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 "4.86"
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$&) are available, but no
2791 message-specific values (such as &$sender_domain$&) are set, because no message
2792 is being processed (but see &%-bem%& and &%-Mset%&).
2794 &*Note*&: If you use this mechanism to test lookups, and you change the data
2795 files or databases you are using, you must exit and restart Exim before trying
2796 the same lookup again. Otherwise, because each Exim process caches the results
2797 of lookups, you will just get the same result as before.
2799 .vitem &%-bem%&&~<&'filename'&>
2801 .cindex "testing" "string expansion"
2802 .cindex "expansion" "testing"
2803 This option operates like &%-be%& except that it must be followed by the name
2804 of a file. For example:
2806 exim -bem /tmp/testmessage
2808 The file is read as a message (as if receiving a locally-submitted non-SMTP
2809 message) before any of the test expansions are done. Thus, message-specific
2810 variables such as &$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,
3053 using the malware scanning framework. The option of &%av_scanner%& influences
3054 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3055 the expansion should have defaults which apply to this invocation. ACLs are
3056 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3057 will never be populated and &%-bmalware%& will fail.
3059 Exim will have changed working directory before resolving the filename, so
3060 using fully qualified pathnames is advisable. Exim will be running as the Exim
3061 user when it tries to open the file, rather than as the invoking user.
3062 This option requires admin privileges.
3064 The &%-bmalware%& option will not be extended to be more generally useful,
3065 there are better tools for file-scanning. This option exists to help
3066 administrators verify their Exim and AV scanner configuration.
3070 .cindex "address qualification, suppressing"
3071 By default, Exim automatically qualifies unqualified addresses (those
3072 without domains) that appear in messages that are submitted locally (that
3073 is, not over TCP/IP). This qualification applies both to addresses in
3074 envelopes, and addresses in header lines. Sender addresses are qualified using
3075 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3076 defaults to the value of &%qualify_domain%&).
3078 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3079 being used to re-submit messages that originally came from remote hosts after
3080 content scanning, you probably do not want to qualify unqualified addresses in
3081 header lines. (Such lines will be present only if you have not enabled a header
3082 syntax check in the appropriate ACL.)
3084 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3085 messages that originate on the local host. When this is used, unqualified
3086 addresses in the envelope provoke errors (causing message rejection) and
3087 unqualified addresses in header lines are left alone.
3092 .cindex "configuration options" "extracting"
3093 .cindex "options" "configuration &-- extracting"
3094 If this option is given with no arguments, it causes the values of all Exim's
3095 main configuration options to be written to the standard output. The values
3096 of one or more specific options can be requested by giving their names as
3097 arguments, for example:
3099 exim -bP qualify_domain hold_domains
3101 .cindex "hiding configuration option values"
3102 .cindex "configuration options" "hiding value of"
3103 .cindex "options" "hiding value of"
3104 However, any option setting that is preceded by the word &"hide"& in the
3105 configuration file is not shown in full, except to an admin user. For other
3106 users, the output is as in this example:
3108 mysql_servers = <value not displayable>
3110 If &%config%& is given as an argument, the config is
3111 output, as it was parsed, any include file resolved, any comment removed.
3113 If &%config_file%& is given as an argument, the name of the run time
3114 configuration file is output. (&%configure_file%& works too, for
3115 backward compatibility.)
3116 If a list of configuration files was supplied, the value that is output here
3117 is the name of the file that was actually used.
3119 .cindex "options" "hiding name of"
3120 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3121 name will not be output.
3123 .cindex "daemon" "process id (pid)"
3124 .cindex "pid (process id)" "of daemon"
3125 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3126 directories where log files and daemon pid files are written are output,
3127 respectively. If these values are unset, log files are written in a
3128 sub-directory of the spool directory called &%log%&, and the pid file is
3129 written directly into the spool directory.
3131 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3133 exim -bP +local_domains
3135 it searches for a matching named list of any type (domain, host, address, or
3136 local part) and outputs what it finds.
3138 .cindex "options" "router &-- extracting"
3139 .cindex "options" "transport &-- extracting"
3140 .cindex "options" "authenticator &-- extracting"
3141 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3142 followed by the name of an appropriate driver instance, the option settings for
3143 that driver are output. For example:
3145 exim -bP transport local_delivery
3147 The generic driver options are output first, followed by the driver's private
3148 options. A list of the names of drivers of a particular type can be obtained by
3149 using one of the words &%router_list%&, &%transport_list%&, or
3150 &%authenticator_list%&, and a complete list of all drivers with their option
3151 settings can be obtained by using &%routers%&, &%transports%&, or
3154 .cindex "options" "macro &-- extracting"
3155 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3156 are available, similarly to the drivers. Because macros are sometimes used
3157 for storing passwords, this option is restricted.
3158 The output format is one item per line.
3162 .cindex "queue" "listing messages on"
3163 .cindex "listing" "messages on the queue"
3164 This option requests a listing of the contents of the mail queue on the
3165 standard output. If the &%-bp%& option is followed by a list of message ids,
3166 just those messages are listed. By default, this option can be used only by an
3167 admin user. However, the &%queue_list_requires_admin%& option can be set false
3168 to allow any user to see the queue.
3170 Each message on the queue is displayed as in the following example:
3172 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3173 red.king@looking-glass.fict.example
3176 .cindex "message" "size in queue listing"
3177 .cindex "size" "of message"
3178 The first line contains the length of time the message has been on the queue
3179 (in this case 25 minutes), the size of the message (2.9K), the unique local
3180 identifier for the message, and the message sender, as contained in the
3181 envelope. For bounce messages, the sender address is empty, and appears as
3182 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3183 the default sender address, the user's login name is shown in parentheses
3184 before the sender address.
3186 .cindex "frozen messages" "in queue listing"
3187 If the message is frozen (attempts to deliver it are suspended) then the text
3188 &"*** frozen ***"& is displayed at the end of this line.
3190 The recipients of the message (taken from the envelope, not the headers) are
3191 displayed on subsequent lines. Those addresses to which the message has already
3192 been delivered are marked with the letter D. If an original address gets
3193 expanded into several addresses via an alias or forward file, the original is
3194 displayed with a D only when deliveries for all of its child addresses are
3200 This option operates like &%-bp%&, but in addition it shows delivered addresses
3201 that were generated from the original top level address(es) in each message by
3202 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3208 .cindex "queue" "count of messages on"
3209 This option counts the number of messages on the queue, and writes the total
3210 to the standard output. It is restricted to admin users, unless
3211 &%queue_list_requires_admin%& is set false.
3216 This option operates like &%-bp%&, but the output is not sorted into
3217 chronological order of message arrival. This can speed it up when there are
3218 lots of messages on the queue, and is particularly useful if the output is
3219 going to be post-processed in a way that doesn't need the sorting.
3223 This option is a combination of &%-bpr%& and &%-bpa%&.
3227 This option is a combination of &%-bpr%& and &%-bpu%&.
3232 This option operates like &%-bp%& but shows only undelivered top-level
3233 addresses for each message displayed. Addresses generated by aliasing or
3234 forwarding are not shown, unless the message was deferred after processing by a
3235 router with the &%one_time%& option set.
3240 .cindex "testing" "retry configuration"
3241 .cindex "retry" "configuration testing"
3242 This option is for testing retry rules, and it must be followed by up to three
3243 arguments. It causes Exim to look for a retry rule that matches the values
3244 and to write it to the standard output. For example:
3246 exim -brt bach.comp.mus.example
3247 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3249 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3250 argument, which is required, can be a complete address in the form
3251 &'local_part@domain'&, or it can be just a domain name. If the second argument
3252 contains a dot, it is interpreted as an optional second domain name; if no
3253 retry rule is found for the first argument, the second is tried. This ties in
3254 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3255 rule is found that matches the host, one that matches the mail domain is
3256 sought. Finally, an argument that is the name of a specific delivery error, as
3257 used in setting up retry rules, can be given. For example:
3259 exim -brt haydn.comp.mus.example quota_3d
3260 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3265 .cindex "testing" "rewriting"
3266 .cindex "rewriting" "testing"
3267 This option is for testing address rewriting rules, and it must be followed by
3268 a single argument, consisting of either a local part without a domain, or a
3269 complete address with a fully qualified domain. Exim outputs how this address
3270 would be rewritten for each possible place it might appear. See chapter
3271 &<<CHAPrewrite>>& for further details.
3275 .cindex "SMTP" "batched incoming"
3276 .cindex "batched SMTP input"
3277 This option is used for batched SMTP input, which is an alternative interface
3278 for non-interactive local message submission. A number of messages can be
3279 submitted in a single run. However, despite its name, this is not really SMTP
3280 input. Exim reads each message's envelope from SMTP commands on the standard
3281 input, but generates no responses. If the caller is trusted, or
3282 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3283 believed; otherwise the sender is always the caller of Exim.
3285 The message itself is read from the standard input, in SMTP format (leading
3286 dots doubled), terminated by a line containing just a single dot. An error is
3287 provoked if the terminating dot is missing. A further message may then follow.
3289 As for other local message submissions, the contents of incoming batch SMTP
3290 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3291 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3292 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3294 Some other SMTP commands are recognized in the input. HELO and EHLO act
3295 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3296 QUIT quits, ignoring the rest of the standard input.
3298 .cindex "return code" "for &%-bS%&"
3299 If any error is encountered, reports are written to the standard output and
3300 error streams, and Exim gives up immediately. The return code is 0 if no error
3301 was detected; it is 1 if one or more messages were accepted before the error
3302 was detected; otherwise it is 2.
3304 More details of input using batched SMTP are given in section
3305 &<<SECTincomingbatchedSMTP>>&.
3309 .cindex "SMTP" "local input"
3310 .cindex "local SMTP input"
3311 This option causes Exim to accept one or more messages by reading SMTP commands
3312 on the standard input, and producing SMTP replies on the standard output. SMTP
3313 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3314 Some user agents use this interface as a way of passing locally-generated
3315 messages to the MTA.
3318 .cindex "sender" "source of"
3319 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3320 set, the senders of messages are taken from the SMTP MAIL commands.
3321 Otherwise the content of these commands is ignored and the sender is set up as
3322 the calling user. Unqualified addresses are automatically qualified using
3323 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3324 &%-bnq%& option is used.
3328 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3329 using a listening daemon. Exim can distinguish the two cases by checking
3330 whether the standard input is a TCP/IP socket. When Exim is called from
3331 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3332 above concerning senders and qualification do not apply. In this situation,
3333 Exim behaves in exactly the same way as it does when receiving a message via
3334 the listening daemon.
3338 .cindex "testing" "addresses"
3339 .cindex "address" "testing"
3340 This option runs Exim in address testing mode, in which each argument is taken
3341 as a recipient address to be tested for deliverability. The results are
3342 written to the standard output. If a test fails, and the caller is not an admin
3343 user, no details of the failure are output, because these might contain
3344 sensitive information such as usernames and passwords for database lookups.
3346 If no arguments are given, Exim runs in an interactive manner, prompting with a
3347 right angle bracket for addresses to be tested.
3349 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3350 &[readline()]& function, because it is running as &'root'& and there are
3353 Each address is handled as if it were the recipient address of a message
3354 (compare the &%-bv%& option). It is passed to the routers and the result is
3355 written to the standard output. However, any router that has
3356 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3357 genuine routing tests if your first router passes everything to a scanner
3360 .cindex "return code" "for &%-bt%&"
3361 The return code is 2 if any address failed outright; it is 1 if no address
3362 failed outright but at least one could not be resolved for some reason. Return
3363 code 0 is given only when all addresses succeed.
3365 .cindex "duplicate addresses"
3366 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3367 addresses after routing is complete, so that only one delivery takes place.
3368 This does not happen when testing with &%-bt%&; the full results of routing are
3371 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3372 routers in the configuration makes any tests on the sender address of a
3374 .oindex "&%-f%&" "for address testing"
3375 you can use the &%-f%& option to set an appropriate sender when running
3376 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3377 default qualifying domain. However, if you have set up (for example) routers
3378 whose behaviour depends on the contents of an incoming message, you cannot test
3379 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3384 .cindex "version number of Exim"
3385 This option causes Exim to write the current version number, compilation
3386 number, and compilation date of the &'exim'& binary to the standard output.
3387 It also lists the DBM library that is being used, the optional modules (such as
3388 specific lookup types), the drivers that are included in the binary, and the
3389 name of the run time configuration file that is in use.
3391 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3392 configuration file. However, this is a static check only. It cannot check
3393 values that are to be expanded. For example, although a misspelt ACL verb is
3394 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3395 alone to discover (for example) all the typos in the configuration; some
3396 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3397 dynamic testing facilities.
3401 .cindex "verifying address" "using &%-bv%&"
3402 .cindex "address" "verification"
3403 This option runs Exim in address verification mode, in which each argument is
3404 taken as a recipient address to be verified by the routers. (This does
3405 not involve any verification callouts). During normal operation, verification
3406 happens mostly as a consequence processing a &%verify%& condition in an ACL
3407 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3408 including callouts, see the &%-bh%& and &%-bhc%& options.
3410 If verification fails, and the caller is not an admin user, no details of the
3411 failure are output, because these might contain sensitive information such as
3412 usernames and passwords for database lookups.
3414 If no arguments are given, Exim runs in an interactive manner, prompting with a
3415 right angle bracket for addresses to be verified.
3417 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3418 &[readline()]& function, because it is running as &'exim'& and there are
3421 Verification differs from address testing (the &%-bt%& option) in that routers
3422 that have &%no_verify%& set are skipped, and if the address is accepted by a
3423 router that has &%fail_verify%& set, verification fails. The address is
3424 verified as a recipient if &%-bv%& is used; to test verification for a sender
3425 address, &%-bvs%& should be used.
3427 If the &%-v%& option is not set, the output consists of a single line for each
3428 address, stating whether it was verified or not, and giving a reason in the
3429 latter case. Without &%-v%&, generating more than one address by redirection
3430 causes verification to end successfully, without considering the generated
3431 addresses. However, if just one address is generated, processing continues,
3432 and the generated address must verify successfully for the overall verification
3435 When &%-v%& is set, more details are given of how the address has been handled,
3436 and in the case of address redirection, all the generated addresses are also
3437 considered. Verification may succeed for some and fail for others.
3440 .cindex "return code" "for &%-bv%&"
3441 return code is 2 if any address failed outright; it is 1 if no address
3442 failed outright but at least one could not be resolved for some reason. Return
3443 code 0 is given only when all addresses succeed.
3445 If any of the routers in the configuration makes any tests on the sender
3446 address of a message, you should use the &%-f%& option to set an appropriate
3447 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3448 calling user at the default qualifying domain.
3452 This option acts like &%-bv%&, but verifies the address as a sender rather
3453 than a recipient address. This affects any rewriting and qualification that
3460 .cindex "inetd" "wait mode"
3461 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3462 similarly to the &%-bd%& option. All port specifications on the command-line
3463 and in the configuration file are ignored. Queue-running may not be specified.
3465 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3466 listening for connections. This permits the system to start up and have
3467 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3468 each port only when the first connection is received.
3470 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3471 which the daemon will exit, which should cause inetd to listen once more.
3473 .vitem &%-C%&&~<&'filelist'&>
3475 .cindex "configuration file" "alternate"
3476 .cindex "CONFIGURE_FILE"
3477 .cindex "alternate configuration file"
3478 This option causes Exim to find the run time configuration file from the given
3479 list instead of from the list specified by the CONFIGURE_FILE
3480 compile-time setting. Usually, the list will consist of just a single file
3481 name, but it can be a colon-separated list of names. In this case, the first
3482 file that exists is used. Failure to open an existing file stops Exim from
3483 proceeding any further along the list, and an error is generated.
3485 When this option is used by a caller other than root, and the list is different
3486 from the compiled-in list, Exim gives up its root privilege immediately, and
3487 runs with the real and effective uid and gid set to those of the caller.
3488 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3489 file contains a list of full pathnames, one per line, for configuration files
3490 which are trusted. Root privilege is retained for any configuration file so
3491 listed, as long as the caller is the Exim user (or the user specified in the
3492 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3493 not writeable by inappropriate users or groups.
3495 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3496 configuration using &%-C%& right through message reception and delivery,
3497 even if the caller is root. The reception works, but by that time, Exim is
3498 running as the Exim user, so when it re-executes to regain privilege for the
3499 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3500 test reception and delivery using two separate commands (one to put a message
3501 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3503 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3504 prefix string with which any file named in a &%-C%& command line option
3505 must start. In addition, the file name must not contain the sequence &`/../`&.
3506 However, if the value of the &%-C%& option is identical to the value of
3507 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3508 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3509 unset, any file name can be used with &%-C%&.
3511 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3512 to a directory to which only root has access. This prevents someone who has
3513 broken into the Exim account from running a privileged Exim with an arbitrary
3516 The &%-C%& facility is useful for ensuring that configuration files are
3517 syntactically correct, but cannot be used for test deliveries, unless the
3518 caller is privileged, or unless it is an exotic configuration that does not
3519 require privilege. No check is made on the owner or group of the files
3520 specified by this option.
3523 .vitem &%-D%&<&'macro'&>=<&'value'&>
3525 .cindex "macro" "setting on command line"
3526 This option can be used to override macro definitions in the configuration file
3527 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3528 unprivileged caller, it causes Exim to give up its root privilege.
3529 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3530 completely disabled, and its use causes an immediate error exit.
3532 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3533 colon-separated list of macros which are considered safe and, if &%-D%& only
3534 supplies macros from this list, and the values are acceptable, then Exim will
3535 not give up root privilege if the caller is root, the Exim run-time user, or
3536 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3537 to be removed in the future. Acceptable values for the macros satisfy the
3538 regexp: &`^[A-Za-z0-9_/.-]*$`&
3540 The entire option (including equals sign if present) must all be within one
3541 command line item. &%-D%& can be used to set the value of a macro to the empty
3542 string, in which case the equals sign is optional. These two commands are
3548 To include spaces in a macro definition item, quotes must be used. If you use
3549 quotes, spaces are permitted around the macro name and the equals sign. For
3552 exim '-D ABC = something' ...
3554 &%-D%& may be repeated up to 10 times on a command line.
3556 Only macro names up to 22 letters long can be set.
3560 .vitem &%-d%&<&'debug&~options'&>
3562 .cindex "debugging" "list of selectors"
3563 .cindex "debugging" "&%-d%& option"
3564 This option causes debugging information to be written to the standard
3565 error stream. It is restricted to admin users because debugging output may show
3566 database queries that contain password information. Also, the details of users'
3567 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3568 writes an error message to the standard error stream and exits with a non-zero
3571 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3572 standard debugging data is output. This can be reduced, or increased to include
3573 some more rarely needed information, by directly following &%-d%& with a string
3574 made up of names preceded by plus or minus characters. These add or remove sets
3575 of debugging data, respectively. For example, &%-d+filter%& adds filter
3576 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3577 no spaces are allowed in the debug setting. The available debugging categories
3580 &`acl `& ACL interpretation
3581 &`auth `& authenticators
3582 &`deliver `& general delivery logic
3583 &`dns `& DNS lookups (see also resolver)
3584 &`dnsbl `& DNS black list (aka RBL) code
3585 &`exec `& arguments for &[execv()]& calls
3586 &`expand `& detailed debugging for string expansions
3587 &`filter `& filter handling
3588 &`hints_lookup `& hints data lookups
3589 &`host_lookup `& all types of name-to-IP address handling
3590 &`ident `& ident lookup
3591 &`interface `& lists of local interfaces
3592 &`lists `& matching things in lists
3593 &`load `& system load checks
3594 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3595 &<<CHAPlocalscan>>&)
3596 &`lookup `& general lookup code and all lookups
3597 &`memory `& memory handling
3598 &`pid `& add pid to debug output lines
3599 &`process_info `& setting info for the process log
3600 &`queue_run `& queue runs
3601 &`receive `& general message reception logic
3602 &`resolver `& turn on the DNS resolver's debugging output
3603 &`retry `& retry handling
3604 &`rewrite `& address rewriting
3605 &`route `& address routing
3606 &`timestamp `& add timestamp to debug output lines
3608 &`transport `& transports
3609 &`uid `& changes of uid/gid and looking up uid/gid
3610 &`verify `& address verification logic
3611 &`all `& almost all of the above (see below), and also &%-v%&
3613 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3614 for &`-all`&. The reason for this is that &`+all`& is something that people
3615 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3616 is included, an awful lot of output that is very rarely of interest is
3617 generated, so it now has to be explicitly requested. However, &`-all`& does
3618 turn everything off.
3620 .cindex "resolver, debugging output"
3621 .cindex "DNS resolver, debugging output"
3622 The &`resolver`& option produces output only if the DNS resolver was compiled
3623 with DEBUG enabled. This is not the case in some operating systems. Also,
3624 unfortunately, debugging output from the DNS resolver is written to stdout
3627 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3628 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3629 However, the &`pid`& selector is forced when debugging is turned on for a
3630 daemon, which then passes it on to any re-executed Exims. Exim also
3631 automatically adds the pid to debug lines when several remote deliveries are
3634 The &`timestamp`& selector causes the current time to be inserted at the start
3635 of all debug output lines. This can be useful when trying to track down delays
3638 If the &%debug_print%& option is set in any driver, it produces output whenever
3639 any debugging is selected, or if &%-v%& is used.
3641 .vitem &%-dd%&<&'debug&~options'&>
3643 This option behaves exactly like &%-d%& except when used on a command that
3644 starts a daemon process. In that case, debugging is turned off for the
3645 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3646 behaviour of the daemon without creating as much output as full debugging does.
3649 .oindex "&%-dropcr%&"
3650 This is an obsolete option that is now a no-op. It used to affect the way Exim
3651 handled CR and LF characters in incoming messages. What happens now is
3652 described in section &<<SECTlineendings>>&.
3656 .cindex "bounce message" "generating"
3657 This option specifies that an incoming message is a locally-generated delivery
3658 failure report. It is used internally by Exim when handling delivery failures
3659 and is not intended for external use. Its only effect is to stop Exim
3660 generating certain messages to the postmaster, as otherwise message cascades
3661 could occur in some situations. As part of the same option, a message id may
3662 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3663 new message contains the id, following &"R="&, as a cross-reference.
3666 .oindex "&%-e%&&'x'&"
3667 There are a number of Sendmail options starting with &%-oe%& which seem to be
3668 called by various programs without the leading &%o%& in the option. For
3669 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3670 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3672 .vitem &%-F%&&~<&'string'&>
3674 .cindex "sender" "name"
3675 .cindex "name" "of sender"
3676 This option sets the sender's full name for use when a locally-generated
3677 message is being accepted. In the absence of this option, the user's &'gecos'&
3678 entry from the password data is used. As users are generally permitted to alter
3679 their &'gecos'& entries, no security considerations are involved. White space
3680 between &%-F%& and the <&'string'&> is optional.
3682 .vitem &%-f%&&~<&'address'&>
3684 .cindex "sender" "address"
3685 .cindex "address" "sender"
3686 .cindex "trusted users"
3687 .cindex "envelope sender"
3688 .cindex "user" "trusted"
3689 This option sets the address of the envelope sender of a locally-generated
3690 message (also known as the return path). The option can normally be used only
3691 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3694 Processes running as root or the Exim user are always trusted. Other
3695 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3696 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3697 of a local message is set to the caller's login name at the default qualify
3700 There is one exception to the restriction on the use of &%-f%&: an empty sender
3701 can be specified by any user, trusted or not, to create a message that can
3702 never provoke a bounce. An empty sender can be specified either as an empty
3703 string, or as a pair of angle brackets with nothing between them, as in these
3704 examples of shell commands:
3706 exim -f '<>' user@domain
3707 exim -f "" user@domain
3709 In addition, the use of &%-f%& is not restricted when testing a filter file
3710 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3713 Allowing untrusted users to change the sender address does not of itself make
3714 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3715 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3716 though this can be overridden by setting &%no_local_from_check%&.
3719 .cindex "&""From""& line"
3720 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3721 given as two arguments or one combined argument). The sender of a
3722 locally-generated message can also be set (when permitted) by an initial
3723 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3724 if &%-f%& is also present, it overrides &"From&~"&.
3728 .cindex "submission fixups, suppressing (command-line)"
3729 This option is equivalent to an ACL applying:
3731 control = suppress_local_fixups
3733 for every message received. Note that Sendmail will complain about such
3734 bad formatting, where Exim silently just does not fix it up. This may change
3737 As this affects audit information, the caller must be a trusted user to use
3740 .vitem &%-h%&&~<&'number'&>
3742 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3743 This option is accepted for compatibility with Sendmail, but has no effect. (In
3744 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3749 .cindex "Solaris" "&'mail'& command"
3750 .cindex "dot" "in incoming non-SMTP message"
3751 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3752 line by itself should not terminate an incoming, non-SMTP message. I can find
3753 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3754 command in Solaris 2.4 uses it. See also &%-ti%&.
3756 .vitem &%-L%&&~<&'tag'&>
3758 .cindex "syslog" "process name; set with flag"
3759 This option is equivalent to setting &%syslog_processname%& in the config
3760 file and setting &%log_file_path%& to &`syslog`&.
3761 Its use is restricted to administrators. The configuration file has to be
3762 read and parsed, to determine access rights, before this is set and takes
3763 effect, so early configuration file errors will not honour this flag.
3765 The tag should not be longer than 32 characters.
3767 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3769 .cindex "forcing delivery"
3770 .cindex "delivery" "forcing attempt"
3771 .cindex "frozen messages" "forcing delivery"
3772 This option requests Exim to run a delivery attempt on each message in turn. If
3773 any of the messages are frozen, they are automatically thawed before the
3774 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3775 and &%hold_domains%& are ignored.
3778 .cindex "hints database" "overriding retry hints"
3779 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3780 the normal retry time has not yet been reached. This option requires the caller
3781 to be an admin user. However, there is an option called &%prod_requires_admin%&
3782 which can be set false to relax this restriction (and also the same requirement
3783 for the &%-q%&, &%-R%&, and &%-S%& options).
3785 The deliveries happen synchronously, that is, the original Exim process does
3786 not terminate until all the delivery attempts have finished. No output is
3787 produced unless there is a serious error. If you want to see what is happening,
3788 use the &%-v%& option as well, or inspect Exim's main log.
3790 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3792 .cindex "message" "adding recipients"
3793 .cindex "recipient" "adding"
3794 This option requests Exim to add the addresses to the list of recipients of the
3795 message (&"ar"& for &"add recipients"&). The first argument must be a message
3796 id, and the remaining ones must be email addresses. However, if the message is
3797 active (in the middle of a delivery attempt), it is not altered. This option
3798 can be used only by an admin user.
3800 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3801 &~<&'message&~id'&>"
3803 .cindex "SMTP" "passed connection"
3804 .cindex "SMTP" "multiple deliveries"
3805 .cindex "multiple SMTP deliveries"
3806 This option is not intended for use by external callers. It is used internally
3807 by Exim to invoke another instance of itself to deliver a waiting message using
3808 an existing SMTP connection, which is passed as the standard input. Details are
3809 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3810 must be root or the Exim user in order to use it.
3814 This option is not intended for use by external callers. It is used internally
3815 by Exim in conjunction with the &%-MC%& option. It signifies that the
3816 connection to the remote host has been authenticated.
3820 This option is not intended for use by external callers. It is used internally
3821 by Exim in conjunction with the &%-MC%& option. It signifies that the
3822 remote host supports the ESMTP &_DSN_& extension.
3826 This option is not intended for use by external callers. It is used internally
3827 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3828 which Exim is connected supports pipelining.
3830 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3832 This option is not intended for use by external callers. It is used internally
3833 by Exim in conjunction with the &%-MC%& option when the original delivery was
3834 started by a queue runner. It passes on the process id of the queue runner,
3835 together with the file descriptor number of an open pipe. Closure of the pipe
3836 signals the final completion of the sequence of processes that are passing
3837 messages through the same SMTP connection.
3841 This option is not intended for use by external callers. It is used internally
3842 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3843 SMTP SIZE option should be used on messages delivered down the existing
3848 This option is not intended for use by external callers. It is used internally
3849 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3850 host to which Exim is connected supports TLS encryption.
3852 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3854 .cindex "hints database" "not overridden by &%-Mc%&"
3855 .cindex "delivery" "manually started &-- not forced"
3856 This option requests Exim to run a delivery attempt on each message in turn,
3857 but unlike the &%-M%& option, it does check for retry hints, and respects any
3858 that are found. This option is not very useful to external callers. It is
3859 provided mainly for internal use by Exim when it needs to re-invoke itself in
3860 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3861 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3862 respects retry times and other options such as &%hold_domains%& that are
3863 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3864 If you want to run a specific delivery as if in a queue run, you should use
3865 &%-q%& with a message id argument. A distinction between queue run deliveries
3866 and other deliveries is made in one or two places.
3868 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3870 .cindex "message" "changing sender"
3871 .cindex "sender" "changing"
3872 This option requests Exim to change the sender address in the message to the
3873 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3874 &"edit sender"&). There must be exactly two arguments. The first argument must
3875 be a message id, and the second one an email address. However, if the message
3876 is active (in the middle of a delivery attempt), its status is not altered.
3877 This option can be used only by an admin user.
3879 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3881 .cindex "freezing messages"
3882 .cindex "message" "manually freezing"
3883 This option requests Exim to mark each listed message as &"frozen"&. This
3884 prevents any delivery attempts taking place until the message is &"thawed"&,
3885 either manually or as a result of the &%auto_thaw%& configuration option.
3886 However, if any of the messages are active (in the middle of a delivery
3887 attempt), their status is not altered. This option can be used only by an admin
3890 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3892 .cindex "giving up on messages"
3893 .cindex "message" "abandoning delivery attempts"
3894 .cindex "delivery" "abandoning further attempts"
3895 This option requests Exim to give up trying to deliver the listed messages,
3896 including any that are frozen. However, if any of the messages are active,
3897 their status is not altered. For non-bounce messages, a delivery error message
3898 is sent to the sender, containing the text &"cancelled by administrator"&.
3899 Bounce messages are just discarded. This option can be used only by an admin
3902 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3904 .cindex "delivery" "cancelling all"
3905 This option requests Exim to mark all the recipient addresses in the messages
3906 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3907 message is active (in the middle of a delivery attempt), its status is not
3908 altered. This option can be used only by an admin user.
3910 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3912 .cindex "delivery" "cancelling by address"
3913 .cindex "recipient" "removing"
3914 .cindex "removing recipients"
3915 This option requests Exim to mark the given addresses as already delivered
3916 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3917 the remaining ones must be email addresses. These are matched to recipient
3918 addresses in the message in a case-sensitive manner. If the message is active
3919 (in the middle of a delivery attempt), its status is not altered. This option
3920 can be used only by an admin user.
3922 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3924 .cindex "removing messages"
3925 .cindex "abandoning mail"
3926 .cindex "message" "manually discarding"
3927 This option requests Exim to remove the given messages from the queue. No
3928 bounce messages are sent; each message is simply forgotten. However, if any of
3929 the messages are active, their status is not altered. This option can be used
3930 only by an admin user or by the user who originally caused the message to be
3931 placed on the queue.
3933 .vitem &%-Mset%&&~<&'message&~id'&>
3935 .cindex "testing" "string expansion"
3936 .cindex "expansion" "testing"
3937 This option is useful only in conjunction with &%-be%& (that is, when testing
3938 string expansions). Exim loads the given message from its spool before doing
3939 the test expansions, thus setting message-specific variables such as
3940 &$message_size$& and the header variables. The &$recipients$& variable is made
3941 available. This feature is provided to make it easier to test expansions that
3942 make use of these variables. However, this option can be used only by an admin
3943 user. See also &%-bem%&.
3945 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3947 .cindex "thawing messages"
3948 .cindex "unfreezing messages"
3949 .cindex "frozen messages" "thawing"
3950 .cindex "message" "thawing frozen"
3951 This option requests Exim to &"thaw"& any of the listed messages that are
3952 &"frozen"&, so that delivery attempts can resume. However, if any of the
3953 messages are active, their status is not altered. This option can be used only
3956 .vitem &%-Mvb%&&~<&'message&~id'&>
3958 .cindex "listing" "message body"
3959 .cindex "message" "listing body of"
3960 This option causes the contents of the message body (-D) spool file to be
3961 written to the standard output. This option can be used only by an admin user.
3963 .vitem &%-Mvc%&&~<&'message&~id'&>
3965 .cindex "message" "listing in RFC 2822 format"
3966 .cindex "listing" "message in RFC 2822 format"
3967 This option causes a copy of the complete message (header lines plus body) to
3968 be written to the standard output in RFC 2822 format. This option can be used
3969 only by an admin user.
3971 .vitem &%-Mvh%&&~<&'message&~id'&>
3973 .cindex "listing" "message headers"
3974 .cindex "header lines" "listing"
3975 .cindex "message" "listing header lines"
3976 This option causes the contents of the message headers (-H) spool file to be
3977 written to the standard output. This option can be used only by an admin user.
3979 .vitem &%-Mvl%&&~<&'message&~id'&>
3981 .cindex "listing" "message log"
3982 .cindex "message" "listing message log"
3983 This option causes the contents of the message log spool file to be written to
3984 the standard output. This option can be used only by an admin user.
3988 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3989 treats it that way too.
3993 .cindex "debugging" "&%-N%& option"
3994 .cindex "debugging" "suppressing delivery"
3995 This is a debugging option that inhibits delivery of a message at the transport
3996 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3997 it just doesn't actually transport the message, but instead behaves as if it
3998 had successfully done so. However, it does not make any updates to the retry
3999 database, and the log entries for deliveries are flagged with &"*>"& rather
4002 Because &%-N%& discards any message to which it applies, only root or the Exim
4003 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4004 words, an ordinary user can use it only when supplying an incoming message to
4005 which it will apply. Although transportation never fails when &%-N%& is set, an
4006 address may be deferred because of a configuration problem on a transport, or a
4007 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4008 the message, and applies to any subsequent delivery attempts that may happen
4013 This option is interpreted by Sendmail to mean &"no aliasing"&.
4014 For normal modes of operation, it is ignored by Exim.
4015 When combined with &%-bP%& it suppresses the name of an option from being output.
4017 .vitem &%-O%&&~<&'data'&>
4019 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4022 .vitem &%-oA%&&~<&'file&~name'&>
4024 .cindex "Sendmail compatibility" "&%-oA%& option"
4025 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4026 alternative alias file name. Exim handles &%-bi%& differently; see the
4029 .vitem &%-oB%&&~<&'n'&>
4031 .cindex "SMTP" "passed connection"
4032 .cindex "SMTP" "multiple deliveries"
4033 .cindex "multiple SMTP deliveries"
4034 This is a debugging option which limits the maximum number of messages that can
4035 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4036 transport. If <&'n'&> is omitted, the limit is set to 1.
4040 .cindex "background delivery"
4041 .cindex "delivery" "in the background"
4042 This option applies to all modes in which Exim accepts incoming messages,
4043 including the listening daemon. It requests &"background"& delivery of such
4044 messages, which means that the accepting process automatically starts a
4045 delivery process for each message received, but does not wait for the delivery
4046 processes to finish.
4048 When all the messages have been received, the reception process exits,
4049 leaving the delivery processes to finish in their own time. The standard output
4050 and error streams are closed at the start of each delivery process.
4051 This is the default action if none of the &%-od%& options are present.
4053 If one of the queueing options in the configuration file
4054 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4055 overrides it if &%queue_only_override%& is set true, which is the default
4056 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4060 .cindex "foreground delivery"
4061 .cindex "delivery" "in the foreground"
4062 This option requests &"foreground"& (synchronous) delivery when Exim has
4063 accepted a locally-generated message. (For the daemon it is exactly the same as
4064 &%-odb%&.) A delivery process is automatically started to deliver the message,
4065 and Exim waits for it to complete before proceeding.
4067 The original Exim reception process does not finish until the delivery
4068 process for the final message has ended. The standard error stream is left open
4071 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4072 false and one of the queueing options in the configuration file is in effect.
4074 If there is a temporary delivery error during foreground delivery, the
4075 message is left on the queue for later delivery, and the original reception
4076 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4077 restricted configuration that never queues messages.
4082 This option is synonymous with &%-odf%&. It is provided for compatibility with
4087 .cindex "non-immediate delivery"
4088 .cindex "delivery" "suppressing immediate"
4089 .cindex "queueing incoming messages"
4090 This option applies to all modes in which Exim accepts incoming messages,
4091 including the listening daemon. It specifies that the accepting process should
4092 not automatically start a delivery process for each message received. Messages
4093 are placed on the queue, and remain there until a subsequent queue runner
4094 process encounters them. There are several configuration options (such as
4095 &%queue_only%&) that can be used to queue incoming messages under certain
4096 conditions. This option overrides all of them and also &%-odqs%&. It always
4101 .cindex "SMTP" "delaying delivery"
4102 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4103 However, like &%-odb%& and &%-odi%&, this option has no effect if
4104 &%queue_only_override%& is false and one of the queueing options in the
4105 configuration file is in effect.
4107 When &%-odqs%& does operate, a delivery process is started for each incoming
4108 message, in the background by default, but in the foreground if &%-odi%& is
4109 also present. The recipient addresses are routed, and local deliveries are done
4110 in the normal way. However, if any SMTP deliveries are required, they are not
4111 done at this time, so the message remains on the queue until a subsequent queue
4112 runner process encounters it. Because routing was done, Exim knows which
4113 messages are waiting for which hosts, and so a number of messages for the same
4114 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4115 configuration option has the same effect for specific domains. See also the
4120 .cindex "error" "reporting"
4121 If an error is detected while a non-SMTP message is being received (for
4122 example, a malformed address), the error is reported to the sender in a mail
4125 .cindex "return code" "for &%-oee%&"
4127 this error message is successfully sent, the Exim receiving process
4128 exits with a return code of zero. If not, the return code is 2 if the problem
4129 is that the original message has no recipients, or 1 for any other error.
4130 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4134 .cindex "error" "reporting"
4135 .cindex "return code" "for &%-oem%&"
4136 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4137 return code, whether or not the error message was successfully sent.
4138 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4142 .cindex "error" "reporting"
4143 If an error is detected while a non-SMTP message is being received, the
4144 error is reported by writing a message to the standard error file (stderr).
4145 .cindex "return code" "for &%-oep%&"
4146 The return code is 1 for all errors.
4150 .cindex "error" "reporting"
4151 This option is supported for compatibility with Sendmail, but has the same
4156 .cindex "error" "reporting"
4157 This option is supported for compatibility with Sendmail, but has the same
4162 .cindex "dot" "in incoming non-SMTP message"
4163 This option, which has the same effect as &%-i%&, specifies that a dot on a
4164 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4165 single dot does terminate, though Exim does no special processing for other
4166 lines that start with a dot. This option is set by default if Exim is called as
4167 &'rmail'&. See also &%-ti%&.
4170 .oindex "&%-oitrue%&"
4171 This option is treated as synonymous with &%-oi%&.
4173 .vitem &%-oMa%&&~<&'host&~address'&>
4175 .cindex "sender" "host address, specifying for local message"
4176 A number of options starting with &%-oM%& can be used to set values associated
4177 with remote hosts on locally-submitted messages (that is, messages not received
4178 over TCP/IP). These options can be used by any caller in conjunction with the
4179 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4180 other circumstances, they are ignored unless the caller is trusted.
4182 The &%-oMa%& option sets the sender host address. This may include a port
4183 number at the end, after a full stop (period). For example:
4185 exim -bs -oMa 10.9.8.7.1234
4187 An alternative syntax is to enclose the IP address in square brackets,
4188 followed by a colon and the port number:
4190 exim -bs -oMa [10.9.8.7]:1234
4192 The IP address is placed in the &$sender_host_address$& variable, and the
4193 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4194 are present on the command line, the sender host IP address is taken from
4195 whichever one is last.
4197 .vitem &%-oMaa%&&~<&'name'&>
4199 .cindex "authentication" "name, specifying for local message"
4200 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4201 option sets the value of &$sender_host_authenticated$& (the authenticator
4202 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4203 This option can be used with &%-bh%& and &%-bs%& to set up an
4204 authenticated SMTP session without actually using the SMTP AUTH command.
4206 .vitem &%-oMai%&&~<&'string'&>
4208 .cindex "authentication" "id, specifying for local message"
4209 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4210 option sets the value of &$authenticated_id$& (the id that was authenticated).
4211 This overrides the default value (the caller's login id, except with &%-bh%&,
4212 where there is no default) for messages from local sources. See chapter
4213 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4215 .vitem &%-oMas%&&~<&'address'&>
4217 .cindex "authentication" "sender, specifying for local message"
4218 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4219 option sets the authenticated sender value in &$authenticated_sender$&. It
4220 overrides the sender address that is created from the caller's login id for
4221 messages from local sources, except when &%-bh%& is used, when there is no
4222 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4223 specified on a MAIL command overrides this value. See chapter
4224 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4226 .vitem &%-oMi%&&~<&'interface&~address'&>
4228 .cindex "interface" "address, specifying for local message"
4229 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4230 option sets the IP interface address value. A port number may be included,
4231 using the same syntax as for &%-oMa%&. The interface address is placed in
4232 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4234 .vitem &%-oMm%&&~<&'message&~reference'&>
4236 .cindex "message reference" "message reference, specifying for local message"
4237 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4238 option sets the message reference, e.g. message-id, and is logged during
4239 delivery. This is useful when some kind of audit trail is required to tie
4240 messages together. The format of the message reference is checked and will
4241 abort if the format is invalid. The option will only be accepted if exim is
4242 running in trusted mode, not as any regular user.
4244 The best example of a message reference is when Exim sends a bounce message.
4245 The message reference is the message-id of the original message for which Exim
4246 is sending the bounce.
4248 .vitem &%-oMr%&&~<&'protocol&~name'&>
4250 .cindex "protocol, specifying for local message"
4251 .vindex "&$received_protocol$&"
4252 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4253 option sets the received protocol value that is stored in
4254 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4255 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4256 SMTP protocol names (see the description of &$received_protocol$& in section
4257 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4258 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4261 .vitem &%-oMs%&&~<&'host&~name'&>
4263 .cindex "sender" "host name, specifying for local message"
4264 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4265 option sets the sender host name in &$sender_host_name$&. When this option is
4266 present, Exim does not attempt to look up a host name from an IP address; it
4267 uses the name it is given.
4269 .vitem &%-oMt%&&~<&'ident&~string'&>
4271 .cindex "sender" "ident string, specifying for local message"
4272 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4273 option sets the sender ident value in &$sender_ident$&. The default setting for
4274 local callers is the login id of the calling process, except when &%-bh%& is
4275 used, when there is no default.
4279 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4280 In Sendmail, this option means &"me too"&, indicating that the sender of a
4281 message should receive a copy of the message if the sender appears in an alias
4282 expansion. Exim always does this, so the option does nothing.
4286 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4287 This option is ignored. In Sendmail it specifies &"old style headers"&,
4288 whatever that means.
4290 .vitem &%-oP%&&~<&'path'&>
4292 .cindex "pid (process id)" "of daemon"
4293 .cindex "daemon" "process id (pid)"
4294 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4295 value. The option specifies the file to which the process id of the daemon is
4296 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4297 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4298 because in those cases, the normal pid file is not used.
4300 .vitem &%-or%&&~<&'time'&>
4302 .cindex "timeout" "for non-SMTP input"
4303 This option sets a timeout value for incoming non-SMTP messages. If it is not
4304 set, Exim will wait forever for the standard input. The value can also be set
4305 by the &%receive_timeout%& option. The format used for specifying times is
4306 described in section &<<SECTtimeformat>>&.
4308 .vitem &%-os%&&~<&'time'&>
4310 .cindex "timeout" "for SMTP input"
4311 .cindex "SMTP" "input timeout"
4312 This option sets a timeout value for incoming SMTP messages. The timeout
4313 applies to each SMTP command and block of data. The value can also be set by
4314 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4315 for specifying times is described in section &<<SECTtimeformat>>&.
4319 This option has exactly the same effect as &%-v%&.
4321 .vitem &%-oX%&&~<&'number&~or&~string'&>
4323 .cindex "TCP/IP" "setting listening ports"
4324 .cindex "TCP/IP" "setting listening interfaces"
4325 .cindex "port" "receiving TCP/IP"
4326 This option is relevant only when the &%-bd%& (start listening daemon) option
4327 is also given. It controls which ports and interfaces the daemon uses. Details
4328 of the syntax, and how it interacts with configuration file options, are given
4329 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4330 file is written unless &%-oP%& is also present to specify a pid file name.
4334 .cindex "Perl" "starting the interpreter"
4335 This option applies when an embedded Perl interpreter is linked with Exim (see
4336 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4337 option, forcing the starting of the interpreter to be delayed until it is
4342 .cindex "Perl" "starting the interpreter"
4343 This option applies when an embedded Perl interpreter is linked with Exim (see
4344 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4345 option, forcing the starting of the interpreter to occur as soon as Exim is
4348 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4350 For compatibility with Sendmail, this option is equivalent to
4352 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4354 It sets the incoming protocol and host name (for trusted callers). The
4355 host name and its colon can be omitted when only the protocol is to be set.
4356 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4357 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4358 or &`s`& using this option (but that does not seem a real limitation).
4362 .cindex "queue runner" "starting manually"
4363 This option is normally restricted to admin users. However, there is a
4364 configuration option called &%prod_requires_admin%& which can be set false to
4365 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4366 and &%-S%& options).
4368 .cindex "queue runner" "description of operation"
4369 The &%-q%& option starts one queue runner process. This scans the queue of
4370 waiting messages, and runs a delivery process for each one in turn. It waits
4371 for each delivery process to finish before starting the next one. A delivery
4372 process may not actually do any deliveries if the retry times for the addresses
4373 have not been reached. Use &%-qf%& (see below) if you want to override this.
4376 .cindex "SMTP" "passed connection"
4377 .cindex "SMTP" "multiple deliveries"
4378 .cindex "multiple SMTP deliveries"
4379 the delivery process spawns other processes to deliver other messages down
4380 passed SMTP connections, the queue runner waits for these to finish before
4383 When all the queued messages have been considered, the original queue runner
4384 process terminates. In other words, a single pass is made over the waiting
4385 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4386 this to be repeated periodically.
4388 Exim processes the waiting messages in an unpredictable order. It isn't very
4389 random, but it is likely to be different each time, which is all that matters.
4390 If one particular message screws up a remote MTA, other messages to the same
4391 MTA have a chance of getting through if they get tried first.
4393 It is possible to cause the messages to be processed in lexical message id
4394 order, which is essentially the order in which they arrived, by setting the
4395 &%queue_run_in_order%& option, but this is not recommended for normal use.
4397 .vitem &%-q%&<&'qflags'&>
4398 The &%-q%& option may be followed by one or more flag letters that change its
4399 behaviour. They are all optional, but if more than one is present, they must
4400 appear in the correct order. Each flag is described in a separate item below.
4404 .cindex "queue" "double scanning"
4405 .cindex "queue" "routing"
4406 .cindex "routing" "whole queue before delivery"
4407 An option starting with &%-qq%& requests a two-stage queue run. In the first
4408 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4409 every domain. Addresses are routed, local deliveries happen, but no remote
4412 .cindex "hints database" "remembering routing"
4413 The hints database that remembers which messages are waiting for specific hosts
4414 is updated, as if delivery to those hosts had been deferred. After this is
4415 complete, a second, normal queue scan happens, with routing and delivery taking
4416 place as normal. Messages that are routed to the same host should mostly be
4417 delivered down a single SMTP
4418 .cindex "SMTP" "passed connection"
4419 .cindex "SMTP" "multiple deliveries"
4420 .cindex "multiple SMTP deliveries"
4421 connection because of the hints that were set up during the first queue scan.
4422 This option may be useful for hosts that are connected to the Internet
4425 .vitem &%-q[q]i...%&
4427 .cindex "queue" "initial delivery"
4428 If the &'i'& flag is present, the queue runner runs delivery processes only for
4429 those messages that haven't previously been tried. (&'i'& stands for &"initial
4430 delivery"&.) This can be helpful if you are putting messages on the queue using
4431 &%-odq%& and want a queue runner just to process the new messages.
4433 .vitem &%-q[q][i]f...%&
4435 .cindex "queue" "forcing delivery"
4436 .cindex "delivery" "forcing in queue run"
4437 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4438 message, whereas without &'f'& only those non-frozen addresses that have passed
4439 their retry times are tried.
4441 .vitem &%-q[q][i]ff...%&
4443 .cindex "frozen messages" "forcing delivery"
4444 If &'ff'& is present, a delivery attempt is forced for every message, whether
4447 .vitem &%-q[q][i][f[f]]l%&
4449 .cindex "queue" "local deliveries only"
4450 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4451 be done. If a message requires any remote deliveries, it remains on the queue
4454 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4455 .cindex "queue" "delivering specific messages"
4456 When scanning the queue, Exim can be made to skip over messages whose ids are
4457 lexically less than a given value by following the &%-q%& option with a
4458 starting message id. For example:
4460 exim -q 0t5C6f-0000c8-00
4462 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4463 second message id is given, messages whose ids are lexically greater than it
4464 are also skipped. If the same id is given twice, for example,
4466 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4468 just one delivery process is started, for that message. This differs from
4469 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4470 that it counts as a delivery from a queue run. Note that the selection
4471 mechanism does not affect the order in which the messages are scanned. There
4472 are also other ways of selecting specific sets of messages for delivery in a
4473 queue run &-- see &%-R%& and &%-S%&.
4475 .vitem &%-q%&<&'qflags'&><&'time'&>
4476 .cindex "queue runner" "starting periodically"
4477 .cindex "periodic queue running"
4478 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4479 starting a queue runner process at intervals specified by the given time value
4480 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4481 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4482 single daemon process handles both functions. A common way of starting up a
4483 combined daemon at system boot time is to use a command such as
4485 /usr/exim/bin/exim -bd -q30m
4487 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4488 process every 30 minutes.
4490 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4491 pid file is written unless one is explicitly requested by the &%-oP%& option.
4493 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4495 This option is synonymous with &%-R%&. It is provided for Sendmail
4498 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4500 This option is synonymous with &%-S%&.
4502 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4504 .cindex "queue runner" "for specific recipients"
4505 .cindex "delivery" "to given domain"
4506 .cindex "domain" "delivery to"
4507 The <&'rsflags'&> may be empty, in which case the white space before the string
4508 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4509 which are the possible values for <&'rsflags'&>. White space is required if
4510 <&'rsflags'&> is not empty.
4512 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4513 perform a single queue run, except that, when scanning the messages on the
4514 queue, Exim processes only those that have at least one undelivered recipient
4515 address containing the given string, which is checked in a case-independent
4516 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4517 regular expression; otherwise it is a literal string.
4519 If you want to do periodic queue runs for messages with specific recipients,
4520 you can combine &%-R%& with &%-q%& and a time value. For example:
4522 exim -q25m -R @special.domain.example
4524 This example does a queue run for messages with recipients in the given domain
4525 every 25 minutes. Any additional flags that are specified with &%-q%& are
4526 applied to each queue run.
4528 Once a message is selected for delivery by this mechanism, all its addresses
4529 are processed. For the first selected message, Exim overrides any retry
4530 information and forces a delivery attempt for each undelivered address. This
4531 means that if delivery of any address in the first message is successful, any
4532 existing retry information is deleted, and so delivery attempts for that
4533 address in subsequently selected messages (which are processed without forcing)
4534 will run. However, if delivery of any address does not succeed, the retry
4535 information is updated, and in subsequently selected messages, the failing
4536 address will be skipped.
4538 .cindex "frozen messages" "forcing delivery"
4539 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4540 all selected messages, not just the first; frozen messages are included when
4543 The &%-R%& option makes it straightforward to initiate delivery of all messages
4544 to a given domain after a host has been down for some time. When the SMTP
4545 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4546 effect is to run Exim with the &%-R%& option, but it can be configured to run
4547 an arbitrary command instead.
4551 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4553 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4555 .cindex "delivery" "from given sender"
4556 .cindex "queue runner" "for specific senders"
4557 This option acts like &%-R%& except that it checks the string against each
4558 message's sender instead of against the recipients. If &%-R%& is also set, both
4559 conditions must be met for a message to be selected. If either of the options
4560 has &'f'& or &'ff'& in its flags, the associated action is taken.
4562 .vitem &%-Tqt%&&~<&'times'&>
4564 This is an option that is exclusively for use by the Exim testing suite. It is not
4565 recognized when Exim is run normally. It allows for the setting up of explicit
4566 &"queue times"& so that various warning/retry features can be tested.
4570 .cindex "recipient" "extracting from header lines"
4571 .cindex "&'Bcc:'& header line"
4572 .cindex "&'Cc:'& header line"
4573 .cindex "&'To:'& header line"
4574 When Exim is receiving a locally-generated, non-SMTP message on its standard
4575 input, the &%-t%& option causes the recipients of the message to be obtained
4576 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4577 from the command arguments. The addresses are extracted before any rewriting
4578 takes place and the &'Bcc:'& header line, if present, is then removed.
4580 .cindex "Sendmail compatibility" "&%-t%& option"
4581 If the command has any arguments, they specify addresses to which the message
4582 is &'not'& to be delivered. That is, the argument addresses are removed from
4583 the recipients list obtained from the headers. This is compatible with Smail 3
4584 and in accordance with the documented behaviour of several versions of
4585 Sendmail, as described in man pages on a number of operating systems (e.g.
4586 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4587 argument addresses to those obtained from the headers, and the O'Reilly
4588 Sendmail book documents it that way. Exim can be made to add argument addresses
4589 instead of subtracting them by setting the option
4590 &%extract_addresses_remove_arguments%& false.
4592 .cindex "&%Resent-%& header lines" "with &%-t%&"
4593 If there are any &%Resent-%& header lines in the message, Exim extracts
4594 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4595 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4596 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4597 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4599 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4600 message is resent several times). The RFC also specifies that they should be
4601 added at the front of the message, and separated by &'Received:'& lines. It is
4602 not at all clear how &%-t%& should operate in the present of multiple sets,
4603 nor indeed exactly what constitutes a &"set"&.
4604 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4605 are often added at the end of the header, and if a message is resent more than
4606 once, it is common for the original set of &%Resent-%& headers to be renamed as
4607 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4611 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4612 compatibility with Sendmail.
4614 .vitem &%-tls-on-connect%&
4615 .oindex "&%-tls-on-connect%&"
4616 .cindex "TLS" "use without STARTTLS"
4617 .cindex "TLS" "automatic start"
4618 This option is available when Exim is compiled with TLS support. It forces all
4619 incoming SMTP connections to behave as if the incoming port is listed in the
4620 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4621 &<<CHAPTLS>>& for further details.
4626 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4627 Sendmail uses this option for &"initial message submission"&, and its
4628 documentation states that in future releases, it may complain about
4629 syntactically invalid messages rather than fixing them when this flag is not
4630 set. Exim ignores this option.
4634 This option causes Exim to write information to the standard error stream,
4635 describing what it is doing. In particular, it shows the log lines for
4636 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4637 dialogue is shown. Some of the log lines shown may not actually be written to
4638 the log if the setting of &%log_selector%& discards them. Any relevant
4639 selectors are shown with each log line. If none are shown, the logging is
4644 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4645 National Language Support extended characters in the body of the mail item"&).
4646 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4649 .vitem &%-X%&&~<&'logfile'&>
4651 This option is interpreted by Sendmail to cause debug information to be sent
4652 to the named file. It is ignored by Exim.
4654 .vitem &%-z%&&~<&'log-line'&>
4656 This option writes its argument to Exim's logfile.
4657 Use is restricted to administrators; the intent is for operational notes.
4658 Quotes should be used to maintain a multi-word item as a single argument,
4666 . ////////////////////////////////////////////////////////////////////////////
4667 . Insert a stylized DocBook comment here, to identify the end of the command
4668 . line options. This is for the benefit of the Perl script that automatically
4669 . creates a man page for the options.
4670 . ////////////////////////////////////////////////////////////////////////////
4673 <!-- === End of command line options === -->
4680 . ////////////////////////////////////////////////////////////////////////////
4681 . ////////////////////////////////////////////////////////////////////////////
4684 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4685 "The runtime configuration file"
4687 .cindex "run time configuration"
4688 .cindex "configuration file" "general description"
4689 .cindex "CONFIGURE_FILE"
4690 .cindex "configuration file" "errors in"
4691 .cindex "error" "in configuration file"
4692 .cindex "return code" "for bad configuration"
4693 Exim uses a single run time configuration file that is read whenever an Exim
4694 binary is executed. Note that in normal operation, this happens frequently,
4695 because Exim is designed to operate in a distributed manner, without central
4698 If a syntax error is detected while reading the configuration file, Exim
4699 writes a message on the standard error, and exits with a non-zero return code.
4700 The message is also written to the panic log. &*Note*&: Only simple syntax
4701 errors can be detected at this time. The values of any expanded options are
4702 not checked until the expansion happens, even when the expansion does not
4703 actually alter the string.
4705 The name of the configuration file is compiled into the binary for security
4706 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4707 most configurations, this specifies a single file. However, it is permitted to
4708 give a colon-separated list of file names, in which case Exim uses the first
4709 existing file in the list.
4712 .cindex "EXIM_GROUP"
4713 .cindex "CONFIGURE_OWNER"
4714 .cindex "CONFIGURE_GROUP"
4715 .cindex "configuration file" "ownership"
4716 .cindex "ownership" "configuration file"
4717 The run time configuration file must be owned by root or by the user that is
4718 specified at compile time by the CONFIGURE_OWNER option (if set). The
4719 configuration file must not be world-writeable, or group-writeable unless its
4720 group is the root group or the one specified at compile time by the
4721 CONFIGURE_GROUP option.
4723 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4724 to root, anybody who is able to edit the run time configuration file has an
4725 easy way to run commands as root. If you specify a user or group in the
4726 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4727 who are members of that group will trivially be able to obtain root privileges.
4729 Up to Exim version 4.72, the run time configuration file was also permitted to
4730 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4731 since it offered a simple privilege escalation for any attacker who managed to
4732 compromise the Exim user account.
4734 A default configuration file, which will work correctly in simple situations,
4735 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4736 defines just one file name, the installation process copies the default
4737 configuration to a new file of that name if it did not previously exist. If
4738 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4739 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4744 .section "Using a different configuration file" "SECID40"
4745 .cindex "configuration file" "alternate"
4746 A one-off alternate configuration can be specified by the &%-C%& command line
4747 option, which may specify a single file or a list of files. However, when
4748 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4749 unless the argument for &%-C%& is identical to the built-in value from
4750 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4751 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4752 is useful mainly for checking the syntax of configuration files before
4753 installing them. No owner or group checks are done on a configuration file
4754 specified by &%-C%&, if root privilege has been dropped.
4756 Even the Exim user is not trusted to specify an arbitrary configuration file
4757 with the &%-C%& option to be used with root privileges, unless that file is
4758 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4759 testing a configuration using &%-C%& right through message reception and
4760 delivery, even if the caller is root. The reception works, but by that time,
4761 Exim is running as the Exim user, so when it re-execs to regain privilege for
4762 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4763 can test reception and delivery using two separate commands (one to put a
4764 message on the queue, using &%-odq%&, and another to do the delivery, using
4767 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4768 prefix string with which any file named in a &%-C%& command line option must
4769 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4770 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4771 name can be used with &%-C%&.
4773 One-off changes to a configuration can be specified by the &%-D%& command line
4774 option, which defines and overrides values for macros used inside the
4775 configuration file. However, like &%-C%&, the use of this option by a
4776 non-privileged user causes Exim to discard its root privilege.
4777 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4778 completely disabled, and its use causes an immediate error exit.
4780 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4781 to declare certain macro names trusted, such that root privilege will not
4782 necessarily be discarded.
4783 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4784 considered safe and, if &%-D%& only supplies macros from this list, and the
4785 values are acceptable, then Exim will not give up root privilege if the caller
4786 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4787 transition mechanism and is expected to be removed in the future. Acceptable
4788 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4790 Some sites may wish to use the same Exim binary on different machines that
4791 share a file system, but to use different configuration files on each machine.
4792 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4793 looks for a file whose name is the configuration file name followed by a dot
4794 and the machine's node name, as obtained from the &[uname()]& function. If this
4795 file does not exist, the standard name is tried. This processing occurs for
4796 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4798 In some esoteric situations different versions of Exim may be run under
4799 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4800 help with this. See the comments in &_src/EDITME_& for details.
4804 .section "Configuration file format" "SECTconffilfor"
4805 .cindex "configuration file" "format of"
4806 .cindex "format" "configuration file"
4807 Exim's configuration file is divided into a number of different parts. General
4808 option settings must always appear at the start of the file. The other parts
4809 are all optional, and may appear in any order. Each part other than the first
4810 is introduced by the word &"begin"& followed by at least one literal
4811 space, and the name of the part. The optional parts are:
4814 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4817 .cindex "AUTH" "configuration"
4818 &'authenticators'&: Configuration settings for the authenticator drivers. These
4819 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4821 &'routers'&: Configuration settings for the router drivers. Routers process
4822 addresses and determine how the message is to be delivered (see chapters
4823 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4825 &'transports'&: Configuration settings for the transport drivers. Transports
4826 define mechanisms for copying messages to destinations (see chapters
4827 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4829 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4830 If there is no retry section, or if it is empty (that is, no retry rules are
4831 defined), Exim will not retry deliveries. In this situation, temporary errors
4832 are treated the same as permanent errors. Retry rules are discussed in chapter
4835 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4836 when new addresses are generated during delivery. Rewriting is discussed in
4837 chapter &<<CHAPrewrite>>&.
4839 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4840 want to use this feature, you must set
4842 LOCAL_SCAN_HAS_OPTIONS=yes
4844 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4845 facility are given in chapter &<<CHAPlocalscan>>&.
4848 .cindex "configuration file" "leading white space in"
4849 .cindex "configuration file" "trailing white space in"
4850 .cindex "white space" "in configuration file"
4851 Leading and trailing white space in configuration lines is always ignored.
4853 Blank lines in the file, and lines starting with a # character (ignoring
4854 leading white space) are treated as comments and are ignored. &*Note*&: A
4855 # character other than at the beginning of a line is not treated specially,
4856 and does not introduce a comment.
4858 Any non-comment line can be continued by ending it with a backslash. Note that
4859 the general rule for white space means that trailing white space after the
4860 backslash and leading white space at the start of continuation
4861 lines is ignored. Comment lines beginning with # (but not empty lines) may
4862 appear in the middle of a sequence of continuation lines.
4864 A convenient way to create a configuration file is to start from the
4865 default, which is supplied in &_src/configure.default_&, and add, delete, or
4866 change settings as required.
4868 The ACLs, retry rules, and rewriting rules have their own syntax which is
4869 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4870 respectively. The other parts of the configuration file have some syntactic
4871 items in common, and these are described below, from section &<<SECTcos>>&
4872 onwards. Before that, the inclusion, macro, and conditional facilities are
4877 .section "File inclusions in the configuration file" "SECID41"
4878 .cindex "inclusions in configuration file"
4879 .cindex "configuration file" "including other files"
4880 .cindex "&`.include`& in configuration file"
4881 .cindex "&`.include_if_exists`& in configuration file"
4882 You can include other files inside Exim's run time configuration file by
4885 &`.include`& <&'file name'&>
4886 &`.include_if_exists`& <&'file name'&>
4888 on a line by itself. Double quotes round the file name are optional. If you use
4889 the first form, a configuration error occurs if the file does not exist; the
4890 second form does nothing for non-existent files. In all cases, an absolute file
4893 Includes may be nested to any depth, but remember that Exim reads its
4894 configuration file often, so it is a good idea to keep them to a minimum.
4895 If you change the contents of an included file, you must HUP the daemon,
4896 because an included file is read only when the configuration itself is read.
4898 The processing of inclusions happens early, at a physical line level, so, like
4899 comment lines, an inclusion can be used in the middle of an option setting,
4902 hosts_lookup = a.b.c \
4905 Include processing happens after macro processing (see below). Its effect is to
4906 process the lines of the included file as if they occurred inline where the
4911 .section "Macros in the configuration file" "SECTmacrodefs"
4912 .cindex "macro" "description of"
4913 .cindex "configuration file" "macros"
4914 If a line in the main part of the configuration (that is, before the first
4915 &"begin"& line) begins with an upper case letter, it is taken as a macro
4916 definition, and must be of the form
4918 <&'name'&> = <&'rest of line'&>
4920 The name must consist of letters, digits, and underscores, and need not all be
4921 in upper case, though that is recommended. The rest of the line, including any
4922 continuations, is the replacement text, and has leading and trailing white
4923 space removed. Quotes are not removed. The replacement text can never end with
4924 a backslash character, but this doesn't seem to be a serious limitation.
4926 Macros may also be defined between router, transport, authenticator, or ACL
4927 definitions. They may not, however, be defined within an individual driver or
4928 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4930 .section "Macro substitution" "SECID42"
4931 Once a macro is defined, all subsequent lines in the file (and any included
4932 files) are scanned for the macro name; if there are several macros, the line is
4933 scanned for each in turn, in the order in which the macros are defined. The
4934 replacement text is not re-scanned for the current macro, though it is scanned
4935 for subsequently defined macros. For this reason, a macro name may not contain
4936 the name of a previously defined macro as a substring. You could, for example,
4939 &`ABCD_XYZ = `&<&'something'&>
4940 &`ABCD = `&<&'something else'&>
4942 but putting the definitions in the opposite order would provoke a configuration
4943 error. Macro expansion is applied to individual physical lines from the file,
4944 before checking for line continuation or file inclusion (see above). If a line
4945 consists solely of a macro name, and the expansion of the macro is empty, the
4946 line is ignored. A macro at the start of a line may turn the line into a
4947 comment line or a &`.include`& line.
4950 .section "Redefining macros" "SECID43"
4951 Once defined, the value of a macro can be redefined later in the configuration
4952 (or in an included file). Redefinition is specified by using &'=='& instead of
4957 MAC == updated value
4959 Redefinition does not alter the order in which the macros are applied to the
4960 subsequent lines of the configuration file. It is still the same order in which
4961 the macros were originally defined. All that changes is the macro's value.
4962 Redefinition makes it possible to accumulate values. For example:
4966 MAC == MAC and something added
4968 This can be helpful in situations where the configuration file is built
4969 from a number of other files.
4971 .section "Overriding macro values" "SECID44"
4972 The values set for macros in the configuration file can be overridden by the
4973 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4974 used, unless called by root or the Exim user. A definition on the command line
4975 using the &%-D%& option causes all definitions and redefinitions within the
4980 .section "Example of macro usage" "SECID45"
4981 As an example of macro usage, consider a configuration where aliases are looked
4982 up in a MySQL database. It helps to keep the file less cluttered if long
4983 strings such as SQL statements are defined separately as macros, for example:
4985 ALIAS_QUERY = select mailbox from user where \
4986 login='${quote_mysql:$local_part}';
4988 This can then be used in a &(redirect)& router setting like this:
4990 data = ${lookup mysql{ALIAS_QUERY}}
4992 In earlier versions of Exim macros were sometimes used for domain, host, or
4993 address lists. In Exim 4 these are handled better by named lists &-- see
4994 section &<<SECTnamedlists>>&.
4997 .section "Conditional skips in the configuration file" "SECID46"
4998 .cindex "configuration file" "conditional skips"
4999 .cindex "&`.ifdef`&"
5000 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5001 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5002 portions of the configuration file. The processing happens whenever the file is
5003 read (that is, when an Exim binary starts to run).
5005 The implementation is very simple. Instances of the first four directives must
5006 be followed by text that includes the names of one or macros. The condition
5007 that is tested is whether or not any macro substitution has taken place in the
5011 message_size_limit = 50M
5013 message_size_limit = 100M
5016 sets a message size limit of 50M if the macro &`AAA`& is defined
5017 (or &`A`& or &`AA`&), and 100M
5018 otherwise. If there is more than one macro named on the line, the condition
5019 is true if any of them are defined. That is, it is an &"or"& condition. To
5020 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5022 Although you can use a macro expansion to generate one of these directives,
5023 it is not very useful, because the condition &"there was a macro substitution
5024 in this line"& will always be true.
5026 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5027 to clarify complicated nestings.
5031 .section "Common option syntax" "SECTcos"
5032 .cindex "common option syntax"
5033 .cindex "syntax of common options"
5034 .cindex "configuration file" "common option syntax"
5035 For the main set of options, driver options, and &[local_scan()]& options,
5036 each setting is on a line by itself, and starts with a name consisting of
5037 lower-case letters and underscores. Many options require a data value, and in
5038 these cases the name must be followed by an equals sign (with optional white
5039 space) and then the value. For example:
5041 qualify_domain = mydomain.example.com
5043 .cindex "hiding configuration option values"
5044 .cindex "configuration options" "hiding value of"
5045 .cindex "options" "hiding value of"
5046 Some option settings may contain sensitive data, for example, passwords for
5047 accessing databases. To stop non-admin users from using the &%-bP%& command
5048 line option to read these values, you can precede the option settings with the
5049 word &"hide"&. For example:
5051 hide mysql_servers = localhost/users/admin/secret-password
5053 For non-admin users, such options are displayed like this:
5055 mysql_servers = <value not displayable>
5057 If &"hide"& is used on a driver option, it hides the value of that option on
5058 all instances of the same driver.
5060 The following sections describe the syntax used for the different data types
5061 that are found in option settings.
5064 .section "Boolean options" "SECID47"
5065 .cindex "format" "boolean"
5066 .cindex "boolean configuration values"
5067 .oindex "&%no_%&&'xxx'&"
5068 .oindex "&%not_%&&'xxx'&"
5069 Options whose type is given as boolean are on/off switches. There are two
5070 different ways of specifying such options: with and without a data value. If
5071 the option name is specified on its own without data, the switch is turned on;
5072 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5073 boolean options may be followed by an equals sign and one of the words
5074 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5075 the following two settings have exactly the same effect:
5080 The following two lines also have the same (opposite) effect:
5085 You can use whichever syntax you prefer.
5090 .section "Integer values" "SECID48"
5091 .cindex "integer configuration values"
5092 .cindex "format" "integer"
5093 If an option's type is given as &"integer"&, the value can be given in decimal,
5094 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5095 number is assumed. Otherwise, it is treated as an octal number unless it starts
5096 with the characters &"0x"&, in which case the remainder is interpreted as a
5099 If an integer value is followed by the letter K, it is multiplied by 1024; if
5100 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5101 of integer option settings are output, values which are an exact multiple of
5102 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5103 and M. The printing style is independent of the actual input format that was
5107 .section "Octal integer values" "SECID49"
5108 .cindex "integer format"
5109 .cindex "format" "octal integer"
5110 If an option's type is given as &"octal integer"&, its value is always
5111 interpreted as an octal number, whether or not it starts with the digit zero.
5112 Such options are always output in octal.
5115 .section "Fixed point numbers" "SECID50"
5116 .cindex "fixed point configuration values"
5117 .cindex "format" "fixed point"
5118 If an option's type is given as &"fixed-point"&, its value must be a decimal
5119 integer, optionally followed by a decimal point and up to three further digits.
5123 .section "Time intervals" "SECTtimeformat"
5124 .cindex "time interval" "specifying in configuration"
5125 .cindex "format" "time interval"
5126 A time interval is specified as a sequence of numbers, each followed by one of
5127 the following letters, with no intervening white space:
5137 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5138 intervals are output in the same format. Exim does not restrict the values; it
5139 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5143 .section "String values" "SECTstrings"
5144 .cindex "string" "format of configuration values"
5145 .cindex "format" "string"
5146 If an option's type is specified as &"string"&, the value can be specified with
5147 or without double-quotes. If it does not start with a double-quote, the value
5148 consists of the remainder of the line plus any continuation lines, starting at
5149 the first character after any leading white space, with trailing white space
5150 removed, and with no interpretation of the characters in the string. Because
5151 Exim removes comment lines (those beginning with #) at an early stage, they can
5152 appear in the middle of a multi-line string. The following two settings are
5153 therefore equivalent:
5155 trusted_users = uucp:mail
5156 trusted_users = uucp:\
5157 # This comment line is ignored
5160 .cindex "string" "quoted"
5161 .cindex "escape characters in quoted strings"
5162 If a string does start with a double-quote, it must end with a closing
5163 double-quote, and any backslash characters other than those used for line
5164 continuation are interpreted as escape characters, as follows:
5167 .irow &`\\`& "single backslash"
5168 .irow &`\n`& "newline"
5169 .irow &`\r`& "carriage return"
5171 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5172 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5176 If a backslash is followed by some other character, including a double-quote
5177 character, that character replaces the pair.
5179 Quoting is necessary only if you want to make use of the backslash escapes to
5180 insert special characters, or if you need to specify a value with leading or
5181 trailing spaces. These cases are rare, so quoting is almost never needed in
5182 current versions of Exim. In versions of Exim before 3.14, quoting was required
5183 in order to continue lines, so you may come across older configuration files
5184 and examples that apparently quote unnecessarily.
5187 .section "Expanded strings" "SECID51"
5188 .cindex "expansion" "definition of"
5189 Some strings in the configuration file are subjected to &'string expansion'&,
5190 by which means various parts of the string may be changed according to the
5191 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5192 is as just described; in particular, the handling of backslashes in quoted
5193 strings is done as part of the input process, before expansion takes place.
5194 However, backslash is also an escape character for the expander, so any
5195 backslashes that are required for that reason must be doubled if they are
5196 within a quoted configuration string.
5199 .section "User and group names" "SECID52"
5200 .cindex "user name" "format of"
5201 .cindex "format" "user name"
5202 .cindex "groups" "name format"
5203 .cindex "format" "group name"
5204 User and group names are specified as strings, using the syntax described
5205 above, but the strings are interpreted specially. A user or group name must
5206 either consist entirely of digits, or be a name that can be looked up using the
5207 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5210 .section "List construction" "SECTlistconstruct"
5211 .cindex "list" "syntax of in configuration"
5212 .cindex "format" "list item in configuration"
5213 .cindex "string" "list, definition of"
5214 The data for some configuration options is a list of items, with colon as the
5215 default separator. Many of these options are shown with type &"string list"& in
5216 the descriptions later in this document. Others are listed as &"domain list"&,
5217 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5218 are all the same; however, those other than &"string list"& are subject to
5219 particular kinds of interpretation, as described in chapter
5220 &<<CHAPdomhosaddlists>>&.
5222 In all these cases, the entire list is treated as a single string as far as the
5223 input syntax is concerned. The &%trusted_users%& setting in section
5224 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5225 in a list, it must be entered as two colons. Leading and trailing white space
5226 on each item in a list is ignored. This makes it possible to include items that
5227 start with a colon, and in particular, certain forms of IPv6 address. For
5230 local_interfaces = 127.0.0.1 : ::::1
5232 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5234 &*Note*&: Although leading and trailing white space is ignored in individual
5235 list items, it is not ignored when parsing the list. The space after the first
5236 colon in the example above is necessary. If it were not there, the list would
5237 be interpreted as the two items 127.0.0.1:: and 1.
5239 .section "Changing list separators" "SECTlistsepchange"
5240 .cindex "list separator" "changing"
5241 .cindex "IPv6" "addresses in lists"
5242 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5243 introduced to allow the separator character to be changed. If a list begins
5244 with a left angle bracket, followed by any punctuation character, that
5245 character is used instead of colon as the list separator. For example, the list
5246 above can be rewritten to use a semicolon separator like this:
5248 local_interfaces = <; 127.0.0.1 ; ::1
5250 This facility applies to all lists, with the exception of the list in
5251 &%log_file_path%&. It is recommended that the use of non-colon separators be
5252 confined to circumstances where they really are needed.
5254 .cindex "list separator" "newline as"
5255 .cindex "newline" "as list separator"
5256 It is also possible to use newline and other control characters (those with
5257 code values less than 32, plus DEL) as separators in lists. Such separators
5258 must be provided literally at the time the list is processed. For options that
5259 are string-expanded, you can write the separator using a normal escape
5260 sequence. This will be processed by the expander before the string is
5261 interpreted as a list. For example, if a newline-separated list of domains is
5262 generated by a lookup, you can process it directly by a line such as this:
5264 domains = <\n ${lookup mysql{.....}}
5266 This avoids having to change the list separator in such data. You are unlikely
5267 to want to use a control character as a separator in an option that is not
5268 expanded, because the value is literal text. However, it can be done by giving
5269 the value in quotes. For example:
5271 local_interfaces = "<\n 127.0.0.1 \n ::1"
5273 Unlike printing character separators, which can be included in list items by
5274 doubling, it is not possible to include a control character as data when it is
5275 set as the separator. Two such characters in succession are interpreted as
5276 enclosing an empty list item.
5280 .section "Empty items in lists" "SECTempitelis"
5281 .cindex "list" "empty item in"
5282 An empty item at the end of a list is always ignored. In other words, trailing
5283 separator characters are ignored. Thus, the list in
5285 senders = user@domain :
5287 contains only a single item. If you want to include an empty string as one item
5288 in a list, it must not be the last item. For example, this list contains three
5289 items, the second of which is empty:
5291 senders = user1@domain : : user2@domain
5293 &*Note*&: There must be white space between the two colons, as otherwise they
5294 are interpreted as representing a single colon data character (and the list
5295 would then contain just one item). If you want to specify a list that contains
5296 just one, empty item, you can do it as in this example:
5300 In this case, the first item is empty, and the second is discarded because it
5301 is at the end of the list.
5306 .section "Format of driver configurations" "SECTfordricon"
5307 .cindex "drivers" "configuration format"
5308 There are separate parts in the configuration for defining routers, transports,
5309 and authenticators. In each part, you are defining a number of driver
5310 instances, each with its own set of options. Each driver instance is defined by
5311 a sequence of lines like this:
5313 <&'instance name'&>:
5318 In the following example, the instance name is &(localuser)&, and it is
5319 followed by three options settings:
5324 transport = local_delivery
5326 For each driver instance, you specify which Exim code module it uses &-- by the
5327 setting of the &%driver%& option &-- and (optionally) some configuration
5328 settings. For example, in the case of transports, if you want a transport to
5329 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5330 a local file you would use the &(appendfile)& driver. Each of the drivers is
5331 described in detail in its own separate chapter later in this manual.
5333 You can have several routers, transports, or authenticators that are based on
5334 the same underlying driver (each must have a different instance name).
5336 The order in which routers are defined is important, because addresses are
5337 passed to individual routers one by one, in order. The order in which
5338 transports are defined does not matter at all. The order in which
5339 authenticators are defined is used only when Exim, as a client, is searching
5340 them to find one that matches an authentication mechanism offered by the
5343 .cindex "generic options"
5344 .cindex "options" "generic &-- definition of"
5345 Within a driver instance definition, there are two kinds of option: &'generic'&
5346 and &'private'&. The generic options are those that apply to all drivers of the
5347 same type (that is, all routers, all transports or all authenticators). The
5348 &%driver%& option is a generic option that must appear in every definition.
5349 .cindex "private options"
5350 The private options are special for each driver, and none need appear, because
5351 they all have default values.
5353 The options may appear in any order, except that the &%driver%& option must
5354 precede any private options, since these depend on the particular driver. For
5355 this reason, it is recommended that &%driver%& always be the first option.
5357 Driver instance names, which are used for reference in log entries and
5358 elsewhere, can be any sequence of letters, digits, and underscores (starting
5359 with a letter) and must be unique among drivers of the same type. A router and
5360 a transport (for example) can each have the same name, but no two router
5361 instances can have the same name. The name of a driver instance should not be
5362 confused with the name of the underlying driver module. For example, the
5363 configuration lines:
5368 create an instance of the &(smtp)& transport driver whose name is
5369 &(remote_smtp)&. The same driver code can be used more than once, with
5370 different instance names and different option settings each time. A second
5371 instance of the &(smtp)& transport, with different options, might be defined
5377 command_timeout = 10s
5379 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5380 these transport instances from routers, and these names would appear in log
5383 Comment lines may be present in the middle of driver specifications. The full
5384 list of option settings for any particular driver instance, including all the
5385 defaulted values, can be extracted by making use of the &%-bP%& command line
5393 . ////////////////////////////////////////////////////////////////////////////
5394 . ////////////////////////////////////////////////////////////////////////////
5396 .chapter "The default configuration file" "CHAPdefconfil"
5397 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5398 .cindex "default" "configuration file &""walk through""&"
5399 The default configuration file supplied with Exim as &_src/configure.default_&
5400 is sufficient for a host with simple mail requirements. As an introduction to
5401 the way Exim is configured, this chapter &"walks through"& the default
5402 configuration, giving brief explanations of the settings. Detailed descriptions
5403 of the options are given in subsequent chapters. The default configuration file
5404 itself contains extensive comments about ways you might want to modify the
5405 initial settings. However, note that there are many options that are not
5406 mentioned at all in the default configuration.
5410 .section "Main configuration settings" "SECTdefconfmain"
5411 The main (global) configuration option settings must always come first in the
5412 file. The first thing you'll see in the file, after some initial comments, is
5415 # primary_hostname =
5417 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5418 to know the official, fully qualified name of your host, and this is where you
5419 can specify it. However, in most cases you do not need to set this option. When
5420 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5422 The first three non-comment configuration lines are as follows:
5424 domainlist local_domains = @
5425 domainlist relay_to_domains =
5426 hostlist relay_from_hosts = 127.0.0.1
5428 These are not, in fact, option settings. They are definitions of two named
5429 domain lists and one named host list. Exim allows you to give names to lists of
5430 domains, hosts, and email addresses, in order to make it easier to manage the
5431 configuration file (see section &<<SECTnamedlists>>&).
5433 The first line defines a domain list called &'local_domains'&; this is used
5434 later in the configuration to identify domains that are to be delivered
5437 .cindex "@ in a domain list"
5438 There is just one item in this list, the string &"@"&. This is a special form
5439 of entry which means &"the name of the local host"&. Thus, if the local host is
5440 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5441 be delivered locally. Because the local host's name is referenced indirectly,
5442 the same configuration file can be used on different hosts.
5444 The second line defines a domain list called &'relay_to_domains'&, but the
5445 list itself is empty. Later in the configuration we will come to the part that
5446 controls mail relaying through the local host; it allows relaying to any
5447 domains in this list. By default, therefore, no relaying on the basis of a mail
5448 domain is permitted.
5450 The third line defines a host list called &'relay_from_hosts'&. This list is
5451 used later in the configuration to permit relaying from any host or IP address
5452 that matches the list. The default contains just the IP address of the IPv4
5453 loopback interface, which means that processes on the local host are able to
5454 submit mail for relaying by sending it over TCP/IP to that interface. No other
5455 hosts are permitted to submit messages for relaying.
5457 Just to be sure there's no misunderstanding: at this point in the configuration
5458 we aren't actually setting up any controls. We are just defining some domains
5459 and hosts that will be used in the controls that are specified later.
5461 The next two configuration lines are genuine option settings:
5463 acl_smtp_rcpt = acl_check_rcpt
5464 acl_smtp_data = acl_check_data
5466 These options specify &'Access Control Lists'& (ACLs) that are to be used
5467 during an incoming SMTP session for every recipient of a message (every RCPT
5468 command), and after the contents of the message have been received,
5469 respectively. The names of the lists are &'acl_check_rcpt'& and
5470 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5471 section of the configuration. The RCPT ACL controls which recipients are
5472 accepted for an incoming message &-- if a configuration does not provide an ACL
5473 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5474 contents of a message to be checked.
5476 Two commented-out option settings are next:
5478 # av_scanner = clamd:/tmp/clamd
5479 # spamd_address = 127.0.0.1 783
5481 These are example settings that can be used when Exim is compiled with the
5482 content-scanning extension. The first specifies the interface to the virus
5483 scanner, and the second specifies the interface to SpamAssassin. Further
5484 details are given in chapter &<<CHAPexiscan>>&.
5486 Three more commented-out option settings follow:
5488 # tls_advertise_hosts = *
5489 # tls_certificate = /etc/ssl/exim.crt
5490 # tls_privatekey = /etc/ssl/exim.pem
5492 These are example settings that can be used when Exim is compiled with
5493 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5494 first one specifies the list of clients that are allowed to use TLS when
5495 connecting to this server; in this case the wildcard means all clients. The
5496 other options specify where Exim should find its TLS certificate and private
5497 key, which together prove the server's identity to any clients that connect.
5498 More details are given in chapter &<<CHAPTLS>>&.
5500 Another two commented-out option settings follow:
5502 # daemon_smtp_ports = 25 : 465 : 587
5503 # tls_on_connect_ports = 465
5505 .cindex "port" "465 and 587"
5506 .cindex "port" "for message submission"
5507 .cindex "message" "submission, ports for"
5508 .cindex "ssmtp protocol"
5509 .cindex "smtps protocol"
5510 .cindex "SMTP" "ssmtp protocol"
5511 .cindex "SMTP" "smtps protocol"
5512 These options provide better support for roaming users who wish to use this
5513 server for message submission. They are not much use unless you have turned on
5514 TLS (as described in the previous paragraph) and authentication (about which
5515 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5516 on end-user networks, so RFC 4409 specifies that message submission should use
5517 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5518 configured to use port 587 correctly, so these settings also enable the
5519 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5520 &<<SECTsupobssmt>>&).
5522 Two more commented-out options settings follow:
5525 # qualify_recipient =
5527 The first of these specifies a domain that Exim uses when it constructs a
5528 complete email address from a local login name. This is often needed when Exim
5529 receives a message from a local process. If you do not set &%qualify_domain%&,
5530 the value of &%primary_hostname%& is used. If you set both of these options,
5531 you can have different qualification domains for sender and recipient
5532 addresses. If you set only the first one, its value is used in both cases.
5534 .cindex "domain literal" "recognizing format"
5535 The following line must be uncommented if you want Exim to recognize
5536 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5537 (an IP address within square brackets) instead of a named domain.
5539 # allow_domain_literals
5541 The RFCs still require this form, but many people think that in the modern
5542 Internet it makes little sense to permit mail to be sent to specific hosts by
5543 quoting their IP addresses. This ancient format has been used by people who
5544 try to abuse hosts by using them for unwanted relaying. However, some
5545 people believe there are circumstances (for example, messages addressed to
5546 &'postmaster'&) where domain literals are still useful.
5548 The next configuration line is a kind of trigger guard:
5552 It specifies that no delivery must ever be run as the root user. The normal
5553 convention is to set up &'root'& as an alias for the system administrator. This
5554 setting is a guard against slips in the configuration.
5555 The list of users specified by &%never_users%& is not, however, the complete
5556 list; the build-time configuration in &_Local/Makefile_& has an option called
5557 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5558 contents of &%never_users%& are added to this list. By default
5559 FIXED_NEVER_USERS also specifies root.
5561 When a remote host connects to Exim in order to send mail, the only information
5562 Exim has about the host's identity is its IP address. The next configuration
5567 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5568 in order to get a host name. This improves the quality of the logging
5569 information, but if you feel it is too expensive, you can remove it entirely,
5570 or restrict the lookup to hosts on &"nearby"& networks.
5571 Note that it is not always possible to find a host name from an IP address,
5572 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5575 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5576 1413 (hence their names):
5579 rfc1413_query_timeout = 0s
5581 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5582 Few hosts offer RFC1413 service these days; calls have to be
5583 terminated by a timeout and this needlessly delays the startup
5584 of an incoming SMTP connection.
5585 If you have hosts for which you trust RFC1413 and need this
5586 information, you can change this.
5588 This line enables an efficiency SMTP option. It is negotiated by clients
5589 and not expected to cause problems but can be disabled if needed.
5594 When Exim receives messages over SMTP connections, it expects all addresses to
5595 be fully qualified with a domain, as required by the SMTP definition. However,
5596 if you are running a server to which simple clients submit messages, you may
5597 find that they send unqualified addresses. The two commented-out options:
5599 # sender_unqualified_hosts =
5600 # recipient_unqualified_hosts =
5602 show how you can specify hosts that are permitted to send unqualified sender
5603 and recipient addresses, respectively.
5605 The &%log_selector%& option is used to increase the detail of logging
5608 log_selector = +smtp_protocol_error +smtp_syntax_error \
5609 +tls_certificate_verified
5612 The &%percent_hack_domains%& option is also commented out:
5614 # percent_hack_domains =
5616 It provides a list of domains for which the &"percent hack"& is to operate.
5617 This is an almost obsolete form of explicit email routing. If you do not know
5618 anything about it, you can safely ignore this topic.
5620 The last two settings in the main part of the default configuration are
5621 concerned with messages that have been &"frozen"& on Exim's queue. When a
5622 message is frozen, Exim no longer continues to try to deliver it. Freezing
5623 occurs when a bounce message encounters a permanent failure because the sender
5624 address of the original message that caused the bounce is invalid, so the
5625 bounce cannot be delivered. This is probably the most common case, but there
5626 are also other conditions that cause freezing, and frozen messages are not
5627 always bounce messages.
5629 ignore_bounce_errors_after = 2d
5630 timeout_frozen_after = 7d
5632 The first of these options specifies that failing bounce messages are to be
5633 discarded after 2 days on the queue. The second specifies that any frozen
5634 message (whether a bounce message or not) is to be timed out (and discarded)
5635 after a week. In this configuration, the first setting ensures that no failing
5636 bounce message ever lasts a week.
5640 .section "ACL configuration" "SECID54"
5641 .cindex "default" "ACLs"
5642 .cindex "&ACL;" "default configuration"
5643 In the default configuration, the ACL section follows the main configuration.
5644 It starts with the line
5648 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5649 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5650 and &%acl_smtp_data%& above.
5652 .cindex "RCPT" "ACL for"
5653 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5654 RCPT command specifies one of the message's recipients. The ACL statements
5655 are considered in order, until the recipient address is either accepted or
5656 rejected. The RCPT command is then accepted or rejected, according to the
5657 result of the ACL processing.
5661 This line, consisting of a name terminated by a colon, marks the start of the
5666 This ACL statement accepts the recipient if the sending host matches the list.
5667 But what does that strange list mean? It doesn't actually contain any host
5668 names or IP addresses. The presence of the colon puts an empty item in the
5669 list; Exim matches this only if the incoming message did not come from a remote
5670 host, because in that case, the remote hostname is empty. The colon is
5671 important. Without it, the list itself is empty, and can never match anything.
5673 What this statement is doing is to accept unconditionally all recipients in
5674 messages that are submitted by SMTP from local processes using the standard
5675 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5678 deny message = Restricted characters in address
5679 domains = +local_domains
5680 local_parts = ^[.] : ^.*[@%!/|]
5682 deny message = Restricted characters in address
5683 domains = !+local_domains
5684 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5686 These statements are concerned with local parts that contain any of the
5687 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5688 Although these characters are entirely legal in local parts (in the case of
5689 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5690 in Internet mail addresses.
5692 The first three have in the past been associated with explicitly routed
5693 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5694 option). Addresses containing these characters are regularly tried by spammers
5695 in an attempt to bypass relaying restrictions, and also by open relay testing
5696 programs. Unless you really need them it is safest to reject these characters
5697 at this early stage. This configuration is heavy-handed in rejecting these
5698 characters for all messages it accepts from remote hosts. This is a deliberate
5699 policy of being as safe as possible.
5701 The first rule above is stricter, and is applied to messages that are addressed
5702 to one of the local domains handled by this host. This is implemented by the
5703 first condition, which restricts it to domains that are listed in the
5704 &'local_domains'& domain list. The &"+"& character is used to indicate a
5705 reference to a named list. In this configuration, there is just one domain in
5706 &'local_domains'&, but in general there may be many.
5708 The second condition on the first statement uses two regular expressions to
5709 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5710 or &"|"&. If you have local accounts that include these characters, you will
5711 have to modify this rule.
5713 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5714 allows them because they have been encountered in practice. (Consider the
5715 common convention of local parts constructed as
5716 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5717 the author of Exim, who has no second initial.) However, a local part starting
5718 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5719 file name (for example, for a mailing list). This is also true for local parts
5720 that contain slashes. A pipe symbol can also be troublesome if the local part
5721 is incorporated unthinkingly into a shell command line.
5723 The second rule above applies to all other domains, and is less strict. This
5724 allows your own users to send outgoing messages to sites that use slashes
5725 and vertical bars in their local parts. It blocks local parts that begin
5726 with a dot, slash, or vertical bar, but allows these characters within the
5727 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5728 and &"!"& is blocked, as before. The motivation here is to prevent your users
5729 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5731 accept local_parts = postmaster
5732 domains = +local_domains
5734 This statement, which has two conditions, accepts an incoming address if the
5735 local part is &'postmaster'& and the domain is one of those listed in the
5736 &'local_domains'& domain list. The &"+"& character is used to indicate a
5737 reference to a named list. In this configuration, there is just one domain in
5738 &'local_domains'&, but in general there may be many.
5740 The presence of this statement means that mail to postmaster is never blocked
5741 by any of the subsequent tests. This can be helpful while sorting out problems
5742 in cases where the subsequent tests are incorrectly denying access.
5744 require verify = sender
5746 This statement requires the sender address to be verified before any subsequent
5747 ACL statement can be used. If verification fails, the incoming recipient
5748 address is refused. Verification consists of trying to route the address, to
5749 see if a bounce message could be delivered to it. In the case of remote
5750 addresses, basic verification checks only the domain, but &'callouts'& can be
5751 used for more verification if required. Section &<<SECTaddressverification>>&
5752 discusses the details of address verification.
5754 accept hosts = +relay_from_hosts
5755 control = submission
5757 This statement accepts the address if the message is coming from one of the
5758 hosts that are defined as being allowed to relay through this host. Recipient
5759 verification is omitted here, because in many cases the clients are dumb MUAs
5760 that do not cope well with SMTP error responses. For the same reason, the
5761 second line specifies &"submission mode"& for messages that are accepted. This
5762 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5763 messages that are deficient in some way, for example, because they lack a
5764 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5765 probably add recipient verification here, and disable submission mode.
5767 accept authenticated = *
5768 control = submission
5770 This statement accepts the address if the client host has authenticated itself.
5771 Submission mode is again specified, on the grounds that such messages are most
5772 likely to come from MUAs. The default configuration does not define any
5773 authenticators, though it does include some nearly complete commented-out
5774 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5775 fact authenticate until you complete the authenticator definitions.
5777 require message = relay not permitted
5778 domains = +local_domains : +relay_to_domains
5780 This statement rejects the address if its domain is neither a local domain nor
5781 one of the domains for which this host is a relay.
5783 require verify = recipient
5785 This statement requires the recipient address to be verified; if verification
5786 fails, the address is rejected.
5788 # deny message = rejected because $sender_host_address \
5789 # is in a black list at $dnslist_domain\n\
5791 # dnslists = black.list.example
5793 # warn dnslists = black.list.example
5794 # add_header = X-Warning: $sender_host_address is in \
5795 # a black list at $dnslist_domain
5796 # log_message = found in $dnslist_domain
5798 These commented-out lines are examples of how you could configure Exim to check
5799 sending hosts against a DNS black list. The first statement rejects messages
5800 from blacklisted hosts, whereas the second just inserts a warning header
5803 # require verify = csa
5805 This commented-out line is an example of how you could turn on client SMTP
5806 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5811 The final statement in the first ACL unconditionally accepts any recipient
5812 address that has successfully passed all the previous tests.
5816 This line marks the start of the second ACL, and names it. Most of the contents
5817 of this ACL are commented out:
5820 # message = This message contains a virus \
5823 These lines are examples of how to arrange for messages to be scanned for
5824 viruses when Exim has been compiled with the content-scanning extension, and a
5825 suitable virus scanner is installed. If the message is found to contain a
5826 virus, it is rejected with the given custom error message.
5828 # warn spam = nobody
5829 # message = X-Spam_score: $spam_score\n\
5830 # X-Spam_score_int: $spam_score_int\n\
5831 # X-Spam_bar: $spam_bar\n\
5832 # X-Spam_report: $spam_report
5834 These lines are an example of how to arrange for messages to be scanned by
5835 SpamAssassin when Exim has been compiled with the content-scanning extension,
5836 and SpamAssassin has been installed. The SpamAssassin check is run with
5837 &`nobody`& as its user parameter, and the results are added to the message as a
5838 series of extra header line. In this case, the message is not rejected,
5839 whatever the spam score.
5843 This final line in the DATA ACL accepts the message unconditionally.
5846 .section "Router configuration" "SECID55"
5847 .cindex "default" "routers"
5848 .cindex "routers" "default"
5849 The router configuration comes next in the default configuration, introduced
5854 Routers are the modules in Exim that make decisions about where to send
5855 messages. An address is passed to each router in turn, until it is either
5856 accepted, or failed. This means that the order in which you define the routers
5857 matters. Each router is fully described in its own chapter later in this
5858 manual. Here we give only brief overviews.
5861 # driver = ipliteral
5862 # domains = !+local_domains
5863 # transport = remote_smtp
5865 .cindex "domain literal" "default router"
5866 This router is commented out because the majority of sites do not want to
5867 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5868 you uncomment this router, you also need to uncomment the setting of
5869 &%allow_domain_literals%& in the main part of the configuration.
5873 domains = ! +local_domains
5874 transport = remote_smtp
5875 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5878 The first uncommented router handles addresses that do not involve any local
5879 domains. This is specified by the line
5881 domains = ! +local_domains
5883 The &%domains%& option lists the domains to which this router applies, but the
5884 exclamation mark is a negation sign, so the router is used only for domains
5885 that are not in the domain list called &'local_domains'& (which was defined at
5886 the start of the configuration). The plus sign before &'local_domains'&
5887 indicates that it is referring to a named list. Addresses in other domains are
5888 passed on to the following routers.
5890 The name of the router driver is &(dnslookup)&,
5891 and is specified by the &%driver%& option. Do not be confused by the fact that
5892 the name of this router instance is the same as the name of the driver. The
5893 instance name is arbitrary, but the name set in the &%driver%& option must be
5894 one of the driver modules that is in the Exim binary.
5896 The &(dnslookup)& router routes addresses by looking up their domains in the
5897 DNS in order to obtain a list of hosts to which the address is routed. If the
5898 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5899 specified by the &%transport%& option. If the router does not find the domain
5900 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5901 the address fails and is bounced.
5903 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5904 be entirely ignored. This option is present because a number of cases have been
5905 encountered where MX records in the DNS point to host names
5906 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5907 Completely ignoring these IP addresses causes Exim to fail to route the
5908 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5909 continue to try to deliver the message periodically until the address timed
5916 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5918 file_transport = address_file
5919 pipe_transport = address_pipe
5921 Control reaches this and subsequent routers only for addresses in the local
5922 domains. This router checks to see whether the local part is defined as an
5923 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5924 data that it looks up from that file. If no data is found for the local part,
5925 the value of the &%data%& option is empty, causing the address to be passed to
5928 &_/etc/aliases_& is a conventional name for the system aliases file that is
5929 often used. That is why it is referenced by from the default configuration
5930 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5931 &_Local/Makefile_& before building Exim.
5936 # local_part_suffix = +* : -*
5937 # local_part_suffix_optional
5938 file = $home/.forward
5943 file_transport = address_file
5944 pipe_transport = address_pipe
5945 reply_transport = address_reply
5947 This is the most complicated router in the default configuration. It is another
5948 redirection router, but this time it is looking for forwarding data set up by
5949 individual users. The &%check_local_user%& setting specifies a check that the
5950 local part of the address is the login name of a local user. If it is not, the
5951 router is skipped. The two commented options that follow &%check_local_user%&,
5954 # local_part_suffix = +* : -*
5955 # local_part_suffix_optional
5957 .vindex "&$local_part_suffix$&"
5958 show how you can specify the recognition of local part suffixes. If the first
5959 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5960 by any sequence of characters, is removed from the local part and placed in the
5961 variable &$local_part_suffix$&. The second suffix option specifies that the
5962 presence of a suffix in the local part is optional. When a suffix is present,
5963 the check for a local login uses the local part with the suffix removed.
5965 When a local user account is found, the file called &_.forward_& in the user's
5966 home directory is consulted. If it does not exist, or is empty, the router
5967 declines. Otherwise, the contents of &_.forward_& are interpreted as
5968 redirection data (see chapter &<<CHAPredirect>>& for more details).
5970 .cindex "Sieve filter" "enabling in default router"
5971 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5972 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5973 is commented out by default), the contents of the file are interpreted as a set
5974 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5975 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5976 separate document entitled &'Exim's interfaces to mail filtering'&.
5978 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5979 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5980 There are two reasons for doing this:
5983 Whether or not a local user has a &_.forward_& file is not really relevant when
5984 checking an address for validity; it makes sense not to waste resources doing
5987 More importantly, when Exim is verifying addresses or handling an EXPN
5988 command during an SMTP session, it is running as the Exim user, not as root.
5989 The group is the Exim group, and no additional groups are set up.
5990 It may therefore not be possible for Exim to read users' &_.forward_& files at
5994 The setting of &%check_ancestor%& prevents the router from generating a new
5995 address that is the same as any previous address that was redirected. (This
5996 works round a problem concerning a bad interaction between aliasing and
5997 forwarding &-- see section &<<SECTredlocmai>>&).
5999 The final three option settings specify the transports that are to be used when
6000 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6001 auto-reply, respectively. For example, if a &_.forward_& file contains
6003 a.nother@elsewhere.example, /home/spqr/archive
6005 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6011 # local_part_suffix = +* : -*
6012 # local_part_suffix_optional
6013 transport = local_delivery
6015 The final router sets up delivery into local mailboxes, provided that the local
6016 part is the name of a local login, by accepting the address and assigning it to
6017 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6018 routers, so the address is bounced. The commented suffix settings fulfil the
6019 same purpose as they do for the &(userforward)& router.
6022 .section "Transport configuration" "SECID56"
6023 .cindex "default" "transports"
6024 .cindex "transports" "default"
6025 Transports define mechanisms for actually delivering messages. They operate
6026 only when referenced from routers, so the order in which they are defined does
6027 not matter. The transports section of the configuration starts with
6031 One remote transport and four local transports are defined.
6037 This transport is used for delivering messages over SMTP connections.
6038 The list of remote hosts comes from the router.
6039 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6040 It is negotiated between client and server
6041 and not expected to cause problems but can be disabled if needed.
6042 All other options are defaulted.
6046 file = /var/mail/$local_part
6053 This &(appendfile)& transport is used for local delivery to user mailboxes in
6054 traditional BSD mailbox format. By default it runs under the uid and gid of the
6055 local user, which requires the sticky bit to be set on the &_/var/mail_&
6056 directory. Some systems use the alternative approach of running mail deliveries
6057 under a particular group instead of using the sticky bit. The commented options
6058 show how this can be done.
6060 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6061 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6062 similarly-named options above.
6068 This transport is used for handling deliveries to pipes that are generated by
6069 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6070 option specifies that any output on stdout or stderr generated by the pipe is to
6071 be returned to the sender.
6079 This transport is used for handling deliveries to files that are generated by
6080 redirection. The name of the file is not specified in this instance of
6081 &(appendfile)&, because it comes from the &(redirect)& router.
6086 This transport is used for handling automatic replies generated by users'
6091 .section "Default retry rule" "SECID57"
6092 .cindex "retry" "default rule"
6093 .cindex "default" "retry rule"
6094 The retry section of the configuration file contains rules which affect the way
6095 Exim retries deliveries that cannot be completed at the first attempt. It is
6096 introduced by the line
6100 In the default configuration, there is just one rule, which applies to all
6103 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6105 This causes any temporarily failing address to be retried every 15 minutes for
6106 2 hours, then at intervals starting at one hour and increasing by a factor of
6107 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6108 is not delivered after 4 days of temporary failure, it is bounced.
6110 If the retry section is removed from the configuration, or is empty (that is,
6111 if no retry rules are defined), Exim will not retry deliveries. This turns
6112 temporary errors into permanent errors.
6115 .section "Rewriting configuration" "SECID58"
6116 The rewriting section of the configuration, introduced by
6120 contains rules for rewriting addresses in messages as they arrive. There are no
6121 rewriting rules in the default configuration file.
6125 .section "Authenticators configuration" "SECTdefconfauth"
6126 .cindex "AUTH" "configuration"
6127 The authenticators section of the configuration, introduced by
6129 begin authenticators
6131 defines mechanisms for the use of the SMTP AUTH command. The default
6132 configuration file contains two commented-out example authenticators
6133 which support plaintext username/password authentication using the
6134 standard PLAIN mechanism and the traditional but non-standard LOGIN
6135 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6136 to support most MUA software.
6138 The example PLAIN authenticator looks like this:
6141 # driver = plaintext
6142 # server_set_id = $auth2
6143 # server_prompts = :
6144 # server_condition = Authentication is not yet configured
6145 # server_advertise_condition = ${if def:tls_in_cipher }
6147 And the example LOGIN authenticator looks like this:
6150 # driver = plaintext
6151 # server_set_id = $auth1
6152 # server_prompts = <| Username: | Password:
6153 # server_condition = Authentication is not yet configured
6154 # server_advertise_condition = ${if def:tls_in_cipher }
6157 The &%server_set_id%& option makes Exim remember the authenticated username
6158 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6159 &%server_prompts%& option configures the &(plaintext)& authenticator so
6160 that it implements the details of the specific authentication mechanism,
6161 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6162 when Exim offers authentication to clients; in the examples, this is only
6163 when TLS or SSL has been started, so to enable the authenticators you also
6164 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6166 The &%server_condition%& setting defines how to verify that the username and
6167 password are correct. In the examples it just produces an error message.
6168 To make the authenticators work, you can use a string expansion
6169 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6171 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6172 usercode and password are in different positions.
6173 Chapter &<<CHAPplaintext>>& covers both.
6175 .ecindex IIDconfiwal
6179 . ////////////////////////////////////////////////////////////////////////////
6180 . ////////////////////////////////////////////////////////////////////////////
6182 .chapter "Regular expressions" "CHAPregexp"
6184 .cindex "regular expressions" "library"
6186 Exim supports the use of regular expressions in many of its options. It
6187 uses the PCRE regular expression library; this provides regular expression
6188 matching that is compatible with Perl 5. The syntax and semantics of
6189 regular expressions is discussed in many Perl reference books, and also in
6190 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6191 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6193 The documentation for the syntax and semantics of the regular expressions that
6194 are supported by PCRE is included in the PCRE distribution, and no further
6195 description is included here. The PCRE functions are called from Exim using
6196 the default option settings (that is, with no PCRE options set), except that
6197 the PCRE_CASELESS option is set when the matching is required to be
6200 In most cases, when a regular expression is required in an Exim configuration,
6201 it has to start with a circumflex, in order to distinguish it from plain text
6202 or an &"ends with"& wildcard. In this example of a configuration setting, the
6203 second item in the colon-separated list is a regular expression.
6205 domains = a.b.c : ^\\d{3} : *.y.z : ...
6207 The doubling of the backslash is required because of string expansion that
6208 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6209 of this issue, and a way of avoiding the need for doubling backslashes. The
6210 regular expression that is eventually used in this example contains just one
6211 backslash. The circumflex is included in the regular expression, and has the
6212 normal effect of &"anchoring"& it to the start of the string that is being
6215 There are, however, two cases where a circumflex is not required for the
6216 recognition of a regular expression: these are the &%match%& condition in a
6217 string expansion, and the &%matches%& condition in an Exim filter file. In
6218 these cases, the relevant string is always treated as a regular expression; if
6219 it does not start with a circumflex, the expression is not anchored, and can
6220 match anywhere in the subject string.
6222 In all cases, if you want a regular expression to match at the end of a string,
6223 you must code the $ metacharacter to indicate this. For example:
6225 domains = ^\\d{3}\\.example
6227 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6230 domains = ^\\d{3}\\.example\$
6232 if you want &'example'& to be the top-level domain. The backslash before the
6233 $ is needed because string expansion also interprets dollar characters.
6237 . ////////////////////////////////////////////////////////////////////////////
6238 . ////////////////////////////////////////////////////////////////////////////
6240 .chapter "File and database lookups" "CHAPfdlookup"
6241 .scindex IIDfidalo1 "file" "lookups"
6242 .scindex IIDfidalo2 "database" "lookups"
6243 .cindex "lookup" "description of"
6244 Exim can be configured to look up data in files or databases as it processes
6245 messages. Two different kinds of syntax are used:
6248 A string that is to be expanded may contain explicit lookup requests. These
6249 cause parts of the string to be replaced by data that is obtained from the
6250 lookup. Lookups of this type are conditional expansion items. Different results
6251 can be defined for the cases of lookup success and failure. See chapter
6252 &<<CHAPexpand>>&, where string expansions are described in detail.
6253 The key for the lookup is specified as part of the string expansion.
6255 Lists of domains, hosts, and email addresses can contain lookup requests as a
6256 way of avoiding excessively long linear lists. In this case, the data that is
6257 returned by the lookup is often (but not always) discarded; whether the lookup
6258 succeeds or fails is what really counts. These kinds of list are described in
6259 chapter &<<CHAPdomhosaddlists>>&.
6260 The key for the lookup is given by the context in which the list is expanded.
6263 String expansions, lists, and lookups interact with each other in such a way
6264 that there is no order in which to describe any one of them that does not
6265 involve references to the others. Each of these three chapters makes more sense
6266 if you have read the other two first. If you are reading this for the first
6267 time, be aware that some of it will make a lot more sense after you have read
6268 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6270 .section "Examples of different lookup syntax" "SECID60"
6271 It is easy to confuse the two different kinds of lookup, especially as the
6272 lists that may contain the second kind are always expanded before being
6273 processed as lists. Therefore, they may also contain lookups of the first kind.
6274 Be careful to distinguish between the following two examples:
6276 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6277 domains = lsearch;/some/file
6279 The first uses a string expansion, the result of which must be a domain list.
6280 No strings have been specified for a successful or a failing lookup; the
6281 defaults in this case are the looked-up data and an empty string, respectively.
6282 The expansion takes place before the string is processed as a list, and the
6283 file that is searched could contain lines like this:
6285 192.168.3.4: domain1:domain2:...
6286 192.168.1.9: domain3:domain4:...
6288 When the lookup succeeds, the result of the expansion is a list of domains (and
6289 possibly other types of item that are allowed in domain lists).
6291 In the second example, the lookup is a single item in a domain list. It causes
6292 Exim to use a lookup to see if the domain that is being processed can be found
6293 in the file. The file could contains lines like this:
6298 Any data that follows the keys is not relevant when checking that the domain
6299 matches the list item.
6301 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6302 Consider a file containing lines like this:
6304 192.168.5.6: lsearch;/another/file
6306 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6307 first &%domains%& setting above generates the second setting, which therefore
6308 causes a second lookup to occur.
6310 The rest of this chapter describes the different lookup types that are
6311 available. Any of them can be used in any part of the configuration where a
6312 lookup is permitted.
6315 .section "Lookup types" "SECID61"
6316 .cindex "lookup" "types of"
6317 .cindex "single-key lookup" "definition of"
6318 Two different types of data lookup are implemented:
6321 The &'single-key'& type requires the specification of a file in which to look,
6322 and a single key to search for. The key must be a non-empty string for the
6323 lookup to succeed. The lookup type determines how the file is searched.
6325 .cindex "query-style lookup" "definition of"
6326 The &'query-style'& type accepts a generalized database query. No particular
6327 key value is assumed by Exim for query-style lookups. You can use whichever
6328 Exim variables you need to construct the database query.
6331 The code for each lookup type is in a separate source file that is included in
6332 the binary of Exim only if the corresponding compile-time option is set. The
6333 default settings in &_src/EDITME_& are:
6338 which means that only linear searching and DBM lookups are included by default.
6339 For some types of lookup (e.g. SQL databases), you need to install appropriate
6340 libraries and header files before building Exim.
6345 .section "Single-key lookup types" "SECTsinglekeylookups"
6346 .cindex "lookup" "single-key types"
6347 .cindex "single-key lookup" "list of types"
6348 The following single-key lookup types are implemented:
6351 .cindex "cdb" "description of"
6352 .cindex "lookup" "cdb"
6353 .cindex "binary zero" "in lookup key"
6354 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6355 string without a terminating binary zero. The cdb format is designed for
6356 indexed files that are read frequently and never updated, except by total
6357 re-creation. As such, it is particularly suitable for large files containing
6358 aliases or other indexed data referenced by an MTA. Information about cdb can
6359 be found in several places:
6361 &url(http://www.pobox.com/~djb/cdb.html)
6362 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6363 &url(http://packages.debian.org/stable/utils/freecdb.html)
6365 A cdb distribution is not needed in order to build Exim with cdb support,
6366 because the code for reading cdb files is included directly in Exim itself.
6367 However, no means of building or testing cdb files is provided with Exim, so
6368 you need to obtain a cdb distribution in order to do this.
6370 .cindex "DBM" "lookup type"
6371 .cindex "lookup" "dbm"
6372 .cindex "binary zero" "in lookup key"
6373 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6374 DBM file by looking up the record with the given key. A terminating binary
6375 zero is included in the key that is passed to the DBM library. See section
6376 &<<SECTdb>>& for a discussion of DBM libraries.
6378 .cindex "Berkeley DB library" "file format"
6379 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6380 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6381 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6382 the DB_UNKNOWN option. This enables it to handle any of the types of database
6383 that the library supports, and can be useful for accessing DBM files created by
6384 other applications. (For earlier DB versions, DB_HASH is always used.)
6386 .cindex "lookup" "dbmjz"
6387 .cindex "lookup" "dbm &-- embedded NULs"
6389 .cindex "dbmjz lookup type"
6390 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6391 interpreted as an Exim list; the elements of the list are joined together with
6392 ASCII NUL characters to form the lookup key. An example usage would be to
6393 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6394 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6395 &(cram_md5)& authenticator.
6397 .cindex "lookup" "dbmnz"
6398 .cindex "lookup" "dbm &-- terminating zero"
6399 .cindex "binary zero" "in lookup key"
6401 .cindex "&_/etc/userdbshadow.dat_&"
6402 .cindex "dbmnz lookup type"
6403 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6404 is not included in the key that is passed to the DBM library. You may need this
6405 if you want to look up data in files that are created by or shared with some
6406 other application that does not use terminating zeros. For example, you need to
6407 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6408 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6409 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6410 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6412 .cindex "lookup" "dsearch"
6413 .cindex "dsearch lookup type"
6414 &(dsearch)&: The given file must be a directory; this is searched for an entry
6415 whose name is the key by calling the &[lstat()]& function. The key may not
6416 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6417 the lookup is the name of the entry, which may be a file, directory,
6418 symbolic link, or any other kind of directory entry. An example of how this
6419 lookup can be used to support virtual domains is given in section
6420 &<<SECTvirtualdomains>>&.
6422 .cindex "lookup" "iplsearch"
6423 .cindex "iplsearch lookup type"
6424 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6425 terminated by a colon or white space or the end of the line. The keys in the
6426 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6427 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6428 being interpreted as a key terminator. For example:
6430 1.2.3.4: data for 1.2.3.4
6431 192.168.0.0/16: data for 192.168.0.0/16
6432 "abcd::cdab": data for abcd::cdab
6433 "abcd:abcd::/32" data for abcd:abcd::/32
6435 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6436 file is searched linearly, using the CIDR masks where present, until a matching
6437 key is found. The first key that matches is used; there is no attempt to find a
6438 &"best"& match. Apart from the way the keys are matched, the processing for
6439 &(iplsearch)& is the same as for &(lsearch)&.
6441 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6442 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6443 lookup types support only literal keys.
6445 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6446 the implicit key is the host's IP address rather than its name (see section
6447 &<<SECThoslispatsikey>>&).
6449 .cindex "linear search"
6450 .cindex "lookup" "lsearch"
6451 .cindex "lsearch lookup type"
6452 .cindex "case sensitivity" "in lsearch lookup"
6453 &(lsearch)&: The given file is a text file that is searched linearly for a
6454 line beginning with the search key, terminated by a colon or white space or the
6455 end of the line. The search is case-insensitive; that is, upper and lower case
6456 letters are treated as the same. The first occurrence of the key that is found
6457 in the file is used.
6459 White space between the key and the colon is permitted. The remainder of the
6460 line, with leading and trailing white space removed, is the data. This can be
6461 continued onto subsequent lines by starting them with any amount of white
6462 space, but only a single space character is included in the data at such a
6463 junction. If the data begins with a colon, the key must be terminated by a
6468 Empty lines and lines beginning with # are ignored, even if they occur in the
6469 middle of an item. This is the traditional textual format of alias files. Note
6470 that the keys in an &(lsearch)& file are literal strings. There is no
6471 wildcarding of any kind.
6473 .cindex "lookup" "lsearch &-- colons in keys"
6474 .cindex "white space" "in lsearch key"
6475 In most &(lsearch)& files, keys are not required to contain colons or #
6476 characters, or white space. However, if you need this feature, it is available.
6477 If a key begins with a doublequote character, it is terminated only by a
6478 matching quote (or end of line), and the normal escaping rules apply to its
6479 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6480 quoted keys (exactly as for unquoted keys). There is no special handling of
6481 quotes for the data part of an &(lsearch)& line.
6484 .cindex "NIS lookup type"
6485 .cindex "lookup" "NIS"
6486 .cindex "binary zero" "in lookup key"
6487 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6488 the given key, without a terminating binary zero. There is a variant called
6489 &(nis0)& which does include the terminating binary zero in the key. This is
6490 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6491 aliases; the full map names must be used.
6494 .cindex "wildlsearch lookup type"
6495 .cindex "lookup" "wildlsearch"
6496 .cindex "nwildlsearch lookup type"
6497 .cindex "lookup" "nwildlsearch"
6498 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6499 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6500 the file may be wildcarded. The difference between these two lookup types is
6501 that for &(wildlsearch)&, each key in the file is string-expanded before being
6502 used, whereas for &(nwildlsearch)&, no expansion takes place.
6504 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6505 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6506 file that are regular expressions can be made case-sensitive by the use of
6507 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6509 . ==== As this is a nested list, any displays it contains must be indented
6510 . ==== as otherwise they are too far to the left.
6513 The string may begin with an asterisk to mean &"ends with"&. For example:
6515 *.a.b.c data for anything.a.b.c
6516 *fish data for anythingfish
6519 The string may begin with a circumflex to indicate a regular expression. For
6520 example, for &(wildlsearch)&:
6522 ^\N\d+\.a\.b\N data for <digits>.a.b
6524 Note the use of &`\N`& to disable expansion of the contents of the regular
6525 expression. If you are using &(nwildlsearch)&, where the keys are not
6526 string-expanded, the equivalent entry is:
6528 ^\d+\.a\.b data for <digits>.a.b
6530 The case-insensitive flag is set at the start of compiling the regular
6531 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6532 For example, to make the entire pattern case-sensitive:
6534 ^(?-i)\d+\.a\.b data for <digits>.a.b
6537 If the regular expression contains white space or colon characters, you must
6538 either quote it (see &(lsearch)& above), or represent these characters in other
6539 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6540 colon. This may be easier than quoting, because if you quote, you have to
6541 escape all the backslashes inside the quotes.
6543 &*Note*&: It is not possible to capture substrings in a regular expression
6544 match for later use, because the results of all lookups are cached. If a lookup
6545 is repeated, the result is taken from the cache, and no actual pattern matching
6546 takes place. The values of all the numeric variables are unset after a
6547 &((n)wildlsearch)& match.
6550 Although I cannot see it being of much use, the general matching function that
6551 is used to implement &((n)wildlsearch)& means that the string may begin with a
6552 lookup name terminated by a semicolon, and followed by lookup data. For
6555 cdb;/some/file data for keys that match the file
6557 The data that is obtained from the nested lookup is discarded.
6560 Keys that do not match any of these patterns are interpreted literally. The
6561 continuation rules for the data are the same as for &(lsearch)&, and keys may
6562 be followed by optional colons.
6564 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6565 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6566 lookup types support only literal keys.
6570 .section "Query-style lookup types" "SECID62"
6571 .cindex "lookup" "query-style types"
6572 .cindex "query-style lookup" "list of types"
6573 The supported query-style lookup types are listed below. Further details about
6574 many of them are given in later sections.
6577 .cindex "DNS" "as a lookup type"
6578 .cindex "lookup" "DNS"
6579 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6580 are given in the supplied query. The resulting data is the contents of the
6581 records. See section &<<SECTdnsdb>>&.
6583 .cindex "InterBase lookup type"
6584 .cindex "lookup" "InterBase"
6585 &(ibase)&: This does a lookup in an InterBase database.
6587 .cindex "LDAP" "lookup type"
6588 .cindex "lookup" "LDAP"
6589 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6590 returns attributes from a single entry. There is a variant called &(ldapm)&
6591 that permits values from multiple entries to be returned. A third variant
6592 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6593 any attribute values. See section &<<SECTldap>>&.
6595 .cindex "MySQL" "lookup type"
6596 .cindex "lookup" "MySQL"
6597 &(mysql)&: The format of the query is an SQL statement that is passed to a
6598 MySQL database. See section &<<SECTsql>>&.
6600 .cindex "NIS+ lookup type"
6601 .cindex "lookup" "NIS+"
6602 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6603 the field to be returned. See section &<<SECTnisplus>>&.
6605 .cindex "Oracle" "lookup type"
6606 .cindex "lookup" "Oracle"
6607 &(oracle)&: The format of the query is an SQL statement that is passed to an
6608 Oracle database. See section &<<SECTsql>>&.
6610 .cindex "lookup" "passwd"
6611 .cindex "passwd lookup type"
6612 .cindex "&_/etc/passwd_&"
6613 &(passwd)& is a query-style lookup with queries that are just user names. The
6614 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6615 success, the result string is the same as you would get from an &(lsearch)&
6616 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6617 password value. For example:
6619 *:42:42:King Rat:/home/kr:/bin/bash
6622 .cindex "PostgreSQL lookup type"
6623 .cindex "lookup" "PostgreSQL"
6624 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6625 PostgreSQL database. See section &<<SECTsql>>&.
6628 .cindex "sqlite lookup type"
6629 .cindex "lookup" "sqlite"
6630 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6631 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6634 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6635 not likely to be useful in normal operation.
6637 .cindex "whoson lookup type"
6638 .cindex "lookup" "whoson"
6639 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6640 allows a server to check whether a particular (dynamically allocated) IP
6641 address is currently allocated to a known (trusted) user and, optionally, to
6642 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6643 at one time for &"POP before SMTP"& authentication, but that approach has been
6644 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6645 &"POP before SMTP"& checking using ACL statements such as
6647 require condition = \
6648 ${lookup whoson {$sender_host_address}{yes}{no}}
6650 The query consists of a single IP address. The value returned is the name of
6651 the authenticated user, which is stored in the variable &$value$&. However, in
6652 this example, the data in &$value$& is not used; the result of the lookup is
6653 one of the fixed strings &"yes"& or &"no"&.
6658 .section "Temporary errors in lookups" "SECID63"
6659 .cindex "lookup" "temporary error in"
6660 Lookup functions can return temporary error codes if the lookup cannot be
6661 completed. For example, an SQL or LDAP database might be unavailable. For this
6662 reason, it is not advisable to use a lookup that might do this for critical
6663 options such as a list of local domains.
6665 When a lookup cannot be completed in a router or transport, delivery
6666 of the message (to the relevant address) is deferred, as for any other
6667 temporary error. In other circumstances Exim may assume the lookup has failed,
6668 or may give up altogether.
6672 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6673 .cindex "wildcard lookups"
6674 .cindex "lookup" "default values"
6675 .cindex "lookup" "wildcard"
6676 .cindex "lookup" "* added to type"
6677 .cindex "default" "in single-key lookups"
6678 In this context, a &"default value"& is a value specified by the administrator
6679 that is to be used if a lookup fails.
6681 &*Note:*& This section applies only to single-key lookups. For query-style
6682 lookups, the facilities of the query language must be used. An attempt to
6683 specify a default for a query-style lookup provokes an error.
6685 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6686 and the initial lookup fails, the key &"*"& is looked up in the file to
6687 provide a default value. See also the section on partial matching below.
6689 .cindex "*@ with single-key lookup"
6690 .cindex "lookup" "*@ added to type"
6691 .cindex "alias file" "per-domain default"
6692 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6693 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6694 character, a second lookup is done with everything before the last @ replaced
6695 by *. This makes it possible to provide per-domain defaults in alias files
6696 that include the domains in the keys. If the second lookup fails (or doesn't
6697 take place because there is no @ in the key), &"*"& is looked up.
6698 For example, a &(redirect)& router might contain:
6700 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6702 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6703 looks up these keys, in this order:
6709 The data is taken from whichever key it finds first. &*Note*&: In an
6710 &(lsearch)& file, this does not mean the first of these keys in the file. A
6711 complete scan is done for each key, and only if it is not found at all does
6712 Exim move on to try the next key.
6716 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6717 .cindex "partial matching"
6718 .cindex "wildcard lookups"
6719 .cindex "lookup" "partial matching"
6720 .cindex "lookup" "wildcard"
6721 .cindex "asterisk" "in search type"
6722 The normal operation of a single-key lookup is to search the file for an exact
6723 match with the given key. However, in a number of situations where domains are
6724 being looked up, it is useful to be able to do partial matching. In this case,
6725 information in the file that has a key starting with &"*."& is matched by any
6726 domain that ends with the components that follow the full stop. For example, if
6727 a key in a DBM file is
6729 *.dates.fict.example
6731 then when partial matching is enabled this is matched by (amongst others)
6732 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6733 by &'dates.fict.example'&, if that does not appear as a separate key in the
6736 &*Note*&: Partial matching is not available for query-style lookups. It is
6737 also not available for any lookup items in address lists (see section
6738 &<<SECTaddresslist>>&).
6740 Partial matching is implemented by doing a series of separate lookups using
6741 keys constructed by modifying the original subject key. This means that it can
6742 be used with any of the single-key lookup types, provided that
6743 partial matching keys
6744 beginning with a special prefix (default &"*."&) are included in the data file.
6745 Keys in the file that do not begin with the prefix are matched only by
6746 unmodified subject keys when partial matching is in use.
6748 Partial matching is requested by adding the string &"partial-"& to the front of
6749 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6750 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6751 is added at the start of the subject key, and it is looked up again. If that
6752 fails, further lookups are tried with dot-separated components removed from the
6753 start of the subject key, one-by-one, and &"*."& added on the front of what
6756 A minimum number of two non-* components are required. This can be adjusted
6757 by including a number before the hyphen in the search type. For example,
6758 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6759 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6760 subject key is &'2250.dates.fict.example'& then the following keys are looked
6761 up when the minimum number of non-* components is two:
6763 2250.dates.fict.example
6764 *.2250.dates.fict.example
6765 *.dates.fict.example
6768 As soon as one key in the sequence is successfully looked up, the lookup
6771 .cindex "lookup" "partial matching &-- changing prefix"
6772 .cindex "prefix" "for partial matching"
6773 The use of &"*."& as the partial matching prefix is a default that can be
6774 changed. The motivation for this feature is to allow Exim to operate with file
6775 formats that are used by other MTAs. A different prefix can be supplied in
6776 parentheses instead of the hyphen after &"partial"&. For example:
6778 domains = partial(.)lsearch;/some/file
6780 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6781 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6782 components is unchanged). The prefix may consist of any punctuation characters
6783 other than a closing parenthesis. It may be empty, for example:
6785 domains = partial1()cdb;/some/file
6787 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6788 &`a.b.c`&, &`b.c`&, and &`c`&.
6790 If &"partial0"& is specified, what happens at the end (when the lookup with
6791 just one non-wild component has failed, and the original key is shortened right
6792 down to the null string) depends on the prefix:
6795 If the prefix has zero length, the whole lookup fails.
6797 If the prefix has length 1, a lookup for just the prefix is done. For
6798 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6800 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6801 remainder is looked up. With the default prefix, therefore, the final lookup is
6802 for &"*"& on its own.
6804 Otherwise, the whole prefix is looked up.
6808 If the search type ends in &"*"& or &"*@"& (see section
6809 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6810 this implies happens after all partial lookups have failed. If &"partial0"& is
6811 specified, adding &"*"& to the search type has no effect with the default
6812 prefix, because the &"*"& key is already included in the sequence of partial
6813 lookups. However, there might be a use for lookup types such as
6814 &"partial0(.)lsearch*"&.
6816 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6817 in domain lists and the like. Partial matching works only in terms of
6818 dot-separated components; a key such as &`*fict.example`&
6819 in a database file is useless, because the asterisk in a partial matching
6820 subject key is always followed by a dot.
6825 .section "Lookup caching" "SECID64"
6826 .cindex "lookup" "caching"
6827 .cindex "caching" "lookup data"
6828 Exim caches all lookup results in order to avoid needless repetition of
6829 lookups. However, because (apart from the daemon) Exim operates as a collection
6830 of independent, short-lived processes, this caching applies only within a
6831 single Exim process. There is no inter-process lookup caching facility.
6833 For single-key lookups, Exim keeps the relevant files open in case there is
6834 another lookup that needs them. In some types of configuration this can lead to
6835 many files being kept open for messages with many recipients. To avoid hitting
6836 the operating system limit on the number of simultaneously open files, Exim
6837 closes the least recently used file when it needs to open more files than its
6838 own internal limit, which can be changed via the &%lookup_open_max%& option.
6840 The single-key lookup files are closed and the lookup caches are flushed at
6841 strategic points during delivery &-- for example, after all routing is
6847 .section "Quoting lookup data" "SECID65"
6848 .cindex "lookup" "quoting"
6849 .cindex "quoting" "in lookups"
6850 When data from an incoming message is included in a query-style lookup, there
6851 is the possibility of special characters in the data messing up the syntax of
6852 the query. For example, a NIS+ query that contains
6856 will be broken if the local part happens to contain a closing square bracket.
6857 For NIS+, data can be enclosed in double quotes like this:
6859 [name="$local_part"]
6861 but this still leaves the problem of a double quote in the data. The rule for
6862 NIS+ is that double quotes must be doubled. Other lookup types have different
6863 rules, and to cope with the differing requirements, an expansion operator
6864 of the following form is provided:
6866 ${quote_<lookup-type>:<string>}
6868 For example, the safest way to write the NIS+ query is
6870 [name="${quote_nisplus:$local_part}"]
6872 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6873 operator can be used for all lookup types, but has no effect for single-key
6874 lookups, since no quoting is ever needed in their key strings.
6879 .section "More about dnsdb" "SECTdnsdb"
6880 .cindex "dnsdb lookup"
6881 .cindex "lookup" "dnsdb"
6882 .cindex "DNS" "as a lookup type"
6883 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6884 of a record type and a domain name, separated by an equals sign. For example,
6885 an expansion string could contain:
6887 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6889 If the lookup succeeds, the result is placed in &$value$&, which in this case
6890 is used on its own as the result. If the lookup does not succeed, the
6891 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6892 &<<SECTforexpfai>>& for an explanation of what this means.
6894 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
6895 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
6896 If no type is given, TXT is assumed.
6898 For any record type, if multiple records are found, the data is returned as a
6899 concatenation, with newline as the default separator. The order, of course,
6900 depends on the DNS resolver. You can specify a different separator character
6901 between multiple records by putting a right angle-bracket followed immediately
6902 by the new separator at the start of the query. For example:
6904 ${lookup dnsdb{>: a=host1.example}}
6906 It is permitted to specify a space as the separator character. Further
6907 white space is ignored.
6908 For lookup types that return multiple fields per record,
6909 an alternate field separator can be specified using a comma after the main
6910 separator character, followed immediately by the field separator.
6912 .cindex "PTR record" "in &(dnsdb)& lookup"
6913 When the type is PTR,
6914 the data can be an IP address, written as normal; inversion and the addition of
6915 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6917 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6919 If the data for a PTR record is not a syntactically valid IP address, it is not
6920 altered and nothing is added.
6922 .cindex "MX record" "in &(dnsdb)& lookup"
6923 .cindex "SRV record" "in &(dnsdb)& lookup"
6924 For an MX lookup, both the preference value and the host name are returned for
6925 each record, separated by a space. For an SRV lookup, the priority, weight,
6926 port, and host name are returned for each record, separated by spaces.
6927 The field separator can be modified as above.
6929 .cindex "TXT record" "in &(dnsdb)& lookup"
6930 .cindex "SPF record" "in &(dnsdb)& lookup"
6931 For TXT records with multiple items of data, only the first item is returned,
6932 unless a field separator is specified.
6933 To concatenate items without a separator, use a semicolon instead.
6935 default behaviour is to concatenate multiple items without using a separator.
6937 ${lookup dnsdb{>\n,: txt=a.b.example}}
6938 ${lookup dnsdb{>\n; txt=a.b.example}}
6939 ${lookup dnsdb{spf=example.org}}
6941 It is permitted to specify a space as the separator character. Further
6942 white space is ignored.
6944 .cindex "SOA record" "in &(dnsdb)& lookup"
6945 For an SOA lookup, while no result is obtained the lookup is redone with
6946 successively more leading components dropped from the given domain.
6947 Only the primary-nameserver field is returned unless a field separator is
6950 ${lookup dnsdb{>:,; soa=a.b.example.com}}
6953 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
6954 .cindex "dnsdb modifiers"
6955 .cindex "modifiers" "dnsdb"
6956 .cindex "options" "dnsdb"
6957 Modifiers for &(dnsdb)& lookups are given by optional keywords,
6958 each followed by a comma,
6959 that may appear before the record type.
6961 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6962 temporary DNS error for any of them, the behaviour is controlled by
6963 a defer-option modifier.
6964 The possible keywords are
6965 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
6966 With &"strict"& behaviour, any temporary DNS error causes the
6967 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6968 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6969 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6970 error causes the whole lookup to defer only if none of the other lookups
6971 succeed. The default is &"lax"&, so the following lookups are equivalent:
6973 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6974 ${lookup dnsdb{a=one.host.com:two.host.com}}
6976 Thus, in the default case, as long as at least one of the DNS lookups
6977 yields some data, the lookup succeeds.
6979 .cindex "DNSSEC" "dns lookup"
6980 Use of &(DNSSEC)& is controlled by a dnssec modifier.
6981 The possible keywords are
6982 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
6983 With &"strict"& or &"lax"& DNSSEC information is requested
6985 With &"strict"& a response from the DNS resolver that
6986 is not labelled as authenticated data
6987 is treated as equivalent to a temporary DNS error.
6988 The default is &"never"&.
6990 See also the &$lookup_dnssec_authenticated$& variable.
6992 .cindex timeout "dns lookup"
6993 .cindex "DNS" timeout
6994 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
6995 The form is &"retrans_VAL"& where VAL is an Exim time specification
6997 The default value is set by the main configuration option &%dns_retrans%&.
6999 Retries for the dnsdb lookup can be controlled by a retry modifier.
7000 The form if &"retry_VAL"& where VAL is an integer.
7001 The default count is set by the main configuration option &%dns_retry%&.
7004 .cindex cacheing "of dns lookup"
7005 .cindex TTL "of dns lookup"
7007 Dnsdb lookup results are cached within a single process (and its children).
7008 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7009 value of the set of returned DNS records.
7013 .section "Pseudo dnsdb record types" "SECID66"
7014 .cindex "MX record" "in &(dnsdb)& lookup"
7015 By default, both the preference value and the host name are returned for
7016 each MX record, separated by a space. If you want only host names, you can use
7017 the pseudo-type MXH:
7019 ${lookup dnsdb{mxh=a.b.example}}
7021 In this case, the preference values are omitted, and just the host names are
7024 .cindex "name server for enclosing domain"
7025 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7026 records on the given domain, but if none are found, it removes the first
7027 component of the domain name, and tries again. This process continues until NS
7028 records are found or there are no more components left (or there is a DNS
7029 error). In other words, it may return the name servers for a top-level domain,
7030 but it never returns the root name servers. If there are no NS records for the
7031 top-level domain, the lookup fails. Consider these examples:
7033 ${lookup dnsdb{zns=xxx.quercite.com}}
7034 ${lookup dnsdb{zns=xxx.edu}}
7036 Assuming that in each case there are no NS records for the full domain name,
7037 the first returns the name servers for &%quercite.com%&, and the second returns
7038 the name servers for &%edu%&.
7040 You should be careful about how you use this lookup because, unless the
7041 top-level domain does not exist, the lookup always returns some host names. The
7042 sort of use to which this might be put is for seeing if the name servers for a
7043 given domain are on a blacklist. You can probably assume that the name servers
7044 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7047 .cindex "CSA" "in &(dnsdb)& lookup"
7048 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7049 records according to the CSA rules, which are described in section
7050 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7051 not sufficient because of the extra parent domain search behaviour of CSA. The
7052 result of a successful lookup such as:
7054 ${lookup dnsdb {csa=$sender_helo_name}}
7056 has two space-separated fields: an authorization code and a target host name.
7057 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7058 authorization required but absent, or &"?"& for unknown.
7060 .cindex "A+" "in &(dnsdb)& lookup"
7061 The pseudo-type A+ performs an AAAA
7062 and then an A lookup. All results are returned; defer processing
7063 (see below) is handled separately for each lookup. Example:
7065 ${lookup dnsdb {>; a+=$sender_helo_name}}
7069 .section "Multiple dnsdb lookups" "SECID67"
7070 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7071 However, you can specify a list of domains or IP addresses in a single
7072 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7073 the default separator, but with the ability to change this. For example:
7075 ${lookup dnsdb{one.domain.com:two.domain.com}}
7076 ${lookup dnsdb{a=one.host.com:two.host.com}}
7077 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7079 In order to retain backwards compatibility, there is one special case: if
7080 the lookup type is PTR and no change of separator is specified, Exim looks
7081 to see if the rest of the string is precisely one IPv6 address. In this
7082 case, it does not treat it as a list.
7084 The data from each lookup is concatenated, with newline separators by default,
7085 in the same way that multiple DNS records for a single item are handled. A
7086 different separator can be specified, as described above.
7091 .section "More about LDAP" "SECTldap"
7092 .cindex "LDAP" "lookup, more about"
7093 .cindex "lookup" "LDAP"
7094 .cindex "Solaris" "LDAP"
7095 The original LDAP implementation came from the University of Michigan; this has
7096 become &"Open LDAP"&, and there are now two different releases. Another
7097 implementation comes from Netscape, and Solaris 7 and subsequent releases
7098 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7099 the lookup function level, their error handling is different. For this reason
7100 it is necessary to set a compile-time variable when building Exim with LDAP, to
7101 indicate which LDAP library is in use. One of the following should appear in
7102 your &_Local/Makefile_&:
7104 LDAP_LIB_TYPE=UMICHIGAN
7105 LDAP_LIB_TYPE=OPENLDAP1
7106 LDAP_LIB_TYPE=OPENLDAP2
7107 LDAP_LIB_TYPE=NETSCAPE
7108 LDAP_LIB_TYPE=SOLARIS
7110 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7111 same interface as the University of Michigan version.
7113 There are three LDAP lookup types in Exim. These behave slightly differently in
7114 the way they handle the results of a query:
7117 &(ldap)& requires the result to contain just one entry; if there are more, it
7120 &(ldapdn)& also requires the result to contain just one entry, but it is the
7121 Distinguished Name that is returned rather than any attribute values.
7123 &(ldapm)& permits the result to contain more than one entry; the attributes
7124 from all of them are returned.
7128 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7129 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7130 the data returned by a successful lookup is described in the next section.
7131 First we explain how LDAP queries are coded.
7134 .section "Format of LDAP queries" "SECTforldaque"
7135 .cindex "LDAP" "query format"
7136 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7137 the configuration of a &(redirect)& router one might have this setting:
7139 data = ${lookup ldap \
7140 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7141 c=UK?mailbox?base?}}
7143 .cindex "LDAP" "with TLS"
7144 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7145 secure (encrypted) LDAP connections. The second of these ensures that an
7146 encrypted TLS connection is used.
7148 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7149 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7150 See the &%ldap_start_tls%& option.
7152 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7153 controlled. Every part of the TLS configuration can be configured by settings in
7154 &_exim.conf_&. Depending on the version of the client libraries installed on
7155 your system, some of the initialization may have required setting options in
7156 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7157 certificates. This revealed a nuance where the current UID that exim was
7158 running as could affect which config files it read. With Exim 4.83, these
7159 methods become optional, only taking effect if not specifically set in
7163 .section "LDAP quoting" "SECID68"
7164 .cindex "LDAP" "quoting"
7165 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7166 and the second because the LDAP query is represented as a URL. Furthermore,
7167 within an LDAP query, two different kinds of quoting are required. For this
7168 reason, there are two different LDAP-specific quoting operators.
7170 The &%quote_ldap%& operator is designed for use on strings that are part of
7171 filter specifications. Conceptually, it first does the following conversions on
7179 in accordance with RFC 2254. The resulting string is then quoted according
7180 to the rules for URLs, that is, all non-alphanumeric characters except
7184 are converted to their hex values, preceded by a percent sign. For example:
7186 ${quote_ldap: a(bc)*, a<yz>; }
7190 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7192 Removing the URL quoting, this is (with a leading and a trailing space):
7194 a\28bc\29\2A, a<yz>;
7196 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7197 base DN specifications in queries. Conceptually, it first converts the string
7198 by inserting a backslash in front of any of the following characters:
7202 It also inserts a backslash before any leading spaces or # characters, and
7203 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7204 is then quoted according to the rules for URLs. For example:
7206 ${quote_ldap_dn: a(bc)*, a<yz>; }
7210 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7212 Removing the URL quoting, this is (with a trailing space):
7214 \ a(bc)*\, a\<yz\>\;\
7216 There are some further comments about quoting in the section on LDAP
7217 authentication below.
7220 .section "LDAP connections" "SECID69"
7221 .cindex "LDAP" "connections"
7222 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7223 is in use, via a Unix domain socket. The example given above does not specify
7224 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7227 ldap://<hostname>:<port>/...
7229 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7230 used. When no server is specified in a query, a list of default servers is
7231 taken from the &%ldap_default_servers%& configuration option. This supplies a
7232 colon-separated list of servers which are tried in turn until one successfully
7233 handles a query, or there is a serious error. Successful handling either
7234 returns the requested data, or indicates that it does not exist. Serious errors
7235 are syntactical, or multiple values when only a single value is expected.
7236 Errors which cause the next server to be tried are connection failures, bind
7237 failures, and timeouts.
7239 For each server name in the list, a port number can be given. The standard way
7240 of specifying a host and port is to use a colon separator (RFC 1738). Because
7241 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7242 doubled. For example
7244 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7246 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7247 to the LDAP library with no server name, and the library's default (normally
7248 the local host) is used.
7250 If you are using the OpenLDAP library, you can connect to an LDAP server using
7251 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7252 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7253 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7256 For this type of connection, instead of a host name for the server, a pathname
7257 for the socket is required, and the port number is not relevant. The pathname
7258 can be specified either as an item in &%ldap_default_servers%&, or inline in
7259 the query. In the former case, you can have settings such as
7261 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7263 When the pathname is given in the query, you have to escape the slashes as
7264 &`%2F`& to fit in with the LDAP URL syntax. For example:
7266 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7268 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7269 a pathname, it uses the Unix domain socket code, even if the query actually
7270 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7271 socket connection. This behaviour means that you can use a setting of
7272 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7273 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7274 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7277 If an explicit &`ldapi`& type is given in a query when a host name is
7278 specified, an error is diagnosed. However, if there are more items in
7279 &%ldap_default_servers%&, they are tried. In other words:
7282 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7285 Using &`ldapi`& with a host name causes an error.
7289 Using &`ldapi`& with no host or path in the query, and no setting of
7290 &%ldap_default_servers%&, does whatever the library does by default.
7294 .section "LDAP authentication and control information" "SECID70"
7295 .cindex "LDAP" "authentication"
7296 The LDAP URL syntax provides no way of passing authentication and other control
7297 information to the server. To make this possible, the URL in an LDAP query may
7298 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7299 spaces. If a value contains spaces it must be enclosed in double quotes, and
7300 when double quotes are used, backslash is interpreted in the usual way inside
7301 them. The following names are recognized:
7303 &`DEREFERENCE`& set the dereferencing parameter
7304 &`NETTIME `& set a timeout for a network operation
7305 &`USER `& set the DN, for authenticating the LDAP bind
7306 &`PASS `& set the password, likewise
7307 &`REFERRALS `& set the referrals parameter
7308 &`SERVERS `& set alternate server list for this query only
7309 &`SIZE `& set the limit for the number of entries returned
7310 &`TIME `& set the maximum waiting time for a query
7312 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7313 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7314 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7315 library from trying to follow referrals issued by the LDAP server.
7317 .cindex LDAP timeout
7318 .cindex timeout "LDAP lookup"
7319 The name CONNECT is an obsolete name for NETTIME, retained for
7320 backwards compatibility. This timeout (specified as a number of seconds) is
7321 enforced from the client end for operations that can be carried out over a
7322 network. Specifically, it applies to network connections and calls to the
7323 &'ldap_result()'& function. If the value is greater than zero, it is used if
7324 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7325 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7326 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7327 Netscape SDK; for OpenLDAP no action is taken.
7329 The TIME parameter (also a number of seconds) is passed to the server to
7330 set a server-side limit on the time taken to complete a search.
7332 The SERVERS parameter allows you to specify an alternate list of ldap servers
7333 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7334 default list of ldap servers, and a single lookup can specify a single ldap
7335 server to use. But when you need to do a lookup with a list of servers that is
7336 different than the default list (maybe different order, maybe a completely
7337 different set of servers), the SERVERS parameter allows you to specify this
7338 alternate list (colon-separated).
7340 Here is an example of an LDAP query in an Exim lookup that uses some of these
7341 values. This is a single line, folded to fit on the page:
7344 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7345 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7348 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7349 any of the auxiliary data. Exim configuration settings that include lookups
7350 which contain password information should be preceded by &"hide"& to prevent
7351 non-admin users from using the &%-bP%& option to see their values.
7353 The auxiliary data items may be given in any order. The default is no
7354 connection timeout (the system timeout is used), no user or password, no limit
7355 on the number of entries returned, and no time limit on queries.
7357 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7358 removes any URL quoting that it may contain before passing it LDAP. Apparently
7359 some libraries do this for themselves, but some do not. Removing the URL
7360 quoting has two advantages:
7363 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7364 DNs as with DNs inside actual queries.
7366 It permits spaces inside USER= DNs.
7369 For example, a setting such as
7371 USER=cn=${quote_ldap_dn:$1}
7373 should work even if &$1$& contains spaces.
7375 Expanded data for the PASS= value should be quoted using the &%quote%&
7376 expansion operator, rather than the LDAP quote operators. The only reason this
7377 field needs quoting is to ensure that it conforms to the Exim syntax, which
7378 does not allow unquoted spaces. For example:
7382 The LDAP authentication mechanism can be used to check passwords as part of
7383 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7388 .section "Format of data returned by LDAP" "SECID71"
7389 .cindex "LDAP" "returned data formats"
7390 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7391 as a sequence of values, for example
7393 cn=manager,o=University of Cambridge,c=UK
7395 The &(ldap)& lookup type generates an error if more than one entry matches the
7396 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7397 the result between the data from different entries. It is possible for multiple
7398 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7399 you know that whatever values are returned all came from a single entry in the
7402 In the common case where you specify a single attribute in your LDAP query, the
7403 result is not quoted, and does not contain the attribute name. If the attribute
7404 has multiple values, they are separated by commas. Any comma that is
7405 part of an attribute's value is doubled.
7407 If you specify multiple attributes, the result contains space-separated, quoted
7408 strings, each preceded by the attribute name and an equals sign. Within the
7409 quotes, the quote character, backslash, and newline are escaped with
7410 backslashes, and commas are used to separate multiple values for the attribute.
7411 Any commas in attribute values are doubled
7412 (permitting treatment of the values as a comma-separated list).
7413 Apart from the escaping, the string within quotes takes the same form as the
7414 output when a single attribute is requested. Specifying no attributes is the
7415 same as specifying all of an entry's attributes.
7417 Here are some examples of the output format. The first line of each pair is an
7418 LDAP query, and the second is the data that is returned. The attribute called
7419 &%attr1%& has two values, one of them with an embedded comma, whereas
7420 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7421 (they have SUP &%attr%& in their schema definitions).
7424 ldap:///o=base?attr1?sub?(uid=fred)
7427 ldap:///o=base?attr2?sub?(uid=fred)
7430 ldap:///o=base?attr?sub?(uid=fred)
7431 value1.1,value1,,2,value two
7433 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7434 attr1="value1.1,value1,,2" attr2="value two"
7436 ldap:///o=base??sub?(uid=fred)
7437 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7440 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7441 results of LDAP lookups.
7442 The &%extract%& operator in string expansions can be used to pick out
7443 individual fields from data that consists of &'key'&=&'value'& pairs.
7444 The &%listextract%& operator should be used to pick out individual values
7445 of attributes, even when only a single value is expected.
7446 The doubling of embedded commas allows you to use the returned data as a
7447 comma separated list (using the "<," syntax for changing the input list separator).
7452 .section "More about NIS+" "SECTnisplus"
7453 .cindex "NIS+ lookup type"
7454 .cindex "lookup" "NIS+"
7455 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7456 and field name. If this is given, the result of a successful query is the
7457 contents of the named field; otherwise the result consists of a concatenation
7458 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7459 values containing spaces are quoted. For example, the query
7461 [name=mg1456],passwd.org_dir
7463 might return the string
7465 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7466 home=/home/mg1456 shell=/bin/bash shadow=""
7468 (split over two lines here to fit on the page), whereas
7470 [name=mg1456],passwd.org_dir:gcos
7476 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7477 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7478 operator is to double any quote characters within the text.
7482 .section "SQL lookups" "SECTsql"
7483 .cindex "SQL lookup types"
7484 .cindex "MySQL" "lookup type"
7485 .cindex "PostgreSQL lookup type"
7486 .cindex "lookup" "MySQL"
7487 .cindex "lookup" "PostgreSQL"
7488 .cindex "Oracle" "lookup type"
7489 .cindex "lookup" "Oracle"
7490 .cindex "InterBase lookup type"
7491 .cindex "lookup" "InterBase"
7492 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7493 databases. Queries for these databases contain SQL statements, so an example
7496 ${lookup mysql{select mailbox from users where id='userx'}\
7499 If the result of the query contains more than one field, the data for each
7500 field in the row is returned, preceded by its name, so the result of
7502 ${lookup pgsql{select home,name from users where id='userx'}\
7507 home=/home/userx name="Mister X"
7509 Empty values and values containing spaces are double quoted, with embedded
7510 quotes escaped by a backslash. If the result of the query contains just one
7511 field, the value is passed back verbatim, without a field name, for example:
7515 If the result of the query yields more than one row, it is all concatenated,
7516 with a newline between the data for each row.
7519 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7520 .cindex "MySQL" "lookup type"
7521 .cindex "PostgreSQL lookup type"
7522 .cindex "lookup" "MySQL"
7523 .cindex "lookup" "PostgreSQL"
7524 .cindex "Oracle" "lookup type"
7525 .cindex "lookup" "Oracle"
7526 .cindex "InterBase lookup type"
7527 .cindex "lookup" "InterBase"
7528 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7529 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7530 option (as appropriate) must be set to a colon-separated list of server
7532 (For MySQL and PostgreSQL only, the global option need not be set if all
7533 queries contain their own server information &-- see section
7534 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7535 items: host name, database name, user name, and password. In the case of
7536 Oracle, the host name field is used for the &"service name"&, and the database
7537 name field is not used and should be empty. For example:
7539 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7541 Because password data is sensitive, you should always precede the setting with
7542 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7543 option. Here is an example where two MySQL servers are listed:
7545 hide mysql_servers = localhost/users/root/secret:\
7546 otherhost/users/root/othersecret
7548 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7549 because this is a colon-separated list, the colon has to be doubled. For each
7550 query, these parameter groups are tried in order until a connection is made and
7551 a query is successfully processed. The result of a query may be that no data is
7552 found, but that is still a successful query. In other words, the list of
7553 servers provides a backup facility, not a list of different places to look.
7556 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7557 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7558 respectively, and the characters single-quote, double-quote, and backslash
7559 itself are escaped with backslashes.
7562 .section "Specifying the server in the query" "SECTspeserque"
7563 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7564 it is possible to specify a list of servers with an individual query. This is
7565 done by starting the query with
7567 &`servers=`&&'server1:server2:server3:...'&&`;`&
7569 Each item in the list may take one of two forms:
7571 If it contains no slashes it is assumed to be just a host name. The appropriate
7572 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7573 of the same name, and the remaining parameters (database, user, password) are
7576 If it contains any slashes, it is taken as a complete parameter set.
7578 The list of servers is used in exactly the same way as the global list.
7579 Once a connection to a server has happened and a query has been
7580 successfully executed, processing of the lookup ceases.
7582 This feature is intended for use in master/slave situations where updates
7583 are occurring and you want to update the master rather than a slave. If the
7584 master is in the list as a backup for reading, you might have a global setting
7587 mysql_servers = slave1/db/name/pw:\
7591 In an updating lookup, you could then write:
7593 ${lookup mysql{servers=master; UPDATE ...} }
7595 That query would then be sent only to the master server. If, on the other hand,
7596 the master is not to be used for reading, and so is not present in the global
7597 option, you can still update it by a query of this form:
7599 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7603 .section "Special MySQL features" "SECID73"
7604 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7605 causes a connection to the server on the local host by means of a Unix domain
7606 socket. An alternate socket can be specified in parentheses.
7608 An option group name for MySQL option files can be specified in square brackets;
7609 the default value is &"exim"&.
7611 The full syntax of each item in &%mysql_servers%& is:
7613 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
7614 <&'database'&>/<&'user'&>/<&'password'&>
7616 Any of the four sub-parts of the first field can be omitted. For normal use on
7617 the local host it can be left blank or set to just &"localhost"&.
7619 No database need be supplied &-- but if it is absent here, it must be given in
7622 If a MySQL query is issued that does not request any data (an insert, update,
7623 or delete command), the result of the lookup is the number of rows affected.
7625 &*Warning*&: This can be misleading. If an update does not actually change
7626 anything (for example, setting a field to the value it already has), the result
7627 is zero because no rows are affected.
7630 .section "Special PostgreSQL features" "SECID74"
7631 PostgreSQL lookups can also use Unix domain socket connections to the database.
7632 This is usually faster and costs less CPU time than a TCP/IP connection.
7633 However it can be used only if the mail server runs on the same machine as the
7634 database server. A configuration line for PostgreSQL via Unix domain sockets
7637 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7639 In other words, instead of supplying a host name, a path to the socket is
7640 given. The path name is enclosed in parentheses so that its slashes aren't
7641 visually confused with the delimiters for the other server parameters.
7643 If a PostgreSQL query is issued that does not request any data (an insert,
7644 update, or delete command), the result of the lookup is the number of rows
7647 .section "More about SQLite" "SECTsqlite"
7648 .cindex "lookup" "SQLite"
7649 .cindex "sqlite lookup type"
7650 SQLite is different to the other SQL lookups because a file name is required in
7651 addition to the SQL query. An SQLite database is a single file, and there is no
7652 daemon as in the other SQL databases. The interface to Exim requires the name
7653 of the file, as an absolute path, to be given at the start of the query. It is
7654 separated from the query by white space. This means that the path name cannot
7655 contain white space. Here is a lookup expansion example:
7657 ${lookup sqlite {/some/thing/sqlitedb \
7658 select name from aliases where id='userx';}}
7660 In a list, the syntax is similar. For example:
7662 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7663 select * from relays where ip='$sender_host_address';
7665 The only character affected by the &%quote_sqlite%& operator is a single
7666 quote, which it doubles.
7668 .cindex timeout SQLite
7669 .cindex sqlite "lookup timeout"
7670 The SQLite library handles multiple simultaneous accesses to the database
7671 internally. Multiple readers are permitted, but only one process can
7672 update at once. Attempts to access the database while it is being updated
7673 are rejected after a timeout period, during which the SQLite library
7674 waits for the lock to be released. In Exim, the default timeout is set
7675 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7681 . ////////////////////////////////////////////////////////////////////////////
7682 . ////////////////////////////////////////////////////////////////////////////
7684 .chapter "Domain, host, address, and local part lists" &&&
7685 "CHAPdomhosaddlists" &&&
7686 "Domain, host, and address lists"
7687 .scindex IIDdohoadli "lists of domains; hosts; etc."
7688 A number of Exim configuration options contain lists of domains, hosts,
7689 email addresses, or local parts. For example, the &%hold_domains%& option
7690 contains a list of domains whose delivery is currently suspended. These lists
7691 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7692 arguments to expansion conditions such as &%match_domain%&.
7694 Each item in one of these lists is a pattern to be matched against a domain,
7695 host, email address, or local part, respectively. In the sections below, the
7696 different types of pattern for each case are described, but first we cover some
7697 general facilities that apply to all four kinds of list.
7699 Note that other parts of Exim use a &'string list'& which does not
7700 support all the complexity available in
7701 domain, host, address and local part lists.
7705 .section "Expansion of lists" "SECID75"
7706 .cindex "expansion" "of lists"
7707 Each list is expanded as a single string before it is used. The result of
7708 expansion must be a list, possibly containing empty items, which is split up
7709 into separate items for matching. By default, colon is the separator character,
7710 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7711 &<<SECTempitelis>>& for details of the list syntax; the second of these
7712 discusses the way to specify empty list items.
7715 If the string expansion is forced to fail, Exim behaves as if the item it is
7716 testing (domain, host, address, or local part) is not in the list. Other
7717 expansion failures cause temporary errors.
7719 If an item in a list is a regular expression, backslashes, dollars and possibly
7720 other special characters in the expression must be protected against
7721 misinterpretation by the string expander. The easiest way to do this is to use
7722 the &`\N`& expansion feature to indicate that the contents of the regular
7723 expression should not be expanded. For example, in an ACL you might have:
7725 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7726 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7728 The first item is a regular expression that is protected from expansion by
7729 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7730 senders based on the receiving domain.
7735 .section "Negated items in lists" "SECID76"
7736 .cindex "list" "negation"
7737 .cindex "negation" "in lists"
7738 Items in a list may be positive or negative. Negative items are indicated by a
7739 leading exclamation mark, which may be followed by optional white space. A list
7740 defines a set of items (domains, etc). When Exim processes one of these lists,
7741 it is trying to find out whether a domain, host, address, or local part
7742 (respectively) is in the set that is defined by the list. It works like this:
7744 The list is scanned from left to right. If a positive item is matched, the
7745 subject that is being checked is in the set; if a negative item is matched, the
7746 subject is not in the set. If the end of the list is reached without the
7747 subject having matched any of the patterns, it is in the set if the last item
7748 was a negative one, but not if it was a positive one. For example, the list in
7750 domainlist relay_to_domains = !a.b.c : *.b.c
7752 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7753 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7754 list is positive. However, if the setting were
7756 domainlist relay_to_domains = !a.b.c
7758 then all domains other than &'a.b.c'& would match because the last item in the
7759 list is negative. In other words, a list that ends with a negative item behaves
7760 as if it had an extra item &`:*`& on the end.
7762 Another way of thinking about positive and negative items in lists is to read
7763 the connector as &"or"& after a positive item and as &"and"& after a negative
7768 .section "File names in lists" "SECTfilnamlis"
7769 .cindex "list" "file name in"
7770 If an item in a domain, host, address, or local part list is an absolute file
7771 name (beginning with a slash character), each line of the file is read and
7772 processed as if it were an independent item in the list, except that further
7773 file names are not allowed,
7774 and no expansion of the data from the file takes place.
7775 Empty lines in the file are ignored, and the file may also contain comment
7779 For domain and host lists, if a # character appears anywhere in a line of the
7780 file, it and all following characters are ignored.
7782 Because local parts may legitimately contain # characters, a comment in an
7783 address list or local part list file is recognized only if # is preceded by
7784 white space or the start of the line. For example:
7786 not#comment@x.y.z # but this is a comment
7790 Putting a file name in a list has the same effect as inserting each line of the
7791 file as an item in the list (blank lines and comments excepted). However, there
7792 is one important difference: the file is read each time the list is processed,
7793 so if its contents vary over time, Exim's behaviour changes.
7795 If a file name is preceded by an exclamation mark, the sense of any match
7796 within the file is inverted. For example, if
7798 hold_domains = !/etc/nohold-domains
7800 and the file contains the lines
7805 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7806 any domain matching &`*.b.c`& is not.
7810 .section "An lsearch file is not an out-of-line list" "SECID77"
7811 As will be described in the sections that follow, lookups can be used in lists
7812 to provide indexed methods of checking list membership. There has been some
7813 confusion about the way &(lsearch)& lookups work in lists. Because
7814 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7815 sometimes thought that it is allowed to contain wild cards and other kinds of
7816 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7817 always fixed strings, just as for any other single-key lookup type.
7819 If you want to use a file to contain wild-card patterns that form part of a
7820 list, just give the file name on its own, without a search type, as described
7821 in the previous section. You could also use the &(wildlsearch)& or
7822 &(nwildlsearch)&, but there is no advantage in doing this.
7827 .section "Named lists" "SECTnamedlists"
7828 .cindex "named lists"
7829 .cindex "list" "named"
7830 A list of domains, hosts, email addresses, or local parts can be given a name
7831 which is then used to refer to the list elsewhere in the configuration. This is
7832 particularly convenient if the same list is required in several different
7833 places. It also allows lists to be given meaningful names, which can improve
7834 the readability of the configuration. For example, it is conventional to define
7835 a domain list called &'local_domains'& for all the domains that are handled
7836 locally on a host, using a configuration line such as
7838 domainlist local_domains = localhost:my.dom.example
7840 Named lists are referenced by giving their name preceded by a plus sign, so,
7841 for example, a router that is intended to handle local domains would be
7842 configured with the line
7844 domains = +local_domains
7846 The first router in a configuration is often one that handles all domains
7847 except the local ones, using a configuration with a negated item like this:
7851 domains = ! +local_domains
7852 transport = remote_smtp
7855 The four kinds of named list are created by configuration lines starting with
7856 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7857 respectively. Then there follows the name that you are defining, followed by an
7858 equals sign and the list itself. For example:
7860 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
7861 addresslist bad_senders = cdb;/etc/badsenders
7863 A named list may refer to other named lists:
7865 domainlist dom1 = first.example : second.example
7866 domainlist dom2 = +dom1 : third.example
7867 domainlist dom3 = fourth.example : +dom2 : fifth.example
7869 &*Warning*&: If the last item in a referenced list is a negative one, the
7870 effect may not be what you intended, because the negation does not propagate
7871 out to the higher level. For example, consider:
7873 domainlist dom1 = !a.b
7874 domainlist dom2 = +dom1 : *.b
7876 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7877 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7878 means it matches the second list as well. The effect is not the same as
7880 domainlist dom2 = !a.b : *.b
7882 where &'x.y'& does not match. It's best to avoid negation altogether in
7883 referenced lists if you can.
7885 Named lists may have a performance advantage. When Exim is routing an
7886 address or checking an incoming message, it caches the result of tests on named
7887 lists. So, if you have a setting such as
7889 domains = +local_domains
7891 on several of your routers
7892 or in several ACL statements,
7893 the actual test is done only for the first one. However, the caching works only
7894 if there are no expansions within the list itself or any sublists that it
7895 references. In other words, caching happens only for lists that are known to be
7896 the same each time they are referenced.
7898 By default, there may be up to 16 named lists of each type. This limit can be
7899 extended by changing a compile-time variable. The use of domain and host lists
7900 is recommended for concepts such as local domains, relay domains, and relay
7901 hosts. The default configuration is set up like this.
7905 .section "Named lists compared with macros" "SECID78"
7906 .cindex "list" "named compared with macro"
7907 .cindex "macro" "compared with named list"
7908 At first sight, named lists might seem to be no different from macros in the
7909 configuration file. However, macros are just textual substitutions. If you
7912 ALIST = host1 : host2
7913 auth_advertise_hosts = !ALIST
7915 it probably won't do what you want, because that is exactly the same as
7917 auth_advertise_hosts = !host1 : host2
7919 Notice that the second host name is not negated. However, if you use a host
7922 hostlist alist = host1 : host2
7923 auth_advertise_hosts = ! +alist
7925 the negation applies to the whole list, and so that is equivalent to
7927 auth_advertise_hosts = !host1 : !host2
7931 .section "Named list caching" "SECID79"
7932 .cindex "list" "caching of named"
7933 .cindex "caching" "named lists"
7934 While processing a message, Exim caches the result of checking a named list if
7935 it is sure that the list is the same each time. In practice, this means that
7936 the cache operates only if the list contains no $ characters, which guarantees
7937 that it will not change when it is expanded. Sometimes, however, you may have
7938 an expanded list that you know will be the same each time within a given
7939 message. For example:
7941 domainlist special_domains = \
7942 ${lookup{$sender_host_address}cdb{/some/file}}
7944 This provides a list of domains that depends only on the sending host's IP
7945 address. If this domain list is referenced a number of times (for example,
7946 in several ACL lines, or in several routers) the result of the check is not
7947 cached by default, because Exim does not know that it is going to be the
7948 same list each time.
7950 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7951 cache the result anyway. For example:
7953 domainlist_cache special_domains = ${lookup{...
7955 If you do this, you should be absolutely sure that caching is going to do
7956 the right thing in all cases. When in doubt, leave it out.
7960 .section "Domain lists" "SECTdomainlist"
7961 .cindex "domain list" "patterns for"
7962 .cindex "list" "domain list"
7963 Domain lists contain patterns that are to be matched against a mail domain.
7964 The following types of item may appear in domain lists:
7967 .cindex "primary host name"
7968 .cindex "host name" "matched in domain list"
7969 .oindex "&%primary_hostname%&"
7970 .cindex "domain list" "matching primary host name"
7971 .cindex "@ in a domain list"
7972 If a pattern consists of a single @ character, it matches the local host name,
7973 as set by the &%primary_hostname%& option (or defaulted). This makes it
7974 possible to use the same configuration file on several different hosts that
7975 differ only in their names.
7977 .cindex "@[] in a domain list"
7978 .cindex "domain list" "matching local IP interfaces"
7979 .cindex "domain literal"
7980 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7981 in square brackets (as in an email address that contains a domain literal), but
7982 only if that IP address is recognized as local for email routing purposes. The
7983 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7984 control which of a host's several IP addresses are treated as local.
7985 In today's Internet, the use of domain literals is controversial.
7988 .cindex "@mx_primary"
7989 .cindex "@mx_secondary"
7990 .cindex "domain list" "matching MX pointers to local host"
7991 If a pattern consists of the string &`@mx_any`& it matches any domain that
7992 has an MX record pointing to the local host or to any host that is listed in
7993 .oindex "&%hosts_treat_as_local%&"
7994 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7995 are similar, except that the first matches only when a primary MX target is the
7996 local host, and the second only when no primary MX target is the local host,
7997 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7998 preference value &-- there may of course be more than one of them.
8000 The MX lookup that takes place when matching a pattern of this type is
8001 performed with the resolver options for widening names turned off. Thus, for
8002 example, a single-component domain will &'not'& be expanded by adding the
8003 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8004 options of the &(dnslookup)& router for a discussion of domain widening.
8006 Sometimes you may want to ignore certain IP addresses when using one of these
8007 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8008 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8009 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8010 on a router). For example:
8012 domains = @mx_any/ignore=127.0.0.1
8014 This example matches any domain that has an MX record pointing to one of
8015 the local host's IP addresses other than 127.0.0.1.
8017 The list of IP addresses is in fact processed by the same code that processes
8018 host lists, so it may contain CIDR-coded network specifications and it may also
8019 contain negative items.
8021 Because the list of IP addresses is a sublist within a domain list, you have to
8022 be careful about delimiters if there is more than one address. Like any other
8023 list, the default delimiter can be changed. Thus, you might have:
8025 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8026 an.other.domain : ...
8028 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8029 involved, it is easiest to change the delimiter for the main list as well:
8031 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8032 an.other.domain ? ...
8035 .cindex "asterisk" "in domain list"
8036 .cindex "domain list" "asterisk in"
8037 .cindex "domain list" "matching &""ends with""&"
8038 If a pattern starts with an asterisk, the remaining characters of the pattern
8039 are compared with the terminating characters of the domain. The use of &"*"& in
8040 domain lists differs from its use in partial matching lookups. In a domain
8041 list, the character following the asterisk need not be a dot, whereas partial
8042 matching works only in terms of dot-separated components. For example, a domain
8043 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8047 .cindex "regular expressions" "in domain list"
8048 .cindex "domain list" "matching regular expression"
8049 If a pattern starts with a circumflex character, it is treated as a regular
8050 expression, and matched against the domain using a regular expression matching
8051 function. The circumflex is treated as part of the regular expression.
8052 Email domains are case-independent, so this regular expression match is by
8053 default case-independent, but you can make it case-dependent by starting it
8054 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8055 are given in chapter &<<CHAPregexp>>&.
8057 &*Warning*&: Because domain lists are expanded before being processed, you
8058 must escape any backslash and dollar characters in the regular expression, or
8059 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8060 it is not to be expanded (unless you really do want to build a regular
8061 expression by expansion, of course).
8063 .cindex "lookup" "in domain list"
8064 .cindex "domain list" "matching by lookup"
8065 If a pattern starts with the name of a single-key lookup type followed by a
8066 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8067 must be a file name in a suitable format for the lookup type. For example, for
8068 &"cdb;"& it must be an absolute path:
8070 domains = cdb;/etc/mail/local_domains.cdb
8072 The appropriate type of lookup is done on the file using the domain name as the
8073 key. In most cases, the data that is looked up is not used; Exim is interested
8074 only in whether or not the key is present in the file. However, when a lookup
8075 is used for the &%domains%& option on a router
8076 or a &%domains%& condition in an ACL statement, the data is preserved in the
8077 &$domain_data$& variable and can be referred to in other router options or
8078 other statements in the same ACL.
8081 Any of the single-key lookup type names may be preceded by
8082 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8084 domains = partial-dbm;/partial/domains
8086 This causes partial matching logic to be invoked; a description of how this
8087 works is given in section &<<SECTpartiallookup>>&.
8090 .cindex "asterisk" "in lookup type"
8091 Any of the single-key lookup types may be followed by an asterisk. This causes
8092 a default lookup for a key consisting of a single asterisk to be done if the
8093 original lookup fails. This is not a useful feature when using a domain list to
8094 select particular domains (because any domain would match), but it might have
8095 value if the result of the lookup is being used via the &$domain_data$&
8098 If the pattern starts with the name of a query-style lookup type followed by a
8099 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8100 pattern must be an appropriate query for the lookup type, as described in
8101 chapter &<<CHAPfdlookup>>&. For example:
8103 hold_domains = mysql;select domain from holdlist \
8104 where domain = '${quote_mysql:$domain}';
8106 In most cases, the data that is looked up is not used (so for an SQL query, for
8107 example, it doesn't matter what field you select). Exim is interested only in
8108 whether or not the query succeeds. However, when a lookup is used for the
8109 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8110 variable and can be referred to in other options.
8112 .cindex "domain list" "matching literal domain name"
8113 If none of the above cases apply, a caseless textual comparison is made
8114 between the pattern and the domain.
8117 Here is an example that uses several different kinds of pattern:
8119 domainlist funny_domains = \
8122 *.foundation.fict.example : \
8123 \N^[1-2]\d{3}\.fict\.example$\N : \
8124 partial-dbm;/opt/data/penguin/book : \
8125 nis;domains.byname : \
8126 nisplus;[name=$domain,status=local],domains.org_dir
8128 There are obvious processing trade-offs among the various matching modes. Using
8129 an asterisk is faster than a regular expression, and listing a few names
8130 explicitly probably is too. The use of a file or database lookup is expensive,
8131 but may be the only option if hundreds of names are required. Because the
8132 patterns are tested in order, it makes sense to put the most commonly matched
8137 .section "Host lists" "SECThostlist"
8138 .cindex "host list" "patterns in"
8139 .cindex "list" "host list"
8140 Host lists are used to control what remote hosts are allowed to do. For
8141 example, some hosts may be allowed to use the local host as a relay, and some
8142 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8143 two different ways, by name or by IP address. In a host list, some types of
8144 pattern are matched to a host name, and some are matched to an IP address.
8145 You need to be particularly careful with this when single-key lookups are
8146 involved, to ensure that the right value is being used as the key.
8149 .section "Special host list patterns" "SECID80"
8150 .cindex "empty item in hosts list"
8151 .cindex "host list" "empty string in"
8152 If a host list item is the empty string, it matches only when no remote host is
8153 involved. This is the case when a message is being received from a local
8154 process using SMTP on the standard input, that is, when a TCP/IP connection is
8157 .cindex "asterisk" "in host list"
8158 The special pattern &"*"& in a host list matches any host or no host. Neither
8159 the IP address nor the name is actually inspected.
8163 .section "Host list patterns that match by IP address" "SECThoslispatip"
8164 .cindex "host list" "matching IP addresses"
8165 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8166 the incoming address actually appears in the IPv6 host as
8167 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8168 list, it is converted into a traditional IPv4 address first. (Not all operating
8169 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8172 The following types of pattern in a host list check the remote host by
8173 inspecting its IP address:
8176 If the pattern is a plain domain name (not a regular expression, not starting
8177 with *, not a lookup of any kind), Exim calls the operating system function
8178 to find the associated IP address(es). Exim uses the newer
8179 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8180 This typically causes a forward DNS lookup of the name. The result is compared
8181 with the IP address of the subject host.
8183 If there is a temporary problem (such as a DNS timeout) with the host name
8184 lookup, a temporary error occurs. For example, if the list is being used in an
8185 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8186 temporary SMTP error code. If no IP address can be found for the host name,
8187 what happens is described in section &<<SECTbehipnot>>& below.
8190 .cindex "@ in a host list"
8191 If the pattern is &"@"&, the primary host name is substituted and used as a
8192 domain name, as just described.
8195 If the pattern is an IP address, it is matched against the IP address of the
8196 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8197 IPv6 addresses can be given in colon-separated format, but the colons have to
8198 be doubled so as not to be taken as item separators when the default list
8199 separator is used. IPv6 addresses are recognized even when Exim is compiled
8200 without IPv6 support. This means that if they appear in a host list on an
8201 IPv4-only host, Exim will not treat them as host names. They are just addresses
8202 that can never match a client host.
8205 .cindex "@[] in a host list"
8206 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8207 the local host. For example, if the local host is an IPv4 host with one
8208 interface address 10.45.23.56, these two ACL statements have the same effect:
8210 accept hosts = 127.0.0.1 : 10.45.23.56
8214 .cindex "CIDR notation"
8215 If the pattern is an IP address followed by a slash and a mask length (for
8216 example 10.11.42.0/24), it is matched against the IP address of the subject
8217 host under the given mask. This allows, an entire network of hosts to be
8218 included (or excluded) by a single item. The mask uses CIDR notation; it
8219 specifies the number of address bits that must match, starting from the most
8220 significant end of the address.
8222 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8223 of a range of addresses. It is the number of bits in the network portion of the
8224 address. The above example specifies a 24-bit netmask, so it matches all 256
8225 addresses in the 10.11.42.0 network. An item such as
8229 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8230 32 for an IPv4 address is the same as no mask at all; just a single address
8233 Here is another example which shows an IPv4 and an IPv6 network:
8235 recipient_unqualified_hosts = 192.168.0.0/16: \
8236 3ffe::ffff::836f::::/48
8238 The doubling of list separator characters applies only when these items
8239 appear inline in a host list. It is not required when indirecting via a file.
8242 recipient_unqualified_hosts = /opt/exim/unqualnets
8244 could make use of a file containing
8249 to have exactly the same effect as the previous example. When listing IPv6
8250 addresses inline, it is usually more convenient to use the facility for
8251 changing separator characters. This list contains the same two networks:
8253 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8256 The separator is changed to semicolon by the leading &"<;"& at the start of the
8262 .section "Host list patterns for single-key lookups by host address" &&&
8263 "SECThoslispatsikey"
8264 .cindex "host list" "lookup of IP address"
8265 When a host is to be identified by a single-key lookup of its complete IP
8266 address, the pattern takes this form:
8268 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8272 hosts_lookup = net-cdb;/hosts-by-ip.db
8274 The text form of the IP address of the subject host is used as the lookup key.
8275 IPv6 addresses are converted to an unabbreviated form, using lower case
8276 letters, with dots as separators because colon is the key terminator in
8277 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8278 quoting the keys, but this is a facility that was added later.] The data
8279 returned by the lookup is not used.
8281 .cindex "IP address" "masking"
8282 .cindex "host list" "masked IP address"
8283 Single-key lookups can also be performed using masked IP addresses, using
8284 patterns of this form:
8286 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8290 net24-dbm;/networks.db
8292 The IP address of the subject host is masked using <&'number'&> as the mask
8293 length. A textual string is constructed from the masked value, followed by the
8294 mask, and this is used as the lookup key. For example, if the host's IP address
8295 is 192.168.34.6, the key that is looked up for the above example is
8296 &"192.168.34.0/24"&.
8298 When an IPv6 address is converted to a string, dots are normally used instead
8299 of colons, so that keys in &(lsearch)& files need not contain colons (which
8300 terminate &(lsearch)& keys). This was implemented some time before the ability
8301 to quote keys was made available in &(lsearch)& files. However, the more
8302 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8303 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8304 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8305 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8306 addresses are always used.
8308 Ideally, it would be nice to tidy up this anomalous situation by changing to
8309 colons in all cases, given that quoting is now available for &(lsearch)&.
8310 However, this would be an incompatible change that might break some existing
8313 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8314 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8315 the former case the key strings include the mask value, whereas in the latter
8316 case the IP address is used on its own.
8320 .section "Host list patterns that match by host name" "SECThoslispatnam"
8321 .cindex "host" "lookup failures"
8322 .cindex "unknown host name"
8323 .cindex "host list" "matching host name"
8324 There are several types of pattern that require Exim to know the name of the
8325 remote host. These are either wildcard patterns or lookups by name. (If a
8326 complete hostname is given without any wildcarding, it is used to find an IP
8327 address to match against, as described in section &<<SECThoslispatip>>&
8330 If the remote host name is not already known when Exim encounters one of these
8331 patterns, it has to be found from the IP address.
8332 Although many sites on the Internet are conscientious about maintaining reverse
8333 DNS data for their hosts, there are also many that do not do this.
8334 Consequently, a name cannot always be found, and this may lead to unwanted
8335 effects. Take care when configuring host lists with wildcarded name patterns.
8336 Consider what will happen if a name cannot be found.
8338 Because of the problems of determining host names from IP addresses, matching
8339 against host names is not as common as matching against IP addresses.
8341 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8342 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8343 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8344 are done can be changed by setting the &%host_lookup_order%& option. For
8345 security, once Exim has found one or more names, it looks up the IP addresses
8346 for these names and compares them with the IP address that it started with.
8347 Only those names whose IP addresses match are accepted. Any other names are
8348 discarded. If no names are left, Exim behaves as if the host name cannot be
8349 found. In the most common case there is only one name and one IP address.
8351 There are some options that control what happens if a host name cannot be
8352 found. These are described in section &<<SECTbehipnot>>& below.
8354 .cindex "host" "alias for"
8355 .cindex "alias for host"
8356 As a result of aliasing, hosts may have more than one name. When processing any
8357 of the following types of pattern, all the host's names are checked:
8360 .cindex "asterisk" "in host list"
8361 If a pattern starts with &"*"& the remainder of the item must match the end of
8362 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8363 &'.b.c'&. This special simple form is provided because this is a very common
8364 requirement. Other kinds of wildcarding require the use of a regular
8367 .cindex "regular expressions" "in host list"
8368 .cindex "host list" "regular expression in"
8369 If the item starts with &"^"& it is taken to be a regular expression which is
8370 matched against the host name. Host names are case-independent, so this regular
8371 expression match is by default case-independent, but you can make it
8372 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8373 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8378 is a regular expression that matches either of the two hosts &'a.c.d'& or
8379 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8380 that backslash and dollar characters are not misinterpreted as part of the
8381 string expansion. The simplest way to do this is to use &`\N`& to mark that
8382 part of the string as non-expandable. For example:
8384 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8386 &*Warning*&: If you want to match a complete host name, you must include the
8387 &`$`& terminating metacharacter in the regular expression, as in the above
8388 example. Without it, a match at the start of the host name is all that is
8395 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8396 .cindex "host" "lookup failures, permanent"
8397 While processing a host list, Exim may need to look up an IP address from a
8398 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8399 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8400 behaviour when it fails to find the information it is seeking is the same.
8402 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8403 apply to temporary DNS errors, whose handling is described in the next section.
8405 .cindex "&`+include_unknown`&"
8406 .cindex "&`+ignore_unknown`&"
8407 Exim parses a host list from left to right. If it encounters a permanent
8408 lookup failure in any item in the host list before it has found a match,
8409 Exim treats it as a failure and the default behavior is as if the host
8410 does not match the list. This may not always be what you want to happen.
8411 To change Exim's behaviour, the special items &`+include_unknown`& or
8412 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8413 not recognized in an indirected file).
8416 If any item that follows &`+include_unknown`& requires information that
8417 cannot found, Exim behaves as if the host does match the list. For example,
8419 host_reject_connection = +include_unknown:*.enemy.ex
8421 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8422 any hosts whose name it cannot find.
8425 If any item that follows &`+ignore_unknown`& requires information that cannot
8426 be found, Exim ignores that item and proceeds to the rest of the list. For
8429 accept hosts = +ignore_unknown : friend.example : \
8432 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8433 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8434 name can be found for 192.168.4.5, it is rejected.
8437 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8438 list. The effect of each one lasts until the next, or until the end of the
8441 .section "Mixing wildcarded host names and addresses in host lists" &&&
8443 .cindex "host list" "mixing names and addresses in"
8445 This section explains the host/ip processing logic with the same concepts
8446 as the previous section, but specifically addresses what happens when a
8447 wildcarded hostname is one of the items in the hostlist.
8450 If you have name lookups or wildcarded host names and
8451 IP addresses in the same host list, you should normally put the IP
8452 addresses first. For example, in an ACL you could have:
8454 accept hosts = 10.9.8.7 : *.friend.example
8456 The reason you normally would order it this way lies in the
8457 left-to-right way that Exim processes lists. It can test IP addresses
8458 without doing any DNS lookups, but when it reaches an item that requires
8459 a host name, it fails if it cannot find a host name to compare with the
8460 pattern. If the above list is given in the opposite order, the
8461 &%accept%& statement fails for a host whose name cannot be found, even
8462 if its IP address is 10.9.8.7.
8465 If you really do want to do the name check first, and still recognize the IP
8466 address, you can rewrite the ACL like this:
8468 accept hosts = *.friend.example
8469 accept hosts = 10.9.8.7
8471 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8472 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8473 &`+ignore_unknown`&, which was discussed in depth in the first example in
8478 .section "Temporary DNS errors when looking up host information" &&&
8480 .cindex "host" "lookup failures, temporary"
8481 .cindex "&`+include_defer`&"
8482 .cindex "&`+ignore_defer`&"
8483 A temporary DNS lookup failure normally causes a defer action (except when
8484 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8485 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8486 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8487 section. These options should be used with care, probably only in non-critical
8488 host lists such as whitelists.
8492 .section "Host list patterns for single-key lookups by host name" &&&
8493 "SECThoslispatnamsk"
8494 .cindex "unknown host name"
8495 .cindex "host list" "matching host name"
8496 If a pattern is of the form
8498 <&'single-key-search-type'&>;<&'search-data'&>
8502 dbm;/host/accept/list
8504 a single-key lookup is performed, using the host name as its key. If the
8505 lookup succeeds, the host matches the item. The actual data that is looked up
8508 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8509 keys in the file, not IP addresses. If you want to do lookups based on IP
8510 addresses, you must precede the search type with &"net-"& (see section
8511 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8512 two items in the same list, one doing an address lookup and one doing a name
8513 lookup, both using the same file.
8517 .section "Host list patterns for query-style lookups" "SECID81"
8518 If a pattern is of the form
8520 <&'query-style-search-type'&>;<&'query'&>
8522 the query is obeyed, and if it succeeds, the host matches the item. The actual
8523 data that is looked up is not used. The variables &$sender_host_address$& and
8524 &$sender_host_name$& can be used in the query. For example:
8526 hosts_lookup = pgsql;\
8527 select ip from hostlist where ip='$sender_host_address'
8529 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8530 can use the &%sg%& expansion item to change this if you need to. If you want to
8531 use masked IP addresses in database queries, you can use the &%mask%& expansion
8534 If the query contains a reference to &$sender_host_name$&, Exim automatically
8535 looks up the host name if it has not already done so. (See section
8536 &<<SECThoslispatnam>>& for comments on finding host names.)
8538 Historical note: prior to release 4.30, Exim would always attempt to find a
8539 host name before running the query, unless the search type was preceded by
8540 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8541 still recognized for query-style lookups, but its presence or absence has no
8542 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8543 See section &<<SECThoslispatsikey>>&.)
8549 .section "Address lists" "SECTaddresslist"
8550 .cindex "list" "address list"
8551 .cindex "address list" "empty item"
8552 .cindex "address list" "patterns"
8553 Address lists contain patterns that are matched against mail addresses. There
8554 is one special case to be considered: the sender address of a bounce message is
8555 always empty. You can test for this by providing an empty item in an address
8556 list. For example, you can set up a router to process bounce messages by
8557 using this option setting:
8561 The presence of the colon creates an empty item. If you do not provide any
8562 data, the list is empty and matches nothing. The empty sender can also be
8563 detected by a regular expression that matches an empty string,
8564 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8566 Non-empty items in an address list can be straightforward email addresses. For
8569 senders = jbc@askone.example : hs@anacreon.example
8571 A certain amount of wildcarding is permitted. If a pattern contains an @
8572 character, but is not a regular expression and does not begin with a
8573 semicolon-terminated lookup type (described below), the local part of the
8574 subject address is compared with the local part of the pattern, which may start
8575 with an asterisk. If the local parts match, the domain is checked in exactly
8576 the same way as for a pattern in a domain list. For example, the domain can be
8577 wildcarded, refer to a named list, or be a lookup:
8579 deny senders = *@*.spamming.site:\
8580 *@+hostile_domains:\
8581 bozo@partial-lsearch;/list/of/dodgy/sites:\
8582 *@dbm;/bad/domains.db
8584 .cindex "local part" "starting with !"
8585 .cindex "address list" "local part starting with !"
8586 If a local part that begins with an exclamation mark is required, it has to be
8587 specified using a regular expression, because otherwise the exclamation mark is
8588 treated as a sign of negation, as is standard in lists.
8590 If a non-empty pattern that is not a regular expression or a lookup does not
8591 contain an @ character, it is matched against the domain part of the subject
8592 address. The only two formats that are recognized this way are a literal
8593 domain, or a domain pattern that starts with *. In both these cases, the effect
8594 is the same as if &`*@`& preceded the pattern. For example:
8596 deny senders = enemy.domain : *.enemy.domain
8599 The following kinds of more complicated address list pattern can match any
8600 address, including the empty address that is characteristic of bounce message
8604 .cindex "regular expressions" "in address list"
8605 .cindex "address list" "regular expression in"
8606 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8607 done against the complete address, with the pattern as the regular expression.
8608 You must take care that backslash and dollar characters are not misinterpreted
8609 as part of the string expansion. The simplest way to do this is to use &`\N`&
8610 to mark that part of the string as non-expandable. For example:
8612 deny senders = \N^.*this.*@example\.com$\N : \
8613 \N^\d{8}.+@spamhaus.example$\N : ...
8615 The &`\N`& sequences are removed by the expansion, so these items do indeed
8616 start with &"^"& by the time they are being interpreted as address patterns.
8619 .cindex "address list" "lookup for complete address"
8620 Complete addresses can be looked up by using a pattern that starts with a
8621 lookup type terminated by a semicolon, followed by the data for the lookup. For
8624 deny senders = cdb;/etc/blocked.senders : \
8625 mysql;select address from blocked where \
8626 address='${quote_mysql:$sender_address}'
8628 Both query-style and single-key lookup types can be used. For a single-key
8629 lookup type, Exim uses the complete address as the key. However, empty keys are
8630 not supported for single-key lookups, so a match against the empty address
8631 always fails. This restriction does not apply to query-style lookups.
8633 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8634 cannot be used, and is ignored if specified, with an entry being written to the
8636 .cindex "*@ with single-key lookup"
8637 However, you can configure lookup defaults, as described in section
8638 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8639 default. For example, with this lookup:
8641 accept senders = lsearch*@;/some/file
8643 the file could contains lines like this:
8645 user1@domain1.example
8648 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8651 nimrod@jaeger.example
8655 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8656 would mean that every address matches, thus rendering the test useless.
8658 &*Warning 2*&: Do not confuse these two kinds of item:
8660 deny recipients = dbm*@;/some/file
8661 deny recipients = *@dbm;/some/file
8663 The first does a whole address lookup, with defaulting, as just described,
8664 because it starts with a lookup type. The second matches the local part and
8665 domain independently, as described in a bullet point below.
8669 The following kinds of address list pattern can match only non-empty addresses.
8670 If the subject address is empty, a match against any of these pattern types
8675 .cindex "@@ with single-key lookup"
8676 .cindex "address list" "@@ lookup type"
8677 .cindex "address list" "split local part and domain"
8678 If a pattern starts with &"@@"& followed by a single-key lookup item
8679 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8680 split into a local part and a domain. The domain is looked up in the file. If
8681 it is not found, there is no match. If it is found, the data that is looked up
8682 from the file is treated as a colon-separated list of local part patterns, each
8683 of which is matched against the subject local part in turn.
8685 .cindex "asterisk" "in address list"
8686 The lookup may be a partial one, and/or one involving a search for a default
8687 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8688 patterns that are looked up can be regular expressions or begin with &"*"&, or
8689 even be further lookups. They may also be independently negated. For example,
8692 deny senders = @@dbm;/etc/reject-by-domain
8694 the data from which the DBM file is built could contain lines like
8696 baddomain.com: !postmaster : *
8698 to reject all senders except &%postmaster%& from that domain.
8700 .cindex "local part" "starting with !"
8701 If a local part that actually begins with an exclamation mark is required, it
8702 has to be specified using a regular expression. In &(lsearch)& files, an entry
8703 may be split over several lines by indenting the second and subsequent lines,
8704 but the separating colon must still be included at line breaks. White space
8705 surrounding the colons is ignored. For example:
8707 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8710 As in all colon-separated lists in Exim, a colon can be included in an item by
8713 If the last item in the list starts with a right angle-bracket, the remainder
8714 of the item is taken as a new key to look up in order to obtain a continuation
8715 list of local parts. The new key can be any sequence of characters. Thus one
8716 might have entries like
8718 aol.com: spammer1 : spammer 2 : >*
8719 xyz.com: spammer3 : >*
8722 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8723 local parts for all domains, in addition to the specific local parts listed for
8724 each domain. Of course, using this feature costs another lookup each time a
8725 chain is followed, but the effort needed to maintain the data is reduced.
8727 .cindex "loop" "in lookups"
8728 It is possible to construct loops using this facility, and in order to catch
8729 them, the chains may be no more than fifty items long.
8732 The @@<&'lookup'&> style of item can also be used with a query-style
8733 lookup, but in this case, the chaining facility is not available. The lookup
8734 can only return a single list of local parts.
8737 &*Warning*&: There is an important difference between the address list items
8738 in these two examples:
8741 senders = *@+my_list
8743 In the first one, &`my_list`& is a named address list, whereas in the second
8744 example it is a named domain list.
8749 .section "Case of letters in address lists" "SECTcasletadd"
8750 .cindex "case of local parts"
8751 .cindex "address list" "case forcing"
8752 .cindex "case forcing in address lists"
8753 Domains in email addresses are always handled caselessly, but for local parts
8754 case may be significant on some systems (see &%caseful_local_part%& for how
8755 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8756 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8757 blocking lists should be done in a case-independent manner. Since most address
8758 lists in Exim are used for this kind of control, Exim attempts to do this by
8761 The domain portion of an address is always lowercased before matching it to an
8762 address list. The local part is lowercased by default, and any string
8763 comparisons that take place are done caselessly. This means that the data in
8764 the address list itself, in files included as plain file names, and in any file
8765 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8766 keys in files that are looked up by a search type other than &(lsearch)& (which
8767 works caselessly) must be in lower case, because these lookups are not
8770 .cindex "&`+caseful`&"
8771 To allow for the possibility of caseful address list matching, if an item in
8772 an address list is the string &"+caseful"&, the original case of the local
8773 part is restored for any comparisons that follow, and string comparisons are no
8774 longer case-independent. This does not affect the domain, which remains in
8775 lower case. However, although independent matches on the domain alone are still
8776 performed caselessly, regular expressions that match against an entire address
8777 become case-sensitive after &"+caseful"& has been seen.
8781 .section "Local part lists" "SECTlocparlis"
8782 .cindex "list" "local part list"
8783 .cindex "local part" "list"
8784 Case-sensitivity in local part lists is handled in the same way as for address
8785 lists, as just described. The &"+caseful"& item can be used if required. In a
8786 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8787 set false, the subject is lowercased and the matching is initially
8788 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8789 matching in the local part list, but not elsewhere in the router. If
8790 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8791 option is case-sensitive from the start.
8793 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8794 comments are handled in the same way as address lists &-- they are recognized
8795 only if the # is preceded by white space or the start of the line.
8796 Otherwise, local part lists are matched in the same way as domain lists, except
8797 that the special items that refer to the local host (&`@`&, &`@[]`&,
8798 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8799 Refer to section &<<SECTdomainlist>>& for details of the other available item
8801 .ecindex IIDdohoadli
8806 . ////////////////////////////////////////////////////////////////////////////
8807 . ////////////////////////////////////////////////////////////////////////////
8809 .chapter "String expansions" "CHAPexpand"
8810 .scindex IIDstrexp "expansion" "of strings"
8811 Many strings in Exim's run time configuration are expanded before use. Some of
8812 them are expanded every time they are used; others are expanded only once.
8814 When a string is being expanded it is copied verbatim from left to right except
8815 when a dollar or backslash character is encountered. A dollar specifies the
8816 start of a portion of the string that is interpreted and replaced as described
8817 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8818 escape character, as described in the following section.
8820 Whether a string is expanded depends upon the context. Usually this is solely
8821 dependent upon the option for which a value is sought; in this documentation,
8822 options for which string expansion is performed are marked with † after
8823 the data type. ACL rules always expand strings. A couple of expansion
8824 conditions do not expand some of the brace-delimited branches, for security
8829 .section "Literal text in expanded strings" "SECTlittext"
8830 .cindex "expansion" "including literal text"
8831 An uninterpreted dollar can be included in an expanded string by putting a
8832 backslash in front of it. A backslash can be used to prevent any special
8833 character being treated specially in an expansion, including backslash itself.
8834 If the string appears in quotes in the configuration file, two backslashes are
8835 required because the quotes themselves cause interpretation of backslashes when
8836 the string is read in (see section &<<SECTstrings>>&).
8838 .cindex "expansion" "non-expandable substrings"
8839 A portion of the string can specified as non-expandable by placing it between
8840 two occurrences of &`\N`&. This is particularly useful for protecting regular
8841 expressions, which often contain backslashes and dollar signs. For example:
8843 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8845 On encountering the first &`\N`&, the expander copies subsequent characters
8846 without interpretation until it reaches the next &`\N`& or the end of the
8851 .section "Character escape sequences in expanded strings" "SECID82"
8852 .cindex "expansion" "escape sequences"
8853 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8854 expanded string is recognized as an escape sequence for the character newline,
8855 carriage return, or tab, respectively. A backslash followed by up to three
8856 octal digits is recognized as an octal encoding for a single character, and a
8857 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8860 These escape sequences are also recognized in quoted strings when they are read
8861 in. Their interpretation in expansions as well is useful for unquoted strings,
8862 and for other cases such as looked-up strings that are then expanded.
8865 .section "Testing string expansions" "SECID83"
8866 .cindex "expansion" "testing"
8867 .cindex "testing" "string expansion"
8869 Many expansions can be tested by calling Exim with the &%-be%& option. This
8870 takes the command arguments, or lines from the standard input if there are no
8871 arguments, runs them through the string expansion code, and writes the results
8872 to the standard output. Variables based on configuration values are set up, but
8873 since no message is being processed, variables such as &$local_part$& have no
8874 value. Nevertheless the &%-be%& option can be useful for checking out file and
8875 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8878 Exim gives up its root privilege when it is called with the &%-be%& option, and
8879 instead runs under the uid and gid it was called with, to prevent users from
8880 using &%-be%& for reading files to which they do not have access.
8883 If you want to test expansions that include variables whose values are taken
8884 from a message, there are two other options that can be used. The &%-bem%&
8885 option is like &%-be%& except that it is followed by a file name. The file is
8886 read as a message before doing the test expansions. For example:
8888 exim -bem /tmp/test.message '$h_subject:'
8890 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8891 Exim message identifier. For example:
8893 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8895 This loads the message from Exim's spool before doing the test expansions, and
8896 is therefore restricted to admin users.
8899 .section "Forced expansion failure" "SECTforexpfai"
8900 .cindex "expansion" "forced failure"
8901 A number of expansions that are described in the following section have
8902 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8903 (which are sometimes called &"curly brackets"&). Which of the two strings is
8904 used depends on some condition that is evaluated as part of the expansion. If,
8905 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8906 the entire string expansion fails in a way that can be detected by the code
8907 that requested the expansion. This is called &"forced expansion failure"&, and
8908 its consequences depend on the circumstances. In some cases it is no different
8909 from any other expansion failure, but in others a different action may be
8910 taken. Such variations are mentioned in the documentation of the option that is
8916 .section "Expansion items" "SECTexpansionitems"
8917 The following items are recognized in expanded strings. White space may be used
8918 between sub-items that are keywords or substrings enclosed in braces inside an
8919 outer set of braces, to improve readability. &*Warning*&: Within braces,
8920 white space is significant.
8923 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8924 .cindex "expansion" "variables"
8925 Substitute the contents of the named variable, for example:
8930 The second form can be used to separate the name from subsequent alphanumeric
8931 characters. This form (using braces) is available only for variables; it does
8932 &'not'& apply to message headers. The names of the variables are given in
8933 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8934 given, the expansion fails.
8936 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8937 .cindex "expansion" "operators"
8938 The string is first itself expanded, and then the operation specified by
8939 <&'op'&> is applied to it. For example:
8943 The string starts with the first character after the colon, which may be
8944 leading white space. A list of operators is given in section &<<SECTexpop>>&
8945 below. The operator notation is used for simple expansion items that have just
8946 one argument, because it reduces the number of braces and therefore makes the
8947 string easier to understand.
8949 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8950 This item inserts &"basic"& header lines. It is described with the &%header%&
8951 expansion item below.
8954 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
8955 .cindex "expansion" "calling an acl"
8956 .cindex "&%acl%&" "call from expansion"
8957 The name and zero to nine argument strings are first expanded separately. The expanded
8958 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
8959 Any unused are made empty. The variable &$acl_narg$& is set to the number of
8960 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
8961 and may use the variables; if another acl expansion is used the values
8962 are restored after it returns. If the ACL sets
8963 a value using a "message =" modifier and returns accept or deny, the value becomes
8964 the result of the expansion.
8965 If no message is set and the ACL returns accept or deny
8966 the expansion result is an empty string.
8967 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
8970 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
8971 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8972 .cindex "expansion" "extracting cerificate fields"
8973 .cindex "&%certextract%&" "certificate fields"
8974 .cindex "certificate" "extracting fields"
8975 The <&'certificate'&> must be a variable of type certificate.
8976 The field name is expanded and used to retrieve the relevant field from
8977 the certificate. Supported fields are:
8981 &`subject `& RFC4514 DN
8982 &`issuer `& RFC4514 DN
8987 &`subj_altname `& tagged list
8991 If the field is found,
8992 <&'string2'&> is expanded, and replaces the whole item;
8993 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8994 variable &$value$& contains the value that has been extracted. Afterwards, it
8995 is restored to any previous value it might have had.
8997 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8998 key is not found. If {<&'string2'&>} is also omitted, the value that was
9001 Some field names take optional modifiers, appended and separated by commas.
9003 The field selectors marked as "RFC4514" above
9004 output a Distinguished Name string which is
9006 parseable by Exim as a comma-separated tagged list
9007 (the exceptions being elements containing commas).
9008 RDN elements of a single type may be selected by
9009 a modifier of the type label; if so the expansion
9010 result is a list (newline-separated by default).
9011 The separator may be changed by another modifier of
9012 a right angle-bracket followed immediately by the new separator.
9013 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9015 The field selectors marked as "time" above
9016 take an optional modifier of "int"
9017 for which the result is the number of seconds since epoch.
9018 Otherwise the result is a human-readable string
9019 in the timezone selected by the main "timezone" option.
9021 The field selectors marked as "list" above return a list,
9022 newline-separated by default,
9023 (embedded separator characters in elements are doubled).
9024 The separator may be changed by a modifier of
9025 a right angle-bracket followed immediately by the new separator.
9027 The field selectors marked as "tagged" above
9028 prefix each list element with a type string and an equals sign.
9029 Elements of only one type may be selected by a modifier
9030 which is one of "dns", "uri" or "mail";
9031 if so the element tags are omitted.
9033 If not otherwise noted field values are presented in human-readable form.
9035 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9036 {*&<&'arg'&>&*}...}*&"
9038 This expansion dynamically loads and then calls a locally-written C function.
9039 This functionality is available only if Exim is compiled with
9043 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9044 object so that it doesn't reload the same object file in the same Exim process
9045 (but of course Exim does start new processes frequently).
9047 There may be from zero to eight arguments to the function. When compiling
9048 a local function that is to be called in this way, &_local_scan.h_& should be
9049 included. The Exim variables and functions that are defined by that API
9050 are also available for dynamically loaded functions. The function itself
9051 must have the following type:
9053 int dlfunction(uschar **yield, int argc, uschar *argv[])
9055 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9056 function should return one of the following values:
9058 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9059 into the expanded string that is being built.
9061 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9062 from &'yield'&, if it is set.
9064 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9065 taken from &'yield'& if it is set.
9067 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9069 When compiling a function that is to be used in this way with gcc,
9070 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9071 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9074 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9075 .cindex "expansion" "extracting value from environment"
9076 .cindex "environment" "value from"
9077 The key is first expanded separately, and leading and trailing white space
9079 This is then searched for as a name in the environment.
9080 If a variable is found then its value is placed in &$value$&
9081 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9083 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9084 appear, for example:
9086 ${env{USER}{$value} fail }
9088 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9089 {<&'string1'&>} must be present for &"fail"& to be recognized.
9091 If {<&'string2'&>} is omitted an empty string is substituted on
9093 If {<&'string1'&>} is omitted the search result is substituted on
9097 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9098 {*&<&'string3'&>&*}}*&"
9099 .cindex "expansion" "extracting substrings by key"
9100 .cindex "&%extract%&" "substrings by key"
9101 The key and <&'string1'&> are first expanded separately. Leading and trailing
9102 white space is removed from the key (but not from any of the strings). The key
9103 must not consist entirely of digits. The expanded <&'string1'&> must be of the
9106 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9109 where the equals signs and spaces (but not both) are optional. If any of the
9110 values contain white space, they must be enclosed in double quotes, and any
9111 values that are enclosed in double quotes are subject to escape processing as
9112 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9113 for the value that corresponds to the key. The search is case-insensitive. If
9114 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9115 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9116 variable &$value$& contains the value that has been extracted. Afterwards, it
9117 is restored to any previous value it might have had.
9119 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9120 key is not found. If {<&'string2'&>} is also omitted, the value that was
9121 extracted is used. Thus, for example, these two expansions are identical, and
9124 ${extract{gid}{uid=1984 gid=2001}}
9125 ${extract{gid}{uid=1984 gid=2001}{$value}}
9127 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9128 appear, for example:
9130 ${extract{Z}{A=... B=...}{$value} fail }
9132 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9133 {<&'string2'&>} must be present for &"fail"& to be recognized.
9136 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9137 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9138 .cindex "expansion" "extracting substrings by number"
9139 .cindex "&%extract%&" "substrings by number"
9140 The <&'number'&> argument must consist entirely of decimal digits,
9141 apart from leading and trailing white space, which is ignored.
9142 This is what distinguishes this form of &%extract%& from the previous kind. It
9143 behaves in the same way, except that, instead of extracting a named field, it
9144 extracts from <&'string1'&> the field whose number is given as the first
9145 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9146 <&'string3'&> as before.
9148 The fields in the string are separated by any one of the characters in the
9149 separator string. These may include space or tab characters.
9150 The first field is numbered one. If the number is negative, the fields are
9151 counted from the end of the string, with the rightmost one numbered -1. If the
9152 number given is zero, the entire string is returned. If the modulus of the
9153 number is greater than the number of fields in the string, the result is the
9154 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9155 provided. For example:
9157 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9161 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9163 yields &"99"&. Two successive separators mean that the field between them is
9164 empty (for example, the fifth field above).
9167 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9168 .cindex "list" "selecting by condition"
9169 .cindex "expansion" "selecting from list by condition"
9171 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9172 default, but the separator can be changed in the usual way. For each item
9173 in this list, its value is place in &$item$&, and then the condition is
9174 evaluated. If the condition is true, &$item$& is added to the output as an
9175 item in a new list; if the condition is false, the item is discarded. The
9176 separator used for the output list is the same as the one used for the
9177 input, but a separator setting is not included in the output. For example:
9179 ${filter{a:b:c}{!eq{$item}{b}}
9181 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9182 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9185 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9186 .cindex "hash function" "textual"
9187 .cindex "expansion" "textual hash"
9188 This is a textual hashing function, and was the first to be implemented in
9189 early versions of Exim. In current releases, there are other hashing functions
9190 (numeric, MD5, and SHA-1), which are described below.
9192 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9193 <&'n'&>. If you are using fixed values for these numbers, that is, if
9194 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9195 use the simpler operator notation that avoids some of the braces:
9197 ${hash_<n>_<m>:<string>}
9199 The second number is optional (in both notations). If <&'n'&> is greater than
9200 or equal to the length of the string, the expansion item returns the string.
9201 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9202 function to the string. The new string consists of characters taken from the
9203 first <&'m'&> characters of the string
9205 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9207 If <&'m'&> is not present the value 26 is used, so that only lower case
9208 letters appear. For example:
9210 &`$hash{3}{monty}} `& yields &`jmg`&
9211 &`$hash{5}{monty}} `& yields &`monty`&
9212 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9215 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9216 &*$h_*&<&'header&~name'&>&*:*&" &&&
9217 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9218 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9219 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9220 &*$rh_*&<&'header&~name'&>&*:*&"
9221 .cindex "expansion" "header insertion"
9222 .vindex "&$header_$&"
9223 .vindex "&$bheader_$&"
9224 .vindex "&$rheader_$&"
9225 .cindex "header lines" "in expansion strings"
9226 .cindex "header lines" "character sets"
9227 .cindex "header lines" "decoding"
9228 Substitute the contents of the named message header line, for example
9232 The newline that terminates a header line is not included in the expansion, but
9233 internal newlines (caused by splitting the header line over several physical
9234 lines) may be present.
9236 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9237 the data in the header line is interpreted.
9240 .cindex "white space" "in header lines"
9241 &%rheader%& gives the original &"raw"& content of the header line, with no
9242 processing at all, and without the removal of leading and trailing white space.
9245 .cindex "base64 encoding" "in header lines"
9246 &%bheader%& removes leading and trailing white space, and then decodes base64
9247 or quoted-printable MIME &"words"& within the header text, but does no
9248 character set translation. If decoding of what looks superficially like a MIME
9249 &"word"& fails, the raw string is returned. If decoding
9250 .cindex "binary zero" "in header line"
9251 produces a binary zero character, it is replaced by a question mark &-- this is
9252 what Exim does for binary zeros that are actually received in header lines.
9255 &%header%& tries to translate the string as decoded by &%bheader%& to a
9256 standard character set. This is an attempt to produce the same string as would
9257 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9258 returned. Translation is attempted only on operating systems that support the
9259 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9260 a system Makefile or in &_Local/Makefile_&.
9263 In a filter file, the target character set for &%header%& can be specified by a
9264 command of the following form:
9266 headers charset "UTF-8"
9268 This command affects all references to &$h_$& (or &$header_$&) expansions in
9269 subsequently obeyed filter commands. In the absence of this command, the target
9270 character set in a filter is taken from the setting of the &%headers_charset%&
9271 option in the runtime configuration. The value of this option defaults to the
9272 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9275 Header names follow the syntax of RFC 2822, which states that they may contain
9276 any printing characters except space and colon. Consequently, curly brackets
9277 &'do not'& terminate header names, and should not be used to enclose them as
9278 if they were variables. Attempting to do so causes a syntax error.
9280 Only header lines that are common to all copies of a message are visible to
9281 this mechanism. These are the original header lines that are received with the
9282 message, and any that are added by an ACL statement or by a system
9283 filter. Header lines that are added to a particular copy of a message by a
9284 router or transport are not accessible.
9286 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
9287 before the DATA ACL, because the header structure is not set up until the
9288 message is received. Header lines that are added in a RCPT ACL (for example)
9289 are saved until the message's incoming header lines are available, at which
9290 point they are added. When a DATA ACL is running, however, header lines added
9291 by earlier ACLs are visible.
9293 Upper case and lower case letters are synonymous in header names. If the
9294 following character is white space, the terminating colon may be omitted, but
9295 this is not recommended, because you may then forget it when it is needed. When
9296 white space terminates the header name, this white space is included in the
9297 expanded string. If the message does not contain the given header, the
9298 expansion item is replaced by an empty string. (See the &%def%& condition in
9299 section &<<SECTexpcond>>& for a means of testing for the existence of a
9302 If there is more than one header with the same name, they are all concatenated
9303 to form the substitution string, up to a maximum length of 64K. Unless
9304 &%rheader%& is being used, leading and trailing white space is removed from
9305 each header before concatenation, and a completely empty header is ignored. A
9306 newline character is then inserted between non-empty headers, but there is no
9307 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9308 those headers that contain lists of addresses, a comma is also inserted at the
9309 junctions between headers. This does not happen for the &%rheader%& expansion.
9312 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9313 .cindex "expansion" "hmac hashing"
9315 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9316 shared secret and some text into a message authentication code, as specified in
9317 RFC 2104. This differs from &`${md5:secret_text...}`& or
9318 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9319 cryptographic hash, allowing for authentication that is not possible with MD5
9320 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9321 present. For example:
9323 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9325 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9328 dd97e3ba5d1a61b5006108f8c8252953
9330 As an example of how this might be used, you might put in the main part of
9331 an Exim configuration:
9333 SPAMSCAN_SECRET=cohgheeLei2thahw
9335 In a router or a transport you could then have:
9338 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9339 ${hmac{md5}{SPAMSCAN_SECRET}\
9340 {${primary_hostname},${message_exim_id},$h_message-id:}}
9342 Then given a message, you can check where it was scanned by looking at the
9343 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9344 this header line is authentic by recomputing the authentication code from the
9345 host name, message ID and the &'Message-id:'& header line. This can be done
9346 using Exim's &%-be%& option, or by other means, for example by using the
9347 &'hmac_md5_hex()'& function in Perl.
9350 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9351 .cindex "expansion" "conditional"
9352 .cindex "&%if%&, expansion item"
9353 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9354 item; otherwise <&'string2'&> is used. The available conditions are described
9355 in section &<<SECTexpcond>>& below. For example:
9357 ${if eq {$local_part}{postmaster} {yes}{no} }
9359 The second string need not be present; if it is not and the condition is not
9360 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9361 be present instead of the second string (without any curly brackets). In this
9362 case, the expansion is forced to fail if the condition is not true (see section
9363 &<<SECTforexpfai>>&).
9365 If both strings are omitted, the result is the string &`true`& if the condition
9366 is true, and the empty string if the condition is false. This makes it less
9367 cumbersome to write custom ACL and router conditions. For example, instead of
9369 condition = ${if >{$acl_m4}{3}{true}{false}}
9373 condition = ${if >{$acl_m4}{3}}
9379 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
9380 .cindex expansion "imap folder"
9381 .cindex "&%imapfolder%& expansion item"
9382 This item converts a (possibly multilevel, or with non-ASCII characters)
9383 folder specification to a Maildir name for filesystem use.
9384 For information on internationalisation support see &<<SECTi18nMDA>>&.
9389 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9390 .cindex "expansion" "string truncation"
9391 .cindex "&%length%& expansion item"
9392 The &%length%& item is used to extract the initial portion of a string. Both
9393 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9394 you are using a fixed value for the number, that is, if <&'string1'&> does not
9395 change when expanded, you can use the simpler operator notation that avoids
9398 ${length_<n>:<string>}
9400 The result of this item is either the first <&'n'&> characters or the whole
9401 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9402 &%strlen%&, which gives the length of a string.
9405 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9406 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9407 .cindex "expansion" "extracting list elements by number"
9408 .cindex "&%listextract%&" "extract list elements by number"
9409 .cindex "list" "extracting elements by number"
9410 The <&'number'&> argument must consist entirely of decimal digits,
9411 apart from an optional leading minus,
9412 and leading and trailing white space (which is ignored).
9414 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9415 default, but the separator can be changed in the usual way.
9417 The first field of the list is numbered one.
9418 If the number is negative, the fields are
9419 counted from the end of the list, with the rightmost one numbered -1.
9420 The numbered element of the list is extracted and placed in &$value$&,
9421 then <&'string2'&> is expanded as the result.
9423 If the modulus of the
9424 number is zero or greater than the number of fields in the string,
9425 the result is the expansion of <&'string3'&>.
9429 ${listextract{2}{x:42:99}}
9433 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9435 yields &"result: 42"&.
9437 If {<&'string3'&>} is omitted, an empty string is used for string3.
9438 If {<&'string2'&>} is also omitted, the value that was
9440 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9443 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9444 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9445 This is the first of one of two different types of lookup item, which are both
9446 described in the next item.
9448 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9449 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9450 .cindex "expansion" "lookup in"
9451 .cindex "file" "lookups"
9452 .cindex "lookup" "in expanded string"
9453 The two forms of lookup item specify data lookups in files and databases, as
9454 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9455 lookups, and the second is used for query-style lookups. The <&'key'&>,
9456 <&'file'&>, and <&'query'&> strings are expanded before use.
9458 If there is any white space in a lookup item which is part of a filter command,
9459 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9460 other place where white space is significant, the lookup item must be enclosed
9461 in double quotes. The use of data lookups in users' filter files may be locked
9462 out by the system administrator.
9465 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9466 During its expansion, the variable &$value$& contains the data returned by the
9467 lookup. Afterwards it reverts to the value it had previously (at the outer
9468 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9469 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9470 string on failure. If <&'string2'&> is provided, it can itself be a nested
9471 lookup, thus providing a mechanism for looking up a default value when the
9472 original lookup fails.
9474 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9475 data for the outer lookup while the parameters of the second lookup are
9476 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9477 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9478 appear, and in this case, if the lookup fails, the entire expansion is forced
9479 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9480 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9481 successful lookup, and nothing in the case of failure.
9483 For single-key lookups, the string &"partial"& is permitted to precede the
9484 search type in order to do partial matching, and * or *@ may follow a search
9485 type to request default lookups if the key does not match (see sections
9486 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9488 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9489 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9490 and non-wild parts of the key during the expansion of the replacement text.
9491 They return to their previous values at the end of the lookup item.
9493 This example looks up the postmaster alias in the conventional alias file:
9495 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9497 This example uses NIS+ to look up the full name of the user corresponding to
9498 the local part of an address, forcing the expansion to fail if it is not found:
9500 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9505 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9506 .cindex "expansion" "list creation"
9508 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9509 default, but the separator can be changed in the usual way. For each item
9510 in this list, its value is place in &$item$&, and then <&'string2'&> is
9511 expanded and added to the output as an item in a new list. The separator used
9512 for the output list is the same as the one used for the input, but a separator
9513 setting is not included in the output. For example:
9515 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9517 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9518 value of &$item$& is restored to what it was before. See also the &*filter*&
9519 and &*reduce*& expansion items.
9521 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9522 .cindex "expansion" "numeric hash"
9523 .cindex "hash function" "numeric"
9524 The three strings are expanded; the first two must yield numbers. Call them
9525 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9526 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9527 can use the simpler operator notation that avoids some of the braces:
9529 ${nhash_<n>_<m>:<string>}
9531 The second number is optional (in both notations). If there is only one number,
9532 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9533 processed by a div/mod hash function that returns two numbers, separated by a
9534 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9537 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9539 returns the string &"6/33"&.
9543 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9544 .cindex "Perl" "use in expanded string"
9545 .cindex "expansion" "calling Perl from"
9546 This item is available only if Exim has been built to include an embedded Perl
9547 interpreter. The subroutine name and the arguments are first separately
9548 expanded, and then the Perl subroutine is called with those arguments. No
9549 additional arguments need be given; the maximum number permitted, including the
9550 name of the subroutine, is nine.
9552 The return value of the subroutine is inserted into the expanded string, unless
9553 the return value is &%undef%&. In that case, the expansion fails in the same
9554 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9555 Whatever you return is evaluated in a scalar context. For example, if you
9556 return the name of a Perl vector, the return value is the size of the vector,
9559 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9560 with the error message that was passed to &%die%&. More details of the embedded
9561 Perl facility are given in chapter &<<CHAPperl>>&.
9563 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9564 out the use of this expansion item in filter files.
9567 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9568 .cindex "&%prvs%& expansion item"
9569 The first argument is a complete email address and the second is secret
9570 keystring. The third argument, specifying a key number, is optional. If absent,
9571 it defaults to 0. The result of the expansion is a prvs-signed email address,
9572 to be typically used with the &%return_path%& option on an &(smtp)& transport
9573 as part of a bounce address tag validation (BATV) scheme. For more discussion
9574 and an example, see section &<<SECTverifyPRVS>>&.
9576 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9577 {*&<&'string'&>&*}}*&"
9578 .cindex "&%prvscheck%& expansion item"
9579 This expansion item is the complement of the &%prvs%& item. It is used for
9580 checking prvs-signed addresses. If the expansion of the first argument does not
9581 yield a syntactically valid prvs-signed address, the whole item expands to the
9582 empty string. When the first argument does expand to a syntactically valid
9583 prvs-signed address, the second argument is expanded, with the prvs-decoded
9584 version of the address and the key number extracted from the address in the
9585 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9587 These two variables can be used in the expansion of the second argument to
9588 retrieve the secret. The validity of the prvs-signed address is then checked
9589 against the secret. The result is stored in the variable &$prvscheck_result$&,
9590 which is empty for failure or &"1"& for success.
9592 The third argument is optional; if it is missing, it defaults to an empty
9593 string. This argument is now expanded. If the result is an empty string, the
9594 result of the expansion is the decoded version of the address. This is the case
9595 whether or not the signature was valid. Otherwise, the result of the expansion
9596 is the expansion of the third argument.
9598 All three variables can be used in the expansion of the third argument.
9599 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9600 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9602 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9603 .cindex "expansion" "inserting an entire file"
9604 .cindex "file" "inserting into expansion"
9605 .cindex "&%readfile%& expansion item"
9606 The file name and end-of-line string are first expanded separately. The file is
9607 then read, and its contents replace the entire item. All newline characters in
9608 the file are replaced by the end-of-line string if it is present. Otherwise,
9609 newlines are left in the string.
9610 String expansion is not applied to the contents of the file. If you want this,
9611 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9612 the string expansion fails.
9614 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9615 locks out the use of this expansion item in filter files.
9619 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9620 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9621 .cindex "expansion" "inserting from a socket"
9622 .cindex "socket, use of in expansion"
9623 .cindex "&%readsocket%& expansion item"
9624 This item inserts data from a Unix domain or TCP socket into the expanded
9625 string. The minimal way of using it uses just two arguments, as in these
9628 ${readsocket{/socket/name}{request string}}
9629 ${readsocket{inet:some.host:1234}{request string}}
9631 For a Unix domain socket, the first substring must be the path to the socket.
9632 For an Internet socket, the first substring must contain &`inet:`& followed by
9633 a host name or IP address, followed by a colon and a port, which can be a
9634 number or the name of a TCP port in &_/etc/services_&. An IP address may
9635 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9638 ${readsocket{inet:[::1]:1234}{request string}}
9640 Only a single host name may be given, but if looking it up yields more than
9641 one IP address, they are each tried in turn until a connection is made. For
9642 both kinds of socket, Exim makes a connection, writes the request string
9643 (unless it is an empty string) and reads from the socket until an end-of-file
9644 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9645 extend what can be done. Firstly, you can vary the timeout. For example:
9647 ${readsocket{/socket/name}{request string}{3s}}
9649 A fourth argument allows you to change any newlines that are in the data
9650 that is read, in the same way as for &%readfile%& (see above). This example
9651 turns them into spaces:
9653 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9655 As with all expansions, the substrings are expanded before the processing
9656 happens. Errors in these sub-expansions cause the expansion to fail. In
9657 addition, the following errors can occur:
9660 Failure to create a socket file descriptor;
9662 Failure to connect the socket;
9664 Failure to write the request string;
9666 Timeout on reading from the socket.
9669 By default, any of these errors causes the expansion to fail. However, if
9670 you supply a fifth substring, it is expanded and used when any of the above
9671 errors occurs. For example:
9673 ${readsocket{/socket/name}{request string}{3s}{\n}\
9676 You can test for the existence of a Unix domain socket by wrapping this
9677 expansion in &`${if exists`&, but there is a race condition between that test
9678 and the actual opening of the socket, so it is safer to use the fifth argument
9679 if you want to be absolutely sure of avoiding an expansion error for a
9680 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9682 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9683 locks out the use of this expansion item in filter files.
9686 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9687 .cindex "expansion" "reducing a list to a scalar"
9688 .cindex "list" "reducing to a scalar"
9691 This operation reduces a list to a single, scalar string. After expansion,
9692 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9693 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9694 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9695 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9696 them. The result of that expansion is assigned to &$value$& before the next
9697 iteration. When the end of the list is reached, the final value of &$value$& is
9698 added to the expansion output. The &*reduce*& expansion item can be used in a
9699 number of ways. For example, to add up a list of numbers:
9701 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9703 The result of that expansion would be &`6`&. The maximum of a list of numbers
9706 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9708 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9709 restored to what they were before. See also the &*filter*& and &*map*&
9712 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9713 This item inserts &"raw"& header lines. It is described with the &%header%&
9714 expansion item above.
9716 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9717 {*&<&'string2'&>&*}}*&"
9718 .cindex "expansion" "running a command"
9719 .cindex "&%run%& expansion item"
9720 The command and its arguments are first expanded as one string. The string is
9721 split apart into individual arguments by spaces, and then the command is run
9722 in a separate process, but under the same uid and gid. As in other command
9723 executions from Exim, a shell is not used by default. If the command requires
9724 a shell, you must explicitly code it.
9726 Since the arguments are split by spaces, when there is a variable expansion
9727 which has an empty result, it will cause the situation that the argument will
9728 simply be omitted when the program is actually executed by Exim. If the
9729 script/program requires a specific number of arguments and the expanded
9730 variable could possibly result in this empty expansion, the variable must be
9731 quoted. This is more difficult if the expanded variable itself could result
9732 in a string containing quotes, because it would interfere with the quotes
9733 around the command arguments. A possible guard against this is to wrap the
9734 variable in the &%sg%& operator to change any quote marks to some other
9737 The standard input for the command exists, but is empty. The standard output
9738 and standard error are set to the same file descriptor.
9739 .cindex "return code" "from &%run%& expansion"
9741 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9742 and replaces the entire item; during this expansion, the standard output/error
9743 from the command is in the variable &$value$&. If the command fails,
9744 <&'string2'&>, if present, is expanded and used. Once again, during the
9745 expansion, the standard output/error from the command is in the variable
9748 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9749 can be the word &"fail"& (not in braces) to force expansion failure if the
9750 command does not succeed. If both strings are omitted, the result is contents
9751 of the standard output/error on success, and nothing on failure.
9753 .vindex "&$run_in_acl$&"
9754 The standard output/error of the command is put in the variable &$value$&.
9755 In this ACL example, the output of a command is logged for the admin to
9758 warn condition = ${run{/usr/bin/id}{yes}{no}}
9759 log_message = Output of id: $value
9761 If the command requires shell idioms, such as the > redirect operator, the
9762 shell must be invoked directly, such as with:
9764 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9768 The return code from the command is put in the variable &$runrc$&, and this
9769 remains set afterwards, so in a filter file you can do things like this:
9771 if "${run{x y z}{}}$runrc" is 1 then ...
9772 elif $runrc is 2 then ...
9776 If execution of the command fails (for example, the command does not exist),
9777 the return code is 127 &-- the same code that shells use for non-existent
9780 &*Warning*&: In a router or transport, you cannot assume the order in which
9781 option values are expanded, except for those preconditions whose order of
9782 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9783 by the expansion of one option, and use it in another.
9785 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9786 out the use of this expansion item in filter files.
9789 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9790 .cindex "expansion" "string substitution"
9791 .cindex "&%sg%& expansion item"
9792 This item works like Perl's substitution operator (s) with the global (/g)
9793 option; hence its name. However, unlike the Perl equivalent, Exim does not
9794 modify the subject string; instead it returns the modified string for insertion
9795 into the overall expansion. The item takes three arguments: the subject string,
9796 a regular expression, and a substitution string. For example:
9798 ${sg{abcdefabcdef}{abc}{xyz}}
9800 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9801 if any $ or \ characters are required in the regular expression or in the
9802 substitution string, they have to be escaped. For example:
9804 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9806 yields &"defabc"&, and
9808 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9810 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9811 the regular expression from string expansion.
9815 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
9816 .cindex sorting "a list"
9817 .cindex list sorting
9818 .cindex expansion "list sorting"
9819 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9820 default, but the separator can be changed in the usual way.
9821 The <&'comparator'&> argument is interpreted as the operator
9822 of a two-argument expansion condition.
9823 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
9824 The comparison should return true when applied to two values
9825 if the first value should sort before the second value.
9826 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
9827 the element being placed in &$item$&,
9828 to give values for comparison.
9830 The item result is a sorted list,
9831 with the original list separator,
9832 of the list elements (in full) of the original.
9836 ${sort{3:2:1:4}{<}{$item}}
9838 sorts a list of numbers, and
9840 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
9842 will sort an MX lookup into priority order.
9845 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9846 .cindex "&%substr%& expansion item"
9847 .cindex "substring extraction"
9848 .cindex "expansion" "substring extraction"
9849 The three strings are expanded; the first two must yield numbers. Call them
9850 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9851 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9852 can use the simpler operator notation that avoids some of the braces:
9854 ${substr_<n>_<m>:<string>}
9856 The second number is optional (in both notations).
9857 If it is absent in the simpler format, the preceding underscore must also be
9860 The &%substr%& item can be used to extract more general substrings than
9861 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9862 length required. For example
9864 ${substr{3}{2}{$local_part}}
9866 If the starting offset is greater than the string length the result is the
9867 null string; if the length plus starting offset is greater than the string
9868 length, the result is the right-hand part of the string, starting from the
9869 given offset. The first character in the string has offset zero.
9871 The &%substr%& expansion item can take negative offset values to count
9872 from the right-hand end of its operand. The last character is offset -1, the
9873 second-last is offset -2, and so on. Thus, for example,
9875 ${substr{-5}{2}{1234567}}
9877 yields &"34"&. If the absolute value of a negative offset is greater than the
9878 length of the string, the substring starts at the beginning of the string, and
9879 the length is reduced by the amount of overshoot. Thus, for example,
9881 ${substr{-5}{2}{12}}
9883 yields an empty string, but
9885 ${substr{-3}{2}{12}}
9889 When the second number is omitted from &%substr%&, the remainder of the string
9890 is taken if the offset is positive. If it is negative, all characters in the
9891 string preceding the offset point are taken. For example, an offset of -1 and
9892 no length, as in these semantically identical examples:
9895 ${substr{-1}{abcde}}
9897 yields all but the last character of the string, that is, &"abcd"&.
9901 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9902 {*&<&'replacements'&>&*}}*&"
9903 .cindex "expansion" "character translation"
9904 .cindex "&%tr%& expansion item"
9905 This item does single-character translation on its subject string. The second
9906 argument is a list of characters to be translated in the subject string. Each
9907 matching character is replaced by the corresponding character from the
9908 replacement list. For example
9910 ${tr{abcdea}{ac}{13}}
9912 yields &`1b3de1`&. If there are duplicates in the second character string, the
9913 last occurrence is used. If the third string is shorter than the second, its
9914 last character is replicated. However, if it is empty, no translation takes
9920 .section "Expansion operators" "SECTexpop"
9921 .cindex "expansion" "operators"
9922 For expansion items that perform transformations on a single argument string,
9923 the &"operator"& notation is used because it is simpler and uses fewer braces.
9924 The substring is first expanded before the operation is applied to it. The
9925 following operations can be performed:
9928 .vitem &*${address:*&<&'string'&>&*}*&
9929 .cindex "expansion" "RFC 2822 address handling"
9930 .cindex "&%address%& expansion item"
9931 The string is interpreted as an RFC 2822 address, as it might appear in a
9932 header line, and the effective address is extracted from it. If the string does
9933 not parse successfully, the result is empty.
9936 .vitem &*${addresses:*&<&'string'&>&*}*&
9937 .cindex "expansion" "RFC 2822 address handling"
9938 .cindex "&%addresses%& expansion item"
9939 The string (after expansion) is interpreted as a list of addresses in RFC
9940 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9941 operative address (&'local-part@domain'&) is extracted from each item, and the
9942 result of the expansion is a colon-separated list, with appropriate
9943 doubling of colons should any happen to be present in the email addresses.
9944 Syntactically invalid RFC2822 address items are omitted from the output.
9946 It is possible to specify a character other than colon for the output
9947 separator by starting the string with > followed by the new separator
9948 character. For example:
9950 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9952 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9953 expansion item, which extracts the working address from a single RFC2822
9954 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9957 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
9958 a strict interpretation of header line formatting. Exim parses the bare,
9959 unquoted portion of an email address and if it finds a comma, treats it as an
9960 email address separator. For the example header line:
9962 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
9964 The first example below demonstrates that Q-encoded email addresses are parsed
9965 properly if it is given the raw header (in this example, &`$rheader_from:`&).
9966 It does not see the comma because it's still encoded as "=2C". The second
9967 example below is passed the contents of &`$header_from:`&, meaning it gets
9968 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
9969 The third example shows that the presence of a comma is skipped when it is
9972 # exim -be '${addresses:From: \
9973 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
9975 # exim -be '${addresses:From: Last, First <user@example.com>}'
9976 Last:user@example.com
9977 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
9981 .vitem &*${base62:*&<&'digits'&>&*}*&
9982 .cindex "&%base62%& expansion item"
9983 .cindex "expansion" "conversion to base 62"
9984 The string must consist entirely of decimal digits. The number is converted to
9985 base 62 and output as a string of six characters, including leading zeros. In
9986 the few operating environments where Exim uses base 36 instead of base 62 for
9987 its message identifiers (because those systems do not have case-sensitive file
9988 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9989 be absolutely clear: this is &'not'& base64 encoding.
9991 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9992 .cindex "&%base62d%& expansion item"
9993 .cindex "expansion" "conversion to base 62"
9994 The string must consist entirely of base-62 digits, or, in operating
9995 environments where Exim uses base 36 instead of base 62 for its message
9996 identifiers, base-36 digits. The number is converted to decimal and output as a
10000 .vitem &*${domain:*&<&'string'&>&*}*&
10001 .cindex "domain" "extraction"
10002 .cindex "expansion" "domain extraction"
10003 The string is interpreted as an RFC 2822 address and the domain is extracted
10004 from it. If the string does not parse successfully, the result is empty.
10007 .vitem &*${escape:*&<&'string'&>&*}*&
10008 .cindex "expansion" "escaping non-printing characters"
10009 .cindex "&%escape%& expansion item"
10010 If the string contains any non-printing characters, they are converted to
10011 escape sequences starting with a backslash. Whether characters with the most
10012 significant bit set (so-called &"8-bit characters"&) count as printing or not
10013 is controlled by the &%print_topbitchars%& option.
10016 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10017 .cindex "expansion" "expression evaluation"
10018 .cindex "expansion" "arithmetic expression"
10019 .cindex "&%eval%& expansion item"
10020 These items supports simple arithmetic and bitwise logical operations in
10021 expansion strings. The string (after expansion) must be a conventional
10022 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10023 logical operators, and parentheses. All operations are carried out using
10024 integer arithmetic. The operator priorities are as follows (the same as in the
10025 C programming language):
10027 .irow &'highest:'& "not (~), negate (-)"
10028 .irow "" "multiply (*), divide (/), remainder (%)"
10029 .irow "" "plus (+), minus (-)"
10030 .irow "" "shift-left (<<), shift-right (>>)"
10031 .irow "" "and (&&)"
10033 .irow &'lowest:'& "or (|)"
10035 Binary operators with the same priority are evaluated from left to right. White
10036 space is permitted before or after operators.
10038 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10039 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10040 decimal, even if they start with a leading zero; hexadecimal numbers are not
10041 permitted. This can be useful when processing numbers extracted from dates or
10042 times, which often do have leading zeros.
10044 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10046 respectively. Negative numbers are supported. The result of the computation is
10047 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10050 &`${eval:1+1} `& yields 2
10051 &`${eval:1+2*3} `& yields 7
10052 &`${eval:(1+2)*3} `& yields 9
10053 &`${eval:2+42%5} `& yields 4
10054 &`${eval:0xc&5} `& yields 4
10055 &`${eval:0xc|5} `& yields 13
10056 &`${eval:0xc^5} `& yields 9
10057 &`${eval:0xc>>1} `& yields 6
10058 &`${eval:0xc<<1} `& yields 24
10059 &`${eval:~255&0x1234} `& yields 4608
10060 &`${eval:-(~255&0x1234)} `& yields -4608
10063 As a more realistic example, in an ACL you might have
10065 deny message = Too many bad recipients
10068 {>{$rcpt_count}{10}} \
10071 {$recipients_count} \
10072 {${eval:$rcpt_count/2}} \
10076 The condition is true if there have been more than 10 RCPT commands and
10077 fewer than half of them have resulted in a valid recipient.
10080 .vitem &*${expand:*&<&'string'&>&*}*&
10081 .cindex "expansion" "re-expansion of substring"
10082 The &%expand%& operator causes a string to be expanded for a second time. For
10085 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10087 first looks up a string in a file while expanding the operand for &%expand%&,
10088 and then re-expands what it has found.
10091 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10093 .cindex "UTF-8" "conversion from"
10094 .cindex "expansion" "UTF-8 conversion"
10095 .cindex "&%from_utf8%& expansion item"
10096 The world is slowly moving towards Unicode, although there are no standards for
10097 email yet. However, other applications (including some databases) are starting
10098 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10099 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10100 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10101 the result is an undefined sequence of bytes.
10103 Unicode code points with values less than 256 are compatible with ASCII and
10104 ISO-8859-1 (also known as Latin-1).
10105 For example, character 169 is the copyright symbol in both cases, though the
10106 way it is encoded is different. In UTF-8, more than one byte is needed for
10107 characters with code values greater than 127, whereas ISO-8859-1 is a
10108 single-byte encoding (but thereby limited to 256 characters). This makes
10109 translation from UTF-8 to ISO-8859-1 straightforward.
10112 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10113 .cindex "hash function" "textual"
10114 .cindex "expansion" "textual hash"
10115 The &%hash%& operator is a simpler interface to the hashing function that can
10116 be used when the two parameters are fixed numbers (as opposed to strings that
10117 change when expanded). The effect is the same as
10119 ${hash{<n>}{<m>}{<string>}}
10121 See the description of the general &%hash%& item above for details. The
10122 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10126 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10127 .cindex "base64 encoding" "conversion from hex"
10128 .cindex "expansion" "hex to base64"
10129 .cindex "&%hex2b64%& expansion item"
10130 This operator converts a hex string into one that is base64 encoded. This can
10131 be useful for processing the output of the MD5 and SHA-1 hashing functions.
10135 .vitem &*${hexquote:*&<&'string'&>&*}*&
10136 .cindex "quoting" "hex-encoded unprintable characters"
10137 .cindex "&%hexquote%& expansion item"
10138 This operator converts non-printable characters in a string into a hex
10139 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10140 as is, and other byte values are converted to &`\xNN`&, for example a
10141 byte value 127 is converted to &`\x7f`&.
10145 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
10146 .cindex "&%ipv6denorm%& expansion item"
10147 .cindex "IP address" normalisation
10148 This expands an IPv6 address to a full eight-element colon-separated set
10149 of hex digits including leading zeroes.
10150 A trailing ipv4-style dotted-decimal set is converted to hex.
10151 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10153 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
10154 .cindex "&%ipv6norm%& expansion item"
10155 .cindex "IP address" normalisation
10156 .cindex "IP address" "canonical form"
10157 This converts an IPv6 address to canonical form.
10158 Leading zeroes of groups are omitted, and the longest
10159 set of zero-valued groups is replaced with a double colon.
10160 A trailing ipv4-style dotted-decimal set is converted to hex.
10161 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10165 .vitem &*${lc:*&<&'string'&>&*}*&
10166 .cindex "case forcing in strings"
10167 .cindex "string" "case forcing"
10168 .cindex "lower casing"
10169 .cindex "expansion" "case forcing"
10170 .cindex "&%lc%& expansion item"
10171 This forces the letters in the string into lower-case, for example:
10176 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10177 .cindex "expansion" "string truncation"
10178 .cindex "&%length%& expansion item"
10179 The &%length%& operator is a simpler interface to the &%length%& function that
10180 can be used when the parameter is a fixed number (as opposed to a string that
10181 changes when expanded). The effect is the same as
10183 ${length{<number>}{<string>}}
10185 See the description of the general &%length%& item above for details. Note that
10186 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10187 when &%length%& is used as an operator.
10190 .vitem &*${listcount:*&<&'string'&>&*}*&
10191 .cindex "expansion" "list item count"
10192 .cindex "list" "item count"
10193 .cindex "list" "count of items"
10194 .cindex "&%listcount%& expansion item"
10195 The string is interpreted as a list and the number of items is returned.
10198 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10199 .cindex "expansion" "named list"
10200 .cindex "&%listnamed%& expansion item"
10201 The name is interpreted as a named list and the content of the list is returned,
10202 expanding any referenced lists, re-quoting as needed for colon-separation.
10203 If the optional type is given it must be one of "a", "d", "h" or "l"
10204 and selects address-, domain-, host- or localpart- lists to search among respectively.
10205 Otherwise all types are searched in an undefined order and the first
10206 matching list is returned.
10209 .vitem &*${local_part:*&<&'string'&>&*}*&
10210 .cindex "expansion" "local part extraction"
10211 .cindex "&%local_part%& expansion item"
10212 The string is interpreted as an RFC 2822 address and the local part is
10213 extracted from it. If the string does not parse successfully, the result is
10217 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10218 .cindex "masked IP address"
10219 .cindex "IP address" "masking"
10220 .cindex "CIDR notation"
10221 .cindex "expansion" "IP address masking"
10222 .cindex "&%mask%& expansion item"
10223 If the form of the string to be operated on is not an IP address followed by a
10224 slash and an integer (that is, a network address in CIDR notation), the
10225 expansion fails. Otherwise, this operator converts the IP address to binary,
10226 masks off the least significant bits according to the bit count, and converts
10227 the result back to text, with mask appended. For example,
10229 ${mask:10.111.131.206/28}
10231 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10232 be mostly used for looking up masked addresses in files, the result for an IPv6
10233 address uses dots to separate components instead of colons, because colon
10234 terminates a key string in lsearch files. So, for example,
10236 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10240 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10242 Letters in IPv6 addresses are always output in lower case.
10245 .vitem &*${md5:*&<&'string'&>&*}*&
10247 .cindex "expansion" "MD5 hash"
10248 .cindex "certificate fingerprint"
10249 .cindex "&%md5%& expansion item"
10250 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10251 as a 32-digit hexadecimal number, in which any letters are in lower case.
10254 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10255 .cindex "expansion" "numeric hash"
10256 .cindex "hash function" "numeric"
10257 The &%nhash%& operator is a simpler interface to the numeric hashing function
10258 that can be used when the two parameters are fixed numbers (as opposed to
10259 strings that change when expanded). The effect is the same as
10261 ${nhash{<n>}{<m>}{<string>}}
10263 See the description of the general &%nhash%& item above for details.
10266 .vitem &*${quote:*&<&'string'&>&*}*&
10267 .cindex "quoting" "in string expansions"
10268 .cindex "expansion" "quoting"
10269 .cindex "&%quote%& expansion item"
10270 The &%quote%& operator puts its argument into double quotes if it
10271 is an empty string or
10272 contains anything other than letters, digits, underscores, dots, and hyphens.
10273 Any occurrences of double quotes and backslashes are escaped with a backslash.
10274 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10275 respectively For example,
10283 The place where this is useful is when the argument is a substitution from a
10284 variable or a message header.
10286 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10287 .cindex "&%quote_local_part%& expansion item"
10288 This operator is like &%quote%&, except that it quotes the string only if
10289 required to do so by the rules of RFC 2822 for quoting local parts. For
10290 example, a plus sign would not cause quoting (but it would for &%quote%&).
10291 If you are creating a new email address from the contents of &$local_part$&
10292 (or any other unknown data), you should always use this operator.
10295 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10296 .cindex "quoting" "lookup-specific"
10297 This operator applies lookup-specific quoting rules to the string. Each
10298 query-style lookup type has its own quoting rules which are described with
10299 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10301 ${quote_ldap:two * two}
10307 For single-key lookup types, no quoting is ever necessary and this operator
10308 yields an unchanged string.
10311 .vitem &*${randint:*&<&'n'&>&*}*&
10312 .cindex "random number"
10313 This operator returns a somewhat random number which is less than the
10314 supplied number and is at least 0. The quality of this randomness depends
10315 on how Exim was built; the values are not suitable for keying material.
10316 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10317 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10318 for versions of GnuTLS with that function.
10319 Otherwise, the implementation may be arc4random(), random() seeded by
10320 srandomdev() or srandom(), or a custom implementation even weaker than
10324 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10325 .cindex "expansion" "IP address"
10326 This operator reverses an IP address; for IPv4 addresses, the result is in
10327 dotted-quad decimal form, while for IPv6 addresses the result is in
10328 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10329 for DNS. For example,
10331 ${reverse_ip:192.0.2.4}
10332 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10337 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10341 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10342 .cindex "expansion" "RFC 2047"
10343 .cindex "RFC 2047" "expansion operator"
10344 .cindex "&%rfc2047%& expansion item"
10345 This operator encodes text according to the rules of RFC 2047. This is an
10346 encoding that is used in header lines to encode non-ASCII characters. It is
10347 assumed that the input string is in the encoding specified by the
10348 &%headers_charset%& option, which gets its default at build time. If the string
10349 contains only characters in the range 33&--126, and no instances of the
10352 ? = ( ) < > @ , ; : \ " . [ ] _
10354 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10355 string, using as many &"encoded words"& as necessary to encode all the
10359 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10360 .cindex "expansion" "RFC 2047"
10361 .cindex "RFC 2047" "decoding"
10362 .cindex "&%rfc2047d%& expansion item"
10363 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10364 bytes are replaced by question marks. Characters are converted into the
10365 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10366 not recognized unless &%check_rfc2047_length%& is set false.
10368 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10369 access a header line, RFC 2047 decoding is done automatically. You do not need
10370 to use this operator as well.
10374 .vitem &*${rxquote:*&<&'string'&>&*}*&
10375 .cindex "quoting" "in regular expressions"
10376 .cindex "regular expressions" "quoting"
10377 .cindex "&%rxquote%& expansion item"
10378 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10379 characters in its argument. This is useful when substituting the values of
10380 variables or headers inside regular expressions.
10383 .vitem &*${sha1:*&<&'string'&>&*}*&
10384 .cindex "SHA-1 hash"
10385 .cindex "expansion" "SHA-1 hashing"
10386 .cindex "certificate fingerprint"
10387 .cindex "&%sha2%& expansion item"
10388 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10389 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10392 .vitem &*${sha256:*&<&'certificate'&>&*}*&
10393 .cindex "SHA-256 hash"
10394 .cindex "certificate fingerprint"
10395 .cindex "expansion" "SHA-256 hashing"
10396 .cindex "&%sha256%& expansion item"
10397 The &%sha256%& operator computes the SHA-256 hash fingerprint of the
10400 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10401 Only arguments which are a single variable of certificate type are supported.
10404 .vitem &*${stat:*&<&'string'&>&*}*&
10405 .cindex "expansion" "statting a file"
10406 .cindex "file" "extracting characteristics"
10407 .cindex "&%stat%& expansion item"
10408 The string, after expansion, must be a file path. A call to the &[stat()]&
10409 function is made for this path. If &[stat()]& fails, an error occurs and the
10410 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10411 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10412 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10413 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10414 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10415 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10416 can extract individual fields using the &%extract%& expansion item.
10418 The use of the &%stat%& expansion in users' filter files can be locked out by
10419 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10420 systems for files larger than 2GB.
10422 .vitem &*${str2b64:*&<&'string'&>&*}*&
10423 .cindex "expansion" "base64 encoding"
10424 .cindex "base64 encoding" "in string expansion"
10425 .cindex "&%str2b64%& expansion item"
10426 This operator converts a string into one that is base64 encoded.
10430 .vitem &*${strlen:*&<&'string'&>&*}*&
10431 .cindex "expansion" "string length"
10432 .cindex "string" "length in expansion"
10433 .cindex "&%strlen%& expansion item"
10434 The item is replace by the length of the expanded string, expressed as a
10435 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10438 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10439 .cindex "&%substr%& expansion item"
10440 .cindex "substring extraction"
10441 .cindex "expansion" "substring expansion"
10442 The &%substr%& operator is a simpler interface to the &%substr%& function that
10443 can be used when the two parameters are fixed numbers (as opposed to strings
10444 that change when expanded). The effect is the same as
10446 ${substr{<start>}{<length>}{<string>}}
10448 See the description of the general &%substr%& item above for details. The
10449 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10451 .vitem &*${time_eval:*&<&'string'&>&*}*&
10452 .cindex "&%time_eval%& expansion item"
10453 .cindex "time interval" "decoding"
10454 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10457 .vitem &*${time_interval:*&<&'string'&>&*}*&
10458 .cindex "&%time_interval%& expansion item"
10459 .cindex "time interval" "formatting"
10460 The argument (after sub-expansion) must be a sequence of decimal digits that
10461 represents an interval of time as a number of seconds. It is converted into a
10462 number of larger units and output in Exim's normal time format, for example,
10465 .vitem &*${uc:*&<&'string'&>&*}*&
10466 .cindex "case forcing in strings"
10467 .cindex "string" "case forcing"
10468 .cindex "upper casing"
10469 .cindex "expansion" "case forcing"
10470 .cindex "&%uc%& expansion item"
10471 This forces the letters in the string into upper-case.
10473 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10474 .cindex "correction of invalid utf-8 sequences in strings"
10475 .cindex "utf-8" "utf-8 sequences"
10476 .cindex "incorrect utf-8"
10477 .cindex "expansion" "utf-8 forcing"
10478 .cindex "&%utf8clean%& expansion item"
10479 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10482 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
10483 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
10484 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
10485 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
10486 .cindex expansion UTF-8
10487 .cindex UTF-8 expansion
10489 .cindex internationalisation
10490 .cindex "&%utf8_domain_to_alabel%& expansion item"
10491 .cindex "&%utf8_domain_from_alabel%& expansion item"
10492 .cindex "&%utf8_localpart_to_alabel%& expansion item"
10493 .cindex "&%utf8_localpart_from_alabel%& expansion item"
10494 These convert EAI mail name components between UTF-8 and a-label forms.
10495 For information on internationalisation support see &<<SECTi18nMTA>>&.
10504 .section "Expansion conditions" "SECTexpcond"
10505 .scindex IIDexpcond "expansion" "conditions"
10506 The following conditions are available for testing by the &%${if%& construct
10507 while expanding strings:
10510 .vitem &*!*&<&'condition'&>
10511 .cindex "expansion" "negating a condition"
10512 .cindex "negation" "in expansion condition"
10513 Preceding any condition with an exclamation mark negates the result of the
10516 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10517 .cindex "numeric comparison"
10518 .cindex "expansion" "numeric comparison"
10519 There are a number of symbolic operators for doing numeric comparisons. They
10525 &`>= `& greater or equal
10527 &`<= `& less or equal
10531 ${if >{$message_size}{10M} ...
10533 Note that the general negation operator provides for inequality testing. The
10534 two strings must take the form of optionally signed decimal integers,
10535 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10536 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10537 As a special case, the numerical value of an empty string is taken as
10540 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10541 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10542 10M, not if 10M is larger than &$message_size$&.
10545 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10546 {*&<&'arg2'&>&*}...}*&
10547 .cindex "expansion" "calling an acl"
10548 .cindex "&%acl%&" "expansion condition"
10549 The name and zero to nine argument strings are first expanded separately. The expanded
10550 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10551 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10552 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10553 and may use the variables; if another acl expansion is used the values
10554 are restored after it returns. If the ACL sets
10555 a value using a "message =" modifier the variable $value becomes
10556 the result of the expansion, otherwise it is empty.
10557 If the ACL returns accept the condition is true; if deny, false.
10558 If the ACL returns defer the result is a forced-fail.
10560 .vitem &*bool&~{*&<&'string'&>&*}*&
10561 .cindex "expansion" "boolean parsing"
10562 .cindex "&%bool%& expansion condition"
10563 This condition turns a string holding a true or false representation into
10564 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10565 (case-insensitively); also integer numbers map to true if non-zero,
10567 An empty string is treated as false.
10568 Leading and trailing whitespace is ignored;
10569 thus a string consisting only of whitespace is false.
10570 All other string values will result in expansion failure.
10572 When combined with ACL variables, this expansion condition will let you
10573 make decisions in one place and act on those decisions in another place.
10576 ${if bool{$acl_m_privileged_sender} ...
10580 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10581 .cindex "expansion" "boolean parsing"
10582 .cindex "&%bool_lax%& expansion condition"
10583 Like &%bool%&, this condition turns a string into a boolean state. But
10584 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10585 loose definition that the Router &%condition%& option uses. The empty string
10586 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10587 true. Leading and trailing whitespace is ignored.
10589 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10591 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10592 .cindex "expansion" "encrypted comparison"
10593 .cindex "encrypted strings, comparing"
10594 .cindex "&%crypteq%& expansion condition"
10595 This condition is included in the Exim binary if it is built to support any
10596 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10597 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10598 included in the binary.
10600 The &%crypteq%& condition has two arguments. The first is encrypted and
10601 compared against the second, which is already encrypted. The second string may
10602 be in the LDAP form for storing encrypted strings, which starts with the
10603 encryption type in curly brackets, followed by the data. If the second string
10604 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10605 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10606 Typically this will be a field from a password file. An example of an encrypted
10607 string in LDAP form is:
10609 {md5}CY9rzUYh03PK3k6DJie09g==
10611 If such a string appears directly in an expansion, the curly brackets have to
10612 be quoted, because they are part of the expansion syntax. For example:
10614 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10616 The following encryption types (whose names are matched case-independently) are
10621 .cindex "base64 encoding" "in encrypted password"
10622 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10623 printable characters to compare with the remainder of the second string. If the
10624 length of the comparison string is 24, Exim assumes that it is base64 encoded
10625 (as in the above example). If the length is 32, Exim assumes that it is a
10626 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10630 .cindex "SHA-1 hash"
10631 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10632 printable characters to compare with the remainder of the second string. If the
10633 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10634 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10635 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10638 .cindex "&[crypt()]&"
10639 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10640 only the first eight characters of the password. However, in modern operating
10641 systems this is no longer true, and in many cases the entire password is used,
10642 whatever its length.
10645 .cindex "&[crypt16()]&"
10646 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10647 use up to 16 characters of the password in some operating systems. Again, in
10648 modern operating systems, more characters may be used.
10650 Exim has its own version of &[crypt16()]&, which is just a double call to
10651 &[crypt()]&. For operating systems that have their own version, setting
10652 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10653 operating system version instead of its own. This option is set by default in
10654 the OS-dependent &_Makefile_& for those operating systems that are known to
10655 support &[crypt16()]&.
10657 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10658 it was not using the same algorithm as some operating systems' versions. It
10659 turns out that as well as &[crypt16()]& there is a function called
10660 &[bigcrypt()]& in some operating systems. This may or may not use the same
10661 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10663 However, since there is now a move away from the traditional &[crypt()]&
10664 functions towards using SHA1 and other algorithms, tidying up this area of
10665 Exim is seen as very low priority.
10667 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10668 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10669 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10670 default is &`{crypt}`&. Whatever the default, you can always use either
10671 function by specifying it explicitly in curly brackets.
10673 .vitem &*def:*&<&'variable&~name'&>
10674 .cindex "expansion" "checking for empty variable"
10675 .cindex "&%def%& expansion condition"
10676 The &%def%& condition must be followed by the name of one of the expansion
10677 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10678 variable does not contain the empty string. For example:
10680 ${if def:sender_ident {from $sender_ident}}
10682 Note that the variable name is given without a leading &%$%& character. If the
10683 variable does not exist, the expansion fails.
10685 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10686 &~&*def:h_*&<&'header&~name'&>&*:*&"
10687 .cindex "expansion" "checking header line existence"
10688 This condition is true if a message is being processed and the named header
10689 exists in the message. For example,
10691 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10693 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10694 the header name must be terminated by a colon if white space does not follow.
10696 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10697 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10698 .cindex "string" "comparison"
10699 .cindex "expansion" "string comparison"
10700 .cindex "&%eq%& expansion condition"
10701 .cindex "&%eqi%& expansion condition"
10702 The two substrings are first expanded. The condition is true if the two
10703 resulting strings are identical. For &%eq%& the comparison includes the case of
10704 letters, whereas for &%eqi%& the comparison is case-independent.
10706 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10707 .cindex "expansion" "file existence test"
10708 .cindex "file" "existence test"
10709 .cindex "&%exists%&, expansion condition"
10710 The substring is first expanded and then interpreted as an absolute path. The
10711 condition is true if the named file (or directory) exists. The existence test
10712 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10713 users' filter files may be locked out by the system administrator.
10715 .vitem &*first_delivery*&
10716 .cindex "delivery" "first"
10717 .cindex "first delivery"
10718 .cindex "expansion" "first delivery test"
10719 .cindex "&%first_delivery%& expansion condition"
10720 This condition, which has no data, is true during a message's first delivery
10721 attempt. It is false during any subsequent delivery attempts.
10724 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10725 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10726 .cindex "list" "iterative conditions"
10727 .cindex "expansion" "&*forall*& condition"
10728 .cindex "expansion" "&*forany*& condition"
10730 These conditions iterate over a list. The first argument is expanded to form
10731 the list. By default, the list separator is a colon, but it can be changed by
10732 the normal method. The second argument is interpreted as a condition that is to
10733 be applied to each item in the list in turn. During the interpretation of the
10734 condition, the current list item is placed in a variable called &$item$&.
10736 For &*forany*&, interpretation stops if the condition is true for any item, and
10737 the result of the whole condition is true. If the condition is false for all
10738 items in the list, the overall condition is false.
10740 For &*forall*&, interpretation stops if the condition is false for any item,
10741 and the result of the whole condition is false. If the condition is true for
10742 all items in the list, the overall condition is true.
10744 Note that negation of &*forany*& means that the condition must be false for all
10745 items for the overall condition to succeed, and negation of &*forall*& means
10746 that the condition must be false for at least one item. In this example, the
10747 list separator is changed to a comma:
10749 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10751 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10752 being processed, to enable these expansion items to be nested.
10754 To scan a named list, expand it with the &*listnamed*& operator.
10757 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10758 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10759 .cindex "string" "comparison"
10760 .cindex "expansion" "string comparison"
10761 .cindex "&%ge%& expansion condition"
10762 .cindex "&%gei%& expansion condition"
10763 The two substrings are first expanded. The condition is true if the first
10764 string is lexically greater than or equal to the second string. For &%ge%& the
10765 comparison includes the case of letters, whereas for &%gei%& the comparison is
10768 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10769 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10770 .cindex "string" "comparison"
10771 .cindex "expansion" "string comparison"
10772 .cindex "&%gt%& expansion condition"
10773 .cindex "&%gti%& expansion condition"
10774 The two substrings are first expanded. The condition is true if the first
10775 string is lexically greater than the second string. For &%gt%& the comparison
10776 includes the case of letters, whereas for &%gti%& the comparison is
10779 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10780 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10781 .cindex "string" "comparison"
10782 .cindex "list" "iterative conditions"
10783 Both strings are expanded; the second string is treated as a list of simple
10784 strings; if the first string is a member of the second, then the condition
10787 These are simpler to use versions of the more powerful &*forany*& condition.
10788 Examples, and the &*forany*& equivalents:
10790 ${if inlist{needle}{foo:needle:bar}}
10791 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10792 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10793 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10796 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10797 &*isip4&~{*&<&'string'&>&*}*& &&&
10798 &*isip6&~{*&<&'string'&>&*}*&
10799 .cindex "IP address" "testing string format"
10800 .cindex "string" "testing for IP address"
10801 .cindex "&%isip%& expansion condition"
10802 .cindex "&%isip4%& expansion condition"
10803 .cindex "&%isip6%& expansion condition"
10804 The substring is first expanded, and then tested to see if it has the form of
10805 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10806 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10808 For an IPv4 address, the test is for four dot-separated components, each of
10809 which consists of from one to three digits. For an IPv6 address, up to eight
10810 colon-separated components are permitted, each containing from one to four
10811 hexadecimal digits. There may be fewer than eight components if an empty
10812 component (adjacent colons) is present. Only one empty component is permitted.
10814 &*Note*&: The checks are just on the form of the address; actual numerical
10815 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10816 check. The main use of these tests is to distinguish between IP addresses and
10817 host names, or between IPv4 and IPv6 addresses. For example, you could use
10819 ${if isip4{$sender_host_address}...
10821 to test which IP version an incoming SMTP connection is using.
10823 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10824 .cindex "LDAP" "use for authentication"
10825 .cindex "expansion" "LDAP authentication test"
10826 .cindex "&%ldapauth%& expansion condition"
10827 This condition supports user authentication using LDAP. See section
10828 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10829 queries. For this use, the query must contain a user name and password. The
10830 query itself is not used, and can be empty. The condition is true if the
10831 password is not empty, and the user name and password are accepted by the LDAP
10832 server. An empty password is rejected without calling LDAP because LDAP binds
10833 with an empty password are considered anonymous regardless of the username, and
10834 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10835 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10839 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10840 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10841 .cindex "string" "comparison"
10842 .cindex "expansion" "string comparison"
10843 .cindex "&%le%& expansion condition"
10844 .cindex "&%lei%& expansion condition"
10845 The two substrings are first expanded. The condition is true if the first
10846 string is lexically less than or equal to the second string. For &%le%& the
10847 comparison includes the case of letters, whereas for &%lei%& the comparison is
10850 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10851 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10852 .cindex "string" "comparison"
10853 .cindex "expansion" "string comparison"
10854 .cindex "&%lt%& expansion condition"
10855 .cindex "&%lti%& expansion condition"
10856 The two substrings are first expanded. The condition is true if the first
10857 string is lexically less than the second string. For &%lt%& the comparison
10858 includes the case of letters, whereas for &%lti%& the comparison is
10862 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10863 .cindex "expansion" "regular expression comparison"
10864 .cindex "regular expressions" "match in expanded string"
10865 .cindex "&%match%& expansion condition"
10866 The two substrings are first expanded. The second is then treated as a regular
10867 expression and applied to the first. Because of the pre-expansion, if the
10868 regular expression contains dollar, or backslash characters, they must be
10869 escaped. Care must also be taken if the regular expression contains braces
10870 (curly brackets). A closing brace must be escaped so that it is not taken as a
10871 premature termination of <&'string2'&>. The easiest approach is to use the
10872 &`\N`& feature to disable expansion of the regular expression.
10875 ${if match {$local_part}{\N^\d{3}\N} ...
10877 If the whole expansion string is in double quotes, further escaping of
10878 backslashes is also required.
10880 The condition is true if the regular expression match succeeds.
10881 The regular expression is not required to begin with a circumflex
10882 metacharacter, but if there is no circumflex, the expression is not anchored,
10883 and it may match anywhere in the subject, not just at the start. If you want
10884 the pattern to match at the end of the subject, you must include the &`$`&
10885 metacharacter at an appropriate point.
10887 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10888 At the start of an &%if%& expansion the values of the numeric variable
10889 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10890 succeeds causes them to be reset to the substrings of that condition and they
10891 will have these values during the expansion of the success string. At the end
10892 of the &%if%& expansion, the previous values are restored. After testing a
10893 combination of conditions using &%or%&, the subsequent values of the numeric
10894 variables are those of the condition that succeeded.
10896 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10897 .cindex "&%match_address%& expansion condition"
10898 See &*match_local_part*&.
10900 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10901 .cindex "&%match_domain%& expansion condition"
10902 See &*match_local_part*&.
10904 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10905 .cindex "&%match_ip%& expansion condition"
10906 This condition matches an IP address to a list of IP address patterns. It must
10907 be followed by two argument strings. The first (after expansion) must be an IP
10908 address or an empty string. The second (not expanded) is a restricted host
10909 list that can match only an IP address, not a host name. For example:
10911 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10913 The specific types of host list item that are permitted in the list are:
10916 An IP address, optionally with a CIDR mask.
10918 A single asterisk, which matches any IP address.
10920 An empty item, which matches only if the IP address is empty. This could be
10921 useful for testing for a locally submitted message or one from specific hosts
10922 in a single test such as
10923 . ==== As this is a nested list, any displays it contains must be indented
10924 . ==== as otherwise they are too far to the left. This comment applies to
10925 . ==== the use of xmlto plus fop. There's no problem when formatting with
10926 . ==== sdop, with or without the extra indent.
10928 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10930 where the first item in the list is the empty string.
10932 The item @[] matches any of the local host's interface addresses.
10934 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10935 even if &`net-`& is not specified. There is never any attempt to turn the IP
10936 address into a host name. The most common type of linear search for
10937 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10938 masks. For example:
10940 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10942 It is of course possible to use other kinds of lookup, and in such a case, you
10943 do need to specify the &`net-`& prefix if you want to specify a specific
10944 address mask, for example:
10946 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10948 However, unless you are combining a &%match_ip%& condition with others, it is
10949 just as easy to use the fact that a lookup is itself a condition, and write:
10951 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10955 Note that <&'string2'&> is not itself subject to string expansion, unless
10956 Exim was built with the EXPAND_LISTMATCH_RHS option.
10958 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10960 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10961 .cindex "domain list" "in expansion condition"
10962 .cindex "address list" "in expansion condition"
10963 .cindex "local part" "list, in expansion condition"
10964 .cindex "&%match_local_part%& expansion condition"
10965 This condition, together with &%match_address%& and &%match_domain%&, make it
10966 possible to test domain, address, and local part lists within expansions. Each
10967 condition requires two arguments: an item and a list to match. A trivial
10970 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10972 In each case, the second argument may contain any of the allowable items for a
10973 list of the appropriate type. Also, because the second argument (after
10974 expansion) is a standard form of list, it is possible to refer to a named list.
10975 Thus, you can use conditions like this:
10977 ${if match_domain{$domain}{+local_domains}{...
10979 .cindex "&`+caseful`&"
10980 For address lists, the matching starts off caselessly, but the &`+caseful`&
10981 item can be used, as in all address lists, to cause subsequent items to
10982 have their local parts matched casefully. Domains are always matched
10985 Note that <&'string2'&> is not itself subject to string expansion, unless
10986 Exim was built with the EXPAND_LISTMATCH_RHS option.
10988 &*Note*&: Host lists are &'not'& supported in this way. This is because
10989 hosts have two identities: a name and an IP address, and it is not clear
10990 how to specify cleanly how such a test would work. However, IP addresses can be
10991 matched using &%match_ip%&.
10993 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10994 .cindex "PAM authentication"
10995 .cindex "AUTH" "with PAM"
10996 .cindex "Solaris" "PAM support"
10997 .cindex "expansion" "PAM authentication test"
10998 .cindex "&%pam%& expansion condition"
10999 &'Pluggable Authentication Modules'&
11000 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
11001 available in the latest releases of Solaris and in some GNU/Linux
11002 distributions. The Exim support, which is intended for use in conjunction with
11003 the SMTP AUTH command, is available only if Exim is compiled with
11007 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11008 in some releases of GNU/Linux &%-ldl%& is also needed.
11010 The argument string is first expanded, and the result must be a
11011 colon-separated list of strings. Leading and trailing white space is ignored.
11012 The PAM module is initialized with the service name &"exim"& and the user name
11013 taken from the first item in the colon-separated data string (<&'string1'&>).
11014 The remaining items in the data string are passed over in response to requests
11015 from the authentication function. In the simple case there will only be one
11016 request, for a password, so the data consists of just two strings.
11018 There can be problems if any of the strings are permitted to contain colon
11019 characters. In the usual way, these have to be doubled to avoid being taken as
11020 separators. If the data is being inserted from a variable, the &%sg%& expansion
11021 item can be used to double any existing colons. For example, the configuration
11022 of a LOGIN authenticator might contain this setting:
11024 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
11026 For a PLAIN authenticator you could use:
11028 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
11030 In some operating systems, PAM authentication can be done only from a process
11031 running as root. Since Exim is running as the Exim user when receiving
11032 messages, this means that PAM cannot be used directly in those systems.
11033 A patched version of the &'pam_unix'& module that comes with the
11034 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
11035 The patched module allows one special uid/gid combination, in addition to root,
11036 to authenticate. If you build the patched module to allow the Exim user and
11037 group, PAM can then be used from an Exim authenticator.
11040 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11041 .cindex "&'pwcheck'& daemon"
11043 .cindex "expansion" "&'pwcheck'& authentication test"
11044 .cindex "&%pwcheck%& expansion condition"
11045 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11046 This is one way of making it possible for passwords to be checked by a process
11047 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11048 deprecated. Its replacement is &'saslauthd'& (see below).
11050 The pwcheck support is not included in Exim by default. You need to specify
11051 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11052 building Exim. For example:
11054 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
11056 You do not need to install the full Cyrus software suite in order to use
11057 the pwcheck daemon. You can compile and install just the daemon alone
11058 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11059 access to the &_/var/pwcheck_& directory.
11061 The &%pwcheck%& condition takes one argument, which must be the user name and
11062 password, separated by a colon. For example, in a LOGIN authenticator
11063 configuration, you might have this:
11065 server_condition = ${if pwcheck{$auth1:$auth2}}
11067 Again, for a PLAIN authenticator configuration, this would be:
11069 server_condition = ${if pwcheck{$auth2:$auth3}}
11071 .vitem &*queue_running*&
11072 .cindex "queue runner" "detecting when delivering from"
11073 .cindex "expansion" "queue runner test"
11074 .cindex "&%queue_running%& expansion condition"
11075 This condition, which has no data, is true during delivery attempts that are
11076 initiated by queue runner processes, and false otherwise.
11079 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11081 .cindex "expansion" "Radius authentication"
11082 .cindex "&%radius%& expansion condition"
11083 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11084 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11085 the Radius client configuration file in order to build Exim with Radius
11088 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11089 library, using the original API. If you are using release 0.4.0 or later of
11090 this library, you need to set
11092 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11094 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11095 &%libradius%& library that comes with FreeBSD. To do this, set
11097 RADIUS_LIB_TYPE=RADLIB
11099 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11100 You may also have to supply a suitable setting in EXTRALIBS so that the
11101 Radius library can be found when Exim is linked.
11103 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11104 Radius client library, which calls the Radius server. The condition is true if
11105 the authentication is successful. For example:
11107 server_condition = ${if radius{<arguments>}}
11111 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11112 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11113 .cindex "&'saslauthd'& daemon"
11115 .cindex "expansion" "&'saslauthd'& authentication test"
11116 .cindex "&%saslauthd%& expansion condition"
11117 This condition supports user authentication using the Cyrus &'saslauthd'&
11118 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11119 Using this daemon is one way of making it possible for passwords to be checked
11120 by a process that is not running as root.
11122 The saslauthd support is not included in Exim by default. You need to specify
11123 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11124 building Exim. For example:
11126 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11128 You do not need to install the full Cyrus software suite in order to use
11129 the saslauthd daemon. You can compile and install just the daemon alone
11130 from the Cyrus SASL library.
11132 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11133 two are mandatory. For example:
11135 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11137 The service and the realm are optional (which is why the arguments are enclosed
11138 in their own set of braces). For details of the meaning of the service and
11139 realm, and how to run the daemon, consult the Cyrus documentation.
11144 .section "Combining expansion conditions" "SECID84"
11145 .cindex "expansion" "combining conditions"
11146 Several conditions can be tested at once by combining them using the &%and%&
11147 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11148 conditions on their own, and precede their lists of sub-conditions. Each
11149 sub-condition must be enclosed in braces within the overall braces that contain
11150 the list. No repetition of &%if%& is used.
11154 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11155 .cindex "&""or""& expansion condition"
11156 .cindex "expansion" "&""or""& of conditions"
11157 The sub-conditions are evaluated from left to right. The condition is true if
11158 any one of the sub-conditions is true.
11161 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11163 When a true sub-condition is found, the following ones are parsed but not
11164 evaluated. If there are several &"match"& sub-conditions the values of the
11165 numeric variables afterwards are taken from the first one that succeeds.
11167 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11168 .cindex "&""and""& expansion condition"
11169 .cindex "expansion" "&""and""& of conditions"
11170 The sub-conditions are evaluated from left to right. The condition is true if
11171 all of the sub-conditions are true. If there are several &"match"&
11172 sub-conditions, the values of the numeric variables afterwards are taken from
11173 the last one. When a false sub-condition is found, the following ones are
11174 parsed but not evaluated.
11176 .ecindex IIDexpcond
11181 .section "Expansion variables" "SECTexpvar"
11182 .cindex "expansion" "variables, list of"
11183 This section contains an alphabetical list of all the expansion variables. Some
11184 of them are available only when Exim is compiled with specific options such as
11185 support for TLS or the content scanning extension.
11188 .vitem "&$0$&, &$1$&, etc"
11189 .cindex "numerical variables (&$1$& &$2$& etc)"
11190 When a &%match%& expansion condition succeeds, these variables contain the
11191 captured substrings identified by the regular expression during subsequent
11192 processing of the success string of the containing &%if%& expansion item.
11193 In the expansion condition case
11194 they do not retain their values afterwards; in fact, their previous
11195 values are restored at the end of processing an &%if%& item. The numerical
11196 variables may also be set externally by some other matching process which
11197 precedes the expansion of the string. For example, the commands available in
11198 Exim filter files include an &%if%& command with its own regular expression
11199 matching condition.
11201 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11202 Within an acl condition, expansion condition or expansion item
11203 any arguments are copied to these variables,
11204 any unused variables being made empty.
11206 .vitem "&$acl_c...$&"
11207 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11208 can be given any name that starts with &$acl_c$& and is at least six characters
11209 long, but the sixth character must be either a digit or an underscore. For
11210 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11211 variables persist throughout the lifetime of an SMTP connection. They can be
11212 used to pass information between ACLs and between different invocations of the
11213 same ACL. When a message is received, the values of these variables are saved
11214 with the message, and can be accessed by filters, routers, and transports
11215 during subsequent delivery.
11217 .vitem "&$acl_m...$&"
11218 These variables are like the &$acl_c...$& variables, except that their values
11219 are reset after a message has been received. Thus, if several messages are
11220 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11221 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11222 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11223 message is received, the values of these variables are saved with the message,
11224 and can be accessed by filters, routers, and transports during subsequent
11227 .vitem &$acl_narg$&
11228 Within an acl condition, expansion condition or expansion item
11229 this variable has the number of arguments.
11231 .vitem &$acl_verify_message$&
11232 .vindex "&$acl_verify_message$&"
11233 After an address verification has failed, this variable contains the failure
11234 message. It retains its value for use in subsequent modifiers. The message can
11235 be preserved by coding like this:
11237 warn !verify = sender
11238 set acl_m0 = $acl_verify_message
11240 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11241 &%log_message%& modifiers, to include information about the verification
11244 .vitem &$address_data$&
11245 .vindex "&$address_data$&"
11246 This variable is set by means of the &%address_data%& option in routers. The
11247 value then remains with the address while it is processed by subsequent routers
11248 and eventually a transport. If the transport is handling multiple addresses,
11249 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11250 for more details. &*Note*&: The contents of &$address_data$& are visible in
11253 If &$address_data$& is set when the routers are called from an ACL to verify
11254 a recipient address, the final value is still in the variable for subsequent
11255 conditions and modifiers of the ACL statement. If routing the address caused it
11256 to be redirected to just one address, the child address is also routed as part
11257 of the verification, and in this case the final value of &$address_data$& is
11258 from the child's routing.
11260 If &$address_data$& is set when the routers are called from an ACL to verify a
11261 sender address, the final value is also preserved, but this time in
11262 &$sender_address_data$&, to distinguish it from data from a recipient
11265 In both cases (recipient and sender verification), the value does not persist
11266 after the end of the current ACL statement. If you want to preserve
11267 these values for longer, you can save them in ACL variables.
11269 .vitem &$address_file$&
11270 .vindex "&$address_file$&"
11271 When, as a result of aliasing, forwarding, or filtering, a message is directed
11272 to a specific file, this variable holds the name of the file when the transport
11273 is running. At other times, the variable is empty. For example, using the
11274 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11276 /home/r2d2/savemail
11278 then when the &(address_file)& transport is running, &$address_file$&
11279 contains the text string &`/home/r2d2/savemail`&.
11280 .cindex "Sieve filter" "value of &$address_file$&"
11281 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11282 then up to the transport configuration to generate an appropriate absolute path
11283 to the relevant file.
11285 .vitem &$address_pipe$&
11286 .vindex "&$address_pipe$&"
11287 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11288 this variable holds the pipe command when the transport is running.
11290 .vitem "&$auth1$& &-- &$auth3$&"
11291 .vindex "&$auth1$&, &$auth2$&, etc"
11292 These variables are used in SMTP authenticators (see chapters
11293 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
11295 .vitem &$authenticated_id$&
11296 .cindex "authentication" "id"
11297 .vindex "&$authenticated_id$&"
11298 When a server successfully authenticates a client it may be configured to
11299 preserve some of the authentication information in the variable
11300 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11301 user/password authenticator configuration might preserve the user name for use
11302 in the routers. Note that this is not the same information that is saved in
11303 &$sender_host_authenticated$&.
11304 When a message is submitted locally (that is, not over a TCP connection)
11305 the value of &$authenticated_id$& is normally the login name of the calling
11306 process. However, a trusted user can override this by means of the &%-oMai%&
11307 command line option.
11309 .vitem &$authenticated_fail_id$&
11310 .cindex "authentication" "fail" "id"
11311 .vindex "&$authenticated_fail_id$&"
11312 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11313 will contain the failed authentication id. If more than one authentication
11314 id is attempted, it will contain only the last one. The variable is
11315 available for processing in the ACL's, generally the quit or notquit ACL.
11316 A message to a local recipient could still be accepted without requiring
11317 authentication, which means this variable could also be visible in all of
11321 .vitem &$authenticated_sender$&
11322 .cindex "sender" "authenticated"
11323 .cindex "authentication" "sender"
11324 .cindex "AUTH" "on MAIL command"
11325 .vindex "&$authenticated_sender$&"
11326 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11327 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11328 described in section &<<SECTauthparamail>>&. Unless the data is the string
11329 &"<>"&, it is set as the authenticated sender of the message, and the value is
11330 available during delivery in the &$authenticated_sender$& variable. If the
11331 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11333 .vindex "&$qualify_domain$&"
11334 When a message is submitted locally (that is, not over a TCP connection), the
11335 value of &$authenticated_sender$& is an address constructed from the login
11336 name of the calling process and &$qualify_domain$&, except that a trusted user
11337 can override this by means of the &%-oMas%& command line option.
11340 .vitem &$authentication_failed$&
11341 .cindex "authentication" "failure"
11342 .vindex "&$authentication_failed$&"
11343 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11344 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11345 possible to distinguish between &"did not try to authenticate"&
11346 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11347 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11348 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11349 negative response to an AUTH command, including (for example) an attempt to use
11350 an undefined mechanism.
11352 .vitem &$av_failed$&
11353 .cindex "content scanning" "AV scanner failure"
11354 This variable is available when Exim is compiled with the content-scanning
11355 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11356 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11357 the ACL malware condition.
11359 .vitem &$body_linecount$&
11360 .cindex "message body" "line count"
11361 .cindex "body of message" "line count"
11362 .vindex "&$body_linecount$&"
11363 When a message is being received or delivered, this variable contains the
11364 number of lines in the message's body. See also &$message_linecount$&.
11366 .vitem &$body_zerocount$&
11367 .cindex "message body" "binary zero count"
11368 .cindex "body of message" "binary zero count"
11369 .cindex "binary zero" "in message body"
11370 .vindex "&$body_zerocount$&"
11371 When a message is being received or delivered, this variable contains the
11372 number of binary zero bytes (ASCII NULs) in the message's body.
11374 .vitem &$bounce_recipient$&
11375 .vindex "&$bounce_recipient$&"
11376 This is set to the recipient address of a bounce message while Exim is creating
11377 it. It is useful if a customized bounce message text file is in use (see
11378 chapter &<<CHAPemsgcust>>&).
11380 .vitem &$bounce_return_size_limit$&
11381 .vindex "&$bounce_return_size_limit$&"
11382 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11383 up to a multiple of 1000. It is useful when a customized error message text
11384 file is in use (see chapter &<<CHAPemsgcust>>&).
11386 .vitem &$caller_gid$&
11387 .cindex "gid (group id)" "caller"
11388 .vindex "&$caller_gid$&"
11389 The real group id under which the process that called Exim was running. This is
11390 not the same as the group id of the originator of a message (see
11391 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11392 incarnation normally contains the Exim gid.
11394 .vitem &$caller_uid$&
11395 .cindex "uid (user id)" "caller"
11396 .vindex "&$caller_uid$&"
11397 The real user id under which the process that called Exim was running. This is
11398 not the same as the user id of the originator of a message (see
11399 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11400 incarnation normally contains the Exim uid.
11402 .vitem &$callout_address$&
11403 .vindex "&$callout_address$&"
11404 After a callout for verification, spamd or malware daemon service, the
11405 address that was connected to.
11407 .vitem &$compile_number$&
11408 .vindex "&$compile_number$&"
11409 The building process for Exim keeps a count of the number
11410 of times it has been compiled. This serves to distinguish different
11411 compilations of the same version of the program.
11413 .vitem &$config_dir$&
11414 .vindex "&$config_dir$&"
11415 The directory name of the main configuration file. That is, the content of
11416 &$config_file$& with the last component stripped. The value does not
11417 contain the trailing slash. If &$config_file$& does not contain a slash,
11418 &$config_dir$& is ".".
11420 .vitem &$config_file$&
11421 .vindex "&$config_file$&"
11422 The name of the main configuration file Exim is using.
11424 .vitem &$demime_errorlevel$&
11425 .vindex "&$demime_errorlevel$&"
11426 This variable is available when Exim is compiled with
11427 the content-scanning extension and the obsolete &%demime%& condition. For
11428 details, see section &<<SECTdemimecond>>&.
11430 .vitem &$demime_reason$&
11431 .vindex "&$demime_reason$&"
11432 This variable is available when Exim is compiled with the
11433 content-scanning extension and the obsolete &%demime%& condition. For details,
11434 see section &<<SECTdemimecond>>&.
11436 .vitem &$dkim_cur_signer$& &&&
11437 &$dkim_verify_status$& &&&
11438 &$dkim_verify_reason$& &&&
11439 &$dkim_domain$& &&&
11440 &$dkim_identity$& &&&
11441 &$dkim_selector$& &&&
11443 &$dkim_canon_body$& &&&
11444 &$dkim_canon_headers$& &&&
11445 &$dkim_copiedheaders$& &&&
11446 &$dkim_bodylength$& &&&
11447 &$dkim_created$& &&&
11448 &$dkim_expires$& &&&
11449 &$dkim_headernames$& &&&
11450 &$dkim_key_testing$& &&&
11451 &$dkim_key_nosubdomains$& &&&
11452 &$dkim_key_srvtype$& &&&
11453 &$dkim_key_granularity$& &&&
11454 &$dkim_key_notes$& &&&
11455 &$dkim_key_length$&
11456 These variables are only available within the DKIM ACL.
11457 For details see chapter &<<CHAPdkim>>&.
11459 .vitem &$dkim_signers$&
11460 .vindex &$dkim_signers$&
11461 When a message has been received this variable contains
11462 a colon-separated list of signer domains and identities for the message.
11463 For details see chapter &<<CHAPdkim>>&.
11465 .vitem &$dnslist_domain$& &&&
11466 &$dnslist_matched$& &&&
11467 &$dnslist_text$& &&&
11469 .vindex "&$dnslist_domain$&"
11470 .vindex "&$dnslist_matched$&"
11471 .vindex "&$dnslist_text$&"
11472 .vindex "&$dnslist_value$&"
11473 .cindex "black list (DNS)"
11474 When a DNS (black) list lookup succeeds, these variables are set to contain
11475 the following data from the lookup: the list's domain name, the key that was
11476 looked up, the contents of any associated TXT record, and the value from the
11477 main A record. See section &<<SECID204>>& for more details.
11480 .vindex "&$domain$&"
11481 When an address is being routed, or delivered on its own, this variable
11482 contains the domain. Uppercase letters in the domain are converted into lower
11483 case for &$domain$&.
11485 Global address rewriting happens when a message is received, so the value of
11486 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11487 is set during user filtering, but not during system filtering, because a
11488 message may have many recipients and the system filter is called just once.
11490 When more than one address is being delivered at once (for example, several
11491 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11492 have the same domain. Transports can be restricted to handling only one domain
11493 at a time if the value of &$domain$& is required at transport time &-- this is
11494 the default for local transports. For further details of the environment in
11495 which local transports are run, see chapter &<<CHAPenvironment>>&.
11497 .oindex "&%delay_warning_condition%&"
11498 At the end of a delivery, if all deferred addresses have the same domain, it is
11499 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11501 The &$domain$& variable is also used in some other circumstances:
11504 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11505 the recipient address. The domain of the &'sender'& address is in
11506 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11507 normally set during the running of the MAIL ACL. However, if the sender address
11508 is verified with a callout during the MAIL ACL, the sender domain is placed in
11509 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11510 the &(smtp)& transport.
11513 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11514 &$domain$& contains the domain portion of the address that is being rewritten;
11515 it can be used in the expansion of the replacement address, for example, to
11516 rewrite domains by file lookup.
11519 With one important exception, whenever a domain list is being scanned,
11520 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11521 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11522 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11523 that, in a RCPT ACL, the sender domain list can be dependent on the
11524 recipient domain (which is what is in &$domain$& at this time).
11527 .cindex "ETRN" "value of &$domain$&"
11528 .oindex "&%smtp_etrn_command%&"
11529 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11530 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11534 .vitem &$domain_data$&
11535 .vindex "&$domain_data$&"
11536 When the &%domains%& option on a router matches a domain by
11537 means of a lookup, the data read by the lookup is available during the running
11538 of the router as &$domain_data$&. In addition, if the driver routes the
11539 address to a transport, the value is available in that transport. If the
11540 transport is handling multiple addresses, the value from the first address is
11543 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11544 domain by means of a lookup. The data read by the lookup is available during
11545 the rest of the ACL statement. In all other situations, this variable expands
11548 .vitem &$exim_gid$&
11549 .vindex "&$exim_gid$&"
11550 This variable contains the numerical value of the Exim group id.
11552 .vitem &$exim_path$&
11553 .vindex "&$exim_path$&"
11554 This variable contains the path to the Exim binary.
11556 .vitem &$exim_uid$&
11557 .vindex "&$exim_uid$&"
11558 This variable contains the numerical value of the Exim user id.
11560 .vitem &$exim_version$&
11561 .vindex "&$exim_version$&"
11562 This variable contains the version string of the Exim build.
11563 The first character is a major version number, currently 4.
11564 Then after a dot, the next group of digits is a minor version number.
11565 There may be other characters following the minor version.
11567 .vitem &$found_extension$&
11568 .vindex "&$found_extension$&"
11569 This variable is available when Exim is compiled with the
11570 content-scanning extension and the obsolete &%demime%& condition. For details,
11571 see section &<<SECTdemimecond>>&.
11573 .vitem &$header_$&<&'name'&>
11574 This is not strictly an expansion variable. It is expansion syntax for
11575 inserting the message header line with the given name. Note that the name must
11576 be terminated by colon or white space, because it may contain a wide variety of
11577 characters. Note also that braces must &'not'& be used.
11579 .vitem &$headers_added$&
11580 .vindex "&$headers_added$&"
11581 Within an ACL this variable contains the headers added so far by
11582 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11583 The headers are a newline-separated list.
11587 When the &%check_local_user%& option is set for a router, the user's home
11588 directory is placed in &$home$& when the check succeeds. In particular, this
11589 means it is set during the running of users' filter files. A router may also
11590 explicitly set a home directory for use by a transport; this can be overridden
11591 by a setting on the transport itself.
11593 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11594 of the environment variable HOME.
11598 If a router assigns an address to a transport (any transport), and passes a
11599 list of hosts with the address, the value of &$host$& when the transport starts
11600 to run is the name of the first host on the list. Note that this applies both
11601 to local and remote transports.
11603 .cindex "transport" "filter"
11604 .cindex "filter" "transport filter"
11605 For the &(smtp)& transport, if there is more than one host, the value of
11606 &$host$& changes as the transport works its way through the list. In
11607 particular, when the &(smtp)& transport is expanding its options for encryption
11608 using TLS, or for specifying a transport filter (see chapter
11609 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11612 When used in the client part of an authenticator configuration (see chapter
11613 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11614 client is connected.
11617 .vitem &$host_address$&
11618 .vindex "&$host_address$&"
11619 This variable is set to the remote host's IP address whenever &$host$& is set
11620 for a remote connection. It is also set to the IP address that is being checked
11621 when the &%ignore_target_hosts%& option is being processed.
11623 .vitem &$host_data$&
11624 .vindex "&$host_data$&"
11625 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11626 result of the lookup is made available in the &$host_data$& variable. This
11627 allows you, for example, to do things like this:
11629 deny hosts = net-lsearch;/some/file
11630 message = $host_data
11632 .vitem &$host_lookup_deferred$&
11633 .cindex "host name" "lookup, failure of"
11634 .vindex "&$host_lookup_deferred$&"
11635 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11636 message comes from a remote host and there is an attempt to look up the host's
11637 name from its IP address, and the attempt is not successful, one of these
11638 variables is set to &"1"&.
11641 If the lookup receives a definite negative response (for example, a DNS lookup
11642 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11645 If there is any kind of problem during the lookup, such that Exim cannot
11646 tell whether or not the host name is defined (for example, a timeout for a DNS
11647 lookup), &$host_lookup_deferred$& is set to &"1"&.
11650 Looking up a host's name from its IP address consists of more than just a
11651 single reverse lookup. Exim checks that a forward lookup of at least one of the
11652 names it receives from a reverse lookup yields the original IP address. If this
11653 is not the case, Exim does not accept the looked up name(s), and
11654 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11655 IP address (for example, the existence of a PTR record in the DNS) is not
11656 sufficient on its own for the success of a host name lookup. If the reverse
11657 lookup succeeds, but there is a lookup problem such as a timeout when checking
11658 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11659 &"1"&. See also &$sender_host_name$&.
11661 .vitem &$host_lookup_failed$&
11662 .vindex "&$host_lookup_failed$&"
11663 See &$host_lookup_deferred$&.
11665 .vitem &$host_port$&
11666 .vindex "&$host_port$&"
11667 This variable is set to the remote host's TCP port whenever &$host$& is set
11668 for an outbound connection.
11672 .vindex "&$inode$&"
11673 The only time this variable is set is while expanding the &%directory_file%&
11674 option in the &(appendfile)& transport. The variable contains the inode number
11675 of the temporary file which is about to be renamed. It can be used to construct
11676 a unique name for the file.
11678 .vitem &$interface_address$&
11679 .vindex "&$interface_address$&"
11680 This is an obsolete name for &$received_ip_address$&.
11682 .vitem &$interface_port$&
11683 .vindex "&$interface_port$&"
11684 This is an obsolete name for &$received_port$&.
11688 This variable is used during the expansion of &*forall*& and &*forany*&
11689 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11690 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11694 .vindex "&$ldap_dn$&"
11695 This variable, which is available only when Exim is compiled with LDAP support,
11696 contains the DN from the last entry in the most recently successful LDAP
11699 .vitem &$load_average$&
11700 .vindex "&$load_average$&"
11701 This variable contains the system load average, multiplied by 1000 so that it
11702 is an integer. For example, if the load average is 0.21, the value of the
11703 variable is 210. The value is recomputed every time the variable is referenced.
11705 .vitem &$local_part$&
11706 .vindex "&$local_part$&"
11707 When an address is being routed, or delivered on its own, this
11708 variable contains the local part. When a number of addresses are being
11709 delivered together (for example, multiple RCPT commands in an SMTP
11710 session), &$local_part$& is not set.
11712 Global address rewriting happens when a message is received, so the value of
11713 &$local_part$& during routing and delivery is the value after rewriting.
11714 &$local_part$& is set during user filtering, but not during system filtering,
11715 because a message may have many recipients and the system filter is called just
11718 .vindex "&$local_part_prefix$&"
11719 .vindex "&$local_part_suffix$&"
11720 If a local part prefix or suffix has been recognized, it is not included in the
11721 value of &$local_part$& during routing and subsequent delivery. The values of
11722 any prefix or suffix are in &$local_part_prefix$& and
11723 &$local_part_suffix$&, respectively.
11725 When a message is being delivered to a file, pipe, or autoreply transport as a
11726 result of aliasing or forwarding, &$local_part$& is set to the local part of
11727 the parent address, not to the file name or command (see &$address_file$& and
11730 When an ACL is running for a RCPT command, &$local_part$& contains the
11731 local part of the recipient address.
11733 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11734 &$local_part$& contains the local part of the address that is being rewritten;
11735 it can be used in the expansion of the replacement address, for example.
11737 In all cases, all quoting is removed from the local part. For example, for both
11740 "abc:xyz"@test.example
11741 abc\:xyz@test.example
11743 the value of &$local_part$& is
11747 If you use &$local_part$& to create another address, you should always wrap it
11748 inside a quoting operator. For example, in a &(redirect)& router you could
11751 data = ${quote_local_part:$local_part}@new.domain.example
11753 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11754 to process local parts in a case-dependent manner in a router, you can set the
11755 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11757 .vitem &$local_part_data$&
11758 .vindex "&$local_part_data$&"
11759 When the &%local_parts%& option on a router matches a local part by means of a
11760 lookup, the data read by the lookup is available during the running of the
11761 router as &$local_part_data$&. In addition, if the driver routes the address
11762 to a transport, the value is available in that transport. If the transport is
11763 handling multiple addresses, the value from the first address is used.
11765 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11766 matches a local part by means of a lookup. The data read by the lookup is
11767 available during the rest of the ACL statement. In all other situations, this
11768 variable expands to nothing.
11770 .vitem &$local_part_prefix$&
11771 .vindex "&$local_part_prefix$&"
11772 When an address is being routed or delivered, and a
11773 specific prefix for the local part was recognized, it is available in this
11774 variable, having been removed from &$local_part$&.
11776 .vitem &$local_part_suffix$&
11777 .vindex "&$local_part_suffix$&"
11778 When an address is being routed or delivered, and a
11779 specific suffix for the local part was recognized, it is available in this
11780 variable, having been removed from &$local_part$&.
11782 .vitem &$local_scan_data$&
11783 .vindex "&$local_scan_data$&"
11784 This variable contains the text returned by the &[local_scan()]& function when
11785 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11787 .vitem &$local_user_gid$&
11788 .vindex "&$local_user_gid$&"
11789 See &$local_user_uid$&.
11791 .vitem &$local_user_uid$&
11792 .vindex "&$local_user_uid$&"
11793 This variable and &$local_user_gid$& are set to the uid and gid after the
11794 &%check_local_user%& router precondition succeeds. This means that their values
11795 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11796 and &%condition%&), for the &%address_data%& expansion, and for any
11797 router-specific expansions. At all other times, the values in these variables
11798 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11800 .vitem &$localhost_number$&
11801 .vindex "&$localhost_number$&"
11802 This contains the expanded value of the
11803 &%localhost_number%& option. The expansion happens after the main options have
11806 .vitem &$log_inodes$&
11807 .vindex "&$log_inodes$&"
11808 The number of free inodes in the disk partition where Exim's
11809 log files are being written. The value is recalculated whenever the variable is
11810 referenced. If the relevant file system does not have the concept of inodes,
11811 the value of is -1. See also the &%check_log_inodes%& option.
11813 .vitem &$log_space$&
11814 .vindex "&$log_space$&"
11815 The amount of free space (as a number of kilobytes) in the disk
11816 partition where Exim's log files are being written. The value is recalculated
11817 whenever the variable is referenced. If the operating system does not have the
11818 ability to find the amount of free space (only true for experimental systems),
11819 the space value is -1. See also the &%check_log_space%& option.
11822 .vitem &$lookup_dnssec_authenticated$&
11823 .vindex "&$lookup_dnssec_authenticated$&"
11824 This variable is set after a DNS lookup done by
11825 a dnsdb lookup expansion, dnslookup router or smtp transport.
11826 .cindex "DNS" "DNSSEC"
11827 It will be empty if &(DNSSEC)& was not requested,
11828 &"no"& if the result was not labelled as authenticated data
11829 and &"yes"& if it was.
11830 Results that are labelled as authoritative answer that match
11831 the &%dns_trust_aa%& configuration variable count also
11832 as authenticated data.
11834 .vitem &$mailstore_basename$&
11835 .vindex "&$mailstore_basename$&"
11836 This variable is set only when doing deliveries in &"mailstore"& format in the
11837 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11838 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11839 contains the basename of the files that are being written, that is, the name
11840 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11843 .vitem &$malware_name$&
11844 .vindex "&$malware_name$&"
11845 This variable is available when Exim is compiled with the
11846 content-scanning extension. It is set to the name of the virus that was found
11847 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
11849 .vitem &$max_received_linelength$&
11850 .vindex "&$max_received_linelength$&"
11851 .cindex "maximum" "line length"
11852 .cindex "line length" "maximum"
11853 This variable contains the number of bytes in the longest line that was
11854 received as part of the message, not counting the line termination
11857 .vitem &$message_age$&
11858 .cindex "message" "age of"
11859 .vindex "&$message_age$&"
11860 This variable is set at the start of a delivery attempt to contain the number
11861 of seconds since the message was received. It does not change during a single
11864 .vitem &$message_body$&
11865 .cindex "body of message" "expansion variable"
11866 .cindex "message body" "in expansion"
11867 .cindex "binary zero" "in message body"
11868 .vindex "&$message_body$&"
11869 .oindex "&%message_body_visible%&"
11870 This variable contains the initial portion of a message's body while it is
11871 being delivered, and is intended mainly for use in filter files. The maximum
11872 number of characters of the body that are put into the variable is set by the
11873 &%message_body_visible%& configuration option; the default is 500.
11875 .oindex "&%message_body_newlines%&"
11876 By default, newlines are converted into spaces in &$message_body$&, to make it
11877 easier to search for phrases that might be split over a line break. However,
11878 this can be disabled by setting &%message_body_newlines%& to be true. Binary
11879 zeros are always converted into spaces.
11881 .vitem &$message_body_end$&
11882 .cindex "body of message" "expansion variable"
11883 .cindex "message body" "in expansion"
11884 .vindex "&$message_body_end$&"
11885 This variable contains the final portion of a message's
11886 body while it is being delivered. The format and maximum size are as for
11889 .vitem &$message_body_size$&
11890 .cindex "body of message" "size"
11891 .cindex "message body" "size"
11892 .vindex "&$message_body_size$&"
11893 When a message is being delivered, this variable contains the size of the body
11894 in bytes. The count starts from the character after the blank line that
11895 separates the body from the header. Newlines are included in the count. See
11896 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11898 .vitem &$message_exim_id$&
11899 .vindex "&$message_exim_id$&"
11900 When a message is being received or delivered, this variable contains the
11901 unique message id that is generated and used by Exim to identify the message.
11902 An id is not created for a message until after its header has been successfully
11903 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11904 line; it is the local id that Exim assigns to the message, for example:
11905 &`1BXTIK-0001yO-VA`&.
11907 .vitem &$message_headers$&
11908 .vindex &$message_headers$&
11909 This variable contains a concatenation of all the header lines when a message
11910 is being processed, except for lines added by routers or transports. The header
11911 lines are separated by newline characters. Their contents are decoded in the
11912 same way as a header line that is inserted by &%bheader%&.
11914 .vitem &$message_headers_raw$&
11915 .vindex &$message_headers_raw$&
11916 This variable is like &$message_headers$& except that no processing of the
11917 contents of header lines is done.
11919 .vitem &$message_id$&
11920 This is an old name for &$message_exim_id$&. It is now deprecated.
11922 .vitem &$message_linecount$&
11923 .vindex "&$message_linecount$&"
11924 This variable contains the total number of lines in the header and body of the
11925 message. Compare &$body_linecount$&, which is the count for the body only.
11926 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
11927 number of lines received. Before delivery happens (that is, before filters,
11928 routers, and transports run) the count is increased to include the
11929 &'Received:'& header line that Exim standardly adds, and also any other header
11930 lines that are added by ACLs. The blank line that separates the message header
11931 from the body is not counted.
11933 As with the special case of &$message_size$&, during the expansion of the
11934 appendfile transport's maildir_tag option in maildir format, the value of
11935 &$message_linecount$& is the precise size of the number of newlines in the
11936 file that has been written (minus one for the blank line between the
11937 header and the body).
11939 Here is an example of the use of this variable in a DATA ACL:
11941 deny message = Too many lines in message header
11943 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
11945 In the MAIL and RCPT ACLs, the value is zero because at that stage the
11946 message has not yet been received.
11948 .vitem &$message_size$&
11949 .cindex "size" "of message"
11950 .cindex "message" "size"
11951 .vindex "&$message_size$&"
11952 When a message is being processed, this variable contains its size in bytes. In
11953 most cases, the size includes those headers that were received with the
11954 message, but not those (such as &'Envelope-to:'&) that are added to individual
11955 deliveries as they are written. However, there is one special case: during the
11956 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11957 doing a delivery in maildir format, the value of &$message_size$& is the
11958 precise size of the file that has been written. See also
11959 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11961 .cindex "RCPT" "value of &$message_size$&"
11962 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11963 contains the size supplied on the MAIL command, or -1 if no size was given. The
11964 value may not, of course, be truthful.
11966 .vitem &$mime_$&&'xxx'&
11967 A number of variables whose names start with &$mime$& are
11968 available when Exim is compiled with the content-scanning extension. For
11969 details, see section &<<SECTscanmimepart>>&.
11971 .vitem "&$n0$& &-- &$n9$&"
11972 These variables are counters that can be incremented by means
11973 of the &%add%& command in filter files.
11975 .vitem &$original_domain$&
11976 .vindex "&$domain$&"
11977 .vindex "&$original_domain$&"
11978 When a top-level address is being processed for delivery, this contains the
11979 same value as &$domain$&. However, if a &"child"& address (for example,
11980 generated by an alias, forward, or filter file) is being processed, this
11981 variable contains the domain of the original address (lower cased). This
11982 differs from &$parent_domain$& only when there is more than one level of
11983 aliasing or forwarding. When more than one address is being delivered in a
11984 single transport run, &$original_domain$& is not set.
11986 If a new address is created by means of a &%deliver%& command in a system
11987 filter, it is set up with an artificial &"parent"& address. This has the local
11988 part &'system-filter'& and the default qualify domain.
11990 .vitem &$original_local_part$&
11991 .vindex "&$local_part$&"
11992 .vindex "&$original_local_part$&"
11993 When a top-level address is being processed for delivery, this contains the
11994 same value as &$local_part$&, unless a prefix or suffix was removed from the
11995 local part, because &$original_local_part$& always contains the full local
11996 part. When a &"child"& address (for example, generated by an alias, forward, or
11997 filter file) is being processed, this variable contains the full local part of
11998 the original address.
12000 If the router that did the redirection processed the local part
12001 case-insensitively, the value in &$original_local_part$& is in lower case.
12002 This variable differs from &$parent_local_part$& only when there is more than
12003 one level of aliasing or forwarding. When more than one address is being
12004 delivered in a single transport run, &$original_local_part$& is not set.
12006 If a new address is created by means of a &%deliver%& command in a system
12007 filter, it is set up with an artificial &"parent"& address. This has the local
12008 part &'system-filter'& and the default qualify domain.
12010 .vitem &$originator_gid$&
12011 .cindex "gid (group id)" "of originating user"
12012 .cindex "sender" "gid"
12013 .vindex "&$caller_gid$&"
12014 .vindex "&$originator_gid$&"
12015 This variable contains the value of &$caller_gid$& that was set when the
12016 message was received. For messages received via the command line, this is the
12017 gid of the sending user. For messages received by SMTP over TCP/IP, this is
12018 normally the gid of the Exim user.
12020 .vitem &$originator_uid$&
12021 .cindex "uid (user id)" "of originating user"
12022 .cindex "sender" "uid"
12023 .vindex "&$caller_uid$&"
12024 .vindex "&$originaltor_uid$&"
12025 The value of &$caller_uid$& that was set when the message was received. For
12026 messages received via the command line, this is the uid of the sending user.
12027 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
12030 .vitem &$parent_domain$&
12031 .vindex "&$parent_domain$&"
12032 This variable is similar to &$original_domain$& (see
12033 above), except that it refers to the immediately preceding parent address.
12035 .vitem &$parent_local_part$&
12036 .vindex "&$parent_local_part$&"
12037 This variable is similar to &$original_local_part$&
12038 (see above), except that it refers to the immediately preceding parent address.
12041 .cindex "pid (process id)" "of current process"
12043 This variable contains the current process id.
12045 .vitem &$pipe_addresses$&
12046 .cindex "filter" "transport filter"
12047 .cindex "transport" "filter"
12048 .vindex "&$pipe_addresses$&"
12049 This is not an expansion variable, but is mentioned here because the string
12050 &`$pipe_addresses`& is handled specially in the command specification for the
12051 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
12052 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12053 It cannot be used in general expansion strings, and provokes an &"unknown
12054 variable"& error if encountered.
12056 .vitem &$primary_hostname$&
12057 .vindex "&$primary_hostname$&"
12058 This variable contains the value set by &%primary_hostname%& in the
12059 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12060 a single-component name, Exim calls &[gethostbyname()]& (or
12061 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12062 qualified host name. See also &$smtp_active_hostname$&.
12066 .vitem &$proxy_host_address$& &&&
12067 &$proxy_host_port$& &&&
12068 &$proxy_target_address$& &&&
12069 &$proxy_target_port$& &&&
12071 These variables are only available when built with Proxy Protocol
12073 For details see chapter &<<SECTproxyInbound>>&.
12077 .vitem &$prdr_requested$&
12078 .cindex "PRDR" "variable for"
12079 This variable is set to &"yes"& if PRDR was requested by the client for the
12080 current message, otherwise &"no"&.
12083 .vitem &$prvscheck_address$&
12084 This variable is used in conjunction with the &%prvscheck%& expansion item,
12085 which is described in sections &<<SECTexpansionitems>>& and
12086 &<<SECTverifyPRVS>>&.
12088 .vitem &$prvscheck_keynum$&
12089 This variable is used in conjunction with the &%prvscheck%& expansion item,
12090 which is described in sections &<<SECTexpansionitems>>& and
12091 &<<SECTverifyPRVS>>&.
12093 .vitem &$prvscheck_result$&
12094 This variable is used in conjunction with the &%prvscheck%& expansion item,
12095 which is described in sections &<<SECTexpansionitems>>& and
12096 &<<SECTverifyPRVS>>&.
12098 .vitem &$qualify_domain$&
12099 .vindex "&$qualify_domain$&"
12100 The value set for the &%qualify_domain%& option in the configuration file.
12102 .vitem &$qualify_recipient$&
12103 .vindex "&$qualify_recipient$&"
12104 The value set for the &%qualify_recipient%& option in the configuration file,
12105 or if not set, the value of &$qualify_domain$&.
12107 .vitem &$rcpt_count$&
12108 .vindex "&$rcpt_count$&"
12109 When a message is being received by SMTP, this variable contains the number of
12110 RCPT commands received for the current message. If this variable is used in a
12111 RCPT ACL, its value includes the current command.
12113 .vitem &$rcpt_defer_count$&
12114 .vindex "&$rcpt_defer_count$&"
12115 .cindex "4&'xx'& responses" "count of"
12116 When a message is being received by SMTP, this variable contains the number of
12117 RCPT commands in the current message that have previously been rejected with a
12118 temporary (4&'xx'&) response.
12120 .vitem &$rcpt_fail_count$&
12121 .vindex "&$rcpt_fail_count$&"
12122 When a message is being received by SMTP, this variable contains the number of
12123 RCPT commands in the current message that have previously been rejected with a
12124 permanent (5&'xx'&) response.
12126 .vitem &$received_count$&
12127 .vindex "&$received_count$&"
12128 This variable contains the number of &'Received:'& header lines in the message,
12129 including the one added by Exim (so its value is always greater than zero). It
12130 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12133 .vitem &$received_for$&
12134 .vindex "&$received_for$&"
12135 If there is only a single recipient address in an incoming message, this
12136 variable contains that address when the &'Received:'& header line is being
12137 built. The value is copied after recipient rewriting has happened, but before
12138 the &[local_scan()]& function is run.
12140 .vitem &$received_ip_address$&
12141 .vindex "&$received_ip_address$&"
12142 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12143 variable is set to the address of the local IP interface, and &$received_port$&
12144 is set to the local port number. (The remote IP address and port are in
12145 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12146 the port value is -1 unless it has been set using the &%-oMi%& command line
12149 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12150 could be used, for example, to make the file name for a TLS certificate depend
12151 on which interface and/or port is being used for the incoming connection. The
12152 values of &$received_ip_address$& and &$received_port$& are saved with any
12153 messages that are received, thus making these variables available at delivery
12155 For outbound connections see &$sending_ip_address$&.
12157 .vitem &$received_port$&
12158 .vindex "&$received_port$&"
12159 See &$received_ip_address$&.
12161 .vitem &$received_protocol$&
12162 .vindex "&$received_protocol$&"
12163 When a message is being processed, this variable contains the name of the
12164 protocol by which it was received. Most of the names used by Exim are defined
12165 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12166 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12167 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12168 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12169 connection and the client was successfully authenticated.
12171 Exim uses the protocol name &"smtps"& for the case when encryption is
12172 automatically set up on connection without the use of STARTTLS (see
12173 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12174 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12175 where the client initially uses EHLO, sets up an encrypted connection using
12176 STARTTLS, and then uses HELO afterwards.
12178 The &%-oMr%& option provides a way of specifying a custom protocol name for
12179 messages that are injected locally by trusted callers. This is commonly used to
12180 identify messages that are being re-injected after some kind of scanning.
12182 .vitem &$received_time$&
12183 .vindex "&$received_time$&"
12184 This variable contains the date and time when the current message was received,
12185 as a number of seconds since the start of the Unix epoch.
12187 .vitem &$recipient_data$&
12188 .vindex "&$recipient_data$&"
12189 This variable is set after an indexing lookup success in an ACL &%recipients%&
12190 condition. It contains the data from the lookup, and the value remains set
12191 until the next &%recipients%& test. Thus, you can do things like this:
12193 &`require recipients = cdb*@;/some/file`&
12194 &`deny `&&'some further test involving'& &`$recipient_data`&
12196 &*Warning*&: This variable is set only when a lookup is used as an indexing
12197 method in the address list, using the semicolon syntax as in the example above.
12198 The variable is not set for a lookup that is used as part of the string
12199 expansion that all such lists undergo before being interpreted.
12201 .vitem &$recipient_verify_failure$&
12202 .vindex "&$recipient_verify_failure$&"
12203 In an ACL, when a recipient verification fails, this variable contains
12204 information about the failure. It is set to one of the following words:
12207 &"qualify"&: The address was unqualified (no domain), and the message
12208 was neither local nor came from an exempted host.
12211 &"route"&: Routing failed.
12214 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12215 or before the MAIL command (that is, on initial connection, HELO, or
12219 &"recipient"&: The RCPT command in a callout was rejected.
12222 &"postmaster"&: The postmaster check in a callout was rejected.
12225 The main use of this variable is expected to be to distinguish between
12226 rejections of MAIL and rejections of RCPT.
12228 .vitem &$recipients$&
12229 .vindex "&$recipients$&"
12230 This variable contains a list of envelope recipients for a message. A comma and
12231 a space separate the addresses in the replacement text. However, the variable
12232 is not generally available, to prevent exposure of Bcc recipients in
12233 unprivileged users' filter files. You can use &$recipients$& only in these
12237 In a system filter file.
12239 In the ACLs associated with the DATA command and with non-SMTP messages, that
12240 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12241 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12242 &%acl_not_smtp_mime%&.
12244 From within a &[local_scan()]& function.
12248 .vitem &$recipients_count$&
12249 .vindex "&$recipients_count$&"
12250 When a message is being processed, this variable contains the number of
12251 envelope recipients that came with the message. Duplicates are not excluded
12252 from the count. While a message is being received over SMTP, the number
12253 increases for each accepted recipient. It can be referenced in an ACL.
12256 .vitem &$regex_match_string$&
12257 .vindex "&$regex_match_string$&"
12258 This variable is set to contain the matching regular expression after a
12259 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12261 .vitem "&$regex1$&, &$regex2$&, etc"
12262 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
12263 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
12264 these variables contain the
12265 captured substrings identified by the regular expression.
12268 .vitem &$reply_address$&
12269 .vindex "&$reply_address$&"
12270 When a message is being processed, this variable contains the contents of the
12271 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12272 contents of the &'From:'& header line. Apart from the removal of leading
12273 white space, the value is not processed in any way. In particular, no RFC 2047
12274 decoding or character code translation takes place.
12276 .vitem &$return_path$&
12277 .vindex "&$return_path$&"
12278 When a message is being delivered, this variable contains the return path &--
12279 the sender field that will be sent as part of the envelope. It is not enclosed
12280 in <> characters. At the start of routing an address, &$return_path$& has the
12281 same value as &$sender_address$&, but if, for example, an incoming message to a
12282 mailing list has been expanded by a router which specifies a different address
12283 for bounce messages, &$return_path$& subsequently contains the new bounce
12284 address, whereas &$sender_address$& always contains the original sender address
12285 that was received with the message. In other words, &$sender_address$& contains
12286 the incoming envelope sender, and &$return_path$& contains the outgoing
12289 .vitem &$return_size_limit$&
12290 .vindex "&$return_size_limit$&"
12291 This is an obsolete name for &$bounce_return_size_limit$&.
12293 .vitem &$router_name$&
12294 .cindex "router" "name"
12295 .cindex "name" "of router"
12296 .vindex "&$router_name$&"
12297 During the running of a router this variable contains its name.
12300 .cindex "return code" "from &%run%& expansion"
12301 .vindex "&$runrc$&"
12302 This variable contains the return code from a command that is run by the
12303 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12304 assume the order in which option values are expanded, except for those
12305 preconditions whose order of testing is documented. Therefore, you cannot
12306 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12309 .vitem &$self_hostname$&
12310 .oindex "&%self%&" "value of host name"
12311 .vindex "&$self_hostname$&"
12312 When an address is routed to a supposedly remote host that turns out to be the
12313 local host, what happens is controlled by the &%self%& generic router option.
12314 One of its values causes the address to be passed to another router. When this
12315 happens, &$self_hostname$& is set to the name of the local host that the
12316 original router encountered. In other circumstances its contents are null.
12318 .vitem &$sender_address$&
12319 .vindex "&$sender_address$&"
12320 When a message is being processed, this variable contains the sender's address
12321 that was received in the message's envelope. The case of letters in the address
12322 is retained, in both the local part and the domain. For bounce messages, the
12323 value of this variable is the empty string. See also &$return_path$&.
12325 .vitem &$sender_address_data$&
12326 .vindex "&$address_data$&"
12327 .vindex "&$sender_address_data$&"
12328 If &$address_data$& is set when the routers are called from an ACL to verify a
12329 sender address, the final value is preserved in &$sender_address_data$&, to
12330 distinguish it from data from a recipient address. The value does not persist
12331 after the end of the current ACL statement. If you want to preserve it for
12332 longer, you can save it in an ACL variable.
12334 .vitem &$sender_address_domain$&
12335 .vindex "&$sender_address_domain$&"
12336 The domain portion of &$sender_address$&.
12338 .vitem &$sender_address_local_part$&
12339 .vindex "&$sender_address_local_part$&"
12340 The local part portion of &$sender_address$&.
12342 .vitem &$sender_data$&
12343 .vindex "&$sender_data$&"
12344 This variable is set after a lookup success in an ACL &%senders%& condition or
12345 in a router &%senders%& option. It contains the data from the lookup, and the
12346 value remains set until the next &%senders%& test. Thus, you can do things like
12349 &`require senders = cdb*@;/some/file`&
12350 &`deny `&&'some further test involving'& &`$sender_data`&
12352 &*Warning*&: This variable is set only when a lookup is used as an indexing
12353 method in the address list, using the semicolon syntax as in the example above.
12354 The variable is not set for a lookup that is used as part of the string
12355 expansion that all such lists undergo before being interpreted.
12357 .vitem &$sender_fullhost$&
12358 .vindex "&$sender_fullhost$&"
12359 When a message is received from a remote host, this variable contains the host
12360 name and IP address in a single string. It ends with the IP address in square
12361 brackets, followed by a colon and a port number if the logging of ports is
12362 enabled. The format of the rest of the string depends on whether the host
12363 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12364 looking up its IP address. (Looking up the IP address can be forced by the
12365 &%host_lookup%& option, independent of verification.) A plain host name at the
12366 start of the string is a verified host name; if this is not present,
12367 verification either failed or was not requested. A host name in parentheses is
12368 the argument of a HELO or EHLO command. This is omitted if it is identical to
12369 the verified host name or to the host's IP address in square brackets.
12371 .vitem &$sender_helo_dnssec$&
12372 .vindex "&$sender_helo_dnssec$&"
12373 This boolean variable is true if a successful HELO verification was
12374 .cindex "DNS" "DNSSEC"
12375 done using DNS information the resolver library stated was authenticated data.
12377 .vitem &$sender_helo_name$&
12378 .vindex "&$sender_helo_name$&"
12379 When a message is received from a remote host that has issued a HELO or EHLO
12380 command, the argument of that command is placed in this variable. It is also
12381 set if HELO or EHLO is used when a message is received using SMTP locally via
12382 the &%-bs%& or &%-bS%& options.
12384 .vitem &$sender_host_address$&
12385 .vindex "&$sender_host_address$&"
12386 When a message is received from a remote host using SMTP,
12387 this variable contains that
12388 host's IP address. For locally non-SMTP submitted messages, it is empty.
12390 .vitem &$sender_host_authenticated$&
12391 .vindex "&$sender_host_authenticated$&"
12392 This variable contains the name (not the public name) of the authenticator
12393 driver that successfully authenticated the client from which the message was
12394 received. It is empty if there was no successful authentication. See also
12395 &$authenticated_id$&.
12397 .vitem &$sender_host_dnssec$&
12398 .vindex "&$sender_host_dnssec$&"
12399 If an attempt to populate &$sender_host_name$& has been made
12400 (by reference, &%hosts_lookup%& or
12401 otherwise) then this boolean will have been set true if, and only if, the
12402 resolver library states that both
12403 the reverse and forward DNS were authenticated data. At all
12404 other times, this variable is false.
12406 .cindex "DNS" "DNSSEC"
12407 It is likely that you will need to coerce DNSSEC support on in the resolver
12408 library, by setting:
12413 Exim does not perform DNSSEC validation itself, instead leaving that to a
12414 validating resolver (e.g. unbound, or bind with suitable configuration).
12416 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12417 mechanism in the list, then this variable will be false.
12420 .vitem &$sender_host_name$&
12421 .vindex "&$sender_host_name$&"
12422 When a message is received from a remote host, this variable contains the
12423 host's name as obtained by looking up its IP address. For messages received by
12424 other means, this variable is empty.
12426 .vindex "&$host_lookup_failed$&"
12427 If the host name has not previously been looked up, a reference to
12428 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12429 A looked up name is accepted only if it leads back to the original IP address
12430 via a forward lookup. If either the reverse or the forward lookup fails to find
12431 any data, or if the forward lookup does not yield the original IP address,
12432 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12434 .vindex "&$host_lookup_deferred$&"
12435 However, if either of the lookups cannot be completed (for example, there is a
12436 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12437 &$host_lookup_failed$& remains set to &"0"&.
12439 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12440 host name again if there is a subsequent reference to &$sender_host_name$&
12441 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12444 Exim does not automatically look up every calling host's name. If you want
12445 maximum efficiency, you should arrange your configuration so that it avoids
12446 these lookups altogether. The lookup happens only if one or more of the
12447 following are true:
12450 A string containing &$sender_host_name$& is expanded.
12452 The calling host matches the list in &%host_lookup%&. In the default
12453 configuration, this option is set to *, so it must be changed if lookups are
12454 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12456 Exim needs the host name in order to test an item in a host list. The items
12457 that require this are described in sections &<<SECThoslispatnam>>& and
12458 &<<SECThoslispatnamsk>>&.
12460 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12461 In this case, the host name is required to compare with the name quoted in any
12462 EHLO or HELO commands that the client issues.
12464 The remote host issues a EHLO or HELO command that quotes one of the
12465 domains in &%helo_lookup_domains%&. The default value of this option is
12466 . ==== As this is a nested list, any displays it contains must be indented
12467 . ==== as otherwise they are too far to the left.
12469 helo_lookup_domains = @ : @[]
12471 which causes a lookup if a remote host (incorrectly) gives the server's name or
12472 IP address in an EHLO or HELO command.
12476 .vitem &$sender_host_port$&
12477 .vindex "&$sender_host_port$&"
12478 When a message is received from a remote host, this variable contains the port
12479 number that was used on the remote host.
12481 .vitem &$sender_ident$&
12482 .vindex "&$sender_ident$&"
12483 When a message is received from a remote host, this variable contains the
12484 identification received in response to an RFC 1413 request. When a message has
12485 been received locally, this variable contains the login name of the user that
12488 .vitem &$sender_rate_$&&'xxx'&
12489 A number of variables whose names begin &$sender_rate_$& are set as part of the
12490 &%ratelimit%& ACL condition. Details are given in section
12491 &<<SECTratelimiting>>&.
12493 .vitem &$sender_rcvhost$&
12494 .cindex "DNS" "reverse lookup"
12495 .cindex "reverse DNS lookup"
12496 .vindex "&$sender_rcvhost$&"
12497 This is provided specifically for use in &'Received:'& headers. It starts with
12498 either the verified host name (as obtained from a reverse DNS lookup) or, if
12499 there is no verified host name, the IP address in square brackets. After that
12500 there may be text in parentheses. When the first item is a verified host name,
12501 the first thing in the parentheses is the IP address in square brackets,
12502 followed by a colon and a port number if port logging is enabled. When the
12503 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12506 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12507 was used and its argument was not identical to the real host name or IP
12508 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12509 all three items are present in the parentheses, a newline and tab are inserted
12510 into the string, to improve the formatting of the &'Received:'& header.
12512 .vitem &$sender_verify_failure$&
12513 .vindex "&$sender_verify_failure$&"
12514 In an ACL, when a sender verification fails, this variable contains information
12515 about the failure. The details are the same as for
12516 &$recipient_verify_failure$&.
12518 .vitem &$sending_ip_address$&
12519 .vindex "&$sending_ip_address$&"
12520 This variable is set whenever an outgoing SMTP connection to another host has
12521 been set up. It contains the IP address of the local interface that is being
12522 used. This is useful if a host that has more than one IP address wants to take
12523 on different personalities depending on which one is being used. For incoming
12524 connections, see &$received_ip_address$&.
12526 .vitem &$sending_port$&
12527 .vindex "&$sending_port$&"
12528 This variable is set whenever an outgoing SMTP connection to another host has
12529 been set up. It contains the local port that is being used. For incoming
12530 connections, see &$received_port$&.
12532 .vitem &$smtp_active_hostname$&
12533 .vindex "&$smtp_active_hostname$&"
12534 During an incoming SMTP session, this variable contains the value of the active
12535 host name, as specified by the &%smtp_active_hostname%& option. The value of
12536 &$smtp_active_hostname$& is saved with any message that is received, so its
12537 value can be consulted during routing and delivery.
12539 .vitem &$smtp_command$&
12540 .vindex "&$smtp_command$&"
12541 During the processing of an incoming SMTP command, this variable contains the
12542 entire command. This makes it possible to distinguish between HELO and EHLO in
12543 the HELO ACL, and also to distinguish between commands such as these:
12548 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12549 command, the address in &$smtp_command$& is the original address before any
12550 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12551 the address after SMTP-time rewriting.
12553 .vitem &$smtp_command_argument$&
12554 .cindex "SMTP" "command, argument for"
12555 .vindex "&$smtp_command_argument$&"
12556 While an ACL is running to check an SMTP command, this variable contains the
12557 argument, that is, the text that follows the command name, with leading white
12558 space removed. Following the introduction of &$smtp_command$&, this variable is
12559 somewhat redundant, but is retained for backwards compatibility.
12561 .vitem &$smtp_count_at_connection_start$&
12562 .vindex "&$smtp_count_at_connection_start$&"
12563 This variable is set greater than zero only in processes spawned by the Exim
12564 daemon for handling incoming SMTP connections. The name is deliberately long,
12565 in order to emphasize what the contents are. When the daemon accepts a new
12566 connection, it increments this variable. A copy of the variable is passed to
12567 the child process that handles the connection, but its value is fixed, and
12568 never changes. It is only an approximation of how many incoming connections
12569 there actually are, because many other connections may come and go while a
12570 single connection is being processed. When a child process terminates, the
12571 daemon decrements its copy of the variable.
12573 .vitem "&$sn0$& &-- &$sn9$&"
12574 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12575 that were current at the end of the system filter file. This allows a system
12576 filter file to set values that can be tested in users' filter files. For
12577 example, a system filter could set a value indicating how likely it is that a
12578 message is junk mail.
12580 .vitem &$spam_$&&'xxx'&
12581 A number of variables whose names start with &$spam$& are available when Exim
12582 is compiled with the content-scanning extension. For details, see section
12583 &<<SECTscanspamass>>&.
12586 .vitem &$spool_directory$&
12587 .vindex "&$spool_directory$&"
12588 The name of Exim's spool directory.
12590 .vitem &$spool_inodes$&
12591 .vindex "&$spool_inodes$&"
12592 The number of free inodes in the disk partition where Exim's spool files are
12593 being written. The value is recalculated whenever the variable is referenced.
12594 If the relevant file system does not have the concept of inodes, the value of
12595 is -1. See also the &%check_spool_inodes%& option.
12597 .vitem &$spool_space$&
12598 .vindex "&$spool_space$&"
12599 The amount of free space (as a number of kilobytes) in the disk partition where
12600 Exim's spool files are being written. The value is recalculated whenever the
12601 variable is referenced. If the operating system does not have the ability to
12602 find the amount of free space (only true for experimental systems), the space
12603 value is -1. For example, to check in an ACL that there is at least 50
12604 megabytes free on the spool, you could write:
12606 condition = ${if > {$spool_space}{50000}}
12608 See also the &%check_spool_space%& option.
12611 .vitem &$thisaddress$&
12612 .vindex "&$thisaddress$&"
12613 This variable is set only during the processing of the &%foranyaddress%&
12614 command in a filter file. Its use is explained in the description of that
12615 command, which can be found in the separate document entitled &'Exim's
12616 interfaces to mail filtering'&.
12618 .vitem &$tls_in_bits$&
12619 .vindex "&$tls_in_bits$&"
12620 Contains an approximation of the TLS cipher's bit-strength
12621 on the inbound connection; the meaning of
12622 this depends upon the TLS implementation used.
12623 If TLS has not been negotiated, the value will be 0.
12624 The value of this is automatically fed into the Cyrus SASL authenticator
12625 when acting as a server, to specify the "external SSF" (a SASL term).
12627 The deprecated &$tls_bits$& variable refers to the inbound side
12628 except when used in the context of an outbound SMTP delivery, when it refers to
12631 .vitem &$tls_out_bits$&
12632 .vindex "&$tls_out_bits$&"
12633 Contains an approximation of the TLS cipher's bit-strength
12634 on an outbound SMTP connection; the meaning of
12635 this depends upon the TLS implementation used.
12636 If TLS has not been negotiated, the value will be 0.
12638 .vitem &$tls_in_ourcert$&
12639 .vindex "&$tls_in_ourcert$&"
12640 This variable refers to the certificate presented to the peer of an
12641 inbound connection when the message was received.
12642 It is only useful as the argument of a
12643 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12644 or a &%def%& condition.
12646 .vitem &$tls_in_peercert$&
12647 .vindex "&$tls_in_peercert$&"
12648 This variable refers to the certificate presented by the peer of an
12649 inbound connection when the message was received.
12650 It is only useful as the argument of a
12651 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12652 or a &%def%& condition.
12653 If certificate verification fails it may refer to a failing chain element
12654 which is not the leaf.
12656 .vitem &$tls_out_ourcert$&
12657 .vindex "&$tls_out_ourcert$&"
12658 This variable refers to the certificate presented to the peer of an
12659 outbound connection. It is only useful as the argument of a
12660 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12661 or a &%def%& condition.
12663 .vitem &$tls_out_peercert$&
12664 .vindex "&$tls_out_peercert$&"
12665 This variable refers to the certificate presented by the peer of an
12666 outbound connection. It is only useful as the argument of a
12667 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12668 or a &%def%& condition.
12669 If certificate verification fails it may refer to a failing chain element
12670 which is not the leaf.
12672 .vitem &$tls_in_certificate_verified$&
12673 .vindex "&$tls_in_certificate_verified$&"
12674 This variable is set to &"1"& if a TLS certificate was verified when the
12675 message was received, and &"0"& otherwise.
12677 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
12678 except when used in the context of an outbound SMTP delivery, when it refers to
12681 .vitem &$tls_out_certificate_verified$&
12682 .vindex "&$tls_out_certificate_verified$&"
12683 This variable is set to &"1"& if a TLS certificate was verified when an
12684 outbound SMTP connection was made,
12685 and &"0"& otherwise.
12687 .vitem &$tls_in_cipher$&
12688 .vindex "&$tls_in_cipher$&"
12689 .vindex "&$tls_cipher$&"
12690 When a message is received from a remote host over an encrypted SMTP
12691 connection, this variable is set to the cipher suite that was negotiated, for
12692 example DES-CBC3-SHA. In other circumstances, in particular, for message
12693 received over unencrypted connections, the variable is empty. Testing
12694 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
12695 non-encrypted connections during ACL processing.
12697 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12698 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12699 becomes the same as &$tls_out_cipher$&.
12701 .vitem &$tls_out_cipher$&
12702 .vindex "&$tls_out_cipher$&"
12704 cleared before any outgoing SMTP connection is made,
12705 and then set to the outgoing cipher suite if one is negotiated. See chapter
12706 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12707 details of the &(smtp)& transport.
12709 .vitem &$tls_in_ocsp$&
12710 .vindex "&$tls_in_ocsp$&"
12711 When a message is received from a remote client connection
12712 the result of any OCSP request from the client is encoded in this variable:
12714 0 OCSP proof was not requested (default value)
12715 1 No response to request
12716 2 Response not verified
12717 3 Verification failed
12718 4 Verification succeeded
12721 .vitem &$tls_out_ocsp$&
12722 .vindex "&$tls_out_ocsp$&"
12723 When a message is sent to a remote host connection
12724 the result of any OCSP request made is encoded in this variable.
12725 See &$tls_in_ocsp$& for values.
12727 .vitem &$tls_in_peerdn$&
12728 .vindex "&$tls_in_peerdn$&"
12729 .vindex "&$tls_peerdn$&"
12730 When a message is received from a remote host over an encrypted SMTP
12731 connection, and Exim is configured to request a certificate from the client,
12732 the value of the Distinguished Name of the certificate is made available in the
12733 &$tls_in_peerdn$& during subsequent processing.
12734 If certificate verification fails it may refer to a failing chain element
12735 which is not the leaf.
12737 The deprecated &$tls_peerdn$& variable refers to the inbound side
12738 except when used in the context of an outbound SMTP delivery, when it refers to
12741 .vitem &$tls_out_peerdn$&
12742 .vindex "&$tls_out_peerdn$&"
12743 When a message is being delivered to a remote host over an encrypted SMTP
12744 connection, and Exim is configured to request a certificate from the server,
12745 the value of the Distinguished Name of the certificate is made available in the
12746 &$tls_out_peerdn$& during subsequent processing.
12747 If certificate verification fails it may refer to a failing chain element
12748 which is not the leaf.
12750 .vitem &$tls_in_sni$&
12751 .vindex "&$tls_in_sni$&"
12752 .vindex "&$tls_sni$&"
12753 .cindex "TLS" "Server Name Indication"
12754 When a TLS session is being established, if the client sends the Server
12755 Name Indication extension, the value will be placed in this variable.
12756 If the variable appears in &%tls_certificate%& then this option and
12757 some others, described in &<<SECTtlssni>>&,
12758 will be re-expanded early in the TLS session, to permit
12759 a different certificate to be presented (and optionally a different key to be
12760 used) to the client, based upon the value of the SNI extension.
12762 The deprecated &$tls_sni$& variable refers to the inbound side
12763 except when used in the context of an outbound SMTP delivery, when it refers to
12766 .vitem &$tls_out_sni$&
12767 .vindex "&$tls_out_sni$&"
12768 .cindex "TLS" "Server Name Indication"
12770 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12773 .vitem &$tod_bsdinbox$&
12774 .vindex "&$tod_bsdinbox$&"
12775 The time of day and the date, in the format required for BSD-style mailbox
12776 files, for example: Thu Oct 17 17:14:09 1995.
12778 .vitem &$tod_epoch$&
12779 .vindex "&$tod_epoch$&"
12780 The time and date as a number of seconds since the start of the Unix epoch.
12782 .vitem &$tod_epoch_l$&
12783 .vindex "&$tod_epoch_l$&"
12784 The time and date as a number of microseconds since the start of the Unix epoch.
12786 .vitem &$tod_full$&
12787 .vindex "&$tod_full$&"
12788 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12789 +0100. The timezone is always given as a numerical offset from UTC, with
12790 positive values used for timezones that are ahead (east) of UTC, and negative
12791 values for those that are behind (west).
12794 .vindex "&$tod_log$&"
12795 The time and date in the format used for writing Exim's log files, for example:
12796 1995-10-12 15:32:29, but without a timezone.
12798 .vitem &$tod_logfile$&
12799 .vindex "&$tod_logfile$&"
12800 This variable contains the date in the format yyyymmdd. This is the format that
12801 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12804 .vitem &$tod_zone$&
12805 .vindex "&$tod_zone$&"
12806 This variable contains the numerical value of the local timezone, for example:
12809 .vitem &$tod_zulu$&
12810 .vindex "&$tod_zulu$&"
12811 This variable contains the UTC date and time in &"Zulu"& format, as specified
12812 by ISO 8601, for example: 20030221154023Z.
12814 .vitem &$transport_name$&
12815 .cindex "transport" "name"
12816 .cindex "name" "of transport"
12817 .vindex "&$transport_name$&"
12818 During the running of a transport, this variable contains its name.
12821 .vindex "&$value$&"
12822 This variable contains the result of an expansion lookup, extraction operation,
12823 or external command, as described above. It is also used during a
12824 &*reduce*& expansion.
12826 .vitem &$verify_mode$&
12827 .vindex "&$verify_mode$&"
12828 While a router or transport is being run in verify mode
12829 or for cutthrough delivery,
12830 contains "S" for sender-verification or "R" for recipient-verification.
12833 .vitem &$version_number$&
12834 .vindex "&$version_number$&"
12835 The version number of Exim.
12837 .vitem &$warn_message_delay$&
12838 .vindex "&$warn_message_delay$&"
12839 This variable is set only during the creation of a message warning about a
12840 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12842 .vitem &$warn_message_recipients$&
12843 .vindex "&$warn_message_recipients$&"
12844 This variable is set only during the creation of a message warning about a
12845 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12851 . ////////////////////////////////////////////////////////////////////////////
12852 . ////////////////////////////////////////////////////////////////////////////
12854 .chapter "Embedded Perl" "CHAPperl"
12855 .scindex IIDperl "Perl" "calling from Exim"
12856 Exim can be built to include an embedded Perl interpreter. When this is done,
12857 Perl subroutines can be called as part of the string expansion process. To make
12858 use of the Perl support, you need version 5.004 or later of Perl installed on
12859 your system. To include the embedded interpreter in the Exim binary, include
12864 in your &_Local/Makefile_& and then build Exim in the normal way.
12867 .section "Setting up so Perl can be used" "SECID85"
12868 .oindex "&%perl_startup%&"
12869 Access to Perl subroutines is via a global configuration option called
12870 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
12871 no &%perl_startup%& option in the Exim configuration file then no Perl
12872 interpreter is started and there is almost no overhead for Exim (since none of
12873 the Perl library will be paged in unless used). If there is a &%perl_startup%&
12874 option then the associated value is taken to be Perl code which is executed in
12875 a newly created Perl interpreter.
12877 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
12878 need backslashes before any characters to escape special meanings. The option
12879 should usually be something like
12881 perl_startup = do '/etc/exim.pl'
12883 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
12884 use from Exim. Exim can be configured either to start up a Perl interpreter as
12885 soon as it is entered, or to wait until the first time it is needed. Starting
12886 the interpreter at the beginning ensures that it is done while Exim still has
12887 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
12888 fact used in a particular run. Also, note that this does not mean that Exim is
12889 necessarily running as root when Perl is called at a later time. By default,
12890 the interpreter is started only when it is needed, but this can be changed in
12894 .oindex "&%perl_at_start%&"
12895 Setting &%perl_at_start%& (a boolean option) in the configuration requests
12896 a startup when Exim is entered.
12898 The command line option &%-ps%& also requests a startup when Exim is entered,
12899 overriding the setting of &%perl_at_start%&.
12902 There is also a command line option &%-pd%& (for delay) which suppresses the
12903 initial startup, even if &%perl_at_start%& is set.
12906 .section "Calling Perl subroutines" "SECID86"
12907 When the configuration file includes a &%perl_startup%& option you can make use
12908 of the string expansion item to call the Perl subroutines that are defined
12909 by the &%perl_startup%& code. The operator is used in any of the following
12913 ${perl{foo}{argument}}
12914 ${perl{foo}{argument1}{argument2} ... }
12916 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
12917 arguments may be passed. Passing more than this results in an expansion failure
12918 with an error message of the form
12920 Too many arguments passed to Perl subroutine "foo" (max is 8)
12922 The return value of the Perl subroutine is evaluated in a scalar context before
12923 it is passed back to Exim to be inserted into the expanded string. If the
12924 return value is &'undef'&, the expansion is forced to fail in the same way as
12925 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
12926 by obeying Perl's &%die%& function, the expansion fails with the error message
12927 that was passed to &%die%&.
12930 .section "Calling Exim functions from Perl" "SECID87"
12931 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
12932 is available to call back into Exim's string expansion function. For example,
12935 my $lp = Exim::expand_string('$local_part');
12937 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
12938 Note those are single quotes and not double quotes to protect against
12939 &$local_part$& being interpolated as a Perl variable.
12941 If the string expansion is forced to fail by a &"fail"& item, the result of
12942 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
12943 expansion string, the Perl call from the original expansion string fails with
12944 an appropriate error message, in the same way as if &%die%& were used.
12946 .cindex "debugging" "from embedded Perl"
12947 .cindex "log" "writing from embedded Perl"
12948 Two other Exim functions are available for use from within Perl code.
12949 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
12950 debugging is enabled. If you want a newline at the end, you must supply it.
12951 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
12952 timestamp. In this case, you should not supply a terminating newline.
12955 .section "Use of standard output and error by Perl" "SECID88"
12956 .cindex "Perl" "standard output and error"
12957 You should not write to the standard error or output streams from within your
12958 Perl code, as it is not defined how these are set up. In versions of Exim
12959 before 4.50, it is possible for the standard output or error to refer to the
12960 SMTP connection during message reception via the daemon. Writing to this stream
12961 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
12962 error streams are connected to &_/dev/null_& in the daemon. The chaos is
12963 avoided, but the output is lost.
12965 .cindex "Perl" "use of &%warn%&"
12966 The Perl &%warn%& statement writes to the standard error stream by default.
12967 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
12968 you have no control. When Exim starts up the Perl interpreter, it arranges for
12969 output from the &%warn%& statement to be written to the Exim main log. You can
12970 change this by including appropriate Perl magic somewhere in your Perl code.
12971 For example, to discard &%warn%& output completely, you need this:
12973 $SIG{__WARN__} = sub { };
12975 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
12976 example, the code for the subroutine is empty, so it does nothing, but you can
12977 include any Perl code that you like. The text of the &%warn%& message is passed
12978 as the first subroutine argument.
12982 . ////////////////////////////////////////////////////////////////////////////
12983 . ////////////////////////////////////////////////////////////////////////////
12985 .chapter "Starting the daemon and the use of network interfaces" &&&
12986 "CHAPinterfaces" &&&
12987 "Starting the daemon"
12988 .cindex "daemon" "starting"
12989 .cindex "interface" "listening"
12990 .cindex "network interface"
12991 .cindex "interface" "network"
12992 .cindex "IP address" "for listening"
12993 .cindex "daemon" "listening IP addresses"
12994 .cindex "TCP/IP" "setting listening interfaces"
12995 .cindex "TCP/IP" "setting listening ports"
12996 A host that is connected to a TCP/IP network may have one or more physical
12997 hardware network interfaces. Each of these interfaces may be configured as one
12998 or more &"logical"& interfaces, which are the entities that a program actually
12999 works with. Each of these logical interfaces is associated with an IP address.
13000 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
13001 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
13002 knowledge about the host's interfaces for use in three different circumstances:
13005 When a listening daemon is started, Exim needs to know which interfaces
13006 and ports to listen on.
13008 When Exim is routing an address, it needs to know which IP addresses
13009 are associated with local interfaces. This is required for the correct
13010 processing of MX lists by removing the local host and others with the
13011 same or higher priority values. Also, Exim needs to detect cases
13012 when an address is routed to an IP address that in fact belongs to the
13013 local host. Unless the &%self%& router option or the &%allow_localhost%&
13014 option of the smtp transport is set (as appropriate), this is treated
13015 as an error situation.
13017 When Exim connects to a remote host, it may need to know which interface to use
13018 for the outgoing connection.
13022 Exim's default behaviour is likely to be appropriate in the vast majority
13023 of cases. If your host has only one interface, and you want all its IP
13024 addresses to be treated in the same way, and you are using only the
13025 standard SMTP port, you should not need to take any special action. The
13026 rest of this chapter does not apply to you.
13028 In a more complicated situation you may want to listen only on certain
13029 interfaces, or on different ports, and for this reason there are a number of
13030 options that can be used to influence Exim's behaviour. The rest of this
13031 chapter describes how they operate.
13033 When a message is received over TCP/IP, the interface and port that were
13034 actually used are set in &$received_ip_address$& and &$received_port$&.
13038 .section "Starting a listening daemon" "SECID89"
13039 When a listening daemon is started (by means of the &%-bd%& command line
13040 option), the interfaces and ports on which it listens are controlled by the
13044 &%daemon_smtp_ports%& contains a list of default ports
13046 (For backward compatibility, this option can also be specified in the singular.)
13048 &%local_interfaces%& contains list of interface IP addresses on which to
13049 listen. Each item may optionally also specify a port.
13052 The default list separator in both cases is a colon, but this can be changed as
13053 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
13054 it is usually best to change the separator to avoid having to double all the
13055 colons. For example:
13057 local_interfaces = <; 127.0.0.1 ; \
13060 3ffe:ffff:836f::fe86:a061
13062 There are two different formats for specifying a port along with an IP address
13063 in &%local_interfaces%&:
13066 The port is added onto the address with a dot separator. For example, to listen
13067 on port 1234 on two different IP addresses:
13069 local_interfaces = <; 192.168.23.65.1234 ; \
13070 3ffe:ffff:836f::fe86:a061.1234
13073 The IP address is enclosed in square brackets, and the port is added
13074 with a colon separator, for example:
13076 local_interfaces = <; [192.168.23.65]:1234 ; \
13077 [3ffe:ffff:836f::fe86:a061]:1234
13081 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13082 default setting contains just one port:
13084 daemon_smtp_ports = smtp
13086 If more than one port is listed, each interface that does not have its own port
13087 specified listens on all of them. Ports that are listed in
13088 &%daemon_smtp_ports%& can be identified either by name (defined in
13089 &_/etc/services_&) or by number. However, when ports are given with individual
13090 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13094 .section "Special IP listening addresses" "SECID90"
13095 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13096 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13097 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13098 instead of setting up separate listening sockets for each interface. The
13099 default value of &%local_interfaces%& is
13101 local_interfaces = 0.0.0.0
13103 when Exim is built without IPv6 support; otherwise it is:
13105 local_interfaces = <; ::0 ; 0.0.0.0
13107 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13111 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13112 The &%-oX%& command line option can be used to override the values of
13113 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13114 instance. Another way of doing this would be to use macros and the &%-D%&
13115 option. However, &%-oX%& can be used by any admin user, whereas modification of
13116 the runtime configuration by &%-D%& is allowed only when the caller is root or
13119 The value of &%-oX%& is a list of items. The default colon separator can be
13120 changed in the usual way if required. If there are any items that do not
13121 contain dots or colons (that is, are not IP addresses), the value of
13122 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13123 items that do contain dots or colons, the value of &%local_interfaces%& is
13124 replaced by those items. Thus, for example,
13128 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13131 -oX 192.168.34.5.1125
13133 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13134 (However, since &%local_interfaces%& now contains no items without ports, the
13135 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13139 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
13140 .cindex "ssmtp protocol"
13141 .cindex "smtps protocol"
13142 .cindex "SMTP" "ssmtp protocol"
13143 .cindex "SMTP" "smtps protocol"
13144 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
13145 before the STARTTLS command was standardized for SMTP. Some legacy clients
13146 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
13147 list of port numbers or service names,
13148 connections to those ports must use SSMTP. The most
13149 common use of this option is expected to be
13151 tls_on_connect_ports = 465
13153 because 465 is the usual port number used by the legacy clients. There is also
13154 a command line option &%-tls-on-connect%&, which forces all ports to behave in
13155 this way when a daemon is started.
13157 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13158 daemon to listen on those ports. You must still specify them in
13159 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13160 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13161 connections via the daemon.)
13166 .section "IPv6 address scopes" "SECID92"
13167 .cindex "IPv6" "address scopes"
13168 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13169 can, in principle, have the same link-local IPv6 address on different
13170 interfaces. Thus, additional information is needed, over and above the IP
13171 address, to distinguish individual interfaces. A convention of using a
13172 percent sign followed by something (often the interface name) has been
13173 adopted in some cases, leading to addresses like this:
13175 fe80::202:b3ff:fe03:45c1%eth0
13177 To accommodate this usage, a percent sign followed by an arbitrary string is
13178 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13179 to convert a textual IPv6 address for actual use. This function recognizes the
13180 percent convention in operating systems that support it, and it processes the
13181 address appropriately. Unfortunately, some older libraries have problems with
13182 &[getaddrinfo()]&. If
13184 IPV6_USE_INET_PTON=yes
13186 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13187 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13188 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13189 function.) Of course, this means that the additional functionality of
13190 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13192 .section "Disabling IPv6" "SECID93"
13193 .cindex "IPv6" "disabling"
13194 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13195 run on a host whose kernel does not support IPv6. The binary will fall back to
13196 using IPv4, but it may waste resources looking up AAAA records, and trying to
13197 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13198 .oindex "&%disable_ipv6%&"
13199 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13200 activities take place. AAAA records are never looked up, and any IPv6 addresses
13201 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13202 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13203 to handle IPv6 literal addresses.
13205 On the other hand, when IPv6 is in use, there may be times when you want to
13206 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13207 option to globally suppress the lookup of AAAA records for specified domains,
13208 and you can use the &%ignore_target_hosts%& generic router option to ignore
13209 IPv6 addresses in an individual router.
13213 .section "Examples of starting a listening daemon" "SECID94"
13214 The default case in an IPv6 environment is
13216 daemon_smtp_ports = smtp
13217 local_interfaces = <; ::0 ; 0.0.0.0
13219 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13220 Either one or two sockets may be used, depending on the characteristics of
13221 the TCP/IP stack. (This is complicated and messy; for more information,
13222 read the comments in the &_daemon.c_& source file.)
13224 To specify listening on ports 25 and 26 on all interfaces:
13226 daemon_smtp_ports = 25 : 26
13228 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13230 local_interfaces = <; ::0.25 ; ::0.26 \
13231 0.0.0.0.25 ; 0.0.0.0.26
13233 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13234 IPv4 loopback address only:
13236 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13238 To specify listening on the default port on specific interfaces only:
13240 local_interfaces = 10.0.0.67 : 192.168.34.67
13242 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13246 .section "Recognizing the local host" "SECTreclocipadd"
13247 The &%local_interfaces%& option is also used when Exim needs to determine
13248 whether or not an IP address refers to the local host. That is, the IP
13249 addresses of all the interfaces on which a daemon is listening are always
13252 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13253 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13254 available interfaces from the operating system, and extracts the relevant
13255 (that is, IPv4 or IPv6) addresses to use for checking.
13257 Some systems set up large numbers of virtual interfaces in order to provide
13258 many virtual web servers. In this situation, you may want to listen for
13259 email on only a few of the available interfaces, but nevertheless treat all
13260 interfaces as local when routing. You can do this by setting
13261 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13262 &"all"& wildcard values. These addresses are recognized as local, but are not
13263 used for listening. Consider this example:
13265 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13267 3ffe:2101:12:1:a00:20ff:fe86:a061
13269 extra_local_interfaces = <; ::0 ; 0.0.0.0
13271 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13272 address, but all available interface addresses are treated as local when
13275 In some environments the local host name may be in an MX list, but with an IP
13276 address that is not assigned to any local interface. In other cases it may be
13277 desirable to treat other host names as if they referred to the local host. Both
13278 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13279 This contains host names rather than IP addresses. When a host is referenced
13280 during routing, either via an MX record or directly, it is treated as the local
13281 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13282 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13286 .section "Delivering to a remote host" "SECID95"
13287 Delivery to a remote host is handled by the smtp transport. By default, it
13288 allows the system's TCP/IP functions to choose which interface to use (if
13289 there is more than one) when connecting to a remote host. However, the
13290 &%interface%& option can be set to specify which interface is used. See the
13291 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13297 . ////////////////////////////////////////////////////////////////////////////
13298 . ////////////////////////////////////////////////////////////////////////////
13300 .chapter "Main configuration" "CHAPmainconfig"
13301 .scindex IIDconfima "configuration file" "main section"
13302 .scindex IIDmaiconf "main configuration"
13303 The first part of the run time configuration file contains three types of item:
13306 Macro definitions: These lines start with an upper case letter. See section
13307 &<<SECTmacrodefs>>& for details of macro processing.
13309 Named list definitions: These lines start with one of the words &"domainlist"&,
13310 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13311 section &<<SECTnamedlists>>&.
13313 Main configuration settings: Each setting occupies one line of the file
13314 (with possible continuations). If any setting is preceded by the word
13315 &"hide"&, the &%-bP%& command line option displays its value to admin users
13316 only. See section &<<SECTcos>>& for a description of the syntax of these option
13320 This chapter specifies all the main configuration options, along with their
13321 types and default values. For ease of finding a particular option, they appear
13322 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13323 are now so many options, they are first listed briefly in functional groups, as
13324 an aid to finding the name of the option you are looking for. Some options are
13325 listed in more than one group.
13327 .section "Miscellaneous" "SECID96"
13329 .row &%bi_command%& "to run for &%-bi%& command line option"
13330 .row &%disable_ipv6%& "do no IPv6 processing"
13331 .row &%keep_malformed%& "for broken files &-- should not happen"
13332 .row &%localhost_number%& "for unique message ids in clusters"
13333 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13334 .row &%message_body_visible%& "how much to show in &$message_body$&"
13335 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13336 .row &%print_topbitchars%& "top-bit characters are printing"
13337 .row &%timezone%& "force time zone"
13341 .section "Exim parameters" "SECID97"
13343 .row &%exim_group%& "override compiled-in value"
13344 .row &%exim_path%& "override compiled-in value"
13345 .row &%exim_user%& "override compiled-in value"
13346 .row &%primary_hostname%& "default from &[uname()]&"
13347 .row &%split_spool_directory%& "use multiple directories"
13348 .row &%spool_directory%& "override compiled-in value"
13353 .section "Privilege controls" "SECID98"
13355 .row &%admin_groups%& "groups that are Exim admin users"
13356 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13357 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13358 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13359 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13360 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13361 .row &%never_users%& "do not run deliveries as these"
13362 .row &%prod_requires_admin%& "forced delivery requires admin user"
13363 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13364 .row &%trusted_groups%& "groups that are trusted"
13365 .row &%trusted_users%& "users that are trusted"
13370 .section "Logging" "SECID99"
13372 .row &%event_action%& "custom logging"
13373 .row &%hosts_connection_nolog%& "exemption from connect logging"
13374 .row &%log_file_path%& "override compiled-in value"
13375 .row &%log_selector%& "set/unset optional logging"
13376 .row &%log_timezone%& "add timezone to log lines"
13377 .row &%message_logs%& "create per-message logs"
13378 .row &%preserve_message_logs%& "after message completion"
13379 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13380 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
13381 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13382 .row &%syslog_facility%& "set syslog &""facility""& field"
13383 .row &%syslog_processname%& "set syslog &""ident""& field"
13384 .row &%syslog_timestamp%& "timestamp syslog lines"
13385 .row &%write_rejectlog%& "control use of message log"
13390 .section "Frozen messages" "SECID100"
13392 .row &%auto_thaw%& "sets time for retrying frozen messages"
13393 .row &%freeze_tell%& "send message when freezing"
13394 .row &%move_frozen_messages%& "to another directory"
13395 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13400 .section "Data lookups" "SECID101"
13402 .row &%ibase_servers%& "InterBase servers"
13403 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13404 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13405 .row &%ldap_cert_file%& "client cert file for LDAP"
13406 .row &%ldap_cert_key%& "client key file for LDAP"
13407 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13408 .row &%ldap_default_servers%& "used if no server in query"
13409 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13410 .row &%ldap_start_tls%& "require TLS within LDAP"
13411 .row &%ldap_version%& "set protocol version"
13412 .row &%lookup_open_max%& "lookup files held open"
13413 .row &%mysql_servers%& "default MySQL servers"
13414 .row &%oracle_servers%& "Oracle servers"
13415 .row &%pgsql_servers%& "default PostgreSQL servers"
13416 .row &%sqlite_lock_timeout%& "as it says"
13421 .section "Message ids" "SECID102"
13423 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13424 .row &%message_id_header_text%& "ditto"
13429 .section "Embedded Perl Startup" "SECID103"
13431 .row &%perl_at_start%& "always start the interpreter"
13432 .row &%perl_startup%& "code to obey when starting Perl"
13437 .section "Daemon" "SECID104"
13439 .row &%daemon_smtp_ports%& "default ports"
13440 .row &%daemon_startup_retries%& "number of times to retry"
13441 .row &%daemon_startup_sleep%& "time to sleep between tries"
13442 .row &%extra_local_interfaces%& "not necessarily listened on"
13443 .row &%local_interfaces%& "on which to listen, with optional ports"
13444 .row &%pid_file_path%& "override compiled-in value"
13445 .row &%queue_run_max%& "maximum simultaneous queue runners"
13450 .section "Resource control" "SECID105"
13452 .row &%check_log_inodes%& "before accepting a message"
13453 .row &%check_log_space%& "before accepting a message"
13454 .row &%check_spool_inodes%& "before accepting a message"
13455 .row &%check_spool_space%& "before accepting a message"
13456 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13457 .row &%queue_only_load%& "queue incoming if load high"
13458 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13459 .row &%queue_run_max%& "maximum simultaneous queue runners"
13460 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13461 .row &%smtp_accept_max%& "simultaneous incoming connections"
13462 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13463 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13464 .row &%smtp_accept_max_per_connection%& "messages per connection"
13465 .row &%smtp_accept_max_per_host%& "connections from one host"
13466 .row &%smtp_accept_queue%& "queue mail if more connections"
13467 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13469 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13470 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13471 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13472 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13473 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13478 .section "Policy controls" "SECID106"
13480 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13481 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13482 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13483 .row &%acl_smtp_auth%& "ACL for AUTH"
13484 .row &%acl_smtp_connect%& "ACL for connection"
13485 .row &%acl_smtp_data%& "ACL for DATA"
13486 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13487 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13488 .row &%acl_smtp_etrn%& "ACL for ETRN"
13489 .row &%acl_smtp_expn%& "ACL for EXPN"
13490 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13491 .row &%acl_smtp_mail%& "ACL for MAIL"
13492 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13493 .row &%acl_smtp_mime%& "ACL for MIME parts"
13494 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
13495 .row &%acl_smtp_predata%& "ACL for start of data"
13496 .row &%acl_smtp_quit%& "ACL for QUIT"
13497 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13498 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13499 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13500 .row &%av_scanner%& "specify virus scanner"
13501 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13503 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13504 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13505 .row &%header_maxsize%& "total size of message header"
13506 .row &%header_line_maxsize%& "individual header line limit"
13507 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13508 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13509 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13510 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13511 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13512 .row &%host_lookup%& "host name looked up for these hosts"
13513 .row &%host_lookup_order%& "order of DNS and local name lookups"
13514 .row &%hosts_proxy%& "use proxy protocol for these hosts"
13515 .row &%host_reject_connection%& "reject connection from these hosts"
13516 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13517 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13518 .row &%message_size_limit%& "for all messages"
13519 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13520 .row &%spamd_address%& "set interface to SpamAssassin"
13521 .row &%strict_acl_vars%& "object to unset ACL variables"
13526 .section "Callout cache" "SECID107"
13528 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13530 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13532 .row &%callout_negative_expire%& "timeout for negative address cache item"
13533 .row &%callout_positive_expire%& "timeout for positive address cache item"
13534 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13539 .section "TLS" "SECID108"
13541 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13542 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13543 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13544 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13545 .row &%tls_certificate%& "location of server certificate"
13546 .row &%tls_crl%& "certificate revocation list"
13547 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13548 .row &%tls_dhparam%& "DH parameters for server"
13549 .row &%tls_eccurve%& "EC curve selection for server"
13550 .row &%tls_ocsp_file%& "location of server certificate status proof"
13551 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13552 .row &%tls_privatekey%& "location of server private key"
13553 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13554 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13555 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13556 .row &%tls_verify_certificates%& "expected client certificates"
13557 .row &%tls_verify_hosts%& "insist on client certificate verify"
13562 .section "Local user handling" "SECID109"
13564 .row &%finduser_retries%& "useful in NIS environments"
13565 .row &%gecos_name%& "used when creating &'Sender:'&"
13566 .row &%gecos_pattern%& "ditto"
13567 .row &%max_username_length%& "for systems that truncate"
13568 .row &%unknown_login%& "used when no login name found"
13569 .row &%unknown_username%& "ditto"
13570 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13571 .row &%uucp_from_sender%& "ditto"
13576 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13578 .row &%header_maxsize%& "total size of message header"
13579 .row &%header_line_maxsize%& "individual header line limit"
13580 .row &%message_size_limit%& "applies to all messages"
13581 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13582 .row &%received_header_text%& "expanded to make &'Received:'&"
13583 .row &%received_headers_max%& "for mail loop detection"
13584 .row &%recipients_max%& "limit per message"
13585 .row &%recipients_max_reject%& "permanently reject excess recipients"
13591 .section "Non-SMTP incoming messages" "SECID111"
13593 .row &%receive_timeout%& "for non-SMTP messages"
13600 .section "Incoming SMTP messages" "SECID112"
13601 See also the &'Policy controls'& section above.
13604 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
13605 .row &%host_lookup%& "host name looked up for these hosts"
13606 .row &%host_lookup_order%& "order of DNS and local name lookups"
13607 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13608 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13609 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13610 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13611 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13612 .row &%smtp_accept_max%& "simultaneous incoming connections"
13613 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13614 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13615 .row &%smtp_accept_max_per_connection%& "messages per connection"
13616 .row &%smtp_accept_max_per_host%& "connections from one host"
13617 .row &%smtp_accept_queue%& "queue mail if more connections"
13618 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13620 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13621 .row &%smtp_active_hostname%& "host name to use in messages"
13622 .row &%smtp_banner%& "text for welcome banner"
13623 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13624 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13625 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13626 .row &%smtp_etrn_command%& "what to run for ETRN"
13627 .row &%smtp_etrn_serialize%& "only one at once"
13628 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13629 .row &%smtp_max_unknown_commands%& "before dropping connection"
13630 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13631 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13632 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13633 .row &%smtp_receive_timeout%& "per command or data line"
13634 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13635 .row &%smtp_return_error_details%& "give detail on rejections"
13640 .section "SMTP extensions" "SECID113"
13642 .row &%accept_8bitmime%& "advertise 8BITMIME"
13643 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13644 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
13645 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13646 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13647 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13648 .row &%prdr_enable%& "advertise PRDR to all hosts"
13649 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
13650 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13655 .section "Processing messages" "SECID114"
13657 .row &%allow_domain_literals%& "recognize domain literal syntax"
13658 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13659 .row &%allow_utf8_domains%& "in addresses"
13660 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13662 .row &%delivery_date_remove%& "from incoming messages"
13663 .row &%envelope_to_remove%& "from incoming messages"
13664 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13665 .row &%headers_charset%& "default for translations"
13666 .row &%qualify_domain%& "default for senders"
13667 .row &%qualify_recipient%& "default for recipients"
13668 .row &%return_path_remove%& "from incoming messages"
13669 .row &%strip_excess_angle_brackets%& "in addresses"
13670 .row &%strip_trailing_dot%& "at end of addresses"
13671 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13676 .section "System filter" "SECID115"
13678 .row &%system_filter%& "locate system filter"
13679 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13681 .row &%system_filter_file_transport%& "transport for delivery to a file"
13682 .row &%system_filter_group%& "group for filter running"
13683 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13684 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13685 .row &%system_filter_user%& "user for filter running"
13690 .section "Routing and delivery" "SECID116"
13692 .row &%disable_ipv6%& "do no IPv6 processing"
13693 .row &%dns_again_means_nonexist%& "for broken domains"
13694 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13695 .row &%dns_dnssec_ok%& "parameter for resolver"
13696 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13697 .row &%dns_retrans%& "parameter for resolver"
13698 .row &%dns_retry%& "parameter for resolver"
13699 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
13700 .row &%dns_use_edns0%& "parameter for resolver"
13701 .row &%hold_domains%& "hold delivery for these domains"
13702 .row &%local_interfaces%& "for routing checks"
13703 .row &%queue_domains%& "no immediate delivery for these"
13704 .row &%queue_only%& "no immediate delivery at all"
13705 .row &%queue_only_file%& "no immediate delivery if file exists"
13706 .row &%queue_only_load%& "no immediate delivery if load is high"
13707 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13708 .row &%queue_only_override%& "allow command line to override"
13709 .row &%queue_run_in_order%& "order of arrival"
13710 .row &%queue_run_max%& "of simultaneous queue runners"
13711 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13712 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13713 .row &%remote_sort_domains%& "order of remote deliveries"
13714 .row &%retry_data_expire%& "timeout for retry data"
13715 .row &%retry_interval_max%& "safety net for retry rules"
13720 .section "Bounce and warning messages" "SECID117"
13722 .row &%bounce_message_file%& "content of bounce"
13723 .row &%bounce_message_text%& "content of bounce"
13724 .row &%bounce_return_body%& "include body if returning message"
13725 .row &%bounce_return_message%& "include original message in bounce"
13726 .row &%bounce_return_size_limit%& "limit on returned message"
13727 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13728 .row &%dsn_from%& "set &'From:'& contents in bounces"
13729 .row &%errors_copy%& "copy bounce messages"
13730 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13731 .row &%delay_warning%& "time schedule"
13732 .row &%delay_warning_condition%& "condition for warning messages"
13733 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13734 .row &%smtp_return_error_details%& "give detail on rejections"
13735 .row &%warn_message_file%& "content of warning message"
13740 .section "Alphabetical list of main options" "SECTalomo"
13741 Those options that undergo string expansion before use are marked with
13744 .option accept_8bitmime main boolean true
13746 .cindex "8-bit characters"
13747 .cindex "log" "selectors"
13748 .cindex "log" "8BITMIME"
13749 This option causes Exim to send 8BITMIME in its response to an SMTP
13750 EHLO command, and to accept the BODY= parameter on MAIL commands.
13751 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13752 takes no steps to do anything special with messages received by this route.
13754 Historically Exim kept this option off by default, but the maintainers
13755 feel that in today's Internet, this causes more problems than it solves.
13756 It now defaults to true.
13757 A more detailed analysis of the issues is provided by Dan Bernstein:
13759 &url(http://cr.yp.to/smtp/8bitmime.html)
13762 To log received 8BITMIME status use
13764 log_selector = +8bitmime
13767 .option acl_not_smtp main string&!! unset
13768 .cindex "&ACL;" "for non-SMTP messages"
13769 .cindex "non-SMTP messages" "ACLs for"
13770 This option defines the ACL that is run when a non-SMTP message has been
13771 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
13774 .option acl_not_smtp_mime main string&!! unset
13775 This option defines the ACL that is run for individual MIME parts of non-SMTP
13776 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
13779 .option acl_not_smtp_start main string&!! unset
13780 .cindex "&ACL;" "at start of non-SMTP message"
13781 .cindex "non-SMTP messages" "ACLs for"
13782 This option defines the ACL that is run before Exim starts reading a
13783 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
13785 .option acl_smtp_auth main string&!! unset
13786 .cindex "&ACL;" "setting up for SMTP commands"
13787 .cindex "AUTH" "ACL for"
13788 This option defines the ACL that is run when an SMTP AUTH command is
13789 received. See chapter &<<CHAPACL>>& for further details.
13791 .option acl_smtp_connect main string&!! unset
13792 .cindex "&ACL;" "on SMTP connection"
13793 This option defines the ACL that is run when an SMTP connection is received.
13794 See chapter &<<CHAPACL>>& for further details.
13796 .option acl_smtp_data main string&!! unset
13797 .cindex "DATA" "ACL for"
13798 This option defines the ACL that is run after an SMTP DATA command has been
13799 processed and the message itself has been received, but before the final
13800 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13802 .option acl_smtp_data_prdr main string&!! accept
13803 .cindex "PRDR" "ACL for"
13804 .cindex "DATA" "PRDR ACL for"
13805 .cindex "&ACL;" "PRDR-related"
13806 .cindex "&ACL;" "per-user data processing"
13807 This option defines the ACL that,
13808 if the PRDR feature has been negotiated,
13809 is run for each recipient after an SMTP DATA command has been
13810 processed and the message itself has been received, but before the
13811 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13813 .option acl_smtp_dkim main string&!! unset
13814 .cindex DKIM "ACL for"
13815 This option defines the ACL that is run for each DKIM signature
13816 of a received message.
13817 See chapter &<<CHAPdkim>>& for further details.
13819 .option acl_smtp_etrn main string&!! unset
13820 .cindex "ETRN" "ACL for"
13821 This option defines the ACL that is run when an SMTP ETRN command is
13822 received. See chapter &<<CHAPACL>>& for further details.
13824 .option acl_smtp_expn main string&!! unset
13825 .cindex "EXPN" "ACL for"
13826 This option defines the ACL that is run when an SMTP EXPN command is
13827 received. See chapter &<<CHAPACL>>& for further details.
13829 .option acl_smtp_helo main string&!! unset
13830 .cindex "EHLO" "ACL for"
13831 .cindex "HELO" "ACL for"
13832 This option defines the ACL that is run when an SMTP EHLO or HELO
13833 command is received. See chapter &<<CHAPACL>>& for further details.
13836 .option acl_smtp_mail main string&!! unset
13837 .cindex "MAIL" "ACL for"
13838 This option defines the ACL that is run when an SMTP MAIL command is
13839 received. See chapter &<<CHAPACL>>& for further details.
13841 .option acl_smtp_mailauth main string&!! unset
13842 .cindex "AUTH" "on MAIL command"
13843 This option defines the ACL that is run when there is an AUTH parameter on
13844 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
13845 &<<CHAPSMTPAUTH>>& for details of authentication.
13847 .option acl_smtp_mime main string&!! unset
13848 .cindex "MIME content scanning" "ACL for"
13849 This option is available when Exim is built with the content-scanning
13850 extension. It defines the ACL that is run for each MIME part in a message. See
13851 section &<<SECTscanmimepart>>& for details.
13853 .option acl_smtp_notquit main string&!! unset
13854 .cindex "not-QUIT, ACL for"
13855 This option defines the ACL that is run when an SMTP session
13856 ends without a QUIT command being received.
13857 See chapter &<<CHAPACL>>& for further details.
13859 .option acl_smtp_predata main string&!! unset
13860 This option defines the ACL that is run when an SMTP DATA command is
13861 received, before the message itself is received. See chapter &<<CHAPACL>>& for
13864 .option acl_smtp_quit main string&!! unset
13865 .cindex "QUIT, ACL for"
13866 This option defines the ACL that is run when an SMTP QUIT command is
13867 received. See chapter &<<CHAPACL>>& for further details.
13869 .option acl_smtp_rcpt main string&!! unset
13870 .cindex "RCPT" "ACL for"
13871 This option defines the ACL that is run when an SMTP RCPT command is
13872 received. See chapter &<<CHAPACL>>& for further details.
13874 .option acl_smtp_starttls main string&!! unset
13875 .cindex "STARTTLS, ACL for"
13876 This option defines the ACL that is run when an SMTP STARTTLS command is
13877 received. See chapter &<<CHAPACL>>& for further details.
13879 .option acl_smtp_vrfy main string&!! unset
13880 .cindex "VRFY" "ACL for"
13881 This option defines the ACL that is run when an SMTP VRFY command is
13882 received. See chapter &<<CHAPACL>>& for further details.
13884 .option admin_groups main "string list&!!" unset
13885 .cindex "admin user"
13886 This option is expanded just once, at the start of Exim's processing. If the
13887 current group or any of the supplementary groups of an Exim caller is in this
13888 colon-separated list, the caller has admin privileges. If all your system
13889 programmers are in a specific group, for example, you can give them all Exim
13890 admin privileges by putting that group in &%admin_groups%&. However, this does
13891 not permit them to read Exim's spool files (whose group owner is the Exim gid).
13892 To permit this, you have to add individuals to the Exim group.
13894 .option allow_domain_literals main boolean false
13895 .cindex "domain literal"
13896 If this option is set, the RFC 2822 domain literal format is permitted in
13897 email addresses. The option is not set by default, because the domain literal
13898 format is not normally required these days, and few people know about it. It
13899 has, however, been exploited by mail abusers.
13901 Unfortunately, it seems that some DNS black list maintainers are using this
13902 format to report black listing to postmasters. If you want to accept messages
13903 addressed to your hosts by IP address, you need to set
13904 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
13905 domains (defined in the named domain list &%local_domains%& in the default
13906 configuration). This &"magic string"& matches the domain literal form of all
13907 the local host's IP addresses.
13910 .option allow_mx_to_ip main boolean false
13911 .cindex "MX record" "pointing to IP address"
13912 It appears that more and more DNS zone administrators are breaking the rules
13913 and putting domain names that look like IP addresses on the right hand side of
13914 MX records. Exim follows the rules and rejects this, giving an error message
13915 that explains the misconfiguration. However, some other MTAs support this
13916 practice, so to avoid &"Why can't Exim do this?"& complaints,
13917 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
13918 recommended, except when you have no other choice.
13920 .option allow_utf8_domains main boolean false
13921 .cindex "domain" "UTF-8 characters in"
13922 .cindex "UTF-8" "in domain name"
13923 Lots of discussion is going on about internationalized domain names. One
13924 camp is strongly in favour of just using UTF-8 characters, and it seems
13925 that at least two other MTAs permit this. This option allows Exim users to
13926 experiment if they wish.
13928 If it is set true, Exim's domain parsing function allows valid
13929 UTF-8 multicharacters to appear in domain name components, in addition to
13930 letters, digits, and hyphens. However, just setting this option is not
13931 enough; if you want to look up these domain names in the DNS, you must also
13932 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
13933 suitable setting is:
13935 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
13936 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
13938 Alternatively, you can just disable this feature by setting
13940 dns_check_names_pattern =
13942 That is, set the option to an empty string so that no check is done.
13945 .option auth_advertise_hosts main "host list&!!" *
13946 .cindex "authentication" "advertising"
13947 .cindex "AUTH" "advertising"
13948 If any server authentication mechanisms are configured, Exim advertises them in
13949 response to an EHLO command only if the calling host matches this list.
13950 Otherwise, Exim does not advertise AUTH.
13951 Exim does not accept AUTH commands from clients to which it has not
13952 advertised the availability of AUTH. The advertising of individual
13953 authentication mechanisms can be controlled by the use of the
13954 &%server_advertise_condition%& generic authenticator option on the individual
13955 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
13957 Certain mail clients (for example, Netscape) require the user to provide a name
13958 and password for authentication if AUTH is advertised, even though it may
13959 not be needed (the host may accept messages from hosts on its local LAN without
13960 authentication, for example). The &%auth_advertise_hosts%& option can be used
13961 to make these clients more friendly by excluding them from the set of hosts to
13962 which Exim advertises AUTH.
13964 .cindex "AUTH" "advertising when encrypted"
13965 If you want to advertise the availability of AUTH only when the connection
13966 is encrypted using TLS, you can make use of the fact that the value of this
13967 option is expanded, with a setting like this:
13969 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
13971 .vindex "&$tls_in_cipher$&"
13972 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
13973 the expansion is empty, thus matching no hosts. Otherwise, the result of the
13974 expansion is *, which matches all hosts.
13977 .option auto_thaw main time 0s
13978 .cindex "thawing messages"
13979 .cindex "unfreezing messages"
13980 If this option is set to a time greater than zero, a queue runner will try a
13981 new delivery attempt on any frozen message, other than a bounce message, if
13982 this much time has passed since it was frozen. This may result in the message
13983 being re-frozen if nothing has changed since the last attempt. It is a way of
13984 saying &"keep on trying, even though there are big problems"&.
13986 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
13987 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
13988 thought to be very useful any more, and its use should probably be avoided.
13991 .option av_scanner main string "see below"
13992 This option is available if Exim is built with the content-scanning extension.
13993 It specifies which anti-virus scanner to use. The default value is:
13995 sophie:/var/run/sophie
13997 If the value of &%av_scanner%& starts with a dollar character, it is expanded
13998 before use. See section &<<SECTscanvirus>>& for further details.
14001 .option bi_command main string unset
14003 This option supplies the name of a command that is run when Exim is called with
14004 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
14005 just the command name, it is not a complete command line. If an argument is
14006 required, it must come from the &%-oA%& command line option.
14009 .option bounce_message_file main string unset
14010 .cindex "bounce message" "customizing"
14011 .cindex "customizing" "bounce message"
14012 This option defines a template file containing paragraphs of text to be used
14013 for constructing bounce messages. Details of the file's contents are given in
14014 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
14017 .option bounce_message_text main string unset
14018 When this option is set, its contents are included in the default bounce
14019 message immediately after &"This message was created automatically by mail
14020 delivery software."& It is not used if &%bounce_message_file%& is set.
14022 .option bounce_return_body main boolean true
14023 .cindex "bounce message" "including body"
14024 This option controls whether the body of an incoming message is included in a
14025 bounce message when &%bounce_return_message%& is true. The default setting
14026 causes the entire message, both header and body, to be returned (subject to the
14027 value of &%bounce_return_size_limit%&). If this option is false, only the
14028 message header is included. In the case of a non-SMTP message containing an
14029 error that is detected during reception, only those header lines preceding the
14030 point at which the error was detected are returned.
14031 .cindex "bounce message" "including original"
14033 .option bounce_return_message main boolean true
14034 If this option is set false, none of the original message is included in
14035 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
14036 &%bounce_return_body%&.
14039 .option bounce_return_size_limit main integer 100K
14040 .cindex "size" "of bounce, limit"
14041 .cindex "bounce message" "size limit"
14042 .cindex "limit" "bounce message size"
14043 This option sets a limit in bytes on the size of messages that are returned to
14044 senders as part of bounce messages when &%bounce_return_message%& is true. The
14045 limit should be less than the value of the global &%message_size_limit%& and of
14046 any &%message_size_limit%& settings on transports, to allow for the bounce text
14047 that Exim generates. If this option is set to zero there is no limit.
14049 When the body of any message that is to be included in a bounce message is
14050 greater than the limit, it is truncated, and a comment pointing this out is
14051 added at the top. The actual cutoff may be greater than the value given, owing
14052 to the use of buffering for transferring the message in chunks (typically 8K in
14053 size). The idea is to save bandwidth on those undeliverable 15-megabyte
14056 .option bounce_sender_authentication main string unset
14057 .cindex "bounce message" "sender authentication"
14058 .cindex "authentication" "bounce message"
14059 .cindex "AUTH" "on bounce message"
14060 This option provides an authenticated sender address that is sent with any
14061 bounce messages generated by Exim that are sent over an authenticated SMTP
14062 connection. A typical setting might be:
14064 bounce_sender_authentication = mailer-daemon@my.domain.example
14066 which would cause bounce messages to be sent using the SMTP command:
14068 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14070 The value of &%bounce_sender_authentication%& must always be a complete email
14073 .option callout_domain_negative_expire main time 3h
14074 .cindex "caching" "callout timeouts"
14075 .cindex "callout" "caching timeouts"
14076 This option specifies the expiry time for negative callout cache data for a
14077 domain. See section &<<SECTcallver>>& for details of callout verification, and
14078 section &<<SECTcallvercache>>& for details of the caching.
14081 .option callout_domain_positive_expire main time 7d
14082 This option specifies the expiry time for positive callout cache data for a
14083 domain. See section &<<SECTcallver>>& for details of callout verification, and
14084 section &<<SECTcallvercache>>& for details of the caching.
14087 .option callout_negative_expire main time 2h
14088 This option specifies the expiry time for negative callout cache data for an
14089 address. See section &<<SECTcallver>>& for details of callout verification, and
14090 section &<<SECTcallvercache>>& for details of the caching.
14093 .option callout_positive_expire main time 24h
14094 This option specifies the expiry time for positive callout cache data for an
14095 address. See section &<<SECTcallver>>& for details of callout verification, and
14096 section &<<SECTcallvercache>>& for details of the caching.
14099 .option callout_random_local_part main string&!! "see below"
14100 This option defines the &"random"& local part that can be used as part of
14101 callout verification. The default value is
14103 $primary_hostname-$tod_epoch-testing
14105 See section &<<CALLaddparcall>>& for details of how this value is used.
14108 .option check_log_inodes main integer 0
14109 See &%check_spool_space%& below.
14112 .option check_log_space main integer 0
14113 See &%check_spool_space%& below.
14115 .oindex "&%check_rfc2047_length%&"
14116 .cindex "RFC 2047" "disabling length check"
14117 .option check_rfc2047_length main boolean true
14118 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14119 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14120 word; strings to be encoded that exceed this length are supposed to use
14121 multiple encoded words. By default, Exim does not recognize encoded words that
14122 exceed the maximum length. However, it seems that some software, in violation
14123 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14124 set false, Exim recognizes encoded words of any length.
14127 .option check_spool_inodes main integer 0
14128 See &%check_spool_space%& below.
14131 .option check_spool_space main integer 0
14132 .cindex "checking disk space"
14133 .cindex "disk space, checking"
14134 .cindex "spool directory" "checking space"
14135 The four &%check_...%& options allow for checking of disk resources before a
14136 message is accepted.
14138 .vindex "&$log_inodes$&"
14139 .vindex "&$log_space$&"
14140 .vindex "&$spool_inodes$&"
14141 .vindex "&$spool_space$&"
14142 When any of these options are set, they apply to all incoming messages. If you
14143 want to apply different checks to different kinds of message, you can do so by
14144 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14145 &$spool_space$& in an ACL with appropriate additional conditions.
14148 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14149 either value is greater than zero, for example:
14151 check_spool_space = 10M
14152 check_spool_inodes = 100
14154 The spool partition is the one that contains the directory defined by
14155 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14158 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14159 files are written if either is greater than zero. These should be set only if
14160 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14162 If there is less space or fewer inodes than requested, Exim refuses to accept
14163 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14164 error response to the MAIL command. If ESMTP is in use and there was a
14165 SIZE parameter on the MAIL command, its value is added to the
14166 &%check_spool_space%& value, and the check is performed even if
14167 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14169 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14170 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
14172 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14173 failure a message is written to stderr and Exim exits with a non-zero code, as
14174 it obviously cannot send an error message of any kind.
14176 .option daemon_smtp_ports main string &`smtp`&
14177 .cindex "port" "for daemon"
14178 .cindex "TCP/IP" "setting listening ports"
14179 This option specifies one or more default SMTP ports on which the Exim daemon
14180 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14181 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14183 .option daemon_startup_retries main integer 9
14184 .cindex "daemon startup, retrying"
14185 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14186 the daemon at startup when it cannot immediately bind a listening socket
14187 (typically because the socket is already in use): &%daemon_startup_retries%&
14188 defines the number of retries after the first failure, and
14189 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14191 .option daemon_startup_sleep main time 30s
14192 See &%daemon_startup_retries%&.
14194 .option delay_warning main "time list" 24h
14195 .cindex "warning of delay"
14196 .cindex "delay warning, specifying"
14197 When a message is delayed, Exim sends a warning message to the sender at
14198 intervals specified by this option. The data is a colon-separated list of times
14199 after which to send warning messages. If the value of the option is an empty
14200 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14201 message has been on the queue for longer than the last time, the last interval
14202 between the times is used to compute subsequent warning times. For example,
14205 delay_warning = 4h:8h:24h
14207 the first message is sent after 4 hours, the second after 8 hours, and
14208 the third one after 24 hours. After that, messages are sent every 16 hours,
14209 because that is the interval between the last two times on the list. If you set
14210 just one time, it specifies the repeat interval. For example, with:
14214 messages are repeated every six hours. To stop warnings after a given time, set
14215 a very large time at the end of the list. For example:
14217 delay_warning = 2h:12h:99d
14219 Note that the option is only evaluated at the time a delivery attempt fails,
14220 which depends on retry and queue-runner configuration.
14221 Typically retries will be configured more frequently than warning messages.
14223 .option delay_warning_condition main string&!! "see below"
14224 .vindex "&$domain$&"
14225 The string is expanded at the time a warning message might be sent. If all the
14226 deferred addresses have the same domain, it is set in &$domain$& during the
14227 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14228 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14229 &"false"& (the comparison being done caselessly) then the warning message is
14230 not sent. The default is:
14232 delay_warning_condition = ${if or {\
14233 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14234 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14235 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14238 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14239 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14240 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14241 &"auto-replied"& in an &'Auto-Submitted:'& header.
14243 .option deliver_drop_privilege main boolean false
14244 .cindex "unprivileged delivery"
14245 .cindex "delivery" "unprivileged"
14246 If this option is set true, Exim drops its root privilege at the start of a
14247 delivery process, and runs as the Exim user throughout. This severely restricts
14248 the kinds of local delivery that are possible, but is viable in certain types
14249 of configuration. There is a discussion about the use of root privilege in
14250 chapter &<<CHAPsecurity>>&.
14252 .option deliver_queue_load_max main fixed-point unset
14253 .cindex "load average"
14254 .cindex "queue runner" "abandoning"
14255 When this option is set, a queue run is abandoned if the system load average
14256 becomes greater than the value of the option. The option has no effect on
14257 ancient operating systems on which Exim cannot determine the load average.
14258 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14261 .option delivery_date_remove main boolean true
14262 .cindex "&'Delivery-date:'& header line"
14263 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14264 message when it is delivered, in exactly the same way as &'Return-path:'& is
14265 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14266 should not be present in incoming messages, and this option causes them to be
14267 removed at the time the message is received, to avoid any problems that might
14268 occur when a delivered message is subsequently sent on to some other recipient.
14270 .option disable_fsync main boolean false
14271 .cindex "&[fsync()]&, disabling"
14272 This option is available only if Exim was built with the compile-time option
14273 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14274 a runtime configuration generates an &"unknown option"& error. You should not
14275 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14276 really, really, really understand what you are doing. &'No pre-compiled
14277 distributions of Exim should ever make this option available.'&
14279 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14280 updated files' data to be written to disc before continuing. Unexpected events
14281 such as crashes and power outages may cause data to be lost or scrambled.
14282 Here be Dragons. &*Beware.*&
14285 .option disable_ipv6 main boolean false
14286 .cindex "IPv6" "disabling"
14287 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14288 activities take place. AAAA records are never looked up, and any IPv6 addresses
14289 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14290 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14291 to handle IPv6 literal addresses.
14294 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14295 .cindex DKIM "controlling calls to the ACL"
14296 This option gives a list of DKIM domains for which the DKIM ACL is run.
14297 It is expanded after the message is received; by default it runs
14298 the ACL once for each signature in the message.
14299 See chapter &<<CHAPdkim>>&.
14302 .option dns_again_means_nonexist main "domain list&!!" unset
14303 .cindex "DNS" "&""try again""& response; overriding"
14304 DNS lookups give a &"try again"& response for the DNS errors
14305 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14306 keep trying to deliver a message, or to give repeated temporary errors to
14307 incoming mail. Sometimes the effect is caused by a badly set up name server and
14308 may persist for a long time. If a domain which exhibits this problem matches
14309 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14310 This option should be used with care. You can make it apply to reverse lookups
14311 by a setting such as this:
14313 dns_again_means_nonexist = *.in-addr.arpa
14315 This option applies to all DNS lookups that Exim does. It also applies when the
14316 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14317 since these are most likely to be caused by DNS lookup problems. The
14318 &(dnslookup)& router has some options of its own for controlling what happens
14319 when lookups for MX or SRV records give temporary errors. These more specific
14320 options are applied after this global option.
14322 .option dns_check_names_pattern main string "see below"
14323 .cindex "DNS" "pre-check of name syntax"
14324 When this option is set to a non-empty string, it causes Exim to check domain
14325 names for characters that are not allowed in host names before handing them to
14326 the DNS resolver, because some resolvers give temporary errors for names that
14327 contain unusual characters. If a domain name contains any unwanted characters,
14328 a &"not found"& result is forced, and the resolver is not called. The check is
14329 done by matching the domain name against a regular expression, which is the
14330 value of this option. The default pattern is
14332 dns_check_names_pattern = \
14333 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
14335 which permits only letters, digits, slashes, and hyphens in components, but
14336 they must start and end with a letter or digit. Slashes are not, in fact,
14337 permitted in host names, but they are found in certain NS records (which can be
14338 accessed in Exim by using a &%dnsdb%& lookup). If you set
14339 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
14342 .option dns_csa_search_limit main integer 5
14343 This option controls the depth of parental searching for CSA SRV records in the
14344 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
14346 .option dns_csa_use_reverse main boolean true
14347 This option controls whether or not an IP address, given as a CSA domain, is
14348 reversed and looked up in the reverse DNS, as described in more detail in
14349 section &<<SECTverifyCSA>>&.
14352 .option dns_dnssec_ok main integer -1
14353 .cindex "DNS" "resolver options"
14354 .cindex "DNS" "DNSSEC"
14355 If this option is set to a non-negative number then Exim will initialise the
14356 DNS resolver library to either use or not use DNSSEC, overriding the system
14357 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14359 If the resolver library does not support DNSSEC then this option has no effect.
14362 .option dns_ipv4_lookup main "domain list&!!" unset
14363 .cindex "IPv6" "DNS lookup for AAAA records"
14364 .cindex "DNS" "IPv6 lookup for AAAA records"
14365 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14366 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14367 (A records) when trying to find IP addresses for hosts, unless the host's
14368 domain matches this list.
14370 This is a fudge to help with name servers that give big delays or otherwise do
14371 not work for the AAAA record type. In due course, when the world's name
14372 servers have all been upgraded, there should be no need for this option.
14375 .option dns_retrans main time 0s
14376 .cindex "DNS" "resolver options"
14377 .cindex timeout "dns lookup"
14378 .cindex "DNS" timeout
14379 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14380 retransmission and retry parameters for DNS lookups. Values of zero (the
14381 defaults) leave the system default settings unchanged. The first value is the
14382 time between retries, and the second is the number of retries. It isn't
14383 totally clear exactly how these settings affect the total time a DNS lookup may
14384 take. I haven't found any documentation about timeouts on DNS lookups; these
14385 parameter values are available in the external resolver interface structure,
14386 but nowhere does it seem to describe how they are used or what you might want
14388 See also the &%slow_lookup_log%& option.
14391 .option dns_retry main integer 0
14392 See &%dns_retrans%& above.
14395 .option dns_trust_aa main "domain list&!!" unset
14396 .cindex "DNS" "resolver options"
14397 .cindex "DNS" "DNSSEC"
14398 If this option is set then lookup results marked with the AA bit
14399 (Authoritative Answer) are trusted the same way as if they were
14400 DNSSEC-verified. The authority section's name of the answer must
14401 match with this expanded domain list.
14403 Use this option only if you talk directly to a resolver that is
14404 authoritative for some zones and does not set the AD (Authentic Data)
14405 bit in the answer. Some DNS servers may have an configuration option to
14406 mark the answers from their own zones as verified (they set the AD bit).
14407 Others do not have this option. It is considered as poor practice using
14408 a resolver that is an authoritative server for some zones.
14410 Use this option only if you really have to (e.g. if you want
14411 to use DANE for remote delivery to a server that is listed in the DNS
14412 zones that your resolver is authoritative for).
14414 If the DNS answer packet has the AA bit set and contains resource record
14415 in the answer section, the name of the first NS record appearing in the
14416 authority section is compared against the list. If the answer packet is
14417 authoritative but the answer section is empty, the name of the first SOA
14418 record in the authoritative section is used instead.
14420 .cindex "DNS" "resolver options"
14421 .option dns_use_edns0 main integer -1
14422 .cindex "DNS" "resolver options"
14423 .cindex "DNS" "EDNS0"
14424 If this option is set to a non-negative number then Exim will initialise the
14425 DNS resolver library to either use or not use EDNS0 extensions, overriding
14426 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14429 If the resolver library does not support EDNS0 then this option has no effect.
14432 .option drop_cr main boolean false
14433 This is an obsolete option that is now a no-op. It used to affect the way Exim
14434 handled CR and LF characters in incoming messages. What happens now is
14435 described in section &<<SECTlineendings>>&.
14437 .option dsn_advertise_hosts main "host list&!!" unset
14438 .cindex "bounce messages" "success"
14439 .cindex "DSN" "success"
14440 .cindex "Delivery Status Notification" "success"
14441 DSN extensions (RFC3461) will be advertised in the EHLO message to,
14442 and accepted from, these hosts.
14443 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
14444 and RET and ORCPT options on MAIL FROM commands.
14445 A NOTIFY=SUCCESS option requests success-DSN messages.
14446 A NOTIFY= option with no argument requests that no delay or failure DSNs
14449 .option dsn_from main "string&!!" "see below"
14450 .cindex "&'From:'& header line" "in bounces"
14451 .cindex "bounce messages" "&'From:'& line, specifying"
14452 This option can be used to vary the contents of &'From:'& header lines in
14453 bounces and other automatically generated messages (&"Delivery Status
14454 Notifications"& &-- hence the name of the option). The default setting is:
14456 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14458 The value is expanded every time it is needed. If the expansion fails, a
14459 panic is logged, and the default value is used.
14461 .option envelope_to_remove main boolean true
14462 .cindex "&'Envelope-to:'& header line"
14463 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14464 message when it is delivered, in exactly the same way as &'Return-path:'& is
14465 handled. &'Envelope-to:'& records the original recipient address from the
14466 message's envelope that caused the delivery to happen. Such headers should not
14467 be present in incoming messages, and this option causes them to be removed at
14468 the time the message is received, to avoid any problems that might occur when a
14469 delivered message is subsequently sent on to some other recipient.
14472 .option errors_copy main "string list&!!" unset
14473 .cindex "bounce message" "copy to other address"
14474 .cindex "copy of bounce message"
14475 Setting this option causes Exim to send bcc copies of bounce messages that it
14476 generates to other addresses. &*Note*&: This does not apply to bounce messages
14477 coming from elsewhere. The value of the option is a colon-separated list of
14478 items. Each item consists of a pattern, terminated by white space, followed by
14479 a comma-separated list of email addresses. If a pattern contains spaces, it
14480 must be enclosed in double quotes.
14482 Each pattern is processed in the same way as a single item in an address list
14483 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14484 the bounce message, the message is copied to the addresses on the list. The
14485 items are scanned in order, and once a matching one is found, no further items
14486 are examined. For example:
14488 errors_copy = spqr@mydomain postmaster@mydomain.example :\
14489 rqps@mydomain hostmaster@mydomain.example,\
14490 postmaster@mydomain.example
14492 .vindex "&$domain$&"
14493 .vindex "&$local_part$&"
14494 The address list is expanded before use. The expansion variables &$local_part$&
14495 and &$domain$& are set from the original recipient of the error message, and if
14496 there was any wildcard matching in the pattern, the expansion
14497 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
14498 variables &$0$&, &$1$&, etc. are set in the normal way.
14501 .option errors_reply_to main string unset
14502 .cindex "bounce message" "&'Reply-to:'& in"
14503 By default, Exim's bounce and delivery warning messages contain the header line
14505 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
14507 .oindex &%quota_warn_message%&
14508 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
14509 A warning message that is generated by the &%quota_warn_message%& option in an
14510 &(appendfile)& transport may contain its own &'From:'& header line that
14511 overrides the default.
14513 Experience shows that people reply to bounce messages. If the
14514 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
14515 and warning messages. For example:
14517 errors_reply_to = postmaster@my.domain.example
14519 The value of the option is not expanded. It must specify a valid RFC 2822
14520 address. However, if a warning message that is generated by the
14521 &%quota_warn_message%& option in an &(appendfile)& transport contain its
14522 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
14527 .option event_action main string&!! unset
14529 This option declares a string to be expanded for Exim's events mechanism.
14530 For details see &<<CHAPevents>>&.
14534 .option exim_group main string "compile-time configured"
14535 .cindex "gid (group id)" "Exim's own"
14536 .cindex "Exim group"
14537 This option changes the gid under which Exim runs when it gives up root
14538 privilege. The default value is compiled into the binary. The value of this
14539 option is used only when &%exim_user%& is also set. Unless it consists entirely
14540 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14541 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
14545 .option exim_path main string "see below"
14546 .cindex "Exim binary, path name"
14547 This option specifies the path name of the Exim binary, which is used when Exim
14548 needs to re-exec itself. The default is set up to point to the file &'exim'& in
14549 the directory configured at compile time by the BIN_DIRECTORY setting. It
14550 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
14552 &*Warning*&: Do not use a macro to define the value of this option, because
14553 you will break those Exim utilities that scan the configuration file to find
14554 where the binary is. (They then use the &%-bP%& option to extract option
14555 settings such as the value of &%spool_directory%&.)
14558 .option exim_user main string "compile-time configured"
14559 .cindex "uid (user id)" "Exim's own"
14560 .cindex "Exim user"
14561 This option changes the uid under which Exim runs when it gives up root
14562 privilege. The default value is compiled into the binary. Ownership of the run
14563 time configuration file and the use of the &%-C%& and &%-D%& command line
14564 options is checked against the values in the binary, not what is set here.
14566 Unless it consists entirely of digits, the string is looked up using
14567 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
14568 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
14569 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
14572 .option extra_local_interfaces main "string list" unset
14573 This option defines network interfaces that are to be considered local when
14574 routing, but which are not used for listening by the daemon. See section
14575 &<<SECTreclocipadd>>& for details.
14578 . Allow this long option name to split; give it unsplit as a fifth argument
14579 . for the automatic .oindex that is generated by .option.
14581 .option "extract_addresses_remove_arguments" main boolean true &&&
14582 extract_addresses_remove_arguments
14584 .cindex "command line" "addresses with &%-t%&"
14585 .cindex "Sendmail compatibility" "&%-t%& option"
14586 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14587 are present on the command line when the &%-t%& option is used to build an
14588 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14589 line addresses are removed from the recipients list. This is also how Smail
14590 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14591 command line addresses are added to those obtained from the header lines. When
14592 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14593 argument headers. If it is set false, Exim adds rather than removes argument
14597 .option finduser_retries main integer 0
14598 .cindex "NIS, retrying user lookups"
14599 On systems running NIS or other schemes in which user and group information is
14600 distributed from a remote system, there can be times when &[getpwnam()]& and
14601 related functions fail, even when given valid data, because things time out.
14602 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14603 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14604 many extra times to find a user or a group, waiting for one second between
14607 .cindex "&_/etc/passwd_&" "multiple reading of"
14608 You should not set this option greater than zero if your user information is in
14609 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14610 search the file multiple times for non-existent users, and also cause delay.
14614 .option freeze_tell main "string list, comma separated" unset
14615 .cindex "freezing messages" "sending a message when freezing"
14616 On encountering certain errors, or when configured to do so in a system filter,
14617 ACL, or special router, Exim freezes a message. This means that no further
14618 delivery attempts take place until an administrator thaws the message, or the
14619 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14620 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14621 warning message whenever it freezes something, unless the message it is
14622 freezing is a locally-generated bounce message. (Without this exception there
14623 is the possibility of looping.) The warning message is sent to the addresses
14624 supplied as the comma-separated value of this option. If several of the
14625 message's addresses cause freezing, only a single message is sent. If the
14626 freezing was automatic, the reason(s) for freezing can be found in the message
14627 log. If you configure freezing in a filter or ACL, you must arrange for any
14628 logging that you require.
14631 .option gecos_name main string&!! unset
14633 .cindex "&""gecos""& field, parsing"
14634 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14635 password file to hold other information in addition to users' real names. Exim
14636 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14637 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14638 of the field are used unchanged, except that, if an ampersand is encountered,
14639 it is replaced by the user's login name with the first character forced to
14640 upper case, since this is a convention that is observed on many systems.
14642 When these options are set, &%gecos_pattern%& is treated as a regular
14643 expression that is to be applied to the field (again with && replaced by the
14644 login name), and if it matches, &%gecos_name%& is expanded and used as the
14647 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14648 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14649 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14650 name terminates at the first comma, the following can be used:
14652 gecos_pattern = ([^,]*)
14656 .option gecos_pattern main string unset
14657 See &%gecos_name%& above.
14660 .option gnutls_compat_mode main boolean unset
14661 This option controls whether GnuTLS is used in compatibility mode in an Exim
14662 server. This reduces security slightly, but improves interworking with older
14663 implementations of TLS.
14666 option gnutls_allow_auto_pkcs11 main boolean unset
14667 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14668 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14671 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14676 .option headers_charset main string "see below"
14677 This option sets a default character set for translating from encoded MIME
14678 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14679 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14680 ultimate default is ISO-8859-1. For more details see the description of header
14681 insertions in section &<<SECTexpansionitems>>&.
14685 .option header_maxsize main integer "see below"
14686 .cindex "header section" "maximum size of"
14687 .cindex "limit" "size of message header section"
14688 This option controls the overall maximum size of a message's header
14689 section. The default is the value of HEADER_MAXSIZE in
14690 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14691 sections are rejected.
14694 .option header_line_maxsize main integer 0
14695 .cindex "header lines" "maximum size of"
14696 .cindex "limit" "size of one header line"
14697 This option limits the length of any individual header line in a message, after
14698 all the continuations have been joined together. Messages with individual
14699 header lines that are longer than the limit are rejected. The default value of
14700 zero means &"no limit"&.
14705 .option helo_accept_junk_hosts main "host list&!!" unset
14706 .cindex "HELO" "accepting junk data"
14707 .cindex "EHLO" "accepting junk data"
14708 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14709 mail, and gives an error response for invalid data. Unfortunately, there are
14710 some SMTP clients that send syntactic junk. They can be accommodated by setting
14711 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14712 if you want to do semantic checking.
14713 See also &%helo_allow_chars%& for a way of extending the permitted character
14717 .option helo_allow_chars main string unset
14718 .cindex "HELO" "underscores in"
14719 .cindex "EHLO" "underscores in"
14720 .cindex "underscore in EHLO/HELO"
14721 This option can be set to a string of rogue characters that are permitted in
14722 all EHLO and HELO names in addition to the standard letters, digits,
14723 hyphens, and dots. If you really must allow underscores, you can set
14725 helo_allow_chars = _
14727 Note that the value is one string, not a list.
14730 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
14731 .cindex "HELO" "forcing reverse lookup"
14732 .cindex "EHLO" "forcing reverse lookup"
14733 If the domain given by a client in a HELO or EHLO command matches this
14734 list, a reverse lookup is done in order to establish the host's true name. The
14735 default forces a lookup if the client host gives the server's name or any of
14736 its IP addresses (in brackets), something that broken clients have been seen to
14740 .option helo_try_verify_hosts main "host list&!!" unset
14741 .cindex "HELO verifying" "optional"
14742 .cindex "EHLO" "verifying, optional"
14743 By default, Exim just checks the syntax of HELO and EHLO commands (see
14744 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
14745 to do more extensive checking of the data supplied by these commands. The ACL
14746 condition &`verify = helo`& is provided to make this possible.
14747 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
14748 to force the check to occur. From release 4.53 onwards, this is no longer
14749 necessary. If the check has not been done before &`verify = helo`& is
14750 encountered, it is done at that time. Consequently, this option is obsolete.
14751 Its specification is retained here for backwards compatibility.
14753 When an EHLO or HELO command is received, if the calling host matches
14754 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
14755 EHLO command either:
14758 is an IP literal matching the calling address of the host, or
14760 .cindex "DNS" "reverse lookup"
14761 .cindex "reverse DNS lookup"
14762 matches the host name that Exim obtains by doing a reverse lookup of the
14763 calling host address, or
14765 when looked up in DNS yields the calling host address.
14768 However, the EHLO or HELO command is not rejected if any of the checks
14769 fail. Processing continues, but the result of the check is remembered, and can
14770 be detected later in an ACL by the &`verify = helo`& condition.
14772 If DNS was used for successful verification, the variable
14773 .cindex "DNS" "DNSSEC"
14774 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
14776 .option helo_verify_hosts main "host list&!!" unset
14777 .cindex "HELO verifying" "mandatory"
14778 .cindex "EHLO" "verifying, mandatory"
14779 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
14780 backwards compatibility. For hosts that match this option, Exim checks the host
14781 name given in the HELO or EHLO in the same way as for
14782 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
14783 rejected with a 550 error, and entries are written to the main and reject logs.
14784 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
14787 .option hold_domains main "domain list&!!" unset
14788 .cindex "domain" "delaying delivery"
14789 .cindex "delivery" "delaying certain domains"
14790 This option allows mail for particular domains to be held on the queue
14791 manually. The option is overridden if a message delivery is forced with the
14792 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
14793 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
14794 item in &%hold_domains%&, no routing or delivery for that address is done, and
14795 it is deferred every time the message is looked at.
14797 This option is intended as a temporary operational measure for delaying the
14798 delivery of mail while some problem is being sorted out, or some new
14799 configuration tested. If you just want to delay the processing of some
14800 domains until a queue run occurs, you should use &%queue_domains%& or
14801 &%queue_smtp_domains%&, not &%hold_domains%&.
14803 A setting of &%hold_domains%& does not override Exim's code for removing
14804 messages from the queue if they have been there longer than the longest retry
14805 time in any retry rule. If you want to hold messages for longer than the normal
14806 retry times, insert a dummy retry rule with a long retry time.
14809 .option host_lookup main "host list&!!" unset
14810 .cindex "host name" "lookup, forcing"
14811 Exim does not look up the name of a calling host from its IP address unless it
14812 is required to compare against some host list, or the host matches
14813 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
14814 option (which normally contains IP addresses rather than host names). The
14815 default configuration file contains
14819 which causes a lookup to happen for all hosts. If the expense of these lookups
14820 is felt to be too great, the setting can be changed or removed.
14822 After a successful reverse lookup, Exim does a forward lookup on the name it
14823 has obtained, to verify that it yields the IP address that it started with. If
14824 this check fails, Exim behaves as if the name lookup failed.
14826 .vindex "&$host_lookup_failed$&"
14827 .vindex "&$sender_host_name$&"
14828 After any kind of failure, the host name (in &$sender_host_name$&) remains
14829 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
14830 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
14831 &`verify = reverse_host_lookup`& in ACLs.
14834 .option host_lookup_order main "string list" &`bydns:byaddr`&
14835 This option specifies the order of different lookup methods when Exim is trying
14836 to find a host name from an IP address. The default is to do a DNS lookup
14837 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
14838 if that fails. You can change the order of these lookups, or omit one entirely,
14841 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
14842 multiple PTR records in the DNS and the IP address is not listed in
14843 &_/etc/hosts_&. Different operating systems give different results in this
14844 case. That is why the default tries a DNS lookup first.
14848 .option host_reject_connection main "host list&!!" unset
14849 .cindex "host" "rejecting connections from"
14850 If this option is set, incoming SMTP calls from the hosts listed are rejected
14851 as soon as the connection is made.
14852 This option is obsolete, and retained only for backward compatibility, because
14853 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
14854 connections immediately.
14856 The ability to give an immediate rejection (either by this option or using an
14857 ACL) is provided for use in unusual cases. Many hosts will just try again,
14858 sometimes without much delay. Normally, it is better to use an ACL to reject
14859 incoming messages at a later stage, such as after RCPT commands. See
14860 chapter &<<CHAPACL>>&.
14863 .option hosts_connection_nolog main "host list&!!" unset
14864 .cindex "host" "not logging connections from"
14865 This option defines a list of hosts for which connection logging does not
14866 happen, even though the &%smtp_connection%& log selector is set. For example,
14867 you might want not to log SMTP connections from local processes, or from
14868 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
14869 the daemon; you should therefore strive to restrict its value to a short inline
14870 list of IP addresses and networks. To disable logging SMTP connections from
14871 local processes, you must create a host list with an empty item. For example:
14873 hosts_connection_nolog = :
14875 If the &%smtp_connection%& log selector is not set, this option has no effect.
14880 .option hosts_proxy main "host list&!!" unset
14881 .cindex proxy "proxy protocol"
14882 This option enables use of Proxy Protocol proxies for incoming
14883 connections. For details see &<<SECTproxyInbound>>&.
14887 .option hosts_treat_as_local main "domain list&!!" unset
14888 .cindex "local host" "domains treated as"
14889 .cindex "host" "treated as local"
14890 If this option is set, any host names that match the domain list are treated as
14891 if they were the local host when Exim is scanning host lists obtained from MX
14893 or other sources. Note that the value of this option is a domain list, not a
14894 host list, because it is always used to check host names, not IP addresses.
14896 This option also applies when Exim is matching the special items
14897 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
14898 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
14899 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
14900 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
14901 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
14902 interfaces and recognizing the local host.
14905 .option ibase_servers main "string list" unset
14906 .cindex "InterBase" "server list"
14907 This option provides a list of InterBase servers and associated connection data,
14908 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
14909 The option is available only if Exim has been built with InterBase support.
14913 .option ignore_bounce_errors_after main time 10w
14914 .cindex "bounce message" "discarding"
14915 .cindex "discarding bounce message"
14916 This option affects the processing of bounce messages that cannot be delivered,
14917 that is, those that suffer a permanent delivery failure. (Bounce messages that
14918 suffer temporary delivery failures are of course retried in the usual way.)
14920 After a permanent delivery failure, bounce messages are frozen,
14921 because there is no sender to whom they can be returned. When a frozen bounce
14922 message has been on the queue for more than the given time, it is unfrozen at
14923 the next queue run, and a further delivery is attempted. If delivery fails
14924 again, the bounce message is discarded. This makes it possible to keep failed
14925 bounce messages around for a shorter time than the normal maximum retry time
14926 for frozen messages. For example,
14928 ignore_bounce_errors_after = 12h
14930 retries failed bounce message deliveries after 12 hours, discarding any further
14931 failures. If the value of this option is set to a zero time period, bounce
14932 failures are discarded immediately. Setting a very long time (as in the default
14933 value) has the effect of disabling this option. For ways of automatically
14934 dealing with other kinds of frozen message, see &%auto_thaw%& and
14935 &%timeout_frozen_after%&.
14938 .option ignore_fromline_hosts main "host list&!!" unset
14939 .cindex "&""From""& line"
14940 .cindex "UUCP" "&""From""& line"
14941 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
14942 the headers of a message. By default this is treated as the start of the
14943 message's body, which means that any following headers are not recognized as
14944 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
14945 match those hosts that insist on sending it. If the sender is actually a local
14946 process rather than a remote host, and is using &%-bs%& to inject the messages,
14947 &%ignore_fromline_local%& must be set to achieve this effect.
14950 .option ignore_fromline_local main boolean false
14951 See &%ignore_fromline_hosts%& above.
14954 .option keep_malformed main time 4d
14955 This option specifies the length of time to keep messages whose spool files
14956 have been corrupted in some way. This should, of course, never happen. At the
14957 next attempt to deliver such a message, it gets removed. The incident is
14961 .option ldap_ca_cert_dir main string unset
14962 .cindex "LDAP", "TLS CA certificate directory"
14963 This option indicates which directory contains CA certificates for verifying
14964 a TLS certificate presented by an LDAP server.
14965 While Exim does not provide a default value, your SSL library may.
14966 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14967 and constrained to be a directory.
14970 .option ldap_ca_cert_file main string unset
14971 .cindex "LDAP", "TLS CA certificate file"
14972 This option indicates which file contains CA certificates for verifying
14973 a TLS certificate presented by an LDAP server.
14974 While Exim does not provide a default value, your SSL library may.
14975 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14976 and constrained to be a file.
14979 .option ldap_cert_file main string unset
14980 .cindex "LDAP" "TLS client certificate file"
14981 This option indicates which file contains an TLS client certificate which
14982 Exim should present to the LDAP server during TLS negotiation.
14983 Should be used together with &%ldap_cert_key%&.
14986 .option ldap_cert_key main string unset
14987 .cindex "LDAP" "TLS client key file"
14988 This option indicates which file contains the secret/private key to use
14989 to prove identity to the LDAP server during TLS negotiation.
14990 Should be used together with &%ldap_cert_file%&, which contains the
14991 identity to be proven.
14994 .option ldap_cipher_suite main string unset
14995 .cindex "LDAP" "TLS cipher suite"
14996 This controls the TLS cipher-suite negotiation during TLS negotiation with
14997 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
14998 cipher-suite options with OpenSSL (as used by LDAP client libraries).
15001 .option ldap_default_servers main "string list" unset
15002 .cindex "LDAP" "default servers"
15003 This option provides a list of LDAP servers which are tried in turn when an
15004 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
15005 details of LDAP queries. This option is available only when Exim has been built
15009 .option ldap_require_cert main string unset.
15010 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
15011 This should be one of the values "hard", "demand", "allow", "try" or "never".
15012 A value other than one of these is interpreted as "never".
15013 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
15014 Although Exim does not set a default, the LDAP library probably defaults
15018 .option ldap_start_tls main boolean false
15019 .cindex "LDAP" "whether or not to negotiate TLS"
15020 If set, Exim will attempt to negotiate TLS with the LDAP server when
15021 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
15022 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
15024 In the event of failure to negotiate TLS, the action taken is controlled
15025 by &%ldap_require_cert%&.
15028 .option ldap_version main integer unset
15029 .cindex "LDAP" "protocol version, forcing"
15030 This option can be used to force Exim to set a specific protocol version for
15031 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
15032 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
15033 the LDAP headers; otherwise it is 2. This option is available only when Exim
15034 has been built with LDAP support.
15038 .option local_from_check main boolean true
15039 .cindex "&'Sender:'& header line" "disabling addition of"
15040 .cindex "&'From:'& header line" "disabling checking of"
15041 When a message is submitted locally (that is, not over a TCP/IP connection) by
15042 an untrusted user, Exim removes any existing &'Sender:'& header line, and
15043 checks that the &'From:'& header line matches the login of the calling user and
15044 the domain specified by &%qualify_domain%&.
15046 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
15047 locally submitted message is automatically qualified by Exim, unless the
15048 &%-bnq%& command line option is used.
15050 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
15051 on the local part. If the &'From:'& header line does not match, Exim adds a
15052 &'Sender:'& header with an address constructed from the calling user's login
15053 and the default qualify domain.
15055 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
15056 and no &'Sender:'& header is ever added. If, in addition, you want to retain
15057 &'Sender:'& header lines supplied by untrusted users, you must also set
15058 &%local_sender_retain%& to be true.
15060 .cindex "envelope sender"
15061 These options affect only the header lines in the message. The envelope sender
15062 is still forced to be the login id at the qualify domain unless
15063 &%untrusted_set_sender%& permits the user to supply an envelope sender.
15065 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
15066 request similar header line checking. See section &<<SECTthesenhea>>&, which
15067 has more details about &'Sender:'& processing.
15072 .option local_from_prefix main string unset
15073 When Exim checks the &'From:'& header line of locally submitted messages for
15074 matching the login id (see &%local_from_check%& above), it can be configured to
15075 ignore certain prefixes and suffixes in the local part of the address. This is
15076 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15077 appropriate lists, in the same form as the &%local_part_prefix%& and
15078 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15081 local_from_prefix = *-
15083 is set, a &'From:'& line containing
15085 From: anything-user@your.domain.example
15087 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15088 matches the actual sender address that is constructed from the login name and
15092 .option local_from_suffix main string unset
15093 See &%local_from_prefix%& above.
15096 .option local_interfaces main "string list" "see below"
15097 This option controls which network interfaces are used by the daemon for
15098 listening; they are also used to identify the local host when routing. Chapter
15099 &<<CHAPinterfaces>>& contains a full description of this option and the related
15100 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15101 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15102 &%local_interfaces%& is
15104 local_interfaces = 0.0.0.0
15106 when Exim is built without IPv6 support; otherwise it is
15108 local_interfaces = <; ::0 ; 0.0.0.0
15111 .option local_scan_timeout main time 5m
15112 .cindex "timeout" "for &[local_scan()]& function"
15113 .cindex "&[local_scan()]& function" "timeout"
15114 This timeout applies to the &[local_scan()]& function (see chapter
15115 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15116 the incoming message is rejected with a temporary error if it is an SMTP
15117 message. For a non-SMTP message, the message is dropped and Exim ends with a
15118 non-zero code. The incident is logged on the main and reject logs.
15122 .option local_sender_retain main boolean false
15123 .cindex "&'Sender:'& header line" "retaining from local submission"
15124 When a message is submitted locally (that is, not over a TCP/IP connection) by
15125 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15126 do not want this to happen, you must set &%local_sender_retain%&, and you must
15127 also set &%local_from_check%& to be false (Exim will complain if you do not).
15128 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15129 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15134 .option localhost_number main string&!! unset
15135 .cindex "host" "locally unique number for"
15136 .cindex "message ids" "with multiple hosts"
15137 .vindex "&$localhost_number$&"
15138 Exim's message ids are normally unique only within the local host. If
15139 uniqueness among a set of hosts is required, each host must set a different
15140 value for the &%localhost_number%& option. The string is expanded immediately
15141 after reading the configuration file (so that a number can be computed from the
15142 host name, for example) and the result of the expansion must be a number in the
15143 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15144 systems). This is available in subsequent string expansions via the variable
15145 &$localhost_number$&. When &%localhost_number is set%&, the final two
15146 characters of the message id, instead of just being a fractional part of the
15147 time, are computed from the time and the local host number as described in
15148 section &<<SECTmessiden>>&.
15152 .option log_file_path main "string list&!!" "set at compile time"
15153 .cindex "log" "file path for"
15154 This option sets the path which is used to determine the names of Exim's log
15155 files, or indicates that logging is to be to syslog, or both. It is expanded
15156 when Exim is entered, so it can, for example, contain a reference to the host
15157 name. If no specific path is set for the log files at compile or run time,
15158 or if the option is unset at run time (i.e. &`log_file_path = `&)
15159 they are written in a sub-directory called &_log_& in Exim's spool directory.
15160 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15161 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15162 used. If this string is fixed at your installation (contains no expansion
15163 variables) it is recommended that you do not set this option in the
15164 configuration file, but instead supply the path using LOG_FILE_PATH in
15165 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15166 early on &-- in particular, failure to read the configuration file.
15169 .option log_selector main string unset
15170 .cindex "log" "selectors"
15171 This option can be used to reduce or increase the number of things that Exim
15172 writes to its log files. Its argument is made up of names preceded by plus or
15173 minus characters. For example:
15175 log_selector = +arguments -retry_defer
15177 A list of possible names and what they control is given in the chapter on
15178 logging, in section &<<SECTlogselector>>&.
15181 .option log_timezone main boolean false
15182 .cindex "log" "timezone for entries"
15183 .vindex "&$tod_log$&"
15184 .vindex "&$tod_zone$&"
15185 By default, the timestamps on log lines are in local time without the
15186 timezone. This means that if your timezone changes twice a year, the timestamps
15187 in log lines are ambiguous for an hour when the clocks go back. One way of
15188 avoiding this problem is to set the timezone to UTC. An alternative is to set
15189 &%log_timezone%& true. This turns on the addition of the timezone offset to
15190 timestamps in log lines. Turning on this option can add quite a lot to the size
15191 of log files because each line is extended by 6 characters. Note that the
15192 &$tod_log$& variable contains the log timestamp without the zone, but there is
15193 another variable called &$tod_zone$& that contains just the timezone offset.
15196 .option lookup_open_max main integer 25
15197 .cindex "too many open files"
15198 .cindex "open files, too many"
15199 .cindex "file" "too many open"
15200 .cindex "lookup" "maximum open files"
15201 .cindex "limit" "open files for lookups"
15202 This option limits the number of simultaneously open files for single-key
15203 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15204 Exim normally keeps these files open during routing, because often the same
15205 file is required several times. If the limit is reached, Exim closes the least
15206 recently used file. Note that if you are using the &'ndbm'& library, it
15207 actually opens two files for each logical DBM database, though it still counts
15208 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15209 open files"& errors with NDBM, you need to reduce the value of
15210 &%lookup_open_max%&.
15213 .option max_username_length main integer 0
15214 .cindex "length of login name"
15215 .cindex "user name" "maximum length"
15216 .cindex "limit" "user name length"
15217 Some operating systems are broken in that they truncate long arguments to
15218 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15219 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15220 an argument that is longer behaves as if &[getpwnam()]& failed.
15223 .option message_body_newlines main bool false
15224 .cindex "message body" "newlines in variables"
15225 .cindex "newline" "in message body variables"
15226 .vindex "&$message_body$&"
15227 .vindex "&$message_body_end$&"
15228 By default, newlines in the message body are replaced by spaces when setting
15229 the &$message_body$& and &$message_body_end$& expansion variables. If this
15230 option is set true, this no longer happens.
15233 .option message_body_visible main integer 500
15234 .cindex "body of message" "visible size"
15235 .cindex "message body" "visible size"
15236 .vindex "&$message_body$&"
15237 .vindex "&$message_body_end$&"
15238 This option specifies how much of a message's body is to be included in the
15239 &$message_body$& and &$message_body_end$& expansion variables.
15242 .option message_id_header_domain main string&!! unset
15243 .cindex "&'Message-ID:'& header line"
15244 If this option is set, the string is expanded and used as the right hand side
15245 (domain) of the &'Message-ID:'& header that Exim creates if a
15246 locally-originated incoming message does not have one. &"Locally-originated"&
15247 means &"not received over TCP/IP."&
15248 Otherwise, the primary host name is used.
15249 Only letters, digits, dot and hyphen are accepted; any other characters are
15250 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15251 empty string, the option is ignored.
15254 .option message_id_header_text main string&!! unset
15255 If this variable is set, the string is expanded and used to augment the text of
15256 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15257 message does not have one. The text of this header is required by RFC 2822 to
15258 take the form of an address. By default, Exim uses its internal message id as
15259 the local part, and the primary host name as the domain. If this option is set,
15260 it is expanded, and provided the expansion is not forced to fail, and does not
15261 yield an empty string, the result is inserted into the header immediately
15262 before the @, separated from the internal message id by a dot. Any characters
15263 that are illegal in an address are automatically converted into hyphens. This
15264 means that variables such as &$tod_log$& can be used, because the spaces and
15265 colons will become hyphens.
15268 .option message_logs main boolean true
15269 .cindex "message logs" "disabling"
15270 .cindex "log" "message log; disabling"
15271 If this option is turned off, per-message log files are not created in the
15272 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
15273 Exim, by reducing the number of files involved in handling a message from a
15274 minimum of four (header spool file, body spool file, delivery journal, and
15275 per-message log) to three. The other major I/O activity is Exim's main log,
15276 which is not affected by this option.
15279 .option message_size_limit main string&!! 50M
15280 .cindex "message" "size limit"
15281 .cindex "limit" "message size"
15282 .cindex "size" "of message, limit"
15283 This option limits the maximum size of message that Exim will process. The
15284 value is expanded for each incoming connection so, for example, it can be made
15285 to depend on the IP address of the remote host for messages arriving via
15286 TCP/IP. After expansion, the value must be a sequence of decimal digits,
15287 optionally followed by K or M.
15289 &*Note*&: This limit cannot be made to depend on a message's sender or any
15290 other properties of an individual message, because it has to be advertised in
15291 the server's response to EHLO. String expansion failure causes a temporary
15292 error. A value of zero means no limit, but its use is not recommended. See also
15293 &%bounce_return_size_limit%&.
15295 Incoming SMTP messages are failed with a 552 error if the limit is
15296 exceeded; locally-generated messages either get a stderr message or a delivery
15297 failure message to the sender, depending on the &%-oe%& setting. Rejection of
15298 an oversized message is logged in both the main and the reject logs. See also
15299 the generic transport option &%message_size_limit%&, which limits the size of
15300 message that an individual transport can process.
15302 If you use a virus-scanner and set this option to to a value larger than the
15303 maximum size that your virus-scanner is configured to support, you may get
15304 failures triggered by large mails. The right size to configure for the
15305 virus-scanner depends upon what data is passed and the options in use but it's
15306 probably safest to just set it to a little larger than this value. E.g., with a
15307 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
15308 some problems may result.
15310 A value of 0 will disable size limit checking; Exim will still advertise the
15311 SIZE extension in an EHLO response, but without a limit, so as to permit
15312 SMTP clients to still indicate the message size along with the MAIL verb.
15315 .option move_frozen_messages main boolean false
15316 .cindex "frozen messages" "moving"
15317 This option, which is available only if Exim has been built with the setting
15319 SUPPORT_MOVE_FROZEN_MESSAGES=yes
15321 in &_Local/Makefile_&, causes frozen messages and their message logs to be
15322 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
15323 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
15324 standard utilities for handling such moved messages, and they do not show up in
15325 lists generated by &%-bp%& or by the Exim monitor.
15328 .option mua_wrapper main boolean false
15329 Setting this option true causes Exim to run in a very restrictive mode in which
15330 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
15331 contains a full description of this facility.
15335 .option mysql_servers main "string list" unset
15336 .cindex "MySQL" "server list"
15337 This option provides a list of MySQL servers and associated connection data, to
15338 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
15339 option is available only if Exim has been built with MySQL support.
15342 .option never_users main "string list&!!" unset
15343 This option is expanded just once, at the start of Exim's processing. Local
15344 message deliveries are normally run in processes that are setuid to the
15345 recipient, and remote deliveries are normally run under Exim's own uid and gid.
15346 It is usually desirable to prevent any deliveries from running as root, as a
15349 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
15350 list of users that must not be used for local deliveries. This list is fixed in
15351 the binary and cannot be overridden by the configuration file. By default, it
15352 contains just the single user name &"root"&. The &%never_users%& runtime option
15353 can be used to add more users to the fixed list.
15355 If a message is to be delivered as one of the users on the fixed list or the
15356 &%never_users%& list, an error occurs, and delivery is deferred. A common
15359 never_users = root:daemon:bin
15361 Including root is redundant if it is also on the fixed list, but it does no
15362 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
15366 .option openssl_options main "string list" "+no_sslv2"
15367 .cindex "OpenSSL "compatibility options"
15368 This option allows an administrator to adjust the SSL options applied
15369 by OpenSSL to connections. It is given as a space-separated list of items,
15370 each one to be +added or -subtracted from the current value.
15372 This option is only available if Exim is built against OpenSSL. The values
15373 available for this option vary according to the age of your OpenSSL install.
15374 The &"all"& value controls a subset of flags which are available, typically
15375 the bug workaround options. The &'SSL_CTX_set_options'& man page will
15376 list the values known on your system and Exim should support all the
15377 &"bug workaround"& options and many of the &"modifying"& options. The Exim
15378 names lose the leading &"SSL_OP_"& and are lower-cased.
15380 Note that adjusting the options can have severe impact upon the security of
15381 SSL as used by Exim. It is possible to disable safety checks and shoot
15382 yourself in the foot in various unpleasant ways. This option should not be
15383 adjusted lightly. An unrecognised item will be detected at startup, by
15384 invoking Exim with the &%-bV%& flag.
15386 The option affects Exim operating both as a server and as a client.
15388 Historical note: prior to release 4.80, Exim defaulted this value to
15389 "+dont_insert_empty_fragments", which may still be needed for compatibility
15390 with some clients, but which lowers security by increasing exposure to
15391 some now infamous attacks.
15395 # Make both old MS and old Eudora happy:
15396 openssl_options = -all +microsoft_big_sslv3_buffer \
15397 +dont_insert_empty_fragments
15399 # Disable older protocol versions:
15400 openssl_options = +no_sslv2 +no_sslv3
15403 Possible options may include:
15407 &`allow_unsafe_legacy_renegotiation`&
15409 &`cipher_server_preference`&
15411 &`dont_insert_empty_fragments`&
15415 &`legacy_server_connect`&
15417 &`microsoft_big_sslv3_buffer`&
15419 &`microsoft_sess_id_bug`&
15421 &`msie_sslv2_rsa_padding`&
15423 &`netscape_challenge_bug`&
15425 &`netscape_reuse_cipher_change_bug`&
15429 &`no_session_resumption_on_renegotiation`&
15443 &`safari_ecdhe_ecdsa_bug`&
15447 &`single_ecdh_use`&
15449 &`ssleay_080_client_dh_bug`&
15451 &`sslref2_reuse_cert_type_bug`&
15453 &`tls_block_padding_bug`&
15457 &`tls_rollback_bug`&
15460 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
15461 all clients connecting using the MacOS SecureTransport TLS facility prior
15462 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
15463 to negotiate TLS then this option value might help, provided that your OpenSSL
15464 release is new enough to contain this work-around. This may be a situation
15465 where you have to upgrade OpenSSL to get buggy clients working.
15468 .option oracle_servers main "string list" unset
15469 .cindex "Oracle" "server list"
15470 This option provides a list of Oracle servers and associated connection data,
15471 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
15472 The option is available only if Exim has been built with Oracle support.
15475 .option percent_hack_domains main "domain list&!!" unset
15476 .cindex "&""percent hack""&"
15477 .cindex "source routing" "in email address"
15478 .cindex "address" "source-routed"
15479 The &"percent hack"& is the convention whereby a local part containing a
15480 percent sign is re-interpreted as a new email address, with the percent
15481 replaced by @. This is sometimes called &"source routing"&, though that term is
15482 also applied to RFC 2822 addresses that begin with an @ character. If this
15483 option is set, Exim implements the percent facility for those domains listed,
15484 but no others. This happens before an incoming SMTP address is tested against
15487 &*Warning*&: The &"percent hack"& has often been abused by people who are
15488 trying to get round relaying restrictions. For this reason, it is best avoided
15489 if at all possible. Unfortunately, a number of less security-conscious MTAs
15490 implement it unconditionally. If you are running Exim on a gateway host, and
15491 routing mail through to internal MTAs without processing the local parts, it is
15492 a good idea to reject recipient addresses with percent characters in their
15493 local parts. Exim's default configuration does this.
15496 .option perl_at_start main boolean false
15497 This option is available only when Exim is built with an embedded Perl
15498 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15501 .option perl_startup main string unset
15502 This option is available only when Exim is built with an embedded Perl
15503 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15506 .option pgsql_servers main "string list" unset
15507 .cindex "PostgreSQL lookup type" "server list"
15508 This option provides a list of PostgreSQL servers and associated connection
15509 data, to be used in conjunction with &(pgsql)& lookups (see section
15510 &<<SECID72>>&). The option is available only if Exim has been built with
15511 PostgreSQL support.
15514 .option pid_file_path main string&!! "set at compile time"
15515 .cindex "daemon" "pid file path"
15516 .cindex "pid file, path for"
15517 This option sets the name of the file to which the Exim daemon writes its
15518 process id. The string is expanded, so it can contain, for example, references
15521 pid_file_path = /var/log/$primary_hostname/exim.pid
15523 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
15525 The value set by the option can be overridden by the &%-oP%& command line
15526 option. A pid file is not written if a &"non-standard"& daemon is run by means
15527 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
15530 .option pipelining_advertise_hosts main "host list&!!" *
15531 .cindex "PIPELINING" "suppressing advertising"
15532 This option can be used to suppress the advertisement of the SMTP
15533 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
15534 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
15535 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
15536 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
15537 that clients will use it; &"out of order"& commands that are &"expected"& do
15538 not count as protocol errors (see &%smtp_max_synprot_errors%&).
15541 .option prdr_enable main boolean false
15542 .cindex "PRDR" "enabling on server"
15543 This option can be used to enable the Per-Recipient Data Response extension
15544 to SMTP, defined by Eric Hall.
15545 If the option is set, PRDR is advertised by Exim when operating as a server.
15546 If the client requests PRDR, and more than one recipient, for a message
15547 an additional ACL is called for each recipient after the message content
15548 is received. See section &<<SECTPRDRACL>>&.
15550 .option preserve_message_logs main boolean false
15551 .cindex "message logs" "preserving"
15552 If this option is set, message log files are not deleted when messages are
15553 completed. Instead, they are moved to a sub-directory of the spool directory
15554 called &_msglog.OLD_&, where they remain available for statistical or debugging
15555 purposes. This is a dangerous option to set on systems with any appreciable
15556 volume of mail. Use with care!
15559 .option primary_hostname main string "see below"
15560 .cindex "name" "of local host"
15561 .cindex "host" "name of local"
15562 .cindex "local host" "name of"
15563 .vindex "&$primary_hostname$&"
15564 This specifies the name of the current host. It is used in the default EHLO or
15565 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
15566 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
15567 The value is also used by default in some SMTP response messages from an Exim
15568 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
15570 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
15571 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
15572 contains only one component, Exim passes it to &[gethostbyname()]& (or
15573 &[getipnodebyname()]& when available) in order to obtain the fully qualified
15574 version. The variable &$primary_hostname$& contains the host name, whether set
15575 explicitly by this option, or defaulted.
15578 .option print_topbitchars main boolean false
15579 .cindex "printing characters"
15580 .cindex "8-bit characters"
15581 By default, Exim considers only those characters whose codes lie in the range
15582 32&--126 to be printing characters. In a number of circumstances (for example,
15583 when writing log entries) non-printing characters are converted into escape
15584 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
15585 is set, code values of 128 and above are also considered to be printing
15588 This option also affects the header syntax checks performed by the
15589 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
15590 the user's full name when constructing From: and Sender: addresses (as
15591 described in section &<<SECTconstr>>&). Setting this option can cause
15592 Exim to generate eight bit message headers that do not conform to the
15596 .option process_log_path main string unset
15597 .cindex "process log path"
15598 .cindex "log" "process log"
15599 .cindex "&'exiwhat'&"
15600 This option sets the name of the file to which an Exim process writes its
15601 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15602 utility script. If this option is unset, the file called &_exim-process.info_&
15603 in Exim's spool directory is used. The ability to specify the name explicitly
15604 can be useful in environments where two different Exims are running, using
15605 different spool directories.
15608 .option prod_requires_admin main boolean true
15612 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15613 admin user unless &%prod_requires_admin%& is set false. See also
15614 &%queue_list_requires_admin%&.
15617 .option qualify_domain main string "see below"
15618 .cindex "domain" "for qualifying addresses"
15619 .cindex "address" "qualification"
15620 This option specifies the domain name that is added to any envelope sender
15621 addresses that do not have a domain qualification. It also applies to
15622 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15623 are accepted by default only for locally-generated messages. Qualification is
15624 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15625 locally-generated messages, unless the &%-bnq%& command line option is used.
15627 Messages from external sources must always contain fully qualified addresses,
15628 unless the sending host matches &%sender_unqualified_hosts%& or
15629 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15630 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15631 necessary. Internally, Exim always works with fully qualified envelope
15632 addresses. If &%qualify_domain%& is not set, it defaults to the
15633 &%primary_hostname%& value.
15636 .option qualify_recipient main string "see below"
15637 This option allows you to specify a different domain for qualifying recipient
15638 addresses to the one that is used for senders. See &%qualify_domain%& above.
15642 .option queue_domains main "domain list&!!" unset
15643 .cindex "domain" "specifying non-immediate delivery"
15644 .cindex "queueing incoming messages"
15645 .cindex "message" "queueing certain domains"
15646 This option lists domains for which immediate delivery is not required.
15647 A delivery process is started whenever a message is received, but only those
15648 domains that do not match are processed. All other deliveries wait until the
15649 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15652 .option queue_list_requires_admin main boolean true
15654 The &%-bp%& command-line option, which lists the messages that are on the
15655 queue, requires the caller to be an admin user unless
15656 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15659 .option queue_only main boolean false
15660 .cindex "queueing incoming messages"
15661 .cindex "message" "queueing unconditionally"
15662 If &%queue_only%& is set, a delivery process is not automatically started
15663 whenever a message is received. Instead, the message waits on the queue for the
15664 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15665 delivered immediately when certain conditions (such as heavy load) occur.
15667 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15668 and &%-odi%& command line options override &%queue_only%& unless
15669 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15670 &%queue_only_load%&, and &%smtp_accept_queue%&.
15673 .option queue_only_file main string unset
15674 .cindex "queueing incoming messages"
15675 .cindex "message" "queueing by file existence"
15676 This option can be set to a colon-separated list of absolute path names, each
15677 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15678 it tests for the existence of each listed path using a call to &[stat()]&. For
15679 each path that exists, the corresponding queueing option is set.
15680 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
15681 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
15683 queue_only_file = smtp/some/file
15685 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
15686 &_/some/file_& exists.
15689 .option queue_only_load main fixed-point unset
15690 .cindex "load average"
15691 .cindex "queueing incoming messages"
15692 .cindex "message" "queueing by load"
15693 If the system load average is higher than this value, incoming messages from
15694 all sources are queued, and no automatic deliveries are started. If this
15695 happens during local or remote SMTP input, all subsequent messages received on
15696 the same SMTP connection are queued by default, whatever happens to the load in
15697 the meantime, but this can be changed by setting &%queue_only_load_latch%&
15700 Deliveries will subsequently be performed by queue runner processes. This
15701 option has no effect on ancient operating systems on which Exim cannot
15702 determine the load average. See also &%deliver_queue_load_max%& and
15703 &%smtp_load_reserve%&.
15706 .option queue_only_load_latch main boolean true
15707 .cindex "load average" "re-evaluating per message"
15708 When this option is true (the default), once one message has been queued
15709 because the load average is higher than the value set by &%queue_only_load%&,
15710 all subsequent messages received on the same SMTP connection are also queued.
15711 This is a deliberate choice; even though the load average may fall below the
15712 threshold, it doesn't seem right to deliver later messages on the same
15713 connection when not delivering earlier ones. However, there are special
15714 circumstances such as very long-lived connections from scanning appliances
15715 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
15716 should be set false. This causes the value of the load average to be
15717 re-evaluated for each message.
15720 .option queue_only_override main boolean true
15721 .cindex "queueing incoming messages"
15722 When this option is true, the &%-od%&&'x'& command line options override the
15723 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
15724 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
15725 to override; they are accepted, but ignored.
15728 .option queue_run_in_order main boolean false
15729 .cindex "queue runner" "processing messages in order"
15730 If this option is set, queue runs happen in order of message arrival instead of
15731 in an arbitrary order. For this to happen, a complete list of the entire queue
15732 must be set up before the deliveries start. When the queue is all held in a
15733 single directory (the default), a single list is created for both the ordered
15734 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
15735 single list is not created when &%queue_run_in_order%& is false. In this case,
15736 the sub-directories are processed one at a time (in a random order), and this
15737 avoids setting up one huge list for the whole queue. Thus, setting
15738 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
15739 when the queue is large, because of the extra work in setting up the single,
15740 large list. In most situations, &%queue_run_in_order%& should not be set.
15744 .option queue_run_max main integer 5
15745 .cindex "queue runner" "maximum number of"
15746 This controls the maximum number of queue runner processes that an Exim daemon
15747 can run simultaneously. This does not mean that it starts them all at once,
15748 but rather that if the maximum number are still running when the time comes to
15749 start another one, it refrains from starting another one. This can happen with
15750 very large queues and/or very sluggish deliveries. This option does not,
15751 however, interlock with other processes, so additional queue runners can be
15752 started by other means, or by killing and restarting the daemon.
15754 Setting this option to zero does not suppress queue runs; rather, it disables
15755 the limit, allowing any number of simultaneous queue runner processes to be
15756 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
15757 the daemon's command line.
15759 .option queue_smtp_domains main "domain list&!!" unset
15760 .cindex "queueing incoming messages"
15761 .cindex "message" "queueing remote deliveries"
15762 When this option is set, a delivery process is started whenever a message is
15763 received, routing is performed, and local deliveries take place.
15764 However, if any SMTP deliveries are required for domains that match
15765 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
15766 message waits on the queue for the next queue run. Since routing of the message
15767 has taken place, Exim knows to which remote hosts it must be delivered, and so
15768 when the queue run happens, multiple messages for the same host are delivered
15769 over a single SMTP connection. The &%-odqs%& command line option causes all
15770 SMTP deliveries to be queued in this way, and is equivalent to setting
15771 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
15775 .option receive_timeout main time 0s
15776 .cindex "timeout" "for non-SMTP input"
15777 This option sets the timeout for accepting a non-SMTP message, that is, the
15778 maximum time that Exim waits when reading a message on the standard input. If
15779 the value is zero, it will wait for ever. This setting is overridden by the
15780 &%-or%& command line option. The timeout for incoming SMTP messages is
15781 controlled by &%smtp_receive_timeout%&.
15783 .option received_header_text main string&!! "see below"
15784 .cindex "customizing" "&'Received:'& header"
15785 .cindex "&'Received:'& header line" "customizing"
15786 This string defines the contents of the &'Received:'& message header that is
15787 added to each message, except for the timestamp, which is automatically added
15788 on at the end (preceded by a semicolon). The string is expanded each time it is
15789 used. If the expansion yields an empty string, no &'Received:'& header line is
15790 added to the message. Otherwise, the string should start with the text
15791 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
15792 header lines. The default setting is:
15795 received_header_text = Received: \
15796 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
15797 {${if def:sender_ident \
15798 {from ${quote_local_part:$sender_ident} }}\
15799 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
15800 by $primary_hostname \
15801 ${if def:received_protocol {with $received_protocol}} \
15802 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
15803 (Exim $version_number)\n\t\
15804 ${if def:sender_address \
15805 {(envelope-from <$sender_address>)\n\t}}\
15806 id $message_exim_id\
15807 ${if def:received_for {\n\tfor $received_for}}
15810 The reference to the TLS cipher is omitted when Exim is built without TLS
15811 support. The use of conditional expansions ensures that this works for both
15812 locally generated messages and messages received from remote hosts, giving
15813 header lines such as the following:
15815 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
15816 by marley.carol.example with esmtp (Exim 4.00)
15817 (envelope-from <bob@carol.example>)
15818 id 16IOWa-00019l-00
15819 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
15820 Received: by scrooge.carol.example with local (Exim 4.00)
15821 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
15823 Until the body of the message has been received, the timestamp is the time when
15824 the message started to be received. Once the body has arrived, and all policy
15825 checks have taken place, the timestamp is updated to the time at which the
15826 message was accepted.
15829 .option received_headers_max main integer 30
15830 .cindex "loop" "prevention"
15831 .cindex "mail loop prevention"
15832 .cindex "&'Received:'& header line" "counting"
15833 When a message is to be delivered, the number of &'Received:'& headers is
15834 counted, and if it is greater than this parameter, a mail loop is assumed to
15835 have occurred, the delivery is abandoned, and an error message is generated.
15836 This applies to both local and remote deliveries.
15839 .option recipient_unqualified_hosts main "host list&!!" unset
15840 .cindex "unqualified addresses"
15841 .cindex "host" "unqualified addresses from"
15842 This option lists those hosts from which Exim is prepared to accept unqualified
15843 recipient addresses in message envelopes. The addresses are made fully
15844 qualified by the addition of the &%qualify_recipient%& value. This option also
15845 affects message header lines. Exim does not reject unqualified recipient
15846 addresses in headers, but it qualifies them only if the message came from a
15847 host that matches &%recipient_unqualified_hosts%&,
15848 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
15849 option was not set.
15852 .option recipients_max main integer 0
15853 .cindex "limit" "number of recipients"
15854 .cindex "recipient" "maximum number"
15855 If this option is set greater than zero, it specifies the maximum number of
15856 original recipients for any message. Additional recipients that are generated
15857 by aliasing or forwarding do not count. SMTP messages get a 452 response for
15858 all recipients over the limit; earlier recipients are delivered as normal.
15859 Non-SMTP messages with too many recipients are failed, and no deliveries are
15862 .cindex "RCPT" "maximum number of incoming"
15863 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
15864 RCPT commands in a single message.
15867 .option recipients_max_reject main boolean false
15868 If this option is set true, Exim rejects SMTP messages containing too many
15869 recipients by giving 552 errors to the surplus RCPT commands, and a 554
15870 error to the eventual DATA command. Otherwise (the default) it gives a 452
15871 error to the surplus RCPT commands and accepts the message on behalf of the
15872 initial set of recipients. The remote server should then re-send the message
15873 for the remaining recipients at a later time.
15876 .option remote_max_parallel main integer 2
15877 .cindex "delivery" "parallelism for remote"
15878 This option controls parallel delivery of one message to a number of remote
15879 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
15880 does all the remote deliveries for a message one by one. Otherwise, if a single
15881 message has to be delivered to more than one remote host, or if several copies
15882 have to be sent to the same remote host, up to &%remote_max_parallel%&
15883 deliveries are done simultaneously. If more than &%remote_max_parallel%&
15884 deliveries are required, the maximum number of processes are started, and as
15885 each one finishes, another is begun. The order of starting processes is the
15886 same as if sequential delivery were being done, and can be controlled by the
15887 &%remote_sort_domains%& option. If parallel delivery takes place while running
15888 with debugging turned on, the debugging output from each delivery process is
15889 tagged with its process id.
15891 This option controls only the maximum number of parallel deliveries for one
15892 message in one Exim delivery process. Because Exim has no central queue
15893 manager, there is no way of controlling the total number of simultaneous
15894 deliveries if the configuration allows a delivery attempt as soon as a message
15897 .cindex "number of deliveries"
15898 .cindex "delivery" "maximum number of"
15899 If you want to control the total number of deliveries on the system, you
15900 need to set the &%queue_only%& option. This ensures that all incoming messages
15901 are added to the queue without starting a delivery process. Then set up an Exim
15902 daemon to start queue runner processes at appropriate intervals (probably
15903 fairly often, for example, every minute), and limit the total number of queue
15904 runners by setting the &%queue_run_max%& parameter. Because each queue runner
15905 delivers only one message at a time, the maximum number of deliveries that can
15906 then take place at once is &%queue_run_max%& multiplied by
15907 &%remote_max_parallel%&.
15909 If it is purely remote deliveries you want to control, use
15910 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
15911 doing the SMTP routing before queueing, so that several messages for the same
15912 host will eventually get delivered down the same connection.
15915 .option remote_sort_domains main "domain list&!!" unset
15916 .cindex "sorting remote deliveries"
15917 .cindex "delivery" "sorting remote"
15918 When there are a number of remote deliveries for a message, they are sorted by
15919 domain into the order given by this list. For example,
15921 remote_sort_domains = *.cam.ac.uk:*.uk
15923 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
15924 then to those in the &%uk%& domain, then to any others.
15927 .option retry_data_expire main time 7d
15928 .cindex "hints database" "data expiry"
15929 This option sets a &"use before"& time on retry information in Exim's hints
15930 database. Any older retry data is ignored. This means that, for example, once a
15931 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
15935 .option retry_interval_max main time 24h
15936 .cindex "retry" "limit on interval"
15937 .cindex "limit" "on retry interval"
15938 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
15939 intervals between delivery attempts for messages that cannot be delivered
15940 straight away. This option sets an overall limit to the length of time between
15941 retries. It cannot be set greater than 24 hours; any attempt to do so forces
15945 .option return_path_remove main boolean true
15946 .cindex "&'Return-path:'& header line" "removing"
15947 RFC 2821, section 4.4, states that an SMTP server must insert a
15948 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
15949 The &'Return-path:'& header preserves the sender address as received in the
15950 MAIL command. This description implies that this header should not be present
15951 in an incoming message. If &%return_path_remove%& is true, any existing
15952 &'Return-path:'& headers are removed from messages at the time they are
15953 received. Exim's transports have options for adding &'Return-path:'& headers at
15954 the time of delivery. They are normally used only for final local deliveries.
15957 .option return_size_limit main integer 100K
15958 This option is an obsolete synonym for &%bounce_return_size_limit%&.
15961 .option rfc1413_hosts main "host list&!!" @[]
15963 .cindex "host" "for RFC 1413 calls"
15964 RFC 1413 identification calls are made to any client host which matches
15965 an item in the list.
15966 The default value specifies just this host, being any local interface
15969 .option rfc1413_query_timeout main time 0s
15970 .cindex "RFC 1413" "query timeout"
15971 .cindex "timeout" "for RFC 1413 call"
15972 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
15973 no RFC 1413 calls are ever made.
15976 .option sender_unqualified_hosts main "host list&!!" unset
15977 .cindex "unqualified addresses"
15978 .cindex "host" "unqualified addresses from"
15979 This option lists those hosts from which Exim is prepared to accept unqualified
15980 sender addresses. The addresses are made fully qualified by the addition of
15981 &%qualify_domain%&. This option also affects message header lines. Exim does
15982 not reject unqualified addresses in headers that contain sender addresses, but
15983 it qualifies them only if the message came from a host that matches
15984 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
15985 using TCP/IP), and the &%-bnq%& option was not set.
15988 .option slow_lookup_log main integer 0
15989 .cindex "logging" "slow lookups"
15990 .cindex "dns" "logging slow lookups"
15991 This option controls logging of slow lookups.
15992 If the value is nonzero it is taken as a number of milliseconds
15993 and lookups taking longer than this are logged.
15994 Currently this applies only to DNS lookups.
15998 .option smtp_accept_keepalive main boolean true
15999 .cindex "keepalive" "on incoming connection"
16000 This option controls the setting of the SO_KEEPALIVE option on incoming
16001 TCP/IP socket connections. When set, it causes the kernel to probe idle
16002 connections periodically, by sending packets with &"old"& sequence numbers. The
16003 other end of the connection should send an acknowledgment if the connection is
16004 still okay or a reset if the connection has been aborted. The reason for doing
16005 this is that it has the beneficial effect of freeing up certain types of
16006 connection that can get stuck when the remote host is disconnected without
16007 tidying up the TCP/IP call properly. The keepalive mechanism takes several
16008 hours to detect unreachable hosts.
16012 .option smtp_accept_max main integer 20
16013 .cindex "limit" "incoming SMTP connections"
16014 .cindex "SMTP" "incoming connection count"
16016 This option specifies the maximum number of simultaneous incoming SMTP calls
16017 that Exim will accept. It applies only to the listening daemon; there is no
16018 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
16019 value is set to zero, no limit is applied. However, it is required to be
16020 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
16021 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
16023 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
16024 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
16025 that limit has not been reached for the client host, &%smtp_accept_reserve%&
16026 and &%smtp_load_reserve%& are then checked before accepting the connection.
16029 .option smtp_accept_max_nonmail main integer 10
16030 .cindex "limit" "non-mail SMTP commands"
16031 .cindex "SMTP" "limiting non-mail commands"
16032 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
16033 the connection if there are too many. This option defines &"too many"&. The
16034 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
16035 client looping sending EHLO, for example. The check is applied only if the
16036 client host matches &%smtp_accept_max_nonmail_hosts%&.
16038 When a new message is expected, one occurrence of RSET is not counted. This
16039 allows a client to send one RSET between messages (this is not necessary,
16040 but some clients do it). Exim also allows one uncounted occurrence of HELO
16041 or EHLO, and one occurrence of STARTTLS between messages. After
16042 starting up a TLS session, another EHLO is expected, and so it too is not
16043 counted. The first occurrence of AUTH in a connection, or immediately
16044 following STARTTLS is not counted. Otherwise, all commands other than
16045 MAIL, RCPT, DATA, and QUIT are counted.
16048 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
16049 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
16050 check by setting this option. The default value makes it apply to all hosts. By
16051 changing the value, you can exclude any badly-behaved hosts that you have to
16055 . Allow this long option name to split; give it unsplit as a fifth argument
16056 . for the automatic .oindex that is generated by .option.
16057 . We insert " &~&~" which is both pretty nasty visually and results in
16058 . non-searchable text. HowItWorks.txt mentions an option for inserting
16059 . zero-width-space, which would be nicer visually and results in (at least)
16060 . html that Firefox will split on when it's forced to reflow (rather than
16061 . inserting a horizontal scrollbar). However, the text is still not
16062 . searchable. NM changed this occurrence for bug 1197 to no longer allow
16063 . the option name to split.
16065 .option "smtp_accept_max_per_connection" main integer 1000 &&&
16066 smtp_accept_max_per_connection
16067 .cindex "SMTP" "limiting incoming message count"
16068 .cindex "limit" "messages per SMTP connection"
16069 The value of this option limits the number of MAIL commands that Exim is
16070 prepared to accept over a single SMTP connection, whether or not each command
16071 results in the transfer of a message. After the limit is reached, a 421
16072 response is given to subsequent MAIL commands. This limit is a safety
16073 precaution against a client that goes mad (incidents of this type have been
16077 .option smtp_accept_max_per_host main string&!! unset
16078 .cindex "limit" "SMTP connections from one host"
16079 .cindex "host" "limiting SMTP connections from"
16080 This option restricts the number of simultaneous IP connections from a single
16081 host (strictly, from a single IP address) to the Exim daemon. The option is
16082 expanded, to enable different limits to be applied to different hosts by
16083 reference to &$sender_host_address$&. Once the limit is reached, additional
16084 connection attempts from the same host are rejected with error code 421. This
16085 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16086 of zero imposes no limit. If this option is set greater than zero, it is
16087 required that &%smtp_accept_max%& be non-zero.
16089 &*Warning*&: When setting this option you should not use any expansion
16090 constructions that take an appreciable amount of time. The expansion and test
16091 happen in the main daemon loop, in order to reject additional connections
16092 without forking additional processes (otherwise a denial-of-service attack
16093 could cause a vast number or processes to be created). While the daemon is
16094 doing this processing, it cannot accept any other incoming connections.
16098 .option smtp_accept_queue main integer 0
16099 .cindex "SMTP" "incoming connection count"
16100 .cindex "queueing incoming messages"
16101 .cindex "message" "queueing by SMTP connection count"
16102 If the number of simultaneous incoming SMTP connections being handled via the
16103 listening daemon exceeds this value, messages received by SMTP are just placed
16104 on the queue; no delivery processes are started automatically. The count is
16105 fixed at the start of an SMTP connection. It cannot be updated in the
16106 subprocess that receives messages, and so the queueing or not queueing applies
16107 to all messages received in the same connection.
16109 A value of zero implies no limit, and clearly any non-zero value is useful only
16110 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16111 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16112 various &%-od%&&'x'& command line options.
16115 . See the comment on smtp_accept_max_per_connection
16117 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16118 smtp_accept_queue_per_connection
16119 .cindex "queueing incoming messages"
16120 .cindex "message" "queueing by message count"
16121 This option limits the number of delivery processes that Exim starts
16122 automatically when receiving messages via SMTP, whether via the daemon or by
16123 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16124 and the number of messages received in a single SMTP session exceeds this
16125 number, subsequent messages are placed on the queue, but no delivery processes
16126 are started. This helps to limit the number of Exim processes when a server
16127 restarts after downtime and there is a lot of mail waiting for it on other
16128 systems. On large systems, the default should probably be increased, and on
16129 dial-in client systems it should probably be set to zero (that is, disabled).
16132 .option smtp_accept_reserve main integer 0
16133 .cindex "SMTP" "incoming call count"
16134 .cindex "host" "reserved"
16135 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16136 number of SMTP connections that are reserved for connections from the hosts
16137 that are specified in &%smtp_reserve_hosts%&. The value set in
16138 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16139 restricted to this number of connections; the option specifies a minimum number
16140 of connection slots for them, not a maximum. It is a guarantee that this group
16141 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16142 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16145 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16146 set to 5, once there are 45 active connections (from any hosts), new
16147 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16148 provided the other criteria for acceptance are met.
16151 .option smtp_active_hostname main string&!! unset
16152 .cindex "host" "name in SMTP responses"
16153 .cindex "SMTP" "host name in responses"
16154 .vindex "&$primary_hostname$&"
16155 This option is provided for multi-homed servers that want to masquerade as
16156 several different hosts. At the start of an incoming SMTP connection, its value
16157 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16158 responses. For example, it is used as domain name in the response to an
16159 incoming HELO or EHLO command.
16161 .vindex "&$smtp_active_hostname$&"
16162 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16163 is saved with any messages that are received. It is therefore available for use
16164 in routers and transports when the message is later delivered.
16166 If this option is unset, or if its expansion is forced to fail, or if the
16167 expansion results in an empty string, the value of &$primary_hostname$& is
16168 used. Other expansion failures cause a message to be written to the main and
16169 panic logs, and the SMTP command receives a temporary error. Typically, the
16170 value of &%smtp_active_hostname%& depends on the incoming interface address.
16173 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16174 {cox.mydomain}{box.mydomain}}
16177 Although &$smtp_active_hostname$& is primarily concerned with incoming
16178 messages, it is also used as the default for HELO commands in callout
16179 verification if there is no remote transport from which to obtain a
16180 &%helo_data%& value.
16182 .option smtp_banner main string&!! "see below"
16183 .cindex "SMTP" "welcome banner"
16184 .cindex "banner for SMTP"
16185 .cindex "welcome banner for SMTP"
16186 .cindex "customizing" "SMTP banner"
16187 This string, which is expanded every time it is used, is output as the initial
16188 positive response to an SMTP connection. The default setting is:
16190 smtp_banner = $smtp_active_hostname ESMTP Exim \
16191 $version_number $tod_full
16193 Failure to expand the string causes a panic error. If you want to create a
16194 multiline response to the initial SMTP connection, use &"\n"& in the string at
16195 appropriate points, but not at the end. Note that the 220 code is not included
16196 in this string. Exim adds it automatically (several times in the case of a
16197 multiline response).
16200 .option smtp_check_spool_space main boolean true
16201 .cindex "checking disk space"
16202 .cindex "disk space, checking"
16203 .cindex "spool directory" "checking space"
16204 When this option is set, if an incoming SMTP session encounters the SIZE
16205 option on a MAIL command, it checks that there is enough space in the
16206 spool directory's partition to accept a message of that size, while still
16207 leaving free the amount specified by &%check_spool_space%& (even if that value
16208 is zero). If there isn't enough space, a temporary error code is returned.
16211 .option smtp_connect_backlog main integer 20
16212 .cindex "connection backlog"
16213 .cindex "SMTP" "connection backlog"
16214 .cindex "backlog of connections"
16215 This option specifies a maximum number of waiting SMTP connections. Exim passes
16216 this value to the TCP/IP system when it sets up its listener. Once this number
16217 of connections are waiting for the daemon's attention, subsequent connection
16218 attempts are refused at the TCP/IP level. At least, that is what the manuals
16219 say; in some circumstances such connection attempts have been observed to time
16220 out instead. For large systems it is probably a good idea to increase the
16221 value (to 50, say). It also gives some protection against denial-of-service
16222 attacks by SYN flooding.
16225 .option smtp_enforce_sync main boolean true
16226 .cindex "SMTP" "synchronization checking"
16227 .cindex "synchronization checking in SMTP"
16228 The SMTP protocol specification requires the client to wait for a response from
16229 the server at certain points in the dialogue. Without PIPELINING these
16230 synchronization points are after every command; with PIPELINING they are
16231 fewer, but they still exist.
16233 Some spamming sites send out a complete set of SMTP commands without waiting
16234 for any response. Exim protects against this by rejecting a message if the
16235 client has sent further input when it should not have. The error response &"554
16236 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16237 for this error cannot be perfect because of transmission delays (unexpected
16238 input may be on its way but not yet received when Exim checks). However, it
16239 does detect many instances.
16241 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
16242 If you want to disable the check selectively (for example, only for certain
16243 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
16244 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
16248 .option smtp_etrn_command main string&!! unset
16249 .cindex "ETRN" "command to be run"
16250 .vindex "&$domain$&"
16251 If this option is set, the given command is run whenever an SMTP ETRN
16252 command is received from a host that is permitted to issue such commands (see
16253 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
16254 are independently expanded. The expansion variable &$domain$& is set to the
16255 argument of the ETRN command, and no syntax checking is done on it. For
16258 smtp_etrn_command = /etc/etrn_command $domain \
16259 $sender_host_address
16261 A new process is created to run the command, but Exim does not wait for it to
16262 complete. Consequently, its status cannot be checked. If the command cannot be
16263 run, a line is written to the panic log, but the ETRN caller still receives
16264 a 250 success response. Exim is normally running under its own uid when
16265 receiving SMTP, so it is not possible for it to change the uid before running
16269 .option smtp_etrn_serialize main boolean true
16270 .cindex "ETRN" "serializing"
16271 When this option is set, it prevents the simultaneous execution of more than
16272 one identical command as a result of ETRN in an SMTP connection. See
16273 section &<<SECTETRN>>& for details.
16276 .option smtp_load_reserve main fixed-point unset
16277 .cindex "load average"
16278 If the system load average ever gets higher than this, incoming SMTP calls are
16279 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
16280 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
16281 the load is over the limit. The option has no effect on ancient operating
16282 systems on which Exim cannot determine the load average. See also
16283 &%deliver_queue_load_max%& and &%queue_only_load%&.
16287 .option smtp_max_synprot_errors main integer 3
16288 .cindex "SMTP" "limiting syntax and protocol errors"
16289 .cindex "limit" "SMTP syntax and protocol errors"
16290 Exim rejects SMTP commands that contain syntax or protocol errors. In
16291 particular, a syntactically invalid email address, as in this command:
16293 RCPT TO:<abc xyz@a.b.c>
16295 causes immediate rejection of the command, before any other tests are done.
16296 (The ACL cannot be run if there is no valid address to set up for it.) An
16297 example of a protocol error is receiving RCPT before MAIL. If there are
16298 too many syntax or protocol errors in one SMTP session, the connection is
16299 dropped. The limit is set by this option.
16301 .cindex "PIPELINING" "expected errors"
16302 When the PIPELINING extension to SMTP is in use, some protocol errors are
16303 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
16304 Exim assumes that PIPELINING will be used if it advertises it (see
16305 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
16306 not count towards the limit.
16310 .option smtp_max_unknown_commands main integer 3
16311 .cindex "SMTP" "limiting unknown commands"
16312 .cindex "limit" "unknown SMTP commands"
16313 If there are too many unrecognized commands in an incoming SMTP session, an
16314 Exim server drops the connection. This is a defence against some kinds of abuse
16317 into making connections to SMTP ports; in these circumstances, a number of
16318 non-SMTP command lines are sent first.
16322 .option smtp_ratelimit_hosts main "host list&!!" unset
16323 .cindex "SMTP" "rate limiting"
16324 .cindex "limit" "rate of message arrival"
16325 .cindex "RCPT" "rate limiting"
16326 Some sites find it helpful to be able to limit the rate at which certain hosts
16327 can send them messages, and the rate at which an individual message can specify
16330 Exim has two rate-limiting facilities. This section describes the older
16331 facility, which can limit rates within a single connection. The newer
16332 &%ratelimit%& ACL condition can limit rates across all connections. See section
16333 &<<SECTratelimiting>>& for details of the newer facility.
16335 When a host matches &%smtp_ratelimit_hosts%&, the values of
16336 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
16337 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
16338 respectively. Each option, if set, must contain a set of four comma-separated
16342 A threshold, before which there is no rate limiting.
16344 An initial time delay. Unlike other times in Exim, numbers with decimal
16345 fractional parts are allowed here.
16347 A factor by which to increase the delay each time.
16349 A maximum value for the delay. This should normally be less than 5 minutes,
16350 because after that time, the client is liable to timeout the SMTP command.
16353 For example, these settings have been used successfully at the site which
16354 first suggested this feature, for controlling mail from their customers:
16356 smtp_ratelimit_mail = 2,0.5s,1.05,4m
16357 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
16359 The first setting specifies delays that are applied to MAIL commands after
16360 two have been received over a single connection. The initial delay is 0.5
16361 seconds, increasing by a factor of 1.05 each time. The second setting applies
16362 delays to RCPT commands when more than four occur in a single message.
16365 .option smtp_ratelimit_mail main string unset
16366 See &%smtp_ratelimit_hosts%& above.
16369 .option smtp_ratelimit_rcpt main string unset
16370 See &%smtp_ratelimit_hosts%& above.
16373 .option smtp_receive_timeout main time&!! 5m
16374 .cindex "timeout" "for SMTP input"
16375 .cindex "SMTP" "input timeout"
16376 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
16377 input, including batch SMTP. If a line of input (either an SMTP command or a
16378 data line) is not received within this time, the SMTP connection is dropped and
16379 the message is abandoned.
16380 A line is written to the log containing one of the following messages:
16382 SMTP command timeout on connection from...
16383 SMTP data timeout on connection from...
16385 The former means that Exim was expecting to read an SMTP command; the latter
16386 means that it was in the DATA phase, reading the contents of a message.
16388 If the first character of the option is a &"$"& the option is
16389 expanded before use and may depend on
16390 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
16394 The value set by this option can be overridden by the
16395 &%-os%& command-line option. A setting of zero time disables the timeout, but
16396 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
16397 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
16398 timeout is controlled by &%receive_timeout%& and &%-or%&.
16401 .option smtp_reserve_hosts main "host list&!!" unset
16402 This option defines hosts for which SMTP connections are reserved; see
16403 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
16406 .option smtp_return_error_details main boolean false
16407 .cindex "SMTP" "details policy failures"
16408 .cindex "policy control" "rejection, returning details"
16409 In the default state, Exim uses bland messages such as
16410 &"Administrative prohibition"& when it rejects SMTP commands for policy
16411 reasons. Many sysadmins like this because it gives away little information
16412 to spammers. However, some other sysadmins who are applying strict checking
16413 policies want to give out much fuller information about failures. Setting
16414 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
16415 example, instead of &"Administrative prohibition"&, it might give:
16417 550-Rejected after DATA: '>' missing at end of address:
16418 550 failing address in "From" header is: <user@dom.ain
16423 .option smtputf8_advertise_hosts main "host list&!!" *
16424 .cindex "SMTPUTF8" "advertising"
16425 When Exim is built with support for internationalised mail names,
16426 the availability therof is advertised in
16427 response to EHLO only to those client hosts that match this option. See
16428 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
16432 .option spamd_address main string "see below"
16433 This option is available when Exim is compiled with the content-scanning
16434 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
16435 The default value is
16439 See section &<<SECTscanspamass>>& for more details.
16443 .option split_spool_directory main boolean false
16444 .cindex "multiple spool directories"
16445 .cindex "spool directory" "split"
16446 .cindex "directories, multiple"
16447 If this option is set, it causes Exim to split its input directory into 62
16448 subdirectories, each with a single alphanumeric character as its name. The
16449 sixth character of the message id is used to allocate messages to
16450 subdirectories; this is the least significant base-62 digit of the time of
16451 arrival of the message.
16453 Splitting up the spool in this way may provide better performance on systems
16454 where there are long mail queues, by reducing the number of files in any one
16455 directory. The msglog directory is also split up in a similar way to the input
16456 directory; however, if &%preserve_message_logs%& is set, all old msglog files
16457 are still placed in the single directory &_msglog.OLD_&.
16459 It is not necessary to take any special action for existing messages when
16460 changing &%split_spool_directory%&. Exim notices messages that are in the
16461 &"wrong"& place, and continues to process them. If the option is turned off
16462 after a period of being on, the subdirectories will eventually empty and be
16463 automatically deleted.
16465 When &%split_spool_directory%& is set, the behaviour of queue runner processes
16466 changes. Instead of creating a list of all messages in the queue, and then
16467 trying to deliver each one in turn, it constructs a list of those in one
16468 sub-directory and tries to deliver them, before moving on to the next
16469 sub-directory. The sub-directories are processed in a random order. This
16470 spreads out the scanning of the input directories, and uses less memory. It is
16471 particularly beneficial when there are lots of messages on the queue. However,
16472 if &%queue_run_in_order%& is set, none of this new processing happens. The
16473 entire queue has to be scanned and sorted before any deliveries can start.
16476 .option spool_directory main string&!! "set at compile time"
16477 .cindex "spool directory" "path to"
16478 This defines the directory in which Exim keeps its spool, that is, the messages
16479 it is waiting to deliver. The default value is taken from the compile-time
16480 configuration setting, if there is one. If not, this option must be set. The
16481 string is expanded, so it can contain, for example, a reference to
16482 &$primary_hostname$&.
16484 If the spool directory name is fixed on your installation, it is recommended
16485 that you set it at build time rather than from this option, particularly if the
16486 log files are being written to the spool directory (see &%log_file_path%&).
16487 Otherwise log files cannot be used for errors that are detected early on, such
16488 as failures in the configuration file.
16490 By using this option to override the compiled-in path, it is possible to run
16491 tests of Exim without using the standard spool.
16493 .option sqlite_lock_timeout main time 5s
16494 .cindex "sqlite lookup type" "lock timeout"
16495 This option controls the timeout that the &(sqlite)& lookup uses when trying to
16496 access an SQLite database. See section &<<SECTsqlite>>& for more details.
16498 .option strict_acl_vars main boolean false
16499 .cindex "&ACL;" "variables, handling unset"
16500 This option controls what happens if a syntactically valid but undefined ACL
16501 variable is referenced. If it is false (the default), an empty string
16502 is substituted; if it is true, an error is generated. See section
16503 &<<SECTaclvariables>>& for details of ACL variables.
16505 .option strip_excess_angle_brackets main boolean false
16506 .cindex "angle brackets, excess"
16507 If this option is set, redundant pairs of angle brackets round &"route-addr"&
16508 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
16509 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
16510 passed on to another MTA, the excess angle brackets are not passed on. If this
16511 option is not set, multiple pairs of angle brackets cause a syntax error.
16514 .option strip_trailing_dot main boolean false
16515 .cindex "trailing dot on domain"
16516 .cindex "dot" "trailing on domain"
16517 If this option is set, a trailing dot at the end of a domain in an address is
16518 ignored. If this is in the envelope and the message is passed on to another
16519 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
16520 domain causes a syntax error.
16521 However, addresses in header lines are checked only when an ACL requests header
16525 .option syslog_duplication main boolean true
16526 .cindex "syslog" "duplicate log lines; suppressing"
16527 When Exim is logging to syslog, it writes the log lines for its three
16528 separate logs at different syslog priorities so that they can in principle
16529 be separated on the logging hosts. Some installations do not require this
16530 separation, and in those cases, the duplication of certain log lines is a
16531 nuisance. If &%syslog_duplication%& is set false, only one copy of any
16532 particular log line is written to syslog. For lines that normally go to
16533 both the main log and the reject log, the reject log version (possibly
16534 containing message header lines) is written, at LOG_NOTICE priority.
16535 Lines that normally go to both the main and the panic log are written at
16536 the LOG_ALERT priority.
16539 .option syslog_facility main string unset
16540 .cindex "syslog" "facility; setting"
16541 This option sets the syslog &"facility"& name, used when Exim is logging to
16542 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
16543 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
16544 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
16545 details of Exim's logging.
16549 .option syslog_processname main string &`exim`&
16550 .cindex "syslog" "process name; setting"
16551 This option sets the syslog &"ident"& name, used when Exim is logging to
16552 syslog. The value must be no longer than 32 characters. See chapter
16553 &<<CHAPlog>>& for details of Exim's logging.
16557 .option syslog_timestamp main boolean true
16558 .cindex "syslog" "timestamps"
16559 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
16560 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
16561 details of Exim's logging.
16564 .option system_filter main string&!! unset
16565 .cindex "filter" "system filter"
16566 .cindex "system filter" "specifying"
16567 .cindex "Sieve filter" "not available for system filter"
16568 This option specifies an Exim filter file that is applied to all messages at
16569 the start of each delivery attempt, before any routing is done. System filters
16570 must be Exim filters; they cannot be Sieve filters. If the system filter
16571 generates any deliveries to files or pipes, or any new mail messages, the
16572 appropriate &%system_filter_..._transport%& option(s) must be set, to define
16573 which transports are to be used. Details of this facility are given in chapter
16574 &<<CHAPsystemfilter>>&.
16577 .option system_filter_directory_transport main string&!! unset
16578 .vindex "&$address_file$&"
16579 This sets the name of the transport driver that is to be used when the
16580 &%save%& command in a system message filter specifies a path ending in &"/"&,
16581 implying delivery of each message into a separate file in some directory.
16582 During the delivery, the variable &$address_file$& contains the path name.
16585 .option system_filter_file_transport main string&!! unset
16586 .cindex "file" "transport for system filter"
16587 This sets the name of the transport driver that is to be used when the &%save%&
16588 command in a system message filter specifies a path not ending in &"/"&. During
16589 the delivery, the variable &$address_file$& contains the path name.
16591 .option system_filter_group main string unset
16592 .cindex "gid (group id)" "system filter"
16593 This option is used only when &%system_filter_user%& is also set. It sets the
16594 gid under which the system filter is run, overriding any gid that is associated
16595 with the user. The value may be numerical or symbolic.
16597 .option system_filter_pipe_transport main string&!! unset
16598 .cindex "&(pipe)& transport" "for system filter"
16599 .vindex "&$address_pipe$&"
16600 This specifies the transport driver that is to be used when a &%pipe%& command
16601 is used in a system filter. During the delivery, the variable &$address_pipe$&
16602 contains the pipe command.
16605 .option system_filter_reply_transport main string&!! unset
16606 .cindex "&(autoreply)& transport" "for system filter"
16607 This specifies the transport driver that is to be used when a &%mail%& command
16608 is used in a system filter.
16611 .option system_filter_user main string unset
16612 .cindex "uid (user id)" "system filter"
16613 If this option is set to root, the system filter is run in the main Exim
16614 delivery process, as root. Otherwise, the system filter runs in a separate
16615 process, as the given user, defaulting to the Exim run-time user.
16616 Unless the string consists entirely of digits, it
16617 is looked up in the password data. Failure to find the named user causes a
16618 configuration error. The gid is either taken from the password data, or
16619 specified by &%system_filter_group%&. When the uid is specified numerically,
16620 &%system_filter_group%& is required to be set.
16622 If the system filter generates any pipe, file, or reply deliveries, the uid
16623 under which the filter is run is used when transporting them, unless a
16624 transport option overrides.
16627 .option tcp_nodelay main boolean true
16628 .cindex "daemon" "TCP_NODELAY on sockets"
16629 .cindex "Nagle algorithm"
16630 .cindex "TCP_NODELAY on listening sockets"
16631 If this option is set false, it stops the Exim daemon setting the
16632 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16633 turns off the &"Nagle algorithm"&, which is a way of improving network
16634 performance in interactive (character-by-character) situations. Turning it off
16635 should improve Exim's performance a bit, so that is what happens by default.
16636 However, it appears that some broken clients cannot cope, and time out. Hence
16637 this option. It affects only those sockets that are set up for listening by the
16638 daemon. Sockets created by the smtp transport for delivering mail always set
16642 .option timeout_frozen_after main time 0s
16643 .cindex "frozen messages" "timing out"
16644 .cindex "timeout" "frozen messages"
16645 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16646 message of any kind that has been on the queue for longer than the given time
16647 is automatically cancelled at the next queue run. If the frozen message is a
16648 bounce message, it is just discarded; otherwise, a bounce is sent to the
16649 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16650 If you want to timeout frozen bounce messages earlier than other kinds of
16651 frozen message, see &%ignore_bounce_errors_after%&.
16653 &*Note:*& the default value of zero means no timeouts; with this setting,
16654 frozen messages remain on the queue forever (except for any frozen bounce
16655 messages that are released by &%ignore_bounce_errors_after%&).
16658 .option timezone main string unset
16659 .cindex "timezone, setting"
16660 The value of &%timezone%& is used to set the environment variable TZ while
16661 running Exim (if it is different on entry). This ensures that all timestamps
16662 created by Exim are in the required timezone. If you want all your timestamps
16663 to be in UTC (aka GMT) you should set
16667 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
16668 or, if that is not set, from the value of the TZ environment variable when Exim
16669 is built. If &%timezone%& is set to the empty string, either at build or run
16670 time, any existing TZ variable is removed from the environment when Exim
16671 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
16672 unfortunately not all, operating systems.
16676 .option tls_advertise_hosts main "host list&!!" *
16678 .cindex "TLS" "advertising"
16679 .cindex "encryption" "on SMTP connection"
16680 .cindex "SMTP" "encrypted connection"
16681 When Exim is built with support for TLS encrypted connections, the availability
16682 of the STARTTLS command to set up an encrypted session is advertised in
16683 response to EHLO only to those client hosts that match this option. See
16684 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
16686 Note that the default value requires that a certificate be supplied
16687 using the &%tls_certificate%& option. If no certificate is available then
16688 the &%tls_advertise_hosts%& option should be set empty.
16692 .option tls_certificate main string&!! unset
16693 .cindex "TLS" "server certificate; location of"
16694 .cindex "certificate" "server, location of"
16695 The value of this option is expanded, and must then be the absolute path to a
16696 file which contains the server's certificates. The server's private key is also
16697 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
16698 &<<CHAPTLS>>& for further details.
16700 &*Note*&: The certificates defined by this option are used only when Exim is
16701 receiving incoming messages as a server. If you want to supply certificates for
16702 use when sending messages as a client, you must set the &%tls_certificate%&
16703 option in the relevant &(smtp)& transport.
16705 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
16706 if the OpenSSL build supports TLS extensions and the TLS client sends the
16707 Server Name Indication extension, then this option and others documented in
16708 &<<SECTtlssni>>& will be re-expanded.
16710 .option tls_crl main string&!! unset
16711 .cindex "TLS" "server certificate revocation list"
16712 .cindex "certificate" "revocation list for server"
16713 This option specifies a certificate revocation list. The expanded value must
16714 be the name of a file that contains a CRL in PEM format.
16716 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16719 .option tls_dh_max_bits main integer 2236
16720 .cindex "TLS" "D-H bit count"
16721 The number of bits used for Diffie-Hellman key-exchange may be suggested by
16722 the chosen TLS library. That value might prove to be too high for
16723 interoperability. This option provides a maximum clamp on the value
16724 suggested, trading off security for interoperability.
16726 The value must be at least 1024.
16728 The value 2236 was chosen because, at time of adding the option, it was the
16729 hard-coded maximum value supported by the NSS cryptographic library, as used
16730 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
16732 If you prefer more security and are willing to break some clients, raise this
16735 Note that the value passed to GnuTLS for *generating* a new prime may be a
16736 little less than this figure, because GnuTLS is inexact and may produce a
16737 larger prime than requested.
16740 .option tls_dhparam main string&!! unset
16741 .cindex "TLS" "D-H parameters for server"
16742 The value of this option is expanded and indicates the source of DH parameters
16743 to be used by Exim.
16745 If it is a filename starting with a &`/`&, then it names a file from which DH
16746 parameters should be loaded. If the file exists, it should hold a PEM-encoded
16747 PKCS#3 representation of the DH prime. If the file does not exist, for
16748 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
16749 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
16750 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
16751 and treated as though the &%tls_dhparam%& were set to "none".
16753 If this option expands to the string "none", then no DH parameters will be
16756 If this option expands to the string "historic" and Exim is using GnuTLS, then
16757 Exim will attempt to load a file from inside the spool directory. If the file
16758 does not exist, Exim will attempt to create it.
16759 See section &<<SECTgnutlsparam>>& for further details.
16761 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
16762 a default DH prime; the default is the 2048 bit prime described in section
16763 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
16764 in IKE is assigned number 23.
16766 Otherwise, the option must expand to the name used by Exim for any of a number
16767 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
16768 "ike" followed by the number used by IKE, of "default" which corresponds to
16771 The available primes are:
16772 &`ike1`&, &`ike2`&, &`ike5`&,
16773 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
16774 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
16776 Some of these will be too small to be accepted by clients.
16777 Some may be too large to be accepted by clients.
16779 The TLS protocol does not negotiate an acceptable size for this; clients tend
16780 to hard-drop connections if what is offered by the server is unacceptable,
16781 whether too large or too small, and there's no provision for the client to
16782 tell the server what these constraints are. Thus, as a server operator, you
16783 need to make an educated guess as to what is most likely to work for your
16786 Some known size constraints suggest that a bit-size in the range 2048 to 2236
16787 is most likely to maximise interoperability. The upper bound comes from
16788 applications using the Mozilla Network Security Services (NSS) library, which
16789 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
16790 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
16791 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
16792 acceptable bound from 1024 to 2048.
16795 .option tls_eccurve main string&!! prime256v1
16796 .cindex TLS "EC cryptography"
16797 If built with a recent-enough version of OpenSSL,
16798 this option selects a EC curve for use by Exim.
16800 Curve names of the form &'prime256v1'& are accepted.
16801 For even more-recent library versions, names of the form &'P-512'&
16802 are also accepted, plus the special value &'auto'&
16803 which tell the library to choose.
16805 If the option is set to an empty string, no EC curves will be enabled.
16808 .option tls_ocsp_file main string&!! unset
16809 .cindex TLS "certificate status"
16810 .cindex TLS "OCSP proof file"
16812 must if set expand to the absolute path to a file which contains a current
16813 status proof for the server's certificate, as obtained from the
16814 Certificate Authority.
16817 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
16821 .option tls_on_connect_ports main "string list" unset
16824 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
16825 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
16826 set up without waiting for the client to issue a STARTTLS command. For
16827 further details, see section &<<SECTsupobssmt>>&.
16831 .option tls_privatekey main string&!! unset
16832 .cindex "TLS" "server private key; location of"
16833 The value of this option is expanded, and must then be the absolute path to a
16834 file which contains the server's private key. If this option is unset, or if
16835 the expansion is forced to fail, or the result is an empty string, the private
16836 key is assumed to be in the same file as the server's certificates. See chapter
16837 &<<CHAPTLS>>& for further details.
16839 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16842 .option tls_remember_esmtp main boolean false
16843 .cindex "TLS" "esmtp state; remembering"
16844 .cindex "TLS" "broken clients"
16845 If this option is set true, Exim violates the RFCs by remembering that it is in
16846 &"esmtp"& state after successfully negotiating a TLS session. This provides
16847 support for broken clients that fail to send a new EHLO after starting a
16851 .option tls_require_ciphers main string&!! unset
16852 .cindex "TLS" "requiring specific ciphers"
16853 .cindex "cipher" "requiring specific"
16854 This option controls which ciphers can be used for incoming TLS connections.
16855 The &(smtp)& transport has an option of the same name for controlling outgoing
16856 connections. This option is expanded for each connection, so can be varied for
16857 different clients if required. The value of this option must be a list of
16858 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
16859 in somewhat different ways. If GnuTLS is being used, the client controls the
16860 preference order of the available ciphers. Details are given in sections
16861 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
16864 .option tls_try_verify_hosts main "host list&!!" unset
16865 .cindex "TLS" "client certificate verification"
16866 .cindex "certificate" "verification of client"
16867 See &%tls_verify_hosts%& below.
16870 .option tls_verify_certificates main string&!! system
16871 .cindex "TLS" "client certificate verification"
16872 .cindex "certificate" "verification of client"
16873 The value of this option is expanded, and must then be either the
16875 or the absolute path to
16876 a file or directory containing permitted certificates for clients that
16877 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
16879 The "system" value for the option will use a
16880 system default location compiled into the SSL library.
16881 This is not available for GnuTLS versions preceding 3.0.20,
16882 and will be taken as empty; an explicit location
16885 The use of a directory for the option value is not available for GnuTLS versions
16886 preceding 3.3.6 and a single file must be used.
16888 With OpenSSL the certificates specified
16890 either by file or directory
16891 are added to those given by the system default location.
16893 These certificates should be for the certificate authorities trusted, rather
16894 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
16895 the value is a file then the certificates are sent by Exim as a server to
16896 connecting clients, defining the list of accepted certificate authorities.
16897 Thus the values defined should be considered public data. To avoid this,
16898 use the explicit directory version.
16900 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16902 A forced expansion failure or setting to an empty string is equivalent to
16906 .option tls_verify_hosts main "host list&!!" unset
16907 .cindex "TLS" "client certificate verification"
16908 .cindex "certificate" "verification of client"
16909 This option, along with &%tls_try_verify_hosts%&, controls the checking of
16910 certificates from clients. The expected certificates are defined by
16911 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
16912 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
16913 &%tls_verify_certificates%& is not set.
16915 Any client that matches &%tls_verify_hosts%& is constrained by
16916 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
16917 present one of the listed certificates. If it does not, the connection is
16918 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
16919 the host to use TLS. It can still send SMTP commands through unencrypted
16920 connections. Forcing a client to use TLS has to be done separately using an
16921 ACL to reject inappropriate commands when the connection is not encrypted.
16923 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
16924 matches this option (but not &%tls_verify_hosts%&), Exim requests a
16925 certificate and checks it against &%tls_verify_certificates%&, but does not
16926 abort the connection if there is no certificate or if it does not match. This
16927 state can be detected in an ACL, which makes it possible to implement policies
16928 such as &"accept for relay only if a verified certificate has been received,
16929 but accept for local delivery if encrypted, even without a verified
16932 Client hosts that match neither of these lists are not asked to present
16936 .option trusted_groups main "string list&!!" unset
16937 .cindex "trusted groups"
16938 .cindex "groups" "trusted"
16939 This option is expanded just once, at the start of Exim's processing. If this
16940 option is set, any process that is running in one of the listed groups, or
16941 which has one of them as a supplementary group, is trusted. The groups can be
16942 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
16943 details of what trusted callers are permitted to do. If neither
16944 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
16947 .option trusted_users main "string list&!!" unset
16948 .cindex "trusted users"
16949 .cindex "user" "trusted"
16950 This option is expanded just once, at the start of Exim's processing. If this
16951 option is set, any process that is running as one of the listed users is
16952 trusted. The users can be specified numerically or by name. See section
16953 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
16954 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
16955 Exim user are trusted.
16957 .option unknown_login main string&!! unset
16958 .cindex "uid (user id)" "unknown caller"
16959 .vindex "&$caller_uid$&"
16960 This is a specialized feature for use in unusual configurations. By default, if
16961 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
16962 gives up. The &%unknown_login%& option can be used to set a login name to be
16963 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
16964 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
16965 is used for the user's real name (gecos field), unless this has been set by the
16968 .option unknown_username main string unset
16969 See &%unknown_login%&.
16971 .option untrusted_set_sender main "address list&!!" unset
16972 .cindex "trusted users"
16973 .cindex "sender" "setting by untrusted user"
16974 .cindex "untrusted user setting sender"
16975 .cindex "user" "untrusted setting sender"
16976 .cindex "envelope sender"
16977 When an untrusted user submits a message to Exim using the standard input, Exim
16978 normally creates an envelope sender address from the user's login and the
16979 default qualification domain. Data from the &%-f%& option (for setting envelope
16980 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
16981 is used) is ignored.
16983 However, untrusted users are permitted to set an empty envelope sender address,
16984 to declare that a message should never generate any bounces. For example:
16986 exim -f '<>' user@domain.example
16988 .vindex "&$sender_ident$&"
16989 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
16990 other envelope sender addresses in a controlled way. When it is set, untrusted
16991 users are allowed to set envelope sender addresses that match any of the
16992 patterns in the list. Like all address lists, the string is expanded. The
16993 identity of the user is in &$sender_ident$&, so you can, for example, restrict
16994 users to setting senders that start with their login ids
16995 followed by a hyphen
16996 by a setting like this:
16998 untrusted_set_sender = ^$sender_ident-
17000 If you want to allow untrusted users to set envelope sender addresses without
17001 restriction, you can use
17003 untrusted_set_sender = *
17005 The &%untrusted_set_sender%& option applies to all forms of local input, but
17006 only to the setting of the envelope sender. It does not permit untrusted users
17007 to use the other options which trusted user can use to override message
17008 parameters. Furthermore, it does not stop Exim from removing an existing
17009 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
17010 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
17011 overriding these actions. The handling of the &'Sender:'& header is also
17012 described in section &<<SECTthesenhea>>&.
17014 The log line for a message's arrival shows the envelope sender following
17015 &"<="&. For local messages, the user's login always follows, after &"U="&. In
17016 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
17017 envelope sender address, the user's login is shown in parentheses after the
17021 .option uucp_from_pattern main string "see below"
17022 .cindex "&""From""& line"
17023 .cindex "UUCP" "&""From""& line"
17024 Some applications that pass messages to an MTA via a command line interface use
17025 an initial line starting with &"From&~"& to pass the envelope sender. In
17026 particular, this is used by UUCP software. Exim recognizes such a line by means
17027 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
17028 matches, the sender address is constructed by expanding the contents of
17029 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
17030 default pattern recognizes lines in the following two forms:
17032 From ph10 Fri Jan 5 12:35 GMT 1996
17033 From ph10 Fri, 7 Jan 97 14:00:00 GMT
17035 The pattern can be seen by running
17037 exim -bP uucp_from_pattern
17039 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
17040 year in the second case. The first word after &"From&~"& is matched in the
17041 regular expression by a parenthesized subpattern. The default value for
17042 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
17043 (&"ph10"& in the example above) as the message's sender. See also
17044 &%ignore_fromline_hosts%&.
17047 .option uucp_from_sender main string&!! &`$1`&
17048 See &%uucp_from_pattern%& above.
17051 .option warn_message_file main string unset
17052 .cindex "warning of delay" "customizing the message"
17053 .cindex "customizing" "warning message"
17054 This option defines a template file containing paragraphs of text to be used
17055 for constructing the warning message which is sent by Exim when a message has
17056 been on the queue for a specified amount of time, as specified by
17057 &%delay_warning%&. Details of the file's contents are given in chapter
17058 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
17061 .option write_rejectlog main boolean true
17062 .cindex "reject log" "disabling"
17063 If this option is set false, Exim no longer writes anything to the reject log.
17064 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
17065 .ecindex IIDconfima
17066 .ecindex IIDmaiconf
17071 . ////////////////////////////////////////////////////////////////////////////
17072 . ////////////////////////////////////////////////////////////////////////////
17074 .chapter "Generic options for routers" "CHAProutergeneric"
17075 .scindex IIDgenoprou1 "options" "generic; for routers"
17076 .scindex IIDgenoprou2 "generic options" "router"
17077 This chapter describes the generic options that apply to all routers.
17078 Those that are preconditions are marked with ‡ in the &"use"& field.
17080 For a general description of how a router operates, see sections
17081 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
17082 which the preconditions are tested. The order of expansion of the options that
17083 provide data for a transport is: &%errors_to%&, &%headers_add%&,
17084 &%headers_remove%&, &%transport%&.
17088 .option address_data routers string&!! unset
17089 .cindex "router" "data attached to address"
17090 The string is expanded just before the router is run, that is, after all the
17091 precondition tests have succeeded. If the expansion is forced to fail, the
17092 router declines, the value of &%address_data%& remains unchanged, and the
17093 &%more%& option controls what happens next. Other expansion failures cause
17094 delivery of the address to be deferred.
17096 .vindex "&$address_data$&"
17097 When the expansion succeeds, the value is retained with the address, and can be
17098 accessed using the variable &$address_data$& in the current router, subsequent
17099 routers, and the eventual transport.
17101 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17102 that runs a user's filter file, the contents of &$address_data$& are accessible
17103 in the filter. This is not normally a problem, because such data is usually
17104 either not confidential or it &"belongs"& to the current user, but if you do
17105 put confidential data into &$address_data$& you need to remember this point.
17107 Even if the router declines or passes, the value of &$address_data$& remains
17108 with the address, though it can be changed by another &%address_data%& setting
17109 on a subsequent router. If a router generates child addresses, the value of
17110 &$address_data$& propagates to them. This also applies to the special kind of
17111 &"child"& that is generated by a router with the &%unseen%& option.
17113 The idea of &%address_data%& is that you can use it to look up a lot of data
17114 for the address once, and then pick out parts of the data later. For example,
17115 you could use a single LDAP lookup to return a string of the form
17117 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17119 In the transport you could pick out the mailbox by a setting such as
17121 file = ${extract{mailbox}{$address_data}}
17123 This makes the configuration file less messy, and also reduces the number of
17124 lookups (though Exim does cache lookups).
17126 .vindex "&$sender_address_data$&"
17127 .vindex "&$address_data$&"
17128 The &%address_data%& facility is also useful as a means of passing information
17129 from one router to another, and from a router to a transport. In addition, if
17130 &$address_data$& is set by a router when verifying a recipient address from an
17131 ACL, it remains available for use in the rest of the ACL statement. After
17132 verifying a sender, the value is transferred to &$sender_address_data$&.
17136 .option address_test routers&!? boolean true
17138 .cindex "router" "skipping when address testing"
17139 If this option is set false, the router is skipped when routing is being tested
17140 by means of the &%-bt%& command line option. This can be a convenience when
17141 your first router sends messages to an external scanner, because it saves you
17142 having to set the &"already scanned"& indicator when testing real address
17147 .option cannot_route_message routers string&!! unset
17148 .cindex "router" "customizing &""cannot route""& message"
17149 .cindex "customizing" "&""cannot route""& message"
17150 This option specifies a text message that is used when an address cannot be
17151 routed because Exim has run out of routers. The default message is
17152 &"Unrouteable address"&. This option is useful only on routers that have
17153 &%more%& set false, or on the very last router in a configuration, because the
17154 value that is used is taken from the last router that is considered. This
17155 includes a router that is skipped because its preconditions are not met, as
17156 well as a router that declines. For example, using the default configuration,
17159 cannot_route_message = Remote domain not found in DNS
17161 on the first router, which is a &(dnslookup)& router with &%more%& set false,
17164 cannot_route_message = Unknown local user
17166 on the final router that checks for local users. If string expansion fails for
17167 this option, the default message is used. Unless the expansion failure was
17168 explicitly forced, a message about the failure is written to the main and panic
17169 logs, in addition to the normal message about the routing failure.
17172 .option caseful_local_part routers boolean false
17173 .cindex "case of local parts"
17174 .cindex "router" "case of local parts"
17175 By default, routers handle the local parts of addresses in a case-insensitive
17176 manner, though the actual case is preserved for transmission with the message.
17177 If you want the case of letters to be significant in a router, you must set
17178 this option true. For individual router options that contain address or local
17179 part lists (for example, &%local_parts%&), case-sensitive matching can be
17180 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
17183 .vindex "&$local_part$&"
17184 .vindex "&$original_local_part$&"
17185 .vindex "&$parent_local_part$&"
17186 The value of the &$local_part$& variable is forced to lower case while a
17187 router is running unless &%caseful_local_part%& is set. When a router assigns
17188 an address to a transport, the value of &$local_part$& when the transport runs
17189 is the same as it was in the router. Similarly, when a router generates child
17190 addresses by aliasing or forwarding, the values of &$original_local_part$&
17191 and &$parent_local_part$& are those that were used by the redirecting router.
17193 This option applies to the processing of an address by a router. When a
17194 recipient address is being processed in an ACL, there is a separate &%control%&
17195 modifier that can be used to specify case-sensitive processing within the ACL
17196 (see section &<<SECTcontrols>>&).
17200 .option check_local_user routers&!? boolean false
17201 .cindex "local user, checking in router"
17202 .cindex "router" "checking for local user"
17203 .cindex "&_/etc/passwd_&"
17205 When this option is true, Exim checks that the local part of the recipient
17206 address (with affixes removed if relevant) is the name of an account on the
17207 local system. The check is done by calling the &[getpwnam()]& function rather
17208 than trying to read &_/etc/passwd_& directly. This means that other methods of
17209 holding password data (such as NIS) are supported. If the local part is a local
17210 user, &$home$& is set from the password data, and can be tested in other
17211 preconditions that are evaluated after this one (the order of evaluation is
17212 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
17213 overridden by &%router_home_directory%&. If the local part is not a local user,
17214 the router is skipped.
17216 If you want to check that the local part is either the name of a local user
17217 or matches something else, you cannot combine &%check_local_user%& with a
17218 setting of &%local_parts%&, because that specifies the logical &'and'& of the
17219 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
17220 setting to achieve this. For example:
17222 local_parts = passwd;$local_part : lsearch;/etc/other/users
17224 Note, however, that the side effects of &%check_local_user%& (such as setting
17225 up a home directory) do not occur when a &(passwd)& lookup is used in a
17226 &%local_parts%& (or any other) precondition.
17230 .option condition routers&!? string&!! unset
17231 .cindex "router" "customized precondition"
17232 This option specifies a general precondition test that has to succeed for the
17233 router to be called. The &%condition%& option is the last precondition to be
17234 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
17235 result is a forced failure, or an empty string, or one of the strings &"0"& or
17236 &"no"& or &"false"& (checked without regard to the case of the letters), the
17237 router is skipped, and the address is offered to the next one.
17239 If the result is any other value, the router is run (as this is the last
17240 precondition to be evaluated, all the other preconditions must be true).
17242 This option is unusual in that multiple &%condition%& options may be present.
17243 All &%condition%& options must succeed.
17245 The &%condition%& option provides a means of applying custom conditions to the
17246 running of routers. Note that in the case of a simple conditional expansion,
17247 the default expansion values are exactly what is wanted. For example:
17249 condition = ${if >{$message_age}{600}}
17251 Because of the default behaviour of the string expansion, this is equivalent to
17253 condition = ${if >{$message_age}{600}{true}{}}
17256 A multiple condition example, which succeeds:
17258 condition = ${if >{$message_age}{600}}
17259 condition = ${if !eq{${lc:$local_part}}{postmaster}}
17263 If the expansion fails (other than forced failure) delivery is deferred. Some
17264 of the other precondition options are common special cases that could in fact
17265 be specified using &%condition%&.
17267 Historical note: We have &%condition%& on ACLs and on Routers. Routers
17268 are far older, and use one set of semantics. ACLs are newer and when
17269 they were created, the ACL &%condition%& process was given far stricter
17270 parse semantics. The &%bool{}%& expansion condition uses the same rules as
17271 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
17272 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
17273 Router rules processing behavior.
17275 This is best illustrated in an example:
17277 # If used in an ACL condition will fail with a syntax error, but
17278 # in a router condition any extra characters are treated as a string
17280 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
17283 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
17286 In each example above, the &%if%& statement actually ends after
17287 &"{google.com}}"&. Since no true or false braces were defined, the
17288 default &%if%& behavior is to return a boolean true or a null answer
17289 (which evaluates to false). The rest of the line is then treated as a
17290 string. So the first example resulted in the boolean answer &"true"&
17291 with the string &" {yes} {no}}"& appended to it. The second example
17292 resulted in the null output (indicating false) with the string
17293 &" {yes} {no}}"& appended to it.
17295 In fact you can put excess forward braces in too. In the router
17296 &%condition%&, Exim's parser only looks for &"{"& symbols when they
17297 mean something, like after a &"$"& or when required as part of a
17298 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
17301 Thus, in a Router, the above expansion strings will both always evaluate
17302 true, as the result of expansion is a non-empty string which doesn't
17303 match an explicit false value. This can be tricky to debug. By
17304 contrast, in an ACL either of those strings will always result in an
17305 expansion error because the result doesn't look sufficiently boolean.
17308 .option debug_print routers string&!! unset
17309 .cindex "testing" "variables in drivers"
17310 If this option is set and debugging is enabled (see the &%-d%& command line
17311 option) or in address-testing mode (see the &%-bt%& command line option),
17312 the string is expanded and included in the debugging output.
17313 If expansion of the string fails, the error message is written to the debugging
17314 output, and Exim carries on processing.
17315 This option is provided to help with checking out the values of variables and
17316 so on when debugging router configurations. For example, if a &%condition%&
17317 option appears not to be working, &%debug_print%& can be used to output the
17318 variables it references. The output happens after checks for &%domains%&,
17319 &%local_parts%&, and &%check_local_user%& but before any other preconditions
17320 are tested. A newline is added to the text if it does not end with one.
17321 The variable &$router_name$& contains the name of the router.
17325 .option disable_logging routers boolean false
17326 If this option is set true, nothing is logged for any routing errors
17327 or for any deliveries caused by this router. You should not set this option
17328 unless you really, really know what you are doing. See also the generic
17329 transport option of the same name.
17331 .option dnssec_request_domains routers "domain list&!!" unset
17332 .cindex "MX record" "security"
17333 .cindex "DNSSEC" "MX lookup"
17334 .cindex "security" "MX lookup"
17335 .cindex "DNS" "DNSSEC"
17336 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17337 the dnssec request bit set.
17338 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17340 .option dnssec_require_domains routers "domain list&!!" unset
17341 .cindex "MX record" "security"
17342 .cindex "DNSSEC" "MX lookup"
17343 .cindex "security" "MX lookup"
17344 .cindex "DNS" "DNSSEC"
17345 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17346 the dnssec request bit set. Any returns not having the Authenticated Data bit
17347 (AD bit) set will be ignored and logged as a host-lookup failure.
17348 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17351 .option domains routers&!? "domain list&!!" unset
17352 .cindex "router" "restricting to specific domains"
17353 .vindex "&$domain_data$&"
17354 If this option is set, the router is skipped unless the current domain matches
17355 the list. If the match is achieved by means of a file lookup, the data that the
17356 lookup returned for the domain is placed in &$domain_data$& for use in string
17357 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
17358 a list of the order in which preconditions are evaluated.
17362 .option driver routers string unset
17363 This option must always be set. It specifies which of the available routers is
17367 .option dsn_lasthop routers boolean false
17368 .cindex "DSN" "success"
17369 .cindex "Delivery Status Notification" "success"
17370 If this option is set true, and extended DSN (RFC3461) processing is in effect,
17371 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
17372 instead send a success DSN as if the next hop does not support DSN.
17373 Not effective on redirect routers.
17377 .option errors_to routers string&!! unset
17378 .cindex "envelope sender"
17379 .cindex "router" "changing address for errors"
17380 If a router successfully handles an address, it may assign the address to a
17381 transport for delivery or it may generate child addresses. In both cases, if
17382 there is a delivery problem during later processing, the resulting bounce
17383 message is sent to the address that results from expanding this string,
17384 provided that the address verifies successfully. The &%errors_to%& option is
17385 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
17387 The &%errors_to%& setting associated with an address can be overridden if it
17388 subsequently passes through other routers that have their own &%errors_to%&
17389 settings, or if the message is delivered by a transport with a &%return_path%&
17392 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
17393 the expansion fails to verify, the errors address associated with the incoming
17394 address is used. At top level, this is the envelope sender. A non-forced
17395 expansion failure causes delivery to be deferred.
17397 If an address for which &%errors_to%& has been set ends up being delivered over
17398 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
17399 any bounces that are generated by other MTAs on the delivery route are also
17400 sent there. You can set &%errors_to%& to the empty string by either of these
17406 An expansion item that yields an empty string has the same effect. If you do
17407 this, a locally detected delivery error for addresses processed by this router
17408 no longer gives rise to a bounce message; the error is discarded. If the
17409 address is delivered to a remote host, the return path is set to &`<>`&, unless
17410 overridden by the &%return_path%& option on the transport.
17412 .vindex "&$address_data$&"
17413 If for some reason you want to discard local errors, but use a non-empty
17414 MAIL command for remote delivery, you can preserve the original return
17415 path in &$address_data$& in the router, and reinstate it in the transport by
17416 setting &%return_path%&.
17418 The most common use of &%errors_to%& is to direct mailing list bounces to the
17419 manager of the list, as described in section &<<SECTmailinglists>>&, or to
17420 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
17424 .option expn routers&!? boolean true
17425 .cindex "address" "testing"
17426 .cindex "testing" "addresses"
17427 .cindex "EXPN" "router skipping"
17428 .cindex "router" "skipping for EXPN"
17429 If this option is turned off, the router is skipped when testing an address
17430 as a result of processing an SMTP EXPN command. You might, for example,
17431 want to turn it off on a router for users' &_.forward_& files, while leaving it
17432 on for the system alias file.
17433 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17436 The use of the SMTP EXPN command is controlled by an ACL (see chapter
17437 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
17438 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
17442 .option fail_verify routers boolean false
17443 .cindex "router" "forcing verification failure"
17444 Setting this option has the effect of setting both &%fail_verify_sender%& and
17445 &%fail_verify_recipient%& to the same value.
17449 .option fail_verify_recipient routers boolean false
17450 If this option is true and an address is accepted by this router when
17451 verifying a recipient, verification fails.
17455 .option fail_verify_sender routers boolean false
17456 If this option is true and an address is accepted by this router when
17457 verifying a sender, verification fails.
17461 .option fallback_hosts routers "string list" unset
17462 .cindex "router" "fallback hosts"
17463 .cindex "fallback" "hosts specified on router"
17464 String expansion is not applied to this option. The argument must be a
17465 colon-separated list of host names or IP addresses. The list separator can be
17466 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
17467 each name or address. In fact, the format of each item is exactly the same as
17468 defined for the list of hosts in a &(manualroute)& router (see section
17469 &<<SECTformatonehostitem>>&).
17471 If a router queues an address for a remote transport, this host list is
17472 associated with the address, and used instead of the transport's fallback host
17473 list. If &%hosts_randomize%& is set on the transport, the order of the list is
17474 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
17475 transport for further details.
17478 .option group routers string&!! "see below"
17479 .cindex "gid (group id)" "local delivery"
17480 .cindex "local transports" "uid and gid"
17481 .cindex "transport" "local"
17482 .cindex "router" "setting group"
17483 When a router queues an address for a transport, and the transport does not
17484 specify a group, the group given here is used when running the delivery
17486 The group may be specified numerically or by name. If expansion fails, the
17487 error is logged and delivery is deferred.
17488 The default is unset, unless &%check_local_user%& is set, when the default
17489 is taken from the password information. See also &%initgroups%& and &%user%&
17490 and the discussion in chapter &<<CHAPenvironment>>&.
17494 .option headers_add routers list&!! unset
17495 .cindex "header lines" "adding"
17496 .cindex "router" "adding header lines"
17497 This option specifies a list of text headers,
17498 newline-separated (by default, changeable in the usual way),
17499 that is associated with any addresses that are accepted by the router.
17500 Each item is separately expanded, at routing time. However, this
17501 option has no effect when an address is just being verified. The way in which
17502 the text is used to add header lines at transport time is described in section
17503 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
17504 message is in the process of being transported. This means that references to
17505 header lines in string expansions in the transport's configuration do not
17506 &"see"& the added header lines.
17508 The &%headers_add%& option is expanded after &%errors_to%&, but before
17509 &%headers_remove%& and &%transport%&. If an item is empty, or if
17510 an item expansion is forced to fail, the item has no effect. Other expansion
17511 failures are treated as configuration errors.
17513 Unlike most options, &%headers_add%& can be specified multiple times
17514 for a router; all listed headers are added.
17516 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
17517 router that has the &%one_time%& option set.
17519 .cindex "duplicate addresses"
17520 .oindex "&%unseen%&"
17521 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17522 additions are deleted when the address is passed on to subsequent routers.
17523 For a &%redirect%& router, if a generated address is the same as the incoming
17524 address, this can lead to duplicate addresses with different header
17525 modifications. Exim does not do duplicate deliveries (except, in certain
17526 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
17527 which of the duplicates is discarded, so this ambiguous situation should be
17528 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
17532 .option headers_remove routers list&!! unset
17533 .cindex "header lines" "removing"
17534 .cindex "router" "removing header lines"
17535 This option specifies a list of text headers,
17536 colon-separated (by default, changeable in the usual way),
17537 that is associated with any addresses that are accepted by the router.
17538 Each item is separately expanded, at routing time. However, this
17539 option has no effect when an address is just being verified. The way in which
17540 the text is used to remove header lines at transport time is described in
17541 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
17542 the message is in the process of being transported. This means that references
17543 to header lines in string expansions in the transport's configuration still
17544 &"see"& the original header lines.
17546 The &%headers_remove%& option is expanded after &%errors_to%& and
17547 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
17548 the item has no effect. Other expansion failures are treated as configuration
17551 Unlike most options, &%headers_remove%& can be specified multiple times
17552 for a router; all listed headers are removed.
17554 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
17555 router that has the &%one_time%& option set.
17557 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17558 removal requests are deleted when the address is passed on to subsequent
17559 routers, and this can lead to problems with duplicates -- see the similar
17560 warning for &%headers_add%& above.
17562 &*Warning 3*&: Because of the separate expansion of the list items,
17563 items that contain a list separator must have it doubled.
17564 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
17568 .option ignore_target_hosts routers "host list&!!" unset
17569 .cindex "IP address" "discarding"
17570 .cindex "router" "discarding IP addresses"
17571 Although this option is a host list, it should normally contain IP address
17572 entries rather than names. If any host that is looked up by the router has an
17573 IP address that matches an item in this list, Exim behaves as if that IP
17574 address did not exist. This option allows you to cope with rogue DNS entries
17577 remote.domain.example. A 127.0.0.1
17581 ignore_target_hosts = 127.0.0.1
17583 on the relevant router. If all the hosts found by a &(dnslookup)& router are
17584 discarded in this way, the router declines. In a conventional configuration, an
17585 attempt to mail to such a domain would normally provoke the &"unrouteable
17586 domain"& error, and an attempt to verify an address in the domain would fail.
17587 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
17588 router declines if presented with one of the listed addresses.
17590 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
17591 means of the first or the second of the following settings, respectively:
17593 ignore_target_hosts = 0.0.0.0/0
17594 ignore_target_hosts = <; 0::0/0
17596 The pattern in the first line matches all IPv4 addresses, whereas the pattern
17597 in the second line matches all IPv6 addresses.
17599 This option may also be useful for ignoring link-local and site-local IPv6
17600 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
17601 is expanded before use as a list, it is possible to make it dependent on the
17602 domain that is being routed.
17604 .vindex "&$host_address$&"
17605 During its expansion, &$host_address$& is set to the IP address that is being
17608 .option initgroups routers boolean false
17609 .cindex "additional groups"
17610 .cindex "groups" "additional"
17611 .cindex "local transports" "uid and gid"
17612 .cindex "transport" "local"
17613 If the router queues an address for a transport, and this option is true, and
17614 the uid supplied by the router is not overridden by the transport, the
17615 &[initgroups()]& function is called when running the transport to ensure that
17616 any additional groups associated with the uid are set up. See also &%group%&
17617 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
17621 .option local_part_prefix routers&!? "string list" unset
17622 .cindex "router" "prefix for local part"
17623 .cindex "prefix" "for local part, used in router"
17624 If this option is set, the router is skipped unless the local part starts with
17625 one of the given strings, or &%local_part_prefix_optional%& is true. See
17626 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
17629 The list is scanned from left to right, and the first prefix that matches is
17630 used. A limited form of wildcard is available; if the prefix begins with an
17631 asterisk, it matches the longest possible sequence of arbitrary characters at
17632 the start of the local part. An asterisk should therefore always be followed by
17633 some character that does not occur in normal local parts.
17634 .cindex "multiple mailboxes"
17635 .cindex "mailbox" "multiple"
17636 Wildcarding can be used to set up multiple user mailboxes, as described in
17637 section &<<SECTmulbox>>&.
17639 .vindex "&$local_part$&"
17640 .vindex "&$local_part_prefix$&"
17641 During the testing of the &%local_parts%& option, and while the router is
17642 running, the prefix is removed from the local part, and is available in the
17643 expansion variable &$local_part_prefix$&. When a message is being delivered, if
17644 the router accepts the address, this remains true during subsequent delivery by
17645 a transport. In particular, the local part that is transmitted in the RCPT
17646 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
17647 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
17648 the relevant transport.
17650 When an address is being verified, &%local_part_prefix%& affects only the
17651 behaviour of the router. If the callout feature of verification is in use, this
17652 means that the full address, including the prefix, will be used during the
17655 The prefix facility is commonly used to handle local parts of the form
17656 &%owner-something%&. Another common use is to support local parts of the form
17657 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
17658 to tell a user their forwarding is broken &-- by placing a router like this one
17659 immediately before the router that handles &_.forward_& files:
17663 local_part_prefix = real-
17665 transport = local_delivery
17667 For security, it would probably be a good idea to restrict the use of this
17668 router to locally-generated messages, using a condition such as this:
17670 condition = ${if match {$sender_host_address}\
17671 {\N^(|127\.0\.0\.1)$\N}}
17674 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
17675 both conditions must be met if not optional. Care must be taken if wildcards
17676 are used in both a prefix and a suffix on the same router. Different
17677 separator characters must be used to avoid ambiguity.
17680 .option local_part_prefix_optional routers boolean false
17681 See &%local_part_prefix%& above.
17685 .option local_part_suffix routers&!? "string list" unset
17686 .cindex "router" "suffix for local part"
17687 .cindex "suffix for local part" "used in router"
17688 This option operates in the same way as &%local_part_prefix%&, except that the
17689 local part must end (rather than start) with the given string, the
17690 &%local_part_suffix_optional%& option determines whether the suffix is
17691 mandatory, and the wildcard * character, if present, must be the last
17692 character of the suffix. This option facility is commonly used to handle local
17693 parts of the form &%something-request%& and multiple user mailboxes of the form
17697 .option local_part_suffix_optional routers boolean false
17698 See &%local_part_suffix%& above.
17702 .option local_parts routers&!? "local part list&!!" unset
17703 .cindex "router" "restricting to specific local parts"
17704 .cindex "local part" "checking in router"
17705 The router is run only if the local part of the address matches the list.
17706 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17708 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
17709 string is expanded, it is possible to make it depend on the domain, for
17712 local_parts = dbm;/usr/local/specials/$domain
17714 .vindex "&$local_part_data$&"
17715 If the match is achieved by a lookup, the data that the lookup returned
17716 for the local part is placed in the variable &$local_part_data$& for use in
17717 expansions of the router's private options. You might use this option, for
17718 example, if you have a large number of local virtual domains, and you want to
17719 send all postmaster mail to the same place without having to set up an alias in
17720 each virtual domain:
17724 local_parts = postmaster
17725 data = postmaster@real.domain.example
17729 .option log_as_local routers boolean "see below"
17730 .cindex "log" "delivery line"
17731 .cindex "delivery" "log line format"
17732 Exim has two logging styles for delivery, the idea being to make local
17733 deliveries stand out more visibly from remote ones. In the &"local"& style, the
17734 recipient address is given just as the local part, without a domain. The use of
17735 this style is controlled by this option. It defaults to true for the &(accept)&
17736 router, and false for all the others. This option applies only when a
17737 router assigns an address to a transport. It has no effect on routers that
17738 redirect addresses.
17742 .option more routers boolean&!! true
17743 The result of string expansion for this option must be a valid boolean value,
17744 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17745 result causes an error, and delivery is deferred. If the expansion is forced to
17746 fail, the default value for the option (true) is used. Other failures cause
17747 delivery to be deferred.
17749 If this option is set false, and the router declines to handle the address, no
17750 further routers are tried, routing fails, and the address is bounced.
17752 However, if the router explicitly passes an address to the following router by
17753 means of the setting
17757 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
17758 does not affect the behaviour if one of the precondition tests fails. In that
17759 case, the address is always passed to the next router.
17761 Note that &%address_data%& is not considered to be a precondition. If its
17762 expansion is forced to fail, the router declines, and the value of &%more%&
17763 controls what happens next.
17766 .option pass_on_timeout routers boolean false
17767 .cindex "timeout" "of router"
17768 .cindex "router" "timeout"
17769 If a router times out during a host lookup, it normally causes deferral of the
17770 address. If &%pass_on_timeout%& is set, the address is passed on to the next
17771 router, overriding &%no_more%&. This may be helpful for systems that are
17772 intermittently connected to the Internet, or those that want to pass to a smart
17773 host any messages that cannot immediately be delivered.
17775 There are occasional other temporary errors that can occur while doing DNS
17776 lookups. They are treated in the same way as a timeout, and this option
17777 applies to all of them.
17781 .option pass_router routers string unset
17782 .cindex "router" "go to after &""pass""&"
17783 Routers that recognize the generic &%self%& option (&(dnslookup)&,
17784 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
17785 routing to continue, and overriding a false setting of &%more%&. When one of
17786 these routers returns &"pass"&, the address is normally handed on to the next
17787 router in sequence. This can be changed by setting &%pass_router%& to the name
17788 of another router. However (unlike &%redirect_router%&) the named router must
17789 be below the current router, to avoid loops. Note that this option applies only
17790 to the special case of &"pass"&. It does not apply when a router returns
17791 &"decline"& because it cannot handle an address.
17795 .option redirect_router routers string unset
17796 .cindex "router" "start at after redirection"
17797 Sometimes an administrator knows that it is pointless to reprocess addresses
17798 generated from alias or forward files with the same router again. For
17799 example, if an alias file translates real names into login ids there is no
17800 point searching the alias file a second time, especially if it is a large file.
17802 The &%redirect_router%& option can be set to the name of any router instance.
17803 It causes the routing of any generated addresses to start at the named router
17804 instead of at the first router. This option has no effect if the router in
17805 which it is set does not generate new addresses.
17809 .option require_files routers&!? "string list&!!" unset
17810 .cindex "file" "requiring for router"
17811 .cindex "router" "requiring file existence"
17812 This option provides a general mechanism for predicating the running of a
17813 router on the existence or non-existence of certain files or directories.
17814 Before running a router, as one of its precondition tests, Exim works its way
17815 through the &%require_files%& list, expanding each item separately.
17817 Because the list is split before expansion, any colons in expansion items must
17818 be doubled, or the facility for using a different list separator must be used.
17819 If any expansion is forced to fail, the item is ignored. Other expansion
17820 failures cause routing of the address to be deferred.
17822 If any expanded string is empty, it is ignored. Otherwise, except as described
17823 below, each string must be a fully qualified file path, optionally preceded by
17824 &"!"&. The paths are passed to the &[stat()]& function to test for the
17825 existence of the files or directories. The router is skipped if any paths not
17826 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
17829 If &[stat()]& cannot determine whether a file exists or not, delivery of
17830 the message is deferred. This can happen when NFS-mounted filesystems are
17833 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
17834 options, so you cannot use it to check for the existence of a file in which to
17835 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
17836 full list of the order in which preconditions are evaluated.) However, as
17837 these options are all expanded, you can use the &%exists%& expansion condition
17838 to make such tests. The &%require_files%& option is intended for checking files
17839 that the router may be going to use internally, or which are needed by a
17840 transport (for example &_.procmailrc_&).
17842 During delivery, the &[stat()]& function is run as root, but there is a
17843 facility for some checking of the accessibility of a file by another user.
17844 This is not a proper permissions check, but just a &"rough"& check that
17845 operates as follows:
17847 If an item in a &%require_files%& list does not contain any forward slash
17848 characters, it is taken to be the user (and optional group, separated by a
17849 comma) to be checked for subsequent files in the list. If no group is specified
17850 but the user is specified symbolically, the gid associated with the uid is
17853 require_files = mail:/some/file
17854 require_files = $local_part:$home/.procmailrc
17856 If a user or group name in a &%require_files%& list does not exist, the
17857 &%require_files%& condition fails.
17859 Exim performs the check by scanning along the components of the file path, and
17860 checking the access for the given uid and gid. It checks for &"x"& access on
17861 directories, and &"r"& access on the final file. Note that this means that file
17862 access control lists, if the operating system has them, are ignored.
17864 &*Warning 1*&: When the router is being run to verify addresses for an
17865 incoming SMTP message, Exim is not running as root, but under its own uid. This
17866 may affect the result of a &%require_files%& check. In particular, &[stat()]&
17867 may yield the error EACCES (&"Permission denied"&). This means that the Exim
17868 user is not permitted to read one of the directories on the file's path.
17870 &*Warning 2*&: Even when Exim is running as root while delivering a message,
17871 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
17872 without root access. In this case, if a check for access by a particular user
17873 is requested, Exim creates a subprocess that runs as that user, and tries the
17874 check again in that process.
17876 The default action for handling an unresolved EACCES is to consider it to
17877 be caused by a configuration error, and routing is deferred because the
17878 existence or non-existence of the file cannot be determined. However, in some
17879 circumstances it may be desirable to treat this condition as if the file did
17880 not exist. If the file name (or the exclamation mark that precedes the file
17881 name for non-existence) is preceded by a plus sign, the EACCES error is treated
17882 as if the file did not exist. For example:
17884 require_files = +/some/file
17886 If the router is not an essential part of verification (for example, it
17887 handles users' &_.forward_& files), another solution is to set the &%verify%&
17888 option false so that the router is skipped when verifying.
17892 .option retry_use_local_part routers boolean "see below"
17893 .cindex "hints database" "retry keys"
17894 .cindex "local part" "in retry keys"
17895 When a delivery suffers a temporary routing failure, a retry record is created
17896 in Exim's hints database. For addresses whose routing depends only on the
17897 domain, the key for the retry record should not involve the local part, but for
17898 other addresses, both the domain and the local part should be included.
17899 Usually, remote routing is of the former kind, and local routing is of the
17902 This option controls whether the local part is used to form the key for retry
17903 hints for addresses that suffer temporary errors while being handled by this
17904 router. The default value is true for any router that has &%check_local_user%&
17905 set, and false otherwise. Note that this option does not apply to hints keys
17906 for transport delays; they are controlled by a generic transport option of the
17909 The setting of &%retry_use_local_part%& applies only to the router on which it
17910 appears. If the router generates child addresses, they are routed
17911 independently; this setting does not become attached to them.
17915 .option router_home_directory routers string&!! unset
17916 .cindex "router" "home directory for"
17917 .cindex "home directory" "for router"
17919 This option sets a home directory for use while the router is running. (Compare
17920 &%transport_home_directory%&, which sets a home directory for later
17921 transporting.) In particular, if used on a &(redirect)& router, this option
17922 sets a value for &$home$& while a filter is running. The value is expanded;
17923 forced expansion failure causes the option to be ignored &-- other failures
17924 cause the router to defer.
17926 Expansion of &%router_home_directory%& happens immediately after the
17927 &%check_local_user%& test (if configured), before any further expansions take
17929 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17931 While the router is running, &%router_home_directory%& overrides the value of
17932 &$home$& that came from &%check_local_user%&.
17934 When a router accepts an address and assigns it to a local transport (including
17935 the cases when a &(redirect)& router generates a pipe, file, or autoreply
17936 delivery), the home directory setting for the transport is taken from the first
17937 of these values that is set:
17940 The &%home_directory%& option on the transport;
17942 The &%transport_home_directory%& option on the router;
17944 The password data if &%check_local_user%& is set on the router;
17946 The &%router_home_directory%& option on the router.
17949 In other words, &%router_home_directory%& overrides the password data for the
17950 router, but not for the transport.
17954 .option self routers string freeze
17955 .cindex "MX record" "pointing to local host"
17956 .cindex "local host" "MX pointing to"
17957 This option applies to those routers that use a recipient address to find a
17958 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
17959 and &(manualroute)& routers.
17960 Certain configurations of the &(queryprogram)& router can also specify a list
17962 Usually such routers are configured to send the message to a remote host via an
17963 &(smtp)& transport. The &%self%& option specifies what happens when the first
17964 host on the list turns out to be the local host.
17965 The way in which Exim checks for the local host is described in section
17966 &<<SECTreclocipadd>>&.
17968 Normally this situation indicates either an error in Exim's configuration (for
17969 example, the router should be configured not to process this domain), or an
17970 error in the DNS (for example, the MX should not point to this host). For this
17971 reason, the default action is to log the incident, defer the address, and
17972 freeze the message. The following alternatives are provided for use in special
17977 Delivery of the message is tried again later, but the message is not frozen.
17979 .vitem "&%reroute%&: <&'domain'&>"
17980 The domain is changed to the given domain, and the address is passed back to
17981 be reprocessed by the routers. No rewriting of headers takes place. This
17982 behaviour is essentially a redirection.
17984 .vitem "&%reroute: rewrite:%& <&'domain'&>"
17985 The domain is changed to the given domain, and the address is passed back to be
17986 reprocessed by the routers. Any headers that contain the original domain are
17991 .vindex "&$self_hostname$&"
17992 The router passes the address to the next router, or to the router named in the
17993 &%pass_router%& option if it is set. This overrides &%no_more%&. During
17994 subsequent routing and delivery, the variable &$self_hostname$& contains the
17995 name of the local host that the router encountered. This can be used to
17996 distinguish between different cases for hosts with multiple names. The
18002 ensures that only those addresses that routed to the local host are passed on.
18003 Without &%no_more%&, addresses that were declined for other reasons would also
18004 be passed to the next router.
18007 Delivery fails and an error report is generated.
18010 .cindex "local host" "sending to"
18011 The anomaly is ignored and the address is queued for the transport. This
18012 setting should be used with extreme caution. For an &(smtp)& transport, it
18013 makes sense only in cases where the program that is listening on the SMTP port
18014 is not this version of Exim. That is, it must be some other MTA, or Exim with a
18015 different configuration file that handles the domain in another way.
18020 .option senders routers&!? "address list&!!" unset
18021 .cindex "router" "checking senders"
18022 If this option is set, the router is skipped unless the message's sender
18023 address matches something on the list.
18024 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18027 There are issues concerning verification when the running of routers is
18028 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
18029 setting, it sets the sender to the null string. When using the &%-bt%& option
18030 to check a configuration file, it is necessary also to use the &%-f%& option to
18031 set an appropriate sender. For incoming mail, the sender is unset when
18032 verifying the sender, but is available when verifying any recipients. If the
18033 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
18037 .option translate_ip_address routers string&!! unset
18038 .cindex "IP address" "translating"
18039 .cindex "packet radio"
18040 .cindex "router" "IP address translation"
18041 There exist some rare networking situations (for example, packet radio) where
18042 it is helpful to be able to translate IP addresses generated by normal routing
18043 mechanisms into other IP addresses, thus performing a kind of manual IP
18044 routing. This should be done only if the normal IP routing of the TCP/IP stack
18045 is inadequate or broken. Because this is an extremely uncommon requirement, the
18046 code to support this option is not included in the Exim binary unless
18047 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
18049 .vindex "&$host_address$&"
18050 The &%translate_ip_address%& string is expanded for every IP address generated
18051 by the router, with the generated address set in &$host_address$&. If the
18052 expansion is forced to fail, no action is taken.
18053 For any other expansion error, delivery of the message is deferred.
18054 If the result of the expansion is an IP address, that replaces the original
18055 address; otherwise the result is assumed to be a host name &-- this is looked
18056 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
18057 produce one or more replacement IP addresses. For example, to subvert all IP
18058 addresses in some specific networks, this could be added to a router:
18060 translate_ip_address = \
18061 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
18064 The file would contain lines like
18066 10.2.3.128/26 some.host
18067 10.8.4.34/26 10.44.8.15
18069 You should not make use of this facility unless you really understand what you
18074 .option transport routers string&!! unset
18075 This option specifies the transport to be used when a router accepts an address
18076 and sets it up for delivery. A transport is never needed if a router is used
18077 only for verification. The value of the option is expanded at routing time,
18078 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
18079 and result must be the name of one of the configured transports. If it is not,
18080 delivery is deferred.
18082 The &%transport%& option is not used by the &(redirect)& router, but it does
18083 have some private options that set up transports for pipe and file deliveries
18084 (see chapter &<<CHAPredirect>>&).
18088 .option transport_current_directory routers string&!! unset
18089 .cindex "current directory for local transport"
18090 This option associates a current directory with any address that is routed
18091 to a local transport. This can happen either because a transport is
18092 explicitly configured for the router, or because it generates a delivery to a
18093 file or a pipe. During the delivery process (that is, at transport time), this
18094 option string is expanded and is set as the current directory, unless
18095 overridden by a setting on the transport.
18096 If the expansion fails for any reason, including forced failure, an error is
18097 logged, and delivery is deferred.
18098 See chapter &<<CHAPenvironment>>& for details of the local delivery
18104 .option transport_home_directory routers string&!! "see below"
18105 .cindex "home directory" "for local transport"
18106 This option associates a home directory with any address that is routed to a
18107 local transport. This can happen either because a transport is explicitly
18108 configured for the router, or because it generates a delivery to a file or a
18109 pipe. During the delivery process (that is, at transport time), the option
18110 string is expanded and is set as the home directory, unless overridden by a
18111 setting of &%home_directory%& on the transport.
18112 If the expansion fails for any reason, including forced failure, an error is
18113 logged, and delivery is deferred.
18115 If the transport does not specify a home directory, and
18116 &%transport_home_directory%& is not set for the router, the home directory for
18117 the transport is taken from the password data if &%check_local_user%& is set for
18118 the router. Otherwise it is taken from &%router_home_directory%& if that option
18119 is set; if not, no home directory is set for the transport.
18121 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18127 .option unseen routers boolean&!! false
18128 .cindex "router" "carrying on after success"
18129 The result of string expansion for this option must be a valid boolean value,
18130 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18131 result causes an error, and delivery is deferred. If the expansion is forced to
18132 fail, the default value for the option (false) is used. Other failures cause
18133 delivery to be deferred.
18135 When this option is set true, routing does not cease if the router accepts the
18136 address. Instead, a copy of the incoming address is passed to the next router,
18137 overriding a false setting of &%more%&. There is little point in setting
18138 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18139 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18140 sometimes true and sometimes false).
18142 .cindex "copy of message (&%unseen%& option)"
18143 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18144 qualifier in filter files. It can be used to cause copies of messages to be
18145 delivered to some other destination, while also carrying out a normal delivery.
18146 In effect, the current address is made into a &"parent"& that has two children
18147 &-- one that is delivered as specified by this router, and a clone that goes on
18148 to be routed further. For this reason, &%unseen%& may not be combined with the
18149 &%one_time%& option in a &(redirect)& router.
18151 &*Warning*&: Header lines added to the address (or specified for removal) by
18152 this router or by previous routers affect the &"unseen"& copy of the message
18153 only. The clone that continues to be processed by further routers starts with
18154 no added headers and none specified for removal. For a &%redirect%& router, if
18155 a generated address is the same as the incoming address, this can lead to
18156 duplicate addresses with different header modifications. Exim does not do
18157 duplicate deliveries (except, in certain circumstances, to pipes -- see section
18158 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
18159 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
18160 &%redirect%& router may be of help.
18162 Unlike the handling of header modifications, any data that was set by the
18163 &%address_data%& option in the current or previous routers &'is'& passed on to
18164 subsequent routers.
18167 .option user routers string&!! "see below"
18168 .cindex "uid (user id)" "local delivery"
18169 .cindex "local transports" "uid and gid"
18170 .cindex "transport" "local"
18171 .cindex "router" "user for filter processing"
18172 .cindex "filter" "user for processing"
18173 When a router queues an address for a transport, and the transport does not
18174 specify a user, the user given here is used when running the delivery process.
18175 The user may be specified numerically or by name. If expansion fails, the
18176 error is logged and delivery is deferred.
18177 This user is also used by the &(redirect)& router when running a filter file.
18178 The default is unset, except when &%check_local_user%& is set. In this case,
18179 the default is taken from the password information. If the user is specified as
18180 a name, and &%group%& is not set, the group associated with the user is used.
18181 See also &%initgroups%& and &%group%& and the discussion in chapter
18182 &<<CHAPenvironment>>&.
18186 .option verify routers&!? boolean true
18187 Setting this option has the effect of setting &%verify_sender%& and
18188 &%verify_recipient%& to the same value.
18191 .option verify_only routers&!? boolean false
18192 .cindex "EXPN" "with &%verify_only%&"
18194 .cindex "router" "used only when verifying"
18195 If this option is set, the router is used only when verifying an address,
18196 delivering in cutthrough mode or
18197 testing with the &%-bv%& option, not when actually doing a delivery, testing
18198 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
18199 restricted to verifying only senders or recipients by means of
18200 &%verify_sender%& and &%verify_recipient%&.
18202 &*Warning*&: When the router is being run to verify addresses for an incoming
18203 SMTP message, Exim is not running as root, but under its own uid. If the router
18204 accesses any files, you need to make sure that they are accessible to the Exim
18208 .option verify_recipient routers&!? boolean true
18209 If this option is false, the router is skipped when verifying recipient
18211 delivering in cutthrough mode
18212 or testing recipient verification using &%-bv%&.
18213 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18215 See also the &$verify_mode$& variable.
18218 .option verify_sender routers&!? boolean true
18219 If this option is false, the router is skipped when verifying sender addresses
18220 or testing sender verification using &%-bvs%&.
18221 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18223 See also the &$verify_mode$& variable.
18224 .ecindex IIDgenoprou1
18225 .ecindex IIDgenoprou2
18232 . ////////////////////////////////////////////////////////////////////////////
18233 . ////////////////////////////////////////////////////////////////////////////
18235 .chapter "The accept router" "CHID4"
18236 .cindex "&(accept)& router"
18237 .cindex "routers" "&(accept)&"
18238 The &(accept)& router has no private options of its own. Unless it is being
18239 used purely for verification (see &%verify_only%&) a transport is required to
18240 be defined by the generic &%transport%& option. If the preconditions that are
18241 specified by generic options are met, the router accepts the address and queues
18242 it for the given transport. The most common use of this router is for setting
18243 up deliveries to local mailboxes. For example:
18247 domains = mydomain.example
18249 transport = local_delivery
18251 The &%domains%& condition in this example checks the domain of the address, and
18252 &%check_local_user%& checks that the local part is the login of a local user.
18253 When both preconditions are met, the &(accept)& router runs, and queues the
18254 address for the &(local_delivery)& transport.
18261 . ////////////////////////////////////////////////////////////////////////////
18262 . ////////////////////////////////////////////////////////////////////////////
18264 .chapter "The dnslookup router" "CHAPdnslookup"
18265 .scindex IIDdnsrou1 "&(dnslookup)& router"
18266 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
18267 The &(dnslookup)& router looks up the hosts that handle mail for the
18268 recipient's domain in the DNS. A transport must always be set for this router,
18269 unless &%verify_only%& is set.
18271 If SRV support is configured (see &%check_srv%& below), Exim first searches for
18272 SRV records. If none are found, or if SRV support is not configured,
18273 MX records are looked up. If no MX records exist, address records are sought.
18274 However, &%mx_domains%& can be set to disable the direct use of address
18277 MX records of equal priority are sorted by Exim into a random order. Exim then
18278 looks for address records for the host names obtained from MX or SRV records.
18279 When a host has more than one IP address, they are sorted into a random order,
18280 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
18281 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
18282 generic option, the router declines.
18284 Unless they have the highest priority (lowest MX value), MX records that point
18285 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
18286 are discarded, together with any other MX records of equal or lower priority.
18288 .cindex "MX record" "pointing to local host"
18289 .cindex "local host" "MX pointing to"
18290 .oindex "&%self%&" "in &(dnslookup)& router"
18291 If the host pointed to by the highest priority MX record, or looked up as an
18292 address record, is the local host, or matches &%hosts_treat_as_local%&, what
18293 happens is controlled by the generic &%self%& option.
18296 .section "Problems with DNS lookups" "SECTprowitdnsloo"
18297 There have been problems with DNS servers when SRV records are looked up.
18298 Some misbehaving servers return a DNS error or timeout when a non-existent
18299 SRV record is sought. Similar problems have in the past been reported for
18300 MX records. The global &%dns_again_means_nonexist%& option can help with this
18301 problem, but it is heavy-handed because it is a global option.
18303 For this reason, there are two options, &%srv_fail_domains%& and
18304 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
18305 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
18306 an attempt to look up an SRV or MX record causes one of these results, and the
18307 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
18308 such record"&. In the case of an SRV lookup, this means that the router
18309 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
18310 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
18311 case routing fails.
18314 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
18315 .cindex "&(dnslookup)& router" "declines"
18316 There are a few cases where a &(dnslookup)& router will decline to accept
18317 an address; if such a router is expected to handle "all remaining non-local
18318 domains", then it is important to set &%no_more%&.
18320 The router will defer rather than decline if the domain
18321 is found in the &%fail_defer_domains%& router option.
18323 Reasons for a &(dnslookup)& router to decline currently include:
18325 The domain does not exist in DNS
18327 The domain exists but the MX record's host part is just "."; this is a common
18328 convention (borrowed from SRV) used to indicate that there is no such service
18329 for this domain and to not fall back to trying A/AAAA records.
18331 Ditto, but for SRV records, when &%check_srv%& is set on this router.
18333 MX record points to a non-existent host.
18335 MX record points to an IP address and the main section option
18336 &%allow_mx_to_ip%& is not set.
18338 MX records exist and point to valid hosts, but all hosts resolve only to
18339 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
18341 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
18342 &%dns_check_names_pattern%& for handling one variant of this)
18344 &%check_secondary_mx%& is set on this router but the local host can
18345 not be found in the MX records (see below)
18351 .section "Private options for dnslookup" "SECID118"
18352 .cindex "options" "&(dnslookup)& router"
18353 The private options for the &(dnslookup)& router are as follows:
18355 .option check_secondary_mx dnslookup boolean false
18356 .cindex "MX record" "checking for secondary"
18357 If this option is set, the router declines unless the local host is found in
18358 (and removed from) the list of hosts obtained by MX lookup. This can be used to
18359 process domains for which the local host is a secondary mail exchanger
18360 differently to other domains. The way in which Exim decides whether a host is
18361 the local host is described in section &<<SECTreclocipadd>>&.
18364 .option check_srv dnslookup string&!! unset
18365 .cindex "SRV record" "enabling use of"
18366 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
18367 addition to MX and address records. The support is disabled by default. To
18368 enable SRV support, set the &%check_srv%& option to the name of the service
18369 required. For example,
18373 looks for SRV records that refer to the normal smtp service. The option is
18374 expanded, so the service name can vary from message to message or address
18375 to address. This might be helpful if SRV records are being used for a
18376 submission service. If the expansion is forced to fail, the &%check_srv%&
18377 option is ignored, and the router proceeds to look for MX records in the
18380 When the expansion succeeds, the router searches first for SRV records for
18381 the given service (it assumes TCP protocol). A single SRV record with a
18382 host name that consists of just a single dot indicates &"no such service for
18383 this domain"&; if this is encountered, the router declines. If other kinds of
18384 SRV record are found, they are used to construct a host list for delivery
18385 according to the rules of RFC 2782. MX records are not sought in this case.
18387 When no SRV records are found, MX records (and address records) are sought in
18388 the traditional way. In other words, SRV records take precedence over MX
18389 records, just as MX records take precedence over address records. Note that
18390 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
18391 defined it. It is apparently believed that MX records are sufficient for email
18392 and that SRV records should not be used for this purpose. However, SRV records
18393 have an additional &"weight"& feature which some people might find useful when
18394 trying to split an SMTP load between hosts of different power.
18396 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
18397 when there is a DNS lookup error.
18402 .option fail_defer_domains dnslookup "domain list&!!" unset
18403 .cindex "MX record" "not found"
18404 DNS lookups for domains matching &%fail_defer_domains%&
18405 which find no matching record will cause the router to defer
18406 rather than the default behaviour of decline.
18407 This maybe be useful for queueing messages for a newly created
18408 domain while the DNS configuration is not ready.
18409 However, it will result in any message with mistyped domains
18413 .option mx_domains dnslookup "domain list&!!" unset
18414 .cindex "MX record" "required to exist"
18415 .cindex "SRV record" "required to exist"
18416 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
18417 record in order to be recognized. (The name of this option could be improved.)
18418 For example, if all the mail hosts in &'fict.example'& are known to have MX
18419 records, except for those in &'discworld.fict.example'&, you could use this
18422 mx_domains = ! *.discworld.fict.example : *.fict.example
18424 This specifies that messages addressed to a domain that matches the list but
18425 has no MX record should be bounced immediately instead of being routed using
18426 the address record.
18429 .option mx_fail_domains dnslookup "domain list&!!" unset
18430 If the DNS lookup for MX records for one of the domains in this list causes a
18431 DNS lookup error, Exim behaves as if no MX records were found. See section
18432 &<<SECTprowitdnsloo>>& for more discussion.
18437 .option qualify_single dnslookup boolean true
18438 .cindex "DNS" "resolver options"
18439 .cindex "DNS" "qualifying single-component names"
18440 When this option is true, the resolver option RES_DEFNAMES is set for DNS
18441 lookups. Typically, but not standardly, this causes the resolver to qualify
18442 single-component names with the default domain. For example, on a machine
18443 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
18444 &'thesaurus.ref.example'& inside the resolver. For details of what your
18445 resolver actually does, consult your man pages for &'resolver'& and
18450 .option rewrite_headers dnslookup boolean true
18451 .cindex "rewriting" "header lines"
18452 .cindex "header lines" "rewriting"
18453 If the domain name in the address that is being processed is not fully
18454 qualified, it may be expanded to its full form by a DNS lookup. For example, if
18455 an address is specified as &'dormouse@teaparty'&, the domain might be
18456 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
18457 occur as a result of setting the &%widen_domains%& option. If
18458 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
18459 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
18460 header lines of the message are rewritten with the full domain name.
18462 This option should be turned off only when it is known that no message is
18463 ever going to be sent outside an environment where the abbreviation makes
18466 When an MX record is looked up in the DNS and matches a wildcard record, name
18467 servers normally return a record containing the name that has been looked up,
18468 making it impossible to detect whether a wildcard was present or not. However,
18469 some name servers have recently been seen to return the wildcard entry. If the
18470 name returned by a DNS lookup begins with an asterisk, it is not used for
18474 .option same_domain_copy_routing dnslookup boolean false
18475 .cindex "address" "copying routing"
18476 Addresses with the same domain are normally routed by the &(dnslookup)& router
18477 to the same list of hosts. However, this cannot be presumed, because the router
18478 options and preconditions may refer to the local part of the address. By
18479 default, therefore, Exim routes each address in a message independently. DNS
18480 servers run caches, so repeated DNS lookups are not normally expensive, and in
18481 any case, personal messages rarely have more than a few recipients.
18483 If you are running mailing lists with large numbers of subscribers at the same
18484 domain, and you are using a &(dnslookup)& router which is independent of the
18485 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18486 lookups for identical domains in one message. In this case, when &(dnslookup)&
18487 routes an address to a remote transport, any other unrouted addresses in the
18488 message that have the same domain are automatically given the same routing
18489 without processing them independently,
18490 provided the following conditions are met:
18493 No router that processed the address specified &%headers_add%& or
18494 &%headers_remove%&.
18496 The router did not change the address in any way, for example, by &"widening"&
18503 .option search_parents dnslookup boolean false
18504 .cindex "DNS" "resolver options"
18505 When this option is true, the resolver option RES_DNSRCH is set for DNS
18506 lookups. This is different from the &%qualify_single%& option in that it
18507 applies to domains containing dots. Typically, but not standardly, it causes
18508 the resolver to search for the name in the current domain and in parent
18509 domains. For example, on a machine in the &'fict.example'& domain, if looking
18510 up &'teaparty.wonderland'& failed, the resolver would try
18511 &'teaparty.wonderland.fict.example'&. For details of what your resolver
18512 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
18514 Setting this option true can cause problems in domains that have a wildcard MX
18515 record, because any domain that does not have its own MX record matches the
18520 .option srv_fail_domains dnslookup "domain list&!!" unset
18521 If the DNS lookup for SRV records for one of the domains in this list causes a
18522 DNS lookup error, Exim behaves as if no SRV records were found. See section
18523 &<<SECTprowitdnsloo>>& for more discussion.
18528 .option widen_domains dnslookup "string list" unset
18529 .cindex "domain" "partial; widening"
18530 If a DNS lookup fails and this option is set, each of its strings in turn is
18531 added onto the end of the domain, and the lookup is tried again. For example,
18534 widen_domains = fict.example:ref.example
18536 is set and a lookup of &'klingon.dictionary'& fails,
18537 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
18538 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
18539 and &%search_parents%& options can cause some widening to be undertaken inside
18540 the DNS resolver. &%widen_domains%& is not applied to sender addresses
18541 when verifying, unless &%rewrite_headers%& is false (not the default).
18544 .section "Effect of qualify_single and search_parents" "SECID119"
18545 When a domain from an envelope recipient is changed by the resolver as a result
18546 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
18547 corresponding address in the message's header lines unless &%rewrite_headers%&
18548 is set false. Exim then re-routes the address, using the full domain.
18550 These two options affect only the DNS lookup that takes place inside the router
18551 for the domain of the address that is being routed. They do not affect lookups
18552 such as that implied by
18556 that may happen while processing a router precondition before the router is
18557 entered. No widening ever takes place for these lookups.
18558 .ecindex IIDdnsrou1
18559 .ecindex IIDdnsrou2
18569 . ////////////////////////////////////////////////////////////////////////////
18570 . ////////////////////////////////////////////////////////////////////////////
18572 .chapter "The ipliteral router" "CHID5"
18573 .cindex "&(ipliteral)& router"
18574 .cindex "domain literal" "routing"
18575 .cindex "routers" "&(ipliteral)&"
18576 This router has no private options. Unless it is being used purely for
18577 verification (see &%verify_only%&) a transport is required to be defined by the
18578 generic &%transport%& option. The router accepts the address if its domain part
18579 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
18580 router handles the address
18584 by setting up delivery to the host with that IP address. IPv4 domain literals
18585 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
18586 are similar, but the address is preceded by &`ipv6:`&. For example:
18588 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
18590 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
18591 grounds that sooner or later somebody will try it.
18593 .oindex "&%self%&" "in &(ipliteral)& router"
18594 If the IP address matches something in &%ignore_target_hosts%&, the router
18595 declines. If an IP literal turns out to refer to the local host, the generic
18596 &%self%& option determines what happens.
18598 The RFCs require support for domain literals; however, their use is
18599 controversial in today's Internet. If you want to use this router, you must
18600 also set the main configuration option &%allow_domain_literals%&. Otherwise,
18601 Exim will not recognize the domain literal syntax in addresses.
18605 . ////////////////////////////////////////////////////////////////////////////
18606 . ////////////////////////////////////////////////////////////////////////////
18608 .chapter "The iplookup router" "CHID6"
18609 .cindex "&(iplookup)& router"
18610 .cindex "routers" "&(iplookup)&"
18611 The &(iplookup)& router was written to fulfil a specific requirement in
18612 Cambridge University (which in fact no longer exists). For this reason, it is
18613 not included in the binary of Exim by default. If you want to include it, you
18616 ROUTER_IPLOOKUP=yes
18618 in your &_Local/Makefile_& configuration file.
18620 The &(iplookup)& router routes an address by sending it over a TCP or UDP
18621 connection to one or more specific hosts. The host can then return the same or
18622 a different address &-- in effect rewriting the recipient address in the
18623 message's envelope. The new address is then passed on to subsequent routers. If
18624 this process fails, the address can be passed on to other routers, or delivery
18625 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
18626 must not be specified for it.
18628 .cindex "options" "&(iplookup)& router"
18629 .option hosts iplookup string unset
18630 This option must be supplied. Its value is a colon-separated list of host
18631 names. The hosts are looked up using &[gethostbyname()]&
18632 (or &[getipnodebyname()]& when available)
18633 and are tried in order until one responds to the query. If none respond, what
18634 happens is controlled by &%optional%&.
18637 .option optional iplookup boolean false
18638 If &%optional%& is true, if no response is obtained from any host, the address
18639 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
18640 delivery to the address is deferred.
18643 .option port iplookup integer 0
18644 .cindex "port" "&(iplookup)& router"
18645 This option must be supplied. It specifies the port number for the TCP or UDP
18649 .option protocol iplookup string udp
18650 This option can be set to &"udp"& or &"tcp"& to specify which of the two
18651 protocols is to be used.
18654 .option query iplookup string&!! "see below"
18655 This defines the content of the query that is sent to the remote hosts. The
18658 $local_part@$domain $local_part@$domain
18660 The repetition serves as a way of checking that a response is to the correct
18661 query in the default case (see &%response_pattern%& below).
18664 .option reroute iplookup string&!! unset
18665 If this option is not set, the rerouted address is precisely the byte string
18666 returned by the remote host, up to the first white space, if any. If set, the
18667 string is expanded to form the rerouted address. It can include parts matched
18668 in the response by &%response_pattern%& by means of numeric variables such as
18669 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
18670 whether or not a pattern is in use. In all cases, the rerouted address must end
18671 up in the form &'local_part@domain'&.
18674 .option response_pattern iplookup string unset
18675 This option can be set to a regular expression that is applied to the string
18676 returned from the remote host. If the pattern does not match the response, the
18677 router declines. If &%response_pattern%& is not set, no checking of the
18678 response is done, unless the query was defaulted, in which case there is a
18679 check that the text returned after the first white space is the original
18680 address. This checks that the answer that has been received is in response to
18681 the correct question. For example, if the response is just a new domain, the
18682 following could be used:
18684 response_pattern = ^([^@]+)$
18685 reroute = $local_part@$1
18688 .option timeout iplookup time 5s
18689 This specifies the amount of time to wait for a response from the remote
18690 machine. The same timeout is used for the &[connect()]& function for a TCP
18691 call. It does not apply to UDP.
18696 . ////////////////////////////////////////////////////////////////////////////
18697 . ////////////////////////////////////////////////////////////////////////////
18699 .chapter "The manualroute router" "CHID7"
18700 .scindex IIDmanrou1 "&(manualroute)& router"
18701 .scindex IIDmanrou2 "routers" "&(manualroute)&"
18702 .cindex "domain" "manually routing"
18703 The &(manualroute)& router is so-called because it provides a way of manually
18704 routing an address according to its domain. It is mainly used when you want to
18705 route addresses to remote hosts according to your own rules, bypassing the
18706 normal DNS routing that looks up MX records. However, &(manualroute)& can also
18707 route to local transports, a facility that may be useful if you want to save
18708 messages for dial-in hosts in local files.
18710 The &(manualroute)& router compares a list of domain patterns with the domain
18711 it is trying to route. If there is no match, the router declines. Each pattern
18712 has associated with it a list of hosts and some other optional data, which may
18713 include a transport. The combination of a pattern and its data is called a
18714 &"routing rule"&. For patterns that do not have an associated transport, the
18715 generic &%transport%& option must specify a transport, unless the router is
18716 being used purely for verification (see &%verify_only%&).
18719 In the case of verification, matching the domain pattern is sufficient for the
18720 router to accept the address. When actually routing an address for delivery,
18721 an address that matches a domain pattern is queued for the associated
18722 transport. If the transport is not a local one, a host list must be associated
18723 with the pattern; IP addresses are looked up for the hosts, and these are
18724 passed to the transport along with the mail address. For local transports, a
18725 host list is optional. If it is present, it is passed in &$host$& as a single
18728 The list of routing rules can be provided as an inline string in
18729 &%route_list%&, or the data can be obtained by looking up the domain in a file
18730 or database by setting &%route_data%&. Only one of these settings may appear in
18731 any one instance of &(manualroute)&. The format of routing rules is described
18732 below, following the list of private options.
18735 .section "Private options for manualroute" "SECTprioptman"
18737 .cindex "options" "&(manualroute)& router"
18738 The private options for the &(manualroute)& router are as follows:
18740 .option host_all_ignored manualroute string defer
18741 See &%host_find_failed%&.
18743 .option host_find_failed manualroute string freeze
18744 This option controls what happens when &(manualroute)& tries to find an IP
18745 address for a host, and the host does not exist. The option can be set to one
18746 of the following values:
18755 The default (&"freeze"&) assumes that this state is a serious configuration
18756 error. The difference between &"pass"& and &"decline"& is that the former
18757 forces the address to be passed to the next router (or the router defined by
18760 overriding &%no_more%&, whereas the latter passes the address to the next
18761 router only if &%more%& is true.
18763 The value &"ignore"& causes Exim to completely ignore a host whose IP address
18764 cannot be found. If all the hosts in the list are ignored, the behaviour is
18765 controlled by the &%host_all_ignored%& option. This takes the same values
18766 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
18768 The &%host_find_failed%& option applies only to a definite &"does not exist"&
18769 state; if a host lookup gets a temporary error, delivery is deferred unless the
18770 generic &%pass_on_timeout%& option is set.
18773 .option hosts_randomize manualroute boolean false
18774 .cindex "randomized host list"
18775 .cindex "host" "list of; randomized"
18776 If this option is set, the order of the items in a host list in a routing rule
18777 is randomized each time the list is used, unless an option in the routing rule
18778 overrides (see below). Randomizing the order of a host list can be used to do
18779 crude load sharing. However, if more than one mail address is routed by the
18780 same router to the same host list, the host lists are considered to be the same
18781 (even though they may be randomized into different orders) for the purpose of
18782 deciding whether to batch the deliveries into a single SMTP transaction.
18784 When &%hosts_randomize%& is true, a host list may be split
18785 into groups whose order is separately randomized. This makes it possible to
18786 set up MX-like behaviour. The boundaries between groups are indicated by an
18787 item that is just &`+`& in the host list. For example:
18789 route_list = * host1:host2:host3:+:host4:host5
18791 The order of the first three hosts and the order of the last two hosts is
18792 randomized for each use, but the first three always end up before the last two.
18793 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
18794 randomized host list is passed to an &(smtp)& transport that also has
18795 &%hosts_randomize set%&, the list is not re-randomized.
18798 .option route_data manualroute string&!! unset
18799 If this option is set, it must expand to yield the data part of a routing rule.
18800 Typically, the expansion string includes a lookup based on the domain. For
18803 route_data = ${lookup{$domain}dbm{/etc/routes}}
18805 If the expansion is forced to fail, or the result is an empty string, the
18806 router declines. Other kinds of expansion failure cause delivery to be
18810 .option route_list manualroute "string list" unset
18811 This string is a list of routing rules, in the form defined below. Note that,
18812 unlike most string lists, the items are separated by semicolons. This is so
18813 that they may contain colon-separated host lists.
18816 .option same_domain_copy_routing manualroute boolean false
18817 .cindex "address" "copying routing"
18818 Addresses with the same domain are normally routed by the &(manualroute)&
18819 router to the same list of hosts. However, this cannot be presumed, because the
18820 router options and preconditions may refer to the local part of the address. By
18821 default, therefore, Exim routes each address in a message independently. DNS
18822 servers run caches, so repeated DNS lookups are not normally expensive, and in
18823 any case, personal messages rarely have more than a few recipients.
18825 If you are running mailing lists with large numbers of subscribers at the same
18826 domain, and you are using a &(manualroute)& router which is independent of the
18827 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18828 lookups for identical domains in one message. In this case, when
18829 &(manualroute)& routes an address to a remote transport, any other unrouted
18830 addresses in the message that have the same domain are automatically given the
18831 same routing without processing them independently. However, this is only done
18832 if &%headers_add%& and &%headers_remove%& are unset.
18837 .section "Routing rules in route_list" "SECID120"
18838 The value of &%route_list%& is a string consisting of a sequence of routing
18839 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
18840 entered as two semicolons. Alternatively, the list separator can be changed as
18841 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
18842 Empty rules are ignored. The format of each rule is
18844 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
18846 The following example contains two rules, each with a simple domain pattern and
18850 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
18851 thes.ref.example mail-3.ref.example:mail-4.ref.example
18853 The three parts of a rule are separated by white space. The pattern and the
18854 list of hosts can be enclosed in quotes if necessary, and if they are, the
18855 usual quoting rules apply. Each rule in a &%route_list%& must start with a
18856 single domain pattern, which is the only mandatory item in the rule. The
18857 pattern is in the same format as one item in a domain list (see section
18858 &<<SECTdomainlist>>&),
18859 except that it may not be the name of an interpolated file.
18860 That is, it may be wildcarded, or a regular expression, or a file or database
18861 lookup (with semicolons doubled, because of the use of semicolon as a separator
18862 in a &%route_list%&).
18864 The rules in &%route_list%& are searched in order until one of the patterns
18865 matches the domain that is being routed. The list of hosts and then options are
18866 then used as described below. If there is no match, the router declines. When
18867 &%route_list%& is set, &%route_data%& must not be set.
18871 .section "Routing rules in route_data" "SECID121"
18872 The use of &%route_list%& is convenient when there are only a small number of
18873 routing rules. For larger numbers, it is easier to use a file or database to
18874 hold the routing information, and use the &%route_data%& option instead.
18875 The value of &%route_data%& is a list of hosts, followed by (optional) options.
18876 Most commonly, &%route_data%& is set as a string that contains an
18877 expansion lookup. For example, suppose we place two routing rules in a file
18880 dict.ref.example: mail-1.ref.example:mail-2.ref.example
18881 thes.ref.example: mail-3.ref.example:mail-4.ref.example
18883 This data can be accessed by setting
18885 route_data = ${lookup{$domain}lsearch{/the/file/name}}
18887 Failure of the lookup results in an empty string, causing the router to
18888 decline. However, you do not have to use a lookup in &%route_data%&. The only
18889 requirement is that the result of expanding the string is a list of hosts,
18890 possibly followed by options, separated by white space. The list of hosts must
18891 be enclosed in quotes if it contains white space.
18896 .section "Format of the list of hosts" "SECID122"
18897 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
18898 always separately expanded before use. If the expansion fails, the router
18899 declines. The result of the expansion must be a colon-separated list of names
18900 and/or IP addresses, optionally also including ports. The format of each item
18901 in the list is described in the next section. The list separator can be changed
18902 as described in section &<<SECTlistconstruct>>&.
18904 If the list of hosts was obtained from a &%route_list%& item, the following
18905 variables are set during its expansion:
18908 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
18909 If the domain was matched against a regular expression, the numeric variables
18910 &$1$&, &$2$&, etc. may be set. For example:
18912 route_list = ^domain(\d+) host-$1.text.example
18915 &$0$& is always set to the entire domain.
18917 &$1$& is also set when partial matching is done in a file lookup.
18920 .vindex "&$value$&"
18921 If the pattern that matched the domain was a lookup item, the data that was
18922 looked up is available in the expansion variable &$value$&. For example:
18924 route_list = lsearch;;/some/file.routes $value
18928 Note the doubling of the semicolon in the pattern that is necessary because
18929 semicolon is the default route list separator.
18933 .section "Format of one host item" "SECTformatonehostitem"
18934 Each item in the list of hosts is either a host name or an IP address,
18935 optionally with an attached port number. When no port is given, an IP address
18936 is not enclosed in brackets. When a port is specified, it overrides the port
18937 specification on the transport. The port is separated from the name or address
18938 by a colon. This leads to some complications:
18941 Because colon is the default separator for the list of hosts, either
18942 the colon that specifies a port must be doubled, or the list separator must
18943 be changed. The following two examples have the same effect:
18945 route_list = * "host1.tld::1225 : host2.tld::1226"
18946 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
18949 When IPv6 addresses are involved, it gets worse, because they contain
18950 colons of their own. To make this case easier, it is permitted to
18951 enclose an IP address (either v4 or v6) in square brackets if a port
18952 number follows. For example:
18954 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
18958 .section "How the list of hosts is used" "SECThostshowused"
18959 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
18960 the hosts is tried, in the order specified, when carrying out the SMTP
18961 delivery. However, the order can be changed by setting the &%hosts_randomize%&
18962 option, either on the router (see section &<<SECTprioptman>>& above), or on the
18965 Hosts may be listed by name or by IP address. An unadorned name in the list of
18966 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
18967 interpreted as an indirection to a sublist of hosts obtained by looking up MX
18968 records in the DNS. For example:
18970 route_list = * x.y.z:p.q.r/MX:e.f.g
18972 If this feature is used with a port specifier, the port must come last. For
18975 route_list = * dom1.tld/mx::1225
18977 If the &%hosts_randomize%& option is set, the order of the items in the list is
18978 randomized before any lookups are done. Exim then scans the list; for any name
18979 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
18980 be an interface on the local host and the item is not the first in the list,
18981 Exim discards it and any subsequent items. If it is the first item, what
18982 happens is controlled by the
18983 .oindex "&%self%&" "in &(manualroute)& router"
18984 &%self%& option of the router.
18986 A name on the list that is followed by &`/MX`& is replaced with the list of
18987 hosts obtained by looking up MX records for the name. This is always a DNS
18988 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
18989 below) are not relevant here. The order of these hosts is determined by the
18990 preference values in the MX records, according to the usual rules. Because
18991 randomizing happens before the MX lookup, it does not affect the order that is
18992 defined by MX preferences.
18994 If the local host is present in the sublist obtained from MX records, but is
18995 not the most preferred host in that list, it and any equally or less
18996 preferred hosts are removed before the sublist is inserted into the main list.
18998 If the local host is the most preferred host in the MX list, what happens
18999 depends on where in the original list of hosts the &`/MX`& item appears. If it
19000 is not the first item (that is, there are previous hosts in the main list),
19001 Exim discards this name and any subsequent items in the main list.
19003 If the MX item is first in the list of hosts, and the local host is the
19004 most preferred host, what happens is controlled by the &%self%& option of the
19007 DNS failures when lookup up the MX records are treated in the same way as DNS
19008 failures when looking up IP addresses: &%pass_on_timeout%& and
19009 &%host_find_failed%& are used when relevant.
19011 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
19012 whether obtained from an MX lookup or not.
19016 .section "How the options are used" "SECThowoptused"
19017 The options are a sequence of words; in practice no more than three are ever
19018 present. One of the words can be the name of a transport; this overrides the
19019 &%transport%& option on the router for this particular routing rule only. The
19020 other words (if present) control randomization of the list of hosts on a
19021 per-rule basis, and how the IP addresses of the hosts are to be found when
19022 routing to a remote transport. These options are as follows:
19025 &%randomize%&: randomize the order of the hosts in this list, overriding the
19026 setting of &%hosts_randomize%& for this routing rule only.
19028 &%no_randomize%&: do not randomize the order of the hosts in this list,
19029 overriding the setting of &%hosts_randomize%& for this routing rule only.
19031 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
19032 find IP addresses. This function may ultimately cause a DNS lookup, but it may
19033 also look in &_/etc/hosts_& or other sources of information.
19035 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
19036 no address records are found. If there is a temporary DNS error (such as a
19037 timeout), delivery is deferred.
19042 route_list = domain1 host1:host2:host3 randomize bydns;\
19043 domain2 host4:host5
19045 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
19046 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
19047 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
19048 or &[gethostbyname()]&, and the result of the lookup is the result of that
19051 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
19052 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
19053 instead of TRY_AGAIN. That is why the default action is to try a DNS
19054 lookup first. Only if that gives a definite &"no such host"& is the local
19059 If no IP address for a host can be found, what happens is controlled by the
19060 &%host_find_failed%& option.
19063 When an address is routed to a local transport, IP addresses are not looked up.
19064 The host list is passed to the transport in the &$host$& variable.
19068 .section "Manualroute examples" "SECID123"
19069 In some of the examples that follow, the presence of the &%remote_smtp%&
19070 transport, as defined in the default configuration file, is assumed:
19073 .cindex "smart host" "example router"
19074 The &(manualroute)& router can be used to forward all external mail to a
19075 &'smart host'&. If you have set up, in the main part of the configuration, a
19076 named domain list that contains your local domains, for example:
19078 domainlist local_domains = my.domain.example
19080 You can arrange for all other domains to be routed to a smart host by making
19081 your first router something like this:
19084 driver = manualroute
19085 domains = !+local_domains
19086 transport = remote_smtp
19087 route_list = * smarthost.ref.example
19089 This causes all non-local addresses to be sent to the single host
19090 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19091 they are tried in order
19092 (but you can use &%hosts_randomize%& to vary the order each time).
19093 Another way of configuring the same thing is this:
19096 driver = manualroute
19097 transport = remote_smtp
19098 route_list = !+local_domains smarthost.ref.example
19100 There is no difference in behaviour between these two routers as they stand.
19101 However, they behave differently if &%no_more%& is added to them. In the first
19102 example, the router is skipped if the domain does not match the &%domains%&
19103 precondition; the following router is always tried. If the router runs, it
19104 always matches the domain and so can never decline. Therefore, &%no_more%&
19105 would have no effect. In the second case, the router is never skipped; it
19106 always runs. However, if it doesn't match the domain, it declines. In this case
19107 &%no_more%& would prevent subsequent routers from running.
19110 .cindex "mail hub example"
19111 A &'mail hub'& is a host which receives mail for a number of domains via MX
19112 records in the DNS and delivers it via its own private routing mechanism. Often
19113 the final destinations are behind a firewall, with the mail hub being the one
19114 machine that can connect to machines both inside and outside the firewall. The
19115 &(manualroute)& router is usually used on a mail hub to route incoming messages
19116 to the correct hosts. For a small number of domains, the routing can be inline,
19117 using the &%route_list%& option, but for a larger number a file or database
19118 lookup is easier to manage.
19120 If the domain names are in fact the names of the machines to which the mail is
19121 to be sent by the mail hub, the configuration can be quite simple. For
19125 driver = manualroute
19126 transport = remote_smtp
19127 route_list = *.rhodes.tvs.example $domain
19129 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
19130 whose names are the same as the mail domains. A similar approach can be taken
19131 if the host name can be obtained from the domain name by a string manipulation
19132 that the expansion facilities can handle. Otherwise, a lookup based on the
19133 domain can be used to find the host:
19136 driver = manualroute
19137 transport = remote_smtp
19138 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
19140 The result of the lookup must be the name or IP address of the host (or
19141 hosts) to which the address is to be routed. If the lookup fails, the route
19142 data is empty, causing the router to decline. The address then passes to the
19146 .cindex "batched SMTP output example"
19147 .cindex "SMTP" "batched outgoing; example"
19148 You can use &(manualroute)& to deliver messages to pipes or files in batched
19149 SMTP format for onward transportation by some other means. This is one way of
19150 storing mail for a dial-up host when it is not connected. The route list entry
19151 can be as simple as a single domain name in a configuration like this:
19154 driver = manualroute
19155 transport = batchsmtp_appendfile
19156 route_list = saved.domain.example
19158 though often a pattern is used to pick up more than one domain. If there are
19159 several domains or groups of domains with different transport requirements,
19160 different transports can be listed in the routing information:
19163 driver = manualroute
19165 *.saved.domain1.example $domain batch_appendfile; \
19166 *.saved.domain2.example \
19167 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
19170 .vindex "&$domain$&"
19172 The first of these just passes the domain in the &$host$& variable, which
19173 doesn't achieve much (since it is also in &$domain$&), but the second does a
19174 file lookup to find a value to pass, causing the router to decline to handle
19175 the address if the lookup fails.
19178 .cindex "UUCP" "example of router for"
19179 Routing mail directly to UUCP software is a specific case of the use of
19180 &(manualroute)& in a gateway to another mail environment. This is an example of
19181 one way it can be done:
19187 command = /usr/local/bin/uux -r - \
19188 ${substr_-5:$host}!rmail ${local_part}
19189 return_fail_output = true
19194 driver = manualroute
19196 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
19198 The file &_/usr/local/exim/uucphosts_& contains entries like
19200 darksite.ethereal.example: darksite.UUCP
19202 It can be set up more simply without adding and removing &".UUCP"& but this way
19203 makes clear the distinction between the domain name
19204 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
19206 .ecindex IIDmanrou1
19207 .ecindex IIDmanrou2
19216 . ////////////////////////////////////////////////////////////////////////////
19217 . ////////////////////////////////////////////////////////////////////////////
19219 .chapter "The queryprogram router" "CHAPdriverlast"
19220 .scindex IIDquerou1 "&(queryprogram)& router"
19221 .scindex IIDquerou2 "routers" "&(queryprogram)&"
19222 .cindex "routing" "by external program"
19223 The &(queryprogram)& router routes an address by running an external command
19224 and acting on its output. This is an expensive way to route, and is intended
19225 mainly for use in lightly-loaded systems, or for performing experiments.
19226 However, if it is possible to use the precondition options (&%domains%&,
19227 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
19228 be used in special cases, even on a busy host. There are the following private
19230 .cindex "options" "&(queryprogram)& router"
19232 .option command queryprogram string&!! unset
19233 This option must be set. It specifies the command that is to be run. The
19234 command is split up into a command name and arguments, and then each is
19235 expanded separately (exactly as for a &(pipe)& transport, described in chapter
19236 &<<CHAPpipetransport>>&).
19239 .option command_group queryprogram string unset
19240 .cindex "gid (group id)" "in &(queryprogram)& router"
19241 This option specifies a gid to be set when running the command while routing an
19242 address for deliver. It must be set if &%command_user%& specifies a numerical
19243 uid. If it begins with a digit, it is interpreted as the numerical value of the
19244 gid. Otherwise it is looked up using &[getgrnam()]&.
19247 .option command_user queryprogram string unset
19248 .cindex "uid (user id)" "for &(queryprogram)&"
19249 This option must be set. It specifies the uid which is set when running the
19250 command while routing an address for delivery. If the value begins with a digit,
19251 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
19252 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
19253 not set, a value for the gid also.
19255 &*Warning:*& Changing uid and gid is possible only when Exim is running as
19256 root, which it does during a normal delivery in a conventional configuration.
19257 However, when an address is being verified during message reception, Exim is
19258 usually running as the Exim user, not as root. If the &(queryprogram)& router
19259 is called from a non-root process, Exim cannot change uid or gid before running
19260 the command. In this circumstance the command runs under the current uid and
19264 .option current_directory queryprogram string /
19265 This option specifies an absolute path which is made the current directory
19266 before running the command.
19269 .option timeout queryprogram time 1h
19270 If the command does not complete within the timeout period, its process group
19271 is killed and the message is frozen. A value of zero time specifies no
19275 The standard output of the command is connected to a pipe, which is read when
19276 the command terminates. It should consist of a single line of output,
19277 containing up to five fields, separated by white space. The maximum length of
19278 the line is 1023 characters. Longer lines are silently truncated. The first
19279 field is one of the following words (case-insensitive):
19282 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
19285 &'Decline'&: the router declines; pass the address to the next router, unless
19286 &%no_more%& is set.
19288 &'Fail'&: routing failed; do not pass the address to any more routers. Any
19289 subsequent text on the line is an error message. If the router is run as part
19290 of address verification during an incoming SMTP message, the message is
19291 included in the SMTP response.
19293 &'Defer'&: routing could not be completed at this time; try again later. Any
19294 subsequent text on the line is an error message which is logged. It is not
19295 included in any SMTP response.
19297 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
19299 &'Pass'&: pass the address to the next router (or the router specified by
19300 &%pass_router%&), overriding &%no_more%&.
19302 &'Redirect'&: the message is redirected. The remainder of the line is a list of
19303 new addresses, which are routed independently, starting with the first router,
19304 or the router specified by &%redirect_router%&, if set.
19307 When the first word is &'accept'&, the remainder of the line consists of a
19308 number of keyed data values, as follows (split into two lines here, to fit on
19311 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
19312 LOOKUP=byname|bydns DATA=<text>
19314 The data items can be given in any order, and all are optional. If no transport
19315 is included, the transport specified by the generic &%transport%& option is
19316 used. The list of hosts and the lookup type are needed only if the transport is
19317 an &(smtp)& transport that does not itself supply a list of hosts.
19319 The format of the list of hosts is the same as for the &(manualroute)& router.
19320 As well as host names and IP addresses with optional port numbers, as described
19321 in section &<<SECTformatonehostitem>>&, it may contain names followed by
19322 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
19323 (see section &<<SECThostshowused>>&).
19325 If the lookup type is not specified, Exim behaves as follows when trying to
19326 find an IP address for each host: First, a DNS lookup is done. If this yields
19327 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
19328 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
19329 result of the lookup is the result of that call.
19331 .vindex "&$address_data$&"
19332 If the DATA field is set, its value is placed in the &$address_data$&
19333 variable. For example, this return line
19335 accept hosts=x1.y.example:x2.y.example data="rule1"
19337 routes the address to the default transport, passing a list of two hosts. When
19338 the transport runs, the string &"rule1"& is in &$address_data$&.
19339 .ecindex IIDquerou1
19340 .ecindex IIDquerou2
19345 . ////////////////////////////////////////////////////////////////////////////
19346 . ////////////////////////////////////////////////////////////////////////////
19348 .chapter "The redirect router" "CHAPredirect"
19349 .scindex IIDredrou1 "&(redirect)& router"
19350 .scindex IIDredrou2 "routers" "&(redirect)&"
19351 .cindex "alias file" "in a &(redirect)& router"
19352 .cindex "address redirection" "&(redirect)& router"
19353 The &(redirect)& router handles several kinds of address redirection. Its most
19354 common uses are for resolving local part aliases from a central alias file
19355 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
19356 files, but it has many other potential uses. The incoming address can be
19357 redirected in several different ways:
19360 It can be replaced by one or more new addresses which are themselves routed
19363 It can be routed to be delivered to a given file or directory.
19365 It can be routed to be delivered to a specified pipe command.
19367 It can cause an automatic reply to be generated.
19369 It can be forced to fail, optionally with a custom error message.
19371 It can be temporarily deferred, optionally with a custom message.
19373 It can be discarded.
19376 The generic &%transport%& option must not be set for &(redirect)& routers.
19377 However, there are some private options which define transports for delivery to
19378 files and pipes, and for generating autoreplies. See the &%file_transport%&,
19379 &%pipe_transport%& and &%reply_transport%& descriptions below.
19381 If success DSNs have been requested
19382 .cindex "DSN" "success"
19383 .cindex "Delivery Status Notification" "success"
19384 redirection triggers one and the DSN options are not passed any further.
19388 .section "Redirection data" "SECID124"
19389 The router operates by interpreting a text string which it obtains either by
19390 expanding the contents of the &%data%& option, or by reading the entire
19391 contents of a file whose name is given in the &%file%& option. These two
19392 options are mutually exclusive. The first is commonly used for handling system
19393 aliases, in a configuration like this:
19397 data = ${lookup{$local_part}lsearch{/etc/aliases}}
19399 If the lookup fails, the expanded string in this example is empty. When the
19400 expansion of &%data%& results in an empty string, the router declines. A forced
19401 expansion failure also causes the router to decline; other expansion failures
19402 cause delivery to be deferred.
19404 A configuration using &%file%& is commonly used for handling users'
19405 &_.forward_& files, like this:
19410 file = $home/.forward
19413 If the file does not exist, or causes no action to be taken (for example, it is
19414 empty or consists only of comments), the router declines. &*Warning*&: This
19415 is not the case when the file contains syntactically valid items that happen to
19416 yield empty addresses, for example, items containing only RFC 2822 address
19421 .section "Forward files and address verification" "SECID125"
19422 .cindex "address redirection" "while verifying"
19423 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
19424 &_.forward_& files, as in the example above. There are two reasons for this:
19427 When Exim is receiving an incoming SMTP message from a remote host, it is
19428 running under the Exim uid, not as root. Exim is unable to change uid to read
19429 the file as the user, and it may not be able to read it as the Exim user. So in
19430 practice the router may not be able to operate.
19432 However, even when the router can operate, the existence of a &_.forward_& file
19433 is unimportant when verifying an address. What should be checked is whether the
19434 local part is a valid user name or not. Cutting out the redirection processing
19435 saves some resources.
19443 .section "Interpreting redirection data" "SECID126"
19444 .cindex "Sieve filter" "specifying in redirection data"
19445 .cindex "filter" "specifying in redirection data"
19446 The contents of the data string, whether obtained from &%data%& or &%file%&,
19447 can be interpreted in two different ways:
19450 If the &%allow_filter%& option is set true, and the data begins with the text
19451 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
19452 &'filtering'& instructions in the form of an Exim or Sieve filter file,
19453 respectively. Details of the syntax and semantics of filter files are described
19454 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
19455 document is intended for use by end users.
19457 Otherwise, the data must be a comma-separated list of redirection items, as
19458 described in the next section.
19461 When a message is redirected to a file (a &"mail folder"&), the file name given
19462 in a non-filter redirection list must always be an absolute path. A filter may
19463 generate a relative path &-- how this is handled depends on the transport's
19464 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
19465 for the &(appendfile)& transport.
19469 .section "Items in a non-filter redirection list" "SECTitenonfilred"
19470 .cindex "address redirection" "non-filter list items"
19471 When the redirection data is not an Exim or Sieve filter, for example, if it
19472 comes from a conventional alias or forward file, it consists of a list of
19473 addresses, file names, pipe commands, or certain special items (see section
19474 &<<SECTspecitredli>>& below). The special items can be individually enabled or
19475 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
19476 depending on their default values. The items in the list are separated by
19477 commas or newlines.
19478 If a comma is required in an item, the entire item must be enclosed in double
19481 Lines starting with a # character are comments, and are ignored, and # may
19482 also appear following a comma, in which case everything between the # and the
19483 next newline character is ignored.
19485 If an item is entirely enclosed in double quotes, these are removed. Otherwise
19486 double quotes are retained because some forms of mail address require their use
19487 (but never to enclose the entire address). In the following description,
19488 &"item"& refers to what remains after any surrounding double quotes have been
19491 .vindex "&$local_part$&"
19492 &*Warning*&: If you use an Exim expansion to construct a redirection address,
19493 and the expansion contains a reference to &$local_part$&, you should make use
19494 of the &%quote_local_part%& expansion operator, in case the local part contains
19495 special characters. For example, to redirect all mail for the domain
19496 &'obsolete.example'&, retaining the existing local part, you could use this
19499 data = ${quote_local_part:$local_part}@newdomain.example
19503 .section "Redirecting to a local mailbox" "SECTredlocmai"
19504 .cindex "routing" "loops in"
19505 .cindex "loop" "while routing, avoidance of"
19506 .cindex "address redirection" "to local mailbox"
19507 A redirection item may safely be the same as the address currently under
19508 consideration. This does not cause a routing loop, because a router is
19509 automatically skipped if any ancestor of the address that is being processed
19510 is the same as the current address and was processed by the current router.
19511 Such an address is therefore passed to the following routers, so it is handled
19512 as if there were no redirection. When making this loop-avoidance test, the
19513 complete local part, including any prefix or suffix, is used.
19515 .cindex "address redirection" "local part without domain"
19516 Specifying the same local part without a domain is a common usage in personal
19517 filter files when the user wants to have messages delivered to the local
19518 mailbox and also forwarded elsewhere. For example, the user whose login is
19519 &'cleo'& might have a &_.forward_& file containing this:
19521 cleo, cleopatra@egypt.example
19523 .cindex "backslash in alias file"
19524 .cindex "alias file" "backslash in"
19525 For compatibility with other MTAs, such unqualified local parts may be
19526 preceded by &"\"&, but this is not a requirement for loop prevention. However,
19527 it does make a difference if more than one domain is being handled
19530 If an item begins with &"\"& and the rest of the item parses as a valid RFC
19531 2822 address that does not include a domain, the item is qualified using the
19532 domain of the incoming address. In the absence of a leading &"\"&, unqualified
19533 addresses are qualified using the value in &%qualify_recipient%&, but you can
19534 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
19536 Care must be taken if there are alias names for local users.
19537 Consider an MTA handling a single local domain where the system alias file
19542 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
19543 messages in the local mailbox, and also forward copies elsewhere. He creates
19546 Sam.Reman, spqr@reme.elsewhere.example
19548 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
19549 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
19550 second time round, because it has previously routed it,
19551 and the following routers presumably cannot handle the alias. The forward file
19552 should really contain
19554 spqr, spqr@reme.elsewhere.example
19556 but because this is such a common error, the &%check_ancestor%& option (see
19557 below) exists to provide a way to get round it. This is normally set on a
19558 &(redirect)& router that is handling users' &_.forward_& files.
19562 .section "Special items in redirection lists" "SECTspecitredli"
19563 In addition to addresses, the following types of item may appear in redirection
19564 lists (that is, in non-filter redirection data):
19567 .cindex "pipe" "in redirection list"
19568 .cindex "address redirection" "to pipe"
19569 An item is treated as a pipe command if it begins with &"|"& and does not parse
19570 as a valid RFC 2822 address that includes a domain. A transport for running the
19571 command must be specified by the &%pipe_transport%& option.
19572 Normally, either the router or the transport specifies a user and a group under
19573 which to run the delivery. The default is to use the Exim user and group.
19575 Single or double quotes can be used for enclosing the individual arguments of
19576 the pipe command; no interpretation of escapes is done for single quotes. If
19577 the command contains a comma character, it is necessary to put the whole item
19578 in double quotes, for example:
19580 "|/some/command ready,steady,go"
19582 since items in redirection lists are terminated by commas. Do not, however,
19583 quote just the command. An item such as
19585 |"/some/command ready,steady,go"
19587 is interpreted as a pipe with a rather strange command name, and no arguments.
19589 Note that the above example assumes that the text comes from a lookup source
19590 of some sort, so that the quotes are part of the data. If composing a
19591 redirect router with a &%data%& option directly specifying this command, the
19592 quotes will be used by the configuration parser to define the extent of one
19593 string, but will not be passed down into the redirect router itself. There
19594 are two main approaches to get around this: escape quotes to be part of the
19595 data itself, or avoid using this mechanism and instead create a custom
19596 transport with the &%command%& option set and reference that transport from
19597 an &%accept%& router.
19600 .cindex "file" "in redirection list"
19601 .cindex "address redirection" "to file"
19602 An item is interpreted as a path name if it begins with &"/"& and does not
19603 parse as a valid RFC 2822 address that includes a domain. For example,
19605 /home/world/minbari
19607 is treated as a file name, but
19609 /s=molari/o=babylon/@x400gate.way
19611 is treated as an address. For a file name, a transport must be specified using
19612 the &%file_transport%& option. However, if the generated path name ends with a
19613 forward slash character, it is interpreted as a directory name rather than a
19614 file name, and &%directory_transport%& is used instead.
19616 Normally, either the router or the transport specifies a user and a group under
19617 which to run the delivery. The default is to use the Exim user and group.
19619 .cindex "&_/dev/null_&"
19620 However, if a redirection item is the path &_/dev/null_&, delivery to it is
19621 bypassed at a high level, and the log entry shows &"**bypassed**"&
19622 instead of a transport name. In this case the user and group are not used.
19625 .cindex "included address list"
19626 .cindex "address redirection" "included external list"
19627 If an item is of the form
19629 :include:<path name>
19631 a list of further items is taken from the given file and included at that
19632 point. &*Note*&: Such a file can not be a filter file; it is just an
19633 out-of-line addition to the list. The items in the included list are separated
19634 by commas or newlines and are not subject to expansion. If this is the first
19635 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
19636 the alias name. This example is incorrect:
19638 list1 :include:/opt/lists/list1
19640 It must be given as
19642 list1: :include:/opt/lists/list1
19645 .cindex "address redirection" "to black hole"
19646 Sometimes you want to throw away mail to a particular local part. Making the
19647 &%data%& option expand to an empty string does not work, because that causes
19648 the router to decline. Instead, the alias item
19649 .cindex "black hole"
19650 .cindex "abandoning mail"
19651 &':blackhole:'& can be used. It does what its name implies. No delivery is
19652 done, and no error message is generated. This has the same effect as specifying
19653 &_/dev/null_& as a destination, but it can be independently disabled.
19655 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
19656 delivery is done for the original local part, even if other redirection items
19657 are present. If you are generating a multi-item list (for example, by reading a
19658 database) and need the ability to provide a no-op item, you must use
19662 .cindex "delivery" "forcing failure"
19663 .cindex "delivery" "forcing deferral"
19664 .cindex "failing delivery" "forcing"
19665 .cindex "deferred delivery, forcing"
19666 .cindex "customizing" "failure message"
19667 An attempt to deliver a particular address can be deferred or forced to fail by
19668 redirection items of the form
19673 respectively. When a redirection list contains such an item, it applies
19674 to the entire redirection; any other items in the list are ignored. Any
19675 text following &':fail:'& or &':defer:'& is placed in the error text
19676 associated with the failure. For example, an alias file might contain:
19678 X.Employee: :fail: Gone away, no forwarding address
19680 In the case of an address that is being verified from an ACL or as the subject
19682 .cindex "VRFY" "error text, display of"
19683 VRFY command, the text is included in the SMTP error response by
19685 .cindex "EXPN" "error text, display of"
19686 The text is not included in the response to an EXPN command. In non-SMTP cases
19687 the text is included in the error message that Exim generates.
19689 .cindex "SMTP" "error codes"
19690 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
19691 &':fail:'&. However, if the message starts with three digits followed by a
19692 space, optionally followed by an extended code of the form &'n.n.n'&, also
19693 followed by a space, and the very first digit is the same as the default error
19694 code, the code from the message is used instead. If the very first digit is
19695 incorrect, a panic error is logged, and the default code is used. You can
19696 suppress the use of the supplied code in a redirect router by setting the
19697 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
19700 .vindex "&$acl_verify_message$&"
19701 In an ACL, an explicitly provided message overrides the default, but the
19702 default message is available in the variable &$acl_verify_message$& and can
19703 therefore be included in a custom message if this is desired.
19705 Normally the error text is the rest of the redirection list &-- a comma does
19706 not terminate it &-- but a newline does act as a terminator. Newlines are not
19707 normally present in alias expansions. In &(lsearch)& lookups they are removed
19708 as part of the continuation process, but they may exist in other kinds of
19709 lookup and in &':include:'& files.
19711 During routing for message delivery (as opposed to verification), a redirection
19712 containing &':fail:'& causes an immediate failure of the incoming address,
19713 whereas &':defer:'& causes the message to remain on the queue so that a
19714 subsequent delivery attempt can happen at a later time. If an address is
19715 deferred for too long, it will ultimately fail, because the normal retry
19719 .cindex "alias file" "exception to default"
19720 Sometimes it is useful to use a single-key search type with a default (see
19721 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
19722 for exceptions to the default. These can be handled by aliasing them to
19723 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
19724 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
19725 results in an empty redirection list has the same effect.
19729 .section "Duplicate addresses" "SECTdupaddr"
19730 .cindex "duplicate addresses"
19731 .cindex "address duplicate, discarding"
19732 .cindex "pipe" "duplicated"
19733 Exim removes duplicate addresses from the list to which it is delivering, so as
19734 to deliver just one copy to each address. This does not apply to deliveries
19735 routed to pipes by different immediate parent addresses, but an indirect
19736 aliasing scheme of the type
19738 pipe: |/some/command $local_part
19742 does not work with a message that is addressed to both local parts, because
19743 when the second is aliased to the intermediate local part &"pipe"& it gets
19744 discarded as being the same as a previously handled address. However, a scheme
19747 localpart1: |/some/command $local_part
19748 localpart2: |/some/command $local_part
19750 does result in two different pipe deliveries, because the immediate parents of
19751 the pipes are distinct.
19755 .section "Repeated redirection expansion" "SECID128"
19756 .cindex "repeated redirection expansion"
19757 .cindex "address redirection" "repeated for each delivery attempt"
19758 When a message cannot be delivered to all of its recipients immediately,
19759 leading to two or more delivery attempts, redirection expansion is carried out
19760 afresh each time for those addresses whose children were not all previously
19761 delivered. If redirection is being used as a mailing list, this can lead to new
19762 members of the list receiving copies of old messages. The &%one_time%& option
19763 can be used to avoid this.
19766 .section "Errors in redirection lists" "SECID129"
19767 .cindex "address redirection" "errors"
19768 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
19769 error is skipped, and an entry is written to the main log. This may be useful
19770 for mailing lists that are automatically managed. Otherwise, if an error is
19771 detected while generating the list of new addresses, the original address is
19772 deferred. See also &%syntax_errors_to%&.
19776 .section "Private options for the redirect router" "SECID130"
19778 .cindex "options" "&(redirect)& router"
19779 The private options for the &(redirect)& router are as follows:
19782 .option allow_defer redirect boolean false
19783 Setting this option allows the use of &':defer:'& in non-filter redirection
19784 data, or the &%defer%& command in an Exim filter file.
19787 .option allow_fail redirect boolean false
19788 .cindex "failing delivery" "from filter"
19789 If this option is true, the &':fail:'& item can be used in a redirection list,
19790 and the &%fail%& command may be used in an Exim filter file.
19793 .option allow_filter redirect boolean false
19794 .cindex "filter" "enabling use of"
19795 .cindex "Sieve filter" "enabling use of"
19796 Setting this option allows Exim to interpret redirection data that starts with
19797 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
19798 are some features of Exim filter files that some administrators may wish to
19799 lock out; see the &%forbid_filter_%&&'xxx'& options below.
19801 It is also possible to lock out Exim filters or Sieve filters while allowing
19802 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
19805 The filter is run using the uid and gid set by the generic &%user%& and
19806 &%group%& options. These take their defaults from the password data if
19807 &%check_local_user%& is set, so in the normal case of users' personal filter
19808 files, the filter is run as the relevant user. When &%allow_filter%& is set
19809 true, Exim insists that either &%check_local_user%& or &%user%& is set.
19813 .option allow_freeze redirect boolean false
19814 .cindex "freezing messages" "allowing in filter"
19815 Setting this option allows the use of the &%freeze%& command in an Exim filter.
19816 This command is more normally encountered in system filters, and is disabled by
19817 default for redirection filters because it isn't something you usually want to
19818 let ordinary users do.
19822 .option check_ancestor redirect boolean false
19823 This option is concerned with handling generated addresses that are the same
19824 as some address in the list of redirection ancestors of the current address.
19825 Although it is turned off by default in the code, it is set in the default
19826 configuration file for handling users' &_.forward_& files. It is recommended
19827 for this use of the &(redirect)& router.
19829 When &%check_ancestor%& is set, if a generated address (including the domain)
19830 is the same as any ancestor of the current address, it is replaced by a copy of
19831 the current address. This helps in the case where local part A is aliased to B,
19832 and B has a &_.forward_& file pointing back to A. For example, within a single
19833 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
19834 &_&~jb/.forward_& contains:
19836 \Joe.Bloggs, <other item(s)>
19838 Without the &%check_ancestor%& setting, either local part (&"jb"& or
19839 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
19840 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
19841 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
19842 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
19843 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
19844 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
19845 original address. See also the &%repeat_use%& option below.
19848 .option check_group redirect boolean "see below"
19849 When the &%file%& option is used, the group owner of the file is checked only
19850 when this option is set. The permitted groups are those listed in the
19851 &%owngroups%& option, together with the user's default group if
19852 &%check_local_user%& is set. If the file has the wrong group, routing is
19853 deferred. The default setting for this option is true if &%check_local_user%&
19854 is set and the &%modemask%& option permits the group write bit, or if the
19855 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
19859 .option check_owner redirect boolean "see below"
19860 When the &%file%& option is used, the owner of the file is checked only when
19861 this option is set. If &%check_local_user%& is set, the local user is
19862 permitted; otherwise the owner must be one of those listed in the &%owners%&
19863 option. The default value for this option is true if &%check_local_user%& or
19864 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
19867 .option data redirect string&!! unset
19868 This option is mutually exclusive with &%file%&. One or other of them must be
19869 set, but not both. The contents of &%data%& are expanded, and then used as the
19870 list of forwarding items, or as a set of filtering instructions. If the
19871 expansion is forced to fail, or the result is an empty string or a string that
19872 has no effect (consists entirely of comments), the router declines.
19874 When filtering instructions are used, the string must begin with &"#Exim
19875 filter"&, and all comments in the string, including this initial one, must be
19876 terminated with newline characters. For example:
19878 data = #Exim filter\n\
19879 if $h_to: contains Exim then save $home/mail/exim endif
19881 If you are reading the data from a database where newlines cannot be included,
19882 you can use the &${sg}$& expansion item to turn the escape string of your
19883 choice into a newline.
19886 .option directory_transport redirect string&!! unset
19887 A &(redirect)& router sets up a direct delivery to a directory when a path name
19888 ending with a slash is specified as a new &"address"&. The transport used is
19889 specified by this option, which, after expansion, must be the name of a
19890 configured transport. This should normally be an &(appendfile)& transport.
19893 .option file redirect string&!! unset
19894 This option specifies the name of a file that contains the redirection data. It
19895 is mutually exclusive with the &%data%& option. The string is expanded before
19896 use; if the expansion is forced to fail, the router declines. Other expansion
19897 failures cause delivery to be deferred. The result of a successful expansion
19898 must be an absolute path. The entire file is read and used as the redirection
19899 data. If the data is an empty string or a string that has no effect (consists
19900 entirely of comments), the router declines.
19902 .cindex "NFS" "checking for file existence"
19903 If the attempt to open the file fails with a &"does not exist"& error, Exim
19904 runs a check on the containing directory,
19905 unless &%ignore_enotdir%& is true (see below).
19906 If the directory does not appear to exist, delivery is deferred. This can
19907 happen when users' &_.forward_& files are in NFS-mounted directories, and there
19908 is a mount problem. If the containing directory does exist, but the file does
19909 not, the router declines.
19912 .option file_transport redirect string&!! unset
19913 .vindex "&$address_file$&"
19914 A &(redirect)& router sets up a direct delivery to a file when a path name not
19915 ending in a slash is specified as a new &"address"&. The transport used is
19916 specified by this option, which, after expansion, must be the name of a
19917 configured transport. This should normally be an &(appendfile)& transport. When
19918 it is running, the file name is in &$address_file$&.
19921 .option filter_prepend_home redirect boolean true
19922 When this option is true, if a &(save)& command in an Exim filter specifies a
19923 relative path, and &$home$& is defined, it is automatically prepended to the
19924 relative path. If this option is set false, this action does not happen. The
19925 relative path is then passed to the transport unmodified.
19928 .option forbid_blackhole redirect boolean false
19929 If this option is true, the &':blackhole:'& item may not appear in a
19933 .option forbid_exim_filter redirect boolean false
19934 If this option is set true, only Sieve filters are permitted when
19935 &%allow_filter%& is true.
19940 .option forbid_file redirect boolean false
19941 .cindex "delivery" "to file; forbidding"
19942 .cindex "Sieve filter" "forbidding delivery to a file"
19943 .cindex "Sieve filter" "&""keep""& facility; disabling"
19944 If this option is true, this router may not generate a new address that
19945 specifies delivery to a local file or directory, either from a filter or from a
19946 conventional forward file. This option is forced to be true if &%one_time%& is
19947 set. It applies to Sieve filters as well as to Exim filters, but if true, it
19948 locks out the Sieve's &"keep"& facility.
19951 .option forbid_filter_dlfunc redirect boolean false
19952 .cindex "filter" "locking out certain features"
19953 If this option is true, string expansions in Exim filters are not allowed to
19954 make use of the &%dlfunc%& expansion facility to run dynamically loaded
19957 .option forbid_filter_existstest redirect boolean false
19958 .cindex "expansion" "statting a file"
19959 If this option is true, string expansions in Exim filters are not allowed to
19960 make use of the &%exists%& condition or the &%stat%& expansion item.
19962 .option forbid_filter_logwrite redirect boolean false
19963 If this option is true, use of the logging facility in Exim filters is not
19964 permitted. Logging is in any case available only if the filter is being run
19965 under some unprivileged uid (which is normally the case for ordinary users'
19966 &_.forward_& files).
19969 .option forbid_filter_lookup redirect boolean false
19970 If this option is true, string expansions in Exim filter files are not allowed
19971 to make use of &%lookup%& items.
19974 .option forbid_filter_perl redirect boolean false
19975 This option has an effect only if Exim is built with embedded Perl support. If
19976 it is true, string expansions in Exim filter files are not allowed to make use
19977 of the embedded Perl support.
19980 .option forbid_filter_readfile redirect boolean false
19981 If this option is true, string expansions in Exim filter files are not allowed
19982 to make use of &%readfile%& items.
19985 .option forbid_filter_readsocket redirect boolean false
19986 If this option is true, string expansions in Exim filter files are not allowed
19987 to make use of &%readsocket%& items.
19990 .option forbid_filter_reply redirect boolean false
19991 If this option is true, this router may not generate an automatic reply
19992 message. Automatic replies can be generated only from Exim or Sieve filter
19993 files, not from traditional forward files. This option is forced to be true if
19994 &%one_time%& is set.
19997 .option forbid_filter_run redirect boolean false
19998 If this option is true, string expansions in Exim filter files are not allowed
19999 to make use of &%run%& items.
20002 .option forbid_include redirect boolean false
20003 If this option is true, items of the form
20005 :include:<path name>
20007 are not permitted in non-filter redirection lists.
20010 .option forbid_pipe redirect boolean false
20011 .cindex "delivery" "to pipe; forbidding"
20012 If this option is true, this router may not generate a new address which
20013 specifies delivery to a pipe, either from an Exim filter or from a conventional
20014 forward file. This option is forced to be true if &%one_time%& is set.
20017 .option forbid_sieve_filter redirect boolean false
20018 If this option is set true, only Exim filters are permitted when
20019 &%allow_filter%& is true.
20022 .cindex "SMTP" "error codes"
20023 .option forbid_smtp_code redirect boolean false
20024 If this option is set true, any SMTP error codes that are present at the start
20025 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
20026 the default codes (451 and 550, respectively) are always used.
20031 .option hide_child_in_errmsg redirect boolean false
20032 .cindex "bounce message" "redirection details; suppressing"
20033 If this option is true, it prevents Exim from quoting a child address if it
20034 generates a bounce or delay message for it. Instead it says &"an address
20035 generated from <&'the top level address'&>"&. Of course, this applies only to
20036 bounces generated locally. If a message is forwarded to another host, &'its'&
20037 bounce may well quote the generated address.
20040 .option ignore_eacces redirect boolean false
20042 If this option is set and an attempt to open a redirection file yields the
20043 EACCES error (permission denied), the &(redirect)& router behaves as if the
20044 file did not exist.
20047 .option ignore_enotdir redirect boolean false
20049 If this option is set and an attempt to open a redirection file yields the
20050 ENOTDIR error (something on the path is not a directory), the &(redirect)&
20051 router behaves as if the file did not exist.
20053 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
20054 router that has the &%file%& option set discovers that the file does not exist
20055 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
20056 against unmounted NFS directories. If the parent can not be statted, delivery
20057 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
20058 is set, because that option tells Exim to ignore &"something on the path is not
20059 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
20060 that some operating systems give ENOENT where others give ENOTDIR.
20064 .option include_directory redirect string unset
20065 If this option is set, the path names of any &':include:'& items in a
20066 redirection list must start with this directory.
20069 .option modemask redirect "octal integer" 022
20070 This specifies mode bits which must not be set for a file specified by the
20071 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
20074 .option one_time redirect boolean false
20075 .cindex "one-time aliasing/forwarding expansion"
20076 .cindex "alias file" "one-time expansion"
20077 .cindex "forward file" "one-time expansion"
20078 .cindex "mailing lists" "one-time expansion"
20079 .cindex "address redirection" "one-time expansion"
20080 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
20081 files each time it tries to deliver a message causes a problem when one or more
20082 of the generated addresses fails be delivered at the first attempt. The problem
20083 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
20084 but of what happens when the redirection list changes during the time that the
20085 message is on Exim's queue. This is particularly true in the case of mailing
20086 lists, where new subscribers might receive copies of messages that were posted
20087 before they subscribed.
20089 If &%one_time%& is set and any addresses generated by the router fail to
20090 deliver at the first attempt, the failing addresses are added to the message as
20091 &"top level"& addresses, and the parent address that generated them is marked
20092 &"delivered"&. Thus, redirection does not happen again at the next delivery
20095 &*Warning 1*&: Any header line addition or removal that is specified by this
20096 router would be lost if delivery did not succeed at the first attempt. For this
20097 reason, the &%headers_add%& and &%headers_remove%& generic options are not
20098 permitted when &%one_time%& is set.
20100 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
20101 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
20102 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
20104 &*Warning 3*&: The &%unseen%& generic router option may not be set with
20107 The original top-level address is remembered with each of the generated
20108 addresses, and is output in any log messages. However, any intermediate parent
20109 addresses are not recorded. This makes a difference to the log only if
20110 &%all_parents%& log selector is set. It is expected that &%one_time%& will
20111 typically be used for mailing lists, where there is normally just one level of
20115 .option owners redirect "string list" unset
20116 .cindex "ownership" "alias file"
20117 .cindex "ownership" "forward file"
20118 .cindex "alias file" "ownership"
20119 .cindex "forward file" "ownership"
20120 This specifies a list of permitted owners for the file specified by &%file%&.
20121 This list is in addition to the local user when &%check_local_user%& is set.
20122 See &%check_owner%& above.
20125 .option owngroups redirect "string list" unset
20126 This specifies a list of permitted groups for the file specified by &%file%&.
20127 The list is in addition to the local user's primary group when
20128 &%check_local_user%& is set. See &%check_group%& above.
20131 .option pipe_transport redirect string&!! unset
20132 .vindex "&$address_pipe$&"
20133 A &(redirect)& router sets up a direct delivery to a pipe when a string
20134 starting with a vertical bar character is specified as a new &"address"&. The
20135 transport used is specified by this option, which, after expansion, must be the
20136 name of a configured transport. This should normally be a &(pipe)& transport.
20137 When the transport is run, the pipe command is in &$address_pipe$&.
20140 .option qualify_domain redirect string&!! unset
20141 .vindex "&$qualify_recipient$&"
20142 If this option is set, and an unqualified address (one without a domain) is
20143 generated, and that address would normally be qualified by the global setting
20144 in &%qualify_recipient%&, it is instead qualified with the domain specified by
20145 expanding this string. If the expansion fails, the router declines. If you want
20146 to revert to the default, you can have the expansion generate
20147 &$qualify_recipient$&.
20149 This option applies to all unqualified addresses generated by Exim filters,
20150 but for traditional &_.forward_& files, it applies only to addresses that are
20151 not preceded by a backslash. Sieve filters cannot generate unqualified
20154 .option qualify_preserve_domain redirect boolean false
20155 .cindex "domain" "in redirection; preserving"
20156 .cindex "preserving domain in redirection"
20157 .cindex "address redirection" "domain; preserving"
20158 If this option is set, the router's local &%qualify_domain%& option must not be
20159 set (a configuration error occurs if it is). If an unqualified address (one
20160 without a domain) is generated, it is qualified with the domain of the parent
20161 address (the immediately preceding ancestor) instead of the global
20162 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
20163 this applies whether or not the address is preceded by a backslash.
20166 .option repeat_use redirect boolean true
20167 If this option is set false, the router is skipped for a child address that has
20168 any ancestor that was routed by this router. This test happens before any of
20169 the other preconditions are tested. Exim's default anti-looping rules skip
20170 only when the ancestor is the same as the current address. See also
20171 &%check_ancestor%& above and the generic &%redirect_router%& option.
20174 .option reply_transport redirect string&!! unset
20175 A &(redirect)& router sets up an automatic reply when a &%mail%& or
20176 &%vacation%& command is used in a filter file. The transport used is specified
20177 by this option, which, after expansion, must be the name of a configured
20178 transport. This should normally be an &(autoreply)& transport. Other transports
20179 are unlikely to do anything sensible or useful.
20182 .option rewrite redirect boolean true
20183 .cindex "address redirection" "disabling rewriting"
20184 If this option is set false, addresses generated by the router are not
20185 subject to address rewriting. Otherwise, they are treated like new addresses
20186 and are rewritten according to the global rewriting rules.
20189 .option sieve_subaddress redirect string&!! unset
20190 The value of this option is passed to a Sieve filter to specify the
20191 :subaddress part of an address.
20193 .option sieve_useraddress redirect string&!! unset
20194 The value of this option is passed to a Sieve filter to specify the :user part
20195 of an address. However, if it is unset, the entire original local part
20196 (including any prefix or suffix) is used for :user.
20199 .option sieve_vacation_directory redirect string&!! unset
20200 .cindex "Sieve filter" "vacation directory"
20201 To enable the &"vacation"& extension for Sieve filters, you must set
20202 &%sieve_vacation_directory%& to the directory where vacation databases are held
20203 (do not put anything else in that directory), and ensure that the
20204 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
20205 needs their own directory; Exim will create it if necessary.
20209 .option skip_syntax_errors redirect boolean false
20210 .cindex "forward file" "broken"
20211 .cindex "address redirection" "broken files"
20212 .cindex "alias file" "broken"
20213 .cindex "broken alias or forward files"
20214 .cindex "ignoring faulty addresses"
20215 .cindex "skipping faulty addresses"
20216 .cindex "error" "skipping bad syntax"
20217 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
20218 non-filter redirection data are skipped, and each failing address is logged. If
20219 &%syntax_errors_to%& is set, a message is sent to the address it defines,
20220 giving details of the failures. If &%syntax_errors_text%& is set, its contents
20221 are expanded and placed at the head of the error message generated by
20222 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
20223 be the same address as the generic &%errors_to%& option. The
20224 &%skip_syntax_errors%& option is often used when handling mailing lists.
20226 If all the addresses in a redirection list are skipped because of syntax
20227 errors, the router declines to handle the original address, and it is passed to
20228 the following routers.
20230 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
20231 error in the filter causes filtering to be abandoned without any action being
20232 taken. The incident is logged, and the router declines to handle the address,
20233 so it is passed to the following routers.
20235 .cindex "Sieve filter" "syntax errors in"
20236 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
20237 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
20238 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
20240 &%skip_syntax_errors%& can be used to specify that errors in users' forward
20241 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
20242 option, used with an address that does not get redirected, can be used to
20243 notify users of these errors, by means of a router like this:
20249 file = $home/.forward
20250 file_transport = address_file
20251 pipe_transport = address_pipe
20252 reply_transport = address_reply
20255 syntax_errors_to = real-$local_part@$domain
20256 syntax_errors_text = \
20257 This is an automatically generated message. An error has\n\
20258 been found in your .forward file. Details of the error are\n\
20259 reported below. While this error persists, you will receive\n\
20260 a copy of this message for every message that is addressed\n\
20261 to you. If your .forward file is a filter file, or if it is\n\
20262 a non-filter file containing no valid forwarding addresses,\n\
20263 a copy of each incoming message will be put in your normal\n\
20264 mailbox. If a non-filter file contains at least one valid\n\
20265 forwarding address, forwarding to the valid addresses will\n\
20266 happen, and those will be the only deliveries that occur.
20268 You also need a router to ensure that local addresses that are prefixed by
20269 &`real-`& are recognized, but not forwarded or filtered. For example, you could
20270 put this immediately before the &(userforward)& router:
20275 local_part_prefix = real-
20276 transport = local_delivery
20278 For security, it would probably be a good idea to restrict the use of this
20279 router to locally-generated messages, using a condition such as this:
20281 condition = ${if match {$sender_host_address}\
20282 {\N^(|127\.0\.0\.1)$\N}}
20286 .option syntax_errors_text redirect string&!! unset
20287 See &%skip_syntax_errors%& above.
20290 .option syntax_errors_to redirect string unset
20291 See &%skip_syntax_errors%& above.
20292 .ecindex IIDredrou1
20293 .ecindex IIDredrou2
20300 . ////////////////////////////////////////////////////////////////////////////
20301 . ////////////////////////////////////////////////////////////////////////////
20303 .chapter "Environment for running local transports" "CHAPenvironment" &&&
20304 "Environment for local transports"
20305 .scindex IIDenvlotra1 "local transports" "environment for"
20306 .scindex IIDenvlotra2 "environment for local transports"
20307 .scindex IIDenvlotra3 "transport" "local; environment for"
20308 Local transports handle deliveries to files and pipes. (The &(autoreply)&
20309 transport can be thought of as similar to a pipe.) Exim always runs transports
20310 in subprocesses, under specified uids and gids. Typical deliveries to local
20311 mailboxes run under the uid and gid of the local user.
20313 Exim also sets a specific current directory while running the transport; for
20314 some transports a home directory setting is also relevant. The &(pipe)&
20315 transport is the only one that sets up environment variables; see section
20316 &<<SECTpipeenv>>& for details.
20318 The values used for the uid, gid, and the directories may come from several
20319 different places. In many cases, the router that handles the address associates
20320 settings with that address as a result of its &%check_local_user%&, &%group%&,
20321 or &%user%& options. However, values may also be given in the transport's own
20322 configuration, and these override anything that comes from the router.
20326 .section "Concurrent deliveries" "SECID131"
20327 .cindex "concurrent deliveries"
20328 .cindex "simultaneous deliveries"
20329 If two different messages for the same local recipient arrive more or less
20330 simultaneously, the two delivery processes are likely to run concurrently. When
20331 the &(appendfile)& transport is used to write to a file, Exim applies locking
20332 rules to stop concurrent processes from writing to the same file at the same
20335 However, when you use a &(pipe)& transport, it is up to you to arrange any
20336 locking that is needed. Here is a silly example:
20340 command = /bin/sh -c 'cat >>/some/file'
20342 This is supposed to write the message at the end of the file. However, if two
20343 messages arrive at the same time, the file will be scrambled. You can use the
20344 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
20345 file using the same algorithm that Exim itself uses.
20350 .section "Uids and gids" "SECTenvuidgid"
20351 .cindex "local transports" "uid and gid"
20352 .cindex "transport" "local; uid and gid"
20353 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
20354 overrides any group that the router set in the address, even if &%user%& is not
20355 set for the transport. This makes it possible, for example, to run local mail
20356 delivery under the uid of the recipient (set by the router), but in a special
20357 group (set by the transport). For example:
20360 # User/group are set by check_local_user in this router
20364 transport = group_delivery
20367 # This transport overrides the group
20369 driver = appendfile
20370 file = /var/spool/mail/$local_part
20373 If &%user%& is set for a transport, its value overrides what is set in the
20374 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
20375 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
20378 .oindex "&%initgroups%&"
20379 When the uid is taken from the transport's configuration, the &[initgroups()]&
20380 function is called for the groups associated with that uid if the
20381 &%initgroups%& option is set for the transport. When the uid is not specified
20382 by the transport, but is associated with the address by a router, the option
20383 for calling &[initgroups()]& is taken from the router configuration.
20385 .cindex "&(pipe)& transport" "uid for"
20386 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
20387 is set and &%user%& is not set, the uid of the process that called Exim to
20388 receive the message is used, and if &%group%& is not set, the corresponding
20389 original gid is also used.
20391 This is the detailed preference order for obtaining a gid; the first of the
20392 following that is set is used:
20395 A &%group%& setting of the transport;
20397 A &%group%& setting of the router;
20399 A gid associated with a user setting of the router, either as a result of
20400 &%check_local_user%& or an explicit non-numeric &%user%& setting;
20402 The group associated with a non-numeric &%user%& setting of the transport;
20404 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
20405 the uid is the creator's uid;
20407 The Exim gid if the Exim uid is being used as a default.
20410 If, for example, the user is specified numerically on the router and there are
20411 no group settings, no gid is available. In this situation, an error occurs.
20412 This is different for the uid, for which there always is an ultimate default.
20413 The first of the following that is set is used:
20416 A &%user%& setting of the transport;
20418 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
20420 A &%user%& setting of the router;
20422 A &%check_local_user%& setting of the router;
20427 Of course, an error will still occur if the uid that is chosen is on the
20428 &%never_users%& list.
20434 .section "Current and home directories" "SECID132"
20435 .cindex "current directory for local transport"
20436 .cindex "home directory" "for local transport"
20437 .cindex "transport" "local; home directory for"
20438 .cindex "transport" "local; current directory for"
20439 Routers may set current and home directories for local transports by means of
20440 the &%transport_current_directory%& and &%transport_home_directory%& options.
20441 However, if the transport's &%current_directory%& or &%home_directory%& options
20442 are set, they override the router's values. In detail, the home directory
20443 for a local transport is taken from the first of these values that is set:
20446 The &%home_directory%& option on the transport;
20448 The &%transport_home_directory%& option on the router;
20450 The password data if &%check_local_user%& is set on the router;
20452 The &%router_home_directory%& option on the router.
20455 The current directory is taken from the first of these values that is set:
20458 The &%current_directory%& option on the transport;
20460 The &%transport_current_directory%& option on the router.
20464 If neither the router nor the transport sets a current directory, Exim uses the
20465 value of the home directory, if it is set. Otherwise it sets the current
20466 directory to &_/_& before running a local transport.
20470 .section "Expansion variables derived from the address" "SECID133"
20471 .vindex "&$domain$&"
20472 .vindex "&$local_part$&"
20473 .vindex "&$original_domain$&"
20474 Normally a local delivery is handling a single address, and in that case the
20475 variables such as &$domain$& and &$local_part$& are set during local
20476 deliveries. However, in some circumstances more than one address may be handled
20477 at once (for example, while writing batch SMTP for onward transmission by some
20478 other means). In this case, the variables associated with the local part are
20479 never set, &$domain$& is set only if all the addresses have the same domain,
20480 and &$original_domain$& is never set.
20481 .ecindex IIDenvlotra1
20482 .ecindex IIDenvlotra2
20483 .ecindex IIDenvlotra3
20491 . ////////////////////////////////////////////////////////////////////////////
20492 . ////////////////////////////////////////////////////////////////////////////
20494 .chapter "Generic options for transports" "CHAPtransportgeneric"
20495 .scindex IIDgenoptra1 "generic options" "transport"
20496 .scindex IIDgenoptra2 "options" "generic; for transports"
20497 .scindex IIDgenoptra3 "transport" "generic options for"
20498 The following generic options apply to all transports:
20501 .option body_only transports boolean false
20502 .cindex "transport" "body only"
20503 .cindex "message" "transporting body only"
20504 .cindex "body of message" "transporting"
20505 If this option is set, the message's headers are not transported. It is
20506 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
20507 or &(pipe)& transports, the settings of &%message_prefix%& and
20508 &%message_suffix%& should be checked, because this option does not
20509 automatically suppress them.
20512 .option current_directory transports string&!! unset
20513 .cindex "transport" "current directory for"
20514 This specifies the current directory that is to be set while running the
20515 transport, overriding any value that may have been set by the router.
20516 If the expansion fails for any reason, including forced failure, an error is
20517 logged, and delivery is deferred.
20520 .option disable_logging transports boolean false
20521 If this option is set true, nothing is logged for any
20522 deliveries by the transport or for any
20523 transport errors. You should not set this option unless you really, really know
20524 what you are doing.
20527 .option debug_print transports string&!! unset
20528 .cindex "testing" "variables in drivers"
20529 If this option is set and debugging is enabled (see the &%-d%& command line
20530 option), the string is expanded and included in the debugging output when the
20532 If expansion of the string fails, the error message is written to the debugging
20533 output, and Exim carries on processing.
20534 This facility is provided to help with checking out the values of variables and
20535 so on when debugging driver configurations. For example, if a &%headers_add%&
20536 option is not working properly, &%debug_print%& could be used to output the
20537 variables it references. A newline is added to the text if it does not end with
20539 The variables &$transport_name$& and &$router_name$& contain the name of the
20540 transport and the router that called it.
20542 .option delivery_date_add transports boolean false
20543 .cindex "&'Delivery-date:'& header line"
20544 If this option is true, a &'Delivery-date:'& header is added to the message.
20545 This gives the actual time the delivery was made. As this is not a standard
20546 header, Exim has a configuration option (&%delivery_date_remove%&) which
20547 requests its removal from incoming messages, so that delivered messages can
20548 safely be resent to other recipients.
20551 .option driver transports string unset
20552 This specifies which of the available transport drivers is to be used.
20553 There is no default, and this option must be set for every transport.
20556 .option envelope_to_add transports boolean false
20557 .cindex "&'Envelope-to:'& header line"
20558 If this option is true, an &'Envelope-to:'& header is added to the message.
20559 This gives the original address(es) in the incoming envelope that caused this
20560 delivery to happen. More than one address may be present if the transport is
20561 configured to handle several addresses at once, or if more than one original
20562 address was redirected to the same final address. As this is not a standard
20563 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
20564 its removal from incoming messages, so that delivered messages can safely be
20565 resent to other recipients.
20568 .option event_action transports string&!! unset
20570 This option declares a string to be expanded for Exim's events mechanism.
20571 For details see &<<CHAPevents>>&.
20575 .option group transports string&!! "Exim group"
20576 .cindex "transport" "group; specifying"
20577 This option specifies a gid for running the transport process, overriding any
20578 value that the router supplies, and also overriding any value associated with
20579 &%user%& (see below).
20582 .option headers_add transports list&!! unset
20583 .cindex "header lines" "adding in transport"
20584 .cindex "transport" "header lines; adding"
20585 This option specifies a list of text headers,
20586 newline-separated (by default, changeable in the usual way),
20587 which are (separately) expanded and added to the header
20588 portion of a message as it is transported, as described in section
20589 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
20590 routers. If the result of the expansion is an empty string, or if the expansion
20591 is forced to fail, no action is taken. Other expansion failures are treated as
20592 errors and cause the delivery to be deferred.
20594 Unlike most options, &%headers_add%& can be specified multiple times
20595 for a transport; all listed headers are added.
20598 .option headers_only transports boolean false
20599 .cindex "transport" "header lines only"
20600 .cindex "message" "transporting headers only"
20601 .cindex "header lines" "transporting"
20602 If this option is set, the message's body is not transported. It is mutually
20603 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
20604 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
20605 checked, since this option does not automatically suppress them.
20608 .option headers_remove transports list&!! unset
20609 .cindex "header lines" "removing"
20610 .cindex "transport" "header lines; removing"
20611 This option specifies a list of header names,
20612 colon-separated (by default, changeable in the usual way);
20613 these headers are omitted from the message as it is transported, as described
20614 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
20616 Each list item is separately expanded.
20617 If the result of the expansion is an empty string, or if the expansion
20618 is forced to fail, no action is taken. Other expansion failures are treated as
20619 errors and cause the delivery to be deferred.
20621 Unlike most options, &%headers_remove%& can be specified multiple times
20622 for a router; all listed headers are removed.
20624 &*Warning*&: Because of the separate expansion of the list items,
20625 items that contain a list separator must have it doubled.
20626 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
20630 .option headers_rewrite transports string unset
20631 .cindex "transport" "header lines; rewriting"
20632 .cindex "rewriting" "at transport time"
20633 This option allows addresses in header lines to be rewritten at transport time,
20634 that is, as the message is being copied to its destination. The contents of the
20635 option are a colon-separated list of rewriting rules. Each rule is in exactly
20636 the same form as one of the general rewriting rules that are applied when a
20637 message is received. These are described in chapter &<<CHAPrewrite>>&. For
20640 headers_rewrite = a@b c@d f : \
20643 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
20644 &'w@z'& in all address-bearing header lines. The rules are applied to the
20645 header lines just before they are written out at transport time, so they affect
20646 only those copies of the message that pass through the transport. However, only
20647 the message's original header lines, and any that were added by a system
20648 filter, are rewritten. If a router or transport adds header lines, they are not
20649 affected by this option. These rewriting rules are &'not'& applied to the
20650 envelope. You can change the return path using &%return_path%&, but you cannot
20651 change envelope recipients at this time.
20654 .option home_directory transports string&!! unset
20655 .cindex "transport" "home directory for"
20657 This option specifies a home directory setting for a local transport,
20658 overriding any value that may be set by the router. The home directory is
20659 placed in &$home$& while expanding the transport's private options. It is also
20660 used as the current directory if no current directory is set by the
20661 &%current_directory%& option on the transport or the
20662 &%transport_current_directory%& option on the router. If the expansion fails
20663 for any reason, including forced failure, an error is logged, and delivery is
20667 .option initgroups transports boolean false
20668 .cindex "additional groups"
20669 .cindex "groups" "additional"
20670 .cindex "transport" "group; additional"
20671 If this option is true and the uid for the delivery process is provided by the
20672 transport, the &[initgroups()]& function is called when running the transport
20673 to ensure that any additional groups associated with the uid are set up.
20677 .option max_parallel transports integer&!! unset
20678 .cindex limit "transport parallelism"
20679 .cindex transport "parallel processes"
20680 .cindex transport "concurrency limit"
20681 .cindex "delivery" "parallelism for transport"
20682 If this option is set and expands to an integer greater than zero
20683 it limits the number of concurrent runs of the transport.
20684 The control does not apply to shadow transports.
20686 .cindex "hints database" "transport concurrency control"
20687 Exim implements this control by means of a hints database in which a record is
20688 incremented whenever a transport process is beaing created. The record
20689 is decremented and possibly removed when the process terminates.
20690 Obviously there is scope for
20691 records to get left lying around if there is a system or program crash. To
20692 guard against this, Exim ignores any records that are more than six hours old.
20694 If you use this option, you should also arrange to delete the
20695 relevant hints database whenever your system reboots. The names of the files
20696 start with &_misc_& and they are kept in the &_spool/db_& directory. There
20697 may be one or two files, depending on the type of DBM in use. The same files
20698 are used for ETRN and smtp transport serialization.
20702 .option message_size_limit transports string&!! 0
20703 .cindex "limit" "message size per transport"
20704 .cindex "size" "of message, limit"
20705 .cindex "transport" "message size; limiting"
20706 This option controls the size of messages passed through the transport. It is
20707 expanded before use; the result of the expansion must be a sequence of decimal
20708 digits, optionally followed by K or M. If the expansion fails for any reason,
20709 including forced failure, or if the result is not of the required form,
20710 delivery is deferred. If the value is greater than zero and the size of a
20711 message exceeds this limit, the address is failed. If there is any chance that
20712 the resulting bounce message could be routed to the same transport, you should
20713 ensure that &%return_size_limit%& is less than the transport's
20714 &%message_size_limit%&, as otherwise the bounce message will fail to get
20719 .option rcpt_include_affixes transports boolean false
20720 .cindex "prefix" "for local part, including in envelope"
20721 .cindex "suffix for local part" "including in envelope"
20722 .cindex "local part" "prefix"
20723 .cindex "local part" "suffix"
20724 When this option is false (the default), and an address that has had any
20725 affixes (prefixes or suffixes) removed from the local part is delivered by any
20726 form of SMTP or LMTP, the affixes are not included. For example, if a router
20729 local_part_prefix = *-
20731 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
20734 RCPT TO:<xyz@some.domain>
20736 This is also the case when an ACL-time callout is being used to verify a
20737 recipient address. However, if &%rcpt_include_affixes%& is set true, the
20738 whole local part is included in the RCPT command. This option applies to BSMTP
20739 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
20740 &(lmtp)& and &(smtp)& transports.
20743 .option retry_use_local_part transports boolean "see below"
20744 .cindex "hints database" "retry keys"
20745 When a delivery suffers a temporary failure, a retry record is created
20746 in Exim's hints database. For remote deliveries, the key for the retry record
20747 is based on the name and/or IP address of the failing remote host. For local
20748 deliveries, the key is normally the entire address, including both the local
20749 part and the domain. This is suitable for most common cases of local delivery
20750 temporary failure &-- for example, exceeding a mailbox quota should delay only
20751 deliveries to that mailbox, not to the whole domain.
20753 However, in some special cases you may want to treat a temporary local delivery
20754 as a failure associated with the domain, and not with a particular local part.
20755 (For example, if you are storing all mail for some domain in files.) You can do
20756 this by setting &%retry_use_local_part%& false.
20758 For all the local transports, its default value is true. For remote transports,
20759 the default value is false for tidiness, but changing the value has no effect
20760 on a remote transport in the current implementation.
20763 .option return_path transports string&!! unset
20764 .cindex "envelope sender"
20765 .cindex "transport" "return path; changing"
20766 .cindex "return path" "changing in transport"
20767 If this option is set, the string is expanded at transport time and replaces
20768 the existing return path (envelope sender) value in the copy of the message
20769 that is being delivered. An empty return path is permitted. This feature is
20770 designed for remote deliveries, where the value of this option is used in the
20771 SMTP MAIL command. If you set &%return_path%& for a local transport, the
20772 only effect is to change the address that is placed in the &'Return-path:'&
20773 header line, if one is added to the message (see the next option).
20775 &*Note:*& A changed return path is not logged unless you add
20776 &%return_path_on_delivery%& to the log selector.
20778 .vindex "&$return_path$&"
20779 The expansion can refer to the existing value via &$return_path$&. This is
20780 either the message's envelope sender, or an address set by the
20781 &%errors_to%& option on a router. If the expansion is forced to fail, no
20782 replacement occurs; if it fails for another reason, delivery is deferred. This
20783 option can be used to support VERP (Variable Envelope Return Paths) &-- see
20784 section &<<SECTverp>>&.
20786 &*Note*&: If a delivery error is detected locally, including the case when a
20787 remote server rejects a message at SMTP time, the bounce message is not sent to
20788 the value of this option. It is sent to the previously set errors address.
20789 This defaults to the incoming sender address, but can be changed by setting
20790 &%errors_to%& in a router.
20794 .option return_path_add transports boolean false
20795 .cindex "&'Return-path:'& header line"
20796 If this option is true, a &'Return-path:'& header is added to the message.
20797 Although the return path is normally available in the prefix line of BSD
20798 mailboxes, this is commonly not displayed by MUAs, and so the user does not
20799 have easy access to it.
20801 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
20802 the delivery SMTP server makes the final delivery"&. This implies that this
20803 header should not be present in incoming messages. Exim has a configuration
20804 option, &%return_path_remove%&, which requests removal of this header from
20805 incoming messages, so that delivered messages can safely be resent to other
20809 .option shadow_condition transports string&!! unset
20810 See &%shadow_transport%& below.
20813 .option shadow_transport transports string unset
20814 .cindex "shadow transport"
20815 .cindex "transport" "shadow"
20816 A local transport may set the &%shadow_transport%& option to the name of
20817 another local transport. Shadow remote transports are not supported.
20819 Whenever a delivery to the main transport succeeds, and either
20820 &%shadow_condition%& is unset, or its expansion does not result in the empty
20821 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
20822 passed to the shadow transport, with the same delivery address or addresses. If
20823 expansion fails, no action is taken except that non-forced expansion failures
20824 cause a log line to be written.
20826 The result of the shadow transport is discarded and does not affect the
20827 subsequent processing of the message. Only a single level of shadowing is
20828 provided; the &%shadow_transport%& option is ignored on any transport when it
20829 is running as a shadow. Options concerned with output from pipes are also
20830 ignored. The log line for the successful delivery has an item added on the end,
20833 ST=<shadow transport name>
20835 If the shadow transport did not succeed, the error message is put in
20836 parentheses afterwards. Shadow transports can be used for a number of different
20837 purposes, including keeping more detailed log information than Exim normally
20838 provides, and implementing automatic acknowledgment policies based on message
20839 headers that some sites insist on.
20842 .option transport_filter transports string&!! unset
20843 .cindex "transport" "filter"
20844 .cindex "filter" "transport filter"
20845 This option sets up a filtering (in the Unix shell sense) process for messages
20846 at transport time. It should not be confused with mail filtering as set up by
20847 individual users or via a system filter.
20849 If unset, or expanding to an empty string, no filtering is done.
20852 When the message is about to be written out, the command specified by
20853 &%transport_filter%& is started up in a separate, parallel process, and
20854 the entire message, including the header lines, is passed to it on its standard
20855 input (this in fact is done from a third process, to avoid deadlock). The
20856 command must be specified as an absolute path.
20858 The lines of the message that are written to the transport filter are
20859 terminated by newline (&"\n"&). The message is passed to the filter before any
20860 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
20861 lines beginning with a dot, and also before any processing implied by the
20862 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
20863 &(pipe)& transports.
20865 The standard error for the filter process is set to the same destination as its
20866 standard output; this is read and written to the message's ultimate
20867 destination. The process that writes the message to the filter, the
20868 filter itself, and the original process that reads the result and delivers it
20869 are all run in parallel, like a shell pipeline.
20871 The filter can perform any transformations it likes, but of course should take
20872 care not to break RFC 2822 syntax. Exim does not check the result, except to
20873 test for a final newline when SMTP is in use. All messages transmitted over
20874 SMTP must end with a newline, so Exim supplies one if it is missing.
20876 .cindex "content scanning" "per user"
20877 A transport filter can be used to provide content-scanning on a per-user basis
20878 at delivery time if the only required effect of the scan is to modify the
20879 message. For example, a content scan could insert a new header line containing
20880 a spam score. This could be interpreted by a filter in the user's MUA. It is
20881 not possible to discard a message at this stage.
20883 .cindex "SMTP" "SIZE"
20884 A problem might arise if the filter increases the size of a message that is
20885 being sent down an SMTP connection. If the receiving SMTP server has indicated
20886 support for the SIZE parameter, Exim will have sent the size of the message
20887 at the start of the SMTP session. If what is actually sent is substantially
20888 more, the server might reject the message. This can be worked round by setting
20889 the &%size_addition%& option on the &(smtp)& transport, either to allow for
20890 additions to the message, or to disable the use of SIZE altogether.
20892 .vindex "&$pipe_addresses$&"
20893 The value of the &%transport_filter%& option is the command string for starting
20894 the filter, which is run directly from Exim, not under a shell. The string is
20895 parsed by Exim in the same way as a command string for the &(pipe)& transport:
20896 Exim breaks it up into arguments and then expands each argument separately (see
20897 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
20898 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
20899 of arguments, one for each address that applies to this delivery. (This isn't
20900 an ideal name for this feature here, but as it was already implemented for the
20901 &(pipe)& transport, it seemed sensible not to change it.)
20904 .vindex "&$host_address$&"
20905 The expansion variables &$host$& and &$host_address$& are available when the
20906 transport is a remote one. They contain the name and IP address of the host to
20907 which the message is being sent. For example:
20909 transport_filter = /some/directory/transport-filter.pl \
20910 $host $host_address $sender_address $pipe_addresses
20913 Two problems arise if you want to use more complicated expansion items to
20914 generate transport filter commands, both of which due to the fact that the
20915 command is split up &'before'& expansion.
20917 If an expansion item contains white space, you must quote it, so that it is all
20918 part of the same command item. If the entire option setting is one such
20919 expansion item, you have to take care what kind of quoting you use. For
20922 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
20924 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
20925 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
20926 stripped by Exim when it read the option's value. When the value is used, if
20927 the single quotes were missing, the line would be split into two items,
20928 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
20929 Exim tried to expand the first one.
20931 Except for the special case of &$pipe_addresses$& that is mentioned above, an
20932 expansion cannot generate multiple arguments, or a command name followed by
20933 arguments. Consider this example:
20935 transport_filter = ${lookup{$host}lsearch{/a/file}\
20936 {$value}{/bin/cat}}
20938 The result of the lookup is interpreted as the name of the command, even
20939 if it contains white space. The simplest way round this is to use a shell:
20941 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
20942 {$value}{/bin/cat}}
20946 The filter process is run under the same uid and gid as the normal delivery.
20947 For remote deliveries this is the Exim uid/gid by default. The command should
20948 normally yield a zero return code. Transport filters are not supposed to fail.
20949 A non-zero code is taken to mean that the transport filter encountered some
20950 serious problem. Delivery of the message is deferred; the message remains on
20951 the queue and is tried again later. It is not possible to cause a message to be
20952 bounced from a transport filter.
20954 If a transport filter is set on an autoreply transport, the original message is
20955 passed through the filter as it is being copied into the newly generated
20956 message, which happens if the &%return_message%& option is set.
20959 .option transport_filter_timeout transports time 5m
20960 .cindex "transport" "filter, timeout"
20961 When Exim is reading the output of a transport filter, it applies a timeout
20962 that can be set by this option. Exceeding the timeout is normally treated as a
20963 temporary delivery failure. However, if a transport filter is used with a
20964 &(pipe)& transport, a timeout in the transport filter is treated in the same
20965 way as a timeout in the pipe command itself. By default, a timeout is a hard
20966 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
20967 becomes a temporary error.
20970 .option user transports string&!! "Exim user"
20971 .cindex "uid (user id)" "local delivery"
20972 .cindex "transport" "user, specifying"
20973 This option specifies the user under whose uid the delivery process is to be
20974 run, overriding any uid that may have been set by the router. If the user is
20975 given as a name, the uid is looked up from the password data, and the
20976 associated group is taken as the value of the gid to be used if the &%group%&
20979 For deliveries that use local transports, a user and group are normally
20980 specified explicitly or implicitly (for example, as a result of
20981 &%check_local_user%&) by the router or transport.
20983 .cindex "hints database" "access by remote transport"
20984 For remote transports, you should leave this option unset unless you really are
20985 sure you know what you are doing. When a remote transport is running, it needs
20986 to be able to access Exim's hints databases, because each host may have its own
20988 .ecindex IIDgenoptra1
20989 .ecindex IIDgenoptra2
20990 .ecindex IIDgenoptra3
20997 . ////////////////////////////////////////////////////////////////////////////
20998 . ////////////////////////////////////////////////////////////////////////////
21000 .chapter "Address batching in local transports" "CHAPbatching" &&&
21002 .cindex "transport" "local; address batching in"
21003 The only remote transport (&(smtp)&) is normally configured to handle more than
21004 one address at a time, so that when several addresses are routed to the same
21005 remote host, just one copy of the message is sent. Local transports, however,
21006 normally handle one address at a time. That is, a separate instance of the
21007 transport is run for each address that is routed to the transport. A separate
21008 copy of the message is delivered each time.
21010 .cindex "batched local delivery"
21011 .oindex "&%batch_max%&"
21012 .oindex "&%batch_id%&"
21013 In special cases, it may be desirable to handle several addresses at once in a
21014 local transport, for example:
21017 In an &(appendfile)& transport, when storing messages in files for later
21018 delivery by some other means, a single copy of the message with multiple
21019 recipients saves space.
21021 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
21022 a single copy saves time, and is the normal way LMTP is expected to work.
21024 In a &(pipe)& transport, when passing the message
21025 to a scanner program or
21026 to some other delivery mechanism such as UUCP, multiple recipients may be
21030 These three local transports all have the same options for controlling multiple
21031 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
21032 repeating the information for each transport, these options are described here.
21034 The &%batch_max%& option specifies the maximum number of addresses that can be
21035 delivered together in a single run of the transport. Its default value is one
21036 (no batching). When more than one address is routed to a transport that has a
21037 &%batch_max%& value greater than one, the addresses are delivered in a batch
21038 (that is, in a single run of the transport with multiple recipients), subject
21039 to certain conditions:
21042 .vindex "&$local_part$&"
21043 If any of the transport's options contain a reference to &$local_part$&, no
21044 batching is possible.
21046 .vindex "&$domain$&"
21047 If any of the transport's options contain a reference to &$domain$&, only
21048 addresses with the same domain are batched.
21050 .cindex "customizing" "batching condition"
21051 If &%batch_id%& is set, it is expanded for each address, and only those
21052 addresses with the same expanded value are batched. This allows you to specify
21053 customized batching conditions. Failure of the expansion for any reason,
21054 including forced failure, disables batching, but it does not stop the delivery
21057 Batched addresses must also have the same errors address (where to send
21058 delivery errors), the same header additions and removals, the same user and
21059 group for the transport, and if a host list is present, the first host must
21063 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
21064 both when the file or pipe command is specified in the transport, and when it
21065 is specified by a &(redirect)& router, but all the batched addresses must of
21066 course be routed to the same file or pipe command. These two transports have an
21067 option called &%use_bsmtp%&, which causes them to deliver the message in
21068 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
21069 &%check_string%& and &%escape_string%& options are forced to the values
21072 escape_string = ".."
21074 when batched SMTP is in use. A full description of the batch SMTP mechanism is
21075 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
21076 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
21078 .cindex "&'Envelope-to:'& header line"
21079 If the generic &%envelope_to_add%& option is set for a batching transport, the
21080 &'Envelope-to:'& header that is added to the message contains all the addresses
21081 that are being processed together. If you are using a batching &(appendfile)&
21082 transport without &%use_bsmtp%&, the only way to preserve the recipient
21083 addresses is to set the &%envelope_to_add%& option.
21085 .cindex "&(pipe)& transport" "with multiple addresses"
21086 .vindex "&$pipe_addresses$&"
21087 If you are using a &(pipe)& transport without BSMTP, and setting the
21088 transport's &%command%& option, you can include &$pipe_addresses$& as part of
21089 the command. This is not a true variable; it is a bit of magic that causes each
21090 of the recipient addresses to be inserted into the command as a separate
21091 argument. This provides a way of accessing all the addresses that are being
21092 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21093 are specified by a &(redirect)& router.
21098 . ////////////////////////////////////////////////////////////////////////////
21099 . ////////////////////////////////////////////////////////////////////////////
21101 .chapter "The appendfile transport" "CHAPappendfile"
21102 .scindex IIDapptra1 "&(appendfile)& transport"
21103 .scindex IIDapptra2 "transports" "&(appendfile)&"
21104 .cindex "directory creation"
21105 .cindex "creating directories"
21106 The &(appendfile)& transport delivers a message by appending it to an existing
21107 file, or by creating an entirely new file in a specified directory. Single
21108 files to which messages are appended can be in the traditional Unix mailbox
21109 format, or optionally in the MBX format supported by the Pine MUA and
21110 University of Washington IMAP daemon, &'inter alia'&. When each message is
21111 being delivered as a separate file, &"maildir"& format can optionally be used
21112 to give added protection against failures that happen part-way through the
21113 delivery. A third form of separate-file delivery known as &"mailstore"& is also
21114 supported. For all file formats, Exim attempts to create as many levels of
21115 directory as necessary, provided that &%create_directory%& is set.
21117 The code for the optional formats is not included in the Exim binary by
21118 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
21119 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
21122 .cindex "quota" "system"
21123 Exim recognizes system quota errors, and generates an appropriate message. Exim
21124 also supports its own quota control within the transport, for use when the
21125 system facility is unavailable or cannot be used for some reason.
21127 If there is an error while appending to a file (for example, quota exceeded or
21128 partition filled), Exim attempts to reset the file's length and last
21129 modification time back to what they were before. If there is an error while
21130 creating an entirely new file, the new file is removed.
21132 Before appending to a file, a number of security checks are made, and the
21133 file is locked. A detailed description is given below, after the list of
21136 The &(appendfile)& transport is most commonly used for local deliveries to
21137 users' mailboxes. However, it can also be used as a pseudo-remote transport for
21138 putting messages into files for remote delivery by some means other than Exim.
21139 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
21144 .section "The file and directory options" "SECTfildiropt"
21145 The &%file%& option specifies a single file, to which the message is appended;
21146 the &%directory%& option specifies a directory, in which a new file containing
21147 the message is created. Only one of these two options can be set, and for
21148 normal deliveries to mailboxes, one of them &'must'& be set.
21150 .vindex "&$address_file$&"
21151 .vindex "&$local_part$&"
21152 However, &(appendfile)& is also used for delivering messages to files or
21153 directories whose names (or parts of names) are obtained from alias,
21154 forwarding, or filtering operations (for example, a &%save%& command in a
21155 user's Exim filter). When such a transport is running, &$local_part$& contains
21156 the local part that was aliased or forwarded, and &$address_file$& contains the
21157 name (or partial name) of the file or directory generated by the redirection
21158 operation. There are two cases:
21161 If neither &%file%& nor &%directory%& is set, the redirection operation
21162 must specify an absolute path (one that begins with &`/`&). This is the most
21163 common case when users with local accounts use filtering to sort mail into
21164 different folders. See for example, the &(address_file)& transport in the
21165 default configuration. If the path ends with a slash, it is assumed to be the
21166 name of a directory. A delivery to a directory can also be forced by setting
21167 &%maildir_format%& or &%mailstore_format%&.
21169 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
21170 used to determine the file or directory name for the delivery. Normally, the
21171 contents of &$address_file$& are used in some way in the string expansion.
21175 .cindex "Sieve filter" "configuring &(appendfile)&"
21176 .cindex "Sieve filter" "relative mailbox path handling"
21177 As an example of the second case, consider an environment where users do not
21178 have home directories. They may be permitted to use Exim filter commands of the
21183 or Sieve filter commands of the form:
21185 require "fileinto";
21186 fileinto "folder23";
21188 In this situation, the expansion of &%file%& or &%directory%& in the transport
21189 must transform the relative path into an appropriate absolute file name. In the
21190 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
21191 is used as a result of a &"keep"& action in the filter. This example shows one
21192 way of handling this requirement:
21194 file = ${if eq{$address_file}{inbox} \
21195 {/var/mail/$local_part} \
21196 {${if eq{${substr_0_1:$address_file}}{/} \
21198 {$home/mail/$address_file} \
21202 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
21203 location, absolute paths are used without change, and other folders are in the
21204 &_mail_& directory within the home directory.
21206 &*Note 1*&: While processing an Exim filter, a relative path such as
21207 &_folder23_& is turned into an absolute path if a home directory is known to
21208 the router. In particular, this is the case if &%check_local_user%& is set. If
21209 you want to prevent this happening at routing time, you can set
21210 &%router_home_directory%& empty. This forces the router to pass the relative
21211 path to the transport.
21213 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
21214 the &%file%& or &%directory%& option is still used if it is set.
21219 .section "Private options for appendfile" "SECID134"
21220 .cindex "options" "&(appendfile)& transport"
21224 .option allow_fifo appendfile boolean false
21225 .cindex "fifo (named pipe)"
21226 .cindex "named pipe (fifo)"
21227 .cindex "pipe" "named (fifo)"
21228 Setting this option permits delivery to named pipes (FIFOs) as well as to
21229 regular files. If no process is reading the named pipe at delivery time, the
21230 delivery is deferred.
21233 .option allow_symlink appendfile boolean false
21234 .cindex "symbolic link" "to mailbox"
21235 .cindex "mailbox" "symbolic link"
21236 By default, &(appendfile)& will not deliver if the path name for the file is
21237 that of a symbolic link. Setting this option relaxes that constraint, but there
21238 are security issues involved in the use of symbolic links. Be sure you know
21239 what you are doing if you set this. Details of exactly what this option affects
21240 are included in the discussion which follows this list of options.
21243 .option batch_id appendfile string&!! unset
21244 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21245 However, batching is automatically disabled for &(appendfile)& deliveries that
21246 happen as a result of forwarding or aliasing or other redirection directly to a
21250 .option batch_max appendfile integer 1
21251 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21254 .option check_group appendfile boolean false
21255 When this option is set, the group owner of the file defined by the &%file%&
21256 option is checked to see that it is the same as the group under which the
21257 delivery process is running. The default setting is false because the default
21258 file mode is 0600, which means that the group is irrelevant.
21261 .option check_owner appendfile boolean true
21262 When this option is set, the owner of the file defined by the &%file%& option
21263 is checked to ensure that it is the same as the user under which the delivery
21264 process is running.
21267 .option check_string appendfile string "see below"
21268 .cindex "&""From""& line"
21269 As &(appendfile)& writes the message, the start of each line is tested for
21270 matching &%check_string%&, and if it does, the initial matching characters are
21271 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
21272 a literal string, not a regular expression, and the case of any letters it
21273 contains is significant.
21275 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
21276 are forced to &"."& and &".."& respectively, and any settings in the
21277 configuration are ignored. Otherwise, they default to &"From&~"& and
21278 &">From&~"& when the &%file%& option is set, and unset when any of the
21279 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
21281 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
21282 suitable for traditional &"BSD"& mailboxes, where a line beginning with
21283 &"From&~"& indicates the start of a new message. All four options need changing
21284 if another format is used. For example, to deliver to mailboxes in MMDF format:
21285 .cindex "MMDF format mailbox"
21286 .cindex "mailbox" "MMDF format"
21288 check_string = "\1\1\1\1\n"
21289 escape_string = "\1\1\1\1 \n"
21290 message_prefix = "\1\1\1\1\n"
21291 message_suffix = "\1\1\1\1\n"
21293 .option create_directory appendfile boolean true
21294 .cindex "directory creation"
21295 When this option is true, Exim attempts to create any missing superior
21296 directories for the file that it is about to write. A created directory's mode
21297 is given by the &%directory_mode%& option.
21299 The group ownership of a newly created directory is highly dependent on the
21300 operating system (and possibly the file system) that is being used. For
21301 example, in Solaris, if the parent directory has the setgid bit set, its group
21302 is propagated to the child; if not, the currently set group is used. However,
21303 in FreeBSD, the parent's group is always used.
21307 .option create_file appendfile string anywhere
21308 This option constrains the location of files and directories that are created
21309 by this transport. It applies to files defined by the &%file%& option and
21310 directories defined by the &%directory%& option. In the case of maildir
21311 delivery, it applies to the top level directory, not the maildir directories
21314 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
21315 &"belowhome"&. In the second and third cases, a home directory must have been
21316 set for the transport. This option is not useful when an explicit file name is
21317 given for normal mailbox deliveries. It is intended for the case when file
21318 names are generated from users' &_.forward_& files. These are usually handled
21319 by an &(appendfile)& transport called &%address_file%&. See also
21320 &%file_must_exist%&.
21323 .option directory appendfile string&!! unset
21324 This option is mutually exclusive with the &%file%& option, but one of &%file%&
21325 or &%directory%& must be set, unless the delivery is the direct result of a
21326 redirection (see section &<<SECTfildiropt>>&).
21328 When &%directory%& is set, the string is expanded, and the message is delivered
21329 into a new file or files in or below the given directory, instead of being
21330 appended to a single mailbox file. A number of different formats are provided
21331 (see &%maildir_format%& and &%mailstore_format%&), and see section
21332 &<<SECTopdir>>& for further details of this form of delivery.
21335 .option directory_file appendfile string&!! "see below"
21337 .vindex "&$inode$&"
21338 When &%directory%& is set, but neither &%maildir_format%& nor
21339 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
21340 whose name is obtained by expanding this string. The default value is:
21342 q${base62:$tod_epoch}-$inode
21344 This generates a unique name from the current time, in base 62 form, and the
21345 inode of the file. The variable &$inode$& is available only when expanding this
21349 .option directory_mode appendfile "octal integer" 0700
21350 If &(appendfile)& creates any directories as a result of the
21351 &%create_directory%& option, their mode is specified by this option.
21354 .option escape_string appendfile string "see description"
21355 See &%check_string%& above.
21358 .option file appendfile string&!! unset
21359 This option is mutually exclusive with the &%directory%& option, but one of
21360 &%file%& or &%directory%& must be set, unless the delivery is the direct result
21361 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
21362 specifies a single file, to which the message is appended. One or more of
21363 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
21366 .cindex "NFS" "lock file"
21367 .cindex "locking files"
21368 .cindex "lock files"
21369 If you are using more than one host to deliver over NFS into the same
21370 mailboxes, you should always use lock files.
21372 The string value is expanded for each delivery, and must yield an absolute
21373 path. The most common settings of this option are variations on one of these
21376 file = /var/spool/mail/$local_part
21377 file = /home/$local_part/inbox
21380 .cindex "&""sticky""& bit"
21381 In the first example, all deliveries are done into the same directory. If Exim
21382 is configured to use lock files (see &%use_lockfile%& below) it must be able to
21383 create a file in the directory, so the &"sticky"& bit must be turned on for
21384 deliveries to be possible, or alternatively the &%group%& option can be used to
21385 run the delivery under a group id which has write access to the directory.
21389 .option file_format appendfile string unset
21390 .cindex "file" "mailbox; checking existing format"
21391 This option requests the transport to check the format of an existing file
21392 before adding to it. The check consists of matching a specific string at the
21393 start of the file. The value of the option consists of an even number of
21394 colon-separated strings. The first of each pair is the test string, and the
21395 second is the name of a transport. If the transport associated with a matched
21396 string is not the current transport, control is passed over to the other
21397 transport. For example, suppose the standard &(local_delivery)& transport has
21400 file_format = "From : local_delivery :\
21401 \1\1\1\1\n : local_mmdf_delivery"
21403 Mailboxes that begin with &"From"& are still handled by this transport, but if
21404 a mailbox begins with four binary ones followed by a newline, control is passed
21405 to a transport called &%local_mmdf_delivery%&, which presumably is configured
21406 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
21407 is assumed to match the current transport. If the start of a mailbox doesn't
21408 match any string, or if the transport named for a given string is not defined,
21409 delivery is deferred.
21412 .option file_must_exist appendfile boolean false
21413 If this option is true, the file specified by the &%file%& option must exist.
21414 A temporary error occurs if it does not, causing delivery to be deferred.
21415 If this option is false, the file is created if it does not exist.
21418 .option lock_fcntl_timeout appendfile time 0s
21419 .cindex "timeout" "mailbox locking"
21420 .cindex "mailbox" "locking, blocking and non-blocking"
21421 .cindex "locking files"
21422 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
21423 when locking an open mailbox file. If the call fails, the delivery process
21424 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
21425 Non-blocking calls are used so that the file is not kept open during the wait
21426 for the lock; the reason for this is to make it as safe as possible for
21427 deliveries over NFS in the case when processes might be accessing an NFS
21428 mailbox without using a lock file. This should not be done, but
21429 misunderstandings and hence misconfigurations are not unknown.
21431 On a busy system, however, the performance of a non-blocking lock approach is
21432 not as good as using a blocking lock with a timeout. In this case, the waiting
21433 is done inside the system call, and Exim's delivery process acquires the lock
21434 and can proceed as soon as the previous lock holder releases it.
21436 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
21437 timeout, are used. There may still be some retrying: the maximum number of
21440 (lock_retries * lock_interval) / lock_fcntl_timeout
21442 rounded up to the next whole number. In other words, the total time during
21443 which &(appendfile)& is trying to get a lock is roughly the same, unless
21444 &%lock_fcntl_timeout%& is set very large.
21446 You should consider setting this option if you are getting a lot of delayed
21447 local deliveries because of errors of the form
21449 failed to lock mailbox /some/file (fcntl)
21452 .option lock_flock_timeout appendfile time 0s
21453 This timeout applies to file locking when using &[flock()]& (see
21454 &%use_flock%&); the timeout operates in a similar manner to
21455 &%lock_fcntl_timeout%&.
21458 .option lock_interval appendfile time 3s
21459 This specifies the time to wait between attempts to lock the file. See below
21460 for details of locking.
21463 .option lock_retries appendfile integer 10
21464 This specifies the maximum number of attempts to lock the file. A value of zero
21465 is treated as 1. See below for details of locking.
21468 .option lockfile_mode appendfile "octal integer" 0600
21469 This specifies the mode of the created lock file, when a lock file is being
21470 used (see &%use_lockfile%& and &%use_mbx_lock%&).
21473 .option lockfile_timeout appendfile time 30m
21474 .cindex "timeout" "mailbox locking"
21475 When a lock file is being used (see &%use_lockfile%&), if a lock file already
21476 exists and is older than this value, it is assumed to have been left behind by
21477 accident, and Exim attempts to remove it.
21480 .option mailbox_filecount appendfile string&!! unset
21481 .cindex "mailbox" "specifying size of"
21482 .cindex "size" "of mailbox"
21483 If this option is set, it is expanded, and the result is taken as the current
21484 number of files in the mailbox. It must be a decimal number, optionally
21485 followed by K or M. This provides a way of obtaining this information from an
21486 external source that maintains the data.
21489 .option mailbox_size appendfile string&!! unset
21490 .cindex "mailbox" "specifying size of"
21491 .cindex "size" "of mailbox"
21492 If this option is set, it is expanded, and the result is taken as the current
21493 size the mailbox. It must be a decimal number, optionally followed by K or M.
21494 This provides a way of obtaining this information from an external source that
21495 maintains the data. This is likely to be helpful for maildir deliveries where
21496 it is computationally expensive to compute the size of a mailbox.
21500 .option maildir_format appendfile boolean false
21501 .cindex "maildir format" "specifying"
21502 If this option is set with the &%directory%& option, the delivery is into a new
21503 file, in the &"maildir"& format that is used by other mail software. When the
21504 transport is activated directly from a &(redirect)& router (for example, the
21505 &(address_file)& transport in the default configuration), setting
21506 &%maildir_format%& causes the path received from the router to be treated as a
21507 directory, whether or not it ends with &`/`&. This option is available only if
21508 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
21509 &<<SECTmaildirdelivery>>& below for further details.
21512 .option maildir_quota_directory_regex appendfile string "See below"
21513 .cindex "maildir format" "quota; directories included in"
21514 .cindex "quota" "maildir; directories included in"
21515 This option is relevant only when &%maildir_use_size_file%& is set. It defines
21516 a regular expression for specifying directories, relative to the quota
21517 directory (see &%quota_directory%&), that should be included in the quota
21518 calculation. The default value is:
21520 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
21522 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
21523 (directories whose names begin with a dot). If you want to exclude the
21525 folder from the count (as some sites do), you need to change this setting to
21527 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
21529 This uses a negative lookahead in the regular expression to exclude the
21530 directory whose name is &_.Trash_&. When a directory is excluded from quota
21531 calculations, quota processing is bypassed for any messages that are delivered
21532 directly into that directory.
21535 .option maildir_retries appendfile integer 10
21536 This option specifies the number of times to retry when writing a file in
21537 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
21540 .option maildir_tag appendfile string&!! unset
21541 This option applies only to deliveries in maildir format, and is described in
21542 section &<<SECTmaildirdelivery>>& below.
21545 .option maildir_use_size_file appendfile&!! boolean false
21546 .cindex "maildir format" "&_maildirsize_& file"
21547 The result of string expansion for this option must be a valid boolean value.
21548 If it is true, it enables support for &_maildirsize_& files. Exim
21549 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
21550 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
21551 value is zero. See &%maildir_quota_directory_regex%& above and section
21552 &<<SECTmaildirdelivery>>& below for further details.
21554 .option maildirfolder_create_regex appendfile string unset
21555 .cindex "maildir format" "&_maildirfolder_& file"
21556 .cindex "&_maildirfolder_&, creating"
21557 The value of this option is a regular expression. If it is unset, it has no
21558 effect. Otherwise, before a maildir delivery takes place, the pattern is
21559 matched against the name of the maildir directory, that is, the directory
21560 containing the &_new_& and &_tmp_& subdirectories that will be used for the
21561 delivery. If there is a match, Exim checks for the existence of a file called
21562 &_maildirfolder_& in the directory, and creates it if it does not exist.
21563 See section &<<SECTmaildirdelivery>>& for more details.
21566 .option mailstore_format appendfile boolean false
21567 .cindex "mailstore format" "specifying"
21568 If this option is set with the &%directory%& option, the delivery is into two
21569 new files in &"mailstore"& format. The option is available only if
21570 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
21571 below for further details.
21574 .option mailstore_prefix appendfile string&!! unset
21575 This option applies only to deliveries in mailstore format, and is described in
21576 section &<<SECTopdir>>& below.
21579 .option mailstore_suffix appendfile string&!! unset
21580 This option applies only to deliveries in mailstore format, and is described in
21581 section &<<SECTopdir>>& below.
21584 .option mbx_format appendfile boolean false
21585 .cindex "locking files"
21586 .cindex "file" "locking"
21587 .cindex "file" "MBX format"
21588 .cindex "MBX format, specifying"
21589 This option is available only if Exim has been compiled with SUPPORT_MBX
21590 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
21591 the message is appended to the mailbox file in MBX format instead of
21592 traditional Unix format. This format is supported by Pine4 and its associated
21593 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
21595 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
21596 automatically changed by the use of &%mbx_format%&. They should normally be set
21597 empty when using MBX format, so this option almost always appears in this
21604 If none of the locking options are mentioned in the configuration,
21605 &%use_mbx_lock%& is assumed and the other locking options default to false. It
21606 is possible to specify the other kinds of locking with &%mbx_format%&, but
21607 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
21608 interworks with &'c-client'&, providing for shared access to the mailbox. It
21609 should not be used if any program that does not use this form of locking is
21610 going to access the mailbox, nor should it be used if the mailbox file is NFS
21611 mounted, because it works only when the mailbox is accessed from a single host.
21613 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
21614 the standard version of &'c-client'&, because as long as it has a mailbox open
21615 (this means for the whole of a Pine or IMAP session), Exim will not be able to
21616 append messages to it.
21619 .option message_prefix appendfile string&!! "see below"
21620 .cindex "&""From""& line"
21621 The string specified here is expanded and output at the start of every message.
21622 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21623 in which case it is:
21625 message_prefix = "From ${if def:return_path{$return_path}\
21626 {MAILER-DAEMON}} $tod_bsdinbox\n"
21628 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21629 &`\n`& to &`\r\n`& in &%message_prefix%&.
21631 .option message_suffix appendfile string&!! "see below"
21632 The string specified here is expanded and output at the end of every message.
21633 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21634 in which case it is a single newline character. The suffix can be suppressed by
21639 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21640 &`\n`& to &`\r\n`& in &%message_suffix%&.
21642 .option mode appendfile "octal integer" 0600
21643 If the output file is created, it is given this mode. If it already exists and
21644 has wider permissions, they are reduced to this mode. If it has narrower
21645 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
21646 if the delivery is the result of a &%save%& command in a filter file specifying
21647 a particular mode, the mode of the output file is always forced to take that
21648 value, and this option is ignored.
21651 .option mode_fail_narrower appendfile boolean true
21652 This option applies in the case when an existing mailbox file has a narrower
21653 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
21654 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
21655 continues with the delivery attempt, using the existing mode of the file.
21658 .option notify_comsat appendfile boolean false
21659 If this option is true, the &'comsat'& daemon is notified after every
21660 successful delivery to a user mailbox. This is the daemon that notifies logged
21661 on users about incoming mail.
21664 .option quota appendfile string&!! unset
21665 .cindex "quota" "imposed by Exim"
21666 This option imposes a limit on the size of the file to which Exim is appending,
21667 or to the total space used in the directory tree when the &%directory%& option
21668 is set. In the latter case, computation of the space used is expensive, because
21669 all the files in the directory (and any sub-directories) have to be
21670 individually inspected and their sizes summed. (See &%quota_size_regex%& and
21671 &%maildir_use_size_file%& for ways to avoid this in environments where users
21672 have no shell access to their mailboxes).
21674 As there is no interlock against two simultaneous deliveries into a
21675 multi-file mailbox, it is possible for the quota to be overrun in this case.
21676 For single-file mailboxes, of course, an interlock is a necessity.
21678 A file's size is taken as its &'used'& value. Because of blocking effects, this
21679 may be a lot less than the actual amount of disk space allocated to the file.
21680 If the sizes of a number of files are being added up, the rounding effect can
21681 become quite noticeable, especially on systems that have large block sizes.
21682 Nevertheless, it seems best to stick to the &'used'& figure, because this is
21683 the obvious value which users understand most easily.
21685 The value of the option is expanded, and must then be a numerical value
21686 (decimal point allowed), optionally followed by one of the letters K, M, or G,
21687 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
21688 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
21691 &*Note*&: A value of zero is interpreted as &"no quota"&.
21693 The expansion happens while Exim is running as root, before it changes uid for
21694 the delivery. This means that files that are inaccessible to the end user can
21695 be used to hold quota values that are looked up in the expansion. When delivery
21696 fails because this quota is exceeded, the handling of the error is as for
21697 system quota failures.
21699 By default, Exim's quota checking mimics system quotas, and restricts the
21700 mailbox to the specified maximum size, though the value is not accurate to the
21701 last byte, owing to separator lines and additional headers that may get added
21702 during message delivery. When a mailbox is nearly full, large messages may get
21703 refused even though small ones are accepted, because the size of the current
21704 message is added to the quota when the check is made. This behaviour can be
21705 changed by setting &%quota_is_inclusive%& false. When this is done, the check
21706 for exceeding the quota does not include the current message. Thus, deliveries
21707 continue until the quota has been exceeded; thereafter, no further messages are
21708 delivered. See also &%quota_warn_threshold%&.
21711 .option quota_directory appendfile string&!! unset
21712 This option defines the directory to check for quota purposes when delivering
21713 into individual files. The default is the delivery directory, or, if a file
21714 called &_maildirfolder_& exists in a maildir directory, the parent of the
21715 delivery directory.
21718 .option quota_filecount appendfile string&!! 0
21719 This option applies when the &%directory%& option is set. It limits the total
21720 number of files in the directory (compare the inode limit in system quotas). It
21721 can only be used if &%quota%& is also set. The value is expanded; an expansion
21722 failure causes delivery to be deferred. A value of zero is interpreted as
21726 .option quota_is_inclusive appendfile boolean true
21727 See &%quota%& above.
21730 .option quota_size_regex appendfile string unset
21731 This option applies when one of the delivery modes that writes a separate file
21732 for each message is being used. When Exim wants to find the size of one of
21733 these files in order to test the quota, it first checks &%quota_size_regex%&.
21734 If this is set to a regular expression that matches the file name, and it
21735 captures one string, that string is interpreted as a representation of the
21736 file's size. The value of &%quota_size_regex%& is not expanded.
21738 This feature is useful only when users have no shell access to their mailboxes
21739 &-- otherwise they could defeat the quota simply by renaming the files. This
21740 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
21741 the file length to the file name. For example:
21743 maildir_tag = ,S=$message_size
21744 quota_size_regex = ,S=(\d+)
21746 An alternative to &$message_size$& is &$message_linecount$&, which contains the
21747 number of lines in the message.
21749 The regular expression should not assume that the length is at the end of the
21750 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
21751 sometimes add other information onto the ends of message file names.
21753 Section &<<SECID136>>& contains further information.
21756 .option quota_warn_message appendfile string&!! "see below"
21757 See below for the use of this option. If it is not set when
21758 &%quota_warn_threshold%& is set, it defaults to
21760 quota_warn_message = "\
21761 To: $local_part@$domain\n\
21762 Subject: Your mailbox\n\n\
21763 This message is automatically created \
21764 by mail delivery software.\n\n\
21765 The size of your mailbox has exceeded \
21766 a warning threshold that is\n\
21767 set by the system administrator.\n"
21771 .option quota_warn_threshold appendfile string&!! 0
21772 .cindex "quota" "warning threshold"
21773 .cindex "mailbox" "size warning"
21774 .cindex "size" "of mailbox"
21775 This option is expanded in the same way as &%quota%& (see above). If the
21776 resulting value is greater than zero, and delivery of the message causes the
21777 size of the file or total space in the directory tree to cross the given
21778 threshold, a warning message is sent. If &%quota%& is also set, the threshold
21779 may be specified as a percentage of it by following the value with a percent
21783 quota_warn_threshold = 75%
21785 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
21786 percent sign is ignored.
21788 The warning message itself is specified by the &%quota_warn_message%& option,
21789 and it must start with a &'To:'& header line containing the recipient(s) of the
21790 warning message. These do not necessarily have to include the recipient(s) of
21791 the original message. A &'Subject:'& line should also normally be supplied. You
21792 can include any other header lines that you want. If you do not include a
21793 &'From:'& line, the default is:
21795 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
21797 .oindex &%errors_reply_to%&
21798 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
21801 The &%quota%& option does not have to be set in order to use this option; they
21802 are independent of one another except when the threshold is specified as a
21806 .option use_bsmtp appendfile boolean false
21807 .cindex "envelope sender"
21808 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
21809 format, with the envelope sender and recipient(s) included as SMTP commands. If
21810 you want to include a leading HELO command with such messages, you can do
21811 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
21812 for details of batch SMTP.
21815 .option use_crlf appendfile boolean false
21816 .cindex "carriage return"
21818 This option causes lines to be terminated with the two-character CRLF sequence
21819 (carriage return, linefeed) instead of just a linefeed character. In the case
21820 of batched SMTP, the byte sequence written to the file is then an exact image
21821 of what would be sent down a real SMTP connection.
21823 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
21824 (which are used to supply the traditional &"From&~"& and blank line separators
21825 in Berkeley-style mailboxes) are written verbatim, so must contain their own
21826 carriage return characters if these are needed. In cases where these options
21827 have non-empty defaults, the values end with a single linefeed, so they must be
21828 changed to end with &`\r\n`& if &%use_crlf%& is set.
21831 .option use_fcntl_lock appendfile boolean "see below"
21832 This option controls the use of the &[fcntl()]& function to lock a file for
21833 exclusive use when a message is being appended. It is set by default unless
21834 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
21835 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
21836 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
21839 .option use_flock_lock appendfile boolean false
21840 This option is provided to support the use of &[flock()]& for file locking, for
21841 the few situations where it is needed. Most modern operating systems support
21842 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
21843 each other. Exim uses &[fcntl()]& locking by default.
21845 This option is required only if you are using an operating system where
21846 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
21847 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
21848 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
21850 .cindex "Solaris" "&[flock()]& support"
21851 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
21852 have it (and some, I think, provide a not quite right version built on top of
21853 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
21854 the ability to use it, and any attempt to do so will cause a configuration
21857 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
21858 is just being mapped onto &[fcntl()]& by the OS).
21861 .option use_lockfile appendfile boolean "see below"
21862 If this option is turned off, Exim does not attempt to create a lock file when
21863 appending to a mailbox file. In this situation, the only locking is by
21864 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
21865 sure that every MUA that is ever going to look at your users' mailboxes uses
21866 &[fcntl()]& rather than a lock file, and even then only when you are not
21867 delivering over NFS from more than one host.
21869 .cindex "NFS" "lock file"
21870 In order to append to an NFS file safely from more than one host, it is
21871 necessary to take out a lock &'before'& opening the file, and the lock file
21872 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
21875 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
21876 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
21877 except when &%mbx_format%& is set.
21880 .option use_mbx_lock appendfile boolean "see below"
21881 This option is available only if Exim has been compiled with SUPPORT_MBX
21882 set in &_Local/Makefile_&. Setting the option specifies that special MBX
21883 locking rules be used. It is set by default if &%mbx_format%& is set and none
21884 of the locking options are mentioned in the configuration. The locking rules
21885 are the same as are used by the &'c-client'& library that underlies Pine and
21886 the IMAP4 and POP daemons that come with it (see the discussion below). The
21887 rules allow for shared access to the mailbox. However, this kind of locking
21888 does not work when the mailbox is NFS mounted.
21890 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
21891 &%use_flock_lock%& to control what kind of locking is used in implementing the
21892 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
21893 without &%use_fcntl_lock%& or &%use_flock_lock%&.
21898 .section "Operational details for appending" "SECTopappend"
21899 .cindex "appending to a file"
21900 .cindex "file" "appending"
21901 Before appending to a file, the following preparations are made:
21904 If the name of the file is &_/dev/null_&, no action is taken, and a success
21908 .cindex "directory creation"
21909 If any directories on the file's path are missing, Exim creates them if the
21910 &%create_directory%& option is set. A created directory's mode is given by the
21911 &%directory_mode%& option.
21914 If &%file_format%& is set, the format of an existing file is checked. If this
21915 indicates that a different transport should be used, control is passed to that
21919 .cindex "file" "locking"
21920 .cindex "locking files"
21921 .cindex "NFS" "lock file"
21922 If &%use_lockfile%& is set, a lock file is built in a way that will work
21923 reliably over NFS, as follows:
21926 Create a &"hitching post"& file whose name is that of the lock file with the
21927 current time, primary host name, and process id added, by opening for writing
21928 as a new file. If this fails with an access error, delivery is deferred.
21930 Close the hitching post file, and hard link it to the lock file name.
21932 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
21933 Unlink the hitching post name.
21935 Otherwise, use &[stat()]& to get information about the hitching post file, and
21936 then unlink hitching post name. If the number of links is exactly two, creation
21937 of the lock file succeeded but something (for example, an NFS server crash and
21938 restart) caused this fact not to be communicated to the &[link()]& call.
21940 If creation of the lock file failed, wait for &%lock_interval%& and try again,
21941 up to &%lock_retries%& times. However, since any program that writes to a
21942 mailbox should complete its task very quickly, it is reasonable to time out old
21943 lock files that are normally the result of user agent and system crashes. If an
21944 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
21945 it before trying again.
21949 A call is made to &[lstat()]& to discover whether the main file exists, and if
21950 so, what its characteristics are. If &[lstat()]& fails for any reason other
21951 than non-existence, delivery is deferred.
21954 .cindex "symbolic link" "to mailbox"
21955 .cindex "mailbox" "symbolic link"
21956 If the file does exist and is a symbolic link, delivery is deferred, unless the
21957 &%allow_symlink%& option is set, in which case the ownership of the link is
21958 checked, and then &[stat()]& is called to find out about the real file, which
21959 is then subjected to the checks below. The check on the top-level link
21960 ownership prevents one user creating a link for another's mailbox in a sticky
21961 directory, though allowing symbolic links in this case is definitely not a good
21962 idea. If there is a chain of symbolic links, the intermediate ones are not
21966 If the file already exists but is not a regular file, or if the file's owner
21967 and group (if the group is being checked &-- see &%check_group%& above) are
21968 different from the user and group under which the delivery is running,
21969 delivery is deferred.
21972 If the file's permissions are more generous than specified, they are reduced.
21973 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
21974 is set false, in which case the delivery is tried using the existing
21978 The file's inode number is saved, and the file is then opened for appending.
21979 If this fails because the file has vanished, &(appendfile)& behaves as if it
21980 hadn't existed (see below). For any other failures, delivery is deferred.
21983 If the file is opened successfully, check that the inode number hasn't
21984 changed, that it is still a regular file, and that the owner and permissions
21985 have not changed. If anything is wrong, defer delivery and freeze the message.
21988 If the file did not exist originally, defer delivery if the &%file_must_exist%&
21989 option is set. Otherwise, check that the file is being created in a permitted
21990 directory if the &%create_file%& option is set (deferring on failure), and then
21991 open for writing as a new file, with the O_EXCL and O_CREAT options,
21992 except when dealing with a symbolic link (the &%allow_symlink%& option must be
21993 set). In this case, which can happen if the link points to a non-existent file,
21994 the file is opened for writing using O_CREAT but not O_EXCL, because
21995 that prevents link following.
21998 .cindex "loop" "while file testing"
21999 If opening fails because the file exists, obey the tests given above for
22000 existing files. However, to avoid looping in a situation where the file is
22001 being continuously created and destroyed, the exists/not-exists loop is broken
22002 after 10 repetitions, and the message is then frozen.
22005 If opening fails with any other error, defer delivery.
22008 .cindex "file" "locking"
22009 .cindex "locking files"
22010 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
22011 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
22012 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
22013 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
22014 file, and an exclusive lock on the file whose name is
22016 /tmp/.<device-number>.<inode-number>
22018 using the device and inode numbers of the open mailbox file, in accordance with
22019 the MBX locking rules. This file is created with a mode that is specified by
22020 the &%lockfile_mode%& option.
22022 If Exim fails to lock the file, there are two possible courses of action,
22023 depending on the value of the locking timeout. This is obtained from
22024 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
22026 If the timeout value is zero, the file is closed, Exim waits for
22027 &%lock_interval%&, and then goes back and re-opens the file as above and tries
22028 to lock it again. This happens up to &%lock_retries%& times, after which the
22029 delivery is deferred.
22031 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
22032 &[flock()]& are used (with the given timeout), so there has already been some
22033 waiting involved by the time locking fails. Nevertheless, Exim does not give up
22034 immediately. It retries up to
22036 (lock_retries * lock_interval) / <timeout>
22038 times (rounded up).
22041 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
22042 and/or &[flock()]& locks) and then deletes the lock file if one was created.
22045 .section "Operational details for delivery to a new file" "SECTopdir"
22046 .cindex "delivery" "to single file"
22047 .cindex "&""From""& line"
22048 When the &%directory%& option is set instead of &%file%&, each message is
22049 delivered into a newly-created file or set of files. When &(appendfile)& is
22050 activated directly from a &(redirect)& router, neither &%file%& nor
22051 &%directory%& is normally set, because the path for delivery is supplied by the
22052 router. (See for example, the &(address_file)& transport in the default
22053 configuration.) In this case, delivery is to a new file if either the path name
22054 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
22056 No locking is required while writing the message to a new file, so the various
22057 locking options of the transport are ignored. The &"From"& line that by default
22058 separates messages in a single file is not normally needed, nor is the escaping
22059 of message lines that start with &"From"&, and there is no need to ensure a
22060 newline at the end of each message. Consequently, the default values for
22061 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
22062 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
22064 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
22065 the files in the delivery directory by default. However, you can specify a
22066 different directory by setting &%quota_directory%&. Also, for maildir
22067 deliveries (see below) the &_maildirfolder_& convention is honoured.
22070 .cindex "maildir format"
22071 .cindex "mailstore format"
22072 There are three different ways in which delivery to individual files can be
22073 done, controlled by the settings of the &%maildir_format%& and
22074 &%mailstore_format%& options. Note that code to support maildir or mailstore
22075 formats is not included in the binary unless SUPPORT_MAILDIR or
22076 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
22078 .cindex "directory creation"
22079 In all three cases an attempt is made to create the directory and any necessary
22080 sub-directories if they do not exist, provided that the &%create_directory%&
22081 option is set (the default). The location of a created directory can be
22082 constrained by setting &%create_file%&. A created directory's mode is given by
22083 the &%directory_mode%& option. If creation fails, or if the
22084 &%create_directory%& option is not set when creation is required, delivery is
22089 .section "Maildir delivery" "SECTmaildirdelivery"
22090 .cindex "maildir format" "description of"
22091 If the &%maildir_format%& option is true, Exim delivers each message by writing
22092 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
22093 directory that is defined by the &%directory%& option (the &"delivery
22094 directory"&). If the delivery is successful, the file is renamed into the
22095 &_new_& subdirectory.
22097 In the file name, <&'stime'&> is the current time of day in seconds, and
22098 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
22099 Exim checks that the time-of-day clock has moved on by at least one microsecond
22100 before terminating the delivery process. This guarantees uniqueness for the
22101 file name. However, as a precaution, Exim calls &[stat()]& for the file before
22102 opening it. If any response other than ENOENT (does not exist) is given,
22103 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
22105 Before Exim carries out a maildir delivery, it ensures that subdirectories
22106 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
22107 do not exist, Exim tries to create them and any superior directories in their
22108 path, subject to the &%create_directory%& and &%create_file%& options. If the
22109 &%maildirfolder_create_regex%& option is set, and the regular expression it
22110 contains matches the delivery directory, Exim also ensures that a file called
22111 &_maildirfolder_& exists in the delivery directory. If a missing directory or
22112 &_maildirfolder_& file cannot be created, delivery is deferred.
22114 These features make it possible to use Exim to create all the necessary files
22115 and directories in a maildir mailbox, including subdirectories for maildir++
22116 folders. Consider this example:
22118 maildir_format = true
22119 directory = /var/mail/$local_part\
22120 ${if eq{$local_part_suffix}{}{}\
22121 {/.${substr_1:$local_part_suffix}}}
22122 maildirfolder_create_regex = /\.[^/]+$
22124 If &$local_part_suffix$& is empty (there was no suffix for the local part),
22125 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
22126 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
22127 not match this name, so Exim will not look for or create the file
22128 &_/var/mail/pimbo/maildirfolder_&, though it will create
22129 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
22131 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
22132 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
22133 does match &%maildirfolder_create_regex%&. In this case, Exim will create
22134 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
22135 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
22137 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
22138 not inadvertently match the toplevel maildir directory, because a
22139 &_maildirfolder_& file at top level would completely break quota calculations.
22141 .cindex "quota" "in maildir delivery"
22142 .cindex "maildir++"
22143 If Exim is required to check a &%quota%& setting before a maildir delivery, and
22144 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
22145 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
22146 Exim assumes the directory is a maildir++ folder directory, which is one level
22147 down from the user's top level mailbox directory. This causes it to start at
22148 the parent directory instead of the current directory when calculating the
22149 amount of space used.
22151 One problem with delivering into a multi-file mailbox is that it is
22152 computationally expensive to compute the size of the mailbox for quota
22153 checking. Various approaches have been taken to reduce the amount of work
22154 needed. The next two sections describe two of them. A third alternative is to
22155 use some external process for maintaining the size data, and use the expansion
22156 of the &%mailbox_size%& option as a way of importing it into Exim.
22161 .section "Using tags to record message sizes" "SECID135"
22162 If &%maildir_tag%& is set, the string is expanded for each delivery.
22163 When the maildir file is renamed into the &_new_& sub-directory, the
22164 tag is added to its name. However, if adding the tag takes the length of the
22165 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
22166 the tag is dropped and the maildir file is created with no tag.
22169 .vindex "&$message_size$&"
22170 Tags can be used to encode the size of files in their names; see
22171 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
22172 happens after the message has been written. The value of the &$message_size$&
22173 variable is set to the number of bytes actually written. If the expansion is
22174 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
22175 be deferred. The expanded tag may contain any printing characters except &"/"&.
22176 Non-printing characters in the string are ignored; if the resulting string is
22177 empty, it is ignored. If it starts with an alphanumeric character, a leading
22178 colon is inserted; this default has not proven to be the path that popular
22179 maildir implementations have chosen (but changing it in Exim would break
22180 backwards compatibility).
22182 For one common implementation, you might set:
22184 maildir_tag = ,S=${message_size}
22186 but you should check the documentation of the other software to be sure.
22188 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
22189 as this allows Exim to extract the size from your tag, instead of having to
22190 &[stat()]& each message file.
22193 .section "Using a maildirsize file" "SECID136"
22194 .cindex "quota" "in maildir delivery"
22195 .cindex "maildir format" "&_maildirsize_& file"
22196 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
22197 storing quota and message size information in a file called &_maildirsize_&
22198 within the toplevel maildir directory. If this file does not exist, Exim
22199 creates it, setting the quota from the &%quota%& option of the transport. If
22200 the maildir directory itself does not exist, it is created before any attempt
22201 to write a &_maildirsize_& file.
22203 The &_maildirsize_& file is used to hold information about the sizes of
22204 messages in the maildir, thus speeding up quota calculations. The quota value
22205 in the file is just a cache; if the quota is changed in the transport, the new
22206 value overrides the cached value when the next message is delivered. The cache
22207 is maintained for the benefit of other programs that access the maildir and
22208 need to know the quota.
22210 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
22211 file is maintained (with a zero quota setting), but no quota is imposed.
22213 A regular expression is available for controlling which directories in the
22214 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
22215 See the description of the &%maildir_quota_directory_regex%& option above for
22219 .section "Mailstore delivery" "SECID137"
22220 .cindex "mailstore format" "description of"
22221 If the &%mailstore_format%& option is true, each message is written as two
22222 files in the given directory. A unique base name is constructed from the
22223 message id and the current delivery process, and the files that are written use
22224 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
22225 contains the message's envelope, and the &_.msg_& file contains the message
22226 itself. The base name is placed in the variable &$mailstore_basename$&.
22228 During delivery, the envelope is first written to a file with the suffix
22229 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
22230 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
22231 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
22232 file before accessing either of them. An alternative approach is to wait for
22233 the absence of a &_.tmp_& file.
22235 The envelope file starts with any text defined by the &%mailstore_prefix%&
22236 option, expanded and terminated by a newline if there isn't one. Then follows
22237 the sender address on one line, then all the recipient addresses, one per line.
22238 There can be more than one recipient only if the &%batch_max%& option is set
22239 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
22240 appended to the file, followed by a newline if it does not end with one.
22242 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
22243 failure, it is ignored. Other expansion errors are treated as serious
22244 configuration errors, and delivery is deferred. The variable
22245 &$mailstore_basename$& is available for use during these expansions.
22248 .section "Non-special new file delivery" "SECID138"
22249 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
22250 file is created directly in the named directory. For example, when delivering
22251 messages into files in batched SMTP format for later delivery to some host (see
22252 section &<<SECTbatchSMTP>>&), a setting such as
22254 directory = /var/bsmtp/$host
22256 might be used. A message is written to a file with a temporary name, which is
22257 then renamed when the delivery is complete. The final name is obtained by
22258 expanding the contents of the &%directory_file%& option.
22259 .ecindex IIDapptra1
22260 .ecindex IIDapptra2
22267 . ////////////////////////////////////////////////////////////////////////////
22268 . ////////////////////////////////////////////////////////////////////////////
22270 .chapter "The autoreply transport" "CHID8"
22271 .scindex IIDauttra1 "transports" "&(autoreply)&"
22272 .scindex IIDauttra2 "&(autoreply)& transport"
22273 The &(autoreply)& transport is not a true transport in that it does not cause
22274 the message to be transmitted. Instead, it generates a new mail message as an
22275 automatic reply to the incoming message. &'References:'& and
22276 &'Auto-Submitted:'& header lines are included. These are constructed according
22277 to the rules in RFCs 2822 and 3834, respectively.
22279 If the router that passes the message to this transport does not have the
22280 &%unseen%& option set, the original message (for the current recipient) is not
22281 delivered anywhere. However, when the &%unseen%& option is set on the router
22282 that passes the message to this transport, routing of the address continues, so
22283 another router can set up a normal message delivery.
22286 The &(autoreply)& transport is usually run as the result of mail filtering, a
22287 &"vacation"& message being the standard example. However, it can also be run
22288 directly from a router like any other transport. To reduce the possibility of
22289 message cascades, messages created by the &(autoreply)& transport always have
22290 empty envelope sender addresses, like bounce messages.
22292 The parameters of the message to be sent can be specified in the configuration
22293 by options described below. However, these are used only when the address
22294 passed to the transport does not contain its own reply information. When the
22295 transport is run as a consequence of a
22297 or &%vacation%& command in a filter file, the parameters of the message are
22298 supplied by the filter, and passed with the address. The transport's options
22299 that define the message are then ignored (so they are not usually set in this
22300 case). The message is specified entirely by the filter or by the transport; it
22301 is never built from a mixture of options. However, the &%file_optional%&,
22302 &%mode%&, and &%return_message%& options apply in all cases.
22304 &(Autoreply)& is implemented as a local transport. When used as a result of a
22305 command in a user's filter file, &(autoreply)& normally runs under the uid and
22306 gid of the user, and with appropriate current and home directories (see chapter
22307 &<<CHAPenvironment>>&).
22309 There is a subtle difference between routing a message to a &(pipe)& transport
22310 that generates some text to be returned to the sender, and routing it to an
22311 &(autoreply)& transport. This difference is noticeable only if more than one
22312 address from the same message is so handled. In the case of a pipe, the
22313 separate outputs from the different addresses are gathered up and returned to
22314 the sender in a single message, whereas if &(autoreply)& is used, a separate
22315 message is generated for each address that is passed to it.
22317 Non-printing characters are not permitted in the header lines generated for the
22318 message that &(autoreply)& creates, with the exception of newlines that are
22319 immediately followed by white space. If any non-printing characters are found,
22320 the transport defers.
22321 Whether characters with the top bit set count as printing characters or not is
22322 controlled by the &%print_topbitchars%& global option.
22324 If any of the generic options for manipulating headers (for example,
22325 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
22326 of the original message that is included in the generated message when
22327 &%return_message%& is set. They do not apply to the generated message itself.
22329 .vindex "&$sender_address$&"
22330 If the &(autoreply)& transport receives return code 2 from Exim when it submits
22331 the message, indicating that there were no recipients, it does not treat this
22332 as an error. This means that autoreplies sent to &$sender_address$& when this
22333 is empty (because the incoming message is a bounce message) do not cause
22334 problems. They are just discarded.
22338 .section "Private options for autoreply" "SECID139"
22339 .cindex "options" "&(autoreply)& transport"
22341 .option bcc autoreply string&!! unset
22342 This specifies the addresses that are to receive &"blind carbon copies"& of the
22343 message when the message is specified by the transport.
22346 .option cc autoreply string&!! unset
22347 This specifies recipients of the message and the contents of the &'Cc:'& header
22348 when the message is specified by the transport.
22351 .option file autoreply string&!! unset
22352 The contents of the file are sent as the body of the message when the message
22353 is specified by the transport. If both &%file%& and &%text%& are set, the text
22354 string comes first.
22357 .option file_expand autoreply boolean false
22358 If this is set, the contents of the file named by the &%file%& option are
22359 subjected to string expansion as they are added to the message.
22362 .option file_optional autoreply boolean false
22363 If this option is true, no error is generated if the file named by the &%file%&
22364 option or passed with the address does not exist or cannot be read.
22367 .option from autoreply string&!! unset
22368 This specifies the contents of the &'From:'& header when the message is
22369 specified by the transport.
22372 .option headers autoreply string&!! unset
22373 This specifies additional RFC 2822 headers that are to be added to the message
22374 when the message is specified by the transport. Several can be given by using
22375 &"\n"& to separate them. There is no check on the format.
22378 .option log autoreply string&!! unset
22379 This option names a file in which a record of every message sent is logged when
22380 the message is specified by the transport.
22383 .option mode autoreply "octal integer" 0600
22384 If either the log file or the &"once"& file has to be created, this mode is
22388 .option never_mail autoreply "address list&!!" unset
22389 If any run of the transport creates a message with a recipient that matches any
22390 item in the list, that recipient is quietly discarded. If all recipients are
22391 discarded, no message is created. This applies both when the recipients are
22392 generated by a filter and when they are specified in the transport.
22396 .option once autoreply string&!! unset
22397 This option names a file or DBM database in which a record of each &'To:'&
22398 recipient is kept when the message is specified by the transport. &*Note*&:
22399 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
22401 If &%once%& is unset, or is set to an empty string, the message is always sent.
22402 By default, if &%once%& is set to a non-empty file name, the message
22403 is not sent if a potential recipient is already listed in the database.
22404 However, if the &%once_repeat%& option specifies a time greater than zero, the
22405 message is sent if that much time has elapsed since a message was last sent to
22406 this recipient. A setting of zero time for &%once_repeat%& (the default)
22407 prevents a message from being sent a second time &-- in this case, zero means
22410 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
22411 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
22412 greater than zero, it changes the way Exim implements the &%once%& option.
22413 Instead of using a DBM file to record every recipient it sends to, it uses a
22414 regular file, whose size will never get larger than the given value.
22416 In the file, Exim keeps a linear list of recipient addresses and the times at
22417 which they were sent messages. If the file is full when a new address needs to
22418 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
22419 means that a given recipient may receive multiple messages, but at
22420 unpredictable intervals that depend on the rate of turnover of addresses in the
22421 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
22424 .option once_file_size autoreply integer 0
22425 See &%once%& above.
22428 .option once_repeat autoreply time&!! 0s
22429 See &%once%& above.
22430 After expansion, the value of this option must be a valid time value.
22433 .option reply_to autoreply string&!! unset
22434 This specifies the contents of the &'Reply-To:'& header when the message is
22435 specified by the transport.
22438 .option return_message autoreply boolean false
22439 If this is set, a copy of the original message is returned with the new
22440 message, subject to the maximum size set in the &%return_size_limit%& global
22441 configuration option.
22444 .option subject autoreply string&!! unset
22445 This specifies the contents of the &'Subject:'& header when the message is
22446 specified by the transport. It is tempting to quote the original subject in
22447 automatic responses. For example:
22449 subject = Re: $h_subject:
22451 There is a danger in doing this, however. It may allow a third party to
22452 subscribe your users to an opt-in mailing list, provided that the list accepts
22453 bounce messages as subscription confirmations. Well-managed lists require a
22454 non-bounce message to confirm a subscription, so the danger is relatively
22459 .option text autoreply string&!! unset
22460 This specifies a single string to be used as the body of the message when the
22461 message is specified by the transport. If both &%text%& and &%file%& are set,
22462 the text comes first.
22465 .option to autoreply string&!! unset
22466 This specifies recipients of the message and the contents of the &'To:'& header
22467 when the message is specified by the transport.
22468 .ecindex IIDauttra1
22469 .ecindex IIDauttra2
22474 . ////////////////////////////////////////////////////////////////////////////
22475 . ////////////////////////////////////////////////////////////////////////////
22477 .chapter "The lmtp transport" "CHAPLMTP"
22478 .cindex "transports" "&(lmtp)&"
22479 .cindex "&(lmtp)& transport"
22480 .cindex "LMTP" "over a pipe"
22481 .cindex "LMTP" "over a socket"
22482 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
22484 or by interacting with a Unix domain socket.
22485 This transport is something of a cross between the &(pipe)& and &(smtp)&
22486 transports. Exim also has support for using LMTP over TCP/IP; this is
22487 implemented as an option for the &(smtp)& transport. Because LMTP is expected
22488 to be of minority interest, the default build-time configure in &_src/EDITME_&
22489 has it commented out. You need to ensure that
22493 .cindex "options" "&(lmtp)& transport"
22494 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
22495 included in the Exim binary. The private options of the &(lmtp)& transport are
22498 .option batch_id lmtp string&!! unset
22499 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22502 .option batch_max lmtp integer 1
22503 This limits the number of addresses that can be handled in a single delivery.
22504 Most LMTP servers can handle several addresses at once, so it is normally a
22505 good idea to increase this value. See the description of local delivery
22506 batching in chapter &<<CHAPbatching>>&.
22509 .option command lmtp string&!! unset
22510 This option must be set if &%socket%& is not set. The string is a command which
22511 is run in a separate process. It is split up into a command name and list of
22512 arguments, each of which is separately expanded (so expansion cannot change the
22513 number of arguments). The command is run directly, not via a shell. The message
22514 is passed to the new process using the standard input and output to operate the
22517 .option ignore_quota lmtp boolean false
22518 .cindex "LMTP" "ignoring quota errors"
22519 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
22520 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
22521 in its response to the LHLO command.
22523 .option socket lmtp string&!! unset
22524 This option must be set if &%command%& is not set. The result of expansion must
22525 be the name of a Unix domain socket. The transport connects to the socket and
22526 delivers the message to it using the LMTP protocol.
22529 .option timeout lmtp time 5m
22530 The transport is aborted if the created process or Unix domain socket does not
22531 respond to LMTP commands or message input within this timeout. Delivery
22532 is deferred, and will be tried again later. Here is an example of a typical
22537 command = /some/local/lmtp/delivery/program
22541 This delivers up to 20 addresses at a time, in a mixture of domains if
22542 necessary, running as the user &'exim'&.
22546 . ////////////////////////////////////////////////////////////////////////////
22547 . ////////////////////////////////////////////////////////////////////////////
22549 .chapter "The pipe transport" "CHAPpipetransport"
22550 .scindex IIDpiptra1 "transports" "&(pipe)&"
22551 .scindex IIDpiptra2 "&(pipe)& transport"
22552 The &(pipe)& transport is used to deliver messages via a pipe to a command
22553 running in another process. One example is the use of &(pipe)& as a
22554 pseudo-remote transport for passing messages to some other delivery mechanism
22555 (such as UUCP). Another is the use by individual users to automatically process
22556 their incoming messages. The &(pipe)& transport can be used in one of the
22560 .vindex "&$local_part$&"
22561 A router routes one address to a transport in the normal way, and the
22562 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
22563 contains the local part of the address (as usual), and the command that is run
22564 is specified by the &%command%& option on the transport.
22566 .vindex "&$pipe_addresses$&"
22567 If the &%batch_max%& option is set greater than 1 (the default is 1), the
22568 transport can handle more than one address in a single run. In this case, when
22569 more than one address is routed to the transport, &$local_part$& is not set
22570 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
22571 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
22572 that are routed to the transport.
22574 .vindex "&$address_pipe$&"
22575 A router redirects an address directly to a pipe command (for example, from an
22576 alias or forward file). In this case, &$address_pipe$& contains the text of the
22577 pipe command, and the &%command%& option on the transport is ignored unless
22578 &%force_command%& is set. If only one address is being transported
22579 (&%batch_max%& is not greater than one, or only one address was redirected to
22580 this pipe command), &$local_part$& contains the local part that was redirected.
22584 The &(pipe)& transport is a non-interactive delivery method. Exim can also
22585 deliver messages over pipes using the LMTP interactive protocol. This is
22586 implemented by the &(lmtp)& transport.
22588 In the case when &(pipe)& is run as a consequence of an entry in a local user's
22589 &_.forward_& file, the command runs under the uid and gid of that user. In
22590 other cases, the uid and gid have to be specified explicitly, either on the
22591 transport or on the router that handles the address. Current and &"home"&
22592 directories are also controllable. See chapter &<<CHAPenvironment>>& for
22593 details of the local delivery environment and chapter &<<CHAPbatching>>&
22594 for a discussion of local delivery batching.
22597 .section "Concurrent delivery" "SECID140"
22598 If two messages arrive at almost the same time, and both are routed to a pipe
22599 delivery, the two pipe transports may be run concurrently. You must ensure that
22600 any pipe commands you set up are robust against this happening. If the commands
22601 write to a file, the &%exim_lock%& utility might be of use.
22603 Alternatively the &%max_parallel%& option could be used with a value
22604 of "1" to enforce serialization.
22610 .section "Returned status and data" "SECID141"
22611 .cindex "&(pipe)& transport" "returned data"
22612 If the command exits with a non-zero return code, the delivery is deemed to
22613 have failed, unless either the &%ignore_status%& option is set (in which case
22614 the return code is treated as zero), or the return code is one of those listed
22615 in the &%temp_errors%& option, which are interpreted as meaning &"try again
22616 later"&. In this case, delivery is deferred. Details of a permanent failure are
22617 logged, but are not included in the bounce message, which merely contains
22618 &"local delivery failed"&.
22620 If the command exits on a signal and the &%freeze_signal%& option is set then
22621 the message will be frozen in the queue. If that option is not set, a bounce
22622 will be sent as normal.
22624 If the return code is greater than 128 and the command being run is a shell
22625 script, it normally means that the script was terminated by a signal whose
22626 value is the return code minus 128. The &%freeze_signal%& option does not
22627 apply in this case.
22629 If Exim is unable to run the command (that is, if &[execve()]& fails), the
22630 return code is set to 127. This is the value that a shell returns if it is
22631 asked to run a non-existent command. The wording for the log line suggests that
22632 a non-existent command may be the problem.
22634 The &%return_output%& option can affect the result of a pipe delivery. If it is
22635 set and the command produces any output on its standard output or standard
22636 error streams, the command is considered to have failed, even if it gave a zero
22637 return code or if &%ignore_status%& is set. The output from the command is
22638 included as part of the bounce message. The &%return_fail_output%& option is
22639 similar, except that output is returned only when the command exits with a
22640 failure return code, that is, a value other than zero or a code that matches
22645 .section "How the command is run" "SECThowcommandrun"
22646 .cindex "&(pipe)& transport" "path for command"
22647 The command line is (by default) broken down into a command name and arguments
22648 by the &(pipe)& transport itself. The &%allow_commands%& and
22649 &%restrict_to_path%& options can be used to restrict the commands that may be
22652 .cindex "quoting" "in pipe command"
22653 Unquoted arguments are delimited by white space. If an argument appears in
22654 double quotes, backslash is interpreted as an escape character in the usual
22655 way. If an argument appears in single quotes, no escaping is done.
22657 String expansion is applied to the command line except when it comes from a
22658 traditional &_.forward_& file (commands from a filter file are expanded). The
22659 expansion is applied to each argument in turn rather than to the whole line.
22660 For this reason, any string expansion item that contains white space must be
22661 quoted so as to be contained within a single argument. A setting such as
22663 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
22665 will not work, because the expansion item gets split between several
22666 arguments. You have to write
22668 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
22670 to ensure that it is all in one argument. The expansion is done in this way,
22671 argument by argument, so that the number of arguments cannot be changed as a
22672 result of expansion, and quotes or backslashes in inserted variables do not
22673 interact with external quoting. However, this leads to problems if you want to
22674 generate multiple arguments (or the command name plus arguments) from a single
22675 expansion. In this situation, the simplest solution is to use a shell. For
22678 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
22681 .cindex "transport" "filter"
22682 .cindex "filter" "transport filter"
22683 .vindex "&$pipe_addresses$&"
22684 Special handling takes place when an argument consists of precisely the text
22685 &`$pipe_addresses`&. This is not a general expansion variable; the only
22686 place this string is recognized is when it appears as an argument for a pipe or
22687 transport filter command. It causes each address that is being handled to be
22688 inserted in the argument list at that point &'as a separate argument'&. This
22689 avoids any problems with spaces or shell metacharacters, and is of use when a
22690 &(pipe)& transport is handling groups of addresses in a batch.
22692 If &%force_command%& is enabled on the transport, Special handling takes place
22693 for an argument that consists of precisely the text &`$address_pipe`&. It
22694 is handled similarly to &$pipe_addresses$& above. It is expanded and each
22695 argument is inserted in the argument list at that point
22696 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
22697 the only item in the argument; in fact, if it were then &%force_command%&
22698 should behave as a no-op. Rather, it should be used to adjust the command
22699 run while preserving the argument vector separation.
22701 After splitting up into arguments and expansion, the resulting command is run
22702 in a subprocess directly from the transport, &'not'& under a shell. The
22703 message that is being delivered is supplied on the standard input, and the
22704 standard output and standard error are both connected to a single pipe that is
22705 read by Exim. The &%max_output%& option controls how much output the command
22706 may produce, and the &%return_output%& and &%return_fail_output%& options
22707 control what is done with it.
22709 Not running the command under a shell (by default) lessens the security risks
22710 in cases when a command from a user's filter file is built out of data that was
22711 taken from an incoming message. If a shell is required, it can of course be
22712 explicitly specified as the command to be run. However, there are circumstances
22713 where existing commands (for example, in &_.forward_& files) expect to be run
22714 under a shell and cannot easily be modified. To allow for these cases, there is
22715 an option called &%use_shell%&, which changes the way the &(pipe)& transport
22716 works. Instead of breaking up the command line as just described, it expands it
22717 as a single string and passes the result to &_/bin/sh_&. The
22718 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
22719 with &%use_shell%&, and the whole mechanism is inherently less secure.
22723 .section "Environment variables" "SECTpipeenv"
22724 .cindex "&(pipe)& transport" "environment for command"
22725 .cindex "environment for pipe transport"
22726 The environment variables listed below are set up when the command is invoked.
22727 This list is a compromise for maximum compatibility with other MTAs. Note that
22728 the &%environment%& option can be used to add additional variables to this
22731 &`DOMAIN `& the domain of the address
22732 &`HOME `& the home directory, if set
22733 &`HOST `& the host name when called from a router (see below)
22734 &`LOCAL_PART `& see below
22735 &`LOCAL_PART_PREFIX `& see below
22736 &`LOCAL_PART_SUFFIX `& see below
22737 &`LOGNAME `& see below
22738 &`MESSAGE_ID `& Exim's local ID for the message
22739 &`PATH `& as specified by the &%path%& option below
22740 &`QUALIFY_DOMAIN `& the sender qualification domain
22741 &`RECIPIENT `& the complete recipient address
22742 &`SENDER `& the sender of the message (empty if a bounce)
22743 &`SHELL `& &`/bin/sh`&
22744 &`TZ `& the value of the &%timezone%& option, if set
22745 &`USER `& see below
22747 When a &(pipe)& transport is called directly from (for example) an &(accept)&
22748 router, LOCAL_PART is set to the local part of the address. When it is
22749 called as a result of a forward or alias expansion, LOCAL_PART is set to
22750 the local part of the address that was expanded. In both cases, any affixes are
22751 removed from the local part, and made available in LOCAL_PART_PREFIX and
22752 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
22753 same value as LOCAL_PART for compatibility with other MTAs.
22756 HOST is set only when a &(pipe)& transport is called from a router that
22757 associates hosts with an address, typically when using &(pipe)& as a
22758 pseudo-remote transport. HOST is set to the first host name specified by
22762 If the transport's generic &%home_directory%& option is set, its value is used
22763 for the HOME environment variable. Otherwise, a home directory may be set
22764 by the router's &%transport_home_directory%& option, which defaults to the
22765 user's home directory if &%check_local_user%& is set.
22768 .section "Private options for pipe" "SECID142"
22769 .cindex "options" "&(pipe)& transport"
22773 .option allow_commands pipe "string list&!!" unset
22774 .cindex "&(pipe)& transport" "permitted commands"
22775 The string is expanded, and is then interpreted as a colon-separated list of
22776 permitted commands. If &%restrict_to_path%& is not set, the only commands
22777 permitted are those in the &%allow_commands%& list. They need not be absolute
22778 paths; the &%path%& option is still used for relative paths. If
22779 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
22780 in the &%allow_commands%& list, or a name without any slashes that is found on
22781 the path. In other words, if neither &%allow_commands%& nor
22782 &%restrict_to_path%& is set, there is no restriction on the command, but
22783 otherwise only commands that are permitted by one or the other are allowed. For
22786 allow_commands = /usr/bin/vacation
22788 and &%restrict_to_path%& is not set, the only permitted command is
22789 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
22790 &%use_shell%& is set.
22793 .option batch_id pipe string&!! unset
22794 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22797 .option batch_max pipe integer 1
22798 This limits the number of addresses that can be handled in a single delivery.
22799 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22802 .option check_string pipe string unset
22803 As &(pipe)& writes the message, the start of each line is tested for matching
22804 &%check_string%&, and if it does, the initial matching characters are replaced
22805 by the contents of &%escape_string%&, provided both are set. The value of
22806 &%check_string%& is a literal string, not a regular expression, and the case of
22807 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
22808 of &%check_string%& and &%escape_string%& are forced to values that implement
22809 the SMTP escaping protocol. Any settings made in the configuration file are
22813 .option command pipe string&!! unset
22814 This option need not be set when &(pipe)& is being used to deliver to pipes
22815 obtained directly from address redirections. In other cases, the option must be
22816 set, to provide a command to be run. It need not yield an absolute path (see
22817 the &%path%& option below). The command is split up into separate arguments by
22818 Exim, and each argument is separately expanded, as described in section
22819 &<<SECThowcommandrun>>& above.
22822 .option environment pipe string&!! unset
22823 .cindex "&(pipe)& transport" "environment for command"
22824 .cindex "environment for &(pipe)& transport"
22825 This option is used to add additional variables to the environment in which the
22826 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
22827 a string which is expanded, and then interpreted as a colon-separated list of
22828 environment settings of the form <&'name'&>=<&'value'&>.
22831 .option escape_string pipe string unset
22832 See &%check_string%& above.
22835 .option freeze_exec_fail pipe boolean false
22836 .cindex "exec failure"
22837 .cindex "failure of exec"
22838 .cindex "&(pipe)& transport" "failure of exec"
22839 Failure to exec the command in a pipe transport is by default treated like
22840 any other failure while running the command. However, if &%freeze_exec_fail%&
22841 is set, failure to exec is treated specially, and causes the message to be
22842 frozen, whatever the setting of &%ignore_status%&.
22845 .option freeze_signal pipe boolean false
22846 .cindex "signal exit"
22847 .cindex "&(pipe)& transport", "signal exit"
22848 Normally if the process run by a command in a pipe transport exits on a signal,
22849 a bounce message is sent. If &%freeze_signal%& is set, the message will be
22850 frozen in Exim's queue instead.
22853 .option force_command pipe boolean false
22854 .cindex "force command"
22855 .cindex "&(pipe)& transport", "force command"
22856 Normally when a router redirects an address directly to a pipe command
22857 the &%command%& option on the transport is ignored. If &%force_command%&
22858 is set, the &%command%& option will used. This is especially
22859 useful for forcing a wrapper or additional argument to be added to the
22860 command. For example:
22862 command = /usr/bin/remote_exec myhost -- $address_pipe
22866 Note that &$address_pipe$& is handled specially in &%command%& when
22867 &%force_command%& is set, expanding out to the original argument vector as
22868 separate items, similarly to a Unix shell &`"$@"`& construct.
22871 .option ignore_status pipe boolean false
22872 If this option is true, the status returned by the subprocess that is set up to
22873 run the command is ignored, and Exim behaves as if zero had been returned.
22874 Otherwise, a non-zero status or termination by signal causes an error return
22875 from the transport unless the status value is one of those listed in
22876 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
22878 &*Note*&: This option does not apply to timeouts, which do not return a status.
22879 See the &%timeout_defer%& option for how timeouts are handled.
22882 .option log_defer_output pipe boolean false
22883 .cindex "&(pipe)& transport" "logging output"
22884 If this option is set, and the status returned by the command is
22885 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
22886 and any output was produced on stdout or stderr, the first line of it is
22887 written to the main log.
22890 .option log_fail_output pipe boolean false
22891 If this option is set, and the command returns any output on stdout or
22892 stderr, and also ends with a return code that is neither zero nor one of
22893 the return codes listed in &%temp_errors%& (that is, the delivery
22894 failed), the first line of output is written to the main log. This
22895 option and &%log_output%& are mutually exclusive. Only one of them may
22899 .option log_output pipe boolean false
22900 If this option is set and the command returns any output on stdout or
22901 stderr, the first line of output is written to the main log, whatever
22902 the return code. This option and &%log_fail_output%& are mutually
22903 exclusive. Only one of them may be set.
22906 .option max_output pipe integer 20K
22907 This specifies the maximum amount of output that the command may produce on its
22908 standard output and standard error file combined. If the limit is exceeded, the
22909 process running the command is killed. This is intended as a safety measure to
22910 catch runaway processes. The limit is applied independently of the settings of
22911 the options that control what is done with such output (for example,
22912 &%return_output%&). Because of buffering effects, the amount of output may
22913 exceed the limit by a small amount before Exim notices.
22916 .option message_prefix pipe string&!! "see below"
22917 The string specified here is expanded and output at the start of every message.
22918 The default is unset if &%use_bsmtp%& is set. Otherwise it is
22921 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
22925 .cindex "&%tmail%&"
22926 .cindex "&""From""& line"
22927 This is required by the commonly used &_/usr/bin/vacation_& program.
22928 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
22929 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
22934 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22935 &`\n`& to &`\r\n`& in &%message_prefix%&.
22938 .option message_suffix pipe string&!! "see below"
22939 The string specified here is expanded and output at the end of every message.
22940 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
22941 The suffix can be suppressed by setting
22945 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22946 &`\n`& to &`\r\n`& in &%message_suffix%&.
22949 .option path pipe string "see below"
22950 This option specifies the string that is set up in the PATH environment
22951 variable of the subprocess. The default is:
22955 If the &%command%& option does not yield an absolute path name, the command is
22956 sought in the PATH directories, in the usual way. &*Warning*&: This does not
22957 apply to a command specified as a transport filter.
22960 .option permit_coredump pipe boolean false
22961 Normally Exim inhibits core-dumps during delivery. If you have a need to get
22962 a core-dump of a pipe command, enable this command. This enables core-dumps
22963 during delivery and affects both the Exim binary and the pipe command run.
22964 It is recommended that this option remain off unless and until you have a need
22965 for it and that this only be enabled when needed, as the risk of excessive
22966 resource consumption can be quite high. Note also that Exim is typically
22967 installed as a setuid binary and most operating systems will inhibit coredumps
22968 of these by default, so further OS-specific action may be required.
22971 .option pipe_as_creator pipe boolean false
22972 .cindex "uid (user id)" "local delivery"
22973 If the generic &%user%& option is not set and this option is true, the delivery
22974 process is run under the uid that was in force when Exim was originally called
22975 to accept the message. If the group id is not otherwise set (via the generic
22976 &%group%& option), the gid that was in force when Exim was originally called to
22977 accept the message is used.
22980 .option restrict_to_path pipe boolean false
22981 When this option is set, any command name not listed in &%allow_commands%& must
22982 contain no slashes. The command is searched for only in the directories listed
22983 in the &%path%& option. This option is intended for use in the case when a pipe
22984 command has been generated from a user's &_.forward_& file. This is usually
22985 handled by a &(pipe)& transport called &%address_pipe%&.
22988 .option return_fail_output pipe boolean false
22989 If this option is true, and the command produced any output and ended with a
22990 return code other than zero or one of the codes listed in &%temp_errors%& (that
22991 is, the delivery failed), the output is returned in the bounce message.
22992 However, if the message has a null sender (that is, it is itself a bounce
22993 message), output from the command is discarded. This option and
22994 &%return_output%& are mutually exclusive. Only one of them may be set.
22998 .option return_output pipe boolean false
22999 If this option is true, and the command produced any output, the delivery is
23000 deemed to have failed whatever the return code from the command, and the output
23001 is returned in the bounce message. Otherwise, the output is just discarded.
23002 However, if the message has a null sender (that is, it is a bounce message),
23003 output from the command is always discarded, whatever the setting of this
23004 option. This option and &%return_fail_output%& are mutually exclusive. Only one
23005 of them may be set.
23009 .option temp_errors pipe "string list" "see below"
23010 .cindex "&(pipe)& transport" "temporary failure"
23011 This option contains either a colon-separated list of numbers, or a single
23012 asterisk. If &%ignore_status%& is false
23013 and &%return_output%& is not set,
23014 and the command exits with a non-zero return code, the failure is treated as
23015 temporary and the delivery is deferred if the return code matches one of the
23016 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
23017 codes are treated as permanent errors. The default setting contains the codes
23018 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
23019 compiled on a system that does not define these macros, it assumes values of 75
23020 and 73, respectively.
23023 .option timeout pipe time 1h
23024 If the command fails to complete within this time, it is killed. This normally
23025 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
23026 specifies no timeout. In order to ensure that any subprocesses created by the
23027 command are also killed, Exim makes the initial process a process group leader,
23028 and kills the whole process group on a timeout. However, this can be defeated
23029 if one of the processes starts a new process group.
23031 .option timeout_defer pipe boolean false
23032 A timeout in a &(pipe)& transport, either in the command that the transport
23033 runs, or in a transport filter that is associated with it, is by default
23034 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
23035 is set true, both kinds of timeout become temporary errors, causing the
23036 delivery to be deferred.
23038 .option umask pipe "octal integer" 022
23039 This specifies the umask setting for the subprocess that runs the command.
23042 .option use_bsmtp pipe boolean false
23043 .cindex "envelope sender"
23044 If this option is set true, the &(pipe)& transport writes messages in &"batch
23045 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
23046 commands. If you want to include a leading HELO command with such messages,
23047 you can do so by setting the &%message_prefix%& option. See section
23048 &<<SECTbatchSMTP>>& for details of batch SMTP.
23050 .option use_classresources pipe boolean false
23051 .cindex "class resources (BSD)"
23052 This option is available only when Exim is running on FreeBSD, NetBSD, or
23053 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
23054 resource limits when a &(pipe)& transport is run to perform a delivery. The
23055 limits for the uid under which the pipe is to run are obtained from the login
23059 .option use_crlf pipe boolean false
23060 .cindex "carriage return"
23062 This option causes lines to be terminated with the two-character CRLF sequence
23063 (carriage return, linefeed) instead of just a linefeed character. In the case
23064 of batched SMTP, the byte sequence written to the pipe is then an exact image
23065 of what would be sent down a real SMTP connection.
23067 The contents of the &%message_prefix%& and &%message_suffix%& options are
23068 written verbatim, so must contain their own carriage return characters if these
23069 are needed. When &%use_bsmtp%& is not set, the default values for both
23070 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
23071 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
23074 .option use_shell pipe boolean false
23075 .vindex "&$pipe_addresses$&"
23076 If this option is set, it causes the command to be passed to &_/bin/sh_&
23077 instead of being run directly from the transport, as described in section
23078 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
23079 where the command is expected to be run under a shell and cannot easily be
23080 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
23081 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
23082 command is expanded as a single string, and handed to &_/bin/sh_& as data for
23087 .section "Using an external local delivery agent" "SECID143"
23088 .cindex "local delivery" "using an external agent"
23089 .cindex "&'procmail'&"
23090 .cindex "external local delivery"
23091 .cindex "delivery" "&'procmail'&"
23092 .cindex "delivery" "by external agent"
23093 The &(pipe)& transport can be used to pass all messages that require local
23094 delivery to a separate local delivery agent such as &%procmail%&. When doing
23095 this, care must be taken to ensure that the pipe is run under an appropriate
23096 uid and gid. In some configurations one wants this to be a uid that is trusted
23097 by the delivery agent to supply the correct sender of the message. It may be
23098 necessary to recompile or reconfigure the delivery agent so that it trusts an
23099 appropriate user. The following is an example transport and router
23100 configuration for &%procmail%&:
23105 command = /usr/local/bin/procmail -d $local_part
23109 check_string = "From "
23110 escape_string = ">From "
23119 transport = procmail_pipe
23121 In this example, the pipe is run as the local user, but with the group set to
23122 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
23123 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
23124 user to supply a correct sender address. If you do not specify either a
23125 &%group%& or a &%user%& option, the pipe command is run as the local user. The
23126 home directory is the user's home directory by default.
23128 &*Note*&: The command that the pipe transport runs does &'not'& begin with
23132 as shown in some &%procmail%& documentation, because Exim does not by default
23133 use a shell to run pipe commands.
23136 The next example shows a transport and a router for a system where local
23137 deliveries are handled by the Cyrus IMAP server.
23140 local_delivery_cyrus:
23142 command = /usr/cyrus/bin/deliver \
23143 -m ${substr_1:$local_part_suffix} -- $local_part
23155 local_part_suffix = .*
23156 transport = local_delivery_cyrus
23158 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
23159 &%return_output%& to cause any text written by Cyrus to be returned to the
23161 .ecindex IIDpiptra1
23162 .ecindex IIDpiptra2
23165 . ////////////////////////////////////////////////////////////////////////////
23166 . ////////////////////////////////////////////////////////////////////////////
23168 .chapter "The smtp transport" "CHAPsmtptrans"
23169 .scindex IIDsmttra1 "transports" "&(smtp)&"
23170 .scindex IIDsmttra2 "&(smtp)& transport"
23171 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
23172 or LMTP protocol. The list of hosts to try can either be taken from the address
23173 that is being processed (having been set up by the router), or specified
23174 explicitly for the transport. Timeout and retry processing (see chapter
23175 &<<CHAPretry>>&) is applied to each IP address independently.
23178 .section "Multiple messages on a single connection" "SECID144"
23179 The sending of multiple messages over a single TCP/IP connection can arise in
23183 If a message contains more than &%max_rcpt%& (see below) addresses that are
23184 routed to the same host, more than one copy of the message has to be sent to
23185 that host. In this situation, multiple copies may be sent in a single run of
23186 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
23187 does when it has too many addresses to send in one message also depends on the
23188 value of the global &%remote_max_parallel%& option. Details are given in
23189 section &<<SECToutSMTPTCP>>&.)
23191 .cindex "hints database" "remembering routing"
23192 When a message has been successfully delivered over a TCP/IP connection, Exim
23193 looks in its hints database to see if there are any other messages awaiting a
23194 connection to the same host. If there are, a new delivery process is started
23195 for one of them, and the current TCP/IP connection is passed on to it. The new
23196 process may in turn send multiple copies and possibly create yet another
23201 For each copy sent over the same TCP/IP connection, a sequence counter is
23202 incremented, and if it ever gets to the value of &%connection_max_messages%&,
23203 no further messages are sent over that connection.
23207 .section "Use of the $host and $host_address variables" "SECID145"
23209 .vindex "&$host_address$&"
23210 At the start of a run of the &(smtp)& transport, the values of &$host$& and
23211 &$host_address$& are the name and IP address of the first host on the host list
23212 passed by the router. However, when the transport is about to connect to a
23213 specific host, and while it is connected to that host, &$host$& and
23214 &$host_address$& are set to the values for that host. These are the values
23215 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
23216 &%serialize_hosts%&, and the various TLS options are expanded.
23219 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
23220 .vindex &$tls_bits$&
23221 .vindex &$tls_cipher$&
23222 .vindex &$tls_peerdn$&
23223 .vindex &$tls_sni$&
23224 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
23225 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
23226 are the values that were set when the message was received.
23227 These are the values that are used for options that are expanded before any
23228 SMTP connections are made. Just before each connection is made, these four
23229 variables are emptied. If TLS is subsequently started, they are set to the
23230 appropriate values for the outgoing connection, and these are the values that
23231 are in force when any authenticators are run and when the
23232 &%authenticated_sender%& option is expanded.
23234 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
23235 and will be removed in a future release.
23238 .section "Private options for smtp" "SECID146"
23239 .cindex "options" "&(smtp)& transport"
23240 The private options of the &(smtp)& transport are as follows:
23243 .option address_retry_include_sender smtp boolean true
23244 .cindex "4&'xx'& responses" "retrying after"
23245 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
23246 is the combination of sender and recipient that is delayed in subsequent queue
23247 runs until the retry time is reached. You can delay the recipient without
23248 reference to the sender (which is what earlier versions of Exim did), by
23249 setting &%address_retry_include_sender%& false. However, this can lead to
23250 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
23252 .option allow_localhost smtp boolean false
23253 .cindex "local host" "sending to"
23254 .cindex "fallback" "hosts specified on transport"
23255 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
23256 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
23257 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
23258 the delivery anyway. This should be used only in special cases when the
23259 configuration ensures that no looping will result (for example, a differently
23260 configured Exim is listening on the port to which the message is sent).
23263 .option authenticated_sender smtp string&!! unset
23265 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
23266 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
23267 overriding any existing authenticated sender value. If the string expansion is
23268 forced to fail, the option is ignored. Other expansion failures cause delivery
23269 to be deferred. If the result of expansion is an empty string, that is also
23272 The expansion happens after the outgoing connection has been made and TLS
23273 started, if required. This means that the &$host$&, &$host_address$&,
23274 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
23275 particular connection.
23277 If the SMTP session is not authenticated, the expansion of
23278 &%authenticated_sender%& still happens (and can cause the delivery to be
23279 deferred if it fails), but no AUTH= item is added to MAIL commands
23280 unless &%authenticated_sender_force%& is true.
23282 This option allows you to use the &(smtp)& transport in LMTP mode to
23283 deliver mail to Cyrus IMAP and provide the proper local part as the
23284 &"authenticated sender"&, via a setting such as:
23286 authenticated_sender = $local_part
23288 This removes the need for IMAP subfolders to be assigned special ACLs to
23289 allow direct delivery to those subfolders.
23291 Because of expected uses such as that just described for Cyrus (when no
23292 domain is involved), there is no checking on the syntax of the provided
23296 .option authenticated_sender_force smtp boolean false
23297 If this option is set true, the &%authenticated_sender%& option's value
23298 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
23299 authenticated as a client.
23302 .option command_timeout smtp time 5m
23303 This sets a timeout for receiving a response to an SMTP command that has been
23304 sent out. It is also used when waiting for the initial banner line from the
23305 remote host. Its value must not be zero.
23308 .option connect_timeout smtp time 5m
23309 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
23310 to a remote host. A setting of zero allows the system timeout (typically
23311 several minutes) to act. To have any effect, the value of this option must be
23312 less than the system timeout. However, it has been observed that on some
23313 systems there is no system timeout, which is why the default value for this
23314 option is 5 minutes, a value recommended by RFC 1123.
23317 .option connection_max_messages smtp integer 500
23318 .cindex "SMTP" "passed connection"
23319 .cindex "SMTP" "multiple deliveries"
23320 .cindex "multiple SMTP deliveries"
23321 This controls the maximum number of separate message deliveries that are sent
23322 over a single TCP/IP connection. If the value is zero, there is no limit.
23323 For testing purposes, this value can be overridden by the &%-oB%& command line
23327 .option data_timeout smtp time 5m
23328 This sets a timeout for the transmission of each block in the data portion of
23329 the message. As a result, the overall timeout for a message depends on the size
23330 of the message. Its value must not be zero. See also &%final_timeout%&.
23333 .option delay_after_cutoff smtp boolean true
23334 This option controls what happens when all remote IP addresses for a given
23335 domain have been inaccessible for so long that they have passed their retry
23338 In the default state, if the next retry time has not been reached for any of
23339 them, the address is bounced without trying any deliveries. In other words,
23340 Exim delays retrying an IP address after the final cutoff time until a new
23341 retry time is reached, and can therefore bounce an address without ever trying
23342 a delivery, when machines have been down for a long time. Some people are
23343 unhappy at this prospect, so...
23345 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
23346 addresses are past their final cutoff time, Exim tries to deliver to those
23347 IP addresses that have not been tried since the message arrived. If there are
23348 none, of if they all fail, the address is bounced. In other words, it does not
23349 delay when a new message arrives, but immediately tries those expired IP
23350 addresses that haven't been tried since the message arrived. If there is a
23351 continuous stream of messages for the dead hosts, unsetting
23352 &%delay_after_cutoff%& means that there will be many more attempts to deliver
23356 .option dns_qualify_single smtp boolean true
23357 If the &%hosts%& or &%fallback_hosts%& option is being used,
23358 and the &%gethostbyname%& option is false,
23359 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
23360 in chapter &<<CHAPdnslookup>>& for more details.
23363 .option dns_search_parents smtp boolean false
23364 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
23365 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
23366 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
23370 .option dnssec_request_domains smtp "domain list&!!" unset
23371 .cindex "MX record" "security"
23372 .cindex "DNSSEC" "MX lookup"
23373 .cindex "security" "MX lookup"
23374 .cindex "DNS" "DNSSEC"
23375 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23376 the dnssec request bit set.
23377 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23381 .option dnssec_require_domains smtp "domain list&!!" unset
23382 .cindex "MX record" "security"
23383 .cindex "DNSSEC" "MX lookup"
23384 .cindex "security" "MX lookup"
23385 .cindex "DNS" "DNSSEC"
23386 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23387 the dnssec request bit set. Any returns not having the Authenticated Data bit
23388 (AD bit) set will be ignored and logged as a host-lookup failure.
23389 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23393 .option dscp smtp string&!! unset
23394 .cindex "DCSP" "outbound"
23395 This option causes the DSCP value associated with a socket to be set to one
23396 of a number of fixed strings or to numeric value.
23397 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
23398 Common values include &`throughput`&, &`mincost`&, and on newer systems
23399 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
23401 The outbound packets from Exim will be marked with this value in the header
23402 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
23403 that these values will have any effect, not be stripped by networking
23404 equipment, or do much of anything without cooperation with your Network
23405 Engineer and those of all network operators between the source and destination.
23408 .option fallback_hosts smtp "string list" unset
23409 .cindex "fallback" "hosts specified on transport"
23410 String expansion is not applied to this option. The argument must be a
23411 colon-separated list of host names or IP addresses, optionally also including
23412 port numbers, though the separator can be changed, as described in section
23413 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23414 item in a &%route_list%& setting for the &(manualroute)& router, as described
23415 in section &<<SECTformatonehostitem>>&.
23417 Fallback hosts can also be specified on routers, which associate them with the
23418 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
23419 &%fallback_hosts%& specified on the transport is used only if the address does
23420 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
23421 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
23422 However, &%hosts_randomize%& does apply to fallback host lists.
23424 If Exim is unable to deliver to any of the hosts for a particular address, and
23425 the errors are not permanent rejections, the address is put on a separate
23426 transport queue with its host list replaced by the fallback hosts, unless the
23427 address was routed via MX records and the current host was in the original MX
23428 list. In that situation, the fallback host list is not used.
23430 Once normal deliveries are complete, the fallback queue is delivered by
23431 re-running the same transports with the new host lists. If several failing
23432 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
23433 copy of the message is sent.
23435 The resolution of the host names on the fallback list is controlled by the
23436 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
23437 both to cases when the host list comes with the address and when it is taken
23438 from &%hosts%&. This option provides a &"use a smart host only if delivery
23442 .option final_timeout smtp time 10m
23443 This is the timeout that applies while waiting for the response to the final
23444 line containing just &"."& that terminates a message. Its value must not be
23447 .option gethostbyname smtp boolean false
23448 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
23449 being used, names are looked up using &[gethostbyname()]&
23450 (or &[getipnodebyname()]& when available)
23451 instead of using the DNS. Of course, that function may in fact use the DNS, but
23452 it may also consult other sources of information such as &_/etc/hosts_&.
23454 .option gnutls_compat_mode smtp boolean unset
23455 This option controls whether GnuTLS is used in compatibility mode in an Exim
23456 server. This reduces security slightly, but improves interworking with older
23457 implementations of TLS.
23459 .option helo_data smtp string&!! "see below"
23460 .cindex "HELO" "argument, setting"
23461 .cindex "EHLO" "argument, setting"
23462 .cindex "LHLO argument setting"
23463 The value of this option is expanded after a connection to a another host has
23464 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
23465 command that starts the outgoing SMTP or LMTP session. The default value of the
23470 During the expansion, the variables &$host$& and &$host_address$& are set to
23471 the identity of the remote host, and the variables &$sending_ip_address$& and
23472 &$sending_port$& are set to the local IP address and port number that are being
23473 used. These variables can be used to generate different values for different
23474 servers or different local IP addresses. For example, if you want the string
23475 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
23476 interface address, you could use this:
23478 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
23479 {$primary_hostname}}
23481 The use of &%helo_data%& applies both to sending messages and when doing
23484 .option hosts smtp "string list&!!" unset
23485 Hosts are associated with an address by a router such as &(dnslookup)&, which
23486 finds the hosts by looking up the address domain in the DNS, or by
23487 &(manualroute)&, which has lists of hosts in its configuration. However,
23488 email addresses can be passed to the &(smtp)& transport by any router, and not
23489 all of them can provide an associated list of hosts.
23491 The &%hosts%& option specifies a list of hosts to be used if the address being
23492 processed does not have any hosts associated with it. The hosts specified by
23493 &%hosts%& are also used, whether or not the address has its own hosts, if
23494 &%hosts_override%& is set.
23496 The string is first expanded, before being interpreted as a colon-separated
23497 list of host names or IP addresses, possibly including port numbers. The
23498 separator may be changed to something other than colon, as described in section
23499 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23500 item in a &%route_list%& setting for the &(manualroute)& router, as described
23501 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
23502 of the &(manualroute)& router is not available here.
23504 If the expansion fails, delivery is deferred. Unless the failure was caused by
23505 the inability to complete a lookup, the error is logged to the panic log as
23506 well as the main log. Host names are looked up either by searching directly for
23507 address records in the DNS or by calling &[gethostbyname()]& (or
23508 &[getipnodebyname()]& when available), depending on the setting of the
23509 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
23510 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
23513 During delivery, the hosts are tried in order, subject to their retry status,
23514 unless &%hosts_randomize%& is set.
23517 .option hosts_avoid_esmtp smtp "host list&!!" unset
23518 .cindex "ESMTP, avoiding use of"
23519 .cindex "HELO" "forcing use of"
23520 .cindex "EHLO" "avoiding use of"
23521 .cindex "PIPELINING" "avoiding the use of"
23522 This option is for use with broken hosts that announce ESMTP facilities (for
23523 example, PIPELINING) and then fail to implement them properly. When a host
23524 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
23525 start of the SMTP session. This means that it cannot use any of the ESMTP
23526 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
23529 .option hosts_avoid_pipelining smtp "host list&!!" unset
23530 .cindex "PIPELINING" "avoiding the use of"
23531 Exim will not use the SMTP PIPELINING extension when delivering to any host
23532 that matches this list, even if the server host advertises PIPELINING support.
23535 .option hosts_avoid_tls smtp "host list&!!" unset
23536 .cindex "TLS" "avoiding for certain hosts"
23537 Exim will not try to start a TLS session when delivering to any host that
23538 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23540 .option hosts_verify_avoid_tls smtp "host list&!!" unset
23541 .cindex "TLS" "avoiding for certain hosts"
23542 Exim will not try to start a TLS session for a verify callout,
23543 or when delivering in cutthrough mode,
23544 to any host that matches this list.
23547 .option hosts_max_try smtp integer 5
23548 .cindex "host" "maximum number to try"
23549 .cindex "limit" "number of hosts tried"
23550 .cindex "limit" "number of MX tried"
23551 .cindex "MX record" "maximum tried"
23552 This option limits the number of IP addresses that are tried for any one
23553 delivery in cases where there are temporary delivery errors. Section
23554 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
23557 .option hosts_max_try_hardlimit smtp integer 50
23558 This is an additional check on the maximum number of IP addresses that Exim
23559 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
23564 .option hosts_nopass_tls smtp "host list&!!" unset
23565 .cindex "TLS" "passing connection"
23566 .cindex "multiple SMTP deliveries"
23567 .cindex "TLS" "multiple message deliveries"
23568 For any host that matches this list, a connection on which a TLS session has
23569 been started will not be passed to a new delivery process for sending another
23570 message on the same connection. See section &<<SECTmulmessam>>& for an
23571 explanation of when this might be needed.
23574 .option hosts_override smtp boolean false
23575 If this option is set and the &%hosts%& option is also set, any hosts that are
23576 attached to the address are ignored, and instead the hosts specified by the
23577 &%hosts%& option are always used. This option does not apply to
23578 &%fallback_hosts%&.
23581 .option hosts_randomize smtp boolean false
23582 .cindex "randomized host list"
23583 .cindex "host" "list of; randomized"
23584 .cindex "fallback" "randomized hosts"
23585 If this option is set, and either the list of hosts is taken from the
23586 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
23587 were not obtained from MX records (this includes fallback hosts from the
23588 router), and were not randomized by the router, the order of trying the hosts
23589 is randomized each time the transport runs. Randomizing the order of a host
23590 list can be used to do crude load sharing.
23592 When &%hosts_randomize%& is true, a host list may be split into groups whose
23593 order is separately randomized. This makes it possible to set up MX-like
23594 behaviour. The boundaries between groups are indicated by an item that is just
23595 &`+`& in the host list. For example:
23597 hosts = host1:host2:host3:+:host4:host5
23599 The order of the first three hosts and the order of the last two hosts is
23600 randomized for each use, but the first three always end up before the last two.
23601 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
23603 .option hosts_require_auth smtp "host list&!!" unset
23604 .cindex "authentication" "required by client"
23605 This option provides a list of servers for which authentication must succeed
23606 before Exim will try to transfer a message. If authentication fails for
23607 servers which are not in this list, Exim tries to send unauthenticated. If
23608 authentication fails for one of these servers, delivery is deferred. This
23609 temporary error is detectable in the retry rules, so it can be turned into a
23610 hard failure if required. See also &%hosts_try_auth%&, and chapter
23611 &<<CHAPSMTPAUTH>>& for details of authentication.
23614 .option hosts_request_ocsp smtp "host list&!!" *
23615 .cindex "TLS" "requiring for certain servers"
23616 Exim will request a Certificate Status on a
23617 TLS session for any host that matches this list.
23618 &%tls_verify_certificates%& should also be set for the transport.
23620 .option hosts_require_ocsp smtp "host list&!!" unset
23621 .cindex "TLS" "requiring for certain servers"
23622 Exim will request, and check for a valid Certificate Status being given, on a
23623 TLS session for any host that matches this list.
23624 &%tls_verify_certificates%& should also be set for the transport.
23626 .option hosts_require_tls smtp "host list&!!" unset
23627 .cindex "TLS" "requiring for certain servers"
23628 Exim will insist on using a TLS session when delivering to any host that
23629 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23630 &*Note*&: This option affects outgoing mail only. To insist on TLS for
23631 incoming messages, use an appropriate ACL.
23633 .option hosts_try_auth smtp "host list&!!" unset
23634 .cindex "authentication" "optional in client"
23635 This option provides a list of servers to which, provided they announce
23636 authentication support, Exim will attempt to authenticate as a client when it
23637 connects. If authentication fails, Exim will try to transfer the message
23638 unauthenticated. See also &%hosts_require_auth%&, and chapter
23639 &<<CHAPSMTPAUTH>>& for details of authentication.
23641 .option hosts_try_prdr smtp "host list&!!" *
23642 .cindex "PRDR" "enabling, optional in client"
23643 This option provides a list of servers to which, provided they announce
23644 PRDR support, Exim will attempt to negotiate PRDR
23645 for multi-recipient messages.
23646 The option can usually be left as default.
23648 .option interface smtp "string list&!!" unset
23649 .cindex "bind IP address"
23650 .cindex "IP address" "binding"
23652 .vindex "&$host_address$&"
23653 This option specifies which interface to bind to when making an outgoing SMTP
23654 call. The value is an IP address, not an interface name such as
23655 &`eth0`&. Do not confuse this with the interface address that was used when a
23656 message was received, which is in &$received_ip_address$&, formerly known as
23657 &$interface_address$&. The name was changed to minimize confusion with the
23658 outgoing interface address. There is no variable that contains an outgoing
23659 interface address because, unless it is set by this option, its value is
23662 During the expansion of the &%interface%& option the variables &$host$& and
23663 &$host_address$& refer to the host to which a connection is about to be made
23664 during the expansion of the string. Forced expansion failure, or an empty
23665 string result causes the option to be ignored. Otherwise, after expansion, the
23666 string must be a list of IP addresses, colon-separated by default, but the
23667 separator can be changed in the usual way. For example:
23669 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
23671 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
23672 connection. If none of them are the correct type, the option is ignored. If
23673 &%interface%& is not set, or is ignored, the system's IP functions choose which
23674 interface to use if the host has more than one.
23677 .option keepalive smtp boolean true
23678 .cindex "keepalive" "on outgoing connection"
23679 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
23680 connections. When set, it causes the kernel to probe idle connections
23681 periodically, by sending packets with &"old"& sequence numbers. The other end
23682 of the connection should send a acknowledgment if the connection is still okay
23683 or a reset if the connection has been aborted. The reason for doing this is
23684 that it has the beneficial effect of freeing up certain types of connection
23685 that can get stuck when the remote host is disconnected without tidying up the
23686 TCP/IP call properly. The keepalive mechanism takes several hours to detect
23690 .option lmtp_ignore_quota smtp boolean false
23691 .cindex "LMTP" "ignoring quota errors"
23692 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
23693 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
23694 has advertised support for IGNOREQUOTA in its response to the LHLO command.
23696 .option max_rcpt smtp integer 100
23697 .cindex "RCPT" "maximum number of outgoing"
23698 This option limits the number of RCPT commands that are sent in a single
23699 SMTP message transaction. Each set of addresses is treated independently, and
23700 so can cause parallel connections to the same host if &%remote_max_parallel%&
23704 .option multi_domain smtp boolean&!! true
23705 .vindex "&$domain$&"
23706 When this option is set, the &(smtp)& transport can handle a number of
23707 addresses containing a mixture of different domains provided they all resolve
23708 to the same list of hosts. Turning the option off restricts the transport to
23709 handling only one domain at a time. This is useful if you want to use
23710 &$domain$& in an expansion for the transport, because it is set only when there
23711 is a single domain involved in a remote delivery.
23713 It is expanded per-address and can depend on any of
23714 &$address_data$&, &$domain_data$&, &$local_part_data$&,
23715 &$host$&, &$host_address$& and &$host_port$&.
23717 .option port smtp string&!! "see below"
23718 .cindex "port" "sending TCP/IP"
23719 .cindex "TCP/IP" "setting outgoing port"
23720 This option specifies the TCP/IP port on the server to which Exim connects.
23721 &*Note:*& Do not confuse this with the port that was used when a message was
23722 received, which is in &$received_port$&, formerly known as &$interface_port$&.
23723 The name was changed to minimize confusion with the outgoing port. There is no
23724 variable that contains an outgoing port.
23726 If the value of this option begins with a digit it is taken as a port number;
23727 otherwise it is looked up using &[getservbyname()]&. The default value is
23728 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
23729 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
23734 .option protocol smtp string smtp
23735 .cindex "LMTP" "over TCP/IP"
23736 .cindex "ssmtp protocol" "outbound"
23737 .cindex "TLS" "SSL-on-connect outbound"
23739 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
23740 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
23741 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
23742 deliveries into closed message stores. Exim also has support for running LMTP
23743 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
23745 If this option is set to &"smtps"&, the default value for the &%port%& option
23746 changes to &"smtps"&, and the transport initiates TLS immediately after
23747 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
23748 The Internet standards bodies strongly discourage use of this mode.
23751 .option retry_include_ip_address smtp boolean&!! true
23752 Exim normally includes both the host name and the IP address in the key it
23753 constructs for indexing retry data after a temporary delivery failure. This
23754 means that when one of several IP addresses for a host is failing, it gets
23755 tried periodically (controlled by the retry rules), but use of the other IP
23756 addresses is not affected.
23758 However, in some dialup environments hosts are assigned a different IP address
23759 each time they connect. In this situation the use of the IP address as part of
23760 the retry key leads to undesirable behaviour. Setting this option false causes
23761 Exim to use only the host name.
23762 Since it is expanded it can be made to depend on the host or domain.
23765 .option serialize_hosts smtp "host list&!!" unset
23766 .cindex "serializing connections"
23767 .cindex "host" "serializing connections"
23768 Because Exim operates in a distributed manner, if several messages for the same
23769 host arrive at around the same time, more than one simultaneous connection to
23770 the remote host can occur. This is not usually a problem except when there is a
23771 slow link between the hosts. In that situation it may be helpful to restrict
23772 Exim to one connection at a time. This can be done by setting
23773 &%serialize_hosts%& to match the relevant hosts.
23775 .cindex "hints database" "serializing deliveries to a host"
23776 Exim implements serialization by means of a hints database in which a record is
23777 written whenever a process connects to one of the restricted hosts. The record
23778 is deleted when the connection is completed. Obviously there is scope for
23779 records to get left lying around if there is a system or program crash. To
23780 guard against this, Exim ignores any records that are more than six hours old.
23782 If you set up this kind of serialization, you should also arrange to delete the
23783 relevant hints database whenever your system reboots. The names of the files
23784 start with &_misc_& and they are kept in the &_spool/db_& directory. There
23785 may be one or two files, depending on the type of DBM in use. The same files
23786 are used for ETRN serialization.
23789 See also the &%max_parallel%& generic transport option.
23793 .option size_addition smtp integer 1024
23794 .cindex "SMTP" "SIZE"
23795 .cindex "message" "size issue for transport filter"
23796 .cindex "size" "of message"
23797 .cindex "transport" "filter"
23798 .cindex "filter" "transport filter"
23799 If a remote SMTP server indicates that it supports the SIZE option of the
23800 MAIL command, Exim uses this to pass over the message size at the start of
23801 an SMTP transaction. It adds the value of &%size_addition%& to the value it
23802 sends, to allow for headers and other text that may be added during delivery by
23803 configuration options or in a transport filter. It may be necessary to increase
23804 this if a lot of text is added to messages.
23806 Alternatively, if the value of &%size_addition%& is set negative, it disables
23807 the use of the SIZE option altogether.
23811 .option socks_proxy smtp string&!! unset
23812 .cindex proxy SOCKS
23813 This option enables use of SOCKS proxies for connections made by the
23814 transport. For details see &<<SECTproxySOCKS>>&.
23818 .option tls_certificate smtp string&!! unset
23819 .cindex "TLS" "client certificate, location of"
23820 .cindex "certificate" "client, location of"
23822 .vindex "&$host_address$&"
23823 The value of this option must be the absolute path to a file which contains the
23824 client's certificate, for possible use when sending a message over an encrypted
23825 connection. The values of &$host$& and &$host_address$& are set to the name and
23826 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
23829 &*Note*&: This option must be set if you want Exim to be able to use a TLS
23830 certificate when sending messages as a client. The global option of the same
23831 name specifies the certificate for Exim as a server; it is not automatically
23832 assumed that the same certificate should be used when Exim is operating as a
23836 .option tls_crl smtp string&!! unset
23837 .cindex "TLS" "client certificate revocation list"
23838 .cindex "certificate" "revocation list for client"
23839 This option specifies a certificate revocation list. The expanded value must
23840 be the name of a file that contains a CRL in PEM format.
23843 .option tls_dh_min_bits smtp integer 1024
23844 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
23845 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
23846 key agreement is negotiated, the server will provide a large prime number
23847 for use. This option establishes the minimum acceptable size of that number.
23848 If the parameter offered by the server is too small, then the TLS handshake
23851 Only supported when using GnuTLS.
23854 .option tls_privatekey smtp string&!! unset
23855 .cindex "TLS" "client private key, location of"
23857 .vindex "&$host_address$&"
23858 The value of this option must be the absolute path to a file which contains the
23859 client's private key. This is used when sending a message over an encrypted
23860 connection using a client certificate. The values of &$host$& and
23861 &$host_address$& are set to the name and address of the server during the
23862 expansion. If this option is unset, or the expansion is forced to fail, or the
23863 result is an empty string, the private key is assumed to be in the same file as
23864 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
23867 .option tls_require_ciphers smtp string&!! unset
23868 .cindex "TLS" "requiring specific ciphers"
23869 .cindex "cipher" "requiring specific"
23871 .vindex "&$host_address$&"
23872 The value of this option must be a list of permitted cipher suites, for use
23873 when setting up an outgoing encrypted connection. (There is a global option of
23874 the same name for controlling incoming connections.) The values of &$host$& and
23875 &$host_address$& are set to the name and address of the server during the
23876 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
23877 is used in different ways by OpenSSL and GnuTLS (see sections
23878 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
23879 ciphers is a preference order.
23883 .option tls_sni smtp string&!! unset
23884 .cindex "TLS" "Server Name Indication"
23885 .vindex "&$tls_sni$&"
23886 If this option is set then it sets the $tls_out_sni variable and causes any
23887 TLS session to pass this value as the Server Name Indication extension to
23888 the remote side, which can be used by the remote side to select an appropriate
23889 certificate and private key for the session.
23891 See &<<SECTtlssni>>& for more information.
23893 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
23899 .option tls_tempfail_tryclear smtp boolean true
23900 .cindex "4&'xx'& responses" "to STARTTLS"
23901 When the server host is not in &%hosts_require_tls%&, and there is a problem in
23902 setting up a TLS session, this option determines whether or not Exim should try
23903 to deliver the message unencrypted. If it is set false, delivery to the
23904 current host is deferred; if there are other hosts, they are tried. If this
23905 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
23906 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
23907 TLS negotiation fails, Exim closes the current connection (because it is in an
23908 unknown state), opens a new one to the same host, and then tries the delivery
23912 .option tls_try_verify_hosts smtp "host list&!!" *
23913 .cindex "TLS" "server certificate verification"
23914 .cindex "certificate" "verification of server"
23915 This option gives a list of hosts for which, on encrypted connections,
23916 certificate verification will be tried but need not succeed.
23917 The &%tls_verify_certificates%& option must also be set.
23918 Note that unless the host is in this list
23919 TLS connections will be denied to hosts using self-signed certificates
23920 when &%tls_verify_certificates%& is matched.
23921 The &$tls_out_certificate_verified$& variable is set when
23922 certificate verification succeeds.
23925 .option tls_verify_cert_hostnames smtp "host list&!!" *
23926 .cindex "TLS" "server certificate hostname verification"
23927 .cindex "certificate" "verification of server"
23928 This option give a list of hosts for which,
23929 while verifying the server certificate,
23930 checks will be included on the host name
23931 (note that this will generally be the result of a DNS MX lookup)
23932 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
23933 limited to being the initial component of a 3-or-more component FQDN.
23935 There is no equivalent checking on client certificates.
23938 .option tls_verify_certificates smtp string&!! system
23939 .cindex "TLS" "server certificate verification"
23940 .cindex "certificate" "verification of server"
23942 .vindex "&$host_address$&"
23943 The value of this option must be either the
23945 or the absolute path to
23946 a file or directory containing permitted certificates for servers,
23947 for use when setting up an encrypted connection.
23949 The "system" value for the option will use a location compiled into the SSL library.
23950 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
23951 is taken as empty and an explicit location
23954 The use of a directory for the option value is not available for GnuTLS versions
23955 preceding 3.3.6 and a single file must be used.
23957 With OpenSSL the certificates specified
23959 either by file or directory
23960 are added to those given by the system default location.
23962 The values of &$host$& and
23963 &$host_address$& are set to the name and address of the server during the
23964 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
23966 For back-compatibility,
23967 if neither tls_verify_hosts nor tls_try_verify_hosts are set
23968 (a single-colon empty list counts as being set)
23969 and certificate verification fails the TLS connection is closed.
23972 .option tls_verify_hosts smtp "host list&!!" unset
23973 .cindex "TLS" "server certificate verification"
23974 .cindex "certificate" "verification of server"
23975 This option gives a list of hosts for which. on encrypted connections,
23976 certificate verification must succeed.
23977 The &%tls_verify_certificates%& option must also be set.
23978 If both this option and &%tls_try_verify_hosts%& are unset
23979 operation is as if this option selected all hosts.
23984 .section "How the limits for the number of hosts to try are used" &&&
23986 .cindex "host" "maximum number to try"
23987 .cindex "limit" "hosts; maximum number tried"
23988 There are two options that are concerned with the number of hosts that are
23989 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
23990 &%hosts_max_try_hardlimit%&.
23993 The &%hosts_max_try%& option limits the number of hosts that are tried
23994 for a single delivery. However, despite the term &"host"& in its name, the
23995 option actually applies to each IP address independently. In other words, a
23996 multihomed host is treated as several independent hosts, just as it is for
23999 Many of the larger ISPs have multiple MX records which often point to
24000 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
24001 created as a result of routing one of these domains.
24003 Trying every single IP address on such a long list does not seem sensible; if
24004 several at the top of the list fail, it is reasonable to assume there is some
24005 problem that is likely to affect all of them. Roughly speaking, the value of
24006 &%hosts_max_try%& is the maximum number that are tried before deferring the
24007 delivery. However, the logic cannot be quite that simple.
24009 Firstly, IP addresses that are skipped because their retry times have not
24010 arrived do not count, and in addition, addresses that are past their retry
24011 limits are also not counted, even when they are tried. This means that when
24012 some IP addresses are past their retry limits, more than the value of
24013 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
24014 that all IP addresses are considered before timing out an email address (but
24015 see below for an exception).
24017 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
24018 list to see if there is a subsequent host with a different (higher valued) MX.
24019 If there is, that host is considered next, and the current IP address is used
24020 but not counted. This behaviour helps in the case of a domain with a retry rule
24021 that hardly ever delays any hosts, as is now explained:
24023 Consider the case of a long list of hosts with one MX value, and a few with a
24024 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
24025 hosts at the top of the list are tried at first. With the default retry rule,
24026 which specifies increasing retry times, the higher MX hosts are eventually
24027 tried when those at the top of the list are skipped because they have not
24028 reached their retry times.
24030 However, it is common practice to put a fixed short retry time on domains for
24031 large ISPs, on the grounds that their servers are rarely down for very long.
24032 Unfortunately, these are exactly the domains that tend to resolve to long lists
24033 of hosts. The short retry time means that the lowest MX hosts are tried every
24034 time. The attempts may be in a different order because of random sorting, but
24035 without the special MX check, the higher MX hosts would never be tried until
24036 all the lower MX hosts had timed out (which might be several days), because
24037 there are always some lower MX hosts that have reached their retry times. With
24038 the special check, Exim considers at least one IP address from each MX value at
24039 every delivery attempt, even if the &%hosts_max_try%& limit has already been
24042 The above logic means that &%hosts_max_try%& is not a hard limit, and in
24043 particular, Exim normally eventually tries all the IP addresses before timing
24044 out an email address. When &%hosts_max_try%& was implemented, this seemed a
24045 reasonable thing to do. Recently, however, some lunatic DNS configurations have
24046 been set up with hundreds of IP addresses for some domains. It can
24047 take a very long time indeed for an address to time out in these cases.
24049 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
24050 Exim never tries more than this number of IP addresses; if it hits this limit
24051 and they are all timed out, the email address is bounced, even though not all
24052 possible IP addresses have been tried.
24053 .ecindex IIDsmttra1
24054 .ecindex IIDsmttra2
24060 . ////////////////////////////////////////////////////////////////////////////
24061 . ////////////////////////////////////////////////////////////////////////////
24063 .chapter "Address rewriting" "CHAPrewrite"
24064 .scindex IIDaddrew "rewriting" "addresses"
24065 There are some circumstances in which Exim automatically rewrites domains in
24066 addresses. The two most common are when an address is given without a domain
24067 (referred to as an &"unqualified address"&) or when an address contains an
24068 abbreviated domain that is expanded by DNS lookup.
24070 Unqualified envelope addresses are accepted only for locally submitted
24071 messages, or for messages that are received from hosts matching
24072 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
24073 appropriate. Unqualified addresses in header lines are qualified if they are in
24074 locally submitted messages, or messages from hosts that are permitted to send
24075 unqualified envelope addresses. Otherwise, unqualified addresses in header
24076 lines are neither qualified nor rewritten.
24078 One situation in which Exim does &'not'& automatically rewrite a domain is
24079 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
24080 such a domain should be rewritten using the &"canonical"& name, and some MTAs
24081 do this. The new RFCs do not contain this suggestion.
24084 .section "Explicitly configured address rewriting" "SECID147"
24085 This chapter describes the rewriting rules that can be used in the
24086 main rewrite section of the configuration file, and also in the generic
24087 &%headers_rewrite%& option that can be set on any transport.
24089 Some people believe that configured address rewriting is a Mortal Sin.
24090 Others believe that life is not possible without it. Exim provides the
24091 facility; you do not have to use it.
24093 The main rewriting rules that appear in the &"rewrite"& section of the
24094 configuration file are applied to addresses in incoming messages, both envelope
24095 addresses and addresses in header lines. Each rule specifies the types of
24096 address to which it applies.
24098 Whether or not addresses in header lines are rewritten depends on the origin of
24099 the headers and the type of rewriting. Global rewriting, that is, rewriting
24100 rules from the rewrite section of the configuration file, is applied only to
24101 those headers that were received with the message. Header lines that are added
24102 by ACLs or by a system filter or by individual routers or transports (which
24103 are specific to individual recipient addresses) are not rewritten by the global
24106 Rewriting at transport time, by means of the &%headers_rewrite%& option,
24107 applies all headers except those added by routers and transports. That is, as
24108 well as the headers that were received with the message, it also applies to
24109 headers that were added by an ACL or a system filter.
24112 In general, rewriting addresses from your own system or domain has some
24113 legitimacy. Rewriting other addresses should be done only with great care and
24114 in special circumstances. The author of Exim believes that rewriting should be
24115 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
24116 Although it can sometimes be used as a routing tool, this is very strongly
24119 There are two commonly encountered circumstances where rewriting is used, as
24120 illustrated by these examples:
24123 The company whose domain is &'hitch.fict.example'& has a number of hosts that
24124 exchange mail with each other behind a firewall, but there is only a single
24125 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
24126 &'hitch.fict.example'& when sending mail off-site.
24128 A host rewrites the local parts of its own users so that, for example,
24129 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
24134 .section "When does rewriting happen?" "SECID148"
24135 .cindex "rewriting" "timing of"
24136 .cindex "&ACL;" "rewriting addresses in"
24137 Configured address rewriting can take place at several different stages of a
24138 message's processing.
24140 .vindex "&$sender_address$&"
24141 At the start of an ACL for MAIL, the sender address may have been rewritten
24142 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
24143 ordinary rewrite rules have yet been applied. If, however, the sender address
24144 is verified in the ACL, it is rewritten before verification, and remains
24145 rewritten thereafter. The subsequent value of &$sender_address$& is the
24146 rewritten address. This also applies if sender verification happens in a
24147 RCPT ACL. Otherwise, when the sender address is not verified, it is
24148 rewritten as soon as a message's header lines have been received.
24150 .vindex "&$domain$&"
24151 .vindex "&$local_part$&"
24152 Similarly, at the start of an ACL for RCPT, the current recipient's address
24153 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
24154 rewrite rules have yet been applied to it. However, the behaviour is different
24155 from the sender address when a recipient is verified. The address is rewritten
24156 for the verification, but the rewriting is not remembered at this stage. The
24157 value of &$local_part$& and &$domain$& after verification are always the same
24158 as they were before (that is, they contain the unrewritten &-- except for
24159 SMTP-time rewriting &-- address).
24161 As soon as a message's header lines have been received, all the envelope
24162 recipient addresses are permanently rewritten, and rewriting is also applied to
24163 the addresses in the header lines (if configured). This happens before adding
24164 any header lines that were specified in MAIL or RCPT ACLs, and
24165 .cindex "&[local_scan()]& function" "address rewriting; timing of"
24166 before the DATA ACL and &[local_scan()]& functions are run.
24168 When an address is being routed, either for delivery or for verification,
24169 rewriting is applied immediately to child addresses that are generated by
24170 redirection, unless &%no_rewrite%& is set on the router.
24172 .cindex "envelope sender" "rewriting at transport time"
24173 .cindex "rewriting" "at transport time"
24174 .cindex "header lines" "rewriting at transport time"
24175 At transport time, additional rewriting of addresses in header lines can be
24176 specified by setting the generic &%headers_rewrite%& option on a transport.
24177 This option contains rules that are identical in form to those in the rewrite
24178 section of the configuration file. They are applied to the original message
24179 header lines and any that were added by ACLs or a system filter. They are not
24180 applied to header lines that are added by routers or the transport.
24182 The outgoing envelope sender can be rewritten by means of the &%return_path%&
24183 transport option. However, it is not possible to rewrite envelope recipients at
24189 .section "Testing the rewriting rules that apply on input" "SECID149"
24190 .cindex "rewriting" "testing"
24191 .cindex "testing" "rewriting"
24192 Exim's input rewriting configuration appears in a part of the run time
24193 configuration file headed by &"begin rewrite"&. It can be tested by the
24194 &%-brw%& command line option. This takes an address (which can be a full RFC
24195 2822 address) as its argument. The output is a list of how the address would be
24196 transformed by the rewriting rules for each of the different places it might
24197 appear in an incoming message, that is, for each different header and for the
24198 envelope sender and recipient fields. For example,
24200 exim -brw ph10@exim.workshop.example
24202 might produce the output
24204 sender: Philip.Hazel@exim.workshop.example
24205 from: Philip.Hazel@exim.workshop.example
24206 to: ph10@exim.workshop.example
24207 cc: ph10@exim.workshop.example
24208 bcc: ph10@exim.workshop.example
24209 reply-to: Philip.Hazel@exim.workshop.example
24210 env-from: Philip.Hazel@exim.workshop.example
24211 env-to: ph10@exim.workshop.example
24213 which shows that rewriting has been set up for that address when used in any of
24214 the source fields, but not when it appears as a recipient address. At the
24215 present time, there is no equivalent way of testing rewriting rules that are
24216 set for a particular transport.
24219 .section "Rewriting rules" "SECID150"
24220 .cindex "rewriting" "rules"
24221 The rewrite section of the configuration file consists of lines of rewriting
24224 <&'source pattern'&> <&'replacement'&> <&'flags'&>
24226 Rewriting rules that are specified for the &%headers_rewrite%& generic
24227 transport option are given as a colon-separated list. Each item in the list
24228 takes the same form as a line in the main rewriting configuration (except that
24229 any colons must be doubled, of course).
24231 The formats of source patterns and replacement strings are described below.
24232 Each is terminated by white space, unless enclosed in double quotes, in which
24233 case normal quoting conventions apply inside the quotes. The flags are single
24234 characters which may appear in any order. Spaces and tabs between them are
24237 For each address that could potentially be rewritten, the rules are scanned in
24238 order, and replacements for the address from earlier rules can themselves be
24239 replaced by later rules (but see the &"q"& and &"R"& flags).
24241 The order in which addresses are rewritten is undefined, may change between
24242 releases, and must not be relied on, with one exception: when a message is
24243 received, the envelope sender is always rewritten first, before any header
24244 lines are rewritten. For example, the replacement string for a rewrite of an
24245 address in &'To:'& must not assume that the message's address in &'From:'& has
24246 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
24247 that the envelope sender has already been rewritten.
24249 .vindex "&$domain$&"
24250 .vindex "&$local_part$&"
24251 The variables &$local_part$& and &$domain$& can be used in the replacement
24252 string to refer to the address that is being rewritten. Note that lookup-driven
24253 rewriting can be done by a rule of the form
24257 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
24258 refer to the address that is being rewritten.
24261 .section "Rewriting patterns" "SECID151"
24262 .cindex "rewriting" "patterns"
24263 .cindex "address list" "in a rewriting pattern"
24264 The source pattern in a rewriting rule is any item which may appear in an
24265 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
24266 single-item address list, which means that it is expanded before being tested
24267 against the address. As always, if you use a regular expression as a pattern,
24268 you must take care to escape dollar and backslash characters, or use the &`\N`&
24269 facility to suppress string expansion within the regular expression.
24271 Domains in patterns should be given in lower case. Local parts in patterns are
24272 case-sensitive. If you want to do case-insensitive matching of local parts, you
24273 can use a regular expression that starts with &`^(?i)`&.
24275 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
24276 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
24277 depending on the type of match which occurred. These can be used in the
24278 replacement string to insert portions of the incoming address. &$0$& always
24279 refers to the complete incoming address. When a regular expression is used, the
24280 numerical variables are set from its capturing subexpressions. For other types
24281 of pattern they are set as follows:
24284 If a local part or domain starts with an asterisk, the numerical variables
24285 refer to the character strings matched by asterisks, with &$1$& associated with
24286 the first asterisk, and &$2$& with the second, if present. For example, if the
24289 *queen@*.fict.example
24291 is matched against the address &'hearts-queen@wonderland.fict.example'& then
24293 $0 = hearts-queen@wonderland.fict.example
24297 Note that if the local part does not start with an asterisk, but the domain
24298 does, it is &$1$& that contains the wild part of the domain.
24301 If the domain part of the pattern is a partial lookup, the wild and fixed parts
24302 of the domain are placed in the next available numerical variables. Suppose,
24303 for example, that the address &'foo@bar.baz.example'& is processed by a
24304 rewriting rule of the form
24306 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
24308 and the key in the file that matches the domain is &`*.baz.example`&. Then
24314 If the address &'foo@baz.example'& is looked up, this matches the same
24315 wildcard file entry, and in this case &$2$& is set to the empty string, but
24316 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
24317 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
24318 whole domain. For non-partial domain lookups, no numerical variables are set.
24322 .section "Rewriting replacements" "SECID152"
24323 .cindex "rewriting" "replacements"
24324 If the replacement string for a rule is a single asterisk, addresses that
24325 match the pattern and the flags are &'not'& rewritten, and no subsequent
24326 rewriting rules are scanned. For example,
24328 hatta@lookingglass.fict.example * f
24330 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
24333 .vindex "&$domain$&"
24334 .vindex "&$local_part$&"
24335 If the replacement string is not a single asterisk, it is expanded, and must
24336 yield a fully qualified address. Within the expansion, the variables
24337 &$local_part$& and &$domain$& refer to the address that is being rewritten.
24338 Any letters they contain retain their original case &-- they are not lower
24339 cased. The numerical variables are set up according to the type of pattern that
24340 matched the address, as described above. If the expansion is forced to fail by
24341 the presence of &"fail"& in a conditional or lookup item, rewriting by the
24342 current rule is abandoned, but subsequent rules may take effect. Any other
24343 expansion failure causes the entire rewriting operation to be abandoned, and an
24344 entry written to the panic log.
24348 .section "Rewriting flags" "SECID153"
24349 There are three different kinds of flag that may appear on rewriting rules:
24352 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
24355 A flag that specifies rewriting at SMTP time: S.
24357 Flags that control the rewriting process: Q, q, R, w.
24360 For rules that are part of the &%headers_rewrite%& generic transport option,
24361 E, F, T, and S are not permitted.
24365 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
24367 .cindex "rewriting" "flags"
24368 If none of the following flag letters, nor the &"S"& flag (see section
24369 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
24370 and to both the sender and recipient fields of the envelope, whereas a
24371 transport-time rewriting rule just applies to all headers. Otherwise, the
24372 rewriting rule is skipped unless the relevant addresses are being processed.
24374 &`E`& rewrite all envelope fields
24375 &`F`& rewrite the envelope From field
24376 &`T`& rewrite the envelope To field
24377 &`b`& rewrite the &'Bcc:'& header
24378 &`c`& rewrite the &'Cc:'& header
24379 &`f`& rewrite the &'From:'& header
24380 &`h`& rewrite all headers
24381 &`r`& rewrite the &'Reply-To:'& header
24382 &`s`& rewrite the &'Sender:'& header
24383 &`t`& rewrite the &'To:'& header
24385 "All headers" means all of the headers listed above that can be selected
24386 individually, plus their &'Resent-'& versions. It does not include
24387 other headers such as &'Subject:'& etc.
24389 You should be particularly careful about rewriting &'Sender:'& headers, and
24390 restrict this to special known cases in your own domains.
24393 .section "The SMTP-time rewriting flag" "SECTrewriteS"
24394 .cindex "SMTP" "rewriting malformed addresses"
24395 .cindex "RCPT" "rewriting argument of"
24396 .cindex "MAIL" "rewriting argument of"
24397 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
24398 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
24399 before any other processing; even before syntax checking. The pattern is
24400 required to be a regular expression, and it is matched against the whole of the
24401 data for the command, including any surrounding angle brackets.
24403 .vindex "&$domain$&"
24404 .vindex "&$local_part$&"
24405 This form of rewrite rule allows for the handling of addresses that are not
24406 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
24407 input). Because the input is not required to be a syntactically valid address,
24408 the variables &$local_part$& and &$domain$& are not available during the
24409 expansion of the replacement string. The result of rewriting replaces the
24410 original address in the MAIL or RCPT command.
24413 .section "Flags controlling the rewriting process" "SECID155"
24414 There are four flags which control the way the rewriting process works. These
24415 take effect only when a rule is invoked, that is, when the address is of the
24416 correct type (matches the flags) and matches the pattern:
24419 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
24420 unqualified local part. It is qualified with &%qualify_recipient%&. In the
24421 absence of &"Q"& the rewritten address must always include a domain.
24423 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
24424 even if no rewriting actually takes place because of a &"fail"& in the
24425 expansion. The &"q"& flag is not effective if the address is of the wrong type
24426 (does not match the flags) or does not match the pattern.
24428 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
24429 address, up to ten times. It can be combined with the &"q"& flag, to stop
24430 rewriting once it fails to match (after at least one successful rewrite).
24432 .cindex "rewriting" "whole addresses"
24433 When an address in a header is rewritten, the rewriting normally applies only
24434 to the working part of the address, with any comments and RFC 2822 &"phrase"&
24435 left unchanged. For example, rewriting might change
24437 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
24441 From: Ford Prefect <prefectf@hitch.fict.example>
24444 Sometimes there is a need to replace the whole address item, and this can be
24445 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
24446 causes an address in a header line to be rewritten, the entire address is
24447 replaced, not just the working part. The replacement must be a complete RFC
24448 2822 address, including the angle brackets if necessary. If text outside angle
24449 brackets contains a character whose value is greater than 126 or less than 32
24450 (except for tab), the text is encoded according to RFC 2047. The character set
24451 is taken from &%headers_charset%&, which gets its default at build time.
24453 When the &"w"& flag is set on a rule that causes an envelope address to be
24454 rewritten, all but the working part of the replacement address is discarded.
24458 .section "Rewriting examples" "SECID156"
24459 Here is an example of the two common rewriting paradigms:
24461 *@*.hitch.fict.example $1@hitch.fict.example
24462 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
24463 {$value}fail}@hitch.fict.example bctfrF
24465 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
24466 the string expansion to fail if the lookup does not succeed. In this context it
24467 has the effect of leaving the original address unchanged, but Exim goes on to
24468 consider subsequent rewriting rules, if any, because the &"q"& flag is not
24469 present in that rule. An alternative to &"fail"& would be to supply &$1$&
24470 explicitly, which would cause the rewritten address to be the same as before,
24471 at the cost of a small bit of processing. Not supplying either of these is an
24472 error, since the rewritten address would then contain no local part.
24474 The first example above replaces the domain with a superior, more general
24475 domain. This may not be desirable for certain local parts. If the rule
24477 root@*.hitch.fict.example *
24479 were inserted before the first rule, rewriting would be suppressed for the
24480 local part &'root'& at any domain ending in &'hitch.fict.example'&.
24482 Rewriting can be made conditional on a number of tests, by making use of
24483 &${if$& in the expansion item. For example, to apply a rewriting rule only to
24484 messages that originate outside the local host:
24486 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
24487 {$1@hitch.fict.example}fail}"
24489 The replacement string is quoted in this example because it contains white
24492 .cindex "rewriting" "bang paths"
24493 .cindex "bang paths" "rewriting"
24494 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
24495 an address it treats it as an unqualified local part which it qualifies with
24496 the local qualification domain (if the source of the message is local or if the
24497 remote host is permitted to send unqualified addresses). Rewriting can
24498 sometimes be used to handle simple bang paths with a fixed number of
24499 components. For example, the rule
24501 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
24503 rewrites a two-component bang path &'host.name!user'& as the domain address
24504 &'user@host.name'&. However, there is a security implication in using this as
24505 a global rewriting rule for envelope addresses. It can provide a backdoor
24506 method for using your system as a relay, because the incoming addresses appear
24507 to be local. If the bang path addresses are received via SMTP, it is safer to
24508 use the &"S"& flag to rewrite them as they are received, so that relay checking
24509 can be done on the rewritten addresses.
24516 . ////////////////////////////////////////////////////////////////////////////
24517 . ////////////////////////////////////////////////////////////////////////////
24519 .chapter "Retry configuration" "CHAPretry"
24520 .scindex IIDretconf1 "retry" "configuration, description of"
24521 .scindex IIDregconf2 "configuration file" "retry section"
24522 The &"retry"& section of the runtime configuration file contains a list of
24523 retry rules that control how often Exim tries to deliver messages that cannot
24524 be delivered at the first attempt. If there are no retry rules (the section is
24525 empty or not present), there are no retries. In this situation, temporary
24526 errors are treated as permanent. The default configuration contains a single,
24527 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
24528 line option can be used to test which retry rule will be used for a given
24529 address, domain and error.
24531 The most common cause of retries is temporary failure to deliver to a remote
24532 host because the host is down, or inaccessible because of a network problem.
24533 Exim's retry processing in this case is applied on a per-host (strictly, per IP
24534 address) basis, not on a per-message basis. Thus, if one message has recently
24535 been delayed, delivery of a new message to the same host is not immediately
24536 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
24537 log selector is set, the message
24538 .cindex "retry" "time not reached"
24539 &"retry time not reached"& is written to the main log whenever a delivery is
24540 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
24541 the handling of errors during remote deliveries.
24543 Retry processing applies to routing as well as to delivering, except as covered
24544 in the next paragraph. The retry rules do not distinguish between these
24545 actions. It is not possible, for example, to specify different behaviour for
24546 failures to route the domain &'snark.fict.example'& and failures to deliver to
24547 the host &'snark.fict.example'&. I didn't think anyone would ever need this
24548 added complication, so did not implement it. However, although they share the
24549 same retry rule, the actual retry times for routing and transporting a given
24550 domain are maintained independently.
24552 When a delivery is not part of a queue run (typically an immediate delivery on
24553 receipt of a message), the routers are always run, and local deliveries are
24554 always attempted, even if retry times are set for them. This makes for better
24555 behaviour if one particular message is causing problems (for example, causing
24556 quota overflow, or provoking an error in a filter file). If such a delivery
24557 suffers a temporary failure, the retry data is updated as normal, and
24558 subsequent delivery attempts from queue runs occur only when the retry time for
24559 the local address is reached.
24561 .section "Changing retry rules" "SECID157"
24562 If you change the retry rules in your configuration, you should consider
24563 whether or not to delete the retry data that is stored in Exim's spool area in
24564 files with names like &_db/retry_&. Deleting any of Exim's hints files is
24565 always safe; that is why they are called &"hints"&.
24567 The hints retry data contains suggested retry times based on the previous
24568 rules. In the case of a long-running problem with a remote host, it might
24569 record the fact that the host has timed out. If your new rules increase the
24570 timeout time for such a host, you should definitely remove the old retry data
24571 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
24572 messages that it should now be retaining.
24576 .section "Format of retry rules" "SECID158"
24577 .cindex "retry" "rules"
24578 Each retry rule occupies one line and consists of three or four parts,
24579 separated by white space: a pattern, an error name, an optional list of sender
24580 addresses, and a list of retry parameters. The pattern and sender lists must be
24581 enclosed in double quotes if they contain white space. The rules are searched
24582 in order until one is found where the pattern, error name, and sender list (if
24583 present) match the failing host or address, the error that occurred, and the
24584 message's sender, respectively.
24587 The pattern is any single item that may appear in an address list (see section
24588 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
24589 which means that it is expanded before being tested against the address that
24590 has been delayed. A negated address list item is permitted. Address
24591 list processing treats a plain domain name as if it were preceded by &"*@"&,
24592 which makes it possible for many retry rules to start with just a domain. For
24595 lookingglass.fict.example * F,24h,30m;
24597 provides a rule for any address in the &'lookingglass.fict.example'& domain,
24600 alice@lookingglass.fict.example * F,24h,30m;
24602 applies only to temporary failures involving the local part &%alice%&.
24603 In practice, almost all rules start with a domain name pattern without a local
24606 .cindex "regular expressions" "in retry rules"
24607 &*Warning*&: If you use a regular expression in a retry rule pattern, it
24608 must match a complete address, not just a domain, because that is how regular
24609 expressions work in address lists.
24611 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
24612 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
24616 .section "Choosing which retry rule to use for address errors" "SECID159"
24617 When Exim is looking for a retry rule after a routing attempt has failed (for
24618 example, after a DNS timeout), each line in the retry configuration is tested
24619 against the complete address only if &%retry_use_local_part%& is set for the
24620 router. Otherwise, only the domain is used, except when matching against a
24621 regular expression, when the local part of the address is replaced with &"*"&.
24622 A domain on its own can match a domain pattern, or a pattern that starts with
24623 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
24624 &%check_local_user%& is true, and false for other routers.
24626 Similarly, when Exim is looking for a retry rule after a local delivery has
24627 failed (for example, after a mailbox full error), each line in the retry
24628 configuration is tested against the complete address only if
24629 &%retry_use_local_part%& is set for the transport (it defaults true for all
24632 .cindex "4&'xx'& responses" "retry rules for"
24633 However, when Exim is looking for a retry rule after a remote delivery attempt
24634 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
24635 whole address is always used as the key when searching the retry rules. The
24636 rule that is found is used to create a retry time for the combination of the
24637 failing address and the message's sender. It is the combination of sender and
24638 recipient that is delayed in subsequent queue runs until its retry time is
24639 reached. You can delay the recipient without regard to the sender by setting
24640 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
24641 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
24646 .section "Choosing which retry rule to use for host and message errors" &&&
24648 For a temporary error that is not related to an individual address (for
24649 example, a connection timeout), each line in the retry configuration is checked
24650 twice. First, the name of the remote host is used as a domain name (preceded by
24651 &"*@"& when matching a regular expression). If this does not match the line,
24652 the domain from the email address is tried in a similar fashion. For example,
24653 suppose the MX records for &'a.b.c.example'& are
24655 a.b.c.example MX 5 x.y.z.example
24659 and the retry rules are
24661 p.q.r.example * F,24h,30m;
24662 a.b.c.example * F,4d,45m;
24664 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
24665 first rule matches neither the host nor the domain, so Exim looks at the second
24666 rule. This does not match the host, but it does match the domain, so it is used
24667 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
24668 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
24669 first retry rule is used, because it matches the host.
24671 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
24672 first rule to determine retry times, but for all the other hosts for the domain
24673 &'a.b.c.example'&, the second rule is used. The second rule is also used if
24674 routing to &'a.b.c.example'& suffers a temporary failure.
24676 &*Note*&: The host name is used when matching the patterns, not its IP address.
24677 However, if a message is routed directly to an IP address without the use of a
24678 host name, for example, if a &(manualroute)& router contains a setting such as:
24680 route_list = *.a.example 192.168.34.23
24682 then the &"host name"& that is used when searching for a retry rule is the
24683 textual form of the IP address.
24685 .section "Retry rules for specific errors" "SECID161"
24686 .cindex "retry" "specific errors; specifying"
24687 The second field in a retry rule is the name of a particular error, or an
24688 asterisk, which matches any error. The errors that can be tested for are:
24691 .vitem &%auth_failed%&
24692 Authentication failed when trying to send to a host in the
24693 &%hosts_require_auth%& list in an &(smtp)& transport.
24695 .vitem &%data_4xx%&
24696 A 4&'xx'& error was received for an outgoing DATA command, either immediately
24697 after the command, or after sending the message's data.
24699 .vitem &%mail_4xx%&
24700 A 4&'xx'& error was received for an outgoing MAIL command.
24702 .vitem &%rcpt_4xx%&
24703 A 4&'xx'& error was received for an outgoing RCPT command.
24706 For the three 4&'xx'& errors, either the first or both of the x's can be given
24707 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
24708 recognize 452 errors given to RCPT commands for addresses in a certain domain,
24709 and have retries every ten minutes with a one-hour timeout, you could set up a
24710 retry rule of this form:
24712 the.domain.name rcpt_452 F,1h,10m
24714 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
24715 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
24718 .vitem &%lost_connection%&
24719 A server unexpectedly closed the SMTP connection. There may, of course,
24720 legitimate reasons for this (host died, network died), but if it repeats a lot
24721 for the same host, it indicates something odd.
24724 A DNS lookup for a host failed.
24725 Note that a &%dnslookup%& router will need to have matched
24726 its &%fail_defer_domains%& option for this retry type to be usable.
24727 Also note that a &%manualroute%& router will probably need
24728 its &%host_find_failed%& option set to &%defer%&.
24730 .vitem &%refused_MX%&
24731 A connection to a host obtained from an MX record was refused.
24733 .vitem &%refused_A%&
24734 A connection to a host not obtained from an MX record was refused.
24737 A connection was refused.
24739 .vitem &%timeout_connect_MX%&
24740 A connection attempt to a host obtained from an MX record timed out.
24742 .vitem &%timeout_connect_A%&
24743 A connection attempt to a host not obtained from an MX record timed out.
24745 .vitem &%timeout_connect%&
24746 A connection attempt timed out.
24748 .vitem &%timeout_MX%&
24749 There was a timeout while connecting or during an SMTP session with a host
24750 obtained from an MX record.
24752 .vitem &%timeout_A%&
24753 There was a timeout while connecting or during an SMTP session with a host not
24754 obtained from an MX record.
24757 There was a timeout while connecting or during an SMTP session.
24759 .vitem &%tls_required%&
24760 The server was required to use TLS (it matched &%hosts_require_tls%& in the
24761 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
24762 to STARTTLS, or there was a problem setting up the TLS connection.
24765 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24768 .vitem &%quota_%&<&'time'&>
24769 .cindex "quota" "error testing in retry rule"
24770 .cindex "retry" "quota error testing"
24771 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24772 transport, and the mailbox has not been accessed for <&'time'&>. For example,
24773 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
24777 .cindex "mailbox" "time of last read"
24778 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
24779 timeouts when the mailbox is full and is not being read by its owner. Ideally,
24780 it should be based on the last time that the user accessed the mailbox.
24781 However, it is not always possible to determine this. Exim uses the following
24785 If the mailbox is a single file, the time of last access (the &"atime"&) is
24786 used. As no new messages are being delivered (because the mailbox is over
24787 quota), Exim does not access the file, so this is the time of last user access.
24789 .cindex "maildir format" "time of last read"
24790 For a maildir delivery, the time of last modification of the &_new_&
24791 subdirectory is used. As the mailbox is over quota, no new files are created in
24792 the &_new_& subdirectory, because no new messages are being delivered. Any
24793 change to the &_new_& subdirectory is therefore assumed to be the result of an
24794 MUA moving a new message to the &_cur_& directory when it is first read. The
24795 time that is used is therefore the last time that the user read a new message.
24797 For other kinds of multi-file mailbox, the time of last access cannot be
24798 obtained, so a retry rule that uses this type of error field is never matched.
24801 The quota errors apply both to system-enforced quotas and to Exim's own quota
24802 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
24803 when a local delivery is deferred because a partition is full (the ENOSPC
24808 .section "Retry rules for specified senders" "SECID162"
24809 .cindex "retry" "rules; sender-specific"
24810 You can specify retry rules that apply only when the failing message has a
24811 specific sender. In particular, this can be used to define retry rules that
24812 apply only to bounce messages. The third item in a retry rule can be of this
24815 &`senders=`&<&'address list'&>
24817 The retry timings themselves are then the fourth item. For example:
24819 * rcpt_4xx senders=: F,1h,30m
24821 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
24822 host. If the address list contains white space, it must be enclosed in quotes.
24825 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
24827 &*Warning*&: This facility can be unhelpful if it is used for host errors
24828 (which do not depend on the recipient). The reason is that the sender is used
24829 only to match the retry rule. Once the rule has been found for a host error,
24830 its contents are used to set a retry time for the host, and this will apply to
24831 all messages, not just those with specific senders.
24833 When testing retry rules using &%-brt%&, you can supply a sender using the
24834 &%-f%& command line option, like this:
24836 exim -f "" -brt user@dom.ain
24838 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
24839 list is never matched.
24845 .section "Retry parameters" "SECID163"
24846 .cindex "retry" "parameters in rules"
24847 The third (or fourth, if a senders list is present) field in a retry rule is a
24848 sequence of retry parameter sets, separated by semicolons. Each set consists of
24850 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
24852 The letter identifies the algorithm for computing a new retry time; the cutoff
24853 time is the time beyond which this algorithm no longer applies, and the
24854 arguments vary the algorithm's action. The cutoff time is measured from the
24855 time that the first failure for the domain (combined with the local part if
24856 relevant) was detected, not from the time the message was received.
24858 .cindex "retry" "algorithms"
24859 .cindex "retry" "fixed intervals"
24860 .cindex "retry" "increasing intervals"
24861 .cindex "retry" "random intervals"
24862 The available algorithms are:
24865 &'F'&: retry at fixed intervals. There is a single time parameter specifying
24868 &'G'&: retry at geometrically increasing intervals. The first argument
24869 specifies a starting value for the interval, and the second a multiplier, which
24870 is used to increase the size of the interval at each retry.
24872 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
24873 retry, the previous interval is multiplied by the factor in order to get a
24874 maximum for the next interval. The minimum interval is the first argument of
24875 the parameter, and an actual interval is chosen randomly between them. Such a
24876 rule has been found to be helpful in cluster configurations when all the
24877 members of the cluster restart at once, and may therefore synchronize their
24878 queue processing times.
24881 When computing the next retry time, the algorithm definitions are scanned in
24882 order until one whose cutoff time has not yet passed is reached. This is then
24883 used to compute a new retry time that is later than the current time. In the
24884 case of fixed interval retries, this simply means adding the interval to the
24885 current time. For geometrically increasing intervals, retry intervals are
24886 computed from the rule's parameters until one that is greater than the previous
24887 interval is found. The main configuration variable
24888 .cindex "limit" "retry interval"
24889 .cindex "retry" "interval, maximum"
24890 .oindex "&%retry_interval_max%&"
24891 &%retry_interval_max%& limits the maximum interval between retries. It
24892 cannot be set greater than &`24h`&, which is its default value.
24894 A single remote domain may have a number of hosts associated with it, and each
24895 host may have more than one IP address. Retry algorithms are selected on the
24896 basis of the domain name, but are applied to each IP address independently. If,
24897 for example, a host has two IP addresses and one is unusable, Exim will
24898 generate retry times for it and will not try to use it until its next retry
24899 time comes. Thus the good IP address is likely to be tried first most of the
24902 .cindex "hints database" "use for retrying"
24903 Retry times are hints rather than promises. Exim does not make any attempt to
24904 run deliveries exactly at the computed times. Instead, a queue runner process
24905 starts delivery processes for delayed messages periodically, and these attempt
24906 new deliveries only for those addresses that have passed their next retry time.
24907 If a new message arrives for a deferred address, an immediate delivery attempt
24908 occurs only if the address has passed its retry time. In the absence of new
24909 messages, the minimum time between retries is the interval between queue runner
24910 processes. There is not much point in setting retry times of five minutes if
24911 your queue runners happen only once an hour, unless there are a significant
24912 number of incoming messages (which might be the case on a system that is
24913 sending everything to a smart host, for example).
24915 The data in the retry hints database can be inspected by using the
24916 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
24917 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
24918 &'exinext'& utility script can be used to find out what the next retry times
24919 are for the hosts associated with a particular mail domain, and also for local
24920 deliveries that have been deferred.
24923 .section "Retry rule examples" "SECID164"
24924 Here are some example retry rules:
24926 alice@wonderland.fict.example quota_5d F,7d,3h
24927 wonderland.fict.example quota_5d
24928 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
24929 lookingglass.fict.example * F,24h,30m;
24930 * refused_A F,2h,20m;
24931 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
24933 The first rule sets up special handling for mail to
24934 &'alice@wonderland.fict.example'& when there is an over-quota error and the
24935 mailbox has not been read for at least 5 days. Retries continue every three
24936 hours for 7 days. The second rule handles over-quota errors for all other local
24937 parts at &'wonderland.fict.example'&; the absence of a local part has the same
24938 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
24939 fail are bounced immediately if the mailbox has not been read for at least 5
24942 The third rule handles all other errors at &'wonderland.fict.example'&; retries
24943 happen every 15 minutes for an hour, then with geometrically increasing
24944 intervals until two days have passed since a delivery first failed. After the
24945 first hour there is a delay of one hour, then two hours, then four hours, and
24946 so on (this is a rather extreme example).
24948 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
24949 They happen every 30 minutes for 24 hours only. The remaining two rules handle
24950 all other domains, with special action for connection refusal from hosts that
24951 were not obtained from an MX record.
24953 The final rule in a retry configuration should always have asterisks in the
24954 first two fields so as to provide a general catch-all for any addresses that do
24955 not have their own special handling. This example tries every 15 minutes for 2
24956 hours, then with intervals starting at one hour and increasing by a factor of
24957 1.5 up to 16 hours, then every 8 hours up to 5 days.
24961 .section "Timeout of retry data" "SECID165"
24962 .cindex "timeout" "of retry data"
24963 .oindex "&%retry_data_expire%&"
24964 .cindex "hints database" "data expiry"
24965 .cindex "retry" "timeout of data"
24966 Exim timestamps the data that it writes to its retry hints database. When it
24967 consults the data during a delivery it ignores any that is older than the value
24968 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
24969 been tried for 7 days, Exim will try to deliver to it immediately a message
24970 arrives, and if that fails, it will calculate a retry time as if it were
24971 failing for the first time.
24973 This improves the behaviour for messages routed to rarely-used hosts such as MX
24974 backups. If such a host was down at one time, and happens to be down again when
24975 Exim tries a month later, using the old retry data would imply that it had been
24976 down all the time, which is not a justified assumption.
24978 If a host really is permanently dead, this behaviour causes a burst of retries
24979 every now and again, but only if messages routed to it are rare. If there is a
24980 message at least once every 7 days the retry data never expires.
24985 .section "Long-term failures" "SECID166"
24986 .cindex "delivery failure, long-term"
24987 .cindex "retry" "after long-term failure"
24988 Special processing happens when an email address has been failing for so long
24989 that the cutoff time for the last algorithm is reached. For example, using the
24990 default retry rule:
24992 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
24994 the cutoff time is four days. Reaching the retry cutoff is independent of how
24995 long any specific message has been failing; it is the length of continuous
24996 failure for the recipient address that counts.
24998 When the cutoff time is reached for a local delivery, or for all the IP
24999 addresses associated with a remote delivery, a subsequent delivery failure
25000 causes Exim to give up on the address, and a bounce message is generated.
25001 In order to cater for new messages that use the failing address, a next retry
25002 time is still computed from the final algorithm, and is used as follows:
25004 For local deliveries, one delivery attempt is always made for any subsequent
25005 messages. If this delivery fails, the address fails immediately. The
25006 post-cutoff retry time is not used.
25008 If the delivery is remote, there are two possibilities, controlled by the
25009 .oindex "&%delay_after_cutoff%&"
25010 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
25011 default. Until the post-cutoff retry time for one of the IP addresses is
25012 reached, the failing email address is bounced immediately, without a delivery
25013 attempt taking place. After that time, one new delivery attempt is made to
25014 those IP addresses that are past their retry times, and if that still fails,
25015 the address is bounced and new retry times are computed.
25017 In other words, when all the hosts for a given email address have been failing
25018 for a long time, Exim bounces rather then defers until one of the hosts' retry
25019 times is reached. Then it tries once, and bounces if that attempt fails. This
25020 behaviour ensures that few resources are wasted in repeatedly trying to deliver
25021 to a broken destination, but if the host does recover, Exim will eventually
25024 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25025 addresses are past their final cutoff time, Exim tries to deliver to those IP
25026 addresses that have not been tried since the message arrived. If there are
25027 no suitable IP addresses, or if they all fail, the address is bounced. In other
25028 words, it does not delay when a new message arrives, but tries the expired
25029 addresses immediately, unless they have been tried since the message arrived.
25030 If there is a continuous stream of messages for the failing domains, setting
25031 &%delay_after_cutoff%& false means that there will be many more attempts to
25032 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
25035 .section "Deliveries that work intermittently" "SECID167"
25036 .cindex "retry" "intermittently working deliveries"
25037 Some additional logic is needed to cope with cases where a host is
25038 intermittently available, or when a message has some attribute that prevents
25039 its delivery when others to the same address get through. In this situation,
25040 because some messages are successfully delivered, the &"retry clock"& for the
25041 host or address keeps getting reset by the successful deliveries, and so
25042 failing messages remain on the queue for ever because the cutoff time is never
25045 Two exceptional actions are applied to prevent this happening. The first
25046 applies to errors that are related to a message rather than a remote host.
25047 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
25048 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
25049 commands, and quota failures. For this type of error, if a message's arrival
25050 time is earlier than the &"first failed"& time for the error, the earlier time
25051 is used when scanning the retry rules to decide when to try next and when to
25052 time out the address.
25054 The exceptional second action applies in all cases. If a message has been on
25055 the queue for longer than the cutoff time of any applicable retry rule for a
25056 given address, a delivery is attempted for that address, even if it is not yet
25057 time, and if this delivery fails, the address is timed out. A new retry time is
25058 not computed in this case, so that other messages for the same address are
25059 considered immediately.
25060 .ecindex IIDretconf1
25061 .ecindex IIDregconf2
25068 . ////////////////////////////////////////////////////////////////////////////
25069 . ////////////////////////////////////////////////////////////////////////////
25071 .chapter "SMTP authentication" "CHAPSMTPAUTH"
25072 .scindex IIDauthconf1 "SMTP" "authentication configuration"
25073 .scindex IIDauthconf2 "authentication"
25074 The &"authenticators"& section of Exim's run time configuration is concerned
25075 with SMTP authentication. This facility is an extension to the SMTP protocol,
25076 described in RFC 2554, which allows a client SMTP host to authenticate itself
25077 to a server. This is a common way for a server to recognize clients that are
25078 permitted to use it as a relay. SMTP authentication is not of relevance to the
25079 transfer of mail between servers that have no managerial connection with each
25082 .cindex "AUTH" "description of"
25083 Very briefly, the way SMTP authentication works is as follows:
25086 The server advertises a number of authentication &'mechanisms'& in response to
25087 the client's EHLO command.
25089 The client issues an AUTH command, naming a specific mechanism. The command
25090 may, optionally, contain some authentication data.
25092 The server may issue one or more &'challenges'&, to which the client must send
25093 appropriate responses. In simple authentication mechanisms, the challenges are
25094 just prompts for user names and passwords. The server does not have to issue
25095 any challenges &-- in some mechanisms the relevant data may all be transmitted
25096 with the AUTH command.
25098 The server either accepts or denies authentication.
25100 If authentication succeeds, the client may optionally make use of the AUTH
25101 option on the MAIL command to pass an authenticated sender in subsequent
25102 mail transactions. Authentication lasts for the remainder of the SMTP
25105 If authentication fails, the client may give up, or it may try a different
25106 authentication mechanism, or it may try transferring mail over the
25107 unauthenticated connection.
25110 If you are setting up a client, and want to know which authentication
25111 mechanisms the server supports, you can use Telnet to connect to port 25 (the
25112 SMTP port) on the server, and issue an EHLO command. The response to this
25113 includes the list of supported mechanisms. For example:
25115 &`$ `&&*&`telnet server.example 25`&*&
25116 &`Trying 192.168.34.25...`&
25117 &`Connected to server.example.`&
25118 &`Escape character is '^]'.`&
25119 &`220 server.example ESMTP Exim 4.20 ...`&
25120 &*&`ehlo client.example`&*&
25121 &`250-server.example Hello client.example [10.8.4.5]`&
25122 &`250-SIZE 52428800`&
25127 The second-last line of this example output shows that the server supports
25128 authentication using the PLAIN mechanism. In Exim, the different authentication
25129 mechanisms are configured by specifying &'authenticator'& drivers. Like the
25130 routers and transports, which authenticators are included in the binary is
25131 controlled by build-time definitions. The following are currently available,
25132 included by setting
25135 AUTH_CYRUS_SASL=yes
25138 AUTH_HEIMDAL_GSSAPI=yes
25143 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
25144 authentication mechanism (RFC 2195), and the second provides an interface to
25145 the Cyrus SASL authentication library.
25146 The third is an interface to Dovecot's authentication system, delegating the
25147 work via a socket interface.
25148 The fourth provides an interface to the GNU SASL authentication library, which
25149 provides mechanisms but typically not data sources.
25150 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
25151 supporting setting a server keytab.
25152 The sixth can be configured to support
25153 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
25154 not formally documented, but used by several MUAs. The seventh authenticator
25155 supports Microsoft's &'Secure Password Authentication'& mechanism.
25156 The eighth is an Exim authenticator but not an SMTP one;
25157 instead it can use information from a TLS negotiation.
25159 The authenticators are configured using the same syntax as other drivers (see
25160 section &<<SECTfordricon>>&). If no authenticators are required, no
25161 authentication section need be present in the configuration file. Each
25162 authenticator can in principle have both server and client functions. When Exim
25163 is receiving SMTP mail, it is acting as a server; when it is sending out
25164 messages over SMTP, it is acting as a client. Authenticator configuration
25165 options are provided for use in both these circumstances.
25167 To make it clear which options apply to which situation, the prefixes
25168 &%server_%& and &%client_%& are used on option names that are specific to
25169 either the server or the client function, respectively. Server and client
25170 functions are disabled if none of their options are set. If an authenticator is
25171 to be used for both server and client functions, a single definition, using
25172 both sets of options, is required. For example:
25176 public_name = CRAM-MD5
25177 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
25179 client_secret = secret2
25181 The &%server_%& option is used when Exim is acting as a server, and the
25182 &%client_%& options when it is acting as a client.
25184 Descriptions of the individual authenticators are given in subsequent chapters.
25185 The remainder of this chapter covers the generic options for the
25186 authenticators, followed by general discussion of the way authentication works
25189 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
25190 per-mechanism basis. Please read carefully to determine which variables hold
25191 account labels such as usercodes and which hold passwords or other
25192 authenticating data.
25194 Note that some mechanisms support two different identifiers for accounts: the
25195 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
25196 and &'authz'& are commonly encountered. The American spelling is standard here.
25197 Conceptually, authentication data such as passwords are tied to the identifier
25198 used to authenticate; servers may have rules to permit one user to act as a
25199 second user, so that after login the session is treated as though that second
25200 user had logged in. That second user is the &'authorization id'&. A robust
25201 configuration might confirm that the &'authz'& field is empty or matches the
25202 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
25203 as verified data, the &'authz'& as an unverified request which the server might
25206 A &'realm'& is a text string, typically a domain name, presented by a server
25207 to a client to help it select an account and credentials to use. In some
25208 mechanisms, the client and server provably agree on the realm, but clients
25209 typically can not treat the realm as secure data to be blindly trusted.
25213 .section "Generic options for authenticators" "SECID168"
25214 .cindex "authentication" "generic options"
25215 .cindex "options" "generic; for authenticators"
25217 .option client_condition authenticators string&!! unset
25218 When Exim is authenticating as a client, it skips any authenticator whose
25219 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
25220 used, for example, to skip plain text authenticators when the connection is not
25221 encrypted by a setting such as:
25223 client_condition = ${if !eq{$tls_out_cipher}{}}
25227 .option client_set_id authenticators string&!! unset
25228 When client authentication succeeds, this condition is expanded; the
25229 result is used in the log lines for outbound messages.
25230 Typically it will be the user name used for authentication.
25233 .option driver authenticators string unset
25234 This option must always be set. It specifies which of the available
25235 authenticators is to be used.
25238 .option public_name authenticators string unset
25239 This option specifies the name of the authentication mechanism that the driver
25240 implements, and by which it is known to the outside world. These names should
25241 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
25242 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
25243 defaults to the driver's instance name.
25246 .option server_advertise_condition authenticators string&!! unset
25247 When a server is about to advertise an authentication mechanism, the condition
25248 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
25249 mechanism is not advertised.
25250 If the expansion fails, the mechanism is not advertised. If the failure was not
25251 forced, and was not caused by a lookup defer, the incident is logged.
25252 See section &<<SECTauthexiser>>& below for further discussion.
25255 .option server_condition authenticators string&!! unset
25256 This option must be set for a &%plaintext%& server authenticator, where it
25257 is used directly to control authentication. See section &<<SECTplainserver>>&
25260 For the &(gsasl)& authenticator, this option is required for various
25261 mechanisms; see chapter &<<CHAPgsasl>>& for details.
25263 For the other authenticators, &%server_condition%& can be used as an additional
25264 authentication or authorization mechanism that is applied after the other
25265 authenticator conditions succeed. If it is set, it is expanded when the
25266 authenticator would otherwise return a success code. If the expansion is forced
25267 to fail, authentication fails. Any other expansion failure causes a temporary
25268 error code to be returned. If the result of a successful expansion is an empty
25269 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25270 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
25271 other result, a temporary error code is returned, with the expanded string as
25275 .option server_debug_print authenticators string&!! unset
25276 If this option is set and authentication debugging is enabled (see the &%-d%&
25277 command line option), the string is expanded and included in the debugging
25278 output when the authenticator is run as a server. This can help with checking
25279 out the values of variables.
25280 If expansion of the string fails, the error message is written to the debugging
25281 output, and Exim carries on processing.
25284 .option server_set_id authenticators string&!! unset
25285 .vindex "&$authenticated_id$&"
25286 When an Exim server successfully authenticates a client, this string is
25287 expanded using data from the authentication, and preserved for any incoming
25288 messages in the variable &$authenticated_id$&. It is also included in the log
25289 lines for incoming messages. For example, a user/password authenticator
25290 configuration might preserve the user name that was used to authenticate, and
25291 refer to it subsequently during delivery of the message.
25292 If expansion fails, the option is ignored.
25295 .option server_mail_auth_condition authenticators string&!! unset
25296 This option allows a server to discard authenticated sender addresses supplied
25297 as part of MAIL commands in SMTP connections that are authenticated by the
25298 driver on which &%server_mail_auth_condition%& is set. The option is not used
25299 as part of the authentication process; instead its (unexpanded) value is
25300 remembered for later use.
25301 How it is used is described in the following section.
25307 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
25308 .cindex "authentication" "sender; authenticated"
25309 .cindex "AUTH" "on MAIL command"
25310 When a client supplied an AUTH= item on a MAIL command, Exim applies
25311 the following checks before accepting it as the authenticated sender of the
25315 If the connection is not using extended SMTP (that is, HELO was used rather
25316 than EHLO), the use of AUTH= is a syntax error.
25318 If the value of the AUTH= parameter is &"<>"&, it is ignored.
25320 .vindex "&$authenticated_sender$&"
25321 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
25322 running, the value of &$authenticated_sender$& is set to the value obtained
25323 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
25324 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
25325 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
25326 given for the MAIL command.
25328 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
25329 is accepted and placed in &$authenticated_sender$& only if the client has
25332 If the AUTH= value was accepted by either of the two previous rules, and
25333 the client has authenticated, and the authenticator has a setting for the
25334 &%server_mail_auth_condition%&, the condition is checked at this point. The
25335 valued that was saved from the authenticator is expanded. If the expansion
25336 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
25337 &$authenticated_sender$& is deleted. If the expansion yields any other value,
25338 the value of &$authenticated_sender$& is retained and passed on with the
25343 When &$authenticated_sender$& is set for a message, it is passed on to other
25344 hosts to which Exim authenticates as a client. Do not confuse this value with
25345 &$authenticated_id$&, which is a string obtained from the authentication
25346 process, and which is not usually a complete email address.
25348 .vindex "&$sender_address$&"
25349 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
25350 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
25351 therefore make use of &$authenticated_sender$&. The converse is not true: the
25352 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
25357 .section "Authentication on an Exim server" "SECTauthexiser"
25358 .cindex "authentication" "on an Exim server"
25359 When Exim receives an EHLO command, it advertises the public names of those
25360 authenticators that are configured as servers, subject to the following
25364 The client host must match &%auth_advertise_hosts%& (default *).
25366 It the &%server_advertise_condition%& option is set, its expansion must not
25367 yield the empty string, &"0"&, &"no"&, or &"false"&.
25370 The order in which the authenticators are defined controls the order in which
25371 the mechanisms are advertised.
25373 Some mail clients (for example, some versions of Netscape) require the user to
25374 provide a name and password for authentication whenever AUTH is advertised,
25375 even though authentication may not in fact be needed (for example, Exim may be
25376 set up to allow unconditional relaying from the client by an IP address check).
25377 You can make such clients more friendly by not advertising AUTH to them.
25378 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
25379 that runs for RCPT) to relay without authentication, you should set
25381 auth_advertise_hosts = ! 10.9.8.0/24
25383 so that no authentication mechanisms are advertised to them.
25385 The &%server_advertise_condition%& controls the advertisement of individual
25386 authentication mechanisms. For example, it can be used to restrict the
25387 advertisement of a particular mechanism to encrypted connections, by a setting
25390 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
25392 .vindex "&$tls_in_cipher$&"
25393 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
25394 yields &"yes"&, which allows the advertisement to happen.
25396 When an Exim server receives an AUTH command from a client, it rejects it
25397 immediately if AUTH was not advertised in response to an earlier EHLO
25398 command. This is the case if
25401 The client host does not match &%auth_advertise_hosts%&; or
25403 No authenticators are configured with server options; or
25405 Expansion of &%server_advertise_condition%& blocked the advertising of all the
25406 server authenticators.
25410 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
25411 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
25412 AUTH is accepted from any client host.
25414 If AUTH is not rejected by the ACL, Exim searches its configuration for a
25415 server authentication mechanism that was advertised in response to EHLO and
25416 that matches the one named in the AUTH command. If it finds one, it runs
25417 the appropriate authentication protocol, and authentication either succeeds or
25418 fails. If there is no matching advertised mechanism, the AUTH command is
25419 rejected with a 504 error.
25421 .vindex "&$received_protocol$&"
25422 .vindex "&$sender_host_authenticated$&"
25423 When a message is received from an authenticated host, the value of
25424 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
25425 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
25426 public name) of the authenticator driver that successfully authenticated the
25427 client from which the message was received. This variable is empty if there was
25428 no successful authentication.
25433 .section "Testing server authentication" "SECID169"
25434 .cindex "authentication" "testing a server"
25435 .cindex "AUTH" "testing a server"
25436 .cindex "base64 encoding" "creating authentication test data"
25437 Exim's &%-bh%& option can be useful for testing server authentication
25438 configurations. The data for the AUTH command has to be sent using base64
25439 encoding. A quick way to produce such data for testing is the following Perl
25443 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
25445 .cindex "binary zero" "in authentication data"
25446 This interprets its argument as a Perl string, and then encodes it. The
25447 interpretation as a Perl string allows binary zeros, which are required for
25448 some kinds of authentication, to be included in the data. For example, a
25449 command line to run this script on such data might be
25451 encode '\0user\0password'
25453 Note the use of single quotes to prevent the shell interpreting the
25454 backslashes, so that they can be interpreted by Perl to specify characters
25455 whose code value is zero.
25457 &*Warning 1*&: If either of the user or password strings starts with an octal
25458 digit, you must use three zeros instead of one after the leading backslash. If
25459 you do not, the octal digit that starts your string will be incorrectly
25460 interpreted as part of the code for the first character.
25462 &*Warning 2*&: If there are characters in the strings that Perl interprets
25463 specially, you must use a Perl escape to prevent them being misinterpreted. For
25464 example, a command such as
25466 encode '\0user@domain.com\0pas$$word'
25468 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
25470 If you have the &%mimencode%& command installed, another way to do produce
25471 base64-encoded strings is to run the command
25473 echo -e -n `\0user\0password' | mimencode
25475 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
25476 in the argument, and the &%-n%& option specifies no newline at the end of its
25477 output. However, not all versions of &%echo%& recognize these options, so you
25478 should check your version before relying on this suggestion.
25482 .section "Authentication by an Exim client" "SECID170"
25483 .cindex "authentication" "on an Exim client"
25484 The &(smtp)& transport has two options called &%hosts_require_auth%& and
25485 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
25486 announces support for authentication, and the host matches an entry in either
25487 of these options, Exim (as a client) tries to authenticate as follows:
25490 For each authenticator that is configured as a client, in the order in which
25491 they are defined in the configuration, it searches the authentication
25492 mechanisms announced by the server for one whose name matches the public name
25493 of the authenticator.
25496 .vindex "&$host_address$&"
25497 When it finds one that matches, it runs the authenticator's client code. The
25498 variables &$host$& and &$host_address$& are available for any string expansions
25499 that the client might do. They are set to the server's name and IP address. If
25500 any expansion is forced to fail, the authentication attempt is abandoned, and
25501 Exim moves on to the next authenticator. Otherwise an expansion failure causes
25502 delivery to be deferred.
25504 If the result of the authentication attempt is a temporary error or a timeout,
25505 Exim abandons trying to send the message to the host for the moment. It will
25506 try again later. If there are any backup hosts available, they are tried in the
25509 If the response to authentication is a permanent error (5&'xx'& code), Exim
25510 carries on searching the list of authenticators and tries another one if
25511 possible. If all authentication attempts give permanent errors, or if there are
25512 no attempts because no mechanisms match (or option expansions force failure),
25513 what happens depends on whether the host matches &%hosts_require_auth%& or
25514 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
25515 delivery is deferred. The error can be detected in the retry rules, and thereby
25516 turned into a permanent error if you wish. In the second case, Exim tries to
25517 deliver the message unauthenticated.
25520 .cindex "AUTH" "on MAIL command"
25521 When Exim has authenticated itself to a remote server, it adds the AUTH
25522 parameter to the MAIL commands it sends, if it has an authenticated sender for
25523 the message. If the message came from a remote host, the authenticated sender
25524 is the one that was receiving on an incoming MAIL command, provided that the
25525 incoming connection was authenticated and the &%server_mail_auth%& condition
25526 allowed the authenticated sender to be retained. If a local process calls Exim
25527 to send a message, the sender address that is built from the login name and
25528 &%qualify_domain%& is treated as authenticated. However, if the
25529 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
25530 the authenticated sender that was received with the message.
25531 .ecindex IIDauthconf1
25532 .ecindex IIDauthconf2
25539 . ////////////////////////////////////////////////////////////////////////////
25540 . ////////////////////////////////////////////////////////////////////////////
25542 .chapter "The plaintext authenticator" "CHAPplaintext"
25543 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
25544 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
25545 The &(plaintext)& authenticator can be configured to support the PLAIN and
25546 LOGIN authentication mechanisms, both of which transfer authentication data as
25547 plain (unencrypted) text (though base64 encoded). The use of plain text is a
25548 security risk; you are strongly advised to insist on the use of SMTP encryption
25549 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
25550 use unencrypted plain text, you should not use the same passwords for SMTP
25551 connections as you do for login accounts.
25553 .section "Plaintext options" "SECID171"
25554 .cindex "options" "&(plaintext)& authenticator (server)"
25555 When configured as a server, &(plaintext)& uses the following options:
25557 .option server_condition authenticators string&!! unset
25558 This is actually a global authentication option, but it must be set in order to
25559 configure the &(plaintext)& driver as a server. Its use is described below.
25561 .option server_prompts plaintext string&!! unset
25562 The contents of this option, after expansion, must be a colon-separated list of
25563 prompt strings. If expansion fails, a temporary authentication rejection is
25566 .section "Using plaintext in a server" "SECTplainserver"
25567 .cindex "AUTH" "in &(plaintext)& authenticator"
25568 .cindex "binary zero" "in &(plaintext)& authenticator"
25569 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
25570 "in &(plaintext)& authenticator"
25571 .vindex "&$auth1$&, &$auth2$&, etc"
25572 .cindex "base64 encoding" "in &(plaintext)& authenticator"
25574 When running as a server, &(plaintext)& performs the authentication test by
25575 expanding a string. The data sent by the client with the AUTH command, or in
25576 response to subsequent prompts, is base64 encoded, and so may contain any byte
25577 values when decoded. If any data is supplied with the command, it is treated as
25578 a list of strings, separated by NULs (binary zeros), the first three of which
25579 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
25580 (neither LOGIN nor PLAIN uses more than three strings).
25582 For compatibility with previous releases of Exim, the values are also placed in
25583 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
25584 variables for this purpose is now deprecated, as it can lead to confusion in
25585 string expansions that also use them for other things.
25587 If there are more strings in &%server_prompts%& than the number of strings
25588 supplied with the AUTH command, the remaining prompts are used to obtain more
25589 data. Each response from the client may be a list of NUL-separated strings.
25591 .vindex "&$authenticated_id$&"
25592 Once a sufficient number of data strings have been received,
25593 &%server_condition%& is expanded. If the expansion is forced to fail,
25594 authentication fails. Any other expansion failure causes a temporary error code
25595 to be returned. If the result of a successful expansion is an empty string,
25596 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25597 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
25598 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
25599 For any other result, a temporary error code is returned, with the expanded
25600 string as the error text
25602 &*Warning*&: If you use a lookup in the expansion to find the user's
25603 password, be sure to make the authentication fail if the user is unknown.
25604 There are good and bad examples at the end of the next section.
25608 .section "The PLAIN authentication mechanism" "SECID172"
25609 .cindex "PLAIN authentication mechanism"
25610 .cindex "authentication" "PLAIN mechanism"
25611 .cindex "binary zero" "in &(plaintext)& authenticator"
25612 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
25613 sent as one item of data (that is, one combined string containing two NUL
25614 separators). The data is sent either as part of the AUTH command, or
25615 subsequently in response to an empty prompt from the server.
25617 The second and third strings are a user name and a corresponding password.
25618 Using a single fixed user name and password as an example, this could be
25619 configured as follows:
25623 public_name = PLAIN
25625 server_condition = \
25626 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
25627 server_set_id = $auth2
25629 Note that the default result strings from &%if%& (&"true"& or an empty string)
25630 are exactly what we want here, so they need not be specified. Obviously, if the
25631 password contains expansion-significant characters such as dollar, backslash,
25632 or closing brace, they have to be escaped.
25634 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
25635 the end of a string list are ignored). If all the data comes as part of the
25636 AUTH command, as is commonly the case, the prompt is not used. This
25637 authenticator is advertised in the response to EHLO as
25641 and a client host can authenticate itself by sending the command
25643 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
25645 As this contains three strings (more than the number of prompts), no further
25646 data is required from the client. Alternatively, the client may just send
25650 to initiate authentication, in which case the server replies with an empty
25651 prompt. The client must respond with the combined data string.
25653 The data string is base64 encoded, as required by the RFC. This example,
25654 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
25655 represents a zero byte. This is split up into three strings, the first of which
25656 is empty. The &%server_condition%& option in the authenticator checks that the
25657 second two are &`username`& and &`mysecret`& respectively.
25659 Having just one fixed user name and password, as in this example, is not very
25660 realistic, though for a small organization with only a handful of
25661 authenticating clients it could make sense.
25663 A more sophisticated instance of this authenticator could use the user name in
25664 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
25665 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
25666 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
25667 This is an incorrect example:
25669 server_condition = \
25670 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
25672 The expansion uses the user name (&$auth2$&) as the key to look up a password,
25673 which it then compares to the supplied password (&$auth3$&). Why is this example
25674 incorrect? It works fine for existing users, but consider what happens if a
25675 non-existent user name is given. The lookup fails, but as no success/failure
25676 strings are given for the lookup, it yields an empty string. Thus, to defeat
25677 the authentication, all a client has to do is to supply a non-existent user
25678 name and an empty password. The correct way of writing this test is:
25680 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
25681 {${if eq{$value}{$auth3}}} {false}}
25683 In this case, if the lookup succeeds, the result is checked; if the lookup
25684 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
25685 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
25686 always fails if its second argument is empty. However, the second way of
25687 writing the test makes the logic clearer.
25690 .section "The LOGIN authentication mechanism" "SECID173"
25691 .cindex "LOGIN authentication mechanism"
25692 .cindex "authentication" "LOGIN mechanism"
25693 The LOGIN authentication mechanism is not documented in any RFC, but is in use
25694 in a number of programs. No data is sent with the AUTH command. Instead, a
25695 user name and password are supplied separately, in response to prompts. The
25696 plaintext authenticator can be configured to support this as in this example:
25700 public_name = LOGIN
25701 server_prompts = User Name : Password
25702 server_condition = \
25703 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
25704 server_set_id = $auth1
25706 Because of the way plaintext operates, this authenticator accepts data supplied
25707 with the AUTH command (in contravention of the specification of LOGIN), but
25708 if the client does not supply it (as is the case for LOGIN clients), the prompt
25709 strings are used to obtain two data items.
25711 Some clients are very particular about the precise text of the prompts. For
25712 example, Outlook Express is reported to recognize only &"Username:"& and
25713 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
25714 strings. It uses the &%ldapauth%& expansion condition to check the user
25715 name and password by binding to an LDAP server:
25719 public_name = LOGIN
25720 server_prompts = Username:: : Password::
25721 server_condition = ${if and{{ \
25724 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
25725 pass=${quote:$auth2} \
25726 ldap://ldap.example.org/} }} }
25727 server_set_id = uid=$auth1,ou=people,o=example.org
25729 We have to check that the username is not empty before using it, because LDAP
25730 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
25731 operator to correctly quote the DN for authentication. However, the basic
25732 &%quote%& operator, rather than any of the LDAP quoting operators, is the
25733 correct one to use for the password, because quoting is needed only to make
25734 the password conform to the Exim syntax. At the LDAP level, the password is an
25735 uninterpreted string.
25738 .section "Support for different kinds of authentication" "SECID174"
25739 A number of string expansion features are provided for the purpose of
25740 interfacing to different ways of user authentication. These include checking
25741 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
25742 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
25748 .section "Using plaintext in a client" "SECID175"
25749 .cindex "options" "&(plaintext)& authenticator (client)"
25750 The &(plaintext)& authenticator has two client options:
25752 .option client_ignore_invalid_base64 plaintext boolean false
25753 If the client receives a server prompt that is not a valid base64 string,
25754 authentication is abandoned by default. However, if this option is set true,
25755 the error in the challenge is ignored and the client sends the response as
25758 .option client_send plaintext string&!! unset
25759 The string is a colon-separated list of authentication data strings. Each
25760 string is independently expanded before being sent to the server. The first
25761 string is sent with the AUTH command; any more strings are sent in response
25762 to prompts from the server. Before each string is expanded, the value of the
25763 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
25764 with &$auth1$& for the first prompt. Up to three prompts are stored in this
25765 way. Thus, the prompt that is received in response to sending the first string
25766 (with the AUTH command) can be used in the expansion of the second string, and
25767 so on. If an invalid base64 string is received when
25768 &%client_ignore_invalid_base64%& is set, an empty string is put in the
25769 &$auth$&<&'n'&> variable.
25771 &*Note*&: You cannot use expansion to create multiple strings, because
25772 splitting takes priority and happens first.
25774 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
25775 the data, further processing is applied to each string before it is sent. If
25776 there are any single circumflex characters in the string, they are converted to
25777 NULs. Should an actual circumflex be required as data, it must be doubled in
25780 This is an example of a client configuration that implements the PLAIN
25781 authentication mechanism with a fixed user name and password:
25785 public_name = PLAIN
25786 client_send = ^username^mysecret
25788 The lack of colons means that the entire text is sent with the AUTH
25789 command, with the circumflex characters converted to NULs. A similar example
25790 that uses the LOGIN mechanism is:
25794 public_name = LOGIN
25795 client_send = : username : mysecret
25797 The initial colon means that the first string is empty, so no data is sent with
25798 the AUTH command itself. The remaining strings are sent in response to
25800 .ecindex IIDplaiauth1
25801 .ecindex IIDplaiauth2
25806 . ////////////////////////////////////////////////////////////////////////////
25807 . ////////////////////////////////////////////////////////////////////////////
25809 .chapter "The cram_md5 authenticator" "CHID9"
25810 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
25811 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
25812 .cindex "CRAM-MD5 authentication mechanism"
25813 .cindex "authentication" "CRAM-MD5 mechanism"
25814 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
25815 sends a challenge string to the client, and the response consists of a user
25816 name and the CRAM-MD5 digest of the challenge string combined with a secret
25817 string (password) which is known to both server and client. Thus, the secret
25818 is not sent over the network as plain text, which makes this authenticator more
25819 secure than &(plaintext)&. However, the downside is that the secret has to be
25820 available in plain text at either end.
25823 .section "Using cram_md5 as a server" "SECID176"
25824 .cindex "options" "&(cram_md5)& authenticator (server)"
25825 This authenticator has one server option, which must be set to configure the
25826 authenticator as a server:
25828 .option server_secret cram_md5 string&!! unset
25829 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
25830 When the server receives the client's response, the user name is placed in
25831 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
25832 obtain the password for that user. The server then computes the CRAM-MD5 digest
25833 that the client should have sent, and checks that it received the correct
25834 string. If the expansion of &%server_secret%& is forced to fail, authentication
25835 fails. If the expansion fails for some other reason, a temporary error code is
25836 returned to the client.
25838 For compatibility with previous releases of Exim, the user name is also placed
25839 in &$1$&. However, the use of this variables for this purpose is now
25840 deprecated, as it can lead to confusion in string expansions that also use
25841 numeric variables for other things.
25843 For example, the following authenticator checks that the user name given by the
25844 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
25845 user name, authentication fails.
25849 public_name = CRAM-MD5
25850 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
25851 server_set_id = $auth1
25853 .vindex "&$authenticated_id$&"
25854 If authentication succeeds, the setting of &%server_set_id%& preserves the user
25855 name in &$authenticated_id$&. A more typical configuration might look up the
25856 secret string in a file, using the user name as the key. For example:
25860 public_name = CRAM-MD5
25861 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
25863 server_set_id = $auth1
25865 Note that this expansion explicitly forces failure if the lookup fails
25866 because &$auth1$& contains an unknown user name.
25868 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
25869 using the relevant libraries, you need to know the realm to specify in the
25870 lookup and then ask for the &"userPassword"& attribute for that user in that
25875 public_name = CRAM-MD5
25876 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
25877 dbmjz{/etc/sasldb2}{$value}fail}
25878 server_set_id = $auth1
25881 .section "Using cram_md5 as a client" "SECID177"
25882 .cindex "options" "&(cram_md5)& authenticator (client)"
25883 When used as a client, the &(cram_md5)& authenticator has two options:
25887 .option client_name cram_md5 string&!! "the primary host name"
25888 This string is expanded, and the result used as the user name data when
25889 computing the response to the server's challenge.
25892 .option client_secret cram_md5 string&!! unset
25893 This option must be set for the authenticator to work as a client. Its value is
25894 expanded and the result used as the secret string when computing the response.
25898 .vindex "&$host_address$&"
25899 Different user names and secrets can be used for different servers by referring
25900 to &$host$& or &$host_address$& in the options. Forced failure of either
25901 expansion string is treated as an indication that this authenticator is not
25902 prepared to handle this case. Exim moves on to the next configured client
25903 authenticator. Any other expansion failure causes Exim to give up trying to
25904 send the message to the current server.
25906 A simple example configuration of a &(cram_md5)& authenticator, using fixed
25911 public_name = CRAM-MD5
25913 client_secret = secret
25915 .ecindex IIDcramauth1
25916 .ecindex IIDcramauth2
25920 . ////////////////////////////////////////////////////////////////////////////
25921 . ////////////////////////////////////////////////////////////////////////////
25923 .chapter "The cyrus_sasl authenticator" "CHID10"
25924 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
25925 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
25926 .cindex "Cyrus" "SASL library"
25928 The code for this authenticator was provided by Matthew Byng-Maddick of A L
25929 Digital Ltd (&url(http://www.aldigital.co.uk)).
25931 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
25932 library implementation of the RFC 2222 (&"Simple Authentication and Security
25933 Layer"&). This library supports a number of authentication mechanisms,
25934 including PLAIN and LOGIN, but also several others that Exim does not support
25935 directly. In particular, there is support for Kerberos authentication.
25937 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
25938 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
25939 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
25940 name of the driver to determine which mechanism to support.
25942 Where access to some kind of secret file is required, for example in GSSAPI
25943 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
25944 user, and that the Cyrus SASL library has no way of escalating privileges
25945 by default. You may also find you need to set environment variables,
25946 depending on the driver you are using.
25948 The application name provided by Exim is &"exim"&, so various SASL options may
25949 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
25950 Kerberos, note that because of limitations in the GSSAPI interface,
25951 changing the server keytab might need to be communicated down to the Kerberos
25952 layer independently. The mechanism for doing so is dependent upon the Kerberos
25955 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
25956 may be set to point to an alternative keytab file. Exim will pass this
25957 variable through from its own inherited environment when started as root or the
25958 Exim user. The keytab file needs to be readable by the Exim user.
25959 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
25960 environment variable. In practice, for those releases, the Cyrus authenticator
25961 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
25962 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
25965 .section "Using cyrus_sasl as a server" "SECID178"
25966 The &(cyrus_sasl)& authenticator has four private options. It puts the username
25967 (on a successful authentication) into &$auth1$&. For compatibility with
25968 previous releases of Exim, the username is also placed in &$1$&. However, the
25969 use of this variable for this purpose is now deprecated, as it can lead to
25970 confusion in string expansions that also use numeric variables for other
25974 .option server_hostname cyrus_sasl string&!! "see below"
25975 This option selects the hostname that is used when communicating with the
25976 library. The default value is &`$primary_hostname`&. It is up to the underlying
25977 SASL plug-in what it does with this data.
25980 .option server_mech cyrus_sasl string "see below"
25981 This option selects the authentication mechanism this driver should use. The
25982 default is the value of the generic &%public_name%& option. This option allows
25983 you to use a different underlying mechanism from the advertised name. For
25987 driver = cyrus_sasl
25988 public_name = X-ANYTHING
25989 server_mech = CRAM-MD5
25990 server_set_id = $auth1
25993 .option server_realm cyrus_sasl string&!! unset
25994 This specifies the SASL realm that the server claims to be in.
25997 .option server_service cyrus_sasl string &`smtp`&
25998 This is the SASL service that the server claims to implement.
26001 For straightforward cases, you do not need to set any of the authenticator's
26002 private options. All you need to do is to specify an appropriate mechanism as
26003 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
26004 PLAIN, you could have two authenticators as follows:
26007 driver = cyrus_sasl
26008 public_name = CRAM-MD5
26009 server_set_id = $auth1
26012 driver = cyrus_sasl
26013 public_name = PLAIN
26014 server_set_id = $auth2
26016 Cyrus SASL does implement the LOGIN authentication method, even though it is
26017 not a standard method. It is disabled by default in the source distribution,
26018 but it is present in many binary distributions.
26019 .ecindex IIDcyrauth1
26020 .ecindex IIDcyrauth2
26025 . ////////////////////////////////////////////////////////////////////////////
26026 . ////////////////////////////////////////////////////////////////////////////
26027 .chapter "The dovecot authenticator" "CHAPdovecot"
26028 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
26029 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
26030 This authenticator is an interface to the authentication facility of the
26031 Dovecot POP/IMAP server, which can support a number of authentication methods.
26032 Note that Dovecot must be configured to use auth-client not auth-userdb.
26033 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
26034 to use the same mechanisms for SMTP authentication. This is a server
26035 authenticator only. There is only one option:
26037 .option server_socket dovecot string unset
26039 This option must specify the socket that is the interface to Dovecot
26040 authentication. The &%public_name%& option must specify an authentication
26041 mechanism that Dovecot is configured to support. You can have several
26042 authenticators for different mechanisms. For example:
26046 public_name = PLAIN
26047 server_socket = /var/run/dovecot/auth-client
26048 server_set_id = $auth1
26053 server_socket = /var/run/dovecot/auth-client
26054 server_set_id = $auth1
26056 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
26057 &$received_ip_address$& (that is, the connection is local), the &"secured"&
26058 option is passed in the Dovecot authentication command. If, for a TLS
26059 connection, a client certificate has been verified, the &"valid-client-cert"&
26060 option is passed. When authentication succeeds, the identity of the user
26061 who authenticated is placed in &$auth1$&.
26062 .ecindex IIDdcotauth1
26063 .ecindex IIDdcotauth2
26066 . ////////////////////////////////////////////////////////////////////////////
26067 . ////////////////////////////////////////////////////////////////////////////
26068 .chapter "The gsasl authenticator" "CHAPgsasl"
26069 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
26070 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
26071 .cindex "authentication" "GNU SASL"
26072 .cindex "authentication" "SASL"
26073 .cindex "authentication" "EXTERNAL"
26074 .cindex "authentication" "ANONYMOUS"
26075 .cindex "authentication" "PLAIN"
26076 .cindex "authentication" "LOGIN"
26077 .cindex "authentication" "DIGEST-MD5"
26078 .cindex "authentication" "CRAM-MD5"
26079 .cindex "authentication" "SCRAM-SHA-1"
26080 The &(gsasl)& authenticator provides server integration for the GNU SASL
26081 library and the mechanisms it provides. This is new as of the 4.80 release
26082 and there are a few areas where the library does not let Exim smoothly
26083 scale to handle future authentication mechanisms, so no guarantee can be
26084 made that any particular new authentication mechanism will be supported
26085 without code changes in Exim.
26088 .option server_channelbinding gsasl boolean false
26089 Some authentication mechanisms are able to use external context at both ends
26090 of the session to bind the authentication to that context, and fail the
26091 authentication process if that context differs. Specifically, some TLS
26092 ciphersuites can provide identifying information about the cryptographic
26095 This means that certificate identity and verification becomes a non-issue,
26096 as a man-in-the-middle attack will cause the correct client and server to
26097 see different identifiers and authentication will fail.
26099 This is currently only supported when using the GnuTLS library. This is
26100 only usable by mechanisms which support "channel binding"; at time of
26101 writing, that's the SCRAM family.
26103 This defaults off to ensure smooth upgrade across Exim releases, in case
26104 this option causes some clients to start failing. Some future release
26105 of Exim may switch the default to be true.
26108 .option server_hostname gsasl string&!! "see below"
26109 This option selects the hostname that is used when communicating with the
26110 library. The default value is &`$primary_hostname`&.
26111 Some mechanisms will use this data.
26114 .option server_mech gsasl string "see below"
26115 This option selects the authentication mechanism this driver should use. The
26116 default is the value of the generic &%public_name%& option. This option allows
26117 you to use a different underlying mechanism from the advertised name. For
26122 public_name = X-ANYTHING
26123 server_mech = CRAM-MD5
26124 server_set_id = $auth1
26128 .option server_password gsasl string&!! unset
26129 Various mechanisms need access to the cleartext password on the server, so
26130 that proof-of-possession can be demonstrated on the wire, without sending
26131 the password itself.
26133 The data available for lookup varies per mechanism.
26134 In all cases, &$auth1$& is set to the &'authentication id'&.
26135 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
26136 if available, else the empty string.
26137 The &$auth3$& variable will always be the &'realm'& if available,
26138 else the empty string.
26140 A forced failure will cause authentication to defer.
26142 If using this option, it may make sense to set the &%server_condition%&
26143 option to be simply "true".
26146 .option server_realm gsasl string&!! unset
26147 This specifies the SASL realm that the server claims to be in.
26148 Some mechanisms will use this data.
26151 .option server_scram_iter gsasl string&!! unset
26152 This option provides data for the SCRAM family of mechanisms.
26153 &$auth1$& is not available at evaluation time.
26154 (This may change, as we receive feedback on use)
26157 .option server_scram_salt gsasl string&!! unset
26158 This option provides data for the SCRAM family of mechanisms.
26159 &$auth1$& is not available at evaluation time.
26160 (This may change, as we receive feedback on use)
26163 .option server_service gsasl string &`smtp`&
26164 This is the SASL service that the server claims to implement.
26165 Some mechanisms will use this data.
26168 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
26169 .vindex "&$auth1$&, &$auth2$&, etc"
26170 These may be set when evaluating specific options, as detailed above.
26171 They will also be set when evaluating &%server_condition%&.
26173 Unless otherwise stated below, the &(gsasl)& integration will use the following
26174 meanings for these variables:
26177 .vindex "&$auth1$&"
26178 &$auth1$&: the &'authentication id'&
26180 .vindex "&$auth2$&"
26181 &$auth2$&: the &'authorization id'&
26183 .vindex "&$auth3$&"
26184 &$auth3$&: the &'realm'&
26187 On a per-mechanism basis:
26190 .cindex "authentication" "EXTERNAL"
26191 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
26192 the &%server_condition%& option must be present.
26194 .cindex "authentication" "ANONYMOUS"
26195 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
26196 the &%server_condition%& option must be present.
26198 .cindex "authentication" "GSSAPI"
26199 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
26200 &$auth2$& will be set to the &'authorization id'&,
26201 the &%server_condition%& option must be present.
26204 An &'anonymous token'& is something passed along as an unauthenticated
26205 identifier; this is analogous to FTP anonymous authentication passing an
26206 email address, or software-identifier@, as the "password".
26209 An example showing the password having the realm specified in the callback
26210 and demonstrating a Cyrus SASL to GSASL migration approach is:
26212 gsasl_cyrusless_crammd5:
26214 public_name = CRAM-MD5
26215 server_realm = imap.example.org
26216 server_password = ${lookup{$auth1:$auth3:userPassword}\
26217 dbmjz{/etc/sasldb2}{$value}fail}
26218 server_set_id = ${quote:$auth1}
26219 server_condition = yes
26223 . ////////////////////////////////////////////////////////////////////////////
26224 . ////////////////////////////////////////////////////////////////////////////
26226 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
26227 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
26228 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
26229 .cindex "authentication" "GSSAPI"
26230 .cindex "authentication" "Kerberos"
26231 The &(heimdal_gssapi)& authenticator provides server integration for the
26232 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
26235 .option server_hostname heimdal_gssapi string&!! "see below"
26236 This option selects the hostname that is used, with &%server_service%&,
26237 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
26238 identifier. The default value is &`$primary_hostname`&.
26240 .option server_keytab heimdal_gssapi string&!! unset
26241 If set, then Heimdal will not use the system default keytab (typically
26242 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
26243 The value should be a pathname, with no &"file:"& prefix.
26245 .option server_service heimdal_gssapi string&!! "smtp"
26246 This option specifies the service identifier used, in conjunction with
26247 &%server_hostname%&, for building the identifier for finding credentials
26251 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
26252 Beware that these variables will typically include a realm, thus will appear
26253 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
26254 not verified, so a malicious client can set it to anything.
26256 The &$auth1$& field should be safely trustable as a value from the Key
26257 Distribution Center. Note that these are not quite email addresses.
26258 Each identifier is for a role, and so the left-hand-side may include a
26259 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
26261 .vindex "&$auth1$&, &$auth2$&, etc"
26263 .vindex "&$auth1$&"
26264 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
26266 .vindex "&$auth2$&"
26267 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
26268 authentication. If that was empty, this will also be set to the
26273 . ////////////////////////////////////////////////////////////////////////////
26274 . ////////////////////////////////////////////////////////////////////////////
26276 .chapter "The spa authenticator" "CHAPspa"
26277 .scindex IIDspaauth1 "&(spa)& authenticator"
26278 .scindex IIDspaauth2 "authenticators" "&(spa)&"
26279 .cindex "authentication" "Microsoft Secure Password"
26280 .cindex "authentication" "NTLM"
26281 .cindex "Microsoft Secure Password Authentication"
26282 .cindex "NTLM authentication"
26283 The &(spa)& authenticator provides client support for Microsoft's &'Secure
26284 Password Authentication'& mechanism,
26285 which is also sometimes known as NTLM (NT LanMan). The code for client side of
26286 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
26287 taken from the Samba project (&url(http://www.samba.org)). The code for the
26288 server side was subsequently contributed by Tom Kistner. The mechanism works as
26292 After the AUTH command has been accepted, the client sends an SPA
26293 authentication request based on the user name and optional domain.
26295 The server sends back a challenge.
26297 The client builds a challenge response which makes use of the user's password
26298 and sends it to the server, which then accepts or rejects it.
26301 Encryption is used to protect the password in transit.
26305 .section "Using spa as a server" "SECID179"
26306 .cindex "options" "&(spa)& authenticator (server)"
26307 The &(spa)& authenticator has just one server option:
26309 .option server_password spa string&!! unset
26310 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
26311 This option is expanded, and the result must be the cleartext password for the
26312 authenticating user, whose name is at this point in &$auth1$&. For
26313 compatibility with previous releases of Exim, the user name is also placed in
26314 &$1$&. However, the use of this variable for this purpose is now deprecated, as
26315 it can lead to confusion in string expansions that also use numeric variables
26316 for other things. For example:
26321 server_password = \
26322 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
26324 If the expansion is forced to fail, authentication fails. Any other expansion
26325 failure causes a temporary error code to be returned.
26331 .section "Using spa as a client" "SECID180"
26332 .cindex "options" "&(spa)& authenticator (client)"
26333 The &(spa)& authenticator has the following client options:
26337 .option client_domain spa string&!! unset
26338 This option specifies an optional domain for the authentication.
26341 .option client_password spa string&!! unset
26342 This option specifies the user's password, and must be set.
26345 .option client_username spa string&!! unset
26346 This option specifies the user name, and must be set. Here is an example of a
26347 configuration of this authenticator for use with the mail servers at
26353 client_username = msn/msn_username
26354 client_password = msn_plaintext_password
26355 client_domain = DOMAIN_OR_UNSET
26357 .ecindex IIDspaauth1
26358 .ecindex IIDspaauth2
26364 . ////////////////////////////////////////////////////////////////////////////
26365 . ////////////////////////////////////////////////////////////////////////////
26367 .chapter "The tls authenticator" "CHAPtlsauth"
26368 .scindex IIDtlsauth1 "&(tls)& authenticator"
26369 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
26370 .cindex "authentication" "Client Certificate"
26371 .cindex "authentication" "X509"
26372 .cindex "Certificate-based authentication"
26373 The &(tls)& authenticator provides server support for
26374 authentication based on client certificates.
26376 It is not an SMTP authentication mechanism and is not
26377 advertised by the server as part of the SMTP EHLO response.
26378 It is an Exim authenticator in the sense that it affects
26379 the protocol element of the log line, can be tested for
26380 by the &%authenticated%& ACL condition, and can set
26381 the &$authenticated_id$& variable.
26383 The client must present a verifiable certificate,
26384 for which it must have been requested via the
26385 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
26386 (see &<<CHAPTLS>>&).
26388 If an authenticator of this type is configured it is
26389 run before any SMTP-level communication is done,
26390 and can authenticate the connection.
26391 If it does, SMTP authentication is not offered.
26393 A maximum of one authenticator of this type may be present.
26396 .cindex "options" "&(tls)& authenticator (server)"
26397 The &(tls)& authenticator has three server options:
26399 .option server_param1 tls string&!! unset
26400 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
26401 This option is expanded after the TLS negotiation and
26402 the result is placed in &$auth1$&.
26403 If the expansion is forced to fail, authentication fails. Any other expansion
26404 failure causes a temporary error code to be returned.
26406 .option server_param2 tls string&!! unset
26407 .option server_param3 tls string&!! unset
26408 As above, for &$auth2$& and &$auth3$&.
26410 &%server_param1%& may also be spelled &%server_param%&.
26417 server_param1 = ${certextract {subj_altname,mail,>:} \
26418 {$tls_in_peercert}}
26419 server_condition = ${if forany {$auth1} \
26421 {${lookup ldap{ldap:///\
26422 mailname=${quote_ldap_dn:${lc:$item}},\
26423 ou=users,LDAP_DC?mailid} {$value}{0} \
26425 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
26427 .ecindex IIDtlsauth1
26428 .ecindex IIDtlsauth2
26431 Note that because authentication is traditionally an SMTP operation,
26432 the &%authenticated%& ACL condition cannot be used in
26433 a connect- or helo-ACL.
26437 . ////////////////////////////////////////////////////////////////////////////
26438 . ////////////////////////////////////////////////////////////////////////////
26440 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
26441 "Encrypted SMTP connections"
26442 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
26443 .scindex IIDencsmtp2 "SMTP" "encryption"
26444 .cindex "TLS" "on SMTP connection"
26447 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
26448 Sockets Layer), is implemented by making use of the OpenSSL library or the
26449 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
26450 cryptographic code in the Exim distribution itself for implementing TLS. In
26451 order to use this feature you must install OpenSSL or GnuTLS, and then build a
26452 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
26453 You also need to understand the basic concepts of encryption at a managerial
26454 level, and in particular, the way that public keys, private keys, and
26455 certificates are used.
26457 RFC 3207 defines how SMTP connections can make use of encryption. Once a
26458 connection is established, the client issues a STARTTLS command. If the
26459 server accepts this, the client and the server negotiate an encryption
26460 mechanism. If the negotiation succeeds, the data that subsequently passes
26461 between them is encrypted.
26463 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
26464 and if so, what cipher suite is in use, whether the client supplied a
26465 certificate, and whether or not that certificate was verified. This makes it
26466 possible for an Exim server to deny or accept certain commands based on the
26469 &*Warning*&: Certain types of firewall and certain anti-virus products can
26470 disrupt TLS connections. You need to turn off SMTP scanning for these products
26471 in order to get TLS to work.
26475 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
26477 .cindex "ssmtp protocol"
26478 .cindex "smtps protocol"
26479 .cindex "SMTP" "ssmtp protocol"
26480 .cindex "SMTP" "smtps protocol"
26481 Early implementations of encrypted SMTP used a different TCP port from normal
26482 SMTP, and expected an encryption negotiation to start immediately, instead of
26483 waiting for a STARTTLS command from the client using the standard SMTP
26484 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
26485 allocated for this purpose.
26487 This approach was abandoned when encrypted SMTP was standardized, but there are
26488 still some legacy clients that use it. Exim supports these clients by means of
26489 the &%tls_on_connect_ports%& global option. Its value must be a list of port
26490 numbers; the most common use is expected to be:
26492 tls_on_connect_ports = 465
26494 The port numbers specified by this option apply to all SMTP connections, both
26495 via the daemon and via &'inetd'&. You still need to specify all the ports that
26496 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
26497 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
26498 an extra port &-- rather, it specifies different behaviour on a port that is
26501 There is also a &%-tls-on-connect%& command line option. This overrides
26502 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
26509 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
26510 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
26511 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
26512 followed later, when the first versions of GnuTLS were released. To build Exim
26513 to use GnuTLS, you need to set
26517 in Local/Makefile, in addition to
26521 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
26522 include files and libraries for GnuTLS can be found.
26524 There are some differences in usage when using GnuTLS instead of OpenSSL:
26527 The &%tls_verify_certificates%& option
26528 cannot be the path of a directory
26529 for GnuTLS versions before 3.3.6
26530 (for later versions, or OpenSSL, it can be either).
26532 The default value for &%tls_dhparam%& differs for historical reasons.
26534 .vindex "&$tls_in_peerdn$&"
26535 .vindex "&$tls_out_peerdn$&"
26536 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
26537 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
26538 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
26540 OpenSSL identifies cipher suites using hyphens as separators, for example:
26541 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
26542 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
26543 in a cipher list. To make life simpler, Exim changes underscores to hyphens
26544 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
26545 to handle its own older variants) when processing lists of cipher suites in the
26546 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
26549 The &%tls_require_ciphers%& options operate differently, as described in the
26550 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
26552 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
26553 When using OpenSSL, this option is ignored.
26554 (If an API is found to let OpenSSL be configured in this way,
26555 let the Exim Maintainers know and we'll likely use it).
26557 Some other recently added features may only be available in one or the other.
26558 This should be documented with the feature. If the documentation does not
26559 explicitly state that the feature is infeasible in the other TLS
26560 implementation, then patches are welcome.
26564 .section "GnuTLS parameter computation" "SECTgnutlsparam"
26565 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
26566 an explicit path; if the latter, then the text about generation still applies,
26567 but not the chosen filename.
26568 By default, as of Exim 4.80 a hard-coded D-H prime is used.
26569 See the documentation of &%tls_dhparam%& for more information.
26571 GnuTLS uses D-H parameters that may take a substantial amount of time
26572 to compute. It is unreasonable to re-compute them for every TLS session.
26573 Therefore, Exim keeps this data in a file in its spool directory, called
26574 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
26576 The file is owned by the Exim user and is readable only by
26577 its owner. Every Exim process that start up GnuTLS reads the D-H
26578 parameters from this file. If the file does not exist, the first Exim process
26579 that needs it computes the data and writes it to a temporary file which is
26580 renamed once it is complete. It does not matter if several Exim processes do
26581 this simultaneously (apart from wasting a few resources). Once a file is in
26582 place, new Exim processes immediately start using it.
26584 For maximum security, the parameters that are stored in this file should be
26585 recalculated periodically, the frequency depending on your paranoia level.
26586 If you are avoiding using the fixed D-H primes published in RFCs, then you
26587 are concerned about some advanced attacks and will wish to do this; if you do
26588 not regenerate then you might as well stick to the standard primes.
26590 Arranging this is easy in principle; just delete the file when you want new
26591 values to be computed. However, there may be a problem. The calculation of new
26592 parameters needs random numbers, and these are obtained from &_/dev/random_&.
26593 If the system is not very active, &_/dev/random_& may delay returning data
26594 until enough randomness (entropy) is available. This may cause Exim to hang for
26595 a substantial amount of time, causing timeouts on incoming connections.
26597 The solution is to generate the parameters externally to Exim. They are stored
26598 in &_gnutls-params-N_& in PEM format, which means that they can be
26599 generated externally using the &(certtool)& command that is part of GnuTLS.
26601 To replace the parameters with new ones, instead of deleting the file
26602 and letting Exim re-create it, you can generate new parameters using
26603 &(certtool)& and, when this has been done, replace Exim's cache file by
26604 renaming. The relevant commands are something like this:
26607 [ look for file; assume gnutls-params-2236 is the most recent ]
26610 # chown exim:exim new-params
26611 # chmod 0600 new-params
26612 # certtool --generate-dh-params --bits 2236 >>new-params
26613 # openssl dhparam -noout -text -in new-params | head
26614 [ check the first line, make sure it's not more than 2236;
26615 if it is, then go back to the start ("rm") and repeat
26616 until the size generated is at most the size requested ]
26617 # chmod 0400 new-params
26618 # mv new-params gnutls-params-2236
26620 If Exim never has to generate the parameters itself, the possibility of
26621 stalling is removed.
26623 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
26624 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
26625 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
26626 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
26627 and Exim does so. This attempt to remove Exim from TLS policy decisions
26628 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
26629 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
26630 which applies to all D-H usage, client or server. If the value returned by
26631 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
26632 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
26633 limit, which is still much higher than Exim historically used.
26635 The filename and bits used will change as the GnuTLS maintainers change the
26636 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
26637 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
26638 2432 bits, while NSS is limited to 2236 bits.
26640 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
26641 increase the chance of the generated prime actually being within acceptable
26642 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
26643 procedure above. There is no sane procedure available to Exim to double-check
26644 the size of the generated prime, so it might still be too large.
26647 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
26648 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
26649 .oindex "&%tls_require_ciphers%&" "OpenSSL"
26650 There is a function in the OpenSSL library that can be passed a list of cipher
26651 suites before the cipher negotiation takes place. This specifies which ciphers
26652 are acceptable. The list is colon separated and may contain names like
26653 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
26654 directly to this function call.
26655 Many systems will install the OpenSSL manual-pages, so you may have
26656 &'ciphers(1)'& available to you.
26657 The following quotation from the OpenSSL
26658 documentation specifies what forms of item are allowed in the cipher string:
26661 It can consist of a single cipher suite such as RC4-SHA.
26663 It can represent a list of cipher suites containing a certain algorithm,
26664 or cipher suites of a certain type. For example SHA1 represents all
26665 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
26668 Lists of cipher suites can be combined in a single cipher string using
26669 the + character. This is used as a logical and operation. For example
26670 SHA1+DES represents all cipher suites containing the SHA1 and the DES
26674 Each cipher string can be optionally preceded by one of the characters &`!`&,
26677 If &`!`& is used, the ciphers are permanently deleted from the list. The
26678 ciphers deleted can never reappear in the list even if they are explicitly
26681 If &`-`& is used, the ciphers are deleted from the list, but some or all
26682 of the ciphers can be added again by later options.
26684 If &`+`& is used, the ciphers are moved to the end of the list. This
26685 option does not add any new ciphers; it just moves matching existing ones.
26688 If none of these characters is present, the string is interpreted as
26689 a list of ciphers to be appended to the current preference list. If the list
26690 includes any ciphers already present they will be ignored: that is, they will
26691 not be moved to the end of the list.
26694 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
26697 # note single-quotes to get ! past any shell history expansion
26698 $ openssl ciphers 'HIGH:!MD5:!SHA1'
26701 This example will let the library defaults be permitted on the MX port, where
26702 there's probably no identity verification anyway, but ups the ante on the
26703 submission ports where the administrator might have some influence on the
26704 choice of clients used:
26706 # OpenSSL variant; see man ciphers(1)
26707 tls_require_ciphers = ${if =={$received_port}{25}\
26714 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
26716 .cindex "GnuTLS" "specifying parameters for"
26717 .cindex "TLS" "specifying ciphers (GnuTLS)"
26718 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
26719 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
26720 .cindex "TLS" "specifying protocols (GnuTLS)"
26721 .cindex "TLS" "specifying priority string (GnuTLS)"
26722 .oindex "&%tls_require_ciphers%&" "GnuTLS"
26723 The GnuTLS library allows the caller to provide a "priority string", documented
26724 as part of the &[gnutls_priority_init]& function. This is very similar to the
26725 ciphersuite specification in OpenSSL.
26727 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
26728 and controls both protocols and ciphers.
26730 The &%tls_require_ciphers%& option is available both as an global option,
26731 controlling how Exim behaves as a server, and also as an option of the
26732 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
26733 the value is string expanded. The resulting string is not an Exim list and
26734 the string is given to the GnuTLS library, so that Exim does not need to be
26735 aware of future feature enhancements of GnuTLS.
26737 Documentation of the strings accepted may be found in the GnuTLS manual, under
26738 "Priority strings". This is online as
26739 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
26740 but beware that this relates to GnuTLS 3, which may be newer than the version
26741 installed on your system. If you are using GnuTLS 3,
26742 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code)
26743 on that site can be used to test a given string.
26747 # Disable older versions of protocols
26748 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
26751 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
26752 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
26753 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
26755 This example will let the library defaults be permitted on the MX port, where
26756 there's probably no identity verification anyway, and lowers security further
26757 by increasing compatibility; but this ups the ante on the submission ports
26758 where the administrator might have some influence on the choice of clients
26762 tls_require_ciphers = ${if =={$received_port}{25}\
26768 .section "Configuring an Exim server to use TLS" "SECID182"
26769 .cindex "TLS" "configuring an Exim server"
26770 When Exim has been built with TLS support, it advertises the availability of
26771 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
26772 but not to any others. The default value of this option is unset, which means
26773 that STARTTLS is not advertised at all. This default is chosen because you
26774 need to set some other options in order to make TLS available, and also it is
26775 sensible for systems that want to use TLS only as a client.
26777 If a client issues a STARTTLS command and there is some configuration
26778 problem in the server, the command is rejected with a 454 error. If the client
26779 persists in trying to issue SMTP commands, all except QUIT are rejected
26782 554 Security failure
26784 If a STARTTLS command is issued within an existing TLS session, it is
26785 rejected with a 554 error code.
26787 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
26788 match some hosts. You can, of course, set it to * to match all hosts.
26789 However, this is not all you need to do. TLS sessions to a server won't work
26790 without some further configuration at the server end.
26792 It is rumoured that all existing clients that support TLS/SSL use RSA
26793 encryption. To make this work you need to set, in the server,
26795 tls_certificate = /some/file/name
26796 tls_privatekey = /some/file/name
26798 These options are, in fact, expanded strings, so you can make them depend on
26799 the identity of the client that is connected if you wish. The first file
26800 contains the server's X509 certificate, and the second contains the private key
26801 that goes with it. These files need to be
26802 PEM format and readable by the Exim user, and must
26803 always be given as full path names.
26804 The key must not be password-protected.
26805 They can be the same file if both the
26806 certificate and the key are contained within it. If &%tls_privatekey%& is not
26807 set, or if its expansion is forced to fail or results in an empty string, this
26808 is assumed to be the case. The certificate file may also contain intermediate
26809 certificates that need to be sent to the client to enable it to authenticate
26810 the server's certificate.
26812 If you do not understand about certificates and keys, please try to find a
26813 source of this background information, which is not Exim-specific. (There are a
26814 few comments below in section &<<SECTcerandall>>&.)
26816 &*Note*&: These options do not apply when Exim is operating as a client &--
26817 they apply only in the case of a server. If you need to use a certificate in an
26818 Exim client, you must set the options of the same names in an &(smtp)&
26821 With just these options, an Exim server will be able to use TLS. It does not
26822 require the client to have a certificate (but see below for how to insist on
26823 this). There is one other option that may be needed in other situations. If
26825 tls_dhparam = /some/file/name
26827 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
26828 with the parameters contained in the file.
26829 Set this to &`none`& to disable use of DH entirely, by making no prime
26834 This may also be set to a string identifying a standard prime to be used for
26835 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
26836 used is &`ike23`&. There are a few standard primes available, see the
26837 documentation for &%tls_dhparam%& for the complete list.
26843 for a way of generating file data.
26845 The strings supplied for these three options are expanded every time a client
26846 host connects. It is therefore possible to use different certificates and keys
26847 for different hosts, if you so wish, by making use of the client's IP address
26848 in &$sender_host_address$& to control the expansion. If a string expansion is
26849 forced to fail, Exim behaves as if the option is not set.
26851 .cindex "cipher" "logging"
26852 .cindex "log" "TLS cipher"
26853 .vindex "&$tls_in_cipher$&"
26854 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
26855 an incoming TLS connection. It is included in the &'Received:'& header of an
26856 incoming message (by default &-- you can, of course, change this), and it is
26857 also included in the log line that records a message's arrival, keyed by
26858 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
26859 condition can be used to test for specific cipher suites in ACLs.
26861 Once TLS has been established, the ACLs that run for subsequent SMTP commands
26862 can check the name of the cipher suite and vary their actions accordingly. The
26863 cipher suite names vary, depending on which TLS library is being used. For
26864 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
26865 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
26866 documentation for more details.
26868 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
26869 (again depending on the &%tls_cipher%& log selector).
26872 .section "Requesting and verifying client certificates" "SECID183"
26873 .cindex "certificate" "verification of client"
26874 .cindex "TLS" "client certificate verification"
26875 If you want an Exim server to request a certificate when negotiating a TLS
26876 session with a client, you must set either &%tls_verify_hosts%& or
26877 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
26878 apply to all TLS connections. For any host that matches one of these options,
26879 Exim requests a certificate as part of the setup of the TLS session. The
26880 contents of the certificate are verified by comparing it with a list of
26881 expected certificates.
26882 These may be the system default set (depending on library version),
26883 an explicit file or,
26884 depending on library version, a directory, identified by
26885 &%tls_verify_certificates%&.
26887 A file can contain multiple certificates, concatenated end to end. If a
26890 each certificate must be in a separate file, with a name (or a symbolic link)
26891 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
26892 certificate. You can compute the relevant hash by running the command
26894 openssl x509 -hash -noout -in /cert/file
26896 where &_/cert/file_& contains a single certificate.
26898 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
26899 what happens if the client does not supply a certificate, or if the certificate
26900 does not match any of the certificates in the collection named by
26901 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
26902 attempt to set up a TLS session is aborted, and the incoming connection is
26903 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
26904 session continues. ACLs that run for subsequent SMTP commands can detect the
26905 fact that no certificate was verified, and vary their actions accordingly. For
26906 example, you can insist on a certificate before accepting a message for
26907 relaying, but not when the message is destined for local delivery.
26909 .vindex "&$tls_in_peerdn$&"
26910 When a client supplies a certificate (whether it verifies or not), the value of
26911 the Distinguished Name of the certificate is made available in the variable
26912 &$tls_in_peerdn$& during subsequent processing of the message.
26914 .cindex "log" "distinguished name"
26915 Because it is often a long text string, it is not included in the log line or
26916 &'Received:'& header by default. You can arrange for it to be logged, keyed by
26917 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
26918 &%received_header_text%& to change the &'Received:'& header. When no
26919 certificate is supplied, &$tls_in_peerdn$& is empty.
26922 .section "Revoked certificates" "SECID184"
26923 .cindex "TLS" "revoked certificates"
26924 .cindex "revocation list"
26925 .cindex "certificate" "revocation list"
26926 .cindex "OCSP" "stapling"
26927 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
26928 certificates are revoked. If you have such a list, you can pass it to an Exim
26929 server using the global option called &%tls_crl%& and to an Exim client using
26930 an identically named option for the &(smtp)& transport. In each case, the value
26931 of the option is expanded and must then be the name of a file that contains a
26933 The downside is that clients have to periodically re-download a potentially huge
26934 file from every certificate authority they know of.
26936 The way with most moving parts at query time is Online Certificate
26937 Status Protocol (OCSP), where the client verifies the certificate
26938 against an OCSP server run by the CA. This lets the CA track all
26939 usage of the certs. It requires running software with access to the
26940 private key of the CA, to sign the responses to the OCSP queries. OCSP
26941 is based on HTTP and can be proxied accordingly.
26943 The only widespread OCSP server implementation (known to this writer)
26944 comes as part of OpenSSL and aborts on an invalid request, such as
26945 connecting to the port and then disconnecting. This requires
26946 re-entering the passphrase each time some random client does this.
26948 The third way is OCSP Stapling; in this, the server using a certificate
26949 issued by the CA periodically requests an OCSP proof of validity from
26950 the OCSP server, then serves it up inline as part of the TLS
26951 negotiation. This approach adds no extra round trips, does not let the
26952 CA track users, scales well with number of certs issued by the CA and is
26953 resilient to temporary OCSP server failures, as long as the server
26954 starts retrying to fetch an OCSP proof some time before its current
26955 proof expires. The downside is that it requires server support.
26957 Unless Exim is built with the support disabled,
26959 or with GnuTLS earlier than version 3.3.16 / 3.4.8
26961 support for OCSP stapling is included.
26963 There is a global option called &%tls_ocsp_file%&.
26964 The file specified therein is expected to be in DER format, and contain
26965 an OCSP proof. Exim will serve it as part of the TLS handshake. This
26966 option will be re-expanded for SNI, if the &%tls_certificate%& option
26967 contains &`tls_in_sni`&, as per other TLS options.
26969 Exim does not at this time implement any support for fetching a new OCSP
26970 proof. The burden is on the administrator to handle this, outside of
26971 Exim. The file specified should be replaced atomically, so that the
26972 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
26973 on each connection, so a new file will be handled transparently on the
26976 When built with OpenSSL Exim will check for a valid next update timestamp
26977 in the OCSP proof; if not present, or if the proof has expired, it will be
26980 For the client to be able to verify the stapled OCSP the server must
26981 also supply, in its stapled information, any intermediate
26982 certificates for the chain leading to the OCSP proof from the signer
26983 of the server certificate. There may be zero or one such. These
26984 intermediate certificates should be added to the server OCSP stapling
26985 file named by &%tls_ocsp_file%&.
26987 Note that the proof only covers the terminal server certificate,
26988 not any of the chain from CA to it.
26990 There is no current way to staple a proof for a client certificate.
26993 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
26994 OCSP server is supplied. The server URL may be included in the
26995 server certificate, if the CA is helpful.
26997 One failure mode seen was the OCSP Signer cert expiring before the end
26998 of validity of the OCSP proof. The checking done by Exim/OpenSSL
26999 noted this as invalid overall, but the re-fetch script did not.
27005 .section "Configuring an Exim client to use TLS" "SECID185"
27006 .cindex "cipher" "logging"
27007 .cindex "log" "TLS cipher"
27008 .cindex "log" "distinguished name"
27009 .cindex "TLS" "configuring an Exim client"
27010 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
27011 deliveries as well as to incoming, the latter one causing logging of the
27012 server certificate's DN. The remaining client configuration for TLS is all
27013 within the &(smtp)& transport.
27015 It is not necessary to set any options to have TLS work in the &(smtp)&
27016 transport. If Exim is built with TLS support, and TLS is advertised by a
27017 server, the &(smtp)& transport always tries to start a TLS session. However,
27018 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
27019 transport) to a list of server hosts for which TLS should not be used.
27021 If you do not want Exim to attempt to send messages unencrypted when an attempt
27022 to set up an encrypted connection fails in any way, you can set
27023 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
27024 those hosts, delivery is always deferred if an encrypted connection cannot be
27025 set up. If there are any other hosts for the address, they are tried in the
27028 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
27029 the message unencrypted. It always does this if the response to STARTTLS is
27030 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
27031 session after a success response code, what happens is controlled by the
27032 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
27033 delivery to this host is deferred, and other hosts (if available) are tried. If
27034 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
27035 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
27036 negotiation fails, Exim closes the current connection (because it is in an
27037 unknown state), opens a new one to the same host, and then tries the delivery
27040 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
27041 transport provide the client with a certificate, which is passed to the server
27042 if it requests it. If the server is Exim, it will request a certificate only if
27043 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
27045 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
27046 specifies a collection of expected server certificates.
27047 These may be the system default set (depending on library version),
27049 depending on library version, a directory,
27050 must name a file or,
27051 for OpenSSL only (not GnuTLS), a directory.
27052 The client verifies the server's certificate
27053 against this collection, taking into account any revoked certificates that are
27054 in the list defined by &%tls_crl%&.
27055 Failure to verify fails the TLS connection unless either of the
27056 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
27058 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
27059 certificate verification to the listed servers. Verification either must
27060 or need not succeed respectively.
27062 The &(smtp)& transport has two OCSP-related options:
27063 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
27064 is requested and required for the connection to proceed. The default
27066 &%hosts_request_ocsp%&; a host-list for which (additionally)
27067 a Certificate Status is requested (but not necessarily verified). The default
27068 value is "*" meaning that requests are made unless configured
27071 The host(s) should also be in &%hosts_require_tls%&, and
27072 &%tls_verify_certificates%& configured for the transport,
27073 for OCSP to be relevant.
27076 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
27077 list of permitted cipher suites. If either of these checks fails, delivery to
27078 the current host is abandoned, and the &(smtp)& transport tries to deliver to
27079 alternative hosts, if any.
27082 These options must be set in the &(smtp)& transport for Exim to use TLS when it
27083 is operating as a client. Exim does not assume that a server certificate (set
27084 by the global options of the same name) should also be used when operating as a
27088 .vindex "&$host_address$&"
27089 All the TLS options in the &(smtp)& transport are expanded before use, with
27090 &$host$& and &$host_address$& containing the name and address of the server to
27091 which the client is connected. Forced failure of an expansion causes Exim to
27092 behave as if the relevant option were unset.
27094 .vindex &$tls_out_bits$&
27095 .vindex &$tls_out_cipher$&
27096 .vindex &$tls_out_peerdn$&
27097 .vindex &$tls_out_sni$&
27098 Before an SMTP connection is established, the
27099 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
27100 variables are emptied. (Until the first connection, they contain the values
27101 that were set when the message was received.) If STARTTLS is subsequently
27102 successfully obeyed, these variables are set to the relevant values for the
27103 outgoing connection.
27107 .section "Use of TLS Server Name Indication" "SECTtlssni"
27108 .cindex "TLS" "Server Name Indication"
27109 .vindex "&$tls_in_sni$&"
27110 .oindex "&%tls_in_sni%&"
27111 With TLS1.0 or above, there is an extension mechanism by which extra
27112 information can be included at various points in the protocol. One of these
27113 extensions, documented in RFC 6066 (and before that RFC 4366) is
27114 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
27115 client in the initial handshake, so that the server can examine the servername
27116 within and possibly choose to use different certificates and keys (and more)
27119 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
27120 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
27123 With SMTP to MX, there are the same problems here as in choosing the identity
27124 against which to validate a certificate: you can't rely on insecure DNS to
27125 provide the identity which you then cryptographically verify. So this will
27126 be of limited use in that environment.
27128 With SMTP to Submission, there is a well-defined hostname which clients are
27129 connecting to and can validate certificates against. Thus clients &*can*&
27130 choose to include this information in the TLS negotiation. If this becomes
27131 wide-spread, then hosters can choose to present different certificates to
27132 different clients. Or even negotiate different cipher suites.
27134 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
27135 if not empty, will be sent on a TLS session as part of the handshake. There's
27136 nothing more to it. Choosing a sensible value not derived insecurely is the
27137 only point of caution. The &$tls_out_sni$& variable will be set to this string
27138 for the lifetime of the client connection (including during authentication).
27140 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
27141 received from a client.
27142 It can be logged with the &%log_selector%& item &`+tls_sni`&.
27144 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
27145 option (prior to expansion) then the following options will be re-expanded
27146 during TLS session handshake, to permit alternative values to be chosen:
27149 .vindex "&%tls_certificate%&"
27150 &%tls_certificate%&
27152 .vindex "&%tls_crl%&"
27155 .vindex "&%tls_privatekey%&"
27158 .vindex "&%tls_verify_certificates%&"
27159 &%tls_verify_certificates%&
27161 .vindex "&%tls_ocsp_file%&"
27165 Great care should be taken to deal with matters of case, various injection
27166 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
27167 can always be referenced; it is important to remember that &$tls_sni$& is
27168 arbitrary unverified data provided prior to authentication.
27170 The Exim developers are proceeding cautiously and so far no other TLS options
27173 When Exim is built against OpenSSL, OpenSSL must have been built with support
27174 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
27175 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
27176 see &`-servername`& in the output, then OpenSSL has support.
27178 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
27179 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
27180 built, then you have SNI support).
27184 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
27186 .cindex "multiple SMTP deliveries with TLS"
27187 .cindex "TLS" "multiple message deliveries"
27188 Exim sends multiple messages down the same TCP/IP connection by starting up
27189 an entirely new delivery process for each message, passing the socket from
27190 one process to the next. This implementation does not fit well with the use
27191 of TLS, because there is quite a lot of state information associated with a TLS
27192 connection, not just a socket identification. Passing all the state information
27193 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
27194 session before passing the socket to a new process. The new process may then
27195 try to start a new TLS session, and if successful, may try to re-authenticate
27196 if AUTH is in use, before sending the next message.
27198 The RFC is not clear as to whether or not an SMTP session continues in clear
27199 after TLS has been shut down, or whether TLS may be restarted again later, as
27200 just described. However, if the server is Exim, this shutdown and
27201 reinitialization works. It is not known which (if any) other servers operate
27202 successfully if the client closes a TLS session and continues with unencrypted
27203 SMTP, but there are certainly some that do not work. For such servers, Exim
27204 should not pass the socket to another process, because the failure of the
27205 subsequent attempt to use it would cause Exim to record a temporary host error,
27206 and delay other deliveries to that host.
27208 To test for this case, Exim sends an EHLO command to the server after
27209 closing down the TLS session. If this fails in any way, the connection is
27210 closed instead of being passed to a new delivery process, but no retry
27211 information is recorded.
27213 There is also a manual override; you can set &%hosts_nopass_tls%& on the
27214 &(smtp)& transport to match those hosts for which Exim should not pass
27215 connections to new processes if TLS has been used.
27220 .section "Certificates and all that" "SECTcerandall"
27221 .cindex "certificate" "references to discussion"
27222 In order to understand fully how TLS works, you need to know about
27223 certificates, certificate signing, and certificate authorities. This is not the
27224 place to give a tutorial, especially as I do not know very much about it
27225 myself. Some helpful introduction can be found in the FAQ for the SSL addition
27226 to Apache, currently at
27228 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
27230 Other parts of the &'modssl'& documentation are also helpful, and have
27231 links to further files.
27232 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
27233 0-201-61598-3), contains both introductory and more in-depth descriptions.
27234 Some sample programs taken from the book are available from
27236 &url(http://www.rtfm.com/openssl-examples/)
27240 .section "Certificate chains" "SECID186"
27241 The file named by &%tls_certificate%& may contain more than one
27242 certificate. This is useful in the case where the certificate that is being
27243 sent is validated by an intermediate certificate which the other end does
27244 not have. Multiple certificates must be in the correct order in the file.
27245 First the host's certificate itself, then the first intermediate
27246 certificate to validate the issuer of the host certificate, then the next
27247 intermediate certificate to validate the issuer of the first intermediate
27248 certificate, and so on, until finally (optionally) the root certificate.
27249 The root certificate must already be trusted by the recipient for
27250 validation to succeed, of course, but if it's not preinstalled, sending the
27251 root certificate along with the rest makes it available for the user to
27252 install if the receiving end is a client MUA that can interact with a user.
27254 Note that certificates using MD5 are unlikely to work on today's Internet;
27255 even if your libraries allow loading them for use in Exim when acting as a
27256 server, increasingly clients will not accept such certificates. The error
27257 diagnostics in such a case can be frustratingly vague.
27261 .section "Self-signed certificates" "SECID187"
27262 .cindex "certificate" "self-signed"
27263 You can create a self-signed certificate using the &'req'& command provided
27264 with OpenSSL, like this:
27265 . ==== Do not shorten the duration here without reading and considering
27266 . ==== the text below. Please leave it at 9999 days.
27268 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
27271 &_file1_& and &_file2_& can be the same file; the key and the certificate are
27272 delimited and so can be identified independently. The &%-days%& option
27273 specifies a period for which the certificate is valid. The &%-nodes%& option is
27274 important: if you do not set it, the key is encrypted with a passphrase
27275 that you are prompted for, and any use that is made of the key causes more
27276 prompting for the passphrase. This is not helpful if you are going to use
27277 this certificate and key in an MTA, where prompting is not possible.
27279 . ==== I expect to still be working 26 years from now. The less technical
27280 . ==== debt I create, in terms of storing up trouble for my later years, the
27281 . ==== happier I will be then. We really have reached the point where we
27282 . ==== should start, at the very least, provoking thought and making folks
27283 . ==== pause before proceeding, instead of leaving all the fixes until two
27284 . ==== years before 2^31 seconds after the 1970 Unix epoch.
27286 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
27287 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
27288 the above command might produce a date in the past. Think carefully about
27289 the lifetime of the systems you're deploying, and either reduce the duration
27290 of the certificate or reconsider your platform deployment. (At time of
27291 writing, reducing the duration is the most likely choice, but the inexorable
27292 progression of time takes us steadily towards an era where this will not
27293 be a sensible resolution).
27295 A self-signed certificate made in this way is sufficient for testing, and
27296 may be adequate for all your requirements if you are mainly interested in
27297 encrypting transfers, and not in secure identification.
27299 However, many clients require that the certificate presented by the server be a
27300 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
27301 certificate. In this situation, the self-signed certificate described above
27302 must be installed on the client host as a trusted root &'certification
27303 authority'& (CA), and the certificate used by Exim must be a user certificate
27304 signed with that self-signed certificate.
27306 For information on creating self-signed CA certificates and using them to sign
27307 user certificates, see the &'General implementation overview'& chapter of the
27308 Open-source PKI book, available online at
27309 &url(http://ospkibook.sourceforge.net/).
27310 .ecindex IIDencsmtp1
27311 .ecindex IIDencsmtp2
27315 . ////////////////////////////////////////////////////////////////////////////
27316 . ////////////////////////////////////////////////////////////////////////////
27318 .chapter "Access control lists" "CHAPACL"
27319 .scindex IIDacl "&ACL;" "description"
27320 .cindex "control of incoming mail"
27321 .cindex "message" "controlling incoming"
27322 .cindex "policy control" "access control lists"
27323 Access Control Lists (ACLs) are defined in a separate section of the run time
27324 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
27325 name, terminated by a colon. Here is a complete ACL section that contains just
27326 one very small ACL:
27330 accept hosts = one.host.only
27332 You can have as many lists as you like in the ACL section, and the order in
27333 which they appear does not matter. The lists are self-terminating.
27335 The majority of ACLs are used to control Exim's behaviour when it receives
27336 certain SMTP commands. This applies both to incoming TCP/IP connections, and
27337 when a local process submits a message using SMTP by specifying the &%-bs%&
27338 option. The most common use is for controlling which recipients are accepted
27339 in incoming messages. In addition, you can define an ACL that is used to check
27340 local non-SMTP messages. The default configuration file contains an example of
27341 a realistic ACL for checking RCPT commands. This is discussed in chapter
27342 &<<CHAPdefconfil>>&.
27345 .section "Testing ACLs" "SECID188"
27346 The &%-bh%& command line option provides a way of testing your ACL
27347 configuration locally by running a fake SMTP session with which you interact.
27348 The host &'relay-test.mail-abuse.org'& provides a service for checking your
27349 relaying configuration (see section &<<SECTcheralcon>>& for more details).
27353 .section "Specifying when ACLs are used" "SECID189"
27354 .cindex "&ACL;" "options for specifying"
27355 In order to cause an ACL to be used, you have to name it in one of the relevant
27356 options in the main part of the configuration. These options are:
27357 .cindex "AUTH" "ACL for"
27358 .cindex "DATA" "ACLs for"
27359 .cindex "ETRN" "ACL for"
27360 .cindex "EXPN" "ACL for"
27361 .cindex "HELO" "ACL for"
27362 .cindex "EHLO" "ACL for"
27363 .cindex "DKIM" "ACL for"
27364 .cindex "MAIL" "ACL for"
27365 .cindex "QUIT, ACL for"
27366 .cindex "RCPT" "ACL for"
27367 .cindex "STARTTLS, ACL for"
27368 .cindex "VRFY" "ACL for"
27369 .cindex "SMTP" "connection, ACL for"
27370 .cindex "non-SMTP messages" "ACLs for"
27371 .cindex "MIME content scanning" "ACL for"
27372 .cindex "PRDR" "ACL for"
27375 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
27376 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
27377 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
27378 .irow &%acl_smtp_auth%& "ACL for AUTH"
27379 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
27380 .irow &%acl_smtp_data%& "ACL after DATA is complete"
27381 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
27382 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
27383 .irow &%acl_smtp_etrn%& "ACL for ETRN"
27384 .irow &%acl_smtp_expn%& "ACL for EXPN"
27385 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
27386 .irow &%acl_smtp_mail%& "ACL for MAIL"
27387 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
27388 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
27389 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
27390 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
27391 .irow &%acl_smtp_quit%& "ACL for QUIT"
27392 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
27393 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
27394 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
27397 For example, if you set
27399 acl_smtp_rcpt = small_acl
27401 the little ACL defined above is used whenever Exim receives a RCPT command
27402 in an SMTP dialogue. The majority of policy tests on incoming messages can be
27403 done when RCPT commands arrive. A rejection of RCPT should cause the
27404 sending MTA to give up on the recipient address contained in the RCPT
27405 command, whereas rejection at other times may cause the client MTA to keep on
27406 trying to deliver the message. It is therefore recommended that you do as much
27407 testing as possible at RCPT time.
27410 .section "The non-SMTP ACLs" "SECID190"
27411 .cindex "non-SMTP messages" "ACLs for"
27412 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
27413 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
27414 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
27415 the state of the SMTP connection such as encryption and authentication) are not
27416 relevant and are forbidden in these ACLs. However, the sender and recipients
27417 are known, so the &%senders%& and &%sender_domains%& conditions and the
27418 &$sender_address$& and &$recipients$& variables can be used. Variables such as
27419 &$authenticated_sender$& are also available. You can specify added header lines
27420 in any of these ACLs.
27422 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
27423 non-SMTP message, before any of the message has been read. (This is the
27424 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
27425 batched SMTP input, it runs after the DATA command has been reached. The
27426 result of this ACL is ignored; it cannot be used to reject a message. If you
27427 really need to, you could set a value in an ACL variable here and reject based
27428 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
27429 controls, and in particular, it can be used to set
27431 control = suppress_local_fixups
27433 This cannot be used in the other non-SMTP ACLs because by the time they are
27434 run, it is too late.
27436 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
27437 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27439 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
27440 kind of rejection is treated as permanent, because there is no way of sending a
27441 temporary error for these kinds of message.
27444 .section "The SMTP connect ACL" "SECID191"
27445 .cindex "SMTP" "connection, ACL for"
27446 .oindex &%smtp_banner%&
27447 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
27448 session, after the test specified by &%host_reject_connection%& (which is now
27449 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
27450 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
27451 the message override the banner message that is otherwise specified by the
27452 &%smtp_banner%& option.
27455 .section "The EHLO/HELO ACL" "SECID192"
27456 .cindex "EHLO" "ACL for"
27457 .cindex "HELO" "ACL for"
27458 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
27459 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
27460 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
27461 Note that a client may issue more than one EHLO or HELO command in an SMTP
27462 session, and indeed is required to issue a new EHLO or HELO after successfully
27463 setting up encryption following a STARTTLS command.
27465 If the command is accepted by an &%accept%& verb that has a &%message%&
27466 modifier, the message may not contain more than one line (it will be truncated
27467 at the first newline and a panic logged if it does). Such a message cannot
27468 affect the EHLO options that are listed on the second and subsequent lines of
27472 .section "The DATA ACLs" "SECID193"
27473 .cindex "DATA" "ACLs for"
27474 Two ACLs are associated with the DATA command, because it is two-stage
27475 command, with two responses being sent to the client.
27476 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
27477 is obeyed. This gives you control after all the RCPT commands, but before
27478 the message itself is received. It offers the opportunity to give a negative
27479 response to the DATA command before the data is transmitted. Header lines
27480 added by MAIL or RCPT ACLs are not visible at this time, but any that
27481 are defined here are visible when the &%acl_smtp_data%& ACL is run.
27483 You cannot test the contents of the message, for example, to verify addresses
27484 in the headers, at RCPT time or when the DATA command is received. Such
27485 tests have to appear in the ACL that is run after the message itself has been
27486 received, before the final response to the DATA command is sent. This is
27487 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
27488 associated with the DATA command.
27490 For both of these ACLs, it is not possible to reject individual recipients. An
27491 error response rejects the entire message. Unfortunately, it is known that some
27492 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
27493 before or after the data) correctly &-- they keep the message on their queues
27494 and try again later, but that is their problem, though it does waste some of
27497 The &%acl_smtp_data%& ACL is run after
27498 the &%acl_smtp_data_prdr%&,
27499 the &%acl_smtp_dkim%&
27500 and the &%acl_smtp_mime%& ACLs.
27502 .section "The SMTP DKIM ACL" "SECTDKIMACL"
27503 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
27504 enabled (which is the default).
27506 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
27507 received, and is executed for each DKIM signature found in a message. If not
27508 otherwise specified, the default action is to accept.
27510 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
27512 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
27515 .section "The SMTP MIME ACL" "SECID194"
27516 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
27517 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27519 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27522 .section "The SMTP PRDR ACL" "SECTPRDRACL"
27523 .cindex "PRDR" "ACL for"
27524 .oindex "&%prdr_enable%&"
27525 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
27526 with PRDR support enabled (which is the default).
27527 It becomes active only when the PRDR feature is negotiated between
27528 client and server for a message, and more than one recipient
27531 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
27532 has been received, and is executed once for each recipient of the message
27533 with &$local_part$& and &$domain$& valid.
27534 The test may accept, defer or deny for individual recipients.
27535 The &%acl_smtp_data%& will still be called after this ACL and
27536 can reject the message overall, even if this ACL has accepted it
27537 for some or all recipients.
27539 PRDR may be used to support per-user content filtering. Without it
27540 one must defer any recipient after the first that has a different
27541 content-filter configuration. With PRDR, the RCPT-time check
27543 .cindex "PRDR" "variable for"
27544 for this can be disabled when the variable &$prdr_requested$&
27547 Any required difference in behaviour of the main DATA-time
27548 ACL should however depend on the PRDR-time ACL having run, as Exim
27549 will avoid doing so in some situations (e.g. single-recipient mails).
27551 See also the &%prdr_enable%& global option
27552 and the &%hosts_try_prdr%& smtp transport option.
27554 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27555 If the ACL is not defined, processing completes as if
27556 the feature was not requested by the client.
27558 .section "The QUIT ACL" "SECTQUITACL"
27559 .cindex "QUIT, ACL for"
27560 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
27561 does not affect the response code to QUIT, which is always 221. Thus, the ACL
27562 does not in fact control any access.
27563 For this reason, it may only accept
27564 or warn as its final result.
27566 This ACL can be used for tasks such as custom logging at the end of an SMTP
27567 session. For example, you can use ACL variables in other ACLs to count
27568 messages, recipients, etc., and log the totals at QUIT time using one or
27569 more &%logwrite%& modifiers on a &%warn%& verb.
27571 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
27572 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
27574 You do not need to have a final &%accept%&, but if you do, you can use a
27575 &%message%& modifier to specify custom text that is sent as part of the 221
27578 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
27579 failure (for example, failure to open a log file, or when Exim is bombing out
27580 because it has detected an unrecoverable error), all SMTP commands from the
27581 client are given temporary error responses until QUIT is received or the
27582 connection is closed. In these special cases, the QUIT ACL does not run.
27585 .section "The not-QUIT ACL" "SECTNOTQUITACL"
27586 .vindex &$acl_smtp_notquit$&
27587 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
27588 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
27589 trouble, such as being unable to write to its log files, this ACL is not run,
27590 because it might try to do things (such as write to log files) that make the
27591 situation even worse.
27593 Like the QUIT ACL, this ACL is provided to make it possible to do customized
27594 logging or to gather statistics, and its outcome is ignored. The &%delay%&
27595 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
27598 .vindex &$smtp_notquit_reason$&
27599 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
27600 to a string that indicates the reason for the termination of the SMTP
27601 connection. The possible values are:
27603 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
27604 .irow &`bad-commands`& "Too many unknown or non-mail commands"
27605 .irow &`command-timeout`& "Timeout while reading SMTP commands"
27606 .irow &`connection-lost`& "The SMTP connection has been lost"
27607 .irow &`data-timeout`& "Timeout while reading message data"
27608 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
27609 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
27610 .irow &`signal-exit`& "SIGTERM or SIGINT"
27611 .irow &`synchronization-error`& "SMTP synchronization error"
27612 .irow &`tls-failed`& "TLS failed to start"
27614 In most cases when an SMTP connection is closed without having received QUIT,
27615 Exim sends an SMTP response message before actually closing the connection.
27616 With the exception of the &`acl-drop`& case, the default message can be
27617 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
27618 &%drop%& verb in another ACL, it is the message from the other ACL that is
27622 .section "Finding an ACL to use" "SECID195"
27623 .cindex "&ACL;" "finding which to use"
27624 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
27625 you can use different ACLs in different circumstances. For example,
27627 acl_smtp_rcpt = ${if ={25}{$interface_port} \
27628 {acl_check_rcpt} {acl_check_rcpt_submit} }
27630 In the default configuration file there are some example settings for
27631 providing an RFC 4409 message submission service on port 587 and a
27632 non-standard &"smtps"& service on port 465. You can use a string
27633 expansion like this to choose an ACL for MUAs on these ports which is
27634 more appropriate for this purpose than the default ACL on port 25.
27636 The expanded string does not have to be the name of an ACL in the
27637 configuration file; there are other possibilities. Having expanded the
27638 string, Exim searches for an ACL as follows:
27641 If the string begins with a slash, Exim uses it as a file name, and reads its
27642 contents as an ACL. The lines are processed in the same way as lines in the
27643 Exim configuration file. In particular, continuation lines are supported, blank
27644 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
27645 If the file does not exist or cannot be read, an error occurs (typically
27646 causing a temporary failure of whatever caused the ACL to be run). For example:
27648 acl_smtp_data = /etc/acls/\
27649 ${lookup{$sender_host_address}lsearch\
27650 {/etc/acllist}{$value}{default}}
27652 This looks up an ACL file to use on the basis of the host's IP address, falling
27653 back to a default if the lookup fails. If an ACL is successfully read from a
27654 file, it is retained in memory for the duration of the Exim process, so that it
27655 can be re-used without having to re-read the file.
27657 If the string does not start with a slash, and does not contain any spaces,
27658 Exim searches the ACL section of the configuration for an ACL whose name
27659 matches the string.
27661 If no named ACL is found, or if the string contains spaces, Exim parses
27662 the string as an inline ACL. This can save typing in cases where you just
27663 want to have something like
27665 acl_smtp_vrfy = accept
27667 in order to allow free use of the VRFY command. Such a string may contain
27668 newlines; it is processed in the same way as an ACL that is read from a file.
27674 .section "ACL return codes" "SECID196"
27675 .cindex "&ACL;" "return codes"
27676 Except for the QUIT ACL, which does not affect the SMTP return code (see
27677 section &<<SECTQUITACL>>& above), the result of running an ACL is either
27678 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
27679 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
27680 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
27681 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
27682 This also causes a 4&'xx'& return code.
27684 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
27685 &"deny"&, because there is no mechanism for passing temporary errors to the
27686 submitters of non-SMTP messages.
27689 ACLs that are relevant to message reception may also return &"discard"&. This
27690 has the effect of &"accept"&, but causes either the entire message or an
27691 individual recipient address to be discarded. In other words, it is a
27692 blackholing facility. Use it with care.
27694 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
27695 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
27696 RCPT ACL is to discard just the one recipient address. If there are no
27697 recipients left when the message's data is received, the DATA ACL is not
27698 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
27699 remaining recipients. The &"discard"& return is not permitted for the
27700 &%acl_smtp_predata%& ACL.
27703 .cindex "&[local_scan()]& function" "when all recipients discarded"
27704 The &[local_scan()]& function is always run, even if there are no remaining
27705 recipients; it may create new recipients.
27709 .section "Unset ACL options" "SECID197"
27710 .cindex "&ACL;" "unset options"
27711 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
27712 all the same. &*Note*&: These defaults apply only when the relevant ACL is
27713 not defined at all. For any defined ACL, the default action when control
27714 reaches the end of the ACL statements is &"deny"&.
27716 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
27717 these two are ACLs that are used only for their side effects. They cannot be
27718 used to accept or reject anything.
27720 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
27721 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
27722 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
27723 when the ACL is not defined is &"accept"&.
27725 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
27726 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
27727 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
27728 messages over an SMTP connection. For an example, see the ACL in the default
27729 configuration file.
27734 .section "Data for message ACLs" "SECID198"
27735 .cindex "&ACL;" "data for message ACL"
27737 .vindex &$local_part$&
27738 .vindex &$sender_address$&
27739 .vindex &$sender_host_address$&
27740 .vindex &$smtp_command$&
27741 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
27742 that contain information about the host and the message's sender (for example,
27743 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
27744 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
27745 &$local_part$& are set from the argument address. The entire SMTP command
27746 is available in &$smtp_command$&.
27748 When an ACL for the AUTH parameter of MAIL is running, the variables that
27749 contain information about the host are set, but &$sender_address$& is not yet
27750 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
27753 .vindex "&$message_size$&"
27754 The &$message_size$& variable is set to the value of the SIZE parameter on
27755 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
27756 that parameter is not given. The value is updated to the true message size by
27757 the time the final DATA ACL is run (after the message data has been
27760 .vindex "&$rcpt_count$&"
27761 .vindex "&$recipients_count$&"
27762 The &$rcpt_count$& variable increases by one for each RCPT command received.
27763 The &$recipients_count$& variable increases by one each time a RCPT command is
27764 accepted, so while an ACL for RCPT is being processed, it contains the number
27765 of previously accepted recipients. At DATA time (for both the DATA ACLs),
27766 &$rcpt_count$& contains the total number of RCPT commands, and
27767 &$recipients_count$& contains the total number of accepted recipients.
27773 .section "Data for non-message ACLs" "SECTdatfornon"
27774 .cindex "&ACL;" "data for non-message ACL"
27775 .vindex &$smtp_command_argument$&
27776 .vindex &$smtp_command$&
27777 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
27778 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
27779 and the entire SMTP command is available in &$smtp_command$&.
27780 These variables can be tested using a &%condition%& condition. For example,
27781 here is an ACL for use with AUTH, which insists that either the session is
27782 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
27783 does not permit authentication methods that use cleartext passwords on
27784 unencrypted connections.
27787 accept encrypted = *
27788 accept condition = ${if eq{${uc:$smtp_command_argument}}\
27790 deny message = TLS encryption or CRAM-MD5 required
27792 (Another way of applying this restriction is to arrange for the authenticators
27793 that use cleartext passwords not to be advertised when the connection is not
27794 encrypted. You can use the generic &%server_advertise_condition%& authenticator
27795 option to do this.)
27799 .section "Format of an ACL" "SECID199"
27800 .cindex "&ACL;" "format of"
27801 .cindex "&ACL;" "verbs, definition of"
27802 An individual ACL consists of a number of statements. Each statement starts
27803 with a verb, optionally followed by a number of conditions and &"modifiers"&.
27804 Modifiers can change the way the verb operates, define error and log messages,
27805 set variables, insert delays, and vary the processing of accepted messages.
27807 If all the conditions are met, the verb is obeyed. The same condition may be
27808 used (with different arguments) more than once in the same statement. This
27809 provides a means of specifying an &"and"& conjunction between conditions. For
27812 deny dnslists = list1.example
27813 dnslists = list2.example
27815 If there are no conditions, the verb is always obeyed. Exim stops evaluating
27816 the conditions and modifiers when it reaches a condition that fails. What
27817 happens then depends on the verb (and in one case, on a special modifier). Not
27818 all the conditions make sense at every testing point. For example, you cannot
27819 test a sender address in the ACL that is run for a VRFY command.
27822 .section "ACL verbs" "SECID200"
27823 The ACL verbs are as follows:
27826 .cindex "&%accept%& ACL verb"
27827 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
27828 of the conditions are not met, what happens depends on whether &%endpass%&
27829 appears among the conditions (for syntax see below). If the failing condition
27830 is before &%endpass%&, control is passed to the next ACL statement; if it is
27831 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
27832 check a RCPT command:
27834 accept domains = +local_domains
27838 If the recipient domain does not match the &%domains%& condition, control
27839 passes to the next statement. If it does match, the recipient is verified, and
27840 the command is accepted if verification succeeds. However, if verification
27841 fails, the ACL yields &"deny"&, because the failing condition is after
27844 The &%endpass%& feature has turned out to be confusing to many people, so its
27845 use is not recommended nowadays. It is always possible to rewrite an ACL so
27846 that &%endpass%& is not needed, and it is no longer used in the default
27849 .cindex "&%message%& ACL modifier" "with &%accept%&"
27850 If a &%message%& modifier appears on an &%accept%& statement, its action
27851 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
27852 (when an &%accept%& verb either accepts or passes control to the next
27853 statement), &%message%& can be used to vary the message that is sent when an
27854 SMTP command is accepted. For example, in a RCPT ACL you could have:
27856 &`accept `&<&'some conditions'&>
27857 &` message = OK, I will allow you through today`&
27859 You can specify an SMTP response code, optionally followed by an &"extended
27860 response code"& at the start of the message, but the first digit must be the
27861 same as would be sent by default, which is 2 for an &%accept%& verb.
27863 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
27864 an error message that is used when access is denied. This behaviour is retained
27865 for backward compatibility, but current &"best practice"& is to avoid the use
27870 .cindex "&%defer%& ACL verb"
27871 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
27872 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
27873 &%defer%& is the same as &%deny%&, because there is no way of sending a
27874 temporary error. For a RCPT command, &%defer%& is much the same as using a
27875 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
27876 be used in any ACL, and even for a recipient it might be a simpler approach.
27880 .cindex "&%deny%& ACL verb"
27881 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
27882 the conditions are not met, control is passed to the next ACL statement. For
27885 deny dnslists = blackholes.mail-abuse.org
27887 rejects commands from hosts that are on a DNS black list.
27891 .cindex "&%discard%& ACL verb"
27892 &%discard%&: This verb behaves like &%accept%&, except that it returns
27893 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
27894 that are concerned with receiving messages. When all the conditions are true,
27895 the sending entity receives a &"success"& response. However, &%discard%& causes
27896 recipients to be discarded. If it is used in an ACL for RCPT, just the one
27897 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
27898 message's recipients are discarded. Recipients that are discarded before DATA
27899 do not appear in the log line when the &%received_recipients%& log selector is set.
27901 If the &%log_message%& modifier is set when &%discard%& operates,
27902 its contents are added to the line that is automatically written to the log.
27903 The &%message%& modifier operates exactly as it does for &%accept%&.
27907 .cindex "&%drop%& ACL verb"
27908 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
27909 forcibly closed after the 5&'xx'& error message has been sent. For example:
27911 drop message = I don't take more than 20 RCPTs
27912 condition = ${if > {$rcpt_count}{20}}
27914 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
27915 The connection is always dropped after sending a 550 response.
27918 .cindex "&%require%& ACL verb"
27919 &%require%&: If all the conditions are met, control is passed to the next ACL
27920 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
27921 example, when checking a RCPT command,
27923 require message = Sender did not verify
27926 passes control to subsequent statements only if the message's sender can be
27927 verified. Otherwise, it rejects the command. Note the positioning of the
27928 &%message%& modifier, before the &%verify%& condition. The reason for this is
27929 discussed in section &<<SECTcondmodproc>>&.
27932 .cindex "&%warn%& ACL verb"
27933 &%warn%&: If all the conditions are true, a line specified by the
27934 &%log_message%& modifier is written to Exim's main log. Control always passes
27935 to the next ACL statement. If any condition is false, the log line is not
27936 written. If an identical log line is requested several times in the same
27937 message, only one copy is actually written to the log. If you want to force
27938 duplicates to be written, use the &%logwrite%& modifier instead.
27940 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
27941 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
27942 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
27943 first failing condition. There is more about adding header lines in section
27944 &<<SECTaddheadacl>>&.
27946 If any condition on a &%warn%& statement cannot be completed (that is, there is
27947 some sort of defer), the log line specified by &%log_message%& is not written.
27948 This does not include the case of a forced failure from a lookup, which
27949 is considered to be a successful completion. After a defer, no further
27950 conditions or modifiers in the &%warn%& statement are processed. The incident
27951 is logged, and the ACL continues to be processed, from the next statement
27955 .vindex "&$acl_verify_message$&"
27956 When one of the &%warn%& conditions is an address verification that fails, the
27957 text of the verification failure message is in &$acl_verify_message$&. If you
27958 want this logged, you must set it up explicitly. For example:
27960 warn !verify = sender
27961 log_message = sender verify failed: $acl_verify_message
27965 At the end of each ACL there is an implicit unconditional &%deny%&.
27967 As you can see from the examples above, the conditions and modifiers are
27968 written one to a line, with the first one on the same line as the verb, and
27969 subsequent ones on following lines. If you have a very long condition, you can
27970 continue it onto several physical lines by the usual backslash continuation
27971 mechanism. It is conventional to align the conditions vertically.
27975 .section "ACL variables" "SECTaclvariables"
27976 .cindex "&ACL;" "variables"
27977 There are some special variables that can be set during ACL processing. They
27978 can be used to pass information between different ACLs, different invocations
27979 of the same ACL in the same SMTP connection, and between ACLs and the routers,
27980 transports, and filters that are used to deliver a message. The names of these
27981 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
27982 an underscore, but the remainder of the name can be any sequence of
27983 alphanumeric characters and underscores that you choose. There is no limit on
27984 the number of ACL variables. The two sets act as follows:
27986 The values of those variables whose names begin with &$acl_c$& persist
27987 throughout an SMTP connection. They are never reset. Thus, a value that is set
27988 while receiving one message is still available when receiving the next message
27989 on the same SMTP connection.
27991 The values of those variables whose names begin with &$acl_m$& persist only
27992 while a message is being received. They are reset afterwards. They are also
27993 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
27996 When a message is accepted, the current values of all the ACL variables are
27997 preserved with the message and are subsequently made available at delivery
27998 time. The ACL variables are set by a modifier called &%set%&. For example:
28000 accept hosts = whatever
28001 set acl_m4 = some value
28002 accept authenticated = *
28003 set acl_c_auth = yes
28005 &*Note*&: A leading dollar sign is not used when naming a variable that is to
28006 be set. If you want to set a variable without taking any action, you can use a
28007 &%warn%& verb without any other modifiers or conditions.
28009 .oindex &%strict_acl_vars%&
28010 What happens if a syntactically valid but undefined ACL variable is
28011 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
28012 false (the default), an empty string is substituted; if it is true, an
28013 error is generated.
28015 Versions of Exim before 4.64 have a limited set of numbered variables, but
28016 their names are compatible, so there is no problem with upgrading.
28019 .section "Condition and modifier processing" "SECTcondmodproc"
28020 .cindex "&ACL;" "conditions; processing"
28021 .cindex "&ACL;" "modifiers; processing"
28022 An exclamation mark preceding a condition negates its result. For example:
28024 deny domains = *.dom.example
28025 !verify = recipient
28027 causes the ACL to return &"deny"& if the recipient domain ends in
28028 &'dom.example'& and the recipient address cannot be verified. Sometimes
28029 negation can be used on the right-hand side of a condition. For example, these
28030 two statements are equivalent:
28032 deny hosts = !192.168.3.4
28033 deny !hosts = 192.168.3.4
28035 However, for many conditions (&%verify%& being a good example), only left-hand
28036 side negation of the whole condition is possible.
28038 The arguments of conditions and modifiers are expanded. A forced failure
28039 of an expansion causes a condition to be ignored, that is, it behaves as if the
28040 condition is true. Consider these two statements:
28042 accept senders = ${lookup{$host_name}lsearch\
28043 {/some/file}{$value}fail}
28044 accept senders = ${lookup{$host_name}lsearch\
28045 {/some/file}{$value}{}}
28047 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
28048 the returned list is searched, but if the lookup fails the behaviour is
28049 different in the two cases. The &%fail%& in the first statement causes the
28050 condition to be ignored, leaving no further conditions. The &%accept%& verb
28051 therefore succeeds. The second statement, however, generates an empty list when
28052 the lookup fails. No sender can match an empty list, so the condition fails,
28053 and therefore the &%accept%& also fails.
28055 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
28056 specify actions that are taken as the conditions for a statement are checked;
28057 others specify text for messages that are used when access is denied or a
28058 warning is generated. The &%control%& modifier affects the way an incoming
28059 message is handled.
28061 The positioning of the modifiers in an ACL statement is important, because the
28062 processing of a verb ceases as soon as its outcome is known. Only those
28063 modifiers that have already been encountered will take effect. For example,
28064 consider this use of the &%message%& modifier:
28066 require message = Can't verify sender
28068 message = Can't verify recipient
28070 message = This message cannot be used
28072 If sender verification fails, Exim knows that the result of the statement is
28073 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
28074 so its text is used as the error message. If sender verification succeeds, but
28075 recipient verification fails, the second message is used. If recipient
28076 verification succeeds, the third message becomes &"current"&, but is never used
28077 because there are no more conditions to cause failure.
28079 For the &%deny%& verb, on the other hand, it is always the last &%message%&
28080 modifier that is used, because all the conditions must be true for rejection to
28081 happen. Specifying more than one &%message%& modifier does not make sense, and
28082 the message can even be specified after all the conditions. For example:
28085 !senders = *@my.domain.example
28086 message = Invalid sender from client host
28088 The &"deny"& result does not happen until the end of the statement is reached,
28089 by which time Exim has set up the message.
28093 .section "ACL modifiers" "SECTACLmodi"
28094 .cindex "&ACL;" "modifiers; list of"
28095 The ACL modifiers are as follows:
28098 .vitem &*add_header*&&~=&~<&'text'&>
28099 This modifier specifies one or more header lines that are to be added to an
28100 incoming message, assuming, of course, that the message is ultimately
28101 accepted. For details, see section &<<SECTaddheadacl>>&.
28103 .vitem &*continue*&&~=&~<&'text'&>
28104 .cindex "&%continue%& ACL modifier"
28105 .cindex "database" "updating in ACL"
28106 This modifier does nothing of itself, and processing of the ACL always
28107 continues with the next condition or modifier. The value of &%continue%& is in
28108 the side effects of expanding its argument. Typically this could be used to
28109 update a database. It is really just a syntactic tidiness, to avoid having to
28110 write rather ugly lines like this:
28112 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
28114 Instead, all you need is
28116 &`continue = `&<&'some expansion'&>
28119 .vitem &*control*&&~=&~<&'text'&>
28120 .cindex "&%control%& ACL modifier"
28121 This modifier affects the subsequent processing of the SMTP connection or of an
28122 incoming message that is accepted. The effect of the first type of control
28123 lasts for the duration of the connection, whereas the effect of the second type
28124 lasts only until the current message has been received. The message-specific
28125 controls always apply to the whole message, not to individual recipients,
28126 even if the &%control%& modifier appears in a RCPT ACL.
28128 As there are now quite a few controls that can be applied, they are described
28129 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
28130 in several different ways. For example:
28132 . ==== As this is a nested list, any displays it contains must be indented
28133 . ==== as otherwise they are too far to the left. That comment applies only
28134 . ==== when xmlto and fop are used; formatting with sdop gets it right either
28138 It can be at the end of an &%accept%& statement:
28140 accept ...some conditions
28141 control = queue_only
28143 In this case, the control is applied when this statement yields &"accept"&, in
28144 other words, when the conditions are all true.
28147 It can be in the middle of an &%accept%& statement:
28149 accept ...some conditions...
28150 control = queue_only
28151 ...some more conditions...
28153 If the first set of conditions are true, the control is applied, even if the
28154 statement does not accept because one of the second set of conditions is false.
28155 In this case, some subsequent statement must yield &"accept"& for the control
28159 It can be used with &%warn%& to apply the control, leaving the
28160 decision about accepting or denying to a subsequent verb. For
28163 warn ...some conditions...
28167 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
28168 &%logwrite%&, so it does not add anything to the message and does not write a
28172 If you want to apply a control unconditionally, you can use it with a
28173 &%require%& verb. For example:
28175 require control = no_multiline_responses
28179 .vitem &*delay*&&~=&~<&'time'&>
28180 .cindex "&%delay%& ACL modifier"
28182 This modifier may appear in any ACL except notquit. It causes Exim to wait for
28183 the time interval before proceeding. However, when testing Exim using the
28184 &%-bh%& option, the delay is not actually imposed (an appropriate message is
28185 output instead). The time is given in the usual Exim notation, and the delay
28186 happens as soon as the modifier is processed. In an SMTP session, pending
28187 output is flushed before the delay is imposed.
28189 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
28192 deny ...some conditions...
28195 The delay happens if all the conditions are true, before the statement returns
28196 &"deny"&. Compare this with:
28199 ...some conditions...
28201 which waits for 30s before processing the conditions. The &%delay%& modifier
28202 can also be used with &%warn%& and together with &%control%&:
28204 warn ...some conditions...
28210 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
28211 responses to several commands are no longer buffered and sent in one packet (as
28212 they would normally be) because all output is flushed before imposing the
28213 delay. This optimization is disabled so that a number of small delays do not
28214 appear to the client as one large aggregated delay that might provoke an
28215 unwanted timeout. You can, however, disable output flushing for &%delay%& by
28216 using a &%control%& modifier to set &%no_delay_flush%&.
28220 .cindex "&%endpass%& ACL modifier"
28221 This modifier, which has no argument, is recognized only in &%accept%& and
28222 &%discard%& statements. It marks the boundary between the conditions whose
28223 failure causes control to pass to the next statement, and the conditions whose
28224 failure causes the ACL to return &"deny"&. This concept has proved to be
28225 confusing to some people, so the use of &%endpass%& is no longer recommended as
28226 &"best practice"&. See the description of &%accept%& above for more details.
28229 .vitem &*log_message*&&~=&~<&'text'&>
28230 .cindex "&%log_message%& ACL modifier"
28231 This modifier sets up a message that is used as part of the log message if the
28232 ACL denies access or a &%warn%& statement's conditions are true. For example:
28234 require log_message = wrong cipher suite $tls_in_cipher
28235 encrypted = DES-CBC3-SHA
28237 &%log_message%& is also used when recipients are discarded by &%discard%&. For
28240 &`discard `&<&'some conditions'&>
28241 &` log_message = Discarded $local_part@$domain because...`&
28243 When access is denied, &%log_message%& adds to any underlying error message
28244 that may exist because of a condition failure. For example, while verifying a
28245 recipient address, a &':fail:'& redirection might have already set up a
28248 The message may be defined before the conditions to which it applies, because
28249 the string expansion does not happen until Exim decides that access is to be
28250 denied. This means that any variables that are set by the condition are
28251 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
28252 variables are set after a DNS black list lookup succeeds. If the expansion of
28253 &%log_message%& fails, or if the result is an empty string, the modifier is
28256 .vindex "&$acl_verify_message$&"
28257 If you want to use a &%warn%& statement to log the result of an address
28258 verification, you can use &$acl_verify_message$& to include the verification
28261 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
28262 the start of the logged message. If the same warning log message is requested
28263 more than once while receiving a single email message, only one copy is
28264 actually logged. If you want to log multiple copies, use &%logwrite%& instead
28265 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
28266 is logged for a successful &%warn%& statement.
28268 If &%log_message%& is not present and there is no underlying error message (for
28269 example, from the failure of address verification), but &%message%& is present,
28270 the &%message%& text is used for logging rejections. However, if any text for
28271 logging contains newlines, only the first line is logged. In the absence of
28272 both &%log_message%& and &%message%&, a default built-in message is used for
28273 logging rejections.
28276 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
28277 .cindex "&%log_reject_target%& ACL modifier"
28278 .cindex "logging in ACL" "specifying which log"
28279 This modifier makes it possible to specify which logs are used for messages
28280 about ACL rejections. Its argument is a colon-separated list of words that can
28281 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
28282 may be empty, in which case a rejection is not logged at all. For example, this
28283 ACL fragment writes no logging information when access is denied:
28285 &`deny `&<&'some conditions'&>
28286 &` log_reject_target =`&
28288 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
28289 permanent and temporary rejections. Its effect lasts for the rest of the
28293 .vitem &*logwrite*&&~=&~<&'text'&>
28294 .cindex "&%logwrite%& ACL modifier"
28295 .cindex "logging in ACL" "immediate"
28296 This modifier writes a message to a log file as soon as it is encountered when
28297 processing an ACL. (Compare &%log_message%&, which, except in the case of
28298 &%warn%& and &%discard%&, is used only if the ACL statement denies
28299 access.) The &%logwrite%& modifier can be used to log special incidents in
28302 &`accept `&<&'some special conditions'&>
28303 &` control = freeze`&
28304 &` logwrite = froze message because ...`&
28306 By default, the message is written to the main log. However, it may begin
28307 with a colon, followed by a comma-separated list of log names, and then
28308 another colon, to specify exactly which logs are to be written. For
28311 logwrite = :main,reject: text for main and reject logs
28312 logwrite = :panic: text for panic log only
28316 .vitem &*message*&&~=&~<&'text'&>
28317 .cindex "&%message%& ACL modifier"
28318 This modifier sets up a text string that is expanded and used as a response
28319 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
28320 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
28321 there is some complication if &%endpass%& is involved; see the description of
28322 &%accept%& for details.)
28324 The expansion of the message happens at the time Exim decides that the ACL is
28325 to end, not at the time it processes &%message%&. If the expansion fails, or
28326 generates an empty string, the modifier is ignored. Here is an example where
28327 &%message%& must be specified first, because the ACL ends with a rejection if
28328 the &%hosts%& condition fails:
28330 require message = Host not recognized
28333 (Once a condition has failed, no further conditions or modifiers are
28336 .cindex "SMTP" "error codes"
28337 .oindex "&%smtp_banner%&
28338 For ACLs that are triggered by SMTP commands, the message is returned as part
28339 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
28340 is meaningful only for SMTP, as no message is returned when a non-SMTP message
28341 is accepted. In the case of the connect ACL, accepting with a message modifier
28342 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
28343 accept message may not contain more than one line (otherwise it will be
28344 truncated at the first newline and a panic logged), and it cannot affect the
28347 When SMTP is involved, the message may begin with an overriding response code,
28348 consisting of three digits optionally followed by an &"extended response code"&
28349 of the form &'n.n.n'&, each code being followed by a space. For example:
28351 deny message = 599 1.2.3 Host not welcome
28352 hosts = 192.168.34.0/24
28354 The first digit of the supplied response code must be the same as would be sent
28355 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
28356 access, but for the predata ACL, note that the default success code is 354, not
28359 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
28360 the message modifier cannot override the 221 response code.
28362 The text in a &%message%& modifier is literal; any quotes are taken as
28363 literals, but because the string is expanded, backslash escapes are processed
28364 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
28367 .vindex "&$acl_verify_message$&"
28368 For ACLs that are called by an &%acl =%& ACL condition, the message is
28369 stored in &$acl_verify_message$&, from which the calling ACL may use it.
28371 If &%message%& is used on a statement that verifies an address, the message
28372 specified overrides any message that is generated by the verification process.
28373 However, the original message is available in the variable
28374 &$acl_verify_message$&, so you can incorporate it into your message if you
28375 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
28376 routers to be passed back as part of the SMTP response, you should either not
28377 use a &%message%& modifier, or make use of &$acl_verify_message$&.
28379 For compatibility with previous releases of Exim, a &%message%& modifier that
28380 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
28381 modifier, but this usage is now deprecated. However, &%message%& acts only when
28382 all the conditions are true, wherever it appears in an ACL command, whereas
28383 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
28384 &%warn%& in an ACL that is not concerned with receiving a message, it has no
28388 .vitem &*remove_header*&&~=&~<&'text'&>
28389 This modifier specifies one or more header names in a colon-separated list
28390 that are to be removed from an incoming message, assuming, of course, that
28391 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
28394 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
28395 .cindex "&%set%& ACL modifier"
28396 This modifier puts a value into one of the ACL variables (see section
28397 &<<SECTaclvariables>>&).
28400 .vitem &*udpsend*&&~=&~<&'parameters'&>
28401 This modifier sends a UDP packet, for purposes such as statistics
28402 collection or behaviour monitoring. The parameters are expanded, and
28403 the result of the expansion must be a colon-separated list consisting
28404 of a destination server, port number, and the packet contents. The
28405 server can be specified as a host name or IPv4 or IPv6 address. The
28406 separator can be changed with the usual angle bracket syntax. For
28407 example, you might want to collect information on which hosts connect
28410 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
28411 $tod_zulu $sender_host_address
28418 .section "Use of the control modifier" "SECTcontrols"
28419 .cindex "&%control%& ACL modifier"
28420 The &%control%& modifier supports the following settings:
28423 .vitem &*control&~=&~allow_auth_unadvertised*&
28424 This modifier allows a client host to use the SMTP AUTH command even when it
28425 has not been advertised in response to EHLO. Furthermore, because there are
28426 apparently some really broken clients that do this, Exim will accept AUTH after
28427 HELO (rather than EHLO) when this control is set. It should be used only if you
28428 really need it, and you should limit its use to those broken clients that do
28429 not work without it. For example:
28431 warn hosts = 192.168.34.25
28432 control = allow_auth_unadvertised
28434 Normally, when an Exim server receives an AUTH command, it checks the name of
28435 the authentication mechanism that is given in the command to ensure that it
28436 matches an advertised mechanism. When this control is set, the check that a
28437 mechanism has been advertised is bypassed. Any configured mechanism can be used
28438 by the client. This control is permitted only in the connection and HELO ACLs.
28441 .vitem &*control&~=&~caseful_local_part*& &&&
28442 &*control&~=&~caselower_local_part*&
28443 .cindex "&ACL;" "case of local part in"
28444 .cindex "case of local parts"
28445 .vindex "&$local_part$&"
28446 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
28447 (that is, during RCPT processing). By default, the contents of &$local_part$&
28448 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
28449 any uppercase letters in the original local part are restored in &$local_part$&
28450 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
28453 These controls affect only the current recipient. Moreover, they apply only to
28454 local part handling that takes place directly in the ACL (for example, as a key
28455 in lookups). If a test to verify the recipient is obeyed, the case-related
28456 handling of the local part during the verification is controlled by the router
28457 configuration (see the &%caseful_local_part%& generic router option).
28459 This facility could be used, for example, to add a spam score to local parts
28460 containing upper case letters. For example, using &$acl_m4$& to accumulate the
28463 warn control = caseful_local_part
28464 set acl_m4 = ${eval:\
28466 ${if match{$local_part}{[A-Z]}{1}{0}}\
28468 control = caselower_local_part
28470 Notice that we put back the lower cased version afterwards, assuming that
28471 is what is wanted for subsequent tests.
28474 .vitem &*control&~=&~cutthrough_delivery*&
28475 .cindex "&ACL;" "cutthrough routing"
28476 .cindex "cutthrough" "requesting"
28477 This option requests delivery be attempted while the item is being received.
28479 The option is usable in the RCPT ACL.
28480 If enabled for a message received via smtp and routed to an smtp transport,
28481 and only one transport, interface, destination host and port combination
28482 is used for all recipients of the message,
28483 then the delivery connection is made while the receiving connection is open
28484 and data is copied from one to the other.
28486 An attempt to set this option for any recipient but the first
28487 for a mail will be quietly ignored.
28488 If a recipient-verify callout connection is subsequently
28489 requested in the same ACL it is held open and used for
28490 any subsequent recipients and the data,
28491 otherwise one is made after the initial RCPT ACL completes.
28493 Note that routers are used in verify mode,
28494 and cannot depend on content of received headers.
28495 Note also that headers cannot be
28496 modified by any of the post-data ACLs (DATA, MIME and DKIM).
28497 Headers may be modified by routers (subject to the above) and transports.
28499 Cutthrough delivery is not supported via transport-filters or when DKIM signing
28500 of outgoing messages is done, because it sends data to the ultimate destination
28501 before the entire message has been received from the source.
28502 It is not supported for messages received with the SMTP PRDR option in use.
28504 Should the ultimate destination system positively accept or reject the mail,
28505 a corresponding indication is given to the source system and nothing is queued.
28506 If there is a temporary error the item is queued for later delivery in the
28507 usual fashion. If the item is successfully delivered in cutthrough mode
28508 the delivery log lines are tagged with ">>" rather than "=>" and appear
28509 before the acceptance "<=" line.
28511 Delivery in this mode avoids the generation of a bounce mail to a
28513 sender when the destination system is doing content-scan based rejection.
28516 .vitem &*control&~=&~debug/*&<&'options'&>
28517 .cindex "&ACL;" "enabling debug logging"
28518 .cindex "debugging" "enabling from an ACL"
28519 This control turns on debug logging, almost as though Exim had been invoked
28520 with &`-d`&, with the output going to a new logfile, by default called
28521 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
28522 may access any variables already defined. The logging may be adjusted with
28523 the &'opts'& option, which takes the same values as the &`-d`& command-line
28524 option. Some examples (which depend on variables that don't exist in all
28528 control = debug/tag=.$sender_host_address
28529 control = debug/opts=+expand+acl
28530 control = debug/tag=.$message_exim_id/opts=+expand
28534 .vitem &*control&~=&~dkim_disable_verify*&
28535 .cindex "disable DKIM verify"
28536 .cindex "DKIM" "disable verify"
28537 This control turns off DKIM verification processing entirely. For details on
28538 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
28541 .vitem &*control&~=&~dscp/*&<&'value'&>
28542 .cindex "&ACL;" "setting DSCP value"
28543 .cindex "DSCP" "inbound"
28544 This option causes the DSCP value associated with the socket for the inbound
28545 connection to be adjusted to a given value, given as one of a number of fixed
28546 strings or to numeric value.
28547 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
28548 Common values include &`throughput`&, &`mincost`&, and on newer systems
28549 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
28551 The outbound packets from Exim will be marked with this value in the header
28552 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
28553 that these values will have any effect, not be stripped by networking
28554 equipment, or do much of anything without cooperation with your Network
28555 Engineer and those of all network operators between the source and destination.
28558 .vitem &*control&~=&~enforce_sync*& &&&
28559 &*control&~=&~no_enforce_sync*&
28560 .cindex "SMTP" "synchronization checking"
28561 .cindex "synchronization checking in SMTP"
28562 These controls make it possible to be selective about when SMTP synchronization
28563 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
28564 state of the switch (it is true by default). See the description of this option
28565 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
28567 The effect of these two controls lasts for the remainder of the SMTP
28568 connection. They can appear in any ACL except the one for the non-SMTP
28569 messages. The most straightforward place to put them is in the ACL defined by
28570 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
28571 before the first synchronization check. The expected use is to turn off the
28572 synchronization checks for badly-behaved hosts that you nevertheless need to
28576 .vitem &*control&~=&~fakedefer/*&<&'message'&>
28577 .cindex "fake defer"
28578 .cindex "defer, fake"
28579 This control works in exactly the same way as &%fakereject%& (described below)
28580 except that it causes an SMTP 450 response after the message data instead of a
28581 550 response. You must take care when using &%fakedefer%& because it causes the
28582 messages to be duplicated when the sender retries. Therefore, you should not
28583 use &%fakedefer%& if the message is to be delivered normally.
28585 .vitem &*control&~=&~fakereject/*&<&'message'&>
28586 .cindex "fake rejection"
28587 .cindex "rejection, fake"
28588 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
28589 words, only when an SMTP message is being received. If Exim accepts the
28590 message, instead the final 250 response, a 550 rejection message is sent.
28591 However, Exim proceeds to deliver the message as normal. The control applies
28592 only to the current message, not to any subsequent ones that may be received in
28593 the same SMTP connection.
28595 The text for the 550 response is taken from the &%control%& modifier. If no
28596 message is supplied, the following is used:
28598 550-Your message has been rejected but is being
28599 550-kept for evaluation.
28600 550-If it was a legitimate message, it may still be
28601 550 delivered to the target recipient(s).
28603 This facility should be used with extreme caution.
28605 .vitem &*control&~=&~freeze*&
28606 .cindex "frozen messages" "forcing in ACL"
28607 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28608 other words, only when a message is being received. If the message is accepted,
28609 it is placed on Exim's queue and frozen. The control applies only to the
28610 current message, not to any subsequent ones that may be received in the same
28613 This modifier can optionally be followed by &`/no_tell`&. If the global option
28614 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
28615 is told about the freezing), provided all the &*control=freeze*& modifiers that
28616 are obeyed for the current message have the &`/no_tell`& option.
28618 .vitem &*control&~=&~no_delay_flush*&
28619 .cindex "SMTP" "output flushing, disabling for delay"
28620 Exim normally flushes SMTP output before implementing a delay in an ACL, to
28621 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28622 use. This control, as long as it is encountered before the &%delay%& modifier,
28623 disables such output flushing.
28625 .vitem &*control&~=&~no_callout_flush*&
28626 .cindex "SMTP" "output flushing, disabling for callout"
28627 Exim normally flushes SMTP output before performing a callout in an ACL, to
28628 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28629 use. This control, as long as it is encountered before the &%verify%& condition
28630 that causes the callout, disables such output flushing.
28632 .vitem &*control&~=&~no_mbox_unspool*&
28633 This control is available when Exim is compiled with the content scanning
28634 extension. Content scanning may require a copy of the current message, or parts
28635 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
28636 or spam scanner. Normally, such copies are deleted when they are no longer
28637 needed. If this control is set, the copies are not deleted. The control applies
28638 only to the current message, not to any subsequent ones that may be received in
28639 the same SMTP connection. It is provided for debugging purposes and is unlikely
28640 to be useful in production.
28642 .vitem &*control&~=&~no_multiline_responses*&
28643 .cindex "multiline responses, suppressing"
28644 This control is permitted for any ACL except the one for non-SMTP messages.
28645 It seems that there are broken clients in use that cannot handle multiline
28646 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
28648 If this control is set, multiline SMTP responses from ACL rejections are
28649 suppressed. One way of doing this would have been to put out these responses as
28650 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
28651 (&"use multiline responses for more"& it says &-- ha!), and some of the
28652 responses might get close to that. So this facility, which is after all only a
28653 sop to broken clients, is implemented by doing two very easy things:
28656 Extra information that is normally output as part of a rejection caused by
28657 sender verification failure is omitted. Only the final line (typically &"sender
28658 verification failed"&) is sent.
28660 If a &%message%& modifier supplies a multiline response, only the first
28664 The setting of the switch can, of course, be made conditional on the
28665 calling host. Its effect lasts until the end of the SMTP connection.
28667 .vitem &*control&~=&~no_pipelining*&
28668 .cindex "PIPELINING" "suppressing advertising"
28669 This control turns off the advertising of the PIPELINING extension to SMTP in
28670 the current session. To be useful, it must be obeyed before Exim sends its
28671 response to an EHLO command. Therefore, it should normally appear in an ACL
28672 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
28673 &%pipelining_advertise_hosts%&.
28675 .vitem &*control&~=&~queue_only*&
28676 .oindex "&%queue_only%&"
28677 .cindex "queueing incoming messages"
28678 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28679 other words, only when a message is being received. If the message is accepted,
28680 it is placed on Exim's queue and left there for delivery by a subsequent queue
28681 runner. No immediate delivery process is started. In other words, it has the
28682 effect as the &%queue_only%& global option. However, the control applies only
28683 to the current message, not to any subsequent ones that may be received in the
28684 same SMTP connection.
28686 .vitem &*control&~=&~submission/*&<&'options'&>
28687 .cindex "message" "submission"
28688 .cindex "submission mode"
28689 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
28690 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
28691 the current message is a submission from a local MUA. In this case, Exim
28692 operates in &"submission mode"&, and applies certain fixups to the message if
28693 necessary. For example, it adds a &'Date:'& header line if one is not present.
28694 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
28695 late (the message has already been created).
28697 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
28698 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
28699 submission mode; the available options for this control are described there.
28700 The control applies only to the current message, not to any subsequent ones
28701 that may be received in the same SMTP connection.
28703 .vitem &*control&~=&~suppress_local_fixups*&
28704 .cindex "submission fixups, suppressing"
28705 This control applies to locally submitted (non TCP/IP) messages, and is the
28706 complement of &`control = submission`&. It disables the fixups that are
28707 normally applied to locally-submitted messages. Specifically:
28710 Any &'Sender:'& header line is left alone (in this respect, it is a
28711 dynamic version of &%local_sender_retain%&).
28713 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
28715 There is no check that &'From:'& corresponds to the actual sender.
28718 This control may be useful when a remotely-originated message is accepted,
28719 passed to some scanning program, and then re-submitted for delivery. It can be
28720 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
28721 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
28724 &*Note:*& This control applies only to the current message, not to any others
28725 that are being submitted at the same time using &%-bs%& or &%-bS%&.
28728 .vitem &*control&~=&~utf8_downconvert*&
28729 This control enables conversion of UTF-8 in message addresses
28731 For details see &<<SECTi18nMTA>>&.
28736 .section "Summary of message fixup control" "SECTsummesfix"
28737 All four possibilities for message fixups can be specified:
28740 Locally submitted, fixups applied: the default.
28742 Locally submitted, no fixups applied: use
28743 &`control = suppress_local_fixups`&.
28745 Remotely submitted, no fixups applied: the default.
28747 Remotely submitted, fixups applied: use &`control = submission`&.
28752 .section "Adding header lines in ACLs" "SECTaddheadacl"
28753 .cindex "header lines" "adding in an ACL"
28754 .cindex "header lines" "position of added lines"
28755 .cindex "&%add_header%& ACL modifier"
28756 The &%add_header%& modifier can be used to add one or more extra header lines
28757 to an incoming message, as in this example:
28759 warn dnslists = sbl.spamhaus.org : \
28760 dialup.mail-abuse.org
28761 add_header = X-blacklisted-at: $dnslist_domain
28763 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
28764 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
28765 receiving a message). The message must ultimately be accepted for
28766 &%add_header%& to have any significant effect. You can use &%add_header%& with
28767 any ACL verb, including &%deny%& (though this is potentially useful only in a
28770 Headers will not be added to the message if the modifier is used in
28771 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
28773 Leading and trailing newlines are removed from
28774 the data for the &%add_header%& modifier; if it then
28775 contains one or more newlines that
28776 are not followed by a space or a tab, it is assumed to contain multiple header
28777 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
28778 front of any line that is not a valid header line.
28780 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
28781 They are added to the message before processing the DATA and MIME ACLs.
28782 However, if an identical header line is requested more than once, only one copy
28783 is actually added to the message. Further header lines may be accumulated
28784 during the DATA and MIME ACLs, after which they are added to the message, again
28785 with duplicates suppressed. Thus, it is possible to add two identical header
28786 lines to an SMTP message, but only if one is added before DATA and one after.
28787 In the case of non-SMTP messages, new headers are accumulated during the
28788 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
28789 message is rejected after DATA or by the non-SMTP ACL, all added header lines
28790 are included in the entry that is written to the reject log.
28792 .cindex "header lines" "added; visibility of"
28793 Header lines are not visible in string expansions
28795 until they are added to the
28796 message. It follows that header lines defined in the MAIL, RCPT, and predata
28797 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
28798 header lines that are added by the DATA or MIME ACLs are not visible in those
28799 ACLs. Because of this restriction, you cannot use header lines as a way of
28800 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
28801 this, you can use ACL variables, as described in section
28802 &<<SECTaclvariables>>&.
28804 The list of headers yet to be added is given by the &%$headers_added%& variable.
28806 The &%add_header%& modifier acts immediately as it is encountered during the
28807 processing of an ACL. Notice the difference between these two cases:
28809 &`accept add_header = ADDED: some text`&
28810 &` `&<&'some condition'&>
28812 &`accept `&<&'some condition'&>
28813 &` add_header = ADDED: some text`&
28815 In the first case, the header line is always added, whether or not the
28816 condition is true. In the second case, the header line is added only if the
28817 condition is true. Multiple occurrences of &%add_header%& may occur in the same
28818 ACL statement. All those that are encountered before a condition fails are
28821 .cindex "&%warn%& ACL verb"
28822 For compatibility with previous versions of Exim, a &%message%& modifier for a
28823 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
28824 effect only if all the conditions are true, even if it appears before some of
28825 them. Furthermore, only the last occurrence of &%message%& is honoured. This
28826 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
28827 are present on a &%warn%& verb, both are processed according to their
28830 By default, new header lines are added to a message at the end of the existing
28831 header lines. However, you can specify that any particular header line should
28832 be added right at the start (before all the &'Received:'& lines), immediately
28833 after the first block of &'Received:'& lines, or immediately before any line
28834 that is not a &'Received:'& or &'Resent-something:'& header.
28836 This is done by specifying &":at_start:"&, &":after_received:"&, or
28837 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
28838 header line, respectively. (Header text cannot start with a colon, as there has
28839 to be a header name first.) For example:
28841 warn add_header = \
28842 :after_received:X-My-Header: something or other...
28844 If more than one header line is supplied in a single &%add_header%& modifier,
28845 each one is treated independently and can therefore be placed differently. If
28846 you add more than one line at the start, or after the Received: block, they end
28847 up in reverse order.
28849 &*Warning*&: This facility currently applies only to header lines that are
28850 added in an ACL. It does NOT work for header lines that are added in a
28851 system filter or in a router or transport.
28855 .section "Removing header lines in ACLs" "SECTremoveheadacl"
28856 .cindex "header lines" "removing in an ACL"
28857 .cindex "header lines" "position of removed lines"
28858 .cindex "&%remove_header%& ACL modifier"
28859 The &%remove_header%& modifier can be used to remove one or more header lines
28860 from an incoming message, as in this example:
28862 warn message = Remove internal headers
28863 remove_header = x-route-mail1 : x-route-mail2
28865 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
28866 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
28867 receiving a message). The message must ultimately be accepted for
28868 &%remove_header%& to have any significant effect. You can use &%remove_header%&
28869 with any ACL verb, including &%deny%&, though this is really not useful for
28870 any verb that doesn't result in a delivered message.
28872 Headers will not be removed to the message if the modifier is used in
28873 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
28875 More than one header can be removed at the same time by using a colon separated
28876 list of header names. The header matching is case insensitive. Wildcards are
28877 not permitted, nor is list expansion performed, so you cannot use hostlists to
28878 create a list of headers, however both connection and message variable expansion
28879 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
28881 warn hosts = +internal_hosts
28882 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
28883 warn message = Remove internal headers
28884 remove_header = $acl_c_ihdrs
28886 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
28887 They are removed from the message before processing the DATA and MIME ACLs.
28888 There is no harm in attempting to remove the same header twice nor is removing
28889 a non-existent header. Further header lines to be removed may be accumulated
28890 during the DATA and MIME ACLs, after which they are removed from the message,
28891 if present. In the case of non-SMTP messages, headers to be removed are
28892 accumulated during the non-SMTP ACLs, and are removed from the message after
28893 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
28894 ACL, there really is no effect because there is no logging of what headers
28895 would have been removed.
28897 .cindex "header lines" "removed; visibility of"
28898 Header lines are not visible in string expansions until the DATA phase when it
28899 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
28900 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
28901 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
28902 this restriction, you cannot use header lines as a way of controlling data
28903 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
28904 you should instead use ACL variables, as described in section
28905 &<<SECTaclvariables>>&.
28907 The &%remove_header%& modifier acts immediately as it is encountered during the
28908 processing of an ACL. Notice the difference between these two cases:
28910 &`accept remove_header = X-Internal`&
28911 &` `&<&'some condition'&>
28913 &`accept `&<&'some condition'&>
28914 &` remove_header = X-Internal`&
28916 In the first case, the header line is always removed, whether or not the
28917 condition is true. In the second case, the header line is removed only if the
28918 condition is true. Multiple occurrences of &%remove_header%& may occur in the
28919 same ACL statement. All those that are encountered before a condition fails
28922 &*Warning*&: This facility currently applies only to header lines that are
28923 present during ACL processing. It does NOT remove header lines that are added
28924 in a system filter or in a router or transport.
28929 .section "ACL conditions" "SECTaclconditions"
28930 .cindex "&ACL;" "conditions; list of"
28931 Some of the conditions listed in this section are available only when Exim is
28932 compiled with the content-scanning extension. They are included here briefly
28933 for completeness. More detailed descriptions can be found in the discussion on
28934 content scanning in chapter &<<CHAPexiscan>>&.
28936 Not all conditions are relevant in all circumstances. For example, testing
28937 senders and recipients does not make sense in an ACL that is being run as the
28938 result of the arrival of an ETRN command, and checks on message headers can be
28939 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
28940 can use the same condition (with different parameters) more than once in the
28941 same ACL statement. This provides a way of specifying an &"and"& conjunction.
28942 The conditions are as follows:
28946 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
28947 .cindex "&ACL;" "nested"
28948 .cindex "&ACL;" "indirect"
28949 .cindex "&ACL;" "arguments"
28950 .cindex "&%acl%& ACL condition"
28951 The possible values of the argument are the same as for the
28952 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
28953 &"accept"& the condition is true; if it returns &"deny"& the condition is
28954 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
28955 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
28956 condition false. This means that further processing of the &%warn%& verb
28957 ceases, but processing of the ACL continues.
28959 If the argument is a named ACL, up to nine space-separated optional values
28960 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
28961 and $acl_narg is set to the count of values.
28962 Previous values of these variables are restored after the call returns.
28963 The name and values are expanded separately.
28964 Note that spaces in complex expansions which are used as arguments
28965 will act as argument separators.
28967 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
28968 the connection is dropped. If it returns &"discard"&, the verb must be
28969 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
28970 conditions are tested.
28972 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
28973 loops. This condition allows you to use different ACLs in different
28974 circumstances. For example, different ACLs can be used to handle RCPT commands
28975 for different local users or different local domains.
28977 .vitem &*authenticated&~=&~*&<&'string&~list'&>
28978 .cindex "&%authenticated%& ACL condition"
28979 .cindex "authentication" "ACL checking"
28980 .cindex "&ACL;" "testing for authentication"
28981 If the SMTP connection is not authenticated, the condition is false. Otherwise,
28982 the name of the authenticator is tested against the list. To test for
28983 authentication by any authenticator, you can set
28988 .vitem &*condition&~=&~*&<&'string'&>
28989 .cindex "&%condition%& ACL condition"
28990 .cindex "customizing" "ACL condition"
28991 .cindex "&ACL;" "customized test"
28992 .cindex "&ACL;" "testing, customized"
28993 This feature allows you to make up custom conditions. If the result of
28994 expanding the string is an empty string, the number zero, or one of the strings
28995 &"no"& or &"false"&, the condition is false. If the result is any non-zero
28996 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
28997 any other value, some error is assumed to have occurred, and the ACL returns
28998 &"defer"&. However, if the expansion is forced to fail, the condition is
28999 ignored. The effect is to treat it as true, whether it is positive or
29002 .vitem &*decode&~=&~*&<&'location'&>
29003 .cindex "&%decode%& ACL condition"
29004 This condition is available only when Exim is compiled with the
29005 content-scanning extension, and it is allowed only in the ACL defined by
29006 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
29007 If all goes well, the condition is true. It is false only if there are
29008 problems such as a syntax error or a memory shortage. For more details, see
29009 chapter &<<CHAPexiscan>>&.
29011 .vitem &*demime&~=&~*&<&'extension&~list'&>
29012 .cindex "&%demime%& ACL condition"
29013 This condition is available only when Exim is compiled with the
29014 content-scanning extension. Its use is described in section
29015 &<<SECTdemimecond>>&.
29017 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
29018 .cindex "&%dnslists%& ACL condition"
29019 .cindex "DNS list" "in ACL"
29020 .cindex "black list (DNS)"
29021 .cindex "&ACL;" "testing a DNS list"
29022 This condition checks for entries in DNS black lists. These are also known as
29023 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
29024 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
29025 different variants of this condition to describe briefly here. See sections
29026 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
29028 .vitem &*domains&~=&~*&<&'domain&~list'&>
29029 .cindex "&%domains%& ACL condition"
29030 .cindex "domain" "ACL checking"
29031 .cindex "&ACL;" "testing a recipient domain"
29032 .vindex "&$domain_data$&"
29033 This condition is relevant only after a RCPT command. It checks that the domain
29034 of the recipient address is in the domain list. If percent-hack processing is
29035 enabled, it is done before this test is done. If the check succeeds with a
29036 lookup, the result of the lookup is placed in &$domain_data$& until the next
29039 &*Note carefully*& (because many people seem to fall foul of this): you cannot
29040 use &%domains%& in a DATA ACL.
29043 .vitem &*encrypted&~=&~*&<&'string&~list'&>
29044 .cindex "&%encrypted%& ACL condition"
29045 .cindex "encryption" "checking in an ACL"
29046 .cindex "&ACL;" "testing for encryption"
29047 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
29048 name of the cipher suite in use is tested against the list. To test for
29049 encryption without testing for any specific cipher suite(s), set
29055 .vitem &*hosts&~=&~*&<&'host&~list'&>
29056 .cindex "&%hosts%& ACL condition"
29057 .cindex "host" "ACL checking"
29058 .cindex "&ACL;" "testing the client host"
29059 This condition tests that the calling host matches the host list. If you have
29060 name lookups or wildcarded host names and IP addresses in the same host list,
29061 you should normally put the IP addresses first. For example, you could have:
29063 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
29065 The lookup in this example uses the host name for its key. This is implied by
29066 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
29067 and it wouldn't matter which way round you had these two items.)
29069 The reason for the problem with host names lies in the left-to-right way that
29070 Exim processes lists. It can test IP addresses without doing any DNS lookups,
29071 but when it reaches an item that requires a host name, it fails if it cannot
29072 find a host name to compare with the pattern. If the above list is given in the
29073 opposite order, the &%accept%& statement fails for a host whose name cannot be
29074 found, even if its IP address is 10.9.8.7.
29076 If you really do want to do the name check first, and still recognize the IP
29077 address even if the name lookup fails, you can rewrite the ACL like this:
29079 accept hosts = dbm;/etc/friendly/hosts
29080 accept hosts = 10.9.8.7
29082 The default action on failing to find the host name is to assume that the host
29083 is not in the list, so the first &%accept%& statement fails. The second
29084 statement can then check the IP address.
29086 .vindex "&$host_data$&"
29087 If a &%hosts%& condition is satisfied by means of a lookup, the result
29088 of the lookup is made available in the &$host_data$& variable. This
29089 allows you, for example, to set up a statement like this:
29091 deny hosts = net-lsearch;/some/file
29092 message = $host_data
29094 which gives a custom error message for each denied host.
29096 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
29097 .cindex "&%local_parts%& ACL condition"
29098 .cindex "local part" "ACL checking"
29099 .cindex "&ACL;" "testing a local part"
29100 .vindex "&$local_part_data$&"
29101 This condition is relevant only after a RCPT command. It checks that the local
29102 part of the recipient address is in the list. If percent-hack processing is
29103 enabled, it is done before this test. If the check succeeds with a lookup, the
29104 result of the lookup is placed in &$local_part_data$&, which remains set until
29105 the next &%local_parts%& test.
29107 .vitem &*malware&~=&~*&<&'option'&>
29108 .cindex "&%malware%& ACL condition"
29109 .cindex "&ACL;" "virus scanning"
29110 .cindex "&ACL;" "scanning for viruses"
29111 This condition is available only when Exim is compiled with the
29112 content-scanning extension. It causes the incoming message to be scanned for
29113 viruses. For details, see chapter &<<CHAPexiscan>>&.
29115 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29116 .cindex "&%mime_regex%& ACL condition"
29117 .cindex "&ACL;" "testing by regex matching"
29118 This condition is available only when Exim is compiled with the
29119 content-scanning extension, and it is allowed only in the ACL defined by
29120 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
29121 with any of the regular expressions. For details, see chapter
29124 .vitem &*ratelimit&~=&~*&<&'parameters'&>
29125 .cindex "rate limiting"
29126 This condition can be used to limit the rate at which a user or host submits
29127 messages. Details are given in section &<<SECTratelimiting>>&.
29129 .vitem &*recipients&~=&~*&<&'address&~list'&>
29130 .cindex "&%recipients%& ACL condition"
29131 .cindex "recipient" "ACL checking"
29132 .cindex "&ACL;" "testing a recipient"
29133 This condition is relevant only after a RCPT command. It checks the entire
29134 recipient address against a list of recipients.
29136 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29137 .cindex "&%regex%& ACL condition"
29138 .cindex "&ACL;" "testing by regex matching"
29139 This condition is available only when Exim is compiled with the
29140 content-scanning extension, and is available only in the DATA, MIME, and
29141 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
29142 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
29144 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
29145 .cindex "&%sender_domains%& ACL condition"
29146 .cindex "sender" "ACL checking"
29147 .cindex "&ACL;" "testing a sender domain"
29148 .vindex "&$domain$&"
29149 .vindex "&$sender_address_domain$&"
29150 This condition tests the domain of the sender of the message against the given
29151 domain list. &*Note*&: The domain of the sender address is in
29152 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
29153 of this condition. This is an exception to the general rule for testing domain
29154 lists. It is done this way so that, if this condition is used in an ACL for a
29155 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
29156 influence the sender checking.
29158 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29159 relaying, because sender addresses are easily, and commonly, forged.
29161 .vitem &*senders&~=&~*&<&'address&~list'&>
29162 .cindex "&%senders%& ACL condition"
29163 .cindex "sender" "ACL checking"
29164 .cindex "&ACL;" "testing a sender"
29165 This condition tests the sender of the message against the given list. To test
29166 for a bounce message, which has an empty sender, set
29170 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29171 relaying, because sender addresses are easily, and commonly, forged.
29173 .vitem &*spam&~=&~*&<&'username'&>
29174 .cindex "&%spam%& ACL condition"
29175 .cindex "&ACL;" "scanning for spam"
29176 This condition is available only when Exim is compiled with the
29177 content-scanning extension. It causes the incoming message to be scanned by
29178 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
29180 .vitem &*verify&~=&~certificate*&
29181 .cindex "&%verify%& ACL condition"
29182 .cindex "TLS" "client certificate verification"
29183 .cindex "certificate" "verification of client"
29184 .cindex "&ACL;" "certificate verification"
29185 .cindex "&ACL;" "testing a TLS certificate"
29186 This condition is true in an SMTP session if the session is encrypted, and a
29187 certificate was received from the client, and the certificate was verified. The
29188 server requests a certificate only if the client matches &%tls_verify_hosts%&
29189 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
29191 .vitem &*verify&~=&~csa*&
29192 .cindex "CSA verification"
29193 This condition checks whether the sending host (the client) is authorized to
29194 send email. Details of how this works are given in section
29195 &<<SECTverifyCSA>>&.
29197 .vitem &*verify&~=&~header_names_ascii*&
29198 .cindex "&%verify%& ACL condition"
29199 .cindex "&ACL;" "verifying header names only ASCII"
29200 .cindex "header lines" "verifying header names only ASCII"
29201 .cindex "verifying" "header names only ASCII"
29202 This condition is relevant only in an ACL that is run after a message has been
29203 received, that is, in an ACL specified by &%acl_smtp_data%& or
29204 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
29205 there are no non-ASCII characters, also excluding control characters. The
29206 allowable characters are decimal ASCII values 33 through 126.
29208 Exim itself will handle headers with non-ASCII characters, but it can cause
29209 problems for downstream applications, so this option will allow their
29210 detection and rejection in the DATA ACL's.
29212 .vitem &*verify&~=&~header_sender/*&<&'options'&>
29213 .cindex "&%verify%& ACL condition"
29214 .cindex "&ACL;" "verifying sender in the header"
29215 .cindex "header lines" "verifying the sender in"
29216 .cindex "sender" "verifying in header"
29217 .cindex "verifying" "sender in header"
29218 This condition is relevant only in an ACL that is run after a message has been
29219 received, that is, in an ACL specified by &%acl_smtp_data%& or
29220 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
29221 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
29222 is loosely thought of as a &"sender"& address (hence the name of the test).
29223 However, an address that appears in one of these headers need not be an address
29224 that accepts bounce messages; only sender addresses in envelopes are required
29225 to accept bounces. Therefore, if you use the callout option on this check, you
29226 might want to arrange for a non-empty address in the MAIL command.
29228 Details of address verification and the options are given later, starting at
29229 section &<<SECTaddressverification>>& (callouts are described in section
29230 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
29231 condition to restrict it to bounce messages only:
29234 message = A valid sender header is required for bounces
29235 !verify = header_sender
29238 .vitem &*verify&~=&~header_syntax*&
29239 .cindex "&%verify%& ACL condition"
29240 .cindex "&ACL;" "verifying header syntax"
29241 .cindex "header lines" "verifying syntax"
29242 .cindex "verifying" "header syntax"
29243 This condition is relevant only in an ACL that is run after a message has been
29244 received, that is, in an ACL specified by &%acl_smtp_data%& or
29245 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
29246 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
29247 and &'Bcc:'&), returning true if there are no problems.
29248 Unqualified addresses (local parts without domains) are
29249 permitted only in locally generated messages and from hosts that match
29250 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
29253 Note that this condition is a syntax check only. However, a common spamming
29254 ploy used to be to send syntactically invalid headers such as
29258 and this condition can be used to reject such messages, though they are not as
29259 common as they used to be.
29261 .vitem &*verify&~=&~helo*&
29262 .cindex "&%verify%& ACL condition"
29263 .cindex "&ACL;" "verifying HELO/EHLO"
29264 .cindex "HELO" "verifying"
29265 .cindex "EHLO" "verifying"
29266 .cindex "verifying" "EHLO"
29267 .cindex "verifying" "HELO"
29268 This condition is true if a HELO or EHLO command has been received from the
29269 client host, and its contents have been verified. If there has been no previous
29270 attempt to verify the HELO/EHLO contents, it is carried out when this
29271 condition is encountered. See the description of the &%helo_verify_hosts%& and
29272 &%helo_try_verify_hosts%& options for details of how to request verification
29273 independently of this condition.
29275 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
29276 option), this condition is always true.
29279 .vitem &*verify&~=&~not_blind*&
29280 .cindex "verifying" "not blind"
29281 .cindex "bcc recipients, verifying none"
29282 This condition checks that there are no blind (bcc) recipients in the message.
29283 Every envelope recipient must appear either in a &'To:'& header line or in a
29284 &'Cc:'& header line for this condition to be true. Local parts are checked
29285 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
29286 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
29287 used only in a DATA or non-SMTP ACL.
29289 There are, of course, many legitimate messages that make use of blind (bcc)
29290 recipients. This check should not be used on its own for blocking messages.
29293 .vitem &*verify&~=&~recipient/*&<&'options'&>
29294 .cindex "&%verify%& ACL condition"
29295 .cindex "&ACL;" "verifying recipient"
29296 .cindex "recipient" "verifying"
29297 .cindex "verifying" "recipient"
29298 .vindex "&$address_data$&"
29299 This condition is relevant only after a RCPT command. It verifies the current
29300 recipient. Details of address verification are given later, starting at section
29301 &<<SECTaddressverification>>&. After a recipient has been verified, the value
29302 of &$address_data$& is the last value that was set while routing the address.
29303 This applies even if the verification fails. When an address that is being
29304 verified is redirected to a single address, verification continues with the new
29305 address, and in that case, the subsequent value of &$address_data$& is the
29306 value for the child address.
29308 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
29309 .cindex "&%verify%& ACL condition"
29310 .cindex "&ACL;" "verifying host reverse lookup"
29311 .cindex "host" "verifying reverse lookup"
29312 This condition ensures that a verified host name has been looked up from the IP
29313 address of the client host. (This may have happened already if the host name
29314 was needed for checking a host list, or if the host matched &%host_lookup%&.)
29315 Verification ensures that the host name obtained from a reverse DNS lookup, or
29316 one of its aliases, does, when it is itself looked up in the DNS, yield the
29317 original IP address.
29319 There is one possible option, &`defer_ok`&. If this is present and a
29320 DNS operation returns a temporary error, the verify condition succeeds.
29322 If this condition is used for a locally generated message (that is, when there
29323 is no client host involved), it always succeeds.
29325 .vitem &*verify&~=&~sender/*&<&'options'&>
29326 .cindex "&%verify%& ACL condition"
29327 .cindex "&ACL;" "verifying sender"
29328 .cindex "sender" "verifying"
29329 .cindex "verifying" "sender"
29330 This condition is relevant only after a MAIL or RCPT command, or after a
29331 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
29332 the message's sender is empty (that is, this is a bounce message), the
29333 condition is true. Otherwise, the sender address is verified.
29335 .vindex "&$address_data$&"
29336 .vindex "&$sender_address_data$&"
29337 If there is data in the &$address_data$& variable at the end of routing, its
29338 value is placed in &$sender_address_data$& at the end of verification. This
29339 value can be used in subsequent conditions and modifiers in the same ACL
29340 statement. It does not persist after the end of the current statement. If you
29341 want to preserve the value for longer, you can save it in an ACL variable.
29343 Details of verification are given later, starting at section
29344 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
29345 to avoid doing it more than once per message.
29347 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
29348 .cindex "&%verify%& ACL condition"
29349 This is a variation of the previous option, in which a modified address is
29350 verified as a sender.
29355 .section "Using DNS lists" "SECTmorednslists"
29356 .cindex "DNS list" "in ACL"
29357 .cindex "black list (DNS)"
29358 .cindex "&ACL;" "testing a DNS list"
29359 In its simplest form, the &%dnslists%& condition tests whether the calling host
29360 is on at least one of a number of DNS lists by looking up the inverted IP
29361 address in one or more DNS domains. (Note that DNS list domains are not mail
29362 domains, so the &`+`& syntax for named lists doesn't work - it is used for
29363 special options instead.) For example, if the calling host's IP
29364 address is 192.168.62.43, and the ACL statement is
29366 deny dnslists = blackholes.mail-abuse.org : \
29367 dialups.mail-abuse.org
29369 the following records are looked up:
29371 43.62.168.192.blackholes.mail-abuse.org
29372 43.62.168.192.dialups.mail-abuse.org
29374 As soon as Exim finds an existing DNS record, processing of the list stops.
29375 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
29376 to test that a host is on more than one list (an &"and"& conjunction), you can
29377 use two separate conditions:
29379 deny dnslists = blackholes.mail-abuse.org
29380 dnslists = dialups.mail-abuse.org
29382 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
29383 behaves as if the host does not match the list item, that is, as if the DNS
29384 record does not exist. If there are further items in the DNS list, they are
29387 This is usually the required action when &%dnslists%& is used with &%deny%&
29388 (which is the most common usage), because it prevents a DNS failure from
29389 blocking mail. However, you can change this behaviour by putting one of the
29390 following special items in the list:
29392 &`+include_unknown `& behave as if the item is on the list
29393 &`+exclude_unknown `& behave as if the item is not on the list (default)
29394 &`+defer_unknown `& give a temporary error
29396 .cindex "&`+include_unknown`&"
29397 .cindex "&`+exclude_unknown`&"
29398 .cindex "&`+defer_unknown`&"
29399 Each of these applies to any subsequent items on the list. For example:
29401 deny dnslists = +defer_unknown : foo.bar.example
29403 Testing the list of domains stops as soon as a match is found. If you want to
29404 warn for one list and block for another, you can use two different statements:
29406 deny dnslists = blackholes.mail-abuse.org
29407 warn message = X-Warn: sending host is on dialups list
29408 dnslists = dialups.mail-abuse.org
29410 .cindex cacheing "of dns lookup"
29412 DNS list lookups are cached by Exim for the duration of the SMTP session
29414 (but limited by the DNS return TTL value),
29416 so a lookup based on the IP address is done at most once for any incoming
29417 connection (assuming long-enough TTL).
29418 Exim does not share information between multiple incoming
29419 connections (but your local name server cache should be active).
29423 .section "Specifying the IP address for a DNS list lookup" "SECID201"
29424 .cindex "DNS list" "keyed by explicit IP address"
29425 By default, the IP address that is used in a DNS list lookup is the IP address
29426 of the calling host. However, you can specify another IP address by listing it
29427 after the domain name, introduced by a slash. For example:
29429 deny dnslists = black.list.tld/192.168.1.2
29431 This feature is not very helpful with explicit IP addresses; it is intended for
29432 use with IP addresses that are looked up, for example, the IP addresses of the
29433 MX hosts or nameservers of an email sender address. For an example, see section
29434 &<<SECTmulkeyfor>>& below.
29439 .section "DNS lists keyed on domain names" "SECID202"
29440 .cindex "DNS list" "keyed by domain name"
29441 There are some lists that are keyed on domain names rather than inverted IP
29442 addresses (see for example the &'domain based zones'& link at
29443 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
29444 with these lists. You can change the name that is looked up in a DNS list by
29445 listing it after the domain name, introduced by a slash. For example,
29447 deny message = Sender's domain is listed at $dnslist_domain
29448 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
29450 This particular example is useful only in ACLs that are obeyed after the
29451 RCPT or DATA commands, when a sender address is available. If (for
29452 example) the message's sender is &'user@tld.example'& the name that is looked
29453 up by this example is
29455 tld.example.dsn.rfc-ignorant.org
29457 A single &%dnslists%& condition can contain entries for both names and IP
29458 addresses. For example:
29460 deny dnslists = sbl.spamhaus.org : \
29461 dsn.rfc-ignorant.org/$sender_address_domain
29463 The first item checks the sending host's IP address; the second checks a domain
29464 name. The whole condition is true if either of the DNS lookups succeeds.
29469 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
29470 .cindex "DNS list" "multiple keys for"
29471 The syntax described above for looking up explicitly-defined values (either
29472 names or IP addresses) in a DNS blacklist is a simplification. After the domain
29473 name for the DNS list, what follows the slash can in fact be a list of items.
29474 As with all lists in Exim, the default separator is a colon. However, because
29475 this is a sublist within the list of DNS blacklist domains, it is necessary
29476 either to double the separators like this:
29478 dnslists = black.list.tld/name.1::name.2
29480 or to change the separator character, like this:
29482 dnslists = black.list.tld/<;name.1;name.2
29484 If an item in the list is an IP address, it is inverted before the DNS
29485 blacklist domain is appended. If it is not an IP address, no inversion
29486 occurs. Consider this condition:
29488 dnslists = black.list.tld/<;192.168.1.2;a.domain
29490 The DNS lookups that occur are:
29492 2.1.168.192.black.list.tld
29493 a.domain.black.list.tld
29495 Once a DNS record has been found (that matches a specific IP return
29496 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
29497 are done. If there is a temporary DNS error, the rest of the sublist of domains
29498 or IP addresses is tried. A temporary error for the whole dnslists item occurs
29499 only if no other DNS lookup in this sublist succeeds. In other words, a
29500 successful lookup for any of the items in the sublist overrides a temporary
29501 error for a previous item.
29503 The ability to supply a list of items after the slash is in some sense just a
29504 syntactic convenience. These two examples have the same effect:
29506 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
29507 dnslists = black.list.tld/a.domain::b.domain
29509 However, when the data for the list is obtained from a lookup, the second form
29510 is usually much more convenient. Consider this example:
29512 deny message = The mail servers for the domain \
29513 $sender_address_domain \
29514 are listed at $dnslist_domain ($dnslist_value); \
29516 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
29517 ${lookup dnsdb {>|mxh=\
29518 $sender_address_domain} }} }
29520 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
29521 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
29522 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
29523 of expanding the condition might be something like this:
29525 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
29527 Thus, this example checks whether or not the IP addresses of the sender
29528 domain's mail servers are on the Spamhaus black list.
29530 The key that was used for a successful DNS list lookup is put into the variable
29531 &$dnslist_matched$& (see section &<<SECID204>>&).
29536 .section "Data returned by DNS lists" "SECID203"
29537 .cindex "DNS list" "data returned from"
29538 DNS lists are constructed using address records in the DNS. The original RBL
29539 just used the address 127.0.0.1 on the right hand side of each record, but the
29540 RBL+ list and some other lists use a number of values with different meanings.
29541 The values used on the RBL+ list are:
29545 127.1.0.3 DUL and RBL
29547 127.1.0.5 RSS and RBL
29548 127.1.0.6 RSS and DUL
29549 127.1.0.7 RSS and DUL and RBL
29551 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
29552 different values. Some DNS lists may return more than one address record;
29553 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
29556 .section "Variables set from DNS lists" "SECID204"
29557 .cindex "expansion" "variables, set from DNS list"
29558 .cindex "DNS list" "variables set from"
29559 .vindex "&$dnslist_domain$&"
29560 .vindex "&$dnslist_matched$&"
29561 .vindex "&$dnslist_text$&"
29562 .vindex "&$dnslist_value$&"
29563 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
29564 the name of the overall domain that matched (for example,
29565 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
29566 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
29567 the DNS record. When the key is an IP address, it is not reversed in
29568 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
29569 cases, for example:
29571 deny dnslists = spamhaus.example
29573 the key is also available in another variable (in this case,
29574 &$sender_host_address$&). In more complicated cases, however, this is not true.
29575 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
29576 might generate a dnslists lookup like this:
29578 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
29580 If this condition succeeds, the value in &$dnslist_matched$& might be
29581 &`192.168.6.7`& (for example).
29583 If more than one address record is returned by the DNS lookup, all the IP
29584 addresses are included in &$dnslist_value$&, separated by commas and spaces.
29585 The variable &$dnslist_text$& contains the contents of any associated TXT
29586 record. For lists such as RBL+ the TXT record for a merged entry is often not
29587 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
29590 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
29591 &-- although these appear before the condition in the ACL, they are not
29592 expanded until after it has failed. For example:
29594 deny hosts = !+local_networks
29595 message = $sender_host_address is listed \
29597 dnslists = rbl-plus.mail-abuse.example
29602 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
29603 .cindex "DNS list" "matching specific returned data"
29604 You can add an equals sign and an IP address after a &%dnslists%& domain name
29605 in order to restrict its action to DNS records with a matching right hand side.
29608 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
29610 rejects only those hosts that yield 127.0.0.2. Without this additional data,
29611 any address record is considered to be a match. For the moment, we assume
29612 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
29613 describes how multiple records are handled.
29615 More than one IP address may be given for checking, using a comma as a
29616 separator. These are alternatives &-- if any one of them matches, the
29617 &%dnslists%& condition is true. For example:
29619 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29621 If you want to specify a constraining address list and also specify names or IP
29622 addresses to be looked up, the constraining address list must be specified
29623 first. For example:
29625 deny dnslists = dsn.rfc-ignorant.org\
29626 =127.0.0.2/$sender_address_domain
29629 If the character &`&&`& is used instead of &`=`&, the comparison for each
29630 listed IP address is done by a bitwise &"and"& instead of by an equality test.
29631 In other words, the listed addresses are used as bit masks. The comparison is
29632 true if all the bits in the mask are present in the address that is being
29633 tested. For example:
29635 dnslists = a.b.c&0.0.0.3
29637 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
29638 want to test whether one bit or another bit is present (as opposed to both
29639 being present), you must use multiple values. For example:
29641 dnslists = a.b.c&0.0.0.1,0.0.0.2
29643 matches if the final component of the address is an odd number or two times
29648 .section "Negated DNS matching conditions" "SECID205"
29649 You can supply a negative list of IP addresses as part of a &%dnslists%&
29652 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29654 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29655 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
29657 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
29659 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29660 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
29661 words, the result of the test is inverted if an exclamation mark appears before
29662 the &`=`& (or the &`&&`&) sign.
29664 &*Note*&: This kind of negation is not the same as negation in a domain,
29665 host, or address list (which is why the syntax is different).
29667 If you are using just one list, the negation syntax does not gain you much. The
29668 previous example is precisely equivalent to
29670 deny dnslists = a.b.c
29671 !dnslists = a.b.c=127.0.0.2,127.0.0.3
29673 However, if you are using multiple lists, the negation syntax is clearer.
29674 Consider this example:
29676 deny dnslists = sbl.spamhaus.org : \
29678 dnsbl.njabl.org!=127.0.0.3 : \
29681 Using only positive lists, this would have to be:
29683 deny dnslists = sbl.spamhaus.org : \
29685 deny dnslists = dnsbl.njabl.org
29686 !dnslists = dnsbl.njabl.org=127.0.0.3
29687 deny dnslists = relays.ordb.org
29689 which is less clear, and harder to maintain.
29694 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
29695 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
29696 thereby providing more than one IP address. When an item in a &%dnslists%& list
29697 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
29698 the match to specific results from the DNS lookup, there are two ways in which
29699 the checking can be handled. For example, consider the condition:
29701 dnslists = a.b.c=127.0.0.1
29703 What happens if the DNS lookup for the incoming IP address yields both
29704 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
29705 condition true because at least one given value was found, or is it false
29706 because at least one of the found values was not listed? And how does this
29707 affect negated conditions? Both possibilities are provided for with the help of
29708 additional separators &`==`& and &`=&&`&.
29711 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
29712 IP addresses matches one of the listed addresses. For the example above, the
29713 condition is true because 127.0.0.1 matches.
29715 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
29716 looked up IP addresses matches one of the listed addresses. If the condition is
29719 dnslists = a.b.c==127.0.0.1
29721 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29722 false because 127.0.0.2 is not listed. You would need to have:
29724 dnslists = a.b.c==127.0.0.1,127.0.0.2
29726 for the condition to be true.
29729 When &`!`& is used to negate IP address matching, it inverts the result, giving
29730 the precise opposite of the behaviour above. Thus:
29732 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
29733 addresses matches one of the listed addresses. Consider:
29735 dnslists = a.b.c!&0.0.0.1
29737 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29738 false because 127.0.0.1 matches.
29740 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
29741 looked up IP address that does not match. Consider:
29743 dnslists = a.b.c!=&0.0.0.1
29745 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29746 true, because 127.0.0.2 does not match. You would need to have:
29748 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
29750 for the condition to be false.
29752 When the DNS lookup yields only a single IP address, there is no difference
29753 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
29758 .section "Detailed information from merged DNS lists" "SECTmordetinf"
29759 .cindex "DNS list" "information from merged"
29760 When the facility for restricting the matching IP values in a DNS list is used,
29761 the text from the TXT record that is set in &$dnslist_text$& may not reflect
29762 the true reason for rejection. This happens when lists are merged and the IP
29763 address in the A record is used to distinguish them; unfortunately there is
29764 only one TXT record. One way round this is not to use merged lists, but that
29765 can be inefficient because it requires multiple DNS lookups where one would do
29766 in the vast majority of cases when the host of interest is not on any of the
29769 A less inefficient way of solving this problem is available. If
29770 two domain names, comma-separated, are given, the second is used first to
29771 do an initial check, making use of any IP value restrictions that are set.
29772 If there is a match, the first domain is used, without any IP value
29773 restrictions, to get the TXT record. As a byproduct of this, there is also
29774 a check that the IP being tested is indeed on the first list. The first
29775 domain is the one that is put in &$dnslist_domain$&. For example:
29778 rejected because $sender_host_address is blacklisted \
29779 at $dnslist_domain\n$dnslist_text
29781 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
29782 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
29784 For the first blacklist item, this starts by doing a lookup in
29785 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
29786 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
29787 value, and as long as something is found, it looks for the corresponding TXT
29788 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
29789 The second blacklist item is processed similarly.
29791 If you are interested in more than one merged list, the same list must be
29792 given several times, but because the results of the DNS lookups are cached,
29793 the DNS calls themselves are not repeated. For example:
29795 reject dnslists = \
29796 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
29797 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
29798 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
29799 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
29801 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
29802 values matches (or if no record is found), this is the only lookup that is
29803 done. Only if there is a match is one of the more specific lists consulted.
29807 .section "DNS lists and IPv6" "SECTmorednslistslast"
29808 .cindex "IPv6" "DNS black lists"
29809 .cindex "DNS list" "IPv6 usage"
29810 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
29811 nibble by nibble. For example, if the calling host's IP address is
29812 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
29814 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
29815 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
29817 (split over two lines here to fit on the page). Unfortunately, some of the DNS
29818 lists contain wildcard records, intended for IPv4, that interact badly with
29819 IPv6. For example, the DNS entry
29821 *.3.some.list.example. A 127.0.0.1
29823 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
29824 Unfortunately, it also matches the entire 3::/4 IPv6 network.
29826 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
29827 &%condition%& condition, as in this example:
29829 deny condition = ${if isip4{$sender_host_address}}
29830 dnslists = some.list.example
29833 If an explicit key is being used for a DNS lookup and it may be an IPv6
29834 address you should specify alternate list separators for both the outer
29835 (DNS list name) list and inner (lookup keys) list:
29837 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
29840 .section "Rate limiting incoming messages" "SECTratelimiting"
29841 .cindex "rate limiting" "client sending"
29842 .cindex "limiting client sending rates"
29843 .oindex "&%smtp_ratelimit_*%&"
29844 The &%ratelimit%& ACL condition can be used to measure and control the rate at
29845 which clients can send email. This is more powerful than the
29846 &%smtp_ratelimit_*%& options, because those options control the rate of
29847 commands in a single SMTP session only, whereas the &%ratelimit%& condition
29848 works across all connections (concurrent and sequential) from the same client
29849 host. The syntax of the &%ratelimit%& condition is:
29851 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
29853 If the average client sending rate is less than &'m'& messages per time
29854 period &'p'& then the condition is false; otherwise it is true.
29856 As a side-effect, the &%ratelimit%& condition sets the expansion variable
29857 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
29858 configured value of &'m'&, and &$sender_rate_period$& to the configured value
29861 The parameter &'p'& is the smoothing time constant, in the form of an Exim
29862 time interval, for example, &`8h`& for eight hours. A larger time constant
29863 means that it takes Exim longer to forget a client's past behaviour. The
29864 parameter &'m'& is the maximum number of messages that a client is permitted to
29865 send in each time interval. It also specifies the number of messages permitted
29866 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
29867 constant, you can allow a client to send more messages in a burst without
29868 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
29869 both small, messages must be sent at an even rate.
29871 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
29872 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
29873 when deploying the &%ratelimit%& ACL condition. The script prints usage
29874 instructions when it is run with no arguments.
29876 The key is used to look up the data for calculating the client's average
29877 sending rate. This data is stored in Exim's spool directory, alongside the
29878 retry and other hints databases. The default key is &$sender_host_address$&,
29879 which means Exim computes the sending rate of each client host IP address.
29880 By changing the key you can change how Exim identifies clients for the purpose
29881 of ratelimiting. For example, to limit the sending rate of each authenticated
29882 user, independent of the computer they are sending from, set the key to
29883 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
29884 example, &$authenticated_id$& is only meaningful if the client has
29885 authenticated (which you can check with the &%authenticated%& ACL condition).
29887 The lookup key does not have to identify clients: If you want to limit the
29888 rate at which a recipient receives messages, you can use the key
29889 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
29892 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
29893 specifies what Exim measures the rate of, for example messages or recipients
29894 or bytes. You can adjust the measurement using the &%unique=%& and/or
29895 &%count=%& options. You can also control when Exim updates the recorded rate
29896 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
29897 separated by a slash, like the other parameters. They may appear in any order.
29899 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
29900 any options that alter the meaning of the stored data. The limit &'m'& is not
29901 stored, so you can alter the configured maximum rate and Exim will still
29902 remember clients' past behaviour. If you change the &%per_*%& mode or add or
29903 remove the &%unique=%& option, the lookup key changes so Exim will forget past
29904 behaviour. The lookup key is not affected by changes to the update mode and
29905 the &%count=%& option.
29908 .section "Ratelimit options for what is being measured" "ratoptmea"
29909 .cindex "rate limiting" "per_* options"
29910 The &%per_conn%& option limits the client's connection rate. It is not
29911 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
29912 &%acl_not_smtp_start%& ACLs.
29914 The &%per_mail%& option limits the client's rate of sending messages. This is
29915 the default if none of the &%per_*%& options is specified. It can be used in
29916 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
29917 &%acl_smtp_data%&, or &%acl_not_smtp%&.
29919 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
29920 the same ACLs as the &%per_mail%& option, though it is best to use this option
29921 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
29922 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
29923 in its MAIL command, which may be inaccurate or completely missing. You can
29924 follow the limit &'m'& in the configuration with K, M, or G to specify limits
29925 in kilobytes, megabytes, or gigabytes, respectively.
29927 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
29928 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
29929 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
29930 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
29931 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
29932 in either case the rate limiting engine will see a message with many
29933 recipients as a large high-speed burst.
29935 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
29936 number of different recipients that the client has sent messages to in the
29937 last time period. That is, if the client repeatedly sends messages to the same
29938 recipient, its measured rate is not increased. This option can only be used in
29941 The &%per_cmd%& option causes Exim to recompute the rate every time the
29942 condition is processed. This can be used to limit the rate of any SMTP
29943 command. If it is used in multiple ACLs it can limit the aggregate rate of
29944 multiple different commands.
29946 The &%count=%& option can be used to alter how much Exim adds to the client's
29947 measured rate. For example, the &%per_byte%& option is equivalent to
29948 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
29949 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
29950 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
29952 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
29955 .section "Ratelimit update modes" "ratoptupd"
29956 .cindex "rate limiting" "reading data without updating"
29957 You can specify one of three options with the &%ratelimit%& condition to
29958 control when its database is updated. This section describes the &%readonly%&
29959 mode, and the next section describes the &%strict%& and &%leaky%& modes.
29961 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
29962 previously-computed rate to check against the limit.
29964 For example, you can test the client's sending rate and deny it access (when
29965 it is too fast) in the connect ACL. If the client passes this check then it
29966 can go on to send a message, in which case its recorded rate will be updated
29967 in the MAIL ACL. Subsequent connections from the same client will check this
29971 deny ratelimit = 100 / 5m / readonly
29972 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
29973 (max $sender_rate_limit)
29976 warn ratelimit = 100 / 5m / strict
29977 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
29978 (max $sender_rate_limit)
29981 If Exim encounters multiple &%ratelimit%& conditions with the same key when
29982 processing a message then it may increase the client's measured rate more than
29983 it should. For example, this will happen if you check the &%per_rcpt%& option
29984 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
29985 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
29986 multiple update problems by using the &%readonly%& option on later ratelimit
29989 The &%per_*%& options described above do not make sense in some ACLs. If you
29990 use a &%per_*%& option in an ACL where it is not normally permitted then the
29991 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
29992 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
29993 next section) so you must specify the &%readonly%& option explicitly.
29996 .section "Ratelimit options for handling fast clients" "ratoptfast"
29997 .cindex "rate limiting" "strict and leaky modes"
29998 If a client's average rate is greater than the maximum, the rate limiting
29999 engine can react in two possible ways, depending on the presence of the
30000 &%strict%& or &%leaky%& update modes. This is independent of the other
30001 counter-measures (such as rejecting the message) that may be specified by the
30004 The &%leaky%& (default) option means that the client's recorded rate is not
30005 updated if it is above the limit. The effect of this is that Exim measures the
30006 client's average rate of successfully sent email, which cannot be greater than
30007 the maximum allowed. If the client is over the limit it may suffer some
30008 counter-measures (as specified in the ACL), but it will still be able to send
30009 email at the configured maximum rate, whatever the rate of its attempts. This
30010 is generally the better choice if you have clients that retry automatically.
30011 For example, it does not prevent a sender with an over-aggressive retry rate
30012 from getting any email through.
30014 The &%strict%& option means that the client's recorded rate is always
30015 updated. The effect of this is that Exim measures the client's average rate
30016 of attempts to send email, which can be much higher than the maximum it is
30017 actually allowed. If the client is over the limit it may be subjected to
30018 counter-measures by the ACL. It must slow down and allow sufficient time to
30019 pass that its computed rate falls below the maximum before it can send email
30020 again. The time (the number of smoothing periods) it must wait and not
30021 attempt to send mail can be calculated with this formula:
30023 ln(peakrate/maxrate)
30027 .section "Limiting the rate of different events" "ratoptuniq"
30028 .cindex "rate limiting" "counting unique events"
30029 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
30030 rate of different events. For example, the &%per_addr%& option uses this
30031 mechanism to count the number of different recipients that the client has
30032 sent messages to in the last time period; it is equivalent to
30033 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
30034 measure the rate that a client uses different sender addresses with the
30035 options &`per_mail/unique=$sender_address`&.
30037 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
30038 has seen for that key. The whole set is thrown away when it is older than the
30039 rate smoothing period &'p'&, so each different event is counted at most once
30040 per period. In the &%leaky%& update mode, an event that causes the client to
30041 go over the limit is not added to the set, in the same way that the client's
30042 recorded rate is not updated in the same situation.
30044 When you combine the &%unique=%& and &%readonly%& options, the specific
30045 &%unique=%& value is ignored, and Exim just retrieves the client's stored
30048 The &%unique=%& mechanism needs more space in the ratelimit database than the
30049 other &%ratelimit%& options in order to store the event set. The number of
30050 unique values is potentially as large as the rate limit, so the extra space
30051 required increases with larger limits.
30053 The uniqueification is not perfect: there is a small probability that Exim
30054 will think a new event has happened before. If the sender's rate is less than
30055 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
30056 the measured rate can go above the limit, in which case Exim may under-count
30057 events by a significant margin. Fortunately, if the rate is high enough (2.7
30058 times the limit) that the false positive rate goes above 9%, then Exim will
30059 throw away the over-full event set before the measured rate falls below the
30060 limit. Therefore the only harm should be that exceptionally high sending rates
30061 are logged incorrectly; any countermeasures you configure will be as effective
30065 .section "Using rate limiting" "useratlim"
30066 Exim's other ACL facilities are used to define what counter-measures are taken
30067 when the rate limit is exceeded. This might be anything from logging a warning
30068 (for example, while measuring existing sending rates in order to define
30069 policy), through time delays to slow down fast senders, up to rejecting the
30070 message. For example:
30072 # Log all senders' rates
30073 warn ratelimit = 0 / 1h / strict
30074 log_message = Sender rate $sender_rate / $sender_rate_period
30076 # Slow down fast senders; note the need to truncate $sender_rate
30077 # at the decimal point.
30078 warn ratelimit = 100 / 1h / per_rcpt / strict
30079 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
30080 $sender_rate_limit }s
30082 # Keep authenticated users under control
30083 deny authenticated = *
30084 ratelimit = 100 / 1d / strict / $authenticated_id
30086 # System-wide rate limit
30087 defer message = Sorry, too busy. Try again later.
30088 ratelimit = 10 / 1s / $primary_hostname
30090 # Restrict incoming rate from each host, with a default
30091 # set using a macro and special cases looked up in a table.
30092 defer message = Sender rate exceeds $sender_rate_limit \
30093 messages per $sender_rate_period
30094 ratelimit = ${lookup {$sender_host_address} \
30095 cdb {DB/ratelimits.cdb} \
30096 {$value} {RATELIMIT} }
30098 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
30099 especially with the &%per_rcpt%& option, you may suffer from a performance
30100 bottleneck caused by locking on the ratelimit hints database. Apart from
30101 making your ACLs less complicated, you can reduce the problem by using a
30102 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
30103 this means that Exim will lose its hints data after a reboot (including retry
30104 hints, the callout cache, and ratelimit data).
30108 .section "Address verification" "SECTaddressverification"
30109 .cindex "verifying address" "options for"
30110 .cindex "policy control" "address verification"
30111 Several of the &%verify%& conditions described in section
30112 &<<SECTaclconditions>>& cause addresses to be verified. Section
30113 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
30114 The verification conditions can be followed by options that modify the
30115 verification process. The options are separated from the keyword and from each
30116 other by slashes, and some of them contain parameters. For example:
30118 verify = sender/callout
30119 verify = recipient/defer_ok/callout=10s,defer_ok
30121 The first stage of address verification, which always happens, is to run the
30122 address through the routers, in &"verify mode"&. Routers can detect the
30123 difference between verification and routing for delivery, and their actions can
30124 be varied by a number of generic options such as &%verify%& and &%verify_only%&
30125 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
30126 The available options are as follows:
30129 If the &%callout%& option is specified, successful routing to one or more
30130 remote hosts is followed by a &"callout"& to those hosts as an additional
30131 check. Callouts and their sub-options are discussed in the next section.
30133 If there is a defer error while doing verification routing, the ACL
30134 normally returns &"defer"&. However, if you include &%defer_ok%& in the
30135 options, the condition is forced to be true instead. Note that this is a main
30136 verification option as well as a suboption for callouts.
30138 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
30139 discusses the reporting of sender address verification failures.
30141 The &%success_on_redirect%& option causes verification always to succeed
30142 immediately after a successful redirection. By default, if a redirection
30143 generates just one address, that address is also verified. See further
30144 discussion in section &<<SECTredirwhilveri>>&.
30147 .cindex "verifying address" "differentiating failures"
30148 .vindex "&$recipient_verify_failure$&"
30149 .vindex "&$sender_verify_failure$&"
30150 .vindex "&$acl_verify_message$&"
30151 After an address verification failure, &$acl_verify_message$& contains the
30152 error message that is associated with the failure. It can be preserved by
30155 warn !verify = sender
30156 set acl_m0 = $acl_verify_message
30158 If you are writing your own custom rejection message or log message when
30159 denying access, you can use this variable to include information about the
30160 verification failure.
30162 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
30163 appropriate) contains one of the following words:
30166 &%qualify%&: The address was unqualified (no domain), and the message
30167 was neither local nor came from an exempted host.
30169 &%route%&: Routing failed.
30171 &%mail%&: Routing succeeded, and a callout was attempted; rejection
30172 occurred at or before the MAIL command (that is, on initial
30173 connection, HELO, or MAIL).
30175 &%recipient%&: The RCPT command in a callout was rejected.
30177 &%postmaster%&: The postmaster check in a callout was rejected.
30180 The main use of these variables is expected to be to distinguish between
30181 rejections of MAIL and rejections of RCPT in callouts.
30186 .section "Callout verification" "SECTcallver"
30187 .cindex "verifying address" "by callout"
30188 .cindex "callout" "verification"
30189 .cindex "SMTP" "callout verification"
30190 For non-local addresses, routing verifies the domain, but is unable to do any
30191 checking of the local part. There are situations where some means of verifying
30192 the local part is desirable. One way this can be done is to make an SMTP
30193 &'callback'& to a delivery host for the sender address or a &'callforward'& to
30194 a subsequent host for a recipient address, to see if the host accepts the
30195 address. We use the term &'callout'& to cover both cases. Note that for a
30196 sender address, the callback is not to the client host that is trying to
30197 deliver the message, but to one of the hosts that accepts incoming mail for the
30200 Exim does not do callouts by default. If you want them to happen, you must
30201 request them by setting appropriate options on the &%verify%& condition, as
30202 described below. This facility should be used with care, because it can add a
30203 lot of resource usage to the cost of verifying an address. However, Exim does
30204 cache the results of callouts, which helps to reduce the cost. Details of
30205 caching are in section &<<SECTcallvercache>>&.
30207 Recipient callouts are usually used only between hosts that are controlled by
30208 the same administration. For example, a corporate gateway host could use
30209 callouts to check for valid recipients on an internal mailserver. A successful
30210 callout does not guarantee that a real delivery to the address would succeed;
30211 on the other hand, a failing callout does guarantee that a delivery would fail.
30213 If the &%callout%& option is present on a condition that verifies an address, a
30214 second stage of verification occurs if the address is successfully routed to
30215 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
30216 &(manualroute)& router, where the router specifies the hosts. However, if a
30217 router that does not set up hosts routes to an &(smtp)& transport with a
30218 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
30219 &%hosts_override%& set, its hosts are always used, whether or not the router
30220 supplies a host list.
30221 Callouts are only supported on &(smtp)& transports.
30223 The port that is used is taken from the transport, if it is specified and is a
30224 remote transport. (For routers that do verification only, no transport need be
30225 specified.) Otherwise, the default SMTP port is used. If a remote transport
30226 specifies an outgoing interface, this is used; otherwise the interface is not
30227 specified. Likewise, the text that is used for the HELO command is taken from
30228 the transport's &%helo_data%& option; if there is no transport, the value of
30229 &$smtp_active_hostname$& is used.
30231 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
30232 test whether a bounce message could be delivered to the sender address. The
30233 following SMTP commands are sent:
30235 &`HELO `&<&'local host name'&>
30237 &`RCPT TO:`&<&'the address to be tested'&>
30240 LHLO is used instead of HELO if the transport's &%protocol%& option is
30243 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
30246 A recipient callout check is similar. By default, it also uses an empty address
30247 for the sender. This default is chosen because most hosts do not make use of
30248 the sender address when verifying a recipient. Using the same address means
30249 that a single cache entry can be used for each recipient. Some sites, however,
30250 do make use of the sender address when verifying. These are catered for by the
30251 &%use_sender%& and &%use_postmaster%& options, described in the next section.
30253 If the response to the RCPT command is a 2&'xx'& code, the verification
30254 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
30255 Exim tries the next host, if any. If there is a problem with all the remote
30256 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
30257 &%callout%& option is given, in which case the condition is forced to succeed.
30259 .cindex "SMTP" "output flushing, disabling for callout"
30260 A callout may take a little time. For this reason, Exim normally flushes SMTP
30261 output before performing a callout in an ACL, to avoid unexpected timeouts in
30262 clients when the SMTP PIPELINING extension is in use. The flushing can be
30263 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
30268 .section "Additional parameters for callouts" "CALLaddparcall"
30269 .cindex "callout" "additional parameters for"
30270 The &%callout%& option can be followed by an equals sign and a number of
30271 optional parameters, separated by commas. For example:
30273 verify = recipient/callout=10s,defer_ok
30275 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
30276 separate verify options, is retained for backwards compatibility, but is now
30277 deprecated. The additional parameters for &%callout%& are as follows:
30281 .vitem <&'a&~time&~interval'&>
30282 .cindex "callout" "timeout, specifying"
30283 This specifies the timeout that applies for the callout attempt to each host.
30286 verify = sender/callout=5s
30288 The default is 30 seconds. The timeout is used for each response from the
30289 remote host. It is also used for the initial connection, unless overridden by
30290 the &%connect%& parameter.
30293 .vitem &*connect&~=&~*&<&'time&~interval'&>
30294 .cindex "callout" "connection timeout, specifying"
30295 This parameter makes it possible to set a different (usually smaller) timeout
30296 for making the SMTP connection. For example:
30298 verify = sender/callout=5s,connect=1s
30300 If not specified, this timeout defaults to the general timeout value.
30302 .vitem &*defer_ok*&
30303 .cindex "callout" "defer, action on"
30304 When this parameter is present, failure to contact any host, or any other kind
30305 of temporary error, is treated as success by the ACL. However, the cache is not
30306 updated in this circumstance.
30308 .vitem &*fullpostmaster*&
30309 .cindex "callout" "full postmaster check"
30310 This operates like the &%postmaster%& option (see below), but if the check for
30311 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
30312 accordance with the specification in RFC 2821. The RFC states that the
30313 unqualified address &'postmaster'& should be accepted.
30316 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
30317 .cindex "callout" "sender when verifying header"
30318 When verifying addresses in header lines using the &%header_sender%&
30319 verification option, Exim behaves by default as if the addresses are envelope
30320 sender addresses from a message. Callout verification therefore tests to see
30321 whether a bounce message could be delivered, by using an empty address in the
30322 MAIL command. However, it is arguable that these addresses might never be used
30323 as envelope senders, and could therefore justifiably reject bounce messages
30324 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
30325 address to use in the MAIL command. For example:
30327 require verify = header_sender/callout=mailfrom=abcd@x.y.z
30329 This parameter is available only for the &%header_sender%& verification option.
30332 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
30333 .cindex "callout" "overall timeout, specifying"
30334 This parameter sets an overall timeout for performing a callout verification.
30337 verify = sender/callout=5s,maxwait=30s
30339 This timeout defaults to four times the callout timeout for individual SMTP
30340 commands. The overall timeout applies when there is more than one host that can
30341 be tried. The timeout is checked before trying the next host. This prevents
30342 very long delays if there are a large number of hosts and all are timing out
30343 (for example, when network connections are timing out).
30346 .vitem &*no_cache*&
30347 .cindex "callout" "cache, suppressing"
30348 .cindex "caching callout, suppressing"
30349 When this parameter is given, the callout cache is neither read nor updated.
30351 .vitem &*postmaster*&
30352 .cindex "callout" "postmaster; checking"
30353 When this parameter is set, a successful callout check is followed by a similar
30354 check for the local part &'postmaster'& at the same domain. If this address is
30355 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
30356 the postmaster check is recorded in a cache record; if it is a failure, this is
30357 used to fail subsequent callouts for the domain without a connection being
30358 made, until the cache record expires.
30360 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
30361 The postmaster check uses an empty sender in the MAIL command by default.
30362 You can use this parameter to do a postmaster check using a different address.
30365 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
30367 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
30368 one overrides. The &%postmaster%& parameter is equivalent to this example:
30370 require verify = sender/callout=postmaster_mailfrom=
30372 &*Warning*&: The caching arrangements for postmaster checking do not take
30373 account of the sender address. It is assumed that either the empty address or
30374 a fixed non-empty address will be used. All that Exim remembers is that the
30375 postmaster check for the domain succeeded or failed.
30379 .cindex "callout" "&""random""& check"
30380 When this parameter is set, before doing the normal callout check, Exim does a
30381 check for a &"random"& local part at the same domain. The local part is not
30382 really random &-- it is defined by the expansion of the option
30383 &%callout_random_local_part%&, which defaults to
30385 $primary_hostname-$tod_epoch-testing
30387 The idea here is to try to determine whether the remote host accepts all local
30388 parts without checking. If it does, there is no point in doing callouts for
30389 specific local parts. If the &"random"& check succeeds, the result is saved in
30390 a cache record, and used to force the current and subsequent callout checks to
30391 succeed without a connection being made, until the cache record expires.
30393 .vitem &*use_postmaster*&
30394 .cindex "callout" "sender for recipient check"
30395 This parameter applies to recipient callouts only. For example:
30397 deny !verify = recipient/callout=use_postmaster
30399 .vindex "&$qualify_domain$&"
30400 It causes a non-empty postmaster address to be used in the MAIL command when
30401 performing the callout for the recipient, and also for a &"random"& check if
30402 that is configured. The local part of the address is &`postmaster`& and the
30403 domain is the contents of &$qualify_domain$&.
30405 .vitem &*use_sender*&
30406 This option applies to recipient callouts only. For example:
30408 require verify = recipient/callout=use_sender
30410 It causes the message's actual sender address to be used in the MAIL
30411 command when performing the callout, instead of an empty address. There is no
30412 need to use this option unless you know that the called hosts make use of the
30413 sender when checking recipients. If used indiscriminately, it reduces the
30414 usefulness of callout caching.
30417 If you use any of the parameters that set a non-empty sender for the MAIL
30418 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
30419 &%use_sender%&), you should think about possible loops. Recipient checking is
30420 usually done between two hosts that are under the same management, and the host
30421 that receives the callouts is not normally configured to do callouts itself.
30422 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
30423 these circumstances.
30425 However, if you use a non-empty sender address for a callout to an arbitrary
30426 host, there is the likelihood that the remote host will itself initiate a
30427 callout check back to your host. As it is checking what appears to be a message
30428 sender, it is likely to use an empty address in MAIL, thus avoiding a
30429 callout loop. However, to be on the safe side it would be best to set up your
30430 own ACLs so that they do not do sender verification checks when the recipient
30431 is the address you use for header sender or postmaster callout checking.
30433 Another issue to think about when using non-empty senders for callouts is
30434 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
30435 by the sender/recipient combination; thus, for any given recipient, many more
30436 actual callouts are performed than when an empty sender or postmaster is used.
30441 .section "Callout caching" "SECTcallvercache"
30442 .cindex "hints database" "callout cache"
30443 .cindex "callout" "cache, description of"
30444 .cindex "caching" "callout"
30445 Exim caches the results of callouts in order to reduce the amount of resources
30446 used, unless you specify the &%no_cache%& parameter with the &%callout%&
30447 option. A hints database called &"callout"& is used for the cache. Two
30448 different record types are used: one records the result of a callout check for
30449 a specific address, and the other records information that applies to the
30450 entire domain (for example, that it accepts the local part &'postmaster'&).
30452 When an original callout fails, a detailed SMTP error message is given about
30453 the failure. However, for subsequent failures use the cache data, this message
30456 The expiry times for negative and positive address cache records are
30457 independent, and can be set by the global options &%callout_negative_expire%&
30458 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
30460 If a host gives a negative response to an SMTP connection, or rejects any
30461 commands up to and including
30465 (but not including the MAIL command with a non-empty address),
30466 any callout attempt is bound to fail. Exim remembers such failures in a
30467 domain cache record, which it uses to fail callouts for the domain without
30468 making new connections, until the domain record times out. There are two
30469 separate expiry times for domain cache records:
30470 &%callout_domain_negative_expire%& (default 3h) and
30471 &%callout_domain_positive_expire%& (default 7d).
30473 Domain records expire when the negative expiry time is reached if callouts
30474 cannot be made for the domain, or if the postmaster check failed.
30475 Otherwise, they expire when the positive expiry time is reached. This
30476 ensures that, for example, a host that stops accepting &"random"& local parts
30477 will eventually be noticed.
30479 The callout caching mechanism is based on the domain of the address that is
30480 being tested. If the domain routes to several hosts, it is assumed that their
30481 behaviour will be the same.
30485 .section "Sender address verification reporting" "SECTsenaddver"
30486 .cindex "verifying" "suppressing error details"
30487 See section &<<SECTaddressverification>>& for a general discussion of
30488 verification. When sender verification fails in an ACL, the details of the
30489 failure are given as additional output lines before the 550 response to the
30490 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
30493 MAIL FROM:<xyz@abc.example>
30495 RCPT TO:<pqr@def.example>
30496 550-Verification failed for <xyz@abc.example>
30497 550-Called: 192.168.34.43
30498 550-Sent: RCPT TO:<xyz@abc.example>
30499 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
30500 550 Sender verification failed
30502 If more than one RCPT command fails in the same way, the details are given
30503 only for the first of them. However, some administrators do not want to send
30504 out this much information. You can suppress the details by adding
30505 &`/no_details`& to the ACL statement that requests sender verification. For
30508 verify = sender/no_details
30511 .section "Redirection while verifying" "SECTredirwhilveri"
30512 .cindex "verifying" "redirection while"
30513 .cindex "address redirection" "while verifying"
30514 A dilemma arises when a local address is redirected by aliasing or forwarding
30515 during verification: should the generated addresses themselves be verified,
30516 or should the successful expansion of the original address be enough to verify
30517 it? By default, Exim takes the following pragmatic approach:
30520 When an incoming address is redirected to just one child address, verification
30521 continues with the child address, and if that fails to verify, the original
30522 verification also fails.
30524 When an incoming address is redirected to more than one child address,
30525 verification does not continue. A success result is returned.
30528 This seems the most reasonable behaviour for the common use of aliasing as a
30529 way of redirecting different local parts to the same mailbox. It means, for
30530 example, that a pair of alias entries of the form
30533 aw123: :fail: Gone away, no forwarding address
30535 work as expected, with both local parts causing verification failure. When a
30536 redirection generates more than one address, the behaviour is more like a
30537 mailing list, where the existence of the alias itself is sufficient for
30538 verification to succeed.
30540 It is possible, however, to change the default behaviour so that all successful
30541 redirections count as successful verifications, however many new addresses are
30542 generated. This is specified by the &%success_on_redirect%& verification
30543 option. For example:
30545 require verify = recipient/success_on_redirect/callout=10s
30547 In this example, verification succeeds if a router generates a new address, and
30548 the callout does not occur, because no address was routed to a remote host.
30550 When verification is being tested via the &%-bv%& option, the treatment of
30551 redirections is as just described, unless the &%-v%& or any debugging option is
30552 also specified. In that case, full verification is done for every generated
30553 address and a report is output for each of them.
30557 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
30558 .cindex "CSA" "verifying"
30559 Client SMTP Authorization is a system that allows a site to advertise
30560 which machines are and are not permitted to send email. This is done by placing
30561 special SRV records in the DNS; these are looked up using the client's HELO
30562 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
30563 Authorization checks in Exim are performed by the ACL condition:
30567 This fails if the client is not authorized. If there is a DNS problem, or if no
30568 valid CSA SRV record is found, or if the client is authorized, the condition
30569 succeeds. These three cases can be distinguished using the expansion variable
30570 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
30571 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
30572 be likely to cause problems for legitimate email.
30574 The error messages produced by the CSA code include slightly more
30575 detail. If &$csa_status$& is &"defer"&, this may be because of problems
30576 looking up the CSA SRV record, or problems looking up the CSA target
30577 address record. There are four reasons for &$csa_status$& being &"fail"&:
30580 The client's host name is explicitly not authorized.
30582 The client's IP address does not match any of the CSA target IP addresses.
30584 The client's host name is authorized but it has no valid target IP addresses
30585 (for example, the target's addresses are IPv6 and the client is using IPv4).
30587 The client's host name has no CSA SRV record but a parent domain has asserted
30588 that all subdomains must be explicitly authorized.
30591 The &%csa%& verification condition can take an argument which is the domain to
30592 use for the DNS query. The default is:
30594 verify = csa/$sender_helo_name
30596 This implementation includes an extension to CSA. If the query domain
30597 is an address literal such as [192.0.2.95], or if it is a bare IP
30598 address, Exim searches for CSA SRV records in the reverse DNS as if
30599 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
30602 verify = csa/$sender_host_address
30604 In fact, this is the check that Exim performs if the client does not say HELO.
30605 This extension can be turned off by setting the main configuration option
30606 &%dns_csa_use_reverse%& to be false.
30608 If a CSA SRV record is not found for the domain itself, a search
30609 is performed through its parent domains for a record which might be
30610 making assertions about subdomains. The maximum depth of this search is limited
30611 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
30612 default. Exim does not look for CSA SRV records in a top level domain, so the
30613 default settings handle HELO domains as long as seven
30614 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
30615 of legitimate HELO domains.
30617 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
30618 direct SRV lookups, this is not sufficient because of the extra parent domain
30619 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
30620 addresses into lookups in the reverse DNS space. The result of a successful
30623 ${lookup dnsdb {csa=$sender_helo_name}}
30625 has two space-separated fields: an authorization code and a target host name.
30626 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
30627 authorization required but absent, or &"?"& for unknown.
30632 .section "Bounce address tag validation" "SECTverifyPRVS"
30633 .cindex "BATV, verifying"
30634 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
30635 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
30636 Genuine incoming bounce messages should therefore always be addressed to
30637 recipients that have a valid tag. This scheme is a way of detecting unwanted
30638 bounce messages caused by sender address forgeries (often called &"collateral
30639 spam"&), because the recipients of such messages do not include valid tags.
30641 There are two expansion items to help with the implementation of the BATV
30642 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
30643 the original envelope sender address by using a simple key to add a hash of the
30644 address and some time-based randomizing information. The &%prvs%& expansion
30645 item creates a signed address, and the &%prvscheck%& expansion item checks one.
30646 The syntax of these expansion items is described in section
30647 &<<SECTexpansionitems>>&.
30649 As an example, suppose the secret per-address keys are stored in an MySQL
30650 database. A query to look up the key for an address could be defined as a macro
30653 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
30654 WHERE sender='${quote_mysql:$prvscheck_address}'\
30657 Suppose also that the senders who make use of BATV are defined by an address
30658 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
30661 # Bounces: drop unsigned addresses for BATV senders
30662 deny message = This address does not send an unsigned reverse path
30664 recipients = +batv_senders
30666 # Bounces: In case of prvs-signed address, check signature.
30667 deny message = Invalid reverse path signature.
30669 condition = ${prvscheck {$local_part@$domain}\
30670 {PRVSCHECK_SQL}{1}}
30671 !condition = $prvscheck_result
30673 The first statement rejects recipients for bounce messages that are addressed
30674 to plain BATV sender addresses, because it is known that BATV senders do not
30675 send out messages with plain sender addresses. The second statement rejects
30676 recipients that are prvs-signed, but with invalid signatures (either because
30677 the key is wrong, or the signature has timed out).
30679 A non-prvs-signed address is not rejected by the second statement, because the
30680 &%prvscheck%& expansion yields an empty string if its first argument is not a
30681 prvs-signed address, thus causing the &%condition%& condition to be false. If
30682 the first argument is a syntactically valid prvs-signed address, the yield is
30683 the third string (in this case &"1"&), whether or not the cryptographic and
30684 timeout checks succeed. The &$prvscheck_result$& variable contains the result
30685 of the checks (empty for failure, &"1"& for success).
30687 There is one more issue you must consider when implementing prvs-signing:
30688 you have to ensure that the routers accept prvs-signed addresses and
30689 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
30690 router to remove the signature with a configuration along these lines:
30694 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
30696 This works because, if the third argument of &%prvscheck%& is empty, the result
30697 of the expansion of a prvs-signed address is the decoded value of the original
30698 address. This router should probably be the first of your routers that handles
30701 To create BATV-signed addresses in the first place, a transport of this form
30704 external_smtp_batv:
30706 return_path = ${prvs {$return_path} \
30707 {${lookup mysql{SELECT \
30708 secret FROM batv_prvs WHERE \
30709 sender='${quote_mysql:$sender_address}'} \
30712 If no key can be found for the existing return path, no signing takes place.
30716 .section "Using an ACL to control relaying" "SECTrelaycontrol"
30717 .cindex "&ACL;" "relay control"
30718 .cindex "relaying" "control by ACL"
30719 .cindex "policy control" "relay control"
30720 An MTA is said to &'relay'& a message if it receives it from some host and
30721 delivers it directly to another host as a result of a remote address contained
30722 within it. Redirecting a local address via an alias or forward file and then
30723 passing the message on to another host is not relaying,
30724 .cindex "&""percent hack""&"
30725 but a redirection as a result of the &"percent hack"& is.
30727 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
30728 A host which is acting as a gateway or an MX backup is concerned with incoming
30729 relaying from arbitrary hosts to a specific set of domains. On the other hand,
30730 a host which is acting as a smart host for a number of clients is concerned
30731 with outgoing relaying from those clients to the Internet at large. Often the
30732 same host is fulfilling both functions,
30734 . as illustrated in the diagram below,
30736 but in principle these two kinds of relaying are entirely independent. What is
30737 not wanted is the transmission of mail from arbitrary remote hosts through your
30738 system to arbitrary domains.
30741 You can implement relay control by means of suitable statements in the ACL that
30742 runs for each RCPT command. For convenience, it is often easiest to use
30743 Exim's named list facility to define the domains and hosts involved. For
30744 example, suppose you want to do the following:
30747 Deliver a number of domains to mailboxes on the local host (or process them
30748 locally in some other way). Let's say these are &'my.dom1.example'& and
30749 &'my.dom2.example'&.
30751 Relay mail for a number of other domains for which you are the secondary MX.
30752 These might be &'friend1.example'& and &'friend2.example'&.
30754 Relay mail from the hosts on your local LAN, to whatever domains are involved.
30755 Suppose your LAN is 192.168.45.0/24.
30759 In the main part of the configuration, you put the following definitions:
30761 domainlist local_domains = my.dom1.example : my.dom2.example
30762 domainlist relay_to_domains = friend1.example : friend2.example
30763 hostlist relay_from_hosts = 192.168.45.0/24
30765 Now you can use these definitions in the ACL that is run for every RCPT
30769 accept domains = +local_domains : +relay_to_domains
30770 accept hosts = +relay_from_hosts
30772 The first statement accepts any RCPT command that contains an address in
30773 the local or relay domains. For any other domain, control passes to the second
30774 statement, which accepts the command only if it comes from one of the relay
30775 hosts. In practice, you will probably want to make your ACL more sophisticated
30776 than this, for example, by including sender and recipient verification. The
30777 default configuration includes a more comprehensive example, which is described
30778 in chapter &<<CHAPdefconfil>>&.
30782 .section "Checking a relay configuration" "SECTcheralcon"
30783 .cindex "relaying" "checking control of"
30784 You can check the relay characteristics of your configuration in the same way
30785 that you can test any ACL behaviour for an incoming SMTP connection, by using
30786 the &%-bh%& option to run a fake SMTP session with which you interact.
30788 For specifically testing for unwanted relaying, the host
30789 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
30790 host from the host on which Exim is running, using the normal telnet port, you
30791 will see a normal telnet connection message and then quite a long delay. Be
30792 patient. The remote host is making an SMTP connection back to your host, and
30793 trying a number of common probes to test for open relay vulnerability. The
30794 results of the tests will eventually appear on your terminal.
30799 . ////////////////////////////////////////////////////////////////////////////
30800 . ////////////////////////////////////////////////////////////////////////////
30802 .chapter "Content scanning at ACL time" "CHAPexiscan"
30803 .scindex IIDcosca "content scanning" "at ACL time"
30804 The extension of Exim to include content scanning at ACL time, formerly known
30805 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
30806 was integrated into the main source for Exim release 4.50, and Tom continues to
30807 maintain it. Most of the wording of this chapter is taken from Tom's
30810 It is also possible to scan the content of messages at other times. The
30811 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
30812 scanning after all the ACLs have run. A transport filter can be used to scan
30813 messages at delivery time (see the &%transport_filter%& option, described in
30814 chapter &<<CHAPtransportgeneric>>&).
30816 If you want to include the ACL-time content-scanning features when you compile
30817 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
30818 &_Local/Makefile_&. When you do that, the Exim binary is built with:
30821 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
30822 for all MIME parts for SMTP and non-SMTP messages, respectively.
30824 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
30825 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
30826 run at the end of message reception (the &%acl_smtp_data%& ACL).
30828 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
30829 of messages, or parts of messages, for debugging purposes.
30831 Additional expansion variables that are set in the new ACL and by the new
30834 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
30837 There is another content-scanning configuration option for &_Local/Makefile_&,
30838 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
30839 condition is compiled, in addition to all the other content-scanning features.
30841 Content-scanning is continually evolving, and new features are still being
30842 added. While such features are still unstable and liable to incompatible
30843 changes, they are made available in Exim by setting options whose names begin
30844 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
30845 this manual. You can find out about them by reading the file called
30846 &_doc/experimental.txt_&.
30848 All the content-scanning facilities work on a MBOX copy of the message that is
30849 temporarily created in a file called:
30851 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
30853 The &_.eml_& extension is a friendly hint to virus scanners that they can
30854 expect an MBOX-like structure inside that file. The file is created when the
30855 first content scanning facility is called. Subsequent calls to content
30856 scanning conditions open the same file again. The directory is recursively
30857 removed when the &%acl_smtp_data%& ACL has finished running, unless
30859 control = no_mbox_unspool
30861 has been encountered. When the MIME ACL decodes files, they are put into the
30862 same directory by default.
30866 .section "Scanning for viruses" "SECTscanvirus"
30867 .cindex "virus scanning"
30868 .cindex "content scanning" "for viruses"
30869 .cindex "content scanning" "the &%malware%& condition"
30870 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
30871 It supports a &"generic"& interface to scanners called via the shell, and
30872 specialized interfaces for &"daemon"& type virus scanners, which are resident
30873 in memory and thus are much faster.
30875 A timeout of 2 minutes is applied to a scanner call (by default);
30876 if it expires then a defer action is taken.
30878 .oindex "&%av_scanner%&"
30879 You can set the &%av_scanner%& option in the main part of the configuration
30880 to specify which scanner to use, together with any additional options that
30881 are needed. The basic syntax is as follows:
30883 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
30885 If you do not set &%av_scanner%&, it defaults to
30887 av_scanner = sophie:/var/run/sophie
30889 If the value of &%av_scanner%& starts with a dollar character, it is expanded
30891 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
30892 The following scanner types are supported in this release:
30896 .cindex "virus scanners" "avast"
30897 This is the scanner daemon of Avast. It has been tested with Avast Core
30898 Security (currently at version 1.1.7).
30899 You can get a trial version at &url(http://www.avast.com) or for Linux
30900 at &url(http://www.avast.com/linux-server-antivirus).
30901 This scanner type takes one option,
30902 which can be either a full path to a UNIX socket,
30903 or host and port specifiers separated by white space.
30904 The host may be a name or an IP address; the port is either a
30905 single number or a pair of numbers with a dash between.
30906 Any further options are given, on separate lines,
30907 to the daemon as options before the main scan command.
30910 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
30911 av_scanner = avast:192.168.2.22 5036
30913 If you omit the argument, the default path
30914 &_/var/run/avast/scan.sock_&
30916 If you use a remote host,
30917 you need to make Exim's spool directory available to it,
30918 as the scanner is passed a file path, not file contents.
30919 For information about available commands and their options you may use
30921 $ socat UNIX:/var/run/avast/scan.sock STDIO:
30928 .vitem &%aveserver%&
30929 .cindex "virus scanners" "Kaspersky"
30930 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
30931 at &url(http://www.kaspersky.com). This scanner type takes one option,
30932 which is the path to the daemon's UNIX socket. The default is shown in this
30935 av_scanner = aveserver:/var/run/aveserver
30940 .cindex "virus scanners" "clamd"
30941 This daemon-type scanner is GPL and free. You can get it at
30942 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
30943 unpack MIME containers, so it used to be recommended to unpack MIME attachments
30944 in the MIME ACL. This is no longer believed to be necessary.
30946 The options are a list of server specifiers, which may be
30947 a UNIX socket specification,
30948 a TCP socket specification,
30949 or a (global) option.
30951 A socket specification consists of a space-separated list.
30952 For a Unix socket the first element is a full path for the socket,
30953 for a TCP socket the first element is the IP address
30954 and the second a port number,
30955 Any further elements are per-server (non-global) options.
30956 These per-server options are supported:
30958 retry=<timespec> Retry on connect fail
30961 The &`retry`& option specifies a time after which a single retry for
30962 a failed connect is made. The default is to not retry.
30964 If a Unix socket file is specified, only one server is supported.
30968 av_scanner = clamd:/opt/clamd/socket
30969 av_scanner = clamd:192.0.2.3 1234
30970 av_scanner = clamd:192.0.2.3 1234:local
30971 av_scanner = clamd:192.0.2.3 1234 retry=10s
30972 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
30974 If the value of av_scanner points to a UNIX socket file or contains the
30976 option, then the ClamAV interface will pass a filename containing the data
30977 to be scanned, which will should normally result in less I/O happening and be
30978 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
30979 Exim does not assume that there is a common filesystem with the remote host.
30980 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
30981 you be running a version of ClamAV prior to 0.95.
30983 The final example shows that multiple TCP targets can be specified. Exim will
30984 randomly use one for each incoming email (i.e. it load balances them). Note
30985 that only TCP targets may be used if specifying a list of scanners; a UNIX
30986 socket cannot be mixed in with TCP targets. If one of the servers becomes
30987 unavailable, Exim will try the remaining one(s) until it finds one that works.
30988 When a clamd server becomes unreachable, Exim will log a message. Exim does
30989 not keep track of scanner state between multiple messages, and the scanner
30990 selection is random, so the message will get logged in the mainlog for each
30991 email that the down scanner gets chosen first (message wrapped to be readable):
30993 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
30994 clamd: connection to localhost, port 3310 failed
30995 (Connection refused)
30998 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
30999 contributing the code for this scanner.
31002 .cindex "virus scanners" "command line interface"
31003 This is the keyword for the generic command line scanner interface. It can be
31004 used to attach virus scanners that are invoked from the shell. This scanner
31005 type takes 3 mandatory options:
31008 The full path and name of the scanner binary, with all command line options,
31009 and a placeholder (&`%s`&) for the directory to scan.
31012 A regular expression to match against the STDOUT and STDERR output of the
31013 virus scanner. If the expression matches, a virus was found. You must make
31014 absolutely sure that this expression matches on &"virus found"&. This is called
31015 the &"trigger"& expression.
31018 Another regular expression, containing exactly one pair of parentheses, to
31019 match the name of the virus found in the scanners output. This is called the
31020 &"name"& expression.
31023 For example, Sophos Sweep reports a virus on a line like this:
31025 Virus 'W32/Magistr-B' found in file ./those.bat
31027 For the trigger expression, we can match the phrase &"found in file"&. For the
31028 name expression, we want to extract the W32/Magistr-B string, so we can match
31029 for the single quotes left and right of it. Altogether, this makes the
31030 configuration setting:
31032 av_scanner = cmdline:\
31033 /path/to/sweep -ss -all -rec -archive %s:\
31034 found in file:'(.+)'
31037 .cindex "virus scanners" "DrWeb"
31038 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface
31040 either a full path to a UNIX socket,
31041 or host and port specifiers separated by white space.
31042 The host may be a name or an IP address; the port is either a
31043 single number or a pair of numbers with a dash between.
31046 av_scanner = drweb:/var/run/drwebd.sock
31047 av_scanner = drweb:192.168.2.20 31337
31049 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
31050 is used. Thanks to Alex Miller for contributing the code for this scanner.
31053 .cindex "virus scanners" "f-protd"
31054 The f-protd scanner is accessed via HTTP over TCP.
31055 One argument is taken, being a space-separated hostname and port number
31059 av_scanner = f-protd:localhost 10200-10204
31061 If you omit the argument, the default values show above are used.
31064 .cindex "virus scanners" "F-Secure"
31065 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
31066 argument which is the path to a UNIX socket. For example:
31068 av_scanner = fsecure:/path/to/.fsav
31070 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
31071 Thelmen for contributing the code for this scanner.
31073 .vitem &%kavdaemon%&
31074 .cindex "virus scanners" "Kaspersky"
31075 This is the scanner daemon of Kaspersky Version 4. This version of the
31076 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
31077 scanner type takes one option, which is the path to the daemon's UNIX socket.
31080 av_scanner = kavdaemon:/opt/AVP/AvpCtl
31082 The default path is &_/var/run/AvpCtl_&.
31085 .cindex "virus scanners" "mksd"
31086 This is a daemon type scanner that is aimed mainly at Polish users, though some
31087 parts of documentation are now available in English. You can get it at
31088 &url(http://linux.mks.com.pl/). The only option for this scanner type is
31089 the maximum number of processes used simultaneously to scan the attachments,
31090 provided that the demime facility is employed and also provided that mksd has
31091 been run with at least the same number of child processes. For example:
31093 av_scanner = mksd:2
31095 You can safely omit this option (the default value is 1).
31098 .cindex "virus scanners" "simple socket-connected"
31099 This is a general-purpose way of talking to simple scanner daemons
31100 running on the local machine.
31101 There are four options:
31102 an address (which may be an IP address and port, or the path of a Unix socket),
31103 a commandline to send (may include a single %s which will be replaced with
31104 the path to the mail file to be scanned),
31105 an RE to trigger on from the returned data,
31106 an RE to extract malware_name from the returned data.
31109 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
31111 Default for the socket specifier is &_/tmp/malware.sock_&.
31112 Default for the commandline is &_%s\n_&.
31113 Both regular-expressions are required.
31116 .cindex "virus scanners" "Sophos and Sophie"
31117 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
31118 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
31119 for this scanner type is the path to the UNIX socket that Sophie uses for
31120 client communication. For example:
31122 av_scanner = sophie:/tmp/sophie
31124 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
31128 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
31129 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
31132 The &%av_scanner%& option is expanded each time &%malware%& is called. This
31133 makes it possible to use different scanners. See further below for an example.
31134 The &%malware%& condition caches its results, so when you use it multiple times
31135 for the same message, the actual scanning process is only carried out once.
31136 However, using expandable items in &%av_scanner%& disables this caching, in
31137 which case each use of the &%malware%& condition causes a new scan of the
31140 The &%malware%& condition takes a right-hand argument that is expanded before
31141 use and taken as a list, slash-separated by default.
31142 The first element can then be one of
31145 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
31146 The condition succeeds if a virus was found, and fail otherwise. This is the
31149 &"false"& or &"0"& or an empty string, in which case no scanning is done and
31150 the condition fails immediately.
31152 A regular expression, in which case the message is scanned for viruses. The
31153 condition succeeds if a virus is found and its name matches the regular
31154 expression. This allows you to take special actions on certain types of virus.
31155 Note that &"/"& characters in the RE must be doubled due to the list-processing,
31156 unless the separator is changed (in the usual way).
31159 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
31160 messages even if there is a problem with the virus scanner.
31161 Otherwise, such a problem causes the ACL to defer.
31163 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
31164 specify a non-default timeout. The default is two minutes.
31167 malware = * / defer_ok / tmo=10s
31169 A timeout causes the ACL to defer.
31171 .vindex "&$callout_address$&"
31172 When a connection is made to the scanner the expansion variable &$callout_address$&
31173 is set to record the actual address used.
31175 .vindex "&$malware_name$&"
31176 When a virus is found, the condition sets up an expansion variable called
31177 &$malware_name$& that contains the name of the virus. You can use it in a
31178 &%message%& modifier that specifies the error returned to the sender, and/or in
31181 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
31182 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
31183 &%malware%& condition.
31185 Beware the interaction of Exim's &%message_size_limit%& with any size limits
31186 imposed by your anti-virus scanner.
31188 Here is a very simple scanning example:
31190 deny message = This message contains malware ($malware_name)
31194 The next example accepts messages when there is a problem with the scanner:
31196 deny message = This message contains malware ($malware_name)
31198 malware = */defer_ok
31200 The next example shows how to use an ACL variable to scan with both sophie and
31201 aveserver. It assumes you have set:
31203 av_scanner = $acl_m0
31205 in the main Exim configuration.
31207 deny message = This message contains malware ($malware_name)
31208 set acl_m0 = sophie
31211 deny message = This message contains malware ($malware_name)
31212 set acl_m0 = aveserver
31217 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
31218 .cindex "content scanning" "for spam"
31219 .cindex "spam scanning"
31220 .cindex "SpamAssassin"
31222 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
31223 score and a report for the message.
31224 Support is also provided for Rspamd.
31226 For more information about installation and configuration of SpamAssassin or
31227 Rspamd refer to their respective websites at
31228 &url(http://spamassassin.apache.org) and &url(http://www.rspamd.com)
31230 SpamAssassin can be installed with CPAN by running:
31232 perl -MCPAN -e 'install Mail::SpamAssassin'
31234 SpamAssassin has its own set of configuration files. Please review its
31235 documentation to see how you can tweak it. The default installation should work
31238 .oindex "&%spamd_address%&"
31239 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
31240 intend to use an instance running on the local host you do not need to set
31241 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
31242 you must set the &%spamd_address%& option in the global part of the Exim
31243 configuration as follows (example):
31245 spamd_address = 192.168.99.45 387
31248 To use Rspamd (which by default listens on all local addresses
31250 you should add &%variant=rspamd%& after the address/port pair, for example:
31252 spamd_address = 127.0.0.1 11333 variant=rspamd
31255 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
31256 sockets. If you want to us these, supply &%spamd_address%& with an absolute
31257 file name instead of an address/port pair:
31259 spamd_address = /var/run/spamd_socket
31261 You can have multiple &%spamd%& servers to improve scalability. These can
31262 reside on other hardware reachable over the network. To specify multiple
31263 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
31264 option, separated with colons (the separator can be changed in the usual way):
31266 spamd_address = 192.168.2.10 783 : \
31267 192.168.2.11 783 : \
31270 Up to 32 &%spamd%& servers are supported.
31271 When a server fails to respond to the connection attempt, all other
31272 servers are tried until one succeeds. If no server responds, the &%spam%&
31275 Unix and TCP socket specifications may be mixed in any order.
31276 Each element of the list is a list itself, space-separated by default
31277 and changeable in the usual way.
31279 For TCP socket specifications a host name or IP (v4 or v6, but
31280 subject to list-separator quoting rules) address can be used,
31281 and the port can be one or a dash-separated pair.
31282 In the latter case, the range is tried in strict order.
31284 Elements after the first for Unix sockets, or second for TCP socket,
31286 The supported options are:
31288 pri=<priority> Selection priority
31289 weight=<value> Selection bias
31290 time=<start>-<end> Use only between these times of day
31291 retry=<timespec> Retry on connect fail
31292 tmo=<timespec> Connection time limit
31293 variant=rspamd Use Rspamd rather than SpamAssassin protocol
31296 The &`pri`& option specifies a priority for the server within the list,
31297 higher values being tried first.
31298 The default priority is 1.
31300 The &`weight`& option specifies a selection bias.
31301 Within a priority set
31302 servers are queried in a random fashion, weighted by this value.
31303 The default value for selection bias is 1.
31305 Time specifications for the &`time`& option are <hour>.<minute>.<second>
31306 in the local time zone; each element being one or more digits.
31307 Either the seconds or both minutes and seconds, plus the leading &`.`&
31308 characters, may be omitted and will be taken as zero.
31310 Timeout specifications for the &`retry`& and &`tmo`& options
31311 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
31313 The &`tmo`& option specifies an overall timeout for communication.
31314 The default value is two minutes.
31316 The &`retry`& option specifies a time after which a single retry for
31317 a failed connect is made.
31318 The default is to not retry.
31320 The &%spamd_address%& variable is expanded before use if it starts with
31321 a dollar sign. In this case, the expansion may return a string that is
31322 used as the list so that multiple spamd servers can be the result of an
31325 .vindex "&$callout_address$&"
31326 When a connection is made to the server the expansion variable &$callout_address$&
31327 is set to record the actual address used.
31329 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
31330 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
31332 deny message = This message was classified as SPAM
31335 The right-hand side of the &%spam%& condition specifies a name. This is
31336 relevant if you have set up multiple SpamAssassin profiles. If you do not want
31337 to scan using a specific profile, but rather use the SpamAssassin system-wide
31338 default profile, you can scan for an unknown name, or simply use &"nobody"&.
31339 Rspamd does not use this setting. However, you must put something on the
31342 The name allows you to use per-domain or per-user antispam profiles in
31343 principle, but this is not straightforward in practice, because a message may
31344 have multiple recipients, not necessarily all in the same domain. Because the
31345 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
31346 read the contents of the message, the variables &$local_part$& and &$domain$&
31348 Careful enforcement of single-recipient messages
31349 (e.g. by responding with defer in the recipient ACL for all recipients
31351 or the use of PRDR,
31352 .cindex "PRDR" "use for per-user SpamAssassin profiles"
31353 are needed to use this feature.
31355 The right-hand side of the &%spam%& condition is expanded before being used, so
31356 you can put lookups or conditions there. When the right-hand side evaluates to
31357 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
31360 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
31361 large ones may cause significant performance degradation. As most spam messages
31362 are quite small, it is recommended that you do not scan the big ones. For
31365 deny message = This message was classified as SPAM
31366 condition = ${if < {$message_size}{10K}}
31370 The &%spam%& condition returns true if the threshold specified in the user's
31371 SpamAssassin profile has been matched or exceeded. If you want to use the
31372 &%spam%& condition for its side effects (see the variables below), you can make
31373 it always return &"true"& by appending &`:true`& to the username.
31375 .cindex "spam scanning" "returned variables"
31376 When the &%spam%& condition is run, it sets up a number of expansion
31378 Except for &$spam_report$&,
31379 these variables are saved with the received message so are
31380 available for use at delivery time.
31383 .vitem &$spam_score$&
31384 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
31385 for inclusion in log or reject messages.
31387 .vitem &$spam_score_int$&
31388 The spam score of the message, multiplied by ten, as an integer value. For
31389 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
31390 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
31391 The integer value is useful for numeric comparisons in conditions.
31393 .vitem &$spam_bar$&
31394 A string consisting of a number of &"+"& or &"-"& characters, representing the
31395 integer part of the spam score value. A spam score of 4.4 would have a
31396 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
31397 headers, since MUAs can match on such strings. The maximum length of the
31398 spam bar is 50 characters.
31400 .vitem &$spam_report$&
31401 A multiline text table, containing the full SpamAssassin report for the
31402 message. Useful for inclusion in headers or reject messages.
31403 This variable is only usable in a DATA-time ACL.
31405 .vitem &$spam_action$&
31406 For SpamAssassin either 'reject' or 'no action' depending on the
31407 spam score versus threshold.
31408 For Rspamd, the recommended action.
31412 The &%spam%& condition caches its results unless expansion in
31413 spamd_address was used. If you call it again with the same user name, it
31414 does not scan again, but rather returns the same values as before.
31416 The &%spam%& condition returns DEFER if there is any error while running
31417 the message through SpamAssassin or if the expansion of spamd_address
31418 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
31419 statement block), append &`/defer_ok`& to the right-hand side of the
31420 spam condition, like this:
31422 deny message = This message was classified as SPAM
31423 spam = joe/defer_ok
31425 This causes messages to be accepted even if there is a problem with &%spamd%&.
31427 Here is a longer, commented example of the use of the &%spam%&
31430 # put headers in all messages (no matter if spam or not)
31431 warn spam = nobody:true
31432 add_header = X-Spam-Score: $spam_score ($spam_bar)
31433 add_header = X-Spam-Report: $spam_report
31435 # add second subject line with *SPAM* marker when message
31436 # is over threshold
31438 add_header = Subject: *SPAM* $h_Subject:
31440 # reject spam at high scores (> 12)
31441 deny message = This message scored $spam_score spam points.
31443 condition = ${if >{$spam_score_int}{120}{1}{0}}
31448 .section "Scanning MIME parts" "SECTscanmimepart"
31449 .cindex "content scanning" "MIME parts"
31450 .cindex "MIME content scanning"
31451 .oindex "&%acl_smtp_mime%&"
31452 .oindex "&%acl_not_smtp_mime%&"
31453 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
31454 each MIME part of an SMTP message, including multipart types, in the sequence
31455 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
31456 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
31457 options may both refer to the same ACL if you want the same processing in both
31460 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
31461 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
31462 the case of a non-SMTP message. However, a MIME ACL is called only if the
31463 message contains a &'Content-Type:'& header line. When a call to a MIME
31464 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
31465 result code is sent to the client. In the case of an SMTP message, the
31466 &%acl_smtp_data%& ACL is not called when this happens.
31468 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
31469 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
31470 condition to match against the raw MIME part. You can also use the
31471 &%mime_regex%& condition to match against the decoded MIME part (see section
31472 &<<SECTscanregex>>&).
31474 At the start of a MIME ACL, a number of variables are set from the header
31475 information for the relevant MIME part. These are described below. The contents
31476 of the MIME part are not by default decoded into a disk file except for MIME
31477 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
31478 part into a disk file, you can use the &%decode%& condition. The general
31481 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
31483 The right hand side is expanded before use. After expansion,
31487 &"0"& or &"false"&, in which case no decoding is done.
31489 The string &"default"&. In that case, the file is put in the temporary
31490 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
31491 a sequential file name consisting of the message id and a sequence number. The
31492 full path and name is available in &$mime_decoded_filename$& after decoding.
31494 A full path name starting with a slash. If the full name is an existing
31495 directory, it is used as a replacement for the default directory. The filename
31496 is then sequentially assigned. If the path does not exist, it is used as
31497 the full path and file name.
31499 If the string does not start with a slash, it is used as the
31500 filename, and the default path is then used.
31502 The &%decode%& condition normally succeeds. It is only false for syntax
31503 errors or unusual circumstances such as memory shortages. You can easily decode
31504 a file with its original, proposed filename using
31506 decode = $mime_filename
31508 However, you should keep in mind that &$mime_filename$& might contain
31509 anything. If you place files outside of the default path, they are not
31510 automatically unlinked.
31512 For RFC822 attachments (these are messages attached to messages, with a
31513 content-type of &"message/rfc822"&), the ACL is called again in the same manner
31514 as for the primary message, only that the &$mime_is_rfc822$& expansion
31515 variable is set (see below). Attached messages are always decoded to disk
31516 before being checked, and the files are unlinked once the check is done.
31518 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
31519 used to match regular expressions against raw and decoded MIME parts,
31520 respectively. They are described in section &<<SECTscanregex>>&.
31522 .cindex "MIME content scanning" "returned variables"
31523 The following list describes all expansion variables that are
31524 available in the MIME ACL:
31527 .vitem &$mime_boundary$&
31528 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
31529 have a boundary string, which is stored in this variable. If the current part
31530 has no boundary parameter in the &'Content-Type:'& header, this variable
31531 contains the empty string.
31533 .vitem &$mime_charset$&
31534 This variable contains the character set identifier, if one was found in the
31535 &'Content-Type:'& header. Examples for charset identifiers are:
31541 Please note that this value is not normalized, so you should do matches
31542 case-insensitively.
31544 .vitem &$mime_content_description$&
31545 This variable contains the normalized content of the &'Content-Description:'&
31546 header. It can contain a human-readable description of the parts content. Some
31547 implementations repeat the filename for attachments here, but they are usually
31548 only used for display purposes.
31550 .vitem &$mime_content_disposition$&
31551 This variable contains the normalized content of the &'Content-Disposition:'&
31552 header. You can expect strings like &"attachment"& or &"inline"& here.
31554 .vitem &$mime_content_id$&
31555 This variable contains the normalized content of the &'Content-ID:'& header.
31556 This is a unique ID that can be used to reference a part from another part.
31558 .vitem &$mime_content_size$&
31559 This variable is set only after the &%decode%& modifier (see above) has been
31560 successfully run. It contains the size of the decoded part in kilobytes. The
31561 size is always rounded up to full kilobytes, so only a completely empty part
31562 has a &$mime_content_size$& of zero.
31564 .vitem &$mime_content_transfer_encoding$&
31565 This variable contains the normalized content of the
31566 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
31567 type. Typical values are &"base64"& and &"quoted-printable"&.
31569 .vitem &$mime_content_type$&
31570 If the MIME part has a &'Content-Type:'& header, this variable contains its
31571 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
31572 are some examples of popular MIME types, as they may appear in this variable:
31576 application/octet-stream
31580 If the MIME part has no &'Content-Type:'& header, this variable contains the
31583 .vitem &$mime_decoded_filename$&
31584 This variable is set only after the &%decode%& modifier (see above) has been
31585 successfully run. It contains the full path and file name of the file
31586 containing the decoded data.
31591 .vitem &$mime_filename$&
31592 This is perhaps the most important of the MIME variables. It contains a
31593 proposed filename for an attachment, if one was found in either the
31594 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
31597 decoded, but no additional sanity checks are done.
31599 found, this variable contains the empty string.
31601 .vitem &$mime_is_coverletter$&
31602 This variable attempts to differentiate the &"cover letter"& of an e-mail from
31603 attached data. It can be used to clamp down on flashy or unnecessarily encoded
31604 content in the cover letter, while not restricting attachments at all.
31606 The variable contains 1 (true) for a MIME part believed to be part of the
31607 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
31611 The outermost MIME part of a message is always a cover letter.
31614 If a multipart/alternative or multipart/related MIME part is a cover letter,
31615 so are all MIME subparts within that multipart.
31618 If any other multipart is a cover letter, the first subpart is a cover letter,
31619 and the rest are attachments.
31622 All parts contained within an attachment multipart are attachments.
31625 As an example, the following will ban &"HTML mail"& (including that sent with
31626 alternative plain text), while allowing HTML files to be attached. HTML
31627 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
31629 deny message = HTML mail is not accepted here
31630 !condition = $mime_is_rfc822
31631 condition = $mime_is_coverletter
31632 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
31634 .vitem &$mime_is_multipart$&
31635 This variable has the value 1 (true) when the current part has the main type
31636 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
31637 Since multipart entities only serve as containers for other parts, you may not
31638 want to carry out specific actions on them.
31640 .vitem &$mime_is_rfc822$&
31641 This variable has the value 1 (true) if the current part is not a part of the
31642 checked message itself, but part of an attached message. Attached message
31643 decoding is fully recursive.
31645 .vitem &$mime_part_count$&
31646 This variable is a counter that is raised for each processed MIME part. It
31647 starts at zero for the very first part (which is usually a multipart). The
31648 counter is per-message, so it is reset when processing RFC822 attachments (see
31649 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
31650 complete, so you can use it in the DATA ACL to determine the number of MIME
31651 parts of a message. For non-MIME messages, this variable contains the value -1.
31656 .section "Scanning with regular expressions" "SECTscanregex"
31657 .cindex "content scanning" "with regular expressions"
31658 .cindex "regular expressions" "content scanning with"
31659 You can specify your own custom regular expression matches on the full body of
31660 the message, or on individual MIME parts.
31662 The &%regex%& condition takes one or more regular expressions as arguments and
31663 matches them against the full message (when called in the DATA ACL) or a raw
31664 MIME part (when called in the MIME ACL). The &%regex%& condition matches
31665 linewise, with a maximum line length of 32K characters. That means you cannot
31666 have multiline matches with the &%regex%& condition.
31668 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
31669 to 32K of decoded content (the whole content at once, not linewise). If the
31670 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
31671 is decoded automatically when &%mime_regex%& is executed (using default path
31672 and filename values). If the decoded data is larger than 32K, only the first
31673 32K characters are checked.
31675 The regular expressions are passed as a colon-separated list. To include a
31676 literal colon, you must double it. Since the whole right-hand side string is
31677 expanded before being used, you must also escape dollar signs and backslashes
31678 with more backslashes, or use the &`\N`& facility to disable expansion.
31679 Here is a simple example that contains two regular expressions:
31681 deny message = contains blacklisted regex ($regex_match_string)
31682 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
31684 The conditions returns true if any one of the regular expressions matches. The
31685 &$regex_match_string$& expansion variable is then set up and contains the
31686 matching regular expression.
31687 The expansion variables &$regex1$& &$regex2$& etc
31688 are set to any substrings captured by the regular expression.
31690 &*Warning*&: With large messages, these conditions can be fairly
31696 .section "The demime condition" "SECTdemimecond"
31697 .cindex "content scanning" "MIME checking"
31698 .cindex "MIME content scanning"
31699 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
31700 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
31701 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
31702 ACL functionality, but provides no additional facilities. Please note that this
31703 condition is deprecated and kept only for backward compatibility. You must set
31704 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
31705 use the &%demime%& condition.
31707 The &%demime%& condition unpacks MIME containers in the message. It detects
31708 errors in MIME containers and can match file extensions found in the message
31709 against a list. Using this facility produces files containing the unpacked MIME
31710 parts of the message in the temporary scan directory. If you do antivirus
31711 scanning, it is recommended that you use the &%demime%& condition before the
31712 antivirus (&%malware%&) condition.
31714 On the right-hand side of the &%demime%& condition you can pass a
31715 colon-separated list of file extensions that it should match against. For
31718 deny message = Found blacklisted file attachment
31719 demime = vbs:com:bat:pif:prf:lnk
31721 If one of the file extensions is found, the condition is true, otherwise it is
31722 false. If there is a temporary error while demimeing (for example, &"disk
31723 full"&), the condition defers, and the message is temporarily rejected (unless
31724 the condition is on a &%warn%& verb).
31726 The right-hand side is expanded before being treated as a list, so you can have
31727 conditions and lookups there. If it expands to an empty string, &"false"&, or
31728 zero (&"0"&), no demimeing is done and the condition is false.
31730 The &%demime%& condition set the following variables:
31733 .vitem &$demime_errorlevel$&
31734 .vindex "&$demime_errorlevel$&"
31735 When an error is detected in a MIME container, this variable contains the
31736 severity of the error, as an integer number. The higher the value, the more
31737 severe the error (the current maximum value is 3). If this variable is unset or
31738 zero, no error occurred.
31740 .vitem &$demime_reason$&
31741 .vindex "&$demime_reason$&"
31742 When &$demime_errorlevel$& is greater than zero, this variable contains a
31743 human-readable text string describing the MIME error that occurred.
31747 .vitem &$found_extension$&
31748 .vindex "&$found_extension$&"
31749 When the &%demime%& condition is true, this variable contains the file
31750 extension it found.
31753 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
31754 the &%demime%& condition, and are not changed on subsequent calls.
31756 If you do not want to check for file extensions, but rather use the &%demime%&
31757 condition for unpacking or error checking purposes, pass &"*"& as the
31758 right-hand side value. Here is a more elaborate example of how to use this
31761 # Reject messages with serious MIME container errors
31762 deny message = Found MIME error ($demime_reason).
31764 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
31766 # Reject known virus spreading file extensions.
31767 # Accepting these is pretty much braindead.
31768 deny message = contains $found_extension file (blacklisted).
31769 demime = com:vbs:bat:pif:scr
31771 # Freeze .exe and .doc files. Postmaster can
31772 # examine them and eventually thaw them.
31773 deny log_message = Another $found_extension file.
31782 . ////////////////////////////////////////////////////////////////////////////
31783 . ////////////////////////////////////////////////////////////////////////////
31785 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
31786 "Local scan function"
31787 .scindex IIDlosca "&[local_scan()]& function" "description of"
31788 .cindex "customizing" "input scan using C function"
31789 .cindex "policy control" "by local scan function"
31790 In these days of email worms, viruses, and ever-increasing spam, some sites
31791 want to apply a lot of checking to messages before accepting them.
31793 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
31794 passing messages to external virus and spam scanning software. You can also do
31795 a certain amount in Exim itself through string expansions and the &%condition%&
31796 condition in the ACL that runs after the SMTP DATA command or the ACL for
31797 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
31799 To allow for further customization to a site's own requirements, there is the
31800 possibility of linking Exim with a private message scanning function, written
31801 in C. If you want to run code that is written in something other than C, you
31802 can of course use a little C stub to call it.
31804 The local scan function is run once for every incoming message, at the point
31805 when Exim is just about to accept the message.
31806 It can therefore be used to control non-SMTP messages from local processes as
31807 well as messages arriving via SMTP.
31809 Exim applies a timeout to calls of the local scan function, and there is an
31810 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
31811 Zero means &"no timeout"&.
31812 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
31813 before calling the local scan function, so that the most common types of crash
31814 are caught. If the timeout is exceeded or one of those signals is caught, the
31815 incoming message is rejected with a temporary error if it is an SMTP message.
31816 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
31817 code. The incident is logged on the main and reject logs.
31821 .section "Building Exim to use a local scan function" "SECID207"
31822 .cindex "&[local_scan()]& function" "building Exim to use"
31823 To make use of the local scan function feature, you must tell Exim where your
31824 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
31825 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
31826 directory, so you might set
31828 LOCAL_SCAN_SOURCE=Local/local_scan.c
31830 for example. The function must be called &[local_scan()]&. It is called by
31831 Exim after it has received a message, when the success return code is about to
31832 be sent. This is after all the ACLs have been run. The return code from your
31833 function controls whether the message is actually accepted or not. There is a
31834 commented template function (that just accepts the message) in the file
31835 _src/local_scan.c_.
31837 If you want to make use of Exim's run time configuration file to set options
31838 for your &[local_scan()]& function, you must also set
31840 LOCAL_SCAN_HAS_OPTIONS=yes
31842 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
31847 .section "API for local_scan()" "SECTapiforloc"
31848 .cindex "&[local_scan()]& function" "API description"
31849 You must include this line near the start of your code:
31851 #include "local_scan.h"
31853 This header file defines a number of variables and other values, and the
31854 prototype for the function itself. Exim is coded to use unsigned char values
31855 almost exclusively, and one of the things this header defines is a shorthand
31856 for &`unsigned char`& called &`uschar`&.
31857 It also contains the following macro definitions, to simplify casting character
31858 strings and pointers to character strings:
31860 #define CS (char *)
31861 #define CCS (const char *)
31862 #define CSS (char **)
31863 #define US (unsigned char *)
31864 #define CUS (const unsigned char *)
31865 #define USS (unsigned char **)
31867 The function prototype for &[local_scan()]& is:
31869 extern int local_scan(int fd, uschar **return_text);
31871 The arguments are as follows:
31874 &%fd%& is a file descriptor for the file that contains the body of the message
31875 (the -D file). The file is open for reading and writing, but updating it is not
31876 recommended. &*Warning*&: You must &'not'& close this file descriptor.
31878 The descriptor is positioned at character 19 of the file, which is the first
31879 character of the body itself, because the first 19 characters are the message
31880 id followed by &`-D`& and a newline. If you rewind the file, you should use the
31881 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
31882 case this changes in some future version.
31884 &%return_text%& is an address which you can use to return a pointer to a text
31885 string at the end of the function. The value it points to on entry is NULL.
31888 The function must return an &%int%& value which is one of the following macros:
31891 .vitem &`LOCAL_SCAN_ACCEPT`&
31892 .vindex "&$local_scan_data$&"
31893 The message is accepted. If you pass back a string of text, it is saved with
31894 the message, and made available in the variable &$local_scan_data$&. No
31895 newlines are permitted (if there are any, they are turned into spaces) and the
31896 maximum length of text is 1000 characters.
31898 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
31899 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
31900 queued without immediate delivery, and is frozen.
31902 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
31903 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
31904 queued without immediate delivery.
31906 .vitem &`LOCAL_SCAN_REJECT`&
31907 The message is rejected; the returned text is used as an error message which is
31908 passed back to the sender and which is also logged. Newlines are permitted &--
31909 they cause a multiline response for SMTP rejections, but are converted to
31910 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
31913 .vitem &`LOCAL_SCAN_TEMPREJECT`&
31914 The message is temporarily rejected; the returned text is used as an error
31915 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
31918 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
31919 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
31920 message is not written to the reject log. It has the effect of unsetting the
31921 &%rejected_header%& log selector for just this rejection. If
31922 &%rejected_header%& is already unset (see the discussion of the
31923 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
31924 same as LOCAL_SCAN_REJECT.
31926 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
31927 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
31928 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
31931 If the message is not being received by interactive SMTP, rejections are
31932 reported by writing to &%stderr%& or by sending an email, as configured by the
31933 &%-oe%& command line options.
31937 .section "Configuration options for local_scan()" "SECTconoptloc"
31938 .cindex "&[local_scan()]& function" "configuration options"
31939 It is possible to have option settings in the main configuration file
31940 that set values in static variables in the &[local_scan()]& module. If you
31941 want to do this, you must have the line
31943 LOCAL_SCAN_HAS_OPTIONS=yes
31945 in your &_Local/Makefile_& when you build Exim. (This line is in
31946 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
31947 file, you must define static variables to hold the option values, and a table
31950 The table must be a vector called &%local_scan_options%&, of type
31951 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
31952 and a pointer to the variable that holds the value. The entries must appear in
31953 alphabetical order. Following &%local_scan_options%& you must also define a
31954 variable called &%local_scan_options_count%& that contains the number of
31955 entries in the table. Here is a short example, showing two kinds of option:
31957 static int my_integer_option = 42;
31958 static uschar *my_string_option = US"a default string";
31960 optionlist local_scan_options[] = {
31961 { "my_integer", opt_int, &my_integer_option },
31962 { "my_string", opt_stringptr, &my_string_option }
31965 int local_scan_options_count =
31966 sizeof(local_scan_options)/sizeof(optionlist);
31968 The values of the variables can now be changed from Exim's runtime
31969 configuration file by including a local scan section as in this example:
31973 my_string = some string of text...
31975 The available types of option data are as follows:
31978 .vitem &*opt_bool*&
31979 This specifies a boolean (true/false) option. The address should point to a
31980 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
31981 that are defined as &"1"& and &"0"&, respectively. If you want to detect
31982 whether such a variable has been set at all, you can initialize it to
31983 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
31986 .vitem &*opt_fixed*&
31987 This specifies a fixed point number, such as is used for load averages.
31988 The address should point to a variable of type &`int`&. The value is stored
31989 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
31992 This specifies an integer; the address should point to a variable of type
31993 &`int`&. The value may be specified in any of the integer formats accepted by
31996 .vitem &*opt_mkint*&
31997 This is the same as &%opt_int%&, except that when such a value is output in a
31998 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
31999 printed with the suffix K or M.
32001 .vitem &*opt_octint*&
32002 This also specifies an integer, but the value is always interpreted as an
32003 octal integer, whether or not it starts with the digit zero, and it is
32004 always output in octal.
32006 .vitem &*opt_stringptr*&
32007 This specifies a string value; the address must be a pointer to a
32008 variable that points to a string (for example, of type &`uschar *`&).
32010 .vitem &*opt_time*&
32011 This specifies a time interval value. The address must point to a variable of
32012 type &`int`&. The value that is placed there is a number of seconds.
32015 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
32016 out the values of all the &[local_scan()]& options.
32020 .section "Available Exim variables" "SECID208"
32021 .cindex "&[local_scan()]& function" "available Exim variables"
32022 The header &_local_scan.h_& gives you access to a number of C variables. These
32023 are the only ones that are guaranteed to be maintained from release to release.
32024 Note, however, that you can obtain the value of any Exim expansion variable,
32025 including &$recipients$&, by calling &'expand_string()'&. The exported
32026 C variables are as follows:
32029 .vitem &*int&~body_linecount*&
32030 This variable contains the number of lines in the message's body.
32032 .vitem &*int&~body_zerocount*&
32033 This variable contains the number of binary zero bytes in the message's body.
32035 .vitem &*unsigned&~int&~debug_selector*&
32036 This variable is set to zero when no debugging is taking place. Otherwise, it
32037 is a bitmap of debugging selectors. Two bits are identified for use in
32038 &[local_scan()]&; they are defined as macros:
32041 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
32042 testing option that is not privileged &-- any caller may set it. All the
32043 other selector bits can be set only by admin users.
32046 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
32047 by the &`+local_scan`& debug selector. It is not included in the default set
32051 Thus, to write to the debugging output only when &`+local_scan`& has been
32052 selected, you should use code like this:
32054 if ((debug_selector & D_local_scan) != 0)
32055 debug_printf("xxx", ...);
32057 .vitem &*uschar&~*expand_string_message*&
32058 After a failing call to &'expand_string()'& (returned value NULL), the
32059 variable &%expand_string_message%& contains the error message, zero-terminated.
32061 .vitem &*header_line&~*header_list*&
32062 A pointer to a chain of header lines. The &%header_line%& structure is
32065 .vitem &*header_line&~*header_last*&
32066 A pointer to the last of the header lines.
32068 .vitem &*uschar&~*headers_charset*&
32069 The value of the &%headers_charset%& configuration option.
32071 .vitem &*BOOL&~host_checking*&
32072 This variable is TRUE during a host checking session that is initiated by the
32073 &%-bh%& command line option.
32075 .vitem &*uschar&~*interface_address*&
32076 The IP address of the interface that received the message, as a string. This
32077 is NULL for locally submitted messages.
32079 .vitem &*int&~interface_port*&
32080 The port on which this message was received. When testing with the &%-bh%&
32081 command line option, the value of this variable is -1 unless a port has been
32082 specified via the &%-oMi%& option.
32084 .vitem &*uschar&~*message_id*&
32085 This variable contains Exim's message id for the incoming message (the value of
32086 &$message_exim_id$&) as a zero-terminated string.
32088 .vitem &*uschar&~*received_protocol*&
32089 The name of the protocol by which the message was received.
32091 .vitem &*int&~recipients_count*&
32092 The number of accepted recipients.
32094 .vitem &*recipient_item&~*recipients_list*&
32095 .cindex "recipient" "adding in local scan"
32096 .cindex "recipient" "removing in local scan"
32097 The list of accepted recipients, held in a vector of length
32098 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
32099 can add additional recipients by calling &'receive_add_recipient()'& (see
32100 below). You can delete recipients by removing them from the vector and
32101 adjusting the value in &%recipients_count%&. In particular, by setting
32102 &%recipients_count%& to zero you remove all recipients. If you then return the
32103 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
32104 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
32105 and then call &'receive_add_recipient()'& as often as needed.
32107 .vitem &*uschar&~*sender_address*&
32108 The envelope sender address. For bounce messages this is the empty string.
32110 .vitem &*uschar&~*sender_host_address*&
32111 The IP address of the sending host, as a string. This is NULL for
32112 locally-submitted messages.
32114 .vitem &*uschar&~*sender_host_authenticated*&
32115 The name of the authentication mechanism that was used, or NULL if the message
32116 was not received over an authenticated SMTP connection.
32118 .vitem &*uschar&~*sender_host_name*&
32119 The name of the sending host, if known.
32121 .vitem &*int&~sender_host_port*&
32122 The port on the sending host.
32124 .vitem &*BOOL&~smtp_input*&
32125 This variable is TRUE for all SMTP input, including BSMTP.
32127 .vitem &*BOOL&~smtp_batched_input*&
32128 This variable is TRUE for BSMTP input.
32130 .vitem &*int&~store_pool*&
32131 The contents of this variable control which pool of memory is used for new
32132 requests. See section &<<SECTmemhanloc>>& for details.
32136 .section "Structure of header lines" "SECID209"
32137 The &%header_line%& structure contains the members listed below.
32138 You can add additional header lines by calling the &'header_add()'& function
32139 (see below). You can cause header lines to be ignored (deleted) by setting
32144 .vitem &*struct&~header_line&~*next*&
32145 A pointer to the next header line, or NULL for the last line.
32147 .vitem &*int&~type*&
32148 A code identifying certain headers that Exim recognizes. The codes are printing
32149 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
32150 Notice in particular that any header line whose type is * is not transmitted
32151 with the message. This flagging is used for header lines that have been
32152 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
32153 lines.) Effectively, * means &"deleted"&.
32155 .vitem &*int&~slen*&
32156 The number of characters in the header line, including the terminating and any
32159 .vitem &*uschar&~*text*&
32160 A pointer to the text of the header. It always ends with a newline, followed by
32161 a zero byte. Internal newlines are preserved.
32166 .section "Structure of recipient items" "SECID210"
32167 The &%recipient_item%& structure contains these members:
32170 .vitem &*uschar&~*address*&
32171 This is a pointer to the recipient address as it was received.
32173 .vitem &*int&~pno*&
32174 This is used in later Exim processing when top level addresses are created by
32175 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
32176 and must always contain -1 at this stage.
32178 .vitem &*uschar&~*errors_to*&
32179 If this value is not NULL, bounce messages caused by failing to deliver to the
32180 recipient are sent to the address it contains. In other words, it overrides the
32181 envelope sender for this one recipient. (Compare the &%errors_to%& generic
32182 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
32183 an unqualified address, Exim qualifies it using the domain from
32184 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
32185 is NULL for all recipients.
32190 .section "Available Exim functions" "SECID211"
32191 .cindex "&[local_scan()]& function" "available Exim functions"
32192 The header &_local_scan.h_& gives you access to a number of Exim functions.
32193 These are the only ones that are guaranteed to be maintained from release to
32197 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
32198 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
32200 This function creates a child process that runs the command specified by
32201 &%argv%&. The environment for the process is specified by &%envp%&, which can
32202 be NULL if no environment variables are to be passed. A new umask is supplied
32203 for the process in &%newumask%&.
32205 Pipes to the standard input and output of the new process are set up
32206 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
32207 standard error is cloned to the standard output. If there are any file
32208 descriptors &"in the way"& in the new process, they are closed. If the final
32209 argument is TRUE, the new process is made into a process group leader.
32211 The function returns the pid of the new process, or -1 if things go wrong.
32213 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
32214 This function waits for a child process to terminate, or for a timeout (in
32215 seconds) to expire. A timeout value of zero means wait as long as it takes. The
32216 return value is as follows:
32221 The process terminated by a normal exit and the value is the process
32227 The process was terminated by a signal and the value is the negation of the
32233 The process timed out.
32237 The was some other error in wait(); &%errno%& is still set.
32240 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
32241 This function provide you with a means of submitting a new message to
32242 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
32243 want, but this packages it all up for you.) The function creates a pipe,
32244 forks a subprocess that is running
32246 exim -t -oem -oi -f <>
32248 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
32249 that is connected to the standard input. The yield of the function is the PID
32250 of the subprocess. You can then write a message to the file descriptor, with
32251 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
32253 When you have finished, call &'child_close()'& to wait for the process to
32254 finish and to collect its ending status. A timeout value of zero is usually
32255 fine in this circumstance. Unless you have made a mistake with the recipient
32256 addresses, you should get a return code of zero.
32259 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
32260 *sender_authentication)*&
32261 This function is a more sophisticated version of &'child_open()'&. The command
32264 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
32266 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
32269 .vitem &*void&~debug_printf(char&~*,&~...)*&
32270 This is Exim's debugging function, with arguments as for &'(printf()'&. The
32271 output is written to the standard error stream. If no debugging is selected,
32272 calls to &'debug_printf()'& have no effect. Normally, you should make calls
32273 conditional on the &`local_scan`& debug selector by coding like this:
32275 if ((debug_selector & D_local_scan) != 0)
32276 debug_printf("xxx", ...);
32279 .vitem &*uschar&~*expand_string(uschar&~*string)*&
32280 This is an interface to Exim's string expansion code. The return value is the
32281 expanded string, or NULL if there was an expansion failure.
32282 The C variable &%expand_string_message%& contains an error message after an
32283 expansion failure. If expansion does not change the string, the return value is
32284 the pointer to the input string. Otherwise, the return value points to a new
32285 block of memory that was obtained by a call to &'store_get()'&. See section
32286 &<<SECTmemhanloc>>& below for a discussion of memory handling.
32288 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
32289 This function allows you to an add additional header line at the end of the
32290 existing ones. The first argument is the type, and should normally be a space
32291 character. The second argument is a format string and any number of
32292 substitution arguments as for &[sprintf()]&. You may include internal newlines
32293 if you want, and you must ensure that the string ends with a newline.
32295 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
32296 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
32297 This function adds a new header line at a specified point in the header
32298 chain. The header itself is specified as for &'header_add()'&.
32300 If &%name%& is NULL, the new header is added at the end of the chain if
32301 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
32302 NULL, the header lines are searched for the first non-deleted header that
32303 matches the name. If one is found, the new header is added before it if
32304 &%after%& is false. If &%after%& is true, the new header is added after the
32305 found header and any adjacent subsequent ones with the same name (even if
32306 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
32307 option controls where the header is added. If it is true, addition is at the
32308 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
32309 headers, or at the top if there are no &'Received:'& headers, you could use
32311 header_add_at_position(TRUE, US"Received", TRUE,
32312 ' ', "X-xxx: ...");
32314 Normally, there is always at least one non-deleted &'Received:'& header, but
32315 there may not be if &%received_header_text%& expands to an empty string.
32318 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
32319 This function removes header lines. If &%occurrence%& is zero or negative, all
32320 occurrences of the header are removed. If occurrence is greater than zero, that
32321 particular instance of the header is removed. If no header(s) can be found that
32322 match the specification, the function does nothing.
32325 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
32326 int&~length,&~BOOL&~notdel)*&"
32327 This function tests whether the given header has the given name. It is not just
32328 a string comparison, because white space is permitted between the name and the
32329 colon. If the &%notdel%& argument is true, a false return is forced for all
32330 &"deleted"& headers; otherwise they are not treated specially. For example:
32332 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
32334 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
32335 .cindex "base64 encoding" "functions for &[local_scan()]& use"
32336 This function base64-encodes a string, which is passed by address and length.
32337 The text may contain bytes of any value, including zero. The result is passed
32338 back in dynamic memory that is obtained by calling &'store_get()'&. It is
32341 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
32342 This function decodes a base64-encoded string. Its arguments are a
32343 zero-terminated base64-encoded string and the address of a variable that is set
32344 to point to the result, which is in dynamic memory. The length of the decoded
32345 string is the yield of the function. If the input is invalid base64 data, the
32346 yield is -1. A zero byte is added to the end of the output string to make it
32347 easy to interpret as a C string (assuming it contains no zeros of its own). The
32348 added zero byte is not included in the returned count.
32350 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
32351 This function checks for a match in a domain list. Domains are always
32352 matched caselessly. The return value is one of the following:
32354 &`OK `& match succeeded
32355 &`FAIL `& match failed
32356 &`DEFER `& match deferred
32358 DEFER is usually caused by some kind of lookup defer, such as the
32359 inability to contact a database.
32361 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
32363 This function checks for a match in a local part list. The third argument
32364 controls case-sensitivity. The return values are as for
32365 &'lss_match_domain()'&.
32367 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
32369 This function checks for a match in an address list. The third argument
32370 controls the case-sensitivity of the local part match. The domain is always
32371 matched caselessly. The return values are as for &'lss_match_domain()'&.
32373 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
32375 This function checks for a match in a host list. The most common usage is
32378 lss_match_host(sender_host_name, sender_host_address, ...)
32380 .vindex "&$sender_host_address$&"
32381 An empty address field matches an empty item in the host list. If the host name
32382 is NULL, the name corresponding to &$sender_host_address$& is automatically
32383 looked up if a host name is required to match an item in the list. The return
32384 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
32385 returns ERROR in the case when it had to look up a host name, but the lookup
32388 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
32390 This function writes to Exim's log files. The first argument should be zero (it
32391 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
32392 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
32393 them. It specifies to which log or logs the message is written. The remaining
32394 arguments are a format and relevant insertion arguments. The string should not
32395 contain any newlines, not even at the end.
32398 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
32399 This function adds an additional recipient to the message. The first argument
32400 is the recipient address. If it is unqualified (has no domain), it is qualified
32401 with the &%qualify_recipient%& domain. The second argument must always be -1.
32403 This function does not allow you to specify a private &%errors_to%& address (as
32404 described with the structure of &%recipient_item%& above), because it pre-dates
32405 the addition of that field to the structure. However, it is easy to add such a
32406 value afterwards. For example:
32408 receive_add_recipient(US"monitor@mydom.example", -1);
32409 recipients_list[recipients_count-1].errors_to =
32410 US"postmaster@mydom.example";
32413 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
32414 This is a convenience function to remove a named recipient from the list of
32415 recipients. It returns true if a recipient was removed, and false if no
32416 matching recipient could be found. The argument must be a complete email
32423 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
32424 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
32425 This function decodes strings that are encoded according to RFC 2047. Typically
32426 these are the contents of header lines. First, each &"encoded word"& is decoded
32427 from the Q or B encoding into a byte-string. Then, if provided with the name of
32428 a charset encoding, and if the &[iconv()]& function is available, an attempt is
32429 made to translate the result to the named character set. If this fails, the
32430 binary string is returned with an error message.
32432 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
32433 maximum MIME word length is enforced. The third argument is the target
32434 encoding, or NULL if no translation is wanted.
32436 .cindex "binary zero" "in RFC 2047 decoding"
32437 .cindex "RFC 2047" "binary zero in"
32438 If a binary zero is encountered in the decoded string, it is replaced by the
32439 contents of the &%zeroval%& argument. For use with Exim headers, the value must
32440 not be 0 because header lines are handled as zero-terminated strings.
32442 The function returns the result of processing the string, zero-terminated; if
32443 &%lenptr%& is not NULL, the length of the result is set in the variable to
32444 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
32446 If an error is encountered, the function returns NULL and uses the &%error%&
32447 argument to return an error message. The variable pointed to by &%error%& is
32448 set to NULL if there is no error; it may be set non-NULL even when the function
32449 returns a non-NULL value if decoding was successful, but there was a problem
32453 .vitem &*int&~smtp_fflush(void)*&
32454 This function is used in conjunction with &'smtp_printf()'&, as described
32457 .vitem &*void&~smtp_printf(char&~*,&~...)*&
32458 The arguments of this function are like &[printf()]&; it writes to the SMTP
32459 output stream. You should use this function only when there is an SMTP output
32460 stream, that is, when the incoming message is being received via interactive
32461 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
32462 is FALSE. If you want to test for an incoming message from another host (as
32463 opposed to a local process that used the &%-bs%& command line option), you can
32464 test the value of &%sender_host_address%&, which is non-NULL when a remote host
32467 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
32468 output function, so it can be used for all forms of SMTP connection.
32470 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
32471 must start with an appropriate response code: 550 if you are going to return
32472 LOCAL_SCAN_REJECT, 451 if you are going to return
32473 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
32474 initial lines of a multi-line response, the code must be followed by a hyphen
32475 to indicate that the line is not the final response line. You must also ensure
32476 that the lines you write terminate with CRLF. For example:
32478 smtp_printf("550-this is some extra info\r\n");
32479 return LOCAL_SCAN_REJECT;
32481 Note that you can also create multi-line responses by including newlines in
32482 the data returned via the &%return_text%& argument. The added value of using
32483 &'smtp_printf()'& is that, for instance, you could introduce delays between
32484 multiple output lines.
32486 The &'smtp_printf()'& function does not return any error indication, because it
32487 does not automatically flush pending output, and therefore does not test
32488 the state of the stream. (In the main code of Exim, flushing and error
32489 detection is done when Exim is ready for the next SMTP input command.) If
32490 you want to flush the output and check for an error (for example, the
32491 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
32492 arguments. It flushes the output stream, and returns a non-zero value if there
32495 .vitem &*void&~*store_get(int)*&
32496 This function accesses Exim's internal store (memory) manager. It gets a new
32497 chunk of memory whose size is given by the argument. Exim bombs out if it ever
32498 runs out of memory. See the next section for a discussion of memory handling.
32500 .vitem &*void&~*store_get_perm(int)*&
32501 This function is like &'store_get()'&, but it always gets memory from the
32502 permanent pool. See the next section for a discussion of memory handling.
32504 .vitem &*uschar&~*string_copy(uschar&~*string)*&
32507 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
32510 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
32511 These three functions create strings using Exim's dynamic memory facilities.
32512 The first makes a copy of an entire string. The second copies up to a maximum
32513 number of characters, indicated by the second argument. The third uses a format
32514 and insertion arguments to create a new string. In each case, the result is a
32515 pointer to a new string in the current memory pool. See the next section for
32521 .section "More about Exim's memory handling" "SECTmemhanloc"
32522 .cindex "&[local_scan()]& function" "memory handling"
32523 No function is provided for freeing memory, because that is never needed.
32524 The dynamic memory that Exim uses when receiving a message is automatically
32525 recycled if another message is received by the same process (this applies only
32526 to incoming SMTP connections &-- other input methods can supply only one
32527 message at a time). After receiving the last message, a reception process
32530 Because it is recycled, the normal dynamic memory cannot be used for holding
32531 data that must be preserved over a number of incoming messages on the same SMTP
32532 connection. However, Exim in fact uses two pools of dynamic memory; the second
32533 one is not recycled, and can be used for this purpose.
32535 If you want to allocate memory that remains available for subsequent messages
32536 in the same SMTP connection, you should set
32538 store_pool = POOL_PERM
32540 before calling the function that does the allocation. There is no need to
32541 restore the value if you do not need to; however, if you do want to revert to
32542 the normal pool, you can either restore the previous value of &%store_pool%& or
32543 set it explicitly to POOL_MAIN.
32545 The pool setting applies to all functions that get dynamic memory, including
32546 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
32547 There is also a convenience function called &'store_get_perm()'& that gets a
32548 block of memory from the permanent pool while preserving the value of
32555 . ////////////////////////////////////////////////////////////////////////////
32556 . ////////////////////////////////////////////////////////////////////////////
32558 .chapter "System-wide message filtering" "CHAPsystemfilter"
32559 .scindex IIDsysfil1 "filter" "system filter"
32560 .scindex IIDsysfil2 "filtering all mail"
32561 .scindex IIDsysfil3 "system filter"
32562 The previous chapters (on ACLs and the local scan function) describe checks
32563 that can be applied to messages before they are accepted by a host. There is
32564 also a mechanism for checking messages once they have been received, but before
32565 they are delivered. This is called the &'system filter'&.
32567 The system filter operates in a similar manner to users' filter files, but it
32568 is run just once per message (however many recipients the message has).
32569 It should not normally be used as a substitute for routing, because &%deliver%&
32570 commands in a system router provide new envelope recipient addresses.
32571 The system filter must be an Exim filter. It cannot be a Sieve filter.
32573 The system filter is run at the start of a delivery attempt, before any routing
32574 is done. If a message fails to be completely delivered at the first attempt,
32575 the system filter is run again at the start of every retry.
32576 If you want your filter to do something only once per message, you can make use
32577 of the &%first_delivery%& condition in an &%if%& command in the filter to
32578 prevent it happening on retries.
32580 .vindex "&$domain$&"
32581 .vindex "&$local_part$&"
32582 &*Warning*&: Because the system filter runs just once, variables that are
32583 specific to individual recipient addresses, such as &$local_part$& and
32584 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
32585 you want to run a centrally-specified filter for each recipient address
32586 independently, you can do so by setting up a suitable &(redirect)& router, as
32587 described in section &<<SECTperaddfil>>& below.
32590 .section "Specifying a system filter" "SECID212"
32591 .cindex "uid (user id)" "system filter"
32592 .cindex "gid (group id)" "system filter"
32593 The name of the file that contains the system filter must be specified by
32594 setting &%system_filter%&. If you want the filter to run under a uid and gid
32595 other than root, you must also set &%system_filter_user%& and
32596 &%system_filter_group%& as appropriate. For example:
32598 system_filter = /etc/mail/exim.filter
32599 system_filter_user = exim
32601 If a system filter generates any deliveries directly to files or pipes (via the
32602 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
32603 specified by setting &%system_filter_file_transport%& and
32604 &%system_filter_pipe_transport%&, respectively. Similarly,
32605 &%system_filter_reply_transport%& must be set to handle any messages generated
32606 by the &%reply%& command.
32609 .section "Testing a system filter" "SECID213"
32610 You can run simple tests of a system filter in the same way as for a user
32611 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
32612 are permitted only in system filters are recognized.
32614 If you want to test the combined effect of a system filter and a user filter,
32615 you can use both &%-bF%& and &%-bf%& on the same command line.
32619 .section "Contents of a system filter" "SECID214"
32620 The language used to specify system filters is the same as for users' filter
32621 files. It is described in the separate end-user document &'Exim's interface to
32622 mail filtering'&. However, there are some additional features that are
32623 available only in system filters; these are described in subsequent sections.
32624 If they are encountered in a user's filter file or when testing with &%-bf%&,
32627 .cindex "frozen messages" "manual thaw; testing in filter"
32628 There are two special conditions which, though available in users' filter
32629 files, are designed for use in system filters. The condition &%first_delivery%&
32630 is true only for the first attempt at delivering a message, and
32631 &%manually_thawed%& is true only if the message has been frozen, and
32632 subsequently thawed by an admin user. An explicit forced delivery counts as a
32633 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
32635 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
32636 specify an &"unseen"& (non-significant) delivery, and that delivery does not
32637 succeed, it will not be tried again.
32638 If you want Exim to retry an unseen delivery until it succeeds, you should
32639 arrange to set it up every time the filter runs.
32641 When a system filter finishes running, the values of the variables &$n0$& &--
32642 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
32643 users' filter files. Thus a system filter can, for example, set up &"scores"&
32644 to which users' filter files can refer.
32648 .section "Additional variable for system filters" "SECID215"
32649 .vindex "&$recipients$&"
32650 The expansion variable &$recipients$&, containing a list of all the recipients
32651 of the message (separated by commas and white space), is available in system
32652 filters. It is not available in users' filters for privacy reasons.
32656 .section "Defer, freeze, and fail commands for system filters" "SECID216"
32657 .cindex "freezing messages"
32658 .cindex "message" "freezing"
32659 .cindex "message" "forced failure"
32660 .cindex "&%fail%&" "in system filter"
32661 .cindex "&%freeze%& in system filter"
32662 .cindex "&%defer%& in system filter"
32663 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
32664 always available in system filters, but are not normally enabled in users'
32665 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
32666 for the &(redirect)& router.) These commands can optionally be followed by the
32667 word &%text%& and a string containing an error message, for example:
32669 fail text "this message looks like spam to me"
32671 The keyword &%text%& is optional if the next character is a double quote.
32673 The &%defer%& command defers delivery of the original recipients of the
32674 message. The &%fail%& command causes all the original recipients to be failed,
32675 and a bounce message to be created. The &%freeze%& command suspends all
32676 delivery attempts for the original recipients. In all cases, any new deliveries
32677 that are specified by the filter are attempted as normal after the filter has
32680 The &%freeze%& command is ignored if the message has been manually unfrozen and
32681 not manually frozen since. This means that automatic freezing by a system
32682 filter can be used as a way of checking out suspicious messages. If a message
32683 is found to be all right, manually unfreezing it allows it to be delivered.
32685 .cindex "log" "&%fail%& command log line"
32686 .cindex "&%fail%&" "log line; reducing"
32687 The text given with a fail command is used as part of the bounce message as
32688 well as being written to the log. If the message is quite long, this can fill
32689 up a lot of log space when such failures are common. To reduce the size of the
32690 log message, Exim interprets the text in a special way if it starts with the
32691 two characters &`<<`& and contains &`>>`& later. The text between these two
32692 strings is written to the log, and the rest of the text is used in the bounce
32693 message. For example:
32695 fail "<<filter test 1>>Your message is rejected \
32696 because it contains attachments that we are \
32697 not prepared to receive."
32700 .cindex "loop" "caused by &%fail%&"
32701 Take great care with the &%fail%& command when basing the decision to fail on
32702 the contents of the message, because the bounce message will of course include
32703 the contents of the original message and will therefore trigger the &%fail%&
32704 command again (causing a mail loop) unless steps are taken to prevent this.
32705 Testing the &%error_message%& condition is one way to prevent this. You could
32708 if $message_body contains "this is spam" and not error_message
32709 then fail text "spam is not wanted here" endif
32711 though of course that might let through unwanted bounce messages. The
32712 alternative is clever checking of the body and/or headers to detect bounces
32713 generated by the filter.
32715 The interpretation of a system filter file ceases after a
32717 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
32718 set up earlier in the filter file are honoured, so you can use a sequence such
32724 to send a specified message when the system filter is freezing (or deferring or
32725 failing) a message. The normal deliveries for the message do not, of course,
32730 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
32731 .cindex "header lines" "adding; in system filter"
32732 .cindex "header lines" "removing; in system filter"
32733 .cindex "filter" "header lines; adding/removing"
32734 Two filter commands that are available only in system filters are:
32736 headers add <string>
32737 headers remove <string>
32739 The argument for the &%headers add%& is a string that is expanded and then
32740 added to the end of the message's headers. It is the responsibility of the
32741 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
32742 space is ignored, and if the string is otherwise empty, or if the expansion is
32743 forced to fail, the command has no effect.
32745 You can use &"\n"& within the string, followed by white space, to specify
32746 continued header lines. More than one header may be added in one command by
32747 including &"\n"& within the string without any following white space. For
32750 headers add "X-header-1: ....\n \
32751 continuation of X-header-1 ...\n\
32754 Note that the header line continuation white space after the first newline must
32755 be placed before the backslash that continues the input string, because white
32756 space after input continuations is ignored.
32758 The argument for &%headers remove%& is a colon-separated list of header names.
32759 This command applies only to those headers that are stored with the message;
32760 those that are added at delivery time (such as &'Envelope-To:'& and
32761 &'Return-Path:'&) cannot be removed by this means. If there is more than one
32762 header with the same name, they are all removed.
32764 The &%headers%& command in a system filter makes an immediate change to the set
32765 of header lines that was received with the message (with possible additions
32766 from ACL processing). Subsequent commands in the system filter operate on the
32767 modified set, which also forms the basis for subsequent message delivery.
32768 Unless further modified during routing or transporting, this set of headers is
32769 used for all recipients of the message.
32771 During routing and transporting, the variables that refer to the contents of
32772 header lines refer only to those lines that are in this set. Thus, header lines
32773 that are added by a system filter are visible to users' filter files and to all
32774 routers and transports. This contrasts with the manipulation of header lines by
32775 routers and transports, which is not immediate, but which instead is saved up
32776 until the message is actually being written (see section
32777 &<<SECTheadersaddrem>>&).
32779 If the message is not delivered at the first attempt, header lines that were
32780 added by the system filter are stored with the message, and so are still
32781 present at the next delivery attempt. Header lines that were removed are still
32782 present, but marked &"deleted"& so that they are not transported with the
32783 message. For this reason, it is usual to make the &%headers%& command
32784 conditional on &%first_delivery%& so that the set of header lines is not
32785 modified more than once.
32787 Because header modification in a system filter acts immediately, you have to
32788 use an indirect approach if you want to modify the contents of a header line.
32791 headers add "Old-Subject: $h_subject:"
32792 headers remove "Subject"
32793 headers add "Subject: new subject (was: $h_old-subject:)"
32794 headers remove "Old-Subject"
32799 .section "Setting an errors address in a system filter" "SECID217"
32800 .cindex "envelope sender"
32801 In a system filter, if a &%deliver%& command is followed by
32803 errors_to <some address>
32805 in order to change the envelope sender (and hence the error reporting) for that
32806 delivery, any address may be specified. (In a user filter, only the current
32807 user's address can be set.) For example, if some mail is being monitored, you
32810 unseen deliver monitor@spying.example errors_to root@local.example
32812 to take a copy which would not be sent back to the normal error reporting
32813 address if its delivery failed.
32817 .section "Per-address filtering" "SECTperaddfil"
32818 .vindex "&$domain$&"
32819 .vindex "&$local_part$&"
32820 In contrast to the system filter, which is run just once per message for each
32821 delivery attempt, it is also possible to set up a system-wide filtering
32822 operation that runs once for each recipient address. In this case, variables
32823 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
32824 filter file could be made dependent on them. This is an example of a router
32825 which implements such a filter:
32830 domains = +local_domains
32831 file = /central/filters/$local_part
32836 The filter is run in a separate process under its own uid. Therefore, either
32837 &%check_local_user%& must be set (as above), in which case the filter is run as
32838 the local user, or the &%user%& option must be used to specify which user to
32839 use. If both are set, &%user%& overrides.
32841 Care should be taken to ensure that none of the commands in the filter file
32842 specify a significant delivery if the message is to go on to be delivered to
32843 its intended recipient. The router will not then claim to have dealt with the
32844 address, so it will be passed on to subsequent routers to be delivered in the
32846 .ecindex IIDsysfil1
32847 .ecindex IIDsysfil2
32848 .ecindex IIDsysfil3
32855 . ////////////////////////////////////////////////////////////////////////////
32856 . ////////////////////////////////////////////////////////////////////////////
32858 .chapter "Message processing" "CHAPmsgproc"
32859 .scindex IIDmesproc "message" "general processing"
32860 Exim performs various transformations on the sender and recipient addresses of
32861 all messages that it handles, and also on the messages' header lines. Some of
32862 these are optional and configurable, while others always take place. All of
32863 this processing, except rewriting as a result of routing, and the addition or
32864 removal of header lines while delivering, happens when a message is received,
32865 before it is placed on Exim's queue.
32867 Some of the automatic processing takes place by default only for
32868 &"locally-originated"& messages. This adjective is used to describe messages
32869 that are not received over TCP/IP, but instead are passed to an Exim process on
32870 its standard input. This includes the interactive &"local SMTP"& case that is
32871 set up by the &%-bs%& command line option.
32873 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
32874 or ::1) are not considered to be locally-originated. Exim does not treat the
32875 loopback interface specially in any way.
32877 If you want the loopback interface to be treated specially, you must ensure
32878 that there are appropriate entries in your ACLs.
32883 .section "Submission mode for non-local messages" "SECTsubmodnon"
32884 .cindex "message" "submission"
32885 .cindex "submission mode"
32886 Processing that happens automatically for locally-originated messages (unless
32887 &%suppress_local_fixups%& is set) can also be requested for messages that are
32888 received over TCP/IP. The term &"submission mode"& is used to describe this
32889 state. Submission mode is set by the modifier
32891 control = submission
32893 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
32894 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
32895 a local submission, and is normally used when the source of the message is
32896 known to be an MUA running on a client host (as opposed to an MTA). For
32897 example, to set submission mode for messages originating on the IPv4 loopback
32898 interface, you could include the following in the MAIL ACL:
32900 warn hosts = 127.0.0.1
32901 control = submission
32903 .cindex "&%sender_retain%& submission option"
32904 There are some options that can be used when setting submission mode. A slash
32905 is used to separate options. For example:
32907 control = submission/sender_retain
32909 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
32910 true and &%local_from_check%& false for the current incoming message. The first
32911 of these allows an existing &'Sender:'& header in the message to remain, and
32912 the second suppresses the check to ensure that &'From:'& matches the
32913 authenticated sender. With this setting, Exim still fixes up messages by adding
32914 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
32915 attempt to check sender authenticity in header lines.
32917 When &%sender_retain%& is not set, a submission mode setting may specify a
32918 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
32921 control = submission/domain=some.domain
32923 The domain may be empty. How this value is used is described in sections
32924 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
32925 that allows you to specify the user's full name for inclusion in a created
32926 &'Sender:'& or &'From:'& header line. For example:
32928 accept authenticated = *
32929 control = submission/domain=wonderland.example/\
32930 name=${lookup {$authenticated_id} \
32931 lsearch {/etc/exim/namelist}}
32933 Because the name may contain any characters, including slashes, the &%name%&
32934 option must be given last. The remainder of the string is used as the name. For
32935 the example above, if &_/etc/exim/namelist_& contains:
32937 bigegg: Humpty Dumpty
32939 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
32942 Sender: Humpty Dumpty <bigegg@wonderland.example>
32944 .cindex "return path" "in submission mode"
32945 By default, submission mode forces the return path to the same address as is
32946 used to create the &'Sender:'& header. However, if &%sender_retain%& is
32947 specified, the return path is also left unchanged.
32949 &*Note*&: The changes caused by submission mode take effect after the predata
32950 ACL. This means that any sender checks performed before the fix-ups use the
32951 untrusted sender address specified by the user, not the trusted sender address
32952 specified by submission mode. Although this might be slightly unexpected, it
32953 does mean that you can configure ACL checks to spot that a user is trying to
32954 spoof another's address.
32956 .section "Line endings" "SECTlineendings"
32957 .cindex "line endings"
32958 .cindex "carriage return"
32960 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
32961 linefeed) is the line ending for messages transmitted over the Internet using
32962 SMTP over TCP/IP. However, within individual operating systems, different
32963 conventions are used. For example, Unix-like systems use just LF, but others
32964 use CRLF or just CR.
32966 Exim was designed for Unix-like systems, and internally, it stores messages
32967 using the system's convention of a single LF as a line terminator. When
32968 receiving a message, all line endings are translated to this standard format.
32969 Originally, it was thought that programs that passed messages directly to an
32970 MTA within an operating system would use that system's convention. Experience
32971 has shown that this is not the case; for example, there are Unix applications
32972 that use CRLF in this circumstance. For this reason, and for compatibility with
32973 other MTAs, the way Exim handles line endings for all messages is now as
32977 LF not preceded by CR is treated as a line ending.
32979 CR is treated as a line ending; if it is immediately followed by LF, the LF
32982 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
32983 nor a local message in the state where a line containing only a dot is a
32986 If a bare CR is encountered within a header line, an extra space is added after
32987 the line terminator so as not to end the header line. The reasoning behind this
32988 is that bare CRs in header lines are most likely either to be mistakes, or
32989 people trying to play silly games.
32991 If the first header line received in a message ends with CRLF, a subsequent
32992 bare LF in a header line is treated in the same way as a bare CR in a header
33000 .section "Unqualified addresses" "SECID218"
33001 .cindex "unqualified addresses"
33002 .cindex "address" "qualification"
33003 By default, Exim expects every envelope address it receives from an external
33004 host to be fully qualified. Unqualified addresses cause negative responses to
33005 SMTP commands. However, because SMTP is used as a means of transporting
33006 messages from MUAs running on personal workstations, there is sometimes a
33007 requirement to accept unqualified addresses from specific hosts or IP networks.
33009 Exim has two options that separately control which hosts may send unqualified
33010 sender or recipient addresses in SMTP commands, namely
33011 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
33012 cases, if an unqualified address is accepted, it is qualified by adding the
33013 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
33015 .oindex "&%qualify_domain%&"
33016 .oindex "&%qualify_recipient%&"
33017 Unqualified addresses in header lines are automatically qualified for messages
33018 that are locally originated, unless the &%-bnq%& option is given on the command
33019 line. For messages received over SMTP, unqualified addresses in header lines
33020 are qualified only if unqualified addresses are permitted in SMTP commands. In
33021 other words, such qualification is also controlled by
33022 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
33027 .section "The UUCP From line" "SECID219"
33028 .cindex "&""From""& line"
33029 .cindex "UUCP" "&""From""& line"
33030 .cindex "sender" "address"
33031 .oindex "&%uucp_from_pattern%&"
33032 .oindex "&%uucp_from_sender%&"
33033 .cindex "envelope sender"
33034 .cindex "Sendmail compatibility" "&""From""& line"
33035 Messages that have come from UUCP (and some other applications) often begin
33036 with a line containing the envelope sender and a timestamp, following the word
33037 &"From"&. Examples of two common formats are:
33039 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
33040 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
33042 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
33043 Exim recognizes such lines at the start of messages that are submitted to it
33044 via the command line (that is, on the standard input). It does not recognize
33045 such lines in incoming SMTP messages, unless the sending host matches
33046 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
33047 and &%ignore_fromline_local%& is set. The recognition is controlled by a
33048 regular expression that is defined by the &%uucp_from_pattern%& option, whose
33049 default value matches the two common cases shown above and puts the address
33050 that follows &"From"& into &$1$&.
33052 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
33053 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
33054 a trusted user, the message's sender address is constructed by expanding the
33055 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
33056 then parsed as an RFC 2822 address. If there is no domain, the local part is
33057 qualified with &%qualify_domain%& unless it is the empty string. However, if
33058 the command line &%-f%& option is used, it overrides the &"From"& line.
33060 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
33061 sender address is not changed. This is also the case for incoming SMTP messages
33062 that are permitted to contain &"From"& lines.
33064 Only one &"From"& line is recognized. If there is more than one, the second is
33065 treated as a data line that starts the body of the message, as it is not valid
33066 as a header line. This also happens if a &"From"& line is present in an
33067 incoming SMTP message from a source that is not permitted to send them.
33071 .section "Resent- header lines" "SECID220"
33072 .cindex "&%Resent-%& header lines"
33073 RFC 2822 makes provision for sets of header lines starting with the string
33074 &`Resent-`& to be added to a message when it is resent by the original
33075 recipient to somebody else. These headers are &'Resent-Date:'&,
33076 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
33077 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
33080 &'Resent fields are strictly informational. They MUST NOT be used in the normal
33081 processing of replies or other such automatic actions on messages.'&
33084 This leaves things a bit vague as far as other processing actions such as
33085 address rewriting are concerned. Exim treats &%Resent-%& header lines as
33089 A &'Resent-From:'& line that just contains the login id of the submitting user
33090 is automatically rewritten in the same way as &'From:'& (see below).
33092 If there's a rewriting rule for a particular header line, it is also applied to
33093 &%Resent-%& header lines of the same type. For example, a rule that rewrites
33094 &'From:'& also rewrites &'Resent-From:'&.
33096 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
33099 For a locally-submitted message,
33100 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
33101 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
33102 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
33103 included in log lines in this case.
33105 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
33106 &%Resent-%& header lines are present.
33112 .section "The Auto-Submitted: header line" "SECID221"
33113 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
33114 includes the header line:
33116 Auto-Submitted: auto-replied
33119 .section "The Bcc: header line" "SECID222"
33120 .cindex "&'Bcc:'& header line"
33121 If Exim is called with the &%-t%& option, to take recipient addresses from a
33122 message's header, it removes any &'Bcc:'& header line that may exist (after
33123 extracting its addresses). If &%-t%& is not present on the command line, any
33124 existing &'Bcc:'& is not removed.
33127 .section "The Date: header line" "SECID223"
33128 .cindex "&'Date:'& header line"
33129 If a locally-generated or submission-mode message has no &'Date:'& header line,
33130 Exim adds one, using the current date and time, unless the
33131 &%suppress_local_fixups%& control has been specified.
33133 .section "The Delivery-date: header line" "SECID224"
33134 .cindex "&'Delivery-date:'& header line"
33135 .oindex "&%delivery_date_remove%&"
33136 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
33137 set. Exim can be configured to add them to the final delivery of messages. (See
33138 the generic &%delivery_date_add%& transport option.) They should not be present
33139 in messages in transit. If the &%delivery_date_remove%& configuration option is
33140 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
33144 .section "The Envelope-to: header line" "SECID225"
33145 .cindex "&'Envelope-to:'& header line"
33146 .oindex "&%envelope_to_remove%&"
33147 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
33148 Exim can be configured to add them to the final delivery of messages. (See the
33149 generic &%envelope_to_add%& transport option.) They should not be present in
33150 messages in transit. If the &%envelope_to_remove%& configuration option is set
33151 (the default), Exim removes &'Envelope-to:'& header lines from incoming
33155 .section "The From: header line" "SECTthefrohea"
33156 .cindex "&'From:'& header line"
33157 .cindex "Sendmail compatibility" "&""From""& line"
33158 .cindex "message" "submission"
33159 .cindex "submission mode"
33160 If a submission-mode message does not contain a &'From:'& header line, Exim
33161 adds one if either of the following conditions is true:
33164 The envelope sender address is not empty (that is, this is not a bounce
33165 message). The added header line copies the envelope sender address.
33167 .vindex "&$authenticated_id$&"
33168 The SMTP session is authenticated and &$authenticated_id$& is not empty.
33170 .vindex "&$qualify_domain$&"
33171 If no domain is specified by the submission control, the local part is
33172 &$authenticated_id$& and the domain is &$qualify_domain$&.
33174 If a non-empty domain is specified by the submission control, the local
33175 part is &$authenticated_id$&, and the domain is the specified domain.
33177 If an empty domain is specified by the submission control,
33178 &$authenticated_id$& is assumed to be the complete address.
33182 A non-empty envelope sender takes precedence.
33184 If a locally-generated incoming message does not contain a &'From:'& header
33185 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
33186 containing the sender's address. The calling user's login name and full name
33187 are used to construct the address, as described in section &<<SECTconstr>>&.
33188 They are obtained from the password data by calling &[getpwuid()]& (but see the
33189 &%unknown_login%& configuration option). The address is qualified with
33190 &%qualify_domain%&.
33192 For compatibility with Sendmail, if an incoming, non-SMTP message has a
33193 &'From:'& header line containing just the unqualified login name of the calling
33194 user, this is replaced by an address containing the user's login name and full
33195 name as described in section &<<SECTconstr>>&.
33198 .section "The Message-ID: header line" "SECID226"
33199 .cindex "&'Message-ID:'& header line"
33200 .cindex "message" "submission"
33201 .oindex "&%message_id_header_text%&"
33202 If a locally-generated or submission-mode incoming message does not contain a
33203 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
33204 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
33205 to the message. If there are any &'Resent-:'& headers in the message, it
33206 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
33207 message id, preceded by the letter E to ensure it starts with a letter, and
33208 followed by @ and the primary host name. Additional information can be included
33209 in this header line by setting the &%message_id_header_text%& and/or
33210 &%message_id_header_domain%& options.
33213 .section "The Received: header line" "SECID227"
33214 .cindex "&'Received:'& header line"
33215 A &'Received:'& header line is added at the start of every message. The
33216 contents are defined by the &%received_header_text%& configuration option, and
33217 Exim automatically adds a semicolon and a timestamp to the configured string.
33219 The &'Received:'& header is generated as soon as the message's header lines
33220 have been received. At this stage, the timestamp in the &'Received:'& header
33221 line is the time that the message started to be received. This is the value
33222 that is seen by the DATA ACL and by the &[local_scan()]& function.
33224 Once a message is accepted, the timestamp in the &'Received:'& header line is
33225 changed to the time of acceptance, which is (apart from a small delay while the
33226 -H spool file is written) the earliest time at which delivery could start.
33229 .section "The References: header line" "SECID228"
33230 .cindex "&'References:'& header line"
33231 Messages created by the &(autoreply)& transport include a &'References:'&
33232 header line. This is constructed according to the rules that are described in
33233 section 3.64 of RFC 2822 (which states that replies should contain such a
33234 header line), and section 3.14 of RFC 3834 (which states that automatic
33235 responses are not different in this respect). However, because some mail
33236 processing software does not cope well with very long header lines, no more
33237 than 12 message IDs are copied from the &'References:'& header line in the
33238 incoming message. If there are more than 12, the first one and then the final
33239 11 are copied, before adding the message ID of the incoming message.
33243 .section "The Return-path: header line" "SECID229"
33244 .cindex "&'Return-path:'& header line"
33245 .oindex "&%return_path_remove%&"
33246 &'Return-path:'& header lines are defined as something an MTA may insert when
33247 it does the final delivery of messages. (See the generic &%return_path_add%&
33248 transport option.) Therefore, they should not be present in messages in
33249 transit. If the &%return_path_remove%& configuration option is set (the
33250 default), Exim removes &'Return-path:'& header lines from incoming messages.
33254 .section "The Sender: header line" "SECTthesenhea"
33255 .cindex "&'Sender:'& header line"
33256 .cindex "message" "submission"
33257 For a locally-originated message from an untrusted user, Exim may remove an
33258 existing &'Sender:'& header line, and it may add a new one. You can modify
33259 these actions by setting the &%local_sender_retain%& option true, the
33260 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
33263 When a local message is received from an untrusted user and
33264 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
33265 control has not been set, a check is made to see if the address given in the
33266 &'From:'& header line is the correct (local) sender of the message. The address
33267 that is expected has the login name as the local part and the value of
33268 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
33269 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
33270 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
33271 line is added to the message.
33273 If you set &%local_from_check%& false, this checking does not occur. However,
33274 the removal of an existing &'Sender:'& line still happens, unless you also set
33275 &%local_sender_retain%& to be true. It is not possible to set both of these
33276 options true at the same time.
33278 .cindex "submission mode"
33279 By default, no processing of &'Sender:'& header lines is done for messages
33280 received over TCP/IP or for messages submitted by trusted users. However, when
33281 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
33282 not specified on the submission control, the following processing takes place:
33284 .vindex "&$authenticated_id$&"
33285 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
33286 authenticated, and &$authenticated_id$& is not empty, a sender address is
33287 created as follows:
33290 .vindex "&$qualify_domain$&"
33291 If no domain is specified by the submission control, the local part is
33292 &$authenticated_id$& and the domain is &$qualify_domain$&.
33294 If a non-empty domain is specified by the submission control, the local part
33295 is &$authenticated_id$&, and the domain is the specified domain.
33297 If an empty domain is specified by the submission control,
33298 &$authenticated_id$& is assumed to be the complete address.
33301 This address is compared with the address in the &'From:'& header line. If they
33302 are different, a &'Sender:'& header line containing the created address is
33303 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
33304 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
33306 .cindex "return path" "created from &'Sender:'&"
33307 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
33308 the message (the envelope sender address) is changed to be the same address,
33309 except in the case of submission mode when &%sender_retain%& is specified.
33313 .section "Adding and removing header lines in routers and transports" &&&
33314 "SECTheadersaddrem"
33315 .cindex "header lines" "adding; in router or transport"
33316 .cindex "header lines" "removing; in router or transport"
33317 When a message is delivered, the addition and removal of header lines can be
33318 specified in a system filter, or on any of the routers and transports that
33319 process the message. Section &<<SECTaddremheasys>>& contains details about
33320 modifying headers in a system filter. Header lines can also be added in an ACL
33321 as a message is received (see section &<<SECTaddheadacl>>&).
33323 In contrast to what happens in a system filter, header modifications that are
33324 specified on routers and transports apply only to the particular recipient
33325 addresses that are being processed by those routers and transports. These
33326 changes do not actually take place until a copy of the message is being
33327 transported. Therefore, they do not affect the basic set of header lines, and
33328 they do not affect the values of the variables that refer to header lines.
33330 &*Note*&: In particular, this means that any expansions in the configuration of
33331 the transport cannot refer to the modified header lines, because such
33332 expansions all occur before the message is actually transported.
33334 For both routers and transports, the argument of a &%headers_add%&
33335 option must be in the form of one or more RFC 2822 header lines, separated by
33336 newlines (coded as &"\n"&). For example:
33338 headers_add = X-added-header: added by $primary_hostname\n\
33339 X-added-second: another added header line
33341 Exim does not check the syntax of these added header lines.
33343 Multiple &%headers_add%& options for a single router or transport can be
33344 specified; the values will append to a single list of header lines.
33345 Each header-line is separately expanded.
33347 The argument of a &%headers_remove%& option must consist of a colon-separated
33348 list of header names. This is confusing, because header names themselves are
33349 often terminated by colons. In this case, the colons are the list separators,
33350 not part of the names. For example:
33352 headers_remove = return-receipt-to:acknowledge-to
33355 Multiple &%headers_remove%& options for a single router or transport can be
33356 specified; the arguments will append to a single header-names list.
33357 Each item is separately expanded.
33358 Note that colons in complex expansions which are used to
33359 form all or part of a &%headers_remove%& list
33360 will act as list separators.
33362 When &%headers_add%& or &%headers_remove%& is specified on a router,
33363 items are expanded at routing time,
33364 and then associated with all addresses that are
33365 accepted by that router, and also with any new addresses that it generates. If
33366 an address passes through several routers as a result of aliasing or
33367 forwarding, the changes are cumulative.
33369 .oindex "&%unseen%&"
33370 However, this does not apply to multiple routers that result from the use of
33371 the &%unseen%& option. Any header modifications that were specified by the
33372 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
33374 Addresses that end up with different &%headers_add%& or &%headers_remove%&
33375 settings cannot be delivered together in a batch, so a transport is always
33376 dealing with a set of addresses that have the same header-processing
33379 The transport starts by writing the original set of header lines that arrived
33380 with the message, possibly modified by the system filter. As it writes out
33381 these lines, it consults the list of header names that were attached to the
33382 recipient address(es) by &%headers_remove%& options in routers, and it also
33383 consults the transport's own &%headers_remove%& option. Header lines whose
33384 names are on either of these lists are not written out. If there are multiple
33385 instances of any listed header, they are all skipped.
33387 After the remaining original header lines have been written, new header
33388 lines that were specified by routers' &%headers_add%& options are written, in
33389 the order in which they were attached to the address. These are followed by any
33390 header lines specified by the transport's &%headers_add%& option.
33392 This way of handling header line modifications in routers and transports has
33393 the following consequences:
33396 The original set of header lines, possibly modified by the system filter,
33397 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
33398 to it, at all times.
33400 Header lines that are added by a router's
33401 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
33402 expansion syntax in subsequent routers or the transport.
33404 Conversely, header lines that are specified for removal by &%headers_remove%&
33405 in a router remain visible to subsequent routers and the transport.
33407 Headers added to an address by &%headers_add%& in a router cannot be removed by
33408 a later router or by a transport.
33410 An added header can refer to the contents of an original header that is to be
33411 removed, even it has the same name as the added header. For example:
33413 headers_remove = subject
33414 headers_add = Subject: new subject (was: $h_subject:)
33418 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
33419 for a &(redirect)& router that has the &%one_time%& option set.
33425 .section "Constructed addresses" "SECTconstr"
33426 .cindex "address" "constructed"
33427 .cindex "constructed address"
33428 When Exim constructs a sender address for a locally-generated message, it uses
33431 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
33435 Zaphod Beeblebrox <zaphod@end.univ.example>
33437 The user name is obtained from the &%-F%& command line option if set, or
33438 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
33439 &"gecos"& field from the password entry. If the &"gecos"& field contains an
33440 ampersand character, this is replaced by the login name with the first letter
33441 upper cased, as is conventional in a number of operating systems. See the
33442 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
33443 The &%unknown_username%& option can be used to specify user names in cases when
33444 there is no password file entry.
33447 In all cases, the user name is made to conform to RFC 2822 by quoting all or
33448 parts of it if necessary. In addition, if it contains any non-printing
33449 characters, it is encoded as described in RFC 2047, which defines a way of
33450 including non-ASCII characters in header lines. The value of the
33451 &%headers_charset%& option specifies the name of the encoding that is used (the
33452 characters are assumed to be in this encoding). The setting of
33453 &%print_topbitchars%& controls whether characters with the top bit set (that
33454 is, with codes greater than 127) count as printing characters or not.
33458 .section "Case of local parts" "SECID230"
33459 .cindex "case of local parts"
33460 .cindex "local part" "case of"
33461 RFC 2822 states that the case of letters in the local parts of addresses cannot
33462 be assumed to be non-significant. Exim preserves the case of local parts of
33463 addresses, but by default it uses a lower-cased form when it is routing,
33464 because on most Unix systems, usernames are in lower case and case-insensitive
33465 routing is required. However, any particular router can be made to use the
33466 original case for local parts by setting the &%caseful_local_part%& generic
33469 .cindex "mixed-case login names"
33470 If you must have mixed-case user names on your system, the best way to proceed,
33471 assuming you want case-independent handling of incoming email, is to set up
33472 your first router to convert incoming local parts in your domains to the
33473 correct case by means of a file lookup. For example:
33477 domains = +local_domains
33478 data = ${lookup{$local_part}cdb\
33479 {/etc/usercased.cdb}{$value}fail}\
33482 For this router, the local part is forced to lower case by the default action
33483 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
33484 up a new local part in the correct case. If you then set &%caseful_local_part%&
33485 on any subsequent routers which process your domains, they will operate on
33486 local parts with the correct case in a case-sensitive manner.
33490 .section "Dots in local parts" "SECID231"
33491 .cindex "dot" "in local part"
33492 .cindex "local part" "dots in"
33493 RFC 2822 forbids empty components in local parts. That is, an unquoted local
33494 part may not begin or end with a dot, nor have two consecutive dots in the
33495 middle. However, it seems that many MTAs do not enforce this, so Exim permits
33496 empty components for compatibility.
33500 .section "Rewriting addresses" "SECID232"
33501 .cindex "rewriting" "addresses"
33502 Rewriting of sender and recipient addresses, and addresses in headers, can
33503 happen automatically, or as the result of configuration options, as described
33504 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
33505 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
33507 Automatic rewriting includes qualification, as mentioned above. The other case
33508 in which it can happen is when an incomplete non-local domain is given. The
33509 routing process may cause this to be expanded into the full domain name. For
33510 example, a header such as
33514 might get rewritten as
33516 To: hare@teaparty.wonderland.fict.example
33518 Rewriting as a result of routing is the one kind of message processing that
33519 does not happen at input time, as it cannot be done until the address has
33522 Strictly, one should not do &'any'& deliveries of a message until all its
33523 addresses have been routed, in case any of the headers get changed as a
33524 result of routing. However, doing this in practice would hold up many
33525 deliveries for unreasonable amounts of time, just because one address could not
33526 immediately be routed. Exim therefore does not delay other deliveries when
33527 routing of one or more addresses is deferred.
33528 .ecindex IIDmesproc
33532 . ////////////////////////////////////////////////////////////////////////////
33533 . ////////////////////////////////////////////////////////////////////////////
33535 .chapter "SMTP processing" "CHAPSMTP"
33536 .scindex IIDsmtpproc1 "SMTP" "processing details"
33537 .scindex IIDsmtpproc2 "LMTP" "processing details"
33538 Exim supports a number of different ways of using the SMTP protocol, and its
33539 LMTP variant, which is an interactive protocol for transferring messages into a
33540 closed mail store application. This chapter contains details of how SMTP is
33541 processed. For incoming mail, the following are available:
33544 SMTP over TCP/IP (Exim daemon or &'inetd'&);
33546 SMTP over the standard input and output (the &%-bs%& option);
33548 Batched SMTP on the standard input (the &%-bS%& option).
33551 For mail delivery, the following are available:
33554 SMTP over TCP/IP (the &(smtp)& transport);
33556 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
33559 LMTP over a pipe to a process running in the local host (the &(lmtp)&
33562 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
33563 the &%use_bsmtp%& option set).
33566 &'Batched SMTP'& is the name for a process in which batches of messages are
33567 stored in or read from files (or pipes), in a format in which SMTP commands are
33568 used to contain the envelope information.
33572 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
33573 .cindex "SMTP" "outgoing over TCP/IP"
33574 .cindex "outgoing SMTP over TCP/IP"
33575 .cindex "LMTP" "over TCP/IP"
33576 .cindex "outgoing LMTP over TCP/IP"
33579 .cindex "SIZE option on MAIL command"
33580 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
33581 The &%protocol%& option selects which protocol is to be used, but the actual
33582 processing is the same in both cases.
33584 If, in response to its EHLO command, Exim is told that the SIZE
33585 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
33586 command. The value of <&'n'&> is the message size plus the value of the
33587 &%size_addition%& option (default 1024) to allow for additions to the message
33588 such as per-transport header lines, or changes made in a
33589 .cindex "transport" "filter"
33590 .cindex "filter" "transport filter"
33591 transport filter. If &%size_addition%& is set negative, the use of SIZE is
33594 If the remote server advertises support for PIPELINING, Exim uses the
33595 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
33596 required for the transaction.
33598 If the remote server advertises support for the STARTTLS command, and Exim
33599 was built to support TLS encryption, it tries to start a TLS session unless the
33600 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
33601 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
33602 is called for verification.
33604 If the remote server advertises support for the AUTH command, Exim scans
33605 the authenticators configuration for any suitable client settings, as described
33606 in chapter &<<CHAPSMTPAUTH>>&.
33608 .cindex "carriage return"
33610 Responses from the remote host are supposed to be terminated by CR followed by
33611 LF. However, there are known to be hosts that do not send CR characters, so in
33612 order to be able to interwork with such hosts, Exim treats LF on its own as a
33615 If a message contains a number of different addresses, all those with the same
33616 characteristics (for example, the same envelope sender) that resolve to the
33617 same set of hosts, in the same order, are sent in a single SMTP transaction,
33618 even if they are for different domains, unless there are more than the setting
33619 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
33620 they are split into groups containing no more than &%max_rcpt%&s addresses
33621 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
33622 in parallel sessions. The order of hosts with identical MX values is not
33623 significant when checking whether addresses can be batched in this way.
33625 When the &(smtp)& transport suffers a temporary failure that is not
33626 message-related, Exim updates its transport-specific database, which contains
33627 records indexed by host name that remember which messages are waiting for each
33628 particular host. It also updates the retry database with new retry times.
33630 .cindex "hints database" "retry keys"
33631 Exim's retry hints are based on host name plus IP address, so if one address of
33632 a multi-homed host is broken, it will soon be skipped most of the time.
33633 See the next section for more detail about error handling.
33635 .cindex "SMTP" "passed connection"
33636 .cindex "SMTP" "batching over TCP/IP"
33637 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
33638 looks in the hints database for the transport to see if there are any queued
33639 messages waiting for the host to which it is connected. If it finds one, it
33640 creates a new Exim process using the &%-MC%& option (which can only be used by
33641 a process running as root or the Exim user) and passes the TCP/IP socket to it
33642 so that it can deliver another message using the same socket. The new process
33643 does only those deliveries that are routed to the connected host, and may in
33644 turn pass the socket on to a third process, and so on.
33646 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
33647 limit the number of messages sent down a single TCP/IP connection.
33649 .cindex "asterisk" "after IP address"
33650 The second and subsequent messages delivered down an existing connection are
33651 identified in the main log by the addition of an asterisk after the closing
33652 square bracket of the IP address.
33657 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
33658 .cindex "error" "in outgoing SMTP"
33659 .cindex "SMTP" "errors in outgoing"
33660 .cindex "host" "error"
33661 Three different kinds of error are recognized for outgoing SMTP: host errors,
33662 message errors, and recipient errors.
33665 .vitem "&*Host errors*&"
33666 A host error is not associated with a particular message or with a
33667 particular recipient of a message. The host errors are:
33670 Connection refused or timed out,
33672 Any error response code on connection,
33674 Any error response code to EHLO or HELO,
33676 Loss of connection at any time, except after &"."&,
33678 I/O errors at any time,
33680 Timeouts during the session, other than in response to MAIL, RCPT or
33681 the &"."& at the end of the data.
33684 For a host error, a permanent error response on connection, or in response to
33685 EHLO, causes all addresses routed to the host to be failed. Any other host
33686 error causes all addresses to be deferred, and retry data to be created for the
33687 host. It is not tried again, for any message, until its retry time arrives. If
33688 the current set of addresses are not all delivered in this run (to some
33689 alternative host), the message is added to the list of those waiting for this
33690 host, so if it is still undelivered when a subsequent successful delivery is
33691 made to the host, it will be sent down the same SMTP connection.
33693 .vitem "&*Message errors*&"
33694 .cindex "message" "error"
33695 A message error is associated with a particular message when sent to a
33696 particular host, but not with a particular recipient of the message. The
33697 message errors are:
33700 Any error response code to MAIL, DATA, or the &"."& that terminates
33703 Timeout after MAIL,
33705 Timeout or loss of connection after the &"."& that terminates the data. A
33706 timeout after the DATA command itself is treated as a host error, as is loss of
33707 connection at any other time.
33710 For a message error, a permanent error response (5&'xx'&) causes all addresses
33711 to be failed, and a delivery error report to be returned to the sender. A
33712 temporary error response (4&'xx'&), or one of the timeouts, causes all
33713 addresses to be deferred. Retry data is not created for the host, but instead,
33714 a retry record for the combination of host plus message id is created. The
33715 message is not added to the list of those waiting for this host. This ensures
33716 that the failing message will not be sent to this host again until the retry
33717 time arrives. However, other messages that are routed to the host are not
33718 affected, so if it is some property of the message that is causing the error,
33719 it will not stop the delivery of other mail.
33721 If the remote host specified support for the SIZE parameter in its response
33722 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
33723 over-large message will cause a message error because the error arrives as a
33726 .vitem "&*Recipient errors*&"
33727 .cindex "recipient" "error"
33728 A recipient error is associated with a particular recipient of a message. The
33729 recipient errors are:
33732 Any error response to RCPT,
33734 Timeout after RCPT.
33737 For a recipient error, a permanent error response (5&'xx'&) causes the
33738 recipient address to be failed, and a bounce message to be returned to the
33739 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
33740 address to be deferred, and routing retry data to be created for it. This is
33741 used to delay processing of the address in subsequent queue runs, until its
33742 routing retry time arrives. This applies to all messages, but because it
33743 operates only in queue runs, one attempt will be made to deliver a new message
33744 to the failing address before the delay starts to operate. This ensures that,
33745 if the failure is really related to the message rather than the recipient
33746 (&"message too big for this recipient"& is a possible example), other messages
33747 have a chance of getting delivered. If a delivery to the address does succeed,
33748 the retry information gets cleared, so all stuck messages get tried again, and
33749 the retry clock is reset.
33751 The message is not added to the list of those waiting for this host. Use of the
33752 host for other messages is unaffected, and except in the case of a timeout,
33753 other recipients are processed independently, and may be successfully delivered
33754 in the current SMTP session. After a timeout it is of course impossible to
33755 proceed with the session, so all addresses get deferred. However, those other
33756 than the one that failed do not suffer any subsequent retry delays. Therefore,
33757 if one recipient is causing trouble, the others have a chance of getting
33758 through when a subsequent delivery attempt occurs before the failing
33759 recipient's retry time.
33762 In all cases, if there are other hosts (or IP addresses) available for the
33763 current set of addresses (for example, from multiple MX records), they are
33764 tried in this run for any undelivered addresses, subject of course to their
33765 own retry data. In other words, recipient error retry data does not take effect
33766 until the next delivery attempt.
33768 Some hosts have been observed to give temporary error responses to every
33769 MAIL command at certain times (&"insufficient space"& has been seen). It
33770 would be nice if such circumstances could be recognized, and defer data for the
33771 host itself created, but this is not possible within the current Exim design.
33772 What actually happens is that retry data for every (host, message) combination
33775 The reason that timeouts after MAIL and RCPT are treated specially is that
33776 these can sometimes arise as a result of the remote host's verification
33777 procedures. Exim makes this assumption, and treats them as if a temporary error
33778 response had been received. A timeout after &"."& is treated specially because
33779 it is known that some broken implementations fail to recognize the end of the
33780 message if the last character of the last line is a binary zero. Thus, it is
33781 helpful to treat this case as a message error.
33783 Timeouts at other times are treated as host errors, assuming a problem with the
33784 host, or the connection to it. If a timeout after MAIL, RCPT,
33785 or &"."& is really a connection problem, the assumption is that at the next try
33786 the timeout is likely to occur at some other point in the dialogue, causing it
33787 then to be treated as a host error.
33789 There is experimental evidence that some MTAs drop the connection after the
33790 terminating &"."& if they do not like the contents of the message for some
33791 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
33792 should be given. That is why Exim treats this case as a message rather than a
33793 host error, in order not to delay other messages to the same host.
33798 .section "Incoming SMTP messages over TCP/IP" "SECID233"
33799 .cindex "SMTP" "incoming over TCP/IP"
33800 .cindex "incoming SMTP over TCP/IP"
33803 Incoming SMTP messages can be accepted in one of two ways: by running a
33804 listening daemon, or by using &'inetd'&. In the latter case, the entry in
33805 &_/etc/inetd.conf_& should be like this:
33807 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
33809 Exim distinguishes between this case and the case of a locally running user
33810 agent using the &%-bs%& option by checking whether or not the standard input is
33811 a socket. When it is, either the port must be privileged (less than 1024), or
33812 the caller must be root or the Exim user. If any other user passes a socket
33813 with an unprivileged port number, Exim prints a message on the standard error
33814 stream and exits with an error code.
33816 By default, Exim does not make a log entry when a remote host connects or
33817 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
33818 unexpected. It can be made to write such log entries by setting the
33819 &%smtp_connection%& log selector.
33821 .cindex "carriage return"
33823 Commands from the remote host are supposed to be terminated by CR followed by
33824 LF. However, there are known to be hosts that do not send CR characters. In
33825 order to be able to interwork with such hosts, Exim treats LF on its own as a
33827 Furthermore, because common code is used for receiving messages from all
33828 sources, a CR on its own is also interpreted as a line terminator. However, the
33829 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
33831 .cindex "EHLO" "invalid data"
33832 .cindex "HELO" "invalid data"
33833 One area that sometimes gives rise to problems concerns the EHLO or
33834 HELO commands. Some clients send syntactically invalid versions of these
33835 commands, which Exim rejects by default. (This is nothing to do with verifying
33836 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
33837 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
33838 match the broken hosts that send invalid commands.
33840 .cindex "SIZE option on MAIL command"
33841 .cindex "MAIL" "SIZE option"
33842 The amount of disk space available is checked whenever SIZE is received on
33843 a MAIL command, independently of whether &%message_size_limit%& or
33844 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
33845 false. A temporary error is given if there is not enough space. If
33846 &%check_spool_space%& is set, the check is for that amount of space plus the
33847 value given with SIZE, that is, it checks that the addition of the incoming
33848 message will not reduce the space below the threshold.
33850 When a message is successfully received, Exim includes the local message id in
33851 its response to the final &"."& that terminates the data. If the remote host
33852 logs this text it can help with tracing what has happened to a message.
33854 The Exim daemon can limit the number of simultaneous incoming connections it is
33855 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
33856 number of simultaneous incoming connections from a single remote host (see the
33857 &%smtp_accept_max_per_host%& option). Additional connection attempts are
33858 rejected using the SMTP temporary error code 421.
33860 The Exim daemon does not rely on the SIGCHLD signal to detect when a
33861 subprocess has finished, as this can get lost at busy times. Instead, it looks
33862 for completed subprocesses every time it wakes up. Provided there are other
33863 things happening (new incoming calls, starts of queue runs), completed
33864 processes will be noticed and tidied away. On very quiet systems you may
33865 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
33866 it will be noticed when the daemon next wakes up.
33868 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
33869 and can also be set up to reject SMTP calls from non-reserved hosts at times of
33870 high system load &-- for details see the &%smtp_accept_reserve%&,
33871 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
33872 applies in both the daemon and &'inetd'& cases.
33874 Exim normally starts a delivery process for each message received, though this
33875 can be varied by means of the &%-odq%& command line option and the
33876 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
33877 number of simultaneously running delivery processes started in this way from
33878 SMTP input can be limited by the &%smtp_accept_queue%& and
33879 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
33880 subsequently received messages are just put on the input queue without starting
33881 a delivery process.
33883 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
33884 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
33885 started up from the &'inetd'& daemon, because in that case each connection is
33886 handled by an entirely independent Exim process. Control by load average is,
33887 however, available with &'inetd'&.
33889 Exim can be configured to verify addresses in incoming SMTP commands as they
33890 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
33891 to rewrite addresses at this time &-- before any syntax checking is done. See
33892 section &<<SECTrewriteS>>&.
33894 Exim can also be configured to limit the rate at which a client host submits
33895 MAIL and RCPT commands in a single SMTP session. See the
33896 &%smtp_ratelimit_hosts%& option.
33900 .section "Unrecognized SMTP commands" "SECID234"
33901 .cindex "SMTP" "unrecognized commands"
33902 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
33903 commands during a single SMTP connection, it drops the connection after sending
33904 the error response to the last command. The default value for
33905 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
33906 abuse that subvert web servers into making connections to SMTP ports; in these
33907 circumstances, a number of non-SMTP lines are sent first.
33910 .section "Syntax and protocol errors in SMTP commands" "SECID235"
33911 .cindex "SMTP" "syntax errors"
33912 .cindex "SMTP" "protocol errors"
33913 A syntax error is detected if an SMTP command is recognized, but there is
33914 something syntactically wrong with its data, for example, a malformed email
33915 address in a RCPT command. Protocol errors include invalid command
33916 sequencing such as RCPT before MAIL. If Exim receives more than
33917 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
33918 drops the connection after sending the error response to the last command. The
33919 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
33920 broken clients that loop sending bad commands (yes, it has been seen).
33924 .section "Use of non-mail SMTP commands" "SECID236"
33925 .cindex "SMTP" "non-mail commands"
33926 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
33927 DATA. Exim counts such commands, and drops the connection if there are too
33928 many of them in a single SMTP session. This action catches some
33929 denial-of-service attempts and things like repeated failing AUTHs, or a mad
33930 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
33931 defines what &"too many"& means. Its default value is 10.
33933 When a new message is expected, one occurrence of RSET is not counted. This
33934 allows a client to send one RSET between messages (this is not necessary,
33935 but some clients do it). Exim also allows one uncounted occurrence of HELO
33936 or EHLO, and one occurrence of STARTTLS between messages. After
33937 starting up a TLS session, another EHLO is expected, and so it too is not
33940 The first occurrence of AUTH in a connection, or immediately following
33941 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
33942 RCPT, DATA, and QUIT are counted.
33944 You can control which hosts are subject to the limit set by
33945 &%smtp_accept_max_nonmail%& by setting
33946 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
33947 the limit apply to all hosts. This option means that you can exclude any
33948 specific badly-behaved hosts that you have to live with.
33953 .section "The VRFY and EXPN commands" "SECID237"
33954 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
33955 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
33956 appropriate) in order to decide whether the command should be accepted or not.
33957 If no ACL is defined, the command is rejected.
33959 .cindex "VRFY" "processing"
33960 When VRFY is accepted, it runs exactly the same code as when Exim is
33961 called with the &%-bv%& option.
33963 .cindex "EXPN" "processing"
33964 When EXPN is accepted, a single-level expansion of the address is done.
33965 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
33966 than a verification (the &%-bv%& option). If an unqualified local part is given
33967 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
33968 of VRFY and EXPN commands are logged on the main and reject logs, and
33969 VRFY verification failures are logged on the main log for consistency with
33974 .section "The ETRN command" "SECTETRN"
33975 .cindex "ETRN" "processing"
33976 RFC 1985 describes an SMTP command called ETRN that is designed to
33977 overcome the security problems of the TURN command (which has fallen into
33978 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
33979 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
33980 should be accepted or not. If no ACL is defined, the command is rejected.
33982 The ETRN command is concerned with &"releasing"& messages that are awaiting
33983 delivery to certain hosts. As Exim does not organize its message queue by host,
33984 the only form of ETRN that is supported by default is the one where the
33985 text starts with the &"#"& prefix, in which case the remainder of the text is
33986 specific to the SMTP server. A valid ETRN command causes a run of Exim with
33987 the &%-R%& option to happen, with the remainder of the ETRN text as its
33988 argument. For example,
33996 which causes a delivery attempt on all messages with undelivered addresses
33997 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
33998 default), Exim prevents the simultaneous execution of more than one queue run
33999 for the same argument string as a result of an ETRN command. This stops
34000 a misbehaving client from starting more than one queue runner at once.
34002 .cindex "hints database" "ETRN serialization"
34003 Exim implements the serialization by means of a hints database in which a
34004 record is written whenever a process is started by ETRN, and deleted when
34005 the process completes. However, Exim does not keep the SMTP session waiting for
34006 the ETRN process to complete. Once ETRN is accepted, the client is sent
34007 a &"success"& return code. Obviously there is scope for hints records to get
34008 left lying around if there is a system or program crash. To guard against this,
34009 Exim ignores any records that are more than six hours old.
34011 .oindex "&%smtp_etrn_command%&"
34012 For more control over what ETRN does, the &%smtp_etrn_command%& option can
34013 used. This specifies a command that is run whenever ETRN is received,
34014 whatever the form of its argument. For
34017 smtp_etrn_command = /etc/etrn_command $domain \
34018 $sender_host_address
34020 .vindex "&$domain$&"
34021 The string is split up into arguments which are independently expanded. The
34022 expansion variable &$domain$& is set to the argument of the ETRN command,
34023 and no syntax checking is done on the contents of this argument. Exim does not
34024 wait for the command to complete, so its status code is not checked. Exim runs
34025 under its own uid and gid when receiving incoming SMTP, so it is not possible
34026 for it to change them before running the command.
34030 .section "Incoming local SMTP" "SECID238"
34031 .cindex "SMTP" "local incoming"
34032 Some user agents use SMTP to pass messages to their local MTA using the
34033 standard input and output, as opposed to passing the envelope on the command
34034 line and writing the message to the standard input. This is supported by the
34035 &%-bs%& option. This form of SMTP is handled in the same way as incoming
34036 messages over TCP/IP (including the use of ACLs), except that the envelope
34037 sender given in a MAIL command is ignored unless the caller is trusted. In
34038 an ACL you can detect this form of SMTP input by testing for an empty host
34039 identification. It is common to have this as the first line in the ACL that
34040 runs for RCPT commands:
34044 This accepts SMTP messages from local processes without doing any other tests.
34048 .section "Outgoing batched SMTP" "SECTbatchSMTP"
34049 .cindex "SMTP" "batched outgoing"
34050 .cindex "batched SMTP output"
34051 Both the &(appendfile)& and &(pipe)& transports can be used for handling
34052 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
34053 be output in BSMTP format. No SMTP responses are possible for this form of
34054 delivery. All it is doing is using SMTP commands as a way of transmitting the
34055 envelope along with the message.
34057 The message is written to the file or pipe preceded by the SMTP commands
34058 MAIL and RCPT, and followed by a line containing a single dot. Lines in
34059 the message that start with a dot have an extra dot added. The SMTP command
34060 HELO is not normally used. If it is required, the &%message_prefix%& option
34061 can be used to specify it.
34063 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
34064 one recipient address at a time by default. However, you can arrange for them
34065 to handle several addresses at once by setting the &%batch_max%& option. When
34066 this is done for BSMTP, messages may contain multiple RCPT commands. See
34067 chapter &<<CHAPbatching>>& for more details.
34070 When one or more addresses are routed to a BSMTP transport by a router that
34071 sets up a host list, the name of the first host on the list is available to the
34072 transport in the variable &$host$&. Here is an example of such a transport and
34077 driver = manualroute
34078 transport = smtp_appendfile
34079 route_list = domain.example batch.host.example
34083 driver = appendfile
34084 directory = /var/bsmtp/$host
34089 This causes messages addressed to &'domain.example'& to be written in BSMTP
34090 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
34091 message (unless there are more than 1000 recipients).
34095 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
34096 .cindex "SMTP" "batched incoming"
34097 .cindex "batched SMTP input"
34098 The &%-bS%& command line option causes Exim to accept one or more messages by
34099 reading SMTP on the standard input, but to generate no responses. If the caller
34100 is trusted, the senders in the MAIL commands are believed; otherwise the
34101 sender is always the caller of Exim. Unqualified senders and receivers are not
34102 rejected (there seems little point) but instead just get qualified. HELO
34103 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
34104 as NOOP; QUIT quits.
34106 Minimal policy checking is done for BSMTP input. Only the non-SMTP
34107 ACL is run in the same way as for non-SMTP local input.
34109 If an error is detected while reading a message, including a missing &"."& at
34110 the end, Exim gives up immediately. It writes details of the error to the
34111 standard output in a stylized way that the calling program should be able to
34112 make some use of automatically, for example:
34114 554 Unexpected end of file
34115 Transaction started in line 10
34116 Error detected in line 14
34118 It writes a more verbose version, for human consumption, to the standard error
34121 An error was detected while processing a file of BSMTP input.
34122 The error message was:
34124 501 '>' missing at end of address
34126 The SMTP transaction started in line 10.
34127 The error was detected in line 12.
34128 The SMTP command at fault was:
34130 rcpt to:<malformed@in.com.plete
34132 1 previous message was successfully processed.
34133 The rest of the batch was abandoned.
34135 The return code from Exim is zero only if there were no errors. It is 1 if some
34136 messages were accepted before an error was detected, and 2 if no messages were
34138 .ecindex IIDsmtpproc1
34139 .ecindex IIDsmtpproc2
34143 . ////////////////////////////////////////////////////////////////////////////
34144 . ////////////////////////////////////////////////////////////////////////////
34146 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
34147 "Customizing messages"
34148 When a message fails to be delivered, or remains on the queue for more than a
34149 configured amount of time, Exim sends a message to the original sender, or
34150 to an alternative configured address. The text of these messages is built into
34151 the code of Exim, but it is possible to change it, either by adding a single
34152 string, or by replacing each of the paragraphs by text supplied in a file.
34154 The &'From:'& and &'To:'& header lines are automatically generated; you can
34155 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
34156 option. Exim also adds the line
34158 Auto-Submitted: auto-generated
34160 to all warning and bounce messages,
34163 .section "Customizing bounce messages" "SECID239"
34164 .cindex "customizing" "bounce message"
34165 .cindex "bounce message" "customizing"
34166 If &%bounce_message_text%& is set, its contents are included in the default
34167 message immediately after &"This message was created automatically by mail
34168 delivery software."& The string is not expanded. It is not used if
34169 &%bounce_message_file%& is set.
34171 When &%bounce_message_file%& is set, it must point to a template file for
34172 constructing error messages. The file consists of a series of text items,
34173 separated by lines consisting of exactly four asterisks. If the file cannot be
34174 opened, default text is used and a message is written to the main and panic
34175 logs. If any text item in the file is empty, default text is used for that
34178 .vindex "&$bounce_recipient$&"
34179 .vindex "&$bounce_return_size_limit$&"
34180 Each item of text that is read from the file is expanded, and there are two
34181 expansion variables which can be of use here: &$bounce_recipient$& is set to
34182 the recipient of an error message while it is being created, and
34183 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
34184 option, rounded to a whole number.
34186 The items must appear in the file in the following order:
34189 The first item is included in the headers, and should include at least a
34190 &'Subject:'& header. Exim does not check the syntax of these headers.
34192 The second item forms the start of the error message. After it, Exim lists the
34193 failing addresses with their error messages.
34195 The third item is used to introduce any text from pipe transports that is to be
34196 returned to the sender. It is omitted if there is no such text.
34198 The fourth, fifth and sixth items will be ignored and may be empty.
34199 The fields exist for back-compatibility
34202 The default state (&%bounce_message_file%& unset) is equivalent to the
34203 following file, in which the sixth item is empty. The &'Subject:'& and some
34204 other lines have been split in order to fit them on the page:
34206 Subject: Mail delivery failed
34207 ${if eq{$sender_address}{$bounce_recipient}
34208 {: returning message to sender}}
34210 This message was created automatically by mail delivery software.
34212 A message ${if eq{$sender_address}{$bounce_recipient}
34213 {that you sent }{sent by
34217 }}could not be delivered to all of its recipients.
34218 This is a permanent error. The following address(es) failed:
34220 The following text was generated during the delivery attempt(s):
34222 ------ This is a copy of the message, including all the headers.
34225 ------ The body of the message is $message_size characters long;
34227 ------ $bounce_return_size_limit or so are included here.
34230 .section "Customizing warning messages" "SECTcustwarn"
34231 .cindex "customizing" "warning message"
34232 .cindex "warning of delay" "customizing the message"
34233 The option &%warn_message_file%& can be pointed at a template file for use when
34234 warnings about message delays are created. In this case there are only three
34238 The first item is included in the headers, and should include at least a
34239 &'Subject:'& header. Exim does not check the syntax of these headers.
34241 The second item forms the start of the warning message. After it, Exim lists
34242 the delayed addresses.
34244 The third item then ends the message.
34247 The default state is equivalent to the following file, except that some lines
34248 have been split here, in order to fit them on the page:
34250 Subject: Warning: message $message_exim_id delayed
34251 $warn_message_delay
34253 This message was created automatically by mail delivery software.
34255 A message ${if eq{$sender_address}{$warn_message_recipients}
34256 {that you sent }{sent by
34260 }}has not been delivered to all of its recipients after
34261 more than $warn_message_delay on the queue on $primary_hostname.
34263 The message identifier is: $message_exim_id
34264 The subject of the message is: $h_subject
34265 The date of the message is: $h_date
34267 The following address(es) have not yet been delivered:
34269 No action is required on your part. Delivery attempts will
34270 continue for some time, and this warning may be repeated at
34271 intervals if the message remains undelivered. Eventually the
34272 mail delivery software will give up, and when that happens,
34273 the message will be returned to you.
34275 .vindex "&$warn_message_delay$&"
34276 .vindex "&$warn_message_recipients$&"
34277 However, in the default state the subject and date lines are omitted if no
34278 appropriate headers exist. During the expansion of this file,
34279 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
34280 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
34281 of recipients for the warning message. There may be more than one if there are
34282 multiple addresses with different &%errors_to%& settings on the routers that
34288 . ////////////////////////////////////////////////////////////////////////////
34289 . ////////////////////////////////////////////////////////////////////////////
34291 .chapter "Some common configuration settings" "CHAPcomconreq"
34292 This chapter discusses some configuration settings that seem to be fairly
34293 common. More examples and discussion can be found in the Exim book.
34297 .section "Sending mail to a smart host" "SECID240"
34298 .cindex "smart host" "example router"
34299 If you want to send all mail for non-local domains to a &"smart host"&, you
34300 should replace the default &(dnslookup)& router with a router which does the
34301 routing explicitly:
34303 send_to_smart_host:
34304 driver = manualroute
34305 route_list = !+local_domains smart.host.name
34306 transport = remote_smtp
34308 You can use the smart host's IP address instead of the name if you wish.
34309 If you are using Exim only to submit messages to a smart host, and not for
34310 receiving incoming messages, you can arrange for it to do the submission
34311 synchronously by setting the &%mua_wrapper%& option (see chapter
34312 &<<CHAPnonqueueing>>&).
34317 .section "Using Exim to handle mailing lists" "SECTmailinglists"
34318 .cindex "mailing lists"
34319 Exim can be used to run simple mailing lists, but for large and/or complicated
34320 requirements, the use of additional specialized mailing list software such as
34321 Majordomo or Mailman is recommended.
34323 The &(redirect)& router can be used to handle mailing lists where each list
34324 is maintained in a separate file, which can therefore be managed by an
34325 independent manager. The &%domains%& router option can be used to run these
34326 lists in a separate domain from normal mail. For example:
34330 domains = lists.example
34331 file = /usr/lists/$local_part
34334 errors_to = $local_part-request@lists.example
34337 This router is skipped for domains other than &'lists.example'&. For addresses
34338 in that domain, it looks for a file that matches the local part. If there is no
34339 such file, the router declines, but because &%no_more%& is set, no subsequent
34340 routers are tried, and so the whole delivery fails.
34342 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
34343 expanded into a file name or a pipe delivery, which is usually inappropriate in
34346 .oindex "&%errors_to%&"
34347 The &%errors_to%& option specifies that any delivery errors caused by addresses
34348 taken from a mailing list are to be sent to the given address rather than the
34349 original sender of the message. However, before acting on this, Exim verifies
34350 the error address, and ignores it if verification fails.
34352 For example, using the configuration above, mail sent to
34353 &'dicts@lists.example'& is passed on to those addresses contained in
34354 &_/usr/lists/dicts_&, with error reports directed to
34355 &'dicts-request@lists.example'&, provided that this address can be verified.
34356 There could be a file called &_/usr/lists/dicts-request_& containing
34357 the address(es) of this particular list's manager(s), but other approaches,
34358 such as setting up an earlier router (possibly using the &%local_part_prefix%&
34359 or &%local_part_suffix%& options) to handle addresses of the form
34360 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
34364 .section "Syntax errors in mailing lists" "SECID241"
34365 .cindex "mailing lists" "syntax errors in"
34366 If an entry in redirection data contains a syntax error, Exim normally defers
34367 delivery of the original address. That means that a syntax error in a mailing
34368 list holds up all deliveries to the list. This may not be appropriate when a
34369 list is being maintained automatically from data supplied by users, and the
34370 addresses are not rigorously checked.
34372 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
34373 entries that fail to parse, noting the incident in the log. If in addition
34374 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
34375 whenever a broken address is skipped. It is usually appropriate to set
34376 &%syntax_errors_to%& to the same address as &%errors_to%&.
34380 .section "Re-expansion of mailing lists" "SECID242"
34381 .cindex "mailing lists" "re-expansion of"
34382 Exim remembers every individual address to which a message has been delivered,
34383 in order to avoid duplication, but it normally stores only the original
34384 recipient addresses with a message. If all the deliveries to a mailing list
34385 cannot be done at the first attempt, the mailing list is re-expanded when the
34386 delivery is next tried. This means that alterations to the list are taken into
34387 account at each delivery attempt, so addresses that have been added to
34388 the list since the message arrived will therefore receive a copy of the
34389 message, even though it pre-dates their subscription.
34391 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
34392 on the &(redirect)& router. If this is done, any addresses generated by the
34393 router that fail to deliver at the first attempt are added to the message as
34394 &"top level"& addresses, and the parent address that generated them is marked
34395 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
34396 subsequent delivery attempts. The disadvantage of this is that if any of the
34397 failing addresses are incorrect, correcting them in the file has no effect on
34398 pre-existing messages.
34400 The original top-level address is remembered with each of the generated
34401 addresses, and is output in any log messages. However, any intermediate parent
34402 addresses are not recorded. This makes a difference to the log only if the
34403 &%all_parents%& selector is set, but for mailing lists there is normally only
34404 one level of expansion anyway.
34408 .section "Closed mailing lists" "SECID243"
34409 .cindex "mailing lists" "closed"
34410 The examples so far have assumed open mailing lists, to which anybody may
34411 send mail. It is also possible to set up closed lists, where mail is accepted
34412 from specified senders only. This is done by making use of the generic
34413 &%senders%& option to restrict the router that handles the list.
34415 The following example uses the same file as a list of recipients and as a list
34416 of permitted senders. It requires three routers:
34420 domains = lists.example
34421 local_part_suffix = -request
34422 file = /usr/lists/$local_part$local_part_suffix
34427 domains = lists.example
34428 senders = ${if exists {/usr/lists/$local_part}\
34429 {lsearch;/usr/lists/$local_part}{*}}
34430 file = /usr/lists/$local_part
34433 errors_to = $local_part-request@lists.example
34438 domains = lists.example
34440 data = :fail: $local_part@lists.example is a closed mailing list
34442 All three routers have the same &%domains%& setting, so for any other domains,
34443 they are all skipped. The first router runs only if the local part ends in
34444 &%-request%&. It handles messages to the list manager(s) by means of an open
34447 The second router runs only if the &%senders%& precondition is satisfied. It
34448 checks for the existence of a list that corresponds to the local part, and then
34449 checks that the sender is on the list by means of a linear search. It is
34450 necessary to check for the existence of the file before trying to search it,
34451 because otherwise Exim thinks there is a configuration error. If the file does
34452 not exist, the expansion of &%senders%& is *, which matches all senders. This
34453 means that the router runs, but because there is no list, declines, and
34454 &%no_more%& ensures that no further routers are run. The address fails with an
34455 &"unrouteable address"& error.
34457 The third router runs only if the second router is skipped, which happens when
34458 a mailing list exists, but the sender is not on it. This router forcibly fails
34459 the address, giving a suitable error message.
34464 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
34466 .cindex "Variable Envelope Return Paths"
34467 .cindex "envelope sender"
34468 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
34469 are a way of helping mailing list administrators discover which subscription
34470 address is the cause of a particular delivery failure. The idea is to encode
34471 the original recipient address in the outgoing envelope sender address, so that
34472 if the message is forwarded by another host and then subsequently bounces, the
34473 original recipient can be extracted from the recipient address of the bounce.
34475 .oindex &%errors_to%&
34476 .oindex &%return_path%&
34477 Envelope sender addresses can be modified by Exim using two different
34478 facilities: the &%errors_to%& option on a router (as shown in previous mailing
34479 list examples), or the &%return_path%& option on a transport. The second of
34480 these is effective only if the message is successfully delivered to another
34481 host; it is not used for errors detected on the local host (see the description
34482 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
34483 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
34489 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34490 {$1-request+$local_part=$domain@your.dom.example}fail}
34492 This has the effect of rewriting the return path (envelope sender) on outgoing
34493 SMTP messages, if the local part of the original return path ends in
34494 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
34495 local part and domain of the recipient into the return path. Suppose, for
34496 example, that a message whose return path has been set to
34497 &'somelist-request@your.dom.example'& is sent to
34498 &'subscriber@other.dom.example'&. In the transport, the return path is
34501 somelist-request+subscriber=other.dom.example@your.dom.example
34503 .vindex "&$local_part$&"
34504 For this to work, you must tell Exim to send multiple copies of messages that
34505 have more than one recipient, so that each copy has just one recipient. This is
34506 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
34507 might be sent to several different recipients in the same domain, in which case
34508 &$local_part$& is not available in the transport, because it is not unique.
34510 Unless your host is doing nothing but mailing list deliveries, you should
34511 probably use a separate transport for the VERP deliveries, so as not to use
34512 extra resources in making one-per-recipient copies for other deliveries. This
34513 can easily be done by expanding the &%transport%& option in the router:
34517 domains = ! +local_domains
34519 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34520 {verp_smtp}{remote_smtp}}
34523 If you want to change the return path using &%errors_to%& in a router instead
34524 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
34525 routers that handle mailing list addresses. This will ensure that all delivery
34526 errors, including those detected on the local host, are sent to the VERP
34529 On a host that does no local deliveries and has no manual routing, only the
34530 &(dnslookup)& router needs to be changed. A special transport is not needed for
34531 SMTP deliveries. Every mailing list recipient has its own return path value,
34532 and so Exim must hand them to the transport one at a time. Here is an example
34533 of a &(dnslookup)& router that implements VERP:
34537 domains = ! +local_domains
34538 transport = remote_smtp
34540 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
34541 {$1-request+$local_part=$domain@your.dom.example}fail}
34544 Before you start sending out messages with VERPed return paths, you must also
34545 configure Exim to accept the bounce messages that come back to those paths.
34546 Typically this is done by setting a &%local_part_suffix%& option for a
34547 router, and using this to route the messages to wherever you want to handle
34550 The overhead incurred in using VERP depends very much on the size of the
34551 message, the number of recipient addresses that resolve to the same remote
34552 host, and the speed of the connection over which the message is being sent. If
34553 a lot of addresses resolve to the same host and the connection is slow, sending
34554 a separate copy of the message for each address may take substantially longer
34555 than sending a single copy with many recipients (for which VERP cannot be
34563 .section "Virtual domains" "SECTvirtualdomains"
34564 .cindex "virtual domains"
34565 .cindex "domain" "virtual"
34566 The phrase &'virtual domain'& is unfortunately used with two rather different
34570 A domain for which there are no real mailboxes; all valid local parts are
34571 aliases for other email addresses. Common examples are organizational
34572 top-level domains and &"vanity"& domains.
34574 One of a number of independent domains that are all handled by the same host,
34575 with mailboxes on that host, but where the mailbox owners do not necessarily
34576 have login accounts on that host.
34579 The first usage is probably more common, and does seem more &"virtual"& than
34580 the second. This kind of domain can be handled in Exim with a straightforward
34581 aliasing router. One approach is to create a separate alias file for each
34582 virtual domain. Exim can test for the existence of the alias file to determine
34583 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
34584 to a router of this form:
34588 domains = dsearch;/etc/mail/virtual
34589 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
34592 The &%domains%& option specifies that the router is to be skipped, unless there
34593 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
34594 domain that is being processed. When the router runs, it looks up the local
34595 part in the file to find a new address (or list of addresses). The &%no_more%&
34596 setting ensures that if the lookup fails (leading to &%data%& being an empty
34597 string), Exim gives up on the address without trying any subsequent routers.
34599 This one router can handle all the virtual domains because the alias file names
34600 follow a fixed pattern. Permissions can be arranged so that appropriate people
34601 can edit the different alias files. A successful aliasing operation results in
34602 a new envelope recipient address, which is then routed from scratch.
34604 The other kind of &"virtual"& domain can also be handled in a straightforward
34605 way. One approach is to create a file for each domain containing a list of
34606 valid local parts, and use it in a router like this:
34610 domains = dsearch;/etc/mail/domains
34611 local_parts = lsearch;/etc/mail/domains/$domain
34612 transport = my_mailboxes
34614 The address is accepted if there is a file for the domain, and the local part
34615 can be found in the file. The &%domains%& option is used to check for the
34616 file's existence because &%domains%& is tested before the &%local_parts%&
34617 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
34618 because that option is tested after &%local_parts%&. The transport is as
34622 driver = appendfile
34623 file = /var/mail/$domain/$local_part
34626 This uses a directory of mailboxes for each domain. The &%user%& setting is
34627 required, to specify which uid is to be used for writing to the mailboxes.
34629 The configuration shown here is just one example of how you might support this
34630 requirement. There are many other ways this kind of configuration can be set
34631 up, for example, by using a database instead of separate files to hold all the
34632 information about the domains.
34636 .section "Multiple user mailboxes" "SECTmulbox"
34637 .cindex "multiple mailboxes"
34638 .cindex "mailbox" "multiple"
34639 .cindex "local part" "prefix"
34640 .cindex "local part" "suffix"
34641 Heavy email users often want to operate with multiple mailboxes, into which
34642 incoming mail is automatically sorted. A popular way of handling this is to
34643 allow users to use multiple sender addresses, so that replies can easily be
34644 identified. Users are permitted to add prefixes or suffixes to their local
34645 parts for this purpose. The wildcard facility of the generic router options
34646 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
34647 example, consider this router:
34652 file = $home/.forward
34653 local_part_suffix = -*
34654 local_part_suffix_optional
34657 .vindex "&$local_part_suffix$&"
34658 It runs a user's &_.forward_& file for all local parts of the form
34659 &'username-*'&. Within the filter file the user can distinguish different
34660 cases by testing the variable &$local_part_suffix$&. For example:
34662 if $local_part_suffix contains -special then
34663 save /home/$local_part/Mail/special
34666 If the filter file does not exist, or does not deal with such addresses, they
34667 fall through to subsequent routers, and, assuming no subsequent use of the
34668 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
34669 control over which suffixes are valid.
34671 Alternatively, a suffix can be used to trigger the use of a different
34672 &_.forward_& file &-- which is the way a similar facility is implemented in
34678 file = $home/.forward$local_part_suffix
34679 local_part_suffix = -*
34680 local_part_suffix_optional
34683 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
34684 example, &_.forward-special_& is used. Once again, if the appropriate file
34685 does not exist, or does not deal with the address, it is passed on to
34686 subsequent routers, which could, if required, look for an unqualified
34687 &_.forward_& file to use as a default.
34691 .section "Simplified vacation processing" "SECID244"
34692 .cindex "vacation processing"
34693 The traditional way of running the &'vacation'& program is for a user to set up
34694 a pipe command in a &_.forward_& file
34695 (see section &<<SECTspecitredli>>& for syntax details).
34696 This is prone to error by inexperienced users. There are two features of Exim
34697 that can be used to make this process simpler for users:
34700 A local part prefix such as &"vacation-"& can be specified on a router which
34701 can cause the message to be delivered directly to the &'vacation'& program, or
34702 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
34703 &_.forward_& file are then much simpler. For example:
34705 spqr, vacation-spqr
34708 The &%require_files%& generic router option can be used to trigger a
34709 vacation delivery by checking for the existence of a certain file in the
34710 user's home directory. The &%unseen%& generic option should also be used, to
34711 ensure that the original delivery also proceeds. In this case, all the user has
34712 to do is to create a file called, say, &_.vacation_&, containing a vacation
34716 Another advantage of both these methods is that they both work even when the
34717 use of arbitrary pipes by users is locked out.
34721 .section "Taking copies of mail" "SECID245"
34722 .cindex "message" "copying every"
34723 Some installations have policies that require archive copies of all messages to
34724 be made. A single copy of each message can easily be taken by an appropriate
34725 command in a system filter, which could, for example, use a different file for
34726 each day's messages.
34728 There is also a shadow transport mechanism that can be used to take copies of
34729 messages that are successfully delivered by local transports, one copy per
34730 delivery. This could be used, &'inter alia'&, to implement automatic
34731 notification of delivery by sites that insist on doing such things.
34735 .section "Intermittently connected hosts" "SECID246"
34736 .cindex "intermittently connected hosts"
34737 It has become quite common (because it is cheaper) for hosts to connect to the
34738 Internet periodically rather than remain connected all the time. The normal
34739 arrangement is that mail for such hosts accumulates on a system that is
34740 permanently connected.
34742 Exim was designed for use on permanently connected hosts, and so it is not
34743 particularly well-suited to use in an intermittently connected environment.
34744 Nevertheless there are some features that can be used.
34747 .section "Exim on the upstream server host" "SECID247"
34748 It is tempting to arrange for incoming mail for the intermittently connected
34749 host to remain on Exim's queue until the client connects. However, this
34750 approach does not scale very well. Two different kinds of waiting message are
34751 being mixed up in the same queue &-- those that cannot be delivered because of
34752 some temporary problem, and those that are waiting for their destination host
34753 to connect. This makes it hard to manage the queue, as well as wasting
34754 resources, because each queue runner scans the entire queue.
34756 A better approach is to separate off those messages that are waiting for an
34757 intermittently connected host. This can be done by delivering these messages
34758 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
34759 format, from where they are transmitted by other software when their
34760 destination connects. This makes it easy to collect all the mail for one host
34761 in a single directory, and to apply local timeout rules on a per-message basis
34764 On a very small scale, leaving the mail on Exim's queue can be made to work. If
34765 you are doing this, you should configure Exim with a long retry period for the
34766 intermittent host. For example:
34768 cheshire.wonderland.fict.example * F,5d,24h
34770 This stops a lot of failed delivery attempts from occurring, but Exim remembers
34771 which messages it has queued up for that host. Once the intermittent host comes
34772 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
34773 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
34774 causes all the queued up messages to be delivered, often down a single SMTP
34775 connection. While the host remains connected, any new messages get delivered
34778 If the connecting hosts do not have fixed IP addresses, that is, if a host is
34779 issued with a different IP address each time it connects, Exim's retry
34780 mechanisms on the holding host get confused, because the IP address is normally
34781 used as part of the key string for holding retry information. This can be
34782 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
34783 Since this has disadvantages for permanently connected hosts, it is best to
34784 arrange a separate transport for the intermittently connected ones.
34788 .section "Exim on the intermittently connected client host" "SECID248"
34789 The value of &%smtp_accept_queue_per_connection%& should probably be
34790 increased, or even set to zero (that is, disabled) on the intermittently
34791 connected host, so that all incoming messages down a single connection get
34792 delivered immediately.
34794 .cindex "SMTP" "passed connection"
34795 .cindex "SMTP" "multiple deliveries"
34796 .cindex "multiple SMTP deliveries"
34797 Mail waiting to be sent from an intermittently connected host will probably
34798 not have been routed, because without a connection DNS lookups are not
34799 possible. This means that if a normal queue run is done at connection time,
34800 each message is likely to be sent in a separate SMTP session. This can be
34801 avoided by starting the queue run with a command line option beginning with
34802 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
34803 first pass, routing is done but no deliveries take place. The second pass is a
34804 normal queue run; since all the messages have been previously routed, those
34805 destined for the same host are likely to get sent as multiple deliveries in a
34806 single SMTP connection.
34810 . ////////////////////////////////////////////////////////////////////////////
34811 . ////////////////////////////////////////////////////////////////////////////
34813 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
34814 "Exim as a non-queueing client"
34815 .cindex "client, non-queueing"
34816 .cindex "smart host" "suppressing queueing"
34817 On a personal computer, it is a common requirement for all
34818 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
34819 configured to operate that way, for all the popular operating systems.
34820 However, there are some MUAs for Unix-like systems that cannot be so
34821 configured: they submit messages using the command line interface of
34822 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
34825 If the personal computer runs continuously, there is no problem, because it can
34826 run a conventional MTA that handles delivery to the smart host, and deal with
34827 any delays via its queueing mechanism. However, if the computer does not run
34828 continuously or runs different operating systems at different times, queueing
34829 email is not desirable.
34831 There is therefore a requirement for something that can provide the
34832 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
34833 any queueing or retrying facilities. Furthermore, the delivery to the smart
34834 host should be synchronous, so that if it fails, the sending MUA is immediately
34835 informed. In other words, we want something that extends an MUA that submits
34836 to a local MTA via the command line so that it behaves like one that submits
34837 to a remote smart host using TCP/SMTP.
34839 There are a number of applications (for example, there is one called &'ssmtp'&)
34840 that do this job. However, people have found them to be lacking in various
34841 ways. For instance, you might want to allow aliasing and forwarding to be done
34842 before sending a message to the smart host.
34844 Exim already had the necessary infrastructure for doing this job. Just a few
34845 tweaks were needed to make it behave as required, though it is somewhat of an
34846 overkill to use a fully-featured MTA for this purpose.
34848 .oindex "&%mua_wrapper%&"
34849 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
34850 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
34851 assumes that it is being used to &"wrap"& a command-line MUA in the manner
34852 just described. As well as setting &%mua_wrapper%&, you also need to provide a
34853 compatible router and transport configuration. Typically there will be just one
34854 router and one transport, sending everything to a smart host.
34856 When run in MUA wrapping mode, the behaviour of Exim changes in the
34860 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
34861 In other words, the only way to submit messages is via the command line.
34863 Each message is synchronously delivered as soon as it is received (&%-odi%& is
34864 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
34865 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
34866 does not finish until the delivery attempt is complete. If the delivery is
34867 successful, a zero return code is given.
34869 Address redirection is permitted, but the final routing for all addresses must
34870 be to the same remote transport, and to the same list of hosts. Furthermore,
34871 the return address (envelope sender) must be the same for all recipients, as
34872 must any added or deleted header lines. In other words, it must be possible to
34873 deliver the message in a single SMTP transaction, however many recipients there
34876 If these conditions are not met, or if routing any address results in a
34877 failure or defer status, or if Exim is unable to deliver all the recipients
34878 successfully to one of the smart hosts, delivery of the entire message fails.
34880 Because no queueing is allowed, all failures are treated as permanent; there
34881 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
34882 smart host. Furthermore, because only a single yes/no response can be given to
34883 the caller, it is not possible to deliver to some recipients and not others. If
34884 there is an error (temporary or permanent) for any recipient, all are failed.
34886 If more than one smart host is listed, Exim will try another host after a
34887 connection failure or a timeout, in the normal way. However, if this kind of
34888 failure happens for all the hosts, the delivery fails.
34890 When delivery fails, an error message is written to the standard error stream
34891 (as well as to Exim's log), and Exim exits to the caller with a return code
34892 value 1. The message is expunged from Exim's spool files. No bounce messages
34893 are ever generated.
34895 No retry data is maintained, and any retry rules are ignored.
34897 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
34898 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
34899 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
34902 The overall effect is that Exim makes a single synchronous attempt to deliver
34903 the message, failing if there is any kind of problem. Because no local
34904 deliveries are done and no daemon can be run, Exim does not need root
34905 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
34906 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
34907 the advantages and disadvantages of running without root privilege.
34912 . ////////////////////////////////////////////////////////////////////////////
34913 . ////////////////////////////////////////////////////////////////////////////
34915 .chapter "Log files" "CHAPlog"
34916 .scindex IIDloggen "log" "general description"
34917 .cindex "log" "types of"
34918 Exim writes three different logs, referred to as the main log, the reject log,
34923 The main log records the arrival of each message and each delivery in a single
34924 line in each case. The format is as compact as possible, in an attempt to keep
34925 down the size of log files. Two-character flag sequences make it easy to pick
34926 out these lines. A number of other events are recorded in the main log. Some of
34927 them are optional, in which case the &%log_selector%& option controls whether
34928 they are included or not. A Perl script called &'eximstats'&, which does simple
34929 analysis of main log files, is provided in the Exim distribution (see section
34930 &<<SECTmailstat>>&).
34932 .cindex "reject log"
34933 The reject log records information from messages that are rejected as a result
34934 of a configuration option (that is, for policy reasons).
34935 The first line of each rejection is a copy of the line that is also written to
34936 the main log. Then, if the message's header has been read at the time the log
34937 is written, its contents are written to this log. Only the original header
34938 lines are available; header lines added by ACLs are not logged. You can use the
34939 reject log to check that your policy controls are working correctly; on a busy
34940 host this may be easier than scanning the main log for rejection messages. You
34941 can suppress the writing of the reject log by setting &%write_rejectlog%&
34944 .cindex "panic log"
34945 .cindex "system log"
34946 When certain serious errors occur, Exim writes entries to its panic log. If the
34947 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
34948 are usually written to the main log as well, but can get lost amid the mass of
34949 other entries. The panic log should be empty under normal circumstances. It is
34950 therefore a good idea to check it (or to have a &'cron'& script check it)
34951 regularly, in order to become aware of any problems. When Exim cannot open its
34952 panic log, it tries as a last resort to write to the system log (syslog). This
34953 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
34954 message itself is written at priority LOG_CRIT.
34957 Every log line starts with a timestamp, in the format shown in the following
34958 example. Note that many of the examples shown in this chapter are line-wrapped.
34959 In the log file, this would be all on one line:
34961 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
34964 By default, the timestamps are in the local timezone. There are two
34965 ways of changing this:
34968 You can set the &%timezone%& option to a different time zone; in particular, if
34973 the timestamps will be in UTC (aka GMT).
34975 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
34978 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
34982 .cindex "log" "process ids in"
34983 .cindex "pid (process id)" "in log lines"
34984 Exim does not include its process id in log lines by default, but you can
34985 request that it does so by specifying the &`pid`& log selector (see section
34986 &<<SECTlogselector>>&). When this is set, the process id is output, in square
34987 brackets, immediately after the time and date.
34992 .section "Where the logs are written" "SECTwhelogwri"
34993 .cindex "log" "destination"
34994 .cindex "log" "to file"
34995 .cindex "log" "to syslog"
34997 The logs may be written to local files, or to syslog, or both. However, it
34998 should be noted that many syslog implementations use UDP as a transport, and
34999 are therefore unreliable in the sense that messages are not guaranteed to
35000 arrive at the loghost, nor is the ordering of messages necessarily maintained.
35001 It has also been reported that on large log files (tens of megabytes) you may
35002 need to tweak syslog to prevent it syncing the file with each write &-- on
35003 Linux this has been seen to make syslog take 90% plus of CPU time.
35005 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
35006 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
35007 configuration. This latter string is expanded, so it can contain, for example,
35008 references to the host name:
35010 log_file_path = /var/log/$primary_hostname/exim_%slog
35012 It is generally advisable, however, to set the string in &_Local/Makefile_&
35013 rather than at run time, because then the setting is available right from the
35014 start of Exim's execution. Otherwise, if there's something it wants to log
35015 before it has read the configuration file (for example, an error in the
35016 configuration file) it will not use the path you want, and may not be able to
35019 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
35020 list, currently limited to at most two items. This is one option where the
35021 facility for changing a list separator may not be used. The list must always be
35022 colon-separated. If an item in the list is &"syslog"& then syslog is used;
35023 otherwise the item must either be an absolute path, containing &`%s`& at the
35024 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
35025 implying the use of a default path.
35027 When Exim encounters an empty item in the list, it searches the list defined by
35028 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
35029 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
35030 mean &"use the path specified at build time"&. It no such item exists, log
35031 files are written in the &_log_& subdirectory of the spool directory. This is
35032 equivalent to the setting:
35034 log_file_path = $spool_directory/log/%slog
35036 If you do not specify anything at build time or run time,
35037 or if you unset the option at run time (i.e. &`log_file_path = `&),
35038 that is where the logs are written.
35040 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
35041 are in use &-- see section &<<SECTdatlogfil>>& below.
35043 Here are some examples of possible settings:
35045 &`LOG_FILE_PATH=syslog `& syslog only
35046 &`LOG_FILE_PATH=:syslog `& syslog and default path
35047 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
35048 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
35050 If there are more than two paths in the list, the first is used and a panic
35055 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
35056 .cindex "log" "cycling local files"
35057 .cindex "cycling logs"
35058 .cindex "&'exicyclog'&"
35059 .cindex "log" "local files; writing to"
35060 Some operating systems provide centralized and standardized methods for cycling
35061 log files. For those that do not, a utility script called &'exicyclog'& is
35062 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
35063 main and reject logs each time it is called. The maximum number of old logs to
35064 keep can be set. It is suggested this script is run as a daily &'cron'& job.
35066 An Exim delivery process opens the main log when it first needs to write to it,
35067 and it keeps the file open in case subsequent entries are required &-- for
35068 example, if a number of different deliveries are being done for the same
35069 message. However, remote SMTP deliveries can take a long time, and this means
35070 that the file may be kept open long after it is renamed if &'exicyclog'& or
35071 something similar is being used to rename log files on a regular basis. To
35072 ensure that a switch of log files is noticed as soon as possible, Exim calls
35073 &[stat()]& on the main log's name before reusing an open file, and if the file
35074 does not exist, or its inode has changed, the old file is closed and Exim
35075 tries to open the main log from scratch. Thus, an old log file may remain open
35076 for quite some time, but no Exim processes should write to it once it has been
35081 .section "Datestamped log files" "SECTdatlogfil"
35082 .cindex "log" "datestamped files"
35083 Instead of cycling the main and reject log files by renaming them
35084 periodically, some sites like to use files whose names contain a datestamp,
35085 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
35086 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
35087 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
35088 point where the datestamp is required. For example:
35090 log_file_path = /var/spool/exim/log/%slog-%D
35091 log_file_path = /var/log/exim-%s-%D.log
35092 log_file_path = /var/spool/exim/log/%D-%slog
35093 log_file_path = /var/log/exim/%s.%M
35095 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
35096 examples of names generated by the above examples:
35098 /var/spool/exim/log/mainlog-20021225
35099 /var/log/exim-reject-20021225.log
35100 /var/spool/exim/log/20021225-mainlog
35101 /var/log/exim/main.200212
35103 When this form of log file is specified, Exim automatically switches to new
35104 files at midnight. It does not make any attempt to compress old logs; you
35105 will need to write your own script if you require this. You should not
35106 run &'exicyclog'& with this form of logging.
35108 The location of the panic log is also determined by &%log_file_path%&, but it
35109 is not datestamped, because rotation of the panic log does not make sense.
35110 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
35111 the string. In addition, if it immediately follows a slash, a following
35112 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
35113 character is removed. Thus, the four examples above would give these panic
35116 /var/spool/exim/log/paniclog
35117 /var/log/exim-panic.log
35118 /var/spool/exim/log/paniclog
35119 /var/log/exim/panic
35123 .section "Logging to syslog" "SECID249"
35124 .cindex "log" "syslog; writing to"
35125 The use of syslog does not change what Exim logs or the format of its messages,
35126 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
35127 Exim's log lines are omitted when these lines are sent to syslog. Apart from
35128 that, the same strings are written to syslog as to log files. The syslog
35129 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
35130 by default, but you can change these by setting the &%syslog_facility%& and
35131 &%syslog_processname%& options, respectively. If Exim was compiled with
35132 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
35133 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
35134 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
35135 the time and host name to each line.
35136 The three log streams are mapped onto syslog priorities as follows:
35139 &'mainlog'& is mapped to LOG_INFO
35141 &'rejectlog'& is mapped to LOG_NOTICE
35143 &'paniclog'& is mapped to LOG_ALERT
35146 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
35147 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
35148 these are routed by syslog to the same place. You can suppress this duplication
35149 by setting &%syslog_duplication%& false.
35151 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
35152 entries contain multiple lines when headers are included. To cope with both
35153 these cases, entries written to syslog are split into separate &[syslog()]&
35154 calls at each internal newline, and also after a maximum of
35155 870 data characters. (This allows for a total syslog line length of 1024, when
35156 additions such as timestamps are added.) If you are running a syslog
35157 replacement that can handle lines longer than the 1024 characters allowed by
35158 RFC 3164, you should set
35160 SYSLOG_LONG_LINES=yes
35162 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
35163 lines, but it still splits at internal newlines in &'reject'& log entries.
35165 To make it easy to re-assemble split lines later, each component of a split
35166 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
35167 where <&'n'&> is the component number and <&'m'&> is the total number of
35168 components in the entry. The / delimiter is used when the line was split
35169 because it was too long; if it was split because of an internal newline, the \
35170 delimiter is used. For example, supposing the length limit to be 50 instead of
35171 870, the following would be the result of a typical rejection message to
35172 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
35173 name, and pid as added by syslog:
35175 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
35176 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
35177 [3/5] when scanning for sender: missing or malformed lo
35178 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
35181 The same error might cause the following lines to be written to &"rejectlog"&
35184 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
35185 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
35186 [3/18] er when scanning for sender: missing or malformed
35187 [4/18] local part in "<>" (envelope sender is <ph10@cam
35189 [6\18] Recipients: ph10@some.domain.cam.example
35190 [7\18] P Received: from [127.0.0.1] (ident=ph10)
35191 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
35192 [9\18] id 16RdAL-0006pc-00
35193 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
35194 [11\18] 09:43 +0100
35196 [13\18] Subject: this is a test header
35197 [18\18] X-something: this is another header
35198 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
35201 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
35203 Log lines that are neither too long nor contain newlines are written to syslog
35204 without modification.
35206 If only syslog is being used, the Exim monitor is unable to provide a log tail
35207 display, unless syslog is routing &'mainlog'& to a file on the local host and
35208 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
35213 .section "Log line flags" "SECID250"
35214 One line is written to the main log for each message received, and for each
35215 successful, unsuccessful, and delayed delivery. These lines can readily be
35216 picked out by the distinctive two-character flags that immediately follow the
35217 timestamp. The flags are:
35219 &`<=`& message arrival
35220 &`=>`& normal message delivery
35221 &`->`& additional address in same delivery
35222 &`>>`& cutthrough message delivery
35223 &`*>`& delivery suppressed by &%-N%&
35224 &`**`& delivery failed; address bounced
35225 &`==`& delivery deferred; temporary problem
35229 .section "Logging message reception" "SECID251"
35230 .cindex "log" "reception line"
35231 The format of the single-line entry in the main log that is written for every
35232 message received is shown in the basic example below, which is split over
35233 several lines in order to fit it on the page:
35235 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
35236 H=mailer.fict.example [192.168.123.123] U=exim
35237 P=smtp S=5678 id=<incoming message id>
35239 The address immediately following &"<="& is the envelope sender address. A
35240 bounce message is shown with the sender address &"<>"&, and if it is locally
35241 generated, this is followed by an item of the form
35245 which is a reference to the message that caused the bounce to be sent.
35249 For messages from other hosts, the H and U fields identify the remote host and
35250 record the RFC 1413 identity of the user that sent the message, if one was
35251 received. The number given in square brackets is the IP address of the sending
35252 host. If there is a single, unparenthesized host name in the H field, as
35253 above, it has been verified to correspond to the IP address (see the
35254 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
35255 by the remote host in the SMTP HELO or EHLO command, and has not been
35256 verified. If verification yields a different name to that given for HELO or
35257 EHLO, the verified name appears first, followed by the HELO or EHLO
35258 name in parentheses.
35260 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
35261 without brackets, in the HELO or EHLO command, leading to entries in
35262 the log containing text like these examples:
35264 H=(10.21.32.43) [192.168.8.34]
35265 H=([10.21.32.43]) [192.168.8.34]
35267 This can be confusing. Only the final address in square brackets can be relied
35270 For locally generated messages (that is, messages not received over TCP/IP),
35271 the H field is omitted, and the U field contains the login name of the caller
35274 .cindex "authentication" "logging"
35275 .cindex "AUTH" "logging"
35276 For all messages, the P field specifies the protocol used to receive the
35277 message. This is the value that is stored in &$received_protocol$&. In the case
35278 of incoming SMTP messages, the value indicates whether or not any SMTP
35279 extensions (ESMTP), encryption, or authentication were used. If the SMTP
35280 session was encrypted, there is an additional X field that records the cipher
35281 suite that was used.
35283 .cindex log protocol
35284 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
35285 hosts that have authenticated themselves using the SMTP AUTH command. The first
35286 value is used when the SMTP connection was encrypted (&"secure"&). In this case
35287 there is an additional item A= followed by the name of the authenticator that
35288 was used. If an authenticated identification was set up by the authenticator's
35289 &%server_set_id%& option, this is logged too, separated by a colon from the
35290 authenticator name.
35292 .cindex "size" "of message"
35293 The id field records the existing message id, if present. The size of the
35294 received message is given by the S field. When the message is delivered,
35295 headers may be removed or added, so that the size of delivered copies of the
35296 message may not correspond with this value (and indeed may be different to each
35299 The &%log_selector%& option can be used to request the logging of additional
35300 data when a message is received. See section &<<SECTlogselector>>& below.
35304 .section "Logging deliveries" "SECID252"
35305 .cindex "log" "delivery line"
35306 The format of the single-line entry in the main log that is written for every
35307 delivery is shown in one of the examples below, for local and remote
35308 deliveries, respectively. Each example has been split into multiple lines in order
35309 to fit it on the page:
35311 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
35312 <marv@hitch.fict.example> R=localuser T=local_delivery
35313 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
35314 monk@holistic.fict.example R=dnslookup T=remote_smtp
35315 H=holistic.fict.example [192.168.234.234]
35317 For ordinary local deliveries, the original address is given in angle brackets
35318 after the final delivery address, which might be a pipe or a file. If
35319 intermediate address(es) exist between the original and the final address, the
35320 last of these is given in parentheses after the final address. The R and T
35321 fields record the router and transport that were used to process the address.
35323 If SMTP AUTH was used for the delivery there is an additional item A=
35324 followed by the name of the authenticator that was used.
35325 If an authenticated identification was set up by the authenticator's &%client_set_id%&
35326 option, this is logged too, separated by a colon from the authenticator name.
35328 If a shadow transport was run after a successful local delivery, the log line
35329 for the successful delivery has an item added on the end, of the form
35331 &`ST=<`&&'shadow transport name'&&`>`&
35333 If the shadow transport did not succeed, the error message is put in
35334 parentheses afterwards.
35336 .cindex "asterisk" "after IP address"
35337 When more than one address is included in a single delivery (for example, two
35338 SMTP RCPT commands in one transaction) the second and subsequent addresses are
35339 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
35340 down a single SMTP connection, an asterisk follows the IP address in the log
35341 lines for the second and subsequent messages.
35343 .cindex "delivery" "cutthrough; logging"
35344 .cindex "cutthrough" "logging"
35345 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
35346 line precedes the reception line, since cutthrough waits for a possible
35347 rejection from the destination in case it can reject the sourced item.
35349 The generation of a reply message by a filter file gets logged as a
35350 &"delivery"& to the addressee, preceded by &">"&.
35352 The &%log_selector%& option can be used to request the logging of additional
35353 data when a message is delivered. See section &<<SECTlogselector>>& below.
35356 .section "Discarded deliveries" "SECID253"
35357 .cindex "discarded messages"
35358 .cindex "message" "discarded"
35359 .cindex "delivery" "discarded; logging"
35360 When a message is discarded as a result of the command &"seen finish"& being
35361 obeyed in a filter file which generates no deliveries, a log entry of the form
35363 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
35364 <low.club@bridge.example> R=userforward
35366 is written, to record why no deliveries are logged. When a message is discarded
35367 because it is aliased to &":blackhole:"& the log line is like this:
35369 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
35370 <hole@nowhere.example> R=blackhole_router
35374 .section "Deferred deliveries" "SECID254"
35375 When a delivery is deferred, a line of the following form is logged:
35377 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
35378 R=dnslookup T=smtp defer (146): Connection refused
35380 In the case of remote deliveries, the error is the one that was given for the
35381 last IP address that was tried. Details of individual SMTP failures are also
35382 written to the log, so the above line would be preceded by something like
35384 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
35385 mail1.endrest.example [192.168.239.239]: Connection refused
35387 When a deferred address is skipped because its retry time has not been reached,
35388 a message is written to the log, but this can be suppressed by setting an
35389 appropriate value in &%log_selector%&.
35393 .section "Delivery failures" "SECID255"
35394 .cindex "delivery" "failure; logging"
35395 If a delivery fails because an address cannot be routed, a line of the
35396 following form is logged:
35398 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
35399 <jim@trek99.example>: unknown mail domain
35401 If a delivery fails at transport time, the router and transport are shown, and
35402 the response from the remote host is included, as in this example:
35404 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
35405 R=dnslookup T=remote_smtp: SMTP error from remote mailer
35406 after pipelined RCPT TO:<ace400@pb.example>: host
35407 pbmail3.py.example [192.168.63.111]: 553 5.3.0
35408 <ace400@pb.example>...Addressee unknown
35410 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
35411 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
35412 disabling PIPELINING. The log lines for all forms of delivery failure are
35413 flagged with &`**`&.
35417 .section "Fake deliveries" "SECID256"
35418 .cindex "delivery" "fake; logging"
35419 If a delivery does not actually take place because the &%-N%& option has been
35420 used to suppress it, a normal delivery line is written to the log, except that
35421 &"=>"& is replaced by &"*>"&.
35425 .section "Completion" "SECID257"
35428 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
35430 is written to the main log when a message is about to be removed from the spool
35431 at the end of its processing.
35436 .section "Summary of Fields in Log Lines" "SECID258"
35437 .cindex "log" "summary of fields"
35438 A summary of the field identifiers that are used in log lines is shown in
35439 the following table:
35441 &`A `& authenticator name (and optional id and sender)
35442 &`C `& SMTP confirmation on delivery
35443 &` `& command list for &"no mail in SMTP session"&
35444 &`CV `& certificate verification status
35445 &`D `& duration of &"no mail in SMTP session"&
35446 &`DN `& distinguished name from peer certificate
35447 &`DT `& on &`=>`& lines: time taken for a delivery
35448 &`F `& sender address (on delivery lines)
35449 &`H `& host name and IP address
35450 &`I `& local interface used
35451 &`id `& message id for incoming message
35452 &`P `& on &`<=`& lines: protocol used
35453 &` `& on &`=>`& and &`**`& lines: return path
35454 &`PRX `& on &'<='& and&`=>`& lines: proxy address
35455 &`QT `& on &`=>`& lines: time spent on queue so far
35456 &` `& on &"Completed"& lines: time spent on queue
35457 &`R `& on &`<=`& lines: reference for local bounce
35458 &` `& on &`=>`& &`**`& and &`==`& lines: router name
35459 &`S `& size of message
35460 &`SNI `& server name indication from TLS client hello
35461 &`ST `& shadow transport name
35462 &`T `& on &`<=`& lines: message subject (topic)
35463 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
35464 &`U `& local user or RFC 1413 identity
35465 &`X `& TLS cipher suite
35469 .section "Other log entries" "SECID259"
35470 Various other types of log entry are written from time to time. Most should be
35471 self-explanatory. Among the more common are:
35474 .cindex "retry" "time not reached"
35475 &'retry time not reached'&&~&~An address previously suffered a temporary error
35476 during routing or local delivery, and the time to retry has not yet arrived.
35477 This message is not written to an individual message log file unless it happens
35478 during the first delivery attempt.
35480 &'retry time not reached for any host'&&~&~An address previously suffered
35481 temporary errors during remote delivery, and the retry time has not yet arrived
35482 for any of the hosts to which it is routed.
35484 .cindex "spool directory" "file locked"
35485 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
35486 some other Exim process is already working on the message. This can be quite
35487 common if queue running processes are started at frequent intervals. The
35488 &'exiwhat'& utility script can be used to find out what Exim processes are
35491 .cindex "error" "ignored"
35492 &'error ignored'&&~&~There are several circumstances that give rise to this
35495 Exim failed to deliver a bounce message whose age was greater than
35496 &%ignore_bounce_errors_after%&. The bounce was discarded.
35498 A filter file set up a delivery using the &"noerror"& option, and the delivery
35499 failed. The delivery was discarded.
35501 A delivery set up by a router configured with
35502 . ==== As this is a nested list, any displays it contains must be indented
35503 . ==== as otherwise they are too far to the left.
35507 failed. The delivery was discarded.
35515 .section "Reducing or increasing what is logged" "SECTlogselector"
35516 .cindex "log" "selectors"
35517 By setting the &%log_selector%& global option, you can disable some of Exim's
35518 default logging, or you can request additional logging. The value of
35519 &%log_selector%& is made up of names preceded by plus or minus characters. For
35522 log_selector = +arguments -retry_defer
35524 The list of optional log items is in the following table, with the default
35525 selection marked by asterisks:
35527 &` 8bitmime `& received 8BITMIME status
35528 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
35529 &` address_rewrite `& address rewriting
35530 &` all_parents `& all parents in => lines
35531 &` arguments `& command line arguments
35532 &`*connection_reject `& connection rejections
35533 &`*delay_delivery `& immediate delivery delayed
35534 &` deliver_time `& time taken to perform delivery
35535 &` delivery_size `& add &`S=`&&'nnn'& to => lines
35536 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
35537 &`*etrn `& ETRN commands
35538 &`*host_lookup_failed `& as it says
35539 &` ident_timeout `& timeout for ident connection
35540 &` incoming_interface `& local interface on <= and => lines
35541 &` incoming_port `& remote port on <= lines
35542 &`*lost_incoming_connection `& as it says (includes timeouts)
35544 &` outgoing_interface `& local interface on => lines
35546 &` outgoing_port `& add remote port to => lines
35547 &`*queue_run `& start and end queue runs
35548 &` queue_time `& time on queue for one recipient
35549 &` queue_time_overall `& time on queue for whole message
35550 &` pid `& Exim process id
35552 &` proxy `& proxy address on <= and => lines
35554 &` received_recipients `& recipients on <= lines
35555 &` received_sender `& sender on <= lines
35556 &`*rejected_header `& header contents on reject log
35557 &`*retry_defer `& &"retry time not reached"&
35558 &` return_path_on_delivery `& put return path on => and ** lines
35559 &` sender_on_delivery `& add sender to => lines
35560 &`*sender_verify_fail `& sender verification failures
35561 &`*size_reject `& rejection because too big
35562 &`*skip_delivery `& delivery skipped in a queue run
35563 &`*smtp_confirmation `& SMTP confirmation on => lines
35564 &` smtp_connection `& incoming SMTP connections
35565 &` smtp_incomplete_transaction`& incomplete SMTP transactions
35566 &` smtp_mailauth `& AUTH argument to MAIL commands
35567 &` smtp_no_mail `& session with no MAIL commands
35568 &` smtp_protocol_error `& SMTP protocol errors
35569 &` smtp_syntax_error `& SMTP syntax errors
35570 &` subject `& contents of &'Subject:'& on <= lines
35571 &`*tls_certificate_verified `& certificate verification status
35572 &`*tls_cipher `& TLS cipher suite on <= and => lines
35573 &` tls_peerdn `& TLS peer DN on <= and => lines
35574 &` tls_sni `& TLS SNI on <= lines
35575 &` unknown_in_list `& DNS lookup failed in list match
35577 &` all `& all of the above
35579 See also the &%slow_lookup_log%& main configuration option,
35580 section &<<SECID99>>&
35582 More details on each of these items follows:
35586 .cindex "log" "8BITMIME"
35587 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
35588 which may help in tracking down interoperability issues with ancient MTAs
35589 that are not 8bit clean. This is added to the &"<="& line, tagged with
35590 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
35591 &`7BIT`& and &`8BITMIME`& respectively.
35593 .cindex "&%warn%& ACL verb" "log when skipping"
35594 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
35595 its conditions cannot be evaluated, a log line to this effect is written if
35596 this log selector is set.
35598 .cindex "log" "rewriting"
35599 .cindex "rewriting" "logging"
35600 &%address_rewrite%&: This applies both to global rewrites and per-transport
35601 rewrites, but not to rewrites in filters run as an unprivileged user (because
35602 such users cannot access the log).
35604 .cindex "log" "full parentage"
35605 &%all_parents%&: Normally only the original and final addresses are logged on
35606 delivery lines; with this selector, intermediate parents are given in
35607 parentheses between them.
35609 .cindex "log" "Exim arguments"
35610 .cindex "Exim arguments, logging"
35611 &%arguments%&: This causes Exim to write the arguments with which it was called
35612 to the main log, preceded by the current working directory. This is a debugging
35613 feature, added to make it easier to find out how certain MUAs call
35614 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
35615 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
35616 that are empty or that contain white space are quoted. Non-printing characters
35617 are shown as escape sequences. This facility cannot log unrecognized arguments,
35618 because the arguments are checked before the configuration file is read. The
35619 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
35620 between the caller and Exim.
35622 .cindex "log" "connection rejections"
35623 &%connection_reject%&: A log entry is written whenever an incoming SMTP
35624 connection is rejected, for whatever reason.
35626 .cindex "log" "delayed delivery"
35627 .cindex "delayed delivery, logging"
35628 &%delay_delivery%&: A log entry is written whenever a delivery process is not
35629 started for an incoming message because the load is too high or too many
35630 messages were received on one connection. Logging does not occur if no delivery
35631 process is started because &%queue_only%& is set or &%-odq%& was used.
35633 .cindex "log" "delivery duration"
35634 &%deliver_time%&: For each delivery, the amount of real time it has taken to
35635 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
35637 .cindex "log" "message size on delivery"
35638 .cindex "size" "of message"
35639 &%delivery_size%&: For each delivery, the size of message delivered is added to
35640 the &"=>"& line, tagged with S=.
35642 .cindex "log" "dnslist defer"
35643 .cindex "DNS list" "logging defer"
35644 .cindex "black list (DNS)"
35645 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
35646 DNS black list suffers a temporary error.
35648 .cindex "log" "ETRN commands"
35649 .cindex "ETRN" "logging"
35650 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
35651 is run to determine whether or not it is actually accepted. An invalid ETRN
35652 command, or one received within a message transaction is not logged by this
35653 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
35655 .cindex "log" "host lookup failure"
35656 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
35657 any addresses, or when a lookup of an IP address fails to find a host name, a
35658 log line is written. This logging does not apply to direct DNS lookups when
35659 routing email addresses, but it does apply to &"byname"& lookups.
35661 .cindex "log" "ident timeout"
35662 .cindex "RFC 1413" "logging timeout"
35663 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
35664 client's ident port times out.
35666 .cindex "log" "incoming interface"
35667 .cindex "log" "local interface"
35668 .cindex "log" "local address and port"
35669 .cindex "TCP/IP" "logging local address and port"
35670 .cindex "interface" "logging"
35671 &%incoming_interface%&: The interface on which a message was received is added
35672 to the &"<="& line as an IP address in square brackets, tagged by I= and
35673 followed by a colon and the port number. The local interface and port are also
35674 added to other SMTP log lines, for example &"SMTP connection from"&, to
35675 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
35677 The latter can be disabled by turning off the &%outgoing_interface%& option.
35681 .cindex log "incoming proxy address"
35682 .cindex proxy "logging proxy address"
35683 .cindex "TCP/IP" "logging proxy address"
35684 &%proxy%&: The internal (closest to the system running Exim) IP address
35685 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
35686 on a proxied connection
35687 or the &"=>"& line for a message delivered on a proxied connection..
35688 See &<<SECTproxyInbound>>& for more information.
35691 .cindex "log" "incoming remote port"
35692 .cindex "port" "logging remote"
35693 .cindex "TCP/IP" "logging incoming remote port"
35694 .vindex "&$sender_fullhost$&"
35695 .vindex "&$sender_rcvhost$&"
35696 &%incoming_port%&: The remote port number from which a message was received is
35697 added to log entries and &'Received:'& header lines, following the IP address
35698 in square brackets, and separated from it by a colon. This is implemented by
35699 changing the value that is put in the &$sender_fullhost$& and
35700 &$sender_rcvhost$& variables. Recording the remote port number has become more
35701 important with the widening use of NAT (see RFC 2505).
35703 .cindex "log" "dropped connection"
35704 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
35705 connection is unexpectedly dropped.
35707 .cindex "log" "outgoing interface"
35708 .cindex "log" "local interface"
35709 .cindex "log" "local address and port"
35710 .cindex "TCP/IP" "logging local address and port"
35711 .cindex "interface" "logging"
35713 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
35714 interface on which a message was sent is added to delivery lines as an I= tag
35715 followed by IP address in square brackets. You can disable this by turning
35716 off the &%outgoing_interface%& option.
35719 .cindex "log" "outgoing remote port"
35720 .cindex "port" "logging outgoint remote"
35721 .cindex "TCP/IP" "logging ougtoing remote port"
35722 &%outgoing_port%&: The remote port number is added to delivery log lines (those
35723 containing => tags) following the IP address.
35725 The local port is also added if &%incoming_interface%& and
35726 &%outgoing_interface%& are both enabled.
35728 This option is not included in the default setting, because for most ordinary
35729 configurations, the remote port number is always 25 (the SMTP port), and the
35730 local port is a random ephemeral port.
35732 .cindex "log" "process ids in"
35733 .cindex "pid (process id)" "in log lines"
35734 &%pid%&: The current process id is added to every log line, in square brackets,
35735 immediately after the time and date.
35737 .cindex "log" "queue run"
35738 .cindex "queue runner" "logging"
35739 &%queue_run%&: The start and end of every queue run are logged.
35741 .cindex "log" "queue time"
35742 &%queue_time%&: The amount of time the message has been in the queue on the
35743 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
35744 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
35745 includes reception time as well as the delivery time for the current address.
35746 This means that it may be longer than the difference between the arrival and
35747 delivery log line times, because the arrival log line is not written until the
35748 message has been successfully received.
35750 &%queue_time_overall%&: The amount of time the message has been in the queue on
35751 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
35752 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
35753 message, so it includes reception time as well as the total delivery time.
35755 .cindex "log" "recipients"
35756 &%received_recipients%&: The recipients of a message are listed in the main log
35757 as soon as the message is received. The list appears at the end of the log line
35758 that is written when a message is received, preceded by the word &"for"&. The
35759 addresses are listed after they have been qualified, but before any rewriting
35761 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
35764 .cindex "log" "sender reception"
35765 &%received_sender%&: The unrewritten original sender of a message is added to
35766 the end of the log line that records the message's arrival, after the word
35767 &"from"& (before the recipients if &%received_recipients%& is also set).
35769 .cindex "log" "header lines for rejection"
35770 &%rejected_header%&: If a message's header has been received at the time a
35771 rejection is written to the reject log, the complete header is added to the
35772 log. Header logging can be turned off individually for messages that are
35773 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
35775 .cindex "log" "retry defer"
35776 &%retry_defer%&: A log line is written if a delivery is deferred because a
35777 retry time has not yet been reached. However, this &"retry time not reached"&
35778 message is always omitted from individual message logs after the first delivery
35781 .cindex "log" "return path"
35782 &%return_path_on_delivery%&: The return path that is being transmitted with
35783 the message is included in delivery and bounce lines, using the tag P=.
35784 This is omitted if no delivery actually happens, for example, if routing fails,
35785 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
35787 .cindex "log" "sender on delivery"
35788 &%sender_on_delivery%&: The message's sender address is added to every delivery
35789 and bounce line, tagged by F= (for &"from"&).
35790 This is the original sender that was received with the message; it is not
35791 necessarily the same as the outgoing return path.
35793 .cindex "log" "sender verify failure"
35794 &%sender_verify_fail%&: If this selector is unset, the separate log line that
35795 gives details of a sender verification failure is not written. Log lines for
35796 the rejection of SMTP commands contain just &"sender verify failed"&, so some
35799 .cindex "log" "size rejection"
35800 &%size_reject%&: A log line is written whenever a message is rejected because
35803 .cindex "log" "frozen messages; skipped"
35804 .cindex "frozen messages" "logging skipping"
35805 &%skip_delivery%&: A log line is written whenever a message is skipped during a
35806 queue run because it is frozen or because another process is already delivering
35808 .cindex "&""spool file is locked""&"
35809 The message that is written is &"spool file is locked"&.
35811 .cindex "log" "smtp confirmation"
35812 .cindex "SMTP" "logging confirmation"
35813 .cindex "LMTP" "logging confirmation"
35814 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
35815 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
35816 A number of MTAs (including Exim) return an identifying string in this
35819 .cindex "log" "SMTP connections"
35820 .cindex "SMTP" "logging connections"
35821 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
35822 established or closed, unless the connection is from a host that matches
35823 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
35824 only when the closure is unexpected.) This applies to connections from local
35825 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
35826 dropped in the middle of a message, a log line is always written, whether or
35827 not this selector is set, but otherwise nothing is written at the start and end
35828 of connections unless this selector is enabled.
35830 For TCP/IP connections to an Exim daemon, the current number of connections is
35831 included in the log message for each new connection, but note that the count is
35832 reset if the daemon is restarted.
35833 Also, because connections are closed (and the closure is logged) in
35834 subprocesses, the count may not include connections that have been closed but
35835 whose termination the daemon has not yet noticed. Thus, while it is possible to
35836 match up the opening and closing of connections in the log, the value of the
35837 logged counts may not be entirely accurate.
35839 .cindex "log" "SMTP transaction; incomplete"
35840 .cindex "SMTP" "logging incomplete transactions"
35841 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
35842 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
35843 and the message sender plus any accepted recipients are included in the log
35844 line. This can provide evidence of dictionary attacks.
35846 .cindex "log" "non-MAIL SMTP sessions"
35847 .cindex "MAIL" "logging session without"
35848 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
35849 connection terminates without having issued a MAIL command. This includes both
35850 the case when the connection is dropped, and the case when QUIT is used. It
35851 does not include cases where the connection is rejected right at the start (by
35852 an ACL, or because there are too many connections, or whatever). These cases
35853 already have their own log lines.
35855 The log line that is written contains the identity of the client in the usual
35856 way, followed by D= and a time, which records the duration of the connection.
35857 If the connection was authenticated, this fact is logged exactly as it is for
35858 an incoming message, with an A= item. If the connection was encrypted, CV=,
35859 DN=, and X= items may appear as they do for an incoming message, controlled by
35860 the same logging options.
35862 Finally, if any SMTP commands were issued during the connection, a C= item
35863 is added to the line, listing the commands that were used. For example,
35867 shows that the client issued QUIT straight after EHLO. If there were fewer
35868 than 20 commands, they are all listed. If there were more than 20 commands,
35869 the last 20 are listed, preceded by &"..."&. However, with the default
35870 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
35871 have been aborted before 20 non-mail commands are processed.
35873 &%smtp_mailauth%&: A third subfield with the authenticated sender,
35874 colon-separated, is appended to the A= item for a message arrival or delivery
35875 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
35876 was accepted or used.
35878 .cindex "log" "SMTP protocol error"
35879 .cindex "SMTP" "logging protocol error"
35880 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
35881 encountered. Exim does not have perfect detection of all protocol errors
35882 because of transmission delays and the use of pipelining. If PIPELINING has
35883 been advertised to a client, an Exim server assumes that the client will use
35884 it, and therefore it does not count &"expected"& errors (for example, RCPT
35885 received after rejecting MAIL) as protocol errors.
35887 .cindex "SMTP" "logging syntax errors"
35888 .cindex "SMTP" "syntax errors; logging"
35889 .cindex "SMTP" "unknown command; logging"
35890 .cindex "log" "unknown SMTP command"
35891 .cindex "log" "SMTP syntax error"
35892 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
35893 encountered. An unrecognized command is treated as a syntax error. For an
35894 external connection, the host identity is given; for an internal connection
35895 using &%-bs%& the sender identification (normally the calling user) is given.
35897 .cindex "log" "subject"
35898 .cindex "subject, logging"
35899 &%subject%&: The subject of the message is added to the arrival log line,
35900 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
35901 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
35902 specifies whether characters with values greater than 127 should be logged
35903 unchanged, or whether they should be rendered as escape sequences.
35905 .cindex "log" "certificate verification"
35906 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
35907 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
35908 verified, and &`CV=no`& if not.
35910 .cindex "log" "TLS cipher"
35911 .cindex "TLS" "logging cipher"
35912 &%tls_cipher%&: When a message is sent or received over an encrypted
35913 connection, the cipher suite used is added to the log line, preceded by X=.
35915 .cindex "log" "TLS peer DN"
35916 .cindex "TLS" "logging peer DN"
35917 &%tls_peerdn%&: When a message is sent or received over an encrypted
35918 connection, and a certificate is supplied by the remote host, the peer DN is
35919 added to the log line, preceded by DN=.
35921 .cindex "log" "TLS SNI"
35922 .cindex "TLS" "logging SNI"
35923 &%tls_sni%&: When a message is received over an encrypted connection, and
35924 the remote host provided the Server Name Indication extension, the SNI is
35925 added to the log line, preceded by SNI=.
35927 .cindex "log" "DNS failure in list"
35928 &%unknown_in_list%&: This setting causes a log entry to be written when the
35929 result of a list match is failure because a DNS lookup failed.
35933 .section "Message log" "SECID260"
35934 .cindex "message" "log file for"
35935 .cindex "log" "message log; description of"
35936 .cindex "&_msglog_& directory"
35937 .oindex "&%preserve_message_logs%&"
35938 In addition to the general log files, Exim writes a log file for each message
35939 that it handles. The names of these per-message logs are the message ids, and
35940 they are kept in the &_msglog_& sub-directory of the spool directory. Each
35941 message log contains copies of the log lines that apply to the message. This
35942 makes it easier to inspect the status of an individual message without having
35943 to search the main log. A message log is deleted when processing of the message
35944 is complete, unless &%preserve_message_logs%& is set, but this should be used
35945 only with great care because they can fill up your disk very quickly.
35947 On a heavily loaded system, it may be desirable to disable the use of
35948 per-message logs, in order to reduce disk I/O. This can be done by setting the
35949 &%message_logs%& option false.
35955 . ////////////////////////////////////////////////////////////////////////////
35956 . ////////////////////////////////////////////////////////////////////////////
35958 .chapter "Exim utilities" "CHAPutils"
35959 .scindex IIDutils "utilities"
35960 A number of utility scripts and programs are supplied with Exim and are
35961 described in this chapter. There is also the Exim Monitor, which is covered in
35962 the next chapter. The utilities described here are:
35964 .itable none 0 0 3 7* left 15* left 40* left
35965 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
35966 "list what Exim processes are doing"
35967 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
35968 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
35969 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
35970 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
35972 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
35973 .irow &<<SECTmailstat>>& &'eximstats'& &&&
35974 "extract statistics from the log"
35975 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
35976 "check address acceptance from given IP"
35977 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
35978 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
35979 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
35980 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
35981 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
35982 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
35985 Another utility that might be of use to sites with many MTAs is Tom Kistner's
35986 &'exilog'&. It provides log visualizations across multiple Exim servers. See
35987 &url(http://duncanthrax.net/exilog/) for details.
35992 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
35993 .cindex "&'exiwhat'&"
35994 .cindex "process, querying"
35996 On operating systems that can restart a system call after receiving a signal
35997 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
35998 a line describing what it is doing to the file &_exim-process.info_& in the
35999 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
36000 processes it can find, having first emptied the file. It then waits for one
36001 second to allow the Exim processes to react before displaying the results. In
36002 order to run &'exiwhat'& successfully you have to have sufficient privilege to
36003 send the signal to the Exim processes, so it is normally run as root.
36005 &*Warning*&: This is not an efficient process. It is intended for occasional
36006 use by system administrators. It is not sensible, for example, to set up a
36007 script that sends SIGUSR1 signals to Exim processes at short intervals.
36010 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
36011 varies in different operating systems. Not only are different options used,
36012 but the format of the output is different. For this reason, there are some
36013 system configuration options that configure exactly how &'exiwhat'& works. If
36014 it doesn't seem to be working for you, check the following compile-time
36017 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
36018 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
36019 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
36020 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
36022 An example of typical output from &'exiwhat'& is
36024 164 daemon: -q1h, listening on port 25
36025 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
36026 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
36027 [10.19.42.42] (editor@ref.example)
36028 10592 handling incoming call from [192.168.243.242]
36029 10628 accepting a local non-SMTP message
36031 The first number in the output line is the process number. The third line has
36032 been split here, in order to fit it on the page.
36036 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
36037 .cindex "&'exiqgrep'&"
36038 .cindex "queue" "grepping"
36039 This utility is a Perl script contributed by Matt Hubbard. It runs
36043 or (in case &*-a*& switch is specified)
36047 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
36048 contain alternate exim configuration the queue management might be using.
36050 to obtain a queue listing, and then greps the output to select messages
36051 that match given criteria. The following selection options are available:
36054 .vitem &*-f*&&~<&'regex'&>
36055 Match the sender address using a case-insensitive search. The field that is
36056 tested is enclosed in angle brackets, so you can test for bounce messages with
36060 .vitem &*-r*&&~<&'regex'&>
36061 Match a recipient address using a case-insensitive search. The field that is
36062 tested is not enclosed in angle brackets.
36064 .vitem &*-s*&&~<&'regex'&>
36065 Match against the size field.
36067 .vitem &*-y*&&~<&'seconds'&>
36068 Match messages that are younger than the given time.
36070 .vitem &*-o*&&~<&'seconds'&>
36071 Match messages that are older than the given time.
36074 Match only frozen messages.
36077 Match only non-frozen messages.
36080 The following options control the format of the output:
36084 Display only the count of matching messages.
36087 Long format &-- display the full message information as output by Exim. This is
36091 Display message ids only.
36094 Brief format &-- one line per message.
36097 Display messages in reverse order.
36100 Include delivered recipients in queue listing.
36103 There is one more option, &%-h%&, which outputs a list of options.
36107 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
36108 .cindex "&'exiqsumm'&"
36109 .cindex "queue" "summary"
36110 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
36111 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
36112 running a command such as
36114 exim -bp | exiqsumm
36116 The output consists of one line for each domain that has messages waiting for
36117 it, as in the following example:
36119 3 2322 74m 66m msn.com.example
36121 Each line lists the number of pending deliveries for a domain, their total
36122 volume, and the length of time that the oldest and the newest messages have
36123 been waiting. Note that the number of pending deliveries is greater than the
36124 number of messages when messages have more than one recipient.
36126 A summary line is output at the end. By default the output is sorted on the
36127 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
36128 the output to be sorted by oldest message and by count of messages,
36129 respectively. There are also three options that split the messages for each
36130 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
36131 separates frozen messages, and &%-s%& separates messages according to their
36134 The output of &'exim -bp'& contains the original addresses in the message, so
36135 this also applies to the output from &'exiqsumm'&. No domains from addresses
36136 generated by aliasing or forwarding are included (unless the &%one_time%&
36137 option of the &(redirect)& router has been used to convert them into &"top
36138 level"& addresses).
36143 .section "Extracting specific information from the log (exigrep)" &&&
36145 .cindex "&'exigrep'&"
36146 .cindex "log" "extracts; grepping for"
36147 The &'exigrep'& utility is a Perl script that searches one or more main log
36148 files for entries that match a given pattern. When it finds a match, it
36149 extracts all the log entries for the relevant message, not just those that
36150 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
36151 given message, or all mail for a given user, or for a given host, for example.
36152 The input files can be in Exim log format or syslog format.
36153 If a matching log line is not associated with a specific message, it is
36154 included in &'exigrep'&'s output without any additional lines. The usage is:
36156 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
36158 If no log file names are given on the command line, the standard input is read.
36160 The &%-t%& argument specifies a number of seconds. It adds an additional
36161 condition for message selection. Messages that are complete are shown only if
36162 they spent more than <&'n'&> seconds on the queue.
36164 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
36165 makes it case-sensitive. This may give a performance improvement when searching
36166 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
36167 option; with &%-I%& they do not. In both cases it is possible to change the
36168 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
36170 The &%-l%& option means &"literal"&, that is, treat all characters in the
36171 pattern as standing for themselves. Otherwise the pattern must be a Perl
36172 regular expression.
36174 The &%-v%& option inverts the matching condition. That is, a line is selected
36175 if it does &'not'& match the pattern.
36177 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
36178 that are generated as a result/response to a message that &'exigrep'& matched
36182 user_a sends a message to user_b, which generates a bounce back to user_b. If
36183 &'exigrep'& is used to search for &"user_a"&, only the first message will be
36184 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
36185 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
36186 when searching for &"user_a"& will show both messages since the bounce is
36187 &"related"& to or a &"result"& of the first message that was found by the
36190 If the location of a &'zcat'& command is known from the definition of
36191 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
36192 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
36193 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
36194 autodetection of some well known compression extensions.
36197 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
36198 .cindex "&'exipick'&"
36199 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
36200 lists messages from the queue according to a variety of criteria. For details
36201 of &'exipick'&'s facilities, visit the web page at
36202 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
36203 the &%--help%& option.
36206 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
36207 .cindex "log" "cycling local files"
36208 .cindex "cycling logs"
36209 .cindex "&'exicyclog'&"
36210 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
36211 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
36212 you are using log files with datestamps in their names (see section
36213 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
36214 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
36215 There are two command line options for &'exicyclog'&:
36217 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
36218 default that is set when Exim is built. The default default is 10.
36220 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
36221 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
36222 overriding the script's default, which is to find the setting from Exim's
36226 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
36227 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
36228 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
36229 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
36230 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
36231 logs are handled similarly.
36233 If the limit is greater than 99, the script uses 3-digit numbers such as
36234 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
36235 to one that is greater, or &'vice versa'&, you will have to fix the names of
36236 any existing log files.
36238 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
36239 the end are deleted. All files with numbers greater than 01 are compressed,
36240 using a compression command which is configured by the COMPRESS_COMMAND
36241 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
36242 root &%crontab%& entry of the form
36244 1 0 * * * su exim -c /usr/exim/bin/exicyclog
36246 assuming you have used the name &"exim"& for the Exim user. You can run
36247 &'exicyclog'& as root if you wish, but there is no need.
36251 .section "Mail statistics (eximstats)" "SECTmailstat"
36252 .cindex "statistics"
36253 .cindex "&'eximstats'&"
36254 A Perl script called &'eximstats'& is provided for extracting statistical
36255 information from log files. The output is either plain text, or HTML.
36256 Exim log files are also supported by the &'Lire'& system produced by the
36257 LogReport Foundation &url(http://www.logreport.org).
36259 The &'eximstats'& script has been hacked about quite a bit over time. The
36260 latest version is the result of some extensive revision by Steve Campbell. A
36261 lot of information is given by default, but there are options for suppressing
36262 various parts of it. Following any options, the arguments to the script are a
36263 list of files, which should be main log files. For example:
36265 eximstats -nr /var/spool/exim/log/mainlog.01
36267 By default, &'eximstats'& extracts information about the number and volume of
36268 messages received from or delivered to various hosts. The information is sorted
36269 both by message count and by volume, and the top fifty hosts in each category
36270 are listed on the standard output. Similar information, based on email
36271 addresses or domains instead of hosts can be requested by means of various
36272 options. For messages delivered and received locally, similar statistics are
36273 also produced per user.
36275 The output also includes total counts and statistics about delivery errors, and
36276 histograms showing the number of messages received and deliveries made in each
36277 hour of the day. A delivery with more than one address in its envelope (for
36278 example, an SMTP transaction with more than one RCPT command) is counted
36279 as a single delivery by &'eximstats'&.
36281 Though normally more deliveries than receipts are reported (as messages may
36282 have multiple recipients), it is possible for &'eximstats'& to report more
36283 messages received than delivered, even though the queue is empty at the start
36284 and end of the period in question. If an incoming message contains no valid
36285 recipients, no deliveries are recorded for it. A bounce message is handled as
36286 an entirely separate message.
36288 &'eximstats'& always outputs a grand total summary giving the volume and number
36289 of messages received and deliveries made, and the number of hosts involved in
36290 each case. It also outputs the number of messages that were delayed (that is,
36291 not completely delivered at the first attempt), and the number that had at
36292 least one address that failed.
36294 The remainder of the output is in sections that can be independently disabled
36295 or modified by various options. It consists of a summary of deliveries by
36296 transport, histograms of messages received and delivered per time interval
36297 (default per hour), information about the time messages spent on the queue,
36298 a list of relayed messages, lists of the top fifty sending hosts, local
36299 senders, destination hosts, and destination local users by count and by volume,
36300 and a list of delivery errors that occurred.
36302 The relay information lists messages that were actually relayed, that is, they
36303 came from a remote host and were directly delivered to some other remote host,
36304 without being processed (for example, for aliasing or forwarding) locally.
36306 There are quite a few options for &'eximstats'& to control exactly what it
36307 outputs. These are documented in the Perl script itself, and can be extracted
36308 by running the command &(perldoc)& on the script. For example:
36310 perldoc /usr/exim/bin/eximstats
36313 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
36314 .cindex "&'exim_checkaccess'&"
36315 .cindex "policy control" "checking access"
36316 .cindex "checking access"
36317 The &%-bh%& command line argument allows you to run a fake SMTP session with
36318 debugging output, in order to check what Exim is doing when it is applying
36319 policy controls to incoming SMTP mail. However, not everybody is sufficiently
36320 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
36321 sometimes you just want to answer the question &"Does this address have
36322 access?"& without bothering with any further details.
36324 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
36325 two arguments, an IP address and an email address:
36327 exim_checkaccess 10.9.8.7 A.User@a.domain.example
36329 The utility runs a call to Exim with the &%-bh%& option, to test whether the
36330 given email address would be accepted in a RCPT command in a TCP/IP
36331 connection from the host with the given IP address. The output of the utility
36332 is either the word &"accepted"&, or the SMTP error response, for example:
36335 550 Relay not permitted
36337 When running this test, the utility uses &`<>`& as the envelope sender address
36338 for the MAIL command, but you can change this by providing additional
36339 options. These are passed directly to the Exim command. For example, to specify
36340 that the test is to be run with the sender address &'himself@there.example'&
36343 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
36344 -f himself@there.example
36346 Note that these additional Exim command line items must be given after the two
36347 mandatory arguments.
36349 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
36350 while running its checks. You can run checks that include callouts by using
36351 &%-bhc%&, but this is not yet available in a &"packaged"& form.
36355 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
36356 .cindex "DBM" "building dbm files"
36357 .cindex "building DBM files"
36358 .cindex "&'exim_dbmbuild'&"
36359 .cindex "lower casing"
36360 .cindex "binary zero" "in lookup key"
36361 The &'exim_dbmbuild'& program reads an input file containing keys and data in
36362 the format used by the &(lsearch)& lookup (see section
36363 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
36364 names as keys and the remainder of the information as data. The lower-casing
36365 can be prevented by calling the program with the &%-nolc%& option.
36367 A terminating zero is included as part of the key string. This is expected by
36368 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
36369 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
36370 strings or the data strings. The &(dbmnz)& lookup type can be used with such
36373 The program requires two arguments: the name of the input file (which can be a
36374 single hyphen to indicate the standard input), and the name of the output file.
36375 It creates the output under a temporary name, and then renames it if all went
36379 If the native DB interface is in use (USE_DB is set in a compile-time
36380 configuration file &-- this is common in free versions of Unix) the two file
36381 names must be different, because in this mode the Berkeley DB functions create
36382 a single output file using exactly the name given. For example,
36384 exim_dbmbuild /etc/aliases /etc/aliases.db
36386 reads the system alias file and creates a DBM version of it in
36387 &_/etc/aliases.db_&.
36389 In systems that use the &'ndbm'& routines (mostly proprietary versions of
36390 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
36391 environment, the suffixes are added to the second argument of
36392 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
36393 when the Berkeley functions are used in compatibility mode (though this is not
36394 recommended), because in that case it adds a &_.db_& suffix to the file name.
36396 If a duplicate key is encountered, the program outputs a warning, and when it
36397 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
36398 option is used. By default, only the first of a set of duplicates is used &--
36399 this makes it compatible with &(lsearch)& lookups. There is an option
36400 &%-lastdup%& which causes it to use the data for the last duplicate instead.
36401 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
36402 &%stderr%&. For other errors, where it doesn't actually make a new file, the
36408 .section "Finding individual retry times (exinext)" "SECTfinindret"
36409 .cindex "retry" "times"
36410 .cindex "&'exinext'&"
36411 A utility called &'exinext'& (mostly a Perl script) provides the ability to
36412 fish specific information out of the retry database. Given a mail domain (or a
36413 complete address), it looks up the hosts for that domain, and outputs any retry
36414 information for the hosts or for the domain. At present, the retry information
36415 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
36416 output. For example:
36418 $ exinext piglet@milne.fict.example
36419 kanga.milne.example:192.168.8.1 error 146: Connection refused
36420 first failed: 21-Feb-1996 14:57:34
36421 last tried: 21-Feb-1996 14:57:34
36422 next try at: 21-Feb-1996 15:02:34
36423 roo.milne.example:192.168.8.3 error 146: Connection refused
36424 first failed: 20-Jan-1996 13:12:08
36425 last tried: 21-Feb-1996 11:42:03
36426 next try at: 21-Feb-1996 19:42:03
36427 past final cutoff time
36429 You can also give &'exinext'& a local part, without a domain, and it
36430 will give any retry information for that local part in your default domain.
36431 A message id can be used to obtain retry information pertaining to a specific
36432 message. This exists only when an attempt to deliver a message to a remote host
36433 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
36434 &'exinext'& is not particularly efficient, but then it is not expected to be
36437 The &'exinext'& utility calls Exim to find out information such as the location
36438 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
36439 passed on to the &'exim'& commands. The first specifies an alternate Exim
36440 configuration file, and the second sets macros for use within the configuration
36441 file. These features are mainly to help in testing, but might also be useful in
36442 environments where more than one configuration file is in use.
36446 .section "Hints database maintenance" "SECThindatmai"
36447 .cindex "hints database" "maintenance"
36448 .cindex "maintaining Exim's hints database"
36449 Three utility programs are provided for maintaining the DBM files that Exim
36450 uses to contain its delivery hint information. Each program requires two
36451 arguments. The first specifies the name of Exim's spool directory, and the
36452 second is the name of the database it is to operate on. These are as follows:
36455 &'retry'&: the database of retry information
36457 &'wait-'&<&'transport name'&>: databases of information about messages waiting
36460 &'callout'&: the callout cache
36462 &'ratelimit'&: the data for implementing the ratelimit ACL condition
36464 &'misc'&: other hints data
36467 The &'misc'& database is used for
36470 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
36472 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
36473 &(smtp)& transport)
36475 Limiting the concurrency of specific transports (when &%max_parallel%& is set
36481 .section "exim_dumpdb" "SECID261"
36482 .cindex "&'exim_dumpdb'&"
36483 The entire contents of a database are written to the standard output by the
36484 &'exim_dumpdb'& program, which has no options or arguments other than the
36485 spool and database names. For example, to dump the retry database:
36487 exim_dumpdb /var/spool/exim retry
36489 Two lines of output are produced for each entry:
36491 T:mail.ref.example:192.168.242.242 146 77 Connection refused
36492 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
36494 The first item on the first line is the key of the record. It starts with one
36495 of the letters R, or T, depending on whether it refers to a routing or
36496 transport retry. For a local delivery, the next part is the local address; for
36497 a remote delivery it is the name of the remote host, followed by its failing IP
36498 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
36499 transport). If the remote port is not the standard one (port 25), it is added
36500 to the IP address. Then there follows an error code, an additional error code,
36501 and a textual description of the error.
36503 The three times on the second line are the time of first failure, the time of
36504 the last delivery attempt, and the computed time for the next attempt. The line
36505 ends with an asterisk if the cutoff time for the last retry rule has been
36508 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
36509 consists of a host name followed by a list of ids for messages that are or were
36510 waiting to be delivered to that host. If there are a very large number for any
36511 one host, continuation records, with a sequence number added to the host name,
36512 may be seen. The data in these records is often out of date, because a message
36513 may be routed to several alternative hosts, and Exim makes no effort to keep
36518 .section "exim_tidydb" "SECID262"
36519 .cindex "&'exim_tidydb'&"
36520 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
36521 database. If run with no options, it removes all records that are more than 30
36522 days old. The age is calculated from the date and time that the record was last
36523 updated. Note that, in the case of the retry database, it is &'not'& the time
36524 since the first delivery failure. Information about a host that has been down
36525 for more than 30 days will remain in the database, provided that the record is
36526 updated sufficiently often.
36528 The cutoff date can be altered by means of the &%-t%& option, which must be
36529 followed by a time. For example, to remove all records older than a week from
36530 the retry database:
36532 exim_tidydb -t 7d /var/spool/exim retry
36534 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
36535 message ids. In the former these appear as data in records keyed by host &--
36536 they were messages that were waiting for that host &-- and in the latter they
36537 are the keys for retry information for messages that have suffered certain
36538 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
36539 message ids in database records are those of messages that are still on the
36540 queue. Message ids for messages that no longer exist are removed from
36541 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
36542 For the &'retry'& database, records whose keys are non-existent message ids are
36543 removed. The &'exim_tidydb'& utility outputs comments on the standard output
36544 whenever it removes information from the database.
36546 Certain records are automatically removed by Exim when they are no longer
36547 needed, but others are not. For example, if all the MX hosts for a domain are
36548 down, a retry record is created for each one. If the primary MX host comes back
36549 first, its record is removed when Exim successfully delivers to it, but the
36550 records for the others remain because Exim has not tried to use those hosts.
36552 It is important, therefore, to run &'exim_tidydb'& periodically on all the
36553 hints databases. You should do this at a quiet time of day, because it requires
36554 a database to be locked (and therefore inaccessible to Exim) while it does its
36555 work. Removing records from a DBM file does not normally make the file smaller,
36556 but all the common DBM libraries are able to re-use the space that is released.
36557 After an initial phase of increasing in size, the databases normally reach a
36558 point at which they no longer get any bigger, as long as they are regularly
36561 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
36562 databases is likely to keep on increasing.
36567 .section "exim_fixdb" "SECID263"
36568 .cindex "&'exim_fixdb'&"
36569 The &'exim_fixdb'& program is a utility for interactively modifying databases.
36570 Its main use is for testing Exim, but it might also be occasionally useful for
36571 getting round problems in a live system. It has no options, and its interface
36572 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
36573 key of a database record can then be entered, and the data for that record is
36576 If &"d"& is typed at the next prompt, the entire record is deleted. For all
36577 except the &'retry'& database, that is the only operation that can be carried
36578 out. For the &'retry'& database, each field is output preceded by a number, and
36579 data for individual fields can be changed by typing the field number followed
36580 by new data, for example:
36584 resets the time of the next delivery attempt. Time values are given as a
36585 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
36586 used as optional separators.
36591 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
36592 .cindex "mailbox" "maintenance"
36593 .cindex "&'exim_lock'&"
36594 .cindex "locking mailboxes"
36595 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
36596 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
36597 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
36598 a user agent while investigating a problem. The utility requires the name of
36599 the file as its first argument. If the locking is successful, the second
36600 argument is run as a command (using C's &[system()]& function); if there is no
36601 second argument, the value of the SHELL environment variable is used; if this
36602 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
36603 is unlocked and the utility ends. The following options are available:
36607 Use &[fcntl()]& locking on the open mailbox.
36610 Use &[flock()]& locking on the open mailbox, provided the operating system
36613 .vitem &%-interval%&
36614 This must be followed by a number, which is a number of seconds; it sets the
36615 interval to sleep between retries (default 3).
36617 .vitem &%-lockfile%&
36618 Create a lock file before opening the mailbox.
36621 Lock the mailbox using MBX rules.
36624 Suppress verification output.
36626 .vitem &%-retries%&
36627 This must be followed by a number; it sets the number of times to try to get
36628 the lock (default 10).
36630 .vitem &%-restore_time%&
36631 This option causes &%exim_lock%& to restore the modified and read times to the
36632 locked file before exiting. This allows you to access a locked mailbox (for
36633 example, to take a backup copy) without disturbing the times that the user
36636 .vitem &%-timeout%&
36637 This must be followed by a number, which is a number of seconds; it sets a
36638 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
36639 default), a non-blocking call is used.
36642 Generate verbose output.
36645 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
36646 default is to create a lock file and also to use &[fcntl()]& locking on the
36647 mailbox, which is the same as Exim's default. The use of &%-flock%& or
36648 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
36649 requires that the directory containing the file be writeable. Locking by lock
36650 file does not last for ever; Exim assumes that a lock file is expired if it is
36651 more than 30 minutes old.
36653 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
36654 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
36655 to be taken out on the open mailbox, and an exclusive lock on the file
36656 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
36657 number of the mailbox file. When the locking is released, if an exclusive lock
36658 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
36660 The default output contains verification of the locking that takes place. The
36661 &%-v%& option causes some additional information to be given. The &%-q%& option
36662 suppresses all output except error messages.
36666 exim_lock /var/spool/mail/spqr
36668 runs an interactive shell while the file is locked, whereas
36670 &`exim_lock -q /var/spool/mail/spqr <<End`&
36671 <&'some commands'&>
36674 runs a specific non-interactive sequence of commands while the file is locked,
36675 suppressing all verification output. A single command can be run by a command
36678 exim_lock -q /var/spool/mail/spqr \
36679 "cp /var/spool/mail/spqr /some/where"
36681 Note that if a command is supplied, it must be entirely contained within the
36682 second argument &-- hence the quotes.
36686 . ////////////////////////////////////////////////////////////////////////////
36687 . ////////////////////////////////////////////////////////////////////////////
36689 .chapter "The Exim monitor" "CHAPeximon"
36690 .scindex IIDeximon "Exim monitor" "description"
36691 .cindex "X-windows"
36692 .cindex "&'eximon'&"
36693 .cindex "Local/eximon.conf"
36694 .cindex "&_exim_monitor/EDITME_&"
36695 The Exim monitor is an application which displays in an X window information
36696 about the state of Exim's queue and what Exim is doing. An admin user can
36697 perform certain operations on messages from this GUI interface; however all
36698 such facilities are also available from the command line, and indeed, the
36699 monitor itself makes use of the command line to perform any actions requested.
36703 .section "Running the monitor" "SECID264"
36704 The monitor is started by running the script called &'eximon'&. This is a shell
36705 script that sets up a number of environment variables, and then runs the
36706 binary called &_eximon.bin_&. The default appearance of the monitor window can
36707 be changed by editing the &_Local/eximon.conf_& file created by editing
36708 &_exim_monitor/EDITME_&. Comments in that file describe what the various
36709 parameters are for.
36711 The parameters that get built into the &'eximon'& script can be overridden for
36712 a particular invocation by setting up environment variables of the same names,
36713 preceded by &`EXIMON_`&. For example, a shell command such as
36715 EXIMON_LOG_DEPTH=400 eximon
36717 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
36718 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
36719 overrides the Exim log file configuration. This makes it possible to have
36720 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
36721 syslog messages are routed to a file on the local host.
36723 X resources can be used to change the appearance of the window in the normal
36724 way. For example, a resource setting of the form
36726 Eximon*background: gray94
36728 changes the colour of the background to light grey rather than white. The
36729 stripcharts are drawn with both the data lines and the reference lines in
36730 black. This means that the reference lines are not visible when on top of the
36731 data. However, their colour can be changed by setting a resource called
36732 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
36733 For example, if your X server is running Unix, you could set up lighter
36734 reference lines in the stripcharts by obeying
36737 Eximon*highlight: gray
36740 .cindex "admin user"
36741 In order to see the contents of messages on the queue, and to operate on them,
36742 &'eximon'& must either be run as root or by an admin user.
36744 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
36745 contain X11 resource parameters interpreted by the X11 library. In addition,
36746 if the first parameter starts with the string "gdb" then it is removed and the
36747 binary is invoked under gdb (the parameter is used as the gdb command-name, so
36748 versioned variants of gdb can be invoked).
36750 The monitor's window is divided into three parts. The first contains one or
36751 more stripcharts and two action buttons, the second contains a &"tail"& of the
36752 main log file, and the third is a display of the queue of messages awaiting
36753 delivery, with two more action buttons. The following sections describe these
36754 different parts of the display.
36759 .section "The stripcharts" "SECID265"
36760 .cindex "stripchart"
36761 The first stripchart is always a count of messages on the queue. Its name can
36762 be configured by setting QUEUE_STRIPCHART_NAME in the
36763 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
36764 configuration script by regular expression matches on log file entries, making
36765 it possible to display, for example, counts of messages delivered to certain
36766 hosts or using certain transports. The supplied defaults display counts of
36767 received and delivered messages, and of local and SMTP deliveries. The default
36768 period between stripchart updates is one minute; this can be adjusted by a
36769 parameter in the &_Local/eximon.conf_& file.
36771 The stripchart displays rescale themselves automatically as the value they are
36772 displaying changes. There are always 10 horizontal lines in each chart; the
36773 title string indicates the value of each division when it is greater than one.
36774 For example, &"x2"& means that each division represents a value of 2.
36776 It is also possible to have a stripchart which shows the percentage fullness of
36777 a particular disk partition, which is useful when local deliveries are confined
36778 to a single partition.
36780 .cindex "&%statvfs%& function"
36781 This relies on the availability of the &[statvfs()]& function or equivalent in
36782 the operating system. Most, but not all versions of Unix that support Exim have
36783 this. For this particular stripchart, the top of the chart always represents
36784 100%, and the scale is given as &"x10%"&. This chart is configured by setting
36785 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
36786 &_Local/eximon.conf_& file.
36791 .section "Main action buttons" "SECID266"
36792 .cindex "size" "of monitor window"
36793 .cindex "Exim monitor" "window size"
36794 .cindex "window size"
36795 Below the stripcharts there is an action button for quitting the monitor. Next
36796 to this is another button marked &"Size"&. They are placed here so that
36797 shrinking the window to its default minimum size leaves just the queue count
36798 stripchart and these two buttons visible. Pressing the &"Size"& button causes
36799 the window to expand to its maximum size, unless it is already at the maximum,
36800 in which case it is reduced to its minimum.
36802 When expanding to the maximum, if the window cannot be fully seen where it
36803 currently is, it is moved back to where it was the last time it was at full
36804 size. When it is expanding from its minimum size, the old position is
36805 remembered, and next time it is reduced to the minimum it is moved back there.
36807 The idea is that you can keep a reduced window just showing one or two
36808 stripcharts at a convenient place on your screen, easily expand it to show
36809 the full window when required, and just as easily put it back to what it was.
36810 The idea is copied from what the &'twm'& window manager does for its
36811 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
36812 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
36814 Normally, the monitor starts up with the window at its full size, but it can be
36815 built so that it starts up with the window at its smallest size, by setting
36816 START_SMALL=yes in &_Local/eximon.conf_&.
36820 .section "The log display" "SECID267"
36821 .cindex "log" "tail of; in monitor"
36822 The second section of the window is an area in which a display of the tail of
36823 the main log is maintained.
36824 To save space on the screen, the timestamp on each log line is shortened by
36825 removing the date and, if &%log_timezone%& is set, the timezone.
36826 The log tail is not available when the only destination for logging data is
36827 syslog, unless the syslog lines are routed to a local file whose name is passed
36828 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
36830 The log sub-window has a scroll bar at its lefthand side which can be used to
36831 move back to look at earlier text, and the up and down arrow keys also have a
36832 scrolling effect. The amount of log that is kept depends on the setting of
36833 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
36834 to use. When this is full, the earlier 50% of data is discarded &-- this is
36835 much more efficient than throwing it away line by line. The sub-window also has
36836 a horizontal scroll bar for accessing the ends of long log lines. This is the
36837 only means of horizontal scrolling; the right and left arrow keys are not
36838 available. Text can be cut from this part of the window using the mouse in the
36839 normal way. The size of this subwindow is controlled by parameters in the
36840 configuration file &_Local/eximon.conf_&.
36842 Searches of the text in the log window can be carried out by means of the ^R
36843 and ^S keystrokes, which default to a reverse and a forward search,
36844 respectively. The search covers only the text that is displayed in the window.
36845 It cannot go further back up the log.
36847 The point from which the search starts is indicated by a caret marker. This is
36848 normally at the end of the text in the window, but can be positioned explicitly
36849 by pointing and clicking with the left mouse button, and is moved automatically
36850 by a successful search. If new text arrives in the window when it is scrolled
36851 back, the caret remains where it is, but if the window is not scrolled back,
36852 the caret is moved to the end of the new text.
36854 Pressing ^R or ^S pops up a window into which the search text can be typed.
36855 There are buttons for selecting forward or reverse searching, for carrying out
36856 the search, and for cancelling. If the &"Search"& button is pressed, the search
36857 happens and the window remains so that further searches can be done. If the
36858 &"Return"& key is pressed, a single search is done and the window is closed. If
36859 ^C is typed the search is cancelled.
36861 The searching facility is implemented using the facilities of the Athena text
36862 widget. By default this pops up a window containing both &"search"& and
36863 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
36864 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
36865 However, the linkers in BSDI and HP-UX seem unable to handle an externally
36866 provided version of &%TextPop%& when the remaining parts of the text widget
36867 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
36868 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
36869 on these systems, at the expense of having unwanted items in the search popup
36874 .section "The queue display" "SECID268"
36875 .cindex "queue" "display in monitor"
36876 The bottom section of the monitor window contains a list of all messages that
36877 are on the queue, which includes those currently being received or delivered,
36878 as well as those awaiting delivery. The size of this subwindow is controlled by
36879 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
36880 at which it is updated is controlled by another parameter in the same file &--
36881 the default is 5 minutes, since queue scans can be quite expensive. However,
36882 there is an &"Update"& action button just above the display which can be used
36883 to force an update of the queue display at any time.
36885 When a host is down for some time, a lot of pending mail can build up for it,
36886 and this can make it hard to deal with other messages on the queue. To help
36887 with this situation there is a button next to &"Update"& called &"Hide"&. If
36888 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
36889 type anything in here and press &"Return"&, the text is added to a chain of
36890 such texts, and if every undelivered address in a message matches at least one
36891 of the texts, the message is not displayed.
36893 If there is an address that does not match any of the texts, all the addresses
36894 are displayed as normal. The matching happens on the ends of addresses so, for
36895 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
36896 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
36897 has been set up, a button called &"Unhide"& is displayed. If pressed, it
36898 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
36899 a hide request is automatically cancelled after one hour.
36901 While the dialogue box is displayed, you can't press any buttons or do anything
36902 else to the monitor window. For this reason, if you want to cut text from the
36903 queue display to use in the dialogue box, you have to do the cutting before
36904 pressing the &"Hide"& button.
36906 The queue display contains, for each unhidden queued message, the length of
36907 time it has been on the queue, the size of the message, the message id, the
36908 message sender, and the first undelivered recipient, all on one line. If it is
36909 a bounce message, the sender is shown as &"<>"&. If there is more than one
36910 recipient to which the message has not yet been delivered, subsequent ones are
36911 listed on additional lines, up to a maximum configured number, following which
36912 an ellipsis is displayed. Recipients that have already received the message are
36915 .cindex "frozen messages" "display"
36916 If a message is frozen, an asterisk is displayed at the left-hand side.
36918 The queue display has a vertical scroll bar, and can also be scrolled by means
36919 of the arrow keys. Text can be cut from it using the mouse in the normal way.
36920 The text searching facilities, as described above for the log window, are also
36921 available, but the caret is always moved to the end of the text when the queue
36922 display is updated.
36926 .section "The queue menu" "SECID269"
36927 .cindex "queue" "menu in monitor"
36928 If the &%shift%& key is held down and the left button is clicked when the mouse
36929 pointer is over the text for any message, an action menu pops up, and the first
36930 line of the queue display for the message is highlighted. This does not affect
36933 If you want to use some other event for popping up the menu, you can set the
36934 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
36935 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
36936 value set in this parameter is a standard X event description. For example, to
36937 run eximon using &%ctrl%& rather than &%shift%& you could use
36939 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
36941 The title of the menu is the message id, and it contains entries which act as
36945 &'message log'&: The contents of the message log for the message are displayed
36946 in a new text window.
36948 &'headers'&: Information from the spool file that contains the envelope
36949 information and headers is displayed in a new text window. See chapter
36950 &<<CHAPspool>>& for a description of the format of spool files.
36952 &'body'&: The contents of the spool file containing the body of the message are
36953 displayed in a new text window. There is a default limit of 20,000 bytes to the
36954 amount of data displayed. This can be changed by setting the BODY_MAX
36955 option at compile time, or the EXIMON_BODY_MAX option at run time.
36957 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
36958 delivery of the message. This causes an automatic thaw if the message is
36959 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
36960 a new text window. The delivery is run in a separate process, to avoid holding
36961 up the monitor while the delivery proceeds.
36963 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
36964 that the message be frozen.
36966 .cindex "thawing messages"
36967 .cindex "unfreezing messages"
36968 .cindex "frozen messages" "thawing"
36969 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
36970 that the message be thawed.
36972 .cindex "delivery" "forcing failure"
36973 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
36974 that Exim gives up trying to deliver the message. A bounce message is generated
36975 for any remaining undelivered addresses.
36977 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
36978 that the message be deleted from the system without generating a bounce
36981 &'add recipient'&: A dialog box is displayed into which a recipient address can
36982 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
36983 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
36984 Otherwise it must be entered as a fully qualified address. Pressing RETURN
36985 causes a call to Exim to be made using the &%-Mar%& option to request that an
36986 additional recipient be added to the message, unless the entry box is empty, in
36987 which case no action is taken.
36989 &'mark delivered'&: A dialog box is displayed into which a recipient address
36990 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
36991 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
36992 Otherwise it must be entered as a fully qualified address. Pressing RETURN
36993 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
36994 recipient address as already delivered, unless the entry box is empty, in which
36995 case no action is taken.
36997 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
36998 mark all recipient addresses as already delivered.
37000 &'edit sender'&: A dialog box is displayed initialized with the current
37001 sender's address. Pressing RETURN causes a call to Exim to be made using the
37002 &%-Mes%& option to replace the sender address, unless the entry box is empty,
37003 in which case no action is taken. If you want to set an empty sender (as in
37004 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
37005 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
37006 the address is qualified with that domain.
37009 When a delivery is forced, a window showing the &%-v%& output is displayed. In
37010 other cases when a call to Exim is made, if there is any output from Exim (in
37011 particular, if the command fails) a window containing the command and the
37012 output is displayed. Otherwise, the results of the action are normally apparent
37013 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
37014 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
37015 if no output is generated.
37017 The queue display is automatically updated for actions such as freezing and
37018 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
37019 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
37020 force an update of the display after one of these actions.
37022 In any text window that is displayed as result of a menu action, the normal
37023 cut-and-paste facility is available, and searching can be carried out using ^R
37024 and ^S, as described above for the log tail window.
37031 . ////////////////////////////////////////////////////////////////////////////
37032 . ////////////////////////////////////////////////////////////////////////////
37034 .chapter "Security considerations" "CHAPsecurity"
37035 .scindex IIDsecurcon "security" "discussion of"
37036 This chapter discusses a number of issues concerned with security, some of
37037 which are also covered in other parts of this manual.
37039 For reasons that this author does not understand, some people have promoted
37040 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
37041 existence of this chapter in the documentation. However, the intent of the
37042 chapter is simply to describe the way Exim works in relation to certain
37043 security concerns, not to make any specific claims about the effectiveness of
37044 its security as compared with other MTAs.
37046 What follows is a description of the way Exim is supposed to be. Best efforts
37047 have been made to try to ensure that the code agrees with the theory, but an
37048 absence of bugs can never be guaranteed. Any that are reported will get fixed
37049 as soon as possible.
37052 .section "Building a more &""hardened""& Exim" "SECID286"
37053 .cindex "security" "build-time features"
37054 There are a number of build-time options that can be set in &_Local/Makefile_&
37055 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
37056 Exim administrator who does not have the root password, or by someone who has
37057 penetrated the Exim (but not the root) account. These options are as follows:
37060 ALT_CONFIG_PREFIX can be set to a string that is required to match the
37061 start of any file names used with the &%-C%& option. When it is set, these file
37062 names are also not allowed to contain the sequence &"/../"&. (However, if the
37063 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
37064 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
37065 default setting for &%ALT_CONFIG_PREFIX%&.
37067 If the permitted configuration files are confined to a directory to
37068 which only root has access, this guards against someone who has broken
37069 into the Exim account from running a privileged Exim with an arbitrary
37070 configuration file, and using it to break into other accounts.
37073 If a non-trusted configuration file (i.e. not the default configuration file
37074 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
37075 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
37076 the next item), then root privilege is retained only if the caller of Exim is
37077 root. This locks out the possibility of testing a configuration using &%-C%&
37078 right through message reception and delivery, even if the caller is root. The
37079 reception works, but by that time, Exim is running as the Exim user, so when
37080 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
37081 privilege to be lost. However, root can test reception and delivery using two
37085 The WHITELIST_D_MACROS build option declares some macros to be safe to override
37086 with &%-D%& if the real uid is one of root, the Exim run-time user or the
37087 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
37088 requiring the run-time value supplied to &%-D%& to match a regex that errs on
37089 the restrictive side. Requiring build-time selection of safe macros is onerous
37090 but this option is intended solely as a transition mechanism to permit
37091 previously-working configurations to continue to work after release 4.73.
37093 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
37096 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
37097 never to be used for any deliveries. This is like the &%never_users%& runtime
37098 option, but it cannot be overridden; the runtime option adds additional users
37099 to the list. The default setting is &"root"&; this prevents a non-root user who
37100 is permitted to modify the runtime file from using Exim as a way to get root.
37105 .section "Root privilege" "SECID270"
37107 .cindex "root privilege"
37108 The Exim binary is normally setuid to root, which means that it gains root
37109 privilege (runs as root) when it starts execution. In some special cases (for
37110 example, when the daemon is not in use and there are no local deliveries), it
37111 may be possible to run Exim setuid to some user other than root. This is
37112 discussed in the next section. However, in most installations, root privilege
37113 is required for two things:
37116 To set up a socket connected to the standard SMTP port (25) when initialising
37117 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
37120 To be able to change uid and gid in order to read users' &_.forward_& files and
37121 perform local deliveries as the receiving user or as specified in the
37125 It is not necessary to be root to do any of the other things Exim does, such as
37126 receiving messages and delivering them externally over SMTP, and it is
37127 obviously more secure if Exim does not run as root except when necessary.
37128 For this reason, a user and group for Exim to use must be defined in
37129 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
37130 group"&. Their values can be changed by the run time configuration, though this
37131 is not recommended. Often a user called &'exim'& is used, but some sites use
37132 &'mail'& or another user name altogether.
37134 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
37135 abdication; the process cannot regain root afterwards. Prior to release 4.00,
37136 &[seteuid()]& was used in some circumstances, but this is no longer the case.
37138 After a new Exim process has interpreted its command line options, it changes
37139 uid and gid in the following cases:
37144 If the &%-C%& option is used to specify an alternate configuration file, or if
37145 the &%-D%& option is used to define macro values for the configuration, and the
37146 calling process is not running as root, the uid and gid are changed to those of
37147 the calling process.
37148 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
37149 option may not be used at all.
37150 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
37151 can be supplied if the calling process is running as root, the Exim run-time
37152 user or CONFIGURE_OWNER, if defined.
37157 If the expansion test option (&%-be%&) or one of the filter testing options
37158 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
37161 If the process is not a daemon process or a queue runner process or a delivery
37162 process or a process for testing address routing (started with &%-bt%&), the
37163 uid and gid are changed to the Exim user and group. This means that Exim always
37164 runs under its own uid and gid when receiving messages. This also applies when
37165 testing address verification
37168 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
37171 For a daemon, queue runner, delivery, or address testing process, the uid
37172 remains as root at this stage, but the gid is changed to the Exim group.
37175 The processes that initially retain root privilege behave as follows:
37178 A daemon process changes the gid to the Exim group and the uid to the Exim
37179 user after setting up one or more listening sockets. The &[initgroups()]&
37180 function is called, so that if the Exim user is in any additional groups, they
37181 will be used during message reception.
37183 A queue runner process retains root privilege throughout its execution. Its
37184 job is to fork a controlled sequence of delivery processes.
37186 A delivery process retains root privilege throughout most of its execution,
37187 but any actual deliveries (that is, the transports themselves) are run in
37188 subprocesses which always change to a non-root uid and gid. For local
37189 deliveries this is typically the uid and gid of the owner of the mailbox; for
37190 remote deliveries, the Exim uid and gid are used. Once all the delivery
37191 subprocesses have been run, a delivery process changes to the Exim uid and gid
37192 while doing post-delivery tidying up such as updating the retry database and
37193 generating bounce and warning messages.
37195 While the recipient addresses in a message are being routed, the delivery
37196 process runs as root. However, if a user's filter file has to be processed,
37197 this is done in a subprocess that runs under the individual user's uid and
37198 gid. A system filter is run as root unless &%system_filter_user%& is set.
37200 A process that is testing addresses (the &%-bt%& option) runs as root so that
37201 the routing is done in the same environment as a message delivery.
37207 .section "Running Exim without privilege" "SECTrunexiwitpri"
37208 .cindex "privilege, running without"
37209 .cindex "unprivileged running"
37210 .cindex "root privilege" "running without"
37211 Some installations like to run Exim in an unprivileged state for more of its
37212 operation, for added security. Support for this mode of operation is provided
37213 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
37214 gid are changed to the Exim user and group at the start of a delivery process
37215 (and also queue runner and address testing processes). This means that address
37216 routing is no longer run as root, and the deliveries themselves cannot change
37220 .cindex "daemon" "restarting"
37221 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
37222 that the daemon can still be started in the usual way, and it can respond
37223 correctly to SIGHUP because the re-invocation regains root privilege.
37225 An alternative approach is to make Exim setuid to the Exim user and also setgid
37226 to the Exim group. If you do this, the daemon must be started from a root
37227 process. (Calling Exim from a root process makes it behave in the way it does
37228 when it is setuid root.) However, the daemon cannot restart itself after a
37229 SIGHUP signal because it cannot regain privilege.
37231 It is still useful to set &%deliver_drop_privilege%& in this case, because it
37232 stops Exim from trying to re-invoke itself to do a delivery after a message has
37233 been received. Such a re-invocation is a waste of resources because it has no
37236 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
37237 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
37238 to the Exim user seems a clean approach, but there is one complication:
37240 In this style of operation, Exim is running with the real uid and gid set to
37241 those of the calling process, and the effective uid/gid set to Exim's values.
37242 Ideally, any association with the calling process' uid/gid should be dropped,
37243 that is, the real uid/gid should be reset to the effective values so as to
37244 discard any privileges that the caller may have. While some operating systems
37245 have a function that permits this action for a non-root effective uid, quite a
37246 number of them do not. Because of this lack of standardization, Exim does not
37247 address this problem at this time.
37249 For this reason, the recommended approach for &"mostly unprivileged"& running
37250 is to keep the Exim binary setuid to root, and to set
37251 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
37252 be used in the most straightforward way.
37254 If you configure Exim not to run delivery processes as root, there are a
37255 number of restrictions on what you can do:
37258 You can deliver only as the Exim user/group. You should explicitly use the
37259 &%user%& and &%group%& options to override routers or local transports that
37260 normally deliver as the recipient. This makes sure that configurations that
37261 work in this mode function the same way in normal mode. Any implicit or
37262 explicit specification of another user causes an error.
37264 Use of &_.forward_& files is severely restricted, such that it is usually
37265 not worthwhile to include them in the configuration.
37267 Users who wish to use &_.forward_& would have to make their home directory and
37268 the file itself accessible to the Exim user. Pipe and append-to-file entries,
37269 and their equivalents in Exim filters, cannot be used. While they could be
37270 enabled in the Exim user's name, that would be insecure and not very useful.
37272 Unless the local user mailboxes are all owned by the Exim user (possible in
37273 some POP3 or IMAP-only environments):
37276 They must be owned by the Exim group and be writeable by that group. This
37277 implies you must set &%mode%& in the appendfile configuration, as well as the
37278 mode of the mailbox files themselves.
37280 You must set &%no_check_owner%&, since most or all of the files will not be
37281 owned by the Exim user.
37283 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
37284 on a newly created mailbox when unprivileged. This also implies that new
37285 mailboxes need to be created manually.
37290 These restrictions severely restrict what can be done in local deliveries.
37291 However, there are no restrictions on remote deliveries. If you are running a
37292 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
37293 gives more security at essentially no cost.
37295 If you are using the &%mua_wrapper%& facility (see chapter
37296 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
37301 .section "Delivering to local files" "SECID271"
37302 Full details of the checks applied by &(appendfile)& before it writes to a file
37303 are given in chapter &<<CHAPappendfile>>&.
37307 .section "Running local commands" "SECTsecconslocalcmds"
37308 .cindex "security" "local commands"
37309 .cindex "security" "command injection attacks"
37310 There are a number of ways in which an administrator can configure Exim to run
37311 commands based upon received, untrustworthy, data. Further, in some
37312 configurations a user who can control a &_.forward_& file can also arrange to
37313 run commands. Configuration to check includes, but is not limited to:
37316 Use of &%use_shell%& in the pipe transport: various forms of shell command
37317 injection may be possible with this option present. It is dangerous and should
37318 be used only with considerable caution. Consider constraints which whitelist
37319 allowed characters in a variable which is to be used in a pipe transport that
37320 has &%use_shell%& enabled.
37322 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
37323 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
37324 &_.forward_& files in a redirect router. If Exim is running on a central mail
37325 hub to which ordinary users do not have shell access, but home directories are
37326 NFS mounted (for instance) then administrators should review the list of these
37327 forbid options available, and should bear in mind that the options that may
37328 need forbidding can change as new features are added between releases.
37330 The &%${run...}%& expansion item does not use a shell by default, but
37331 administrators can configure use of &_/bin/sh_& as part of the command.
37332 Such invocations should be viewed with prejudicial suspicion.
37334 Administrators who use embedded Perl are advised to explore how Perl's
37335 taint checking might apply to their usage.
37337 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
37338 administrators are well advised to view its use with suspicion, in case (for
37339 instance) it allows a local-part to contain embedded Exim directives.
37341 Use of &%${match_local_part...}%& and friends becomes more dangerous if
37342 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
37343 each can reference arbitrary lists and files, rather than just being a list
37345 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
37346 real-world security vulnerabilities caused by its use with untrustworthy data
37347 injected in, for SQL injection attacks.
37348 Consider the use of the &%inlisti%& expansion condition instead.
37354 .section "Trust in configuration data" "SECTsecconfdata"
37355 .cindex "security" "data sources"
37356 .cindex "security" "regular expressions"
37357 .cindex "regular expressions" "security"
37358 .cindex "PCRE" "security"
37359 If configuration data for Exim can come from untrustworthy sources, there
37360 are some issues to be aware of:
37363 Use of &%${expand...}%& may provide a path for shell injection attacks.
37365 Letting untrusted data provide a regular expression is unwise.
37367 Using &%${match...}%& to apply a fixed regular expression against untrusted
37368 data may result in pathological behaviour within PCRE. Be aware of what
37369 "backtracking" means and consider options for being more strict with a regular
37370 expression. Avenues to explore include limiting what can match (avoiding &`.`&
37371 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
37372 possessive quantifiers or just not using regular expressions against untrusted
37375 It can be important to correctly use &%${quote:...}%&,
37376 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
37377 items to ensure that data is correctly constructed.
37379 Some lookups might return multiple results, even though normal usage is only
37380 expected to yield one result.
37386 .section "IPv4 source routing" "SECID272"
37387 .cindex "source routing" "in IP packets"
37388 .cindex "IP source routing"
37389 Many operating systems suppress IP source-routed packets in the kernel, but
37390 some cannot be made to do this, so Exim does its own check. It logs incoming
37391 IPv4 source-routed TCP calls, and then drops them. Things are all different in
37392 IPv6. No special checking is currently done.
37396 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
37397 Support for these SMTP commands is disabled by default. If required, they can
37398 be enabled by defining suitable ACLs.
37403 .section "Privileged users" "SECID274"
37404 .cindex "trusted users"
37405 .cindex "admin user"
37406 .cindex "privileged user"
37407 .cindex "user" "trusted"
37408 .cindex "user" "admin"
37409 Exim recognizes two sets of users with special privileges. Trusted users are
37410 able to submit new messages to Exim locally, but supply their own sender
37411 addresses and information about a sending host. For other users submitting
37412 local messages, Exim sets up the sender address from the uid, and doesn't
37413 permit a remote host to be specified.
37416 However, an untrusted user is permitted to use the &%-f%& command line option
37417 in the special form &%-f <>%& to indicate that a delivery failure for the
37418 message should not cause an error report. This affects the message's envelope,
37419 but it does not affect the &'Sender:'& header. Untrusted users may also be
37420 permitted to use specific forms of address with the &%-f%& option by setting
37421 the &%untrusted_set_sender%& option.
37423 Trusted users are used to run processes that receive mail messages from some
37424 other mail domain and pass them on to Exim for delivery either locally, or over
37425 the Internet. Exim trusts a caller that is running as root, as the Exim user,
37426 as any user listed in the &%trusted_users%& configuration option, or under any
37427 group listed in the &%trusted_groups%& option.
37429 Admin users are permitted to do things to the messages on Exim's queue. They
37430 can freeze or thaw messages, cause them to be returned to their senders, remove
37431 them entirely, or modify them in various ways. In addition, admin users can run
37432 the Exim monitor and see all the information it is capable of providing, which
37433 includes the contents of files on the spool.
37437 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
37438 delivery of messages on its queue is restricted to admin users. This
37439 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
37440 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
37441 queue is also restricted to admin users. This restriction can be relaxed by
37442 setting &%no_queue_list_requires_admin%&.
37444 Exim recognizes an admin user if the calling process is running as root or as
37445 the Exim user or if any of the groups associated with the calling process is
37446 the Exim group. It is not necessary actually to be running under the Exim
37447 group. However, if admin users who are not root or the Exim user are to access
37448 the contents of files on the spool via the Exim monitor (which runs
37449 unprivileged), Exim must be built to allow group read access to its spool
37454 .section "Spool files" "SECID275"
37455 .cindex "spool directory" "files"
37456 Exim's spool directory and everything it contains is owned by the Exim user and
37457 set to the Exim group. The mode for spool files is defined in the
37458 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
37459 any user who is a member of the Exim group can access these files.
37463 .section "Use of argv[0]" "SECID276"
37464 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
37465 of specific strings, Exim assumes certain options. For example, calling Exim
37466 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
37467 to calling it with the option &%-bS%&. There are no security implications in
37472 .section "Use of %f formatting" "SECID277"
37473 The only use made of &"%f"& by Exim is in formatting load average values. These
37474 are actually stored in integer variables as 1000 times the load average.
37475 Consequently, their range is limited and so therefore is the length of the
37480 .section "Embedded Exim path" "SECID278"
37481 Exim uses its own path name, which is embedded in the code, only when it needs
37482 to re-exec in order to regain root privilege. Therefore, it is not root when it
37483 does so. If some bug allowed the path to get overwritten, it would lead to an
37484 arbitrary program's being run as exim, not as root.
37488 .section "Dynamic module directory" "SECTdynmoddir"
37489 Any dynamically loadable modules must be installed into the directory
37490 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
37494 .section "Use of sprintf()" "SECID279"
37495 .cindex "&[sprintf()]&"
37496 A large number of occurrences of &"sprintf"& in the code are actually calls to
37497 &'string_sprintf()'&, a function that returns the result in malloc'd store.
37498 The intermediate formatting is done into a large fixed buffer by a function
37499 that runs through the format string itself, and checks the length of each
37500 conversion before performing it, thus preventing buffer overruns.
37502 The remaining uses of &[sprintf()]& happen in controlled circumstances where
37503 the output buffer is known to be sufficiently long to contain the converted
37508 .section "Use of debug_printf() and log_write()" "SECID280"
37509 Arbitrary strings are passed to both these functions, but they do their
37510 formatting by calling the function &'string_vformat()'&, which runs through
37511 the format string itself, and checks the length of each conversion.
37515 .section "Use of strcat() and strcpy()" "SECID281"
37516 These are used only in cases where the output buffer is known to be large
37517 enough to hold the result.
37518 .ecindex IIDsecurcon
37523 . ////////////////////////////////////////////////////////////////////////////
37524 . ////////////////////////////////////////////////////////////////////////////
37526 .chapter "Format of spool files" "CHAPspool"
37527 .scindex IIDforspo1 "format" "spool files"
37528 .scindex IIDforspo2 "spool directory" "format of files"
37529 .scindex IIDforspo3 "spool files" "format of"
37530 .cindex "spool files" "editing"
37531 A message on Exim's queue consists of two files, whose names are the message id
37532 followed by -D and -H, respectively. The data portion of the message is kept in
37533 the -D file on its own. The message's envelope, status, and headers are all
37534 kept in the -H file, whose format is described in this chapter. Each of these
37535 two files contains the final component of its own name as its first line. This
37536 is insurance against disk crashes where the directory is lost but the files
37537 themselves are recoverable.
37539 Some people are tempted into editing -D files in order to modify messages. You
37540 need to be extremely careful if you do this; it is not recommended and you are
37541 on your own if you do it. Here are some of the pitfalls:
37544 You must ensure that Exim does not try to deliver the message while you are
37545 fiddling with it. The safest way is to take out a write lock on the -D file,
37546 which is what Exim itself does, using &[fcntl()]&. If you update the file in
37547 place, the lock will be retained. If you write a new file and rename it, the
37548 lock will be lost at the instant of rename.
37550 .vindex "&$body_linecount$&"
37551 If you change the number of lines in the file, the value of
37552 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
37553 present, this value is not used by Exim, but there is no guarantee that this
37554 will always be the case.
37556 If the message is in MIME format, you must take care not to break it.
37558 If the message is cryptographically signed, any change will invalidate the
37561 All in all, modifying -D files is fraught with danger.
37563 Files whose names end with -J may also be seen in the &_input_& directory (or
37564 its subdirectories when &%split_spool_directory%& is set). These are journal
37565 files, used to record addresses to which the message has been delivered during
37566 the course of a delivery attempt. If there are still undelivered recipients at
37567 the end, the -H file is updated, and the -J file is deleted. If, however, there
37568 is some kind of crash (for example, a power outage) before this happens, the -J
37569 file remains in existence. When Exim next processes the message, it notices the
37570 -J file and uses it to update the -H file before starting the next delivery
37573 .section "Format of the -H file" "SECID282"
37574 .cindex "uid (user id)" "in spool file"
37575 .cindex "gid (group id)" "in spool file"
37576 The second line of the -H file contains the login name for the uid of the
37577 process that called Exim to read the message, followed by the numerical uid and
37578 gid. For a locally generated message, this is normally the user who sent the
37579 message. For a message received over TCP/IP via the daemon, it is
37580 normally the Exim user.
37582 The third line of the file contains the address of the message's sender as
37583 transmitted in the envelope, contained in angle brackets. The sender address is
37584 empty for bounce messages. For incoming SMTP mail, the sender address is given
37585 in the MAIL command. For locally generated mail, the sender address is
37586 created by Exim from the login name of the current user and the configured
37587 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
37588 leading &"From&~"& line if the caller is trusted, or if the supplied address is
37589 &"<>"& or an address that matches &%untrusted_set_senders%&.
37591 The fourth line contains two numbers. The first is the time that the message
37592 was received, in the conventional Unix form &-- the number of seconds since the
37593 start of the epoch. The second number is a count of the number of messages
37594 warning of delayed delivery that have been sent to the sender.
37596 There follow a number of lines starting with a hyphen. These can appear in any
37597 order, and are omitted when not relevant:
37600 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
37601 This item is obsolete, and is not generated from Exim release 4.61 onwards;
37602 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
37603 recognized, to provide backward compatibility. In the old format, a line of
37604 this form is present for every ACL variable that is not empty. The number
37605 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
37606 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
37607 the data string for the variable. The string itself starts at the beginning of
37608 the next line, and is followed by a newline character. It may contain internal
37611 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
37612 A line of this form is present for every ACL connection variable that is
37613 defined. Note that there is a space between &%-aclc%& and the rest of the name.
37614 The length is the length of the data string for the variable. The string itself
37615 starts at the beginning of the next line, and is followed by a newline
37616 character. It may contain internal newlines.
37618 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
37619 A line of this form is present for every ACL message variable that is defined.
37620 Note that there is a space between &%-aclm%& and the rest of the name. The
37621 length is the length of the data string for the variable. The string itself
37622 starts at the beginning of the next line, and is followed by a newline
37623 character. It may contain internal newlines.
37625 .vitem "&%-active_hostname%&&~<&'hostname'&>"
37626 This is present if, when the message was received over SMTP, the value of
37627 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
37629 .vitem &%-allow_unqualified_recipient%&
37630 This is present if unqualified recipient addresses are permitted in header
37631 lines (to stop such addresses from being qualified if rewriting occurs at
37632 transport time). Local messages that were input using &%-bnq%& and remote
37633 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
37635 .vitem &%-allow_unqualified_sender%&
37636 This is present if unqualified sender addresses are permitted in header lines
37637 (to stop such addresses from being qualified if rewriting occurs at transport
37638 time). Local messages that were input using &%-bnq%& and remote messages from
37639 hosts that match &%sender_unqualified_hosts%& set this flag.
37641 .vitem "&%-auth_id%&&~<&'text'&>"
37642 The id information for a message received on an authenticated SMTP connection
37643 &-- the value of the &$authenticated_id$& variable.
37645 .vitem "&%-auth_sender%&&~<&'address'&>"
37646 The address of an authenticated sender &-- the value of the
37647 &$authenticated_sender$& variable.
37649 .vitem "&%-body_linecount%&&~<&'number'&>"
37650 This records the number of lines in the body of the message, and is always
37653 .vitem "&%-body_zerocount%&&~<&'number'&>"
37654 This records the number of binary zero bytes in the body of the message, and is
37655 present if the number is greater than zero.
37657 .vitem &%-deliver_firsttime%&
37658 This is written when a new message is first added to the spool. When the spool
37659 file is updated after a deferral, it is omitted.
37661 .vitem "&%-frozen%&&~<&'time'&>"
37662 .cindex "frozen messages" "spool data"
37663 The message is frozen, and the freezing happened at <&'time'&>.
37665 .vitem "&%-helo_name%&&~<&'text'&>"
37666 This records the host name as specified by a remote host in a HELO or EHLO
37669 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
37670 This records the IP address of the host from which the message was received and
37671 the remote port number that was used. It is omitted for locally generated
37674 .vitem "&%-host_auth%&&~<&'text'&>"
37675 If the message was received on an authenticated SMTP connection, this records
37676 the name of the authenticator &-- the value of the
37677 &$sender_host_authenticated$& variable.
37679 .vitem &%-host_lookup_failed%&
37680 This is present if an attempt to look up the sending host's name from its IP
37681 address failed. It corresponds to the &$host_lookup_failed$& variable.
37683 .vitem "&%-host_name%&&~<&'text'&>"
37684 .cindex "reverse DNS lookup"
37685 .cindex "DNS" "reverse lookup"
37686 This records the name of the remote host from which the message was received,
37687 if the host name was looked up from the IP address when the message was being
37688 received. It is not present if no reverse lookup was done.
37690 .vitem "&%-ident%&&~<&'text'&>"
37691 For locally submitted messages, this records the login of the originating user,
37692 unless it was a trusted user and the &%-oMt%& option was used to specify an
37693 ident value. For messages received over TCP/IP, this records the ident string
37694 supplied by the remote host, if any.
37696 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
37697 This records the IP address of the local interface and the port number through
37698 which a message was received from a remote host. It is omitted for locally
37699 generated messages.
37702 The message is from a local sender.
37704 .vitem &%-localerror%&
37705 The message is a locally-generated bounce message.
37707 .vitem "&%-local_scan%&&~<&'string'&>"
37708 This records the data string that was returned by the &[local_scan()]& function
37709 when the message was received &-- the value of the &$local_scan_data$&
37710 variable. It is omitted if no data was returned.
37712 .vitem &%-manual_thaw%&
37713 The message was frozen but has been thawed manually, that is, by an explicit
37714 Exim command rather than via the auto-thaw process.
37717 A testing delivery process was started using the &%-N%& option to suppress any
37718 actual deliveries, but delivery was deferred. At any further delivery attempts,
37721 .vitem &%-received_protocol%&
37722 This records the value of the &$received_protocol$& variable, which contains
37723 the name of the protocol by which the message was received.
37725 .vitem &%-sender_set_untrusted%&
37726 The envelope sender of this message was set by an untrusted local caller (used
37727 to ensure that the caller is displayed in queue listings).
37729 .vitem "&%-spam_score_int%&&~<&'number'&>"
37730 If a message was scanned by SpamAssassin, this is present. It records the value
37731 of &$spam_score_int$&.
37733 .vitem &%-tls_certificate_verified%&
37734 A TLS certificate was received from the client that sent this message, and the
37735 certificate was verified by the server.
37737 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
37738 When the message was received over an encrypted connection, this records the
37739 name of the cipher suite that was used.
37741 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
37742 When the message was received over an encrypted connection, and a certificate
37743 was received from the client, this records the Distinguished Name from that
37747 Following the options there is a list of those addresses to which the message
37748 is not to be delivered. This set of addresses is initialized from the command
37749 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
37750 is set; otherwise it starts out empty. Whenever a successful delivery is made,
37751 the address is added to this set. The addresses are kept internally as a
37752 balanced binary tree, and it is a representation of that tree which is written
37753 to the spool file. If an address is expanded via an alias or forward file, the
37754 original address is added to the tree when deliveries to all its child
37755 addresses are complete.
37757 If the tree is empty, there is a single line in the spool file containing just
37758 the text &"XX"&. Otherwise, each line consists of two letters, which are either
37759 Y or N, followed by an address. The address is the value for the node of the
37760 tree, and the letters indicate whether the node has a left branch and/or a
37761 right branch attached to it, respectively. If branches exist, they immediately
37762 follow. Here is an example of a three-node tree:
37764 YY darcy@austen.fict.example
37765 NN alice@wonderland.fict.example
37766 NN editor@thesaurus.ref.example
37768 After the non-recipients tree, there is a list of the message's recipients.
37769 This is a simple list, preceded by a count. It includes all the original
37770 recipients of the message, including those to whom the message has already been
37771 delivered. In the simplest case, the list contains one address per line. For
37775 editor@thesaurus.ref.example
37776 darcy@austen.fict.example
37778 alice@wonderland.fict.example
37780 However, when a child address has been added to the top-level addresses as a
37781 result of the use of the &%one_time%& option on a &(redirect)& router, each
37782 line is of the following form:
37784 <&'top-level address'&> <&'errors_to address'&> &&&
37785 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
37787 The 01 flag bit indicates the presence of the three other fields that follow
37788 the top-level address. Other bits may be used in future to support additional
37789 fields. The <&'parent number'&> is the offset in the recipients list of the
37790 original parent of the &"one time"& address. The first two fields are the
37791 envelope sender that is associated with this address and its length. If the
37792 length is zero, there is no special envelope sender (there are then two space
37793 characters in the line). A non-empty field can arise from a &(redirect)& router
37794 that has an &%errors_to%& setting.
37797 A blank line separates the envelope and status information from the headers
37798 which follow. A header may occupy several lines of the file, and to save effort
37799 when reading it in, each header is preceded by a number and an identifying
37800 character. The number is the number of characters in the header, including any
37801 embedded newlines and the terminating newline. The character is one of the
37805 .row <&'blank'&> "header in which Exim has no special interest"
37806 .row &`B`& "&'Bcc:'& header"
37807 .row &`C`& "&'Cc:'& header"
37808 .row &`F`& "&'From:'& header"
37809 .row &`I`& "&'Message-id:'& header"
37810 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
37811 .row &`R`& "&'Reply-To:'& header"
37812 .row &`S`& "&'Sender:'& header"
37813 .row &`T`& "&'To:'& header"
37814 .row &`*`& "replaced or deleted header"
37817 Deleted or replaced (rewritten) headers remain in the spool file for debugging
37818 purposes. They are not transmitted when the message is delivered. Here is a
37819 typical set of headers:
37821 111P Received: by hobbit.fict.example with local (Exim 4.00)
37822 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
37823 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
37824 038* X-rewrote-sender: bb@hobbit.fict.example
37825 042* From: Bilbo Baggins <bb@hobbit.fict.example>
37826 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
37827 099* To: alice@wonderland.fict.example, rdo@foundation,
37828 darcy@austen.fict.example, editor@thesaurus.ref.example
37829 104T To: alice@wonderland.fict.example, rdo@foundation.example,
37830 darcy@austen.fict.example, editor@thesaurus.ref.example
37831 038 Date: Fri, 11 May 2001 10:28:59 +0100
37833 The asterisked headers indicate that the envelope sender, &'From:'& header, and
37834 &'To:'& header have been rewritten, the last one because routing expanded the
37835 unqualified domain &'foundation'&.
37836 .ecindex IIDforspo1
37837 .ecindex IIDforspo2
37838 .ecindex IIDforspo3
37840 . ////////////////////////////////////////////////////////////////////////////
37841 . ////////////////////////////////////////////////////////////////////////////
37843 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
37847 DKIM is a mechanism by which messages sent by some entity can be provably
37848 linked to a domain which that entity controls. It permits reputation to
37849 be tracked on a per-domain basis, rather than merely upon source IP address.
37850 DKIM is documented in RFC 4871.
37852 Since version 4.70, DKIM support is compiled into Exim by default. It can be
37853 disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
37855 Exim's DKIM implementation allows to
37857 Sign outgoing messages: This function is implemented in the SMTP transport.
37858 It can co-exist with all other Exim features
37859 (including transport filters)
37860 except cutthrough delivery.
37862 Verify signatures in incoming messages: This is implemented by an additional
37863 ACL (acl_smtp_dkim), which can be called several times per message, with
37864 different signature contexts.
37867 In typical Exim style, the verification implementation does not include any
37868 default "policy". Instead it enables you to build your own policy using
37869 Exim's standard controls.
37871 Please note that verification of DKIM signatures in incoming mail is turned
37872 on by default for logging purposes. For each signature in incoming email,
37873 exim will log a line displaying the most important signature details, and the
37874 signature status. Here is an example (with line-breaks added for clarity):
37876 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
37877 d=facebookmail.com s=q1-2009b
37878 c=relaxed/relaxed a=rsa-sha1
37879 i=@facebookmail.com t=1252484542 [verification succeeded]
37881 You might want to turn off DKIM verification processing entirely for internal
37882 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
37883 control modifier. This should typically be done in the RCPT ACL, at points
37884 where you accept mail from relay sources (internal hosts or authenticated
37888 .section "Signing outgoing messages" "SECID513"
37889 .cindex "DKIM" "signing"
37891 Signing is implemented by setting private options on the SMTP transport.
37892 These options take (expandable) strings as arguments.
37894 .option dkim_domain smtp string&!! unset
37896 The domain you want to sign with. The result of this expanded
37897 option is put into the &%$dkim_domain%& expansion variable.
37899 .option dkim_selector smtp string&!! unset
37901 This sets the key selector string. You can use the &%$dkim_domain%& expansion
37902 variable to look up a matching selector. The result is put in the expansion
37903 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
37904 option along with &%$dkim_domain%&.
37906 .option dkim_private_key smtp string&!! unset
37908 This sets the private key to use. You can use the &%$dkim_domain%& and
37909 &%$dkim_selector%& expansion variables to determine the private key to use.
37910 The result can either
37912 be a valid RSA private key in ASCII armor, including line breaks.
37914 start with a slash, in which case it is treated as a file that contains
37917 be "0", "false" or the empty string, in which case the message will not
37918 be signed. This case will not result in an error, even if &%dkim_strict%&
37922 .option dkim_canon smtp string&!! unset
37924 This option sets the canonicalization method used when signing a message.
37925 The DKIM RFC currently supports two methods: "simple" and "relaxed".
37926 The option defaults to "relaxed" when unset. Note: the current implementation
37927 only supports using the same canonicalization method for both headers and body.
37929 .option dkim_strict smtp string&!! unset
37931 This option defines how Exim behaves when signing a message that
37932 should be signed fails for some reason. When the expansion evaluates to
37933 either "1" or "true", Exim will defer. Otherwise Exim will send the message
37934 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
37937 .option dkim_sign_headers smtp string&!! unset
37939 When set, this option must expand to (or be specified as) a colon-separated
37940 list of header names. Headers with these names will be included in the message
37941 signature. When unspecified, the header names recommended in RFC4871 will be
37945 .section "Verifying DKIM signatures in incoming mail" "SECID514"
37946 .cindex "DKIM" "verification"
37948 Verification of DKIM signatures in incoming email is implemented via the
37949 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
37950 syntactically(!) correct signature in the incoming message.
37951 A missing ACL definition defaults to accept.
37952 If any ACL call does not accept, the message is not accepted.
37953 If a cutthrough delivery was in progress for the message it is
37954 summarily dropped (having wasted the transmission effort).
37956 To evaluate the signature in the ACL a large number of expansion variables
37957 containing the signature status and its details are set up during the
37958 runtime of the ACL.
37960 Calling the ACL only for existing signatures is not sufficient to build
37961 more advanced policies. For that reason, the global option
37962 &%dkim_verify_signers%&, and a global expansion variable
37963 &%$dkim_signers%& exist.
37965 The global option &%dkim_verify_signers%& can be set to a colon-separated
37966 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
37967 called. It is expanded when the message has been received. At this point,
37968 the expansion variable &%$dkim_signers%& already contains a colon-separated
37969 list of signer domains and identities for the message. When
37970 &%dkim_verify_signers%& is not specified in the main configuration,
37973 dkim_verify_signers = $dkim_signers
37975 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
37976 DKIM signature in the message. Current DKIM verifiers may want to explicitly
37977 call the ACL for known domains or identities. This would be achieved as follows:
37979 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
37981 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
37982 and "ebay.com", plus all domains and identities that have signatures in the message.
37983 You can also be more creative in constructing your policy. For example:
37985 dkim_verify_signers = $sender_address_domain:$dkim_signers
37988 If a domain or identity is listed several times in the (expanded) value of
37989 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
37992 Inside the &%acl_smtp_dkim%&, the following expansion variables are
37993 available (from most to least important):
37997 .vitem &%$dkim_cur_signer%&
37998 The signer that is being evaluated in this ACL run. This can be a domain or
37999 an identity. This is one of the list items from the expanded main option
38000 &%dkim_verify_signers%& (see above).
38001 .vitem &%$dkim_verify_status%&
38002 A string describing the general status of the signature. One of
38004 &%none%&: There is no signature in the message for the current domain or
38005 identity (as reflected by &%$dkim_cur_signer%&).
38007 &%invalid%&: The signature could not be verified due to a processing error.
38008 More detail is available in &%$dkim_verify_reason%&.
38010 &%fail%&: Verification of the signature failed. More detail is
38011 available in &%$dkim_verify_reason%&.
38013 &%pass%&: The signature passed verification. It is valid.
38015 .vitem &%$dkim_verify_reason%&
38016 A string giving a little bit more detail when &%$dkim_verify_status%& is either
38017 "fail" or "invalid". One of
38019 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
38020 key for the domain could not be retrieved. This may be a temporary problem.
38022 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
38023 record for the domain is syntactically invalid.
38025 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
38026 body hash does not match the one specified in the signature header. This
38027 means that the message body was modified in transit.
38029 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
38030 could not be verified. This may mean that headers were modified,
38031 re-written or otherwise changed in a way which is incompatible with
38032 DKIM verification. It may of course also mean that the signature is forged.
38034 .vitem &%$dkim_domain%&
38035 The signing domain. IMPORTANT: This variable is only populated if there is
38036 an actual signature in the message for the current domain or identity (as
38037 reflected by &%$dkim_cur_signer%&).
38038 .vitem &%$dkim_identity%&
38039 The signing identity, if present. IMPORTANT: This variable is only populated
38040 if there is an actual signature in the message for the current domain or
38041 identity (as reflected by &%$dkim_cur_signer%&).
38042 .vitem &%$dkim_selector%&
38043 The key record selector string.
38044 .vitem &%$dkim_algo%&
38045 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
38046 .vitem &%$dkim_canon_body%&
38047 The body canonicalization method. One of 'relaxed' or 'simple'.
38048 .vitem &%dkim_canon_headers%&
38049 The header canonicalization method. One of 'relaxed' or 'simple'.
38050 .vitem &%$dkim_copiedheaders%&
38051 A transcript of headers and their values which are included in the signature
38052 (copied from the 'z=' tag of the signature).
38053 .vitem &%$dkim_bodylength%&
38054 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
38055 limit was set by the signer, "9999999999999" is returned. This makes sure
38056 that this variable always expands to an integer value.
38057 .vitem &%$dkim_created%&
38058 UNIX timestamp reflecting the date and time when the signature was created.
38059 When this was not specified by the signer, "0" is returned.
38060 .vitem &%$dkim_expires%&
38061 UNIX timestamp reflecting the date and time when the signer wants the
38062 signature to be treated as "expired". When this was not specified by the
38063 signer, "9999999999999" is returned. This makes it possible to do useful
38064 integer size comparisons against this value.
38065 .vitem &%$dkim_headernames%&
38066 A colon-separated list of names of headers included in the signature.
38067 .vitem &%$dkim_key_testing%&
38068 "1" if the key record has the "testing" flag set, "0" if not.
38069 .vitem &%$dkim_key_nosubdomains%&
38070 "1" if the key record forbids subdomaining, "0" otherwise.
38071 .vitem &%$dkim_key_srvtype%&
38072 Service type (tag s=) from the key record. Defaults to "*" if not specified
38074 .vitem &%$dkim_key_granularity%&
38075 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
38077 .vitem &%$dkim_key_notes%&
38078 Notes from the key record (tag n=).
38079 .vitem &%$dkim_key_length%&
38080 Number of bits in the key.
38083 In addition, two ACL conditions are provided:
38086 .vitem &%dkim_signers%&
38087 ACL condition that checks a colon-separated list of domains or identities
38088 for a match against the domain or identity that the ACL is currently verifying
38089 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
38090 verb to a group of domains or identities. For example:
38093 # Warn when Mail purportedly from GMail has no signature at all
38094 warn log_message = GMail sender without DKIM signature
38095 sender_domains = gmail.com
38096 dkim_signers = gmail.com
38100 .vitem &%dkim_status%&
38101 ACL condition that checks a colon-separated list of possible DKIM verification
38102 results against the actual result of verification. This is typically used
38103 to restrict an ACL verb to a list of verification outcomes, for example:
38106 deny message = Mail from Paypal with invalid/missing signature
38107 sender_domains = paypal.com:paypal.de
38108 dkim_signers = paypal.com:paypal.de
38109 dkim_status = none:invalid:fail
38112 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
38113 see the documentation of the &%$dkim_verify_status%& expansion variable above
38114 for more information of what they mean.
38117 . ////////////////////////////////////////////////////////////////////////////
38118 . ////////////////////////////////////////////////////////////////////////////
38120 .chapter "Proxies" "CHAPproxies" &&&
38122 .cindex "proxy support"
38123 .cindex "proxy" "access via"
38126 A proxy is an intermediate system through which communication is passed.
38127 Proxies may provide a security, availability or load-distribution function.
38130 .section "Inbound proxies" SECTproxyInbound
38131 .cindex proxy inbound
38132 .cindex proxy "server side"
38133 .cindex proxy "Proxy protocol"
38134 .cindex "Proxy protocol" proxy
38136 Exim has support for receiving inbound SMTP connections via a proxy
38137 that uses &"Proxy Protocol"& to speak to it.
38138 To include this support, include &"SUPPORT_PROXY=yes"&
38141 It was built on specifications from:
38142 http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt
38143 That URL was revised in May 2014 to version 2 spec:
38144 http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e
38146 The purpose of this facility is so that an application load balancer,
38147 such as HAProxy, can sit in front of several Exim servers
38148 to distribute load.
38149 Exim uses the local protocol communication with the proxy to obtain
38150 the remote SMTP system IP address and port information.
38151 There is no logging if a host passes or
38152 fails Proxy Protocol negotiation, but it can easily be determined and
38153 recorded in an ACL (example is below).
38155 Use of a proxy is enabled by setting the &%hosts_proxy%&
38156 main configuration option to a hostlist; connections from these
38157 hosts will use Proxy Protocol.
38159 The following expansion variables are usable
38160 (&"internal"& and &"external"& here refer to the interfaces
38163 &'proxy_host_address '& internal IP address of the proxy
38164 &'proxy_host_port '& internal TCP port of the proxy
38165 &'proxy_target_address '& external IP address of the proxy
38166 &'proxy_target_port '& external TCP port of the proxy
38167 &'proxy_session '& boolean: SMTP connection via proxy
38169 If &$proxy_session$& is set but &$proxy_host_address$& is empty
38170 there was a protocol error.
38172 Since the real connections are all coming from the proxy, and the
38173 per host connection tracking is done before Proxy Protocol is
38174 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
38175 handle all of the parallel volume you expect per inbound proxy.
38176 With the option set so high, you lose the ability
38177 to protect your server from many connections from one IP.
38178 In order to prevent your server from overload, you
38179 need to add a per connection ratelimit to your connect ACL.
38180 A possible solution is:
38182 # Set max number of connections per host
38184 # Or do some kind of IP lookup in a flat file or database
38185 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
38187 defer message = Too many connections from this IP right now
38188 ratelimit = LIMIT / 5s / per_conn / strict
38193 .section "Outbound proxies" SECTproxySOCKS
38194 .cindex proxy outbound
38195 .cindex proxy "client side"
38196 .cindex proxy SOCKS
38197 .cindex SOCKS proxy
38198 Exim has support for sending outbound SMTP via a proxy
38199 using a protocol called SOCKS5 (defined by RFC1928).
38200 The support can be optionally included by defining SUPPORT_SOCKS=yes in
38203 Use of a proxy is enabled by setting the &%socks_proxy%& option
38204 on an smtp transport.
38205 The option value is expanded and should then be a list
38206 (colon-separated by default) of proxy specifiers.
38207 Each proxy specifier is a list
38208 (space-separated by default) where the initial element
38209 is an IP address and any subsequent elements are options.
38211 Options are a string <name>=<value>.
38212 The list of options is in the following table:
38214 &'auth '& authentication method
38215 &'name '& authentication username
38216 &'pass '& authentication password
38218 &'tmo '& connection timeout
38220 &'weight '& selection bias
38223 More details on each of these options follows:
38226 .cindex authentication "to proxy"
38227 .cindex proxy authentication
38228 &%auth%&: Either &"none"& (default) or &"name"&.
38229 Using &"name"& selects username/password authentication per RFC 1929
38230 for access to the proxy.
38231 Default is &"none"&.
38233 &%name%&: sets the username for the &"name"& authentication method.
38236 &%pass%&: sets the password for the &"name"& authentication method.
38239 &%port%&: the TCP port number to use for the connection to the proxy.
38242 &%tmo%&: sets a connection timeout in seconds for this proxy.
38245 &%pri%&: specifies a priority for the proxy within the list,
38246 higher values being tried first.
38247 The default priority is 1.
38249 &%weight%&: specifies a selection bias.
38250 Within a priority set servers are queried in a random fashion,
38251 weighted by this value.
38252 The default value for selection bias is 1.
38255 Proxies from the list are tried according to their priority
38256 and weight settings until one responds. The timeout for the
38257 overall connection applies to the set of proxied attempts.
38259 .section Logging SECTproxyLog
38260 To log the (local) IP of a proxy in the incoming or delivery logline,
38261 add &"+proxy"& to the &%log_selector%& option.
38262 This will add a component tagged with &"PRX="& to the line.
38265 . ////////////////////////////////////////////////////////////////////////////
38266 . ////////////////////////////////////////////////////////////////////////////
38268 .chapter "Internationalisation" "CHAPi18n" &&&
38269 "Internationalisation""
38270 .cindex internationalisation "email address"
38273 .cindex UTF-8 "mail name handling"
38276 Exim has support for Internationalised mail names.
38277 To include this it must be built with SUPPORT_I18N and the libidn library.
38278 Standards supported are RFCs 2060, 5890, 6530 and 6533.
38280 .section "MTA operations" SECTi18nMTA
38281 .cindex SMTPUTF8 "ESMTP option"
38282 The main configuration option &%smtputf8_advertise_hosts%& specifies
38283 a host list. If this matches the sending host and
38284 accept_8bitmime is true (the default) then the ESMTP option
38285 SMTPUTF8 will be advertised.
38287 If the sender specifies the SMTPUTF8 option on a MAIL command
38288 international handling for the message is enabled and
38289 the expansion variable &$message_smtputf8$& will have value TRUE.
38291 The option &%allow_utf8_domains%& is set to true for this
38292 message. All DNS lookups are converted to a-label form
38293 whatever the setting of &%allow_utf8_domains%&
38294 when Exim is built with SUPPORT_I18N.
38296 Both localparts and domain are maintained as the original
38297 UTF-8 form internally; any comparison or regular-expression use will
38298 require appropriate care. Filenames created, eg. by
38299 the appendfile transport, will have UTF-8 names.
38301 Helo names sent by the smtp transport will have any UTF-8
38302 components expanded to a-label form,
38303 and any certificate name checks will be done using the a-label
38306 .cindex log protocol
38307 .cindex SMTPUTF8 logging
38308 Log lines and Received-by: header lines will acquire a "utf8"
38309 prefix on the protocol element, eg. utf8esmtp.
38311 The following expansion operator can be used:
38313 ${utf8_domain_to_alabel:str}
38314 ${utf8_domain_from_alabel:str}
38315 ${utf8_localpart_to_alabel:str}
38316 ${utf8_localpart_from_alabel:str}
38319 ACLs may use the following modifier:
38321 control = utf8_downconvert
38322 control = utf8_downconvert/<value>
38324 This sets a flag requiring that addresses are converted to
38325 a-label form before smtp delivery, for use in a
38326 Message Submission Agent context.
38327 If a value is appended it may be:
38329 &`1 `& (default) mandatory downconversion
38330 &`0 `& no downconversion
38331 &`-1 `& if SMTPUTF8 not supported by destination host
38334 If mua_wrapper is set, the utf8_downconvert control
38335 is initially set to -1.
38338 There is no explicit support for VRFY and EXPN.
38339 Configurations supporting these should inspect
38340 &$smtp_command_argument$& for an SMTPUTF8 argument.
38342 There is no support for LMTP on Unix sockets.
38343 Using the "lmtp" protocol option on an smtp transport,
38344 for LMTP over TCP, should work as expected.
38346 There is no support for DSN unitext handling,
38347 and no provision for converting logging from or to UTF-8.
38351 .section "MDA operations" SECTi18nMDA
38352 To aid in constructing names suitable for IMAP folders
38353 the following expansion operator can be used:
38355 ${imapfolder {<string>} {<sep>} {<specials>}}
38358 The string is converted from the charset specified by
38359 the "headers charset" command (in a filter file)
38360 or &%headers_charset%& main configuration option (otherwise),
38362 modified UTF-7 encoding specified by RFC 2060,
38363 with the following exception: All occurences of <sep>
38364 (which has to be a single character)
38365 are replaced with periods ("."), and all periods and slashes that are not
38366 <sep> and are not in the <specials> string are BASE64 encoded.
38368 The third argument can be omitted, defaulting to an empty string.
38369 The second argument can be omitted, defaulting to "/".
38371 This is the encoding used by Courier for Maildir names on disk, and followed
38372 by many other IMAP servers.
38376 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
38377 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
38378 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
38381 Note that the source charset setting is vital, and also that characters
38382 must be representable in UTF-16.
38386 . ////////////////////////////////////////////////////////////////////////////
38387 . ////////////////////////////////////////////////////////////////////////////
38389 .chapter "Events" "CHAPevents" &&&
38394 The events mechanism in Exim can be used to intercept processing at a number
38395 of points. It was originally invented to giave a way to do customised logging
38396 actions (for example, to a database) but can also be used to modify some
38397 processing actions.
38399 Most installations will never need to use Events.
38400 The support can be left out of a build by defining DISABLE_EVENT=yes
38401 in &_Local/Makefile_&.
38403 There are two major classes of events: main and transport.
38404 The main configuration option &%event_action%& controls reception events;
38405 a transport option &%event_action%& controls delivery events.
38407 Both options are a string which is expanded when the event fires.
38408 An example might look like:
38409 .cindex logging custom
38411 event_action = ${if eq {msg:delivery}{$event_name} \
38412 {${lookup pgsql {SELECT * FROM record_Delivery( \
38413 '${quote_pgsql:$sender_address_domain}',\
38414 '${quote_pgsql:${lc:$sender_address_local_part}}', \
38415 '${quote_pgsql:$domain}', \
38416 '${quote_pgsql:${lc:$local_part}}', \
38417 '${quote_pgsql:$host_address}', \
38418 '${quote_pgsql:${lc:$host}}', \
38419 '${quote_pgsql:$message_exim_id}')}} \
38423 Events have names which correspond to the point in process at which they fire.
38424 The name is placed in the variable &$event_name$& and the event action
38425 expansion must check this, as it will be called for every possible event type.
38427 The current list of events is:
38429 &`msg:complete after main `& per message
38430 &`msg:delivery after transport `& per recipient
38431 &`msg:rcpt:host:defer after transport `& per recipient per host
38432 &`msg:rcpt:defer after transport `& per recipient
38433 &`msg:host:defer after transport `& per attempt
38434 &`msg:fail:delivery after main `& per recipient
38435 &`msg:fail:internal after main `& per recipient
38436 &`tcp:connect before transport `& per connection
38437 &`tcp:close after transport `& per connection
38438 &`tls:cert before both `& per certificate in verification chain
38439 &`smtp:connect after transport `& per connection
38441 New event types may be added in future.
38443 The event name is a colon-separated list, defining the type of
38444 event in a tree of possibilities. It may be used as a list
38445 or just matched on as a whole. There will be no spaces in the name.
38447 The second column in the table above describes whether the event fires
38448 before or after the action is associates with. Those which fire before
38449 can be used to affect that action (more on this below).
38451 An additional variable, &$event_data$&, is filled with information varying
38452 with the event type:
38454 &`msg:delivery `& smtp confirmation mssage
38455 &`msg:rcpt:host:defer `& error string
38456 &`msg:rcpt:defer `& error string
38457 &`msg:host:defer `& error string
38458 &`tls:cert `& verification chain depth
38459 &`smtp:connect `& smtp banner
38462 The :defer events populate one extra variable: &$event_defer_errno$&.
38464 For complex operations an ACL expansion can be used in &%event_action%&
38465 however due to the multiple contextx that Exim operates in during
38466 the course of its processing:
38468 variables set in transport events will not be visible outside that
38471 acl_m variables in a server context are lost on a new connection,
38472 and after smtp helo/ehlo/mail/starttls/rset commands
38474 Using an ACL expansion with the logwrite modifier can be
38475 a useful way of writing to the main log.
38477 The expansion of the event_action option should normally
38478 return an empty string. Should it return anything else the
38479 following will be forced:
38481 &`msg:delivery `& (ignored)
38482 &`msg:host:defer `& (ignored)
38483 &`msg:fail:delivery`& (ignored)
38484 &`tcp:connect `& do not connect
38485 &`tcp:close `& (ignored)
38486 &`tls:cert `& refuse verification
38487 &`smtp:connect `& close connection
38489 No other use is made of the result string.
38491 For a tcp:connect event, if the connection is being made to a proxy
38492 then the address and port variables will be that of the proxy and not
38495 For tls:cert events, if GnuTLS is in use this will trigger only per
38496 chain element received on the connection.
38497 For OpenSSL it will trigger for every chain element including those
38501 . ////////////////////////////////////////////////////////////////////////////
38502 . ////////////////////////////////////////////////////////////////////////////
38504 .chapter "Adding new drivers or lookup types" "CHID13" &&&
38505 "Adding drivers or lookups"
38506 .cindex "adding drivers"
38507 .cindex "new drivers, adding"
38508 .cindex "drivers" "adding new"
38509 The following actions have to be taken in order to add a new router, transport,
38510 authenticator, or lookup type to Exim:
38513 Choose a name for the driver or lookup type that does not conflict with any
38514 existing name; I will use &"newdriver"& in what follows.
38516 Add to &_src/EDITME_& the line:
38518 <&'type'&>&`_NEWDRIVER=yes`&
38520 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
38521 code is not to be included in the binary by default, comment this line out. You
38522 should also add any relevant comments about the driver or lookup type.
38524 Add to &_src/config.h.defaults_& the line:
38526 #define <type>_NEWDRIVER
38529 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
38530 and create a table entry as is done for all the other drivers and lookup types.
38532 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
38533 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
38534 Add your &`NEWDRIVER`& to that list.
38535 As long as the dynamic module would be named &_newdriver.so_&, you can use the
38536 simple form that most lookups have.
38538 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
38539 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
38540 driver or lookup type and add it to the definition of OBJ.
38542 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
38545 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
38546 as for other drivers and lookups.
38549 Then all you need to do is write the code! A good way to start is to make a
38550 proforma by copying an existing module of the same type, globally changing all
38551 occurrences of the name, and cutting out most of the code. Note that any
38552 options you create must be listed in alphabetical order, because the tables are
38553 searched using a binary chop procedure.
38555 There is a &_README_& file in each of the sub-directories of &_src_& describing
38556 the interface that is expected.
38561 . ////////////////////////////////////////////////////////////////////////////
38562 . ////////////////////////////////////////////////////////////////////////////
38564 . /////////////////////////////////////////////////////////////////////////////
38565 . These lines are processing instructions for the Simple DocBook Processor that
38566 . Philip Hazel has developed as a less cumbersome way of making PostScript and
38567 . PDFs than using xmlto and fop. They will be ignored by all other XML
38569 . /////////////////////////////////////////////////////////////////////////////
38574 foot_right_recto="&chaptertitle;"
38575 foot_right_verso="&chaptertitle;"
38579 .makeindex "Options index" "option"
38580 .makeindex "Variables index" "variable"
38581 .makeindex "Concept index" "concept"
38584 . /////////////////////////////////////////////////////////////////////////////
38585 . /////////////////////////////////////////////////////////////////////////////