& option, their mode is specified by this option.
21609 .option escape_string appendfile string "see description"
21610 See &%check_string%& above.
21613 .option file appendfile string&!! unset
21614 This option is mutually exclusive with the &%directory%& option, but one of
21615 &%file%& or &%directory%& must be set, unless the delivery is the direct result
21616 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
21617 specifies a single file, to which the message is appended. One or more of
21618 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
21621 .cindex "NFS" "lock file"
21622 .cindex "locking files"
21623 .cindex "lock files"
21624 If you are using more than one host to deliver over NFS into the same
21625 mailboxes, you should always use lock files.
21627 The string value is expanded for each delivery, and must yield an absolute
21628 path. The most common settings of this option are variations on one of these
21631 file = /var/spool/mail/$local_part
21632 file = /home/$local_part/inbox
21635 .cindex "&""sticky""& bit"
21636 In the first example, all deliveries are done into the same directory. If Exim
21637 is configured to use lock files (see &%use_lockfile%& below) it must be able to
21638 create a file in the directory, so the &"sticky"& bit must be turned on for
21639 deliveries to be possible, or alternatively the &%group%& option can be used to
21640 run the delivery under a group id which has write access to the directory.
21644 .option file_format appendfile string unset
21645 .cindex "file" "mailbox; checking existing format"
21646 This option requests the transport to check the format of an existing file
21647 before adding to it. The check consists of matching a specific string at the
21648 start of the file. The value of the option consists of an even number of
21649 colon-separated strings. The first of each pair is the test string, and the
21650 second is the name of a transport. If the transport associated with a matched
21651 string is not the current transport, control is passed over to the other
21652 transport. For example, suppose the standard &(local_delivery)& transport has
21655 file_format = "From : local_delivery :\
21656 \1\1\1\1\n : local_mmdf_delivery"
21658 Mailboxes that begin with &"From"& are still handled by this transport, but if
21659 a mailbox begins with four binary ones followed by a newline, control is passed
21660 to a transport called &%local_mmdf_delivery%&, which presumably is configured
21661 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
21662 is assumed to match the current transport. If the start of a mailbox doesn't
21663 match any string, or if the transport named for a given string is not defined,
21664 delivery is deferred.
21667 .option file_must_exist appendfile boolean false
21668 If this option is true, the file specified by the &%file%& option must exist.
21669 A temporary error occurs if it does not, causing delivery to be deferred.
21670 If this option is false, the file is created if it does not exist.
21673 .option lock_fcntl_timeout appendfile time 0s
21674 .cindex "timeout" "mailbox locking"
21675 .cindex "mailbox" "locking, blocking and non-blocking"
21676 .cindex "locking files"
21677 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
21678 when locking an open mailbox file. If the call fails, the delivery process
21679 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
21680 Non-blocking calls are used so that the file is not kept open during the wait
21681 for the lock; the reason for this is to make it as safe as possible for
21682 deliveries over NFS in the case when processes might be accessing an NFS
21683 mailbox without using a lock file. This should not be done, but
21684 misunderstandings and hence misconfigurations are not unknown.
21686 On a busy system, however, the performance of a non-blocking lock approach is
21687 not as good as using a blocking lock with a timeout. In this case, the waiting
21688 is done inside the system call, and Exim's delivery process acquires the lock
21689 and can proceed as soon as the previous lock holder releases it.
21691 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
21692 timeout, are used. There may still be some retrying: the maximum number of
21695 (lock_retries * lock_interval) / lock_fcntl_timeout
21697 rounded up to the next whole number. In other words, the total time during
21698 which &(appendfile)& is trying to get a lock is roughly the same, unless
21699 &%lock_fcntl_timeout%& is set very large.
21701 You should consider setting this option if you are getting a lot of delayed
21702 local deliveries because of errors of the form
21704 failed to lock mailbox /some/file (fcntl)
21707 .option lock_flock_timeout appendfile time 0s
21708 This timeout applies to file locking when using &[flock()]& (see
21709 &%use_flock%&); the timeout operates in a similar manner to
21710 &%lock_fcntl_timeout%&.
21713 .option lock_interval appendfile time 3s
21714 This specifies the time to wait between attempts to lock the file. See below
21715 for details of locking.
21718 .option lock_retries appendfile integer 10
21719 This specifies the maximum number of attempts to lock the file. A value of zero
21720 is treated as 1. See below for details of locking.
21723 .option lockfile_mode appendfile "octal integer" 0600
21724 This specifies the mode of the created lock file, when a lock file is being
21725 used (see &%use_lockfile%& and &%use_mbx_lock%&).
21728 .option lockfile_timeout appendfile time 30m
21729 .cindex "timeout" "mailbox locking"
21730 When a lock file is being used (see &%use_lockfile%&), if a lock file already
21731 exists and is older than this value, it is assumed to have been left behind by
21732 accident, and Exim attempts to remove it.
21735 .option mailbox_filecount appendfile string&!! unset
21736 .cindex "mailbox" "specifying size of"
21737 .cindex "size" "of mailbox"
21738 If this option is set, it is expanded, and the result is taken as the current
21739 number of files in the mailbox. It must be a decimal number, optionally
21740 followed by K or M. This provides a way of obtaining this information from an
21741 external source that maintains the data.
21744 .option mailbox_size appendfile string&!! unset
21745 .cindex "mailbox" "specifying size of"
21746 .cindex "size" "of mailbox"
21747 If this option is set, it is expanded, and the result is taken as the current
21748 size the mailbox. It must be a decimal number, optionally followed by K or M.
21749 This provides a way of obtaining this information from an external source that
21750 maintains the data. This is likely to be helpful for maildir deliveries where
21751 it is computationally expensive to compute the size of a mailbox.
21755 .option maildir_format appendfile boolean false
21756 .cindex "maildir format" "specifying"
21757 If this option is set with the &%directory%& option, the delivery is into a new
21758 file, in the &"maildir"& format that is used by other mail software. When the
21759 transport is activated directly from a &(redirect)& router (for example, the
21760 &(address_file)& transport in the default configuration), setting
21761 &%maildir_format%& causes the path received from the router to be treated as a
21762 directory, whether or not it ends with &`/`&. This option is available only if
21763 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
21764 &<<SECTmaildirdelivery>>& below for further details.
21767 .option maildir_quota_directory_regex appendfile string "See below"
21768 .cindex "maildir format" "quota; directories included in"
21769 .cindex "quota" "maildir; directories included in"
21770 This option is relevant only when &%maildir_use_size_file%& is set. It defines
21771 a regular expression for specifying directories, relative to the quota
21772 directory (see &%quota_directory%&), that should be included in the quota
21773 calculation. The default value is:
21775 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
21777 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
21778 (directories whose names begin with a dot). If you want to exclude the
21780 folder from the count (as some sites do), you need to change this setting to
21782 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
21784 This uses a negative lookahead in the regular expression to exclude the
21785 directory whose name is &_.Trash_&. When a directory is excluded from quota
21786 calculations, quota processing is bypassed for any messages that are delivered
21787 directly into that directory.
21790 .option maildir_retries appendfile integer 10
21791 This option specifies the number of times to retry when writing a file in
21792 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
21795 .option maildir_tag appendfile string&!! unset
21796 This option applies only to deliveries in maildir format, and is described in
21797 section &<<SECTmaildirdelivery>>& below.
21800 .option maildir_use_size_file appendfile&!! boolean false
21801 .cindex "maildir format" "&_maildirsize_& file"
21802 The result of string expansion for this option must be a valid boolean value.
21803 If it is true, it enables support for &_maildirsize_& files. Exim
21804 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
21805 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
21806 value is zero. See &%maildir_quota_directory_regex%& above and section
21807 &<<SECTmaildirdelivery>>& below for further details.
21809 .option maildirfolder_create_regex appendfile string unset
21810 .cindex "maildir format" "&_maildirfolder_& file"
21811 .cindex "&_maildirfolder_&, creating"
21812 The value of this option is a regular expression. If it is unset, it has no
21813 effect. Otherwise, before a maildir delivery takes place, the pattern is
21814 matched against the name of the maildir directory, that is, the directory
21815 containing the &_new_& and &_tmp_& subdirectories that will be used for the
21816 delivery. If there is a match, Exim checks for the existence of a file called
21817 &_maildirfolder_& in the directory, and creates it if it does not exist.
21818 See section &<<SECTmaildirdelivery>>& for more details.
21821 .option mailstore_format appendfile boolean false
21822 .cindex "mailstore format" "specifying"
21823 If this option is set with the &%directory%& option, the delivery is into two
21824 new files in &"mailstore"& format. The option is available only if
21825 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
21826 below for further details.
21829 .option mailstore_prefix appendfile string&!! unset
21830 This option applies only to deliveries in mailstore format, and is described in
21831 section &<<SECTopdir>>& below.
21834 .option mailstore_suffix appendfile string&!! unset
21835 This option applies only to deliveries in mailstore format, and is described in
21836 section &<<SECTopdir>>& below.
21839 .option mbx_format appendfile boolean false
21840 .cindex "locking files"
21841 .cindex "file" "locking"
21842 .cindex "file" "MBX format"
21843 .cindex "MBX format, specifying"
21844 This option is available only if Exim has been compiled with SUPPORT_MBX
21845 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
21846 the message is appended to the mailbox file in MBX format instead of
21847 traditional Unix format. This format is supported by Pine4 and its associated
21848 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
21850 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
21851 automatically changed by the use of &%mbx_format%&. They should normally be set
21852 empty when using MBX format, so this option almost always appears in this
21859 If none of the locking options are mentioned in the configuration,
21860 &%use_mbx_lock%& is assumed and the other locking options default to false. It
21861 is possible to specify the other kinds of locking with &%mbx_format%&, but
21862 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
21863 interworks with &'c-client'&, providing for shared access to the mailbox. It
21864 should not be used if any program that does not use this form of locking is
21865 going to access the mailbox, nor should it be used if the mailbox file is NFS
21866 mounted, because it works only when the mailbox is accessed from a single host.
21868 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
21869 the standard version of &'c-client'&, because as long as it has a mailbox open
21870 (this means for the whole of a Pine or IMAP session), Exim will not be able to
21871 append messages to it.
21874 .option message_prefix appendfile string&!! "see below"
21875 .cindex "&""From""& line"
21876 The string specified here is expanded and output at the start of every message.
21877 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21878 in which case it is:
21880 message_prefix = "From ${if def:return_path{$return_path}\
21881 {MAILER-DAEMON}} $tod_bsdinbox\n"
21883 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21884 &`\n`& to &`\r\n`& in &%message_prefix%&.
21886 .option message_suffix appendfile string&!! "see below"
21887 The string specified here is expanded and output at the end of every message.
21888 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21889 in which case it is a single newline character. The suffix can be suppressed by
21894 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21895 &`\n`& to &`\r\n`& in &%message_suffix%&.
21897 .option mode appendfile "octal integer" 0600
21898 If the output file is created, it is given this mode. If it already exists and
21899 has wider permissions, they are reduced to this mode. If it has narrower
21900 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
21901 if the delivery is the result of a &%save%& command in a filter file specifying
21902 a particular mode, the mode of the output file is always forced to take that
21903 value, and this option is ignored.
21906 .option mode_fail_narrower appendfile boolean true
21907 This option applies in the case when an existing mailbox file has a narrower
21908 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
21909 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
21910 continues with the delivery attempt, using the existing mode of the file.
21913 .option notify_comsat appendfile boolean false
21914 If this option is true, the &'comsat'& daemon is notified after every
21915 successful delivery to a user mailbox. This is the daemon that notifies logged
21916 on users about incoming mail.
21919 .option quota appendfile string&!! unset
21920 .cindex "quota" "imposed by Exim"
21921 This option imposes a limit on the size of the file to which Exim is appending,
21922 or to the total space used in the directory tree when the &%directory%& option
21923 is set. In the latter case, computation of the space used is expensive, because
21924 all the files in the directory (and any sub-directories) have to be
21925 individually inspected and their sizes summed. (See &%quota_size_regex%& and
21926 &%maildir_use_size_file%& for ways to avoid this in environments where users
21927 have no shell access to their mailboxes).
21929 As there is no interlock against two simultaneous deliveries into a
21930 multi-file mailbox, it is possible for the quota to be overrun in this case.
21931 For single-file mailboxes, of course, an interlock is a necessity.
21933 A file's size is taken as its &'used'& value. Because of blocking effects, this
21934 may be a lot less than the actual amount of disk space allocated to the file.
21935 If the sizes of a number of files are being added up, the rounding effect can
21936 become quite noticeable, especially on systems that have large block sizes.
21937 Nevertheless, it seems best to stick to the &'used'& figure, because this is
21938 the obvious value which users understand most easily.
21940 The value of the option is expanded, and must then be a numerical value
21941 (decimal point allowed), optionally followed by one of the letters K, M, or G,
21942 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
21943 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
21946 &*Note*&: A value of zero is interpreted as &"no quota"&.
21948 The expansion happens while Exim is running as root, before it changes uid for
21949 the delivery. This means that files that are inaccessible to the end user can
21950 be used to hold quota values that are looked up in the expansion. When delivery
21951 fails because this quota is exceeded, the handling of the error is as for
21952 system quota failures.
21954 By default, Exim's quota checking mimics system quotas, and restricts the
21955 mailbox to the specified maximum size, though the value is not accurate to the
21956 last byte, owing to separator lines and additional headers that may get added
21957 during message delivery. When a mailbox is nearly full, large messages may get
21958 refused even though small ones are accepted, because the size of the current
21959 message is added to the quota when the check is made. This behaviour can be
21960 changed by setting &%quota_is_inclusive%& false. When this is done, the check
21961 for exceeding the quota does not include the current message. Thus, deliveries
21962 continue until the quota has been exceeded; thereafter, no further messages are
21963 delivered. See also &%quota_warn_threshold%&.
21966 .option quota_directory appendfile string&!! unset
21967 This option defines the directory to check for quota purposes when delivering
21968 into individual files. The default is the delivery directory, or, if a file
21969 called &_maildirfolder_& exists in a maildir directory, the parent of the
21970 delivery directory.
21973 .option quota_filecount appendfile string&!! 0
21974 This option applies when the &%directory%& option is set. It limits the total
21975 number of files in the directory (compare the inode limit in system quotas). It
21976 can only be used if &%quota%& is also set. The value is expanded; an expansion
21977 failure causes delivery to be deferred. A value of zero is interpreted as
21981 .option quota_is_inclusive appendfile boolean true
21982 See &%quota%& above.
21985 .option quota_size_regex appendfile string unset
21986 This option applies when one of the delivery modes that writes a separate file
21987 for each message is being used. When Exim wants to find the size of one of
21988 these files in order to test the quota, it first checks &%quota_size_regex%&.
21989 If this is set to a regular expression that matches the file name, and it
21990 captures one string, that string is interpreted as a representation of the
21991 file's size. The value of &%quota_size_regex%& is not expanded.
21993 This feature is useful only when users have no shell access to their mailboxes
21994 &-- otherwise they could defeat the quota simply by renaming the files. This
21995 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
21996 the file length to the file name. For example:
21998 maildir_tag = ,S=$message_size
21999 quota_size_regex = ,S=(\d+)
22001 An alternative to &$message_size$& is &$message_linecount$&, which contains the
22002 number of lines in the message.
22004 The regular expression should not assume that the length is at the end of the
22005 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
22006 sometimes add other information onto the ends of message file names.
22008 Section &<<SECID136>>& contains further information.
22011 .option quota_warn_message appendfile string&!! "see below"
22012 See below for the use of this option. If it is not set when
22013 &%quota_warn_threshold%& is set, it defaults to
22015 quota_warn_message = "\
22016 To: $local_part@$domain\n\
22017 Subject: Your mailbox\n\n\
22018 This message is automatically created \
22019 by mail delivery software.\n\n\
22020 The size of your mailbox has exceeded \
22021 a warning threshold that is\n\
22022 set by the system administrator.\n"
22026 .option quota_warn_threshold appendfile string&!! 0
22027 .cindex "quota" "warning threshold"
22028 .cindex "mailbox" "size warning"
22029 .cindex "size" "of mailbox"
22030 This option is expanded in the same way as &%quota%& (see above). If the
22031 resulting value is greater than zero, and delivery of the message causes the
22032 size of the file or total space in the directory tree to cross the given
22033 threshold, a warning message is sent. If &%quota%& is also set, the threshold
22034 may be specified as a percentage of it by following the value with a percent
22038 quota_warn_threshold = 75%
22040 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
22041 percent sign is ignored.
22043 The warning message itself is specified by the &%quota_warn_message%& option,
22044 and it must start with a &'To:'& header line containing the recipient(s) of the
22045 warning message. These do not necessarily have to include the recipient(s) of
22046 the original message. A &'Subject:'& line should also normally be supplied. You
22047 can include any other header lines that you want. If you do not include a
22048 &'From:'& line, the default is:
22050 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
22052 .oindex &%errors_reply_to%&
22053 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
22056 The &%quota%& option does not have to be set in order to use this option; they
22057 are independent of one another except when the threshold is specified as a
22061 .option use_bsmtp appendfile boolean false
22062 .cindex "envelope sender"
22063 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
22064 format, with the envelope sender and recipient(s) included as SMTP commands. If
22065 you want to include a leading HELO command with such messages, you can do
22066 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
22067 for details of batch SMTP.
22070 .option use_crlf appendfile boolean false
22071 .cindex "carriage return"
22073 This option causes lines to be terminated with the two-character CRLF sequence
22074 (carriage return, linefeed) instead of just a linefeed character. In the case
22075 of batched SMTP, the byte sequence written to the file is then an exact image
22076 of what would be sent down a real SMTP connection.
22078 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
22079 (which are used to supply the traditional &"From&~"& and blank line separators
22080 in Berkeley-style mailboxes) are written verbatim, so must contain their own
22081 carriage return characters if these are needed. In cases where these options
22082 have non-empty defaults, the values end with a single linefeed, so they must be
22083 changed to end with &`\r\n`& if &%use_crlf%& is set.
22086 .option use_fcntl_lock appendfile boolean "see below"
22087 This option controls the use of the &[fcntl()]& function to lock a file for
22088 exclusive use when a message is being appended. It is set by default unless
22089 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
22090 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
22091 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
22094 .option use_flock_lock appendfile boolean false
22095 This option is provided to support the use of &[flock()]& for file locking, for
22096 the few situations where it is needed. Most modern operating systems support
22097 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
22098 each other. Exim uses &[fcntl()]& locking by default.
22100 This option is required only if you are using an operating system where
22101 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
22102 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
22103 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
22105 .cindex "Solaris" "&[flock()]& support"
22106 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
22107 have it (and some, I think, provide a not quite right version built on top of
22108 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
22109 the ability to use it, and any attempt to do so will cause a configuration
22112 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
22113 is just being mapped onto &[fcntl()]& by the OS).
22116 .option use_lockfile appendfile boolean "see below"
22117 If this option is turned off, Exim does not attempt to create a lock file when
22118 appending to a mailbox file. In this situation, the only locking is by
22119 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
22120 sure that every MUA that is ever going to look at your users' mailboxes uses
22121 &[fcntl()]& rather than a lock file, and even then only when you are not
22122 delivering over NFS from more than one host.
22124 .cindex "NFS" "lock file"
22125 In order to append to an NFS file safely from more than one host, it is
22126 necessary to take out a lock &'before'& opening the file, and the lock file
22127 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
22130 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
22131 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
22132 except when &%mbx_format%& is set.
22135 .option use_mbx_lock appendfile boolean "see below"
22136 This option is available only if Exim has been compiled with SUPPORT_MBX
22137 set in &_Local/Makefile_&. Setting the option specifies that special MBX
22138 locking rules be used. It is set by default if &%mbx_format%& is set and none
22139 of the locking options are mentioned in the configuration. The locking rules
22140 are the same as are used by the &'c-client'& library that underlies Pine and
22141 the IMAP4 and POP daemons that come with it (see the discussion below). The
22142 rules allow for shared access to the mailbox. However, this kind of locking
22143 does not work when the mailbox is NFS mounted.
22145 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
22146 &%use_flock_lock%& to control what kind of locking is used in implementing the
22147 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
22148 without &%use_fcntl_lock%& or &%use_flock_lock%&.
22153 .section "Operational details for appending" "SECTopappend"
22154 .cindex "appending to a file"
22155 .cindex "file" "appending"
22156 Before appending to a file, the following preparations are made:
22159 If the name of the file is &_/dev/null_&, no action is taken, and a success
22163 .cindex "directory creation"
22164 If any directories on the file's path are missing, Exim creates them if the
22165 &%create_directory%& option is set. A created directory's mode is given by the
22166 &%directory_mode%& option.
22169 If &%file_format%& is set, the format of an existing file is checked. If this
22170 indicates that a different transport should be used, control is passed to that
22174 .cindex "file" "locking"
22175 .cindex "locking files"
22176 .cindex "NFS" "lock file"
22177 If &%use_lockfile%& is set, a lock file is built in a way that will work
22178 reliably over NFS, as follows:
22181 Create a &"hitching post"& file whose name is that of the lock file with the
22182 current time, primary host name, and process id added, by opening for writing
22183 as a new file. If this fails with an access error, delivery is deferred.
22185 Close the hitching post file, and hard link it to the lock file name.
22187 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
22188 Unlink the hitching post name.
22190 Otherwise, use &[stat()]& to get information about the hitching post file, and
22191 then unlink hitching post name. If the number of links is exactly two, creation
22192 of the lock file succeeded but something (for example, an NFS server crash and
22193 restart) caused this fact not to be communicated to the &[link()]& call.
22195 If creation of the lock file failed, wait for &%lock_interval%& and try again,
22196 up to &%lock_retries%& times. However, since any program that writes to a
22197 mailbox should complete its task very quickly, it is reasonable to time out old
22198 lock files that are normally the result of user agent and system crashes. If an
22199 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
22200 it before trying again.
22204 A call is made to &[lstat()]& to discover whether the main file exists, and if
22205 so, what its characteristics are. If &[lstat()]& fails for any reason other
22206 than non-existence, delivery is deferred.
22209 .cindex "symbolic link" "to mailbox"
22210 .cindex "mailbox" "symbolic link"
22211 If the file does exist and is a symbolic link, delivery is deferred, unless the
22212 &%allow_symlink%& option is set, in which case the ownership of the link is
22213 checked, and then &[stat()]& is called to find out about the real file, which
22214 is then subjected to the checks below. The check on the top-level link
22215 ownership prevents one user creating a link for another's mailbox in a sticky
22216 directory, though allowing symbolic links in this case is definitely not a good
22217 idea. If there is a chain of symbolic links, the intermediate ones are not
22221 If the file already exists but is not a regular file, or if the file's owner
22222 and group (if the group is being checked &-- see &%check_group%& above) are
22223 different from the user and group under which the delivery is running,
22224 delivery is deferred.
22227 If the file's permissions are more generous than specified, they are reduced.
22228 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
22229 is set false, in which case the delivery is tried using the existing
22233 The file's inode number is saved, and the file is then opened for appending.
22234 If this fails because the file has vanished, &(appendfile)& behaves as if it
22235 hadn't existed (see below). For any other failures, delivery is deferred.
22238 If the file is opened successfully, check that the inode number hasn't
22239 changed, that it is still a regular file, and that the owner and permissions
22240 have not changed. If anything is wrong, defer delivery and freeze the message.
22243 If the file did not exist originally, defer delivery if the &%file_must_exist%&
22244 option is set. Otherwise, check that the file is being created in a permitted
22245 directory if the &%create_file%& option is set (deferring on failure), and then
22246 open for writing as a new file, with the O_EXCL and O_CREAT options,
22247 except when dealing with a symbolic link (the &%allow_symlink%& option must be
22248 set). In this case, which can happen if the link points to a non-existent file,
22249 the file is opened for writing using O_CREAT but not O_EXCL, because
22250 that prevents link following.
22253 .cindex "loop" "while file testing"
22254 If opening fails because the file exists, obey the tests given above for
22255 existing files. However, to avoid looping in a situation where the file is
22256 being continuously created and destroyed, the exists/not-exists loop is broken
22257 after 10 repetitions, and the message is then frozen.
22260 If opening fails with any other error, defer delivery.
22263 .cindex "file" "locking"
22264 .cindex "locking files"
22265 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
22266 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
22267 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
22268 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
22269 file, and an exclusive lock on the file whose name is
22271 /tmp/.<device-number>.<inode-number>
22273 using the device and inode numbers of the open mailbox file, in accordance with
22274 the MBX locking rules. This file is created with a mode that is specified by
22275 the &%lockfile_mode%& option.
22277 If Exim fails to lock the file, there are two possible courses of action,
22278 depending on the value of the locking timeout. This is obtained from
22279 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
22281 If the timeout value is zero, the file is closed, Exim waits for
22282 &%lock_interval%&, and then goes back and re-opens the file as above and tries
22283 to lock it again. This happens up to &%lock_retries%& times, after which the
22284 delivery is deferred.
22286 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
22287 &[flock()]& are used (with the given timeout), so there has already been some
22288 waiting involved by the time locking fails. Nevertheless, Exim does not give up
22289 immediately. It retries up to
22291 (lock_retries * lock_interval) / <timeout>
22293 times (rounded up).
22296 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
22297 and/or &[flock()]& locks) and then deletes the lock file if one was created.
22300 .section "Operational details for delivery to a new file" "SECTopdir"
22301 .cindex "delivery" "to single file"
22302 .cindex "&""From""& line"
22303 When the &%directory%& option is set instead of &%file%&, each message is
22304 delivered into a newly-created file or set of files. When &(appendfile)& is
22305 activated directly from a &(redirect)& router, neither &%file%& nor
22306 &%directory%& is normally set, because the path for delivery is supplied by the
22307 router. (See for example, the &(address_file)& transport in the default
22308 configuration.) In this case, delivery is to a new file if either the path name
22309 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
22311 No locking is required while writing the message to a new file, so the various
22312 locking options of the transport are ignored. The &"From"& line that by default
22313 separates messages in a single file is not normally needed, nor is the escaping
22314 of message lines that start with &"From"&, and there is no need to ensure a
22315 newline at the end of each message. Consequently, the default values for
22316 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
22317 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
22319 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
22320 the files in the delivery directory by default. However, you can specify a
22321 different directory by setting &%quota_directory%&. Also, for maildir
22322 deliveries (see below) the &_maildirfolder_& convention is honoured.
22325 .cindex "maildir format"
22326 .cindex "mailstore format"
22327 There are three different ways in which delivery to individual files can be
22328 done, controlled by the settings of the &%maildir_format%& and
22329 &%mailstore_format%& options. Note that code to support maildir or mailstore
22330 formats is not included in the binary unless SUPPORT_MAILDIR or
22331 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
22333 .cindex "directory creation"
22334 In all three cases an attempt is made to create the directory and any necessary
22335 sub-directories if they do not exist, provided that the &%create_directory%&
22336 option is set (the default). The location of a created directory can be
22337 constrained by setting &%create_file%&. A created directory's mode is given by
22338 the &%directory_mode%& option. If creation fails, or if the
22339 &%create_directory%& option is not set when creation is required, delivery is
22344 .section "Maildir delivery" "SECTmaildirdelivery"
22345 .cindex "maildir format" "description of"
22346 If the &%maildir_format%& option is true, Exim delivers each message by writing
22347 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
22348 directory that is defined by the &%directory%& option (the &"delivery
22349 directory"&). If the delivery is successful, the file is renamed into the
22350 &_new_& subdirectory.
22352 In the file name, <&'stime'&> is the current time of day in seconds, and
22353 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
22354 Exim checks that the time-of-day clock has moved on by at least one microsecond
22355 before terminating the delivery process. This guarantees uniqueness for the
22356 file name. However, as a precaution, Exim calls &[stat()]& for the file before
22357 opening it. If any response other than ENOENT (does not exist) is given,
22358 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
22360 Before Exim carries out a maildir delivery, it ensures that subdirectories
22361 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
22362 do not exist, Exim tries to create them and any superior directories in their
22363 path, subject to the &%create_directory%& and &%create_file%& options. If the
22364 &%maildirfolder_create_regex%& option is set, and the regular expression it
22365 contains matches the delivery directory, Exim also ensures that a file called
22366 &_maildirfolder_& exists in the delivery directory. If a missing directory or
22367 &_maildirfolder_& file cannot be created, delivery is deferred.
22369 These features make it possible to use Exim to create all the necessary files
22370 and directories in a maildir mailbox, including subdirectories for maildir++
22371 folders. Consider this example:
22373 maildir_format = true
22374 directory = /var/mail/$local_part\
22375 ${if eq{$local_part_suffix}{}{}\
22376 {/.${substr_1:$local_part_suffix}}}
22377 maildirfolder_create_regex = /\.[^/]+$
22379 If &$local_part_suffix$& is empty (there was no suffix for the local part),
22380 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
22381 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
22382 not match this name, so Exim will not look for or create the file
22383 &_/var/mail/pimbo/maildirfolder_&, though it will create
22384 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
22386 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
22387 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
22388 does match &%maildirfolder_create_regex%&. In this case, Exim will create
22389 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
22390 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
22392 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
22393 not inadvertently match the toplevel maildir directory, because a
22394 &_maildirfolder_& file at top level would completely break quota calculations.
22396 .cindex "quota" "in maildir delivery"
22397 .cindex "maildir++"
22398 If Exim is required to check a &%quota%& setting before a maildir delivery, and
22399 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
22400 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
22401 Exim assumes the directory is a maildir++ folder directory, which is one level
22402 down from the user's top level mailbox directory. This causes it to start at
22403 the parent directory instead of the current directory when calculating the
22404 amount of space used.
22406 One problem with delivering into a multi-file mailbox is that it is
22407 computationally expensive to compute the size of the mailbox for quota
22408 checking. Various approaches have been taken to reduce the amount of work
22409 needed. The next two sections describe two of them. A third alternative is to
22410 use some external process for maintaining the size data, and use the expansion
22411 of the &%mailbox_size%& option as a way of importing it into Exim.
22416 .section "Using tags to record message sizes" "SECID135"
22417 If &%maildir_tag%& is set, the string is expanded for each delivery.
22418 When the maildir file is renamed into the &_new_& sub-directory, the
22419 tag is added to its name. However, if adding the tag takes the length of the
22420 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
22421 the tag is dropped and the maildir file is created with no tag.
22424 .vindex "&$message_size$&"
22425 Tags can be used to encode the size of files in their names; see
22426 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
22427 happens after the message has been written. The value of the &$message_size$&
22428 variable is set to the number of bytes actually written. If the expansion is
22429 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
22430 be deferred. The expanded tag may contain any printing characters except &"/"&.
22431 Non-printing characters in the string are ignored; if the resulting string is
22432 empty, it is ignored. If it starts with an alphanumeric character, a leading
22433 colon is inserted; this default has not proven to be the path that popular
22434 maildir implementations have chosen (but changing it in Exim would break
22435 backwards compatibility).
22437 For one common implementation, you might set:
22439 maildir_tag = ,S=${message_size}
22441 but you should check the documentation of the other software to be sure.
22443 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
22444 as this allows Exim to extract the size from your tag, instead of having to
22445 &[stat()]& each message file.
22448 .section "Using a maildirsize file" "SECID136"
22449 .cindex "quota" "in maildir delivery"
22450 .cindex "maildir format" "&_maildirsize_& file"
22451 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
22452 storing quota and message size information in a file called &_maildirsize_&
22453 within the toplevel maildir directory. If this file does not exist, Exim
22454 creates it, setting the quota from the &%quota%& option of the transport. If
22455 the maildir directory itself does not exist, it is created before any attempt
22456 to write a &_maildirsize_& file.
22458 The &_maildirsize_& file is used to hold information about the sizes of
22459 messages in the maildir, thus speeding up quota calculations. The quota value
22460 in the file is just a cache; if the quota is changed in the transport, the new
22461 value overrides the cached value when the next message is delivered. The cache
22462 is maintained for the benefit of other programs that access the maildir and
22463 need to know the quota.
22465 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
22466 file is maintained (with a zero quota setting), but no quota is imposed.
22468 A regular expression is available for controlling which directories in the
22469 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
22470 See the description of the &%maildir_quota_directory_regex%& option above for
22474 .section "Mailstore delivery" "SECID137"
22475 .cindex "mailstore format" "description of"
22476 If the &%mailstore_format%& option is true, each message is written as two
22477 files in the given directory. A unique base name is constructed from the
22478 message id and the current delivery process, and the files that are written use
22479 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
22480 contains the message's envelope, and the &_.msg_& file contains the message
22481 itself. The base name is placed in the variable &$mailstore_basename$&.
22483 During delivery, the envelope is first written to a file with the suffix
22484 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
22485 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
22486 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
22487 file before accessing either of them. An alternative approach is to wait for
22488 the absence of a &_.tmp_& file.
22490 The envelope file starts with any text defined by the &%mailstore_prefix%&
22491 option, expanded and terminated by a newline if there isn't one. Then follows
22492 the sender address on one line, then all the recipient addresses, one per line.
22493 There can be more than one recipient only if the &%batch_max%& option is set
22494 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
22495 appended to the file, followed by a newline if it does not end with one.
22497 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
22498 failure, it is ignored. Other expansion errors are treated as serious
22499 configuration errors, and delivery is deferred. The variable
22500 &$mailstore_basename$& is available for use during these expansions.
22503 .section "Non-special new file delivery" "SECID138"
22504 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
22505 file is created directly in the named directory. For example, when delivering
22506 messages into files in batched SMTP format for later delivery to some host (see
22507 section &<<SECTbatchSMTP>>&), a setting such as
22509 directory = /var/bsmtp/$host
22511 might be used. A message is written to a file with a temporary name, which is
22512 then renamed when the delivery is complete. The final name is obtained by
22513 expanding the contents of the &%directory_file%& option.
22514 .ecindex IIDapptra1
22515 .ecindex IIDapptra2
22522 . ////////////////////////////////////////////////////////////////////////////
22523 . ////////////////////////////////////////////////////////////////////////////
22525 .chapter "The autoreply transport" "CHID8"
22526 .scindex IIDauttra1 "transports" "&(autoreply)&"
22527 .scindex IIDauttra2 "&(autoreply)& transport"
22528 The &(autoreply)& transport is not a true transport in that it does not cause
22529 the message to be transmitted. Instead, it generates a new mail message as an
22530 automatic reply to the incoming message. &'References:'& and
22531 &'Auto-Submitted:'& header lines are included. These are constructed according
22532 to the rules in RFCs 2822 and 3834, respectively.
22534 If the router that passes the message to this transport does not have the
22535 &%unseen%& option set, the original message (for the current recipient) is not
22536 delivered anywhere. However, when the &%unseen%& option is set on the router
22537 that passes the message to this transport, routing of the address continues, so
22538 another router can set up a normal message delivery.
22541 The &(autoreply)& transport is usually run as the result of mail filtering, a
22542 &"vacation"& message being the standard example. However, it can also be run
22543 directly from a router like any other transport. To reduce the possibility of
22544 message cascades, messages created by the &(autoreply)& transport always have
22545 empty envelope sender addresses, like bounce messages.
22547 The parameters of the message to be sent can be specified in the configuration
22548 by options described below. However, these are used only when the address
22549 passed to the transport does not contain its own reply information. When the
22550 transport is run as a consequence of a
22552 or &%vacation%& command in a filter file, the parameters of the message are
22553 supplied by the filter, and passed with the address. The transport's options
22554 that define the message are then ignored (so they are not usually set in this
22555 case). The message is specified entirely by the filter or by the transport; it
22556 is never built from a mixture of options. However, the &%file_optional%&,
22557 &%mode%&, and &%return_message%& options apply in all cases.
22559 &(Autoreply)& is implemented as a local transport. When used as a result of a
22560 command in a user's filter file, &(autoreply)& normally runs under the uid and
22561 gid of the user, and with appropriate current and home directories (see chapter
22562 &<<CHAPenvironment>>&).
22564 There is a subtle difference between routing a message to a &(pipe)& transport
22565 that generates some text to be returned to the sender, and routing it to an
22566 &(autoreply)& transport. This difference is noticeable only if more than one
22567 address from the same message is so handled. In the case of a pipe, the
22568 separate outputs from the different addresses are gathered up and returned to
22569 the sender in a single message, whereas if &(autoreply)& is used, a separate
22570 message is generated for each address that is passed to it.
22572 Non-printing characters are not permitted in the header lines generated for the
22573 message that &(autoreply)& creates, with the exception of newlines that are
22574 immediately followed by white space. If any non-printing characters are found,
22575 the transport defers.
22576 Whether characters with the top bit set count as printing characters or not is
22577 controlled by the &%print_topbitchars%& global option.
22579 If any of the generic options for manipulating headers (for example,
22580 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
22581 of the original message that is included in the generated message when
22582 &%return_message%& is set. They do not apply to the generated message itself.
22584 .vindex "&$sender_address$&"
22585 If the &(autoreply)& transport receives return code 2 from Exim when it submits
22586 the message, indicating that there were no recipients, it does not treat this
22587 as an error. This means that autoreplies sent to &$sender_address$& when this
22588 is empty (because the incoming message is a bounce message) do not cause
22589 problems. They are just discarded.
22593 .section "Private options for autoreply" "SECID139"
22594 .cindex "options" "&(autoreply)& transport"
22596 .option bcc autoreply string&!! unset
22597 This specifies the addresses that are to receive &"blind carbon copies"& of the
22598 message when the message is specified by the transport.
22601 .option cc autoreply string&!! unset
22602 This specifies recipients of the message and the contents of the &'Cc:'& header
22603 when the message is specified by the transport.
22606 .option file autoreply string&!! unset
22607 The contents of the file are sent as the body of the message when the message
22608 is specified by the transport. If both &%file%& and &%text%& are set, the text
22609 string comes first.
22612 .option file_expand autoreply boolean false
22613 If this is set, the contents of the file named by the &%file%& option are
22614 subjected to string expansion as they are added to the message.
22617 .option file_optional autoreply boolean false
22618 If this option is true, no error is generated if the file named by the &%file%&
22619 option or passed with the address does not exist or cannot be read.
22622 .option from autoreply string&!! unset
22623 This specifies the contents of the &'From:'& header when the message is
22624 specified by the transport.
22627 .option headers autoreply string&!! unset
22628 This specifies additional RFC 2822 headers that are to be added to the message
22629 when the message is specified by the transport. Several can be given by using
22630 &"\n"& to separate them. There is no check on the format.
22633 .option log autoreply string&!! unset
22634 This option names a file in which a record of every message sent is logged when
22635 the message is specified by the transport.
22638 .option mode autoreply "octal integer" 0600
22639 If either the log file or the &"once"& file has to be created, this mode is
22643 .option never_mail autoreply "address list&!!" unset
22644 If any run of the transport creates a message with a recipient that matches any
22645 item in the list, that recipient is quietly discarded. If all recipients are
22646 discarded, no message is created. This applies both when the recipients are
22647 generated by a filter and when they are specified in the transport.
22651 .option once autoreply string&!! unset
22652 This option names a file or DBM database in which a record of each &'To:'&
22653 recipient is kept when the message is specified by the transport. &*Note*&:
22654 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
22656 If &%once%& is unset, or is set to an empty string, the message is always sent.
22657 By default, if &%once%& is set to a non-empty file name, the message
22658 is not sent if a potential recipient is already listed in the database.
22659 However, if the &%once_repeat%& option specifies a time greater than zero, the
22660 message is sent if that much time has elapsed since a message was last sent to
22661 this recipient. A setting of zero time for &%once_repeat%& (the default)
22662 prevents a message from being sent a second time &-- in this case, zero means
22665 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
22666 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
22667 greater than zero, it changes the way Exim implements the &%once%& option.
22668 Instead of using a DBM file to record every recipient it sends to, it uses a
22669 regular file, whose size will never get larger than the given value.
22671 In the file, Exim keeps a linear list of recipient addresses and the times at
22672 which they were sent messages. If the file is full when a new address needs to
22673 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
22674 means that a given recipient may receive multiple messages, but at
22675 unpredictable intervals that depend on the rate of turnover of addresses in the
22676 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
22679 .option once_file_size autoreply integer 0
22680 See &%once%& above.
22683 .option once_repeat autoreply time&!! 0s
22684 See &%once%& above.
22685 After expansion, the value of this option must be a valid time value.
22688 .option reply_to autoreply string&!! unset
22689 This specifies the contents of the &'Reply-To:'& header when the message is
22690 specified by the transport.
22693 .option return_message autoreply boolean false
22694 If this is set, a copy of the original message is returned with the new
22695 message, subject to the maximum size set in the &%return_size_limit%& global
22696 configuration option.
22699 .option subject autoreply string&!! unset
22700 This specifies the contents of the &'Subject:'& header when the message is
22701 specified by the transport. It is tempting to quote the original subject in
22702 automatic responses. For example:
22704 subject = Re: $h_subject:
22706 There is a danger in doing this, however. It may allow a third party to
22707 subscribe your users to an opt-in mailing list, provided that the list accepts
22708 bounce messages as subscription confirmations. Well-managed lists require a
22709 non-bounce message to confirm a subscription, so the danger is relatively
22714 .option text autoreply string&!! unset
22715 This specifies a single string to be used as the body of the message when the
22716 message is specified by the transport. If both &%text%& and &%file%& are set,
22717 the text comes first.
22720 .option to autoreply string&!! unset
22721 This specifies recipients of the message and the contents of the &'To:'& header
22722 when the message is specified by the transport.
22723 .ecindex IIDauttra1
22724 .ecindex IIDauttra2
22729 . ////////////////////////////////////////////////////////////////////////////
22730 . ////////////////////////////////////////////////////////////////////////////
22732 .chapter "The lmtp transport" "CHAPLMTP"
22733 .cindex "transports" "&(lmtp)&"
22734 .cindex "&(lmtp)& transport"
22735 .cindex "LMTP" "over a pipe"
22736 .cindex "LMTP" "over a socket"
22737 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
22739 or by interacting with a Unix domain socket.
22740 This transport is something of a cross between the &(pipe)& and &(smtp)&
22741 transports. Exim also has support for using LMTP over TCP/IP; this is
22742 implemented as an option for the &(smtp)& transport. Because LMTP is expected
22743 to be of minority interest, the default build-time configure in &_src/EDITME_&
22744 has it commented out. You need to ensure that
22748 .cindex "options" "&(lmtp)& transport"
22749 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
22750 included in the Exim binary. The private options of the &(lmtp)& transport are
22753 .option batch_id lmtp string&!! unset
22754 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22757 .option batch_max lmtp integer 1
22758 This limits the number of addresses that can be handled in a single delivery.
22759 Most LMTP servers can handle several addresses at once, so it is normally a
22760 good idea to increase this value. See the description of local delivery
22761 batching in chapter &<<CHAPbatching>>&.
22764 .option command lmtp string&!! unset
22765 This option must be set if &%socket%& is not set. The string is a command which
22766 is run in a separate process. It is split up into a command name and list of
22767 arguments, each of which is separately expanded (so expansion cannot change the
22768 number of arguments). The command is run directly, not via a shell. The message
22769 is passed to the new process using the standard input and output to operate the
22772 .option ignore_quota lmtp boolean false
22773 .cindex "LMTP" "ignoring quota errors"
22774 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
22775 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
22776 in its response to the LHLO command.
22778 .option socket lmtp string&!! unset
22779 This option must be set if &%command%& is not set. The result of expansion must
22780 be the name of a Unix domain socket. The transport connects to the socket and
22781 delivers the message to it using the LMTP protocol.
22784 .option timeout lmtp time 5m
22785 The transport is aborted if the created process or Unix domain socket does not
22786 respond to LMTP commands or message input within this timeout. Delivery
22787 is deferred, and will be tried again later. Here is an example of a typical
22792 command = /some/local/lmtp/delivery/program
22796 This delivers up to 20 addresses at a time, in a mixture of domains if
22797 necessary, running as the user &'exim'&.
22801 . ////////////////////////////////////////////////////////////////////////////
22802 . ////////////////////////////////////////////////////////////////////////////
22804 .chapter "The pipe transport" "CHAPpipetransport"
22805 .scindex IIDpiptra1 "transports" "&(pipe)&"
22806 .scindex IIDpiptra2 "&(pipe)& transport"
22807 The &(pipe)& transport is used to deliver messages via a pipe to a command
22808 running in another process. One example is the use of &(pipe)& as a
22809 pseudo-remote transport for passing messages to some other delivery mechanism
22810 (such as UUCP). Another is the use by individual users to automatically process
22811 their incoming messages. The &(pipe)& transport can be used in one of the
22815 .vindex "&$local_part$&"
22816 A router routes one address to a transport in the normal way, and the
22817 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
22818 contains the local part of the address (as usual), and the command that is run
22819 is specified by the &%command%& option on the transport.
22821 .vindex "&$pipe_addresses$&"
22822 If the &%batch_max%& option is set greater than 1 (the default is 1), the
22823 transport can handle more than one address in a single run. In this case, when
22824 more than one address is routed to the transport, &$local_part$& is not set
22825 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
22826 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
22827 that are routed to the transport.
22829 .vindex "&$address_pipe$&"
22830 A router redirects an address directly to a pipe command (for example, from an
22831 alias or forward file). In this case, &$address_pipe$& contains the text of the
22832 pipe command, and the &%command%& option on the transport is ignored unless
22833 &%force_command%& is set. If only one address is being transported
22834 (&%batch_max%& is not greater than one, or only one address was redirected to
22835 this pipe command), &$local_part$& contains the local part that was redirected.
22839 The &(pipe)& transport is a non-interactive delivery method. Exim can also
22840 deliver messages over pipes using the LMTP interactive protocol. This is
22841 implemented by the &(lmtp)& transport.
22843 In the case when &(pipe)& is run as a consequence of an entry in a local user's
22844 &_.forward_& file, the command runs under the uid and gid of that user. In
22845 other cases, the uid and gid have to be specified explicitly, either on the
22846 transport or on the router that handles the address. Current and &"home"&
22847 directories are also controllable. See chapter &<<CHAPenvironment>>& for
22848 details of the local delivery environment and chapter &<<CHAPbatching>>&
22849 for a discussion of local delivery batching.
22852 .section "Concurrent delivery" "SECID140"
22853 If two messages arrive at almost the same time, and both are routed to a pipe
22854 delivery, the two pipe transports may be run concurrently. You must ensure that
22855 any pipe commands you set up are robust against this happening. If the commands
22856 write to a file, the &%exim_lock%& utility might be of use.
22857 Alternatively the &%max_parallel%& option could be used with a value
22858 of "1" to enforce serialization.
22863 .section "Returned status and data" "SECID141"
22864 .cindex "&(pipe)& transport" "returned data"
22865 If the command exits with a non-zero return code, the delivery is deemed to
22866 have failed, unless either the &%ignore_status%& option is set (in which case
22867 the return code is treated as zero), or the return code is one of those listed
22868 in the &%temp_errors%& option, which are interpreted as meaning &"try again
22869 later"&. In this case, delivery is deferred. Details of a permanent failure are
22870 logged, but are not included in the bounce message, which merely contains
22871 &"local delivery failed"&.
22873 If the command exits on a signal and the &%freeze_signal%& option is set then
22874 the message will be frozen in the queue. If that option is not set, a bounce
22875 will be sent as normal.
22877 If the return code is greater than 128 and the command being run is a shell
22878 script, it normally means that the script was terminated by a signal whose
22879 value is the return code minus 128. The &%freeze_signal%& option does not
22880 apply in this case.
22882 If Exim is unable to run the command (that is, if &[execve()]& fails), the
22883 return code is set to 127. This is the value that a shell returns if it is
22884 asked to run a non-existent command. The wording for the log line suggests that
22885 a non-existent command may be the problem.
22887 The &%return_output%& option can affect the result of a pipe delivery. If it is
22888 set and the command produces any output on its standard output or standard
22889 error streams, the command is considered to have failed, even if it gave a zero
22890 return code or if &%ignore_status%& is set. The output from the command is
22891 included as part of the bounce message. The &%return_fail_output%& option is
22892 similar, except that output is returned only when the command exits with a
22893 failure return code, that is, a value other than zero or a code that matches
22898 .section "How the command is run" "SECThowcommandrun"
22899 .cindex "&(pipe)& transport" "path for command"
22900 The command line is (by default) broken down into a command name and arguments
22901 by the &(pipe)& transport itself. The &%allow_commands%& and
22902 &%restrict_to_path%& options can be used to restrict the commands that may be
22905 .cindex "quoting" "in pipe command"
22906 Unquoted arguments are delimited by white space. If an argument appears in
22907 double quotes, backslash is interpreted as an escape character in the usual
22908 way. If an argument appears in single quotes, no escaping is done.
22910 String expansion is applied to the command line except when it comes from a
22911 traditional &_.forward_& file (commands from a filter file are expanded). The
22912 expansion is applied to each argument in turn rather than to the whole line.
22913 For this reason, any string expansion item that contains white space must be
22914 quoted so as to be contained within a single argument. A setting such as
22916 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
22918 will not work, because the expansion item gets split between several
22919 arguments. You have to write
22921 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
22923 to ensure that it is all in one argument. The expansion is done in this way,
22924 argument by argument, so that the number of arguments cannot be changed as a
22925 result of expansion, and quotes or backslashes in inserted variables do not
22926 interact with external quoting. However, this leads to problems if you want to
22927 generate multiple arguments (or the command name plus arguments) from a single
22928 expansion. In this situation, the simplest solution is to use a shell. For
22931 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
22934 .cindex "transport" "filter"
22935 .cindex "filter" "transport filter"
22936 .vindex "&$pipe_addresses$&"
22937 Special handling takes place when an argument consists of precisely the text
22938 &`$pipe_addresses`&. This is not a general expansion variable; the only
22939 place this string is recognized is when it appears as an argument for a pipe or
22940 transport filter command. It causes each address that is being handled to be
22941 inserted in the argument list at that point &'as a separate argument'&. This
22942 avoids any problems with spaces or shell metacharacters, and is of use when a
22943 &(pipe)& transport is handling groups of addresses in a batch.
22945 If &%force_command%& is enabled on the transport, Special handling takes place
22946 for an argument that consists of precisely the text &`$address_pipe`&. It
22947 is handled similarly to &$pipe_addresses$& above. It is expanded and each
22948 argument is inserted in the argument list at that point
22949 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
22950 the only item in the argument; in fact, if it were then &%force_command%&
22951 should behave as a no-op. Rather, it should be used to adjust the command
22952 run while preserving the argument vector separation.
22954 After splitting up into arguments and expansion, the resulting command is run
22955 in a subprocess directly from the transport, &'not'& under a shell. The
22956 message that is being delivered is supplied on the standard input, and the
22957 standard output and standard error are both connected to a single pipe that is
22958 read by Exim. The &%max_output%& option controls how much output the command
22959 may produce, and the &%return_output%& and &%return_fail_output%& options
22960 control what is done with it.
22962 Not running the command under a shell (by default) lessens the security risks
22963 in cases when a command from a user's filter file is built out of data that was
22964 taken from an incoming message. If a shell is required, it can of course be
22965 explicitly specified as the command to be run. However, there are circumstances
22966 where existing commands (for example, in &_.forward_& files) expect to be run
22967 under a shell and cannot easily be modified. To allow for these cases, there is
22968 an option called &%use_shell%&, which changes the way the &(pipe)& transport
22969 works. Instead of breaking up the command line as just described, it expands it
22970 as a single string and passes the result to &_/bin/sh_&. The
22971 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
22972 with &%use_shell%&, and the whole mechanism is inherently less secure.
22976 .section "Environment variables" "SECTpipeenv"
22977 .cindex "&(pipe)& transport" "environment for command"
22978 .cindex "environment" "&(pipe)& transport"
22979 The environment variables listed below are set up when the command is invoked.
22980 This list is a compromise for maximum compatibility with other MTAs. Note that
22981 the &%environment%& option can be used to add additional variables to this
22982 environment. The environment for the &(pipe)& transport is not subject
22983 to the &%add_environment%& and &%keep_environment%& main config options.
22985 &`DOMAIN `& the domain of the address
22986 &`HOME `& the home directory, if set
22987 &`HOST `& the host name when called from a router (see below)
22988 &`LOCAL_PART `& see below
22989 &`LOCAL_PART_PREFIX `& see below
22990 &`LOCAL_PART_SUFFIX `& see below
22991 &`LOGNAME `& see below
22992 &`MESSAGE_ID `& Exim's local ID for the message
22993 &`PATH `& as specified by the &%path%& option below
22994 &`QUALIFY_DOMAIN `& the sender qualification domain
22995 &`RECIPIENT `& the complete recipient address
22996 &`SENDER `& the sender of the message (empty if a bounce)
22997 &`SHELL `& &`/bin/sh`&
22998 &`TZ `& the value of the &%timezone%& option, if set
22999 &`USER `& see below
23001 When a &(pipe)& transport is called directly from (for example) an &(accept)&
23002 router, LOCAL_PART is set to the local part of the address. When it is
23003 called as a result of a forward or alias expansion, LOCAL_PART is set to
23004 the local part of the address that was expanded. In both cases, any affixes are
23005 removed from the local part, and made available in LOCAL_PART_PREFIX and
23006 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
23007 same value as LOCAL_PART for compatibility with other MTAs.
23010 HOST is set only when a &(pipe)& transport is called from a router that
23011 associates hosts with an address, typically when using &(pipe)& as a
23012 pseudo-remote transport. HOST is set to the first host name specified by
23016 If the transport's generic &%home_directory%& option is set, its value is used
23017 for the HOME environment variable. Otherwise, a home directory may be set
23018 by the router's &%transport_home_directory%& option, which defaults to the
23019 user's home directory if &%check_local_user%& is set.
23022 .section "Private options for pipe" "SECID142"
23023 .cindex "options" "&(pipe)& transport"
23027 .option allow_commands pipe "string list&!!" unset
23028 .cindex "&(pipe)& transport" "permitted commands"
23029 The string is expanded, and is then interpreted as a colon-separated list of
23030 permitted commands. If &%restrict_to_path%& is not set, the only commands
23031 permitted are those in the &%allow_commands%& list. They need not be absolute
23032 paths; the &%path%& option is still used for relative paths. If
23033 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
23034 in the &%allow_commands%& list, or a name without any slashes that is found on
23035 the path. In other words, if neither &%allow_commands%& nor
23036 &%restrict_to_path%& is set, there is no restriction on the command, but
23037 otherwise only commands that are permitted by one or the other are allowed. For
23040 allow_commands = /usr/bin/vacation
23042 and &%restrict_to_path%& is not set, the only permitted command is
23043 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
23044 &%use_shell%& is set.
23047 .option batch_id pipe string&!! unset
23048 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23051 .option batch_max pipe integer 1
23052 This limits the number of addresses that can be handled in a single delivery.
23053 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23056 .option check_string pipe string unset
23057 As &(pipe)& writes the message, the start of each line is tested for matching
23058 &%check_string%&, and if it does, the initial matching characters are replaced
23059 by the contents of &%escape_string%&, provided both are set. The value of
23060 &%check_string%& is a literal string, not a regular expression, and the case of
23061 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
23062 of &%check_string%& and &%escape_string%& are forced to values that implement
23063 the SMTP escaping protocol. Any settings made in the configuration file are
23067 .option command pipe string&!! unset
23068 This option need not be set when &(pipe)& is being used to deliver to pipes
23069 obtained directly from address redirections. In other cases, the option must be
23070 set, to provide a command to be run. It need not yield an absolute path (see
23071 the &%path%& option below). The command is split up into separate arguments by
23072 Exim, and each argument is separately expanded, as described in section
23073 &<<SECThowcommandrun>>& above.
23076 .option environment pipe string&!! unset
23077 .cindex "&(pipe)& transport" "environment for command"
23078 .cindex "environment" "&(pipe)& transport"
23079 This option is used to add additional variables to the environment in which the
23080 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
23081 a string which is expanded, and then interpreted as a colon-separated list of
23082 environment settings of the form <&'name'&>=<&'value'&>.
23085 .option escape_string pipe string unset
23086 See &%check_string%& above.
23089 .option freeze_exec_fail pipe boolean false
23090 .cindex "exec failure"
23091 .cindex "failure of exec"
23092 .cindex "&(pipe)& transport" "failure of exec"
23093 Failure to exec the command in a pipe transport is by default treated like
23094 any other failure while running the command. However, if &%freeze_exec_fail%&
23095 is set, failure to exec is treated specially, and causes the message to be
23096 frozen, whatever the setting of &%ignore_status%&.
23099 .option freeze_signal pipe boolean false
23100 .cindex "signal exit"
23101 .cindex "&(pipe)& transport", "signal exit"
23102 Normally if the process run by a command in a pipe transport exits on a signal,
23103 a bounce message is sent. If &%freeze_signal%& is set, the message will be
23104 frozen in Exim's queue instead.
23107 .option force_command pipe boolean false
23108 .cindex "force command"
23109 .cindex "&(pipe)& transport", "force command"
23110 Normally when a router redirects an address directly to a pipe command
23111 the &%command%& option on the transport is ignored. If &%force_command%&
23112 is set, the &%command%& option will used. This is especially
23113 useful for forcing a wrapper or additional argument to be added to the
23114 command. For example:
23116 command = /usr/bin/remote_exec myhost -- $address_pipe
23120 Note that &$address_pipe$& is handled specially in &%command%& when
23121 &%force_command%& is set, expanding out to the original argument vector as
23122 separate items, similarly to a Unix shell &`"$@"`& construct.
23125 .option ignore_status pipe boolean false
23126 If this option is true, the status returned by the subprocess that is set up to
23127 run the command is ignored, and Exim behaves as if zero had been returned.
23128 Otherwise, a non-zero status or termination by signal causes an error return
23129 from the transport unless the status value is one of those listed in
23130 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
23132 &*Note*&: This option does not apply to timeouts, which do not return a status.
23133 See the &%timeout_defer%& option for how timeouts are handled.
23136 .option log_defer_output pipe boolean false
23137 .cindex "&(pipe)& transport" "logging output"
23138 If this option is set, and the status returned by the command is
23139 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
23140 and any output was produced on stdout or stderr, the first line of it is
23141 written to the main log.
23144 .option log_fail_output pipe boolean false
23145 If this option is set, and the command returns any output on stdout or
23146 stderr, and also ends with a return code that is neither zero nor one of
23147 the return codes listed in &%temp_errors%& (that is, the delivery
23148 failed), the first line of output is written to the main log. This
23149 option and &%log_output%& are mutually exclusive. Only one of them may
23153 .option log_output pipe boolean false
23154 If this option is set and the command returns any output on stdout or
23155 stderr, the first line of output is written to the main log, whatever
23156 the return code. This option and &%log_fail_output%& are mutually
23157 exclusive. Only one of them may be set.
23160 .option max_output pipe integer 20K
23161 This specifies the maximum amount of output that the command may produce on its
23162 standard output and standard error file combined. If the limit is exceeded, the
23163 process running the command is killed. This is intended as a safety measure to
23164 catch runaway processes. The limit is applied independently of the settings of
23165 the options that control what is done with such output (for example,
23166 &%return_output%&). Because of buffering effects, the amount of output may
23167 exceed the limit by a small amount before Exim notices.
23170 .option message_prefix pipe string&!! "see below"
23171 The string specified here is expanded and output at the start of every message.
23172 The default is unset if &%use_bsmtp%& is set. Otherwise it is
23175 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
23179 .cindex "&%tmail%&"
23180 .cindex "&""From""& line"
23181 This is required by the commonly used &_/usr/bin/vacation_& program.
23182 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
23183 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
23188 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23189 &`\n`& to &`\r\n`& in &%message_prefix%&.
23192 .option message_suffix pipe string&!! "see below"
23193 The string specified here is expanded and output at the end of every message.
23194 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
23195 The suffix can be suppressed by setting
23199 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23200 &`\n`& to &`\r\n`& in &%message_suffix%&.
23203 .option path pipe string "see below"
23204 This option specifies the string that is set up in the PATH environment
23205 variable of the subprocess. The default is:
23209 If the &%command%& option does not yield an absolute path name, the command is
23210 sought in the PATH directories, in the usual way. &*Warning*&: This does not
23211 apply to a command specified as a transport filter.
23214 .option permit_coredump pipe boolean false
23215 Normally Exim inhibits core-dumps during delivery. If you have a need to get
23216 a core-dump of a pipe command, enable this command. This enables core-dumps
23217 during delivery and affects both the Exim binary and the pipe command run.
23218 It is recommended that this option remain off unless and until you have a need
23219 for it and that this only be enabled when needed, as the risk of excessive
23220 resource consumption can be quite high. Note also that Exim is typically
23221 installed as a setuid binary and most operating systems will inhibit coredumps
23222 of these by default, so further OS-specific action may be required.
23225 .option pipe_as_creator pipe boolean false
23226 .cindex "uid (user id)" "local delivery"
23227 If the generic &%user%& option is not set and this option is true, the delivery
23228 process is run under the uid that was in force when Exim was originally called
23229 to accept the message. If the group id is not otherwise set (via the generic
23230 &%group%& option), the gid that was in force when Exim was originally called to
23231 accept the message is used.
23234 .option restrict_to_path pipe boolean false
23235 When this option is set, any command name not listed in &%allow_commands%& must
23236 contain no slashes. The command is searched for only in the directories listed
23237 in the &%path%& option. This option is intended for use in the case when a pipe
23238 command has been generated from a user's &_.forward_& file. This is usually
23239 handled by a &(pipe)& transport called &%address_pipe%&.
23242 .option return_fail_output pipe boolean false
23243 If this option is true, and the command produced any output and ended with a
23244 return code other than zero or one of the codes listed in &%temp_errors%& (that
23245 is, the delivery failed), the output is returned in the bounce message.
23246 However, if the message has a null sender (that is, it is itself a bounce
23247 message), output from the command is discarded. This option and
23248 &%return_output%& are mutually exclusive. Only one of them may be set.
23252 .option return_output pipe boolean false
23253 If this option is true, and the command produced any output, the delivery is
23254 deemed to have failed whatever the return code from the command, and the output
23255 is returned in the bounce message. Otherwise, the output is just discarded.
23256 However, if the message has a null sender (that is, it is a bounce message),
23257 output from the command is always discarded, whatever the setting of this
23258 option. This option and &%return_fail_output%& are mutually exclusive. Only one
23259 of them may be set.
23263 .option temp_errors pipe "string list" "see below"
23264 .cindex "&(pipe)& transport" "temporary failure"
23265 This option contains either a colon-separated list of numbers, or a single
23266 asterisk. If &%ignore_status%& is false
23267 and &%return_output%& is not set,
23268 and the command exits with a non-zero return code, the failure is treated as
23269 temporary and the delivery is deferred if the return code matches one of the
23270 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
23271 codes are treated as permanent errors. The default setting contains the codes
23272 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
23273 compiled on a system that does not define these macros, it assumes values of 75
23274 and 73, respectively.
23277 .option timeout pipe time 1h
23278 If the command fails to complete within this time, it is killed. This normally
23279 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
23280 specifies no timeout. In order to ensure that any subprocesses created by the
23281 command are also killed, Exim makes the initial process a process group leader,
23282 and kills the whole process group on a timeout. However, this can be defeated
23283 if one of the processes starts a new process group.
23285 .option timeout_defer pipe boolean false
23286 A timeout in a &(pipe)& transport, either in the command that the transport
23287 runs, or in a transport filter that is associated with it, is by default
23288 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
23289 is set true, both kinds of timeout become temporary errors, causing the
23290 delivery to be deferred.
23292 .option umask pipe "octal integer" 022
23293 This specifies the umask setting for the subprocess that runs the command.
23296 .option use_bsmtp pipe boolean false
23297 .cindex "envelope sender"
23298 If this option is set true, the &(pipe)& transport writes messages in &"batch
23299 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
23300 commands. If you want to include a leading HELO command with such messages,
23301 you can do so by setting the &%message_prefix%& option. See section
23302 &<<SECTbatchSMTP>>& for details of batch SMTP.
23304 .option use_classresources pipe boolean false
23305 .cindex "class resources (BSD)"
23306 This option is available only when Exim is running on FreeBSD, NetBSD, or
23307 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
23308 resource limits when a &(pipe)& transport is run to perform a delivery. The
23309 limits for the uid under which the pipe is to run are obtained from the login
23313 .option use_crlf pipe boolean false
23314 .cindex "carriage return"
23316 This option causes lines to be terminated with the two-character CRLF sequence
23317 (carriage return, linefeed) instead of just a linefeed character. In the case
23318 of batched SMTP, the byte sequence written to the pipe is then an exact image
23319 of what would be sent down a real SMTP connection.
23321 The contents of the &%message_prefix%& and &%message_suffix%& options are
23322 written verbatim, so must contain their own carriage return characters if these
23323 are needed. When &%use_bsmtp%& is not set, the default values for both
23324 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
23325 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
23328 .option use_shell pipe boolean false
23329 .vindex "&$pipe_addresses$&"
23330 If this option is set, it causes the command to be passed to &_/bin/sh_&
23331 instead of being run directly from the transport, as described in section
23332 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
23333 where the command is expected to be run under a shell and cannot easily be
23334 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
23335 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
23336 command is expanded as a single string, and handed to &_/bin/sh_& as data for
23341 .section "Using an external local delivery agent" "SECID143"
23342 .cindex "local delivery" "using an external agent"
23343 .cindex "&'procmail'&"
23344 .cindex "external local delivery"
23345 .cindex "delivery" "&'procmail'&"
23346 .cindex "delivery" "by external agent"
23347 The &(pipe)& transport can be used to pass all messages that require local
23348 delivery to a separate local delivery agent such as &%procmail%&. When doing
23349 this, care must be taken to ensure that the pipe is run under an appropriate
23350 uid and gid. In some configurations one wants this to be a uid that is trusted
23351 by the delivery agent to supply the correct sender of the message. It may be
23352 necessary to recompile or reconfigure the delivery agent so that it trusts an
23353 appropriate user. The following is an example transport and router
23354 configuration for &%procmail%&:
23359 command = /usr/local/bin/procmail -d $local_part
23363 check_string = "From "
23364 escape_string = ">From "
23373 transport = procmail_pipe
23375 In this example, the pipe is run as the local user, but with the group set to
23376 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
23377 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
23378 user to supply a correct sender address. If you do not specify either a
23379 &%group%& or a &%user%& option, the pipe command is run as the local user. The
23380 home directory is the user's home directory by default.
23382 &*Note*&: The command that the pipe transport runs does &'not'& begin with
23386 as shown in some &%procmail%& documentation, because Exim does not by default
23387 use a shell to run pipe commands.
23390 The next example shows a transport and a router for a system where local
23391 deliveries are handled by the Cyrus IMAP server.
23394 local_delivery_cyrus:
23396 command = /usr/cyrus/bin/deliver \
23397 -m ${substr_1:$local_part_suffix} -- $local_part
23409 local_part_suffix = .*
23410 transport = local_delivery_cyrus
23412 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
23413 &%return_output%& to cause any text written by Cyrus to be returned to the
23415 .ecindex IIDpiptra1
23416 .ecindex IIDpiptra2
23419 . ////////////////////////////////////////////////////////////////////////////
23420 . ////////////////////////////////////////////////////////////////////////////
23422 .chapter "The smtp transport" "CHAPsmtptrans"
23423 .scindex IIDsmttra1 "transports" "&(smtp)&"
23424 .scindex IIDsmttra2 "&(smtp)& transport"
23425 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
23426 or LMTP protocol. The list of hosts to try can either be taken from the address
23427 that is being processed (having been set up by the router), or specified
23428 explicitly for the transport. Timeout and retry processing (see chapter
23429 &<<CHAPretry>>&) is applied to each IP address independently.
23432 .section "Multiple messages on a single connection" "SECID144"
23433 The sending of multiple messages over a single TCP/IP connection can arise in
23437 If a message contains more than &%max_rcpt%& (see below) addresses that are
23438 routed to the same host, more than one copy of the message has to be sent to
23439 that host. In this situation, multiple copies may be sent in a single run of
23440 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
23441 does when it has too many addresses to send in one message also depends on the
23442 value of the global &%remote_max_parallel%& option. Details are given in
23443 section &<<SECToutSMTPTCP>>&.)
23445 .cindex "hints database" "remembering routing"
23446 When a message has been successfully delivered over a TCP/IP connection, Exim
23447 looks in its hints database to see if there are any other messages awaiting a
23448 connection to the same host. If there are, a new delivery process is started
23449 for one of them, and the current TCP/IP connection is passed on to it. The new
23450 process may in turn send multiple copies and possibly create yet another
23455 For each copy sent over the same TCP/IP connection, a sequence counter is
23456 incremented, and if it ever gets to the value of &%connection_max_messages%&,
23457 no further messages are sent over that connection.
23461 .section "Use of the $host and $host_address variables" "SECID145"
23463 .vindex "&$host_address$&"
23464 At the start of a run of the &(smtp)& transport, the values of &$host$& and
23465 &$host_address$& are the name and IP address of the first host on the host list
23466 passed by the router. However, when the transport is about to connect to a
23467 specific host, and while it is connected to that host, &$host$& and
23468 &$host_address$& are set to the values for that host. These are the values
23469 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
23470 &%serialize_hosts%&, and the various TLS options are expanded.
23473 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
23474 .vindex &$tls_bits$&
23475 .vindex &$tls_cipher$&
23476 .vindex &$tls_peerdn$&
23477 .vindex &$tls_sni$&
23478 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
23479 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
23480 are the values that were set when the message was received.
23481 These are the values that are used for options that are expanded before any
23482 SMTP connections are made. Just before each connection is made, these four
23483 variables are emptied. If TLS is subsequently started, they are set to the
23484 appropriate values for the outgoing connection, and these are the values that
23485 are in force when any authenticators are run and when the
23486 &%authenticated_sender%& option is expanded.
23488 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
23489 and will be removed in a future release.
23492 .section "Private options for smtp" "SECID146"
23493 .cindex "options" "&(smtp)& transport"
23494 The private options of the &(smtp)& transport are as follows:
23497 .option address_retry_include_sender smtp boolean true
23498 .cindex "4&'xx'& responses" "retrying after"
23499 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
23500 is the combination of sender and recipient that is delayed in subsequent queue
23501 runs until the retry time is reached. You can delay the recipient without
23502 reference to the sender (which is what earlier versions of Exim did), by
23503 setting &%address_retry_include_sender%& false. However, this can lead to
23504 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
23506 .option allow_localhost smtp boolean false
23507 .cindex "local host" "sending to"
23508 .cindex "fallback" "hosts specified on transport"
23509 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
23510 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
23511 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
23512 the delivery anyway. This should be used only in special cases when the
23513 configuration ensures that no looping will result (for example, a differently
23514 configured Exim is listening on the port to which the message is sent).
23517 .option authenticated_sender smtp string&!! unset
23519 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
23520 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
23521 overriding any existing authenticated sender value. If the string expansion is
23522 forced to fail, the option is ignored. Other expansion failures cause delivery
23523 to be deferred. If the result of expansion is an empty string, that is also
23526 The expansion happens after the outgoing connection has been made and TLS
23527 started, if required. This means that the &$host$&, &$host_address$&,
23528 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
23529 particular connection.
23531 If the SMTP session is not authenticated, the expansion of
23532 &%authenticated_sender%& still happens (and can cause the delivery to be
23533 deferred if it fails), but no AUTH= item is added to MAIL commands
23534 unless &%authenticated_sender_force%& is true.
23536 This option allows you to use the &(smtp)& transport in LMTP mode to
23537 deliver mail to Cyrus IMAP and provide the proper local part as the
23538 &"authenticated sender"&, via a setting such as:
23540 authenticated_sender = $local_part
23542 This removes the need for IMAP subfolders to be assigned special ACLs to
23543 allow direct delivery to those subfolders.
23545 Because of expected uses such as that just described for Cyrus (when no
23546 domain is involved), there is no checking on the syntax of the provided
23550 .option authenticated_sender_force smtp boolean false
23551 If this option is set true, the &%authenticated_sender%& option's value
23552 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
23553 authenticated as a client.
23556 .option command_timeout smtp time 5m
23557 This sets a timeout for receiving a response to an SMTP command that has been
23558 sent out. It is also used when waiting for the initial banner line from the
23559 remote host. Its value must not be zero.
23562 .option connect_timeout smtp time 5m
23563 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
23564 to a remote host. A setting of zero allows the system timeout (typically
23565 several minutes) to act. To have any effect, the value of this option must be
23566 less than the system timeout. However, it has been observed that on some
23567 systems there is no system timeout, which is why the default value for this
23568 option is 5 minutes, a value recommended by RFC 1123.
23571 .option connection_max_messages smtp integer 500
23572 .cindex "SMTP" "passed connection"
23573 .cindex "SMTP" "multiple deliveries"
23574 .cindex "multiple SMTP deliveries"
23575 This controls the maximum number of separate message deliveries that are sent
23576 over a single TCP/IP connection. If the value is zero, there is no limit.
23577 For testing purposes, this value can be overridden by the &%-oB%& command line
23581 .option data_timeout smtp time 5m
23582 This sets a timeout for the transmission of each block in the data portion of
23583 the message. As a result, the overall timeout for a message depends on the size
23584 of the message. Its value must not be zero. See also &%final_timeout%&.
23587 .option dkim_domain smtp string&!! unset
23588 .option dkim_selector smtp string&!! unset
23589 .option dkim_private_key smtp string&!! unset
23590 .option dkim_canon smtp string&!! unset
23591 .option dkim_strict smtp string&!! unset
23592 .option dkim_sign_headers smtp string&!! unset
23593 DKIM signing options. For details see &<<SECDKIMSIGN>>&.
23596 .option delay_after_cutoff smtp boolean true
23597 This option controls what happens when all remote IP addresses for a given
23598 domain have been inaccessible for so long that they have passed their retry
23601 In the default state, if the next retry time has not been reached for any of
23602 them, the address is bounced without trying any deliveries. In other words,
23603 Exim delays retrying an IP address after the final cutoff time until a new
23604 retry time is reached, and can therefore bounce an address without ever trying
23605 a delivery, when machines have been down for a long time. Some people are
23606 unhappy at this prospect, so...
23608 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
23609 addresses are past their final cutoff time, Exim tries to deliver to those
23610 IP addresses that have not been tried since the message arrived. If there are
23611 none, of if they all fail, the address is bounced. In other words, it does not
23612 delay when a new message arrives, but immediately tries those expired IP
23613 addresses that haven't been tried since the message arrived. If there is a
23614 continuous stream of messages for the dead hosts, unsetting
23615 &%delay_after_cutoff%& means that there will be many more attempts to deliver
23619 .option dns_qualify_single smtp boolean true
23620 If the &%hosts%& or &%fallback_hosts%& option is being used,
23621 and the &%gethostbyname%& option is false,
23622 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
23623 in chapter &<<CHAPdnslookup>>& for more details.
23626 .option dns_search_parents smtp boolean false
23627 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
23628 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
23629 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
23633 .option dnssec_request_domains smtp "domain list&!!" unset
23634 .cindex "MX record" "security"
23635 .cindex "DNSSEC" "MX lookup"
23636 .cindex "security" "MX lookup"
23637 .cindex "DNS" "DNSSEC"
23638 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23639 the dnssec request bit set.
23640 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23644 .option dnssec_require_domains smtp "domain list&!!" unset
23645 .cindex "MX record" "security"
23646 .cindex "DNSSEC" "MX lookup"
23647 .cindex "security" "MX lookup"
23648 .cindex "DNS" "DNSSEC"
23649 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
23650 the dnssec request bit set. Any returns not having the Authenticated Data bit
23651 (AD bit) set will be ignored and logged as a host-lookup failure.
23652 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23656 .option dscp smtp string&!! unset
23657 .cindex "DCSP" "outbound"
23658 This option causes the DSCP value associated with a socket to be set to one
23659 of a number of fixed strings or to numeric value.
23660 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
23661 Common values include &`throughput`&, &`mincost`&, and on newer systems
23662 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
23664 The outbound packets from Exim will be marked with this value in the header
23665 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
23666 that these values will have any effect, not be stripped by networking
23667 equipment, or do much of anything without cooperation with your Network
23668 Engineer and those of all network operators between the source and destination.
23671 .option fallback_hosts smtp "string list" unset
23672 .cindex "fallback" "hosts specified on transport"
23673 String expansion is not applied to this option. The argument must be a
23674 colon-separated list of host names or IP addresses, optionally also including
23675 port numbers, though the separator can be changed, as described in section
23676 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23677 item in a &%route_list%& setting for the &(manualroute)& router, as described
23678 in section &<<SECTformatonehostitem>>&.
23680 Fallback hosts can also be specified on routers, which associate them with the
23681 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
23682 &%fallback_hosts%& specified on the transport is used only if the address does
23683 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
23684 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
23685 However, &%hosts_randomize%& does apply to fallback host lists.
23687 If Exim is unable to deliver to any of the hosts for a particular address, and
23688 the errors are not permanent rejections, the address is put on a separate
23689 transport queue with its host list replaced by the fallback hosts, unless the
23690 address was routed via MX records and the current host was in the original MX
23691 list. In that situation, the fallback host list is not used.
23693 Once normal deliveries are complete, the fallback queue is delivered by
23694 re-running the same transports with the new host lists. If several failing
23695 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
23696 copy of the message is sent.
23698 The resolution of the host names on the fallback list is controlled by the
23699 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
23700 both to cases when the host list comes with the address and when it is taken
23701 from &%hosts%&. This option provides a &"use a smart host only if delivery
23705 .option final_timeout smtp time 10m
23706 This is the timeout that applies while waiting for the response to the final
23707 line containing just &"."& that terminates a message. Its value must not be
23710 .option gethostbyname smtp boolean false
23711 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
23712 being used, names are looked up using &[gethostbyname()]&
23713 (or &[getipnodebyname()]& when available)
23714 instead of using the DNS. Of course, that function may in fact use the DNS, but
23715 it may also consult other sources of information such as &_/etc/hosts_&.
23717 .option gnutls_compat_mode smtp boolean unset
23718 This option controls whether GnuTLS is used in compatibility mode in an Exim
23719 server. This reduces security slightly, but improves interworking with older
23720 implementations of TLS.
23722 .option helo_data smtp string&!! "see below"
23723 .cindex "HELO" "argument, setting"
23724 .cindex "EHLO" "argument, setting"
23725 .cindex "LHLO argument setting"
23726 The value of this option is expanded after a connection to a another host has
23727 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
23728 command that starts the outgoing SMTP or LMTP session. The default value of the
23733 During the expansion, the variables &$host$& and &$host_address$& are set to
23734 the identity of the remote host, and the variables &$sending_ip_address$& and
23735 &$sending_port$& are set to the local IP address and port number that are being
23736 used. These variables can be used to generate different values for different
23737 servers or different local IP addresses. For example, if you want the string
23738 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
23739 interface address, you could use this:
23741 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
23742 {$primary_hostname}}
23744 The use of &%helo_data%& applies both to sending messages and when doing
23747 .option hosts smtp "string list&!!" unset
23748 Hosts are associated with an address by a router such as &(dnslookup)&, which
23749 finds the hosts by looking up the address domain in the DNS, or by
23750 &(manualroute)&, which has lists of hosts in its configuration. However,
23751 email addresses can be passed to the &(smtp)& transport by any router, and not
23752 all of them can provide an associated list of hosts.
23754 The &%hosts%& option specifies a list of hosts to be used if the address being
23755 processed does not have any hosts associated with it. The hosts specified by
23756 &%hosts%& are also used, whether or not the address has its own hosts, if
23757 &%hosts_override%& is set.
23759 The string is first expanded, before being interpreted as a colon-separated
23760 list of host names or IP addresses, possibly including port numbers. The
23761 separator may be changed to something other than colon, as described in section
23762 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23763 item in a &%route_list%& setting for the &(manualroute)& router, as described
23764 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
23765 of the &(manualroute)& router is not available here.
23767 If the expansion fails, delivery is deferred. Unless the failure was caused by
23768 the inability to complete a lookup, the error is logged to the panic log as
23769 well as the main log. Host names are looked up either by searching directly for
23770 address records in the DNS or by calling &[gethostbyname()]& (or
23771 &[getipnodebyname()]& when available), depending on the setting of the
23772 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
23773 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
23776 During delivery, the hosts are tried in order, subject to their retry status,
23777 unless &%hosts_randomize%& is set.
23780 .option hosts_avoid_esmtp smtp "host list&!!" unset
23781 .cindex "ESMTP, avoiding use of"
23782 .cindex "HELO" "forcing use of"
23783 .cindex "EHLO" "avoiding use of"
23784 .cindex "PIPELINING" "avoiding the use of"
23785 This option is for use with broken hosts that announce ESMTP facilities (for
23786 example, PIPELINING) and then fail to implement them properly. When a host
23787 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
23788 start of the SMTP session. This means that it cannot use any of the ESMTP
23789 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
23792 .option hosts_avoid_pipelining smtp "host list&!!" unset
23793 .cindex "PIPELINING" "avoiding the use of"
23794 Exim will not use the SMTP PIPELINING extension when delivering to any host
23795 that matches this list, even if the server host advertises PIPELINING support.
23798 .option hosts_avoid_tls smtp "host list&!!" unset
23799 .cindex "TLS" "avoiding for certain hosts"
23800 Exim will not try to start a TLS session when delivering to any host that
23801 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23803 .option hosts_verify_avoid_tls smtp "host list&!!" unset
23804 .cindex "TLS" "avoiding for certain hosts"
23805 Exim will not try to start a TLS session for a verify callout,
23806 or when delivering in cutthrough mode,
23807 to any host that matches this list.
23810 .option hosts_max_try smtp integer 5
23811 .cindex "host" "maximum number to try"
23812 .cindex "limit" "number of hosts tried"
23813 .cindex "limit" "number of MX tried"
23814 .cindex "MX record" "maximum tried"
23815 This option limits the number of IP addresses that are tried for any one
23816 delivery in cases where there are temporary delivery errors. Section
23817 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
23820 .option hosts_max_try_hardlimit smtp integer 50
23821 This is an additional check on the maximum number of IP addresses that Exim
23822 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
23827 .option hosts_nopass_tls smtp "host list&!!" unset
23828 .cindex "TLS" "passing connection"
23829 .cindex "multiple SMTP deliveries"
23830 .cindex "TLS" "multiple message deliveries"
23831 For any host that matches this list, a connection on which a TLS session has
23832 been started will not be passed to a new delivery process for sending another
23833 message on the same connection. See section &<<SECTmulmessam>>& for an
23834 explanation of when this might be needed.
23837 .option hosts_override smtp boolean false
23838 If this option is set and the &%hosts%& option is also set, any hosts that are
23839 attached to the address are ignored, and instead the hosts specified by the
23840 &%hosts%& option are always used. This option does not apply to
23841 &%fallback_hosts%&.
23844 .option hosts_randomize smtp boolean false
23845 .cindex "randomized host list"
23846 .cindex "host" "list of; randomized"
23847 .cindex "fallback" "randomized hosts"
23848 If this option is set, and either the list of hosts is taken from the
23849 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
23850 were not obtained from MX records (this includes fallback hosts from the
23851 router), and were not randomized by the router, the order of trying the hosts
23852 is randomized each time the transport runs. Randomizing the order of a host
23853 list can be used to do crude load sharing.
23855 When &%hosts_randomize%& is true, a host list may be split into groups whose
23856 order is separately randomized. This makes it possible to set up MX-like
23857 behaviour. The boundaries between groups are indicated by an item that is just
23858 &`+`& in the host list. For example:
23860 hosts = host1:host2:host3:+:host4:host5
23862 The order of the first three hosts and the order of the last two hosts is
23863 randomized for each use, but the first three always end up before the last two.
23864 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
23866 .option hosts_require_auth smtp "host list&!!" unset
23867 .cindex "authentication" "required by client"
23868 This option provides a list of servers for which authentication must succeed
23869 before Exim will try to transfer a message. If authentication fails for
23870 servers which are not in this list, Exim tries to send unauthenticated. If
23871 authentication fails for one of these servers, delivery is deferred. This
23872 temporary error is detectable in the retry rules, so it can be turned into a
23873 hard failure if required. See also &%hosts_try_auth%&, and chapter
23874 &<<CHAPSMTPAUTH>>& for details of authentication.
23877 .option hosts_request_ocsp smtp "host list&!!" *
23878 .cindex "TLS" "requiring for certain servers"
23879 Exim will request a Certificate Status on a
23880 TLS session for any host that matches this list.
23881 &%tls_verify_certificates%& should also be set for the transport.
23883 .option hosts_require_ocsp smtp "host list&!!" unset
23884 .cindex "TLS" "requiring for certain servers"
23885 Exim will request, and check for a valid Certificate Status being given, on a
23886 TLS session for any host that matches this list.
23887 &%tls_verify_certificates%& should also be set for the transport.
23889 .option hosts_require_tls smtp "host list&!!" unset
23890 .cindex "TLS" "requiring for certain servers"
23891 Exim will insist on using a TLS session when delivering to any host that
23892 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23893 &*Note*&: This option affects outgoing mail only. To insist on TLS for
23894 incoming messages, use an appropriate ACL.
23896 .option hosts_try_auth smtp "host list&!!" unset
23897 .cindex "authentication" "optional in client"
23898 This option provides a list of servers to which, provided they announce
23899 authentication support, Exim will attempt to authenticate as a client when it
23900 connects. If authentication fails, Exim will try to transfer the message
23901 unauthenticated. See also &%hosts_require_auth%&, and chapter
23902 &<<CHAPSMTPAUTH>>& for details of authentication.
23905 .option hosts_try_chunking smtp "host list&!!" *
23906 .cindex CHUNKING "enabling, in client"
23907 .cindex BDAT "SMTP command"
23908 .cindex "RFC 3030" "CHUNKING"
23909 This option provides a list of server to which, provided they announce
23910 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
23911 BDAT will not be used in conjuction with a transport filter.
23914 .option hosts_try_prdr smtp "host list&!!" *
23915 .cindex "PRDR" "enabling, optional in client"
23916 This option provides a list of servers to which, provided they announce
23917 PRDR support, Exim will attempt to negotiate PRDR
23918 for multi-recipient messages.
23919 The option can usually be left as default.
23921 .option interface smtp "string list&!!" unset
23922 .cindex "bind IP address"
23923 .cindex "IP address" "binding"
23925 .vindex "&$host_address$&"
23926 This option specifies which interface to bind to when making an outgoing SMTP
23927 call. The value is an IP address, not an interface name such as
23928 &`eth0`&. Do not confuse this with the interface address that was used when a
23929 message was received, which is in &$received_ip_address$&, formerly known as
23930 &$interface_address$&. The name was changed to minimize confusion with the
23931 outgoing interface address. There is no variable that contains an outgoing
23932 interface address because, unless it is set by this option, its value is
23935 During the expansion of the &%interface%& option the variables &$host$& and
23936 &$host_address$& refer to the host to which a connection is about to be made
23937 during the expansion of the string. Forced expansion failure, or an empty
23938 string result causes the option to be ignored. Otherwise, after expansion, the
23939 string must be a list of IP addresses, colon-separated by default, but the
23940 separator can be changed in the usual way. For example:
23942 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
23944 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
23945 connection. If none of them are the correct type, the option is ignored. If
23946 &%interface%& is not set, or is ignored, the system's IP functions choose which
23947 interface to use if the host has more than one.
23950 .option keepalive smtp boolean true
23951 .cindex "keepalive" "on outgoing connection"
23952 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
23953 connections. When set, it causes the kernel to probe idle connections
23954 periodically, by sending packets with &"old"& sequence numbers. The other end
23955 of the connection should send a acknowledgment if the connection is still okay
23956 or a reset if the connection has been aborted. The reason for doing this is
23957 that it has the beneficial effect of freeing up certain types of connection
23958 that can get stuck when the remote host is disconnected without tidying up the
23959 TCP/IP call properly. The keepalive mechanism takes several hours to detect
23963 .option lmtp_ignore_quota smtp boolean false
23964 .cindex "LMTP" "ignoring quota errors"
23965 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
23966 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
23967 has advertised support for IGNOREQUOTA in its response to the LHLO command.
23969 .option max_rcpt smtp integer 100
23970 .cindex "RCPT" "maximum number of outgoing"
23971 This option limits the number of RCPT commands that are sent in a single
23972 SMTP message transaction. Each set of addresses is treated independently, and
23973 so can cause parallel connections to the same host if &%remote_max_parallel%&
23977 .option multi_domain smtp boolean&!! true
23978 .vindex "&$domain$&"
23979 When this option is set, the &(smtp)& transport can handle a number of
23980 addresses containing a mixture of different domains provided they all resolve
23981 to the same list of hosts. Turning the option off restricts the transport to
23982 handling only one domain at a time. This is useful if you want to use
23983 &$domain$& in an expansion for the transport, because it is set only when there
23984 is a single domain involved in a remote delivery.
23986 It is expanded per-address and can depend on any of
23987 &$address_data$&, &$domain_data$&, &$local_part_data$&,
23988 &$host$&, &$host_address$& and &$host_port$&.
23990 .option port smtp string&!! "see below"
23991 .cindex "port" "sending TCP/IP"
23992 .cindex "TCP/IP" "setting outgoing port"
23993 This option specifies the TCP/IP port on the server to which Exim connects.
23994 &*Note:*& Do not confuse this with the port that was used when a message was
23995 received, which is in &$received_port$&, formerly known as &$interface_port$&.
23996 The name was changed to minimize confusion with the outgoing port. There is no
23997 variable that contains an outgoing port.
23999 If the value of this option begins with a digit it is taken as a port number;
24000 otherwise it is looked up using &[getservbyname()]&. The default value is
24001 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
24002 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
24007 .option protocol smtp string smtp
24008 .cindex "LMTP" "over TCP/IP"
24009 .cindex "ssmtp protocol" "outbound"
24010 .cindex "TLS" "SSL-on-connect outbound"
24012 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
24013 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
24014 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
24015 deliveries into closed message stores. Exim also has support for running LMTP
24016 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
24018 If this option is set to &"smtps"&, the default value for the &%port%& option
24019 changes to &"smtps"&, and the transport initiates TLS immediately after
24020 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
24021 The Internet standards bodies strongly discourage use of this mode.
24024 .option retry_include_ip_address smtp boolean&!! true
24025 Exim normally includes both the host name and the IP address in the key it
24026 constructs for indexing retry data after a temporary delivery failure. This
24027 means that when one of several IP addresses for a host is failing, it gets
24028 tried periodically (controlled by the retry rules), but use of the other IP
24029 addresses is not affected.
24031 However, in some dialup environments hosts are assigned a different IP address
24032 each time they connect. In this situation the use of the IP address as part of
24033 the retry key leads to undesirable behaviour. Setting this option false causes
24034 Exim to use only the host name.
24035 Since it is expanded it can be made to depend on the host or domain.
24038 .option serialize_hosts smtp "host list&!!" unset
24039 .cindex "serializing connections"
24040 .cindex "host" "serializing connections"
24041 Because Exim operates in a distributed manner, if several messages for the same
24042 host arrive at around the same time, more than one simultaneous connection to
24043 the remote host can occur. This is not usually a problem except when there is a
24044 slow link between the hosts. In that situation it may be helpful to restrict
24045 Exim to one connection at a time. This can be done by setting
24046 &%serialize_hosts%& to match the relevant hosts.
24048 .cindex "hints database" "serializing deliveries to a host"
24049 Exim implements serialization by means of a hints database in which a record is
24050 written whenever a process connects to one of the restricted hosts. The record
24051 is deleted when the connection is completed. Obviously there is scope for
24052 records to get left lying around if there is a system or program crash. To
24053 guard against this, Exim ignores any records that are more than six hours old.
24055 If you set up this kind of serialization, you should also arrange to delete the
24056 relevant hints database whenever your system reboots. The names of the files
24057 start with &_misc_& and they are kept in the &_spool/db_& directory. There
24058 may be one or two files, depending on the type of DBM in use. The same files
24059 are used for ETRN serialization.
24061 See also the &%max_parallel%& generic transport option.
24064 .option size_addition smtp integer 1024
24065 .cindex "SMTP" "SIZE"
24066 .cindex "message" "size issue for transport filter"
24067 .cindex "size" "of message"
24068 .cindex "transport" "filter"
24069 .cindex "filter" "transport filter"
24070 If a remote SMTP server indicates that it supports the SIZE option of the
24071 MAIL command, Exim uses this to pass over the message size at the start of
24072 an SMTP transaction. It adds the value of &%size_addition%& to the value it
24073 sends, to allow for headers and other text that may be added during delivery by
24074 configuration options or in a transport filter. It may be necessary to increase
24075 this if a lot of text is added to messages.
24077 Alternatively, if the value of &%size_addition%& is set negative, it disables
24078 the use of the SIZE option altogether.
24081 .option socks_proxy smtp string&!! unset
24082 .cindex proxy SOCKS
24083 This option enables use of SOCKS proxies for connections made by the
24084 transport. For details see &<<SECTproxySOCKS>>&.
24087 .option tls_certificate smtp string&!! unset
24088 .cindex "TLS" "client certificate, location of"
24089 .cindex "certificate" "client, location of"
24091 .vindex "&$host_address$&"
24092 The value of this option must be the absolute path to a file which contains the
24093 client's certificate, for possible use when sending a message over an encrypted
24094 connection. The values of &$host$& and &$host_address$& are set to the name and
24095 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
24098 &*Note*&: This option must be set if you want Exim to be able to use a TLS
24099 certificate when sending messages as a client. The global option of the same
24100 name specifies the certificate for Exim as a server; it is not automatically
24101 assumed that the same certificate should be used when Exim is operating as a
24105 .option tls_crl smtp string&!! unset
24106 .cindex "TLS" "client certificate revocation list"
24107 .cindex "certificate" "revocation list for client"
24108 This option specifies a certificate revocation list. The expanded value must
24109 be the name of a file that contains a CRL in PEM format.
24112 .option tls_dh_min_bits smtp integer 1024
24113 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
24114 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
24115 key agreement is negotiated, the server will provide a large prime number
24116 for use. This option establishes the minimum acceptable size of that number.
24117 If the parameter offered by the server is too small, then the TLS handshake
24120 Only supported when using GnuTLS.
24123 .option tls_privatekey smtp string&!! unset
24124 .cindex "TLS" "client private key, location of"
24126 .vindex "&$host_address$&"
24127 The value of this option must be the absolute path to a file which contains the
24128 client's private key. This is used when sending a message over an encrypted
24129 connection using a client certificate. The values of &$host$& and
24130 &$host_address$& are set to the name and address of the server during the
24131 expansion. If this option is unset, or the expansion is forced to fail, or the
24132 result is an empty string, the private key is assumed to be in the same file as
24133 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
24136 .option tls_require_ciphers smtp string&!! unset
24137 .cindex "TLS" "requiring specific ciphers"
24138 .cindex "cipher" "requiring specific"
24140 .vindex "&$host_address$&"
24141 The value of this option must be a list of permitted cipher suites, for use
24142 when setting up an outgoing encrypted connection. (There is a global option of
24143 the same name for controlling incoming connections.) The values of &$host$& and
24144 &$host_address$& are set to the name and address of the server during the
24145 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
24146 is used in different ways by OpenSSL and GnuTLS (see sections
24147 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
24148 ciphers is a preference order.
24152 .option tls_sni smtp string&!! unset
24153 .cindex "TLS" "Server Name Indication"
24154 .vindex "&$tls_sni$&"
24155 If this option is set then it sets the $tls_out_sni variable and causes any
24156 TLS session to pass this value as the Server Name Indication extension to
24157 the remote side, which can be used by the remote side to select an appropriate
24158 certificate and private key for the session.
24160 See &<<SECTtlssni>>& for more information.
24162 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
24168 .option tls_tempfail_tryclear smtp boolean true
24169 .cindex "4&'xx'& responses" "to STARTTLS"
24170 When the server host is not in &%hosts_require_tls%&, and there is a problem in
24171 setting up a TLS session, this option determines whether or not Exim should try
24172 to deliver the message unencrypted. If it is set false, delivery to the
24173 current host is deferred; if there are other hosts, they are tried. If this
24174 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
24175 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
24176 TLS negotiation fails, Exim closes the current connection (because it is in an
24177 unknown state), opens a new one to the same host, and then tries the delivery
24181 .option tls_try_verify_hosts smtp "host list&!!" *
24182 .cindex "TLS" "server certificate verification"
24183 .cindex "certificate" "verification of server"
24184 This option gives a list of hosts for which, on encrypted connections,
24185 certificate verification will be tried but need not succeed.
24186 The &%tls_verify_certificates%& option must also be set.
24187 Note that unless the host is in this list
24188 TLS connections will be denied to hosts using self-signed certificates
24189 when &%tls_verify_certificates%& is matched.
24190 The &$tls_out_certificate_verified$& variable is set when
24191 certificate verification succeeds.
24194 .option tls_verify_cert_hostnames smtp "host list&!!" *
24195 .cindex "TLS" "server certificate hostname verification"
24196 .cindex "certificate" "verification of server"
24197 This option give a list of hosts for which,
24198 while verifying the server certificate,
24199 checks will be included on the host name
24200 (note that this will generally be the result of a DNS MX lookup)
24201 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
24202 limited to being the initial component of a 3-or-more component FQDN.
24204 There is no equivalent checking on client certificates.
24207 .option tls_verify_certificates smtp string&!! system
24208 .cindex "TLS" "server certificate verification"
24209 .cindex "certificate" "verification of server"
24211 .vindex "&$host_address$&"
24212 The value of this option must be either the
24214 or the absolute path to
24215 a file or directory containing permitted certificates for servers,
24216 for use when setting up an encrypted connection.
24218 The "system" value for the option will use a location compiled into the SSL library.
24219 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
24220 is taken as empty and an explicit location
24223 The use of a directory for the option value is not available for GnuTLS versions
24224 preceding 3.3.6 and a single file must be used.
24226 With OpenSSL the certificates specified
24228 either by file or directory
24229 are added to those given by the system default location.
24231 The values of &$host$& and
24232 &$host_address$& are set to the name and address of the server during the
24233 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
24235 For back-compatibility,
24236 if neither tls_verify_hosts nor tls_try_verify_hosts are set
24237 (a single-colon empty list counts as being set)
24238 and certificate verification fails the TLS connection is closed.
24241 .option tls_verify_hosts smtp "host list&!!" unset
24242 .cindex "TLS" "server certificate verification"
24243 .cindex "certificate" "verification of server"
24244 This option gives a list of hosts for which, on encrypted connections,
24245 certificate verification must succeed.
24246 The &%tls_verify_certificates%& option must also be set.
24247 If both this option and &%tls_try_verify_hosts%& are unset
24248 operation is as if this option selected all hosts.
24253 .section "How the limits for the number of hosts to try are used" &&&
24255 .cindex "host" "maximum number to try"
24256 .cindex "limit" "hosts; maximum number tried"
24257 There are two options that are concerned with the number of hosts that are
24258 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
24259 &%hosts_max_try_hardlimit%&.
24262 The &%hosts_max_try%& option limits the number of hosts that are tried
24263 for a single delivery. However, despite the term &"host"& in its name, the
24264 option actually applies to each IP address independently. In other words, a
24265 multihomed host is treated as several independent hosts, just as it is for
24268 Many of the larger ISPs have multiple MX records which often point to
24269 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
24270 created as a result of routing one of these domains.
24272 Trying every single IP address on such a long list does not seem sensible; if
24273 several at the top of the list fail, it is reasonable to assume there is some
24274 problem that is likely to affect all of them. Roughly speaking, the value of
24275 &%hosts_max_try%& is the maximum number that are tried before deferring the
24276 delivery. However, the logic cannot be quite that simple.
24278 Firstly, IP addresses that are skipped because their retry times have not
24279 arrived do not count, and in addition, addresses that are past their retry
24280 limits are also not counted, even when they are tried. This means that when
24281 some IP addresses are past their retry limits, more than the value of
24282 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
24283 that all IP addresses are considered before timing out an email address (but
24284 see below for an exception).
24286 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
24287 list to see if there is a subsequent host with a different (higher valued) MX.
24288 If there is, that host is considered next, and the current IP address is used
24289 but not counted. This behaviour helps in the case of a domain with a retry rule
24290 that hardly ever delays any hosts, as is now explained:
24292 Consider the case of a long list of hosts with one MX value, and a few with a
24293 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
24294 hosts at the top of the list are tried at first. With the default retry rule,
24295 which specifies increasing retry times, the higher MX hosts are eventually
24296 tried when those at the top of the list are skipped because they have not
24297 reached their retry times.
24299 However, it is common practice to put a fixed short retry time on domains for
24300 large ISPs, on the grounds that their servers are rarely down for very long.
24301 Unfortunately, these are exactly the domains that tend to resolve to long lists
24302 of hosts. The short retry time means that the lowest MX hosts are tried every
24303 time. The attempts may be in a different order because of random sorting, but
24304 without the special MX check, the higher MX hosts would never be tried until
24305 all the lower MX hosts had timed out (which might be several days), because
24306 there are always some lower MX hosts that have reached their retry times. With
24307 the special check, Exim considers at least one IP address from each MX value at
24308 every delivery attempt, even if the &%hosts_max_try%& limit has already been
24311 The above logic means that &%hosts_max_try%& is not a hard limit, and in
24312 particular, Exim normally eventually tries all the IP addresses before timing
24313 out an email address. When &%hosts_max_try%& was implemented, this seemed a
24314 reasonable thing to do. Recently, however, some lunatic DNS configurations have
24315 been set up with hundreds of IP addresses for some domains. It can
24316 take a very long time indeed for an address to time out in these cases.
24318 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
24319 Exim never tries more than this number of IP addresses; if it hits this limit
24320 and they are all timed out, the email address is bounced, even though not all
24321 possible IP addresses have been tried.
24322 .ecindex IIDsmttra1
24323 .ecindex IIDsmttra2
24329 . ////////////////////////////////////////////////////////////////////////////
24330 . ////////////////////////////////////////////////////////////////////////////
24332 .chapter "Address rewriting" "CHAPrewrite"
24333 .scindex IIDaddrew "rewriting" "addresses"
24334 There are some circumstances in which Exim automatically rewrites domains in
24335 addresses. The two most common are when an address is given without a domain
24336 (referred to as an &"unqualified address"&) or when an address contains an
24337 abbreviated domain that is expanded by DNS lookup.
24339 Unqualified envelope addresses are accepted only for locally submitted
24340 messages, or for messages that are received from hosts matching
24341 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
24342 appropriate. Unqualified addresses in header lines are qualified if they are in
24343 locally submitted messages, or messages from hosts that are permitted to send
24344 unqualified envelope addresses. Otherwise, unqualified addresses in header
24345 lines are neither qualified nor rewritten.
24347 One situation in which Exim does &'not'& automatically rewrite a domain is
24348 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
24349 such a domain should be rewritten using the &"canonical"& name, and some MTAs
24350 do this. The new RFCs do not contain this suggestion.
24353 .section "Explicitly configured address rewriting" "SECID147"
24354 This chapter describes the rewriting rules that can be used in the
24355 main rewrite section of the configuration file, and also in the generic
24356 &%headers_rewrite%& option that can be set on any transport.
24358 Some people believe that configured address rewriting is a Mortal Sin.
24359 Others believe that life is not possible without it. Exim provides the
24360 facility; you do not have to use it.
24362 The main rewriting rules that appear in the &"rewrite"& section of the
24363 configuration file are applied to addresses in incoming messages, both envelope
24364 addresses and addresses in header lines. Each rule specifies the types of
24365 address to which it applies.
24367 Whether or not addresses in header lines are rewritten depends on the origin of
24368 the headers and the type of rewriting. Global rewriting, that is, rewriting
24369 rules from the rewrite section of the configuration file, is applied only to
24370 those headers that were received with the message. Header lines that are added
24371 by ACLs or by a system filter or by individual routers or transports (which
24372 are specific to individual recipient addresses) are not rewritten by the global
24375 Rewriting at transport time, by means of the &%headers_rewrite%& option,
24376 applies all headers except those added by routers and transports. That is, as
24377 well as the headers that were received with the message, it also applies to
24378 headers that were added by an ACL or a system filter.
24381 In general, rewriting addresses from your own system or domain has some
24382 legitimacy. Rewriting other addresses should be done only with great care and
24383 in special circumstances. The author of Exim believes that rewriting should be
24384 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
24385 Although it can sometimes be used as a routing tool, this is very strongly
24388 There are two commonly encountered circumstances where rewriting is used, as
24389 illustrated by these examples:
24392 The company whose domain is &'hitch.fict.example'& has a number of hosts that
24393 exchange mail with each other behind a firewall, but there is only a single
24394 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
24395 &'hitch.fict.example'& when sending mail off-site.
24397 A host rewrites the local parts of its own users so that, for example,
24398 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
24403 .section "When does rewriting happen?" "SECID148"
24404 .cindex "rewriting" "timing of"
24405 .cindex "&ACL;" "rewriting addresses in"
24406 Configured address rewriting can take place at several different stages of a
24407 message's processing.
24409 .vindex "&$sender_address$&"
24410 At the start of an ACL for MAIL, the sender address may have been rewritten
24411 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
24412 ordinary rewrite rules have yet been applied. If, however, the sender address
24413 is verified in the ACL, it is rewritten before verification, and remains
24414 rewritten thereafter. The subsequent value of &$sender_address$& is the
24415 rewritten address. This also applies if sender verification happens in a
24416 RCPT ACL. Otherwise, when the sender address is not verified, it is
24417 rewritten as soon as a message's header lines have been received.
24419 .vindex "&$domain$&"
24420 .vindex "&$local_part$&"
24421 Similarly, at the start of an ACL for RCPT, the current recipient's address
24422 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
24423 rewrite rules have yet been applied to it. However, the behaviour is different
24424 from the sender address when a recipient is verified. The address is rewritten
24425 for the verification, but the rewriting is not remembered at this stage. The
24426 value of &$local_part$& and &$domain$& after verification are always the same
24427 as they were before (that is, they contain the unrewritten &-- except for
24428 SMTP-time rewriting &-- address).
24430 As soon as a message's header lines have been received, all the envelope
24431 recipient addresses are permanently rewritten, and rewriting is also applied to
24432 the addresses in the header lines (if configured). This happens before adding
24433 any header lines that were specified in MAIL or RCPT ACLs, and
24434 .cindex "&[local_scan()]& function" "address rewriting; timing of"
24435 before the DATA ACL and &[local_scan()]& functions are run.
24437 When an address is being routed, either for delivery or for verification,
24438 rewriting is applied immediately to child addresses that are generated by
24439 redirection, unless &%no_rewrite%& is set on the router.
24441 .cindex "envelope sender" "rewriting at transport time"
24442 .cindex "rewriting" "at transport time"
24443 .cindex "header lines" "rewriting at transport time"
24444 At transport time, additional rewriting of addresses in header lines can be
24445 specified by setting the generic &%headers_rewrite%& option on a transport.
24446 This option contains rules that are identical in form to those in the rewrite
24447 section of the configuration file. They are applied to the original message
24448 header lines and any that were added by ACLs or a system filter. They are not
24449 applied to header lines that are added by routers or the transport.
24451 The outgoing envelope sender can be rewritten by means of the &%return_path%&
24452 transport option. However, it is not possible to rewrite envelope recipients at
24458 .section "Testing the rewriting rules that apply on input" "SECID149"
24459 .cindex "rewriting" "testing"
24460 .cindex "testing" "rewriting"
24461 Exim's input rewriting configuration appears in a part of the run time
24462 configuration file headed by &"begin rewrite"&. It can be tested by the
24463 &%-brw%& command line option. This takes an address (which can be a full RFC
24464 2822 address) as its argument. The output is a list of how the address would be
24465 transformed by the rewriting rules for each of the different places it might
24466 appear in an incoming message, that is, for each different header and for the
24467 envelope sender and recipient fields. For example,
24469 exim -brw ph10@exim.workshop.example
24471 might produce the output
24473 sender: Philip.Hazel@exim.workshop.example
24474 from: Philip.Hazel@exim.workshop.example
24475 to: ph10@exim.workshop.example
24476 cc: ph10@exim.workshop.example
24477 bcc: ph10@exim.workshop.example
24478 reply-to: Philip.Hazel@exim.workshop.example
24479 env-from: Philip.Hazel@exim.workshop.example
24480 env-to: ph10@exim.workshop.example
24482 which shows that rewriting has been set up for that address when used in any of
24483 the source fields, but not when it appears as a recipient address. At the
24484 present time, there is no equivalent way of testing rewriting rules that are
24485 set for a particular transport.
24488 .section "Rewriting rules" "SECID150"
24489 .cindex "rewriting" "rules"
24490 The rewrite section of the configuration file consists of lines of rewriting
24493 <&'source pattern'&> <&'replacement'&> <&'flags'&>
24495 Rewriting rules that are specified for the &%headers_rewrite%& generic
24496 transport option are given as a colon-separated list. Each item in the list
24497 takes the same form as a line in the main rewriting configuration (except that
24498 any colons must be doubled, of course).
24500 The formats of source patterns and replacement strings are described below.
24501 Each is terminated by white space, unless enclosed in double quotes, in which
24502 case normal quoting conventions apply inside the quotes. The flags are single
24503 characters which may appear in any order. Spaces and tabs between them are
24506 For each address that could potentially be rewritten, the rules are scanned in
24507 order, and replacements for the address from earlier rules can themselves be
24508 replaced by later rules (but see the &"q"& and &"R"& flags).
24510 The order in which addresses are rewritten is undefined, may change between
24511 releases, and must not be relied on, with one exception: when a message is
24512 received, the envelope sender is always rewritten first, before any header
24513 lines are rewritten. For example, the replacement string for a rewrite of an
24514 address in &'To:'& must not assume that the message's address in &'From:'& has
24515 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
24516 that the envelope sender has already been rewritten.
24518 .vindex "&$domain$&"
24519 .vindex "&$local_part$&"
24520 The variables &$local_part$& and &$domain$& can be used in the replacement
24521 string to refer to the address that is being rewritten. Note that lookup-driven
24522 rewriting can be done by a rule of the form
24526 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
24527 refer to the address that is being rewritten.
24530 .section "Rewriting patterns" "SECID151"
24531 .cindex "rewriting" "patterns"
24532 .cindex "address list" "in a rewriting pattern"
24533 The source pattern in a rewriting rule is any item which may appear in an
24534 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
24535 single-item address list, which means that it is expanded before being tested
24536 against the address. As always, if you use a regular expression as a pattern,
24537 you must take care to escape dollar and backslash characters, or use the &`\N`&
24538 facility to suppress string expansion within the regular expression.
24540 Domains in patterns should be given in lower case. Local parts in patterns are
24541 case-sensitive. If you want to do case-insensitive matching of local parts, you
24542 can use a regular expression that starts with &`^(?i)`&.
24544 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
24545 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
24546 depending on the type of match which occurred. These can be used in the
24547 replacement string to insert portions of the incoming address. &$0$& always
24548 refers to the complete incoming address. When a regular expression is used, the
24549 numerical variables are set from its capturing subexpressions. For other types
24550 of pattern they are set as follows:
24553 If a local part or domain starts with an asterisk, the numerical variables
24554 refer to the character strings matched by asterisks, with &$1$& associated with
24555 the first asterisk, and &$2$& with the second, if present. For example, if the
24558 *queen@*.fict.example
24560 is matched against the address &'hearts-queen@wonderland.fict.example'& then
24562 $0 = hearts-queen@wonderland.fict.example
24566 Note that if the local part does not start with an asterisk, but the domain
24567 does, it is &$1$& that contains the wild part of the domain.
24570 If the domain part of the pattern is a partial lookup, the wild and fixed parts
24571 of the domain are placed in the next available numerical variables. Suppose,
24572 for example, that the address &'foo@bar.baz.example'& is processed by a
24573 rewriting rule of the form
24575 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
24577 and the key in the file that matches the domain is &`*.baz.example`&. Then
24583 If the address &'foo@baz.example'& is looked up, this matches the same
24584 wildcard file entry, and in this case &$2$& is set to the empty string, but
24585 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
24586 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
24587 whole domain. For non-partial domain lookups, no numerical variables are set.
24591 .section "Rewriting replacements" "SECID152"
24592 .cindex "rewriting" "replacements"
24593 If the replacement string for a rule is a single asterisk, addresses that
24594 match the pattern and the flags are &'not'& rewritten, and no subsequent
24595 rewriting rules are scanned. For example,
24597 hatta@lookingglass.fict.example * f
24599 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
24602 .vindex "&$domain$&"
24603 .vindex "&$local_part$&"
24604 If the replacement string is not a single asterisk, it is expanded, and must
24605 yield a fully qualified address. Within the expansion, the variables
24606 &$local_part$& and &$domain$& refer to the address that is being rewritten.
24607 Any letters they contain retain their original case &-- they are not lower
24608 cased. The numerical variables are set up according to the type of pattern that
24609 matched the address, as described above. If the expansion is forced to fail by
24610 the presence of &"fail"& in a conditional or lookup item, rewriting by the
24611 current rule is abandoned, but subsequent rules may take effect. Any other
24612 expansion failure causes the entire rewriting operation to be abandoned, and an
24613 entry written to the panic log.
24617 .section "Rewriting flags" "SECID153"
24618 There are three different kinds of flag that may appear on rewriting rules:
24621 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
24624 A flag that specifies rewriting at SMTP time: S.
24626 Flags that control the rewriting process: Q, q, R, w.
24629 For rules that are part of the &%headers_rewrite%& generic transport option,
24630 E, F, T, and S are not permitted.
24634 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
24636 .cindex "rewriting" "flags"
24637 If none of the following flag letters, nor the &"S"& flag (see section
24638 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
24639 and to both the sender and recipient fields of the envelope, whereas a
24640 transport-time rewriting rule just applies to all headers. Otherwise, the
24641 rewriting rule is skipped unless the relevant addresses are being processed.
24643 &`E`& rewrite all envelope fields
24644 &`F`& rewrite the envelope From field
24645 &`T`& rewrite the envelope To field
24646 &`b`& rewrite the &'Bcc:'& header
24647 &`c`& rewrite the &'Cc:'& header
24648 &`f`& rewrite the &'From:'& header
24649 &`h`& rewrite all headers
24650 &`r`& rewrite the &'Reply-To:'& header
24651 &`s`& rewrite the &'Sender:'& header
24652 &`t`& rewrite the &'To:'& header
24654 "All headers" means all of the headers listed above that can be selected
24655 individually, plus their &'Resent-'& versions. It does not include
24656 other headers such as &'Subject:'& etc.
24658 You should be particularly careful about rewriting &'Sender:'& headers, and
24659 restrict this to special known cases in your own domains.
24662 .section "The SMTP-time rewriting flag" "SECTrewriteS"
24663 .cindex "SMTP" "rewriting malformed addresses"
24664 .cindex "RCPT" "rewriting argument of"
24665 .cindex "MAIL" "rewriting argument of"
24666 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
24667 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
24668 before any other processing; even before syntax checking. The pattern is
24669 required to be a regular expression, and it is matched against the whole of the
24670 data for the command, including any surrounding angle brackets.
24672 .vindex "&$domain$&"
24673 .vindex "&$local_part$&"
24674 This form of rewrite rule allows for the handling of addresses that are not
24675 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
24676 input). Because the input is not required to be a syntactically valid address,
24677 the variables &$local_part$& and &$domain$& are not available during the
24678 expansion of the replacement string. The result of rewriting replaces the
24679 original address in the MAIL or RCPT command.
24682 .section "Flags controlling the rewriting process" "SECID155"
24683 There are four flags which control the way the rewriting process works. These
24684 take effect only when a rule is invoked, that is, when the address is of the
24685 correct type (matches the flags) and matches the pattern:
24688 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
24689 unqualified local part. It is qualified with &%qualify_recipient%&. In the
24690 absence of &"Q"& the rewritten address must always include a domain.
24692 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
24693 even if no rewriting actually takes place because of a &"fail"& in the
24694 expansion. The &"q"& flag is not effective if the address is of the wrong type
24695 (does not match the flags) or does not match the pattern.
24697 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
24698 address, up to ten times. It can be combined with the &"q"& flag, to stop
24699 rewriting once it fails to match (after at least one successful rewrite).
24701 .cindex "rewriting" "whole addresses"
24702 When an address in a header is rewritten, the rewriting normally applies only
24703 to the working part of the address, with any comments and RFC 2822 &"phrase"&
24704 left unchanged. For example, rewriting might change
24706 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
24710 From: Ford Prefect <prefectf@hitch.fict.example>
24713 Sometimes there is a need to replace the whole address item, and this can be
24714 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
24715 causes an address in a header line to be rewritten, the entire address is
24716 replaced, not just the working part. The replacement must be a complete RFC
24717 2822 address, including the angle brackets if necessary. If text outside angle
24718 brackets contains a character whose value is greater than 126 or less than 32
24719 (except for tab), the text is encoded according to RFC 2047. The character set
24720 is taken from &%headers_charset%&, which gets its default at build time.
24722 When the &"w"& flag is set on a rule that causes an envelope address to be
24723 rewritten, all but the working part of the replacement address is discarded.
24727 .section "Rewriting examples" "SECID156"
24728 Here is an example of the two common rewriting paradigms:
24730 *@*.hitch.fict.example $1@hitch.fict.example
24731 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
24732 {$value}fail}@hitch.fict.example bctfrF
24734 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
24735 the string expansion to fail if the lookup does not succeed. In this context it
24736 has the effect of leaving the original address unchanged, but Exim goes on to
24737 consider subsequent rewriting rules, if any, because the &"q"& flag is not
24738 present in that rule. An alternative to &"fail"& would be to supply &$1$&
24739 explicitly, which would cause the rewritten address to be the same as before,
24740 at the cost of a small bit of processing. Not supplying either of these is an
24741 error, since the rewritten address would then contain no local part.
24743 The first example above replaces the domain with a superior, more general
24744 domain. This may not be desirable for certain local parts. If the rule
24746 root@*.hitch.fict.example *
24748 were inserted before the first rule, rewriting would be suppressed for the
24749 local part &'root'& at any domain ending in &'hitch.fict.example'&.
24751 Rewriting can be made conditional on a number of tests, by making use of
24752 &${if$& in the expansion item. For example, to apply a rewriting rule only to
24753 messages that originate outside the local host:
24755 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
24756 {$1@hitch.fict.example}fail}"
24758 The replacement string is quoted in this example because it contains white
24761 .cindex "rewriting" "bang paths"
24762 .cindex "bang paths" "rewriting"
24763 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
24764 an address it treats it as an unqualified local part which it qualifies with
24765 the local qualification domain (if the source of the message is local or if the
24766 remote host is permitted to send unqualified addresses). Rewriting can
24767 sometimes be used to handle simple bang paths with a fixed number of
24768 components. For example, the rule
24770 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
24772 rewrites a two-component bang path &'host.name!user'& as the domain address
24773 &'user@host.name'&. However, there is a security implication in using this as
24774 a global rewriting rule for envelope addresses. It can provide a backdoor
24775 method for using your system as a relay, because the incoming addresses appear
24776 to be local. If the bang path addresses are received via SMTP, it is safer to
24777 use the &"S"& flag to rewrite them as they are received, so that relay checking
24778 can be done on the rewritten addresses.
24785 . ////////////////////////////////////////////////////////////////////////////
24786 . ////////////////////////////////////////////////////////////////////////////
24788 .chapter "Retry configuration" "CHAPretry"
24789 .scindex IIDretconf1 "retry" "configuration, description of"
24790 .scindex IIDregconf2 "configuration file" "retry section"
24791 The &"retry"& section of the runtime configuration file contains a list of
24792 retry rules that control how often Exim tries to deliver messages that cannot
24793 be delivered at the first attempt. If there are no retry rules (the section is
24794 empty or not present), there are no retries. In this situation, temporary
24795 errors are treated as permanent. The default configuration contains a single,
24796 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
24797 line option can be used to test which retry rule will be used for a given
24798 address, domain and error.
24800 The most common cause of retries is temporary failure to deliver to a remote
24801 host because the host is down, or inaccessible because of a network problem.
24802 Exim's retry processing in this case is applied on a per-host (strictly, per IP
24803 address) basis, not on a per-message basis. Thus, if one message has recently
24804 been delayed, delivery of a new message to the same host is not immediately
24805 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
24806 log selector is set, the message
24807 .cindex "retry" "time not reached"
24808 &"retry time not reached"& is written to the main log whenever a delivery is
24809 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
24810 the handling of errors during remote deliveries.
24812 Retry processing applies to routing as well as to delivering, except as covered
24813 in the next paragraph. The retry rules do not distinguish between these
24814 actions. It is not possible, for example, to specify different behaviour for
24815 failures to route the domain &'snark.fict.example'& and failures to deliver to
24816 the host &'snark.fict.example'&. I didn't think anyone would ever need this
24817 added complication, so did not implement it. However, although they share the
24818 same retry rule, the actual retry times for routing and transporting a given
24819 domain are maintained independently.
24821 When a delivery is not part of a queue run (typically an immediate delivery on
24822 receipt of a message), the routers are always run, and local deliveries are
24823 always attempted, even if retry times are set for them. This makes for better
24824 behaviour if one particular message is causing problems (for example, causing
24825 quota overflow, or provoking an error in a filter file). If such a delivery
24826 suffers a temporary failure, the retry data is updated as normal, and
24827 subsequent delivery attempts from queue runs occur only when the retry time for
24828 the local address is reached.
24830 .section "Changing retry rules" "SECID157"
24831 If you change the retry rules in your configuration, you should consider
24832 whether or not to delete the retry data that is stored in Exim's spool area in
24833 files with names like &_db/retry_&. Deleting any of Exim's hints files is
24834 always safe; that is why they are called &"hints"&.
24836 The hints retry data contains suggested retry times based on the previous
24837 rules. In the case of a long-running problem with a remote host, it might
24838 record the fact that the host has timed out. If your new rules increase the
24839 timeout time for such a host, you should definitely remove the old retry data
24840 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
24841 messages that it should now be retaining.
24845 .section "Format of retry rules" "SECID158"
24846 .cindex "retry" "rules"
24847 Each retry rule occupies one line and consists of three or four parts,
24848 separated by white space: a pattern, an error name, an optional list of sender
24849 addresses, and a list of retry parameters. The pattern and sender lists must be
24850 enclosed in double quotes if they contain white space. The rules are searched
24851 in order until one is found where the pattern, error name, and sender list (if
24852 present) match the failing host or address, the error that occurred, and the
24853 message's sender, respectively.
24856 The pattern is any single item that may appear in an address list (see section
24857 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
24858 which means that it is expanded before being tested against the address that
24859 has been delayed. A negated address list item is permitted. Address
24860 list processing treats a plain domain name as if it were preceded by &"*@"&,
24861 which makes it possible for many retry rules to start with just a domain. For
24864 lookingglass.fict.example * F,24h,30m;
24866 provides a rule for any address in the &'lookingglass.fict.example'& domain,
24869 alice@lookingglass.fict.example * F,24h,30m;
24871 applies only to temporary failures involving the local part &%alice%&.
24872 In practice, almost all rules start with a domain name pattern without a local
24875 .cindex "regular expressions" "in retry rules"
24876 &*Warning*&: If you use a regular expression in a retry rule pattern, it
24877 must match a complete address, not just a domain, because that is how regular
24878 expressions work in address lists.
24880 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
24881 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
24885 .section "Choosing which retry rule to use for address errors" "SECID159"
24886 When Exim is looking for a retry rule after a routing attempt has failed (for
24887 example, after a DNS timeout), each line in the retry configuration is tested
24888 against the complete address only if &%retry_use_local_part%& is set for the
24889 router. Otherwise, only the domain is used, except when matching against a
24890 regular expression, when the local part of the address is replaced with &"*"&.
24891 A domain on its own can match a domain pattern, or a pattern that starts with
24892 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
24893 &%check_local_user%& is true, and false for other routers.
24895 Similarly, when Exim is looking for a retry rule after a local delivery has
24896 failed (for example, after a mailbox full error), each line in the retry
24897 configuration is tested against the complete address only if
24898 &%retry_use_local_part%& is set for the transport (it defaults true for all
24901 .cindex "4&'xx'& responses" "retry rules for"
24902 However, when Exim is looking for a retry rule after a remote delivery attempt
24903 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
24904 whole address is always used as the key when searching the retry rules. The
24905 rule that is found is used to create a retry time for the combination of the
24906 failing address and the message's sender. It is the combination of sender and
24907 recipient that is delayed in subsequent queue runs until its retry time is
24908 reached. You can delay the recipient without regard to the sender by setting
24909 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
24910 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
24915 .section "Choosing which retry rule to use for host and message errors" &&&
24917 For a temporary error that is not related to an individual address (for
24918 example, a connection timeout), each line in the retry configuration is checked
24919 twice. First, the name of the remote host is used as a domain name (preceded by
24920 &"*@"& when matching a regular expression). If this does not match the line,
24921 the domain from the email address is tried in a similar fashion. For example,
24922 suppose the MX records for &'a.b.c.example'& are
24924 a.b.c.example MX 5 x.y.z.example
24928 and the retry rules are
24930 p.q.r.example * F,24h,30m;
24931 a.b.c.example * F,4d,45m;
24933 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
24934 first rule matches neither the host nor the domain, so Exim looks at the second
24935 rule. This does not match the host, but it does match the domain, so it is used
24936 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
24937 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
24938 first retry rule is used, because it matches the host.
24940 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
24941 first rule to determine retry times, but for all the other hosts for the domain
24942 &'a.b.c.example'&, the second rule is used. The second rule is also used if
24943 routing to &'a.b.c.example'& suffers a temporary failure.
24945 &*Note*&: The host name is used when matching the patterns, not its IP address.
24946 However, if a message is routed directly to an IP address without the use of a
24947 host name, for example, if a &(manualroute)& router contains a setting such as:
24949 route_list = *.a.example 192.168.34.23
24951 then the &"host name"& that is used when searching for a retry rule is the
24952 textual form of the IP address.
24954 .section "Retry rules for specific errors" "SECID161"
24955 .cindex "retry" "specific errors; specifying"
24956 The second field in a retry rule is the name of a particular error, or an
24957 asterisk, which matches any error. The errors that can be tested for are:
24960 .vitem &%auth_failed%&
24961 Authentication failed when trying to send to a host in the
24962 &%hosts_require_auth%& list in an &(smtp)& transport.
24964 .vitem &%data_4xx%&
24965 A 4&'xx'& error was received for an outgoing DATA command, either immediately
24966 after the command, or after sending the message's data.
24968 .vitem &%mail_4xx%&
24969 A 4&'xx'& error was received for an outgoing MAIL command.
24971 .vitem &%rcpt_4xx%&
24972 A 4&'xx'& error was received for an outgoing RCPT command.
24975 For the three 4&'xx'& errors, either the first or both of the x's can be given
24976 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
24977 recognize 452 errors given to RCPT commands for addresses in a certain domain,
24978 and have retries every ten minutes with a one-hour timeout, you could set up a
24979 retry rule of this form:
24981 the.domain.name rcpt_452 F,1h,10m
24983 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
24984 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
24987 .vitem &%lost_connection%&
24988 A server unexpectedly closed the SMTP connection. There may, of course,
24989 legitimate reasons for this (host died, network died), but if it repeats a lot
24990 for the same host, it indicates something odd.
24993 A DNS lookup for a host failed.
24994 Note that a &%dnslookup%& router will need to have matched
24995 its &%fail_defer_domains%& option for this retry type to be usable.
24996 Also note that a &%manualroute%& router will probably need
24997 its &%host_find_failed%& option set to &%defer%&.
24999 .vitem &%refused_MX%&
25000 A connection to a host obtained from an MX record was refused.
25002 .vitem &%refused_A%&
25003 A connection to a host not obtained from an MX record was refused.
25006 A connection was refused.
25008 .vitem &%timeout_connect_MX%&
25009 A connection attempt to a host obtained from an MX record timed out.
25011 .vitem &%timeout_connect_A%&
25012 A connection attempt to a host not obtained from an MX record timed out.
25014 .vitem &%timeout_connect%&
25015 A connection attempt timed out.
25017 .vitem &%timeout_MX%&
25018 There was a timeout while connecting or during an SMTP session with a host
25019 obtained from an MX record.
25021 .vitem &%timeout_A%&
25022 There was a timeout while connecting or during an SMTP session with a host not
25023 obtained from an MX record.
25026 There was a timeout while connecting or during an SMTP session.
25028 .vitem &%tls_required%&
25029 The server was required to use TLS (it matched &%hosts_require_tls%& in the
25030 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
25031 to STARTTLS, or there was a problem setting up the TLS connection.
25034 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25037 .vitem &%quota_%&<&'time'&>
25038 .cindex "quota" "error testing in retry rule"
25039 .cindex "retry" "quota error testing"
25040 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25041 transport, and the mailbox has not been accessed for <&'time'&>. For example,
25042 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
25046 .cindex "mailbox" "time of last read"
25047 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
25048 timeouts when the mailbox is full and is not being read by its owner. Ideally,
25049 it should be based on the last time that the user accessed the mailbox.
25050 However, it is not always possible to determine this. Exim uses the following
25054 If the mailbox is a single file, the time of last access (the &"atime"&) is
25055 used. As no new messages are being delivered (because the mailbox is over
25056 quota), Exim does not access the file, so this is the time of last user access.
25058 .cindex "maildir format" "time of last read"
25059 For a maildir delivery, the time of last modification of the &_new_&
25060 subdirectory is used. As the mailbox is over quota, no new files are created in
25061 the &_new_& subdirectory, because no new messages are being delivered. Any
25062 change to the &_new_& subdirectory is therefore assumed to be the result of an
25063 MUA moving a new message to the &_cur_& directory when it is first read. The
25064 time that is used is therefore the last time that the user read a new message.
25066 For other kinds of multi-file mailbox, the time of last access cannot be
25067 obtained, so a retry rule that uses this type of error field is never matched.
25070 The quota errors apply both to system-enforced quotas and to Exim's own quota
25071 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
25072 when a local delivery is deferred because a partition is full (the ENOSPC
25077 .section "Retry rules for specified senders" "SECID162"
25078 .cindex "retry" "rules; sender-specific"
25079 You can specify retry rules that apply only when the failing message has a
25080 specific sender. In particular, this can be used to define retry rules that
25081 apply only to bounce messages. The third item in a retry rule can be of this
25084 &`senders=`&<&'address list'&>
25086 The retry timings themselves are then the fourth item. For example:
25088 * rcpt_4xx senders=: F,1h,30m
25090 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
25091 host. If the address list contains white space, it must be enclosed in quotes.
25094 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
25096 &*Warning*&: This facility can be unhelpful if it is used for host errors
25097 (which do not depend on the recipient). The reason is that the sender is used
25098 only to match the retry rule. Once the rule has been found for a host error,
25099 its contents are used to set a retry time for the host, and this will apply to
25100 all messages, not just those with specific senders.
25102 When testing retry rules using &%-brt%&, you can supply a sender using the
25103 &%-f%& command line option, like this:
25105 exim -f "" -brt user@dom.ain
25107 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
25108 list is never matched.
25114 .section "Retry parameters" "SECID163"
25115 .cindex "retry" "parameters in rules"
25116 The third (or fourth, if a senders list is present) field in a retry rule is a
25117 sequence of retry parameter sets, separated by semicolons. Each set consists of
25119 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
25121 The letter identifies the algorithm for computing a new retry time; the cutoff
25122 time is the time beyond which this algorithm no longer applies, and the
25123 arguments vary the algorithm's action. The cutoff time is measured from the
25124 time that the first failure for the domain (combined with the local part if
25125 relevant) was detected, not from the time the message was received.
25127 .cindex "retry" "algorithms"
25128 .cindex "retry" "fixed intervals"
25129 .cindex "retry" "increasing intervals"
25130 .cindex "retry" "random intervals"
25131 The available algorithms are:
25134 &'F'&: retry at fixed intervals. There is a single time parameter specifying
25137 &'G'&: retry at geometrically increasing intervals. The first argument
25138 specifies a starting value for the interval, and the second a multiplier, which
25139 is used to increase the size of the interval at each retry.
25141 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
25142 retry, the previous interval is multiplied by the factor in order to get a
25143 maximum for the next interval. The minimum interval is the first argument of
25144 the parameter, and an actual interval is chosen randomly between them. Such a
25145 rule has been found to be helpful in cluster configurations when all the
25146 members of the cluster restart at once, and may therefore synchronize their
25147 queue processing times.
25150 When computing the next retry time, the algorithm definitions are scanned in
25151 order until one whose cutoff time has not yet passed is reached. This is then
25152 used to compute a new retry time that is later than the current time. In the
25153 case of fixed interval retries, this simply means adding the interval to the
25154 current time. For geometrically increasing intervals, retry intervals are
25155 computed from the rule's parameters until one that is greater than the previous
25156 interval is found. The main configuration variable
25157 .cindex "limit" "retry interval"
25158 .cindex "retry" "interval, maximum"
25159 .oindex "&%retry_interval_max%&"
25160 &%retry_interval_max%& limits the maximum interval between retries. It
25161 cannot be set greater than &`24h`&, which is its default value.
25163 A single remote domain may have a number of hosts associated with it, and each
25164 host may have more than one IP address. Retry algorithms are selected on the
25165 basis of the domain name, but are applied to each IP address independently. If,
25166 for example, a host has two IP addresses and one is unusable, Exim will
25167 generate retry times for it and will not try to use it until its next retry
25168 time comes. Thus the good IP address is likely to be tried first most of the
25171 .cindex "hints database" "use for retrying"
25172 Retry times are hints rather than promises. Exim does not make any attempt to
25173 run deliveries exactly at the computed times. Instead, a queue runner process
25174 starts delivery processes for delayed messages periodically, and these attempt
25175 new deliveries only for those addresses that have passed their next retry time.
25176 If a new message arrives for a deferred address, an immediate delivery attempt
25177 occurs only if the address has passed its retry time. In the absence of new
25178 messages, the minimum time between retries is the interval between queue runner
25179 processes. There is not much point in setting retry times of five minutes if
25180 your queue runners happen only once an hour, unless there are a significant
25181 number of incoming messages (which might be the case on a system that is
25182 sending everything to a smart host, for example).
25184 The data in the retry hints database can be inspected by using the
25185 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
25186 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
25187 &'exinext'& utility script can be used to find out what the next retry times
25188 are for the hosts associated with a particular mail domain, and also for local
25189 deliveries that have been deferred.
25192 .section "Retry rule examples" "SECID164"
25193 Here are some example retry rules:
25195 alice@wonderland.fict.example quota_5d F,7d,3h
25196 wonderland.fict.example quota_5d
25197 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
25198 lookingglass.fict.example * F,24h,30m;
25199 * refused_A F,2h,20m;
25200 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
25202 The first rule sets up special handling for mail to
25203 &'alice@wonderland.fict.example'& when there is an over-quota error and the
25204 mailbox has not been read for at least 5 days. Retries continue every three
25205 hours for 7 days. The second rule handles over-quota errors for all other local
25206 parts at &'wonderland.fict.example'&; the absence of a local part has the same
25207 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
25208 fail are bounced immediately if the mailbox has not been read for at least 5
25211 The third rule handles all other errors at &'wonderland.fict.example'&; retries
25212 happen every 15 minutes for an hour, then with geometrically increasing
25213 intervals until two days have passed since a delivery first failed. After the
25214 first hour there is a delay of one hour, then two hours, then four hours, and
25215 so on (this is a rather extreme example).
25217 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
25218 They happen every 30 minutes for 24 hours only. The remaining two rules handle
25219 all other domains, with special action for connection refusal from hosts that
25220 were not obtained from an MX record.
25222 The final rule in a retry configuration should always have asterisks in the
25223 first two fields so as to provide a general catch-all for any addresses that do
25224 not have their own special handling. This example tries every 15 minutes for 2
25225 hours, then with intervals starting at one hour and increasing by a factor of
25226 1.5 up to 16 hours, then every 8 hours up to 5 days.
25230 .section "Timeout of retry data" "SECID165"
25231 .cindex "timeout" "of retry data"
25232 .oindex "&%retry_data_expire%&"
25233 .cindex "hints database" "data expiry"
25234 .cindex "retry" "timeout of data"
25235 Exim timestamps the data that it writes to its retry hints database. When it
25236 consults the data during a delivery it ignores any that is older than the value
25237 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
25238 been tried for 7 days, Exim will try to deliver to it immediately a message
25239 arrives, and if that fails, it will calculate a retry time as if it were
25240 failing for the first time.
25242 This improves the behaviour for messages routed to rarely-used hosts such as MX
25243 backups. If such a host was down at one time, and happens to be down again when
25244 Exim tries a month later, using the old retry data would imply that it had been
25245 down all the time, which is not a justified assumption.
25247 If a host really is permanently dead, this behaviour causes a burst of retries
25248 every now and again, but only if messages routed to it are rare. If there is a
25249 message at least once every 7 days the retry data never expires.
25254 .section "Long-term failures" "SECID166"
25255 .cindex "delivery failure, long-term"
25256 .cindex "retry" "after long-term failure"
25257 Special processing happens when an email address has been failing for so long
25258 that the cutoff time for the last algorithm is reached. For example, using the
25259 default retry rule:
25261 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
25263 the cutoff time is four days. Reaching the retry cutoff is independent of how
25264 long any specific message has been failing; it is the length of continuous
25265 failure for the recipient address that counts.
25267 When the cutoff time is reached for a local delivery, or for all the IP
25268 addresses associated with a remote delivery, a subsequent delivery failure
25269 causes Exim to give up on the address, and a bounce message is generated.
25270 In order to cater for new messages that use the failing address, a next retry
25271 time is still computed from the final algorithm, and is used as follows:
25273 For local deliveries, one delivery attempt is always made for any subsequent
25274 messages. If this delivery fails, the address fails immediately. The
25275 post-cutoff retry time is not used.
25277 If the delivery is remote, there are two possibilities, controlled by the
25278 .oindex "&%delay_after_cutoff%&"
25279 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
25280 default. Until the post-cutoff retry time for one of the IP addresses is
25281 reached, the failing email address is bounced immediately, without a delivery
25282 attempt taking place. After that time, one new delivery attempt is made to
25283 those IP addresses that are past their retry times, and if that still fails,
25284 the address is bounced and new retry times are computed.
25286 In other words, when all the hosts for a given email address have been failing
25287 for a long time, Exim bounces rather then defers until one of the hosts' retry
25288 times is reached. Then it tries once, and bounces if that attempt fails. This
25289 behaviour ensures that few resources are wasted in repeatedly trying to deliver
25290 to a broken destination, but if the host does recover, Exim will eventually
25293 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25294 addresses are past their final cutoff time, Exim tries to deliver to those IP
25295 addresses that have not been tried since the message arrived. If there are
25296 no suitable IP addresses, or if they all fail, the address is bounced. In other
25297 words, it does not delay when a new message arrives, but tries the expired
25298 addresses immediately, unless they have been tried since the message arrived.
25299 If there is a continuous stream of messages for the failing domains, setting
25300 &%delay_after_cutoff%& false means that there will be many more attempts to
25301 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
25304 .section "Deliveries that work intermittently" "SECID167"
25305 .cindex "retry" "intermittently working deliveries"
25306 Some additional logic is needed to cope with cases where a host is
25307 intermittently available, or when a message has some attribute that prevents
25308 its delivery when others to the same address get through. In this situation,
25309 because some messages are successfully delivered, the &"retry clock"& for the
25310 host or address keeps getting reset by the successful deliveries, and so
25311 failing messages remain on the queue for ever because the cutoff time is never
25314 Two exceptional actions are applied to prevent this happening. The first
25315 applies to errors that are related to a message rather than a remote host.
25316 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
25317 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
25318 commands, and quota failures. For this type of error, if a message's arrival
25319 time is earlier than the &"first failed"& time for the error, the earlier time
25320 is used when scanning the retry rules to decide when to try next and when to
25321 time out the address.
25323 The exceptional second action applies in all cases. If a message has been on
25324 the queue for longer than the cutoff time of any applicable retry rule for a
25325 given address, a delivery is attempted for that address, even if it is not yet
25326 time, and if this delivery fails, the address is timed out. A new retry time is
25327 not computed in this case, so that other messages for the same address are
25328 considered immediately.
25329 .ecindex IIDretconf1
25330 .ecindex IIDregconf2
25337 . ////////////////////////////////////////////////////////////////////////////
25338 . ////////////////////////////////////////////////////////////////////////////
25340 .chapter "SMTP authentication" "CHAPSMTPAUTH"
25341 .scindex IIDauthconf1 "SMTP" "authentication configuration"
25342 .scindex IIDauthconf2 "authentication"
25343 The &"authenticators"& section of Exim's run time configuration is concerned
25344 with SMTP authentication. This facility is an extension to the SMTP protocol,
25345 described in RFC 2554, which allows a client SMTP host to authenticate itself
25346 to a server. This is a common way for a server to recognize clients that are
25347 permitted to use it as a relay. SMTP authentication is not of relevance to the
25348 transfer of mail between servers that have no managerial connection with each
25351 .cindex "AUTH" "description of"
25352 Very briefly, the way SMTP authentication works is as follows:
25355 The server advertises a number of authentication &'mechanisms'& in response to
25356 the client's EHLO command.
25358 The client issues an AUTH command, naming a specific mechanism. The command
25359 may, optionally, contain some authentication data.
25361 The server may issue one or more &'challenges'&, to which the client must send
25362 appropriate responses. In simple authentication mechanisms, the challenges are
25363 just prompts for user names and passwords. The server does not have to issue
25364 any challenges &-- in some mechanisms the relevant data may all be transmitted
25365 with the AUTH command.
25367 The server either accepts or denies authentication.
25369 If authentication succeeds, the client may optionally make use of the AUTH
25370 option on the MAIL command to pass an authenticated sender in subsequent
25371 mail transactions. Authentication lasts for the remainder of the SMTP
25374 If authentication fails, the client may give up, or it may try a different
25375 authentication mechanism, or it may try transferring mail over the
25376 unauthenticated connection.
25379 If you are setting up a client, and want to know which authentication
25380 mechanisms the server supports, you can use Telnet to connect to port 25 (the
25381 SMTP port) on the server, and issue an EHLO command. The response to this
25382 includes the list of supported mechanisms. For example:
25384 &`$ `&&*&`telnet server.example 25`&*&
25385 &`Trying 192.168.34.25...`&
25386 &`Connected to server.example.`&
25387 &`Escape character is '^]'.`&
25388 &`220 server.example ESMTP Exim 4.20 ...`&
25389 &*&`ehlo client.example`&*&
25390 &`250-server.example Hello client.example [10.8.4.5]`&
25391 &`250-SIZE 52428800`&
25396 The second-last line of this example output shows that the server supports
25397 authentication using the PLAIN mechanism. In Exim, the different authentication
25398 mechanisms are configured by specifying &'authenticator'& drivers. Like the
25399 routers and transports, which authenticators are included in the binary is
25400 controlled by build-time definitions. The following are currently available,
25401 included by setting
25404 AUTH_CYRUS_SASL=yes
25407 AUTH_HEIMDAL_GSSAPI=yes
25412 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
25413 authentication mechanism (RFC 2195), and the second provides an interface to
25414 the Cyrus SASL authentication library.
25415 The third is an interface to Dovecot's authentication system, delegating the
25416 work via a socket interface.
25417 The fourth provides an interface to the GNU SASL authentication library, which
25418 provides mechanisms but typically not data sources.
25419 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
25420 supporting setting a server keytab.
25421 The sixth can be configured to support
25422 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
25423 not formally documented, but used by several MUAs. The seventh authenticator
25424 supports Microsoft's &'Secure Password Authentication'& mechanism.
25425 The eighth is an Exim authenticator but not an SMTP one;
25426 instead it can use information from a TLS negotiation.
25428 The authenticators are configured using the same syntax as other drivers (see
25429 section &<<SECTfordricon>>&). If no authenticators are required, no
25430 authentication section need be present in the configuration file. Each
25431 authenticator can in principle have both server and client functions. When Exim
25432 is receiving SMTP mail, it is acting as a server; when it is sending out
25433 messages over SMTP, it is acting as a client. Authenticator configuration
25434 options are provided for use in both these circumstances.
25436 To make it clear which options apply to which situation, the prefixes
25437 &%server_%& and &%client_%& are used on option names that are specific to
25438 either the server or the client function, respectively. Server and client
25439 functions are disabled if none of their options are set. If an authenticator is
25440 to be used for both server and client functions, a single definition, using
25441 both sets of options, is required. For example:
25445 public_name = CRAM-MD5
25446 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
25448 client_secret = secret2
25450 The &%server_%& option is used when Exim is acting as a server, and the
25451 &%client_%& options when it is acting as a client.
25453 Descriptions of the individual authenticators are given in subsequent chapters.
25454 The remainder of this chapter covers the generic options for the
25455 authenticators, followed by general discussion of the way authentication works
25458 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
25459 per-mechanism basis. Please read carefully to determine which variables hold
25460 account labels such as usercodes and which hold passwords or other
25461 authenticating data.
25463 Note that some mechanisms support two different identifiers for accounts: the
25464 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
25465 and &'authz'& are commonly encountered. The American spelling is standard here.
25466 Conceptually, authentication data such as passwords are tied to the identifier
25467 used to authenticate; servers may have rules to permit one user to act as a
25468 second user, so that after login the session is treated as though that second
25469 user had logged in. That second user is the &'authorization id'&. A robust
25470 configuration might confirm that the &'authz'& field is empty or matches the
25471 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
25472 as verified data, the &'authz'& as an unverified request which the server might
25475 A &'realm'& is a text string, typically a domain name, presented by a server
25476 to a client to help it select an account and credentials to use. In some
25477 mechanisms, the client and server provably agree on the realm, but clients
25478 typically can not treat the realm as secure data to be blindly trusted.
25482 .section "Generic options for authenticators" "SECID168"
25483 .cindex "authentication" "generic options"
25484 .cindex "options" "generic; for authenticators"
25486 .option client_condition authenticators string&!! unset
25487 When Exim is authenticating as a client, it skips any authenticator whose
25488 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
25489 used, for example, to skip plain text authenticators when the connection is not
25490 encrypted by a setting such as:
25492 client_condition = ${if !eq{$tls_out_cipher}{}}
25496 .option client_set_id authenticators string&!! unset
25497 When client authentication succeeds, this condition is expanded; the
25498 result is used in the log lines for outbound messages.
25499 Typically it will be the user name used for authentication.
25502 .option driver authenticators string unset
25503 This option must always be set. It specifies which of the available
25504 authenticators is to be used.
25507 .option public_name authenticators string unset
25508 This option specifies the name of the authentication mechanism that the driver
25509 implements, and by which it is known to the outside world. These names should
25510 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
25511 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
25512 defaults to the driver's instance name.
25515 .option server_advertise_condition authenticators string&!! unset
25516 When a server is about to advertise an authentication mechanism, the condition
25517 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
25518 mechanism is not advertised.
25519 If the expansion fails, the mechanism is not advertised. If the failure was not
25520 forced, and was not caused by a lookup defer, the incident is logged.
25521 See section &<<SECTauthexiser>>& below for further discussion.
25524 .option server_condition authenticators string&!! unset
25525 This option must be set for a &%plaintext%& server authenticator, where it
25526 is used directly to control authentication. See section &<<SECTplainserver>>&
25529 For the &(gsasl)& authenticator, this option is required for various
25530 mechanisms; see chapter &<<CHAPgsasl>>& for details.
25532 For the other authenticators, &%server_condition%& can be used as an additional
25533 authentication or authorization mechanism that is applied after the other
25534 authenticator conditions succeed. If it is set, it is expanded when the
25535 authenticator would otherwise return a success code. If the expansion is forced
25536 to fail, authentication fails. Any other expansion failure causes a temporary
25537 error code to be returned. If the result of a successful expansion is an empty
25538 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25539 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
25540 other result, a temporary error code is returned, with the expanded string as
25544 .option server_debug_print authenticators string&!! unset
25545 If this option is set and authentication debugging is enabled (see the &%-d%&
25546 command line option), the string is expanded and included in the debugging
25547 output when the authenticator is run as a server. This can help with checking
25548 out the values of variables.
25549 If expansion of the string fails, the error message is written to the debugging
25550 output, and Exim carries on processing.
25553 .option server_set_id authenticators string&!! unset
25554 .vindex "&$authenticated_id$&"
25555 When an Exim server successfully authenticates a client, this string is
25556 expanded using data from the authentication, and preserved for any incoming
25557 messages in the variable &$authenticated_id$&. It is also included in the log
25558 lines for incoming messages. For example, a user/password authenticator
25559 configuration might preserve the user name that was used to authenticate, and
25560 refer to it subsequently during delivery of the message.
25561 If expansion fails, the option is ignored.
25564 .option server_mail_auth_condition authenticators string&!! unset
25565 This option allows a server to discard authenticated sender addresses supplied
25566 as part of MAIL commands in SMTP connections that are authenticated by the
25567 driver on which &%server_mail_auth_condition%& is set. The option is not used
25568 as part of the authentication process; instead its (unexpanded) value is
25569 remembered for later use.
25570 How it is used is described in the following section.
25576 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
25577 .cindex "authentication" "sender; authenticated"
25578 .cindex "AUTH" "on MAIL command"
25579 When a client supplied an AUTH= item on a MAIL command, Exim applies
25580 the following checks before accepting it as the authenticated sender of the
25584 If the connection is not using extended SMTP (that is, HELO was used rather
25585 than EHLO), the use of AUTH= is a syntax error.
25587 If the value of the AUTH= parameter is &"<>"&, it is ignored.
25589 .vindex "&$authenticated_sender$&"
25590 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
25591 running, the value of &$authenticated_sender$& is set to the value obtained
25592 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
25593 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
25594 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
25595 given for the MAIL command.
25597 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
25598 is accepted and placed in &$authenticated_sender$& only if the client has
25601 If the AUTH= value was accepted by either of the two previous rules, and
25602 the client has authenticated, and the authenticator has a setting for the
25603 &%server_mail_auth_condition%&, the condition is checked at this point. The
25604 valued that was saved from the authenticator is expanded. If the expansion
25605 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
25606 &$authenticated_sender$& is deleted. If the expansion yields any other value,
25607 the value of &$authenticated_sender$& is retained and passed on with the
25612 When &$authenticated_sender$& is set for a message, it is passed on to other
25613 hosts to which Exim authenticates as a client. Do not confuse this value with
25614 &$authenticated_id$&, which is a string obtained from the authentication
25615 process, and which is not usually a complete email address.
25617 .vindex "&$sender_address$&"
25618 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
25619 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
25620 therefore make use of &$authenticated_sender$&. The converse is not true: the
25621 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
25626 .section "Authentication on an Exim server" "SECTauthexiser"
25627 .cindex "authentication" "on an Exim server"
25628 When Exim receives an EHLO command, it advertises the public names of those
25629 authenticators that are configured as servers, subject to the following
25633 The client host must match &%auth_advertise_hosts%& (default *).
25635 It the &%server_advertise_condition%& option is set, its expansion must not
25636 yield the empty string, &"0"&, &"no"&, or &"false"&.
25639 The order in which the authenticators are defined controls the order in which
25640 the mechanisms are advertised.
25642 Some mail clients (for example, some versions of Netscape) require the user to
25643 provide a name and password for authentication whenever AUTH is advertised,
25644 even though authentication may not in fact be needed (for example, Exim may be
25645 set up to allow unconditional relaying from the client by an IP address check).
25646 You can make such clients more friendly by not advertising AUTH to them.
25647 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
25648 that runs for RCPT) to relay without authentication, you should set
25650 auth_advertise_hosts = ! 10.9.8.0/24
25652 so that no authentication mechanisms are advertised to them.
25654 The &%server_advertise_condition%& controls the advertisement of individual
25655 authentication mechanisms. For example, it can be used to restrict the
25656 advertisement of a particular mechanism to encrypted connections, by a setting
25659 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
25661 .vindex "&$tls_in_cipher$&"
25662 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
25663 yields &"yes"&, which allows the advertisement to happen.
25665 When an Exim server receives an AUTH command from a client, it rejects it
25666 immediately if AUTH was not advertised in response to an earlier EHLO
25667 command. This is the case if
25670 The client host does not match &%auth_advertise_hosts%&; or
25672 No authenticators are configured with server options; or
25674 Expansion of &%server_advertise_condition%& blocked the advertising of all the
25675 server authenticators.
25679 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
25680 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
25681 AUTH is accepted from any client host.
25683 If AUTH is not rejected by the ACL, Exim searches its configuration for a
25684 server authentication mechanism that was advertised in response to EHLO and
25685 that matches the one named in the AUTH command. If it finds one, it runs
25686 the appropriate authentication protocol, and authentication either succeeds or
25687 fails. If there is no matching advertised mechanism, the AUTH command is
25688 rejected with a 504 error.
25690 .vindex "&$received_protocol$&"
25691 .vindex "&$sender_host_authenticated$&"
25692 When a message is received from an authenticated host, the value of
25693 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
25694 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
25695 public name) of the authenticator driver that successfully authenticated the
25696 client from which the message was received. This variable is empty if there was
25697 no successful authentication.
25702 .section "Testing server authentication" "SECID169"
25703 .cindex "authentication" "testing a server"
25704 .cindex "AUTH" "testing a server"
25705 .cindex "base64 encoding" "creating authentication test data"
25706 Exim's &%-bh%& option can be useful for testing server authentication
25707 configurations. The data for the AUTH command has to be sent using base64
25708 encoding. A quick way to produce such data for testing is the following Perl
25712 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
25714 .cindex "binary zero" "in authentication data"
25715 This interprets its argument as a Perl string, and then encodes it. The
25716 interpretation as a Perl string allows binary zeros, which are required for
25717 some kinds of authentication, to be included in the data. For example, a
25718 command line to run this script on such data might be
25720 encode '\0user\0password'
25722 Note the use of single quotes to prevent the shell interpreting the
25723 backslashes, so that they can be interpreted by Perl to specify characters
25724 whose code value is zero.
25726 &*Warning 1*&: If either of the user or password strings starts with an octal
25727 digit, you must use three zeros instead of one after the leading backslash. If
25728 you do not, the octal digit that starts your string will be incorrectly
25729 interpreted as part of the code for the first character.
25731 &*Warning 2*&: If there are characters in the strings that Perl interprets
25732 specially, you must use a Perl escape to prevent them being misinterpreted. For
25733 example, a command such as
25735 encode '\0user@domain.com\0pas$$word'
25737 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
25739 If you have the &%mimencode%& command installed, another way to do produce
25740 base64-encoded strings is to run the command
25742 echo -e -n `\0user\0password' | mimencode
25744 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
25745 in the argument, and the &%-n%& option specifies no newline at the end of its
25746 output. However, not all versions of &%echo%& recognize these options, so you
25747 should check your version before relying on this suggestion.
25751 .section "Authentication by an Exim client" "SECID170"
25752 .cindex "authentication" "on an Exim client"
25753 The &(smtp)& transport has two options called &%hosts_require_auth%& and
25754 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
25755 announces support for authentication, and the host matches an entry in either
25756 of these options, Exim (as a client) tries to authenticate as follows:
25759 For each authenticator that is configured as a client, in the order in which
25760 they are defined in the configuration, it searches the authentication
25761 mechanisms announced by the server for one whose name matches the public name
25762 of the authenticator.
25765 .vindex "&$host_address$&"
25766 When it finds one that matches, it runs the authenticator's client code. The
25767 variables &$host$& and &$host_address$& are available for any string expansions
25768 that the client might do. They are set to the server's name and IP address. If
25769 any expansion is forced to fail, the authentication attempt is abandoned, and
25770 Exim moves on to the next authenticator. Otherwise an expansion failure causes
25771 delivery to be deferred.
25773 If the result of the authentication attempt is a temporary error or a timeout,
25774 Exim abandons trying to send the message to the host for the moment. It will
25775 try again later. If there are any backup hosts available, they are tried in the
25778 If the response to authentication is a permanent error (5&'xx'& code), Exim
25779 carries on searching the list of authenticators and tries another one if
25780 possible. If all authentication attempts give permanent errors, or if there are
25781 no attempts because no mechanisms match (or option expansions force failure),
25782 what happens depends on whether the host matches &%hosts_require_auth%& or
25783 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
25784 delivery is deferred. The error can be detected in the retry rules, and thereby
25785 turned into a permanent error if you wish. In the second case, Exim tries to
25786 deliver the message unauthenticated.
25789 .cindex "AUTH" "on MAIL command"
25790 When Exim has authenticated itself to a remote server, it adds the AUTH
25791 parameter to the MAIL commands it sends, if it has an authenticated sender for
25792 the message. If the message came from a remote host, the authenticated sender
25793 is the one that was receiving on an incoming MAIL command, provided that the
25794 incoming connection was authenticated and the &%server_mail_auth%& condition
25795 allowed the authenticated sender to be retained. If a local process calls Exim
25796 to send a message, the sender address that is built from the login name and
25797 &%qualify_domain%& is treated as authenticated. However, if the
25798 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
25799 the authenticated sender that was received with the message.
25800 .ecindex IIDauthconf1
25801 .ecindex IIDauthconf2
25808 . ////////////////////////////////////////////////////////////////////////////
25809 . ////////////////////////////////////////////////////////////////////////////
25811 .chapter "The plaintext authenticator" "CHAPplaintext"
25812 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
25813 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
25814 The &(plaintext)& authenticator can be configured to support the PLAIN and
25815 LOGIN authentication mechanisms, both of which transfer authentication data as
25816 plain (unencrypted) text (though base64 encoded). The use of plain text is a
25817 security risk; you are strongly advised to insist on the use of SMTP encryption
25818 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
25819 use unencrypted plain text, you should not use the same passwords for SMTP
25820 connections as you do for login accounts.
25822 .section "Plaintext options" "SECID171"
25823 .cindex "options" "&(plaintext)& authenticator (server)"
25824 When configured as a server, &(plaintext)& uses the following options:
25826 .option server_condition authenticators string&!! unset
25827 This is actually a global authentication option, but it must be set in order to
25828 configure the &(plaintext)& driver as a server. Its use is described below.
25830 .option server_prompts plaintext string&!! unset
25831 The contents of this option, after expansion, must be a colon-separated list of
25832 prompt strings. If expansion fails, a temporary authentication rejection is
25835 .section "Using plaintext in a server" "SECTplainserver"
25836 .cindex "AUTH" "in &(plaintext)& authenticator"
25837 .cindex "binary zero" "in &(plaintext)& authenticator"
25838 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
25839 "in &(plaintext)& authenticator"
25840 .vindex "&$auth1$&, &$auth2$&, etc"
25841 .cindex "base64 encoding" "in &(plaintext)& authenticator"
25843 When running as a server, &(plaintext)& performs the authentication test by
25844 expanding a string. The data sent by the client with the AUTH command, or in
25845 response to subsequent prompts, is base64 encoded, and so may contain any byte
25846 values when decoded. If any data is supplied with the command, it is treated as
25847 a list of strings, separated by NULs (binary zeros), the first three of which
25848 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
25849 (neither LOGIN nor PLAIN uses more than three strings).
25851 For compatibility with previous releases of Exim, the values are also placed in
25852 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
25853 variables for this purpose is now deprecated, as it can lead to confusion in
25854 string expansions that also use them for other things.
25856 If there are more strings in &%server_prompts%& than the number of strings
25857 supplied with the AUTH command, the remaining prompts are used to obtain more
25858 data. Each response from the client may be a list of NUL-separated strings.
25860 .vindex "&$authenticated_id$&"
25861 Once a sufficient number of data strings have been received,
25862 &%server_condition%& is expanded. If the expansion is forced to fail,
25863 authentication fails. Any other expansion failure causes a temporary error code
25864 to be returned. If the result of a successful expansion is an empty string,
25865 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25866 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
25867 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
25868 For any other result, a temporary error code is returned, with the expanded
25869 string as the error text
25871 &*Warning*&: If you use a lookup in the expansion to find the user's
25872 password, be sure to make the authentication fail if the user is unknown.
25873 There are good and bad examples at the end of the next section.
25877 .section "The PLAIN authentication mechanism" "SECID172"
25878 .cindex "PLAIN authentication mechanism"
25879 .cindex "authentication" "PLAIN mechanism"
25880 .cindex "binary zero" "in &(plaintext)& authenticator"
25881 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
25882 sent as one item of data (that is, one combined string containing two NUL
25883 separators). The data is sent either as part of the AUTH command, or
25884 subsequently in response to an empty prompt from the server.
25886 The second and third strings are a user name and a corresponding password.
25887 Using a single fixed user name and password as an example, this could be
25888 configured as follows:
25892 public_name = PLAIN
25894 server_condition = \
25895 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
25896 server_set_id = $auth2
25898 Note that the default result strings from &%if%& (&"true"& or an empty string)
25899 are exactly what we want here, so they need not be specified. Obviously, if the
25900 password contains expansion-significant characters such as dollar, backslash,
25901 or closing brace, they have to be escaped.
25903 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
25904 the end of a string list are ignored). If all the data comes as part of the
25905 AUTH command, as is commonly the case, the prompt is not used. This
25906 authenticator is advertised in the response to EHLO as
25910 and a client host can authenticate itself by sending the command
25912 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
25914 As this contains three strings (more than the number of prompts), no further
25915 data is required from the client. Alternatively, the client may just send
25919 to initiate authentication, in which case the server replies with an empty
25920 prompt. The client must respond with the combined data string.
25922 The data string is base64 encoded, as required by the RFC. This example,
25923 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
25924 represents a zero byte. This is split up into three strings, the first of which
25925 is empty. The &%server_condition%& option in the authenticator checks that the
25926 second two are &`username`& and &`mysecret`& respectively.
25928 Having just one fixed user name and password, as in this example, is not very
25929 realistic, though for a small organization with only a handful of
25930 authenticating clients it could make sense.
25932 A more sophisticated instance of this authenticator could use the user name in
25933 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
25934 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
25935 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
25936 This is an incorrect example:
25938 server_condition = \
25939 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
25941 The expansion uses the user name (&$auth2$&) as the key to look up a password,
25942 which it then compares to the supplied password (&$auth3$&). Why is this example
25943 incorrect? It works fine for existing users, but consider what happens if a
25944 non-existent user name is given. The lookup fails, but as no success/failure
25945 strings are given for the lookup, it yields an empty string. Thus, to defeat
25946 the authentication, all a client has to do is to supply a non-existent user
25947 name and an empty password. The correct way of writing this test is:
25949 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
25950 {${if eq{$value}{$auth3}}} {false}}
25952 In this case, if the lookup succeeds, the result is checked; if the lookup
25953 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
25954 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
25955 always fails if its second argument is empty. However, the second way of
25956 writing the test makes the logic clearer.
25959 .section "The LOGIN authentication mechanism" "SECID173"
25960 .cindex "LOGIN authentication mechanism"
25961 .cindex "authentication" "LOGIN mechanism"
25962 The LOGIN authentication mechanism is not documented in any RFC, but is in use
25963 in a number of programs. No data is sent with the AUTH command. Instead, a
25964 user name and password are supplied separately, in response to prompts. The
25965 plaintext authenticator can be configured to support this as in this example:
25969 public_name = LOGIN
25970 server_prompts = User Name : Password
25971 server_condition = \
25972 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
25973 server_set_id = $auth1
25975 Because of the way plaintext operates, this authenticator accepts data supplied
25976 with the AUTH command (in contravention of the specification of LOGIN), but
25977 if the client does not supply it (as is the case for LOGIN clients), the prompt
25978 strings are used to obtain two data items.
25980 Some clients are very particular about the precise text of the prompts. For
25981 example, Outlook Express is reported to recognize only &"Username:"& and
25982 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
25983 strings. It uses the &%ldapauth%& expansion condition to check the user
25984 name and password by binding to an LDAP server:
25988 public_name = LOGIN
25989 server_prompts = Username:: : Password::
25990 server_condition = ${if and{{ \
25993 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
25994 pass=${quote:$auth2} \
25995 ldap://ldap.example.org/} }} }
25996 server_set_id = uid=$auth1,ou=people,o=example.org
25998 We have to check that the username is not empty before using it, because LDAP
25999 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
26000 operator to correctly quote the DN for authentication. However, the basic
26001 &%quote%& operator, rather than any of the LDAP quoting operators, is the
26002 correct one to use for the password, because quoting is needed only to make
26003 the password conform to the Exim syntax. At the LDAP level, the password is an
26004 uninterpreted string.
26007 .section "Support for different kinds of authentication" "SECID174"
26008 A number of string expansion features are provided for the purpose of
26009 interfacing to different ways of user authentication. These include checking
26010 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
26011 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
26017 .section "Using plaintext in a client" "SECID175"
26018 .cindex "options" "&(plaintext)& authenticator (client)"
26019 The &(plaintext)& authenticator has two client options:
26021 .option client_ignore_invalid_base64 plaintext boolean false
26022 If the client receives a server prompt that is not a valid base64 string,
26023 authentication is abandoned by default. However, if this option is set true,
26024 the error in the challenge is ignored and the client sends the response as
26027 .option client_send plaintext string&!! unset
26028 The string is a colon-separated list of authentication data strings. Each
26029 string is independently expanded before being sent to the server. The first
26030 string is sent with the AUTH command; any more strings are sent in response
26031 to prompts from the server. Before each string is expanded, the value of the
26032 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
26033 with &$auth1$& for the first prompt. Up to three prompts are stored in this
26034 way. Thus, the prompt that is received in response to sending the first string
26035 (with the AUTH command) can be used in the expansion of the second string, and
26036 so on. If an invalid base64 string is received when
26037 &%client_ignore_invalid_base64%& is set, an empty string is put in the
26038 &$auth$&<&'n'&> variable.
26040 &*Note*&: You cannot use expansion to create multiple strings, because
26041 splitting takes priority and happens first.
26043 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
26044 the data, further processing is applied to each string before it is sent. If
26045 there are any single circumflex characters in the string, they are converted to
26046 NULs. Should an actual circumflex be required as data, it must be doubled in
26049 This is an example of a client configuration that implements the PLAIN
26050 authentication mechanism with a fixed user name and password:
26054 public_name = PLAIN
26055 client_send = ^username^mysecret
26057 The lack of colons means that the entire text is sent with the AUTH
26058 command, with the circumflex characters converted to NULs. A similar example
26059 that uses the LOGIN mechanism is:
26063 public_name = LOGIN
26064 client_send = : username : mysecret
26066 The initial colon means that the first string is empty, so no data is sent with
26067 the AUTH command itself. The remaining strings are sent in response to
26069 .ecindex IIDplaiauth1
26070 .ecindex IIDplaiauth2
26075 . ////////////////////////////////////////////////////////////////////////////
26076 . ////////////////////////////////////////////////////////////////////////////
26078 .chapter "The cram_md5 authenticator" "CHID9"
26079 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
26080 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
26081 .cindex "CRAM-MD5 authentication mechanism"
26082 .cindex "authentication" "CRAM-MD5 mechanism"
26083 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
26084 sends a challenge string to the client, and the response consists of a user
26085 name and the CRAM-MD5 digest of the challenge string combined with a secret
26086 string (password) which is known to both server and client. Thus, the secret
26087 is not sent over the network as plain text, which makes this authenticator more
26088 secure than &(plaintext)&. However, the downside is that the secret has to be
26089 available in plain text at either end.
26092 .section "Using cram_md5 as a server" "SECID176"
26093 .cindex "options" "&(cram_md5)& authenticator (server)"
26094 This authenticator has one server option, which must be set to configure the
26095 authenticator as a server:
26097 .option server_secret cram_md5 string&!! unset
26098 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
26099 When the server receives the client's response, the user name is placed in
26100 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
26101 obtain the password for that user. The server then computes the CRAM-MD5 digest
26102 that the client should have sent, and checks that it received the correct
26103 string. If the expansion of &%server_secret%& is forced to fail, authentication
26104 fails. If the expansion fails for some other reason, a temporary error code is
26105 returned to the client.
26107 For compatibility with previous releases of Exim, the user name is also placed
26108 in &$1$&. However, the use of this variables for this purpose is now
26109 deprecated, as it can lead to confusion in string expansions that also use
26110 numeric variables for other things.
26112 For example, the following authenticator checks that the user name given by the
26113 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
26114 user name, authentication fails.
26118 public_name = CRAM-MD5
26119 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
26120 server_set_id = $auth1
26122 .vindex "&$authenticated_id$&"
26123 If authentication succeeds, the setting of &%server_set_id%& preserves the user
26124 name in &$authenticated_id$&. A more typical configuration might look up the
26125 secret string in a file, using the user name as the key. For example:
26129 public_name = CRAM-MD5
26130 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
26132 server_set_id = $auth1
26134 Note that this expansion explicitly forces failure if the lookup fails
26135 because &$auth1$& contains an unknown user name.
26137 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
26138 using the relevant libraries, you need to know the realm to specify in the
26139 lookup and then ask for the &"userPassword"& attribute for that user in that
26144 public_name = CRAM-MD5
26145 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
26146 dbmjz{/etc/sasldb2}{$value}fail}
26147 server_set_id = $auth1
26150 .section "Using cram_md5 as a client" "SECID177"
26151 .cindex "options" "&(cram_md5)& authenticator (client)"
26152 When used as a client, the &(cram_md5)& authenticator has two options:
26156 .option client_name cram_md5 string&!! "the primary host name"
26157 This string is expanded, and the result used as the user name data when
26158 computing the response to the server's challenge.
26161 .option client_secret cram_md5 string&!! unset
26162 This option must be set for the authenticator to work as a client. Its value is
26163 expanded and the result used as the secret string when computing the response.
26167 .vindex "&$host_address$&"
26168 Different user names and secrets can be used for different servers by referring
26169 to &$host$& or &$host_address$& in the options. Forced failure of either
26170 expansion string is treated as an indication that this authenticator is not
26171 prepared to handle this case. Exim moves on to the next configured client
26172 authenticator. Any other expansion failure causes Exim to give up trying to
26173 send the message to the current server.
26175 A simple example configuration of a &(cram_md5)& authenticator, using fixed
26180 public_name = CRAM-MD5
26182 client_secret = secret
26184 .ecindex IIDcramauth1
26185 .ecindex IIDcramauth2
26189 . ////////////////////////////////////////////////////////////////////////////
26190 . ////////////////////////////////////////////////////////////////////////////
26192 .chapter "The cyrus_sasl authenticator" "CHID10"
26193 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
26194 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
26195 .cindex "Cyrus" "SASL library"
26197 The code for this authenticator was provided by Matthew Byng-Maddick of A L
26198 Digital Ltd (&url(http://www.aldigital.co.uk)).
26200 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
26201 library implementation of the RFC 2222 (&"Simple Authentication and Security
26202 Layer"&). This library supports a number of authentication mechanisms,
26203 including PLAIN and LOGIN, but also several others that Exim does not support
26204 directly. In particular, there is support for Kerberos authentication.
26206 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
26207 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
26208 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
26209 name of the driver to determine which mechanism to support.
26211 Where access to some kind of secret file is required, for example in GSSAPI
26212 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
26213 user, and that the Cyrus SASL library has no way of escalating privileges
26214 by default. You may also find you need to set environment variables,
26215 depending on the driver you are using.
26217 The application name provided by Exim is &"exim"&, so various SASL options may
26218 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
26219 Kerberos, note that because of limitations in the GSSAPI interface,
26220 changing the server keytab might need to be communicated down to the Kerberos
26221 layer independently. The mechanism for doing so is dependent upon the Kerberos
26224 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
26225 may be set to point to an alternative keytab file. Exim will pass this
26226 variable through from its own inherited environment when started as root or the
26227 Exim user. The keytab file needs to be readable by the Exim user.
26228 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
26229 environment variable. In practice, for those releases, the Cyrus authenticator
26230 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
26231 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
26234 .section "Using cyrus_sasl as a server" "SECID178"
26235 The &(cyrus_sasl)& authenticator has four private options. It puts the username
26236 (on a successful authentication) into &$auth1$&. For compatibility with
26237 previous releases of Exim, the username is also placed in &$1$&. However, the
26238 use of this variable for this purpose is now deprecated, as it can lead to
26239 confusion in string expansions that also use numeric variables for other
26243 .option server_hostname cyrus_sasl string&!! "see below"
26244 This option selects the hostname that is used when communicating with the
26245 library. The default value is &`$primary_hostname`&. It is up to the underlying
26246 SASL plug-in what it does with this data.
26249 .option server_mech cyrus_sasl string "see below"
26250 This option selects the authentication mechanism this driver should use. The
26251 default is the value of the generic &%public_name%& option. This option allows
26252 you to use a different underlying mechanism from the advertised name. For
26256 driver = cyrus_sasl
26257 public_name = X-ANYTHING
26258 server_mech = CRAM-MD5
26259 server_set_id = $auth1
26262 .option server_realm cyrus_sasl string&!! unset
26263 This specifies the SASL realm that the server claims to be in.
26266 .option server_service cyrus_sasl string &`smtp`&
26267 This is the SASL service that the server claims to implement.
26270 For straightforward cases, you do not need to set any of the authenticator's
26271 private options. All you need to do is to specify an appropriate mechanism as
26272 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
26273 PLAIN, you could have two authenticators as follows:
26276 driver = cyrus_sasl
26277 public_name = CRAM-MD5
26278 server_set_id = $auth1
26281 driver = cyrus_sasl
26282 public_name = PLAIN
26283 server_set_id = $auth2
26285 Cyrus SASL does implement the LOGIN authentication method, even though it is
26286 not a standard method. It is disabled by default in the source distribution,
26287 but it is present in many binary distributions.
26288 .ecindex IIDcyrauth1
26289 .ecindex IIDcyrauth2
26294 . ////////////////////////////////////////////////////////////////////////////
26295 . ////////////////////////////////////////////////////////////////////////////
26296 .chapter "The dovecot authenticator" "CHAPdovecot"
26297 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
26298 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
26299 This authenticator is an interface to the authentication facility of the
26300 Dovecot POP/IMAP server, which can support a number of authentication methods.
26301 Note that Dovecot must be configured to use auth-client not auth-userdb.
26302 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
26303 to use the same mechanisms for SMTP authentication. This is a server
26304 authenticator only. There is only one option:
26306 .option server_socket dovecot string unset
26308 This option must specify the socket that is the interface to Dovecot
26309 authentication. The &%public_name%& option must specify an authentication
26310 mechanism that Dovecot is configured to support. You can have several
26311 authenticators for different mechanisms. For example:
26315 public_name = PLAIN
26316 server_socket = /var/run/dovecot/auth-client
26317 server_set_id = $auth1
26322 server_socket = /var/run/dovecot/auth-client
26323 server_set_id = $auth1
26325 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
26326 &$received_ip_address$& (that is, the connection is local), the &"secured"&
26327 option is passed in the Dovecot authentication command. If, for a TLS
26328 connection, a client certificate has been verified, the &"valid-client-cert"&
26329 option is passed. When authentication succeeds, the identity of the user
26330 who authenticated is placed in &$auth1$&.
26331 .ecindex IIDdcotauth1
26332 .ecindex IIDdcotauth2
26335 . ////////////////////////////////////////////////////////////////////////////
26336 . ////////////////////////////////////////////////////////////////////////////
26337 .chapter "The gsasl authenticator" "CHAPgsasl"
26338 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
26339 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
26340 .cindex "authentication" "GNU SASL"
26341 .cindex "authentication" "SASL"
26342 .cindex "authentication" "EXTERNAL"
26343 .cindex "authentication" "ANONYMOUS"
26344 .cindex "authentication" "PLAIN"
26345 .cindex "authentication" "LOGIN"
26346 .cindex "authentication" "DIGEST-MD5"
26347 .cindex "authentication" "CRAM-MD5"
26348 .cindex "authentication" "SCRAM-SHA-1"
26349 The &(gsasl)& authenticator provides server integration for the GNU SASL
26350 library and the mechanisms it provides. This is new as of the 4.80 release
26351 and there are a few areas where the library does not let Exim smoothly
26352 scale to handle future authentication mechanisms, so no guarantee can be
26353 made that any particular new authentication mechanism will be supported
26354 without code changes in Exim.
26357 .option server_channelbinding gsasl boolean false
26358 Some authentication mechanisms are able to use external context at both ends
26359 of the session to bind the authentication to that context, and fail the
26360 authentication process if that context differs. Specifically, some TLS
26361 ciphersuites can provide identifying information about the cryptographic
26364 This means that certificate identity and verification becomes a non-issue,
26365 as a man-in-the-middle attack will cause the correct client and server to
26366 see different identifiers and authentication will fail.
26368 This is currently only supported when using the GnuTLS library. This is
26369 only usable by mechanisms which support "channel binding"; at time of
26370 writing, that's the SCRAM family.
26372 This defaults off to ensure smooth upgrade across Exim releases, in case
26373 this option causes some clients to start failing. Some future release
26374 of Exim may switch the default to be true.
26377 .option server_hostname gsasl string&!! "see below"
26378 This option selects the hostname that is used when communicating with the
26379 library. The default value is &`$primary_hostname`&.
26380 Some mechanisms will use this data.
26383 .option server_mech gsasl string "see below"
26384 This option selects the authentication mechanism this driver should use. The
26385 default is the value of the generic &%public_name%& option. This option allows
26386 you to use a different underlying mechanism from the advertised name. For
26391 public_name = X-ANYTHING
26392 server_mech = CRAM-MD5
26393 server_set_id = $auth1
26397 .option server_password gsasl string&!! unset
26398 Various mechanisms need access to the cleartext password on the server, so
26399 that proof-of-possession can be demonstrated on the wire, without sending
26400 the password itself.
26402 The data available for lookup varies per mechanism.
26403 In all cases, &$auth1$& is set to the &'authentication id'&.
26404 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
26405 if available, else the empty string.
26406 The &$auth3$& variable will always be the &'realm'& if available,
26407 else the empty string.
26409 A forced failure will cause authentication to defer.
26411 If using this option, it may make sense to set the &%server_condition%&
26412 option to be simply "true".
26415 .option server_realm gsasl string&!! unset
26416 This specifies the SASL realm that the server claims to be in.
26417 Some mechanisms will use this data.
26420 .option server_scram_iter gsasl string&!! unset
26421 This option provides data for the SCRAM family of mechanisms.
26422 &$auth1$& is not available at evaluation time.
26423 (This may change, as we receive feedback on use)
26426 .option server_scram_salt gsasl string&!! unset
26427 This option provides data for the SCRAM family of mechanisms.
26428 &$auth1$& is not available at evaluation time.
26429 (This may change, as we receive feedback on use)
26432 .option server_service gsasl string &`smtp`&
26433 This is the SASL service that the server claims to implement.
26434 Some mechanisms will use this data.
26437 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
26438 .vindex "&$auth1$&, &$auth2$&, etc"
26439 These may be set when evaluating specific options, as detailed above.
26440 They will also be set when evaluating &%server_condition%&.
26442 Unless otherwise stated below, the &(gsasl)& integration will use the following
26443 meanings for these variables:
26446 .vindex "&$auth1$&"
26447 &$auth1$&: the &'authentication id'&
26449 .vindex "&$auth2$&"
26450 &$auth2$&: the &'authorization id'&
26452 .vindex "&$auth3$&"
26453 &$auth3$&: the &'realm'&
26456 On a per-mechanism basis:
26459 .cindex "authentication" "EXTERNAL"
26460 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
26461 the &%server_condition%& option must be present.
26463 .cindex "authentication" "ANONYMOUS"
26464 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
26465 the &%server_condition%& option must be present.
26467 .cindex "authentication" "GSSAPI"
26468 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
26469 &$auth2$& will be set to the &'authorization id'&,
26470 the &%server_condition%& option must be present.
26473 An &'anonymous token'& is something passed along as an unauthenticated
26474 identifier; this is analogous to FTP anonymous authentication passing an
26475 email address, or software-identifier@, as the "password".
26478 An example showing the password having the realm specified in the callback
26479 and demonstrating a Cyrus SASL to GSASL migration approach is:
26481 gsasl_cyrusless_crammd5:
26483 public_name = CRAM-MD5
26484 server_realm = imap.example.org
26485 server_password = ${lookup{$auth1:$auth3:userPassword}\
26486 dbmjz{/etc/sasldb2}{$value}fail}
26487 server_set_id = ${quote:$auth1}
26488 server_condition = yes
26492 . ////////////////////////////////////////////////////////////////////////////
26493 . ////////////////////////////////////////////////////////////////////////////
26495 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
26496 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
26497 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
26498 .cindex "authentication" "GSSAPI"
26499 .cindex "authentication" "Kerberos"
26500 The &(heimdal_gssapi)& authenticator provides server integration for the
26501 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
26504 .option server_hostname heimdal_gssapi string&!! "see below"
26505 This option selects the hostname that is used, with &%server_service%&,
26506 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
26507 identifier. The default value is &`$primary_hostname`&.
26509 .option server_keytab heimdal_gssapi string&!! unset
26510 If set, then Heimdal will not use the system default keytab (typically
26511 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
26512 The value should be a pathname, with no &"file:"& prefix.
26514 .option server_service heimdal_gssapi string&!! "smtp"
26515 This option specifies the service identifier used, in conjunction with
26516 &%server_hostname%&, for building the identifier for finding credentials
26520 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
26521 Beware that these variables will typically include a realm, thus will appear
26522 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
26523 not verified, so a malicious client can set it to anything.
26525 The &$auth1$& field should be safely trustable as a value from the Key
26526 Distribution Center. Note that these are not quite email addresses.
26527 Each identifier is for a role, and so the left-hand-side may include a
26528 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
26530 .vindex "&$auth1$&, &$auth2$&, etc"
26532 .vindex "&$auth1$&"
26533 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
26535 .vindex "&$auth2$&"
26536 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
26537 authentication. If that was empty, this will also be set to the
26542 . ////////////////////////////////////////////////////////////////////////////
26543 . ////////////////////////////////////////////////////////////////////////////
26545 .chapter "The spa authenticator" "CHAPspa"
26546 .scindex IIDspaauth1 "&(spa)& authenticator"
26547 .scindex IIDspaauth2 "authenticators" "&(spa)&"
26548 .cindex "authentication" "Microsoft Secure Password"
26549 .cindex "authentication" "NTLM"
26550 .cindex "Microsoft Secure Password Authentication"
26551 .cindex "NTLM authentication"
26552 The &(spa)& authenticator provides client support for Microsoft's &'Secure
26553 Password Authentication'& mechanism,
26554 which is also sometimes known as NTLM (NT LanMan). The code for client side of
26555 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
26556 taken from the Samba project (&url(http://www.samba.org)). The code for the
26557 server side was subsequently contributed by Tom Kistner. The mechanism works as
26561 After the AUTH command has been accepted, the client sends an SPA
26562 authentication request based on the user name and optional domain.
26564 The server sends back a challenge.
26566 The client builds a challenge response which makes use of the user's password
26567 and sends it to the server, which then accepts or rejects it.
26570 Encryption is used to protect the password in transit.
26574 .section "Using spa as a server" "SECID179"
26575 .cindex "options" "&(spa)& authenticator (server)"
26576 The &(spa)& authenticator has just one server option:
26578 .option server_password spa string&!! unset
26579 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
26580 This option is expanded, and the result must be the cleartext password for the
26581 authenticating user, whose name is at this point in &$auth1$&. For
26582 compatibility with previous releases of Exim, the user name is also placed in
26583 &$1$&. However, the use of this variable for this purpose is now deprecated, as
26584 it can lead to confusion in string expansions that also use numeric variables
26585 for other things. For example:
26590 server_password = \
26591 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
26593 If the expansion is forced to fail, authentication fails. Any other expansion
26594 failure causes a temporary error code to be returned.
26600 .section "Using spa as a client" "SECID180"
26601 .cindex "options" "&(spa)& authenticator (client)"
26602 The &(spa)& authenticator has the following client options:
26606 .option client_domain spa string&!! unset
26607 This option specifies an optional domain for the authentication.
26610 .option client_password spa string&!! unset
26611 This option specifies the user's password, and must be set.
26614 .option client_username spa string&!! unset
26615 This option specifies the user name, and must be set. Here is an example of a
26616 configuration of this authenticator for use with the mail servers at
26622 client_username = msn/msn_username
26623 client_password = msn_plaintext_password
26624 client_domain = DOMAIN_OR_UNSET
26626 .ecindex IIDspaauth1
26627 .ecindex IIDspaauth2
26633 . ////////////////////////////////////////////////////////////////////////////
26634 . ////////////////////////////////////////////////////////////////////////////
26636 .chapter "The tls authenticator" "CHAPtlsauth"
26637 .scindex IIDtlsauth1 "&(tls)& authenticator"
26638 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
26639 .cindex "authentication" "Client Certificate"
26640 .cindex "authentication" "X509"
26641 .cindex "Certificate-based authentication"
26642 The &(tls)& authenticator provides server support for
26643 authentication based on client certificates.
26645 It is not an SMTP authentication mechanism and is not
26646 advertised by the server as part of the SMTP EHLO response.
26647 It is an Exim authenticator in the sense that it affects
26648 the protocol element of the log line, can be tested for
26649 by the &%authenticated%& ACL condition, and can set
26650 the &$authenticated_id$& variable.
26652 The client must present a verifiable certificate,
26653 for which it must have been requested via the
26654 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
26655 (see &<<CHAPTLS>>&).
26657 If an authenticator of this type is configured it is
26658 run before any SMTP-level communication is done,
26659 and can authenticate the connection.
26660 If it does, SMTP authentication is not offered.
26662 A maximum of one authenticator of this type may be present.
26665 .cindex "options" "&(tls)& authenticator (server)"
26666 The &(tls)& authenticator has three server options:
26668 .option server_param1 tls string&!! unset
26669 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
26670 This option is expanded after the TLS negotiation and
26671 the result is placed in &$auth1$&.
26672 If the expansion is forced to fail, authentication fails. Any other expansion
26673 failure causes a temporary error code to be returned.
26675 .option server_param2 tls string&!! unset
26676 .option server_param3 tls string&!! unset
26677 As above, for &$auth2$& and &$auth3$&.
26679 &%server_param1%& may also be spelled &%server_param%&.
26686 server_param1 = ${certextract {subj_altname,mail,>:} \
26687 {$tls_in_peercert}}
26688 server_condition = ${if forany {$auth1} \
26690 {${lookup ldap{ldap:///\
26691 mailname=${quote_ldap_dn:${lc:$item}},\
26692 ou=users,LDAP_DC?mailid} {$value}{0} \
26694 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
26696 This accepts a client certificate that is verifiable against any
26697 of your configured trust-anchors
26698 which usually means the full set of public CAs)
26699 and which has a SAN with a good account name.
26700 Note that the client cert is on the wire in-clear, including the SAN,
26701 whereas a plaintext SMTP AUTH done inside TLS is not.
26703 . An alternative might use
26705 . server_param1 = ${sha256:$tls_in_peercert}
26707 . to require one of a set of specific certs that define a given account
26708 . (the verification is still required, but mostly irrelevant).
26709 . This would help for per-device use.
26711 . However, for the future we really need support for checking a
26712 . user cert in LDAP - which probably wants a base-64 DER.
26714 .ecindex IIDtlsauth1
26715 .ecindex IIDtlsauth2
26718 Note that because authentication is traditionally an SMTP operation,
26719 the &%authenticated%& ACL condition cannot be used in
26720 a connect- or helo-ACL.
26724 . ////////////////////////////////////////////////////////////////////////////
26725 . ////////////////////////////////////////////////////////////////////////////
26727 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
26728 "Encrypted SMTP connections"
26729 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
26730 .scindex IIDencsmtp2 "SMTP" "encryption"
26731 .cindex "TLS" "on SMTP connection"
26734 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
26735 Sockets Layer), is implemented by making use of the OpenSSL library or the
26736 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
26737 cryptographic code in the Exim distribution itself for implementing TLS. In
26738 order to use this feature you must install OpenSSL or GnuTLS, and then build a
26739 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
26740 You also need to understand the basic concepts of encryption at a managerial
26741 level, and in particular, the way that public keys, private keys, and
26742 certificates are used.
26744 RFC 3207 defines how SMTP connections can make use of encryption. Once a
26745 connection is established, the client issues a STARTTLS command. If the
26746 server accepts this, the client and the server negotiate an encryption
26747 mechanism. If the negotiation succeeds, the data that subsequently passes
26748 between them is encrypted.
26750 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
26751 and if so, what cipher suite is in use, whether the client supplied a
26752 certificate, and whether or not that certificate was verified. This makes it
26753 possible for an Exim server to deny or accept certain commands based on the
26756 &*Warning*&: Certain types of firewall and certain anti-virus products can
26757 disrupt TLS connections. You need to turn off SMTP scanning for these products
26758 in order to get TLS to work.
26762 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
26764 .cindex "ssmtp protocol"
26765 .cindex "smtps protocol"
26766 .cindex "SMTP" "ssmtp protocol"
26767 .cindex "SMTP" "smtps protocol"
26768 Early implementations of encrypted SMTP used a different TCP port from normal
26769 SMTP, and expected an encryption negotiation to start immediately, instead of
26770 waiting for a STARTTLS command from the client using the standard SMTP
26771 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
26772 allocated for this purpose.
26774 This approach was abandoned when encrypted SMTP was standardized, but there are
26775 still some legacy clients that use it. Exim supports these clients by means of
26776 the &%tls_on_connect_ports%& global option. Its value must be a list of port
26777 numbers; the most common use is expected to be:
26779 tls_on_connect_ports = 465
26781 The port numbers specified by this option apply to all SMTP connections, both
26782 via the daemon and via &'inetd'&. You still need to specify all the ports that
26783 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
26784 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
26785 an extra port &-- rather, it specifies different behaviour on a port that is
26788 There is also a &%-tls-on-connect%& command line option. This overrides
26789 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
26796 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
26797 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
26798 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
26799 followed later, when the first versions of GnuTLS were released. To build Exim
26800 to use GnuTLS, you need to set
26804 in Local/Makefile, in addition to
26808 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
26809 include files and libraries for GnuTLS can be found.
26811 There are some differences in usage when using GnuTLS instead of OpenSSL:
26814 The &%tls_verify_certificates%& option
26815 cannot be the path of a directory
26816 for GnuTLS versions before 3.3.6
26817 (for later versions, or OpenSSL, it can be either).
26819 The default value for &%tls_dhparam%& differs for historical reasons.
26821 .vindex "&$tls_in_peerdn$&"
26822 .vindex "&$tls_out_peerdn$&"
26823 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
26824 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
26825 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
26827 OpenSSL identifies cipher suites using hyphens as separators, for example:
26828 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
26829 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
26830 in a cipher list. To make life simpler, Exim changes underscores to hyphens
26831 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
26832 to handle its own older variants) when processing lists of cipher suites in the
26833 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
26836 The &%tls_require_ciphers%& options operate differently, as described in the
26837 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
26839 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
26840 When using OpenSSL, this option is ignored.
26841 (If an API is found to let OpenSSL be configured in this way,
26842 let the Exim Maintainers know and we'll likely use it).
26844 Some other recently added features may only be available in one or the other.
26845 This should be documented with the feature. If the documentation does not
26846 explicitly state that the feature is infeasible in the other TLS
26847 implementation, then patches are welcome.
26851 .section "GnuTLS parameter computation" "SECTgnutlsparam"
26852 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
26853 an explicit path; if the latter, then the text about generation still applies,
26854 but not the chosen filename.
26855 By default, as of Exim 4.80 a hard-coded D-H prime is used.
26856 See the documentation of &%tls_dhparam%& for more information.
26858 GnuTLS uses D-H parameters that may take a substantial amount of time
26859 to compute. It is unreasonable to re-compute them for every TLS session.
26860 Therefore, Exim keeps this data in a file in its spool directory, called
26861 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
26863 The file is owned by the Exim user and is readable only by
26864 its owner. Every Exim process that start up GnuTLS reads the D-H
26865 parameters from this file. If the file does not exist, the first Exim process
26866 that needs it computes the data and writes it to a temporary file which is
26867 renamed once it is complete. It does not matter if several Exim processes do
26868 this simultaneously (apart from wasting a few resources). Once a file is in
26869 place, new Exim processes immediately start using it.
26871 For maximum security, the parameters that are stored in this file should be
26872 recalculated periodically, the frequency depending on your paranoia level.
26873 If you are avoiding using the fixed D-H primes published in RFCs, then you
26874 are concerned about some advanced attacks and will wish to do this; if you do
26875 not regenerate then you might as well stick to the standard primes.
26877 Arranging this is easy in principle; just delete the file when you want new
26878 values to be computed. However, there may be a problem. The calculation of new
26879 parameters needs random numbers, and these are obtained from &_/dev/random_&.
26880 If the system is not very active, &_/dev/random_& may delay returning data
26881 until enough randomness (entropy) is available. This may cause Exim to hang for
26882 a substantial amount of time, causing timeouts on incoming connections.
26884 The solution is to generate the parameters externally to Exim. They are stored
26885 in &_gnutls-params-N_& in PEM format, which means that they can be
26886 generated externally using the &(certtool)& command that is part of GnuTLS.
26888 To replace the parameters with new ones, instead of deleting the file
26889 and letting Exim re-create it, you can generate new parameters using
26890 &(certtool)& and, when this has been done, replace Exim's cache file by
26891 renaming. The relevant commands are something like this:
26894 [ look for file; assume gnutls-params-2236 is the most recent ]
26897 # chown exim:exim new-params
26898 # chmod 0600 new-params
26899 # certtool --generate-dh-params --bits 2236 >>new-params
26900 # openssl dhparam -noout -text -in new-params | head
26901 [ check the first line, make sure it's not more than 2236;
26902 if it is, then go back to the start ("rm") and repeat
26903 until the size generated is at most the size requested ]
26904 # chmod 0400 new-params
26905 # mv new-params gnutls-params-2236
26907 If Exim never has to generate the parameters itself, the possibility of
26908 stalling is removed.
26910 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
26911 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
26912 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
26913 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
26914 and Exim does so. This attempt to remove Exim from TLS policy decisions
26915 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
26916 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
26917 which applies to all D-H usage, client or server. If the value returned by
26918 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
26919 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
26920 limit, which is still much higher than Exim historically used.
26922 The filename and bits used will change as the GnuTLS maintainers change the
26923 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
26924 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
26925 2432 bits, while NSS is limited to 2236 bits.
26927 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
26928 increase the chance of the generated prime actually being within acceptable
26929 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
26930 procedure above. There is no sane procedure available to Exim to double-check
26931 the size of the generated prime, so it might still be too large.
26934 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
26935 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
26936 .oindex "&%tls_require_ciphers%&" "OpenSSL"
26937 There is a function in the OpenSSL library that can be passed a list of cipher
26938 suites before the cipher negotiation takes place. This specifies which ciphers
26939 are acceptable. The list is colon separated and may contain names like
26940 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
26941 directly to this function call.
26942 Many systems will install the OpenSSL manual-pages, so you may have
26943 &'ciphers(1)'& available to you.
26944 The following quotation from the OpenSSL
26945 documentation specifies what forms of item are allowed in the cipher string:
26948 It can consist of a single cipher suite such as RC4-SHA.
26950 It can represent a list of cipher suites containing a certain algorithm,
26951 or cipher suites of a certain type. For example SHA1 represents all
26952 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
26955 Lists of cipher suites can be combined in a single cipher string using
26956 the + character. This is used as a logical and operation. For example
26957 SHA1+DES represents all cipher suites containing the SHA1 and the DES
26961 Each cipher string can be optionally preceded by one of the characters &`!`&,
26964 If &`!`& is used, the ciphers are permanently deleted from the list. The
26965 ciphers deleted can never reappear in the list even if they are explicitly
26968 If &`-`& is used, the ciphers are deleted from the list, but some or all
26969 of the ciphers can be added again by later options.
26971 If &`+`& is used, the ciphers are moved to the end of the list. This
26972 option does not add any new ciphers; it just moves matching existing ones.
26975 If none of these characters is present, the string is interpreted as
26976 a list of ciphers to be appended to the current preference list. If the list
26977 includes any ciphers already present they will be ignored: that is, they will
26978 not be moved to the end of the list.
26981 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
26984 # note single-quotes to get ! past any shell history expansion
26985 $ openssl ciphers 'HIGH:!MD5:!SHA1'
26988 This example will let the library defaults be permitted on the MX port, where
26989 there's probably no identity verification anyway, but ups the ante on the
26990 submission ports where the administrator might have some influence on the
26991 choice of clients used:
26993 # OpenSSL variant; see man ciphers(1)
26994 tls_require_ciphers = ${if =={$received_port}{25}\
27001 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
27003 .cindex "GnuTLS" "specifying parameters for"
27004 .cindex "TLS" "specifying ciphers (GnuTLS)"
27005 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
27006 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
27007 .cindex "TLS" "specifying protocols (GnuTLS)"
27008 .cindex "TLS" "specifying priority string (GnuTLS)"
27009 .oindex "&%tls_require_ciphers%&" "GnuTLS"
27010 The GnuTLS library allows the caller to provide a "priority string", documented
27011 as part of the &[gnutls_priority_init]& function. This is very similar to the
27012 ciphersuite specification in OpenSSL.
27014 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
27015 and controls both protocols and ciphers.
27017 The &%tls_require_ciphers%& option is available both as an global option,
27018 controlling how Exim behaves as a server, and also as an option of the
27019 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
27020 the value is string expanded. The resulting string is not an Exim list and
27021 the string is given to the GnuTLS library, so that Exim does not need to be
27022 aware of future feature enhancements of GnuTLS.
27024 Documentation of the strings accepted may be found in the GnuTLS manual, under
27025 "Priority strings". This is online as
27026 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
27027 but beware that this relates to GnuTLS 3, which may be newer than the version
27028 installed on your system. If you are using GnuTLS 3,
27029 then the example code
27030 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
27031 on that site can be used to test a given string.
27035 # Disable older versions of protocols
27036 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
27039 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
27040 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
27041 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
27043 This example will let the library defaults be permitted on the MX port, where
27044 there's probably no identity verification anyway, and lowers security further
27045 by increasing compatibility; but this ups the ante on the submission ports
27046 where the administrator might have some influence on the choice of clients
27050 tls_require_ciphers = ${if =={$received_port}{25}\
27056 .section "Configuring an Exim server to use TLS" "SECID182"
27057 .cindex "TLS" "configuring an Exim server"
27058 When Exim has been built with TLS support, it advertises the availability of
27059 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
27060 but not to any others. The default value of this option is unset, which means
27061 that STARTTLS is not advertised at all. This default is chosen because you
27062 need to set some other options in order to make TLS available, and also it is
27063 sensible for systems that want to use TLS only as a client.
27065 If a client issues a STARTTLS command and there is some configuration
27066 problem in the server, the command is rejected with a 454 error. If the client
27067 persists in trying to issue SMTP commands, all except QUIT are rejected
27070 554 Security failure
27072 If a STARTTLS command is issued within an existing TLS session, it is
27073 rejected with a 554 error code.
27075 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
27076 must be set to match some hosts. The default is * which matches all hosts.
27079 If this is all you do, TLS encryption will be enabled but not authentication -
27080 meaning that the peer has no assurance it is actually you he is talking to.
27081 You gain protection from a passive sniffer listening on the wire but not
27082 from someone able to intercept the communication.
27085 Further protection requires some further configuration at the server end.
27087 It is rumoured that all existing clients that support TLS/SSL use RSA
27088 encryption. To make this work you need to set, in the server,
27090 tls_certificate = /some/file/name
27091 tls_privatekey = /some/file/name
27093 These options are, in fact, expanded strings, so you can make them depend on
27094 the identity of the client that is connected if you wish. The first file
27095 contains the server's X509 certificate, and the second contains the private key
27096 that goes with it. These files need to be
27097 PEM format and readable by the Exim user, and must
27098 always be given as full path names.
27099 The key must not be password-protected.
27100 They can be the same file if both the
27101 certificate and the key are contained within it. If &%tls_privatekey%& is not
27102 set, or if its expansion is forced to fail or results in an empty string, this
27103 is assumed to be the case. The certificate file may also contain intermediate
27104 certificates that need to be sent to the client to enable it to authenticate
27105 the server's certificate.
27107 If you do not understand about certificates and keys, please try to find a
27108 source of this background information, which is not Exim-specific. (There are a
27109 few comments below in section &<<SECTcerandall>>&.)
27111 &*Note*&: These options do not apply when Exim is operating as a client &--
27112 they apply only in the case of a server. If you need to use a certificate in an
27113 Exim client, you must set the options of the same names in an &(smtp)&
27116 With just these options, an Exim server will be able to use TLS. It does not
27117 require the client to have a certificate (but see below for how to insist on
27118 this). There is one other option that may be needed in other situations. If
27120 tls_dhparam = /some/file/name
27122 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
27123 with the parameters contained in the file.
27124 Set this to &`none`& to disable use of DH entirely, by making no prime
27129 This may also be set to a string identifying a standard prime to be used for
27130 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
27131 used is &`ike23`&. There are a few standard primes available, see the
27132 documentation for &%tls_dhparam%& for the complete list.
27138 for a way of generating file data.
27140 The strings supplied for these three options are expanded every time a client
27141 host connects. It is therefore possible to use different certificates and keys
27142 for different hosts, if you so wish, by making use of the client's IP address
27143 in &$sender_host_address$& to control the expansion. If a string expansion is
27144 forced to fail, Exim behaves as if the option is not set.
27146 .cindex "cipher" "logging"
27147 .cindex "log" "TLS cipher"
27148 .vindex "&$tls_in_cipher$&"
27149 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
27150 an incoming TLS connection. It is included in the &'Received:'& header of an
27151 incoming message (by default &-- you can, of course, change this), and it is
27152 also included in the log line that records a message's arrival, keyed by
27153 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
27154 condition can be used to test for specific cipher suites in ACLs.
27156 Once TLS has been established, the ACLs that run for subsequent SMTP commands
27157 can check the name of the cipher suite and vary their actions accordingly. The
27158 cipher suite names vary, depending on which TLS library is being used. For
27159 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
27160 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
27161 documentation for more details.
27163 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
27164 (again depending on the &%tls_cipher%& log selector).
27167 .section "Requesting and verifying client certificates" "SECID183"
27168 .cindex "certificate" "verification of client"
27169 .cindex "TLS" "client certificate verification"
27170 If you want an Exim server to request a certificate when negotiating a TLS
27171 session with a client, you must set either &%tls_verify_hosts%& or
27172 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
27173 apply to all TLS connections. For any host that matches one of these options,
27174 Exim requests a certificate as part of the setup of the TLS session. The
27175 contents of the certificate are verified by comparing it with a list of
27176 expected certificates.
27177 These may be the system default set (depending on library version),
27178 an explicit file or,
27179 depending on library version, a directory, identified by
27180 &%tls_verify_certificates%&.
27182 A file can contain multiple certificates, concatenated end to end. If a
27185 each certificate must be in a separate file, with a name (or a symbolic link)
27186 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
27187 certificate. You can compute the relevant hash by running the command
27189 openssl x509 -hash -noout -in /cert/file
27191 where &_/cert/file_& contains a single certificate.
27193 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
27194 what happens if the client does not supply a certificate, or if the certificate
27195 does not match any of the certificates in the collection named by
27196 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
27197 attempt to set up a TLS session is aborted, and the incoming connection is
27198 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
27199 session continues. ACLs that run for subsequent SMTP commands can detect the
27200 fact that no certificate was verified, and vary their actions accordingly. For
27201 example, you can insist on a certificate before accepting a message for
27202 relaying, but not when the message is destined for local delivery.
27204 .vindex "&$tls_in_peerdn$&"
27205 When a client supplies a certificate (whether it verifies or not), the value of
27206 the Distinguished Name of the certificate is made available in the variable
27207 &$tls_in_peerdn$& during subsequent processing of the message.
27209 .cindex "log" "distinguished name"
27210 Because it is often a long text string, it is not included in the log line or
27211 &'Received:'& header by default. You can arrange for it to be logged, keyed by
27212 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
27213 &%received_header_text%& to change the &'Received:'& header. When no
27214 certificate is supplied, &$tls_in_peerdn$& is empty.
27217 .section "Revoked certificates" "SECID184"
27218 .cindex "TLS" "revoked certificates"
27219 .cindex "revocation list"
27220 .cindex "certificate" "revocation list"
27221 .cindex "OCSP" "stapling"
27222 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
27223 certificates are revoked. If you have such a list, you can pass it to an Exim
27224 server using the global option called &%tls_crl%& and to an Exim client using
27225 an identically named option for the &(smtp)& transport. In each case, the value
27226 of the option is expanded and must then be the name of a file that contains a
27228 The downside is that clients have to periodically re-download a potentially huge
27229 file from every certificate authority they know of.
27231 The way with most moving parts at query time is Online Certificate
27232 Status Protocol (OCSP), where the client verifies the certificate
27233 against an OCSP server run by the CA. This lets the CA track all
27234 usage of the certs. It requires running software with access to the
27235 private key of the CA, to sign the responses to the OCSP queries. OCSP
27236 is based on HTTP and can be proxied accordingly.
27238 The only widespread OCSP server implementation (known to this writer)
27239 comes as part of OpenSSL and aborts on an invalid request, such as
27240 connecting to the port and then disconnecting. This requires
27241 re-entering the passphrase each time some random client does this.
27243 The third way is OCSP Stapling; in this, the server using a certificate
27244 issued by the CA periodically requests an OCSP proof of validity from
27245 the OCSP server, then serves it up inline as part of the TLS
27246 negotiation. This approach adds no extra round trips, does not let the
27247 CA track users, scales well with number of certs issued by the CA and is
27248 resilient to temporary OCSP server failures, as long as the server
27249 starts retrying to fetch an OCSP proof some time before its current
27250 proof expires. The downside is that it requires server support.
27252 Unless Exim is built with the support disabled,
27253 or with GnuTLS earlier than version 3.3.16 / 3.4.8
27254 support for OCSP stapling is included.
27256 There is a global option called &%tls_ocsp_file%&.
27257 The file specified therein is expected to be in DER format, and contain
27258 an OCSP proof. Exim will serve it as part of the TLS handshake. This
27259 option will be re-expanded for SNI, if the &%tls_certificate%& option
27260 contains &`tls_in_sni`&, as per other TLS options.
27262 Exim does not at this time implement any support for fetching a new OCSP
27263 proof. The burden is on the administrator to handle this, outside of
27264 Exim. The file specified should be replaced atomically, so that the
27265 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
27266 on each connection, so a new file will be handled transparently on the
27269 When built with OpenSSL Exim will check for a valid next update timestamp
27270 in the OCSP proof; if not present, or if the proof has expired, it will be
27273 For the client to be able to verify the stapled OCSP the server must
27274 also supply, in its stapled information, any intermediate
27275 certificates for the chain leading to the OCSP proof from the signer
27276 of the server certificate. There may be zero or one such. These
27277 intermediate certificates should be added to the server OCSP stapling
27278 file named by &%tls_ocsp_file%&.
27280 Note that the proof only covers the terminal server certificate,
27281 not any of the chain from CA to it.
27283 There is no current way to staple a proof for a client certificate.
27286 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
27287 OCSP server is supplied. The server URL may be included in the
27288 server certificate, if the CA is helpful.
27290 One failure mode seen was the OCSP Signer cert expiring before the end
27291 of validity of the OCSP proof. The checking done by Exim/OpenSSL
27292 noted this as invalid overall, but the re-fetch script did not.
27298 .section "Configuring an Exim client to use TLS" "SECID185"
27299 .cindex "cipher" "logging"
27300 .cindex "log" "TLS cipher"
27301 .cindex "log" "distinguished name"
27302 .cindex "TLS" "configuring an Exim client"
27303 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
27304 deliveries as well as to incoming, the latter one causing logging of the
27305 server certificate's DN. The remaining client configuration for TLS is all
27306 within the &(smtp)& transport.
27308 It is not necessary to set any options to have TLS work in the &(smtp)&
27309 transport. If Exim is built with TLS support, and TLS is advertised by a
27310 server, the &(smtp)& transport always tries to start a TLS session. However,
27311 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
27312 transport) to a list of server hosts for which TLS should not be used.
27314 If you do not want Exim to attempt to send messages unencrypted when an attempt
27315 to set up an encrypted connection fails in any way, you can set
27316 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
27317 those hosts, delivery is always deferred if an encrypted connection cannot be
27318 set up. If there are any other hosts for the address, they are tried in the
27321 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
27322 the message unencrypted. It always does this if the response to STARTTLS is
27323 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
27324 session after a success response code, what happens is controlled by the
27325 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
27326 delivery to this host is deferred, and other hosts (if available) are tried. If
27327 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
27328 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
27329 negotiation fails, Exim closes the current connection (because it is in an
27330 unknown state), opens a new one to the same host, and then tries the delivery
27333 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
27334 transport provide the client with a certificate, which is passed to the server
27335 if it requests it. If the server is Exim, it will request a certificate only if
27336 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
27338 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
27339 specifies a collection of expected server certificates.
27340 These may be the system default set (depending on library version),
27342 depending on library version, a directory,
27343 must name a file or,
27344 for OpenSSL only (not GnuTLS), a directory.
27345 The client verifies the server's certificate
27346 against this collection, taking into account any revoked certificates that are
27347 in the list defined by &%tls_crl%&.
27348 Failure to verify fails the TLS connection unless either of the
27349 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
27351 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
27352 certificate verification to the listed servers. Verification either must
27353 or need not succeed respectively.
27355 The &(smtp)& transport has two OCSP-related options:
27356 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
27357 is requested and required for the connection to proceed. The default
27359 &%hosts_request_ocsp%&; a host-list for which (additionally)
27360 a Certificate Status is requested (but not necessarily verified). The default
27361 value is "*" meaning that requests are made unless configured
27364 The host(s) should also be in &%hosts_require_tls%&, and
27365 &%tls_verify_certificates%& configured for the transport,
27366 for OCSP to be relevant.
27369 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
27370 list of permitted cipher suites. If either of these checks fails, delivery to
27371 the current host is abandoned, and the &(smtp)& transport tries to deliver to
27372 alternative hosts, if any.
27375 These options must be set in the &(smtp)& transport for Exim to use TLS when it
27376 is operating as a client. Exim does not assume that a server certificate (set
27377 by the global options of the same name) should also be used when operating as a
27381 .vindex "&$host_address$&"
27382 All the TLS options in the &(smtp)& transport are expanded before use, with
27383 &$host$& and &$host_address$& containing the name and address of the server to
27384 which the client is connected. Forced failure of an expansion causes Exim to
27385 behave as if the relevant option were unset.
27387 .vindex &$tls_out_bits$&
27388 .vindex &$tls_out_cipher$&
27389 .vindex &$tls_out_peerdn$&
27390 .vindex &$tls_out_sni$&
27391 Before an SMTP connection is established, the
27392 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
27393 variables are emptied. (Until the first connection, they contain the values
27394 that were set when the message was received.) If STARTTLS is subsequently
27395 successfully obeyed, these variables are set to the relevant values for the
27396 outgoing connection.
27400 .section "Use of TLS Server Name Indication" "SECTtlssni"
27401 .cindex "TLS" "Server Name Indication"
27402 .vindex "&$tls_in_sni$&"
27403 .oindex "&%tls_in_sni%&"
27404 With TLS1.0 or above, there is an extension mechanism by which extra
27405 information can be included at various points in the protocol. One of these
27406 extensions, documented in RFC 6066 (and before that RFC 4366) is
27407 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
27408 client in the initial handshake, so that the server can examine the servername
27409 within and possibly choose to use different certificates and keys (and more)
27412 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
27413 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
27416 With SMTP to MX, there are the same problems here as in choosing the identity
27417 against which to validate a certificate: you can't rely on insecure DNS to
27418 provide the identity which you then cryptographically verify. So this will
27419 be of limited use in that environment.
27421 With SMTP to Submission, there is a well-defined hostname which clients are
27422 connecting to and can validate certificates against. Thus clients &*can*&
27423 choose to include this information in the TLS negotiation. If this becomes
27424 wide-spread, then hosters can choose to present different certificates to
27425 different clients. Or even negotiate different cipher suites.
27427 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
27428 if not empty, will be sent on a TLS session as part of the handshake. There's
27429 nothing more to it. Choosing a sensible value not derived insecurely is the
27430 only point of caution. The &$tls_out_sni$& variable will be set to this string
27431 for the lifetime of the client connection (including during authentication).
27433 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
27434 received from a client.
27435 It can be logged with the &%log_selector%& item &`+tls_sni`&.
27437 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
27438 option (prior to expansion) then the following options will be re-expanded
27439 during TLS session handshake, to permit alternative values to be chosen:
27442 .vindex "&%tls_certificate%&"
27443 &%tls_certificate%&
27445 .vindex "&%tls_crl%&"
27448 .vindex "&%tls_privatekey%&"
27451 .vindex "&%tls_verify_certificates%&"
27452 &%tls_verify_certificates%&
27454 .vindex "&%tls_ocsp_file%&"
27458 Great care should be taken to deal with matters of case, various injection
27459 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
27460 can always be referenced; it is important to remember that &$tls_sni$& is
27461 arbitrary unverified data provided prior to authentication.
27463 The Exim developers are proceeding cautiously and so far no other TLS options
27466 When Exim is built against OpenSSL, OpenSSL must have been built with support
27467 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
27468 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
27469 see &`-servername`& in the output, then OpenSSL has support.
27471 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
27472 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
27473 built, then you have SNI support).
27477 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
27479 .cindex "multiple SMTP deliveries with TLS"
27480 .cindex "TLS" "multiple message deliveries"
27481 Exim sends multiple messages down the same TCP/IP connection by starting up
27482 an entirely new delivery process for each message, passing the socket from
27483 one process to the next. This implementation does not fit well with the use
27484 of TLS, because there is quite a lot of state information associated with a TLS
27485 connection, not just a socket identification. Passing all the state information
27486 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
27487 session before passing the socket to a new process. The new process may then
27488 try to start a new TLS session, and if successful, may try to re-authenticate
27489 if AUTH is in use, before sending the next message.
27491 The RFC is not clear as to whether or not an SMTP session continues in clear
27492 after TLS has been shut down, or whether TLS may be restarted again later, as
27493 just described. However, if the server is Exim, this shutdown and
27494 reinitialization works. It is not known which (if any) other servers operate
27495 successfully if the client closes a TLS session and continues with unencrypted
27496 SMTP, but there are certainly some that do not work. For such servers, Exim
27497 should not pass the socket to another process, because the failure of the
27498 subsequent attempt to use it would cause Exim to record a temporary host error,
27499 and delay other deliveries to that host.
27501 To test for this case, Exim sends an EHLO command to the server after
27502 closing down the TLS session. If this fails in any way, the connection is
27503 closed instead of being passed to a new delivery process, but no retry
27504 information is recorded.
27506 There is also a manual override; you can set &%hosts_nopass_tls%& on the
27507 &(smtp)& transport to match those hosts for which Exim should not pass
27508 connections to new processes if TLS has been used.
27513 .section "Certificates and all that" "SECTcerandall"
27514 .cindex "certificate" "references to discussion"
27515 In order to understand fully how TLS works, you need to know about
27516 certificates, certificate signing, and certificate authorities. This is not the
27517 place to give a tutorial, especially as I do not know very much about it
27518 myself. Some helpful introduction can be found in the FAQ for the SSL addition
27519 to Apache, currently at
27521 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
27523 Other parts of the &'modssl'& documentation are also helpful, and have
27524 links to further files.
27525 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
27526 0-201-61598-3), contains both introductory and more in-depth descriptions.
27527 Some sample programs taken from the book are available from
27529 &url(http://www.rtfm.com/openssl-examples/)
27533 .section "Certificate chains" "SECID186"
27534 The file named by &%tls_certificate%& may contain more than one
27535 certificate. This is useful in the case where the certificate that is being
27536 sent is validated by an intermediate certificate which the other end does
27537 not have. Multiple certificates must be in the correct order in the file.
27538 First the host's certificate itself, then the first intermediate
27539 certificate to validate the issuer of the host certificate, then the next
27540 intermediate certificate to validate the issuer of the first intermediate
27541 certificate, and so on, until finally (optionally) the root certificate.
27542 The root certificate must already be trusted by the recipient for
27543 validation to succeed, of course, but if it's not preinstalled, sending the
27544 root certificate along with the rest makes it available for the user to
27545 install if the receiving end is a client MUA that can interact with a user.
27547 Note that certificates using MD5 are unlikely to work on today's Internet;
27548 even if your libraries allow loading them for use in Exim when acting as a
27549 server, increasingly clients will not accept such certificates. The error
27550 diagnostics in such a case can be frustratingly vague.
27554 .section "Self-signed certificates" "SECID187"
27555 .cindex "certificate" "self-signed"
27556 You can create a self-signed certificate using the &'req'& command provided
27557 with OpenSSL, like this:
27558 . ==== Do not shorten the duration here without reading and considering
27559 . ==== the text below. Please leave it at 9999 days.
27561 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
27564 &_file1_& and &_file2_& can be the same file; the key and the certificate are
27565 delimited and so can be identified independently. The &%-days%& option
27566 specifies a period for which the certificate is valid. The &%-nodes%& option is
27567 important: if you do not set it, the key is encrypted with a passphrase
27568 that you are prompted for, and any use that is made of the key causes more
27569 prompting for the passphrase. This is not helpful if you are going to use
27570 this certificate and key in an MTA, where prompting is not possible.
27572 . ==== I expect to still be working 26 years from now. The less technical
27573 . ==== debt I create, in terms of storing up trouble for my later years, the
27574 . ==== happier I will be then. We really have reached the point where we
27575 . ==== should start, at the very least, provoking thought and making folks
27576 . ==== pause before proceeding, instead of leaving all the fixes until two
27577 . ==== years before 2^31 seconds after the 1970 Unix epoch.
27579 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
27580 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
27581 the above command might produce a date in the past. Think carefully about
27582 the lifetime of the systems you're deploying, and either reduce the duration
27583 of the certificate or reconsider your platform deployment. (At time of
27584 writing, reducing the duration is the most likely choice, but the inexorable
27585 progression of time takes us steadily towards an era where this will not
27586 be a sensible resolution).
27588 A self-signed certificate made in this way is sufficient for testing, and
27589 may be adequate for all your requirements if you are mainly interested in
27590 encrypting transfers, and not in secure identification.
27592 However, many clients require that the certificate presented by the server be a
27593 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
27594 certificate. In this situation, the self-signed certificate described above
27595 must be installed on the client host as a trusted root &'certification
27596 authority'& (CA), and the certificate used by Exim must be a user certificate
27597 signed with that self-signed certificate.
27599 For information on creating self-signed CA certificates and using them to sign
27600 user certificates, see the &'General implementation overview'& chapter of the
27601 Open-source PKI book, available online at
27602 &url(http://ospkibook.sourceforge.net/).
27603 .ecindex IIDencsmtp1
27604 .ecindex IIDencsmtp2
27608 . ////////////////////////////////////////////////////////////////////////////
27609 . ////////////////////////////////////////////////////////////////////////////
27611 .chapter "Access control lists" "CHAPACL"
27612 .scindex IIDacl "&ACL;" "description"
27613 .cindex "control of incoming mail"
27614 .cindex "message" "controlling incoming"
27615 .cindex "policy control" "access control lists"
27616 Access Control Lists (ACLs) are defined in a separate section of the run time
27617 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
27618 name, terminated by a colon. Here is a complete ACL section that contains just
27619 one very small ACL:
27623 accept hosts = one.host.only
27625 You can have as many lists as you like in the ACL section, and the order in
27626 which they appear does not matter. The lists are self-terminating.
27628 The majority of ACLs are used to control Exim's behaviour when it receives
27629 certain SMTP commands. This applies both to incoming TCP/IP connections, and
27630 when a local process submits a message using SMTP by specifying the &%-bs%&
27631 option. The most common use is for controlling which recipients are accepted
27632 in incoming messages. In addition, you can define an ACL that is used to check
27633 local non-SMTP messages. The default configuration file contains an example of
27634 a realistic ACL for checking RCPT commands. This is discussed in chapter
27635 &<<CHAPdefconfil>>&.
27638 .section "Testing ACLs" "SECID188"
27639 The &%-bh%& command line option provides a way of testing your ACL
27640 configuration locally by running a fake SMTP session with which you interact.
27643 .section "Specifying when ACLs are used" "SECID189"
27644 .cindex "&ACL;" "options for specifying"
27645 In order to cause an ACL to be used, you have to name it in one of the relevant
27646 options in the main part of the configuration. These options are:
27647 .cindex "AUTH" "ACL for"
27648 .cindex "DATA" "ACLs for"
27649 .cindex "ETRN" "ACL for"
27650 .cindex "EXPN" "ACL for"
27651 .cindex "HELO" "ACL for"
27652 .cindex "EHLO" "ACL for"
27653 .cindex "DKIM" "ACL for"
27654 .cindex "MAIL" "ACL for"
27655 .cindex "QUIT, ACL for"
27656 .cindex "RCPT" "ACL for"
27657 .cindex "STARTTLS, ACL for"
27658 .cindex "VRFY" "ACL for"
27659 .cindex "SMTP" "connection, ACL for"
27660 .cindex "non-SMTP messages" "ACLs for"
27661 .cindex "MIME content scanning" "ACL for"
27662 .cindex "PRDR" "ACL for"
27665 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
27666 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
27667 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
27668 .irow &%acl_smtp_auth%& "ACL for AUTH"
27669 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
27670 .irow &%acl_smtp_data%& "ACL after DATA is complete"
27671 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
27672 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
27673 .irow &%acl_smtp_etrn%& "ACL for ETRN"
27674 .irow &%acl_smtp_expn%& "ACL for EXPN"
27675 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
27676 .irow &%acl_smtp_mail%& "ACL for MAIL"
27677 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
27678 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
27679 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
27680 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
27681 .irow &%acl_smtp_quit%& "ACL for QUIT"
27682 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
27683 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
27684 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
27687 For example, if you set
27689 acl_smtp_rcpt = small_acl
27691 the little ACL defined above is used whenever Exim receives a RCPT command
27692 in an SMTP dialogue. The majority of policy tests on incoming messages can be
27693 done when RCPT commands arrive. A rejection of RCPT should cause the
27694 sending MTA to give up on the recipient address contained in the RCPT
27695 command, whereas rejection at other times may cause the client MTA to keep on
27696 trying to deliver the message. It is therefore recommended that you do as much
27697 testing as possible at RCPT time.
27700 .section "The non-SMTP ACLs" "SECID190"
27701 .cindex "non-SMTP messages" "ACLs for"
27702 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
27703 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
27704 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
27705 the state of the SMTP connection such as encryption and authentication) are not
27706 relevant and are forbidden in these ACLs. However, the sender and recipients
27707 are known, so the &%senders%& and &%sender_domains%& conditions and the
27708 &$sender_address$& and &$recipients$& variables can be used. Variables such as
27709 &$authenticated_sender$& are also available. You can specify added header lines
27710 in any of these ACLs.
27712 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
27713 non-SMTP message, before any of the message has been read. (This is the
27714 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
27715 batched SMTP input, it runs after the DATA command has been reached. The
27716 result of this ACL is ignored; it cannot be used to reject a message. If you
27717 really need to, you could set a value in an ACL variable here and reject based
27718 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
27719 controls, and in particular, it can be used to set
27721 control = suppress_local_fixups
27723 This cannot be used in the other non-SMTP ACLs because by the time they are
27724 run, it is too late.
27726 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
27727 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27729 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
27730 kind of rejection is treated as permanent, because there is no way of sending a
27731 temporary error for these kinds of message.
27734 .section "The SMTP connect ACL" "SECID191"
27735 .cindex "SMTP" "connection, ACL for"
27736 .oindex &%smtp_banner%&
27737 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
27738 session, after the test specified by &%host_reject_connection%& (which is now
27739 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
27740 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
27741 the message override the banner message that is otherwise specified by the
27742 &%smtp_banner%& option.
27745 .section "The EHLO/HELO ACL" "SECID192"
27746 .cindex "EHLO" "ACL for"
27747 .cindex "HELO" "ACL for"
27748 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
27749 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
27750 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
27751 Note that a client may issue more than one EHLO or HELO command in an SMTP
27752 session, and indeed is required to issue a new EHLO or HELO after successfully
27753 setting up encryption following a STARTTLS command.
27755 Note also that a deny neither forces the client to go away nor means that
27756 mail will be refused on the connection. Consider checking for
27757 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
27759 If the command is accepted by an &%accept%& verb that has a &%message%&
27760 modifier, the message may not contain more than one line (it will be truncated
27761 at the first newline and a panic logged if it does). Such a message cannot
27762 affect the EHLO options that are listed on the second and subsequent lines of
27766 .section "The DATA ACLs" "SECID193"
27767 .cindex "DATA" "ACLs for"
27768 Two ACLs are associated with the DATA command, because it is two-stage
27769 command, with two responses being sent to the client.
27770 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
27771 is obeyed. This gives you control after all the RCPT commands, but before
27772 the message itself is received. It offers the opportunity to give a negative
27773 response to the DATA command before the data is transmitted. Header lines
27774 added by MAIL or RCPT ACLs are not visible at this time, but any that
27775 are defined here are visible when the &%acl_smtp_data%& ACL is run.
27777 You cannot test the contents of the message, for example, to verify addresses
27778 in the headers, at RCPT time or when the DATA command is received. Such
27779 tests have to appear in the ACL that is run after the message itself has been
27780 received, before the final response to the DATA command is sent. This is
27781 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
27782 associated with the DATA command.
27785 .cindex CHUNKING "BDAT command"
27786 .cindex BDAT "SMTP command"
27787 .cindex "RFC 3030" CHUNKING
27788 If CHUNKING was advertised and a BDAT command sequence is received,
27789 the &%acl_smtp_predata%& ACL is not run.
27790 . XXX why not? It should be possible, for the first BDAT.
27791 The &%acl_smtp_data%& is run after the last BDAT command and all of
27792 the data specified is received.
27795 For both of these ACLs, it is not possible to reject individual recipients. An
27796 error response rejects the entire message. Unfortunately, it is known that some
27797 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
27798 before or after the data) correctly &-- they keep the message on their queues
27799 and try again later, but that is their problem, though it does waste some of
27802 The &%acl_smtp_data%& ACL is run after
27803 the &%acl_smtp_data_prdr%&,
27804 the &%acl_smtp_dkim%&
27805 and the &%acl_smtp_mime%& ACLs.
27807 .section "The SMTP DKIM ACL" "SECTDKIMACL"
27808 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
27809 enabled (which is the default).
27811 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
27812 received, and is executed for each DKIM signature found in a message. If not
27813 otherwise specified, the default action is to accept.
27815 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
27817 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
27820 .section "The SMTP MIME ACL" "SECID194"
27821 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
27822 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27824 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27827 .section "The SMTP PRDR ACL" "SECTPRDRACL"
27828 .cindex "PRDR" "ACL for"
27829 .oindex "&%prdr_enable%&"
27830 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
27831 with PRDR support enabled (which is the default).
27832 It becomes active only when the PRDR feature is negotiated between
27833 client and server for a message, and more than one recipient
27836 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
27837 has been received, and is executed once for each recipient of the message
27838 with &$local_part$& and &$domain$& valid.
27839 The test may accept, defer or deny for individual recipients.
27840 The &%acl_smtp_data%& will still be called after this ACL and
27841 can reject the message overall, even if this ACL has accepted it
27842 for some or all recipients.
27844 PRDR may be used to support per-user content filtering. Without it
27845 one must defer any recipient after the first that has a different
27846 content-filter configuration. With PRDR, the RCPT-time check
27847 .cindex "PRDR" "variable for"
27848 for this can be disabled when the variable &$prdr_requested$&
27850 Any required difference in behaviour of the main DATA-time
27851 ACL should however depend on the PRDR-time ACL having run, as Exim
27852 will avoid doing so in some situations (e.g. single-recipient mails).
27854 See also the &%prdr_enable%& global option
27855 and the &%hosts_try_prdr%& smtp transport option.
27857 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27858 If the ACL is not defined, processing completes as if
27859 the feature was not requested by the client.
27861 .section "The QUIT ACL" "SECTQUITACL"
27862 .cindex "QUIT, ACL for"
27863 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
27864 does not affect the response code to QUIT, which is always 221. Thus, the ACL
27865 does not in fact control any access.
27866 For this reason, it may only accept
27867 or warn as its final result.
27869 This ACL can be used for tasks such as custom logging at the end of an SMTP
27870 session. For example, you can use ACL variables in other ACLs to count
27871 messages, recipients, etc., and log the totals at QUIT time using one or
27872 more &%logwrite%& modifiers on a &%warn%& verb.
27874 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
27875 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
27877 You do not need to have a final &%accept%&, but if you do, you can use a
27878 &%message%& modifier to specify custom text that is sent as part of the 221
27881 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
27882 failure (for example, failure to open a log file, or when Exim is bombing out
27883 because it has detected an unrecoverable error), all SMTP commands from the
27884 client are given temporary error responses until QUIT is received or the
27885 connection is closed. In these special cases, the QUIT ACL does not run.
27888 .section "The not-QUIT ACL" "SECTNOTQUITACL"
27889 .vindex &$acl_smtp_notquit$&
27890 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
27891 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
27892 trouble, such as being unable to write to its log files, this ACL is not run,
27893 because it might try to do things (such as write to log files) that make the
27894 situation even worse.
27896 Like the QUIT ACL, this ACL is provided to make it possible to do customized
27897 logging or to gather statistics, and its outcome is ignored. The &%delay%&
27898 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
27901 .vindex &$smtp_notquit_reason$&
27902 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
27903 to a string that indicates the reason for the termination of the SMTP
27904 connection. The possible values are:
27906 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
27907 .irow &`bad-commands`& "Too many unknown or non-mail commands"
27908 .irow &`command-timeout`& "Timeout while reading SMTP commands"
27909 .irow &`connection-lost`& "The SMTP connection has been lost"
27910 .irow &`data-timeout`& "Timeout while reading message data"
27911 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
27912 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
27913 .irow &`signal-exit`& "SIGTERM or SIGINT"
27914 .irow &`synchronization-error`& "SMTP synchronization error"
27915 .irow &`tls-failed`& "TLS failed to start"
27917 In most cases when an SMTP connection is closed without having received QUIT,
27918 Exim sends an SMTP response message before actually closing the connection.
27919 With the exception of the &`acl-drop`& case, the default message can be
27920 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
27921 &%drop%& verb in another ACL, it is the message from the other ACL that is
27925 .section "Finding an ACL to use" "SECID195"
27926 .cindex "&ACL;" "finding which to use"
27927 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
27928 you can use different ACLs in different circumstances. For example,
27930 acl_smtp_rcpt = ${if ={25}{$interface_port} \
27931 {acl_check_rcpt} {acl_check_rcpt_submit} }
27933 In the default configuration file there are some example settings for
27934 providing an RFC 4409 message submission service on port 587 and a
27935 non-standard &"smtps"& service on port 465. You can use a string
27936 expansion like this to choose an ACL for MUAs on these ports which is
27937 more appropriate for this purpose than the default ACL on port 25.
27939 The expanded string does not have to be the name of an ACL in the
27940 configuration file; there are other possibilities. Having expanded the
27941 string, Exim searches for an ACL as follows:
27944 If the string begins with a slash, Exim uses it as a file name, and reads its
27945 contents as an ACL. The lines are processed in the same way as lines in the
27946 Exim configuration file. In particular, continuation lines are supported, blank
27947 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
27948 If the file does not exist or cannot be read, an error occurs (typically
27949 causing a temporary failure of whatever caused the ACL to be run). For example:
27951 acl_smtp_data = /etc/acls/\
27952 ${lookup{$sender_host_address}lsearch\
27953 {/etc/acllist}{$value}{default}}
27955 This looks up an ACL file to use on the basis of the host's IP address, falling
27956 back to a default if the lookup fails. If an ACL is successfully read from a
27957 file, it is retained in memory for the duration of the Exim process, so that it
27958 can be re-used without having to re-read the file.
27960 If the string does not start with a slash, and does not contain any spaces,
27961 Exim searches the ACL section of the configuration for an ACL whose name
27962 matches the string.
27964 If no named ACL is found, or if the string contains spaces, Exim parses
27965 the string as an inline ACL. This can save typing in cases where you just
27966 want to have something like
27968 acl_smtp_vrfy = accept
27970 in order to allow free use of the VRFY command. Such a string may contain
27971 newlines; it is processed in the same way as an ACL that is read from a file.
27977 .section "ACL return codes" "SECID196"
27978 .cindex "&ACL;" "return codes"
27979 Except for the QUIT ACL, which does not affect the SMTP return code (see
27980 section &<<SECTQUITACL>>& above), the result of running an ACL is either
27981 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
27982 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
27983 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
27984 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
27985 This also causes a 4&'xx'& return code.
27987 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
27988 &"deny"&, because there is no mechanism for passing temporary errors to the
27989 submitters of non-SMTP messages.
27992 ACLs that are relevant to message reception may also return &"discard"&. This
27993 has the effect of &"accept"&, but causes either the entire message or an
27994 individual recipient address to be discarded. In other words, it is a
27995 blackholing facility. Use it with care.
27997 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
27998 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
27999 RCPT ACL is to discard just the one recipient address. If there are no
28000 recipients left when the message's data is received, the DATA ACL is not
28001 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
28002 remaining recipients. The &"discard"& return is not permitted for the
28003 &%acl_smtp_predata%& ACL.
28006 .cindex "&[local_scan()]& function" "when all recipients discarded"
28007 The &[local_scan()]& function is always run, even if there are no remaining
28008 recipients; it may create new recipients.
28012 .section "Unset ACL options" "SECID197"
28013 .cindex "&ACL;" "unset options"
28014 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
28015 all the same. &*Note*&: These defaults apply only when the relevant ACL is
28016 not defined at all. For any defined ACL, the default action when control
28017 reaches the end of the ACL statements is &"deny"&.
28019 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
28020 these two are ACLs that are used only for their side effects. They cannot be
28021 used to accept or reject anything.
28023 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
28024 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
28025 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
28026 when the ACL is not defined is &"accept"&.
28028 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
28029 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
28030 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
28031 messages over an SMTP connection. For an example, see the ACL in the default
28032 configuration file.
28037 .section "Data for message ACLs" "SECID198"
28038 .cindex "&ACL;" "data for message ACL"
28040 .vindex &$local_part$&
28041 .vindex &$sender_address$&
28042 .vindex &$sender_host_address$&
28043 .vindex &$smtp_command$&
28044 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
28045 that contain information about the host and the message's sender (for example,
28046 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
28047 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
28048 &$local_part$& are set from the argument address. The entire SMTP command
28049 is available in &$smtp_command$&.
28051 When an ACL for the AUTH parameter of MAIL is running, the variables that
28052 contain information about the host are set, but &$sender_address$& is not yet
28053 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
28056 .vindex "&$message_size$&"
28057 The &$message_size$& variable is set to the value of the SIZE parameter on
28058 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
28059 that parameter is not given. The value is updated to the true message size by
28060 the time the final DATA ACL is run (after the message data has been
28063 .vindex "&$rcpt_count$&"
28064 .vindex "&$recipients_count$&"
28065 The &$rcpt_count$& variable increases by one for each RCPT command received.
28066 The &$recipients_count$& variable increases by one each time a RCPT command is
28067 accepted, so while an ACL for RCPT is being processed, it contains the number
28068 of previously accepted recipients. At DATA time (for both the DATA ACLs),
28069 &$rcpt_count$& contains the total number of RCPT commands, and
28070 &$recipients_count$& contains the total number of accepted recipients.
28076 .section "Data for non-message ACLs" "SECTdatfornon"
28077 .cindex "&ACL;" "data for non-message ACL"
28078 .vindex &$smtp_command_argument$&
28079 .vindex &$smtp_command$&
28080 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
28081 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
28082 and the entire SMTP command is available in &$smtp_command$&.
28083 These variables can be tested using a &%condition%& condition. For example,
28084 here is an ACL for use with AUTH, which insists that either the session is
28085 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
28086 does not permit authentication methods that use cleartext passwords on
28087 unencrypted connections.
28090 accept encrypted = *
28091 accept condition = ${if eq{${uc:$smtp_command_argument}}\
28093 deny message = TLS encryption or CRAM-MD5 required
28095 (Another way of applying this restriction is to arrange for the authenticators
28096 that use cleartext passwords not to be advertised when the connection is not
28097 encrypted. You can use the generic &%server_advertise_condition%& authenticator
28098 option to do this.)
28102 .section "Format of an ACL" "SECID199"
28103 .cindex "&ACL;" "format of"
28104 .cindex "&ACL;" "verbs, definition of"
28105 An individual ACL consists of a number of statements. Each statement starts
28106 with a verb, optionally followed by a number of conditions and &"modifiers"&.
28107 Modifiers can change the way the verb operates, define error and log messages,
28108 set variables, insert delays, and vary the processing of accepted messages.
28110 If all the conditions are met, the verb is obeyed. The same condition may be
28111 used (with different arguments) more than once in the same statement. This
28112 provides a means of specifying an &"and"& conjunction between conditions. For
28115 deny dnslists = list1.example
28116 dnslists = list2.example
28118 If there are no conditions, the verb is always obeyed. Exim stops evaluating
28119 the conditions and modifiers when it reaches a condition that fails. What
28120 happens then depends on the verb (and in one case, on a special modifier). Not
28121 all the conditions make sense at every testing point. For example, you cannot
28122 test a sender address in the ACL that is run for a VRFY command.
28125 .section "ACL verbs" "SECID200"
28126 The ACL verbs are as follows:
28129 .cindex "&%accept%& ACL verb"
28130 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
28131 of the conditions are not met, what happens depends on whether &%endpass%&
28132 appears among the conditions (for syntax see below). If the failing condition
28133 is before &%endpass%&, control is passed to the next ACL statement; if it is
28134 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
28135 check a RCPT command:
28137 accept domains = +local_domains
28141 If the recipient domain does not match the &%domains%& condition, control
28142 passes to the next statement. If it does match, the recipient is verified, and
28143 the command is accepted if verification succeeds. However, if verification
28144 fails, the ACL yields &"deny"&, because the failing condition is after
28147 The &%endpass%& feature has turned out to be confusing to many people, so its
28148 use is not recommended nowadays. It is always possible to rewrite an ACL so
28149 that &%endpass%& is not needed, and it is no longer used in the default
28152 .cindex "&%message%& ACL modifier" "with &%accept%&"
28153 If a &%message%& modifier appears on an &%accept%& statement, its action
28154 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
28155 (when an &%accept%& verb either accepts or passes control to the next
28156 statement), &%message%& can be used to vary the message that is sent when an
28157 SMTP command is accepted. For example, in a RCPT ACL you could have:
28159 &`accept `&<&'some conditions'&>
28160 &` message = OK, I will allow you through today`&
28162 You can specify an SMTP response code, optionally followed by an &"extended
28163 response code"& at the start of the message, but the first digit must be the
28164 same as would be sent by default, which is 2 for an &%accept%& verb.
28166 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
28167 an error message that is used when access is denied. This behaviour is retained
28168 for backward compatibility, but current &"best practice"& is to avoid the use
28173 .cindex "&%defer%& ACL verb"
28174 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
28175 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
28176 &%defer%& is the same as &%deny%&, because there is no way of sending a
28177 temporary error. For a RCPT command, &%defer%& is much the same as using a
28178 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
28179 be used in any ACL, and even for a recipient it might be a simpler approach.
28183 .cindex "&%deny%& ACL verb"
28184 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
28185 the conditions are not met, control is passed to the next ACL statement. For
28188 deny dnslists = blackholes.mail-abuse.org
28190 rejects commands from hosts that are on a DNS black list.
28194 .cindex "&%discard%& ACL verb"
28195 &%discard%&: This verb behaves like &%accept%&, except that it returns
28196 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
28197 that are concerned with receiving messages. When all the conditions are true,
28198 the sending entity receives a &"success"& response. However, &%discard%& causes
28199 recipients to be discarded. If it is used in an ACL for RCPT, just the one
28200 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
28201 message's recipients are discarded. Recipients that are discarded before DATA
28202 do not appear in the log line when the &%received_recipients%& log selector is set.
28204 If the &%log_message%& modifier is set when &%discard%& operates,
28205 its contents are added to the line that is automatically written to the log.
28206 The &%message%& modifier operates exactly as it does for &%accept%&.
28210 .cindex "&%drop%& ACL verb"
28211 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
28212 forcibly closed after the 5&'xx'& error message has been sent. For example:
28214 drop message = I don't take more than 20 RCPTs
28215 condition = ${if > {$rcpt_count}{20}}
28217 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
28218 The connection is always dropped after sending a 550 response.
28221 .cindex "&%require%& ACL verb"
28222 &%require%&: If all the conditions are met, control is passed to the next ACL
28223 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
28224 example, when checking a RCPT command,
28226 require message = Sender did not verify
28229 passes control to subsequent statements only if the message's sender can be
28230 verified. Otherwise, it rejects the command. Note the positioning of the
28231 &%message%& modifier, before the &%verify%& condition. The reason for this is
28232 discussed in section &<<SECTcondmodproc>>&.
28235 .cindex "&%warn%& ACL verb"
28236 &%warn%&: If all the conditions are true, a line specified by the
28237 &%log_message%& modifier is written to Exim's main log. Control always passes
28238 to the next ACL statement. If any condition is false, the log line is not
28239 written. If an identical log line is requested several times in the same
28240 message, only one copy is actually written to the log. If you want to force
28241 duplicates to be written, use the &%logwrite%& modifier instead.
28243 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
28244 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
28245 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
28246 first failing condition. There is more about adding header lines in section
28247 &<<SECTaddheadacl>>&.
28249 If any condition on a &%warn%& statement cannot be completed (that is, there is
28250 some sort of defer), the log line specified by &%log_message%& is not written.
28251 This does not include the case of a forced failure from a lookup, which
28252 is considered to be a successful completion. After a defer, no further
28253 conditions or modifiers in the &%warn%& statement are processed. The incident
28254 is logged, and the ACL continues to be processed, from the next statement
28258 .vindex "&$acl_verify_message$&"
28259 When one of the &%warn%& conditions is an address verification that fails, the
28260 text of the verification failure message is in &$acl_verify_message$&. If you
28261 want this logged, you must set it up explicitly. For example:
28263 warn !verify = sender
28264 log_message = sender verify failed: $acl_verify_message
28268 At the end of each ACL there is an implicit unconditional &%deny%&.
28270 As you can see from the examples above, the conditions and modifiers are
28271 written one to a line, with the first one on the same line as the verb, and
28272 subsequent ones on following lines. If you have a very long condition, you can
28273 continue it onto several physical lines by the usual backslash continuation
28274 mechanism. It is conventional to align the conditions vertically.
28278 .section "ACL variables" "SECTaclvariables"
28279 .cindex "&ACL;" "variables"
28280 There are some special variables that can be set during ACL processing. They
28281 can be used to pass information between different ACLs, different invocations
28282 of the same ACL in the same SMTP connection, and between ACLs and the routers,
28283 transports, and filters that are used to deliver a message. The names of these
28284 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
28285 an underscore, but the remainder of the name can be any sequence of
28286 alphanumeric characters and underscores that you choose. There is no limit on
28287 the number of ACL variables. The two sets act as follows:
28289 The values of those variables whose names begin with &$acl_c$& persist
28290 throughout an SMTP connection. They are never reset. Thus, a value that is set
28291 while receiving one message is still available when receiving the next message
28292 on the same SMTP connection.
28294 The values of those variables whose names begin with &$acl_m$& persist only
28295 while a message is being received. They are reset afterwards. They are also
28296 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
28299 When a message is accepted, the current values of all the ACL variables are
28300 preserved with the message and are subsequently made available at delivery
28301 time. The ACL variables are set by a modifier called &%set%&. For example:
28303 accept hosts = whatever
28304 set acl_m4 = some value
28305 accept authenticated = *
28306 set acl_c_auth = yes
28308 &*Note*&: A leading dollar sign is not used when naming a variable that is to
28309 be set. If you want to set a variable without taking any action, you can use a
28310 &%warn%& verb without any other modifiers or conditions.
28312 .oindex &%strict_acl_vars%&
28313 What happens if a syntactically valid but undefined ACL variable is
28314 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
28315 false (the default), an empty string is substituted; if it is true, an
28316 error is generated.
28318 Versions of Exim before 4.64 have a limited set of numbered variables, but
28319 their names are compatible, so there is no problem with upgrading.
28322 .section "Condition and modifier processing" "SECTcondmodproc"
28323 .cindex "&ACL;" "conditions; processing"
28324 .cindex "&ACL;" "modifiers; processing"
28325 An exclamation mark preceding a condition negates its result. For example:
28327 deny domains = *.dom.example
28328 !verify = recipient
28330 causes the ACL to return &"deny"& if the recipient domain ends in
28331 &'dom.example'& and the recipient address cannot be verified. Sometimes
28332 negation can be used on the right-hand side of a condition. For example, these
28333 two statements are equivalent:
28335 deny hosts = !192.168.3.4
28336 deny !hosts = 192.168.3.4
28338 However, for many conditions (&%verify%& being a good example), only left-hand
28339 side negation of the whole condition is possible.
28341 The arguments of conditions and modifiers are expanded. A forced failure
28342 of an expansion causes a condition to be ignored, that is, it behaves as if the
28343 condition is true. Consider these two statements:
28345 accept senders = ${lookup{$host_name}lsearch\
28346 {/some/file}{$value}fail}
28347 accept senders = ${lookup{$host_name}lsearch\
28348 {/some/file}{$value}{}}
28350 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
28351 the returned list is searched, but if the lookup fails the behaviour is
28352 different in the two cases. The &%fail%& in the first statement causes the
28353 condition to be ignored, leaving no further conditions. The &%accept%& verb
28354 therefore succeeds. The second statement, however, generates an empty list when
28355 the lookup fails. No sender can match an empty list, so the condition fails,
28356 and therefore the &%accept%& also fails.
28358 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
28359 specify actions that are taken as the conditions for a statement are checked;
28360 others specify text for messages that are used when access is denied or a
28361 warning is generated. The &%control%& modifier affects the way an incoming
28362 message is handled.
28364 The positioning of the modifiers in an ACL statement is important, because the
28365 processing of a verb ceases as soon as its outcome is known. Only those
28366 modifiers that have already been encountered will take effect. For example,
28367 consider this use of the &%message%& modifier:
28369 require message = Can't verify sender
28371 message = Can't verify recipient
28373 message = This message cannot be used
28375 If sender verification fails, Exim knows that the result of the statement is
28376 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
28377 so its text is used as the error message. If sender verification succeeds, but
28378 recipient verification fails, the second message is used. If recipient
28379 verification succeeds, the third message becomes &"current"&, but is never used
28380 because there are no more conditions to cause failure.
28382 For the &%deny%& verb, on the other hand, it is always the last &%message%&
28383 modifier that is used, because all the conditions must be true for rejection to
28384 happen. Specifying more than one &%message%& modifier does not make sense, and
28385 the message can even be specified after all the conditions. For example:
28388 !senders = *@my.domain.example
28389 message = Invalid sender from client host
28391 The &"deny"& result does not happen until the end of the statement is reached,
28392 by which time Exim has set up the message.
28396 .section "ACL modifiers" "SECTACLmodi"
28397 .cindex "&ACL;" "modifiers; list of"
28398 The ACL modifiers are as follows:
28401 .vitem &*add_header*&&~=&~<&'text'&>
28402 This modifier specifies one or more header lines that are to be added to an
28403 incoming message, assuming, of course, that the message is ultimately
28404 accepted. For details, see section &<<SECTaddheadacl>>&.
28406 .vitem &*continue*&&~=&~<&'text'&>
28407 .cindex "&%continue%& ACL modifier"
28408 .cindex "database" "updating in ACL"
28409 This modifier does nothing of itself, and processing of the ACL always
28410 continues with the next condition or modifier. The value of &%continue%& is in
28411 the side effects of expanding its argument. Typically this could be used to
28412 update a database. It is really just a syntactic tidiness, to avoid having to
28413 write rather ugly lines like this:
28415 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
28417 Instead, all you need is
28419 &`continue = `&<&'some expansion'&>
28422 .vitem &*control*&&~=&~<&'text'&>
28423 .cindex "&%control%& ACL modifier"
28424 This modifier affects the subsequent processing of the SMTP connection or of an
28425 incoming message that is accepted. The effect of the first type of control
28426 lasts for the duration of the connection, whereas the effect of the second type
28427 lasts only until the current message has been received. The message-specific
28428 controls always apply to the whole message, not to individual recipients,
28429 even if the &%control%& modifier appears in a RCPT ACL.
28431 As there are now quite a few controls that can be applied, they are described
28432 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
28433 in several different ways. For example:
28435 . ==== As this is a nested list, any displays it contains must be indented
28436 . ==== as otherwise they are too far to the left. That comment applies only
28437 . ==== when xmlto and fop are used; formatting with sdop gets it right either
28441 It can be at the end of an &%accept%& statement:
28443 accept ...some conditions
28444 control = queue_only
28446 In this case, the control is applied when this statement yields &"accept"&, in
28447 other words, when the conditions are all true.
28450 It can be in the middle of an &%accept%& statement:
28452 accept ...some conditions...
28453 control = queue_only
28454 ...some more conditions...
28456 If the first set of conditions are true, the control is applied, even if the
28457 statement does not accept because one of the second set of conditions is false.
28458 In this case, some subsequent statement must yield &"accept"& for the control
28462 It can be used with &%warn%& to apply the control, leaving the
28463 decision about accepting or denying to a subsequent verb. For
28466 warn ...some conditions...
28470 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
28471 &%logwrite%&, so it does not add anything to the message and does not write a
28475 If you want to apply a control unconditionally, you can use it with a
28476 &%require%& verb. For example:
28478 require control = no_multiline_responses
28482 .vitem &*delay*&&~=&~<&'time'&>
28483 .cindex "&%delay%& ACL modifier"
28485 This modifier may appear in any ACL except notquit. It causes Exim to wait for
28486 the time interval before proceeding. However, when testing Exim using the
28487 &%-bh%& option, the delay is not actually imposed (an appropriate message is
28488 output instead). The time is given in the usual Exim notation, and the delay
28489 happens as soon as the modifier is processed. In an SMTP session, pending
28490 output is flushed before the delay is imposed.
28492 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
28495 deny ...some conditions...
28498 The delay happens if all the conditions are true, before the statement returns
28499 &"deny"&. Compare this with:
28502 ...some conditions...
28504 which waits for 30s before processing the conditions. The &%delay%& modifier
28505 can also be used with &%warn%& and together with &%control%&:
28507 warn ...some conditions...
28513 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
28514 responses to several commands are no longer buffered and sent in one packet (as
28515 they would normally be) because all output is flushed before imposing the
28516 delay. This optimization is disabled so that a number of small delays do not
28517 appear to the client as one large aggregated delay that might provoke an
28518 unwanted timeout. You can, however, disable output flushing for &%delay%& by
28519 using a &%control%& modifier to set &%no_delay_flush%&.
28523 .cindex "&%endpass%& ACL modifier"
28524 This modifier, which has no argument, is recognized only in &%accept%& and
28525 &%discard%& statements. It marks the boundary between the conditions whose
28526 failure causes control to pass to the next statement, and the conditions whose
28527 failure causes the ACL to return &"deny"&. This concept has proved to be
28528 confusing to some people, so the use of &%endpass%& is no longer recommended as
28529 &"best practice"&. See the description of &%accept%& above for more details.
28532 .vitem &*log_message*&&~=&~<&'text'&>
28533 .cindex "&%log_message%& ACL modifier"
28534 This modifier sets up a message that is used as part of the log message if the
28535 ACL denies access or a &%warn%& statement's conditions are true. For example:
28537 require log_message = wrong cipher suite $tls_in_cipher
28538 encrypted = DES-CBC3-SHA
28540 &%log_message%& is also used when recipients are discarded by &%discard%&. For
28543 &`discard `&<&'some conditions'&>
28544 &` log_message = Discarded $local_part@$domain because...`&
28546 When access is denied, &%log_message%& adds to any underlying error message
28547 that may exist because of a condition failure. For example, while verifying a
28548 recipient address, a &':fail:'& redirection might have already set up a
28551 The message may be defined before the conditions to which it applies, because
28552 the string expansion does not happen until Exim decides that access is to be
28553 denied. This means that any variables that are set by the condition are
28554 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
28555 variables are set after a DNS black list lookup succeeds. If the expansion of
28556 &%log_message%& fails, or if the result is an empty string, the modifier is
28559 .vindex "&$acl_verify_message$&"
28560 If you want to use a &%warn%& statement to log the result of an address
28561 verification, you can use &$acl_verify_message$& to include the verification
28564 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
28565 the start of the logged message. If the same warning log message is requested
28566 more than once while receiving a single email message, only one copy is
28567 actually logged. If you want to log multiple copies, use &%logwrite%& instead
28568 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
28569 is logged for a successful &%warn%& statement.
28571 If &%log_message%& is not present and there is no underlying error message (for
28572 example, from the failure of address verification), but &%message%& is present,
28573 the &%message%& text is used for logging rejections. However, if any text for
28574 logging contains newlines, only the first line is logged. In the absence of
28575 both &%log_message%& and &%message%&, a default built-in message is used for
28576 logging rejections.
28579 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
28580 .cindex "&%log_reject_target%& ACL modifier"
28581 .cindex "logging in ACL" "specifying which log"
28582 This modifier makes it possible to specify which logs are used for messages
28583 about ACL rejections. Its argument is a colon-separated list of words that can
28584 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
28585 may be empty, in which case a rejection is not logged at all. For example, this
28586 ACL fragment writes no logging information when access is denied:
28588 &`deny `&<&'some conditions'&>
28589 &` log_reject_target =`&
28591 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
28592 permanent and temporary rejections. Its effect lasts for the rest of the
28596 .vitem &*logwrite*&&~=&~<&'text'&>
28597 .cindex "&%logwrite%& ACL modifier"
28598 .cindex "logging in ACL" "immediate"
28599 This modifier writes a message to a log file as soon as it is encountered when
28600 processing an ACL. (Compare &%log_message%&, which, except in the case of
28601 &%warn%& and &%discard%&, is used only if the ACL statement denies
28602 access.) The &%logwrite%& modifier can be used to log special incidents in
28605 &`accept `&<&'some special conditions'&>
28606 &` control = freeze`&
28607 &` logwrite = froze message because ...`&
28609 By default, the message is written to the main log. However, it may begin
28610 with a colon, followed by a comma-separated list of log names, and then
28611 another colon, to specify exactly which logs are to be written. For
28614 logwrite = :main,reject: text for main and reject logs
28615 logwrite = :panic: text for panic log only
28619 .vitem &*message*&&~=&~<&'text'&>
28620 .cindex "&%message%& ACL modifier"
28621 This modifier sets up a text string that is expanded and used as a response
28622 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
28623 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
28624 there is some complication if &%endpass%& is involved; see the description of
28625 &%accept%& for details.)
28627 The expansion of the message happens at the time Exim decides that the ACL is
28628 to end, not at the time it processes &%message%&. If the expansion fails, or
28629 generates an empty string, the modifier is ignored. Here is an example where
28630 &%message%& must be specified first, because the ACL ends with a rejection if
28631 the &%hosts%& condition fails:
28633 require message = Host not recognized
28636 (Once a condition has failed, no further conditions or modifiers are
28639 .cindex "SMTP" "error codes"
28640 .oindex "&%smtp_banner%&
28641 For ACLs that are triggered by SMTP commands, the message is returned as part
28642 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
28643 is meaningful only for SMTP, as no message is returned when a non-SMTP message
28644 is accepted. In the case of the connect ACL, accepting with a message modifier
28645 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
28646 accept message may not contain more than one line (otherwise it will be
28647 truncated at the first newline and a panic logged), and it cannot affect the
28650 When SMTP is involved, the message may begin with an overriding response code,
28651 consisting of three digits optionally followed by an &"extended response code"&
28652 of the form &'n.n.n'&, each code being followed by a space. For example:
28654 deny message = 599 1.2.3 Host not welcome
28655 hosts = 192.168.34.0/24
28657 The first digit of the supplied response code must be the same as would be sent
28658 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
28659 access, but for the predata ACL, note that the default success code is 354, not
28662 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
28663 the message modifier cannot override the 221 response code.
28665 The text in a &%message%& modifier is literal; any quotes are taken as
28666 literals, but because the string is expanded, backslash escapes are processed
28667 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
28670 .vindex "&$acl_verify_message$&"
28671 For ACLs that are called by an &%acl =%& ACL condition, the message is
28672 stored in &$acl_verify_message$&, from which the calling ACL may use it.
28674 If &%message%& is used on a statement that verifies an address, the message
28675 specified overrides any message that is generated by the verification process.
28676 However, the original message is available in the variable
28677 &$acl_verify_message$&, so you can incorporate it into your message if you
28678 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
28679 routers to be passed back as part of the SMTP response, you should either not
28680 use a &%message%& modifier, or make use of &$acl_verify_message$&.
28682 For compatibility with previous releases of Exim, a &%message%& modifier that
28683 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
28684 modifier, but this usage is now deprecated. However, &%message%& acts only when
28685 all the conditions are true, wherever it appears in an ACL command, whereas
28686 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
28687 &%warn%& in an ACL that is not concerned with receiving a message, it has no
28692 .vitem &*queue*&&~=&~<&'text'&>
28693 This modifier specifies the use of a named queue for spool files
28695 It can only be used before the message is received (i.e. not in
28697 This could be used, for example, for known high-volume burst sources
28698 of traffic, or for quarantine of messages.
28699 Separate queue-runner processes will be needed for named queues.
28700 If the text after expansion is empty, the default queue is used.
28704 .vitem &*remove_header*&&~=&~<&'text'&>
28705 This modifier specifies one or more header names in a colon-separated list
28706 that are to be removed from an incoming message, assuming, of course, that
28707 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
28710 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
28711 .cindex "&%set%& ACL modifier"
28712 This modifier puts a value into one of the ACL variables (see section
28713 &<<SECTaclvariables>>&).
28716 .vitem &*udpsend*&&~=&~<&'parameters'&>
28717 This modifier sends a UDP packet, for purposes such as statistics
28718 collection or behaviour monitoring. The parameters are expanded, and
28719 the result of the expansion must be a colon-separated list consisting
28720 of a destination server, port number, and the packet contents. The
28721 server can be specified as a host name or IPv4 or IPv6 address. The
28722 separator can be changed with the usual angle bracket syntax. For
28723 example, you might want to collect information on which hosts connect
28726 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
28727 $tod_zulu $sender_host_address
28734 .section "Use of the control modifier" "SECTcontrols"
28735 .cindex "&%control%& ACL modifier"
28736 The &%control%& modifier supports the following settings:
28739 .vitem &*control&~=&~allow_auth_unadvertised*&
28740 This modifier allows a client host to use the SMTP AUTH command even when it
28741 has not been advertised in response to EHLO. Furthermore, because there are
28742 apparently some really broken clients that do this, Exim will accept AUTH after
28743 HELO (rather than EHLO) when this control is set. It should be used only if you
28744 really need it, and you should limit its use to those broken clients that do
28745 not work without it. For example:
28747 warn hosts = 192.168.34.25
28748 control = allow_auth_unadvertised
28750 Normally, when an Exim server receives an AUTH command, it checks the name of
28751 the authentication mechanism that is given in the command to ensure that it
28752 matches an advertised mechanism. When this control is set, the check that a
28753 mechanism has been advertised is bypassed. Any configured mechanism can be used
28754 by the client. This control is permitted only in the connection and HELO ACLs.
28757 .vitem &*control&~=&~caseful_local_part*& &&&
28758 &*control&~=&~caselower_local_part*&
28759 .cindex "&ACL;" "case of local part in"
28760 .cindex "case of local parts"
28761 .vindex "&$local_part$&"
28762 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
28763 (that is, during RCPT processing). By default, the contents of &$local_part$&
28764 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
28765 any uppercase letters in the original local part are restored in &$local_part$&
28766 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
28769 These controls affect only the current recipient. Moreover, they apply only to
28770 local part handling that takes place directly in the ACL (for example, as a key
28771 in lookups). If a test to verify the recipient is obeyed, the case-related
28772 handling of the local part during the verification is controlled by the router
28773 configuration (see the &%caseful_local_part%& generic router option).
28775 This facility could be used, for example, to add a spam score to local parts
28776 containing upper case letters. For example, using &$acl_m4$& to accumulate the
28779 warn control = caseful_local_part
28780 set acl_m4 = ${eval:\
28782 ${if match{$local_part}{[A-Z]}{1}{0}}\
28784 control = caselower_local_part
28786 Notice that we put back the lower cased version afterwards, assuming that
28787 is what is wanted for subsequent tests.
28790 .vitem &*control&~=&~cutthrough_delivery*&
28791 .cindex "&ACL;" "cutthrough routing"
28792 .cindex "cutthrough" "requesting"
28793 This option requests delivery be attempted while the item is being received.
28795 The option is usable in the RCPT ACL.
28796 If enabled for a message received via smtp and routed to an smtp transport,
28797 and only one transport, interface, destination host and port combination
28798 is used for all recipients of the message,
28799 then the delivery connection is made while the receiving connection is open
28800 and data is copied from one to the other.
28802 An attempt to set this option for any recipient but the first
28803 for a mail will be quietly ignored.
28804 If a recipient-verify callout
28806 connection is subsequently
28807 requested in the same ACL it is held open and used for
28808 any subsequent recipients and the data,
28809 otherwise one is made after the initial RCPT ACL completes.
28811 Note that routers are used in verify mode,
28812 and cannot depend on content of received headers.
28813 Note also that headers cannot be
28814 modified by any of the post-data ACLs (DATA, MIME and DKIM).
28815 Headers may be modified by routers (subject to the above) and transports.
28817 All the usual ACLs are called; if one results in the message being
28818 rejected, all effort spent in delivery (including the costs on
28819 the ultimate destination) will be wasted.
28820 Note that in the case of data-time ACLs this includes the entire
28823 Cutthrough delivery is not supported via transport-filters or when DKIM signing
28824 of outgoing messages is done, because it sends data to the ultimate destination
28825 before the entire message has been received from the source.
28826 It is not supported for messages received with the SMTP PRDR option in use.
28828 Should the ultimate destination system positively accept or reject the mail,
28829 a corresponding indication is given to the source system and nothing is queued.
28830 If there is a temporary error the item is queued for later delivery in the
28831 usual fashion. If the item is successfully delivered in cutthrough mode
28832 the delivery log lines are tagged with ">>" rather than "=>" and appear
28833 before the acceptance "<=" line.
28835 Delivery in this mode avoids the generation of a bounce mail to a
28837 sender when the destination system is doing content-scan based rejection.
28840 .vitem &*control&~=&~debug/*&<&'options'&>
28841 .cindex "&ACL;" "enabling debug logging"
28842 .cindex "debugging" "enabling from an ACL"
28843 This control turns on debug logging, almost as though Exim had been invoked
28844 with &`-d`&, with the output going to a new logfile, by default called
28845 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
28846 may access any variables already defined. The logging may be adjusted with
28847 the &'opts'& option, which takes the same values as the &`-d`& command-line
28850 Logging may be stopped, and the file removed, with the &'kill'& option.
28852 Some examples (which depend on variables that don't exist in all
28856 control = debug/tag=.$sender_host_address
28857 control = debug/opts=+expand+acl
28858 control = debug/tag=.$message_exim_id/opts=+expand
28859 control = debug/kill
28863 .vitem &*control&~=&~dkim_disable_verify*&
28864 .cindex "disable DKIM verify"
28865 .cindex "DKIM" "disable verify"
28866 This control turns off DKIM verification processing entirely. For details on
28867 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
28870 .vitem &*control&~=&~dscp/*&<&'value'&>
28871 .cindex "&ACL;" "setting DSCP value"
28872 .cindex "DSCP" "inbound"
28873 This option causes the DSCP value associated with the socket for the inbound
28874 connection to be adjusted to a given value, given as one of a number of fixed
28875 strings or to numeric value.
28876 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
28877 Common values include &`throughput`&, &`mincost`&, and on newer systems
28878 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
28880 The outbound packets from Exim will be marked with this value in the header
28881 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
28882 that these values will have any effect, not be stripped by networking
28883 equipment, or do much of anything without cooperation with your Network
28884 Engineer and those of all network operators between the source and destination.
28887 .vitem &*control&~=&~enforce_sync*& &&&
28888 &*control&~=&~no_enforce_sync*&
28889 .cindex "SMTP" "synchronization checking"
28890 .cindex "synchronization checking in SMTP"
28891 These controls make it possible to be selective about when SMTP synchronization
28892 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
28893 state of the switch (it is true by default). See the description of this option
28894 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
28896 The effect of these two controls lasts for the remainder of the SMTP
28897 connection. They can appear in any ACL except the one for the non-SMTP
28898 messages. The most straightforward place to put them is in the ACL defined by
28899 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
28900 before the first synchronization check. The expected use is to turn off the
28901 synchronization checks for badly-behaved hosts that you nevertheless need to
28905 .vitem &*control&~=&~fakedefer/*&<&'message'&>
28906 .cindex "fake defer"
28907 .cindex "defer, fake"
28908 This control works in exactly the same way as &%fakereject%& (described below)
28909 except that it causes an SMTP 450 response after the message data instead of a
28910 550 response. You must take care when using &%fakedefer%& because it causes the
28911 messages to be duplicated when the sender retries. Therefore, you should not
28912 use &%fakedefer%& if the message is to be delivered normally.
28914 .vitem &*control&~=&~fakereject/*&<&'message'&>
28915 .cindex "fake rejection"
28916 .cindex "rejection, fake"
28917 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
28918 words, only when an SMTP message is being received. If Exim accepts the
28919 message, instead the final 250 response, a 550 rejection message is sent.
28920 However, Exim proceeds to deliver the message as normal. The control applies
28921 only to the current message, not to any subsequent ones that may be received in
28922 the same SMTP connection.
28924 The text for the 550 response is taken from the &%control%& modifier. If no
28925 message is supplied, the following is used:
28927 550-Your message has been rejected but is being
28928 550-kept for evaluation.
28929 550-If it was a legitimate message, it may still be
28930 550 delivered to the target recipient(s).
28932 This facility should be used with extreme caution.
28934 .vitem &*control&~=&~freeze*&
28935 .cindex "frozen messages" "forcing in ACL"
28936 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28937 other words, only when a message is being received. If the message is accepted,
28938 it is placed on Exim's queue and frozen. The control applies only to the
28939 current message, not to any subsequent ones that may be received in the same
28942 This modifier can optionally be followed by &`/no_tell`&. If the global option
28943 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
28944 is told about the freezing), provided all the &*control=freeze*& modifiers that
28945 are obeyed for the current message have the &`/no_tell`& option.
28947 .vitem &*control&~=&~no_delay_flush*&
28948 .cindex "SMTP" "output flushing, disabling for delay"
28949 Exim normally flushes SMTP output before implementing a delay in an ACL, to
28950 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28951 use. This control, as long as it is encountered before the &%delay%& modifier,
28952 disables such output flushing.
28954 .vitem &*control&~=&~no_callout_flush*&
28955 .cindex "SMTP" "output flushing, disabling for callout"
28956 Exim normally flushes SMTP output before performing a callout in an ACL, to
28957 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28958 use. This control, as long as it is encountered before the &%verify%& condition
28959 that causes the callout, disables such output flushing.
28961 .vitem &*control&~=&~no_mbox_unspool*&
28962 This control is available when Exim is compiled with the content scanning
28963 extension. Content scanning may require a copy of the current message, or parts
28964 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
28965 or spam scanner. Normally, such copies are deleted when they are no longer
28966 needed. If this control is set, the copies are not deleted. The control applies
28967 only to the current message, not to any subsequent ones that may be received in
28968 the same SMTP connection. It is provided for debugging purposes and is unlikely
28969 to be useful in production.
28971 .vitem &*control&~=&~no_multiline_responses*&
28972 .cindex "multiline responses, suppressing"
28973 This control is permitted for any ACL except the one for non-SMTP messages.
28974 It seems that there are broken clients in use that cannot handle multiline
28975 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
28977 If this control is set, multiline SMTP responses from ACL rejections are
28978 suppressed. One way of doing this would have been to put out these responses as
28979 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
28980 (&"use multiline responses for more"& it says &-- ha!), and some of the
28981 responses might get close to that. So this facility, which is after all only a
28982 sop to broken clients, is implemented by doing two very easy things:
28985 Extra information that is normally output as part of a rejection caused by
28986 sender verification failure is omitted. Only the final line (typically &"sender
28987 verification failed"&) is sent.
28989 If a &%message%& modifier supplies a multiline response, only the first
28993 The setting of the switch can, of course, be made conditional on the
28994 calling host. Its effect lasts until the end of the SMTP connection.
28996 .vitem &*control&~=&~no_pipelining*&
28997 .cindex "PIPELINING" "suppressing advertising"
28998 This control turns off the advertising of the PIPELINING extension to SMTP in
28999 the current session. To be useful, it must be obeyed before Exim sends its
29000 response to an EHLO command. Therefore, it should normally appear in an ACL
29001 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
29002 &%pipelining_advertise_hosts%&.
29004 .vitem &*control&~=&~queue_only*&
29005 .oindex "&%queue_only%&"
29006 .cindex "queueing incoming messages"
29007 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
29008 other words, only when a message is being received. If the message is accepted,
29009 it is placed on Exim's queue and left there for delivery by a subsequent queue
29010 runner. No immediate delivery process is started. In other words, it has the
29011 effect as the &%queue_only%& global option. However, the control applies only
29012 to the current message, not to any subsequent ones that may be received in the
29013 same SMTP connection.
29015 .vitem &*control&~=&~submission/*&<&'options'&>
29016 .cindex "message" "submission"
29017 .cindex "submission mode"
29018 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
29019 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
29020 the current message is a submission from a local MUA. In this case, Exim
29021 operates in &"submission mode"&, and applies certain fixups to the message if
29022 necessary. For example, it adds a &'Date:'& header line if one is not present.
29023 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
29024 late (the message has already been created).
29026 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
29027 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
29028 submission mode; the available options for this control are described there.
29029 The control applies only to the current message, not to any subsequent ones
29030 that may be received in the same SMTP connection.
29032 .vitem &*control&~=&~suppress_local_fixups*&
29033 .cindex "submission fixups, suppressing"
29034 This control applies to locally submitted (non TCP/IP) messages, and is the
29035 complement of &`control = submission`&. It disables the fixups that are
29036 normally applied to locally-submitted messages. Specifically:
29039 Any &'Sender:'& header line is left alone (in this respect, it is a
29040 dynamic version of &%local_sender_retain%&).
29042 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
29044 There is no check that &'From:'& corresponds to the actual sender.
29047 This control may be useful when a remotely-originated message is accepted,
29048 passed to some scanning program, and then re-submitted for delivery. It can be
29049 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
29050 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
29053 &*Note:*& This control applies only to the current message, not to any others
29054 that are being submitted at the same time using &%-bs%& or &%-bS%&.
29056 .vitem &*control&~=&~utf8_downconvert*&
29057 This control enables conversion of UTF-8 in message addresses
29059 For details see &<<SECTi18nMTA>>&.
29063 .section "Summary of message fixup control" "SECTsummesfix"
29064 All four possibilities for message fixups can be specified:
29067 Locally submitted, fixups applied: the default.
29069 Locally submitted, no fixups applied: use
29070 &`control = suppress_local_fixups`&.
29072 Remotely submitted, no fixups applied: the default.
29074 Remotely submitted, fixups applied: use &`control = submission`&.
29079 .section "Adding header lines in ACLs" "SECTaddheadacl"
29080 .cindex "header lines" "adding in an ACL"
29081 .cindex "header lines" "position of added lines"
29082 .cindex "&%add_header%& ACL modifier"
29083 The &%add_header%& modifier can be used to add one or more extra header lines
29084 to an incoming message, as in this example:
29086 warn dnslists = sbl.spamhaus.org : \
29087 dialup.mail-abuse.org
29088 add_header = X-blacklisted-at: $dnslist_domain
29090 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29091 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29092 receiving a message). The message must ultimately be accepted for
29093 &%add_header%& to have any significant effect. You can use &%add_header%& with
29094 any ACL verb, including &%deny%& (though this is potentially useful only in a
29097 Headers will not be added to the message if the modifier is used in
29098 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
29100 Leading and trailing newlines are removed from
29101 the data for the &%add_header%& modifier; if it then
29102 contains one or more newlines that
29103 are not followed by a space or a tab, it is assumed to contain multiple header
29104 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
29105 front of any line that is not a valid header line.
29107 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
29108 They are added to the message before processing the DATA and MIME ACLs.
29109 However, if an identical header line is requested more than once, only one copy
29110 is actually added to the message. Further header lines may be accumulated
29111 during the DATA and MIME ACLs, after which they are added to the message, again
29112 with duplicates suppressed. Thus, it is possible to add two identical header
29113 lines to an SMTP message, but only if one is added before DATA and one after.
29114 In the case of non-SMTP messages, new headers are accumulated during the
29115 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
29116 message is rejected after DATA or by the non-SMTP ACL, all added header lines
29117 are included in the entry that is written to the reject log.
29119 .cindex "header lines" "added; visibility of"
29120 Header lines are not visible in string expansions
29122 until they are added to the
29123 message. It follows that header lines defined in the MAIL, RCPT, and predata
29124 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
29125 header lines that are added by the DATA or MIME ACLs are not visible in those
29126 ACLs. Because of this restriction, you cannot use header lines as a way of
29127 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
29128 this, you can use ACL variables, as described in section
29129 &<<SECTaclvariables>>&.
29131 The list of headers yet to be added is given by the &%$headers_added%& variable.
29133 The &%add_header%& modifier acts immediately as it is encountered during the
29134 processing of an ACL. Notice the difference between these two cases:
29136 &`accept add_header = ADDED: some text`&
29137 &` `&<&'some condition'&>
29139 &`accept `&<&'some condition'&>
29140 &` add_header = ADDED: some text`&
29142 In the first case, the header line is always added, whether or not the
29143 condition is true. In the second case, the header line is added only if the
29144 condition is true. Multiple occurrences of &%add_header%& may occur in the same
29145 ACL statement. All those that are encountered before a condition fails are
29148 .cindex "&%warn%& ACL verb"
29149 For compatibility with previous versions of Exim, a &%message%& modifier for a
29150 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
29151 effect only if all the conditions are true, even if it appears before some of
29152 them. Furthermore, only the last occurrence of &%message%& is honoured. This
29153 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
29154 are present on a &%warn%& verb, both are processed according to their
29157 By default, new header lines are added to a message at the end of the existing
29158 header lines. However, you can specify that any particular header line should
29159 be added right at the start (before all the &'Received:'& lines), immediately
29160 after the first block of &'Received:'& lines, or immediately before any line
29161 that is not a &'Received:'& or &'Resent-something:'& header.
29163 This is done by specifying &":at_start:"&, &":after_received:"&, or
29164 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
29165 header line, respectively. (Header text cannot start with a colon, as there has
29166 to be a header name first.) For example:
29168 warn add_header = \
29169 :after_received:X-My-Header: something or other...
29171 If more than one header line is supplied in a single &%add_header%& modifier,
29172 each one is treated independently and can therefore be placed differently. If
29173 you add more than one line at the start, or after the Received: block, they end
29174 up in reverse order.
29176 &*Warning*&: This facility currently applies only to header lines that are
29177 added in an ACL. It does NOT work for header lines that are added in a
29178 system filter or in a router or transport.
29182 .section "Removing header lines in ACLs" "SECTremoveheadacl"
29183 .cindex "header lines" "removing in an ACL"
29184 .cindex "header lines" "position of removed lines"
29185 .cindex "&%remove_header%& ACL modifier"
29186 The &%remove_header%& modifier can be used to remove one or more header lines
29187 from an incoming message, as in this example:
29189 warn message = Remove internal headers
29190 remove_header = x-route-mail1 : x-route-mail2
29192 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29193 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29194 receiving a message). The message must ultimately be accepted for
29195 &%remove_header%& to have any significant effect. You can use &%remove_header%&
29196 with any ACL verb, including &%deny%&, though this is really not useful for
29197 any verb that doesn't result in a delivered message.
29199 Headers will not be removed from the message if the modifier is used in
29200 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
29202 More than one header can be removed at the same time by using a colon separated
29203 list of header names. The header matching is case insensitive. Wildcards are
29204 not permitted, nor is list expansion performed, so you cannot use hostlists to
29205 create a list of headers, however both connection and message variable expansion
29206 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
29208 warn hosts = +internal_hosts
29209 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
29210 warn message = Remove internal headers
29211 remove_header = $acl_c_ihdrs
29213 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
29214 They are removed from the message before processing the DATA and MIME ACLs.
29215 There is no harm in attempting to remove the same header twice nor is removing
29216 a non-existent header. Further header lines to be removed may be accumulated
29217 during the DATA and MIME ACLs, after which they are removed from the message,
29218 if present. In the case of non-SMTP messages, headers to be removed are
29219 accumulated during the non-SMTP ACLs, and are removed from the message after
29220 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
29221 ACL, there really is no effect because there is no logging of what headers
29222 would have been removed.
29224 .cindex "header lines" "removed; visibility of"
29225 Header lines are not visible in string expansions until the DATA phase when it
29226 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
29227 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
29228 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
29229 this restriction, you cannot use header lines as a way of controlling data
29230 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
29231 you should instead use ACL variables, as described in section
29232 &<<SECTaclvariables>>&.
29234 The &%remove_header%& modifier acts immediately as it is encountered during the
29235 processing of an ACL. Notice the difference between these two cases:
29237 &`accept remove_header = X-Internal`&
29238 &` `&<&'some condition'&>
29240 &`accept `&<&'some condition'&>
29241 &` remove_header = X-Internal`&
29243 In the first case, the header line is always removed, whether or not the
29244 condition is true. In the second case, the header line is removed only if the
29245 condition is true. Multiple occurrences of &%remove_header%& may occur in the
29246 same ACL statement. All those that are encountered before a condition fails
29249 &*Warning*&: This facility currently applies only to header lines that are
29250 present during ACL processing. It does NOT remove header lines that are added
29251 in a system filter or in a router or transport.
29256 .section "ACL conditions" "SECTaclconditions"
29257 .cindex "&ACL;" "conditions; list of"
29258 Some of the conditions listed in this section are available only when Exim is
29259 compiled with the content-scanning extension. They are included here briefly
29260 for completeness. More detailed descriptions can be found in the discussion on
29261 content scanning in chapter &<<CHAPexiscan>>&.
29263 Not all conditions are relevant in all circumstances. For example, testing
29264 senders and recipients does not make sense in an ACL that is being run as the
29265 result of the arrival of an ETRN command, and checks on message headers can be
29266 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
29267 can use the same condition (with different parameters) more than once in the
29268 same ACL statement. This provides a way of specifying an &"and"& conjunction.
29269 The conditions are as follows:
29273 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
29274 .cindex "&ACL;" "nested"
29275 .cindex "&ACL;" "indirect"
29276 .cindex "&ACL;" "arguments"
29277 .cindex "&%acl%& ACL condition"
29278 The possible values of the argument are the same as for the
29279 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
29280 &"accept"& the condition is true; if it returns &"deny"& the condition is
29281 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
29282 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
29283 condition false. This means that further processing of the &%warn%& verb
29284 ceases, but processing of the ACL continues.
29286 If the argument is a named ACL, up to nine space-separated optional values
29287 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
29288 and $acl_narg is set to the count of values.
29289 Previous values of these variables are restored after the call returns.
29290 The name and values are expanded separately.
29291 Note that spaces in complex expansions which are used as arguments
29292 will act as argument separators.
29294 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
29295 the connection is dropped. If it returns &"discard"&, the verb must be
29296 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
29297 conditions are tested.
29299 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
29300 loops. This condition allows you to use different ACLs in different
29301 circumstances. For example, different ACLs can be used to handle RCPT commands
29302 for different local users or different local domains.
29304 .vitem &*authenticated&~=&~*&<&'string&~list'&>
29305 .cindex "&%authenticated%& ACL condition"
29306 .cindex "authentication" "ACL checking"
29307 .cindex "&ACL;" "testing for authentication"
29308 If the SMTP connection is not authenticated, the condition is false. Otherwise,
29309 the name of the authenticator is tested against the list. To test for
29310 authentication by any authenticator, you can set
29315 .vitem &*condition&~=&~*&<&'string'&>
29316 .cindex "&%condition%& ACL condition"
29317 .cindex "customizing" "ACL condition"
29318 .cindex "&ACL;" "customized test"
29319 .cindex "&ACL;" "testing, customized"
29320 This feature allows you to make up custom conditions. If the result of
29321 expanding the string is an empty string, the number zero, or one of the strings
29322 &"no"& or &"false"&, the condition is false. If the result is any non-zero
29323 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
29324 any other value, some error is assumed to have occurred, and the ACL returns
29325 &"defer"&. However, if the expansion is forced to fail, the condition is
29326 ignored. The effect is to treat it as true, whether it is positive or
29329 .vitem &*decode&~=&~*&<&'location'&>
29330 .cindex "&%decode%& ACL condition"
29331 This condition is available only when Exim is compiled with the
29332 content-scanning extension, and it is allowed only in the ACL defined by
29333 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
29334 If all goes well, the condition is true. It is false only if there are
29335 problems such as a syntax error or a memory shortage. For more details, see
29336 chapter &<<CHAPexiscan>>&.
29338 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
29339 .cindex "&%dnslists%& ACL condition"
29340 .cindex "DNS list" "in ACL"
29341 .cindex "black list (DNS)"
29342 .cindex "&ACL;" "testing a DNS list"
29343 This condition checks for entries in DNS black lists. These are also known as
29344 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
29345 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
29346 different variants of this condition to describe briefly here. See sections
29347 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
29349 .vitem &*domains&~=&~*&<&'domain&~list'&>
29350 .cindex "&%domains%& ACL condition"
29351 .cindex "domain" "ACL checking"
29352 .cindex "&ACL;" "testing a recipient domain"
29353 .vindex "&$domain_data$&"
29354 This condition is relevant only after a RCPT command. It checks that the domain
29355 of the recipient address is in the domain list. If percent-hack processing is
29356 enabled, it is done before this test is done. If the check succeeds with a
29357 lookup, the result of the lookup is placed in &$domain_data$& until the next
29360 &*Note carefully*& (because many people seem to fall foul of this): you cannot
29361 use &%domains%& in a DATA ACL.
29364 .vitem &*encrypted&~=&~*&<&'string&~list'&>
29365 .cindex "&%encrypted%& ACL condition"
29366 .cindex "encryption" "checking in an ACL"
29367 .cindex "&ACL;" "testing for encryption"
29368 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
29369 name of the cipher suite in use is tested against the list. To test for
29370 encryption without testing for any specific cipher suite(s), set
29376 .vitem &*hosts&~=&~*&<&'host&~list'&>
29377 .cindex "&%hosts%& ACL condition"
29378 .cindex "host" "ACL checking"
29379 .cindex "&ACL;" "testing the client host"
29380 This condition tests that the calling host matches the host list. If you have
29381 name lookups or wildcarded host names and IP addresses in the same host list,
29382 you should normally put the IP addresses first. For example, you could have:
29384 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
29386 The lookup in this example uses the host name for its key. This is implied by
29387 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
29388 and it wouldn't matter which way round you had these two items.)
29390 The reason for the problem with host names lies in the left-to-right way that
29391 Exim processes lists. It can test IP addresses without doing any DNS lookups,
29392 but when it reaches an item that requires a host name, it fails if it cannot
29393 find a host name to compare with the pattern. If the above list is given in the
29394 opposite order, the &%accept%& statement fails for a host whose name cannot be
29395 found, even if its IP address is 10.9.8.7.
29397 If you really do want to do the name check first, and still recognize the IP
29398 address even if the name lookup fails, you can rewrite the ACL like this:
29400 accept hosts = dbm;/etc/friendly/hosts
29401 accept hosts = 10.9.8.7
29403 The default action on failing to find the host name is to assume that the host
29404 is not in the list, so the first &%accept%& statement fails. The second
29405 statement can then check the IP address.
29407 .vindex "&$host_data$&"
29408 If a &%hosts%& condition is satisfied by means of a lookup, the result
29409 of the lookup is made available in the &$host_data$& variable. This
29410 allows you, for example, to set up a statement like this:
29412 deny hosts = net-lsearch;/some/file
29413 message = $host_data
29415 which gives a custom error message for each denied host.
29417 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
29418 .cindex "&%local_parts%& ACL condition"
29419 .cindex "local part" "ACL checking"
29420 .cindex "&ACL;" "testing a local part"
29421 .vindex "&$local_part_data$&"
29422 This condition is relevant only after a RCPT command. It checks that the local
29423 part of the recipient address is in the list. If percent-hack processing is
29424 enabled, it is done before this test. If the check succeeds with a lookup, the
29425 result of the lookup is placed in &$local_part_data$&, which remains set until
29426 the next &%local_parts%& test.
29428 .vitem &*malware&~=&~*&<&'option'&>
29429 .cindex "&%malware%& ACL condition"
29430 .cindex "&ACL;" "virus scanning"
29431 .cindex "&ACL;" "scanning for viruses"
29432 This condition is available only when Exim is compiled with the
29433 content-scanning extension. It causes the incoming message to be scanned for
29434 viruses. For details, see chapter &<<CHAPexiscan>>&.
29436 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29437 .cindex "&%mime_regex%& ACL condition"
29438 .cindex "&ACL;" "testing by regex matching"
29439 This condition is available only when Exim is compiled with the
29440 content-scanning extension, and it is allowed only in the ACL defined by
29441 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
29442 with any of the regular expressions. For details, see chapter
29445 .vitem &*ratelimit&~=&~*&<&'parameters'&>
29446 .cindex "rate limiting"
29447 This condition can be used to limit the rate at which a user or host submits
29448 messages. Details are given in section &<<SECTratelimiting>>&.
29450 .vitem &*recipients&~=&~*&<&'address&~list'&>
29451 .cindex "&%recipients%& ACL condition"
29452 .cindex "recipient" "ACL checking"
29453 .cindex "&ACL;" "testing a recipient"
29454 This condition is relevant only after a RCPT command. It checks the entire
29455 recipient address against a list of recipients.
29457 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29458 .cindex "&%regex%& ACL condition"
29459 .cindex "&ACL;" "testing by regex matching"
29460 This condition is available only when Exim is compiled with the
29461 content-scanning extension, and is available only in the DATA, MIME, and
29462 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
29463 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
29465 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
29466 .cindex "&%sender_domains%& ACL condition"
29467 .cindex "sender" "ACL checking"
29468 .cindex "&ACL;" "testing a sender domain"
29469 .vindex "&$domain$&"
29470 .vindex "&$sender_address_domain$&"
29471 This condition tests the domain of the sender of the message against the given
29472 domain list. &*Note*&: The domain of the sender address is in
29473 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
29474 of this condition. This is an exception to the general rule for testing domain
29475 lists. It is done this way so that, if this condition is used in an ACL for a
29476 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
29477 influence the sender checking.
29479 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29480 relaying, because sender addresses are easily, and commonly, forged.
29482 .vitem &*senders&~=&~*&<&'address&~list'&>
29483 .cindex "&%senders%& ACL condition"
29484 .cindex "sender" "ACL checking"
29485 .cindex "&ACL;" "testing a sender"
29486 This condition tests the sender of the message against the given list. To test
29487 for a bounce message, which has an empty sender, set
29491 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29492 relaying, because sender addresses are easily, and commonly, forged.
29494 .vitem &*spam&~=&~*&<&'username'&>
29495 .cindex "&%spam%& ACL condition"
29496 .cindex "&ACL;" "scanning for spam"
29497 This condition is available only when Exim is compiled with the
29498 content-scanning extension. It causes the incoming message to be scanned by
29499 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
29501 .vitem &*verify&~=&~certificate*&
29502 .cindex "&%verify%& ACL condition"
29503 .cindex "TLS" "client certificate verification"
29504 .cindex "certificate" "verification of client"
29505 .cindex "&ACL;" "certificate verification"
29506 .cindex "&ACL;" "testing a TLS certificate"
29507 This condition is true in an SMTP session if the session is encrypted, and a
29508 certificate was received from the client, and the certificate was verified. The
29509 server requests a certificate only if the client matches &%tls_verify_hosts%&
29510 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
29512 .vitem &*verify&~=&~csa*&
29513 .cindex "CSA verification"
29514 This condition checks whether the sending host (the client) is authorized to
29515 send email. Details of how this works are given in section
29516 &<<SECTverifyCSA>>&.
29518 .vitem &*verify&~=&~header_names_ascii*&
29519 .cindex "&%verify%& ACL condition"
29520 .cindex "&ACL;" "verifying header names only ASCII"
29521 .cindex "header lines" "verifying header names only ASCII"
29522 .cindex "verifying" "header names only ASCII"
29523 This condition is relevant only in an ACL that is run after a message has been
29524 received, that is, in an ACL specified by &%acl_smtp_data%& or
29525 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
29526 there are no non-ASCII characters, also excluding control characters. The
29527 allowable characters are decimal ASCII values 33 through 126.
29529 Exim itself will handle headers with non-ASCII characters, but it can cause
29530 problems for downstream applications, so this option will allow their
29531 detection and rejection in the DATA ACL's.
29533 .vitem &*verify&~=&~header_sender/*&<&'options'&>
29534 .cindex "&%verify%& ACL condition"
29535 .cindex "&ACL;" "verifying sender in the header"
29536 .cindex "header lines" "verifying the sender in"
29537 .cindex "sender" "verifying in header"
29538 .cindex "verifying" "sender in header"
29539 This condition is relevant only in an ACL that is run after a message has been
29540 received, that is, in an ACL specified by &%acl_smtp_data%& or
29541 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
29542 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
29543 is loosely thought of as a &"sender"& address (hence the name of the test).
29544 However, an address that appears in one of these headers need not be an address
29545 that accepts bounce messages; only sender addresses in envelopes are required
29546 to accept bounces. Therefore, if you use the callout option on this check, you
29547 might want to arrange for a non-empty address in the MAIL command.
29549 Details of address verification and the options are given later, starting at
29550 section &<<SECTaddressverification>>& (callouts are described in section
29551 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
29552 condition to restrict it to bounce messages only:
29555 message = A valid sender header is required for bounces
29556 !verify = header_sender
29559 .vitem &*verify&~=&~header_syntax*&
29560 .cindex "&%verify%& ACL condition"
29561 .cindex "&ACL;" "verifying header syntax"
29562 .cindex "header lines" "verifying syntax"
29563 .cindex "verifying" "header syntax"
29564 This condition is relevant only in an ACL that is run after a message has been
29565 received, that is, in an ACL specified by &%acl_smtp_data%& or
29566 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
29567 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
29568 and &'Bcc:'&), returning true if there are no problems.
29569 Unqualified addresses (local parts without domains) are
29570 permitted only in locally generated messages and from hosts that match
29571 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
29574 Note that this condition is a syntax check only. However, a common spamming
29575 ploy used to be to send syntactically invalid headers such as
29579 and this condition can be used to reject such messages, though they are not as
29580 common as they used to be.
29582 .vitem &*verify&~=&~helo*&
29583 .cindex "&%verify%& ACL condition"
29584 .cindex "&ACL;" "verifying HELO/EHLO"
29585 .cindex "HELO" "verifying"
29586 .cindex "EHLO" "verifying"
29587 .cindex "verifying" "EHLO"
29588 .cindex "verifying" "HELO"
29589 This condition is true if a HELO or EHLO command has been received from the
29590 client host, and its contents have been verified. If there has been no previous
29591 attempt to verify the HELO/EHLO contents, it is carried out when this
29592 condition is encountered. See the description of the &%helo_verify_hosts%& and
29593 &%helo_try_verify_hosts%& options for details of how to request verification
29594 independently of this condition.
29596 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
29597 option), this condition is always true.
29600 .vitem &*verify&~=&~not_blind*&
29601 .cindex "verifying" "not blind"
29602 .cindex "bcc recipients, verifying none"
29603 This condition checks that there are no blind (bcc) recipients in the message.
29604 Every envelope recipient must appear either in a &'To:'& header line or in a
29605 &'Cc:'& header line for this condition to be true. Local parts are checked
29606 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
29607 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
29608 used only in a DATA or non-SMTP ACL.
29610 There are, of course, many legitimate messages that make use of blind (bcc)
29611 recipients. This check should not be used on its own for blocking messages.
29614 .vitem &*verify&~=&~recipient/*&<&'options'&>
29615 .cindex "&%verify%& ACL condition"
29616 .cindex "&ACL;" "verifying recipient"
29617 .cindex "recipient" "verifying"
29618 .cindex "verifying" "recipient"
29619 .vindex "&$address_data$&"
29620 This condition is relevant only after a RCPT command. It verifies the current
29621 recipient. Details of address verification are given later, starting at section
29622 &<<SECTaddressverification>>&. After a recipient has been verified, the value
29623 of &$address_data$& is the last value that was set while routing the address.
29624 This applies even if the verification fails. When an address that is being
29625 verified is redirected to a single address, verification continues with the new
29626 address, and in that case, the subsequent value of &$address_data$& is the
29627 value for the child address.
29629 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
29630 .cindex "&%verify%& ACL condition"
29631 .cindex "&ACL;" "verifying host reverse lookup"
29632 .cindex "host" "verifying reverse lookup"
29633 This condition ensures that a verified host name has been looked up from the IP
29634 address of the client host. (This may have happened already if the host name
29635 was needed for checking a host list, or if the host matched &%host_lookup%&.)
29636 Verification ensures that the host name obtained from a reverse DNS lookup, or
29637 one of its aliases, does, when it is itself looked up in the DNS, yield the
29638 original IP address.
29640 There is one possible option, &`defer_ok`&. If this is present and a
29641 DNS operation returns a temporary error, the verify condition succeeds.
29643 If this condition is used for a locally generated message (that is, when there
29644 is no client host involved), it always succeeds.
29646 .vitem &*verify&~=&~sender/*&<&'options'&>
29647 .cindex "&%verify%& ACL condition"
29648 .cindex "&ACL;" "verifying sender"
29649 .cindex "sender" "verifying"
29650 .cindex "verifying" "sender"
29651 This condition is relevant only after a MAIL or RCPT command, or after a
29652 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
29653 the message's sender is empty (that is, this is a bounce message), the
29654 condition is true. Otherwise, the sender address is verified.
29656 .vindex "&$address_data$&"
29657 .vindex "&$sender_address_data$&"
29658 If there is data in the &$address_data$& variable at the end of routing, its
29659 value is placed in &$sender_address_data$& at the end of verification. This
29660 value can be used in subsequent conditions and modifiers in the same ACL
29661 statement. It does not persist after the end of the current statement. If you
29662 want to preserve the value for longer, you can save it in an ACL variable.
29664 Details of verification are given later, starting at section
29665 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
29666 to avoid doing it more than once per message.
29668 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
29669 .cindex "&%verify%& ACL condition"
29670 This is a variation of the previous option, in which a modified address is
29671 verified as a sender.
29676 .section "Using DNS lists" "SECTmorednslists"
29677 .cindex "DNS list" "in ACL"
29678 .cindex "black list (DNS)"
29679 .cindex "&ACL;" "testing a DNS list"
29680 In its simplest form, the &%dnslists%& condition tests whether the calling host
29681 is on at least one of a number of DNS lists by looking up the inverted IP
29682 address in one or more DNS domains. (Note that DNS list domains are not mail
29683 domains, so the &`+`& syntax for named lists doesn't work - it is used for
29684 special options instead.) For example, if the calling host's IP
29685 address is 192.168.62.43, and the ACL statement is
29687 deny dnslists = blackholes.mail-abuse.org : \
29688 dialups.mail-abuse.org
29690 the following records are looked up:
29692 43.62.168.192.blackholes.mail-abuse.org
29693 43.62.168.192.dialups.mail-abuse.org
29695 As soon as Exim finds an existing DNS record, processing of the list stops.
29696 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
29697 to test that a host is on more than one list (an &"and"& conjunction), you can
29698 use two separate conditions:
29700 deny dnslists = blackholes.mail-abuse.org
29701 dnslists = dialups.mail-abuse.org
29703 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
29704 behaves as if the host does not match the list item, that is, as if the DNS
29705 record does not exist. If there are further items in the DNS list, they are
29708 This is usually the required action when &%dnslists%& is used with &%deny%&
29709 (which is the most common usage), because it prevents a DNS failure from
29710 blocking mail. However, you can change this behaviour by putting one of the
29711 following special items in the list:
29713 &`+include_unknown `& behave as if the item is on the list
29714 &`+exclude_unknown `& behave as if the item is not on the list (default)
29715 &`+defer_unknown `& give a temporary error
29717 .cindex "&`+include_unknown`&"
29718 .cindex "&`+exclude_unknown`&"
29719 .cindex "&`+defer_unknown`&"
29720 Each of these applies to any subsequent items on the list. For example:
29722 deny dnslists = +defer_unknown : foo.bar.example
29724 Testing the list of domains stops as soon as a match is found. If you want to
29725 warn for one list and block for another, you can use two different statements:
29727 deny dnslists = blackholes.mail-abuse.org
29728 warn message = X-Warn: sending host is on dialups list
29729 dnslists = dialups.mail-abuse.org
29731 .cindex cacheing "of dns lookup"
29733 DNS list lookups are cached by Exim for the duration of the SMTP session
29734 (but limited by the DNS return TTL value),
29735 so a lookup based on the IP address is done at most once for any incoming
29736 connection (assuming long-enough TTL).
29737 Exim does not share information between multiple incoming
29738 connections (but your local name server cache should be active).
29742 .section "Specifying the IP address for a DNS list lookup" "SECID201"
29743 .cindex "DNS list" "keyed by explicit IP address"
29744 By default, the IP address that is used in a DNS list lookup is the IP address
29745 of the calling host. However, you can specify another IP address by listing it
29746 after the domain name, introduced by a slash. For example:
29748 deny dnslists = black.list.tld/192.168.1.2
29750 This feature is not very helpful with explicit IP addresses; it is intended for
29751 use with IP addresses that are looked up, for example, the IP addresses of the
29752 MX hosts or nameservers of an email sender address. For an example, see section
29753 &<<SECTmulkeyfor>>& below.
29758 .section "DNS lists keyed on domain names" "SECID202"
29759 .cindex "DNS list" "keyed by domain name"
29760 There are some lists that are keyed on domain names rather than inverted IP
29761 addresses (see for example the &'domain based zones'& link at
29762 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
29763 with these lists. You can change the name that is looked up in a DNS list by
29764 listing it after the domain name, introduced by a slash. For example,
29766 deny message = Sender's domain is listed at $dnslist_domain
29767 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
29769 This particular example is useful only in ACLs that are obeyed after the
29770 RCPT or DATA commands, when a sender address is available. If (for
29771 example) the message's sender is &'user@tld.example'& the name that is looked
29772 up by this example is
29774 tld.example.dsn.rfc-ignorant.org
29776 A single &%dnslists%& condition can contain entries for both names and IP
29777 addresses. For example:
29779 deny dnslists = sbl.spamhaus.org : \
29780 dsn.rfc-ignorant.org/$sender_address_domain
29782 The first item checks the sending host's IP address; the second checks a domain
29783 name. The whole condition is true if either of the DNS lookups succeeds.
29788 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
29789 .cindex "DNS list" "multiple keys for"
29790 The syntax described above for looking up explicitly-defined values (either
29791 names or IP addresses) in a DNS blacklist is a simplification. After the domain
29792 name for the DNS list, what follows the slash can in fact be a list of items.
29793 As with all lists in Exim, the default separator is a colon. However, because
29794 this is a sublist within the list of DNS blacklist domains, it is necessary
29795 either to double the separators like this:
29797 dnslists = black.list.tld/name.1::name.2
29799 or to change the separator character, like this:
29801 dnslists = black.list.tld/<;name.1;name.2
29803 If an item in the list is an IP address, it is inverted before the DNS
29804 blacklist domain is appended. If it is not an IP address, no inversion
29805 occurs. Consider this condition:
29807 dnslists = black.list.tld/<;192.168.1.2;a.domain
29809 The DNS lookups that occur are:
29811 2.1.168.192.black.list.tld
29812 a.domain.black.list.tld
29814 Once a DNS record has been found (that matches a specific IP return
29815 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
29816 are done. If there is a temporary DNS error, the rest of the sublist of domains
29817 or IP addresses is tried. A temporary error for the whole dnslists item occurs
29818 only if no other DNS lookup in this sublist succeeds. In other words, a
29819 successful lookup for any of the items in the sublist overrides a temporary
29820 error for a previous item.
29822 The ability to supply a list of items after the slash is in some sense just a
29823 syntactic convenience. These two examples have the same effect:
29825 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
29826 dnslists = black.list.tld/a.domain::b.domain
29828 However, when the data for the list is obtained from a lookup, the second form
29829 is usually much more convenient. Consider this example:
29831 deny message = The mail servers for the domain \
29832 $sender_address_domain \
29833 are listed at $dnslist_domain ($dnslist_value); \
29835 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
29836 ${lookup dnsdb {>|mxh=\
29837 $sender_address_domain} }} }
29839 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
29840 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
29841 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
29842 of expanding the condition might be something like this:
29844 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
29846 Thus, this example checks whether or not the IP addresses of the sender
29847 domain's mail servers are on the Spamhaus black list.
29849 The key that was used for a successful DNS list lookup is put into the variable
29850 &$dnslist_matched$& (see section &<<SECID204>>&).
29855 .section "Data returned by DNS lists" "SECID203"
29856 .cindex "DNS list" "data returned from"
29857 DNS lists are constructed using address records in the DNS. The original RBL
29858 just used the address 127.0.0.1 on the right hand side of each record, but the
29859 RBL+ list and some other lists use a number of values with different meanings.
29860 The values used on the RBL+ list are:
29864 127.1.0.3 DUL and RBL
29866 127.1.0.5 RSS and RBL
29867 127.1.0.6 RSS and DUL
29868 127.1.0.7 RSS and DUL and RBL
29870 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
29871 different values. Some DNS lists may return more than one address record;
29872 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
29875 .section "Variables set from DNS lists" "SECID204"
29876 .cindex "expansion" "variables, set from DNS list"
29877 .cindex "DNS list" "variables set from"
29878 .vindex "&$dnslist_domain$&"
29879 .vindex "&$dnslist_matched$&"
29880 .vindex "&$dnslist_text$&"
29881 .vindex "&$dnslist_value$&"
29882 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
29883 the name of the overall domain that matched (for example,
29884 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
29885 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
29886 the DNS record. When the key is an IP address, it is not reversed in
29887 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
29888 cases, for example:
29890 deny dnslists = spamhaus.example
29892 the key is also available in another variable (in this case,
29893 &$sender_host_address$&). In more complicated cases, however, this is not true.
29894 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
29895 might generate a dnslists lookup like this:
29897 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
29899 If this condition succeeds, the value in &$dnslist_matched$& might be
29900 &`192.168.6.7`& (for example).
29902 If more than one address record is returned by the DNS lookup, all the IP
29903 addresses are included in &$dnslist_value$&, separated by commas and spaces.
29904 The variable &$dnslist_text$& contains the contents of any associated TXT
29905 record. For lists such as RBL+ the TXT record for a merged entry is often not
29906 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
29909 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
29910 &-- although these appear before the condition in the ACL, they are not
29911 expanded until after it has failed. For example:
29913 deny hosts = !+local_networks
29914 message = $sender_host_address is listed \
29916 dnslists = rbl-plus.mail-abuse.example
29921 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
29922 .cindex "DNS list" "matching specific returned data"
29923 You can add an equals sign and an IP address after a &%dnslists%& domain name
29924 in order to restrict its action to DNS records with a matching right hand side.
29927 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
29929 rejects only those hosts that yield 127.0.0.2. Without this additional data,
29930 any address record is considered to be a match. For the moment, we assume
29931 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
29932 describes how multiple records are handled.
29934 More than one IP address may be given for checking, using a comma as a
29935 separator. These are alternatives &-- if any one of them matches, the
29936 &%dnslists%& condition is true. For example:
29938 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29940 If you want to specify a constraining address list and also specify names or IP
29941 addresses to be looked up, the constraining address list must be specified
29942 first. For example:
29944 deny dnslists = dsn.rfc-ignorant.org\
29945 =127.0.0.2/$sender_address_domain
29948 If the character &`&&`& is used instead of &`=`&, the comparison for each
29949 listed IP address is done by a bitwise &"and"& instead of by an equality test.
29950 In other words, the listed addresses are used as bit masks. The comparison is
29951 true if all the bits in the mask are present in the address that is being
29952 tested. For example:
29954 dnslists = a.b.c&0.0.0.3
29956 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
29957 want to test whether one bit or another bit is present (as opposed to both
29958 being present), you must use multiple values. For example:
29960 dnslists = a.b.c&0.0.0.1,0.0.0.2
29962 matches if the final component of the address is an odd number or two times
29967 .section "Negated DNS matching conditions" "SECID205"
29968 You can supply a negative list of IP addresses as part of a &%dnslists%&
29971 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29973 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29974 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
29976 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
29978 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29979 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
29980 words, the result of the test is inverted if an exclamation mark appears before
29981 the &`=`& (or the &`&&`&) sign.
29983 &*Note*&: This kind of negation is not the same as negation in a domain,
29984 host, or address list (which is why the syntax is different).
29986 If you are using just one list, the negation syntax does not gain you much. The
29987 previous example is precisely equivalent to
29989 deny dnslists = a.b.c
29990 !dnslists = a.b.c=127.0.0.2,127.0.0.3
29992 However, if you are using multiple lists, the negation syntax is clearer.
29993 Consider this example:
29995 deny dnslists = sbl.spamhaus.org : \
29997 dnsbl.njabl.org!=127.0.0.3 : \
30000 Using only positive lists, this would have to be:
30002 deny dnslists = sbl.spamhaus.org : \
30004 deny dnslists = dnsbl.njabl.org
30005 !dnslists = dnsbl.njabl.org=127.0.0.3
30006 deny dnslists = relays.ordb.org
30008 which is less clear, and harder to maintain.
30013 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
30014 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
30015 thereby providing more than one IP address. When an item in a &%dnslists%& list
30016 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
30017 the match to specific results from the DNS lookup, there are two ways in which
30018 the checking can be handled. For example, consider the condition:
30020 dnslists = a.b.c=127.0.0.1
30022 What happens if the DNS lookup for the incoming IP address yields both
30023 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
30024 condition true because at least one given value was found, or is it false
30025 because at least one of the found values was not listed? And how does this
30026 affect negated conditions? Both possibilities are provided for with the help of
30027 additional separators &`==`& and &`=&&`&.
30030 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
30031 IP addresses matches one of the listed addresses. For the example above, the
30032 condition is true because 127.0.0.1 matches.
30034 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
30035 looked up IP addresses matches one of the listed addresses. If the condition is
30038 dnslists = a.b.c==127.0.0.1
30040 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30041 false because 127.0.0.2 is not listed. You would need to have:
30043 dnslists = a.b.c==127.0.0.1,127.0.0.2
30045 for the condition to be true.
30048 When &`!`& is used to negate IP address matching, it inverts the result, giving
30049 the precise opposite of the behaviour above. Thus:
30051 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
30052 addresses matches one of the listed addresses. Consider:
30054 dnslists = a.b.c!&0.0.0.1
30056 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30057 false because 127.0.0.1 matches.
30059 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
30060 looked up IP address that does not match. Consider:
30062 dnslists = a.b.c!=&0.0.0.1
30064 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30065 true, because 127.0.0.2 does not match. You would need to have:
30067 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
30069 for the condition to be false.
30071 When the DNS lookup yields only a single IP address, there is no difference
30072 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
30077 .section "Detailed information from merged DNS lists" "SECTmordetinf"
30078 .cindex "DNS list" "information from merged"
30079 When the facility for restricting the matching IP values in a DNS list is used,
30080 the text from the TXT record that is set in &$dnslist_text$& may not reflect
30081 the true reason for rejection. This happens when lists are merged and the IP
30082 address in the A record is used to distinguish them; unfortunately there is
30083 only one TXT record. One way round this is not to use merged lists, but that
30084 can be inefficient because it requires multiple DNS lookups where one would do
30085 in the vast majority of cases when the host of interest is not on any of the
30088 A less inefficient way of solving this problem is available. If
30089 two domain names, comma-separated, are given, the second is used first to
30090 do an initial check, making use of any IP value restrictions that are set.
30091 If there is a match, the first domain is used, without any IP value
30092 restrictions, to get the TXT record. As a byproduct of this, there is also
30093 a check that the IP being tested is indeed on the first list. The first
30094 domain is the one that is put in &$dnslist_domain$&. For example:
30097 rejected because $sender_host_address is blacklisted \
30098 at $dnslist_domain\n$dnslist_text
30100 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
30101 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
30103 For the first blacklist item, this starts by doing a lookup in
30104 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
30105 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
30106 value, and as long as something is found, it looks for the corresponding TXT
30107 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
30108 The second blacklist item is processed similarly.
30110 If you are interested in more than one merged list, the same list must be
30111 given several times, but because the results of the DNS lookups are cached,
30112 the DNS calls themselves are not repeated. For example:
30114 reject dnslists = \
30115 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
30116 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
30117 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
30118 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
30120 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
30121 values matches (or if no record is found), this is the only lookup that is
30122 done. Only if there is a match is one of the more specific lists consulted.
30126 .section "DNS lists and IPv6" "SECTmorednslistslast"
30127 .cindex "IPv6" "DNS black lists"
30128 .cindex "DNS list" "IPv6 usage"
30129 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
30130 nibble by nibble. For example, if the calling host's IP address is
30131 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
30133 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
30134 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
30136 (split over two lines here to fit on the page). Unfortunately, some of the DNS
30137 lists contain wildcard records, intended for IPv4, that interact badly with
30138 IPv6. For example, the DNS entry
30140 *.3.some.list.example. A 127.0.0.1
30142 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
30143 Unfortunately, it also matches the entire 3::/4 IPv6 network.
30145 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
30146 &%condition%& condition, as in this example:
30148 deny condition = ${if isip4{$sender_host_address}}
30149 dnslists = some.list.example
30152 If an explicit key is being used for a DNS lookup and it may be an IPv6
30153 address you should specify alternate list separators for both the outer
30154 (DNS list name) list and inner (lookup keys) list:
30156 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
30159 .section "Rate limiting incoming messages" "SECTratelimiting"
30160 .cindex "rate limiting" "client sending"
30161 .cindex "limiting client sending rates"
30162 .oindex "&%smtp_ratelimit_*%&"
30163 The &%ratelimit%& ACL condition can be used to measure and control the rate at
30164 which clients can send email. This is more powerful than the
30165 &%smtp_ratelimit_*%& options, because those options control the rate of
30166 commands in a single SMTP session only, whereas the &%ratelimit%& condition
30167 works across all connections (concurrent and sequential) from the same client
30168 host. The syntax of the &%ratelimit%& condition is:
30170 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
30172 If the average client sending rate is less than &'m'& messages per time
30173 period &'p'& then the condition is false; otherwise it is true.
30175 As a side-effect, the &%ratelimit%& condition sets the expansion variable
30176 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
30177 configured value of &'m'&, and &$sender_rate_period$& to the configured value
30180 The parameter &'p'& is the smoothing time constant, in the form of an Exim
30181 time interval, for example, &`8h`& for eight hours. A larger time constant
30182 means that it takes Exim longer to forget a client's past behaviour. The
30183 parameter &'m'& is the maximum number of messages that a client is permitted to
30184 send in each time interval. It also specifies the number of messages permitted
30185 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
30186 constant, you can allow a client to send more messages in a burst without
30187 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
30188 both small, messages must be sent at an even rate.
30190 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
30191 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
30192 when deploying the &%ratelimit%& ACL condition. The script prints usage
30193 instructions when it is run with no arguments.
30195 The key is used to look up the data for calculating the client's average
30196 sending rate. This data is stored in Exim's spool directory, alongside the
30197 retry and other hints databases. The default key is &$sender_host_address$&,
30198 which means Exim computes the sending rate of each client host IP address.
30199 By changing the key you can change how Exim identifies clients for the purpose
30200 of ratelimiting. For example, to limit the sending rate of each authenticated
30201 user, independent of the computer they are sending from, set the key to
30202 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
30203 example, &$authenticated_id$& is only meaningful if the client has
30204 authenticated (which you can check with the &%authenticated%& ACL condition).
30206 The lookup key does not have to identify clients: If you want to limit the
30207 rate at which a recipient receives messages, you can use the key
30208 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
30211 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
30212 specifies what Exim measures the rate of, for example messages or recipients
30213 or bytes. You can adjust the measurement using the &%unique=%& and/or
30214 &%count=%& options. You can also control when Exim updates the recorded rate
30215 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
30216 separated by a slash, like the other parameters. They may appear in any order.
30218 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
30219 any options that alter the meaning of the stored data. The limit &'m'& is not
30220 stored, so you can alter the configured maximum rate and Exim will still
30221 remember clients' past behaviour. If you change the &%per_*%& mode or add or
30222 remove the &%unique=%& option, the lookup key changes so Exim will forget past
30223 behaviour. The lookup key is not affected by changes to the update mode and
30224 the &%count=%& option.
30227 .section "Ratelimit options for what is being measured" "ratoptmea"
30228 .cindex "rate limiting" "per_* options"
30229 The &%per_conn%& option limits the client's connection rate. It is not
30230 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
30231 &%acl_not_smtp_start%& ACLs.
30233 The &%per_mail%& option limits the client's rate of sending messages. This is
30234 the default if none of the &%per_*%& options is specified. It can be used in
30235 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
30236 &%acl_smtp_data%&, or &%acl_not_smtp%&.
30238 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
30239 the same ACLs as the &%per_mail%& option, though it is best to use this option
30240 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
30241 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
30242 in its MAIL command, which may be inaccurate or completely missing. You can
30243 follow the limit &'m'& in the configuration with K, M, or G to specify limits
30244 in kilobytes, megabytes, or gigabytes, respectively.
30246 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
30247 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
30248 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
30249 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
30250 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
30251 in either case the rate limiting engine will see a message with many
30252 recipients as a large high-speed burst.
30254 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
30255 number of different recipients that the client has sent messages to in the
30256 last time period. That is, if the client repeatedly sends messages to the same
30257 recipient, its measured rate is not increased. This option can only be used in
30260 The &%per_cmd%& option causes Exim to recompute the rate every time the
30261 condition is processed. This can be used to limit the rate of any SMTP
30262 command. If it is used in multiple ACLs it can limit the aggregate rate of
30263 multiple different commands.
30265 The &%count=%& option can be used to alter how much Exim adds to the client's
30266 measured rate. For example, the &%per_byte%& option is equivalent to
30267 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
30268 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
30269 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
30271 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
30274 .section "Ratelimit update modes" "ratoptupd"
30275 .cindex "rate limiting" "reading data without updating"
30276 You can specify one of three options with the &%ratelimit%& condition to
30277 control when its database is updated. This section describes the &%readonly%&
30278 mode, and the next section describes the &%strict%& and &%leaky%& modes.
30280 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
30281 previously-computed rate to check against the limit.
30283 For example, you can test the client's sending rate and deny it access (when
30284 it is too fast) in the connect ACL. If the client passes this check then it
30285 can go on to send a message, in which case its recorded rate will be updated
30286 in the MAIL ACL. Subsequent connections from the same client will check this
30290 deny ratelimit = 100 / 5m / readonly
30291 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
30292 (max $sender_rate_limit)
30295 warn ratelimit = 100 / 5m / strict
30296 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
30297 (max $sender_rate_limit)
30300 If Exim encounters multiple &%ratelimit%& conditions with the same key when
30301 processing a message then it may increase the client's measured rate more than
30302 it should. For example, this will happen if you check the &%per_rcpt%& option
30303 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
30304 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
30305 multiple update problems by using the &%readonly%& option on later ratelimit
30308 The &%per_*%& options described above do not make sense in some ACLs. If you
30309 use a &%per_*%& option in an ACL where it is not normally permitted then the
30310 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
30311 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
30312 next section) so you must specify the &%readonly%& option explicitly.
30315 .section "Ratelimit options for handling fast clients" "ratoptfast"
30316 .cindex "rate limiting" "strict and leaky modes"
30317 If a client's average rate is greater than the maximum, the rate limiting
30318 engine can react in two possible ways, depending on the presence of the
30319 &%strict%& or &%leaky%& update modes. This is independent of the other
30320 counter-measures (such as rejecting the message) that may be specified by the
30323 The &%leaky%& (default) option means that the client's recorded rate is not
30324 updated if it is above the limit. The effect of this is that Exim measures the
30325 client's average rate of successfully sent email, which cannot be greater than
30326 the maximum allowed. If the client is over the limit it may suffer some
30327 counter-measures (as specified in the ACL), but it will still be able to send
30328 email at the configured maximum rate, whatever the rate of its attempts. This
30329 is generally the better choice if you have clients that retry automatically.
30330 For example, it does not prevent a sender with an over-aggressive retry rate
30331 from getting any email through.
30333 The &%strict%& option means that the client's recorded rate is always
30334 updated. The effect of this is that Exim measures the client's average rate
30335 of attempts to send email, which can be much higher than the maximum it is
30336 actually allowed. If the client is over the limit it may be subjected to
30337 counter-measures by the ACL. It must slow down and allow sufficient time to
30338 pass that its computed rate falls below the maximum before it can send email
30339 again. The time (the number of smoothing periods) it must wait and not
30340 attempt to send mail can be calculated with this formula:
30342 ln(peakrate/maxrate)
30346 .section "Limiting the rate of different events" "ratoptuniq"
30347 .cindex "rate limiting" "counting unique events"
30348 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
30349 rate of different events. For example, the &%per_addr%& option uses this
30350 mechanism to count the number of different recipients that the client has
30351 sent messages to in the last time period; it is equivalent to
30352 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
30353 measure the rate that a client uses different sender addresses with the
30354 options &`per_mail/unique=$sender_address`&.
30356 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
30357 has seen for that key. The whole set is thrown away when it is older than the
30358 rate smoothing period &'p'&, so each different event is counted at most once
30359 per period. In the &%leaky%& update mode, an event that causes the client to
30360 go over the limit is not added to the set, in the same way that the client's
30361 recorded rate is not updated in the same situation.
30363 When you combine the &%unique=%& and &%readonly%& options, the specific
30364 &%unique=%& value is ignored, and Exim just retrieves the client's stored
30367 The &%unique=%& mechanism needs more space in the ratelimit database than the
30368 other &%ratelimit%& options in order to store the event set. The number of
30369 unique values is potentially as large as the rate limit, so the extra space
30370 required increases with larger limits.
30372 The uniqueification is not perfect: there is a small probability that Exim
30373 will think a new event has happened before. If the sender's rate is less than
30374 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
30375 the measured rate can go above the limit, in which case Exim may under-count
30376 events by a significant margin. Fortunately, if the rate is high enough (2.7
30377 times the limit) that the false positive rate goes above 9%, then Exim will
30378 throw away the over-full event set before the measured rate falls below the
30379 limit. Therefore the only harm should be that exceptionally high sending rates
30380 are logged incorrectly; any countermeasures you configure will be as effective
30384 .section "Using rate limiting" "useratlim"
30385 Exim's other ACL facilities are used to define what counter-measures are taken
30386 when the rate limit is exceeded. This might be anything from logging a warning
30387 (for example, while measuring existing sending rates in order to define
30388 policy), through time delays to slow down fast senders, up to rejecting the
30389 message. For example:
30391 # Log all senders' rates
30392 warn ratelimit = 0 / 1h / strict
30393 log_message = Sender rate $sender_rate / $sender_rate_period
30395 # Slow down fast senders; note the need to truncate $sender_rate
30396 # at the decimal point.
30397 warn ratelimit = 100 / 1h / per_rcpt / strict
30398 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
30399 $sender_rate_limit }s
30401 # Keep authenticated users under control
30402 deny authenticated = *
30403 ratelimit = 100 / 1d / strict / $authenticated_id
30405 # System-wide rate limit
30406 defer message = Sorry, too busy. Try again later.
30407 ratelimit = 10 / 1s / $primary_hostname
30409 # Restrict incoming rate from each host, with a default
30410 # set using a macro and special cases looked up in a table.
30411 defer message = Sender rate exceeds $sender_rate_limit \
30412 messages per $sender_rate_period
30413 ratelimit = ${lookup {$sender_host_address} \
30414 cdb {DB/ratelimits.cdb} \
30415 {$value} {RATELIMIT} }
30417 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
30418 especially with the &%per_rcpt%& option, you may suffer from a performance
30419 bottleneck caused by locking on the ratelimit hints database. Apart from
30420 making your ACLs less complicated, you can reduce the problem by using a
30421 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
30422 this means that Exim will lose its hints data after a reboot (including retry
30423 hints, the callout cache, and ratelimit data).
30427 .section "Address verification" "SECTaddressverification"
30428 .cindex "verifying address" "options for"
30429 .cindex "policy control" "address verification"
30430 Several of the &%verify%& conditions described in section
30431 &<<SECTaclconditions>>& cause addresses to be verified. Section
30432 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
30433 The verification conditions can be followed by options that modify the
30434 verification process. The options are separated from the keyword and from each
30435 other by slashes, and some of them contain parameters. For example:
30437 verify = sender/callout
30438 verify = recipient/defer_ok/callout=10s,defer_ok
30440 The first stage of address verification, which always happens, is to run the
30441 address through the routers, in &"verify mode"&. Routers can detect the
30442 difference between verification and routing for delivery, and their actions can
30443 be varied by a number of generic options such as &%verify%& and &%verify_only%&
30444 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
30445 The available options are as follows:
30448 If the &%callout%& option is specified, successful routing to one or more
30449 remote hosts is followed by a &"callout"& to those hosts as an additional
30450 check. Callouts and their sub-options are discussed in the next section.
30452 If there is a defer error while doing verification routing, the ACL
30453 normally returns &"defer"&. However, if you include &%defer_ok%& in the
30454 options, the condition is forced to be true instead. Note that this is a main
30455 verification option as well as a suboption for callouts.
30457 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
30458 discusses the reporting of sender address verification failures.
30460 The &%success_on_redirect%& option causes verification always to succeed
30461 immediately after a successful redirection. By default, if a redirection
30462 generates just one address, that address is also verified. See further
30463 discussion in section &<<SECTredirwhilveri>>&.
30466 .cindex "verifying address" "differentiating failures"
30467 .vindex "&$recipient_verify_failure$&"
30468 .vindex "&$sender_verify_failure$&"
30469 .vindex "&$acl_verify_message$&"
30470 After an address verification failure, &$acl_verify_message$& contains the
30471 error message that is associated with the failure. It can be preserved by
30474 warn !verify = sender
30475 set acl_m0 = $acl_verify_message
30477 If you are writing your own custom rejection message or log message when
30478 denying access, you can use this variable to include information about the
30479 verification failure.
30481 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
30482 appropriate) contains one of the following words:
30485 &%qualify%&: The address was unqualified (no domain), and the message
30486 was neither local nor came from an exempted host.
30488 &%route%&: Routing failed.
30490 &%mail%&: Routing succeeded, and a callout was attempted; rejection
30491 occurred at or before the MAIL command (that is, on initial
30492 connection, HELO, or MAIL).
30494 &%recipient%&: The RCPT command in a callout was rejected.
30496 &%postmaster%&: The postmaster check in a callout was rejected.
30499 The main use of these variables is expected to be to distinguish between
30500 rejections of MAIL and rejections of RCPT in callouts.
30505 .section "Callout verification" "SECTcallver"
30506 .cindex "verifying address" "by callout"
30507 .cindex "callout" "verification"
30508 .cindex "SMTP" "callout verification"
30509 For non-local addresses, routing verifies the domain, but is unable to do any
30510 checking of the local part. There are situations where some means of verifying
30511 the local part is desirable. One way this can be done is to make an SMTP
30512 &'callback'& to a delivery host for the sender address or a &'callforward'& to
30513 a subsequent host for a recipient address, to see if the host accepts the
30514 address. We use the term &'callout'& to cover both cases. Note that for a
30515 sender address, the callback is not to the client host that is trying to
30516 deliver the message, but to one of the hosts that accepts incoming mail for the
30519 Exim does not do callouts by default. If you want them to happen, you must
30520 request them by setting appropriate options on the &%verify%& condition, as
30521 described below. This facility should be used with care, because it can add a
30522 lot of resource usage to the cost of verifying an address. However, Exim does
30523 cache the results of callouts, which helps to reduce the cost. Details of
30524 caching are in section &<<SECTcallvercache>>&.
30526 Recipient callouts are usually used only between hosts that are controlled by
30527 the same administration. For example, a corporate gateway host could use
30528 callouts to check for valid recipients on an internal mailserver. A successful
30529 callout does not guarantee that a real delivery to the address would succeed;
30530 on the other hand, a failing callout does guarantee that a delivery would fail.
30532 If the &%callout%& option is present on a condition that verifies an address, a
30533 second stage of verification occurs if the address is successfully routed to
30534 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
30535 &(manualroute)& router, where the router specifies the hosts. However, if a
30536 router that does not set up hosts routes to an &(smtp)& transport with a
30537 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
30538 &%hosts_override%& set, its hosts are always used, whether or not the router
30539 supplies a host list.
30540 Callouts are only supported on &(smtp)& transports.
30542 The port that is used is taken from the transport, if it is specified and is a
30543 remote transport. (For routers that do verification only, no transport need be
30544 specified.) Otherwise, the default SMTP port is used. If a remote transport
30545 specifies an outgoing interface, this is used; otherwise the interface is not
30546 specified. Likewise, the text that is used for the HELO command is taken from
30547 the transport's &%helo_data%& option; if there is no transport, the value of
30548 &$smtp_active_hostname$& is used.
30550 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
30551 test whether a bounce message could be delivered to the sender address. The
30552 following SMTP commands are sent:
30554 &`HELO `&<&'local host name'&>
30556 &`RCPT TO:`&<&'the address to be tested'&>
30559 LHLO is used instead of HELO if the transport's &%protocol%& option is
30562 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
30565 A recipient callout check is similar. By default, it also uses an empty address
30566 for the sender. This default is chosen because most hosts do not make use of
30567 the sender address when verifying a recipient. Using the same address means
30568 that a single cache entry can be used for each recipient. Some sites, however,
30569 do make use of the sender address when verifying. These are catered for by the
30570 &%use_sender%& and &%use_postmaster%& options, described in the next section.
30572 If the response to the RCPT command is a 2&'xx'& code, the verification
30573 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
30574 Exim tries the next host, if any. If there is a problem with all the remote
30575 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
30576 &%callout%& option is given, in which case the condition is forced to succeed.
30578 .cindex "SMTP" "output flushing, disabling for callout"
30579 A callout may take a little time. For this reason, Exim normally flushes SMTP
30580 output before performing a callout in an ACL, to avoid unexpected timeouts in
30581 clients when the SMTP PIPELINING extension is in use. The flushing can be
30582 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
30587 .section "Additional parameters for callouts" "CALLaddparcall"
30588 .cindex "callout" "additional parameters for"
30589 The &%callout%& option can be followed by an equals sign and a number of
30590 optional parameters, separated by commas. For example:
30592 verify = recipient/callout=10s,defer_ok
30594 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
30595 separate verify options, is retained for backwards compatibility, but is now
30596 deprecated. The additional parameters for &%callout%& are as follows:
30600 .vitem <&'a&~time&~interval'&>
30601 .cindex "callout" "timeout, specifying"
30602 This specifies the timeout that applies for the callout attempt to each host.
30605 verify = sender/callout=5s
30607 The default is 30 seconds. The timeout is used for each response from the
30608 remote host. It is also used for the initial connection, unless overridden by
30609 the &%connect%& parameter.
30612 .vitem &*connect&~=&~*&<&'time&~interval'&>
30613 .cindex "callout" "connection timeout, specifying"
30614 This parameter makes it possible to set a different (usually smaller) timeout
30615 for making the SMTP connection. For example:
30617 verify = sender/callout=5s,connect=1s
30619 If not specified, this timeout defaults to the general timeout value.
30621 .vitem &*defer_ok*&
30622 .cindex "callout" "defer, action on"
30623 When this parameter is present, failure to contact any host, or any other kind
30624 of temporary error, is treated as success by the ACL. However, the cache is not
30625 updated in this circumstance.
30627 .vitem &*fullpostmaster*&
30628 .cindex "callout" "full postmaster check"
30629 This operates like the &%postmaster%& option (see below), but if the check for
30630 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
30631 accordance with the specification in RFC 2821. The RFC states that the
30632 unqualified address &'postmaster'& should be accepted.
30635 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
30636 .cindex "callout" "sender when verifying header"
30637 When verifying addresses in header lines using the &%header_sender%&
30638 verification option, Exim behaves by default as if the addresses are envelope
30639 sender addresses from a message. Callout verification therefore tests to see
30640 whether a bounce message could be delivered, by using an empty address in the
30641 MAIL command. However, it is arguable that these addresses might never be used
30642 as envelope senders, and could therefore justifiably reject bounce messages
30643 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
30644 address to use in the MAIL command. For example:
30646 require verify = header_sender/callout=mailfrom=abcd@x.y.z
30648 This parameter is available only for the &%header_sender%& verification option.
30651 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
30652 .cindex "callout" "overall timeout, specifying"
30653 This parameter sets an overall timeout for performing a callout verification.
30656 verify = sender/callout=5s,maxwait=30s
30658 This timeout defaults to four times the callout timeout for individual SMTP
30659 commands. The overall timeout applies when there is more than one host that can
30660 be tried. The timeout is checked before trying the next host. This prevents
30661 very long delays if there are a large number of hosts and all are timing out
30662 (for example, when network connections are timing out).
30665 .vitem &*no_cache*&
30666 .cindex "callout" "cache, suppressing"
30667 .cindex "caching callout, suppressing"
30668 When this parameter is given, the callout cache is neither read nor updated.
30670 .vitem &*postmaster*&
30671 .cindex "callout" "postmaster; checking"
30672 When this parameter is set, a successful callout check is followed by a similar
30673 check for the local part &'postmaster'& at the same domain. If this address is
30674 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
30675 the postmaster check is recorded in a cache record; if it is a failure, this is
30676 used to fail subsequent callouts for the domain without a connection being
30677 made, until the cache record expires.
30679 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
30680 The postmaster check uses an empty sender in the MAIL command by default.
30681 You can use this parameter to do a postmaster check using a different address.
30684 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
30686 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
30687 one overrides. The &%postmaster%& parameter is equivalent to this example:
30689 require verify = sender/callout=postmaster_mailfrom=
30691 &*Warning*&: The caching arrangements for postmaster checking do not take
30692 account of the sender address. It is assumed that either the empty address or
30693 a fixed non-empty address will be used. All that Exim remembers is that the
30694 postmaster check for the domain succeeded or failed.
30698 .cindex "callout" "&""random""& check"
30699 When this parameter is set, before doing the normal callout check, Exim does a
30700 check for a &"random"& local part at the same domain. The local part is not
30701 really random &-- it is defined by the expansion of the option
30702 &%callout_random_local_part%&, which defaults to
30704 $primary_hostname-$tod_epoch-testing
30706 The idea here is to try to determine whether the remote host accepts all local
30707 parts without checking. If it does, there is no point in doing callouts for
30708 specific local parts. If the &"random"& check succeeds, the result is saved in
30709 a cache record, and used to force the current and subsequent callout checks to
30710 succeed without a connection being made, until the cache record expires.
30712 .vitem &*use_postmaster*&
30713 .cindex "callout" "sender for recipient check"
30714 This parameter applies to recipient callouts only. For example:
30716 deny !verify = recipient/callout=use_postmaster
30718 .vindex "&$qualify_domain$&"
30719 It causes a non-empty postmaster address to be used in the MAIL command when
30720 performing the callout for the recipient, and also for a &"random"& check if
30721 that is configured. The local part of the address is &`postmaster`& and the
30722 domain is the contents of &$qualify_domain$&.
30724 .vitem &*use_sender*&
30725 This option applies to recipient callouts only. For example:
30727 require verify = recipient/callout=use_sender
30729 It causes the message's actual sender address to be used in the MAIL
30730 command when performing the callout, instead of an empty address. There is no
30731 need to use this option unless you know that the called hosts make use of the
30732 sender when checking recipients. If used indiscriminately, it reduces the
30733 usefulness of callout caching.
30736 If you use any of the parameters that set a non-empty sender for the MAIL
30737 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
30738 &%use_sender%&), you should think about possible loops. Recipient checking is
30739 usually done between two hosts that are under the same management, and the host
30740 that receives the callouts is not normally configured to do callouts itself.
30741 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
30742 these circumstances.
30744 However, if you use a non-empty sender address for a callout to an arbitrary
30745 host, there is the likelihood that the remote host will itself initiate a
30746 callout check back to your host. As it is checking what appears to be a message
30747 sender, it is likely to use an empty address in MAIL, thus avoiding a
30748 callout loop. However, to be on the safe side it would be best to set up your
30749 own ACLs so that they do not do sender verification checks when the recipient
30750 is the address you use for header sender or postmaster callout checking.
30752 Another issue to think about when using non-empty senders for callouts is
30753 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
30754 by the sender/recipient combination; thus, for any given recipient, many more
30755 actual callouts are performed than when an empty sender or postmaster is used.
30760 .section "Callout caching" "SECTcallvercache"
30761 .cindex "hints database" "callout cache"
30762 .cindex "callout" "cache, description of"
30763 .cindex "caching" "callout"
30764 Exim caches the results of callouts in order to reduce the amount of resources
30765 used, unless you specify the &%no_cache%& parameter with the &%callout%&
30766 option. A hints database called &"callout"& is used for the cache. Two
30767 different record types are used: one records the result of a callout check for
30768 a specific address, and the other records information that applies to the
30769 entire domain (for example, that it accepts the local part &'postmaster'&).
30771 When an original callout fails, a detailed SMTP error message is given about
30772 the failure. However, for subsequent failures use the cache data, this message
30775 The expiry times for negative and positive address cache records are
30776 independent, and can be set by the global options &%callout_negative_expire%&
30777 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
30779 If a host gives a negative response to an SMTP connection, or rejects any
30780 commands up to and including
30784 (but not including the MAIL command with a non-empty address),
30785 any callout attempt is bound to fail. Exim remembers such failures in a
30786 domain cache record, which it uses to fail callouts for the domain without
30787 making new connections, until the domain record times out. There are two
30788 separate expiry times for domain cache records:
30789 &%callout_domain_negative_expire%& (default 3h) and
30790 &%callout_domain_positive_expire%& (default 7d).
30792 Domain records expire when the negative expiry time is reached if callouts
30793 cannot be made for the domain, or if the postmaster check failed.
30794 Otherwise, they expire when the positive expiry time is reached. This
30795 ensures that, for example, a host that stops accepting &"random"& local parts
30796 will eventually be noticed.
30798 The callout caching mechanism is based on the domain of the address that is
30799 being tested. If the domain routes to several hosts, it is assumed that their
30800 behaviour will be the same.
30804 .section "Sender address verification reporting" "SECTsenaddver"
30805 .cindex "verifying" "suppressing error details"
30806 See section &<<SECTaddressverification>>& for a general discussion of
30807 verification. When sender verification fails in an ACL, the details of the
30808 failure are given as additional output lines before the 550 response to the
30809 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
30812 MAIL FROM:<xyz@abc.example>
30814 RCPT TO:<pqr@def.example>
30815 550-Verification failed for <xyz@abc.example>
30816 550-Called: 192.168.34.43
30817 550-Sent: RCPT TO:<xyz@abc.example>
30818 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
30819 550 Sender verification failed
30821 If more than one RCPT command fails in the same way, the details are given
30822 only for the first of them. However, some administrators do not want to send
30823 out this much information. You can suppress the details by adding
30824 &`/no_details`& to the ACL statement that requests sender verification. For
30827 verify = sender/no_details
30830 .section "Redirection while verifying" "SECTredirwhilveri"
30831 .cindex "verifying" "redirection while"
30832 .cindex "address redirection" "while verifying"
30833 A dilemma arises when a local address is redirected by aliasing or forwarding
30834 during verification: should the generated addresses themselves be verified,
30835 or should the successful expansion of the original address be enough to verify
30836 it? By default, Exim takes the following pragmatic approach:
30839 When an incoming address is redirected to just one child address, verification
30840 continues with the child address, and if that fails to verify, the original
30841 verification also fails.
30843 When an incoming address is redirected to more than one child address,
30844 verification does not continue. A success result is returned.
30847 This seems the most reasonable behaviour for the common use of aliasing as a
30848 way of redirecting different local parts to the same mailbox. It means, for
30849 example, that a pair of alias entries of the form
30852 aw123: :fail: Gone away, no forwarding address
30854 work as expected, with both local parts causing verification failure. When a
30855 redirection generates more than one address, the behaviour is more like a
30856 mailing list, where the existence of the alias itself is sufficient for
30857 verification to succeed.
30859 It is possible, however, to change the default behaviour so that all successful
30860 redirections count as successful verifications, however many new addresses are
30861 generated. This is specified by the &%success_on_redirect%& verification
30862 option. For example:
30864 require verify = recipient/success_on_redirect/callout=10s
30866 In this example, verification succeeds if a router generates a new address, and
30867 the callout does not occur, because no address was routed to a remote host.
30869 When verification is being tested via the &%-bv%& option, the treatment of
30870 redirections is as just described, unless the &%-v%& or any debugging option is
30871 also specified. In that case, full verification is done for every generated
30872 address and a report is output for each of them.
30876 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
30877 .cindex "CSA" "verifying"
30878 Client SMTP Authorization is a system that allows a site to advertise
30879 which machines are and are not permitted to send email. This is done by placing
30880 special SRV records in the DNS; these are looked up using the client's HELO
30881 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
30882 Authorization checks in Exim are performed by the ACL condition:
30886 This fails if the client is not authorized. If there is a DNS problem, or if no
30887 valid CSA SRV record is found, or if the client is authorized, the condition
30888 succeeds. These three cases can be distinguished using the expansion variable
30889 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
30890 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
30891 be likely to cause problems for legitimate email.
30893 The error messages produced by the CSA code include slightly more
30894 detail. If &$csa_status$& is &"defer"&, this may be because of problems
30895 looking up the CSA SRV record, or problems looking up the CSA target
30896 address record. There are four reasons for &$csa_status$& being &"fail"&:
30899 The client's host name is explicitly not authorized.
30901 The client's IP address does not match any of the CSA target IP addresses.
30903 The client's host name is authorized but it has no valid target IP addresses
30904 (for example, the target's addresses are IPv6 and the client is using IPv4).
30906 The client's host name has no CSA SRV record but a parent domain has asserted
30907 that all subdomains must be explicitly authorized.
30910 The &%csa%& verification condition can take an argument which is the domain to
30911 use for the DNS query. The default is:
30913 verify = csa/$sender_helo_name
30915 This implementation includes an extension to CSA. If the query domain
30916 is an address literal such as [192.0.2.95], or if it is a bare IP
30917 address, Exim searches for CSA SRV records in the reverse DNS as if
30918 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
30921 verify = csa/$sender_host_address
30923 In fact, this is the check that Exim performs if the client does not say HELO.
30924 This extension can be turned off by setting the main configuration option
30925 &%dns_csa_use_reverse%& to be false.
30927 If a CSA SRV record is not found for the domain itself, a search
30928 is performed through its parent domains for a record which might be
30929 making assertions about subdomains. The maximum depth of this search is limited
30930 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
30931 default. Exim does not look for CSA SRV records in a top level domain, so the
30932 default settings handle HELO domains as long as seven
30933 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
30934 of legitimate HELO domains.
30936 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
30937 direct SRV lookups, this is not sufficient because of the extra parent domain
30938 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
30939 addresses into lookups in the reverse DNS space. The result of a successful
30942 ${lookup dnsdb {csa=$sender_helo_name}}
30944 has two space-separated fields: an authorization code and a target host name.
30945 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
30946 authorization required but absent, or &"?"& for unknown.
30951 .section "Bounce address tag validation" "SECTverifyPRVS"
30952 .cindex "BATV, verifying"
30953 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
30954 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
30955 Genuine incoming bounce messages should therefore always be addressed to
30956 recipients that have a valid tag. This scheme is a way of detecting unwanted
30957 bounce messages caused by sender address forgeries (often called &"collateral
30958 spam"&), because the recipients of such messages do not include valid tags.
30960 There are two expansion items to help with the implementation of the BATV
30961 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
30962 the original envelope sender address by using a simple key to add a hash of the
30963 address and some time-based randomizing information. The &%prvs%& expansion
30964 item creates a signed address, and the &%prvscheck%& expansion item checks one.
30965 The syntax of these expansion items is described in section
30966 &<<SECTexpansionitems>>&.
30968 As an example, suppose the secret per-address keys are stored in an MySQL
30969 database. A query to look up the key for an address could be defined as a macro
30972 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
30973 WHERE sender='${quote_mysql:$prvscheck_address}'\
30976 Suppose also that the senders who make use of BATV are defined by an address
30977 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
30980 # Bounces: drop unsigned addresses for BATV senders
30981 deny message = This address does not send an unsigned reverse path
30983 recipients = +batv_senders
30985 # Bounces: In case of prvs-signed address, check signature.
30986 deny message = Invalid reverse path signature.
30988 condition = ${prvscheck {$local_part@$domain}\
30989 {PRVSCHECK_SQL}{1}}
30990 !condition = $prvscheck_result
30992 The first statement rejects recipients for bounce messages that are addressed
30993 to plain BATV sender addresses, because it is known that BATV senders do not
30994 send out messages with plain sender addresses. The second statement rejects
30995 recipients that are prvs-signed, but with invalid signatures (either because
30996 the key is wrong, or the signature has timed out).
30998 A non-prvs-signed address is not rejected by the second statement, because the
30999 &%prvscheck%& expansion yields an empty string if its first argument is not a
31000 prvs-signed address, thus causing the &%condition%& condition to be false. If
31001 the first argument is a syntactically valid prvs-signed address, the yield is
31002 the third string (in this case &"1"&), whether or not the cryptographic and
31003 timeout checks succeed. The &$prvscheck_result$& variable contains the result
31004 of the checks (empty for failure, &"1"& for success).
31006 There is one more issue you must consider when implementing prvs-signing:
31007 you have to ensure that the routers accept prvs-signed addresses and
31008 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
31009 router to remove the signature with a configuration along these lines:
31013 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
31015 This works because, if the third argument of &%prvscheck%& is empty, the result
31016 of the expansion of a prvs-signed address is the decoded value of the original
31017 address. This router should probably be the first of your routers that handles
31020 To create BATV-signed addresses in the first place, a transport of this form
31023 external_smtp_batv:
31025 return_path = ${prvs {$return_path} \
31026 {${lookup mysql{SELECT \
31027 secret FROM batv_prvs WHERE \
31028 sender='${quote_mysql:$sender_address}'} \
31031 If no key can be found for the existing return path, no signing takes place.
31035 .section "Using an ACL to control relaying" "SECTrelaycontrol"
31036 .cindex "&ACL;" "relay control"
31037 .cindex "relaying" "control by ACL"
31038 .cindex "policy control" "relay control"
31039 An MTA is said to &'relay'& a message if it receives it from some host and
31040 delivers it directly to another host as a result of a remote address contained
31041 within it. Redirecting a local address via an alias or forward file and then
31042 passing the message on to another host is not relaying,
31043 .cindex "&""percent hack""&"
31044 but a redirection as a result of the &"percent hack"& is.
31046 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
31047 A host which is acting as a gateway or an MX backup is concerned with incoming
31048 relaying from arbitrary hosts to a specific set of domains. On the other hand,
31049 a host which is acting as a smart host for a number of clients is concerned
31050 with outgoing relaying from those clients to the Internet at large. Often the
31051 same host is fulfilling both functions,
31053 . as illustrated in the diagram below,
31055 but in principle these two kinds of relaying are entirely independent. What is
31056 not wanted is the transmission of mail from arbitrary remote hosts through your
31057 system to arbitrary domains.
31060 You can implement relay control by means of suitable statements in the ACL that
31061 runs for each RCPT command. For convenience, it is often easiest to use
31062 Exim's named list facility to define the domains and hosts involved. For
31063 example, suppose you want to do the following:
31066 Deliver a number of domains to mailboxes on the local host (or process them
31067 locally in some other way). Let's say these are &'my.dom1.example'& and
31068 &'my.dom2.example'&.
31070 Relay mail for a number of other domains for which you are the secondary MX.
31071 These might be &'friend1.example'& and &'friend2.example'&.
31073 Relay mail from the hosts on your local LAN, to whatever domains are involved.
31074 Suppose your LAN is 192.168.45.0/24.
31078 In the main part of the configuration, you put the following definitions:
31080 domainlist local_domains = my.dom1.example : my.dom2.example
31081 domainlist relay_to_domains = friend1.example : friend2.example
31082 hostlist relay_from_hosts = 192.168.45.0/24
31084 Now you can use these definitions in the ACL that is run for every RCPT
31088 accept domains = +local_domains : +relay_to_domains
31089 accept hosts = +relay_from_hosts
31091 The first statement accepts any RCPT command that contains an address in
31092 the local or relay domains. For any other domain, control passes to the second
31093 statement, which accepts the command only if it comes from one of the relay
31094 hosts. In practice, you will probably want to make your ACL more sophisticated
31095 than this, for example, by including sender and recipient verification. The
31096 default configuration includes a more comprehensive example, which is described
31097 in chapter &<<CHAPdefconfil>>&.
31101 .section "Checking a relay configuration" "SECTcheralcon"
31102 .cindex "relaying" "checking control of"
31103 You can check the relay characteristics of your configuration in the same way
31104 that you can test any ACL behaviour for an incoming SMTP connection, by using
31105 the &%-bh%& option to run a fake SMTP session with which you interact.
31110 . ////////////////////////////////////////////////////////////////////////////
31111 . ////////////////////////////////////////////////////////////////////////////
31113 .chapter "Content scanning at ACL time" "CHAPexiscan"
31114 .scindex IIDcosca "content scanning" "at ACL time"
31115 The extension of Exim to include content scanning at ACL time, formerly known
31116 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
31117 was integrated into the main source for Exim release 4.50, and Tom continues to
31118 maintain it. Most of the wording of this chapter is taken from Tom's
31121 It is also possible to scan the content of messages at other times. The
31122 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
31123 scanning after all the ACLs have run. A transport filter can be used to scan
31124 messages at delivery time (see the &%transport_filter%& option, described in
31125 chapter &<<CHAPtransportgeneric>>&).
31127 If you want to include the ACL-time content-scanning features when you compile
31128 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
31129 &_Local/Makefile_&. When you do that, the Exim binary is built with:
31132 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
31133 for all MIME parts for SMTP and non-SMTP messages, respectively.
31135 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
31136 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
31137 run at the end of message reception (the &%acl_smtp_data%& ACL).
31139 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
31140 of messages, or parts of messages, for debugging purposes.
31142 Additional expansion variables that are set in the new ACL and by the new
31145 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
31148 Content-scanning is continually evolving, and new features are still being
31149 added. While such features are still unstable and liable to incompatible
31150 changes, they are made available in Exim by setting options whose names begin
31151 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
31152 this manual. You can find out about them by reading the file called
31153 &_doc/experimental.txt_&.
31155 All the content-scanning facilities work on a MBOX copy of the message that is
31156 temporarily created in a file called:
31158 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
31160 The &_.eml_& extension is a friendly hint to virus scanners that they can
31161 expect an MBOX-like structure inside that file. The file is created when the
31162 first content scanning facility is called. Subsequent calls to content
31163 scanning conditions open the same file again. The directory is recursively
31164 removed when the &%acl_smtp_data%& ACL has finished running, unless
31166 control = no_mbox_unspool
31168 has been encountered. When the MIME ACL decodes files, they are put into the
31169 same directory by default.
31173 .section "Scanning for viruses" "SECTscanvirus"
31174 .cindex "virus scanning"
31175 .cindex "content scanning" "for viruses"
31176 .cindex "content scanning" "the &%malware%& condition"
31177 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
31178 It supports a &"generic"& interface to scanners called via the shell, and
31179 specialized interfaces for &"daemon"& type virus scanners, which are resident
31180 in memory and thus are much faster.
31182 A timeout of 2 minutes is applied to a scanner call (by default);
31183 if it expires then a defer action is taken.
31185 .oindex "&%av_scanner%&"
31186 You can set the &%av_scanner%& option in the main part of the configuration
31187 to specify which scanner to use, together with any additional options that
31188 are needed. The basic syntax is as follows:
31190 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
31192 If you do not set &%av_scanner%&, it defaults to
31194 av_scanner = sophie:/var/run/sophie
31196 If the value of &%av_scanner%& starts with a dollar character, it is expanded
31198 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
31199 The following scanner types are supported in this release:
31203 .cindex "virus scanners" "avast"
31204 This is the scanner daemon of Avast. It has been tested with Avast Core
31205 Security (currently at version 1.1.7).
31206 You can get a trial version at &url(http://www.avast.com) or for Linux
31207 at &url(http://www.avast.com/linux-server-antivirus).
31208 This scanner type takes one option,
31209 which can be either a full path to a UNIX socket,
31210 or host and port specifiers separated by white space.
31211 The host may be a name or an IP address; the port is either a
31212 single number or a pair of numbers with a dash between.
31213 Any further options are given, on separate lines,
31214 to the daemon as options before the main scan command.
31217 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
31218 av_scanner = avast:192.168.2.22 5036
31220 If you omit the argument, the default path
31221 &_/var/run/avast/scan.sock_&
31223 If you use a remote host,
31224 you need to make Exim's spool directory available to it,
31225 as the scanner is passed a file path, not file contents.
31226 For information about available commands and their options you may use
31228 $ socat UNIX:/var/run/avast/scan.sock STDIO:
31235 .vitem &%aveserver%&
31236 .cindex "virus scanners" "Kaspersky"
31237 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
31238 at &url(http://www.kaspersky.com). This scanner type takes one option,
31239 which is the path to the daemon's UNIX socket. The default is shown in this
31242 av_scanner = aveserver:/var/run/aveserver
31247 .cindex "virus scanners" "clamd"
31248 This daemon-type scanner is GPL and free. You can get it at
31249 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
31250 unpack MIME containers, so it used to be recommended to unpack MIME attachments
31251 in the MIME ACL. This is no longer believed to be necessary.
31253 The options are a list of server specifiers, which may be
31254 a UNIX socket specification,
31255 a TCP socket specification,
31256 or a (global) option.
31258 A socket specification consists of a space-separated list.
31259 For a Unix socket the first element is a full path for the socket,
31260 for a TCP socket the first element is the IP address
31261 and the second a port number,
31262 Any further elements are per-server (non-global) options.
31263 These per-server options are supported:
31265 retry=<timespec> Retry on connect fail
31268 The &`retry`& option specifies a time after which a single retry for
31269 a failed connect is made. The default is to not retry.
31271 If a Unix socket file is specified, only one server is supported.
31275 av_scanner = clamd:/opt/clamd/socket
31276 av_scanner = clamd:192.0.2.3 1234
31277 av_scanner = clamd:192.0.2.3 1234:local
31278 av_scanner = clamd:192.0.2.3 1234 retry=10s
31279 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
31281 If the value of av_scanner points to a UNIX socket file or contains the
31283 option, then the ClamAV interface will pass a filename containing the data
31284 to be scanned, which will should normally result in less I/O happening and be
31285 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
31286 Exim does not assume that there is a common filesystem with the remote host.
31287 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
31288 you be running a version of ClamAV prior to 0.95.
31290 The final example shows that multiple TCP targets can be specified. Exim will
31291 randomly use one for each incoming email (i.e. it load balances them). Note
31292 that only TCP targets may be used if specifying a list of scanners; a UNIX
31293 socket cannot be mixed in with TCP targets. If one of the servers becomes
31294 unavailable, Exim will try the remaining one(s) until it finds one that works.
31295 When a clamd server becomes unreachable, Exim will log a message. Exim does
31296 not keep track of scanner state between multiple messages, and the scanner
31297 selection is random, so the message will get logged in the mainlog for each
31298 email that the down scanner gets chosen first (message wrapped to be readable):
31300 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
31301 clamd: connection to localhost, port 3310 failed
31302 (Connection refused)
31305 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
31306 contributing the code for this scanner.
31309 .cindex "virus scanners" "command line interface"
31310 This is the keyword for the generic command line scanner interface. It can be
31311 used to attach virus scanners that are invoked from the shell. This scanner
31312 type takes 3 mandatory options:
31315 The full path and name of the scanner binary, with all command line options,
31316 and a placeholder (&`%s`&) for the directory to scan.
31319 A regular expression to match against the STDOUT and STDERR output of the
31320 virus scanner. If the expression matches, a virus was found. You must make
31321 absolutely sure that this expression matches on &"virus found"&. This is called
31322 the &"trigger"& expression.
31325 Another regular expression, containing exactly one pair of parentheses, to
31326 match the name of the virus found in the scanners output. This is called the
31327 &"name"& expression.
31330 For example, Sophos Sweep reports a virus on a line like this:
31332 Virus 'W32/Magistr-B' found in file ./those.bat
31334 For the trigger expression, we can match the phrase &"found in file"&. For the
31335 name expression, we want to extract the W32/Magistr-B string, so we can match
31336 for the single quotes left and right of it. Altogether, this makes the
31337 configuration setting:
31339 av_scanner = cmdline:\
31340 /path/to/sweep -ss -all -rec -archive %s:\
31341 found in file:'(.+)'
31344 .cindex "virus scanners" "DrWeb"
31345 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface
31347 either a full path to a UNIX socket,
31348 or host and port specifiers separated by white space.
31349 The host may be a name or an IP address; the port is either a
31350 single number or a pair of numbers with a dash between.
31353 av_scanner = drweb:/var/run/drwebd.sock
31354 av_scanner = drweb:192.168.2.20 31337
31356 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
31357 is used. Thanks to Alex Miller for contributing the code for this scanner.
31360 .cindex "virus scanners" "f-protd"
31361 The f-protd scanner is accessed via HTTP over TCP.
31362 One argument is taken, being a space-separated hostname and port number
31366 av_scanner = f-protd:localhost 10200-10204
31368 If you omit the argument, the default values show above are used.
31371 .cindex "virus scanners" "F-Secure"
31372 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
31373 argument which is the path to a UNIX socket. For example:
31375 av_scanner = fsecure:/path/to/.fsav
31377 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
31378 Thelmen for contributing the code for this scanner.
31380 .vitem &%kavdaemon%&
31381 .cindex "virus scanners" "Kaspersky"
31382 This is the scanner daemon of Kaspersky Version 4. This version of the
31383 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
31384 scanner type takes one option, which is the path to the daemon's UNIX socket.
31387 av_scanner = kavdaemon:/opt/AVP/AvpCtl
31389 The default path is &_/var/run/AvpCtl_&.
31392 .cindex "virus scanners" "mksd"
31393 This is a daemon type scanner that is aimed mainly at Polish users, though some
31394 parts of documentation are now available in English. You can get it at
31395 &url(http://linux.mks.com.pl/). The only option for this scanner type is
31396 the maximum number of processes used simultaneously to scan the attachments,
31397 provided that mksd has
31398 been run with at least the same number of child processes. For example:
31400 av_scanner = mksd:2
31402 You can safely omit this option (the default value is 1).
31405 .cindex "virus scanners" "simple socket-connected"
31406 This is a general-purpose way of talking to simple scanner daemons
31407 running on the local machine.
31408 There are four options:
31409 an address (which may be an IP address and port, or the path of a Unix socket),
31410 a commandline to send (may include a single %s which will be replaced with
31411 the path to the mail file to be scanned),
31412 an RE to trigger on from the returned data,
31413 an RE to extract malware_name from the returned data.
31416 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
31418 Default for the socket specifier is &_/tmp/malware.sock_&.
31419 Default for the commandline is &_%s\n_&.
31420 Both regular-expressions are required.
31423 .cindex "virus scanners" "Sophos and Sophie"
31424 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
31425 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
31426 for this scanner type is the path to the UNIX socket that Sophie uses for
31427 client communication. For example:
31429 av_scanner = sophie:/tmp/sophie
31431 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
31435 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
31436 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
31439 The &%av_scanner%& option is expanded each time &%malware%& is called. This
31440 makes it possible to use different scanners. See further below for an example.
31441 The &%malware%& condition caches its results, so when you use it multiple times
31442 for the same message, the actual scanning process is only carried out once.
31443 However, using expandable items in &%av_scanner%& disables this caching, in
31444 which case each use of the &%malware%& condition causes a new scan of the
31447 The &%malware%& condition takes a right-hand argument that is expanded before
31448 use and taken as a list, slash-separated by default.
31449 The first element can then be one of
31452 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
31453 The condition succeeds if a virus was found, and fail otherwise. This is the
31456 &"false"& or &"0"& or an empty string, in which case no scanning is done and
31457 the condition fails immediately.
31459 A regular expression, in which case the message is scanned for viruses. The
31460 condition succeeds if a virus is found and its name matches the regular
31461 expression. This allows you to take special actions on certain types of virus.
31462 Note that &"/"& characters in the RE must be doubled due to the list-processing,
31463 unless the separator is changed (in the usual way).
31466 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
31467 messages even if there is a problem with the virus scanner.
31468 Otherwise, such a problem causes the ACL to defer.
31470 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
31471 specify a non-default timeout. The default is two minutes.
31474 malware = * / defer_ok / tmo=10s
31476 A timeout causes the ACL to defer.
31478 .vindex "&$callout_address$&"
31479 When a connection is made to the scanner the expansion variable &$callout_address$&
31480 is set to record the actual address used.
31482 .vindex "&$malware_name$&"
31483 When a virus is found, the condition sets up an expansion variable called
31484 &$malware_name$& that contains the name of the virus. You can use it in a
31485 &%message%& modifier that specifies the error returned to the sender, and/or in
31488 Beware the interaction of Exim's &%message_size_limit%& with any size limits
31489 imposed by your anti-virus scanner.
31491 Here is a very simple scanning example:
31493 deny message = This message contains malware ($malware_name)
31496 The next example accepts messages when there is a problem with the scanner:
31498 deny message = This message contains malware ($malware_name)
31499 malware = */defer_ok
31501 The next example shows how to use an ACL variable to scan with both sophie and
31502 aveserver. It assumes you have set:
31504 av_scanner = $acl_m0
31506 in the main Exim configuration.
31508 deny message = This message contains malware ($malware_name)
31509 set acl_m0 = sophie
31512 deny message = This message contains malware ($malware_name)
31513 set acl_m0 = aveserver
31518 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
31519 .cindex "content scanning" "for spam"
31520 .cindex "spam scanning"
31521 .cindex "SpamAssassin"
31523 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
31524 score and a report for the message.
31525 Support is also provided for Rspamd.
31527 For more information about installation and configuration of SpamAssassin or
31528 Rspamd refer to their respective websites at
31529 &url(http://spamassassin.apache.org) and &url(http://www.rspamd.com)
31531 SpamAssassin can be installed with CPAN by running:
31533 perl -MCPAN -e 'install Mail::SpamAssassin'
31535 SpamAssassin has its own set of configuration files. Please review its
31536 documentation to see how you can tweak it. The default installation should work
31539 .oindex "&%spamd_address%&"
31540 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
31541 intend to use an instance running on the local host you do not need to set
31542 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
31543 you must set the &%spamd_address%& option in the global part of the Exim
31544 configuration as follows (example):
31546 spamd_address = 192.168.99.45 387
31549 To use Rspamd (which by default listens on all local addresses
31551 you should add &%variant=rspamd%& after the address/port pair, for example:
31553 spamd_address = 127.0.0.1 11333 variant=rspamd
31556 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
31557 sockets. If you want to us these, supply &%spamd_address%& with an absolute
31558 file name instead of an address/port pair:
31560 spamd_address = /var/run/spamd_socket
31562 You can have multiple &%spamd%& servers to improve scalability. These can
31563 reside on other hardware reachable over the network. To specify multiple
31564 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
31565 option, separated with colons (the separator can be changed in the usual way):
31567 spamd_address = 192.168.2.10 783 : \
31568 192.168.2.11 783 : \
31571 Up to 32 &%spamd%& servers are supported.
31572 When a server fails to respond to the connection attempt, all other
31573 servers are tried until one succeeds. If no server responds, the &%spam%&
31576 Unix and TCP socket specifications may be mixed in any order.
31577 Each element of the list is a list itself, space-separated by default
31578 and changeable in the usual way; take care to not double the separator.
31580 For TCP socket specifications a host name or IP (v4 or v6, but
31581 subject to list-separator quoting rules) address can be used,
31582 and the port can be one or a dash-separated pair.
31583 In the latter case, the range is tried in strict order.
31585 Elements after the first for Unix sockets, or second for TCP socket,
31587 The supported options are:
31589 pri=<priority> Selection priority
31590 weight=<value> Selection bias
31591 time=<start>-<end> Use only between these times of day
31592 retry=<timespec> Retry on connect fail
31593 tmo=<timespec> Connection time limit
31594 variant=rspamd Use Rspamd rather than SpamAssassin protocol
31597 The &`pri`& option specifies a priority for the server within the list,
31598 higher values being tried first.
31599 The default priority is 1.
31601 The &`weight`& option specifies a selection bias.
31602 Within a priority set
31603 servers are queried in a random fashion, weighted by this value.
31604 The default value for selection bias is 1.
31606 Time specifications for the &`time`& option are <hour>.<minute>.<second>
31607 in the local time zone; each element being one or more digits.
31608 Either the seconds or both minutes and seconds, plus the leading &`.`&
31609 characters, may be omitted and will be taken as zero.
31611 Timeout specifications for the &`retry`& and &`tmo`& options
31612 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
31614 The &`tmo`& option specifies an overall timeout for communication.
31615 The default value is two minutes.
31617 The &`retry`& option specifies a time after which a single retry for
31618 a failed connect is made.
31619 The default is to not retry.
31621 The &%spamd_address%& variable is expanded before use if it starts with
31622 a dollar sign. In this case, the expansion may return a string that is
31623 used as the list so that multiple spamd servers can be the result of an
31626 .vindex "&$callout_address$&"
31627 When a connection is made to the server the expansion variable &$callout_address$&
31628 is set to record the actual address used.
31630 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
31631 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
31633 deny message = This message was classified as SPAM
31636 The right-hand side of the &%spam%& condition specifies a name. This is
31637 relevant if you have set up multiple SpamAssassin profiles. If you do not want
31638 to scan using a specific profile, but rather use the SpamAssassin system-wide
31639 default profile, you can scan for an unknown name, or simply use &"nobody"&.
31640 Rspamd does not use this setting. However, you must put something on the
31643 The name allows you to use per-domain or per-user antispam profiles in
31644 principle, but this is not straightforward in practice, because a message may
31645 have multiple recipients, not necessarily all in the same domain. Because the
31646 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
31647 read the contents of the message, the variables &$local_part$& and &$domain$&
31649 Careful enforcement of single-recipient messages
31650 (e.g. by responding with defer in the recipient ACL for all recipients
31652 or the use of PRDR,
31653 .cindex "PRDR" "use for per-user SpamAssassin profiles"
31654 are needed to use this feature.
31656 The right-hand side of the &%spam%& condition is expanded before being used, so
31657 you can put lookups or conditions there. When the right-hand side evaluates to
31658 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
31661 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
31662 large ones may cause significant performance degradation. As most spam messages
31663 are quite small, it is recommended that you do not scan the big ones. For
31666 deny message = This message was classified as SPAM
31667 condition = ${if < {$message_size}{10K}}
31671 The &%spam%& condition returns true if the threshold specified in the user's
31672 SpamAssassin profile has been matched or exceeded. If you want to use the
31673 &%spam%& condition for its side effects (see the variables below), you can make
31674 it always return &"true"& by appending &`:true`& to the username.
31676 .cindex "spam scanning" "returned variables"
31677 When the &%spam%& condition is run, it sets up a number of expansion
31679 Except for &$spam_report$&,
31680 these variables are saved with the received message so are
31681 available for use at delivery time.
31684 .vitem &$spam_score$&
31685 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
31686 for inclusion in log or reject messages.
31688 .vitem &$spam_score_int$&
31689 The spam score of the message, multiplied by ten, as an integer value. For
31690 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
31691 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
31692 The integer value is useful for numeric comparisons in conditions.
31694 .vitem &$spam_bar$&
31695 A string consisting of a number of &"+"& or &"-"& characters, representing the
31696 integer part of the spam score value. A spam score of 4.4 would have a
31697 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
31698 headers, since MUAs can match on such strings. The maximum length of the
31699 spam bar is 50 characters.
31701 .vitem &$spam_report$&
31702 A multiline text table, containing the full SpamAssassin report for the
31703 message. Useful for inclusion in headers or reject messages.
31704 This variable is only usable in a DATA-time ACL.
31706 Beware that SpamAssassin may return non-ASCII characters, especially
31707 when running in country-specific locales, which are not legal
31708 unencoded in headers.
31711 .vitem &$spam_action$&
31712 For SpamAssassin either 'reject' or 'no action' depending on the
31713 spam score versus threshold.
31714 For Rspamd, the recommended action.
31718 The &%spam%& condition caches its results unless expansion in
31719 spamd_address was used. If you call it again with the same user name, it
31720 does not scan again, but rather returns the same values as before.
31722 The &%spam%& condition returns DEFER if there is any error while running
31723 the message through SpamAssassin or if the expansion of spamd_address
31724 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
31725 statement block), append &`/defer_ok`& to the right-hand side of the
31726 spam condition, like this:
31728 deny message = This message was classified as SPAM
31729 spam = joe/defer_ok
31731 This causes messages to be accepted even if there is a problem with &%spamd%&.
31733 Here is a longer, commented example of the use of the &%spam%&
31736 # put headers in all messages (no matter if spam or not)
31737 warn spam = nobody:true
31738 add_header = X-Spam-Score: $spam_score ($spam_bar)
31739 add_header = X-Spam-Report: $spam_report
31741 # add second subject line with *SPAM* marker when message
31742 # is over threshold
31744 add_header = Subject: *SPAM* $h_Subject:
31746 # reject spam at high scores (> 12)
31747 deny message = This message scored $spam_score spam points.
31749 condition = ${if >{$spam_score_int}{120}{1}{0}}
31754 .section "Scanning MIME parts" "SECTscanmimepart"
31755 .cindex "content scanning" "MIME parts"
31756 .cindex "MIME content scanning"
31757 .oindex "&%acl_smtp_mime%&"
31758 .oindex "&%acl_not_smtp_mime%&"
31759 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
31760 each MIME part of an SMTP message, including multipart types, in the sequence
31761 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
31762 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
31763 options may both refer to the same ACL if you want the same processing in both
31766 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
31767 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
31768 the case of a non-SMTP message. However, a MIME ACL is called only if the
31769 message contains a &'Content-Type:'& header line. When a call to a MIME
31770 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
31771 result code is sent to the client. In the case of an SMTP message, the
31772 &%acl_smtp_data%& ACL is not called when this happens.
31774 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
31775 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
31776 condition to match against the raw MIME part. You can also use the
31777 &%mime_regex%& condition to match against the decoded MIME part (see section
31778 &<<SECTscanregex>>&).
31780 At the start of a MIME ACL, a number of variables are set from the header
31781 information for the relevant MIME part. These are described below. The contents
31782 of the MIME part are not by default decoded into a disk file except for MIME
31783 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
31784 part into a disk file, you can use the &%decode%& condition. The general
31787 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
31789 The right hand side is expanded before use. After expansion,
31793 &"0"& or &"false"&, in which case no decoding is done.
31795 The string &"default"&. In that case, the file is put in the temporary
31796 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
31797 a sequential file name consisting of the message id and a sequence number. The
31798 full path and name is available in &$mime_decoded_filename$& after decoding.
31800 A full path name starting with a slash. If the full name is an existing
31801 directory, it is used as a replacement for the default directory. The filename
31802 is then sequentially assigned. If the path does not exist, it is used as
31803 the full path and file name.
31805 If the string does not start with a slash, it is used as the
31806 filename, and the default path is then used.
31808 The &%decode%& condition normally succeeds. It is only false for syntax
31809 errors or unusual circumstances such as memory shortages. You can easily decode
31810 a file with its original, proposed filename using
31812 decode = $mime_filename
31814 However, you should keep in mind that &$mime_filename$& might contain
31815 anything. If you place files outside of the default path, they are not
31816 automatically unlinked.
31818 For RFC822 attachments (these are messages attached to messages, with a
31819 content-type of &"message/rfc822"&), the ACL is called again in the same manner
31820 as for the primary message, only that the &$mime_is_rfc822$& expansion
31821 variable is set (see below). Attached messages are always decoded to disk
31822 before being checked, and the files are unlinked once the check is done.
31824 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
31825 used to match regular expressions against raw and decoded MIME parts,
31826 respectively. They are described in section &<<SECTscanregex>>&.
31828 .cindex "MIME content scanning" "returned variables"
31829 The following list describes all expansion variables that are
31830 available in the MIME ACL:
31833 .vitem &$mime_boundary$&
31834 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
31835 have a boundary string, which is stored in this variable. If the current part
31836 has no boundary parameter in the &'Content-Type:'& header, this variable
31837 contains the empty string.
31839 .vitem &$mime_charset$&
31840 This variable contains the character set identifier, if one was found in the
31841 &'Content-Type:'& header. Examples for charset identifiers are:
31847 Please note that this value is not normalized, so you should do matches
31848 case-insensitively.
31850 .vitem &$mime_content_description$&
31851 This variable contains the normalized content of the &'Content-Description:'&
31852 header. It can contain a human-readable description of the parts content. Some
31853 implementations repeat the filename for attachments here, but they are usually
31854 only used for display purposes.
31856 .vitem &$mime_content_disposition$&
31857 This variable contains the normalized content of the &'Content-Disposition:'&
31858 header. You can expect strings like &"attachment"& or &"inline"& here.
31860 .vitem &$mime_content_id$&
31861 This variable contains the normalized content of the &'Content-ID:'& header.
31862 This is a unique ID that can be used to reference a part from another part.
31864 .vitem &$mime_content_size$&
31865 This variable is set only after the &%decode%& modifier (see above) has been
31866 successfully run. It contains the size of the decoded part in kilobytes. The
31867 size is always rounded up to full kilobytes, so only a completely empty part
31868 has a &$mime_content_size$& of zero.
31870 .vitem &$mime_content_transfer_encoding$&
31871 This variable contains the normalized content of the
31872 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
31873 type. Typical values are &"base64"& and &"quoted-printable"&.
31875 .vitem &$mime_content_type$&
31876 If the MIME part has a &'Content-Type:'& header, this variable contains its
31877 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
31878 are some examples of popular MIME types, as they may appear in this variable:
31882 application/octet-stream
31886 If the MIME part has no &'Content-Type:'& header, this variable contains the
31889 .vitem &$mime_decoded_filename$&
31890 This variable is set only after the &%decode%& modifier (see above) has been
31891 successfully run. It contains the full path and file name of the file
31892 containing the decoded data.
31897 .vitem &$mime_filename$&
31898 This is perhaps the most important of the MIME variables. It contains a
31899 proposed filename for an attachment, if one was found in either the
31900 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
31903 decoded, but no additional sanity checks are done.
31905 found, this variable contains the empty string.
31907 .vitem &$mime_is_coverletter$&
31908 This variable attempts to differentiate the &"cover letter"& of an e-mail from
31909 attached data. It can be used to clamp down on flashy or unnecessarily encoded
31910 content in the cover letter, while not restricting attachments at all.
31912 The variable contains 1 (true) for a MIME part believed to be part of the
31913 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
31917 The outermost MIME part of a message is always a cover letter.
31920 If a multipart/alternative or multipart/related MIME part is a cover letter,
31921 so are all MIME subparts within that multipart.
31924 If any other multipart is a cover letter, the first subpart is a cover letter,
31925 and the rest are attachments.
31928 All parts contained within an attachment multipart are attachments.
31931 As an example, the following will ban &"HTML mail"& (including that sent with
31932 alternative plain text), while allowing HTML files to be attached. HTML
31933 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
31935 deny message = HTML mail is not accepted here
31936 !condition = $mime_is_rfc822
31937 condition = $mime_is_coverletter
31938 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
31940 .vitem &$mime_is_multipart$&
31941 This variable has the value 1 (true) when the current part has the main type
31942 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
31943 Since multipart entities only serve as containers for other parts, you may not
31944 want to carry out specific actions on them.
31946 .vitem &$mime_is_rfc822$&
31947 This variable has the value 1 (true) if the current part is not a part of the
31948 checked message itself, but part of an attached message. Attached message
31949 decoding is fully recursive.
31951 .vitem &$mime_part_count$&
31952 This variable is a counter that is raised for each processed MIME part. It
31953 starts at zero for the very first part (which is usually a multipart). The
31954 counter is per-message, so it is reset when processing RFC822 attachments (see
31955 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
31956 complete, so you can use it in the DATA ACL to determine the number of MIME
31957 parts of a message. For non-MIME messages, this variable contains the value -1.
31962 .section "Scanning with regular expressions" "SECTscanregex"
31963 .cindex "content scanning" "with regular expressions"
31964 .cindex "regular expressions" "content scanning with"
31965 You can specify your own custom regular expression matches on the full body of
31966 the message, or on individual MIME parts.
31968 The &%regex%& condition takes one or more regular expressions as arguments and
31969 matches them against the full message (when called in the DATA ACL) or a raw
31970 MIME part (when called in the MIME ACL). The &%regex%& condition matches
31971 linewise, with a maximum line length of 32K characters. That means you cannot
31972 have multiline matches with the &%regex%& condition.
31974 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
31975 to 32K of decoded content (the whole content at once, not linewise). If the
31976 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
31977 is decoded automatically when &%mime_regex%& is executed (using default path
31978 and filename values). If the decoded data is larger than 32K, only the first
31979 32K characters are checked.
31981 The regular expressions are passed as a colon-separated list. To include a
31982 literal colon, you must double it. Since the whole right-hand side string is
31983 expanded before being used, you must also escape dollar signs and backslashes
31984 with more backslashes, or use the &`\N`& facility to disable expansion.
31985 Here is a simple example that contains two regular expressions:
31987 deny message = contains blacklisted regex ($regex_match_string)
31988 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
31990 The conditions returns true if any one of the regular expressions matches. The
31991 &$regex_match_string$& expansion variable is then set up and contains the
31992 matching regular expression.
31993 The expansion variables &$regex1$& &$regex2$& etc
31994 are set to any substrings captured by the regular expression.
31996 &*Warning*&: With large messages, these conditions can be fairly
32004 . ////////////////////////////////////////////////////////////////////////////
32005 . ////////////////////////////////////////////////////////////////////////////
32007 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
32008 "Local scan function"
32009 .scindex IIDlosca "&[local_scan()]& function" "description of"
32010 .cindex "customizing" "input scan using C function"
32011 .cindex "policy control" "by local scan function"
32012 In these days of email worms, viruses, and ever-increasing spam, some sites
32013 want to apply a lot of checking to messages before accepting them.
32015 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
32016 passing messages to external virus and spam scanning software. You can also do
32017 a certain amount in Exim itself through string expansions and the &%condition%&
32018 condition in the ACL that runs after the SMTP DATA command or the ACL for
32019 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
32021 To allow for further customization to a site's own requirements, there is the
32022 possibility of linking Exim with a private message scanning function, written
32023 in C. If you want to run code that is written in something other than C, you
32024 can of course use a little C stub to call it.
32026 The local scan function is run once for every incoming message, at the point
32027 when Exim is just about to accept the message.
32028 It can therefore be used to control non-SMTP messages from local processes as
32029 well as messages arriving via SMTP.
32031 Exim applies a timeout to calls of the local scan function, and there is an
32032 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
32033 Zero means &"no timeout"&.
32034 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
32035 before calling the local scan function, so that the most common types of crash
32036 are caught. If the timeout is exceeded or one of those signals is caught, the
32037 incoming message is rejected with a temporary error if it is an SMTP message.
32038 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
32039 code. The incident is logged on the main and reject logs.
32043 .section "Building Exim to use a local scan function" "SECID207"
32044 .cindex "&[local_scan()]& function" "building Exim to use"
32045 To make use of the local scan function feature, you must tell Exim where your
32046 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
32047 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
32048 directory, so you might set
32050 LOCAL_SCAN_SOURCE=Local/local_scan.c
32052 for example. The function must be called &[local_scan()]&. It is called by
32053 Exim after it has received a message, when the success return code is about to
32054 be sent. This is after all the ACLs have been run. The return code from your
32055 function controls whether the message is actually accepted or not. There is a
32056 commented template function (that just accepts the message) in the file
32057 _src/local_scan.c_.
32059 If you want to make use of Exim's run time configuration file to set options
32060 for your &[local_scan()]& function, you must also set
32062 LOCAL_SCAN_HAS_OPTIONS=yes
32064 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
32069 .section "API for local_scan()" "SECTapiforloc"
32070 .cindex "&[local_scan()]& function" "API description"
32071 You must include this line near the start of your code:
32073 #include "local_scan.h"
32075 This header file defines a number of variables and other values, and the
32076 prototype for the function itself. Exim is coded to use unsigned char values
32077 almost exclusively, and one of the things this header defines is a shorthand
32078 for &`unsigned char`& called &`uschar`&.
32079 It also contains the following macro definitions, to simplify casting character
32080 strings and pointers to character strings:
32082 #define CS (char *)
32083 #define CCS (const char *)
32084 #define CSS (char **)
32085 #define US (unsigned char *)
32086 #define CUS (const unsigned char *)
32087 #define USS (unsigned char **)
32089 The function prototype for &[local_scan()]& is:
32091 extern int local_scan(int fd, uschar **return_text);
32093 The arguments are as follows:
32096 &%fd%& is a file descriptor for the file that contains the body of the message
32097 (the -D file). The file is open for reading and writing, but updating it is not
32098 recommended. &*Warning*&: You must &'not'& close this file descriptor.
32100 The descriptor is positioned at character 19 of the file, which is the first
32101 character of the body itself, because the first 19 characters are the message
32102 id followed by &`-D`& and a newline. If you rewind the file, you should use the
32103 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
32104 case this changes in some future version.
32106 &%return_text%& is an address which you can use to return a pointer to a text
32107 string at the end of the function. The value it points to on entry is NULL.
32110 The function must return an &%int%& value which is one of the following macros:
32113 .vitem &`LOCAL_SCAN_ACCEPT`&
32114 .vindex "&$local_scan_data$&"
32115 The message is accepted. If you pass back a string of text, it is saved with
32116 the message, and made available in the variable &$local_scan_data$&. No
32117 newlines are permitted (if there are any, they are turned into spaces) and the
32118 maximum length of text is 1000 characters.
32120 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
32121 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32122 queued without immediate delivery, and is frozen.
32124 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
32125 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32126 queued without immediate delivery.
32128 .vitem &`LOCAL_SCAN_REJECT`&
32129 The message is rejected; the returned text is used as an error message which is
32130 passed back to the sender and which is also logged. Newlines are permitted &--
32131 they cause a multiline response for SMTP rejections, but are converted to
32132 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
32135 .vitem &`LOCAL_SCAN_TEMPREJECT`&
32136 The message is temporarily rejected; the returned text is used as an error
32137 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
32140 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
32141 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
32142 message is not written to the reject log. It has the effect of unsetting the
32143 &%rejected_header%& log selector for just this rejection. If
32144 &%rejected_header%& is already unset (see the discussion of the
32145 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
32146 same as LOCAL_SCAN_REJECT.
32148 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
32149 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
32150 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
32153 If the message is not being received by interactive SMTP, rejections are
32154 reported by writing to &%stderr%& or by sending an email, as configured by the
32155 &%-oe%& command line options.
32159 .section "Configuration options for local_scan()" "SECTconoptloc"
32160 .cindex "&[local_scan()]& function" "configuration options"
32161 It is possible to have option settings in the main configuration file
32162 that set values in static variables in the &[local_scan()]& module. If you
32163 want to do this, you must have the line
32165 LOCAL_SCAN_HAS_OPTIONS=yes
32167 in your &_Local/Makefile_& when you build Exim. (This line is in
32168 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
32169 file, you must define static variables to hold the option values, and a table
32172 The table must be a vector called &%local_scan_options%&, of type
32173 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
32174 and a pointer to the variable that holds the value. The entries must appear in
32175 alphabetical order. Following &%local_scan_options%& you must also define a
32176 variable called &%local_scan_options_count%& that contains the number of
32177 entries in the table. Here is a short example, showing two kinds of option:
32179 static int my_integer_option = 42;
32180 static uschar *my_string_option = US"a default string";
32182 optionlist local_scan_options[] = {
32183 { "my_integer", opt_int, &my_integer_option },
32184 { "my_string", opt_stringptr, &my_string_option }
32187 int local_scan_options_count =
32188 sizeof(local_scan_options)/sizeof(optionlist);
32190 The values of the variables can now be changed from Exim's runtime
32191 configuration file by including a local scan section as in this example:
32195 my_string = some string of text...
32197 The available types of option data are as follows:
32200 .vitem &*opt_bool*&
32201 This specifies a boolean (true/false) option. The address should point to a
32202 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
32203 that are defined as &"1"& and &"0"&, respectively. If you want to detect
32204 whether such a variable has been set at all, you can initialize it to
32205 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
32208 .vitem &*opt_fixed*&
32209 This specifies a fixed point number, such as is used for load averages.
32210 The address should point to a variable of type &`int`&. The value is stored
32211 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
32214 This specifies an integer; the address should point to a variable of type
32215 &`int`&. The value may be specified in any of the integer formats accepted by
32218 .vitem &*opt_mkint*&
32219 This is the same as &%opt_int%&, except that when such a value is output in a
32220 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
32221 printed with the suffix K or M.
32223 .vitem &*opt_octint*&
32224 This also specifies an integer, but the value is always interpreted as an
32225 octal integer, whether or not it starts with the digit zero, and it is
32226 always output in octal.
32228 .vitem &*opt_stringptr*&
32229 This specifies a string value; the address must be a pointer to a
32230 variable that points to a string (for example, of type &`uschar *`&).
32232 .vitem &*opt_time*&
32233 This specifies a time interval value. The address must point to a variable of
32234 type &`int`&. The value that is placed there is a number of seconds.
32237 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
32238 out the values of all the &[local_scan()]& options.
32242 .section "Available Exim variables" "SECID208"
32243 .cindex "&[local_scan()]& function" "available Exim variables"
32244 The header &_local_scan.h_& gives you access to a number of C variables. These
32245 are the only ones that are guaranteed to be maintained from release to release.
32246 Note, however, that you can obtain the value of any Exim expansion variable,
32247 including &$recipients$&, by calling &'expand_string()'&. The exported
32248 C variables are as follows:
32251 .vitem &*int&~body_linecount*&
32252 This variable contains the number of lines in the message's body.
32254 .vitem &*int&~body_zerocount*&
32255 This variable contains the number of binary zero bytes in the message's body.
32257 .vitem &*unsigned&~int&~debug_selector*&
32258 This variable is set to zero when no debugging is taking place. Otherwise, it
32259 is a bitmap of debugging selectors. Two bits are identified for use in
32260 &[local_scan()]&; they are defined as macros:
32263 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
32264 testing option that is not privileged &-- any caller may set it. All the
32265 other selector bits can be set only by admin users.
32268 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
32269 by the &`+local_scan`& debug selector. It is not included in the default set
32273 Thus, to write to the debugging output only when &`+local_scan`& has been
32274 selected, you should use code like this:
32276 if ((debug_selector & D_local_scan) != 0)
32277 debug_printf("xxx", ...);
32279 .vitem &*uschar&~*expand_string_message*&
32280 After a failing call to &'expand_string()'& (returned value NULL), the
32281 variable &%expand_string_message%& contains the error message, zero-terminated.
32283 .vitem &*header_line&~*header_list*&
32284 A pointer to a chain of header lines. The &%header_line%& structure is
32287 .vitem &*header_line&~*header_last*&
32288 A pointer to the last of the header lines.
32290 .vitem &*uschar&~*headers_charset*&
32291 The value of the &%headers_charset%& configuration option.
32293 .vitem &*BOOL&~host_checking*&
32294 This variable is TRUE during a host checking session that is initiated by the
32295 &%-bh%& command line option.
32297 .vitem &*uschar&~*interface_address*&
32298 The IP address of the interface that received the message, as a string. This
32299 is NULL for locally submitted messages.
32301 .vitem &*int&~interface_port*&
32302 The port on which this message was received. When testing with the &%-bh%&
32303 command line option, the value of this variable is -1 unless a port has been
32304 specified via the &%-oMi%& option.
32306 .vitem &*uschar&~*message_id*&
32307 This variable contains Exim's message id for the incoming message (the value of
32308 &$message_exim_id$&) as a zero-terminated string.
32310 .vitem &*uschar&~*received_protocol*&
32311 The name of the protocol by which the message was received.
32313 .vitem &*int&~recipients_count*&
32314 The number of accepted recipients.
32316 .vitem &*recipient_item&~*recipients_list*&
32317 .cindex "recipient" "adding in local scan"
32318 .cindex "recipient" "removing in local scan"
32319 The list of accepted recipients, held in a vector of length
32320 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
32321 can add additional recipients by calling &'receive_add_recipient()'& (see
32322 below). You can delete recipients by removing them from the vector and
32323 adjusting the value in &%recipients_count%&. In particular, by setting
32324 &%recipients_count%& to zero you remove all recipients. If you then return the
32325 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
32326 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
32327 and then call &'receive_add_recipient()'& as often as needed.
32329 .vitem &*uschar&~*sender_address*&
32330 The envelope sender address. For bounce messages this is the empty string.
32332 .vitem &*uschar&~*sender_host_address*&
32333 The IP address of the sending host, as a string. This is NULL for
32334 locally-submitted messages.
32336 .vitem &*uschar&~*sender_host_authenticated*&
32337 The name of the authentication mechanism that was used, or NULL if the message
32338 was not received over an authenticated SMTP connection.
32340 .vitem &*uschar&~*sender_host_name*&
32341 The name of the sending host, if known.
32343 .vitem &*int&~sender_host_port*&
32344 The port on the sending host.
32346 .vitem &*BOOL&~smtp_input*&
32347 This variable is TRUE for all SMTP input, including BSMTP.
32349 .vitem &*BOOL&~smtp_batched_input*&
32350 This variable is TRUE for BSMTP input.
32352 .vitem &*int&~store_pool*&
32353 The contents of this variable control which pool of memory is used for new
32354 requests. See section &<<SECTmemhanloc>>& for details.
32358 .section "Structure of header lines" "SECID209"
32359 The &%header_line%& structure contains the members listed below.
32360 You can add additional header lines by calling the &'header_add()'& function
32361 (see below). You can cause header lines to be ignored (deleted) by setting
32366 .vitem &*struct&~header_line&~*next*&
32367 A pointer to the next header line, or NULL for the last line.
32369 .vitem &*int&~type*&
32370 A code identifying certain headers that Exim recognizes. The codes are printing
32371 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
32372 Notice in particular that any header line whose type is * is not transmitted
32373 with the message. This flagging is used for header lines that have been
32374 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
32375 lines.) Effectively, * means &"deleted"&.
32377 .vitem &*int&~slen*&
32378 The number of characters in the header line, including the terminating and any
32381 .vitem &*uschar&~*text*&
32382 A pointer to the text of the header. It always ends with a newline, followed by
32383 a zero byte. Internal newlines are preserved.
32388 .section "Structure of recipient items" "SECID210"
32389 The &%recipient_item%& structure contains these members:
32392 .vitem &*uschar&~*address*&
32393 This is a pointer to the recipient address as it was received.
32395 .vitem &*int&~pno*&
32396 This is used in later Exim processing when top level addresses are created by
32397 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
32398 and must always contain -1 at this stage.
32400 .vitem &*uschar&~*errors_to*&
32401 If this value is not NULL, bounce messages caused by failing to deliver to the
32402 recipient are sent to the address it contains. In other words, it overrides the
32403 envelope sender for this one recipient. (Compare the &%errors_to%& generic
32404 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
32405 an unqualified address, Exim qualifies it using the domain from
32406 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
32407 is NULL for all recipients.
32412 .section "Available Exim functions" "SECID211"
32413 .cindex "&[local_scan()]& function" "available Exim functions"
32414 The header &_local_scan.h_& gives you access to a number of Exim functions.
32415 These are the only ones that are guaranteed to be maintained from release to
32419 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
32420 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
32422 This function creates a child process that runs the command specified by
32423 &%argv%&. The environment for the process is specified by &%envp%&, which can
32424 be NULL if no environment variables are to be passed. A new umask is supplied
32425 for the process in &%newumask%&.
32427 Pipes to the standard input and output of the new process are set up
32428 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
32429 standard error is cloned to the standard output. If there are any file
32430 descriptors &"in the way"& in the new process, they are closed. If the final
32431 argument is TRUE, the new process is made into a process group leader.
32433 The function returns the pid of the new process, or -1 if things go wrong.
32435 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
32436 This function waits for a child process to terminate, or for a timeout (in
32437 seconds) to expire. A timeout value of zero means wait as long as it takes. The
32438 return value is as follows:
32443 The process terminated by a normal exit and the value is the process
32449 The process was terminated by a signal and the value is the negation of the
32455 The process timed out.
32459 The was some other error in wait(); &%errno%& is still set.
32462 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
32463 This function provide you with a means of submitting a new message to
32464 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
32465 want, but this packages it all up for you.) The function creates a pipe,
32466 forks a subprocess that is running
32468 exim -t -oem -oi -f <>
32470 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
32471 that is connected to the standard input. The yield of the function is the PID
32472 of the subprocess. You can then write a message to the file descriptor, with
32473 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
32475 When you have finished, call &'child_close()'& to wait for the process to
32476 finish and to collect its ending status. A timeout value of zero is usually
32477 fine in this circumstance. Unless you have made a mistake with the recipient
32478 addresses, you should get a return code of zero.
32481 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
32482 *sender_authentication)*&
32483 This function is a more sophisticated version of &'child_open()'&. The command
32486 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
32488 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
32491 .vitem &*void&~debug_printf(char&~*,&~...)*&
32492 This is Exim's debugging function, with arguments as for &'(printf()'&. The
32493 output is written to the standard error stream. If no debugging is selected,
32494 calls to &'debug_printf()'& have no effect. Normally, you should make calls
32495 conditional on the &`local_scan`& debug selector by coding like this:
32497 if ((debug_selector & D_local_scan) != 0)
32498 debug_printf("xxx", ...);
32501 .vitem &*uschar&~*expand_string(uschar&~*string)*&
32502 This is an interface to Exim's string expansion code. The return value is the
32503 expanded string, or NULL if there was an expansion failure.
32504 The C variable &%expand_string_message%& contains an error message after an
32505 expansion failure. If expansion does not change the string, the return value is
32506 the pointer to the input string. Otherwise, the return value points to a new
32507 block of memory that was obtained by a call to &'store_get()'&. See section
32508 &<<SECTmemhanloc>>& below for a discussion of memory handling.
32510 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
32511 This function allows you to an add additional header line at the end of the
32512 existing ones. The first argument is the type, and should normally be a space
32513 character. The second argument is a format string and any number of
32514 substitution arguments as for &[sprintf()]&. You may include internal newlines
32515 if you want, and you must ensure that the string ends with a newline.
32517 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
32518 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
32519 This function adds a new header line at a specified point in the header
32520 chain. The header itself is specified as for &'header_add()'&.
32522 If &%name%& is NULL, the new header is added at the end of the chain if
32523 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
32524 NULL, the header lines are searched for the first non-deleted header that
32525 matches the name. If one is found, the new header is added before it if
32526 &%after%& is false. If &%after%& is true, the new header is added after the
32527 found header and any adjacent subsequent ones with the same name (even if
32528 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
32529 option controls where the header is added. If it is true, addition is at the
32530 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
32531 headers, or at the top if there are no &'Received:'& headers, you could use
32533 header_add_at_position(TRUE, US"Received", TRUE,
32534 ' ', "X-xxx: ...");
32536 Normally, there is always at least one non-deleted &'Received:'& header, but
32537 there may not be if &%received_header_text%& expands to an empty string.
32540 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
32541 This function removes header lines. If &%occurrence%& is zero or negative, all
32542 occurrences of the header are removed. If occurrence is greater than zero, that
32543 particular instance of the header is removed. If no header(s) can be found that
32544 match the specification, the function does nothing.
32547 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
32548 int&~length,&~BOOL&~notdel)*&"
32549 This function tests whether the given header has the given name. It is not just
32550 a string comparison, because white space is permitted between the name and the
32551 colon. If the &%notdel%& argument is true, a false return is forced for all
32552 &"deleted"& headers; otherwise they are not treated specially. For example:
32554 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
32556 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
32557 .cindex "base64 encoding" "functions for &[local_scan()]& use"
32558 This function base64-encodes a string, which is passed by address and length.
32559 The text may contain bytes of any value, including zero. The result is passed
32560 back in dynamic memory that is obtained by calling &'store_get()'&. It is
32563 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
32564 This function decodes a base64-encoded string. Its arguments are a
32565 zero-terminated base64-encoded string and the address of a variable that is set
32566 to point to the result, which is in dynamic memory. The length of the decoded
32567 string is the yield of the function. If the input is invalid base64 data, the
32568 yield is -1. A zero byte is added to the end of the output string to make it
32569 easy to interpret as a C string (assuming it contains no zeros of its own). The
32570 added zero byte is not included in the returned count.
32572 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
32573 This function checks for a match in a domain list. Domains are always
32574 matched caselessly. The return value is one of the following:
32576 &`OK `& match succeeded
32577 &`FAIL `& match failed
32578 &`DEFER `& match deferred
32580 DEFER is usually caused by some kind of lookup defer, such as the
32581 inability to contact a database.
32583 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
32585 This function checks for a match in a local part list. The third argument
32586 controls case-sensitivity. The return values are as for
32587 &'lss_match_domain()'&.
32589 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
32591 This function checks for a match in an address list. The third argument
32592 controls the case-sensitivity of the local part match. The domain is always
32593 matched caselessly. The return values are as for &'lss_match_domain()'&.
32595 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
32597 This function checks for a match in a host list. The most common usage is
32600 lss_match_host(sender_host_name, sender_host_address, ...)
32602 .vindex "&$sender_host_address$&"
32603 An empty address field matches an empty item in the host list. If the host name
32604 is NULL, the name corresponding to &$sender_host_address$& is automatically
32605 looked up if a host name is required to match an item in the list. The return
32606 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
32607 returns ERROR in the case when it had to look up a host name, but the lookup
32610 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
32612 This function writes to Exim's log files. The first argument should be zero (it
32613 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
32614 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
32615 them. It specifies to which log or logs the message is written. The remaining
32616 arguments are a format and relevant insertion arguments. The string should not
32617 contain any newlines, not even at the end.
32620 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
32621 This function adds an additional recipient to the message. The first argument
32622 is the recipient address. If it is unqualified (has no domain), it is qualified
32623 with the &%qualify_recipient%& domain. The second argument must always be -1.
32625 This function does not allow you to specify a private &%errors_to%& address (as
32626 described with the structure of &%recipient_item%& above), because it pre-dates
32627 the addition of that field to the structure. However, it is easy to add such a
32628 value afterwards. For example:
32630 receive_add_recipient(US"monitor@mydom.example", -1);
32631 recipients_list[recipients_count-1].errors_to =
32632 US"postmaster@mydom.example";
32635 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
32636 This is a convenience function to remove a named recipient from the list of
32637 recipients. It returns true if a recipient was removed, and false if no
32638 matching recipient could be found. The argument must be a complete email
32645 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
32646 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
32647 This function decodes strings that are encoded according to RFC 2047. Typically
32648 these are the contents of header lines. First, each &"encoded word"& is decoded
32649 from the Q or B encoding into a byte-string. Then, if provided with the name of
32650 a charset encoding, and if the &[iconv()]& function is available, an attempt is
32651 made to translate the result to the named character set. If this fails, the
32652 binary string is returned with an error message.
32654 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
32655 maximum MIME word length is enforced. The third argument is the target
32656 encoding, or NULL if no translation is wanted.
32658 .cindex "binary zero" "in RFC 2047 decoding"
32659 .cindex "RFC 2047" "binary zero in"
32660 If a binary zero is encountered in the decoded string, it is replaced by the
32661 contents of the &%zeroval%& argument. For use with Exim headers, the value must
32662 not be 0 because header lines are handled as zero-terminated strings.
32664 The function returns the result of processing the string, zero-terminated; if
32665 &%lenptr%& is not NULL, the length of the result is set in the variable to
32666 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
32668 If an error is encountered, the function returns NULL and uses the &%error%&
32669 argument to return an error message. The variable pointed to by &%error%& is
32670 set to NULL if there is no error; it may be set non-NULL even when the function
32671 returns a non-NULL value if decoding was successful, but there was a problem
32675 .vitem &*int&~smtp_fflush(void)*&
32676 This function is used in conjunction with &'smtp_printf()'&, as described
32679 .vitem &*void&~smtp_printf(char&~*,&~...)*&
32680 The arguments of this function are like &[printf()]&; it writes to the SMTP
32681 output stream. You should use this function only when there is an SMTP output
32682 stream, that is, when the incoming message is being received via interactive
32683 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
32684 is FALSE. If you want to test for an incoming message from another host (as
32685 opposed to a local process that used the &%-bs%& command line option), you can
32686 test the value of &%sender_host_address%&, which is non-NULL when a remote host
32689 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
32690 output function, so it can be used for all forms of SMTP connection.
32692 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
32693 must start with an appropriate response code: 550 if you are going to return
32694 LOCAL_SCAN_REJECT, 451 if you are going to return
32695 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
32696 initial lines of a multi-line response, the code must be followed by a hyphen
32697 to indicate that the line is not the final response line. You must also ensure
32698 that the lines you write terminate with CRLF. For example:
32700 smtp_printf("550-this is some extra info\r\n");
32701 return LOCAL_SCAN_REJECT;
32703 Note that you can also create multi-line responses by including newlines in
32704 the data returned via the &%return_text%& argument. The added value of using
32705 &'smtp_printf()'& is that, for instance, you could introduce delays between
32706 multiple output lines.
32708 The &'smtp_printf()'& function does not return any error indication, because it
32709 does not automatically flush pending output, and therefore does not test
32710 the state of the stream. (In the main code of Exim, flushing and error
32711 detection is done when Exim is ready for the next SMTP input command.) If
32712 you want to flush the output and check for an error (for example, the
32713 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
32714 arguments. It flushes the output stream, and returns a non-zero value if there
32717 .vitem &*void&~*store_get(int)*&
32718 This function accesses Exim's internal store (memory) manager. It gets a new
32719 chunk of memory whose size is given by the argument. Exim bombs out if it ever
32720 runs out of memory. See the next section for a discussion of memory handling.
32722 .vitem &*void&~*store_get_perm(int)*&
32723 This function is like &'store_get()'&, but it always gets memory from the
32724 permanent pool. See the next section for a discussion of memory handling.
32726 .vitem &*uschar&~*string_copy(uschar&~*string)*&
32729 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
32732 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
32733 These three functions create strings using Exim's dynamic memory facilities.
32734 The first makes a copy of an entire string. The second copies up to a maximum
32735 number of characters, indicated by the second argument. The third uses a format
32736 and insertion arguments to create a new string. In each case, the result is a
32737 pointer to a new string in the current memory pool. See the next section for
32743 .section "More about Exim's memory handling" "SECTmemhanloc"
32744 .cindex "&[local_scan()]& function" "memory handling"
32745 No function is provided for freeing memory, because that is never needed.
32746 The dynamic memory that Exim uses when receiving a message is automatically
32747 recycled if another message is received by the same process (this applies only
32748 to incoming SMTP connections &-- other input methods can supply only one
32749 message at a time). After receiving the last message, a reception process
32752 Because it is recycled, the normal dynamic memory cannot be used for holding
32753 data that must be preserved over a number of incoming messages on the same SMTP
32754 connection. However, Exim in fact uses two pools of dynamic memory; the second
32755 one is not recycled, and can be used for this purpose.
32757 If you want to allocate memory that remains available for subsequent messages
32758 in the same SMTP connection, you should set
32760 store_pool = POOL_PERM
32762 before calling the function that does the allocation. There is no need to
32763 restore the value if you do not need to; however, if you do want to revert to
32764 the normal pool, you can either restore the previous value of &%store_pool%& or
32765 set it explicitly to POOL_MAIN.
32767 The pool setting applies to all functions that get dynamic memory, including
32768 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
32769 There is also a convenience function called &'store_get_perm()'& that gets a
32770 block of memory from the permanent pool while preserving the value of
32777 . ////////////////////////////////////////////////////////////////////////////
32778 . ////////////////////////////////////////////////////////////////////////////
32780 .chapter "System-wide message filtering" "CHAPsystemfilter"
32781 .scindex IIDsysfil1 "filter" "system filter"
32782 .scindex IIDsysfil2 "filtering all mail"
32783 .scindex IIDsysfil3 "system filter"
32784 The previous chapters (on ACLs and the local scan function) describe checks
32785 that can be applied to messages before they are accepted by a host. There is
32786 also a mechanism for checking messages once they have been received, but before
32787 they are delivered. This is called the &'system filter'&.
32789 The system filter operates in a similar manner to users' filter files, but it
32790 is run just once per message (however many recipients the message has).
32791 It should not normally be used as a substitute for routing, because &%deliver%&
32792 commands in a system router provide new envelope recipient addresses.
32793 The system filter must be an Exim filter. It cannot be a Sieve filter.
32795 The system filter is run at the start of a delivery attempt, before any routing
32796 is done. If a message fails to be completely delivered at the first attempt,
32797 the system filter is run again at the start of every retry.
32798 If you want your filter to do something only once per message, you can make use
32799 of the &%first_delivery%& condition in an &%if%& command in the filter to
32800 prevent it happening on retries.
32802 .vindex "&$domain$&"
32803 .vindex "&$local_part$&"
32804 &*Warning*&: Because the system filter runs just once, variables that are
32805 specific to individual recipient addresses, such as &$local_part$& and
32806 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
32807 you want to run a centrally-specified filter for each recipient address
32808 independently, you can do so by setting up a suitable &(redirect)& router, as
32809 described in section &<<SECTperaddfil>>& below.
32812 .section "Specifying a system filter" "SECID212"
32813 .cindex "uid (user id)" "system filter"
32814 .cindex "gid (group id)" "system filter"
32815 The name of the file that contains the system filter must be specified by
32816 setting &%system_filter%&. If you want the filter to run under a uid and gid
32817 other than root, you must also set &%system_filter_user%& and
32818 &%system_filter_group%& as appropriate. For example:
32820 system_filter = /etc/mail/exim.filter
32821 system_filter_user = exim
32823 If a system filter generates any deliveries directly to files or pipes (via the
32824 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
32825 specified by setting &%system_filter_file_transport%& and
32826 &%system_filter_pipe_transport%&, respectively. Similarly,
32827 &%system_filter_reply_transport%& must be set to handle any messages generated
32828 by the &%reply%& command.
32831 .section "Testing a system filter" "SECID213"
32832 You can run simple tests of a system filter in the same way as for a user
32833 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
32834 are permitted only in system filters are recognized.
32836 If you want to test the combined effect of a system filter and a user filter,
32837 you can use both &%-bF%& and &%-bf%& on the same command line.
32841 .section "Contents of a system filter" "SECID214"
32842 The language used to specify system filters is the same as for users' filter
32843 files. It is described in the separate end-user document &'Exim's interface to
32844 mail filtering'&. However, there are some additional features that are
32845 available only in system filters; these are described in subsequent sections.
32846 If they are encountered in a user's filter file or when testing with &%-bf%&,
32849 .cindex "frozen messages" "manual thaw; testing in filter"
32850 There are two special conditions which, though available in users' filter
32851 files, are designed for use in system filters. The condition &%first_delivery%&
32852 is true only for the first attempt at delivering a message, and
32853 &%manually_thawed%& is true only if the message has been frozen, and
32854 subsequently thawed by an admin user. An explicit forced delivery counts as a
32855 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
32857 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
32858 specify an &"unseen"& (non-significant) delivery, and that delivery does not
32859 succeed, it will not be tried again.
32860 If you want Exim to retry an unseen delivery until it succeeds, you should
32861 arrange to set it up every time the filter runs.
32863 When a system filter finishes running, the values of the variables &$n0$& &--
32864 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
32865 users' filter files. Thus a system filter can, for example, set up &"scores"&
32866 to which users' filter files can refer.
32870 .section "Additional variable for system filters" "SECID215"
32871 .vindex "&$recipients$&"
32872 The expansion variable &$recipients$&, containing a list of all the recipients
32873 of the message (separated by commas and white space), is available in system
32874 filters. It is not available in users' filters for privacy reasons.
32878 .section "Defer, freeze, and fail commands for system filters" "SECID216"
32879 .cindex "freezing messages"
32880 .cindex "message" "freezing"
32881 .cindex "message" "forced failure"
32882 .cindex "&%fail%&" "in system filter"
32883 .cindex "&%freeze%& in system filter"
32884 .cindex "&%defer%& in system filter"
32885 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
32886 always available in system filters, but are not normally enabled in users'
32887 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
32888 for the &(redirect)& router.) These commands can optionally be followed by the
32889 word &%text%& and a string containing an error message, for example:
32891 fail text "this message looks like spam to me"
32893 The keyword &%text%& is optional if the next character is a double quote.
32895 The &%defer%& command defers delivery of the original recipients of the
32896 message. The &%fail%& command causes all the original recipients to be failed,
32897 and a bounce message to be created. The &%freeze%& command suspends all
32898 delivery attempts for the original recipients. In all cases, any new deliveries
32899 that are specified by the filter are attempted as normal after the filter has
32902 The &%freeze%& command is ignored if the message has been manually unfrozen and
32903 not manually frozen since. This means that automatic freezing by a system
32904 filter can be used as a way of checking out suspicious messages. If a message
32905 is found to be all right, manually unfreezing it allows it to be delivered.
32907 .cindex "log" "&%fail%& command log line"
32908 .cindex "&%fail%&" "log line; reducing"
32909 The text given with a fail command is used as part of the bounce message as
32910 well as being written to the log. If the message is quite long, this can fill
32911 up a lot of log space when such failures are common. To reduce the size of the
32912 log message, Exim interprets the text in a special way if it starts with the
32913 two characters &`<<`& and contains &`>>`& later. The text between these two
32914 strings is written to the log, and the rest of the text is used in the bounce
32915 message. For example:
32917 fail "<<filter test 1>>Your message is rejected \
32918 because it contains attachments that we are \
32919 not prepared to receive."
32922 .cindex "loop" "caused by &%fail%&"
32923 Take great care with the &%fail%& command when basing the decision to fail on
32924 the contents of the message, because the bounce message will of course include
32925 the contents of the original message and will therefore trigger the &%fail%&
32926 command again (causing a mail loop) unless steps are taken to prevent this.
32927 Testing the &%error_message%& condition is one way to prevent this. You could
32930 if $message_body contains "this is spam" and not error_message
32931 then fail text "spam is not wanted here" endif
32933 though of course that might let through unwanted bounce messages. The
32934 alternative is clever checking of the body and/or headers to detect bounces
32935 generated by the filter.
32937 The interpretation of a system filter file ceases after a
32939 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
32940 set up earlier in the filter file are honoured, so you can use a sequence such
32946 to send a specified message when the system filter is freezing (or deferring or
32947 failing) a message. The normal deliveries for the message do not, of course,
32952 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
32953 .cindex "header lines" "adding; in system filter"
32954 .cindex "header lines" "removing; in system filter"
32955 .cindex "filter" "header lines; adding/removing"
32956 Two filter commands that are available only in system filters are:
32958 headers add <string>
32959 headers remove <string>
32961 The argument for the &%headers add%& is a string that is expanded and then
32962 added to the end of the message's headers. It is the responsibility of the
32963 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
32964 space is ignored, and if the string is otherwise empty, or if the expansion is
32965 forced to fail, the command has no effect.
32967 You can use &"\n"& within the string, followed by white space, to specify
32968 continued header lines. More than one header may be added in one command by
32969 including &"\n"& within the string without any following white space. For
32972 headers add "X-header-1: ....\n \
32973 continuation of X-header-1 ...\n\
32976 Note that the header line continuation white space after the first newline must
32977 be placed before the backslash that continues the input string, because white
32978 space after input continuations is ignored.
32980 The argument for &%headers remove%& is a colon-separated list of header names.
32981 This command applies only to those headers that are stored with the message;
32982 those that are added at delivery time (such as &'Envelope-To:'& and
32983 &'Return-Path:'&) cannot be removed by this means. If there is more than one
32984 header with the same name, they are all removed.
32986 The &%headers%& command in a system filter makes an immediate change to the set
32987 of header lines that was received with the message (with possible additions
32988 from ACL processing). Subsequent commands in the system filter operate on the
32989 modified set, which also forms the basis for subsequent message delivery.
32990 Unless further modified during routing or transporting, this set of headers is
32991 used for all recipients of the message.
32993 During routing and transporting, the variables that refer to the contents of
32994 header lines refer only to those lines that are in this set. Thus, header lines
32995 that are added by a system filter are visible to users' filter files and to all
32996 routers and transports. This contrasts with the manipulation of header lines by
32997 routers and transports, which is not immediate, but which instead is saved up
32998 until the message is actually being written (see section
32999 &<<SECTheadersaddrem>>&).
33001 If the message is not delivered at the first attempt, header lines that were
33002 added by the system filter are stored with the message, and so are still
33003 present at the next delivery attempt. Header lines that were removed are still
33004 present, but marked &"deleted"& so that they are not transported with the
33005 message. For this reason, it is usual to make the &%headers%& command
33006 conditional on &%first_delivery%& so that the set of header lines is not
33007 modified more than once.
33009 Because header modification in a system filter acts immediately, you have to
33010 use an indirect approach if you want to modify the contents of a header line.
33013 headers add "Old-Subject: $h_subject:"
33014 headers remove "Subject"
33015 headers add "Subject: new subject (was: $h_old-subject:)"
33016 headers remove "Old-Subject"
33021 .section "Setting an errors address in a system filter" "SECID217"
33022 .cindex "envelope sender"
33023 In a system filter, if a &%deliver%& command is followed by
33025 errors_to <some address>
33027 in order to change the envelope sender (and hence the error reporting) for that
33028 delivery, any address may be specified. (In a user filter, only the current
33029 user's address can be set.) For example, if some mail is being monitored, you
33032 unseen deliver monitor@spying.example errors_to root@local.example
33034 to take a copy which would not be sent back to the normal error reporting
33035 address if its delivery failed.
33039 .section "Per-address filtering" "SECTperaddfil"
33040 .vindex "&$domain$&"
33041 .vindex "&$local_part$&"
33042 In contrast to the system filter, which is run just once per message for each
33043 delivery attempt, it is also possible to set up a system-wide filtering
33044 operation that runs once for each recipient address. In this case, variables
33045 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
33046 filter file could be made dependent on them. This is an example of a router
33047 which implements such a filter:
33052 domains = +local_domains
33053 file = /central/filters/$local_part
33058 The filter is run in a separate process under its own uid. Therefore, either
33059 &%check_local_user%& must be set (as above), in which case the filter is run as
33060 the local user, or the &%user%& option must be used to specify which user to
33061 use. If both are set, &%user%& overrides.
33063 Care should be taken to ensure that none of the commands in the filter file
33064 specify a significant delivery if the message is to go on to be delivered to
33065 its intended recipient. The router will not then claim to have dealt with the
33066 address, so it will be passed on to subsequent routers to be delivered in the
33068 .ecindex IIDsysfil1
33069 .ecindex IIDsysfil2
33070 .ecindex IIDsysfil3
33077 . ////////////////////////////////////////////////////////////////////////////
33078 . ////////////////////////////////////////////////////////////////////////////
33080 .chapter "Message processing" "CHAPmsgproc"
33081 .scindex IIDmesproc "message" "general processing"
33082 Exim performs various transformations on the sender and recipient addresses of
33083 all messages that it handles, and also on the messages' header lines. Some of
33084 these are optional and configurable, while others always take place. All of
33085 this processing, except rewriting as a result of routing, and the addition or
33086 removal of header lines while delivering, happens when a message is received,
33087 before it is placed on Exim's queue.
33089 Some of the automatic processing takes place by default only for
33090 &"locally-originated"& messages. This adjective is used to describe messages
33091 that are not received over TCP/IP, but instead are passed to an Exim process on
33092 its standard input. This includes the interactive &"local SMTP"& case that is
33093 set up by the &%-bs%& command line option.
33095 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
33096 or ::1) are not considered to be locally-originated. Exim does not treat the
33097 loopback interface specially in any way.
33099 If you want the loopback interface to be treated specially, you must ensure
33100 that there are appropriate entries in your ACLs.
33105 .section "Submission mode for non-local messages" "SECTsubmodnon"
33106 .cindex "message" "submission"
33107 .cindex "submission mode"
33108 Processing that happens automatically for locally-originated messages (unless
33109 &%suppress_local_fixups%& is set) can also be requested for messages that are
33110 received over TCP/IP. The term &"submission mode"& is used to describe this
33111 state. Submission mode is set by the modifier
33113 control = submission
33115 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
33116 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
33117 a local submission, and is normally used when the source of the message is
33118 known to be an MUA running on a client host (as opposed to an MTA). For
33119 example, to set submission mode for messages originating on the IPv4 loopback
33120 interface, you could include the following in the MAIL ACL:
33122 warn hosts = 127.0.0.1
33123 control = submission
33125 .cindex "&%sender_retain%& submission option"
33126 There are some options that can be used when setting submission mode. A slash
33127 is used to separate options. For example:
33129 control = submission/sender_retain
33131 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
33132 true and &%local_from_check%& false for the current incoming message. The first
33133 of these allows an existing &'Sender:'& header in the message to remain, and
33134 the second suppresses the check to ensure that &'From:'& matches the
33135 authenticated sender. With this setting, Exim still fixes up messages by adding
33136 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
33137 attempt to check sender authenticity in header lines.
33139 When &%sender_retain%& is not set, a submission mode setting may specify a
33140 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
33143 control = submission/domain=some.domain
33145 The domain may be empty. How this value is used is described in sections
33146 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
33147 that allows you to specify the user's full name for inclusion in a created
33148 &'Sender:'& or &'From:'& header line. For example:
33150 accept authenticated = *
33151 control = submission/domain=wonderland.example/\
33152 name=${lookup {$authenticated_id} \
33153 lsearch {/etc/exim/namelist}}
33155 Because the name may contain any characters, including slashes, the &%name%&
33156 option must be given last. The remainder of the string is used as the name. For
33157 the example above, if &_/etc/exim/namelist_& contains:
33159 bigegg: Humpty Dumpty
33161 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
33164 Sender: Humpty Dumpty <bigegg@wonderland.example>
33166 .cindex "return path" "in submission mode"
33167 By default, submission mode forces the return path to the same address as is
33168 used to create the &'Sender:'& header. However, if &%sender_retain%& is
33169 specified, the return path is also left unchanged.
33171 &*Note*&: The changes caused by submission mode take effect after the predata
33172 ACL. This means that any sender checks performed before the fix-ups use the
33173 untrusted sender address specified by the user, not the trusted sender address
33174 specified by submission mode. Although this might be slightly unexpected, it
33175 does mean that you can configure ACL checks to spot that a user is trying to
33176 spoof another's address.
33178 .section "Line endings" "SECTlineendings"
33179 .cindex "line endings"
33180 .cindex "carriage return"
33182 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
33183 linefeed) is the line ending for messages transmitted over the Internet using
33184 SMTP over TCP/IP. However, within individual operating systems, different
33185 conventions are used. For example, Unix-like systems use just LF, but others
33186 use CRLF or just CR.
33188 Exim was designed for Unix-like systems, and internally, it stores messages
33189 using the system's convention of a single LF as a line terminator. When
33190 receiving a message, all line endings are translated to this standard format.
33191 Originally, it was thought that programs that passed messages directly to an
33192 MTA within an operating system would use that system's convention. Experience
33193 has shown that this is not the case; for example, there are Unix applications
33194 that use CRLF in this circumstance. For this reason, and for compatibility with
33195 other MTAs, the way Exim handles line endings for all messages is now as
33199 LF not preceded by CR is treated as a line ending.
33201 CR is treated as a line ending; if it is immediately followed by LF, the LF
33204 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
33205 nor a local message in the state where a line containing only a dot is a
33208 If a bare CR is encountered within a header line, an extra space is added after
33209 the line terminator so as not to end the header line. The reasoning behind this
33210 is that bare CRs in header lines are most likely either to be mistakes, or
33211 people trying to play silly games.
33213 If the first header line received in a message ends with CRLF, a subsequent
33214 bare LF in a header line is treated in the same way as a bare CR in a header
33222 .section "Unqualified addresses" "SECID218"
33223 .cindex "unqualified addresses"
33224 .cindex "address" "qualification"
33225 By default, Exim expects every envelope address it receives from an external
33226 host to be fully qualified. Unqualified addresses cause negative responses to
33227 SMTP commands. However, because SMTP is used as a means of transporting
33228 messages from MUAs running on personal workstations, there is sometimes a
33229 requirement to accept unqualified addresses from specific hosts or IP networks.
33231 Exim has two options that separately control which hosts may send unqualified
33232 sender or recipient addresses in SMTP commands, namely
33233 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
33234 cases, if an unqualified address is accepted, it is qualified by adding the
33235 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
33237 .oindex "&%qualify_domain%&"
33238 .oindex "&%qualify_recipient%&"
33239 Unqualified addresses in header lines are automatically qualified for messages
33240 that are locally originated, unless the &%-bnq%& option is given on the command
33241 line. For messages received over SMTP, unqualified addresses in header lines
33242 are qualified only if unqualified addresses are permitted in SMTP commands. In
33243 other words, such qualification is also controlled by
33244 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
33249 .section "The UUCP From line" "SECID219"
33250 .cindex "&""From""& line"
33251 .cindex "UUCP" "&""From""& line"
33252 .cindex "sender" "address"
33253 .oindex "&%uucp_from_pattern%&"
33254 .oindex "&%uucp_from_sender%&"
33255 .cindex "envelope sender"
33256 .cindex "Sendmail compatibility" "&""From""& line"
33257 Messages that have come from UUCP (and some other applications) often begin
33258 with a line containing the envelope sender and a timestamp, following the word
33259 &"From"&. Examples of two common formats are:
33261 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
33262 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
33264 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
33265 Exim recognizes such lines at the start of messages that are submitted to it
33266 via the command line (that is, on the standard input). It does not recognize
33267 such lines in incoming SMTP messages, unless the sending host matches
33268 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
33269 and &%ignore_fromline_local%& is set. The recognition is controlled by a
33270 regular expression that is defined by the &%uucp_from_pattern%& option, whose
33271 default value matches the two common cases shown above and puts the address
33272 that follows &"From"& into &$1$&.
33274 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
33275 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
33276 a trusted user, the message's sender address is constructed by expanding the
33277 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
33278 then parsed as an RFC 2822 address. If there is no domain, the local part is
33279 qualified with &%qualify_domain%& unless it is the empty string. However, if
33280 the command line &%-f%& option is used, it overrides the &"From"& line.
33282 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
33283 sender address is not changed. This is also the case for incoming SMTP messages
33284 that are permitted to contain &"From"& lines.
33286 Only one &"From"& line is recognized. If there is more than one, the second is
33287 treated as a data line that starts the body of the message, as it is not valid
33288 as a header line. This also happens if a &"From"& line is present in an
33289 incoming SMTP message from a source that is not permitted to send them.
33293 .section "Resent- header lines" "SECID220"
33294 .cindex "&%Resent-%& header lines"
33295 RFC 2822 makes provision for sets of header lines starting with the string
33296 &`Resent-`& to be added to a message when it is resent by the original
33297 recipient to somebody else. These headers are &'Resent-Date:'&,
33298 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
33299 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
33302 &'Resent fields are strictly informational. They MUST NOT be used in the normal
33303 processing of replies or other such automatic actions on messages.'&
33306 This leaves things a bit vague as far as other processing actions such as
33307 address rewriting are concerned. Exim treats &%Resent-%& header lines as
33311 A &'Resent-From:'& line that just contains the login id of the submitting user
33312 is automatically rewritten in the same way as &'From:'& (see below).
33314 If there's a rewriting rule for a particular header line, it is also applied to
33315 &%Resent-%& header lines of the same type. For example, a rule that rewrites
33316 &'From:'& also rewrites &'Resent-From:'&.
33318 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
33321 For a locally-submitted message,
33322 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
33323 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
33324 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
33325 included in log lines in this case.
33327 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
33328 &%Resent-%& header lines are present.
33334 .section "The Auto-Submitted: header line" "SECID221"
33335 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
33336 includes the header line:
33338 Auto-Submitted: auto-replied
33341 .section "The Bcc: header line" "SECID222"
33342 .cindex "&'Bcc:'& header line"
33343 If Exim is called with the &%-t%& option, to take recipient addresses from a
33344 message's header, it removes any &'Bcc:'& header line that may exist (after
33345 extracting its addresses). If &%-t%& is not present on the command line, any
33346 existing &'Bcc:'& is not removed.
33349 .section "The Date: header line" "SECID223"
33350 .cindex "&'Date:'& header line"
33351 If a locally-generated or submission-mode message has no &'Date:'& header line,
33352 Exim adds one, using the current date and time, unless the
33353 &%suppress_local_fixups%& control has been specified.
33355 .section "The Delivery-date: header line" "SECID224"
33356 .cindex "&'Delivery-date:'& header line"
33357 .oindex "&%delivery_date_remove%&"
33358 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
33359 set. Exim can be configured to add them to the final delivery of messages. (See
33360 the generic &%delivery_date_add%& transport option.) They should not be present
33361 in messages in transit. If the &%delivery_date_remove%& configuration option is
33362 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
33366 .section "The Envelope-to: header line" "SECID225"
33367 .cindex "&'Envelope-to:'& header line"
33368 .oindex "&%envelope_to_remove%&"
33369 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
33370 Exim can be configured to add them to the final delivery of messages. (See the
33371 generic &%envelope_to_add%& transport option.) They should not be present in
33372 messages in transit. If the &%envelope_to_remove%& configuration option is set
33373 (the default), Exim removes &'Envelope-to:'& header lines from incoming
33377 .section "The From: header line" "SECTthefrohea"
33378 .cindex "&'From:'& header line"
33379 .cindex "Sendmail compatibility" "&""From""& line"
33380 .cindex "message" "submission"
33381 .cindex "submission mode"
33382 If a submission-mode message does not contain a &'From:'& header line, Exim
33383 adds one if either of the following conditions is true:
33386 The envelope sender address is not empty (that is, this is not a bounce
33387 message). The added header line copies the envelope sender address.
33389 .vindex "&$authenticated_id$&"
33390 The SMTP session is authenticated and &$authenticated_id$& is not empty.
33392 .vindex "&$qualify_domain$&"
33393 If no domain is specified by the submission control, the local part is
33394 &$authenticated_id$& and the domain is &$qualify_domain$&.
33396 If a non-empty domain is specified by the submission control, the local
33397 part is &$authenticated_id$&, and the domain is the specified domain.
33399 If an empty domain is specified by the submission control,
33400 &$authenticated_id$& is assumed to be the complete address.
33404 A non-empty envelope sender takes precedence.
33406 If a locally-generated incoming message does not contain a &'From:'& header
33407 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
33408 containing the sender's address. The calling user's login name and full name
33409 are used to construct the address, as described in section &<<SECTconstr>>&.
33410 They are obtained from the password data by calling &[getpwuid()]& (but see the
33411 &%unknown_login%& configuration option). The address is qualified with
33412 &%qualify_domain%&.
33414 For compatibility with Sendmail, if an incoming, non-SMTP message has a
33415 &'From:'& header line containing just the unqualified login name of the calling
33416 user, this is replaced by an address containing the user's login name and full
33417 name as described in section &<<SECTconstr>>&.
33420 .section "The Message-ID: header line" "SECID226"
33421 .cindex "&'Message-ID:'& header line"
33422 .cindex "message" "submission"
33423 .oindex "&%message_id_header_text%&"
33424 If a locally-generated or submission-mode incoming message does not contain a
33425 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
33426 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
33427 to the message. If there are any &'Resent-:'& headers in the message, it
33428 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
33429 message id, preceded by the letter E to ensure it starts with a letter, and
33430 followed by @ and the primary host name. Additional information can be included
33431 in this header line by setting the &%message_id_header_text%& and/or
33432 &%message_id_header_domain%& options.
33435 .section "The Received: header line" "SECID227"
33436 .cindex "&'Received:'& header line"
33437 A &'Received:'& header line is added at the start of every message. The
33438 contents are defined by the &%received_header_text%& configuration option, and
33439 Exim automatically adds a semicolon and a timestamp to the configured string.
33441 The &'Received:'& header is generated as soon as the message's header lines
33442 have been received. At this stage, the timestamp in the &'Received:'& header
33443 line is the time that the message started to be received. This is the value
33444 that is seen by the DATA ACL and by the &[local_scan()]& function.
33446 Once a message is accepted, the timestamp in the &'Received:'& header line is
33447 changed to the time of acceptance, which is (apart from a small delay while the
33448 -H spool file is written) the earliest time at which delivery could start.
33451 .section "The References: header line" "SECID228"
33452 .cindex "&'References:'& header line"
33453 Messages created by the &(autoreply)& transport include a &'References:'&
33454 header line. This is constructed according to the rules that are described in
33455 section 3.64 of RFC 2822 (which states that replies should contain such a
33456 header line), and section 3.14 of RFC 3834 (which states that automatic
33457 responses are not different in this respect). However, because some mail
33458 processing software does not cope well with very long header lines, no more
33459 than 12 message IDs are copied from the &'References:'& header line in the
33460 incoming message. If there are more than 12, the first one and then the final
33461 11 are copied, before adding the message ID of the incoming message.
33465 .section "The Return-path: header line" "SECID229"
33466 .cindex "&'Return-path:'& header line"
33467 .oindex "&%return_path_remove%&"
33468 &'Return-path:'& header lines are defined as something an MTA may insert when
33469 it does the final delivery of messages. (See the generic &%return_path_add%&
33470 transport option.) Therefore, they should not be present in messages in
33471 transit. If the &%return_path_remove%& configuration option is set (the
33472 default), Exim removes &'Return-path:'& header lines from incoming messages.
33476 .section "The Sender: header line" "SECTthesenhea"
33477 .cindex "&'Sender:'& header line"
33478 .cindex "message" "submission"
33479 For a locally-originated message from an untrusted user, Exim may remove an
33480 existing &'Sender:'& header line, and it may add a new one. You can modify
33481 these actions by setting the &%local_sender_retain%& option true, the
33482 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
33485 When a local message is received from an untrusted user and
33486 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
33487 control has not been set, a check is made to see if the address given in the
33488 &'From:'& header line is the correct (local) sender of the message. The address
33489 that is expected has the login name as the local part and the value of
33490 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
33491 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
33492 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
33493 line is added to the message.
33495 If you set &%local_from_check%& false, this checking does not occur. However,
33496 the removal of an existing &'Sender:'& line still happens, unless you also set
33497 &%local_sender_retain%& to be true. It is not possible to set both of these
33498 options true at the same time.
33500 .cindex "submission mode"
33501 By default, no processing of &'Sender:'& header lines is done for messages
33502 received over TCP/IP or for messages submitted by trusted users. However, when
33503 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
33504 not specified on the submission control, the following processing takes place:
33506 .vindex "&$authenticated_id$&"
33507 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
33508 authenticated, and &$authenticated_id$& is not empty, a sender address is
33509 created as follows:
33512 .vindex "&$qualify_domain$&"
33513 If no domain is specified by the submission control, the local part is
33514 &$authenticated_id$& and the domain is &$qualify_domain$&.
33516 If a non-empty domain is specified by the submission control, the local part
33517 is &$authenticated_id$&, and the domain is the specified domain.
33519 If an empty domain is specified by the submission control,
33520 &$authenticated_id$& is assumed to be the complete address.
33523 This address is compared with the address in the &'From:'& header line. If they
33524 are different, a &'Sender:'& header line containing the created address is
33525 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
33526 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
33528 .cindex "return path" "created from &'Sender:'&"
33529 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
33530 the message (the envelope sender address) is changed to be the same address,
33531 except in the case of submission mode when &%sender_retain%& is specified.
33535 .section "Adding and removing header lines in routers and transports" &&&
33536 "SECTheadersaddrem"
33537 .cindex "header lines" "adding; in router or transport"
33538 .cindex "header lines" "removing; in router or transport"
33539 When a message is delivered, the addition and removal of header lines can be
33540 specified in a system filter, or on any of the routers and transports that
33541 process the message. Section &<<SECTaddremheasys>>& contains details about
33542 modifying headers in a system filter. Header lines can also be added in an ACL
33543 as a message is received (see section &<<SECTaddheadacl>>&).
33545 In contrast to what happens in a system filter, header modifications that are
33546 specified on routers and transports apply only to the particular recipient
33547 addresses that are being processed by those routers and transports. These
33548 changes do not actually take place until a copy of the message is being
33549 transported. Therefore, they do not affect the basic set of header lines, and
33550 they do not affect the values of the variables that refer to header lines.
33552 &*Note*&: In particular, this means that any expansions in the configuration of
33553 the transport cannot refer to the modified header lines, because such
33554 expansions all occur before the message is actually transported.
33556 For both routers and transports, the argument of a &%headers_add%&
33557 option must be in the form of one or more RFC 2822 header lines, separated by
33558 newlines (coded as &"\n"&). For example:
33560 headers_add = X-added-header: added by $primary_hostname\n\
33561 X-added-second: another added header line
33563 Exim does not check the syntax of these added header lines.
33565 Multiple &%headers_add%& options for a single router or transport can be
33566 specified; the values will append to a single list of header lines.
33567 Each header-line is separately expanded.
33569 The argument of a &%headers_remove%& option must consist of a colon-separated
33570 list of header names. This is confusing, because header names themselves are
33571 often terminated by colons. In this case, the colons are the list separators,
33572 not part of the names. For example:
33574 headers_remove = return-receipt-to:acknowledge-to
33577 Multiple &%headers_remove%& options for a single router or transport can be
33578 specified; the arguments will append to a single header-names list.
33579 Each item is separately expanded.
33580 Note that colons in complex expansions which are used to
33581 form all or part of a &%headers_remove%& list
33582 will act as list separators.
33584 When &%headers_add%& or &%headers_remove%& is specified on a router,
33585 items are expanded at routing time,
33586 and then associated with all addresses that are
33587 accepted by that router, and also with any new addresses that it generates. If
33588 an address passes through several routers as a result of aliasing or
33589 forwarding, the changes are cumulative.
33591 .oindex "&%unseen%&"
33592 However, this does not apply to multiple routers that result from the use of
33593 the &%unseen%& option. Any header modifications that were specified by the
33594 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
33596 Addresses that end up with different &%headers_add%& or &%headers_remove%&
33597 settings cannot be delivered together in a batch, so a transport is always
33598 dealing with a set of addresses that have the same header-processing
33601 The transport starts by writing the original set of header lines that arrived
33602 with the message, possibly modified by the system filter. As it writes out
33603 these lines, it consults the list of header names that were attached to the
33604 recipient address(es) by &%headers_remove%& options in routers, and it also
33605 consults the transport's own &%headers_remove%& option. Header lines whose
33606 names are on either of these lists are not written out. If there are multiple
33607 instances of any listed header, they are all skipped.
33609 After the remaining original header lines have been written, new header
33610 lines that were specified by routers' &%headers_add%& options are written, in
33611 the order in which they were attached to the address. These are followed by any
33612 header lines specified by the transport's &%headers_add%& option.
33614 This way of handling header line modifications in routers and transports has
33615 the following consequences:
33618 The original set of header lines, possibly modified by the system filter,
33619 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
33620 to it, at all times.
33622 Header lines that are added by a router's
33623 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
33624 expansion syntax in subsequent routers or the transport.
33626 Conversely, header lines that are specified for removal by &%headers_remove%&
33627 in a router remain visible to subsequent routers and the transport.
33629 Headers added to an address by &%headers_add%& in a router cannot be removed by
33630 a later router or by a transport.
33632 An added header can refer to the contents of an original header that is to be
33633 removed, even it has the same name as the added header. For example:
33635 headers_remove = subject
33636 headers_add = Subject: new subject (was: $h_subject:)
33640 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
33641 for a &(redirect)& router that has the &%one_time%& option set.
33647 .section "Constructed addresses" "SECTconstr"
33648 .cindex "address" "constructed"
33649 .cindex "constructed address"
33650 When Exim constructs a sender address for a locally-generated message, it uses
33653 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
33657 Zaphod Beeblebrox <zaphod@end.univ.example>
33659 The user name is obtained from the &%-F%& command line option if set, or
33660 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
33661 &"gecos"& field from the password entry. If the &"gecos"& field contains an
33662 ampersand character, this is replaced by the login name with the first letter
33663 upper cased, as is conventional in a number of operating systems. See the
33664 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
33665 The &%unknown_username%& option can be used to specify user names in cases when
33666 there is no password file entry.
33669 In all cases, the user name is made to conform to RFC 2822 by quoting all or
33670 parts of it if necessary. In addition, if it contains any non-printing
33671 characters, it is encoded as described in RFC 2047, which defines a way of
33672 including non-ASCII characters in header lines. The value of the
33673 &%headers_charset%& option specifies the name of the encoding that is used (the
33674 characters are assumed to be in this encoding). The setting of
33675 &%print_topbitchars%& controls whether characters with the top bit set (that
33676 is, with codes greater than 127) count as printing characters or not.
33680 .section "Case of local parts" "SECID230"
33681 .cindex "case of local parts"
33682 .cindex "local part" "case of"
33683 RFC 2822 states that the case of letters in the local parts of addresses cannot
33684 be assumed to be non-significant. Exim preserves the case of local parts of
33685 addresses, but by default it uses a lower-cased form when it is routing,
33686 because on most Unix systems, usernames are in lower case and case-insensitive
33687 routing is required. However, any particular router can be made to use the
33688 original case for local parts by setting the &%caseful_local_part%& generic
33691 .cindex "mixed-case login names"
33692 If you must have mixed-case user names on your system, the best way to proceed,
33693 assuming you want case-independent handling of incoming email, is to set up
33694 your first router to convert incoming local parts in your domains to the
33695 correct case by means of a file lookup. For example:
33699 domains = +local_domains
33700 data = ${lookup{$local_part}cdb\
33701 {/etc/usercased.cdb}{$value}fail}\
33704 For this router, the local part is forced to lower case by the default action
33705 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
33706 up a new local part in the correct case. If you then set &%caseful_local_part%&
33707 on any subsequent routers which process your domains, they will operate on
33708 local parts with the correct case in a case-sensitive manner.
33712 .section "Dots in local parts" "SECID231"
33713 .cindex "dot" "in local part"
33714 .cindex "local part" "dots in"
33715 RFC 2822 forbids empty components in local parts. That is, an unquoted local
33716 part may not begin or end with a dot, nor have two consecutive dots in the
33717 middle. However, it seems that many MTAs do not enforce this, so Exim permits
33718 empty components for compatibility.
33722 .section "Rewriting addresses" "SECID232"
33723 .cindex "rewriting" "addresses"
33724 Rewriting of sender and recipient addresses, and addresses in headers, can
33725 happen automatically, or as the result of configuration options, as described
33726 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
33727 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
33729 Automatic rewriting includes qualification, as mentioned above. The other case
33730 in which it can happen is when an incomplete non-local domain is given. The
33731 routing process may cause this to be expanded into the full domain name. For
33732 example, a header such as
33736 might get rewritten as
33738 To: hare@teaparty.wonderland.fict.example
33740 Rewriting as a result of routing is the one kind of message processing that
33741 does not happen at input time, as it cannot be done until the address has
33744 Strictly, one should not do &'any'& deliveries of a message until all its
33745 addresses have been routed, in case any of the headers get changed as a
33746 result of routing. However, doing this in practice would hold up many
33747 deliveries for unreasonable amounts of time, just because one address could not
33748 immediately be routed. Exim therefore does not delay other deliveries when
33749 routing of one or more addresses is deferred.
33750 .ecindex IIDmesproc
33754 . ////////////////////////////////////////////////////////////////////////////
33755 . ////////////////////////////////////////////////////////////////////////////
33757 .chapter "SMTP processing" "CHAPSMTP"
33758 .scindex IIDsmtpproc1 "SMTP" "processing details"
33759 .scindex IIDsmtpproc2 "LMTP" "processing details"
33760 Exim supports a number of different ways of using the SMTP protocol, and its
33761 LMTP variant, which is an interactive protocol for transferring messages into a
33762 closed mail store application. This chapter contains details of how SMTP is
33763 processed. For incoming mail, the following are available:
33766 SMTP over TCP/IP (Exim daemon or &'inetd'&);
33768 SMTP over the standard input and output (the &%-bs%& option);
33770 Batched SMTP on the standard input (the &%-bS%& option).
33773 For mail delivery, the following are available:
33776 SMTP over TCP/IP (the &(smtp)& transport);
33778 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
33781 LMTP over a pipe to a process running in the local host (the &(lmtp)&
33784 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
33785 the &%use_bsmtp%& option set).
33788 &'Batched SMTP'& is the name for a process in which batches of messages are
33789 stored in or read from files (or pipes), in a format in which SMTP commands are
33790 used to contain the envelope information.
33794 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
33795 .cindex "SMTP" "outgoing over TCP/IP"
33796 .cindex "outgoing SMTP over TCP/IP"
33797 .cindex "LMTP" "over TCP/IP"
33798 .cindex "outgoing LMTP over TCP/IP"
33801 .cindex "SIZE option on MAIL command"
33802 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
33803 The &%protocol%& option selects which protocol is to be used, but the actual
33804 processing is the same in both cases.
33806 If, in response to its EHLO command, Exim is told that the SIZE
33807 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
33808 command. The value of <&'n'&> is the message size plus the value of the
33809 &%size_addition%& option (default 1024) to allow for additions to the message
33810 such as per-transport header lines, or changes made in a
33811 .cindex "transport" "filter"
33812 .cindex "filter" "transport filter"
33813 transport filter. If &%size_addition%& is set negative, the use of SIZE is
33816 If the remote server advertises support for PIPELINING, Exim uses the
33817 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
33818 required for the transaction.
33820 If the remote server advertises support for the STARTTLS command, and Exim
33821 was built to support TLS encryption, it tries to start a TLS session unless the
33822 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
33823 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
33824 is called for verification.
33826 If the remote server advertises support for the AUTH command, Exim scans
33827 the authenticators configuration for any suitable client settings, as described
33828 in chapter &<<CHAPSMTPAUTH>>&.
33830 .cindex "carriage return"
33832 Responses from the remote host are supposed to be terminated by CR followed by
33833 LF. However, there are known to be hosts that do not send CR characters, so in
33834 order to be able to interwork with such hosts, Exim treats LF on its own as a
33837 If a message contains a number of different addresses, all those with the same
33838 characteristics (for example, the same envelope sender) that resolve to the
33839 same set of hosts, in the same order, are sent in a single SMTP transaction,
33840 even if they are for different domains, unless there are more than the setting
33841 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
33842 they are split into groups containing no more than &%max_rcpt%&s addresses
33843 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
33844 in parallel sessions. The order of hosts with identical MX values is not
33845 significant when checking whether addresses can be batched in this way.
33847 When the &(smtp)& transport suffers a temporary failure that is not
33848 message-related, Exim updates its transport-specific database, which contains
33849 records indexed by host name that remember which messages are waiting for each
33850 particular host. It also updates the retry database with new retry times.
33852 .cindex "hints database" "retry keys"
33853 Exim's retry hints are based on host name plus IP address, so if one address of
33854 a multi-homed host is broken, it will soon be skipped most of the time.
33855 See the next section for more detail about error handling.
33857 .cindex "SMTP" "passed connection"
33858 .cindex "SMTP" "batching over TCP/IP"
33859 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
33860 looks in the hints database for the transport to see if there are any queued
33861 messages waiting for the host to which it is connected. If it finds one, it
33862 creates a new Exim process using the &%-MC%& option (which can only be used by
33863 a process running as root or the Exim user) and passes the TCP/IP socket to it
33864 so that it can deliver another message using the same socket. The new process
33865 does only those deliveries that are routed to the connected host, and may in
33866 turn pass the socket on to a third process, and so on.
33868 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
33869 limit the number of messages sent down a single TCP/IP connection.
33871 .cindex "asterisk" "after IP address"
33872 The second and subsequent messages delivered down an existing connection are
33873 identified in the main log by the addition of an asterisk after the closing
33874 square bracket of the IP address.
33879 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
33880 .cindex "error" "in outgoing SMTP"
33881 .cindex "SMTP" "errors in outgoing"
33882 .cindex "host" "error"
33883 Three different kinds of error are recognized for outgoing SMTP: host errors,
33884 message errors, and recipient errors.
33887 .vitem "&*Host errors*&"
33888 A host error is not associated with a particular message or with a
33889 particular recipient of a message. The host errors are:
33892 Connection refused or timed out,
33894 Any error response code on connection,
33896 Any error response code to EHLO or HELO,
33898 Loss of connection at any time, except after &"."&,
33900 I/O errors at any time,
33902 Timeouts during the session, other than in response to MAIL, RCPT or
33903 the &"."& at the end of the data.
33906 For a host error, a permanent error response on connection, or in response to
33907 EHLO, causes all addresses routed to the host to be failed. Any other host
33908 error causes all addresses to be deferred, and retry data to be created for the
33909 host. It is not tried again, for any message, until its retry time arrives. If
33910 the current set of addresses are not all delivered in this run (to some
33911 alternative host), the message is added to the list of those waiting for this
33912 host, so if it is still undelivered when a subsequent successful delivery is
33913 made to the host, it will be sent down the same SMTP connection.
33915 .vitem "&*Message errors*&"
33916 .cindex "message" "error"
33917 A message error is associated with a particular message when sent to a
33918 particular host, but not with a particular recipient of the message. The
33919 message errors are:
33922 Any error response code to MAIL, DATA, or the &"."& that terminates
33925 Timeout after MAIL,
33927 Timeout or loss of connection after the &"."& that terminates the data. A
33928 timeout after the DATA command itself is treated as a host error, as is loss of
33929 connection at any other time.
33932 For a message error, a permanent error response (5&'xx'&) causes all addresses
33933 to be failed, and a delivery error report to be returned to the sender. A
33934 temporary error response (4&'xx'&), or one of the timeouts, causes all
33935 addresses to be deferred. Retry data is not created for the host, but instead,
33936 a retry record for the combination of host plus message id is created. The
33937 message is not added to the list of those waiting for this host. This ensures
33938 that the failing message will not be sent to this host again until the retry
33939 time arrives. However, other messages that are routed to the host are not
33940 affected, so if it is some property of the message that is causing the error,
33941 it will not stop the delivery of other mail.
33943 If the remote host specified support for the SIZE parameter in its response
33944 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
33945 over-large message will cause a message error because the error arrives as a
33948 .vitem "&*Recipient errors*&"
33949 .cindex "recipient" "error"
33950 A recipient error is associated with a particular recipient of a message. The
33951 recipient errors are:
33954 Any error response to RCPT,
33956 Timeout after RCPT.
33959 For a recipient error, a permanent error response (5&'xx'&) causes the
33960 recipient address to be failed, and a bounce message to be returned to the
33961 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
33962 address to be deferred, and routing retry data to be created for it. This is
33963 used to delay processing of the address in subsequent queue runs, until its
33964 routing retry time arrives. This applies to all messages, but because it
33965 operates only in queue runs, one attempt will be made to deliver a new message
33966 to the failing address before the delay starts to operate. This ensures that,
33967 if the failure is really related to the message rather than the recipient
33968 (&"message too big for this recipient"& is a possible example), other messages
33969 have a chance of getting delivered. If a delivery to the address does succeed,
33970 the retry information gets cleared, so all stuck messages get tried again, and
33971 the retry clock is reset.
33973 The message is not added to the list of those waiting for this host. Use of the
33974 host for other messages is unaffected, and except in the case of a timeout,
33975 other recipients are processed independently, and may be successfully delivered
33976 in the current SMTP session. After a timeout it is of course impossible to
33977 proceed with the session, so all addresses get deferred. However, those other
33978 than the one that failed do not suffer any subsequent retry delays. Therefore,
33979 if one recipient is causing trouble, the others have a chance of getting
33980 through when a subsequent delivery attempt occurs before the failing
33981 recipient's retry time.
33984 In all cases, if there are other hosts (or IP addresses) available for the
33985 current set of addresses (for example, from multiple MX records), they are
33986 tried in this run for any undelivered addresses, subject of course to their
33987 own retry data. In other words, recipient error retry data does not take effect
33988 until the next delivery attempt.
33990 Some hosts have been observed to give temporary error responses to every
33991 MAIL command at certain times (&"insufficient space"& has been seen). It
33992 would be nice if such circumstances could be recognized, and defer data for the
33993 host itself created, but this is not possible within the current Exim design.
33994 What actually happens is that retry data for every (host, message) combination
33997 The reason that timeouts after MAIL and RCPT are treated specially is that
33998 these can sometimes arise as a result of the remote host's verification
33999 procedures. Exim makes this assumption, and treats them as if a temporary error
34000 response had been received. A timeout after &"."& is treated specially because
34001 it is known that some broken implementations fail to recognize the end of the
34002 message if the last character of the last line is a binary zero. Thus, it is
34003 helpful to treat this case as a message error.
34005 Timeouts at other times are treated as host errors, assuming a problem with the
34006 host, or the connection to it. If a timeout after MAIL, RCPT,
34007 or &"."& is really a connection problem, the assumption is that at the next try
34008 the timeout is likely to occur at some other point in the dialogue, causing it
34009 then to be treated as a host error.
34011 There is experimental evidence that some MTAs drop the connection after the
34012 terminating &"."& if they do not like the contents of the message for some
34013 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
34014 should be given. That is why Exim treats this case as a message rather than a
34015 host error, in order not to delay other messages to the same host.
34020 .section "Incoming SMTP messages over TCP/IP" "SECID233"
34021 .cindex "SMTP" "incoming over TCP/IP"
34022 .cindex "incoming SMTP over TCP/IP"
34025 Incoming SMTP messages can be accepted in one of two ways: by running a
34026 listening daemon, or by using &'inetd'&. In the latter case, the entry in
34027 &_/etc/inetd.conf_& should be like this:
34029 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
34031 Exim distinguishes between this case and the case of a locally running user
34032 agent using the &%-bs%& option by checking whether or not the standard input is
34033 a socket. When it is, either the port must be privileged (less than 1024), or
34034 the caller must be root or the Exim user. If any other user passes a socket
34035 with an unprivileged port number, Exim prints a message on the standard error
34036 stream and exits with an error code.
34038 By default, Exim does not make a log entry when a remote host connects or
34039 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
34040 unexpected. It can be made to write such log entries by setting the
34041 &%smtp_connection%& log selector.
34043 .cindex "carriage return"
34045 Commands from the remote host are supposed to be terminated by CR followed by
34046 LF. However, there are known to be hosts that do not send CR characters. In
34047 order to be able to interwork with such hosts, Exim treats LF on its own as a
34049 Furthermore, because common code is used for receiving messages from all
34050 sources, a CR on its own is also interpreted as a line terminator. However, the
34051 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
34053 .cindex "EHLO" "invalid data"
34054 .cindex "HELO" "invalid data"
34055 One area that sometimes gives rise to problems concerns the EHLO or
34056 HELO commands. Some clients send syntactically invalid versions of these
34057 commands, which Exim rejects by default. (This is nothing to do with verifying
34058 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
34059 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
34060 match the broken hosts that send invalid commands.
34062 .cindex "SIZE option on MAIL command"
34063 .cindex "MAIL" "SIZE option"
34064 The amount of disk space available is checked whenever SIZE is received on
34065 a MAIL command, independently of whether &%message_size_limit%& or
34066 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
34067 false. A temporary error is given if there is not enough space. If
34068 &%check_spool_space%& is set, the check is for that amount of space plus the
34069 value given with SIZE, that is, it checks that the addition of the incoming
34070 message will not reduce the space below the threshold.
34072 When a message is successfully received, Exim includes the local message id in
34073 its response to the final &"."& that terminates the data. If the remote host
34074 logs this text it can help with tracing what has happened to a message.
34076 The Exim daemon can limit the number of simultaneous incoming connections it is
34077 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
34078 number of simultaneous incoming connections from a single remote host (see the
34079 &%smtp_accept_max_per_host%& option). Additional connection attempts are
34080 rejected using the SMTP temporary error code 421.
34082 The Exim daemon does not rely on the SIGCHLD signal to detect when a
34083 subprocess has finished, as this can get lost at busy times. Instead, it looks
34084 for completed subprocesses every time it wakes up. Provided there are other
34085 things happening (new incoming calls, starts of queue runs), completed
34086 processes will be noticed and tidied away. On very quiet systems you may
34087 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
34088 it will be noticed when the daemon next wakes up.
34090 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
34091 and can also be set up to reject SMTP calls from non-reserved hosts at times of
34092 high system load &-- for details see the &%smtp_accept_reserve%&,
34093 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
34094 applies in both the daemon and &'inetd'& cases.
34096 Exim normally starts a delivery process for each message received, though this
34097 can be varied by means of the &%-odq%& command line option and the
34098 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
34099 number of simultaneously running delivery processes started in this way from
34100 SMTP input can be limited by the &%smtp_accept_queue%& and
34101 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
34102 subsequently received messages are just put on the input queue without starting
34103 a delivery process.
34105 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
34106 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
34107 started up from the &'inetd'& daemon, because in that case each connection is
34108 handled by an entirely independent Exim process. Control by load average is,
34109 however, available with &'inetd'&.
34111 Exim can be configured to verify addresses in incoming SMTP commands as they
34112 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
34113 to rewrite addresses at this time &-- before any syntax checking is done. See
34114 section &<<SECTrewriteS>>&.
34116 Exim can also be configured to limit the rate at which a client host submits
34117 MAIL and RCPT commands in a single SMTP session. See the
34118 &%smtp_ratelimit_hosts%& option.
34122 .section "Unrecognized SMTP commands" "SECID234"
34123 .cindex "SMTP" "unrecognized commands"
34124 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
34125 commands during a single SMTP connection, it drops the connection after sending
34126 the error response to the last command. The default value for
34127 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
34128 abuse that subvert web servers into making connections to SMTP ports; in these
34129 circumstances, a number of non-SMTP lines are sent first.
34132 .section "Syntax and protocol errors in SMTP commands" "SECID235"
34133 .cindex "SMTP" "syntax errors"
34134 .cindex "SMTP" "protocol errors"
34135 A syntax error is detected if an SMTP command is recognized, but there is
34136 something syntactically wrong with its data, for example, a malformed email
34137 address in a RCPT command. Protocol errors include invalid command
34138 sequencing such as RCPT before MAIL. If Exim receives more than
34139 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
34140 drops the connection after sending the error response to the last command. The
34141 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
34142 broken clients that loop sending bad commands (yes, it has been seen).
34146 .section "Use of non-mail SMTP commands" "SECID236"
34147 .cindex "SMTP" "non-mail commands"
34148 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
34149 DATA. Exim counts such commands, and drops the connection if there are too
34150 many of them in a single SMTP session. This action catches some
34151 denial-of-service attempts and things like repeated failing AUTHs, or a mad
34152 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
34153 defines what &"too many"& means. Its default value is 10.
34155 When a new message is expected, one occurrence of RSET is not counted. This
34156 allows a client to send one RSET between messages (this is not necessary,
34157 but some clients do it). Exim also allows one uncounted occurrence of HELO
34158 or EHLO, and one occurrence of STARTTLS between messages. After
34159 starting up a TLS session, another EHLO is expected, and so it too is not
34162 The first occurrence of AUTH in a connection, or immediately following
34163 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
34164 RCPT, DATA, and QUIT are counted.
34166 You can control which hosts are subject to the limit set by
34167 &%smtp_accept_max_nonmail%& by setting
34168 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
34169 the limit apply to all hosts. This option means that you can exclude any
34170 specific badly-behaved hosts that you have to live with.
34175 .section "The VRFY and EXPN commands" "SECID237"
34176 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
34177 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
34178 appropriate) in order to decide whether the command should be accepted or not.
34180 .cindex "VRFY" "processing"
34181 When no ACL is defined for VRFY, or if it rejects without
34182 setting an explicit response code, the command is accepted
34183 (with a 252 SMTP response code)
34184 in order to support awkward clients that do a VRFY before every RCPT.
34185 When VRFY is accepted, it runs exactly the same code as when Exim is
34186 called with the &%-bv%& option, and returns 250/451/550
34187 SMTP response codes.
34189 .cindex "EXPN" "processing"
34190 If no ACL for EXPN is defined, the command is rejected.
34191 When EXPN is accepted, a single-level expansion of the address is done.
34192 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
34193 than a verification (the &%-bv%& option). If an unqualified local part is given
34194 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
34195 of VRFY and EXPN commands are logged on the main and reject logs, and
34196 VRFY verification failures are logged on the main log for consistency with
34201 .section "The ETRN command" "SECTETRN"
34202 .cindex "ETRN" "processing"
34203 RFC 1985 describes an SMTP command called ETRN that is designed to
34204 overcome the security problems of the TURN command (which has fallen into
34205 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
34206 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
34207 should be accepted or not. If no ACL is defined, the command is rejected.
34209 The ETRN command is concerned with &"releasing"& messages that are awaiting
34210 delivery to certain hosts. As Exim does not organize its message queue by host,
34211 the only form of ETRN that is supported by default is the one where the
34212 text starts with the &"#"& prefix, in which case the remainder of the text is
34213 specific to the SMTP server. A valid ETRN command causes a run of Exim with
34214 the &%-R%& option to happen, with the remainder of the ETRN text as its
34215 argument. For example,
34223 which causes a delivery attempt on all messages with undelivered addresses
34224 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
34225 default), Exim prevents the simultaneous execution of more than one queue run
34226 for the same argument string as a result of an ETRN command. This stops
34227 a misbehaving client from starting more than one queue runner at once.
34229 .cindex "hints database" "ETRN serialization"
34230 Exim implements the serialization by means of a hints database in which a
34231 record is written whenever a process is started by ETRN, and deleted when
34232 the process completes. However, Exim does not keep the SMTP session waiting for
34233 the ETRN process to complete. Once ETRN is accepted, the client is sent
34234 a &"success"& return code. Obviously there is scope for hints records to get
34235 left lying around if there is a system or program crash. To guard against this,
34236 Exim ignores any records that are more than six hours old.
34238 .oindex "&%smtp_etrn_command%&"
34239 For more control over what ETRN does, the &%smtp_etrn_command%& option can
34240 used. This specifies a command that is run whenever ETRN is received,
34241 whatever the form of its argument. For
34244 smtp_etrn_command = /etc/etrn_command $domain \
34245 $sender_host_address
34247 .vindex "&$domain$&"
34248 The string is split up into arguments which are independently expanded. The
34249 expansion variable &$domain$& is set to the argument of the ETRN command,
34250 and no syntax checking is done on the contents of this argument. Exim does not
34251 wait for the command to complete, so its status code is not checked. Exim runs
34252 under its own uid and gid when receiving incoming SMTP, so it is not possible
34253 for it to change them before running the command.
34257 .section "Incoming local SMTP" "SECID238"
34258 .cindex "SMTP" "local incoming"
34259 Some user agents use SMTP to pass messages to their local MTA using the
34260 standard input and output, as opposed to passing the envelope on the command
34261 line and writing the message to the standard input. This is supported by the
34262 &%-bs%& option. This form of SMTP is handled in the same way as incoming
34263 messages over TCP/IP (including the use of ACLs), except that the envelope
34264 sender given in a MAIL command is ignored unless the caller is trusted. In
34265 an ACL you can detect this form of SMTP input by testing for an empty host
34266 identification. It is common to have this as the first line in the ACL that
34267 runs for RCPT commands:
34271 This accepts SMTP messages from local processes without doing any other tests.
34275 .section "Outgoing batched SMTP" "SECTbatchSMTP"
34276 .cindex "SMTP" "batched outgoing"
34277 .cindex "batched SMTP output"
34278 Both the &(appendfile)& and &(pipe)& transports can be used for handling
34279 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
34280 be output in BSMTP format. No SMTP responses are possible for this form of
34281 delivery. All it is doing is using SMTP commands as a way of transmitting the
34282 envelope along with the message.
34284 The message is written to the file or pipe preceded by the SMTP commands
34285 MAIL and RCPT, and followed by a line containing a single dot. Lines in
34286 the message that start with a dot have an extra dot added. The SMTP command
34287 HELO is not normally used. If it is required, the &%message_prefix%& option
34288 can be used to specify it.
34290 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
34291 one recipient address at a time by default. However, you can arrange for them
34292 to handle several addresses at once by setting the &%batch_max%& option. When
34293 this is done for BSMTP, messages may contain multiple RCPT commands. See
34294 chapter &<<CHAPbatching>>& for more details.
34297 When one or more addresses are routed to a BSMTP transport by a router that
34298 sets up a host list, the name of the first host on the list is available to the
34299 transport in the variable &$host$&. Here is an example of such a transport and
34304 driver = manualroute
34305 transport = smtp_appendfile
34306 route_list = domain.example batch.host.example
34310 driver = appendfile
34311 directory = /var/bsmtp/$host
34316 This causes messages addressed to &'domain.example'& to be written in BSMTP
34317 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
34318 message (unless there are more than 1000 recipients).
34322 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
34323 .cindex "SMTP" "batched incoming"
34324 .cindex "batched SMTP input"
34325 The &%-bS%& command line option causes Exim to accept one or more messages by
34326 reading SMTP on the standard input, but to generate no responses. If the caller
34327 is trusted, the senders in the MAIL commands are believed; otherwise the
34328 sender is always the caller of Exim. Unqualified senders and receivers are not
34329 rejected (there seems little point) but instead just get qualified. HELO
34330 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
34331 as NOOP; QUIT quits.
34333 Minimal policy checking is done for BSMTP input. Only the non-SMTP
34334 ACL is run in the same way as for non-SMTP local input.
34336 If an error is detected while reading a message, including a missing &"."& at
34337 the end, Exim gives up immediately. It writes details of the error to the
34338 standard output in a stylized way that the calling program should be able to
34339 make some use of automatically, for example:
34341 554 Unexpected end of file
34342 Transaction started in line 10
34343 Error detected in line 14
34345 It writes a more verbose version, for human consumption, to the standard error
34348 An error was detected while processing a file of BSMTP input.
34349 The error message was:
34351 501 '>' missing at end of address
34353 The SMTP transaction started in line 10.
34354 The error was detected in line 12.
34355 The SMTP command at fault was:
34357 rcpt to:<malformed@in.com.plete
34359 1 previous message was successfully processed.
34360 The rest of the batch was abandoned.
34362 The return code from Exim is zero only if there were no errors. It is 1 if some
34363 messages were accepted before an error was detected, and 2 if no messages were
34365 .ecindex IIDsmtpproc1
34366 .ecindex IIDsmtpproc2
34370 . ////////////////////////////////////////////////////////////////////////////
34371 . ////////////////////////////////////////////////////////////////////////////
34373 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
34374 "Customizing messages"
34375 When a message fails to be delivered, or remains on the queue for more than a
34376 configured amount of time, Exim sends a message to the original sender, or
34377 to an alternative configured address. The text of these messages is built into
34378 the code of Exim, but it is possible to change it, either by adding a single
34379 string, or by replacing each of the paragraphs by text supplied in a file.
34381 The &'From:'& and &'To:'& header lines are automatically generated; you can
34382 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
34383 option. Exim also adds the line
34385 Auto-Submitted: auto-generated
34387 to all warning and bounce messages,
34390 .section "Customizing bounce messages" "SECID239"
34391 .cindex "customizing" "bounce message"
34392 .cindex "bounce message" "customizing"
34393 If &%bounce_message_text%& is set, its contents are included in the default
34394 message immediately after &"This message was created automatically by mail
34395 delivery software."& The string is not expanded. It is not used if
34396 &%bounce_message_file%& is set.
34398 When &%bounce_message_file%& is set, it must point to a template file for
34399 constructing error messages. The file consists of a series of text items,
34400 separated by lines consisting of exactly four asterisks. If the file cannot be
34401 opened, default text is used and a message is written to the main and panic
34402 logs. If any text item in the file is empty, default text is used for that
34405 .vindex "&$bounce_recipient$&"
34406 .vindex "&$bounce_return_size_limit$&"
34407 Each item of text that is read from the file is expanded, and there are two
34408 expansion variables which can be of use here: &$bounce_recipient$& is set to
34409 the recipient of an error message while it is being created, and
34410 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
34411 option, rounded to a whole number.
34413 The items must appear in the file in the following order:
34416 The first item is included in the headers, and should include at least a
34417 &'Subject:'& header. Exim does not check the syntax of these headers.
34419 The second item forms the start of the error message. After it, Exim lists the
34420 failing addresses with their error messages.
34422 The third item is used to introduce any text from pipe transports that is to be
34423 returned to the sender. It is omitted if there is no such text.
34425 The fourth, fifth and sixth items will be ignored and may be empty.
34426 The fields exist for back-compatibility
34429 The default state (&%bounce_message_file%& unset) is equivalent to the
34430 following file, in which the sixth item is empty. The &'Subject:'& and some
34431 other lines have been split in order to fit them on the page:
34433 Subject: Mail delivery failed
34434 ${if eq{$sender_address}{$bounce_recipient}
34435 {: returning message to sender}}
34437 This message was created automatically by mail delivery software.
34439 A message ${if eq{$sender_address}{$bounce_recipient}
34440 {that you sent }{sent by
34444 }}could not be delivered to all of its recipients.
34445 This is a permanent error. The following address(es) failed:
34447 The following text was generated during the delivery attempt(s):
34449 ------ This is a copy of the message, including all the headers.
34452 ------ The body of the message is $message_size characters long;
34454 ------ $bounce_return_size_limit or so are included here.
34457 .section "Customizing warning messages" "SECTcustwarn"
34458 .cindex "customizing" "warning message"
34459 .cindex "warning of delay" "customizing the message"
34460 The option &%warn_message_file%& can be pointed at a template file for use when
34461 warnings about message delays are created. In this case there are only three
34465 The first item is included in the headers, and should include at least a
34466 &'Subject:'& header. Exim does not check the syntax of these headers.
34468 The second item forms the start of the warning message. After it, Exim lists
34469 the delayed addresses.
34471 The third item then ends the message.
34474 The default state is equivalent to the following file, except that some lines
34475 have been split here, in order to fit them on the page:
34477 Subject: Warning: message $message_exim_id delayed
34478 $warn_message_delay
34480 This message was created automatically by mail delivery software.
34482 A message ${if eq{$sender_address}{$warn_message_recipients}
34483 {that you sent }{sent by
34487 }}has not been delivered to all of its recipients after
34488 more than $warn_message_delay on the queue on $primary_hostname.
34490 The message identifier is: $message_exim_id
34491 The subject of the message is: $h_subject
34492 The date of the message is: $h_date
34494 The following address(es) have not yet been delivered:
34496 No action is required on your part. Delivery attempts will
34497 continue for some time, and this warning may be repeated at
34498 intervals if the message remains undelivered. Eventually the
34499 mail delivery software will give up, and when that happens,
34500 the message will be returned to you.
34502 .vindex "&$warn_message_delay$&"
34503 .vindex "&$warn_message_recipients$&"
34504 However, in the default state the subject and date lines are omitted if no
34505 appropriate headers exist. During the expansion of this file,
34506 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
34507 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
34508 of recipients for the warning message. There may be more than one if there are
34509 multiple addresses with different &%errors_to%& settings on the routers that
34515 . ////////////////////////////////////////////////////////////////////////////
34516 . ////////////////////////////////////////////////////////////////////////////
34518 .chapter "Some common configuration settings" "CHAPcomconreq"
34519 This chapter discusses some configuration settings that seem to be fairly
34520 common. More examples and discussion can be found in the Exim book.
34524 .section "Sending mail to a smart host" "SECID240"
34525 .cindex "smart host" "example router"
34526 If you want to send all mail for non-local domains to a &"smart host"&, you
34527 should replace the default &(dnslookup)& router with a router which does the
34528 routing explicitly:
34530 send_to_smart_host:
34531 driver = manualroute
34532 route_list = !+local_domains smart.host.name
34533 transport = remote_smtp
34535 You can use the smart host's IP address instead of the name if you wish.
34536 If you are using Exim only to submit messages to a smart host, and not for
34537 receiving incoming messages, you can arrange for it to do the submission
34538 synchronously by setting the &%mua_wrapper%& option (see chapter
34539 &<<CHAPnonqueueing>>&).
34544 .section "Using Exim to handle mailing lists" "SECTmailinglists"
34545 .cindex "mailing lists"
34546 Exim can be used to run simple mailing lists, but for large and/or complicated
34547 requirements, the use of additional specialized mailing list software such as
34548 Majordomo or Mailman is recommended.
34550 The &(redirect)& router can be used to handle mailing lists where each list
34551 is maintained in a separate file, which can therefore be managed by an
34552 independent manager. The &%domains%& router option can be used to run these
34553 lists in a separate domain from normal mail. For example:
34557 domains = lists.example
34558 file = /usr/lists/$local_part
34561 errors_to = $local_part-request@lists.example
34564 This router is skipped for domains other than &'lists.example'&. For addresses
34565 in that domain, it looks for a file that matches the local part. If there is no
34566 such file, the router declines, but because &%no_more%& is set, no subsequent
34567 routers are tried, and so the whole delivery fails.
34569 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
34570 expanded into a file name or a pipe delivery, which is usually inappropriate in
34573 .oindex "&%errors_to%&"
34574 The &%errors_to%& option specifies that any delivery errors caused by addresses
34575 taken from a mailing list are to be sent to the given address rather than the
34576 original sender of the message. However, before acting on this, Exim verifies
34577 the error address, and ignores it if verification fails.
34579 For example, using the configuration above, mail sent to
34580 &'dicts@lists.example'& is passed on to those addresses contained in
34581 &_/usr/lists/dicts_&, with error reports directed to
34582 &'dicts-request@lists.example'&, provided that this address can be verified.
34583 There could be a file called &_/usr/lists/dicts-request_& containing
34584 the address(es) of this particular list's manager(s), but other approaches,
34585 such as setting up an earlier router (possibly using the &%local_part_prefix%&
34586 or &%local_part_suffix%& options) to handle addresses of the form
34587 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
34591 .section "Syntax errors in mailing lists" "SECID241"
34592 .cindex "mailing lists" "syntax errors in"
34593 If an entry in redirection data contains a syntax error, Exim normally defers
34594 delivery of the original address. That means that a syntax error in a mailing
34595 list holds up all deliveries to the list. This may not be appropriate when a
34596 list is being maintained automatically from data supplied by users, and the
34597 addresses are not rigorously checked.
34599 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
34600 entries that fail to parse, noting the incident in the log. If in addition
34601 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
34602 whenever a broken address is skipped. It is usually appropriate to set
34603 &%syntax_errors_to%& to the same address as &%errors_to%&.
34607 .section "Re-expansion of mailing lists" "SECID242"
34608 .cindex "mailing lists" "re-expansion of"
34609 Exim remembers every individual address to which a message has been delivered,
34610 in order to avoid duplication, but it normally stores only the original
34611 recipient addresses with a message. If all the deliveries to a mailing list
34612 cannot be done at the first attempt, the mailing list is re-expanded when the
34613 delivery is next tried. This means that alterations to the list are taken into
34614 account at each delivery attempt, so addresses that have been added to
34615 the list since the message arrived will therefore receive a copy of the
34616 message, even though it pre-dates their subscription.
34618 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
34619 on the &(redirect)& router. If this is done, any addresses generated by the
34620 router that fail to deliver at the first attempt are added to the message as
34621 &"top level"& addresses, and the parent address that generated them is marked
34622 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
34623 subsequent delivery attempts. The disadvantage of this is that if any of the
34624 failing addresses are incorrect, correcting them in the file has no effect on
34625 pre-existing messages.
34627 The original top-level address is remembered with each of the generated
34628 addresses, and is output in any log messages. However, any intermediate parent
34629 addresses are not recorded. This makes a difference to the log only if the
34630 &%all_parents%& selector is set, but for mailing lists there is normally only
34631 one level of expansion anyway.
34635 .section "Closed mailing lists" "SECID243"
34636 .cindex "mailing lists" "closed"
34637 The examples so far have assumed open mailing lists, to which anybody may
34638 send mail. It is also possible to set up closed lists, where mail is accepted
34639 from specified senders only. This is done by making use of the generic
34640 &%senders%& option to restrict the router that handles the list.
34642 The following example uses the same file as a list of recipients and as a list
34643 of permitted senders. It requires three routers:
34647 domains = lists.example
34648 local_part_suffix = -request
34649 file = /usr/lists/$local_part$local_part_suffix
34654 domains = lists.example
34655 senders = ${if exists {/usr/lists/$local_part}\
34656 {lsearch;/usr/lists/$local_part}{*}}
34657 file = /usr/lists/$local_part
34660 errors_to = $local_part-request@lists.example
34665 domains = lists.example
34667 data = :fail: $local_part@lists.example is a closed mailing list
34669 All three routers have the same &%domains%& setting, so for any other domains,
34670 they are all skipped. The first router runs only if the local part ends in
34671 &%-request%&. It handles messages to the list manager(s) by means of an open
34674 The second router runs only if the &%senders%& precondition is satisfied. It
34675 checks for the existence of a list that corresponds to the local part, and then
34676 checks that the sender is on the list by means of a linear search. It is
34677 necessary to check for the existence of the file before trying to search it,
34678 because otherwise Exim thinks there is a configuration error. If the file does
34679 not exist, the expansion of &%senders%& is *, which matches all senders. This
34680 means that the router runs, but because there is no list, declines, and
34681 &%no_more%& ensures that no further routers are run. The address fails with an
34682 &"unrouteable address"& error.
34684 The third router runs only if the second router is skipped, which happens when
34685 a mailing list exists, but the sender is not on it. This router forcibly fails
34686 the address, giving a suitable error message.
34691 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
34693 .cindex "Variable Envelope Return Paths"
34694 .cindex "envelope sender"
34695 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
34696 are a way of helping mailing list administrators discover which subscription
34697 address is the cause of a particular delivery failure. The idea is to encode
34698 the original recipient address in the outgoing envelope sender address, so that
34699 if the message is forwarded by another host and then subsequently bounces, the
34700 original recipient can be extracted from the recipient address of the bounce.
34702 .oindex &%errors_to%&
34703 .oindex &%return_path%&
34704 Envelope sender addresses can be modified by Exim using two different
34705 facilities: the &%errors_to%& option on a router (as shown in previous mailing
34706 list examples), or the &%return_path%& option on a transport. The second of
34707 these is effective only if the message is successfully delivered to another
34708 host; it is not used for errors detected on the local host (see the description
34709 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
34710 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
34716 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34717 {$1-request+$local_part=$domain@your.dom.example}fail}
34719 This has the effect of rewriting the return path (envelope sender) on outgoing
34720 SMTP messages, if the local part of the original return path ends in
34721 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
34722 local part and domain of the recipient into the return path. Suppose, for
34723 example, that a message whose return path has been set to
34724 &'somelist-request@your.dom.example'& is sent to
34725 &'subscriber@other.dom.example'&. In the transport, the return path is
34728 somelist-request+subscriber=other.dom.example@your.dom.example
34730 .vindex "&$local_part$&"
34731 For this to work, you must tell Exim to send multiple copies of messages that
34732 have more than one recipient, so that each copy has just one recipient. This is
34733 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
34734 might be sent to several different recipients in the same domain, in which case
34735 &$local_part$& is not available in the transport, because it is not unique.
34737 Unless your host is doing nothing but mailing list deliveries, you should
34738 probably use a separate transport for the VERP deliveries, so as not to use
34739 extra resources in making one-per-recipient copies for other deliveries. This
34740 can easily be done by expanding the &%transport%& option in the router:
34744 domains = ! +local_domains
34746 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34747 {verp_smtp}{remote_smtp}}
34750 If you want to change the return path using &%errors_to%& in a router instead
34751 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
34752 routers that handle mailing list addresses. This will ensure that all delivery
34753 errors, including those detected on the local host, are sent to the VERP
34756 On a host that does no local deliveries and has no manual routing, only the
34757 &(dnslookup)& router needs to be changed. A special transport is not needed for
34758 SMTP deliveries. Every mailing list recipient has its own return path value,
34759 and so Exim must hand them to the transport one at a time. Here is an example
34760 of a &(dnslookup)& router that implements VERP:
34764 domains = ! +local_domains
34765 transport = remote_smtp
34767 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
34768 {$1-request+$local_part=$domain@your.dom.example}fail}
34771 Before you start sending out messages with VERPed return paths, you must also
34772 configure Exim to accept the bounce messages that come back to those paths.
34773 Typically this is done by setting a &%local_part_suffix%& option for a
34774 router, and using this to route the messages to wherever you want to handle
34777 The overhead incurred in using VERP depends very much on the size of the
34778 message, the number of recipient addresses that resolve to the same remote
34779 host, and the speed of the connection over which the message is being sent. If
34780 a lot of addresses resolve to the same host and the connection is slow, sending
34781 a separate copy of the message for each address may take substantially longer
34782 than sending a single copy with many recipients (for which VERP cannot be
34790 .section "Virtual domains" "SECTvirtualdomains"
34791 .cindex "virtual domains"
34792 .cindex "domain" "virtual"
34793 The phrase &'virtual domain'& is unfortunately used with two rather different
34797 A domain for which there are no real mailboxes; all valid local parts are
34798 aliases for other email addresses. Common examples are organizational
34799 top-level domains and &"vanity"& domains.
34801 One of a number of independent domains that are all handled by the same host,
34802 with mailboxes on that host, but where the mailbox owners do not necessarily
34803 have login accounts on that host.
34806 The first usage is probably more common, and does seem more &"virtual"& than
34807 the second. This kind of domain can be handled in Exim with a straightforward
34808 aliasing router. One approach is to create a separate alias file for each
34809 virtual domain. Exim can test for the existence of the alias file to determine
34810 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
34811 to a router of this form:
34815 domains = dsearch;/etc/mail/virtual
34816 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
34819 The &%domains%& option specifies that the router is to be skipped, unless there
34820 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
34821 domain that is being processed. When the router runs, it looks up the local
34822 part in the file to find a new address (or list of addresses). The &%no_more%&
34823 setting ensures that if the lookup fails (leading to &%data%& being an empty
34824 string), Exim gives up on the address without trying any subsequent routers.
34826 This one router can handle all the virtual domains because the alias file names
34827 follow a fixed pattern. Permissions can be arranged so that appropriate people
34828 can edit the different alias files. A successful aliasing operation results in
34829 a new envelope recipient address, which is then routed from scratch.
34831 The other kind of &"virtual"& domain can also be handled in a straightforward
34832 way. One approach is to create a file for each domain containing a list of
34833 valid local parts, and use it in a router like this:
34837 domains = dsearch;/etc/mail/domains
34838 local_parts = lsearch;/etc/mail/domains/$domain
34839 transport = my_mailboxes
34841 The address is accepted if there is a file for the domain, and the local part
34842 can be found in the file. The &%domains%& option is used to check for the
34843 file's existence because &%domains%& is tested before the &%local_parts%&
34844 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
34845 because that option is tested after &%local_parts%&. The transport is as
34849 driver = appendfile
34850 file = /var/mail/$domain/$local_part
34853 This uses a directory of mailboxes for each domain. The &%user%& setting is
34854 required, to specify which uid is to be used for writing to the mailboxes.
34856 The configuration shown here is just one example of how you might support this
34857 requirement. There are many other ways this kind of configuration can be set
34858 up, for example, by using a database instead of separate files to hold all the
34859 information about the domains.
34863 .section "Multiple user mailboxes" "SECTmulbox"
34864 .cindex "multiple mailboxes"
34865 .cindex "mailbox" "multiple"
34866 .cindex "local part" "prefix"
34867 .cindex "local part" "suffix"
34868 Heavy email users often want to operate with multiple mailboxes, into which
34869 incoming mail is automatically sorted. A popular way of handling this is to
34870 allow users to use multiple sender addresses, so that replies can easily be
34871 identified. Users are permitted to add prefixes or suffixes to their local
34872 parts for this purpose. The wildcard facility of the generic router options
34873 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
34874 example, consider this router:
34879 file = $home/.forward
34880 local_part_suffix = -*
34881 local_part_suffix_optional
34884 .vindex "&$local_part_suffix$&"
34885 It runs a user's &_.forward_& file for all local parts of the form
34886 &'username-*'&. Within the filter file the user can distinguish different
34887 cases by testing the variable &$local_part_suffix$&. For example:
34889 if $local_part_suffix contains -special then
34890 save /home/$local_part/Mail/special
34893 If the filter file does not exist, or does not deal with such addresses, they
34894 fall through to subsequent routers, and, assuming no subsequent use of the
34895 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
34896 control over which suffixes are valid.
34898 Alternatively, a suffix can be used to trigger the use of a different
34899 &_.forward_& file &-- which is the way a similar facility is implemented in
34905 file = $home/.forward$local_part_suffix
34906 local_part_suffix = -*
34907 local_part_suffix_optional
34910 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
34911 example, &_.forward-special_& is used. Once again, if the appropriate file
34912 does not exist, or does not deal with the address, it is passed on to
34913 subsequent routers, which could, if required, look for an unqualified
34914 &_.forward_& file to use as a default.
34918 .section "Simplified vacation processing" "SECID244"
34919 .cindex "vacation processing"
34920 The traditional way of running the &'vacation'& program is for a user to set up
34921 a pipe command in a &_.forward_& file
34922 (see section &<<SECTspecitredli>>& for syntax details).
34923 This is prone to error by inexperienced users. There are two features of Exim
34924 that can be used to make this process simpler for users:
34927 A local part prefix such as &"vacation-"& can be specified on a router which
34928 can cause the message to be delivered directly to the &'vacation'& program, or
34929 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
34930 &_.forward_& file are then much simpler. For example:
34932 spqr, vacation-spqr
34935 The &%require_files%& generic router option can be used to trigger a
34936 vacation delivery by checking for the existence of a certain file in the
34937 user's home directory. The &%unseen%& generic option should also be used, to
34938 ensure that the original delivery also proceeds. In this case, all the user has
34939 to do is to create a file called, say, &_.vacation_&, containing a vacation
34943 Another advantage of both these methods is that they both work even when the
34944 use of arbitrary pipes by users is locked out.
34948 .section "Taking copies of mail" "SECID245"
34949 .cindex "message" "copying every"
34950 Some installations have policies that require archive copies of all messages to
34951 be made. A single copy of each message can easily be taken by an appropriate
34952 command in a system filter, which could, for example, use a different file for
34953 each day's messages.
34955 There is also a shadow transport mechanism that can be used to take copies of
34956 messages that are successfully delivered by local transports, one copy per
34957 delivery. This could be used, &'inter alia'&, to implement automatic
34958 notification of delivery by sites that insist on doing such things.
34962 .section "Intermittently connected hosts" "SECID246"
34963 .cindex "intermittently connected hosts"
34964 It has become quite common (because it is cheaper) for hosts to connect to the
34965 Internet periodically rather than remain connected all the time. The normal
34966 arrangement is that mail for such hosts accumulates on a system that is
34967 permanently connected.
34969 Exim was designed for use on permanently connected hosts, and so it is not
34970 particularly well-suited to use in an intermittently connected environment.
34971 Nevertheless there are some features that can be used.
34974 .section "Exim on the upstream server host" "SECID247"
34975 It is tempting to arrange for incoming mail for the intermittently connected
34976 host to remain on Exim's queue until the client connects. However, this
34977 approach does not scale very well. Two different kinds of waiting message are
34978 being mixed up in the same queue &-- those that cannot be delivered because of
34979 some temporary problem, and those that are waiting for their destination host
34980 to connect. This makes it hard to manage the queue, as well as wasting
34981 resources, because each queue runner scans the entire queue.
34983 A better approach is to separate off those messages that are waiting for an
34984 intermittently connected host. This can be done by delivering these messages
34985 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
34986 format, from where they are transmitted by other software when their
34987 destination connects. This makes it easy to collect all the mail for one host
34988 in a single directory, and to apply local timeout rules on a per-message basis
34991 On a very small scale, leaving the mail on Exim's queue can be made to work. If
34992 you are doing this, you should configure Exim with a long retry period for the
34993 intermittent host. For example:
34995 cheshire.wonderland.fict.example * F,5d,24h
34997 This stops a lot of failed delivery attempts from occurring, but Exim remembers
34998 which messages it has queued up for that host. Once the intermittent host comes
34999 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
35000 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
35001 causes all the queued up messages to be delivered, often down a single SMTP
35002 connection. While the host remains connected, any new messages get delivered
35005 If the connecting hosts do not have fixed IP addresses, that is, if a host is
35006 issued with a different IP address each time it connects, Exim's retry
35007 mechanisms on the holding host get confused, because the IP address is normally
35008 used as part of the key string for holding retry information. This can be
35009 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
35010 Since this has disadvantages for permanently connected hosts, it is best to
35011 arrange a separate transport for the intermittently connected ones.
35015 .section "Exim on the intermittently connected client host" "SECID248"
35016 The value of &%smtp_accept_queue_per_connection%& should probably be
35017 increased, or even set to zero (that is, disabled) on the intermittently
35018 connected host, so that all incoming messages down a single connection get
35019 delivered immediately.
35021 .cindex "SMTP" "passed connection"
35022 .cindex "SMTP" "multiple deliveries"
35023 .cindex "multiple SMTP deliveries"
35024 Mail waiting to be sent from an intermittently connected host will probably
35025 not have been routed, because without a connection DNS lookups are not
35026 possible. This means that if a normal queue run is done at connection time,
35027 each message is likely to be sent in a separate SMTP session. This can be
35028 avoided by starting the queue run with a command line option beginning with
35029 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
35030 first pass, routing is done but no deliveries take place. The second pass is a
35031 normal queue run; since all the messages have been previously routed, those
35032 destined for the same host are likely to get sent as multiple deliveries in a
35033 single SMTP connection.
35037 . ////////////////////////////////////////////////////////////////////////////
35038 . ////////////////////////////////////////////////////////////////////////////
35040 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
35041 "Exim as a non-queueing client"
35042 .cindex "client, non-queueing"
35043 .cindex "smart host" "suppressing queueing"
35044 On a personal computer, it is a common requirement for all
35045 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
35046 configured to operate that way, for all the popular operating systems.
35047 However, there are some MUAs for Unix-like systems that cannot be so
35048 configured: they submit messages using the command line interface of
35049 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
35052 If the personal computer runs continuously, there is no problem, because it can
35053 run a conventional MTA that handles delivery to the smart host, and deal with
35054 any delays via its queueing mechanism. However, if the computer does not run
35055 continuously or runs different operating systems at different times, queueing
35056 email is not desirable.
35058 There is therefore a requirement for something that can provide the
35059 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
35060 any queueing or retrying facilities. Furthermore, the delivery to the smart
35061 host should be synchronous, so that if it fails, the sending MUA is immediately
35062 informed. In other words, we want something that extends an MUA that submits
35063 to a local MTA via the command line so that it behaves like one that submits
35064 to a remote smart host using TCP/SMTP.
35066 There are a number of applications (for example, there is one called &'ssmtp'&)
35067 that do this job. However, people have found them to be lacking in various
35068 ways. For instance, you might want to allow aliasing and forwarding to be done
35069 before sending a message to the smart host.
35071 Exim already had the necessary infrastructure for doing this job. Just a few
35072 tweaks were needed to make it behave as required, though it is somewhat of an
35073 overkill to use a fully-featured MTA for this purpose.
35075 .oindex "&%mua_wrapper%&"
35076 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
35077 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
35078 assumes that it is being used to &"wrap"& a command-line MUA in the manner
35079 just described. As well as setting &%mua_wrapper%&, you also need to provide a
35080 compatible router and transport configuration. Typically there will be just one
35081 router and one transport, sending everything to a smart host.
35083 When run in MUA wrapping mode, the behaviour of Exim changes in the
35087 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
35088 In other words, the only way to submit messages is via the command line.
35090 Each message is synchronously delivered as soon as it is received (&%-odi%& is
35091 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
35092 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
35093 does not finish until the delivery attempt is complete. If the delivery is
35094 successful, a zero return code is given.
35096 Address redirection is permitted, but the final routing for all addresses must
35097 be to the same remote transport, and to the same list of hosts. Furthermore,
35098 the return address (envelope sender) must be the same for all recipients, as
35099 must any added or deleted header lines. In other words, it must be possible to
35100 deliver the message in a single SMTP transaction, however many recipients there
35103 If these conditions are not met, or if routing any address results in a
35104 failure or defer status, or if Exim is unable to deliver all the recipients
35105 successfully to one of the smart hosts, delivery of the entire message fails.
35107 Because no queueing is allowed, all failures are treated as permanent; there
35108 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
35109 smart host. Furthermore, because only a single yes/no response can be given to
35110 the caller, it is not possible to deliver to some recipients and not others. If
35111 there is an error (temporary or permanent) for any recipient, all are failed.
35113 If more than one smart host is listed, Exim will try another host after a
35114 connection failure or a timeout, in the normal way. However, if this kind of
35115 failure happens for all the hosts, the delivery fails.
35117 When delivery fails, an error message is written to the standard error stream
35118 (as well as to Exim's log), and Exim exits to the caller with a return code
35119 value 1. The message is expunged from Exim's spool files. No bounce messages
35120 are ever generated.
35122 No retry data is maintained, and any retry rules are ignored.
35124 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
35125 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
35126 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
35129 The overall effect is that Exim makes a single synchronous attempt to deliver
35130 the message, failing if there is any kind of problem. Because no local
35131 deliveries are done and no daemon can be run, Exim does not need root
35132 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
35133 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
35134 the advantages and disadvantages of running without root privilege.
35139 . ////////////////////////////////////////////////////////////////////////////
35140 . ////////////////////////////////////////////////////////////////////////////
35142 .chapter "Log files" "CHAPlog"
35143 .scindex IIDloggen "log" "general description"
35144 .cindex "log" "types of"
35145 Exim writes three different logs, referred to as the main log, the reject log,
35150 The main log records the arrival of each message and each delivery in a single
35151 line in each case. The format is as compact as possible, in an attempt to keep
35152 down the size of log files. Two-character flag sequences make it easy to pick
35153 out these lines. A number of other events are recorded in the main log. Some of
35154 them are optional, in which case the &%log_selector%& option controls whether
35155 they are included or not. A Perl script called &'eximstats'&, which does simple
35156 analysis of main log files, is provided in the Exim distribution (see section
35157 &<<SECTmailstat>>&).
35159 .cindex "reject log"
35160 The reject log records information from messages that are rejected as a result
35161 of a configuration option (that is, for policy reasons).
35162 The first line of each rejection is a copy of the line that is also written to
35163 the main log. Then, if the message's header has been read at the time the log
35164 is written, its contents are written to this log. Only the original header
35165 lines are available; header lines added by ACLs are not logged. You can use the
35166 reject log to check that your policy controls are working correctly; on a busy
35167 host this may be easier than scanning the main log for rejection messages. You
35168 can suppress the writing of the reject log by setting &%write_rejectlog%&
35171 .cindex "panic log"
35172 .cindex "system log"
35173 When certain serious errors occur, Exim writes entries to its panic log. If the
35174 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
35175 are usually written to the main log as well, but can get lost amid the mass of
35176 other entries. The panic log should be empty under normal circumstances. It is
35177 therefore a good idea to check it (or to have a &'cron'& script check it)
35178 regularly, in order to become aware of any problems. When Exim cannot open its
35179 panic log, it tries as a last resort to write to the system log (syslog). This
35180 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
35181 message itself is written at priority LOG_CRIT.
35184 Every log line starts with a timestamp, in the format shown in the following
35185 example. Note that many of the examples shown in this chapter are line-wrapped.
35186 In the log file, this would be all on one line:
35188 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
35191 By default, the timestamps are in the local timezone. There are two
35192 ways of changing this:
35195 You can set the &%timezone%& option to a different time zone; in particular, if
35200 the timestamps will be in UTC (aka GMT).
35202 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
35205 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
35209 .cindex "log" "process ids in"
35210 .cindex "pid (process id)" "in log lines"
35211 Exim does not include its process id in log lines by default, but you can
35212 request that it does so by specifying the &`pid`& log selector (see section
35213 &<<SECTlogselector>>&). When this is set, the process id is output, in square
35214 brackets, immediately after the time and date.
35219 .section "Where the logs are written" "SECTwhelogwri"
35220 .cindex "log" "destination"
35221 .cindex "log" "to file"
35222 .cindex "log" "to syslog"
35224 The logs may be written to local files, or to syslog, or both. However, it
35225 should be noted that many syslog implementations use UDP as a transport, and
35226 are therefore unreliable in the sense that messages are not guaranteed to
35227 arrive at the loghost, nor is the ordering of messages necessarily maintained.
35228 It has also been reported that on large log files (tens of megabytes) you may
35229 need to tweak syslog to prevent it syncing the file with each write &-- on
35230 Linux this has been seen to make syslog take 90% plus of CPU time.
35232 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
35233 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
35234 configuration. This latter string is expanded, so it can contain, for example,
35235 references to the host name:
35237 log_file_path = /var/log/$primary_hostname/exim_%slog
35239 It is generally advisable, however, to set the string in &_Local/Makefile_&
35240 rather than at run time, because then the setting is available right from the
35241 start of Exim's execution. Otherwise, if there's something it wants to log
35242 before it has read the configuration file (for example, an error in the
35243 configuration file) it will not use the path you want, and may not be able to
35246 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
35247 list, currently limited to at most two items. This is one option where the
35248 facility for changing a list separator may not be used. The list must always be
35249 colon-separated. If an item in the list is &"syslog"& then syslog is used;
35250 otherwise the item must either be an absolute path, containing &`%s`& at the
35251 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
35252 implying the use of a default path.
35254 When Exim encounters an empty item in the list, it searches the list defined by
35255 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
35256 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
35257 mean &"use the path specified at build time"&. It no such item exists, log
35258 files are written in the &_log_& subdirectory of the spool directory. This is
35259 equivalent to the setting:
35261 log_file_path = $spool_directory/log/%slog
35263 If you do not specify anything at build time or run time,
35264 or if you unset the option at run time (i.e. &`log_file_path = `&),
35265 that is where the logs are written.
35267 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
35268 are in use &-- see section &<<SECTdatlogfil>>& below.
35270 Here are some examples of possible settings:
35272 &`LOG_FILE_PATH=syslog `& syslog only
35273 &`LOG_FILE_PATH=:syslog `& syslog and default path
35274 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
35275 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
35277 If there are more than two paths in the list, the first is used and a panic
35282 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
35283 .cindex "log" "cycling local files"
35284 .cindex "cycling logs"
35285 .cindex "&'exicyclog'&"
35286 .cindex "log" "local files; writing to"
35287 Some operating systems provide centralized and standardized methods for cycling
35288 log files. For those that do not, a utility script called &'exicyclog'& is
35289 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
35290 main and reject logs each time it is called. The maximum number of old logs to
35291 keep can be set. It is suggested this script is run as a daily &'cron'& job.
35293 An Exim delivery process opens the main log when it first needs to write to it,
35294 and it keeps the file open in case subsequent entries are required &-- for
35295 example, if a number of different deliveries are being done for the same
35296 message. However, remote SMTP deliveries can take a long time, and this means
35297 that the file may be kept open long after it is renamed if &'exicyclog'& or
35298 something similar is being used to rename log files on a regular basis. To
35299 ensure that a switch of log files is noticed as soon as possible, Exim calls
35300 &[stat()]& on the main log's name before reusing an open file, and if the file
35301 does not exist, or its inode has changed, the old file is closed and Exim
35302 tries to open the main log from scratch. Thus, an old log file may remain open
35303 for quite some time, but no Exim processes should write to it once it has been
35308 .section "Datestamped log files" "SECTdatlogfil"
35309 .cindex "log" "datestamped files"
35310 Instead of cycling the main and reject log files by renaming them
35311 periodically, some sites like to use files whose names contain a datestamp,
35312 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
35313 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
35314 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
35315 point where the datestamp is required. For example:
35317 log_file_path = /var/spool/exim/log/%slog-%D
35318 log_file_path = /var/log/exim-%s-%D.log
35319 log_file_path = /var/spool/exim/log/%D-%slog
35320 log_file_path = /var/log/exim/%s.%M
35322 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
35323 examples of names generated by the above examples:
35325 /var/spool/exim/log/mainlog-20021225
35326 /var/log/exim-reject-20021225.log
35327 /var/spool/exim/log/20021225-mainlog
35328 /var/log/exim/main.200212
35330 When this form of log file is specified, Exim automatically switches to new
35331 files at midnight. It does not make any attempt to compress old logs; you
35332 will need to write your own script if you require this. You should not
35333 run &'exicyclog'& with this form of logging.
35335 The location of the panic log is also determined by &%log_file_path%&, but it
35336 is not datestamped, because rotation of the panic log does not make sense.
35337 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
35338 the string. In addition, if it immediately follows a slash, a following
35339 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
35340 character is removed. Thus, the four examples above would give these panic
35343 /var/spool/exim/log/paniclog
35344 /var/log/exim-panic.log
35345 /var/spool/exim/log/paniclog
35346 /var/log/exim/panic
35350 .section "Logging to syslog" "SECID249"
35351 .cindex "log" "syslog; writing to"
35352 The use of syslog does not change what Exim logs or the format of its messages,
35353 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
35354 Exim's log lines are omitted when these lines are sent to syslog. Apart from
35355 that, the same strings are written to syslog as to log files. The syslog
35356 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
35357 by default, but you can change these by setting the &%syslog_facility%& and
35358 &%syslog_processname%& options, respectively. If Exim was compiled with
35359 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
35360 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
35361 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
35362 the time and host name to each line.
35363 The three log streams are mapped onto syslog priorities as follows:
35366 &'mainlog'& is mapped to LOG_INFO
35368 &'rejectlog'& is mapped to LOG_NOTICE
35370 &'paniclog'& is mapped to LOG_ALERT
35373 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
35374 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
35375 these are routed by syslog to the same place. You can suppress this duplication
35376 by setting &%syslog_duplication%& false.
35378 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
35379 entries contain multiple lines when headers are included. To cope with both
35380 these cases, entries written to syslog are split into separate &[syslog()]&
35381 calls at each internal newline, and also after a maximum of
35382 870 data characters. (This allows for a total syslog line length of 1024, when
35383 additions such as timestamps are added.) If you are running a syslog
35384 replacement that can handle lines longer than the 1024 characters allowed by
35385 RFC 3164, you should set
35387 SYSLOG_LONG_LINES=yes
35389 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
35390 lines, but it still splits at internal newlines in &'reject'& log entries.
35392 To make it easy to re-assemble split lines later, each component of a split
35393 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
35394 where <&'n'&> is the component number and <&'m'&> is the total number of
35395 components in the entry. The / delimiter is used when the line was split
35396 because it was too long; if it was split because of an internal newline, the \
35397 delimiter is used. For example, supposing the length limit to be 50 instead of
35398 870, the following would be the result of a typical rejection message to
35399 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
35400 name, and pid as added by syslog:
35402 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
35403 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
35404 [3/5] when scanning for sender: missing or malformed lo
35405 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
35408 The same error might cause the following lines to be written to &"rejectlog"&
35411 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
35412 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
35413 [3/18] er when scanning for sender: missing or malformed
35414 [4/18] local part in "<>" (envelope sender is <ph10@cam
35416 [6\18] Recipients: ph10@some.domain.cam.example
35417 [7\18] P Received: from [127.0.0.1] (ident=ph10)
35418 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
35419 [9\18] id 16RdAL-0006pc-00
35420 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
35421 [11\18] 09:43 +0100
35423 [13\18] Subject: this is a test header
35424 [18\18] X-something: this is another header
35425 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
35428 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
35430 Log lines that are neither too long nor contain newlines are written to syslog
35431 without modification.
35433 If only syslog is being used, the Exim monitor is unable to provide a log tail
35434 display, unless syslog is routing &'mainlog'& to a file on the local host and
35435 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
35440 .section "Log line flags" "SECID250"
35441 One line is written to the main log for each message received, and for each
35442 successful, unsuccessful, and delayed delivery. These lines can readily be
35443 picked out by the distinctive two-character flags that immediately follow the
35444 timestamp. The flags are:
35446 &`<=`& message arrival
35447 &`(=`& message fakereject
35448 &`=>`& normal message delivery
35449 &`->`& additional address in same delivery
35450 &`>>`& cutthrough message delivery
35451 &`*>`& delivery suppressed by &%-N%&
35452 &`**`& delivery failed; address bounced
35453 &`==`& delivery deferred; temporary problem
35457 .section "Logging message reception" "SECID251"
35458 .cindex "log" "reception line"
35459 The format of the single-line entry in the main log that is written for every
35460 message received is shown in the basic example below, which is split over
35461 several lines in order to fit it on the page:
35463 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
35464 H=mailer.fict.example [192.168.123.123] U=exim
35465 P=smtp S=5678 id=<incoming message id>
35467 The address immediately following &"<="& is the envelope sender address. A
35468 bounce message is shown with the sender address &"<>"&, and if it is locally
35469 generated, this is followed by an item of the form
35473 which is a reference to the message that caused the bounce to be sent.
35477 For messages from other hosts, the H and U fields identify the remote host and
35478 record the RFC 1413 identity of the user that sent the message, if one was
35479 received. The number given in square brackets is the IP address of the sending
35480 host. If there is a single, unparenthesized host name in the H field, as
35481 above, it has been verified to correspond to the IP address (see the
35482 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
35483 by the remote host in the SMTP HELO or EHLO command, and has not been
35484 verified. If verification yields a different name to that given for HELO or
35485 EHLO, the verified name appears first, followed by the HELO or EHLO
35486 name in parentheses.
35488 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
35489 without brackets, in the HELO or EHLO command, leading to entries in
35490 the log containing text like these examples:
35492 H=(10.21.32.43) [192.168.8.34]
35493 H=([10.21.32.43]) [192.168.8.34]
35495 This can be confusing. Only the final address in square brackets can be relied
35498 For locally generated messages (that is, messages not received over TCP/IP),
35499 the H field is omitted, and the U field contains the login name of the caller
35502 .cindex "authentication" "logging"
35503 .cindex "AUTH" "logging"
35504 For all messages, the P field specifies the protocol used to receive the
35505 message. This is the value that is stored in &$received_protocol$&. In the case
35506 of incoming SMTP messages, the value indicates whether or not any SMTP
35507 extensions (ESMTP), encryption, or authentication were used. If the SMTP
35508 session was encrypted, there is an additional X field that records the cipher
35509 suite that was used.
35511 .cindex log protocol
35512 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
35513 hosts that have authenticated themselves using the SMTP AUTH command. The first
35514 value is used when the SMTP connection was encrypted (&"secure"&). In this case
35515 there is an additional item A= followed by the name of the authenticator that
35516 was used. If an authenticated identification was set up by the authenticator's
35517 &%server_set_id%& option, this is logged too, separated by a colon from the
35518 authenticator name.
35520 .cindex "size" "of message"
35521 The id field records the existing message id, if present. The size of the
35522 received message is given by the S field. When the message is delivered,
35523 headers may be removed or added, so that the size of delivered copies of the
35524 message may not correspond with this value (and indeed may be different to each
35527 The &%log_selector%& option can be used to request the logging of additional
35528 data when a message is received. See section &<<SECTlogselector>>& below.
35532 .section "Logging deliveries" "SECID252"
35533 .cindex "log" "delivery line"
35534 The format of the single-line entry in the main log that is written for every
35535 delivery is shown in one of the examples below, for local and remote
35536 deliveries, respectively. Each example has been split into multiple lines in order
35537 to fit it on the page:
35539 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
35540 <marv@hitch.fict.example> R=localuser T=local_delivery
35541 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
35542 monk@holistic.fict.example R=dnslookup T=remote_smtp
35543 H=holistic.fict.example [192.168.234.234]
35545 For ordinary local deliveries, the original address is given in angle brackets
35546 after the final delivery address, which might be a pipe or a file. If
35547 intermediate address(es) exist between the original and the final address, the
35548 last of these is given in parentheses after the final address. The R and T
35549 fields record the router and transport that were used to process the address.
35551 If SMTP AUTH was used for the delivery there is an additional item A=
35552 followed by the name of the authenticator that was used.
35553 If an authenticated identification was set up by the authenticator's &%client_set_id%&
35554 option, this is logged too, separated by a colon from the authenticator name.
35556 If a shadow transport was run after a successful local delivery, the log line
35557 for the successful delivery has an item added on the end, of the form
35559 &`ST=<`&&'shadow transport name'&&`>`&
35561 If the shadow transport did not succeed, the error message is put in
35562 parentheses afterwards.
35564 .cindex "asterisk" "after IP address"
35565 When more than one address is included in a single delivery (for example, two
35566 SMTP RCPT commands in one transaction) the second and subsequent addresses are
35567 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
35568 down a single SMTP connection, an asterisk follows the IP address in the log
35569 lines for the second and subsequent messages.
35571 .cindex "delivery" "cutthrough; logging"
35572 .cindex "cutthrough" "logging"
35573 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
35574 line precedes the reception line, since cutthrough waits for a possible
35575 rejection from the destination in case it can reject the sourced item.
35577 The generation of a reply message by a filter file gets logged as a
35578 &"delivery"& to the addressee, preceded by &">"&.
35580 The &%log_selector%& option can be used to request the logging of additional
35581 data when a message is delivered. See section &<<SECTlogselector>>& below.
35584 .section "Discarded deliveries" "SECID253"
35585 .cindex "discarded messages"
35586 .cindex "message" "discarded"
35587 .cindex "delivery" "discarded; logging"
35588 When a message is discarded as a result of the command &"seen finish"& being
35589 obeyed in a filter file which generates no deliveries, a log entry of the form
35591 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
35592 <low.club@bridge.example> R=userforward
35594 is written, to record why no deliveries are logged. When a message is discarded
35595 because it is aliased to &":blackhole:"& the log line is like this:
35597 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
35598 <hole@nowhere.example> R=blackhole_router
35602 .section "Deferred deliveries" "SECID254"
35603 When a delivery is deferred, a line of the following form is logged:
35605 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
35606 R=dnslookup T=smtp defer (146): Connection refused
35608 In the case of remote deliveries, the error is the one that was given for the
35609 last IP address that was tried. Details of individual SMTP failures are also
35610 written to the log, so the above line would be preceded by something like
35612 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
35613 mail1.endrest.example [192.168.239.239]: Connection refused
35615 When a deferred address is skipped because its retry time has not been reached,
35616 a message is written to the log, but this can be suppressed by setting an
35617 appropriate value in &%log_selector%&.
35621 .section "Delivery failures" "SECID255"
35622 .cindex "delivery" "failure; logging"
35623 If a delivery fails because an address cannot be routed, a line of the
35624 following form is logged:
35626 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
35627 <jim@trek99.example>: unknown mail domain
35629 If a delivery fails at transport time, the router and transport are shown, and
35630 the response from the remote host is included, as in this example:
35632 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
35633 R=dnslookup T=remote_smtp: SMTP error from remote mailer
35634 after pipelined RCPT TO:<ace400@pb.example>: host
35635 pbmail3.py.example [192.168.63.111]: 553 5.3.0
35636 <ace400@pb.example>...Addressee unknown
35638 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
35639 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
35640 disabling PIPELINING. The log lines for all forms of delivery failure are
35641 flagged with &`**`&.
35645 .section "Fake deliveries" "SECID256"
35646 .cindex "delivery" "fake; logging"
35647 If a delivery does not actually take place because the &%-N%& option has been
35648 used to suppress it, a normal delivery line is written to the log, except that
35649 &"=>"& is replaced by &"*>"&.
35653 .section "Completion" "SECID257"
35656 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
35658 is written to the main log when a message is about to be removed from the spool
35659 at the end of its processing.
35664 .section "Summary of Fields in Log Lines" "SECID258"
35665 .cindex "log" "summary of fields"
35666 A summary of the field identifiers that are used in log lines is shown in
35667 the following table:
35669 &`A `& authenticator name (and optional id and sender)
35670 &`C `& SMTP confirmation on delivery
35671 &` `& command list for &"no mail in SMTP session"&
35672 &`CV `& certificate verification status
35673 &`D `& duration of &"no mail in SMTP session"&
35674 &`DN `& distinguished name from peer certificate
35675 &`DS `& DNSSEC secured lookups
35676 &`DT `& on &`=>`& lines: time taken for a delivery
35677 &`F `& sender address (on delivery lines)
35678 &`H `& host name and IP address
35679 &`I `& local interface used
35680 &`K `& CHUNKING extension used
35681 &`id `& message id for incoming message
35682 &`P `& on &`<=`& lines: protocol used
35683 &` `& on &`=>`& and &`**`& lines: return path
35684 &`PRDR`& PRDR extension used
35685 &`PRX `& on &'<='& and &`=>`& lines: proxy address
35686 &`Q `& alternate queue name
35687 &`QT `& on &`=>`& lines: time spent on queue so far
35688 &` `& on &"Completed"& lines: time spent on queue
35689 &`R `& on &`<=`& lines: reference for local bounce
35690 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
35691 &`S `& size of message in bytes
35692 &`SNI `& server name indication from TLS client hello
35693 &`ST `& shadow transport name
35694 &`T `& on &`<=`& lines: message subject (topic)
35695 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
35696 &`U `& local user or RFC 1413 identity
35697 &`X `& TLS cipher suite
35701 .section "Other log entries" "SECID259"
35702 Various other types of log entry are written from time to time. Most should be
35703 self-explanatory. Among the more common are:
35706 .cindex "retry" "time not reached"
35707 &'retry time not reached'&&~&~An address previously suffered a temporary error
35708 during routing or local delivery, and the time to retry has not yet arrived.
35709 This message is not written to an individual message log file unless it happens
35710 during the first delivery attempt.
35712 &'retry time not reached for any host'&&~&~An address previously suffered
35713 temporary errors during remote delivery, and the retry time has not yet arrived
35714 for any of the hosts to which it is routed.
35716 .cindex "spool directory" "file locked"
35717 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
35718 some other Exim process is already working on the message. This can be quite
35719 common if queue running processes are started at frequent intervals. The
35720 &'exiwhat'& utility script can be used to find out what Exim processes are
35723 .cindex "error" "ignored"
35724 &'error ignored'&&~&~There are several circumstances that give rise to this
35727 Exim failed to deliver a bounce message whose age was greater than
35728 &%ignore_bounce_errors_after%&. The bounce was discarded.
35730 A filter file set up a delivery using the &"noerror"& option, and the delivery
35731 failed. The delivery was discarded.
35733 A delivery set up by a router configured with
35734 . ==== As this is a nested list, any displays it contains must be indented
35735 . ==== as otherwise they are too far to the left.
35739 failed. The delivery was discarded.
35747 .section "Reducing or increasing what is logged" "SECTlogselector"
35748 .cindex "log" "selectors"
35749 By setting the &%log_selector%& global option, you can disable some of Exim's
35750 default logging, or you can request additional logging. The value of
35751 &%log_selector%& is made up of names preceded by plus or minus characters. For
35754 log_selector = +arguments -retry_defer
35756 The list of optional log items is in the following table, with the default
35757 selection marked by asterisks:
35759 &` 8bitmime `& received 8BITMIME status
35760 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
35761 &` address_rewrite `& address rewriting
35762 &` all_parents `& all parents in => lines
35763 &` arguments `& command line arguments
35764 &`*connection_reject `& connection rejections
35765 &`*delay_delivery `& immediate delivery delayed
35766 &` deliver_time `& time taken to perform delivery
35767 &` delivery_size `& add &`S=`&&'nnn'& to => lines
35768 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
35769 &` dnssec `& DNSSEC secured lookups
35770 &`*etrn `& ETRN commands
35771 &`*host_lookup_failed `& as it says
35772 &` ident_timeout `& timeout for ident connection
35773 &` incoming_interface `& local interface on <= and => lines
35774 &` incoming_port `& remote port on <= lines
35775 &`*lost_incoming_connection `& as it says (includes timeouts)
35776 &` outgoing_interface `& local interface on => lines
35777 &` outgoing_port `& add remote port to => lines
35778 &`*queue_run `& start and end queue runs
35779 &` queue_time `& time on queue for one recipient
35780 &` queue_time_overall `& time on queue for whole message
35781 &` pid `& Exim process id
35782 &` proxy `& proxy address on <= and => lines
35783 &` received_recipients `& recipients on <= lines
35784 &` received_sender `& sender on <= lines
35785 &`*rejected_header `& header contents on reject log
35786 &`*retry_defer `& &"retry time not reached"&
35787 &` return_path_on_delivery `& put return path on => and ** lines
35788 &` sender_on_delivery `& add sender to => lines
35789 &`*sender_verify_fail `& sender verification failures
35790 &`*size_reject `& rejection because too big
35791 &`*skip_delivery `& delivery skipped in a queue run
35792 &`*smtp_confirmation `& SMTP confirmation on => lines
35793 &` smtp_connection `& incoming SMTP connections
35794 &` smtp_incomplete_transaction`& incomplete SMTP transactions
35795 &` smtp_mailauth `& AUTH argument to MAIL commands
35796 &` smtp_no_mail `& session with no MAIL commands
35797 &` smtp_protocol_error `& SMTP protocol errors
35798 &` smtp_syntax_error `& SMTP syntax errors
35799 &` subject `& contents of &'Subject:'& on <= lines
35800 &`*tls_certificate_verified `& certificate verification status
35801 &`*tls_cipher `& TLS cipher suite on <= and => lines
35802 &` tls_peerdn `& TLS peer DN on <= and => lines
35803 &` tls_sni `& TLS SNI on <= lines
35804 &` unknown_in_list `& DNS lookup failed in list match
35806 &` all `& all of the above
35808 See also the &%slow_lookup_log%& main configuration option,
35809 section &<<SECID99>>&
35811 More details on each of these items follows:
35815 .cindex "log" "8BITMIME"
35816 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
35817 which may help in tracking down interoperability issues with ancient MTAs
35818 that are not 8bit clean. This is added to the &"<="& line, tagged with
35819 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
35820 &`7BIT`& and &`8BITMIME`& respectively.
35822 .cindex "&%warn%& ACL verb" "log when skipping"
35823 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
35824 its conditions cannot be evaluated, a log line to this effect is written if
35825 this log selector is set.
35827 .cindex "log" "rewriting"
35828 .cindex "rewriting" "logging"
35829 &%address_rewrite%&: This applies both to global rewrites and per-transport
35830 rewrites, but not to rewrites in filters run as an unprivileged user (because
35831 such users cannot access the log).
35833 .cindex "log" "full parentage"
35834 &%all_parents%&: Normally only the original and final addresses are logged on
35835 delivery lines; with this selector, intermediate parents are given in
35836 parentheses between them.
35838 .cindex "log" "Exim arguments"
35839 .cindex "Exim arguments, logging"
35840 &%arguments%&: This causes Exim to write the arguments with which it was called
35841 to the main log, preceded by the current working directory. This is a debugging
35842 feature, added to make it easier to find out how certain MUAs call
35843 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
35844 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
35845 that are empty or that contain white space are quoted. Non-printing characters
35846 are shown as escape sequences. This facility cannot log unrecognized arguments,
35847 because the arguments are checked before the configuration file is read. The
35848 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
35849 between the caller and Exim.
35851 .cindex "log" "connection rejections"
35852 &%connection_reject%&: A log entry is written whenever an incoming SMTP
35853 connection is rejected, for whatever reason.
35855 .cindex "log" "delayed delivery"
35856 .cindex "delayed delivery, logging"
35857 &%delay_delivery%&: A log entry is written whenever a delivery process is not
35858 started for an incoming message because the load is too high or too many
35859 messages were received on one connection. Logging does not occur if no delivery
35860 process is started because &%queue_only%& is set or &%-odq%& was used.
35862 .cindex "log" "delivery duration"
35863 &%deliver_time%&: For each delivery, the amount of real time it has taken to
35864 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
35866 .cindex "log" "message size on delivery"
35867 .cindex "size" "of message"
35868 &%delivery_size%&: For each delivery, the size of message delivered is added to
35869 the &"=>"& line, tagged with S=.
35871 .cindex "log" "dnslist defer"
35872 .cindex "DNS list" "logging defer"
35873 .cindex "black list (DNS)"
35874 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
35875 DNS black list suffers a temporary error.
35878 .cindex dnssec logging
35879 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
35880 dns lookups gave secure results a tag of DS is added.
35881 For acceptance this covers the reverse and forward lookups for host name verification.
35882 It does not cover helo-name verification.
35883 For delivery this covers the SRV, MX, A and/or AAAA lookups.
35885 .cindex "log" "ETRN commands"
35886 .cindex "ETRN" "logging"
35887 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
35888 is run to determine whether or not it is actually accepted. An invalid ETRN
35889 command, or one received within a message transaction is not logged by this
35890 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
35892 .cindex "log" "host lookup failure"
35893 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
35894 any addresses, or when a lookup of an IP address fails to find a host name, a
35895 log line is written. This logging does not apply to direct DNS lookups when
35896 routing email addresses, but it does apply to &"byname"& lookups.
35898 .cindex "log" "ident timeout"
35899 .cindex "RFC 1413" "logging timeout"
35900 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
35901 client's ident port times out.
35903 .cindex "log" "incoming interface"
35904 .cindex "log" "local interface"
35905 .cindex "log" "local address and port"
35906 .cindex "TCP/IP" "logging local address and port"
35907 .cindex "interface" "logging"
35908 &%incoming_interface%&: The interface on which a message was received is added
35909 to the &"<="& line as an IP address in square brackets, tagged by I= and
35910 followed by a colon and the port number. The local interface and port are also
35911 added to other SMTP log lines, for example &"SMTP connection from"&, to
35912 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
35913 The latter can be disabled by turning off the &%outgoing_interface%& option.
35915 .cindex log "incoming proxy address"
35916 .cindex proxy "logging proxy address"
35917 .cindex "TCP/IP" "logging proxy address"
35918 &%proxy%&: The internal (closest to the system running Exim) IP address
35919 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
35920 on a proxied connection
35921 or the &"=>"& line for a message delivered on a proxied connection..
35922 See &<<SECTproxyInbound>>& for more information.
35924 .cindex "log" "incoming remote port"
35925 .cindex "port" "logging remote"
35926 .cindex "TCP/IP" "logging incoming remote port"
35927 .vindex "&$sender_fullhost$&"
35928 .vindex "&$sender_rcvhost$&"
35929 &%incoming_port%&: The remote port number from which a message was received is
35930 added to log entries and &'Received:'& header lines, following the IP address
35931 in square brackets, and separated from it by a colon. This is implemented by
35932 changing the value that is put in the &$sender_fullhost$& and
35933 &$sender_rcvhost$& variables. Recording the remote port number has become more
35934 important with the widening use of NAT (see RFC 2505).
35936 .cindex "log" "dropped connection"
35937 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
35938 connection is unexpectedly dropped.
35940 .cindex "log" "outgoing interface"
35941 .cindex "log" "local interface"
35942 .cindex "log" "local address and port"
35943 .cindex "TCP/IP" "logging local address and port"
35944 .cindex "interface" "logging"
35945 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
35946 interface on which a message was sent is added to delivery lines as an I= tag
35947 followed by IP address in square brackets. You can disable this by turning
35948 off the &%outgoing_interface%& option.
35950 .cindex "log" "outgoing remote port"
35951 .cindex "port" "logging outgoint remote"
35952 .cindex "TCP/IP" "logging ougtoing remote port"
35953 &%outgoing_port%&: The remote port number is added to delivery log lines (those
35954 containing => tags) following the IP address.
35955 The local port is also added if &%incoming_interface%& and
35956 &%outgoing_interface%& are both enabled.
35957 This option is not included in the default setting, because for most ordinary
35958 configurations, the remote port number is always 25 (the SMTP port), and the
35959 local port is a random ephemeral port.
35961 .cindex "log" "process ids in"
35962 .cindex "pid (process id)" "in log lines"
35963 &%pid%&: The current process id is added to every log line, in square brackets,
35964 immediately after the time and date.
35966 .cindex "log" "queue run"
35967 .cindex "queue runner" "logging"
35968 &%queue_run%&: The start and end of every queue run are logged.
35970 .cindex "log" "queue time"
35971 &%queue_time%&: The amount of time the message has been in the queue on the
35972 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
35973 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
35974 includes reception time as well as the delivery time for the current address.
35975 This means that it may be longer than the difference between the arrival and
35976 delivery log line times, because the arrival log line is not written until the
35977 message has been successfully received.
35979 &%queue_time_overall%&: The amount of time the message has been in the queue on
35980 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
35981 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
35982 message, so it includes reception time as well as the total delivery time.
35984 .cindex "log" "recipients"
35985 &%received_recipients%&: The recipients of a message are listed in the main log
35986 as soon as the message is received. The list appears at the end of the log line
35987 that is written when a message is received, preceded by the word &"for"&. The
35988 addresses are listed after they have been qualified, but before any rewriting
35990 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
35993 .cindex "log" "sender reception"
35994 &%received_sender%&: The unrewritten original sender of a message is added to
35995 the end of the log line that records the message's arrival, after the word
35996 &"from"& (before the recipients if &%received_recipients%& is also set).
35998 .cindex "log" "header lines for rejection"
35999 &%rejected_header%&: If a message's header has been received at the time a
36000 rejection is written to the reject log, the complete header is added to the
36001 log. Header logging can be turned off individually for messages that are
36002 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
36004 .cindex "log" "retry defer"
36005 &%retry_defer%&: A log line is written if a delivery is deferred because a
36006 retry time has not yet been reached. However, this &"retry time not reached"&
36007 message is always omitted from individual message logs after the first delivery
36010 .cindex "log" "return path"
36011 &%return_path_on_delivery%&: The return path that is being transmitted with
36012 the message is included in delivery and bounce lines, using the tag P=.
36013 This is omitted if no delivery actually happens, for example, if routing fails,
36014 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
36016 .cindex "log" "sender on delivery"
36017 &%sender_on_delivery%&: The message's sender address is added to every delivery
36018 and bounce line, tagged by F= (for &"from"&).
36019 This is the original sender that was received with the message; it is not
36020 necessarily the same as the outgoing return path.
36022 .cindex "log" "sender verify failure"
36023 &%sender_verify_fail%&: If this selector is unset, the separate log line that
36024 gives details of a sender verification failure is not written. Log lines for
36025 the rejection of SMTP commands contain just &"sender verify failed"&, so some
36028 .cindex "log" "size rejection"
36029 &%size_reject%&: A log line is written whenever a message is rejected because
36032 .cindex "log" "frozen messages; skipped"
36033 .cindex "frozen messages" "logging skipping"
36034 &%skip_delivery%&: A log line is written whenever a message is skipped during a
36035 queue run because it is frozen or because another process is already delivering
36037 .cindex "&""spool file is locked""&"
36038 The message that is written is &"spool file is locked"&.
36040 .cindex "log" "smtp confirmation"
36041 .cindex "SMTP" "logging confirmation"
36042 .cindex "LMTP" "logging confirmation"
36043 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
36044 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
36045 A number of MTAs (including Exim) return an identifying string in this
36048 .cindex "log" "SMTP connections"
36049 .cindex "SMTP" "logging connections"
36050 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
36051 established or closed, unless the connection is from a host that matches
36052 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
36053 only when the closure is unexpected.) This applies to connections from local
36054 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
36055 dropped in the middle of a message, a log line is always written, whether or
36056 not this selector is set, but otherwise nothing is written at the start and end
36057 of connections unless this selector is enabled.
36059 For TCP/IP connections to an Exim daemon, the current number of connections is
36060 included in the log message for each new connection, but note that the count is
36061 reset if the daemon is restarted.
36062 Also, because connections are closed (and the closure is logged) in
36063 subprocesses, the count may not include connections that have been closed but
36064 whose termination the daemon has not yet noticed. Thus, while it is possible to
36065 match up the opening and closing of connections in the log, the value of the
36066 logged counts may not be entirely accurate.
36068 .cindex "log" "SMTP transaction; incomplete"
36069 .cindex "SMTP" "logging incomplete transactions"
36070 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
36071 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
36072 and the message sender plus any accepted recipients are included in the log
36073 line. This can provide evidence of dictionary attacks.
36075 .cindex "log" "non-MAIL SMTP sessions"
36076 .cindex "MAIL" "logging session without"
36077 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
36078 connection terminates without having issued a MAIL command. This includes both
36079 the case when the connection is dropped, and the case when QUIT is used. It
36080 does not include cases where the connection is rejected right at the start (by
36081 an ACL, or because there are too many connections, or whatever). These cases
36082 already have their own log lines.
36084 The log line that is written contains the identity of the client in the usual
36085 way, followed by D= and a time, which records the duration of the connection.
36086 If the connection was authenticated, this fact is logged exactly as it is for
36087 an incoming message, with an A= item. If the connection was encrypted, CV=,
36088 DN=, and X= items may appear as they do for an incoming message, controlled by
36089 the same logging options.
36091 Finally, if any SMTP commands were issued during the connection, a C= item
36092 is added to the line, listing the commands that were used. For example,
36096 shows that the client issued QUIT straight after EHLO. If there were fewer
36097 than 20 commands, they are all listed. If there were more than 20 commands,
36098 the last 20 are listed, preceded by &"..."&. However, with the default
36099 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
36100 have been aborted before 20 non-mail commands are processed.
36102 &%smtp_mailauth%&: A third subfield with the authenticated sender,
36103 colon-separated, is appended to the A= item for a message arrival or delivery
36104 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
36105 was accepted or used.
36107 .cindex "log" "SMTP protocol error"
36108 .cindex "SMTP" "logging protocol error"
36109 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
36110 encountered. Exim does not have perfect detection of all protocol errors
36111 because of transmission delays and the use of pipelining. If PIPELINING has
36112 been advertised to a client, an Exim server assumes that the client will use
36113 it, and therefore it does not count &"expected"& errors (for example, RCPT
36114 received after rejecting MAIL) as protocol errors.
36116 .cindex "SMTP" "logging syntax errors"
36117 .cindex "SMTP" "syntax errors; logging"
36118 .cindex "SMTP" "unknown command; logging"
36119 .cindex "log" "unknown SMTP command"
36120 .cindex "log" "SMTP syntax error"
36121 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
36122 encountered. An unrecognized command is treated as a syntax error. For an
36123 external connection, the host identity is given; for an internal connection
36124 using &%-bs%& the sender identification (normally the calling user) is given.
36126 .cindex "log" "subject"
36127 .cindex "subject, logging"
36128 &%subject%&: The subject of the message is added to the arrival log line,
36129 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
36130 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
36131 specifies whether characters with values greater than 127 should be logged
36132 unchanged, or whether they should be rendered as escape sequences.
36134 .cindex "log" "certificate verification"
36135 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
36136 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
36137 verified, and &`CV=no`& if not.
36139 .cindex "log" "TLS cipher"
36140 .cindex "TLS" "logging cipher"
36141 &%tls_cipher%&: When a message is sent or received over an encrypted
36142 connection, the cipher suite used is added to the log line, preceded by X=.
36144 .cindex "log" "TLS peer DN"
36145 .cindex "TLS" "logging peer DN"
36146 &%tls_peerdn%&: When a message is sent or received over an encrypted
36147 connection, and a certificate is supplied by the remote host, the peer DN is
36148 added to the log line, preceded by DN=.
36150 .cindex "log" "TLS SNI"
36151 .cindex "TLS" "logging SNI"
36152 &%tls_sni%&: When a message is received over an encrypted connection, and
36153 the remote host provided the Server Name Indication extension, the SNI is
36154 added to the log line, preceded by SNI=.
36156 .cindex "log" "DNS failure in list"
36157 &%unknown_in_list%&: This setting causes a log entry to be written when the
36158 result of a list match is failure because a DNS lookup failed.
36162 .section "Message log" "SECID260"
36163 .cindex "message" "log file for"
36164 .cindex "log" "message log; description of"
36165 .cindex "&_msglog_& directory"
36166 .oindex "&%preserve_message_logs%&"
36167 In addition to the general log files, Exim writes a log file for each message
36168 that it handles. The names of these per-message logs are the message ids, and
36169 they are kept in the &_msglog_& sub-directory of the spool directory. Each
36170 message log contains copies of the log lines that apply to the message. This
36171 makes it easier to inspect the status of an individual message without having
36172 to search the main log. A message log is deleted when processing of the message
36173 is complete, unless &%preserve_message_logs%& is set, but this should be used
36174 only with great care because they can fill up your disk very quickly.
36176 On a heavily loaded system, it may be desirable to disable the use of
36177 per-message logs, in order to reduce disk I/O. This can be done by setting the
36178 &%message_logs%& option false.
36184 . ////////////////////////////////////////////////////////////////////////////
36185 . ////////////////////////////////////////////////////////////////////////////
36187 .chapter "Exim utilities" "CHAPutils"
36188 .scindex IIDutils "utilities"
36189 A number of utility scripts and programs are supplied with Exim and are
36190 described in this chapter. There is also the Exim Monitor, which is covered in
36191 the next chapter. The utilities described here are:
36193 .itable none 0 0 3 7* left 15* left 40* left
36194 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
36195 "list what Exim processes are doing"
36196 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
36197 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
36198 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
36199 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
36201 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
36202 .irow &<<SECTmailstat>>& &'eximstats'& &&&
36203 "extract statistics from the log"
36204 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
36205 "check address acceptance from given IP"
36206 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
36207 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
36208 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
36209 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
36210 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
36211 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
36214 Another utility that might be of use to sites with many MTAs is Tom Kistner's
36215 &'exilog'&. It provides log visualizations across multiple Exim servers. See
36216 &url(http://duncanthrax.net/exilog/) for details.
36221 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
36222 .cindex "&'exiwhat'&"
36223 .cindex "process, querying"
36225 On operating systems that can restart a system call after receiving a signal
36226 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
36227 a line describing what it is doing to the file &_exim-process.info_& in the
36228 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
36229 processes it can find, having first emptied the file. It then waits for one
36230 second to allow the Exim processes to react before displaying the results. In
36231 order to run &'exiwhat'& successfully you have to have sufficient privilege to
36232 send the signal to the Exim processes, so it is normally run as root.
36234 &*Warning*&: This is not an efficient process. It is intended for occasional
36235 use by system administrators. It is not sensible, for example, to set up a
36236 script that sends SIGUSR1 signals to Exim processes at short intervals.
36239 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
36240 varies in different operating systems. Not only are different options used,
36241 but the format of the output is different. For this reason, there are some
36242 system configuration options that configure exactly how &'exiwhat'& works. If
36243 it doesn't seem to be working for you, check the following compile-time
36246 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
36247 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
36248 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
36249 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
36251 An example of typical output from &'exiwhat'& is
36253 164 daemon: -q1h, listening on port 25
36254 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
36255 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
36256 [10.19.42.42] (editor@ref.example)
36257 10592 handling incoming call from [192.168.243.242]
36258 10628 accepting a local non-SMTP message
36260 The first number in the output line is the process number. The third line has
36261 been split here, in order to fit it on the page.
36265 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
36266 .cindex "&'exiqgrep'&"
36267 .cindex "queue" "grepping"
36268 This utility is a Perl script contributed by Matt Hubbard. It runs
36272 or (in case &*-a*& switch is specified)
36276 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
36277 contain alternate exim configuration the queue management might be using.
36279 to obtain a queue listing, and then greps the output to select messages
36280 that match given criteria. The following selection options are available:
36283 .vitem &*-f*&&~<&'regex'&>
36284 Match the sender address using a case-insensitive search. The field that is
36285 tested is enclosed in angle brackets, so you can test for bounce messages with
36289 .vitem &*-r*&&~<&'regex'&>
36290 Match a recipient address using a case-insensitive search. The field that is
36291 tested is not enclosed in angle brackets.
36293 .vitem &*-s*&&~<&'regex'&>
36294 Match against the size field.
36296 .vitem &*-y*&&~<&'seconds'&>
36297 Match messages that are younger than the given time.
36299 .vitem &*-o*&&~<&'seconds'&>
36300 Match messages that are older than the given time.
36303 Match only frozen messages.
36306 Match only non-frozen messages.
36309 The following options control the format of the output:
36313 Display only the count of matching messages.
36316 Long format &-- display the full message information as output by Exim. This is
36320 Display message ids only.
36323 Brief format &-- one line per message.
36326 Display messages in reverse order.
36329 Include delivered recipients in queue listing.
36332 There is one more option, &%-h%&, which outputs a list of options.
36336 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
36337 .cindex "&'exiqsumm'&"
36338 .cindex "queue" "summary"
36339 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
36340 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
36341 running a command such as
36343 exim -bp | exiqsumm
36345 The output consists of one line for each domain that has messages waiting for
36346 it, as in the following example:
36348 3 2322 74m 66m msn.com.example
36350 Each line lists the number of pending deliveries for a domain, their total
36351 volume, and the length of time that the oldest and the newest messages have
36352 been waiting. Note that the number of pending deliveries is greater than the
36353 number of messages when messages have more than one recipient.
36355 A summary line is output at the end. By default the output is sorted on the
36356 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
36357 the output to be sorted by oldest message and by count of messages,
36358 respectively. There are also three options that split the messages for each
36359 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
36360 separates frozen messages, and &%-s%& separates messages according to their
36363 The output of &'exim -bp'& contains the original addresses in the message, so
36364 this also applies to the output from &'exiqsumm'&. No domains from addresses
36365 generated by aliasing or forwarding are included (unless the &%one_time%&
36366 option of the &(redirect)& router has been used to convert them into &"top
36367 level"& addresses).
36372 .section "Extracting specific information from the log (exigrep)" &&&
36374 .cindex "&'exigrep'&"
36375 .cindex "log" "extracts; grepping for"
36376 The &'exigrep'& utility is a Perl script that searches one or more main log
36377 files for entries that match a given pattern. When it finds a match, it
36378 extracts all the log entries for the relevant message, not just those that
36379 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
36380 given message, or all mail for a given user, or for a given host, for example.
36381 The input files can be in Exim log format or syslog format.
36382 If a matching log line is not associated with a specific message, it is
36383 included in &'exigrep'&'s output without any additional lines. The usage is:
36385 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
36387 If no log file names are given on the command line, the standard input is read.
36389 The &%-t%& argument specifies a number of seconds. It adds an additional
36390 condition for message selection. Messages that are complete are shown only if
36391 they spent more than <&'n'&> seconds on the queue.
36393 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
36394 makes it case-sensitive. This may give a performance improvement when searching
36395 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
36396 option; with &%-I%& they do not. In both cases it is possible to change the
36397 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
36399 The &%-l%& option means &"literal"&, that is, treat all characters in the
36400 pattern as standing for themselves. Otherwise the pattern must be a Perl
36401 regular expression.
36403 The &%-v%& option inverts the matching condition. That is, a line is selected
36404 if it does &'not'& match the pattern.
36406 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
36407 that are generated as a result/response to a message that &'exigrep'& matched
36411 user_a sends a message to user_b, which generates a bounce back to user_b. If
36412 &'exigrep'& is used to search for &"user_a"&, only the first message will be
36413 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
36414 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
36415 when searching for &"user_a"& will show both messages since the bounce is
36416 &"related"& to or a &"result"& of the first message that was found by the
36419 If the location of a &'zcat'& command is known from the definition of
36420 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
36421 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
36422 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
36423 autodetection of some well known compression extensions.
36426 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
36427 .cindex "&'exipick'&"
36428 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
36429 lists messages from the queue according to a variety of criteria. For details
36430 of &'exipick'&'s facilities, visit the web page at
36431 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
36432 the &%--help%& option.
36435 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
36436 .cindex "log" "cycling local files"
36437 .cindex "cycling logs"
36438 .cindex "&'exicyclog'&"
36439 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
36440 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
36441 you are using log files with datestamps in their names (see section
36442 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
36443 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
36444 There are two command line options for &'exicyclog'&:
36446 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
36447 default that is set when Exim is built. The default default is 10.
36449 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
36450 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
36451 overriding the script's default, which is to find the setting from Exim's
36455 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
36456 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
36457 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
36458 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
36459 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
36460 logs are handled similarly.
36462 If the limit is greater than 99, the script uses 3-digit numbers such as
36463 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
36464 to one that is greater, or &'vice versa'&, you will have to fix the names of
36465 any existing log files.
36467 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
36468 the end are deleted. All files with numbers greater than 01 are compressed,
36469 using a compression command which is configured by the COMPRESS_COMMAND
36470 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
36471 root &%crontab%& entry of the form
36473 1 0 * * * su exim -c /usr/exim/bin/exicyclog
36475 assuming you have used the name &"exim"& for the Exim user. You can run
36476 &'exicyclog'& as root if you wish, but there is no need.
36480 .section "Mail statistics (eximstats)" "SECTmailstat"
36481 .cindex "statistics"
36482 .cindex "&'eximstats'&"
36483 A Perl script called &'eximstats'& is provided for extracting statistical
36484 information from log files. The output is either plain text, or HTML.
36485 Exim log files are also supported by the &'Lire'& system produced by the
36486 LogReport Foundation &url(http://www.logreport.org).
36488 The &'eximstats'& script has been hacked about quite a bit over time. The
36489 latest version is the result of some extensive revision by Steve Campbell. A
36490 lot of information is given by default, but there are options for suppressing
36491 various parts of it. Following any options, the arguments to the script are a
36492 list of files, which should be main log files. For example:
36494 eximstats -nr /var/spool/exim/log/mainlog.01
36496 By default, &'eximstats'& extracts information about the number and volume of
36497 messages received from or delivered to various hosts. The information is sorted
36498 both by message count and by volume, and the top fifty hosts in each category
36499 are listed on the standard output. Similar information, based on email
36500 addresses or domains instead of hosts can be requested by means of various
36501 options. For messages delivered and received locally, similar statistics are
36502 also produced per user.
36504 The output also includes total counts and statistics about delivery errors, and
36505 histograms showing the number of messages received and deliveries made in each
36506 hour of the day. A delivery with more than one address in its envelope (for
36507 example, an SMTP transaction with more than one RCPT command) is counted
36508 as a single delivery by &'eximstats'&.
36510 Though normally more deliveries than receipts are reported (as messages may
36511 have multiple recipients), it is possible for &'eximstats'& to report more
36512 messages received than delivered, even though the queue is empty at the start
36513 and end of the period in question. If an incoming message contains no valid
36514 recipients, no deliveries are recorded for it. A bounce message is handled as
36515 an entirely separate message.
36517 &'eximstats'& always outputs a grand total summary giving the volume and number
36518 of messages received and deliveries made, and the number of hosts involved in
36519 each case. It also outputs the number of messages that were delayed (that is,
36520 not completely delivered at the first attempt), and the number that had at
36521 least one address that failed.
36523 The remainder of the output is in sections that can be independently disabled
36524 or modified by various options. It consists of a summary of deliveries by
36525 transport, histograms of messages received and delivered per time interval
36526 (default per hour), information about the time messages spent on the queue,
36527 a list of relayed messages, lists of the top fifty sending hosts, local
36528 senders, destination hosts, and destination local users by count and by volume,
36529 and a list of delivery errors that occurred.
36531 The relay information lists messages that were actually relayed, that is, they
36532 came from a remote host and were directly delivered to some other remote host,
36533 without being processed (for example, for aliasing or forwarding) locally.
36535 There are quite a few options for &'eximstats'& to control exactly what it
36536 outputs. These are documented in the Perl script itself, and can be extracted
36537 by running the command &(perldoc)& on the script. For example:
36539 perldoc /usr/exim/bin/eximstats
36542 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
36543 .cindex "&'exim_checkaccess'&"
36544 .cindex "policy control" "checking access"
36545 .cindex "checking access"
36546 The &%-bh%& command line argument allows you to run a fake SMTP session with
36547 debugging output, in order to check what Exim is doing when it is applying
36548 policy controls to incoming SMTP mail. However, not everybody is sufficiently
36549 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
36550 sometimes you just want to answer the question &"Does this address have
36551 access?"& without bothering with any further details.
36553 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
36554 two arguments, an IP address and an email address:
36556 exim_checkaccess 10.9.8.7 A.User@a.domain.example
36558 The utility runs a call to Exim with the &%-bh%& option, to test whether the
36559 given email address would be accepted in a RCPT command in a TCP/IP
36560 connection from the host with the given IP address. The output of the utility
36561 is either the word &"accepted"&, or the SMTP error response, for example:
36564 550 Relay not permitted
36566 When running this test, the utility uses &`<>`& as the envelope sender address
36567 for the MAIL command, but you can change this by providing additional
36568 options. These are passed directly to the Exim command. For example, to specify
36569 that the test is to be run with the sender address &'himself@there.example'&
36572 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
36573 -f himself@there.example
36575 Note that these additional Exim command line items must be given after the two
36576 mandatory arguments.
36578 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
36579 while running its checks. You can run checks that include callouts by using
36580 &%-bhc%&, but this is not yet available in a &"packaged"& form.
36584 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
36585 .cindex "DBM" "building dbm files"
36586 .cindex "building DBM files"
36587 .cindex "&'exim_dbmbuild'&"
36588 .cindex "lower casing"
36589 .cindex "binary zero" "in lookup key"
36590 The &'exim_dbmbuild'& program reads an input file containing keys and data in
36591 the format used by the &(lsearch)& lookup (see section
36592 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
36593 names as keys and the remainder of the information as data. The lower-casing
36594 can be prevented by calling the program with the &%-nolc%& option.
36596 A terminating zero is included as part of the key string. This is expected by
36597 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
36598 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
36599 strings or the data strings. The &(dbmnz)& lookup type can be used with such
36602 The program requires two arguments: the name of the input file (which can be a
36603 single hyphen to indicate the standard input), and the name of the output file.
36604 It creates the output under a temporary name, and then renames it if all went
36608 If the native DB interface is in use (USE_DB is set in a compile-time
36609 configuration file &-- this is common in free versions of Unix) the two file
36610 names must be different, because in this mode the Berkeley DB functions create
36611 a single output file using exactly the name given. For example,
36613 exim_dbmbuild /etc/aliases /etc/aliases.db
36615 reads the system alias file and creates a DBM version of it in
36616 &_/etc/aliases.db_&.
36618 In systems that use the &'ndbm'& routines (mostly proprietary versions of
36619 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
36620 environment, the suffixes are added to the second argument of
36621 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
36622 when the Berkeley functions are used in compatibility mode (though this is not
36623 recommended), because in that case it adds a &_.db_& suffix to the file name.
36625 If a duplicate key is encountered, the program outputs a warning, and when it
36626 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
36627 option is used. By default, only the first of a set of duplicates is used &--
36628 this makes it compatible with &(lsearch)& lookups. There is an option
36629 &%-lastdup%& which causes it to use the data for the last duplicate instead.
36630 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
36631 &%stderr%&. For other errors, where it doesn't actually make a new file, the
36637 .section "Finding individual retry times (exinext)" "SECTfinindret"
36638 .cindex "retry" "times"
36639 .cindex "&'exinext'&"
36640 A utility called &'exinext'& (mostly a Perl script) provides the ability to
36641 fish specific information out of the retry database. Given a mail domain (or a
36642 complete address), it looks up the hosts for that domain, and outputs any retry
36643 information for the hosts or for the domain. At present, the retry information
36644 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
36645 output. For example:
36647 $ exinext piglet@milne.fict.example
36648 kanga.milne.example:192.168.8.1 error 146: Connection refused
36649 first failed: 21-Feb-1996 14:57:34
36650 last tried: 21-Feb-1996 14:57:34
36651 next try at: 21-Feb-1996 15:02:34
36652 roo.milne.example:192.168.8.3 error 146: Connection refused
36653 first failed: 20-Jan-1996 13:12:08
36654 last tried: 21-Feb-1996 11:42:03
36655 next try at: 21-Feb-1996 19:42:03
36656 past final cutoff time
36658 You can also give &'exinext'& a local part, without a domain, and it
36659 will give any retry information for that local part in your default domain.
36660 A message id can be used to obtain retry information pertaining to a specific
36661 message. This exists only when an attempt to deliver a message to a remote host
36662 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
36663 &'exinext'& is not particularly efficient, but then it is not expected to be
36666 The &'exinext'& utility calls Exim to find out information such as the location
36667 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
36668 passed on to the &'exim'& commands. The first specifies an alternate Exim
36669 configuration file, and the second sets macros for use within the configuration
36670 file. These features are mainly to help in testing, but might also be useful in
36671 environments where more than one configuration file is in use.
36675 .section "Hints database maintenance" "SECThindatmai"
36676 .cindex "hints database" "maintenance"
36677 .cindex "maintaining Exim's hints database"
36678 Three utility programs are provided for maintaining the DBM files that Exim
36679 uses to contain its delivery hint information. Each program requires two
36680 arguments. The first specifies the name of Exim's spool directory, and the
36681 second is the name of the database it is to operate on. These are as follows:
36684 &'retry'&: the database of retry information
36686 &'wait-'&<&'transport name'&>: databases of information about messages waiting
36689 &'callout'&: the callout cache
36691 &'ratelimit'&: the data for implementing the ratelimit ACL condition
36693 &'misc'&: other hints data
36696 The &'misc'& database is used for
36699 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
36701 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
36702 &(smtp)& transport)
36704 Limiting the concurrency of specific transports (when &%max_parallel%& is set
36710 .section "exim_dumpdb" "SECID261"
36711 .cindex "&'exim_dumpdb'&"
36712 The entire contents of a database are written to the standard output by the
36713 &'exim_dumpdb'& program, which has no options or arguments other than the
36714 spool and database names. For example, to dump the retry database:
36716 exim_dumpdb /var/spool/exim retry
36718 Two lines of output are produced for each entry:
36720 T:mail.ref.example:192.168.242.242 146 77 Connection refused
36721 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
36723 The first item on the first line is the key of the record. It starts with one
36724 of the letters R, or T, depending on whether it refers to a routing or
36725 transport retry. For a local delivery, the next part is the local address; for
36726 a remote delivery it is the name of the remote host, followed by its failing IP
36727 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
36728 transport). If the remote port is not the standard one (port 25), it is added
36729 to the IP address. Then there follows an error code, an additional error code,
36730 and a textual description of the error.
36732 The three times on the second line are the time of first failure, the time of
36733 the last delivery attempt, and the computed time for the next attempt. The line
36734 ends with an asterisk if the cutoff time for the last retry rule has been
36737 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
36738 consists of a host name followed by a list of ids for messages that are or were
36739 waiting to be delivered to that host. If there are a very large number for any
36740 one host, continuation records, with a sequence number added to the host name,
36741 may be seen. The data in these records is often out of date, because a message
36742 may be routed to several alternative hosts, and Exim makes no effort to keep
36747 .section "exim_tidydb" "SECID262"
36748 .cindex "&'exim_tidydb'&"
36749 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
36750 database. If run with no options, it removes all records that are more than 30
36751 days old. The age is calculated from the date and time that the record was last
36752 updated. Note that, in the case of the retry database, it is &'not'& the time
36753 since the first delivery failure. Information about a host that has been down
36754 for more than 30 days will remain in the database, provided that the record is
36755 updated sufficiently often.
36757 The cutoff date can be altered by means of the &%-t%& option, which must be
36758 followed by a time. For example, to remove all records older than a week from
36759 the retry database:
36761 exim_tidydb -t 7d /var/spool/exim retry
36763 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
36764 message ids. In the former these appear as data in records keyed by host &--
36765 they were messages that were waiting for that host &-- and in the latter they
36766 are the keys for retry information for messages that have suffered certain
36767 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
36768 message ids in database records are those of messages that are still on the
36769 queue. Message ids for messages that no longer exist are removed from
36770 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
36771 For the &'retry'& database, records whose keys are non-existent message ids are
36772 removed. The &'exim_tidydb'& utility outputs comments on the standard output
36773 whenever it removes information from the database.
36775 Certain records are automatically removed by Exim when they are no longer
36776 needed, but others are not. For example, if all the MX hosts for a domain are
36777 down, a retry record is created for each one. If the primary MX host comes back
36778 first, its record is removed when Exim successfully delivers to it, but the
36779 records for the others remain because Exim has not tried to use those hosts.
36781 It is important, therefore, to run &'exim_tidydb'& periodically on all the
36782 hints databases. You should do this at a quiet time of day, because it requires
36783 a database to be locked (and therefore inaccessible to Exim) while it does its
36784 work. Removing records from a DBM file does not normally make the file smaller,
36785 but all the common DBM libraries are able to re-use the space that is released.
36786 After an initial phase of increasing in size, the databases normally reach a
36787 point at which they no longer get any bigger, as long as they are regularly
36790 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
36791 databases is likely to keep on increasing.
36796 .section "exim_fixdb" "SECID263"
36797 .cindex "&'exim_fixdb'&"
36798 The &'exim_fixdb'& program is a utility for interactively modifying databases.
36799 Its main use is for testing Exim, but it might also be occasionally useful for
36800 getting round problems in a live system. It has no options, and its interface
36801 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
36802 key of a database record can then be entered, and the data for that record is
36805 If &"d"& is typed at the next prompt, the entire record is deleted. For all
36806 except the &'retry'& database, that is the only operation that can be carried
36807 out. For the &'retry'& database, each field is output preceded by a number, and
36808 data for individual fields can be changed by typing the field number followed
36809 by new data, for example:
36813 resets the time of the next delivery attempt. Time values are given as a
36814 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
36815 used as optional separators.
36820 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
36821 .cindex "mailbox" "maintenance"
36822 .cindex "&'exim_lock'&"
36823 .cindex "locking mailboxes"
36824 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
36825 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
36826 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
36827 a user agent while investigating a problem. The utility requires the name of
36828 the file as its first argument. If the locking is successful, the second
36829 argument is run as a command (using C's &[system()]& function); if there is no
36830 second argument, the value of the SHELL environment variable is used; if this
36831 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
36832 is unlocked and the utility ends. The following options are available:
36836 Use &[fcntl()]& locking on the open mailbox.
36839 Use &[flock()]& locking on the open mailbox, provided the operating system
36842 .vitem &%-interval%&
36843 This must be followed by a number, which is a number of seconds; it sets the
36844 interval to sleep between retries (default 3).
36846 .vitem &%-lockfile%&
36847 Create a lock file before opening the mailbox.
36850 Lock the mailbox using MBX rules.
36853 Suppress verification output.
36855 .vitem &%-retries%&
36856 This must be followed by a number; it sets the number of times to try to get
36857 the lock (default 10).
36859 .vitem &%-restore_time%&
36860 This option causes &%exim_lock%& to restore the modified and read times to the
36861 locked file before exiting. This allows you to access a locked mailbox (for
36862 example, to take a backup copy) without disturbing the times that the user
36865 .vitem &%-timeout%&
36866 This must be followed by a number, which is a number of seconds; it sets a
36867 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
36868 default), a non-blocking call is used.
36871 Generate verbose output.
36874 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
36875 default is to create a lock file and also to use &[fcntl()]& locking on the
36876 mailbox, which is the same as Exim's default. The use of &%-flock%& or
36877 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
36878 requires that the directory containing the file be writeable. Locking by lock
36879 file does not last for ever; Exim assumes that a lock file is expired if it is
36880 more than 30 minutes old.
36882 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
36883 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
36884 to be taken out on the open mailbox, and an exclusive lock on the file
36885 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
36886 number of the mailbox file. When the locking is released, if an exclusive lock
36887 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
36889 The default output contains verification of the locking that takes place. The
36890 &%-v%& option causes some additional information to be given. The &%-q%& option
36891 suppresses all output except error messages.
36895 exim_lock /var/spool/mail/spqr
36897 runs an interactive shell while the file is locked, whereas
36899 &`exim_lock -q /var/spool/mail/spqr <<End`&
36900 <&'some commands'&>
36903 runs a specific non-interactive sequence of commands while the file is locked,
36904 suppressing all verification output. A single command can be run by a command
36907 exim_lock -q /var/spool/mail/spqr \
36908 "cp /var/spool/mail/spqr /some/where"
36910 Note that if a command is supplied, it must be entirely contained within the
36911 second argument &-- hence the quotes.
36915 . ////////////////////////////////////////////////////////////////////////////
36916 . ////////////////////////////////////////////////////////////////////////////
36918 .chapter "The Exim monitor" "CHAPeximon"
36919 .scindex IIDeximon "Exim monitor" "description"
36920 .cindex "X-windows"
36921 .cindex "&'eximon'&"
36922 .cindex "Local/eximon.conf"
36923 .cindex "&_exim_monitor/EDITME_&"
36924 The Exim monitor is an application which displays in an X window information
36925 about the state of Exim's queue and what Exim is doing. An admin user can
36926 perform certain operations on messages from this GUI interface; however all
36927 such facilities are also available from the command line, and indeed, the
36928 monitor itself makes use of the command line to perform any actions requested.
36932 .section "Running the monitor" "SECID264"
36933 The monitor is started by running the script called &'eximon'&. This is a shell
36934 script that sets up a number of environment variables, and then runs the
36935 binary called &_eximon.bin_&. The default appearance of the monitor window can
36936 be changed by editing the &_Local/eximon.conf_& file created by editing
36937 &_exim_monitor/EDITME_&. Comments in that file describe what the various
36938 parameters are for.
36940 The parameters that get built into the &'eximon'& script can be overridden for
36941 a particular invocation by setting up environment variables of the same names,
36942 preceded by &`EXIMON_`&. For example, a shell command such as
36944 EXIMON_LOG_DEPTH=400 eximon
36946 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
36947 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
36948 overrides the Exim log file configuration. This makes it possible to have
36949 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
36950 syslog messages are routed to a file on the local host.
36952 X resources can be used to change the appearance of the window in the normal
36953 way. For example, a resource setting of the form
36955 Eximon*background: gray94
36957 changes the colour of the background to light grey rather than white. The
36958 stripcharts are drawn with both the data lines and the reference lines in
36959 black. This means that the reference lines are not visible when on top of the
36960 data. However, their colour can be changed by setting a resource called
36961 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
36962 For example, if your X server is running Unix, you could set up lighter
36963 reference lines in the stripcharts by obeying
36966 Eximon*highlight: gray
36969 .cindex "admin user"
36970 In order to see the contents of messages on the queue, and to operate on them,
36971 &'eximon'& must either be run as root or by an admin user.
36973 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
36974 contain X11 resource parameters interpreted by the X11 library. In addition,
36975 if the first parameter starts with the string "gdb" then it is removed and the
36976 binary is invoked under gdb (the parameter is used as the gdb command-name, so
36977 versioned variants of gdb can be invoked).
36979 The monitor's window is divided into three parts. The first contains one or
36980 more stripcharts and two action buttons, the second contains a &"tail"& of the
36981 main log file, and the third is a display of the queue of messages awaiting
36982 delivery, with two more action buttons. The following sections describe these
36983 different parts of the display.
36988 .section "The stripcharts" "SECID265"
36989 .cindex "stripchart"
36990 The first stripchart is always a count of messages on the queue. Its name can
36991 be configured by setting QUEUE_STRIPCHART_NAME in the
36992 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
36993 configuration script by regular expression matches on log file entries, making
36994 it possible to display, for example, counts of messages delivered to certain
36995 hosts or using certain transports. The supplied defaults display counts of
36996 received and delivered messages, and of local and SMTP deliveries. The default
36997 period between stripchart updates is one minute; this can be adjusted by a
36998 parameter in the &_Local/eximon.conf_& file.
37000 The stripchart displays rescale themselves automatically as the value they are
37001 displaying changes. There are always 10 horizontal lines in each chart; the
37002 title string indicates the value of each division when it is greater than one.
37003 For example, &"x2"& means that each division represents a value of 2.
37005 It is also possible to have a stripchart which shows the percentage fullness of
37006 a particular disk partition, which is useful when local deliveries are confined
37007 to a single partition.
37009 .cindex "&%statvfs%& function"
37010 This relies on the availability of the &[statvfs()]& function or equivalent in
37011 the operating system. Most, but not all versions of Unix that support Exim have
37012 this. For this particular stripchart, the top of the chart always represents
37013 100%, and the scale is given as &"x10%"&. This chart is configured by setting
37014 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
37015 &_Local/eximon.conf_& file.
37020 .section "Main action buttons" "SECID266"
37021 .cindex "size" "of monitor window"
37022 .cindex "Exim monitor" "window size"
37023 .cindex "window size"
37024 Below the stripcharts there is an action button for quitting the monitor. Next
37025 to this is another button marked &"Size"&. They are placed here so that
37026 shrinking the window to its default minimum size leaves just the queue count
37027 stripchart and these two buttons visible. Pressing the &"Size"& button causes
37028 the window to expand to its maximum size, unless it is already at the maximum,
37029 in which case it is reduced to its minimum.
37031 When expanding to the maximum, if the window cannot be fully seen where it
37032 currently is, it is moved back to where it was the last time it was at full
37033 size. When it is expanding from its minimum size, the old position is
37034 remembered, and next time it is reduced to the minimum it is moved back there.
37036 The idea is that you can keep a reduced window just showing one or two
37037 stripcharts at a convenient place on your screen, easily expand it to show
37038 the full window when required, and just as easily put it back to what it was.
37039 The idea is copied from what the &'twm'& window manager does for its
37040 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
37041 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
37043 Normally, the monitor starts up with the window at its full size, but it can be
37044 built so that it starts up with the window at its smallest size, by setting
37045 START_SMALL=yes in &_Local/eximon.conf_&.
37049 .section "The log display" "SECID267"
37050 .cindex "log" "tail of; in monitor"
37051 The second section of the window is an area in which a display of the tail of
37052 the main log is maintained.
37053 To save space on the screen, the timestamp on each log line is shortened by
37054 removing the date and, if &%log_timezone%& is set, the timezone.
37055 The log tail is not available when the only destination for logging data is
37056 syslog, unless the syslog lines are routed to a local file whose name is passed
37057 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
37059 The log sub-window has a scroll bar at its lefthand side which can be used to
37060 move back to look at earlier text, and the up and down arrow keys also have a
37061 scrolling effect. The amount of log that is kept depends on the setting of
37062 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
37063 to use. When this is full, the earlier 50% of data is discarded &-- this is
37064 much more efficient than throwing it away line by line. The sub-window also has
37065 a horizontal scroll bar for accessing the ends of long log lines. This is the
37066 only means of horizontal scrolling; the right and left arrow keys are not
37067 available. Text can be cut from this part of the window using the mouse in the
37068 normal way. The size of this subwindow is controlled by parameters in the
37069 configuration file &_Local/eximon.conf_&.
37071 Searches of the text in the log window can be carried out by means of the ^R
37072 and ^S keystrokes, which default to a reverse and a forward search,
37073 respectively. The search covers only the text that is displayed in the window.
37074 It cannot go further back up the log.
37076 The point from which the search starts is indicated by a caret marker. This is
37077 normally at the end of the text in the window, but can be positioned explicitly
37078 by pointing and clicking with the left mouse button, and is moved automatically
37079 by a successful search. If new text arrives in the window when it is scrolled
37080 back, the caret remains where it is, but if the window is not scrolled back,
37081 the caret is moved to the end of the new text.
37083 Pressing ^R or ^S pops up a window into which the search text can be typed.
37084 There are buttons for selecting forward or reverse searching, for carrying out
37085 the search, and for cancelling. If the &"Search"& button is pressed, the search
37086 happens and the window remains so that further searches can be done. If the
37087 &"Return"& key is pressed, a single search is done and the window is closed. If
37088 ^C is typed the search is cancelled.
37090 The searching facility is implemented using the facilities of the Athena text
37091 widget. By default this pops up a window containing both &"search"& and
37092 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
37093 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
37094 However, the linkers in BSDI and HP-UX seem unable to handle an externally
37095 provided version of &%TextPop%& when the remaining parts of the text widget
37096 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
37097 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
37098 on these systems, at the expense of having unwanted items in the search popup
37103 .section "The queue display" "SECID268"
37104 .cindex "queue" "display in monitor"
37105 The bottom section of the monitor window contains a list of all messages that
37106 are on the queue, which includes those currently being received or delivered,
37107 as well as those awaiting delivery. The size of this subwindow is controlled by
37108 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
37109 at which it is updated is controlled by another parameter in the same file &--
37110 the default is 5 minutes, since queue scans can be quite expensive. However,
37111 there is an &"Update"& action button just above the display which can be used
37112 to force an update of the queue display at any time.
37114 When a host is down for some time, a lot of pending mail can build up for it,
37115 and this can make it hard to deal with other messages on the queue. To help
37116 with this situation there is a button next to &"Update"& called &"Hide"&. If
37117 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
37118 type anything in here and press &"Return"&, the text is added to a chain of
37119 such texts, and if every undelivered address in a message matches at least one
37120 of the texts, the message is not displayed.
37122 If there is an address that does not match any of the texts, all the addresses
37123 are displayed as normal. The matching happens on the ends of addresses so, for
37124 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
37125 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
37126 has been set up, a button called &"Unhide"& is displayed. If pressed, it
37127 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
37128 a hide request is automatically cancelled after one hour.
37130 While the dialogue box is displayed, you can't press any buttons or do anything
37131 else to the monitor window. For this reason, if you want to cut text from the
37132 queue display to use in the dialogue box, you have to do the cutting before
37133 pressing the &"Hide"& button.
37135 The queue display contains, for each unhidden queued message, the length of
37136 time it has been on the queue, the size of the message, the message id, the
37137 message sender, and the first undelivered recipient, all on one line. If it is
37138 a bounce message, the sender is shown as &"<>"&. If there is more than one
37139 recipient to which the message has not yet been delivered, subsequent ones are
37140 listed on additional lines, up to a maximum configured number, following which
37141 an ellipsis is displayed. Recipients that have already received the message are
37144 .cindex "frozen messages" "display"
37145 If a message is frozen, an asterisk is displayed at the left-hand side.
37147 The queue display has a vertical scroll bar, and can also be scrolled by means
37148 of the arrow keys. Text can be cut from it using the mouse in the normal way.
37149 The text searching facilities, as described above for the log window, are also
37150 available, but the caret is always moved to the end of the text when the queue
37151 display is updated.
37155 .section "The queue menu" "SECID269"
37156 .cindex "queue" "menu in monitor"
37157 If the &%shift%& key is held down and the left button is clicked when the mouse
37158 pointer is over the text for any message, an action menu pops up, and the first
37159 line of the queue display for the message is highlighted. This does not affect
37162 If you want to use some other event for popping up the menu, you can set the
37163 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
37164 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
37165 value set in this parameter is a standard X event description. For example, to
37166 run eximon using &%ctrl%& rather than &%shift%& you could use
37168 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
37170 The title of the menu is the message id, and it contains entries which act as
37174 &'message log'&: The contents of the message log for the message are displayed
37175 in a new text window.
37177 &'headers'&: Information from the spool file that contains the envelope
37178 information and headers is displayed in a new text window. See chapter
37179 &<<CHAPspool>>& for a description of the format of spool files.
37181 &'body'&: The contents of the spool file containing the body of the message are
37182 displayed in a new text window. There is a default limit of 20,000 bytes to the
37183 amount of data displayed. This can be changed by setting the BODY_MAX
37184 option at compile time, or the EXIMON_BODY_MAX option at run time.
37186 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
37187 delivery of the message. This causes an automatic thaw if the message is
37188 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
37189 a new text window. The delivery is run in a separate process, to avoid holding
37190 up the monitor while the delivery proceeds.
37192 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
37193 that the message be frozen.
37195 .cindex "thawing messages"
37196 .cindex "unfreezing messages"
37197 .cindex "frozen messages" "thawing"
37198 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
37199 that the message be thawed.
37201 .cindex "delivery" "forcing failure"
37202 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
37203 that Exim gives up trying to deliver the message. A bounce message is generated
37204 for any remaining undelivered addresses.
37206 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
37207 that the message be deleted from the system without generating a bounce
37210 &'add recipient'&: A dialog box is displayed into which a recipient address can
37211 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
37212 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
37213 Otherwise it must be entered as a fully qualified address. Pressing RETURN
37214 causes a call to Exim to be made using the &%-Mar%& option to request that an
37215 additional recipient be added to the message, unless the entry box is empty, in
37216 which case no action is taken.
37218 &'mark delivered'&: A dialog box is displayed into which a recipient address
37219 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
37220 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
37221 Otherwise it must be entered as a fully qualified address. Pressing RETURN
37222 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
37223 recipient address as already delivered, unless the entry box is empty, in which
37224 case no action is taken.
37226 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
37227 mark all recipient addresses as already delivered.
37229 &'edit sender'&: A dialog box is displayed initialized with the current
37230 sender's address. Pressing RETURN causes a call to Exim to be made using the
37231 &%-Mes%& option to replace the sender address, unless the entry box is empty,
37232 in which case no action is taken. If you want to set an empty sender (as in
37233 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
37234 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
37235 the address is qualified with that domain.
37238 When a delivery is forced, a window showing the &%-v%& output is displayed. In
37239 other cases when a call to Exim is made, if there is any output from Exim (in
37240 particular, if the command fails) a window containing the command and the
37241 output is displayed. Otherwise, the results of the action are normally apparent
37242 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
37243 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
37244 if no output is generated.
37246 The queue display is automatically updated for actions such as freezing and
37247 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
37248 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
37249 force an update of the display after one of these actions.
37251 In any text window that is displayed as result of a menu action, the normal
37252 cut-and-paste facility is available, and searching can be carried out using ^R
37253 and ^S, as described above for the log tail window.
37260 . ////////////////////////////////////////////////////////////////////////////
37261 . ////////////////////////////////////////////////////////////////////////////
37263 .chapter "Security considerations" "CHAPsecurity"
37264 .scindex IIDsecurcon "security" "discussion of"
37265 This chapter discusses a number of issues concerned with security, some of
37266 which are also covered in other parts of this manual.
37268 For reasons that this author does not understand, some people have promoted
37269 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
37270 existence of this chapter in the documentation. However, the intent of the
37271 chapter is simply to describe the way Exim works in relation to certain
37272 security concerns, not to make any specific claims about the effectiveness of
37273 its security as compared with other MTAs.
37275 What follows is a description of the way Exim is supposed to be. Best efforts
37276 have been made to try to ensure that the code agrees with the theory, but an
37277 absence of bugs can never be guaranteed. Any that are reported will get fixed
37278 as soon as possible.
37281 .section "Building a more &""hardened""& Exim" "SECID286"
37282 .cindex "security" "build-time features"
37283 There are a number of build-time options that can be set in &_Local/Makefile_&
37284 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
37285 Exim administrator who does not have the root password, or by someone who has
37286 penetrated the Exim (but not the root) account. These options are as follows:
37289 ALT_CONFIG_PREFIX can be set to a string that is required to match the
37290 start of any file names used with the &%-C%& option. When it is set, these file
37291 names are also not allowed to contain the sequence &"/../"&. (However, if the
37292 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
37293 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
37294 default setting for &%ALT_CONFIG_PREFIX%&.
37296 If the permitted configuration files are confined to a directory to
37297 which only root has access, this guards against someone who has broken
37298 into the Exim account from running a privileged Exim with an arbitrary
37299 configuration file, and using it to break into other accounts.
37302 If a non-trusted configuration file (i.e. not the default configuration file
37303 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
37304 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
37305 the next item), then root privilege is retained only if the caller of Exim is
37306 root. This locks out the possibility of testing a configuration using &%-C%&
37307 right through message reception and delivery, even if the caller is root. The
37308 reception works, but by that time, Exim is running as the Exim user, so when
37309 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
37310 privilege to be lost. However, root can test reception and delivery using two
37314 The WHITELIST_D_MACROS build option declares some macros to be safe to override
37315 with &%-D%& if the real uid is one of root, the Exim run-time user or the
37316 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
37317 requiring the run-time value supplied to &%-D%& to match a regex that errs on
37318 the restrictive side. Requiring build-time selection of safe macros is onerous
37319 but this option is intended solely as a transition mechanism to permit
37320 previously-working configurations to continue to work after release 4.73.
37322 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
37325 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
37326 never to be used for any deliveries. This is like the &%never_users%& runtime
37327 option, but it cannot be overridden; the runtime option adds additional users
37328 to the list. The default setting is &"root"&; this prevents a non-root user who
37329 is permitted to modify the runtime file from using Exim as a way to get root.
37334 .section "Root privilege" "SECID270"
37336 .cindex "root privilege"
37337 The Exim binary is normally setuid to root, which means that it gains root
37338 privilege (runs as root) when it starts execution. In some special cases (for
37339 example, when the daemon is not in use and there are no local deliveries), it
37340 may be possible to run Exim setuid to some user other than root. This is
37341 discussed in the next section. However, in most installations, root privilege
37342 is required for two things:
37345 To set up a socket connected to the standard SMTP port (25) when initialising
37346 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
37349 To be able to change uid and gid in order to read users' &_.forward_& files and
37350 perform local deliveries as the receiving user or as specified in the
37354 It is not necessary to be root to do any of the other things Exim does, such as
37355 receiving messages and delivering them externally over SMTP, and it is
37356 obviously more secure if Exim does not run as root except when necessary.
37357 For this reason, a user and group for Exim to use must be defined in
37358 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
37359 group"&. Their values can be changed by the run time configuration, though this
37360 is not recommended. Often a user called &'exim'& is used, but some sites use
37361 &'mail'& or another user name altogether.
37363 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
37364 abdication; the process cannot regain root afterwards. Prior to release 4.00,
37365 &[seteuid()]& was used in some circumstances, but this is no longer the case.
37367 After a new Exim process has interpreted its command line options, it changes
37368 uid and gid in the following cases:
37373 If the &%-C%& option is used to specify an alternate configuration file, or if
37374 the &%-D%& option is used to define macro values for the configuration, and the
37375 calling process is not running as root, the uid and gid are changed to those of
37376 the calling process.
37377 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
37378 option may not be used at all.
37379 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
37380 can be supplied if the calling process is running as root, the Exim run-time
37381 user or CONFIGURE_OWNER, if defined.
37386 If the expansion test option (&%-be%&) or one of the filter testing options
37387 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
37390 If the process is not a daemon process or a queue runner process or a delivery
37391 process or a process for testing address routing (started with &%-bt%&), the
37392 uid and gid are changed to the Exim user and group. This means that Exim always
37393 runs under its own uid and gid when receiving messages. This also applies when
37394 testing address verification
37397 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
37400 For a daemon, queue runner, delivery, or address testing process, the uid
37401 remains as root at this stage, but the gid is changed to the Exim group.
37404 The processes that initially retain root privilege behave as follows:
37407 A daemon process changes the gid to the Exim group and the uid to the Exim
37408 user after setting up one or more listening sockets. The &[initgroups()]&
37409 function is called, so that if the Exim user is in any additional groups, they
37410 will be used during message reception.
37412 A queue runner process retains root privilege throughout its execution. Its
37413 job is to fork a controlled sequence of delivery processes.
37415 A delivery process retains root privilege throughout most of its execution,
37416 but any actual deliveries (that is, the transports themselves) are run in
37417 subprocesses which always change to a non-root uid and gid. For local
37418 deliveries this is typically the uid and gid of the owner of the mailbox; for
37419 remote deliveries, the Exim uid and gid are used. Once all the delivery
37420 subprocesses have been run, a delivery process changes to the Exim uid and gid
37421 while doing post-delivery tidying up such as updating the retry database and
37422 generating bounce and warning messages.
37424 While the recipient addresses in a message are being routed, the delivery
37425 process runs as root. However, if a user's filter file has to be processed,
37426 this is done in a subprocess that runs under the individual user's uid and
37427 gid. A system filter is run as root unless &%system_filter_user%& is set.
37429 A process that is testing addresses (the &%-bt%& option) runs as root so that
37430 the routing is done in the same environment as a message delivery.
37436 .section "Running Exim without privilege" "SECTrunexiwitpri"
37437 .cindex "privilege, running without"
37438 .cindex "unprivileged running"
37439 .cindex "root privilege" "running without"
37440 Some installations like to run Exim in an unprivileged state for more of its
37441 operation, for added security. Support for this mode of operation is provided
37442 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
37443 gid are changed to the Exim user and group at the start of a delivery process
37444 (and also queue runner and address testing processes). This means that address
37445 routing is no longer run as root, and the deliveries themselves cannot change
37449 .cindex "daemon" "restarting"
37450 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
37451 that the daemon can still be started in the usual way, and it can respond
37452 correctly to SIGHUP because the re-invocation regains root privilege.
37454 An alternative approach is to make Exim setuid to the Exim user and also setgid
37455 to the Exim group. If you do this, the daemon must be started from a root
37456 process. (Calling Exim from a root process makes it behave in the way it does
37457 when it is setuid root.) However, the daemon cannot restart itself after a
37458 SIGHUP signal because it cannot regain privilege.
37460 It is still useful to set &%deliver_drop_privilege%& in this case, because it
37461 stops Exim from trying to re-invoke itself to do a delivery after a message has
37462 been received. Such a re-invocation is a waste of resources because it has no
37465 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
37466 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
37467 to the Exim user seems a clean approach, but there is one complication:
37469 In this style of operation, Exim is running with the real uid and gid set to
37470 those of the calling process, and the effective uid/gid set to Exim's values.
37471 Ideally, any association with the calling process' uid/gid should be dropped,
37472 that is, the real uid/gid should be reset to the effective values so as to
37473 discard any privileges that the caller may have. While some operating systems
37474 have a function that permits this action for a non-root effective uid, quite a
37475 number of them do not. Because of this lack of standardization, Exim does not
37476 address this problem at this time.
37478 For this reason, the recommended approach for &"mostly unprivileged"& running
37479 is to keep the Exim binary setuid to root, and to set
37480 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
37481 be used in the most straightforward way.
37483 If you configure Exim not to run delivery processes as root, there are a
37484 number of restrictions on what you can do:
37487 You can deliver only as the Exim user/group. You should explicitly use the
37488 &%user%& and &%group%& options to override routers or local transports that
37489 normally deliver as the recipient. This makes sure that configurations that
37490 work in this mode function the same way in normal mode. Any implicit or
37491 explicit specification of another user causes an error.
37493 Use of &_.forward_& files is severely restricted, such that it is usually
37494 not worthwhile to include them in the configuration.
37496 Users who wish to use &_.forward_& would have to make their home directory and
37497 the file itself accessible to the Exim user. Pipe and append-to-file entries,
37498 and their equivalents in Exim filters, cannot be used. While they could be
37499 enabled in the Exim user's name, that would be insecure and not very useful.
37501 Unless the local user mailboxes are all owned by the Exim user (possible in
37502 some POP3 or IMAP-only environments):
37505 They must be owned by the Exim group and be writeable by that group. This
37506 implies you must set &%mode%& in the appendfile configuration, as well as the
37507 mode of the mailbox files themselves.
37509 You must set &%no_check_owner%&, since most or all of the files will not be
37510 owned by the Exim user.
37512 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
37513 on a newly created mailbox when unprivileged. This also implies that new
37514 mailboxes need to be created manually.
37519 These restrictions severely restrict what can be done in local deliveries.
37520 However, there are no restrictions on remote deliveries. If you are running a
37521 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
37522 gives more security at essentially no cost.
37524 If you are using the &%mua_wrapper%& facility (see chapter
37525 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
37530 .section "Delivering to local files" "SECID271"
37531 Full details of the checks applied by &(appendfile)& before it writes to a file
37532 are given in chapter &<<CHAPappendfile>>&.
37536 .section "Running local commands" "SECTsecconslocalcmds"
37537 .cindex "security" "local commands"
37538 .cindex "security" "command injection attacks"
37539 There are a number of ways in which an administrator can configure Exim to run
37540 commands based upon received, untrustworthy, data. Further, in some
37541 configurations a user who can control a &_.forward_& file can also arrange to
37542 run commands. Configuration to check includes, but is not limited to:
37545 Use of &%use_shell%& in the pipe transport: various forms of shell command
37546 injection may be possible with this option present. It is dangerous and should
37547 be used only with considerable caution. Consider constraints which whitelist
37548 allowed characters in a variable which is to be used in a pipe transport that
37549 has &%use_shell%& enabled.
37551 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
37552 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
37553 &_.forward_& files in a redirect router. If Exim is running on a central mail
37554 hub to which ordinary users do not have shell access, but home directories are
37555 NFS mounted (for instance) then administrators should review the list of these
37556 forbid options available, and should bear in mind that the options that may
37557 need forbidding can change as new features are added between releases.
37559 The &%${run...}%& expansion item does not use a shell by default, but
37560 administrators can configure use of &_/bin/sh_& as part of the command.
37561 Such invocations should be viewed with prejudicial suspicion.
37563 Administrators who use embedded Perl are advised to explore how Perl's
37564 taint checking might apply to their usage.
37566 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
37567 administrators are well advised to view its use with suspicion, in case (for
37568 instance) it allows a local-part to contain embedded Exim directives.
37570 Use of &%${match_local_part...}%& and friends becomes more dangerous if
37571 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
37572 each can reference arbitrary lists and files, rather than just being a list
37574 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
37575 real-world security vulnerabilities caused by its use with untrustworthy data
37576 injected in, for SQL injection attacks.
37577 Consider the use of the &%inlisti%& expansion condition instead.
37583 .section "Trust in configuration data" "SECTsecconfdata"
37584 .cindex "security" "data sources"
37585 .cindex "security" "regular expressions"
37586 .cindex "regular expressions" "security"
37587 .cindex "PCRE" "security"
37588 If configuration data for Exim can come from untrustworthy sources, there
37589 are some issues to be aware of:
37592 Use of &%${expand...}%& may provide a path for shell injection attacks.
37594 Letting untrusted data provide a regular expression is unwise.
37596 Using &%${match...}%& to apply a fixed regular expression against untrusted
37597 data may result in pathological behaviour within PCRE. Be aware of what
37598 "backtracking" means and consider options for being more strict with a regular
37599 expression. Avenues to explore include limiting what can match (avoiding &`.`&
37600 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
37601 possessive quantifiers or just not using regular expressions against untrusted
37604 It can be important to correctly use &%${quote:...}%&,
37605 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
37606 items to ensure that data is correctly constructed.
37608 Some lookups might return multiple results, even though normal usage is only
37609 expected to yield one result.
37615 .section "IPv4 source routing" "SECID272"
37616 .cindex "source routing" "in IP packets"
37617 .cindex "IP source routing"
37618 Many operating systems suppress IP source-routed packets in the kernel, but
37619 some cannot be made to do this, so Exim does its own check. It logs incoming
37620 IPv4 source-routed TCP calls, and then drops them. Things are all different in
37621 IPv6. No special checking is currently done.
37625 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
37626 Support for these SMTP commands is disabled by default. If required, they can
37627 be enabled by defining suitable ACLs.
37632 .section "Privileged users" "SECID274"
37633 .cindex "trusted users"
37634 .cindex "admin user"
37635 .cindex "privileged user"
37636 .cindex "user" "trusted"
37637 .cindex "user" "admin"
37638 Exim recognizes two sets of users with special privileges. Trusted users are
37639 able to submit new messages to Exim locally, but supply their own sender
37640 addresses and information about a sending host. For other users submitting
37641 local messages, Exim sets up the sender address from the uid, and doesn't
37642 permit a remote host to be specified.
37645 However, an untrusted user is permitted to use the &%-f%& command line option
37646 in the special form &%-f <>%& to indicate that a delivery failure for the
37647 message should not cause an error report. This affects the message's envelope,
37648 but it does not affect the &'Sender:'& header. Untrusted users may also be
37649 permitted to use specific forms of address with the &%-f%& option by setting
37650 the &%untrusted_set_sender%& option.
37652 Trusted users are used to run processes that receive mail messages from some
37653 other mail domain and pass them on to Exim for delivery either locally, or over
37654 the Internet. Exim trusts a caller that is running as root, as the Exim user,
37655 as any user listed in the &%trusted_users%& configuration option, or under any
37656 group listed in the &%trusted_groups%& option.
37658 Admin users are permitted to do things to the messages on Exim's queue. They
37659 can freeze or thaw messages, cause them to be returned to their senders, remove
37660 them entirely, or modify them in various ways. In addition, admin users can run
37661 the Exim monitor and see all the information it is capable of providing, which
37662 includes the contents of files on the spool.
37666 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
37667 delivery of messages on its queue is restricted to admin users. This
37668 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
37669 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
37670 queue is also restricted to admin users. This restriction can be relaxed by
37671 setting &%no_queue_list_requires_admin%&.
37673 Exim recognizes an admin user if the calling process is running as root or as
37674 the Exim user or if any of the groups associated with the calling process is
37675 the Exim group. It is not necessary actually to be running under the Exim
37676 group. However, if admin users who are not root or the Exim user are to access
37677 the contents of files on the spool via the Exim monitor (which runs
37678 unprivileged), Exim must be built to allow group read access to its spool
37683 .section "Spool files" "SECID275"
37684 .cindex "spool directory" "files"
37685 Exim's spool directory and everything it contains is owned by the Exim user and
37686 set to the Exim group. The mode for spool files is defined in the
37687 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
37688 any user who is a member of the Exim group can access these files.
37692 .section "Use of argv[0]" "SECID276"
37693 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
37694 of specific strings, Exim assumes certain options. For example, calling Exim
37695 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
37696 to calling it with the option &%-bS%&. There are no security implications in
37701 .section "Use of %f formatting" "SECID277"
37702 The only use made of &"%f"& by Exim is in formatting load average values. These
37703 are actually stored in integer variables as 1000 times the load average.
37704 Consequently, their range is limited and so therefore is the length of the
37709 .section "Embedded Exim path" "SECID278"
37710 Exim uses its own path name, which is embedded in the code, only when it needs
37711 to re-exec in order to regain root privilege. Therefore, it is not root when it
37712 does so. If some bug allowed the path to get overwritten, it would lead to an
37713 arbitrary program's being run as exim, not as root.
37717 .section "Dynamic module directory" "SECTdynmoddir"
37718 Any dynamically loadable modules must be installed into the directory
37719 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
37723 .section "Use of sprintf()" "SECID279"
37724 .cindex "&[sprintf()]&"
37725 A large number of occurrences of &"sprintf"& in the code are actually calls to
37726 &'string_sprintf()'&, a function that returns the result in malloc'd store.
37727 The intermediate formatting is done into a large fixed buffer by a function
37728 that runs through the format string itself, and checks the length of each
37729 conversion before performing it, thus preventing buffer overruns.
37731 The remaining uses of &[sprintf()]& happen in controlled circumstances where
37732 the output buffer is known to be sufficiently long to contain the converted
37737 .section "Use of debug_printf() and log_write()" "SECID280"
37738 Arbitrary strings are passed to both these functions, but they do their
37739 formatting by calling the function &'string_vformat()'&, which runs through
37740 the format string itself, and checks the length of each conversion.
37744 .section "Use of strcat() and strcpy()" "SECID281"
37745 These are used only in cases where the output buffer is known to be large
37746 enough to hold the result.
37747 .ecindex IIDsecurcon
37752 . ////////////////////////////////////////////////////////////////////////////
37753 . ////////////////////////////////////////////////////////////////////////////
37755 .chapter "Format of spool files" "CHAPspool"
37756 .scindex IIDforspo1 "format" "spool files"
37757 .scindex IIDforspo2 "spool directory" "format of files"
37758 .scindex IIDforspo3 "spool files" "format of"
37759 .cindex "spool files" "editing"
37760 A message on Exim's queue consists of two files, whose names are the message id
37761 followed by -D and -H, respectively. The data portion of the message is kept in
37762 the -D file on its own. The message's envelope, status, and headers are all
37763 kept in the -H file, whose format is described in this chapter. Each of these
37764 two files contains the final component of its own name as its first line. This
37765 is insurance against disk crashes where the directory is lost but the files
37766 themselves are recoverable.
37768 Some people are tempted into editing -D files in order to modify messages. You
37769 need to be extremely careful if you do this; it is not recommended and you are
37770 on your own if you do it. Here are some of the pitfalls:
37773 You must ensure that Exim does not try to deliver the message while you are
37774 fiddling with it. The safest way is to take out a write lock on the -D file,
37775 which is what Exim itself does, using &[fcntl()]&. If you update the file in
37776 place, the lock will be retained. If you write a new file and rename it, the
37777 lock will be lost at the instant of rename.
37779 .vindex "&$body_linecount$&"
37780 If you change the number of lines in the file, the value of
37781 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
37782 present, this value is not used by Exim, but there is no guarantee that this
37783 will always be the case.
37785 If the message is in MIME format, you must take care not to break it.
37787 If the message is cryptographically signed, any change will invalidate the
37790 All in all, modifying -D files is fraught with danger.
37792 Files whose names end with -J may also be seen in the &_input_& directory (or
37793 its subdirectories when &%split_spool_directory%& is set). These are journal
37794 files, used to record addresses to which the message has been delivered during
37795 the course of a delivery attempt. If there are still undelivered recipients at
37796 the end, the -H file is updated, and the -J file is deleted. If, however, there
37797 is some kind of crash (for example, a power outage) before this happens, the -J
37798 file remains in existence. When Exim next processes the message, it notices the
37799 -J file and uses it to update the -H file before starting the next delivery
37802 .section "Format of the -H file" "SECID282"
37803 .cindex "uid (user id)" "in spool file"
37804 .cindex "gid (group id)" "in spool file"
37805 The second line of the -H file contains the login name for the uid of the
37806 process that called Exim to read the message, followed by the numerical uid and
37807 gid. For a locally generated message, this is normally the user who sent the
37808 message. For a message received over TCP/IP via the daemon, it is
37809 normally the Exim user.
37811 The third line of the file contains the address of the message's sender as
37812 transmitted in the envelope, contained in angle brackets. The sender address is
37813 empty for bounce messages. For incoming SMTP mail, the sender address is given
37814 in the MAIL command. For locally generated mail, the sender address is
37815 created by Exim from the login name of the current user and the configured
37816 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
37817 leading &"From&~"& line if the caller is trusted, or if the supplied address is
37818 &"<>"& or an address that matches &%untrusted_set_senders%&.
37820 The fourth line contains two numbers. The first is the time that the message
37821 was received, in the conventional Unix form &-- the number of seconds since the
37822 start of the epoch. The second number is a count of the number of messages
37823 warning of delayed delivery that have been sent to the sender.
37825 There follow a number of lines starting with a hyphen. These can appear in any
37826 order, and are omitted when not relevant:
37829 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
37830 This item is obsolete, and is not generated from Exim release 4.61 onwards;
37831 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
37832 recognized, to provide backward compatibility. In the old format, a line of
37833 this form is present for every ACL variable that is not empty. The number
37834 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
37835 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
37836 the data string for the variable. The string itself starts at the beginning of
37837 the next line, and is followed by a newline character. It may contain internal
37840 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
37841 A line of this form is present for every ACL connection variable that is
37842 defined. Note that there is a space between &%-aclc%& and the rest of the name.
37843 The length is the length of the data string for the variable. The string itself
37844 starts at the beginning of the next line, and is followed by a newline
37845 character. It may contain internal newlines.
37847 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
37848 A line of this form is present for every ACL message variable that is defined.
37849 Note that there is a space between &%-aclm%& and the rest of the name. The
37850 length is the length of the data string for the variable. The string itself
37851 starts at the beginning of the next line, and is followed by a newline
37852 character. It may contain internal newlines.
37854 .vitem "&%-active_hostname%&&~<&'hostname'&>"
37855 This is present if, when the message was received over SMTP, the value of
37856 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
37858 .vitem &%-allow_unqualified_recipient%&
37859 This is present if unqualified recipient addresses are permitted in header
37860 lines (to stop such addresses from being qualified if rewriting occurs at
37861 transport time). Local messages that were input using &%-bnq%& and remote
37862 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
37864 .vitem &%-allow_unqualified_sender%&
37865 This is present if unqualified sender addresses are permitted in header lines
37866 (to stop such addresses from being qualified if rewriting occurs at transport
37867 time). Local messages that were input using &%-bnq%& and remote messages from
37868 hosts that match &%sender_unqualified_hosts%& set this flag.
37870 .vitem "&%-auth_id%&&~<&'text'&>"
37871 The id information for a message received on an authenticated SMTP connection
37872 &-- the value of the &$authenticated_id$& variable.
37874 .vitem "&%-auth_sender%&&~<&'address'&>"
37875 The address of an authenticated sender &-- the value of the
37876 &$authenticated_sender$& variable.
37878 .vitem "&%-body_linecount%&&~<&'number'&>"
37879 This records the number of lines in the body of the message, and is always
37882 .vitem "&%-body_zerocount%&&~<&'number'&>"
37883 This records the number of binary zero bytes in the body of the message, and is
37884 present if the number is greater than zero.
37886 .vitem &%-deliver_firsttime%&
37887 This is written when a new message is first added to the spool. When the spool
37888 file is updated after a deferral, it is omitted.
37890 .vitem "&%-frozen%&&~<&'time'&>"
37891 .cindex "frozen messages" "spool data"
37892 The message is frozen, and the freezing happened at <&'time'&>.
37894 .vitem "&%-helo_name%&&~<&'text'&>"
37895 This records the host name as specified by a remote host in a HELO or EHLO
37898 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
37899 This records the IP address of the host from which the message was received and
37900 the remote port number that was used. It is omitted for locally generated
37903 .vitem "&%-host_auth%&&~<&'text'&>"
37904 If the message was received on an authenticated SMTP connection, this records
37905 the name of the authenticator &-- the value of the
37906 &$sender_host_authenticated$& variable.
37908 .vitem &%-host_lookup_failed%&
37909 This is present if an attempt to look up the sending host's name from its IP
37910 address failed. It corresponds to the &$host_lookup_failed$& variable.
37912 .vitem "&%-host_name%&&~<&'text'&>"
37913 .cindex "reverse DNS lookup"
37914 .cindex "DNS" "reverse lookup"
37915 This records the name of the remote host from which the message was received,
37916 if the host name was looked up from the IP address when the message was being
37917 received. It is not present if no reverse lookup was done.
37919 .vitem "&%-ident%&&~<&'text'&>"
37920 For locally submitted messages, this records the login of the originating user,
37921 unless it was a trusted user and the &%-oMt%& option was used to specify an
37922 ident value. For messages received over TCP/IP, this records the ident string
37923 supplied by the remote host, if any.
37925 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
37926 This records the IP address of the local interface and the port number through
37927 which a message was received from a remote host. It is omitted for locally
37928 generated messages.
37931 The message is from a local sender.
37933 .vitem &%-localerror%&
37934 The message is a locally-generated bounce message.
37936 .vitem "&%-local_scan%&&~<&'string'&>"
37937 This records the data string that was returned by the &[local_scan()]& function
37938 when the message was received &-- the value of the &$local_scan_data$&
37939 variable. It is omitted if no data was returned.
37941 .vitem &%-manual_thaw%&
37942 The message was frozen but has been thawed manually, that is, by an explicit
37943 Exim command rather than via the auto-thaw process.
37946 A testing delivery process was started using the &%-N%& option to suppress any
37947 actual deliveries, but delivery was deferred. At any further delivery attempts,
37950 .vitem &%-received_protocol%&
37951 This records the value of the &$received_protocol$& variable, which contains
37952 the name of the protocol by which the message was received.
37954 .vitem &%-sender_set_untrusted%&
37955 The envelope sender of this message was set by an untrusted local caller (used
37956 to ensure that the caller is displayed in queue listings).
37958 .vitem "&%-spam_score_int%&&~<&'number'&>"
37959 If a message was scanned by SpamAssassin, this is present. It records the value
37960 of &$spam_score_int$&.
37962 .vitem &%-tls_certificate_verified%&
37963 A TLS certificate was received from the client that sent this message, and the
37964 certificate was verified by the server.
37966 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
37967 When the message was received over an encrypted connection, this records the
37968 name of the cipher suite that was used.
37970 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
37971 When the message was received over an encrypted connection, and a certificate
37972 was received from the client, this records the Distinguished Name from that
37976 Following the options there is a list of those addresses to which the message
37977 is not to be delivered. This set of addresses is initialized from the command
37978 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
37979 is set; otherwise it starts out empty. Whenever a successful delivery is made,
37980 the address is added to this set. The addresses are kept internally as a
37981 balanced binary tree, and it is a representation of that tree which is written
37982 to the spool file. If an address is expanded via an alias or forward file, the
37983 original address is added to the tree when deliveries to all its child
37984 addresses are complete.
37986 If the tree is empty, there is a single line in the spool file containing just
37987 the text &"XX"&. Otherwise, each line consists of two letters, which are either
37988 Y or N, followed by an address. The address is the value for the node of the
37989 tree, and the letters indicate whether the node has a left branch and/or a
37990 right branch attached to it, respectively. If branches exist, they immediately
37991 follow. Here is an example of a three-node tree:
37993 YY darcy@austen.fict.example
37994 NN alice@wonderland.fict.example
37995 NN editor@thesaurus.ref.example
37997 After the non-recipients tree, there is a list of the message's recipients.
37998 This is a simple list, preceded by a count. It includes all the original
37999 recipients of the message, including those to whom the message has already been
38000 delivered. In the simplest case, the list contains one address per line. For
38004 editor@thesaurus.ref.example
38005 darcy@austen.fict.example
38007 alice@wonderland.fict.example
38009 However, when a child address has been added to the top-level addresses as a
38010 result of the use of the &%one_time%& option on a &(redirect)& router, each
38011 line is of the following form:
38013 <&'top-level address'&> <&'errors_to address'&> &&&
38014 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
38016 The 01 flag bit indicates the presence of the three other fields that follow
38017 the top-level address. Other bits may be used in future to support additional
38018 fields. The <&'parent number'&> is the offset in the recipients list of the
38019 original parent of the &"one time"& address. The first two fields are the
38020 envelope sender that is associated with this address and its length. If the
38021 length is zero, there is no special envelope sender (there are then two space
38022 characters in the line). A non-empty field can arise from a &(redirect)& router
38023 that has an &%errors_to%& setting.
38026 A blank line separates the envelope and status information from the headers
38027 which follow. A header may occupy several lines of the file, and to save effort
38028 when reading it in, each header is preceded by a number and an identifying
38029 character. The number is the number of characters in the header, including any
38030 embedded newlines and the terminating newline. The character is one of the
38034 .row <&'blank'&> "header in which Exim has no special interest"
38035 .row &`B`& "&'Bcc:'& header"
38036 .row &`C`& "&'Cc:'& header"
38037 .row &`F`& "&'From:'& header"
38038 .row &`I`& "&'Message-id:'& header"
38039 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
38040 .row &`R`& "&'Reply-To:'& header"
38041 .row &`S`& "&'Sender:'& header"
38042 .row &`T`& "&'To:'& header"
38043 .row &`*`& "replaced or deleted header"
38046 Deleted or replaced (rewritten) headers remain in the spool file for debugging
38047 purposes. They are not transmitted when the message is delivered. Here is a
38048 typical set of headers:
38050 111P Received: by hobbit.fict.example with local (Exim 4.00)
38051 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
38052 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
38053 038* X-rewrote-sender: bb@hobbit.fict.example
38054 042* From: Bilbo Baggins <bb@hobbit.fict.example>
38055 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
38056 099* To: alice@wonderland.fict.example, rdo@foundation,
38057 darcy@austen.fict.example, editor@thesaurus.ref.example
38058 104T To: alice@wonderland.fict.example, rdo@foundation.example,
38059 darcy@austen.fict.example, editor@thesaurus.ref.example
38060 038 Date: Fri, 11 May 2001 10:28:59 +0100
38062 The asterisked headers indicate that the envelope sender, &'From:'& header, and
38063 &'To:'& header have been rewritten, the last one because routing expanded the
38064 unqualified domain &'foundation'&.
38065 .ecindex IIDforspo1
38066 .ecindex IIDforspo2
38067 .ecindex IIDforspo3
38069 . ////////////////////////////////////////////////////////////////////////////
38070 . ////////////////////////////////////////////////////////////////////////////
38072 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
38076 DKIM is a mechanism by which messages sent by some entity can be provably
38077 linked to a domain which that entity controls. It permits reputation to
38078 be tracked on a per-domain basis, rather than merely upon source IP address.
38079 DKIM is documented in RFC 4871.
38081 DKIM support is compiled into Exim by default if TLS support is present.
38082 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
38084 Exim's DKIM implementation allows to
38086 Sign outgoing messages: This function is implemented in the SMTP transport.
38087 It can co-exist with all other Exim features
38088 (including transport filters)
38089 except cutthrough delivery.
38091 Verify signatures in incoming messages: This is implemented by an additional
38092 ACL (acl_smtp_dkim), which can be called several times per message, with
38093 different signature contexts.
38096 In typical Exim style, the verification implementation does not include any
38097 default "policy". Instead it enables you to build your own policy using
38098 Exim's standard controls.
38100 Please note that verification of DKIM signatures in incoming mail is turned
38101 on by default for logging purposes. For each signature in incoming email,
38102 exim will log a line displaying the most important signature details, and the
38103 signature status. Here is an example (with line-breaks added for clarity):
38105 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
38106 d=facebookmail.com s=q1-2009b
38107 c=relaxed/relaxed a=rsa-sha1
38108 i=@facebookmail.com t=1252484542 [verification succeeded]
38110 You might want to turn off DKIM verification processing entirely for internal
38111 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
38112 control modifier. This should typically be done in the RCPT ACL, at points
38113 where you accept mail from relay sources (internal hosts or authenticated
38117 .section "Signing outgoing messages" "SECDKIMSIGN"
38118 .cindex "DKIM" "signing"
38120 Signing is enabled by setting private options on the SMTP transport.
38121 These options take (expandable) strings as arguments.
38123 .option dkim_domain smtp string&!! unset
38125 The domain you want to sign with. The result of this expanded
38126 option is put into the &%$dkim_domain%& expansion variable.
38128 .option dkim_selector smtp string&!! unset
38130 This sets the key selector string. You can use the &%$dkim_domain%& expansion
38131 variable to look up a matching selector. The result is put in the expansion
38132 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
38133 option along with &%$dkim_domain%&.
38135 .option dkim_private_key smtp string&!! unset
38137 This sets the private key to use. You can use the &%$dkim_domain%& and
38138 &%$dkim_selector%& expansion variables to determine the private key to use.
38139 The result can either
38141 be a valid RSA private key in ASCII armor, including line breaks.
38143 start with a slash, in which case it is treated as a file that contains
38146 be "0", "false" or the empty string, in which case the message will not
38147 be signed. This case will not result in an error, even if &%dkim_strict%&
38151 .option dkim_canon smtp string&!! unset
38153 This option sets the canonicalization method used when signing a message.
38154 The DKIM RFC currently supports two methods: "simple" and "relaxed".
38155 The option defaults to "relaxed" when unset. Note: the current implementation
38156 only supports using the same canonicalization method for both headers and body.
38158 .option dkim_strict smtp string&!! unset
38160 This option defines how Exim behaves when signing a message that
38161 should be signed fails for some reason. When the expansion evaluates to
38162 either "1" or "true", Exim will defer. Otherwise Exim will send the message
38163 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
38166 .option dkim_sign_headers smtp string&!! unset
38168 When set, this option must expand to (or be specified as) a colon-separated
38169 list of header names. Headers with these names will be included in the message
38170 signature. When unspecified, the header names recommended in RFC4871 will be
38174 .section "Verifying DKIM signatures in incoming mail" "SECID514"
38175 .cindex "DKIM" "verification"
38177 Verification of DKIM signatures in SMTP incoming email is implemented via the
38178 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
38179 syntactically(!) correct signature in the incoming message.
38180 A missing ACL definition defaults to accept.
38181 If any ACL call does not accept, the message is not accepted.
38182 If a cutthrough delivery was in progress for the message it is
38183 summarily dropped (having wasted the transmission effort).
38185 To evaluate the signature in the ACL a large number of expansion variables
38186 containing the signature status and its details are set up during the
38187 runtime of the ACL.
38189 Calling the ACL only for existing signatures is not sufficient to build
38190 more advanced policies. For that reason, the global option
38191 &%dkim_verify_signers%&, and a global expansion variable
38192 &%$dkim_signers%& exist.
38194 The global option &%dkim_verify_signers%& can be set to a colon-separated
38195 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
38196 called. It is expanded when the message has been received. At this point,
38197 the expansion variable &%$dkim_signers%& already contains a colon-separated
38198 list of signer domains and identities for the message. When
38199 &%dkim_verify_signers%& is not specified in the main configuration,
38202 dkim_verify_signers = $dkim_signers
38204 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
38205 DKIM signature in the message. Current DKIM verifiers may want to explicitly
38206 call the ACL for known domains or identities. This would be achieved as follows:
38208 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
38210 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
38211 and "ebay.com", plus all domains and identities that have signatures in the message.
38212 You can also be more creative in constructing your policy. For example:
38214 dkim_verify_signers = $sender_address_domain:$dkim_signers
38217 If a domain or identity is listed several times in the (expanded) value of
38218 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
38221 Inside the &%acl_smtp_dkim%&, the following expansion variables are
38222 available (from most to least important):
38226 .vitem &%$dkim_cur_signer%&
38227 The signer that is being evaluated in this ACL run. This can be a domain or
38228 an identity. This is one of the list items from the expanded main option
38229 &%dkim_verify_signers%& (see above).
38230 .vitem &%$dkim_verify_status%&
38231 A string describing the general status of the signature. One of
38233 &%none%&: There is no signature in the message for the current domain or
38234 identity (as reflected by &%$dkim_cur_signer%&).
38236 &%invalid%&: The signature could not be verified due to a processing error.
38237 More detail is available in &%$dkim_verify_reason%&.
38239 &%fail%&: Verification of the signature failed. More detail is
38240 available in &%$dkim_verify_reason%&.
38242 &%pass%&: The signature passed verification. It is valid.
38244 .vitem &%$dkim_verify_reason%&
38245 A string giving a little bit more detail when &%$dkim_verify_status%& is either
38246 "fail" or "invalid". One of
38248 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
38249 key for the domain could not be retrieved. This may be a temporary problem.
38251 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
38252 record for the domain is syntactically invalid.
38254 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
38255 body hash does not match the one specified in the signature header. This
38256 means that the message body was modified in transit.
38258 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
38259 could not be verified. This may mean that headers were modified,
38260 re-written or otherwise changed in a way which is incompatible with
38261 DKIM verification. It may of course also mean that the signature is forged.
38263 .vitem &%$dkim_domain%&
38264 The signing domain. IMPORTANT: This variable is only populated if there is
38265 an actual signature in the message for the current domain or identity (as
38266 reflected by &%$dkim_cur_signer%&).
38267 .vitem &%$dkim_identity%&
38268 The signing identity, if present. IMPORTANT: This variable is only populated
38269 if there is an actual signature in the message for the current domain or
38270 identity (as reflected by &%$dkim_cur_signer%&).
38271 .vitem &%$dkim_selector%&
38272 The key record selector string.
38273 .vitem &%$dkim_algo%&
38274 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
38275 .vitem &%$dkim_canon_body%&
38276 The body canonicalization method. One of 'relaxed' or 'simple'.
38277 .vitem &%dkim_canon_headers%&
38278 The header canonicalization method. One of 'relaxed' or 'simple'.
38279 .vitem &%$dkim_copiedheaders%&
38280 A transcript of headers and their values which are included in the signature
38281 (copied from the 'z=' tag of the signature).
38282 .vitem &%$dkim_bodylength%&
38283 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
38284 limit was set by the signer, "9999999999999" is returned. This makes sure
38285 that this variable always expands to an integer value.
38286 .vitem &%$dkim_created%&
38287 UNIX timestamp reflecting the date and time when the signature was created.
38288 When this was not specified by the signer, "0" is returned.
38289 .vitem &%$dkim_expires%&
38290 UNIX timestamp reflecting the date and time when the signer wants the
38291 signature to be treated as "expired". When this was not specified by the
38292 signer, "9999999999999" is returned. This makes it possible to do useful
38293 integer size comparisons against this value.
38294 .vitem &%$dkim_headernames%&
38295 A colon-separated list of names of headers included in the signature.
38296 .vitem &%$dkim_key_testing%&
38297 "1" if the key record has the "testing" flag set, "0" if not.
38298 .vitem &%$dkim_key_nosubdomains%&
38299 "1" if the key record forbids subdomaining, "0" otherwise.
38300 .vitem &%$dkim_key_srvtype%&
38301 Service type (tag s=) from the key record. Defaults to "*" if not specified
38303 .vitem &%$dkim_key_granularity%&
38304 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
38306 .vitem &%$dkim_key_notes%&
38307 Notes from the key record (tag n=).
38308 .vitem &%$dkim_key_length%&
38309 Number of bits in the key.
38312 In addition, two ACL conditions are provided:
38315 .vitem &%dkim_signers%&
38316 ACL condition that checks a colon-separated list of domains or identities
38317 for a match against the domain or identity that the ACL is currently verifying
38318 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
38319 verb to a group of domains or identities. For example:
38322 # Warn when Mail purportedly from GMail has no signature at all
38323 warn log_message = GMail sender without DKIM signature
38324 sender_domains = gmail.com
38325 dkim_signers = gmail.com
38329 .vitem &%dkim_status%&
38330 ACL condition that checks a colon-separated list of possible DKIM verification
38331 results against the actual result of verification. This is typically used
38332 to restrict an ACL verb to a list of verification outcomes, for example:
38335 deny message = Mail from Paypal with invalid/missing signature
38336 sender_domains = paypal.com:paypal.de
38337 dkim_signers = paypal.com:paypal.de
38338 dkim_status = none:invalid:fail
38341 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
38342 see the documentation of the &%$dkim_verify_status%& expansion variable above
38343 for more information of what they mean.
38346 . ////////////////////////////////////////////////////////////////////////////
38347 . ////////////////////////////////////////////////////////////////////////////
38349 .chapter "Proxies" "CHAPproxies" &&&
38351 .cindex "proxy support"
38352 .cindex "proxy" "access via"
38354 A proxy is an intermediate system through which communication is passed.
38355 Proxies may provide a security, availability or load-distribution function.
38358 .section "Inbound proxies" SECTproxyInbound
38359 .cindex proxy inbound
38360 .cindex proxy "server side"
38361 .cindex proxy "Proxy protocol"
38362 .cindex "Proxy protocol" proxy
38364 Exim has support for receiving inbound SMTP connections via a proxy
38365 that uses &"Proxy Protocol"& to speak to it.
38366 To include this support, include &"SUPPORT_PROXY=yes"&
38369 It was built on specifications from:
38370 http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt
38371 That URL was revised in May 2014 to version 2 spec:
38372 http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e
38374 The purpose of this facility is so that an application load balancer,
38375 such as HAProxy, can sit in front of several Exim servers
38376 to distribute load.
38377 Exim uses the local protocol communication with the proxy to obtain
38378 the remote SMTP system IP address and port information.
38379 There is no logging if a host passes or
38380 fails Proxy Protocol negotiation, but it can easily be determined and
38381 recorded in an ACL (example is below).
38383 Use of a proxy is enabled by setting the &%hosts_proxy%&
38384 main configuration option to a hostlist; connections from these
38385 hosts will use Proxy Protocol.
38388 The following expansion variables are usable
38389 (&"internal"& and &"external"& here refer to the interfaces
38392 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
38393 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
38394 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
38395 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
38396 &'proxy_session '& boolean: SMTP connection via proxy
38398 If &$proxy_session$& is set but &$proxy_external_address$& is empty
38399 there was a protocol error.
38402 Since the real connections are all coming from the proxy, and the
38403 per host connection tracking is done before Proxy Protocol is
38404 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
38405 handle all of the parallel volume you expect per inbound proxy.
38406 With the option set so high, you lose the ability
38407 to protect your server from many connections from one IP.
38408 In order to prevent your server from overload, you
38409 need to add a per connection ratelimit to your connect ACL.
38410 A possible solution is:
38412 # Set max number of connections per host
38414 # Or do some kind of IP lookup in a flat file or database
38415 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
38417 defer message = Too many connections from this IP right now
38418 ratelimit = LIMIT / 5s / per_conn / strict
38423 .section "Outbound proxies" SECTproxySOCKS
38424 .cindex proxy outbound
38425 .cindex proxy "client side"
38426 .cindex proxy SOCKS
38427 .cindex SOCKS proxy
38428 Exim has support for sending outbound SMTP via a proxy
38429 using a protocol called SOCKS5 (defined by RFC1928).
38430 The support can be optionally included by defining SUPPORT_SOCKS=yes in
38433 Use of a proxy is enabled by setting the &%socks_proxy%& option
38434 on an smtp transport.
38435 The option value is expanded and should then be a list
38436 (colon-separated by default) of proxy specifiers.
38437 Each proxy specifier is a list
38438 (space-separated by default) where the initial element
38439 is an IP address and any subsequent elements are options.
38441 Options are a string <name>=<value>.
38442 The list of options is in the following table:
38444 &'auth '& authentication method
38445 &'name '& authentication username
38446 &'pass '& authentication password
38448 &'tmo '& connection timeout
38450 &'weight '& selection bias
38453 More details on each of these options follows:
38456 .cindex authentication "to proxy"
38457 .cindex proxy authentication
38458 &%auth%&: Either &"none"& (default) or &"name"&.
38459 Using &"name"& selects username/password authentication per RFC 1929
38460 for access to the proxy.
38461 Default is &"none"&.
38463 &%name%&: sets the username for the &"name"& authentication method.
38466 &%pass%&: sets the password for the &"name"& authentication method.
38469 &%port%&: the TCP port number to use for the connection to the proxy.
38472 &%tmo%&: sets a connection timeout in seconds for this proxy.
38475 &%pri%&: specifies a priority for the proxy within the list,
38476 higher values being tried first.
38477 The default priority is 1.
38479 &%weight%&: specifies a selection bias.
38480 Within a priority set servers are queried in a random fashion,
38481 weighted by this value.
38482 The default value for selection bias is 1.
38485 Proxies from the list are tried according to their priority
38486 and weight settings until one responds. The timeout for the
38487 overall connection applies to the set of proxied attempts.
38489 .section Logging SECTproxyLog
38490 To log the (local) IP of a proxy in the incoming or delivery logline,
38491 add &"+proxy"& to the &%log_selector%& option.
38492 This will add a component tagged with &"PRX="& to the line.
38494 . ////////////////////////////////////////////////////////////////////////////
38495 . ////////////////////////////////////////////////////////////////////////////
38497 .chapter "Internationalisation" "CHAPi18n" &&&
38498 "Internationalisation""
38499 .cindex internationalisation "email address"
38502 .cindex UTF-8 "mail name handling"
38504 Exim has support for Internationalised mail names.
38505 To include this it must be built with SUPPORT_I18N and the libidn library.
38506 Standards supported are RFCs 2060, 5890, 6530 and 6533.
38508 .section "MTA operations" SECTi18nMTA
38509 .cindex SMTPUTF8 "ESMTP option"
38510 The main configuration option &%smtputf8_advertise_hosts%& specifies
38511 a host list. If this matches the sending host and
38512 accept_8bitmime is true (the default) then the ESMTP option
38513 SMTPUTF8 will be advertised.
38515 If the sender specifies the SMTPUTF8 option on a MAIL command
38516 international handling for the message is enabled and
38517 the expansion variable &$message_smtputf8$& will have value TRUE.
38519 The option &%allow_utf8_domains%& is set to true for this
38520 message. All DNS lookups are converted to a-label form
38521 whatever the setting of &%allow_utf8_domains%&
38522 when Exim is built with SUPPORT_I18N.
38524 Both localparts and domain are maintained as the original
38525 UTF-8 form internally; any comparison or regular-expression use will
38526 require appropriate care. Filenames created, eg. by
38527 the appendfile transport, will have UTF-8 names.
38529 HELO names sent by the smtp transport will have any UTF-8
38530 components expanded to a-label form,
38531 and any certificate name checks will be done using the a-label
38534 .cindex log protocol
38535 .cindex SMTPUTF8 logging
38536 Log lines and Received-by: header lines will acquire a "utf8"
38537 prefix on the protocol element, eg. utf8esmtp.
38539 The following expansion operators can be used:
38541 ${utf8_domain_to_alabel:str}
38542 ${utf8_domain_from_alabel:str}
38543 ${utf8_localpart_to_alabel:str}
38544 ${utf8_localpart_from_alabel:str}
38547 ACLs may use the following modifier:
38549 control = utf8_downconvert
38550 control = utf8_downconvert/<value>
38552 This sets a flag requiring that addresses are converted to
38553 a-label form before smtp delivery, for use in a
38554 Message Submission Agent context.
38555 If a value is appended it may be:
38557 &`1 `& (default) mandatory downconversion
38558 &`0 `& no downconversion
38559 &`-1 `& if SMTPUTF8 not supported by destination host
38562 If mua_wrapper is set, the utf8_downconvert control
38563 is initially set to -1.
38566 There is no explicit support for VRFY and EXPN.
38567 Configurations supporting these should inspect
38568 &$smtp_command_argument$& for an SMTPUTF8 argument.
38570 There is no support for LMTP on Unix sockets.
38571 Using the "lmtp" protocol option on an smtp transport,
38572 for LMTP over TCP, should work as expected.
38574 There is no support for DSN unitext handling,
38575 and no provision for converting logging from or to UTF-8.
38579 .section "MDA operations" SECTi18nMDA
38580 To aid in constructing names suitable for IMAP folders
38581 the following expansion operator can be used:
38583 ${imapfolder {<string>} {<sep>} {<specials>}}
38586 The string is converted from the charset specified by
38587 the "headers charset" command (in a filter file)
38588 or &%headers_charset%& main configuration option (otherwise),
38590 modified UTF-7 encoding specified by RFC 2060,
38591 with the following exception: All occurences of <sep>
38592 (which has to be a single character)
38593 are replaced with periods ("."), and all periods and slashes that are not
38594 <sep> and are not in the <specials> string are BASE64 encoded.
38596 The third argument can be omitted, defaulting to an empty string.
38597 The second argument can be omitted, defaulting to "/".
38599 This is the encoding used by Courier for Maildir names on disk, and followed
38600 by many other IMAP servers.
38604 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
38605 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
38606 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
38609 Note that the source charset setting is vital, and also that characters
38610 must be representable in UTF-16.
38613 . ////////////////////////////////////////////////////////////////////////////
38614 . ////////////////////////////////////////////////////////////////////////////
38616 .chapter "Events" "CHAPevents" &&&
38620 The events mechanism in Exim can be used to intercept processing at a number
38621 of points. It was originally invented to giave a way to do customised logging
38622 actions (for example, to a database) but can also be used to modify some
38623 processing actions.
38625 Most installations will never need to use Events.
38626 The support can be left out of a build by defining DISABLE_EVENT=yes
38627 in &_Local/Makefile_&.
38629 There are two major classes of events: main and transport.
38630 The main configuration option &%event_action%& controls reception events;
38631 a transport option &%event_action%& controls delivery events.
38633 Both options are a string which is expanded when the event fires.
38634 An example might look like:
38635 .cindex logging custom
38637 event_action = ${if eq {msg:delivery}{$event_name} \
38638 {${lookup pgsql {SELECT * FROM record_Delivery( \
38639 '${quote_pgsql:$sender_address_domain}',\
38640 '${quote_pgsql:${lc:$sender_address_local_part}}', \
38641 '${quote_pgsql:$domain}', \
38642 '${quote_pgsql:${lc:$local_part}}', \
38643 '${quote_pgsql:$host_address}', \
38644 '${quote_pgsql:${lc:$host}}', \
38645 '${quote_pgsql:$message_exim_id}')}} \
38649 Events have names which correspond to the point in process at which they fire.
38650 The name is placed in the variable &$event_name$& and the event action
38651 expansion must check this, as it will be called for every possible event type.
38653 The current list of events is:
38655 &`msg:complete after main `& per message
38656 &`msg:delivery after transport `& per recipient
38657 &`msg:rcpt:host:defer after transport `& per recipient per host
38658 &`msg:rcpt:defer after transport `& per recipient
38659 &`msg:host:defer after transport `& per attempt
38660 &`msg:fail:delivery after main `& per recipient
38661 &`msg:fail:internal after main `& per recipient
38662 &`tcp:connect before transport `& per connection
38663 &`tcp:close after transport `& per connection
38664 &`tls:cert before both `& per certificate in verification chain
38665 &`smtp:connect after transport `& per connection
38667 New event types may be added in future.
38669 The event name is a colon-separated list, defining the type of
38670 event in a tree of possibilities. It may be used as a list
38671 or just matched on as a whole. There will be no spaces in the name.
38673 The second column in the table above describes whether the event fires
38674 before or after the action is associates with. Those which fire before
38675 can be used to affect that action (more on this below).
38677 An additional variable, &$event_data$&, is filled with information varying
38678 with the event type:
38680 &`msg:delivery `& smtp confirmation mssage
38681 &`msg:rcpt:host:defer `& error string
38682 &`msg:rcpt:defer `& error string
38683 &`msg:host:defer `& error string
38684 &`tls:cert `& verification chain depth
38685 &`smtp:connect `& smtp banner
38688 The :defer events populate one extra variable: &$event_defer_errno$&.
38690 For complex operations an ACL expansion can be used in &%event_action%&
38691 however due to the multiple contextx that Exim operates in during
38692 the course of its processing:
38694 variables set in transport events will not be visible outside that
38697 acl_m variables in a server context are lost on a new connection,
38698 and after smtp helo/ehlo/mail/starttls/rset commands
38700 Using an ACL expansion with the logwrite modifier can be
38701 a useful way of writing to the main log.
38703 The expansion of the event_action option should normally
38704 return an empty string. Should it return anything else the
38705 following will be forced:
38707 &`msg:delivery `& (ignored)
38708 &`msg:host:defer `& (ignored)
38709 &`msg:fail:delivery`& (ignored)
38710 &`tcp:connect `& do not connect
38711 &`tcp:close `& (ignored)
38712 &`tls:cert `& refuse verification
38713 &`smtp:connect `& close connection
38715 No other use is made of the result string.
38717 For a tcp:connect event, if the connection is being made to a proxy
38718 then the address and port variables will be that of the proxy and not
38721 For tls:cert events, if GnuTLS is in use this will trigger only per
38722 chain element received on the connection.
38723 For OpenSSL it will trigger for every chain element including those
38726 . ////////////////////////////////////////////////////////////////////////////
38727 . ////////////////////////////////////////////////////////////////////////////
38729 .chapter "Adding new drivers or lookup types" "CHID13" &&&
38730 "Adding drivers or lookups"
38731 .cindex "adding drivers"
38732 .cindex "new drivers, adding"
38733 .cindex "drivers" "adding new"
38734 The following actions have to be taken in order to add a new router, transport,
38735 authenticator, or lookup type to Exim:
38738 Choose a name for the driver or lookup type that does not conflict with any
38739 existing name; I will use &"newdriver"& in what follows.
38741 Add to &_src/EDITME_& the line:
38743 <&'type'&>&`_NEWDRIVER=yes`&
38745 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
38746 code is not to be included in the binary by default, comment this line out. You
38747 should also add any relevant comments about the driver or lookup type.
38749 Add to &_src/config.h.defaults_& the line:
38751 #define <type>_NEWDRIVER
38754 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
38755 and create a table entry as is done for all the other drivers and lookup types.
38757 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
38758 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
38759 Add your &`NEWDRIVER`& to that list.
38760 As long as the dynamic module would be named &_newdriver.so_&, you can use the
38761 simple form that most lookups have.
38763 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
38764 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
38765 driver or lookup type and add it to the definition of OBJ.
38767 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
38770 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
38771 as for other drivers and lookups.
38774 Then all you need to do is write the code! A good way to start is to make a
38775 proforma by copying an existing module of the same type, globally changing all
38776 occurrences of the name, and cutting out most of the code. Note that any
38777 options you create must be listed in alphabetical order, because the tables are
38778 searched using a binary chop procedure.
38780 There is a &_README_& file in each of the sub-directories of &_src_& describing
38781 the interface that is expected.
38786 . ////////////////////////////////////////////////////////////////////////////
38787 . ////////////////////////////////////////////////////////////////////////////
38789 . /////////////////////////////////////////////////////////////////////////////
38790 . These lines are processing instructions for the Simple DocBook Processor that
38791 . Philip Hazel has developed as a less cumbersome way of making PostScript and
38792 . PDFs than using xmlto and fop. They will be ignored by all other XML
38794 . /////////////////////////////////////////////////////////////////////////////
38799 foot_right_recto="&chaptertitle;"
38800 foot_right_verso="&chaptertitle;"
38804 .makeindex "Options index" "option"
38805 .makeindex "Variables index" "variable"
38806 .makeindex "Concept index" "concept"
38809 . /////////////////////////////////////////////////////////////////////////////
38810 . /////////////////////////////////////////////////////////////////////////////